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

Abstract

Disclosed are a method and apparatus for roaming based on a multi-link device (MLD) in a wireless LAN system. A method performed by a first STA in a wireless LAN system comprises the steps of: receiving, from a first access point (AP) belonging to a first group, advertisement information including first information related to whether to support addition of at least one link to the first STA; transmitting a request frame including a link ID of a second AP belonging to a second group to the first AP; and receiving, from the first AP, a response frame including a link ID of the second AP, where the request frame may include second information requesting to add or delete a link between the first STA and the second AP.

Description

TECHNICAL FIELD

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

[0002] New technologies for improving transmission rates, increasing bandwidth, improving reliability, reducing errors, and reducing latency have been introduced for wireless LANs (WLANs). Among the WLAN technologies, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 series standards can be referred to as Wi-Fi. For example, technologies recently introduced to WLANs include very high throughput (VHT) enhancements of the 802.11ac standard and high efficiency (HE) enhancements of the IEEE 802.11ax standard.

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

[0004] TECHNICAL PROBLEM

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

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

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

[0008] The technical objects to be achieved by the disclosure are not limited to the aforementioned technical objects and other technical objects not described herein will be clearly understood from the following description by one of ordinary skill in the art.

[0009] TECHNICAL SOLUTION

[0010] A method performed by a first station (STA) in a wireless LAN system according to one aspect of the disclosure can include receiving advertisement information from a first access point (AP) affiliated with a first group, the advertisement information including first information related to whether to support adding at least one link for the first STA, transmitting a request frame including a link ID of a second AP affiliated with a second group to the first AP, and receiving a response frame including the link ID of the second AP from the first AP, and the request frame can include second information requesting to add or delete a link between the first STA and the second AP.

[0011] A method performed by a first access point (AP) included in a first group in a wireless LAN system according to another aspect of the disclosure can include transmitting advertisement information to a first station (STA), the advertisement information including first information about whether to support adding at least one link for the first STA, receiving a request frame including a link ID of a second AP affiliated with a second group from the first STA, and transmitting a response frame including the link ID of the second AP to the first STA, and the request frame can include second information requesting to add or delete a link between the first STA and the second AP.

[0012] Technical Effects

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

[0014] According to the disclosure, a method and an apparatus for supporting or performing roaming of a station (STA) between different access points (APs) affiliated with a common MLD in a wireless LAN system can be provided.

[0015] According to the disclosure, an additional technical problem of the disclosure is a method and an apparatus for performing communication by adding / deleting a temporary link when performing an MLD based roaming procedure in a wireless LAN system.

[0016] Effects that can be achieved by the disclosure are not limited to the above-mentioned effects, and other effects not described herein can be clearly understood by those skilled in the art from the following description. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

[0020] Figure 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0021] Figure 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0022] Figure 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0023] Figure 6 is a diagram for explaining an example of a frame structure used in a WLAN system to which the present disclosure can be applied.

[0024] Figure 7 is a diagram illustrating an example of a PPDU defined in an IEEE 802.11 standard to which the present disclosure can be applied.

[0025] Figure 8 illustrates an example structure of an ML element to which the present disclosure can be applied.

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

[0027] Figure 10 is a diagram illustrating BSS transition in a legacy wireless LAN system.

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

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

[0031] Figure 14 is a diagram illustrating an example of an element including announcement information according to the present disclosure.

[0032] Figure 15 , Figure 16 and Figure 17 is a diagram illustrating an example of a reconfiguration ML element according to the present disclosure.

[0033] Figure 18 is a diagram illustrating an example of a structure and procedure of MLD-based roaming according to the present disclosure. DETAILED DESCRIPTION

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

[0035] In some cases, known structures and devices can be omitted or can be shown in the form of a block diagram based on a core function in order to facilitate the prevention of obscuring the concept of the present disclosure.

[0036] In the present disclosure, when an element is referred to as being "connected", "combined", or "linked" to another element, it can include an indirect connection relationship between the other element and a further element existing therebetween as well as a direct connection relationship. In addition, in the present disclosure, the term "comprising" or "having" specifies the existence of the mentioned features, steps, operations, components, and / or elements, but does not exclude the existence or addition of one or more other features, stages, operations, components, elements, and / or groups thereof.

[0037] In the present disclosure, terms such as "first", "second", and the like are used only to distinguish one element from another element and are not used to limit the elements, unless otherwise specified, and do not limit the order or importance between the elements, etc. Therefore, within the scope of the present disclosure, a first element in an embodiment can be referred to as a second element in another embodiment, and likewise, a second element in an embodiment can be referred to as a first element in another embodiment.

[0038] The terms used in the present disclosure are intended to describe specific embodiments, and are not intended to limit the claims. As used in the description of the embodiments and the appended claims, the singular form is intended to include the plural form, unless the context clearly dictates otherwise. The term "and / or" used in the present disclosure can refer to one of the relevant listed items, or mean that it refers to and includes any and all possible combinations of two or more of them. In addition, unless otherwise specified, " / " and "and / or" between words in the present disclosure have the same meaning.

[0039] Examples of the present disclosure can be applied to various wireless communication systems. For example, examples of the present disclosure can be applied to a wireless LAN system. For example, examples of the present disclosure can be applied to a wireless LAN based on IEEE 802.11a / g / n / ac / ax standards. Further, examples of the present disclosure can be applied to a wireless LAN based on a newly proposed IEEE 802.11be (or EHT) standard. Examples of the present disclosure can be applied to a wireless LAN based on IEEE 802.11be version 2 standards corresponding to additional enhancement technologies of IEEE 802.11be version 1 standards. In addition, examples of the present disclosure can be applied to a wireless LAN based on next-generation standards after IEEE 802.11be. Further, examples of the present disclosure can be applied to a cellular wireless communication system. For example, it can be applied to a long-term evolution (LTE)-based technology based on third generation partnership project (3GPP) standards and a cellular wireless communication system based on 5G new radio (NR) technology.

[0040] Hereinafter, technical features to which examples of the present disclosure can be applied will be described.

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

[0042] Figure 1 The first device 100 and the second device 200 exemplified in the middle can be replaced with various terms such as a terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a mobile subscriber unit (MSU), a subscriber station (SS), an advanced mobile station (AMS), a wireless terminal (WT), or simply a user, etc. In addition, the first device 100 and the second device 200 include an access point (AP), a base station (BS), a fixed station, a node B, a base transceiver system (BTS), a network. It can be replaced with various terms such as an artificial intelligence (AI) system, a road side unit (RSU), a repeater, a router, a relay, and a gateway.

[0043] Figure 1 The devices 100 and 200 exemplified in the middle can be referred to as a station (STA). For example, Figure 1The apparatuses 100 and 200 exemplified can be referred to with various terms such as a transmitting apparatus, a receiving apparatus, a transmitting STA, and a receiving STA. For example, the STAs 100 and 200 can perform an access point (AP) role or a non-AP role. That is, in the present disclosure, the STAs 100 and 200 can perform the functions of an AP and / or a non-AP. When the STAs 100 and 200 perform the AP function, they can be simply referred to as an AP, and when the STAs 100 and 200 perform the non-AP function, they can be simply referred to as a STA. In addition, in the present disclosure, an AP can also be indicated as an AP STA.

[0044] Referring to Figure 1 The first apparatus 100 and the second apparatus 200 can transmit and receive radio signals through various wireless LAN technologies (for example, IEEE 802.11 series). The first apparatus 100 and the second apparatus 200 can include an interface for a medium access control (MAC) layer and a physical layer (PHY) to comply with the IEEE 802.11 standard.

[0045] In addition, the first apparatus 100 and the second apparatus 200 can additionally support various communication standard (for example, 3GPP LTE series, 5G NR series standards, etc.) technologies in addition to the wireless LAN technology. In addition, the apparatuses of the present disclosure can be implemented in various apparatuses such as a mobile phone, a vehicle, a personal computer, an augmented reality (AR) device, and a virtual reality (VR) device, etc. In addition, the STAs of the present specification can support various communication services such as a voice call, a video call, data communication, autonomous driving, machine type communication (MTC), machine-to-machine (M2M), device-to-device (D2D), IoT (Internet of Things), etc.

[0046] The first apparatus 100 can include one or more processors 102 and one or more memories 104, and can additionally include one or more transceivers 106 and / or one or more antennas 108. The processor 102 can control the memory 104 and / or the transceiver 106, and can be configured to implement descriptions, functions, procedures, suggestions, methods and / or operational flowcharts included in the present disclosure. For example, the processor 102 can generate first information / signal by processing information in the memory 104, and then transmit a wireless signal including the first information / signal through the transceiver 106. Also, the processor 102 can receive a wireless signal including second information / signal through the transceiver 106, and then store information obtained by processing a signal of the second information / signal in the memory 104. The memory 104 can be connected to the processor 102 and can store a variety of information related to operations of the processor 102. For example, the memory 104 can store software code including instructions for performing all or a part of processes controlled by the processor 102 or for performing descriptions, functions, procedures, suggestions, methods and / or operational flowcharts included in the present disclosure. Here, the processor 102 and the memory 104 can be a part of a communication modem / circuit / chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). The transceiver 106 can be connected to the processor 102 and can transmit and / or receive a wireless signal through the one or more antennas 108. The transceiver 106 can include a transmitter and / or a receiver. The transceiver 106 can be used together with an RF (Radio Frequency) unit. In the present disclosure, a wireless device can mean a communication modem / circuit / chip.

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

[0048] Hereinafter, the hardware elements of the apparatuses 100, 200 will be described in more detail. Without limitation, one or more protocol layers can be implemented by the one or more processors 102, 202. For example, the one or more processors 102, 202 can implement one or more layers (e.g., functional layers such as PHY, MAC). The one or more processors 102, 202 can generate one or more PDUs (Protocol Data Units) and / or one or more SDUs (Service Data Units) according to the descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts disclosed in the present disclosure. The one or more processors 102, 202 can generate messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts disclosed in the present disclosure. The one or more processors 102, 202 can generate signals (e.g., baseband signals) including the PDUs, SDUs, messages, control information, data, or information according to the functions, procedures, suggestions, and / or methods disclosed in the present disclosure to provide the same to the one or more transceivers 106, 206. The one or more processors 102, 202 can receive signals (e.g., baseband signals) from the one or more transceivers 106, 206 according to the descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts included in the present disclosure, and obtain the PDUs, SDUs, messages, control information, data, or information.

[0049] The one or more processors 102, 202 can be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors 102, 202 can 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 Processors Devices), one or more PLDs (Programmable Logic Devices), or one or more FPGAs (Field Programmable Gate Arrays) can be included in the one or more processors 102, 202. The descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts included in the present disclosure can be implemented by using firmware or software, and the firmware or software can be implemented as including modules, procedures, functions, etc. The firmware or software configured to perform the descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts included in the present disclosure can be included in the one or more processors 102, 202, or can be stored in the one or more memories 104, 204 and driven by the one or more processors 102, 202. The descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts included in the present disclosure can be implemented by using firmware or software in the form of codes, instructions, and / or instruction sets.

