VHT Link Adaptations Date: 2011-1-18 Authors: Month Year Month Year doc.: IEEE 802.11-yy/xxxxr0 doc.: IEEE 802.11-yy/xxxxr0 VHT Link Adaptations Date: 2011-1-18 Authors: Page 1 John Doe, Some Company John Doe, Some Company

FLA Categories Solicited MFB Unsolicited MFB MRQ with NDP Sounding that requests beamforming/MU FB, MFB sent with sounding FB frame. MRQ that is not tied up with beamforming exchange, MFB sent in regular uplink frame. Unsolicited MFB Unsolicited MFB with Sounding FB. Unsolicited MFB sent in regular uplink frame.

Solicited Link Adaptation in 11n MRQ shall be sent in HTC along with sounding (see 9.18.2). +HTC MRQ=1 NDPA NDP MFB MRQ is sent with sounding, so that the Rx can fully derive MIMO channel est and compute appropriate Mod/rate/Nss. Slide 3

Difference in 11ac NDPA+NDP sequence is tied up with SU-BF or MU-MIMO sounding. Refer to NDPA frame definition Therefore it is not possible to send a VHT MRQ in NDPA that only requests MFB and not request BF feedback. i.e. MRQ in NDPA has to be tied up with BF. Note that MRQ in NDPA means MFB has to be measured based on NDP.

MCS versus SNR FB It is arguable whether the Rx or Tx should compute the MCS. Tx needs to offset its power difference on sending different MCSs, the Rx does not know the Tx power control. Rx does not know whether Tx will apply optional PHY modes such as STBC, LDPC, TxBF, or other proprietary technology. Desirable to feedback both MCS and SNR. SNR is defined as 8bit 2’s complement number, averaged over all the tones and all the space-time streams Represent [-10, 53]dB, same as SNR report in Compressed V FB (11n, 11ac)

Solicited/Unsolicited Example of VHTC Format Details refer to [1]. B0 B1 B2 B3-B5 B6-B8 B9-B11 B12-B15 B16-B23 HT/VHT Solicited/Unsolicited MRQ MSI MFSI/GID-L Nsts MCS SNR 1 4 3 8 B24-B26 B27 B28 B29 B30 B31 GID-H Coding Type FB TX Type Reserved AC Constraint RDG/More PPDU 3 1

Link Adaptation with SU BF We already have rule on MFB in SU BF feedback frame: MFB+SNR assumes the same CV will be applied, and Nsts=Nc. Need a rule for responding MRQ with NDPA. Proposal: if the MRQ is in NDPA that requests SUBF feedback, BFMee SHALL include the MFB only in SU-BF feedback. Reason: SU-BF FB already has SNR and Nsts ready, it is just one step from computing MCS, easy to implement. Delayed MFB in this case will complicate the situation. MRQ NDPA NDP MFB+SNR SUBF FB Slide 7

Pre-Motion 1 Do you agree to add the following sentence in spec frame work 6.x VHT Link Adaptation MRQ in VHT Control Field could be sent with any frame (i.e. not only with NDPA). Yes No Abstain

Pre-Motion 2 Do you agree to add the following sentence in spec frame work 6.x VHT Link Adaptation An SNR Feedback field is included in VHT Control Field, which is defined as 8bit 2’s complement number, averaged over all the tones and all the space-time streams. Yes No Abstain

Pre-Motion 3 Do you agree to add the following sentence in spec frame work 6.x VHT Link Adaptation If the MFB requester sends MRQ in an VHT NDP announcement frame requesting only SU-BF Feedbacks, then the MFB responder shall include the corresponding MFB and SNR feedback in the VHT Compressed Beamforming frame that is the response of the same NDP-A and NDP sequence. Yes No Abstain

References [1] 11-11-0040-00-00ac-VHT-Control-and-Link-Adaptation.pptx