Method and apparatus for listening interval-based transmission or reception for multilink apparatus in wireless LAN system

Abstract

Disclosed are a method and apparatus for listening interval-based transmission or reception for a multilink device (MLD) in a wireless LAN system. According to one embodiment of the present disclosure, a method performed by a station (STA) in a wireless LAN system may comprise the steps of: detecting, by the STA belonging to a non-access point (non-AP) MLD, a change in state of one or more links among a plurality of links; determining an updated MLD listening interval based on the one or more enabled links; and performing transmission or reception with the AP MLD based on the updated MLD listening interval.

Description

Technical Field

[0001] The present disclosure relates to a listening interval-based transmission or reception method and apparatus for a multi-link device (MLD) in a wireless local area network (WLAN) system. Background Art

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

[0003] In order to provide a more advanced wireless communication environment, improved technologies for extremely high throughput (EHT) are being discussed. For example, technologies for MIMO and multi-access point (AP) coordination that support increased bandwidth, efficient use of multiple frequency bands, and increased spatial streams are being studied, and specifically, various technologies are being studied to support low latency or real-time services. In addition, new technologies are being discussed to support ultra-high reliability (UHR), including improvements or extensions of EHT technologies. Summary of the invention

[0004] Technical issues

[0005] The technical problem of the present disclosure is to provide a sending or receiving method and a device for updating a listening interval for a multi-link device (MLD) based on after multi-link establishment in a WLAN system.

[0006] An additional technical problem of the present disclosure is to provide a method and apparatus for efficiently updating a listening interval for a multi-link (MLD) based on a change of the MLD in a WLAN system.

[0007] The technical objectives to be achieved by the present disclosure are not limited to the above-mentioned technical objectives, and those skilled in the art can clearly understand other technical objectives not described herein through the following description.

[0008] Technical Solution

[0009] According to one aspect of the present disclosure, a method performed by a station (STA) in a WLAN system may include: detecting, by a STA belonging to a non-access point (non-AP) multi-link device (MLD), a change in the state of at least one link among multiple links; determining an updated MLD listening interval based on at least one enabled link; and performing transmission or reception with the APMLD based on the updated MLD listening interval.

[0010] According to additional aspects of the present disclosure, a method performed by an access point (AP) in a WLAN system may include: determining, by an AP belonging to an AP multi-link device (MLD), an updated MLD listening interval based on at least one enabled link associated with a change in the state of at least one link among multiple links; and performing transmission or reception with a non-AP MLD based on the updated MLD listening interval.

[0011] Technical Effects

[0012] According to the present disclosure, a transmission or reception method and device for updating a listening interval for a multi-link device (MLD) after multi-link establishment in a WLAN system may be provided.

[0013] According to the present disclosure, a method and apparatus for efficiently updating a listening interval for a multi-link (MLD) based on a change of the MLD in a WLAN system may be provided.

[0014] Effects achievable by the present disclosure are not limited to the above-described effects, and other effects not described herein may be clearly understood by those skilled in the relevant art through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are included as a part of the detailed description for understanding the present disclosure, provide embodiments of the present disclosure and describe technical features of the present disclosure together with the detailed description.

[0016] Figure 1 A configuration block diagram of a wireless communication device according to an embodiment of the present disclosure is illustrated.

[0017] Figure 2 is a diagram illustrating an exemplary structure of a WLAN system to which the present disclosure can be applied.

[0018] Figure 3 It is a diagram for explaining a link establishment process to which the present disclosure can be applied.

[0019] Figure 4 This is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0020] Figure 5 It is a diagram for explaining a frame transmission operation based on CSMA / CA to which the present disclosure can be applied.

[0021] Figure 6 is a diagram for explaining an example of a frame structure used in a WLAN system to which the present disclosure can be applied.

[0022] Figure 7 is a diagram illustrating an example of a PPDU defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0023] Figure 8 is a diagram illustrating an example of an operation based on an MLD listening interval related to the present disclosure.

[0024] Fig. 9 is a diagram illustrating additional examples of operations based on an MLD listening interval related to the present disclosure.

[0025] Fig.10 is a diagram for explaining an example of a method performed in a STA based on an MLD listening interval according to the present disclosure.

[0026] Fig.11 is a diagram for explaining an example of a method performed in an AP based on an MLD listening interval according to the present disclosure.

[0027] Fig.12 is a diagram illustrating an example of an operation based on an MLD listening interval according to the present disclosure. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description disclosed by the accompanying drawings is intended to describe exemplary embodiments of the present disclosure, rather than to represent the only embodiment in which the present disclosure can be implemented. The following detailed description includes specific details to provide a complete understanding of the present disclosure. However, those skilled in the relevant art know that the present disclosure can be implemented without these specific details.

[0029] In some cases, well-known structures and devices may be omitted, or may be shown in the form of a block diagram based on the core functions of each structure and device in order to prevent ambiguity of the concepts of the present disclosure.

[0030] In the present disclosure, when an element is referred to as being "connected", "combined" or "linked" to another element, it may include an indirect connection relationship between another element and a direct connection relationship. In addition, in the present disclosure, the term "comprising" or "having" specifies the presence of the mentioned features, steps, operations, components and / or elements, but does not exclude the presence or addition of one or more other features, stages, operations, components, elements and / or groups thereof.

[0031] In the present disclosure, terms such as "first", "second", etc. are only used to distinguish one element from another element and are not used to limit the elements, and unless otherwise specified, they do not limit the order or importance between elements, etc. Therefore, within the scope of the present disclosure, the first element in an embodiment may be referred to as the second element in another embodiment, and similarly, the second element in an embodiment may be referred to as the first element in another embodiment.

[0032] The terms used in this disclosure are intended to describe specific embodiments, rather than to limit the claims. As used in the description of the embodiments and the appended claims, the singular form is intended to include the plural form, unless the context clearly indicates otherwise. The term "and / or" used in this disclosure may refer to one of the related enumerated items, or mean that it refers to and includes any and all possible combinations of two or more of them. In addition, unless otherwise stated, the " / " between words in this disclosure has the same meaning as "and / or".

[0033] Examples of the present disclosure can be applied to various wireless communication systems. For example, examples of the present disclosure can be applied to wireless LAN systems. For example, examples of the present disclosure can be applied to wireless LANs based on IEEE 802.11a / g / n / ac / ax standards. In addition, examples of the present disclosure can be applied to wireless LANs based on the newly proposed IEEE 802.11be (or EHT) standard. Examples of the present disclosure can be applied to wireless LANs based on the IEEE802.11be version 2 standard corresponding to the additional enhanced technology of the IEEE 802.11be version 1 standard. In addition, examples of the present disclosure can be applied to wireless LANs based on next-generation standards after IEEE 802.11be. In addition, examples of the present disclosure can be applied to cellular wireless communication systems. For example, it can be applied to cellular wireless communication systems based on long-term evolution (LTE) technology and 5G new radio (NR) technology based on the third generation partnership project (3GPP) standard.

[0034] Hereinafter, technical features of examples to which the present disclosure can be applied will be described.

[0035] Figure 1 A block diagram of a wireless communication device according to an embodiment of the present disclosure is illustrated.

[0036] Figure 1 The first device 100 and the second device 200 illustrated in the figure may be replaced with various terms such as terminal, wireless device, wireless transmit / receive unit (WTRU), user equipment (UE), mobile station (MS), user terminal (UT), mobile subscriber station (MSS), mobile subscriber unit (MSU), subscriber station (SS), advanced mobile station (AMS), wireless terminal (WT) or simple user, etc. In addition, the first device 100 and the second device 200 include an access point (AP), a base station (BS), a fixed station, a node B, a base transceiver system (BTS), a network. It may be replaced with various terms such as an artificial intelligence (AI) system, a roadside unit (RSU), a repeater, a router, a relay and a gateway.

[0037] Figure 1The devices 100 and 200 illustrated in the example may be referred to as stations (STAs). Figure 1 The devices 100 and 200 illustrated in the figure 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 and 200 may perform an access point (AP) role or a non-AP role. That is, in the present disclosure, the STAs 110 and 200 may perform the functions of an AP and / or a non-AP. When the STAs 110 and 200 perform the AP function, they may be simply referred to as APs, and when the STAs 110 and 200 perform the non-AP function, they may be simply referred to as STAs. In addition, in the present disclosure, an AP may also be indicated as an AP STA.

[0038] Reference Figure 1 , the first device 100 and the second device 200 can send and receive radio signals through various wireless LAN technologies (e.g., IEEE802.11 series). The first device 100 and the second device 200 may include interfaces for a media access control (MAC) layer and a physical layer (PHY) that conform to the IEEE802.11 standard.

[0039] In addition, in addition to the wireless LAN technology, the first device 100 and the second device 200 may further support various communication standards (e.g., 3GPP LTE series, 5G NR series standards, etc.) technologies. In addition, the device of the present disclosure may be implemented in various devices such as mobile phones, vehicles, personal computers, augmented reality (AR) devices, and virtual reality (VR) devices. In addition, the STA of the present specification may support various communication services such as voice calls, video calls, data communications, autonomous driving, machine type communications (MTC), machine to machine (M2M), device to device (D2D), IoT (Internet of Things), etc.

[0040] The first device 100 may include one or more processors 102 and one or more memories 104, and may further include one or more transceivers 106 and / or one or more antennas 108. The processor 102 may control the memory 104 and / or the transceiver 106, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts included in the present disclosure. For example, the processor 102 may send a wireless signal including the first information / signal through the transceiver 106 after generating the first information / signal by processing the information in the memory 104. In addition, the processor 102 may receive a wireless signal including the second information / signal through the transceiver 106, and then store the information obtained by the 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 store software codes including instructions for executing all or part of the processing controlled by the processor 102 or for executing the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts included in the present disclosure. Here, the processor 102 and the memory 104 may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). The transceiver 106 may be connected to the processor 102 and may send and / or receive wireless signals through one or more antennas 108. The transceiver 106 may include a transmitter and / or a receiver. The transceiver 106 may be used in conjunction with an RF (radio frequency) unit. In the present disclosure, a wireless device may refer to a communication modem / circuit / chip.

