doc.:IEEE /1568r1 Submission Nov Brian Hart, Cisco SystemsSlide 1 STA Antenna Indication in VHT Capabilities Date:

doc.:IEEE /1568r1 Submission Nov Executive Summary Situation  Via VHT Capabilities element, an AP can find out the minimum number of RX and TX antennas of a STA  A client might silently have additional antennas and use them for proprietary PHY processing Problem  AP cannot make optimal decisions with silent antennas  E.g. a client switches antennas after sounding and AP sees unexpectedly lower BFing performance, and could lead AP to sound a channel more often than needed Solution  We propose to redefine two reserved bits in “VHT Capabilities Info field” to provide indication of the possibility of antenna pattern change. Slide 2

doc.:IEEE /1568r1 Submission Nov Situation: A STA advertizes min capabilities only RX/TX MCS Map in VHT Supported MCS Set field in VHT Capabilities element lists the number of spatial streams and supported MCSs per SS So AP can infer the minimum number of RX and TX antennas Yet, there are many devices with more antennas than they indicate in their RX/TX MCS Map The additional antennas are usually used for various PHY processing to enhance PHY layer robustness by antenna diversity techniques ac forces a STA to remain silent about its additional antennas Slide 3

doc.:IEEE /1568r1 Submission Nov Problem: AP lacks info to make better decisions There are devices with more RX antennas that perform antenna switching Antenna switching causes the already sounded channel to be mostly useless for subsequent transmissions without AP knowing it, particularly for MU transmission Frequent antenna switching could appear as channel change due to mobility, leading AP to interpret the associated client as a mobile STA and to sound the channel more frequently than it’s needed Some STAs might switch RX antennas often, even per frame A STA after antenna switching usually stays on the selected antenna(s), causing its TX antenna pattern to change without AP knowing it This causes problem for the AP that performs advanced signal processing Slide 4

doc.:IEEE /1568r1 Submission Nov Solution: Allow STA to clarify its antenna capabilities 1 bit: “RX Antenna Pattern Consistency” in VHT Capabilities element Set to 0 if RX antenna pattern can change during association Set to 1 if RX antenna pattern remains fixed during association 1 bit: “TX Antenna Pattern Consistency” in VHT Capabilities element Set to 0 if TX antenna pattern can change during association Set to 1 if TX antenna pattern remains fixed during association Slide 5 B13 B15B16 B18B19B20B21B22B23 B25B26 B27B28B29B30-B31 Compressed Steering Number of BF Antennas Supported Number of Sounding Dimensions MU BFer Capable MU BFee Capable VHT TXOP PS +HTC-VHT Capable Max A- MPDU Length Exponent VHT Link Adaptation Capable RX Antenna Pattern Consistency TX Antenna Pattern Consistency Reserved Bits: