Wireless communication method using multilink and wireless communication terminal using the same

Abstract

This invention provides a wireless communication method using a multilink device (MLD) and a wireless communication terminal using the same. [Solution] In a wireless communication system, the method for transmitting and receiving frames performed by a first MLD including multiple stations each operating on multiple links is as follows: The first MLD transmits a request frame to a second station among multiple stations included in a second MLD, each operating on at least one link, via a first station among the multiple stations included in the first MLD, and receives a response frame from the second station as a response to the request frame via the first station. At this time, the request frame includes information of other stations included in the first MLD, and the response frame includes information of other stations included in the second MLD.

Description

Technical Field

[0001] The present invention relates to a wireless communication method using multiple links and a wireless communication terminal using the same.

Background Art

[0002] Recently, as the spread of mobile devices has expanded, wireless LAN (Local Area Network) technology that can provide fast wireless Internet services to them has been in the spotlight. Wireless LAN technology is a technology that enables mobile devices such as smartphones, smart pads, laptop computers, portable multimedia players, and embedded devices to be wirelessly connected to the Internet in homes, companies, or specific service-providing areas based on wireless communication technology at short distances.

[0003] Since IEEE (Institute of Electrical and Electronics Engineers) 802.11 supported the initial wireless LAN technology using the 2.4 GHz frequency, various technology standards have been put into practical use or are under development. First, IEEE 802.11b uses the frequency of the 2.4 GHz band and supports a communication speed of up to 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the frequency of the 5 GHz band instead of the 2.4 GHz band, reducing the impact on interference compared to the rather congested 2.4 GHz band frequency, and uses OFDM (Orthogonal Frequency Division Multiplexing) technology to improve the communication speed up to 54 Mbps. However, IEEE 802.11a has the disadvantage of having a shorter communication distance than IEEE 802.11b. And IEEE 802.11g uses the same 2.4 GHz band frequency as IEEE 802.11b and implements a maximum communication speed of 54 Mbps, satisfying backward compatibility and receiving considerable attention, but it is also superior to IEEE 802.11a in terms of communication distance.

[0004] Furthermore, IEEE 802.11n is a technical standard established to overcome the limitations in communication speed that had been pointed out as a vulnerability in wireless LANs. The purpose of IEEE 802.11n is to increase network speed and reliability and extend the operating range of wireless networks. Specifically, IEEE 802.11n supports high throughput (HT) with a data processing speed of up to 540 Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas at both the transmitter and receiver ends to minimize transmission errors and optimize data speed. In addition, this standard uses a coding method that transmits multiple duplicate copies to improve data reliability.

[0005] As the proliferation of wireless LANs accelerates and the applications using them diversify, there is a growing need for new wireless LAN systems that can support very high throughput (VHT) higher than the data processing speed supported by IEEE 802.11n. Among these, IEEE 802.11ac supports a wide bandwidth (80MHz to 160MHz) at the 5GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5GHz band, early 11ac chipsets are expected to support operation in the 2.4GHz band for backward compatibility with older 2.4GHz band products. Theoretically, this standard allows for a minimum wireless LAN speed of 1Gbps and a maximum single-link speed of 500Mbps. This is achieved by extending the wireless interface concepts accepted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Another method for transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz band is IEEE 802.11ad. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, making it suitable for streaming large amounts of data and high-bitrate video such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage of being difficult to pass through obstacles, limiting its use to devices in short-range spaces.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard has been developed and is nearing completion as a wireless LAN standard for 802.11ac and 802.11ad and beyond, to provide highly efficient and high-performance wireless LAN communication technology in high-density environments where access points (APs) and terminals are densely packed. In an 802.11ax-based wireless LAN environment, it is necessary to provide highly frequency-efficient communication indoors and outdoors in the presence of high-density stations and APs (Access Points), and various technologies have been developed to realize this.

