Method and apparatus for multi-access point cooperative sounding in wireless LAN system

Abstract

Disclosed are a method and apparatus for multi-access point (AP) cooperative sounding in a wireless LAN system. The method according to an aspect of the present disclosure may comprise the steps of: receiving, from a second access point (AP) by a first AP, modulation and coding scheme (MCS) information that is recommended; transmitting, to a station (STA) by the first AP, a trigger frame soliciting channel state information from the STA; and receiving, by the first AP, the channel state information from the STA. The MCS information that is recommended may be MCS information that is recommended for channel state information feedback.

Description

Method and device for multi-access point cooperative sounding in a wireless LAN system

[0001] The present disclosure relates to a method and apparatus for cooperative sounding of multiple access points (APs) in a Wireless Local Area Network (WLAN) system.

[0002] New technologies have been introduced for wireless LANs (WLANs) to improve transmission rates, increase bandwidth, enhance reliability, reduce errors, and reduce latency. Among wireless LAN technologies, the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards can be referred to as Wi-Fi. For example, technologies recently introduced to wireless LANs include enhancements for Very High-Throughput (VHT) in the 802.11ac standard and enhancements for High Efficiency (HE) in the IEEE 802.11ax standard.

[0003] To provide an improved wireless communication environment, advanced technologies for Extremely High Throughput (EHT) are being discussed. For example, technologies for Multiple Input Multiple Output (MIMO) supporting increased bandwidth, efficient utilization of multiple bands, and increased spatial streams, as well as technologies for multiple access points (AP) coordination, are being researched. In particular, various technologies are being studied to support traffic with low latency or real-time characteristics. Furthermore, new technologies to support ultra-high reliability (UHR), including improvements or extensions of EHT technology, are being discussed.

[0004] The technical problem of the present disclosure is to provide a method and apparatus for multi-AP cooperative sounding in a wireless LAN system.

[0005] 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 belongs from the description below.

[0006] A method according to one aspect of the present disclosure may include: receiving recommended modulation and coding scheme (MCS) information from a second AP by a first access point (AP); transmitting a trigger frame soliciting channel state information from a station (STA) to the STA by the first AP; and receiving the channel state information from the STA by the first AP. The recommended MCS information may be MCS information recommended for channel state information feedback.

[0007] A method according to a further aspect of the present disclosure may include the step of transmitting recommended modulation and coding scheme (MCS) information to a first AP by a second access point (AP); and the step of receiving channel state information from a station (STA) solicited by a trigger frame from the first AP by the second AP. The recommended MCS information may be MCS information recommended for channel state information feedback.

[0008] According to the present disclosure, a multi-AP cooperative sounding method and device may be provided in a wireless LAN system.

[0009] The effects obtainable from 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 belongs from the description below.

[0010] The accompanying drawings, which are included as part of the detailed description to aid in understanding the present disclosure, provide embodiments of the present disclosure and explain the technical features of the present disclosure together with the detailed description.

[0011] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0012] FIG. 2 is a drawing showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0013] FIG. 3 is a diagram illustrating a link setup process to which the present disclosure can be applied.

[0014] FIG. 4 is a drawing illustrating a backoff process to which the present disclosure may be applied.

[0015] FIG. 5 is a diagram illustrating a CSMA / CA-based frame transmission operation to which the present disclosure may be applied.

[0016] FIG. 6 is a drawing for illustrating an example of a frame structure used in a wireless LAN system to which the present disclosure may be applied.

[0017] FIG. 7 is a drawing illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure may be applied.

[0018] FIG. 8 is a drawing showing an exemplary format of a trigger frame to which the present disclosure can be applied.

[0019] FIG. 9 shows an exemplary format of an NDP notice frame to which the present disclosure may be applied.

[0020] FIG. 10 is a drawing for explaining an example of the operation of a first AP according to the present disclosure.

[0021] FIG. 11 is a drawing for explaining an example of the operation of a second AP according to the present disclosure.

[0022] FIG. 12 is a diagram illustrating an example of a multi-AP cooperative sounding process according to the present disclosure.

[0023] FIG. 13 is a diagram showing exemplary formats of the STA information field of an NDPA frame according to the present disclosure.

[0024] Hereinafter, preferred embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description disclosed below, together with the accompanying drawings, is intended to describe exemplary embodiments of the present disclosure and is not intended to represent the only embodiment in which the present disclosure may be practiced. The following detailed description includes specific details to provide a complete understanding of the present disclosure. However, those skilled in the art will know that the present disclosure may be practiced without such specific details.

[0025] In some cases, to avoid obscuring the concept of the present disclosure, known structures and devices may be omitted or illustrated in the form of a block diagram focusing on the core functions of each structure and device.

[0026] In the present disclosure, when a component is described as being “connected,” “combined,” or “joined” with another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, in the present disclosure, the terms “comprising” or “having” specify the presence of the mentioned features, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, actions, elements, components, and / or groups thereof.

[0027] In the present disclosure, terms such as "first," "second," etc. are used solely for the purpose of distinguishing one component from another and are not used to limit the components, nor do they limit the order or importance of the components unless specifically stated otherwise. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and likewise, a second component in one embodiment may be referred to as a first component in another embodiment.

[0028] The terms used in this disclosure are for the description of specific embodiments and are not intended to limit the claims. As used in the description of embodiments and in the appended claims, the singular form is intended to include the plural form unless the context clearly indicates otherwise. The term "and / or" as used in this disclosure may refer to any one of the related enumerated items, or refers to and includes any and all possible combinations of two or more of them. Additionally, the " / " between words in this disclosure has the same meaning as "and / or" unless otherwise noted.

[0029] The embodiments of the present disclosure may be applied to various wireless communication systems. For example, the embodiments of the present disclosure may be applied to wireless LAN systems. For example, the embodiments of the present disclosure may be applied to wireless LANs based on IEEE 802.11a / g / n / ac / ax / be standards. Furthermore, the embodiments of the present disclosure may be applied to wireless LANs based on newly proposed IEEE 802.11bn (or UHR) standards. Additionally, the embodiments of the present disclosure may be applied to wireless LANs based on next-generation standards following IEEE 802.11bn. Furthermore, the embodiments of the present disclosure may be applied to cellular wireless communication systems. For example, they may be applied to cellular wireless communication systems based on LTE (Long Term Evolution) series technologies and 5G NR (New Radio) series technologies of 3GPP (3rd Generation Partnership Project) standards.

[0030] The following describes the technical features to which the examples of the present disclosure may be applied.

[0031] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0032] The first device (100) and the second device (200) exemplified in FIG. 1 may be replaced with various terms such as terminal, wireless device, WTRU (Wireless Transmit Receive Unit), UE (User Equipment), MS (Mobile Station), UT (user terminal), MSS (Mobile Subscriber Station), MSS (Mobile Subscriber Unit), SS (Subscriber Station), AMS (Advanced Mobile Station), WT (Wireless terminal), or simply user. Additionally, the first device (100) and the second device (200) may be replaced with various terms such as access point (AP), base station (BS), fixed station, Node B, base transceiver system (BTS), network, artificial intelligence (AI) system, road side unit (RSU), repeater, router, relay, gateway, etc.

[0033] The device (100, 200) exemplified in FIG. 1 may be referred to as a station (STA). For example, the device (100, 200) exemplified in FIG. 1 may be referred to by various terms such as a transmitting device, a receiving device, a transmitting STA, or a receiving STA. For example, the STA (110, 200) may perform the role of an access point (AP) or a non-AP. That is, in the present disclosure, the STA (110, 200) may perform the functions of an AP and / or a non-AP. If the STA (110, 200) performs the AP function, it may simply be referred to as an AP, and if the STA (110, 200) performs the non-AP function, it may simply be referred to as a STA. Additionally, in the present disclosure, the AP may also be indicated as an AP STA.

[0034] Referring to FIG. 1, the first device (100) and the second device (200) can transmit and receive wireless signals through various wireless LAN technologies (e.g., IEEE 802.11 series). The first device (100) and the second device (200) may include interfaces for the medium access control (MAC) layer and the physical layer (PHY) that comply with the specifications of the IEEE 802.11 standard.

[0035] In addition, the first device (100) and the second device (200) may additionally support various communication standards other than wireless LAN technology (e.g., 3GPP LTE series, 5G NR series standards, etc.). In addition, the device of the present disclosure may be implemented as various devices such as mobile phones, vehicles, personal computers, AR (Augmented Reality) equipment, VR (Virtual Reality) equipment, etc. Furthermore, the STA of the present specification may support various communication services such as voice calls, video calls, data communication, autonomous driving, MTC (Machine-Type Communication), M2M (Machine-to-Machine), D2D (Device-to-Device), and IoT (Internet-of-Things).

[0036] The first device (100) includes one or more processors (102) and one or more memories (104), and may additionally include one or more transceivers (106) and / or one or more antennas (108). The processor (102) controls the memory (104) and / or transceivers (106) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (102) may process information within the memory (104) to generate a first information / signal and then transmit a wireless signal containing the first information / signal through the transceiver (106). Additionally, the processor (102) may receive a wireless signal containing a second information / signal through the transceiver (106) and then store information obtained from the signal processing of the second information / signal in the memory (104). Memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, memory (104) may store software code including instructions for performing some or all of the processes controlled by the processor (102) or for performing the descriptions, functions, procedures, proposals, methods, and / or sequences of operation disclosed in this disclosure. Here, the processor (102) and memory (104) may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). A transceiver (106) may be connected to the processor (102) and may transmit and / or receive wireless signals through one or more antennas (108). The transceiver (106) may include a transmitter and / or receiver. The transceiver (106) may be combined with an RF (Radio Frequency) unit. In the present disclosure, the device may refer to a communication modem / circuit / chip.

[0037] The second device (200) includes one or more processors (202) and one or more memories (204), and may additionally include one or more transceivers (206) and / or one or more antennas (208). The processor (202) controls the memory (204) and / or transceivers (206) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (202) may process information within the memory (204) to generate a third information / signal and then transmit a wireless signal containing the third information / signal through the transceiver (206). Additionally, the processor (202) may receive a wireless signal containing a fourth information / signal through the transceiver (206) and then store information obtained from the signal processing of the fourth information / signal in the memory (204). The memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, the memory (204) may store software code containing instructions for performing some or all of the processes controlled by the processor (202) or for performing the descriptions, functions, procedures, proposals, methods, and / or sequences of operation disclosed in this disclosure. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). The transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals through one or more antennas (208). The transceiver (206) may include a transmitter and / or receiver. The transceiver (206) may be used in combination with an RF unit. In the present disclosure, the device may refer to a communication modem / circuit / chip.

[0038] Hereinafter, hardware elements of the device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as PHY, MAC). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and / or Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts of operation disclosed in this disclosure. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts of operation disclosed in this disclosure. One or more processors (102, 202) may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this disclosure and provide it to one or more transceivers (106, 206). One or more processors (102, 202) may receive a signal (e.g., a baseband signal) from one or more transceivers (106, 206) and may obtain a PDU, SDU, message, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this disclosure.

[0039] One or more processors (102, 202) may be referred to as a controller, microcontroller, microprocessor, or microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. Firmware or software configured to perform the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure may be included in one or more processors (102, 202) or stored in one or more memories (104, 204) and driven by one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure may be implemented using firmware or software in the form of code, instructions, and / or sets of instructions.

[0040] One or more memories (104, 204) may be connected to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. One or more memories (104, 204) may be composed of ROM, RAM, EPROM, flash memory, hard drive, registers, cache memory, computer read storage media, and / or combinations thereof. One or more memories (104, 204) may be located inside and / or outside of one or more processors (102, 202). Additionally, one or more memories (104, 204) may be connected to one or more processors (102, 202) through various technologies such as wired or wireless connections.

[0041] One or more transceivers (106, 206) may transmit user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or operation flowcharts, etc., of the present disclosure to one or more other devices. One or more transceivers (106, 206) may receive user data, control information, wireless signals / channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and / or operation flowcharts, etc., disclosed in the present disclosure from one or more other devices. For example, one or more transceivers (106, 206) may be connected to one or more processors (102, 202) and may transmit and receive wireless signals. For example, one or more processors (102, 202) may control one or more transceivers (106, 206) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (106, 206) may be connected to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, wireless signals / channels, etc., as described in the descriptions, functions, procedures, proposals, methods, and / or flowcharts of operation disclosed in this disclosure through one or more antennas (108, 208). In this disclosure, one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). One or more transceivers (106, 206) can convert the received wireless signal / channel, etc. from an RF band signal to a baseband signal in order to process the received user data, control information, wireless signal / channel, etc. using one or more processors (102, 202).One or more transceivers (106, 206) can convert user data, control information, wireless signals / channels, etc. processed using one or more processors (102, 202) from baseband signals to RF band signals. To this end, one or more transceivers (106, 206) may include (analog) oscillators and / or filters.

