WO2025188161A1 - Method and apparatus for negotiating coordinated service period between access points in wireless lan system - Google Patents

Abstract

Disclosed are a method and an apparatus for negotiating a coordinated service period between access points in a wireless LAN system. The method according to an embodiment of the present disclosure may comprise the steps of: transmitting a first frame including a first target wake time (TWT) element to a second AP by a first access point (AP); and receiving a second frame from the second AP in response to the first frame by the first AP. The first TWT element may include a control field and a first broadcast TWT parameter set field. The control field may include a negotiation type field. The negotiation type field may have a value set to be associated with the first broadcast TWT parameter set. The first broadcast TWT parameter set field may include one or more pieces of scheduling-related information. Each of the one or more pieces of scheduling-related information may be set to have a value based on the reference timing of the second AP.

Description

Method and device for negotiating the cooperation service period between access points in a wireless LAN system

The present disclosure relates to a method and device for negotiating a coordinated service period between access points in a wireless local area network (WLAN) system.

New technologies have been introduced for wireless local area networks (WLANs) to improve transmission rates, increase bandwidth, enhance reliability, reduce errors, and reduce latency. Among WLAN technologies, the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards can be referred to as Wi-Fi. For example, recently introduced technologies for WLANs include enhancements for Very High Throughput (VHT) in the 802.11ac standard and enhancements for High Efficiency (HE) in the IEEE 802.11ax standard.

To provide a more advanced wireless communication environment, improved technologies for Extremely High Throughput (EHT) are being discussed. For example, technologies for Multiple Input Multiple Output (MIMO), which supports increased bandwidth, efficient utilization of multiple bands, and increased spatial streams, and for coordination of multiple access points (APs), are being studied. In particular, various technologies are being studied to support low latency or real-time traffic. Furthermore, new technologies are being discussed to support ultra-high reliability (UHR), including improvements or extensions of EHT technology.

The technical problem of the present disclosure is to provide a method and device for negotiating a cooperation service period between access points in a wireless local area network (WLAN) system.

The technical problem of the present disclosure is to provide a signaling method and device between access points in a procedure for negotiating a cooperation service period between access points in a wireless LAN system.

The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

A method according to one aspect of the present disclosure may include: transmitting, by a first access point (AP), a first frame including a first target wake time element (TWT) element to a second AP; and receiving, by the first AP, a second frame from the second AP in response to the first frame. The first TWT element includes a control field and a first broadcast TWT parameter set field, wherein the control field includes a negotiation type field, and a value of the negotiation type field may be set to a value associated with the first broadcast TWT parameter set. The first broadcast TWT parameter set field includes one or more scheduling-related information, and each of the one or more scheduling-related information may be set to a value based on a reference timing of the second AP.

A method according to an additional aspect of the present disclosure may include receiving, by a second access point (AP), a first frame from a first AP, the first frame including a first target wake time element (TWT element); and transmitting, by the second AP, a second frame to the first AP in response to the first frame. The first TWT element includes a control field and a first broadcast TWT parameter set field, the control field including a negotiation type field, and a value of the negotiation type field may be set to a value associated with the first broadcast TWT parameter set. The first broadcast TWT parameter set field includes one or more scheduling-related information, and each of the one or more scheduling-related information may be set to a value based on a reference timing of the second AP.

According to the present disclosure, a signaling method and device may be provided during a negotiation process for a cooperative service period between access points in a wireless local area network (WLAN) system.

According to the present disclosure, a signaling method and device between access points in a procedure for negotiating a cooperation service period between access points in a wireless LAN system can be provided.

The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

The accompanying drawings, which are incorporated in and are part of the detailed description to aid in understanding the present disclosure, provide embodiments of the present disclosure and, together with the detailed description, describe the technical features of the present disclosure.

FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

FIG. 5 is a diagram for explaining a CSMA/CA-based frame transmission operation to which the present disclosure can be applied.

FIG. 6 is a drawing for explaining an example of a frame structure used in a wireless LAN system to which the present disclosure can be applied.

FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

FIG. 8 is a diagram for explaining various transmission and reception techniques in a MAP environment to which the present disclosure can be applied.

FIG. 9 is a diagram illustrating an example of an individual TWT operation to which the present disclosure can be applied.

FIG. 10 is a diagram illustrating an example of a broadcast TWT operation to which the present disclosure can be applied.

FIG. 11 is a diagram exemplarily showing APs and STAs in an OBSS to which the present disclosure can be applied.

Figure 12 is a diagram illustrating examples of individual TWT parameter set field formats.

Figure 13 is a diagram illustrating examples of broadcast TWT parameter set field formats.

FIG. 14 is a diagram exemplarily showing APs and STAs in an OBSS to which the present disclosure can be applied.

FIG. 15 is a drawing showing an example of the operation of the first AP according to the present disclosure.

FIG. 16 is a drawing showing an example of the operation of a second AP according to the present disclosure.

FIG. 17 is a diagram illustrating examples of broadcast TWT parameter sets related to TWT cooperation between APs in the present disclosure.

FIG. 18 is a diagram illustrating other examples of broadcast TWT parameter sets related to TWT cooperation between APs in the present disclosure.

FIG. 19 is a diagram illustrating examples of notifying cooperative R-TWT schedule information according to the present disclosure.

FIG. 20 and FIG. 21 are diagrams illustrating examples of 2-way TWT cooperation according to the present disclosure.

FIGS. 22 to 24 are diagrams illustrating examples of 3-way TWT cooperation according to the present disclosure.

FIGS. 25 to 27 are diagrams illustrating examples of a cooperative method within a nested cooperative R-TWT SP according to the present disclosure.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description set forth below, together with the accompanying drawings, is intended to explain exemplary embodiments of the present disclosure and is not intended to represent the only embodiments in which the present disclosure may be practiced. The following detailed description includes specific details to provide a thorough understanding of the present disclosure. However, one of ordinary skill in the art will appreciate that the present disclosure may be practiced without these specific details.

In some cases, to avoid obscuring the concepts of the present disclosure, known structures and devices may be omitted or illustrated in block diagram form focusing on the core functions of each structure and device.

In the present disclosure, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, the terms "comprises" or "has" in the present disclosure specify the presence of the mentioned features, steps, operations, elements, and/or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.

In this disclosure, terms such as “first,” “second,” etc. are used only to distinguish one component from another and are not used to limit the components, and do not limit the order or importance between the components unless specifically stated otherwise. Accordingly, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to limit the scope of the claims. As used in the description of the embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. The term "and/or" as used herein may refer to any one of the associated enumerated items, or is meant to refer to and encompass any and all possible combinations of two or more of them. Furthermore, the use of "/" between words in this disclosure has the same meaning as "and/or" unless otherwise stated.

The examples of the present disclosure can be applied to various wireless communication systems. For example, the examples of the present disclosure can be applied to a wireless LAN system. For example, the examples of the present disclosure can be applied to a wireless LAN based on the IEEE 802.11a/g/n/ac/ax/be standards. Furthermore, the examples of the present disclosure can be applied to a wireless LAN based on the newly proposed IEEE 802.11bn (or UHR) standard. Additionally, the examples of the present disclosure can be applied to a wireless LAN based on the next-generation standard after IEEE 802.11bn. Furthermore, the examples of the present disclosure can be applied to a cellular wireless communication system. For example, the examples of the present disclosure can be applied to a cellular wireless communication system based on the LTE (Long Term Evolution) series of technologies and the 5G NR (New Radio) series of technologies of the 3rd Generation Partnership Project (3GPP) standard.

Below, technical features to which examples of the present disclosure can be applied are described.

FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

The first device (100) and the second device (200) illustrated in FIG. 1 may be replaced with various terms such as a terminal, a wireless device, a WTRU (Wireless Transmit Receive Unit), a UE (User Equipment), an MS (Mobile Station), a UT (user terminal), an MSS (Mobile Subscriber Station), an MSS (Mobile Subscriber Unit), an SS (Subscriber Station), an AMS (Advanced Mobile Station), a WT (Wireless terminal), or simply a user. In addition, the first device (100) and the second device (200) may be replaced with various terms such as an access point (AP), a BS (Base Station), a fixed station, a Node B, a BTS (Base Transceiver System), a network, an AI (Artificial Intelligence) system, an RSU (road side unit), a repeater, a router, a relay, a gateway, etc.

The devices (100, 200) illustrated in FIG. 1 may also be referred to as stations (STAs). For example, the devices (100, 200) illustrated in FIG. 1 may be referred to by various terms such as transmitting device, receiving device, transmitting STA, and receiving STA. For example, the STAs (110, 200) may perform an AP (access point) role or a non-AP role. That is, in the present disclosure, the STAs (110, 200) may perform the functions of an AP and/or a non-AP. When the STAs (110, 200) perform an AP function, they may simply be referred to as APs, and when the STAs (110, 200) perform a non-AP function, they may simply be referred to as STAs. In addition, in the present disclosure, the APs may also be referred to as AP STAs.

Referring to FIG. 1, the first device (100) and the second device (200) can transmit and receive wireless signals through various wireless LAN technologies (e.g., IEEE 802.11 series). The first device (100) and the second device (200) can include interfaces for a medium access control (MAC) layer and a physical layer (PHY) that follow the provisions of the IEEE 802.11 standard.

In addition, the first device (100) and the second device (200) may additionally support various communication standards (e.g., 3GPP LTE series, 5G NR series standards, etc.) other than wireless LAN technology. In addition, the device of the present disclosure may be implemented as various devices such as a mobile phone, a vehicle, a personal computer, an AR (Augmented Reality) device, a VR (Virtual Reality) device, etc. In addition, the STA of the present specification may support various communication services such as voice calls, video calls, data communications, autonomous driving, MTC (Machine-Type Communication), M2M (Machine-to-Machine), D2D (Device-to-Device), and IoT (Internet-of-Things).

A first device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (106) and/or one or more antennas (108). The processor (102) controls the memories (104) and/or the transceivers (106), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in the present disclosure. For example, the processor (102) may process information in the memories (104) to generate first information/signals, and then transmit a wireless signal including the first information/signals via the transceivers (106). Furthermore, the processor (102) may receive a wireless signal including second information/signals via the transceivers (106), and then store information obtained from signal processing of the second information/signals in the memory (104). The memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, the memory (104) may perform some or all of the processes controlled by the processor (102), or may store software code including instructions for performing the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in the present disclosure. Here, the processor (102) and the memory (104) may be part of a communication modem/circuit/chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). The transceiver (106) may be connected to the processor (102) and may transmit and/or receive wireless signals via one or more antennas (108). The transceiver (106) may include a transmitter and/or a receiver. The transceiver (106) may be used interchangeably with an RF (Radio Frequency) unit. In the present disclosure, a device may also mean a communication modem/circuit/chip.

The second device (200) includes one or more processors (202), one or more memories (204), and may further include one or more transceivers (206) and/or one or more antennas (208). The processor (202) controls the memories (204) and/or the transceivers (206), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in the present disclosure. For example, the processor (202) may process information in the memory (204) to generate third information/signals, and then transmit a wireless signal including the third information/signals via the transceivers (206). Furthermore, the processor (202) may receive a wireless signal including fourth information/signals via the transceivers (206), and then store information obtained from signal processing of the fourth information/signals in the memory (204). The memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, the memory (204) may perform some or all of the processes controlled by the processor (202), or may store software code including instructions for performing the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in the present disclosure. Here, the processor (202) and the memory (204) may be part of a communication modem/circuit/chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). The transceiver (206) may be connected to the processor (202) and may transmit and/or receive wireless signals via one or more antennas (208). The transceiver (206) may include a transmitter and/or a receiver. The transceiver (206) may be used interchangeably with an RF unit. In the present disclosure, a device may also mean a communication modem/circuit/chip.

Hereinafter, the hardware elements of the device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as PHY, MAC). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and/or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in the present disclosure. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in the present disclosure. One or more processors (102, 202) can generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, procedures, proposals and/or methods disclosed in the present disclosure, and provide the signals to one or more transceivers (106, 206). One or more processors (102, 202) can receive signals (e.g., baseband signals) from one or more transceivers (106, 206) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and/or operational flowcharts disclosed in the present disclosure.

One or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, proposals, methods and/or operation flowcharts disclosed in this disclosure may be implemented using firmware or software configured to perform one or more processors (102, 202) or stored in one or more memories (104, 204) and driven by one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods and/or operation flowcharts disclosed in this disclosure may be implemented using firmware or software in the form of codes, instructions and/or sets of instructions.

One or more memories (104, 204) may be coupled to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and/or commands. The one or more memories (104, 204) may be configured as ROM, RAM, EPROM, flash memory, hard drives, registers, cache memory, computer-readable storage media, and/or combinations thereof. The one or more memories (104, 204) may be located internally and/or externally to the one or more processors (102, 202). Additionally, the one or more memories (104, 204) may be coupled to the one or more processors (102, 202) via various technologies, such as wired or wireless connections.

One or more transceivers (106, 206) can transmit user data, control information, wireless signals/channels, etc., as mentioned in the methods and/or flowcharts of the present disclosure, to one or more other devices. One or more transceivers (106, 206) can receive user data, control information, wireless signals/channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and/or flowcharts of the present disclosure, from one or more other devices. For example, one or more transceivers (106, 206) can be coupled to one or more processors (102, 202) and can transmit and receive wireless signals. For example, one or more processors (102, 202) can control one or more transceivers (106, 206) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (106, 206) may be coupled to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, wireless signals/channels, or the like, as referred to in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in the present disclosure, via one or more antennas (108, 208). In the present disclosure, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) may convert received user data, control information, wireless signals/channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals/channels, etc. using one or more processors (102, 202). One or more transceivers (106, 206) may convert processed user data, control information, wireless signals/channels, etc. from baseband signals to RF band signals using one or more processors (102, 202). For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and/or a filter.

For example, one of the STAs (100, 200) may perform the intended operation of an AP, and the other of the STAs (100, 200) may perform the intended operation of a non-AP STA. For example, the transceivers (106, 206) of FIG. 1 may perform transmission and reception operations of signals (e.g., packets or PPDUs (Physical layer Protocol Data Units) according to IEEE 802.11a/b/g/n/ac/ax/be/bn, etc.). In addition, in the present disclosure, operations in which various STAs generate transmission and reception signals or perform data processing or calculations in advance for transmission and reception signals may be performed in the processors (102, 202) of FIG. 1. For example, an example of an operation for generating a transmission/reception signal or performing data processing or operation in advance for a transmission/reception signal may include 1) an operation for determining/obtaining/configuring/computing/decoding/encoding bit information of a field (SIG (signal), STF (short training field), LTF (long training field), Data, etc.) included in a PPDU, 2) an operation for determining/configuring/obtaining time resources or frequency resources (e.g., subcarrier resources) used for a field (SIG, STF, LTF, Data, etc.) included in a PPDU, 3) an operation for determining/configuring/obtaining a specific sequence (e.g., a pilot sequence, an STF/LTF sequence, an extra sequence applied to SIG) used for a field (SIG, STF, LTF, Data, etc.) included in a PPDU, 4) a power control operation and/or a power saving operation applied to an STA, 5) an operation related to determining/obtaining/configuring/computing/decoding/encoding an ACK signal, etc. Additionally, in the examples below, various information (e.g., information related to fields/subfields/control fields/parameters/power, etc.) used by various STAs for determining/acquiring/configuring/computing/decoding/encoding transmission/reception signals can be stored in the memory (104, 204) of FIG. 1.

Hereinafter, downlink (DL) refers to a link for communication from an AP STA to a non-AP STA, and downlink PPDUs/packets/signals, etc. can be transmitted and received through the downlink. In downlink communication, the transmitter may be part of an AP STA, and the receiver may be part of a non-AP STA. Uplink (UL) refers to a link for communication from a non-AP STA to an AP STA, and uplink PPDUs/packets/signals, etc. can be transmitted and received through the uplink. In uplink communication, the transmitter may be part of a non-AP STA, and the receiver may be part of an AP STA.

FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

The structure of a wireless LAN system can be composed of multiple components. Through the interaction of multiple components, a wireless LAN that supports transparent STA mobility to the upper layer can be provided. A Basic Service Set (BSS) corresponds to a basic building block of a wireless LAN. FIG. 2 illustrates, by way of example, the existence of two BSSs (BSS1 and BSS2) and the inclusion of two STAs as members of each BSS (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2). The oval representing a BSS in FIG. 2 can also be understood as representing a coverage area in which STAs included in the corresponding BSS maintain communication. This area can be referred to as a Basic Service Area (BSA). When an STA moves outside of a BSA, it cannot directly communicate with other STAs within the BSA.

If we do not consider the DS illustrated in Figure 2, the most basic type of BSS in a wireless LAN is an Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For example, assuming other components are omitted, BSS1 consisting of only STA1 and STA2, or BSS2 consisting of only STA3 and STA4, can be representative examples of an IBSS, respectively. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, in this type of WLAN, a LAN can be configured when needed rather than being planned in advance, and this can be called an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. That is, in an IBSS, STAs are managed in a distributed manner. In IBSS, all STAs can be mobile STAs, and access to distributed systems (DS) is not permitted, forming a self-contained network.

An STA's membership in a BSS can dynamically change, for example, when an STA is turned on or off, or when an STA enters or leaves a BSS area. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services in the BSS infrastructure, an STA must be associated with the BSS. This association can be dynamically established and may involve the use of a Distribution System Service (DSS).

In a wireless LAN, the direct STA-to-STA distance can be limited by PHY performance. While this distance limit may be sufficient in some cases, communication between STAs over longer distances may be required in other cases. To support extended coverage, a distributed system (DS) can be configured.

DS refers to a structure in which BSSs are interconnected. Specifically, a BSS may exist as an extended component of a network composed of multiple BSSs, as illustrated in Figure 2. DS is a logical concept and can be specified by the characteristics of a distributed system medium (DSM). In this regard, the Wireless Medium (WM) and DSM can be logically distinguished. Each logical medium is used for a different purpose and by different components. These media are neither limited to being identical nor limited to being different. This logical difference between multiple media explains the flexibility of the WLAN architecture (DS architecture or other network architectures). In other words, the WLAN architecture can be implemented in various ways, and the physical characteristics of each implementation can independently specify the WLAN architecture.

A DS can support mobile devices by providing seamless integration of multiple BSSs and the logical services necessary to handle addresses to destinations. Additionally, a DS may further include a component called a portal, which acts as a bridge for connecting wireless LANs to other networks (e.g., IEEE 802.X).

