Broadcast TWT-based multi-AP operation method and apparatus in wireless LAN system

Abstract

The present disclosure relates to an improved wireless LAN system. The present disclosure proposes a method and apparatus for an operation considering an M-AP in order to efficiently improve management of multi-AP in the improved wireless LAN system. Specifically, the present disclosure proposes a method of a procedure for a broadcast TWT-based M-AP operation, and an apparatus for performing the method.

Description

Method and device for operating multiple APs based on broadcast TWT in a wireless LAN system

[0001] The present disclosure relates to a wireless local area network (WLAN) system. Specifically, the present disclosure relates to a method of operation and apparatus considering multiple access points (APs) in a wireless LAN system.

[0002] Wireless LAN (WLAN) systems are evolving for various purposes, such as improving transmission rates, increasing bandwidth, enhancing reliability, reducing errors, and reducing latency. The Institute of Electrical and Electronics Engineers (IEEE) publishes the 802.11 standard specification for wireless LAN systems, and the technology described in the 802.11 standard specification can be referred to as WiFi (or Wi-Fi, Wireless Fidelity).

[0003] Wi-Fi technology has evolved through several generations of 802.11 standards. For example, the 802.11ac standard covers improvements for VHT (very high throughput), the 802.11ax standard covers improvements for HE (high efficiency), and the 802.11be standard covers improvements for EHT (extreme high throughput).

[0004] Meanwhile, technologies to provide an improved wireless communication environment in wireless LAN systems are being discussed, and various technologies are being proposed and researched in response to the demand to further enhance the reliability of wireless LAN systems.

[0005] The present disclosure proposes a method and apparatus for operating a device considering multi-AP operation for operation between APs in a wireless LAN system. In particular, the present disclosure proposes procedures for a device to set and operate sections for multi-AP operation. Furthermore, the present disclosure also proposes frame and element structures for multi-AP operation.

[0006] The technical objectives to be achieved in this disclosure are not limited to those mentioned above, and other unmentioned technical problems may be considered by those skilled in the art from the embodiments of the present invention described below.

[0007] According to various embodiments of the present disclosure, a method performed by a first access point (AP) of a wireless local area network (WLAN) system comprises: transmitting a first frame to a second AP to request the setup of a multi-AP (M-AP) target wakeup time (TWT) service period (SP); receiving a second frame from the second AP to respond to the setup of the M-AP TWT SP; and exchanging frames for the management of a first M-AP operation between the first AP and the second AP within the M-AP TWT SP, wherein the first frame may include a broadcast TWT recommendation field containing a value for indicating the M-AP TWT SP and an M-AP information field for indicating a parameter associated with the M-AP TWT SP.

[0008] According to various embodiments of the present disclosure, a method performed by a second access point (AP) of a wireless local area network (WLAN) system comprises: receiving a first frame from a first AP to request the setup of a multi-AP (M-AP) target wakeup time (TWT) service period (SP); transmitting a second frame to the first AP to respond to the setup of the M-AP TWT SP; and exchanging frames for the management of a first M-AP operation between the first AP and the second AP within the M-AP TWT SP, wherein the first frame may include a broadcast TWT recommendation field containing a value for indicating the M-AP TWT SP and an M-AP information field for indicating a parameter associated with the M-AP TWT SP.

[0009] According to various embodiments of the present disclosure, a first access point (AP) of a wireless local area network (WLAN) system comprises: a transceiver; and a controller coupled to the transceiver, wherein the controller is configured to transmit a first frame to a second AP to request the setup of a multi-AP (M-AP) target wakeup time (TWT) service period (SP), receive a second frame from the second AP to respond to the setup of the multi-AP TWT SP, and exchange frames for the management of a first M-AP operation between the first AP and the second AP within the multi-AP TWT SP, wherein the first frame may include a broadcast TWT recommendation field containing a value for indicating the multi-AP TWT SP and an M-AP information field for indicating a parameter associated with the multi-AP TWT SP.

[0010] According to various embodiments of the present disclosure, a second access point (AP) of a wireless local area network (WLAN) system comprises: a transceiver; and a controller coupled to the transceiver, wherein the controller is configured to receive a first frame from the first AP for requesting the setup of a multi-AP (M-AP) target wakeup time (TWT) service period (SP), transmit a second frame to the first AP for responding to the setup of the M-AP TWT SP, and exchange frames for the management of a first M-AP operation between the first AP and the second AP within the M-AP TWT SP, and wherein the first frame may include a broadcast TWT recommendation field containing a value for indicating the M-AP TWT SP and an M-AP information field for indicating a parameter associated with the M-AP TWT SP.

[0011] According to the various embodiments proposed in this disclosure, the reliability of traffic transmission and reception in a wireless LAN system can be improved. In addition, the efficiency of device operation can be improved by simplifying the procedures for improving reliability.

[0012] FIG. 1 illustrates the configuration of a device for wireless communication according to various embodiments of the present disclosure.

[0013] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0014] FIG. 3 illustrates a link setup process related to the present disclosure.

[0015] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0016] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0017] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0018] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0019] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0020] FIG. 9 illustrates an exemplary format of a target wakeup time (TWT) element related to the present disclosure.

[0021] FIG. 10 illustrates an exemplary format of an individual TWT parameter set field related to the present disclosure.

[0022] FIG. 11 illustrates an exemplary format of a broadcast TWT parameter set field related to the present disclosure.

[0023] FIG. 12 illustrates an exemplary format of a broadcast TWT parameter set field related to the present disclosure.

[0024] FIG. 13 illustrates the flow of signals between devices for M-AP (multi-AP) operation according to various embodiments of the present disclosure.

[0025] FIG. 14 illustrates an exemplary format of a broadcast TWT parameter set field according to various embodiments of the present disclosure.

[0026] FIG. 15 illustrates exemplary values ​​of a broadcast TWT recommendation field according to various embodiments of the present disclosure.

[0027] FIG. 16 illustrates the operation of devices for an M-AP TWT SP (service period) according to various embodiments of the present disclosure.

[0028] FIG. 17 illustrates an exemplary format of a broadcast TWT parameter set field according to various embodiments of the present disclosure.

[0029] FIG. 18a illustrates the operation of devices for starter correction of M-AP TWT SP according to various embodiments of the present disclosure.

[0030] FIG. 18b illustrates an exemplary format of an initial control response (ICR) according to various embodiments of the present disclosure.

[0031] FIG. 19a illustrates a signal flow for managing multiple M-AP operations within a single M-AP TWT SP according to various embodiments of the present disclosure.

[0032] FIG. 19b illustrates the operation of devices for managing a plurality of M-AP operations within a single M-AP TWT SP according to various embodiments of the present disclosure.

[0033] FIG. 19c illustrates an exemplary format for managing multiple M-AP operations within a single M-AP TWT SP according to various embodiments of the present disclosure.

[0034] FIG. 20 illustrates the flow of signals between devices for M-AP operation according to various embodiments of the present disclosure.

[0035] FIG. 21 illustrates the operation flow of an AP according to various embodiments of the present disclosure.

[0036] FIG. 22 illustrates the operation flow of another AP according to various embodiments of the present disclosure.

[0037] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that identical components in the accompanying drawings are represented by the same reference numerals whenever possible. Furthermore, detailed descriptions of known functions and configurations that could obscure the essence of the present disclosure will be omitted.

[0038] In describing the embodiments in this specification, technical details that are well known in the technical field to which this disclosure belongs and are not directly related to this disclosure are omitted. This is intended to convey the essence of this disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0039] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the size of each component does not entirely reflect its actual dimensions.

[0040] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims.

[0041] At this time, it will be understood that each block of the flowcharts and combinations of the flowcharts can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a specialized computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flowchart block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing the means of instruction to perform the function described in the flowchart block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0042] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specified logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For instance, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order according to their corresponding functions.

[0043] In this embodiment, the term "part" refers to a software or hardware component, such as an FPGA or ASIC, and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or configured to operate one or more processors. Thus, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." Furthermore, the components and "parts" may be implemented to operate one or more CPUs within a device or secure multimedia card.

[0044] In the present disclosure, when a component is described as being “connected,” “combined,” or “joined” with another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, in the present disclosure, the terms “comprising” or “having” specify the presence of the mentioned features, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, actions, elements, components, and / or groups thereof.

[0045] In the present disclosure, terms such as "first," "second," etc. are used solely for the purpose of distinguishing one component from another and are not used to limit the components, nor do they limit the order or importance of the components unless specifically stated otherwise. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and likewise, a second component in one embodiment may be referred to as a first component in another embodiment.

[0046] The terms used in this disclosure are for the description of specific embodiments and are not intended to limit the claims. As used in the description of embodiments and in the appended claims, the singular form is intended to include the plural form unless the context clearly indicates otherwise. The term "and / or" as used in this disclosure may refer to any one of the related enumerated items, or refers to and includes any and all possible combinations of two or more of them. Additionally, the " / " between words in this disclosure has the same meaning as "and / or" unless otherwise noted.

[0047] The embodiments of the present disclosure may be applied to various wireless communication systems. For example, the embodiments of the present disclosure may be applied to wireless LAN systems. For example, the embodiments of the present disclosure may be applied to wireless LAN systems based on the IEEE 802.11a / g / n / ac / ax / be standards. Furthermore, the embodiments of the present disclosure may be applied to wireless LAN systems based on the newly discussed IEEE 802.11bn (or UHR (ultra high reliability)) standards. Additionally, the embodiments of the present disclosure may be applied to next-generation wireless LAN systems based on new standards that improve upon IEEE 802.11bn.

[0048] In addition, the examples of the present disclosure may be applied to cellular wireless communication systems. For example, the examples of the present disclosure may be applied to cellular wireless communication systems based on LTE (Long Term Evolution), LTE-A (LTE advanced), and NR (New Radio) technologies based on 3GPP (3rd Generation Partnership Project) standard documents.

[0049] FIG. 1 illustrates the configuration of a device for wireless communication according to various embodiments of the present disclosure.

[0050] The first device (100) and the second device (200) of FIG. 1 may be replaced with various terms such as terminal, wireless device, WTRU (Wireless Transmit and Receive Unit), UE (User Equipment), MS (Mobile Station), UT (user terminal), MSS (Mobile Subscriber Station), MSS (Mobile Subscriber Unit), SS (Subscriber Station), AMS (Advanced Mobile Station), WT (Wireless terminal), client terminal, or simply user.

[0051] In addition, the first device (100) and the second device (200) can be replaced with various terms such as Access Point (AP), Base Station (BS), fixed station, Node B, base transceiver system (BTS), network, Artificial Intelligence (AI) system, road side unit (RSU), repeater, router, relay, gateway, etc.

[0052] The device (100, 200) exemplified in FIG. 1 may be referred to as a station (STA). For example, the device (100, 200) exemplified in FIG. 1 may be referred to by various terms such as a transmitting device, a receiving device, a transmitting STA, or a receiving STA. For example, the STA (110, 200) may perform the role of an access point (AP) or a non-AP. That is, in the present disclosure, the STA (110, 200) may perform the functions of an AP and / or a non-AP. If the STA (110, 200) performs the AP function, it may simply be referred to as an AP, and if the STA (110, 200) performs the non-AP function, it may simply be referred to as a STA. Additionally, in the present disclosure, the AP may also be indicated as an AP STA.

[0053] Referring to FIG. 1, the first device (100) and the second device (200) can transmit and / or receive wireless signals through various wireless LAN technologies (e.g., technologies based on the IEEE 802.11 standard). The first device (100) and the second device (200) may include interfaces for the MAC (medium access control) layer and the PHY (physical) layer that comply with the specifications of the IEEE 802.11 standard.

[0054] In addition, the first device (100) and the second device (200) may additionally support various wireless communication technologies other than wireless LAN technology (e.g., 3GPP LTE, LTE-A, or technologies based on NR standard documents). In addition, the device of the present disclosure may be implemented as various devices such as mobile phones, vehicles, personal computers, AR (Augmented Reality) equipment, VR (Virtual Reality) equipment, etc. Furthermore, the STA of the present specification may support various communication services such as voice calls, video calls, data communication, autonomous driving, MTC (Machine-Type Communication), M2M (Machine-to-Machine), D2D (Device-to-Device), and IoT (Internet-of-Things).

[0055] The first device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (or transceivers, transceivers) (106) and / or one or more antennas (108). The processor (102) controls the memory (104) and / or transceivers (106) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (102) may process information within the memory (104) to generate first information and / or a first signal, and then transmit a wireless signal including the first information and / or the first signal through the transceiver (106). Additionally, the processor (102) may receive a wireless signal including second information and / or a second signal through a transceiver (106) and then store the information obtained through signal processing of the second information and / or the second signal 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 store software code including instructions for performing some or all of the processes controlled by the processor (102) or for performing the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure. Here, the processor (102) and the memory (104) may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., technology based on the IEEE 802.11 document). The transceiver (106) may be connected to the processor (102) and may transmit and / or receive wireless signals through one or more antennas (108). The transceiver (106) may include a transmitter and / or receiver. The transceiver (106) may be used in combination with an RF (Radio Frequency) unit.