[0042] For example, one of the STAs (100, 200) may perform the intended operation of an AP, and the other of the STAs (100, 200) may perform the intended operation of a non-AP STA. For example, the transceiver (106, 206) of FIG. 1 may perform the operation of transmitting and receiving signals (e.g., packets or PPDU (Physical Layer Protocol Data Unit) according to IEEE 802.11a / b / g / n / ac / ax / be / bn, etc.). Additionally, the operation of generating transmission and reception signals or performing data processing or calculations in advance for transmission and reception signals by various STAs in the present disclosure may be performed by the processor (102, 202) of FIG. 1. For example, an example of an operation to generate a transmission and reception signal or to perform data processing or operations in advance for a transmission and reception signal may include: 1) an operation to determine / acquire / configure / operate / decode / encode bit information of fields (SIG (signal), STF (short training field), LTF (long training field), Data, etc.) included in the PPDU; 2) an operation to determine / configure / acquire time resources or frequency resources (e.g., subcarrier resources) used for fields (SIG, STF, LTF, Data, etc.) included in the PPDU; 3) an operation to determine / configure / acquire specific sequences (e.g., pilot sequence, STF / LTF sequence, extra sequence applied to SIG) used for fields (SIG, STF, LTF, Data, etc.) included in the PPDU; 4) power control operations and / or power saving operations applied to the STA; and 5) operations related to determining / acquiring / configuring / operating / decoding / encoding of an ACK signal. In addition, in the following example, various information (e.g., information related to fields, subfields, control fields, parameters, power, etc.) used by various STAs for determining / acquiring / configuring / calculating / decoding / encoding of transmission and reception signals can be stored in the memory (104, 204) of FIG. 1.

[0043] In the following, the downlink (DL) refers to a link for communication from an AP STA to a non-AP STA, and downlink PPDUs, packets, signals, etc., can be transmitted and received through the downlink. In downlink communication, the transmitter may be part of the AP STA, and the receiver may be part of the non-AP STA. The uplink (UL) refers to a link for communication from a non-AP STA to an AP STA, and uplink PPDUs, packets, signals, etc., can be transmitted and received through the uplink. In uplink communication, the transmitter may be part of the non-AP STA, and the receiver may be part of the AP STA.

[0044] FIG. 2 is a drawing showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0045] The structure of a wireless LAN system can be composed of multiple components. Through the interaction of multiple components, a wireless LAN that supports STA mobility transparent to the upper layer can be provided. A Basic Service Set (BSS) corresponds to the basic building block of a wireless LAN. Figure 2 exemplarily illustrates the existence of two BSSs (BSS1 and BSS2) and the inclusion of two STAs as members of each BSS (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2). In Figure 2, the ellipse representing the BSS can also be understood as representing the coverage area where the STAs included in the corresponding BSS maintain communication. This area can be referred to as a Basic Service Area (BSA). If a STA moves outside the BSA, it becomes unable to communicate directly with other STAs within that BSA.

[0046] Excluding the DS illustrated in Fig. 2, the most basic type of BSS in a wireless LAN is the Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For instance, assuming other components are omitted, a BSS1 composed of only STA1 and STA2, or a BSS2 composed of only STA3 and STA4, can each be considered a representative example of an IBSS. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, this type of wireless LAN is not configured through pre-planning but can be configured when a LAN is needed, and this can be referred to as an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. In other words, in an IBSS, STAs are managed in a distributed manner. In IBSS, all STAs can be mobile STAs, and since connections to distributed systems (DS) are not allowed, they form a self-contained network.

[0047] The membership of an STA in a BSS can be dynamically changed by the STA being turned on or off, or by the STA entering or leaving the BSS area. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services of the BSS infrastructure, an STA must be associated with the BSS. This association can be configured dynamically and may include the use of a Distribution System Service (DSS).

[0048] In a wireless LAN, the direct STA-to-STA distance may be limited by PHY performance. In some cases, this distance limit may be sufficient, but in others, communication between STAs over longer distances may be required. To support extended coverage, a distributed system (DS) may be configured.

[0049] DS refers to a structure in which BSSs are interconnected. Specifically, as shown in FIG. 2, a BSS may exist as a component in an extended form of a network composed of multiple BSSs. DS is a logical concept and can be specified by the characteristics of the Distributed System Medium (DSM). In this regard, the Wireless Medium (WM) and the DSM can be logically distinguished. Each logical medium is used for a different purpose and is utilized by different components. These media are not limited to being identical or different. The flexibility of the wireless LAN structure (DS structure or other network structure) can be explained by the fact that multiple media are logically distinct in this way. That is, the wireless LAN structure can be implemented in various ways, and the corresponding wireless LAN structure can be specified independently by the physical characteristics of each implementation.

[0050] DS can support mobile devices by providing seamless integration of multiple BSSs and providing logical services necessary for handling addresses to destinations. Additionally, DS may include a component called a portal that acts as a bridge for connecting the wireless LAN with another network (e.g., IEEE 802.X).

[0051] An AP refers to an entity that enables access to a DS via a WM for combined non-AP STAs and also possesses the functionality of an STA. Data movement between a BSS and a DS can be performed through the AP. For example, STA2 and STA3 shown in FIG. 2 possess the functionality of an STA and provide the ability for combined non-AP STAs (STA1 and STA4) to access a DS. Furthermore, since all APs fundamentally correspond to STAs, all APs are addressable entities. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM do not necessarily have to be the same. A BSS composed of an AP and one or more STAs can be referred to as an infrastructure BSS.

[0052] Data transmitted from one of the STA(s) coupled to the AP to the STA address of the AP can always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity. Additionally, if the controlled port is authenticated, the transmitted data (or frame) can be forwarded to the DS.

[0053] In addition to the structure of the aforementioned DS, an Extended Service Set (ESS) may be configured to provide wider coverage.

[0054] An ESS refers to a network of arbitrary size and complexity composed of DSs and BSSs. An ESS can correspond to a set of BSSs connected to a single DS. However, an ESS does not contain a DS. An ESS network is characterized by appearing as an IBSS at the Logical Link Control (LLC) layer. STAs included in an ESS can communicate with each other, and mobile STAs can move from one BSS to another (within the same ESS) transparently to the LLC. APs included in a single ESS can have the same Service Set Identification (SSID). The SSID is distinct from the BSSID, which is the identifier for the BSS.

[0055] In wireless LAN systems, no assumptions are made regarding the relative physical locations of BSSs, and all of the following forms are possible. BSSs may partially overlap, which is a form commonly used to provide continuous coverage. Additionally, BSSs may not be physically connected, and logically, there is no limit to the distance between BSSs. Furthermore, BSSs may be located in the same physical location, which can be used to provide redundancy. Also, one (or more) IBSS or ESS networks may physically exist in the same space as one (or more) ESS networks. This may apply to ESS network forms such as when an ad-hoc network operates at a location where an ESS network exists, when wireless networks that physically overlap are configured by different organizations, or when two or more different access and security policies are required at the same location.

[0056] FIG. 3 is a diagram illustrating a link setup process to which the present disclosure can be applied.

[0057] 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 processes of discovery, authentication, association, and security setup in the link setup process can be collectively referred to as the association process.

[0058] In step S310, the STA may perform a network discovery operation. The network discovery operation may include the STA's scanning operation. That is, in order for the STA to access a network, it must find a network it can join. Before joining a wireless network, the STA must identify a compatible network, and the process of identifying networks existing in a specific area is called scanning.

[0059] Scanning methods include active scanning and passive scanning. Figure 3 illustrates a network discovery operation that includes an active scanning process as an example. In active scanning, the STA performing the scanning moves between channels to search for nearby APs, transmits a probe request frame, and waits for a response. The responder transmits a probe response frame as a response to the probe request frame to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted a beacon frame from the BSS of the channel being scanned. In a BSS, the AP becomes the responder because it transmits the beacon frame; however, in an IBSS, the responder is not constant because STAs within the IBSS take turns transmitting the beacon frame. For example, an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 can store BSS-related information included in the received probe response frame and move to the next channel (e.g., channel 2) to perform scanning in the same way (i.e., transmit and receive probe request / response on channel 2).

[0060] Although not illustrated in FIG. 3, the scanning operation may be performed using a passive scanning method. In passive scanning, the STA performing the scanning waits for a beacon frame while switching between channels. A beacon frame is one of the management frames defined in IEEE 802.11, which is periodically transmitted to announce the presence of a wireless network and to allow the scanning STA to find the wireless network and join it. In a BSS, the AP performs the role of periodically transmitting beacon frames, and in an IBSS, the STAs within the IBSS take turns transmitting beacon frames. When the scanning STA receives a beacon frame, it stores the information about the BSS included in the beacon frame and records the beacon frame information in each channel while moving to another channel. The STA that receives the beacon frame stores the BSS-related information included in the received beacon frame, moves to the next channel, and can perform scanning in the next channel in the same way. When comparing active scanning and passive scanning, active scanning has the advantage of lower delay and power consumption than passive scanning.

[0061] After the STA discovers the network, an authentication process may be performed in step S320. This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation in step S340 described later.

[0062] The authentication process involves the STA sending an authentication request frame to the AP, and the AP sending an authentication response frame to the STA in response. The authentication frame used in the authentication request / response corresponds to a management frame.

[0063] The authentication frame may include information regarding the authentication algorithm number, authentication transaction sequence number, status code, challenge text, Robust Security Network (RSN), Finite Cyclic Group, etc. These are some examples of information that may be included in the authentication request / response frame, and they may be replaced with other information or additional information may be included.

[0064] The STA can send an authentication request frame to the AP. Based on the information contained in the received authentication request frame, the AP can determine whether to allow authentication for the STA. The AP can provide the result of the authentication process to the STA through an authentication response frame.

[0065] After the STA is successfully authenticated, the association process can be performed in step S330. The association process includes the STA transmitting an association request frame to the AP, and in response, the AP transmitting an association response frame to the STA.

[0066] For example, the association request frame may include information regarding various capabilities, beacon listen interval, service set identifier (SSID), supported rates, supported channels, RSN, mobility domain, supported operating classes, Traffic Indication Map Broadcast request, interworking service capabilities, etc. For example, the association response frame may include information regarding various capabilities, status code, Association ID (AID), supported rates, Enhanced Distributed Channel Access (EDCA) parameter set, Received Channel Power Indicator (RCPI), Received Signal to Noise Indicator (RSNI), mobility domain, timeout interval (e.g., association comeback time), overlapping BSS scan parameters, TIM broadcast response, Quality of Service (QoS) map, etc. These are some examples of information that may be included in a combined request / response frame, and may be replaced with other information or additional information may be included.

[0067] After the STA is successfully joined to the network, a security setup process can be performed in step S340. The security setup process in step S340 may be described as an authentication process through RSNA (Robust Security Network Association) requests / responses, and the authentication process in step S320 may be referred to as the first authentication process, and the security setup process in step S340 may simply be referred to as the authentication process.

[0068] The security setup process of step S340 may include, for example, a private key setup process through a 4-way handshake via an EAPOL (Extensible Authentication Protocol over LAN) frame. Additionally, the security setup process may be performed according to a security method not defined in the IEEE 802.11 standard.

[0069] FIG. 4 is a drawing illustrating a backoff process to which the present disclosure may be applied.

[0070] In wireless LAN systems, the basic access mechanism for MAC (Medium Access Control) is the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism. The CSMA / CA mechanism is also known as the Distributed Coordination Function (DCF) of IEEE 802.11 MAC, and it basically employs a "listen before talk" access mechanism. According to this type of access mechanism, the AP and / or STA may perform Clear Channel Assessment (CCA) to sense the wireless channel or medium for a predetermined time interval (e.g., DIFS (DCF Inter-Frame Space)) before starting transmission. If the sensing result determines that the medium is in an idle status, it starts transmitting a frame through that medium. On the other hand, if the medium is detected to be occupied or busy, the AP and / or STA may not start its own transmission but wait by setting a delay period for medium access (e.g., a random backoff period) before attempting to transmit a frame. By applying a random backoff period, multiple STAs are expected to attempt to transmit frames after waiting for different periods of time, thereby minimizing collisions.

[0071] In addition, the IEEE 802.11 MAC protocol provides a Hybrid Coordination Function (HCF). The HCF is based on the aforementioned Point Coordination Function (PCF). The PCF is a polling-based synchronous access method that periodically polls to ensure all receiving APs and / or STAs can receive data frames. Furthermore, the HCF includes Enhanced Distributed Channel Access (EDCA) and Controlled Channel Access (HCCA). EDCA is a contention-based access method for a provider to offer data frames to multiple users, while HCCA uses a non-contention-based channel access method utilizing a polling mechanism. Additionally, the HCF includes a media access mechanism to improve the Quality of Service (QoS) of the wireless LAN and can transmit QoS data during both the Contention Period (CP) and the Contention-Free Period (CFP).