An AP is an entity that enables access to a DS through a WM for associated non-AP STAs and also has the functionality of an STA. Data movement between a BSS and a DS can be performed through an AP. For example, STA2 and STA3 illustrated in FIG. 2 have the functionality of an STA and provide the function of allowing associated non-AP STAs (STA1 and STA4) to access the DS. In addition, since all APs are basically STAs, all APs are addressable entities. The address used by an AP for communication on a WM and the address used by an AP for communication on a DSM do not necessarily have to be the same. A BSS consisting of an AP and one or more STAs can be referred to as an infrastructure BSS.

Data transmitted from one of the STA(s) associated with an AP to the STA address of that AP may always be received on an uncontrolled port and processed by an IEEE 802.1X port access entity. In addition, if the controlled port is authenticated, the transmitted data (or frame) may be forwarded to the DS.

In addition to the structure of the DS described above, an extended service set (ESS) may be established to provide wider coverage.

An ESS is a network of arbitrary size and complexity, consisting of DSs and BSSs. An ESS may correspond to a set of BSSs connected to a DS. However, an ESS does not include a DS. An ESS network is characterized by appearing as an IBSS at the Logical Link Control (LLC) layer. STAs within an ESS can communicate with each other, and mobile STAs can move from one BSS to another (within the same ESS) transparently to the LLC. APs within an ESS may have the same SSID (service set identification). The SSID is distinct from the BSSID, which is the identifier of the BSS.

In a wireless LAN system, no assumptions are made about the relative physical locations of BSSs, and all of the following configurations are possible: BSSs can be partially overlapping, which is commonly used to provide continuous coverage. BSSs can also be physically disconnected, and there is no logical distance limit between them. BSSs can also be physically co-located, which can be used to provide redundancy. Furthermore, one (or more) IBSS or ESS networks can physically co-exist with one (or more) ESS networks. This can occur in cases where an ad-hoc network operates at the same location as an ESS network, where physically overlapping wireless networks are configured by different organizations, or where two or more different access and security policies are required at the same location.

FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

For an STA to set up a link and transmit and receive data on a network, it must first discover the network, perform authentication, establish an association, and complete security authentication procedures. The link setup process can also be referred to as the session initiation process or session setup process. Furthermore, the discovery, authentication, association, and security setup processes of the link setup process can be collectively referred to as the association process.

In step S310, the STA may perform a network discovery operation. This network discovery operation may include scanning operations by the STA. That is, for the STA to access a network, it must search for available networks. Before joining a wireless network, the STA must identify compatible networks. The process of identifying networks in a specific area is called scanning.

Scanning methods include active scanning and passive scanning. Figure 3 illustrates a network discovery operation including an active scanning process as an example. In active scanning, an STA performing scanning transmits a probe request frame to discover any APs in the vicinity while moving between channels and waits for a response. The responder transmits a probe response frame in response to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted a beacon frame in the BSS of the channel being scanned. In the BSS, the AP transmits the beacon frame, so the AP becomes the responder. In the IBSS, the STAs within the IBSS take turns transmitting beacon frames, so the responder is not fixed. For example, an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 can store BSS-related information included in the received probe response frame and move to the next channel (e.g., channel 2) to perform scanning (i.e., transmitting and receiving probe requests/responses on channel 2) in the same manner.

Although not shown in Figure 3, the scanning operation can also be performed in a passive scanning manner. In passive scanning, the STA performing the scanning moves between channels and waits for a beacon frame. A beacon frame is one of the management frames defined in IEEE 802.11. It announces the existence of a wireless network and is periodically transmitted so that the STA performing the scanning can find the wireless network and participate in the wireless network. In the BSS, the AP performs the role of periodically transmitting the beacon frame, and in the IBSS, the STAs within the IBSS take turns transmitting the beacon frame. When the STA performing the scanning receives a beacon frame, it stores the information about the BSS included in the beacon frame and moves to another channel, recording the beacon frame information on each channel. The STA receiving the beacon frame stores the BSS-related information included in the received beacon frame and moves to the next channel to perform scanning on the next channel in the same manner. Comparing active scanning and passive scanning, active scanning has the advantage of lower delay and power consumption than passive scanning.

After the STA discovers the network, an authentication process may be performed in step S320. This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation of step S340 described below.

The authentication process involves the STA sending an authentication request frame to the AP, and the AP responding by sending an authentication response frame to the STA. The authentication frame used for the authentication request/response corresponds to a management frame.

The authentication frame may include information such as an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a Robust Security Network (RSN), and a Finite Cyclic Group. These are just some examples of information that may be included in an authentication request/response frame, and may be replaced with other information or include additional information.

An STA can send an authentication request frame to an AP. The AP can determine whether to grant authentication to the STA based on the information contained in the received authentication request frame. The AP can provide the result of the authentication process to the STA via an authentication response frame.

After the STA is successfully authenticated, an association process may be performed in step S330. The association process includes a process in which the STA transmits an association request frame to the AP, and in response, the AP transmits an association response frame to the STA.

For example, the association request frame may include information about various capabilities, a beacon listen interval, a service set identifier (SSID), supported rates, supported channels, an RSN, a mobility domain, supported operating classes, a Traffic Indication Map Broadcast request, interworking service capabilities, etc. For example, the association response frame may include information about various capabilities, a status code, an Association ID (AID), supported rates, an Enhanced Distributed Channel Access (EDCA) parameter set, a Received Channel Power Indicator (RCPI), a Received Signal to Noise Indicator (RSNI), a mobility domain, a timeout interval (e.g., an association comeback time), overlapping BSS scan parameters, a TIM broadcast response, a Quality of Service (QoS) map, etc. These are just some examples of information that may be included in a combined request/response frame, and may be replaced by other information or include additional information.

After the STA successfully joins the network, a security setup process may be performed in step S340. The security setup process in step S340 may be referred to as an authentication process through a Robust Security Network Association (RSNA) request/response, the authentication process in step S320 may be referred to as a first authentication process, and the security setup process in step S340 may also be referred to simply as an authentication process.

The security setup process of step S340 may include, for example, a process of establishing a private key through a four-way handshaking using an Extensible Authentication Protocol over LAN (EAPOL) frame. Furthermore, the security setup process may be performed according to a security method not defined in the IEEE 802.11 standard.

FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

In wireless LAN systems, the basic access mechanism of MAC (Medium Access Control) is Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The CSMA/CA mechanism, also known as the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC, essentially employs a "listen before talk" access mechanism. According to this type of access mechanism, the AP and/or STA may perform a Clear Channel Assessment (CCA) to sense the wireless channel or medium for a predetermined time period (e.g., a DCF Inter-Frame Space (DIFS)) before starting transmission. If the sensing result determines that the medium is in an idle state, the AP and/or STA may start transmitting frames through the medium. On the other hand, if the medium is detected to be occupied or busy, the AP and/or STA may not start its own transmission, but may wait for a delay period (e.g., a random backoff period) for medium access before attempting to transmit frames. By applying a random backoff period, multiple STAs are expected to attempt to transmit frames after waiting for different periods of time, thereby minimizing collisions.

In addition, the IEEE 802.11 MAC protocol provides the Hybrid Coordination Function (HCF). The HCF is based on the DCF and the Point Coordination Function (PCF). The PCF is a polling-based synchronous access method that periodically polls all receiving APs and/or STAs to ensure that they receive data frames. In addition, the HCF has the Enhanced Distributed Channel Access (EDCA) and the HCF Controlled Channel Access (HCCA). The EDCA is a contention-based access method for a provider to provide data frames to multiple users, while the HCCA uses a non-contention-based channel access method that utilizes a polling mechanism. In addition, the HCF includes a medium access mechanism to improve the Quality of Service (QoS) of the wireless LAN, and can transmit QoS data in both the Contention Period (CP) and the Contention Free Period (CFP).

Referring to Fig. 4, an operation based on a random backoff period is described. When an occupied/busy medium changes to an idle state, multiple STAs may attempt to transmit data (or frames). To minimize collisions, each STA may select a random backoff count, wait for the corresponding slot time, and then attempt transmission. The random backoff count has a pseudo-random integer value and may be determined as one of the values in the range of 0 to CW. Here, CW is a contention window parameter value. The CW parameter is initially given a value of CWmin, but may double the value in case of a transmission failure (e.g., if an ACK for a transmitted frame is not received). When the CW parameter value becomes CWmax, data transmission may be attempted while maintaining the CWmax value until data transmission is successful, and if data transmission is successful, it is reset to the CWmin value. It is desirable that the CW, CWmin and CWmax values be set to 2 ⁿ -1 (n=0, 1, 2, ...).

Once the random backoff process begins, the STA continues to monitor the medium while counting down the backoff slots according to the determined backoff count value. If the medium is monitored as occupied, the countdown stops and waits. When the medium becomes idle, the remaining countdown resumes.

In the example of FIG. 4, when a packet to be transmitted reaches the MAC of STA3, STA3 can immediately transmit a frame if it confirms that the medium is idle for DIFS. The remaining STAs monitor the medium for occupied/busy states and wait. In the meantime, data to be transmitted may also occur in each of STA1, STA2, and STA5, and each STA can count down the backoff slot according to a random backoff count value selected by each STA after waiting for DIFS if the medium is monitored as idle. Assume that STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value. In other words, this example shows a case where the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1 when STA2 finishes the backoff count and starts frame transmission. STA1 and STA5 briefly stop counting down and wait while STA2 occupies the medium. When STA2's occupation ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the backoff count that they had stopped. That is, they can start transmitting frames after counting down the remaining backoff slots equal to the remaining backoff time. Since STA5's remaining backoff time is shorter than STA1's, STA5 starts transmitting frames. While STA2 occupies the medium, STA4 may also have data to transmit. From STA4's perspective, when the medium becomes idle, it waits for DIFS, counts down according to its selected random backoff count value, and then starts transmitting frames. In the example of Figure 4, the remaining backoff time of STA5 coincidentally matches the random backoff count value of STA4, in which case a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 will receive an ACK, resulting in a failure in data transmission. In this case, STA4 and STA5 can select a random backoff count value and perform a countdown after doubling the CW value. STA1 waits while the medium is occupied by transmissions from STA4 and STA5, and when the medium becomes idle, it waits for DIFS and can start transmitting frames after the remaining backoff time elapses.

As in the example of Fig. 4, a data frame is a frame used for transmitting data forwarded to a higher layer, and can be transmitted after a backoff performed after DIFS elapses from when the medium becomes idle. Additionally, a management frame is a frame used for exchanging management information that is not forwarded to a higher layer, and is transmitted after a backoff performed after an IFS elapses, such as DIFS or PIFS (Point coordination function IFS). Subtype frames of a management frame include a beacon, an association request/response, a re-association request/response, a probe request/response, and an authentication request/response. A control frame is a frame used to control access to the medium. The subtype frames of the control frame include Request-To-Send (RTS), Clear-To-Send (CTS), Acknowledgment (ACK), Power Save-Poll (PS-Poll), Block ACK (BlockAck), Block ACK Request (BlockACKReq), Null Data Packet Announcement (NDP), and Trigger. If the control frame is not a response frame to the previous frame, it is transmitted after a backoff performed after the DIFS (Direct Inverse Frame Stop) has elapsed, and if it is a response frame to the previous frame, it is transmitted without a backoff performed after the SIFS (short IFS). The type and subtype of the frame can be identified by the type field and subtype field in the Frame Control (FC) field.

A QoS (Quality of Service) STA can transmit a frame after a backoff performed after the AIFS (arbitration IFS) for the access category (AC) to which the frame belongs, i.e., AIFS[i] (where i is a value determined by the AC), has elapsed. Here, the frames for which AIFS[i] can be used can be data frames, management frames, and also control frames that are not response frames.

FIG. 5 is a diagram for explaining a CSMA/CA-based frame transmission operation to which the present disclosure can be applied.

As mentioned above, the CSMA/CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, in which STAs directly sense the medium. Virtual carrier sensing is intended to address potential issues in medium access, such as the hidden node problem. For virtual carrier sensing, the MAC of an STA can utilize a Network Allocation Vector (NAV). The NAV is a value that an STA that is currently using or has the right to use the medium indicates to other STAs the remaining time until the medium becomes available. Therefore, the value set as NAV corresponds to the period during which the STA transmitting the frame is scheduled to use the medium, and an STA receiving the NAV value is prohibited from accessing the medium during that period. For example, the NAV can be set based on the value of the "duration" field in the MAC header of the frame.

In the example of FIG. 5, it is assumed that STA1 wants to transmit data to STA2, and STA3 is in a position to overhear some or all of the frames transmitted and received between STA1 and STA2.

In order to reduce the possibility of collisions in transmissions of multiple STAs in a CSMA/CA-based frame transmission operation, a mechanism using RTS/CTS frames may be applied. In the example of FIG. 5, while STA1 is transmitting, STA3 may determine that the medium is idle based on carrier sensing results. That is, STA1 may correspond to a hidden node for STA3. Alternatively, in the example of FIG. 5, while STA2 is transmitting, STA3 may determine that the medium is idle based on carrier sensing results. That is, STA2 may correspond to a hidden node for STA3. By exchanging RTS/CTS frames before performing data transmission and reception between STA1 and STA2, STAs outside the transmission range of either STA1 or STA2, or STAs outside the carrier sensing range for transmissions from STA1 or STA3, may not attempt to occupy the channel during data transmission and reception between STA1 and STA2.

Specifically, STA1 can determine whether a channel is occupied through carrier sensing. In terms of physical carrier sensing, STA1 can determine channel occupancy idleness based on the energy level or signal correlation detected in the channel. Furthermore, in terms of virtual carrier sensing, STA1 can determine the channel occupancy status using a network allocation vector (NAV) timer.

STA1 can transmit an RTS frame to STA2 after performing a backoff if the channel is idle during the DIFS. STA2 can transmit a CTS frame, which is a response to the RTS frame, to STA1 after an SIFS if it receives the RTS frame.

If STA3 cannot overhear a CTS frame from STA2 but can overhear an RTS frame from STA1, STA3 can use the duration information contained in the RTS frame to set a NAV timer for the subsequent consecutively transmitted frame transmission period (e.g., SIFS + CTS frame + SIFS + data frame + SIFS + ACK frame). Alternatively, if STA3 cannot overhear an RTS frame from STA1 but can overhear a CTS frame from STA2, STA3 can use the duration information contained in the CTS frame to set a NAV timer for the subsequent consecutively transmitted frame transmission period (e.g., SIFS + data frame + SIFS + ACK frame). That is, if STA3 can overhear one or more of the RTS or CTS frames from one or more of STA1 or STA2, it can set a NAV accordingly. If STA3 receives a new frame before the NAV timer expires, it can update the NAV timer using the duration information contained in the new frame. STA3 does not attempt channel access until the NAV timer expires.

If STA1 receives a CTS frame from STA2, it can transmit a data frame to STA2 after SIFS from the time when the CTS frame is completely received. If STA2 successfully receives the data frame, it can transmit an ACK frame in response to the data frame to STA1 after SIFS. STA3 can determine whether the channel is in use through carrier sensing if the NAV timer expires. If STA3 determines that the channel is not in use by another terminal during the DIFS after the NAV timer expires, it can attempt channel access after a contention window (CW) based on a random backoff has elapsed.

FIG. 6 is a drawing for explaining an example of a frame structure used in a wireless LAN system to which the present disclosure can be applied.

The PHY layer can prepare an MPDU (MAC PDU) to be transmitted based on an instruction or primitive (meaning a set of instructions or parameters) from the MAC layer. For example, when a command requesting the start of transmission of the PHY layer is received from the MAC layer, the PHY layer can switch to transmission mode and transmit the information (e.g., data) provided by the MAC layer in the form of a frame. In addition, when the PHY layer detects a valid preamble of the received frame, it monitors the header of the preamble and sends a command to the MAC layer notifying the start of reception of the PHY layer.

In this way, information transmission/reception in a wireless LAN system is done in the form of frames, and for this purpose, the PHY layer Protocol Data Unit (PPDU) format is defined.

A basic PPDU may include a Short Training Field (STF), a Long Training Field (LTF), a SIGNAL (SIG) field, and a Data field. The most basic (e.g., non-HT (High Throughput) as illustrated in FIG. 7) PPDU format may consist of only the Legacy-STF (L-STF), Legacy-LTF (L-LTF), Legacy-SIG (L-SIG) fields, and a Data field. Additionally, depending on the type of PPDU format (e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (Very High Throughput) PPDU, etc.), additional (or different types of) RL-SIG, U-SIG, non-legacy SIG field, non-legacy STF, non-legacy LTF, (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) may be included between the L-SIG field and the data field. More specific details will be described later with reference to FIG. 7.

STF is a signal for signal detection, AGC (Automatic Gain Control), diversity selection, and precise time synchronization, while LTF is a signal for channel estimation, frequency error estimation, etc. STF and LTF can be said to be signals for synchronization and channel estimation of the OFDM physical layer.

The SIG field may include various information related to PPDU transmission and reception. For example, the L-SIG field may consist of 24 bits and may include a 4-bit Rate field, a 1-bit Reserved bit, a 12-bit Length field, a 1-bit Parity field, and a 6-bit Tail field. The RATE field may include information about the modulation and coding rate of data. For example, the 12-bit Length field may include information about the length or time duration of the PPDU. For example, the value of the 12-bit Length field may be determined based on the type of the PPDU. For example, for a non-HT, HT, VHT, or EHT PPDU, the value of the Length field may be determined as a multiple of 3. For example, for HE PPDU, the value of the Length field can be determined as a multiple of 3 + 1 or a multiple of 3 + 2.

The data field may include a SERVICE field, a Physical layer Service Data Unit (PSDU), a PPDU TAIL bit, and, if necessary, padding bits. Some bits of the SERVICE field may be used to synchronize the descrambler at the receiving end. The PSDU corresponds to a MAC PDU defined at the MAC layer and may contain data generated/used by upper layers. The PPDU TAIL bit may be used to return the encoder to a 0 state. The padding bit may be used to adjust the length of the data field to a predetermined unit.

MAC PDUs are defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a Frame Check Sequence (FCS). A MAC frame is composed of MAC PDUs and can be transmitted/received through the PSDU in the data portion of the PPDU format.

The MAC header includes a Frame Control field, a Duration/ID field, an Address field, etc. The Frame Control field may include control information required for frame transmission/reception. The Duration/ID field may be set to a time for transmitting the corresponding frame, etc. The Address subfields may indicate the receiver address, transmitter address, destination address, and source address of the frame, and some Address subfields may be omitted. For specific details of each subfield of the MAC header, including the Sequence Control, QoS Control, and HT Control subfields, refer to the IEEE 802.11 standard document.

