doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 1 On The Use Of Multiple Antennae For Monisha Ghosh, Xuemei Ouyang, Guido Dolmans Philips Research.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 2 Goal Of Next Generation WLANS? Increased robustness. (-> fewer errors -> less retransmission -> higher throughput) Increased data rate in terms of raw Mbps. Backward compatibility through headers.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 3 Exploiting Channel Diversity Frequency diversity: Bit interleaved coded modulation. Space diversity: Multiple antennae. Question: In an indoor situation, is there sufficient diversity among closely spaced antennae? Answer: Preliminary measurements in 5 gHz indicate that there is.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 4 Channel Measurements At 5gHz

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 5 Multiple Antennae Well studied topic for the last few years. OFDM is very well suited for use with multiple antennae. ( has an optional mode using multiple antennae.) Many (all?) receivers already have 2 antennae, using switched diversity. Additional component required for exploiting full diversity is an additional RF front-end. Recent advances in RF technology will make this cost effective in the near future.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 6 Higher (> 100 Mbps) Data Rate Options For Larger Constellation: 54Mbps already uses 64 QAM. Can a wireless system support a larger constellation? Turbo-coding: Requires at least 3 or 4 iterations for good performance. Double bandwidth: Inefficient use of bandwidth. Multiple antenna: Cost is in the additional antenna and RF front end, the DSP does not add much complexity to existing receivers.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 7 Possible Configurations For 2x2 system 1 Tx/2 Rx: same data rate, increased robustness, backward compatible. 2 Tx/1 Rx, space-time coded (e.g. Alamouti): same data rate, increased robustness, backward compatiblity through header. 2 Tx/2Rx, space-time coded: same data rate, increased robustness, backward compatibility through header. 2 Tx/2 Rx, MIMO: Increased data rate and robustness.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 8 1 Tx, 2 Rx System Performance

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 9 2 Tx, 1 Rx System Performance

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 10 2 Antennae At AP

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 11 2 Tx/2 Rx MIMO Performance

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 12 2 Antennae At AP, 1 Antenna At Mobile Use transmit diversity from AP to mobile: would require a change to allow for Alamouti encoding. Gives 2 to 4 dB gain over 1 Tx/1 Rx. Use receive diversity for mobile to AP. Gives 4 to 6 dB over 1 Tx/1 Rx. Simple way to increase robustness for all mobiles by the addition of a single extra antenna and RF unit at the AP.

doc.: IEEE /180r0 Submission March 2002 Monisha Ghosh, et al., Philips Slide 13 Conclusions A simple 2 x 2 antennae system can improve both robustness and bit-rate. Various options possible, depending on level of complexity desired. Backward compatibility easily maintained through header.