[0072] Referring to FIG. 4, the operation based on the random backoff period is described. When a medium in an occupied / busy state changes to an idle state, multiple STAs may attempt to transmit data (or frames). As a measure to minimize collisions, each STA may select a random backoff count and attempt transmission after waiting for the corresponding slot time. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​in the range from 0 to CW. Here, CW is the Contention Window parameter value. The CW parameter is given an initial value of CWmin, but in the case of transmission failure (e.g., failure to receive an ACK for a transmitted frame), it may take a value twice that amount. When the CW parameter value becomes CWmax, data transmission may be attempted while maintaining the CWmax value until data transmission is successful; if data transmission is successful, it is reset to the CWmin value. The values ​​of CW, CWmin, and CWmax are 2 n It is desirable to set it to -1 (n=0, 1, 2, ...).

[0073] When the random backoff process begins, the STA continues to monitor the media while counting down the backoff slots according to the determined backoff count value. When the media is monitored as occupied, it stops the countdown and waits, and when the media becomes idle, it resumes the remaining countdown.

[0074] In the example of Fig. 4, when a packet to be transmitted arrives at the MAC of STA3, STA3 confirms that the medium is idle for DIFS and can immediately transmit the frame. The remaining STAs monitor whether the medium is occupied or busy and wait. Meanwhile, data to be transmitted may also arise from each of STA1, STA2, and STA5, and each STA can perform a countdown of the backoff slot according to a random backoff count value selected by each after waiting for DIFS when the medium is monitored to be idle. Assume the case where STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value. That is, this exemplifies a case where, at the point when STA2 finishes the backoff count and starts transmitting the frame, the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1. STA1 and STA5 pause the countdown briefly and wait while STA2 occupies the medium. When STA2's possession ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the paused backoff count. That is, they can start transmitting a frame after counting down the remaining backoff slots corresponding to the remaining backoff time. Since STA5's remaining backoff time was shorter than STA1's, STA5 starts transmitting the frame. While STA2 is occupying the medium, data to be transmitted may also be generated by STA4. From STA4's perspective, when the medium becomes idle, it waits for DIFS, performs a countdown based on a random backoff count value selected by itself, and can start transmitting a frame. The example in Figure 4 illustrates a case where STA5's remaining backoff time happens to match STA4's random backoff count value; in this case, a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receives an ACK, resulting in a failure to transmit data.In this case, STA4 and STA5 can double the CW value, select a random backoff count value, and perform a countdown. STA1 waits while the medium is occupied due to transmission by STA4 and STA5, and when the medium becomes idle, it waits for DIFS, and then can start transmitting frames after the remaining backoff time has passed.

[0075] As shown in the example in Fig. 4, a data frame is a frame used for transmitting data that is forwarded to an upper layer, and can be transmitted after a backoff performed after the elapsed time of DIFS from when the medium becomes idle. Additionally, a management frame is a frame used for exchanging management information that is not forwarded to an upper layer, and is transmitted after a backoff performed after the elapsed time of an IFS such as DIFS or PIFS (Point coordination function IFS). Subtypes of management frames include Beacon, Association request / response, re-association request / response, probe request / response, and authentication request / response. A control frame is a frame used to control access to the medium. Subtype frames of control frames include RTS (Request-To-Send), CTS (Clear-To-Send), ACK (Acknowledgment), PS-Poll (Power Save-Poll), Block ACK (BlockAck), Block ACK Request (BlockACKReq), NDP Announcement (null data packet announcement), and Trigger. If a control frame is not an acknowledgment frame of a previous frame, it is transmitted after a backoff performed after the elapsed DIFS; if it is an acknowledgment frame of a previous frame, it is transmitted after the elapsed SIFS (short IFS) without a backoff. The type and subtype of a frame can be identified by the type field and subtype field within the Frame Control (FC) field.

[0076] A QoS (Quality of Service) STA can transmit a frame after backoff, which is performed after the passage of the arbitration IFS (AIFS) for the access category (AC) to which the frame belongs, i.e., AIFS[i] (where i is a value determined by the AC). Here, the frame for which AIFS[i] can be used can be a data frame or a management frame, and can also be a control frame rather than a response frame.

[0077] FIG. 5 is a diagram illustrating a CSMA / CA-based frame transmission operation to which the present disclosure may be applied.

[0078] As previously mentioned, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, where the STA directly senses the medium. Virtual carrier sensing is intended to mitigate problems that may occur in medium access, such as the hidden node problem. For virtual carrier sensing, the STA's MAC can utilize the Network Allocation Vector (NAV). The NAV is a value that indicates to other STAs the time remaining until the medium becomes available, provided that the STA currently using or authorized to use the medium is using it. Therefore, the value set as the NAV corresponds to the period during which the medium is scheduled to be used by the STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during that period. For example, the NAV can be set based on the value of the "duration" field in the frame's MAC header.

[0079] In the example of FIG. 5, it is assumed that STA1 intends to transmit data to STA2, and STA3 is located in a position where it can overhear part or all of the frames transmitted and received between STA1 and STA2.

[0080] In order to reduce the possibility of collisions between multiple STAs in a CSMA / CA-based frame transmission operation, a mechanism utilizing RTS / CTS frames may be applied. In the example of FIG. 5, while STA1 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA1 may be a hidden node to STA3. Alternatively, in the example of FIG. 5, while STA2 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA2 may be a hidden node to STA3. By exchanging RTS / CTS frames before performing data transmission and reception between STA1 and STA2, it is possible to prevent a STA outside the transmission range of either STA1 or STA2, or a STA outside the carrier sensing range for transmission from STA1 or STA3, from attempting to occupy the channel during data transmission and reception between STA1 and STA2.

[0081] Specifically, STA1 can determine whether the channel is in use through carrier sensing. In terms of physical carrier sensing, STA1 can determine the channel occupancy idle state based on the energy magnitude or signal correlation detected in the channel. Additionally, in terms of virtual carrier sensing, STA1 can determine the channel occupancy state using a NAV (network allocation vector) timer.

[0082] If the channel is idle during DIFS, STA1 can send an RTS frame to STA2 after performing backoff. If STA2 receives the RTS frame, it can send a CTS frame to STA1 as a response to the RTS frame after SIFS.

[0083] If STA3 cannot overhear a CTS frame from STA2 but can overhear an RTS frame from STA1, STA3 can set a NAV timer for the duration of subsequently transmitted frames (e.g., SIFS + CTS frame + SIFS + data frame + SIFS + ACK frame) using the duration information included in the RTS frame. Alternatively, if STA3 cannot overhear an RTS frame from STA1 but can overhear a CTS frame from STA2, STA3 can set a NAV timer for the duration of subsequently transmitted frames (e.g., SIFS + data frame + SIFS + ACK frame) using the duration information included in the CTS frame. That is, if STA3 can overhear one or more of the RTS or CTS frames from one or more of STA1 or STA2, it can set a NAV accordingly. If STA3 receives a new frame before the NAV timer expires, it can update the NAV timer using the duration information contained in the new frame. STA3 does not attempt channel access until the NAV timer expires.

[0084] If STA1 receives a CTS frame from STA2, it may transmit a data frame to STA2 after SIFS from the time the reception of the CTS frame is completed. If STA2 successfully receives the data frame, it may transmit an ACK frame to STA1 as an acknowledgment to the data frame after SIFS. STA3 may determine whether the channel is in use through carrier sensing when the NAV timer expires. If STA3 determines that the channel is not in use by another terminal during DIFS from the time the NAV timer expires, it may attempt channel access after a contention window (CW) based on random backoff has passed.

[0085] FIG. 6 is a drawing for illustrating an example of a frame structure used in a wireless LAN system to which the present disclosure may be applied.

[0086] Based on instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare the MPDU (MAC PDU) to be transmitted. For example, upon receiving an instruction from the MAC layer requesting the start of transmission, the PHY layer switches to transmit mode and can construct the information provided by the MAC layer (e.g., data) into a frame for transmission. Additionally, if the PHY layer detects a valid preamble of a received frame, it monitors the preamble header and sends an instruction to the MAC layer indicating the start of reception.

[0087] As such, information transmission and reception in wireless LAN systems are carried out in the form of frames, and for this purpose, the Physical Layer Protocol Data Unit (PPDU) format is defined.

[0088] A basic PPDU may include a Short Training Field (STF), a Long Training Field (LTF), a Signal (SIGNAL) field, and a Data field. The most basic (e.g., the non-HT (High Throughput)) PPDU format illustrated in FIG. 7 may consist only of Legacy-STF (Legacy-STF), Legacy-LTF (Legacy-LTF), Legacy-SIG (Legacy-SIG) fields and a Data field. In addition, depending on the type of PPDU format (e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (Very High Throughput) PPDU, etc.), additional (or other types of) RL-SIG, U-SIG, non-legacy SIG fields, non-legacy STF, non-legacy LTF, (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) may be included between the L-SIG field and the data field. More specific details will be described later with reference to FIG. 7.

[0089] STF is a signal for signal detection, AGC (Automatic Gain Control), diversity selection, and precise time synchronization, while LTF is a signal for channel estimation and frequency error estimation. STF and LTF can be considered signals for synchronization and channel estimation in the OFDM physical layer.

[0090] The SIG field may contain various information related to the transmission and reception of the PPDU. For example, the L-SIG field consists of 24 bits and may include a 4-bit Rate field, a 1-bit Reserved bit, a 12-bit Length field, a 1-bit Parity field, and a 6-bit Tail field. The RATE field may contain information regarding the modulation and coding rates of the data. For example, the 12-bit Length field may contain information regarding the length or time duration of the PPDU. For example, the value of the 12-bit Length field may be determined based on the type of the PPDU. For example, for non-HT, HT, VHT, or EHT PPDUs, the value of the Length field may be determined as a multiple of 3. For example, for HE PPDUs, the value of the Length field may be determined as a multiple of 3 + 1 or a multiple of 3 + 2.

[0091] The data field may include a SERVICE field, a PSDU (Physical layer Service Data Unit), and PPDU TAIL bits, and may also include padding bits if necessary. Some bits of the SERVICE field may be used for synchronization of the descrambler at the receiver. The PSDU corresponds to a MAC PDU defined at the MAC layer and may contain data generated or used by the upper layer. The PPDU TAIL bits may be used to return the encoder to a 0 state. Padding bits may be used to adjust the length of the data field to a predetermined unit.

[0092] A MAC PDU is defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a Frame Check Sequence (FCS). A MAC frame is composed of a MAC PDU and can be transmitted or received through the PSDU of the data portion in the PPDU format.

[0093] The MAC header includes a Frame Control field, a Duration / ID field, an Address field, etc. The Frame Control field may contain control information necessary for transmitting or receiving frames. The Duration / ID field may be set as the time for transmitting the corresponding frame. Address subfields may indicate the frame's receiver address, transmitter address, destination address, and source address, and some address subfields may be omitted. Specific details regarding each subfield of the MAC header, including Sequence Control, QoS Control, and HT Control subfields, can be found in the IEEE 802.11 standard document.

[0094] The Null-Data PPDU (NDP) format refers to a PPDU format that does not include a data field. In other words, NDP is a frame format that includes the PPDU preamble (i.e., L-STF, L-LTF, L-SIG fields, and additionally, non-legacy SIG, non-legacy STF, and non-legacy LTF if present) from a standard PPDU format, but excludes the remaining parts (i.e., the data field).

[0095] FIG. 7 is a drawing illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure may be applied.

[0096] Various forms of PPDU have been used in standards such as IEEE 802.11a / g / n / ac / ax. The basic PPDU format (IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and Data fields. The basic PPDU format may also be referred to as the non-HT PPDU format (Fig. 7(a)).

[0097] The HT PPDU format (IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT(s) fields in addition to the basic PPDU format. The HT PPDU format illustrated in FIG. 7(b) may be referred to as the HT-mixed format. Additionally, an HT-greenfield format PPDU may be defined, which corresponds to a format consisting of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTFs, and a Data field, without including L-STF, L-LTF, and L-SIG (not shown).

[0098] An example of the VHT PPDU format (IEEE 802.11ac) includes the VHT SIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields in addition to the basic PPDU format (Fig. 7(c)).

[0099] An example of the HE PPDU format (IEEE 802.11ax) includes the RL-SIG (Repeated L-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF(s), and PE (Packet Extension) fields in addition to the basic PPDU format (Fig. 7(d)). Depending on specific examples of the HE PPDU format, some fields may be excluded or their lengths may vary. For example, the HE-SIG-B field is included in the HE PPDU format for multiple users (MU), but is not included in the HE PPDU format for single users (SU). Additionally, the HE trigger-based (TB) PPDU format does not include HE-SIG-B, and the length of the HE-STF field may vary to 8 microseconds (us). The HE ER (Extended Range) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16us. For example, RL-SIG can be configured identically to L-SIG. Based on the presence of RL-SIG, the receiving STA can determine that the received PPDU is a HE PPDU or the EHT PPDU described later.

