1. Link Adaptation Subfield for VHT
May 2010
doc.: IEEE /0570r0
September 2010
Link Adaptation Subfield for VHT
Date:
Authors:
Matthew Fischer, Broadcom
Sameer Vermani, Qualcomm

2. Link Adaptation (LA) Subfield
September 2010
Link Adaptation (LA) Subfield
HTC field contains the Link Adaptation subfield
Link Adaptation field contains Training Request, MCS Feedback Request and MCS FB ID, and Antenna selection information
When used for MCS Feedback
Format of field fits n MCS values
Confusion when using Tgac MCS values
TGac proposes overloading MCS values
Inability to include Nsts value for Tgac
Proposed TGac MCS coding does not include streams
Matthew Fischer, Broadcom

3. Proposed Modification to LA Subfield
September 2010
Proposed Modification to LA Subfield
Need solution to allow differentiation between HT MCS and VHT MCS plus NSTS in MFB subfield
Propose to use Link Adaptation bit 0 which is currently reserved
LinkAdaptation[0] == 0 => MFB value is HT MCS
LinkAdaptation[0] == 1 => MFB value is VHT MCS (4bits) plus Nsts (3bits)
Matthew Fischer, Broadcom

4. New LA Subfield Current Link Adaptation subfield:
September 2010
New LA Subfield
Current Link Adaptation subfield:
Proposed Link Adaptation subfield: B0 B1 B2 B5 B6 B8 B9
B15
RESV
TRQ
MAI
MFSI
MFB/ASELC
Bits: 1 1 4 3 7 B0 B1 B2 B5 B6 B8 B9
B15
VHT_MFB
TRQ
MAI
MFSI
MFB/ASELC
Bits: 1 1 4 3 7
VHT_MCS
VHT_NSTS
When VHT_MFB=1 : 4 3
Matthew Fischer, Broadcom

5. September 2010
Strawpoll #1
Do you support a modification of the TGac specification framework document to indicate that the reserved bit 0 of the Link Adaptation Control subfield of the Link Adaptation subfield of the HT Control field is renamed to VHT_MFB and that a value of 1 for the VHT_MFB bit indicates that the value in the MFB subfield of the Link Adaptation Control subfield contains 4 bits of VHT MCS and 3 bits of NSTS, and a value of 0 for the VHT_MFB bit indicates that the value in the MFB subfield of the Link Adaptation Control subfield contains HT MCS feedback?
Matthew Fischer, Broadcom