1EF89_Interference_Hunting_FSH
Contents
1. 3 Interference Hunting Steps eee seee essere 4 Detecting the Interfering Signal aan AGA 4 Working with the Spectrogram Function esses 7 Characterizing the Interfering Signal e e eeeeeeee ee ceeeeee n 9 Documenting the Results with R amp S FSHAView nerne nere nrr renerne 11 Working with the Interference Analyzer a 12 Locating the Interference SOUR ANA 14 Downloading Maps and Loading Them to the FSH oococcccccocccnncccnnnccononnnanccnnononancnnnnns 16 Working with the Triangulation Function a 17 Working with the Tone Function 11 kk tk kk nnnm 22 Working with the Save on Event and the Geotagging Function 23 Common Interference SoUrces scenerne 27 Noise and Spurious Emissions 0ncccconcnnnccccnncnnncncnnnnnncnncnnnnnncorennnnnncrrnnnnnnnrrrennannnannna 27 Harmonics and Intermodulation ccccccssssseeessessseeeeceesseeeeseeesseeeseeeesseeeseoeenseeesens 29 Biairectional AMPIMICES AA 30 Cable Leakage aaa AA AA 32 Unlicensed or Wrong Band Operation Musse aaa 32 Jammers and Deliberate Interference ccsececeeessseeeeceeeseeeeeeeenseeeeseoenseeeeseoeees 33 ABER e 35 LIE Frequency Bands usa 35 WCDMA UMTS Frequency Bands esses esses eee nennen nnns 37 GSM Frequency BANGS2. 10 01 2 2 1 Interference Hunting Steps Characterizing the Interfering Signal Documenting the Results with R amp S FSH4View Once the interferer has been found the results may need to be reported to the responsible frequency regulation authority For this purpose the network operator needs to document all relevant information related to the interference case such as 1 Affected network element i e sector s or cell s and address 1 Effect of the interference i e calls dropped service inaccessibility 1 When does it happen continuously or at certain times or on certain days 1 Interfered frequency band and frequency channels 1 Measured interference levels frequency level date and time of the measurements 1 Suspected interference source interferer type location In addition signal plots like those shown in Fig 7 and Fig 8 as well as screenshots of maps may be added to the report The R amp S FSH4View software is extremely useful for editing and preparing the measurement results to report It allows you to transfer files between the instrument and the PC and edit measurement results edit add markers limit lines etc It also enables you to perform many other tasks such as generating reports setting up templates for limit lines channel tables cable models etc In addition the R amp S FSH4View software lets you control the FSH remotely via a LAN or a USB connection from any Windows based PC usin
3. Schwarz 19 01 Interference Hunting Steps Locating the Interference Source 07 08 14 16 12 il GPS N 48 7 8 163 E 11 41 39 902 Alt 451 9 m Comp 358 Sats 12 Freq 796 MH Power 69 3 Ti da Pi DH t Em E ay E E i C Pa co C E gt a a P i d F En De fod Rey 7 gt N ta ES c m MES y biel f i MEG ra gebiet p jofstrabe F 10 m ie Meas GPS i Mode Position zoom In Zoom Out Settings Fig 20 Message in map triangulation display Saving a GPS position with bearing using R amp S HL300 switch If you are using an R amp S HE300 antenna to save a position you have to click Save Current Position and Azimuth under the GPS Position menu The switch on top of the R amp S HE300 antenna only turns on the R amp S HE300 preamplifier If an antenna other than the R amp S HL300 or R amp S HE300 is used the antenna does not need to be set up We recommend using the R amp S HA Z240 GPS receiver it needs to be enabled under the Instrument Setup menu To save measurements click Save Azimuth Only This will automatically save the measurement with GPS position data from the FSH The bearing data can either be typed in manually or selected using the rotary knob save Current Position and Azimuth save Manual Position and Azimuth Show Saved Positions GPS Position List Go To Triangulation Position Triangulate save Triangulation Meas G
4. which helps to speed up the direction finding in dense urban areas The Triangulation Technique Suburban or Rural Areas In suburban or rural areas the FSH mapping function allows you to triangulate the interferer narrowing down the search to a much smaller area The quality of the measurement results depends on the choice of the measurement sites These should be elevated and ideally have line of sight to the signal source Since the location of the signal source is unknown the success of triangulation in dense urban areas is limited since signal reflections in buildings multipath and shadow effects will falsify the measurement results Log periodic antennas such as the R amp S HL300 or R amp S HE300 cover all frequency bands up to 8 GHz and 7 5 GHz respectively which makes it possible to measure harmonics of the main interfering signal In addition they feature a built in GPS and electronic compass which allows the FSH to display the user s position and the antenna s direction You can configure the FSH to play an audio signal when it receives a signal The audio signal will increase its frequency and volume as the interference signal level increases thus helping you to find the strongest direction without constantly looking at the FSH screen Sections 2 3 2 and 2 3 4 explain how to set up the triangulation and tone functions in the FSH y Fig 13 Locating interference source with the FSH and the R amp S HL300 directional
5. in order to see the interferer as well However this is usually time consuming and sometimes special authorization is needed to access the site In some countries however connecting to the base station may be done as the first step to know what the interferer looks like before going out into the field In traditional macro BTS architectures where the baseband unit and the antenna system are connected with RF feeder cables there is usually an RF sniffer port However many deployments are making use of remote radio heads RRF where the antenna system and the RF unit are all mounted up on the tower and the data is carried to the ground over a fiber optic link Some remote radio heads do not have an RF sniffer port and need to be shut down to measure through the BTS antenna On the other hand RRHs may not be easily accessible i e installed on a tower That is in many cases we now have no choice but to drive the sector and search a relatively wide frequency span looking for the interfering signal Rohde amp Schwarz 6 01 Interference Hunting Steps Detecting the Interfering Signal 2 1 1 Working with the Spectrogram Function With the FSH K14 or FSH K15 option you can view measurement results in a spectrogram The spectrogram is extremely useful in interference hunting It lets you observe a signal s behavior over time and helps to detect pulsed or intermittent signals The spectrogram shows the spectral density vers
6. 2 esmo 750 7472722 Tiara esn TOSMBIO e0 80629212 8512 8002 ayame 7 GSM 850 850 824 2 849 2 869 2 894 2 128 251 5 North America Latin America P GSM 900 890 0 915 0 935 0 960 0 1 124 Europe Middle East Africa Australia Oceania Asia some countries in Latin America EGSM900 900 88009150 9250 9600 075 1023 0124 8 RGSMO0 900 8760 9150 9210 9600 955 199 0 24 T GSMo0 900 87048760 91549210 dynamo PCS 1900 1900 1 850 2 1 909 8 1 930 2 1 989 8 512 810 2 North America Latin America Source http en wikipedia org wiki GSM frequency bands GSM frequency usage around the world Rohde amp Schwarz 38 References 01 5 References 1 R amp S FSH4 8 13 20 Operating Manual 2 Rohde amp Schwarz white paper An Introduction to Interference Hunting by Paul Denisowski 3 R amp S PR100 Locating a Signal Source Application brochure 4 R amp S OSM Wizard User Manual 5 DECT Technology http en wikipedia org wiki Digital Enhanced Cordless Telecommunications http de wikipedia org wiki Digital Enhanced Cordless Telecommunications Rohde amp Schwarz 39 Ordering Information 6 Ordering Information Designation Order No Handheld Spectrum Analyzer 9 kHz to 3 6 GHz with preamplifier 1309 6000 04 Handheld Spectrum Analyzer 9 kHz to 8 GHz with preamplifier 1309 6000 08 Handheld Spectrum Analyzer 9 kHz to 13 6 GHz with preamplifier 1314 2000 13 Handheld S
