Method and apparatus for performing sounding between bss in wireless LAN system

Abstract

The present disclosure relates to a method and apparatus for transmitting a signal in a wireless LAN network system, and more particularly, to a method and apparatus for effectively performing a sounding operation for supporting coordinated-beamforming (Co-BF).

Description

Method and device for performing sounding between BSSs in a wireless LAN system

[0001] The present disclosure relates to a method and apparatus for transmitting a signal in a wireless LAN network system, and more specifically, to a method and apparatus for effectively performing a sounding operation.

[0002] A Wireless Local Area Network (WLAN), also known as Wi-Fi, is a network that enables internet access via mobile devices or laptops within a certain distance from an access point (AP). WLAN technology continues to evolve in line with the rise of the internet and the expansion of the smartphone market, and is being utilized to provide high-speed data services throughout the city, including in schools, airports, hotels, and offices.

[0003] The WiFi Alliance defines WiFi as a Wireless Local Area Network (WLAN) product based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. IEEE 802.11a and b, published in 1997 and 1999 respectively, are standards utilizing unlicensed bands at 2.4 GHz or 5 GHz; IEEE 802.11b provides a transmission speed of 11 Mbps, while IEEE 802.11a provides a transmission speed of 54 Mbps. IEEE 802.11g provides a transmission speed of 54 Mbps by applying Orthogonal Frequency-Division Multiplexing (OFDM) at 2.4 GHz. IEEE 802.11n applies multiple input multiple output OFDM (MIMO-OFDM) to provide a transmission speed of 300 Mbps using four spatial streams. IEEE 802.11n supports a channel bandwidth of up to 40 MHz, in which case it provides a transmission speed of 600 Mbps.

[0004] Subsequently, the IEEE 802.11ac standard was introduced, utilizing a maximum bandwidth of 160 MHz and supporting eight spatial streams to achieve speeds of up to 1 Gbit / s. This was followed by the IEEE 802.11ax, which provides multi-user MIMO (MU-MIMO) on both uplink and downlink, and supports spatial frequency reuse and dynamic fragmentation. Later, 802.11be (Wi-Fi 7) was introduced, aiming to theoretically achieve speeds of 46 Gbps by supporting up to 320 ultra-wide channels, multi-link operation, and 4kQAM.

[0005] The 802.11bn currently under research can be referred to as Wi-Fi 8. 802.11bn is being researched to introduce transmission and reception operations through the coordination of multiple APs, to provide links in the millimeter wave (mmWave) band, and to provide operations for packets requiring low latency.

[0006] In 802.11, various methods are being studied to achieve more effective frame transmission and reception through coordination operations between multiple APs (multi-AP, MAP). One of these is coordinated-beamforming (Co-BF), which can be used not only to increase the efficiency of frame transmission and reception between one AP and a STA but also to reduce the degree of interference acting on frame transmission and reception between other APs and STAs. To perform such Co-BF, it is necessary to perform an operation that reports the status of the radio channel between the AP and the STA, and such an operation can be referred to as sounding. The present disclosure proposes a method for an AP or / and a STA to perform effective sounding in a MAP environment, and an apparatus for performing said method.

[0007] The present disclosure invention for solving the above-mentioned problems comprises a method performed by a first AP (access point) of a wireless LAN system, the method comprising: transmitting a first frame containing Co-BF (coordinated beamforming) agreement request element information to a second AP, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support; and receiving a second frame containing Co-BF agreement response element information as a response to the first frame from the second AP, wherein the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support.

[0008] The above sounding method is characterized by including direct sounding or indirect sounding.

[0009] In addition, a method performed by a second AP (access point) of a wireless LAN system comprises the steps of: receiving a first frame containing Co-BF (coordinated beamforming) agreement request element information from a first AP, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support; and transmitting a second frame containing Co-BF agreement response element information to the first AP in response to the first frame, wherein the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support, and wherein the sounding method includes direct sounding or indirect sounding.

[0010] Additionally, in a first AP (access point) of a wireless LAN system, the system comprises: a transceiver; and a control unit configured to transmit a first frame containing Co-BF (coordinated beamforming) agreement request element information to a second AP, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support, and receive a second frame containing Co-BF agreement response element information as a response to the first frame from the second AP, wherein the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support, and wherein the sounding method includes direct sounding or indirect sounding.

[0011] Additionally, in a second AP (access point) of a wireless LAN system, the system comprises: a transceiver; and a control unit configured to receive a first frame containing Co-BF (coordinated beamforming) agreement request element information from a first AP, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support, and transmit a second frame containing Co-BF agreement response element information to the first AP in response to the first frame, wherein the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support, and wherein the sounding method includes direct sounding or indirect sounding.

[0012] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure pertains from the description below.

[0013] According to a method according to at least one embodiment of the present disclosure, AP and / or STA can perform an effective sounding operation. The effects obtainable in the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0014] Figure 1 is a diagram illustrating an example of a wireless communication network.

[0015] Figure 2 is a diagram illustrating an example of the structure of an electronic device that performs WLAN connection.

[0016] Figure 3 is a diagram illustrating an example of a link setup process for a typical wireless LAN.

[0017] Figure 4 is a diagram illustrating an example of a hidden node and an exposed node, and an example of an RTS and CTS for solving the problem of a hidden node and an exposed node.

[0018] Figure 5 is a diagram illustrating an example of a frame structure used in an IEEE 802.11 system.

[0019] Figure 6 is a diagram illustrating an example of a NAV setting.

[0020] Figure 7 is a diagram illustrating an example of TXOP.

[0021] FIG. 8 is a diagram illustrating an example of the configuration of a plurality of AP (MAP) frameworks of a wireless LAN system according to one embodiment of the present disclosure.

[0022] FIG. 9 is a diagram illustrating an example of a sequential null data packet-based sounding operation for performing Co-BF.

[0023] FIG. 10 is a diagram illustrating an example of a joint NDP-based sounding operation for performing Co-BF.

[0024] FIG. 11 is a diagram illustrating an example of sequential sounding operation for Co-BF performed between BSSs.

[0025] FIG. 12 is a diagram illustrating an example of a joint sounding operation for Co-BF performed between BSSs.

[0026] FIG. 13 is a diagram illustrating an example of signaling for coordinating the use of Co-BF operation between multiple APs.

[0027] FIG. 14 is a drawing illustrating an example of an element format constituting a Multi-AP capability advertisement frame in a wireless LAN system according to one embodiment of the present disclosure.

[0028] FIG. 15 is a diagram illustrating an example of a Co-BF preparation procedure. FIG. 15 includes a process for obtaining the security keys of neighboring APs and STAs.

[0029] FIG. 16 is a drawing illustrating an example of a frame used to convey Co-BF negotiation / agreement request element information or / and Co-BF negotiation / agreement response element information.

[0030] Figure 17 is a diagram illustrating an example of a MAP operation parameter information format.

[0031] FIG. 18a is a diagram illustrating an example of type-dependent information when MAP operation parameter information is set for Co-BF.

[0032] FIG. 18b is a diagram illustrating another example of type-dependent information when MAP operation parameter information is set for Co-BF.

[0033] FIG. 19 is a diagram illustrating an example of a method in which a UHR non-AP STA informs a UHR AP STA of its Co-BF sounding-related capability.

[0034] Figure 20 is a diagram illustrating an example of Co-BF capabilities.

[0035] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

[0036] In describing the embodiments, technical details that are well known in the art 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.

[0037] 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. Identical or corresponding components in each drawing have been assigned the same reference number.

[0038] 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. The embodiments of the present disclosure are provided merely to make the present disclosure 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. Throughout the specification, like reference numerals refer to like components.

[0039] At this point, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose 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 flow diagram 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 means of instruction to perform the function described in the flow diagram block(s).

[0040] Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that execute a computer or other programmable data processing equipment by performing a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer may also provide steps for executing the functions described in the flowchart block(s).

[0041] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific 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 depending on the corresponding function.

[0042] In this embodiment, the term "part" as used refers to a software or hardware component such as a field programmable gate array (FPGA) or an application-specific integrated circuit (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 may be configured to run one or more processors. Accordingly, according to some embodiments, 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." In addition, the components and 'parts' may be implemented to utilize one or more CPUs within the device or secure multimedia card. Also, according to some embodiments, the 'parts' may include one or more processors.

[0043] Exemplary embodiments are described below in relation to wireless LAN systems solely for the sake of simplicity. It should be understood that the exemplary embodiments are equally applicable to systems using signals of one or more wired standards or protocols (e.g., Ethernet and / or HomePlug, PLC standards), as well as other wireless networks (e.g., cellular networks, pico networks, femto networks, satellite networks). As used herein, the terms WLAN and Wi-Fi® may include communications controlled by the IEEE 802.11 family of standards, BLUETOOTH®, HiperLAN (a set of wireless standards comparable to IEEE 802.11 standards, mainly used in Europe), and other technologies having a relatively short wireless propagation range. Accordingly, the terms WLAN and Wi-Fi may be used interchangeably herein. Additionally, although the following describes an infrastructure WLAN system including one or more APs and multiple wireless stations (STAs), exemplary embodiments are equally applicable to other WLAN systems including, for example, multiple WLANs, peer-to-peer (or independent basic service set) systems, Wi-Fi Direct systems and / or hotspots.

[0044] Additionally, while this specification describes the exchange of data frames between wireless devices, exemplary embodiments may be applied to the exchange of any data unit, packet, and / or frame between wireless devices. Accordingly, the term "frame" may include any frame, packet, or data unit such as, for example, protocol data units (PDUs), MAC (media access control) protocol data units (MPDUs), and PLCP (physical layer convergence procedure) protocol data units. The term "A-MPDU" may mean aggregated MPDUs. In the following, a wireless LAN, or WLAN network, may be a network implementing at least one of the IEEE 802.11 wireless communication protocol standard family, such as as defined by the IEEE 802.11-2016 standard or its amendments (including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be).

[0045] In the following description, many specific details, such as examples of specific components, circuits, and processes, are presented to provide a thorough understanding of the present disclosure. As used herein, the term “connected” means being directly connected or being connected through one or more intervening components or circuits. The term “connected AP” means an access point to which a given wireless station is currently associated and / or connected (e.g., there exists a communication channel or link established between the access point and the given wireless station). Additionally, in the following description and for illustrative purposes, specific nomenclature is presented to provide a thorough understanding of exemplary embodiments. However, it will be apparent to those skilled in the art that these specific details may not be necessary to carry out the exemplary embodiments. In other cases, well-known circuits and devices are depicted in block diagram form to avoid obscuring the present disclosure. Also, the description of A / B means A or / and B, or at least one of A or B.

[0046] The operating principles of the present disclosure will be described in detail below with reference to the attached drawings. In describing the present disclosure below, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the present disclosure. Furthermore, the terms described below are defined in consideration of their functions in the present disclosure, and these may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0047] FIG. 1 is a diagram illustrating an example of a wireless communication network. The wireless communication network (100) may be an example of a wireless LAN, such as a Wi-Fi network. The wireless communication network (100) may include a number of wireless communication devices, such as an access point (AP, 102) and a number of stations (STA, 104). Although only one AP (102) is illustrated, the wireless communication network (100) may also include a number of APs (102).

[0048] A STA is a logical entity that includes a physical layer interface for a MAC and a wireless medium, and includes APs and non-AP STAs (Non-AP stations). Among the STAs, a portable terminal operated by a user is a Non-AP STA, and when simply referred to as STA, it may also refer to a Non-AP STA. Hereinafter, STA may refer to a non-AP STA. Each of the STAs (104) may be referred to as a terminal or a device. The terms 'terminal' or 'device' used in this specification may be referred to as a mobile station (MS), user equipment (UE), user terminal (UT), wireless terminal, access terminal (AT), terminal, subscriber unit, subscriber station (SS), wireless device, wireless communication device, wireless transmit / receive unit (WTRU), mobile node, mobile, or other terms. Various embodiments of the terminal may include cellular telephones, smartphones with wireless communication capabilities, personal handheld terminals (PDAs) with wireless communication capabilities, wireless modems, portable computers with wireless communication capabilities, imaging devices such as digital cameras with wireless communication capabilities, gaming devices with wireless communication capabilities, music storage and playback appliances with wireless communication capabilities, internet appliances capable of wireless internet access and browsing, as well as portable units or terminals integrating combinations of such functions. Additionally, the terminal may include machine-to-machine (M2M) terminals and machine-type communication (MTC) terminals / devices, but is not limited thereto. In this specification, the terminal may be referred to as an electronic device or simply a device.

