Propagation Channel Modeling for Wideband Radio Systems

Transcription

1 UEC Tokyo EuCAP 204 April 9, 204 Propagation Channel Modeling for Wideband Radio Systems - How to create realistic MIMO propagation environment for OTA measurements - Yoshio Karasawa Advanced Wireless Communication research Center (AWCC) University of Electro-Communications (UEC Tokyo)

2 UEC Tokyo Outline. Introduction: MIMO and MIMO-OTA 2. Channel Model for MIMO OTA Systems - Simplified Configuration - Channel Model 3. Two-Stage Scheme for MIMO Fading Emulator 4. Development of MIMO Fading Emulator using FPGA 5. Application Examples 6. Conclusion 2

3 UEC Tokyo Outline. Introduction: MIMO and MIMO-OTA 2. Channel Model for MIMO OTA Systems - Simplified Configuration - Channel Model 3. Two-Stage Scheme for MIMO Fading Emulator 4. Development of MIMO Fading Emulator using FPGA 5. Application Examples 6. Conclusion

4 UEC Tokyo MIMO Technologies Radiowave Propagation MIMO covers wide technical areas Tx signal Tx array Encoding with time and space domain Rx array Decoding with time and space domain Rx signal Multi-path propagation Information theory and coding theory Adaptive array and adaptive signal processing Applications are from W-LAN to next-generation mobile wireless systems. 3

5 UEC Tokyo Trend of MIMO R&D Transmission scheme System application (from WLAN to LTE-advanced) System development (MU-MIMO, large-scale MIMO) Establishment of performance evaluation system for MIMO user terminal (MIMO-OTA) - Handset-related problem such as antenna coupling effect - High needs to the measurement system development - Insufficient research for MIMO-OTA - Establishment of standard scheme 4

6 5 UEC Tokyo We want to evaluate MIMO user terminal performance. Necessity of evaluation environment Construction of MIMO-OTA Measuring System Fading Emulator Type Reverberation Chamber Type Hybrid Structure Type

7 MIMO (Tx) MIMO (Rx) UEC Tokyo Two Types of MIMO-OTA Systems Fading Emulator Type (FE) Fading Emulator Full functions Higher Flexibility Higher Construction Cost Reverberation Chamber Type (RC) Multipath-rich Environment with large delay Lower Construction Cost Lower Flexiblility MIMO (Tx) MIMO (Rx) 6

8 UEC Tokyo Outline. Introduction: MIMO and MIMO-OTA 2. Channel Model for MIMO OTA Systems - Simplified Configuration - Channel Model 3. Two-Stage Scheme for MIMO Fading Emulator 4. Development of MIMO Fading Emulator using FPGA 5. Application Examples 6. Conclusion 7

9 8 UEC Tokyo Required Function for MIMO-OTA Measurement System Real Channel Tx Rx Tx-side Spatial Correlation (depending on Angle of Departure) Delay Profile (Delay Spread) Doppler Spectrum (Doppler Spread) Rx-side Spatial Correlation (depending on Angle of Arrival) OTA Environment Generated OTA Channel Tx Signal Processing (Fading Emulator)

10 9 UEC Tokyo Fading Emulator-type MIMO OTA System Multiple Input (Transmitting Antenna ports: M) Probe Antennas: L Multipath environment -Spatial correlation -Doppler spectrum -Delay profile M Multipath channel generation L DUT Multiple Output (Receiving Antenna ports : N)

11 M L UEC Tokyo Basic Configuration of Multipath Fading Generation Part Path-Controlled Scheme Number of delay units: MLK Number of Rayleigh faders: MLK (K: Number of multipath delays) Almost perfectly controllable Large scale configuration Antenna-Branch-Controlled Scheme M NW (Hadamard Matrix connection) L Number of delay units: LK Number of Doppler shifters: L Flexibly controllable (realization of some functions is limited.) Simplified configuration (easy to FPGA implementation) 0

12 Time-invariable delay channel generation Doppler-shift addition UEC Tokyo Functional Block Configuration of Antenna-Branch-Controlled Scheme M L L L Walsh-Hadamard code weighting Fixed amplitude f Dl Delay t