[0100] The EHT PPDU format may include the EHT MU (multi-user) of FIG. 7(e) and the EHT TB (trigger-based) PPDU of FIG. 7(f). The EHT PPDU format is similar to the HE PPDU format in that it includes RL-SIG following L-SIG, but it may include U (universal)-SIG, EHT-SIG, EHT-STF, and EHT-LTF following RL-SIG.

[0101] The EHT MU PPDU of FIG. 7(e) corresponds to a PPDU that carries one or more data (or PSDU) for one or more users. That is, the EHT MU PPDU can be used for both SU transmission and MU transmission. For example, the EHT MU PPDU can correspond to a PPDU for one receiving STA or multiple receiving STAs.

[0102] The EHT-SIG is omitted in the EHT TB PPDU of FIG. 7(f) compared to the EHT MU PPDU. A STA that receives a trigger for UL MU transmission (e.g., a trigger frame or TRS (triggered response scheduling)) can perform UL transmission based on the EHT TB PPDU format.

[0103] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated so that demodulation and decoding can be attempted even on legacy STAs, and mapped based on a defined subcarrier frequency interval (e.g., 312.5 kHz). These can be referred to as pre-EHT modulated fields. Next, the EHT-STF, EHT-LTF, Data, and PE fields can be encoded and modulated so that they can be demodulated and decoded by a STA that has successfully decoded a non-legacy SIG (e.g., U-SIG and / or EHT-SIG) to obtain the information contained in the corresponding fields, and mapped based on a defined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

[0104] Similarly, in the HE PPDU format, the L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, and HE-SIG-B fields can be referred to as pre-HE modulation fields, and the HE-STF, HE-LTF, Data, and PE fields can be referred to as HE modulation fields. Also, in the VHT PPDU format, the L-STF, L-LTF, L-SIG, and VHT-SIG-A fields can be referred to as pre-VHT modulation fields, and the VHT STF, VHT-LTF, VHT-SIG-B, and Data fields can be referred to as VHT modulation fields.

[0105] The U-SIG included in the EHT PPDU format of FIG. 7 can be constructed based on, for example, two symbols (e.g., two consecutive OFDM symbols). Each symbol for the U-SIG (e.g., OFDM symbol) can have a duration of 4 µs, and the U-SIG can have a total duration of 8 µs. Each symbol of the U-SIG can be used to transmit 26 bits of information. For example, each symbol of the U-SIG can be transmitted and received based on 52 data tones and 4 pilot tones.

[0106] U-SIGs can be configured in 20 MHz units. For example, if an 80 MHz PPDU is configured, the same U-SIG can be duplicated in 20 MHz units. That is, four identical U-SIGs can be included within an 80 MHz PPDU. If the bandwidth exceeds 80 MHz, for example, for a 160 MHz PPDU, the U-SIG of the first 80 MHz unit and the U-SIG of the second 80 MHz unit may be different.

[0107] For example, A number of uncoded bits may be transmitted through U-SIG, and the first symbol of U-SIG (e.g., U-SIG-1 symbol) transmits the first X bits of the total A bit information, and the second symbol of U-SIG (e.g., U-SIG-2 symbol) transmits the remaining Y bits of the total A bit information. The A bit information (e.g., 52 uncoded bits) may include a CRC field (e.g., a field of 4 bits) and a tail field (e.g., a field of 6 bits). The tail field may be used to terminate the trellis of the convolution decoder and may be set to, for example, 0.

[0108] A bit information transmitted by U-SIG can be divided into version-independent bits and version-dependent bits. For example, U-SIG may be included in a new PPDU format not shown in FIG. 7 (e.g., UHR PPDU format), and in the format of the U-SIG field included in the EHT PPDU format and the format of the U-SIG field included in the UHR PPDU format, the version-independent bits may be the same, and some or all of the version-dependent bits may be different.

[0109] For example, the size of the version-independent bits of U-SIG may be fixed or variable. The version-independent bits may be assigned only to U-SIG-1 symbols or to both U-SIG-1 and U-SIG-2 symbols. The version-independent bits and version-dependent bits may be referred to by various names, such as the first control bit and the second control bit.

[0110] For example, the version-independent bits of U-SIG may include a 3-bit physical layer version identifier (PHY version identifier), and this information may indicate the PHY version of the transmitted / received PPDU (e.g., EHT, UHR, etc.). The version-independent bits of U-SIG may include a 1-bit UL / DL flag field. The first value of the 1-bit UL / DL flag field relates to UL communication, and the second value of the UL / DL flag field relates to DL communication. The version-independent bits of U-SIG may include information regarding the length of the TXOP (transmission opportunity) and information regarding the BSS color ID.

[0111] For example, the version-dependent bits of U-SIG may contain information that directly or indirectly indicates the type of PPDU (e.g., SU PPDU, MU PPDU, TB PPDU, etc.).

[0112] Information necessary for PPDU transmission and reception may be included in the U-SIG. For example, the U-SIG may further include information regarding bandwidth, information regarding MCS techniques applied to non-legacy SIGs (e.g., EHT-SIG or UHR-SIG, etc.), information indicating whether DCM (dual carrier modulation) techniques (e.g., techniques to achieve an effect similar to frequency diversity by reusing the same signal on two subcarriers) are applied to non-legacy SIGs, information regarding the number of symbols used for non-legacy SIGs, and information regarding whether non-legacy SIGs are generated across the entire band.

[0113] Some of the information required for PPDU transmission and reception may be included in U-SIG and / or non-legacy SIGs (e.g., EHT-SIG or UHR-SIG, etc.). For example, information regarding the type of non-legacy LTF / STF (e.g., EHT-LTF / EHT-STF or UHR-LTF / UHR-STF, etc.), information regarding the length of non-legacy LTF and cyclic prefix (CP) length, information regarding guard interval (GI) applied to non-legacy LTF, information regarding preamble puncturing applicable to PPDU, information regarding resource unit (RU) allocation, etc., may be included only in U-SIG, may be included only in non-legacy SIG, or may be indicated by a combination of information included in U-SIG and information included in non-legacy SIG.

[0114] Preamble puncturing may refer to the transmission of a PPDU in which a signal is not present in one or more frequency units within the PPDU bandwidth. For example, the size of the frequency unit (or the resolution of preamble puncturing) may be defined as 20 MHz, 40 MHz, etc. For example, preamble puncturing may be applied to a PPDU bandwidth of a predetermined size or larger.

[0115] In the example of FIG. 7, non-legacy SIGs such as HE-SIG-B and EHT-SIG may include control information for the receiving STA. A non-legacy SIG may be transmitted through at least one symbol, and one symbol may have a length of 4 µs. Information regarding the number of symbols used for EHT-SIG may be included in the previous SIG (e.g., HE-SIG-A, U-SIG, etc.).

[0116] Non-legacy SIGs, such as HE-SIG-B and EHT-SIG, may include common fields and user-specific fields. Common fields and user-specific fields may be coded individually.

[0117] In some cases, the common field may be omitted. For example, in a compression mode where non-OFDMA (orthogonal frequency multiple access) is applied, the common field may be omitted, and multiple STAs may receive PPDUs (e.g., the data field of the PPDU) over the same frequency band. In a non-compression mode where OFDMA is applied, multiple users may receive PPDUs (e.g., the data field of the PPDU) over different frequency bands.

[0118] The number of user-specific fields can be determined based on the number of users. A single user block field can contain up to two user fields. Each user field may be related to MU-MIMO allocation or non-MU-MIMO allocation.

[0119] The common field may include CRC bits and Tail bits, the length of the CRC bits may be determined to be 4 bits, and the length of the Tail bits may be determined to be 6 bits and set to 000000. The common field may include RU allocation information. The RU allocation information may include information regarding the location of the RU to which a plurality of users (i.e., a plurality of receiving STAs) are allocated.

[0120] An RU may include multiple subcarriers (or tones). An RU may be used when transmitting signals to multiple STAs based on the OFDMA technique. Additionally, an RU may be defined when transmitting signals to a single STA. Resources may be allocated on an RU basis for non-legacy STF, non-legacy LTF, and Data fields.

[0121] Applicable RU sizes can be defined according to the PPDU bandwidth. RUs may be defined identically or differently for the applicable PPDU format (e.g., HE PPDU, EHT PPDU, UHR PPDU, etc.). For example, in the case of an 80 MHz PPDU, the RU placement for HE PPDU and EHT PPDU may differ. The applicable RU sizes, number of RUs, RU locations, DC (direct current) subcarrier locations and numbers, null subcarrier locations and numbers, and guard subcarrier locations and numbers for each PPDU bandwidth can be referred to as a tone-plan. For example, a tone-plan for a wide bandwidth may be defined as a multiple repetition of a tone-plan for a low bandwidth.

[0122] RUs of various sizes can be defined as 26-ton RUs, 52-ton RUs, 106-ton RUs, 242-ton RUs, 484-ton RUs, 996-ton RUs, 2x996-ton RUs, 4x996-ton RUs, etc. An MRU (multiple RU) is distinguished from multiple individual RUs and corresponds to a group of subcarriers composed of multiple RUs. For example, one MRU can be defined as 52+26-tons, 106+26-tons, 484+242-tons, 996+484-tons, 996+484+242-tons, 2x996+484-tons, 3x996-tons, or 3x996+484-tons. In addition, multiple RUs constituting a single MRU may be continuous or non-continuous in the frequency domain.

[0123] The specific size of the RU may be reduced or expanded. Accordingly, the specific size of each RU (i.e., the number of corresponding tones) in this disclosure is not limited and is exemplary. Additionally, within a given bandwidth (e.g., 20, 40, 80, 160, 320 MHz, ...) in this disclosure, the number of RUs may vary depending on the RU size.

[0124] The names of the respective fields in the PPDU formats of FIG. 7 are exemplary and the scope of the present disclosure is not limited by such names. Furthermore, the examples of the present disclosure may be applied not only to the PPDU formats exemplified in FIG. 7, but also to new PPDU formats based on the PPDU formats of FIG. 7 in which some fields are excluded and / or some fields are added.

[0125] FIG. 8 is a drawing showing an exemplary format of a trigger frame to which the present disclosure can be applied.

[0126] A trigger frame may allocate resources for one or more TB PPDU transmissions and request TB PPDU transmissions. The trigger frame may also include other information required by an STA that transmits a TB PPDU in response. The trigger frame may include common info and user info list fields in the frame body.

[0127] The common information field may include information commonly applicable to one or more TB PPDU transmissions requested by a trigger frame, such as trigger type, UL length, whether a subsequent trigger frame exists (e.g., More TF), whether a CS (channel sensing) is required, UL BW (bandwidth), etc. FIG. 8 illustrates an exemplary format for the common information field of an EHT variant.

[0128] The 4-bit trigger type subfield can have values ​​from 0 to 15. Among these, the values ​​0, 1, 2, 3, 4, 5, 6, and 7 of the trigger type subfield are defined to correspond to basic, BFRP (Beamforming Report Poll), MU-BAR (multi-user-block acknowledgement request), MU-RTS (multi-user-request to send), BSRP (Buffer Status Report Poll), GCR (groupcast with retries) MU-BAR, BQRP (Bandwidth Query Report Poll), and NFRP (NDP Feedback Report Poll), respectively, and the values ​​8 to 15 are defined as reserved.

[0129] Among the common information, the trigger-dependent common info subfield may include information that is optionally included based on the trigger type.

[0130] A special user info field may be included within the trigger frame. The special user info field does not contain user-specific information, but rather contains extended common information not provided in the common information field.

[0131] The user information list contains zero or more user info fields. Figure 8 illustrates an exemplary EHT variant user info field format.

[0132] The AID12 subfield basically indicates that it is a user information field for the STA with the corresponding AID. Additionally, if the AID12 field has a specific predetermined value, it may be utilized for other purposes, such as assigning a Random Access (RA)-RU or being configured as a special user info field. A special user info field is a user information field that does not contain user-specific information but includes extended common information not provided in the common information field. For example, a special user info field can be identified by an AID12 value of 2007, and a special user info field flag subfield within the common information field can indicate whether the special user info field is included.

[0133] The RU allocation subfield can indicate the size and location of the RU / MRU. To this end, the RU allocation subfield may be interpreted together with the PS160 (primary / secondary 160MHz) subfield of the user information field, the UL BW subfield of the common information field, etc.