7. 5 Mem e o ss ies Defaut Indicator 1 Maximum Zoom Distance R amp S FSH Mapping ROHDE4SCHWARZ Il Measurement0010 kmz Worst Signal Level Fig 29 Geotagging measurement results displayed in Google Earth Rohde amp Schwarz 26 01 Common Interference Sources Noise and Spurious Emissions 3 Common Interference Sources 3 1 The variety of interference sources is almost endless It will vary depending on the country and RF environment A large number of interferers often share common characteristics An awareness of these frequently recurring interference sources can save a substantial amount of time and effort when investigating interference This section describes the most common external interference sources in wireless networks For more information refer to the Rohde amp Schwarz Interference Hunting Learning Center http www rohde schwarz wireless com IH Noise and Spurious Emissions Electrical noise sources tend to be many megahertz wide and periodic in frequency and or time Examples are emissions from electric motors welding equipment vehicle ignition systems electrical fences faulty transformers ballasts etc Electrical noise shows up as jumps in the noise floor or as a wide random spectral pattern Noise from electronic sources sometimes also referred to as spurious emissions or spurs is usually less than one megahertz wide and tends to be continuous alth
8. antenna Rohde amp Schwarz 15 Interference Hunting Steps Locating the Interference Source 2 3 2 Downloading Maps and Loading Them to the FSH Before you can use any features based on maps you have to download and install the maps on the FSH The FSH supports the map material supplied by the Open Street Maps project http www openstreetmaps org To transfer maps to the FSH use the R2 S OpenStreetMap Wizard OSM wizard The OSM wizard is available for download on the FSH product homepage http www rohde schwarz com product fsh htmi The OSM wizard establishes a connection to the Open Street Maps database and therefore requires a connection to the Internet To select your area of interest navigate by dragging the map and using the zoom buttons The zoom level is adjustable from levels 1 to 18 To download the maps click the Start button Use the Browse button to specify the destination folder In a scenario where the Current Zoomlevel is set to 10 and a Download Zoomlevel of 14 is selected the OSM tiles from zoom levels 10 11 12 13 and 14 within the current map area will be stored on disk In order to avoid huge downloads which are not permitted by the Open Street Map server you cannot set wide map areas and deep zoom ranges For example if a Current Zoomlevel of 10 is set then the Download Zoomlevel may only be increased to 14 D RsOsmWizard SES 0 0 Latitude 51 5076 Source j
9. areas with poor reception They operate by amplifying and retransmitting both downlink and uplink signals and are not a source of interference when properly installed and operated They most commonly cause interference when there Is insufficient physical separation between the serving and donor antennas leading to a feedback loop that substantially increases the noise floor over the entire uplink band typically a range of 30 MHz to 40 MHz or when the BDA is malfunctioning The presence of a small Yagi or directional antenna on a building roof or of panel or dome type indoor antennas is a good visual clue as to the presence of a bidirectional amplifier The BDAs are difficult to troubleshoot but a very common source of interference in the cellular bands Unlicensed use is illegal in many countries Rohde 4 Schwarz 30 Common Interference Sources Bidirectional Amplifiers Fig 34 Typical bidirectional amplifier installation UREW Ref 52 4 dBm RBW 3 MHz SWT 20ms Trace Clear Write Att 0 dB VBW 3 MHz Trig Free Run Detect RMS ot ET m on Pree mi TE EE Center 825 MHz Span 100 MHz Span Span Span Fig 35 Oscillating BDA signal in 800 MHz LTE band Rohde amp Schwarz 31 01 3 4 3 5 Common Interference Sources Cable Leakage 01 08 14 12 22 MN Ref 30 0 dBm RBW 3MHz SWT 20 ms Trace Clear Write Att 0 dB VBW 3 MHz Trig Free Run Detect RMS M Center 944 474921
10. in a nonlinear circuit Sum and difference frequencies can be created from the mixing of fundamentals and harmonics and these intermodulation products can occur at frequencies substantially removed from their component signals Interference due to intermodulation can appear when high power transmitters share an antenna feeder line or tower system It is caused by the nonlinear behavior of corroded metals in RF joints Defective components such as old GSM base station antennas can cause intermodulation in the WCDMA UL thus disturbing the cellular communications in the affected sector This problem is usually solved by replacing the damaged GSM antenna Rohde amp Schwarz 29 01 3 3 Common Interference Sources Bidirectional Amplifiers 01 08 14 12 10 MN e Ref 30 0 dBm RBW 300 kHz SWT 20 ms Trace Clear Write Att 0 dB PA VBW 3 MHz Trig Free Run Detect RMS 1 9203 GHz 72 3 dBm M2 1 82525 GHz 84 7 dBm 1 9302 GHz 78 2 dBm MA 1 93515 GHz 90 7 dBm 1 921390794 GHz 47 7 dBm Center 1 92774 GHz Span 20 MHz New Marker Delete Select Marker Marker Marker Marker Function Fig 33 Intermodulation product of a GSM900 mobile phone signal repeater interfering with the WCDMA uplink M1 to M4 mark the WCDMA bands boundaries Bidirectional Amplifiers Bidirectional amplifiers BDA also called cellphone repeaters or signal boosters are devices used to extend cellular coverage within buildings or in other
11. sakuna EEN eee aaa 38 So et 39 Orderm INFO MANO 40 Rohde amp Schwarz 2 01 Why Do We Need Interference Hunting Detecting the Interfering Signal Why Do We Need Interference Hunting Mobile subscribers expect mobile services to be available reliable and to have good performance in terms of voice quality and throughput Based on these criteria subscribers may pick or change their service provider This is why service providers are making big efforts to provide their subscribers with a good quality of experience New frequency bands are acquired or refarmed to get a wider spectrum and increase network capacity and speed Many of the initial LTE deployments took place in spectrum that had been refarmed that is the previous occupants of the spectrum were moved to different frequencies in order to make room for new services For example the LTE band 3 around 1800 MHz previously allocated to GSM services is now used for LTE in many countries And WCDMA band 8 around 900 MHz was previously used for GSM LTE also uses frequency bands that were previously allocated to analog TV services in Europe 800 MHz and the US 700 MHz Technologies such as LTE LTE Advanced are deployed to deliver higher data rates at lower costs compared with older technologies such as GSM WCDMA Increased throughput is obtained through the use of higher order modulation for instance by using 64QAM in the downlink and multi antenna technology MIMO B
