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Re: [STDS-802-11-TGAC] IEEE 802.11ac telecon



Hi Matt,

My opinion is that there is no need to add so much new text/figure to describe the MU BA procedure. In fact the text you propose is essentially reiterating on mechanisms described somewhere else, so it is not adding much new information. 

The figure referred by the comment was there to illustrate the TXOP sharing concept, not the BA procedure; why not remove the BAs from that figure instead?    

Regarding the text you propose:
 
These two paragraphs could be OK as a clarification note placed somewhere

	"The acknowledgement procedure performed by a STA that receives MPDUs that were transmitted within an MU PPDU is the same as the acknowledgement procedure for 	MPDUs that were not transmitted within an MU PPDU.
	NOTE - All MPDUs transmitted within an MU PPDU are contained within A-MPDUs and the rules specified in 8.6.3 (A-MPDU contents) ensure that there is no more than one 	immediate response required for an A-MPDU, and further indicate that there can only be one immediate response to an MU PPDU."


But this one does not tell much, and may generate further comments  (e.g. the ones from Mark, below...)

	"Responses to A-MPDUs within an MU PPDU that are not immediate responses to the MU PPDU are transmitted in response to explicit BlockAckRequest frames by the STA 	transmitting the MU PPDU.
		--> no new info. how else could it happen? Also, does response indicate immediate response? What about delayed BA? 
	
	"An MU PPDU frame exchange sequence is shown in Figure 9-9a (The MU PPDU acknowledgement procedure)"
		--> I foresee additional comments regarding this figure in later drafts

	Recovery within the TXOP can be performed 	according to the rules of 9.19.2.4 (Multiple frame transmission in an EDCA TXOP). BlockAckRequest frames can be transmitted in a TXOP separate from the one 	that contained the MU PPDU.
		--> no new info 

Simone

-----Original Message-----
From: *** 802.11 TGac - VHT below 6GHz*** [mailto:STDS-802-11-TGAC@xxxxxxxx] On Behalf Of Mark Rison
Sent: Wednesday, August 29, 2012 10:27 AM
To: STDS-802-11-TGAC@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-11-TGAC] IEEE 802.11ac telecon

I will not be able to attend, but assuming 1021r3 will be presented, I have the following comments thereon:

- I think "ensure that there is no more than one immediate response
  required for an A-MPDU" in the first NOTE is a statement of the
  blindingly obvious, and should be deleted.  I also think "indicate"
  should be changed to "ensure".  The NOTE should read simply "NOTE---
  All MPDUs transmitted within an MU PPDU are contained within A-MPDUs
  and the rules specified in 8.6.3 (A-MPDU contents) ensure that there
  can only be one immediate response to an MU PPDU."

- The figure should show BA/ACK rather than just BA in the green boxes
  (for the reasons given in NOTE 1).  The last of the three figures
  shown (page 5) is correct.

- The NOTE 1 should just be a NOTE (since there's only one of them).

- "BAR frames" should be "BlockAckReq frames" (twice).

- "STA transmitting the MU PPDU" should be changed to "AP" (to match
  the figure).

- "HT-delayed BlockAck" should be "HT-delayed Block Ack" (it's not the
  frame, it's the behaviour).

- I think the baseline mostly calls for a "frame" after "A BlockAck or
  an ACK" and "No BlockAckRequest".

- The case where none of the A-MPDUs in the MU PPDU requires immediate
  acknowledgement is not covered.  What happens in this case?  Does a
  BAR follow the MU PPDU after SIFS?

- I'm guessing the "should" in the "No BlockAckRequest should be sent
  to a STA in the case where the A-MPDU to that STA contained no MPDUs
  requiring acknowledgement." is to cover the case where although the
  A-MPDU did not have any MPDUs requiring ack, the AP wants to get a
  BA for some MPDUs sent earlier which do require ack.  But this is
  not clear and should be spelt out (perhaps another NOTE?).

Mark, who hadn't realised MU ack was such a can of worms!

-- 
Mark RISON, Systems Architect, Wi-Fi    English/Esperanto/Francais
CSR, Cambridge Business Park            Tel: +44 1223  692000
Cowley Road, Cambridge CB4 0WZ          Fax: +44 1223  692001
ROYAUME UNI                             WWW: http://www.csr.com

> -----Original Message-----
> From: *** 802.11 TGac - VHT below 6GHz*** 
> [mailto:STDS-802-11-TGAC@xxxxxxxx] On Behalf Of Osama AboulMagd
> Sent: 28 August 2012 13:04
> To: STDS-802-11-TGAC@xxxxxxxxxxxxxxxxx
> Subject: Re: [STDS-802-11-TGAC] IEEE 802.11ac telecon
> 
> Hello All,
> 
> There is a TGac conference call scheduled for Thursday, August 30 at 
> 20:00 ET. Please let me know if you plan a presentation.
> 
> Dial in information is available below.
> 
> The latest revision of LB188 Comment spread sheet is available at:
> https://mentor.ieee.org/802.11/dcn/12/11-12-0752-08-00ac-lb188-comment
> s-tgac-d3-0.xls 
> <https://mentor.ieee.org/802.11/dcn/12/11-12-0752-08-00ac-lb188-commen
> ts-tgac-d3-0.xls>
> 
> Teleconferences are bound by the conditions stipulated by the 
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> Regards;
> Osama.
> 
> 
> 
> -----Original Appointment-----
> From: Brian Hart (brianh) [mailto:brianh@xxxxxxxxx]
> Sent: Monday, July 23, 2012 12:15 PM
> To: Brian Hart (brianh); Reza Hedayat (rehedaya); Perahia, Eldad; 
> Osama AboulMagd; Stephens, Adrian P
> Cc: Luoyi (Roy); auyehara@xxxxxxxxxxx; Daniel Camps Mur; 
> mesem@xxxxxxxxxxxx
> Subject: IEEE 802.11ac telecon
> When: Thursday, August 30, 2012 8:00 PM-10:00 PM (UTC-05:00) Eastern Time (US & Canada).
> Where: Webex
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> 
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