The Null-Data PPDU (NDP) format refers to a PPDU format that does not include a data field. In other words, NDP refers to a frame format that includes a PPDU preamble (i.e., L-STF, L-LTF, L-SIG fields, and, if additionally present, non-legacy SIG, non-legacy STF, and non-legacy LTF) in the general PPDU format, and does not include the remaining part (i.e., data field).

FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

Standards such as IEEE 802.11a/g/n/ac/ax use various PPDU formats. The basic PPDU format (IEEE 802.11a/g) includes L-LTF, L-STF, L-SIG, and Data fields. The basic PPDU format can also be referred to as the non-HT PPDU format (Fig. 7(a)).

The HT PPDU format (IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT(s) fields in addition to the basic PPDU format. The HT PPDU format illustrated in Fig. 7(b) may be referred to as an HT-mixed format. Additionally, an HT-greenfield format PPDU may be defined, which corresponds to a format that does not include L-STF, L-LTF, and L-SIG, but consists of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTF, and Data fields (not illustrated).

An example of the VHT PPDU format (IEEE 802.11ac) includes VHT SIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields in addition to the basic PPDU format (Fig. 7(c)).

An example of a HE PPDU format (IEEE 802.11ax) additionally includes RL-SIG (Repeated L-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF(s), and PE (Packet Extension) fields in addition to the basic PPDU format (Fig. 7(d)). Depending on specific examples of the HE PPDU format, some fields may be excluded or their lengths may vary. For example, the HE-SIG-B field is included in the HE PPDU format for multi-users (MUs), but the HE PPDU format for single users (SUs) does not include the HE-SIG-B. In addition, the HE trigger-based (TB) PPDU format does not include the HE-SIG-B, and the length of the HE-STF field may vary to 8us. The HE ER (Extended Range) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16us. For example, RL-SIG can be configured identically to L-SIG. The receiving STA can determine that the received PPDU is a HE PPDU or an EHT PPDU, described later, based on the presence of RL-SIG.

The EHT PPDU format may include the EHT MU (multi-user) PPDU of FIG. 7(e) and the EHT TB (trigger-based) PPDU of FIG. 7(f). The EHT PPDU format is similar to the HE PPDU format in that it includes an RL-SIG following an L-SIG, but may include a U (universal)-SIG, an EHT-SIG, an EHT-STF, and an EHT-LTF following the RL-SIG.

The EHT MU PPDU in FIG. 7(e) corresponds to a PPDU that carries one or more data (or PSDUs) for one or more users. That is, the EHT MU PPDU can be used for both SU transmission and MU transmission. For example, the EHT MU PPDU can correspond to a PPDU for one receiving STA or multiple receiving STAs.

The EHT TB PPDU of Fig. 7(f) omits the EHT-SIG compared to the EHT MU PPDU. An STA that has received a trigger for UL MU transmission (e.g., a trigger frame or TRS (triggered response scheduling)) can perform UL transmission based on the EHT TB PPDU format.

The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated to allow legacy STAs to attempt demodulation and decoding, and mapped based on a predetermined subcarrier frequency interval (e.g., 312.5 kHz). These can be referred to as pre-EHT modulated fields. Next, the EHT-STF, EHT-LTF, Data, and PE fields can be encoded and modulated to allow STAs that have successfully decoded non-legacy SIGs (e.g., U-SIG and/or EHT-SIG) and obtained the information contained in the fields, and mapped based on a predetermined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

Similarly, in the HE PPDU format, the L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, and HE-SIG-B fields may be referred to as pre-HE modulation fields, and the HE-STF, HE-LTF, Data, and PE fields may be referred to as HE modulation fields. Additionally, in the VHT PPDU format, the L-STF, L-LTF, L-SIG, and VHT-SIG-A fields may be referred to as pre-VHT modulation fields, and the VHT STF, VHT-LTF, VHT-SIG-B, and Data fields may be referred to as VHT modulation fields.

The U-SIG included in the EHT PPDU format of FIG. 7 can be configured based on, for example, two symbols (e.g., two consecutive OFDM symbols). Each symbol (e.g., OFDM symbol) for the U-SIG can have a duration of 4 us, and the U-SIG can have a total duration of 8 us. Each symbol of the U-SIG can be used to transmit 26 bits of information. For example, each symbol of the U-SIG can be transmitted and received based on 52 data tones and 4 pilot tones.

U-SIGs can be configured in 20MHz units. For example, when an 80MHz PPDU is configured, the same U-SIG can be duplicated in 20MHz units. That is, four identical U-SIGs can be included in an 80MHz PPDU. When the bandwidth exceeds 80MHz, for example, for a 160MHz PPDU, the U-SIGs in the first 80MHz unit and the U-SIGs in the second 80MHz unit can be different.

For example, A uncoded bits may be transmitted via U-SIG, and a first symbol of U-SIG (e.g., a U-SIG-1 symbol) may transmit the first X bits of information out of a total A bits of information, and a second symbol of U-SIG (e.g., a U-SIG-2 symbol) may transmit the remaining Y bits of information out of a total A bits of information. The A bits of information (e.g., 52 uncoded bits) may include a CRC field (e.g., a field of 4 bits in length) and a tail field (e.g., a field of 6 bits in length). The tail field may be used to terminate the trellis of the convolutional decoder and may be set to 0, for example.

The A bit information transmitted by U-SIG can be divided into version-independent bits and version-dependent bits. For example, U-SIG can be included in a new PPDU format (e.g., UHR PPDU format) not shown in FIG. 7, and in the format of the U-SIG field included in the EHT PPDU format and the format of the U-SIG field included in the UHR PPDU format, the version-independent bits can be the same, and some or all of the version-dependent bits can be different.

For example, the size of the version-independent bits of U-SIG can be fixed or variable. The version-independent bits can be assigned only to U-SIG-1 symbols, or to both U-SIG-1 symbols and U-SIG-2 symbols. The version-independent bits and the version-dependent bits can be called by various names, such as the first control bit and the second control bit.

For example, the version-independent bits of the U-SIG may include a 3-bit PHY version identifier, which may indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted and received PPDUs. The version-independent bits of the U-SIG may include a 1-bit UL/DL flag field. The first value of the 1-bit UL/DL flag field relates to UL communication, and the second value of the UL/DL flag field relates to DL communication. The version-independent bits of the U-SIG may include information about the length of a transmission opportunity (TXOP) and information about a BSS color ID.

For example, the version-dependent bits of the U-SIG may contain information that directly or indirectly indicates the type of PPDU (e.g., SU PPDU, MU PPDU, TB PPDU, etc.).

Information required for PPDU transmission and reception may be included in the U-SIG. For example, the U-SIG may further include information about bandwidth, information about the MCS technique applied to the non-legacy SIG (e.g., EHT-SIG or UHR-SIG), information indicating whether a dual carrier modulation (DCM) technique (e.g., a technique to achieve an effect similar to frequency diversity by reusing the same signal on two subcarriers) is applied to the non-legacy SIG, information about the number of symbols used for the non-legacy SIG, information about whether the non-legacy SIG is generated across the entire band, etc.

Some of the information required for transmitting and receiving a PPDU may be included in the U-SIG and/or the non-legacy SIG (e.g., EHT-SIG or UHR-SIG, etc.). For example, information about the type of the non-legacy LTF/STF (e.g., EHT-LTF/EHT-STF or UHR-LTF/UHR-STF, etc.), information about the length of the non-legacy LTF and the cyclic prefix (CP) length, information about the guard interval (GI) applicable to the non-legacy LTF, information about preamble puncturing applicable to the PPDU, information about resource unit (RU) allocation, etc. may be included only in the U-SIG, may be included only in the non-legacy SIG, or may be indicated by a combination of the information included in the U-SIG and the information included in the non-legacy SIG.

Preamble puncturing may refer to the transmission of a PPDU in which no signal is present in one or more frequency units within the PPDU's bandwidth. For example, the size of the frequency unit (or the resolution of the preamble puncturing) may be defined as 20 MHz, 40 MHz, etc. For example, preamble puncturing may be applied to a PPDU bandwidth greater than a certain size.

In the example of FIG. 7, non-legacy SIGs such as HE-SIG-B and EHT-SIG may include control information for the receiving STA. The non-legacy SIG may be transmitted over at least one symbol, and each symbol may have a length of 4 us. Information regarding the number of symbols used for the EHT-SIG may be included in a previous SIG (e.g., HE-SIG-A, U-SIG, etc.).

Non-legacy SIGs, such as HE-SIG-B and EHT-SIG, may contain common fields and user-specific fields. Common and user-specific fields may be coded separately.

In some cases, common fields may be omitted. For example, in a compressed mode where non-OFDMA (orthogonal frequency multiple access) is applied, common fields may be omitted, and multiple STAs may receive PPDUs (e.g., data fields of PPDUs) over the same frequency band. In a non-compressed mode where OFDMA is applied, multiple users may receive PPDUs (e.g., data fields of PPDUs) over different frequency bands.

The number of user-specific fields can be determined based on the number of users. A single user block field can contain up to two user fields. Each user field can be associated with either MU-MIMO allocation or non-MU-MIMO allocation.

The common field may include CRC bits and Tail bits, the length of the CRC bits may be determined as 4 bits, and the length of the Tail bits may be determined as 6 bits and set to 000000. The common field may include RU allocation information. The RU allocation information may include information about the location of RUs to which multiple users (i.e., multiple receiving STAs) are allocated.

An RU can contain multiple subcarriers (or tones). RUs can be used when transmitting signals to multiple STAs based on OFDMA techniques. RUs can also be defined when transmitting signals to a single STA. Resources can be allocated on an RU basis for non-legacy STFs, non-legacy LTFs, and data fields.

Depending on the PPDU bandwidth, an applicable RU size can be defined. The RU may be defined identically or differently for the applicable PPDU format (e.g., HE PPDU, EHT PPDU, UHR PPDU, etc.). For example, in the case of an 80MHz PPDU, the RU arrangements of HE PPDU and EHT PPDU may be different. The applicable RU size, RU number, RU position, DC (direct current) subcarrier position and number, null subcarrier position and number, guard subcarrier position and number, etc. for each PPDU bandwidth can be referred to as a tone plan. For example, a tone plan for a wide bandwidth can be defined in the form of multiple repetitions of a low bandwidth tone plan.

RUs of different sizes can be defined, such as 26-ton RU, 52-ton RU, 106-ton RU, 242-ton RU, 484-ton RU, 996-ton RU, 2X996-ton RU, 4X996-ton RU, etc. A multiple RU (MRU) is distinguished from multiple individual RUs and corresponds to a group of subcarriers consisting of multiple RUs. For example, one MRU can be defined as 52+26-tons, 106+26-tons, 484+242-tons, 996+484-tons, 996+484+242-tons, 2X996+484-tons, 3X996-tons, or 3X996+484-tons. Additionally, multiple RUs constituting one MRU may or may not be consecutive in the frequency domain.

The specific size of an RU may be reduced or expanded. Therefore, the specific size of each RU (i.e., the number of corresponding tones) in the present disclosure is not limited and is exemplary. Furthermore, within a given bandwidth (e.g., 20, 40, 80, 160, 320 MHz, etc.) in the present disclosure, the number of RUs may vary depending on the RU size.

The names of each field in the PPDU formats of FIG. 7 are exemplary and the scope of the present disclosure is not limited by those names. Furthermore, the examples of the present disclosure can be applied not only to the PPDU format exemplified in FIG. 7, but also to a new PPDU format in which some fields are excluded and/or some fields are added based on the PPDU formats of FIG. 7.

Multi-Access Point (MAP) operation

Below, examples of the present disclosure for multi-access point (MAP) operation are described.

MAP operation can be defined as an operation between a master AP (or sharing AP) and a slave AP (or shared AP).

The master AP initiates and controls MAP operations for transmission and reception between multiple APs. It groups slave APs and manages links with them to enable information sharing. The master AP manages information about the BSS comprised of the slave APs and the STAs associated with that BSS.

Slave APs can associate with a master AP and share control information, management information, and data traffic. Slave APs perform the same basic functions as APs, establishing a base station service (BSS) in a wireless LAN.

In MAP operation, an STA can associate with a slave AP or a master AP and form a BSS.

In a MAP environment, the master AP and slave APs can directly transmit and receive with each other. The master AP and STA may not be able to directly transmit and receive with each other. A slave AP (e.g., a slave AP associated with an STA) can directly transmit and receive with the STA. One of the slave APs can become the master AP.

MAP operation is a technique in which one or more APs transmit and receive information to one or more STAs. For example, coordinated-time division multiple access (C-TDMA), which divides allocations between APs along the time axis, coordinated-orthogonal frequency division multiple access (C-OFDMA), which divides allocations along the frequency axis, and coordinated-spatial reuse (C-SR) techniques that utilize spatial reuse can be applied for MAP operation. Alternatively, coordinated beamforming (C-BF) or joint beamforming techniques, which cooperatively perform simultaneous transmission and reception, can also be applied to MAP operation.

FIG. 8 is a diagram for explaining various transmission and reception techniques in a MAP environment to which the present disclosure can be applied.

As in the conventional method, when a BSS AP transmits to a BSS STA, this can be referred to as STX (single transmission). STX suffers from the problem of reduced transmission and reception performance for users/STAs located at the cell edge due to interference with neighboring APs. For example, as shown in Figure 8(a), if AP1 and AP2 transmit to STA1 and STA2, respectively, at the same time and within the same frequency bandwidth, a collision may occur on the wireless medium.

In the MAP technique, performance can be improved by reducing inter-symbol interference (ISI) through cooperation between neighboring APs, or by performing joint transmissions. For example, in the C-OFDMA method of Fig. 8(b), interference can be avoided by simultaneously transmitting to STA1 in the first bandwidth and transmitting to STA2 in the second bandwidth. The example of Fig. 8(c) shows a cooperative beamforming or nulling technique in which AP1 nulls the interference to AP2 and/or STA2 while transmitting to STA1, and AP2 nulls the interference to AP1 and/or STA1 while transmitting to STA2. Fig. 8(d) shows an AP selection method in which an AP with a good channel condition among neighboring APs performs transmission. Joint transmission (JTX) or joint reception (JRX) may be applied, in which multiple APs cooperate to transmit or receive simultaneously, as in the example of Fig. 8(e), and further, joint MU-MIMO may be supported.

In the examples of this disclosure, multi-AP operation is assumed to be performed as follows.

Step 1: Allocate resource areas to each AP through a trigger frame from the master AP (i.e., AP-to-AP trigger frame, or master trigger frame).

Step 2: Each AP performs DL (i.e., from AP to STA) data transmission in the resource area allocated to it, or transmits a trigger frame (i.e., AP-to-STA trigger frame) for UL (i.e., from STA to AP) data transmission in the resource area allocated to it.

Step 3: STA sends a response to DL data or sends UL data (e.g., TB PPDU)

If the resources distributed between APs are frequency resources, it may correspond to the C-OFDMA method, if it is time resources, it may correspond to the C-TDMA technique, and if it is space resources (or beams), it may correspond to the CBF method. In the examples described below, it is assumed that the C-OFDMA technique, i.e., multi-AP operation is performed using resources distinguished in the frequency domain, is representative. However, the scope of the present disclosure is not limited thereto, and may additionally or alternatively include multi-AP operation using resources distinguished in other domains (e.g., time domain and/or space domain).

target wake time (TWT)

Below, we explain TWT (target wake time).

TWT is a power saving technology that can improve the energy efficiency of non-AP STAs by defining a service period (SP) between an AP and non-AP STAs and sharing information about the SP to reduce contention of the medium. In the TWT setup phase, an STA that performs requests/suggestions/demands, etc., can be called a TWT requesting STA. In addition, an AP that responds to the request with an acceptance/rejection, etc., can be called a TWT responding STA. The setup phase can include a process of determining/defining a TWT request from an STA to the AP, the type of TWT operation to be performed, and the type of frames to be transmitted and received. TWT operations can be divided into individual TWT and broadcast TWT.

FIG. 9 is a diagram illustrating an example of an individual TWT operation to which the present disclosure can be applied.

Individual TWT is a mechanism in which an AP and a non-AP STA negotiate the awake/doze status of a non-AP STA by sending and receiving TWT request/response frames, and then exchange data. In the example of Fig. 9, the AP and STA1 can form a trigger-enabled TWT agreement through a TWT request frame and a TWT response frame. Here, the method used by STA1 is a solicited TWT method, in which STA1 transmits a TWT request frame to the AP, and STA1 receives information for TWT operation from the AP through a TWT response frame. On the other hand, STA2, which performs the unsolicited TWT method, can receive information about the trigger-enabled TWT agreement setup from the AP through the unsolicited TWT response. Specifically, STA2 can calculate the next TWT by adding a specific number to the current TWT value. During the trigger-enabled TWT SP, the AP can transmit a trigger frame to the STAs. The trigger frame can inform the STAs that the AP has buffered data. In response, STA1 can inform the AP of its awake state by transmitting a PS-Poll frame. Additionally, STA2 can inform the AP of its activated state by transmitting a QoS Null frame. Here, the data frames transmitted by STA1 and STA2 can be frames in the TB PPDU format. After checking the status of STA1 and STA2, the AP can transmit DL MU PPDUs to the activated STAs. When the corresponding TWT SP expires, STA1 and STA2 can transition to a doze state.

FIG. 10 is a diagram illustrating an example of a broadcast TWT operation to which the present disclosure can be applied.

Broadcast TWT is a TWT in which a non-AP STA (or TWT scheduling STA) obtains information such as target beacon transmission time (TBTT) and listen interval by transmitting and receiving TWT request/response frames with the AP (or TWT scheduled STA). Here, a negotiation operation for TBTT may be performed. Based on this, the AP can define a frame to include TWT scheduling information through a beacon frame. In Fig. 10, STA1 performs a requested TWT operation, and STA2 performs an unsolicited TWT operation. The AP can transmit a DL MU PPDU after checking the awake status of the STAs through the trigger it transmitted. This may be the same as the process of an individual TWT. In broadcast TWT, a trigger-enabled TWT SP including a beacon frame may be repeated multiple times at a regular cycle.

Transmission of TWT information can be accomplished through a TWT information frame and a TWT information element.

The TWT information frame is transmitted by an STA to request or convey information about a TWT agreement, and is transmitted by one of the STAs of an existing TWT agreement. The action frame of the TWT information frame includes a TWT information field. The TWT Information field may include a 3-bit TWT flow identifier subfield, a 1-bit response requested subfield, a 1-bit next TWT request subfield, a 2-bit next TWT subfield size subfield, a 1-bit all TWT subfield, and a 0/32/48/64-bit next TWT subfield.

Figure 11 is a drawing for explaining an example of a TWT information element format.