[0049] An AP (102) is an entity that provides access to a distribution system (DS) via a wireless medium to an associated STA (STA) connected to it. The AP may also be called a central controller, a base station (BS), a Node-B, a base transceiver system (BTS), or a site controller.

[0050] An exemplary coverage area (106) of an AP (102) capable of representing the basic service area (BSA) of a wireless communication network (100) is illustrated. The AP (102) periodically broadcasts beacon frames (beacon frames may be interchangeable with beacons) containing a basic service set identifier (BSSID) to enable any STA (104) within the wireless range of the AP (102) to be associated with or re-associated with the AP (102) to establish or maintain individual communication links (108) (or may be referred to as Wi-Fi links) with the AP (102). The AP (102) can provide access to external networks for various STAs (104) within the WLAN through individual communication links (108).

[0051] A single AP (102) and an associated set of STAs (104) may be referred to as a basic service set (BSS) managed by the individual AP (102). The BSS may be identified to users by a service set identifier (SSID), as well as to other devices by a BSSID, which may be the MAC address of the AP (102).

[0052] BSS can be classified into infrastructure BSS and independent BSS (IBSS). The BSS shown in Fig. 1 is an IBSS, and it is also possible to establish an infrastructure BSS (not shown). An infrastructure BSS includes one or more STAs and APs, and in principle, communication between non-AP STAs in an infrastructure BSS is carried out via an AP, but if a direct link is established between non-AP STAs, direct communication between non-AP STAs is also possible.

[0053] Multiple infrastructure BSSs can be interconnected via DS. Multiple BSSs connected via DS are called an extended service set (ESS). STAs included in an ESS can communicate with each other, and within the same ESS, STAs can move from one BSS to another while communicating seamlessly.

[0054] A DS is a mechanism that connects multiple APs; it does not necessarily have to be a network, and there are no restrictions on its form as long as it can provide a specified distribution service. For example, a DS can be a wireless network such as a mesh network, or it can be a physical structure that connects APs to each other.

[0055] Additionally, AP (102) and STA (104) may be referred to as AP-MLD (access point multi-link device) and STA-MLD, respectively. This may mean that AP and STA can support multi-link operation.

[0056] Below, an example of a hierarchical structure according to the 802.11 standard is described.

[0057] The 802.11 standard document develops MAC and PHY protocols corresponding to Wi-Fi wireless access technology. The Data Link Layer (DLL) includes the MAC sublayer, which is responsible for media access control. It receives packets from the upper layer, 802.1X Port Filtering, via the MAC_SAP interface, constructs them into IEEE 802.11 MAC frames, and transmits them to the physical layer. The physical layer includes the PLCP (Physical Layer Convergence Procedure) sublayer and the PDM (Physical Medium Dependent) sublayer. The PLCP sublayer is responsible for converting the IEEE 802.11 MAC frames constructed by the MAC sublayer into PLCP frames. The PLCP frames are then transmitted to the target terminal through the PMD sublayer.

[0058] Various management frames that manage Wi-Fi wireless access are not transmitted at the upper layers of 802.1X. Instead, these management frames are transmitted as requests and responses between Station Management Entities (SMEs) located within each terminal. An SME is a layer-independent entity that may exist within a separate management plane or appear to be off-the-side. For example, if an AP wants to configure a BSS, it instructs the transmission of beacons via the MLME_SAP interface, specifically the MLME-START.request and MLME-START.confirm primitives. If an STA wants to establish an association with the corresponding AP, it instructs the transmission of association Request / Response frames via the MLME-ASSOCIATE.request, MLME-ASSOCIATE.response, MLME-ASSOCIATE.confirm, and MLME-ASSOCIATE.indication primitives. Meanwhile, if you wish to set operational parameter values ​​related to the physical layer, the SME can set various physical layer parameter values ​​through the PLCP_SAP interface.

[0059] FIG. 2 is a diagram illustrating an example of the structure of an electronic device performing a WLAN connection. Referring to FIG. 2, the electronic device (200) may be connected to an AP (210), and the electronic device (200) may include a processor (230) and a communication module (220). The electronic device (200) may be the STA (104) of FIG. 1, in which case the electronic device (200) may be connected to the AP (210) as illustrated. Alternatively, the electronic device (200) may be the AP (102) of FIG. 1, in which case the electronic device may be connected to the STA (104) and / or another AP as illustrated in FIG. 1.

[0060] The communication module (220) can receive a communication signal from the outside or transmit a communication signal to the outside based on a Wi-Fi communication method (e.g., IEEE Std 802.11™). For example, the communication module (220) can operate based on Wi-Fi communication methods such as IEEE 802.11ac, 802.11ax, 802.11be, or 802.11bn, and in particular, IEEE 802.11be or 802.11bn supports a wider bandwidth, higher data throughput, and shorter latency compared to IEEE 802.11ax, thereby improving performance.

[0061] The communication module (220) may include a transceiver (224) for transmitting and receiving data with an external device and a communication processor (222) (e.g., a communication processor (not shown), or a short-range wireless communication module (e.g., a Wi-Fi chipset)). Depending on various embodiments, the communication module (220) may further include memory.

[0062] According to various embodiments, the transceiver (224) can convert a baseband transmission signal into a wireless signal or convert a received wireless signal into a baseband reception signal.

[0063] According to various embodiments, the communication module (220) may further include, in addition to the transceiver (224) and the communication processor (222), components for OFDM or OFDMA (orthogonal frequency division multiple access), such as a modulator, a digital-analog converter, a frequency converter, an A / D converter, an amplifier, and / or a demodulator.

[0064] According to various embodiments not shown, the electronic device (200) may be electrically connected to a communication module of the AP (210) and may include at least one antenna module that supports a communication protocol and / or frequency band supported by the communication module of the AP (210).

[0065] A communication processor (222) can control a transceiver (224) to form a communication connection with an AP (210). For example, the communication connection may include a Wi-Fi network. For example, a communication processor (222) can control a transceiver (224) to form a wireless connection with an AP (200) using a WLAN standard in the 2.4 GHz, 5 GHz, or 6 GHz band such as IEEE 802.11ac, 802.11ax, 802.11be, or 802.11bn. Alternatively, a communication processor (222) can control a transceiver (224) to form a wireless connection with an AP (210) using a WLAN standard in the 60 GHz band such as IEEE 802.11ad or 802.11ay. In addition, the method of communicating between the electronic device (200) and the AP (210) using a WLAN standard can be referred to as a communication method based on STA mode.

[0066] According to various embodiments, the processor (230) may include an application processor. The processor (230) may perform a specified operation of the electronic device (200) or control other hardware (e.g., a communication module (220)) to perform a specified operation.

[0067] According to various embodiments, the AP (210) may support the operation of transmitting packets to an external network and / or the operation of receiving packets from an external network based on a connection between a plurality of electronic devices (e.g., electronic device (200)) and an external network (e.g., the Internet, an external LAN, or a cellular network).

[0068] For example, the AP (210) may be a wireless router. The AP (210) may be a dedicated wireless router or a general-purpose device that supports mobile hotspot functions, and there are no limitations on its implementation. For example, the AP (210) may include the same components (e.g., a processor and / or a communication module) as the electronic device (200). Additionally, the AP (210) may transmit and receive data with an external device, such as a server. For example, the AP (210) may transmit at least some of the data received from the server to the electronic device (200).

[0069] If the electronic device (200) of FIG. 2 corresponds to the AP (102), the electronic device (200) may include a separate communication module for connection with an external network, although not shown. This communication module may be controlled by a processor (230) or by a separate processor. The separate communication module may include a transceiver and a processor, and may also include memory. Additionally, the electronic device (200) may include a separate antenna module or a wired connection device for connection with an external network.

[0070] Figure 3 is a diagram illustrating an example of a link setup process for a typical wireless LAN.

[0071] In order for an STA to set up a link and transmit and receive data on a network, it must first discover the network, perform authentication, establish an association, and go through authentication procedures for security. The link setup process can also be referred to as the session initiation process or the session setup process. Additionally, the discovery, authentication, association, and security setup processes of the link setup process can be collectively referred to as the association process.

[0072] Referring to FIG. 3, the STA (300) can perform a network discovery operation. The network discovery operation may include a scanning operation of the STA (300). That is, in order for the STA (300) to access a network, it must find a network that it can join. Before joining a wireless network, the STA (300) must identify a compatible network, and the process of identifying networks existing in a specific area is called scanning.

[0073] Scanning methods include active scanning and passive scanning. In active scanning, the STA (300) performing the scanning moves between channels and sends a probe request frame (322) to search for nearby APs and waits for a response. The responder sends a probe response frame (324) as a response to the probe request frame to the STA that sent the probe request frame. Here, the responder may be the AP or STA that last sent a beacon frame from the BSS of the channel being scanned. FIG. 3 illustrates an example of a BSS that becomes the responder because the AP (310) sends a beacon frame (320). In an IBSS, the responder is not constant because the STAs within the IBSS take turns sending beacon frames. For example, if an STA transmits a probe request frame on channel 1 and receives a probe response frame on channel 1, the STA can store the BSS-related information included in the received probe response frame and move to the next channel to perform scanning in the same way.

[0074] Scanning operations may be performed using a passive scanning method. In passive scanning, the STA performing the scanning detects beacon frames while switching between channels. A beacon frame is one of the management frames 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. Figure 3 illustrates an example of a BSS in which an AP (310) periodically transmits beacon frames (320) to an STA (300), and in an IBSS, STAs within the IBSS take turns transmitting beacon frames. When the scanning STA receives a beacon frame, it stores information about the BSS included in the beacon frame and records the beacon frame information in each channel while moving to another channel. When comparing active scanning and passive scanning, active scanning has the advantage of having less delay and power consumption than passive scanning.

[0075] After the STA (300) discovers the network, an authentication process may be performed. This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation (350) described later. The authentication process includes the STA (300) sending an authentication request frame (330) to the AP (310), and in response, the AP (310) sending an authentication response frame (332) to the STA (300). The authentication frame used in the authentication request / response corresponds to a management frame.

[0076] The authentication frame may include information such as the authentication algorithm number, authentication transaction sequence number, status code, challenge text, RSN (robust security network), finite cyclic group, etc. These are some examples of information that may be included in the authentication request / response frame, and may be replaced with other information or additional information may be included.

[0077] AP (310) can determine whether to allow authentication for the STA based on the information included in the received authentication request frame. AP (310) can provide the result of the authentication processing to the STA (300) through an authentication response frame.

[0078] After the STA is successfully authenticated, an association process may be performed. The association process includes the STA (300) sending an association request frame (340) to the AP (310), and in response, the AP (310) sending an association response frame (342) to the STA (300).

[0079] For example, the associated request frame may include information regarding various capabilities, beacon listen interval, SSID, supported rates, supported channels, RSN (robust security network), mobility domain, supported operating classes, traffic indication map broadcast request, interworking service capabilities, etc.

[0080] For example, an association response frame may include information related to various capabilities, status code, association ID (AID), support rate, enhanced distributed channel access (EDCA) parameter set, received channel power indicator (RCPI), received signal to noise indicator (RSNI), mobility domain, timeout interval (association comeback time), overlapping BSS scan parameters, TIM broadcast response, QoS map, etc.

[0081] This is a partial example of the information that may be included in the associated request / response frame, and it may be replaced with other information or additional information may be included.

[0082] Although not yet described, a security setup process can be performed after the STA is successfully associated with the network. The security setup process may be described as an authentication process through RSNA (robust security network association) requests / responses, and the authentication process (330) may be called the first authentication process, and the security setup process may also be called the authentication process.

[0083] The security setup process 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, or it may be performed according to a security method not defined in the IEEE 802.11 standard.

[0084] The following describes the Media Access Control Protocol provided by 802.11.