[0050] One or more memories 104, 204 can be connected to one or more processors 102, 202 and can store data, signals, messages, information, programs, codes, instructions, and / or commands in various forms. One or more memories 104, 204 can be configured with ROM, RAM, EPROM, flash memory, hard drives, registers, cache memories, computer-readable storage media, and / or combinations thereof. One or more memories 104, 204 can be located internal and / or external to one or more processors 102, 202. In addition, one or more memories 104, 204 can be connected to one or more processors 102, 202 by various technologies such as wired or wireless connections.

[0051] The one or more transceivers 106, 206 can transmit user data, control information, wireless signals / channels, etc. mentioned in the methods and / or operational flowcharts, etc. of the disclosure to one or more other apparatuses. The 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 operational flowcharts, etc. included in the disclosure from one or more other apparatuses. For example, the one or more transceivers 106, 206 can be connected to the one or more processors 102, 202 and can transmit and receive wireless signals. For example, the one or more processors 102, 202 can control the one or more transceivers 106, 206 to transmit user data, control information, or wireless signals to one or more other apparatuses. In addition, the one or more processors 102, 202 can control the one or more transceivers 106, 206 to receive user data, control information, or wireless signals from one or more other apparatuses. In addition, the one or more transceivers 106, 206 can be connected to the one or more antennas 108, 208, and the one or more transceivers 106, 206 can be configured to transmit and receive user data, control information, wireless signals / channels, etc. mentioned in the descriptions, functions, processes, suggestions, methods and / or operational flowcharts, etc. included in the disclosure through the one or more antennas 108, 208. In the disclosure, the one or more antennas can be a plurality of physical antennas or a plurality of logical antennas (for example, antenna ports). The one or more transceivers 106, 206 can convert received wireless signals / channels, etc. from RF band signals to baseband signals to process received user data, control information, wireless signals / channels, etc. by using the one or more processors 102, 202. The one or more transceivers 106, 206 can convert user data, control information, wireless signals / channels, etc. processed by using the one or more processors 102, 202 from baseband signals to RF band signals. Accordingly, the one or more transceivers 106, 206 can include (analog) oscillators and / or filters.

[0052] For example, one of the STAs 100 and 200 can perform the intended operation of an AP, and the other of the STAs 100 and 200 can perform the intended operation of a non-AP STA. For example, Figure 1 The transceivers 106 and 206 of the STA 100 and 200 can perform transmission and reception operations of signals (for example, packets or physical layer protocol data units (PPDUs) conforming to IEEE 802.11a / b / g / n / ac / ax / be / bn). In addition, in the disclosure, operations in which various STAs generate transmission / reception signals or perform data processing or calculation in advance for transmission / reception signals can be performed by the one or more processors 102, 202. Figure 1The operations of generating a transmission / reception signal or performing data processing or calculation in advance for the operations of the transmission / reception signal can include, for example, 1) determining / acquiring / configuring / calculating / decoding / encoding bit information of a field (a signal (SIG), a short training field (STF), a long training field (LTF), data, etc.) included in a PPDU; 2) determining / configuring / acquiring a time resource or a frequency resource (e.g., a subcarrier resource) for a field (SIG, STF, LTF, data, etc.) included in a PPDU; 3) determining / configuring / acquiring a specific sequence (e.g., a pilot sequence, an STF / LTF sequence, an additional sequence applied to SIG) for a field (SIG, STF, LTF, data, etc.) included in a PPDU action; 4) a power control operation and / or a power saving operation applied to a STA; 5) an operation related to ACK signal determination / acquisition / configuration / calculation / decoding / encoding, etc. In addition, in the following examples, various information (e.g., information related to a field / subfield / control field / parameter / power, etc.) used by various STAs to determine / acquire / configure / calculate / decode / encode a transmission signal and a reception signal can be stored in the memories 104 and 204 of the processors 102 and 202. Figure 1

[0053] Hereinafter, a downlink (DL) can mean a link for communication from an AP STA to a non-AP STA, and a DL PPDU / packet / signal can be transmitted and received through the DL. In the DL communication, a transmitter can be a part of the AP STA, and a receiver can be a part of the non-AP STA. An uplink (UL) can mean a link for communication from a non-AP STA to an AP STA, and a UL PPDU / packet / signal can be transmitted and received through the UL. In the UL communication, a transmitter can be a part of the non-AP STA, and a receiver can be a part of the AP STA.

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

[0055] The structure of the wireless LAN system can be composed of a plurality of components. The wireless LAN supporting mobility of a STA transparent to an upper layer can be provided through the interaction of the plurality of components. A basic service set (BSS) corresponds to a basic building block of the wireless LAN. Figure 2 Exemplarily, it is shown that there are two BSSs (BSS1 and BSS2), and two STAs (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2) are included as members of each BSS. Figure 2 ​The ellipse representing the BSS can also be understood to represent a coverage area in which the STAs included in the corresponding BSS maintain communication. This area can be referred to as a basic service area (BSA). When a STA moves outside the BSA, it cannot directly communicate with other STAs within the BSA.

[0056] If the DS shown in Figure 2 The most basic BSS type in a wireless LAN is an independent BSS (IBSS) if the DS shown in

[0057] The membership of STAs in a BSS can be dynamically changed by turning on or off a STA, entering or exiting a BSS area, etc. In order to become a member of a BSS, a STA can join the BSS using a synchronization process. In order to access all services of the BSS infrastructure, a STA should be associated with the BSS. The association can be dynamically established and can include the use of a distribution system service (DSS).

[0058] The direct STA-to-STA distance in a wireless LAN can be limited by the PHY performance. In some cases, this distance limitation can be sufficient, but in some cases, communication between STAs at a longer distance can be required. A distribution system (DS) can be configured to support extended coverage.

[0059] The DS means a structure for interconnecting BSSs. Specifically, as Figure 2As shown, the BSS can exist as an extended form of a network composed of a plurality of BSSs. The DS is a logical concept, and can be specified by the characteristics of a distributed system medium (DSM). In this regard, the wireless medium (WM) and the DSM can be logically separated. Each logical medium is used for a different purpose, and is used by a different component. These media are not limited to being the same, nor are they limited to being different. In this way, the flexibility of the wireless LAN structure (DS structure or other network structure) can be interpreted as the plurality of media being logically different. That is, the wireless LAN structure can be implemented in various ways, and the corresponding wireless LAN structure can be independently specified by the physical characteristics of each implementation.

[0060] The DS can support mobile devices by providing seamless integration of a plurality of BSSs and providing logical services necessary for addressing addresses leading to destinations. In addition, the DS can also include a component called a portal, which is used as a bridge for a connection between the wireless LAN and other networks (for example, IEEE 802.X).

[0061] The AP enables access to the DS through the WM for an associated non-AP STA, and means an entity that also has the function of a STA. Data movement between the BSS and the DS can be performed through the AP. For example, Figure 2 The STAs 2 and 3 shown in FIG. 1 have the function of a STA, and provide a function that allows an associated non-AP STA (STAs 1 and 4) to access the DS. In addition, since all APs basically correspond to STAs, all APs are addressable entities. The address used by the AP to communicate on the WM is not necessarily the same as the address used by the AP to communicate on the DSM. A BSS composed of an AP and one or more STAs can be referred to as an infrastructure BSS.

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

[0063] In addition to the structure of the DS described above, an extended service set (ESS) can be configured to provide a wide coverage range.

[0064] The ESS means a network composed of DSs and BSSs with arbitrary size and complexity. The ESS can correspond to a set of BSSs connected to one DS. However, the ESS does not include the DS. The ESS network is characterized as IBSS in the logical link control (LLC) layer. STAs included in the ESS can communicate with each other, and a mobile STA can move from one BSS to another BSS (within the same ESS) transparently to the LLC. The APs included in one ESS can have the same service set identification (SSID). The SSID is distinguished from the BSSID which is an identifier of the BSS.

[0065] The wireless LAN system does not assume anything about the relative physical locations of BSSs, and all of the following forms are possible. BSSs can partially overlap, which is a form commonly used to provide continuous coverage. In addition, BSSs can not be physically connected, and logically, there is no limit to the distance between BSSs. In addition, BSSs can be physically located at the same location, which can be used to provide redundancy. In addition, one (or more than one) IBSS or ESS network can physically exist in the same space as one (or more than one) ESS network. This can correspond to a form of ESS network when an ad hoc network operates in a location where an ESS network exists, when physically overlapping wireless networks are configured by different organizations, or when two or more different access and security policies are required in the same location, and the like.

[0066] Figure 3 is a diagram for explaining a link establishment process to which the present disclosure can be applied.

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

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

[0069] The scanning scheme includes active scanning and passive scanning. Figure 3A network discovery operation including an active scan process is exemplarily illustrated. In the active scan, the STA performing the scan transmits a probe request frame to discover what APs exist around it while the channel moves and waits for a response thereto. The responder transmits a probe response frame as a response to the probe request frame to the STA having transmitted the probe request frame. Here, the responder can be the STA which last transmitted a beacon frame in the BSS of the channel being scanned. In the BSS, since the AP transmits the beacon frame, the AP becomes the responder, and in the IBSS, the STAs in the IBSS rotate to transmit the beacon frame, so the responder is not constant. For example, the STA which transmits the probe request frame on channel 1 and receives the probe response frame on channel 1 can store the BSS-related information included in the received probe response frame, and can move to the next channel (e.g., channel 2) and perform the scan in the same manner (i.e., transmission and reception of the probe request / response on channel 2).

[0070] Although not shown in Figure 3 , a scan operation can be performed in a passive scan manner. In the passive scan, the STA performing the scan waits for a beacon frame while the channel moves. The beacon frame is one of the management frames defined in IEEE 802.11, and is periodically transmitted to notify of the existence of a wireless network, and to allow the STA performing the scan to find the wireless network and participate in the wireless network. In the BSS, the AP is used to periodically transmit the beacon frame, and in the IBSS, the STAs within the IBSS rotate to transmit the beacon frame. When the STA performing the scan receives the beacon frame, the STA stores the information of the BSS included in the beacon frame, and records the beacon frame information in each channel while moving to another channel. The STA receiving the beacon frame can store the BSS-related information included in the received beacon frame, move to the next channel, and perform the scan in the next channel in the same manner. Comparing the active scan with the passive scan, the active scan has an advantage in that it has less delay and less power consumption than the passive scan.

[0071] After the STA discovers the network, an authentication process can be performed at step S320. In order to clearly distinguish from a security establishment operation of step S340 which will be described later, the authentication process can be referred to as a first authentication process.

[0072] The authentication process includes a process in which the STA transmits an authentication request frame to the AP, and in response thereto, the AP transmits an authentication response frame to the STA. The authentication frame for the authentication request / response corresponds to a management frame.

[0073] The authentication frame includes an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a robust security network (RSN), and a finite cyclic group, and the like. This corresponds to some examples of information that can be included in an authentication request / response frame, and can be replaced with other information, or additional information can also be included.

[0074] The STA can transmit an authentication request frame to the AP. The AP can determine whether to allow authentication of the corresponding STA based on information included in the received authentication request frame. The AP can provide the result of the authentication process to the STA through an authentication response frame.

