5G The overall test challenge from system to device 5G NR T&M aspects

Transcription

1 5G The overall test challenge from system to device 5G NR T&M aspects embb Reiner Stuhlfauth Technology Manager Wireless Rohde & Schwarz miot / mmtc URLLC

2 Optimizing the present. Designing the future. embb Cybersecurity mmtc URLLC µ-wave Broadcast& Media Aerospace& Defence T&M EMC + Automotive 2

3 5G testing aspects - outline 5G NR RF measurements Over the air a paradigm change in testing setups Can we measure in the Near-field? How to obtain Far-field condition for UEs and basestations? 3GPP status on OTA testing Outlook future and additional aspects of OTA testing System and field testing of 5G NR 3

4 NR Frame spectrum analysis 5G NR critical RF parameters compared to LTE testing: - Power flatness over wide bandwidth (~100MHz) - Spectrum emission mask - EVM performance=> Impact of phase noise - EVM vs. Subcarrier => Impact of DC leakage - Power vs. Time => shorter Symbols and wider bandwidth - Symbol allocation => much higher flexibility of RF layer What are we going to test in 5G NR? => For sure the usual suspects: power, spectrum, modulation, receiver, etc. 4

5 NR Frame spectrum analysis 5G NR critical RF parameters compared to LTE testing: - Power flatness over wide bandwidth (~100MHz) - Spectrum emission mask - EVM performance=> Impact of phase noise - EVM vs. Subcarrier => Impact of DC leakage - Power vs. Time => shorter Symbols and wider bandwidth - Symbol allocation => much higher flexibility of RF layer Analysis of different numerologies and carrier bandwidth parts with different modulation schemes 5

6 You can t cheat physics! Bandwidth ı Significant higher data rates / capacity is only possible with higher bandwidth C = B log S N ı Higher bandwidth is only possible at higher spectrum ı We do know the challenges of propagation at cm- /mm-wave spectrum Example: field 6

7 You can t cheat physics but an engineer will find a solution! ı Active antenna systems with a high number of antenna elements, which can be individually controlled in phase and amplitude, enable high antenna gains and beam steering. Massive MIMO Antenna@ 3.5GHz Reconfigurable 28GHz All-Silicon Array 7

8 An engineer solves his problem by creating another engineers problem! ı High number of antenna elements each connected to phase shifters and PAs Limited test interfaces ı High integration in particular at cm- and mm-wave spectrum No RF connectors RFIC RFIC FPGA Digital IQ TRx Development challenges like phase shifter tolerances, thermal effects of the PAs, frequency drifts between modules, desired beam patterns, Over the air (OTA) measurements in far field becomes the default test scenario OTA measurements require shielding Cost / Complexity impact 8

9 Fraunhofer distance. Near field vs. far field Far field= magnitude Near field measurements: values depend on phase & magnitude not simple for modulated signals (wide bandwidth, phase coherent receiver needed) multiple samples are needed, i.e. spherical scan near-field to far-field transformation is needed (additional time + effort) => single probe + rotation concept (accurate positioner needed) or multi-antenna probe (calibration complexity) Smaller chamber sizes Very nearfield region 0.62 D 3 / λ Near-field region = phase & magnitude 2D 2 / λ Far field measurements: values depend on magnitude only suitable for modulated signals one sample is sufficient, no NF/FF post-processing Larger chamber sizes required or hardware FF transformation like PWC or CATR (higher complexity) 9

10 Measurement dilemma: can we do measurements in near field? E.g. EVM aspects NF vs. FF Measuring EVM in near field: Near field samples are varying in phase + amplitude => certain unaccuracy is the result Measuring EVM in far field: Pathloss will reduce the received signal to noise ratio DUT has to be measured at max and min power Sensitivity level of test instrument has to be considered 10

11 Measurement results Active antenna 28GHz ı ı 5G NR signal (100 MHz, 64QAM data, fully allocated) with crest factor of 11.5dB Generated with SMW200A and received/analyzed with FSW43 EVM measurement in NF possible? EVM <0,7% when sufficient SNR. Problem at higher power due to overdriven PA 11

12 What is the Far-field distance? 2 additional methods Dant=4cm 28GHz UE Subarray (HPBW=15 ) DUT=10cm Criteria Far-field Distance 2λ/HPBW meters θ 28GHz Entire UE HPBW (radians) Half-power beam width R FF = 2D2 λ or 2λ HPBW 2 2D 2 /λ 1.86 meters 3dB power difference R ffd = λ πd λ πd λ cm 24 GHz FHD = 3.6 m RffD = 1.14 m Consideration only in peak beam direction allows to re-consider FF distances: APEMC 2018 [Derat, «5G antenna characterization in the far-field How close can far-field be?»] - based on spherical wave expansion 12