TWT information elements can be transmitted and received in beacons, probe responses, (re)association response frames, etc. The TWT information elements can include an element identifier (ID) field, a length field, a control field, and a TWT parameter information field.

The control fields of a TWT information element have the same format regardless of whether it is an individual TWT or a broadcast TWT.

The NDP paging indicator subfield can have a value of 1 if the NDP paging field exists, and a value of 0 if the NDP paging field does not exist.

The responder PM mode subfield may indicate a power management (PM) mode.

The negotiation type subfield may indicate whether the information contained in the TWT element is about negotiation of parameters of a broadcast TWT or individual TWT(s), or about a wake TBTT interval.

For example, if the negotiation type subfield has a value of 0, the TWT subfield is for a future individual TWT SP start time, and the TWT element contains one individual set of TWT parameters. This may correspond to an individual TWT negotiation between a TWT requesting STA and a TWT responding STA, or to an individual TWT announcement by a TWT responder.

For example, if the value of the Agreement Type subfield is 1, the TWT subfield is for the next TBTT time, and the TWT element contains one individual set of TWT parameters. This may correspond to the wake TBTT and wake interval negotiation between the TWT scheduled STA and the TWT scheduling AP.

For example, if the value of the Agreement Type subfield is 2, the TWT subfield is for a future broadcast TWT SP start time, and the TWT element contains one or more broadcast TWT parameter sets. This may correspond to providing a broadcast TWT schedule to a TWT-scheduled STA by including the TWT element in a broadcast management frame transmitted by the TWT scheduling AP.

For example, if the value of the Agreement Type subfield is 3, the TWT subfield is for a future broadcast TWT SP start time, and the TWT element contains one or more sets of broadcast TWT parameters. This may correspond to managing membership in a broadcast TWT schedule by including the TWT element in individually addressed management frames transmitted by either the TWT-scheduling STA or the TWT-scheduling AP.

If the TWT information frame disabled subfield is set to 1, it indicates that reception of TWT information frames by the STA is disabled, otherwise it may be set to 0.

The wake duration unit subfield indicates the unit of the nominal minimum TWT wake duration field. The wake duration unit subfield may be set to 0 if the unit is 256 us and set to 1 if the unit is TU. For non-HE/EHT STAs, the wake duration unit subfield may be set to 0.

The most significant bit (MSB) of the agreement type field may correspond to a broadcast field. If the broadcast field is 1, a TWT element may contain one or more broadcast TWT parameter sets. If the broadcast field is 0, only one individual TWT parameter set may be contained in the TWT element. A TWT element with the broadcast field set to 1 may be referred to as a broadcast TWT element.

Fig. 12 is a diagram illustrating examples of individual TWT parameter set field formats. Fig. 13 is a diagram illustrating examples of broadcast TWT parameter set field formats.

The TWT parameter information field included in the TWT element of Fig. 11 may have a different configuration depending on the individual TWT or broadcast TWT.

For individual TWTs, the TWT parameter information field within the TWT element contains a single individual TWT parameter set field.

In the case of a broadcast TWT, the TWT parameter information field within the TWT element contains one or more broadcast TWT parameter set fields. Each broadcast TWT parameter set may contain specific information about one broadcast TWT.

As illustrated in FIGS. 12 and 13, the individual TWT parameter set field and the broadcast TWT parameter set field include common subfields.

The request type subfield may be the same size as the individual TWT parameter set field and the broadcast TWT parameter set field, but may have different detailed configurations. This will be described later.

The target wake time subfield indicates the start time of the upcoming individual/broadcast TWT SP.

The nominal maximum TWT wake duration subfield indicates the minimum interval during which a TWT requesting STA expects to wake up to complete a frame exchange associated with a TWT flow identifier during the TWT wake interval duration. Here, the TWT wake interval may mean the average time between consecutive TWT SPs expected by the TWT requesting STA.

The TWT Wake Interval Mantissa subfield can be expressed as a binary value of the TWT wake interval value in microseconds.

Referring to Figure 12, the TWT group assignment subfield, TWT channel, and NDP paging subfield are included only in the individual TWT parameter set fields.

The TWT Group Assignment subfield provides the TWT requesting STA with information about the TWT group to which the STA is assigned. This information can be used to calculate the TWT value within the TWT group. The TWT value of the STA may be equal to the value of the zero offset multiplied by the value of the TWT offset multiplied by the value of the TWT unit.

The TWT Channel subfield indicates a bitmap indicating allowed channels. When transmitted by a TWT requesting STA, the TWT Channel subfield may include a bitmap indicating a channel that the STA requests to use as a temporary default channel during the TWT SP. When transmitted by a TWT responding STA, the TWT Channel subfield may include a bitmap indicating a channel on which the TWT request is allowed.

The NDP paging subfield is optional and may include information such as an identifier of the STA being paged, the maximum number of TWT wake intervals between NDP paging frames, etc.

Referring to FIG. 13, the broadcast TWT info subfield is included only in the broadcast TWT parameter set field. The broadcast TWT info subfield may include a 3-bit reserved bit, a 5-bit broadcast TWT identifier (ID) subfield, and an 8-bit broadcast TWT persistence subfield. The broadcast TWT identifier subfield indicates the broadcast ID of a specific broadcast TWT for which an STA requests participation or provides TWT parameters, depending on the value of the TWT setup command subfield of the TWT element. The broadcast TWT persistence subfield indicates the number of TBTTs planned in the schedule of the broadcast TWT.

Next, we will explain the detailed configuration of the request type subfield.

First, the format of the request type subfield of the individual TWT parameter set field is described with reference to FIG. 12.

The TWT request subfield can indicate whether the STA is a requesting STA or a responding STA. If the value is 1, it indicates that the STA is a TWT requesting STA or a scheduled STA, and if it is 0, it indicates that the STA is a TWT responding STA or a scheduling AP.

The TWT setup command subfield can represent commands such as Request, Suggest, Demand, Accept, Alternate, Dictate, and Reject.

The trigger subfield indicates whether a trigger frame is used in the TWT SP. If the value is 1, the trigger is used, and if it is 0, the trigger is not used.

The implicit subfield can indicate whether the TWT is implicit or explicit. A value of 1 indicates implicit TWT, while a value of 0 indicates explicit TWT.

The flow type subfield may indicate the type of interaction between a TWT requesting STA (or a TWT-scheduled STA) and a TWT responding STA (or an AP that schedules the TWT). If the value is 1, it may mean announced TWT, in which the STA sends a wake-up signal to the AP by transmitting a PS-Poll or APSD (automatic power save delivery) trigger frame before a non-trigger frame is transmitted from the AP to the STA. If the value is 0, it may mean unannounced TWT.

The TWT flow identifier subfield may contain a 3-bit value that uniquely identifies specific information about the TWT request in other requests made between the same TWT requesting STA and TWT responding STA pair.

The TWT wake interval exponent subfield can set the TWT wake interval value in binary microseconds. For individual TWTs, this can mean the interval between individual TWT SPs. The TWT wake interval of the requesting STA can be defined as [TWT Wake Interval Mantissa * 2 * TWT Wake Interval Exponent].

The TWT protection subfield can indicate whether a TWT protection mechanism is used. If the value is 1, TXOPs within a TWT SP can be initiated with a NAV protection mechanism, such as (MU)RTS/CTS or CTS-to-self frames. If the value is 0, the NAV protection mechanism may not be applied.

Referring to FIG. 13, some of the subfields of the request type subfield of the broadcast TWT parameter set field are common to the subfields of the request type subfield of the individual TWT parameter set fields, and therefore, a description thereof is omitted. The subfields included only in the broadcast TWT parameter set are described below.

The Last Broadcast Parameter Set subfield indicates whether this is the last broadcast TWT parameter set. A value of 1 indicates that this is the last broadcast TWT parameter set, while a value of 0 indicates that there is a next broadcast TWT parameter set.

The Broadcast TWT Recommendation subfield may indicate recommendations for the frame types transmitted by the AP during a Broadcast TWT SP, with values from 1 to 7.

The last bit of the Request Type subfield of the Broadcast TWT Parameter Set field may be reserved.

With the recent explosion in wired and wireless traffic, latency-sensitive traffic has also increased significantly. Latency-sensitive traffic includes real-time audio/video transmission, and the proliferation of multimedia devices has increased the need to support this traffic in wireless environments. However, supporting latency-sensitive traffic in wireless environments requires more considerations than in wired environments. This is because wireless environments have lower transmission speeds and must also consider interference from surrounding environments. In particular, in WLAN systems, multiple STAs must compete equally for medium access in the Industry-Science-Medical (ISM) band, making it relatively more difficult to support latency-sensitive traffic compared to cellular communication networks, which rely on centralized radio resource scheduling. This disclosure describes a novel approach for supporting latency-sensitive traffic in WLAN systems.

In the present disclosure, latency may refer to latency defined in the IEEE 802.11 series standards. For example, it may refer to the time from when a frame to be transmitted enters the queue of the MAC layer of the transmitting STA, until the transmitting STA successfully completes transmission in the PHY layer, and the transmitting STA receives an ACK/block ACK, etc. from the receiving STA, and the corresponding frame is deleted from the MAC layer queue of the transmitting STA. In addition, in the present disclosure, a non-AP STA that supports transmission of latency-sensitive data may be referred to as a low latency STA. In addition, data other than latency-sensitive data may be referred to as regular data.

Restricted TWT (r-TWT) can support securing data transmission possibility for low-latency STAs transmitting latency-sensitive data preferentially over other STAs by having the AP set a special broadcast TWT for the low-latency STAs. The STAs can establish membership in one or more r-TWT schedules with respect to the AP. Here, the r-TWT agreement can be established by the same process as the broadcast TWT agreement, and the broadcast TWT element for this can be defined to include an r-TWT parameter set field. For example, the r-TWT parameter set can refer to a specific broadcast TWT parameter set field that is distinct from other broadcast TWT parameter set fields. That is, the r-TWT parameter set field can correspond to a special case of the broadcast TWT parameter set field. In addition, the AP can announce an r-TWT SP.

Basically, if another STA supporting r-TWT operation is a TXOP holder, the TXOP must end before the start time of the r-TWT SP advertised by the associated AP. Accordingly, the STA related to the r-TWT (i.e., the low-latency STA) can transmit and receive traffic with priority over the other STAs within the r-TWT SP.

In the present disclosure, a low-latency STA associated with a specific r-TWT, as described above, is referred to as a member r-TWT scheduled STA, and other STAs are referred to as non-member STAs. A non-member STA may be an STA that has the capability to support r-TWT operation but is not a member of any r-TWT, or that supports r-TWT operation but is a member of another r-TWT, or that does not have the capability to support r-TWT operation.

An STA (e.g., a low-latency STA) that supports limited SP (or r-TWT SP) operation of broadcast TWT can inform the AP that it needs to transmit latency-sensitive data based on r-TWT operation. If the AP supports r-TWT operation/mode, the AP can transmit a frame containing scheduling information of TWTs requested by each STA to the low-latency STA and other STA(s). For example, in order to perform operation for r-TWT, non-AP STAs can obtain r-TWT related information from the AP through a beacon frame, a probe response frame, a (re)association response frame, or other frames in an undefined format (e.g., frames for broadcast, advertisement, or announcement purposes).

According to the restricted TWT operation, a separate TXOP (i.e., to which access of other STAs is restricted) can be secured within the r-TWT SP by using a NAV such as (MU) RTS/CTS or CTS-to-self, or a quiet interval. Before a specific r-TWT SP starts, if there is a TXOP of another STA (i.e., a non-member STA) other than the STA having the membership for the specific r-TWT schedule, it must be stopped. And the TXOP of the other STA (i.e., the non-member STA) can be additionally performed after the specific r-TWT SP ends.

Negotiation process related to TWT's coordination

In a multi-BSS environment, when APs are located within a range where they can receive each other's beacon frames, an OBSS (overlapping BSS) range can be formed, which is a range where the transmission and reception ranges (i.e., BSS) of the APs overlap.

FIG. 14 is a diagram exemplarily showing APs and STAs in an OBSS to which the present disclosure can be applied.

As illustrated in FIG. 14, the signaling range of AP1 (e.g., the range corresponding to BSS 1) and the signaling range of AP2 (e.g., the range corresponding to BSS 2) may overlap. In this way, when AP1 and AP2 are located within a range where they can receive (i.e., overhear) each other, AP1 and AP2 can negotiate for coordination for their own scheduled R-TWT SPs (service periods) via (wireless/wired) communication. This case corresponds to a case where AP1 and AP2 are located within the range of OBSSs where their transmission and reception ranges overlap, unlike the case where AP1 and AP2 are hidden nodes.

In this regard, STAs located within the overlapping range can receive beacon frames not only from the AP with which they are associated, but also from APs with which they are not associated. For example, STA 1-2 can receive a beacon frame from AP1 with which it is associated, and can also receive (i.e., overhear) a beacon frame from AP2 with which it is not associated. For example, STA2-3 can receive a beacon frame from AP2 with which it is associated, and can also receive (i.e., overhear) a beacon frame from AP1 with which it is not associated.

The examples of the present disclosure are not limited to the situations of APs and/or STAs illustrated in FIG. 14, and may be applied to various situations requiring agreement on a cooperative service period between APs. For example, AP1 may be in a position/situation where it can receive AP2's beacon frame, while AP2 may be in a position/situation where it cannot receive AP1's beacon frame. Alternatively, AP1 and AP2 may be in a position/situation where they can receive each other's beacon frames. Alternatively, AP1 may be in a position/situation where it cannot receive AP2's beacon frame, while AP2 may be in a position/situation where it can receive AP1's beacon frame.

A beacon frame may contain restricted-TWT (R-TWT) scheduling information that an AP assigns to STAs associated with it, and STAs receiving the R-TWT scheduling information are required to protect R-TWT SPs of which they are not a member (e.g., terminating a TXOP of the STA if it is in progress before the start time of the R-TWT SP, as described above). That is, an STA receiving a beacon frame including R-TWT scheduling information may mean that it is in a position to protect the corresponding R-TWT SP. On the other hand, it is not yet defined whether an STA should protect the corresponding R-TWT SP or transmit/receive low-latency traffic/data during the corresponding R-TWT SP when it receives R-TWT scheduling information advertised by an AP to which it is not associated (or a neighboring AP).

The present disclosure describes a method for performing negotiation for coordination for R-TWT based on scheduling information for R-TWT scheduled by an associated AP (e.g., AP1) and/or scheduling information for R-TWT scheduled by a non-associated (or neighboring) AP (e.g., AP2). In the following description, an R-TWT SP scheduled by another AP (e.g., a non-associated AP or a neighboring AP) is referred to as an OBSS R-TWT SP to distinguish it from an R-TWT SP scheduled by an associated AP. The scope of the present disclosure is not limited by the name OBSS R-TWT.

In addition, although various examples of cooperation/negotiation schemes for R-TWT scheduling between a combined AP and a neighboring AP are described in this disclosure, the scope of this disclosure is not limited thereto, and examples of this disclosure can also be applied to cooperation/negotiation for individual TWT scheduling, broadcast TWT scheduling, etc.

In this disclosure, a case in which a cooperation request is transmitted by a coupled AP and a cooperation response thereto is transmitted by a non-coupled (or neighboring) AP is mainly used as a representative example for explanation, but this is for clarity of explanation, and the proposed method in this disclosure can also be applied to a case in which a cooperation request is transmitted by a non-coupled (or neighboring) AP and a cooperation response thereto is transmitted by a coupled AP.

The present disclosure describes a signaling method for negotiating a cooperative service period (SP) between APs in a multi-AP or multi-BSS environment.

This disclosure assumes APs with overlapping BSSs. One of the APs may be an associated AP from the perspective of a specific STA, and the other AP may be a neighboring AP or an OBSS AP. For example, from the perspective of an STA associated with a first AP, the first AP may be an associated AP, and the second AP may be an OBSS AP. From the perspective of an STA associated with a second AP, the second AP may be an associated AP, and the first AP may be an OBSS AP.

Cooperation between the combined AP and the OBSS AP for R-TWT SPs can be implemented based on the success of wireless/wired negotiation. Each AP can agree on whether to provide protection for the OBSS R-TWT SP within the other BSS.

In this disclosure, it is assumed that such R-TWT cooperation is performed using the TWT setup frame. While the TWT setup frame is defined to negotiate TWT scheduling between an AP and an STA, the TWT setup frame can be modified or redefined for use in TWT negotiation between APs in this disclosure.

This disclosure describes examples of TWT negotiation signaling between APs using TWT elements included in a TWT setup frame, control fields included in the TWT elements, and broadcast TWT parameter set fields. However, the scope of the present disclosure is not limited thereto, and examples of the present disclosure may also be applied to newly defined frames for cooperation requests and cooperation responses, and/or newly defined elements for TWT negotiation between APs.

In the present disclosure, the broadcast TWT parameter set field may correspond to a TWT parameter set field including a restricted TWT (R-TWT) schedule.

In the existing technology, when information on a restricted TWT (R-TWT) schedule is included in a broadcast TWT parameter set field, the value of the broadcast TWT recommendation field can be set to 4 to indicate that the TWT parameter set field includes information on the restricted TWT schedule, which can be referred to as a restricted TWT parameter set field. In the present disclosure, the value of the broadcast TWT recommendation field is not limited to 4, and since the TWT that is the target of cooperation between APs needs to be distinguished from the restricted TWT (R-TWT) between the existing AP and STA, the name "restricted TWT parameter set field" is not used, but the name "broadcast TWT parameter set field" is used for description. However, the scope of the present disclosure is not limited by the exemplary names of the fields, and examples of the present disclosure can be applied to fields with other names.

The TWT cooperation described in this disclosure may include not only the purpose of an AP cooperating with an OBSS AP on a TWT schedule, but also the purpose of an AP providing/sharing information about a TWT schedule with an OBSS AP. Various examples distinguishing these purposes are also described below.

Although various examples of the present disclosure are described based on a TWT setup frame including a TWT element, it does not exclude that information for R-TWT cooperation that is not included in the TWT element may be included in the TWT setup frame (or a newly defined frame). Information for R-TWT cooperation that is not included in the TWT element may include, for example, new elements including information for supporting or related to an AP cooperative transmission scheme (e.g., C-TDMA, C-SR, C-OFDAM, etc.) used during a coordinated R-TWT service period (SP), and/or EDCA parameter set elements of APs, OBSS APs, and/or STAs belonging to each BSS for coordinated EDCA parameter set negotiation to resolve unfairness issues arising from random access between APs during a coordinated R-TWT SP.

FIG. 15 is a drawing showing an example of the operation of the first AP according to the present disclosure.

