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1. 223337 In Figure 5 19 we assume the use of 35 ceiling mounted AP1240AG access points each of which is equipped with a pair of 2 2dBi AIR ANT4941 antennas for 802 11bg and a pair of 3 5 dBi AIR ANT5951 antennas for 802 1 1a The access points and the antennas are mounted at a height of 10 feet The design is intended to provide a minimum of 67 dBm signal level and a data rate of at least 24 Mbps on 802 11a for VoWLAN and high speed data clients and a minimum of 67 dBm signal level and data rate of at least 11 Mbps on 802 11bg for legacy data and voice clients 802 11a VoWLAN devices are assumed to be Cisco 7921G VoWLAN IP phones with integrated antenna Legacy voice and data client devices are assumed to possess nominal antenna gain of 0 dBi Inter access point spacing is approximately 42 7 feet and was selected to allow for a uniform distribution of access points within the floor interior and also ensure that the access point power levels required to produce our desired cell to cell overlap would fall within the capabilities of our client devices Note the following e With the exception of access points 1 5 32 and 34 access points are not located directly at the floor perimeter This is not optimal for the support of good location accuracy in all areas of the floor e The lack of perimeter access points in the right hand corners of Figure 5 19 Because of this there are areas in
2. 190539 0 1 2 3 4 5 6 7 8 9 Because of fading and other phenomena the observed signal strength of a mobile device at a particular location is not static but is seen to vary over time As a result calibration phase software typically records many samples of signal strength for a mobile device during the actual sampling process Depending on technique the actual vector array element recorded may account for this variation via one or more creative approaches A popular simple to implement method is to represent the array element associated with any specific receiver as the mean signal strength of all measurements of that mobile device made by that receiver sensor for the reported sample coordinates The location vector therefore becomes a vector array of mean signal strength elements as shown in the following equation where x and y represent the reported coordinates of the sample and r represents the reported RSSI Y Tapit apz Tapa apa Operational Phase In the operational phase a group of receiving sensors provide signal strength measurements pertaining to a tracked mobile device network side reporting implementation and forwards that information to a location tracking server The location server uses a complex positioning algorithm and the radio map database to estimate the location of the mobile device The server then reports the location estimate to the location client application requesting the po
3. Chapter5 Best Practices Location Aware WLAN Design Considerations Calibration W Figure 5 36 Unicast Radio Measurement Request ES 02 11 MAC Header Version 0 0 Mask 0x03 Type 10 Data 0 Mask 0x0C Subtype 0000 Date Only 0 Mask OxFO Y Frame Control Flags 00000010 Duration 44 Microseconds 2 3 H9 Destination 0 74 9 E9 Bssip 00 14 1B 59 42 72 10 15 EJ Source 00 14 1B 59 42 72 16 21 Seq Number 1006 22 23 Mask OxFFFO Frag Number O 22 Mask Ox0F fT 24 183 02 2 D O0xAA SNAP S O0xAA SNAP C 0x03 GY FCs Frame Check Sequence ECS Ox3F89F118 Calculated gay TJSXJ J J J SSS 08 02 2C 00 00 40 96 00 14 1B 59 biegnie Roa acter 252 0010 00 14 1B 59 42 72 EO 3E AA AA 03 00 40 96 00 00 YBr gt 00 98 32 01 00 00 00 00 00 00 00 00 ore c E 48 03 00 00 ut ECR COMO OEIC g6 _ 00 08 00_ 00 00 Sceosncooock coc 03 00 00 03 03 O01 OA 00 WES Soe ADOD 0060 04 01 OA OO 26 OO 08 OO OS 00 00 03 OS O1 OA OO amp 0070 26 00 08 00 06 OO OO 03 06 O1 OA 00 26 00 08 OO Gaoi 0080 07 00 00 03 07 O1 OA OO 26 00 08 00 08 00 00 03 Ge wie winnie 0090 08 01 OA 00 26 00 08 00 09 00 00 03 09 01 OA OO 6 wae 0040 26 00 08 OO OA OO 00 03 OA Ol OA 00 26 00 08 OO amp amp is 0080 OB 00 00 03 OB 01 OA 00 00 00 00 00 eee ee 8 The fields in the unicast Radio Measurement Request shown in Figure 5 36
4. Regional ee eee ee a Remote Locations Remote Locations Eee aa F cce a K ro e aa aS EP ay aa Soy Ge Vax ca v 223344 Each of the four regions depicted inFigure 5 28 contains a total of 290 access points with a WCS server resident at each regional headquarters As we discussed in the previous section two location appliances are deployed per region and physically reside within each regional headquarters location managing the two location domains present within each region A national headquarters campus provides overall management for the entire enterprise and contains 200 access points and a total of 2 100 tracked devices Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 N Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Multiple Location Appliance Designs of its own with WLAN controller services provided by a resident WiSM equipped Catalyst 6500 The national headquarters location contains a single management and a single location domain primarily dedicated to the WLAN and location tracking needs of the national headquarters staff itself This design contains a total of nine location domains and five management domains To provide top down management of the entire Unified Wireless Network WCS Navigator is deployed at the national headquarters location providing both management and location visibility internally as well as to all four regional campuse
5. General Data Rates 802 11b g Network Status IV Enabled 1 Mbps Mandatory x 802 11g Support M Enabled 2 Mbps Mandatory X Beacon Period 100 5 5 Mbps Mandatory E DTIM Period beacon 6 Mbps Supported intervals 9 Mbps Supported a Fragmentation Threshold 2346 11 Mbps Mandatory bytes 12 Mbps Supported Short Preamble M Enabled 18 Mbps Supported X Pico Cell Mode I Enable 24 Mbps Supported x Ti late Applied 802 11bConfig_166 AR RARIS onng_ 36 Mbps Supported x 48 Mbps Supported x 802 11b g Power Status 54 Mbps Supported x Dynamic Assignment automatic z y 7 Noise Interference Rogue Monitoring Channels Current Tx Level fs Channel List oca Channels x Control Interval sec 600 Dynamic Tx Power Control M Enabled CCX Location Measurement V Enabled 802 11b g Channel Status Made M 7 Interval seconds feo ail Assignment Mode Automatic x Update Interval sec 600 CCX Location Measurement Interval can be changed only when measurement mode is Avoid Foreign AP Interference M Enabled enabled Avoid Cisco AP load I Enabled Avoid non 802 11 Noise M Enabled Signal Strength Contribution I Enabled Controller must be rebooted for new value to take an effect Save Audit 190542 If the Cisco Compatible Extensions Location Measurement parameter is enabled Radio Measurement Requests will be broadcast to all associated WLAN clients regardless of their capability to support Cis
6. Hs Tracking Clients Assets and Rogue Devices Asset tag location history may be displayed by selecting Location History from the dropdown menu at the top right hand corner of the screen shown in Figure 3 20 and then clicking on Go Past location history stored within the location appliance will be displayed for the asset tag along with last values recorded for location statistics tag telemetry battery and emergency status as shown in Figure 3 21 Figure 3 21 Asset Tag Location History Wireless Control System ts Configure v Aeroscout Tag 00 0c cc 5 05 17 Select a command G0 Asset Name Asset Group Asset Category MAC Address 00 0c cc 5c 05 17 From Wed Aug 15 17 10 37 EDT 2007 Tos Wed Aug 15 19 07 40 EDT 2007 Time Stamp Floor Battery Status 2 Wed Aug 15 19 06 40 EDT Alpharetta Campus gt 4P1242 Building gt Test 80 2007 Lab Annex 2 3 Wed Aug 15 19 05 40 EDT Alpharetta Campus gt 4P1242 Building gt Test 80 2007 Lab Annex 2 7 Change selection every fz secs R Play Stop Location Tag Statistics Location Wed Aug 15 19 08 39 EDT 2007 Data Collected Wed Aug 15 19 08 36 EDT 2007 Floor Alpharetta Campus gt A4P1242 Bytes received 162597 Building gt Test Lab Annex 2 Packets received 3122 Telemetry Data TEMPERATURE 100 0 degrees Celsius QUANTITY 29 MOTION 29 0576 meters sec MOTIONPROB No Movement FUEL 29 0576 liters Enlarge Emergency Data Tag Properties Reason Panic Button Pre
7. OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter6 RFID Tag Considerations W sChokepoint Considerations Figure 6 34 illustrates the use of this capability for an AeroScout EX 2000 Exciter and AeroScout tags In this figure the Exciter instructs the tag to append vendor specific information in addition to the vendor specific Exciter ID to each tag transmission frame sent as a result of stimulation received from the Exciter Figure 6 34 AeroScout Vendor Specific Information Options y 802 11 IMC Header Version 0 0 Mask Type 10 Data k 0x0C Exciter Properties Subtype 0000 Date Only 0 Mask OxF 6 Y Frame Control Flags 00000011 Settings Taa Reaction Taq Transmission Parameters Advanced Duration 0 Microseconds WD Receiver 01 40 96 00 00 03 4 9 r Messages and Data Transmitter 00 0C CC SD 4E AS AeroScout D 4B AS 10 15 E9 Destination 61 3B 50 00 00 02 16 21 C Send only Exciter ID Seq Number 3346 22 Mask OxFFFO Send Frag Number O 22 Mask F 9 Massage E9 Source 00 00 00 00 00 00 Xerox 00 00 00 24 29 I tie message NTAN record aime 5 Y 802 2 cal Link Control LLC Meader C Send stored message number f C Send Telemetry data retrieved from host 0x00 Null SAP Null LSAP Source SAP OxOD 31 Response 0x0606 Numbered Information No Final Trans Send Seq Num 3 Trans Recy Seq Num 3 9 45 bytes 17 FCS 0x102D
8. s Control System Navigator a sant Monitor Reports Configure Administration Help v Search Eir Name or vac gt etiam Advanced Search Network Summary Inventory Status Clients vs Time Total Issue For Access Points 32 gt 36 00S Radios Clients X Controllers 10 gt 6 Unreachable Criteria Edi Location Servers 2 0 Unreachable Select New or Saved E 30 AM 8 45 AM 9 00 AM 9 15 AM 10 08 10 08 10 08 10 08 Alarm Summary Q Rogue AP o EA Unreachable 00s Critical Major Minor Location Location Coverage Time Wireless Control Systems Edit view F o Name Status IP Address Version Controllers Controllers APs Radios Clients Alarms Alarms Alarms Alarms Servers Security opaa wcs uP 10 1 56 63 4 1 83 0 5 33 11 10 0 349 o 20 0 1 Controllers 1 o o wcs 2 uP 10 1 56 31 4 1 83 0 5 33 21 D26 0 363 o 341 917 1 Access Paints 52 o o0 click on a WCS name to get redirected to the WCS summary page through single sign on lo Location oj o jeca st Mesh Links oj oj o 8 wes o a WCS Navigator allows for the location of individual clients asset tags and rogues to be determined by searching across the entire set of WCS servers Tracked device searches can be conducted based on IP address user name MAC address or asset name category or group WCS displays the output of such searches in a list format shown in the top half of Figure 5 30 Clicking on any of the tag MAC addresses controller or
9. Step 4 Step 5 Verifying Asset Tag Telemetry and Events W For example the following output snippet illustrates that indication of a panic button being depressed on an asset tag has been received along with vendor specific data pertaining to the event lt snip gt Telemetry Group Motion Probability ic cssass ict be ee dae bees teee No Motion EMERGENCY RSS OM as tates fs tts fa te a aeee reee ea NENEA Panic Button Vendor Data 0x6e 0x13 Oxa3 0x0 0x0 If the notification is not seen above in the controller s RFID database enable the following debugs on the controller to validate that it is receiving the notifications debug mac addr lt tag mac addr gt debug dot11 rfid enable 00 0c cc 5e 82 8d Parsing Cisco Tag RFID packet 62 00 0c cc 5e 82 8d System group 51 00 0c cc 5e 82 8d Battery group status 0x42 days 0 age 0 00 0c cc 5e 82 8d Chokepoint group option 0x8 power 0 range 128 00 0c cc 5e 82 8d Emergency group 00 0c cc 5e 82 8d LOCP Buffer 0x133245ec buffer 0x1332460a msgLen 30 msgId 18 transId 808989330 00 0c cc 5e 82 8d Notifying LBS of emergency 00 0c cc 5e 82 8d rfid Aerosct updated by AP 00 14 1B 59 41 F0O Incoming rssi 49 snr 50 New saved values rssi 48 snr 49 timestamp 3444175997 If output similar to that above is not seen use an RF protocol analyzer to capture the packets being transmitted by the tag during the send of telemetry or high priority events to verify that data is being tr
10. 3 1b 01 96 18 Campus gt AP1242 1b 45 WCS1 Aeroscout Loci 10 1 96 18 80 Building gt Test Lab 00 0c Roswell e Ci gt AP1242 4d west Aeroscout Loc 10 1 96 18 80 Building gt Test Lab 223347 Antenna Considerations Third Party Antennas When engineering in building WLAN solutions varying facility sizes construction materials and interior divisions can all pose concerns that need to be considered during design and deployment Cisco Systems is committed to providing not only the best WLAN infrastructure and client components in the industry but also providing complete WLAN solutions To this end Cisco Systems provides the widest range of antennas cabling and accessories available from any wireless LAN manufacturer With a full suite of directional and omni directional antennas low loss cable mounting hardware and other accessories installers and designers of Cisco supplied wireless solutions that meets the requirements of some of the most challenging wireless LAN applications In the Cisco Unified Wireless Network antennas available from Cisco Systems are pre configured in WCS and available for assignment to access points via the drop down menus found at Monitor gt Maps gt Position APs Selecting a Cisco antenna from this list automatically defines the antenna s gain and propagation patterns to WCS and the location appliance which helps facilitate optimal localization of tracked devices Wi Fi L
11. Degraded accuracy has been observed in lab testing of monitor mode access points when compared to local mode The use of Monitor Mode in location aware designs with software Release 4 1 is not recommended at this time CSCsh88795 CCX 36 Beacon Measurement Request Dual Band Support CCX S36 Beacon Request includes channels from the same band as association but not the other band This can affect the reliability of performing simultaneous calibration data collection on both bands when using dual band clients The band currently associated will typically calibrate reliably whereas the other band does not experience the same degree of reliable probe request generation that is brought about by the use of unicast Radio Measurement Requests Workaround It is recommended that calibration data collection be performed for each band individually at this time even when using dual band clients To accomplish this use either of the following alternatives 1 Perform the calibration data collection on each band individually using a single laptop equipped with a dual band client adapter compatible with the Cisco Compatible Extensions specification for WLAN devices specification at version 2 or higher and capable of recognizing and responding to S36 unicast radio measurement requests An example of such a client is the Cisco Aironet 802 1 1a b g Wireless CardBus Adapter AIR CB21AG For example proceed to disable the 5 GHz band and complete the data c
12. Most Likely OOOO Least Likely 190778 If WCS is licensed for only basic functionality as shown in Figure 3 7 RF Fingerprinting is not employed to determine location Instead on demand location for a single WLAN client or rogue device is performed based on the access point that is detecting the mobile device with the highest signal strength a derivation of the nearest access point concept Figure 3 7 WCS Licensed for Only Basic Functions ahali Wireless Control System cisco Version 4 1 91 0 Host weswin Type Basic t9 Licensed APs 50 g Wi Fi Location Based Services 4 1 Design Guide Eu 0L 11612 01 Chapter3 Cisco Location Based Services Architecture Accuracy and Precision W When using this approach the tracked device s location is approximated by placing the device icon at the location of the access point detecting it with the highest signal strength as shown in Figure 3 8 No location probability is displayed in this case Figure 3 8 On Demand Client Localization using WCS with Basic License Cisco Wireless Control System Monitor Configure Location Administration Help v Maps gt Campus gt 4P1000 Building gt Test Lab Annex Oca j Apioo0 6 190777 Note A WCS server that is not licensed for location usage cannot be used as a location or control client to the Cisco Wireless Location Appliance Commencing with software Release 4 1 of the
13. System 223302 Figure 3 3 summarizes the following events At each tag transmission interval the asset tag transmits a multicast frame on each of its configured channels At least three access points detect the asset tag s transmission It is forwarded to the WLAN controller WLC to which the detecting access points are registered The WLC stores the information payload associated with the asset tag in an internal tag information table indexed by the asset tag MAC address This information payload can contain information such as battery status and tag or asset telemetry For tags detected in the network by access points registered to this WLC the WLC places the following asset tag information in an internal RSSI table a Tag MAC address b AP MAC address c AP interface d RSSI measurement The location appliance periodically polls the WLC for the contents of the tag RSSI table using SNMP OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture HE Location Aware Cisco UWN Architecture Step 6 Step 7 Step 8 Step 9 Commencing with software Release 4 1 of the Cisco UWN the WLC is polled for the contents of the tag information table using the Cisco Location Control Protocol LOCP The location appliance calculates the location of the asset tag using the RSSI information and stores the location information in its database
14. e Tag deactivation e Tag transmission interval change e Indicator lamp activation e Storage of floor or cell identifiers e Appending of additional messages to tag multicast messages such as Chokepoint identification Pre configured message data Telemetry data Not every active tag vendor supports the use of chokepoint triggers with their tags Of those that do the use of chokepoint triggers tends to be tag vendor specific Each vendor offering asset tags that are compliant with the Cisco Compatible Extensions for Wi Fi Tags specification usually supplies chokepoint triggers that are designed specifically for compatibility with those tags At the current time chokepoint triggers are not interoperable between asset tags from different manufacturers Range may vary between models and manufacturers with those chokepoint triggers used with asset tags compliant with the Cisco Compatible Extensions for Wi Fi tags specification typically possessing effective ranges between 10 inches and approximately 25 feet These products operate using low frequency magnetic signaling Range tends to be predictable with excellent penetration of typical building materials and their contents OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations E RFD Tag Technology Figure 6 12 depicts low frequency magnetic signaling based chokepoint trigger devices from AeroScout and WhereNet AeroScout refers
15. option When the user has completed tracking a specific MAC address usage of that device Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Using Test Points to Verify Accuracy W as a test point can be terminated by highlighting the device MAC address in the test point MAC address drop down menu and clicking on the Stop option When all tracking has been completed and the accumulated tracked data is no longer needed all test points and their test point tracking data can be removed by using the Clear Logs option Additional information regarding the configuration of the test point facility for use can be found at the following URL http www cisco com en US docs wireless location 2700 3 0 configuration guide lacg_ch7 html wp 1 066057 Note that before the Analyze feature can provide any useful feedback at least one device category poll period must occur This is so as to allow the location appliance sufficient time to obtain location information regarding the test points note that historical location data is not used by the test point facility It is recommended to allow at least several poll periods to transpire in order to provide the best possible indication of long term location accuracy Figure 5 48 illustrates an example of the output provided by the Analyze feature of the test point facility Figure 5 48 Test Point Fac
16. s baseline specification The test point facility is useful when there are tagged assets wireless client devices or even rogues ona floor whose actual physical location is known and which move very infrequently or not at all An example of this might be asset tags that are deployed attached to shipping containers that will not be used during this shift or a wireless equipped desktop computer that does not move from its deployed location at a supervisor s workstation If the MAC address of these devices are known and their actual location will be fixed for an extended period of time the test point facility can be used to perform a running comparison of their estimated versus actual location and the results reported back to the user When the actual location of a device is specified by the user of the test point facility and the device s MAC address is added as an active test point WCS works in concert with the location appliance s debugging facility to compare the device s actual location to its estimated location after each SNMP poll period for that device category WCS performs these comparisons and calculates the percentage of occurrences where the estimated location of each tracked device is within the baseline performance specification of the location appliance This information is reported to the WCS user whenever the user highlights the device MAC address in the test point s MAC address drop down menu and clicks on the Analyze
17. Alpharetta Campus gt 4P1242 Building gt Test Lab Annex 2 190584 Figure 5 46 illustrates an usage example for the Location Inspection tool Here we have performed a location inspection after a calibration has been completed for a test lab facility The results indicate the level of accuracy and precision the location appliance delivered during the calibration In this example using an 802 1 1bg only calibration client the location appliance is seen as capable of delivering a level of accuracy and precision based on conditions in place at the time of calibration of 7 meters or 23 feet with 90 precision over the majority of the test lab area Looking at a single calibration data point in specific artificially indicated in the figure by a yellow arrow to represent the point at which a mouse over was performed we see the estimated location indicated by X as well as the details behind the degree of location error for this particular case 16 8 feet Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 mw 565 Chapter5 Best Practices Location Aware WLAN Design Considerations HI inspecting Location Quality Figure 5 46 802 11bg Location Inspection Inspect Location Quality gt Calibration Model gt Concannon Test Lab Floor Client Type Percentage of Location Errors under l 7m23ft x Alpharetta Campus gt Concannon Building gt Main Floor 802 11b 9 n only client worse i 602 114 n only client 802 11b
18. O Clients O 802 11 Tags M Rogue APs O Rogue Clients mi O coverageAreas O Markers O Chokepoints Save Settings Grid 223318 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter3 Cisco Location Based Services Architecture Hs Tracking Clients Assets and Rogue Devices It is possible to filter the location information displayed by the WCS based on the age of the information In Figure 3 22 WCS displays location appliance information that has aged up to 15 minutes Alternatively this value could be set to 2 or 5 minutes for more recent location information or 1 2 1 3 6 12 or 24 hours for older information By clicking on the blue chevron that is displayed to the right of the Rogue APs checkbox rogue access point filtering options can be specified and additional information can be displayed such as e The total number of rogue access points detected on this floor e Small icons shown above or standard size icons can be selected When using small icons text is not displayed on the floor map for the rogue access point except when a mouse over is performed When using standard size icons an on screen tag displaying the MAC address of the rogue access point appears e Either all rogue access points can be displayed or filtering can be performed to select which rogue access points to display on the floor map This is based primarily on MAC address but can be augmented by filtering on the
19. SOAP or SNMP traps I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations RFID Tag Technology Figure 6 14 WCS Floor Map With Chokepoints Egg aPi2az 2 Figg a1 24285 t TUZE pene Front Lobby Front Lobby inresa 1 gt Basement Entrance 2 aPi2a2 6 223365 k ceea In Release 4 1 of the Cisco UWN software after a tag has left the range of a chokepoint trigger the location appliance continues to indicate the tag s location as being within the configured range of the chokepoint trigger until one of the following events occur e The tag indicates that it is now out of range of that chokepoint trigger e The value configured for the Chokepoint Out of Range Timeout expires shown in Figure 6 15 default 60 seconds After one of these events occur the location appliance uses RF Fingerprinting to calculate the location of the device until such point that it enters into another chokepoint area and into the stimulation zone of another chokepoint trigger If the device is then stimulated by a subsequent chokepoint trigger and successfully reports this stimulation to the Cisco UWN the location appliance then places the tracked device at the location of the new chokepoint Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 6 RFID Tag Considerations Using Wi Fi RFID Tags with t
20. These access point locations have been selected traditionally on the basis of coverage WLAN bandwidth channel reuse cell to cell overlap security aesthetics and deployment feasibility In a location aware WLAN design the requirements of underlying data and voice applications should be combined with the requirements for good location fidelity Depending on the particular site the requirements of the location aware Cisco UWN are flexible enough such that the addition of location tracking to voice installations already designed in accordance with Cisco best practices for example may not require extensive reworking Rather infrastructure already deployed in accordance with accepted voice best practices can often be augmented such that location tracking best practice requirements are met as well such as perimeter and corner access point placement for example depending on the characteristics of the areas involved In a location ready design it is important to ensure that access points are not solely clustered in the interior and toward the center of floors Rather perimeter access points should complement access points located within floor interior areas In addition access points should be placed in each of the four corners of the floor and at any other corners that are encountered along the floor perimeter These perimeter access points play a vital role in ensuring good location fidelity within the areas they encircle and in some cases may
21. and be sure to take a sufficient number of new data points directly in these white areas After completion rerun the Calibration phase and re inspect location quality These white areas should now be totally eliminated or at least significantly reduced The process can be repeated if necessary to further address any remaining white areas if still present Note Using Test Signal strength information for each selected band as well as the test client s actual location coordinates must be available for each floor targeted by the location inspection tool Even if multiple floors share the same RF model only the floor upon which the model was actually calibrated is eligible for location inspection Points to Verify Accuracy Complementing the capabilities found in Location Inspection beginning with software Release 4 1 the location aware Cisco UWN allows for impromptu go no go verification of whether the location appliance s baseline accuracy and precision specification has been met on a particular floor This can be done using the test point facility which is accessible from the WCS main menu via Monitor gt Maps gt floor map name gt Position Test Point For a specified device MAC address the test point facility keeps track of the total number of location test point samples taken and can calculate the percentage of the total number of test point samples taken whose location accuracy are within the location appliance
22. as necessary to meet location tracking requirements Prior to software Release 4 1 the automated placement capabilities of the planning tool were limited to floors and buildings whose shapes were simple polygons such as squares and rectangles A new capability added in this release allows the planning tool to accommodate irregularly shaped floor areas To accomplish this an irregular coverage perimeter is drawn using the WCS Map Editor and when saved becomes available for use in the planning tool When designing new floor layouts using the planning tool the user is allowed to choose between using the traditional closed polygon or the newly created irregular shape Further information on this newly introduced capability can be found in the chapter Using the Map Editor to Draw Polygon Areas in the document entitled Cisco Wireless Control System Configuration Guide Release 4 1 at the following URL http www cisco com en US docs wireless wes 4 1 configuration guide wcsmaps html wp 1 104253 With this enhancement the planning tool becomes more useful to designers when working with common buildings having irregular shapes such as a building with an open courtyard as shown in Figure 5 13 In Figure 5 13 we see a location design performed using the automatic planning tool mode Note the red outlined perimeter of the building which was added to the floor image using the Map Editor and is now eligible for use within the planning tool Using WCS Plan
23. e the number of registered access points that are within range of the tag and that have detected the tag s chokepoint related transmissions e the number of times the tag will transmit a multicast frame on each configured 802 11 channel in response to chokepoint trigger stimulation This can be expressed mathematically as LOCP Measurement Notifications cyoxepoinr Detecting APSrorar 802 11 Repetitions per CHANNEL Note the following considerations 1 This calculation yields the number of LOCP Measurement Notifications that result from a single tag reacting to a single chokepoint stimulation event 2 Chokepoint triggers by default transmit multiple stimulation packets over their magnetic signaling medium This could result in multiple stimulation events which is highly dependent on the amount of time spent within the chokepoint stimulation zone and other factors 3 This calculation yields a maximized value for LOCP Measurement Notifications as it assumes that all frames transmitted by the tag are successfully detected by the number of access points specified in Detecting APS7zo7 none are dropped due to interference contention or other RF anomalies In the majority of cases e Chokepoints are deployed in areas where the surrounding access point spacing meets the requirements discussed in Access Point Placement page 5 5 e Access points and tags are configured to operate on the non overlapping 2 4 GHz channels channels 1 2412
24. gt Load Location Server data as old as Rogue access points are access points that are detected by the wireless LAN infrastructure and determined not to be members of the same RF group or WLAN system In addition any devices that are participating as members of ad hoc networks are also detected as rogue access points but with a rogue type of AD_HOC unless location appliance rogue access point polling has been configured to exclude ad hoc rogues Rogue access points are indicated on WCS location floor maps using an icon representing a skull and crossbones within a black circle as shown in Figure 3 22 They may be totally wireless connected to the same wired infrastructure as the detecting WLAN or connected to an entirely different wired infrastructure To display rogue access points on the WCS location floor map ensure that the Rogue APs checkbox option is enabled from the Layers dropdown selector at the top of the floor map display and click Load in the left hand column To avoid excessive clutter WCS will display the first 250 rogue access points on the floor map To view the location of rogue access points beyond the first 250 rogue access point filtering must be used Rogue Access Point Location Map Wireless Control System Configure Location Administration Help v Maps gt Cisco SJ Site 5 gt BLD 14 gt 3rd floor RSSI Color Lookup Zoom Refresh 90 dBm 100 Yo z s min z Full Screen O AP Heatmaps
25. i Ba 9 1000000 190576 However in the case of larger campuses the total number of tracked devices may exceed the capacity of a single location appliance making it necessary to use multiple location appliances and multiple location domains in the design Some organizations may in fact choose to purposely divide the tracked device load among two or more location appliances for internal reasons such as to better accommodate internal cost accounting within the organization or to better accommodate growth A good example of this might be a campus medical center WLAN that is tracking a large amount of patient related medical assets in addition to the internal IT assets of the organization It may wish to use separate location appliances to partition the tracking of assets as well as to provide clear delineation of equipment and cost separation between departments Note Keep in mind that if there are more than 250 tracked devices detected in a particular device category WCS displays only the first 250 tracked devices After displaying the initial 250 tracked devices WCS will prompt the user to initiate the use of device filtering in order to display the remainder Wi Fi Location Based Services 4 1 Design Guide a OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Multiple Location Appliance Designs W In software Release 4 1 WLAN controllers offer the device capacities shown in T
26. is highly consistent approximately 5 dBm per 20 foot change in distance This results in the slope of the graph between points a and b being fairly steep As the distance continues to increase beyond point b the slope of our graph begins to diminish and the level of RSSI differentiation decreases providing increasingly less differentiation in received signal strength per unit change in distance Note that the slope of the graph between points b and c is not nearly as steep as it is between points a and b As distance begins to significantly exceed point b in this example the slope of the graph will diminish even further This greatly reduced slope and steepness results in a decreased level of differentiation in signal level with increasing distance When this occurs at extended distances it becomes more difficult to accurately predict changes in distance based on detected changes in RSSI Jateration The risk of this lack of RSSI differentiation having a significant impact on location accuracy can be reduced if steps are taken to avoid areas of the RSSI versus distance curve where this phenomena is known to exist most prominently In general for access points deployed indoors at antenna heights of 20 feet or less this can be achieved if the range of any point on the floor to at least three detecting access points on that floor one in each of at least three of the four quadrants surrounding it is maintained within approximately 70 feet in an indoo
27. variety of topics from access point placement and separation multiple location appliance designs Wi Fi Location Based Services 4 1 Design Guide ma OL 11612 01 Chapter 1 Overview About the Guide W and antenna considerations to calibration and challenging location environments All the information contained in this section is aimed at assisting designers in optimizing location aware designs for improved location fidelity e Provide the reader having limited exposure to RFID tag technology with a basic understanding of how these various types of tags relate to the location aware Cisco UWN Chapter 6 RFID Tag Considerations provides details regarding RFID asset tags and how these products function This section also places considerable emphasis on the proper configuration of Cisco WLAN controllers the WCS and the location appliance when using RFID tags Additional Reference Documents It is assumed the reader is familiar with the following documents e Cisco Wireless Location Appliance Support Documentation for Release 3 0 http www cisco com en US products ps6386 tsd_products_support_series_home html e Cisco Wireless Control System Support Documentation for Release 4 1 http www cisco com en US products ps6305 tsd_products_support_series_home htm e Cisco 4400 Series WLAN Controller Support Documentation for Release 4 1 http www cisco com en US products ps6366 tsd_products_support_series_home html e Cisco 2100
28. 0 0 Mask 0x03 Type 10 Data 0 Mask c Subtype 0000 Data Only 0 Mask OxFO f Frame Control Flags 00000011 1 g Oise dowry Non strict order g s0 ee Nom Protected Frane i 20 2 No More Data gs 220 Power Management active mode sg 0 This is not a Re Transmission g 0 Last or Unfragmented Frane sg eek Exit from the Distribution Syster O gies lt e e 1 To the Distribution Syster Duration 0 Microseconds 2 3 HJ Receiver 01 40 96 00 00 03 4 EJ Transmitter 00 0C CC SE 82 8D AeroScout SE 82 8D 10 15 E3 Destination 11 30 10 00 00 42 Seq Number gt Frag Number EJ Source 00 00 00 00 00 00 Xerox 00 00 00 24 29 5 y 802 2 cal Link Control LLC Header Dest SAP 0x00 Nell SAP Null LSAP 30 Source SAP OxOD 31 Response 0x0106 Receiver Ready No Final 32 33 Mask Ox0OFF g Transmitter Recv Sequence Number 3 Packet Data 34 bytes 34 67 00 00 OD 0 O6 G 0 BPJ sneee abe aoe cC 00 00 00 00 secede Besnasenesnesan sensaneeses 223430 This asset tag shown in Figure B 1 is not configured to transmit external sensor telemetry In addition the RF frame also includes the following information e Five byte Cisco Compatible Extensions for Wi Fi Tags header black rectangle e Tag product type identification yellow rectangle e Optional battery telemetry red rectangle e Optional vendor specific information green rectangles The length o
29. 11a n covered 802 11b g n Covered E 802 11a b g n Covered Suggested Location E Visited Location Wireless Control System Horizontal Vertical Zoom Logout Refresh Monitor Reports Configure Location Administration Help v Calibrating Model Test 2 on Floor Alpharetta Campus gt Concannon Building gt Main Floor Select a command z Calibrating using Client 00 40 96 a1 9d 47 Click on the map where the client is currently located and click on Save Delete Data Points Generate RSSI vs Distance Graph Generate RSSI vs Log Distance Graph Total 802 11a n Data Points 0 Total 802 11b g n Data Points 0 0 0 Save Cancel 75 E I Show grid 7 Show APs M Show Data Points to Lo ra oO N Calibration Validity Strictly speaking a properly performed site calibration is considered valid as long as the fundamental environmental factors affecting RF propagation between clients and access points have not deviated significantly from the state under which the original calibration was performed For example significant changes in the material contents of the target environment may have an impact on the path losses experienced within that environment Performing a re calibration allows the system to better understand the current level of attenuation and fading present in the envi
30. 11b asset tag that is transmitting tag layer two multicast messages e An 802 11b asset tag acting as a WLAN client that is issuing probe requests e An 802 11b asset tag acting as a WLAN client that actively associates First and foremost it should be clearly understood that 802 11b asset tags that transmit tag messages using Layer 2 multicasts and do not attempt to associate to any WLANs will not cause the initiation of any 802 11g protection modes under any circumstances This includes asset tags operating in strict compliance with version of the Cisco Compatible Extensions for Wi Fi tags specification Laboratory research and analysis have shown that protection mechanisms are not initiated throughout an entire network of access points if an 802 11b asset tag or WLAN client is simply powered on In fact the following are observed e A probe request from an 802 11b asset tag that is not associated to any access point on a particular channel does not in and of itself cause the initiation of protection mode by an 802 11g access point that detects it e Protection mode is not initiated until the 802 11b asset tag successfully associates to either the cell in question or an adjacent cell on the same channel At that point the target cell as well as any other cells on the same channel and RF adjacent to the target cell initiate protection mode e Access points that are not on the same channel as the 802 1 1b asset tag or not RF adjacent to i
31. 90 has migrated from the domain of location appliance Loc1 to the domain of location appliance Loc2 The access points of the two buildings are registered to different controllers and these controllers are individually contained within two different location domains For example the controller servicing the hypothetical Havermeyer Building is being polled by the Loc1 location appliance while the controller servicing the hypothetical Pupin Hall Building is being polled by the Loc2 location appliance Duplicate Device Appearances Due to Device Migration Asset Asset Battery n Asset Name Group Taser Stat N e Eanan endor Loc Server Controller F Map Location Nashville Aeroscout 10 1 56 12 80 Campus gt Havermeyer gt Main Floor Nashville Cam gt Pupin Aeroscout Loc2 10 1 56 10 80 Hall gt Floor 1 Nashville Campus gt Pupin Aeroscout 10 1 56 10 80 PEENES R Note that in Figure 5 25 the asset tag MAC address 00 0C CC 5E 82 90 appears twice found in two different location appliances and with locations listed for two different buildings If we were to display the map locations listed at the extreme right of Figure 5 25 we would see a tag icon displayed on both the main floor of the Havermeyer Building as well as floor number one of Pupin Hall In order to differentiate between which of these two entries represents the latest and true location of asset tag 00 0C CC 5E 82 90 we can use the information provided by the
32. Adapter AIR CB21AG is recommended by Cisco Systems for location calibration data collection Wi Fi Location Based Services 4 1 Design Guide ou 11612 01 EEN Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration In most cases WCS will handle the maintenance of the controller location calibration tables inserting client MAC addresses as needed for calibration data collection and removing them when they are no longer necessary Proper maintenance of this table is important since every client compliant with the Cisco Compatible Extensions specification version 2 that is present in the table up to a maximum of five will receive unicast radio measurement requests whenever they are associated to any access point registered to that controller This occurs regardless of whether the client is actively collecting calibration data points or being used simply as an associated mobile workstation during non calibration periods Because of this residual client MAC addresses in controller location calibration tables can result in unnecessary load and traffic e Each WLAN controller containing these entries should perform the following every four seconds Issue radio measurement requests to each client in the table Process incoming probe requests from each client in the table Process incoming radio measurement responses from each client in the table e Each WLAN client present in the location calibration t
33. B 1 Asset Tags Not Detected B 6 Verifying Asset Tag Telemetry and Events B 8 wi Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 CHAPTER Overview Introduction 802 11 wireless has truly blossomed in the past decade moving from a technology that was once thought of as primarily a productivity enhancement for vertical industries to one now pervasive throughout society The wide spread acceptance of Wi Fi networks has fueled this dramatic adoption from deployments in offices and distribution centers to homes and ever multiplying wireless metropolitan areas Maturing rapidly and reaching critical mass this widespread adoption has driven down the cost of wireless infrastructure dramatically and has resulted in the availability of higher quality equipment at lower cost The rapid increase in the adoption rate of Wi Fi coupled with the availability of high quality infrastructure at reasonable cost are key factors behind the flurry of activity regarding Wi Fi location based services Not to be confused with solutions requiring a dedicated independent infrastructure of location receivers and RFID tag readers research and development in Wi Fi location prediction techniques has facilitated the emergence of indoor RF location tracking systems based fundamentally on IEEE 802 11 infrastructure In combination with the frenetic race to implement RFID systems in the consumer and distribution supply chains these have all combined to
34. Cisco Technology Development Partners CTDP and encourages the development of interoperable active RFID tag hardware in compliance with the specification Better accuracy and precision Cisco RF Fingerprinting yields significantly better performance than solutions employing pure triangulation or RSS lateration techniques These techniques typically do not account for effects of attenuation in the environment making them highly susceptible to reductions in performance The advantages of Cisco RF Fingerprinting technology start where these traditional approaches leave off Cisco RF Fingerprinting begins with a significantly better understanding of RF propagation as it relates specifically to the environment in question With the exception of the calibration phase in location patterning none of the traditional lateration or angulation approaches discussed thus far take environmental considerations directly into account in this manner RF Fingerprinting then goes a step further by applying statistical analysis techniques to the set of collected calibration data This allows the Cisco Location Appliance to further refine predicted location possibilities for mobile clients culling out illogical or improbable possibilities and refining accuracy The net result of these efforts is not only better accuracy but significantly improved precision over traditional solutions Reduced calibration effort The Cisco RF Fingerprinting technology offers the key advant
35. Cisco Radio Resource Manager RRM can be used instead RRM can be used to dynamically control access point transmit power based on real time WLAN conditions Under normal circumstances transmit power is maintained across all access points to maintain capacity and reduce interference If a failed access point is detected transmit power can be automatically increased on surrounding access points to fill the gap created by the loss in coverage Should a coverage hole occur RRM can use any remaining transmit power reserve on surrounding access points to raise the adjacent coverage levels and address the coverage hole until it can be investigated and resolved In either case it is recommended that a verification of access point transmit power settings be performed periodically If you opt to manually administer access point transmit power settings you should examine the overall performance of your system to ensure that your original design assumptions are still valid and that there have not been significant changes in your environment that might warrant reconsideration of those assumptions When using RRM it will monitor your system for changes that might warrant an increase or decrease in access point transmit power settings for you After your system has been installed various adjustments can be made to RRM to bring its selection of access point transmit power levels and other parameters within your expectations for the environment at hand Keep in m
36. GHz 6 2437 GHz and 11 2462 GHz in the Americas for example Most chokepoint triggers assume a default value of one for the number of times they repeat per channel tag multicast transmissions indicating that the tag has been successfully stimulated by a chokepoint trigger Only a single tag multicast transmission frame containing the stimulating chokepoint trigger s MAC address need be received in order to result in the generation of a LOCP Measurement Notification Because of this the default value for the number of times these chokepoint related tag transmissions are repeated per channel is usually sufficient especially since this tag transmission will typically be repeated across three 2 4 GHz channels resulting in more than one access point receiving the tag transmission even without increasing the repetition count However in some cases where interference or congestion may be extremely high it may make sense to increase the repetition count slightly In other cases involving tagged assets traversing through chokepoint areas at high speed or at fringe distances from OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations Chokepoint Considerations chokepoint triggers this parameter can be used to increase the likelihood of reliable stimulation see Appendix A Chokepoint Transmission Interval Analysis for more details In all cases however such increases should be done
37. H 47 dem i1b a n 823 secs A me Pu aN E gaan x a oS age Le RSSI Age Comparison for Duplicate Tag Entries Tags gt Aeroscout Tag 00 0c cc 5e 82 90 Tag Properties Aeroscout r 10 1 5612 Batt remaining 80 Days remaining 0 Tolerance 20 Battery Age 0 Battery Life Location Nashville Campus gt Havermeyer gt Main Floor ed Oct 7 2007 12 38 04 PM Loci Multiple Location Appliance Designs Select a command 160 Asset Info m m SS F Enabled Update j Name Group Category Location Debug 1 Information on the Map Statistics B o TOREJ I Readings oam T Be Detected RSS Radio Type Aamaghen Located H Eose 69 dam ibron g g at a g B After the location appliance s absent data cleanup interval has expired our lab test tag report appears as shown in Figure 5 27 Note that our migrated asset tag with MAC address 00 0C CC 5E 82 90 has been pruned from the active location database of location appliance Loc1 Figure 5 27 Tag Report After Device Pruning Tags MAC Addr AssetName Asset Group Aseet Yendor Loc Server Controller Gather Map Location Aeroscout Loc2 10 1 56 10 80 E ropuscPupin fsa Aeroscout Loc2 10 1 56 10 80 SEUR 3 N Relating this to the example shown in Figure 5 24 devices moving between metro remote buildings 3 4 and 5 would not be affected by this anomaly sinc
38. MAC addresses will share a Retry Count Refresh Time parameter set As an example assume that the location appliance has been configured to transmit SNMP email and syslog northbound notifications when a high priority condition arises for a specific asset tag For the purpose of this example let us assume the high priority event is the depression of a call button on an asset tag such as the AeroScout T2 or T3 Also assume that the notification Refresh Time is set to sixty minutes and the notification Retry Count is set to one the default values Under these conditions the location appliance will generate SNMP email and syslog northbound notifications for each high priority event occurring for this tag up to a maximum of two northbound notifications After the value of one plus the Retry Count has been reached the location appliance will skip firing any further northbound notifications for this condition and device for the time period specified by the Refresh Time Once the Refresh Time has expired this cycle will repeat unless the event has been cleared OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter 4 Installation and Configuration Hs Configuring Location Appliance Notification Parameters Refresh Time Refresh Time specifies the length of the wait period between transmission of northbound notification sets for a specific event condition and device as described above in Retry Count page 4 9 After the
39. SD 4E AS 1N 0010 61 2F 68 00 00 02 70 17 00 00 00 00 00 00 00 12 a h p 0020 06 06 Ol 00 02 00 33 02 07 42 00 00 00 00 00 00 _ 3 B 0030 01 09 00 00 80 00 oc CC 60 1B 61S ve O0 Ue te a g 0040 IIE EIJ FS pi B9 EF Eves aoe Although both the standard chokepoint information as well as the optional vendor specific information travels from the tag to the access point contained within the same tag multicast frame in software Release 4 1 the WLAN controller parses this into two separate LOCP notifications e An LOCP Measurement Notification containing the chokepoint group information that is 160 bytes in length e An LOCP Information Notification containing the vendor specific information that is 138 bytes in length The precise composition of the vendor specific fields varies depending on the chokepoint and tag vendor For example AeroScout allows for additional message information to be appended to the Exciter ID via the Tag Reaction tab of the Exciter Properties menu in the AeroScout System Manager and AeroScout Network Exciter Manager These capabilities are also available via the Exciter Manager utility for users of the AeroScout EX 3100 Exciter Vendor specific information can be e Directly entered and saved on a per Exciter basis e Saved to tag memory for later reuse e Consist of one of ten preconfigured messages programmed into tags e Emanate from a host attached to the tag
40. Site 5 gt BLD 14 gt 3rd floor M sjci4 31b ap5 M sjct4 32b ap6 RSSI Color Lookup Zoom Refresh M sjc14 31b ap3 j Layers O Access Points gt O AP Heatmaps O Clients IRETE p 802 11 Tags Loading Chokepoints Loaded 0 chokepoints O Rogue APs Done ba 4 5 3 O Rogue Clients O Grid Load Location Server data as P PSE O coveragedreas old as O Markers O Chokepoints Save Settings 223308 Note that the graphical location information shown can be filtered by WCS based on the age of the information Thus in Figure 3 12 WCS displays device location information that has aged up to 15 minutes This value can be set to 2 or 5 minutes if you would like to view location information received more recently or 1 2 1 3 6 12 or 24 hours for information that is older By clicking on the blue chevron that is displayed to the right of the Clients checkbox option client filtering options can be specified and additional information retrieved such as e The total number of WLAN clients detected on this floor e Small icons shown in Figure 3 12 or standard size icons can be selected When using small icons descriptive text is not displayed on the floor map for the client except when a mouse over is performed When using standard size icons an on screen tag is displayed that is configurable for IP address user name MAC address asset name asset group or asset category Wi Fi Loca
41. UWN While some clients perform active scans and issue probe quite regularly others may be seen to probe quite minimally Cisco Compatible Extensions Location Measurements The impact of variations in client probing may be greatly reduced by standardizing on clients that are compliant with the Cisco Compatible Extensions for WLAN Devices specification at version 2 or greater Compatible clients that support the S36 Radio Measurement Requests introduced in Cisco Compatible Extensions for WLAN Devices specification version 2 will perform active scanning and probe all configured SSIDs upon command Support of this capability enables clients to participate in features such as Cisco Compatible Extensions Location Measurement When this feature is enabled registered lightweight access points broadcast Radio Measurement Request frames to their associated clients via each enabled SSID and radio interface at a configurable interval from 60 default to 32 400 seconds see Figure 3 10 Each Radio Measurement Request contains a beacon request that elicits compatible clients to respond by transmitting probe requests on the channels specified within the Radio Measurement Request The consistency inherent to this mechanism helps enhance location accuracy for clients so equipped Note that in software Release 4 1 DFS channels are not included in Radio Measurement Requests Using the WCS or controller GUI Cisco Compatible Extensions Location Measurement can be
42. Valid values are to 120 seconds with the default value being 15 seconds e Neighbor Dead Interval The minimum time interval in seconds that the location appliance will wait before marking a WLAN controller not responding to its Echo Requests as dead This value should not be less than twice the Echo Interval Recommended values are 2 to 240 seconds with the default value being 30 seconds e Response Timeout The maximum time interval in seconds within which the WLAN controller must respond to requests sent by the location appliance Valid values are 1 to 99 999 seconds with the default value being 1 second e Retransmit Interval The minimum time interval in seconds the location appliance waits before retransmitting a LOCP request when it does not get a response back from the WLAN controller Valid values are 1 to 99 999 seconds with the default value being 3 seconds e Maximum Retransmits The maximum number of retransmissions that will be attempted by the location appliance when a response is not received for a LOCP Request Valid values are to 99 999 attempts with the default value being 5 attempts Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 a 337 Chapter3 Cisco Location Based Services Architecture HI Cisco Location Control Protocol LOCP Note that the first two parameters are applicable only to Echo Request and Echo Reply control messages while the remaining parameters pertain to all data me
43. a general network recommendation establishing synchronized internal clocks facilitates troubleshooting by making it much easier to correlate log messages between components Whether viewing independent log files from various components or a combined syslog having log entries use consistent time stamp references in their message text only serves to make such messages more logical and easier to understand 190561 This usefulness of consistent timestamps becomes especially clear when multiple location appliances are configured to send asynchronous northbound notifications to a common destination such as email messages for example Location appliances configured with the incorrect system time may issue notification messages as shown in Figure 4 5 bearing incorrect or inconsistent times that may appear confusing to operators at network operations centers NOCs or other control points Figure 4 5 Date Sat 20 May 2006 09 24 01 0400 EDT From locserver st9731 testlab com To wirelessguy st9 31 testlab com Subject TAG ENTERING TEST AREA X Mailer smtpsend Tag 00 0c cc 5b ff 44 is in Area Rear Conference Room Test Lab Annex 2 AP 1242 Building Alpharetta Campus_Group Alpharetta Campus Email Notification Message Bearing Time Stamp of Location Appliance 190562 w Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 _ Chapter 4 Installation and Configuration Quiescing the Location Appliance W Network Tim
44. a new calibration model via Monitor gt Maps gt RF Calibration Models gt Create New Model A step by step description of the calibration process can be found in the following two documents e Creating and Applying Calibration Models in the Cisco Wireless Control System Configuration Guide http www cisco com en US products ps6305 products_configuration_guide_chapter09186a0080 83196d html wp 1089489 e Cisco Wireless Location Appliance Deployment Guide at the following URL http www cisco com en US products ps6386 prod_technical_reference09 186a008059ce3 1 html During the data point collection process the calibration client repeatedly transmits probe requests on all channels Depending on the particular calibration client being used the client may be triggered to transmit probe requests on demand via a network request Clients that are incapable of recognizing these requests may be de authenticated and disassociated in order to cause them to issue probe requests to the wireless medium and subsequently re associate re authenticate Access points in the vicinity of the client detect the RSSI of these probe requests and pass this information to their registered controllers Controllers furnish the RSSI information detected during the calibration process to the location appliance and WCS for use in computing the path losses that will ultimately be associated with the new calibration model The data point collection phase of the calibr
45. access the location server application via the SOAP XML API needs to be changed accordingly You may prefer to define a totally separate userid for each third party location client that accesses the location appliance instead of allowing them to use the admin account Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 a 413 Chapter 4 Installation and Configuration HI Location Appliance Time Synchronization Figure 4 4 Cisco Wireless Control System Monitor Configure v Location Administration v Specifying Location Server Application Login Credentials Help v Location Server Administration v General Properties Polling Parameters History Parameters Advanced Parameters Location Parameters Notification Parameters Active Sessions Import Asset Information Export Asset Information Maintenance Accounts x Users Groups Host Access Status gt Logs Location Server gt General Properties gt AeS_Loc2 General Server Name version Start Time IP Address Contact Name User Name Password Port HTTPS Save Cancel AeS_Loc2 2 1 34 0 6 29 06 4 26 PM 10 1 56 21 EAA ldmin S esses bor o I Enable Location Appliance Time Synchronization In order to assure reliable and consistent operation across the network it is recommended that the WLAN controllers location appliances and WCS systems within the Cisco UWN maintain synchronized internal clocks As