[0056] The second device (200) includes one or more processors (202) and one or more memories (204), and may further include one or more transceivers (or transceivers) (206) and / or one or more antennas (208). The processor (202) controls the memory (204) and / or transceivers (206) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (202) may process information within the memory (204) to generate third information and / or a third signal, and then transmit a wireless signal including the third information and / or the third signal through the transceiver (206). Additionally, the processor (202) may receive a wireless signal including fourth information and / or a fourth signal through the transceiver (206), and then store information obtained through signal processing of the fourth information and / or the fourth signal 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 store software code containing instructions for performing some or all of the processes controlled by the processor (202) or for performing the descriptions, functions, procedures, proposals, methods, and / or sequence diagrams of operation disclosed in this disclosure. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., technology based on the IEEE 802.11 document). The transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals through one or more antennas (208). The transceiver (206) may include a transmitter and / or receiver. The transceiver (206) may be combined with an RF unit.

[0057] Hereinafter, the hardware elements of the device (100, 200) will be described in more detail. Although not limited to the following, the operation of 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 the operation of 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 Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this 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 operation sequences disclosed in this disclosure. One or more processors (102, 202) may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, traffic, or information according to the functions, procedures, proposals, and / or methods disclosed in this disclosure and provide it to one or more transceivers (106, 206). One or more processors (102, 202) may receive a signal (e.g., a baseband signal) from one or more transceivers (106, 206) and may obtain a PDU, SDU, message, control information, data, traffic, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this disclosure.

[0058] One or more memories (104, 204) may be connected to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. One or more memories (104, 204) may be composed of ROM (read-only memory), RAM (random access memory), EPROM (erasable programmable ROM), EEPROM (electronically EPROM), flash memory, hard drive, registers, cache memory, computer-readable storage media, and / or combinations thereof. One or more memories (104, 204) may be located inside and / or outside of one or more processors (102, 202). Additionally, one or more memories (104, 204) may be connected to one or more processors (102, 202) through various technologies such as wired or wireless connections.

[0059] One or more transceivers (106, 206) may transmit user data, control information, data, traffic, wireless signals, and / or channels, etc., as mentioned in the methods and / or operation flowcharts, etc., of the present disclosure to one or more other devices. One or more transceivers (106, 206) may receive user data, control information, data, traffic, wireless signals, and / or channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts, etc., disclosed in the present disclosure from one or more other devices. For example, one or more transceivers (106, 206) may be connected to one or more processors (102, 202) and may transmit and receive wireless signals. For example, one or more processors (102, 202) may control one or more transceivers (106, 206) to transmit user data, control information, traffic, wireless signals, and / or channels 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, traffic, wireless signals and / or channels from one or more other devices. Additionally, one or more transceivers (106, 206) may be connected 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, traffic, wireless signals and / or channels, etc., as described in the descriptions, functions, procedures, proposals, methods and / or flowcharts, etc. disclosed in this disclosure through one or more antennas (108, 208). In this disclosure, one or more antennas (108, 208) may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).One or more transceivers (106, 206) can convert received wireless signals / channels, etc. from RF band signals to baseband signals in order to process received user data, control information, wireless signals / channels, etc. using one or more processors (102, 202). One or more transceivers (106, 206) can convert processed user data, control information, wireless signals / channels, etc. from baseband signals to RF band signals using one or more processors (102, 202). To this end, one or more transceivers (106, 206) may include (analog) oscillators and / or filters.

[0060] In one example, one of the devices (100, 200) may perform the intended operation of an AP, and the other of the devices (100, 200) may perform the intended operation of a non-AP STA. In another example, the transceiver (106, 206) of FIG. 1 may perform the transmission and / or reception operation of a signal (e.g., a packet or PPDU (physical layer protocol data unit) according to IEEE 802.11a / b / g / n / ac / ax / be / bn, etc.).

[0061] In addition, in the present disclosure, the operation of generating transmission and reception signals or performing data processing or calculations in advance for transmission and reception signals by various STAs can be performed in the processor (102, 202) of FIG. 1. For example, examples of operations for generating transmit / receive signals or performing data processing or operations in advance for transmit / receive signals include: 1) operations for determining / acquiring / configuring / operating / decoding / encoding bit information of fields included in the PPDU (e.g., SIG (signal), STF (short training field), LTF (long training field), Data, etc.); 2) operations for determining / configuring / acquiring time resources or frequency resources (e.g., subcarrier resources) used for fields included in the PPDU (e.g., SIG, STF, LTF, Data, etc.); 3) operations for determining / configuring / acquiring specific sequences (e.g., pilot sequence, STF / LTF sequence, extra sequence applied to SIG) used for fields included in the PPDU (e.g., SIG, STF, LTF, Data, etc.); 4) power control operations and / or power saving operations applied to the STA; and 5) of the ACK (acknowledgement) signal. It may include operations related to determination / acquisition / configuration / operation / decoding / encoding, etc. In addition, in the following example, various information (e.g., information related to fields / subfields / control fields / parameters / power, etc.) used by various STAs for determination / acquisition / configuration / operation / decoding / encoding of transmission and reception signals may be stored in the memory (104, 204) of FIG. 1.

[0062] In the following, the 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 the AP STA, and the receiver may be part of the non-AP STA. The 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 the non-AP STA, and the receiver may be part of the AP STA.

[0063] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0064] A wireless LAN system may have a structure composed of multiple components. Through the interaction of these multiple components, the wireless LAN system can support transparent STA mobility relative to the upper layer. A Basic Service Set (BSS) corresponds to the basic building block of a wireless LAN. Figure 2 exemplarily illustrates the existence of two BSSs (BSS 1 and BSS 2), each containing two STAs as members (STA 1 and STA 2 are included in BSS 1, and STA 3 and STA 4 are included in BSS 2). In Figure 2, the ellipse representing the BSS can also be understood as representing the coverage area where the STAs included in the corresponding BSS maintain communication. This area can be referred to as a Basic Service Area (BSA). If a STA moves outside the BSA, it cannot communicate directly with other STAs within that BSA.

[0065] Excluding the distributed system (DS) illustrated in Fig. 2, the most basic type of BSS in a wireless LAN is the Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For instance, assuming other components are omitted, a BSS 1 composed of only STA 1 and STA 2, or a BSS 2 composed of only STA 3 and STA 4, can each be considered a representative example of an IBSS. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, this type of wireless LAN is not configured through pre-planning but can be established when a LAN (local area network) is required, and it may also be referred to as an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. In other words, in an IBSS, STAs are managed in a distributed manner. In IBSS, all STAs can be mobile STAs, and since connections to DS are not allowed, they form a self-contained network.

[0066] The membership of an STA in a BSS can be dynamically changed by the STA being turned on or off, or by the STA entering or leaving the BSS area. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services of the BSS infrastructure, an STA must be associated with the BSS. This association can be configured dynamically and may include the use of a Distribution System Service (DSS).

[0067] In a wireless LAN, the direct STA-to-STA distance can be limited by PHY performance. In some cases, this distance limit may be sufficient, but in others, communication between STAs over longer distances may be required. A DS can be configured to support extended coverage.

[0068] DS refers to a structure in which BSSs are interconnected. Specifically, as shown in FIG. 2, a BSS may exist as a component in an extended form of a network composed of multiple BSSs. DS is a logical concept and can be specified by the characteristics of the Distributed System Medium (DSM, DS medium). In this regard, the Wireless Medium (WM) and the DSM can be logically distinguished. Each logical medium is used for a different purpose and is utilized by different components. These media are not limited to being identical or different. The flexibility of the wireless LAN structure (DS structure or other network structure) can be explained by the fact that multiple media are logically distinct in this way. That is, the wireless LAN structure can be implemented in various ways, and the corresponding wireless LAN structure can be independently specified by the physical characteristics of each implementation.

[0069] DS can support mobile devices by providing seamless integration of multiple BSSs and providing logical services necessary for handling addresses to destinations. Additionally, DS may include a component called a portal that acts as a bridge for connecting the wireless LAN with other networks (e.g., IEEE 802.X).

[0070] An AP enables access to the DS via the WM for non-AP STAs coupled with it. An AP can refer to an entity that also possesses the functionality of an STA, and data movement between the BSS and the DS can be performed through the AP. For example, STA 2 and STA 3 shown in FIG. 2 possess the functionality of an STA and provide the function of enabling coupled non-AP STAs (STA 1 and STA 4) to access the DS. Furthermore, since all APs fundamentally correspond to STAs, all APs are addressable entities. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM do not necessarily have to be the same. A BSS composed of an AP and one or more STAs can be referred to as an infrastructure BSS.

[0071] Data transmitted from one of the STA(s) coupled to the AP to the STA address of the AP can always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity. Additionally, if the controlled port is authenticated, the transmitted data (or frame) can be forwarded to the DS.

[0072] In addition to the structure of the aforementioned DS, an Extended Service Set (ESS) may be configured to provide wider coverage.

[0073] An ESS is a network of arbitrary size and complexity that can correspond to a set of BSSs connected to a single DS. However, an ESS does not contain a DS. An ESS network is characterized by appearing as an IBSS at the Logical Link Control (LLC) layer. STAs included in an ESS can communicate with each other, and mobile STAs can move from one BSS to another (i.e., within the same ESS) transparently to the LLC. APs included in a single ESS can have the same Service Set Identifier (SSID). The SSID is distinguished from the BSSID (BSS SSID), which is the identifier of the BSS.

[0074] In wireless LAN systems, no assumptions are made regarding the relative physical locations of BSSs, and all of the following forms are possible. BSSs may partially overlap, which is a form commonly used to provide continuous coverage. Additionally, BSSs may not be physically connected, and logically, there is no limit to the distance between BSSs. Furthermore, BSSs may be located in the same physical location, which can be used to provide redundancy. Additionally, one or more IBSS or ESS networks may physically exist in the same space as one (or more) ESS networks. This may apply to ESS network configurations where an ad-hoc network operates at a location where an ESS network exists, where wireless networks are physically overlapping by different organizations, or where two or more different access and security policies are required at the same location.

[0075] FIG. 3 illustrates a link setup process related to the present disclosure.

[0076] In order for an STA to set up links and transmit and receive data on a network, it must discover the network through an AP, perform authentication, establish an association, and set up security. The link setup process can also be referred to as the session initiation process or the session setup process. Additionally, the processes of discovery, authentication, association, and security setup within the link setup process can be collectively referred to as the association process.

[0077] In step (310), the STA can perform a network discovery operation. The network discovery operation may include the STA's scanning operation. That is, in order for the STA to access a network, it must find a network that it can join. Before joining a wireless network, the STA must identify a compatible network, and the process of identifying networks existing in a specific area is called scanning.

[0078] Scanning methods include active scanning and passive scanning. Figure 3 illustrates a network discovery operation that includes an active scanning process as an example. In active scanning, the STA performing the scanning moves between channels to search for nearby APs, transmits a probe request frame, and waits for a response. The responder transmits a probe response frame as a response to the probe request frame to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted a beacon frame from the BSS of the channel being scanned. In a BSS, the AP becomes the responder because it transmits the beacon frame; however, in an IBSS, the responder is not constant because STAs within the IBSS take turns transmitting the beacon frame. 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 in the same way (i.e., transmit and receive probe request / response on channel 2).

[0079] Although not illustrated in FIG. 3, the scanning operation may be performed using a passive scanning method. In passive scanning, the STA performing the scanning waits for a beacon frame while switching between channels. A beacon frame is one of the management frames defined in IEEE 802.11, which announces the presence of a wireless network and is periodically transmitted to allow the scanning STA to find the wireless network and join it. In a BSS, the AP performs the role of periodically transmitting beacon frames, and in an IBSS, the STAs within the IBSS take turns transmitting beacon frames. When the scanning STA receives a beacon frame, it stores the information about the BSS included in the beacon frame and records the beacon frame information in each channel while moving to another channel. The STA that receives the beacon frame stores the BSS-related information included in the received beacon frame, moves to the next channel, and can perform scanning in the next channel in the same way. When comparing active scanning and passive scanning, active scanning has the advantage of lower delay and power consumption than passive scanning.

[0080] After the STA discovers the network, an authentication process may be performed in step (320). This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation of step (340) described later.

[0081] The authentication process involves the STA sending an authentication request frame to the AP, and the AP sending an authentication response frame to the STA in response. The authentication request frame and the authentication response frame used in the authentication process belong to management frames.

[0082] The authentication frame may include information regarding the authentication algorithm number, authentication transaction sequence number, status code, challenge text, Robust Security Network (RSN), Finite Cyclic Group, etc. These are some examples of information that may be included in the authentication request / response frame, and they may be replaced with other information or additional information may be included.

[0083] The STA can send an authentication request frame to the AP. Based on the information contained in the received authentication request frame, the AP can determine whether to allow authentication for the STA. The AP can provide the result of the authentication process to the STA through an authentication response frame.

[0084] After the STA is successfully authenticated, an association process may be performed in step (330). The association process includes the STA sending an association request frame to the AP, and in response, the AP sending an association response frame to the STA.

[0085] The association request frame may include information regarding various capabilities, beacon listen interval, service set identifier (SSID), supported rates, supported channels, robust security network (RSN), mobility domain, supported operating classes, Traffic Indication Map Broadcast request, interworking service capability, etc. For example, the association response frame may include information regarding various capabilities, status code, Association ID (AID), supported rates, Enhanced Distributed Channel Access (EDCA) parameter set, Received Channel Power Indicator (RCPI), Received Signal to Noise Indicator (RSNI), mobility domain, timeout interval (e.g., association comeback time), overlapping BSS scan parameters, TIM broadcast response, Quality of Service (QoS) map, etc. These are some examples of information that may be included in a combined request / response frame, and the combined request / response frame may include other additional information.