In step S1510, the first AP can transmit a first frame including a first TWT element to the second AP.

For example, the first AP and the second AP may be APs in an OBSS AP relationship in which the BSS overlaps.

In some examples, the first TWT element may include a control field and a first broadcast TWT parameter set field. The control field may include a negotiation type field. The value of the negotiation type field may be set to a value associated with the first broadcast TWT parameter set. For example, the negotiation type field may be set to a value (e.g., 3) indicating that the broadcast TWT parameter set is used for signaling TWT cooperation between APs.

In some examples, the first broadcast TWT parameter set field may include one or more scheduling-related information. Each of the one or more scheduling-related information may be set to a value based on the reference timing of the second AP. For example, the reference timing of the second AP may correspond to a timing synchronization function (TSF) value of the second AP. For example, the one or more scheduling-related information may include one or more of the following:

- Target wake time field in the first broadcast TWT parameter set field;

- a nominal minimum TWT wake duration field within the first broadcast TWT parameter set field;

- TWT wake interval mantissa field within the first broadcast TWT parameter set field;

- a TWT wake interval exponent field within the request type field within the first broadcast TWT parameter set field; or

- A broadcast TWT persistence field within the broadcast TWT info field within the first broadcast TWT parameter set field.

To indicate that a frame/TWT element/broadcast TWT parameter set is associated with TWT negotiation between APs in some examples: the value of the Broadcast TWT Recommendation field within the first Broadcast TWT Parameter Set field may be set to a specific value (e.g., one of 3, 5, 6, or 7); or the value of the NDP Paging Indicator field within the Control field within the first Broadcast TWT Parameter Set field may be set to a specific value (e.g., 1).

In some examples, the first broadcast TWT parameter set field may include a request type field. Here, the value of the TWT request field in the request type field is set to 1 (e.g., indicating that the first AP is requesting TWT parameter related information), and the TWT setup command field in the request type field may be set to a value corresponding to one of request, suggest, or demand.

In some examples, the first broadcast TWT parameter set field may further include information indicating whether membership of a station (STA) associated with a second AP is allowed for a TWT schedule associated with the first broadcast TWT parameter set field. For example, the information indicating whether membership of an STA associated with a second AP is allowed may be an aligned field within a request type field within the first broadcast TWT parameter set field. If membership of an STA associated with a second AP is allowed, the value of the aligned field may be set to 1, and if membership of an STA associated with a second AP is not allowed, the value of the aligned field may be set to 0.

In step S1520, the first AP can receive a second frame responding to the first frame from the second AP.

In some examples, the second frame may include a second TWT element, and a second broadcast TWT parameter set field within the second TWT element may include a request type field. Here, the value of the TWT request field within the request type field may be set to 0 (e.g., indicating that this is a response of the second AP to the TWT parameter related information requested by the first AP), and the TWT setup command field within the request type field may be set to a value corresponding to one of accept, alternate, dictate, or reject.

In some examples, the second TWT element may additionally include a third broadcast TWT parameter set field in addition to the second broadcast TWT parameter set field. The third broadcast TWT parameter set field may include a request type field, and a value of a TWT request field in the request type field may be set to 1 (e.g., indicating that the second AP is requesting TWT parameter related information), and a TWT setup command field in the request type field may be set to a value corresponding to one of a request, a proposal, or a demand.

In some examples, the value of the last broadcast parameter set field in the request type field of the second broadcast TWT parameter set field may be set to 0, and the value of the last broadcast parameter set field in the request type field of the third broadcast TWT parameter set field may be set to 1.

Although not shown in FIG. 15, in some examples, a third frame responding to the second frame may be transmitted from the first AP to the second AP. For example, the third frame may include a third TWT element. A fourth broadcast TWT parameter set field within the third TWT element may include a request type field, and a value of a TWT request field within the request type field may be set to 0 (e.g., indicating that this is a response from the first AP to the TWT parameter related information requested by the second AP), and a TWT setup command field within the request type field may be set to a value corresponding to one of accept, alternate, dictate, or reject.

In some examples, the first frame and the second frame may correspond to TWT setup frames.

The method described in the example of FIG. 15 may be performed by the first device (100) of FIG. 1. For example, one or more processors (102) of the first device (100) (or the first AP) of FIG. 1 may be configured to transmit a first frame including a first TWT element to a second device (200) (or the second AP) through one or more transceivers (106), and receive a second frame from the second device (200) (or the second AP) through one or more transceivers (106) in response to the first frame. Furthermore, one or more memories (104) of the first device (100) may store commands for performing the method described in the example of FIG. 19 or the examples described below when executed by one or more processors (102).

For example, one or more processors (102) can generate a MAC frame corresponding to a cooperation request based on information about an R-TWT service period (SP) for negotiating cooperation with a second device (200) and information necessary for negotiation, and can generate a PPDU including the MAC frame and transmit the PPDU to the second device (200) via one or more transceivers (106). For example, when a PPDU is received from the second device (200) via one or more transceivers (106), one or more processors (102) can parse a MAC frame obtained through PHY decoding of a data field of the PPDU, check information about R-TWT for which cooperation is requested by the second device (200) from the parsed MAC frame, and generate a PPDU including a cooperation response thereto, and transmit the PPDU including a cooperation response thereto to the second device (200) via one or more transceivers (106).

FIG. 16 is a drawing showing an example of the operation of a second AP according to the present disclosure.

In step S1610, the second AP may receive a first frame including a first TWT element from the first AP.

In step S1620, the second AP may transmit a second frame responding to the first frame to the first AP.

In the example of Fig. 16, the specific descriptions of the first frame, the second frame, the first TWT element and its subfields included in the first frame, the elements/fields included in the second frame, and additionally the third frame received by the second AP are the same as those in the example of Fig. 15, so redundant descriptions are omitted.

The method described in the example of FIG. 16 may be performed by the second device (200) of FIG. 1. For example, one or more processors (202) of the second device (200) of FIG. 1 (e.g., the second AP) may be configured to receive a first frame including a first TWT element from the first device (100) (or the first AP) through one or more transceivers (206), and transmit a second frame to the first device (100) (or the first AP) through one or more transceivers (206) in response to the first frame. Furthermore, one or more memories (204) of the second device (200) may store commands for performing the method described in the example of FIG. 20 or the examples described below when executed by one or more processors (202).

The first AP in FIG. 15 may correspond to a transmitting AP, and the second AP in FIG. 16 may correspond to a receiving AP.

These transmitting APs and receiving APs can perform signaling for R-TWT cooperation between APs. The transmitting STA can initially transmit to the receiving AP a frame including information for the purpose of requesting R-TWT cooperation (e.g., R-TWT schedule information). The receiving STA receives the frame including the purpose of the R-TWT cooperation request from the transmitting STA, and based on the R-TWT schedule information included in the frame, can transmit to the transmitting STA a frame additionally including a value indicating whether to protect the corresponding SP (e.g., a response meaning accept, reject, alternative, dictate, etc. for the request) and/or a new R-TWT cooperation request. The transmitting STA that receives a response to its own R-TWT cooperation request from the receiving STA can operate as follows according to the response.

If the response from the receiving STA is an acceptance-related value, this may indicate that R-TWT negotiation/cooperation has been successfully performed with the receiving STA in response to the request from the transmitting STA. Accordingly, the R-TWT SP negotiated between the transmitting AP and the receiving AP can be obtained. In this case, the transmitting STA may not transmit additional frames regarding the R-TWT cooperation to the receiving STA.

If the response from the receiving STA is a rejection-related value, the transmitting STA may not transmit additional frames to the receiving STA.

If the response from the receiving STA is a value related to the proposal (e.g., an alternative or a dictate, etc.), a frame may be constructed and transmitted based on a value indicating whether the transmitting STA protects the corresponding SP (e.g., a cooperative response) for the R-TWT schedule information corresponding to the request of the receiving STA, not the request of the transmitting STA.

Even if a transmitting STA receives R-TWT schedule information corresponding to a new R-TWT cooperation request from a receiving STA, it can construct and transmit a frame containing a response to the request (e.g., a value indicating whether the corresponding SP is protected). The receiving STA that receives the response can determine whether cooperation is provided for the R-TWT schedule it requested based on the response.

If the response from the transmitting STA is an acceptance-related value, this may indicate that R-TWT negotiation/cooperation has been successfully performed with the transmitting STA in response to the receiving STA's request. Accordingly, the R-TWT SP negotiated between the transmitting AP and the receiving AP can be obtained.

The examples of FIGS. 15 and 16 may correspond to some of the various examples of the present disclosure. Below, various examples of the present disclosure, including the examples of FIGS. 15 and 16, are described in more detail.

Although the examples of the present disclosure are described in the following embodiments assuming two APs with (partial) overlapping neighbors or BSSs, the scope of the present disclosure is not limited thereto, and the examples of the present disclosure can be equally applied to a set of channel access parameters applied in a cooperative service period between three or more APs/BSSs.

In the examples below, the term field may be replaced with subfield, and the term subfield may be replaced with the term field.

Example 1

This embodiment relates to a frame for R-TWT cooperation transmitted and received between APs.

Below are examples of how an OBSS AP recognizes that a frame it transmits is a frame sent to the OBSS AP for the purpose of requesting or responding to cooperation for R-TWT. Similarly, below are examples of how an AP recognizes that a frame it receives is a frame sent from the OBSS AP for the purpose of requesting or responding to cooperation for R-TWT.

Example 1-1

If a PPDU received by an AP is a DL PPDU that includes a different BSS color from that of the receiving AP (i.e., itself), and the RA (receiver address) of the MAC header of the TWT setup frame included in the DL PPDU points to the MAC address of the receiving AP, the receiving AP can recognize that the frame is related to R-TWT cooperation transmitted by the OBSS AP to the receiving AP.

Example 1-2

A new framework for R-TWT cooperation between APs can be defined.

An AP receiving this newly defined frame can recognize that it is a frame related to R-TWT cooperation transmitted by an OBSS AP to the receiving AP (i.e., itself).

Example 1-3

Elements for R-TWT cooperation between APs can be newly defined. For example, a newly defined frame can include information related to the R-TWT schedule and be given an element ID that distinguishes it from other elements. An AP that receives a frame containing such an element ID can recognize that the frame contains elements related to R-TWT cooperation transmitted by the OBSS to the receiving AP (i.e., itself).

Example 1-4

The value of the broadcast TWT recommendation field in the broadcast TWT parameter set of the TWT setup frame may indicate that it contains an R-TWT schedule for TWT setup between APs.

For example, a particular value (e.g., one of 4-7) in the Broadcast TWT Recommendation field within the Request Type field within the Broadcast TWT Parameter Set may be defined to indicate that the TWT setup being negotiated between APs corresponds to that value.

In this case, the value of the negotiation type field in the control field within a specific element of the TWT setup frame (e.g., the TWT element) may be set to 3.

Additionally or alternatively, the value of the Agreement Type field within the Control field within a specific element of the TWT Setup frame (e.g., the TWT element) may be set to another value to signify that the TWT Parameter Set field is intended for sharing and/or cooperating with the R-TWT schedule between APs.

Example 1-5

It may be indicated that the TWT setup frame contains an R-TWT schedule for TWT setup between APs via an NDP paging indicator field within a control field within a specific element (e.g., a TWT element) of the TWT setup frame.

For example, if the value of the NDP paging indicator field in the control field received by the AP is set to 1, it can be recognized that it contains an R-TWT schedule for TWT setup between the AP and the AP.

An AP that receives a frame with the NDP paging indicator field set to 1 can recognize that it is a TWT setup frame received from an S1G (sub-1GHz) STA. Accordingly, the AP can recognize that it is a TWT setup frame received from an OBSS AP (for example, whether it is a frame received from an OBSS AP can be identified according to Example 1-1) and also that it is a received TWT setup frame when the value of the NDP paging indicator field is 1.

Additionally or alternatively, if the value of the NDP paging indicator field is set to 1 and the value of the broadcast TWT recommendation field is set to a specific value (e.g., embodiment 1-4), the AP may recognize that the frame is related to R-TWT cooperation received from the OBSS AP.

Example 2

This embodiment relates to a set of TWT parameters corresponding to an R-TWT cooperation request and/or an R-TWT cooperation response.

In the present disclosure, an R-TWT cooperation request or R-TWT cooperation response negotiated between APs can be identified/recognized based on the following method.

If R-TWT cooperation is performed based on TWT elements of existing TWT setup frames or new elements/new frames, each individual/broadcast/restricted TWT parameter set field can be regarded as a cooperation request or cooperation response, depending on the value of the TWT setup command field. That is, if the value of the TWT setup command field indicates 0 (request), 1 (suggest TWT), or 2 (demand TWT), a TWT parameter set field containing the corresponding value can be regarded as a cooperation request. In addition, if the value of the TWT setup command field indicates 4 (accept TWT), 5 (alternate TWT), 6 (dictate TWT), or 7 (reject TWT), a TWT parameter set field containing the corresponding value can be regarded as a cooperation response.

Additionally or alternatively, if R-TWT cooperation is performed based on a TWT element of an existing TWT setup frame or a new element/new frame, each individual/broadcast/limited TWT parameter set field may be considered a cooperation request or a cooperation response, depending on the value of the TWT request field. That is, if the value of the TWT request field is 1, a TWT parameter set field containing that value may be considered a cooperation request. Also, if the value of the TWT request field is 0, a TWT parameter set field containing that value may be considered a cooperation response.

Additionally or alternatively, if R-TWT cooperation is performed based on a TWT element of an existing TWT setup frame or a new element/new frame, each broadcast/restricted TWT parameter set field may be regarded as a cooperation request or a cooperation response, depending on the values of the TWT request field and the TWT setup command field. That is, if the value of the TWT request field is set to 1 and the value of the TWT setup command field indicates 0 (request TWT), 1 (propose TWT), or 2 (request TWT), the TWT parameter set field containing that value may be regarded as a cooperation request. Also, if the value of the TWT request field is set to 0 and the value of the TWT setup command field indicates 4 (accept TWT), 5 (alternative TWT), 6 (dictate TWT), or 7 (reject TWT), the TWT parameter set field containing that value may be regarded as a cooperation response.

If a new element for R-TWT cooperation is defined based on an existing TWT element and is distinct from the existing TWT, the new element may include one or more sets of fields containing one R-TWT schedule information. Each set may include a TWT setup command field, and a cooperation request or cooperation response may be identified through values such as request, update, proposal, acceptance, or rejection. That is, if the value of the TWT setup command field indicates a request or update, the set may be considered a cooperation request. Alternatively, if the value of the TWT setup command field indicates a proposal, acceptance, or rejection, the set may be considered a cooperation response.

Additionally or alternatively, a request may be considered a collaboration request if indicated in the TWT setup command field, and an update may be considered a collaboration update (as distinct from a collaboration request) if indicated in the TWT setup command field.

Additionally, alternatively, a case in which the TWT setup command field indicates an accept or reject may be considered a cooperative response, and a case in which the TWT setup command field indicates an offer may be considered a cooperative offer (as distinct from a cooperative response).

Additionally or alternatively, during the negotiation process for R-TWT cooperation between APs, an example of a case in which an AP receiving a cooperation request responds with acceptance or rejection for an R-TWT schedule included in the cooperation request is as follows. If the R-TWT schedule included in the cooperation request overlaps/overlaps in whole or in part with an R-TWT schedule scheduled within the BSS of the AP that receives the cooperation request and attempts to transmit a cooperation response, the AP that received the cooperation request may transmit a cooperation response including a rejection response for the R-TWT schedule. If the R-TWT schedule does not overlap in whole or in part, the AP that received the cooperation request may transmit a cooperation response including an acceptance response for the R-TWT schedule.

Example 3

This embodiment details the configuration of fields within a broadcast TWT parameter set for R-TWT cooperation. The broadcast TWT parameter set for R-TWT cooperation may correspond to a limited TWT parameter set defined as one type of broadcast TWT.

FIG. 17 is a diagram illustrating examples of broadcast TWT parameter sets related to TWT cooperation between APs in the present disclosure.

The example of FIG. 17 may correspond to a variation in which some field(s) of the broadcast TWT parameter set of FIG. 14 are added/modified/reserved/redefined. For example, a TWT channel field may be added to the broadcast parameter set. For example, a flow type (see FIG. 14) field may be reserved in a request type field within the broadcast parameter set. For example, a TWT bandwidth field and/or a cooperative TWT ID field may be added within the broadcast TWT information field within the broadcast parameter set. For example, a broadcast TWT ID field within the broadcast TWT information field within the broadcast parameter set may be excluded or modified to a cooperative TWT ID field.

In the example of FIG. 17, the TWT setup command field and/or the broadcast TWT recommendation field in the request type field within the broadcast parameter set may be redefined with the information they indicate. In the example of FIG. 17, the aligned field in the request type field within the broadcast parameter set may be added compared to the example of FIG. 14, and may be redefined to indicate other information than whether the original aligned field indicates whether the corresponding broadcast TWT schedule is aligned with the broadcast TWT schedule(s) of one or more other links of the AP MLD (multi-link device).

Although the format of the broadcast TWT parameter set field for R-TWT cooperation between APs is illustrated in FIG. 17, the scope of the present disclosure is not limited thereto, and new field(s) not illustrated in FIG. 17 may be added, some field(s) illustrated in FIG. 17 may be excluded, and the positions of the fields are not limited to the example in FIG. 17.

Additionally or alternatively, the length of the fields related to the schedule information of the TWT described below may be the same as the length of the corresponding fields in the existing TWT parameter set field, or may be redefined as fields of a different length (e.g., a longer or shorter length). If a field redefined to a longer length than the existing field is applied, the length of the new field may be defined to be shorter.

The broadcast TWT parameter set in the examples described below may be referred to as a new TWT parameter set to distinguish it from the existing broadcast TWT parameter set, or may be referred to simply as a broadcast TWT parameter set if there is no need for distinction.

Example 3-1

For scheduling information of R-TWT, the following fields can be used in the same way as the definitions of existing broadcast TWT parameter set fields.

The information of the TWT schedule included in the new broadcast TWT parameter set field included in the corresponding TWT cooperation may have the values of the fields below set based on the TSF of the receiving AP (or the AP receiving the cooperation request). This example of the present disclosure is distinguished from the information in the existing broadcast TWT parameter set field in which the value is set based on the TSF of the transmitting AP. Here, information related to the TSF of the receiving AP can be recognized by the transmitting AP (or the AP transmitting the cooperation request)/STAs based on the information in the overhearing beacon frame.