12. settings in the User Preference Setup menu S 29 02 14 U 23 27 2B GPS N 35 52 7868 W 78 40 5538 Alt 132 9 m Comp 128 Sats 0 Freq 782 MH Power 85 4 Fils ait i Zoom Qut Settings Fig 27 FSH map display with geotagging measurement results The standard R amp S FSHAView software provides an interface that allows you to export and review your recorded data with Google Earth This interface transforms gpx files into kmz files required by Google Earth It also contains a plug in that illustrates the signal levels measured at the GPS coordinates that you have added to the gpx file gt First transfer the GPX file to the PC using R amp S FSH4view gt In R amp S FSH4View use the GPX conversion function Make sure the settings are correct then click the Save as KMZ button to save the file in Google Earth format and export it to Google Earth Please refer to section 2 2 1 for more information about the R amp S FSH4view software Rohde amp Schwarz 25 Interference Hunting Steps Locating the Interference Source IC aang O a m SIE Gpx Files GPS Positions Include Latitude Longtude Level Name Description gt N 48 7 63911 E 11 36 70639 64 1 dBm Measurement0010 ONDATEN presentations 12013 12 LISANMeasuremer i TR N 48 7 63867 E11 36 707 4 55 5 dBm Measurement 0011 Color Settings Color em mang
13. signal source but it helps to narrow down the target area Then the homing technique can be used to determine the signal source Working with the Tone Function The FSH can be configured to play an audio signal or a tone when it receives a signal The audio signal changes its volume and frequency depending on the strength of the received signal This function is helpful for finding the direction bearing from which the strongest signal is coming from without you having to constantly look at the received level displayed It does not matter whether the homing or the triangulation technique is being used The higher the measured level is the higher the frequency of the tone Changes in the level that occur while rotating with the antenna can be heard as well as seen on the display There are different parameters you need to set in order to use this function To optimally configure the tone so that you can hear variations in the signal level we recommend the following Squelch level Defines the signal level above which the audio signal starts to play gt Set the squelch quite low i e to around 90 dBm Tone threshold The audio signal has a specific frequency that is coupled to a specific signal level As the received signal gets stronger or weaker the audio signal frequency goes up or down You can define the threshold of the base tone as necessary Rohde amp Schwarz 22 01 2 3 5 Interference Hunting Steps Loc
14. 0 0 60 0 0 0 30 0 100 0 110 0 120 0 Operator FEW 1mHz SWT 200 us YEW 10 MHz Start Frequency 1329327302 GHz Center Frequency 1929327302 GHz Trigger Mode Video Trigger Stop Frequency Span Measurement Setup Trace Mode Clear Write Trace Detector RMS Trace Mode Clear i write Mame Sweep Trace Detector AMS Date 20712014 Time Latitude Longitude Instrument Firmware Version Instrument Mode Meas Mode Uplink Downlink Channel uplink Center Frequency Frequency Offset Span Ref Level Ref Offset Range RF Attenuation AF Attenuator RF Input REY YEW SWwT Trigger Mode Trigger Level Trigger Delay Trace Mode Trace Math Trace Detector Limit Line 1 Limit Line 2 Gated Trigger Gate Mode Gate Delay Gate Length Result Limit Line 1 Average Count P 1329327302 GHz Zero Span Measurement Results Result Limit Line 2 11 54 50 FSHS 1050231028 12 50 Primary Transducer Secondary Transducer Spectrum Spectrum 1323327302 GHz 0 Hz Zero Span 20 0 dEm B dE 100 dE Manual O dE 50 Ohm 1 MHz 10 MHz 200 us Video Trigger BB Ng O Clear Write OFF ARMAS OFF Edge O 400 Marker M1 835us 50 07 dBm Fig 8 Interfering signal in time domain zero span sweep time 200 ps DECT short burst Rohde amp Schwarz
15. 0 MHz band Marker Function menu Jammers and Deliberate Interference There are also cases of deliberate interference Deliberate narrowband interference is usually unlicensed pirate analog modulated voice signals transmitted in licensed bands Sometimes these signals may be intermittent in nature making it very difficult to locate the source Recording the content of these transmissions is important if legal action needs to be taken Deliberate wideband interferers are known as jammers devices designed to limit or deny the ability to use a certain frequency range by raising the noise floor to a high level typically around 50 dBm in the affected area Jammers generate a wide strong continuous signal and are therefore relatively easy to identify and locate Jammers are often designed to affect particular services GPS Wi Fi etc and or frequency bands 850 MHz 1900 MHz etc but often create problems for services and frequencies well outside of their target range Rohde amp Schwarz 33 01 Common Interference Sources Jammers and Deliberate Interference Jammers typically have one antenna per jamming band technology Battery powered jammers are small but have a limited jamming radius 10 to 25 meters More powerful jammers usually require AC power and tend to run hot so you should look for devices with fans and or large heat sinks Jammers may also be placed at certain public places like cinemas churches and mosques to
16. 0 to the AUX port on the left side of the FSH gt Connect the GPS compass cable of the R amp S HE300 to the power sensor jack on the top of the FSH Instrument Setup Auto Accessory Detection On Detected Accessory BNC 1 Trigger Input IF Qut Antenna Disabled Compass Disabled Show Compass Information HL300 Side HE300 Top Assign Antenna Switch to Magnetic Declinatio aes BERGE Weng Zii vice Menu HE3 GPS GPS Disabled Show GPS Information Disabled Coordinate Format ddd mm ss sss hd Measure Instrument User Setup Setup Preference Fig 17 Antenna setup menu The R amp S HL300 antenna switch can be set up to either make a measurement i e Save Current GPS Position default setting or switch on the FSH preamplifier as indicated in Fig 18 Antenna Antenna HL300 Side Compass Enabled Show Compass Information Disabled Save Current GPS Position Save Current GPS Position Assign Antenna Switch to EE Service Menu HL300 Fig 18 FSH HL300 setup menu To use the FSH triangulation function select three measurements from different locations with GPS location and azimuth information and display them on the map To make a measurement set the FSH center frequency to the interferer s frequency To determine the direction from which the signal is arriving hold the directional antenna and rotate in place to complete a full circle within 30 s in order to get a gener
17. 00 MHz whereas DECT phones from the US or Canada will operate between 1920 MHz and 1930 MHz thus overlapping with the European WCDMA UL band between 1920 MHz and 1980 MHZ DECT phones from the US or Canada are sometimes imported by users to Europe without knowing they will interfere with the wireless network In the worst case if the interferer is placed close to the base station it may even block the complete WCDMA BTS from making calls Interference in WCDMA UL caused by DECT phones is a common interference source in Europe Other common interference sources are explained in section 3 Rohde amp Schwarz 9 01 Spectrum Ref Level 80 0 dBm RF Attenuator O dB Fig 7 Interference signal characterization in zero span RB W 300 kHz VBW 3MHz M1 Start Frequency 1 929327302 GHz Center Frequency 1 929327302 GHz Interference Hunting Steps Characterizing the Interfering Signal SWT 100 ms Trigger Mode Free Run D3 pa Markers 35 7143 ms 87 64 dBm 10 ms 0 09 dB 20 ms 0 17 dB 30 ms 0 04 dB Stop Frequency 1 929327302 GHz Span Zero Span Fig 7 shows a DECT burst measured in zero span When measuring burst signals you usually apply a trigger If the video trigger level is at 66 of the range of the vertical axis the FSH triggers a measurement if the rising edge of the burst exceeds this 66 line Spectrum Ref Level 20 0 dem AF Attenuator dE dEm 20 0 30 0 4
