IEEE 802.11-23/1980r1 Coordinated AP-assisted Medium Synchronization Recovery
This document from December 2023 discusses medium synchronization recovery leveraging multi-AP coordination for multi-link devices. It covers features such as Multi-link device (MLD), Multi-link operation (MLO), and Ultra High Reliability (UHR) capability defined in P802.11bn for improvements in rate-vs-range, latency, and power consumption for APs compared to P802.11be EHT MAC/PHY operation. The proposal focuses on assisting non-AP STAs affiliated with an MLD that has lost medium synchronization to transmit frames without collisions, enhancing channel access through multi-AP coordination.
- IEEE 802.11-23
- Medium Synchronization Recovery
- Multi-AP Coordination
- UHR Capability
- Wireless Networking
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December 2023 doc.: IEEE 802.11-23/1980r1 Coordinated AP-assisted Medium Synchronization Recovery Date: 2023-12-13 Authors: Name Affiliations Address Phone Email Jiayi Zhang jzhang@ofinno.com Leonardo Lanante Jeongki Kim Ofinno Reston, VA 20190 Serhat Erkucuk Tuncer Baykas Submission Slide 1 Jiayi Zhang, Ofinno
December 2023 doc.: IEEE 802.11-23/1980r1 Abstract Multi-link device (MLD) and multi-link operation (MLO) between two MLDs are key features supported in P802.11be Extremely High Throughput (EHT) [1]. In PAR of P802.11bn, the Ultra High Reliability (UHR) capability has been defined to improve Rate-vs-Range enhancement, reduce latency, and reduce power consumption for AP, compared to P802.11be EHT MAC/PHY operation [2]. Multi-AP operation (aka. Multi-AP coordination/transmission) has been discussed as one of the key candidate features to meet the requirement of UHR capability. For example, UHR enhanced channel access is considered for multi-AP coordination [3]. In this contribution, we propose medium synchronization recovery leveraging multi-AP coordination for multi-link devices (MLDs). Submission Slide 2 Jiayi Zhang, Ofinno
December 2023 doc.: IEEE 802.11-23/1980r1 Recap: AP-assisted medium synchronization recovery (1/2) [1] Non-simultaneous transmit and receive (NSTR) link pair A pair of links corresponding to STAs affiliated with an MLD for which receiver requirements are not met on one of the links when a STA affiliated with the MLD is transmitting on the other link. Each link of such a pair is a member of the NSTR link pair. A STA affiliated with a non-AP MLD that operates on an NSTR link pair is considered to have lost medium synchronization when another STA, affiliated with the same MLD and operating on the NSTR link pair, transmits a PPDU. AP-assisted medium synchronization recovery is a service provided by an AP MLD to assist a non-AP STA affiliated with a non-AP MLD that has lost medium synchronization to transmit a frame without causing a collision with another transmission. BA Link 1 AP 1 STA 1 Data with AAR Non-AP MLD AP MLD Trigger Link 2 AP 2 STA 2 Data MediumSyncDelay timer Trigger Link 3 AP 3 STA 3 Data MediumSyncDelay timer [1] Draft P802.11be D4.1 Jiayi Zhang, Ofinno Submission Slide 3
December 2023 doc.: IEEE 802.11-23/1980r1 AP-assisted medium synchronization recovery (2/2) AP MLD may suffer from OBSS interference on link 1 at the time of transmission by non-AP MLD of a data frame comprising an AP assisted request (AAR). AP 2 cannot transmit a trigger frame to non-AP MLD to assist STA 2 in recovering medium synchronization on link 2. STA 2 has to wait for the expiration of the MediumSyncDelay timer before it recovers medium synchronization and can transmit a frame via link 2 to AP 2. As such, traffic for transmission at STA 2 may be delayed. OBSS Interference BA Link 1 STA 1 AP 1 Data (AAR) MediumSyncDelay timer Non-AP MLD AP MLD Link 2 Trigger STA 2 AP 2 Data Submission Slide 4 Jiayi Zhang, Ofinno
December 2023 doc.: IEEE 802.11-23/1980r1 Coordinated AP Assisted Medium Synchronization Recovery - Solution 1 BA Link 1 AP MLD 2 can overhear transmissions from AP MLD 1 and non-AP MLD 1. STA 1-1 may transmit a data frame including AAR to AP 1-1 for AP MLD 1 for link 2. Since AP MLD 2 does not hear a BA frame from AP MLD 1, AP MLD 2 may transmit to AP MLD 1 (e.g., via link 2) a management frame (e.g., action frame) informing AP MLD 1 of the AAR included in the data frame. By receiving the management frame, AP 1-2 may transmit a trigger frame to STA 1-2, to recover the medium synchronization for STA 1-2. AP 1-1 OBSS Interference AP MLD 1 Trigger Link 2 AP 1-2 Link 1 AP 2-1 Data (AAR) AP MLD 2 Mgmt Link 2 AP 2-2 Data (AAR) Link 1 STA 1-1 MediumSyncDelay timer Non-AP MLD 1 Data Link 2 STA 1-2 Submission Slide 5 Jiayi Zhang, Ofinno
December 2023 doc.: IEEE 802.11-23/1980r1 Coordinated AP Assisted Medium Synchronization Recovery - Solution 2 AP MLD 2 can overhear transmissions from AP MLD 1 and non-AP MLD 1. STA 1-1 may transmit a data frame including AAR to AP 1-1 for AP MLD 1 for link 2. Since AP MLD 2 does not hear a BA frame from AP MLD 1, AP MLD 2 may transmit to non-AP MLD 1 (e.g., via link 2) a control frame (e.g., trigger frame) to recover the medium synchronization for STA 1-2. BA Link 1 AP 1-1 OBSS Interference AP MLD 1 Link 2 AP 1-2 Link 1 AP 2-1 Data (AAR) AP MLD 2 Control Link 2 AP 2-2 Data (AAR) Link 1 STA 1-1 MediumSyncDelay timer Non-AP MLD 1 Data Link 2 STA 1-2 Submission Slide 6 Jiayi Zhang, Ofinno
December 2023 doc.: IEEE 802.11-23/1980r1 Summary In this contribution, we proposed the methods of coordinated AP-assisted medium synchronization recovery for MLDs. Submission Slide 7 Jiayi Zhang, Ofinno
December 2023 doc.: IEEE 802.11-23/1980r1 References 1. 2. 3. IEEE P802.11be Draft 5.0 IEEE 802.11-23/0480r3, P802.11bn Project Authorization Request (Draft) IEEE 802.11-23/1973r0, Discussion on UHR enhanced channel access, 2023-11-04 Submission Slide 8 Jiayi Zhang, Ofinno