[0085] In wireless LAN systems based on IEEE 802.11, the basic access mechanism of a MAC is based on a distributed coordination function (DCF) utilizing the carrier sense multiple access with collision avoidance (CSMA / CA) method. There are two methods for detecting carriers in DCF: physical carrier sense and virtual carrier sense. The physical carrier sense method detects channel conditions at the physical layer and informs the MAC layer, while the virtual carrier sense method reserves a channel in advance by broadcasting the channel occupancy time to surrounding stations. An STA or AP that has secured a transmission channel records and transmits this channel occupancy time within an RTS and / or CTS or data frame; other STAs receiving this information determine that the channel is in use during this time and avoid channel occupancy contention, thereby avoiding collisions.

[0086] The physical carrier sensing method basically employs a listen before talk access mechanism, and according to this type of access mechanism, the AP and / or STA can perform a clear channel assessment (CCA) to sense the wireless channel, carrier, or medium for a predetermined time interval before starting transmission. The predetermined time interval is referred to as the inter-frame space (IFS) and may vary depending on the priority of the traffic to be transmitted. That is, priority can be determined by the length of the time interval, and packets with higher priority may have shorter time intervals.

[0087] The above IFS may include SIFS (short IFS), PIFS (PCF IFS), DIFS (DCF IFS), AIFS (arbitration IFS), etc. SIFS is the shortest time interval and can be used primarily as a waiting time for control information. PIFS is a medium-length time interval and can be for packets of medium priority (PIFS = SIFS + 1 slot time). DIFS is the longest time interval compared to SIFS and PIFS, has a low priority, and can be used primarily as a waiting time to check channel usage (DIFS = SIFS + 2 slot time). That is, for example, an STA intending to perform transmission can listen to (or detect channel) the channel usage during the DIFS period.

[0088] If sensing results determine that the medium is in an idle state, the AP and / or STA initiate frame transmission through that medium. Conversely, if the medium is detected to be in an occupied state, the AP and / or STA may attempt frame transmission after waiting for a delay period for medium access (e.g., a random backoff period) without initiating their own transmission. For instance, the AP and / or STA may randomly select a timer value within the contention window (CW) range, wait until the timer expires, and then sense the channel again. At this point, if the medium is idle, the AP and / or STA may initiate frame transmission; if the medium is occupied, the AP and / or STA doubles the size of the contention window and selects a timer value again. The size of the initially applied contention window is the minimum window size (contention window minimum, CW). min It is referred to as the maximum window size (contention window maximum, CW), and the maximum size of the contention window that can be applied is called the maximum window size (contention window maximum, CW max It is referred to as a ). By applying a random backoff period, multiple STAs are expected to attempt to transmit frames after waiting for different periods of time, thus minimizing collisions.

[0089] However, since this DCF method does not consider the priority between STAs, it has the problem of being difficult to support various forms of data transmission and QoS (quality of service); therefore, HCF (hybrid coordination function) was introduced. HCF is based on the aforementioned DCF and PCF (point coordination function). 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. HCF includes EDCA (enhanced distributed channel access), a contention-based channel access method, and HCCA (HCF controlled channel access), a contention-based method utilizing a polling mechanism. In addition, HCF includes a media access mechanism to improve WLAN QoS and can transmit QoS data during both the contention period (CP) and the contention-free period (CFP).

[0090] According to EDCA, data has priorities ranging from 0 to 7 based on traffic type, and data arriving at the MAC layer is mapped to four access categories (ACs) according to these priorities. Higher priorities correspond to higher priority, and since each AC has its own parameters and backoff is performed using differently configured AC parameter values, data has different channel access priorities depending on the AC. The AC parameters include AIFS and CW. min , CW max , TXOP limits, etc. may exist. AIFS and CW minThe smaller the value, the higher the priority, and accordingly, the channel access delay is shortened, allowing data to use more bandwidth in a given traffic environment. The backoff process of EDCA, which generates a new backoff counter when a collision occurs between STAs during frame transmission, is similar to the existing DCF, and transmission based on traffic priority is guaranteed through EDCA parameters that include priority per AC.

[0091] Figure 4 is a diagram illustrating an example of a hidden node and an exposed node, and an example of an RTS and CTS for solving the problem of a hidden node and an exposed node.

[0092] Figure 4 (a) (400) is an example of a hidden node. When STA A and STA B are communicating and STA C has information to transmit, STA A is transmitting information to STA B, but when STA C performs carrier sensing before sending data to STA B, it can be determined that the medium is idle. This is because STA C may not be able to sense STA A's transmission (i.e., medium occupancy) at its location. In this case, a collision occurs because STA B receives information from STA A and STA C simultaneously. At this time, STA A can be considered a hidden node of STA C.

[0093] (b)(410) is an example of an exposed node. In a situation where STA B is transmitting data to STA A, STA C may have information to transmit to STA D. In this case, if STA C performs carrier sensing, it can determine that the medium is occupied due to the transmission by STA B. Accordingly, STA C must wait until the medium becomes idle, even if it has information to transmit to STA D. However, in reality, since STA A is outside the transmission range of STA C, the transmission from STA C and the transmission from STA B may not conflict from STA A's perspective, so STA C ends up waiting unnecessarily until STA B stops transmitting. In this case, STA C can be referred to as the exposed node of STA B.

[0094] In order to efficiently utilize the collision avoidance mechanism in the above situation, short signaling packets such as RTS (request to send) and CTS (clear to send) may be used. An STA intending to transmit data transmits an RTS to a STA intending to receive data, and the receiving STA that receives the RTS responds to the transmitting STA with a CTS frame. The RTS and / or CTS between the two STAs may cause surrounding STA(s) to overhear, thereby causing the surrounding STA(s) to consider whether to transmit information between the two STAs.

[0095] (c)(420) is an example of how to solve the hidden node problem. Assume that both STA A and STA C intend to transmit data to STA B. When STA A transmits an RTS to STA B, STA B transmits a CTS to STA A. STA C, which overhears the RTS and CTS, delays its media access until the data transmission of STA A and STA B is finished, thereby avoiding collisions.

[0096] (d)(430) is an example of a method for solving the exposed node problem. STA B, which intends to send data to STA A, sends an RTS, and STA A, which is to receive the data, sends a CTS to respond to the RTS. In this case, if STA C receives only the RTS sent by STA B and does not receive the CTS sent by STA A, STA C can determine that STA A is outside the carrier sensing area of ​​STC C. In this case, STA C can determine that no collision will occur even if it sends data to another STA (e.g., STA D) and can send the data.

[0097] Figure 5 is a diagram illustrating an example of a frame structure used in an IEEE 802.11 system.

[0098] The PPDU (physical layer protocol data unit) format can be configured to include the STF (short training field), LTF (long training field), SIG (signal) field, and data field. The most basic (e.g., non-HT (high throughput)) PPDU frame format can be configured to include only the L-STF (legacy-STF), L-LTF (legacy-LTF), SIG field, and data field.

[0099] STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization. LTF can be used for fine frequency / time synchronization and channel estimation. STF and LTF together can be referred to as the PLCP preamble, and the PLCP preamble can be described as a signal for synchronization and channel estimation in the OFDM physical layer.

[0100] The SIG field can be used to transmit control information for demodulation and decoding of the data field. The SIG field may include information regarding the data rate and data length. Additionally, the SIG field may include a parity bit, a SIG TAIL bit, etc.

[0101] 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 the descrambler at the receiver. The PSDU corresponds to the MPDU (MAC protocol data unit) defined at the MAC layer and may contain data generated or used by the upper layer. The PPDU TAIL bit may be set to 0 to flush the decoder. Padding bits may be used to adjust the length of the data field to a predetermined unit.

[0102] MPDUs are defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a frame check sequence (FCS). A MAC frame is composed of an MPDU and can be transmitted or received through the PSDU of the data portion in the PPDU format.

[0103] The MAC header is defined as an area containing the frame control field, duration / ID field, address 1 field, address 2 field, address 3 field, sequence control field, address 4 field, QoS control field, and HT control field.

[0104] The frame control field contains information about the corresponding MAC frame characteristics. The interval / identifier field can be implemented to have different values ​​depending on the type and subtype of the corresponding MAC frame.

[0105] Fields 1 through 4 of the address are used to indicate the BSSID, source address (SA), destination address (DA), transmitting address (TA) representing the transmitting STA address, and receiving address (RA) representing the receiving STA address.

[0106] The sequence control field is configured to include a sequence number and a fragment number. The sequence number may indicate the sequence number assigned to the corresponding MAC frame. The fragment number may indicate the number of each fragment of the corresponding MAC frame.

[0107] The QoS control field contains information related to QoS. The QoS control field may be included if the Subtype subfield indicates a QoS data frame. The HT control field contains control information related to HT and / or VHT transmission and reception techniques.

[0108] The frame body is defined as the MAC payload, contains the data to be transmitted from the upper layer, and has a variable size. For example, the maximum MPDU size can be 11,454 octets, and the maximum PPDU size can be 5.484 ms.

[0109] FCS is defined as the MAC footer and is used for error detection in MAC frames.

[0110] The first three fields (frame control field, interval / identifier field, and address 1 field) and the very last field (FCS field) constitute the minimum frame format and are present in all frames. Other fields may exist only in specific frame types.

[0111] The following describes the network allocation vector (NAV) used in wireless LAN networks.

[0112] As previously mentioned, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, where the AP and / or STA directly senses the medium. Virtual carrier sensing is intended to compensate for problems that may occur in medium access, such as hidden node issues. For virtual carrier sensing, the MAC of a wireless LAN system may utilize NAV. NAV is a value that indicates to other APs and / or STAs the time remaining until the medium becomes available, provided that the AP and / or STA currently using or authorized to use the medium is using the medium. Therefore, the value set as NAV corresponds to the period during which the medium is scheduled to be used by the AP and / or STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during that period. NAV can be set, for example, based on the value of the duration field in the MAC header of the frame.

[0113] Figure 6 is a diagram illustrating an example of a NAV setting.

[0114] Referring to FIG. 6, the source STA (source STA, 600) transmits an RTS frame after DIFS, and the destination (610) transmits a CTS frame after SIFS. The destination STA designated as the recipient via the RTS frame does not set the NAV. Some of the remaining STAs (620) receive the RTS frame and set the NAV (630), while others receive the CTS frame and set the NAV (640).

[0115] If a CTS frame (e.g., PHY-RXSTART.indication primitive) is not received within a certain period from the time an RTS frame is received (e.g., when a MAC receives the PHY-RXEND.indication primitive corresponding to the RTS frame), STAs that set or updated the NAV via the RTS frame may reset the NAV (e.g., to 0) (or this case may be referred to as NAVtimeout). The certain period may be (2*aSIFSTime + CTS_Time + aRxPHYStartDelay + 2*aSlotTime), which may be referred to as the NAVtimeout period. CTS_Time may be calculated based on the length and data rate of the CTS frame indicated by the RTS frame.

[0116] In FIG. 6, for convenience, NAV setting or updating is exemplified through an RTS frame or a CTS frame, but NAV setting / resetting / updating may also be performed based on the interval field of various other frames, such as non-HT PPDU, HT PPDU, VHT PPDU, or HE PPDU (for example, the interval field within the MAC header of a MAC frame).

[0117] In addition, 802.11ax introduced basic NAV and intra-BSS NAV. Basic NAV is always set (mandatory) to NAV based on frames transmitted by APs or STAs other than itself, while intra-BSS NAV can be optionally set to NAV based on frames transmitted by the BSS to which it belongs. An AP or STA can access the medium when both NAV timers have expired (or after the NAV time interval has elapsed).

[0118] The following describes TXOP. TXOP (transmission opportunity) was newly introduced in 802.11e MACs to guarantee QoS and increase channel utilization. To guarantee QoS, TXOP can be used to allocate an opportunity for priority transmission when two or more packets belong to the same AC (access category).

[0119] Figure 7 illustrates an example of a TXOP. An STA participating in QoS transmission can obtain a TXOP that allows it to transmit traffic for a certain period using two channel access methods, such as EDCA and HCCA. TXOP acquisition is possible by succeeding in EDCA contention or by receiving a QoS CF-Poll frame from an AP; the former is referred to as an EDCA TXOP, and the latter as a Polled TXOP. In this way, the concept of a TXOP can be used to grant a certain amount of time to any STA to transmit a frame, or to forcibly limit the transmission time.

