LTE Base Station Testing Basics

14,893 views

Published on

Published in: Technology, Business
5 Comments
46 Likes
Statistics
Notes
No Downloads
Views
Total views
14,893
On SlideShare
0
From Embeds
0
Number of Embeds
154
Actions
Shares
0
Downloads
0
Comments
5
Likes
46
Embeds 0
No embeds

No notes for slide

LTE Base Station Testing Basics

  1. 1. 1 of 30 LTE Base Station Testing Basics Emilio Franchy Senior Product Manager March 31st, 2010
  2. 2. 2 of 30 Agenda   LTE Technology Overview   LTE Terms   LTE vs. 3G Comparison   LTE RF Measurements   LTE Modulation Measurements   LTE Over-the-Air (OTA) Measurements   Question & Answer
  3. 3. 3 of 30   In the downlink, Orthogonal Frequency Division Multiplexing (OFDMA) is selected as the air-interface for LTE.   OFDMA communication systems do not rely on increased symbol rates in order to achieve higher data rates.   Transmission by means of OFDM is a particular form of multi-carrier modulation (MCM) i.e. a parallel transmission method which divides an RF channel into several narrower bandwidth subcarriers.   Sub-carrier typically 15 kHz   Standard allows for other values LTE Basic Technologies – OFDMA
  4. 4. 4 of 30 What is OFDMA?   “Orthogonal Frequency Division Multiple Access”   Assigns different subcarriers & symbols to each user   Can dynamically change   Each subcarrier is modulated with QAM or PSK   LTE uses QPSK, 16 QAM, and 64 QAM   BPSK for some control signals   PHICH, PUCCH   Allows many users to be supported   At variable bit rate   Scheduling many users   With different quality of service   Complex Time Subcarrier Different users System Overhead
  5. 5. 5 of 30 LTE Physical Channel Names (Downlink)   RS   Reference Signal   Similar to Pilots in 802.11   Subcarrier varies with MIMO transmitter & Cell ID   P-SS, S-SS   Primary & Secondary Synchronizing Signals   Contains cell ID   PCFICH   Physical Control Format Indicator Channel   How many symbols are used for PDCCH   PBCH   Physical Broadcast Channel   PHICH (not shown)   Physical Hybrid ARQ Indicator Channel   Sends Acknowledgements or Not Acknowledgements   Part of Error Protection system for the uplink   PDCCH   Physical Downlink Control Channel   Who’s assigned to what resources?   PDSCH   Physical Downlink Shared Channel   Where all the user data goes Time Subcarrier Shared Shared Shared
  6. 6. 6 of 30 LTE Frame Structure (FDD)   Frame   10 ms   Subframe   1 ms   10 per frame   Slot   500 us   2 per subframe, 20 per frame   7 or 6 symbols (normal or extended CP)   Limited usefulness, as scheduling limited to subframes Subframe Frame 10 ms
  7. 7. 7 of 30 Resource Blocks   Resource Block (RB)   12 subcarriers * 1 slot   1 slot = 0.5 ms   2 slots/subframe   10 subframes/frame   1 frame = 10 ms Subframe Subcarrier
  8. 8. 8 of 30 Compatible Bandwidths Control Channels in center of channel BW 20 MHz BW 5 MHz BW 1.4 MHz BW 10 MHz BW 15 MHz BW 3 MHz BW Time Frequency
  9. 9. 9 of 30 MIMO (2X2 examples)   MIMO = Multiple Input, Multiple Output   MIMO (Transmit Diversity)   Multi-beam antenna’s   Dual 2X2   (eNodeB Tx) 4X2 (UE Rx)   Quad 4X4   Data stream repeated   All signal paths   Increase coverage   MIMO (Spatial Multiplexing)   Different data streams   Higher data rate   Relies on Multi-path MIMO Tx Diversity MIMO Spatial Multiplexing
  10. 10. 10 of 30 LTE terms similarity to 3G terms LTE CDMA W-CDMA   RS (Reference Signal) Pilot CPICH   P-SS (Primary Synchronizing Signals) Sync P-SCH   S-SS (Secondary Synchronizing Signals) NA S-SCH   PCFICH (Physical Control Format Indicator Channel) NA NA   PBCH (Physical Broadcast Channel) Paging BCCH   PHICH (Physical Hybrid ARQ Indicator Channel) NA NA   PDCCH (Physical Downlink Control Channel ) Paging P/S-CCPCH & PICH   PDSCH (Physical Downlink Shared Channel) Traffic Traffic   EVM (Signal Quality) Rho EVM   Frequency Accuracy Freq Accy Freq Accy
  11. 11. 11 of 30 LTE Measurements vs. W-CDMA Measurements   RF   Channel Spectrum   Power vs. Time   Spectral Emission Mask   ACLR   Modulation Quality   Resource Element Power   Control & Traffic Channel Power   Spectral Flatness   Constellation   OTA   Sync Signal Scan   Channel Power Monitor   RF   Channel Spectrum   Power vs. Time   Spurious Emission   ACLR   Demodulator   CDP (Code Domain Power)   Control & Traffic Channel Power   Constellation   OTA   Pilot Scan   Multipath