13 Far-field in Near-field Systems: Hardware Fourier Transforms Complex near-field wave generated f x,y = A ඵ E x,y e +jk r dxdy Amplitude Phase Plane wave farfield received DUT Fresnel Lens (Fourier Optics) Reflector: Compact Antenna Test Range Array: Plane Wave Convertor 13

14 How to achieve far-field conditions? Basestation plane wave idea Based on principle of beamforming: Antenna array with phase shifters. Goal is not beamforming, but plane wave. Frequency restricted but allows modulated wideband signals analysis 14

15 R&S PWC200: Gain & Pattern Results 5G Certified Lab Results (Spain) LTE signal: PWC200 Results 1.5m from DUT Single Antenna 1.5m from DUT EVM = 0.41% Roughly the internal EVM of measurement instruments 15

16 3GPP status UE testing > 24GHz (note that below 6GHz conducted testing is still used) ı Background information in 3GPP TR ı 3GPP distinguishes between RF, RRM and demodulation and CSI testing and testing methodologies UE RF testing: Permitted test methods are direct far field (DFF) testing and indirect far field (IFF), i.e. CATR EIRP, TRP, EIS, EVM, spurious emissions and blocking metrics can be tested Stable already! UE RRM testing Only baseline measurement setup defined so far Work in progress! UE demodulation and CSI testing Only baseline measurement setup defined so far 16

17 3GPP Status UE testing RF testing Indirect far field: e.g. CATR z 1 DUT y x Range antenna reflector Direct far field: Measurement & Link antenna (combined Or separated) Measurement Antenna for centre and off centre of beam measurements Link Antenna for beam steering Feed antenna Link/Measurement Antenna for beam steering and centre of beam measurements Positioner controller PM/SG PC 17

18 Quiet Zone (D) What is the Quiet zone? R R Point Source (Measurement Antenna) d φ(r) φ(r+d) +D/2 -D/2 Quiet Zone Phase Deviation vs. Measurement Error R min = Rmin(N) D 2 /λ 2D 2 /λ 4D 2 /λ 8D 2 /λ πd2 = ND2 4λΔφ max λ Phase Deviation 45 degrees 22.5 degrees 11.2 degrees 5.6 degrees -20 db -25 db -30 db N = N = 2 N = 4 High Gain Antenna Pattern Note: Near field regions don t have quiet zones 18

19 DFF solution for Whitebox IFF solution for Blackbox Direct far field: typically smaller QZ Indirect far field: typically larger QZ Elevation arm Both systems fit in ATS form factor Azimuth +/- 180 Azimuth & Theta +/

20 3GPP Status UE testing RRM testing ı The exact list of RRM tests for UE can only be determined once the core requirements are settled ı The baseline measurement setup for f > 6 GHz is capable of establishing an OTA link between the DUT and a number of emulated gnb sources ı Up to 2 NR transmission reception points TRxPs are emulated ı N dual-polarized antennas transmitting the signals from the emulated gnb sources to the DUT. ı N N MAX_AoAs, where N MAX_AoAs is the maximum number of simultaneously active (emulating signal) angles of arrival AoAs. For the scope of Rel-15 testing, it is assumed that N MAX_AoAs = [2]. ı In case of multiple DL transmission antenna ports are required for RRM testing, the transmission scheme is polarization diversity. ı Fading propagation conditions between the DUT and the emulated gnb sources are modelled as Tapped Delay Line (TDL). 20

21 OTA testing with temperature control S21 parameter influenced by temperature changes 21

22 RRM case study : OTA 3D Measurements UE RSRQ measurement does not depend on the receiver antenna characteristics Serving cell emulation Neighbour (interfering) Cell emulation The receiver antenna characteristics determines UE RSRP measurement. 22

23 RF Scanner TSMx / ROMES for mm-wave testing 5G NR scanning of SSB R&S TSMA6 Autonomes Mobile Network Scanner and R&S ROMES Drive Test Software Receive antenna IF: 3 GHz R&S TSME30DC Downconverter R&S TSME6 Ultra Compact Drive Test Scanner R&S ROMES Drive Test Software 23

24 What can be measured? NR - 28GHz channels 24

25 If you want to go fast, go alone. If you want to go far, go together! African proverb 25