46. access the Cisco Wireless Location Appliance provisioning services and exchange data in XML format The location appliance API is available to the Cisco development community along with tools to facilitate solution development Integration support is available via the Cisco Developer Services Program a subscription based service Note Complete details on the Cisco Developer Service Program may be found at the Cisco Developer Support website located at the following URL http www cisco com en US products svcs ps3034 ps5408 ps5418 serv_home html Location Tracking without a Location Appliance In order to access any RF Fingerprinting based location tracking features in the Cisco UWN or even to configure the Cisco Wireless Location Appliance the Cisco WCS must be appropriately licensed for location usage When a location licensed version of WCS is used verified using WCS main menu bar option Help gt About the Software Figure 3 5 RF Fingerprinting techniques are used to determine non chokepoint based location When a location appliance is not used with a location licensed version of WCS RF Fingerprinting techniques are still used to determine location of tracked devices but only on demand and only for a single tracked device at a time Figure 3 5 WCS Licensed for Location ajah Wireless Control System cisco Version 4 1 91 0 Host weswin Type Base Location 223304 Licensed APs 100 If a location licensed WCS is used withou
47. and also every i440 minutes Advanced Parameters Location Parameters Notification Parameters Enable History of Interval mins Active Sessi s 3 sbiedeer tala oD Client Stations 360 Import Asset Information Export Asset Information Rogues 720 Maintenance gt O Asset Tags real Accounts r Save Cancel Status gt Logs 190602 I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations W Using Wi Fi RFID Tags with the Cisco UWN Enable Asset Tag Display For WCS to display the location of asset tags asset tag display must be explicitly enabled via Monitor gt Maps gt Campus gt Building gt Floor as shown in Figure 6 20 To enable the display of asset tags make sure that 802 11 Tags is selected from the dropdown Layers menu Refresh or reload the WCS floor map page and yellow tag icons is used on the floor map to denote the current location of any detected asset tags Figure 6 20 Enabling Display of Asset Tags on WCS afiafi cisco Contributing APs Wireless Control System Monitor Reports Configure Location Administration Help v Maps gt Cisco SJ Site 5 gt BLD 14 gt 3rd floor M sjcl4 31b ap5 v sjcl4 32b ap6 Vv sjcl4 31b ap3 RSSI Color Lookup Zoom Refresh O Acce O AP Heatmaps O Clients ET 802 11 Tags Loading Chokepoints a Loaded 0 chokepoints Done ia 4 H Load Location Server data as C Rogue APs C Rog
48. and require almost zero maintenance These traits of long life and low cost make passive RFID tags attractive to retailers and manufacturers for unit case and pallet level tagging in open loop supply chains Open loop supply chains typically allow little to no regulation of whether RFID tags leave the control of the tag owner or originator Because of their dependence on external reader energy fields and their low reflected power output passive RFID tags have a much shorter read range from a few inches for tags using load modulation up to a few meters for those using backscatter modulation as well as lower read reliability when compared to active RFID tags The passive RFID tag is available commercially packaged in a wide variety of designs from mounting on a simple substrate to creating a classic hard tag sandwiched between adhesive and paper commonly referred to as an RFID smart label The form factor used depends primarily on the application intended for the passive RFID tag and can represent the bulk of the passive RFID tag cost Semi Passive RFID Tags Semi passive RFID tags overcome two key disadvantages of pure passive RFID tag designs e The lack of a continuous source of power for onboard telemetry and sensor asset monitoring circuits e Short range Semi passive tags differ from passive tags in that they use an onboard battery to provide power to communication and ancillary support circuits such as temperature and shock
49. been put to use more productively and could negatively impact performance In general for a given population of asset tags with the same transmission interval the most productive and efficient polling is found to occur when the location appliance s asset tag polling interval is configured to be greater than or equal to the asset tag s transmission interval For example in a population of 100 asset tags each with a transmission interval of 60 seconds if the location appliance s asset tag polling interval is left at the default of 120 seconds twice the tag transmission interval it is likely that controllers will receive updated RSSI from all 100 tags at least once and most likely twice within the 120 second time interval Setting the asset tag polling interval to 30 seconds in an attempt to increase the frequency of tag location updates might indeed accomplish this goal for some tags however overall polling efficiency is likely to decline In a population of asset tags that are configured with mixed transmission intervals a tradeoff typically is required between the desire to acquire frequently updated RSSI information from tags possessing the shortest transmission intervals versus overall polling efficiency for the general tag population Shorter asset tag polling intervals can be configured to favor tags that transmit multicast frames more frequently but depending on the number of WLAN controllers deployed asset tag polling intervals should n
50. chief location tracking concerns of most designers wishing to track asset tags clients or rogues will center around e Perimeter and corner access point placement Perimeter and corner access point placement is very important to good location accuracy Refer to Figure 5 4 and the previous discussion surrounding the concept of a convex hull As described earlier location accuracy tends to fall off the further one strays outside the convex hull encompassing the set of potential device locations on the floor e Staggered pattern Access points should be located on the floor in a staggered fashion to both facilitate an acceptable inter access point spacing as well bolster the system s ability to perform RSSI multi lateration for tracked devices e Antenna mounting height In most indoor location applications antenna mounting height above the area where devices are to be tracked should be ideally between 10 and 15 feet with 20 feet being a recommended maximum e Inter access point spacing Access points should be situated so as to minimize any potential risk of degraded location accuracy rises due to Non monotonic RSSI versus distance behavior at close range Degradation in the ability of the system to resolve distance based on changes in RSSI Generally this results in access points being deployed with an inter access point distance of between 40 and 70 feet However the coverage requirements of demanding applications such as voi
51. clients supporting S36 Radio Measurement Requests should e Perform radio measurements on the channel over which the Measurement Request was received without significantly degrading performance e Perform measurements on non serving channels while temporarily buffering outgoing traffic e Respond to each Radio Measurement Request frame accepted with a Radio Measurement Report frame e Disregard any measurement requests that would significantly degrade performance of the client device e Support active scanning OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture W Tracking Clients Assets and Rogue Devices WLAN Clients Wireless LAN clients and properly configured work group bridges are displayed on the WCS location floor maps using a blue rectangle icon as shown in Figure 3 12 To display WLAN clients on the WCS location floor map ensure that the Clients checkbox option is enabled from the Layers dropdown selector at the top of the floor map display and click Load in the left hand column To avoid excessive clutter WCS will display the first 250 WLAN clients on the floor map To view the location of WLAN clients beyond the first 250 client filtering must be used Figure 3 12 WCS WLAN Client Location Map abafi Wireless Control System cisco Contributing APs Monitor Reports Configure Location Administration Help v Maps gt Cisco SJ
52. compliant with the Cisco Compatible Extensions for Wi Fi Tags specification are recognized and distinguished from other tracked devices in the network In this example we use an AeroScout T2 asset tag with firmware version 4 33 Assets tags that are supplied by other vendors that are also compliant with the Cisco Compatible Extensions for Wi Fi Tags specification can be expected to be recognized by the Cisco UWN in a similar fashion Figure B 1 depicts the layer two multicast frame that is transmitted at the expiration of every tag transmission interval for an AeroScout T2 asset tag configured for a basic set of operational parameters In Figure B 1 the tag configuration includes e Periodic 60 second tag transmission interval across three channels 1 6 11 e Chokepoint out of range indication indicated by the blue rectangle in Figure B 1 e Onboard motion and temperature detection sensors disabled Wi Fi Location Based Services 4 1 Design Guide 0L 11612 01 g en Appendix B Verifying Detection of Asset Tags in WLAN Controllers HI AssetTags Detection Figure B 1 RF Protocol Analysis of Tag Multicast Frame Cisco Compatible Extensions for Wi Fi Tag Compliant Packet Info Packet Number 2 Flags 0x00000000 Status 0x00000000 Packet Length 72 Timestamp 11 48 27 876639000 08 22 2007 Data Rate 2 2 0 Mbps Channel l 24212MHz 302 i1bg Signal dBu 40 Noise dBu 5 y 802 11 MAC Header Version
53. enabled or disabled per radio interface type such as 802 11bg or 802 11a on each WLAN controller It can also be enabled or disabled globally across controllers using WCS templates In some cases more granular control over the Cisco Compatible Extensions Location measurement parameter may be desired such as when performing testing in specific areas To support such cases the WLAN controller CLI allows the Cisco Compatible Extensions Location Measurement feature to be applied to only specific access points if desired For more information on configuring the Cisco Compatible Extensions Location Measurement using the WLAN controller CLI refer to the Cisco WLAN Controller Configuration Guide at the following URL http www cisco com en US products ps6366 products_configuration_guide_chapter09 186a008082d6 c5 html wp1121089 1 This is one of the features comprising referred to as the RF Scanning and Reporting category of Cisco Compatible Extensions for WLAN Devices A complete list of Cisco Compatible Extensions features are found at the following URL http www cisco com web partners pr46 pr 147 program_additional_information_new_release_features htm Wi Fi Location Based Services 4 1 Design Guide P34 OL 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices Mi Figure 3 10 Enabling CCX Location Measurement Using WCS Controller Template 10 1 56 18 gt 802 11b g Parameters
54. expiration of the Refresh Time the event condition is eligible for re evaluation and if still present may once again result in the generation of northbound notifications Refresh Time and Retry Count are used cooperatively to help limit the number of northbound notifications that are repeatedly generated for uncleared events Retry Count limits the number of northbound notifications that are sent by the location appliance while Refresh Time imposes a waiting period during which time no further northbound notifications will be sent for this event condition and device Refresh Time is specified in minutes with the default being 60 minutes Notifications Dropped This is a read only counter field indicating the total number of notifications that have been dropped from the notification queue since the location appliance was started Note that stopping and restarting the location appliance software application locserverd will reset this counter The Notifications Dropped counter should be used in conjunction with the Queue Limit parameter to reduce the number of total dropped notifications Configuring Location Appliance LOCP Parameters The configuration of Location Server gt Administration gt LOCP Parameters is discussed in Cisco Wireless Location Appliance Configuration Guide Configuring LOCP Parameters at the following URL http www cisco com en US products ps6386 products_configuration_guide_chapter09186a008082d7 2f html wp105
55. form a perfect storm of sorts transforming what was once a general market passing interest in location based services into one that well positions 802 11 based location based services as a potential must have application for Wi Fi wireless It is not difficult to understand why this is so With integrated location tracking enterprise wireless LANs become much more valuable as a corporate business asset This is especially true in today s fast paced and highly competitive marketplace where an otherwise well positioned enterprise may falter against its peers not because of a lack of necessary assets but rather due to its inability to quickly locate and re deploy those assets to address today s rapidly changing business climate Enterprise network administrators security personnel users asset owners and others have expressed great interest in location based services to allow them to better address key issues in their environments such as the following e The need to quickly and efficiently locate valuable assets and key personnel e Improving productivity via effective asset and personnel allocation e Reducing loss because of the unauthorized removal of assets from company premises e Improving customer satisfaction by rapid location of critical service impacting assets e Improving WLAN planning and tuning capabilities e Coordinating Wi Fi device location with security policy enforcement e Determining the location of rogue device
56. frame s transmission time is shorter Data Frame Format This parameter should be changed from the default value of IBSS to CCX Destination Address This value must be specified as 01 40 96 00 00 03 for use with software Release 4 1 and later releases c Data Transmission Mode Parameters Normal Tag Transmission without additional message Select this parameter unless you have valid reasons to configure it otherwise For example the location client you are using in conjunction with your asset tags may be able to process additional stored messages on your tag sent as part of tag payloads or you may be using an AeroScout T2 telemetry tag that allows for telemetry to be read directly from sensors onboard custom integrated host peripheral devices d Supplementary Settings e Call CCX Options Transmit Out of Range Chokepoint Group should be enabled Buttons Primary Configure these options if you wish to use call button signaling Panic Button alerting with software Release 4 1 Short Clicks button depression that last less than 2 seconds Enable Short Clicks should be checked OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations W Using Wi Fi RFID Tags with the Cisco UWN e Number of Short Clicks 1 e Tag Reaction Parameters Send Standard Tag Transmission e Message Repetition 1 Long Clicks button depression that lasts at least 2 seconds e Enabl
57. in the Radio Measurement Request Figure 3 11 highlights only two of them the first contained within a red rectangle and the second within a green rectangle This is understandable given that this Radio Measurement Request is being issued on a 802 11b g radio interface that is operating in the North American regulatory domain with eleven available channels In the subsequent measurement requests indicated by the green rectangle the Channel Number field seen at hex offset 0x44 is sequentially incremented by 1 from that of the initial measurement request This continues in the Measurement Request Element fields that follow until the value of OxB 11 is reached 802 1 1bg clients compliant with the Cisco Compatible Extensions for WLAN Devices specification version 2 or greater and supporting S36 Radio Measurement Requests receive the frame shown in Figure 3 11 and will perform an active scan of the specified channels as part of the radio measurement process When the probe requests are received by access points in the vicinity of such clients they forward via their registered controller signal strength measurements to the location appliance that is used to localize the client In addition clients also collect the RSSI information of all probe responses received during the measurement duration and forward this to the Cisco UWN in a Radio Measurement Report frame As per the Cisco Compatible Extensions for WLAN Devices specification version 2 WLAN
58. inter access point separation that would be in effect if we were to uniformly expand the current formations seen as equilateral triangles in Figure 5 19 we need to perform some basic geometrical calculations We determine the new inter access point separation required by assuming that the current top and bottom rows of access points are relocated such that they are positioned at the actual top and bottom floor perimeter For the 275 x 159 floor in Figure 5 19 this is performed by dividing the top to bottom width of the floor 159 feet by the number of desired rows of equilateral triangular formations 4 thereby yielding a projected formation height of 39 75 feet From the premise that in an equilateral triangle each angle is equal to 60 Shown in Figure 5 20 we calculate the length of any side s from the height h of our equilateral triangle formations as follows h s sin 60 Figure 5 20 Equilateral Access Point Formation 223338 h 39 73 Solving for s we calculate sin60 or 866 45 9 feet Thus we would need to expand our current inter access point spacing from 42 7 feet to 45 9 feet in order to move both the top and bottom rows of outermost access points to the actual building perimeter As this represents a relatively minor increase in inter access point spacing it should be easily accommodated by a correspondingly minor increase in transmit power if any at all In our next step we determine the new cell size that woul
59. interfaces The durability of the tag housing also affects price with the more durable or specialized housings required for specific tag applications coming at increased cost As with most electronic components of this nature prices for active tags can be expected to decline as technological advances production efficiencies and product commoditization all exert a downward influence on market pricing Beaconing Active RFID Tags Beaconing active RFID tags are used in many RTLS systems and are primarily useful when the location of an asset needs to be tracked anywhere and anytime via the use of location receivers With a beaconing active RFID tag a short message payload containing the unique identifier of the RFID tag is emitted at pre programmed intervals This interval is programmed into the tag by the tag owner or user and it can be set appropriately depending on how often tag RSSI updates are required A shorter tag transmission interval typically results in shorter tag battery life but may improve tag location accuracy in some cases since tag RSSI is reported more often Longer tag transmission intervals increase tag battery life but as tag RSSI is reported less often the frequency of location update will be less 802 11 Active RFID Tags 802 11 Wi Fi active RFID tags shown in Figure 6 9 are designed to operate in the unlicensed ISM bands of 2 4 to 2 4835 GHz or 5 8 to 5 825 GHz Currently manufactured 802 11 Wi Fi active RFID tags avail
60. is disabled In this case the remaining capacity on the location appliance 1000 tracked devices also referred to as headroom would allow for 500 minutes of operation at this rate of device migration before the potential for tracked device capacity exhaustion becomes a concern To help avoid this situation the Absent Data Cleanup Interval should be set below 500 minutes for example 440 or 470 minutes in order to reclaim tracked device capacity prior to headroom depletion A common question that often arises is why not just set the Absent Data Cleanup Interval to a very short interval initially The answer revolves has to do with decreases in the Absent Data Cleanup Interval not being entirely without tradeoffs e While reducing the location appliance s Absent Data Cleanup Interval to an arbitrarily short value may have the effect of freeing up device capacity quickly it can also effect the ability to view prior location and statistics for all categories of tracked devices asset tags clients and rogues for which updated RSSI information has not been received within the ADCI time period If the ADCI has been reduced and a device has been removed from the active location database the ability to view past location information via the Load Location Data as Old As dropdown menu in the left hand margin of WCS floor maps display screens will now be limited to the reduced length of the Absent Data Cleanup Interval Normally this f
61. judiciously given the ability of this parameter to affect the amount of traffic added per stimulated tag in large tag environments It should be noted that the repetition count that applies to the tag multicast frames sent in response to chokepoint stimulation is usually managed independently of the repetition count for other tag events such as telemetry high priority notifications or periodic tag transmissions sent as a result of the tag s configured transmission interval When configuring tags and chokepoint triggers it is important to maintain this distinction For example with AeroScout tags the repetition count that applies to the 802 11 frames sent by a tag in response to a chokepoint stimulation event is known as the Tag Repetition of an Exciter event parameter It is configured on a per Exciter basis using the AeroScout System Manager Exciter Manager or ANEM utility In contrast the tag repetition parameter used for non Exciter related events is known as the Message Repetitions transmission parameter It is set on a per tag basis using the Transmission Settings panel of the AeroScout Tag Manager as shown in Figure 6 32 Figure 6 32 Transmission Settings Panel in AeroScout Tag Manager not used for Exciter Events Transmission Settings 223394 As mentioned earlier the length of each 802 11 multicast tag frame transmitted by a tag in response to chokepoint stimulation is approximately 63 bytes which includes only a single chok
62. just entered can be presented as visual confirmation to the user If the user manually positions the crosshairs to the test point s location and then clicks on preview they will not receive any feedback The preview feature is not intended to display the estimated location of the test point device In Figure 5 48 note that the Total Test Points quantity reflected in the output of the analyze command does not indicate the total number of test point devices currently in use Rather it indicates the total number of test point location samples taken for the highlighted device MAC address Although multiple devices can be selected on the Position Test Point WCS screen test points can only be added using Save one device at a time The MAC address of the last device used for a save or stop operation is retained and shown under the Last Used heading Any test points that have been added using Save will no longer be accessible to the user if they log out of WCS and then log back in at a later time In order to ensure that all such residual test points are cleared prior to beginning a new test session it is a good idea to issue Clear Logs before beginning the definition of a new set of test points Test points that have been added will not survive a reboot or restart of the appliance Collected test data will still be resident on the location appliance however it will not be possible to add further test point data to t
63. limitations due to co channel interference from other access points on those same channels Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Figure 5 12 CAE Ld as en amn me amp Access Point Separation W best practices the inter access point spacing should be reduced below the general guideline of 40 feet Note that good location accuracy is achievable at inter access point ranges below 40 feet provided that the access point spacing is not decreased so much that the negative effects of close range non monotonicity come into play Generally this should not be an issue if the inter access point distances are above 25 to 28 feet when using low gain omni directional antennas mounted at an installation height of approximately 10 feet in an indoor environment Figure 5 12 illustrates an example of access point placement and inter access point spacing offering a foundation for a location aware design The environment in Figure 5 12 consists of drywall offices and cubicle office spaces with a total space of approximately 275 feet by 159 feet Taking into consideration the location tracking requirement for illustrative purposes only our inter access point linear spacing recommendations of 40 to 70 feet suggests approximately 22 location aware access points as an initial estimate Incorporating the placement strategies made in preceding se
64. network or part of a network its location domain and is primarily responsible for running the algorithms that predict client location The location server may also provide for the storage of historical location information A location server can communicate with multiple location or control clients In the location aware Cisco UWN the Cisco Wireless Location Appliance fulfills the role of the location server The Cisco Location Appliance is also capable of issuing notifications to external systems via email SMTP syslog SNMP traps or the SOAP XML protocol e Wireless LAN System The wireless LAN system is comprised of Embedded software contained within WLAN controllers that functions as an aggregation point for information regarding station tag rogue discovery device tracking and statistics The mobile devices tags mobile stations rogue clients and rogue access points that interact with the wireless network and whose location the location aware Cisco UWN will monitor Optional infrastructure components such as chokepoint triggers that enhance the functionality available from active RFID tags and allow for increased granularity in the localization of these asset tags Although it is possible to access the location appliance directly via a console session all end user interaction with the location appliance is typically via WCS or a third party location client application The integration of a Cisco Location Appliance into
65. packet 68 00 0c cc 5e 82 8d System group 51 00 0c cc 5e 82 8d Battery group status 0x42 days 0 age 0 00 0c cc 5e 82 8d Chokepoint group option 0x8 power 0 range 128 00 0c cc 5e 82 8d Vendor group 00 0c cc 5e 82 8d LOCPBuffer 0x133245ec buffer 0x13324611 msgLen 37 msgId 18 transId 816848706 00 0c cc 5e 82 8d Notifying LBS of vendor specific data 00 0c cc 5e 82 8d rfid Aerosct updated by AP 00 14 1B 59 41 F0O Incoming rssi 47 snr 53 New saved values rssi 48 snr 49 timestamp 3402186024 Note Step 6 It is recommended that the debug mac addr command be used when debugging in this fashion This will help avoid a flood of debug messages in environments where there are many tags active If the debug command output indicates that packets from this asset tag are not received by the controller you may want to continue debugging on the console of an access point that is known to be within range of the asset tag In order to verify the detection of an RFID tag by an access point perform the following steps a Verify whether RFID tag detection has been enabled on the access point and the channel that the access point is currently configured for This can be done on the access point console using the following command show controller Dot11Radio 0 lt snipped capture gt Current Frequency 2412 MHz Channel 1 RFID Tag Detection Enabled If tag detection is found to be disabled on the access point enable tag detection by i
66. relationship between LOCP and SNMP polls and their impact on the receipt of tag telemetry We see that temperature telemetry is transmitted from a Cisco Compatible Extensions for Wi Fi Tags compatible tag with MAC address 00 0C CC 5D 4D AB at time t 60 seconds This transmission is received by one or more access points These access points pass the telemetry information temperature of 38 C in our example to their respective registered WLAN controllers Since Figure 3 28 shows that the SNMP poll occurring at time t 90 seconds is the very first poll which also implies that no previous LOCP polls have occurred the controller will receives a LOCP poll at time t 90 seconds as well This is indicated in the figure by the receipt of the Information Request frame The controller responds to the poll by passing any accumulated tag telemetry information to the location appliance in a LOCP Information Response frame If tags are configured to send multiple frame copies or bursts per channel the controller eliminates any duplicate tag telemetry and passes the distilled telemetry values to the location appliance The location appliance then updates its databases with this telemetry information and makes it available to location clients via the SOAP XML API Subsequent inbound telemetry is handled in an analogous fashion For example in Figure 3 28 at time t 120 seconds we see an inbound temperature telemetry update indicating that the temperature has increas
67. requests tend to be detected quickly and relayed to the controllers to which the access points are registered Asset tags do not transmit probe requests but rather multicast tag messages on the channels for which the tags have been configured These multicasts are quickly detected by infrastructure access points operating on these channels in the vicinity of the asset tags Rogue devices may not be operating on the same channels to which your infrastructure access points have been assigned Because of this these rogue devices may be detected during periodic off channel scans conducted by infrastructure access points For an LWAPP access point operating in local mode this off channel scans typically occur for about 500 milliseconds out of every 180 seconds of operation or about 50 milliseconds per non primary channel per 180 second interval Wi Fi Location Based Services 4 1 Design Guide 334 Bs OL 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices W Workgroup Bridges amp Some Cisco autonomous access points can connect to the Cisco UWN in a special mode of operation known as workgroup bridge WGB mode Access points configured as workgroup bridges can provide wireless connectivity to the Cisco UWN for groups of wired clients making the wired clients essentially appear as wireless clients to the UWN Cisco AP1121 AP1130 AP1231 AP1240 and AP1310 access points contain
68. respective location domain Each of these individual network designs would then be synchronized to the appropriate location appliance along with the controller s that the location appliance will service While this approach is indeed functional in general the single network design approach is preferred from a convenience and ease of maintenance perspective On the other hand when working with very large network designs the dual network design approach may be preferable By splitting the environment into two distinct network designs it avoids loading the details about unnecessary access points buildings floors and the graphical images representing them into location appliances that have no need for this information In any design containing two or more independent location domains it is important to be aware of the degree and frequency of inter domain tracked device migration if any Some designs involving two or more location domains are meant to operate as pure closed loop systems This implies that tracked devices are added and removed under very controlled circumstances with the exception of any newly discovered rogues In a closed loop system the number of non rogue tracked devices in each location domain can be expected to remain fairly constant However many actual deployments may employ open loop business processes where some degree of uncontrolled device addition removal or migration can and often will occur OL 1
69. standalone Exciter software configuration utility specifically designed for users of AeroScout Exciters and the Cisco UWN AeroScout Engine Version 3 2 User s Guide AeroScout Network Exciter Manager ANEM User s Guide Technical documentation for WhereNet WherePort chokepoint triggers and the necessary software and hardware for configuration of WherePorts is available from WhereNet Corporation http www wherenet com via your WhereNet account representative Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter6 RFID Tag Considerations Chokepoint Considerations W Defining Chokepoint Triggers to the Cisco UWN Figure 6 30 stlietle cisco Chokepoints Search for Chokepoint by MAC Address x Enter Chokepoint MAC Address Nowe Joooccceoress CS Identification Number froos D E IP Address f 0 1 53 22 7 Connected to Network Port fsm Wireless Control System Mop ID mo o Map Name Fest Lab Annex Monitor Reports Configure Location Administration Help v Coordinates meters x fer 42 12 22 zj Modify Chokepoint ON MAC Address 00 0c cc 60 1b 61 Name 7009 Range feat C Inseconds fi Chokepoint Range is a visual aid representation only C In minutes fi z Actual range must be configured separately using Chokepoint vendors software ee o OK Cancel E Enable cieming Actes M l a Boa Maser Excter 7 Positioning Parameters Multiple Maps Excite
70. state of the rogue detection Alert Known Acknowledged Contained Threat or Known Contained as well as whether or not the rogue access point was seen to be connected to the same wired network as the detecting wireless system As mentioned previously only up to 250 rogue access points will be shown at any one time on floor maps If there are greater than 250 rogue access points detected the total number found will be indicated in the left hand column status area during each communication cycle between WCS and the location appliance It is recommended that filtering be used to reduce the total number of rogue access points selected for display if you receive this warning In software Release 4 1 of the Cisco UWN WLAN controllers provide support for the maximum number of rogue access points shown in Table 3 3 Table 3 3 Maximum WLC Rogue Access Point Capacity Controller Model Rogue APs Supported 2006 125 2106 125 4402 625 4404 625 WiSM 1250 NM WLC6 125 NME WLC8 12 125 3750G 625 Complete information on any displayed rogue access point can be obtained simply by left clicking the cursor on the circular skull and crossbones icon representing the desired rogue access point on the floor map Doing this yields a screen containing detailed information as shown in Figure 3 23 Note however there is no RSSI information displayed for rogue access points when the location map is enlarged Using the dropdow
71. stations locating and identifying a BSS or IBSS OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter6 RFID Tag Considerations Hi RFID Tag Technology Figure 6 1 Active and Passive RFID Comparison pod Active RFID Passive RFID Tag Power Source Internal to tag Energy transferred from the reader via RF Availability of Tag Power Only within field of reader Required Signal Strength from Very High Reader to Tag must power the tag from Tag to Reader Ranae 100m or more 3m or less Sensor Ability to continuously Ability to read and Capability monitor and record transfer sensor values sensor input data time only when tag is powered stamp for sensor events by reader no date time stamp Data Storage Large read write data Small read write data storage 128KB with storage e g 128 bytes sophisticated data search and access capabilities available 190588 Recent market developments have brought yet another category of RFID tag into the spotlight Known as hybrid or multimode tags these combine several different tag technologies into a versatile package that can be tracked by one or more location technologies Multimode RFID tags are typically low power small form factor devices that allow a single physical tag to assume multiple personalities and perform tasks that previously would have required several individual physical tags to be attached to the asset A multimode tag for
72. that Tx Power assignment mode for the Radios 802 11a n amp 802 11b 9 n on the selected foor is set to Custom OR the controllers Dynamic Power Assignment is set to Disable After you are done with calibration you can turn on the automatic bower assignment 4 Calibration of Non Uniform Environments In some cases the network designer is faced with challenges because of an environment that is of non uniform construction An example is a single floor consisting of a large call center cubicle area path loss exponent of 3 3 dense metal racking and electronic equipment in a second area path loss exponent of 4 3 and a large group of individual offices with drywall walls in a third area path loss exponent of 3 5 Cases such as this can be addressed via one of two options 1 Calibrate in the area with highest expected attenuation path loss The most straightforward method in which to handle this situation is to perform the calibration in the areas possessing the highest overall attenuation i e the highest path loss exponent and apply the resulting RF model to all areas of the floor In mathematical simulations as well as lab research the application of an RF model that is based upon a higher level of path loss to areas where the actual path loss is lower has shown to provide better location accuracy than the converse approach Thus in our example it would be recommended that the calibration be performed in the area with the dense
73. that name group and category information can be assigned to the client under the location submenu which can then be used to identify the asset on the floor map display OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide gO Chapter3 Cisco Location Based Services Architecture W Tracking Clients Assets and Rogue Devices Figure 3 13 WLAN Client Detailed Information s tog anres Prnt view Logout Refresh Print View Wireless Control System Wireless Control System Client Cisco a8 aa f5 F Select s commana co Client Cisco a8 aa fS eer a G0 Generel statistics s etecetion fices Stetistics finecon Chent Statistics Client Properties RF Propertios 631944 k 63 dm perme 14ste s PA 171 70 34 23 Cisco AP no o wss O0 40 96 08 00 fS AC 00 15 67 89344 b0 bead Caco a0i ade 3 ALTRI toca s ee aia Client RSSI History dBm Client SNR History Unknown wy asst sa E 10 0 0 0 0 usie wos ik ton OPENSYSTEM m m riti a exe Not Supported SVE a oO A ee Regular Chent Authenticated No a 4 T vaknown pong t NONE hd 20 Unknown Ss iz om 9 00 PH 11 15 PM 1 90 AM 3 45 AM 6 00AM 0 15 AV 9 00 PM R1 15 PM 1 90AM 3 45 AM 6 00 AM MIS AM a ia omis Ovis omis omis CHAS Onia omis ONS ORS Omis Ovis Wireless Control System Client Cisco a8 aa f5 General Statisties Location Client Location Asset Info Cisco 5 She S gt BLD 14 gt 4th oor Name Prevent Hap apn Revohison hug 35
74. that the password for the root userid be changed during initial configuration of the location appliance to ensure optimum network security This can be done during the execution of the initial setup script as described in Installation and Configuration section of the Cisco 2700 Series Location Appliance Installation and Configuration Guide located at http www cisco com en US docs wireless location 2700 quick guide li3 1main html wp 1049597 When logged in the Linux command passwd can be used to change the root system password as follows AeS_Loc login root Password Last login Thu Oct 22 09 53 21 on ttyS0O root AeS_ Loc root passwd Changing password for user root New password Retype new password passwd all authentication tokens updated successfully root AeS_Loc root OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide gO Chapter 4 Installation and Configuration Hs Changing Location Appliance Default Passwords Changing the admin Location Server Application Password The location server application on the location appliance ships with an administrator user account and group predefined The userid is admin and the password is admin After WCS has successfully contacted the location server application using the factory default administrator credentials the default password on the admin account can be changed to a less well known value via the WCS menu Location gt Accounts gt Users m
75. that the receiving client station perform active or passive scanning see the Scan Mode Definition field below and forward the results of those scans upstream to the UWN when it has completed When performing an active scan the client device transmits probe request frames that solicit probe responses from receiving access points In contrast a passive mode scan requests that 802 11 client devices simply listen for beacon or probe response frames but does not require active solicitation The Channel Number that the Beacon Request should apply to This is the second octet of the measurement request detail field and can seen at hex offset 0x003C with a value of 0x01 The Scan Mode Definition of 0x01 the third octet of the management request detail field This can be seen at hex offset 0x003D A Scan Mode Definition of 0x01 indicates that an active scan should be performed From a strict location fidelity perspective a passive scan would do little to enhance client location fidelity since no probe requests are generated Therefore when CCX Location Measurement is enabled on the controller the Scan Mode Definition will always be set to request that active scanning be performed Taking all three Radio Measurement Detail fields into consideration we see that this Radio Measurement Request Element contains a Beacon Request for an active scan to be performed on Channel one Note that there are eleven Measurement Request Element fields contained
76. the RFID reader detects this action as amplitude modulation of the signal voltage at the reader s antenna Load modulation and inductive coupling can be found among passive RFID tags using frequencies from 125 to 135 kHz and 13 56 MHz Limitations that exist with regard to the use of such low frequencies include the 1 A technique based on Faraday s principle of magnetic induction Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 a 63 Chapter6 RFID Tag Considerations RFID Tag Technology necessity to use larger antennas low data rate and bandwidth and a rather dramatic decay in the strength of the electromagnetic field 1 r where r represents the distance between a low frequency interrogator and a passive RFID tag Figure 6 4 Passive Tag Load Modulation Tag Reader Tag modulates inductive coupling Reader detects Tag Reflects electromagnetic Reader detects changes 190591 load modulation Backscatter modulation and electromagnetic coupling in the far field In this approach shown in Figure 6 5 the RFID reader provides a medium range electromagnetic field that the passive RFID tag uses for both power and a communication medium Via a technique known as electromagnetic or far field coupling the passive RFID tag draws energy from the electromagnetic field of the RFID reader However the energy contained in the incoming electromagnetic field is partially reflected back to the R
77. the location appliance database can be found at WCS gt Location Server gt Advanced Parameters gt DB Disk Memory In the case of the system used for this example DB Disk Memory 24 608 768 bytes or 0246 GB Thus OSApplSpace 3 2 0246 GB or 3 175 GB Substituting the values for TotalSpace and OSApplSpace into the equation you can calculate the maximum recommended size to which the location appliance database should be allowed to grow as 77 GB 3 175 GB 2 3 73 825 2 3 32 0 GB Therefore to ensure proper operation of the database backup mechanism in a location appliance with an 80 GB unformatted capacity hard disk drive the maximum recommended size of the location database as indicated by DB Disk Memory should not be allowed to exceed 32 GB Configuring Location Appliance Location Parameters The configuration of Location Server gt Administration gt Location Parameters is discussed in Cisco Wireless Location Appliance Configuration Guide Editing Location Parameters at the following URL http www cisco com en US products ps6386 products_configuration_guide_chapter09186a008082d7 2f html wp 1050973 Further clarification regarding select parameters is provided in subsequent sections Enable Calculation Time The enable calculation time location parameter refers to an advanced debugging option that enables logging of the amount of time that internal localization calculations consume It is disabled by default and s
78. this circular plot As in other techniques input from other receivers in other cells in this case signal strength information or RSSI can be used to perform RSS tri lateration or RSS multi lateration to further refine location accuracy The signal strength information used to determine position can be obtained from one of two sources e The network infrastructure reporting the received signal strength at which it receives mobile device transmissions network side e The mobile device reporting the signal strength at which it receives transmissions from the network client side In 802 11 WLANSs the granularity with which RSSI is reported typically varies from radio vendor to radio vendor In fact 802 11 client devices produced by different silicon manufacturers may report received signal strength using inconsistent metrics This can result in degraded and inconsistent location tracking performance Location tracking solutions that utilize network side RSSI measurements avoid this potential pitfall when supporting mobile devices from various manufacturers since all measurement of RSSI is performed at the network infrastructure not at the mobile device This is a straightforward approach and is approach most often implemented by vendors of RSS lateration solutions since a much higher degree of control is typically exercised over consistency in network infrastructure versus end user client mobile devices Location trackin
79. to report the location of a user placing an emergency 911 call Multiple tower sites calculate the AoA of the signal of the cellular user and use this information to perform Wi Fi Location Based Services 4 1 Design Guide 210 i OL 11612 01 Chapter 2 Location Tracking Approaches Location Patterning Pattern Recognition Techniques _ tri angulation That information is relayed to switching processors that calculate the user location and convert the AoA data to latitude and longitude coordinates which in turn is provided to emergency responder dispatch systems A common drawback that AoA shares with some of the other techniques mentioned is its susceptibility to multipath interference As stated earlier AoA works well in situations with direct line of sight but suffers from decreased accuracy and precision when confronted with signal reflections from surrounding objects Unfortunately in dense urban areas AoA becomes barely usable because line of sight to two or more base stations is seldom present Location Patterning Pattern Recognition Techniques Location patterning refers to a technique that is based on the sampling and recording of radio signal behavior patterns in specific environments Technically speaking a location patterning solution does not require specialized hardware in either the mobile device or the receiving sensor although at least one well known location patterning based RTLS requires proprietary RFID
80. to their chokepoint triggers as Exciters and WhereNet refers to their products as WherePorts The AeroScout EX 2000 Exciter and the WhereNet WherePort products are larger footprint models capable of providing the maximum possible range for large chokepoint areas or room based presence detection applications These products are intended for vehicular doorways gates and other large chokepoint areas with adjustable ranges that can exceed 20 feet The compact AeroScout EX 3100 and EX 3200 Exciters are intended for short range use in smaller chokepoints such as doorways shelves and racks The range of these products spans from 8 inches to a maximum of 6 5 and 9 75 feet respectively Figure 6 12 AeroScout Exciters and WhereNet WherePorts AeroScout EX 3100 D AeroScout EX 3200 WhereNet WherePort 223363 AeroScout EX 2000 Additional information on these products can be found at the following vendor web sites http www aeroscout com content asp page exciter http www wherenet com products_whereport shtml Note The Cisco WCS is used to define chokepoint triggers to the location aware Cisco UWN but cannot be used to configure the chokepoint triggers themselves at this time This must be accomplished using software provided by the vendor of the chokepoint trigger the AeroScout Network Exciter Manager ANEM and the WhereNet SystemBuilder WhereWand are two examples Chokepoint triggers that have been added to WCS without p
81. x y plane the difference of whose distances from the two foci that is the two receiving sensors A and C is equal to k c meters Mathematically this can be seen as representing all possible locations of mobile device X such that OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter2 Location Tracking Approaches Hi sCODistance Based Lateration Techniques Figure 2 4 illustrates how the intersection of the two hyperbolas TDoAc_ and TDoAg_ is used to resolve the position of station X Figure 2 4 Time Difference of Arrival TDoA TDOAg a 190537 A fourth receiving sensor and third hyperbola may be added as an enhancement to perform TDoA hyperbolic multi lateration This may be required to solve for cases where there may be more than one solution when using TDoA hyperbolic tri lateration Modern TDoA system designers have derived methods of coping with local clock oscillator drift that are intended to avoid the strict requirement for precision time synchronization of TDoA receivers For example time adjustments can be calculated periodically with regard to a reference clock source These clock adjustments can then be used to correct for offsets from the reference clock elsewhere in the system In the case of TDoA receivers that are capable of transmitting packets for example a TDoA receiver that may be integrated into an 802 11 WLAN access point another innovative approach may involve the periodic
82. 0 Cisco Controller gt config rfid timeout 480 cisco Controller gt Cisco Controller gt show rfid config RFID Tag data Collection 20000 e eee Enabled OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations HI Using Wi Fi RFID Tags with the Cisco UWN REID data Cimeotls cas cide eaea sae sae via seas ss 480 seconds To ensure proper collection of updated asset tag RSSI from WLAN controllers it is recommended that the RFID data timeout always be greater than the asset tag polling interval on the location appliance which is discussed in the next section Enable Asset Tag Polling To use the location appliance for asset tag tracking SNMP asset tag polling must be explicitly enabled via the Locate gt Location Server gt Polling Parameters GUI panel To enable it use the checkbox indicated by the red rectangle in Figure 6 17 Figure 6 17 Enabling RFID Tag Polling Cisco Wireless Control System Monitor Configure Location Administration Help v Location Server Location Server gt Polling Parameters gt Administration wes Polling Parameters General Properties Polling Parameters History Parameters Timeout secs Advanced Parameters Location Parameters Notification Parameters Enable Polling Interval secs Active Sessions Import Asset Information Retry Count il l M Client Stations 120 Export Asset Information Vv Rogues 6
83. 00 Maintenance gt O Asset Tags 120 Eec gt O Statistics 300 Status gt Save Cancel Logs 190601 The default polling interval value represents the time period between the start of subsequent polling cycles in which the location appliance polls the controller using SNMP For example if a polling cycle requires 30 seconds to complete and the polling interval is 300 seconds polling cycles start every 330 seconds as shown in Figure 6 18 Figure 6 18 Polling Interval pigesne Polling cycle Polling interval Polling cycle 300 330 630 660 Seconds amp Depending on the degree of asset movement updated tag RSSI information obtained via shorter polling intervals may be translated into more frequent location updates in some cases However depending on the time lag between the asset tag polling interval configured on the location appliance and the average transmission interval configured amongst the general tag population a risk of reduced asset tag polling efficiency may occur In extreme cases of deployments with a large number of WLAN controllers a too Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 _ Chapter 6 RFID Tag Considerations Using Wi Fi RFID Tags with the Cisco UWN W short asset tag polling interval could burden both the location appliance as well as the WLAN controllers with almost constant and often times unproductive polling This wastes resources that could have
84. 00 0000 00 ee 3 Figure 3 11 provides several key pieces of information that supports our understanding of the effect of Radio Measurement Requests on WLAN clients We see in Figure 3 11 that the frame broadcast to the associated clients actually contains multiple Radio Measurement Request Elements the first of which is highlighted within the red rectangle beginning at hex offset 0x0034 Looking closer into the Radio Measure Request Element we see the following e The element ID of 0x2600 appears at hex offset 0x0034 identifying that what follows is a Measurement Request Element shown in yellow e The measurement token of 0x01 appears at offset 0x0038 This is a non zero hex value that is unique amongst the Measurement Request Elements in a particular Measurement Request frame 1 Fields in the radio information elements follow the 802 11 convention of sending the least significant byte first Wi Fi Location Based Services 4 1 Design Guide Ea 0L 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices Mi e At HEX offset 0x003B we see the first of several Radio Measurement Request Element detail fields the first three bytes of each shown highlighted within blue rectangles Upon closer examination we can see that each detail field contains The Measurement Type Definition of 0x03 indicating that this is a Beacon Request This measurement type requests
85. 0918 Location Appliance Dual Ethernet Operation The Cisco Wireless Location Appliance is equipped with two 10 100 1000BASE T Gigabit Ethernet ports that can be used to dual home the location appliance to two different IP networks This makes it a simple affair for example to configure a location appliance for service on network A while affording it the capability to be managed out of band on network B if the need arises Complete step by step guidelines to accomplish this are available in Cisco Wireless Location Appliance Installation Guide Configuring the Location Appliance at the following URL http www cisco com en US products ps6386 products_installation_and_configuration_guide_chapter 09186a00804fab8e html wp 1040488 Particular attention should be paid to the fact that the dual onboard Ethernet controllers on the location appliance are not intended for redundant or simultaneous connection to the same IP network Configurations aimed at establishing parallel load balancing or redundant Ethernet connections to the same IP network are not recommended at this time Wi Fi Location Based Services 4 1 Design Guide P40 i OL 11612 01 Chapter4 _ Installation and Configuration Changing Location Appliance Default Passwords W Changing Location Appliance Default Passwords Changing the root User Linux System Password The location appliance ships with a default root userid and password It is recommended
86. 10AD 223396 In Figure 6 34 we see the message CISCO CCX being defined to the Exciter as well as the complete 83 byte message transmitted by the tag when stimulated by the Exciter This 83 byte message includes the standard information regarding the MAC address of the stimulating Exciter as well as the vendor specific information Note that the text defined to the Exciter in the AeroScout System Manager is seen transmitted by the tag at offset x0046 in the trace you can see the ASCII text CISCO CCX shown at the right in Figure 6 34 Every access point receiving this information will forward it to their registered controller where a 160 byte LOCP Measurement Notification as well as a 148 byte LOCP Information Notification will be sent to the location appliance Although this information was hard coded at the Exciter the Exciter could have just as easily instructed the tag to instead include telemetry data that it retrieved from the asset host that it is attached to such as embedded sensor data Keep in mind that results of our test observations obviously are in this case AeroScout specific as other vendors may or may not opt to allow the inclusion of vendor specific information to the same degree w Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 sze a cnaprer Caveats This chapter provides the caveats discovered in lab testing CSCse14724 Degraded Location Accuracy with Monitor Mode APs
87. 1612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Multiple Location Appliance Designs Figure 5 25 Tags This can be significant since tracked devices that migrate from one location domain to another may appear in the active location database of each location appliance until such time that they are pruned A tracked device will be pruned from the active location database of a location appliance when all of the following conditions are true 1 The device is no longer being detected by any of the access points registered to any controller being serviced by that location appliance 1 e any controller that has been synchronized to that location appliance 2 All controllers whose access points have detected the tracked device have ceased reporting RSSI for the device to the location appliance typically after the controller s RFID timeout or client user timeout has expired 3 the location appliance Absent Data Cleanup Interval ADCI has expired default is 1440 minutes During the time that a tracked device is present in more than one location appliance multiple entries for the same device may appear in WCS client tag or rogue display menus An example of this is depicted in Figure 5 25 which illustrates the results of an asset tag search across all location appliances in lab testing In this test an asset tag with MAC address 00 0C CC 5E 82
88. 2 Table 3 2 Maximum WLC Asset Tag Capacity Controller Model Asset Tags Supported 2006 500 2106 500 4402 1250 4404 2500 WiSM 5000 NM WLC6 500 NME WLC8 12 500 3750G 1250 Complete information on any displayed asset tag can be obtained by clicking on the yellow tag icon associated with the tag WCS responds with the information shown in Figure 3 17 Beginning with software Release 4 1 of the location aware Cisco UWN tag telemetry chokepoint and tag status information are also displayed on the Tag Details screen shown in Figure 3 17 along with enhanced battery reporting information Wi Fi Location Based Services 4 1 Design Guide M324 i OL 11612 01 Chapter3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices W Figure 3 17 RFID Tag Detailed Information ahaj Wireless Control System cisco Tags gt Aeroscout Tag 00 0c cc 5 05 17 Select a command E Go Location History Tag Properties Asset Info Vendor 4eroscout Name Controller 10 1 96 18 Group Battery Batt remaining 80 Days remaining Category 0 Tolerance 20 Battery Age Life o i iii Location Debug V Enabled Update Location This will show AP RSSI Information on the Map Alpharetta Campus gt 4P1242 icti Floor Building gt Test Lab Annex 2 statistics Last located at Aug 15 2007 4 16 35 PM Bytes received 104877 On Location AeS_Loct Pac
89. 2 Building gt Test Lab Annex 2 E 602 11b 9 n only client worst i M 223306 Wi Fi Location Based Services 4 1 Design Guide Ea 0L 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices Mi Using these tools the system architect as well as the installation team can not only plan towards the achievement of stated performance goals but can verify that these targets are indeed being met For those interested in a professional service offering that includes the tuning of location performance and much more Cisco offers a Wireless LAN Location Planning and Design Professional Service This service offering enlists the skills of trained WLAN engineers to deliver an integrated solution that includes the services Cisco has identified as essential for successful deployment of a secure location based services solution Further information on Cisco Wireless LAN Location Planning and Design Professional Services may be found located at the Cisco Wireless LAN Services website which is located at the following URL http www cisco com en US products ps8306 serv_home html Tracking Clients Assets and Rogue Devices This section discusses the mechanics behind the WLAN client probing mechanism and explains how variations in client probing can affect location accuracy In addition Cisco Compatible Extensions Location Measurements are explained in detail along with a close
90. 2007 6 17 06 AM n echoed ategory a Location Debug Enabled Update Location Notifications a ry a a 223309 Note that Figure 3 13 also includes a hyperlinked listing of location notifications as well as a miniature location map showing the client location By enlarging the map and enabling the Location Debug parameter WCS displays the last detected RSSI levels of each access point detecting the WLAN client as shown in Figure 3 14 Note The setting of the Location Debug Enable checkbox does not survive a restart of the locserverd application or a reboot of the location appliance This RSSI information is collected in a similar fashion to that shown by the show client detail lt mac address gt command and provides an alternative to the CLI command for determining the detected RSSI of WLAN clients see Figure 3 14 Wi Fi Location Based Services 4 1 Design Guide P320 By OL 11612 01 Chapter3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices W Figure 3 14 WLAN Client Detected RSSI with Location Debug Enabled abafi Wireless Control System cisco Client Intel 09 75 aa General Statistics Location Client Location Asset Info Alpharetta Campus gt AP1242 Building gt Test Lab Annex Name Floor 2 Group Last located at Aug 15 2007 11 36 13 AM Category On Location 4eS_Locl Location Debug WM Enabled Server Update This will show AP RSSI
91. 3 EDT 2007 Time Stamp Floor Battery Status 17 Sat Apr 28 10 03 04 EDT 2007 Alpharetta Campus gt 4P1242 Building gt Test Lab Annex 2 18 Fri Apr 27 21 09 29 EDT 2007 Alpharetta Carmpus gt A4P1242 Building gt Test Lab Annex 2 Change selection every E secs E Play Stop Location Tag Statistics Location Fri Apr 27 19 08 25 EDT 2007 Data Collected Fri Apr 27 19 07 37 EDT 2007 Calculated tes cei Alpharetta Campus gt A4P1242 Dytesracewad 349228 Roni Building gt Test Lab Annex 2 Packets received 6601 Telemetry Data MOTIONPROB Movement Emergency Data Reason Tampering Tamper State Active Enlarge Tag Properties Data Collected Fri Apr 27 19 07 25 EDT 2007 Controller 10 1 96 18 Battery Status 80 223374 The default configuration of some active RFID tags may provide for transmitting only one tag transmission per channel per transmission interval While this setting can help optimize the battery life of the tag in some cases this single transmission per channel may not always be successfully detected by the expected number of access points especially in RF noisy or congested environments This can result in missing RSSI readings which can cause location inaccuracy Therefore in such environments it is recommended that tags be configured to transmit multiple transmission repetitions per channel at each transmission interval which should aid in improving tag detection and location accuracy as well as increa
