From 2G to 4G and MIMO. Sacha Emery

Transcription

1 From 2G to 4G and MIMO Understanding Cellular Measurements Sacha Emery Automated Test Systems Engineer

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 MIMO configurations

3 Back to the Phone

4 Mobile Phone Industry Where is it used 4 billion mobile phone subscribers Why is test important Government compliance Manufacturer s name brand Logistic and phones (yields, etc) Needs of test market Low cost Fast Adoption %

5 Why is 3GPP so important? 3 rd Generation Partnership Project Based off of GSM radio networks and technology in Dec 1998 Organisation followed by major phone and network providers Includes everything for phone standards to even recommended testing Currently working on Release 10 Release 8 included LTE

6 NI Platform for Software-defined RF Test LTE WiMAX WLAN GSM/EDGE & WCDMA PXI System with 6.6 GHz Vector Signal Generator and Analyser ZigBee GPS

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

8 Introduction to GSM/EDGE Measurements

9 Overview of GSM/EDGE GSM 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 Tx Measurements 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)

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

12 Phase and Frequency Error (PFER) Metric of GSM modulation quality R t b l ith k h b d d fi d Reports symbol with peak phase based on predefined pattern

13 GSM/EDGE Demo

14 Overview of 3GPP WCDMA Evolution 3GPP Released 1999 (1 st Generation WCDMA) Downlink uses QPSK Uplink uses BPSK High Speed Packet Access (HSPA) released 2006 HSDPA (Downlink) uses QPSK, 16-QAM HSUPA (Uplink) uses QPSK Evolved HSPA (HSPA+) released 2008 Downlink uses 64-QAM Uplink uses 16-QAM

15 Intro to WCDMA Measurements Power Channel Power Code Domain Power (CDP) Modulation Quality Constellation EVM Modulation Accuracy y( (ModAcc) Frequency Domain Adjacent Channel Leakage Ratio (ACLR) Spectral Emissions Mask (SEM) Occupied Bandwidth (OBW)

16 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 Both require attention ti to reference levell

17 Introduction to LTE Measurements

18 LTE PHY Layer Overview Channel bandwidth 1.4 MHz 3 MHz 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)

19 What is MIMO? Low Frequency Simple Modulation Schemes Higher Frequencies Compression MIMO h 11 MU X T X h 12 h 31 R X DS P Rx 1 =h 11 Tx 1 +h 12 Tx 2 +h 13 Tx 3 Rx 2 =h 21 Tx 1 +h 22 Tx 2 + h 23 Tx 3 Rx 3 =h 31 Tx 1 +h 32 Tx 2 + h 33 Tx 3 [Rx] = [H] * [Tx]

20 Higher Frequencies & Compression

21 MIMO

22 LTE Measurements Power Measurements Transmit power CCDF Modulation Quality Measurements EVM (per trace, symbol, etc.) Spectral Measurements Spectrum flatness Spectral emissions mask Adjacent channel power

23 Overview of LTE Toolkit Releases in Q4, 2010 Supports FDD LTE Bandwidths: 1.4 MHz to 20 MHz Modulation types: QPSK to 64-QAM Downlink: OFDMA 4x4 MIMO TX Diversity, Spatial Multiplexing Uplink SC-FDMA SISO

24 Pat O Halloran, Benetel

25 Summary Cellular measurement can be classified by Power measurements Modulation quality measurements Spectral measurements WCDMA and LTE share several measurements Error vector magnitude Adjacent channel power LTE PHY layer contains several optimisations Data rate increases with use of OFDMA SC-FDMA mitigates OFDM PAPR issue