WO2025150817A1 - Method and device for ndp sounding in wireless lan system - Google Patents

Abstract

Disclosed are a method and device for NDP sounding in a wireless LAN system. The method according to an embodiment of the present disclosure may comprise the steps in which: an STA receives an NDP announcement frame from a first AP; and the STA transmits a frame including channel state information to the first AP.

Description

NDP sounding method and device in wireless LAN system

The present disclosure relates to a method and device for sounding null data physical protocol data unit (PPDU) (NDP: null data PPUD) in a Wireless Local Area Network (WLAN) system.

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

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

The technical problem of the present disclosure is to provide an NDP sounding method and device.

An additional technical problem of the present disclosure is to provide an NDP sounding method and device for obtaining channel information for an overlapping basic service set (OBSS) STA in a wireless LAN system supporting multi-AP (multi access point) operation.

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

A method according to one aspect of the present disclosure may include: receiving, by a station (STA), a null data PPDU (physical protocol data unit) (NDP: null data PPDU) announcement frame from a first access point (AP); and transmitting, by the STA, a frame including channel state information to the first AP. The NDP announcement frame includes a plurality of STA information fields, and a variant of the NDP announcement frame may be identified by at least a first STA information field among the plurality of STA information fields.

A method according to an additional aspect of the present disclosure may include: transmitting, by a first access point (AP), a null data PPDU (physical protocol data unit) (NDP: null data PPDU) announcement frame to a station (STA); and receiving, by the first AP, a frame including channel state information from the STA. The NDP announcement frame includes a plurality of STA information fields, and a variant of the NDP announcement frame may be identified by a first one or more STA information fields among the plurality of STA information fields.

According to the present disclosure, it is possible to obtain channel information for an OBSS STA as well as channel information for a BSS STA.

In addition, according to the present disclosure, multi-AP (multi access point) operation can be smoothly supported by acquiring channel information for an OBSS STA.

In addition, according to the present disclosure, frequency resources can be efficiently utilized as they can be recycled according to a spatial reuse technique in which multiple BSSs cooperate.

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

The accompanying drawings, which are incorporated in and are incorporated in and are intended to provide a further understanding of the present disclosure, illustrate embodiments of the present disclosure and together with the description serve to explain the technical features of the present disclosure.

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

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

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

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

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

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

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

Figure 8 illustrates an exemplary format of an NDP announcement frame to which the present disclosure can be applied.

FIG. 9 illustrates an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

FIG. 10 illustrates an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

FIG. 11 illustrates a STA information field of an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

FIG. 12 illustrates a STA information field of an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

FIG. 13 is a diagram illustrating the operation of an STA for an NDP sounding method according to one embodiment of the present disclosure.

FIG. 14 is a diagram illustrating the operation of an AP for an NDP sounding method according to one embodiment of the present disclosure.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The one or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. The 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 the one or more processors (102, 202). The descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed in this disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this disclosure may be implemented using firmware or software configured to perform one or more of the following: included in one or more processors (102, 202), or stored in one or more memories (104, 204) and driven by one or more of the processors (102, 202). The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this disclosure may be implemented using firmware or software in the form of codes, instructions and/or sets of instructions.

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

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

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

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

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

The structure of a wireless LAN system can be composed of multiple components. A wireless LAN supporting transparent STA mobility to a higher layer can be provided through the interaction of multiple components. A BSS (Basic Service Set) corresponds to a basic configuration block of a wireless LAN. FIG. 2 illustrates an example in which two BSSs (BSS1 and BSS2) exist and two STAs are included as members of each BSS (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2). An ellipse representing a BSS in FIG. 2 can also be understood as representing a coverage area in which STAs included in the corresponding BSS maintain communication. This area can be referred to as a BSA (Basic Service Area). If an STA moves out of the BSA, it cannot directly communicate with other STAs within the corresponding BSA.

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

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

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

DS refers to a structure in which BSSs are interconnected. Specifically, a BSS may exist as an extended component of a network composed of multiple BSSs, as shown in FIG. 2. DS is a logical concept and can be specified by the characteristics of a distributed system medium (DSM). In this regard, a wireless medium (WM) and a DSM can be logically distinguished. Each logical medium is used for a different purpose and is used by different components. These media are neither limited to being the same nor limited to being different. In this way, the flexibility of a wireless LAN structure (DS structure or other network structure) can be explained in that multiple media are logically different. In other words, a wireless LAN structure can be implemented in various ways, and each wireless LAN structure can be independently specified by the physical characteristics of each implementation example.

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

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

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

In addition to the structure of the DS described above, an Extended Service Set (ESS) may be established to provide wider coverage.

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

In a wireless LAN system, no assumption is made about the relative physical locations of the BSSs, and all of the following configurations are possible: The BSSs can be partially overlapped, which is a common configuration used to provide continuous coverage. Also, the BSSs can be physically unconnected, and logically there is no limit to the distance between the BSSs. Also, the BSSs can be physically co-located, which can be used to provide redundancy. Also, one (or more) IBSS or ESS networks can physically co-exist in the same space as one (or more) ESS networks. This can correspond to ESS network configurations such as cases where ad-hoc networks operate at locations where ESS networks exist, cases where physically overlapping wireless networks are configured by different organizations, or cases where two or more different access and security policies are required at the same location.

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

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

In step S310, the STA may perform a network discovery operation. The network discovery operation may include a scanning operation of the STA. That is, in order for the STA to access the network, it must find a network that it can participate in. The STA must identify a compatible network before participating in the wireless network, and the process of identifying networks existing in a specific area is called scanning.

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

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

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

The authentication process includes 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 for the authentication request/response corresponds to a management frame.

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

The STA may transmit an authentication request frame to the AP. The AP may determine whether to allow authentication for the STA based on information included in the received authentication request frame. The AP may provide the result of the authentication processing to the STA through an authentication response frame.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

If STA3 cannot overhear the CTS frame from STA2 but can overhear the RTS frame from STA1, STA3 can set a NAV timer for the subsequently transmitted frame transmission period (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 the RTS frame from STA1 but can overhear the CTS frame from STA2, STA3 can set a NAV timer for the subsequently transmitted frame transmission period (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. STA3 can update the NAV timer using the duration information contained in the new frame if it receives a new frame before the NAV timer expires. STA3 does not attempt to access the channel until the NAV timer expires.

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

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

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

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

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

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

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

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

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

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

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

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

Various forms of PPDUs are 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 can also be called a non-HT PPDU format (Fig. 7(a)).

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

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

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

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

The EHT MU PPDU in Fig. 7(e) corresponds to a PPDU that carries one or more data (or 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.

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

The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated and mapped based on a predetermined subcarrier frequency interval (e.g., 312.5 kHz) so that even legacy STAs can attempt to demodulate and decode them. 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 and mapped based on a predetermined subcarrier frequency interval (e.g., 78.125 kHz) so that they can be demodulated and decoded by an STA that successfully decodes a non-legacy SIG (e.g., U-SIG and/or EHT-SIG) and obtains the information included in the corresponding fields. These can be referred to as EHT modulated fields.

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

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

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

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

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

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

For example, the version-independent bits of U-SIG may include a 3-bit PHY version identifier, which may indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted and received PPDU. 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 about the length of a TXOP (transmission opportunity) and information about a BSS color ID.

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

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

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

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

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

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

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

The number of user-specific fields can be determined based on the number of users. One user block field can include at most two user fields. Each user field can be associated with an MU-MIMO allocation or associated with a non-MU-MIMO allocation.