[0041] The second device 200 may include one or more processors 202 and one or more memories 204, and may further include one or more transceivers 206 and / or one or more antennas 208. The processor 202 may control the memory 204 and / or the transceiver 206, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in the present disclosure. For example, the processor 202 may generate third information / signals by processing the information in the memory 204, and then send a wireless signal including the third information / signal through the transceiver 206. In addition, the processor 202 may receive a wireless signal including fourth information / signals through the transceiver 206, and then store information obtained by signal processing of the fourth information / signal in the memory 204. The memory 204 may be connected to the processor 202 and may store various information related to the operation of the processor 202. For example, the memory 204 may store software codes including instructions for executing all or part of the processing controlled by the processor 202 or for executing the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in the present disclosure. Here, the processor 202 and the memory 204 may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). The transceiver 206 may be connected to the processor 202 and may send and / or receive wireless signals through one or more antennas 208. The transceiver 206 may include a transmitter and / or a receiver. The transceiver 206 may be used in conjunction with an RF unit. In the present disclosure, a device may refer to a communication modem / circuit / chip.

[0042] In the following, the hardware elements of the apparatus 100, 200 will be described in more detail. Without limitation 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 PDUs (protocol data units) and / or one or more SDUs (service data units) according to the description, function, process, suggestion, method, and / or operation flow chart disclosed in the present disclosure. One or more processors 102, 202 may generate messages, control information, data, or information according to the description, function, process, suggestion, method, and / or operation flow chart disclosed in the present disclosure. One or more processors 102, 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the functions, processes, suggestions, and / or methods disclosed in the present disclosure to provide them to one or more transceivers 106, 206. One or more processors 102, 202 may receive a signal (e.g., a baseband signal) from one or more transceivers 106, 206 according to the descriptions, functions, processes, suggestions, methods, and / or operational flow charts included in the present disclosure and obtain a PDU, SDU, message, control information, data, or information.

[0043] One or more processors 102, 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. One or more processors 102, 202 may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more ASICs (Application Specific Integrated Circuits), one or more DSPs (Digital Signal Processors), one or more DSPDs (Digital Signal Processing Devices), one or more PLDs (Programmable Logic Devices), or one or more FPGAs (Field Programmable Gate Arrays) may be included in one or more processors 102, 202. The descriptions, functions, processes, suggestions, methods, and / or operational flow charts included in the present disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, processes, functions, and the like. Firmware or software configured to execute the descriptions, functions, processes, suggestions, methods, and / or operational flow charts included in the present disclosure may be included in one or more processors 102, 202, or may be stored in one or more memories 104, 204 and driven by one or more processors 102, 202. The descriptions, functions, processes, suggestions, methods and / or operational flow charts included in the present disclosure may be implemented using firmware or software in the form of codes, instructions and / or instruction sets.

[0044] One or more memories 104, 204 may be connected to one or more processors 102, 202 and may store data, signals, messages, information, programs, codes, instructions, and / or commands in various forms. One or more memories 104, 204 may be configured with ROM, RAM, EPROM, flash memory, hard drive, registers, cache memory, computer-readable storage media, and / or combinations thereof. One or more memories 104, 204 may be located inside and / or outside one or more processors 102, 202. In addition, one or more memories 104, 204 may be connected to one or more processors 102, 202 via various technologies such as wired or wireless connections.

[0045] One or more transceivers 106, 206 may send user data, control information, wireless signals / channels, etc. mentioned in the method and / or operation flow chart of the present disclosure to one or more other devices. One or more transceivers 106, 206 may receive user data, control information, wireless signals / channels, etc. mentioned in the description, function, process, suggestion, method and / or operation flow chart, etc. included in the present disclosure from one or more other devices. For example, one or more transceivers 106, 206 may be connected to one or more processors 102, 202 and may send and receive wireless signals. For example, one or more processors 102, 202 may control one or more transceivers 106, 206 to send user data, control information or wireless signals to one or more other devices. In addition, 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. In addition, one or more transceivers 106, 206 may be connected to one or more antennas 108, 208, and one or more transceivers 106, 206 may be configured to send and receive user data, control information, wireless signals / channels, etc. mentioned in the description, functions, processes, suggestions, methods and / or operation flow charts, etc. included in the present disclosure through 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 wireless signals / channels, etc. from RF band signals into baseband signals to process received user data, control information, wireless signals / channels, etc. by using one or more processors 102, 202. One or more transceivers 106, 206 may convert user data, control information, wireless signals / channels, etc. processed by using one or more processors 102, 202 from baseband signals into RF band signals. Thus, one or more of the transceivers 106 , 206 may include (analog) oscillators and / or filters.

[0046] For example, one of the STAs 100 and 200 may perform the expected operation of an AP, and the other of the STAs 100 and 200 may perform the expected operation of a non-AP STA. Figure 1 The transceivers 106 and 206 of the present invention may perform transmission and reception operations of signals (e.g., packets or physical layer protocol data units (PPDUs) compliant with IEEE 802.11a / b / g / n / ac / ax / be / bn). In addition, in the present disclosure, operations of various STAs generating transmission / reception signals or performing data processing or calculations on transmission / reception signals in advance may be performed by Figure 1The processors 102 and 202 are executed. For example, examples of operations of generating a transmission / reception signal or performing data processing or calculation for the transmission / reception signal in advance may include: 1) determining / obtaining / configuring / calculating / decoding / encoding bit information of fields (signal (SIG), short training field (STF), long training field (LTF), data, etc.) included in the PPDU; 2) determining / configuring / obtaining time resources or frequency resources (e.g., subcarrier resources) for fields (SIG, STF, LTF, data, etc.) included in the PPDU; 3) determining / configuring / obtaining a specific sequence (e.g., pilot sequence, STF / LTF sequence, additional sequence applied to SIG) for fields (SIG, STF, LTF, data, etc.) included in the PPDU action; 4) power control operations and / or power saving operations applied to STAs; 5) operations related to ACK signal determination / obtaining / configuring / calculating / decoding / encoding, etc. In addition, in the following example, various information used by various STAs to determine / acquire / configure / calculate / decode / encode transmission signals and reception signals (e.g., information related to fields / subfields / control fields / parameters / power, etc.) may be stored in Figure 1 in the memories 104 and 204.

[0047] Hereinafter, a downlink (DL) may mean a link for communication from an AP STA to a non-AP STA, and a DL PPDU / packet / signal may be transmitted and received through the DL. In DL communication, a transmitter may be a part of an AP STA, and a receiver may be a part of a non-AP STA. An uplink (UL) may mean a link for communication from a non-AP STA to an AP STA, and a UL PPDU / packet / signal may be transmitted and received through the UL. In UL communication, a transmitter may be a part of a non-AP STA, and a receiver may be a part of an AP STA.

[0048] Figure 2 is a diagram illustrating an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0049] The structure of the wireless LAN system may be composed of a plurality of components. A wireless LAN supporting STA mobility transparent to an upper layer may be provided through the interaction of the plurality of components. A basic service set (BSS) corresponds to a basic building block of a wireless LAN. Figure 2 It is exemplarily shown that two BSSs (BSS1 and BSS2) exist, and two STAs (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2) are included as members of each BSS. Figure 2The ellipse representing the BSS in the figure can also be understood as representing the coverage area in which the STAs included in the corresponding BSS maintain communication. This area can be called a basic service area (BSA). When a STA moves outside the BSA, it cannot communicate directly with other STAs in the BSA.

[0050] If you don't consider Figure 2 , the most basic BSS type in the wireless LAN is an independent BSS (IBSS), if the DS is shown in FIG. 1 . For example, an IBSS may have a minimum form containing only two STAs. For example, assuming that other components are omitted, a BSS1 containing only STA1 and STA2 or a BSS2 containing only STA3 and STA4 may correspond to representative examples of IBSSs, respectively. This configuration is possible when STAs can communicate directly without an AP. In addition, in this type of wireless LAN, it is not pre-configured but can be configured when a LAN is needed, and this may be referred to as an ad-hoc network. Since the IBSS does not include an AP, there is no centralized management entity. That is, in the IBSS, STAs are managed in a distributed manner. In the IBSS, all STAs may be composed of mobile STAs, and access to the distributed system (DS) is not allowed, thereby forming a self-contained network.

[0051] The membership of a STA in a BSS can be changed dynamically by turning the STA on or off, entering or exiting a BSS region, etc. In order to become a member of a BSS, a STA can join the BSS using a synchronization process. In order to access all services of the BSS infrastructure, a STA should associate with the BSS. This association can be established dynamically and can include the use of a distributed system service (DSS).

[0052] The direct STA-to-STA distance in a wireless LAN may be limited by PHY performance. In some cases, this distance limitation may be sufficient, but in some cases, communication between STAs at longer distances may be required. A distributed system (DS) can be configured to support extended coverage.

[0053] DS refers to the structure of BSS interconnection. Specifically, Figure 2As shown, the BSS can exist as an extended form of a network composed of multiple BSSs. DS is a logical concept and can be specified by the characteristics of the distributed system medium (DSM). At this point, the wireless medium (WM) and the DSM can be logically separated. Each logical medium is used for different purposes and is used by different components. These media are not limited to being the same, nor are they limited to being different. In this way, the flexibility of the wireless LAN structure (DS structure or other network structure) can be interpreted as multiple media being logically different. That is, the wireless LAN structure can be implemented in various ways, and the corresponding wireless LAN structure can be independently specified by the physical characteristics of each implementation.

[0054] DS can support mobile devices by providing seamless integration of multiple BSSs and providing logical services necessary to address the address leading to the destination. In addition, DS can also include a component called a portal, which is used as a bridge for connection between wireless LAN and other networks (e.g., IEEE 802.X).

[0055] The AP enables access to the DS through the WM for associated non-AP STAs and means an entity that also has STA functionality. Data movement between the BSS and the DS can be performed through the AP. For example, Figure 2 STA2 and STA3 shown in the figure have the function of STA and provide the function of allowing the associated non-AP STA (STA1 and STA4) to access the DS. In addition, since all APs basically correspond to STAs, all APs are addressable entities. The address used by the AP to communicate on the WM is not necessarily the same as the address used by the AP to communicate on the DSM. A BSS composed of an AP and one or more STAs may be referred to as an infrastructure BSS.

[0056] Data sent from one of the STAs associated with the AP to the STA address of the corresponding AP can always be received at the uncontrolled port and can be processed by the IEEE 802.1X port access entity. In addition, when the controlled port is authenticated, the transmitted data (or frame) can be delivered to the DS.

[0057] In addition to the above-mentioned structure of the DS, an extended service set (ESS) may also be configured to provide wide coverage.

[0058] ESS means a network with arbitrary size and complexity consisting of DS and BSS. ESS may correspond to a set of BSSs connected to one DS. However, ESS does not include DS. The ESS network is characterized by being regarded as an IBSS in the logical link control (LLC) layer. The STAs included in the ESS can communicate with each other, and the mobile STA can move from one BSS to another (within the same ESS) transparently for LLC. The APs included in one ESS may have the same service set identifier (SSID). SSID is distinguished from BSSID, which is an identifier of BSS.

