IEEE 802.11-19/1459r0: Applicability of HARQ Operation to A-MPDU
In this document, the applicability of Hybrid Automatic Repeat reQuest (HARQ) operation to Aggregate MAC Protocol Data Unit (A-MPDU) is discussed for improving link throughput by minimizing MAC-level retransmission. The concept of HARQ Applicable A-MPDU and its benefits are detailed along with examples of MPDU groups within an A-MPDU.
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September 2019 doc.: IEEE 802.11-19/1459r0 HARQ Applicable A-MPDU Date: 2019-09-14 Authors: Name Lei Huang Company Address Phone Email lei.huang@sg.panasonic.com Panasonic Corporation Yanyi Ding Rojan Chitrakar Yoshio Urabe Submission Slide 1 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Background Many contributions have discussed how HARQ operation is applied to A-MPDU [1]-[3]. Codeword level HARQ operation may be a natural choice for 11be [1]. In this contribution, we like to discuss the applicability of HARQ operation to A-MPDU and introduce a new terminology called HARQ Applicable A-MPDU. We then discuss codeword level HARQ feedback for HARQ applicable A-MPDU. Submission Slide 2 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Recap: A-MPDU Format A-MPDU pre-EOF padding A-MPDU subframe 1 A-MPDU subframe 2 ... A-MPDU subframe n EOF Padding MPDU delimiter MPDU Padding Octets: 4 variable 0 - 3 MPDU Length Delimiter Signature EOF Reserved CRC Bits: 1 1 14 8 8 A-MPDU pre-EOF padding includes any A-MPDU subframes with 0 in the MPDU Length field and 0 in the EOF field inserted in order to meet the minimum MPDU start spacing requirement. Rules for MPDU ordering in an A-MPDU: if an Ack, Compressed BlockAck or Multi-STA BlockAck frame is present in an A-MPDU, it shall be the first MPDU in the A-MPDU. if one or more Trigger frame is present in an A-MPDU, the one or more Trigger frame is the first MPDU of the A-MPDU unless the A-MPDU also carries an Ack, Compressed BlockAck or Multi-STA BlockAck frame in which case the one or more Trigger frame is included immediately after the Ack, Compressed BlockAck or Multi-STA BlockAck frame. Submission Slide 3 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Applicability of HARQ Operation to A-MPDU The purpose of applying HARQ operation to A-MPDU is to improve link throughput by minimizing MAC-level retransmission. When an A-MPDU does not include any MPDU that solicits acknowledgement, no MAC-level retransmission is required for the A-MPDU. In this case, it does not make sense to apply HARQ operation to the A-MPDU. Proposal: HARQ operation shall be disabled for an A-MPDU that is not a HARQ applicable A-MPDU, e.g. an A-MPDU that is transmitted in the Control Response context. HARQ Applicable A-MPDU is an A-MPDU containing at least one MPDU that solicits acknowledgement, e.g. ack-enabled A-MPDU non-ack-enabled multi-TID A-MPDU ack-enabled multi-TID A-MPDU Submission Slide 4 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 HARQ Applicable A-MPDU In a HARQ Applicable A-MPDU, one or more MPDUs may not solicit acknowledgement. A HARQ Applicable A-MPDU may comprise two MPDU groups: MPDU group 1 comprises MPDU(s) that do not solicit acknowledgement MPDU group 2 comprises MPDU(s) that solicit acknowledgement Example HARQ Applicable A-MPDU MPDU group 1 MPDU group 2 ack-enabled A-MPDU zero or one Ack, Compressed BlockAck or Multi-STA BlockAck frame; zero or more Action No Ack frames; zero or more QoS Null frames with No Ack ack policy or Trigger frames. one QoS Data frame with Normal Ack or HTP Ack ack policy or Management frame that solicits an immediate response. Submission Slide 5 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Codeword Level HARQ Feedback Group 1 MPDUs do not require MAC level retransmissions and thus it is meaningless to apply codeword level retransmissions to Group 1 MPDUs. Proposal: HARQ feedback is not required for codewords that do not correspond to group 2 MPDUs. Pros: HARQ feedback overhead may be reduced. Cons: MAC needs to inform PHY the boundary between group 1 MPDUs and group 2 MPDUs. Group 1 MPDU Group 2 MPDU HARQ Applicable A-MPDU (e.g. ack-enabled A-MPDU) MPDU #1 MPDU #2 MPDU #3 MPDU #4 HARQ feedback is not required CW#1 CW#2 CW#3 CW#4 CW#5 CW#6 CW#7 CW#8 CW#9 CW#10 CW#11 CW#12 CW#13 CW#14 Submission Slide 6 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Summary A new terminology HARQ Applicable A-MPDU is introduced. It is proposed that HARQ operation shall be disabled for an A-MPDU that is not a HARQ Applicable A-MPDU. It is also proposed that HARQ feedback is not required for codewords not corresponding to MPDUs that solicit acknowledgement in a HARQ Applicable A-MPDU. Submission Slide 7 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Reference 1) 2) 3) IEEE 802.11-19/0873r1, HARQ Framing, July 2019 IEEE 802.11-19/1038r1, HARQ with A-MPDU, July 2019 IEEE 802.11-19/1131r0, Consideration on HARQ Unit, July 2019 Submission Slide 8 Lei Huang (Panasonic)
September 2019 doc.: IEEE 802.11-19/1459r0 Straw Poll Do you support that HARQ operation shall be disabled for an A- MPDU that is not a HARQ Applicable A-MPDU? Note: HARQ Applicable A-MPDU is an A-MPDU containing at least one MPDU that solicits acknowledgement. Yes: No: Abstain: Submission Slide 9 Lei Huang (Panasonic)