92. 6 ai D 0060 W 7 00 amp a When the tag multicast address is recognized by the controller the identity and type of sender is established via the payload information contained in the frame Depending on the type of information contained within the tag payload it will be passed to the location appliance using either traditional SNMP poll responses or the new LOCP introduced in software Release 4 1 Note the sequence number 1189 and fragment fields 0 that appear in both the RF as well as the LWAPP frame analysis This is an important piece of information that can be very useful when matching packets that flow into access points via 802 11 and out of them via LWAPP The sequence number for a particular tag frame indicates the number of the tag message and is assigned from a single modulo 4096 counter starting at zero and is incremented by 1 for each tag message cycle The fragment number specifies the specific frame within a burst of frames transmitted on a single channel The fragment number should always start from zero even if the burst length is zero For a packet burst the fragment number should be set to n where n is the packet index within the burst starting from 0 For example if a tag is configured to transmit a burst of length 5 then the fragment number would start at 0 for the first packet in the burst 1 for the second packet and so on up to 4 for the last packet in the burst Wi Fi Location Based Services 4 1 Design Guide lt a O
93. 802 118 n Data Points O Total 802 11b g n Data Points 0 802 11a n Done pozstbevosn Horizontal Vertical Zoom Done 23 8 94 Cancel 7s R VV Show grid M Show APs V Show Data Points CU arizazes EXC AP124287 E 202 11a n Covered E 802 11b g n Covered E 802 11a b g n Covered Suggested Location Microsoft Internet Explorer E Visited Location y Client does not seem to be getting detected at this time Please make sure that you have connectivity and try again caa a 223354 Sy AP1242 6 In cases where the contents of the controller s location calibration table is in question it can be queried directly using the CLI command Cisco Controller gt show client location calibration summary MAC Address interval 00 40 96 a1 9d 47 4 In situations where there are unnecessary residual entries present in a controller s location calibration table from prior calibration data collections they can be removed manually using the following controller CLI command Cisco Controller gt config client location calibration disable 00 40 96 a1 9d 47 Note Before removing any entries in controller location calibration tables it is good practice to be sure that these entries are not in use by other users performing a calibration data collection Calibration data collection should be performed after the system has been fully installed basic coverage checks are completed and the recommended R
94. 802 Heim Done E 02 11a n Covered E 802 11b g n Covered i 802 11a b g n Covered Suggested Location E Visited Location 223353 Once the data collection has completed the data collection screen will be re displayed with the new data points illustrated on the map In extraordinary situations the data collection process may take a few minutes to complete or timeout in about 90 to 120 seconds due to an unexpected interruption in calibration client connectivity such as moving into a coverage hole for example If the user becomes impatient and decides to abruptly terminate the calibration by selecting a different menu option from the WCS main menu residual controller location calibration table entries may occur To avoid this it is recommended that all calibration users refrain from this behavior and instead exercise patience in waiting for the data collection to complete or timeout shown in Figure 5 39 Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Calibration W Figure 5 39 Data Collection Timeout Message alali Wireless Control System cisco Monitor Reports Configure y Location y Administration Help v Calibrating Model on Floor Alpharetta Campus gt AP1242 Building gt Test Lab Annex 2 Calibrating using Client 00 40 96 a1 9d 47 Click on the map where the client is currently located and click on Save Total
95. 809 technologies_tech_note09186a008072c759 shtml In addition it is recommended that all users considering using RRM in VoWLAN designs refer to the Voice Over Wireless LAN 4 1 Design Guide which can be found at the following URL http www cisco com en US docs solutions Enterprise Mobility vowlan 4 1dg vowlan4 1dg book html Figure 5 21 illustrates the updated access point layout using the information from the calculations above along with perimeter access point placement which is discussed next Layout for 5GHz Voice and High Speed Data 2 4GHz Legacy with Location 223339 In Figure 5 21 we can see the effects of the increase in inter access point distance e The top row access points 1 6 11 16 21 26 and 31 and bottom row access points 5 10 15 20 25 30 and 35 of access points are now located at the actual top and bottom floor perimeter e On the right side of the floor perimeter access points 31 and 35 have been moved into the right hand corners of the floor Access point 33 has been moved to the right side of the floor perimeter As a group access points 31 through 35 now comprise the right side of the floor perimeter e On the left side of the floor perimeter access points 1 and 5 have been moved into the left hand corners of the floor In addition two new access
96. Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations HI Using Test Points to Verify Accuracy location inspection here is that the modeling of future scenarios where increased accuracy may be required can be performed using the information collected during a current calibration without involving actual users and without requiring them to participate in trial and error testing In both Figure 5 46 and Figure 5 47 note the appearance of calibration data points all along the perimeter of the test lab between the perimeter access points These data points were purposely placed there in order to eliminate or at least reduce the appearance of white space along the perimeter during location inspection When pure white spaces occur in location inspection output often times it is due to a lack of data in those areas which prevents location inspection tool from calculating a valid representation of accuracy and precision at those points Rather than attempt to provide an estimation based on little or no information the location inspection tool leaves these areas blank To help avoid such behavior it is suggested that calibration data points be taken along the perimeter as well as in areas contained within the perimeter Perimeter data points can be added after the initial calibration if desired To do this simply rerun the Add Data Points data collection phase for the calibration model
97. CUWN software Release 4 1 introduces the Cisco Location Control Protocol LOCP an architectural enhancement that improves communication efficiency and supports new capabilities between the location appliances and one or more WLAN controllers LOCP is a bi directional protocol that can be run over a connection oriented or connectionless transport LOCP provides for an ongoing exchange of control messages that allows either endpoint to determine if its partner is still active Figure 3 26 illustrates the basic LOCP packet flow between the location appliance and each WLAN controller Figure 3 26 Location Appliance WLAN Controller LOCP Session Location Appliance WLAN Controller eae aaa TLS Initialization oe Echo Request Echo Response ee Control Message Exchange Data Messages ee Echo Request Echo Response Encrypted LOCP Session Control Message Exchange hhh 223322 In Release 4 1 the location appliance is pre configured by the user with regard to the IP addresses of the controllers it is to communicate with Once the connection between the controller and the location appliance is initialized an encrypted TLS session is established between the two endpoints over which Wi Fi Location Based Services 4 1 Design Guide M336 Bs OL 11612 01 Chapter3 Cisco Location Based Services Architecture Cisco Location Control Protocol LOCP W all further LOCP traffic will travel Each endpoint periodically verif
98. Cisco UWN on demand location tracking of asset tags is not possible when using a WCS that is not licensed for location use Accuracy and Precision For most users the performance metric having the most familiarity and significance is accuracy which typically refers to the quality of the information you are receiving Location accuracy refers specifically to the quantifiable error distance between the estimated and the actual location of a tracked device In most real world applications however a statement of location accuracy has little value without the ability of the solution to repeatedly and reliably perform at this level Precision is a direct measure reflecting on the reproducibility of the stated location accuracy Any indication of location accuracy should therefore include an indication of the confidence interval or percentage of successful location detection as well otherwise known as the location precision Wi Fi Location Based Services 4 1 Design Guide T 0L 11612 01 n Chapter3 Cisco Location Based Services Architecture W Accuracy and Precision With deployment in accordance with the best practices outlined in this document the location aware Cisco UWN is capable of meeting a baseline performance specification of at least 10 meters accuracy with 90 percent precision When combined with chokepoint location support this level of performance can be increased for asset tags possessing chokepoint location capabilities
99. D tag technology Wi Fi Location Based Services 4 1 Design Guide lt OL 11612 01 _ Chapter 6 RFID Tag Considerations Figure 6 8 RFID Tag Technology W Active RFID Tags wo D SE D D Active tags can contain 512 KB or more of RAM which enables the active tag to store information from attached assets for transmission at the next beacon interval or when polled This large memory capacity also makes active RFID preferable to passive RFID in situations when the RFID tag cannot simply be used as a license plate or reference to enable an immediate lookup in a host database A good example of this might be a remote military installation where a host database may or may not be available at all times By storing critical asset data directly on the tag itself this information can be retrieved directly from the tag and used regardless of the availability of the host system Active RFID tags can be found operating at frequencies including 303 315 418 433 868 915 and 2400 MHz with read ranges of 60 to 300 feet Active RFID tag technology typically display very high read rates and read reliability because of their higher transmitter output optimized antenna and reliable source of onboard power Active RFID tag cost can vary significantly depending on the amount of memory the battery life required and whether the tag includes added value features such as onboard temperature sensors motion detection or telemetry
100. FID reader by the passive tag antenna The precise characteristics of this reflection depend on the load resistance connected to the antenna The tag varies the size of the load that is placed in parallel with the antenna in order to apply amplitude modulation to the reflected electromagnetic waves thereby enabling it to communicate information payloads back to the RFID reader via backscatter modulation Tags using backscatter modulation and electromagnetic coupling typically provide longer range than inductively coupled tags and can be found most commonly among passive RFID tags operating at 868 MHz and higher frequencies Far field coupled tags typically provide significantly longer range than inductively coupled tags principally due to the much slower rate of attenuation 1 r2 associated with the electromagnetic far field Antennas used for tag employing far field coupling are typically smaller than their inductively coupled counterparts Figure 6 5 Passive Tag Backscatter Modulation 190592 waves in reflected power Note that neither of these two techniques allows passive RFID tags to communicate directly with 802 11 infrastructure access points All communication from the passive RFID tag occurs via the RFID reader Wi Fi Location Based Services 4 1 Design Guide oa E OL 11612 01 _ Chapter 6 RFID Tag Considerations RFID Tag Technology W Passive RFID tags are less costly to manufacture than active RFID tags
101. Figure 5 43 on page 5 61 illustrate how this is performed An example of a Radio Measurement Request can be seen in Figure 3 11 This request is seen to emanate from an access point with a 802 11b g interface MAC address of 00 14 1B 59 42 72 Figure 3 11 Broadcast Radio Measurement Request 02 11 MAC Header Version 0 0 Mask 0x03 Type 10 Data 0 Mask 0x0C Subtype 0000 Data Only 0 Mask OxFO YT Frame Control Flags 00000010 Duration 0 Microseconds 2 3 Destination FF FF FF FF FF FF Ethernet Broadcast 4 9 S9 Bssip 00 14 1B 89 42 72 10 185 P Source 00 14 1B 59 42 72 16 21 Seq Number 1295 22 23 Mask OxFFFO Frag Number O 22 Mask OxOF tT 24 183 802 2 D 0xAA SNAP S 0x A SNAP C 0x03 GY ECS Frame Check Sequence ECS Ox64F30048 Cealculeted ee OVA IBSA 722 Seren cme eteretete SBE Pee eee 0010 00 14 1B 2 AA AA 03 00 40 96 00 00 0020 Dela B5942 72 Pe2oeeeee Yer 0030 e Ga ten Perce ees teat ats 0040 ZEXODRORN00 See a E E 0050 03 00 00 6100108200104 00 00 M lt c 6a 0060 Dao 0A 00 26 00 08 5 00 00 ME OA 00 6 0070 26 00 08 00 06 00 00 De oeol OA 00 26 00 08 00 6 0080 07 00 00 Dao OA 00 26 00 O8 00 og 00 OO MS 6 0090 PS0 o 00 26 00 og 00 09 00 00 Deog oI OA 00 6 0OAO 26 00 08 00 OA 00 00 0S 0A 0I OA 00 26 00 08 00 6 5 0080 OB 00 00 OS0OBIOI 0A 00
102. Information on the Map Location Notifications Absence Containment Distance All ele ire ire Enlarge Fig 66 dBm AP 00 14 1b 59 43 80 AP1242 5 RSSI Readings Detected RSSI Radio Type Age when Located 53 dBm 1ib g n 63 secs GALE dem 2 Ea 223310 Wireless client device location history may be displayed by selecting Location History from the dropdown menu at the top right hand corner of the screen illustrated in the location screen view of Figure 3 14 and clicking Go Past location history stored within the location appliance is displayed for the wireless client via the screen shown in Figure 3 15 Wi Fi Location Based Services 4 1 Design Guide T 0L 11612 01 EZEN Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices Figure 3 15 Wireless Control System Client Cisco a8 aa fS Client User Name Client IP Address From Mon Jul 16 03 03 28 EOT 2007 To Wed Aug 15 10 35 05 EDT 2007 Time Stamp Wed Aug 15 08 35 05 EDT 2007 Wed Aug 15 06 35 05 EDT 2007 Wed Aug 15 04 35 05 EDT 2007 Wed Aug 15 02 35 05 EDT 2007 Client Location Location Client Properties Data Collected Wee buo 15 10 26 33 171 71 128 78 Port 2 Controller 9 0 0 0 WLAN Client Location History Client MAC Address Client Vendor Floor Cisco S Site S gt BLD 14 gt 4th floor Cisco SJ Site S gt BLD 14 gt 4t
103. L 11612 01 AppendixB Verifying Detection of Asset Tags in WLAN Controllers Asset Tags Detection W For example assume that an asset tag is configured to send a burst length of 3 packets for each of channels 1 6 and 11 In the case of an AeroScout asset tag the burst length is configured by using the tag message repetitions transmission parameter The expected fragment and sequence numbers would be as shown in Tab Table B 1 le B 1 Packet Fragment and Sequence Numbers Packet Instance Fragment Number Sequence Number Channel 0 0 0 1 1 1 0 1 2 2 0 1 3 0 0 6 4 1 0 6 5 2 0 6 6 0 0 11 7 1 0 11 8 2 0 11 Assume a second asset tag is configured to send a single message on each of channels 1 6 and 11 every 60 seconds The expected fragment and sequence numbers occurring over the next 120 seconds would be as shown in Table B 2 to Table B 4 Table B 2 Time 0 Packet Instance Fragment Number Sequence Number Channel 0 0 0 1 1 0 0 6 2 0 0 11 Table B 3 Time 60 Packet Instance Fragment Number Sequence Number Channel 0 0 1 1 1 0 1 6 2 0 1 11 Table B 4 Time 120 Packet Instance Fragment Number Sequence Number Channel 0 0 2 1 1 0 2 6 2 0 2 11 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Appendix B Verifying Detection of Asset Tags in WLAN Controllers HI AssetTags Not Detected Ass
104. Last Located At time stamp and the age of the RSSI readings used to locate the device To obtain the RSSI age information we click on each appearance of device MAC address 00 0C CC 5E 82 90 enable the location debug option on the tag detail screen that appears and view the age of the RSSI readings used to establish the device location shown in Figure 5 26 1 The length of the location appliance s polling cycle for the particular category of device may also play a role The precise degree of impact will be dependent on the point within the polling cycle the tracked device was prior to migrating out of the location domain Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Figure 5 26 Tags gt Aeroscout Tag 00 0c cc 5e 82 90 Select a command G0 Tag Properties Asset Info Vendor Aeroscout Name Controller 10 1 56 10 Group Battery Batt remaining 80 Days remaining Category Life 0 Tolerance 20 Battery Age 0 Location Debug M Enabled Update Location This will show AP RSSI Information on the Map Floor Nashville Campus gt Pupin Statistics Hall gt Floor 1 Last located at Oct 7 2007 12 36 38 PM Bytes received 952 cation toed Packets received 14 J aS 4 a aS ss D See OH AP _00 18 74 7 fd 40 AP1242 N1 RSSI Readings Detected RSSI Radio Type Age when Located 5 a
105. OAP XML directly to specified destinations These notifications can be triggered if the client or asset Changes location Strays beyond a set distance from pre determined marker locations Becomes missing or enters leaves coverage areas Experiences a change in battery level Enters the stimulation zone of a chokepoint trigger Experiences one or more priority conditions such as e Depression of a tag call button e Detachment of a tag from its asset 1 If tracked devices roam between location domains the aggregate tracked device capacity may be reduced Wi Fi Location Based Services 4 1 Design Guide EN OL 11612 01 _ Chapter 3 Cisco Location Based Services Architecture amp Role of the Location Appliance W e An attempt at internal tampering SOAP XML Location Application Programming Interface API The Location Appliance API allows customers and partners to create customized location based programs that interface with the Cisco Wireless Location Appliance These programs can be developed to support a variety of unique and innovative applications including real time location based data retrieval telemetric device management workflow automation enhanced WLAN security and people or device tracking The API provides a mechanism for inserting retrieving updating and removing data from the Cisco Wireless Location Appliance configuration database using a SOAP XML interface Developers can
106. Origin XXXEXERD In its simplest form this technique makes no explicit attempt to resolve the position of the mobile device beyond indicating the cell with which the mobile device is or has been registered When applied to 802 11 systems this technique tracks the cell to which a mobile device associates The primary advantage of this technique is ease of implementation Cell of origin does not require the implementation of complicated algorithms and thus positioning performance is very fast Almost all cell based WLANs and other cellular based RF systems can be easily and cost effectively adapted to provide cell of origin positioning capability However the overwhelming drawback of pure cell of origin positioning approaches continues to be coarse granularity For various reasons mobile devices can be associated to cells that are not in close physical proximity despite the fact that other nearby cells would be better candidates This coarse granularity can be especially frustrating when attempting to resolve the actual location of a mobile device in a multi story structure where there is considerable floor to floor cell overlap To better determine which areas of the cell possess the highest probability of containing the mobile device some additional method of resolving location within the cell is usually required This can either be a manual method such as a human searching the entire cell for the device or a computer assisted method When r
107. P gt E Enable 802 1 Authentication Type PEAP m Step 1 of 2 PEAP User Authentication Protocol mscn i User Credentials User Name festus Domain a Password F Confirm Password Ed 224160 In Figure 5 42 under the Security Settings panel of the Intel ProSet configuration select the Enterprise Security option highlighted by the red circle instead of the default Personal Security option Configure the appropriate authentication and authentication types and select Cisco Options highlighted by the blue circle This will present the panel shown in Figure 5 43 Wi Fi Location Based Services 4 1 Design Guide 5 60 fs OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Calibration W Figure 5 43 Intel ProSet Cisco Compatible Extensions Cisco Compatible Extensions Options IV Allow Fast Roaming CCKM Enable if your wireless network has fast roaming configured Fast roaming allows the device to roam between access points without involving the main server IV Enable Cisco Compatible Extension Select to enable Lisco Compatible Extensions for this wireless connection profile V Enable Radio Management Support Enable this feature so that the client adapter will provide Radio Management to the Cisco infrastructure If the Cisco Radio Manager utility is used on the infrastructure it will configure radio parameters detect interference and detect
108. Rogue APs E Enable Mixed Cells Mode Cisco infrastructure supports mixed cells where some clients use encryption and others do not Ina bility bit for privacy will not be set in beacons and probe response packets 224161 In Figure 5 43 Cisco Compatible Extensions should be enabled as indicated by the red circle Note that Cisco Compatible Extensions is automatically enabled when configuring profiles for CKIP LEAP or EAP FAST Note For additional information regarding the configuration of the Intel PRO Wireless 3945ABG Network Connection or Intel PRO Wireless 2915ABG Network Connection adapters refer to the following documents from Intel Corporation ftp download intel com support wireless wlan sb 3945abgug pdf ftp download intel com support wireless wlan pro29 5abg sb 29 15SABG_UG pdf Calibration should be performed using a calibration client and a suitable laptop computer with a fully charged battery The following recommendations should be considered when performing calibration data collection 1 Ensure that your calibration client is being detected by the access points on the floor where you wish to perform the calibration 2 Temporarily disable Dynamic Transmit Power Control DTPC prior to conducting calibration data collection DTPC must be disabled separately for each band using either the controller GUI the controller CLI or WCS for each controller whose registered access points are expected to p
109. SSI cutoff typically 75 dB or better to a minimum of three access points has been verified All access points should be in place properly oriented and registered to their respective controllers with WCS and the location appliance fully operational For optimum ease of use and visibility during the data collection procedure a portable laptop or tablet computer or computer on wheels cart setup with a large clear and bright screen is recommended especially in areas of bright ambient light OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration During the calibration data collection process WCS suggests locations on the floor map where samples should be taken shown in Figure 5 40 along with graphical indication of the degree of progress achieved At any point during the calibration data collection process a graphical representation of the calibration points captured thus far can be generated by clicking on the dropdown menu in the upper right hand corner of the calibration data collection screen The calibration data collection process can be completed in one session or the session can be stopped and returned to at a later time This process can be repeated as often as necessary to complete calibration data collection for a floor Figure 5 40 Calibration Data Collection Screen abali cisco 802 11a n peban E 202
110. Series WLAN Controller Support Documentation for Release 4 1 http www cisco com en US products ps7206 tsd_products_support_model_home html e Cisco Catalyst 3750 Series Integrated Wireless LAN Controllers Support Documentation http www cisco com en US products ps69 15 tsd_products_support_model_home html e Cisco Wireless LAN Controller Module Support Documentation http www cisco com en US products ps6730 tsd_products_support_model_home html e Cisco Catalyst 6500 Series Wireless Services Module WiSM Support Documentation http www cisco com en US products ps6526 tsd_products_support_model_home html Note Despite the difference in nomenclature software Release 3 0 of the Cisco Location Appliance is generally included in any reference made to software Release 4 1 of the Cisco Unified Wireless Network UWN within this document Additional design considerations surrounding the use of the InnerWireless formerly PanGo Vision Locator location client in an integrated Cisco InnerWireless solution can be found in the following document e Design Considerations for Cisco PanGo Asset Tracking http www cisco com univercd cc td doc solution pangoex pdf The following guide is recommended as a design reference when considering the deployment of voice over WLAN VoWLAN handsets and supporting infrastructure in conjunction with location based services Voice over Wireless LAN 4 1 Design Guide http www cisco co
111. The location appliance dispatches any northbound notifications such as SNMP traps emails syslog or SOAP XML messages based on the updated asset tag location Location end users make use of WCS or a third party location client to request location information based on floor maps or search criteria A request for location information is made from the location to the location appliance via a SOAP XML online query Beginning with software Release 4 1 of the location aware Cisco UWN LOCP provides for the transmission of asynchronous high priority messages from the WLAN controller to the location appliance Included in this category are high priority tag events such as tag call button alerts chokepoint proximity and vendor specific tag payloads WCS and the location appliance exchange information such as calibration maps and network designs during a process known as synchronization During this process the partner possessing the more recent information will update the other partner Synchronization occurs either on demand or as a scheduled task the timing of which is determined by the Administration gt Scheduled Tasks main menu option under the Cisco Wireless Control System WCS main menu bar Location information is displayed to the end user using a location client application in conjunction with the Cisco Wireless Location Appliance Typically this role is fulfilled by the Cisco WCS which as will be further explained in subsequent sectio
112. This is because despite their similarity the probability that the location vectors collected at the same positions on each floor being identical is significantly low All other variables being equal location patterning accuracy is typically at its zenith immediately after a calibration At that time the information is current and indicative of conditions within the environment As time progresses and changes occur that affect RF propagation accuracy can be expected to degrade in accordance with the level of environmental change For example in an active logistics shipping and receiving area such as a large scale cross docking facility accuracy degradation of 20 percent can reasonably be expected in a thirty day period Because calibration data maps degrade over time if a high degree of consistent accuracy is necessary location patterning solutions require periodic re verification and possible re calibration For example it is not unreasonable to expect to re verify calibration data accuracy quarterly and to plan for a complete re calibration semi annually Wi Fi Location Based Services 4 1 Design Guide P24 OL 11612 01 CHAPTER Cisco Location Based Services Architecture This chapter describes the Cisco Location Based Services LBS architecture and has the following main sections e RF Fingerprinting page 3 1 e Location Aware Cisco UWN Architecture page 3 4 e Role of the Location Appliance page 3 7 e Accuracy and Precisi
113. _book09 186a00804fa761 html OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter 4 Installation and Configuration Quiescing the Location Appliance Step 1 Step 2 Step 3 Manually stop the location server software by issuing the follow command and observing the indicated etc init d locserverd stop Shutting down locserverd Request server shutdown now Waiting for server 2 secs Waiting for server 4 secs Waiting for server 60 secs Server shutdown complete Before removing power to the location appliance issue the following command to properly unmount all file systems stop all services and initiate an orderly shutdown of the Linux operating system shutdown h now Issuing this command from the CLI console device in the following output Shutting down console mouse services OK Stopping sshd OK Stopping xinetd OK Stopping crond OK Saving random seed OK Killing mdmonitor OK Shutting down kernel logger OK Shutting down system logger OK Shutting down interface eth0 OK Shutting down loopback interface OK Shutting down audit subsystem OK Starting killall OK Sending all processes the TERM signal Sending all processes the KILL signal Syncing hardware clock to system time Turning off swap Turning off quotas Unmounting file systems Halting system md stopping all md devices flushing ide de
114. a Cisco Unified Wireless Network architecture immediately enables location improvements over and above the baseline capabilities of the Cisco UWN such as e Scalability Adding a Cisco Location Appliance greatly increases the scalability of the location aware Cisco UWN from on demand tracking of a single device to a maximum capacity of 2500 devices WLAN clients RFID tags rogue access points and rogue clients To handle situations requiring tracking of more than 2500 devices in the enterprise additional location appliances can be deployed The design can then be partitioned by assigning specific controllers to each appliance Each appliance is responsible for tracking up to 2500 devices for the controllers and access points within its location domain and may be managed by a common WCS e Chokepoint Location The addition of a Cisco Location Appliance under software Release 4 1 or subsequent releases allows for the use of optional chokepoint triggers from Cisco technology partners such as AeroScout and WhereNet These devices can assist in providing very granular asset tag location within a range of less than one foot to over twenty feet e Historical and Statistics Trending The appliance records and maintains historical location and statistics information which is available for viewing via WCS e Location Notifications The Cisco Location Appliance can dispatch location based event notifications via email SMTP syslog SNMP traps and S
115. able 5 2 Table 5 2 WLAN Controller Device Capacities WLAN Clients Asset Tags Rogue APs Controller Model Supported Supported Supported Rogue Clients 2006 256 500 125 100 2106 256 500 125 100 4402 2 500 1250 625 500 4404 5 000 2500 625 500 WiSM 10 000 5000 1250 1000 NM WLC6 256 500 125 100 NME WLC8 12 350 500 125 100 3750G 2 500 1250 625 500 The subsections that follow examine how WCS the location appliance and WCS Navigator can be combined to satisfy the needs of more demanding designs that are typically beyond the capabilities of single management location domain combinations OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Multiple Location Appliance Designs Single Management Domain with Multiple Location Domains In this design approach the network management needs of the enterprise WLAN are expected to be well within the capacity of a single WCS management domain However there is a need to track a combination of more than 2500 clients rogues and asset tags This can be accomplished using multiple location domains that are managed via a single management domain as shown in Figure 5 24 Figure 5 24 Single Management Domain with Multiple Location Domains Regional Headquarters ee pee OF 4 i Ej ea hae ey L a ZZ L d aay Sa Se cy A bd 4 Figure 5 24 i
116. able at publication are limited to 2 4 GHz These tags exhibit the characteristics of active RFID tags but also comply with applicable IEEE 802 11 standards and protocols Wi Fi RFID tags can readily communicate directly with standard Wi Fi infrastructure without any special hardware or firmware modifications and can co exist alongside Wi Fi clients such as laptops VoWLAN phones and so on When powered on assets equipped with 802 11 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations Hi RFID Tag Technology Wi Fi client radios can be tracked natively without the need to have an asset tag attached Other assets lacking an internal 802 11 Wi Fi client radio can be tracked via a physically attached 802 11 active RFID tag A physically attached 802 11 active RFID tag also makes it possible to use the location aware Cisco UWN to track assets with integrated Wi Fi client radios when those radios are powered off Figure 6 9 802 11 Wi Fi Active RFID Tags 223360 Multimode RFID Tags As mentioned previously transponder active RFID tags offer the combination of a primary tag operational mode with a secondary method of communication that can be used for a plethora of added value functions such as activation deactivation behavior modification and so on This type of tag has been used for quite some time in highway toll plaza applications for example where tags are triggered to transmit w
117. ables must perform the following every four seconds Issue one or more probe requests per channel in the regulatory channel set Process one or more incoming probe responses Generate a radio measurement response report containing the results of all probe responses received During normal calibration procedures WCS will manage the addition and deletion of entries from the location calibration tables However there are some situations where residual stray entries may be observed A common cause is improper termination of calibration data collection by the user two examples of which might include e WCS normally adds the client MAC address to the location calibration table immediately after the parameters on the Maps gt RF Calibration Models gt Add Data Points GUI menu panel are completed If data point collection is aborted at this point by simply selecting a different WCS function from the main WCS menu entries in controller location calibration tables will remain To avoid this situation it is recommended that users wishing to abort data collection use the Cancel option instead shown in Figure 5 37 before returning to a previous menu Wi Fi Location Based Services 4 1 Design Guide n OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Figure 5 37 Calibration Using the Cancel Option to Help Trigger Location Calibration Cleanup stftetfes Wireless Control System
118. access points can impact location performance as well as the performance of co resident voice and data applications From a location perspective while location tracking inter access point spacing requirements tend to be relatively flexible and supportive of the coverage needs of underlying applications very small or very large inter access point separation distances are usually best avoided An excessive inter access point distance can detract from good location accuracy by not providing sufficient signal strength differentiation at extended distance Insufficient inter access point distance can expose the system to short range antenna pattern anomalies which may also be non conducive to good location accuracy From the perspective of co resident voice and data applications the inter access point distance is one of the key factors determining whether required minimum signal level thresholds data rate thresholds signal to noise ratios SNR and required coverage overlap will be met From a location accuracy perspective the range of acceptable inter access point distance tends to be rather broad and can provide excellent location accuracy while accommodating the needs of most co resident voice and data applications The techniques incorporated in the location aware Cisco UWN to localize tracked devices operate most effectively when RSSI and distance are seen to possess a clearly monotonic relationship To better understand what is meant by this w
119. acking is required outside the access point perimeter and thus outside the convex hull such placement may lead to reduced location fidelity in those areas Wi Fi Location Based Services 4 1 Design Guide T 0L 11612 01 57 Chapter5 Best Practices Location Aware WLAN Design Considerations HE Access Point Placement Figure 5 6 illustrates an example of a less than desirable situation where the placement of access points has been restricted to hallway corridors and administrative storage facilities located within the areas encircled by the corridors For aesthetic reasons facilities management has decided that access points will not be placed within any of the executive offices or conference rooms located between the hallway corridors and the physical perimeter Because of these restrictions our convex hull now lies at the outside edge of the corridor indicated by the blue rectangle and not at the true physical perimeter of the floor Figure 5 6 Artificially Constrained Access Point Perimeter LT faa O eg fes a O Oo 224158 Given what we know about the distribution of location errors when operating outside the convex hull it is logical to expect that location accuracy will not be as good in the offices and rooms located there These areas of potentially lower accuracy are highlighted in red in Figure 5 6 Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Locati
120. addresses of clients that are compatible with the Cisco Compatible Extensions specification version 2 or greater appear in the location calibration table of controllers unicast Radio Measurement Requests will be sent to these clients see Figure 5 36 Similar to how broadcast Radio Measurement Requests help improve the location accuracy of compatible clients during normal operation unicast Radio Measurement Requests sent at short regular intervals 4 seconds should cause compatible calibration clients to transmit probe requests very frequently The use of Cisco Compatible Extensions Radio Measurement Requests and Cisco Compatible Extensions version 2 or greater clients allows this to occur without the need to force the client to continually disassociate and re associate This allows more consistent and reliable probing of the network and allows smoother operation of the calibration client especially if it is being used as a workstation that is interacting with WCS via the calibration data collection GUI Note Unicast Radio Measurement Requests will not be sent to clients that are associated to WLANs where the Aironet Information Element Aironet IE has not been enabled on the supporting controller For best calibration results with calibration clients supporting the Cisco Compatible Extensions specification version 2 or greater ensure that Aironet IE support is enabled Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01
121. ager 3 Place up to 50 AeroScout tags within about three feet of the Tag Activator and detect the tags using the Detect Tags feature as shown in Figure 6 23 Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter6 RFID Tag Considerations Using Wi Fi RFID Tags with the Cisco UWN W Figure 6 23 Detecting Tags using Tag Manager v3 04 eroScout Tag Manager Sei Tag Detection ASe There are no items to show in this view 223369 4 Once the tags have been detected Figure 6 24 select all tags by clicking on their checkboxes as shown in the right hand column of the screen depicted in Figure 6 25 Figure 6 24 Successful Tag Detection using Tag Manager v3 04 El AeroScout Tag Manager Mel Tag Detection Aeroc Tag Detection I Ki ee 223370 Figure 6 25 Selecting Tags to Configure E AeroScout Tag Manager Se Tag Detection Yieres lt ou iS Sen M oocccse7B6 M o00cccse7B6 M 00cccse767 M 00cccse787 M o0cccsesz2et _ _ a _ _ M ioocecses2a1 M j0cccsespc DetectTags M o0cCc5E8DD JINNNNNNN 223371 5 Select the configuration option from the left hand column of the Tag Detection menu which yields the Tag Configuration menu shown in Figure 6 26 Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 E 623 Chapter 6 RFID Tag Considerations HT Using Wi Fi RFID Tags with the Cisco UWN D Note When making minor modifications
122. ages of an indoor location patterning solution but with significantly less effort required for system calibration Although both solutions support on site calibration the Cisco RF Fingerprinting approach offers less frequent re calibration and can operate with a larger inter access point spacing than location patterning solutions Cisco RF Fingerprinting can also share RF models among similar types of environments and includes pre packaged calibration models that can facilitate rapid deployment in typical indoor office environments OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter 3 Cisco Location Based Services Architecture Hs Location Aware Cisco UWN Architecture Location Aware Cisco UWN Architecture The overall architecture of the location aware Cisco Unified Wireless Network is shown in Figure 3 2 Figure 3 2 Location Aware Cisco UWN Architecture Ci WCS Client EI Third Party I Browser Z Location Applications pC a us ur HTTPS SOAP XML LAN WCS Location H aS SOAPIXML __ X Appliance Notifcations _ ol EMAIL s Ee SYSLOG SOAP XML SNMP TRAP LOCP Wireless LAN p Controllers eae A N LWAPP Wi Fi Handsets Clients Rogues Wi Fi Tags and Chokepoints O eq ied N N Access points forward information to WLAN controllers regarding the detected signal strength of any WLAN clients asset tags rogue access points or rogue clients In normal oper
123. al best practices with regard to NTP in your network may be found in the Network Time Protocol Best Practices document which can be found at the following URL http www cisco com en US tech tk869 tk769 technologies_white_paper09 186a0080117070 shtml Quiescing the Location Appliance amp Although the location appliance is designed to be installed and operated in a continuous fashion there may be times when it is necessary to power down the appliance in preparation for extraordinary events such as a physical equipment move or the orderly shutdown of a data center Simply removing power to the location appliance without undergoing an orderly shutdown may result in any files open at the time becoming corrupted Although the location appliance s operating system uses an ext3 journaling file system that minimizes the possibility of file system corruption it is generally regarded as a best practice to follow the procedure outlined below to initiate an orderly shutdown of all appliance software facilities To power down the location appliance perform the following steps via either the appliance CLI console or a remote SSH device session Note For information on how to connect a CLI console to the location appliance see Connecting and Using the CLI Console section in the Cisco Wireless Location Appliance Installation Guide at the following URL http www cisco com en US products ps6386 products_installation_and_configuration_guide
124. and compatible with the Cisco Compatible Extensions for Wi Fi Tags specification Depending on the configured range of the specific chokepoint trigger deployed a location resolution radius of as little as one foot is possible This location appliance s baseline performance level can be achieved by following the best practices along with the use of the design calibration and deployment tools described in this and other reference documents These tools would include predicative pre deployment tools such as the Location Planning and Location Readiness utilities as well as post deployment tools such as the Location Inspection tool In order to determine those areas where baseline performance improvements may be necessary the Location Inspection tool shown in Figure 3 9 can be used to evaluate what the current post calibration levels of accuracy and precision are in the environment The Location Inspection tool displays in color coded format the level of precision at any point from 0 to 5 percent to a maximum of 95 to 100 percent After viewing the output the system designer can work with the installation and deployment teams to address any areas requiring remedial attention if necessary Post Calibration Location Inspection e Li t Refresh Wireless Control System PT e Inspect Location Quality gt Calibration Model gt Suburban Office Floor Client Type Percentage of Location Errors under 10 m 33 ft z Alpharetta Campus gt 4P124
125. and determine location With TDoA a transmission with an unknown starting time is received at various receiving sensors with only the receivers requiring time synchronization TDoA implementations are rooted upon a mathematical concept known as hyperbolic lateration In this approach at least three time synchronized receiving sensors are required In Figure 2 4 assume that when station X transmits a message this message arrives at receiving sensor A with time T and at receiving station B with time T The time difference of arrival for this message is calculated between the locations of sensors B and A as the positive constant k such that TDoAg Tg Tal k The value of TDoAg _ can be used to construct a hyperbola with foci at the locations of both receiving sensors A and B This hyperbola represents the locus of all the points in the x y plane the difference of whose distances from the two foci is equal to k c meters Mathematically this represents all possible locations of mobile device X such that Dyg Dya k c The probable location of mobile station X can then be represented by a point along this hyperbola To further resolve the location of station X a third receiving sensor at location C is used to calculate the message time difference of arrival between sensors C and A or TDoAc To Tal k Knowledge of constant k allows for the construction of a second hyperbola representing the locus of all the points in the
126. and finished products can be precisely tracked as they move between the various production stations This helps ensure not only that all required process stations are visited but that they are visited in the proper sequence e Inventory control By strategically equipping all distribution center entrances and exits with chokepoint location tracking capabilities inventory databases can be automatically updated as product enters or leaves the distribution center e Security The movement of tagged assets can be tracked and monitored to protect against unauthorized removal from the premises or unauthorized movement within the facility itself structure Low power short range chokepoint triggers make it possible to expand usage beyond traditional entry and exit passages Low output power enables customization of the chokepoint trigger s effective range to better correspond to very small tightly defined areas such as shelves racks storage bins workstations and patient beds The movement of assets into or away from such limited areas can be then be precisely monitored such as the placement or removal of equipment in a rack for example in a similar fashion to that of the higher power chokepoint triggers described earlier The specific changes in tag behavior that can be enacted by a chokepoint are vendor dependent Tag behavior modification may include but are not limited to e Immediate tag multicast message transmission e Tag reactivation
127. ansmitted in the correct format You will need the assistance of the Cisco Technical Assistance Center to confirm this If the packets that the tag transmits over the air are deemed by the Cisco TAC not to be valid verify that the level of firmware being used in the asset tag is compliant with the Cisco Compatible Extensions for Wi Fi Tags specification and that it supports the telemetry or high priority functions desired If the telemetry or high priority events are seen in the controller s RFID database check to see if they are being sent to the location appliance look for Notifying LBS of emergency in the output above Issue the following command to verify that the LOCP connection between the controller and the location appliance is up and functioning Cisco Controller gt show LOCP status LocServer IP TxEchoResp RxEchoReq TxData RxData 1051256521 5300 5300 83597 441 Normally if the LOCP connection is up and running properly you should see the echo counts regularly increment based on the settings of the echo interval in the location appliance In addition as emergencies and telemetry events occur that require transport via LOCP you will see the data fields OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Appendix B Verifying Detection of Asset Tags in WLAN Controllers Verifying Asset Tag Telemetry and Events increment as well If a controller is rebooted and repeatedly fails to establish a connection
128. apter compatible with the Cisco Compatible Extensions specification for WLAN devices specification at version 2 or higher and capable of recognizing and responding to S36 unicast radio measurement requests An example of such a client is the Cisco AIR CB21AG For example proceed to disable the 5 GHz band and complete the data collection using the 2 4 GHz band only Then disable the 2 4 GHz band and enable the 5 GHz band and proceed to repeat the data collection using the 5 GHz band only 2 Perform the calibration data collection using two operators and two independent laptops Each laptop should be equipped with a dual band client adapter compatible with the Cisco Compatible Extensions specification for WLAN devices specification at version 2 or higher and capable of recognizing and responding to S36 unicast radio measurement requests An example of such a client is the Cisco AIR CB21AG Each laptop should be associated to the infrastructure using a different band The two calibration data collection operators may function independently there is no need for them to visit each data point at the same time or to even visit the same data points In this way a complete calibration data collection can be performed across both bands in half the amount of time compared to option 1 above Some embedded laptop client adapters may not transmit probe requests at these power levels but instead are restricted to lower transmit power levels for example 15dB
129. articipate in calibration data collection After calibration data collection has been performed DTPC should be re enabled for normal production operation 3 Ensure that the WLAN to which your calibration client will associate is configured to support Aironet Information Elements Aironet IE Doing so will enable the use of unicast radio resource measurement requests during calibration data collection for more efficient operation To obtain best performance when displaying access point coverage heat maps and tracking devices in most cases calibration clients should be pre configured as closely as possible to transmit power levels of 63mW 18dBm for 2 4GHz and 32mW 15dBm for 5 GHz Note that it is imperative that DTPC be disabled item number two above such that these transmit power levels do not vary during calibration data collection OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations Calibration Due to an open caveat concerning dual band calibration clients when attempting to perform a simultaneous data collection on both bands it is recommended that calibration data collection be performed for each band individually at this time In order to do this using a dual band client use either of the following alternatives 1 Perform the calibration data collection on each band individually using a single laptop equipped with a dual band client ad
130. ated within 70 feet of the point in question Figure 5 15 illustrates our three location readiness rules where the green and yellow circles represent access point locations and the point in question is represented by a red dot Figure 5 15 Definition of a Location Ready Point O O 223334 Figure 5 16 shows an example of a floor deployment where not all areas have passed three point location readiness assessment described earlier for 10m 90 accuracy Although there are green areas toward the center of the figure notice that red areas abound as you get beyond the perimeter access points representing the convex hull By establishing a solid understanding of the requirements that define location readiness the information contained in Figure 5 15 can be used to help determine how access points may be required to be relocated or additional access points introduced to improve performance For example if 10m 90 or better location accuracy is required within the red areas additional access points could be introduced to establish a more clearly delineated floor perimeter including the placement of access points in the corners of the floor and re checking inter access point distances By implementing these types of modifications the ability of the Cisco UWN to resolve the location of tracked devices in these highlighted areas is likely to be significantly enhanced I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapt
131. ation access points focus their collection activities for this information on their primary channel of operation going off channel and scanning the other channels in their regulatory channel set periodically The collected signal strength information is forwarded to the WLAN controller to which the access point is currently registered which aggregates the information The location appliance uses SNMP to poll each controller for the latest signal strength information for each tracked category of device In the case of a location tracking system deployed without a location appliance WCS obtains this information from the appropriate controller s directly w_ Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter3 Cisco Location Based Services Architecture Step 1 Step 2 Step 3 Step 4 Step 5 Location Aware Cisco UWN Architecture W A step by step flow diagram of this process is provided in Figure 3 3 where the flow of signal strength and tag payload information is shown for active RFID asset tags that communicate via the use of layer two multicasts Figure 3 3 LWAPP Access Point Multicast Tag Packet Calculated Locations Location Database Information Flow for Asset Tag RSSI Data WLAN Controller Tag Payload Info Tag RSSI Info SNMP Polling LOCP Polling LOCP Notifications Location SNMP Traps Appliance SOAP XML Wireless Control
132. ation appliance via either the CLI serial console or an SSH session When logged in use the Linux command df H to display disk free space as follows root AeS_Loc root df H Filesystem Size Used Avail Use Mounted on dev sda2 77G 3 2G 70G 5 dev sdal 104M 16M 83M 16 boot none 526M 0 526M 0 dev shm root AeS_ Loc root Note The df H command is used above because it is a commonplace practice for most computer disk manufacturers to assume 1 GB 1 000 000 000 bytes The H option displays output as powers of 1000 rather than 1024 Use df h if your preference is for the contrary The df display output shown here is for a location appliance containing a hard disk drive with an unformatted capacity of 80 GB Notice that there are two main file systems defined dev sdal which is the Linux boot file system and dev sda2 which contains the root directory as well as the location application and all databases You can clearly see from the display above that only 5 percent of all available space on dev sda2 is currently being used That being the case there is an abundance of free space available and defragmentation is unlikely to be required at this time You can use the information in the df output along with the knowledge of the size of the location database from DB Disk Memory described in Memory Information page 4 6 to approximate the maximum recommended size to which the location appliance database should be allo
133. ation process in WCS can be performed using one of two methods It can be performed from a single web enabled mobile device associated to the WLAN which controls both the probing of the network as well as the actual data collection Alternatively the data collection phase can be performed from two separate devices that are associated to the WLAN infrastructure In this case interaction with the WCS GUI is controlled from a primary device that is equipped with keyboard and mouse capabilities while the actual generation of probe requests occurs on a second device Due to an open caveat concerning the use of dual band calibration clients and performing a location calibration data collection on both bands simultaneously it is recommended that calibration data collection be performed for each band individually at this time When using a dual band client use either of the following alternatives 1 Perform the calibration data collection using a single laptop equipped with a Cisco Aironet 802 1 1a b g Wireless CardBus Adapter AIR CB21AG on each band individually For example proceed to disable the 5 GHz band and complete the data collection using the 2 4 GHz band only Then disable the 2 4 GHz band and enable the 5 GHz band and proceed to repeat the data collection using the 5 GHz band only 2 Perform the calibration using two people and two laptops Each laptop should have a Cisco AIR CB21AG and be associated to the infrastructure using a differ
134. ave and initiating data collection Although they are only suggested locations the blue crosshairs are an excellent way to stay on track and uniformly cover ground especially within large environments The calibration grid will be updated to indicate the locations actually visited with the surrounding area of localization that is now covered being indicated by a blue color for 802 11b g yellow for 802 1 1a and green for both bands as illustrated in Figure 5 41 Note In order to promote better location fidelity every attempt should be made to be as accurate as possible when indicating the calibration client s actual physical position using the red crosshairs in Figure 5 40 and Figure 5 41 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration Figure 5 41 Example of a Completed Calibration Data Collection for Both Bands Cisco Wireless Control System Logout Refresh Print View Monitor Configure Location Administration Help v Calibrating Model Beringer Suburban Office Calibration Status Select a command z Go 802 114 Building gt Test Lab Annex 2 aia Calibrating using Client 00 0f b5 10 62 97 Click on the map where the client is currently located and click on Save Total 802 114 Data Points 258 Total 802 11b g Data Points 259 m Dona Horizontal Vertical Zoom Legend 0 0 Save Canc
135. ays the last detected RSSI levels of each access point detecting the asset tag This RSSI information is collected in a similar fashion to that shown by the show rfid detail lt mac address gt command and provides an alternative to the CLI command for determining the detected RSSI of asset tags As can be seen in Figure 3 20 additional information regarding the radio type and age of the last detected signal strength reading is available by performing a mouse over of any access point Figure 3 20 Asset Tag Detected RSSI with Location Debug Enabled apalie Wireless Control System cisco Tags gt Aeroscout Tag 00 0c cc 5 05 17 Select a command E GO Tag Properties Asset Info vendor 4eroscout Name Controller 10 1 96 18 Group Batt remaining 80 Days remaining Categor aid 0 Tolerance 20 Battery Age ii ife 20 Location Debug M Enabled Update Location This will show AP RSSI Information on the Map Alpharetta Campus gt AP1242 icti Floor Building gt Test Lab Annex 2 Smusucs Last located at Aug 15 2007 5 53 55 PM Bytes received 104877 On Location AeS Loci Packets received 2012 Server Last Chokepoint_00 0c cc 60 1e 8a 1 ag Gm O O AP 00 14 1b 59 43 80 AP1242 5 RSSI Readings Detected RSSI Radio Type Age when Located 50 dBm 11b 9 n 2 secs PP aATA OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter3 Cisco Location Based Services Architecture
136. be augmented or redesigned in favor of those that combine center access point placement with perimeter and corner placement Figure 5 8 Basic Example of Location Aware Access Point Deployment Recommended Not Recommended AP AP m Device m Device e AP AP AP AP AP e AP m Device AP AP AP AP AP oApP APe m Device 223328 If possible mount antennas such that they have an unencumbered 360 view of all areas around them without being blocked at close range by large objects For example if possible avoid placing access point antennas directly against large objects such as steel columns as illustrated in Figure 5 9 One option is to mount the access point along with its antennas to a ceiling location provided that this allows an acceptable mounting height Another option is to use short low loss cable extension to allow separation between antennas and such obstructions Figure 5 9 Access Point Mounted Directly to Steel Column 119142 Additional discussion of proper access point placement can be found in Cisco Wireless Location Appliance Deployment Guide at the following URL http www cisco com en US products ps6386 prod_technical_reference09186a008059ce31 html Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 n Chapter5 Best Practices Location Aware WLAN Design Considerations W Access Point Separation Access Point Separation The distance between deployed
137. bility vowlan 4 1dg vowlan4 1dg book html We opted for a dual band infrastructure with an 802 11a 5 GHz WLAN that is used by 7921G VoWLAN handsets and high speed WLAN client devices 802 11bg 2 4 GHz operation is also supported but due to the substantially reduced overall capacity on 802 11bg brought about by the existence of only three non interfering channels its use is restricted to legacy data and voice devices as well as active RFID asset tags that are in compliance with the Cisco Compatible Extensions for Wi Fi Tags specification Legacy data devices would include devices that are unable to migrate to 802 1 1a for reasons such as the client hardware device being no longer offered for sale battery life concerns and so on Candidate legacy devices might include PDAs bar code scanners and other devices with embedded wireless onboard that is not easily upgradeable In the case of our example we assume that there are still some OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations HE Location Voice and Data Coexistence users of 802 11b voice devices present in the environment for example legacy Cisco 7920 VOWLAN IP phones or similar legacy 802 11b only devices from third parties that have not yet been addressed with 802 11a replacements Figure 5 19 Layout for 5GHz Voice and High Speed Data 2 4GHz Legacy Srey Ct Ret