[0086] After the STA is successfully joined to the network through the AP, a security setup process may be performed in step (340). The security setup process in step (340) may include an authentication process through RSNA (Robust Security Network Association) requests / responses. Additionally, if the authentication process in step (320) is referred to as the first authentication process, the security setup process in step (340) may also be referred to simply as the authentication process.

[0087] The security setup process of step (340) may include, for example, a process of setting up a private key through a 4-way handshake via an EAPOL (Extensible Authentication Protocol over LAN) frame. Additionally, the security setup process may be performed according to a security method not defined in the IEEE 802.11 standard.

[0088] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0089] In wireless LAN systems, the basic access mechanism of a MAC is the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism. The CSMA / CA mechanism is also known as the Distributed Coordination Function (DCF) of IEEE 802.11 MACs, and it basically employs a "listen before talk" access mechanism. According to this type of access mechanism, the AP and / or STA perform Clear Channel Assessment (CCA) to sense the wireless channel or medium for a predetermined time interval (e.g., DIFS (DCF Inter-Frame Space)) before starting transmission. If the sensing result determines that the medium is in an idle status, the AP and / or STA start transmitting a frame through that medium. On the other hand, if the medium is detected to be occupied or busy, the AP and / or STA may not start their own transmission but wait for a predetermined delay period for medium access (e.g., a random backoff period) before attempting to transmit a frame. By applying a random backoff period, multiple STAs attempt to transmit frames after waiting for different periods of time, thereby minimizing collisions.

[0090] In addition, the IEEE 802.11 MAC protocol provides a Hybrid Coordination Function (HCF). The HCF is based on the aforementioned Point Coordination Function (PCF). The PCF is a polling-based synchronous access method that refers to a method of periodically polling so that all receiving APs and / or STAs can receive data frames. Furthermore, the HCF includes Enhanced Distributed Channel Access (EDCA) and Controlled Channel Access (HCCA). EDCA is a contention-based access method for a provider to provide data frames to multiple users, while HCCA uses a non-contention-based channel access method utilizing a polling mechanism. Additionally, the HCF includes a media access mechanism to improve the Quality of Service (QoS) of a wireless LAN and can transmit QoS data during both the Contention Period (CP) and the Contention-Free Period (CFP).

[0091] With reference to FIG. 4, the operation based on the random backoff period is described. When a medium that was in an occupied / busy state changes to an idle state, multiple STAs may attempt to transmit data (or frames). As a measure to minimize collisions, each STA may select a random backoff count and attempt transmission after waiting for the corresponding slot time. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​in the range from 0 to CW. Here, CW is the Contention Window parameter value. The CW parameter is given an initial value of CWmin, but in the event of transmission failure (e.g., failure to receive an ACK for a transmitted frame), the STA may double the CW. When the CW parameter value reaches CWmax, the STA may attempt to transmit data while maintaining the CWmax value until data transmission is successful, and if data transmission is successful, the CW is reset to the CWmin value. The values ​​of CW, CWmin, and CWmax can be set to 2n-1 (n=0, 1, 2, ...).

[0092] When the random backoff process begins, the STA continues to monitor the media while counting down the backoff slots according to the determined backoff count value. When the media is monitored as occupied, it stops the countdown and waits, and when the media becomes idle, it resumes the remaining countdown.

[0093] In the example of Fig. 4, when a packet to be transmitted arrives at the MAC of STA3, STA3 confirms that the medium is idle for DIFS and can immediately transmit the frame. The remaining STAs monitor whether the medium is occupied or idle and wait. Meanwhile, data to be transmitted may also arise at each of STA1, STA2, and STA5, and each STA, once it confirms that the medium is idle, waits for DIFS and then performs a countdown of the backoff slot according to a random backoff count value selected by each. Assume the case where STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value. That is, it exemplifies a case where, at the point when STA2 finishes the backoff count and starts transmitting the frame, the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1. STA1 and STA5 pause the countdown briefly and wait while STA2 occupies the medium. When STA2's possession ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the paused backoff count. That is, STA1 and STA5 can start frame transmission after counting down the remaining backoff slots corresponding to the remaining backoff time. Since STA5's remaining backoff time was shorter than STA1's, STA5 starts frame transmission. Data to be transmitted may also occur in STA4 while STA2 is occupying the medium. When the medium becomes idle, STA4 waits for DIFS, performs a countdown based on a random backoff count value selected by itself, and can start frame transmission. The example in Figure 4 illustrates a case where STA5's remaining backoff time happens to match STA4's random backoff count value; in this case, a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receives an ACK, resulting in a failure of data transmission.In this case, STA4 and STA5 can double the CW value, select a random backoff count value, and perform a countdown. STA1 waits while the medium is occupied due to the transmission of STA4 and STA5, and when the medium becomes idle, it waits for DIFS, and then can start transmitting frames after the remaining backoff time has elapsed.

[0094] As shown in the example in Fig. 4, a data frame is a frame used for transmitting data to an upper layer and can be transmitted after a backoff performed after the elapsed time of DIFS from when the medium becomes idle. Additionally, a management frame is a frame used for exchanging management information without being transmitted to an upper layer, and is transmitted after a backoff performed after the elapsed time of an IFS such as DIFS or PIFS (Point coordination function IFS). A management frame may include a beacon, association request / response, re-association request / response, probe request / response, authentication request / response, etc., as a subtype frame. A control frame is a frame used to control access to the medium. A control frame is a subtype frame and may include a Request-To-Send (RTS), Clear-To-Send (CTS), Acknowledgment (ACK), Power Save-Poll (PS-Poll), Block ACK (B-ACK or BlockAck), Block ACK Request (BlockACKReq), Null Data Packet Announcement (NDP), Trigger, etc. If the control frame is not an acknowledgment frame of the previous frame, it is transmitted after a backoff performed after the elapsed DIFS; if it is an acknowledgment frame of the previous frame, it is transmitted after the short IFS (SIFS) elapsed without a backoff. The type and subtype of the frame can be identified by the type field and subtype field within the frame control (FC) field.

[0095] A QoS (Quality of Service) STA can transmit a frame after backoff, which is performed after the elapsed time of the arbitration IFS (AIFS) for the access category (AC) to which the frame belongs, i.e., AIFS[i] (where i is a value determined by the AC). Here, the frames for which AIFS[i] can be used can be data frames, management frames, and control frames rather than response frames.

[0096] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0097] As previously mentioned, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, where the STA directly senses the medium. Virtual carrier sensing is intended to mitigate problems that may occur in medium access, such as the hidden node problem. For virtual carrier sensing, the STA's MAC can utilize the Network Allocation Vector (NAV). The NAV is a value that indicates to other STAs the time remaining until the medium becomes available, provided that the STA currently using or authorized to use the medium is using it. Therefore, the value set as the NAV corresponds to the period during which the medium is scheduled to be used by the STA transmitting the frame, and the 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 frame's MAC header.

[0098] In the example of FIG. 5, STA1 wants to transmit data to STA2, and STA3 is in a position to overhear part or all of the frames transmitted and received between STA1 and STA2.

[0099] In order to reduce the possibility of collisions between multiple STAs in a CSMA / CA-based frame transmission operation, a mechanism utilizing RTS / CTS frames may be applied. In the example of FIG. 5, while STA1 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA1 may be a hidden node to STA3. Alternatively, in the example of FIG. 5, while STA2 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA2 may be a hidden node to STA3. By exchanging RTS / CTS frames before performing data transmission and reception between STA1 and STA2, it is possible to prevent a STA outside the transmission range of either STA1 or STA2, or a STA outside the carrier sensing range for transmission from STA1 or STA3, from attempting to occupy the channel during data transmission and reception between STA1 and STA2.

[0100] Specifically, STA1 can determine whether the channel is in use through carrier sensing. In terms of physical carrier sensing, STA1 can determine the channel occupancy idle state based on the energy magnitude or signal correlation detected in the channel. Additionally, in terms of virtual carrier sensing, STA1 can determine the channel occupancy state using a NAV timer.

[0101] If the channel is idle during DIFS, STA1 can send an RTS frame to STA2 after performing backoff. If STA2 receives the RTS frame, it can send a CTS frame to STA1 as a response to the RTS frame after SIFS.

[0102] If STA3 cannot overhear a CTS frame from STA2 but can overhear an RTS frame from STA1, STA3 can set a NAV timer for the duration of subsequent consecutive frame transmissions (e.g., SIFS + CTS frame + SIFS + data frame + SIFS + ACK frame) using the duration information included in the RTS frame. Alternatively, if STA3 cannot overhear an RTS frame from STA1 but can overhear a CTS frame from STA2, STA3 can set a NAV timer for the duration of subsequent consecutive frame transmissions (e.g., SIFS + data frame + SIFS + ACK frame) using the duration information included in the CTS 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.

[0103] If STA1 receives a CTS frame from STA2, it may transmit a data frame to STA2 after SIFS from the time the reception of the CTS frame is completed. If STA2 successfully receives the data frame, it may transmit an ACK frame, which is an acknowledgment of the data frame, to STA1 after SIFS. STA3 may determine whether the channel is in use through carrier sensing when the NAV timer expires. If STA3 determines that the channel is not in use by another terminal during DIFS from the time the NAV timer expires, it may attempt channel access after a contention window (CW) based on random backoff has passed.

[0104] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0105] Based on instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare the MPDU (MAC PDU) to be transmitted. When the PHY layer receives an instruction from the MAC layer requesting the start of transmission, it switches to transmission mode and can construct the information provided by the MAC layer (e.g., data) into a frame and transmit it. Additionally, if the PHY layer detects a valid preamble of the received frame, it can monitor the preamble header and send an instruction to the MAC layer indicating the start of reception.

[0106] As such, information transmission and reception in wireless LAN systems are carried out in the form of frames, and for this purpose, the Physical Layer Protocol Data Unit (PPDU) frame format is defined.

[0107] A basic PPDU frame may include a short training field (STF), a long training field (LTF), a signal field (SIG), and a data field. The most basic (e.g., non-HT (high throughput)) PPDU frame format may consist only of a legacy-STF (Legacy-STF), a greenfield field (Legacy-LTF), a signal field, and a data field. Additionally, depending on the type of PPDU frame format (e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (very high throughput) PPDU, etc.), additional (or different types of) STF, LTF, and signal fields may be included between the signal field and the data field. Specific types of frame formats will be described later in FIG. 7.

[0108] 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 and frequency error estimation. STF and LTF are signals for synchronization and channel estimation in the physical layer of OFDM (orthogonal frequency division multiplexing).

[0109] The SIG field may include a RATE field and a LENGTH field, etc. The RATE field may include information regarding the modulation and coding rates of the data. The LENGTH field may include information regarding the length of the data. Additionally, the SIG field may include a parity bit, a SIG TAIL bit, etc.

[0110] The data field may include a SERVICE field, a PSDU (physical layer service data unit), and PPDU TAIL bits, and may also include padding bits if necessary. Some bits of the SERVICE field may be used for synchronization of the descrambler at the receiver. The PSDU corresponds to a MAC PDU defined at the MAC layer and may contain data generated or used by the upper layer. The PPDU TAIL bits may be used to return the encoder to a 0 state. Padding bits may be used to adjust the length of the data field to a predetermined unit.

[0111] A MAC PDU is 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 a MAC PDU and can be transmitted or received through the PSDU of the data portion of the PPDU frame format.

[0112] The MAC header includes a frame control field, a duration / ID field, an address field, etc. The frame control field may contain control information necessary for frame transmission / reception. The duration / ID field may be set as the time for transmitting the corresponding frame, etc. The specific details of the Sequence Control, QoS Control, and HT Control subfields of the MAC header are omitted.

[0113] Although not illustrated in Fig. 6, the null-data packet (NDP) frame format refers to a frame format that does not include data packets. That is, an NDP frame refers to a frame format that includes the PLCP (physical layer convergence procedure) header portion (i.e., STF, LTF, and SIG fields) in a standard PPDU frame format, but excludes the remaining portion (i.e., data fields). An NDP frame may also be referred to as a short frame format.

[0114] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0115] Standards such as IEEE 802.11a / g / n / ac / ax / be use various forms of PPDU. The basic PPDU format (the format of IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and Data fields. The basic PPDU format may also be referred to as the non-HT PPDU format.

[0116] The HT PPDU format (the format of 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 can be referred to as the HT-mixed format. Although not illustrated, an HT-greenfield format PPDU may be defined, which is 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-LTFs, and Data fields.

[0117] The VHT PPDU format (the format of IEEE 802.11ac) additionally includes VHT SIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields in addition to the basic PPDU format.

[0118] The HE PPDU format (the format of IEEE 802.11ax) additionally includes the 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. 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-user (MU), but is not included in the HE PPDU format for single-user (SU). Additionally, the HE trigger-based (TB) PPDU format does not include HE-SIG-B, and the length of the HE-STF field may vary to 8 us. 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 16 us.