18. Interference Hunting with R amp S FSH Handheld Spectrum Analyzer Application Note Products R amp S FSH 1 R amp S FSH K14 R amp S FSH K15 1 R amp S FSH K16 This application note explains how to detect characterize find and document interferers in cellular networks using the R amp S FSH spectrum analyzer from now on referred to as the FSH First it explains how to use the spectrum and interference analysis functions during each step of interference hunting It also illustrates the explanations with a common interferer example Then it points out the most common interference sources in cellular networks and gives tips on how to identify them To execute the tests described in this application note the FSH handheld spectrum analyzer needs to be equipped with a directional antenna and the following options FSH K14 or K15 to work with the spectrogram FSH K15 to work with the mapping triangulation the tone function and the interference analyzer FSH K16 to work with the geotagging function R amp S HA Z240 GPS receiver unless R amp S HL300 or R amp S HE300 antennas are used Application Note Laura S nchez Frank Bramer Paul Denisowski 7 10 2014 1EF89 V1 0 01 2 1 2 1 1 2 2 2 2 1 2 2 2 2 3 2 3 2 2 3 3 2 3 4 2 3 5 3 1 3 2 3 3 3 4 3 5 3 6 4 1 4 2 4 3 Table of Contents Table of Contents Why Do We Need Interference Hunting
19. MESS pa Munich Tone Volume 55 TG NG Barcelona Tone In Zoom Out Settings Fig 15 FSH Map menu with OSM maps map display settings The Auto Select menu item automatically selects the map that is most fitting for your current location To use automatic selection you need a GPS receiver Under the Settings menu you can configure which settings to display on the map screen If no screen element has been selected the FSH only shows the map Working with the Triangulation Function With the FSH K15 option and a directional antenna the FSH is able to triangulate the interferer location Triangulation is based on measurements coming from different sites Ideally these measurement bearing lines intersect at the signal source s position Remersdort Ru Receiver Mode t UH ae an ie Interference Analyzer a L Pa 1 r y 1 NUNG a Bis ae n E r ap edd HA NetWork Dig Mod Distance Power Receiver 7 EI Analyzer Analyzer to Fault Meter Interference Fig 16 Triangulation function menus The FSH performs triangulation measurements using any directional antenna If you use the R amp S HL300 or R amp S HE300 with built in GPS and electronic compass to do the triangulation configure them under the Instrument Setup menu Fig 17 Rohde amp Schwarz 17 01 Interference Hunting Steps Locating the Interference Source gt Connect the GPS compass cable of the R amp S HL30
20. MHz Span 400 MHz Marker Fig 36 GSM900 mobile phone signal repeater interference signal Cable Leakage Cable egress or leakage occurs when the RF signals used in cable television systems escape from the shielded cables and devices that carry them Since the frequencies used in cable television systems can extend up to 1 GHz there is an overlap with many commercial government and cellular services The most common cause of egress is the presence of physical faults in the cable infrastructure such as cracked damaged cables faulty splices unterminated connectors and loose amplifier and tap housings Fortunately cable egress is very easy to diagnose due to its regular continuous pattern of 6 MHz wide channels Cable egress is a very common interference source in countries such as the US where cable TV providers use the same frequency band as LTE Unlicensed or Wrong Band Operation This kind of interference is caused by the use of transmitters designed for use in countries with different frequency allocations or it can also result from spectrum refarming Unlicensed transmitters operating around 1930 MHz such as DECT telephones brought from overseas can transmit with power up to 250 mW If unlicensed DECT telephones are being used near a WCDMA base station it may become impossible for a UE to increase its power above the noise floor to communicate with the base station i e calls cannot be established and data services are not a
21. P o m Center 1 92774 GHz Span 20 MHz Messk Messk Modus Detektor anzeigen STATT Fig 2 Interference signal in the WCDMA UL band right WCMDA call left The max hold trace is useful in detecting short duration signals or looking for an elevated noise floor In Fig 3 the max hold trace shows the maximum signal amplitude versus frequency indicating signals that are not currently present Rohde amp Schwarz 5 01 Interference Hunting Steps Detecting the Interfering Signal 02 07 14 14 53 MM Ref 75 0 dBm RBW 300 kHz SWT 20 ms Trace Max Hold Att 0dB PA VBW 3 MHz Trig Free Run Detect Max Peak 1 9203 GHz 110 1 dBm 18 0 dB 1 92525 GHz 110 8 dBm 1 9302 GHz 109 2 dBm 1 93515 GHz 108 3 dBm Span 20 MHz Fig 3 Combined traces Trace 1 RMS detector Trace 2 Max peak detector shows uplink level increase due to phone calls While driving around the interfered area if the interference signal is not easily spotted make sure the FSH preamplifier is switched on and the input attenuator is switched off Operators sometimes use bandpass filters to block other bands that are not the band of interest This helps to reduce the noise level and find the interfering signal more easily If the interferer has not been spotted after a reasonable amount of time the operator will connect the FSH to the base transceiver station BTS antenna to measure the same spectrum that is received by the BTS
22. PS Mode Position Zoom Fig 21 FSH rotary knob and GPS Position menu Triangulation requires at least two but preferably three measurements from different sites If three measurements are used for triangulation the overall result will be more precise than if only two measurements are used and will avoid any unambiguity After saving measurements from different locations select three measurements from the GPS Position List menu Fig 22 Rohde amp Schwarz 20 GPS Position List 1 E 117 41 54317 2 n N 48 7 20755 E11741 22656 82 Drosselweg 3 c N 48 7 51940 E 11 40 58065 112 Rappenst 22 4 c N48 7 13596 E11 41 66490 321 Drost 3 5 c N48 7 13606 E 11 41 66485 314 Dros 4 6 c N4877 13638 E11 41 66509 354 Dros5 7 c NM48 7 51940 E 11 40 58065 125 Build5a B c N48 7 51940 E 11 40 58065 118 Buildda 9 m WN 48 7 51940 E 11 40 58065 115 Buildba 10 c N4B77 20755 E11741 22656 75 RAPx 11 c N48 7 2075b E11741 22656 65 RAPx 12 m N4B871137 E 11 41 03333 30 T 13 m N48 7 91867 E 11 41 44163 181 R Arc1 Include View Delete 06 08 14 14 03 NG bekide Re ESA A NA Delete All Interference Hunting Steps Locating the Interference Source Fig 22 GPS Position List menu Three positions selected to triangulate Next go to the GPS Position menu and click Triangulate The FSH calculates the intersection point of the selected measurement bearing lines The resu
