Method and apparatus for multi-link device-based roaming in wireless LAN system

Abstract

Disclosed are a method and an apparatus for multi-link device (MLD)-based roaming in a wireless LAN system. According to an embodiment of the present disclosure, a method performed by a first STA in a wireless LAN system may comprise the steps of: transmitting, to a first access point (AP) included in a first group, a first roaming request frame including a link identifier of a second AP and a group ID related to a second group to which the second AP belongs; receiving a first roaming response frame from the first AP, the first roaming response frame including a first traffic indication map (TIM) field associated with the second AP; and receiving first downlink (DL) data from the second AP based on the first TIM field.

Description

Technical Field

[0001] This disclosure relates to a roaming method and apparatus based on multi-link device (MLD) in a wireless local area network (WLAN) system. Background Technology

[0002] New technologies have been introduced for Wireless LANs (WLANs) to improve transmission rates, increase bandwidth, enhance reliability, reduce errors, and decrease latency. Within WLAN technology, the IEEE 802.11 series of standards can be referred to as Wi-Fi. For example, recent technologies introduced into WLAN include the Ultra High Throughput (VHT) enhancement of the 802.11 ac standard and the High Efficiency (HE) enhancement of the IEEE 802.11 ax standard.

[0003] To provide a more advanced wireless communication environment, improved techniques for Extremely High Throughput (EHT) are being discussed. For example, techniques for MIMO and multiple access point (AP) coordination that support increased bandwidth, efficient use of multiple frequency bands, and increased spatial flow are being investigated. Specifically, various techniques are being explored to support low latency or real-time traffic. Furthermore, new technologies to support Ultra-High Reliability (UHR), including improvements or extensions to EHT techniques, are being discussed. Summary of the Invention

[0004] Technical issues

[0005] The technical problem of this disclosure is to provide a method and apparatus for roaming based on multi-link device (MLD) in a wireless LAN system.

[0006] An additional technical problem of this disclosure is to provide methods and apparatus in a wireless LAN system for supporting or enabling a station (STA) to roam between different access points (APs) attached to a common MLD.

[0007] An additional technical problem of this disclosure is to provide a method and apparatus in a wireless LAN system for performing communication by adding / removing temporary links during an MLD-based roaming process.

[0008] The technical objectives to be achieved by this disclosure are not limited to those described above, and other technical objectives not described herein will be clearly understood by those skilled in the art through the following description.

[0009] Technical solution

[0010] A method performed by a first station (STA) in a wireless LAN system according to one aspect of the present disclosure may include: sending a first roaming request frame to a first access point (AP) included in a first group, the first roaming request frame including a link identifier of a second AP and a group ID associated with a second group to which the second AP is attached; receiving a first roaming response frame from the first AP, the first roaming response frame including a first traffic indication mapping (TIM) field associated with the second AP; and receiving first downlink (DL) data from the second AP based on the first TIM field.

[0011] A method performed by a first access point (AP) in a first group in a wireless LAN system according to another aspect of this disclosure may include: receiving a first roaming request frame from a first STA, the first roaming request frame including a link identifier of a second AP and a group ID associated with a second group to which the second AP belongs; sending a first roaming response frame to the first STA, the first roaming response frame including a first traffic indication mapping (TIM) field associated with the second AP; and sending first downlink (DL) data from the second AP to the first STA based on the first TIM field.

[0012] Technical effect

[0013] According to this disclosure, a method and apparatus for roaming based on multi-link device (MLD) in a wireless LAN system can be provided.

[0014] According to this disclosure, a method and apparatus may be provided in a wireless LAN system for supporting or enabling a station (STA) to roam between different access points (APs) attached to a common MLD.

[0015] According to this disclosure, an additional technical problem is to provide a method and apparatus in a wireless LAN system for performing communication by adding / removing temporary links during an MLD-based roaming process.

[0016] The effects achievable by this disclosure are not limited to those described above, and those skilled in the art can clearly understand other effects not described herein through the following description. Attached Figure Description

[0017] The accompanying drawings, which are included as part of the detailed description of this disclosure, provide embodiments of the disclosure and, together with the detailed description, describe the technical features of the disclosure.

[0018] Figure 1 A configuration block diagram of a wireless communication device according to an embodiment of the present disclosure is illustrated.

[0019] Figure 2This is a diagram illustrating an exemplary structure of a WLAN system to which this disclosure can be applied.

[0020] Figure 3 This is a diagram used to illustrate the link establishment process that can be applied to this disclosure.

[0021] Figure 4 This is a diagram used to illustrate the backoff processing that can be applied to this disclosure.

[0022] Figure 5 This is a diagram illustrating the CSMA / CA-based frame transmission operation that can be applied to this disclosure.

[0023] Figure 6 This is a diagram illustrating an example of a frame structure that can be used in a WLAN system to which this disclosure may be applied.

[0024] Figure 7 This is a diagram illustrating an example of a PPDU as defined in the IEEE 802.11 standard of this disclosure.

[0025] Figure 8 Exemplary structures for which the ML elements of this disclosure can be applied are illustrated.

[0026] Figure 9 This is a diagram illustrating an example of a high-level structure for which the AP MLD of this disclosure can be applied.

[0027] Figure 10 This is a diagram illustrating BSS switching in a traditional wireless LAN system.

[0028] Figure 11 This is a diagram illustrating an example of a method for performing MLD-based roaming by a STA according to the present disclosure.

[0029] Figure 12 This is a diagram illustrating an example of an MLD-based roaming method for AP-supported STA according to the present disclosure.

[0030] Figure 13 This is a diagram illustrating an example of the structure and process of an MLD-based roaming according to this disclosure.

[0031] Figure 14 This is a diagram illustrating an example of an element including notification information according to this disclosure.

[0032] Figure 15 , Figure 16 and Figure 17 This is a diagram illustrating an example of reconfiguring ML elements according to this disclosure.

[0033] Figure 18 and Figure 19This is a diagram illustrating an example of the structure and process of an MLD-based roaming according to this disclosure. Detailed Implementation

[0034] In the following, embodiments according to this disclosure will be described in detail with reference to the accompanying drawings. The detailed description disclosed with reference to the drawings is intended to describe exemplary embodiments of this disclosure and not to represent the only embodiments in which this disclosure can be implemented. The following detailed description includes specific details to provide a complete understanding of this disclosure. However, those skilled in the art will recognize that this disclosure can be implemented without these specific details.

[0035] In some cases, known structures and devices may be omitted, or they may be shown in block diagram form based on the core functions of each structure and device in order to prevent ambiguity in the concepts of this disclosure.

[0036] In this disclosure, when an element is referred to as “connected,” “combined,” or “linked” to another element, it can include both indirect and direct connections between the two elements. Furthermore, in this disclosure, the terms “comprising” or “having” specify the presence of the mentioned features, steps, operations, components, and / or elements, but do not exclude the presence or addition of one or more other features, stages, operations, components, elements, and / or groups thereof.

[0037] In this disclosure, terms such as "first" and "second" are used only to distinguish one element from another and are not used to limit the elements. Unless otherwise stated, they do not limit the order or importance of the elements. Therefore, within the scope of this disclosure, a first element in one embodiment may be referred to as a second element in another embodiment, and similarly, a second element in one embodiment may be referred to as a first element in another embodiment.

[0038] The terminology used in this disclosure is for the purpose of describing particular embodiments and not for limiting the claims. As used in the description of 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” as used in this disclosure may refer to one of the associated enumerations, or is intended to refer to and include any and all possible combinations of two or more of them. Furthermore, unless otherwise stated, the “ / ” between words in this disclosure has the same meaning as “and / or”.

[0039] The examples disclosed herein can be applied to various wireless communication systems. For example, the examples disclosed herein can be applied to wireless LAN systems. For example, the examples disclosed herein can be applied to wireless LANs based on the IEEE 802.11a / g / n / ac / ax standards. Furthermore, the examples disclosed herein can be applied to wireless LANs based on the newly proposed IEEE 802.11be (or EHT) standard. The examples disclosed herein can be applied to wireless LANs based on the IEEE 802.11be version 2 standard, corresponding to the additional enhancements of the IEEE 802.11be version 1 standard. Additionally, the examples disclosed herein can be applied to wireless LANs based on next-generation standards following IEEE 802.11be. Furthermore, the examples disclosed herein can be applied to cellular wireless communication systems. For example, it can be applied to cellular wireless communication systems based on 3GPP standards using Long Term Evolution (LTE) technology and 5G New Radio (NR) technology.

[0040] The technical features that can be applied to examples of this disclosure will be described below.

[0041] Figure 1 A block diagram illustrating a wireless communication device according to an embodiment of the present disclosure is shown.

[0042] Figure 1 The first device 100 and the second device 200 illustrated herein can be replaced by various terms such as terminal, wireless device, wireless transceiver 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 simply user. Furthermore, the first device 100 and the second device 200 include access point (AP), base station (BS), fixed station, node B, base transceiver system (BTS), and network. It can be replaced by various terms such as artificial intelligence (AI) system, roadside unit (RSU), repeater, router, relay, and gateway.

[0043] Figure 1 The devices 100 and 200 illustrated herein may be referred to as stations (STAs). For example, Figure 1The devices 100 and 200 illustrated herein may be referred to by various terms such as transmitting device, receiving device, transmitting STA, and receiving STA. For example, STA 110 and 200 may perform an access point (AP) role or a non-AP role. That is, in this disclosure, STA 110 and 200 may perform AP and / or non-AP functions. When STA 110 and 200 perform AP functions, they may simply be referred to as APs, and when STA 110 and 200 perform non-AP functions, they may simply be referred to as STAs. Alternatively, in this disclosure, AP may also be referred to as AP STA.

[0044] Reference Figure 1 The first device 100 and the second device 200 can transmit and receive radio signals via various wireless LAN technologies (e.g., IEEE 802.11 series). The first device 100 and the second device 200 may include interfaces for the Media Access Control (MAC) layer and Physical Layer (PHY) conforming to the IEEE 802.11 standard.

[0045] In addition to wireless LAN technology, the first device 100 and the second device 200 can also support various communication standards (e.g., 3GPP LTE series, 5G NR series standards, etc.). Furthermore, the devices disclosed herein can be implemented in various devices such as mobile phones, vehicles, personal computers, augmented reality (AR) devices, and virtual reality (VR) devices. Additionally, the STA of this specification can support various communication services such as voice calls, video calls, data communication, autonomous driving, machine-type communication (MTC), machine-to-machine (M2M), device-to-device (D2D), and IoT (Internet of Things).

[0046] The first device 100 may include one or more processors 102 and one or more memories 104, and may additionally include one or more transceivers 106 and / or one or more antennas 108. The processors 102 may control the memories 104 and / or the transceivers 106, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. For example, the processor 102 may transmit a wireless signal including the first information / signal via the transceivers 106 after generating first information / signal by processing information in the memories 104. Additionally, the processor 102 may receive a wireless signal including second information / signal via the transceivers 106, and then store information obtained through signal processing of the second information / signal in the memories 104. The memories 104 may be connected to the processor 102 and may store various information related to the operation of the processor 102. For example, the memories 104 may store software code including instructions for performing all or part of the processing controlled by the processor 102 or for performing the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. Here, processor 102 and memory 104 may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). Transceiver 106 may be connected to processor 102 and may transmit and / or receive wireless signals via one or more antennas 108. Transceiver 106 may include a transmitter and / or a receiver. Transceiver 106 may be used with an RF (radio frequency) unit. In this disclosure, wireless device may refer to a communication modem / circuit / chip.

[0047] The second device 200 may include one or more processors 202 and one or more memories 204, and may additionally include one or more transceivers 206 and / or one or more antennas 208. The processors 202 may control the memories 204 and / or the transceivers 206, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. For example, the processors 202 may generate third information / signals by processing information in the memories 204, and then transmit a wireless signal including the third information / signals via the transceivers 206. Additionally, the processors 202 may receive wireless signals including fourth information / signals via the transceivers 206, and then store information obtained through signal processing of the fourth information / signals in the memories 204. The memories 204 may be connected to the processors 202 and may store various information related to the operation of the processors 202. For example, the memories 204 may store software code including instructions for performing all or part of the processing controlled by the processors 202 or for performing the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. Here, processor 202 and memory 204 may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). Transceiver 206 may be connected to processor 202 and may transmit and / or receive wireless signals via one or more antennas 208. Transceiver 206 may include a transmitter and / or a receiver. Transceiver 206 may be used with an RF unit. In this disclosure, apparatus may refer to a communication modem / circuit / chip.

[0048] The hardware elements of devices 100 and 200 will be described in more detail below. Not limited thereto, one or more protocol layers may be implemented by one or more processors 102 and 202. For example, one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as PHY and MAC). One or more processors 102 and 202 may generate one or more PDUs (Protocol Data Units) and / or one or more SDUs (Service Data Units) according to the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 202 may generate messages, control information, data, or information according to the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 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 this disclosure to provide them to one or more transceivers 106 and 206. One or more processors 102, 202 may receive signals (e.g., baseband signals) from one or more transceivers 106, 206 and obtain PDUs, SDUs, messages, control information, data or information, in accordance with the description, functions, processes, suggestions, methods and / or operation flowcharts included in this disclosure.

[0049] 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 operation flowcharts included in this disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, processes, functions, etc. Firmware or software configured to execute the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this 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 operation flowcharts included in this disclosure can be implemented using firmware or software in the form of code, instructions and / or instruction sets.

[0050] One or more memories 104, 204 may be connected to one or more processors 102, 202 and may store data, signals, messages, information, programs, code, instructions, and / or commands in various forms. One or more memories 104, 204 may be configured with ROM, RAM, EPROM, flash memory, hard disk drive, registers, cache memory, computer-readable storage media, and / or combinations thereof. One or more memories 104, 204 may be located internally and / or externally to one or more processors 102, 202. Furthermore, 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.

