Performance of Smart Antennas and PCF 20 September 2018 vinayak.nandi@gmail.com Performance of Smart Antennas and PCF Vinayak Nandikal Courtesy: Nokia Research Center Vinayak Nandikal

20 September 2018 vinayak.nandi@gmail.com 20 September 2018 Introduction IEEE802.11 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 IEEE802.11 capacity without changing the existing PHYs Vinayak Nandikal Vinayak Nandikal

20 September 2018 vinayak.nandi@gmail.com 20 September 2018 What is a SMART Antenna? AP STA Antenna that adjusts its beam pattern based upon the channel and interference between AP and STA Vinayak Nandikal Vinayak Nandikal

Approach to Model Performance 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 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 Vinayak Nandikal Vinayak Nandikal

PHY Simulation Parameters 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 PHY Simulation Parameters Vinayak Nandikal Vinayak Nandikal

PHY Channel Sounder Approach 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 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. 39-44, 1999. Vinayak Nandikal Vinayak Nandikal

Smart Antenna Operation (5GHz) 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 Smart Antenna Operation (5GHz) RF A/D FFT Antenna Combining Weight Calculation Decoding STA OFDM Symbol Index Subcarrier Uplink Operation D/A RF IFFT Antenna Weighting Coding & Modulation STA Downlink Operation Vinayak Nandikal Vinayak Nandikal

20 September 2018 vinayak.nandi@gmail.com 20 September 2018 Channel Correlation 50 100 150 200 250 300 350 400 450 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1 time [ms] amplitude correlation coefficient average over TX positions Ruoholahti Heikkiläntie Airport Airport 2 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 Vinayak Nandikal Vinayak Nandikal

MAC Simulation Parameters 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 MAC Simulation Parameters Vinayak Nandikal Vinayak Nandikal

Traffic Model: All traffic measured in data-units/slot-time 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 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 Vinayak Nandikal Vinayak Nandikal

Traffic Model (cont.): Real-time traffic load = 20 September 2018 vinayak.nandi@gmail.com 20 September 2018 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 Vinayak Nandikal Vinayak Nandikal

Throughput & Latency Curves: Audio Packets 20 September 2018 Throughput & Latency Curves: Audio Packets Packets/Seconds Packets/Second Normalized Througput PCF Latencies 0.5 1 1.5 2 2.5 x 10 4 10 -4 -3 -2 -1 No SDMA 3-channel SDMA DCF:PCF = 1:1 Audio Packets 0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9 DCF:PCF = 1:1 Vinayak Nandikal

Throughput & Latency Curves: Audio Packets 20 September 2018 Throughput & Latency Curves: Audio Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies 1 2 3 4 x 10 10 -4 -3 -2 -1 No SDMA 3-channel SDMA DCF:PCF = 1:3 Audio Packets 0.5 1.5 2.5 3.5 0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9 Aduio Packets Vinayak Nandikal

Throughput & Latency Curves: Video Packets 20 September 2018 Throughput & Latency Curves: Video Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies 100 200 300 400 500 10 -4 -3 -2 -1 No SDMA 3-channel SDMA DCF:PCF = 1:1 Video Packets 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Vinayak Nandikal

Throughput & Latency Curves: Video Packets 20 September 2018 Throughput & Latency Curves: Video Packets Packets/Seconds Packets/Second Normalized Throughput PCF Latencies 200 400 600 800 10 -4 -3 -2 -1 No SDMA 3-channel SDMA DCF:PCF = 1:3 Video Packets 100 300 500 700 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Vinayak Nandikal

New Control Frame Subtypes for Smart Antennas 20 September 2018 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 TA FCS Message Fields Frame Control Vinayak Nandikal

Remove Polling Dependence 20 September 2018 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". Vinayak Nandikal

20 September 2018 vinayak.nandi@gmail.com 20 September 2018 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 Vinayak Nandikal Vinayak Nandikal