[0134] For example, as shown in Table 1 below, the mapping of B7-B1 of the RU allocation subfield can be defined along with the settings of B0 and PS160 of the RU allocation subfield. Table 1 shows an example of the encoding of the PS160 subfield and the RU allocation subfield of the EHT variant user information field.

[0135]

[0136]

[0137]

[0138] If B0 of the RU allocation subfield is set to 0, it indicates that the RU / MRU allocation is applied to the primary 80MHz channel, and if the value is set to 1, it indicates that the RU allocation is applied to the secondary 80MHz channel of the primary 160MHz. If B0 of the RU allocation subfield is set to 0, it indicates that the RU / MRU allocation is applied to the lower 80MHz of the secondary 160MHz, and if the value is set to 1, it indicates that the RU allocation is applied to the upper 80MHz of the secondary 160MHz.

[0139] In the trigger frame RU allocation table of Table 1, the parameter N can be calculated based on the formula N=2*X1+X0. For bandwidths of 80 MHz or less, the values ​​of PS160, B0, X0, and X1 can be set to 0. For 160 MHz and 320 MHz bandwidths, the values ​​of PS160, B0, X0, and X1 can be set as shown in Table 2. These settings represent the absolute frequency order for the primary and secondary 80 MHz and 160 MHz channels. The order from left to right indicates the order from lowest to highest frequency. The primary 80 MHz channel is designated as P80, the secondary 80 MHz channel as S80, and the secondary 160 MHz channel as S160.

[0140]

[0141] NDP Announcement Frame

[0142] In wireless LAN systems, sounding procedures / protocols are used to determine channel state information. A beamformer STA requesting channel state information can transmit a training signal to beamformee STA(s). The beamformee STA can measure the channel using the training signal (e.g., sounding NDP) and feed back an estimate of the channel state to the beamformer STA. The beamformer STA can derive a steering matrix or a beamforming matrix using the feedback estimate.

[0143] The beamforming STA can feed back estimates of the channel state to the beamformer STA through a compressed beamforming / CQI (channel quality indication) report frame. The information fed back may include single-user (SU) feedback, multi-user (MU) feedback, CQI feedback, etc.

[0144] The beamformer STA can transmit an NDP announcement and NDP to the beamformer(s) and receive feedback information from the beamformer STA(s). Additionally or alternatively, the beamformer STA can transmit an NDP announcement and NDP to the beamformer(s) and transmit a beamforming report poll (BFRP) or BFRP trigger to the beamformer(s) to receive feedback information from the beamformer(s).

[0145] NDP Notice (NDPA) frames can have multiple types or variants. For example, NDP Notice frames can be composed of various formats, such as VHT NDP Notice frames, HE NDP Notice frames, and EHT NDP Notice frames. These formats can be distinguished by the NDP Notice variant subfield within the sounding dialog token field.

[0146] FIG. 9 shows an exemplary format of an NDP notice frame to which the present disclosure may be applied.

[0147] An NDP notice frame may include one or more STA information (Info) fields. If an NDP notice frame includes only one STA Info field, the RA (receiver address) field may be set to the address of an STA capable of providing feedback. If an NDP notice frame includes multiple STA Info fields, the RA field may be set to a broadcast address.

[0148] The TA (transmitter address) field may be set to the address of the STA transmitting the NDP notice frame or to the bandwidth signaling TA of the STA transmitting the NDP notice frame. For example, in a non-HT or non-HT duplicate format, if the scrambling sequence (or scrambling sequence and service field) includes parameters for channel bandwidth, the TA field may be set to the bandwidth signaling TA.

[0149] The first two bits (B0 and B1) of the eight bits (B0-B7) of the sounding dialogue token field can be used to indicate the type / variant of the NDP notice frame. For example, for VHT or HE, B0 has a value of 0, and if the value of B1 is 0, it may indicate a VHT NDP notice frame, and if the value of B1 is 1, it may indicate an HE NDP notice frame. For example, an EHT NDP notice frame may correspond when both the values ​​of B0 and B1 are set to 1. If the value of B0 is 1 and the value of B1 is 0, it may correspond to a ranging NDP notice frame.

[0150] In the case of VHT STA, the first two bits (B0 and B1) of the sounding dialogue token field are defined as reserved, so VHT STA can recognize the sounding dialogue token number field of bits B2-B7 regardless of the values ​​of B0 and B1.

[0151] For VHT STA, the first two bits (B0 and B1) of the sounding dialogue token field are defined as reserved. Therefore, VHT STA can recognize the sounding dialogue token number field of bits B2-B7 regardless of the values ​​of B0 and B1.

[0152] For HE STA, the first bit (B0) of the sounding dialogue token field is defined as reserved, and the value of the second bit (B1) is defined as indicating a VHT NDP notice frame if the value of B1 is 0 and indicating an HE NDP notice frame if the value of B1 is 1. Therefore, HE STA can recognize the sounding dialogue token number field of bits B2-B7 when the value of B1 is 1, regardless of the value of B0.

[0153] The sounding dialogue token number subfield (bit positions B2-B7) may include a value for identifying an NDP notification frame selected by the beamformer.

[0154] An NDP notification frame may contain n (where n is an integer greater than or equal to 1) STA Info fields. Each STA Info field has a size of K octets, and K=2 in a VHT NDP notification frame, and K=4 in a HE NDP notification frame or an EHT NDP notification frame.

[0155] As shown in the example of FIG. 9(a), the STA Info field of the VHT NDP notification frame may include AID12, feedback type, and Nc index subfields.

[0156] The AID12 subfield contains 12 LSB (least significant bits) of the AID of the STA expected to process the subsequent NDP and prepare sounding feedback.

[0157] The feedback type subfield indicates the type of feedback required, and corresponds to SU if the value is 0 and MU if the value is 1.

[0158] The Nc index subfield indicates the value obtained by subtracting 1 from the number of columns (i.e., Nc) in the compressed beamforming feedback matrix (i.e., Nc-1) when the feedback type is MU. When it is SU, the Nc index field is reserved.

[0159] The example in Fig. 9(b) shows the format of the STA Info field of the HE NDP notification frame when the value of the AID11 field is not a specific value (e.g., 2047).

[0160] Values ​​of the AID11 subfield other than a specific value (e.g., 2047) include 11 LSB among the AIDs of the STA expected to process the subsequent NDP and prepare sounding feedback.

[0161] The partial BW Info subfield may include a 7-bit (B0-B6) RU start index and a 7-bit (B7-B13) RU end index. The RU index may be determined based on the bandwidth of the NDP notice frame, and the unit may be 26-tone RU. For example, to indicate a 26-tone RU index X, the value of the start / end RU index subfield may be set to X-1.

[0162] The feedback type and Ng subfield, in combination with the codebook size subfield, can indicate whether SU / MU / CQI feedback is requested for trigger-based (TB) sounding, Ng=4 or 16, and the quantization resolution. For non-TB sounding, the feedback type and Ng subfield and the codebook size subfield can indicate SU or CQI.

[0163] The disambiguation subfield is set to 1 to help prevent non-HE STAs (e.g., VHT STAs) from misinterpreting the field as an AID field.

[0164] The Nc subfield is set to a value of Nc-1. If the feedback type is SU or MU, Nc corresponds to the number of columns in the compressed beamforming feedback matrix, and if the feedback type is CQI, Nc may correspond to the number of space-time streams (STS). For NDP notice frames that have an AID11 subfield value other than 2047 and are individually addressed for a single STA, the Nc subfield may be reserved.

[0165] The example in Fig. 9(c) shows the format of the STA Info field of the HE NDP notification frame when the value of the AID11 field is a specific value (e.g., 2047).

[0166] The disallowed subchannel bitmap subfield indicates the 20 MHz subchannel(s) and 242-tone RU(s) present in the sounding NDPs announced by the NDP announcement frame, and the 242-tone RU(s) to be included in the requested sounding feedback. The lowest numbered bit of the disallowed subchannel bitmap corresponds to the 20 MHz subchannel located at the lowest frequency among all 20 MHz subchannels within the BSS bandwidth. Each subsequent bit in the bitmap corresponds to the next highest 20 MHz subchannel. A bit set to 1 in the bitmap may indicate that no energy is present in the sounding NDP associated with the NDP announcement frame. For each disallowed 20 MHz subchannel, the 242-tone RU that is closest in frequency to the corresponding 20 Hz subchannel may be disallowed for a PPDU using a specific tone plan. The STA(s) addressed by the NDP notice frame do not include tones from the 242-tone RU that are not allowed when determining the average SNR of STS 1 through Nc in generating the requested sounding feedback. If a 20 MHz subchannel and its corresponding 242-tone RU are allowed, the corresponding bit in the bitmap is set to 0.

[0167] The example in Fig. 9(d) shows the format of the STA Info field of the EHT NDP notification frame.

[0168] AID11 subfields can be defined as shown in Table 3. By default, AID11 subfields contain the identifier of the STA expected to process the subsequent NDP and prepare sounding feedback.

[0169] Description of AID Subfield Value NDP Notice Frame Type / Variant Applicability 0- Addressed for a combined AP, mesh AP, or IBSS STA where the STA Info field is located. Applicable to all variants 1- 2007- If the NDP notice frame is not a ranging variant, the STA Info field is addressed for a combined STA having the same AID as the value of the AID11 subfield. - If the NDP notice frame is a ranging variant, the STA Info field is addressed for an uncombined STA or combined STA having the same RSID / AID as the value of the RSID11 / AID11 subfield. - For EHT variants, the 2007 value is reserved. Applicable to all variants 2008- 2042 Reserved. Not applicable to all variants 2043- If the NDP notice frame is a ranging variant, the STA Info field is sequence Includes authentication code. - Otherwise, the AID11 value is reserved. Applicable only to the ranging variant. 2044 - If the NDP announcement frame is a ranging variant, the STA Info field includes a partial TSF (timing synchronization function). - Otherwise, the AID11 value is reserved. Applicable only to the ranging variant. 2045 - If the NDP announcement frame is a ranging variant, the STA Info field includes ranging measurement parameters. - Otherwise, the AID11 value is reserved. Applicable only to the ranging variant. 2046 Reserved. Not applicable to all variants. 2047 - If the NDP announcement frame is an HE variant, the STA Info field includes an unauthorized subchannel bitmap. - Otherwise, the AID11 value is reserved. Applicable only to the HE variant.

[0170] The partial BW subfield may include a 1-bit (B0) resolution subfield and an 8-bit (B1-B8) feedback bitmap. The resolution subfield indicates a resolution bandwidth (e.g., 20 MHz or 40 MHz) for each bit of the feedback bitmap subfield. The feedback bitmap subfield may indicate requests for each resolution bandwidth from low frequency to high frequency, and the first bit (B1) of the bitmap corresponds to the lowest resolution bandwidth. Each bit of the feedback bitmap is set to 1 when feedback for the corresponding resolution bandwidth is requested. If the bandwidth of the EHT NDP notification frame is less than 320 MHz, the value of the resolution bit (B0) may be set to 0 to indicate a resolution of 20 MHz.

[0171] If the bandwidth of the EHT NDP notification frame is 20 MHz, B1 is set to 1 to indicate that feedback for 242-tone RU is requested, and B2-B8 can be reserved and set to 0.

[0172] When the bandwidth of the EHT NDP notice frame is 40 MHz, B1 and B2 indicate that feedback is requested at each of the two 242-tone RUs from low frequency to high frequency, and B3-B8 may be reserved and set to 0.

[0173] If the bandwidth of the PPDU carrying the EHT NDP notice frame is 80 MHz, B0 can be set to 0 to indicate a resolution of 20 MHz. If B1-B4 are all set to 1, it can indicate that feedback is requested for the 996-tone RU. Otherwise, B1-B4 indicate that feedback is requested for each of the four 242-tone RUs from the low frequency to the high frequency, and B5-B8 can be reserved and set to 0.

[0174] If the bandwidth of the PPDU carrying the EHT NDP notice frame is 160 MHz, B0 can be set to 0 to indicate a resolution of 20 MHz. If B1-B4 are all set to 1, it can indicate that feedback is requested for the lower 996-tone RU; otherwise, B1-B4 can indicate that feedback is requested for each of the four 242-tone RUs from the low frequency to the high frequency in the lower 80 MHz. If B5-B8 are all set to 1, it can indicate that feedback is requested for the upper 996-tone RU; otherwise, B5-B8 can indicate that feedback is requested for each of the four 242-tone RUs from the low frequency to the high frequency in the upper 80 MHz.

