LTE Signal Quality Analysis. BTS Master, Cell Master,, Spectrum Master

Transcription

1 LTE Signal Quality Analysis BTS Master, Cell Master,, Spectrum Master Slide 1

2 Anritsu LTE Test Instrument Portfolio Signaling Tester Fading Simulator Signal Analyzers Vector Signal Generator Radio Communication Analyzer Rapid Test Designer (RTD) LTE Protocol Conformance Test System LTE RF Conformance Test System Slide 2

3 Introducing the Next generation Anritsu Master family MT8221B MT8212E MS2712E MS2721B MT8222B MT8213E MS2713E MS2722C MS2723C MS2724C MS2725C MS2726C Slide 3

4 Cover all defined frequency plans and bandwidths Frequency bands All E-UTRA E Operating Bands 700 MHz 2700 MHz Channel bandwidths 20, 15, 10, 5, 3, 1.4 MHz BTS Master MT8221B Spectrum Master MS2722/23/24/25/26C LTE Bandwidth Selection 10, 5, 3, 1.4 MHz BTS Master MT8222A Cell Master MT8212/13E Spectrum Master MS2712/13E Spectrum Master MS2721/23/24B Slide 4

5 A Family of LTE Signal Quality Analyzers RF Quality Analyzer RF Measurements Modulation Quality Analyzer Modulation Measurements DL Coverage Quality Analyzer LTE Measurement Summary Over-the the-air Measurements Pass/Fail Analyzer LTE Measurement Summary Slide 5

6 LTE RF Quality Measurements Channel Spectrum Channel Power Occupied Bandwidth ACLR Spectral Emission Mask (SEM) RF Measurement Summary RF Measurement Summary Slide 6

7 LTE Modulation Quality Measurements Constellation QPSK, 16 QAM, 64 QAM Control Channel Power Modulation Summary Modulation Measurement Summary Slide 7

8 LTE Downlink Coverage Quality Measurements Scanner Six Sync Signal Power Levels Cell ID Sector ID Group ID Dominance OTA Scanner Measurements Auto Save Slide 8

9 Key Performance Indicators vs. LTE Field Measurement Key Performance Indicators vs. Test Sync Power RS Power Occupied BW, ACLR, & SEM EVM (pk) EVM Freq Error Rx Noise Floor OTA EVM Call/Session Blocking Power shortage x x x Resource Block shortage x xx xx UL Interference x xx Call/Session Drop Radio Link Timeout x x x x X x x UL Interference x x DL Interference x x x x x x x = probable, xx = most probable Slide 9

10 LTE Field Measurement vs. BTS Field Replaceable Units Test vs. BTS Field Replaceable Units Freq Ref Signal Generation MCPA Filters Antenna Antenna Down Tilt Sync Power x xx x RS Power x xx x Occupied BW x xx xx Adjacent Channel Leakage Ratio (ACLR) x x xx x Spectral Emission Mask (SEM) x x xx x Error Vector Magnitude Peak (EVM pk) x xx Error Vector Magnitude (EVM) x x x x Frequency Error xx OTA EVM x x x x x x = probable, xx = most probable Slide 10

11 LTE Pass/Fail Mode Guidelines Direct Connect OTA Per Vendor Consequences Inconsistent settings between Pass/Fail Test base stations, leads to inconsistent network behavior LTE Pass/Fail Set up common test limits, or sets of limits, for each instrument User modify via MST to set-up system-wide maintenance operating practice Slide 11

12 LTE Occupied Bandwidth Guideline Direct Connect Less than defined LTE bandwidth 1.4, 3.0, 5.0, 10, 15, 20 MHz Consequences Leads to interference with neighboring carriers Dropped calls Low capacity RF Quality Occupied Bandwidth A measurement of the spectrum used by the carrier Common Faults Tx filter MCPA The occupied bandwidth contains 99% of the signal s s RF power Signal processing Antennas Slide 12