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

[0076] For example, the association request frame can include information related to various capabilities, a beacon listen interval, a service set identifier (SSID), supported rates, supported channels, an RSN, a mobility domain, supported operating classes, a traffic indication map broadcast request (TIM broadcast request), interworking service capabilities, and the like. For example, the association response frame can include information related to various capabilities, a status code, an association ID (AID), supported rates, an enhanced distributed channel access (EDCA) parameter set, a received channel power indicator (RCPI), a received signal to noise indicator (RSNI), a mobility domain, a super interval (e.g., an association recovery time), an overlapping BSS scan parameter, a TIM broadcast response, a quality of service (QoS) map, and the like. This corresponds to some examples of information that can be included in an association request / response frame, and can be replaced with other information, or additional information can also be included.

[0077] After the STA is successfully associated with the network, a security establishment process can be performed at step S340. The security establishment process of step S340 can be referred to as an authentication process through a robust security network association (RSNA) request / response, the authentication process of step S320 is referred to as a first authentication process, and the security establishment process of step S340 can also be simply referred to as an authentication process.

[0078] The security establishment process of step S340 can include, for example, a process of establishing a private key through extensible authentication protocol (EAPOL) frames over a LAN using a four-way handshake. In addition, the security establishment process can be performed according to a security scheme that is not defined in the IEEE 802.11 standard.

[0079] Figure 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0080] In a wireless LAN system, a basic access mechanism of a medium access control (MAC) is a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism. The CSMA / CA mechanism is also referred to as a distributed coordination function (DCF) of IEEE 802.11 MAC, and basically adopts a "listen before talk" access mechanism. According to this type of access mechanism, an AP and / or a STA can perform an explicit channel assessment (CCA) of sensing a wireless channel or medium during a predetermined time interval (e.g., a DCF interframe space (DIFS)) before starting transmission. As a result of sensing, if it is determined that the medium is in an idle state, a frame transmission is started through the corresponding medium. On the other hand, if it is detected that the medium is occupied or busy, the corresponding AP and / or STA does not start its own transmission, and can set a delay period (e.g., a random backoff period) for medium access and attempt frame transmission after waiting. By applying the random backoff period, since a plurality of STAs are expected to attempt frame transmission after waiting for different time periods, a collision can be minimized.

[0081] In addition, the IEEE 802.11 MAC protocol provides a hybrid coordination function (HCF). The HCF is based on the DCF and a point coordination function (PCF). The PCF is a polling-based synchronous access method, and refers to a method in which all receiving APs and / or STAs are periodically polled to receive data frames. In addition, the HCF has an enhanced distributed channel access (EDCA) and an HCF controlled channel access (HCCA). The EDCA is a contention-based access method that provides data frames to a plurality of users, and the HCCA uses a non-contention-based channel access method using a polling mechanism. In addition, the HCF includes a medium access mechanism for improving the QoS (quality of service) of a wireless LAN, and can transmit QoS data in a contention period (CP) and a contention free period (CFP).

[0082] Reference Figure 4An operation based on a random backoff period will be described. When the occupied / busy medium becomes an idle state, a plurality of STAs can attempt to transmit data (or frames). As a method of minimizing collisions, each of the STAs can respectively select a random backoff count, and attempt transmission after waiting for a corresponding slot time. The random backoff count has a pseudo-random integer value, and can be determined as one of values ranging from 0 to CW. Here, CW is a contention window parameter value. The CW parameter is given a CWmin as an initial value, but can take a value twice as large in the case of transmission failure (for example, when an ACK is not received for a transmitted frame). When the CW parameter value reaches CWmax, data transmission can be attempted while maintaining the CWmax value until data transmission is successful, and when data transmission is successful, the CWmin value is reset. The values of CW, CWmin, and CWmax are preferably set to 2n-1 (n=0, 1, 2,...).

[0083] When the random backoff process starts, the STA continuously monitors the medium according to the determined backoff count value for the backoff slot countdown. When the medium is monitored for occupation, it stops the countdown and waits, and when the medium becomes idle, it restarts the remaining portion of the countdown.

[0084] In the example of FIG. 3, Figure 4 When a packet to be transmitted arrives at the MAC of STA 3, STA 3 can transmit a frame immediately after confirming that the medium is idle for a DIFS. The remaining STAs monitor and wait for the medium to be occupied / busy. Meanwhile, data to be transmitted can also occur in each of STA 1, STA 2, and STA 5, and when the medium is monitored to be idle, each STA waits for a DIFS, and then can perform a countdown of a backoff slot according to a random backoff count value selected by each STA. It is assumed that STA 2 selects the smallest backoff count value, and STA 1 selects the largest backoff count value. That is, a case is exemplified in which the remaining backoff time of STA 5 is shorter than that of STA 1 when STA 2 completes the backoff count and starts frame transmission. STA 1 and STA 5 temporarily stop the countdown, and wait while STA 2 occupies the medium. When the occupation of STA 2 ends and the medium becomes idle again, STA 1 and STA 5 wait for a DIFS and restart the stopped backoff count. That is, frame transmission can start after a remaining backoff slot is counted for a remaining backoff time. Since the remaining backoff time of STA 5 is shorter than that of STA 1, STA 5 starts frame transmission. Data to be transmitted can also occur in STA 4 while STA 2 occupies the medium. From the perspective of STA 4, when the medium becomes idle, STA 4 can wait for a DIFS, then can perform a countdown according to a random backoff count value selected by STA 4, and start to transmit a frame. 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 described above, the CSMA / CA mechanism includes virtual carrier sensing in addition to the physical carrier sensing in which the STA directly senses the medium. The virtual carrier sensing aims to compensate for problems that can occur in medium access such as the hidden node problem. For the virtual carrier sensing, the MAC of the STA can use a network allocation vector (NAV). The NAV is a value that indicates to other STAs the remaining time until the medium is available for use by the currently using or entitled STA. Thus, the value set to the NAV corresponds to the period in which the STA that transmits the frame plans to use the medium, and during the corresponding period, the STA that receives the NAV value is prohibited from accessing the medium. The NAV can be configured, for example, based on the value of the "Duration" field of the MAC header of the frame.

[0089] In Figure 5 the example, it is assumed that STA1 intends to transmit data to STA2, and STA3 is in a position capable of overhearing some or all of the frames transmitted and received between STA1 and STA2.

[0090] To reduce the possibility of transmission collision of multiple STAs in the CSMA / CA-based frame transmission operation, a mechanism using RTS / CTS frames can be applied. In Figure 5 the example, when the transmission of STA1 is being performed, it can be determined that the medium is in an idle state as a result of the carrier sensing of STA3. That is, STA1 can correspond to a hidden node with respect to STA3. Alternatively, in Figure 5 the example, it can be determined that the medium is in an idle state as a result of the carrier sensing of STA3 when the transmission of STA2 is being performed. That is, STA2 can correspond to a hidden node with respect to STA3. By exchanging the RTS / CTS frames before the data transmission and reception between STA1 and STA2, the STA outside the transmission range of one of STA1 or STA2 or the STA outside the carrier sensing range of the transmission of STA1 or STA3 can not attempt to occupy the channel during the data transmission and reception between STA1 and STA2.

[0091] Specifically, STA1 can determine whether the channel is being used through carrier sensing. In terms of the physical carrier sensing, STA1 can determine the channel occupancy idle state based on the energy level or signal correlation detected in the channel. In addition, in terms of the virtual carrier sensing, STA1 can determine the channel occupancy state using a network allocation vector (NAV) timer.

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

[0093] If the STA 3 cannot overhear the CTS frame from the STA 2 but can overhear the RTS frame from the STA 1, the STA 3 can set the NAV timer for the frame transmission period (e.g., SIFS + CTS frame + SIFS + data frame + SIFS + ACK frame) thereafter using the duration information included in the RTS frame. Alternatively, if the STA 3 can overhear the CTS frame from the STA 2, the STA 3 can set the NAV timer for the frame transmission period (e.g., SIFS + data frame + SIFS + ACK frame) thereafter using the duration information included in the CTS frame, although the STA 3 cannot overhear the RTS frame from the STA 1. That is, if the STA 3 can overhear one or more of the RTS frame or the CTS frame from one or more of the STA 1 or the STA 2, the STA 3 can set the NAV accordingly. When the STA 3 receives a new frame before the NAV timer expires, the STA 3 can update the NAV timer using the duration information included in the new frame. The STA 3 does not attempt channel access until the NAV timer expires.

[0094] When the STA 1 receives the CTS frame from the STA 2, the STA 1 can transmit a data frame to the STA 2 after SIFS from the time point at which reception of the CTS frame is completed. When the STA 2 successfully receives the data frame, the STA 2 can transmit an ACK frame to the STA 1 after SIFS as a response to the data frame. When the NAV timer expires, the STA 3 can determine whether the channel is being used through carrier sensing. When the STA 3 determines that the channel is not being used by other terminals during DIFS after the NAV timer expires, the STA 3 can attempt channel access after a contention window (CW) according to random backoff has passed.

[0095] Figure 6 is a diagram for explaining an example of a frame structure used in a WLAN system to which the disclosure can be applied.

[0096] The PHY layer can prepare a MAC PDU (MPDU) to be transmitted by means of an instruction or primitive (meaning a set of instructions or parameters) from the MAC layer. For example, when a command requesting start of transmission of the PHY layer is received from the MAC layer, the PHY layer switches to a transmission mode, and configures information (e.g., data) provided from the MAC layer in the form of a frame and transmits it. In addition, when the PHY layer detects a valid preamble of a received frame, the PHY layer monitors a header of the preamble, and transmits a command informing start of reception of the PHY layer to the MAC layer.

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

[0098] A basic PPDU can include a short training field (STF), a long training field (LTF), a signal (SIG) field, and a data (Data) field. The most basic PPDU format (e.g., non-HT (high throughput) as shown in FIG. 1A) can consist of only a legacy-STF (L-STF), a legacy-LTF (L-LTF), a legacy-SIG (L-SIG) field, and a data field. In addition, depending on the type of PPDU format (e.g., HT mixed format PPDU, HT greenfield format PPDU, VHT (very high throughput) PPDU, etc.), an additional (or different type of) RL-SIG, U-SIG, non-legacy SIG field, non-legacy STF, non-legacy LTF (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) can be included between the L-SIG field and the data field. Figure 7

[0099] The STF is a signal for signal detection, automatic gain control (AGC), diversity selection, accurate time synchronization, etc., and the LTF is a signal for channel estimation and frequency error estimation. The STF and the LTF can be referred to as signals for synchronization and channel estimation of an 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 the L-SIG field can include a 4-bit rate field, a 1-bit reserved bit, a 12-bit length field, a 1-bit parity check field, and a 6-bit tail field. The RATE field can include information about the modulation and coding rate of 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 as a multiple of 3. For example, for HE PPDUs, the value of the length field can be determined as a multiple of 3+1 or a multiple of 3+2.

[0101] ​The data field can include a service (SERVICE) field, a physical layer service data unit (PSDU), and a PPDU tail bit, and padding bits if necessary. Some bits of the service field can be used for synchronization of a descrambler at a receiving end. The PSDU corresponds to a MAC PDU defined in a MAC layer, and can include data generated / used in an upper layer. The PPDU tail bit can be used to return an encoder to a 0 state. The padding bits can be used to adjust the length of the data field by a predetermined unit.

[0102] A MAC PDU is defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a frame check sequence (FCS). A MAC frame can consist of a MAC PDU and be transmitted / received through a PSDU of a data part of a PPDU format.

