Cisco Systems 7911 IP Phone User Manual
Contents
1. tg ee 9 48 43 2 11k SS 1 1b 7 ouea Maa aa a a aa ael 135090 To survey a group of access points using the Active Mode tool configure the tool with an SSID that is configured on the access points To begin the data collection in active mode select a starting position near the perimeter of the area to be covered Click this location on the floor map to indicate the starting point A small stick figure appears on that spot Begin the walkabout by moving at a smooth rate to the next vertex in the path stop briefly to click this spot and continue The survey tool control area displays various real time data as you conduct the survey Use the data to monitor the state of the link The signal strength noise level link speed and packet loss statistics are all displayed Figure 4 7 shows the complete walkabout path taken for an example coverage area Note that the path includes a section outside the perimeter walls of the building Continuing the walkabout outdoors measures possible propagation outside of the building where the signal level should be as low as possible without compromising connectivity to the interior areas which helps prevent unauthorized connections to the WLAN Site Survey Guide for Deploying Cisco 7920 IP Phones Pas W O1 6315 01 Chapter4 Conducting a WIPT Survey How To Survey for the WIPT W Figure 4 7 AirMagnet Client Walkabout En SiteViewer Air t onet Project MySiteSurvey svp Ele2. Cisco recommends that all WIPT site surveys use diversity enabled access points and diversity antennas because a diversity configuration provides better throughput performance A simple throughput test using an FTP data transfer of 50 MB in an office environment with low multi path signals shows a 3 second improvement when using a diversity configuration Diversity configurations are especially important in environments such as shop floors and hospitals which often have heavy multi path signals Cisco also recommends that you use 256 byte packets when you perform receive and transmit tests during the survey Voice traffic consists of two way transmissions usually a burst of packets in one direction followed by a burst of packets in the other direction You should check performance error rates and signal levels in both directions This document also describes how to use signal levels and signal to noise ratios SNRs in WIPT site surveys WLAN site surveys that use only signal level tests are designed to identify the wireless network coverage area Previous site surveys have shown that signal level tests alone are not sufficient for voice traffic and many times are not sufficient for data traffic WIPT site surveys must also consider voice call capacity within a wireless cell Currently call loading is 7 active voice calls per channel using the G711 codec This number is based on simultaneous requirements for data clients and quality voice calls w
3. 2 13 shows the AirMagnet jitter tool Figure 2 13 AirMagnet Jitter Tool i 9 AirMagnet Tools x STA 1 Q AP LJR 11b 151 CH 1 Uti 210 Noise 93 CRC 0 DTIM 2 48 11 28 ACL Coverage Signal Dist Survey Perfomance Ping Jitter Find GPS Log 135087 The AirMagnet jitter tool allows for the monitoring of a WIPT client during an active call The tool reports the standard deviation STD of the transmit side and the receive side of the client packets It reports the average interpacket delay plus the minimum and maximum delays The jitter measurement of this tool is just from access point to WIPT client and WIPT client to the access point This is not an end to end measurement of jitter or latency for a VoIP call Figure 2 14 shows there is significant data and noise on all channels The effect of the data and noise on the quality of voice is shown with STD values of 4 87 and 6 02 The channel utilization is 30 65 The Cisco AV VID design guide states for quality VoIP calls the Delay Variation Jitter should not exceed 30 ms In an office with heavy use of 802 11 the average in packet delay might vary from 19ms to a high of 32ms and the average out packet delay might vary from 18 ms to a high of 41 ms Those delay averages would produce intermittent but noticeable jitter during active calls and a noticeable delay during roams I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones jg Chapter
4. A1 SE D1 O0 0F 90 64 E7 80 04 050431 0010F 90164 E7 90 O01 40 961A1 8E 01 04 050500 O0 0F 90 64 E7 B0 OO 40 S6 Al GE D1 00 0F 90 64 7 B0 04 051007 Ox CAC frrer 0205 Encrypted au OF 80 OF 147899400 04 33 2004 zz a AiroPeek has options to show real time graphs of current signal strength and current noise levels both in dBm and percentages but it does not have a survey tool like ACU or AirMagnet Figure 2 8 shows the AiroPeek real time graphs Site Survey Guide for Deploying Cisco 7920 IP Phones oL 6315 01 E Chapter2 Survey Tools Figure 2 8 AiroPeek dBm and Signal Percentage Real Time Graphs AiroPeek a D i QRAAGA A NTLO MmM NO Capture 1 Packets received 423 172 Memory usage 3 gt Packets filtered 428 172 Filter state Accept all packets A n Signal Strength dBm 135100 Sniffer Pro from Network Associates shows the signal strength in a percent value There is no option to show RSSI or dBm values Sniffer Pro is trace utility with no support for a site survey Figure 2 9 shows the Sniffer Pro window with signal strength at 28 percent Figure 2 9 Wireless Sniffer Pro Displays Percent of Signal Strength 4 Snif 1 Decode 9041 ANs Ff rames y Na Status Source Addere e DestAddress S a LE E Ael Te 6 00078SB36AC4 Broadcast Signale 1x 133 0 00 00 004 6 irontJ181CF Broadcast Signal x 67 0 00 00 007 OO09EBACA796 Broadcast Signal x 34 0 00 00 014 000C309D4473 Broadcast Signals
5. Guide for Deploying Cisco 7920 IP Phones Chapter2 Survey Tools The Cisco CB21 ADU reports signal strength in dBm Figure 2 4 shows the ADU Advanced Status window Figure 2 4 ADU Advanced Status Window I allia Advanced Status Site Survey Guide for Deploying Cisco 7920 IP Phones cana Chapter2 Survey Tools Figure 2 5 AirMagnet Survey Tool ry AirMagnet Tools x AP TME LIRAOS 11b 802 11b gt Q m Associated AP status Bssip TME LJR IOS 11b Speed 11 0 SSID voice no wep Channel 1 Sorsi 53 MMMM Nose 5 m Packet status 1 143286 _ bytes s 143 packets s Lost 0 x 0 packets s Retry 42 61 packets s location F Diag Find 136095 Site Survey Guide for Deploying Cisco 7920 IP Phones T 0L 6315 01 EN Chapter2 Survey Tools The AirMagnet Survey packet decode tool shows signal strength in dBm Figure 2 6 shows the AirMagnet Survey Packet Decode window Figure 2 6 AirMagnet Packet Decode Window iag dtm fie Yew Look Help Channel 1 e TCP port 1030 gt port 20 802 11 enceypied data tenestamp S ZS 14 33 57 047 799 opel strength 100 6 dim rone weel 1 20 den frana langih 78 data rate 11 mbps cannel t CAC error no frame coetrol dvation 117 use bosd 00 05 90cm 72 3C wt sh O0r40 9604290841 dest add 00 10 44 D0 72C2 frag ambar 0 ooo mbe 1920 le 136093 Scan
