1. 9.19.2.5 Comment Resolutions Date: 2011-07-06 Authors: February 2008
doc.: IEEE /2376r0
Date: July, 2011
Comment Resolutions
Date:
Authors:
Liwen Chu Etc.
Liwen Chu, STMicroelectronics

2. Comments Date: July, 2011 Comment Propose Change CID Clause Page Line
3746 84
49～50
One of the backoff condition is "c) The expected immediate response to the initial frame of a TXOP of that AC no received". This rule only consider initialize the TXOP by a SU frame. When initializing a TXOP by a MU frame, one more rule is need to clearify the backoff.
Refer to contribution "Backoff for MU-MIMO TXOP".
3752
42-65
There is no description on the case that one AC's transmission attempt collides internally with another EDCAF of an AC that has higher priority but it gains the TXOP sharing by the AC has higher priority. The state machine is not complete.
Add some description and make the state machine complete accordingly. Refer to contribution xxxx-xx-00ac-resolution-to-comments-xxx for a suggested change.
3793 11
This section is missing backoff procedures for secondary ACs. For example, what should a secondary AC adjust its CW and backoff timer when 1) its last PPDU has been sucessfully transmitted, 2) its transmission has failed, and 3) it is able to avoid an internal collision by MU-MIMI transmission.
Add defined backoff procedures for secondary ACs.
3406 42
According to the current backoff rule, a backoff procedure shall be invoked when an internal collision between ACs occurs. However, if those ACs share TXOP, it could be not reasonable to make the secondary AC backoff with increasing CW. Different backoff rule for TXOP sharing may be preferred.
Define a different backoff rule for internal collisions with TXOP sharing.
3421 2

3. PSMP TXOP Sharing VS DL MU-MIMO TXOP Sharing
Date: July, 2011
PSMP TXOP Sharing VS DL MU-MIMO TXOP Sharing
RA=STA1, ACVI
In a TXOP with PSMP, frames from multiple ACs can be transmitted.
802.11REVmb already defines backoff procedure of PSMP TXOP sharing.
In DL MU-MIMO TXOP sharing, frames from multiple ACs can be transmitted.
DL MU-MIMO TXOP sharing can use the current REVmb backoff procedure.
RA=STA2, ACVE
BlkAck
Req
BlkAck
Req
VHT AP
RA=STA3, ACVI
VHT STA1
BlkAck
VHT STA2
BlkAck
VHT STA3
BlkAck
PSMP
RA=STA1, ACVI
RA=STA2, ACVE
RA=STA3, ACVI
VHT AP
PSMP DTT1
PSMP DTT2
PSMP DTT3
VHT STA1
BlkAck
PSMP UTT1
VHT STA2
RA=AP, ACVE
PSMP UTT2
VHT STA3
RA=AP, ACVI
PSMP UTT3 3

4. PSMP Backoff and Retransmission
Date: July, 2011
PSMP Backoff and Retransmission
PSMP does not require backoff procedure change.
There is no new rules for internal collision even if PSMP TXOP supports TXOP sharing.
Whichever frame transmission fails, only the backoff parameters of the AC acquiring TXOP is influenced.
When the transmission of the TXOP is successful, only the backoff parameters of the AC that acquires the TXOP are adjusted.
The normal multiple frame transmission rules are used for PSMP.
The valid respond to the initial frame means that the TXOP holder can transmit multiple frames.
PIFS
PSMP
RA=STA1, ACVI
RA=STA2, ACVE
RA=STA3, ACVI
PSMP
VHT AP
PSMP DTT1
PSMP DTT2
PSMP DTT3
VHT STA1
BlkAck
PSMP UTT1
VHT STA2
RA=AP, ACVE
PSMP UTT2
VHT STA3
RA=AP, ACVI
PSMP UTT3
AC VI’s backoff timer counts to 0.
AC VE’s backoff parameters keep the same.
PSMP
RA=STA1, ACVI
RA=STA2, ACVE
VHT AP
PSMP DTT1
PSMP DTT2
The TXOP holder decides to do backoff
instead of PIFS recovery.
VHT STA1
BlkAck
PSMP UTT1
VHT STA2 4

5. DL MU-MIMO Backoff and Retransmission
Date: July, 2011
DL MU-MIMO Backoff and Retransmission
DL MU-MIMO does not require backoff procedure change.
This follows PSMP backoff rules.
Since the secondary AC may be any AC and the frames of the related AC may belong to STAs other than DL MU-MIMO destinations, internal collision resolution makes backoff complicated.
When the secondary ACs collide with the primary AC, REVmb’s rule is used for secondary ACs.
Whichever frame transmission fails or succeeds, only the backoff parameters of the AC acquiring TXOP is influenced.
The normal multiple frame transmission rules are used for DL MU-MIMO TXOP sharing.
The blockack of MU-MIMO PPDU without blockackReq is the valid respond to the initial frame.
The valid respond to the initial frame means that the TXOP holder can transmit multiple frames.
RA=STA1, ACVI
PIFS
RA=STA2, ACVE
BlkAck
Req
BlkAck
Req
BlkAck
Req
VHT AP
RA=STA3, ACVI
VHT STA1
BlkAck
VHT STA2
BlkAck
BlkAck
VHT STA3 5

6. Date: July, 2011
Proposed Resolution
Discussion:PSMP also allows (AC) TXOP sharing. PSMP does not require new backoff and TXOP acquiring rules. So the current backoff, TXOP obtaining rules can be used to DL MU-MIMO TXOP sharing without change.
Proposed resolution: Disagree 6

7. Date: July, 2011
Comments
CID
Clause
Page
Line
Comment
Propose Change
3794 84 65
Not sure whether this note is correct. It says "the backoff is a continuation of the TXOP, not the start of a new TXOP". I believe once a TXOP owner invokes backoff, it loses the ownership of the TXOP. So saying the backoff is a continuation of the TXOP may be inaccurate.
Don't see this sentence helpful. Maybe we can delete the note.
Discussion: This note is from the REVmb draft. The reason is to guarantee fairness among STAs. The commenter is encouraged to submit the comment to 11 REVmb.
Proposed resolution: Disagree 7

8. Date: July, 2011
Comments
CID
Clause
Page
Line
Comment
Propose Change
2888 85 30
Doesn't deleting the first sentence change the behaviour for 11n STAs?
Clarify
3379
Discussion: ac draft 1.0 adds the following sentence in section “All references to medium idle and medium busy within this subclause refer specifically to the medium condition on the primary channel”. This can cover the deleted 11n case and not change the behavior for 11n STAs.
Proposed resolution: Disagree 8