138. c t where e D distance meters e c propagation speed of 300 meters microsecond e f time in microseconds With distance used as a radius a circular representation of the area around the receiving sensor can be constructed for which the location of the mobile device is highly probable ToA information from two sensors resolves a mobile device position to two equally probable points ToA tri lateration makes use of three sensors to allow the mobile device location to be resolved with improved accuracy Figure 2 3 illustrates the concept of ToA tri lateration The amount of time required for a message transmitted from station X to arrive at receiving sensors A B and C is precisely measured as t4 tg and tc Given a known propagation velocity stated as c the mobile device distance from each of these three receiving sensors can then be calculated as D4 Dg and Dc respectively Each calculated distance value is used to construct a circular plot around the respective receiving sensor From the individual perspective of each receiver station X is believed to reside somewhere along this plot The intersection of the three circular plots resolves the location of station X as illustrated in Figure 2 3 In some cases there may be more than one possible solution for the location of mobile device station X even when using three remote sensors to perform tri lateration In these cases four or more receiving sensors are employed to perform ToA multi
139. case a nationwide retailer has mandated that all electronic infrastructure components be accessible to store employees using the ten foot step ladders commonly available at each store location Here we see that the access point is mounted at 10 feet for easy access while the antennas are mounted at 15 feet In cases such as this the value specified for AP Height in Figure 5 34 should reflect the height of the antennas and not the height of the access point OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration Figure 5 35 Example of Differing Antenna and Access Point Heights Antennas 15 feet W E Access Point 10 feet 223350 Calibration The Cisco WCS and the location appliance are shipped with default RF models that facilitate setup under two of the most common indoor office environments One of these models represents a typical corporate office environment with both cubicles and drywall offices and the other represents a similar environment with drywall offices only These RF models provide an estimate of the path losses found in these typical indoor commercial office environments and can be very useful when the primary requirement at hand is to provide a working location tracking system in the shortest amount of time possible Some indoor environments may possess more attenuation than is found in a typical off
140. cation Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture Cisco Location Control Protocol LOCP AS Note Complete details regarding the configuration of the Cisco IOS mobile station command can be found in Cisco IOS 12 4 3g JA for Access Points and Bridges mobile station command reference page located at the following URL http cisco com en US docs wireless access_point 12 4_3g JA command reference cr43 main html w p2593116 The values for period and threshold should be adjusted for your specific environment in order to balance the need for consistent and regular probe requests against the possibility of excessive roaming Decreasing the threshold value to a very low value causing an active scan to always occur at each period interval for example will typically improve the location fidelity of work group bridges that seldom roam significantly The trade off with doing this however is that such settings may also increase the frequency with which the workgroup bridge roams However this trade off is generally viewed as equitable since in properly deployed environments with good coverage and access point placement the increase in WGB roaming should be negligible whereas the improvement in mobile workgroup bridge location fidelity in cases where there is seldom roaming between access points can be very significant Cisco Location Control Protocol LOCP Cisco Unified Wireless Network
141. cation appliance Vendor specific information that is sent within a high priority event can also be pushed to location clients from the location appliance via an asynchronous northbound notification from the location appliance to location clients using SMTP UDP Syslog SNMP traps or SOAP transports Location clients must be capable of receiving and processing these notifications on the aforementioned ports in order to provide real time notification of such events to end users Figure 3 29 clearly indicates that unlike tag telemetry there is no dependency on any polling mechanism between the location appliance and the WLAN controller LOCP notifications will be generated from the WLAN controller to the location appliance as tags communicate those events High priority tag events vendor specific data and chokepoint in range information are not aggregated by WLAN controllers in Release 4 1 of the Cisco UWN Each incoming tag multicast message bearing such information received by a WLAN controller from each registered access point results in the generation of an information notification or a measurement notification frame from the WLAN controller to the location appliance No dependency exists between the transmission of tag telemetry and the transmission of chokepoint high priority or vendor specific information For example a tag may be relaying telemetry information about an asset as it traverses through the range of chokepoints in an environme
142. ccess points The data accumulated during the calibration phase is statistically processed and groomed then used to build an RF propagation model used to predict tracked device RSSI around each access point where the path loss exponent shadow fading standard deviation and PL meter values are calculated from the sample calibration data so as to better reflect specific propagation anomalies present in the environment This process consists of several computational cycles where the previously mentioned parameters are calculated for each band The minimum mean square error MMSE estimation technique is used to obtain the initial values for the parameters as shown in Figure 3 1 where the path loss exponent is represented by the slope of the applicable MMSE line of best fit that is either default or corrected fit However note that in the RF Fingerprinting approach the selection of a location path loss model does OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter3 Cisco Location Based Services Architecture E RF Fingerprinting not end with MMSE Rather MMSE is used only as the starting point for the selection of finalized parameters for each band with the ultimate goal being the optimization of the final path loss model as it pertains to location accuracy RF Fingerprinting does not rely on good location performance being a by product of a RF propagation model that simply provides good coverage mapping Figur
143. ce and high speed data may require more dense deployments under certain circumstances The question that comes to mind then is can the requirements described earlier for voice and data applications be met in combination with the requirements of location tracking The answer is yes with the precise mechanics of how it is done dependent upon the specific requirements of the voice and data applications themselves the access point and antenna configuration being considered and the physical characteristics of the environment into which the infrastructure will be deployed In order to explore this further we examine the details behind how an access point layout primarily intended for high speed data and 7921G voice applications can be further optimized to include location tracking As an example let us examine a voice access point layout for the 275 x 159 foot facility first presented in Figure 5 11 This represents a drywall office and indoor commercial office environment with a path loss exponent of 3 5 see Figure 5 19 These access point locations were selected based on desired signal strength and overlap calculations that were performed by the original designer In architecting this design the designer s intention was to provide a solution that closely followed Cisco VoWLAN design best practices described in Voice Over Wireless LAN 4 1 Design Guide which is available at the following URL http www cisco com en US docs solutions Enterprise Mo
144. ceived phase at each element In a properly constructed array there is a small but discernible per element arrival time and a difference in phase Sometimes referred to as reverse beam forming this technique involves directly measuring the arrival time of the signal at each element computing the TDoA between array elements and converting this information to an AoA measurement This is made possible because of the fact that in beam forming the signal from each element is time delayed phase shifted to steer the gain of the antenna array A well known implementation of AoA is the VOR VHF Omnidirectional Range system used for aircraft navigation from 108 1 to 117 95 MHz VOR beacons around the United States and elsewhere transmit multiple VHF radials with each radial emanating at a different angle of incidence The VOR receiver in an aircraft can determine the radial on which the aircraft is situated as it is approaching the VOR beacon and thus its angle of incidence with respect to the beacon Using a minimum of two VOR beacons the aircraft navigator is able to use onboard AoA ranging equipment to conduct angulation or tri angulation if using three VOR beacons and accurately determine the position of the aircraft AoA techniques have also been applied in the cellular industry in early efforts to provide location tracking services for mobile phone users This was primarily intended to comply with regulations requiring cell systems
145. cent location information or 1 2 1 3 6 12 or 24 hours to include information that is older By clicking on the blue chevron that is displayed to the right of the 802 11 Tags checkbox option tag filtering options and additional information can be displayed such as e The total number of asset tags detected on this floor can be displayed e Small icons shown in Figure 3 16 or standard size icons can be selected When using small icons text is not displayed on the floor map for the asset tag except when a mouse over is performed When using standard size icons an on screen tag is displayed which is configurable for MAC address asset name asset group or asset category e Either all asset tags can be displayed or filtering can be performed to select which asset tags to display on the floor map This can be based on MAC address asset name asset group asset category or controller As mentioned previously only up to 250 asset tags will be shown on the floor maps at any one time If there are greater than 250 asset tags detected the total number found will be indicated in the left hand column status area during each communication cycle between WCS and the location appliance It is recommended that filtering be used to reduce the total number of asset tags selected for display if you receive this warning In software Release 4 1 of the Cisco UWN WLAN controllers provide support for the maximum number of asset tags listed in Table 3
146. ces 4 1 Design Guide gO Appendix B Verifying Detection of Asset Tags in WLAN Controllers W sAsset Tags Detection Figure B 2 LWAPP Capture of Tag Multicast Frame Cisco Compatible Extensions for Wi Fi Tag Compliant Frame 6385 116 bytes on wire 116 bytes captured Ethernet II Src Cisco_ed 49 44 00 14 1c ed 49 44 Dst Airespac_40 98 03 00 0b 85 40 98 03 Internet Protocol Src 10 1 95 252 10 1 95 252 Dst 10 1 92 19 10 1 92 19 amp User Datagram Protocol Src Port 54420 54420 Dst Port 12222 12222 Source port 54420 54420 Destination port 12222 12222 Length 82 Checksum Ox828c correct LWAPP Encapsulated Packet Version 0 slotId 0 P Oa Type Encapsulated 80211 0 Fragment Set 0 Fragment Type Set Fragment Id 0x00 Length 68 RSSI Oxc9 SNR Ox2c a IEEE 802 11 Type Subtype Data 0x20 a Frame Control 0x0308 CSwapped Version 0 Type Data frame 2 Subtype 0 Flags 0x3 Duration 0 Receiver address Cisco_59 41 f0 00 14 1b 59 41 f0 Transmitter address Aeroscou_5e 82 8d 00 0c cc 5e 82 8d Destination address 01 40 96 00 00 03 01 40 96 00 00 03 Fragment number 0 Sequence number 1189 Source address 00 00 00_00 00 00 00 00 00 00 00 00 0010 00 66 00 1c 00 00 ff 11 eb 59 Oa 01 5f fc Oa 01 a eee Pa eee 0020 5c 13 A EEE tS cites Diy 0030 03 08 00 00 00 14 1b 59 41 fO 00 Oc cc 5e 82 8d_ Y AL AL 0040 01 40 n ERE PD eis twee 0050 01 0
147. cisco Monitor Reports Configure Location Administration Help v Calibrating Model on Floor Alpharetta Campus gt AP1242 Building gt Test Lab Annex 2 802 11a n Calibrating using Client 00 40 96 a1 9d 47 Click on the map where the client is currently located and click on Save E Dene Total 802 11a n Data Points 0 Total 802 11b g n Data Points 0 802 11b a n Horizontal Vertical Zoom Done E 23 8 94 Save concer 75 M sor Show grid Show APs Show Data Points cise AP 1242 7 E 202 11a n covered E 802 11b g n Covered E 802 11a b g n Covered Suggested Location E Visited Location K A Api242 6 ro e WCS adds the client address to the location calibration table immediately after clicking on the Save button shown in Figure 5 37 and initiating the data collection process for a particular data 223352 point While data is being collected for the calibration client the screen shown in Figure 5 38 will be displayed OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration Figure 5 38 Data Point Collection in Progress ajia Wireless Control System cisco Monitor Reports Configure Location v Administration Help v Please wait Data Points are being collected from your test location Some points may take longer to process Please wait 802 11a n Done eee ee
148. city is allocated to each tracked device category i e WLAN clients asset tags and rogue devices Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations amp Multiple Location Appliance Designs W e Cisco WCS Release 4 1 can support between 500 and 3000 access points and between 125 and 750 WLAN controllers depending on hardware configuration as follows e WCS high end server Supports up to 3000 access points and 750 WLAN controllers e WCS standard server Supports up to 2000 access points and 500 WLAN controllers e WCS on Cisco Wireless LAN Solutions Engine WLSE hardware Supports up to 1500 access points and 100 WLAN controllers e WCS low end server Supports up to 500 access points and 125 WLAN controllers Note For complete details see the Cisco Wireless Control System Configuration Guide System Requirements at the following URL http www cisco com en US products ps6305 products_configuration_guide_chapter09186a00808317 da html wp 1061082 The maximum size of the WCS management domain that is the total number of devices managed by a single WCS is related to the choice of server platform In very large networks it may be necessary to partition the network into multiple management domains each with a separate WCS managing it Beginning with software Release 4 1 Cisco introduces the WCS Navigator which is a manag
149. co Compatible Extensions Clients that do not support S36 Radio Measurement Requests such as those supporting Cisco Compatible Extensions version 1 or those not compatible with the Cisco Compatible Extensions for WLAN Devices specification at all will ignore any Radio Measurement Requests that are received Note When using clients equipped with the Intel PRO Wireless 3945ABG Network Connection or the Intel PRO Wireless 2915ABG Network Connection adapter it is important to note that the default Personal Security settings of the Intel ProSet Configuration Utility do not include compatibility with the Cisco Compatible Extensions specification When using this default personal level of wireless security which is not intended for enterprise use clients equipped with the Intel 3945ABG or 2915ABG client adapters will not support S36 broadcast radio measurement requests and are not compliant with the Cisco Compatible Extensions specification for WLAN devices In order to enable compatibility with the Cisco Compatible Extensions specification and the support of S36 radio OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture W Tracking Clients Assets and Rogue Devices measurement requests the Intel ProSet client supplicant must be used to reconfigure the client for Enterprise Security and enable Cisco Compatible Extensions Figure 5 42 on page 5 60 and
150. coverage hole situations while still using transmit power levels that are achievable by the client devices In order to facilitate optimal location tracking with this design a few changes additions and adjustments will be necessary Examining the current voice and data design and its associated parameters the current access point spacing antenna installation height and placement pattern appear to be acceptable for location usage However the lack of access points located at the actual floor perimeters and in the corners of the floor are a concern that should be addressed This can be seen from the dashed line in Figure 5 19 which illustrates the convex hull established by the current perimeter of access points Note that areas at each corner and along each upper and lower perimeter lie outside of this boundary Although these areas may not prove to be a hindrance to some users for the purposes of this example our goal is to assure optimal location accuracy in all areas of the floor This includes the conference rooms in the corners of the floor and in all perimeter areas Therefore establishing a proper floor perimeter will be our first order of business The first step is to implement top and bottom access point perimeters as close to the building perimeter as feasible while attempting to maintain the uniform density of access points shown in Figure 5 19 to the highest degree possible Maintaining a high degree of access point uniformity is es
151. ctions interior perimeter and corner access points are placed to facilitate multi lateration and establish a clearly delineated convex hull around the floor Note In an actual installation involving WLAN applications deployed in conjunction with location tracking interior access point design should be conducted prior to instituting design modifications in support of location tracking modifications to ensure that best practice recommendations for signal strength overlap and signal to noise ratio requirements of data and voice applications are met An Example of Location Aware Access Point Placement TO EN Mini EE we oe we oii LA Wp i Gad a7 La ha E pos os noj maj as ow on f ne THA WANT pemn igar OT v we es ws ei fo aE Ca G Gal La G La Ga dg LA uad laad a lai os ott Gey os b aQ ZA h 223331 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter5 Best Practices Location Aware WLAN Design Considerations W Access Point Separation WCS includes a planning tool that allows designers to model what if design scenarios The WCS Planning Tool is accessible via the Monitor gt Maps gt floormapname gt Planning Mode dropdown menu selection This is a predictive modeling tool that is used on a per floor basis to provide initial guidance on access point placement as well as an interactive representation of predicted access point sig
152. d In this particular case the option to expand our inter access point separation is an acceptable alternative Due to the increase in the inter access point separation from 42 7 feet to 45 9 feet a 3 dBm increase is required to both our 802 11a and 802 1 1bg access point transmit power settings in order to remain in strict compliance with our calculated requirements Despite the increase in access point transmit power level additional transmit power is left in reserve on both bands to address potential coverage holes or other anomalies that could occur due to changes in the environment If this had not been the case we would have proceeded with our second option which entails contracting our inter access point spacing and introducing a sixth row of access points The main differences in our calculations would be to divide the size of floor by five instead of four rows of equilateral triangular formations This would have resulted in a smaller formation height a smaller inter access point separation and therefore smaller cell to cell radii and lower transmit powers Note The signal level measurements and the calculations described in this section while based on generally accepted RF theory are intended for planning purposes only It is reasonable to expect some level of signal level variation from these theoretical calculations in different environments Rather than statically administering access point transmission power levels the
153. d well in advance of a low disk space situation These aggressive data pruning intervals may need to be combined with a shorter history archive interval if the adjusted pruning intervals alone are not sufficient in addressing the low free disk space situation Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 EN Chapter4 Installation and Configuration Hs Configuring Location Appliance Advanced Parameters Configuring Location Appliance Advanced Parameters The configuration of Location Server gt Administration gt Advanced Parameters is discussed in the document entitled Cisco Wireless Location Appliance Configuration Guide Editing Advanced Parameters at the following URL http www cisco com en US products ps6386 products_configuration_guide_chapter09 186a008082d7 2f html wp 1050981 Further clarification regarding a subset of the Advanced Parameters is provided in the following subsections Absent Data Cleanup Interval The Absent Data Cleanup Interval or ADCI range 1 to 99 999 minutes specifies the amount of time that an entry is kept for a tracked entity WLAN client tag rogue access point or rogue client in the active location database The ADCI specifies the amount of time that must expire before the tracked device entry is removed from the active location database if no recent updates have been received for that device For example if the RSSI information for an asset tag was last recorded by th
154. d be required to support the recommended levels of overlap given our newly calculated inter access point spacing Using this new value for inter access point spacing we first calculate the 67dBm cell signal boundary with a 15 cell to cell overlap for 802 11a We then calculate the 67dBm cell signal boundary with a 20 cell to cell overlap for our legacy data and voice devices that will be using 802 11bg With the assumption that the radii of any two adjacent access point cells are equal that is RI R2 R we can use the equation for the area of a circle circle intersection as the basis for this calculation To determine the cell radius given that the inter access point separation and the percentage of overlap are known we proceed as follows OTR 2R arccos E Zavar a7 Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Location Voice and Data Coexistence Hi where e O the desired overlap percentage divided by 100 d arccos e 2R is expressed in radians e d the inter access point distance in feet e R the cell radius in feet We substitute either 15 for 802 1 1a or 10 for 802 1 1bg as the percentage of overlap O and 45 9 feet for the inter access point distance d Solving for R as an approximate root of the function shown above we determine that the cell radii should be equal to 30 88 feet for a 15 cell to cell ove
155. d from the Layers drop down selector at the top of the floor map display and click Load in the left hand column To avoid excessive clutter WCS will display the first 250 asset tags on the floor map To view the location of asset tags beyond the first 250 asset tag filtering must be used It is assumed that all other components of the location aware Cisco UWN have been properly configured to collect asset tag information Figure 3 16 RFID Tag Location Map abale Wireless Control System cisco Monitor Reports Configure Location Administration Help v Sontriboting Abe Maps gt Cisco SJ Site 5 gt BLD 14 gt 3rd floor M sjct4 31b ap5 M sjc14 32b ap6 RSSI Color Lookup Zoom Refresh M sjci4 31b ap3 35 dBm 90 dBm 100 z s min z Full Screen Load Loading Chokepoints a Loaded 0 chokepoints Done bd 4 gt Load Location Server data as old as M 802 11 Tags C Rogue APs O Rogue Clients O Grid O coverageAreas O Markers O Chokepoints Save Settings 223312 Wi Fi Location Based Services 4 1 Design Guide 0L 11612 01 a 323 Chapter3 Cisco Location Based Services Architecture Hs Tracking Clients Assets and Rogue Devices The graphical location information shown can be filtered by WCS based on the age of the information In Figure 3 16 WCS displays location appliance information that has aged up to 15 minutes This value can be set to 2 or 5 minutes if it is desired to view only very re
156. defined as a separate floor in WCS Individual calibrations are then performed in each of the sub floor areas applied to their pseudo floor definition within WCS and then synchronized with the location appliance Because this approach allows for the provisioning of separate path loss models that are attuned to the characteristics of each sub floor area improved accuracy and precision is possible However potential tradeoffs may include additional management overhead on the part of the WCS administrator An organized naming convention is typically required for floors and sub floors such that they are easily recognizable by WCS users and able to be logically considered as a group Each sub floor area should be considered as an independent location area subject to the location aware design recommendations made in this document Also it should be noted that accuracy may degrade as devices approach the edges and borders of sub floors since the location appliance positioning engine does not consider signal strength readings from access points that are resident on a different floor in software Release 4 1 In addition to these two mainline options it is possible to treat each of the three areas as separate floors in WCS and thereby allow the development of RF models attuned to each area s characteristics However this approach possesses a serious limitation that must be understood In addition to the management overhead of developing floor and sub floo
157. dication of an insufficient internal lubrication which could result in costly repairs As described in the section entitled Asset Tag Telemetry Using LOCP page 3 38 beginning with the Cisco UWN software Release 4 1 all tag telemetry sent by tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification is aggregated by WLAN controllers and passed to the Cisco Wireless Location Appliance In software Release 4 1 LOCP uses a polled mechanism to collect tag telemetry after the fact the timing of which is tied to the traditional SNMP polling mechanism used to gather asset tag RSSI information The location appliance updates the telemetry information for each asset tag in its databases with that received from the most recently responding WLAN controller that has OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide O Chapter6 RFID Tag Considerations Tag Telemetry and Notification Considerations included telemetry information for that specific tag s MAC address If archiving of tag historical information has been enabled on the location appliance tag telemetry information is included along with other tag information shown in Figure 6 28 Figure 6 28 Archive Playback of Tag Telemetry and Emergency Data Aeroscout Tag 00 0 c 5 05 13 Select a command i 60 Asset Name Asset Group Asset Category MAC Address 00 O0c ce 5ce 05 13 From Tue Apr 24 23 01 53 EDT 2007 To Tue May 15 19 13 2
158. dministration gt Location Parameters menu in Release 4 1 of WCS for backward compatibility with these earlier releases However with software Release 4 1 there is no benefit to be gained by changing this parameter from its default setting RSSI Discard Times e Relative RSSI Discard Time This parameter denotes the relative boundary of RSSI sample times used in location calculations It specifies the time between the most recent RSSI sample and the oldest usable RSSI sample The default relative RSSI discard time is 3 minutes During normal operation of the location appliance this parameter should be left at the default value and should not be changed except on the advice and recommendation of the Cisco Technical Assistance Center TAC or Cisco Engineering e Absolute RSSI Discard Time This parameter denotes the absolute boundary of RSSI sample times used in location calculations The default is 60 minutes which means that RSSI samples older than 60 minutes are not used in location calculations regardless of relative RSSI discard time During normal operation of the location appliance this parameter should be left at the default value and should not be changed except on advice of the Cisco Technical Assistance Center TAC or Cisco Engineering RSSI Cutoff In addition to enforcing the aforementioned relative and absolute time constraints against received RSSI reports the location appliance also applies a parameter known as the RSSI cuto
159. during a representative period in the operation of the site variations such as attenuation from walls and other objects can be directly accounted for during the calibration phase Calibration Phase During the calibration phase data is accumulated by performing a walk around of the target environment with a mobile device and allowing multiple receiving sensors access points in the case of 802 11 WLANs to sample the signal strength of the mobile device this refers to a network side implementation of location patterning A graphical representation of the area to be calibrated is typically overlaid with a set of grid points or notations to guide the operator in determining precisely where sample data should be acquired At each sample location the array or location vector of RSS values associated with the calibration device is recorded into a database known as a radio map or training set The size of the vector for this sample OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter2 Location Tracking Approaches Hi Location Patterning Pattern Recognition Techniques location is determined by the number of receiving stations that can detect the mobile device Figure 2 6 provides a simplified illustration of this approach showing two sample points and how their respective location vectors might be formed from detected client RSSI Figure 2 6 Location Patterning Calibration 9
160. e placement of the red crosshairs during calibration data collection is very important The results of each data point comparison are used to graphically express the overall accuracy of the path loss model at various points on the floor This provides the system designer or installer with real world feedback with regard to how the expected performance of the system compares to its actual performance given the calibration client used and the condition of the environment at the time of calibration Location inspection is accessible from the Monitor gt Maps gt RF Calibration Model gt model name WCS menu via the Inspect Location Quality hyperlink located next to the name of the floor where data collection for the calibration model was performed as shown in Figure 5 45 Wi Fi Location Based Services 4 1 Design Guide n OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Inspecting Location Quality E Figure 5 45 Accessing Location Inspection Calibration Model gt Beringer Suburban Office 2 Status Calibrated Last Calibrated On July 5 2006 11 18 19 PM EDT Total 802 11a Data 258 Points Total 802 11b g Data A 359 Points 802 11a Calibration Done Yes 154 done 802 11b g Calibration Done Yes 152 done Calibration Floors Alpharetta Campus gt 4P1242 Building gt Test Lab Annex 2 Inspect Location Quality Floors Applied To Alpharetta Campus gt Building 935 gt Atrium Floor
161. e 3 1 MMSE Estimation Measured Path Loss vs Distance Pathloss dB raw data corrected fit default model 20 40 60 80 100 Range ft 190540 To locate a mobile client during the operational phase of RF Fingerprinting RSS multi lateration is performed using either a pre packaged RF model or a customized model created during the calibration phase This process yields the coordinates of the data point with the highest potential of correctly representing the tracked device s current location Additional information gleaned from statistical analysis of the distribution of calibration data is then used to further improve location accuracy and precision Cisco RF Fingerprinting offers several key advantages over traditional approaches e Uses existing LWAPP enabled Cisco Unified Networking Components Unlike some other solutions the location aware Cisco UWN with RF Fingerprinting provides a Wi Fi based RTLS alongside of voice and data services using a combined infrastructure The Cisco Location Appliance supports location and statistics history and serves as a centralized positioning engine for the simultaneous tracking of up to 2500 devices per appliance Optional chokepoint triggers can be added to the solution to provide presence and proximity detection if desired allowing for very granular detection of asset tags within a range of 25 feet to less than one foot depending on the hardware selected e No proprietary client ha
162. e 5 6 but with minimal visible footprint to the casual observer As mentioned earlier the floor plans shown in Figure 5 5 and Figure 5 6 are commonplace but by no means exclusive For example some modern building designs may possess hallway corridors that are located directly alongside the actual floor and building perimeter typically allowing a panoramic view of campus environs as visitors move about between offices and conference rooms In this case all offices and conference facilities are located within the area between the corridors and the center of the floor Figure 5 7 provides an illustration of such a floor plan Note that with this floor layout placement along the outer edge of the hallway corridor places the access points along the actual physical perimeter by default OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter5 Best Practices Location Aware WLAN Design Considerations HE Access Point Placement Figure 5 7 Perimeter Corridor Floor Plan CORRIDOR CORRIDOR o e O o je 8 224159 Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Access Point Placement W Figure 5 8 provides simple illustrations summarizing the access point placement concepts discussed in this section so far Note that designs that make use of only clustered or straight line access point placement should
163. e Based Lateration Techniques 2 3 Time of Arrival 2 3 Time Difference of Arrival TDoA 2 5 Received Signal Strength RSS 2 7 Angle Based Angulation Techniques 2 9 Angle of Arrival AoA 2 9 Location Patterning Pattern Recognition Techniques 2 11 Calibration Phase 2 11 Operational Phase 2 12 CHAPTER 3 Cisco Location Based Services Architecture 3 1 RF Fingerprinting 3 1 Location Aware Cisco UWN Architecture 3 4 Role of the Location Appliance 3 7 Location Tracking without a Location Appliance 3 9 Accuracy and Precision 3 11 Tracking Clients Assets and Rogue Devices 3 13 Client Probing 3 13 Cisco Compatible Extensions Location Measurements 3 14 WLAN Clients 3 18 802 11 Active RFID Tags 3 23 Rogue Access Points 3 29 CONTENTS Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 an E Contents Rogue Clients 3 32 Workgroup Bridges 3 35 Cisco Location Control Protocol LOCP 3 36 Asset Tag Telemetry Using LOCP 3 38 Asset Tag Notifications Using LOCP 3 41 CHAPTER 4 Installation and Configuration 4 1 Installing and Configuring the Location Appliance 4 1 Configuring Cisco WCS for Location Tracking 4 1 Configuring Location Appliance History Parameters 4 2 History Archive Period 4 2 History Database Pruning 4 3 Configuring Location Appliance Advanced Parameters 4 4 Absent Data Cleanup Interval 4 4 Memory Information 4 6 Advanced Commands 4 6 Configuring Location Appliance Location Parameters 4 7 Enable Calc
164. e Long Clicks should be checked e Number of Long Clicks 1 e Tag Reaction Parameters Send Standard Tag Transmission f Call Buttons Secondary These are identical options to those listed for Call Buttons Primary but are only available if you are using T3 asset tags g Sensors Motion These options can be used to enable the on board motion sensor if desired Temperature These options can be used to enable on board temperature sensors if desired Note that the on board temperature sensor is not supported in T2 tags with v4 3x firmware Tamper tThis option can be enabled for T3 tags only Enabling this option allows tag tamper indication to be sent to the Cisco UWN 7 In some cases the existing configuration of an AeroScout asset tag may be in question and need verification Using Tag Manager v3 04 this is a straightforward process Simply right click on any detected tag and click on Status from the pop up menu This brings up a listing of basic tag configuration parameters with further detail available by selecting Advanced Configuration as shown in Figure 6 27 Figure 6 27 Retrieving The Configuration of a Single Tag 223373 Wi Fi Location Based Services 4 1 Design Guide _ Chapter 6 RFID Tag Considerations Tag Telemetry and Notification Considerations W The preceding quick seven step configuration guide is just a short synopsis of the required steps to configure and activate AeroScou
165. e Protection ceeeeeeees No BAP IMIG aAA meson wu DANAE Unknown WTI Ta sc a ocala at anal Sictialsaaie ete miehbinie Hilisialmes sie vlan64 MANS ais Res vcore re wae oes E To ate Stel NAA Gre ANNE 64 Client Capabilities CF POllan ES eae tee eee eee Not implemented CF Poll Pogues toaono eaen nla 2s meee Not implemented SHOE Se ENT RAS ane A esecaveteteretere Imp lemented PBC Sie ened sete sewea UEC eeCabaeD peueees Not implemented Channel AGT Tiea ra a Not implemented Listen INOPIA oneen 0 Client Statistics Number of Bytes Received 00005 2816 Number of Bytes Sent cc cece cease 872 Number of Packets Received 005 19 Number of PACKETS SEM Gs rrean EDATEA 6 NUNWERLOT POHE EMOS saaa anle R E 0 Radio Signal Strength Indicator 45 dBm Signal CO NOMS RATIO aucian 55 dB Nearby AP Statistics TxExcessiveRetries 0 TxRetries 0 RtsSuccessCnt 0 RtsFailcnt 0 TxFiltered 0 antennaO 82 seconds ago 63 dBm antennal seconds AP1242 2 slot 0 4 antenna 82 seconds ago antennal seconds AP1242 3 slot 0 antenna 82 seconds ago antennal seconds AP1242 4 slot 0 antennaO 82 seconds ago antennal seconds AP1242 5 slot 0 antennaO 82 seconds ago antennal seconds 223326 In either case these techniques should be used with representative test clients or asset tags in the area where localization is desired When performing this check it is important to ensure that all acce
166. e Protocol NTP is the recommended method with which to establish a common clock source and maintain ongoing internal clock synchronization The Cisco Wireless Location Appliance contains a utility daemon known as ntpd that can act as an NTP client to an NTP server located within the enterprise network A network NTP server provides a common time source reference to all devices typically using the Coordinated Universal Time UTC standard formerly referred to as Greenwich Mean Time GMT Note In software releases up to and including Release 4 1 proper time synchronization is recommended However with Release 4 2 and beyond proper time synchronization is mandatory for proper authentication between the location appliance and WLAN controllers Complete guidance on configuring and activating the ntpd daemon on the location appliance can be found in the following document under the NTP Configuration and Synchronization for Unified Wireless Network Devices Set Up NTP on the Location Appliance section which can be found at the following URL http www cisco com en US products ps6366 products_configuration_example09 186a0080811274 sht ml setup la NTP setup information can also be found in the Cisco 2700 Series Location Appliance Installation and Configuration Guide found at the following URL http www cisco com en US docs wireless location 2700 quick guide li3 1main html wp 1057105 Additional background information and gener
167. e antenna graphics contains a blue arrow as well For omni directional antennas use unique identifying factors that are associated with the antenna such as the right angled flexible antenna connector shown at the bottom of the 2 2dBi black whip antenna in Figure 5 33 to assist in proper positioning For directional antennas use unique physical characteristics of the antenna such as the exit location of the cable for example cable exiting up or cable exiting down or other unique marks and construction characteristics Wi Fi Location Based Services 4 1 Design Guide o OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Antenna Considerations W Figure 5 33 Antenna Orientation lt 0 0 360 degrees 9 For internal antenna same angle applies to both radios 223348 In software Release 4 1 of the location aware Cisco UWN the ability to specify installed access point and antenna characteristics has been enhanced Whereas prior releases assumed all access point antennas were uniformly installed at the same height on a floor software Release 4 1 now provides the ability to account for antenna installations at varying heights In this software release the ceiling height that was configured when the floor was defined is used as the initial default for each access point However this can now be easily overridden on a per access point basis as shown in Figure 5 34 This capability allows th
168. e examine a simulated plot of a tracked device s detected RSSI as the distance between it and a detecting access point is increased see Figure 5 10 While the relationship between RSSI and distance varies depending on different combinations of antenna antenna height and environmental characteristics the graph shown in Figure 5 10 for an access point mounted at approximately twelve feet elevation can be used to better understand the concepts discussed here Figure 5 10 An Example of the Relationship Between RSSI and Distance oe an sce al 1 i i i RSSI dBm E m az ao N 325 0 20 40 60 80 100 120 Distance ft a 1 As discussed in a later section of this design guide excessive antenna heights can also contribute to diminished accuracy Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Access Point Separation W In Figure 5 10 we see that beginning at some point a fairly near the access point and ranging to another point c further in distance the two variables exhibit a strict monotonically decreasing relationship as distance between the tracked device and the access point increases the RSSI at which the access point detects the device is shown to decrease Between point a and another point b the amount of change in RSSI dBm that occurs per unit change in distance feet
169. e location appliance to incorporate varied access point antenna heights in its lateration calculations an approach that more realistically approximates installations especially in non carpeted office type environments Note that the individual height specified for an access point antennas cannot exceed the height of the floor Figure 5 34 Defining Individual Access Point Heights Position access points on Floor Area Test Lab Annex 2 Horiz Vert AP Height Zoom apizaz 4 x faz 3 24 7 jz fico Yo Save Cancel select each AP by clicking on it Update its position antenna information height and when done with all APs click on Save 223349 Note The antenna propagation characteristics of the AP1131 access point are optimal along its azimuth plane when ceiling mounted For optimal location performance when using the AP1131 it is preferred that the access point be ceiling mounted rather than wall mounted In some cases it is desirable to separate access points from antennas using a short length less than 10 feet of low loss antenna cable Reasons for this might include avoidance of obstacles or simply the desire to position access points and other active electronic infrastructure components within easy reach of local employees using commonly available ladders and stepladders This facilitates easy removal and installation of these components should they require replacement An example of this is shown in Figure 5 35 In this
170. e location appliance two days ago and the cleanup interval is set to the default value of 1440 minutes 24 hours or 1 day the station will be removed from the active location database after the expiration of the 24 hour absent data cleanup interval Note that once the device is removed from the active location database it will not be possible to scroll back and review the last known location of the device using the load location server data as old as dropdown menu control The limit of 2500 total tracked devices in the location appliance applies strictly to those devices that are in the active location database Once the total number of devices clients tags and rogues in the active database reaches 2500 additional devices cannot be tracked by this location appliance until some of the currently tracked devices contained in the active location database expire and are pruned from the database In some cases the default value for the Absent Data Cleanup Interval may be found to excessively delay the clean up of devices that have been recently removed from the tracked environment A good case in point might be a location appliance with 1500 tracked asset tags and client stations where an operator has enabled rogue location tracking in an environment with a high concentration of rogue devices If the system were to discover 1000 rogue devices for example these would be added to the active location database and would bring the total number
171. e specified for antennas that are not on the dropdown list of standard antennas This can be performed using the Other antenna option shown in Figure 5 32 Custom azimuth and elevation propagation patterns for Other third party antennas cannot be defined to either WCS or the location appliance note the loss of the antenna orientation compass in Figure 5 32 when using the Other antenna option Because of this access points that are defined as being equipped with third party antennas will not be included in coverage heat maps and will not participate in client tag or rogue on demand location tracking Figure 5 32 Specifying Other Antennas on WCS Floor Maps AIR LAP1242AG A AP Model AIR LAP12424G 4 AP Mode K9 K9 Radio 30211 E Radio 802 113 E Type Type Antenna Antenna AIR ANTS19SV R x AIR ANTS135D R AIR ANTS145V R AIR ANTS160V R Gain 0 0 dBi AIR ANTS170V R Antenna Orientation 0 180 360 degrees For internal antenna same angle applies to both radios 190579 I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations HE Antenna Considerations Since the exact propagation pattern of third party antennas cannot be specified a question often asked is whether the propagation patterns for a pre defined Cisco Systems supplied antenna can be substituted when the antenna from Cisco Sys
172. e the limits of higher or lower levels of accuracy and precision This can be useful for example when planning for future location applications or in analyzing what areas of the current environment might require additional attention For example it is quite easy for us to use both of these controls to visualize the limits of location precision at the 5 meter accuracy level using 802 11a instead of 802 11bg as shown in Figure 5 47 Figure 5 47 802 11a Location Inspection Example at 5 m Accuracy Inspect Location Quality gt Calibration Model gt Concannon Test Lab Floor Client Type Percentage of Location Errors under 5 m 16 ft X Alpharetta Campus gt Concannon Building gt Main Floor e02 11a n only client _ worst i Best a Datapoint true location X Y ft Datapoint estimated location X Y ft 63 9 0 8 Location Error ft 15 2 Timestamp Thu Oct 11 22 20 35 EDT 2007 00 40 96 a1 9d 47 51 6 9 7 Client MAC Address 223358 In the case of our test lab example in Figure 5 47 we see that the infrastructure appears to be capable of delivering 5 meter accuracy using 802 1 1a with a precision of 85 percent or better in the top two thirds of the test lab floor However the bottom area of the figure reveals that challenges exist in meeting this level of accuracy in the lower third of the floor thereby meriting further investigation The value of OL 11612 01 Wi Fi Location
173. e these buildings are all contained within the location domain of appliance 2710 2 However it would be of concern with devices migrating between any of the metro remote buildings and regional headquarters buildings 1 and 2 since the regional headquarters buildings are contained within a different location domain In cases where tracked devices may migrate between location domains at a more or less equal rate that is the rate of devices leaving a location domain is approximately the same as that of those entering and the absent data cleanup interval is left at the system default the situation illustrated above may persist for approximately 1440 minutes 24 hours If a significant degree of device migration is expected it is a good idea to tune the absent data cleanup interval to the anticipated level of migration expected at your site This will help make more efficient use of location appliance resources and help avoid the possibility of exhausting tracked device capacity I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Multiple Location Appliance Designs For example assume a situation where a particular site begins its workday with e Its location appliance s tracked device capacity at 60 1500 devices e A bi directional two device per minute migration rate clients and tags e No other tracked device additions or removals rogue tracking
174. eceiving cells provide received signal strength indication RSSI for mobile devices the use of the highest signal strength technique can improve location granularity over the cell of origin In this approach the localization of the mobile device is performed based on the cell that detects the mobile device with the highest signal strength This is shown in Figure 2 2 where the blue rectangular client device icon is placed nearest the cell that has detected it with the highest signal strength Wi Fi Location Based Services 4 1 Design Guide P22 E OL 11612 01 Chapter2 Location Tracking Approaches Distance Based Lateration Techniques _ Figure 2 2 Highest Signal Strength Technique AP1000 2 i AP1000 5 F H AaPi000 4 00 40 96 a1 9d 47 Asz AP1O00 1 AP1000 3 Using this technique the probability of selecting the true nearest cell is increased over that seen with pure cell of origin Depending on the accuracy requirements of the underlying business application performance may be more than sufficient for casual location of mobile clients using the highest signal strength technique For instance users intending to use location based services only when necessary to help them find misplaced client devices in non mission critical situations may be very comfortable with the combination of price and performance afforded by solutions using the highest signal strength approach However users requiring more precise location would f
175. ed at a time when such levels are at or near their peak For example the calibration should be performed during business hours when the facility contains a representative population of people human attenuation as well as material on shelves material attenuation If carts racks beds or other large metallic objects are normally used in this environment these should also be present during calibration If large doors are present in the environment they should be positioned as they would normally be during business hours In most cases calibrations performed during normal business hours are more likely to be representative of the levels of attenuation found in the production daily environment than off hours calibration Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Calibration W Often the most convenient time to perform a calibration may be after construction is completed but before people and contents are moved into a site Cisco Systems highly recommends against performing calibrations of such empty rooms Once these areas are stocked and occupied attempting to localize tracked devices using a RF model based on data collected in an empty and barren environment is not likely to provide optimal results When presented with a choice between calibrating when stockroom shelves are only at half capacity or at full capacity the calibration tha
176. ed services with a basic foundation in technical aspects of location tracking and positioning systems Chapter 2 Location Tracking Approaches provides substantial background information on positioning system techniques such as cell of origin time of arrival time difference of arrival angle of arrival and pattern recognition Describe and define RF Fingerprinting the technology at the heart of the location aware Cisco UWN Chapter 3 Cisco Location Based Services Architecture discusses the similarities and differences between RF Fingerprinting and other approaches described in Chapter 2 Location Tracking Approaches and how RF Fingerprinting addresses the deployment of cost effective indoor Wi Fi location tracking solutions This knowledge is useful when comparing the location aware Cisco Unified Wireless Network to other approaches for indoor location tracking Review the procedures required to install and configure a location aware Cisco UWN consisting of LWAPP enabled access points third party chokepoint triggers WLAN controllers WCS and the location appliance Provide information that aids in proper installation and understanding of some of the more advanced parameters used see Chapter 4 Installation and Configuration Describe best practices that should be followed in designing and deploying location aware wireless LANs Chapter 5 Best Practices Location Aware WLAN Design Considerations focuses on a
177. ed to 40 C The aforementioned cycle of events would reoccur culminating in the telemetry update being transmitted to the location appliance at time t 270 seconds It is important to understand why the tag telemetry is passed to the location appliance at time t 270 seconds and not at time t 180 seconds which is where we observe an SNMP poll occurring As explained earlier LOCP polling only occurs if the time delta since the last LOCP poll is 180 seconds or more At time t 180 seconds the time delta since the previous LOCP poll is only 90 seconds thus no LOCP poll occurs at that time While Figure 3 28 illustrates the simple case of a single tag passing only a single telemetry value it should be noted that LOCP is designed to efficiently transport telemetry values from multiple tags just as easily Each Information Response frame allows multiple tag MAC addresses to be specified by the controller with each MAC address being associated with one or more telemetry values For example instead of passing only temperature telemetry the tag shown in Figure 3 28 could include temperature pressure humidity and so on All of this information would be included in the Information Response transmitted at the next LOCP poll Inbound telemetry traffic from multiple tags would be aggregated by the controller in a similar fashion with each LOCP endpoint capable of performing LOCP frame fragmentation and reassembly if necessary With the exception of battery sta
178. either internal or external antennas it is highly recommended that both the placement of the access point as well as the orientation selected for the access point antennas in WCS match the actual physical access point placement and antenna orientation This helps to ensure accuracy and precision in both location tracking as well as the display of predictive heat maps The typical Cisco Aironet access point is installed using antenna diversity Antenna diversity helps ensure optimal range and throughput in high multipath environments With few exceptions it is recommended that antenna diversity always be enabled The location aware Cisco UWN is designed to take RSSI information from both access point antennas into account when localizing tracked devices For good accuracy ensure that antennas are physically present on all enabled access point antenna ports Failure to do so may cause inordinately low RSSI readings to be reported on enabled antenna ports that do not have an attached antenna The use of abnormally low RSSI from antenna ports without antennas is not conducive to good location accuracy and should be avoided Figure 5 33 illustrates how the configuration of the antenna s azimuth orientation within WCS is mapped to the actual physical orientation of the antenna The blue triangle in the azimuth compass rose shown at the right of the figure indicates how the actual antenna should be physically positioned during deployment notice that each of th
179. el 7s Ye z I Show grid 7 Show APs V Show Data Points Ey 02 11a covered E 202 11b g Covered 02 11a b g Covered Suggested Location E visited Location 190583 Keep in mind that the calibration utility is not able to recognize floor plan obstructions or hazards such as interior walls pipes racks or other structures Therefore it is not unusual to have a suggested data point crosshair appear in an area that is physically inaccessible to the operator In that case simply visit a location as close as possible to the inaccessible location and perform the calibration data collection there Make sure however that the red cross hair is positioned to correctly indicate the physical location where the data collection actually took place Calibrating Under Representative Conditions As mentioned previously the location appliance and the Cisco WCS use the information gathered during a calibration data collection to better understand the propagation characteristics present within the environment This information is culled from the aggregate of all the data points accumulated during calibration data collection To facilitate an accurate calibration it is recommended that the environment in which the calibration data collection is performed be representative of the daily production environment For environments that experience variations in the level of material and personnel present it is recommended that calibration be perform
180. ement aggregation platform for the enhanced scalability manageability and visibility of large scale implementations of the Cisco Unified Wireless Network WCS Navigator is a software based solution that enables overall management of multiple Cisco WCS management platforms regardless of their physical location Cisco WCS Navigator runs on a separate server platform with an embedded database and supports up to 20 Cisco WCS management platforms and up to 20 000 access points Additional information regarding Cisco WCS Navigator can be found at the following URL http www cisco com en US products ps7305 index html Although the maximum size of the each management domain is related to the capacity of the WCS platform managing it the maximum size of the location domain that is the number of devices tracked by a single location appliance is limited by the tracked device capacity of the location appliance In a large percentage of mid to large size deployments the standard deployment model of a single WCS management domain combined with a single location domain Figure 5 23 can meet the device tracking and management needs OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Multiple Location Appliance Designs Figure 5 23 Single Management and Location Domains ao ie a A Day o TERE ENE EnaA IEEE EEEE Campus fe
181. endor on the Cisco Compatible Extensions website indicate that the asset tag has passed stringent validation testing as part of the Cisco Compatible Extensions Program for Wi Fi tags The Cisco Compatible Extensions program for Wi Fi tags allows customers with a location aware Cisco Unified Wireless Network to benefit from the latest innovation and technology advancements offered by Cisco s technology partners Registered channel partners may view the guidelines for the Cisco Compatible Extensions Program for Wi Fi Tags at the following URL http www cisco com web partners downloads partner W WChannels download wifiguide pdf In some cases passive or non 802 11 active RFID reader interrogators may be deployed in an environment that is also serviced by a Cisco LWAPP enabled wireless network independently of the location tracking capabilities of the Cisco UWN and the location appliance These reader interrogators may be using traditional wired Ethernet as their uplink to the network or they may have an integrated Wi Fi client radio such as the case of portable RFID interrogators like those shown in Figure 6 16 Although it is not possible at this time to track the individual passive RFID tags associated with these portable RFID tag readers using the Cisco location appliance tracking the portable readers themselves is typically feasible because of their use of industry standard 802 11 client radios As long as these readers act as standard WLAN clie
182. ent band The two calibration operators may operate independently there is no need for them to visit each data point together In this way a complete calibration data collection can be performed across both bands in half the amount of time as option 1 above 1 For further information refer to CSCsh88795 CCX S36 Beacon Measurement Request Dual Band Support page 7 1 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration When a client compatible with the Cisco Compatible Extensions specification version 2 or greater is associated to the WLAN infrastructure and is specified as the calibration client in WCS the client s MAC address will be inserted into the location calibration table of all controllers servicing the access points contained on the floor being calibrated This insertion initially occurs immediately after the MAC address of the calibrating client and calibration campus building and floor are specified via WCS Maps gt RF Calibration Models gt Add Data Points After each save of a collected data point the client MAC address will be removed from the controller s location calibration table The client MAC address will then be briefly reinserted into controller location calibration tables upon each subsequent data point save and immediately removed thereafter This process repeats for each data point collected When the MAC