6. SSAP 00 LLC SSAP 00 LLC SSAP 00 LLC SSAP 00 135113 The 7920 survey tool reports the signal strength of the signal from the access point as an RSSI value Most client card utilities report signal strength as dBm or percent of signal strength In this chapter each of the tools tested will be reviewed showing how they measure signal strength Table 2 1 provides a cross reference of RSSI dBm and percent of signal strength as reported by different cards and utilities The numbers were captured in a live over the air test with each device in the same location for comparison These are not exact numbers A plus or minus of five percent in radio to radio performance is considered within tolerance All surveys regardless of the tool used must be measured to the signal strength requirements of the 7920 Cisco recommends that cell size for the 7920 be an RSSI value of 35 for the 7920 survey utility this equals a PCM350 ACU value of 67 dBm and a Cisco a b g client Aironet Desktop Utility ADU value of 66dBm Table 2 1 1200 Series Access Point 11 Mbps 20 mW with 2 2 dBm Antennas RSSI dBm and Signal Strength Cross Referenced for 7920 Phones SniffPro access 350 ACU AirMagnet AiroPeek ADU CB21 Feet Signal pointdBm 7920 RSSI dBm 350 PDA CB21dBm dBm 10 78 55 52 gt 45 47 51 51 20 72 60 46 52 49 52 53 30 68 67 46 55 54 58 60 40 63 72 43 59 54 68
7. Stopped BBstan Chanel LD iofrastructure AirWISE jCharts HpDecodes Tools Back The AiroPeek trace shows the signal dBm value and signal percentage with the PCM 350 client radio It does give relative time between packets so that jitter can be investigated if you suspect inter packet delays Figure 2 7 shows the AiroPeek window Site Survey Guide for Deploying Cisco 7920 IP Phones P26 W O1L 6315 01 Chapter2 Survey Tools Figure 2 7 AiroPeek Window 04 035033 O0 0F 90 64 87 50 00 0F 90 64 00 40 96 AL 04 036351 00 40 96 Al BE 00 OF 90 64 E7 80 04 036453 ODIOF SOr64 Z71B0 OO SO S6 AlrGErD1 90 0F 90 64 E7 80 04 037735 0010F 90 64 E7 D0 00 40 S6c Al OErd1 04 037048 OO OF 90 64 27 60 OO OF 90 64 E7 B0 00 40 96 Al 8E Di 04 099845 OO 40 96 Al 8E D1 00 0F 90 64 57 80 04 039949 0010Ff 90 64 7 B0 00 0F 90 64 7 B0 O00 40 96 AL 6E D1 04 04134 OO 40 S6 ALOErD1 O0 0F 90 64 87 B0 04 041449 OO OF 90 64 27 50 O0 40 96 AL GE D1 00 0F 90 64 7 80 04 042572 O0 0OF 90 64 E7 D0 ON 40 96 Ai 6E D1 04 042716 00 0F 90 64 7 DO0 001 40 96 Al BEd 04 043285 OO 40 S6 AL GE D1 00 07 90 64 27 30 04 044795 OO OF 90 64 E7 B0 O00 0F 90 64 E7 B0 106 Al BE Di 04 046064 DO 40 SSsAlL BErD1 O0 0F 90 64 57 80 04 046162 00 40 961A 0EtD1 O010F 90 64 E7 B0 04 047571 O0 0F 90 04 E D0 00 0F 90 64 E7 D0 00 40 96 Al 0E p1 04 040974 00 40 96 A1 6E p1 O0 0F 90 64 E7 80 04 045976 O0 0F 90 64 E7 B0 O00 40 96
8. series access point and 1200 series access point running Cisco IOS software default to short headers as do the Cisco 7920 handsets Note amp Older clients might require long headers The Cisco 7920 works correctly with long headers as should all client devices 802 11b might use a long 144 bit preamble or a shorter 72 bit preamble The short preamble cuts 96 ms off the transmission time of every packet It can significantly improve performance especially for smaller sized voice packets There is a throughput hit with long headers of about 500 000 kbps with a 256 byte packet at the 11 Mbps data rate Note An 802 11 transmission channel is simplex only Only one device can transmit at a time exactly like shared Ethernet Site Survey Guide for Deploying Cisco 7920 IP Phones ie E OL 6315 01 _ Chapter 1 Overview Recommendations for Successful VoIP Surveys W The characteristics of VoIP require a meticulous WIPT site survey To avoid a call with jitter the delay variation between packets should not exceed 30 ms The one way delay should not exceed 150 ms and packet loss should not exceed one percent Surveying for a one percent packet loss is important because VoIP uses the Real Time Transport Protocol RTP which does not retransmit for lost packets Voice packets are small but are sent at consistent intervals The 7920 client assumes that it has lost its connection to an access point if it misses 3 consecu
9. tagged with their MAC addresses The room walls on this floor had 6 dB of attenuation and the doors had 7 dB of attenuation The through floor attenuation was 7 dB Figure 1 6 Hospital Floor Survey with AirMagnet Surveyor Ae Veonet Surveyor fees Ds mrret rye ELN 7 modrs TN P Pemer rt y Pat PPUWE D RAPE OG dl 2 paion 521 608 Gage OD 136109 Figure 1 7 shows the manual survey results of a group of survey engineers The AirMagnet Surveyor report shows a remarkable similarity to the manual survey The survey in Figure 1 6 shows that throughout the floor the signal is above 65 dBm The manual survey was done with a cell edge requirement of 65 dBm The manual survey was completed several weeks before the AirMagnet Surveyor survey The floor plans used for AirMagnet Surveyor were imported from the drawings provided by the contracted survey team By necessity the survey team spent a great deal of time determining the proper location power settings and antenna types to be used on the floor However the AirMagnet Surveyor provided an updated survey in a couple of minutes from a walkabout that took less than 20 minutes Site Survey Guide for Deploying Cisco 7920 IP Phones OL 6315 01 Chapter1 Overview l Recommendations for Successful VolP Surveys W Figure 1 7 Hospital Floor Survey by a Survey Crew Site Survey Guide for Deploying Cisco 7920 IP Phones F OL 6315 01 Chapter1 Ove
10. that can be decoded but which are not from clients associated to the access point Random data traffic can originate from a shared media or from a client device that is transmitting at a data rate that the access point does not support In Figure 1 1 the noise level reported by the ACU is 92 dBm and the PCM350 receiver sensitivity at 11 Mbps is 84 dBm which provides a margin of 8 dB at the receiver A signal strength value of 48 dBm less the noise value of 92 dBm equals an SNR of 44 dB as reported by the ACU see Figure 1 2 I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones Chapter1 Overview HZ Recommendations for Successful VolP Surveys Figure 1 2 Signal to Noise Ratio Power dBm RSS Signal Strength Signal to Noise Ratio Noise Level 136116 Time seconds Minimum Requirements for WIPT Cells Table 1 1 lists the minimum values for voice and data cells For WIPT cells Cisco recommends that the cell edge be 67 dBm and the SNR be 25 dB using a data rate of 11 Mbps These values are much more restrictive than those needed for data because of the sensitivity to delays and retries for voice clients Table 1 1 Minimum Signal Strength and Signal to Noise Ratios for Voice and Data Cells Data Cell WIPT Cell Minimum Cell Minimum Cell Edge Signal Edge Signal Data Rate Mbps Strength Minimum SNR Strength Minimum SNR 54 71 25 36 73 18 24
11. the requirements of the RF network Determine what the coverage areas are or will become Determine the number of RF network users by location in the site If the site already has an active RF network learn the site s radio frequencies equipment locations and equipment characteristics Next do a complete scan for RF signals throughout the site Determine the levels of RF at the site and verify that the information you ve been given about the locations of RF devices is correct Report your findings to the site administrators Cisco recommends that the next step is to find on the drawings the locations of the existing RF devices Use the drawings to estimate the cells based on the requirements for 7920 call capacities and cell design Plan the antennas needed and transmit powers required for the access points within the site When surveying with an existing WLAN plan for the areas to be filled in and for changes to existing data rate and transmit power settings Plan on possible changes to antenna types At a multi floor site plan the survey of the coverage for the floor above and below When doing a manual survey record the cell edges of the current floor and then use your survey tool on other floors to measure and record the signal levels When doing an automated survey include the access point on the floors above and below in the walk through survey When you survey a site without an installed 802 11 network plan to use two or three access p