[0120] The transmission start time and maximum transmission time of a TXOP are determined by the AP, and this is notified to the STA by a beacon frame in the case of an EDCA TXOP, and by a QoS CF-Poll frame in the case of a Polled TXOP.

[0121] NAV can be understood as a type of timer designed to protect the TXOP of a transmitting STA (e.g., a TXOP holder). An STA can protect the TXOPs of other STAs by not performing channel access during the period when the NAV set for it is valid. In current wireless LAN systems, the TXOP duration is set via the duration field of the MAC header. That is, the TXOP holder and the TXOP responder (e.g., an Rx STA) include all the TXOP information necessary for transmitting and receiving frames in the duration field of the frames being exchanged between them. Third-party STAs that are not the TXOP holder or TXOP responder (e.g., third-party STAs) check the duration field of the frames exchanged between the TXOP holder and the TXOP responder, and delay channel usage until the NAV period expires by setting or updating the NAV.

[0122] The primary channel and secondary channel are described below. The primary channel is a common channel operated by all STAs that are members of the BSS. For example, in a 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 80 + 80 MHz BSS, the primary channel may be the primary 20 MHz channel. In this case, the 40 and 80 MHz channels containing the primary 20 MHz channel may be referred to as the primary 40 and 80 MHz channels, respectively, and the primary channel may generally be referred to as the primary 20 MHz channel.

[0123] A secondary channel is a channel associated with a primary channel and is used to create a channel wider than the primary channel. For example, in a 40 MHz, 80 MHz, and 160 MHz BSS, the 40 MHz channel may be the sum of the primary 20 MHz channel and the secondary 20 MHz channel, the 80 MHz channel may be the sum of the primary 40 MHz channel and the secondary 40 MHz channel, and the 160 MHz channel may be the sum of the primary 80 MHz channel and the secondary 80 MHz channel.

[0124] Currently, it is common for multiple APs to operate in specific areas, and in such cases, wireless LAN network performance degradation occurs due to coverage overlap between APs. This is because the APs of each BSS and the STAs connected to them are affected by signals from adjacent BSSs, leading to interference and a reduction in transmission rates caused by collisions between signals transmitted simultaneously. BSSs that can affect signal transmission in this way (or have overlapping coverage) can be referred to as overlapping BSSs (OBSS). To address this problem, interference avoidance techniques are being researched, such as dividing the bandwidth available to each user so that it does not overlap or performing channel switching to unused channels, as well as interference alignment techniques that minimize the impact of interference even when using the same bandwidth.

[0125] The 802.11be standard is described below. Also known as EHT (extremely high throughput), 802.11be operates across the 2.4, 5, and 6 GHz bands. It is being developed to provide low latency and high network throughput by introducing a 320 MHz wide bandwidth, 4096QAM, multiple resource units (RUs), and multi-link operation (MLO), offering speeds up to 46 Gbps—4.8 times faster than WiFi 6. Specifically, 802.11be provides a 320 MHz wide bandwidth in the 6 GHz band and can transmit data via MU-MIMO, which offers 16 spatial streams in both uplink and downlink. It also achieves high transmission efficiency by adopting 4096QAM. Furthermore, it features enhanced spectrum efficiency by flexibly performing spectrum resource scheduling through multiple RUs, and the ability to simultaneously transmit and receive data across various frequency bands and channels through multi-link operation.

[0126] The following describes TXOP sharing. TXOP sharing is a technology defined in 802.11be, based on the concept of an AP transferring remaining TXOP resources to a STA within a BSS after using the TXOPs it has acquired. An AP can transfer TXOPs to a STA using a multi-user RTS (MU-RTS) TXOP sharing (TXS) trigger frame (TF), specifically the MU-RTS TXS TF; the STA receiving the TXOP is indicated within the MU-RTS TXS TF. Recently, TXOP sharing between APs has been under research. Through TXOP sharing between APs, an AP holding TXOPs can share the remaining TXOPs with an adjacent AP after using them for traffic processing within its BSS. This allows for the efficient use of frequency and space resources, thereby increasing network throughput and reducing latency. TXOP sharing between APs can be referred to as AP TXOP sharing or Coordinated TDMA (C-TDMA).

[0127] In addition to C-TDMA, transmission methods that improve efficiency and / or reliability through the coordination of multiple APs (multi-AP, MAP, M-AP) (hereinafter, the coordination of multiple APs may be expressed interchangeably as MAP, M-AP, and MAPC) are being studied. Examples of such Multi-AP coordination (MAPC) schemes include Co-JT (coordinated joint transmission), Co-BF (coordinated beamforming), Co-SR (coordinated spatial reuse), Co-OFDMA (coordinated orthogonal frequency division multiple access), and Co-R-TWT (coordinated restricted target wake time). Furthermore, a set of APs capable of performing MAPC scheme operations can be referred to as a MAPC AP set. The aforementioned MAPC scheme may be referred to as M-AP operation or M-AP scheme.

[0128] Channel sounding is described below. To determine the weight of the transmitter's transmit beamforming (TxBF), the transmitter requires channel state information (CSI), and the transmitter can send a sounding packet to the receiver, and the receiver can feed back the channel state information to the transmitter. The sounding packet may be a null data packet (NDP) or a packet that extends the number of long training symbols in the LTF of the packet's preamble. An NDP does not contain a data field and may contain a predetermined symbol.

[0129] The aforementioned channel state information being fed back may be CSI feedback, uncompressed beamforming weight feedback, or compressed beamforming weight feedback. CSI feedback involves feeding back the CSI matrix, while uncompressed beamforming weight feedback involves the receiver calculating beamforming weights and feeding them back to the transmitter, allowing the transmitter to apply the received beamforming weights to transmit the signal. Compressed beamforming weight feedback is a method of feeding back the beamforming weights calculated by the receiver while reducing the number of bits required for the feedback.

[0130] Specifically, the channel state information may include, for example, information indicating a compressed beamforming weight and signal-to-noise ratio (SNR) information. The compressed beamforming weight may be indicated by a channel matrix element index.

[0131] FIG. 8 is a diagram illustrating an example of the configuration of a plurality of AP (MAP) frameworks of a wireless LAN system according to one embodiment of the present disclosure. The process of FIG. 8 can be understood as illustrating a general framework configuration process for M-AP operation.

[0132] Referring to Fig. 8, in 802.11bn, the process of sharing or advertising (hereinafter referred to as advertisement) the M-AP capabilities supported by each AP and negotiating or agreeing on which M-AP scheme to use can be defined as a general M-AP framework.

[0133] More specifically, in step 800, the advertisement of M-AP capability may be a broadcast or announcement of information regarding each AP's M-AP capability through a management frame. Additionally, the management frame for the advertisement of M-AP capability may be referred to as an M-AP capability advertisement frame. Thus, M-AP capability may be shared or exchanged between at least two APs (hereinafter referred to as AP1 and AP2) in an unencrypted state. Furthermore, the broadcasted M-AP capability of a specific AP may be discovered by at least one other AP. For example, at least one neighboring AP may overhear information from the AP broadcasting the M-AP capability, which may be referred to as M-AP discovery passive scanning (e.g., the passive scanning method of FIG. 3 described above). Thus, information related to M-AP between APs may be identified by the advertisement of M-AP capability. For example, the AP can identify information regarding whether at least one other AP supports M-AP or the status of M-AP operation. In one embodiment, the AP can identify at least one other AP capable of participating in or supporting M-AP operation. In one embodiment, the APs participating in M-AP operation may identify which M-AP operation (e.g., M-AP scheme) to perform based on information regarding the discovered M-AP capability. Of course, the M-AP scheme may be determined in a step after step 800 (e.g., an ICF (initial control frame) and ICR (initial control response) exchange operation at the TXOP level).

[0134] In step 810, based on the M-AP capabilities exchanged between the APs, the APs can perform authentication. The authentication operation in step 810 may include an authentication procedure to determine whether M-AP operations can be performed between the APs. The authentication operation in step 810 may be one of the IEEE 802.11 authentication methods (e.g., FT (fast BSS transition) authentication, SAE (simultaneous authentication of equals), FILS authentication, PASN (pre-association security negotiation) authentication, or WP3 (Wi-Fi protected access 3) based authentication). If the authentication operation in step 810 is the FT authentication, SAE, FILS authentication, PASN authentication, or WP3-based authentication operation exemplified above, an authentication procedure to determine whether M-AP operations can be performed between the APs may be performed by including it in part of the detailed message of the aforementioned authentication operation. An AP can enhance security through an authentication operation to perform M-AP operations with an authenticated OBSS (overlapping basic service set) AP (e.g., an AP of another BSS that overlaps with its own BSS). However, Step 810 may not be a mandatory step and may be performed optionally depending on security requirements. For example, if authentication between APs is completed prior to the operation of the present disclosure, Step 810 may be omitted. As another example, Step 810 may be performed as a separate step prior to Step 840 below, or combined with Step 850. Meanwhile, the present disclosure may be a case where the authentication step between APs in Step 810 is performed as a single independent step.

[0135] In step 820, based on steps 800 and 810, a combination or connection between APs (hereinafter referred to as M-AP combination) may be performed. For example, through step 800, M-AP capabilities are detected and mutually discovered APs may be assigned an M-AP AID (e.g., an AID between APs) to each AP for combination. Meanwhile, the M-AP AID assigned for mutual identification between APs may be referred to as an AID below, but it should be noted that it may refer to a different meaning from the AID assigned between an AP and a non-AP STA as described above. Additionally, the assigned AID is exchanged between APs so that the APs can identify each other's AIDs. In one embodiment, an AID may be assigned to each AP. In another embodiment, in addition to the M-AP AID, an ID to designate an AP pair or AP group may be additionally assigned, which may be referred to as an M-AP Group ID (or M-AP GID).

[0136] In step 830, APs can generate and negotiate security keys to support trigger frames based on WPS, etc. or MAC header protection. At this time, signaling may be possible by adopting security procedures defined in IEEE 802.11 (e.g., Wi-Fi Protection Setup between APs or RSNA (robust security network association)).

[0137] In step 840, APs may perform negotiation and agreement on M-AP features or features. Even when referred to as a negotiation procedure or an agreement procedure in this disclosure, it may mean a procedure that includes both negotiation and agreement operations of step 840. Additionally, M-AP features may refer to features or functions that are distinguished according to an M-AP scheme, or, even if they relate to the same M-AP scheme, are distinguished according to a logical session (hereinafter referred to as a session) created when different sessions are created through negotiation / agreement between APs.

[0138] In step 850, APs can perform actions corresponding to the M-AP scheme(s) agreed upon between APs through the aforementioned steps 800 or 840.

[0139] The names of each step in FIG. 8 described above are merely examples to explain the operation of the corresponding step and are not limited to the examples provided. Therefore, each step may be replaced with an appropriate term to describe the corresponding operation. For example, the M-AP combination in step 830 described above may be referred to as M-AP link establishment, M-AP pre-negotiation, M-AP pre-configuration, or M-AP ID allocation. Additionally, although the description in FIG. 9 describes M-AP operations performed between two APs, it can be applied in the same way when performed between three or more APs (e.g., a group of APs).

[0140] FIG. 9 illustrates an example of sequential null data packet sounding operation for performing Co-BF. According to FIG. 9, AP1 (900) transmits an NDPA (null-data packet announcement, 920) to STA1 (910) associated with it. The NDPA (920) contains information that AP1 (900) transmits an NDP (922) for channel measurement between AP1 (900) and STA1 (910), and that STA1 (910) responds to the transmission of the NDP. Specifically, the NDPA includes a sounding dialog token field, information about the STA to receive the NDP (STA info list), etc., and the information about the STA may include an AID, the requested feedback type of the STA, etc. The information (STA info list) for the STA to receive the NDP of the above NDPA (920) may include not only the STA to respond to the transmission of the NDP, but also information for AP2 (902) to which a MAP connection has been established, which is AP information to transmit the NDP.