  12. 12. 12 of 30 LTE Measurements vs. CDMA Measurements   RF   Channel Spectrum   Power vs. Time   Operating Band Unwanted Emissions (Spectrum Emission Mask)   ACLR   Modulation Quality   Resource Element Power   Control & Traffic Channel Power   Spectral Flatness   Constellation   OTA   Sync Signal Scan   Channel Power Monitor   RF   Channel Spectrum   Power vs. Time   Spurious Emission   ACPR   Demodulator   CDP (CDP MAC/Data, Graph/Table)   Control Channels   OTA   Pilot Scan   Multipath
  13. 13. 13 of 30 eNodeB : Traditional install   Traditional configuration   2x2 MIMO   2 Radios per sector   Extreme weather   Key HW in shelter   Traditional Testing   Test Needs   Transmitter   Antenna & jumper cables   LTE signal quality   Direct Connect   Use Test Port   Interference   Coverage   Backhaul   Fiber Directional Coupler / Test Port Channel Cards Power Supply Remote Radio Heads located close to Base Band Radio Radio Server Coaxial/Waveguide RF Cable Jumper if close to antenna Backhaul GigE GPS Antenna Fiber Optic Baseband Cable with DC Power – short run Antennas Air Interface Interference Traditional TMA’s Coaxial Feedline to TMA Tx1 / Rx1 Tx2 / Rx2
  14. 14. 14 of 30 Key Performance Indicators vs. LTE Field Measurement x = probable, xx = most probable 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
  15. 15. 15 of 30 LTE Field Measurement vs. eNodeB Field Replaceable Units x = probable, xx = most probable 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
  16. 16. 16 of 30 LTE (RF) Occupied Bandwidth   Occupied Bandwidth   A measurement of the spectrum used by the carrier   The occupied bandwidth contains 99% of the signal’s RF power   Guideline – Direct Connect   Per defined LTE bandwidth   1.4, 3.0, 5.0, 10, 15, 20 MHz   Consequences   Leads to interference with neighboring carriers   Dropped calls/data sessions   Low capacity   Common Faults   Tx filter   MCPA   Channel cards   Antennas
  17. 17. 17 of 30 LTE Adjacent Channel Leakage Ratio (ACLR)   ACLR (single-carrier displayed)   Measures how much of the carrier gets into neighboring RF channels   Checks the closest (adjacent) and the next closest (alternate)   Guideline – Direct Connect   -45 dBc for the adjacent channels   -45 dBc for the alternate channels   Consequences   Leads to interference with neighboring carriers   Low capacity   Blocked calls/data sessions   Common Faults   Tx filter   MCPA   Channel cards   Cable connectors
  18. 18. 18 of 30 LTE Spectral Emission Mask (SEM)   Spectral Emission Mask   SEM checks closer to the signal than ACLR does   Regulators may require regular measurements of spectral emissions   Guideline – Direct Connect   Must be below mask   Received power levels matter so be sure to use the right external attenuation value   Consequences   Interference with neighboring carriers   Legal liability   Low signal quality   Common Faults   Check amplifier output filtering   Look for intermodulation distortion   Look for spectral re-growth
  19. 19. 19 of 30 LTE Error Vector Magnitude (EVM)   EVM   The ratio of errors, or distortions, in the actual signal, compared to a perfect signal   EVM applies to the entire signal   Guidelines – Direct Connect   QPSK - 17.5%   16 QAM – 12.5%   64 QAM – 8%   Consequences   dropped calls/data sessions   low data rate   low sector capacity   blocked calls/data sessions   Common Faults   distortion in the channel cards   Power amplifier   filter   antenna system
  20. 20. 20 of 30 LTE Control Channels   Control Channels   Verifies Control Channel power is set correctly   Guideline   Per RF Engineering ± 0.5 dB   Consequences   If power set too low   Blocked calls/data sessions   Initiating calls/data sessions   Dropped calls/data sessions   During handoffs   If power set too high   Possible interference   Lower Throughput   Common Faults   Improper settings in the eNodeB   Signal processing   Control section
  21. 21. 21 of 30 LTE Frequency Error   Frequency Error   Checks to see that the carrier frequency is precisely correct   Regulatory requirement in many countries   Guideline – OTA with GPS   ± 0.05 ppm (wide area BS)   ± 0.1 (local area BS)   ± 0.25 (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   Common Faults   Reference frequency   Frequency distribution system   GPS, if used   Backhaul
