LTE UE RF measurements An introduction and overview

Transcription

1 An introduction and overview February 2010 Andreas Roessler Technology Manager North America Rohde & Schwarz, Germany Guenter Pfeifer Product Manager CMW500 Rohde & Schwarz, Germany

2 Your presenters today Andreas Roessler Technology Manager North America Rohde & Schwarz, Germany Guenter Pfeifer Product Manager CMW500 Rohde & Schwarz, Germany A. Roessler and G. Pfeifer February

3 Outline l Introduction, l Overview and market update, l Status of standardization, l, l Prerequisites, LTE Call Setup, l TX measurements Power measurements, transmit signal quality, spectrum, l RX measurements, l Summary & conclusion. A. Roessler and G. Pfeifer February

4 Overview, market update l The LTE eco-system is building up, l Several LTE platforms have been announced and demonstrated by leading device / chipset manufacturer on various trade shows around the globe in 2009, l Various field trials are ongoing, using different infrastructure providers, l Several test systems and instruments are available, l 1 st (pre-)commercial network launch in Europe end of 2009, more expected during 2010 with a rapid deployment in 2011/2012, l 51 global network operator commitments to LTE in 24 countries, l LTE offers migration part not only for traditional GSM/WCDMA carrier but also for CDMA2000 1xRTT/1xEV-DO carrier, l Market research or what analyst say about LTE, l The global LTE handset market will increase from 70 million sales units in 2012 to 150 million by 2013, l LTE subscribers to reach 380 million by 2015, l By 2013 operators will spend over $8.6 billion on LTE base stations infrastructure, l LTE will grow faster than 3G, l Status standardization (3GPP), l Actual specification is Dec 09 baseline, l Core specification (RAN1 to RAN4) now stable, l UE test specifications (RAN5) is subject to change. A. Roessler and G. Pfeifer February

5 UE testing according to standards (3GPP) RF, RRM and protocol conformance l 3GPP TS , l Part 1 l Part 3 RF conformance testing, Section 6 (= Tx), Section 7 (= Rx), Section 8 (= Performance), Section 9 (= CQI, PMI reporting), Radio Resource Management (RRM) conformance testing, l 3GPP TS , l Part 1 Protocol conformance specification, l Work items closed *), specification of priority #1 and #2 test cases used for LTE UE certification are complete. *) based on TSG RAN#46 in Sanya/China, December-1 st -4 th 2009 A. Roessler and G. Pfeifer February

6 Migration to R&S CMW500 hardware platform R&S CMU200 Radio Communication Tester One HW platform configurable as l Non-signaling production unit All cellular standards, WLAN, FM, GPS, WiMAX, DVB l LTE/HSPA+ Protocol Tester, l LTE/HSPA+ RF Test Set, R&S CMW500 also 2G/2.5G also CDMA2000/1xEV-DO, Bluetooth, FM R&S CRTU-G/W Protocol Test Platform (picture showing configuration as LTE RF Tester) l...as well as future proofed platform for the upcoming challenges Rel-99 Rel-4 Rel-5 Rel-6 Rel-7 Rel-8 Rel-9 Rel-10 A. Roessler and G. Pfeifer February

7 LTE UE RF testing aspects User Equipment (UE) according to 3GPP TS l Tx characteristic (section 6), l Transmit power, Maximum UE output power, Maximum Power Reduction (MPR), Additional MPR, configured UE transmitted output power, l Output power dynamics, Minimum output power, Transmit OFF power, ON/OFF time mask, power control, l Transmit Signal Quality, Frequency error, EVM vs. subcarrier, EVM vs. symbol, LO leakage, IQ imbalance, Inband emission, spectrum flatness, l Output RF spectrum emissions, Occupied bandwidth, Spectrum Emission Mask (SEM), Adjacent Channel Leakage Power Ratio (ACLR), spurious emission band UE coexistence, l Transmit Intermodulation, Captured in TS UE radio transmission and reception and TS UE conformance specification, Part 1 A. Roessler and G. Pfeifer February l Rx characteristics (section 7), l Reference sensitivity level, Maximum input level, Adjacent channel selectivity (ACS), Blocking characteristics, Spurious response, Intermodulation characteristics, Spurious emissions, l Performance requirements (section 8), l Demodulation of PDSCH (/TDD), Single antenna, transmit diversity(2x2, 4x2), open and closed loop spatial multiplexing (2x2, 4x2), l Demodulation of PCFICH/PDCCH (/TDD), Single antenna, transmit diversity, l Demodulation of PHICH, Single antenna, transmit diversity, l Demodulation of PBCH, l Reporting of CQI/PMI (section 9), l CQI reporting under AWGN and fading conditions, single and multiple PMI reporting.