[0051] One or more transceivers 106, 206 can transmit user data, control information, wireless signals / channels, etc., mentioned in the methods and / or operation flowcharts of this disclosure to one or more other devices. One or more transceivers 106, 206 can receive user data, control information, wireless signals / channels, etc., mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure from one or more other devices. For example, one or more transceivers 106, 206 can be connected to one or more processors 102, 202 and can transmit and receive wireless signals. For example, one or more processors 102, 202 can control one or more transceivers 106, 206 to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors 102, 202 can control one or more transceivers 106, 206 to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers 106, 206 may be connected to one or more antennas 108, 208, and one or more transceivers 106, 206 may be configured to transmit and receive user data, control information, wireless signals / channels, etc., mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure, via one or more antennas 108, 208. In this 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 for processing using one or more processors 102, 202. One or more transceivers 106, 206 may convert user data, control information, wireless signals / channels, etc., processed using one or more processors 102, 202, from baseband signals into RF band signals. Therefore, one or more transceivers 106, 206 may include (analog) oscillators and / or filters.

[0052] For example, one of STAs 100 and 200 can perform the expected operation of an AP, and the other of STAs 100 and 200 can perform the expected operation of a non-AP STA. For example, Figure 1 Transceivers 106 and 206 can perform transmission and reception operations of signals (e.g., packet or physical layer protocol data units (PPDUs) conforming to IEEE 802.11a / b / g / n / ac / ax / be / bn). Additionally, in this disclosure, the various STAs can generate transmit / receive signals or perform data processing or calculations on the transmit / receive signals in advance by [the relevant entity / component]. Figure 1Processors 102 and 202 perform the following operations: For example, examples of generating transmit / receive signals or performing data processing or computations on transmit / receive signals in advance may include: 1) determining / acquiring / configuring / computing / decoding / encoding bit information of fields (signals (SIG), short training field (STF), long training field (LTF), data, etc.) included in the PPDU; 2) determining / configuring / acquiring time or frequency resources (e.g., subcarrier resources) for the fields (SIG, STF, LTF, data, etc.) included in the PPDU; 3) determining / configuring / acquiring specific sequences (e.g., pilot sequences, STF / LTF sequences, additional sequences applied to SIG) for the fields (SIG, STF, LTF, data, etc.) included in the PPDU action; 4) power control operations and / or power saving operations applied to the STA; 5) operations related to determining / acquiring / configuring / computing / decoding / encoding of the ACK signal. Additionally, in the example below, various information used by different STAs to determine / acquire / configure / calculate / decode / encode transmitted and received signals (e.g., information related to fields / subfields / control fields / parameters / power, etc.) can be stored. Figure 1 In memory 104 and 204.

[0053] In the following text, downlink (DL) can refer to a link used for communication from an AP STA to a non-AP STA, and DL PPDU / packets / signals can be sent and received via DL. In DL communication, the transmitter can be part of an AP STA, and the receiver can be part of a non-AP STA. Uplink (UL) can refer to a link used for communication from a non-AP STA to an AP STA, and UL PPDU / packets / signals can be sent and received via UL. In UL communication, the transmitter can be part of a non-AP STA, and the receiver can be part of an AP STA.

[0054] Figure 2 This is a diagram illustrating an exemplary structure of a wireless LAN system to which this disclosure can be applied.

[0055] A wireless LAN system can be structured by multiple components. These components interact to provide STA mobility support that is transparent to upper layers. The Basic Service Set (BSS) corresponds to the basic building blocks of a wireless LAN. Figure 2 An example is shown where there are two BSSs (BSS1 and BSS2), and two STAs included as members of each BSS (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2). Figure 2The ellipse representing the BSS can also be interpreted as representing the coverage area within the corresponding BSS where STAs maintain communication. This area can be called the Basic Service Area (BSA). When a STA moves outside the BSA, it cannot communicate directly with other STAs within the BSA.

[0056] If we do not consider Figure 2 The DS shown in the diagram represents the most basic BSS type in a wireless LAN: the Independent BSS (IBSS). For example, an IBSS can have a minimal form containing only two STAs. For instance, assuming other components are omitted, BSS1 containing only STA1 and STA2, or BSS2 containing only STA3 and STA4, can respectively correspond to representative examples of IBSS. This configuration is possible when STAs can communicate directly without an AP. Furthermore, in this type of wireless LAN, it is not pre-configured but can be configured as needed, and this can be called an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. That is, in an IBSS, STAs are managed in a distributed manner. In an IBSS, all STAs can consist of mobile STAs and are not allowed to access the Distributed System (DS), thus forming a self-contained network.

[0057] Membership of an STA in a BSS can be dynamically changed by opening or closing an STA, or by entering or leaving a BSS zone. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services of the BSS infrastructure, an STA must be associated with the BSS. This association can be dynamically established and may include the use of Distributed System Services (DSS).

[0058] 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 others, longer distances between STAs may be required for communication. Distributed systems (DS) can be configured to support extended coverage.

[0059] DS refers to the structure of BSS interconnection. Specifically, such as... Figure 2As shown, a BSS can exist as an extension of a network composed of multiple BSSs. A DS is a logical concept and can be specified through 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 a different purpose and 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 a wireless LAN architecture (DS architecture or other network architectures) can be interpreted as multiple media being logically different. That is, a wireless LAN architecture can be implemented in various ways, and the corresponding wireless LAN architecture can be independently specified by the physical characteristics of each implementation.

[0060] The DS can support mobile devices by providing seamless integration of multiple BSSs and offering the logical services necessary for addressing to the destination. Additionally, the DS may include a component called a portal, which acts as a bridge between the wireless LAN and other networks, such as IEEE 802.X.

[0061] AP enables access to DS via WM for associated non-AP STAs, and refers to entities that also have STA functionality. Data movement between BSS and DS can be performed through AP. For example, Figure 2 STA2 and STA3, shown in the diagram, have the functionality of STAs and provide the ability for associated non-AP STAs (STA1 and STA4) to access the DS. Furthermore, since all APs essentially correspond to STAs, all APs are addressable entities. The address used by an AP for communication on the WM is not necessarily the same as the address used by the AP for communication on the DSM. A BSS consisting of APs and one or more STAs can be referred to as an infrastructure BSS.

[0062] Data sent from one of the STAs associated with the AP to the corresponding STA address of the AP can always be received on an uncontrolled port and can be processed by the IEEE 802.1X port access entity. Alternatively, when the controlled port is authenticated, the transmitted data (or frames) can be delivered to the DS.

[0063] In addition to the DS structure described above, Extended Service Sets (ESS) can also be configured to provide wide coverage.

[0064] An ESS (Service Set Identity) refers to a network of arbitrary size and complexity consisting of DS (Service Controller) and BSS (Service Set Service). An ESS can correspond to a set of BSSs connected to a DS. However, an ESS does not include the DS. An ESS network is characterized as an IBSS (Integrated Service Set Service) within the Logical Link Control (LLC) layer. STAs included in an ESS can communicate with each other, and a moving STA can transparently move from one BSS to another (within the same ESS) to the LLC. APs included in an ESS can have the same Service Set Identity (SSID). The SSID is distinguished from the BSSID, which serves as the identifier for the BSS.

[0065] Wireless LAN systems make no assumptions about the relative physical locations of BSSs, and all of the following forms are possible. BSSs can partially overlap, a form commonly used to provide continuous coverage. Additionally, BSSs may not be physically connected, and logically, there is no limit to the distance between BSSs. Furthermore, BSSs can be physically located in the same location, which can be used to provide redundancy. Additionally, one (or more) IBSS or ESS networks can physically exist in the same space as one (or more) ESS networks. This can correspond to the form of ESS networks 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, etc.

[0066] Figure 3 This is a diagram illustrating the link establishment process that can be applied to this disclosure.

[0067] In order for a STA to establish a link with the network and send / receive data, it first discovers the network, performs authentication, establishes an association, and performs authentication processing for security. The link establishment process can also be called session initiation processing or session establishment processing. Furthermore, the discovery, authentication, association, and security establishment processes of the link establishment process can be collectively referred to as association processing.

[0068] In step S310, the STA can perform a network discovery operation. The network discovery operation may include a scanning operation by the STA. That is, in order for the STA to access a network, it needs to find networks it can participate in. The STA should identify compatible networks before participating in a wireless network, and the process of identifying networks existing in a specific area is called scanning.

[0069] Scanning schemes include active scanning and passive scanning. Figure 3An exemplary network discovery operation including active scanning processing is illustrated. In active scanning, the STA performing the scan sends a probe request frame to discover which APs are present around it as the channel moves and awaits a response. The responder sends a probe response frame as a response to the probe request frame to the STA that 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, the AP becomes the responder because it sends a beacon frame, and in the IBSS, the STAs in the IBSS rotate to send beacon frames, so the responder is not constant. For example, an 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 a scan in the same manner (i.e., sending and receiving probe requests / responses on channel 2).

[0070] Although not in Figure 3 As shown, scanning can be performed passively. In passive scanning, the STA performing the scan waits for beacon frames while moving through the channel. Beacon frames are one of the management frames defined in IEEE 802.11 and are sent periodically to notify of the existence of a wireless network and allow the STA performing the scan to find and participate in the wireless network. In the BSS, the AP periodically sends beacon frames, and in the IBSS, the STA within the IBSS rotates to send beacon frames. When the STA performing the scan receives a beacon frame, it stores the BSS information included in the beacon frame and records the beacon frame information for 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 and passive scanning, active scanning has the advantages of less latency and less power consumption.

[0071] After the STA discovers the network, an authentication process can be performed in step S320. To clearly distinguish it from the security establishment operation in step S340, which will be described later, this authentication process can be referred to as the first authentication process.

[0072] The authentication process includes the following steps: the STA sends an authentication request frame to the AP, and in response, the AP sends an authentication response frame to the STA. The authentication frame used for the authentication request / response corresponds to the management frame.

[0073] An authentication frame includes the authentication algorithm number, authentication transaction sequence number, status code, challenge text, robust security network (RSN), and finite circular group. These correspond 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 may be included.

[0074] A STA can send an authentication request frame to an AP. The AP can determine whether to allow the corresponding STA's authentication based on the information included in the received authentication request frame. The AP can then provide the STA with the authentication processing result via an authentication response frame.

[0075] After the STA is successfully authenticated, the association process can be performed in step S330. The association process includes the following steps: the STA sends an association request frame to the AP, and in response, the AP sends an association response frame to the STA.

[0076] For example, an association request frame may include information related to various capabilities, beacon listening intervals, service set identifiers (SSIDs), supported rates, supported channels, RSNs, mobile domains, supported operation classes, traffic indication mapping broadcast requests (TIM broadcast requests), interoperability capabilities, etc. Similarly, an association response frame may include information related to various capabilities, status codes, association IDs (AIDs), supported rates, enhanced distributed channel access (EDCA) parameter sets, received channel power indicators (RCPIs), received signal-to-noise ratio indicators (RSNIs), mobile domains, timeout intervals (e.g., association recovery time), overlapping BSS scan parameters, TIM broadcast responses, quality of service (QoS) mappings, etc. These correspond to some examples of information that can be included in association request / response frames and may be replaced with other information, or additional information may be included.

[0077] After the STA successfully associates with the network, a security establishment process can be performed in step S340. The security establishment process in step S340 can be referred to as the authentication process via a Robust Secure Network Association (RSNA) request / response, the authentication process in step S320 is referred to as the first authentication process, and the security establishment process in step S340 can also be simply referred to as the authentication process.

[0078] The secure establishment process in step S340 may include, for example, the process of establishing a private key using a four-way handshake via Extensible Authentication Protocol (EAPOL) frames over the LAN. Alternatively, the secure establishment process may be performed according to a security scheme not defined in the IEEE 802.11 standard.

[0079] Figure 4 This is a diagram illustrating the fallback process that can be applied to this disclosure.

[0080] In wireless LAN systems, the basic access mechanism for Media Access Control (MAC) is Carrier Sensing Multiple Access with Collision Avoidance (CSMA / CA). Also known as the Distributed Coordination Function (DCF) of IEEE 802.11 MAC, CSMA / CA essentially employs a "listen-before-talk" access mechanism. Under this type of access mechanism, before commencing transmission, the AP and / or STA can perform explicit channel assessment (CCA) of the sensing radio channel or medium during a predetermined time interval (e.g., the DCF inter-frame interval (DIFS)). As a result of the sensing, if it is determined that the medium is idle, frame transmission begins via the corresponding medium. Conversely, if the medium is detected to be occupied or busy, the corresponding AP and / or STA does not begin its own transmission and can set a delay period for medium access (e.g., a random backoff period) and attempt frame transmission after waiting. By applying a random backoff period, collisions can be minimized because multiple STAs are expected to attempt frame transmission after waiting for different time periods.

[0081] 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 polling-based synchronous access method, meaning that all receiving APs and / or STAs periodically poll to receive data frames. Furthermore, HCF includes Enhanced Distributed Channel Access (EDCA) and HCF Control Channel Access (HCCA). EDCA is a contention-based access method that provides data frames to multiple users, while HCCA uses a non-contention-based channel access method that utilizes a polling mechanism. Additionally, HCF includes a media access mechanism for improving the QoS (Quality of Service) of wireless LANs and can transmit QoS data during contention periods (CP) and contention-free periods (CFP).