183. enu Step1 Begin by clicking on the admin userid as shown in Figure 4 2 Figure 4 2 Default Location Appliance User ID Cisco Wireless Control System Monitor Configure Location Administration y Help v Location Server Location Server gt Users gt AeS_Loc2 ini i gt Administration O Username Group Name Permission Maintenance gt admin Full Access Accounts v Users Groups Host Access Status gt Logs 190559 Step2 Clicking on the Admin box brings up the menu shown in Figure 4 3 which allows the password to be changed for the admin userid Wi Fi Location Based Services 4 1 Design Guide Ca OL 11612 01 Chapter4 _ Installation and Configuration Changing Location Appliance Default Passwords W Figure 4 3 Modifying the Admin Password Monitor Configure Location Administration y Help v Location Server Modify User gt admin Administration General Maintenance Username admin Password eceee Accounts Users Group Name admin Groups Permission Full Access Host Access Status Save Cancel Logs Oo iB Ej Step3 Finally change the value for the password used by WCS to access the location server application to the new value that was specified in Figure 4 3 This can be performed via Location Server gt Administration gt General Properties as shown in Figure 4 4 Note that any third party location clients that have been configured to also use the admin userid to
184. epoint MAC address and does not include any historical chokepoint information We mentioned earlier that it was observed during testing that the 802 11 multicast frame transmitted by an AeroScout T2 tag also contains eight bytes of vendor specific information Figure 6 33 illustrates this with the mandatory chokepoint information contained within the yellow rectangle and the additional vendor specific information contained within the blue rectangle Wi Fi Location Based Services 4 1 Design Guide Chapter 6 RFID Tag Considerations Chokepoint Considerations W Figure 6 33 Vendor Specific Information Included in Tag Chokepoint Transmission f 802 11 MAC Header Version O 0 Mask 0x03 Type 10 Date 0 Mask O0x0C Subtype 0000 Date Only 0 Mask OxFO Y Frame Control Flags 00000011 1 g 0 Non strict order g 0 Nom Protected Frame g 0 No More Data g 0 Power Management active mode g 0 This is not a Re Transmission g 0 Last or Unfragmented Frame g 2 Exit from the Distribution System g 2 To the Distribution System Duration 0 Microseconds 2 IJ Receiver 01 40 96 00 00 03 4 9 EJ Transmitter O0 0C CC SD 4E AS AeroScout S5D 4B AS 10 15 JJ Destination 61 2F 68 00 00 02 16 21 Seq Number 37S 22 23 Mask OxFFFO Frag Number O 22 Mask Ox0F a Source 00 00 00 00 00 00 Xerox 00 00 00 24 29 ee 0000 08 03 00 00 O1 papier Heese OC CC
185. er5 Best Practices Location Aware WLAN Design Considerations HE Location Voice and Data Coexistence Figure 5 16 Example of Location Readiness Tool Usage Cisco Wireless Control System Monitor Configure v Location Administration Help v Location Ready Note In a Location Ready region estimated locations should be within 10 meters of corresponding true locations at least 90 of the time Inspect Location Readiness gt Note The above display assumes that all interfaces of the Access Points shown are enabled 190571 Once again keep in mind that location readiness inspection is a distance based predictive tool As is the case with most predictive tools it can be expected that some degree of variance will occur between predicted and actual results Cisco recommends that the location readiness tool be used in conjunction with other best practice techniques outlined in this document including the location quality inspection Location Voice and Data Coexistence The location aware Cisco Unified Wireless Network is a multi purpose wireless platform that allows enterprises to bring consistency and efficiency to their business processes providing increased overall effectiveness A key advantage of the location aware Cisco UWN is the integration and the cost advantage that stems from its ability to perform high quality location tracking of clients asset tags and rogue devices with only reasonable additio
186. ereas the receiver address is a multicast address used by all asset tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification regardless of vendor origin The destination and source addresses shown within the 802 11 MAC header are not used by the Cisco UWN for asset tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification These are typically set to all zeroes although vendor specific usage of the destination address field by tag vendors is possible as we see with the AeroScout T2 tag shown in Figure B 1 After the frame shown in Figure B 1 is received by access points it will be transmitted to the controller s to which these access points are registered using the LWAPP protocol as shown in Figure B 2 Here we see the IP source address associated with the receiving access point and the IP destination address associated with the AP Manager interface of the controller to which the receiving access point is registered When comparing the two figures notice in Figure B 2 that Cisco Aironet access points make two modifications to the frame information prior to dispatching to the controller via LWAPP e It copies the access point s base radio MAC address base BSSID to the receiver address field in the encapsulated 802 11 header e It copies the CCX multicast address of 01 40 96 00 00 03 to the destination address field in the encapsulated 802 11 header OL 11612 01 Wi Fi Location Based Servi
187. ersus its last known position These weights are assigned as shown in Table 5 1 Table 5 1 Smoothing Factor Weight Assignments Smooth Location Positions Weight Assigned to Previous Weight Assigned to New Value Position Position Off no smoothing 0 100 Less smoothing 25 75 Average smoothing 50 50 More smoothing default 75 25 Maximum smoothing 90 10 As the weight assigned to the previous position is increased in relation to the weight assigned to the new position the amount of displayed device movement is decreased Note that the use of location smoothing will not eliminate all observed movement in the location display for that device Rather the use of location smoothing simply limits the rate at which such changes are communicated to the end user The use of location smoothing involves a small tradeoff between location viewing stability and the reaction time of the location display to changes in position For most environments the use of the default smoothing factor should provide an improved viewing experience Higher smoothing factors are best reserved for environments where there is very infrequent movement of WLAN clients and tagged assets Low smoothing factors or no smoothing may provide better results in situations where tagged assets and clients are frequently moving and in some cases experiencing constant or near constant motion Users that are primarily concerned with minimizing displayed
188. ess location history and playback information for the rogue client that is similar in format and function to that described previously for WLAN clients active RFID tags and rogue access points OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture W Tracking Clients Assets and Rogue Devices Figure 3 25 Rogue Client Detailed Information Wireless Control System cisco Rogue Client 00 16 6f 1b 4b dc Select a command z Go Client MAC Address Number of detecting APs First Heard Last Heard Rogue AP MAC Address Status Location Floor Last located at On Location Server Select a command S te to Unk Alert 00 16 6f 1b 4bide Or State tO ae eee iene 2 1 AP Containment 2 AP Containment Fri Aug 17 01 44 47 2007 3 AP Containment Fri Aug 17 01 53 13 2007 4 AP Containment 00 14 1b b6 ed cd Alert Location History Location Notifications Cisco S Site 5 gt BLD 14 gt 3rd Absence 0 floor Containment 0 Aug 16 2007 6 59 07 PM ican o All a loc 2 2 223221 It is important to understand how localization of rogue access points and clients differs from that of WLAN clients and asset tags Recall from prior discussion that WLAN clients transmit probe requests periodically across multiple channels Because infrastructure access points are spending the vast majority of their time on their assigned channels these probe
189. esses Location appliance 2710 1 is assigned to track assets within the regional headquarters complex only and location appliance 2710 2 tracks assets across all three of the metropolitan locations Note that location appliance 2710 2 does not track devices in the regional headquarters complex We can use WCS to create a single network design a set of outdoor campus building and floor maps along with access point and chokepoint placements that encompassing the entire extended campus shown in Figure 5 24 We first add in buildings and 2 and the floors that are included in each building for the regional headquarters location The 140 access points that are registered to controller WiSM 1 along with any chokepoints that are in use at the regional headquarters are assigned to this network design In addition an event notification group is created for the regional headquarters location WCS is then used to add metro remote buildings 3 4 and 5 and their respective floors The 150 access points that are registered to controller WiSM 2 along with any chokepoint triggers in the metro remote locations are assigned to this network design A separate event notification group is created for the metro remote locations The critical step in this process is not only to share the network design between both location appliances but to ensure that the WLAN controllers we wish included within the location domain of each location appliance are correctly synchron
190. esults 802 11bg TXpower 67 dBm 0 2 2 dBi 40 dB 10log 10 18 5 0 0 29 2 10 3 527 TXpower 6 07 dBm or approximately 8 dBm 802 11a TXpower 67 dBm 0 3 5 dBi 46 dB 10log 9 41 5 3 0 0 24 5 10 3 408 3 TXpower 12 58 dBm or approximately 14 dBm 1 A computer algebra system CAS capable of both symbolic and numeric calculations such as Maple Mathematica or Maxima was found to be helpful in solving such calculations See Appendix B of this document for information regarding how to use Maxima to calculate R as an approximate root of the aforementioned equation over the closed interval d 2 d OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations Location Voice and Data Coexistence Note that these power levels have been rounded upward to the next available transmit power increment available on the AP1240AG access point Since this is 1 93 dBm higher than the required transmit power to achieve our recommended 20 overlap goal at a cell signal boundary of 67 dBm we can expect that the overlap will exceed the 20 target This is acceptable as the 20 overlap is a minimum target Similarly for 802 11a the access point transmit power level of 14 dBm is 1 42 dBm higher than what is required to achieve the recommended 15 overlap once again resulting in more overlap between cells than expecte
191. et Tags Not Detected Step 1 Step 2 Step 3 Step 4 In situations where asset tags are not being detected properly despite configuration of the system in accordance with best practices re verification of proper configuration should be performed It is also recommended that verification of proper asset tag RSSI detection and message forwarding be conducted The following steps are recommended to accomplish this Verify if tag is properly detected by WLAN controllers by using the show rfid summary command Controller gt show rfid summary Total Number of RFID 12 RFID ID VENDOR Closest AP RSSI Time Since Last Heard 00 0c cc 5d 4c 5e Aerosct AP0014 6a1lb 41 0 34 24 seconds ago 00 12 b8 00 20 52 G2 AP001a al0e 2ffa 61 16 seconds ago 00 14 7e 00 30 a1 Pango AP0014 6a1b 41f0 65 2 seconds ago If the controller does not detect the tag use the command show rfid config to verify that RFID tag detection has been enabled on the controller Controller gt show rfid config RFID Tag data Collection Enabled RFID Tag Auto Timeout Disabled RFID timebot ecr ec ee r kirika 1200 seconds If the RFID tag detection is not enabled enable it using the command shown below Note that starting with the Cisco UWN software Release 4 1 RFID tag detection is enabled by default config rfid status enable Ensure that the RFID tag timeout is set to a recommended minimum of three times and a recommended maximum of eight times t
192. examination of how location for each of the different device categories are displayed by the location client present within WCS Client Probing Fundamentally the location of WLAN clients is determined based on the RSSI of probe requests detected by access points and forwarded via their registered WLAN controllers to the location appliance Therefore the probing behavior of the WLAN and rogue clients in your network can be expected to have a significant impact on the ability of the location appliance to provide accurate location tracking Because consistent and regular probing of the network is so important to good WLAN client location fidelity it is important to understand the mechanics of the process The process begins with clients issuing probe requests in order to discover the existence of 802 11 networks in their immediate vicinity An unassociated client may be seen to generate probe requests quite regularly while clients that are currently associated to a network will typically be seen to issue probe requests less often Associated clients periodically check their environment for potential access points and networks that they can roam to through a process called scanning In active scanning the client will issue probe requests to solicit probe responses from any access points in its vicinity From these responses the client forms a list of potential access point roam candidates Clients may however adopt a listen only approach and simply no
193. example may combine multiple active tag subcategories along with a passive tag into a single homogenous product Passive RFID Tags Passive RFID tags typically do not possess an onboard source of power Instead the passive RFID tag receives its power from the energizing electromagnetic field of an RFID reader or interrogator The energy coupled from the electromagnetic field undergoes rectification and voltage multiplication in order to allow it to be used to power the passive tag s microelectronics In the typical passive RFID tag design the tag cannot communicate with host applications unless it is within the range of an RFID reader Interrogators come in many forms with two common examples being handheld reader interrogators shown on the left in Figure 6 2 and large stationary models capable of reading many tags simultaneously as they pass shown in the center of Figure 6 2 Embedded sub miniature passive RFID readers and tags shown on the right in Figure 6 2 can be used in applications requiring immediate action verification Examples of this might include immediate verification of proper supply line hose connections In these types of applications passive RFID tags and microreaders embedded into hose plugs and receptacles ensure that the proper supply hoses are connected to the proper material sources at all times Should an incorrect connection be made the mismatch is detected and the system refuses to open an electromagnetic flow cont
194. exchange of timing packets between receivers In this approach time offsets between each receiver and a reference receiver can be quantized with the resulting time adjustment applied accordingly within the system Airport ranging systems are a well known example of TDoA systems in use today In the world of cellular telephony TDoA is also referred to as Enhanced Observed Time Difference E OTD and in this specific application offers an outdoor accuracy in that application of about 60 meters in rural areas and 200 meters in RF heavy urban areas ToA and TDoA have several similarities Both have proven to be highly suitable for large scale outdoor positioning systems In addition good results have been obtained from ToA and TDoA systems in semi outdoor environments such as amphitheaters and stadiums as well as contained outdoor environments such as car rental and new car lots or ports of entry Indoors TDoA systems exhibit their best performance in buildings that are large and relatively open with low levels of overall obstruction and high ceilings that afford large areas of clearance between building contents and the interior ceiling It is precisely in these open spacious environments that TDoA and ToA based systems operate at their peak efficiency and performance Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 2 Location Tracking Approaches Distance Based Lateration Techniques _ Recei
195. f the multicast frames is dependent upon the tag s configuration and the optional features supported by the tag and tag vendor In this case the length of the multicast frame shown in Figure B 1 is 72 bytes If additional features such as on board temperature sensing were enabled or if the tag were transmitting a multicast message due to stimulation from a chokepoint trigger the frame length would be greater For example a typical length for tag multicasts transmitted as a result of stimulation from a chokepoint trigger is 88 bytes The added length in this case comes primarily from the inclusion of the stimulating chokepoint trigger s MAC address and additional vendor specific information Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 AppendixB Verifying Detection of Asset Tags in WLAN Controllers Asset Tags Detection W The AeroScout T2 tag initiates Clear Channel Assessment CCA for 100 microseconds If the channel is clear it then multicasts its payload at 1 Mbps These frames are sent at 1 Mbps with the To Distribution System ToDS and Exit From Distribution System FromDS bits in the 802 11 MAC header both set to 1 Note that the Wireless Distribution System WDS four address frame format is being used indicated by the presence of the receiver and transmitter addresses in Figure B 1 The transmitter address will always indicate the MAC address of the asset tag responsible for transmitting the frame wh
196. face of the receiving antenna Path loss does not take antenna gains or cable losses into consideration Path loss represents the level of signal attenuation present in the environment due to the effects of free space propagation reflection diffraction and scattering The path loss exponent n indicates the rate at which the path loss increases with distance The value of path loss exponent depends on frequency and environment and is highly dependent on the degree of obstruction or clutter present in the environment Common path loss exponents range from a value of 2 for open free space to values greater than 2 in environments where obstructions are present A typical path loss exponent for an indoor office environment may be 3 5 a dense commercial or industrial environment 3 7 to 4 0 and a dense home environment might be as high as 4 5 The standard deviation of shadow fading s represents a measure of signal strength variability sometimes referred to as noise from sources that are not accounted for in the aforementioned path loss equation This include factors such as attenuation due to the number of obstructions present orientation differences between location receiver antennas and the antennas of client devices reflections due to multipath and so on Diversity antenna implementations reduce perceived signal variation due to shadow fading and for this reason diversity antennas are almost universally recommended In many indoo
197. ff Subject to the time constraints described in RSSI Discard Times the location appliance retains the four highest signal strength reports plus any signal strength reports that meet or exceed the value specified for RSSI cutoff The default value for RSSI cutoff is 75 dBm The application of the RSSI cutoff threshold is illustrated in the following examples e Four RSSI reports of 68dBm 70dBm 72dBm and 80dBm AII four reports are retained because they are the four highest reports e Five RSSI reports of 66dBm 68dBm 70dBm 72dBm and 74dBm Alll five reports are retained because they all meet or exceed the default RSSI cutoff threshold e Five RSSI reports of 66dBm 68dBm 70dBm 72dBm and 80dBm tThe first four reports are retained the fifth report of 80dBm is discarded because it does not meet the default RSSI cutoff threshold of 75 dBm and there already exists four other signal reports that meet or exceed the threshold Wi Fi Location Based Services 4 1 Design Guide Pas W OL 11612 01 Chapter4 _ Installation and Configuration Configuring Location Appliance Notification Parameters W Configuring Location Appliance Notification Parameters Queue Limit Retry Count The configuration of Location Server gt Administration gt Notification Parameters is discussed in Cisco Wireless Location Appliance Configuration Guide Configuring Notification Parameters at the following URL http www cisco com e
198. fication 5D33CF This represents the last 3 bytes of the asset tag s MAC address If you would like to view the multicast address and tag MAC address in their unabbreviated format issue the command no debug dot11 Dot11Radio 0 print short command at the access point console If information similar to that shown above is seen on the debug output it indicates that the access point is receiving and forwarding asset tag packets to the controller If the controller still does not show the asset tag packets being received use an ethernet protocol analyzer capable of decoding LWAPP encapsulated 802 11 frames such as WireShark or OmniPeek on the LWAPP ethernet connection between the access point and controller to verify that the asset tag packets are indeed reaching the controller The format of these packets should similar to that shown in Figure B 2 If these packets are seen on the protocol analyzer trace and the controller still does not indicate that asset tag packets are successfully received capture all the details collected so far including the protocol analyzer traces and contact the Cisco Technical Assistance Center for further debugging assistance If the tag multicast messages are not seen in the access point debug output use an RF protocol analyzer such as OmniPeek or WireShark to verify that asset tags are indeed successfully transmitting packets in the format expected on all three 2 4 GHz channels or the channels that your infrast
199. g solutions that rely on client side RSSI measurements must take extra steps to avoid location inaccuracies that may be due to inconsistent mobile device hardware Since it is not realistic to assume that every mobile device will be provided by the same hardware vendor a method of equalizing any variations in relation to some assumed reference model is necessary For example assume that a particular positioning system expects to see reported RSSI in a range from 127dBm to 127dBm in 254 increments of 1 dBm each Mathematical compensation will be required if only some mobile devices in the system can support this expectation for example other devices in the system may only be able to report RSSI in a range from 111dBm to 111 dBm in 74 increments of 3dBm each Typically the responsibility for providing such equalization lies with the provider of the location solution It is common to see such adjustments made through proprietary client software that installed on each mobile device in order to ensure all mobile devices can be located with approximate equal consistency Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter2 Location Tracking Approaches Angle Based Angulation Techniques oO To date implementations using RSS lateration have enjoyed a cost advantage by not requiring specialized hardware at the mobile device or network infrastructure locations This makes signal strength based lateratio
200. ge uniformity and proper cell to cell overlap are the predominant concerns This has been driven by increasing interest in deploying new wireless applications such as wireless voice with its intolerance jitter and high roaming delays In a similar fashion deploying location based applications using a Wi Fi wireless LAN requires augmenting our traditional approaches both in the design of greenfield location aware installations as well as the augmentation or retrofit of existing designs This chapter describes best practices that should be followed in designing and deploying location aware wireless LANs and includes the following main sections e Minimum Signal Level Thresholds page 5 2 e Access Point Placement page 5 5 e Access Point Separation page 5 12 e Determining Location Readiness page 5 18 e Location Voice and Data Coexistence page 5 20 e Avoiding Location Display Jitter page 5 31 e Multiple Location Appliance Designs page 5 32 e Antenna Considerations page 5 44 e Calibration page 5 48 e Inspecting Location Quality page 5 64 e Using Test Points to Verify Accuracy page 5 68 Wi Fi Location Based Services 4 1 Design Guide I oL 11612 01 EN Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Minimum Signal Level Thresholds Minimum Signal Level Thresholds AS For mobile devices to be tracked properly a minimum of three access points with four or more preferred for better accurac
201. gn Guide oL 11612 01 E 5a Chapter5 Best Practices Location Aware WLAN Design Considerations HE Antenna Considerations example of this for two tracked asset tags 00 0C CC 73 14 D9 and 00 0C CC 73 2A 4D As described in the preceding section judicious adjustment of the Absent Data Cleanup Interval can be used to reduce the lifetime of duplicate entries and help mitigate this condition Figure 5 31 Duplicate Devices in WCS Navigator Due to Device Migration n Navigator Monitor Reports Configure Administration Help Search Tag Search Results Modify Search Go Advanced Search MAC Addr wcs Asset Name pee Asset Group Vendor Loc Server Controller Status Map Location For Alpharetta PERRE EN RE iaa Campus gt AP1242 Tas E 00 0c cc Se 8d cce WCS2 Aeroscout Loc2 10 1 96 16 80 ampuszAPL a A 2 Criteria Edit PEE pharetta Select New or Saved z Naca aa p Eos Campus gt AP1242 0O0 0c cc 73 14 d9 WCS 2 Aeroscout Loc2 10 1 96 16 80 Buildin sTest LAR ANNE Alpharetta QO0 Occe 73 2a 4d WCS2 Aeroscout Loc2 10 1 96 16 80 Campus gt AP1242 Building gt Test Lab Annex 2 Roswell gt ra 0 8 lt sdi 90 wcsi Aeroscout Loci 10 1 96 18 80 rite a mh q gt Te 00 0c cc 5e 8 Roswell om x gt 42 te Ja n i p 1 1 9 gt Campus gt AP1242 ee wes 1 Aeroscout Loci 10 1 96 18 80 Building gt Test Lab Roswell 3 18 ba WCS1 Aeroscout Loci 10 14 96 18 ia Building gt Test Lab Roswell
202. h floor Cisco S Site 5 gt BLD 14 gt 4th floor Cisco S Site 5 gt BLD 14 gt 4th floor Change selection every Ere Play Stop Client Statistics Calculated Wed Aug 15 10 26 33 EDT 2007 Data Collected ce Cisco S Site S gt BLD 14 gt 4th Bytes received 698622 floor Bytes sent 170998 gt Packets received 24165 z mE 7 ezi E Packets sent 548 Hii aE oo Policy errors 0 Se aR Sas RSSI 60d8m SNR 32 RF Properties AP Name AP Type AP Base Radio MAC EOT Protocol AP Mode SSID Association Id 802 11 State Associated Reason Code Mobility Role Unknown 802 11 Authentication Policy Manager Status Code State Anchor Address 0 0 0 0 CF Pollable ccx vs CF Poll Request E2E Not Supported Short Preamble PBCC Security Channel Agility Timeout Authenticated No WEP State Policy Type Unknown Encryption Cypher 5 EAP Type Unknown E Select a command z Go 00 40 96 a8 aa f5 Wed Aug 15 10 21 44 EOT 2007 14 41b ap5 Cisco AP 00 15 c7 a9 43 10 802 114 local 10 0 0 i Not implemented Not Implemented Not Implemented Not Implemented Not Implemented 0 ENABLE 223311 In many cases it is desirable to sequentially display the location history of a client device in order to better visualize and trace the movement of the client throughout the environment over time This can be very useful for example in security and monitoring applications Cisco WCS and the location appliance make it possible t
203. hat already collected In order to proceed with further test point data collection and analysis it is recommended that the device MAC address be stopped or the Clear Logs option be used The Clear Logs option clears all test point data logs and resets any assigned test point devices Keep in mind that clearing the logs will delete not only the test points created by the current user but those test points created by any other users that are logged in and authorized to make use of the test point facility as well In software Release 4 1 the Analyze option performs its calculations in regard to a single device MAC address at a time If multiple device MAC addresses are added as test points examine the test point data for each device MAC address individually by highlighting the MAC address of the device in the drop down selector and then clicking on Analyze Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 CHAPTER RFID Tag Considerations This chapter has the following main sections e RFID Tag Technology page 6 1 e Using Wi Fi RFID Tags with the Cisco UWN page 6 15 e Tag Telemetry and Notification Considerations page 6 27 e Chokepoint Considerations page 6 31 RFID Tag Technology amp The majority of RFID tags produced today are passive RFID tags comprised basically of a micro circuit and an antenna They are referred to as passive tags because the only time at which they are activel
204. he Cisco UWN W Figure 6 15 Chokepoint Out of Range Timeout Location Server gt Location Parameters gt AeS_Loc2 Location Parameters Enable calculation time I Enable Enable OW Location I Enable Relative discard RSSI time BE minutes Absolute discard RSSI time feo minutes RSSI Cutoff 75 dBm Smooth Location Positions More smoothing new value weighted less x Chokepoint Usage VV Enable Chokepoint Out of Range Timeout jo seconds 223366 Save Cancel Using Wi Fi RFID Tags with the Cisco UWN Compatible RFID Tags An often asked question revolves around whether the Cisco Location Appliance can be leveraged to track RFID tags that already are being deployed by product and durable goods manufacturers as part of a larger business initiative Often applied en masse to manufactured or distributed goods these tags are most commonly passive RFID designs but in the case of some durable high cost goods active RFID may also be used In many cases products and goods are being tagged at the time of production or initial distribution in compliance with mandates set forth by large commercial or governmental entities The answer depends on the type of RFID tag being used As of Cisco UWN software Release 4 1 only 802 11 Wi Fi active RFID tags or multimode asset tags containing 802 11 Wi Fi active RFID capabilities can communicate directly with Wi Fi access points including Cisco Wi Fi access points At th
205. he currently reported location vector x y and each location vector in the calibration radio map as follows d Ja x Olah eek The physical coordinates F associated with the database location vector possessing the minimum Euclidean distance from the reported location vector of the mobile device is generally regarded as being the correct estimate of the position of the mobile device In a similar fashion to RSS lateration solutions real time location systems using location patterning typically allow vendors to make good use of existing wireless infrastructure This can often be an advantage over AoA ToA and TDoA approaches depending on the particular implementation Location patterning solutions are capable of providing very good performance in indoor environments with a minimum of three reporting receivers required to be in range of mobile devices at all times Increased accuracy and performance often well in excess of 5 meters accuracy is possible when six to ten receivers are in range of the mobile device Location patterning applications perform well when there are sufficient array entries per location vector to allow individual locations to be readily distinguishable by the positioning application However this requirement can also contribute to some less than desirable deployment characteristics With location OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter2 Location Tracking Approaches Loca
206. he longest tag transmission interval found in the tag population inclusive of stationary as well as any in motion tag transmission intervals The valid range of values for this parameter is 60 to 7200 seconds and the default value is 1200 seconds For example Controller gt config rfid timeout 1200 Check that the RSSI expiry timeout are set as follows Controller gt show advanced location summary Advanced Location Summary Algorithm used Average Client RSSI expiry timeout 150 sec half life 60 sec Calibrating Client RSSI expiry timeout 30sec halflife 0 sec Rogue AP RSSI expiry timeout 1200 sec half life 120 sec RFID Tag RSSI expiry timeout 1200 sec half life 120 sec If the values are different from default as shown above set them to default using the following configuration commands config advanced location expiry calibrating client client rogue aps tags lt seconds gt Wi Fi Location Based Services 4 1 Design Guide lt OL 11612 01 AppendixB Verifying Detection of Asset Tags in WLAN Controllers Step 5 Asset Tags Not Detected Hil config advanced location rssi half life calibrating client client rogue aps tags lt seconds gt If asset tags are still not detected by the controller using the show rfid summary command enable the following debugs on the controller debug mac addr lt tag mac addr gt debug dot11 rfid enable 00 0c cc 5e 82 8d Parsing Cisco Tag RFID
207. he recommended best practices found in the Voice Over Wireless LAN 4 1 Design Guide suggest that the cell to cell overlap should be approximately 20 percent when using 802 11bg and approximately 15 percent when using 802 1 1a Figure 5 17 20 Inter Cell overlap Overlap Data applications on the other hand typically do not display the same level of sensitivity to packet loss as do voice applications hence they seldom require the same degree of cell to cell overlap In most cases a minimum 10 cell to cell overlap is sufficient for reliable roaming with data applications as illustrated in Figure 5 18 High speed data applications and applications combining voice and data capabilities in a single device smartphones for example may require cell to cell overlap that resembles a VOWLAN design much more than a data design Figure 5 18 10 Inter Cell Overlap Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Location Voice and Data Coexistence Ii Although they are possible and do exist network designs for the location aware Cisco UWN performed with only location tracking as a use case represent a minority of all Cisco mobility customer installations Therefore the designer striving towards completing an optimized location design is likely to be attempting to satisfy the four primary concerns of VOWLAN and data WLAN designers concurrently The
208. hen in proximity of high speed activators thereby triggering a debit to the user s account for the toll charge A relatively new development has been the introduction of multimode RFID tags that leverage multiple location technologies Multimode tags offer the functional equivalent of having assets equipped with several individual tags in one physical package This can be very useful when assets must travel outside of a single enterprise closed loop system into other systems where the same type of location tracking technology may not be in use For example consider the case where reusable shipping containers must be tracked at a manufacturer a distributor and a retailer using a combination of IS024730 2 TDoA 802 11 Wi Fi Active RFID and passive RFID A multimode tag could offer all three of these technologies in a single small form factor low power draw package Such a device may also include the capability to use tag magnetic signaling proximity communication devices as well This can offer distinct advantages in terms of management maintenance and overall ease of deployment especially when compared to equipping assets with three or more physically separate RFID tags Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter6 RFID Tag Considerations RFID Tag Technology W Multimode tags of this nature have been made much more feasible by the availability of highly integrated tag OEM silicon that combines two or more dis
209. here it is necessary to ensure that a high percentage of packets are successfully decoded in each cell and jitter is kept to a minimum For example with a Cisco 7921G VoWLAN handset the recommended SNR to ensure a good user VoWLAN experience is 25 dB Keep in mind that if the signal to noise ratio is insufficient due to a high noise floor proper operation of the wireless device may be difficult to achieve in spite of high overall received signal levels SNR and minimum received signal levels should be considered together in order to assure that a new deployment has met design standards and is ready for production pilot testing e Data rate Data bit rates are enabled or disabled via the wireless infrastructure with minimum signal level thresholds and the signal to noise ratio determining which of the enabled bit rates will actually be usable For example with the Cisco 7921G the combination of a 67dBm minimum signal level and a 25dB signal to noise ratio generally makes the use of 24 Mbps or greater data rates possible e Cell to cell overlap In a very simple sense we can think of each of our access points as residing at the center of an RF cell with a spherical boundary of RF coverage around them Our primary interest is in the coverage boundary associated with our desired minimal signal threshold In order to provide consistent coverage and availability across our floor each of our cells should join with each adjacent cell at a coverage b
210. hese tags are assumed to have left the chokepoint and are reverted back to being localized using standard RF Fingerprinting techniques Chokepoint Trigger Traffic Considerations Beginning with Cisco UWN software Release 4 1 tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification can use a consistent method to inform the UWN that they are within or have left the proximity of a chokepoint trigger Once received by access points and forwarded to registered controllers this information is passed to the location appliance using LOCP Measurement Notifications which have already been described in Cisco Location Control Protocol LOCP page 3 36 The length of each 802 11 tag multicast frame transmitted in response to stimulation received from a chokepoint trigger is approximately 63 bytes which includes only a single chokepoint MAC address and does not include any historical chokepoint information The length of the frame could increase due to the inclusion of a historical list of chokepoints traversed or it may be larger than 63 bytes due to vendor specific information that may be included in the frame For example during lab testing with Wi Fi Location Based Services 4 1 Design Guide lt OL 11612 01 _ Chapter 6 RFID Tag Considerations Chokepoint Considerations W AeroScout T2 tags it was observed that the typical size of the tag multicast frame emitted when in proximity of a chokepoint trigger is app
211. highlighted with colored rectangles are very similar to that of the broadcast Radio Measurement Request discussed previously in this document However Cisco Compatible Extensions Location Measurement broadcasts Radio Measurement Requests to all associated clients whereas during calibration data collection Radio Measurement Requests are unicast only to calibration client MAC addresses that are contained in WLAN controller location calibration tables For example in Figure 5 36 we see that the MAC address we are unicasting the Radio Measurement Requests to is 00 40 96 A1 9D 47 Calibration clients that are compliant with the Cisco Compatible Extensions specification version 1 or not compliant with the Cisco Compatible Extensions specification at all will not respond to unicast radio measurement requests Instead these clients will be forced to re associate and re authenticate in order to generate probe requests If the Cisco Compatible Extensions Location Measurement parameter discussed in the section entitled Tracking Assets and Devices in the Cisco UWN is enabled on a controller for which a Cisco Compatible Extensions specification version 2 or greater client is being used for calibration the calibration client should respond to both the broadcast request used for Cisco Compatible Extensions Location Measurement as well as the unicast Radio Measurement Requests used for calibration amp Note The Cisco Aironet 802 11a b g Wireless CardBus
212. his for co located access points in a lecture hall for example would be to place the access points on different walls and perhaps the ceiling as well with appropriate inter access point spacing In general then most indoor location tracking deployments with access point antennas installed at heights of between ten and twenty feet can be well served with an inter access point spacing of between 40 and 70 feet especially when combined with the signal threshold and access point placement recommendations suggested in the preceding sections of this document In some cases however inter access point spacing below 40 feet may be necessary to satisfy the requirements of some applications for high signal strength thresholds especially in environments where high path loss is present An example of this might be a voice application deployed in such an environment for example a path loss exponent of 4 0 where a high degree of environmental clutter is present Best practices for Cisco 7921G VoWLAN deployments would suggest a minimum signal level of 67dBm 20 inter cell overlap and signal to noise ratio of 25 dB for 802 11g in this type of situation Applying these requirements mathematically we calculate an estimated cell size of 24 feet and an inter access point spacing of 33 feet In this case in order to deploy our voice application in accordance with recommended 1 Note that any realized increase in bandwidth from co located access points is subject to
213. hould be enabled only on the recommendation of the Cisco Technical Assistance Center TAC or Cisco Engineering because it adds overhead to the location calculations OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter 4 Installation and Configuration Hs Configuring Location Appliance Location Parameters Enable OW Outer Wall Location Although the WCS Map Editor allows interior walls to be placed within floor maps the location appliance only takes into consideration up to 50 heavy walls when evaluating path loss models and conducting positioning calculations Heavy walls are those defined in the Map Editor with attenuation values of 13 dB When the Wall Usage Calibration parameter in WCS Monitor gt Maps gt Properties gt Wall Usage Calibration is set to Auto the location appliance will dynamically determine whether to use the attenuation introduced by heavy walls during the calculations performed as part of the calibration process The system administrator can however opt to include heavy wall attenuation in all cases by setting this parameter to Use Walls or disable the use of heavy walls entirely by setting it to Do Not Use Walls Enable OW Location is a parameter that was used with software releases prior to release 4 0 of the Cisco UWN i e prior to Release 2 1 of the Cisco Wireless Location Appliance Enable OW Location is still displayed on the Location Server gt A
214. ice environment In properly designed indoor installations where increased attenuation may be a factor contributing to less than optimal location accuracy a site calibration may help restore lost performance When an on site calibration is performed the system is allowed to sample path losses from known points throughout the environment allowing it to formulate a custom RF model that provides a better understanding of the propagation characteristics specific to that environment 1 A third RF calibration model is provided for designers wishing to attempt outdoor deployments using the Cisco Wireless Location Appliance This white paper does not address outdoor location design guidelines at this time Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Calibration W In many cases using the information collected during calibration instead of a default model can markedly reduce the degree of error between reported and observed client location In environments where many floors share almost identical attenuation characteristics such as the floors of a library containing similar arrangements of book shelves for example these strong similarities may allow for the RF model created by a calibration performed on any one of the floors to be applied to all floors with good results Calibration is actually a multi step process that begins with the definition of
215. ies that its partner is active and ready to accept requests by participating in Echo Request Response control message exchange as shown in Figure 3 26 If a location appliance detects that a WLC is no longer responding it will temporarily disable any other requests to that WLC until the WLC becomes active again The connection between the location appliance and the WLC can be maintained for multiple exchanges the typical case or can be initiated and disconnected for each data request The basic parameters controlling the LOCP session between the location appliance and the WLAN controllers defined to it are specified using the Location Servers gt LOCP Parameters panel as shown in Figure 3 27 Figure 3 27 Setting LOCP Session Parameters ahali Wireless Control System cisco Monitor Reports Configure Location Administration Help v Location Server Location Server gt LOCP Parameters gt AeS_Loc2 TO ee LOCP Parameters Advanced Echo Interval 1 120 fis seconds Advanced Parameters Location Parameters Sarad Daad Interval ta so seconds Notification Parameters meee Response Timeout ft seconds SSS Retransmit Interval fa seconds aintenance Maximum Retransmits E Accounts SAR ave ance L ogs 4 cy The meaning of the LOCP session parameters shown in Figure 3 27 are as follows e Echo Interval The minimum time interval in seconds between echo requests sent from the location appliance to the WLAN controller
216. ility Position Test Point on Floor Main Floor Debug In Location Server MAC Addr Horiz a Location Server E es_Loct i J Save Eer Client L List Ga Preview Clear Logs 00 40 96 a1 9d 47 Microsoft Internet Explorer x Success Total test points 91 Percentage accurate 99 7 Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 nE O 223359 Chapter5 Best Practices Location Aware WLAN Design Considerations HI Using Test Points to Verify Accuracy When using the test point facility keep in mind the following Advanced Debug must be enabled on WCS prior to attempting to use the test point facility If Advanced Debug is not enabled on WCS the Position Test Point option will not appear in the dropdown menu located at Monitor gt Maps gt floor map name Although it is a recommended best practice to enable the Advanced Debug on the location appliance prior to using the test point facility it will be enabled automatically whenever a test point is added using the Save option The Preview option is used to position the red cross hair on the Position Test Point floor map only when the user is directly specifying horizontal and vertical x y coordinates This is done instead of manually positioning the red crosshair to the test point s actual location The preview capability is provided so that graphical indication of the location corresponding to the x y coordinates
217. ination port 16113 LOCP Information Requests are the primary mechanism used in software Release 4 1 to conduct LOCP polling e Information Response Sent periodically by each WLAN controller in response to the receipt of a LOCP Information Request frame LOCP Polling The basic size of a LOCP Information Request Ethernet frame for a controller that has not detected any tags is 113 bytes If one tag is detected this frame size will increase to 144 bytes and for two tags it will increase to 175 bytes these frame sizes do not include any telemetry data Frame sizes will increase based on the number of tags currently active in the controller s database as well as the amount of telemetry that has been collected Support for fragmentation and reassembly of combined tag payloads is inherently to LOCP To ensure proper LOCP operation between the location appliance and any WLAN controllers defined to it ensure that port 16113 is not blocked by any firewalls or other security devices When designing solutions that will rely on the reporting and collection of tag telemetry with Release 4 1 there are a few considerations that should be kept in mind 1 Telemetry Timing Since in Release 4 1 telemetry is aggregated on a per tag basis by WLAN controllers and passed to the location appliance only during a periodic LOCP polling cycle users of software Release 4 1 should not rely on the receipt of tag telemetry to be real time in nature It is reasonable to e
218. ind that immediately after installation and for a period of time after it is reasonable to see a fair degree of RRM activity as the system settles in and final parameter selections are made At the conclusion of this settling in period the system designer should ensure that the choices made by RRM are inline with the overall expectations of the design Once the system has settled there should be little to no change in RRM managed parameters over time as barring any significant environmental or equipment changes the selections made for access point transmit power levels should remain fairly static Any indication of constant fluctuation in assigned access point transmit power levels or channels should be regarded by the system administrator as potential indication of other anomalies that may be developing within the environment The root causes behind such frequent fluctuations should be investigated and addressed promptly Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Figure 5 21 Location Voice and Data Coexistence Hi Note A comprehensive discussion of the mechanics of RRM is beyond the scope of this document For information of this nature it is highly recommended that readers refer to Radio Resource Management under Unified Wireless Networks document which can be found at the following URL http www cisco com en US tech tk722 tk
219. ind the inability of the highest signal strength technique to isolate the location of a mobile device with finer granularity than that of an entire coverage cell to be a serious limitation These users are better served by those approaches using the techniques of lateration angulation and location patterning that provide finer resolution and improved accuracy These techniques are discussed in subsequent sections 190535 Distance Based Lateration Techniques Time of Arrival Time of Arrival ToA systems are based on the precise measurement of the arrival time of a signal transmitted from a mobile device to several receiving sensors Because signals travel with a known velocity approximately the speed of light c or 300 meters per microsecond the distance between the mobile device and each receiving sensor can be determined from the elapsed propagation time of the Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 EN Chapter2 Location Tracking Approaches Hi Distance Based Lateration Techniques Figure 2 3 signal traveling between them The ToA technique requires very precise knowledge of the transmission start time s and must ensure that all receiving sensors as well as the mobile device are accurately synchronized with a precise time source From knowledge of both propagation speed and measured time it is possible to calculate the distance D between the mobile device and the receiving station D
220. ine position on the basis of the following e Cell of origin nearest cell e Distance Jateration e Angle angulation e Location patterning pattern recognition An RTLS designer can choose to implement one or more of these techniques This may be clearly seen in some approaches that attempt to optimize performance in two or more environments with very different propagation characteristics The popularity of this approach is such that it is often not unusual to hear arguments supporting the case for a fifth category that encompasses RTLS offerings that sense and measure position using a combination of at least two of these methods Keep in mind that regardless of the underlying positioning technology the real time nature of an RTLS is only as real time as its most current timestamps signal strength readings or angle of incidence measurements The timing of probe responses tag transmissions and location server polling intervals can introduce discrepancies between the actual and reported device position observed during each reporting interval OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter2 Location Tracking Approaches W Cell of Origin Cell of Origin One of the simplest mechanisms of estimating approximate location in any system based on RF cells is the concept of cell of origin or associated access point in Wi Fi 802 11 systems as shown in Figure 2 1 Figure 2 1 Cell of
221. information updates have not been received by the location appliance meeting the ADCI time criteria will be removed In our example this means that not only would our unwanted rogues be removed but so would any clients or asset tags for whom we have not received any updates in the last sixty minutes as well Such behavior could prove surprising to location client users that have come to depend on a 24 hour window of prior location information in order to locate lost assets for which current location information is not available In lab testing it was found that the use of the location history database can partially mitigate this in cases where tracked devices have been removed from the active location database but are later re detected by the UWN In such cases any prior collected location history records will once again be available unless their history archive period has expired and the history records themselves have been pruned History records for devices that have been deleted from the active location database but have not been re detected by access points will not be accessible via location clients In some cases it may be desirable to alter the default value for Absent Data Cleanup Interval on a more permanent basis One example of such a case might be an facility that employs location tracking but has a large number of transient Wi Fi devices such as client laptops PDAs and so on residing onsite only a few hours before moving on a
222. ing Cisco IOS Release 12 4 3g JA or greater on 32 MB access points or Cisco IOS Release 12 3 8 JEB or greater on 16 MB access points can be configured for workgroup bridge mode Note For further information about the configuration of workgroup bridges and their role in the Cisco UWN refer to The Workgroup Bridge in a Lightweight Environment located at the following URL http cisco com en US docs wireless access_point 12 4_3g_JA configuration guide s43hot html wp1 059452 The default roaming behavior for workgroup bridges is to delay active scanning for potential access point roam candidates until the WGB has lost its association While such behavior may be perfectly acceptable when workgroup bridges are used in stationary applications it can cause concern in mobile WGB applications such as a mobile cart based array of Ethernet only medical equipment because of the following e Delaying the search for potential access point roam candidates until association is lost can introduce unnecessary application delays which may negatively the performance of mobile timing sensitive applications and cause application lockups or time outs e Depending on the environment mobile workgroup bridges may move about for considerable distances while associated to the same access point In this case the default WGB behavior will result in an absence of probe requests causing the location appliance to rely on stale probe request RSSI information and p
223. ion Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations E RFD Tag Technology Figure 6 7 Semi Passive RFID Tags 190594 Several varieties of semi passive RFID tags exist with and without onboard NVRAM real time clocks and various types of environmental sensors Semi passive RFID tags also support interfaces to tamper indicators shock sensors and so on Common applications of semi passive RFID tags include but are not limited to vehicle asset tracking security access systems supply chain automation cold storage management and hierarchical asset tracking systems Active RFID Tags Active tags are typically used in real time tracking of high value assets in closed loop systems that is systems in which the tags are not intended to physically leave the control premises of the tag owner or originator Higher value assets can usually justify the higher cost of the active tag and presents strong motivation for tag reuse Medical equipment electronic test gear computer equipment reusable shipping containers and assembly line material in process are all excellent examples of applications for active tag technology Active RFID tags see Figure 6 8 can provide tracking in terms of presence positive or negative indication of whether an asset is present in a particular area or real time location Active RFID tags are usually physically larger than passive RFID tags Most RTLS systems are based on the use of active RFI
224. ion Interval 223391 Note that each vendor maintains their set of software tools necessary for configuration of their chokepoint triggers These software configuration tools are not interoperable between vendors for example AeroScout software configuration tools cannot be used to configure WhereNet chokepoint triggers or vice versa In general the individual configuration of each vendor s chokepoint trigger device is beyond the scope of this white paper This document does however attempt to shed light on specific chokepoint trigger configuration parameters that are of particular significance in solving design challenges As necessary the topical sections of this document make reference to such parameters as necessary However complete and detailed configuration information relating to the specific configuration of each vendor s chokepoint trigger can be found in the appropriate vendor s documentation Available from AeroScout Corporation AeroScout EX 3100 Exciters AeroScout Exciter EX 3100 User Manual AeroScout EX 3100 Exciter Manager User s Manual AeroScout EX 3200 Exciters AeroScout EX 3200 User Guide AeroScout EX 2000 Exciters AeroScout Exciter EX 2000 User Guide The following reference manuals are recommended for configuration of AeroScout EX 2000 and EX 3200 Exciters using either the AeroScout System Manager or the AeroScout Network Exciter Manager ANEM The AeroScout Network Exciter Manager is a
225. ion client The Cisco Location Appliance is also capable of issuing northbound notifications to external systems via email SMTP syslog SNMP traps or the SOAP XML protocol The issuance of these northbound notifications is dependent on the occurrence of one or more of a variety of events and is discussed in further detail within subsequent sections of this document Wi Fi Location Based Services 4 1 Design Guide E OL 11612 01 Chapter3 Cisco Location Based Services Architecture Role of the Location Appliance W Role of the Location Appliance The location aware Cisco UWN can be broken down into four basic component groups as shown in Figure 3 4 Figure 3 4 Components of the Location Aware Cisco UWN Location Client SOAP XML ea A CS Location eve SOAP XML X Appliance Control Client Location Client PP lt Location Server A Wireless LAN A Controllers EP Eee wnat WAPP AccessPoint AccessPoint MecesePoint LF Zz T AR I I l l l l I l l l I I l i l I ia s l l I l l l I I l 223303 e Location Client The primary role of the location client is to serve as the user interface to the location and asset information contained on the location server One or more location clients may receive information on a request basis pull mode or they may assume a listening role awaiting regular transmissions of information from the locat
226. ion server based on pre defined criteria push mode e WCS WCS serves as the default location client to the location appliance providing location display capabilities that can satisfy most IT centric and network monitoring requirements The inherent flexibility afforded by the location appliance API allows for third party location clients to reside in the UWN in a complementary fashion to WCS These third party products may provide a very business focused UI that concentrates on the management of assets and de emphasizes the details of RFID localization and network management e Control Client The control client is capable of administering the location server as well as reading or writing all location and configuration data on the location server In the location aware Cisco UWN the role of control client is performed by the Cisco WCS The control client s primary function is to populate the server with information about the physical environment network designs floors maps calibration models access point locations etc and the network elements that should be monitored The control client may also have management capabilities over one or more of the location servers deployed in the network Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 37 Chapter3 Cisco Location Based Services Architecture HI Role of the Location Appliance e Location Server The location server provides general location services for a
227. ions that are sent periodically based on the expiration of a tag transmission interval It should also be noted that this calculation yields the maximum possible value for LOCP Information NotificationsSroraz as it assumes that all notification repetitions coming from the tag are successfully detected by all access points included within Detecting APSToTAL and none are dropped due to interference contention or other RF anomalies Using our formula we can calculate the expected number of LOCP Information Notifications that will be generated if the call button is depressed once on an asset tag compliant with the Cisco Compatible Extensions for Wi Fi Tags specification within the following Release 4 1 environment e Two WLAN controllers e Three access points registered to each controller for a total of six detecting access points e Tags send one notification for each call button depression on each of channels 1 6 and 11 Substituting this information into the aforementioned equation we see that 6 or 6 total LOCP Information Notifications will be transmitted from the WLAN controllers to the location appliance in this example Note that although both WLAN controllers will be sources of LOCP Notifications in this example the number of WLAN controllers present in the environment has no bearing on the number of LOCP Notifications that will be sent to the location appliance We could have substituted three WLAN controllers with two access points registe