[0141] AP1 (900) sends an NDP (922) to STA1 (910) and a beamforming report poll (BFRP, 924) to receive feedback on channel state information (CSI). The BFRP is sent to request a beamforming report containing CSI. Upon receiving the BFRP, STA1 (910) reports the CSI to AP1 (900) (926). Subsequently, AP1 (900) sends an NDPA (928) containing information that AP2 (902), which has established a MAP connection with AP1 (900), sends an NDP (930) to STA1 (910). Afterwards, AP2 (902) sends an NDP (930), AP1 (900) sends a BFRP (932) to STA1 (910) to report a CSI for AP2 (902), and STA1 (910) reports a CSI (934) for AP2 (902) to AP1 (900). If AP2 (902) can directly receive and decode the CSI (934) transmitted by STA1 (910), AP1 (900) does not need to separately transmit the CSI (934) transmitted by STA1 (910) to AP2 (902); however, if not, AP1 (900), although not shown in the drawing, separately transmits the CSI (934) transmitted by STA1 (910) to AP2 (902) so that AP2 (902) can use the CSI (934) of STA1 (910) during Co-BF operation.

[0142] Similarly, AP2 (902) transmits an NDPA to STA2 (912) associated with it (936). The NDPA contains information that AP2 (902) transmits an NDP for channel measurement between AP2 (902) and STA2 (912). Then, AP2 (902) transmits a BFRP (940) to receive feedback on the NDP (938) and CSI, and STA2 (912) transmits a CSI (942) to AP2 (902). Then, AP2 (902) transmits an NDPA (944) containing information that AP1 (900) transmits an NDP to STA2 (912). Subsequently, AP1 (900) transmits an NDP (946), AP2 (902) transmits a BFRP (948) to STA2 (912) to report a CSI for AP1 (902), and STA2 (912) reports a CSI (950) for AP1 (900) to AP2 (902). The information (STA info list) for the STA to receive the NDP of the NDPA (936) may include not only the STA to respond to the transmission of the NDP, but also information for AP1 (900) to which a MAP connection has been established, which is AP information to transmit the NDP.

[0143] As described above, FIG. 9 illustrates an example of an operation in which APs sequentially transmit NDPs to a specific STA, and the specific STA reports a CSI in response to the NDP. That is, sounding can be performed sequentially. In this case, the NDPA transmitted by the specific AP may be transmitted only to the STA associated with it. Through such an operation, AP1 can obtain a CSI for the channel between STA1 associated with it and AP1 and AP2, and AP2 can obtain a CSI for the channel between STA2 associated with it and AP1 and AP2. In the example of FIG. 9, the CSI reported by the STA may correspond to one of the CSIs described above. An example such as FIG. 9 illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the example. For example, a series of operations may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, each operation may be omitted or replaced with another operation.

[0144] FIG. 10 illustrates an example of a joint NDP-based sounding operation for performing Co-BF. According to FIG. 10, AP1 (1000) transmits an NDPA (1020) containing information that AP1 (1000) and AP2 (1002) transmit NDPs to STA1 (1010) associated with it. Subsequently, AP1 (1000) and AP2 (1002) simultaneously transmit NDPs (1022, 1024). Subsequently, AP1 (1000) transmits a BFRP (1026) instructing STA1 (1010) to report a CSI, and STA1 (1010), having received the NDPs (1022, 1024), performs feedback (1028) containing CSIs for AP1 (1000) and AP2 (1002). In this case, the feedback may be feedback for the beamforming weight V calculated based on the eigenvectors for the channels between STA1 (1010), AP1 (1000), and AP2 (1002). Alternatively, other CSI feedback may be used.

[0145] Subsequently, AP2 (1002) transmits an NDPA (1030) containing information that AP1 (1000) and AP2 (1002) are transmitting an NDP to STA2 (1012) associated with it. Subsequently, AP1 (1000) and AP2 (1002) simultaneously transmit an NDP (1032, 1034). Subsequently, AP2 (1002) transmits a BFRP (1036) instructing STA2 (1012) to report a CSI, and STA2 (1012), having received the NDP (1032, 1034), performs feedback (1038) containing a CSI for AP1 (1000) and AP2 (1002). The content of the feedback (1038) may be the same as the content of the feedback (1028).

[0146] As described above, FIG. 10 illustrates an example of an operation in which APs simultaneously transmit NDPs to a specific STA, and the specific STA reports CSIs for multiple APs in response to the NDPs. That is, sounding can be performed together. In this case, the NDPA transmitted by the specific AP may be transmitted only to the STA associated with it. Through such an operation, AP1 can obtain CSIs for the channel between STA1 associated with it and AP1 and AP2, and AP2 can obtain CSIs for the channel between STA2 associated with it and AP1 and AP2. An example such as FIG. 10 illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the example. For example, a series of operations may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, each operation may be omitted or replaced by another operation.

[0147] According to the operation of FIGS. 9 and 10 as described above, CSI reporting is performed between a specific AP and a STA associated with the specific AP. However, for example, in order for AP2 to obtain the AP2-related CSI that STA1 has fed back to AP2, it must receive the CSI reported by STA1 from AP1. Alternatively, if AP2 receives the CSI directly from STA1, the sounding procedure can be performed more quickly.

[0148] FIG. 11 illustrates an example of a sequential sounding operation for Co-BF performed between BSSs. According to FIG. 11, AP1 (1102) can transmit an NDPA (1110) to STA1 (1100) associated with itself and to AP2 (1104) performing the Co-BF operation. The TA field of the NDPA (1110) may be set to the address of AP1, and the RA field may be set to a BA (broadcast address); and each of the two STA info fields may be set one for STA1 (1100) and one for AP2 (1104). The NDPA may include instructions for AP2 (1104) to transmit an NDP. The NDPA corresponds to a frame that can be transmitted within and between BSSs.

[0149] Afterward, AP2 (1104) transmits an NDP (1120). The NDP (1120) may not be encrypted or protected, and if the NDP transmitted by AP2 (1104) is correct, it may be necessary to verify the integrity of the transmitted message through a message integrity check (MIC).

[0150] Subsequently, AP1 (1102) sends a BFRP (1130) to STA1 (1100) requesting feedback on the received NDP. Upon receiving the BFRP (1130), STA1 (1100) can report the CSI in the following two ways. The first method is for STA1 (1100) to send the CSI for AP2 (1104) to AP1 (1102) (1140), and for AP1 (1102) to send the received CSI to AP2 (1104) (1160). According to the first method, the transmission of CSI between STA1 (1100) and AP1 (1102) corresponds to transmission between BSSs, and the transmission of CSI from AP1 (1102) to AP2 (1104) can utilize the AP-to-AP channel. The first method can be referred to as Co-BF Indirect sounding.

[0151] The second method is for AP2 (1104) to receive (1150) the CSI transmitted by STA1 (1100). In order to obtain the CSI received by AP2 (1104), AP2 (1104) must know the security key between STA1 (1100) and AP1 (1102) in advance and decrypt the frame containing the CSI transmitted by STA1 (1100) using the security key between STA1 (1100) and AP1 (1102). At this time, STA and AP need to decide whether to report the CSI using the first method or the second method. The second method can be referred to as Co-BF Direct sounding. Consultation and decision on whether AP1 (1102) and AP2 (1104) will perform Co-BF Indirect sounding or Co-BF Direct sounding may be performed in step 840 of FIG. 8, steps 1320 to 1350 of FIG. 13 to be described later, or the Co-BF negotiation / agreement (1540) step of FIG. 15 to be described later. Additionally, AP1 (1102) and STA1 (1100) must also consult or decide whether to perform Co-BF Indirect sounding or Co-BF Direct sounding, and this process may be consulted or decided when STA1 (1100) exchanges probe request / response or (re)association request / response with AP1 (1102).

[0152] An example such as FIG. 11 illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the example. For example, a series of operations may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, each operation may be omitted or replaced with another operation.

[0153] FIG. 12 illustrates an example of a joint sounding operation for Co-BF performed between BSSs. According to FIG. 12, AP1 (1202) can transmit an NDPA (1210) to its associated STA1 (1200) and AP2 (1204). The TA field of the NDPA (1210) can be set to the address of AP1, and the RA field can be set to a BA (broadcast address); and each of the two STA info fields can be set one for STA1 (1200) and one for AP2 (1204). The NDPA may include instructions for AP2 (1204) to transmit an NDP. The NDPA corresponds to a frame that can be transmitted within and between BSSs.

[0154] Subsequently, AP1 (1202) and AP2 (1204) simultaneously transmit NDPs (1220, 1230). At this time, the NDP (1220) transmitted by AP1 (1202) may be a conventional NDP, but the NDP (1230) transmitted by AP2 (1204) may have the same or different preamble and part of the PHY header as the NDP (1220) transmitted by AP1 (1202), and does not include a MAC header and payload. This is because the CSI reported by STA1 (1200) based on two NDPs (1220, 1230) must be in a form that only increases the dimension of the matrix when compared to a CSI based on one NDP.

[0155] Subsequently, AP1 (1202) sends a BFRP (1240) to STA1 (1200) requesting feedback on the received NDP. Upon receiving the BFRP (1240), STA1 (1200) can report the CSI in the following two ways. The first method is for STA1 (1200) to send the CSI for AP1 (1200) and AP2 (1204) to AP1 (1202) (1250), and for AP1 (1202) to send the received CSI to AP2 (1204) (1270). According to the first method, the transmission of CSI between STA1 (1200) and AP1 (1202) corresponds to transmission between BSSs, and the transmission of CSI from AP1 (1202) to AP2 (1204) can utilize the AP-to-AP channel. The first method can be called Co-BF Indirect sounding.

[0156] The second method is for AP2 (1204) to receive (1250) the CSI transmitted by STA1 (1200). In order to obtain the CSI received by AP2 (1204), AP2 (1204) must know the security key between STA1 (1200) and AP1 (1202) in advance and decrypt the frame containing the CSI transmitted by STA1 (1200) using the security key. The second method can be called Co-BF Indirect Sounding. As in FIG. 11, the consultation and decision regarding whether AP1 (1202) and AP2 (1204) will perform Co-BF Indirect sounding or Co-BF Direct sounding may be performed in step 840 of FIG. 8, steps 1320 to 1350 of FIG. 13 to be described later, or the Co-BF negotiation / agreement (1540) step of FIG. 15 to be described later. Additionally, AP2 (1202) and STA1 (1200) must also consult or decide whether to perform Co-BF Indirect sounding or Co-BF Direct sounding, and this process may be consulted or decided when STA1 (1200) exchanges probe request / response or (re)association request / response with AP1 (1202).

[0157] An example such as FIG. 12 illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the example. For example, a series of operations may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, each operation may be omitted or replaced with another operation.

[0158] The first CSI transmission method illustrated in Figures 11 and 12 can be referred to as Co-BF Indirect Sounding, and the second CSI transmission method can be referred to as Co-BF Direct Sounding. For example, if a STA, which is limited in transmission power compared to an AP, transmits CSI via direct sounding, the CSI transmission performance may be degraded; therefore, CSI can be transmitted via indirect sounding using an AP with high transmission power. To support the Co-BF Direct Sounding method, AP2 must obtain in advance the security key used to transmit CSI between AP1 and STA1, and conversely, AP1 also needs to obtain in advance the security key used to transmit CSI between AP2 and STA2.

[0159] FIG. 13 illustrates an example of signaling for coordinating the use of Co-BF operations between multiple APs. According to FIG. 13, AP1 (1300) may be a Co-BF negotiation (or agreement, hereinafter referred to as negotiation / agreement) requesting AP, and AP2 (1302) may be a Co-BF negotiation / agreement responding AP.

[0160] AP1 (1300) and AP2 (1302) can perform a procedure to mutually discover that they are APs that support M-AP operation within each other's coverage through an M-AP Discovery passive scanning process or an M-AP Discovery active scanning process (1310). According to the present invention, M-AP operation can be specified as Co-BF.