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

An RU may include multiple subcarriers (or tones). An RU may be used when transmitting signals to multiple STAs based on the OFDMA technique. An RU may also be defined when transmitting signals to one STA. Resources may be allocated in RU units for non-legacy STFs, non-legacy LTFs, and Data fields.

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

RUs of different sizes can be defined, such as 26-tone RU, 52-tone RU, 106-tone RU, 242-tone RU, 484-tone RU, 996-tone RU, 2Х996-tone RU, 3Х996-tone RU, etc. A multiple RU (MRU) is distinct from multiple individual RUs and corresponds to a group of subcarriers consisting of multiple RUs. For example, one MRU can be defined as 52+26-tones, 106+26-tones, 484+242-tones, 996+484-tones, 996+484+242-tones, 2Х996+484-tones, 3Х996-tones, or 3Х996+484-tones. Additionally, multiple RUs constituting one MRU may or may not be consecutive in the frequency domain.

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

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

Null data PPDU (NDP: null data PPDU) announcement (NDPA: NDP announcement) frame

In a wireless LAN system, a sounding procedure/protocol is 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 fed-back estimate.

The beamforming STA can feed back an estimate of the channel status to the beamformer STA through a compressed beamforming/CQI (channel quality indication) report frame. The fed back information can include single user (SU) feedback, multi-user (MU) feedback, CQI feedback, etc.

A beamformer STA may transmit an NDP announcement and an NDP to the beamformer(s), and receive feedback information from the beamformer STA(s). Additionally or alternatively, the beamformer STA may transmit an NDP announcement and an NDP to the beamformer(s), and transmit a beamforming report poll (BFRP) or a BFRP trigger to the beamformer(s), and receive feedback information from the beamformer(s).

The NDP Announcement (NDPA) frame may have multiple types/variants. For example, the NDP Announcement frame may be composed of various formats such as VHT NDP Announcement frame, HE NDP Announcement frame, EHT NDP Announcement frame, etc. These formats may be distinguished by the NDP Announcement Variant subfield in the sounding dialog token field.

Figure 8 illustrates an exemplary format of an NDP announcement frame to which the present disclosure can be applied.

The NDP announcement frame may include one or more STA information (Info) fields. If the NDP announcement frame includes only one STA Info field, the RA (receiver address) field may be set to the address of an STA that can provide feedback. If the NDP announcement frame includes multiple STA Info fields, the RA field may be set to a broadcast address.

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

Among the eight bits (B0-B7) of the Sounding Dialog Token field, the first two bits (B0 and B1) can be used to indicate the type/variant of the NDP announcement frame. For example, for VHT or HE, B0 can have a value of 0, and if the value of B1 is 0, it can indicate a VHT NDP announcement frame, and if the value of B1 is 1, it can indicate a HE NDP announcement frame. For example, an EHT NDP announcement frame can correspond to the case where the values of B0 and B1 are both set to 1. If the value of B0 is 1 and the value of B1 is 0, it can correspond to a ranging NDP announcement frame.

For VHT STA, the first two bits (B0 and B1) of the Sounding Dialog Token field are defined as reserved, so VHT STA can recognize the Sounding Dialog Token Number field of bits B2-B7 regardless of the values of B0 and B1.

For VHT STA, the first two bits (B0 and B1) of the Sounding Dialog Token field are defined as reserved. Therefore, a VHT STA can recognize the Sounding Dialog Token Number field of bits B2-B7, regardless of the values of B0 and B1.

For HE STA, the first bit (B0) of the Sounding Dialog Token field is defined as reserved, and the value of the second bit (B1) is defined as 0 to indicate a VHT NDP announcement frame, and as 1 to indicate a HE NDP announcement frame. Therefore, HE STA can recognize the Sounding Dialog Token Number field of bits B2-B7 when the value of B1 is 1, regardless of the value of B0.

The Sounding Dialog Token Number subfield (bit positions B2-B7) may contain a value identifying the NDP announcement frame selected by the beamformer.

An NDP announcement frame may contain n STA Info fields, where n is an integer greater than or equal to 1. A single STA Info field has a size of K octets, where K=2 for a VHT NDP announcement frame and K=4 for a HE NDP announcement frame or an EHT NDP announcement frame.

As in the example of Fig. 8(a), the STA Info field of the VHT NDP announcement frame may include AID12, feedback type, and Nc index subfields.

The AID12 subfield contains the 12 least significant bits (LSBs) of the AID of the STA that is expected to process a subsequent NDP and prepare sounding feedback.

The feedback type subfield indicates the type of feedback requested, with a value of 0 corresponding to SU and a value of 1 corresponding to MU.

The Nc index subfield indicates the number of columns (i.e., Nc) in the compressed beamforming feedback matrix minus 1 (i.e., Nc-1) when the feedback type is MU. In the case of SU, the Nc index field is reserved.

The example in Fig. 8(b) shows the format of the STA Info field of the HE NDP announcement frame when the value of the AID11 field is not a specific value (e.g., 2047).

A value of the AID11 subfield other than a specific value (e.g., 2047) contains the 11 LSBs of the AID of the STA that is expected to process the subsequent NDP and prepare sounding feedback.

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 according to the bandwidth of the NDP announcement frame, and its unit may be a 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.

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

The disambiguation subfield may be set to 1 to help non-HE STAs (e.g., VHT STAs) avoid misinterpreting this field as an AID field.

The Nc subfield is set to a value of Nc-1. When the feedback type is SU or MU, Nc corresponds to the number of columns in the compressed beamforming feedback matrix, and when the feedback type is CQI, Nc may correspond to the number of STS (space-time streams). For NDP announcement frames individually addressed to a single STA with an AID11 subfield value other than 2047, the Nc subfield may be reserved.

The example in Fig. 8(c) shows the format of the STA Info field of the HE NDP announcement frame when the value of the AID11 field is a specific value (e.g., 2047).

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 in the disallowed subchannel bitmap corresponds to the 20 MHz subchannel having the lowest frequency among all 20 MHz subchannels within the BSS bandwidth. Each subsequent bit in the bitmap corresponds to the next higher 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 that 20 MHz subchannel may be disallowed for PPDUs using that particular tone plan. STA(s) addressed by the NDP announcement frame shall not include tones from disallowed 242-tone RUs when determining the average SNR of STS 1 to 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.

An example of Fig. 8(d) shows the format of the STA Info field of the EHT NDP announcement frame.

The AID11 subfield can be defined as shown in Table 1. Basically, the AID11 subfield contains the identifier of the STA that is expected to process the subsequent NDP and prepare sounding feedback.

The value of the AID subfield explanation NDP Announcement Frame Type/Variant
Applicability 0 - Addressed to an AP or mesh AP or IBSS STA with a combined STA Info field. Applicable to all variants 1-2007 - If the NDP announcement frame is not a ranging variant, the STA Info field is addressed to the associated STA having an AID equal to the value of the AID11 subfield.- If the NDP announcement frame is a ranging variant, the STA Info field is addressed to the non-associated STA or associated STA having an RSID/AID equal to the value of the RSID11/AID11 subfield.
- 2007 values are reserved for EHT variants. Applicable to all variants 2008-2042 reserved Not applicable to all variants 2043 - If the NDP announcement frame is a ranging variant, the STA Info field contains a sequence authentication code. - Otherwise, the AID11 value is reserved. Applies only to ranging variants 2044 - If the NDP announcement frame is a ranging variant, the STA Info field contains a partial TSF (timing synchronization function). - Otherwise, the AID11 value is reserved. Applies only to ranging variants 2045 - If the NDP announcement frame is a ranging variant, the STA Info field contains ranging measurement parameters. - Otherwise, the AID11 value is reserved. Applies only to ranging variants 2046 reserved Not applicable to all variants 2047 - If the NDP announcement frame is a HE variant, the STA Info field contains the disallowed subchannel bitmap. - Otherwise, the AID11 value is reserved. Applicable to HE variant only

The partial bandwidth (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 a request for each resolution bandwidth from low to high frequency, with the first bit (B1) of the bitmap corresponding to the lowest resolution bandwidth. Each bit of the feedback bitmap is set to 1 if feedback is requested for the corresponding resolution bandwidth.