[0082] Reference Figure 4This section describes the operation based on a random backoff period. When an occupied / busy medium becomes idle, multiple STAs can attempt to transmit data (or frames). As a method to minimize collisions, each STA can individually select a random backoff count and attempt to transmit after waiting for the corresponding time slot. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​ranging from 0 to CW. Here, CW is the contention window parameter value. The CW parameter is assigned an initial value of CWmin, but can take a value twice as large as in the event of transmission failure (e.g., when no ACK is received for the transmitted frame). When the CW parameter value reaches CWmax, data transmission can be attempted while maintaining the CWmax value until successful data transmission, and when successful, the CWmin value is reset. The values ​​of CW, CWmin, and CWmax are preferably set to 2n-1 (n=0, 1, 2, ...).

[0083] When random backoff processing begins, the STA continuously monitors the medium during the backoff time slot countdown based on the determined backoff count value. When monitoring the medium for occupancy, it stops the countdown and waits, and restarts the remainder of the countdown when the medium becomes idle.

[0084] exist Figure 4 In the example, when the packet to be sent arrives at STA 3's MAC, STA 3 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. Meanwhile, the data to be sent can also occur in each of STA 1, STA 2, and STA 5, and when the medium is detected as idle, each STA waits for up to DIFS, and then performs a countdown for the backoff slot based on a random backoff count value chosen by each STA. Assume STA 2 chooses the minimum backoff count value, and STA 1 chooses the maximum backoff count value. That is, the example illustrates the case where STA 5's remaining backoff time is shorter than STA 1's remaining backoff time when STA 2 completes its backoff count and begins frame transmission. STA 1 and STA 5 temporarily stop the countdown and wait while STA 2 occupies the medium. When STA 2's occupancy ends and the medium becomes idle again, STA 1 and STA 5 wait for DIFS and restart the stopped backoff count. In other words, frame transmission can begin after a countdown for the remaining backoff slot based on the remaining backoff time. Since STA5 has a shorter remaining backoff time than STA1, STA5 begins frame transmission. Data to be transmitted can also occur in STA4 while STA2 is occupying the medium. From STA4's perspective, when the medium becomes idle, STA4 can wait for DIFS, then execute a countdown based on a random backoff count value selected by STA4, and begin transmitting frames. Figure 4The example illustrates a scenario where the remaining backoff time of STA5 accidentally conflicts 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 situation, STA4 and STA5 can double the CW value, select a random backoff count value, and begin a countdown. While the medium is occupied due to the transmissions of STA4 and STA5, STA1 waits; when the medium becomes idle, STA1 waits for DIFS, and then begins frame transmission after the remaining backoff time has elapsed.

[0085] As in Figure 4 In the example, data frames are frames used to send data forwarded to higher layers and can be sent after a backoff performed after DIFS (Distributed Access Frame) from the time the medium becomes idle. Additionally, management frames are frames used to exchange management information that has not been forwarded to higher layers and are sent after a backoff performed after an IFS (Information Support Function) such as DIFS or Point Coordination Function IFS (PIFS). Subtypes of management frames include beacons, association requests / responses, reassociation requests / responses, probe requests / responses, authentication requests / responses, etc. Control frames are frames used to control access to the medium. Subtypes of control frames include request-to-transmit (RTS), clear-to-transmit (CTS), acknowledgment (ACK), power-saving polling (PS-Poll), block ACK (BlockAck), block ACK request (BlockACKReq), null data packet advertisement (NDP advertisement), and triggers, etc. If the control frame is not a response frame to the previous frame, it is sent after backoff following the DIFS; if it is a response frame to the previous frame, it is sent without backoff following the Short IFS (SIFS). The type and subtype of a frame can be identified by the type field and subtype field in the Frame Control (FC) field.

[0086] The Quality of Service (QoS) ST can perform a backoff following the Arbitration IFS (AIFS) for the Access Class (AC) to which the frame belongs (i.e., AIFS where i is a value determined by the AC) before the frame can be transmitted. Here, the frame that can use AIFS can be a data frame, management frame, or control frame, rather than a response frame.

[0087] Figure 5 This is a diagram illustrating the CSMA / CA-based frame transmission operation that can be applied to this disclosure.

[0088] As mentioned above, in addition to physical carrier sensing of the medium directly sensed by the STA, the CSMA / CA mechanism also includes virtual carrier sensing. Virtual carrier sensing aims to compensate for problems such as hidden node issues that may occur during medium access. For virtual carrier sensing, the STA's MAC can use the Network Allocation Vector (NAV). The NAV is a value that indicates to other STAs the remaining time until the medium is available for current use or for STAs authorized to use the medium. Therefore, a 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, STAs receiving the NAV value are prohibited from accessing the medium. For example, the NAV can be configured based on the value of the "Duration" field in the frame's MAC header.

[0089] exist Figure 5 In the example, it is assumed that STA1 intends to send data to STA2, and STA3 is in a position that can eavesdrop on some or all of the frames sent and received between STA1 and STA2.

[0090] To reduce the likelihood of transmission conflicts among multiple STAs in CSMA / CA-based frame transmission operations, a mechanism using RTS / CTS frames can be applied. Figure 5 In the example, when STA1 is transmitting, as a result of carrier sensing by STA3, it can be determined that the medium is in an idle state. That is, STA1 can correspond to a hidden node with respect to STA3. Alternatively, in Figure 5 In the example, it can be determined that while STA2 is transmitting, the carrier sensing result medium of STA3 is in an idle state. That is, STA2 can 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 either STA1 or STA2, or STAs outside the carrier sensing range of transmissions from STA1 or STA3, can avoid attempting to occupy the channel during data transmission and reception between STA1 and STA2.

[0091] Specifically, STA1 can determine whether a channel is in use through carrier sensing. Regarding physical carrier sensing, STA1 can determine the channel occupancy / idle status based on the energy level or signal correlation detected in the channel. Alternatively, regarding virtual carrier sensing, STA1 can use a Network Allocation Vector (NAV) timer to determine the channel occupancy status.

[0092] When the channel is idle during DIFS, STA1 can send an RTS frame to STA2 after performing backoff. When STA2 receives the RTS frame, STA2 can send a CTS frame to STA1 after SIFS as a response to the RTS frame.

[0093] If STA3 cannot eavesdrop on CTS frames from STA2 but can eavesdrop on RTS frames from STA1, STA3 can use the duration information included in the RTS frame to set the NAV timer for the subsequent consecutive frame transmission period (e.g., SIFS+CTS frame+SIFS+data frame+SIFS+ACK frame). Alternatively, if STA3 can eavesdrop on CTS frames from STA2, STA3 can also use the duration information included in the CTS frame to set the NAV timer for the subsequent consecutive frame transmission period (e.g., SIFS+data frame+SIFS+ACK frame) even though STA3 cannot eavesdrop on RTS frames from STA1. That is, if STA3 can eavesdrop on one or more RTS frames or CTS frames from 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.

[0094] When STA1 receives a CTS frame from STA2, STA1 can send a data frame to STA2 after SIFS, starting from the time point when the CTS frame reception is complete. When STA2 successfully receives the data frame, STA2 can send an ACK frame to STA1 after SIFS as a response to the data frame. When the NAV timer expires, STA3 can determine whether the channel is in use through carrier sensing. If STA3 determines that the channel is not in use by other terminals during DIFS after the NAV timer expires, STA3 can attempt channel access after the contention window (CW) for random backoff has passed.

[0095] Figure 6 This is a diagram illustrating an example of a frame structure that can be used in a WLAN system to which this disclosure may be applied.

[0096] Using instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare the MAC PDU (MPDU) to be transmitted. For example, when the PHY layer receives a command from the MAC layer requesting the start of transmission, it switches to transmit mode, configures the information (e.g., data) provided by the MAC layer in the form of a frame, and transmits it. Additionally, when the PHY layer detects a valid preamble in a received frame, it monitors the preamble header and sends a command to the MAC layer notifying the PHY layer of the start of reception.

[0097] In this way, information transmission / reception in a wireless LAN system is performed in the form of frames, and for this purpose, the PHY layer Protocol Data Unit (PPDU) format is defined.

[0098] A basic PPDU can include a Short Training Field (STF), a Long Training Field (LTF), a Signal (SIG) field, and a Data field. The most basic PPDU format (e.g., Figure 7 The non-HT (High Throughput) fields shown can consist solely of a Traditional-STF (L-STF), Traditional-LTF (L-LTF), Traditional-SIG (L-SIG) field, and a data field. Additionally, depending on the PPDU format type (e.g., HT mixed format PPDU, HT green format PPDU, VHT (Very High Throughput) PPDU, etc.), additional (or different types) RL-SIG, U-SIG, non-traditional SIG fields, non-traditional STF, non-traditional LTF (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) can be included between the L-SIG field and the data field.

[0099] STF is a signal used for signal detection, automatic gain control (AGC), diversity selection, precise time synchronization, etc., while LTF is a signal used for channel estimation and frequency error estimation. STF and LTF can be referred to as signals used for synchronization and channel estimation in the OFDM physical layer.

[0100] The SIG field can include various information related to PPDU transmission and reception. For example, the L-SIG field consists of 24 bits and can 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 can include information about the modulation and coding rate of the data. For example, the 12-bit length field can include information about the length or duration of the PPDU. For example, the value of the 12-bit length field can be determined based on the type of PPDU. For example, for non-HT, HT, VHT, or EHT PPDUs, the value of the length field can be determined to be a multiple of 3. For example, for HEPPDUs, the value of the length field can be determined to be a multiple of 3+1 or 3+2.

[0101] The data field may include a 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 can be used for synchronization of the descrambler at the receiver. 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 can be used to return the encoder to a 0 state. Padding bits can be used to adjust the length of the data field by predetermined units.

[0102] MAC PDUs are defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a Frame Check Sequence (FCS). MAC frames can be composed of MAC PDUs and transmitted / received via PSDUs in the data portion of the PPDU format.

[0103] The MAC header includes a frame control field, a duration / ID field, and an address field. The frame control field can include control information required for frame transmission / reception. The duration / ID field can be set to the time used to transmit the corresponding frame, etc. For details on the sequence control, QoS control, and HT control subfields of the MAC header, refer to the IEEE 802.11 standard document.

[0104] The Narrow Data PPDU (NDP) format refers to a PPDU format that does not include the data field. In other words, NDP is a frame format that includes the PPDU preamble of the general PPDU format (i.e., the L-STF, L-LTF, L-SIG fields and other non-traditional SIG, non-traditional STF, and non-traditional LTF (if present)) and does not include the remaining part (i.e., the data field).

[0105] Figure 7 This is a diagram illustrating an example of a PPDU as defined in the IEEE 802.11 standard of this disclosure.

[0106] Various types of PPDUs have been used in standards such as IEEE 802.11a / g / n / ac / ax. The basic PPDU format (IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and a data field. The basic PPDU format can also be referred to as a non-HT PPDU format (such as...). Figure 7 (as shown in (a)).

[0107] Compared to the basic PPDU format, the HT PPDU format (IEEE 802.11n) additionally includes the HT-SIG, HT-STF, and HT-LFT fields. Figure 7The HT PPDU format shown in (b) can be referred to as the HT hybrid format. Furthermore, an HT green format PPDU can be defined, and this corresponds to a format consisting of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTFs and data fields, excluding L-STF, L-LTF, and L-SIG (not shown).

[0108] Compared to the basic PPDU format, examples of the VHT PPDU format (IEEE 802.11ac) additionally include VHTSIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields (such as...). Figure 7 (as shown in (c)).

[0109] Compared to the basic PPDU format, examples of the HE PPDU format (IEEE 802.11ax) additionally include repeated L-SIG (RL-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, and Packet Extension (PE) fields (such as...). Figure 7 (as shown in (d)). Some fields can be excluded, or their lengths can vary depending on the detailed examples of the HE PPDU format. For example, the HE-SIG-B field is included in the HE PPDU format for multi-user (MU), but not in the HE PPDU format for single-user (SU). Furthermore, the HE-Trigger-Based (TB) PPDU format does not include HE-SIG-B, and the length of the HE-STF field can vary up to 8 μs. 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 can vary up to 16 μs. For example, RL-SIG can be configured to be the same as L-SIG. Based on the presence of RL-SIG, the receiving STA can determine whether the received PPDU is an HE PPDU or an EHT PPDU, which will be described later.

[0110] EHT PPDU format can include Figure 7 EHT MU (Multi-user) in (e) and Figure 7 The EHT TB (trigger-based) PPDU in (f). The EHT PPDU format is similar to the HE PPDU format in that it includes RL-SIG following L-SIG, but it can include U (generic)-SIG, EHT-SIG, EHT-STF and EHT-LTF following RL-SIG.

[0111] Figure 7In (e), the EHT MU PPDU 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 and MU transmissions. For example, the EHT MU PPDU can correspond to a PPDU for one or more receiving STAs.

[0112] Compared to EHT MU PPDU, Figure 7 In (f), the EHT-SIG is omitted from the EHT TB PPDU. The STA that receives the trigger for UL MU transmission (e.g., trigger frame or trigger response schedule (TRS)) can perform UL transmission based on the EHT TB PPDU format.

[0113] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (general signal), and EHT-SIG fields can be encoded and modulated so that even conventional STAs can attempt demodulation and decoding, and can be mapped based on a determined subcarrier frequency interval (e.g., 312.5 kHz). These can be referred to as pre-EHT modulated fields. Next, the EHT-STF, EHT-LTF, data, and PE fields can be encoded and modulated for demodulation and decoding by an STA that has successfully decoded a non-conventional SIG (e.g., U-SIG and / or EHT-SIG) and obtained the information contained in that field, and can be mapped based on a determined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

[0114] Similarly, in the HE PPDU format, the L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, and HE-SIG-B fields can be referred to as pre-HE modulation fields, and the HE-STF, HE-LTF, data, and PE fields can be referred to as HE modulation fields. Additionally, in the VHT PPDU format, the L-STF, L-LTF, L-SIG, and VHT-SIG-A fields can be referred to as non-VHT modulation fields, and the VHT STF, VHT-LTF, VHT-SIG-B, and data fields can be referred to as VHT modulation fields.