[0007] Furthermore, in order to support new multimedia applications such as high-definition video and real-time games, development has begun on a new wireless LAN standard to increase the maximum transmission speed. The 7th generation wireless LAN standard, IEEE 802.11be (Extremely High Throughput, EHT), is being developed with the goal of supporting a maximum transmission rate of 30 Gbps in the 2.4 / 5 / 6 GHz band through wider bandwidth, increased spatial streams, and multiple AP coordination. [Overview of the project] [Problems that the invention aims to solve]

[0008] One embodiment of the present invention aims to provide a wireless communication method using multiple links and a wireless communication terminal using the same.

[0009] The technical problems that this specification aims to solve are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those with ordinary skill in the art to which this invention pertains from the following description. [Means for solving the problem]

[0010] A first multi-link device (MLD) according to the present invention, which includes a plurality of stations each operating on a plurality of links, includes a processor, the processor transmits a request frame to a second station of a second plurality of stations included in a second MLD each operating on at least one link, via a first station of the first plurality of stations included in the first multi-link device, the first station and the second station operate in a specific bandwidth, and the first station receives a response frame from the second station as a response to the request frame, the second station transmits the response frame including the capability element and / or operation element of the second station for the specific bandwidth, excluding the capability element and / or operation element of the second station for other bandwidths in a specific legacy format, the response frame includes multi-link information for coupling between a first at least one station of the first plurality of stations excluding the first station and a second at least one station of the second plurality of stations excluding the second station.

[0011] Furthermore, in the present invention, the multilink information includes capability elements and / or operational elements of each of the second or at least one station in a legacy format corresponding to each of the other bandwidths.

[0012] Furthermore, in the present invention, each capability element and / or operating element of the second at least one station is at least one of the following: an HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, an HT operating element, a VHT operating element, or an HE (High Efficiency) operating element including VHT operating information.

[0013] Furthermore, in the present invention, the specific frequency band is 6 GHz, and the other frequency bands are 2.4 GHz and / or 5 GHz.

[0014] Furthermore, in the present invention, the processor includes a multi-link element in the request frame which includes a Per-STA profile subelement corresponding to each of the second at least one station, and the Per-STA profile subelement includes a complete profile subfield indicating whether or not it is a request for all information for the corresponding station among the second at least one station.

[0015] Furthermore, in the present invention, when the complete profile subfield indicates a request for all of the above information, the multilink information of the response frame includes capability elements and / or operational elements of the station among the second at least one station corresponding to the complete profile subfield indicating a request for all of the above information.

[0016] Furthermore, in the present invention, the processor performs a multilink setting procedure to set up a link between the second MLD and the first at least one station and the second at least one station based on the multilink information.

[0017] Furthermore, in the present invention, the requested frame includes a multi-link element which includes at least one Per-STA profile subelement corresponding to each of the first at least one station, and each of the at least one Per-STA profile subelements of the multi-link element includes legacy format capability elements and / or operational elements for a specific station among the first at least one station.

[0018] Furthermore, in the present invention, the specified station is a station that operates in at least one of the other bands, and the first station transmits the capability element and / or operation element of the first station for the specified band, excluding the capability element and / or operation element of the first station for the other bands in a specific legacy format, in the request frame.

[0019] Furthermore, in the present invention, the response frame is one of the following: an association request frame, an association response frame, or a multi-link (ML) probe response frame.

[0020] The present invention also provides a method comprising the steps of: transmitting a request frame from a first station among a first plurality of stations included in the first multilink device to a second station among a second plurality of stations included in a second MLD, each operating on at least one link, wherein the first station and the second station operate in a specific band; and receiving a response frame from the second station as a response to the request frame via the first station, wherein the second station transmits a radio frame including the capability element and / or operation element of the second station for the specific band, excluding the capability element and / or operation element of the second station for other bands, and the radio frame includes multilink information for coupling between a first at least one station among the first plurality of stations excluding the first station and a second at least one station among the second plurality of stations excluding the second station. [Effects of the Invention]

[0021] One embodiment of the present invention provides a wireless communication method that efficiently uses multi-links and a wireless communication terminal using the same.

