From 2G to 4G UE Measurements from GSM to LTE. David Hall RF Product Manager

Transcription

1 From 2G to 4G UE Measurements from GSM to LTE David Hall RF Product Manager

2 Agenda: Testing 2G to 4G Devices The progression of standards GSM/EDGE measurements WCDMA measurements LTE Measurements LTE theory of operation PHY layer measurements LTE Advanced

3 NI Software-defined RF Test GSM/EDGE WCDMA & HSPA+ LTE WiMAX ZigBee RFID WLAN GPS Early Access Early Access AM/FM Bluetooth CDMA2000 EV-DO

4 Overview of 3GPP Standards GSM/EDGE WCDMA / HSPA / HSPA+ 3GPP LTE Deployment Date Modulation 1991 (GSM) 2003 (EDGE) GMSK, 8-PSK, 2001 (WCDMA) 2008 (HSPA) QPSK, 16-QAM, 64- QAM Channel BW 200 khz 5 MHz 2010 (Trial) QPSK, 16-QAM, 64- QAM Variablefrom 1.5 to 20 MHz Carrier Structure Single-Carrier Modulation WCDMA OFDMA (DL) TD-SCDMA (UL) Peak Downlink Data Rate Up to kbps (DL-EDGE) Up to 42.2 Mbps (DL- HSPA+) Up to 300 Mbps (4x4 MIMO) Duplexing FDD (TDMA) FDD (CDMA) FDD & TDD Next Evolution Evolved EDGE HSPA+ LTE Advanced

5 TDD vs. FDD Frequency Division Duplexing(FDD) Frequency Time Division Duplexing(TDD) Frequency UL Band DL Band MS 1 MS 2 MS 1 MS 2 MS 3 Single Band Uplink Sub-frame Downlink Sub-frame Time Time

6 CDMA vs. FDMA Frequency Division Multiple Access (FDMA) Frequency Frequency Code Division Multiple Access (CDMA) MS 4 DL Band MS 1 MS 2 MS 5 DL Band Radio Frame N each MS with unique code Radio Frame N+1 each MS with unique code MS 3 MS 6 Time Time

7 Introduction to GSM/EDGE Measurements

8 GSM/EDGE Measurement Suite Standard Support GSM, EDGE UE and BS testing Software support API for LabVIEWand C/C++ Interactive soft front panels Teststand example sequences Measurement performance Modulation ORFS (GSM): -68 dbc RMS EVM (EDGE): < 0.5%

9 GSM Overview of GSM/EDGE Uses Gaussian Minimum Shift Keying (GMSK) No transitions through center of constellation Peak-to-average power ratio (PAPR) < 1 db Can be used with non-linear PA EDGE Uses offset 3π/8 8-PSK 3π/8 8-PSK uses 16 symbol locations (shifted 3π/8) No transitions through center of constellation PAPR 3 db Requires linear PA

10 GSM/EDGE Overview Frame Structure 8 timeslots/frame 573 μs/timeslot Training sequence in middle of data burst for synchronization slot #1 slot #2 slot #3 slot #4 slot #5 slot #6 slot #7 slot #8 midamble

11 GSM/EDGE TxMeasurements GSM Measurements Transmit Power (TxP) Power versus Time (PvT) Phase and Frequency Error (PFER) Output RF Spectrum (ORFS) EDGE Measurements Transmit Power (TxP) Power versus Time (PvT) Error Vector Magnitude (EVM) Output RF Spectrum (ORFS)

12 Power Versus Time (PVT) Measures burst power and average power Measures compliance versus PVT mask Provides traces to determine relative margin

13 Phase and Frequency Error (PFER) Metric of GSM modulation quality Reports symbol with peak phase Why not a constellation trace?

14 EDGE Error Vector Magnitude (EVM) Metric of modulation quality Encapsulates a wide range of signal errors Compression, SNR, and Quadrature impairments

15 Output RF Spectrum (ORFS) Measures spectral power at various offset frequencies Use Auto Level or set appropriate reference level Measurement is SNR limited by VSA noise floor Measurement captures DUT nonlinearity

16 GSM/EDGE Demo

17 WCDMA/HSPA+ Measurement Suite Standard Support WCDMA, HSPA, and HSPA+ UE and BS testing Software support API for LabVIEWand C/C++ Interactive soft front panels Teststandexample sequences Measurement performance ACLR (Uplink): -63 dbc RMS EVM (Uplink): < 0.5%

18 Intro to WCDMA Measurements UE Conformance Spec: 3GPP TS , Sec 5 Power Channel Power Code Domain Power (CDP) Frequency Domain Adjacent Channel Leakage Ratio (ACLR) Spectral Emissions Mask (SEM) Occupied Bandwidth (OBW) Modulation Quality Constellation EVM Modulation Accuracy (ModAcc)

19 Adjacent Channel Leakage Ratio Best metric of UE transmitter output linearity Defined by 3GPP TS , Sec 5.10 WCDMA Channel Power 3.84 MHz BW - 33 dbc - 43 dbc Negative Alternate (-10 MHz) Negative Adjacent (+ 5 MHz) Positive Adjacent (+ 5 MHz) Positive Alternate (+ 10 MHz) Frequency