[0115] Included Figure 7In the EHT PPDU format, U-SIG can be configured based on, for example, two symbols (e.g., two consecutive OFDM symbols). Each symbol used for U-SIG (e.g., an OFDM symbol) can have a duration of 4 μs, and U-SIG can have a total duration of 8 μs. Each symbol of U-SIG can be used to transmit 26 bits of information. For example, each symbol of U-SIG can be transmitted and received based on 52 data tones and 4 pilot tones.

[0116] U-SIGs can be constructed in 20 MHz units. For example, if an 80 MHz PPDU is constructed, U-SIGs can be replicated. That is, the same four U-SIGs can be included in an 80 MHz PPDU. PPDUs with bandwidths exceeding 80 MHz can include different U-SIGs.

[0117] For example, A uncoded bits can be sent via U-SIG. The first symbol of U-SIG (e.g., U-SIG-1 symbol) can send the first X bits of the total A bits, and the second symbol of U-SIG (e.g., U-SIG-2 symbol) can send the remaining Y bits of the total A bits. The A bits (e.g., 52 uncoded bits) can include a CRC field (e.g., a 4-bit field) and a tail field (e.g., a 6-bit field). For example, the tail field can be used to terminate the lattice structure of the convolutional decoder and can be set to 0.

[0118] Bit information sent via U-SIG can be divided into version-independent bits and version-dependent bits. For example, U-SIG can be included in... Figure 7 The new PPDU format (e.g., UHR PPDU format) not shown in the figure can be included in the format of the U-SIG field included in the EHTPPDU format and the format of the U-SIG field included in the UHR PPDU format. The version-independent bits can be the same, and some or all of the version-related bits can be different.

[0119] For example, the size of the version-independent bits in U-SIG can be fixed or variable. Version-independent bits can be assigned only to the U-SIG-1 symbol, or to both the U-SIG-1 and U-SIG-2 symbols. Version-independent and version-dependent bits can be referred to by various names, such as first control bit and second control bit.

[0120] For example, the version-independent bits of U-SIG may include a 3-bit Physical Layer Version Identifier (PHY Version Identifier), which can indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted / received PPDU. The version-independent bits of U-SIG may include a 1-bit UL / DL Flag field. The first value of the 1-bit UL / DL Flag field is related to UL communication, and the second value is related to DL communication. The version-independent bits of U-SIG may include information about the length of the Transmission Opportunity (TXOP) and information about the BSS color ID.

[0121] For example, the version-related bits of U-SIG may include information that directly or indirectly indicates the type of PPDU (e.g., SU PPDU, MU PPDU, TB PPDU, etc.).

[0122] Information required for PPDU transmission and reception can be included in the U-SIG. For example, the U-SIG may also include information about bandwidth, information about the MCS technique applied to non-traditional SIGs (e.g., EHT-SIG or UHR-SIG), information indicating whether DCM (dual-carrier modulation) techniques (e.g., techniques used to achieve effects similar to frequency diversity by reusing the same signal on two subcarriers) are applied to non-traditional SIGs, information about the number of symbols used for non-traditional SIGs, and information about whether non-traditional SIGs are generated across the entire frequency band.

[0123] Some of the information required for PPDU transmission and reception may be included in U-SIG and / or non-traditional SIG (e.g., EHT-SIG or UHR-SIG). For example, information about the type of non-traditional LTF / STF (e.g., EHT-LTF / EHT-STF or UHR-LTF / UHR-STF), the length of the non-traditional LTF and the CP (cyclic prefix) length, the GI (guard interval) applicable to the non-traditional LTF, the preamble punching information applicable to the PPDU, and the resource unit (RU) allocation may be included only in U-SIG, only in non-traditional SIG, or may be indicated by a combination of information included in U-SIG and information included in non-traditional SIG.

[0124] Preamble puncturing can represent the transmission of a PPDU where no signal is present in one or more frequency units within the bandwidth of the PPDU. For example, the size of the frequency unit (or the resolution of the preamble puncturing) can be defined as 20 MHz, 40 MHz, etc. For example, preamble puncturing can be applied to PPDU bandwidths of a predetermined size or larger.

[0125] exist Figure 7In the examples, non-traditional SIGs such as HE-SIG-B and EHT-SIG can include control information for receiving STAs. Non-traditional SIGs can be transmitted on at least one symbol, and a symbol can have a length of 4 μs. Information regarding the number of symbols used for EHT-SIGs can be included in previous SIGs (e.g., HE-SIG-A, U-SIG, etc.).

[0126] Non-traditional SIGs such as HE-SIG-B and EHT-SIG can include both public and user-specific fields. These public and user-specific fields can be encoded separately.

[0127] In some cases, the common field can be omitted. For example, in compressed mode using non-OFDMA (Orthogonal Frequency Division Multiple Access), the common field can be omitted, and multiple STAs can receive PPDUs (e.g., the data field of the PPDU) through the same frequency band. In uncompressed mode using OFDMA, multiple users can receive PPDUs (e.g., the data field of the PPDU) through different frequency bands.

[0128] The number of user-specific fields can be determined based on the number of users. A user block field can include up to two user fields. Each user field can be associated with either a MU-MIMO allocation or a non-MU-MIMO allocation.

[0129] The common fields may include CRC bits and a tail bit, where the length of the CRC bits can be determined to be 4 bits, and the length of the tail bit can be determined to be 6 bits and set to 000000. The common fields may include RU allocation information. RU allocation information may include information about the locations of RUs assigned to multiple users (i.e., multiple receiving STAs).

[0130] An RU can include multiple subcarriers (or tones). RUs can be used when transmitting signals to multiple STAs based on OFDMA technology. Additionally, RUs can be defined even when transmitting signals to a single STA. Resources can be allocated in units of RUs for non-traditional STFs, non-traditional LTFs, and data fields.

[0131] The appropriate RU size can be defined based on the PPDU bandwidth. RUs can be defined the same or different for the applied PPDU format (e.g., HEPPDU, EHT PPDU, UHR PPDU, etc.). For example, in the case of an 80 MHz PPDU, the RU layout for HEPPDU and EHT PPDU can be different. The appropriate RU size, number and location of RUs, DC (direct current) subcarrier locations and numbers, empty subcarrier locations and numbers, guard subcarrier locations and numbers, etc., for each PPDU bandwidth can be referred to as the tone scheme. For example, a tone scheme for high bandwidth can be defined as multiple iterations of a low-bandwidth tone scheme.

[0132] RUs of various sizes can 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 (Multiple RUs) differ from multiple individual RUs and correspond to a group of subcarriers composed of multiple RUs. For example, an MRU can 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. Furthermore, the multiple RUs constituting an MRU can be consecutive or non-consecutive in the frequency domain.

[0133] The specific size of the RU can be reduced or expanded. Therefore, the specific size of each RU in this disclosure (i.e., the number of corresponding tones) is not limiting but illustrative. In addition, in this disclosure, the number of RUs can vary depending on the RU size within a predetermined bandwidth (e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz...).

[0134] Figure 7 The names of each field in the PPDU format are exemplary, and the scope of this disclosure is not limited to these names. Furthermore, the examples in this disclosure can be applied to… Figure 7 The PPDU format shown and based on Figure 7 A new PPDU format that excludes some fields and / or adds some fields, based on the PPDU format.

[0135] Multi-link operation

[0136] The following describes multi-link (ML) operation supported by STA according to this disclosure.

[0137] The STAs (AP STAs and / or non-AP STAs) described in this disclosure can support multi-link (ML) communication. ML communication can refer to communication supporting multiple links. Links associated with ML communication can include channels (e.g., 20 / 40 / 80 / 160 / 240 / 320MHz channels) in the frequency band in which the STA operates (e.g., 2.4GHz band, 5GHz band, 6GHz band, etc.). Multiple links for ML communication can be configured in various ways. For example, multiple links supported for a single STA for ML communication can belong to the same frequency band or different frequency bands. Furthermore, each link can correspond to a frequency unit of a predetermined size (e.g., channel, sub-channel, RU, etc.). Additionally, some or all of the multiple links can be frequency units of the same size or different sizes.

[0138] When a STA supports multiple links, the transmitting or receiving devices supporting each link can operate like a logical STA. That is, an MLD refers to a device having one or more attached STAs as logical entities and a single MAC Service Access Point (SAP) for MAC data service and logical link control (LLC). A non-AP MLD is an MLD where each STA attached to the MLD is a non-AP STA. A multi-radio non-AP MLD is a non-AP MLD that supports receiving or exchanging frames on more than one link at a time. An AP MLD is an MLD where each STA attached to the MLD is an AP STA.

[0139] Multi-link operation (MLO) enables non-AP MLDs to discover, authenticate, and associate with AP MLDs and establish multiple links with them. Based on the supported capabilities exchanged during the association process, each link can enable channel access and frame switching between the non-AP MLD and the AP MLD. STAs attached to an MLD can independently select and manage their capabilities and operating parameters from other STAs attached to the same MLD.

[0140] Through the multi-link establishment process, the AP MLD and / or non-AP MLD can send and receive link-related information that the MLD can support. Link-related information may include one or more of the following: information about whether the MLD supports simultaneous transmit and receive (STR) operation (which allows simultaneous transmission and reception on multiple links) or non-simultaneous transmit and receive (NSTR) operation; information about the number / upper limit of UL / DL links; information about the location / band / resources of UL / DL links; information about the frame types available or preferred in at least one UL / DL link (e.g., management, control, data); information about the ACK policies available or preferred in at least one UL / DL link; or information about the traffic identifiers (TIDs) available on at least one UL / DL link.

[0141] An AP MLD (e.g., an NSTR mobile AP MLD) can configure one of multiple links as the primary link. An AP MLD can transmit beacon frames, probe response frames, and group addressing data frames only on the primary link. The remaining links in the multiple links can be referred to as non-primary links. An AP MLD operating on a non-primary link can operate without transmitting beacon frames or probe response frames. Additionally, a non-AP MLD can perform authentication, (re)association, and frame exchange during the four-way handshake only on the primary link.

[0142] An established link is defined as enabled if at least one Traffic Identifier (TID) is mapped to a link through the multi-link establishment process, and an established link can be defined as disabled if no TID is mapped to a link. Unless admission control is used, a TID must always be mapped to at least one established link. By default, TIDs are mapped to all established links, thus enabling all established links.

[0143] When a link is enabled, it can be used for frame switching depending on the power status of the non-AP STAs operating on it. Only MSDUs or A-MSDUs with a TID mapped to the enabled link can be transmitted on the link. Management and control frames can be transmitted only on the enabled link.

[0144] When a link is disabled, it may not be used for frame switching, including management frames used for both DL and UL.

[0145] During the multi-link establishment process, TID-to-link mapping can be used to indicate the enabling / disabling of each link. TID-to-link mapping can be performed in the default mapping mode or / and negotiated mapping mode.

[0146] A STA attached to an MLD can provide information about one or more links other than the link it resides on, for multi-link discovery (e.g., obtaining information about multiple links, including the corresponding link, on a single link) or multi-link establishment (e.g., simultaneously associating on multiple links by exchanging association request / response frames on a single link). A multi-link (ML) element can be defined to provide this information.

[0147] Figure 8 The structure of the ML element to which this disclosure can be applied is illustrated illustratively.

[0148] In an ML element, the element ID field and the element ID extended field can have specific values ​​(e.g., 255 and 107) indicating that it is an ML element, and the length field can have a value indicating the length of the remaining fields besides the element ID field and the length field (e.g., octet units).

[0149] The multilink control field is defined as a two-octet size and may include a 3-bit type subfield, a 1-bit reserved bit, and a 12-bit presence bitmap subfield. The type subfield may have values ​​indicating one of the following types: basic, probe request, reconfiguration, tunnel direct link establishment (TDLS), and preferred access. The presence bitmap subfield indicates the presence of various subfields within the common information field and can be defined in different formats depending on various variants (or types) of the ML element.

[0150] The common information field is defined as having a variable size and may include a 6-octet MLD MAC address subfield, which may have a value specifying the MAC address of the MLD to which the STA sending the basic ML element belongs. Additionally, the link ID information subfield, BSS parameter change count subfield, media synchronization delay information subfield, enhanced multilink (EML) capability subfield, and MLD capability subfield may or may not be included in the common information field.

[0151] The Link Information field is defined to be variable in size and can include link-specific information and can be optional. If a Link Information field is present, it can include one or more sub-elements. The format and order of sub-elements can be defined in various ways. As an example of the optional sub-element ID for the basic variant ML element, the sub-element ID value 0 corresponds to the name of each STA profile and is extensible, and the value 221 corresponds to the name of a vendor-specific name, and whether it is extensible can be determined by the vendor, and the remaining values ​​1-220 and 222-255 can be reserved.

[0152] Each STA profile sub-element may include a 1-octet sub-element ID sub-field, a 1-octet length sub-field, a 2-octet STA control sub-field, a variable-size STA information sub-field, and a variable-size STA profile sub-field. The STA control sub-field may include information such as the link ID, whether a complete profile is included, and whether a STA MAC address exists. The STA information sub-field may include information such as the STA MAC address. Depending on whether the reported STA is an AP STA or a non-AP STA, the STA profile sub-field may include information included in the probe response or probe request frame body, information included in the (re)association response or (re)association request frame body, etc.

