EP-4742809-A1 - METHOD AND APPARATUS FOR SHARING TXOP FOR C-TDMA OPERATION BY SWITCHING TXOP HOLDER IN MULTI-AP COMMUNICATION IN WIRELESS LAN SYSTEM

Abstract

Proposed are a method and apparatus for sharing a TXOP for a C-TDMA operation by switching a TXOP holder in multi-AP communication in a wireless LAN system. Specifically, a first AP receives an MU-RTS trigger frame from a second AP. The first AP transmits a CTS frame to the second AP. The first AP receives or senses a CF-End frame from the second AP. The first AP exchanges a first frame with a first non-AP when an SIFS or PIFS has elapsed after the CF-End frame is transmitted.

Inventors

• KIM, Geonhwan
• CHOI, JINSOO
• JANG, Insun
• BAEK, Sunhee
• YOON, Yelin
• CHA, Dongju

Assignees

• LG Electronics Inc.

Dates

Publication Date

20260513

Application Date

20240729

Claims (16)

1. A method in a wireless local area network (WLAN) system, the method comprising: receiving, by a first access point (AP), a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame from a second AP; transmitting, by the first AP, a Clear to Send (CTS) frame to the second AP; receiving or detecting, by the first AP, a Contention Free (CF)-End frame from the second AP; and exchanging, by the first AP, a first frame with a first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted, wherein the second AP is a Sharing AP that controls cooperation between multiple APs, wherein the first AP is a Shared AP that receives resources allocated or shared from the Sharing AP, and wherein the first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP.
2. The method of claim 1, wherein a first TXOP is switched to a second TXOP starting from transmission of the CF-End frame, and wherein the first TXOP is a TXOP acquired by the second AP, and the second TXOP is a TXOP acquired by the first AP.
3. The method of claim 2, wherein the CF-End frame includes the same BSS color, BSS Identifier (BSSID) or Receiver Address (RA) as the MU-RTS TXS trigger frame, wherein the first TXOP ends at a first time when the CF-End frame is transmitted, wherein the second AP exchanges a second frame with a second non-AP STA until the first time, and wherein the second non-AP STA is a non-AP STA within the BSS of the second AP.
4. The method of claim 3, further comprising: transmitting, by the first AP, a TXOP return sequence to the second AP after the exchange of the first frame is completed, wherein the second TXOP ends at a second time at which the TXOP return sequence is transmitted, and wherein the second time is determined based on a value of an Allocation Duration subfield of a User Info field of the MU-RTS TXS trigger frame.
5. The method of claim 4, wherein the second AP receives the TXOP return sequence and transmits a third frame to the second non-AP STA after SIFS or PIFS, wherein the second TXOP is switched to a third TXOP starting from transmission of the third frame, and wherein the third TXOP is a remaining TXOP that the second AP acquires again.
6. The method of claim 5, wherein the first frame includes a first trigger frame or a first control frame, wherein a Duration or ID field of the first trigger frame or the first control frame includes information on the second time, wherein the second frame includes a second trigger frame or a second control frame, wherein a Duration or ID field of the second trigger frame or the second control frame includes information on a third time, wherein the third frame includes a third trigger frame or a third control frame, wherein a Duration or ID field of the third trigger frame or the third control frame includes information on the third time, and wherein the third time is a time at which the third TXOP ends or a time at which an entire TXOP for the cooperation between the multiple APs ends.
7. A first access point (AP) in a wireless local area network (WLAN) system, the first AP comprising: a memory; a transceiver; and a processor being operatively connected to the memory and the transceiver, wherein the processor is configured to: receive a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame from a second AP; transmit a Clear to Send (CTS) frame to the second AP; receive or detect a Contention Free (CF)-End frame from the second AP; and exchange a first frame with a first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted, wherein the second AP is a Sharing AP that controls cooperation between multiple APs, wherein the first AP is a Shared AP that receives resources allocated or shared from the Sharing AP, and wherein the first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP.