[0161] The M-AP discovery passive scanning process may refer to a process in which an AP includes information about the M-AP scheme it supports within the beacon messages it periodically broadcasts, thereby enabling an adjacent AP receiving the beacon to know the M-AP scheme supported by the sending AP. M-AP discovery active scanning may be a process in which two adjacent APs exchange mutually supported M-AP schemes and related information through a procedure in which an AP transmits an M-AP discovery request—suggesting information regarding M-AP operation support, authentication requirements, or the need to form a secure channel—by sending a public action frame, UHR action frame, or protected UHR action frame with the adjacent AP designated as the destination address (RA) of the frame, and the receiving AP responds to this request.

[0162] According to process 1310, one of two APs (AP1 (1300)) that are mutually recognized as supporting an M-AP scheme, particularly Co-BF, may transmit a Co-BF negotiation / agreement request frame containing Co-BF negotiation / agreement request element information to AP2 (1302) (1320). The Co-BF negotiation / agreement request element information may be information for M-AP coupling functions and Co-BF specialized negotiation and may include at least one of the following parameters, but the present disclosure is not limited by such technology.

[0163] - AP ID: The AID used by AP1 to refer to AP2. It is the value assigned by AP1 to AP2.

[0164] - Name of the M-AP scheme to be negotiated through this request: Co-BF

[0165] - M-AP agreement ID, which collectively refers to the M-AP scheme and its operational parameters negotiated through the relevant negotiation / agreement process and is used for future status management or operational parameter updates.

[0166] - Specialized negotiation information related to Co-BF, the M-AP scheme intended for negotiation through this request. Details will be provided later.

[0167] The 1320 process can also be used as a Co-BF specific parameter negotiation request.

[0168] AP2 (1302), having received Co-BF negotiation / agreement request element information from AP1 (1300) through the process 1320, can transmit Co-BF negotiation / agreement response element information to AP1 (1300) in response (1330). The Co-BF negotiation / agreement response element information may include at least one of the following information, and the present disclosure is not limited by such technology.

[0169] - AP ID: The AID used by AP2 to refer to AP1. It is the value assigned by AP2 to AP1.

[0170] - Name of the M-AP scheme to be negotiated through the request: In this disclosure, the name of the M-AP scheme may be Co-BF.

[0171] - M-AP agreement ID, which collectively refers to the M-AP scheme negotiated through the relevant negotiation / agreement process and its corresponding operational parameters, and is used for future status management or operational parameter updates: This may be transmitted as the same value as the one provided by AP1 or omitted.

[0172] - Co-BF specific negotiation information, which is the M-AP scheme to be negotiated through the request: In particular, the information included in the response element info may include a status code indicating whether AP2 accepts or approves, rejects, or counter-proposes alternative parameters the negotiation content included in the Co-BF specific negotiation information transmitted by AP1. If AP2 counter-proposes alternative parameters, the alternative parameters may be included in the Co-BF negotiation / agreement response element information.

[0173] The 1330 process can also be used as a Co-BF specific parameter negotiation response.

[0174] AP1, having received a response from AP2 according to process 1330, may optionally send a frame containing Co-BF negotiation / agreement confirm element information to AP2 to indicate whether it has finally approved the negotiation (1340). This process may be omitted. This may explicitly mean that AP1 has received AP2's response and has finally approved the negotiation content. If AP1 does not intend to engage in Co-BF negotiation, the confirm element information may include an indicator indicating rejection of the negotiation content and failure of negotiation. Process 1340 may also be used as a Co-BF specific parameter negotiation confirmation.

[0175] AP2 (1302) may optionally transmit an acknowledgment of the confirm element information content of AP1 (1300) (1350).

[0176] The process of Fig. 13 may correspond to a part of the process of Fig. 8. For example, process 1310 may correspond to process 800 of Fig. 8, and processes 1320 and 1330 may correspond to process 840. When the process of Fig. 13 is performed, the process of Fig. 8, which is not shown in Fig. 13, may be performed together.

[0177] An example such as FIG. 13 illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the example. For example, a series of operations may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, each operation may be omitted or replaced with another operation.

[0178] FIG. 14 is a drawing illustrating an example of an element format constituting a Multi-AP capability advertisement frame in a wireless LAN system according to one embodiment of the present disclosure.

[0179] Referring to FIG. 14, an example of the configuration of an element format for an M-AP operation included in a beacon frame required for advertising M-AP capabilities (e.g., step 1310 of FIG. 13) is illustrated. For example, a beacon frame used by an AP to broadcast information regarding its M-AP capabilities may further include at least one field for an M-AP procedure. In this case, the beacon frame may be based on a beacon frame defined in IEEE 802.11 or may be newly defined.

[0180] Referring again to FIG. 14, the element format for M-AP operation included in the beacon frame may be referred to as the M-AP operation element format. Of course, it is not limited to the above name. In one embodiment, the M-AP operation element format may include at least some of an element ID field (1410), a length field (1420), an element ID extension field (1430), a control field (1440, the control field may refer to one or more control fields), a MAP support field (1450), a protected MAP support field (1460), or a MAP operation parameter field (1470). The Element ID field (1410) contains one octet and may represent a beacon element ID. For example, the Element ID field (1410) may have a value of 255. The Length field (1420) contains one octet and may include a value for the length of the information transmitted through the M-AP operation element format. The Element ID extension field (1430) contains 1 octet and can represent the extension value of element ID 255.

[0181] The Control field (1440) contains one octet and may contain a value related to M-AP control. At this time, the configuration of the sub-fields constituting the Control field (1440) is described in detail below in FIG. 14. The MAP support field (1450) contains one octet and may contain information regarding M-AP schemes supported by the AP transmitting the beacon frame.

[0182] The protected MAP support field (1460) contains one octet and may include information regarding M-AP schemes (or specific features) that require security among the M-AP schemes supported by the AP transmitting the beacon frame. For example, the security requirement for a specific feature may include cases where the security requirement may be applied differently depending on the beam type in the case of C-BF. However, the protected MAP support field (1460) may be omitted depending on the case. In one embodiment, if the MAP support field (1450) contains only information regarding M-AP schemes supported by the AP transmitting the beacon frame, the M-AP operation element format may include the protected MAP support field (1460). In this case, the protected MAP support field (1460) may include information regarding the security requirement for each of the M-AP schemes included in the MAP support field (1450). In another embodiment, if the MAP support field (1450) includes information regarding M-AP schemes supported by the AP transmitting the beacon frame and information regarding the need for security for each M-AP scheme, the M-AP operation element format may not include the protected MAP support field (1460). In yet another embodiment, if the control field (1440) indicates that security is not required, the M-AP operation element format may not include the protected MAP support field (1460).

[0183] Meanwhile, the structure of the format, field names, values ​​indicated by the fields, the number of fields to which meaningful values ​​are assigned, the order of the fields, the number of octets or bits, and whether fields are included in the format, etc., as illustrated in FIG. 14 are merely examples and may be changed differently from the illustrated and described embodiments.

[0184] According to the present disclosure, the following control field (1440) may additionally include at least one of the following control fields.

[0185] - UHR Control field (1442) or UHR Extended Control field

[0186] - Co-BF Control field (1444)

[0187] In addition, the element format for M-AP operation may include the following information.

[0188] - Co-BF Operation Parameter Information (1470)

[0189] The UHR Control field (1442) may include at least one of the following fields. At least one of the Extended control, MAP control, and Co-BF control fields, whose existence is indicated by at least one of the following fields, may include detailed control field(s) related to Co-BF.

[0190] - Extended control field present (1482)

[0191] - MAP control field present (1484)

[0192] - Co-BF control field present (1486)

[0193] - Co-BF Operation Information Element Present (1488)

[0194] Co-BF Control field (1444) and Co-BF Control field Present field (1486): The Co-BF Control field may include fields expressing capabilities related to Co-BF, and some or all of the detailed fields of the Co-BF Control field may be included as sub-fields of other fields. The Co-BF control field may include at least one of the detailed fields below, and the present disclosure is not limited by the description below. Additionally, the detailed fields below that may be included within the Co-BF control field may be included within the Extended control field, the MAP control field, or the Co-BF Operation Parameter field.

[0195] - Co-BF Joint Sounding Supported (1492): If the value is 1, the AP supports Co-BF Joint Sounding.

[0196] - Co-BF Direct Sounding Supported (1494): If the value is 1, the AP supports Co-BF Direct sounding (or Mode 1) functionality. If the value is 0, the AP must operate as a Co-BF indirect sounding (or Mode 2) sequence.

[0197] - Co-BF Indirect Sounding Supported (1496): If the value is 1, the AP supports Co-BF Indirect Sounding (Mode 2). If the value is 0, the AP must operate as a Co-BF direct sounding (Mode 1) sequence.

[0198] - Co-BF Operation Information Element Present (1498) (The Co-BF Operation Information Element Present field may be located in the same location as the Co-BF Joint Sounding Supported (1492), Co-BF Direct Sounding Supported (1494), and Co-BF Indirect Sounding Supported (1496) fields, or may be located in the same location as the Co-BF Operation Information Element Present (1498) within the UHR Control (1440) field.

[0199] At this time, the Co-BF Direct / Indirect Sounding Supported field (1494, 1496) may be replaced with a single field 'Co-BF Sounding Mode' instead of capability, allowing one of the two to be selected and used during Co-BF agreement. Alternatively, instead of the two fields as described above, the support for Direct or Indirect Sounding may be indicated by a single Co-BF Indirect Sounding Supported field. For example, if the field does not exist, only 'Co-BF Indirect Sounding' may be supported, and if the field exists and the value is 0, only 'Co-BF Direct Sounding' may be supported. If the field exists and the value is 1, both may be supported.

[0200] The names and values ​​of the information or fields described above are merely examples, and it is fully possible to replace them with information or fields of different names or apply different values.

[0201] FIG. 15 is a diagram illustrating an example of a Co-BF preparation procedure. FIG. 15 includes a process for obtaining the security keys of neighboring APs and STAs.

[0202] According to FIG. 15, AP1 (1500, Co-BF negotiation / agreement requesting AP) and AP2 (1502, Co-BF negotiation / agreement responding AP) perform a Co-BF Discovery passive scanning (1520) or M-AP Discovery active scanning (1530) process. The above 1520 and 1530 processes may refer to the 1310 process of FIG. 13.

[0203] AP1 (1500) and AP2 (1502) perform a Co-BF negotiation / agreement process (1540). The above 1540 process may refer to the 1330 and 1340 processes of FIG. 13. Subsequently, STA1 (1510) and AP2 (1502) connected to AP1 (1500) can perform a Co-BF key negotiation / agreement process to share the security key between STA1 (1510) and AP1 (1500) with AP2 (1502) (1550). Additionally, STA2 (1512) and AP1 (1500) connected to AP2 (1502) can perform a Co-BF key negotiation / agreement process to share the security key between STA2 (1512) and AP2 (1502) with AP1 (1500) (1560). Through the above 1550 and 1560 processes, the AP can obtain the security key of the STA associated with the other AP and the other AP.

[0204] Afterwards, AP1 (1500), STA1 (1510), AP2 (1502), and STA2 (1512) can perform Co-BF operations (1570). AP1 (1500), STA1 (1510), AP2 (1502), and STA2 (1512) can perform sequential NDP-based sounding or / and joint NDP-based sounding as part of the sounding for Co-BF as shown in FIG. 11 and 12, and can perform Co-BF operations based on the received CSI.

[0205] An example such as FIG. 15 illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the example. For example, a series of operations may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, each operation may be omitted or replaced with another operation.

[0206] Below, we describe Co-BF negotiation / agreement request / response element information that can be included in the 1320 and 1330 processes of Fig. 13. Co-BF negotiation / agreement request / response element information can be transmitted by being included within a public action or UHR (protected) Action frame.

[0207] FIG. 16 is a drawing illustrating an example of a frame (in particular an action frame) used to convey Co-BF negotiation / agreement request element information or / and Co-BF negotiation / agreement response element information (hereinafter Co-BF negotiation / agreement request / response element information).

[0208] According to FIG. 16, Category (1600) may be a value indicating one of Public, Protected Dual of Public, UHR, or Protected UHR. The UHR Action frame or Protected UHR Action frame may be a newly defined Action frame to support the UHR feature defined in 802.11bn.