23. Site position reporting and documentations by BTS service teams Save own position on the map Geotagging results can be viewed directly on the FSH map or exported to kmz files to be displayed in Google Earth To use this function the FSH requires any antenna and the R amp S HA Z240 GPS receiver option unless the R amp S HL300 or R amp S HE300 antenna is used To automatically record measurements the FSH uses the save on event function This function can be activated from the Geotagging Settings menu A green S at the top of the screen indicates that the save on event function is active and measurements are being recorded Rohde Schwarz 23 01 Interference Hunting Steps Locating the Interference Source 23 02 14 GPS N 35 52 47 210 W 78 40 3 X Save On Event Power dBm Event Source Paran Daanan Dalar Fig 25 Save on event icon When Save On Event is selected an event source must be specified The event source can be set under the Settings menu in the geotagging mode or under the FSH User Preference Setup menu There are four different event sources gt Time Interval saves measurement every X seconds gt Limit Failure saves measurement if a limit line is violated gt Distance Interval saves measurement after moving a given distance gt Every Sweep saves measurement for each sweep performed Geotagging defines three received power levels good average and bad The values for
24. a Depending on the environment there are different location techniques and antenna types you can use The Homing Technique Dense Urban Areas With this technique you walk with the FSH and a directional antenna going in the direction where the interfering signal is the strongest until the signal source is reached To determine the direction from which the signal arrives hold the directional antenna and rotate in place slowly around 30 seconds for a complete turn attempting to determine the direction from where the maximum level is coming from that direction will be the direction in which you have to walk in order to find the interferer Then move slowly in the direction toward the interferer moving the antenna slightly side to side Pay attention to make sure the measured signal is coming directly from the interfering source and not being reflected by a building nearby or by other reflective objects such as vehicles This technique makes sense if either of the following holds true gt The source is likely to be located nearby or indoors in these cases maps and bearing information are not necessary Rohde amp Schwarz 14 01 Interference Hunting Steps Locating the Interference Source gt You are in a dense urban area where tall buildings close to one another cause many signal reflections Yagi or planar antennas usually only cover a single frequency band per antenna but have a narrower beam width and a higher gain
25. al idea of the direction from which the signal is being received at the maximum level If possible at the selected site repeat this rotation a few meters away from the first position in order to eliminate any secondary maximum levels The direction from which the maximum level is transmitted must be determined precisely Especially when working with long distances even deviations of just a few degrees can lead to major errors Rohde amp Schwarz 18 01 Interference Hunting Steps Locating the Interference Source Based on the approximate maximum level move the directional antenna to the left and to the right until the displayed level value changes by a few dBs to determine the maximum level s direction as precisely as possible Save the position once the maximum level s direction has been determined To save a position move the R8 S HL300 antenna switch back and forth or click Save Current Position under the GPS Position menu The message Saving GPS Position will shortly appear on the FSH screen indicating that the measurement has been saved correctly Fig 19 Measurements using the FSH and the R2 S HL300 antenna in the R amp S HA Z222 carrying holster If you perform measurements with the FSH and a directional antenna for longer periods we recommend that you use the R amp S HA Z222 carrying holster It includes a chest harness which eliminates the need to carry the FSH in your hands and a rain cover Rohde
26. ating the Interference Source The tone threshold must be adjusted continuously especially when the homing method is used because ideally the user comes closer and closer to the signal causing the level of the received signal to rise The tone threshold should be set so that the FSH emits an audible tone allowing you to easily perceive even small changes in the level gt Set the threshold level as high as possible so that you can barely hear a very low tone and increase the threshold as you come closer to the interferer Tone gain The change of frequency in the audio signal is either one octave per 20 dB or one octave per 40 dB gt Select Octave 20 dB so that the tone is more sensitive to changes in signal level squelch Level Tone Threshold Tons a gt RESU Tone Volume 48 5 Octave 40 dB In Zoom Out Settings Fig 24 Tone Settings menu We recommend using headphones with the tone function Working with the Save on Event and the Geotagging Function The FSH geotagging feature FSH K16 option saves a geotag position and level information automatically when user defined criteria are met These criteria may be level distance traveled or elapsed time The main applications for this function are 1 Analysis of the coverage interference conditions around the BTS area signal strength measurement 1 Interferer search support record measurements based on level distance or time threshold save on event 1
27. can be configured in the User Preference Setup menu see Fig 6 Other events and applications for the save on event function are described in section 2 3 5 Rohde amp Schwarz 8 Interference Hunting Steps Characterizing the Interfering Signal 01 2 2 User Preference Setup Save On Event Save On Event On Time Interval 25 Distance Interval 10m Limits Save Mode Save Only Failures Recording storage SD card Capture Screen On Capture Dataset On Capture GPX Off Default Filename Measurement Filename Counter Starts at 1140 Capture Screen Format Default Dataset Name i Data Measure Instrument User HI set005 WSW Installed Setup Setup Preference Info Options Fig 6 Save On Event for limit failure in the User Preference Setup menu Characterizing the Interfering Signal If the detected interfering signal level is strong enough you can analyze its pattern The FSH spectrum analyzer in zero span helps to analyze the characteristics of the interfering signal in the time domain You have to make sure that the whole signal is within the selected resolution bandwidth lowering the sweep time in a way that the different signal components are visible In Fig 7 the interferer is a DECT base station erroneously transmitting in the WCMDA UL frequency band You can recognize the different signal pulses spaced 10 milliseconds apart In Europe DECT telephones are allowed to transmit between 1880 MHz and 19
28. ccessible in the cell coverage area Rohde amp Schwarz 32 01 3 6 Common Interference Sources Jammers and Deliberate Interference Interference in the WCDMA UL caused by DECT phones operating in the wrong frequency band is a common interference source in Europe Sections 2 1 and 2 2 show an example and explain how to detect and characterize this type of interference Some frequency bands previously used for other services have been refarmed for use with LTE or WCDMA But there are still devices transmitting in bands that cause interference Wireless microphones are often used by clubs organizations schools churches etc and most commonly transmit analog narrowband FM signals Problems can occur when these microphones operate outside of their allowed frequency ranges Wireless microphone can also be very powerful transmitters for their size Audio demodulation is an excellent way of tracking down interference from wireless microphones and other narrowband interferers 01 08 14 07 50 ME amp Ref 30 0 dBm RBW 300kHz SWT 20ms Trace Clear Write s Att 0 dB PA VBW 3 MHz Trig Free Run Detect RMS S 812 811111 MHz 53 3 dBm Marker Mode Frequency Count Marker Display Frequency 0 Marker Demodulation Volume 89 Marker Center 812 811111 MHz Span 11 MHz Marker Function Marker Type Marker Marker Function Fig 37 FM modulated wireless microphone operating in the 80