  22. 22. 22 of 30 eNode-B ; Remote Radio Unit   Single Sector   2x2 MIMO   2 Radios per sector   Tx1 has Sync Signal   Tx2 may have Sync Signal   Test Needs   Transmitter   Antenna & jumper cables   LTE signal quality   OTA if No Access to RRU   Interference   Coverage   Backhaul   Fiber Company Confidential Tx1 / Rx1 Tx2 / Rx2 DirectionalCoupler/ TestPort Channel Cards Power Supply Remote Radio Heads Ideally located close to antenna Radio Server RF Cable Jumper if close to antenna Backhaul GigE …. GPS Antenna Fiber Optic Baseband Cable with DC Power Antennas Air Interface Interference
  23. 23. 23 of 30 LTE Synchronization Signal Scanner   Synchronization Signal Power   Indicates which sectors are present at the current location   Too many strong sectors creates pilot pollution   Guideline – Direct Connect   3 or fewer codes   Within 10 dB of dominant code   Over 95% of the coverage area   Consequences   Low data rate   Low capacity   Excessive soft handoffs   Common faults   Antenna down tilt   Scrambling code power   Illegal repeaters Downlink Coverage Quality
  24. 24. 24 of 30 LTE OTA Modulation Quality Testing   MIMO presents a challenge to measure EVM   Need to measure PBCH which has Transmit Diversity   Measures both Tx1 & Tx2   Valid EVM OTA measurement OTA Modulation Quality   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 Scanner validates location   Dominance >10 dB   If Pass – becomes sweet spot   Note GPS location   Becomes location for future OTA Modulation Quality Testing   Record and create OTA Pass/Fail limits
  25. 25. 25 of 30 Downlink Coverage Mapping   OTA Scanner has Auto-Save   Need GPS Receiver and Antenna   Collects data ≈ every 5-10 s   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 Downlink Coverage Quality
  26. 26. 26 of 30 One quick test – OTA Pass/Fail – checks health of cell site   Find valid Over-the-Air (OTA) location   If not, direct connect   Run one-step Pass/Fail Test   Checks Feed Line Quality, if OTA   Checks RF Quality   Checks Modulation Quality   Test data throughput   Use PC data card   If everything passes   DONE   If not troubleshoot   Feed lines and antenna system   Base station field replaceable units   Downlink Coverage issues   Interference problems   Backhaul bit-error-rates Found Valid OTA spot? Run OTA or Direct Connect Pass/Fail Test Start Start Direct Connect Transmitter TestN Done Run PC-based Throughput Test Pass? Troubleshoot Feed Lines Base Station Coverage Interference N Good Through- put? Troubleshoot Backhaul N Y Y Y
  27. 27. 27 of 30 Troubleshooting Guide and Coverage Mapping App Note
  28. 28. 28 of 30 LTE Measurements Training Course   LTE Theory and Measurements Using the BTS & Spectrum Masters An intense two-day instructor led training course that focuses on LTE Base Station measurements, helping you reduce operating expenses by enhancing the skill set of your employees. Available at your site or at a nearby Anritsu facility.   Who Should Attend   Cell Technicians   System Performance Engineers/Field Engineers   Base Station OEMs   Site Managers   BTS Installers   How You Will Benefit   Spectrum Analysis Basics - how to use a spectrum analyzer, identifying signal types, common measurements such as Occupied Bandwidth, ACLR and Channel Power. Includes extensive labs.   Digital Modulation Theory – PSK and QAM, EVM, Bit error rate vs. CINR, Orthogonal FDM theory   RF Propagation & LTE Air Interface theory– time and frequency structure, air interface, MIMO, diversity, physical channels description, 3GPP Transmitter performance specs, frequency reuse, C/I vs. co-channel reuse. Includes extensive labs.   LTE Downlink Quality Measurement – Channel Power, Occupied Bandwidth, Spectral Emission mask, EVM, Constellation, Frequency error, OTA measurements such as Multiple-signal inventory, dominance, and modulation quality. Includes extensive labs.   LTE Pass/Fail Measurements - Learn what is critical and what is acceptable.   See http://www.us.anritsu.com/training/ for more info.
  29. 29. 29 of 30 Question & Answers   Thank you for your participation   More information available at www.us.anritsu.com
  30. 30. 30

×