[0209] The Protected dual of Public Action frame is a frame used for robust STA-STA communication and can transmit the same information as that included in the Public Action frame. Depending on the Public Action field value within the Protected dual of Public Action frame, the field value following the category field within the Protected dual of Public Action frame may vary, and this configuration is similar to the Public Action frame format.

[0210] Depending on the value of the Public Action field included in the Public Action or Protected Public Action frame, the purpose for which the frame is used can be distinguished. The details of the Action frame may be as follows. For example, if the action frame is a UHR Action frame, the UHR action frame format may be as shown in Table 1 below. Order 2 and below may be included in the action details (1610) of FIG. 16.

[0211] OrderMeaning1Category2UHR Action3Dialog Token (omitted depending on UHR Action)4UHR Action field value-dependent field format

[0212] For example, if the action frame is a Protected UHR Action frame, the protected UHR action frame format may be as shown in Table 2 below. Order 2 and below may be included in the action details (1610) of FIG. 16.

[0213] OrderMeaning1Category2Protected UHR Action3Dialog Token (omitted depending on UHR Action)4Protected UHR Action field value-dependent field format

[0214] For example, if the action frame is a Public Action or Protected Dual of Public Action frame, the public action frame format may be as shown in Table 3 below. Order 2 and below may be included in the action details (1610) of FIG. 16.

[0215] OrderMeaning1Category2Public Action3Public Action field value-dependent field format4...

[0216] The value of the Action field (order 2 of Tables 1 to 3 above) located at the very beginning of the Action details (1610) may be, for example, as shown in Table 4 below. According to the present invention, values ​​such as xx7, xx8, xx9, etc., may be used to indicate at least one of Co-BF agreement request, response, and confirmation as the value of the action field, and the present disclosure is not limited to such examples.

[0217] ValueMeaningXx1UHR feature 1 function requestXx2UHR feature 1 function responseXx3UHR feature 1 function notification

[0218] Below, we describe the Co-BF Request / Response Element, which has a value appropriately set for Co-BF agreement in the MAP Operation Parameter included in the Co-BF negotiation / agreement request / response element information. FIG. 17 is a diagram illustrating an example of the MAP operation parameter information format. The MAP operation parameter information of FIG. 17 can be included in the action details (1610) of FIG. 16.

[0219] The MAP operation parameter information of FIG. 17 can be used to indicate operations related to a MAP operation (or M-AP scheme). When used for a general MAP operation, the contents of each field are as follows. The M-AP Management Type field (1700) can indicate one of the following.

[0220] - Establishment of a new M-AP scheme agreement

[0221] ○ M-AP agreement request, response, confirmation, acknowledgment

[0222] - Parameter update for an M-AP scheme agreement:

[0223] ○ M-AP parameter update request / response / confirmation

[0224] - Status change of an M-AP scheme agreement

[0225] ○ The M-AP suspend / resume / teardown ... M-AP scheme field (1710) may refer to the M-AP scheme to be formed through the frame. The M-AP schemes that can be set may include the M-AP scheme described above.

[0226] The M-AP MID (management ID) field (1720) may be an indicator that collectively indicates the operation parameters associated with the M-AP agreement negotiated through the frame. The M-AP MID field may be included in a frame that updates the status (suspension, resumption, termination, etc.) or operation parameters of the M-AP agreement and may be used to update the status or operation parameters of the M-AP agreement corresponding to the value of the M-AP MID field. The M-AP MID may also be called the M-AP agreement ID or MAPC agreement ID.

[0227] The Type-dependent Information field (1730) contains a parameter or element corresponding to the value of the M-AP management type.

[0228] In particular, the M-AP Management type (1700) may have values ​​as shown in Table 5 below, for example, and the present disclosure is not limited to such examples.

[0229] b3b2b1b0Description0000M-AP agreement request0010M-AP agreement response0001M-AP agreement confirmation0011M-AP agreement acknowledgment1000M-AP parameter update request1010M-AP parameter update response1001M-AP parameter update confirmation1101M-AP suspend1110M-AP resume1111M-AP teardown..reserved..

[0230] When the MAP operation parameter information of FIG. 17 is used for Co-BF, the values ​​may be as follows, for example. The M-AP Management Type field (1700) may be b0000, a value indicating an M-AP agreement request, as shown in Table 5, for example. The M-AP scheme field (1710) may be a value indicating Co-BF. The M-AP MID field (1720) may be a value of MID indicating a specific Co-BF agreement. The Type-dependent Information (1730) may be a Co-BF agreement request parameter, for example, when the M-AP Management Type field (1700) is b0000, a value indicating an M-AP agreement request, and may be set according to the value of the M-AP Management Type field (1700). FIG. 18a is a diagram illustrating an example of type-dependent information when the MAP operation parameter information is set for Co-BF. FIG. 18a is an example in which a Type-dependent Information field included in the MAP operation parameter information format within an Action frame is configured as a Co-BF agreement request element field. The Co-BF agreement request element field may be identical to the Co-BF negotiation request element information when the M-AP Management Type field is set to Co-BF negotiation request.

[0231] The Co-BF agreement request element of FIG. 18a is an example in which the MAP operation parameter information of FIG. 17 is configured for the Co-BF agreement request. Here, the M-AP management type field (1700) may be configured as an M-AP agreement request, and the M-AP scheme field (1710) may be configured as Co-BF. At this time, the type-dependent information field (1730) may be configured as a Co-BF agreement request element (1800), and the Co-BF agreement request element may be configured as follows, but is not limited by this description.

[0232] - Co-BF Control (1810)

[0233] - Co-BF non-AP STA Info List (1820)

[0234] Co-BF Control (1810) may include at least one of the Co-BF Joint Sounding Supported field (1830), Co-BF Direct Sounding Support field (1832), Co-BF Indirect Sounding Supported field (1834), and Co-BF non-AP STA info list size (1836), and may also include additional fields.

[0235] The Co-BF sounding operation mode, determined by the values ​​of the Co-BF Joint Sounding Supported field (1830), Co-BF Direct Sounding Support field (1832), and Co-BF Indirect Sounding Supported field (1834) in the Co-BF Control (1810), can be applied collectively to one or more non-AP STAs (that will perform Co-BF operations) included in the Co-BF non-AP STA Info List (1820) that follows. The non-AP STA(s) may be STAs associated with the AP that transmitted the Co-BF agreement request element. For example, if the Co-BF Joint Sounding Supported field (1830) is set to 1, it may mean that joint sounding operations are supported for the STAs indicated by the Co-BF non-AP STA Info list (1820). When the Co-BF Direct Sounding Support field (1832) is set to 1, it may mean that Co-BF Direct sounding operation is supported for the STAs indicated by the Co-BF non-AP STA Info list (1820). In this case, the indicated STAs may perform a security key exchange procedure with an adjacent AP as shown in FIG. 15 to provide CSI directly to an adjacent AP receiving a Co-BF agreement request element, or they may additionally perform a separate security key exchange procedure for Co-BF channel feedback with an associated AP. When the Co-BF Indirect Sounding Supported field (1834) is set to 1, the STAs indicated by the Co-BF non-AP STA Info list (1820) perform Co-BF Indirect sounding. In this case, it may be indicated that one or more sounding methods are supported.

[0236] The AP transmitting the above Co-BF agreement request element can set up the above Co-BF Control (1810) and Co-BF non-AP STA Info List (1820) based on the Co-BF sounding-related capability received from the STAs. A method for receiving the Co-BF sounding-related capability from the STAs will be described later.

[0237] The Co-BF Direct / Indirect Sounding Supported field (1832, 1834) may be replaced with a single field 'Co-BF Sounding Mode' instead of capability, allowing one of the two to be selected and used during Co-BF agreement.

[0238] Alternatively, instead of the two fields as described above, the support for Direct or Indirect Sounding may be indicated by a single Co-BF Indirect Sounding Supported field. For example, if the field does not exist, only 'Co-BF Indirect Sounding' may be supported, and if the field exists and its value is 0, only 'Co-BF Direct Sounding' may be supported. If the field exists and its value is 1, both may be supported.

[0239] The Co-BF non-AP STA Info List (1820) can be configured as follows.

[0240] - AID(1840): The STA AID to which the corresponding Co-BF request content will be applied. There may be as many AID fields as there are Co-BF non-AP STA Info List Sizes.

[0241] FIG. 18a illustrates an example in which a single combination of information about Co-BF sounding and information about the STA(s) to which the Co-BF sounding is applied is included in the Co-BF control (1810), but multiple combinations may also be included. In this case, different Co-BF sounding methods may be applied to each Co-BF non-AP STA Info List.

[0242] FIG. 18b illustrates another example of type-dependent information when MAP operation parameter information is configured for Co-BF. FIG. 18b is an example in which the Type-dependent Information field included in the MAP operation parameter information format within the Action frame is composed of a Co-BF agreement response element field. The Co-BF agreement response element may be identical to the Co-BF negotiation / agreement response element information.

[0243] The Co-BF agreement response element of FIG. 18b is an example in which the MAP operation parameter information of FIG. 17 is configured for the Co-BF agreement response. In this case, the M-AP management type field may be configured as the M-AP agreement response, and the M-AP scheme field may be configured as Co-BF. In this case, the type-dependent information field may be configured as the Co-BF agreement response element (1850), and the Co-BF agreement response element may be configured as follows, but is not limited by this description.

[0244] The Co-BF agreement response element can be configured as follows and is not limited by such technology.

[0245] - Co-BF Control (1860)

[0246] - Co-BF non-AP STA Info List (1862)

[0247] Co-BF Control (1860) may include at least one of the Co-BF Joint Sounding Supported field (1830), Co-BF Direct Sounding Support field (1832), Co-BF Indirect Sounding Supported field (1834), and Co-BF non-AP STA info list size (1836), and may also include additional fields.

[0248] The Co-BF sounding operation mode determined by the values ​​of the Co-BF Joint Sounding Supported field (1870), Co-BF Direct Sounding Support field (1872), and Co-BF Indirect Sounding Supported field (1874) in the Co-BF Control (1860) is applied to one or more non-AP STAs (that will perform Co-BF operations) included in the Co-BF non-AP STA Info List (1862) that follows. The non-AP STA(s) may be STAs associated with the AP that transmitted the Co-BF agreement response element. For example, if the Co-BF Joint Sounding Supported field (1870) is set to 0, the joint sounding operation is not applied to the STAs indicated by the Co-BF non-AP STA Info list (1820), which may mean that the APs transmitting and receiving the Co-BF agreement response element must perform the Co-BF sequential sounding operation for the Co-BF operation. If the Co-BF Direct Sounding Support field (1872) is set to 1, it may mean that the STAs indicated by the Co-BF non-AP STA Info list (1862) can perform Co-BF Direct sounding. In this case, the indicated STAs may perform a security key exchange procedure with an adjacent AP as shown in FIG. 15 to directly provide CSI to an adjacent AP receiving the Co-BF agreement response element, or they may additionally perform a separate security key exchange procedure for Co-BF channel feedback with an associated AP.If the Co-BF Indirect Sounding Supported field (1874) is set to 1, it means that the STAs indicated by the Co-BF non-AP STA Info list (1862) can perform Co-BF Direct sounding.

[0249] According to some embodiments, an AP transmitting a Co-BF agreement response element may respond by selecting one of the following: a Co-BF non-AP STA Info List and either i) a Co-BF sounding method that it supports or ii) a Co-BF sounding method that the requesting AP can extract from the Co-BF Control field included in the Co-BF agreement request element by the AP transmitting the Co-BF agreement request element. For example, if a Co-BF agreement request AP transmits a Co-BF agreement request element indicating that both Co-BF Direct sounding and Co-BF Indirect sounding are possible within the Co-BF agreement request element, the Co-BF agreement response AP may respond by specifying one preferred sounding technique among them, even if the non-AP STA to perform Co-BF within itself and its BSS supports both Co-BF Direct sounding and Co-BF Indirect sounding. In this case, the Co-BF agreement response AP can respond by setting only one of Co-BF Direct Sounding Supported or Co-BF Indirect Sounding Supported to 1.

[0250] The AP transmitting the above Co-BF agreement response element can set up the above Co-BF Control (1860) and Co-BF non-AP STA Info List (1862) based on the Co-BF sounding-related capability received from the STAs. A method for receiving Co-BF sounding-related capability from the STAs will be described later.