If the bandwidth of the EHT NDP announcement frame is less than 320 MHz, the resolution bit (B0) can be set to 0 to indicate a resolution of 20 MHz.

When the bandwidth of the EHT NDP announcement frame is 20 MHz, B1 is set to 1 to indicate that feedback for 242-tone RU is requested, and B2-B8 are reserved and can be set to 0.

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

When the bandwidth of the PPDU carrying the EHT NDP announcement 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 low to high frequency, and B5-B8 can be reserved and set to 0.

When the bandwidth of the PPDU carrying the EHT NDP announcement 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 low to 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 low to high frequency in the upper 80 MHz.

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

The partial bandwidth subfield can have values such as the examples in Table 2, depending on the relevant settings.

For TB sounding, the feedback type and Ng subfields and the codebook size subfield can be set according to examples as shown in Table 3.

For non-TB sounding, the feedback type and Ng subfields and the codebook size subfield can be set according to examples as shown in Table 4.

The disambiguation subfield may be set to 1 to help non-EHT STAs (e.g., VHT STAs) avoid misinterpreting the field as an AID field.

In the EHT NDP announcement frame, RA is set to a broadcast address, and the following may apply. If the Feedback Type and Ng subfield 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 in the Nc index subfield exceeding 7 are reserved. If the Feedback Type and Ng subfield 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 in the Nc index subfield exceeding 7 are reserved. One or more STA Info fields may be present.

In an EHT NDP announcement frame with a single STA Info field, the RA field is set to an individual address and the Nc index subfield may be reserved.

Multi-link (ML) operation

Below, the multi-link (ML) operation supported by the STA according to the present disclosure is described.

The STA (AP STA and/or non-AP STA) described in the present disclosure can support multi-link (ML) communication. ML communication can mean communication supporting multiple links. Links related to ML communication can include channels (e.g., 20/40/80/160/240/320MHz channels) of a frequency band (e.g., 2.4GHz band, 5GHz band, 6GHz band, etc.) in which the STA operates. Multiple links used for ML communication can be configured in various ways. For example, multiple links supported for one STA for ML communication may belong to the same frequency band or may belong to different frequency bands. In addition, each link may correspond to a frequency unit of a predetermined size (e.g., channel, subchannel, RU, etc.). In addition, some or all of the multiple links may be frequency units of the same size or may be frequency units of different sizes.

When one STA supports multiple links, the transmitting and receiving devices supporting each link can operate as one logical STA. That is, a multi-link device (MLD) means a device that has one or more affiliated STAs as a logical entity and a single MAC data service and a single MAC service access point (SAP) for logical link control (LLC). A non-AP MLD means an MLD in which each STA affiliated with the MLD is a non-AP STA. A multi-radio non-AP MLD means a non-AP MLD that supports receiving or exchanging frames on more than one link at a time. An AP MLD means an MLD in which each STA affiliated with the MLD is an AP STA.

Multi-link operation (MLO) may enable a non-AP MLD to discover, authenticate, associate, and set up multiple links with an AP MLD. Based on the supported capabilities exchanged during the association procedure, each link may enable channel access and frame exchange between the non-AP MLD and the AP MLD. An STA affiliated to an MLD may select and manage its capabilities and operating parameters independently from other STA(s) affiliated to the same MLD.

Through the multi-link setup process, the AP MLD and/or the non-AP MLD can transmit and receive link-related information that the MLD can support. The link-related information may include one or more of information about whether the MLD supports simultaneous transmit and receive (STR) operation or non-simultaneous transmit and receive (NSTR) operation on multiple links, information about the number/upper limit of UL/DL links, information about locations/bandwidths/resources of UL/DL links, information about frame types (e.g., management, control, data, etc.) that are available or preferred on at least one UL/DL link, information about ACK policies that are available or preferred on at least one UL/DL link, or information about traffic identifiers (TIDs) that are available on at least one UL/DL link.

An AP MLD (e.g., NSTR mobile AP MLD) may set one of the multiple links as the primary link. The AP MLD may transmit beacon frames, probe response frames, and group addressed data frames only on the primary link. The remaining other link(s) of the multiple links may be referred to as non-primary links. An AP MLD operating on a non-primary link may operate not to transmit beacon frames or probe response frames. In addition, a non-AP MLD may perform frame exchange during authentication, (re)association, and 4-way handshaking only on the primary link.

A setup link is defined as enabled if at least one traffic identifier (TID) is mapped to the link through the multi-link setup process, and a setup link can be defined as disabled if no TID is mapped to the link. A TID must always be mapped to at least one setup link unless admission control is used. By default, a TID is mapped to all setup links, so all setup links can be enabled.

When a link is activated, the link can be used for frame exchange depending on the power state of the non-AP STAs operating on the link. Only MSDUs or A-MSDUs with TIDs mapped to the activated link can be transmitted on the link. Management frames and control frames can only be transmitted on the activated link.

When a link is disabled, that link may not be used for frame exchange, including management frames for both DL and UL.

During the multi-link setup process, activation/deactivation of each link can be instructed through TID-to-Link mapping. TID-to-Link mapping can be performed in default mapping mode or/and negotiation mapping mode.

Among the STAs belonging to the MLD, one STA may provide information about one or more links other than the link on which it is located, for multi-link discovery (e.g., obtaining information about multiple links including the corresponding link on one link) or multi-link setup (e.g., simultaneously associating on multiple links by exchanging association request/response frames on one link). A multi-link (ML) element may be defined to provide such information.

Multi-AP operation

Multi-AP operation to which the method proposed in this disclosure can be applied is described.

Multi-AP operation is a general term for a technique in which multiple APs/STAs cooperate with each other to transmit and receive data when communicating with STA(s). For example, the following techniques can be used.

- Type 1: Co-transmission of Multi-APs/STAs: This transmission technique refers to a technique in which multiple APs transmit to STA(s) simultaneously. Co-transmission can be classified in detail as follows:

i) Co-transmission of Multi-APs/STAs to each STA (e.g., cooperative spatial reuse (C-SR)): APs/STAs share channel information (e.g., transmit power (Tx Power), received signal strength indicator (RSSI), etc.) with STA(s), and communication between each AP and STA can be performed at the same time based on the shared channel information.

ii) Joint transmission of Multi-APs/STAs to the same STA(s) (e.g., joint transmission (J-TX))

Multiple APs/STAs can share channel information and data with STA(s), and communication between multiple APs and STA(s) can be performed at the same time based on the shared channel information and data.

- Type 2: Multi-AP/STA coordination: Among multiple APs, an appropriate AP can divide the appropriate area (i.e. frequency/time/space area) and transmit to the appropriate STA(s).

i) Distinction by frequency domain (e.g., coordinated OFDMA (C-OFDMA)): APs/STAs share channel information according to frequency bands with STA(s), and based on the shared channel information, each AP selects an appropriate frequency band to perform communication between each AP and STA.

ii) Distinction by spatial domain (e.g., coordinated beamforming (C-BF)): APs/STAs share channel information with STA(s), and based on the shared channel information, a beamforming (BF) matrix suitable for communication of each AP or that does not interfere with other APs is calculated to perform communication between each AP and STA.

iii) Distinction by time domain (e.g., AP selection, relay, virtual BSS (V-BSS)): The representative AP selects suitable APs/STAs for the STA(s) (including the representative AP) and controls communication between the AP/STA and the STA.