[0022] The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

[0023] [Figure 1] It is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] It is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] It is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] It is a diagram showing the configuration of an access point according to an embodiment of the present invention. [Figure 5] It is a diagram schematically showing the process in which a STA sets a link with an AP. [Figure 6] It is a diagram showing the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] It is a diagram showing an example of PPDU (PLCP Protocol Data Unit) formats for various standard generations. [Figure 8] It is a diagram showing an example of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats according to an embodiment of the present invention and a method for instructing the same. [Figure 9] It is a diagram showing a multi-link device according to an embodiment of the present invention. [Figure 10] It is a diagram showing that transmissions of different links are simultaneously performed in multi-link operation according to an embodiment of the present invention. [Figure 11] This figure shows the operation of a multilink device when the link is changed according to one embodiment of the present invention. [Figure 12] This figure shows that, according to one embodiment of the present invention, when one station of a non-STR multilink device is receiving signals, channel access for other stations of the non-STR multilink device is prohibited. [Figure 13] This figure shows the operation of releasing the channel access ban when it is confirmed that the intended recipient of the PPDU received by a station in a non-STR multilink device is not the station, according to an embodiment of the present invention. [Figure 14] This figure shows an embodiment of the present invention in which a station performs channel access after the channel access ban has been lifted. [Figure 15] This figure shows the operation of a station transmitting after the channel access ban has been lifted, according to one embodiment of the present invention. [Figure 16] This figure shows a transmission performed based on the status of a station in a non-STR multilink device, according to an embodiment of the present invention. [Figure 17] This diagram shows the conditions under which interference or collision between links may occur. [Figure 18] This figure shows the operation by which an STR multilink device ceases transmission to a non-STR multilink device according to one embodiment of the present invention. [Figure 19] This figure shows how, according to an embodiment of the present invention, the STR multilink device processes the CW value when it detects a transmission collision between links. [Figure 20] This figure shows an example of a transmission management method for a non-AP multilink device according to an embodiment of the present invention. [Figure 21]This figure shows an example of the content of a beacon frame transmitted by an AP of AP MLD and an example of the TBTT (target beacon transmission time) information field format included in the RNR (Reduced Neighbor Report) element, according to one embodiment of the present invention. [Figure 22] This figure shows yet another example of a TBTT information field format according to one embodiment of the present invention. [Figure 23] This figure shows an example of an Information Length subfield that indicates a TBTT information field containing an MLD AP TBTT offset subfield, according to one embodiment of the present invention. [Figure 24] This figure shows an example of the profile subelement format for each STA according to one embodiment of the present invention. [Figure 25] This figure shows an example of the process by which a non-AP MLD, set up with an NSTR (Non-Simultaneous Transmission and Reception) Soft AP MLD according to one embodiment of the present invention, updates information on the non-primary link. [Figure 26] This flowchart shows an example of a procedure in which a non-AP STA MLD, associated with an NSTR AP MLD, updates the parameters of a non-primary link, according to one embodiment of the present invention. [Figure 27] This figure shows an example of the format of an element according to one embodiment of the present invention. [Figure 28] This figure shows an example of the process by which NSTR AP MLD sets (defines) a non-primary Quiet interval according to one embodiment of the present invention. [Figure 29] This figure shows an example of a method by which an NSTR AP MLD performs a non-primary channel switch according to one embodiment of the present invention. [Figure 30] This figure shows examples of probe request frames, association request frames, and association response frames transmitted by a station operating within a specific bandwidth. [Figure 31] This figure shows an example of a method for setting up multiple links by exchanging HT (High Throughput) / VHT (Very High Throughput) related element information over other links that do not have a specific bandwidth, according to one embodiment of the present invention. [Figure 32] This figure illustrates a part of the configuration of a management frame for explaining a method for inheriting a complete Per-STA profile according to one embodiment of the present invention. [Figure 33] This flowchart shows an example of the operation of a non-AP MLD according to one embodiment of the present invention. [Modes for carrying out the invention]

[0024] The terminology used herein has been selected to the greatest extent possible from currently widely used general terms, taking into account the function of the present invention; however, this may differ depending on the intent, conventions, or emergence of new technologies of the articulate persons in the relevant field. In addition, in certain cases, the applicant has arbitrarily selected some terms, and in such cases, the meaning of these terms will be described in the relevant section of the invention description. Therefore, it should be made clear that the terms used herein are not merely names of terms, but should be interpreted based on the substantive meaning of the terms and the content of this specification as a whole.