13 Received Signal Channel Characteristics r( t) H( t, t) s( t) n( t) H( t, t ) A A RX ADoppler ( t) Hdelay( t ) Multipath Delay TX A TX w m w w w UEC Tokyo Channel Model Independent fluctuation for each input signal 2 w M T m wm 2 wml WH code Doppler shift Generation H delay A K ( k ) ( t ) A ( t t ) ( k) dalay k dalay diag ( k) c k k ( k) 2 c k ( k) L c k A RX u l u A u Doppler u2 u L T l ul 2 uln u ln e ( t) L diag jkd cos( l 0 ) n e e j2 fdt j2 fd2t j2 f e DL t f Dl v cos( l l ) Array antenna reception in the case of a linear array without antenna coupling 2

14 Amplitude 3 UEC Tokyo Probe antenna arrangement having all different Doppler-shift values Regular arrangement (Synmetric arrangement) Doppler-shift frequency (Hz)

15 Amplitude 4 UEC Tokyo Probe antenna arrangement having all different Doppler-shift values 2 Regular arrangement with fixed offset Doppler-shift frequency (Hz)

16 Amplitude 5 UEC Tokyo Probe antenna arrangement having all different Doppler-shift values 3 Proposed arrangement (double offset) Non symmetrical arrangement for any combination of two antennas Doppler-shift frequency (Hz)

17 UEC Tokyo Cumulative probability Amplitude CDF of Generated signal amplitude Theoretical (uniform) Regular position Fixed offset Proposed allocation Regular 2 Single offset 3 Double offset Cumulative probability Rayleigh L=8 L=8 l Doppler-shift Amplitude (db) 6

18 UEC Tokyo Eigenvalue characteristics of 4 x 4 MIMO in i.i.d. condition Cumulative probability M = N = 4 L = 6 Theoretical (iid) Generated ~ 4 : Eigenvalues of H AA where A is channel matrix Eigenvalue i 7

19 UEC Tokyo Weight Matrix (=Connection Matrix) for realizing independent fluctuations of all delayed paths Doppler-shifted fixed amplitude delay waves Independent Rayleigh fluctuations Input FE + Output 2 L W WH _ L W WH _ delay W WH _ TX Probe antenna weighting matrix Delay signal Tx-port signal (KMxKM) connection matrix (KxK) connection matrix (MxM) 8

20 UEC Tokyo Amplitude distribution of each generated delay paths #5 (0.2) Cumulative probability #6 (0.) #4 (0.4) #3 (0.6) #2 (0.8) # (.0) M = N = 2 L = Theoretical (iid) Generated Fig Amplitude (db) 9

21 UEC Tokyo Outline. Introduction: MIMO and MIMO-OTA 2. Channel Model for MIMO OTA Systems - Simplified Configuration - Channel Model 3. Two-Stage Scheme for MIMO Fading Emulator 4. Development of MIMO Fading Emulator using FPGA 5. Application Examples 6. Conclusion 20

22 2 When the chamber space is not sufficiently large to arrange the probe antennas in the chamber, and if the range in one direction is enough, then. UEC Tokyo For example, antenna array mounted in a car

23 22 UEC Tokyo Two-Stage Scheme MIMO Fading Emulator

24 UEC Tokyo Outline. Introduction: MIMO and MIMO-OTA 2. Channel Model for MIMO OTA Systems - Simplified Configuration - Channel Model 3. Two-Stage Scheme for MIMO Fading Emulator 4. Development of MIMO Fading Emulator using FPGA 5. Application Examples 6. Conclusion 23

25 UEC Tokyo Specification and Performance of Developed System based on Two-Stage Scheme FPGA IC XILINX Virtex 6 LX240T Baseboard XILINX ML605 Input/Output ADC 4DSP FMC04 (4bit) DAC 4DSP FMC204 (6bit) Input ports M 4 Output ports N 4 Signal processing Clock frequency f s 60MHz IF frequency 40MHz Bandwidth 40MHz (max) Propagation parameters Probe antennas L 6 or 32 Delay paths K 8 Maximum delay 50ms (for k=-6), 200ms (k=7,8) Delay resolution 6.25ns ( when f s =60MHz) Doppler frequency up to0khz 24