In order to support the above Multi-AP operation, the representative AP can select and instruct an AP/STA (hereinafter referred to as a participating AP/STA) for communication with the STA. Here, the meanings of the representative AP and participating AP/STA are as follows.

i) Representative AP (also called master AP or sharing AP)

- The representative AP initiates and controls Multi-AP operation, a technology for transmission and reception by multiple APs.

- The representative AP groups the participating APs and manages the links with the participating APs so that information (e.g., information about channels and/or data) can be shared between the participating APs.

- The representative AP manages information about the BSS comprised of participating APs and information about STAs associated with the BSS.

ii) Participating AP (also called slave AP or shared AP)

- Participating APs are associated with a representative AP and can share control information, management information, and data traffic with each other.

- Participating APs basically perform the same functions as APs that can establish a BSS in a conventional WLAN system.

iii) Participating STA

- As in existing WLANs, a BSS is formed by association with a representative AP or participating AP.

Additionally, the Multi-AP operating environment is as follows.

The representative AP and the participating AP may be capable of direct transmission and reception of wired or wireless (e.g., control information and/or data) signals with each other. In addition, the representative AP and the STA may not be capable of direct transmission and reception of wireless signals (e.g., control information and/or data) with each other. In addition, the participating AP (i.e., associated with the STA) and the STA may be capable of direct transmission and reception of wireless signals (e.g., control information and/or data) with each other. In addition, one of the participating APs may become the representative AP.

Additionally, a rough example of a DL or UL procedure for Multi-AP operation can be performed as follows.

1. The representative AP instructs the participating AP(s) (e.g., initiation of multi-AP operation, scheduling information, etc.).

Here, after receiving an acknowledgment (Ack) from participating APs in response to the representative AP's instruction (e.g., initiation of Multi-AP operation, scheduling information, etc.), the representative AP can instruct Multi-AP operation by re-scheduling only the APs that transmitted the Ack.

2. Participating AP(s) transmit DL data transmission or DL trigger (i.e., trigger for UL data transmission of STA) to STA(s).

3. The receiving STA(s) transmits an Ack (i.e., when DL data is received) or UL data (i.e., when a trigger for UL data transmission is received) to the participating AP(s).

Here, for UL procedures (i.e., when STA transmits UL data to participating AP(s)), if necessary, participating AP(s) may also transmit Ack to STA(s).

4. Participating AP(s) can report results (or completion of multi-AP operation) to the representative AP.

Hereinafter, in the description of the present disclosure, for the convenience of explanation, the AP transmitting the trigger frame in step 1 is referred to as a representative AP, but is not limited thereto, and may be referred to as a master AP, a sharing AP, a primary AP, etc. In addition, the AP receiving the trigger frame in step 1 is referred to as a participating AP, but is not limited thereto, and may be referred to as a slave AP, a shared AP, a secondary AP, etc.

In this disclosure, we propose step 1 of the above-described procedure, i.e., a method in which a representative AP triggers (instructs to initiate) Multi-AP operation.

With respect to the above step 1, the way in which the representative AP instructs the Multi-AP operation (i.e., the way in which the Multi-AP operation is triggered) can be as follows.

1) Direct transmission instructions (or short-term instructions)

In this way, the representative AP can directly instruct the participating AP(s) to transmit. In other words, this can mean a method in which the representative AP dynamically instructs the participating AP(s) whenever a Multi-AP operation is initiated.

A frame that triggers a multi-AP operation may be referred to as a multi-AP downlink trigger frame (MAD trigger frame: Multi-AP DL Trigger frame), but the present disclosure is not limited thereto.

The MAD trigger frame can reuse the existing basic trigger frame structure. Alternatively, the MAD trigger frame can be configured as a new type of trigger frame. In this case, for example, the new type of MAD trigger frame can be indicated in the trigger type subfield. Alternatively, the MAD trigger frame can be defined as a new control frame.

While the existing trigger frame was transmitted for the purpose of triggering UL TB PPDU transmission of non-AP STAs, the MAD trigger frame is transmitted for the purpose of triggering DL PPDU transmission of participating APs participating in multi-AP operation, so their purposes are different.

1) Transmission section indication (or mid-term indication)

A representative AP can inform the participating AP(s) of the Multi-AP operation period. For example, a MU-RTS TXS trigger frame (i.e., a trigger frame that triggers the TXOP sharing procedure described above) can be used.

The existing MU-RTS TXS trigger frame notifies the TXOP section with the AP or another STA associated with the scheduled STA as the value of the triggered TXOP sharing mode subfield is set to 1 or 2. As an example of a method of applying the MU-RTS TXS trigger frame to the multi-AP operation in the present disclosure, the values of 1 or 2 of the triggered TXOP sharing mode subfield may be used identically. As another example, the reserved value 3 of the triggered TXOP sharing mode subfield may be used to separately define a TXOP allocation method for the multi-AP procedure. In addition, in order to support such a multi-AP operation, unlike the existing MU-RTS TXS trigger frame, it may be allowed to include one or more User Info fields.

NDPA Frame Format for OBSS NDP Sounding Procedures

In the current standard, the NDP sounding procedure means a procedure in which a BSS AP (hereinafter referred to as AP1) transmits a sounding NDP to STAs associated with the AP or STAs belonging to the BSS (hereinafter referred to as STA1), and receives feedback on measured and calculated channel information from STA1.

If a multi-AP technique is introduced, APs/STAs within a BSS may require channel information with APs/STAs (hereinafter referred to as OBSSs) of non-associated adjacent BSSs other than the BSS AP (hereinafter referred to as AP2/STA2, respectively). In this disclosure, a method for obtaining channel information using an NDP sounding procedure is proposed. However, since the AP and the STA in this disclosure may not be the same BSS, even if the existing NDP sounding procedure is used, the transmission and reception methods may be different accordingly. In this disclosure, such a channel measurement technique is collectively referred to as OBSS NDP sounding, and an OBSS NDP sounding procedure/configuration is proposed. In particular, a notification method for indicating NDP sounding is proposed.

In the present disclosure, a BSS and an OBSS are adjacent to each other, and AP1 (an AP of the BSS) and AP2 (an AP of the OBSS) can hear each other's signals (or a device that transmits each other's signals may exist between AP1 and AP2), STA1 (an AP of the BSS) can hear not only a signal of AP1 but also a signal of AP2, and STA2 (an STA of the OBSS) can hear not only a signal of AP2 but also a signal of AP1. (Some STA1 and STA2 may not be able to hear. Such STA1 and STA2 are referred to as STA1' and STA2' hereinafter.) In addition, AP1, AP2, STA1, and STA2 have the capability for Multi-AP operation and can perform Multi-AP operation depending on a situation or an instruction. AP1 and AP2 can be a sharing AP or a shared AP depending on a situation, and for example, an AP that has obtained a TXOP can be a sharing AP. Alternatively, a third AP can act as a sharing AP.

Although the present disclosure mainly describes a method for applying an OBSS NDP sounding procedure to a BSS AP/STA and an OBSS AP/STA for the convenience of explanation, the present disclosure is not limited thereto. That is, the present OBSS NDP sounding procedure can be extended to be applied to channel measurement of AP/STA(s) or relay AP/STA(s) for each link of an MLD, and in this case, the proposed method of the present disclosure can be referred to as an NDP sounding procedure for adjacent/different links. For example, when the proposed method of the present disclosure is applied to an MLD device, for example, in the description of the present disclosure, AP1 and AP2 can be included in a single MLD, and STA 1 and STA 2 can be included in a single MLD.