12. to radio communications Operation of this equipment in a residential area is likely to cause harmful interference in which case users will be required to correct the interference at their own expense The following information is for FCC compliance of Class B devices The equipment described in this manual generates and may radiate radio frequency energy If it is not installed in accordance with Cisco s installation instructions it may cause interference with radio and television reception This equipment has been tested and found to comply with the limits for a Class B digital device in accordance with the specifications in part 15 of the FCC rules These specifications are designed to provide reasonable protection against such interference in a residential installation However there is no guarantee that interference will not occur in a particular installation Modifying the equipment without Cisco s written authorization may result in the equipment no longer complying with FCC requirements for Class A or Class B digital devices In that event your right to use the equipment may be limited by FCC regulations and you may be required to correct any interference to radio or television communications at your own expense You can determine whether your equipment is causing interference by turning it off If the interference stops it was probably caused by the Cisco equipment or one of its peripheral devices If the equipment causes interference to ra
13. 2 Survey Tools HZ Survey Tools for Packet Jitter Figure 2 14 AirMagnet Jitter Tool in an Enterprise Office with High 802 11 Traffic r3 Ari umt LiveCaptere votoe ag alee Fie Vew Took Het gt 2 Ait ret Toels MOD 1 i it Ue 2S Nowe 2 coc bre J oe i i iiis a b ms t To in Pits Ady 3 70 i W _ O tae L test h t lt m amp 211 unton 380 ETT Pwr awe 87 171 164 a 55477 s Broadcast Figure 2 15 and Figure 2 16 show the LiveCapture window and the Station window results in a home office with low 802 11 traffic Figure 2 15 AirMagnet in a Home Office with Low 802 11 Traffic F 3 Nir net LiveCapture voice ag ean Fie View Jute Hate 7 f S ji i 135092 W sear 2 Channet KD Infrastructure Airwist Jats B Decodes GQ Took Back Site Survey Guide for Deploying Cisco 7920 IP Phones Ea OL 6315 01 Chapter2 Survey Tools Survey Tools for Packet Jitter W Home office utilization is 2 18 percent and the throughput is 246 kbps for 11 Mbps only calls with a single active WIPT call but utilization is 15 41 percent with throughput of 248 kbps for 1 Mbps only calls Figure 2 16 AirMagnet in a Home Office with Low 802 11 Traffic O AirMagnet Tools x stafina roenn A O AP LJR 11b 151 CH 1 Utl 14 15 Notse 95 CRC 0 DTIM 2 135086 The 14 15 percent utilization result reflects a call at 1 Mbps Site Survey Guide for De
14. 68 50 68 74 37 59 58 68 70 60 72 72 38 63 64 68 67 70 30 78 35 67 67 68 66 Site Survey Guide for Deploying Cisco 7920 IP Phones P22 E OL 6315 01 _ Chapter 2 Survey Tools Table 2 1 1200 Series Access Point 11 Mbps 20 mW with 2 2 dBm Antennas RSSI dBm and Signal Strength Cross Referenced for 7920 Phones continued SniffPro access 350 ACU AirMagnet AiroPeek ADU CB21 Feet Signal pointdBm 7920 RSSI dBm 350 PDA CB21 dBm dBm 80 47 74 34 69 67 72 69 90 59 84 31 68 70 71 71 100 28 80 31 72 78 69 75 110 28 78 34 78 70 77 79 120 33 84 32 77 71 77 78 The data in Table 2 1 was created from live tests Each tool and card combination data point was taken at the same time from the same distance The environment was an open office The floor plan used for the test is shown in Figure 2 12 Figure 2 3 shows the ACU screen for dBm The signal strength shown is 48 dBm which is equal to a 7920 RSSI value of 51 Figure 2 3 ACU Site Survey Window Site Survey 350 Series Passive Mode Enterprise CISCO Signal Strength n Link Speed 11 Mbps Signal to Noise Ratio Associated Access Point Access Point IP Address Channel Frequency Restart Card Setup Start Noise Level 92 dBm 44 dB req01 21 ap3 cis 0 0 0 0 6 2437 MHz Cancel Help 136082 I OL 6315 01 Site Survey
15. 77 12 12 or 11 82 10 67 25 6 or 5 5 89 8 74 23 2 91 6 76 21 1 94 4 79 19 Figure 1 3 shows how the difference in transmit powers between the access point and the WIPT client creates different effective ranges The 5 mW signal probably would continue all the way to the access point but if the access point antennas do not have enough gain to make up the difference in received signal of the WIPT client then the WIPT packets will not be decoded A high gain antenna on an access point will receive a signal from a 5 mW client from a greater distance than a low gain antenna It is the Site Survey Guide for Deploying Cisco 7920 IP Phones ia E OL 6315 01 Chapter1 Overview Recommendations for Successful VoIP Surveys W difference in transmitter power and receiver sensitivity that matters because the gain of an antenna is reciprocal To verify the cell coverage edge of 67 dBm while the client is actively sending and receiving voice size packets check the access point s Station Information and Status page for a dBm value of 67 dBm or higher Figure 1 3 Transmit Power Imbalance ver i 135108 The Ideal WIPT Environment Figure 1 4 shows the ideal WIPT cell with the recommended cell edge signal strength value of 67 dBm at an 11 Mbps data rate and the recommended same channel separation of 19 dBm at an 11 Mbps data rate The two yellow cells have a cell edge of 67 dBm The measured overlap of
16. Cisco SYSTEMS Site Survey Guide for Deploying Cisco 7920 IP Phones April 2005 Corporate 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 408 526 4100 Text Part Number OL 6315 01 Y THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE ALL STATEMENTS INFORMATION AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS THE SOFTWARE LICENSE AND LIMITED WARRANTY FOR THE ACCOMPANYING PRODUCT ARE SET FORTH IN THE INFORMATION PACKET THAT SHIPPED WITH THE PRODUCT AND ARE INCORPORATED HEREIN BY THIS REFERENCE IF YOU ARE UNABLE TO LOCATE THE SOFTWARE LICENSE OR LIMITED WARRANTY CONTACT YOUR CISCO REPRESENTATIVE FOR A COPY The following information is for FCC compliance of Class A devices This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC rules These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment This equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with the instruction manual may cause harmful interference