[0175] If the bandwidth of the PPDU carrying the EHT NDP notice frame is 320 MHz, B0 can be set to 1 to indicate a resolution of 40 MHz. If both B1 and B2 are set to 1, it can indicate that feedback is requested for the first 996-tone RU; otherwise, B1 and B2 can indicate that feedback is requested for each of the two 484-tone RUs from low to high frequency in the first 80 MHz. If both B3 and B4 are set to 1, it can indicate that feedback is requested for the second 996-tone RU; otherwise, B3 and B4 can indicate that feedback is requested for each of the two 484-tone RUs from low to high frequency in the second 80 MHz. If both B5 and B6 are set to 1, it may indicate that feedback is requested for the third 996-tone RU; otherwise, B5 and B6 may indicate that feedback is requested for each of the two 484-tone RUs from low to high frequency at the third 80 MHz. If both B7 and B8 are set to 1, it may indicate that feedback is requested for the fourth 996-tone RU; otherwise, B7 and B8 may indicate that feedback is requested for each of the two 484-tone RUs from low to high frequency at the fourth 80 MHz. The feedback tone set for each 484-tone RU may consist of the feedback tone set of two 242-tone RUs that overlap with the 484-tone RU.

[0176] The partial bandwidth subfield can have values ​​such as the example in Table 4 depending on the relevant settings.

[0177]

[0178] For TB sounding, the feedback type, Ng subfield, and codebook size subfield can be set according to the example in Table 5.

[0179]

[0180] For non-TB sounding, the feedback type and Ng subfield and codebook size subfield can be set according to the example in Table 6.

[0181]

[0182] The disambiguation subfield is set to 1 to help prevent non-EHT STAs (e.g., VHT STAs) from misinterpreting the field as an AID field.

[0183] In an EHT NDP announcement frame, RA is set to the broadcast address, and the following may apply. If the feedback type and Ng subfields and the codebook size subfield indicate SU or MU, the Nc index subfield is set to a value of Nc-1, where Nc corresponds to the number of columns in the compressed beamforming feedback matrix, and values ​​greater than 7 in the Nc index subfield are reserved. If the feedback type and Ng subfields and the codebook size subfield indicate CQI, the Nc index subfield is set to a value of Nc-1, where Nc corresponds to the number of STS (space-time streams), and values ​​greater than 7 in the Nc index subfield are reserved. One or more STA Info fields may exist.

[0184] In an EHT NDP notice frame having a single STA Info field, the RA field is set to an individual address, and the Nc index subfield may be reserved.

[0185] Multi-AP cooperation sounding

[0186] A multi-AP coordination framework can support procedures for APs of different BSSs to reduce interference levels and improve network performance on the same channel (e.g., a 20 MHz primary channel) by applying techniques such as coordinated-beamforming (Co-BF). Co-BF technology can support simultaneous transmission from multiple APs by eliminating or reducing interference directed toward STAs of adjacent BSSs. For example, Co-BF may include each AP deriving and applying a precoder (or beamforming matrix) that can reduce interference directed toward neighboring BSS (or overlapping BSS (OBSS)) STAs. Accordingly, system performance (e.g., throughput, latency, media utilization efficiency, communication reliability, etc.) can be improved.

[0187] For Co-BF, the BSS AP may receive channel state information regarding the downlink channel from the BSS AP to the OBSS STA from the OBSS STA. Additionally, the BSS AP may receive channel state information regarding the downlink channel from the OBSS AP to the BSS STA from the BSS STA. This channel state information may be measured based on the NDP transmitted from the OBSS AP or the BSS AP. An NDP Notice (NDPA) frame may be transmitted prior to the transmission of the NDP. The BSS AP transmits a trigger frame (e.g., a beamforming report poll (BFRP) trigger frame) soliciting feedback of channel state information from the BSS STA or the OBSS STA, and in response, a frame containing channel state information (e.g., a compressed beamforming information / channel quality indicator (CQI) frame) may be transmitted from the STA. To support this operation, new sounding and feedback procedures need to be defined. This new sounding procedure may also be referred to as OBSS sounding or Co-BF sounding.

[0188] In order for a BSS AP to petition for and receive feedback from an OBSS STA, the overhead and complexity of having to decode packets transmitted from BSSs other than the BSS it is associated with may increase. To minimize this increase in complexity, a method of transmitting NDPA frames and BFRP trigger frames to the BSS STA without transmitting them to the OBSS STA may be considered. For example, a procedure may be defined in which the NDPA frame is transmitted (e.g., broadcast) by the BSS AP, and the NDP following the NDPA frame is transmitted by the OBSS AP. Unlike conventional NDPA frame transmission and NDP transmission, which are performed by a single AP, in the present disclosure, a first AP may transmit the NDPA frame and a second AP may transmit the NDP.

[0189] A multi-AP cooperative sounding procedure may include an NDP sounding procedure initiated by a first AP and an NDP sounding procedure initiated by a second AP. For example, the NDP sounding procedure initiated by the first AP may include the second AP transmitting an NDP triggered by an NDPA from the first AP, and a first STA associated with the first AP reporting channel state information (CSI) based on the NDP from the second AP to the first AP in response to a BFRP trigger frame from the first AP. For example, the NDP sounding procedure initiated by the second AP may include the first AP transmitting an NDP triggered by an NDPA from the second AP, and a second STA associated with the second AP reporting CSI based on the NDP from the first AP to the second AP in response to a BFRP trigger frame from the first AP. Furthermore, the examples of the present disclosure may also apply to cases where an NDP from the first AP and an NDP from the second AP are transmitted simultaneously based on an NDPA from the first AP, or where an NDP from the first AP and an NDP from the second AP are transmitted simultaneously based on an NDPA from the second AP. In accordance with such multi-AP cooperative sounding, each BSS AP may acquire a CSI for a downlink channel from the OBSS AP to its BSS STA and, based thereon, apply beamforming / precoding for Co-BF.

[0190] If BSS AP is the first AP, OBSS AP is the second AP, and OBSS STA may be the STA associated with the second AP. If BSS AP is the second AP, OBSS AP is the first AP, and OBSS STA may be the STA associated with the first AP.

[0191] In this process, if each BSS AP can acquire a feedback signal containing the CSI that the OBSS STA reports to the associated OBSS AP, it can more accurately determine beamforming / precoding for Co-BF. For example, if the BSS AP and the OBSS AP are connected via wired backhaul, they can easily exchange this information. In the absence of a wired backhaul connection, the BSS AP may overhear frames containing the CSI that the OBSS STA reports to the associated OBSS AP over the wireless medium.

[0192] Frames containing CSI from the OBSS STA are triggered by the OBSS AP, so they may be difficult for the BSS AP to receive easily. For example, the modulation and coding scheme (MCS) and / or number of spatial streams (Nss) applied to the CSI feedback frame of the OBSS STA may be specified by the trigger frame of the OBSS AP. Here, since the quality of the overhearing channel from the OBSS STA to the BSS AP is unknown to the OBSS AP, the MCS / Nss applied to the CSI feedback frame of the OBSS STA cannot be determined by taking this into account. Specifically, since the OBSS AP transmits a BFRP trigger frame for the OBSS STA without knowing the channel quality from the OBSS STA to the BSS AP, the BSS AP may find it difficult to overhear the CSI feedback frame transmitted from the OBSS STA to the OBSS AP.

[0193] Accordingly, the present disclosure may provide in advance an MCS (and / or Nss and / or SNR (signal-to-noise ratio)) recommended by the BSS AP to the OBSS AP. This may be an MCS / Nss / SNR recommended (by the BSS AP) for CSI feedback from the OBSS STA to the OBSS AP. Based on this, the OBSS AP may consider / apply the MCS / Nss / SNR when triggering CSI feedback to the OBSS STA.

[0194] In the following examples, MCS is assumed as a representative example of a parameter to be applied to the CSI feedback of OBSS STA based on the recommendation of BSS AP, but the scope of the present disclosure is not limited thereto, and the examples of the present disclosure can be equally applied to Nss, SNR, etc.

[0195] FIG. 10 is a drawing for explaining an example of the operation of a first AP according to the present disclosure.

[0196] In step S1010, the first AP can receive recommended modulation and coding scheme (MCS) information from the second AP.

[0197] In some examples, the recommended MCS information may be the recommended MCS information for channel state information feedback. For example, channel state information transmitted by an STA associated with a first AP is for a channel between a second AP and the STA, and the second AP may recommend an MCS to be applied for channel state information feedback in order to facilitate the reception of such channel state information.

[0198] In some examples, recommended MCS information may be included in an NDPA frame transmitted from the second AP. For example, an NDP notification frame from the second AP may be transmitted during the first sounding process, and a trigger frame from the first AP, described below, may be transmitted during the second sounding process. For example, the NDPA frame may include a plurality of STA information fields, and recommended MCS information may be included in a specific subfield (e.g., position B20-B24) of a specific STA information field (e.g., the second STA information field) among the plurality of STA information fields. For example, a specific value of the specific subfield may indicate no recommendation for MCS.

[0199] In step S1020, the first AP can transmit a trigger frame to the STA soliciting channel state information from the STA.

[0200] In some examples, the trigger frame may include recommended MCS information. For example, the trigger frame may be a BFRP trigger frame. For example, an MCS value based on the recommended MCS information of the second AP (e.g., determined by the first AP in consideration of or following the same) may be included in the trigger frame. The MCS value included in the trigger frame may correspond to a parameter instructed to be applied to a frame responding to the trigger frame (e.g., a compressed beamforming / CQI reporting frame responding to the BFRP trigger frame).

[0201] In some examples, the first AP may transmit a trigger frame to the STA(s) associated with it. For example, if channel state information of multiple STAs is petitioned by the trigger frame, the recommended MCS information may correspond to the lowest MCS for the multiple STAs.

[0202] In step S1030, the first AP can receive channel state information from the STA.

[0203] In some examples, the transmission of channel state information by the STA may be based on recommended MCS information from the second AP provided to the STA through a trigger frame. For example, for a frame containing channel state information transmitted by the STA (e.g., a compressed beamforming / CQI report frame), the MCS indicated through the trigger frame (e.g., a value corresponding to the recommended MCS information provided by the second AP) may be applied.

[0204] In some examples, channel state information from the STA may also be received by the second AP. For example, channel state information included in a frame transmitted by the STA (in response to a trigger frame of the first AP) based on the recommended MCS information of the second AP corresponds to the channel from the second AP to the STA (e.g., the STA associated with the first AP), and this channel state information may be used for precoding / beamforming decisions for Co-BF performed by the first AP and the second AP.

[0205] In some examples, the second AP may be the AP that transmitted the NDP. For example, based on the NDP transmitted from the second AP, the STA (e.g., the STA associated with the first AP) may determine / calculate channel state information for the channel from the second AP to the STA. Such transmission of the NDP from the second AP and the feedback of the channel state information from the STA based thereon may be included in the aforementioned second sounding process.

[0206] The method described in the example of FIG. 10 can be performed by the first device (100) of FIG. 1. For example, one or more processors (102) of the first device (100) of FIG. 1 may be configured to receive recommended MCS information from the second AP through one or more transceivers (106), transmit a trigger frame requesting channel state information from the STA through one or more transceivers (106) to the STA, and receive channel state information from the STA through one or more transceivers (106). Furthermore, one or more memories (104) of the first device (100) may store instructions for performing the method described in the example of FIG. 10 or the examples described below when executed by one or more processors (102).

[0207] For example, the memory (104) may store various information related to recommended MCS information according to the present disclosure, MCS information included in a trigger frame, etc. Based on the information stored in the memory (104), the processor (102) may generate a field containing recommended MCS information, generate a trigger frame containing said field, generate an RU, generate a PPDU, and transmit the generated PPDU through the transceiver (106). Additionally, the processor (102) may generate a transmitted PPDU and store information regarding the transmitted PPDU in the memory (104). For example, the processor (102) may be configured to perform the operation of a first STA according to an example of the present disclosure.

[0208] FIG. 11 is a drawing for illustrating an example of the operation of the second AP according to the present disclosure.

[0209] In step S1110, the second AP can transmit recommended MCS information to the first AP.

[0210] In step S1120, the second AP can receive channel status information from the STA that is petitioned by a trigger frame from the first AP.

[0211] In the example of Fig. 11, the details regarding the recommended MCS information, the field / frame containing the recommended MCS information, the trigger frame, and the channel status information are the same as those in the example of Fig. 10, so a redundant description is omitted.

[0212] The method described in the example of FIG. 11 may be performed by the second device (200) of FIG. 1. For example, one or more processors (202) of the second device (200) of FIG. 1 may be configured to transmit recommended MCS information to the first AP through one or more transceivers (206) and to receive channel status information from the STA petitioned by a trigger frame from the first AP through one or more transceivers (206). Furthermore, one or more memories (204) of the second device (200) may store instructions for performing the method described in the example of FIG. 11 or the examples described below when executed by one or more processors (202).