[0153] Figure 8 The format of the ML element in the MLD is exemplary, and the order, name, size, etc. of the fields / subfields can be changed. Additional fields / subfields can be further defined, and some fields / subfields may not be included. In short, the public information field can include public information between STAs in the MLD, and the link information field can include specific information for each STA / link (e.g., in the per-STA profile sub-element that includes the link ID corresponding to the STA).

[0154] Figure 9 This is a diagram illustrating an example of a high-level structure for which the AP MLD of this disclosure can be applied.

[0155] An AP MLD can include one or more APs. An AP MLD can have, for example... Figure 9 The high-level architecture is illustrated. For example, the MLD can use the upper MAC sublayer to control various processes / parameters shared by multiple APs. For instance, authentication, association, sequence number (SN) / packet number (PN) allocation, power-saving buffers for individual addressed frames, etc., can be shared among APs attached to the AP MLD.

[0156] Each affiliated AP (e.g., AP 1, ..., AP n) can provide upper-layer MAC sublayer functionality for non-MLD data frames (e.g., traffic sent and received with non-MLD STAs, group-addressed MLD traffic, etc.). AP MLD can provide upper-layer MAC sublayer functionality for MLD data frames (e.g., traffic sent and received with MLD STAs) and provides MLD data to the lower-layer MAC sublayer of each affiliated AP. Each affiliated AP can provide PHY functionality (e.g., PHY 1, ..., PHY n). Both ML operations (MLO) and non-MLO can be performed on the links corresponding to each PHY (e.g., link 1, ..., link n).

[0157] MLD-based roaming

[0158] Before describing MLD-based roaming according to this disclosure, the process of a non-AP STA moving or roaming from one AP to another in an existing wireless LAN system (e.g., BSS switching) is first described.

[0159] Figure 10 This is a diagram used to explain BSS transitions in existing wireless LAN systems.

[0160] In the case of the FT (Fast BSS Transition) method (which is a representative example of BSS transition (or roaming), various processes such as authentication requests / responses and re-association requests / responses are required between the FTO (FT Initiator) and the target FTR in order to move from the current FTR (FT Responder) to the target FTR. That is, in existing BSS transition methods, a re-association process is required on the same mobility domain.

[0161] In addition, Figure 10 Following the process illustrated, various operational parameters are reset, such as protocols related to BA (Block Ack) or SCS (Class of Service), SN, EDCAF (EDCA Function) parameters, etc. Therefore, the FTO must perform a large number of frame exchanges for the FT and must re-execute the protocol / configuration with the new FTR. Consequently, the FT process is complex and costly, and data loss may occur during the FT process. This makes it difficult to provide seamless roaming to STAs in existing wireless LAN systems.

[0162] This disclosure describes examples for seamless roaming based on MLD. For example, based on reference Figure 9 The described APMLD functionality allows non-AP STAs to maintain, without resetting, MLD-level parameters / configurations / agreements when moving / roaming between entities attached to a single MLD.

[0163] In the following description, the STA performing the roaming is referred to as RSTA, the currently associated AP is referred to as OAP (Old AP) or First AP (or AP 1), and the AP to be newly associated is referred to as NAP (New AP) or Second AP (or AP 2). Furthermore, the MLD-based roaming newly proposed in this disclosure can be simply referred to as MLD roaming.

[0164] In addition, each of RSTA, OAP, and NAP can be a STA attached to a different MLD.

[0165] For example, an RSTA is a non-AP STA attached to a non-AP MLD and can perform MLD roaming simultaneously / together with one or more other non-AP STAs.

[0166] For example, an OAP can be an AP STA attached to AP MLD 1, and other APs besides the OAP can be attached to APMLD 1.

[0167] For example, a NAP can be an AP STA attached to AP MLD 2, and other APs besides NAP can be attached to APMLD 2.

[0168] For example, OAP and NAP can be attached to the same upper-level MLD (or roaming MLD or AP MLD 0). For example, AP MLD 1 to which OAP is attached can be attached to an upper-level MLD (e.g., AP MLD 0), and AP MLD 2 to which NAP is attached can be attached to the same upper-level MLD (e.g., AP MLD 0). Alternatively, among the APs attached to AP MLD 1, at least one AP including OAP can be attached to an upper-level MLD (e.g., AP MLD 0), and other APs may not be attached to the same upper-level MLD (e.g., AP MLD 0), or may be attached to another upper-level MLD, or may not be attached to an upper-level MLD. Similarly, among the APs attached to AP MLD 2, at least one AP including NAP can be attached to an upper-level MLD (e.g., AP MLD 0), and other APs may not be attached to the same upper-level MLD (e.g., AP MLD 0), or may be attached to another upper-level MLD, or may not be attached to an upper-level MLD.

[0169] Furthermore, considering non-AP MLDs, at least one OAP attached to AP MLD 1 can be attached to an upper-level MLD, and at least one NAP attached to AP MLD 2 can be attached to the same upper-level MLD. For example, MLD-based roaming from multiple OAPs to multiple NAPs can be performed.

[0170] The process of performing an MLD-based roaming operation for STA is described in detail below.

[0171] Figure 11 This is a diagram illustrating an example of an MLD-based roaming method for performing a first STA according to this disclosure. Figure 11 and Figure 12 In this context, the first STA can be attached to a non-AP MLD. Furthermore, the first STA can be associated with a first AP attached to the first (AP) group to send and receive data.

[0172] The first STA can send a first (MLD) roaming request frame to the first AP attached to the first group. The first (MLD) roaming request frame includes the link identifier of the second AP and the group ID associated with the second group to which the second AP is attached (S1110).

[0173] Prior to step S1110, the first STA may receive notification information from the first AP. Here, the notification information may be included in an MLD-based roaming element or a simplified neighbor report (RNR) element included in the management frame. The MLD-based roaming element or RNR element may include a subfield associated with at least one group ID and / or information about whether adding at least one link for the first STA is supported.

[0174] Additionally, prior to step S1110, the first STA may receive a beacon frame from the first AP, the beacon frame including a second TIM field indicating whether there is second DL data to be sent from the first AP to the first STA.

[0175] Through a first roaming request frame, a first STA can request to roam from a first AP to a second AP. The first roaming request frame includes the link identifier of the second AP and the group ID associated with the second group to which the second AP belongs.

[0176] For example, the first group and the second group can be attached to the same AP MLD. In order to roam from the first AP included in the first group to the second AP included in the second group, the first STA can send a first request frame to the first AP.

[0177] In another example of this disclosure, each of the first and second groups can be mapped to a separate AP MLD. For example, the first group can be mapped to a first AP MLD, and the second group can be mapped to a second AP MLD. That is, in describing this disclosure, each group can be represented by a separate AP MLD. Furthermore, the first and second AP MLDs can be attached to separate group entities (or the entire AP MLD). The group entity (or the entire AP MLD) can be collectively referred to as the specific entity to which each AP MLD is attached.

[0178] Group objects can correspond to Figure 9 , Figure 13 and Figure 18 The (entire) AP MLD is shown. For example, group objects can execute references. Figure 9 Describe the functionality of the upper MAC sublayer of MLD.

[0179] The first STA can receive a first roaming response frame from the first AP, the first roaming response frame including a first traffic indication mapping field associated with the second AP (S1120).

[0180] Specifically, the first roaming response frame may include information indicating acceptance of the first STA roaming to the second AP, information related to the second AP (e.g., a group ID associated with the second group to which the second AP is attached), roaming timer information related to the time when the first DL data can be received from the second AP (i.e., the MLD roaming timer), and / or a first TIM field related to the second AP (e.g., information indicating whether there is first DL data to be sent from the second AP to the first STA).

[0181] The information indicating acceptance of roaming from the first STA to the second AP and the first TIM field can be included in the common information field (e.g., the basic ML element of the first roaming response frame) or the link information field (e.g., the per-STA profile sub-element corresponding to the first STA included in the link information field of the first roaming response frame).

[0182] Based on the first roaming response frame being sent to the first STA, a link can be added between the first STA and the second AP. That is, while the link between the first STA and the first AP is being established, the link between the first STA and the second AP can also be established. Furthermore, the first STA can perform frame switching via either the link connected to the first AP or the link connected to the second AP.

[0183] For example, a first STA can perform frame switching via a link connected to a second AP. Specifically, frame switching can be performed after a link switching operation from the first AP to the second AP is executed. Here, the link switching operation from the first AP to the second AP can include operations where the link between the first STA and the first AP is changed to a disabled state and the link between the first STA and the second AP is changed to an enabled state.

[0184] In other words, while the link between the first STA and the first AP is established, the link between the first STA and the second AP can also be established. Then, based on the fact that the link between the first STA and the first AP is disabled and the link between the first STA and the second AP is enabled, data frame exchange between the first STA and the second AP can be performed through the enabled link.

[0185] The first STA can receive the first DL data from the second AP based on the first TIM field (S1130).

[0186] As an example of this disclosure, based on the indication via a first TIM field that first DL data exists (to be sent from the second AP to the first STA), the first STA can receive a PS (Power Saving) polling frame from the second AP for sending the first DL data. However, this is merely an implementation method, and the first STA can receive the first DL data from the second AP without sending a PS polling frame. Here, the first STA can be in a state where both the first AP and the second AP are connected.

[0187] Based on the first DL data being sent from the second AP to the first STA, the first STA can send a second roaming request frame to the second AP to request the deletion of the link connection between the first AP and the first STA. The first STA can receive a second roaming response frame from the second AP to authorize the deletion of the link between the first AP and the first STA. Therefore, the roaming process from the first AP to the second AP can be completed.

[0188] exist Figure 11 The method described in the example, executed by the first STA, can be performed by... Figure 1 The first device (100) is executed. For example, Figure 1 One or more processors (102) of the first device (100) may send a first roaming request frame to a first AP included in a first group via one or more transceivers (106). The first roaming request frame includes a link identifier of a second AP and a group ID associated with a second group to which the second AP belongs. One or more processors (102) may receive a first roaming response frame from the first AP via one or more transceivers (106). The first roaming response frame includes a first TIM field associated with the second AP. One or more processors (102) may receive first DL data from the second AP via one or more transceivers (106) based on the first TIM field.

[0189] The aforementioned memory (104) may store data for execution by one or more processors (102). Figure 11 The instructions for the methods described in the example.

[0190] Figure 12 This is a diagram illustrating an example of a method for performing a first AP based on MLD, according to this disclosure.

[0191] The first AP, which is attached to the first group, can receive a first roaming request frame from the first STA. The first roaming request frame includes the link identifier of the second AP and the group ID associated with the second group to which the second AP is attached (S1210).

[0192] Before step S1210, the first AP may send a notification message to the first STA, which includes at least one group ID and information related to whether the first STA supports adding at least one link. The first AP can confirm the roaming request information of the first STA through the first roaming request frame.

[0193] The first AP can send a first roaming response frame to the first STA, which includes a first TIM field associated with the second AP (S1220).

[0194] Specifically, the first AP can send a first roaming response frame to the first STA. The first roaming response frame includes information about the second AP and a first TIM field indicating whether there is first data to be sent from the second AP to the first STA. Thus, the link between the first STA and the second AP can be additionally connected, and the first STA can receive first DL data from the second AP based on the first TIM field.

[0195] exist Figure 12 The method described in the example, executed by the first AP, can be performed by... Figure 1 The second device (200) performs the operation. For example, Figure 1 One or more processors (202) of the second device (200) can receive a first roaming request frame from the first STA via one or more transceivers (206). The first roaming request frame includes a link identifier of the second AP and a group ID associated with a second group to which the second AP belongs. One or more processors (202) can send a first roaming response frame to the first STA via one or more transceivers (206). The first roaming response frame includes a first TIM field associated with the second AP.

[0196] Furthermore, one or more memories (204) of the second device (200) may store information for execution by one or more processors (202) in order to perform the operation. Figure 10 The command for the method described in the example.

[0197] Figure 11 and Figure 12 Examples of this disclosure may correspond to some of the various examples of this disclosure. The various examples of this disclosure will be described in more detail below, including... Figure 11 and Figure 12 Examples.

[0198] Implementation Method 1

[0199] Implementation 1 describes exemplary operation of STAs and APs for MLD-based roaming. As an example of this disclosure, Figure 13This is a diagram illustrating an example of the structure and process of an MLD-based roaming according to the present disclosure.

[0200] like Figure 13 As shown, AP 1, AP 2, and AP 3 can be attached to AP group 1, and AP 4 and AP 5 can be attached to AP group 2. Each AP group may not be co-located, and APs attached to each AP group may be co-located in the same or similar positions. Co-location of each AP may include not only the case where each AP is attached to the exact same device, but also the case where each AP is co-located in logically similar positions (even if it does not belong to the exact same device).

[0201] Since an AP MLD is a logical entity, it can be implemented as a specific physical device, but it refers to an MLD that covers affiliated APs regardless of location and performs / applies an MLO. In other words, all APs belonging to an AP group can include affiliated APs of an AP MLD.

[0202] As an example of this disclosure, such as Figure 13 As shown, assume a non-AP MLD establishes a multi-link connection with an AP MLD, and STA 1 and STA 2 are each connected to AP 2 and AP 3, which are included in AP group 1. When the non-AP MLD moves to an area containing AP group 2, it may need to roam from AP group 1 to AP group 2. That is, through roaming, STA 1 can connect to AP 4, and STA 2 can connect to AP 5. Here, during the roaming process, STA 1 and STA 2 can temporarily associate with AP 4 and AP 5 respectively, so that AP 4 and AP 5 can send frames to STA 1 and STA 2 respectively.

[0203] Here, a non-AP MLD may include multiple affiliated STAs, or it may include a single STA. Figure 13 The roaming operation / architecture shown can be applied to non-AP MLDs that include one or more affiliated STAs, and the roaming operation / architecture can also be applied to non-AP STAs that do not form an MLD.