[0119] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0120] The EHT PPDU format of FIG. 8 (format of IEEE 802.11be) may include the EHT MU PPDU format and the EHT TB PPDU format. The EHT MU PPDU format corresponds to a PPDU that carries one or more data (or PSDU) for one or more users. The EHT MU PPDU may be used for both SU transmission and MU transmission, and the EHT MU PPDU may correspond to a PPDU for one receiving STA or multiple receiving STAs. The EHT-SIG is omitted in the EHT TB PPDU compared to the EHT MU PPDU. A STA that receives a trigger for UL MU transmission (e.g., a trigger frame or an RTS frame) may perform UL transmission based on the EHT TB PPDU format.

[0121] The EHT PPDU format additionally includes RL-SIG, U-SIG (Universal SIG), EHT-SIG, EHT-STF, EHT-LTF(s), and PE fields in addition to the basic PPDU format. Depending on the specific examples of the EHT PPDU format, some fields may be excluded or their lengths may vary. For example, depending on the previously described EHT MU PPDU format and EHT TB PPDU format, some fields of the EHT PPDU format may be included or excluded, or the length of specific fields may vary.

[0122] TWT (target wakeup time) is described below.

[0123] TWT is a power saving (PS) technology that can improve the energy efficiency of non-AP STAs by defining a specific service period (SP) and sharing information about the SP among devices to reduce contention. A STA that performs a request / suggest / demand during the TWT setup phase can be called a TWT requesting STA. Additionally, an AP that responds with acceptance or rejection to the request / suggest / demand of the TWT requesting STA can be called a TWT responding AP. TWT operations can be classified into TWT operations based on individual TWTs and TWT operations based on broadcast TWTs.

[0124] According to various embodiments of the present disclosure, in recent wireless LAN systems, cooperative communication between APs is required for operation between multiple APs. For example, APs can perform various multi-AP operations (or M-AP schemes or C-AP schemes), including C (coordinated)-TDMA (time division multiple access), CR-TWT (restricted-TWT), C-SR (spatial reuse), or C-BF (beamforming), and TWT SPs may be used for stable and periodic communication between these APs. More specifically, similar to the TWT operation between an AP and a STA described above, a TWT between an AP and another AP(s) may be defined, and a channel access rule based on an R-TWT method may be applied to eliminate interference from devices other than the APs participating in the TWT. Hereinafter, according to various embodiments, methods for performing efficient operation between APs are described through a procedure for defining an M-AP TWT SP for multi-AP operation and a specific message format thereof.

[0125] FIG. 9 illustrates an exemplary format of a target wake-up time (TWT) element related to the present disclosure. Hereinafter, the TWT element illustrated in FIG. 9 is described based on a TWT element for defining the TWT between an AP and a STA, but these contents may also be applied to an M-AP TWT element for defining the TWT between an AP and another AP. When the contents of FIG. 9 are applied to an M-AP TWT element, the following descriptions regarding the relationship between an AP and a STA may be interpreted as being replaced with the content regarding the relationship between an AP and another AP.

[0126] The TWT element illustrated in FIG. 9(a) can be included in a TWT setup frame, a beacon frame, a probe response frame, or a (re)combination response frame, and can be transmitted and received between a TWT requesting STA and a TWT responding AP. According to one embodiment, an M-AP TWT element for multiple APs can be transmitted and received between a TWT requesting AP and a TWT responding AP. The TWT element may include an element identifier (identity, ID) field of one octet, a length field of one octet, a control field of one octet, and a TWT parameter information field of variable length. The control field of the TWT element has the same format for individual TWTs and broadcast TWTs, while the TWT parameter information field of the TWT element has a different format for individual TWTs and broadcast TWTs.

[0127] Below, each subfield included in the control field of the TWT element illustrated in FIG. 9 (b) will be described in detail. The NDP (null data packet) paging indication subfield may include a value of 1 if an NDP paging field exists in the TWT parameter information field, and a value of 0 if an NDP paging field does not exist in the TWT parameter information field.

[0128] The responder PM (power management) mode subfield may include a value to indicate the power management (PM) mode.

[0129] The negotiation type subfield may include a value to indicate whether the information contained in the TWT element is for parameter negotiation of a broadcast TWT, for parameter negotiation of an individual TWT, or for a wake TBTT (target beacon transmission time) interval.

[0130] If the value of the negotiation type subfield is 0, the TWT element is for a future individual TWT SP start time, and the TWT parameter information field contains a single individual TWT parameter set. This individual TWT parameter set may correspond to an individual TWT negotiation between a TWT requesting STA (or AP) and a TWT responding STA (or AP), or to an individual TWT announcement of a TWT responding AP.

[0131] If the value of the negotiation type subfield is 1, the TWT element is for the next TBTT time, and the TWT parameter information field contains a single set of individual TWT parameters. This set of individual TWT parameters may correspond to the wake TBTT and wake interval negotiation between the TWT scheduled STA (or AP) and the TWT scheduling AP.

[0132] When the value of the negotiation type subfield is 2, the TWT element is for a future broadcast TWT SP start time, and the TWT parameter information field contains one or more broadcast TWT parameter sets. These broadcast TWT parameter sets 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.

[0133] When the value of the negotiation type subfield is 3, the TWT element is for a future broadcast TWT SP start time, and the TWT parameter information field contains one or more broadcast TWT parameter sets. These broadcast TWT parameter sets may correspond to managing membership in a broadcast TWT schedule by including the TWT element in an individually addressed management frame transmitted by either a TWT scheduled STA (or AP) or a TWT scheduling AP.

[0134] That is, the MSB (most significant bit) of the negotiation type subfield can be interpreted as a broadcast field. If the value of the broadcast field is 1 (i.e., the value of the MSB of the negotiation type subfield is 1), the TWT element may contain one or more sets of broadcast TWT parameters. If the value of the broadcast field is 0 (i.e., the value of the MSB of the negotiation type subfield is 0), the TWT element may contain one set of individual TWT parameters. A TWT element in which the value of the broadcast field is 1 (i.e., the value of the MSB of the negotiation type subfield is 1) may be referred to as a broadcast TWT element.

[0135] If the TWT information frame disabled subfield contains a value of 1, it indicates that reception of the TWT information frame by the STA is disabled, otherwise the TWT information frame disabled subfield may contain a value of 0.

[0136] The wake duration unit subfield indicates the unit of the nominal minimum TWT wake duration field. If the unit of the nominal minimum TWT wake duration field is 256us, the wake duration unit subfield contains a value of 0, and if the unit of the nominal minimum TWT wake duration field is TU (time unit), the wake duration unit subfield may contain a value of 1. If it is not HE / EHT STA, the wake duration unit subfield may contain a value of 0.

[0137] The link ID bitmap present field may include a value to indicate whether the link ID bitmap subfield is included in the TWT parameter information field.

[0138] The aligned TWT field may include a value to indicate whether the aligned TWT link bitmap subfield is included in the TWT parameter information field.

[0139] FIG. 10 illustrates an exemplary format of an individual TWT parameter set field related to the present disclosure.

[0140] In the individual TWT parameter set field illustrated in FIG. 10(a), the request type subfield may have the same size as the individual TWT parameter set field and the broadcast TWT parameter set field, but the detailed configuration may differ. Specific details regarding the request type subfield will be described later.

[0141] The target wake time subfield indicates the start time of an upcoming individual / broadcast TWT SP.

[0142] The TWT group assignment subfield contains information to provide information about the TWT group assigned to the TWT requesting STA (or AP). The TWT requesting STA (or AP) can use this information to calculate the TWT value within the TWT group. The TWT value of the TWT requesting STA (or AP) may be equal to the zero offset value and the TWT offset value multiplied by the TWT unit value.

[0143] The nominal maximum TWT wake duration subfield represents the minimum unit that a TWT requesting STA (or AP) expects to wake up to complete the exchange of frames associated with the TWT flow identifier during the TWT wake duration. The TWT wake duration may refer to the average time between consecutive TWT SPs expected by the TWT requesting STA (or AP).

[0144] The TWT Wake Interval Mantissa subfield can be expressed as the binary value of the TWT Wake Interval in microseconds.

[0145] The TWT channel subfield includes a bitmap to indicate an allowed channel. If the TWT element is transmitted by a TWT requesting STA (or AP), the TWT channel subfield may include a bitmap indicating a channel that the TWT requesting STA (or AP) requests to use as a temporary default channel during the TWT SP. If the TWT element is transmitted by a TWT responding AP, the TWT channel subfield may include a bitmap indicating a channel that is allowed for the TWT request.

[0146] The NDP paging subfield may include information related to the identifier of the STA being paged, the maximum number of TWT wake intervals between NDP paging frames, etc.

[0147] The link ID bitmap subfield may contain information to indicate whether a TWT element transmitted by an STA (STA affiliated with MLD) (or AP) associated with a multi-link device (MLD) applies to a specific link.

[0148] The aligned TWT link bitmap field may contain information for indicating a link having an aligned TWT SP for the link indicated by the link ID bitmap subfield.

[0149] Next, the detailed configuration of the request type subfield is explained.

[0150] The TWT request subfield illustrated in FIG. 10 (b) may indicate whether the TWT element is transmitted by a TWT requesting STA (or AP) or by a TWT responding AP. If the value of the TWT request subfield is 1, it may indicate that it is a TWT requesting STA (or AP) or a TWT scheduled STA (or AP), and if the value of the TWT request subfield is 0, it may indicate that it is a TWT responding AP (or STA) or a TWT scheduling AP.

[0151] The TWT setup command subfield can represent commands such as request, suggest, demand, grouping, accept, alternate, dictate, and reject.

[0152] The trigger subfield indicates whether to use the trigger frame in the TWT SP. If the value of the trigger subfield is 1, the trigger is used, and if the value of the trigger subfield is 0, the trigger may not be used.

[0153] The implicit subfield may indicate whether it is an implicit TWT or an explicit TWT. If the value of the implicit subfield is 1, it indicates an implicit TWT, and if the value of the implicit subfield is 0, it indicates an explicit TWT.

[0154] The flow type subfield can indicate the type of interaction between a TWT requesting STA (or TWT scheduled STA) (or AP) and a TWT responding AP (or TWT scheduling AP). If the value of the flow type subfield is 1, it may indicate an announced TWT, where the STA sends a PS-Poll or APSD (automatic power save delivery) trigger frame to signal the AP to wake up before a non-trigger frame is transmitted from the AP to the STA. If the value of the flow type subfield is 0, it may indicate an unannounced TWT.

[0155] The TWT flow identifier subfield may include a 3-bit value for uniquely identifying specific information about the TWT request in other requests made between the same TWT requesting STA (or AP) and TWT responding AP pair.

[0156] The TWT wake interval exponent subfield may contain a value to represent the TWT wake interval value in binary microseconds. For individual TWTs, the TWT wake interval exponent subfield may represent the interval between individual TWT SPs. The TWT wake interval of a TWT requesting STA (or AP) may be defined as TWT Wake Interval Mantissa * 2 * TWT Wake Interval Exponent.

[0157] The TWT protection subfield may indicate whether the TWT protection mechanism is used. If the value of the TWT protection subfield is 1, the transmission opportunity (TXOP) within the TWT SP may be initiated by a NAV protection mechanism such as (MU)RTS / CTS or CTS-to-self frames, and if the value of the TWT protection subfield is 0, the NAV protection mechanism may not be applied.

[0158] FIG. 11 illustrates an exemplary format of a broadcast TWT parameter set field related to the present disclosure. A detailed description of subfields in the format of FIG. 11 that overlap with the format of FIG. 10 is omitted.

[0159] In the broadcast TWT parameter set field illustrated in FIG. 11 (a), the request type subfield may include the following subfields in addition to the various subfields described in FIG. 10.

[0160] The last broadcast parameter set subfield shown in Fig. 11 (b) indicates whether the corresponding broadcast TWT parameter set field is the last broadcast TWT parameter set. If the value of the last broadcast parameter set subfield is 1, it indicates that the corresponding broadcast TWT parameter set field is the last broadcast TWT parameter set within the TWT element, and if the value of the last broadcast parameter set subfield is 0, it may indicate that there is a next broadcast TWT parameter set within the TWT element.

[0161] The broadcast TWT recommendation subfield contains 3 bits and can represent recommendations for frame types transmitted by the AP during the broadcast TWT SP with a value from 0 to 7.

[0162] The last bit of the request type subfield of the broadcast TWT parameter set field can be reserved.

[0163] A detailed description of the broadcast TWT info field and the restricted TWT traffic info field included in the broadcast TWT parameter set field will be provided later through Fig. 12.

[0164] FIG. 12 illustrates an exemplary format of a broadcast TWT parameter set field related to the present disclosure.

[0165] The broadcast TWT parameter set field illustrated in FIG. 12(a) may include a broadcast TWT info subfield of 2 octets and a restricted TWT traffic info subfield of 0 or 3 octets. Among the other subfields included in the broadcast TWT parameter set field, any content that overlaps with the subfield described in FIG. 10 is omitted.

[0166] The broadcast TWT info subfield may include a restricted TWT traffic info present subfield, a restricted TWT schedule info subfield, a broadcast TWT identifier (ID) subfield, and a broadcast TWT persistence subfield.