17. DENTAL DAMAGES INCLUDING WITHOUT LIMITATION LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL EVEN IF CISCO OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES CCSP CCVP the Cisco Square Bridge logo Follow Me Browsing and StackWise are trademarks of Cisco Systems Inc Changing the Way We Work Live Play and Learn and iQuick Study are service marks of Cisco Systems Inc and Access Registrar Aironet ASIST BPX Catalyst CCDA CCDP CCIE CCIP CCNA CCNP Cisco the Cisco Certified Internetwork Expert logo Cisco IOS Cisco Press Cisco Systems Cisco Systems Capital the Cisco Systems logo Cisco Unity Empowering the Internet Generation Enterprise Solver EtherChannel EtherFast EtherSwitch Fast Step FormShare GigaDrive GigaStack HomeLink Internet Quotient IOS IP TV iQ Expertise the iQ logo iQ Net Readiness Scorecard LightStream Linksys MeetingPlace MGX the Networkers logo Networking Academy Network Registrar Packet PIX Post Routing Pre Routing ProConnect RateMUX ScriptShare SlideCast SMARTnet StrataView Plus TeleRouter 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 p
18. Help 136082 Noise is defined as a 2 4 GHz signal that is not in an 802 11 DSSS format but is in the frequency range of the access point s configured channel The noise can originate from an 802 11 2 4 GHz frequency hopping radio a 2 4 GHz wireless phone a 2 4 GHz HAM radio a Microwave oven or a Bluetooth radio Signals from a distant out of network 802 11b or 802 11g radio may also be seen as noise Any 2 4 GHz signal that the access point cannot decode is considered noise However valid data packets from 802 11b or 802 11g radios that are not associated to the access point are considered data traffic Those packets are decoded by the access point and client devices but are discarded However they increase the channel utilization on the access point thus limiting the number of voice clients that can associate Same channel interference must be minimized If the signal strength on a valid packet is higher than the receiver threshold of the access point radio or the client device radio the data packet is decoded Most 802 11 radios have a receiver sensitivity value of 94 dBm to 85 dBm at a data rate of 1 Mbps the lower the dBm value the better the radio s receiver sensitivity Radio receiver sensitivity changes with data rates for example an access point radio might have a receiver sensitivity of 94 dBm at 1 Mbps but the radio sensitivity might be 84 dBm at 11 Mbps The access point discards random data traffic valid packets
19. P Phone Survey Screen 135080 You can also use AirMagnet Surveyor to determine channel separation Figure 2 12 shows the two access points on channel 1 with 1 mW transmit power The dBm values from 0 to 70 dBm are shown in brown Any signal below that is shown in dark grey You can control the values that appear in grey by sliding the Signal gauge The popup bubble shows the signal at any location in the coverage area Figure 2 12 AirMagnet Surveyor Tool 5 bp Seven Oe P Pareretievey Imm eed oR tava har Pasetvetuevey lew path PS a0e grsaessesse a Ld m i a a H t Sona tate 37 3S fh 69 678 Site Survey Guide for Deploying Cisco 7920 IP Phones _ Chapter 2 Survey Tools Survey Tools for Packet Jitter W Survey Tools for Packet Jitter Typically voice packets are sent every 20 ms Voice calls are usually bursty consisting of a group of tightly packed packets in a transmit direction followed by a tightly packed group in a receive direction The users of WIPT are typically mobile users who have active calls while moving between WLAN coverage cells and hence roaming between coverage cells AirMagnet Surveyor provides a tool for this type of possible packet jitter and the trace decode tool provides interpacket timings Over the air packet jitter tools measure the WLAN packets A WIPT call will also at some point be on a wired segment or segments which could also be a source of jitter Figure
20. View Help MySeeSurvey rep IF Ste tae v MF bo bro R Survey Path CH e PLPL e ORr 136098 72398 476 628 When you select display mode on the bottom tool bar SiteViewer displays data collected during the survey Two new panels appear in this mode the Filter area in the center left panel and the map zoom box in the lower left You can display one or more survey data sets by clicking the appropriate check box in the data catalog area in the upper left of the window You can also select the display parameter for the data sets from the menu in the upper right corner of the floor plan display area The choices include Signal Noise Speed SNR You can enable appropriate filters for the data The survey data is displayed in color coded zones In Figure 4 8 colored areas represent signal level in 10 dBm increments Site Survey Guide for Deploying Cisco 7920 IP Phones T 0L 6315 01 E Chapter4 Conducting a WIPT Survey W How To Survey for the WIPT Figure 4 8 AirMagnet Showing Access Points and Merged Display jetcainex PRPP 135099 Figure 4 9 shows SiteViewer s four panel display Viewing more than one survey data type helps you compare measurement factors Site Survey Guide for Deploying Cisco 7920 IP Phones Chapter4 Conducting a WIPT Survey How To Survey forthe WIPT W Figure 4 9 AirMagnet Four Panel Display s Jutut nn gS a j minm W nose Z b pil eful il CTT Ta x
21. a channel should not exceed 86 dBm from the center of the measured cell to the edge of the neighboring cell of the same channel This is the value of 67 dBm plus the 19 dBm for separation Keeping the separation at 19 dBm between same channel cells produces a cell with minimal throughput degradation because of media contention This helps maintain up to 7 good quality WIPT calls in a cell Figure 1 4 Ideal WIPT Environment e A typical deployment showing a 15 20 overlap from each of the adjoining cells e Provides almost complete redundancy throughout the cell The radius of the gt cell should be fe The separation of 67 dBm ave same channel cells Par should be A P S 19 dBm F eee 7920 RSSI 20 m aed i 7 1 Channel y gt 4 1 A Se ao N id bara elseesee l See i A Wire ee Channel eae an E 11 o Channel ME 6 D Site Survey Guide for Deploying Cisco 7920 IP Phones OL 6315 01 EN Chapter1 Overview HZ Recommendations for Successful VolP Surveys Figure 1 4 also illustrates the recommended overlap of 15 to 20 percent for WIPT cells larger than the 10 to 15 percent for data cells The reason for the increase in overlap is to provide enough capacity for quality calls efficient roams and better load balancing With a 15 to 20 overlap the call capacity would be double that of a cell without overlap However it is important to avoid excess ove
22. a requisite Cisco also recommends that technicians study the Cisco Wireless IP Phone 7920 Deployment Recommendations before studying this white paper There are two types of wireless LAN VoIP surveys e A survey performed with Wireless IP Telephony WIPT handsets e A survey that simulates WIPT operation Cisco recommends that if possible you install the VoIP network following AVVID design guidelines before surveying for a WIPT network Tip Click this link to browse to a library of AVVID design guides http www cisco com warp public 779 largeent it ese srnd html Recommendations for Successful VolP Surveys The most effective surveys are performed using Cisco access points and Cisco WIPT handsets on active calls through Cisco s Call Manager In the site survey it is important that you test performance from the source to the end point and also from the end point to the source For example your WIPT site survey should use a wired VoIP phone such as a Cisco 7960 in the core of the network to a WIPT such as a Cisco 7920 handset with a live conversation going in both directions The Cisco 7920 WIPT handset enables you to audibly monitor the quality of the call Cisco also recommends that you use the customer s actual handset configuration when performing the survey Cisco considers it necessary to re survey for voice at a site that has a trouble free WLAN data network Voice traffic is isochronous to be usable it must be tra