In the examples described below, the expression that a first field (or element) does not include a second field may include cases where the second field is reserved within the first field (i.e., the corresponding bit position(s) are present but do not indicate meaningful information), or the second field itself is excluded from the first field (i.e., the corresponding bit position(s) are deleted or allocated for another field).

- Target wake time field

- Nominal minimum TWT wake duration field

Alternatively, although the nominal minimum TWT wake duration field is included in the example of FIG. 17, in the R-TWT cooperation process for the purpose of protecting the R-TWT schedule of a neighboring AP, the nominal minimum TWT wake duration field may not be included in the broadcast TWT parameter set field. For example, for the purpose of protecting non-overlapping R-TWT SPs described below, the duration information field may not be included in the broadcast TWT parameter set field.

- TWT wake interval singer field

- TWT wake interval index field within the request type field

- Broadcast TWT persistence field within the Broadcast TWT information field

The broadcast TWT duration field may indicate the number of times the corresponding R-TWT SP lasts, etc., but if the broadcast TWT duration field is not included in the broadcast TWT parameter set field during the R-TWT cooperation process between APs, it may operate or imply such operation to maintain protection for the cooperated R-TWT schedule within each BSS until the AP that transmitted the cooperation request transmits a frame containing a request for the end of cooperation (delete/finish/termination, etc.) for the cooperated R-TWT schedule to the AP that transmitted the cooperation response.

Example 3-2

A broadcast TWT parameter set may include information in a trigger field indicating whether a trigger frame is transmitted or received during an R-TWT SP. The existing trigger field is included in the request type of the individual TWT parameter set field (see FIG. 13), but a broadcast TWT parameter set for cooperative TWT between APs may also include a trigger field, and its meaning may be defined as follows.

For example, during an overlapping R-TWT SP, an AP and an OBSS AP can negotiate during the R-TWT cooperation process whether to transmit or receive trigger frames to their associated STAs belonging to the corresponding R-TWT SP. This allows only the AP or the OBSS AP to prevent or allow the transmission of trigger frames to their associated STAs belonging to the corresponding R-TWT SP during the overlapping R-TWT SP. As a result of the negotiation, the AP and the OBSS AP that announce the overlapping R-TWT schedule in their BSS can set the value of the trigger field in the TWT parameter set field including the corresponding R-TWT schedule to be the same (i.e., the same as whether to allow triggering for the cooperative R-TWT SP).

Example 3-3

In order to construct a frame for scheduling cooperation request/response of R-TWT between APs, some field(s) within the existing broadcast TWT parameter set field may be included in the new broadcast TWT parameter set as in the examples below, and the field(s) may be interpreted (i.e., indicate specific information) as in the examples below.

- TWT request fields within the request type field

If the TWT request field has a value of 1, it may indicate that this is a broadcast TWT parameter set containing a TWT schedule for requesting cooperation between APs.

If the TWT request field has a value of 0, it may indicate that this is a broadcast TWT parameter set containing a TWT schedule for responding to requested cooperation between APs.

Here, the TWT setup frame that the AP transmits to the OBSS AP for R-TWT cooperation may simultaneously include a broadcast TWT parameter set with the TWT request field set to 1 and a broadcast TWT parameter set with the TWT request field set to 0.

- TWT setup command field within the request type field

If the TWT setup command field has a value of 0 (request TWT), 1 (propose TWT), or 2 (request TWT), it may be considered a cooperation request, as in the examples described above.

Additionally or alternatively, if the frame/element is for R-TWT coordination between APs, the values of the corresponding fields may be defined to indicate one or more of the following purposes: add, new, update, modify, delete, terminate, or end of coordination:

Add/New may be for the purpose of cooperating with a new R-TWT schedule.

The purpose of an update/modify may be to update a successfully coordinated R-TWT schedule. For example, the purpose of updating a certain coordinated R-TWT SP may be specified through a coordinated TWT ID. Based on the values of fields in the broadcast TWT parameter set field that contain the coordinated TWT ID corresponding to the successfully coordinated R-TWT schedule and have different values from the values of the existing R-TWT schedule, the existing R-TWT schedule information may be updated and notified to the associated STAs. Upon successful completion of the update request, the APs/STAs of the corresponding BSS may perform protection and operation for the changed coordinated R-TWT SP.

Delete/terminate/end of coordination may be intended to end coordination on a successfully coordinated R-TWT schedule. For example, the purpose of terminating coordination on a certain cooperating R-TWT SP may be specified via the coordination TWT ID. A deletion, etc. may be requested by setting all fields except for the fields related to the R-TWT schedule and/or some fields in the broadcast TWT parameter set field, which includes the coordination TWT ID corresponding to the successfully coordinated R-TWT schedule, to 0 (or reserved). Based on this, the AP may stop notifying the coordinated R-TWT schedule to the associated STAs. If the deletion request is successfully performed, the APs/STAs of the corresponding BSS will not perform protection or operation on the corresponding OBSS R-TWT SP.

Additionally or alternatively, in the case of a frame/element for R-TWT cooperation between APs, a new request type field that can indicate newly defined information as described above may be defined using one or more of the reserved field positions in the example of FIG. 17. For example, the value of the TWT setup command field may be set to 0 (request TWT), and the value of the new request type field may also be set to a value indicating addition, update, or deletion.

Additionally or alternatively, the existing TWT setup command field may be replaced with a reserved field, and a new request type field may be utilized to indicate the purpose of the broadcast TWT parameter set field. In this case, a new status field (e.g., a field indicating a status code such as Accept/Alternative/Dictate/Reject) for indicating a response to the requested broadcast TWT parameter set field may also be defined using one or more of the reserved field positions in the example of FIG. 17.

If the TWT setup command field has a value of 4 (accept TWT), 5 (alternative TWT), 6 (dictate TWT), or 7 (reject TWT), it may be considered a cooperative response, as in the examples above.

Additionally or alternatively, if the value of the TWT setup command field within the broadcast TWT parameter set field for R-TWT cooperation between APs is overridden, it may have the value of Accept, Reject or other status codes (e.g., Alternate/Dictate, etc.).

- The last broadcast parameter set field within the request type field.

When multiple broadcast TWT parameter set fields are included within a TWT element, the last broadcast parameter set field may have its value set to 1 for the last broadcast parameter set field in the last order. For other cases (i.e., non-last broadcast parameter set fields), the value of the last broadcast parameter set field may be set to 0.

- Broadcast TWT recommendation field within the request type field

When the value of the Broadcast TWT Recommendation field is set to one of 0 to 3, it can indicate a recommendation for the type of traffic/frame to be transmitted and received during the negotiating TWT SP.

When the value of the Broadcast TWT Recommendation field is set to a value of 4, it may indicate that the negotiated TWT SP is for a restricted TWT SP.

When the value of the Broadcast TWT Recommendation field is set to one of 5 to 7, it may indicate that a TWT schedule negotiated between APs, rather than a TWT schedule between an AP and a STA, is included in the broadcast TWT parameter set.

- Sorted fields within the request type field

Unlike the existing aligned field which indicates the alignment of TWT schedules on the links of the AP MLD, the aligned field of the present disclosure can indicate whether the negotiated R-TWT SP corresponds to an overlapping R-TWT SP.

In order to indicate that the TWT schedule negotiated between the AP and the OBSS AP is an R-TWT schedule in which not only the associated STAs within their own BSS can form membership, but also the associated STAs within the OBSS can form membership, the value of the aligned field may be set to 1. That is, STAs allowed random access during an R-TWT schedule included in a broadcast TWT parameter set having the value of the aligned field as 1 include not only the AP of the BSS and the STAs associated with the BSS, but also the AP of the OBSS and the STAs associated with the OBSS. Such an R-TWT SP may be referred to as a nested R-TWT SP. In the nested R-TWT SP, the AP/STA within the BSS and the AP/STA within the OBSS can obtain an opportunity to transmit and receive latency-sensitive traffic through random access. If random access of BSS AP/STA is not allowed during R-TWT SP, or random access of OBSS AP/STA is not allowed, it can be called non-overlapping R-TWT SP.

Additionally or alternatively, a separate field (other than the aligned field) may be defined to indicate whether the schedule included in the corresponding broadcast TWT parameter set corresponds to an overlapping R-TWT SP, and may be utilized in the R-TWT cooperation request and R-TWT cooperation response.

Additionally or alternatively, whether a schedule included in the corresponding broadcast TWT parameter set corresponds to a nested R-TWT SP may be indicated by utilizing reserved values of existing fields. For example, when redefining a TWT setup command in R-TWT cooperation between APs, a reserved value may exist in the TWT setup command field. The reserved value of this TWT setup command field may be defined as a cooperation request/proposal for a nested R-TWT SP. Accordingly, in the R-TWT cooperation request, the TWT schedule included in the corresponding broadcast TWT parameter set field may be indicated as a nested R-TWT schedule. Alternatively, for example, the reserved value of the broadcast TWT recommendation field may be utilized to indicate whether a TWT schedule included in the corresponding broadcast TWT parameter set field is a nested R-TWT schedule.

Example 3-4

In the examples above, unused fields can be changed to reserved fields or replaced with other fields as follows.

- Limited TWT schedule information fields

In the example of Figure 17, a restricted TWT schedule information field may be included in a location marked as reserved within the existing broadcast TWT information field. If a restricted TWT schedule information field is included during the R-TWT cooperation process between APs, the following behavior may occur:

If the value of the Limited TWT Schedule Information field in the cooperation request has a value indicating an "active R-TWT schedule" (e.g., a value of 1) or a "full R-TWT schedule" (e.g., a value of 2), the AP receiving the cooperation request may accept, reject, or negotiate the proposal.

If the value of the restricted TWT schedule information field in the cooperation request indicates an "idle R-TWT schedule" (e.g., a value of 0), the AP receiving the cooperation request may accept, reject, or negotiate the proposal. In this case, if the cooperation for the corresponding R-TWT schedule is accepted, the AP transmitting the cooperation response may not perform protection for the corresponding R-TWT schedule. That is, although the cooperated R-TWT SP has been acquired, since it is an idle R-TWT schedule and does not affect the immediate DL/UL data transmission and reception, protection may not be performed for the corresponding R-TWT schedule. If the value of the restricted TWT schedule information field for the corresponding R-TWT SP indicates an "active R-TWT schedule" (e.g., a value of 1) or a "full R-TWT schedule" (e.g., a value of 2), the receiving AP may perform protection for the cooperated R-TWT schedule upon receiving the cooperation request.

If cooperation for the corresponding R-TWT schedule is rejected, the AP sending the cooperation request may request cooperation for the corresponding R-TWT schedule again if the value of the restricted TWT schedule information field for the corresponding R-TWT schedule indicates that it is an "active R-TWT schedule" (e.g., a value of 1) or a "full R-TWT schedule" (e.g., a value of 2).

- Collaborative TWT ID field

The Broadcast TWT ID field within the Broadcast TWT Information field may be replaced with a Collaboration TWT ID field that indicates the value of a Collaboration TWT ID corresponding to a specific R-TWT cooperation request negotiated/exchanged between APs. The value of this Collaboration TWT ID may be used to indicate which R-TWT cooperation request the response corresponds to in the R-TWT cooperation response.

The length of the field may be the same as the length of the broadcast TWT ID field in the existing TWT parameter set field, or may be shorter. That is, the length of the cooperative TWT ID field in the new broadcast TWT parameter set field may be 5 bits or may be less than 5 bits. This is because the number of candidate IDs required for TWT schedule negotiation between APs may be smaller than the number of candidate IDs required for TWT schedule negotiation between APs and STAs.

Additionally or alternatively, the value of the cooperation TWT ID referred to herein may be identical to the value of the ID of the R-TWT scheduled by the AP sending the cooperation request. For example, the cooperation TWT ID may be defined to have the same value as the broadcast TWT ID defined between the cooperation requesting AP and the AP associated with the AP. That is, the requesting AP may request to use one of its broadcast TWTs as the cooperation TWT. If the negotiation/cooperation is successfully performed, the cooperation responding AP may notify its associated STAs by setting the broadcast TWT ID value to 31 for the cooperation TWT.

- Field indicating whether there are nested R-TWT schedules

If the broadcast TWT parameter set includes not only an R-TWT schedule for which the associated STAs within its own BSS can form membership, but also an R-TWT schedule for which the associated STAs within the OBSS can form membership (i.e., a nested R-TWT SP), this can be indicated using one or more of the fields marked as reserved in the example of FIG. 17. That is, a separate field indicating whether it is a nested R-TWT SP can be defined. If the value of the nested R-TWT SP indication field in the R-TWT cooperation request and R-TWT cooperation response is 1, it can be indicated that the TWT schedule included in the broadcast TWT parameter set field is a nested R-TWT schedule.

- Field indicating whether TWT schedule is negotiated between APs (or TWT type field)

In the example of FIG. 17, one or more of the reserved fields may indicate whether a TWT schedule negotiated between APs, rather than a TWT schedule between an AP and a STA, is included in the corresponding broadcast TWT parameter set. The field may also be referred to as a TWT type field, and may indicate whether the corresponding broadcast TWT parameter set field means a broadcast TWT schedule or a restricted TWT schedule.

In this case, the Broadcast TWT Recommendation field within the Broadcast TWT Parameter Set field may be replaced with a reserved field or a field indicating other information.

Additionally or alternatively, when the value of the restricted TWT traffic info present field in the broadcast TWT info field is 1, the broadcast TWT parameter set field may indicate that the broadcast TWT parameter set field includes the configuration and contents of a broadcast TWT parameter set field that includes information for cooperation on an R-TWT schedule between APs. In this case, even if the value is set to 1, it may not indicate that the restricted TWT traffic info field exists, but may indicate another meaning (i.e., that it includes information for cooperation on an R-TWT schedule between APs).

- Field indicating TBTT count information

An AP sending a cooperation request can notify associated STAs about the cooperating (R-)TWT after N TBTTs after the successful negotiation/cooperation for the cooperating R-TWT SP, or after the first beacon frame is transmitted after the successful negotiation/cooperation, during the negotiation process for (R-)TWT cooperation, to the AP sending the cooperation response. This can be referred to as the number of TBTT field.

The TBTT Count field may be included in a limited TWT schedule information field (e.g., a part marked as reserved in FIG. 17) having a length of 2 bits within the broadcast TWT information field within the existing broadcast TWT parameter set field. Alternatively, the TBTT Count field may not be included in the negotiation process via the broadcast TWT parameter set field for (R-)TWT cooperation between APs, but may be defined as a new field other than the broadcast TWT parameter set field. The scope of the present disclosure is not limited thereto, and the TBTT Count field may be included in another reserved field/bit within the broadcast TWT parameter set field included in the negotiation for (R-)TWT cooperation between APs. Alternatively, the TBTT Count field may be included in an element (e.g., a TWT element, a TWT information extension element, etc.) including the broadcast TWT parameter set field included in the negotiation for (R-)TWT cooperation between APs.

If the value of the TBTT count field is 0, this may mean that the first beacon frame is transmitted with the coordinated (R-)TWT schedule included after the (R-)TWT negotiation/cooperation between APs is successfully performed. If the value of the TBTT count field is 1, 2, or 3, this may mean that the coordinated (R-)TWT schedule is transmitted in the beacon frame transmitted after 1 TBTT, 2 TBTT, or 3 TBTT, respectively, after the negotiation/cooperation is successfully performed or after the first beacon frame is transmitted after the negotiation/cooperation is successfully performed.

Additionally or alternatively, if the value of the TBTT count field is 1, 2, or 3, it may mean that the coordinated (R-)TWT schedule is transmitted in the beacon frame transmitted after 1*M TBTT, 2*M TBTT, or 3*M TBTT, respectively, after successful negotiation/cooperation or after the first beacon frame is transmitted after successful negotiation, where M may correspond to a value greater than or equal to 2.

Example 3-5

A TWT bandwidth field may be newly defined, indicating the bandwidth information at which the R-TWT schedule, which is coordinated between APs, will operate. The value of the field may indicate one of 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, or 640 MHz. The location of the TWT bandwidth field may be as shown in FIG. 17, but is not limited thereto.

The bandwidth indicated by this field refers to the bandwidth of the BSS AP that is influenced by the bandwidth of the OBSS AP. In other words, it may correspond to the size of the bandwidth of the BSS AP that overlaps with the bandwidth of the OBSS AP. Depending on the frequency location of the two bandwidths, the size of the overlapping bandwidth may vary or may not overlap.

For example, let's assume that the bandwidth at which the OBSS AP operates is 80MHz and the bandwidth at which the BSS AP operates is 160MHz. In this case, if the overlapping bandwidth between the bandwidth of the BSS AP and the bandwidth of the OBSS AP is 80MHz (or 40MHz, or 20MHz), the TWT bandwidth field can be set to a value indicating 80MHz (or 40MHz, or 20MHz).

For example, even if the bandwidth of an OBSS AP and a BSS AP are both 320MHz, their secondary channels may have different bandwidths. For example, in the 6GHz band, the bandwidths of the primary 160 channel of 320MHz overlap, but if the BSS AP operates on the secondary channel of 160-1 and the OBSS AP operates on the secondary channel of 160-2 (i.e., secondary channels in different frequency positions), only the size of the common/overlapping bandwidth of 160MHz can be indicated, excluding the non-overlapping bandwidth. For example, in the 2.4GHz band, if a BSS AP and an OBSS AP operate on the bandwidth of 40MHz and their primary 20 channels overlap, but they operate on the secondary 20 channels in different frequency positions, only the size of the common/overlapping bandwidth of 20MHz can be indicated, excluding the non-overlapping bandwidth.

Example 3-6

A new TWT channel field may be defined that indicates channel information on which a cooperative R-TWT schedule between APs will operate. The location of this TWT channel field may be located after the broadcast TWT information field, as in the example of FIG. 17, but is not limited thereto.

For example, information about a channel to which an R-TWT schedule applies can be indicated through a bitmap-format TWT channel field. In this case, the bitmap may be formatted such that one bit position maps to one 20MHz channel based on the bandwidth indicated by the TWT bandwidth. In other words, the length of the TWT channel field may vary depending on the value of the TWT bandwidth field.

For example, if the TWT channel field has a length of 1 octet and the value of the TWT bandwidth field is set to a value indicating 40 MHz, the TWT channel field may include information on the channel to which the R-TWT schedule is to be applied through 2 bits, and the remaining 6 bits may be set to reserved values. For example, the 2 bits may indicate not applied to both 20 MHz channels (value of bit 2 00), not applied to the first 20 MHz channel but applied to the second 20 MHz channel (value of bit 2 01), applied to the first 20 MHz channel but not applied to the second 20 MHz channel (value of bit 2 10), or applied to both 20 MHz channels (value of bit 2 11).