8. A method in a wireless local area network (WLAN) system, the method comprising: transmitting, by a second access point (AP), a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame to a first AP; receiving, by the second AP, a Clear to Send (CTS) frame from the first AP; and transmitting, by the second AP, a Contention Free (CF)-End frame to the first AP, wherein a first frame is exchanged between the first AP and a first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted, wherein the second AP is a Sharing AP that controls cooperation between multiple APs, wherein the first AP is a Shared AP that receives resources allocated or shared from the Sharing AP, and wherein the first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP.
9. The method of claim 8, wherein a first TXOP is switched to a second TXOP starting from transmission of the CF-End frame, and wherein the first TXOP is a TXOP acquired by the second AP, and the second TXOP is a TXOP acquired by the first AP.
10. The method of claim 9, wherein the CF-End frame includes the same BSS color, BSS Identifier (BSSID) or Receiver Address (RA) as the MU-RTS TXS trigger frame, wherein the first TXOP ends at a first time when the CF-End frame is transmitted, wherein the second AP exchanges a second frame with a second non-AP STA until the first time, and wherein the second non-AP STA is a non-AP STA within the BSS of the second AP.
11. The method of claim 10, further comprising: receiving, by the second AP, a TXOP return sequence from the first AP after the exchange of the first frame is completed, wherein the second TXOP ends at a second time at which the TXOP return sequence is transmitted, and wherein the second time is determined based on a value of an Allocation Duration subfield of a User Info field of the MU-RTS TXS trigger frame.
12. The method of claim 11, wherein the second AP receives the TXOP return sequence and transmits a third frame to the second non-AP STA after SIFS or PIFS, wherein the second TXOP is switched to a third TXOP starting from transmission of the third frame, and wherein the third TXOP is a remaining TXOP that the second AP acquires again.
13. The method of claim 12, wherein the first frame includes a first trigger frame or a first control frame, wherein a Duration or ID field of the first trigger frame or the first control frame includes information on the second time, wherein the second frame includes a second trigger frame or a second control frame, wherein a Duration or ID field of the second trigger frame or the second control frame includes information on a third time, wherein the third frame includes a third trigger frame or a third control frame, wherein a Duration or ID field of the third trigger frame or the third control frame includes information on the third time, and wherein the third time is a time at which the third TXOP ends or a time at which an entire TXOP for the cooperation between the multiple APs ends.
14. A second access point (AP) in a wireless local area network (WLAN) system, the second AP comprising: a memory; a transceiver; and a processor being operatively connected to the memory and the transceiver, wherein the processor is configured to: transmit a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame to a first AP; receive a Clear to Send (CTS) frame from the first AP; and transmit a Contention Free (CF)-End frame to the first AP, wherein a first frame is exchanged between the first AP and the first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted, wherein the second AP is a Sharing AP that controls cooperation between multiple APs, wherein the first AP is a Shared AP that receives resources allocated or shared from the Sharing AP, and wherein the first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP.
15. A computer readable medium including an instruction being executed by at least one processor and performing a method comprising the steps of: receiving a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame from a second access point (AP); transmitting a Clear to Send (CTS) frame to the second AP; receiving or detecting a Contention Free (CF)-End frame from the second AP; and exchanging a first frame with a first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted, wherein the second AP is a Sharing AP that controls cooperation between multiple APs, wherein a first AP is a Shared AP that receives resources allocated or shared from the Sharing AP, and wherein the first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP.
16. A device in a wireless local area network (WLAN) system, the device comprising: a memory; and a processor being operatively connected to the memory, wherein the processor is configured to: receive a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame from a second access point (AP); transmit a Clear to Send (CTS) frame to the second AP; receive or detect a Contention Free (CF)-End frame from the second AP; and exchange a first frame with a first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted, wherein the second AP is a Sharing AP that controls cooperation between multiple APs, wherein a first AP is a Shared AP that receives resources allocated or shared from the Sharing AP, and wherein the first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP.