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

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

[0105] Figure 7 is a diagram illustrating an example of a PPDU defined in an IEEE 802.11 standard to which the disclosure can be applied.

[0106] In standards such as IEEE 802.11a / g / n / ac / ax, various types of PPDUs have been used. A 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 (as Figure 7 indicated in (a) of FIG. 1).

[0107] Compared to the basic PPDU format, the HT PPDU format (IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT fields. Figure 7The HT PPDU format shown in (b) 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 7The EHT MU PPDU in (e) corresponds to a PPDU carrying one or more data (or PSDU) for one or more users. That is, the EHT MU PPDU can be used for both SU transmission and MU transmission. For example, the EHT MU PPDU can correspond to a PPDU for one receiving STA or multiple receiving STAs.

[0112] In comparison with the EHT MU PPDU, Figure 7 The EHT TB PPDU in (f) omits the EHT-SIG. The STA receiving the trigger (e.g., trigger frame or triggered response schedule (TRS)) for UL MU transmission can perform the UL transmission based on the EHT TB PPDU format.

[0113] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal Signal), EHT-SIG field can be encoded and modulated such that even legacy STAs can attempt to demodulate and decode, and can be mapped based on the determined subcarrier frequency spacing (e.g., 312.5 kHz). These can be referred to as pre-EHT modulation fields. Next, the EHT-STF, EHT-LTF, data, PE field can be encoded and modulated to be demodulated and decoded by STAs that successfully decoded the non-legacy SIG (e.g., U-SIG and / or EHT-SIG) and obtained the information included in the field, and can be mapped based on the determined subcarrier frequency spacing (e.g., 78.125 kHz). These can be referred to as EHT modulation fields.

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

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

[0116] The U-SIG can be constructed in units of 20 MHz. For example, if an 80 MHz PPDU is constructed, the U-SIG can be duplicated. That is, the same 4 U-SIGs can be included in the 80 MHz PPDU. A PPDU that exceeds the 80 MHz bandwidth can include a different U-SIG.

[0117] For example, A unencoded bits can be transmitted through the U-SIG, a first symbol (e.g., U-SIG-1 symbol) of the U-SIG can transmit a first X bits of information out of a total of A bits of information, and a second symbol (e.g., U-SIG-2 symbol) of the U-SIG can transmit a remaining Y bits of information out of the total of A bits of information. The A bits of information (e.g., 52 unencoded bits) can include a CRC field (e.g., 4-bit long field) and a tail field (e.g., 6-bit long field). For example, the tail field can be used to terminate a trellis structure of a convolutional decoder and can be set to 0.

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

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

[0120] For example, the version-independent bits of the U-SIG can include a 3-bit physical layer version identifier (PHY version identifier), and this information can indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted / received PPDU. The version-independent bits of the U-SIG can include a 1-bit UL / DL flag field. A first value of the 1-bit UL / DL flag field is related to UL communication, and a second value of the UL / DL flag field is related to DL communication. The version-independent bits of the U-SIG can include information on the length of a transmit opportunity (TXOP) and information on a BSS color ID.

[0121] For example, the version-dependent bits of the U-SIG can include information directly or indirectly indicating the type of the 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 can further include information on a bandwidth, information on an MCS technique applied to a non-legacy SIG (e.g., EHT-SIG or UHR-SIG, etc.), information indicating whether a DCM (Dual Carrier Modulation) technique (e.g., a technique for achieving an effect similar to frequency diversity by reusing the same signal on two subcarriers) is applied to the non-legacy SIG, information on the number of symbols for the non-legacy SIG, information on whether the non-legacy SIG is generated across the entire frequency band.

[0123] Some of the information required for PPDU transmission and reception can be included in the U-SIG and / or the non-legacy SIG (e.g., EHT-SIG or UHR-SIG, etc.). For example, information on the type of the non-legacy LTF / STF (e.g., EHT-LTF / EHT-STF or UHR-LTF / UHR-STF, etc.), information on the length of the non-legacy LTF and the CP (Cyclic Prefix) length, information on the GI (Guard Interval) applicable to the non-legacy LTF, information on the preamble puncturing applicable to the PPDU, information on the resource unit (RU) allocation, etc. can be included only in the U-SIG, only in the non-legacy SIG, or can be indicated by a combination of the information included in the U-SIG and the information included in the non-legacy SIG.

[0124] Preamble puncturing can denote transmission of a PPDU in which there is no signal in one or more frequency units among 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, the preamble puncturing can be applied to a PPDU bandwidth of a predetermined size or more.

[0125] In Figure 7In an example of the HE-SIG-B and the EHT-SIG, a non-legacy SIG such as the HE-SIG-B and the EHT-SIG can include control information for a receiving STA. The non-legacy SIG can be transmitted over at least one symbol, and one symbol can have a length of 4 µs. Information about a number of symbols for the EHT-SIG can be included in a previous SIG (e.g., the HE-SIG-A, the U-SIG, etc.).

[0126] The non-legacy SIG such as the HE-SIG-B and the EHT-SIG can include a common field and a user-specific field. The common field and the user-specific field can be encoded separately.

[0127] In some cases, the common field can be omitted. For example, in a compressed mode applying non-OFDMA (orthogonal frequency division multiple access), the common field can be omitted, and multiple STAs can receive a PPDU (e.g., a data field of the PPDU) through the same frequency band. In a non-compressed mode applying OFDMA, multiple users can receive a PPDU (e.g., a data field of the PPDU) through different frequency bands.

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

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

[0130] An RU can include a plurality of subcarriers (or tones). The RU can be used when a signal is transmitted to a plurality of STAs based on an OFDMA technology. In addition, the RU can be defined even when a signal is transmitted to one STA. A non-legacy STF, a non-legacy LTF, and a data field can be allocated resources in units of the RU.

[0131] An RU of an applicable size can be defined according to a PPDU bandwidth. An RU can be defined identically or differently for an applied PPDU format (e.g., HE PPDU, EHT PPDU, UHR PPDU, etc.). For example, in the case of an 80 MHz PPDU, the RU layout of an HE PPDU and an EHT PPDU can be different. An applicable RU size per PPDU bandwidth, a number and a location of RUs, a DC (direct current) subcarrier location and number, a null subcarrier location and number, a guard subcarrier location and number, etc. can be referred to as a tone plan. For example, a tone plan for a high bandwidth can be defined in the form of multiple iterations of a low bandwidth tone plan.

[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, 2x996-tone RUs, 3x996-tone RUs, etc. An MRU (multi-RU) is different from a plurality of individual RUs and corresponds to a group of subcarriers consisting of a plurality of RUs. For example, one MRU can be defined as 52+26-tone, 106+26-tone, 484+242-tone, 996+484-tone, 996+484+242-tone, 2x996+484-tone, 3x996-tone, or 3x996+484-tone. In addition, the plurality of RUs constituting one MRU can be continuous or can not be continuous in the frequency domain.

[0133] A specific size of an RU can be reduced or expanded. Accordingly, a specific size (i.e., a number of corresponding tones) of each RU in the disclosure is not restrictive but illustrative. In addition, in the disclosure, the number of RUs can vary according to an 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 of are exemplary, and the scope of the disclosure is not limited by the names. In addition, examples of the disclosure can be applied to the PPDU format shown in and a new PPDU format that excludes some fields and / or adds some fields based on the PPDU format of Figure 7 . Multi-link operation .

[0135] Figure 8

[0136] Hereinafter, a multi-link (ML) operation supported by a STA according to the disclosure is described.

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

[0138] When one STA supports multiple links, the transmitting or receiving apparatus that supports each link can operate like one logical STA. That is, an MLD refers to an apparatus that has one or more affiliated STAs as logical entities and a single MAC service access point (SAP) for one MAC data service and logical link control (LLC). A non-AP MLD refers to an MLD for which each STA affiliated to the MLD is a non-AP STA. A multi-radio non-AP MLD refers to a non-AP MLD that supports receiving or exchanging frames in more than one link at a time. An AP MLD refers to an MLD for which each STA affiliated to the MLD is an AP STA.

[0139] Multi-link operation (MLO) can enable a non-AP MLD to discover, authenticate, and associate with an AP MLD and establish multiple links with the AP MLD. Based on supported capabilities exchanged during an association procedure, each link can enable channel access and frame exchange between the non-AP MLD and the AP MLD. A STA affiliated to an MLD can select and manage its capabilities and operating parameters independently of other STAs affiliated to the same MLD.

[0140] Through the multi-link setup procedure, the AP MLD and / or the non-AP MLD can send and receive link-related information that the MLD can support. The link-related information can 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 the UL / DL links, information about the frame types (e.g., management, control, data) that are available or preferred in at least one UL / DL link, information about the ACK policy that is available or preferred in at least one UL / DL link, or information about the traffic identifiers (TIDs) that are available on at least one UL / DL link.

[0141] The AP MLD (e.g., NSTR mobile AP MLD) can configure one of the multiple links as a primary link. The AP MLD can only transmit beacon frames, probe response frames, and group-addressed data frames on the primary link. The remaining links in the multiple links can be referred to as non-primary links. The AP MLD operating on the non-primary links can operate not to transmit beacon frames or probe response frames. In addition, the non-AP MLD can only perform authentication, (re)association, and frame exchange during the 4-way handshake on the primary link.

[0142] If at least one traffic identifier (TID) is mapped to a link through the multi-link setup procedure, the established link is defined as enabled, and if no TID is mapped to a link, the established link can be defined as disabled. Unless admission control is used, a TID must always be mapped to at least one established link. By default, a TID is mapped to all established links, so all established links can be enabled.

[0143] When a link is enabled, the link can be used for frame exchange depending on the power state of the non-AP STA operating on the link. Only MSDUs or A-MSDUs with TIDs mapped to the enabled link can be transmitted in the link. Management and control frames can only be transmitted on the enabled link.

[0144] When a link is disabled, the link can not be used for frame exchange, including management frames for both DL and UL.

[0145] During the multi-link setup procedure, the enable / disable of each link can be indicated through TID-to-link mapping. The TID-to-link mapping can be performed in a default mapping mode or / and a negotiated mapping mode.

[0146] One of the STAs affiliated to the MLD can provide information about one or more links other than the link on which it is located, for multi-link discovery (e.g., obtaining information about multiple links including the corresponding link on one link) or multi-link setup (e.g., associating on multiple links simultaneously through the exchange of association request / response frames on one link). A multi-link (ML) element can be defined to provide this information.

[0147] Figure 8 An exemplary structure to which the ML element of the present disclosure can be applied is illustrated.

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

[0149] The multi-link control field is defined to be 2 octets in size, and can include a 3-bit type subfield, a 1-bit reserved bit, and a 12-bit presence bitmap subfield. The type subfield can have a value indicating one of the following types: basic, probe request, reconfiguration, tunnel direct link setup (TDLS), and priority access. The presence bitmap subfield indicates whether various subfields are present within the common information field, and can be defined in different formats according to various variants (or types) of the ML element.