23. artnership relationship between Cisco and any other company 0502R Site Survey Guide for Deploying Cisco 7920 IP Phones Copyright 2005 Cisco Systems Inc All rights reserved Preface v CHAPTER 1 Overview 1 1 Recommendations for Successful VolP Surveys 1 1 Getting started 1 2 Minimum Requirements for WIPT Cells 1 4 The Ideal WIPT Environment 1 5 Data Rate and Signal Strength Considerations 1 6 Multi floor survey 1 7 Comparison of a Manual Survey and an Automated Survey 1 8 CHAPTER 2 Survey Tools 2 1 Survey Tools for Packet Jitter 2 11 CHAPTER 3 Surveying for Cell Capacity and Channel Re Use 3 1 Survey Design for Cell Capacity 3 1 CHAPTER 4 Conducting a WIPT Survey 3 How To Survey for the WIPT 3 Channel Re Use 4 Manual Survey for the WIPT 5 Automated Survey for the WIPT 6 CHAPTER 5 Positioning Access Points and Antennas for Site Surveys 4 1 Access Point Positioning 4 1 Antennas and Antenna Positioning 4 2 APPENDIX A Additional Sources of Information A 1 Site Survey Guide for Deploying Cisco 7920 IP Phones T 0L 6315 01 a E Contents Site Survey Guide for Deploying Cisco 7920 IP Phones a OL 6315 01 Preface This document provides instructions and guidelines for conducting a site survey for wireless LANs using Voice over IP VoIP on Cisco 7920 IP Phones With the introduction of voice to a predominantly wireless data network the methodology of site surveys will have to be alt
24. dio or television reception try to correct the interference by using one or more of the following measures e Turn the television or radio antenna until the interference stops e Move the equipment to one side or the other of the television or radio e Move the equipment farther away from the television or radio e Plug the equipment into an outlet that is on a different circuit from the television or radio That is make certain the equipment and the television or radio are on circuits controlled by different circuit breakers or fuses Modifications to this product not authorized by Cisco Systems Inc could void the FCC approval and negate your authority to operate the product The Cisco implementation of TCP header compression is an adaptation of a program developed by the University of California Berkeley UCB as part of UCB s public domain version of the UNIX operating system All rights reserved Copyright 1981 Regents of the University of California NOTWITHSTANDING ANY OTHER WARRANTY HEREIN ALL DOCUMENT FILES AND SOFTWARE OF THESE SUPPLIERS ARE PROVIDED AS IS WITH ALL FAULTS CISCO AND THE ABOVE NAMED SUPPLIERS DISCLAIM ALL WARRANTIES EXPRESSED OR IMPLIED INCLUDING WITHOUT LIMITATION THOSE 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 INCI
25. e 1 Mbps data rate has a theoretical throughput of 650 000 bits per second for 256 byte packets The codec used by the Cisco 7920 has a packet size of 236 bytes The data rate of 11 Mbps has a theoretical throughput of 2 000 000 bits per second for 256 byte packets This means the Cisco 7920 packets require almost 4 times more time at the 1 Mbps than at the11 Mbps data rate Another important reason for using the 11 Mbps data rate is the reduced cell size At 11 Mbps the 802 11b g radio of the access point has an open office cell size with a radius of 160 feet The 1 Mbps cell size for the same radio has a radius of over 400 feet The larger the cell size the more clients that can be active in the cell For the Cisco 7920 we recommend only 7 handsets in a cell which results in better quality calls The data rates configured on the access point depend on the other types of client devices used at the customer site The customer might have an installed base of legacy 802 11 clients that require support of a 2 Mbps data rate It is highly unlikely that any 802 11b network would need support for a data rate of 1 Mbps This rate should be disabled because it uses long headers and the slowest required data rate is the data rate used by the access point to send 802 11 control and management packets Other configuration parameters that could have negative impact on legacy 802 11 performance are short headers and beacon rates The 350 series access point the 1100
26. e primary lobe area A low gain directional antenna such as a 6 5 dBi patch will receive signal from the sides and the back but the primary coverage area will be forward The coverage in Figure 1 5 represents an Omni antenna coverage The cell coverage overlap and same channel separation should be maintained at a multi floor site Figure 1 5 Survey in a Building with Multiple Floors 136112 Different types of facilities such as hospitals and schools have different signal propagation patterns multipath levels and attenuation levels I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones jg Chapter1 Overview HZ Recommendations for Successful VolP Surveys Comparison of a Manual Survey and an Automated Survey Figure 1 6 shows an actual hospital survey done using AirMagnet Surveyor with an 802 11b Cisco PCM350 client card Four panels on the AirMagnet window show the survey results The top left panel shows that the survey data was collected in passive mode The middle left panel shows the access points seen by the survey client while doing the passive mode walkabout to collect survey data The right panel shows the floor plan that was imported and the strength of signal as reported by the client walkabout for the survey area The dark green to light blue colors indicate that the signal strength on the floor of the hospital wing varied from 30 dBm to 55 dBm The five access points that are located on the floor are
27. ered Voice over WLAN is a new application to wireless technology Many of the survey techniques used for WLAN must be updated This document is intended to identify many of the recommended techniques and tools needed to successfully deploy VoIP over an 802 11 wireless network The recommendations made in this document supersede all other guides on doing site surveys However other site survey guides or training documents are valuable and a necessary prerequisite to this recommendation guide Surveying for wireless voice coverage requires more effort and time than for data only coverage at the same site A voice survey requires planning of coverage plus the planning of capacity Wireless data is less susceptible to disruption than wireless voice when it comes to cell overlap RF noise and packet delay I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones Preface Site Survey Guide for Deploying Cisco 7920 IP Phones PvE OL 6315 01 S CHAPTER 1 Overview This document begins by identifying the specific radio environmental values that are needed for a successful voice deployment Note Cisco offers a Cisco Aironet Wireless Site Survey class for technical individuals who will be performing site surveys for wireless LAN solutions This white paper does not replace the information in the site survey class Cisco recommends that wireless LAN survey technicians take the Aironet Wireless Site Survey class as