228. is time most commonly available pure passive RFID tags or non Wi Fi active RFID tags are not capable of communicating with the location aware Cisco UWN and the Cisco Wireless Location Appliance Of the available 802 11 Wi Fi active tag designs currently on the market not all are compliant with the Cisco Compatible Extensions for Wi Fi Tags specification Non compliant asset tags from PanGo InnerWireless and AeroScout Ltd can be recognized by the location aware Cisco UWN However these tags will not be able to make use of the advanced features in the Cisco Compatible Extensions for Wi Fi Tags specification and introduced in Release 4 1 Non compliant asset tags from vendors other than PanGo Networks and AeroScout are not supported for use with the Cisco Wireless Location Appliance To determine whether a Wi Fi active RFID tag is compatible with the Cisco Compatible Extensions for Wi Fi Tags specification and capable of taking advantage of the advanced features of the location aware Cisco UWN the Cisco Compatible Extensions website http www cisco com web partners pr46 pr147 ccx_wifi_tags html should be consulted A current listing of all tags and tag vendors compatible with the Cisco Compatible Extensions for Wi Fi Tags specification may be found there OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations HI Using Wi Fi RFID Tags with the Cisco UWN The listing of the tag and tag v
229. istance Center because longer history periods typically increase the amount of space consumed by the location history database Because newer history data within the archive period does not overwrite older data the combination of a large number of devices an injudicious selection of history categories and an excessive history archive period can increase the risk of exhausting available free space To illustrate this point we can compare the amount of disk storage that is consumed when selecting one combination of history category archival period and archival interval versus another To do this let us assume an environment consisting of 1100 WLAN clients 300 asset tags 20 rogue access points and 30 rogue clients Figure 4 1 illustrates the effect on consumed disk storage of the following e Increasing the default archive period to 365 days for all device categories e Reducing the default history archive interval for clients mobile devices and asset tags to 60 minutes Wi Fi Location Based Services 4 1 Design Guide P42 E OL 11612 01 Chapter4 _ Installation and Configuration Configuring Location Appliance History Parameters E Figure 4 1 Impact of History Interval and Archive Period on Database Size Location History Location History bytes bytes Number of Mobile Devices 1100 28 248 000 Number of Mobile Devices 1100 2 062 104 000 History Interval 360 mins History Interval 60 mins Archive Period 30 days Arch
230. ive Period 365 days Number of Tags 300 1 296 000 Number of Tags 300 189 216 000 History Interval 720 mins History Interv al 60 mins Archive Period 30 days Archive Period 365 days Number of Rogue APs 20 117 600 Number of Rogue APs 20 1 430 800 History Interval 720 mins History Interv al 720 mins Archive Period 30 days Archive Period 365 days Number of Rogue Clients 30 118 800 Number of Rogue Clients 30 1 445 400 History Interval 720 mins History Interv al 720 mins o Archive Period 30 days Archive Period 365 days A 29 780 400 bytes 2 254 196 200 bytes 5 Although the estimates shown in Figure 4 1 are only an approximation they do not account for per record display string sizes and database overhead for example you can see that database size increases from about 30 MB to over 2 25 GB because of these changes in location history alone The database backup mechanism on the location appliance requires that there be at least as much free space available as is used in order to support reliable extraction and compression thereby bringing the total estimated space requirement to over 5 GB History Database Pruning Database pruning is especially important in situations when there is a high risk of a situation occurring where available hard disk space becomes critically low If low available disk space situations re occur more aggressive data pruning intervals may be warranted such that pruning occurs more frequently an
231. ized to and only to that location appliance Thus while our campus network design is synchronized to both location appliance 2710 1 and 2710 2 only controller WiSM 1 is synchronized to location appliance 2710 1 and only controller WiSM 2 is synchronized to location appliance 2710 2 After these actions are performed we will be able to manage the entire campus from the single WCS management domain while dividing the aggregate number of tracked devices between two separate location domains Once implemented the entire enterprise is managed as a single management domain with all management polling and reporting emanating from a centralized WCS Location appliance 2710 1 handles polling controller WiSM 1 for all information pertaining to tracked devices found within its location domain which is the regional headquarters Location appliance 2710 2 handles the polling of controller WiSM 2 with regard to all tracked devices found in its location domain which are the regional metro locations Except for the fact that the two location domains operate across a common network are managed from a common management domain and possesses a controller that co resides on the same physical WiSM module at the regional headquarters the two location domains essentially exist independent of one another An alternate approach would entail creating two separate location appliance network designs containing only the portion of the campus network encompassed within each
232. ked device can potentially combine to degrade monotonicity As a result RSSI cannot be depended on as a reliable predictor of distance in this part of the curve since it may be possible that more than one equally likely value for distance exists at a particular detected RSSI level Figure 5 11 illustrates this case depicting how a tracked device s RSSI reading of 40dBm can be associated with three different distances 5 7 and 12 feet from the access point antenna when operating in this close range non monotonic region of the RSSI versus distance graph This behavior is typically the result of a variation in an overhead antenna s propagation pattern as a device approaches it begins to venture into the area almost directly beneath it Obviously these effects vary depending on the propagation pattern of the specific antennas used and their installation height above the area where tracked devices is located However the lesson to be learned from this is that although increased access point density can often be conducive to better location accuracy the effect is not without its limits OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations W Access Point Separation Figure 5 11 Example of Close Range Non Monotonicity RSSI 40 dBm 5 feet 12 feet mmm Distance 223330 Clearly such RSSI ambiguity can be confusing especially when attempting to
233. kes into consideration the placement of each access point along with the inter access point spacing indicated on floor maps to predict whether estimated location tracking accuracy will be within 10 meters in 90 percent of all cases The output of the location readiness inspection is a go no go graphical representation of the areas that are predicted to be likely candidates for producing this level of accuracy as well as those that are not e Note that unlike the planning tool described earlier the location readiness tool assumes that access points and controllers are known to WCS and have been defined on the WCS floor maps using Monitor gt Maps gt Position APs While it is not necessary to actually install access points and antennas on walls and ceilings in order to conduct a location readiness assessment you must add any applicable controllers to WCS along with their registered access points and place the icons representing the access points on the appropriate floor maps In order to do this initially all such controllers and access points must be physically present powered on and online to the network These access points and controllers need not be deployed and installed they can be on a floor Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Determining Location Readiness W tabletop or other temporary location as long as the access
234. kets received 2012 Server o i Last Chokepoint 00 0c cc 60 1e 8a Location Notifications Chokepoint Wed Aug 15 16 00 41 EDT 2007 Absence Encountered Containment lo lo lo lo Distance all Enlarge Telemetry Data Emergency Data TEMPERATURE 100 0 degrees Celsius Reason Panic Button Pressed QUANTITY 29 MOTION 29 0576 meters sec HUMIDITY 80 MOTIONPROB Acceleration FUEL 29 0576 liters 223313 In some cases the location appliance may place two or more asset tags at the same predicted location such that any attempt to graphically represent them as individual icons would result in almost complete overlap A tag summary icon a yellow tag with black horizontal lines is used to resolve such situations as shown in Figure 3 18 Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 TEN Chapter3 Cisco Location Based Services Architecture Hs Tracking Clients Assets and Rogue Devices Figure 3 18 Tag Summary Icon and Summary Descriptor 1of2 Prev Next Details Tag 00 0c cc 5c 07 a6 Asset Name Asset Group Asset Category Type 4eroscout Battery Life Normal Last Located 8 15 07 10 11 4M 223414 Performing a mouse over of the tag summary icon brings up a tag summary descriptor shown which summarizes pertinent tag characteristics Clicking on Next scrolls through the descriptor information for each tag MAC address at this location and clicking on Details at any time bring
235. lateration Time of Arrival ToA Wi Fi Location Based Services 4 1 Design Guide P24 Ds OL 11612 01 Chapter 2 Location Tracking Approaches Distance Based Lateration Techniques _ ToA techniques are capable of resolving location in two dimensional as well as three dimensional planes 3D resolution can be performed by constructing spherical instead of circular models A drawback of the ToA approach is the requirement for precise time synchronization of all stations especially the mobile device which can be a daunting challenge for some 802 11 client device implementations Given the high propagation speeds very small discrepancies in time synchronization can result in very large errors in location accuracy For example a time measurement error as small as 100 nanoseconds can result in a localization error of 30 meters ToA based positioning solutions are typically challenged in environments where a large amount of multipath interference or noise may exist The Global Positioning System GPS is a example of a well known ToA system where precision timing is provided by atomic clocks Time Difference of Arrival TDoA Time Difference of Arrival TDoA techniques use relative time measurements at each receiving sensor in place of absolute time measurements Because of this TDoA does not require the use of a synchronized time source at the point of transmission i e the mobile device in order to resolve timestamps
236. lc 04 and channel number 6 is detected by AP sjc14 32b ap9 Radio type 802 11b with RSSI 77 and SNR 1 Location Notifications Absence Containment Distance All lo lo lo lo Location Cisco SJ Site 5 gt BLD 14 gt 3rd Floor floor Last located at Aug 16 2007 6 59 12 PM On Location Server loc 2 2 Enlarge Roque Clients Event History 223319 Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter3 Cisco Location Based Services Architecture W Tracking Clients Assets and Rogue Devices Rogue Clients Rogue clients are clients associated to rogue access points Rogue clients are displayed on the WCS location floor maps using a black rectangle icon with a skull and crossbones as shown in Figure 3 24 To display rogue clients on the WCS location floor map ensure that the Rogue Clients checkbox option is enabled from the Layers dropdown selector at the top of the floor map display and click Load in the left hand column To avoid excessive clutter WCS will display the first 250 rogue clients on the floor map To view the location of rogue clients beyond the first 250 rogue client filtering must be used Figure 3 24 Rogue Client Location Map ahali Wireless Control System cisco Contributing APs Monitor Reports Configure Location Administration Help v Maps gt Cisco SJ Site 5 gt BLD 14 gt 3rd floor M sjct4 31b ap5 M sjct4 32b ap6 RSSI Co
237. less Location Appliance Installation Guide http www cisco com en US products ps6386 products_installation_and_configuration_guide_bo 0k09186a00804fa761 html e Cisco Wireless Location Appliance Configuration Guide http www cisco com en US products ps6386 products_installation_and_configuration_guides_lis t html Configuring Cisco WCS for Location Tracking It is assumed that the reader has installed either a Windows or Linux based version of WCS that is appropriately licensed for location use with the Cisco Wireless Location Appliance Detailed procedures for configuring the Wireless Control System for location use with the Cisco Wireless Location Appliance can be found in the following documents e Cisco Wireless Control System Release Notes Release 4 1 http www cisco com en US products ps6305 prod_release_notes_list html e Cisco Wireless Control System Configuration Guide Release 4 1 http www cisco com en US products ps6305 products_installation_and_configuration_guides_lis t html e Cisco Wireless Location Appliance Deployment Guide http www cisco com en US products ps6386 prod_technical_reference09186a008059ce3 html Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 EN Chapter4 Installation and Configuration HI Configuring Location Appliance History Parameters Configuring Location Appliance History Parameters The configuration of Location Server gt Administration gt History Pa
238. listic approaches One such approach involves the assumption that location patterning is far too complex to be analyzed mathematically and requires the application of non linear discriminant functions for classification neural networks Another technique known as support vector modeling or SVM is based on risk minimization and combines statistics machine learning and the principles of neural networks To gain insight into how such location patterning algorithms operate we can examine a simple example that demonstrates the use of a deterministic algorithm which in this case will be the Euclidean distance As stated earlier deterministic algorithms compute the minimum statistical signal distance which may or may not be equal to the minimum physical distance between the actual device physical location and the recorded location of the calibration sample For example assume two access points X and Y and a mobile device Z Access point X reports mobile device Z with an RSS sample of x Almost simultaneously access point Y reports mobile device Z with an RSS sample of y These two RSS reports can be represented as location vector of x y Assume that during the calibration phase a large population of location vectors of the format F x y were populated into the location server calibration database where F represents the actual physical coordinates of the recorded location The location server can calculate the Euclidean distance d between t
239. llustrates a single campus WCS server providing WLAN management services for a large regional headquarters campus location as well as three extended regional metropolitan campus locations In this case all are located within a major metropolitan city N N CETT N M amp a ET e y v v 4 223340 amp Note Although the locations in this example are geographically dispersed the concepts discussed regarding multiple location domains and controller assignments also applies to the case of a single contiguous campus where the total number of tracked devices exceeds 2500 In the example depicted in Figure 5 24 the regional headquarters location contains 140 access points and each metro location contains 50 access points along with an unspecified number of chokepoint triggers The design calls for the use of a centralized Cisco Catalyst 6500 with Wireless Service Module WiSM The WiSM contains two embedded controllers per service module which are referred to as WiSM 1 and WiSM 2 WiSM 1 is used to service access points at the regional headquarters location while WiSM 2 services access points located at the metropolitan locations Two Cisco 2710 Wireless Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Multiple Location Appliance Designs W Location Appliances provide the capacity to track up to a maximum of 5000 device MAC addr
240. location appliance using a LOCP Notification frame as shown in Figure 3 29 Figure 3 29 LOCP Notifications Location Appliance WLAN Controller AP A EP EF ay 2 MAC 000CCC5D4DAB Echo Request EMAIL Northbound Eeno Response E SNMP Asynchronous Measurement Notification Chokepoint 1 Chokepoint 1 t 70 al remen EEE gocecas cece easan SYSLOG Notification XML t 70 Info Request LOCP Poll Info Response temp 38 C fe L t 90 Measurement Notification Chokepoint 2 es ali en t 100 ee Information Notification Vendor Specific Echo Request EMAIL Northbound Echo Response SNMP _ Asynchronous Information Notification Panic Alert Call Button Depressed 4 4140 lt lt fe ee ee eee eee eee SYSLOG Notification XML tea T10 Figure 3 29 shows the two basic types of LOCP notifications supported in Cisco UWN software Release 4 1 the Measurement Notification and the Information Notification e Measurement Notifications In Release 4 1 measurement notifications are used to convey information regarding the identity of any chokepoint proximity devices into whose range a tag may have entered Tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification include chokepoint identification in the tag content field such as the chokepoint MAC address This information is passed to the location appliance along with the tag MAC address in real time and can be used by location clients such as WCS to indicate that a
241. location latency albeit at the risk of some location jitter should choose low values for location smoothing or disable location smoothing altogether Multiple Location Appliance Designs As stated earlier a single Cisco Wireless Location Appliance can track up to 2500 devices which includes WLAN clients asset tags rogue access points and rogue clients The location appliance allows for specific tracked device categories to be enabled via Location gt Location Server gt Administration gt Polling Parameters To make best use of the capacity of each location appliance Cisco recommends enabling only those polling categories client stations rogues asset tags or statistics in which there is genuine interest and that require simultaneous tracking historical location For example if the primary interest is in tracking asset tags only do not enable the client and rogue polling categories because this only adds to overall network traffic between the location appliance and WLAN controllers as well as unnecessarily consuming a portion of the 2500 device tracking capacity By disabling polling for device categories for which there is little interest the full capacity of the location appliance can be better used Note Although not the focus of this document Release 4 2 of the location aware Cisco UWN introduces a enhancement that allows for individual limits to be placed on what portion of the location appliance s entire tracked device capa
242. lor Lookup Zoom Refresh M sjcl4 31b ap3 O ace O AP Heatmaps O Clients Load O 802 11 Tags Loading Chokepoints Loaded 0 chokepoints Done eal 4 rf oad Location Server data as bid as C Rogue APs M Rogue Clients O Grid O coverage reas O Markers O Chokepoints Save Settings 223320 It is possible to filter the location information displayed by WCS based on the age of the information In Figure 3 24 WCS displays location appliance information that has aged up to 15 minutes Alternatively this value could be set to 2 or 5 minutes for more recent location information or 1 2 1 3 6 12 or 24 hours for older information By clicking on the blue chevron that is displayed to the right of the Rogue Clients checkbox rogue client filtering options can be specified and additional information can be displayed such as e The total number of rogue clients detected on this floor e Small icons shown above or standard sized icons can be selected When using small icons no text is displayed on the floor map for the rogue client except when a mouse over is performed When using standard size icons an on screen tag displays the rogue client s MAC address Wi Fi Location Based Services 4 1 Design Guide 332 By OL 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices Mi e Either all rogue clients can be displayed or filtering can be performed
243. lps protect against lost tag transmissions which results in lost RSSI readings Lost RSSI readings is a confirmed cause of degraded location accuracy especially in environments where there is a significant likelihood of tag transmissions being interfered with or dropped due to congestion or interference Avoid configuring an excessive number of message repetitions as there are few conditions where a message repetition factor greater than 3 would be truly required The setting of three message repetitions works very well for the majority of environments Setting this parameter above a value of 5 is typically not considered necessary Message Repetitions Interval The delay between subsequent message repetitions on the same channel specified as either 128 256 or 512 milliseconds The default value is 512 milliseconds Transmission Power dBm The default value for transmission power is typically 18dBm on T2 model AeroScout asset tags The location aware Cisco UWN is capable of discerning the transmission power used by tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification Data Rate Data rates of 2 Mbps can only be specified for T3 tags Although the message payloads and frame sizes associated with asset tags are very small the use of a faster transmission speed can allow T3 tags to transmit their payloads faster and free the channel for use by other stations sooner This can also reduce battery consumption since each
244. m en US docs solutions Enterprise Mobility vowlan 41dg vowlan4 1dg book html OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter1 Overview W Hardware and Software Components Hardware and Software Components Table 1 1 lists the hardware and software used in the writing of this guide D Note Other supported hardware or software can be found by referring to the information located at the following URL http www cisco com en US products ps6386 index html Table 1 1 Tested Hardware and Software Location Appliance AIR LOC2700 L K9 Location Appliance 2700 Series software release 3 0 42 0 Wireless Control System WCS WCS STANDARD K9 4 1 91 0 Wireless Control System Release 4 1 91 0 for Windows 2003 exe Server WLAN Controllers AIR WLC4402 12 K9 4400 Series WLAN Controller Release 4 1 185 0 AIR WLC2106 K9 2106 Series WLAN Controller Release 4 1 185 0 Access Points AIR LAP1242AG A K9 802 1 lag LWAPP AP North American version 12 3 11 JX External Antennas AIR ANT4941 2 4 GHz 2 2 dBi Dipole AIR ANT5135D R 5 GHz 3 5 dBi Dipole 1 The Cisco Wireless Location Appliance 2710 AIR LOC2710 L K9 model is the successor to the 2700 AIR LOC2700 L K9 model There is no functional difference between the 2700 and 2710 models both models support the same features and functionality 2 Requires appropriate licensing for Location Based Services suppor
245. m for 2 4 GHz Generally these clients can still be localized with acceptable accuracy when calibration data collection is performed according to the guidelines outlined above However a slight increase in location accuracy may be possible if the calibration data collection is performed at power levels with which we expect the embedded laptop client to transmit its probe requests A tradeoff that must be considered when opting for this approach is the possibility of reduced access point heat map accuracy heat maps are most accurate when calibration is performed at 63mW 18dBm for 2 4GHz and 32mW 15dBm for 5 GHz After calibration data collection has been completed all temporarily configured parameter changes should be returned to their normal settings In some cases the device that is used to control the calibration data collection process may not be the same device that is used to transmit probe requests For example a laptop with an embedded wireless adapter compatible with the Cisco Compatible Extensions specification version might be a user s preferred device based on a ergonomic or special accommodation feature that he or she requires Since this device is not compatible with the Cisco Compatible Extensions specification at version 2 or greater its use is not recommended for optimal results when performing calibration data collection However we can use this device to log into the UWN and control the data collection process remotely as
246. map links transports the user to the appropriate detail screen using information from the responsible WCS server as shown in the lower half of Figure 5 30 Note that when this occurs Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Multiple Location Appliance Designs W additional fields highlighted in blue ovals are inserted into the WCS menus to indicate that the user has arrived at these WCS menus via the WCS Navigator and provide for an easy return path back to the main menu Figure 5 30 Result of Tag Search Across Multiple WCS Servers n Navigator Monitor Reports Configure Administration Help Search Tag Search Results Eo Advanced Search For Tags Criteria Edit Select New or Saved Jy Modify Search MAC Addr wes AssetName S CA o AssetGroup Yendor Loc Server Controller Battery Map Location Alpharetta PE Campus gt AP1242 c 9 Car 00 0e cc Se 8d cc WCS 2 Aeroscout Loc2 10 1 96 16 80 SOPRURE EEL ELS eae 2 Alpharetts 00 0cicc 73 14 d9 WCS 2 Aeroscout Loc2 10 1 96 16 80 Campus gt AP12a2 2 Alpharetta 0 1 9 C 21242 lscccseazsa wes2 Reroscout toc 0 96 16 so SAE rey i is wes 1 Aeroscout Loci 19 1 9618 80 5 i AETA reek a Roswell i Campus gt AP1242 wes 1 Aeroscout Loci 10 1 9618 80 S r pusa A Roswell p m Campus g
247. metal racking and electronic equipment path loss exponent of 4 3 and the RF model that results from this calibration used for the entire floor Calibrate across all areas of the floor This approach takes into account all areas of the floor and attempts to produce a balanced RF calibration model While performance may be acceptable using this approach depending on the accuracy needs of the location application laboratory testing indicates that in general improved results are obtained when using option one above Note that if there are large differences in size between the different floor areas that result in significant differences in the number of calibration data points collected within each area the final path loss model using this approach may be biased in the direction of the path loss associated with the larger areas I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations E Inspecting Location Quality Inspecting 3 Address the different areas of the floor as if they were individual floors In some cases improved accuracy can be obtained within each individual area with a tradeoff of increased management overhead and some potential edge accuracy degradation Since WCS and the location appliance do not allow for the provisioning of different RF models to sub floor areas in software Release 4 1 each of these sub floor areas would need to be
248. mmended that the reader consult the examples given in Multiple Location Appliance Designs page 5 32 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter4 Installation and Configuration Hs Configuring Location Appliance Advanced Parameters Memory Information e DB Disk Memory A misnomer this parameter does not refer to memory on the location appliance Rather it displays the amount of disk space that has been consumed by the location appliance database This information is useful when determining whether a database de fragmentation should be performed see Advanced Commands page 4 6 e Run Java GC This command runs a general memory clean up immediately Normally memory cleanup is initiated by the system automatically and thus does not require manual initiation Therefore Java General Cleanup need only be run when directed by the Cisco Technical Assistance Center TAC or Cisco Engineering Advanced Commands The Defragment Database advanced command defragments the location database and reclaims allocated but unused disk space A database defragmentation can be beneficial if free disk space on the location appliance is running low because of large database size or if the response time of the location appliance appears noticeably slower when data is requested by location clients To determine how much free space is currently available on the location appliance it is necessary to log into the loc
249. monitoring It is interesting to note that although they employ an onboard power source semi passive RFID tags do not use it to directly generate RF electromagnetic energy Rather these tags typically make use of backscatter modulation and reflect electromagnetic energy from the RFID reader to generate a tag response similar to that of standard passive tags see Figure 6 6 The onboard battery is used only to provide power for telemetry and backscatter enabling circuits on the tag not to generate RF energy directly Figure 6 6 Backscatter Modulation in Semi Passive RFID Tags Reader detects changes in reflected power 190593 Semi passive RFID tags operating in the ISM band shown in Figure 6 7 can have a range of up to 30 meters with onboard lithium cell batteries lasting several years Range is vastly improved over conventional passive RFID tags primarily because of the use of a backscatter optimized antenna in the semi passive design Unlike a conventional backscatter modulated passive RFID tag the antenna contained in a semi passive tag is dedicated to backscatter modulation and there is no dependence on the semi passive RFID tag antenna to be a reliable conduit of power for the tag Therefore the semi passive tag antenna can be optimized to make most efficient use of the backscatter technique and provide far better performance than purely passive RFID tag antenna designs OL 11612 01 Wi Fi Locat
250. mpossible to calculate This is why the find_root function is limited to the closed interval from d 2 to d wxMaxima 0 7 3a http wxmaxima sourceforge net Maxima 5 13 0 http maxima sourceforge net Using Lisp GNU Common Lisp GCL GCL 2 6 8 aka GCL Distributed under the GNU Public License S the file COPYING Dedicated to the memory of William Schelter 04 28 49573663945017 15 find_root Oa pi R 2 2 R 2 acos d 2 R 1 2 d sqrt 4 R 2 d 2 R d 2 d 05 30 87736860938116 Si1 d 45 9 01 45 9 i2 Obg 0 10 02 0 1 i3 Oa 0 15 03 0 15 i4 find_root Obg pi R 2 2 R 2 acos d 2 R 1 2 d sqrt 4 R 2 d 2 R d 2 qd Note Maxima is not produced marketed sold or supported by Cisco Maxima is a publically available computer algebra system CAS that has been released under the GNU Public License Further details regarding Maxima its capabilities and its use including downloads for various operating systems can be found at the following URL http maxima sourceforge net Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 At Appendix A Determining Approximate Roots using Maxima Wi Fi Location Based Services 4 1 Design Guide a2 E OL 11612 01 APPENDIX E Verifying Detection of Asset Tags in WLAN Controllers Asset Tags Detection The protocol analyzer trace in Figure B 1 provides important information with regard to how asset tags
251. n US products ps6386 products_configuration_guide_chapter09 186a008082d7 44 html wp 1053921 Further clarification regarding select parameters is provided in the following sections The Queue Limit parameter specifies the size of the output notification queue of the location appliance This value normally defaults to 500 The location appliance drops any outbound notifications above this limit if the output notification queue size is exceeded Therefore if you notice that some outbound notifications are being dropped via the Notifications Dropped field you may want to increase the queue limit size For each matching condition the Retry Count specifies the number of northbound notification firings that will be allowed for the same device over and above the initial firing before the wait period specified by the Refresh Time parameter begins Thus the total number of firings of northbound notifications allowed between Refresh Time periods will be equal to one plus the value specified for Retry Count The default value for Retry Count is one Keep in mind that e More than one physical northbound notification message can be sent per firing for example SMTP Syslog SNMP or SOAP e Retry Count and Refresh Time apply independently to each matching device MAC address e Retry Count and Refresh Time apply independently to event definitions However event definitions that apply the same trigger conditions to the same device
252. n a manual mode to place access points on floor maps as they see fit and adjust several criteria in order to see their effect such as transmit power antenna type and so on Alternatively the WCS planning tool also allows automated access point placement based on the type of deployment model desired Those users and designers desiring that the system make an initial design suggestion can use the planning tool in an automated mode thereby specifying the type of design they wish and allowing the planning tool to examine their requirements and make qualified suggestions For designers wishing to combine voice and data designs meeting Cisco VoWLAN best practices with location tracking it is recommended that the planning tool be first used to model voice and data designs separately from location tracking requirements Once a satisfactory voice and data design has been created any modifications necessary to provide for good location fidelity can then be manually incorporated The planning tool assumes a transmit power of 18dBm for 802 1 1bg and 15dBm for 802 1 1a along with an antenna azimuth position of 180 elevation height of ten feet and elevation angle of 0 Transmit power access point type antenna type and azimuth position can be changed individually for each access point In addition planning tool users can specify a several additional criteria to further fine tune data and voice designs Note For complete information about planning to
253. n client transmit power resulting in changes in detected RSSI e Environmental changes including semi permanent obstructions that may have shifted position result in variations in attenuation and multi path e Changes in client orientation e Shadow fading Location smoothing allows for varying degrees of averaging to be applied to device location Smoothing factors are set in Location gt Location Server gt Administration gt Location Parameters through the Smooth Location Positions parameter as shown in Figure 5 22 Figure 5 22 Configuring Location Smoothing Location Server gt Location Parameters gt AeS_Loc2 Location Parameters Enable calculation time I Enable Enable OW Location I Enable Relative discard RSSI time E minutes Absolute discard RSSI time jo minutes RSSI Cutoff 2 F5 db Smooth Location Positions More smoothing new value weighted less x Off no smoothing Less smoothing new value weighted more s c I Average smoothing new value weighted same Sve ARER More smoothing new value weighted less Maximum smoothing new value weig 190572 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Multiple Location Appliance Designs The various smoothing factor options impact the displayed location position by assigning different weights to the latest calculated position of the device v
254. n fluid gear oil etc e Changes in interior walls A newly remodeled office facility was last calibrated prior to the installation of several new walls with improved fire protection and interior sound deadening insulation e Changes in stocking density A large library was originally calibrated when it was still using older bookshelves that contained six to eight shelves per stack However it has since been upgraded and now sports new bookshelves that contain between ten to twelve shelves per stack e Changes in access point density A manufacturing site was originally calibrated for location tracking with 50 access points and an inter access point spacing of 40 feet However due to a business slowdown a large portion of the plant has been mothballed with 50 of the access points powered down The effective inter access point spacing at this point is 65 feet Tips for Successful Calibrations Data Collection As stated earlier the WCS calibration process helps ensure that a sufficient number of calibration data point measurements are collected before allowing the calibration user to move forward with calibrating the model and applying it to floors During the calibration process use the blue crosshairs on the calibration grid shown in Figure 5 41 as suggestions with regard to where the calibration client should be positioned when collecting data points Always make sure you accurately position the red cross hairs prior to clicking on S
255. n menu located in the upper right hand corner location history and playback information for the rogue access point in question can be accessed similar in format and function to that described previously for WLAN clients and 802 11 active RFID tags Wi Fi Location Based Services 4 1 Design Guide P330 By OL 11612 01 Chapter3 Cisco Location Based Services Architecture Figure 3 23 Tracking Clients Assets and Rogue Devices Rogue Access Point Detailed Information Wireless Control System Logout Refresh Print View Alarms gt Rogue 00 1 b0 eb e2 30 General Rogue MAC Address Vendor Rogue Type On Network Owner State SSID Channel Number Containment Level Radio Type Strongest AP RSSI No of Rogue Clients Created Modified Generated By Severity Previous Severity Annotations Annotations go here 00 1c b0 eb e2 30 Unknown AP No Alert loc wle 04 6 Unassigned b a 77 0 Aug 15 2007 3 23 13 PM 4ug 16 2007 6 50 35 PM Controller Select a comman Go Set State to Unknown Alert Message Set State to Known Internal Rogue AP 00 1c b0 eb e2 30 with SSID loc wlc 04 Set State to Acknowledged External and channel number 6 is detected by AP sjc14 32b ap9 Radio type 802 11b with RSSI 77 and SNR 1 1 AP Containment 2 AP Containment 3 AP Containment Help 4 AP Containment Rogue AP 00 1c b0 eb e2 30 with SSID loc w
256. n techniques very attractive from a cost performance standpoint to designers of 802 11 based WLAN systems wishing to offer integrated lateration based positioning solutions However a known drawback to pure RSS lateration is that propagation anomalies brought about by anisotropic conditions in the environment may degrade accuracy significantly This is due in part because in reality propagation in any cell is far from a purely circular pattern based on an ideal path loss model Textbook theoretical RSS lateration models in their purest form do not provide for the measurement or consideration of variations seen within actual sites typically assuming only well known values for path loss and shadow fading Pure RSS based lateration techniques that do not take additional steps to account for attenuation and multipath in the environment rarely produce acceptable results except in very controlled situations This includes those controlled situations where there is always established clear line of sight between the mobile device and the receiving sensors with little attenuation to be concerned other than free space path loss and minor impact from multipath Angle Based Angulation Techniques Angle of Arrival AoA The Angle of Arrival AoA technique sometimes referred to as Direction of Arrival DoA locates the mobile station by determining the angle of incidence at which signals arrive at the receiving sensor Geometric relationships ca
257. n then be used to estimate location from the intersection of two lines of bearing LoBs formed by a radial line to each receiving sensor as illustrated in Figure 2 5 Ina two dimensional plane at least two receiving sensors are required for location estimation with improved accuracy coming from at least three or more receiving sensors triangulation OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter2 Location Tracking Approaches E Angle Based Angulation Techniques Figure 2 5 Angle of Arrival AoA In its purest form that is where clear line of sight is evident between the mobile device X and receiving sensors A and B mechanically agile directional antennas deployed at the receiving sensors are adjusted to the point of highest signal strength The positioning of the directional antennas can be directly used to determine the LoBs and measure the angles of incidence 04 and Op In practical commercial and military implementations of AoA multiple element antenna arrays are used to sample the receiving signal thereby eliminating the need for more complex and maintenance intensive mechanical antenna systems Electronic switching can be performed between arrays or portions of each array and mathematical computations handled by a background computing system used to extract the angles of incidence This technique actually involves calculating TDoA between elements of the array by measuring the difference in re
258. nal strength and data rate information It can be safely used without impacting any actual deployment of access points that may already be in service The WCS Map Editor is accessible from the top line hyperlink bar of the planning tool and can be used to add wall attenuation information to floor maps Wall information added via the Map Editor does not affect access point placement or location designs however it will be used by the planning tool when displaying predicted RF coverage maps for planned access points The planning tool operates purely on a hypothetical basis without the need to connect or deploy any access points or controllers Since it is WCS feature a WCS server must be installed somewhere in network before the planning tool can be used If there are any existing access points that have been deployed and defined to WCS already the planning tool allows for the configuration of those access points to be copied into the planning virtual environment allowing you to safely model with a virtual copy of your production environment Before using the planning tool for RF coverage planning ensure that an appropriate path loss model has been assigned to the floor upon which you wish to conduct your planning WCS will use the coverage reference path losses and path loss exponents when it plots the predicted coverage heatmaps from each access point in the planning tool Seasoned WLAN veteran designers have the option of using the planning tool i
259. nal investment required beyond that necessary to support other enterprise wireless applications such as VOWLAN and high speed data Note This section describes the pertinent characteristics of voice and data designs only as they relate to co existence with the location tracking capabilities of the Cisco UWN For a more comprehensive examination of Cisco Unified Wireless Network VoWLAN solution design and Cisco recommended best practices refer to the Voice Over Wireless LAN 4 1 Design Guide which can be found at the following URL http www cisco com en US docs solutions Enterprise Mobility vowlan 4 1dg vowlan41dg book html Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Location Voice and Data Coexistence W amp Note For a more comprehensive examination of the Cisco Unified Wireless Network data solution design and best practices refer to Enterprise Mobility 4 1 Design Guide at the following URL http www cisco com go srnd When architecting VoWLAN and high speed data designs and determining subsequent access point placement the primary concerns of the designer should include e Minimum desired cell signal level threshold For example when designing VoWLAN solutions that involve the Cisco 7921G VoWLAN handset current VoWLAN best practices suggest a minimum planned signal level thresh
260. nce Absolute discard RSSI time minutes RSSI Cutoff 75 dBm Accounts Smooth Location Positions or no smoothing EJ Status Chokepoint Usage MV Enable Logs Chokepoint Out of Range Timeout 60 seconds Save Cancel e Chokepoint Usage This checkbox shown within the red rectangle in Figure 6 31 must be enabled in order for the location appliance to use chokepoint location techniques to localize tags This occurs when it receives incoming LOCP Measurement Notifications indicating that a tagged asset has been stimulated by a chokepoint trigger With regard to the chokepoint capabilities contained with the Cisco location appliance and the location aware Cisco UWN these techniques are only used with asset tags that are compliant with the Cisco Compatible Extensions for Wi Fi Tag specification If this parameter is disabled the appliance will use the standard mechanism of RSSI based RF Fingerprinting to calculate tag location at all times 223393 e Chokepoint Out of Range Timeout This parameter shown within the blue rectangle in Figure 6 31 specifies the timer used to age the last in range report received from for an asset tag that is being localized using chokepoint location techniques It assures that any tags no longer transmitting frames indicating they are within range of a chokepoint trigger are removed from that chokepoint in the active location database once the Chokepoint Out of Range Timeout has expired T
261. nd then not returning for several days Another example might be a logistics cross docking facility that may only contain 2000 tagged asset containers during any four hour period but through whose doors a volume of 10 000 or more tagged asset containers may pass within a 24 hour period In either of these cases the quantity of track able Wi Fi client devices or asset tags actually on site at any one time may be significantly less than the maximum tracked device capacity of the location appliance However the number of transient devices that may pass through the facility over a 24 hour period will easily exceed 2500 Should this occur while using the default value for Absent Data Cleanup Interval there may be a risk of the location appliance s tracking capacity becoming exhausted as devices that may have left the facility several hours ago will not be removed from the active location database until the 24 hour ADCI has expired Setting the value for Absent Data Cleanup Interval to a lower value say for example four hours or 240 minutes would expedite the cleanup of these migrated devices and release tracked device capacity on the location appliance for use by recent device arrivals Reducing the value of the Absent Data Cleanup Interval is not without its tradeoffs however For further discussion of the Absent Data Cleanup Interval the potential tradeoffs involved in changing it and how this may factor into your overall design approach it is reco
262. ng the Way We Work Live Play and Learn is a service mark of Cisco Systems Inc and Access Registrar Aironet BPX Catalyst CCDA CCDP CCIE CCIP CCNA CCNP CCSP Cisco the Cisco Certified Internetwork Expert logo Cisco IOS Cisco Press Cisco Systems Cisco Systems Capital the Cisco Systems logo Cisco Unity Enterprise Solver EtherChannel EtherFast EtherSwitch Fast Step Follow Me Browsing FormShare GigaDrive GigaStack HomeLink Internet Quotient IOS iPhone IP TV iQ Expertise the iQ logo iQ Net Readiness Scorecard iQuick Study LightStream Linksys MeetingPlace MGX Networking Academy Network Registrar Packet PIX ProConnect RateMUX ScriptShare SlideCast SMARTnet StackWise The Fastest Way to Increase Your Internet Quotient and TransPath are registered trademarks of Cisco Systems Inc and or its affiliates in the United States and certain other countries All other trademarks mentioned in this document or Website are the property of their respective owners The use of the word partner does not imply a partnership relationship between Cisco and any other company 0612R Wi Fi Location Based Services 4 1 Design Guide 2008 Cisco Systems Inc All rights reserved CHAPTER 1 Overview 1 1 Introduction 1 1 About the Guide 1 2 Target Audience 1 2 Objective 1 2 Additional Reference Documents 1 3 Hardware and Software Components 1 4 CHAPTER 2 Location Tracking Approaches 2 1 Cell of Origin 2 2 Distanc
263. ng with software Release 4 1 of the Cisco UWN asset tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification may transmit high priority and vendor specific notifications to the location aware Cisco UWN This information is transmitted as part of a tag transmission that is sent on demand and is passed from WLAN controllers to the Cisco Wireless Location Appliance using LOCP Keep in mind that the format of the tag message sent by the tag when a high priority type event occurs is very similar to the standard tag multicast transmission sent during each tag transmission interval except that it contains additional information that conveys the nature of the high priority event It is important to note that information contained in the tag notifications received over RF by the WLAN controller is passed with minimal delay to the location appliance in the form of LOCP Information Notifications Thus for example when a call button is depressed on an asset tag that is compatible with the Cisco Compatible Extensions for Wi Fi Tags specification a LOCP Information Notification is transmitted by the WLAN controller to the location appliance very shortly after the tag notification has been received by the controller s registered access points Once received by the location appliance the updated call button status is reflected in the location appliance database for example panic button depressed and made available to location client
264. ning Tool with an Irregularly Shaped Floor Plan More complex designs containing totally enclosed interior voids for example a building with a fully enclosed interior atrium as shown in Figure 5 14 with the perimeter of the building shown by a red outline may not lend themselves well to automatic access point placement The planning tool does not currently allow the exclusion of zones into which access point placement should not occur Note in Figure 5 14 the placement of access points 2 4 9 and 24 in the atrium area indicated by the blue outline The placement of these access points in this area is incorrect since the floor map is for the building s third floor This should be corrected by manual intervention and moving the access points into correct locations or eliminating them entirely if not necessary OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations HI Determining Location Readiness Figure 5 14 Example of Floor Plan with Fully Enclosed Interior Atrium Lia isi Was ee Determining Location Readiness The Inspect Location Readiness feature Monitor gt Maps gt floormapname gt Inspect Location Readiness allows the network designer to perform a quick predictive check of the location performance for a floor before time is invested in pulling cable deploying equipment and performing calibrations Inspect Location Readiness ta
265. ns of this document As a location client Cisco WCS is capable of displaying a wide multitude of information regarding the current and past location of clients asset tags rogue access points and rogue clients Note For important information regarding compatibility between versions of WCS and the Cisco Wireless Location Appliance refer to Release Notes for Cisco Wireless Location Appliance Release 3 0 at the following URL http www cisco com en US products ps6386 prod_release_notes_list html Location client functionality is not limited to WCS Third party applications written in accordance with the Cisco Location Appliance Application Programming Interface API can also serve as a location client to the Wireless Location Appliance as shown in Figure 3 2 The same information contained in the location appliance that is made available to WCS including vendor specific information that may have been received from asset tags is also made available to third party same location clients via the location appliance API Third party location clients can synchronize their network designs with the location appliance in a similar fashion to WCS In this case the location appliance updates location clients with the latest information regarding network designs and map images As with WCS synchronization occurs either on demand or on a scheduled basis the timing of which is typically determined by configuration parameters contained within the locat
266. nt As seen in Figure 3 29 the tag telemetry is retained by the WLAN controller until the next LOCP polling interval whereas indication of chokepoints that are in range is sent immediately by the WLAN controller to the location appliance in the form of a measurement notification In addition to providing updated information to clients via the SOAP XMP API for example when a location client issues a XML GetTagInfo or GetTagLocation request the location appliance can also dispatch external asynchronous northbound notifications upon receipt of LOCP measurement or information notifications refer once again to Figure 3 29 These external northbound notifications are sent for the following conditions using SNMP SMTP SOAP or UDP Syslog transports e Call Button Tag Tampering or Tag Detached e Chokepoint in range e Other Priority Events user defined For information regarding deployment considerations surrounding tag notifications refer to Tag Telemetry and Notification Considerations page 6 27 Wi Fi Location Based Services 4 1 Design Guide M342 i OL 11612 01 onarte Installation and Configuration Installing and Configuring the Location Appliance Detailed procedures for installing and configuring the Cisco Location Appliance can be found in the following documents e Release Notes for Cisco Wireless Location Appliance Release 3 0 http www cisco com en US products ps6386 prod_release_notes_list html e Cisco Wire
267. ntroller Cisco Controller gt show client detail 00 07 50 d5 e4 77 eT TLR aL Sete te ol PRON Ree ECR AICP arr ICR Ee CRON Ty FS 00 07 50 d5 e4 77 CLICHE USEENAME oeno iT asa aea ETAN ETA N A ARENAEN EE ANSIA 00 14 1b 59 41 f0 a RE a AANA E EL A E T N eet E Associated Wireless LAN IA inneoin o a S TRE 1 BSS ic T teas paced aid mee 00 14 1b 59 41 f0 ra E a I Spec E ave Site tenavaralenaratelatatavelicrarers 1 I AOS Senan E T Wis ETSI native AVERT 10 1 67 252 PES OCA RE OF Els css unraissavecejaxepsiarauarsieiasoinioiw einseieuioiieissimione 1 Authentication Algorithm Open System kesson COE ck rsenn ieam ra SERCUS COUG aoi5 5 16 0 0 514 5 0 2 00 a sin epene aasa aaia aaeeea 0 SESS TON TIMU oe onae na tle weer wee REEE DiE 0 CHaht CENX VERS NOM ace carerevaxe raves ERE 2 MINPOPING 225 cc wccancctses vecsteeccsemee sedlad ace Disabled POG BEVBI ct A E seeetersteleert Gisele wa lnios tom errata Silver Diff Serv Code Point DSCP cc eee eee ee eee disabled BOD LE PrI EY TANTO cakane ed pe hina ea EEA AG disabled WAM SUPPONE s a ra EEEE ERE aia a Disabled HOGERE SEADE o riaa A a a aA ENE Local MOBT ELE MOVE COUN TE roo I VE AN o a ANS 0 SECUI EV POLICY COMO BOG oana Yes PORTCY MAST SCAG ices osaicewrasnce 6cs asaver0i0evuseisenesensyaraserece RUN Policy Manager Rule Created 0e ee eeee Yes NPL Fast Fast WEINI Odina EN Yes POLICY UIE so e ece more auereiaieemiaiocacon pieseraipcneiaceonscsecnie mame N A Management Fram
268. nts and authenticate associate to WLAN SSIDs serviced by controllers defined to the location appliance they are treated just as other WLAN clients and are indicated on floor maps by a blue rectangular icon Figure 6 16 Portable RFID Interrogators with Integrated Wi Fi Uplink Pp T 190600 Using 802 11b Tags in an 802 11g Environment Another common question that often arises is about the potential performance impact of using an 802 11b asset tag in a network that otherwise consists entirely of 802 11g clients and access points The crux of such discussions is typically centered around whether or not protection mechanisms such as RTS CTS or CTS to self are initiated by the 802 11g network to assure compatibility between the 802 11b asset tags and the 802 11g network Note For an explanation of 802 11g performance capacity and protection mechanisms see the whitepaper entitled Capacity Coverage and Deployment Considerations for IEEE 802 11 gat the following URL http www cisco com en US products hw wireless ps430 products_white_paper09186a00801d61a3 sh tml Wi Fi Location Based Services 4 1 Design Guide Peis i OL 11612 01 Chapter 6 RFID Tag Considerations Using Wi Fi RFID Tags with the Cisco UWN W A popular point of discussion often revolves around whether these protection mechanisms are initiated upon the introduction of one or more of the following to the all 802 11g wireless infrastructure e An 802
269. o the stimulation zone of chokepoint triggers For example an asset tag connected to the fuel level sensor of a forklift may be able to pass fuel level telemetry via the Cisco UWN to the location appliance and its location clients which could include WCS and third party location clients The ability of the asset tag to perform these telemetry functions is dependent upon the asset tag manufacturer and typically requires the appropriate level of integration and physical connectivity between the tag and sensors found aboard the attached asset Note that some asset tags are available with their own onboard sensors which can measure certain ambient environmental characteristics such as temperature and humidity external to tagged assets without any dependence on embedded sensors Onboard tag sensors for example might be appropriate where the primary concern surrounds general environmental conditions effecting both the asset tag as well as the asset to which it is attached Thus an asset tag equipped with onboard temperature sensors would be appropriate in detecting whether an attached asset was incorrectly stored in temperatures outside recommended ranges Embedded sensors within the asset itself would be more appropriate when the goal is to alert the system administrator to an internal condition resulting from improper use that could result in costly damage to the asset if not addressed promptly A good example of this might be an engine providing in
270. o view each location history record in this fashion played back with a configurable time delay The granularity of the movement shown depends on the interval with which client history records are recorded in the database To see location history played back in this fashion simply click on the Play button shown in Figure 3 15 w_ Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices W 802 11 Active RFID Tags The location aware Cisco UWN readily detects 802 11 Wi Fi active RFID tags that are compliant with the Cisco Compatible Extensions for Wi Fi Tags specification such as those from AeroScout WhereNet G2 Microsystems and InnerWireless PanGo amongst others and displays them on WCS floor maps using a yellow tag icon as shown in Figure 3 16 These asset tags typically do not associate to the WLAN infrastructure and are not typically located on the basis of probe requests Instead these asset tags transmit messages to the location aware UWN on a periodic basis using layer two multicasts If an asset tag has an optional mode that allows for full WLAN association those tags will be represented on WCS location floor maps as blue rectangles WLAN clients during the time they are operating in this mode To display the location of asset tags on the WCS location floor map ensure that the Clients checkbox option is enable
271. ocation Based Services 4 1 Design Guide a OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Antenna Considerations W In some specialized cases however there may be reasons to consider the use of third party antennas that are not found on the WCS antenna list These reasons may include Retrofit of a pre existing installation If a pre existing autonomous network is being upgraded to the LWAPP based UWN solution or if a pre existing UWN installation is being upgraded there already a large install base of third party antennas already deployed Depending on their physical condition and their regulatory approval status for use with the latest 802 11 technologies designers may wish to consider re deployment Specific Product Requirements In some cases a specific physical or electrical requirement of the design might dictate the use of a niche third party antenna not contained on the WCS supported list For example a fashion retailer may require the use of a zero footprint antenna or an antenna available in a specific shape or color to augment the decor of a Fifth Avenue flagship retail location Or an electronics manufacturing facility requires a directional antenna with a unique and very specific coverage pattern or polarization to better cover a specific area of the plant floor while minimizing interference with sensitive equipment in a particular location WCS allows for antenna gain to b
272. of tracked devices for this location appliance to its maximum capacity of 2500 If location tracking of tagged assets and WLAN clients are considered to be a higher priority than the tracking of rogue devices a potential problem could exist If new tags or clients are added to the environment there may not be any available capacity to track them until some of the currently tracked devices existing WLAN clients asset tags or rogue devices expire and are pruned from the active location database D Note Version 4 2 of the location aware Cisco UWN introduces a enhancement that allows for individual limits to be placed on what portion of the location appliance s aggregate tracked device capacity is allocated to each tracked device category i e WLAN clients asset tags or rogue devices It is important to note that in this situation disabling the tracking of rogue devices in the location appliance entirely will not immediately remove the 1 000 tracked but unwanted rogue devices from the active location database Rather the Absent Data Cleanup Interval will by default maintain each currently tracked rogue device in the active location database for a period of 1440 minutes past the time Wi Fi Location Based Services 4 1 Design Guide aa E OL 11612 01 _ Chapter 4 Installation and Configuration Configuring Location Appliance Advanced Parameters W of its last RSSI update Plainly put in the case of our example using the defa