[0150] The common information field is defined to have a variable size, and can include a 6-octet MLD MAC address subfield, and this subfield can have a value specifying the MAC address of the MLD to which the STA that transmits the basic ML element belongs. In addition, a link ID information subfield, a BSS parameter change count subfield, a medium synchronization delay information subfield, an enhanced multi-link (EML) capability subfield, an MLD capability subfield, etc. can or can 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 the link information field is present, it can include one or more sub-elements. The format and order of the sub-elements can be defined in various ways. As an example of the optional sub-element ID for the basic variant ML element, the value 0 of the sub-element ID corresponds to the name of the per-STA profile and is extensible, and the value 221 corresponds to the name of the 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 can include a 1-octet sub-element ID subfield, a 1-octet length subfield, a 2-octet STA control subfield, a variable size STA information subfield, and a variable size STA profile subfield. The STA control subfield can include information such as a link ID, whether a full profile is included, whether a STA MAC address is present, etc. The STA information subfield can include information such as a STA MAC address. The STA profile subfield can include information included in a probe response or probe request frame body, information included in an (re)association response or (re)association request frame body, etc., depending on whether the reporting STA is an AP STA or a non-AP STA.

[0153] Figure 9 The format of the ML element in is exemplary and can change the order, name, size, etc. of the fields / subfields, can further define additional fields / subfields, and can not include some fields / subfields. In short, the common information field can include common information among STAs in the MLD, and the link information field can include specific information for each STA / link (e.g., in each STA profile sub-element including a link ID corresponding to a STA).

[0154] Figure 9 is a diagram illustrating an example of a high-level structure for an AP MLD to which the present disclosure can apply.

[0155] An AP MLD can include one or more APs. The AP MLD can have a high-level architecture as shown in MLD based roaming For example, the MLD can use an upper layer MAC sublayer to control various procedures / parameters common to multiple APs. For example, authentication, association, sequence number (SN) / packet number (PN) allocation, power save buffering for individually addressed frames, etc. can be controlled commonly among APs affiliated 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.). The AP MLD can provide upper layer MAC sublayer functionality for MLD data frames (e.g., traffic sent and received with MLD STAs) and provide 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 MLO and non-MLO operations can be performed on links (e.g., link 1, …, link n) corresponding to each PHY.

[0157] Figure 10

[0158] Before describing the MLD-based roaming according to the disclosure, the procedure in which a non-AP STA moves or roams from one AP in an existing wireless LAN system to another (e.g., BSS transition) is first described.

[0159] Figure 10 is a diagram for explaining the BSS transition in the existing wireless LAN system.

[0160] In the case of the FT (Fast BSS Transition) method, which is a representative example of the BSS transition (or roaming), various procedures such as authentication request / response and re-association request / response are required between an FTO (FT initiator) and a target FTR in order to move from a current FTR (FT responder) to the target FTR. That is, in the existing BSS transition method, a re-association procedure is required on the same mobility domain.

[0161] In addition, after the procedure exemplified in Figure 9 , various operation parameters such as agreements related to BA (Block Ack) or SCS (Service Classification Service), SN, EDCAF (EDCA function) parameters, etc. are reset. Therefore, the FTO must perform a large number of frame exchanges for the FT, and must perform agreements / configurations with the new FTR again. Therefore, the complexity and overhead of the FT procedure are high, and data loss can occur during the FT procedure. As such, it is difficult to provide seamless roaming to the STA in the existing wireless LAN system.

[0162] The disclosure describes an example for MLD-based seamless roaming. For example, based on the AP MLD function described by referring to Figure 11 , when a non-AP STA moves / roams between entities attached to a single MLD, the MLD level parameters / configurations / agreements can be maintained without being reset.

[0163] In the following description, the STA performing roaming is referred to as an RSTA, the currently associated AP is referred to as an OAP (old AP) or a first AP (or AP 1), and the AP to be newly associated is referred to as an NAP (new AP) or a second AP (or AP 2). In addition, the newly proposed MLD-based roaming in the disclosure can be simply referred to as MLD roaming.

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

[0165] For example, the 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, the OAP can be an AP STA affiliated with the AP MLD 1, and other APs than the OAP can be affiliated with the AP MLD 1.

[0167] For example, the NAP can be an AP STA affiliated with the AP MLD 2, and other APs than the NAP can be affiliated with the AP MLD 2.

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

[0169] Further, considering a non-AP MLD, at least one OAP affiliated with the AP MLD 1 can be affiliated with an upper layer MLD, and at least one NAP affiliated with the AP MLD 2 can be affiliated with the same upper layer MLD. For example, MLD-based roaming from a plurality of OAPs to a plurality of NAPs can be performed.

[0170] Hereinafter, a procedure for performing MLD-based roaming of a STA is described in detail.

[0171] Figure 11 is a diagram illustrating an example of a method for performing MLD-based roaming of a first STA according to the disclosure. In Figure 12 and Figure 9 The first STA can be affiliated with a non-AP MLD in and. Further, the first STA can be associated with a first AP affiliated with a first (AP) group to transmit and receive data.

[0172] The first STA can receive, from a first access point (AP) affiliated with the first group, announcement information including first information related to whether to support addition of at least one link for the first STA (S1110).

[0173] Here, the announcement information can be included in an MLD-based roaming element or a reduced neighbor report (RNR) element included in a management frame. The MLD-based roaming element or the RNR element can include a first subfield related to at least one group ID and a second subfield related to first information (e.g., a temporary link addition subfield).

[0174] For example, based on the first information, it is indicated through the second subfield that at least one link is supported for the first STA to add, the first STA can add a link with another AP while maintaining a link with the first AP.

[0175] The first STA can transmit a request frame including a link ID of the second AP affiliated to the second group to the first AP (S1120).

[0176] That is, the first STA can transmit a request frame for the first AP to request MLD-based roaming to the second AP affiliated to the first group to the first AP. The request frame can include a group ID associated with the second group to which the second AP is affiliated.

[0177] For example, group 1 and group 2 can be affiliated to the same AP MLD. In order to roam from the first AP included in group 1 to the second AP included in group 2, the first STA can transmit a first request frame to the first AP.

[0178] In another example of the disclosure, each of the first group and the second group 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 the disclosure, each group can be represented by a separate AP MLD. In addition, the first AP MLD and the second AP MLD can be affiliated to a separate group entity (or the entire AP MLD). The group entity (or the entire AP MLD) can be collectively referred to as a specific entity to which each AP MLD is affiliated.

[0179] The group object can correspond to Figure 13 , Figure 18 and Figure 9 the (entire) AP MLD as shown in Figure 11 For example, the group object can perform the functions of the upper MAC sublayer of the MLD described with reference to

[0180] For example, the request frame can include second information requesting to add or delete a link between the first STA and the second AP. In addition, the request frame can include third information about whether the addition or deletion of the link between the first STA and the second AP is a temporary link addition or deletion.

[0181] For example, the second information and the third information can be indicated via a single subfield included in a reconfiguration multi-link element of the request frame. For example, the second information and the third information can be indicated via a single subfield disclosed in Table 2, which will be described later.

[0182] As another example, the common information field or the STA control field of the reconfiguration multi-link element can include a third subfield (e.g., a type subfield) related to the second information and a fourth subfield (e.g., a temporary subfield) related to the third information. That is, the second information and the third information can each be indicated by a separate subfield.

[0183] For example, based on requesting a link addition between the first STA and the second AP via the third subfield and the fourth subfield (e.g., based on information indicating a request for a link addition between the first STA and the second AP by the third subfield and information indicating a request for a temporary link addition or deletion by the fourth subfield), the link between the first STA and the second AP can be connected at the same time as the link between the first STA and the first AP is connected.

[0184] The first STA can receive a response frame including a link ID of the second AP from the first AP (S1130).

[0185] Based on the fact that the response frame includes information indicating that the roaming to the second AP is accepted, an association procedure between the first STA and the second AP can be initiated. In addition, the response frame can include a basic ML element, and the basic ML element can include an AID for the first STA and traffic identifier-to-link mapping information.

[0186] Based on the completion of the roaming procedure to the second AP (e.g., the completion of the association procedure between the first STA and the second AP), the link between the first STA and the first AP can be deleted.

[0187] As an example of the disclosure, a roaming procedure of a second STA attached to a non-AP MLD can be performed at the same time as a roaming procedure of a first STA is being performed. That is, a roaming procedure of another STA attached to a non-AP MLD can be performed when a roaming procedure of a first STA is being performed / completed. As another example of the disclosure, a roaming procedure of a second STA can be performed at the same time as a roaming procedure of a first STA is being performed. That is, each of a first STA and a second STA attached to a non-AP MLD can perform a roaming procedure at the same time. As another example, each STA attached to a non-AP MLD can perform a roaming procedure regardless of the order.

[0188] As another example, the response frame can include fourth information related to a multi-link device (MLD) roaming timer. After transmitting the response frame, the MLD roaming timer can start running. Based on expiration of the MLD roaming timer, the link between the first STA and the first AP can be deleted, and the first STA can communicate with an associated second AP.

[0189] In an example described above, the method performed by the first STA can be performed by a first device (100) of Figure 1 In an example described above, the method performed by the first STA can be performed by a first device (100) of Figure 1 For example, one or more processors (102) of the first device (100) can receive, from a first AP affiliated with a first group, advertisement information including first information related to whether to support addition of at least one link for the first STA through one or more transceivers (106). The one or more processors (102) can transmit, to the first AP, a request frame including a link ID of a second AP affiliated with a second group through the one or more transceivers (106). The one or more processors (102) can receive, from the first AP, a response frame including the link ID of the second AP through the one or more transceivers (106). Figure 11

[0190] The above-described memory (104) can store instructions for performing the method described in the example of Figure 12 when executed by the one or more processors (102).

[0191] Figure 12 is a diagram illustrating an example of a method of a first AP supporting MLD-based roaming of a STA according to the present disclosure.

[0192] The first AP can transmit, to a first STA affiliated with a first group, advertisement information including first information related to whether to support addition of at least one link for the first STA (S1210). That is, the first AP can transmit, to the first STA, advertisement information including a parameter related to MLD-based roaming and information on whether to support simultaneous connection of two or more links of the first STA.

[0193] The first AP can receive, from the first STA, a request frame including a link ID of a second AP affiliated with a second group (S1220). The request frame can include the link ID of the second AP and a group ID associated with the second group to which the second AP is affiliated. The AP can identify, through the link ID and the group ID, the AP to which the first STA intends to roam.

[0194] In addition, the first AP can confirm, through the request frame, that the first STA requests connection of a (temporary) additional link with the second AP.

[0195] ​The first AP can transmit, to the first STA, a response frame including the link ID of the second AP (S1230). The first AP can transmit, to the first STA, a response frame containing information about roaming between the first STA and the second AP. Accordingly, the (temporary) link between the first STA and the second AP can be additionally connected. In addition, an association procedure between the first STA and the second AP can be initiated through the response frame.

[0196] In Figure 1 the examples described by the method performed by the first AP can be performed by the second apparatus (200) of Figure 1 For example, Figure 10 The one or more processors (202) of the second apparatus (200) of

[0197] In addition, the one or more memories (204) of the second apparatus (200) can store instructions to perform the method described in the examples of Figure 11 when executed by the one or more processors (202).

[0198] Figure 12 and Figure 11 The examples of Figure 12 and Embodiment 1 may correspond to some of the various examples of the present disclosure. Below, the various examples of the present disclosure will be described in more detail, including

[0199] Figure 13

[0200] Embodiment 1 describes exemplary operations of a STA and an AP for MLD-based roaming. As an example of the present disclosure, Figure 13 is a diagram illustrating an example of a structure and procedure for MLD-based roaming according to the present disclosure.