Description

TECHNICAL FIELD This specification relates to a technique for sharing a TXOP for C-TDMA operation by switching a TXOP holder in multi-AP communication in a wireless LAN system, and more specifically, to a method and device for switching the TXOP holder from SAP to DAP through a CF-End frame, thereby performing frame exchange with the DAP by a non-AP STA within a BSS of the DAP without being affected by a NAV of the SAP. BACKGROUND Next-generation Wi-Fi (e.g., IEEE 802.1 The and/or later) aims to support ultra-high reliability when transmitting signals to STAs. To achieve this, various technologies are being considered to support high throughput, low latency, and extended range. For example, multiple APs can cooperate to perform TXOP sharing procedures. DISCLOSURE TECHNICAL PROBLEM This specification proposes a method and device for sharing a TXOP for C-TDMA operation by switching a TXOP holder in multi-AP communication in a wireless LAN system. TECHNICAL SOLUTION An example of this specification proposes a method for sharing a TXOP for C-TDMA operation by switching a TXOP holder in multi-AP communication. This embodiment may be performed in a network environment that supports a next-generation wireless LAN system (Ultra High Reliability (UHR) wireless LAN system or next Wi-Fi). The next-generation wireless LAN system is an improved version of the 802.1 The system and can satisfy backward compatibility with the 802.1 The system. The present embodiment is performed in a first AP, the first AP may be set as a shared AP (DAP) after negotiation in multi-AP communication, and the second AP may be set as a sharing AP (SAP) after negotiation in the multi-AP communication. First and second non-AP STAs of the present embodiment may correspond to at least one station (STA). The present embodiment proposes a method for performing TXOP sharing by switching the TXOP holder when performing C-TDMA operation in multi-access point (multi-AP) communication (or multi-AP operation). In particular, the present embodiment proposes a method for performing frame exchange with the DAP without being affected by the NAV of the SAP by switching the TXOP holder from the SAP to the DAP through the CF-End frame. In addition, the present embodiment also proposes a method for utilizing the remaining TXOP by switching the TXOP holder from the DAP back to the SAP through the TXOP return sequence. A first access point (AP) receives a Multi User-Request to Send (MU-RTS) transmission opportunity (TXOP) sharing (TXS) trigger frame from a second AP. The first AP transmits a Clear to Send (CTS) frame to the second AP. The first AP receives or detects a Contention Free (CF)-End frame from the second AP. The first AP exchanges a first frame with a first non-AP station (STA) after SIFS (Short Inter Frame Space) or PIFS (PCF (Point Coordination Function) IFS) from a time the CF-End frame is transmitted. At this time, the second AP is a Sharing AP that controls cooperation between multiple APs, and the first AP is a Shared AP that receives resources allocated or shared from the Sharing AP. The first non-AP STA is a non-AP STA within a Basic Service Set (BSS) of the first AP. The technique for cooperation between the multiple APs may include a coordinated multi-AP technique such as Coordinated-Time Division Multiplexing Access (C-TDMA), Coordinated-Spatial Reuse (C-SR), Coordinated-beamforming (C-BF), or Coordinated-Orthogonal Frequency Division Multiple Access (C-OFMA). In an example of C-TDMA operation, the entity sharing the TXOP (SAP, here the second AP) and the entity receiving the TXOP (DAP, here the first AP) are APs with different BSSs. That is, because frame transmission within the BSS of the SAP may cause non-AP STAs within the BSS of the DAP to set the basic NAV and not be able to exchange frames smoothly with the DAP, protection rules related to Network Allocation Vector (NAV) settings must be precisely applied to ensure smooth cooperation between APs and frame exchange within each BSS. In particular, non-AP STAs connected to the DAP can receive/detect frames transmitted from the SAP or non-AP STAs connected to the SAP and CTS frames transmitted from the DAP and set the basic NAV for the SAP. At this time, a problem may occur in which non-AP STAs connected to the DAP cannot transmit UL PPDUs or frames to the DAP due to the basic NAV. This embodiment proposes a TXOP sharing method in a multi-AP cooperative environment, in which a TXOP holder is switched from a SAP to a DAP or back to a SAP and performs a C-TDMA procedure. Through the C-TDMA operation procedure proposed in this embodiment, a DAP and some non-AP STAs within the BSS of the DAP can exchange frames with the DAP without being affected by the NAV of the SAP. For example, when the associated non-AP STAs of the DAP receive a trigger frame to which a resource unit (RU) that enables transmission of a PPDU or frame is allocated from the DAP, the non-AP STAs can transmit the PPDU or frame