8 Why testing LTE at all? Some bullet points l LTE uses a complex physical layer with a high demand on testing, l OFDM is in general very sensitive to frequency and clock offsets, l SC-FDMA: verify that the PAPR 1) is really low(er) to minimize UL interference, l Bandwidths up to 20 MHz are used by LTE, which requires power amplifier and IQ modulators to have a flat frequency response, l Usage of higher-order modulation schemes (16QAM, 64QAM) requires high modulation accuracy even when noise, fading and interferences are present, l No transmit filter definition in LTE, as for 3G technologies, l In-channel performance (i.e. EVM) and out-of-channel performance (i.e. ACLR, SEM) requirements need to be met by the design, l Testing multiple use of antennas (MIMO) as part of performance requirements, l Transmit diversity, spatial multiplexing (closed-looped and open loop). 1) Peak-to-Average Power Ratio A. Roessler and G. Pfeifer February

9 On what type of channels and signals measurements can be made in the uplink? Multipath propagation Path loss UL interference LTE-capable base station (enhanced Node B, enb) Physical Uplink Control Channel (PUCCH) (Demodulation Reference Signal, occupied time slot position depends on used format) Physical Uplink Shared Channel (PUSCH) (Demodulation Reference Signal, over entire bandwidth in time slots #3 and #10) Sounding Reference Signals (SRS) LTE-capable terminal (User Equipment, UE) A. Roessler and G. Pfeifer February

10 A first challenge LTE frequency bands... E-UTRA Operating Band 1 2 Uplink (UL) operating band BS receive UE transmit Downlink (DL) operating band BS transmit UE receive F UL_low F UL_high F DL_low F DL_high 1920 MHz 1850 MHz 1980 MHz 1910 MHz 2110 MHz 1930 MHz 2170 MHz 1990 MHz Europe, Japan, Korea MHz 1785 MHz 1805 MHz 1880 MHz MHz 1755 MHz 2110 MHz 2155 MHz MHz 849 MHz 869 MHz 894MHz MHz 2500 MHz 840 MHz 2570 MHz 875 MHz 2620 MHz 885 MHz 2690 MHz Europe MHz 915 MHz 925 MHz 960 MHz MHz MHz MHz MHz MHz 1770 MHz 2110 MHz 2170 MHz by GCF prioritized frequency bands for LTE MHz 698 MHz 777 MHz 788 MHz 704 MHz MHz 716 MHz 787 MHz 798 MHz 716 MHz MHz 728 MHz 746 MHz 758 MHz 734 MHz MHz 746 MHz 756 MHz 768 MHz 746 MHz US MHz 830 MHz 860 MHz 875 MHz MHz 845 MHz 875 MHz 890 MHz MHz 1920 MHz 1900 MHz 1920 MHz TDD MHz 2025 MHz 2010 MHz 2025 MHz TDD MHz 1910 MHz 1850 MHz 1910 MHz TDD MHz 1990 MHz 1930 MHz 1990 MHz TDD MHz 1930 MHz 1910 MHz 1930 MHz TDD MHz 2620 MHz 2570 MHz 2620 MHz TDD China MHz 1920 MHz 1880 MHz A. Roessler 2300 MHz and G. Pfeifer 2400 MHz February MHz MHz 2400 MHz TDD TDD

11 but the R&S CMW500 supports already all bands and bandwidths! Pick any 3GPP frequency band and select channel number or carrier frequency! F F DL UL = = F F DL _ low UL _ low ( N DL NOffs DL ) ( N N ) UL Offs UL A. Roessler and G. Pfeifer February

12 Setup a LTE call with R&S CMW500 l Insert the video A. Roessler and G. Pfeifer February

13 Measurements as usual? No! Multi-evaluation measurement for LTE /TDD Modulation Resource Allocation Table Power, power control Spectrum A. Roessler and G. Pfeifer February

14 UE maximum output power l One power class has been defined for all applicable 3GPP frequency bands: Power class 3: +23 dbm ± 2.7 db, at the edge of spectrum lower tolerance is -4.2 db, The period of measurement shall be at least one subframe (= 1ms), Measurement defined for all bandwidths, using QPSK modulation and partial RB allocation (always 1 RB, size of 2 nd allocation depends on BW, i.e MHz), l However the flexibility of the LTE air interface in terms of bandwidth and modulation requires Maximum Power Reduction (MPR) when using higher order modulation schemes and increasing transmission bandwidth, Modulation 1.4 MHz Channel bandwidth / Transmission bandwidth configuration [RB] 3.0 MHz 5 MHz 10 MHz 15 MHz 20 MHz MPR (db) QPSK > 5 > 4 > 8 > 12 > 16 > QAM QAM > 5 > 4 > 8 > 12 > 16 > 18 2 For some 3GPP frequency bands network signaling informs the UE about an additional maximum power reduction (A-MPR) to meet additional requirements, i.e. for SEM or spurious emissions, A. Roessler and G. Pfeifer February