29. ddle East a 49 00000 East Oceania 48 350 8390 20 04 7685 Ye Sources Appendix http www radio electronics com info cellulartelecomms lte long term evolution lte frequency spectrum php http en wikipedia org wiki List of LTE networks General information Rohde amp Schwarz 36 01 4 2 WCDMA UMTS Frequency Bands Operating Frequency Common name band band MHz 1 2100 IMT Latin America Europe Asia Africa Oceania 2 1900 PCS A F North America Latin America 3 1800 China A as 1700 AWS A F North America Latin America 5 850 CLR North America Latin America Asia Oceania 08 Wy 7 YY 7 39 ME E GSM U 900 Latin America Europe Asia Africa BN Budd e o mo m EAWS A G 900 1500 LPDC Japan USA Canada USA Canada USA Canada USA Canada Japan LSMH A B C USMH C USMH D LSMH B C 50 N EUDD P UPC FPCS A G EOL Source http en wikipedia org wiki UMTS frequency bands 1 2 2 2 2 10 11 12 13 14 9 0 1 2 5 6 2 Appendix Rohde amp Schwarz 37 01 Appendix 4 3 GSM Frequency Bands System Band Uplink MHz Dow nlink MHz Channel number Equivalent Region UMTS LTE band T esm3eo aso 9002 9008 3002 3998 dynamo Tesmao 410 4102 498 42024208 ayare Gsiraso 450 4506 4576 4006 076 259 98 St GSM4B 480 47904860 4890 060 seso GST no 6982 7162 7282462 ayame
30. g the remote display application within R amp S FSH4View R amp S FSH4View is delivered with the FSH as standard and is available for download on the Rohde amp Schwarz website http www rohde schwarz com en software fsh Rohde amp Schwarz 11 01 2 2 2 Interference Hunting Steps Characterizing the Interfering Signal FSH4View i File Edit View Instrument Tools Options Window Help Screen0063 2 set ES JL e s Spectrum Measurement Setup Ref Level 80 0 dBm RE W 300 kHz SWT 100 ms Trace Mode Clear Write Mame Sweep RF Attenuator 0 dB VBwW 3MHz Trigger Mode Free Run Trace Detector RMS Date 2 7 2014 dBm Time 1 24 32 Instrument FSH8 1050237028 4 80 0 m p2 p3 D Firmware Version V2 50 i Instrument Mode Spectrum Meas Mode Spectrum Uplink Df 25 0 Downlink H i i Channel uplink eee Center Frequency 4929327302 GHz Frequency Offset O Hz 90 0 Span Zero Span Ref Level 80 0 dBm Ref Offset 00 dB Range 50 dB 95 0 f E puru Select Markers i 2 2 ju 400 0 Markers Delta Markers Set Marker Y Marker 1 M1 M1 105 0 Marker 2 M2 v Delta 2 D2 eir erem Restore Marker 3 M3 iw Delta 3 D3 D3 Next Peak 110 0 Marker 4 M4 iv Delta 4 D4 C D4 Marker 5 M5 Delta 5 D5 C Minimum mn Marker 6 M6 Delta 6 D6 120 0 Clear All Markers Clear All Delta Markers All Markers To Peak Search range limit
31. irst marker is placed on the peak power level i e carrier level The second marker is positioned on the second strongest level that has been measured Next Peak or interferer The difference between the two signal levels is the carrier to interference ratio 15 07 14 15 18 amp Ref 61 0 dBm RBW 300 kHz SWT 20ms Trace Clear Write s Att 0 dB a VBW 3 MHz Trig Free Run Detect RMS C 791 8723518 MHz M1 791 873016 MHz 58 1 dBm 786 31746 MHz 93 2 dBm C N 352 Span 100 MHz qmm E Fig 11 Carrier to noise measurement The interference analyzer also provides a quick way to compare the current results with a previous one When you turn on the Diff Mode the FSH saves the current trace and will subtract this trace from the live traces resulting from future sweeps This makes it easy to detect changes in the spectrum see Fig 12 Rohde Schwarz 13 01 2 3 Interference Hunting Steps Locating the Interference Source 15 07 14 15 09 gt Ref 17 0 dBm e RBW 300 kHz SWT 20 ms Trace Clear Write e Att 0 dB e VBW 3 MHz Trig Free Run Detect RMS Center 863 492063 MHz Span 300 MHz Mode Fig 12 Diff Mode measurement display Locating the Interference Source Once the interference signal has been spotted and characterized the next step is to find it Now is the time to set the FSH center frequency to the interferer s frequency and drive or walk around with the FSH and a directional antenn
32. lt is displayed on the map as a dot surrounded by a circle Fig 23 the circle radius is indicated on the screen The circle indicates the area where the signal source can be expected In Fig 23 the dot and circle are blue and the measurement bearing lines are black However you can assign a different color to the triangulation results and to the measurement lines Rohde amp Schwarz 21 01 2 3 4 Interference Hunting Steps Locating the Interference Source TANYA EE Triang N 48 7 23 089 E 11 41 21 414 4276m Incl Pos 9 12 13 N H a A EY EL JE 2 7 PE e Lx E T um Wo cem da Mo Ds feld mail us Ki rd F F Eirchtrud ring e osa aglinezirk 3m 15 Truderag Piem ES werbegebigt r7 vablhofst Ae les y WED a P Paga NG TA na r ee is or PN mo br A LNG la Pt ng i Save Current Position Save Manual Position and Azimuth c p m1 l N nl e PAN Pm Me RE de Lon irt dn Jy Save AZIMUIN UN Y GPS Position List Go To Triangulation Position X Triangulate x Save Triangulation MSS A ENT EM Co i M mel n Zoom In Zoom Out Settings Map Mode Position Fig 23 Triangulation result The environment the antenna the choice of measurement sites and the exact determination of the direction of the maximum level influence triangulation accuracy The result of triangulation is not the direct physical discovery of a
33. mission generated by a power supply at 1 9311 MHz 1 38 MHz wide WCMDA UL Rohde amp Schwarz 28 Common Interference Sources Harmonics and Intermodulation 3 2 Harmonics and Intermodulation Harmonics are a normal by product of almost all RF transmitters A harmonic is a copy of the fundamental signal appearing at whole number multiples of the original frequency For example a transmitter operating at f 450 MHz can produce harmonics at 2x f 2 900 MHz 3x f 2 1350 MHz etc Although the level of harmonics normally decreases as the frequency increases many narrowband interferers turn out to be harmonics of signals operating at lower frequencies A good rule is to always check whether a narrowband interferer is a harmonic Since the fundamental signal is always significantly stronger than its harmonics it is often easier to track down the fundamental itself 01 08 14 12 47 MA amp Ref 10 0 dBm RBW 3 MHz SWT 43ms Trace Clear Write s Att 0 dB VBW 3 MHz Trig Free Run Detect RMS M1 945 198641 MHz 6 9 dBm M2 1 836341164 GHz 40 9 dBm M3 2 829812894 GHz 640 dBm 3 772318755 GHz 70 6 dBm LI MM I ama BF UH T aL era e ex puro T aa e o f n Start 659 754009 MHz Stop 4 052775111 GHz New Marker Delete Select ETE Marker Marker Marker Function Fig 32 Harmonics of fundamental frequency at 945 MHz with harmonics at 1 83 GHz 2 82 GHz and 3 77 GHz Intermodulation is caused by two or more signals appearing