When performing R-TWT schedule cooperation between APs, a TWT channel field may be included in a broadcast TWT parameter set field containing information on an overlapped R-TWT schedule. In this case, information on a channel on which the overlapped R-TWT schedule requested by the AP to the OBSS AP can be operated may be indicated through the value of the TWT channel field. Based on this, the OBSS AP may apply the overlapped R-TWT schedule on a channel corresponding to a value of 1 (i.e., a value indicating that the corresponding R-TWT schedule will be operated) in the TWT channel field. Alternatively, the OBSS AP may not apply the overlapped R-TWT schedule on a channel corresponding to a value of 0 (i.e., a value indicating that the corresponding R-TWT schedule will not be operated) that is not a bit reserved (i.e., a bit having a value of 0 or null to match the length of the field).

Additionally or alternatively, the TWT channel field may be defined utilizing one or more of the reserved fields illustrated in FIG. 17.

FIG. 18 is a diagram illustrating other examples of broadcast TWT parameter sets related to TWT cooperation between APs in the present disclosure.

In the example of FIG. 18, the Nominal Minimum TWT Wake Duration field (1 octet) of the Basic Broadcast TWT Parameter Set field is shown as an example in which it is reserved. Additionally or alternatively, the Restricted TWT Traffic Information Present field (1 bit) and/or the Restricted TWT Schedule Information field (2 bits) in the Broadcast TWT Information field of the Basic Broadcast TWT Parameter Set field may be reserved. Additionally or alternatively, the Trigger field (1 bit), the Flow Type field (1 bit), and/or the Aligned field (1 bit) in the Request Type field of the Basic Broadcast TWT Parameter Set field may be reserved.

In this way, among the various fields within the existing broadcast TWT parameter set field, fields that are not necessary for (R-)TWT cooperation between APs can be modified to be reserved. In the examples of the present disclosure, new field(s) that can be added in relation to cooperation between APs (e.g., TWT channel, TWT bandwidth, TBTT count, wake duration unit field, etc.) may be defined in the position indicated as reserved in the example of FIG. 18, but the scope of the present disclosure is not limited thereto, and such new field(s) may be included as new fields other than within the existing (broadcast) TWT parameter set field (e.g., within an element including the existing (broadcast) TWT parameter set field).

FIG. 19 is a diagram illustrating examples of notifying cooperative R-TWT schedule information according to the present disclosure.

In the examples described above, after successfully performing the negotiation for cooperative R-TWT between an AP and a neighboring AP (hereinafter, R-TWT cooperation), the APs can announce the schedule information of the cooperative R-TWT by including it in a beacon frame and/or a probe response frame within their respective BSSs. That is, the AP can transmit the schedule information of the cooperative R-TWT starting from the first beacon frame and/or the first probe response frame (b2 in the example of FIG. 19) that it transmits to STAs after transmitting or receiving the cooperative response.

Additionally or alternatively, the schedule information of the cooperative R-TWT may be included in the beacon frame and/or probe response frame (b1 in the example of FIG. 19) transmitted while performing R-TWT cooperation between the AP and its neighboring AP. This may be the case when the AP transmitting the cooperation response wants (or plans to) send a cooperation response that includes a response corresponding to acceptance for the R-TWT schedule included in the cooperation request. This corresponds to a method in which the AP transmitting the cooperation response determines that it has acquired the cooperated R-TWT schedule based on its own decision and notifies its associated STAs before notifying the AP that transmitted the cooperation request that it has acquired the cooperated R-TWT schedule through the acceptance response.

Additionally or alternatively, it may be assumed that R-TWT cooperation between an AP and a neighboring AP is successfully performed and a cooperative R-TWT schedule is acquired. In this case, the AP transmitting the cooperation request may transmit and receive a value (e.g., the value of the TBTT number field in the examples described above) during the R-TWT cooperation process, instructing the AP transmitting the cooperation response to notify its associated STAs about the cooperated (R-)TWT schedule after N TBTTs after the cooperation is successfully performed or after the first beacon frame is transmitted after the cooperation is successfully performed. For example, based on the value of the TBTT number field (e.g., n), the AP transmitting the cooperation response may transmit the cooperated (R-)TWT schedule in a beacon frame (e.g., b3 in the example of FIG. 19) transmitted after n TBTTs (or n*M TBTTs, where M is a constant greater than or equal to 2).

Example 4

Examples of the consultation process for cooperation between the first AP (or AP1) and the second AP (or AP2) are described below.

Example 4-1

FIG. 20 and FIG. 21 are diagrams illustrating examples of 2-way TWT cooperation according to the present disclosure.

For example, R-TWT cooperation between AP1 and AP2 can be achieved through a cooperation request and cooperation response. In this case, the cooperation request and cooperation response can be configured as follows. In addition, although the description assumes that the cooperation request and cooperation response are transmitted and received through TWT elements within an existing TWT setup frame, the scope of the present disclosure is not limited thereto, and may be performed through other frames and/or other elements.

- Request for cooperation

The value of the TWT request field in the request type field = 1 (request)

TWT setup command field in the request type field = 0 (request TWT), 1 (proposed TWT), or 2 (request TWT)

Broadcast TWT Recommended Field = Value 4 or 5 or higher

Information related to R-TWT schedule information may be included in fields within the TWT element in the examples of the present disclosure.

- Cooperative response

TWT request field in the request type field = 0 (response or not a request)

TWT setup command field in the request type field = 4 (accept TWT), 5 (alternative TWT), 6 (dictate TWT), or 7 (reject TWT)

If the value of the TWT setup command field is 4 (accept TWT) or 7 (reject TWT), the other information may be set to the same values as those included in the cooperation request and included in the cooperation response.

If the value of the TWT setup command field is an alternative TWT or a dictated TWT, the collaboration response may include TWT schedule information set to values different from those included in the collaboration request.

Fig. 20 may be an example for a non-overlapping R-TWT schedule, and Fig. 21 may be an example for an overlapping R-TWT schedule.

In the example of Fig. 20, AP1 transmits a cooperation request including information of an R-TWT SP scheduled by AP1 to AP2 (e.g., TWT request=1, TWT setup command=2). Based on the cooperation request, AP2 transmits a cooperation response including an accepted TWT (e.g., TWT request=0, TWT setup command=4). In conclusion, AP1 and AP2 successfully agree on protection for the R-TWT scheduled by AP1 based on the cooperation request and cooperation response. That is, STAs belonging to AP1 and STAs belonging to AP2 all terminate their TXOPs before the start time of the R-TWT SP scheduled by AP1. In addition, AP1 and STAs belonging to a BSS of AP1 that supports R-TWT and has membership in the R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP.

In the example of FIG. 21, AP1 transmits a cooperation request to AP2 (e.g., TWT request=1, TWT setup command=2, Aligned=1), which includes information about the R-TWT SP scheduled by AP1 and indicates that STAs belonging to the BSS of AP2 can support R-TWT operation for the R-TWT SP (i.e., indicates that it corresponds to an overlapping R-TWT SP). Based on the cooperation request, AP2 transmits a cooperation response including an accepted TWT (e.g., TWT request=0, TWT setup command=4, Aligned=1). In conclusion, AP1 and AP2 successfully agree to perform protection for the R-TWT scheduled by AP1 based on the cooperation request and cooperation response above and to perform R-TWT operation during the agreed SP. That is, STAs belonging to AP1 and STAs belonging to AP2 both terminate their TXOPs before the start times of the R-TWT SPs scheduled by AP1 and AP2. And STAs belonging to the BSS of AP1/AP2 that support R-TWT and have membership in the corresponding R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP (or overlapping R-TWT SP).

When performing R-TWT cooperation based on the TWT element within the existing TWT setup frame, examples of values of the TWT setup command field set by the AP and OBSS APs and examples of operations according to the values can be referred to Table 1 below. That is, Table 1 shows examples of operations of the AP and OBSS based on 2-way operation for R-TWT cooperation.

If, during the R-TWT cooperation process between APs, the meaning of a response to a request included in a cooperation request and cooperation response frame is not defined in the TWT setup command within the existing TWT element, the value and its corresponding meaning may be applied as shown in Table 3 below.

Broadcast TWT parameter set field(s) within a frame for R-TWT cooperation transmitted from an AP to an OBSS AP. Broadcast TWT Parameter Set field(s) within a frame for R-TWT cooperation transmitted from an OBSS AP to an AP. R-TWT SP negotiated/coordinated between AP and OBSS AP based on R-TWT cooperation TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2 TWT request field = 0 (collaborative response)
TWT Setup Command Field = 4 An OBSS AP that transmits a cooperation response to an R-TWT SP of an AP that transmitted a frame containing a cooperation request also terminates all TXOPs within the BSS to which it belongs before the start time of the corresponding R-TWT SP. TWT Request Field = 1 TWT Setup Command Field = 0, 1, or 2 TWT request fields = 0
TWT Setup Command Field = 7 An OBSS AP that transmits a cooperation response to an R-TWT SP of an AP that transmitted a frame containing a cooperation request may not terminate all TXOPs within the BSS to which it belongs before the start time of the corresponding R-TWT SP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2 TWT request field = 0 (collaborative response)
TWT setup command field = 5 or 6 An OBSS AP that transmits a cooperation response to an R-TWT SP of an AP that transmitted a frame containing a cooperation request may also terminate all TXOPs within its BSS before the start time of the corresponding R-TWT SP. TWT Request Field = 1 TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT request fields = 0
TWT Setup Command Field = 4 An OBSS AP that transmits a cooperation response to an R-TWT SP of an AP that transmitted a frame containing a cooperation request also terminates all TXOPs within the BSS to which it belongs before the start time of the corresponding R-TWT SP.
Additionally, during the R-TWT SP, STAs within the BSS of the AP and OBSS AP can obtain TXOP based on random access rules to transmit and receive latency-sensitive traffic. TWT Request Field = 1 TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT request fields = 0
TWT Setup Command Field = 7 An OBSS AP that transmits a cooperation response to an R-TWT SP of an AP that transmitted a frame containing a cooperation request may not terminate all TXOPs within the BSS to which it belongs before the start time of the corresponding R-TWT SP. TWT Request Field = 1 TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT request fields = 0
TWT setup command field = 5 or 6 An OBSS AP that transmits a cooperation response to an R-TWT SP of an AP that transmitted a frame containing a cooperation request may also terminate all TXOPs within its BSS before the start time of the corresponding R-TWT SP.
Additionally, during the R-TWT SP, STAs within the BSS of the AP and OBSS AP may obtain TXOP based on random access rules to transmit and receive latency-sensitive traffic.

Example 4-2

FIGS. 22 to 24 are diagrams illustrating examples of 3-way TWT cooperation according to the present disclosure.

For example, R-TWT cooperation between AP1 and AP2 can be comprised of a cooperation request, a cooperation response and request, and a cooperation response. In this case, the cooperation request, the cooperation response and request, and the cooperation response can be configured as follows. In addition, although the description assumes that the cooperation request, the cooperation response and request, and the cooperation response are transmitted and received through TWT elements within an existing TWT setup frame, the scope of the present disclosure is not limited thereto, and may be performed through other frames and/or other elements.

- Request for cooperation (frame 1)

TWT request field in the request type field = 1 (request)

TWT setup command field in the request type field = 0 (request TWT), 1 (proposed TWT), or 2 (request TWT)

Broadcast TWT Recommended Field = Value 4 or 5 or higher

Information related to R-TWT schedule information may be included in fields within the TWT element in the examples of the present disclosure.

- Collaborative response and request (frame 2)

This corresponds to a method in which an AP sends an additional cooperation request along with a cooperation response when receiving a cooperation request. The AP generates a response to the received cooperation request using the first broadcast TWT parameter set fields, which are considered a cooperation response, and additionally generates the second broadcast TWT parameter set fields, which are considered an additional cooperation request, and transmits them to the OBSS AP by including them in a single frame.

The method of including both a cooperation request and a cooperation response within a single frame can correspond to a case where both TWT parameter set fields corresponding to a TWT setup request and a TWT setup response are included within a single existing TWT setup frame. However, the TWT setup operation between a TWT requesting STA and a TWT responding STA as currently defined is not allowed. Therefore, the method of including both TWT parameter sets corresponding to two purposes within a single frame, such as the 3-way method according to the present disclosure, has the effect of reducing the number of medium access and backoff attempts as frames corresponding to the purposes of each request/response are transmitted and received, so that the consultation between the two STAs can be performed more efficiently.

The collaboration response portion of the collaboration response and request can be set as follows:

TWT request field in the request type field = 0 (response, or not a request)

That is, it indicates that the TWT parameter set field is considered a cooperation response, responding to the TWT parameter set field considered a cooperation request within the received frame.

TWT setup command field in the request type field = 4 (accept TWT), 5 (alternative TWT), 6 (dictate TWT), or 7 (reject TWT)

If the value of the TWT setup command field in the TWT parameter set field considered as the corresponding cooperative response is 5 (alternative TWT) or 6 (dictated TWT), new R-TWT schedule information may be included instead of the existing R-TWT schedule information.

If the value of the TWT setup command field is 4 (accept TWT) or 7 (reject TWT), other information may be included in the TWT parameter set field, which is considered a cooperation response and is set to the same values as those included in the cooperation request.

If a cooperation response corresponding to a received cooperation request is first included in a frame and then the cooperation request is included in that frame, the value of the last broadcast parameter set field in the TWT parameter set field corresponding to the cooperation response may be set to 0.

The collaboration request portion of the collaboration response and request can be set as follows:

TWT request field in the request type field = 1 (request)

If there is a TWT parameter set field that is considered a cooperation response within a frame, a TWT parameter set field that is considered a cooperation request may be added.

For example, if the value of the TWT setup command field in the TWT parameter set field corresponding to the cooperation response in one frame includes the meaning of 4 (accept) or 7 (reject TWT), the frame may additionally include a TWT parameter set field corresponding to the cooperation request. However, the scope of the present disclosure is not limited to these examples. For example, if the value of the TWT setup command field in the TWT parameter set field corresponding to the cooperation response in one frame includes the meaning of 5 (alternative TWT) or 6 (dictated TWT), the frame may additionally include a TWT parameter set field corresponding to the cooperation request.

If an AP that has received a cooperation request does not include a TWT parameter set corresponding to a cooperation response in a frame that it intends to transmit, it may be defined that the frame does not include a TWT parameter set corresponding to the cooperation request. In other words, an AP that has received a cooperation request may be allowed to transmit additional cooperation requests only if it transmits a cooperation response.

TWT setup command field in the request type field = 0 (request TWT), 1 (proposed TWT), or 2 (request TWT)

Broadcast TWT Recommended Field = Value 4 or 5 or higher

Information related to R-TWT schedule information may be included in fields within the TWT element in the examples of the present disclosure.

- Collaborative response (3rd frame)

TWT request field in the request type field = 0 (response or not a request)

In the case where the value of the TWT setup command field in the TWT parameter set field, which is considered as a cooperation response received in the second frame, for the cooperation request transmitted in the first frame, is 5 (alternative TWT) or 6 (dictated TWT), the third frame may include a TWT parameter set field corresponding to a response to the schedule information of the R-TWT included in the cooperation response of the second frame.

TWT setup command field in the request type field = 4 (accept TWT), 5 (alternative TWT), 6 (dictate TWT), or 7 (reject TWT)

Other information can be set as follows:

If the value of the TWT setup command field is 4 (accept TWT) or 7 (reject TWT), the other information may be set to the same values as those included in the cooperation request and included in the cooperation response.

If the value of the TWT setup command field is an alternative TWT or a dictated TWT, the collaboration response may include TWT schedule information set to values different from those included in the collaboration request.

FIG. 22 may be an example for two non-overlapping R-TWT schedules, FIG. 23 may be an example for one overlapping R-TWT schedule, and FIG. 24 may be an example for one non-overlapping R-TWT schedule and one overlapping R-TWT schedule.

In Fig. 22, AP1 transmits a cooperation request including information of an R-TWT SP scheduled by AP1 to AP2 (e.g., TWT request=1, TWT setup command=2). Based on the cooperation request, AP2 constructs a cooperation response including an accepted TWT and a cooperation request including information of an R-TWT SP scheduled by AP2 into one frame and transmits the frame to AP1 (e.g., TWT request=0, TWT setup command=4 in the cooperation response part; TWT request=1, TWT setup command=2 in the cooperation request part). Upon receiving the frame including the cooperation response and cooperation request, AP1 transmits a cooperation response including an acceptance response to the cooperation request requested by AP2 to AP2 (e.g., TWT request=0, TWT setup command=4). As a result of the R-TWT cooperation, protection is successfully agreed upon for the R-TWT scheduled by AP1 and the R-TWT scheduled by AP2. That is, STAs belonging to AP1 and STAs belonging to AP2 terminate their TXOPs not only before the start time of the R-TWT SP scheduled by AP1 but also before the start time of the R-TWT SP scheduled by AP2. In this case, during the R-TWT scheduled by AP1, STAs belonging to AP1's BSS that supports R-TWT and has membership in the R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP (or non-overlapping R-TWT SP). During the R-TWT scheduled by AP2, STAs belonging to AP2's BSS that supports R-TWT and has membership in the R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP (or non-overlapping R-TWT SP).

In FIG. 23, AP1 transmits a cooperation request including information of an R-TWT SP scheduled by AP1 to AP2 (e.g., TWT request=1, TWT setup command=2). Based on the cooperation request, AP2 transmits to AP1 a frame including a cooperation response including a rejection TWT and a cooperation request including information of an R-TWT SP scheduled by AP2 and indicating that STAs belonging to the BSS of AP1 can support the operation of R-TWT for the R-TWT SP (e.g., TWT request=0, TWT setup command=7 in the cooperation response part; TWT request=1, TWT setup command=2, aligned=1 in the cooperation request part). Upon receiving the cooperation response and the frame including the cooperation request, AP1 transmits to AP2 a cooperation response including an acceptance response to the cooperation request requested by AP2 (e.g., TWT request=0, TWT setup command=4, aligned=1). As a result of R-TWT cooperation, in addition to protecting the R-TWT scheduled by AP2, AP1 can schedule an R-TWT SP identical to the R-TWT scheduled by AP2 and notify the STAs within its BSS to which it belongs. Therefore, the R-TWT SP can be regarded as the R-TWT scheduled by AP1 and AP2. That is, the STAs belonging to AP1 and STAs belonging to AP2 terminate all their TXOPs before the start time of the R-TWT SP scheduled by AP1 and AP2. In addition, STAs belonging to the BSS of AP1/AP2 that support R-TWT and have membership in the R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP (or overlapping R-TWT SP).