273. ol options such as data coverage voice location demand and override consult the chapter Using Planning Mode to Calculate Access Point Requirements found in the document entitled Cisco Wireless Control System Configuration Guide Release 4 1 at the following URL http www cisco com en US docs wireless wes 4 1 configuration guide wcsmaps html wp1 104248 Selecting the location planning option results in the planning mode access points being placed along the perimeter and in the corners of a floor in addition to the interior of the floor as necessary At least four access points are assumed to be present in every location design and access points are placed using a spacing of up to 70 feet Note that when using the location planning option the resulting design may meet best practice recommendations for voice and data although the signal strength and overlap requirements of co resident applications are not explicitly taken into account Therefore in designs where location tracking is intended to co reside with voice and high speed data it is recommended that Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Figure 5 13 Access Point Separation W these application designs be addressed first according to Cisco recommended best practices Once a design satisfying application needs has been completed the design can then be modified or augmented
274. old of 67dBm Other voice devices may have differing requirements such as the Vocera Communications badge which requires a signal level threshold of 65dBm Requirements for data devices will depend on the transmission rate that they are required to operate at Lower speed devices such as handheld bar code or RFID computers that operate at data rates up to 11 Mbps typically do not have very demanding minimum signal requirements often times in the range of 73 to 76 dBm Data devices used to pass streaming multimedia and other bandwidth intensive applications will typically require higher data transmission rates and consequently higher minimum signal levels e Signal to Noise Ratio SNR This is the ratio of the signal strength at the receiver to the noise floor and is measured in dB Since both components of the ratio are specified in dBm the SNR can be calculated by simply subtracting the noise value from the signal strength value The minimum required SNR for a receiver to operate properly varies depending on construction of the receiver as well as the bit rate or modulation it is expected to operate at A typical example is shown below Transmission Rate Mbps 1 2 45 5 11 6 9 12 18 24 36 48 54 Signal to Noise Ratio dB 4 6 8 10 j4 5 7 9 12 16 20 21 Ensuring the existence of sufficient SNR is very important when designing for robust and reliable wireless application support This is especially so in wireless voice applications w
275. olitan remote office extended campus locations that we discussed in Figure 5 24 actually comprise a regional entity with the headquarters location in Figure 5 24 now representing a regional headquarters location Each regional headquarters reports to a national headquarters location and there are three other regional headquarters locations that are very similar to what we described in Figure 5 28 In other words we see that the enterprise we discussed in Figure 5 24 is really part of a much larger entity In this section this larger entity is discussed in detail using Figure 5 28 with much of our discussion building on the information we covered in the previous section and Figure 5 24 Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Multiple Location Appliance Designs W Figure 5 28 Multiple Management Domains with Multiple Location Domains National Headquarters Regional Headquarters Regional Headquarters Campus Northern i Southern Region Region Regional 5 gt Regional Remote Locations Remote Locations ahs BAS Si Aa Fag E Regional Headquarters Regional Headquarters I Campus lt gt 2710 i I l Ey l l cs Gl aaa Eastern VLEs 2710 Western l EE i Region Region i i Regional 5
276. ollection using the 2 4 GHz band only Then disable the 2 4 GHz band and enable the 5 GHz band and proceed to repeat the data collection using the 5 GHz band only 2 Perform the calibration data collection using two operators and two independent laptops Each laptop should be equipped with a dual band client adapter compatible with the Cisco Compatible Extensions specification for WLAN devices specification at version 2 or higher and capable of recognizing and responding to S36 unicast radio measurement requests An example of such a client OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter7 Caveats WE CSCsi95122 WCS Does Not Dispatch Northbound Emails for Location Notifications is the Cisco AIR CB21AG Each laptop should be associated to the infrastructure using a different band The two calibration data collection operators may function independently there is no need for them to visit each data point at the same time or to even visit the same data points In this way a complete calibration data collection can be performed across both bands in half the time as option 1 above CSCsi95122 WCS Does Not Dispatch Northbound Emails for Location Notifications WCS does not send email notifications for any location notification alarm categories Alarms for location notifications appear on the alarm console however email notifications do not get transmitted Workaround Use email northbound notifications
277. ommunication with the location aware Cisco UWN It does not attempt to serve as a substitute for the much more comprehensive vendor documentation offered by AeroScout in this regard The following AeroScout documents should serve as the primary reference materials with regard to configuration of AeroScout asset tags using Tag Manager e AeroScout Tag Manager Quick Start e AeroScout Tag Manager 3 0 User Guide In order to take advantage of the new capabilities introduced by the Cisco Compatible Extensions for Wi Fi Tags specification AeroScout asset tags should contain the following tag firmware levels see Figure 6 21 e AeroScout T2 Firmware Release 4 3x or greater e AeroScout T3 Firmware Release 6 0x or greater AeroScout asset tags with firmware releases prior to those listed will still interoperate with software Release 4 1 of the location aware Cisco UWN However tags not meeting these specifications will not take advantage of the capabilities introduced by the Cisco Compatible Extensions for Wi Fi Tags specification that are present in software Release 4 1 Figure 6 21 AeroScout T2 and T3 Asset Tags ee esoScout ITT 223368 AeroScout asset tags contain both a 2 4 GHz IEEE 802 11b transceiver as well as a low frequency short range 125 kHz magnetic signaling receiver 2 4 GHz output power is configurable up to a maximum of 19dBm 81mW During tag configuration AeroScout asset tags use their 802 11b interface
278. on page 3 11 e Tracking Clients Assets and Rogue Devices page 3 13 e Cisco Location Control Protocol LOCP page 3 36 RF Fingerprinting Cisco RF Fingerprinting refers to a new and innovative approach that significantly improves the accuracy and precision of traditional signal strength lateration techniques Cisco RF Fingerprinting offers the simplicity of an RSSI based lateration approach with the customized calibration capabilities and indoor performance previously available only in location patterning solutions RF Fingerprinting significantly enhances RSS lateration by using RF propagation models developed from radio propagation data gathered directly from the target environment or environments very similar to it RF Fingerprinting offers the ability to calibrate an RF model to a particular environment in a fashion similar to but more expeditious than that described for location patterning In addition to the use of prepackaged propagation models RF Fingerprinting offers the ability to develop customized models that are based on on site data collection This process allows for the overall attenuation characteristics of the actual environment to be taken into consideration during the derivation of both 2 4 GHz and 5 GHz path loss models For each calibration grid location the physical location coordinates of the calibration client provided by the calibration operator are recorded along with the client RSSI from three or more LWAPP enabled a
279. on Aware WLAN Design Considerations Access Point Placement W With our recommendation of establishing the convex hull at the true floor physical perimeter notwithstanding in practice the difference in location error rate between points located within the convex hull and outside it may be tolerable in some situations These might include situations where such areas extend beyond the office perimeter for only a short distance for example small 10x10 foot rooms lining the walls of a corridor For example looking at the areas highlighted in red in Figure 5 6 the potential increase in location error would be less in the smaller offices located at the right side of the floor plan than in any other affected area Depending on magnitude the effect of operation outside the convex hull will likely be the least In contrast the areas at the bottom of the floor plan with larger offices and multiple wall partitions would be potentially effected to a significantly higher degree In cases where access point placement in perimeter offices and conference rooms is restricted due to aesthetic concerns a potential compromise may be possible using a very low profile antenna such as the Cisco AIR ANT5959 or Cisco AIR 5145V R along with access point mounting in a plenum rated enclosure where permitted by local codes This would offer the ability to mount access points at the proper perimeter and corner locations thereby avoiding the quandary described in Figur
280. ot be set so short that the location appliance is spending the bulk of its time constantly polling controllers which could impact performance in an environment with many controllers present Remember that the speed at which location updates are displayed on location client screens depends not only on the frequency of updates between controllers and the location appliance but also upon the frequency with which the location client polls the location appliance for updates Recording of asset tag location history is disabled by default If location trending and the analysis of past asset tag location history is desired location history recording should be enabled via the Location gt History Parameters screen as shown in Figure 6 19 Enable the Asset Tags line item and specify the history archival interval between writes of historical data to the database default is 720 seconds Note that the recording of location history is not mandatory to perform asset tag tracking but is often desirable as it allows the location appliance to playback the history of locations the asset tag has visited Figure 6 19 Enabling RFID Tag History Cisco Wireless Control System Monitor Configure Location y Administration Help v Location Server Location Server gt History Parameters gt Administration z History Parameters General Properties 8 po Polling Parameters Archive for ao days History Parameters Prune data starting at z3 Hrs so Mins
281. otentially leading to poor WGB location fidelity until the WGB is faced with a roaming event Access points configured in WGB mode do not respond to broadcast Radio Measurement Requests that are sent as a result of the Cisco Compatible Extensions Location Measurement parameter being enabled Therefore Cisco Compatible Extensions Location Measurement cannot be used as a mechanism with which to trigger consistent periodic probing in work group bridges The Cisco IOS CLI mobile station command can be used on the workgroup bridge to provide a significant degree of improvement in workgroup bridge location fidelity When you enable this setting in the workgroup bridge it causes it to perform an active scan when it detects low access point RSSI excessive radio interference or a high percentage of frame loss The workgroup bridge will use the information it learns from the active scan to determine whether any access points offering better service are available to it and will roam to a new access point before it loses its current association The basic format of the command is mobile station period lt seconds gt threshold lt dBm gt where the value for period denotes how often the workgroup bridge checks the RSSI of its currently associated access point and the value for threshold specifies the absolute value of the minimum acceptable access point RSSI in dBm The default values are 20 seconds and 70 dBm respectively OL 11612 01 Wi Fi Lo
282. otfoctdns CISCO Wi Fi Location Based Services 4 1 Design Guide May 20 2008 Americas Headquarters Cisco Systems Inc 170 West Tasman Drive San Jose CA 95134 1706 USA http www cisco com Tel 408 526 4000 800 553 NETS 6387 Fax 408 527 0883 Text Part Number OL 11612 01 ALL DESIGNS SPECIFICATIONS STATEMENTS INFORMATION AND RECOMMENDATIONS COLLECTIVELY DESIGNS IN THIS MANUAL ARE PRESENTED AS IS WITH ALL FAULTS CISCO AND ITS SUPPLIERS DISCLAIM ALL WARRANTIES INCLUDING WITHOUT LIMITATION THE WARRANTY OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OR ARISING FROM A COURSE OF DEALING USAGE OR TRADE PRACTICE IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT SPECIAL CONSEQUENTIAL OR INCIDENTAL DAMAGES INCLUDING WITHOUT LIMITATION LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THE DESIGNS EVEN IF CISCO OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES THE DESIGNS ARE SUBJECT TO CHANGE WITHOUT NOTICE USERS ARE SOLELY RESPONSIBLE FOR THEIR APPLICATION OF THE DESIGNS THE DESIGNS DO NOT CONSTITUTE THE TECHNICAL OR OTHER PROFESSIONAL ADVICE OF CISCO ITS SUPPLIERS OR PARTNERS USERS SHOULD CONSULT THEIR OWN TECHNICAL ADVISORS BEFORE IMPLEMENTING THE DESIGNS RESULTS MAY VARY DEPENDING ON FACTORS NOT TESTED BY CISCO CCVP the Cisco Logo and the Cisco Square Bridge logo are trademarks of Cisco Systems Inc Changi
283. oundary that is greater than our desired minimal signal threshold How much greater That is determined by the amount of cell to cell overlap we wish to implement in our design which in conjunction with the other parameters we have described will dictate the potential packet loss experienced by VoWLAN devices before a roam event occurs Wi Fi Location Based Services 4 1 Design Guide ou 11612 01 E 521 Chapter5 Best Practices Location Aware WLAN Design Considerations Location Voice and Data Coexistence The application of cell to cell overlap is intended to increase the probability that VoWLAN clients will quickly detect and roam to an adjacent cell without enduring an excessive degree of rate shifting and re transmission as the device approaches the cell boundary Excessive rate shifting and packet re transmission is especially counter productive for VoWLAN devices as such behavior typically results in packet loss which usually translates into jitter Since jitter is well established to be detrimental to a high quality VoWLAN user experience we strive to minimize jitter in our VoWLAN designs by ensuring that devices have the opportunity to roam well before the quality of the user s voice call is in jeopardy We accomplish this by assuring that the recommended degree of cell to cell overlap exists in our designs Figure 5 17 illustrates the concept of cell overlap for a Cisco 7921G VoWLAN handset using 802 1 1bg For the Cisco 7921G t
284. participate in the provisioning of general voice or data coverage as well If using chokepoint location verify that all areas planned for chokepoint trigger installation are clearly within the range of your access points In addition to ensuring that messages transmitted by asset tags located within chokepoint areas are properly received by the system proper planning can help assure I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter5 Best Practices Location Aware WLAN Design Considerations HE Access Point Placement that asset tags can be tracked using RF Fingerprinting as they approach and exit chokepoints The ability to track asset tags using RF Fingerprinting complements the system s ability to locate tagged assets within chokepoint areas using highly granular chokepoint location techniques The access points that form the perimeter and corners of the floor can be thought of as outlining the convex hull or set of possible device locations where the best potential for high accuracy and precision exists By definition the convex hull of a set S of points denoted hull S can be regarded as the smallest polygon P for which each point of S is located either on the boundary or within the interior of P Figure 5 4 illustrates the concept of a convex hull In Figure 5 4 assume the set of access point locations is denoted by the black dots which we refer to as set S The convex hull of set S or Hull S is figu
285. pecially beneficial to those users that depend on the Cisco Radio Resource Management RRM to maintain transmit power control and perform coverage hole remediation RRM functions most effectively when the distribution of access points on a floor is as uniform as possible At this point we must decide on one of the following options 1 Expand the equilateral formations comprising our existing access point constellation to accommodate rearranging the top and bottom rows of access points to form the upper and lower portions of the floor perimeter With this option and our example environment a minimal number of additional access points would be required as their primary use is to fill in any missing areas on the left and right side perimeters Since it requires expanding the separation between access points this option is considered more aggressive when compared to option 2 below Caution must be exercised to avoid modifying the design beyond the limits imposed on access point transmit power see below 2 Contract the equilateral formations comprising our existing access point constellation to accommodate shifting upward the current top row of access points and subsequently introducing a sixth row of access points at the bottom to form a new lower perimeter This option requires a greater number of additional access points when compared to option 1 above However since we are reducing the inter access point distances this option typically does no
286. personnel present Prior observation of activity in this manner allows the designer to plan for the optimum time to perform the calibration so as to yield the most representative results and also to not excessively inconvenience the personnel employed at the facility Recommended Calibration Clients and Techniques The Cisco Aironet 802 1 1a b g Wireless CardBus Adapter AIR CB21AG is highly recommended for use as a calibration client by Cisco This client is compatible with the Cisco Compatible Extensions specification for WLAN devices at version 5 and fully supports the use of both broadcast and unicast radio measurement requests as described earlier in this section If a Cisco Aironet 802 1 1a b g Wireless CardBus Adapter AIR CB21AG cannot be used as a calibration client a third party client device that is compatible with the Cisco Compatible Extensions specification for WLAN devices at version 2 or higher may be used In order to assure a reliable calibration data collection any third party WLAN client used for location data collection should be capable of recognizing and responding to S36 unicast radio measurement requests sent during calibration Also the transmit power level used by third party clients when transmitting probe requests should be known WLAN client devices that are not compatible with the Cisco Compatible Extensions for WLAN devices specification or compatible only with version 1 of the specification are not considered o
287. points 36 and 37 indicated by adjacent yellow stars have been added to the design to complete the formation of the left side of the floor perimeter The two new access points added in Figure 5 21 bring the total access point count for the integrated voice data and location design to 37 access points The primary source of voice and data coverage in this design still emanates from the access points participating in the equilateral formations seen across OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter5 Best Practices Location Aware WLAN Design Considerations HE Location Voice and Data Coexistence the floor i e this can be seen in Figure 5 21 as the set of access points depicted in red Access points 32 34 36 and 37 are necessary to establish a location perimeter but based on the assumptions and calculations presented here may not be required to participate in providing voice or data coverage in either band That being the case these access points can be statically configured to operate at significantly reduced transmit power such as 1 dBm for example which also minimizes the co channel interference contribution of these access points as well Note For information regarding co channel interference concerns in VoWLAN designs it is recommended that readers refer to the Voice Over Wireless LAN 4 1 Design Guide which can be found at the following URL http www cisco com en US docs solutions En
288. points and controllers are capable of communicating with WCS The Cisco Wireless Location Appliance need not be present in order to conduct a location readiness assessment Once the access points that you wish to place on floor maps have been added to the WCS database subsequent location readiness assessments can be conducted using these same access points even if they are not reachable from WCS at that time Because the location readiness inspection is based on access point placement and the inter access point distances shown on the floor maps accurate map placement of access points is very highly recommended The location readiness tool is used to only assess the preparedness of the design to perform RF Fingerprinting based location tracking It does not validate any aspect of the design to perform chokepoint location especially with regard to the definition or positioning of chokepoint triggers After access point placement has been performed select the floor map that you wish to verify the location readiness of and then choose Inspect Location Readiness from the upper right hand dropdown command menu A point is defined as being location ready if the following are all determined to be true At least four access points are deployed on the floor At least one access point is found to be resident in each quadrant surrounding the point in question At least one access point residing in each of at least three of the surrounding quadrants is loc
289. points to participate in the provisioning of voice or data service to the floor Figure 5 5 provides an illustration where these concepts are applied to a floor with a type of floor plan found in many enterprises that of rooms or offices contained by and surrounding an interior corridor In this case the area in which we desire to locate tracked assets is the entire floor In Figure 5 5 note that the access points located towards the center of the floor are complemented by those that have been Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Access Point Placement W placed along the perimeter As is the case in most proper location aware designs the set of location data points possessing the highest potential for good location accuracy is contained within the convex hull which in Figure 5 5 is represented by the blue rectangle and encompasses the entire floor Figure 5 5 Proper Access Point Perimeter Placement CORRIDOR O g g a a cc co a a 8 8 224157 In some cases customer preferences or deployment restrictions may factor into the access point placement decision and the placement of access points at the floor perimeter may be restricted in one way or another While this still may result in acceptable placement from the perspective of providing basic RF coverage because there may be significant areas where asset tr
290. present in the Location Appliance instead of WCS with software Release 4 1 For additional caveats than those discussed above refer to the following documents e Release Notes for Cisco Wireless Location Appliance 3 0 http www cisco com en US products ps6386 prod_release_notes_list html e Release Notes for the Cisco Wireless Control System WCS 4 1 http www cisco com en US products ps6305 prod_release_notes_list html e Release Note for Cisco WLAN Controllers and Lightweight Access Points 4 1 http www cisco com en US products ps6366 prod_release_notes_list html e Release Notes for Cisco Aironet Access Points for Cisco IOS Release 12 3 11 JA1 http www cisco com en US products hw wireless ps430 prod_release_notes_list html e Cisco Bug Toolkit http www cisco com pcgi bin Support Bugtool home pl Wi Fi Location Based Services 4 1 Design Guide a OL 11612 01 APPENDIX A Determining Approximate Roots using Maxima In the circle circle intersection equations below e d represents the inter access point distance in feet e Obg represents the percentage of overlap desired for 802 11bg e Oda represents the percentage of overlap desired for 802 11a e R represents the cell radius in feet Note that zero overlap occurs when the distance between the centers of the two circles is equal to twice the radius d 2R This relationship becomes invalid if d is allowed to exceed 2R as an area of intersection would be i
291. ptimal for use in location calibration data collection Note that when using a laptop computer containing the Intel PRO Wireless 3945ABG Network Connection or the Intel PRO Wireless 2915ABG Network Connection adapter the default configuration is for a Personal level of security settings intended for non enterprise use that does not include compatibility with the Cisco Compatible Extensions specification When using this default Personal level of wireless security clients equipped with the Intel 3945ABG or 2915ABG client adapters will not support S36 unicast or broadcast radio measurement requests and are not compliant with the Cisco Compatible Extensions specification for WLAN devices OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations W Calibration In order to enable compatibility with the Cisco Compatible Extensions specification the Intel ProSet client supplicant must be used to reconfigure the client for Enterprise Security and enable Cisco Compatible Extensions Figure 5 42 and Figure 5 43 illustrate how this is performed Figure 5 42 Intel ProSet Security Settings Panel Wireless Profile Properties secure_PEAP x Profile Name secure_PEAP A A S General Settings Security Settings 8 Security Settings Personal Security Enterprise Security PEAP Server Network Authentication wra2 Enterprise Data Encryption aes CCM
292. q n only Datapoint true location xX Y ft Datapoint estimated location X Y ft 60 8 40 6 77 2 44 3 Location Error ft 16 8 Timestamp Client MAC Address B Thu Oct 11 22 32 55 EDT 2007 00 40 96 a1 9d 47 N When a mouse over is performed of any calibration data point whose location is indicated using small crosshair and is based on the actual coordinates reported by the calibration operator the following information is displayed e The predicted location of the calibration client depicted on the location inspection display by X e The RSSI detected by each contributing access point and the band the contribution was made on as shown in Figure 5 46 by symbols such as BG 74 or A 59 e The true and estimated location of the calibration data point listed numerically in terms of x and y coordinates e The estimated location error e A time stamp indicating when the calibration information was collected and the MAC address of the calibration client used to perform the collection Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Inspecting Location Quality Hii Note that the band can be specified 2 4 GHz 5GHz or both as well as the performance criteria The flexibility imparted by this level of control allows the system designer to perform what if planning based on the results of location inspection and examin
293. r As mentioned earlier after chokepoint triggers have been individually configured using the configuration tools supplied by the vendor they must be defined to WCS placed on appropriate floor maps and synchronized with the location appliance as part of an updated network design Only then can they can be used to track asset tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification Complete step by step guidance regarding how to define compatible chokepoint triggers to WCS and the location appliance can be found at the following location http www cisco com en US products ps6386 products_configuration_guide_chapter09186a008082d7 d2 html wp 1058654 When defining chokepoint triggers it should be noted that the range is specified in both the vendor s configuration program as well as in WCS shown in Figure 6 30 However it is the range configuration parameter specified in the vendor s configuration program that actually sets the transmission range of the chokepoint trigger not the range setting in WCS The value that is specified for the range of the chokepoint trigger in WCS simply sets the size of the gray concentric rings that appear surrounding each chokepoint icon on WCS floor maps These concentric rings are visual aids placed simply to serve as a convenient reminder of the range associated with the chokepoint trigger WCS and Vendor Range Parameters Compared Settinas Taq Reaction Taq Transmission Parame
294. r Manager standalone software utility must be used shown on the left in Figure 6 29 For WhereNet WherePort chokepoint triggers the WhereNet System Builder shown on the right in Figure 6 29 and the WhereNet Where Wand are used OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations Figure 6 29 Transmssion interval mec Operation Mode C Actos Stave Exciter Actos Standalone Mastor Exctor Tog Response Select he Tag response whan nggered by Excaor Send ony Exciter A r E C Activate Tag and send Excitar O C Send Excter ID ond deactivate Tog J atom General Cor guraton Ce C Send Excter ID and change Tog tansenission mode Chokepoint Considerations Vendor Specific Configuration Utilities Asano WherePart Identity WherePort Location Advanced Settings Excteri0 rate 000C OC E0 TE BA WherePort Identity Date Installed Tag Onentation Maximum Transmission Range om 200 gt Exoter ID 7818 Number 10 Enabled Used To Locate 7 WP Type WPI X Transmit ID 2224 Short Xmit ID s Barcode ID WP Health Tag TagiD 18000101 67 7 2006 X Orientation G Random C Controlled nom Standalone Master Tag Height it Mnf 40 Enabled G Hoir C Vet M l 40 C Up Down Serial Number z Operations Votage 5 Side View Trontmissio nRange 2 Transmiss
295. r environment This is a general recommendation that is intended to assist designers in avoiding situations where excessive inter access point distance may be a contributing factor to location inaccuracy As shown in Figure 5 10 diminished RSSI differentiation with increasing distance is a gradually increasing phenomenon therefore a degree of flexibility is implied in this recommendation In practice in addition to being conducive to good location accuracy this recommendation applies well to deployments where location tracking is deployed in conjunction with other WLAN applications such as voice and high speed data in accordance with current recommended best practices This is especially true for environments where the expected path loss exponent is 3 5 walled office environment or higher as the required inter access point spacing tends to generally fall within this range In addition to the potential effects of a lack of RSSI differentiation at distance extremes inter access point distances significantly greater than 70 to 80 feet can make it more challenging to satisfy the best practice signal strength and overlap requirements of VoWLAN devices such as the Cisco 7921G and the Vocera Communication Badge in environments with high path loss At ranges closer than point a in our example propagation anomalies that are due to the elevation pattern of the chosen antenna the antenna s installation height and the current physical location of the trac
296. r installations using diversity antennas the standard deviation of shadow fading is often seen between 3 and 7 dB The generally accepted method to calculate receiver signal strength given known quantities for transmit power path loss antenna gain and cable losses is as follows RXpwr TXpwr Lossyy Gainyy PL Gaingy Losspy OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter2 Location Tracking Approaches Hi Distance Based Lateration Techniques We can directly substitute our equation for path loss into the equation above This enables us to solve for distance d as follows TX pwr RX pwr Lossry Gainry PL meter ts Gdinpy LOSSpy d 10 10n where the meaning of the terms in the equation above are e RXpwp represents the detected receive signal strength in dB e Txpwp represents the transmitter output power in dB e Lossyy represents the sum of all transmit side cable and connector losses in dB e Gain y represents the transmit side antenna gain in dBi e LossSpxy represents the sum of all receive side cable and connector losses in dB e Gainpgy represents the receive side antenna gain in dBi Note that all of these are to be specified as positive values Solving for distance between the receiver and mobile device allows a circular area to be plotted around the location of the receiver using the distance d as the radius The location of the mobile device is believed to be somewhere on
297. r naming conventions that bring a modicum of sensibility to such an approach a technical limitation exists whereupon the location appliance currently does not take into account tracked device RSSI coming from access points that are deemed to be located on a different floor than the tracked device itself Thus when physical floors are divided into areas that are then defined to WCS as individual floors themselves tracked devices that venture into the edge boundary areas of these newly defined floors may experience degraded accuracy Unless the designer as well as the system user is comfortable with this limitation and its potential impact on boundary area accuracy this approach is best avoided While there is no ideal solution to situations where the degree of uniformity is vastly different across a floor in general option 1 is observed to offer the best compromise between ease of implementation and performance Location Quality Location inspection allows path loss model accuracy to be validated by comparing the actual versus the predicted location of calibration data points Unlike the location planner or location readiness tools which are purely predictive in nature when you perform location inspection you are directly comparing the predicted locations of calibration data points to the actual physical locations originally specified by the calibration operator In order for location inspection to deliver on its true value however accurat
298. rameters is discussed in the document entitled Cisco Wireless Location Appliance Configuration Guide Editing History Parameters at the following URL http www cisco com en US products ps6386 products_configuration_guide_chapter09 186a008082d7 2f html wp 1046373 Further clarification regarding some of these parameters is provided in the subsections that follow A common misconception about the history capabilities of the location appliance is that it somehow stores a historical record of all locations the client has ever encountered As is discussed in the following two sections the location application stores history information based on the values of the archive period and archive interval parameters If a history record for a device is recorded at time T and the archive period is 30 the next history record for that device is written at Ty 39 The device may have undergone several changes in location between To and T9 39 however only the location states at time To and To 39 are recorded in the history database History Archive Period The history archive period shown as Archive For specifies the number of days that the location appliance retains location history records for each enabled history collection category The default archive period is 30 days Changes to the default history archive period should be done with careful consideration after consultation with your Cisco field technical representative or the Cisco Technical Ass
299. ratively represented as an elastic band shown by the blue line that is stretched and allowed to snap over the outermost members of the set which in this case represents perimeter and corner access points The interior area encompassed by this band depicted in green can be considered as possessing high potential for good location accuracy As tracked devices stray into the area outside the convex hull outside the green area in Figure 5 4 accuracy can begin to deteriorate Although it may vary given the number of access points deployed and their inter access point spacing generally speaking the rate of this accuracy degradation has been seen to be almost linear as the tracked device moves further and further outside the convex hull For example a device that experiences less than or equal to 10m 90 accuracy within the convex hull may deteriorate to 18m 90 by the time the device moves to a point 20 feet outside it Figure 5 4 The Convex Hull of a Set of Points In order to assure proper convex hull establishment around the set of location data points possessing high potential for good accuracy access points should be placed in each corner of the floor as well as along the floor perimeter between corners Inter access point separation along the perimeter should be in accordance with the general access point separation guidelines described in a subsequent section The designer may reduce this spacing if necessary in order for these access
300. rdware or software required The location aware Cisco UWN with RF Fingerprinting uses a network side location model Because of this Cisco RF Fingerprinting can provide location tracking for a wide variety of industry standard Wi Fi clients and not just those Wi Fi Location Based Services 4 1 Design Guide P32 E OL 11612 01 _ Chapter 3 Cisco Location Based Services Architecture RF Fingerprinting E with popular Windows based operating systems without the need to load proprietary client tracking software or location enabled wireless drivers in each client This includes popular VoIP handsets such as the Cisco 7920 and 7921G devices for which such proprietary add on location tracking client software is not available Supports popular Wi Fi active RFID asset tags Because the location aware Cisco UWN implements RF Fingerprinting as a network side model there is no dependency on proprietary software being resident in RFID asset tags in order to allow for localization This enables the location aware Cisco UWN to interoperate with active RFID asset tags from popular vendors including AeroScout PanGo Networks WhereNet G2 Microsystems and others Asset tags that support the Cisco Compatible Extensions for Wi Fi Tags specification can take advantage of advanced features introduced with software Release 4 1 such as the ability to pass tag telemetry and chokepoint information to the Cisco UWN Cisco makes this specification available to
301. re 5 2 and Figure 5 3 Figure 5 2 _ Tags gt Tag Asset Tag Properties Vendor Controller Battery Life Location Floor Last located at On Location Server Enlarge AeS_Loc2 Aeroscout 10 1 56 18 Normal Alpharetta Campus_Group gt AP1242 Building gt Test Lab Annex 2 May 2 2006 10 03 19 PM Enabling Location Debug Select a command Go Asset Info Name Group AeroScout RFID Category Location Debug V Enabled Update This will show AP RSSI Information on the Map Statistics Bytes received 101040 Packets received 3368 Location Notifications Absence Containment Distance lo lo o All 190564 w_ Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Access Point Placement W Figure 5 3 Displaying Detected RSSI via the GUI Cs Cs 71 dem RSSI Readings Detected RSSI Radio Type Age when Located 71 dBm 11bg 16 secs AP 00 14 1b 59 42 70 AP1242 2 CI 190565 CEs dem Access Point Placement Proper placement of access points is one of several best practices that should be adhered to in order to unleash the full performance potential of the location aware Cisco Unified Wireless Network In many existing office wireless LANs access points are distributed mainly throughout interior spaces providing service to the surrounding work areas
302. red to each in this example and the calculated value for LOCP Wi Fi Location Based Services 4 1 Design Guide Pe30 i OL 11612 01 _ Chapter 6 RFID Tag Considerations Chokepoint Considerations W Information Notifications rgr 4 would have been the same It is the number of access points that detect the tag multicast transmissions bearing the high priority notification information sent that is pertinent to the number of LOCP Notifications that will be generated from controllers to the location appliance To ensure proper LOCP operation between the location appliance and any WLAN controllers defined to it always ensure that port 16113 is not blocked by any firewalls or other security devices Configuring Tags for Telemetry and Notifications While the support of tag telemetry and notifications are basic components of the Cisco Compatible Extensions for Wi Fi Tags specification each tag vendor uses their GUI or CLI based tag software to enable disable or otherwise customize precisely how these features are supported in their products While a limited amount of AeroScout tag configuration information has been already provided in prior sections of this document more comprehensive information specifically relating to the configuration of external telemetry sensors and asset tags is available from asset tag vendors but is beyond the scope of this document Readers seeking such information are directed to the following sources of info
303. rior rooms or floors such as doorways ramps gates stairwells elevator entrances and so on e Adjacent structures such as passageways or tunnels or the interior and exterior of structures main and auxiliary entrances loading docks fire exits and so on Chokepoint triggers can initiate behavioral changes in tags that can immediately alert the location system that the tagged asset has entered or exited the chokepoint area Due to the comparatively modest range of chokepoint triggers in relation to the overall area covered by an RTLS the RTLS is able to deterministically localize the asset to the confines of the chokepoint area relatively quickly and with excellent reliability In addition to displaying the chokepoint area on floor maps the RTLS can use the Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 _ Chapter 6 RFID Tag Considerations RFID Tag Technology W detection of assets within chokepoints to trigger events in external systems These can include database updates notification alerts or alarms When properly augmented by appropriate application software chokepoint applications may include e Tracking of high value assets Chokepoint location tracking can help ensure that valuable assets intended for a particular area stay within such areas If these assets are detected as being removed via entrances or exits for example the RTLS is alerted e Manufacturing process control Equipment parts
304. rlap using 802 11a and 33 4 feet for a 20 cell to cell overlap using 802 11bg At this point we have the information necessary to calculate the access point transmission power settings that will be necessary to achieve our desired cell signal boundaries This can be performed using a form of the equation presented earlier to calculate receive signal strength TXpowgr from knowledge of our reference path loss path loss exponent transmit power and various miscellaneous receive and transmit gains and losses This was discussed in Received Signal Strength RSS page 2 7 As it is the transmit power TXpower of our access points that we wish to calculate and not the receive signal strength we shall use a modified form of the equation as follows TX power RX power LOSS Gain PLi merer 10log D s Gain LOSS py For the purposes of this example we have assumed e That transmission losses due to cables connectors etc Lossy and Losspy are equal to 0 dB e 0 dB shadow fading standard deviation e Receive antenna gain for our legacy 2 4 GHz data client devices of 0 dBi Substituting the appropriate values along with our expectation of a 67 dBm minimum receive signal strength RXpower for both 802 11a 802 11bg as well as the appropriate antenna gains our cell radius in meters 30 88 feet 9 41 meters 33 4 feet 10 18 meters an estimated path loss exponent n of 3 5 and our reference path losses we obtain the following r
305. rmation e AeroScout T2 Tag User Guide e AeroScout Tag Manager User Guide version 3 0 e http www aeroscout com or your AeroScout account and technical support team For asset tags from other vendors that are compatible with the Cisco Compatible Extensions for Wi Fi Tags specification it is recommended to contact those vendors directly These would include e InnerWireless formerly PanGo Networks http www innerwireless com e WhereNet http www wherenet com Chokepoint Considerations Configuring Chokepoint Triggers In order to use chokepoint triggers with the Cisco UWN they must be properly configured using the appropriate vendor supplied software utility defined to WCS placed on floor maps and synchronized as part of an updated network design to the location appliance After all of this is complete the location appliance will be able to recognize that asset tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification have been stimulated by a particular chokepoint trigger MAC address and proceed to localize the asset tag Location clients may then display the asset tag s location at the chokepoint icon associated with the chokepoint trigger s MAC address Various chokepoint trigger specific parameters such as transmission range IP address transmission interval transmission repetitions and so on are set using vendor specific utilities For non IP addressable AeroScout EX 3100 series Exciters the AeroScout Excite
306. rol Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter6 RFID Tag Considerations RFID Tag Technology Wl Figure 6 2 Passive RFID Interrogators lel Passive RFID tags shown in Figure 6 3 consist of a coil and a microcircuit that includes basic modulation circuitry an antenna and non volatile memory 190589 Figure 6 3 Passive RFID Tags 190590 Passive RFID tags vary in how they communicate data to RFID readers and how they receive power from the RFID reader s inductive or electromagnetic field This is commonly performed via two basic methods e Load modulation and inductive coupling in the near field In this approach see Figure 6 4 the RFID reader provides a short range alternating current magnetic field that the passive RFID tag uses for both power and as a communication medium Via a technique known as inductive or near field coupling this magnetic field induces a voltage in the antenna coil of the RFID tag which in turn powers the tag The tag transmits its information to the RFID reader by taking advantage of the fact that each time the tag draws energy from the RFID reader s magnetic field the RFID reader itself can detect a corresponding voltage drop across its antenna leads Capitalizing on this phenomenon the tag can communicate binary information to the reader by switching ON and OFF a load resistor to perform load modulation When the tag performs load modulation
307. ronment and allow it to re calculate the path loss model In many cases this can help to restore lost accuracy and performance to the system From a practical standpoint the location aware Cisco UWN is seen to be more tolerant of environmental path loss changes when those changes move from higher path losses to lower path losses relative to the path loss model currently in use Therefore if faced with designing a location tracking for an environment where seasonal content variations are the norm it is recommended that the calibration of the site be performed at peak content levels when path losses would be expected to be at their highest The use of a high path loss model when actual path loss is lower than expected has been shown to produce better location performance than the use of a path loss model with low path loss when the actual path loss of the environment is higher than expected Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Calibration W Examples of the types of changes where a re calibration may be recommended if a significant drop in performance is noticed include but are not limited to the following cases e Changes in stocked material A floor of an supply warehouse that was last calibrated when it contained paper products has now been converted to stocking bulk metal containers of dense liquids such as motor oil transmissio
308. roper configuration by the vendor s chokepoint management software may not function properly Once configured chokepoint triggers can operate in one of two modes e An online mode where their status is monitored by software supplied by the chokepoint trigger vendor via an Ethernet or serial data connection e An offline mode where the configured chokepoint trigger operates with only a power connection required Chokepoint triggers are identified by unique addresses that enables tags receiving their transmission to clearly identify the chokepoint trigger responsible for stimulating them This identifier is typically the MAC address of the chokepoint trigger for Ethernet based models but could be any locally administered and assigned identifier such as a Transmit ID of a WhereNet WherePort In Release 4 1 of the location aware Cisco UWN shown in Figure 6 13 when an asset tag compatible with the Cisco Wi Fi Location Based Services 4 1 Design Guide Ca OL 11612 01 _ Chapter 6 RFID Tag Considerations RFID Tag Technology W Compatible Extensions for Wi Fi Tags specification enters the effective range of a chokepoint trigger the tag is stimulated by the chokepoint trigger and identifies the source of such stimulation to the location aware Cisco UWN using a tag multicast frame that is sent via using 802 11 All access points detecting this tag multicast frame forwards it to their registered controller which in turn res
309. roximately 71 bytes slightly larger than the multicast frame transmitted by these same tags during routine periodic transmissions 56 bytes This 71 byte length is greater than the expected 63 bytes and upon further examination it is discovered that eight additional bytes of vendor specific information is included The Cisco Compatible Extensions for Wi Fi Tags specification also allows asset tags to communicate historical information about the chokepoints they traverse to the Cisco UWN This could increase the size of the frame by approximately 10 bytes per chokepoint trigger encountered depending on the number of historical entries maintained The basic size of a LOCP Measurement Notification Ethernet frame is approximately 160 bytes Frame sizes may be larger based on additional information included in the frame such as historical chokepoint information In software Release 4 1 LOCP Measurement Notifications are not aggregated by WLAN controllers WLAN controllers will transmit a LOCP Measurement Notification frame to the location appliance for each incoming tag multicast transmission received by each of its registered access points that indicates that the tag has been successfully stimulated by a chokepoint trigger Therefore the number of LOCP Measurement Notifications generated by one or more WLAN controllers for a single tag transmitting multicast frames indicating that the tag has been stimulated by a chokepoint trigger is dependent upon
310. ructure is configured for as seen in Figure B 1 If the proper frame formats are not seen on the protocol analyzer trace this should be addressed via the asset tag configuration or by replacing the asset tag if necessary especially if the asset tag firmware is out of date If the proper frames are seen on the RF protocol analyzer attempt to reset tag detection in the controller by issuing the following commands config rfid status disable config rfid status enable If the issue continues to persist despite these suggestions it is recommended that you capture all the details collected so far including the protocol analyzer traces and contact the Cisco Technical Assistance Center for further debugging assistance Verifying Asset Tag Telemetry and Events B 8 Step 1 Step 2 In order to verify that WLAN controllers are detecting asset tag telemetry and high priority events and forwarding that information to the location appliance using LOCP the following procedure may be used Make sure that the asset tag is detected by the WLAN controller using the procedure outlined in the previous section Verify that the telemetry or high priority emergency event information you are concerned with has been recorded in the RFID database on the controller show rfid detail lt tag mac addr gt Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 AppendixB Verifying Detection of Asset Tags in WLAN Controllers Step 3
311. s OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter1 Overview HE About the Guide Monitoring the health and status of key assets in their environment and receiving prompt notification of changes Receiving prompt notification when unauthorized addition or removal of assets occurs This guide discusses the location aware Cisco Unified Wireless Network UWN It is focused on indoor location based services design considerations and select deployment topics References to applicable existing documentation are made throughout the document and a wealth of material is provided addressing topics such as The fundamentals of positioning technologies including lateration angulation and pattern recognition approaches How Cisco RF Fingerprinting operates and how it compares to other approaches The architecture of the location aware Cisco UWN Design best practices including voice data and location based service coexistence Tips on proper installation and configuration About the Guide Target Audience This guide is intended for individuals interested in designing and deploying indoor Cisco wireless LAN WLAN solutions that include the Cisco Wireless Location Appliance the Cisco Wireless Control System WCS and other components of the Cisco Unified Wireless Network UWN Objective This guide is intended to accomplish the following objectives Provide the reader unfamiliar with location bas
312. s Each WCS server communicates with WCS Navigator via its northbound API allowing for the events activities and resources of each regional management domain to be monitored and managed via a centralized portal Figure 5 28 contains a single management and a single location domain primarily dedicated to the WLAN and location tracking needs of the national headquarters staff itself This design contains a total of nine location domains and five management domains To provide top down management of the entire Unified Wireless Network WCS Navigator is also deployed in the national headquarters location providing both management and location visibility to all four regional campuses in addition to the national headquarters WCS Navigator communicates with each of the five WCS servers via the WCS server s northbound API allowing for the events activities and resources of each regional management domain to be monitored and managed via a centralized portal Figure 5 29 illustrates the network summary screen of WCS Navigator where we can see its ability to monitor the status of multiple WCS servers as well as their location appliances The alarm counts shown here represent aggregate quantities across all the monitored management domains Clicking on any link takes the user to the appropriate detail screen using information retrieved from the WCS server that is responsible for the particular domain being queried Figure 5 29 WCS Navigator Summary Screen
313. s If archiving of tag historical information has been enabled on the location appliance tag emergency information is archived along with other tag information shown in Figure 6 28 The basic size of a LOCP Information Notification Ethernet frame is approximately 130 bytes Frame sizes can be larger based on additional information included in the frame such as tampering information or vendor specific data In Release 4 1 LOCP Information Notifications are not aggregated by WLAN controllers WLAN controllers will transmit a LOCP Information Notification frame to the location appliance for each tag high priority notification received via each of its registered access points including any high priority notification repetitions Expressed mathematically it can be stated that for each notification event coming from a tag the total number of LOCP Information Notifications that can be expected to be transmitted from a WLAN controller to the location appliance can be calculated as LOCP Information Notificationsrorar Detecting APSrorar High Priority Notification Repetitions per CHANNEL where High Priority Notification Repetitions pgp cyanner represents the total number of high priority notifications that are sent by the tag on a single RF channel Note that the number of high priority notification repetitions per channel should not be confused with the standard setting for tag message notifications per channel which applies to tag transmiss
314. s 5 63 Inspecting Location Quality 5 64 Using Test Points to Verify Accuracy 5 68 CHAPTER 6 RFID Tag Considerations 6 1 RFID Tag Technology 6 1 Passive RFID Tags 6 2 Semi Passive RFID Tags 6 5 Active RFID Tags 6 6 Beaconing Active RFID Tags 6 7 802 11 Active RFID Tags 6 7 Multimode RFID Tags 6 8 Chokepoint Triggers 6 9 Using Wi Fi RFID Tags with the Cisco UWN 6 15 Compatible RFID Tags 6 15 Using 802 11b Tags in an 802 11g Environment 6 16 Enabling Asset Tag Tracking 6 17 Enable Asset Tag RF Data Timeout 6 17 Enable Asset Tag Polling 6 18 Enable Asset Tag Display 6 20 Configuring Asset Tags 6 20 Tag Telemetry and Notification Considerations 6 27 Deploying Tag Telemetry 6 27 Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Contents W E Contents Deploying Tag High Priority Notifications 6 30 Configuring Tags for Telemetry and Notifications 6 31 Chokepoint Considerations 6 31 Configuring Chokepoint Triggers 6 31 Defining Chokepoint Triggers to the Cisco UWN 6 33 Chokepoint Trigger Traffic Considerations 6 34 CHAPTER 7 Caveats 7 1 CSCse14724 Degraded Location Accuracy with Monitor Mode APs 7 1 CSCsh88795 CCX S36 Beacon Measurement Request Dual Band Support 7 1 CSCsi95122 WCS Does Not Dispatch Northbound Emails for Location Notifications 7 2 appendix A Determining Approximate Roots using Maxima A 1 aprPenpix B Verifying Detection of Asset Tags in WLAN Controllers B 1 Asset Tags Detection
315. s up the Tag Details panel shown in Figure 3 17 The tag summary icon becomes especially useful when chokepoint location introduced with software Release 4 1 of the Cisco UWN is used When chokepoints have been defined to the system and properly defined on floor maps the icon of any asset tag that known to be within range of the chokepoint trigger will be placed at the center of the chokepoint icon shown in Figure 3 19 at the Breakroom chokepoint However if more than one asset tag is in proximity of the same chokepoint the tag icons will overlap and usability will suffer In this situation the tag summary icon shown in Figure 3 18 once again is used to restore clarity An example of the tag summary icon being used in this can be seen in Figure 3 19 at the chokepoint labeled Lower Level Entrance Figure 3 19 Tag Summary Icon and Chokepoint Location ZEA Fig API 242 5 Flag LOZEJ p AP1242 4 00 0c cc 5c 05 4f Breakroom t EEN Lower Level Entrance EER UZRA 2 OZE a 223315 Wi Fi Location Based Services 4 1 Design Guide 326 i 0L 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices W Note that Figure 3 20 also includes a hyperlinked listing of location notifications as well as a miniature location map of the asset tag s location By enabling the Location Debug parameter and enlarging the map WCS displ
316. signing the role of transmitting probe requests to another device that is for example equipped with a Cisco AIR CB21AG As shown in Figure 5 44 this arrangement allows the location of the probing client otherwise referred to as a remote calibration client as well as the timing of each data collection to be fully controlled from the laptop The probing client with MAC address 00 1a a1 92 a1 20 in Figure 5 44 is remotely instructed to issue probe requests to the network infrastructure appropriately 1 For further information refer to CSCsh88795 CCX S36 Beacon Measurement Request Dual Band Support page 7 1 Wi Fi Location Based Services 4 1 Design Guide n OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Calibration W Figure 5 44 Controlling Calibration Data Collection Remotely stints Wireless Control System cisco Monitor Reports Configure Location Administration Help v Quick Search Calibration Model gt Test 3 gt Start Calibrating Enter MAC Address of Client Joo 1a a1 92 a1 20 Search Maps Choose the Floor on which this Model is intended to be calibrated Saved Searches Edit Campus Alpharetta Campus z Select Search z Building Concannon Building Floor Area Main Floor z Next Cancel Client should be detected by APs on the chosen floor For calibration Automatic power assignment should be turned off This can be done by making sure
317. sing the reliability of tag telemetry as well It is recommended that the tag vendor s configuration software should be used to set the number of tag transmissions to three but not more than five per channel per transmission interval Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 _ Chapter 6 RFID Tag Considerations Tag Telemetry and Notification Considerations W Although it is unlikely that LOCP telemetry collection will burden modern wired and wireless networks nevertheless it is good practice for the network designer to understand the nature of the traffic that can be expected in their designs The following traffic and frame size information has been observed during LOCP telemetry testing in support of this document e Echo Request Sent periodically by the location appliance to each defined WLAN controller based on the configuration of the Echo Interval parameter Location Servers gt Advanced gt LOCP Parameters LOCP Echo Request Ethernet frames are 100 bytes in length and are transmitted to TCP destination port 16113 e Echo Response Sent periodically by each WLAN controller in response to an Echo Request see above Like Echo Requests LOCP Echo Response Ethernet frames are 100 bytes in length e Information Request Sent periodically by the Location appliance to each WLAN controller to request information LOCP Information Request Ethernet frames are 106 bytes in length are transmitted to TCP dest
318. sitioning information Wi Fi Location Based Services 4 1 Design Guide Ea OL 11612 01 Chapter 2 Location Tracking Approaches Location Patterning Pattern Recognition Techniques _ Location patterning positioning algorithms can be classified into three basic groups e Deterministic algorithms attempt to find minimum statistical signal distance between a detected RSSI location vector and the location vectors of the various calibration sample points This may or may not be equal to the minimum physical distance between the actual device physical location and the recorded location of the calibration sample The sample point with the minimum statistical signal distance between itself and the detected location vector is generally regarded as the best raw location estimate contained in the calibration database Examples of deterministic algorithms are those based on the computation of Euclidean Manhattan or Mahalanobis distances e Probabilistic algorithms use probability inferences to determine the likelihood of a particular location given that a particular location vector array has already been detected The calibration database itself is considered as an a priori conditional probability distribution by the algorithm to determine the likelihood of a particular location occurrence Examples of such approaches include those using Bayesian probability inferences e Other techniques go outside the boundaries of deterministic and probabi
