IEEE 802.11-19/1172r0 HARQ Procedures
Explore the IEEE 802.11-19/1172r0 document discussing Hybrid ARQ (HARQ) mechanisms, retransmission strategies, control information, and more. Learn about contention-based and scheduled retransmissions, control information transmission methods, and the considerations surrounding HARQ processes in wireless communication standards.
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July 2019 doc.: IEEE 802.11-19/1172r0 Discussion on HARQ Date: 2019-07-15 Authors: Name Affiliations Address Phone email Ruchen Duan Samsung r.duan@samsung.com Mostafa Ibrahim Samsung ms.ibrahim@samsung.com Wook Bong Lee Samsung wookong.lee@samsung.com Submission Slide 1 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 Introduction Hybrid ARQ (HARQ) exploits a retransmission and combination mechanism Receiver stores erroneously received packets Receiver combines the retransmitted signal with the stored signal The following topics are considered Retransmission scheduling Control information for HARQ procedures HARQ unit ACK/NACK Submission Slide 2 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 Retransmission We consider the following two retransmission strategies Contention based retransmission Back to back retransmission New transmission and retransmission in same TXOP Submission Slide 3 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 Contention Based Retransmission Perform contention before retransmission No changes to current IEEE 802.11 retransmission except combining transmissions Issues: Large number of HARQ processes are needed, e.g. HARQ process/memory per TID and per STA Backoff and contention ReTransmit n fail HARQ Units Transmitter Transmit N HARQ Units SIFS SIFS Receiver Block ACK Block ACK Submission Slide 4 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 Scheduled Retransmission Reserve TXOP including HARQ retransmission Smaller amount of memory is required. Fast retransmission is possible Issues: Number of HARQ retransmissions is limited to TXOP limit Can be inefficient when number of retransmissions is less than expected. Tx duration of T SIFS ReTransmit n fail HARQ Units Transmitter Transmit N HARQ Units Request tx duration of T SIFS SIFS Receiver Block ACK Block ACK Submission Slide 5 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 Control Information Two potential ways to carry HARQ control information PLCP header Data SIGs New MAC control frame MAC Control Frame HARQ PPDU HARQ control information Transmitter and receiver ID HARQ parameters Feedback related information (if needed) HARQ process ID (if needed) Submission Slide 6 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 HARQ Unit HARQ Unit: unit for retransmission Size of HARQ Unit can be varying to optimize resource utilization, overhead, etc. Option 1: HARQ unit contains one or more MPDU(s) ACK/NACK for each MPDU [or HARQ unit] Pros: no CRC needed per HARQ unit, reuse BA for feedback Cons: padding overhead MAC Packets MPDU 1 MPDU 2 MPDU 3 MPDU 4 MPDU 5 MPDU 6 MPDU 7 MPDU 8 MPDU 9 HARQ Unit HARQ Unit HARQ Unit PHY structure PLCP Header MPDU 1 MPDU 2 MPDU 3 MPDU 4 MPDU 5 MPDU 6 MPDU 7 MPDU 8 MPDU 9 Padding Submission Slide 7 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 HARQ Unit (Cont.) HARQ Unit: unit for retransmission Option 2: HARQ unit is not aligned with MPDU boundary ACK/NACK for each or group of HARQ unit(s) Pros: minimize padding overhead by using dynamic fragmentation Cons: need to store partially decoded MPDU that staggers over two HARQ units MAC Packets MPDU 1 MPDU 2 MPDU 3 MPDU 4 MPDU 5 MPDU 6 MPDU 7 MPDU 8 MPDU 9 HARQ Unit HARQ Unit HARQ Unit HARQ Unit PHY structure PLCP Header MPDU 1 MPDU 2 MPDU 3 MPDU 4 MPDU 5 MPDU 6 MPDU 7 MPDU 8 MPDU 9 Note that, we may consider fragmentation to eliminate padding issue for option 1 or partially decoded MPDU that staggers over two HARQ units for option 2. Submission Slide 8 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 ACK/NACK Channel Two potential ways to carry HARQ ACK/NACK information MAC BA: minimal design effort New PHY feedback: optimize overhead, e.g. omitting transmitter and receiver ID Submission Slide 9 Ruchen Duan, Samsung
July 2019 doc.: IEEE 802.11-19/1172r0 Summary Discussed about Retransmission scheduling HARQ control information and its exchange HARQ Unit for retransmission ACK/NACK channel Submission Slide 10 Ruchen Duan, Samsung