[0167] The restricted TWT traffic info present subfield shown in FIG. 12 (b) indicates whether the restricted TWT traffic info is present, and if the value of the restricted TWT traffic info present subfield is 1, the restricted TWT traffic info subfield is present. For Non-EHT STA, this field value may be reserved for other purposes.

[0168] The restricted TWT schedule info subfield is included when the restricted TWT parameter set subfield is passed to a TWT element where the value of the negotiation type field is 2.

[0169] If the value of the restricted TWT schedule information subfield is 0, the schedule of the restricted TWT (restricted TWT, R-TWT) is an idle R-TWT schedule, which means that there are no member STAs in the R-TWT schedule or the schedule is suspended for all STAs.

[0170] If the value of the restricted TWT schedule information subfield is 1, it means that the schedule of the R-TWT is an active R-TWT schedule, which means that there is at least one member STA in the R-TWT schedule.

[0171] If the value of the restricted TWT schedule information subfield is 2, it means that the R-TWT schedule is a full R-TWT schedule, which means that the resources of the R-TWT schedule are insufficient or there are too many existing member STAs to accept new STAs as members.

[0172] If the value of the restricted TWT schedule information subfield is 3, the R-TWT schedule means that the advertised R-TWT schedule is active, and it is for an AP corresponding to a non-transmitted BSSID that is a member of the same multiple BSSID set or co-hosted BSSID set that transmits the restricted TWT schedule information subfield.

[0173] The broadcast TWT identifier subfield represents the broadcast ID of a specific broadcast TWT that the STA (or AP) requests to join or provides TWT parameters for, depending on the value of the TWT setup command subfield of the TWT element.

[0174] The Broadcast TWT persistence subfield is a value representing the number of TBTTs for the duration that the Broadcast TWT SP corresponding to the Broadcast TWT parameter set is included. For example, if the value of the Broadcast TWT persistence subfield is 10, it means that the Broadcast TWT SP composed of the corresponding parameters is in operation for the duration that 10 beacon frames are transmitted, and if the value is 255, it means that the Broadcast TWT SP is applied permanently.

[0175] The restricted TWT traffic info subfield may include a traffic info control subfield, a restricted TWT DL TID (traffic identifier) ​​bitmap subfield, and a restricted TWT UL TID bitmap subfield.

[0176] The traffic information control subfield illustrated in Fig. 12 (c) may include a DL TID bitmap valid subfield and a UL TID bitmap valid subfield, and the six bits included in the traffic information control subfield may be reserved.

[0177] The restricted TWT DL TID bitmap field and the restricted TWT UL TID bitmap field represent TIDs identified as latency-sensitive traffic of the downlink and uplink, respectively, in bitmap form.

[0178] The DL TID bitmap valid subfield and the UL TID bitmap valid subfield included in the traffic information control subfield illustrated in FIG. 12 (d) indicate whether the restricted TWT DL TID bitmap subfield and the restricted TWT UL TID bitmap subfield are included in the restricted TWT traffic information subfield, respectively. If the value of the DL TID bitmap valid subfield (or UL TID bitmap valid subfield) is 1, it indicates that the restricted TWT DL TID bitmap subfield (or restricted TWT UL TID bitmap subfield) is included in the restricted TWT traffic information subfield, and if the value of the DL TID bitmap valid subfield (or UL TID bitmap valid subfield) is 0, all TIDs are classified as delay-sensitive traffic within the corresponding R-TWT membership.

[0179] FIG. 13 illustrates the flow of signals between devices for M-AP (multi-AP) operation according to various embodiments of the present disclosure.

[0180] As described above, in recent wireless LAN systems, multi-AP coordination is defined as a technology for negotiating multi-AP operations and the operational parameters used therein among multiple APs, so that two or more APs can interact to enable optimized communication with other devices. Here, multi-AP operations among multiple APs may include channel access operations, the transfer of TXOPs occupied via EDCA (enhanced distributed channel access), operations to adjust transmission signal strength, or operations to perform beamforming. In particular, multiple APs require communication to exchange various parameters or features for multi-AP operations as a prerequisite for performing various multi-AP operations, including C-TDMA, CR-TWT, C-SR, or C-BF. Additionally, multiple APs may require frame exchange for periodic / non-periodic parameter renegotiation or updating to periodically reflect the number of STAs existing within their BSS or the state changes over time of the STAs subject to multi-AP coordination operations. To reliably perform information exchange between APs performing such multi-AP operations, an M-AP TWT SP may be defined for communication between APs that exclude interference or influence from other STAs not participating in multi-AP (or M-AP) operations. For example, APs may form a TWT SP as a separate time interval for coordinating M-AP operations and utilize it to manage or coordinate their respective M-AP operations. A TWT SP formed for the purpose of frame exchange for consultation, periodic management, and parameter updates regarding M-AP operations between two APs may be referred to as a Multi-AP TWT SP (M-AP TWT SP).Hereinafter, with reference to FIG. 13, the flow of signals between APs for performing multi-AP operation is illustrated. However, according to various embodiments, this is merely an example and is not limited thereto, and each step is not an essential component, and one embodiment may include at least one of all, some, or a combination of some steps.

[0181] In step (1310), the first AP may transmit a frame for AP discovery to the second AP, and such frame may include information for advertising M-AP capability information. Alternatively, the first AP and the second AP may exchange information on authentication / encryption algorithms supported by each AP. Here, the first AP may be an M-AP TWT requesting AP for requesting M-AP TWT setup, and the second AP may be an M-AP TWT responding AP. Additionally, the second AP is described in the singular for convenience of explanation, but the second AP exchanging signals with the first AP may include one or more APs included in a group for multi-AP operation.

[0182] After the first AP and the second AP have discovered at least one AP for M-AP operation, in step (1320), the first AP and the second AP may perform an M-AP authentication process. The authentication process may include the second AP transmitting an M-AP authentication request frame to the first AP, and in response, the first AP transmitting an M-AP authentication response frame to the second AP. Each of the M-AP authentication request frame and the M-AP authentication response frame used in the authentication process may be an individually addressed frame. In the case of a MAC service data unit (MSDU), the individually addressed frame may include an individual address as a Destination Address (DA). In the case of a MAC protocol data unit (MPDU), the individually addressed frame may include an Address 1 field containing an individual address. The M-AP authentication request frame and the M-AP authentication response frame may each be an individually addressed management frame. The authentication process between APs in step (1320) can proceed substantially similarly to the authentication process between APs and STAs in step (320) illustrated in FIG. 3.

[0183] After authentication between APs is successfully performed, in step (1330), the first AP and the second AP may perform an M-AP association process. The association process may include the second AP transmitting an M-AP association request frame to the first AP, and in response, the first AP transmitting an M-AP association response frame to the second AP. Each of the M-AP association request frame and the M-AP association response frame used in the association process may be an individually addressed frame. Each of the M-AP association request frame and the M-AP association response frame may include an individually addressed management frame. The M-AP association process may be performed for the first AP to establish an M-AP group with a neighboring second AP, for the first AP and the second AP to assign an AID for mutual designation, or for the first AP to assign an M-AP management ID (M-AP MID) that directs the M-AP association process. The configuration of an M-AP group may include the exchange of AP characteristics, the sharing of participating STAs and resources, etc., which may be related to the exchange of characteristics for subsequent M-AP operations.

[0184] According to one embodiment, APs (including two or more than two APs) that have completed the M-AP combination procedure for at least one M-AP operation may be managed as an M-AP group. Additionally, if there are two APs in an M-AP group, the M-AP group may be referred to as an M-AP pair, and APs included in the same M-AP group may be referred to as member APs.

[0185] According to various embodiments of the present disclosure, during or thereafter, the first AP and the second AP may exchange frames for setting up an M-AP TWT, which is a time interval for exchanging frames for the purpose of M-AP operation consultation and operation parameter setting, or periodic management and parameter updating. For example, it is necessary to define an M-AP TWT SP, which is a time interval for performing negotiation, agreement, or management to determine the discovery of an AP capable of M-AP operation, mutual authentication for M-AP operation, mutual association between APs for M-AP operation, or M-AP TWT SP to be used by two APs (or more than two APs) thereafter (M-AP operations include C-TDMA, CR-TWT, C-BF, C-SR, etc.). To this end, the first AP may transmit an M-AP TWT setup request frame to the second AP. In response to this, the second AP may transmit an M-AP TWT setup response frame. More specifically, during the M-AP coupling process, the first AP and the second AP may exchange parameters such as the start time, interval, channel bandwidth, minimum nominal TWT duration, or parameters for matching a starter to operate the M-AP TWT SP.

[0186] According to one embodiment, an M-AP TWT setup request frame transmitted by the first AP may include an element (e.g., an M-AP TWT element) representing information or parameters for an M-AP TWT setup request. The M-AP TWT element may be for setting up a TWT SP (i.e., an M-AP TWT SP) for an M-AP pair (or M-AP group) including the first AP and the second AP to perform periodic negotiation of M-AP parameters, setting updates, etc. For example, the M-AP TWT setup request frame transmitted by the first AP may include an M-AP TWT element in which some parameters included in the existing TWT element are added or changed, or based on the existing TWT element.

[0187] Likewise, the M-AP TWT setup response frame transmitted by the second AP may include an element (e.g., an M-AP TWT element) representing information or parameters for the M-AP TWT setup response. The element regarding the M-AP TWT setup response information may be intended to set up a TWT SP (i.e., an M-AP TWT SP) for an M-AP pair (or M-AP group) including the first AP and the second AP to perform periodic negotiation of M-AP parameters, setup updates, etc. For example, the M-AP TWT setup response frame transmitted by the second AP may include an M-AP TWT element in which some parameters included in the existing TWT element are added or changed, or based on the existing TWT element. According to one embodiment, the above-described M-AP TWT setup request frame and M-AP TWT setup response frame are described in more detail in FIGS. 14 and FIG. 15.

[0188] According to various embodiments of the present disclosure, as described above, the procedure for exchanging frames to set up an M-AP TWT may use frames substantially identical to the frames exchanged during the M-AP joining process of step (1330). Meanwhile, it is understood that frames related to M-AP TWT setup may be exchanged using separate management frames in a procedure separate from the M-AP joining process. In the latter case, the M-AP TWT request frame transmitted by the first AP and the M-AP TWT response frame transmitted by the second AP may be exchanged through a separate procedure after step (1330), step (1350), or after the M-AP group is created. According to one embodiment, frame exchange between the first AP and the second AP for such a separate procedure may be performed by the first AP or the second AP acquiring an EDCA TXOP to transmit a frame with the other party's address as the recipient address when the first AP and the second AP use the same primary channel (PCH). According to one embodiment, frame exchange between the first AP and the second AP for a separate procedure may be performed through the overlapping channel between the operating bandwidth of the first AP and the operating bandwidth of the second AP by the first AP or the second AP transmitting a non-HT duplicate PPDU when the first AP and the second AP use different primary channels. According to one embodiment, frame exchange between the first AP and the second AP for a separate procedure may be performed after one of the two APs instantaneously changes its primary channel to the other's primary channel so that the first AP and the second AP operate on the same primary channel instantaneously.In this case, an AP that instantaneously changes the primary channel can communicate with the STA connected to it by changing the primary channel after notifying it of unavailability for a certain period of time or signaling that frame exchange between the AP and the STA is impossible because it is in power saving mode.

[0189] According to one embodiment, a plurality of APs may apply the following various details to an M-AP TWT SP formed according to an M-AP TWT setup related frame.

[0190] For example, only member APs participating in the same M-AP group can participate in the M-AP TWT. That is, within the M-AP TWT SP, frame exchange is essentially only allowed between APs participating in the same M-AP group, and the same M-AP group can be identified based on at least one of an M-AP AID pair or an M-ID (M-AP-ID).

[0191] As another example, there are cases where a non-AP STA of a BSS operated by an AP participating in the M-AP TWT may also participate in the M-AP TWT, but for this purpose, frame exchange between such AP and non-AP STA may be limited to trigger-based cases. That is, this may mean a case of frame exchange triggered by an AP in relation to an M-AP operation that requires the intervention of a non-AP STA.

[0192] In step (1340), the first AP and the second AP can perform a security setup process. An optional Wi-Fi protection setup (WPS) procedure performed by the first AP and the second AP can proceed similarly to step (340) of FIG. 3.

[0193] In step (1350), the first AP and the second AP may perform negotiation, agreement, or management procedures for M-AP characteristics. For example, the first AP and the second AP may exchange frames for management to perform M-AP operations within the formed M-AP TWT SP. That is, the first AP and the second AP may individually exchange frames for management for M-AP negotiation / agreement or frames for parameter updates for M-AP operations within the M-AP TWT SP. For example, when the first AP and the second AP negotiate to perform C-TDMA operations, the first AP and the second AP may agree on conditions for valid C-TDMA operations, such as the length of a minimum TXOP for which C-TDMA operations are possible (e.g., shared TXOP duration), or the urgency of traffic for which C-TDMA is possible (e.g., traffic priority). As another example, when the first AP and the second AP negotiate to perform C-BF operations, the first AP and the second AP may negotiate information about non-AP STAs that support data transmission via C-BF, the level of traffic, the amount of buffer, required latency, or information for sounding and joint sounding. As another example, when the first AP and the second AP perform C-SR operations, the first AP and the second AP may negotiate values ​​such as minimum transmit power or maximum transmit power.