34. nterferers In practice this is very rare and would be difficult to detect without turning off the base station External interference is almost exclusively an uplink issue i e in the spectrum used by the mobile phones when transmitting to the base station Interference in the uplink generally causes problems because it impairs the base station s ability to hear the relatively weak signals being sent by the user equipment UE Base stations normally can detect the presence of interference in the uplink frequency band e g an excessively high RSSI typically 2100 dBm or higher or poor performance in certain KPIs such as throughput or call retainability In the LTE and WCDMA uplink all mobile phones transmit on the same frequency This makes the uplink especially vulnerable to high levels of noise and interference where highly interfered areas can become coverage holes in the network An example of uplink interference in WCDMA networks caused by unlicensed DECT telephones will be shown in the next sections Detecting the Interfering Signal The first step is to drive around the affected cells coverage area until the interfering signal is detected The FSH is typically connected to an omnidirectional antenna like the R amp S TS95A16 on the top of the measurement vehicle but directional antennas like the R amp S HL300 or the customer s own antennas may also be used For use in vehicles the R amp S HA Z202 car adapter is available t
35. o power the FSH using the standard 12 V vehicle power supply The spectrum view in combination with the spectrogram helps to detect interferers that are visible only for a fraction of time In Fig 1 the spectrogram in the lower part of the display shows an intermittent frequency hopping interferer red dots The markers M1 to M4 are used to delimit the different frequency channels Rohde amp Schwarz 4 01 Interference Hunting Steps Detecting the Interfering Signal spectrogram 02 07 14 11 05 Il Ref 75 0 dBm REW 300kHz SWT 20 ms Trace Clear Write Att 0dB PA VBW 3MHz Trig Free Run Detect RMS 1 9203 GHz 110 4 dBm 1 92525 GHz 111 9 dBm 1 9302 GHz 109 5 dBm 1 93515 GHz 110 0 dBm 1 93515 GHz Lal GU eS Um AA E Rl ECTS EJ A AO RAR e A AS A Center 1 92774 GHz mnm Span 20 MHz Fig 1 Spectrum analyzer and spectrogram trace shows the interference signal in UL spectrum red dots using the RMS detector Once the interfering signal has been spotted move closer to the area where you assume the interference signal becomes stronger until you can clearly see the interference signal Fig 2 shows the same interferer that was spotted in Fig 1 but from a closer location Spectrogram 02 07 14 15 51 E Ref 20 0 dBm eRBW 300kHz SWT 20ms Trace Max Hold Att 0 dB VBW 3 MHz Trig Free Run Detect RMS 1 9203 GHz 87 8 dBm M2 1 82525 GHz 88 8 dBm 1 9302 GHz 88 1 dBm 1 93515 GHz 89 4 dBm i
36. ough in some cases it may vary in frequency i e be oscillating or drifting Most consumer and commercial electronics can radiate spurious emissions at numerous frequencies It is the level of these emissions that determines whether or not they are truly sources of interference For example a plasma TV can generate unacceptable levels of noise that interfere with the cellular UL Satellite transmitters emissions in the IF band between 950 MHz and 2150 MHz as well as lighting ballasts and mains adapters are also a source of interference Rohde amp Schwarz 27 Common Interference Sources Noise and Spurious Emissions 02 07 14 15 25 Ref 60 0 dBm s REW 300 kHz SWT 20 ms Trace Clear Write Att 0 dB PA VBW 3MHz Trig Free Run Detect RMS 1 9203 GHz 96 3 dBm 1 92525 GHz 97 1 dBm 1 9302 GHz 98 5 dBm 1 93515 GHz 99 6 dBm Center 1 92774 GHz Span 20 MHz Fig 30 Spurious emission generated by a power supply at 1 9311 MHz WCMDA UL Spectrum Ret Level 45 0 dBm RBW 300 kHz SWT 20ms Trace Mode Clear 1 Write RF Attenuator 0 dB VBW 3MHz Trigger Mode Free Run Trace Detector RIMS pop M1 M2 03 45 0 yy n Markers 49304813127 GHz 98 87 dBm 55 0 19310990734 GHz 60 54 dBm 13839614 MH 0 14 dB 65 0 75 0 5 0 95 0 105 0 115 0 125 0 135 0 145 0 A Start Frequency 131774 GHz Stop Frequency 193774 GHz Operator Center Frequency 192774 GHz Span 20 MHz Fig 31 Spurious e
37. pectrum Analyzer 9 kHz to 20 GHz with preamplifier R amp S FSH20 1314 2000 20 Spectrogram Measurement Application R amp S FSH K14 1304 5770 02 Interference Analysis Measurement Application R amp S FSH K15 1309 7488 02 software license Geotagging Measurement Application software license R amp S FSH K16 1309 7494 02 Handheld Log Periodic Antenna 450 MHz to 8 GHz R amp S HL300 4097 3005 02 Active Directional Antenna 20 MHz to 7 5 GHz with mechanical R amp S HE300 4067 5900 02 compass Active Directional Antenna 20 MHz to 7 5 GHz with GPS and R amp S HE300 4067 5900 03 electronic compass GSM UMTS CDMA Antenna with magnetic mount R amp S TS95A16 1118 6943 16 850 900 1800 1900 2100 band N connector GPS Receiver R amp S HA Z240 1309 6700 03 Carrying Holster including chest harness and rain cover R amp S HA Z222 1309 6198 00 12 V Car Adapter R amp S HA Z202 1309 6117 00 Loop Antenna for R amp S HE300 9 kHz to 20 MHz R amp S HE300 HF 4067 6806 02 Rohde amp Schwarz 40 PAD T M 3573 7380 02 02 01 EN About Rohde 4 Schwarz Rohde amp Schwarz is an independent group of companies specializing in electronics It is a leading supplier of solutions in the fields of test and measurement broadcasting radiomonitoring and radiolocation as well as secure communications Established more than 80 years ago Rohde amp Schwarz has a global presence and a dedicated service network in over 70 countries Company head
38. prevent the use of mobile phones Rohde amp Schwarz 34 Appendix 4 Appendix 4 1 LTE Frequency Bands FDD LTE BANDS 8 FREQUENCIES LTE BAND UPLINK DOWNLINK WIDTH DUPLEX BAND GAP REGION OF BAND SPACING MHZ NUM BER MHZ MHZ MHZ MHZ 1 1920 1980 2110 2170 60 190 180 Arca Asia 2 180 1810 1990 190 60 80 20 Ameca 3 1710 1785 1805 1880 75 95 20 Africa America Asia Europe Middle East Oceania 6 83 80 85 86 i 35 2 Middle East 8 80 905 925 980 85 45 10 Asa 9 1749 7849 18449 1809 35 95 60 AR o mono 20270 6 40 90 03 mwa 74 76 d a Amos M 78 78 758 78 0 3 4 15 190 1920 2600 2620 20 700 60 16 2010 2025 2505 200 15 55 50 nmm mm Lo m m Middle East 82 940 9800 3510 900 90 30 10 es 800 2000 2180 2200 20 180 140 84 16255 16605 1825 1559 94 aots 1885 25 1850 1915 1930 1995 65 80 15 America Oceania 86 84 89 8509 804 30 40 10 Amma O er 807 824 89 89 17 4 898 039 w mS wu 80 2905 8315 2950 8900 10 45 35 9 485 485 495 478 8 to 8 Rohde amp Schwarz 35 01 TDD LTE BANDS 8 FREQUENCIES LTEBAND ALLOCATION WIDTH OF REGION MHZ BAND MHZ 1900 1920 2010 2025 095 oo a o NUM BER 1930 1990 1910 1930 2570 2620 Africa America Europe Mi
39. quarters are in Munich Germany Regional contact Europe Africa Middle East 49 89 4129 12345 customersupport rohde schwarz com North America 1 888 TEST RSA 1 888 837 8772 customer support rsa rohde schwarz com Latin America 1 410 910 7988 customersupport la rohde schwarz com Asia Pacific 65 65 13 04 88 customersupport asia rohde schwarz com China 86 800 810 8228 86 400 650 5896 customersupport china rohde schwarz com Environmental commitment I Energy efficient products I Continuous improvement in environmental sustainability I ISO 14001 certified environmental management system This application note and the supplied programs may only be used subject to the conditions of use set forth in the download area of the Rohde amp Schwarz website R amp S is a registered trademark of Rohde amp Schwarz GmbH 8 Co KG Trade names are trademarks of the owners