[0025] Throughout the specification, when one component is described as being "connected" to another, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" with other components in between. Furthermore, when a component is described as "containing" a particular component, this means, unless otherwise stated, that it may contain other components rather than excluding them. In addition, limitations such as "greater than or equal to" or "less than or equal to" a specific critical value may be appropriately replaced by "greater than" or "less than" depending on the embodiment.

[0026] In the present invention, the terms "field" and "subfield" may be used interchangeably.

[0027] Figure 1 shows a wireless LAN system according to one embodiment of the present invention.

[0028] A wireless LAN system includes one or more Basic Service Sets (BSS), where a BSS represents a set of devices that have successfully synchronized and can communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

[0029] As shown in Figure 1, the infrastructure BSS BSS1, BSS2 includes one or more stations STA1, STA2, STA3, STA4, STA5, access points AP-1, AP-2 which are stations that provide distribution services, and a distribution system DS that connects multiple access points AP-1, AP-2.

[0030] A Station (STA) is any device that includes Medium Access Control (MAC) and a Physical Layer interface to a wireless medium in accordance with the IEEE 802.11 standard, and in a broad sense includes not only non-AP stations but also all access points (APs). In this specification, "terminal" is used to refer to non-APs, APs, or both. A station for wireless communication includes a processor and a communication unit, and depending on the embodiment, further includes a user interface unit and a display unit, etc. The processor generates frames to be transmitted over the wireless network or processes frames received over the wireless network, and performs various other processing for controlling the station. The communication unit is functionally connected to the processor and sends and receives frames over the wireless network for the station. In this invention, "terminal" is used as a term that includes user equipment (UE).

[0031] An Access Point (AP) is an individual device that provides connectivity to a distribution system (DS) via a wireless medium for stations associated with it. In infrastructure BSS, communication between non-AP stations is generally conducted via APs, however, direct communication is possible between non-AP stations if a direct link is configured. In this invention, AP is used as a concept that includes PCP (Personal BSS Coordination Point), but in a broader sense, it includes all concepts such as central controllers, base stations (BS), node B, BTS (Base Transceiver System), or site controllers. In this invention, AP is also referred to as a base wireless communication terminal, but in a broader sense, base wireless communication terminal is used as a term that includes APs, base stations, eNBs (eNodeBs), and transmission points (TPs). Furthermore, base wireless communication terminals include various forms of wireless communication terminals that allocate and schedule communication medium resources in communication with multiple wireless communication terminals.

[0032] Multiple infrastructure BSSs are connected to each other via a distribution system DS. In this case, multiple BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0033] Figure 2 shows an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of Figure 2, redundant explanations are omitted for parts that are the same as or corresponding to the embodiment of Figure 1.

[0034] As shown in Figure 2, BSS3 is an independent BSS and does not include APs, so all stations (STA6, STA7) are not connected to APs. An independent BSS is not allowed to connect to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) is directly connected to one another.

[0035] Figure 3 is a block diagram showing the configuration of station 100 according to one embodiment of the present invention. As shown, station 100 according to the embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0036] First, the communication unit 120 transmits and receives wireless signals such as wireless LAN packets and may be incorporated into the station 100 or provided externally. According to one embodiment, the communication unit 120 may include at least one communication module using different frequency bands. For example, the communication unit 120 may include communication modules of different frequency bands such as 2.4GHz, 5GHz, 6GHz, and 60GHz. According to one embodiment, the station 100 may include a communication module using a frequency band of 7.125GHz or higher and a communication module using a frequency band of 7.125GHz or lower. Each communication module can perform wireless communication with an AP or external station based on the wireless LAN standard of the frequency band supported by the communication module. Depending on the performance and requirements of the station 100, the communication unit 120 may operate only one communication module at a time or operate multiple communication modules together simultaneously. When the station 100 includes multiple communication modules, each communication module may be provided in an independent form, or the multiple modules may be integrated as a single chip. In embodiments of the present invention, the communication unit 120 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0037] Next, the user interface 140 includes various forms of input / output means provided in the station 100. In other words, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. The user interface unit 140 also outputs based on instructions from the processor 110 using various output means.