[0201] As Figure 13As shown, AP 1, AP 2, and AP 3 can belong to AP group 1, and AP 4 and AP 5 can belong to AP group 2. Each AP group can not be collocated, and the APs belonging to each AP group can be collocated at the same or similar location. Each AP being collocated can include not only the case where each AP belongs to the same device, but also the case where each AP is collocated at a logically similar location (even if it does not belong to the same device).

[0202] Since the AP MLD is a logical entity, it can be implemented as a specific physical device, but it refers to an MLD that covers the belonging APs regardless of the location and performs / applies MLO. In other words, all the APs belonging to an AP group can include the belonging APs of one AP MLD.

[0203] As an example of the present disclosure, as Figure 13 As shown, it is assumed that a non-AP MLD performs multi-link setup with an AP MLD, and STA 1 and STA 2 are each connected to AP 2 and AP 3 included in AP group 1. When the non-AP MLD moves to an area where AP group 2 exists, it can be necessary to roam from AP group 1 to AP group 2. That is, by roaming, STA 1 can be connected to AP 4, and STA 2 can be connected to AP 5. Here, during the roaming process, STA 1 and STA 2 can be temporarily associated with AP 4 and AP 5, respectively, so that AP 4 and AP 5 can transmit frames to STA 1 and STA 2, respectively.

[0204] Here, the non-AP MLD can include a plurality of belonging STAs, or can include one STA. Embodiment 1-1 The roaming operation / architecture shown can be applied to a non-AP MLD including one or more belonging STAs, and the roaming operation / architecture can also be applied to a non-AP STA that does not form an MLD.

[0205] In describing the present disclosure, roaming can be applied not only to movement between groups, but also to movement between APs within a specific AP group. In addition, MLD-based roaming according to the present disclosure can be performed by changing the link while maintaining the ML setup without tearing down the existing ML setup. For example, while maintaining the ML setup of the upper MLD for AP 1 and AP 2, the STA MLD can move from AP group 1 to AP group 2 by changing the link within the upper MLD. Therefore, compared to the existing BSS transition, the overhead and the risk of data loss can be reduced.

[0206] The MLD-based roaming procedure can include AP group ID setting (implementation 1-1), AP advertisement (implementation 1-2), and frame exchange between the AP and the STA (request of implementation 1-3 and response of implementation 1-4).

[0207] An ID can be assigned / set for each AP group (consisting of APs deployed at the same location). In the present disclosure, the ID assigned / set for each AP group will be referred to as a group ID. For example, the group ID can be set as a unique ID within a single AP group. For another example, the group ID can be set as a unique ID for each AP group within the entire AP MLD.

[0208] The advertisement can correspond to a procedure in which each AP affiliated to an upper layer MLD informs a STA of information such as whether MLD-based roaming is supported. Frame exchange between the STA and the AP can be performed based on the advertisement information.

[0209] The frame exchange can correspond to a procedure of transmitting and receiving a frame that triggers / initiates MLD-based roaming between the AP and the STA. Through the frame exchange, information and settings required for MLD-based roaming can be negotiated between the AP and the STA, and MLD-based roaming can be completed based on the negotiated information / settings. Accordingly, the STA can no longer operate with an OAP (old AP) (e.g., an AP included in AP group 1) and can operate with an NAP (new AP) (e.g., an AP included in AP group 2).

[0210] In this way, in order to trigger / initiate MLD-based roaming, frame exchange is required between the STA and the AP. The exchanged frame can correspond to a management frame (e.g., a beacon, an (re)association request / response, a probe request / response, an action frame, etc.). For example, an action frame, which is one type of management frame, can be used for frame exchange.

[0211] In the examples described below, a frame transmitted by a STA (or an AP) to an AP (or a STA) to request MLD roaming is referred to as an MLD roaming request frame, and a frame transmitted by an AP (or a STA) to a STA (or an AP) in response to an MLD roaming request frame is referred to as an MLD roaming response frame.

[0212] Hereinafter, specific examples of a procedure for setting a group ID for each AP group, a procedure for requesting information about an AP within each AP group, a notification procedure for MLD-based roaming, and a frame exchange procedure are described.

[0213] In addition, a method for temporarily adding / deleting a link for MLD-based roaming is described. Accordingly, the STA can maintain two links for a certain period of time when performing MLD-based roaming.

[0214] Embodiment 1-1-1

[0215] Embodiment 1-1 relates to a procedure for setting a group ID for each AP group. A mobile MLD (or STA) can need to identify at least one AP it is connected to among AP MLDs to perform roaming. In addition, when the MLD (or STA) requests roaming, depending on which NAP the MLD (or STA) is moving to, the AP MLD can check data and management information to be transmitted from the OAP to the NAP. Accordingly, Embodiment 1-1 describes an identification method considering the affiliated APs within the AP MLD that are not arranged at the same location (i.e., a method for setting an ID for roaming in the AP MLD).

[0216] An ID (i.e., a group ID) can be assigned to a group of APs collocated at the same location. For example, a unique group ID can be set within an AP group (Embodiment 1-1-1). As another example, a unique ID can be set for each AP group within the entire AP MLD (Embodiment 1-1-2).

[0217] Embodiment 1-1-2

[0218] Embodiment 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 one AP group.

[0219] As an example of the present disclosure, the group ID can be set as an integer greater than or equal to 0. For example, if a field indicating the group ID consists of 4 bits, the group ID can be set as one of 0 to 15. As another example, if a field indicating the group ID consists of 8 bits, the group ID can be set as one of 0 to 127.

[0220] For example, if the group ID is 0, the AP having the group ID can be affiliated to the same AP group deployed at the same location. That is, the MLD (or STA) can determine that the AP having the group ID is deployed at the same location. Other group IDs can be mapped so that they can be uniquely identified to each group.

[0221] In addition, since other APs (e.g., a transmitted BSSID (i.e., TxBSSID) or a non-transmitted BSSID (nonTxBSSID)) in the set of multiple BSSIDs to which each AP in the AP group belongs also use the same physical resource, the same group ID can be assigned to the other APs. However, the AP MLD ID of the AP MLD to which the other APs belong can be different.

[0222] Embodiment 1-2

[0223] Embodiment 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.

[0224] As described above, the group ID can be set as an integer greater than or equal to 0. For example, if a field indicating the group ID consists of 4 bits, the group ID can be set as one of 0 to 15. As another example, if a field indicating the group ID consists of 8 bits, the group ID can be set as one of 0 to 127.

[0225] In addition, the group ID of the AP performing roaming can be set. That is, an MLD roaming ID for MLD roaming can be set between APs having a corresponding group ID.

[0226] The existing MDID (Mobile Domain ID) field can be used to set the MLD roaming ID and / or the group ID, but since the MDID field has a size of 2 octets, the MLD roaming ID and / or the group ID can be set in a smaller field.

[0227] Figure 14

[0228] Embodiment 1-2 relates to an announcement procedure for MLD-based roaming based on a group ID.

[0229] Each AP included in the AP MLD can announce whether MLD-based roaming described in the present disclosure is possible and a group ID, etc. For example, each AP can transmit announcement information including information indicating whether roaming is possible (e.g., "MLD roaming enabled"), a group ID, an MLD roaming ID, and / or temporary link addition / deletion information. The information indicating whether roaming is possible can consist of 1 bit, but is not limited thereto. In addition, the group ID refers to a group ID of an AP group constituting the AP MLD as described above. That is, APs having the same group ID can belong to the same AP group.

[0230] The announcement information can be transmitted via a management frame (e.g., a beacon frame, a probe frame, an (re)association response frame, etc.). For example, it can be included in an MLD roaming information element (IE) containing the announcement information or a reduced neighbor report (RNR) IE.

[0231] For example, the RNR IE can include a target beacon transmission time (TBTT) information header, an operation category, a channel number, and a TBTT information set field. Among these, the TBTT information set can include one or more TBTT information fields. As described above, the TBTT information set can include one or more TBTT information fields. Figure 14As 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] As another example, such as Embodiment 1-3 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.

[0236] Additionally or alternatively, the above notification information may be included in the basic multi-link IE.

[0237] Figure 15

[0238] 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.

[0239] [Table 1]

[0240]

[0241] The category of Sequence 1 can be set to a value indicating a category corresponding to the MLD roaming request frame. For example, the category can 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 having a different name. The UHR action or the protected UHR action of Sequence 2 can be set to a value corresponding to the MLD roaming request.

[0242] The conversation token of Sequence 3 can be set to a value for matching the request and the response.

[0243] The reconfiguration ML element of Sequence 4 corresponds to an element including information required for the MLD-based roaming request. This is exemplary, and an element / field having other names containing information required for the MLD roaming request can be defined and used.

[0244] Figure 15 is a diagram illustrating an example of a reconfiguration ML element including request information according to the disclosure.

[0245] Figure 8 (a) of illustrates an example of a presence bitmap field (e.g., Figure 15 in the multi-link control field in ). The presence bitmap of the reconfiguration ML element can include information on whether the MLD MAC address subfield is present. In addition, the presence bitmap according to the disclosure can indicate, through a specific bit position in the bitmap, whether an enhanced ML (EML) capability subfield is present in the common information field and whether an MLD capability and operation subfield is present in the common information field.

[0246] Figure 8 (b) of illustrates an example of a common information field (e.g., Figure 15 of ). The common information field of the reconfiguration ML element can include a common information length subfield and an MLD MAC address subfield. In addition, the common information field according to the disclosure can include both an EML capability subfield or an MLD capability and operation subfield, one of them, or neither of them (depending on the value at the corresponding bit position of the presence bitmap).

[0247] When more than one STA moving to the NAP (especially, in the case of a non-AP MLD) simultaneously performs MLD-based roaming, the EML capability information / MLD capability and operation information can be different, and thus the information can be provided to the AP as MLD roaming request information.

[0248] Figure 8 (c) of illustrates a link information field (e.g.,Figure 8 STA control (e.g., in each STA profile sub-element of the link info field of the reconfiguration ML element) in the MLD roaming request frame. Figure 15 An example of the STA control field of (a). Figure 8 (d) of (a) shows the STA info (e.g., in each STA profile sub-element of the link info field of the reconfiguration ML element) included in the MLD roaming request frame. Figure 8 An example of the STA info field of (d). Figure 15 An example of the STA info field of (d).

[0249] When more than one STA performs MLD-based roaming at the same time, one or more each STA profile sub-elements can be included in the MLD roaming request frame.

[0250] The presence or absence of each subfield included in the STA info field can be indicated by the presence subfield of the corresponding subfield in the STA control field. For example, the NSTR indication bitmap presence subfield of the STA control field can indicate whether the NSTR indication bitmap subfield is present in the STA info field, and if so, the bitmap size can be indicated by the NSTR bitmap size subfield of the STA control field. For example, the MLD roaming timer presence subfield of the STA control field can indicate whether the MLD roaming timer subfield is present in the STA info field.