In FIG. 24, AP1 transmits a cooperation request including information of an R-TWT SP scheduled by AP1 to AP2 (e.g., TWT request=1, TWT setup command=2). Based on the cooperation request, AP2 includes a cooperation response including an accepted TWT, and a cooperation request including information of an R-TWT SP scheduled by AP2 and indicating that STAs belonging to the BSS of AP1 can support the operation of R-TWT for the R-TWT SP, all in one frame and transmits them to AP1 (e.g., TWT request=0, TWT setup command=4 in the cooperation response part; TWT request=1, TWT setup command=2, aligned=1 in the cooperation request part). Upon receiving the frame including the cooperation response and cooperation request, AP1 transmits a cooperation response including an acceptance response to the cooperation request requested by AP2 to AP2 (e.g., TWT request=0, TWT setup command=4, aligned=1). As a result of R-TWT cooperation, protection for R-TWT scheduled by AP1 and R-TWT scheduled by AP2 is successfully agreed upon. In this case, AP1 can schedule the same R-TWT SP as the R-TWT scheduled by AP2 and notify the STAs within its BSS. Therefore, the R-TWT SP can be regarded as the R-TWT scheduled by AP1 and AP2. That is, STAs belonging to AP1 and STAs belonging to AP2 terminate their TXOPs not only before the start time of the R-TWT SP scheduled by AP1 but also before the start times of the R-TWT SPs scheduled by AP1/AP2. During the R-TWT scheduled by AP1 in the first R-TWT SP (or non-overlapping R-TWT SP), STAs belonging to AP1's BSS that support R-TWT and have membership in the R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP. In the second R-TWT SP (or nested R-TWT SP), AP1/AP2 and STAs belonging to the BSS of AP1/AP2 that support R-TWT and have membership in the R-TWT SP can transmit and receive latency-sensitive traffic within the R-TWT SP.

When performing R-TWT cooperation based on the TWT element in the existing TWT setup frame, examples of values of the TWT setup command field set by the AP and OBSS APs and examples of operations according to the values can be referred to Table 2 below. That is, Table 2 shows examples of operations of the AP and OBSS based on a 3-way operation for R-TWT cooperation (i.e., cooperation request, cooperation response and request, cooperation response). However, the scope of the present disclosure is not limited thereto, and one or more cooperation responses and requests may be transmitted and received between the first cooperation request and the last cooperation response.

If, during the R-TWT cooperation process between APs, the meaning of a response to a request included in a cooperation request and cooperation response frame is not defined in the TWT setup command within the existing TWT element, the value and its corresponding meaning may be applied as shown in Table 3 below.

Broadcast TWT parameter set field(s) within a frame for R-TWT cooperation transmitted from an AP to an OBSS AP. Broadcast TWT Parameter Set field(s) within a frame for R-TWT cooperation transmitted from an OBSS AP to an AP. Broadcast TWT parameter set field(s) within a frame for R-TWT cooperation transmitted from an AP to an OBSS AP. R-TWT SP negotiated/coordinated between AP and OBSS AP based on R-TWT cooperation TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4 or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for the R-TWT scheduled by each AP and OBSS AP.
If the value of the TWT setup command field in the cooperation response from an OBSS AP to an AP or the value of the TWT setup command field in the cooperation response from an AP to an OBSS AP has the value 4 and the value 7, respectively, cooperation is completed for the R-TWT scheduled by the AP or the OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 5 or 6
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for the R-TWT scheduled by the OBSS AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 7, there is no R-TWT negotiated through R-TWT cooperation. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4 or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 0 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for (overlapping) R-TWT scheduled by each AP/OBSS AP and (non-overlapping) R-TWT scheduled by the OBSS AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP or the value of the TWT setup command field in the cooperation response from AP to OBSS AP have the value 4 and the value 7, respectively, cooperation is completed for the R-TWT scheduled by AP/OBSS AP or OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 0 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4 or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 1 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for the R-TWT scheduled by each AP and the R-TWT scheduled by the AP/OBSS AP.
If the value of the TWT setup command field in the cooperation response from an OBSS AP to an AP or the value of the TWT setup command field in the cooperation response from an AP to an OBSS AP has the value 4 and the value 7, respectively, cooperation is completed for the R-TWT scheduled by the AP or AP/OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4 or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 1 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for the R-TWT scheduled by AP/OBSS AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP or the value of the TWT setup command field in the cooperation response from AP to OBSS AP have the values 4 and 7, respectively, cooperation is completed for the R-TWT scheduled by the AP/OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 5 or 6
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 0 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for the R-TWT scheduled by the OBSS AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 7, there is no R-TWT negotiated through R-TWT cooperation. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 0 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 5 or 6
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 1 TWT request field = 0 (collaborative response)
TWT setup command field = 4 or 7 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 4, cooperation is completed for the R-TWT scheduled by the AP/OBSS AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 7, there is no R-TWT negotiated through R-TWT cooperation. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4, 5, 6, or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2 TWT request field = 0 (collaborative response)
TWT setup command field = 5 or 6 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation is completed for the R-TWT scheduled by each AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 7 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP and/or OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4, 5, 6, or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2 TWT request field = 0 (collaborative response)
TWT setup command field = 5 or 6 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation is completed for the R-TWT scheduled by AP/OBSS AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 7 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP and/or OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 0 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4, 5, 6, or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 1 TWT request field = 0 (collaborative response)
TWT setup command field = 5 or 6 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation is completed for the R-TWT scheduled by the AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 7 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP and/or OBSS AP. TWT Request Field = 1 (Request for Cooperation) TWT Setup Command Field = 0, 1, or 2
Sorted = 1 TWT Request Field = 0 (Cooperation Response) (This means the TWT parameter set field corresponding to the cooperation response to the received cooperation request)
TWT setup command field = 4, 5, 6, or 7
or,

TWT Request Field = 1 (Request for Cooperation)
TWT setup command field = 0, 1, or 2
Sorted = 1 TWT request field = 0 (collaborative response)
TWT setup command field = 5 or 6 If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 4 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation is completed for AP/OBSS AP and/or R-TWT scheduled by AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 7 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for the R-TWT scheduled by each AP.
If the value of the TWT setup command field in the cooperation response from OBSS AP to AP is 5 or 6 & if the value of the TWT setup command field in the cooperation response from AP to OBSS AP is 5 or 6, cooperation may be completed for each AP/OBSS AP, AP and/or OBSS AP scheduled R-TWT.

The value of the TWT setup command field in the TWT parameter set field within an existing TWT element. Meaning of the TWT setup command (which may be referred to as a status code) in the cooperation response to the redefined cooperation request for R-TWT cooperation between APs. Acceptance TWT Successful negotiation/agreement on the requested R-TWT AP (success to negotiate/agree the requested R-TWT SP) Reject TWT Reject to negotiate/agree the requested R-TWT SP Alternative TWT Suggest to negotiate/agree new R-TWT SP Dictate TWT Strongly suggest to negotiate/agree new R-TWT SP

Example 4-3

FIGS. 25 to 27 are diagrams illustrating examples of a cooperative method within a nested cooperative R-TWT SP according to the present disclosure.

During the overlapping cooperative R-TWT schedules through TWT cooperation between AP1 and AP2, latency-sensitive traffic can be transmitted and received utilizing one or more of the AP cooperative transmission and reception methods. For example, FIG. 25 may be an example of the C-SR method, FIG. 26 may be an example of the C-TDMA method, and FIG. 27 may be an example of the C-OFDMA method.

Here, AP1 and STAs coupled to AP1, and AP2 and STAs coupled to AP2 may perform an operation of terminating their TXOPs before the start time of the corresponding R-TWT SP for notification and protection of the overlapping cooperative R-TWT schedule.

In the examples of FIGS. 25 to 27, BSS1 refers to the BSS of AP1, and BSS2 refers to the BSS of AP2. Information for negotiating exemplary AP cooperation methods may be included in frames for requesting cooperation and frames for responding cooperation during the TWT cooperation process, but the scope of the present disclosure is not limited thereto. For example, a separate consultation frame for the AP cooperation transmission and reception method between AP1 and AP2 may be transmitted and received between the requesting cooperation and the response, or may be transmitted and received after the requesting cooperation and the response.

Figure 25 shows an example of AP1 and AP2 transmitting and receiving latency sensitive traffic using C-SR during overlapping cooperative R-TWT schedules.

For example, a cooperation request transmitted by AP1 may include an R-TWT schedule by AP1, and the R-TWT schedule may include information about overlapping TWTs that are allowed to be used together with AP2 in a C-SR manner. AP2 may transmit a cooperation response indicating acceptance of the cooperation request.

AP1 and AP2 can utilize C-SR to control their signal strength through power control during their coordinated overlapping R-TWT schedules, thereby minimizing interference between them during the same time slot. Accordingly, AP1 and its STAs, and AP2 and its STAs, can transmit and receive latency-sensitive traffic during the TXOPs they have acquired through contention, provided they have membership in the overlapping R-TWT SP, while minimizing interference from OBSS data transmission and reception within each AP's BSS during the SP.

Figure 26 shows an example of AP1 and AP2 transmitting and receiving latency sensitive traffic using C-TDMA during overlapping cooperative R-TWT schedules.

For example, a cooperation request transmitted by AP1 may include an R-TWT schedule by AP1, and the R-TWT schedule may include information about overlapping TWTs that are allowed to be used together with AP2 in a C-TDMA manner. AP2 may transmit a cooperation response indicating acceptance of the cooperation request.

AP1 and AP2 can minimize interference with each other's BSS by securing time for transmitting and receiving latency-sensitive traffic within each BSS by utilizing C-TDMA during the cooperative overlapping R-TWT schedule. Accordingly, AP1 and STAs belonging to AP1, and AP2 and STAs belonging to AP2, if they have membership in the overlapping R-TWT SP, can transmit and receive latency-sensitive traffic within the BSS of each AP during the SP with minimal interference due to data transmission and reception of OBSS. For example, as shown in FIG. 26, after latency-sensitive traffic is transmitted and received in BSS1 within AP1, AP1 can transmit an MU-RTS TXS TF (multi-user request to send TXOP sharing trigger frame) to AP2. AP2, which responds by transmitting a CTS frame, can transmit and receive latency-sensitive traffic in BSS2 within AP2.

Figure 27 shows an example of AP1 and AP2 transmitting and receiving latency sensitive traffic using C-OFDMA during overlapping cooperative R-TWT schedules.

For example, a cooperation request transmitted by AP1 may include an R-TWT schedule by AP1, and the R-TWT schedule may include information about overlapping TWTs that are allowed to be used together with AP2 in a C-OFDMA manner. AP2 may transmit a cooperation response indicating acceptance of the cooperation request.

AP1 and AP2 can minimize interference with each other's BSS by utilizing C-OFDMA during the cooperative overlapping R-TWT schedule to secure channels and bandwidth for transmitting and receiving latency-sensitive traffic within each BSS. For example, when utilizing C-OFDMA during the cooperative overlapping R-TWT schedule, AP1 and AP2 can exchange information about the overlapping bandwidth between the two BSSs during TWT cooperation and channel information for operating the R-TWT by including them in a frame containing a cooperation request or a separate consultation frame for the AP cooperation method.

Accordingly, AP1 and STAs belonging to AP1, and AP2 and STAs belonging to AP2, if they have membership in the overlapping R-TWT SP, can transmit and receive latency-sensitive traffic within the BSS of each AP during the SP while minimizing interference due to data transmission and reception of the OBSS. For example, as shown in FIG. 27, latency-sensitive traffic can be transmitted and received on the primary 80MHz channel during the coordinated overlapping R-TWT within BSS1 of AP1, and latency-sensitive traffic can be transmitted and received on the secondary 80MHz channel during the coordinated overlapping R-TWT within BSS2 of AP2.

Unlike conventional wireless LAN systems where TWT is set between APs and STAs within a single BSS, the examples of the present disclosure support protection/sharing of TWT schedules between APs belonging to different BSSs, thereby achieving a new effect of supporting transmission and reception within each BSS within overlapping TWT SPs while avoiding interference between APs.

The embodiments described above are combinations of components and features of the present disclosure in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, it is also possible to form embodiments of the present disclosure by combining some components and/or features. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form embodiments or incorporated as new claims through post-application amendments.

It will be apparent to those skilled in the art that the present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present disclosure are intended to be included within the scope of the present disclosure.

The scope of the present disclosure includes software or machine-executable instructions (e.g., an operating system, an application, firmware, a program, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer. Instructions that can be used to program a processing system to perform the features described in the present disclosure can be stored on/in a storage medium or a computer-readable storage medium, and a computer program product including such a storage medium can be used to implement the features described in the present disclosure. The storage medium can include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices, and can include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. The memory optionally includes one or more storage devices remotely located from the processor(s). The memory or, alternatively, the non-volatile memory device(s) within the memory comprise a non-transitory computer-readable storage medium. The features described in this disclosure may be incorporated into software and/or firmware stored on any of the machine-readable media, which may control the hardware of the processing system and allow the processing system to interact with other mechanisms that utilize results according to embodiments of the present disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments/containers.

The method proposed in this disclosure is described with a focus on examples applied to IEEE 802.11-based systems, but can be applied to various wireless LANs or wireless communication systems in addition to IEEE 802.11-based systems.

Claims (22)

A step of transmitting a first frame including a first target wake time element (TWT element) by a first access point (AP) to a second AP; and In response to the first frame, the step of receiving a second frame from the second AP by the first AP, The first TWT element includes a control field and a first broadcast TWT parameter set field, the control field includes a negotiation type field, and the value of the negotiation type field is set to a value associated with the first broadcast TWT parameter set, A method wherein the first broadcast TWT parameter set field includes one or more scheduling-related information, and each of the one or more scheduling-related information is set to a value based on the reference timing of the second AP. In the first paragraph, A method in which the value of the above agreement type field is set to 3. In the first paragraph, A method in which the reference timing of the second AP corresponds to the TSF (timing synchronization function) value of the second AP. In the first paragraph, A method wherein the first broadcast TWT parameter set field further includes a broadcast TWT recommendation field, and the broadcast TWT recommendation field is set to a value associated with TWT negotiation between APs. In paragraph 4, A method wherein the above broadcast TWT recommendation field is set to any one of 3, 5, 6, or 7. In the first paragraph, The above control field further includes an NDP (null data physical layer protocol data unit) paging indicator field, A method in which the value of the above NDP paging indicator field is set to 1. In the first paragraph, One or more of the above scheduling related information: Within the first broadcast TWT parameter set field, a target wake time field, a nominal minimum TWT wake duration field, or a TWT wake interval mantissa field; A TWT wake interval exponent field within the request type field within the first broadcast TWT parameter set field; or A broadcast TWT persistence field within the broadcast TWT information (info) field within the first broadcast TWT parameter set field. A method corresponding to one or more of the following. In the first paragraph, The first broadcast TWT parameter set field includes a request type field, The value of the TWT request field in the above request type field is set to 1, A method in which the TWT setup command field within the above request type field is set to a value corresponding to one of request, suggest, or demand. In the first paragraph, The second frame includes a second TWT element, and a second broadcast TWT parameter set field within the second TWT element includes a request type field, The value of the TWT request field in the above request type field is set to 0, A method wherein the TWT setup command field within the above request type field is set to a value corresponding to one of accept, alternate, dictate, or reject. In paragraph 9, The third broadcast TWT parameter set field within the second TWT element includes a request type field, The value of the TWT request field in the above request type field is set to 1, A method wherein the TWT setup command field within the above request type field is set to a value corresponding to one of a request, a proposal, or a demand. In paragraph 10, The value of the last broadcast parameter set field in the request type field of the second broadcast TWT parameter set field is set to 0, A method wherein the value of the last broadcast parameter set field in the request type field of the third broadcast TWT parameter set field is set to 1. In paragraph 10, A method in which a third frame responding to the second frame is transmitted from the first AP to the second AP. In paragraph 12, The third frame includes a third TWT element, and the fourth broadcast TWT parameter set field within the third TWT element includes a request type field, The value of the TWT request field in the above request type field is set to 0, A method wherein the TWT setup command field within the above request type field is set to a value corresponding to one of accept, alternative, dictate, or reject. In the first paragraph, A method wherein the first broadcast TWT parameter set field further includes information indicating whether membership of a station (STA) associated with the second AP for a TWT schedule associated with the first broadcast TWT parameter set field is permitted. In paragraph 14, Information indicating whether membership of the STA associated with the second AP is permitted is an aligned field within the request type field within the first broadcast TWT parameter set field, A method in which the value of the sorted field is set to 1 based on the membership of the STA that is associated with the second AP being allowed. In the first paragraph, A method wherein the BSS (basic service set) of the first AP and the BSS of the second AP overlap. In the first paragraph, A method wherein the first frame and the second frame correspond to TWT setup frames. one or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: Transmitting a first frame including a first target wake time element (TWT element) to a second access point (AP) via the one or more transceivers; and In response to the first frame, a second frame is set to be received from the second AP through the one or more transceivers, The first TWT element includes a control field and a first broadcast TWT parameter set field, the control field includes a negotiation type field, and the value of the negotiation type field is set to a value associated with the first broadcast TWT parameter set, A first AP, wherein the first broadcast TWT parameter set field includes one or more scheduling-related information, and each of the one or more scheduling-related information is set to a value based on the reference timing of the second AP. A step of receiving a first frame including a first target wake time element (TWT element) from a first access point (AP) by a second access point (AP); and Including a step of transmitting a second frame to the first AP by the second AP in response to the first frame, The first TWT element includes a control field and a first broadcast TWT parameter set field, the control field includes a negotiation type field, and the value of the negotiation type field is set to a value associated with the first broadcast TWT parameter set, A method wherein the first broadcast TWT parameter set field includes one or more scheduling-related information, and each of the one or more scheduling-related information is set to a value based on the reference timing of the second AP. one or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: Receiving a first frame including a first target wake time element (TWT element) from a first access point (AP) through the one or more transceivers; and In response to the first frame, a second frame is set to be transmitted to the first AP through the one or more transceivers, The first TWT element includes a control field and a first broadcast TWT parameter set field, the control field includes a negotiation type field, and the value of the negotiation type field is set to a value associated with the first broadcast TWT parameter set, A second AP, wherein the first broadcast TWT parameter set field includes one or more scheduling-related information, and each of the one or more scheduling-related information is set to a value based on the reference timing of the second AP. one or more processors; and A processing device comprising one or more computer memories operatively connected to said one or more processors and storing instructions for performing a method according to any one of claims 1 to 17 based on execution by said one or more processors. One or more non-transitory computer-readable media storing one or more instructions that are executed by one or more processors to control the performance of a method according to any one of claims 1 to 17.