US-12628227-B2 - Method and apparatus for using AAR to support EMLSR operation

US12628227B2US 12628227 B2US12628227 B2US 12628227B2US-12628227-B2

Abstract

Methods and apparatuses for facilitating recovery from loss of medium synchronization for multi-link devices (MLDs) and renegotiating traffic identifier (TID)-to-link mapping for enhanced multi-link single radio (EMLSR) operation of MLDs in a wireless local area network. A non-access point (AP) MLD comprises STAs, each comprising a transceiver configured to form a link with a corresponding AP of an AP MLD, and a processor operably coupled to the STAs. A subset of the links are EMLSR links that are configured to operate in an EMLSR mode of operation. The processor is configured to generate, based on a determination that an EMLSR frame exchange sequence is occurring on a first one of the EMLSR links, a request for AP-assisted medium synchronization recovery (AAR) for a set of the other EMLSR links. At least one of the transceivers is further configured to transmit, to the AP MLD, the request for AAR.

Inventors

Vishnu Vardhan Ratnam
Peshal Nayak
Boon Loong Ng
Rubayet Shafin
Ahmed Atef Ibrahim Ibrahim

Assignees

SAMSUNG ELECTRONICS CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20220923

Claims (14)

1 . A non-access point (AP) multi-link device (MLD), comprising: stations (STAs), each comprising a transceiver configured to form a link with a corresponding AP of an AP MLD, wherein at least a subset of the links are enhanced multi-link single radio (EMLSR) links that are configured to operate in an EMLSR mode of operation; and a processor operably coupled to the STAs, the processor configured to generate, based on a determination that an EMLSR frame exchange sequence is occurring on a first one of the EMLSR links, a request for AP-assisted medium synchronization recovery (AAR) for a set of the other EMLSR links, wherein: at least one of the transceivers is further configured to transmit, to the AP MLD, the request for AAR over the first EMLSR link within a frame of the EMLSR frame exchange sequence, and the processor is further configured to generate the request for AAR as an AAR Control subfield in a frame of the EMLSR frame exchange sequence, the AAR Control subfield including: an Assisted AP Link ID bitmap that indicates each EMLSR link of the set of other EMLSR links for which AAR is requested, and a prioritized access bit that indicates that the request for AAR is either: a request for trigger-based uplink assistance from the AP MLD on one of the EMLSR links indicated in the Assisted AP Link ID bitmap; or a request for one of the EMLSR links indicated in the Assisted AP Link ID bitmap to be prioritized by the AP MLD for a next EMLSR frame exchange sequence.
2 . The non-AP MLD of claim 1 , wherein: at least one of the transceivers is further configured to receive, from the AP MLD after the EMLSR frame exchange sequence has ended, a trigger frame over a second EMLSR link, which is one of the set of other EMLSR links for which AAR is requested, and the trigger frame solicits an uplink frame from the STA that corresponds to the second EMLSR link.
3 . The non-AP MLD of claim 1 , wherein: at least one of the transceivers is further configured to receive, from the AP MLD after the EMLSR frame exchange sequence has ended, an initial control frame over a second EMLSR link, which is one of the set of other EMLSR links for which AAR is requested, and the initial control frame initiates a next downlink EMLSR frame exchange sequence on the second EMLSR link with the STA that corresponds to the second EMLSR link.
4 . The non-AP MLD of claim 1 , wherein: the processor is further configured to identify, in the request for AAR, the set of other EMLSR links for which AAR is requested.
5 . The non-AP MLD of claim 1 , wherein: the processor is further configured to include, in the request for AAR, an indication that the request for AAR is either: a request for trigger-based uplink assistance from the AP MLD on one of the set of other EMLSR links, or a request for one of the set of other EMLSR links to be prioritized by the AP MLD for a next downlink EMLSR frame exchange sequence.