The transmission and reception frames required for the OBSS NDP sounding procedure may be as follows. In addition, trigger frames, BA (block ack) frames, etc. may be required.

- NDP announcement frame indicating OBSS sounding (hereinafter, for convenience of explanation, may be referred to as ONDPA (OBSS NDP announcement) frame)

- Sounding NDP

- Feedback frames (e.g. compressed beamforming/channel quality indication (CQI) reporting frames)

The operations of AP and STA for the OBSS sounding procedure of AP 1 (i.e., method of acquiring channel information from STA 2 of AP 1) are exemplified as follows. These procedures can be equally applied to the OBSS sounding procedure of AP 2 (i.e., method of acquiring channel information from STA 1 of AP 2).

- Example of AP operation

i) AP1 or AP2 or Sharing AP transmits ONDPA frame.

ii) AP1 transmits (sounding) NDP after xIFS (e.g. SIFS).

iii) When certain circumstances arise (e.g., requesting feedback from one or more STAs or when the RA field is broadcast), after xIFS (e.g., SIFS), AP1 or AP2 or the Sharing AP may transmit a beamforming report poll (BFRP) trigger frame.

iv) After xIFS (e.g., SIFS), AP1 can obtain OBSS channel information by receiving a feedback frame transmitted by STA2(s). Alternatively, AP2 or Sharing AP can transmit the OBSS channel information obtained after receiving the feedback frame transmitted by STA2(s) to AP1 (or Sharing AP).

v) AP1, AP2 or Sharing AP can collect this channel information and perform Multi-AP operation.

- Example of STA2 operation

i) STA2(s) receives an ONDPA frame from AP1 or AP2 or Sharing AP.

ii) If the received ONDPA frame includes information requesting feedback to STA2 (e.g., STA2's AID or OAID (OBSS AID), etc.), STA 2(s) receive (sounding) NDP transmitted after xIFS (e.g., SIFS) and generate channel information as instructed. If the ONDPA frame does not request feedback to itself, STA 2(s) can perform NAV setting.

iii) When a specific situation occurs (for example, when the RA field of the ONDPA frame is broadcast), STA 2(s) can receive a BFRP trigger frame transmitted by AP1 or AP2 or Sharing AP after xIFS (for example, SIFS) to determine resource information to be fed back, etc.

iv) After xIFS (e.g. SIFS), STA2(s) can transmit the generated channel information to AP1 or AP2 or Sharing AP through a feedback frame.

Among the above procedures/frames, in particular, the present disclosure proposes the following configuration/format of an NDP announcement frame indicating OBSS sounding. For example, the ONDPA frame may have a different configuration/format from the existing NDP announcement frame in that the AP indicates to OBSS STA(s) that are not associated with it, or the configuration/format of the existing NDP announcement frame may be used in the same manner.

Example 1: NDPA frame configuration to indicate OBSS sounding

A new format may be established/defined for NDPA frames to indicate OBSS sounding as follows:

FIG. 9 illustrates an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

Referring to FIG. 9, an NDPA frame for indicating OBSS sounding may be configured to include a frame control field, a duration field, a receiver address (RA) field, a transmitter address (TA) field, a source address (SA) or an AP address (AA) field, a sounding dialog token field, one or more STA information (Info) fields (i.e., a STA information list), and a Frame Check Sequence (FCS).

The frame control field can be set to Type=01 (i.e., control frame indication), subtype=0101 (i.e., NDPA frame indication). That is, it can be set to the same value as the existing NDPA frame.

Both the ToDS subfield and the FromDS subfield in the frame control field can be set to 1. In the case of existing NDPA frames, both the ToDS subfield and the FromDS subfield in the frame control field are set to 0, but in an NDPA frame to indicate OBSS sounding, both can be set to 1.

The SA(source address) or AA(AP address) field can be configured as follows: i) when the ToDS subfield is set to '1', or ii) when the FromDS subfield is set to '1', or iii) when both the ToDS subfield and the FromDS subfield are set to '1', a third address Address3) field can be included in the NDPA frame to indicate OBSS sounding, which can be defined as the SA field or the AA field. This field can separately indicate the MAC address of the AP of the BSS that the receiving STA includes/belongs to.

For example, the SA field can be set to include the definition described above in the meaning of the existing SA (source address) as follows.

- SA field: Indicates an individual address that identifies the MAC entity that initiated the transmission of the MSDU (MAC service data unit) (or a fragment of the MSDU) or A-MSDU (aggregated MSDU) included in the frame body field. Or, indicates the address of the AP with which the intended direct recipient STA(s) are associated.

As another example, a new AA (AP address) field can be defined as follows:

- AA field: Indicates the address of the AP with which the intended direct recipient STA(s) are associated.

Here, in the control frame for supporting Multi-AP operation as well as the ONDPA frame, there may be a case where an AP other than the BSS AP transmits a control frame for supporting Multi-AP operation. Therefore, unlike the conventional case, the control frame for supporting Multi-AP operation may be configured to include a third address (Address3) field in the control frame by setting the ToDS subfield to '1', or the FromDS subfield to '1', or both subfields to '1'.

The last 6 bits (B2 to B7) of the sounding dialog token field can be set as a sounding dialog token number subfield, and the first 2 bits (B0 to B1) can be defined as reserved. Alternatively, a value of '00' in B0 to B1 can be set to indicate an ONDPA frame, and other values can be defined as reserved. Alternatively, the values of B0 to B1 can also indicate the type of ONDPA frame. Alternatively, like the existing NDPA frame, the first 2 bits (B0 and B1) of the 8 bits (B0 to B7) of the sounding dialog token field can be used to indicate the type/variant of the NDP announcement frame.

The STA information (STA Info) field(s) included in the STA information list (STA Info list) may use the same format as the field defined in the existing EHT NDPA frame (i.e., see FIG. 8(d)). The AID11 subfield may include the AID value of the STA that must measure NDP and feed back. Here, the AID may be an AID value defined in the BSS and may also be used in the ONDPA frame of the OBSS AP, or may be a newly defined OAID (OBSS AID) value that the OBSS AP can use.

Fields/subfields not specifically described here may follow the format/structure of a conventional control frame or NDPA frame.

Meanwhile, the frame control field of the NDPA frame for indicating OBSS sounding may be set to Type=01 (i.e., control frame indication) and subtype=0110 (i.e., control frame extension indication). In addition, the control frame extension subfield may be defined with one of the previously reserved values from 1100 to 1111, so that the NDPA frame for indicating OBSS sounding may be configured as a new control frame. Since the configurations of the other fields are the same as the description described above, a detailed description is omitted.

Example 2: NDPA frame configuration to indicate OBSS sounding

The NDPA frame for indicating OBSS sounding can be set/defined using the same format and structure as the existing NDPA frame.

FIG. 10 illustrates an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

Referring to FIG. 10, an NDPA frame for indicating OBSS sounding may be configured to include a frame control field, a duration field, a receiver address (RA) field, a transmitter address (TA) field, a sounding dialog token field, one or more STA information (Info) fields (i.e., a STA information list), and a Frame Check Sequence (FCS).

The frame control field can be set to Type=01 (i.e., control frame indication), subtype=0101 (i.e., NDPA frame indication). In addition, both the ToDS subfield and the FromDS subfield can be set to '0'. That is, they can be set to the same value as the existing NDPA frame.