[0251] Figure 15 The value of the link ID subfield of the STA control field in (c) of (a) can be set to a link identifier value corresponding to one of the NAPs (e.g., AP 2 affiliated to the AP MLD 2, and if present, other APs affiliated to the AP MLD 2). For example, the link ID subfield of the STA control field of the first each STA profile sub-element can be set to a link identifier value corresponding to AP 2 affiliated to the AP MLD 2, and the link ID subfield of the STA control field of the second each STA profile sub-element can be set to a link identifier value corresponding to another NAP affiliated to the AP MLD 2.

[0252] Figure 15 The full profile of the STA control field of (c) of (a) can correspond to the full information of the STA (i.e., all information included in the (re)association request frame). In the MLD-based roaming procedure, since the new STA is not associated with the AP affiliated to the upper MLD, but the existing STA moves between the APs affiliated to the corresponding upper MLD, it can be considered that the capabilities and operating parameters of the STA, etc. do not change. Considering the case where the upper MLD knows the information of the STA, Figure 8 The full profile subfield of (c) of (a) can be set to a value indicating the profile information (or partial profile information) including the changes.

[0253] 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 15 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).

[0254] 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).

[0255] 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.

[0256] 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.

[0257] 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.

[0258] In addition, it is assumed that a temporary link addition is indicated for the STA (i.e., two or more multi-link connections are supported for the STA for a temporary period of time). In this case, the expiration of the MLD roaming timer can mean that the STA has completely terminated the connection with the OAP (i.e., temporarily deleted or deleted) and connected to the NAP. In this case, the MLD roaming timer can also be used as a deletion timer.

[0259] When the MLD roaming timer is commonly applied to all APs, information about the MLD roaming timer can be included in the common information field. In this case, the presence or absence of the MLD roaming timer can be indicated in the common information field by a presence bitmap.

[0260] A group ID can be added to the Reconfig ML element shown in Embodiment 1-3-1 The group ID refers to the ID of the AP group to which the non-AP MLD (or STA) roams.

[0261] Figure 16

[0262] As an example of the present disclosure, the group ID can be included in the common information field of the Reconfig ML element. Specifically, as shown in (a) of Figure 16 , the presence or absence of the group ID included in the common information field of the Reconfig ML element can be indicated by a presence bitmap of the Reconfig ML element. As shown in (b) of Figure 16 , when the group ID is included only in the common information field, roaming to an AP in an AP group having the same group ID can be requested by the MLD roaming request frame.

[0263] That is, if the group ID is included in the common information field, the 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 common information field, the non-AP MLD (or STA) cannot request roaming to an AP within its current AP group or an AP in an AP group other than the specific AP group. However, when roaming between groups, the method according to Embodiment 1-3-1 can have reduced overhead compared to the case in which the group ID is included in the link information field.

[0264] In addition, the common information field of the Reconfig ML element can include a type subfield as a field for including the capability of temporarily adding / deleting a link for MLD-based roaming.

[0265] As an example of the present disclosure, the type subfield can consist of 2 bits, but is not limited thereto. For example, if the type subfield consists of 2 bits, the type field can be composed as shown in Table 2. However, this is an embodiment, and the type corresponding to the type subfield value can be defined as a different type. In addition, "temporarily deleted" in Table 2 can be replaced with "deleted" corresponding to the type subfield value 1.

[0266] [Table 2]

[0267]

[0268] If "add" is indicated through the type subfield, this can mean that the STA of the non-AP MLD requests an additional link connection with the AP (e.g., NAP) of the specific AP MLD. If "delete" is indicated through the type subfield, this can mean that the STA of the non-AP MLD requests to disconnect the current link (e.g., disconnect the link with the OAP). If "temporarily add" is indicated through the type subfield, this can mean that the STA of the non-AP MLD requests to add a link with another AP (e.g., NAP) other than the AP (e.g., OAP) to which the current link is connected.

[0269] As another example of the present disclosure, as shown in (b) of FIG. 10, Embodiment 1-3-2 As an example, each of the temporary subfield and the type subfield can consist of 1 bit, and the type subfield can indicate "add" or "delete". In addition, the temporary subfield can indicate information about the "add" or "delete" indication of the type subfield that the operation indicated by the type subfield is a temporary operation.

[0270] For example, if "add" is indicated through the type subfield, and information that the operation indicated by the type subfield is a temporary operation is indicated through the temporary subfield, this can correspond to "temporarily add" in Table 2.

[0271] When the type and / or temporary subfield is included in the common information field, the STA included in the non-AP MLD can perform only one operation with respect to all APs. That is, when "add" is indicated through the type and / or temporary subfield, the STA can make a request to add a link with respect to each AP only.

[0272] Figure 16

[0273] As an example of the present disclosure, as shown in (b) of FIG. 10, Figure 16As illustrated in (c) of FIG. 1, the reconfigured ML element can include a link information field, and the link information field can include one or more per STA profile sub-elements. As illustrated in (d) of FIG. 1, a roaming request for a specific AP belonging to a specific AP group can be indicated by a link ID and a group ID included in a STA control field of the per STA profile sub-element. Figure 16 As illustrated in (d) of FIG. 1, a roaming request for a specific AP belonging to a specific AP group can be indicated by a link ID and a group ID included in a STA control field of the per STA profile sub-element.

[0274] Additionally or alternatively, as illustrated in (d) of FIG. 1, the STA control field can include a type and / or temporary sub-field (i.e., the type and / or temporary sub-field described in Embodiment 1-3-1). That is, the type and / or temporary sub-field for temporarily adding / deleting a link 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 sub-field have been described above, redundant descriptions will be omitted. Embodiment 1-3-3

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

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

[0277] Figure 17

[0278] As an example of the present disclosure, as illustrated in (a) of FIG. 1, the STA control field of the per STA profile sub-element includes a group ID present sub-field, and the group ID present sub-field can indicate whether an AP group ID to which an AP corresponding to a specific link ID belongs is present. In addition, as illustrated in (b) of FIG. 1, the group ID can be included in the STA information field or the STA profile field. Figure 17 Embodiment 1-4

[0279] ​​​Roaming can be requested for one or more APs corresponding to one or more group IDs via one or more STA-specific profile sub-elements. Specifically, assume a case in conjunction with the method according to Embodiment 1-3-1, i.e., a method of including a group ID in a common information field. In this case, if roaming is requested for an AP corresponding to the same group ID, the group ID can not be included in the STA information field or the STA profile field, thereby reducing overhead.

[0280] As another example, if a group ID is indicated through a common information field, it can be implicitly indicated that roaming to an AP corresponding to the same group ID is requested. Accordingly, the group ID can not be included in the STA information field or the STA profile field, and a group ID present field can also not be present.

[0281] Figure 8

[0282] Response information for an MLD-based roaming request can be included in a management frame, e.g., an MLD roaming response frame. For example, the MLD roaming response frame can have the exemplary format of Table 3. The format in Table 3 is exemplary, and some fields can be omitted or additional fields not illustrated can be included.

[0283] [Table 3]

[0284]

[0285] The MLD roaming response frame can include a link-level parameter. For example, the link-level parameter can include information necessary to change a link while maintaining an ML setup. A category of order 1 can be set to a value indicating a category corresponding to the MLD roaming response frame. For example, the category can correspond to a new UHR action or a protected UHR action. This is exemplary, and the MLD roaming response frame can also be defined as a category having a name.

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

[0287] A conversation token of order 3 can be set to a value for matching a request and a response.

[0288] A status code of order 4 can be set to one of various values indicating success, failure, accept, reject, not supported, invalid, error, etc. Among the values indicated by the status code, failure, reject, not supported, invalid, error, etc. can be defined different values depending on the cause.

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

[0290] For example, the public information field of the basic ML element can have a format similar to that of the public information field of Figure 8 Here, the public information field of the basic ML element of the MLD roaming response frame can include information common to or corresponding to the NAP through which one or more STAs perform MLD-based roaming.

[0291] For example, the link information field of the basic ML element can basically have a format similar to that of the link information field of Figure 16 Here, when one or more STAs simultaneously perform MLD-based roaming, the link information field of the basic ML element of the MLD roaming response frame can include one or more per-STA profile sub-elements for the corresponding AP. Accordingly, the STA control field, the STA information field, and / or the STA profile field included in the per-STA profile sub-element of the link information field of the basic ML element of the MLD roaming response frame can include the following characteristics.

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

[0293] The full profile of the STA control field can correspond to the full 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 MLD (or roaming MLD), it can be considered that the capabilities or operating parameters of the AP, etc. do not change. In this case, the full profile subfield can be set to a value (e.g., 0) indicating a profile information (or partial profile information) including changes. Accordingly, the STA profile field in the per-STA profile sub-element can include only the changed information field / element (i.e., information changed in the NAP compared to the OAP).

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

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

[0296] The STA control field can include a field indicating whether an MLD roaming timer is present. If the MLD roaming timer is indicated to be present, the STA information field can include an MLD roaming timer subfield. The MLD roaming timer subfield can indicate a time based on which the MLD-based roaming is completed 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 can 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 is changed). For example, if the value of the MLD roaming timer requested by the STA is used as it is and the value of the status code is set to a value indicating success / acceptance, the MLD roaming timer subfield can not be included in the MLD roaming response frame.

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

[0298] In addition, the basic ML element can include a group ID.

[0299] As an example of the present disclosure, the group ID can be included in the common information field of the basic ML element as in Embodiment 1-3-1, and whether the group ID is present in the common information field can be indicated by the presence bitmap subfield of the basic ML element. Thus, the MLD roaming response frame can include information about the APs affiliated to the same AP group having the group ID indicated through the common information field.

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

[0301] Specifically, the link info field of the basic ML element can 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 can include a link ID and a group ID (i.e., an ID of an AP group).

[0302] Information about one or more APs corresponding to one or more group IDs can be provided through the one or more per-STA profile sub-elements. However, when information about APs having the same group ID is provided, the overhead can be greater than the method according to embodiment 1-5-1.

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

[0304] That is, through the group ID presence information of the STA control field included in the per-STA profile sub-element, it can be indicated whether the ID (i.e., group ID) of the AP group to which the AP corresponding to the link ID included in the STA control field belongs is present in the per-STA profile sub-element. Here, the group ID can be included in the STA info field or the STA profile field of the per-STA profile sub-element.

[0305] Information about one or more APs corresponding to one or more group IDs can be provided via the one or more per-STA profile sub-elements.

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

[0307] As an example of the disclosure, when a unique ID is set within an AP group in the AP MLD as described in embodiment 1-1-1, if the group ID is 0, the group ID can be omitted. That is, when the group ID is not present, the AP receiving the MLD roaming request frame can implicitly determine that the request frame is a request for information about other APs belonging to the group to which it belongs.

[0308] As another example of the 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 information about the AP corresponding to the same group ID. Accordingly, the group ID present field can not be included in the MLD roaming response frame.

[0309] The group key information of sequence 6 can be set to a value indicating the group key information for the NAP. Since the group key can be different for each link, it is necessary to provide the group key information for the NAP. For example, a field corresponding to the group key information can include a subfield indicating the length of the group key information subfield and a subfield set to the value of the group key information. The group key information can include an MLO GTK (Group Temporal Key) KDE (Key Data Encapsulation) format, an MLO IGTK (Integrity Group Temporal Key) KDE, an MLO BIGTK (Beacon Integrity Group Temporal Key) KDE format, etc., including the link identifier of the NAP.