[0059] The wireless LAN system does not assume anything about the relative physical location of the BSS, and all of the following forms are possible. The BSS may partially overlap, which is a form commonly used to provide continuous coverage. In addition, the BSS may not be physically connected, and logically, there is no limit on the distance between the BSS. In addition, the BSS may be physically located in the same location, which can be used to provide redundancy. In addition, one (or more than one) IBSS or ESS network may physically exist in the same space as one (or more than one) ESS network. When an ad hoc network operates in a location where an ESS network exists, when physically overlapping wireless networks are configured by different organizations, or when two or more different access and security policies are required in the same location, this may correspond to the form of an ESS network, etc.

[0060] Figure 3 is a diagram for explaining a link establishment process to which the present disclosure can be applied.

[0061] In order for a STA to establish a link with respect to a network and send / receive data, it first discovers the network, performs authentication, establishes association, and needs to perform authentication processing for security. The link establishment processing may also be referred to as a session initiation processing or a session establishment processing. In addition, the discovery, authentication, association, and security establishment processing of the link establishment processing may be collectively referred to as an association processing.

[0062] 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 a network, it needs to find a network that it can participate in. The STA should identify compatible networks before participating in a wireless network, and the process of identifying networks present in a specific area is called scanning.

[0063] Scanning schemes include active scanning and passive scanning. Figure 3The network discovery operation including active scanning processing is exemplarily illustrated. In active scanning, the STA performing the scan sends a probe request frame to discover which APs exist around it while the channel moves and waits for a response thereto. The responder sends a probe response frame as a response to the probe request frame to the STA that has sent the probe request frame. Here, the responder may be the STA that last sent a beacon frame in the BSS of the channel being scanned. In the BSS, since the AP sends a beacon frame, the AP becomes the responder, and in the IBSS, the STAs in the IBSS rotate to send beacon frames, so the responder is not constant. For example, a STA that sends a probe request frame on channel 1 and receives a probe response frame on channel 1 may store the BSS-related information included in the received probe response frame, and may move to the next channel (e.g., channel 2), and perform scanning in the same manner (i.e., sending and receiving probe requests / responses on channel 2).

[0064] Although not in Figure 3 , but the scanning operation can be performed in a passive scanning manner. In passive scanning, the STA performing the scan waits for a beacon frame while the channel moves. The beacon frame is one of the management frames defined in IEEE 802.11, and is periodically sent to notify the existence of a wireless network and allow the STA performing the scan to find the wireless network and participate in the wireless network. In the BSS, the AP is used to periodically send beacon frames, and in the IBSS, the STAs within the IBSS rotate to send beacon frames. When the STA performing the scan receives the beacon frame, the STA stores the information of the BSS included in the beacon frame, and records the beacon frame information in each channel while moving to another channel. The STA receiving the beacon frame can store the BSS-related information included in the received beacon frame, move to the next channel, and perform scanning in the next channel in the same manner. Comparing active scanning with passive scanning, the advantage of active scanning is that it has less delay and less power consumption than passive scanning.

[0065] After the STA discovers the network, an authentication process may be performed at step S320. In order to clearly distinguish from the security establishment operation of step S340 to be described later, this authentication process may be referred to as a first authentication process.

[0066] The authentication process includes the following process: the STA sends an authentication request frame to the AP, and in response thereto, the AP sends an authentication response frame to the STA. The authentication frame for authentication request / response corresponds to a management frame.

[0067] The authentication frame includes an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a robust security network (RSN), a limited cycle group, etc. This corresponds to some examples of information that can be included in the authentication request / response frame, and can be replaced with other information, or additional information can also be included.

[0068] The STA may send an authentication request frame to the AP. The AP may determine whether to allow authentication of the corresponding STA based on the information included in the received authentication request frame. The AP may provide the result of the authentication process to the STA via an authentication response frame.

[0069] After the STA is successfully authenticated, an association process may be performed at step S330. The association process includes the following processes: the STA sends an association request frame to the AP, and in response, the AP sends an association response frame to the STA.

[0070] For example, the association request frame may include information related to various capabilities, a beacon listening interval, a service set identifier (SSID), supported rates, supported channels, RSN, a mobile domain, supported operation categories, a traffic indication map broadcast request (TIM broadcast request), interworking service capabilities, etc. For example, the association response frame may include information related to 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 ratio indicator (RSNI), a mobile domain, a timeout interval (e.g., an association recovery time), an overlapping BSS scan parameter, a TIM broadcast response, a quality of service (QoS) map, etc. This corresponds to some examples of information that may be included in an association request / response frame, and may be replaced with other information, or may also include additional information.

[0071] After the STA successfully associates with the network, a security establishment process may be performed at step S340. The security establishment process at step S340 may be referred to as an authentication process through a robust security network association (RSNA) request / response, the authentication process at step S320 may be referred to as a first authentication process, and the security establishment process at step S340 may also be referred to simply as an authentication process.

[0072] The security establishment process of step S340 may include, for example, a process of establishing a private key through an Extensible Authentication Protocol over LAN (EAPOL) frame using a four-way handshake. In addition, the security establishment process may be performed according to a security scheme not defined in the IEEE 802.11 standard.

[0073] Figure 4 It is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0074] In a wireless LAN system, the basic access mechanism of the medium access control (MAC) is a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism. The CSMA / CA mechanism is also known as the distributed coordination function (DCF) of the IEEE 802.11 MAC, and basically adopts a "listen before talk" access mechanism. According to this type of access mechanism, before starting to send, the AP and / or STA may perform a clear channel assessment (CCA) of sensing the radio channel or medium during a predetermined time interval (e.g., DCF interframe space (DIFS)). As a result of the sensing, if it is determined that the medium is in an idle state, frame transmission is started through the corresponding medium. On the other hand, if it is detected that the medium is occupied or busy, the corresponding AP and / or STA does not start its own transmission, and a delay period (e.g., a random backoff period) for medium access may be set and frame transmission may be attempted after waiting. By applying a random backoff period, since multiple STAs are expected to attempt frame transmission after waiting for different time periods, conflicts can be minimized.

[0075] In addition, the IEEE 802.11 MAC protocol provides a hybrid coordination function (HCF). HCF is based on DCF and point coordination function (PCF). PCF is a synchronous access method based on polling, and refers to a method in which all receiving APs and / or STAs periodically poll to receive data frames. In addition, HCF has enhanced distributed channel access (EDCA) and HCF controlled channel access (HCCA). EDCA is a contention-based access method that provides data frames to multiple users in a direction, and HCCA uses a non-contention-based channel access method that utilizes a polling mechanism. In addition, HCF includes a medium access mechanism for improving the QoS (quality of service) of a wireless LAN, and QoS data can be sent during a contention period (CP) and a contention-free period (CFP).

[0076] Reference Figure 4, the operation based on the random backoff period will be described. When the occupied / busy medium becomes idle, multiple STAs may attempt to send data (or frames). As a method of minimizing conflicts, each of the STAs may select a random backoff count respectively and attempt to send after waiting for the corresponding time slot time. The random backoff count has a pseudo-random integer value and may be determined as one of the values ​​ranging from 0 to CW. Here, CW is a contention window parameter value. The CW parameter is assigned CWmin as an initial value, but may take a value twice as large in the event of a transmission failure (e.g., when an ACK for a transmitted frame is not received). When the CW parameter value reaches CWmax, data transmission may be attempted while maintaining the CWmax value until data transmission is successful, and when data transmission is successful, the CWmin value is reset. The values ​​of CW, CWmin, and CWmax are preferably set to 2n-1 (n=0, 1, 2, ...).

[0077] When the random backoff process starts, the STA continuously monitors the medium in the backoff slot countdown according to the determined backoff count value. When the medium is monitored for occupancy, it stops the countdown and waits, and restarts the remaining part of the countdown when the medium becomes idle.

[0078] exist Figure 4 In the example of , when the packet to be sent arrives at the MAC of STA3, STA3 can send the frame immediately after confirming that the medium has been idle for up to DIFS. The remaining STAs monitor and wait for the medium to be occupied / busy. At the same time, the data to be sent can also occur in each of STA1, STA2 and STA5, and when the medium is monitored as idle, each STA waits for up to DIFS, and then the countdown of the backoff slot can be performed according to the random backoff count value selected by each STA. Assume that STA2 selects the minimum backoff count value and STA1 selects the maximum backoff count value. That is, the example illustrates a case where the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1 when STA2 completes the backoff count and starts frame transmission. STA1 and STA5 temporarily stop the countdown and wait when STA2 occupies the medium. When STA2's occupancy ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and restart the stopped backoff count. That is, frame transmission can start after counting down the remaining backoff slot for the remaining backoff time. Since the remaining backoff time of STA5 is shorter than that of STA1, STA5 starts frame transmission. The data to be transmitted may also occur in STA4 while STA2 occupies the medium. From the perspective of STA4, when the medium becomes idle, STA4 may wait for DIFS, and then may perform a countdown according to a random backoff count value selected by STA4, and start transmitting frames. Figure 4The example shows a case where the remaining backoff time of STA5 accidentally collides with the random backoff count value of STA4. In this case, a collision may occur between STA4 and STA5. When a collision occurs, neither STA4 nor STA5 receives an ACK, so data transmission fails. In this case, STA4 and STA5 can double the CW value, select a random backoff count value, and perform a countdown. While the medium is occupied due to the transmission of STA4 and STA5, STA1 waits, and when the medium becomes idle, STA1 waits DIFS, and then starts frame transmission after the remaining backoff time has passed.

[0079] As in Figure 4 In the example of , a data frame is a frame for sending data forwarded to a higher layer, and may be sent after a backoff performed after DIFS has passed since the medium became idle. In addition, a management frame is a frame for exchanging management information that is not forwarded to a higher layer, and is sent after a backoff is performed after an IFS such as DIFS or a point coordination function IFS (PIFS). As subtype frames of the management frame, there are beacons, association requests / responses, reassociation requests / responses, probe requests / responses, authentication requests / responses, and the like. A control frame is a frame for controlling access to a medium. As subtype frames of the control frame, there are request to send (RTS), clear to send (CTS), acknowledgement (ACK), power save poll (PS-Poll), block ACK (BlockAck), block ACK request (BlockACKReq), empty data packet announcement (NDP announcement), and trigger, and the like. If the control frame is not a response frame of the previous frame, it is sent after a backoff is performed after DIFS has passed, and if it is a response frame of the previous frame, it is sent without performing a backoff after a short IFS (SIFS). The type and subtype of a frame may be identified by the type field and subtype field in the frame control (FC) field.