28. ess 00g AOG cf79 Name larryr Address 0000 lees theri Dowe a chert oftware Version 2 State Associated Prem rer sst seversyvsughn VLAN none Hops To ir estructure 1 ormum ahon Over interface Redo M2 11G Chertse Assocested 0 Repesters Ascocrsted Key Mara type NONE Encrypteor oF Current Gate Mb sec 10 apateity short ete Supported Ratee Mb eec t0 20 55 110 Aseoctstion id 6 gna Strength dBm H Connected For se LETE Signe Qusity WA Actwity TeneDut leer 16 Powe cave OF Last Actiity sec 10 Total Packets input 687 Total Packets Output 22007 3 Tote Bytes Input EP Tote Bytes Ovipit awe amp The survey utility for the 7920 is hidden by default To enter the survey tool and to change the settings for data rate and transmit power follow these steps Step 1 Select Menu Step2 Press once Step3 Press twice Step4 Press the send key which on the 7920 is the key labeled with a green phone symbol Step5 Choose the Network Config tab Step6 Scroll down to the 802 11b Configuration option and choose it Step7 Choose Wireless Settings Step8 Choose Data Rate Step9 Choose 11Mb Step 10 Choose Transmit Power Step 11 Choose the power value that matches the power setting on the access point Site Survey Guide for Deploying Cisco 7920 IP Phones T 0L 6315 01 EN Chapter2 Survey Tools Figure 2 11 shows that the 7920 hears three access points and the RSSI values of those access points are 18 31 and 48 Figure 2 11 Cisco 7920 I
29. et Surveyor uses a client walkabout function that formulates coverage in both signal strength and signal to noise ratio from all the data points taken during the walkabout You can configure the AirMagnet surveyor client to associate and authenticate to the network When the unit associates begin the walkabout You should walk at a slow pace the program takes a data point about once per second Site Survey Guide for Deploying Cisco 7920 IP Phones Pas W OL 6315 01 Chapter4 Conducting a WIPT Survey How To Survey forthe WIPT W The AirMagnet surveyor works very well for surveying a site with an installed WLAN or for surveying a site without a WLAN The tool works with the existing transmit power of the access points but allows you to redisplay coverage areas with simulated transmit power settings another time saving feature over manual surveys Figure 4 5 shows the AirMagnet Surveyor main window Figure 4 6 shows the Active Mode window Figure 4 5 AirMagnet Surveyor Main T tato Airiingnet Project Untitled Ste Map Saree Pet 2b wl SoS e CRs 136096 Site Survey Guide for Deploying Cisco 7920 IP Phones F OL 6315 01 47 Chapter4 Conducting a WIPT Survey HZ How To Survey for the WIPT Figure 4 6 AirMagnet Survey Active Mode E SiteViewer Airloonet Project MySiteSurvey svp Ete Yow Helo prepreg Memm TERED EJ Ste Mas V Myo ap bro tno me R Survey Pat sh PLPP e ORY
30. hed to a hidden access point Figure 5 4 Patch Antenna Mounted on a Wall Figure 5 5 shows a dual radio access point mounted on a wall The removable antennas are pointed up and the paddle antenna is folded against the body of the access point Figure 5 5 Access Point Mounted on a Wall 136105 Site Survey Guide for Deploying Cisco 7920 IP Phones 0L 6315 01 EN Chapter5 Positioning Access Points and Antennas for Site Surveys W Antennas and Antenna Positioning Figure 5 6 shows a patch antenna mounted on a suspended ceiling The cables are hidden and are routed above the ceiling to the access point Figure 5 6 Patch Antenna Mounted on a Suspended Ceiling Site Survey Guide for Deploying Cisco 7920 IP Phones TE APPENDIX A Additional Sources of Information This appendix lists documents that provide additional information about site surveys e Cisco Wireless IP Phone 7920 Deployment Recommendations http www cisco com en US products hw phones ps379 products_white_paper0900aecd800f6d97 shtml e Solution Reference Network Designs Best Practices for Building a Cisco AVVID Network Infrastructure http www cisco com warp public 779 largeent it ese srnd html Site Survey Guide for Deploying Cisco 7920 IP Phones OL 6315 01 EN Appendix A Additional Sources of Information Site Survey Guide for Deploying Cisco 7920 IP Phones a2 E OL 6315 01
31. ing a WIPT Survey HZ How To Survey for the WIPT Figure 4 4 ACU Site Survey Active Mode Site Survey 350 Series Active Mode Class Lab Signal Strength Noise Level 92 dim Link Speed 11 Mbps Signal To Noise Ratio Associated Access Point AP1200 d268e6 Access Point IP Address 10 0 0 1 Channel Frequency 6 2437 MHz Percent Complete Percent Successful ee Lost To Target 0 Lost To Source 1 Click OK to return to the Site Survey screen Click Start to start the site survey in active mode 136081 This information updates constantly during the survey e Percent Complete the percentage of packets that have been sent When you select continuous link test this field shows the percentage of packets that have been sent When it reaches 100 it starts over e Percent Successful the number of packets the have been successfully sent and received Notice the red threshold line If the percentage drops below this line the bars become yellow e Lost to Target the number of packets that were lost between the client and the access point e Lost to Source the number of packets that successfully reached the access point but did not reach the client Click Stop or OK to stop the survey The goal for a site survey for 7920 phones is 99 percent of packets successfully sent and received for each cell Automated Survey for the WIPT Cisco recommends the use of AirMagnet Surveyor for automated surveys AirMagn
32. ith current data rates and packet sizes Cisco recommends that all WIPT site surveys and installations use non overlapping channels For 802 1 1b g operation the non overlapping channels are a minimum of 5 radio channels apart Cisco also recommends that you use a data rate of 11 Mbps to determine the cell size for the Cisco 7920 WIPT handset If other data rates are allowed call capacity might be substantially lower Getting started Part of any site survey is measuring the noise level within a wireless cell Noise levels vary from site to site and also within different locations of a site The noise level affects a radio s ability to receive data or voice packets Figure 1 1 uses the Cisco Aironet Client Utility ACU and a Cisco PCM350 client adapter to identify the noise level signal strength and SNR at a specific location with a wireless cell The ACU window shows that the signal strength is 48 dBm the noise level is 92 dBm and the SNR is 44 dB Site Survey Guide for Deploying Cisco 7920 IP Phones i2 g OL 6315 01 _ Chapter 1 Overview Recommendations for Successful VoIP Surveys W Figure 1 1 ACU Site Survey Window Site Survey 350 Series Passive Mode Enterprise CISCO x Signal Strength Noise Level Link Speed 11 Mbps Signal to Noise Ratio 44 dB Associated Access Point req01 21 ap3 cis Access Point IP Address 0 0 0 0 Channel Frequency 6 2437 MHz Restart Card Setup Start E Cancel