319. ss points and antennas are installed and representative of the final configuration The maximum transmit power level supported as well as the probing behavior of the test client should be as close as possible to that of the production clients you wish to track Figure 5 1 indicates that the output of the CLI command displaying the signal strength of the client as detected by all of the access points detecting the client registered to the same controller In situations where the detecting access point registrations are distributed among two or more controllers more than one CLI session is required From the information provided within the red rectangular area in Figure 5 1 it can clearly be seen whether or not the client in Wi Fi Location Based Services 4 1 Design Guide T 0L 11612 01 o5 Chapter5 Best Practices Location Aware WLAN Design Considerations Hs Minimum Signal Level Thresholds question is being detected by three or more access points at the recommended signal strength level or better In a similar fashion to that shown for WLAN clients in Figure 5 1 the CLI command show rfid detail lt mac address gt can be used to display detected RSSI information for an asset tag This same information can be obtained graphically via the location map GUI by clicking on either a WLAN client icon blue rectangle or asset tag icon yellow tag enabling the location debug checkbox and then enlarging the miniature location map as shown in Figu
320. ssages such as Information and Measurement Requests and Responses Cisco Unified Wireless Network software Release 4 1 introduces the initial phase of LOCP In this release LOCP is used to augment traditional SNMP polling by transporting Cisco Compatible Tag Extensions for Wi Fi tags telemetry and notification traffic from WLAN controllers to the location appliance This traffic includes e Cisco Compatible Extensions for Wi Fi tag telemetry such as Motion temperature pressure humidity distance quantity and status Battery state and predicted remaining life e High priority Cisco Compatible Extensions tag traffic such as Call button tag detached and tamper alert events Entry into the range of a chokepoint trigger Vendor specific tag information used by third party location clients amp Note Commencing with software Release 4 2 the Location Control Protocol LOCP receives additional enhancements and evolves into the Network Mobility Services Protocol NMSP Asset Tag Telemetry Using LOCP Beginning with Cisco UWN software Release 4 1 Wi Fi RFID tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification may optionally pass tag telemetry information to the location aware Cisco UWN as part of their tag message payload This telemetry information is received by access points and collected by WLAN controllers The location appliance periodically polls the WLAN controllers for tag telemetr
321. ssed Data Collected Wed Aug 15 19 07 39 EDT 2007 Tamper State mace Controller 10 1 96 18 Battery Status 80 223317 In many cases it is desirable to sequentially display the location history of an asset tag so as to better visualize and trace the movement of the asset tag and the attached asset throughout the environment over time This can be very useful for example in establishing a trail of motion in security and monitoring applications Cisco WCS and the location appliance make it possible to do this by playing back each location history record with a configurable time delay The granularity of the movement shown depends on the interval with which client history records are recorded in the database Wi Fi Location Based Services 4 1 Design Guide 328 i 0L 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices To see location history played back in this fashion simply click the Play button shown in Figure 3 21 and past location history should start being displayed both in tabular form and graphically Large amounts of location history data may be more readily viewed by reducing the Change Selection Every interval shown in Figure 3 21 from 2 seconds to 1 second Rogue Access Points Figure 3 22 stfecttes cisco Contributing APs M sjct4 31b ap5 M sjct4 32b ap6 v sjcl4 31b ap3 Load Loading Chokepoints Loaded 0 chokepoints Done h 4
322. ssuing the following command on the controller config rfid status enable Note that some access point commands can also be executed remotely from the controller using the access point remote debugging feature debug ap enable lt Cisco AP gt debug ap command lt command gt lt Cisco AP gt b If tag detection is enabled and the asset tag is configured to transmit on the channel the access point is configured for check to see that the access point is forwarding the tag multicast packet to the controller by enabling the following debugs on the access point debug dot11 Dot11Radio 0 trace print mcast amp Note In software Release 4 1 in order for the output of the debug dot11 Dot11Radio 0 trace print mcast command to be viewed the command must be entered directly at the access point console It cannot be entered remotely from the controller OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide gO Appendix B Verifying Detection of Asset Tags in WLAN Controllers HI Verifying Asset Tag Telemetry and Events 4A1F8FBO r 1 60 38 0803 000 m014096 5D33CF m61356B 6D00 000000 173 0012 0606 0100 0200 3302 0742 0000 0000 0000 0302 0A03 0109 0000 8000 occc 6010 BF04 0800 OCCC 6E10 BFOO 0000 019C 917C 00B8 F564 608F FDO5 0000 m014096 The 3 bytes following the letter m represents the first 3 bytes of the multicast address used for asset tags compliant with the Cisco Compatible Extensions for Wi Fi Tags speci
323. t AP1242 wes 1 Aeroscout Loci 10 1 96 18 80 Building gt Test Le Username Navigator User Logout Refresh Print View gt back to Navigator E Wireless Control Syste Tags gt Aeroscout Ta Select a command a 160 Tag Properties Asset Info Vendor Aeroscout Name Controller 10 1 96 16 Group Batt remaining 80 Days remaining Category reall 0 Tolerance 20 Battery Age Life o Location Debug I Enabled Update Location This will show AP RSSI Information on the Map Alpharetta Campus gt AP1242 Statistics Floor Building gt Test Lab Annex 2 Last located ae Location Server did not return any statistics at Oct 6 2007 10 24 53 AM information for this tag ove Loc2 3 r Location Notifications Absence g Containment 2 Distance Q All 2 wW pse a Enlarge J The cautions stated earlier with regard to the degree and frequency of device migration between location domains also apply here That is attention should be paid to the level of tracked device migration that may occur intra regionally inter regionally or between any of the regions and the national headquarters In this case when tracked devices migrate between location domains and are included in the active location database of two or more location appliances duplicate entries may not only be seen in local WCS servers as described earlier but also in WCS Navigator Figure 5 31 provides an illustrative Wi Fi Location Based Services 4 1 Desi
324. t a location appliance the following capabilities will be unavailable Ability to configure any Cisco Wireless Location Appliances Historical accumulation and playback of location data Tag telemetry and high priority notifications Chokepoint location The capability to interface to external third party applications via the SOAP XML API Simultaneous tracking of multiple devices on a floor map Location tracking services will be available only as an on demand service and only for a single device at a time Figure 3 6 illustrates the use of on demand localization for a single WLAN client When using on demand localization in this manner it should be noted that colors surrounding the device icon provide an idea of the degree OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture HI Role of the Location Appliance of location error associated with the icon placement The darker colors surrounding the icon represent those areas where confidence is high the probability is higher that the device is physically located where the icon is placed or within this area The lighter colors represent those areas of lower confidence the probability is lower that the device is physically located within these areas Figure 3 6 On Demand WLAN Client Localization using WCS with Location License Maps gt Cisco SJ Site 5 gt BLD 14 gt 3rd floor Location Error Lookup Zoom
325. t and total number of access points supported Table 1 2 Additional Hardware and Software Components AeroScout Ltd System Manager Version 3 2 20 1 Network Exciter Manager ANEM version 1 2 EX 3100 Exciter Manager 1 0 20 Exciter EX 2000 DSP 216 SB 50008 HW v2 Exciter EX 3100 310 01 Exciter EX 3200 DSP 30007 SB 60007 HW v2 ADP 030 power supply NA ADP 040 power supply NA Tag Manager 3 0 4 Wi Fi Location Based Services 4 1 Design Guide ia OL 11612 01 Chapter1 Overview Hardware and Software Components W Table 1 2 Additional Hardware and Software Components Tag Activator BWH1000 02 TA DSP 22059 FPGA 5201 SB 175 CPLD 5107 BWH 3000CT T2 RFID Tag 4 33 EDK 200 T2 Telemetry Tag 4 33 ExciterConfig exe 1 3 1 Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 g is Chapter1 Overview W Hardware and Software Components Wi Fi Location Based Services 4 1 Design Guide ss OL 11612 01 CHAPTER Location Tracking Approaches Location tracking and positioning systems can be classified by the measurement techniques they employ to determine mobile device location localization These approaches differ in terms of the specific technique used to sense and measure the position of the mobile device in the target environment under observation Typically Real Time Location Systems RTLS can be grouped into four basic categories of systems that determ
326. t does not initiate protection mode Some 802 11b asset tags may as an optional feature periodically probe and attempt to briefly associate to the wireless infrastructure in order to conduct over the air firmware or configuration updates The observations stated above would apply to these tags but only during the brief periods during which these extended modes of communication are in use Enabling Asset Tag Tracking Beginning with the Cisco UWN Release 4 1 it is no longer necessary to enable asset tag tracking in WLAN controllers using the config status rfid enable CLI command RFID tag data collection in controllers containing Release 4 1 is now enabled by default Enable Asset Tag RF Data Timeout The RFID Data Timeout parameter sets a static time value in seconds that must elapse without any access points on the controller detecting an asset tag before that asset tag is removed from the internal tables of the controller For general usage it is recommended that this parameter be set to a minimum of three times and a maximum of eight times the longest tag transmission interval found in the general tag population This should be inclusive of stationary as well as any in motion transmission intervals The valid range of values for this parameter is 60 7200 seconds and the default value is 1200 seconds For example for a tag with a constant transmission interval of 60 seconds you may choose to set the RFID data timeout to 48
327. t is done at full capacity will typically yield better accuracy even when used at times when the stockroom is only half full If it is necessary to deliver an operational location tracking system on day one for a newly constructed area you may wish to use one of the RF models that are supplied with WCS and the location appliance as a temporary measure Once the area has been fully stocked and staffed perform calibration data collection under conditions that would be considered representative of its peak or normal capacity After the calibration has been completed use the newly created RF model instead of the supplied model chosen originally In this way the supplied model initially chosen allows for users and administrators to quickly familiarize themselves with the system and the subsequent switch to a properly calibrated RF model should provide for better overall performance In order to plan for the most optimal time to perform a calibration of the area the designer should work closely with those personnel possessing an intimate knowledge of the business patterns and processes occurring there This is especially true if seasonal variation in stocking levels may occur as would be the case in a retail or logistics site If it cannot be determined from prior conversations with site personnel one way to determine a good time to perform a calibration is to visit the site beforehand and observe the activity pattern of both the facility and the
328. t possess the risk of increasing access point transmit power levels beyond that of the original design and is considered the more conservative option of the two When considering the first option it is necessary to examine the current inter access point spacing and transmit power levels and estimate the increase that will be required to the inter access point separation in order to place the existing outer rows of access points at the actual floor perimeters If current access point transmit power levels are already at high levels relative to the power capabilities of our client devices and the estimated increase to inter access point separation appears to be large then expanding the constellation of existing access points to accommodate perimeter placement may not be the best OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide Chapter5 Best Practices Location Aware WLAN Design Considerations HE Location Voice and Data Coexistence option This is mainly because it may require the use of higher than desirable access point transmit power levels In such cases it is recommended to pursue the second option which contracts the equilateral formations and results in shorter inter access point separation typically with the same or reduced access point transmit power levels Recall from our discussion that our transmit power levels are configured at 5dBm for 802 1 1bg and 11 dBm for 802 1 1a In order to determine the new
329. t tags for use with the Cisco UWN software Release 4 1 Refer to the AeroScout Tag Manager v3 0 User s Guide for more detailed information as well as information on several other useful configuration options in the Tag Manager Tag Telemetry and Notification Considerations Beginning with software Release 4 1 the location aware Cisco UWN will recognize tag telemetry and high priority notifications transmitted by Wi Fi Tags specification may transmit tag telemetry and high priority notifications to the location aware Cisco UWN This information is passed from WLAN controllers to the Cisco Wireless Location Appliance using the Location Control Protocol LOCP which is described in Cisco Location Control Protocol LOCP page 3 36 This section provides initial best practice recommendations and other information and should be kept in mind when designing solutions that are dependent on telemetry and high priority notification functions found in Cisco UWN software Release 4 1 Deploying Tag Telemetry Active RFID tags supplied by tag vendors in compliance with the Cisco Compatible Extensions for Wi Fi Tags specification may include the ability to accept telemetry data from onboard sensors or from sensors integrated into the asset to which the tag is attached If configured to do so these active RFID tags can pass this telemetry data as part of the tag transmissions that are sent to the Cisco UWN at periodic transmission intervals or when entering int
330. tag hardware There are no cables that interconnect the two and the use of the Tag Activator eliminates disturbing the environmental seal of the tag casing for configuration modifications Minimal disruption of tag seals is an advantage if the asset tag is intended for use in harsh or wet environments where tight environmental sealing is required Figure 6 22 AeroScout Tag Activator 190607 The following AeroScout document should serve as the primary reference with regard to the AeroScout Tag Activator e AeroScout Tag Activator User s Guide In order to configure AeroScout T2 or T3 asset tags for basic communication with software Release 4 1 the following steps should be followed 1 Deploy the AeroScout Tag Activator in accordance with the vendor s recommendations as outlined in the AeroScout Tag Activator User s Guide The AeroScout tag activator may be powered directly from a 802 3af compliant switch or from a non 802 3af switch using the provided AC power supply included with the product Spanning tree portfast should be configured on any Cisco switch port to which the AeroScout Tag Activator is attached to avoid potential instability 2 Configure the AeroScout Tag Manager to communicate with the Tag Activator as per the vendor s recommendations as outlined in the AeroScout Tag Activator User s Guide and the AeroScout Tag Manager version 3 0 Quick Start Guide Ensure that the Tag Activator is properly recognized by the Tag Man
331. tag is now within range or out of range of a particular chokepoint Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 EN Chapter3 Cisco Location Based Services Architecture HI Cisco Location Control Protocol LOCP e Information Notifications In Release 4 1 information notifications are used to convey vendor specific data and tag high priority events such as When a tag user depresses a tag call button When a tag detects that it has been removed from its carrier or attached asset When a tag detects tampering When any other high priority tag events occur While each tag vendor is responsible for determining the precise set of capabilities they choose to include in their product offering the Cisco Compatible Extensions for Wi Fi Tags specification provides for high priority information to be uniformly included in the tag content field This information is passed to the location appliance along with the tag MAC address and can be used by location clients such as WCS to indicate that a high priority tag event has taken place The Cisco Compatible Extensions for Wi Fi Tags specification allows each tag vendor to pass vendor specific information such as proprietary tag messages or additional vendor specific chokepoint information from their tags into the Cisco UWN in real time Vendor specific information will be made available unaltered to location clients via the SOAP XML API interface of the Cisco lo
332. tags and software on each client device to enable client side reporting of RSSI to its location positioning server Location patterning may be implemented totally in software which can reduce complexity and cost significantly compared to angulation or purely time based lateration systems Location patterning techniques fundamentally assume the following e That each potential device location ideally possesses a distinctly unique RF signature The closer to reality this assumption is the better the performance of the location patterning solution e That each floor or subsection possesses unique signal propagation characteristics Despite all efforts at identical equipment placement no two floors buildings or campuses are truly identical from the perspective of a pattern recognition RTLS solution Although most commercially location patterning solutions typically base such signatures on received signal strength RSSI pattern recognition can be extended to include ToA AoA or TDoA based RF signatures as well Deployment of patterning based positioning systems can typically be divided into two phases e Calibration phase e Operation phase During the operational phase solutions based on location patterning rely on the ability to match the reported RF signature of a tracked device against the database of RF signatures amassed during the calibration phase Because the database of recorded RF signatures is meant to be compiled
333. te information which can be pushed via asynchronous northbound notifications from the location appliance tag telemetry is made available to location clients only via the SOAP XML API sas X bg A 1 The ceiling function al l represents the application of the ceiling function to the positive integer x This rounds up x upwards returning the smallest integer that is greater than or equal to x Wi Fi Location Based Services 4 1 Design Guide 340 i OL 11612 01 Chapter3 Cisco Location Based Services Architecture Cisco Location Control Protocol LOCP W For information regarding tag telemetry deployment considerations refer to Tag Telemetry and Notification Considerations page 6 27 Asset Tag Notifications Using LOCP Beginning with Cisco UWN software Release 4 1 Wi Fi active RFID tags compliant with the Cisco Compatible Extensions Wi Fi tag specification can pass optional high priority chokepoint and vendor specific notification events to the location aware Cisco UWN Indication of high priority tag events are received by one or more access points via tag multicast messages frames that contain additional payload information indicating the nature of the event This information is typically dispatched by asset tags at the time the tag detects that the event has occurred Once received by the WLAN controller these time critical events are handled outside the polled LOCP polling process and passed immediately to the
334. te the beacons and probe responses they receive from access points around them without actually soliciting these responses themselves passive scanning Clients that use passive scanning to determine potential access point roam candidates do not issue probe requests hence passive scanning in and of itself does little to promote improved location fidelity It is not unusual to see some clients use a combination of both techniques Since the location aware Cisco UWN uses client probe requests to determine client location it logically follows that the more consistent the client is in transmitting probe responses the better the ability of the system will be to provide accurate location tracking of that client For example location accuracy can be degraded if a client e Refrains from active scanning for long periods e Does not transmit probe requests across all channels in use e Does not transmit probe requests for all configured SSIDs e Transmits probe requests at power levels that deviate abnormally from that expected by the RTLS OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices IEEE 802 11 standards leave such areas open for interpretation which does not lead to consistent probing behavior across vendors This can have both good and not so good connotations from the standpoint of WLAN client location fidelity in the Cisco
335. tems is regarded as being a close match for the third party antenna The answer to this popular question depends on several factors For optimal location fidelity it is recommended that one of the antennas listed within WCS be used whenever possible However if this is impossible the following suggestions should be considered before performing such substitutions e For third party antennas providing a gain of 6dBi gain or less the difference in gain between the third party antenna and the Cisco equivalent should not exceed 3 dBi e For third party antennas providing greater than 6dBi gain the difference in gain between the third party antenna and the Cisco equivalent should not exceed 3 dBi In addition the gain of the third party antenna must not exceed the gain of the Cisco equivalent The latter condition must be enforced to avoid circumstances where excessive antenna gain may lead to regulatory compliance issues FCC regulatory domain other regulatory domains may differ e The third party antenna should be of the same type as the Cisco equivalent In other words omni directionals should only be substituted for omni directionals yagis for yagis etc amp Note Keep in mind that substitution of third party antennas while configuring WCS for the nearest Cisco equivalent may not be supported by the Cisco Technical Assistance Center TAC Antenna Orientation and Access Point Placement When installing access points using
336. terprise Mobility vowlan 4 1dg vowlan4 1dg book html When using Cisco RRM to manage power levels access points that are placed into the design solely for location purposes should not be included in either the Radio Resource Management transmit power control or coverage hole remediation processes Configuring a custom access point transmit power level using the custom TX power option on WCS or the controller GUI will automatically exclude these access points from transmit power and coverage hole remediation algorithms Based on our planning output and our calculations our original voice and data design shown in Figure 5 19 can be migrated to a location ready design that is in compliance with the best practices described in the Voice Over Wireless LAN 4 1 Design Guide with only minor changes in both layout and configuration The result is a combined design that is well suited to support VoWLAN high speed data and location tracking on 5 GHz as well as legacy data and voice support with location tracking on 2 4 GHz Additional activities that can be performed to improve designs and design implementation include e Performing a walk around of the site and verifying that areas on the floor plan where access point mounting is desired can actually accommodate it This is always a good idea since floor plans and blueprints do not always indicate the precise conditions present at each location where an access point may be mounted For example
337. ters Advanced General BASmission Interval In milliseconds 200 Triggered Tag s Location Report According to Exciter s Location on Map According to Calculated TDOA RSSI Location 223392 Note that these concentric rings do not represent any type of special area For example when RF Fingerprinting is being used to as the means of localizing tags instead of chokepoint location tags may be placed by the system anywhere on floor maps including within these gray concentric rings if that is the location deemed to be correct by the location appliance There are also two additional parameters regarding the use of chokepoints that are found on the Location gt Location Servers gt Advanced gt Location Parameters menu screen as shown in Figure 6 31 I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide jg Chapter6 RFID Tag Considerations W sChokepoint Considerations Figure 6 31 Chokepoint Advanced Location Parameters apial Wireless Control System cisco Monitor Reports Configure Location Administration y Help v Location Server Location Server gt Location Parameters gt loc 2 Administration Location Parameters Advanced Enable calculation time I Enable Advanced Parameters Location Parameters Enable OW Location I Enable Notification Parameters LOCP Parameters Relative discard RSSI time B minutes i i 60 i Maintaine
338. the vicinity of access points 31 32 34 and 35 where the location requirement for each point to lie within 70 feet of three different access points in at least three different quadrants with an access point present in the fourth quadrant at any range will not be satisfied e Transmit power for each access point has been configured to 5dBm for 802 11bg and 11 dBm for 802 1la This results in a 67 dBm cell radius of approximately 28 72 feet with a cell to cell overlap of 15 for 802 11a VoWLAN and high speed data clients For 802 11bg legacy clients it results in a 67 dBm cell radius of approximately 31 feet with a 20 cell to cell overlap Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Location Voice and Data Coexistence Ii Note The transmit power configured for access points should be within the range of the transmit power levels supported by clients to help avoid potential one way audio telephony calls When using Cisco s Radio Resource Manager to manage access point power levels it is further recommended that designers target achieving the required coverage radii and overlap at transmit power levels that are less than the maximum supported transmit power level of the client device This is recommended in order to allow the Radio Resource Manager some degree of power allocation headroom that can be used to address potential
339. there are not these channels can be made available for use by enabling DFS on your WLAN controllers Wi Fi Location Based Services 4 1 Design Guide u OL 11612 01 Chapter 5 Best Practices Location Aware WLAN Design Considerations Avoiding Location Display Jitter E Note In software Release 4 1 of the Cisco Unified Wireless Network Cisco Compatible Extensions Location Measurements are not enabled for any 802 11a channels on which DFS operation has been mandated For DFS channels RSSI from probe requests transmitted by WLAN clients as a part of their normal operation will be used for location tracking purposes The techniques and principles described in this section illustrate how a design performed in accordance with VoWLAN and data best practices can be upgraded to being location ready The key concepts behind how inter access point separation cell radius and transmit power are inter related and how these factors can be used to determine coverage overlap can be applied to designs of various different sizes and shapes as well as environments with varying path loss characteristics and shadowing Avoiding Location Display Jitter Location smoothing was introduced to enable the network administrator to compensate for cases of location instability sometimes seen with clients that are not actually experiencing any change in movement This can be due to a variety of factors including the following e Variations i
340. ties in a small highly integrated design Chokepoint Triggers Chokepoint triggers are proximity communication devices that trigger asset tags to alter their configuration or behavior when the asset tag enters the chokepoint trigger s area of operation This alteration could be as simple as causing the asset tag to transmit its unique identifier or more complex including causing the tag to change its internal configuration or status One of the prime functions of a chokepoint trigger is to stimulate the asset tag such that it provides indication to the RTLS that the tag Wi Fi Location Based Services 4 1 Design Guide oL 11612 01 g co Chapter6 RFID Tag Considerations RFID Tag Technology has entered or exited the confines of an area known as a chokepoint Chokepoints are tightly defined physical areas such as entrances exits or other types of constrictions that provide passage between connected regions Figure 6 11 illustrates some common examples of chokepoints Note While chokepoint triggers are typically deployed within chokepoints it is often commonplace to hear the term chokepoint used to refer to a chokepoint trigger Figure 6 11 Common Chokepoint Areas Kitt tsi R X XKIEL D ees gt l IO OE Outdoor chokepoint locations may include a fenced gate bridge toll plaza or similar passageway Indoor chokepoint locations includes connecting entrances or exits between e A building s inte
341. tinct RFID tag technologies into a single chip or chipset This is exemplified by the G2C501 from G2 Microsystems shown in Figure 6 10 which is a complete Wi Fi system on chip SoC that includes 802 11b Wi Fi active RFID 900 MHz EPC Global Gen 1 Class 0 passive RFID 2 4 GHz ISO24730 2 TDoA a 32 bit CPU crypto accelerator real time clock and sensor interfaces Figure 6 10 G2C501 RFID System On A Chip SoC 2 4 GHz Low Crypto Power Transceiver Accelerator lt 802 11b and ISO 24730 2 32 bit CPU PHY and MAC Subsystem CPU General Sensor gt Interface 80 KB 320 KB RAM ROM 125 kHz Magnetic Digital Interface a Receiver External Flash SPI lt z GPIO UART 2 Power lt gt 900 MHz EPC Management Unit lt gt The use of highly integrated tag silicon offers many advantages to the tag vendor including e Small form factor e Low power consumption e Well documented software and hardware interfaces e Flexible support for multiple location technologies A good example of a multimode tag that capitalizes on such capabilities is the WhereNet IV asset tag from WhereNet Corporation http www wherenet com shown in the lower left hand quadrant of Figure 6 9 The WhereNet IV combines a Cisco Compatible Extensions compliant 802 11 Wi Fi active tag implementation along with 125kHz magnetic signaling and ISO 24730 2 capabili
342. tion Based Services 4 1 Design Guide Ea 0L 11612 01 _ Chapter 3 Cisco Location Based Services Architecture Tracking Clients Assets and Rogue Devices Mi e Either all WLAN clients can be displayed or filtering can be performed to select which clients to display on the floor map This can be based on IP address user name MAC address asset name asset group asset category or controller Additional filtering can be specified for SSID and RF protocol 802 11a or 802 11b g As mentioned previously only up to 250 WLAN clients will be shown at on the floor maps at any one time If there are greater than 250 WLAN clients detected the total number found will be indicated in the left hand column status area during each communication cycle between WCS and the location appliance It is recommended that filtering be used to reduce the total number of WLAN clients selected for display if you receive this warning In software Release 4 1 of the Cisco UWN WLAN controllers provide support for the maximum number of WLAN clients listed in Table 3 1 Table 3 1 Maximum WLC Client Capacity Controller Model WLAN Clients Supported 2006 256 2106 256 4402 2 500 4404 5 000 WiSM 10 000 NM WLC6 256 NME WLC8 12 350 3750G 2 500 Complete information on any displayed WLAN client can be obtained simply by left clicking on the appropriate blue rectangular icon on the floor map as shown in Figure 3 13 Note
343. tion Patterning Pattern Recognition Techniques patterning achieving high performance levels typically requires not only higher numbers of receivers or access points for 802 11 but also much tighter spacing In large areas where it is possible for clients to move about almost anywhere calibration times can be quite long For this reason some commercial implementations of location patterning allow the user to segment the target location environment into areas where client movement is likely and those where client movement is possible but significantly less likely as well as areas where client location is impossible such as within the thick walls of a tunnel for example or suspended within the open air space of an indoor building atrium The amount of calibration as well as computational resources allocated to these two classes of areas is adjusted by the positioning application according to the relative probability of a client being located there The radio maps or calibration databases used by pattern recognition positioning engines tend to be very specific to the areas used in their creation with little opportunity for re use The likelihood is very low that any two areas no matter how identical they may seem in construction and layout will yield identical calibration data sets Because of this it is not possible to use the same calibration data set for multiple floors of a high rise office building when using a location patterning solution
344. to preconfigured tags it is recommended that the current configuration of the tag be imported into Tag Manager and used as a configuration template with any modifications then applied to that configuration The result can then be applied to one or more tags To do this after selecting the Configuration menu option place the mouse cursor over the tag that you would like to use as a template Right click and select Get Tag Configuration respond Yes when asked to proceed Figure 6 26 Tag Manager 3 04 Configuration Panel AeroScout Tag Manager Configuration M 00CCC5E7B6 M 00CCC5E7B6 M 00CCC5E7B6 M 00ccc5E7B7 M o0ccc5E7B7 M oocccseszet M wocccses2g1 M 0CCCSEBDC M oocccsespD T T2 T2 T2 T2 T2 T2 T2 T2 E Aleroscout Wamper 223372 6 Configure each parameter subcategory for basic operation of T2 or T3 tags with the Cisco UWN software Release 4 1 If you have selected both T2 and T3 tags note that only the configuration options that apply to both tag models are available Once all parameters in a configuration group have been configured they may be applied to the selected tags by clicking on the Apply button that appears within each group Alternatively you may delay applying changes until all groups have been configured use the Apply Multiple Configuration option shown at the bottom of Figure 6 26 All parameters selected are applied to all selected asset tags and will override any other values that ma
345. to reply to commands and data received from a programming device known as a Tag Activator which is an Ethernet addressable low frequency 125 kHz magnetic signaling transmitter housed in combination with a 802 11b receiver Tag Activators are designed to be used in conjunction with Windows based tag configuration software known as Tag Manager It is important to note that AeroScout asset tags are only capable of receiving information from Tag Activators via their magnetic signaling 125 kHz receiver AeroScout asset tags are not equipped with a magnetic signaling transmitters and Tag Activators are not equipped with magnetic signaling receivers AeroScout asset tags receive commands and data from Tag Activators via magnetic signaling and respond back to the Tag Manager application confirming those transmissions using their 802 11b capabilities and the 802 11b receiver in the Tag Activator OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations W Using Wi Fi RFID Tags with the Cisco UWN The AeroScout Tag Activator shown in Figure 6 22 can be powered via 802 3af Ethernet or an external SVDC power source The Tag Activator works in conjunction with AeroScout Tag Manager software to configure program activate or deactivate up to 50 AeroScout asset tags simultaneously at a range of up to approximately three feet The use of a Tag Activator is completely non intrusive in relation to the AeroScout
346. to select which rogue clients to display on the floor map Filtering can be based on the MAC address of rogue access point to which it is believed the rogue client is associated or it can be based on the state of the rogue client alert contained or threat As mentioned previously only up to 250 rogue clients will be shown at any one time on floor maps If there are greater than 250 rogue clients detected the total number found will be indicated in the left hand column status area during each communication cycle between WCS and the location appliance It is recommended that filtering be used to reduce the total number of rogue clients selected for display if you receive this warning In software Release 4 1 of the Cisco UWN WLAN controllers provide support for the maximum number of rogue clients shown in Figure 3 24 Table 3 4 Maximum WLC Rogue Client Capacity Controller Model Rogue Clients 2006 100 2106 100 4402 500 4404 500 WiSM 1000 NM WLC6 100 NME WLC8 12 100 3750G 500 Complete information on any displayed rogue client can be obtained simply by left clicking the cursor on the rectangular black skull and crossbones icon representing the desired rogue client on the floor map This yields the screen shown in Figure 3 25 However RSSI information is not displayed for rogue access points when the location map is enlarged Using the dropdown menu located in the upper right hand corner you can acc
347. to the location appliance you will fail to see an IP address listed for the location appliance and the Tx Rx counts will be blank If the TxData fields fail to increment in spite of known emergencies and telemetry data being sent by tags verify that the LOCP send to the location appliance is successful using the following debug command debug LOCP event enable The output should look similar to the following LOCP TX message Sending LOCP_APP_INFO_NOTIF_MSG to LocServer 0 Tx OK If messages are received indicating that there are LOCP failures contact the Cisco Technical Assistance Center for further troubleshooting assistance Wi Fi Location Based Services 4 1 Design Guide B10 i OL 11612 01
348. tware release supports LOCP LOCP polls will not be sent to controllers If the time interval since the last LOCP poll is 180 seconds then LOCP polling will be performed during this asset tag SNMP polling cycle LOCP Information Requests will be sent to all LOCP capable controllers currently defined to the location appliance during this asset tag SNMP polling cycle If the interval since the last LOCP poll lt 180 seconds then LOCP polling will not be performed I OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter3 Cisco Location Based Services Architecture HI Cisco Location Control Protocol LOCP The LOCP polling interval used by a location appliance to collect asset tag telemetry information in software Release 4 1 can be calculated from the asset tag SNMP polling interval using the following formula 180 Poll yusp ll Poll o TAG Poll ocp represents the LOCP polling interval and Poll7 specifies the poll interval at which the location appliance polls the controller for asset tag location information via SNMP Both of these values are specified in seconds The value for PollTAG is configured in WCS using Location Servers gt Polling Parameters For example using an asset tag SNMP polling interval Poll of 120 seconds the LOCP polling interval Poll gcp used by the location appliance is calculated to be 240 seconds Figure 3 28 helps to provide clarity to understanding the
349. ue Clients O Grid verageAreas O Markers old as Save Settings 229367 Configuring Asset Tags w_ Wi Fi Location Based Services 4 1 Design Guide In order to communicate with the location aware Cisco UWN asset tags must be properly configured for parameters such as channels transmission interval and data formats In this section we examine the basic parameter settings necessary for AeroScout tags to be recognized by the UWN and properly localized Note AeroScout asset tags are highlighted in this section only as an example of how to configure asset tags that are compliant with the Cisco Compatible Extensions for Wi Fi Tags specification Keep in mind that each vendor s asset tags require configuration using vendor specific tools Users of AeroScout InnerWireless PanGo WhereNet G2 or other asset tag vendors offering similar products should always consult their vendor s product documentation for appropriate configuration guidelines OL 11612 01 Chapter 6 RFID Tag Considerations Using Wi Fi RFID Tags with the Cisco UWN W In comparison to the earlier 2 x versions of AeroScout Tag Manager version 3 x introduces several new features designed to support AeroScout asset tags that are compliant with the Cisco Compatible Extensions for Wi Fi Tags specification including the recently introduced AeroScout T3 asset tags This section outlines the steps necessary to configure AeroScout asset tags for basic c
350. ulation Time 4 7 Enable OW Outer Wall Location 4 8 RSSI Discard Times 4 8 RSSI Cutoff 4 8 Configuring Location Appliance Notification Parameters 4 9 Queue Limit 4 9 Retry Count 4 9 Refresh Time 4 10 Notifications Dropped 4 10 Configuring Location Appliance LOCP Parameters 4 10 Location Appliance Dual Ethernet Operation 4 10 Changing Location Appliance Default Passwords 4 11 Changing the root User Linux System Password 4 11 Changing the admin Location Server Application Password 4 12 Location Appliance Time Synchronization 4 14 Quiescing the Location Appliance 4 15 CHAPTER 5 Best Practices Location Aware WLAN Design Considerations 5 1 Minimum Signal Level Thresholds 5 2 Access Point Placement 5 5 Access Point Separation 5 12 Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 Determining Location Readiness 5 18 Location Voice and Data Coexistence 5 20 Avoiding Location Display Jitter 5 31 Multiple Location Appliance Designs 5 32 Single Management Domain with Multiple Location Domains 5 36 Multiple Management Domains with Multiple Location Domains 5 40 Antenna Considerations 5 44 Third Party Antennas 5 44 Antenna Orientation and Access Point Placement 5 46 Calibration 5 48 Calibration Validity 5 56 Tips for Successful Calibrations 5 57 Data Collection 5 57 Calibrating Under Representative Conditions 5 58 Recommended Calibration Clients and Techniques 5 59 Calibration of Non Uniform Environment
351. ult value for the ADCI disabling rogue location tracking today will not prune those tracked device entries from the active location database until approximately the same time tomorrow To work around this and remove the unwanted devices from the active location database more expeditiously we can temporarily set the Absent Data Cleanup Interval to a much lower value for a brief duration in order to accelerate the pruning of any unwanted tracked devices from the active location database For example our hypothetical operator might choose to temporarily set the Absent Data Cleanup Interval to sixty minutes after disabling location appliance polling for rogue devices Sixty minutes after this setting has been applied the location appliance will remove all devices from the active location database for which updated information has not been received from WLAN controllers within the last hour including the undesired rogue devices Once this has occurred the Number of Tracked Elements field shown on the Location Servers gt Advanced Parameters menu page should decrease reflecting the number of devices removed from the active location database The Absent Data Cleanup Interval is a single parameter that applies to all device categories Thus a potential drawback of temporarily lowering the ADCI in this way is that the removal of tracked devices from the active location database occurs in a non selective fashion That is to say all devices for which
352. ults in the generation of LOCP Measurement Notification frames destined for the location appliance Note Communication between chokepoint triggers and asset tags is unidirectional from the chokepoint trigger to the asset tag In software Release 4 1 there is no direct communication between chokepoint triggers and the location aware Cisco UWN Figure 6 13 Location Aware Cisco UWN with Chokepoint Triggers Browser Based Remote Console for Cisco WCS zj El 7 T Cisco Wireless pipe Control System ee WCS Cisco M J PY Nireless ee Bilis aT EE Appliance P Cisco Wireless LAN Controller Cisco Aironet LE Access Point Chokepoint Trigger Chokepoint Trigger Cisco Compatible Extensions Wi Fi Tag 223364 The location appliance uses the information provided to it by the LOCP Measurement Notification to indicate that the tag s current location is within the configured range of the specified chokepoint This information is placed in the appropriate location appliance databases and made available to location clients via the location appliance API Location clients may display chokepoint location information on floor maps An example is the WCS floor map shown in Figure 6 14 where we can see two RFID tags located at the chokepoint labeled Basement Entrance The location appliance can also trigger alerts and other asynchronous northbound notifications to WCS and external applications using email syslog
353. unction allows information to be extracted from the active location database for up to a full 24 hour period matching the default time period of the Absent Data Cleanup Interval If the Absent Data Cleanup Interval is reduced the maximum scope of the Load Location Data As Old As dropdown is reduced to the new value for the Absent Data Cleanup Interval despite values higher than this being displayed in the dropdown selector e When devices are pruned from the active location databases historical location information on that location appliance will not be accessible for those device MAC addresses until such time that these devices re enter the location domain and are re added to the active location database This assumes that the historical location information has not been pruned via an the independent location history pruning process that occurs periodically Multiple Management Domains with Multiple Location Domains In this section we examine the case where both of the following are true e The combined number of access points and controllers managed within the enterprise cannot be contained within a single management domain e The number of tracked devices in the enterprise exceeds the capacity of a single location domain We revisit the enterprise depicted in Figure 5 24 except we now examine the organization s structure from a perspective higher up in the organization s hierarchy We see that the headquarters location and the metrop
354. use RSSI to accurately laterate distance Such ambiguous behavior is generally not conducive to good location fidelity In tests conducted with access points at an installed height of 10 feet in with 2 2dBi omni directional antennas in an environment with a path loss exponent of 3 4 this behavior could sporadically be observed out to a distance of almost 14 feet In the specific case of this example it would be best to maintain the inter access point spacing above 28 feet in other words twice the distance at which such behavior would be expected in order to reduce the potential of this phenomena occurring In some application designs it may be desirable to deploy multiple access points on non overlapping channels in order to potentially increase the amount of RF bandwidth available to users collocated non overlapping access points This approach is often seen in classrooms and conference halls where there may be a large number of mobile users If location tracking of WLAN clients and other devices is desirable in situations where some rooms may possess several collocated access points it is suggested that the co located access points not be deployed within very close proximity i e a few feet of each other Rather every attempt should be made to obtain as much separation as possible between these co located access points so as to avoid any of the close range effects that can be detrimental to good location fidelity One way to accomplish t
355. ved Signal Strength RSS Thus far we have discussed two lateration techniques ToA and TDoA that use elapsed time to measure distance Lateration can also be performed by using received signal strength RSS in place of time With this approach RSS is measured by either the mobile device or the receiving sensor Knowledge of the transmitter output power cable losses and antenna gains as well as the appropriate path loss model allows you to solve for the distance between the two stations The following is an example of a common path loss model used for indoor propagation PL Ply Olog d 5 In this model e PL represents the total path loss experienced between the receiver and sender in dB This will typically be a value greater than or equal to zero PLiverer represents the reference path loss in dB for the desired frequency when the receiver to transmitter distance is meter This must be specified as a value greater than or equal to zero e drepresents the distance between the transmitter and receiver in meters e n represents the path loss exponent for the environment e s represents the standard deviation associated with the degree of shadow fading present in the environment in dB This must be specified as a value greater than or equal to zero Path loss PL is the difference between the level of the transmitted signal measured at face of the transmitting antenna and the level at of the received signal measured at the
356. vices Power down Note that issuing the shutdown command from a remote SSH client in your SSH session becoming disconnected The location appliance still initiates the shutdown procedure but your SSH session becomes disconnected before the command completes Therefore you are not able to view all the command output as you would on a CLI console device To avoid this lack of visibility Cisco recommends that a terminal or PC attached to the location appliance console terminal be used to perform this task rather than an SSH session if possible The final step is to remove power to the location appliance by using the front panel ON OFF switch to turn the location appliance off This should be done after the power down message is seen on the CLI console shown in bold above Note that if using a remote SSH session you will not see the power down message because your session will be disconnected shortly after issuing the shutdown command In this case you should wait approximately two minutes for the shutdown command to complete before removing power to the location appliance using the front panel power switch Wi Fi Location Based Services 4 1 Design Guide Ca OL 11612 01 CHAPTER Best Practices Location Aware WLAN Design Considerations In the past decade the design of enterprise ready wireless LANs has evolved from being centered around the model of maximum coverage with minimum AP count to a model where covera
357. wed to grow At first glance this may appear intuitive that is max recommended database size total available disk space OS size location application size However you should also account for the creation of a flat file that is used during the database backup process Using the formula below you can calculate the maximum recommended size of the location database including this additional free space plus a small additional amount to account for system overhead such as the downloading of an location appliance upgrade image Wi Fi Location Based Services 4 1 Design Guide Mae W OL 11612 01 _ Chapter 4 Installation and Configuration Configuring Location Appliance Location Parameters il TotalSpace OSApp Space 2 3 MaxDatabaseSize Where e MaxDatabaseSize is the maximum recommended size of the database in bytes amp Note MaxDatabaseSize assumes the user has performed a cleanup of any residual location appliance upgrade images Multiple residual upgrade images may consume additional free space exceeding these allotments e TotalSpace is the total amount of available space on dev sda2 in GB e OSApplSpace is the amount of space occupied by the Linux OS and the location appliance application on dev sda2 This can be calculated for the example shown above as the amount of used disk space in Gigabytes the current size of the location appliance database in Gigabytes The current size of
358. xpect that there will be a delay between the time the tag sends the telemetry information and the time it is updated in the location appliance database and made available to location clients 2 Northbound Asynchronous Notifications In Release 4 1 of the location aware Cisco UWN the location appliance does not issue asynchronous northbound notifications in the form of email SNMP SOAP or UDP Syslog messages for telemetry received from tags Therefore any external applications such as paging systems text messaging enterprise management consoles and so on relying on northbound notifications in these formats must receive them from an alternate source having visibility to tag telemetry such as a third party location client Battery telemetry however is an exception In this case the location appliance will trigger northbound asynchronous notifications based on remaining battery life for tags compliant with the Cisco Compatible Extensions for Wi Fi Tags specification These notifications are generated as per the following trigger condition definitions e Battery Level is Low Reported battery life remaining is 30 e Battery Level is Medium 75 battery remaining gt 30 e Battery Level is Normal Battery remaining is gt 75 OL 11612 01 Wi Fi Location Based Services 4 1 Design Guide E Chapter6 RFID Tag Considerations Tag Telemetry and Notification Considerations Deploying Tag High Priority Notifications Beginni
359. y be present a General Parameters Channel Selection It is recommended that tags be configured for the standard set of 802 11b non overlapping channels typically channels 1 6 and 11 or otherwise depending on your regulatory domain m_ Wi Fi Location Based Services 4 1 Design Guide OL 11612 01 _ Chapter 6 RFID Tag Considerations Using Wi Fi RFID Tags with the Cisco UWN W LED Indication In most cases it is useful to have visual indication of when the tag is using its communication interfaces In cases where there are reasons why such indication is undesirable such as in a light sensitive security or other stealth application the LED can be disabled Transmission Interval When Not In Motion Select an appropriate tag transmission interval for your asset tagging application in seconds or milliseconds Typically tags are configured to transmit less frequently when stationary using this parameter setting as compared to when they are in motion In motion transmission intervals are set using the Motion Sensor category settings b Transmission Parameters Message repetitions Standard operation for the AeroScout tag is to transmit a single multicast transmission on all defined channels This parameter controls the number of times each transmitted message is repeated per channel It is generally recommended that this parameter be raised from the default value of one to a value of three Doing this he
360. y communicating is when they are within relatively close proximity of a passive RFID tag reader or interrogator Another type of common RFID tag in the marketplace today is known as the active RFID tag which usually contains a battery that directly powers RF communication This onboard power source allows an active RFID tag to transmit information about itself at great range either by constantly beaconing this information to a RFID tag reader or by transmitting only when it is prompted to do so Active tags are usually larger in size and can contain substantially more information because of higher amounts of memory than do pure passive tag designs The tables shown in Figure 6 1 provide a quick reference of common comparisons between active and passive RFID tags Within these basic categories of RFID tags can be found subcategories such as semi passive RFID tags Note The terms beacon and beaconing have been used in the RFID industry for some time predating the establishment of the formal 802 11 standards When an active RFID tag periodically beacons it is simply transmitting a tag message much like any other messages the tag might send at a set interval Despite the use of similar terminology this should not be confused with an 802 11 Beacon An 802 11 Beacon is a management frame that the 802 11 access point or the beacon sender in an IBSS transmits to provide time synchronization and PHY specific parameters in order to facilitate mobile
361. y and precision should be detecting and reporting the received signal strength RSSI of any client station asset tag or rogue device being tracked It is preferred that this detected signal strength level be 75dBm or better Note As of WLAN controller software Release 4 1 185 0 each tracked entity WLAN client RFID tag rogue access point or rogue client is detected by up to sixteen registered access points at any time on each WLAN controller This helps to improve the tracking of devices in motion across many access point coverage cells by assuring that the latest device RSSI is properly reflected When performing a site survey of an area where clients or tags are tracked the RSSI of representative devices should be verified to ensure compliance with the minimum number of recommended access points and the recommended detected signal strength This should be performed via one of two techniques e Viewing detected RSSI for the client or asset tag using the show client detail lt mac address gt or show rfid detail lt mac address gt controller CLI command as shown in Figure 5 1 e Viewing detected RSSI for the client or asset tag using the location floor map GUI as described in Figure 5 2 and Figure 5 3 Wi Fi Location Based Services 4 1 Design Guide 2 OL 11612 01 Chapter5 Best Practices Location Aware WLAN Design Considerations Minimum Signal Level Thresholds Hl Figure 5 1 Checking Client RSSI at the WLAN Co
362. y using LOCP Information Requests The controller will respond with the telemetry information it has received for each tag MAC address since the last LOCP polling cycle via a LOCP Information Response frame These frames as well as the polling exchange process are illustrated in Figure 3 28 Keep in mind that all frames shown between the location appliance and the WLAN controller travel are encrypted Wi Fi Location Based Services 4 1 Design Guide 338 E OL 11612 01 Chapter3 Cisco Location Based Services Architecture Figure 3 28 LOCP Information Request Polling Location Appliance 2a n WLAN Controller Echo Request Echo Response Info Response _temp 38 C t 90 P Echo Request Echo Response Info Request LOCP Poll Echo Request Echo Response Echo Request Echo Response Info Request LOCP Poll 40 t 270 Info temp 40 C Cisco Location Control Protocol LOCP W CCX WiFi Tag ai x EP 000000 MAC 000CCC5D4DAB 223324 As you may have noticed in Figure 3 27 the LOCP polling interval is not directly configured in the location appliance configuration Rather it is derived from the asset tag SNMP polling interval occurring between the location appliance and WLAN controllers In order to determine when a LOCP poll should be sent the location appliance evaluates the following conditions during each controller polling cycle that are not LOCP capable Whether the controller sof
363. you may find that certain locations that appear to be viable candidates on paper actually are inaccessible such as an electrical closet inappropriate such as an outdoor balcony or are otherwise not acceptable In such cases access points should be relocated close to the original location such that the impact on the overall design is minimal In Figure 5 21 some common sense obstacles have been avoided and the affected access points have been moved slightly e Verifying RF propagation and coverage assumptions by temporarily installing a few access points in various test areas of the floor and measuring actual RF signal strength and cell to cell overlap using a portable client device with appropriate site survey software tools This is an excellent time to measure the ambient noise levels of the potential access point cells as well and determine whether the projected signal to noise ratio will be sufficient Note that Cisco s RRM feature also monitors client SNR and increases access point power if a number of clients are noticed to fall below a prescribed SNR threshold For more information about RRM refer to the Radio Resource Management under Unified Wireless Networks at the following URL http www cisco com en US tech tk722 tk809 technologies_tech_note09186a008072c759 shtml e Validating whether there are any radar users present in your locale that may interfere with the use of the additional 802 1 1a that are subject to DFS If

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