13 LTE Adjacent Channel Leakage Ratio (ACLR) Guideline Direct Connect -45 dbc adjacent channels -45 dbc alternate channels Consequences RF Quality Interference Low capacity Blocked calls Common Faults ACLR (single-carrier displayed) Measures how much of the carrier gets into neighboring RF channels Checks the closest (adjacent) and the next closest (alternate) Tx filter MCPA Channel cards Cable connectors Slide 13

14 LTE Spectral Emission Mask (SEM) Guideline Direct Connect Must be below mask Consequences Interference with neighboring carriers Legal liability Low data rate RF Quality Spectral Emission Mask SEM checks closer to the signal than ACLR does Common Faults Check amplifier output filtering Look for intermodulation distortion It also is sensitive to absolute power levels Look for spectral re-growth May be requirement of regulators Slide 14

15 LTE Error Vector Magnitude (EVM) Guidelines Direct Connect QPSK % 16 QAM 12.5% 64 QAM 8% Consequences dropped calls low data rate low sector capacity blocked calls EVM Modulation Quality The ratio of errors, or distortions, in the actual signal, compared to a perfect signal EVM measures the PBCH, if there is no data traffic and the PDSCH if there is traffic Common Faults distortion in the channel cards Power amplifier filter antenna system Slide 15

16 LTE Frequency Error Guideline OTA with GPS ± 0.05 ppm wide area BS ± 0.10 ppm local area BS ± 0.25 ppm home BS Consequences Calls will drop when mobiles travel at higher speed In some cases, cell phones cannot hand off into, or out of the cell Modulation Quality Frequency Error Common Faults Reference frequency Checks to see that the carrier frequency is precisely correct Regulatory requirement in many countries Frequency distribution system GPS, if used Backhaul Slide 16

17 LTE Synchronization Signal Scanner Guideline Direct Connect 3 or fewer codes Within 10 db of dominant code Over 95% of the coverage area Consequences Downlink Coverage Quality Low data rate Low capacity Common faults Synchronization Signal Power Indicates which sectors are present at the current location Too many strong sectors creates frequency avoidance diminishing capacity Antenna down tilt Damaged antennas Control channel power settings Illegal repeaters Slide 17

18 Downlink Coverage Mapping OTA Scanner has Auto-Save Need GPS Receiver and Antenna Collects data every s Downlink Coverage Quality Time depends on number of Sync codes and whether Modulation is turned on Master Software Tools can export data to a KML file Import into Google Maps/Earth Mouse over point to see Scanner results Slide 18

19 LTE OTA Modulation Quality Testing OTA Modulation Quality Testing Valid signal quality measurements can be made OTA Guidelines are established from a known good base station Must be taken in valid location Valid OTA Location OTA Modulation Quality OTA Scanner validates location Dominance >10 db If Pass becomes sweet spot Valid EVM OTA measurement MIMO presents a challenge to measure EVM OTA Need to measure EVM of PBCH which has Transmit Diversity Measures both Tx1 & Tx2 Note GPS location Becomes location for future OTA Modulation Quality Testing Record and create OTA Pass/Fail limits Slide 19

20 One quick test OTA Pass/Fail checks health of cell site Start Find valid Over-the the-air (OTA) location If not, direct connect Found Valid OTA spot? N Start Direct Connect Transmitter Test Run one-step Pass/Fail Test Checks Feed Line Quality, if OTA Y Checks RF Quality Run OTA or Direct Connect Pass/Fail Test Checks Modulation Quality Test data throughput Pass? Y N Troubleshoot Feed Lines Base Station Coverage Interference Use PC data card If everything passes DONE Run PC-based Throughput Test If not troubleshoot Feed lines and antenna system Good Throughput? N Troubleshoot Backhaul Base station field replaceable units Downlink Coverage issues Y Done Interference problems Backhaul bit-error error-ratesrates Slide 20

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