33. nsmitted without delay Voice traffic has strict resource requirements for guaranteed bandwidth low latency low jitter and low packet loss The 7920 G 711 codec voice packets require a guaranteed bandwidth of 80 kbps The G 711 packets have a 160 byte payload plus a 40 byte RTP UDP IP protocol overhead Typically voice packets are sent every 20 milliseconds ms and a corresponding service rate is expected from the network by the voice application A delay or loss of two or more contiguous voice packets is generally noticeable as quality I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones Chapter1 Overview HZ Recommendations for Successful VolP Surveys degradation This quality requirement also dictates the need for a fast roaming solution between access points where the network can reassociate a client to a new access point within 100 ms that is without suffering at most one packet delay or loss People often walk around while talking on the phone so users making voice calls tend to roam more than users of wireless computers Users of wireless computers roam but because very few users walk and use their computers at the same time computer users are not using their computers when the roam occurs Because it might not be possible to have a VoIP network and WLAN network in place before the WIPT site survey this document also describes a WIPT site survey process using standard wireless client cards and utilities
34. oints to measure cell coverage and cell overlap The cell edge for the 7920 at the 11 Mbps data rate is 67 dBm The signal strength at the edge of that cell needs to be 19 dB weaker than the signal from the next cell on the same channel That means at the 67 dBm edge of the cell the next cell on the same channel should measure 86 dBm as shown in Figure 4 1 I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones Chapter4 Conducting a WIPT Survey HZ How To Survey for the WIPT Figure 4 1 Channel Re Use Ideal WIPT Environment e A typical deployment showing a 15 20 overlap from each of the adjoining cells e Provides almost complete redundancy throughout the cell The radius of the D cell should be Yt N The separation of 67 dBm ha i same channel cells 2N S should be k M N 19 dBm f g o gt es 7920 RSSI 20 oo i xp x N Fi N F A 7 F E ll TTS 67dB 86qB 135075 Figure 4 2 shows the typical channel re use for 802 11b and 802 11g WLANs The two gold channel 1 cells are 86 dBm apart from center to center The same separation should be maintained between floors of a multi floor site Figure 4 2 802 11b 802 11g Channel Reuse Diagram 136106 You can use the two Aironet client tools and the survey tool in the 7920 to measure cell separation The ACU for the PCM350 client has an active survey mode Cisco recommends an active survey where there are tran
35. ploying Cisco 7920 IP Phones OL 6315 01 SEE Chapter2 Survey Tools HZ Survey Tools for Packet Jitter Site Survey Guide for Deploying Cisco 7920 IP Phones P24 OL 6315 01 CHAPTER Surveying for Cell Capacity and Channel Re Use This chapter describes how to perform a site survey to design a wireless LAN for cell capacity and channel re use Survey Design for Cell Capacity Cisco recommends that you install enough access points to provide all users with quality calls Maintaining high call quality might require small coverage cells that limit the number of calls per access point to 7 to meet the QBSS level on access points below 35 With a recommended RSSI level of 20 dB throughout the RF network the access point transmit powers could be as low as 20mW with low gain antennas on the access points You should consider these design factors to ensure adequate capacity and coverage e removing interfering devices e configuring older 802 11 devices to lower transmit power e configuring older 802 11 devices to the highest possible data rate When you configure the access points for higher data rates and lower transmit power the cell coverage from the access point becomes smaller However if you adjust the access points for high data rates and low transmit power but you do not make similar adjustments on the clients the cell might be unbalanced as in Figure 3 1 except that the client signal exceeds the access point signal Figu
36. re 3 1 Unbalanced Cell Due to Mismatched Transmit Power and Data Rate Settings if 100mW 4 135108 Depending on the configurable and non configurable parameters of the client it might continue to transmit packets at a 1 Mbps data rate The transmit coverage of a client could be 400 feet when the transmit coverage of the access point is 100 feet This mismatch could affect the call capacity and QBSS of an access point several cells away from the access point to which the client is associated I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones Chapter3 Surveying for Cell Capacity and Channel Re Use HZ Survey Design for Cell Capacity amp Note If the Cisco access point is configured to disable data rates 1 2 and 5 5 clients are not required to transmit only at 11 Mbps In fact older client devices might not be programmed to recognize the access point configuration for data rates Cisco recommends that customers update their 802 11 clients to run the newest firmware and drivers available Vendors generally update power and data rate options as their products mature Site Survey Guide for Deploying Cisco 7920 IP Phones P32 E OL 6315 01 CHAPTER Conducting a WIPT Survey This chapter describes specific steps for performing a site survey for WIPT How To Survey for the WIPT Cisco recommends that the first step of a survey is to work with administrators at the local site to determine
37. rlap because it can cause frequent roams by the WIPT clients which may result in lower quality calls Data Rate and Signal Strength Considerations You should consider data rate and signal strength before beginning any WIPT site survey Signal strength or transmitting power of the access point radio combines the configured transmit power of the access point and the antenna attached to it If an additional antenna cable is placed between the access point and the existing antenna cable there is a loss in transmitted power Generally the longer the cable between the access point and the antenna the lower the transmitted signal strength will be The combination of radio transmit power antenna cable loss and antenna gain is known as Effective Isotropic Radiated Power EIRP For example if the 100mW transmit power of the radio equals 20 dBm the loss of a 100 foot cable is 6 dB and the gain of an antenna is 3 dBi the result is an EIRP of 17 dBm Using the EIRP value of 17 dBm from this example and considering the receiver sensitivity of the Cisco 7920 radio the coverage area in an open office without noise would be about 140 feet from the access point at a data rate of 11 Mbps This example highlights the guidelines for surveying for the Cisco 7920 WIPT handset Cisco recommends an access point data rate configuration of 11 Mbps for WIPT cells The faster data rate means that packets take less time to be received and results in higher call quality Th
38. rview HZ Recommendations for Successful VolP Surveys Site Survey Guide for Deploying Cisco 7920 IP Phones i10 i OL 6315 01 Survey Tools CHAPTER AirMagnet offers many tools for analyzing 802 11 performance at a site Figure 2 1 shows the AirMagnet Survey tool Cisco recommends AirMagnet for data and WIPT surveys Figure 2 1 AirMagnet Survey Tool Tools F AirMagnet AP v 00 0F 90 43 96 E0 802119 m Associated AP status assip LIR 11b 151 SSID voice no wep Speed 11 0 Channel 1 Signal So SSE Noce m Packet status 26000 bytes s Lost UES Retry 0 100 packets s 0 packets s 0 packets s Location EAA Survey Signal Dist Diag Whois Coverage GPS Log 135094 An accurate survey requires packets sent in both directions The size of the packets needs to equal the size of the packets used by the primary applications used at the survey site Figure 2 2 shows a packet capture of the AirMagnet Survey tool survey packets This window shows that the AirMagnet tool is actively sending packets I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones j Chapter 2 Survey Tools Figure 2 2 AirMagnet Packet Decode Tool l Filter ScanStorped i Start GHChannel infrastructure MB AirWISE jCharts HpDecodes amp LLC SSAP 00 LLC SSAP 00 ULC SSAP 00 LLC SSAP 00 LLC