[0080] Quality of Service (QoS) STA can perform a backoff performed after arbitration IFS (AIFS) (i.e., AIFS (where i is a value determined by AC)) for the access category (AC) to which the frame belongs, and then can send the frame. Here, the frame that can use AIFS may be a data frame, a management frame, or a control frame instead of a response frame.

[0081] Figure 5 is a diagram for explaining a frame transmission operation based on CSMA / CA to which the present disclosure can be applied.

[0082] As described above, in addition to the physical carrier sensing in which the STA directly senses the medium, the CSMA / CA mechanism also includes virtual carrier sensing. Virtual carrier sensing is intended to compensate for problems such as hidden node problems that may occur in medium access. For virtual carrier sensing, the MAC of the STA can use a network allocation vector (NAV). NAV is a value that indicates to other STAs the remaining time until the medium is available for use by the STA that is currently using or has the right to use the medium. Therefore, the value set to NAV corresponds to the period during which the STA sending the frame plans to use the medium, and during the corresponding period, the STA receiving the NAV value is prohibited from accessing the medium. For example, the NAV can be configured based on the value of the "Duration" field of the MAC header of the frame.

[0083] exist Figure 5 In the example of FIG. 1 , it is assumed that STA1 intends to send data to STA2, and STA3 is in a position to be able to eavesdrop on some or all frames sent and received between STA1 and STA2.

[0084] In order to reduce the possibility of transmission conflicts among multiple STAs in the CSMA / CA-based frame transmission operation, a mechanism using RTS / CTS frames can be applied. Figure 5 In the example of , when STA1's transmission is being performed, as a result of STA3's carrier sensing, it can be determined that the medium is in an idle state. That is, STA1 may correspond to a hidden node with respect to STA3. Alternatively, in Figure 5 In the example of , it can be determined that the carrier sensing result medium of STA3 is in an idle state while the transmission of STA2 is being performed. That is, STA2 may correspond to a hidden node with respect to STA3. By exchanging RTS / CTS frames before performing data transmission and reception between STA1 and STA2, STAs outside the transmission range of one of STA1 or STA2 or STAs outside the carrier sensing range of the transmission from STA1 or STA3 may not attempt to occupy the channel during data transmission and reception between STA1 and STA2.

[0085] Specifically, STA1 can determine whether the channel is being used by carrier sensing. In terms of physical carrier sensing, STA1 can determine the channel occupancy idle state based on the energy level or signal correlation detected in the channel. In addition, in terms of virtual carrier sensing, STA1 can use the network allocation vector (NAV) timer to determine the channel occupancy state.

[0086] When the channel is in an idle state during DIFS, STA1 may send an RTS frame to STA2 after performing backoff. When STA2 receives the RTS frame, STA2 may send a CTS frame to STA1 as a response to the RTS frame after SIFS.

[0087] If STA3 cannot eavesdrop on the CTS frame from STA2 but can eavesdrop on the RTS frame from STA1, STA3 can set the NAV timer for the frame transmission period (e.g., SIFS+CTS frame+SIFS+data frame+SIFS+ACK frame) that is continuously transmitted thereafter using the duration information included in the RTS frame. Alternatively, if STA3 can eavesdrop on the CTS frame from STA2, STA3 can set the NAV timer for the frame transmission period (e.g., SIFS+data frame+SIFS+ACK frame) that is continuously transmitted thereafter using the duration information included in the CTS frame even though STA3 cannot eavesdrop on the RTS frame from STA1. That is, if STA3 can eavesdrop on one or more of the RTS frame or the CTS frame from one or more of STA1 or STA2, STA3 can set the NAV accordingly. When STA3 receives a new frame before the NAV timer expires, STA3 can update the NAV timer using the duration information included in the new frame. STA3 does not attempt channel access until the NAV timer expires.

[0088] When STA1 receives a CTS frame from STA2, STA1 may send a data frame to STA2 after SIFS, starting from the time point when reception of the CTS frame is completed. When STA2 successfully receives the data frame, STA2 may send an ACK frame to STA1 after SIFS as a response to the data frame. When the NAV timer expires, STA3 may determine whether the channel is being used by carrier sensing. When STA3 determines that the channel is not being used by other terminals during the DIFS period after the NAV timer expires, STA3 may attempt channel access after the contention window (CW) according to the random backoff has passed.

[0089] Figure 6 is a diagram for explaining an example of a frame structure used in a WLAN system to which the present disclosure can be applied.

[0090] With the help of instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare a MAC PDU (MPDU) to be transmitted. For example, when a command requesting the PHY layer to start transmitting is received from the MAC layer, the PHY layer switches to a transmission mode, and configures information (e.g., data) provided from the MAC layer in the form of a frame and transmits it. In addition, when the PHY layer detects a valid preamble of a received frame, the PHY layer monitors the header of the preamble and transmits a command notifying the start of reception of the PHY layer to the MAC layer.

[0091] In this manner, information transmission / reception in the wireless LAN system is performed in the form of a frame, and for this purpose, a PHY layer protocol data unit (PPDU) format is defined.

[0092] The basic PPDU may include a short training field (STF), a long training field (LTF), a signal (SIG) field, and a data (Data) field. The most basic PPDU format (e.g., Figure 7 The non-HT (high throughput) shown in the figure may consist of only the legacy-STF (L-STF), the legacy-LTF (L-LTF), the legacy-SIG (L-SIG) field and the data field. In addition, depending on the type of PPDU format (e.g., HT mixed format PPDU, HT greenfield format PPDU, VHT (very high throughput) PPDU, etc.), additional (or different types of) RL-SIG, U-SIG, non-legacy SIG field, non-legacy STF, non-legacy LTF (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) and the like may be included between the L-SIG field and the data field.

[0093] STF is a signal used for signal detection, automatic gain control (AGC), diversity selection, precise time synchronization, etc., and LTF is a signal used for channel estimation and frequency error estimation. STF and LTF can be called signals for synchronization and channel estimation of the OFDM physical layer.

[0094] The SIG field may include various information related to the transmission and reception of the PPDU. For example, the L-SIG field consists of 24 bits, and the L-SIG field may include a 4-bit rate field, a 1-bit reserved bit, a 12-bit length field, a 1-bit parity field, and a 6-bit tail field. The RATE field may include information about the modulation and coding rate of the data. For example, the 12-bit length field may include information about the length or duration of the PPDU. For example, the value of the 12-bit length field may be determined based on the type of the PPDU. For example, for non-HT, HT, VHT, or EHT PPDUs, the value of the length field may be determined as a multiple of 3. For example, for HEPPDUs, the value of the length field may be determined as a multiple of 3+1 or a multiple of 3+2.

[0095] The data field may include a service (SERVICE) field, a physical layer service data unit (PSDU) and a PPDU tail bit, and may also include padding bits if necessary. Some bits of the service field may be used for synchronization of the descrambler at the receiving end. The PSDU corresponds to the MAC PDU defined in the MAC layer and may include data generated / used in the upper 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 in predetermined units.

[0096] MAC PDU is defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a frame check sequence (FCS). A MAC frame may consist of a MAC PDU and be transmitted / received through a PSDU of a data portion of a PPDU format.

[0097] 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 the time for transmitting the corresponding frame, etc. For details of the sequence control, QoS control, and HT control subfields of the MAC header, refer to the IEEE 802.11 standard document.

[0098] The null data PPDU (NDP) format refers to a PPDU format that does not include a data field. In other words, NDP refers to a frame format that includes a PPDU preamble (i.e., L-STF, L-LTF, L-SIG fields and additional non-legacy SIG, non-legacy STF, non-legacy LTF (if present)) of a general PPDU format and does not include the remaining part (i.e., the data field).

[0099] Figure 7 is a diagram illustrating an example of a PPDU defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0100] In standards such as IEEE 802.11a / g / n / ac / ax, various types of PPDUs have been used. The basic PPDU format (IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and data fields. The basic PPDU format may also be referred to as a non-HT PPDU format (such as Figure 7 (as shown in (a)).

[0101] Compared to the basic PPDU format, the HT PPDU format (IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT fields. Figure 7The HT PPDU format shown in (b) may be referred to as an HT mixed format. In addition, an HT greenfield format PPDU may be defined, and this corresponds to a format consisting of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTFs, and a data field, excluding L-STF, L-LTF, and L-SIG (not shown).

[0102] Compared to the basic PPDU format, an example of the VHT PPDU format (IEEE 802.11ac) additionally includes VHTSIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields (eg, Figure 7 (as shown in (c)).

[0103] Compared to the basic PPDU format, an example of the HE PPDU format (IEEE 802.11ax) additionally includes a repeated L-SIG (RL-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, a packet extension (PE) field (such as Figure 7 (d) of the HE PPDU format). Some fields may be excluded or their lengths may vary according to the detailed example of the HE PPDU format. For example, the HE-SIG-B field is included in the HE PPDU format for multi-user (MU), and the HE-SIG-B is not included in the HE PPDU format for single user (SU). In addition, the HE trigger-based (TB) PPDU format does not include the HE-SIG-B, and the length of the HE-STF field may vary to 8μs. The extended range (HE ER) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16μs. For example, the RL-SIG may be configured to be the same as the L-SIG. Based on the presence of the RL-SIG, the receiving STA may know that the received PPDU is a HE PPDU or an EHT PPDU, which will be described later.

[0104] The EHT PPDU format may include Figure 7 (e) EHT MU (multi-user) and Figure 7 The EHT TB (trigger-based) PPDU in (f) of FIG. The EHT PPDU format is similar to the HE PPDU format in that it includes the RL-SIG following the L-SIG, but may include the U (Universal)-SIG, the EHT-SIG, the EHT-STF, and the EHT-LTF following the RL-SIG.

[0105] Figure 7The EHT MU PPDU in (e) corresponds to a PPDU carrying 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.

[0106] Compared with EHT MU PPDU, Figure 7 The EHT TB PPDU in (f) omits the EHT-SIG. A STA that receives a trigger for ULMU transmission (eg, a trigger frame or a triggered response schedule (TRS)) may perform UL transmission based on the EHT TB PPDU format.

[0107] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal Signal), EHT-SIG fields may be coded and modulated so that even legacy STAs may attempt to demodulate and decode, and may be mapped based on a determined subcarrier frequency interval (e.g., 312.5kHz). These may be referred to as pre-EHT modulation fields. Next, the EHT-STF, EHT-LTF, data, PE fields may be coded and modulated so that they may be demodulated and decoded by a STA that successfully decodes a non-legacy SIG (e.g., U-SIG and / or EHT-SIG) and obtains the information included in the field, and may be mapped based on a determined subcarrier frequency interval (e.g., 78.125kHz). These may be referred to as EHT modulation fields.