[0194] In step (1360), the first AP and the second AP can perform M-AP characteristic-specific operations. According to one embodiment, the M-AP characteristic-specific operations can be performed based on frames and information exchanged between the first AP and the second AP within the M-AP TWT SP.

[0195] FIG. 14 illustrates an exemplary format of a broadcast TWT parameter set field according to various embodiments of the present disclosure. FIG. 14 illustrates an exemplary format of a broadcast TWT parameter set field of a TWT element used for the setup of an M-AP TWT SP (or the setup of an M-AP TWT) proposed in the present disclosure. Among the fields / subfields shown in FIG. 14 (a), (b), and (c), specific descriptions are omitted for content that overlaps with the description of the broadcast TWT parameter set field in FIG. 11 and FIG. 12.

[0196] According to one embodiment, the broadcast TWT parameter set field format illustrated in FIG. 14 (a) may further include an M-AP info field (1410) in addition to the various fields described above. The M-AP info field (1410) may include various parameters and information required for multiple APs to utilize the M-AP TWT SP and operate on the M-AP TWT SP. A more specific M-AP info field (1410) is described in FIG. 17.

[0197] Among the subfields of the request type field illustrated in FIG. 14 (b), the broadcast TWT recommendation subfield (1420) includes 3 bits. According to one embodiment, the broadcast TWT recommendation subfield (1420) may include one of 5 to 7 reserved values ​​(e.g., value 5) to indicate that the TWT element includes the M-AP information field (1410) described above. Examples of values ​​represented by the 3 bits of the broadcast TWT recommendation subfield (1420) are described in detail later in FIG. 15.

[0198] The subfields included in the broadcast TWT information subfields shown in Fig. 14 (c) are omitted as they were specifically described in Fig. 12.

[0199] FIG. 15 illustrates exemplary values ​​of a broadcast TWT recommendation field according to various embodiments of the present disclosure. As previously described, the broadcast TWT recommendation subfield included in the request type field of a TWT element includes 3 bits, and the broadcast TWT recommendation subfield according to one embodiment may represent different meanings depending on the value represented by the 3 bits.

[0200] In one embodiment, if the value of the broadcast TWT recommendation field is 0, it indicates that there are no restrictions on frames transmitted during the broadcast TWT SP. If the value of the broadcast TWT recommendation field is 1, it indicates that frames transmitted by the TWT scheduled STA during the broadcast TWT SP are recommended to be restricted to the solicited status and solicited feedback, and that random access (RA) is not allowed. If the value of the broadcast TWT recommendation field is 2, it indicates that frames transmitted by the TWT scheduled STA during the broadcast TWT SP are recommended to be restricted to the solicited status and solicited feedback, and that random access (RA) is allowed. If the value of the Broadcast TWT Recommendation field is 3, it indicates that there are no restrictions on frames transmitted during the Broadcast TWT SP for opportunistic power save (OPS), but the AP may transmit a TIM (traffic indicator map) frame or a FILS (fast initial link setup) discovery frame at the beginning of each TWT SP. If the value of the Broadcast TWT Recommendation field is 4, it indicates that the Broadcast TWT SP corresponds to a restricted TWT (R-TWT).

[0201] According to one embodiment, the TWT element included in the M-AP TWT setup request frame and the M-AP TWT setup response frame may include a broadcast TWT recommendation field, and if the value of the broadcast TWT recommendation field is any one of the reserved values ​​(e.g., 5, 6, or 7), the broadcast TWT recommendation field may indicate that the broadcast TWT SP is a TWT SP for M-AP TWT operation (e.g., M-AP TWT SP) (1510). If the value of the broadcast TWT recommendation field is any one of the reserved values ​​(or another value distinct from a predefined value), the broadcast TWT parameter included in the TWT element may specify an M-AP TWT SP for indicating a channel or bandwidth, etc., for performing negotiation of M-AP operation between multiple APs. When an M-AP TWT is successfully formed between two APs performing M-AP operations through an M-AP TWT setup request frame and an M-AP TWT setup response frame, each AP may broadcast a beacon or probe response frame containing a TWT element that includes a broadcast TWT parameter set (e.g., FIG. 14 (a)) containing information about the M-AP TWT. Non-AP STAs connected to the AP for M-AP operations may receive the beacon or probe response or other frames containing the TWT element, and may identify the broadcast TWT parameter set fields included in the TWT element to obtain broadcast TWT schedule information that the AP transmitting it is operating.In addition, non-AP STAs that have obtained broadcast TWT schedule information can identify that the TWT schedule is schedule information related to the TWT time interval for exchanging frames between APs for Multi-AP management purposes, if the value of the broadcast TWT recommendation field of the broadcast TWT parameter set is a value (e.g., 5, 6, or 7) that designates a TWT SP for M-AP TWT operation. In addition, through the method described above, surrounding APs can also obtain information about the M-AP TWT schedule in operation by the AP transmitting the broadcast TWT element.

[0202] According to one embodiment, when the broadcast TWT recommendation field includes the value of any one of the reserved values ​​(in FIG. 15, the case of 5 is illustrated exemplarily), at least one AP within the M-AP group may exchange frames (e.g., individually delivered management frames) for M-AP parameter negotiation and consensus during the M-AP TWT SP represented by the broadcast TWT recommendation field.

[0203] According to one embodiment, at least one member AP associated with the M-AP TWT SP may determine an M-AP operation to be used between member APs within the M-AP TWT SP interval, determine to stop an M-AP operation, or determine to tear down the M-AP group.

[0204] According to one embodiment, during the M-AP TWT SP, at least one member AP may exchange frames to update M-AP parameters for a previously set M-AP operation.

[0205] According to one embodiment, if the broadcast TWT recommendation field includes a value of any one of the reserved values ​​(e.g., one of 5-7), the broadcast TWT recommendation field may indicate that an M-AP information field is additionally included within the TWT element.

[0206] FIG. 16 illustrates the operation of devices for an M-AP TWT SP (service period) according to various embodiments of the present disclosure.

[0207] Referring to FIG. 16, AP1 and AP2 may be adjacent APs, STA1 may be a non-AP STA included within the BSS provided by AP1, and STA2 may be a non-AP STA included within the BSS provided by AP2. AP2 transmits a frame to AP1 to request the creation, setup, or configuration of an M-AP TWT SP (1610), and this frame may include a TWT element according to the previously described embodiment. AP1 transmits a frame to AP2 to approve (or respond to) the creation, setup, or configuration of an M-AP TWT SP in response to the received request (1620), and this frame may include a TWT element according to the previously described embodiment. This series of processes may also be referred to as the M-AP TWT setup process. In the following, an AP (AP2 in the illustrated embodiment) that requests the creation, setup, or configuration of an M-AP TWT SP may be referred to as the M-AP TWT requesting AP, and an AP (AP1 in the illustrated embodiment) that responds to the creation, setup, or configuration of an M-AP TWT SP to support the M-AP operation of the M-AP TWT requesting AP may be referred to as the M-AP TWT responding AP.

[0208] According to one embodiment, a frame (1610) transmitted by an M-AP TWT requesting AP (AP2 in FIG. 16) to an M-AP TWT responding AP (AP1 in FIG. 16) for a request for M-AP TWT may include TWT elements, and such a frame may mean various types of frames, such as a management frame, a control frame, or a new type of frame. Alternatively, according to one embodiment, a frame containing TWT elements transmitted by the M-AP TWT requesting AP may be an M-AP TWT setup request frame, but is not limited to such types of frames and may include an M-AP combination request frame exchanged during the M-AP combination process as described in FIG. 13. In addition, according to one embodiment, a frame containing a TWT element transmitted by an M-AP TWT requesting AP may be exchanged in the M-AP feature negotiation / agreement / management step corresponding to step (1350) of FIG. 13, in which case step (1350) is not limited to being performed within an M-AP TWT SP.

[0209] According to one embodiment, a frame (1620) transmitted by an M-AP TWT responding AP (AP1 in FIG. 16) to an M-AP TWT requesting AP (AP2 in FIG. 16) for a response from an M-AP TWT SP may include TWT elements, and such a frame may include various types of frames, such as a management frame, a control frame, or a new type of frame. Alternatively, according to one embodiment, a frame containing TWT elements transmitted by the M-AP TWT responding AP may be an M-AP TWT setup response frame, but is not limited to such types of frames and may include an M-AP combination response frame exchanged during the M-AP combination process as described in FIG. 13.

[0210] According to one embodiment, the M-AP TWT SP is started after a predetermined time (e.g., a time defined as the start time of the TWT) has elapsed after the M-AP TWT responding AP transmits a response to the M-AP TWT requesting AP, and information regarding the time at which the M-AP TWT SP is started and information regarding the duration of the M-AP TWT SP may be agreed upon during the frame exchange process between the M-AP TWT requesting AP and the M-AP TWT responding AP.

[0211] According to one embodiment, an M-AP TWT responding AP that has received a request from an M-AP TWT may be unable to send a response to an M-AP TWT requesting AP. For example, the M-AP TWT responding AP may be unable to configure the TWT due to reasons such as failure to occupy a channel or resource; in this case, the M-AP TWT responding AP may be unable to send a response to the M-AP TWT requesting AP even though it has received the request from the M-AP TWT. At this time, the M-AP TWT requesting AP that has not received a response may retransmit the M-AP TWT request. For example, the M-AP TWT request retransmitted by the M-AP TWT requesting AP may be retransmitted periodically until a response is received. Alternatively, the M-AP TWT requesting AP may have a timer for receiving a response pre-set and may retransmit the M-AP TWT request until the timer expires. According to one embodiment, if an abnormal case is identified, such as when the timer described above expires or when a change in channel occupancy occurs, the M-AP TWT requesting AP may abort the retransmission of the M-AP TWT request. As described above, the maximum number of M-AP TWT request frames that the M-AP TWT requesting AP retransmits (e.g., M-AP TWT requesting retransmission count) or the timeout value for waiting for an M-AP TWT response from the M-AP TWT responding AP (e.g., M-AP TWT requesting timeout) can be set through the AP's Multi-AP capability.The M-AP TWT requesting retransmission count or M-AP TWT requesting timeout can be delivered to nearby APs by being included in the beacon or by being included in a frame transmitted to nearby APs via broadcast or unicast.

[0212] According to one embodiment, after performing frame exchange for M-AP TWT SP, AP1 may transmit a beacon frame to STA1 in AP1's BSS to notify M-AP TWT. Additionally, AP2 may transmit a beacon frame to STA2 in AP2's BSS to notify M-AP TWT. Accordingly, non-AP STAs including STA1 and STA2 may terminate an ongoing TXOP before the start of the M-AP TWT SP broadcast by each of the received beacon frames.

[0213] According to one embodiment, within the M-AP TWT SP interval, AP1 and AP2 may exchange management frames for M-AP negotiation / agreement or frames for parameter updates for M-AP operations. At this time, within the M-AP TWT SP interval, non-AP STAs STA1 and STA2 may not be able to access the channel except in special cases, similar to the case of R-TWT SP. According to one embodiment, subsequently, the M-AP TWT SP may be set to occur periodically, and such a period may be referred to as the TWT interval or M-AP TWT interval.

[0214] According to one embodiment of the M-AP TWT setup process of FIG. 16, the TWT element included in the frame transmitted by AP2 to AP1 may have a value of 3 for the negotiation type subfield (i.e., indicating a broadcast TWT membership exchange), a value of 1 for the TWT request subfield (i.e., indicating that it is an M-AP TWT scheduling AP), a value of 0, 1, or 2 for the TWT setup command subfield (i.e., indicating that it is a request, suggest, or demand TWT), a value of 0, 1, or 2 for the nominal minimum TWT wake duration subfield (i.e., indicating the M-AP TWT SP duration), and a value of 5 or one of other reserved values ​​for the broadcast TWT suggest subfield (i.e., indicating that it is an M-AP TWT SP). However, depending on the various embodiments, the value indicated by the field or subfield described above is merely illustrative and may include other values ​​that include substantially the same definition.

[0215] According to one embodiment of the M-AP TWT setup process of FIG. 16, the TWT element included in the frame transmitted by AP1 to AP2 may have a value of 3 for the TWT request subfield (i.e., indicating that it is an M-AP TWT scheduled AP) and a value of 5 or one of other reserved values ​​for the broadcast TWT recommendation subfield (i.e., indicating that it is an M-AP TWT SP) to indicate that the M-AP TWT responding AP acknowledges and responds to the creation / setup / configuration of the M-AP TWT SP.

[0216] FIG. 17 illustrates an exemplary format of a broadcast TWT parameter set field according to various embodiments of the present disclosure.

[0217] The M-AP information field illustrated in FIG. 17(a) may include various parameters and information required for APs to operate in the M-AP TWT SP. For example, the M-AP information field may include channel information or bandwidth information for APs to perform M-AP TWT operations in the M-AP TWT SP. More specifically, APs for M-AP operations may occupy different channels (or primary channels). To this end, common channel information capable of exchanging management frames for M-AP negotiation needs to be shared among the APs first. That is, multiple APs can exchange M-AP information fields to first identify a channel to be used in common for M-AP negotiation. According to one embodiment, the M-AP information field may further include time synchronization information among APs to match the start time of the M-AP TWT SP. Hereinafter, specific channel or bandwidth information included in the M-AP information field may be included in exemplary fields such as (b-1) or (b-2) below.

