Proposal for Enhancing A-MPDU Coexistence Feedback in IEEE 802.11-24
This proposal suggests a mechanism to address coexistence issues during A-MPDU reception in IEEE 802.11-24 networks. It aims to improve feedback for A-MPDU reception, enabling differentiation between channel errors and failures caused by interference. By enhancing the BlockAck frame, this solution provides new information to help originators handle coex and channel issues effectively.
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April 2025 doc.: IEEE 802.11-24/0002r1 A-MPDU Coexistence Feedback Date: 2025-04-15 Authors: Name Michail KOUNDOURAKIS Ian HUNTER Affiliations Samsung Cambridge Solution Centre Samsung Cambridge Solution Centre Samsung Cambridge Solution Centre Device Solutions Research America, Samsung Semiconductor Address SJH, CB4 0DS, U.K. Phone +44 1223 434600 email m.koundou@partner.sams ung.com i.hunter@samsung.com SJH, CB4 0DS, U.K. +44 1223 434600 at samsung (a global commercial entity) I'm the letter emme then dot rison srini.k1@samsung.com Mark RISON SJH, CB4 0DS, U.K. +44 1223 434600 Srini KANDALA 3655 N 1st St, San Jose, California, USA +1 408 5444000 Submission Slide 1 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Abstract This submission proposes a mechanism to mitigate problems with coex during A-MPDU reception Multi-STA BA enhanced in TGbn, to provide feedback in ICR frame This proposal enables use of Multi-STA BA in place of BA, to provide rich A-MPDU RX feedback to the AP This proposal enables an AP to differentiate between real channel errors and failures caused by IDC (at the non-AP STA) Submission Slide 2 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Problem A STA might be unable to receive an MPDU in an A-MPDU because of coex issues If the recipient STA does not ack MPDUs for this reason, the originating STA will typically assume a channel problem and reduce the rate for subsequent transmissions This worsens the problem, since the consequent increased PPDU duration increases the likelihood of coex collision In the worst case, the rate is reduced so much that even a single MPDU does not fit between consecutive coex events; as a result data flow stops and the link is dropped Submission Slide 3 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Solution Enable the BlockAck frame(s) to carry new information, to help the originator distinguish between coex issues and channel issues Coex issues might include hidden node issues, if these can be identified Specifically, return (feed back to the A-MPDU originator) 1. The number of bad A-MPDU subframe headers / bad MPDU FCSes received Not caused by Coex Can t be a perfect count of missed MPDUs, since if A-MPDU subframe header is corrupted resync to next header is not guaranteed Not counting when didn t even try to receive, due to coex issues 2. The cumulative away time during the PPDU (caused by Coex) Submission Slide 4 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Possible originator behaviour If the originator had many MPDUs unacknowledged: If the recipient only reported a few bad MPDUs/subframes and a significant cumulative away time, the originator could surmise the recipient was just away due to coex issues for the unacked MPDUs, and use this as a hint notto change the rate If the recipient reported many bad MPDUs/subframes, the originator could surmise bad radio conditions, and use this as a hint to rate-adapt If the recipient only reported a few bad MPDUs/subframes and a zero or small cumulative away time, or there was no BA, the originator could surmise really bad radio conditions, and use this as a hint to rate-adapt Submission Slide 5 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 AP cannot differentiate errors using only the BlockAck feedback Case 1: ALL errors caused by Coex. Correct AP action: No TX PHY rate change 24/0414 in use: DL A-MPDU ... MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU AP IDC event (DL PPDU cannot be partially RXd) BA Non-AP STA In all 3 cases: Internal (in device) Error Occurred bit is 1 X usec Case 2: Some errors caused by Coex. Some errors caused by Channel errors. Correct AP action: Consider TX PHY rate change DL A-MPDU ... MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU AP IDC event (DL PPDU cannot be partially RXd) BA Non-AP STA Problem: AP might ignore real channel errors Question: How can AP Link Adaptation work? AP knows 6 MPDUs are successfully RXd. Internal (in device) Error Occurred bit is 1 X usec Case 3: A few MPDUs failed due to Coex. Most errors were caused by Channel errors. Correct AP action: Change TX PHY rate DL A-MPDU ... MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU AP IDC event (DL PPDU cannot be partially RXd) BA Non-AP STA AP knows 5 MPDUs are successfully RXd. Internal (in device) Error Occurred bit is 1 Y usec Submission Slide 6 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 AP gets rich feedback, so it can take correct action Case 1: ALL errors caused by Coex. Correct AP action: No TX PHY rate change This proposal: DL A-MPDU ... MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU AP Multi- STA BA IDC event (DL PPDU cannot be partially RXd) Non-AP STA Provide: bad A-MPDU subframe headers / bad MPDU FCSes Unavailability duration AP knows 10 MPDUs are successfully RXd. Some MPDUs failed due to Coex (duration) Bad MPDU count = 0 Unavailability Duration = X X usec ... Case 2: Some errors caused by Coex. Some errors caused by Channel errors. Correct AP action: Consider TX PHY rate change DL A-MPDU ... MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU AP Multi- STA BA IDC event (DL PPDU cannot be partially RXd) Non-AP STA AP knows 6 MPDUs are successfully RXd. Some MPDUs failed due to Coex (duration) 4 MPDUs failed due to channel errors Bad MPDU count = 4 Unavailability Duration = X X usec ... Case 3: A few MPDUs failed due to Coex. Most errors caused by Channel errors. Correct AP action: Change TX PHY rate DL A-MPDU ... MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU MPDU AP Multi- STA BA IDC event (DL PPDU cannot be partially RXd) Non-AP STA Bad MPDU count = 9 Unavailability Duration = Y Y usec ... Submission Slide 7 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Multi-STA BlockAck Proposed changes: Multi-STA BA as a response frame to DL A- MPDU - from non-AP STA to AP Additional BA information field added to provide new information/ feedback: Bad MPDU count = bad A-MPDU subframe headers / bad MPDU FCSes Unavailability duration = time away from DL A-MPDU RX DL A-MPDU AP Multi- STA BA IDC event (DL PPDU cannot be partially RXd) Non-AP STA X ms BA FC S MAC header contro l BA information BA information B1 1 B1 1 B0 B0 AID TID Info BA SSC BlockAck Bitmap AID TID Info BA SSC BlockAck Bitmap Bad MPDU count Unavailability Duration Fragment Number Feedback Type New TID value to indicate to-AP (or can re-use value from MAP Coordination AID TID Reserved Length and Type of Feedback (e.g. RX feedback) New TID value to indicate special Feedback format Submission Slide 8 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Changes required in the TGbn D0.x 1. Allow Multi-STA BA as response frame to DL A-MPDU (it is already allowed as a control response frame) 2. Add a new Feedback Type value in the Multi-STA BA to allow Multi- STA BA to carry RX (DL A-MPDU) feedback information Submission Slide 9 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 Straw poll Do you support to define a Multi-STA BlockAck variant that a non-AP STA can use as a response frame to a DL A-MPDU, in order to provide information on bad MPDUs/subframes and cumulative away time for previous PPDU, so that the AP originator can try to distinguish coex issues from channel issues? Y N A Submission Slide 10 Michail Koundourakis, Samsung
April 2025 doc.: IEEE 802.11-24/0002r1 References 11-24-1247-00 icf-icr-design-for-coex 11-25-0063-00 indication-of-the-unavailability-information-for-idc 11-24-0414 Improving acknowledgment mechanisms Submission Slide 11 Michail Koundourakis, Samsung