26 TX Connection Matrix Delay Connection Matrix for k-th delayed wave Amplitude of each probe antenna for k-th delayed wave Doppler shift addition RX Connection Matrix UEC Tokyo Input s(t) M(4) FPGA Implementation of 4x4 MIMO Fading Emulator Delay generation Delay Delay Delay t k k K k k l= l K k= + + l Hilbert Transformation l Output r(t) N(4) W TX Delay k L + L L (k ) wwh bk A Doppler A RX FPGA PC Parameters value setting 25

27 UEC Tokyo Developed MIMO Fading Emulator with FPGA Implementation All necessary functions to generate multipath environment is implemented in this small box. (Size: 28cm 22cm 5cm) 26

28 UEC Tokyo Element pattern pattern and corresponding Doppler spectrum v v 27

29 UEC Tokyo Outline. Introduction: MIMO and MIMO-OTA 2. Channel Model for MIMO OTA Systems - Simplified Configuration - Channel Model 3. Two-Stage Scheme for MIMO Fading Emulator 4. Development of MIMO Fading Emulator using FPGA 5. Application Examples 6. Conclusion 28

30 UEC Tokyo Application Example : WLAN (IEEE 802.n) Throughput Evaluation AP UE/UT データ 受信確認 WZR-AMPG300NH Intel Centrino Advanced-n

31 WLAN (AP) Down Conv. Down Conv. MIMO Fading Emulator (FPGA) Up Conv. Up Conv. UEC Tokyo Application Example : WLAN (IEEE 802.n) Throughput Evaluation [down link (40MHz)] (5GHz) (40MHz) (5GHz) Circulator Circulator WLAN (UE) Tx Data ATT ATT PC [up link (5GHz)] Channel-control signal Rx Data AP: BUFFALO WZR-AMPG300NH UE: Intel Centrino Advanced-N

32 3 UEC Tokyo Evaluation Examples Data rate Change ドップラーを変える the Doppler spread スループット 00Hz f D =0Hz Data rate スループット Change the Delay Difference 遅延量を変える ms t=200ns time 時間 time 時間 Change of Doppler spread Change of delay difference

33 ドップラーシフト [Hz] Throughput [bps] スループット [bps] UEC Tokyo Evaluation example in Rayleigh fading environment GI 遅延量

34 UEC Tokyo Application 2: Channel Capacity Evaluation in the case of Antenna Coupling and Spatial Correlation No.2 No. No.3 No.4 Sleeve antenna: 33mm (0.56) No. No.2 No.3 No.4 (a) d r = (/8) (b) d r = (3/2) 33

35 34 Element Antenna Pattern for N=4 [deg] UEC Tokyo d=(/8) d=(/2) Each element pattern without coupling

36 35 Developed MIMO Fading Emulator UEC Tokyo Multiple Input Multiple Output Multipath Multipath Genaration Part DUT A RX Measured Antenna Pattern data

37 36 UEC Tokyo MIMO Channel Capacity Decrease due to Antenna Coupling Experiment in RC using actual antenna Simulation using antenna pattern data i.i.d. (without SC and AC)

38 UEC Tokyo Conclusions We discussed a propagation channel model for OTA test systems. One of the primary practical advantages of the proposed scheme is the realization of a flexible MIMO OTA testing system in a very simplified configuration without the loss of necessary functions. Due to the way that the fading functions are configured in a cascade, an implementation of the scheme into FPGA circuit is promising from a practical viewpoint. We showed detailed performance of the FPGA-implemented fading emulator and a couple of applications of the system to wireless communication performance evaluations. 37

39 38 UEC Tokyo What I want to say is MIMO Fading Emulator/Simulator having all necessary propagation functions can be realized easily without expensive cost.

40 UEC Tokyo Thank you very much for your kind attention!!