[0213] For example, the memory (204) may store various information related to the recommended MCS information and channel state information according to the present disclosure. The transceiver (206) may receive a PPDU based on the control of the processor (202). The PPDU received through the transceiver (206) may be stored in the memory (204). For example, the processor (202) may acquire control information regarding the bandwidth / tone-plan / RU included in the PPDU (e.g., information included in the SIG field of the PPDU) and store the acquired control information in the memory (204). The processor (202) may perform decoding on the received PPDU. For example, it may perform operations to restore the results of cyclic shift delay (CSD), spatial mapping, inverse discrete Fourier transform (IDFT) / inverse fast Fourier transform (IFFT) operations, and guard interval (GI) insertion applied to the PPDU. Additionally, the processor (202) can decode the data field of the PPDU received through the transceiver (206) and process the decoded data. For example, the processor (202) can transmit information regarding the decoded data field to an upper layer (e.g., MAC layer). Additionally, if the generation of a signal is instructed from the upper layer to the PHY layer in response to the data transmitted to the upper layer, subsequent operations can be performed. For example, the processor can parse the MAC PDU obtained through PHY decoding of the DATA field of the PPDU received through the transceiver (206).

[0214] Additionally, the processor (202) may be configured to acquire various information related to NDPA and channel state information included in the MAC PDU and to perform operations accordingly (e.g., NDP transmission, Co-BF based on acquired channel state information, etc.). For example, the processor (202) of the receiving device may be configured to perform the operation of the second STA according to the example of the present disclosure.

[0215] As described with reference to FIGS. 10 and FIG. 11, the first AP can receive recommended MCS information from the second AP. Then, when an NDP transmission from the second AP is performed during a sounding process initiated by the first AP (e.g., in response to an NDPA from the first AP), the first AP can transmit a BFRP trigger frame to its associated STA(s) to receive feedback on channel state information (e.g., channel state information based on the NDP from the second AP). This BFRP trigger frame may include / indicate MCS information for channel state information feedback, which may be based on the recommended MCS information of the second AP.

[0216] The second AP may transmit its recommended MCS information to the first AP. Then, during the sounding process initiated by the first AP (e.g., in response to an NDPA from the first AP), the second AP may transmit an NDP. When the associated STA(s) of the first AP provide feedback on channel state information (e.g., channel state information based on an NDP from the second AP) via the first AP's BFRP trigger frame, the second AP may also receive / overhear / acquire such channel state information. The first AP's BFRP trigger frame may include / indicate an MCS value based on the second AP's recommended MCS information.

[0217] The STA receives an NDPA frame transmitted from the first AP, receives an NDP transmitted from the second AP, and receives a BFRP trigger frame from the first AP, and can transmit channel state information (e.g., channel state information based on the NDP from the second AP). If the STA is included among the recipients of the channel state information feedback in the BFRP trigger frame, the STA can transmit the channel state information to the first AP. The second AP may overhear the channel state information transmitted in this manner to obtain the status information of the downlink channel from itself to the STA. This channel state information can be referenced by the second AP when determining beamforming / precoding during subsequent Co-BF operations.

[0218] FIG. 12 is a diagram illustrating an example of a multi-AP cooperative sounding process according to the present disclosure.

[0219] First, AP2 can transmit information regarding its recommended MCS, etc. to AP1. As described below, AP2's recommended MCS may be transmitted through various fields / frames. For example, AP2 may provide the recommended MCS information to AP1 through an NDPA frame during the OBSS sounding (or Co-BF sounding) process that it initiates. Alternatively, AP2's recommended MCS information may be provided to AP1 in advance through another process or another frame.

[0220] Subsequently, during the OBSS sounding (or Co-BF sounding) process initiated by AP1, AP2 may serve as the responding AP. AP1 may first request STA1 (and other STA(s)) within the BSS to participate in the sounding by transmitting (e.g., broadcasting) an NDPA. Additionally, the NDPA frame transmitted by AP1 may trigger the transmission of an NDP by the OBSS AP (e.g., AP2). Accordingly, AP2 can receive the NDPA frame and recognize that it needs to transmit an NDP. Examples of the format / configuration of the NDPA frame for this purpose will be described below.

[0221] STA1 can estimate the channel state for the downlink channel from AP2 to STA1 (e.g., OBSS DL channel) (e.g., using the NDP transmitted by AP2) and prepare for feedback of channel state information. AP1 can transmit a BFRP trigger frame targeting STA1 (e.g., to trigger / petition STA1's beamforming feedback). Accordingly, STA1 can feed back channel state information for the OBSS DL channel to AP1. AP2 can also receive / overhear / acquire this channel state information feedback.

[0222] Example 1

[0223] In the OBSS sounding process for Co-BF, an OBSS AP (e.g., AP1) may transmit a BFRP trigger frame to an OBSS STA (e.g., STA1 associated with AP1) to collect feedback on the downlink channel from a BSS AP (e.g., AP2). Since the STA determines / calculates channel state information based on the NDP from the BSS AP (e.g., AP1), the transmission of such channel state information is triggered by the OBSS AP (e.g., AP2), but the AP that actually needs such channel state information may be the BSS AP (e.g., AP2). Therefore, the BSS AP (e.g., AP2) can receive / overhear / acquire the CSI feedback report from the OBSS STA (e.g., STA1) and utilize it for its own data transmission (e.g., Co-BF).

[0224] An OBSS AP (e.g., AP1) may trigger channel state information feedback by considering only the characteristics of the receiving channel from the STA it knows (e.g., the channel from the OBSS STA (e.g., STA1) to the OBSS AP (e.g., AP1)) without knowing the channel characteristics (e.g., quality) from the OBSS STA (e.g., STA1) to the BSS AP (e.g., AP2). In this case, the BSS AP (e.g., AP2) that requires channel state information feedback for OBSS sounding may not be able to properly receive / overhear the channel state information feedback, and consequently may not be able to efficiently perform Co-BF transmission.

[0225] To solve this problem, a BSS AP (e.g., AP2) may provide information regarding channel characteristics between itself and an OBSS STA (e.g., STA1) to an OBSS AP (e.g., AP1) in advance. To do this, prior to the OBSS sounding process initiated by the OBSS AP (e.g., AP1), the BSS AP (e.g., AP2) may assume that the channel characteristics / quality between the OBSS STA (e.g., STA1) and the BSS AP (e.g., AP2) is measurable. Based on the measured channel characteristics / quality, the BSS AP (e.g., AP2) may provide the SNR of the corresponding channel / link to the OBSS AP (e.g., AP1), or provide desired / recommended MCS / Nss information to the OBSS AP (e.g., AP1).

[0226] Alternatively, an OBSS AP (e.g., AP1) may instruct an OBSS STA (e.g., STA1) to apply the lowest / robust MCS (e.g., MCS 0) to the triggered channel state information feedback frame via a BFRP trigger frame. In this case, channel characteristic / quality information recommended by the BSS AP does not need to be provided in advance, but the channel state information feedback, which has relatively high overhead, is always transmitted with a low MCS, which may result in lower media utilization efficiency.

[0227] Therefore, by having the BSS AP (e.g., AP2) provide channel characteristic / quality related information (e.g., recommended MCS information) to the OBSS AP (e.g., AP1) in advance, it is possible to facilitate efficient channel status information feedback and the reception / overhearing of channel status information by the BSS AP.

[0228] Example 2

[0229] Examples of channel characteristic / quality information regarding the channel from OBSS STA (e.g., STA1 associated with AP1) to BSS AP (e.g., AP2), which BSS AP (e.g., AP2) transmits in advance to OBSS AP (e.g., AP1), are described below.

[0230] Example 2-1

[0231] Information / fields that can indicate link / channel quality, such as SNR / SINR (signal to interference plus noise ratio) / RSSI (received signal strength indicator), for a channel from an OBSS STA (e.g., STA1 associated with AP1) to a BSS AP (e.g., AP2), may be transmitted in advance from the BSS AP (e.g., AP2) to the OBSS AP (e.g., AP1). Using this information such as SNR / SINR / RSSI, the OBSS AP (e.g., AP1) may determine the MCS / Nss of a feedback frame to be triggered and provide the determined MCS / Nss to the OBSS STA (e.g., STA1 associated with AP1) through a BFRP trigger frame.

[0232] Example 2-2

[0233] MCS and / or Nss information desired or recommended by the BSS AP (e.g., AP2) may be transmitted in advance from the BSS AP (e.g., AP2) to the OBSS AP (e.g., AP1). By notifying the OBSS AP (e.g., AP1) of the MCS / Nss of the feedback frame from the OBSS STA (e.g., STA1) desired / recommended by the BSS AP (e.g., AP2), the characteristics / quality of the channel from the OBSS STA (e.g., STA1 associated with AP1) to the BSS AP (e.g., AP2) may be indirectly communicated to the OBSS AP (e.g., AP1).

[0234] For example, among the candidate values ​​of MCS information, a specific value corresponding to "no recommendation" may be predefined. If the MCS information is set to a specific value, it may indicate that there is no desired / recommended MCS by the BSS AP (e.g., AP2). In this case, the OBSS AP (e.g., AP1) can independently determine the MCS to be applied to the feedback frame without the recommendation of the BSS AP.

[0235] Examples 2-3

[0236] ID information (e.g., AID12 field) of an OBSS STA (e.g., STA1 associated with AP1) can be transmitted in advance from a BSS AP (e.g., AP2) to an OBSS AP (e.g., AP1). For example, channel state information for a specific STA(s) among several STAs can be obtained, and Co-BF transmission for that specific STA(s) can be performed.

[0237] Information regarding the number of OBSS STAs can be transmitted in advance from the BSS AP (e.g., AP2) to the OBSS AP (e.g., AP1). For example, channel state information for a specific number of STA(s) can be obtained, and based on this, Co-BF transmission for the specific number of STA(s) can be performed.

[0238] Alternatively, the trigger frame and / or the frame containing channel status information may include STA AID information and / or information about the number of STAs.

[0239] Examples 2-4

[0240] When channel characteristic / quality related information transmitted in advance by a BSS AP (e.g., AP2) to an OBSS AP (e.g., AP1) is included in a special user information (or STA Info) field of an NDPA frame, a flag indicating whether the next special user information (or STA Info) field exists may be transmitted in advance from the BSS AP (e.g., AP2) to the OBSS AP (e.g., AP1). If the value of the flag information is 1, it may indicate that a subsequent field exists, and if the value is 0, it may indicate that a subsequent field does not exist.

[0241] Alternatively, flag information may be included in a frame containing trigger frames and / or channel status information.

[0242] Example 3

[0243] Examples of fields / frames containing channel characteristic / quality information (e.g., MCS / Nss / SNR) for a channel from an OBSS STA (e.g., STA1 associated with AP1) to a BSS AP (e.g., AP2), which is transmitted in advance by a BSS AP (e.g., AP2) to an OBSS AP (e.g., AP1).

[0244] Example 3-1

[0245] The aforementioned channel characteristic / quality-related information can be transmitted by utilizing the PHY reserved field of the NDP. The reserved field may include some or all of the 5 bits corresponding to disregard in the U-SIG 1 field, 1 bit corresponding to validate in the U-SIG 1 field, 2 bits corresponding to validate in the U-SIG 2 field, and 2 bits corresponding to disregard in the EHT-SIG.

[0246] For example, in the case where only one STA exists, even if the NDP includes the aforementioned channel characteristic / quality-related information, it can be identified as belonging to that single STA. In this case, the ID information of the STA may not be included in the NDP.

[0247] Example 3-2

[0248] Instead of transmitting an NDP in response to an NDPA frame, it is defined to transmit a general PPDU (e.g., a PPDU containing a DATA field such as a MU PPDU), and the MAC frame of such a general PPDU may include the aforementioned channel characteristic / quality related information. Accordingly, an OBSS AP (e.g., AP1) may receive the aforementioned channel characteristic / quality related information through the MAC frame of the general PPDU. Based on the aforementioned channel characteristic / quality related information, the OBSS AP (e.g., AP1) may transmit a trigger frame indicating an appropriate MCS / Nss for channel state information feedback of an OBSS STA (e.g., STA1 associated with AP1).

[0249] For sounding based on a standard PPDU transmitted instead of an NDP, the PPDU may include the following characteristics.

[0250] For example, beamforming may not be applied to the corresponding PPDU.

[0251] For example, the number of LTFs of the PPDU may be determined based on the number of antennas of the AP transmitting the PPDU. Alternatively, the number of LTFs of the PPDU may be determined based on the transmission dimension (or number of spatial streams) to be sounded.

[0252] For example, between the transmitting and receiving sides of the PPDU, the V matrix associated with the PPDU (e.g., a beamforming steering matrix associated with compressed channel state information) can be pre-set / defined as a default matrix. For example, if the size of the V matrix is ​​4 by 2, the default matrix can be pre-set / defined as [[1 0 ; 0 1 ; 1 0 ; 0 1].