[0108] 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. In addition, in the VHT PPDU format, the L-STF, L-LTF, L-SIG, and VHT-SIG-A fields may be referred to as non-VHT modulation fields, and the VHT STF, VHT-LTF, VHT-SIG-B, and data fields may be referred to as VHT modulation fields.

[0109] Included in Figure 7The U-SIG in the EHT PPDU format may be configured based on, for example, two symbols (e.g., two consecutive OFDM symbols). Each symbol (e.g., OFDM symbol) used for the U-SIG may have a duration of 4 μs, and the U-SIG may have a total duration of 8 μs. Each symbol of the U-SIG may be used to send 26 bits of information. For example, each symbol of the U-SIG may be sent and received based on 52 data tones and 4 pilot tones.

[0110] The U-SIG may be constructed in units of 20 MHz. For example, if an 80 MHz PPDU is constructed, the U-SIG may be duplicated. That is, the same 4 U-SIGs may be included in the 80 MHz PPDU. A PPDU with a bandwidth exceeding 80 MHz may include a different U-SIG.

[0111] For example, A uncoded bits may be sent via U-SIG, the first symbol of U-SIG (e.g., U-SIG-1 symbol) may send the first X bits of information out of a total of A bits of information, and the second symbol of U-SIG (e.g., U-SIG-2 symbol) may send the remaining Y bits of information out of a total of A bits of information. The A bits of information (e.g., 52 uncoded bits) may include a CRC field (e.g., a 4-bit long field) and a tail field (e.g., a 6-bit long field). For example, the tail field may be used to terminate the trellis structure of the convolutional decoder and may be set to 0.

[0112] The bit information sent through U-SIG can be divided into version-independent bits and version-dependent bits. For example, U-SIG can be included in Figure 7 In a new PPDU format not shown in the EHT PPDU format (e.g., UHR PPDU format), and may be included 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-related bits may be different.

[0113] For example, the size of the version-independent bit of the U-SIG may be fixed or variable. The version-independent bit may be assigned only to the U-SIG-1 symbol, or to both the U-SIG-1 symbol and the U-SIG-2 symbol. The version-independent bit and the version-dependent bit may be referred to by various names, such as a first control bit and a second control bit.

[0114] For example, the version-independent bits of the U-SIG may include a 3-bit physical layer version identifier (PHY version identifier), and this information may indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted / received PPDU. The version-independent bits of the U-SIG may include a 1-bit UL / DL flag field. The first value of the 1-bit UL / DL flag field is related to UL communication, and the second value of the UL / DL flag field is related to DL communication. The version-independent bits of the U-SIG may include information about the length of a transmit opportunity (TXOP) and information about a BSS color ID.

[0115] For example, the version-related bits of the U-SIG may include information directly or indirectly indicating the type of the PPDU (eg, SU PPDU, MU PPDU, TB PPDU, etc.).

[0116] Information required for PPDU transmission and reception may be included in the U-SIG. For example, the U-SIG may also include information about bandwidth, information about an MCS technology applied to a non-legacy SIG (e.g., EHT-SIG or UHR-SIG, etc.), information indicating whether a DCM (dual carrier modulation) technology (e.g., a technology 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, and information about whether the non-legacy SIG is generated across the entire frequency band.

[0117] 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 CP (cyclic prefix) length, information about the GI (guard interval) applicable to the non-legacy LTF, information about preamble puncturing applicable to the PPDU, information about resource unit (RU) allocation, etc. may be included only in the U-SIG, only in the non-legacy SIG, or may be indicated by a combination of information included in the U-SIG and information included in the non-legacy SIG.

[0118] Preamble puncturing may indicate the transmission of a PPDU in which there is no signal in one or more frequency units in 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 of a predetermined size or greater.

[0119] exist Figure 7In the example of , non-legacy SIGs such as HE-SIG-B and EHT-SIG may include control information for receiving STAs. The non-legacy SIG may be transmitted on at least one symbol, and one symbol may have a length of 4 μs. Information about the number of symbols used for the EHT-SIG may be included in a previous SIG (eg, HE-SIG-A, U-SIG, etc.).

[0120] Non-legacy SIGs such as HE-SIG-B and EHT-SIG may include a common field and a user-specific field. The common field and the user-specific field may be encoded separately.

[0121] In some cases, the common field may be omitted. For example, in a compressed mode that does not apply OFDMA (Orthogonal Frequency Division Multiple Access), the common field may be omitted, and multiple STAs may receive the PPDU (e.g., the data field of the PPDU) through the same frequency band. In a non-compressed mode that applies OFDMA, multiple users may receive the PPDU (e.g., the data field of the PPDU) through different frequency bands.

[0122] The number of user-specific fields may be determined based on the number of users. A user block field may include up to two user fields. Each user field may be associated with a MU-MIMO allocation or may be associated with a non-MU-MIMO allocation.

[0123] The common field may include a CRC bit and a tail bit, and the length of the CRC bit may be determined to be 4 bits, and the length of the tail bit may be determined to be 6 bits and set to 000000. The common field may include RU allocation information. The RU allocation information may include information about the positions of RUs to which multiple users (ie, multiple receiving STAs) are assigned.

[0124] RU can include multiple subcarriers (or tones). RU can be used when sending signals to multiple STAs based on OFDMA technology. In addition, RU can be defined even when sending signals to one STA. Resources can be allocated to non-traditional STF, non-traditional LTF and data fields in units of RU.

[0125] The RU of applicable size may be defined according to the PPDU bandwidth. The RU may be defined identically or differently for the applied PPDU format (e.g., HEPPDU, EHT PPDU, UHRPPDU, etc.). For example, in the case of an 80MHz PPDU, the RU layout of the HEPPDU and EHT PPDU may be different. The applicable RU size, the number of RUs and RU positions, the DC (direct current) subcarrier position and number, the empty subcarrier position and number, the guard subcarrier position and number, etc. for each PPDU bandwidth may be referred to as a tone plan. For example, a tone plan for high bandwidth may be defined in the form of multiple iterations of a low bandwidth tone plan.

[0126] RUs of various sizes may be defined as 26-tone RUs, 52-tone RUs, 106-tone RUs, 242-tone RUs, 484-tone RUs, 996-tone RUs, 2×996-tone RUs, 3×996-tone RUs, etc. MRUs (multi-RUs) are different from multiple individual RUs and correspond to a group of subcarriers consisting of multiple RUs. For example, one MRU may be defined as 52+26 tones, 106+26 tones, 484+242 tones, 996+484 tones, 996+484+242 tones, 2×996+484 tones, 3×996 tones, or 3×996+484 tones. In addition, the multiple RUs constituting one MRU may or may not be continuous in the frequency domain.

[0127] The specific size of the RU may be reduced or expanded. Therefore, the specific size of each RU in the present disclosure (i.e., the number of corresponding tones) is not restrictive but illustrative. In addition, in the present disclosure, within a predetermined bandwidth (e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz ...), the number of RUs may vary according to the RU size.

[0128] Figure 7 The names of each field in the PPDU format are exemplary, and the scope of the present disclosure is not limited by these names. In addition, the examples of the present disclosure can be applied to Figure 7 The PPDU format shown in Figure 7 A new PPDU format that excludes some fields and / or adds some fields.

[0129] Multi-link operation

[0130] Hereinafter, a multi-link operation supported by a STA according to the present disclosure will be described.

[0131] The STA (AP STA and / or non-AP STA) described in the present disclosure may support multi-link (ML) communication. ML communication may refer to communication that supports multiple links. Links related to ML communication may include channels (e.g., 20 / 40 / 80 / 160 / 240 / 320 MHz channels) in the frequency band (e.g., 2.4 GHz band, 5 GHz band, 6 GHz band, etc.) in which the STA operates. Multiple links for ML communication may be configured in various ways. For example, multiple links supported by one STA for ML communication may belong to the same frequency band or to different frequency bands. In addition, each link may correspond to a frequency unit (e.g., channel, sub-channel, RU, etc.) of a predetermined size. In addition, all or part of the multiple links may be frequency units of the same size, or may be frequency units of different sizes.

[0132] When a STA supports multiple links, the transmission or reception device supporting each link can operate like one logical STA. In other words, MLD refers to a device having at least one subordinate STA as a logical entity and having a single MAC service access point (SAP) for one MAC data service and logical link control (LLC). Non-AP MLD refers to an MLD in which each STA attached to the corresponding MLD is a non-AP STA. Multi-radio non-AP MLD refers to a non-AP MLD that supports receiving or exchanging frames in at least one link at a time. AP MLD refers to an MLD in which each STA attached to the corresponding MLD is an AP STA.

[0133] Multi-link Operation (MLO) enables non-AP MLDs to discover, authenticate, and associate with AP MLDs and establish multiple links. Each link can enable channel access and frame exchange between non-AP MLDs and AP MLDs based on the supported capabilities exchanged during the association process. STAs attached to an MLD can select and manage their capabilities and operating parameters independently of other STAs attached to the same MLD.

[0134] Through the multi-link establishment process, the AP MLD and / or the non-AP MLD may send or receive link-related information that the corresponding MLD may support. The link-related information may include at least one of the following: whether it is a simultaneous transmission and reception (STR) operation that can simultaneously transmit or receive on multiple links or a non-simultaneous transmission and reception (NSTR) operation that cannot simultaneously transmit or receive, information about the number / upper limit of UL / DL links, information about the location / band / resource of the UL / DL links, information about a frame type (e.g., management, control, data) available or preferred in at least one UL / DL link, information about an available or preferred ACK strategy in at least one UL / DL link, or information about a traffic identifier (TID) available in at least one UL / DL link supported by the corresponding MLD.

[0135] An AP MLD (e.g., NSTR mobile AP MLD) may configure one of the multiple links as a primary link. The AP MLD may perform beacon frames, probe response frames, and group-addressed data frames only on the primary link. The remaining other links in the multiple links may be referred to as non-primary links. An AP MLD operating on a non-primary link may operate to not send beacon frames or probe response frames. In addition, a non-AP MLD may perform frame exchanges only on the primary link during authentication, (re)association, and a 4-way handshake.

[0136] When at least one traffic identifier (TID) is mapped to a corresponding link through a multi-link establishment procedure, the established link may be defined as enabled, and when there is no TID mapped to the corresponding link, the established link may be defined as disabled. Unless admission control is used, a TID should always be mapped to at least one established link. Basically, a TID is mapped to all established links, and thus all established links may be activated.

[0137] When a link is activated, the corresponding link can be used for frame exchange according to the power state of the non-AP STA operating in the corresponding link. Only the MSDU or A-MSDU with the TID mapped to the active link can be sent in the corresponding link. Management frames and control frames can be sent only in the active link.