6 . An access point (AP) multi-link device (MLD), comprising: APs, each comprising a transceiver configured to form a link with a corresponding station (STA) of a non-AP MLD, wherein: at least a subset of the links are enhanced multi-link single radio (EMLSR) links that are configured to operate in an EMLSR mode of operation, and at least one of the transceivers is further configured to receive, from the non-AP MLD, a request for AP-assisted medium synchronization recovery (AAR) over a first EMLSR link within a frame of an EMLSR frame exchange sequence; and a processor operably coupled to the APs, the processor configured to determine that the request for AAR is a request to perform, after an EMLSR frame exchange sequence on a first one of the EMLSR links has ended, AAR for a set of the EMLSR links, wherein: the request for AAR is an AAR Control subfield in a frame of the EMLSR frame exchange sequence, the AAR Control subfield including: an Assisted AP Link ID bitmap that indicates each EMLSR link of the set of other EMLSR links for which AAR is requested, and a prioritized access bit that indicates that the request for AAR is either: a request for trigger-based uplink assistance from the AP MLD on one of the EMLSR links indicated in the Assisted AP Link ID bitmap; or a request for one of the EMLSR links indicated in the Assisted AP Link ID bitmap to be prioritized by the AP MLD for a next EMLSR frame exchange sequence.
7 . The AP MLD of claim 6 , wherein: at least one of the transceivers is further configured to transmit, to the non-AP MLD after the EMLSR frame exchange sequence has ended, a trigger frame over a second EMLSR link, which is one of the set of other EMLSR links for which AAR is requested, and the trigger frame solicits an uplink frame from the STA that corresponds to the second EMLSR link.
8 . The AP MLD of claim 6 , wherein: at least one of the transceivers is further configured to transmit, to the non-AP MLD after the EMLSR frame exchange sequence has ended, an initial control frame over a second EMLSR link, which is one of the set of other EMLSR links for which AAR is requested, and the initial control frame initiates a next downlink EMLSR frame exchange sequence on the second EMLSR link with the STA that corresponds to the second EMLSR link.
9 . The AP MLD of claim 6 , wherein: the processor is further configured to determine, from the request for AAR, the set of other EMLSR links for which AAR is requested.
10 . The AP MLD of claim 6 , wherein: the processor is further configured to determine, from an indication in the request for AAR, that the request for AAR is either: a request for trigger-based uplink assistance from the AP MLD on one of the set of other EMLSR links, or a request for one of the set of other EMLSR links to be prioritized by the AP MLD for a next downlink EMLSR frame exchange sequence.
11 . A method of wireless communication performed by a non-access point (AP) multi-link device (MLD), the method comprising: generating, based on a determination that an EMLSR frame exchange sequence is occurring on a first one of enhanced multi-link single radio (EMLSR) links, a request for AP-assisted medium synchronization recovery (AAR) for a set of the other EMLSR links, wherein the non-AP MLD comprises stations (STAs) that each comprise a transceiver configured to form a link with a corresponding AP of an AP MLD and wherein at least a subset of the links are the EMLSR links that are configured to operate in an EMLSR mode of operation; and transmitting, to the AP MLD, the request for AAR over the first EMLSR link within a frame of the EMLSR frame exchange sequence; wherein: the request for AAR is an AAR Control subfield in a frame of the EMLSR frame exchange sequence, the AAR Control subfield including: an Assisted AP Link ID bitmap that indicates each EMLSR link of the set of other EMLSR links for which AAR is requested, and a prioritized access bit that indicates that the request for AAR is either: a request for trigger-based uplink assistance from the AP MLD on one of the EMLSR links indicated in the Assisted AP Link ID bitmap; or a request for one of the EMLSR links indicated in the Assisted AP Link ID bitmap to be prioritized by the AP MLD for a next EMLSR frame exchange sequence.
12 . The method of claim 11 , further comprising: receiving, from the AP MLD after the EMLSR frame exchange sequence has ended, a trigger frame over a second EMLSR link, which is one of the set of other EMLSR links for which AAR is requested, wherein the trigger frame solicits an uplink frame from the STA that corresponds to the second EMLSR link.
13 . The method of claim 11 , further comprising: receiving, from the AP MLD after the EMLSR frame exchange sequence has ended, an initial control frame over a second EMLSR link, which is one of the set of other EMLSR links for which AAR is requested, wherein the initial control frame initiates a next downlink EMLSR frame exchange sequence on the second EMLSR link with the STA that corresponds to the second EMLSR link.
14 . The method of claim 11 , further comprising identifying, in the request for AAR, the set of other EMLSR links for which AAR is requested.