- RA field

If the NDPA frame for indicating OBSS sounding requests OBSS sounding to one STA, the RA field may be set to the address of the STA. Or, if the NDPA frame requests OBSS sounding to two or more STAs, the RA field may be set to a broadcast address.

Alternatively, the RA field may be set to a specific address value (e.g., specifying a group address such as a multicast-group address or a broadcast address) to indicate that the frame is an NDPA frame for indicating OBSS sounding. In this case, STAs having OBSS sounding capability (or capability for Multi-AP operation) can identify that the frame is an NDPA frame for indicating OBSS sounding through the specific address value even if the value of the RA field is not their own address, and can determine whether the frame includes an indication for themselves after decoding the frame.

- TA field

The TA field may be set to the address of the AP/STA transmitting the NDPA frame to indicate OBSS sounding or to the bandwidth signaling TA.

Alternatively, the TA field may be set to a specific address value (e.g., specifying a group address such as a multicast-group address or a broadcast address) to indicate that the frame is an NDPA frame for indicating OBSS sounding. In this case, STAs having OBSS sounding capability (or capability for Multi-AP operation) can identify that the frame is an NDPA frame for indicating OBSS sounding through the specific address value even if the value of the TA field is not the AP address of the BSS to which they belong, and can determine whether the frame includes an instruction for themselves after decoding the frame.

- Sounding dialog token field

The sounding dialog token field may consist of an NDP announcement variant subfield (first two bits) and a sounding dialog token number subfield (last six bits).

The existing NDP announcement variant subfield can identify the NDPA frame variant as shown in Table 5.

Referring to Table 5, according to the conventional method, if the value of the NDP Announcement Variant subfield is set to 0, the frame is identified as a VHT NDPA frame, if the value of the NDP Announcement Variant subfield is set to 1, the frame is identified as a Ranging NDPA frame, if the value of the NDP Announcement Variant subfield is set to 2, the frame is identified as a HE NDPA frame, and if the value of the NDP Announcement Variant subfield is set to 3, the frame is identified as an EHT NDPA frame.

Method 1: When the NDP announcement variant subfield = 1, the frame can be identified as a Ranging NDPA frame or an NDPA frame for indicating OBSS sounding. Here, as an example of a method for distinguishing between a Ranging NDPA frame and an NDPA frame for indicating OBSS sounding, one bit of the reserved bits of the STA Info field can be used. That is, when the one bit is '0' (or '1'), the frame can be identified as a Ranging NDPA frame, and when it is '1' (or '0'), the frame can be identified as an NDPA frame for indicating OBSS sounding. In this case, the STA Info field can be configured differently depending on whether the frame is a Ranging NDPA frame or an NDPA frame for indicating OBSS sounding. A specific description thereof will be described later.

Method 2: When the NDP announcement variant subfield = 3, the frame can be identified as an EHT NDPA frame or an NDPA frame for indicating OBSS sounding. Here, as an example of a method for distinguishing between an EHT NDPA frame and an NDPA frame for indicating OBSS sounding, a specific value (e.g., a value from 2007 to 2047) of the AID11 subfield of the first STA information (STA Info) field (i.e., a subfield carrying 11 least significant bits (LSBs) of an association identifier (AID) of an STA) can be used. For example, when the AID11 subfield is set to the specific value, the frame can be identified as an NDPA frame for indicating OBSS sounding. In this case, the first STA information (STA Info) field can include common information necessary for OBSS sounding. A detailed explanation of this will be provided later.

- STA info field

Configuration 1: When following Method 1 for the sounding dialog token field described above, the structure/format of the STA information field of the Ranging NDPA frame can be utilized.

FIG. 11 illustrates a STA information field of an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

Referring to FIG. 11, each STA information field included in the STA information list may be configured to include an AID11 subfield, an LTF offset subfield, an R2I NSTS subfield, an R2I Rep subfield, an I2R NSTS subfield, a reserved bit, a disambiguation subfield, an I2R Rep subfield, and a reserved bit.

The AP can use the structure of the STA information field of the Ranging NDPA of Fig. 11 to instruct each STA to perform OBSS NDP sounding. For example, if the frame is an NDPA frame for instructing OBSS sounding, the last bit (B31) of the STA information field can be set to '1'. If the STA to which the STA information field points (i.e., the STA identified by the AID11 subfield in the STA information field) reads B31, it can recognize that the frame is an NDPA frame for instructing OBSS sounding. However, in this case, since it is possible to distinguish whether the frame is a Ranging NDPA frame or an NDPA frame for instructing OBSS sounding only after checking B31 of each STA information field, this can be a decoding burden for the STAs. In this case, the burden can be reduced by notifying in advance that it is an ONDPA frame as another method, and the 'PHY (physical layer) instruction' method described later can be used.

In addition, each subfield in the STA information field of the NDPA frame for indicating OBSS sounding as exemplified in FIG. 11 can be defined with the same structure as each subfield in the STA information field of the Ranging NDPA frame, and a detailed description thereof is omitted.

Configuration 2: When the STA Information field containing a specific AID11 value (for example, one of 2007 to 2047) is set as the first STA Information, the frame can be identified as an NDPA frame for indicating OBSS sounding. This can be applied regardless of the NDP Announcement Variant value according to Table 5.

The STA information field containing this specific AID11 value may include instructions and information common to all STAs. In the present disclosure, for convenience of explanation, this may be referred to as a common STA info field.

FIG. 12 illustrates a STA information field of an NDPA frame for indicating OBSS sounding according to one embodiment of the present disclosure.

Referring to FIG. 12, the first one (or two or more) STA information fields in the STA information list may be configured as common STA information fields containing common information. The subsequent STA information field(s) may contain individual STA information.

Although FIG. 12 illustrates a case where the first two STA information fields constitute a common STA field, the present disclosure is not limited thereto. That is, the first one STA information field may also be configured as a common STA field.

Here, as an example of a common STA information field, the common STA information field may include common information by configuring some or all of the other subfields differently, except for the AID11 subfield and the Disambiguation subfield (i.e., including them equally).

Here, as an example of common information, at least one of the BSSID or part of the BSSID of the STA or AP transmitting the NDPA frame for indicating OBSS sounding, the BSSID or part of the BSS AP to which the STA that must perform OBSS sounding belongs, or the Multi-AP group information may be included. Here, instead of the BSSID, when Multi-AP is operated, the representative information/number of the corresponding AP (e.g., group ID, BSS color (i.e., a 6-bit identifier for distinguishing BSSs operating on the same channel)) may be included.

In order to include the entire BSSID, for example, the common STA information field may be defined to consist of two or more consecutive STA information fields as in Fig. 12. Referring to Fig. 12, one BSSID may be expressed/indicated consecutively from BSSID(1) to BSSID(4).

The STA information field(s) following the common STA information field may include instructions and information individually required for each STA. As an example of the configuration, the configuration/format of the STA information field of the existing EHT NDPA frame (see FIG. 8(d)) as shown in FIG. 12 may be used in the same manner.

Meanwhile, for both configuration 1 and configuration 2 of the STA information field described above, when transmitting the STA information field individually to each STA, the value included in the AID11 subfield may vary depending on the transmitting entity of the NDPA frame for indicating OBSS sounding.

For example, in the case of OBSS NDP sounding to know channel information between AP1 and STA2, (sounding) NDP can be transmitted by AP1. Here, the NDPA frame indicating OBSS NDP sounding can be transmitted by AP2. In this case, the same AID as before can be used for STA2.