39. smitted and received packets of the same size as a voice packet Site Survey Guide for Deploying Cisco 7920 IP Phones 0L 6315 01 _ Chapter 4 Conducting a WIPT Survey How To Survey forthe WIPT W Manual Survey for the WIPT You can use passive or active mode when you use ACU to run a site survey Figure 4 3 shows the ACU Site Survey windows Figure 4 3 ACU Site Survey Windows Site Survey Active Mode Setup Unk seeed 11 ope NN Signal To Noise Ratio 33 dB Associated Access Point LAB 1200 Access Point IP Address 192 168 1 102 Channel Frequency 1 2412 MHz Percent Complete EE SNS race success MT Lost To Target o Lost To Source 1 Restas Cord Spo zo Q 135083 To set up active mode click the Setup button at the bottom of the screen If the Setup button is unavailable the client is using a version of firmware that does not support active mode and you should upgrade the firmware The destination MAC address should belong to the access point to which you want to test coverage The destination MAC address prevents the client from roaming to another AP For most surveys you should uncheck the Destination is Another Cisco Device check box Set the packet size to 256 Set the Data Rate to 11 Mbps On the access point set the 11 Mbps data rate to required and set all other data rates to disabled I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones gy Chapter4 Conduct
40. t i i EEEEE TEETER Tee tie Site Survey Guide for Deploying Cisco 7920 IP Phones T 0L 6315 01 EIN Chapter4 Conducting a WIPT Survey HZ How To Survey for the WIPT Site Survey Guide for Deploying Cisco 7920 IP Phones Ca OL 6315 01 CHAPTER Positioning Access Points and Antennas for Site Surveys When you perform a site survey it is important to position wireless equipment for optimal coverage This chapter describes best practices for positioning access points and antennas Access Point Positioning In industrial environments such as warehouses a common installation point for access points is on girders or I beams However an I beam reflects both received packets and transmitted packets resulting in poor signal quality because of nulls and high strength mulitpath signals Figure 5 1 shows the I beam installation and the resulting signal propagation The null is created by the crossing of signal waves shown in the scattered waveforms diagram The multipath is shown as the multiple waves in the signal Figure 5 1 Access Point Installed on Il Beam Reflected Signal gt Waves gt l Beam Null Signal Waves Incoming Signal Waves Q I OL 6315 01 Site Survey Guide for Deploying Cisco 7920 IP Phones jg Chapter5 Positioning Access Points and Antennas for Site Surveys W Antennas and Antenna Positioning The access point in Figure 5 2 provides better coverage because the reflec
41. ted signal produces fewer nulls and less multipath than the I beam placement However because there is only one floor in this industrial building there is no need for the antennas to be above the access point The signal could be improved by inverting the access point so that the antennas point to the ground Figure 5 2 Access Point Installed on a Wall Incoming Signal ay Partial Thru Signal Partial Reflected Signal eer Surface 136103 Antennas and Antenna Positioning Interference and multipath cause the transmitted signal to fluctuate Interference increases the required signal to noise ratio for a particular data rate The packet retry count goes up in areas where interference or multipath are high Changing the type and location of the antenna can reduce multipath interference Antenna gain adds to the system gain and improves the signal to noise requirement Figure 5 3 shows proper positioning of the antennas on a dual radio access point mounted on a suspended ceiling Both the removable antennas and the paddle antenna are pointed down at the floor Figure 5 3 Access Point Installed on a Suspended Ceiling 136102 Site Survey Guide for Deploying Cisco 7920 IP Phones OL 6315 01 Chapter5 Positioning Access Points and Antennas for Site Surveys Antennas and Antenna Positioning W Figure 5 4 shows a patch antenna mounted on a wall The antenna cables are routed above the suspended ceiling and are attac
42. tive beacons The access point sends a beacon every 100 ms which means that the Cisco 7920 looks for another access point if it does not see beacons every 300 ms from the access point to which it is associated Multi floor survey At many sites it is important to consider the effect of above floor and below floor coverage An antenna placed near a ceiling in a multi floor facility can easily provide coverage to the floor above There will be considerable loss in dBm signal strength but the signal can still have enough quality to be usable Depending on the capacity throughput and coverage requirement for the site the power of the access point may be turned down to minimize the signal coverage between floors An Omni antenna propagates directly above it into the floor above A patch antenna will also propagate signal into the floor above but not directly above as the Omni antenna will Although directional antennas help focus the signal energy in a particular direction which can help to overcome fading and multipath signals multipath signals reduce the focused power of a directional antenna and the amount of multipath seen by a user at a long distance from the access point can be much greater Directional antennas used indoors typically are low gain 5 dBi to 10 dBi and therefore have lower front to back and front to side lobe ratios This reduces the radio s ability to reject or reduce the interference signals received from directions outside th
43. x 104 0 00 00 017 DLC DIC Header 43 DLC Lj DLC Frane 1 arrived at 14 28 39 0072 frame size is 124 007C hex bytes 43 DLC Signal level 28 gt ij DLC Channel 00000000 80 00 00 OO ff ff ff ff ff ff 00 40 9i f4 t yy y vy 1G61 00000010 DO 40 96 47 f4 6c d0 1 3d bs 86 11 4e 07 00 00 Peira N 9 2 00000040 86 12 07 OO f 03 11 00 61 70 33 35 30 2d 49 AE y ap350 10 00000050 53 2d d 69 61 64 c 65 00 00 00 22 dd 06 00 40 S miadle as AR 00000060 6 01 01 00 dd 16 00 40 96 O4 00 Od 06 a5 00 00 9 a y 00000070 22 a3 00 00 41 54 00 00 61 43 00 00 E AT aC 135117 Site Survey Guide for Deploying Cisco 7920 IP Phones OL 6315 01 Chapter2 Survey Tools a The Cisco access point displays the signal strength of the packets from the client The signal strength of the access point as reported by the client utility should be relatively close to the signal strength reported by the access point for the client It is important that the signals between the access point and the 7920 be relatively the same This design avoids a call in which one side of the call has poor connectivity The Station Information and Status page on the access point shows the signal strength of the client as seen by the access point Figure 2 10 shows the access point Station Information and Status page with client signal strength at 31 dBm Figure 2 10 Access Point Station Information and Status Page MAL Addr
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