40. s 125 0 Off Start Search 1 o B e 430 0 Stop Search1 190 m y e gt Start Frequency 1329 Operator Center Frequency 1929 Start Search 2 fo cl r Stop Search 2 1 00 sl ms v 9 3 Noise Marker Cancel Off Fig 9 Editing a measurement setup using R4S FSH4View Working with the Interference Analyzer The interference analyzer available with the FSH K15 option provides in addition to the spectrogram and the mapping functions the ability to visualize and measure spectrum similar to the spectrum analyzer mode Receiver Mode Interference Analyzer Center 723 MHz P a LA prm AS Spectrum p Fig 10 Interference analyzer mode It also supports measurements such as carrier to noise carrier to interference and trace mathematics Diff Mode The carrier to noise C N measurement places two markers on the trace The first marker is placed on the peak power level which the FSH assumes as the level of the Rohde amp Schwarz 12 01 Interference Hunting Steps Characterizing the Interfering Signal carrier The second marker is positioned on the lowest level that has been measured Min Peak The difference between the two signal levels is the displayed carrier to noise ratio The carrier to interference ratio measurement is a tool used to determine if a signal is affected by interference from neighboring channels It places two markers on the trace The f
41. start Fig 14 OSM wizard with OSM map displayed After you have downloaded the maps you need save them to an SD card which you can use with the FSH 01 Rohde amp Schwarz 16 01 2 3 3 Interference Hunting Steps Locating the Interference Source b Enter the Maps mode b Press the MEAS key gt Press the Map softkey The FSH opens a menu that contains all maps that you have stored on the SD card the names correspond to the folder names for every area you have downloaded b A AS n li Ta tu 4 SN D YA Kha MM GE Show GPS Information RAG ma s y Mina di s nod 85 ww Show Compass Information i TN nalin Y Orchard c gt i T A oe 2 Mil M Y NG Nad y gt S e ce Selegie 2 EU i a 7 E Antenna Queenstown f its En po mt f B gisy T A P ENT SE LENA GPS I NE NAAN ap Bras Basah SA fu Sars pe gt AN AKA BE Suntec ag mo aen Compass ht Hall B ad 3 m As ag Y at opu yi Current Position Color a ui M L Bukit Merah tong AS E esl x Saved Positions Color n Tl China Town n NG ive N SS gt c M f Alexandra Triangulation Color Show Power Bar 5 1 A Ma r ir c gt 7 4 podle Ey gt Mos ENJE Show Power Result ES VES Frankfurt Show Hardware Settings P t M Madrid Squelch Level Bawa do j Nuernberg Threshold Tone Frequency CEL al i X KA Singapore Tone Gain b A
42. these levels and their colors are defined by the user Note that the FSH stores the actual measured values the coverage levels are only used to define how these results are displayed i e which colors to use for which levels The colors used to represent current position as well as good average and bad coverage are all user definable This allows you to define higher signal levels interference as red and lower signal levels normal noise floor as green The FSH can save different types of information when an event occurs Screen capture jpg or png data set set for the sweep containing the event an entry in a gpx file containing GPS coordinates and bearing information or combinations of these are also possible Captured data is stored in the Save On Event Results directory on the SD card Make sure that the SD card is not locked and has enough free space to save the measurements Rohde amp Schwarz 24 Interference Hunting Steps Locating the Interference Source User Preference Setup VVO RNY UMC y Save On Event Save On Event On Event Source Time Interval Time Interval 10s Distance Interval 100m Limits Save Mode start On Failure Recording storage SD card Capture Capture Screen Off Capture Dataset Off Default Filename Measurement Filename Counter Starts at 0073 Capture Screen Format PNG Dataset Capture GPX On Default Dataset Name Dataset Fig 26 Save On Event
43. us frequency and versus time simultaneously The amplitude is displayed as a third dimension by mapping different colors to power levels You can set the color scheme the reference level and the range for best viewing results You can also adjust the level range using the spectrogram auto range function so that the weakest part of the signal is mapped to the lower end of the color map and the strongest part of the signal to the upper end To get a better result change the spectrogram reference level to a level near the maximum power level that has been measured This will eliminate irrelevant very low amplitudes By default the spectrogram reference level does not affect the spectrum result display and the spectrum reference level Amplitude menu does not affect the spectrogram But if required you can couple the spectrogram to spectrum in the Spectrogram Settings menu 15 07 14 1429 MJ Ref 42 1 dBm RBW 3 MHz SWT 20 ms Trace Clear Write Att 0 dB eVBW 300 kHz Trig Free Run Detect RMS 62 1 H lo E EMEN 12 1 p26 IU JHO Spectrogram Reference Level Spectrogram Level Range Spectrogram Auto Range Spectrogram Color Table Spectrogram Full Screen Center 863 4 X Couple Sp Spectrum Span 300 MHz p ectrogram to 5 hectrogram ma m Playback Clear spectrogram Mode Settings Fig 4 Spectrogram Settings menu Spectrograms can be saved and played back directly on the FSH or b
44. ut in all communications systems higher order modulation schemes typically require a cleaner RF environment with a lower noise floor If the level of noise or interference rises in the network the network will typically drop to lower order modulation schemes 16QAM or even QPSK thus significantly degrading the throughput and other advantages of using LTE Interference affects our ability to use wireless communications systems with the effects ranging from a mild decrease in overall network effectiveness e g slightly reduced throughput all the way up to a complete failure of the network but most interference issues tend to fall somewhere in the middle Rapid detection location and resolution of interference problems is a critical component in delivering optimal quality of experience Rohde amp Schwarz 3 01 Interference Hunting Steps Detecting the Interfering Signal 2 Interference Hunting Steps 2 1 Before going out in the field to measure interference it is important to make sure that the problem is really caused by interference and not by malfunction of tower mounted amplifiers or other network components Downlink interference is typically caused within the operator s own network Internal interference problems can normally be solved by changing the antenna tilt or azimuth of the affected cells or making some changes in the network parameters Downlink interference can also be caused by jammers i e intentional i
45. y using the R amp S FSH4 View software on a PC When playing back a spectrogram the FSH displays two timelines T1 and T2 The timelines can be set to show the absolute or relative timestamp By moving the timelines you can browse through the history of spectra stored in memory Rohde amp Schwarz 7 01 Interference Hunting Steps Detecting the Interfering Signal 15 07 14 14 52 Ref 20 0 dBm RBW 3 MHz SWT 20 ms Trace Clear Write e Att 0 dB eVBW 300 kHz Trig Free Run Detect RMS 14 49 45 15 07 2014 gt 14 49 37 15 07 2014 T1 Line O Center 863 492063 MHz Span 300 MHz mL Save Recall S gt Mode Settings Update Spectrogram Spectrogram Time Line Fig 5 Spectrogram playback Working with the Save on Event Function The spectrogram and the spectrum analyzer mode can be also used in combination with the save on event function The save on event function is standard in the FSH It allows you to automatically save data sets screenshots and or coordinates bearing information when a certain event occurs For example save on event can be configured to save measurement data if a limit line is violated There are three different modes for handling limit check failures Start on failure Starts saving measurement data if a limit line is violated Stop on failure Stops saving measurement data if a limit line is violated Save only failure Saves only the sweeps that actually fail a limit check This
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