On The Use Of Reed Solomon Codes For 802.11n Jan 2004 On The Use Of Reed Solomon Codes For 802.11n Xuemei Ouyang, Monisha Ghosh Philips Research. Pen C. Li Philips Semiconductors Monisha Ghosh, et al., Philips

Past History with RS codes Jan 2004 Past History with RS codes Performance was evaluated only for AWGN channel: gain was about 2 dB at PER of 10% Protection only on MPDU, PHY header becomes the weakest point RS codes were proposed for 802.11e, in the MAC layer, with no interleaving among codewords. Was discarded, since the gains were not considered substantial enough, and wouldn’t help the robustness of the link Monisha Ghosh, et al., Philips

Performance of RS(220,200) In AWGN Jan 2004 Performance of RS(220,200) In AWGN 14 15 16 17 18 19 20 10 -2 -1 64QAM, 0.8us GI, 128 FFT, 40MHz Ch, RS(220,200), 3/4 CC SNR (Es/No) dB PER without RS with RS Monisha Ghosh, et al., Philips

RS Codes and MIMO The question of RS codes needs to be revisited. Jan 2004 RS Codes and MIMO The question of RS codes needs to be revisited. Channel model is no longer AWGN. Can use RS codes in the PHY layer now, and hence some interleaving is possible Question: What kind of performance gains are possible in a MIMO channel with multipath Rayleigh fading? Answer:Substantial gains in 20ns and 50 ns channels, not so much in flat fading, as expected. Monisha Ghosh, et al., Philips

Simulation Parameters For MIMO Jan 2004 Simulation Parameters For MIMO 2 X 2 MIMO, 64 QAM, ¾ CC, 64 FFT, 0.8 ms guard interval. 1000 data byte packets, RS(220,200) over GF(256): 5 RS codewords per packet. Channel model: uncorrelated channels, exponential Rayleigh fading on each channel. Data rate with RS coding: 98 Mbps (108 Mbps without RS). Receiver: weighted zero-forcing. Monisha Ghosh, et al., Philips

RS Performance For 2X2 MIMO Jan 2004 RS Performance For 2X2 MIMO Monisha Ghosh, et al., Philips

Simulation Parameters For 40 Mhz Jan 2004 Simulation Parameters For 40 Mhz 64 QAM, ¾ CC, 128 FFT, 108 data carriers, 0.4 ms guard interval. 1000 data byte packets, RS(220,200) over GF(256): 5 RS codewords per packet. Channel model: exponential Rayleigh fading. Data rate with RS coding: 123Mbps (135 Mbps without RS). Receiver: weighted zero-forcing. Monisha Ghosh, et al., Philips

RS Performance In 40Mhz channel Jan 2004 RS Performance In 40Mhz channel Monisha Ghosh, et al., Philips

Jan 2004 Conclusions RS codes can give substantial performance improvement, especially at low PERs, for both MIMO and double-bandwidth systems. Interleaving among codewords can give an additional 1-1.5 dB gain. The overhead penalty (~10%) can be made up by increasing the symbol length and/or reducing the guard interval. Reducing the guard interval to 0.4 ms did not have any adverse performance effect with upto 50 ns delay spreads channels. Monisha Ghosh, et al., Philips