[0251] The Co-BF Direct / Indirect Sounding Supported field (1872, 1874) may be replaced with a single field 'Co-BF Sounding Mode' instead of capability, allowing one of the two to be selected and used during Co-BF agreement.

[0252] Alternatively, instead of the two fields as described above, the support for Direct or Indirect Sounding may be indicated by a single Co-BF Indirect Sounding Supported field. For example, if the field does not exist, only 'Co-BF Indirect Sounding' may be supported, and if the field exists and its value is 0, only 'Co-BF Direct Sounding' may be supported. If the field exists and its value is 1, both may be supported.

[0253] The Co-BF non-AP STA Info List (1862) can be configured as follows.

[0254] - AID(1840): The STA AID to which the corresponding Co-BF request content will be applied. There may be as many AID fields as there are Co-BF non-AP STA Info List Sizes.

[0255] FIG. 18b illustrates an example in which a single combination of information about Co-BF sounding and information about the STA(s) to which the Co-BF sounding is applied is included in the Co-BF control (1810), but multiple combinations may be included. In this case, different Co-BF sounding methods may be applied to each Co-BF non-AP STA Info List.

[0256] In addition, if the Co-BF agreement requesting AP (AP1, 1300) and the Co-BF agreement responding AP (AP2, 1302) each indicate that one or more sounding techniques are possible within the Co-BF agreement request element (1320) and the Co-BF agreement response element (1330) respectively (for example, if both APs indicate that Co-BF joint sounding is possible, and Co-BF Direct sounding and Co-BF indirect sounding are possible), the Co-BF agreement requesting AP (1300) may transmit a Co-BF agreement confirm element (1340) specifying one sounding method to the Co-BF agreement responding AP (1302).

[0257] In this case, the Co-BF agreement confirm element (1340) may include the same structure as FIG. 18a or FIG. 18b. For example, if Co-BF Joint Sounding Supported in the Co-BF agreement confirm element (1340) is 1, the two APs must use Co-BF Joint Sounding, and if Co-BF Indirect Sounding Supported is 1, the two APs must perform Co-BF Indirect Sounding. And if Co-BF Indirect Sounding Supported is 1, Co-BF Direct Sounding Supported must have a value of 0, and the opposite case is also true.

[0258] Although not shown in the drawing above, the AP transmitting the Co-BF agreement response element (Co-BF agreement responding AP) may include information instructing to confirm, accept, reject, or suggest to change the information included in the Co-BF agreement request element, in addition to information regarding the sounding performed by the non-AP STA that will perform Co-BF within itself and its BSS. The separate instructions for confirmation, rejection, or suggestion to change may follow the structure of FIG. 18a or FIG. 18b.

[0259] For example, if a specific field within the Co-BF agreement response element indicates approval of the information included in the Co-BF agreement request element, the transmission of the Co-BF agreement confirm element of Fig. 13 may be omitted, and the AP transmitting the Co-BF agreement request element (Co-BF agreement requesting AP) can confirm that it can perform the Co-BF operation through the sounding method it requested. For example, if a specific field within the Co-BF agreement response element indicates rejection of the information included in the Co-BF agreement request element, the transmission of the Co-BF agreement confirm element of Fig. 13 may be omitted, and the Co-BF agreement requesting AP can confirm that the sounding method it requested is unavailable and that the Co-BF agreement negotiation has failed.

[0260] For example, if a specific field within a Co-BF agreement response element instructs a modification of the information included in a Co-BF agreement request element, the Co-BF agreement response element may further include a field instructing a modified sounding method proposed to the Co-BF agreement requesting AP. In this case, the Co-BF agreement requesting AP of FIG. 13 may transmit a Co-BF agreement confirm element to indicate that it approves the sounding method proposed by the Co-BF agreement responding AP, and a Co-BF operation may be performed through the sounding method proposed by the Co-BF agreement responding AP.

[0261] FIG. 19 illustrates an example of a method in which a UHR non-AP STA informs a UHR AP STA of its Co-BF sounding-related capability. This method may be performed before the transmission or reception of Co-BF negotiation / agreement request element information or / and Co-BF negotiation / agreement response element information.

[0262] Notification of the above capabilities is possible through the following frame.

[0263] - Probe request

[0264] - (Re)association request

[0265] The above frames may include elements such as the UHR MAC Capabilities Information field or the UHR Co-BF Capabilities information field, which includes fields related to Co-BF Capabilities.

[0266] Referring to FIG. 19, a non-AP STA (1900) can send a Probe request frame or a (Re)association request frame to an AP STA (1902) (1910). For example, the format of a Probe request or (re)association request frame may include information such as that shown in Table 6 below.

[0267] OrderInformationNotes...<Lastassigned value + 1>UHR CapabilitiesThe UHR Capabilities element is present if dot11UHROptionImplemented is true; otherwise, it is not present<Lastassigned value + 2>Co-BF CapabilitiesThe Co-BF Capabilities element if present if dot11UHROptionImplemented is true; otherwise, it is not present<Lastassigned value + 3>UHR OperationsThe UHR Operation element is present if dot11UHROptionImplemented is true; otherwise; it is not present.

[0268] The AP STA (1902) may transmit a Probe response or (re)association request frame in response to the above frame (1920). At this time, the frame may include Co-BF capabilities and Co-BF operation elements such as those in FIG. 14. The AP STA (1902) may transmit Co-BF sounding related capabilities and the Co-BF sounding mode to be used by sending a Probe response or (re)association response frame in response to the Probe request or (re)association request frame of the UHR non-AP STA. For example, the beacon, Probe response, or (re)association response frame format may include information such as that in Table 6 above. The above flowchart illustrates an exemplary method that can be implemented according to the principles of the present disclosure, and various modifications may be made to the method illustrated in the flowchart in this specification. For example, although illustrated as a series of steps, the various steps in each figure may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, steps may be omitted or replaced with other steps.

[0269] Figure 20 is a diagram illustrating an example of Co-BF capabilities. The Co-BF Capabilities transmitted by the UHR non-AP STA of Table 6 above may include fields such as those shown in Figure 20.

[0270] UHR capabilities include UHR Co-BF capabilities information (2000), and the UHR Co-BF capabilities information (2000) may include Co-BF Support (2010), Co-BF Joint Sounding Support (2012), Co-BF Direct Sounding Support (2014), and Co-BF Indirect Sounding Support (2016). All of the above fields have a length of 1-bit, and unless otherwise noted, a value of 0 indicates that support is not possible, and a value of 1 indicates that support is possible.

[0271] - Co-BF Support (2010): Indicates whether the UHR non-AP STA supports Co-BF.

[0272] - Co-BF Joint Sounding Support (2012): Indicates whether the UHR non-AP STA supports Co-BF Joint Sounding operation. If the Co-BF Support value is 1 and the Co-BF Joint Sounding Support value is 0, the UHR non-AP STA supports only Co-BF sequential sounding.

[0273] - Co-BF Direct Sounding Support (2014): Indicates whether the UHR non-AP STA supports Co-BF Direct Sounding mode. If the value is 1, it indicates that the UHR non-AP STA may have a security key exchange procedure with the adjacent AP (Co-BF participating AP) to directly provide CSI to the adjacent AP, or may additionally perform a separate security key exchange procedure for Co-BF channel feedback with the associated AP.

[0274] - Co-BF Indirect Sounding Support (2016): Indicates whether the UHR non-AP STA supports Co-BF Indirect Sounding mode.

[0275] The above fields may be included within the Co-BF Capabilities field, but are not limited thereto, and may be included and transmitted as detailed fields of any field transmitted within the Probe request or (re)association request frame, such as the UHR Capabilities field or the UHR MAC Capabilities information field.

[0276] The Co-BF sounding-related capability described above can be transmitted by including it in the UHR MAC Capabilities Information or Co-BF Capabilities field within the UHR Capabilities element.

[0277] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present disclosure are possible. Furthermore, each of the above embodiments may be combined and operated together as needed. For example, parts of one embodiment of the present disclosure and another embodiment may be combined to operate AP and STA.

[0278] Meanwhile, the order of description in the drawings explaining the method of the present invention does not necessarily correspond to the order of execution, and the order of precedence may be changed or executed in parallel. Alternatively, the drawings explaining the method of the present invention may omit some components and include only some components to the extent that the essence of the present invention is not compromised.

Claims

1. A method performed by the first AP (access point) of a wireless LAN system, A step of transmitting a first frame containing Co-BF (coordinated beamforming) agreement request element information to a second AP, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support; The method comprises the step of receiving a second frame from the second AP as a response to the first frame, wherein the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support. The above sounding method is characterized by including direct sounding or indirect sounding.

2. In Paragraph 1, A method characterized in that the first frame and the second frame are action frames.

3. In Paragraph 1, A method characterized in that the above Co-BF agreement request element information includes an identifier of one or more first stations (stations, STAs) that perform sounding for Co-BF associated with the first AP, and information indicating a sounding method that can be applied to the one or more first STAs.

4. In Paragraph 1, A method characterized in that the above Co-BF agreement response element information includes an identifier of one or more second stations (station, STA) that perform sounding for Co-BF associated with the second AP, and information indicating a sounding method that can be applied to the one or more second STAs.

5. A method performed by a second AP (access point) of a wireless LAN system, A step of receiving a first frame from a first AP containing Co-BF (coordinated beamforming) agreement request element information, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support; The method comprises the step of transmitting a second frame containing Co-BF agreement response element information to the first AP in response to the first frame, wherein the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support. The above sounding method is characterized by including direct sounding or indirect sounding.

6. In Paragraph 5, A method characterized in that the first frame and the second frame are action frames.

7. In Paragraph 5, A method characterized in that the above Co-BF agreement request element information includes an identifier of one or more first stations (stations, STAs) that perform sounding for Co-BF associated with the first AP, and information indicating a sounding method that can be applied to the one or more first STAs.

8. In Paragraph 5, A method characterized in that the above Co-BF agreement response element information includes an identifier of one or more second stations (station, STA) that perform sounding for Co-BF associated with the second AP, and information indicating a sounding method that can be applied to the one or more second STAs.

9. In the first AP (access point) of a wireless LAN system, Transmitter / receiver; and Transmit a first frame containing Co-BF (coordinated beamforming) agreement request element information to the second AP, wherein the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support. A second frame including Co-BF agreement response element information is received from the second AP in response to the first frame, and the control unit is configured such that the Co-BF agreement response element information includes information indicating a sounding method that the second AP can support. The above sounding method is characterized by including direct sounding or indirect sounding, in the first AP.

10. In Paragraph 9, A first AP characterized in that the first frame and the second frame are action frames.

11. In Paragraph 9, The first AP is characterized in that the above Co-BF agreement request element information includes an identifier of one or more first stations (stations, STAs) that perform sounding for a Co-BF associated with the first AP, and information indicating a sounding method that can be applied to the one or more first STAs.

12. In Paragraph 9, The first AP is characterized in that the above Co-BF agreement response element information includes an identifier of one or more second stations (stations, STAs) that perform sounding for Co-BF associated with the second AP, and information indicating a sounding method that can be applied to the one or more second STAs.

13. In a second AP (access point) of a wireless LAN system, Transmitter / receiver; and A first frame is received from a first AP containing Co-BF (coordinated beamforming) agreement request element information, and the Co-BF agreement request element information includes information indicating a sounding method that the first AP can support. A second frame including Co-BF agreement response element information is transmitted to the first AP in response to the first frame, and the Co-BF agreement response element information includes a control unit configured to include information indicating a sounding method that the second AP can support. The above sounding method is characterized by including direct sounding or indirect sounding, in the second AP.

14. In Paragraph 13, A second AP characterized in that the first frame and the second frame are action frames.

15. In Paragraph 13, The above Co-BF agreement request element information includes information indicating an identifier of one or more first stations (stations, STAs) that perform sounding for Co-BF associated with the first AP, and a sounding method that can be applied to the one or more first STAs, or The second AP is characterized in that the above Co-BF agreement response element information includes an identifier of one or more second stations (stations, STAs) that perform sounding for Co-BF associated with the second AP, and information indicating a sounding method that can be applied to the one or more second STAs.

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