15 LTE power measurements with R&S CMW500 RB power = Resource Block Power, power of 1 RB TX power = integrated power of all assigned RBs Power TX power value corresponds to the maximum UE output power depending on the settings! Frequency A. Roessler and G. Pfeifer February

16 In-band emissions measurement l Estimate the interference to non-allocated resource blocks, as the UE shares transmission bandwidth with other UE s, l 3 types of in-band emissions: general, DC image and IQ image. Channel bandwidth (e.g. 20 MHz = 100 RB) Used allocation < ½ channel bandwidth A. Roessler and G. Pfeifer February

17 Transmit signal quality Power level Frequency error f = ±0.1ppm+15Hz RF carrier IQ component RB 0 RB 1 RB N-1 RB N frequency EVM, Spectrum flatness In-band emissions A. Roessler and G. Pfeifer February

18 Error Vector Magnitude (EVM) EVM vs. subcarrier f Integration of all Error Vectors to Display EVM curve f 0 f 1 f 2 f 3 Limits: BPSK+QPSK (17.5%), 16QAM (12.5%), 64QAM (tbd) Error vector.... Error vector A. Roessler and G. Pfeifer February

19 Error Vector Magnitude (EVM) EVM vs. symbol 1 Time Slot = 0.5 ms 7 SC-FDMA symbols (normal Cyclic Prefix (CP)) 1 SC-FDMA symbol Time 1 subframe = 1 ms [minimum Transmit Time Interval (TTI)] Frequency but there are 2 results displayed per SC-FDMA symbol Why? A. Roessler and G. Pfeifer February

20 Error Vector Magnitude (EVM) EVM vs. symbol How is this EVM measured? 4.7 (144 samples), 5.2 (160) µs for normal CP, 16.7 (512) µs for extended CP T Symbol = 66.7µs (2048 samples) Symbol part equal to Cyclic Prefix (CP) length CP SC-FDMA Data Symbol #0 Start for EVM low W (e.g. 136 samples) Start for EVM high FFT length (2048 samples) FFT window size does not capture the full length: symbol + CP FFT window size depends on system bandwidth and CP length Channel Bandwidth [MHz] Cyclic Prefix (CP) length N cp for symbol 0 Cyclic Prefix (CP) length N cp for symbols 1 to 6 Nominal FFT size Cyclic prefix for symbols 1 to 6 in FFT samples EVM window length W in FFT samples Ratio of W to CP for symbols 1 to [5] [55.6] [12] [66.7] [32] [66] [88.9] [91.7] [102] [94.4] [136] [94.4] 3GPP TS V8.8.0, Annex F, Table F for normal cyclic prefix A. Roessler and G. Pfeifer February

21 Error Vector Magnitude (EVM) EVM vs. Symbol How is this EVM measured? EVM low EVM high A. Roessler and G. Pfeifer February

22 Spectral flatness Nominal subcarriers Amplitude Equalizer coefficients Equalized subcarriers f f 0 f 1 f 2 f 3 Integration of all Amplitude Equalizer Coefficients to display spectral flatness curve A. Roessler and G. Pfeifer February

23 Output RF spectrum emissions SEM ACLR From modulation process Harmonics, parasitc emissions, intermodulation and frequency conversion Spurious domain f OOB Channel bandwidth f OOB Spurious domain RB E-UTRA Band Worst case: Resource Blocks allocated up to/at channel edge A. Roessler and G. Pfeifer February

24 Adjacent Channel Leakage Ratio (ACLR) Active LTE carrier, 20MHz BW 1 adjacent LTE carrier, 20MHz BW 2 adjacent WCDMA carriers, 5MHz BW A. Roessler and G. Pfeifer February

25 Spectrum Emission Mask, SEM OBW: Occupied bandwidth, defined as 99% of power spectal density SEM: Spectrum Emission Mask, measured with different resolution bandwidth, 1 MHz (away from carrier) or 30 khz (close to carrier) RBW 99% 1 MHz RBW 30 khz RBW A. Roessler and G. Pfeifer February

26 LTE RX Measurements l Receive Sensitivity Tests Transmit data on PDSCH AWGN Blockers Adjacent channels + Specifies DL scheduling parameters like RB allocation Modulation, etc. for every TTI (1ms) Receive data on PUSCH or PUCCH ACK/NACK Counting A. Roessler and G. Pfeifer February

27 LTE RX Measurements l Rx Measurements l Counting ACKnowledgement (ACK) NonACKnowledgement (NACK) l Calculating l BLER (NACK/ALL) l Throughput [kbps] A. Roessler and G. Pfeifer February

28 Thank you for your attention. Question & answers Visit us at the Mobile World Congress 2010 in Barcelona, Hall 1, booth 1D33. A. Roessler and G. Pfeifer February