Description

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63/253,656 filed on Oct. 8, 2021, and U.S. Provisional Patent Application No. 63/277,952 filed on Nov. 10, 2021, which are hereby incorporated by reference in their entirety. TECHNICAL FIELD This disclosure relates generally to transmission efficiency in wireless communications systems that include multi-link devices. Embodiments of this disclosure relate to methods and apparatuses for improving the speed of medium synchronization recovery for links in a multi-link device in a wireless local area network communications system. Embodiments of this disclosure further relate to methods and apparatuses for ensuring that traffic identifiers are mapped to appropriate links in a multi-link device in a wireless local area network communications system. BACKGROUND Wireless local area network (WLAN) technology allows devices to access the internet in the 2.4 GHz, 5 GHz, 6 GHz, or 60 GHz frequency bands. WLANs are based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standards. The IEEE 802.11 family of standards aim to increase speed and reliability and to extend the operating range of wireless networks. Multi-link operation (MLO) is a key feature for next generation extremely high throughput (EHT) WI-FI systems, e.g., IEEE 802.11be. The WI-FI devices that support MLO are referred to as multi-link devices (MLDs). With MLO, it is possible for a non-access point (non-AP) MLD to discover, authenticate, associate, and set up multiple links with an AP MLD. Channel access and frame exchange is possible on each link that is set up between the AP MLD and non-AP MLD. The component of an MLD that is responsible for transmission and reception on one link is referred to as a station (STA). In several embodiments of non-AP MLDs, transmission on one of the links can cause limitations or impairments on the STAs of the non-AP MLD operating other links. For example, in one class of non-AP MLDs, a pair of links can form a non-simultaneous transmit and receive (NSTR) pair. In an NSTR pair of links, transmission on one link by a STA of the non-AP MLD can cause a very high self-interference at the STA of the non-AP MLD operating on the other link of the NSTR pair. Thus, during a transmission on one link by a non-AP MLD, the STA on the other link may be incapable of sensing the channel occupancy and its network allocation vector (NAV) timer may become outdated, causing a loss of medium synchronization. To prevent a loss of medium synchronization from affecting other transmissions in the network, a medium synchronization recovery procedure is defined in IEEE 802.11be which shall be followed by a STA that has lost medium synchronization after it is able to reliably sense the channel again, e.g., in the case of a STA operating on a link of an NSTR link pair, after the transmission from the other STA of the NSTR link pair has ended. In essence, the medium synchronization recovery procedure involves the affected STA initializing a timer called a MediumSyncDelay timer and pursuing a more conservative channel access procedure until either the expiration of the timer or recovery of medium synchronization, whichever occurs earlier. This conservative approach of initiating a transmit opportunity (TXOP) by the non-AP STA when its MediumSyncDelay>0 involves transmission of a request-to-send (RTS) as the first frame to gain TXOP, not attempting more than MSD_TXOP_MAX TXOPs (default 1) and using CCA_ED threshold equal to dot11MSDOFDMEDthreshold (default −72 dBm). The conservative channel access procedure for a STA of a non-AP MLD during MediumSyncDelay>0 can be inefficient and can cause degradation in the system throughput. This is especially true since such loss of medium synchronization may happen frequently in NSTR devices. It may also be unnecessary in lightly loaded scenarios where such conservative access is not required. Thus, to improve performance, an AP-assisted mechanism for medium synchronization recovery has been defined for NSTR scenarios called AP-assisted recovery (AAR). A non-AP STA affiliated with a non-AP MLD that supports AAR and that is performing a frame exchange with an associated AP affiliated with an AP MLD can include a frame in the frame exchange that signals the AP MLD to transmit a Trigger frame to another non-AP STA affiliated with the non-AP MLD in order to solicit an uplink (UL) physical protocol data unit (PPDU) from the other non-AP STA, thereby assisting the other non-AP STA to quickly gain access to the channel. An MLD may also serve several different types of traffic categories, each being identified by a traffic identifier (TID) and having a different requirement on throughput, latency, etc. For prioritization of channel access to different TIDs on the different links, and to limit contention, the AP MLD and non-AP MLD may also negoti