doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 1 Performance of Smart Antennas and PCF Ari Alastalo, Steven Gray and Venkatesh Vadde Nokia Research Center

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 2 Introduction IEEE will be an important method for providing high rate low mobility data services While existing capacity may seem high, particularly for IEEE802.11a, the enterprise environment may experience capacity limits Antenna technologies offer a means to boast IEEE capacity without changing the existing PHYs

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 3 What is a SMART Antenna? AP STA Antenna that adjusts its beam pattern based upon the channel and interference between AP and STA

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 4 Approach to Model Performance Measure channel using a channel sounder to determine –Multipath power profile as a function of time –Signal-to-interference ratio Simulate PHY to obtain PER information as a function of channel measurements and the number of packets delivered as a function of time Use PER, number of packets delivered by the PHY as a function of time and models of real-time traffic to examine delay and throughput using a PHY with and without smart antennas PCF is used for delivery of audio and video packets

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 5 PHY Simulation Parameters

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 6 PHY Channel Sounder Approach 127 chip pn sequence is transmitted at 5.3 GHz with a bandpass bandwidth of 30 MHz A 32 element array with 0.5 wavelength space is used to downconvert the transmitted pn sequence Snap shots of the delay spread are written to memory and stored on a hard disk For further information see: Jarmo Kivinen, Timo O. Korhonen, Pauli Aikio, Ralf Gruber, Pertti Vainikainen, and Sven-Gustav Häggman, IEEE Transactions on Instrumentation and Measurement, vol. 48, no. 1, pp , 1999.

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 7 Smart Antenna Operation (5GHz) RFA/D FFT RFA/D FFT RFA/D FFT Antenna Combining Weight Calculation Decoding STA OFDM Symbol Index Subcarrier D/A RF D/A RF D/A RF IFFT Antenna Weighting Coding & Modulation STA Uplink Operation Downlink Operation

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 8 Channel Correlation The figure to the right shows the correlation coefficient for different measurement environments For smart antenna operation, the AP needs the ability to probe the channel between any STA and AP Note: Ruholahti and Heikkiläntie are Nokia office buildings

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 9 MAC Simulation Parameters

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 10 Traffic Model: All traffic measured in data-units/slot-time –1 data-unit takes 1 slot-time for transmission –Max traffic in network = 1.0 Audio and video traffic originates from “calls” made by the user Calls are Poisson distributed; once placed, each call generates periodic packet traffic Mean inter-call-arrival-time controls load on the network

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 11 Traffic Model (cont.): Real-time traffic load = apkt_sz: audio packet size vpkt_sz: video packet size int_call_arvl_time: mean intercall arrival time (8:1 ratio between audio and video calls) int_apkt_arvl_time, int_vpkt_arvl_time: arrival time between audio packets and video packets respectively acalls, vcalls: number of audio anc video calls respectively

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 12 Throughput & Latency Curves: Audio Packets Packets/Seconds Packets/Second Normalized Througput PCF Latencies x No SDMA 3-channel SDMA DCF:PCF = 1:1 Audio Packets x No SDMA 3-channel SDMA DCF:PCF = 1:1 Audio Packets

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 13 Throughput & Latency Curves: Audio Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies x No SDMA 3-channel SDMA DCF:PCF = 1:3 Audio Packets x No SDMA 3-channel SDMA DCF:PCF = 1:3 Aduio Packets

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 14 Throughput & Latency Curves: Video Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies No SDMA 3-channel SDMA DCF:PCF = 1:1 Video Packets No SDMA 3-channel SDMA DCF:PCF = 1:1 Video Packets

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 15 Throughput & Latency Curves: Video Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies No SDMA 3-channel SDMA DCF:PCF = 1:3 Video Packets No SDMA 3-channel SDMA DCF:PCF = 1:3 Video Packets

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 16 New Control Frame Subtypes for Smart Antennas AP to STA –A message requesting the STA to transmit a preamble (null frame) for channel estimation –Channel Id Request STA to AP –A response to the above request –Channel Id Response Duration RA TAFCS Message Fields Frame Control

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 17 Remove Polling Dependence The existing standards reads, "During each CFP, the PC shall issue polls to a subset of the STAs on the polling list in order by ascending AID value".

doc.: IEEE /269 Submission September 2000 Steven Gray, NokiaSlide 18 Conclusions Particularly in a large enterprise environment, smart antennas can help boast capacity –Wireless office replacement for "wired" Ethernet –Public service networks such as airports Changes to the existing MAC are minor to enable antenna technologies in IEEE802.11a networks SDMA is not for all WLANS –Multiple antennas cost additional money for the AP that may not be required in homes and small businesses