[0218] According to one embodiment, with reference to (b-1) of FIG. 17, the M-AP information field may include at least one of a control field, a CCFS0 (channel center frequency segment 0) field, a CCFS1 field, or a disabled subchannel bitmap field to indicate channel information or bandwidth information.

[0219] Here, the control field may include at least one of a channel width field indicating the bandwidth of the channel, a disabled subchannel bitmap present field indicating whether there is a disabled subchannel bitmap, or a reserved field. The CCFS0 field may include information indicating the center frequency of the channel when the channel bandwidth is 20, 40, or 80 MHz. The CCFS1 field may include information indicating the center frequency of the channel when the channel bandwidth is 160 or 320 MHz. The disabled subchannel bitmap is information regarding puncturing and may include information indicating the punctured subchannel in the form of a bitmap when a specific subchannel is punctured and cannot be used. For example, a bit corresponding to a punctured subchannel may be set to 1, a bit corresponding to a non-punctured subchannel may be set to 0, and vice versa. However, according to various embodiments, the method of indicating a punctured subchannel in the form of a bitmap is merely an example, and it is also possible to indicate a resource that cannot be used through other methods. Likewise, the channel width included in the control channel may indicate one of 20, 40, 80, 160, or 320 MHz, but is not limited thereto, and it is also possible to indicate the center frequency of the channel as a single field regardless of the channel width. The names of the fields described above are merely examples, and it goes without saying that they may be referred to by various names that perform the same function.

[0220] According to one embodiment, with reference to (b-2) of FIG. 17, the channel information or bandwidth information included in the M-AP information field may include at least one of a lowest frequency subchannel field or a subchannel bitmap field.

[0221] Here, the lowest frequency subchannel field may include information indicating the channel number of a 20 MHz subchannel having the lowest center frequency among the channels on which the AP operates. The subchannel bitmap field is a bitmap indicating the subchannels required for the M-AP TWT, and bits corresponding to subchannels used in the M-AP TWT SP may be set to 1, while bits corresponding to subchannels not used may be set to 0, and vice versa. However, depending on various embodiments, this is merely an example, and it goes without saying that subchannels used in the M-AP TWT SP may be indicated by methods other than a bitmap. The names of the fields described above are merely examples, and it goes without saying that they may be referred to by various names that perform the same function.

[0222] FIG. 18a illustrates the operation of devices for starter correction of M-AP TWT SP according to various embodiments of the present disclosure.

[0223] As described above, APs performing M-AP operations may form an M-AP TWT SP for negotiation or management regarding M-AP operations. In this case, a time synchronization method between APs may be required to define the same start time of the same M-AP TWT SP among the APs. More specifically, to resolve clock drift between APs and synchronize the start time of the M-AP TWT, APs may periodically or non-periodically exchange information regarding clock drift or time offset.

[0224] According to various embodiments, information regarding time coordination for time synchronization between APs regarding M-AP TWT may be included in the M-AP information field of an M-AP TWT setup request frame or an M-AP TWT setup response frame and transmitted and received periodically. For example, APs participating in an M-AP TWT SP may transmit and receive information for correcting the starter in a frame that can be exchanged continuously between APs. As an example, APs exchanging frames to form an M-AP TWT SP may transmit and receive information for correcting the starter in an M-AP TWT element that includes the M-AP information field and broadcast TWT parameters according to the embodiments described above. Accordingly, APs participating in the M-AP TWT SP can update the information for correcting the starter. According to one embodiment, information for correcting the time of the M-AP TWT may be exchanged through a frame transmitted and received for parameter updating or management within the M-AP TWT SP interval formed between APs.

[0225] According to various embodiments, information regarding time adjustment for time synchronization between APs for M-AP TWT may be transmitted and received non-periodically through an ICF (initial control frame) and ICR (initial control response) exchange procedure between AP1 and AP2. For example, APs participating in an M-AP TWT SP may transmit and receive M-AP TWT elements including M-AP information fields and broadcast TWT parameters through an ICF and ICR exchange process of a TXOP in which M-AP operations between APs are performed, and thereby update information for correcting the starter.

[0226] Referring to FIG. 18a, the operation of non-periodically exchanging information regarding starter correction between APs through ICF and ICR is specifically illustrated.

[0227] For example, if we describe C-TDMA, which is one of the M-AP operations, C-TDMA may refer to a procedure for a specific AP to share the time resources of a TXOP it has acquired with a set of other APs. In this way, APs may occupy a TXOP for an M-AP operation and exchange frames related to the M-AP operation within the TXOP. More specifically, AP2, having acquired the TXOP, may announce to AP1 its intention to share at least a portion of the time resources of the acquired TXOP, and this process may be accomplished by transmitting an ICF at the beginning of the TXOP. Upon receiving the ICF, AP1 may transmit an ICR to AP2 to respond to the ICF. AP2 may transmit information for the M-AP operation or a PPDU to AP1 within its TXOP, and AP1 may transmit a BA (block ack) to AP2 in response to the reception of the PPDU. Subsequently, for example, AP1 and AP2 can synchronize the start time of the next M-AP TWT SP according to the value of the starter information contained in the ICF or ICR.

[0228] According to one embodiment, an ICF transmitted by AP2 may include information for correcting the starters between the APs described above. For example, information for correcting the starters of the M-AP TWT between APs transmitted by AP2 may be included in a BSRP (buffer status report poll) trigger frame. The BSRP trigger frame may include a frame transmitted to enable the AP to find devices waiting for transmission, thereby enabling efficient scheduling of uplink traffic.

[0229] According to one embodiment, the ICR transmitted by AP1 may include information for reporting starter correction between the APs described above. For example, information for reporting the correction of the starter of the M-AP TWT between the APs transmitted by AP1 may be included in a Multi-STA BA (block ACK) frame. The Multi-STA BA frame may include a frame for an ACK for UL MU transmission, the details of which are described more specifically in FIG. 8b.

[0230] FIG. 18b illustrates an exemplary format of an initial control response (ICR) according to various embodiments of the present disclosure. As described in FIG. 18a, AP1, having received an ICF, can transmit an ICR to AP2 to synchronize the start time of the M-AP TWT SP between the APs.

[0231] FIG. 18b describes the detailed format structure of a multi-STA block ack (M-BA) frame included in an ICR for M-AP. The M-BA frame illustrated in FIG. 18b(a) may be a type of control frame and may include a frame control field, a duration field, a receiving address (RA) field, a transmitter address (TA) field, a block ack control field, a BA information field, and a frame check sequence (FCS) field. The BA information field includes a per AID TID information field<AID, TID> It can be included in every tuple.

[0232] A single Per AID TID information field illustrated in (b) of FIG. 18b may include an AID TID information field, a Block ack starting sequence control field, and a Block ack bitmap field. Here, the Block ack bitmap may include information related to M-AP operations. More specifically, the M-AP TWT negotiation element included in the Block ack bitmap may include M-AP authentication information, etc. If the Block ack bitmap field includes time synchronization response information, the Block ack bitmap field may include at least one of a clock drift value for the AP that transmitted the ICF, a unit of the clock drift value, a time offset (e.g., timestamp offset) representing the difference between the timestamp of the AP that transmitted the ICF included in the ICF and the timestamp of the AP that received the ICF currently in operation, or a unit of the time offset.

[0233] The AID TID information field illustrated in (c) of FIG. 18b may include an AID11 field, an Ack Type field, and a TID field. Here, the format of the AID TID information field may correspond to cases where the AID sub-field for the AID is not 2045. The AID11 field may include a value indicating whether the corresponding Block Ack bitmap field contains time coordination information of the M-AP TWT SP. The ACK Type field and the TID field may include a value indicating a special Per AID TID Info field for the time coordination information of the M-AP TWT SP.

[0234] The Block Ack start sequence control field illustrated in (c) of FIG. 18b may include a fragment number field and a starting sequence number field. Here, the fragment number may include a value indicating the length of the time adjustment information of the M-AP TWT SP for the M-AP TWT SP within the BA information field.

[0235] FIG. 19a illustrates a signal flow for managing multiple M-AP operations within a single M-AP TWT SP according to various embodiments of the present disclosure. More specifically, APs performing M-AP operations may perform one or more M-AP operations. To this end, APs may include M-AP TWT information during an M-AP combination or negotiation process for managing multiple M-AP operations (e.g., M-AP schemes).

[0236] In step (1910), AP1 and AP2 may exchange frames for M-AP combination / negotiation / agreement for the first M-AP operation (M-AP scheme 1 in FIG. 19a). More specifically, AP1 may transmit a request frame to AP2 to request M-AP combination / negotiation / agreement for the first M-AP operation. In response, AP2 may transmit a response frame to AP1 to respond to the M-AP combination / negotiation / agreement for the first M-AP operation.

[0237] In step (1920), AP1 and AP2 may form (or establish) an M-AP TWT SP for managing a periodic first M-AP operation. At this time, the M-AP TWT SP for managing the first M-AP operation may be identified by a corresponding TWT ID (e.g., TWT ID=xx).

[0238] The steps (1910) and (1920) described above may proceed substantially identically or similarly to the operations described in FIGS. 13 to 18b. For example, the process of exchanging M-AP request / response frames and forming M-AP TWT SPs in steps (1910) and (1920) may be performed by being included in the M-AP combined request / response process, or through a separate M-AP TWT setup process.

[0239] In step (1930), AP1 and AP2 may exchange frames for M-AP combination / negotiation / agreement for a second M-AP operation (M-AP scheme 2 in FIG. 19a) different from the first M-AP operation. More specifically, AP1 may send a request frame to AP2 to request M-AP combination / negotiation / agreement for the second M-AP operation. In response, AP2 may send a response frame to AP1 to respond to the M-AP combination / negotiation / agreement for the second M-AP operation.

[0240] In step (1940), AP1 and AP2 may form (or establish) an M-AP TWT SP for managing periodic second M-AP operations. At this time, the M-AP TWT SP for managing the second M-AP operations may be identified by a corresponding TWT ID (e.g., TWT ID=xx), which may be the same as the M-AP TWT SP for managing the first M-AP operations. In other words, AP1 and AP2 may jointly perform management for other M-AP operations including the second M-AP operations by using the M-AP TWT SP interval formed in advance through the M-AP TWT setup process performed for the first M-AP operations.

[0241] FIG. 19b illustrates the operation of devices for managing multiple M-AP operations within a single M-AP TWT SP according to various embodiments of the present disclosure. With reference to FIG. 19b, a specific operation for managing multiple M-AP operations of AP1 and AP2 within an M-AP TWT SP, as described in FIG. 19a, is illustrated. Thus, it is obvious that some or all of the embodiments described in FIG. 19a may be applied identically or similarly to FIG. 19b without further explanation.

[0242] According to one embodiment, AP1 and AP2 can exchange frames for M-AP combination / negotiation / agreement for a first M-AP operation. Subsequently, M-AP TWT SP and TWT intervals for periodic M-AP TWT SP can be set up accordingly.

[0243] Next, AP1 and AP2 can perform management of the first M-AP operation (e.g., long-term management) during the M-AP TWT SP interval. AP1 and AP2 can perform the first M-AP operation according to the management of the first M-AP operation, and the first M-AP operation may be performed periodically.

[0244] After the TWT interval of the M-AP TWT SP has passed, AP1 and AP2 can perform management for the first M-AP operation during the next M-AP TWT SP interval. AP1 and AP2 can perform the first M-AP operation according to the management of the first M-AP operation, and the first M-AP operation may be performed periodically. At this time, AP1 and AP2 can exchange frames for M-AP combination / negotiation / agreement regarding the second M-AP operation during the process of the M-AP operation. At this time, the M-AP TWT SP for managing the second M-AP operation may be identified by the same TWT ID (e.g., TWT ID=xx) as the M-AP TWT SP for managing the first M-AP operation, and in this case, AP1 and AP2 can perform management for multiple M-AP operations using the same M-AP TWT SP interval. Alternatively, the frame for M-AP combination / negotiation / agreement for the second M-AP operation may include a separate M-AP TWT setup frame, and accordingly, an M-AP TWT SP for managing the second M-AP operation may be identified.

[0245] For example, when the next M-AP TWT SP interval begins, AP1 and AP2 can perform management for the first M-AP operation and the second M-AP operation. Furthermore, AP1 and AP2 can perform the first M-AP operation and the second M-AP operation according to the management for the first M-AP operation and the second M-AP operation, and the first M-AP operation or the second M-AP operation may be performed periodically.

[0246] FIG. 19c illustrates an exemplary format for managing multiple M-AP operations within a single M-AP TWT SP according to various embodiments of the present disclosure.

[0247] As described in FIGS. 19a and 19b, multiple APs can perform a combination / negotiation process for M-AP operation. More specifically, multiple APs can exchange frames for combination / negotiation for M-AP operation, and such frames may include parameters for setting up an M-AP TWT or include the TWT ID of an existing M-AP TWT.

[0248] For example, to perform a joining / negotiation process for M-AP operation, AP1 and AP2 can exchange frames. The frames exchanged by AP and AP2 as illustrated in (a) of FIG. 19c may include an M-AP ID request mode field, an M-AP AID allocation field, an M-AP MID allocation field, a common M-AP info field, and a Per-M-AP specific info field.