Or, in the case of OBSS NDP sounding to know the channel information between AP1 and STA2, (sounding) NDP is transmitted by AP1, and AP1 may also transmit an NDPA frame indicating OBSS NDP sounding. In this case, the AID of STA2 may be configured differently from before. That is, since the AID is generally a value defined within the BSS to which the STA belongs, the same value may refer to different STAs in different BSSs, so a method to prevent this is required. An example of the method is as follows.

For example, AIDs can be allocated so that STAs' AIDs do not overlap between BSSs performing Multi-AP operation together. In this case, the ONDPA frame can also include the AID11 subfield in the conventional manner.

As another example, a new AID for an OBSS STA may be assigned. For example, a separate AID may be defined that is used when AP1 indicates STA2 or when AP2 indicates STA1. In this case, the ONDPA frame may include the OAID in the AID11 subfield.

'PHY(physical layer) instruction' method

ONDPA frames can be in Non-HT DUP (duplicated) format or UHR PPDU format.

Here, in addition to the above-described methods, a PHY signal in UHR PPDU format may be used for faster recognition of ONDPA frames. That is, by setting the PPDU format of the ONDPA frame to UHR PPDU format and setting the BSS color of U-SIG to a specific value, it is possible to indicate that it is an ONDPA frame. Here, the specific value may be defined/set as a fixed single value for Multi-AP operation, or the specific value may be allocated one by one for each AP group performing Multi-AP operation together. In the former case, one value may be designated, and in the latter case, signaling for allocation may be required before OBSS sounding.

FIG. 13 is a diagram illustrating the operation of an STA for an NDP sounding method according to one embodiment of the present disclosure.

In Fig. 13, the first AP and the second AP correspond to different APs, and the BSS of the first AP and the BSS of the second AP operate on the same channel and may overlap. In addition, the STA may correspond to an STA belonging to the BSS of the first AP (and/or associated with the first AP).

Referring to FIG. 13, the STA receives an NDP announcement frame from the first AP (S1301).

Here, the NDP announcement frame includes a plurality of STA information fields, and a variant of the NDP announcement frame (e.g., an NDP announcement frame indicating OBSS sounding) can be identified by at least one STA information field from among the first one or more of the plurality of STA information fields.

Additionally, a first STA information field among the one or more STA information fields includes an AID11 subfield, and based on the AID11 subfield being set to a specific value (e.g., 2047), a variant of the NDP announcement frame (e.g., an NDP announcement frame indicating OBSS sounding) can be identified.

In addition, the NDP announcement frame may further include a sounding dialog token field, and the sounding dialog token field may include an NDP announcement variant subfield and a sounding dialog token number subfield. Here, even if the NDP announcement variant subfield value is set to 3, the NDP announcement frame may be distinguished from an EHT (extremely high throughput) NDP announcement frame based on the AID11 subfield being set to a specific value. That is, a variant of the NDP announcement frame (e.g., an NDP announcement frame indicating OBSS sounding) may be identified.

Additionally, the one or more STA information fields (e.g., two STA information fields) may include common information for multiple STAs associated with the NDP announcement frame.

Here, the common information may include a basic service set (BSS) color of the first AP and/or identification information (e.g., AID, BSSID, etc. of the AP) for the second AP transmitting the NDP to the STA.

Additionally, the remaining STA information fields following one or more of the above STA information fields may contain individual information for each STA.

The STA transmits a frame containing channel state information to the first AP (S1302).

As described above, the STA may belong to the BSS of the first AP, but the STA may not belong to the BSS of the second AP. Although not illustrated in FIG. 13, the STA may receive an NDP from the second AP. That is, the STA may receive an NDPA from the first AP for the BSS to which it belongs, but may receive an NDP from the second AP for the BSS to which it does not belong. In this case, the channel state information may be generated based on the NDP. Alternatively, although not illustrated in FIG. 13, the STA may receive an NDP from the first AP. In this case, the channel state information may be generated based on the NDP.

Additionally, although not shown in FIG. 13, the STA may receive a BFRP trigger frame from the first AP. In this case, the frame including the channel state information may be transmitted through resources allocated by the BFRP trigger frame.

A PPDU containing/carrying an NDP announcement frame in step S1301 and/or a frame in step S1302 may be composed of a legacy part, a SIG part (e.g., U-SIG, UHR-SIG, etc.), an STF part (e.g., UHR-STF), an LTF part (e.g., UHR-LTF), and a data part.

All or part of any part (i.e., field) may be divided into multiple sub-parts/sub-fields. Each field (and its sub-fields) may be transmitted in units of 4us * N (N is an integer). In addition, a guard interval (GI) may be included. A common subcarrier frequency spacing value (delta_f=312.5 kHz / N or 312.5 kHz * N, where N=integer) may be applied to all of the fields, or a first delta_f may be applied to the first part (e.g., all of legacy part, all/part of SIG part), and a second delta_f (e.g., a value smaller than the first delta_f) may be applied to all/part of the remaining parts.

Some of the fields described above may be omitted, and the order of the fields may be changed in various ways. For example, the subfields of the signal part may be placed before the STF part, and the remaining subfields of the SIG part may be placed after the STF part.

The legacy portion described above may include at least one of a conventional L-STF (Non-HT Short Training Field), L-LTF (Non-HT Long Training Field), and L-SIG (Non-HT Signal Field).

The above-mentioned SIG-part (e.g., including the U-SIG field, UHR-SIG field, etc.) may include various control information for the transmitted PPDU. For example, it may include the STF-part, the LTF-part, and control information for decoding data.

The above-described STF portion may contain an STF sequence.

The above-described LTF portion may include a training field (i.e., an LTF sequence) for channel estimation.

The data-part described above may include user data and may include packets for upper layers (e.g., MPDUs).

The method described in the example of FIG. 13 may 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 an NDP announcement frame from a second device (200) (i.e., an AP) through the transceiver(s) (106), and transmit a frame including channel state information to the second device (200) through the transceiver(s) (106). Furthermore, one or more memories (104) of the first device (100) may store commands for performing the method described in the example of FIG. 13 or the examples described above when executed by one or more processors (102).

FIG. 14 is a diagram illustrating the operation of an AP for an NDP sounding method according to one embodiment of the present disclosure.

In Fig. 14, the first AP and the second AP correspond to different APs, and the BSS of the first AP and the BSS of the second AP operate on the same channel and may overlap. In addition, the STA may correspond to an STA belonging to the BSS of the first AP (and/or associated with the first AP).

Referring to FIG. 14, the first AP transmits an NDP announcement frame to the STA(s) (S1401).

Here, the NDP announcement frame includes a plurality of STA information fields, and a variant of the NDP announcement frame (e.g., an NDP announcement frame indicating OBSS sounding) can be identified by at least one STA information field from among the first one or more of the plurality of STA information fields.

Additionally, a first STA information field among the one or more STA information fields includes an AID11 subfield, and based on the AID11 subfield being set to a specific value (e.g., 2047), a variant of the NDP announcement frame (e.g., an NDP announcement frame indicating OBSS sounding) can be identified.

In addition, the NDP announcement frame may further include a sounding dialog token field, and the sounding dialog token field may include an NDP announcement variant subfield and a sounding dialog token number subfield. Here, even if the NDP announcement variant subfield value is set to 3, the NDP announcement frame may be distinguished from an EHT (extremely high throughput) NDP announcement frame based on the AID11 subfield being set to a specific value. That is, a variant of the NDP announcement frame (e.g., an NDP announcement frame indicating OBSS sounding) may be identified.

Additionally, the one or more STA information fields (e.g., two STA information fields) may include common information for multiple STAs associated with the NDP announcement frame.