[0204] In describing this disclosure, roaming can be applied not only to movement between groups but also to movement between APs within a specific AP group. Furthermore, the MLD-based roaming according to this disclosure can be performed by changing the link while maintaining the ML establishment without dismantling the existing ML establishment. For example, while maintaining the ML establishment for the upper-layer MLDs of AP 1 and AP 2, the STAMLD can move from AP group 1 to AP group 2 by changing the link within the upper-layer MLD. Therefore, compared to existing BSS transitions, overhead and the risk of data loss can be reduced.

[0205] The MLD-based roaming process may include AP group ID setting (Implementation 1-1), AP announcement (Implementation 1-2), and frame exchange between AP and STA (Request in Implementation 1-3 and Response in Implementation 1-4).

[0206] An ID can be assigned / set for each AP group (consisting of APs deployed in the same location). In this disclosure, the ID assigned / set for each AP group will be referred to as the group ID. For example, the group ID can be set as a unique ID within a single AP group. Alternatively, the group ID can be set as a unique ID for each AP group within the entire AP MLD.

[0207] This notification could correspond to the process by which each AP attached to the upper-layer MLD notifies the STA of information such as whether MLD-based roaming is supported. Frame exchange between the STA and AP can be performed based on this notification information.

[0208] Frame switching corresponds to the process of sending and receiving frames that trigger / initiate MLD-based roaming between an AP and a STA. Through frame switching, the information and settings required for MLD-based roaming can be negotiated between the AP and STA, and MLD-based roaming can be completed based on the negotiated information / settings. Therefore, a STA can operate independently of an OAP (older AP) (e.g., APs included in AP group 1) and can operate with a NAP (newer AP) (e.g., APs included in AP group 2).

[0209] In this way, frame exchange is required between the STA and AP to trigger / initiate MLD-based roaming. The exchanged frames can correspond to management frames (e.g., beacons, (re)association requests / responses, probe requests / responses, action frames, etc.). For example, action frames, as a type of management frame, can be used for frame exchange.

[0210] In the example described below, a frame sent by the STA (or AP) to the AP (or STA) to request MLD roaming is called an MLD roaming request frame, and a frame sent by the AP (or STA) in response to the MLD roaming request frame to the STA (or AP) is called an MLD roaming response frame.

[0211] The following describes specific examples of the procedures for setting a group ID for each AP group, the procedures for requesting information about APs within each AP group, the notification procedures for MLD-based roaming, and the frame switching procedures.

[0212] Additionally, each STA belonging to one or more STAs not connected to an AP MLD can use one radio resource to establish multiple links. That is, a STA can add or remove links, and therefore two or more links can be connected to the STA.

[0213] However, when a link exchange frame is sent, frame exchange may not be performed on the remaining links, and the remaining links may be in a dormant or disabled state. Therefore, a non-AP MLD can send capabilities related to ML establishment (e.g., indicating whether simultaneous link aggregation is supported) via an association request frame during ML establishment. For example, a non-AP MLD can send capabilities related to ML establishment via a management frame that includes the basic multi-link elements described later.

[0214] If all STAs have the capability related to ML establishment, the capability related to ML establishment can be indicated by the MLD capability and operation subfields included in the common information field of the basic multilink element. If only a specific STA has the capability related to ML establishment, the capability related to ML establishment can be indicated by the link information field corresponding to the specific STA (e.g., the per-STA configuration file sub-element corresponding to the specific STA).

[0215] The capability information, indicated by the single radio ML establishment enable subfield, suggests that at least one STA attached to a non-AP MLD can establish multiple links using a single radio resource. This subfield can also indicate that at least one STA can connect to two or more links.

[0216] Implementation Method 1-1

[0217] Implementation 1-1 relates to a process for setting a group ID for each AP group. A mobile MLD (or STA) may need to identify at least one AP it is connected to within the AP MLD to perform roaming. Furthermore, when an MLD (or STA) requests roaming, depending on which NAP the MLD (or STA) is moving to, the AP MLD can check the data and management information to be sent from the OAP to the NAP. Therefore, Implementation 1-1 describes a method for identifying affiliated APs within the AP MLD that are not located in the same position (i.e., a method for setting IDs for roaming within the AP MLD).

[0218] An ID (i.e., a group ID) can be assigned to a group of APs located in the same position. For example, a unique group ID can be set within an AP group (Implementation 1-1-1). As another example, a unique ID can be set for each AP group within the entire AP MLD (Implementation 1-1-2).

[0219] Implementation method 1-1-1

[0220] Implementation method 1-1-1 relates to a method for setting a unique ID within an AP group in an AP MLD. That is, the group ID can be unique within an AP group.

[0221] As an example of this disclosure, the group ID can be set to an integer greater than or equal to 0. For example, if the field indicating the group ID consists of 4 bits, the group ID can be set to one of 0 to 15. As another example, if the field indicating the group ID consists of 8 bits, the group ID can be set to one of 0 to 127.

[0222] For example, if the group ID is 0, an AP with that group ID can be attached to the same AP group deployed in the same location. That is, the MLD (or STA) can determine that APs with that group ID are deployed in the same location. Other group IDs can be mapped so that they can be uniquely identified to each group.

[0223] Additionally, since other APs in the set of multiple BSSIDs to which each AP belongs in an AP group (e.g., sent BSSIDs (i.e., TxBSSIDs) or unsent BSSIDs (nonTxBSSIDs)) also use the same physical resources, the same group ID can be assigned to other APs. However, the AP MLD IDs of the AP MLDs to which other APs belong can be different.

[0224] Implementation Method 1-1-2

[0225] Implementation method 1-1-2 relates to a method for setting a unique ID within an AP MLD. That is, a group ID can be uniquely set for each AP group within the entire AP MLD.

[0226] As mentioned above, the group ID can be set to an integer greater than or equal to 0. For example, if the field indicating the group ID consists of 4 bits, the group ID can be set to one of 0 to 15. As another example, if the field indicating the group ID consists of 8 bits, the group ID can be set to one of 0 to 127.

[0227] Additionally, you can set the group ID of the AP that performs roaming. In other words, you can set an MLD roaming ID for MLD roaming between APs with corresponding group IDs.

[0228] The existing MDID (Mobile Domain ID) field can be used to set the MLD roaming ID and / or group ID, but since the MDID field is 2 octets in size, the MLD roaming ID and / or group ID can be set in a smaller field.

[0229] Implementation Methods 1-2

[0230] Implementation methods 1-2 relate to an announcement process for MLD-based roaming based on group ID.

[0231] Each AP included in the AP MLD can announce whether MLD-based roaming is possible, as described in this disclosure, and its group ID, etc. For example, each AP can send an announcement message including information indicating whether roaming is possible (e.g., "MLD roaming enabled"), a group ID, an MLD roaming ID, and / or temporary link addition / removal information. The information indicating whether roaming is possible can consist of 1 bit, but is not limited to this. Furthermore, the group ID refers to the group ID of the AP group that constitutes the AP MLD as described above. That is, APs with the same group ID can belong to the same AP group.

[0232] The announcement information can be sent via management frames (e.g., beacon frames, probe frames, (re)association response frames, etc.). For example, it can be included in an MLD roaming information element (IE) or a simplified neighbor report (RNR) IE that contains the announcement information.

[0233] For example, the RNR IE may include a Target Beacon Transmission Time (TBTT) information header, operation category, channel number, and TBTT information set field. The TBTT information set may include one or more TBTT information fields. Figure 14 As shown in (a), the TBTT information field may include adjacent AP TBTT offset, BSSID, short BSSID, BSS parameters, 20MHz PSD (power spectral density), and MLD parameter subfields. In addition to AP MLD ID, link ID, BSS parameter change count, and all included update and disable link indication fields, the MLD parameters may also include an MLD roaming enable subfield corresponding to the advertised information.

[0234] Additionally, the TBTT information field may include MLD roaming parameters, and the MLD roaming parameters may include announcement information (i.e., MLD roaming activation information, group ID information, MLD roaming ID, and temporary link addition information, etc.). Figure 14 The example in (a) corresponds to a situation where the size of the MLD parameter subfield is insufficient to include the announcement information. Although the size of the MLD parameter subfield can be changed, this can cause decoding problems for STAs based on IEEE 802.11be.

[0235] Here, since the fact that the MLD roaming parameters are included in the TBTT information field itself implies that MLD roaming is possible, the MLD roaming enable information can be omitted.

[0236] like Figure 14 The subfield indicating temporary link addition information shown in (a) can indicate whether a link can be temporarily added or removed for a STA. That is, the subfield indicating temporary link addition information can indicate that a STA supports having two or more links within a specific time period. For example, the subfield indicating temporary link addition information can consist of 1 bit, but is not limited to this.

[0237] As another example, such as Figure 14 As shown in (b), MLD roaming enable information can be included in the MLD Parameter subfield. Furthermore, the MLD roaming ID and / or group ID can be sent via the MLD roaming parameter subfield or as a separate field.

[0238] Additionally or alternatively, the above notification information may be included in the basic multi-link IE.

[0239] Implementation methods 1-3

[0240] Request information used to trigger / initiate MLD-based roaming can be included in management frames (e.g., MLD roaming request frames). For example, an MLD roaming request frame can have the exemplary format shown in Table 1. The formats in Table 1 are exemplary, and some fields may be omitted or may include additional fields not shown.

[0241] [Table 1]

[0242]

[0243] The category for Sequence 1 can be set to a value indicating the category corresponding to the MLD roaming request frame. For example, the category could correspond to a new UHR action or a protected UHR action. This is exemplary, and the MLD roaming request frame can also be defined as a category with a different name. The UHR action or protected UHR action for Sequence 2 can be set to a value corresponding to the MLD roaming request.

[0244] Sequence 3 dialogue tokens can be set to values ​​used to match requests and responses.

[0245] The reconfigured ML element in sequence 4 corresponds to the element that includes the information required for an MLD-based roaming request. This is an example, and elements / fields with other names that contain the information required for an MLD roaming request can be defined and used.

[0246] Figure 15 This is a diagram illustrating an example of reconfiguring an ML element, including request information, according to this disclosure.

[0247] Figure 15Example (a) shows the presence of a bitmap field (e.g., Figure 8 An example of an existence bitmap in the multi-link control field. Reconfiguring the existence bitmap of an ML element can include information about the presence of the MLD MAC address subfield. Furthermore, according to this disclosure, the existence bitmap can indicate the presence of the Enhanced ML (EML) capability subfield in the public information field and the presence of the MLD capability and operation subfields in the public information field by specific bit positions in the bitmap.

[0248] Figure 15 (b) Examples of public information fields (e.g., Figure 8 Examples of public information fields. The public information fields of a reconfigured ML element may include a public information length subfield and an MLD MAC address subfield. Furthermore, the public information fields according to this disclosure may include an EML capability subfield or both, or both, of the MLD capability and operation subfields (based on the values ​​at the corresponding bit positions in the bitmap).

[0249] When more than one STA moving to the NAP (especially in the case of non-AP MLD) simultaneously performs MLD-based roaming, the EML capability information / MLD capability and operational information may differ, so this information can be provided to the AP as MLD roaming request information.

[0250] Figure 15 Example (c) illustrates the inclusion of the link information field in the reconfiguration ML element (e.g., Figure 8 The STA control (e.g., the link information field) in each STA configuration file sub-element. Figure 8 Example of a field for STA control. Figure 15 (d) shows the link information field included in the reconfigured ML element (e.g., Figure 8 The STA information in each STA configuration file sub-element (e.g., the link information field) is the STA information (e.g., the link information field). Figure 8 Example of a field for STA information.

[0251] When more than one STA performs MLD-based roaming simultaneously, one or more per-STA profile sub-elements can be included in the MLD roaming request frame.

[0252] The presence or absence of each subfield included in the STA Information field can be indicated by the presence subfield of the corresponding subfield in the STA Control field. For example, the NSTR Indicator Bitmap Presence subfield of the STA Control field can indicate whether the NSTR Indicator Bitmap subfield exists in the STA Information field, and if it exists, the bitmap size can be indicated by the NSTR Bitmap Size subfield of the STA Control field. Similarly, the MLD Roaming Timer Presence subfield of the STA Control field can indicate whether the MLD Roaming Timer subfield exists in the STA Information field.

[0253] Figure 15 In (c), the value of the Link ID subfield of the STA control field can be set to a link identifier value corresponding to one of the NAPs (e.g., AP 2 attached to AP MLD 2, and, if any, other APs attached to AP MLD 2). For example, the Link ID subfield of the STA control field of the first perSTA profile sub-element can be set to a link identifier value corresponding to AP 2 attached to AP MLD 2, and the Link ID subfield of the STA control field of the second perSTA profile sub-element can be set to a link identifier value corresponding to another NAP attached to AP MLD 2.

[0254] Figure 15 The complete configuration file of the STA control field in (c) can correspond to the complete information of the STA (i.e., all information included in the (re)association request frame). During MLD-based roaming, since the new STA is not associated with an AP attached to the upper-layer MLD, but the existing STA moves between APs attached to the corresponding upper-layer MLD, it can be assumed that the STA's capabilities and operating parameters remain unchanged. Consider the case where the upper-layer MLD knows the STA's information. Figure 15 The full configuration file subfield of (c) can be set to a value that indicates the configuration file information (or part of the configuration file information) that has been changed.

[0255] For example, a partial configuration file may correspond to a case where the value of a complete configuration file sub-field of the STA control field is 0, and may only include the STA configuration file fields within each STA configuration file sub-element (e.g., Figure 8 The information fields / elements that have changed in the STA configuration file field (i.e., information that has changed compared to OAP when moving to NAP). Alternatively, the full configuration file subfield of the STA control field can be changed to the name of the changed configuration file subfield, and when the value of the subfield is 1, it can include only the information fields / elements that have changed in the STA configuration file field (i.e., information that has changed compared to OAP when moving to NAP).