[0249] The common M-AP information field illustrated in (b) of FIG. 19c may include an M-AP TWT setup request element field or an M-AP TWT-TO-BE-USED field. The M-AP TWT setup request element field may include a TWT element containing a set of broadcast TWT parameters indicating the M-AP TWT described in FIG. 14. The M-AP TWT-TO-BE-USED field may include a value for an ID that explicitly indicates an already formed M-AP TWT. Here, the ID indicating the M-AP TWT may be the value of the broadcast TWT ID field contained in the broadcast TWT information field within the already exchanged broadcast TWT parameter set. Alternatively, the ID indicating the M-AP TWT may be an M-AP TWT ID defined as a sub-field within the M-AP information field contained in the M-AP TWT described in FIG. 14.

[0250] FIGS. 20 to 22 below are flowcharts illustrating the operations between APs according to the various embodiments described in FIGS. 13 to 19c in chronological order. Therefore, it is obvious that some or all of the embodiments described above may be applied identically or similarly to FIGS. 20 to 22 without further explanation.

[0251] FIG. 20 illustrates the flow of signals between devices for M-AP operation according to various embodiments of the present disclosure. However, according to various embodiments of the present disclosure, the steps described below are not all essential components, and the embodiments may include at least one of all, some, or a combination of some of the steps below. Additionally, with reference to FIG. 20, AP2 is depicted as a single AP, but this is merely an example, and it is obvious that AP2 may include a plurality of APs included in the same group as AP1.

[0252] In step (2010), AP1 transmits an M-AP TWT setup request frame containing parameters related to M-AT TWT SP to AP2, and AP2 transmits an M-AP TWT setup response frame to AP1. According to one embodiment, the M-AP TWT setup request frame transmitted by the first AP may include an element (e.g., an M-AP TWT element) representing information or parameters for the M-AP TWT setup request. The M-AP TWT element may be for setting up a TWT SP (i.e., an M-AP TWT SP) for an M-AP pair (or M-AP group) including the first AP and the second AP to perform periodic negotiation of M-AP parameters, setting updates, etc. For example, the M-AP TWT setup request frame transmitted by the first AP may include an M-AP TWT element in which some parameters included in the existing TWT element are added or changed, or based on the existing TWT element. Likewise, an M-AP TWT setup response frame transmitted by the second AP may include an element (e.g., an M-AP TWT element) representing information or parameters for an M-AP TWT setup response. The element regarding the M-AP TWT setup response information may be intended to establish a TWT SP (i.e., an M-AP TWT SP) for an M-AP pair (or M-AP group) including the first AP and the second AP to perform periodic negotiation of M-AP parameters, setup updates, etc. For example, an M-AP TWT setup response frame transmitted by the second AP may include an M-AP TWT element in which some parameters included in the existing TWT element are added or changed, or based on the existing TWT element.

[0253] In step (2020), within the M-AP TWT SP interval, AP1 and AP2 can exchange frames for first M-AP operation management. AP1 and AP2 can perform negotiation, consensus, or management procedures for M-AP characteristics. For example, within the formed M-AP TWT SP, AP1 and AP2 can exchange frames for management to perform M-AP operations. That is, within the M-AP TWT SP, AP1 and AP2 can individually exchange management frames for M-AP negotiation / consensus or frames for parameter updates for M-AP operations.

[0254] In step (2030), AP1 transmits an ICF for starter correction to AP2, and AP2 transmits an ICR containing starter correction information to AP1. In order to resolve clock drift between APs and synchronize the start time of the M-AP TWT, AP1 and AP2 may periodically or non-periodically exchange information regarding clock drift or information regarding time offset. Information regarding time adjustment for time synchronization between APs for the M-AP TWT may be included in the M-AP information field of the M-AP TWT setup frame and transmitted periodically, or it may be transmitted non-periodically through the exchange procedure of an ICF (initial control frame) and an ICR (initial control response) between AP1 and AP2. Specific embodiments related to step (2030) are specifically described in FIGS. 18a and 18b.

[0255] In step (2040), AP1 may transmit a frame to AP2 to request a second M-AP operation, and AP2 may transmit a frame to AP1 to respond to the second M-AP operation. AP1 and AP2 may exchange frames for M-AP combination / negotiation / agreement for a second M-AP operation different from the first M-AP operation. More specifically, AP1 may transmit a request frame to AP2 to request M-AP combination / negotiation / agreement for the second M-AP operation. In response, AP2 may transmit a response frame to AP1 to respond to the M-AP combination / negotiation / agreement for the second M-AP operation.

[0256] In step (2050), within the M-AP TWT SP section, AP1 and AP2 can exchange frames for first M-AP operation management and second M-AP operation management. After forming an M-AP TWT SP for periodic management of the second M-AP operation, AP1 and AP2 can perform management for multiple M-AP operations using the M-AP TWT SP section formed through the M-AP TWT setup process, etc. Specific embodiments related to steps (2040) and (2050) are specifically described in FIGS. 19a to 19c.

[0257] FIG. 21 illustrates the operation flow of an AP according to various embodiments of the present disclosure. In FIG. 21, various operations of the M-AP TWT requesting AP described in FIG. 13 to FIG. 19c may be applied identically or similarly, and specific descriptions of content that overlap with previously described content are omitted. However, according to various embodiments of the present disclosure, not all of the steps described below are considered essential components, and the embodiments may include at least one of all, some, or a combination of some of the steps below.

[0258] In step (2110), the AP may transmit a frame to request the setup of the M-AP TWT SP, and in step (2120), the AP may receive a frame to respond to the setup of the M-AP TWT SP. According to one embodiment, the frame transmitted by the AP may include a broadcast TWT recommendation field containing a value for indicating the M-AP TWT SP and an M-AP information field for indicating parameters associated with the M-AP TWT SP. Additionally, the value for indicating the M-AP TWT SP may include any one of the values ​​reserved for the broadcast TWT recommendation field, and the parameters associated with the M-AP TWT SP may include at least one of channel information or bandwidth information for managing M-AP operations.

[0259] In step (2130), the AP may exchange frames for M-AP operation management within the M-AP TWT SP. According to one embodiment, the frames exchanged by the AP for M-AP operation management may include frames for requesting other M-AP operations, which may include a broadcast TWT recommendation field and an M-AP information field, or may include a value indicating an ID for identifying the formed M-AP TWT SP.

[0260] FIG. 22 illustrates the operation flow of another AP according to various embodiments of the present disclosure. In FIG. 22, various operations of the M-AP TWT responding AP described in FIG. 13 to FIG. 19c may be applied identically or similarly, and specific descriptions of content that overlap with previously described content are omitted. However, according to various embodiments of the present disclosure, not all of the steps described below are considered essential components, and the embodiments may include at least one of all, some, or a combination of some of the steps below.

[0261] In step (2210), the AP may receive a frame requesting the setup of the M-AP TWT SP, and in step (2220), the AP may transmit a frame in response to the setup of the M-AP TWT SP. According to one embodiment, the frame received by the AP may include a broadcast TWT recommendation field containing a value for indicating the M-AP TWT SP and an M-AP information field for indicating parameters associated with the M-AP TWT SP. Additionally, the value for indicating the M-AP TWT SP may include any one of the values ​​reserved for the broadcast TWT recommendation field, and the parameters associated with the M-AP TWT SP may include at least one of channel information or bandwidth information for managing M-AP operations.

[0262] In step (2230), the AP may exchange frames for M-AP operation management within the M-AP TWT SP. According to one embodiment, the frames exchanged by the AP for M-AP operation management may include frames for requesting other M-AP operations, which may include a broadcast TWT recommendation field and an M-AP information field, or may include a value indicating an ID for identifying the formed M-AP TWT SP.

[0263] Meanwhile, the present specification and drawings disclose preferred embodiments of the present disclosure. Although specific terms have been used, they are used merely in a general sense to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the disclosure, and are not intended to limit the scope of the present disclosure.

[0264] Furthermore, it is obvious to those skilled in the art that, in addition to the embodiments described in this disclosure, other variations based on the technical concept of this disclosure are possible. For example, some or all of the contents of one embodiment described above may be combined with some or all of one or more other embodiments, and such combination is also included in the embodiments proposed in this disclosure.

Claims

1. A method performed by a first access point (AP) of a wireless local area network (WLAN) system, A step of transmitting a first frame to the second AP to request the setup of an M-AP (multi-AP) TWT (target wakeup time) SP (service period); A step of receiving a second frame from the second AP to respond to the setup of the M-AP TWT SP; The method includes the step of exchanging frames for the management of the first M-AP operation between the first AP and the second AP within the above M-AP TWT SP, and A method in which the first frame comprises a broadcast TWT recommendation field containing a value for indicating the M-AP TWP SP and an M-AP information field for indicating a parameter associated with the M-AP TWT SP.

2. In Claim 1, The value for indicating the above M-AP TWT SP includes any one of 5, 6, or 7, which is a reserved value for the above broadcast TWT recommendation field, and A method in which parameters associated with the above M-AP TWT SP include at least one of channel information or bandwidth information for managing the above first M-AP operation.

3. In Claim 1, A step of transmitting to the second AP a third frame containing information related to the synchronization of the M-AP TWT SP; and The method further includes the step of receiving a fourth frame from the second AP containing information for adjusting the start time of the M-AP TWP SP, and The above third frame includes an ICF (initial control frame), and The above fourth frame is a method including an ICR (initial control response).

4. In Claim 1, A step of transmitting a fifth frame to the second AP to request a second M-AP operation between the first AP and the second AP; and The method further includes the step of receiving a sixth frame from the second AP to respond to the second M-AP operation, and A method in which the above-mentioned fifth frame includes the broadcast TWT recommendation field and the M-AP information field, or includes a value indicating an ID (identifier) ​​for identifying the M-AP TWT SP.

5. In Claim 4, The management of the above second M-AP operation is performed within the above M-AP TWT SP.

6. A method performed by a second access point (AP) of a wireless local area network (WLAN) system, A step of receiving a first frame from the first AP to request the setup of an M-AP (multi-AP) TWT (target wakeup time) SP (service period); A step of transmitting a second frame to the first AP to respond to the setup of the M-AP TWT SP; The method includes the step of exchanging frames for the management of the first M-AP operation between the first AP and the second AP within the above M-AP TWT SP, and A method in which the first frame comprises a broadcast TWT recommendation field containing a value for indicating the M-AP TWP SP and an M-AP information field for indicating a parameter associated with the M-AP TWT SP.

7. In Claim 6, The value for indicating the above M-AP TWT SP includes any one of 5, 6, or 7, which is a reserved value for the above broadcast TWT recommendation field, and A method in which parameters associated with the above M-AP TWT SP include at least one of channel information or bandwidth information for managing the above first M-AP operation.

8. In Claim 6, A step of receiving a third frame from the first AP containing information related to the synchronization of the M-AP TWT SP; and The method includes the step of transmitting a fourth frame containing information for adjusting the start time of the M-AP TWP SP to the first AP, and The above third frame includes an ICF (initial control frame), and The above fourth frame is a method including an ICR (initial control response).

9. In Claim 6, A step of receiving a fifth frame from the first AP to request a second M-AP operation between the first AP and the second AP; and The method includes the step of transmitting a sixth frame to the first AP to respond to the second M-AP operation, A method in which the above-mentioned fifth frame includes the broadcast TWT recommendation field and the M-AP information field, or includes a value indicating an ID (identifier) ​​for identifying the M-AP TWT SP.

10. In Claim 9, The management of the above second M-AP operation is performed within the above M-AP TWT SP.

11. The first access point (AP) of a wireless local area network (WLAN) system is, transceiver; and It includes a controller coupled to the above-mentioned transmitting and receiving unit, and The above controller is, Transmit a first frame to the second AP to request the setup of an M-AP (multi-AP) TWT (target wakeup time) SP (service period), and Receive a second frame from the second AP to respond to the setup of the M-AP TWT SP, and It is configured to exchange frames for the management of the first M-AP operation between the first AP and the second AP within the above M-AP TWT SP, and The first frame comprises a first AP including a broadcast TWT recommendation field containing a value for indicating the M-AP TWP SP and an M-AP information field for indicating a parameter associated with the M-AP TWT SP.

12. In Claim 11, The value for indicating the above M-AP TWT SP includes any one of 5, 6, or 7, which is a reserved value for the above broadcast TWT recommendation field, and The parameter associated with the above M-AP TWT SP is a first AP comprising at least one of channel information or bandwidth information for managing the operation of the above first M-AP.

13. In claim 11, the controller is, Transmit a third frame containing information related to the synchronization of the M-AP TWT SP to the second AP, and It is further configured to receive a fourth frame from the second AP containing information for adjusting the start time of the M-AP TWP SP, and The above third frame includes an ICF (initial control frame), and The above fourth frame is a first AP including an ICR (initial control response).

14. In claim 11, the controller is, Transmit a fifth frame to the second AP to request a second M-AP operation between the first AP and the second AP, and Further configured to receive a sixth frame for responding to the second M-AP operation from the second AP, and The above 5th frame includes the broadcast TWT recommendation field and the M-AP information field, or a first AP including a value indicating an ID (identifier) ​​for identifying the M-AP TWT SP.

15. In Claim 14, The management of the above second M-AP operation is the first AP performed within the above M-AP TWT SP.

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