[0138] When a link is deactivated, the corresponding link may not be used for frame exchange by including management frames for both DL and UL.

[0139] In the multi-link establishment process, activation / deactivation of each link may be indicated by TID-to-link mapping. TID-to-link mapping may be performed in a default mapping mode or / and a negotiated mapping mode.

[0140] One STA among the STAs belonging to the MLD may provide information about at least one link other than the link it uses for multi-link discovery (e.g., obtaining information about multiple links including the corresponding link on one link) or multi-link establishment (e.g., simultaneously associating on multiple links through exchange of association request / response frames on one link). In order to provide this information, a multi-link (ML) element may be defined.

[0141] AP and AP MLD aging function

[0142] The AP aging function or the AP MLD aging function may be defined so that the buffered BU is not discarded after a period shorter than the period indicated by the STA for the buffered bufferable unit (BU) in the Listen Interval field of the (re)association request frame. In other words, according to the AP aging function or the AP MLD aging function, the buffered data (e.g., DLBU) for the corresponding STA may be discarded after the Listen Interval of the STA has passed.

[0143] The aging function can be implemented in various ways. In addition, the aging function can be applied independently or additionally to other reasons for MSDU discard in the MAC entity (for example, data life-related operations).

[0144] Listen Interval Field

[0145] For normal (re)association (or not MLD association), the Listen Interval field may be used to inform the AP how often a STA in power save mode wakes up and listens to beacon frames. It may also be used to inform the AP of the duration required for a STA in non-TIM mode to send at least one frame addressed to the associated AP. The Listen Interval field may have a value in units of beacon intervals or a value in units of short beacon intervals.

[0146] For (re)association for MLD association, when all STAs belonging to the non-AP MLD are in power saving mode, the Listen Interval field may be used to inform the AP MLD how frequently at least one STA belonging to the non-AP MLD wakes up and listens to beacon frames. The Listen Interval field may have a value whose unit is the maximum value among a plurality of beacon intervals corresponding to a plurality of links that the non-AP MLD wants to establish in the (re)association request frame.

[0147] The length of the Listen Interval field may be 2 octets. A value of 0 of the Listen Interval field may be used by STAs that do not belong to an MLD, or may be used when all STAs that belong to a non-AP MLD do not enter a power saving mode.

[0148] For a normal (re)association (not an MLD association), the AP may use the Listen Interval to determine the lifetime of frames buffered for the STA.

[0149] For (re)association for MLD association, the AP may use the Listen Interval to determine the lifetime of frames buffered for non-AP MLD.

[0150] Operations for MLD listening interval

[0151] During multi-link (ML) (re)establishment, the value included in the Listen Interval field of the (re)association request frame sent by a non-AP STA belonging to a non-AP MLD to an AP belonging to an AP MLD is requested at the MLD level. The value of the Listen Interval field may have a value whose unit is the maximum value among a plurality of beacon intervals corresponding to a plurality of links that the non-AP MLD wants to establish in the (re)association request frame. The AP belonging to the AP MLD may refuse the (re)establishment because the Listen Interval requested by the non-AP MLD is too large. After a successful ML (re)establishment, the AP MLD may use the Listen Interval to determine the lifetime of the frames buffered for the non-AP MLD. For example, the value of the Listen Interval field may be defined to not change after a successful ML (re)establishment.

[0152] The AP MLD may delete the buffered BUs for various reasons, including the use of an aging function and the availability of a buffer (e.g., AP MLD aging function, etc.). Here, the aging function may be based on a listening interval indicated by the non-AP MLD in a (re)association request frame or a WNM sleep interval specified by the non-AP MLD in a request frame in a wireless network management (WNM) sleep mode.

[0153] When all non-AP STAs belonging to a non-AP MLD and operating on an enabled link are in a power saving mode, at least one of these non-AP STAs needs to wake up and listen to at least one beacon frame. Such at least one beacon frame is scheduled within an interval having the same duration as the listening interval indicated by the non-AP MLD in a (re)association request frame, which interval may start from the last target beacon transmission time (TBTT) during which the corresponding non-AP STA or another non-AP STA belonging to the corresponding non-AP MLD was in an awake state.

[0154] Figure 8 is a diagram illustrating an example of an operation based on an MLD listening interval related to the present disclosure.

[0155] exist Figure 8In the example of , it is assumed that AP MLD has three subordinate APs, namely, AP 1 operating on link 1, AP 2 operating on link 2, and AP 3 operating on link 3. It is assumed that the beacon intervals of link 1, link 2, and link 3 are 250ms, 200ms, and 70ms, respectively.

[0156] Non-AP STA1 belonging to non-AP MLD may transmit an association request frame to AP 1 belonging to AP MLD. Non-AP STA1 may request to establish three links (i.e., link 1 between AP 1 and non-AP STA1, link 2 between AP 2 and non-AP STA 2, and link 3 between AP 3 and non-AP STA 3). The value of the Listen Interval field included in the Association Request frame may be configured as 1, and the value corresponds to a value in units of the maximum beacon interval (i.e., 250 ms). Therefore, the value of the Listen Interval requested by the non-AP MLD is 250 ms.

[0157] AP 1 belonging to AP MLD can accept three links for ML establishment (i.e., link 1 between AP 1 and non-AP STA 1, link 2 between AP 2 and non-AP STA 2, and link 3 between AP 3 and non-AP STA 3) by sending an association response frame to non-AP STA 1 belonging to non-AP MLD.

[0158] After successful ML establishment, non-AP STA2 and non-AP STA3 may enter power saving mode. Thereafter, non-AP STA1 may enter power saving mode. For example, PM set to value 1 may be signaled.

[0159] In this case, the AP MLD may buffer the DL BU for the non-AP MLD for at least 250ms. For example, at time point T1, the non-AP STA1 needs to receive a beacon frame on link 1, and the non-AP STA belonging to the non-AP MLD needs to wake up before time point T2 (e.g., T2=T1+250ms) to receive at least one beacon frame. For example, the non-AP STA1 may receive the second beacon frame on link 1 (at T1+250ms), or the non-AP STA2 may receive the second beacon frame on link 2 (at T1+200ms), or the non-AP STA 3 may receive the fourth beacon frame on link 3 (at T1+280ms). For the sake of brevity, Figure 8 The example illustratively shows the situation where the first beacon frames on all links are aligned with the same time point, but in reality, the first TBTTs on all links may not be aligned.

[0160] Fig. 9is a diagram illustrating additional examples of operations based on an MLD listening interval related to the present disclosure.

[0161] exist Fig. 9 In the example of , it is assumed that AP MLD has three subordinate APs, namely, AP 1 operating on link 1, AP 2 operating on link 2, and AP 3 operating on link 3. It is assumed that the beacon intervals of link 1, link 2, and link 3 are 250ms, 200ms, and 70ms, respectively.

[0162] Non-AP STA 2 belonging to non-AP MLD may transmit an association request frame to AP 2 belonging to AP MLD. Non-AP STA 2 may request to establish three links (i.e., link 1 between AP 1 and non-AP STA 1, link 2 between AP 2 and non-AP STA 2, and link 3 between AP 3 and non-AP STA 3). The value of the Listen Interval field included in the Association Request frame may be configured as 1, and the value corresponds to a value in units of the maximum beacon interval (i.e., 250 ms). Therefore, the value of the Listen Interval requested by the non-AP MLD is 250 ms.

[0163] AP 2 belonging to AP MLD may accept two links (ie, link 2 between AP 2 and non-AP STA2 and link 3 between AP 3 and non-AP STA3) for ML establishment by sending an association response frame to non-AP STA1 belonging to non-AP MLD.

[0164] Here, the listening interval requested by the non-AP MLD is still 250 ms and does not change according to the link accepted during the ML establishment process.

[0165] After successful ML establishment, non-AP STA 3 may enter power saving mode. Afterwards, non-AP STA 2 may enter power saving mode. For example, PM set to value 1 may be signaled.

[0166] In this case, the AP MLD may buffer the DLBU for the non-AP MLD for at least 250ms. For example, at time point T1, non-AP STA2 needs to receive a beacon frame on link 2, and one of non-AP STA2 or non-AP STA 3 belonging to the non-AP MLD needs to wake up before time point T2 (e.g., T2=T1+250ms) to receive at least one beacon frame. For example, non-AP STA2 may receive the second beacon frame on link 2 (at T1+200ms), or non-AP STA3 may receive the fourth beacon frame on link 3 (at T1+280ms). For simplicity, Fig. 9The example illustratively shows the situation where the first beacon frames on all links are aligned with the same time point, but in reality, the first TBTTs on all links may not be aligned.

[0167] As described above, the STA may set the Listen Interval field in the (re)association request frame to a value corresponding to the Listen Interval length expected / requested by the corresponding STA and send it to the AP. The length of the Listen Interval requested by the STA may be determined by the STA based on information such as TIM, Transfer TIM (DTIM), Beacon Interval, etc. included in a beacon frame or a probe response frame, etc. received by the STA from the AP. When the AP cannot accept the Listen Interval requested by the STA, it may send a (re)association response frame to the STA, the (re)association response frame including a status code set to a value indicating rejection and a reason thereof (e.g., status code value 51 (DENIED_LISTEN_INTERVAL_TOO_LARGE) due to too long a Listen Interval). When the AP may accept the Listen Interval requested by the STA, the AP may set the value of the status code in the (re)association response frame to a value indicating acceptance and send it to the STA.

[0168] When the AP buffers data (e.g., beacon frame, DLBU, etc.) to the STA based on the listening interval configured through this procedure and the STA in the dormant / sleep state enters the awake state after the listening interval and sends a PS-Poll frame to the AP, the AP may send the buffered data / frame to the STA in response thereto. If the AP does not receive the PS-Poll frame from the STA even after the listening interval, and thus it cannot confirm whether the STA in the dormant / sleep state is in the awake state, or it confirms that the STA is not in the awake state, the AP may delete / discard the buffered data / frame for the corresponding STA after a predetermined period of time.

[0169] The listening interval on the MLD can be configured by negotiation including the exchange of the ML (re)establishment request and the ML (re)establishment response. The ML (re)establishment request and the ML (re)establishment response can be performed by sending / receiving the (re)association request frame and the (re)association response frame, respectively. The STA can set the value of the listening interval field included in the (re)association request frame based on the longest value among the beacon intervals of multiple APs within the AP MLD (i.e., by using the maximum value among the beacon intervals as a unit, for example, set to a value that is an integer multiple of the maximum value). For example, APs belonging to the AP MLD have beacon intervals of different values, and the listening interval of the MLD level can be configured based on one (e.g., the largest) beacon interval among them (i.e., configured as a value that is an integer multiple of one beacon interval).

