1. Philips Research 11-02-708r0-WNG 1 / 23 IEEE 802.11 session Hawaii November 2002 Alexei Gorokhov, Paul Mattheijssen, Manel Collados, Bertrand Vandewiele, Gunnar Wetzker Philips Research PHY options for high throughput wireless LANs Right time and place for MIMO? Performance enhancement via antenna selection Experimental set-up and channel measurements MIMO architectures for high data rates Experimental results

2. Philips Research 11-02-708r0-WNG 2 / 23 Requirements  Higher data rates (> 100Mbps)  Increased throughput  Extended range  Better coverage  Higher network capacity Possible solutions  Increase bandwidth per link  Higher order modulation  More powerful CODEC  TX / RX diversity  MIMO

3. Philips Research 11-02-708r0-WNG 3 / 23 Requirements Possible solutions  Increase bandwidth per link  Higher order modulation  More powerful CODEC  TX / RX diversity  MIMO  Currently  12 channels 2 x rate  6 channels

4. Philips Research 11-02-708r0-WNG 4 / 23 Requirements Possible solutions  Increase bandwidth per link  Higher order modulation  More powerful CODEC  TX / RX diversity  MIMO  Over 64-QAM: severe requirements to analogue & mixed signal circuits

5. Philips Research 11-02-708r0-WNG 5 / 23 Requirements Possible solutions  Increase bandwidth per link  Higher order modulation  More powerful CODEC  TX / RX diversity  MIMO  Higher complexity: power & area  Iterative demodulation with “anti-Gray” maps  Turbo coded CODEC

6. Philips Research 11-02-708r0-WNG 6 / 23 Possible solutions  Increase bandwidth per link  Higher order modulation  More powerful CODEC  TX / RX diversity  MIMO Requirements

7. Philips Research 11-02-708r0-WNG 7 / 23 Requirements Higher data rates (> 100Mbps) Higher data rates (> 100Mbps) Increased throughput Increased throughput Extended range Extended range Better coverage Better coverage  Higher network capacity Possible solutions  Increase bandwidth per link  Higher order modulation  More powerful CODEC  TX / RX diversity  MIMO

8. Philips Research 11-02-708r0-WNG 8 / 23 TX RX Theoretical throughput scales linearly w.r.t. the # of antennas: Increased range / coverage in NLOS environments Cheap RF-CMOS technology: fractional cost per RF front-end (5.x GHz)  Keep DSP complexity limited Motivation Constraint

9. Philips Research 11-02-708r0-WNG 9 / 23 TX RX  Need for extra degrees of freedom at RX to ensure enough diversity ( )  High incremental cost of adding RF front-end versus the cost of antenna  Use antennas and front-ends at RX, select adaptively a subset of antennas, select out of antennas  optimal selection is rather complex simple sub-optimal selection possible

10. Philips Research 11-02-708r0-WNG 10 / 23 Receiver Transmitter 4 TX chains 4 RX chains f ~ 5.8GHz BW 20MHz 14 bit ADC 35 dB AGC

11. Philips Research 11-02-708r0-WNG 11 / 23 DAC/ADC LNA mixer AGC+LPF Monopoles

12. Philips Research 11-02-708r0-WNG 12 / 23 1 23456789101112  “soft” walls, much glass  few heavy metallic constructions  lots of furniture  few concrete walls / blocks Total TX power 14dBm

13. Philips Research 11-02-708r0-WNG 13 / 23 RMS delay spread versus range Signal-to-noise ratio per RX antenna versus range

14. Philips Research 11-02-708r0-WNG 14 / 23 FEC encoder interleaver mapper IFFT cyclic extension pulse shaping FEC encoder interleaver mapper IFFT cyclic extension pulse shaping FEC encoder FFT sampling pulse shaping FEC encoder FFT sampling pulse shaping MUX DEMUX stream cycling MMSE filter MRC + + interleaver mapper FEC encoder - - latency of ~ one TX/RX cycle deinterleave demap TX signal path RX signal path deinterleave demap

15. Philips Research 11-02-708r0-WNG 15 / 23 space frequency interleaver mapper IFFT cyclic extension pulse shaping FEC decoder FFT sampling pulse shaping FFT sampling pulse shaping FEC encoder mapper IFFT cyclic extension pulse shaping space frequency de- interleaver 2 x 2 MMSE filter TX signal path RX signal path demapper

16. Philips Research 11-02-708r0-WNG 16 / 23 Outage capacities versus range outage rate 1% optimal RX antenna selection S-F modulation / layered RX MIMO channel

17. Philips Research 11-02-708r0-WNG 17 / 23 Outage capacities versus range outage rate 1% optimal RX antenna selection S-F interleaving / MMSE MIMO channel

18. Philips Research 11-02-708r0-WNG 18 / 23 Outage capacities versus range outage rate 1% optimal RX antenna selection S-F interleaving / MMSE S-F modulation / layered RX

19. Philips Research 11-02-708r0-WNG 19 / 23 MIMO capacities MIMO capacity scales almost linearly w.r.t. the number of TX/RX antennas space-frequency modulation with layered RX : ~90% of theoretical limit space-frequency interleaving with MMSE: ~60% of theoretical limit …………… with adaptive RX selection: ~80% of theoretical limit Feasibility aspects  channel processing beyond 2 x 2 system is hardly feasible (baseband)  layered reception yields higher complexity & processing latency, seems prohibitive beyond 2 x 2 systems  sub-optimal RX antenna selection looks attractive

20. Philips Research 11-02-708r0-WNG 20 / 23 Outage capacities versus range outage rate 1%  S-F modulation with MMSE receiver & sub-optimal RX selection looks attractive S-F modulation / layered RX S-F interleaving / MMSE

21. Philips Research 11-02-708r0-WNG 21 / 23 Candidate FEC structures  Standard convolutional code rate (1/2) 64-state (NASA) code [133,171] 8 puncture to achieve mandatory / supplementary rate modes soft-input Viterbi decoding at RX easy to implement, IEEE 802.11 acceptance  expected to be sensitive to SINR discrepancy  Turbo- CODEC similar to that of UMTS rate (1/3) PCCC with 8-state components [13,15] 8 puncture to achieve desired rates iterative SISO decoding (Max-Log-MAP) reduced SINR margin, less sensitive to SINR discrepancy  rather high complexity

22. Philips Research 11-02-708r0-WNG 22 / 23 108Mbps  64QAM, rate 3/4 96Mbps  64QAM, rate 2/3 72Mbps  16QAM, rate 3/4 64Mbps  16QAM, rate 2/3 36Mbps  16QAM, rate 3/4 32Mbps  QPSK, rate 2/3 24Mbps  QPSK, rate 1/2 Signalling

23. Philips Research 11-02-708r0-WNG 23 / 23 Observations  Maximum data rate scales linearly w.r.t. to the number of antennas  Receive antenna selection improves substantially maximum data rates (limited number of TX/RX chains)  2 x 2 space division multiplexing with selection 2 of 4 RX antennas  200%-300% of single-antenna rates