[0256] Alternatively, it can be assumed that the capabilities and operating parameters of the STA are completely altered during the MLD-based roaming process. In this case, Figure 15 The value of the complete profile subfield in (c) can be set to 1, and the STA profile field can include complete information (e.g., all information included in the (re)association request frame).

[0257] When a STA moves to a different AP, the information about STR or NSTR for each link may differ from the perspective of a non-AP MLD; therefore, the NSTR indicator bitmap (e.g., Figure 15 The NSTR indicator bitmap subfield in (d) can be included in the MLD roaming request frame.

[0258] The MLD roaming timer subfield indicates the point in time when MLD-based roaming is complete and the STA no longer operates with the OAP but with the NAP. The MLD roaming timer value included in the request frame sent by the STA can be interpreted / used as reference information in the AP or the upper-layer MLD.

[0259] Additionally or alternatively, MLD roaming timer information may include values ​​for each of one or more NAPs, or may include values ​​shared by one or more NAPs. For example, the number of individual MLD roaming timer information corresponding to the number of NAPs may be included in the per STA profile sub-element of the MLD roaming request frame. For example, a single MLD roaming timer information shared by one or more NAPs may be included in the common information field of the MLD roaming request frame.

[0260] When the MLD roaming timer is publicly applied to all APs, information about the MLD roaming timer can be included in the public information field. In this case, the presence or absence of the MLD roaming timer can be indicated in the public information field via an existence bitmap.

[0261] Group IDs can be added Figure 15 The reconfigured ML element is shown below. The group ID refers to the ID of the AP group to which the non-AP MLD (or STA) roams.

[0262] Implementation method 1-3-1

[0263] As an example of this disclosure, the group ID can be included in the public information field of a reconfigured ML element. Specifically, such as Figure 16 As shown in (a), the presence bitmap of a reconfigured ML element can be used to indicate whether the group ID is included in the public information field of the reconfigured ML element. Figure 16As shown in (b), when the group ID is only included in the public information field, roaming to an AP in the same AP group with the same group ID can be requested via an MLD roaming request frame.

[0264] In other words, if the group ID is included in the public information field, a non-AP MLD (or STA) cannot request roaming for multiple group IDs, even within the same AP MLD. For example, if the group ID of a specific AP group is included in the public information field, a non-AP MLD (or STA) cannot request roaming to an AP within its current AP group or to an AP in an AP group other than the specific AP group. However, when performing roaming between groups, the method according to implementation 1-3-1 can have reduced overhead compared to the case where the group ID is included in the link information field.

[0265] Additionally, reconfiguring the public information fields of ML elements can include a type subfield as a field for including the ability to temporarily add / remove links for MLD-based roaming.

[0266] As an example of this disclosure, the type subfield may consist of 2 bits, but is not limited to this. For example, if the type subfield consists of 2 bits, the type field may be composed as shown in Table 2. However, this is an implementation method, and the type corresponding to the type subfield value can be defined as different types. Furthermore, "temporary deletion" in Table 2 can be replaced with "delete" corresponding to type subfield value 1.

[0267] [Table 2]

[0268]

[0269] If the type subfield indicates "Add", this could mean that a STA from a non-AP MLD requests an additional link connection to an AP (e.g., a NAP) of a specific AP MLD. If the type subfield indicates "Delete", this could mean that a STA from a non-AP MLD requests to disconnect the current link (e.g., disconnect the link with an OAP). If the type subfield indicates "Temporary Add", this could mean that a STA from a non-AP MLD requests to add a link to another AP (e.g., a NAP) besides the AP to which the current link is connected (e.g., an OAP). As another example of this disclosure, such as Figure 16As shown in (b), the public information field (or the body of the MLD roaming request frame) may include a temporary subfield and a type subfield as fields for including the function of temporarily adding / removing links for MLD-based roaming. As an example, each of the temporary subfield and the type subfield may consist of 1 bit, and the type subfield may indicate "add" or "remove". Furthermore, the temporary subfield may indicate information regarding the "add" or "remove" of the type subfield, indicating temporary addition or removal.

[0270] For example, if the type subfield indicates "add" and the temporary subfield indicates that the operation indicated by the type subfield is a temporary operation, then this could correspond to "temporary add" in Table 2.

[0271] When the type and / or temporary subfields are included in the public information field, the STA included in the non-AP MLD can perform only one operation for all APs. That is, when "Add" is indicated by the type and / or temporary subfields, the STA can only make a request to add a link for each AP.

[0272] Implementation Method 1-3-2

[0273] As an example of this disclosure, such as Figure 16 As shown in (c), a reconfigured ML element can include a link information field, and the link information field can include one or more per-STA configuration file sub-elements. Figure 16 As shown in (d), a roaming request for a specific AP belonging to a specific AP group can be indicated by the link ID and group ID included in the STA control field of the sub-element of each STA configuration file.

[0274] Additional or alternative land, such as Figure 16 As illustrated in (d), the STA control field may include a type and / or temporary subfield (i.e., the type and / or temporary subfield described in Implementation 1-3-1). In other words, the type and / or temporary subfield used for temporarily adding / removing links for MLD-based roaming can be included in the STA control field format (included in the link information field). Since the configuration and function of the type and / or temporary subfield have already been described above, redundant descriptions will be omitted.

[0275] When the type and / or temporary subfield is included in the link information field, STAs included in the non-AP MLD can request different actions for each AP. That is, STAs can request a "temporary addition" for one AP and a "deletion" for another AP via the type and / or temporary subfield.

[0276] Roaming can be requested for one or more APs corresponding to one or more group IDs via one or more perSTA profile sub-elements. However, if roaming is requested based on the same group ID, the overhead may be greater than the method according to implementation 1-5-1.

[0277] Implementation method 1-3-3

[0278] As an example of this disclosure, such as Figure 17 As shown in (a), the STA control field of each STA configuration file sub-element includes a group ID presence sub-field, and the group ID presence sub-field can indicate whether there is an AP group ID to which the AP belongs corresponding to a specific link ID. Additionally, as... Figure 17 As shown in (b), the group ID can be included in the STA information field or the STA configuration file field.

[0279] Roaming requests can be made for one or more APs corresponding to one or more group IDs via one or more STA-specific configuration file sub-elements. Specifically, this is assumed to be combined with the method according to implementation 1-3-1 (i.e., the method of including the group ID in the public information field). In this case, if a roaming request is made for an AP corresponding to the same group ID, the group ID may not be included in the STA information field or the STA configuration file field, thereby reducing overhead.

[0280] As another example, if the group ID is indicated through a public information field, it can implicitly indicate a request to roam to the AP corresponding to the same group ID. Therefore, the group ID may not be included in the STA information field or the STA profile field, and the group ID presence field may or may not exist.

[0281] Implementation methods 1-4

[0282] Response information to MLD-based roaming requests can be included in management frames (e.g., MLD roaming response frames). For example, an MLD roaming response frame can have the exemplary format shown in Table 3. The formats in Table 3 are exemplary, and some fields may be omitted or may include additional fields not shown.

[0283] [Table 3]

[0284]

[0285] MLD roaming response frames can include link-level parameters. For example, link-level parameters can include information necessary to change the link while maintaining ML establishment. The category in sequence 1 can be set to a value indicating the category corresponding to the MLD roaming response frame. For example, the category could correspond to a new UHR action or a protected UHR action. This is exemplary, and MLD roaming response frames can also be defined as categories with names.

[0286] The UHR action of sequence 2 or the protected UHR action can be set to a value corresponding to the MLD roaming response.

[0287] Sequence 3 dialogue tokens can be set to values ​​used to match requests and responses.

[0288] The status code Sequence 4 can be set to one of various values ​​indicating success, failure, acceptance, rejection, unsupported, invalid, error, etc. Among the values ​​indicated by the status code, failure, rejection, unsupported, invalid, error, etc., can be defined with different values ​​depending on the reason.

[0289] The basic ML element in sequence 5 can include information required for roaming related to the upper-level MLD (or roaming MLD) and the roaming target AP / AP MLD (e.g., NAP or AP MLD including NAP). For this purpose, some fields in the existing basic ML element format can be modified, omitted, or new fields can be added.

[0290] For example, the public information field of a basic ML element can have the same characteristics as... Figure 8 The format is similar to that of the public information field. Here, the public information field of the basic ML element of the MLD roaming response frame may include information shared or corresponding to one or more STAs through which they perform MLD-based roaming NAPs.

[0291] For example, the link information field of a basic ML element can essentially have the same characteristics as... Figure 8 The link information field follows a similar format to the example. Here, when one or more STAs simultaneously perform MLD-based roaming, the link information field of the basic ML element in the MLD roaming response frame may include one or more per-STA profile sub-elements for the corresponding AP. Therefore, the STA control field, STA information field, and / or STA profile field included in the per-STA profile sub-elements of the link information field of the basic ML element in the MLD roaming response frame may include the following characteristics.

[0292] The Link ID subfield of the STA control field can be set to the Link ID value corresponding to the NAP.

[0293] The complete profile of the STA control field can correspond to the complete information of the AP (i.e., all information included in the (re)association response frame). When the STA performs MLD-based roaming between APs attached to the same upper-layer MLD (or roaming MLD), cases where the AP's capabilities or operating parameters remain unchanged can be considered. In this case, the complete profile subfield can be set to a value indicating that changed profile information (or partial profile information) is included (e.g., 0). Therefore, the STA profile field in each STA profile sub-element can include only the changed information fields / elements (i.e., information that has changed in the NAP compared to the OAP).

[0294] Alternatively, the capabilities and operating parameters of the AP can be considered to have changed completely during the MLD-based roaming. In this case, the value of the full profile subfield can be set to 1, and the STA profile field can contain complete information (e.g., all information included in the (re)association response frame).

[0295] Furthermore, based on the type of the MLD roaming request frame and / or the temporary subfield indicating (temporary) deletion, the full profile for the corresponding AP may already be known, so the full profile subfield value can be indicated as 0.

[0296] The STA control field may include a field indicating whether an MLD roaming timer exists. If the presence of an MLD roaming timer is indicated, the STA information field may include an MLD roaming timer subfield. The MLD roaming timer subfield may indicate the time when MLD-based roaming is complete and the STA no longer operates with the OAP but with the NAP. The value of the MLD roaming timer included in the MLD roaming response frame may be set based on / using the value of the MLD roaming timer included in the MLD roaming request frame (e.g., set to the changed value when the requested timer value changes). For example, if the value of the MLD roaming timer requested by the STA is used as is and the status code is set to a value indicating success / acceptance, the MLD roaming timer subfield may not be included in the MLD roaming response frame.

[0297] Additionally or alternatively, MLD roaming timer information may include a value for each of one or more NAPs, or may include a value shared by one or more NAPs. For example, the number of individual MLD roaming timer information corresponding to the number of NAPs may be included in the per STA profile sub-element of the MLD roaming response frame. For example, a single MLD roaming timer information shared by one or more NAPs may be included in the common information field of the MLD roaming response frame.

[0298] Additionally, basic ML elements can include group IDs.

[0299] As an example of this disclosure, the group ID may be included in the public information field of the basic ML element, as in embodiment 1-3-1, and the presence or absence of the group ID in the public information field may be indicated by the presence bitmap subfield of the basic ML element. Therefore, the MLD roaming response frame may include information about APs belonging to the same AP group having a group ID indicated by the public information field.

[0300] As an example of this disclosure, when an MLD roaming response frame including a group ID is sent as in embodiment 1-3-2 (i.e., when the group ID is included in the link information field), the group ID may be included in the link information field of the basic ML element of the MLD roaming response frame.

[0301] Specifically, the link information field of a basic ML element may include one or more per-STA profile sub-elements, and the STA control field of each of the one or more per-STA profile sub-elements may include a link ID and a group ID (i.e., the ID of the AP group).

[0302] Information about one or more APs corresponding to one or more group IDs can be provided through one or more perSTA configuration file sub-elements. However, when providing information about APs with the same group ID, the overhead may be greater than the method according to implementation 1-5-1.

[0303] As another example of this disclosure, the STA control field of each perSTA profile sub-element may include information indicating whether a group ID exists in each of one or more perSTA profile sub-elements (i.e., group ID presence information).

[0304] In other words, the presence of the group ID in the STA control field included in each STA configuration file sub-element indicates whether there is an ID (i.e., group ID) of the AP group to which the AP belongs, corresponding to the link ID included in the STA control field, in each STA configuration file sub-element. Here, the group ID can be included in the STA information field or the STA configuration file field of each STA configuration file sub-element.

[0305] Information about one or more APs corresponding to one or more group IDs can be provided via one or more perSTA configuration file sub-elements.

[0306] Additionally or alternatively, the method of Implementation 1-3-1 (i.e., the method in which the group ID is included in the public information field) and the method of Implementation 1-3-3 (i.e., the method in which information indicating whether the group ID exists in the STA control field) can be combined. If only information about the AP corresponding to the same group ID is provided, the group ID does not need to be included in the STA-specific configuration file sub-element, thereby reducing overhead.

[0307] As an example of this disclosure, when a unique ID is set within the AP group in the AP MLD as described in Embodiment 1-1-1, the group ID can be omitted if the group ID is 0. That is, when the group ID does not exist, the AP receiving the MLD roaming request frame can implicitly determine that the request frame is a request for information about other APs in its group.

[0308] As another example of this disclosure, if the group ID is included in the public information field, the STA can implicitly determine that the information included in the MLD roaming response frame is about the AP corresponding to the same group ID. Therefore, the group ID presence field may not be included in the MLD roaming response frame.