[0170] Operation for enhanced MLD listening interval

[0171] As in the above Figure 8 In the example of , when accepting ML (re)establishment for Link 1, Link 2, and Link 3, a listening interval of 250 ms (i.e., an integer multiple of 250 ms) can be configured as the maximum value among the beacon intervals of Link 1, Link 2, and Link 3. Fig. 9 In the example of , when AP 1 on link 1 has a maximum beacon interval within AP MLD and link 1 / AP 1 is rejected during the ML (re)establishment process, the listening interval of the MLD level can be configured based on the beacon interval with the maximum value, regardless of whether the link / AP is rejected.

[0172] The state of each link belonging to the ML may have an enabled state and a disabled state. The enabled state may correspond to a state in which data transmission or reception on the corresponding link is possible, and the disabled state may correspond to a state in which data transmission or reception on the corresponding link is impossible. The disabled state and the enabled state may be temporary. In other words, a temporarily disabled link may be returned to the enabled state. In addition, the state of the link may include a deleted state. Unlike the disabled state, the deleted state corresponds to a state in which it is impossible to return to the enabled state.

[0173] In the existing WLAN system, when a link / AP whose beacon interval is the maximum value among APs in the AP MLD requesting ML (re)establishment is rejected, an operation for configuring the MLD listening interval is defined, but when a link / AP whose beacon interval is the maximum value is deleted, how to configure the MLD listening interval is not defined. Even when a link / AP whose beacon interval is the maximum value is deleted, when the MLD listening interval is configured or maintained based on the corresponding beacon interval, an MLD listening interval based on a beacon interval longer than that of the remaining APs that are not deleted is applied. In this case, there is a problem that the AP must maintain the buffered frames for an unnecessary long time, and the STA operates in a power saving mode for an unnecessary long time or during a time period that is not suitable for the beacon interval of the remaining APs.

[0174] As described above, for the operation of the existing MLD listening interval, the listening interval for the AP MLD can be determined through the ML establishment process based on the longest listening interval among multiple APs. It is defined that even when the link or AP associated with the MLD is excluded during the ML establishment process or after a successful ML establishment, the configured listening interval does not change. In other words, in the existing WLAN system, the MLD listening interval is only defined as being determined in units of the maximum value among multiple beacon intervals of multiple links / APs of the AP MLD, and the MLD listening interval is determined regardless of the state of the link / AP. If the excluded link / AP is associated with the longest listening interval, there is a problem of applying an inefficiently long or inappropriate listening interval to the remaining links / APs. Here, the excluded link / AP may correspond to a state of rejection, deletion, or another name that does not belong to the MLD.

[0175] To eliminate or prevent this inefficiency, a new method for determining or updating / modifying the MLD listening interval based on changes in the status of the link / AP is needed.

[0176] Fig.10 is a diagram for explaining an example of a method performed in a STA based on an MLD listening interval according to the present disclosure.

[0177] In S1010 , the STA may detect a change in a state of at least one link among a plurality of links.

[0178] The STA may be one of multiple STAs in the non-AP MLD.

[0179] The change of the link state may correspond to a change of the state of the AP. For example, when the link / AP corresponds to a state in which it is excluded from the ML or MLD (e.g., a state in which it is deleted after a successful ML establishment, a state in which it is not accepted to establish a link during ML establishment (i.e., the rejection is indicated by a (re)association response to a (re)association request, etc.), the change of the state of the link / AP may include a case in which the beacon interval of the link / AP is changed / updated to a value longer than the existing beacon interval (e.g., a value longer than the existing maximum beacon interval (i.e., a value that is a basis / unit of the MLD listening interval) among a plurality of links / APs belonging to the ML / MLD).

[0180] In S1020 , the STA may determine an updated MLD listening interval based on at least one enabled link.

[0181] In other words, the updated MLD listening interval may be configured based on a maximum value (ie, in units of a maximum value) of at least one beacon interval corresponding to at least one enabled link / AP.

[0182] For example, when one of the three links / APs is rejected / deleted, the updated MLD listening interval may be determined based on the maximum value among the beacon intervals of the remaining two enabled links / APs. If the beacon interval of the rejected / deleted link / AP is not the maximum value among the beacon intervals, even when the MLD listening interval is based on the same beacon interval as before (i.e., in units of the same beacon interval), it may not be updated or may be configured as a different value (i.e., a change in a multiple of the beacon interval).

[0183] For example, when the beacon interval of at least one link / AP is changed even when no link / AP among three links / APs is rejected / deleted, the updated MLD listening interval may be determined based on the maximum value among the beacon intervals of enabled (e.g., all three) links / APs including the link / AP with the changed beacon interval. If the changed beacon interval is a value smaller than the beacon interval that is the basis / unit of the existing MLD listening interval, the MLD listening interval may not be updated or may be configured as a different value (i.e., a change in a multiple of the beacon interval) even when the MLD listening interval is based on the same beacon interval as before (i.e., in the same beacon interval unit).

[0184] The STA can obtain the beacon interval of the corresponding link / AP through the beacon frame or the probe response frame on each link, and determine the updated MLD listening interval based on the beacon interval with the maximum value among them. In addition, each AP belonging to the AP MLD can obtain the beacon interval of other APs, and determine the updated MLD listening interval based on the beacon interval with the maximum value among them. Here, when the value of the beacon interval on which the existing MLD listening interval is based (i.e., used as a unit) is updated to determine the updated MLD listening interval, the integer applied as a multiple of the updated beacon interval (i.e., X in the relationship "listening interval = X*beacon interval") can remain as is the integer value (i.e., X) corresponding to the calculated multiple applied to the existing MLD listening interval. Therefore, the updated MLD listening intervals determined separately can be configured / calculated as the same value without any signaling exchange between the AP MLD and the non-AP MLD.

[0185] Additionally or alternatively, the updated MLD listening interval may be determined based on an exchange of requests and responses between a STA (or non-AP MLD) and an AP (or AP MLD) or based on an announcement from an AP (or AP MLD). For example, the STA may determine the updated MLD listening interval and request the AP, or may request the AP to update the MLD listening interval. In response, the AP may accept or reject the request from the STA, or may provide the STA with information about the (changed) updated MLD listening interval. Alternatively, the AP may send information about the updated MLD listening interval to the STA without a request from the STA. QoS empty frames, management frames, etc. may be used to send or receive information about the updated MLD listening interval. Here, when the value of the beacon interval on which the existing MLD listening interval is based (i.e., used as a unit) is updated to determine the updated MLD listening interval, the integer applied as a multiple of the updated beacon interval may remain as is the integer value corresponding to the calculated multiple applied to the existing MLD listening interval, or an updated multiple value may be applied. In other words, an updated MLD listening interval including at least one of an updated (basic) beacon interval or an updated multiple may be configured through a request-response or announcement between the AP MLD and the non-AP MLD.

[0186] In S1030 , the STA may perform transmission or reception with the AP MLD based on the updated MLD listening interval.

[0187] For example, it may include the STA entering a power saving mode (or a sleep mode or a hibernation mode) after receiving a beacon frame at time point T1, and waking up before time point T2 to receive at least one beacon frame on one of the at least one enabled links. Here, time point T2 is a time point X time interval after time point T1, and X may correspond to an updated MLD listening interval.

[0188] Fig.10 The method described in the example can be Figure 1 The first device (100) performs. For example, Figure 1 At least one processor (102) of the first device (100) may be configured to detect a link state change, perform an operation for updating an MLD listening interval, and perform transmission or reception with the AP MLD through at least one transceiver (106) based on the updated MLD listening interval. In addition, at least one memory (104) of the first device (100) may store an instruction for executing, when executed by the at least one processor (102), Fig.10 Examples or instructions of the methods described in the examples described below.

[0189] Fig.11is a diagram for explaining an example of a method performed in an AP based on an MLD listening interval according to the present disclosure.

[0190] In S1110 , the AP may determine an updated MLD listening interval based on at least one enabled link associated with a change in a state of at least one link among the plurality of links.

[0191] The AP may be one of the multiple APs in the AP MLD. Since the updated MLD listening interval is determined based on the enabled links and the change in the link status, the AP MLD listening interval is different from the AP MLD listening interval for the AP. Fig.11 The descriptions of the examples are the same, so overlapping descriptions are omitted.

[0192] In S1120 , the AP may perform transmission or reception with the non-AP MLD based on the updated MLD listening interval.

[0193] For example, the AP may determine the time for maintaining the DLBU in the buffer for the non-AP MLD based on the updated MLD listening interval. When a PS-poll frame is received from the STA during the time during which the DLBU is maintained in the buffer, the corresponding DLBU may be sent to the STA. When a PS-poll frame is not received from the STA during the time during which the DLBU is maintained in the buffer, the AP may discard the corresponding DLBU.

[0194] Fig.11 The method described in the example can be Figure 1 The second device (200) is executed. For example, Figure 1 At least one processor (202) of the second device (200) may be configured to determine an updated MLD listening interval associated with a change in link state, and perform transmission or reception with the non-AP MLD through at least one transceiver (206) based on the updated MLD listening interval. In addition, at least one memory (204) of the second device (200) may store instructions for executing when executed by the at least one processor (202) Fig.11 Examples or instructions of the methods described in the examples described below.

[0195] Fig.10 and Fig.11 Examples of may correspond to some of the various examples of the present disclosure. In the following, the examples including Fig.10 and Fig.11 Various examples of the present disclosure including examples of .

[0196] In the embodiments described below, the case of excluding the link / AP having the maximum beacon interval among multiple links / APs is described as a representative example of applying the present disclosure, but the embodiments described below can be equally applied to various reasons or various situations in which the maximum beacon interval value among multiple beacon intervals corresponding to multiple links / APs changes. In other words, for various situations in which the maximum value among multiple beacon intervals changes, the MLD listening interval can be updated / modified based on the changed maximum beacon interval.

[0197] Implementation Method 1

[0198] This embodiment can be applied to a case where an AP with a longest beacon interval among the APs of the AP MLD for which ML establishment is requested is deleted, a case where the beacon interval of the AP in the AP MLD for which ML establishment is requested is updated to a value longer than the listening interval of the MLD level (or the value of the beacon interval that is the basis / unit of the MLD listening interval), and a case where the APMLD sends a (re)association response frame including a status code corresponding to rejection (e.g., status code 51 (DENIED_LISTEN_INTERVAL_TOO_LARGE)) with respect to the value of the listening interval field in the (re)association request frame of the ML establishment request. The case where this embodiment is applied is exemplary and not restrictive.