Here, the common information may include a basic service set (BSS) color of the first AP and/or identification information (e.g., AID, BSSID, etc. of the AP) for the second AP transmitting the NDP to the STA.

Additionally, the remaining STA information fields following one or more of the above STA information fields may contain individual information for each STA.

The first AP receives a frame containing channel state information from the STA(s) (S1402).

As described above, the STA may belong to the BSS of the first AP, but the STA may not belong to the BSS of the second AP. Although not shown in FIG. 14, the second AP may transmit an NDP to the STA(s). That is, the STA may receive an NDPA from the first AP for the BSS to which it belongs, but may receive an NDP from the second AP for the BSS to which it does not belong. In this case, the channel state information may be generated based on the NDP. Alternatively, although not shown in FIG. 14, the first AP may transmit an NDP to the STA(s). In this case, the channel state information may be generated based on the NDP.

Additionally, although not shown in FIG. 14, the first AP may transmit a BFRP trigger frame to the STA. In this case, the frame including the channel state information may be transmitted through resources allocated by the BFRP trigger frame.

A PPDU containing/carrying an NDP announcement frame in step S1401 and/or a frame in step S1402 may be configured to include a legacy part, a SIG part (e.g., U-SIG, UHR-SIG, etc.), an STF part (e.g., UHR-STF), an LTF part (e.g., UHR-LTF), and a data part.

All or part of any part (i.e., field) may be divided into multiple sub-parts/sub-fields. Each field (and its sub-fields) may be transmitted in units of 4us * N (N is an integer). In addition, a guard interval (GI) may be included. A common subcarrier frequency spacing value (delta_f=312.5 kHz / N or 312.5 kHz * N, where N=integer) may be applied to all of the fields, or a first delta_f may be applied to the first part (e.g., all of legacy part, all/part of SIG part), and a second delta_f (e.g., a value smaller than the first delta_f) may be applied to all/part of the remaining parts.

Some of the fields described above may be omitted, and the order of the fields may be changed in various ways. For example, the subfields of the signal part may be placed before the STF part, and the remaining subfields of the SIG part may be placed after the STF part.

The legacy portion described above may include at least one of a conventional L-STF (Non-HT Short Training Field), L-LTF (Non-HT Long Training Field), and L-SIG (Non-HT Signal Field).

The above-mentioned SIG-part (e.g., including the U-SIG field, UHR-SIG field, etc.) may include various control information for the transmitted PPDU. For example, it may include the STF-part, the LTF-part, and control information for decoding data.

The above-described STF portion may contain an STF sequence.

The above-described LTF portion may include a training field (i.e., an LTF sequence) for channel estimation.

The data-part described above may include user data and may include packets for upper layers (e.g., MPDUs).

The method described in the example of FIG. 14 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 an NDP announcement frame via the transceiver(s) (106) and receive a frame including channel state information from the first device (200) via the transceiver(s) (206). Furthermore, one or more memories (204) of the second device (200) may store commands for performing the method described in the example of FIG. 14 or the examples described below when executed by one or more processors (202).

Unlike the NDP sounding method in the existing wireless LAN system, the NDP sounding method according to the examples of the present disclosure has the feature of supporting OBSS sounding as described above. Accordingly, channel information for OBSS STA can be acquired, so that multi-AP operation can be performed smoothly. In addition, since frequency resources can be reused according to the spatial reuse technique in which multiple BSSs cooperate, the effect of efficiently utilizing frequency resources can be achieved.

The embodiments described above are combinations of components and features of the present disclosure in a given form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, it is also possible to combine some components and/or features to form an embodiment of the present disclosure. 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 claims that do not have an explicit citation relationship in the scope of the patent may be combined to form an embodiment or may be included as a new claim by post-application amendment.

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

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

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

Claims (15)

A step of receiving a null data PPDU (physical protocol data unit) (NDP: null data PPDU) announcement frame from a first access point (AP: access point) by a station (STA: station); and A step of transmitting, by the STA, a frame including channel state information to the first AP, The above NDP notification frame includes multiple STA information fields, A method wherein a variant of the NDP announcement frame is identified by at least one STA information field among the plurality of STA information fields. In the first paragraph, The first STA information field among the above one or more STA information fields includes an AID11 subfield, A method wherein a variant of the NDP announcement frame is identified based on the AID11 subfield being set to a specific value. In the second paragraph, The above NDP notification frame further includes a sounding dialog token field, The above sounding dialog token field includes an NDP announcement variant subfield and a sounding dialog token number subfield, A method in which the NDP announcement frame is distinguished from an EHT (extremely high throughput) NDP announcement frame based on the AID11 subfield being set to a specific value, even if the NDP announcement variant subfield value is set to 3. In the first paragraph, A method wherein said one or more STA information fields include common information for a plurality of STAs associated with said NDP announcement frame. In paragraph 4, A method wherein the common information includes a basic service set (BSS) color of the first AP and/or identification information for the second AP transmitting the NDP to the STA. In paragraph 4, A method wherein the remaining STA information fields following one or more of the above STA information fields contain individual information for each STA. In the first paragraph, Further comprising a step of receiving an NDP from a second AP by the above STA, The STA belongs to the BSS of the first AP, but the STA does not belong to the BSS of the second AP, A method wherein the above channel state information is generated based on the NDP. In the first paragraph, Further comprising a step of receiving an NDP from the first AP by the above STA, The STA belongs to the BSS of the first AP, but the STA does not belong to the BSS of the second AP, A method wherein the above channel state information is generated based on the NDP. In the first paragraph, Further comprising a step of receiving, by the STA, a beamforming report poll (BFRP) trigger frame from the first AP, A method wherein the frame including the channel state information is transmitted through resources allocated by the BFRP trigger frame. In the first paragraph, A method wherein the above STA is an STA belonging to a basic service set (BSS) of the first AP. The station (STA: station) device: one or more transmitters and receivers; and comprising one or more processors coupled to said one or more transceivers; One or more of the above processors: Receives a null data PPDU (physical protocol data unit) (NDP: null data PPDU) announcement frame from the first access point (AP: access point), and It is set to transmit a frame including channel state information to the first AP, The above NDP notification frame includes multiple STA information fields, A device, wherein a variant of the NDP announcement frame is identified by at least one of the first STA information fields among the plurality of STA information fields. A step of transmitting a null data PPDU (physical protocol data unit) (NDP: null data PPDU) announcement frame to a station (STA: station) by a first access point (AP: access point); and A step of receiving a frame including channel state information from the STA by the first AP, The above NDP notification frame includes multiple STA information fields, A method wherein a variant of the NDP announcement frame is identified by at least one STA information field among the plurality of STA information fields. The first access point (AP) device is: one or more transmitters and receivers; and comprising one or more processors coupled to said one or more transceivers; One or more of the above processors: Transmits a null data PPDU (physical protocol data unit) (NDP: null data PPDU) announcement frame to the station (STA: station), and is set to receive a frame including channel state information from the STA; The above NDP notification frame includes multiple STA information fields, A device, wherein a variant of the NDP announcement frame is identified by at least one of the first STA information fields among the plurality of STA information fields. In a processing device configured to control a station (STA: station) in a wireless LAN system, the processing device: one or more processors; and A processing device comprising one or more computer memories operatively connected to said one or more processors and storing instructions that, when executed by said one or more processors, perform a method according to any one of claims 1 to 10. One or more non-transitory computer-readable media storing one or more instructions, A computer-readable medium, wherein the one or more commands are executed by one or more processors to control a device in a wireless LAN system to perform a method according to any one of claims 1 to 10.