20 Constellation EVM vs. Mod Accuracy Constellation EVM Measure EVM un-spread chips Takes less time Configure + Measure Time = 47 ms on PXIe-8106 Modulation Accuracy (ModAcc) De-spreads all chips and recovers symbols for each channel Takes longer Configure + Measure Time = 600 ms on PXIe-8106 Standard allows 17.5% (3GPP TS , Sec )

21 WCDMA Demo

22 Introduction to LTE Measurements

23 OFDMA Basics Each 12 sub-carriers grouped into resource blocks Each UE is allocated specific RB s and timeslots Transmission BW can be limited to active RB s Unused RBs Active RBs Transmission BW 5 MHz LTE Channel BW (25 RB) 3GPP TS , Sec 5.4.2

24 LTE PHY Layer Overview Channel bandwidth 1.4 MHz 3MHz 5 MHz 10 MHz 15 MHz 20 MHz Subcarriers Used # Resource Blocks Modulation Multiple Access Peak Data Rate Downlink: QPSK, 16-QAM, and 64-QAM Uplink: QPSK, 16-QAM, and 64-QAM Downlink: Orthogonal Frequency Division Multiple Access (OFDMA) Uplink: Single Carrier Frequency Division Multiple Access (SC-FDMA) Downlink: 300 Mbps (4x4 MIMO, 20 MHz) Uplink:75 Mbps (20 MHz)

25 LTE Frame Structure One Sub-Frame = 1 ms One Radio Frame = 10 ms #0 #1.... #18 #19 One Slot = 0.5 ms 7 symbols per slot, 6 if long cyclic prefix Frequency sub-carriers per resource block Time

26 LTE PHY Layer: Uplink Uses Single-Carrier FDMA (SC-FDMA) Similar to OFDM & OFDMA DFT pre-coding helps preduce PAPR Enables better RF front end efficiency Deserializer N-point DFT Subcarrie r Mapping M-point IDFT Serializer Cyclic Prefix Insertion Denotes unique to SC-FDMA (not OFDM)

27 LTE Measurement Suite Based on 3GPP, release 9 Interactive Soft Front Panels TestStandSupport API for LV and above API for C, C++, and.net API

28 Intro to LTE Measurements UE Conformance Test Specification 3GPP TS Power Measurements Transmit power CCDF Modulation Quality EVM (per trace, symbol, etc.) Spectral Measurements Spectrum flatness Spectral emissions mask Adjacent channel power

29 UE Maximum Output Power UE maximum power limited to +23 dbm(sec ) Peak power is much higher because of OFDM PAPR PAPR Characterized by CCDF Trace CCDF illustrates PAPR 7 db Higher PAPR evident in PVT trace

30 Error Vector Magnitude (EVM) Measures modulation quality Influenced by the broadest range of impairments Quadrature(IQ gain imbalance, skew) Signal to Noise Ratio Non-linearity 3GPP TS defines EVM in percent (%) EVM = 20log 100 ( ) db EVM % Modulation Spec Limit (%) Spec Limit (db) BPSK or QPSK 17.5% db 16QAM 12.5% db 3GPP TS , Sec

31 Modulation Quality -Constellation

32 EVM Versus Symbol Peak RMS EVM < -47 db at 4 th symbol

33 EVM Versus Sub-Carrier Peak RMS EVM < db

34 LTE ACP Measurements E-UTRA defines power of adjacent LTE carrier Measured with a square measurement filter UE spec limit is 30 dbc UTRA defines power of adjacent WCDMA carrier Measured with a RRC filter (alpha = 0.22) UE spec limit is 33 dbc E-UTRA ACLR1 (channel BW) UTRA ACLR1 (3.84 MHz) UTRA ACLR1 (3.84 MHz) Active RBs 3GPP TS , Sec

35 Tradeoff Between EVM and ACLR Window Length: 64 Samples RMS EVM: -40 db ACP: -55 dbc (UTRA) Caused by discontinuities between cyclic prefix and next symbol Window Length: 0 Symbols RMS EVM: -49 db ACP: -45 dbc (UTRA)

36 Spectral Emissions Mask

37 Spectrum Flatness Spectrum flatness < ±0.15 db

38 LTE Demo

39 Looking Forward to LTE Advanced Carrier aggregation Allows for up to five 20 MHz carriers (100 MHz total BW) Enables downlink data rates of up to 1 Gbps Enhanced MIMO support Up to 8 downlink transmission antennas (currently 4) Up to 4 uplink transmission antennas (currently 1) 20 MHz Channels 100 MHz Total BW

40 Summary Cellular measurement can be classified by Power measurements Spectral measurements Modulation quality measurements Data rate drive wider BW and better spectrum utilization LTE PHY layer contains several optimizations Better spectral efficiency using OFDMA SC-FDMA mitigates classing OFDM PAPR issues LTE Advanced adds MIMO measurement challenges