[0199] The embodiment may include determining a listening interval of an updated MLD level based on an enabled link associated with a change in a state of the link, and performing transmission / reception between the AP MLD and the non-AP MLD based on the updated MLD listening interval.

[0200] The method for updating / modifying the listening interval of the MLD level may include an implicit method and an explicit method.

[0201] Implementation Method 1-1

[0202] According to this embodiment, the MLD listening interval update can be implicitly updated / changed, i.e., without exchanging separate negotiation messages between MLDs (AP MLD and non-AP MLD). STA (or non-AP MLD) can obtain information about the beacon interval of AP (i.e., each AP in AP MLD) through a beacon frame or a probe response frame, etc. Both non-AP MLD and AP MLD can have information about the beacon interval of AP in AP MLD. Therefore, when two MLDs (i.e., AP MLD and non-AP MLD) identify / detect that the AP with the longest value of the beacon interval in AP MLD is excluded (e.g., deleted), the two MLDs (i.e., AP MLD and non-AP MLD) can update / change the listening interval of the MLD level based on the value of the longest beacon interval among APs excluding the excluded (e.g., deleted) AP in AP MLD. In other words, the MLD listening interval can be determined based on the beacon interval of (remaining) enabled links / APs (in units thereof) instead of the excluded links / APs.

[0203] This implicit method can be applied when the AP provides an ML establishment response indicating a specific status code (i.e., rejected due to a too long listening interval requested) for the ML establishment request of the STA. For example, the status code 51 corresponds to the following rejection reason, which indicates that the value of the listening interval field in the (re)association request frame of the ML establishment requested by the non-AP MLD has a too long length value based on the beacon interval with the longest value among the beacon intervals of the APs in the APMLD. In this case, since both the non-AP MLD and the AP MLD obtain / have the values ​​of all beacon intervals of the APs in the AP MLD, the two MLDs (i.e., the AP MLD and the non-AP MLD) can configure the listening interval of the MLD level based on the link / AP with the longest value of the beacon interval in the AP MLD excluding the rejected link / AP.

[0204] Implementation 1-2

[0205] According to this embodiment, the MLD listening interval update may be explicitly updated / changed, that is, the MLD-level listening interval may be updated / changed by sending / receiving a negotiation message between MLDs.

[0206] For example, based on a request frame sent from a non-AP MLD, the AP MLD may notify an updated MLD listening interval through a response frame. For example, the updated MLD listening interval may be notified to the STA through a frame announced by the AP. Such a request / response frame or announcement frame may be defined and used as a new frame that was not previously defined. For example, such a new frame may be defined in a format including a listening interval field such as a QoS null frame, a management frame, or the like.

[0207] Fig.12 is a diagram illustrating an example of an operation based on an MLD listening interval according to the present disclosure.

[0208] Fig.12 The example assumes that Figure 8 As in the example of FIG. 1 , link 1 , link 2 , and link 3 are accepted as established links through the initial ML establishment and the initial MLD listening interval is configured as 250 ms, and then the case where the MLD listening interval is updated in an explicit manner or implicit manner as in the above-mentioned embodiment is shown.

[0209] For example, when AP 1 on Link 1 is deleted in AP MLD, there may be a problem that the AP needs to buffer DLBUs unnecessarily because the length of the initially configured MLD listening interval (i.e., 250 ms) is longer than the value based on the beacon interval of other APs. Fig.12 From the second beacon frame on link 2 in to the initial point in time at which the AP may discard the DLBU according to the initial configuration, the AP MLD may need to maintain the DLBU in the buffer unnecessarily.

[0210] According to the present disclosure, the listening interval of the MLD level can be reconfigured / updated based on the maximum beacon interval (in units of the maximum beacon interval) among the remaining (enabled) links / APs excluding the deleted links / APs. The updated MLD listening interval can be determined based on the maximum value 200ms among the remaining beacon intervals of 200ms and 70ms excluding the beacon interval 250ms of Link 1 / AP 1 (determined as an integer multiple of 200ms).

[0211] For example, when the updated MLD listening interval is 200ms, the STA can wake up and receive at least one beacon frame or send a PS-Poll frame before time point T2' (= T1 + 200ms). In addition, the time point when the AP MLD can discard the DLBU can be changed (or advanced) to after time point T2'.

[0212] In the existing WLAN system, although some links / APs among multiple links / APs are rejected in the ML / MLD operation, the MLD listening interval is determined based on the maximum beacon interval including the beacon intervals of the rejected links / APs, so there may be a problem of configuring an unnecessarily long MLD listening interval. According to the present disclosure, the MLD listening interval can be determined / updated based on the maximum beacon interval among the beacon intervals of enabled / available links / APs, so that the effect of efficiently determining and applying the optimal MLD listening interval can be achieved.

[0213] The above-mentioned embodiments are to combine the elements and features of the present disclosure in a predetermined form. Unless otherwise explicitly mentioned, each element or feature should be regarded as optional. Each element or feature can be implemented in a form that is not combined with other elements or features. In addition, the embodiments of the present disclosure may include a combination of some elements and / or features. The order of the operations described in the embodiments of the present disclosure may be changed. Some elements or features of an embodiment may be included in other embodiments, or may be replaced by corresponding elements or features of other embodiments. Obviously, the embodiments may include claims that do not have a clear reference relationship in the combined claims, or may be included as new claims by modification after application.

[0214] It is clear to those skilled in the relevant art that the present disclosure can be implemented in other specific forms within the scope of the essential features of the present disclosure. Therefore, the above detailed description should not be interpreted restrictively in every aspect, but should be considered as illustrative. The scope of the present disclosure should be determined by the reasonable interpretation of the attached claims, and all changes within the equivalent scope of the present disclosure are included in the scope of the present disclosure.

[0215] The scope of the present disclosure includes software or machine executable commands (e.g., operating systems, applications, firmware, programs, etc.) that perform operations in a device or computer according to the methods of various embodiments, and non-transitory computer-readable media that enable software or commands, etc. to be stored and executable in a device or computer. Commands that can be used to program a processing system that performs the features described in the present disclosure can be stored in a storage medium or a computer-readable storage medium, and the features described in the present disclosure can be implemented by using a computer program product that includes such a storage medium. The storage medium may include a high-speed random access memory, such as, for example, DRAM, SRAM, DDR RAM, or other random access solid-state storage devices, but is not limited thereto, and it may include non-volatile memory, such as, for example, 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 located away from the processor. The memory, or alternatively, the non-volatile memory device in the memory includes a non-transitory computer-readable storage medium. The features described in this disclosure may be stored in any machine-readable medium to control the hardware of a processing system, and may be integrated into software and / or firmware that allows the processing system to interact with other mechanisms using the results from the embodiments of this disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0216] Industrial Applicability

[0217] The method proposed in the present disclosure is mainly described based on an example applied to a system based on IEEE 802.11, but may be applied to various WLAN or wireless communication systems other than the system based on IEEE 802.11.

Claims

1. A method performed by a station STA in a wireless local area network WLAN system, the method comprising the following steps: Detecting, by the STA belonging to a non-AP multi-link device MLD, a change in a state of at least one link among a plurality of links; determining an updated MLD listening interval based on at least one enabled link; as well as The AP MLD is transmitted or received based on the updated MLD listening interval.

2. The method according to claim 1, wherein: The updated MLD listening interval is based on a maximum value among at least one beacon interval corresponding to the at least one enabled link.

3. The method according to claim 2, wherein: The beacon interval for each of the at least one enabled link is acquired through a beacon frame or a probe response frame on the corresponding link.

4. The method according to claim 2, wherein: The updated MLD listening interval is determined by each access point AP on the at least one enabled link.

5. The method according to claim 1, wherein: The updated MLD listening interval is determined based on a response from the AP MLD to the request of the STA, or based on an announcement from the AP MLD.

6. The method according to claim 5, wherein: The updated MLD listening interval is based on a maximum value among at least one beacon interval corresponding to the at least one enabled link.

7. The method according to claim 5, wherein: Information about the updated MLD listening interval is included in at least one of a Quality of Service (QoS) null frame or a management frame.

8. The method according to claim 1, wherein: The change of the state of the at least one link comprises: The at least one link among the plurality of links is deleted after a successful multi-link ML establishment, or The at least one link among the plurality of links is not accepted as an established link during ML establishment.

9. The method according to claim 8, wherein: The step of not accepting the link established for the STA includes an association response or a reassociation response indicating a rejection of the association request or the reassociation request from the STA.

10. The method according to claim 1, wherein: The sending or receiving with the AP MLD based on the updated MLD listening interval includes the STA entering a power saving mode after receiving a beacon frame at a time point T1, and waking up before a time point T2 to receive a beacon frame or send a power saving polling PS-Poll frame on one of the at least one enabled links, T2 is T1+X, and X is the updated MLD listening interval.

11. The method according to claim 1, wherein: Based on the updated MLD listening interval, a downlink bufferable unit BU for the non-AP MLD is buffered in the AP MLD.

12. A station STA device in a wireless local area network (WLAN) system, the device comprising: at least one transceiver; as well as at least one processor connected to the at least one transceiver, Wherein, the at least one processor is configured to: Detecting, by the STA belonging to a non-AP multi-link device MLD, a change in a state of at least one link among a plurality of links; determining an updated MLD listening interval based on at least one enabled link; and The at least one transceiver performs transmission or reception with the AP MLD based on the updated MLD listening interval.

13. A method performed by an access point (AP) in a wireless local area network (WLAN) system, the method comprising the following steps: determining, by the AP belonging to an AP multi-link device MLD, an updated MLD listening interval based on at least one enabled link associated with a change in a state of at least one link among a plurality of links; as well as The transmission or reception is performed with the non-AP MLD based on the updated MLD listening interval.

14. An access point AP device in a wireless local area network (WLAN) system, the device comprising: at least one transceiver; as well as at least one processor connected to the at least one transceiver, Wherein, the at least one processor is configured to: determining, by the AP belonging to an AP multi-link device MLD, an updated MLD listening interval based on at least one enabled link associated with a change in a state of at least one link among a plurality of links; and The at least one transceiver performs transmission or reception with the non-AP MLD based on the updated MLD listening interval.

15. A processing unit configured to control a station STA in a wireless local area network WLAN system, the processing unit comprising: at least one processor; as well as At least one computer memory operatively connected to the at least one processor, the at least one computer memory storing instructions for performing the method according to any one of claims 1 to 11 based on execution by the at least one processor.

16. At least one non-transitory computer-readable medium storing at least one instruction, wherein: The at least one instruction is executed by at least one processor to control a device to execute the method according to any one of claims 1 to 11 in a wireless local area network (WLAN) system.

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