[0309] The group key information in sequence 6 can be set to a value indicating the group key information for NAP. Since the group key may be different for each link, group key information for NAP needs to be provided. For example, the fields corresponding to the group key information may include subfields indicating the length of the group key information subfields and subfields set to the values ​​of the group key information. The group key information may include MLO GTK (Group Temporary Key) KDE (Key Data Encapsulation) format, MLO IGTK (Integrity Group Temporary Key) KDE format, MLO BIGTK (Beacon Integrity Group Temporary Key) KDE format, etc., including the NAP link identifier.

[0310] The AID information in step 7 can manage AIDs for each group. Since the total AID space is limited, AIDs can be managed by AP groups. That is, when roaming to another group, a separate AID can be assigned. However, when roaming to another group and being assigned the same AID, or when the entire AID space is managed by AP MLD as described above, the AID information in step 7 may not be required.

[0311] When all APs with MLD-based roaming enabled are operating on the same channel, the channel handover announcement elements (sequences 8 and 9) and the extended channel handover announcement element information can be omitted from the MLD roaming response frame. When MLD-based roaming is performed on different channels, channel information can be provided through the (extended) channel handover announcement element. Alternatively or additionally, the (extended) channel handover announcement element can be included in the STA information / STA profile field of the basic ML element (sequence 5).

[0312] The TID-to-link mapping information in sequence 10 can be used to pre-map TIDs by performing TID-to-link mapping for links in new connections. If TID-to-link mapping is not performed separately, the default mapping can be applied to links in new connections. If the default mapping mode is applied, all TIDs can be mapped to links established for both DL and UL, and all established links can be enabled.

[0313] Additionally, the AP MLD can include the aforementioned MLD roaming timer for reconfiguring ML elements in the MLD roaming response frame. That is, the AP MLD can control the MLD-based roaming process and therefore can set / indicate the MLD roaming timer. For example, suppose the STA sends an MLD roaming request frame that does not include the MLD roaming timer, or the information about the MLD roaming timer sent by the STA is determined by the AP to be inappropriate. In this case, the AP MLD can send the STA an MLD roaming response frame that includes information for setting the MLD roaming timer.

[0314] Here, the expiration of the MLD roaming timer can mean that the point in time when the STA no longer performs various operations with the OAP but with the NAP after the MLD-based roaming is completed has passed. For example, suppose the STA sends an MLD roaming request frame that includes a request to add a temporary link with the NAP. In this case, if the MLD roaming timer expires, the STA can disconnect (i.e., "delete" or "temporarily delete") the link from the OAP and establish a connection with the NAP.

[0315] If the MLD roaming timer is publicly applied to all APs, information about the MLD roaming timer can be included in the public information field of the reconfigured / default ML element, such as... Figure 16 As shown in (b). Additionally, information indicating the presence of an MLD roaming timer in the public information field can be included in the presence bitmap subfield of the reconfigured / default ML element.

[0316] Additionally, the MLD roaming response frame may include information about the MLD roaming timer. For this purpose, the STA control field may include an MLD roaming timer presence field, and the STA information field may include an MLD roaming timer field. The MLD roaming timer indicates the remaining time until the STA can receive data from the AP it is roaming to, and is associated with the TIM field. The MLD roaming timer can be set based on the MLD roaming timer information sent by the STA.

[0317] MLD roaming process based on TIM information

[0318] As an example of this disclosure, Figure 18 The diagram illustrates the process for performing MLD-based roaming. Assume STA 1, attached to a non-APMLD, is currently connected to AP 1 in AP group 1, and STA 2, attached to a non-AP MLD, is currently connected to AP2 in AP group 1. Here, when STA 1 and STA 2 move from AP group 1 to AP group 2, STA 1 can perform a roaming procedure to AP 4 in AP group 2, and STA 2 can perform a roaming procedure to AP 5 in AP group 2.

[0319] For example, AP 1 can exchange MLD roaming response / request frames with STA 1. Here, the MLD roaming request frame may include the group ID associated with AP group 2 and the link ID corresponding to AP 4, and the MLD roaming response frame may include basic ML elements, which include information about whether MLD roaming is accepted and information about AP 4.

[0320] AP 2 and STA 2 can exchange MLD roaming response / request frames. Here, the MLD roaming request frame may include the group ID associated with AP group 2 and the link ID corresponding to AP 5, and the MLD roaming response frame may include basic ML elements, which include information about whether MLD roaming is accepted and information about AP 5.

[0321] Once the above process is complete, STA 1 can temporarily connect to AP 1 and AP 4, and STA 2 can connect to AP 2 and AP 5. Here, STA 1 can exchange frames with either AP 1 or AP 4. That is, STA 1 may not be able to exchange frames with AP 4 while simultaneously performing frame exchange with AP 1. To allow STA 1 to fully roam from AP 1 to AP 4, the following steps can be performed... Figure 19 The illustrated process.

[0322] Reference Figure 19AP 1 can indicate information about the existence of data to be sent to STA 1 via the TIM field in a beacon frame. Here, to perform roaming from AP 1 to AP 4, STA 1 can send an MLD roaming request frame to AP 1, which includes information for adding a link connection with AP 4. Figure 19 The example only illustrates the process of STA 1 requesting / performing a roaming from AP 1 to AP 4, but it is also possible for STA 2 to request / perform a roaming from AP 2 to AP 5 (e.g., the process of STA 2 requesting to add a link to AP 5, etc.).

[0323] After confirming the MLD roaming request frame, AP 1 can send an MLD roaming response frame to STA 1, indicating receipt of the roaming process from AP 4. However, STA 1 can receive information from AP 1's most recent beacon frame regarding whether DL data is stored in the buffer, or even if DL data is stored in the buffer, it may not have been received from AP 1 yet. Therefore, AP 1 can notify STA 1 that AP 4 or AP MLD has DL data (e.g., DL data to be sent to STA 1). Thus, STA 1 can send a PS (Power Saving) polling frame to AP 4 upon switching to AP 4 without waiting until it receives a beacon frame from AP 4, etc. Subsequently, AP 4 can send DL data to STA 1 in response to the PS polling frame.

[0324] For the process described above, the MLD roaming response frame sent by AP 1 to STA 1 may include a TIM field. The TIM field may indicate that the AP (e.g., the AP from which STA 1 requested roaming) (e.g., AP 4) or the AP MLD is currently buffering DL data for the requested STA. For example, the TIM field may consist of 1 bit, but is not limited to this.

[0325] From an MLD-level perspective, the AP MLD can indicate that it is buffering DL data for a requested STA, and the TIM field can be included in the body of the MLD roaming response frame or in the public information field.

[0326] For example, from the AP's perspective, AP 1 can indicate that AP 4 has DL data before STA 1 switches to AP 4, and the TIM field can be included in the link information field.

[0327] Additionally, an STA (e.g., STA 1) can use the MLD roaming timer of the MLD roaming response frame to set the time to switch to another AP (e.g., AP 4).

[0328] For example, if the remaining time before STA 1 receives DL data from the AP it is to roam to (e.g., AP 4) exceeds a predefined time before the handover, STA 1 can first receive DL data by sending PS polling frames to the currently connected AP (e.g., AP 1) if needed. STA 1 can then perform the handover procedure to AP 4. Here, STA 1 performing the handover procedure to AP 4 can mean that STA 1 performs the operation of disabling the existing link (i.e., the link between STA 1 and AP 1) and enabling the link between STA 1 and AP 4.

[0329] As another example, if STA 1 can switch to AP 4 and immediately receive DL data, then STA 1 can immediately perform the switchover process to AP 4 and receive DL data from AP 4.

[0330] The above embodiments combine the elements and features of this disclosure in a predetermined form. Unless otherwise expressly stated, each element or feature should be considered optional. Each element or feature may be implemented without being combined with other elements or features. Furthermore, embodiments of this disclosure may include combinations of some elements and / or features. The order of operations described in embodiments of this disclosure may be changed. Some elements or features of one embodiment may be included in other embodiments, or may be replaced by corresponding elements or features of other embodiments. Obviously, embodiments may include claims that are not explicitly referenced in the claims, or may be included as new claims after the application has been amended.

[0331] It will be apparent to those skilled in the art that this disclosure may be implemented in other specific forms without departing from its essential characteristics. Therefore, the above detailed description should not be construed as restrictive in every respect, but rather as illustrative. The scope of this disclosure should be determined by a reasonable interpretation of the appended claims, and all variations within the equivalent scope of this disclosure are included within its scope.

[0332] The scope of this disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) that operate in a device or computer according to methods of various embodiments, as well as non-transitory computer-readable media that cause software or commands to be stored and executable in a device or computer. Commands that can be used to program a processing system to perform the features described in this disclosure can be stored in a storage medium or a computer-readable storage medium, and the features described in this disclosure can be implemented by using a computer program product including such a storage medium. The storage medium may include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid-state storage devices, and may include non-volatile memory, such as one or more disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory may optionally include one or more storage devices located remotely from the processor. The memory, or alternatively, the non-volatile memory devices in the memory include non-transitory computer-readable storage media. The features described in this disclosure can be stored in any machine-readable medium to control the hardware of a processing system and can be integrated into software and / or firmware that allows the processing system to interact with other mechanisms using the results of 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.

[0333] Industrial applicability

[0334] The method proposed in this disclosure has been described in reference to examples applied to IEEE 802.11-based systems, but the method can also be applied to various wireless LAN or wireless communication systems other than IEEE 802.11-based systems.

Claims

1. A method performed by a first station (STA) in a wireless LAN system, the method comprising the following steps: Send a first roaming request frame to a first access point (AP) attached to a first group, the first roaming request frame including the link identifier of the second AP and the group ID associated with the second group to which the second AP is attached; Receive a first roaming response frame from the first AP, the first roaming response frame including a first traffic indication mapping (TIM) field associated with the second AP; as well as The first downlink DL data is received from the second AP based on the first TIM field.

2. The method according to claim 1, wherein, The first STA is instructed to accept roaming information to the second AP and the first TIM field is included in the common information field or link information field of the first roaming response frame.

3. The method according to claim 1, wherein, The first TIM field includes information indicating whether there is first DL data to be sent from the second AP to the first STA.

4. The method according to claim 1, wherein, The first TIM field includes information indicating whether there is first DL data to be sent from the second AP to the first STA.

5. The method according to claim 1, wherein, Based on the first roaming response frame being sent to the first STA, a link is added between the first STA and the second AP, and Frame exchange is performed via the link between the first STA and the first AP or the link between the first STA and the second AP.

6. The method according to claim 5, wherein, Based on the fact that the link between the first STA and the first AP is disabled and the link between the first STA and the second AP is enabled, data frame exchange between the first STA and the second AP is performed through the enabled link.

7. The method according to claim 1, wherein, The first roaming response frame includes a group ID associated with the second group to which the second AP belongs.

8. The method according to claim 1, wherein, A beacon frame including a second TIM field is sent from the first AP to the first STA, the second TIM field indicating whether there is second DL data to be sent from the first AP to the first STA.

9. The method according to claim 1, wherein, Based on the first DL data being sent from the second AP to the first STA, a second roaming request frame is sent from the first STA to the second AP requesting the deletion of the link connection between the first AP and the first STA.

10. The method according to claim 1, wherein, The first roaming response frame includes roaming timer information related to the time when the first DL data can be received from the second AP.

11. The method according to claim 1, wherein, Each of the first and second groups is mapped to a separate AP MLD.

12. The method according to claim 1, wherein, The first STA is attached to a non-AP MLD.

13. A first station STA operating in a wireless LAN system, the first STA comprising: At least one transceiver; as well as At least one processor, said at least one processor being connected to said at least one transceiver, Wherein, the at least one processor is configured to: A first roaming request frame is sent to a first access point (AP) attached to a first group via the at least one transceiver. The first roaming request frame includes a link identifier of the second AP and a group ID associated with the second group to which the second AP is attached. A first roaming response frame is received from the first AP via the at least one transceiver. The first roaming response frame includes a first traffic indication mapping (TIM) field associated with the second AP. The first downlink DL data is received from the second AP by the at least one transceiver based on the first TIM field.

14. A method performed by a first access point (AP) included in a first group in a wireless LAN system, the method comprising the steps of: A first roaming request frame is received from the first STA, the first roaming request frame including the link identifier of the second AP and the group ID associated with the second group to which the second AP belongs; as well as A first roaming response frame is sent to the first STA, the first roaming response frame including a first traffic indication mapping (TIM) field associated with the second AP. Specifically, based on the first TIM field, the second AP sends the first downlink DL data to the first STA.

15. An access point (AP) operating in a wireless LAN system, the AP comprising: At least one transceiver; as well as At least one processor, said at least one processor being connected to said at least one transceiver, Wherein, the at least one processor is configured to: A first roaming request frame is received from a first STA via the at least one transceiver. The first roaming request frame includes a link identifier of the second AP and a group ID associated with a second group to which the second AP belongs. A first roaming response frame is sent to the first STA via the at least one transceiver. The first roaming response frame includes a first traffic indication mapping (TIM) field associated with the second AP. Specifically, based on the first TIM field, the second AP sends the first downlink DL data to the first STA.

16. A processing apparatus configured to control a first station STA in a wireless LAN system, the processing apparatus comprising: At least one processor; as well as At least one computer memory, operatively connected to the at least one processor and storing instructions for performing the method according to claim 1 based on execution by the at least one processor.

17. At least one non-transitory computer-readable medium, said at least one non-transitory computer-readable medium storing at least one instruction, The at least one instruction is executed by at least one processor to control the first station STA in the wireless LAN system to perform the method according to claim 1.

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