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

[0311] When all APs enabling MLD-based roaming operate in the same channel, the channel switch announcement element information and extended channel switch announcement element information of sequences 8 and 9 can be omitted from the MLD roaming response frame. When MLD-based roaming is performed in different channels, channel information can be provided through the (extended) channel switch announcement element. Additionally or alternatively, the (extended) channel switch announcement element can be included in the STA information / STA profile field of the basic ML element of sequence 5.

[0312] The TID-to-link mapping information of sequence 10 can be used to map the TID in advance through the TID-to-link mapping for the newly connected link. If the TID-to-link mapping is not performed separately, a default mapping can be applied to the newly connected link. If the default mapping mode is applied, all TIDs can be mapped to the link established for both DL and UL, and all established links can be enabled.

[0313] In addition, the AP MLD can include the MLD roaming timer of the reconfiguration ML element in the MLD roaming response frame described above. That is, the AP MLD can control the MLD-based roaming procedure, and thus can set / indicate the MLD roaming timer. For example, it is assumed that the STA transmits the MLD roaming request frame not including the MLD roaming timer, or information about the MLD roaming timer transmitted by the STA is determined by the AP to be inappropriate. In this case, the AP MLD can transmit the MLD roaming response frame including information for setting the MLD roaming timer to the STA.

[0314] Here, the expiration of the MLD roaming timer can mean that the point in time at which the STA no longer performs various operations with the OAP but performs various operations with the NAP has passed when the MLD-based roaming is completed. For example, it is assumed that the STA transmits the MLD roaming request frame including a request for adding 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 perform connection with the NAP.

[0315] If the MLD roaming timer is commonly applied to all APs, information about the MLD roaming timer can be included in the common information field of the reconfiguration / default ML element as shown in (b) of MLD roaming request / response frame exchange procedure In addition, information indicating whether the MLD roaming timer is present in the common information field can be included in the presence bitmap subfield of the reconfiguration / default ML element.

[0316] Figure 18

[0317] As an example of the present disclosure, ​ illustrates a procedure for performing MLD-based roaming. It is assumed that the STA 1 attached to the non-AP MLD is currently connected to the AP 1 of the AP group 1, and the STA 2 attached to the non-AP MLD is currently connected to the AP 2 of the AP group 1. Here, when the STA 1 and the STA 2 move from the AP group 1 to the AP group 2, the STA 1 can perform a roaming procedure to the AP 4 of the AP group 2, and the STA 2 can perform a roaming procedure to the AP 5 of the AP group 2.

[0318] STA 1 can exchange MLD roaming request / response frames with AP 1 to temporarily connect to AP 4 (i.e., add a temporary link) while being connected to AP 1. Here, the MLD roaming request frame can include information requesting a temporary link connection with AP 4. Here, the MLD roaming request frame can include a link ID of AP 4 and a group ID of AP group 2 to which AP 4 belongs. Accordingly, AP 1 can transmit, to STA 1 through the MLD roaming response frame, a basic ML element including information indicating that it approves the MLD-based roaming request and information about AP 4.

[0319] Similar to the above-described method, STA 2 can exchange MLD roaming request / response frames with AP 2 to temporarily connect to AP 5 (i.e., add a temporary link) while being connected to AP 2. Here, the MLD roaming request frame can include information requesting a temporary link connection with AP 5. Here, the MLD roaming request frame can include a link ID of AP 5 and a group ID of AP group 2 to which AP 5 belongs. Accordingly, AP 2 can transmit, to STA 2 through the MLD roaming response frame, a basic ML element including information indicating that it approves the MLD-based roaming request and information about AP 5.

[0320] When the above-described procedure is completed, STA 1 can be temporarily connected to AP 1 and AP 4, and STA 2 can be temporarily connected to AP 2 and AP 5. Accordingly, STA 1 can transmit and receive data to and from AP 1 and AP 4, and STA 2 can transmit and receive data to and from AP 2 and AP 5.

[0321] Then, STA 1 can perform a (temporary) connection deletion operation with AP 1, and STA 2 can perform a (temporary) connection deletion operation with AP 2. Accordingly, STA 1 can complete the MLD-based roaming procedure to AP 4, and STA 2 can complete the MLD-based roaming procedure to AP 5.

[0322] The above-described procedure involves a procedure in which a STA temporarily adds a link and deletes a link with an OAP. An MLD roaming timer can be used in the procedure for temporarily adding and deleting a link.

[0323] For example, STA 1 and STA 2 can each transmit and receive MLD roaming request / response frames to and from AP 1 and AP 2, respectively. STA 1 and STA 2 can each request a temporary link addition to AP 4 and AP 5, respectively, through MLD roaming request frames. Here, as described above, an MLD roaming timer can be set by a non-AP MLD or an AP MLD through an MLD roaming response frame. After successfully transmitting the MLD roaming response frame, the MLD roaming timer can run. When the MLD roaming timer expires, the link between STA 1 and AP 1 can be deleted, and the link between STA 1 and AP 4 can be fully connected. Also, when the MLD roaming timer expires, the link between STA 2 and AP 2 can be deleted, and the link between STA 2 and AP 5 can be fully connected.

[0324] Through the above-described procedure, each STA included in a non-AP MLD can transmit and receive data with a previously connected AP and an AP to which it attempts to roam at the same time when performing an MLD roaming procedure. This allows a more efficient and seamless MLD-based roaming procedure.

[0325] The above-described embodiments are combinations of elements and features of the present disclosure in a predetermined form. Each of the elements or features should be considered selectively unless explicitly mentioned otherwise. Each of the elements or features can be implemented in a form not combining with other elements or features. Also, the embodiments of the present disclosure can include a combination of some or all of the elements and / or features. The order of the operations described in the embodiments of the present disclosure can be changed. Some elements or features of one embodiment can be included in another embodiment, or can be replaced with corresponding elements or features of another embodiment. It is obvious that the embodiments can include a combination of claims not explicitly mentioned, or can be included as new claims by modification after the application.

[0326] It will be apparent to those skilled in the art that the present disclosure can be embodied in other specific forms without departing from the essential characteristics of the present disclosure. Therefore, the above-described detailed description is not to be limited in all aspects, but is to be considered as illustrative. The scope of the present disclosure should be determined by reasonable interpretation of the appended claims, and variations within the scope of the present disclosure are included in the scope of the present disclosure.

[0327] The scope of the present disclosure includes software or machine-executable commands (e.g., operating systems, application programs, firmware, programs, etc.) that perform operations according to the methods of various embodiments in an apparatus or computer, and a non-transitory computer-readable medium that causes the software or commands, etc. to be stored and executable in the apparatus or computer. Commands that can be used to program processing systems to perform the features described in the present disclosure can be stored in storage media or computer-readable storage media, and the features described in the present disclosure can be implemented by using a computer program product including such storage media. The storage media can include a high-speed random access memory such as a DRAM, SRAM, DDR RAM, or other random access solid state storage device, but is not limited thereto, and it can include a non-volatile memory such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. The memory optionally includes one or more storage devices that are located remotely from the processor. The memory, or alternatively the non-volatile memory device in the memory, includes a non-transitory computer-readable storage medium. The features described in the present disclosure can be stored in any one of machine-readable media to control the hardware of the processing system, and can be integrated into software and / or firmware that allows the processing system to interact with other mechanisms with results from the embodiments of the present disclosure. Such software or firmware can include application code, device drivers, operating systems, and execution environments / containers, but is not limited thereto.

[0328] Industrial applicability

[0329] The method proposed in the present disclosure has been described with attention to an example applied to an IEEE 802.11-based system, but the method can also be applied to various wireless LANs 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: Receive notification information from a first access point (AP) attached to the first group, the notification information including first information related to whether adding at least one link to the first STA is supported; Send a request frame to the first AP, including the link ID of the second AP belonging to the second group; as well as Receive a response frame from the first AP that includes the link ID of the second AP. The request frame includes second information requesting the addition or removal of a link between the first STA and the second AP.

2. The method according to claim 1, wherein, The notification information is included in the MLD-based roaming element or the simplified neighbor report (RNR) element included in the management frame, and The MLD-based roaming element or the RNR element includes a first subfield associated with at least one group ID and a second subfield associated with the first information.

3. The method according to claim 1, wherein, The request frame includes third information related to whether the addition or removal of the link between the first STA and the second AP is a temporary link addition or removal.

4. The method according to claim 3, wherein, The request frame includes reconfiguration of multi-link elements, and The public information field or STA control field of the reconfigured multi-link element includes a third sub-field related to the second information and a fourth sub-field related to the third information.

5. The method according to claim 3, wherein, Based on the request to add a link between the first STA and the second AP through the third subfield and the fourth subfield, the link between the first STA and the second AP is connected simultaneously with the link between the first STA and the first AP.

6. The method according to claim 5, wherein, Based on the completion of the roaming process to the second AP, the link between the first STA and the first AP is deleted.

7. The method according to claim 1, wherein, Each of the request frame and the response frame includes a group ID associated with the second group.

8. The method according to claim 5, wherein, The response frame includes fourth information related to the multi-link device MLD roaming timer, and The link between the first STA and the first AP is deleted based on the expiration of the MLD roaming timer.

9. The method according to claim 1, wherein, The response frame includes basic ML elements, and The basic ML elements include AID and traffic identifier-to-link mapping information for the first STA.

10. The method according to claim 1, wherein, Based on the information in the response frame indicating that roaming to the second AP has been accepted, an association process with the second AP is initiated.

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. The method according to claim 12, wherein, While performing the roaming process of the first STA, the roaming process of the second STA attached to the non-AP MLD is also performed.

14. 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 coupled to said at least one transceiver, Wherein, the at least one processor is configured to: The at least one transceiver receives notification information from a first access point (AP) attached to the first group, the notification information including first information related to whether adding at least one link to the first STA is supported; A request frame, including the link ID of a second AP belonging to the second group, is sent to the first AP via the at least one transceiver; and The at least one transceiver receives a response frame from the first AP that includes the link ID of the second AP. The request frame includes second information requesting the addition or removal of a link between the first STA and the second AP.

15. A method performed by a first access point (AP) included in a first group in a wireless LAN system, the method comprising the following steps: Send a notification message to the first STA, the notification message including first information about whether it is supported to add at least one link to the first STA; Receive a request frame from the first STA that includes the link ID of the second AP belonging to the second group; as well as Send a response frame to the first STA, including the link ID of the second AP. The request frame includes second information requesting the addition or removal of a link between the first STA and the second AP.

16. A first access point (AP) operating in a wireless LAN system, the first AP comprising: At least one transceiver; as well as At least one processor, said at least one processor being coupled to said at least one transceiver, Wherein, the at least one processor is configured to: The at least one transceiver sends a notification message to the first STA, the notification message including first information about whether it is supported to add at least one link to the first STA; Receive, via the at least one transceiver, a request frame including the link ID of the second AP belonging to the second group from the first STA; and A response frame including the link ID of the second AP is sent to the first STA via the at least one transceiver. The request frame includes second information requesting the addition or removal of a link between the first STA and the second AP.

17. A processing device configured to control a first station STA in a wireless LAN system, the processing device 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.

18. At least one non-transitory computer-readable medium, said non-transitory computer-readable medium storing at least one instruction, in, The at least one instruction is executed by the 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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