1. Comments Clarification on VHT Format HT Control Field
January 2010
2019/5/12June 2010
doc.: IEEE /0084r3
Comments Clarification on VHT Format HT Control Field
Date:
Authors:
Xie Gang, Cisco Systems
, Cisco Systems

2. 2019/5/12June 2010
doc.: IEEE /xxxxr0
Introduction
This presentation is comments clarification on VHT format HT Control field in Draft P802.11ac_D1.0.
Currently, the Subfield of “MRQ, Unsolicited MFB” and each meaning of subfield in table 8-ac1 cannot satisfy the VHT requirement, and we propose our revise advice.
And the MCS subfield in table 8-ac2 also exist this problem.
The N_STS and NSTS definition is not definite and we propose some revise advice.
Slide 2
Page 2
Xie Gang, Cisco Systems
Xie Gang, Cisco Systems

3. VHT format HT Control field Problem Statement
In VHT format HT Control field, MFB has four subfields (VHT N_STS, MCS, BW, SNR), so “MCS feedback” cannot represent the whole MFB meaning in VHT.
And MRQ has been used in IEEE n just meaning MCS request, but MCS in VHT is just one MFB subfield, so “MCS request” cannot represent the VHT MRQ meaning.
MRQ and MFB are used for VHT link adaptation. According to the context of the P802.11ac_D1.0 ( Link adaptation using…) , MRQ meaning is “MFB request”, so “MRQ meaning” in table 8-ac1 cannot satisfy the VHT requirement.
Slide 3

4. Recommend changes for VHT format HT Control field
we propose our revise advice:
The MRQ in table 8-ac1 should be changed into “VHT MRQ” and its meaning should be changed into “MFB request”.
The Unsolicited MFB’s meaning in table 8-ac1 should be changed into “Unsolicited MFB indicator”.
Table 8-ac1
Subfield
Meaning
Definition
VHT MRQ
MFB request
Set to 1 to request MCS feedback (solicited MFB), otherwise set to 0. …
Unsolicited MFB
Unsolicited MFB indicator
Set to 1 if the MFB is not a response to an MRQ.
Set to 0 if the MFB is a response to an MRQ.
Slide 4

5. Recommend changes for VHT format HT Control field
The meaning of MCS subfield in table 8-ac2 should be the Recommended MCS, not the Recommended MCS feedback, the word "feedback" is redundant.
we propose our revise advice:
The MCS meaning in table 8-ac2 should be changed into “Recommended MCS”.
Table 8-ac2
Subfield
Meaning
Definition
MCS
Recommended MCS
Indicates the recommended VHT MCS as defined in (Link adaptation using the VHT format of the HT Control field).
Slide 5

6. Recommend changes for N_STS and NSTS
NSTS is a parameter in 11ac, and N_STS is a subfield in table 8-ac1, which both means "Number of space time streams".
we propose our revise advice:
NSTS should be revised to N_STS in page 4 and should add a note for NSTS definition for its first time appearance.
3.3 Abbreviations and acronyms …
N_STS: Number of space time streams.
Subfield
Meaning
Definition …
VHT N_STS
Recommended VHT NSTS
Indicates the recommended VHT NSTS
as defined in (Link adaptation using the VHT format of the HT Control field).
Add a Note blow the table 8-ac2: NSTS : Number of space time streams.
Slide 6

7. Summary The problems are:
MRQ and Unsolicited MFB Subfield and their meaning in table 8-ac1 cannot satisfy the VHT requirement.
And the MCS subfield in table 8-ac2 also exist this problem.
The N_STS and NSTS definition is not definite
These slides provide solutions to the problems:
The MRQ in table 8-ac1 should be changed into “VHT MRQ” and its meaning should be changed into “MFB request”.
The Unsolicited MFB’s meaning in table 8-ac1 should be changed into “Unsolicited MFB indicator”.
The MCS meaning in table 8-ac2 is changed into “Recommended MCS”.
NSTS should be revised to N_STS in page 4 and should add a note for NSTS definition for its first time appearance
Slide 7

8. Reference
[1] IEEE P802.11ac/D1.0: Wireless Medium Access Control (MAC) and physical layer(PHY) specifications: Enhancements for Very High Throughput for Operation in Bands below 6 GHz, 2011.
[2] IEEE P802.11n: Wireless LAN Medium Access Control MAC) and Physical Layer (PHY) specifications: Enhancements for Higher Throughput, Oct
[3] ac-tgac-d0-1-comments
Slide 8