[0253] Example 3-3

[0254] During the OBSS sounding process, the transmission of NDPA frames by the OBSS AP (e.g., AP1) and the transmission of NDPs by the BSS AP (e.g., AP2) are performed in the same manner as before, and the BSS AP (e.g., AP2) may additionally transmit a PPDU containing the aforementioned channel characteristic / quality related information. In this case, the time interval between the NDPA frame, the NDP, and the additional PPDU may be SIFS.

[0255] For example, additional PPDUs may be transmitted by the BSS AP (e.g., AP2) after the transmission of the NDP of the BSS AP (e.g., AP2) and before the transmission of the trigger frame of the OBSS AP (e.g., AP1).

[0256] Accordingly, the aforementioned channel characteristic / quality information can be transmitted between APs without significantly altering the existing sounding and feedback sequences. A MAC frame containing the aforementioned channel characteristic / quality information within an additional PPDU may be identical to an existing MAC frame, a modified MAC frame, or a newly defined MAC frame (e.g., a new frame for overhearing assistance purposes).

[0257] For example, the Co-BF sounding invite frame or Co-BF sounding response frame transmitted or received before the Co-BF sounding NDPA (or UHR NDPA) frame of the initiating AP is transmitted may contain the aforementioned channel characteristic / quality related information. Alternatively, an additional PPDU transmitted by the BSS AP (e.g., AP2) after the transmission of the NDP of the BSS AP (e.g., AP2) and before the transmission of the trigger frame of the OBSS AP (e.g., AP1) may include the Co-BF sounding invite frame or Co-BF sounding response frame.

[0258] Examples 3-4

[0259] The NDPA frame transmitted by the BSS AP (e.g., AP2) may include the aforementioned channel characteristic / quality related information.

[0260] For example, among the multiple STA Info fields (e.g., special STA Info fields) included in the Co-BF NDPA (or UHR NDPA, or UHR Co-BF NDPA) frame defined for OBSS sounding (or Co-BF sounding), the second STA Info field may include the aforementioned channel characteristic / quality related information (e.g., recommended MCS information).

[0261] For example, during the OBSS sounding process performed in the first phase, an AP (e.g., AP2) transmitting an NDPA frame can transmit desired / recommended MCS / Nss / SNR information regarding channel state information feedback to another AP (e.g., AP1). When the AP (e.g., AP1) that receives the recommended MCS transmits a BFRP trigger frame to request CSI feedback from the STA(s) during the OBSS sounding process performed in the second phase, it can set the MCS / Nss to be applied to the CSI feedback based on the recommended MCS / Nss / SNR information from the first phase. Accordingly, the AP of the other BSS (e.g., AP2) can easily receive the CSI feedback (e.g., compressed beamforming / CQI frame) transmitted by the STA.

[0262] For example, in the initial OBSS sounding process, since there is no prior information, the lowest / strongest MCS / NSS (e.g., MCS 0 and 1 SS) can be applied to transmit CSI feedback.

[0263] Examples of the aforementioned channel characteristic / quality-related information (e.g., recommended MCS information) being included in the NDPA frame are described below.

[0264] FIG. 13 is a diagram showing exemplary formats of the STA information field of an NDPA frame according to the present disclosure.

[0265] The examples in FIG. 13 show subfields included in a specific STA Info field (e.g., the second STA Info field) within an NDPA frame. In the examples in FIG. 13, the names, locations, and sizes of each subfield are merely exemplary, and channel characteristic / quality related information (e.g., recommended MCS information) according to the present disclosure may be included in subfields with different names, locations, and sizes.

[0266] In the example of FIG. 13(a), the AID11 subfield of the second STA Info field can be set to the ID of the responding AP receiving the NDPA frame. The STA Info field may include both the recommended MCS subfield and the recommended Nss subfield, or only one of them. Alternatively, instead of the two fields, an SNR subfield of a specific bit width may be included.

[0267] There is a problem in that the overhead is too high for an AP (e.g., AP2) transmitting an NDPA frame to transmit MCS / Nss / SNR information for each of all STAs associated with the responding AP (e.g., AP1) to the responding AP (e.g., AP1). Therefore, the AP (e.g., AP2) transmitting the NDPA frame can select the lowest / strongest MCS / Nss among the MCS / Nss for multiple STAs and include the selected MCS / Nss information in the second STA Info field of the Co-BF NDPA frame and transmit it to the responding AP (e.g., AP1).

[0268] In the previous sounding process, when the responding AP (e.g., AP1) sends a trigger frame petitioning the STA(s) to feed back channel state information based on the NDP from the AP of another BSS (e.g., AP2) in the Co-BF sounding process initiated by itself, the trigger frame may indicate an MCS / Nss value based on the lowest / strongest MCS / Nss selected by the AP of the other BSS (e.g., AP2).

[0269] Examples 3-5

[0270] The NDPA frame transmitted by the BSS AP (e.g., AP2) may include the aforementioned channel characteristic / quality related information.

[0271] When an AP (e.g., AP2) transmitting an NDPA frame selects the lowest / strongest MCS / Nss among multiple STAs associated with a responding AP (e.g., AP1) and transmits the selected MCS / Nss information through an NDPA frame, it may be difficult to achieve the effect of reducing the time the CSI feedback transmission occupies the medium because the probability of the lowest MCS / Nss being selected may be too high.

[0272] An AP transmitting an NDPA frame (e.g., AP2) transmits MCS / Nss / SNR information for each of all STAs associated with the responding AP (e.g., AP1) to the responding AP (e.g., AP1), and the responding AP (e.g., AP1) determines only the STA(s) among its associated STA(s) to participate in Co-BF sounding, and can select the lowest / strongest MCS / Nss among the determined STA(s).

[0273] When a response AP (e.g., AP1) in a previous sounding process sends a trigger frame requesting that the STA(s) feed back channel state information based on an NDP from another BSS AP (e.g., AP2) in a Co-BF sounding process initiated by itself, the trigger frame may indicate an MCS / Nss value selected by itself (e.g., AP1).

[0274] Recommended MCS / Nss information for multiple STAs included in an NDPA frame can be included in a special STA Info field for each STA. FIG. 13(b) shows an exemplary format of a special STA Info field containing recommended MCS / Nss information for a single STA. Special STA Info fields of the format shown in FIG. 13(b) can be included in the NDPA frame as many times as there are STAs.

[0275] In FIG. 13(b), the AID11 subfield may be set to a value of 2047, as with the first STA Info field, or to a reserved value (e.g., one of the ranges from 2008 to 2044). The STA ID subfield may identify which STA the recommended MCS subfield and / or recommended Nss subfield corresponds to. The corresponding STA Info field may include both the recommended MCS subfield and the recommended Nss subfield, or only one of them. Alternatively, instead of the two fields, an SNR subfield of a specific bit width may be included.

[0276] The flag field can indicate whether a subsequent special STA Info field exists.

[0277] In existing wireless LAN systems, NDP sounding between APs is not defined, and when NDP sounding between APs is introduced for Co-BF sounding, information regarding the recommended MCS of the second AP, etc., may be transmitted to the first AP in advance according to the examples according to the present disclosure. The first AP may instruct the STA(s) to provide information such as the MCS based on the recommended MCS of the second AP through a BFRP trigger frame requesting feedback on channel state information of its associated STA(s) (e.g., channel state information regarding the channel between the second AP and the STA). Accordingly, a frame containing channel state information transmitted by the STA(s) can be easily received / acquired by the second AP. Accordingly, since the APs can apply beamforming / precoding for Co-BF using the acquired channel information, Co-BF performance can be improved.

[0278] The embodiments described above are combinations of the components and features of the present disclosure in a specific form. Each component or feature should be considered optional unless otherwise explicitly stated. Each component or feature may be implemented in a form not combined with other components or features. Additionally, it is possible to construct embodiments of the present disclosure by combining some components and / or features. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment, or may be replaced with corresponding components or features of another embodiment. It is obvious that embodiments may be constructed by combining claims that are not explicitly related in the claims, or that they may be included as new claims by amendment after filing.

[0279] It is obvious to those skilled in the art that the present disclosure may be embodied in other specific forms without departing from the essential features of the present disclosure. Accordingly, the detailed description set forth above should not be interpreted restrictively in all respects and should be considered exemplary. The scope of the present disclosure shall be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present disclosure are included within the scope of the present disclosure.

[0280] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that enable operations according to the methods of various embodiments to be executed on a device or computer, and a non-transitory computer-readable medium on which such software or instructions, etc. are stored and executable on a device or computer. Instructions that may be used to program a processing system to perform the features described in the present disclosure may be stored on or within a storage medium or a computer-readable storage medium, and the features described in the present disclosure may be implemented using a computer program product comprising such a storage medium. The storage medium may include, but is not limited to, high-speed random access memory such as DRAM, SRAM, DDR RAM, or other random access solid-state memory devices, and may include non-volatile memory such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory may optionally include one or more storage devices located remotely from the processor(s). Memory or alternatively, non-volatile memory device(s) within memory comprises a non-transient computer-readable storage medium. The features described in this disclosure may be stored in any one of the machine-readable media and integrated into software and / or firmware that can control the hardware of a processing system and allow the processing system to interact with other mechanisms utilizing results according to the embodiments of this disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0281] Although the method proposed in this disclosure has been described with an example applied to an IEEE 802.11-based system, it can be applied to various wireless LANs or wireless communication systems in addition to IEEE 802.11-based systems.

Claims

1. A step of receiving recommended MCS (modulation and coding scheme) information from the second AP via the first access point (AP); A step of transmitting a trigger frame soliciting channel state information from a station (STA) to the STA by the first AP; and The method includes the step of receiving the channel status information from the STA by the first AP, The above recommended MCS information is a method in which the recommended MCS information is the MCS information recommended for channel state information feedback.

2. In Paragraph 1, The transmission of the channel status information by the above STA is a method based on the above recommended MCS information.

3. In Paragraph 1, The above trigger frame includes the above recommended MCS information, a method.

4. In Paragraph 1, A method in which the channel status information transmitted by the STA is received by the second AP.

5. In Paragraph 1, A method in which the above-mentioned second AP is an AP that transmits NDP (null data physical layer (PHY) protocol data unit (PPDU)).

6. In Paragraph 1, A method in which the above-mentioned recommended MCS information is included in an NDP announcement frame from the above-mentioned second AP.

7. In Paragraph 6, The above NDP notice frame is transmitted during the first sounding process, and The above trigger frame is transmitted during the second sounding process, a method.

8. In Paragraph 7, A method in which the above channel status information is based on the NDP transmitted from the second AP during the above second sounding process.

9. In Paragraph 6, The above NDP notice frame includes multiple STA information (STA Info) fields, and A method in which the recommended MCS information is included in a specific subfield of a specific STA Info field among the plurality of STA Info fields.

10. In Paragraph 9, A method in which a specific value of the above specific subfield indicates that there is no recommended MCS.

11. In Paragraph 1, A method in which, based on channel state information of a plurality of STAs being petitioned by the above trigger frame, the recommended MCS information corresponds to the lowest MCS for the plurality of STAs.

12. In Paragraph 1, A method in which the first AP and the second AP perform coordinated beamforming (Co-BF).

13. In Paragraph 1, The above trigger frame is a BFRP (beamforming report poll) trigger frame, a method.

14. In Paragraph 1, The above STA is a non-AP STA associated with the above 1 AP, method.

15. One or more transceivers; and It includes one or more processors connected to the above one or more transmitters and receivers, and The above one or more processors are: Receive recommended MCS (modulation and coding scheme) information from a second access point (AP) through one or more of the above-mentioned transceivers; Transmitting a trigger frame soliciting channel state information from a station (STA) to the STA through the one or more transceivers; and The above channel status information is configured to be received from the STA through the one or more transceivers, and The above recommended MCS information is the first AP, which is the recommended MCS information regarding channel state information feedback.

16. A step of transmitting recommended MCS (modulation and coding scheme) information to the first AP via the second access point (AP); and The method includes the step of receiving channel status information from a station (STA) solicited by a trigger frame from the first AP via the second AP. The above recommended MCS information is the recommended MCS information regarding channel status information feedback, method.

17. One or more transceivers; and It includes one or more processors connected to the above one or more transmitters and receivers, and The above one or more processors are: Transmitting recommended MCS (modulation and coding scheme) information to a first access point (AP) through one or more transceivers; and Channel status information from a station (STA) solicited by a trigger frame from the first AP is configured to be received through the one or more transceivers, and The above recommended MCS information is the second AP, which is the recommended MCS information regarding channel status information feedback.

18. One or more processors; and A processing device comprising one or more computer memories that are operably connected to one or more processors and store instructions for performing a method according to any one of claims 1 to 14 based on execution by one or more processors.

19. One or more non-transitory computer-readable media storing one or more instructions that are executed by one or more processors to control the execution of a method according to any one of claims 1 through 14.

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