[0038] Next, the display unit 150 outputs an image to the display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or user interfaces based on control instructions from the processor 110. The memory 160 stores control programs used by the station 100 and various data associated with them. Such control programs include connection programs necessary for the station 100 to connect with APs or external stations.

[0039] The processor 110 of the present invention executes various instructions or programs and processes data within the station 100. The processor 110 also controls each unit of the station 100 and controls the transmission and reception of data between units. According to an embodiment of the present invention, the processor 110 executes a program for connection with the AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information regarding the priority conditions of the station 100 contained in the communication setup message and requests a connection to the AP based on the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling a part of the station 100's configuration, such as the communication unit 120. In other words, the processor 110 may be a modem or a modulator and / or demodulator that modulates and demodulates the wireless signals transmitted and received from the communication unit 120. The processor 110 controls various operations of wireless signal transmission and reception of the station 100 according to an embodiment of the present invention. A detailed embodiment relating to this will be described later.

[0040] The station 100 shown in Figure 3 is a block diagram according to one embodiment of the present invention, and the separately shown blocks represent logically distinguished elements of the device. Therefore, the above-described elements of the device are mounted on one chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated and implemented on a single chip, or they may be implemented on separate chips. Furthermore, in the embodiment of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively provided in the station 100.

[0041] Figure 4 is a block diagram showing the configuration of AP200 according to one embodiment of the present invention. As shown, AP200 according to an embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In Figure 4, redundant explanations are omitted for parts of the AP200 configuration that are the same as or correspond to the configuration of station 100 in Figure 3.

[0042] Referring to Figure 4, the AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of Figure 3, the communication unit 220 of the AP 200 can also include a plurality of communication modules using different frequency bands. That is, the AP 200 according to an embodiment of the present invention can include two or more communication modules using different frequency bands, for example, 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 can include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can communicate wirelessly with the station based on the wireless LAN standard of the frequency band supported by the communication module. Depending on the performance and requirements of the AP 200, the communication unit 220 can operate only one communication module at a time or operate multiple communication modules together simultaneously. In an embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0043] Next, the memory 260 stores the control program used by the AP200 and various data associated with it. Such a control program includes a connection program that manages station connections. The processor 210 controls each unit of the AP200 and controls the transmission and reception of data between units. According to one embodiment of the present invention, the processor 210 executes the program for connecting with stations stored in the memory 260 and transmits a communication setting message to one or more stations. In this case, the communication setting message includes information regarding the connection priority conditions of each station. The processor 210 also performs connection settings in response to connection requests from stations. According to one embodiment, the processor 210 is a modem or modulation / demodulation unit that modulates and demodulates the wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations of wireless signal transmission and reception of the AP200 according to the embodiment of the present invention. A detailed embodiment relating thereto will be described later.

[0044] Figure 5 is a schematic diagram illustrating the process by which STA establishes a link with AP.

[0045] Referring to Figure 5, the link between STA100 and AP200 is established through three main steps: scanning, authentication, and association. First, the scanning step is the step in which STA100 obtains connection information for the BSS operated by AP200. There are two methods for performing scanning: passive scanning, which uses only the beacon message S101 transmitted periodically by AP200 to obtain information, and active scanning, in which STA100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and obtains connection information.

[0046] In the scanning step, STA100, having successfully received wireless connection information, transmits an authentication request (S107a), receives an authentication response from AP200 (S107b), and performs the authentication step. After the authentication step is performed, STA100 transmits an association request (S109a), receives an association response from AP200 (S109b), and performs the association step. In this specification, "association" basically means wireless coupling, but the present invention is not limited to this, and in a broad sense, coupling includes both wireless and wired coupling.

[0047] On the other hand, an additional 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are performed. In Figure 5, Server 300 is a server that processes authentication between STA100 and the 802.1X-based system, and may be physically connected to AP200 or exist as a separate server.

[0048] Figure 6 shows the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0049] A terminal performing wireless LAN communication checks whether a channel is busy by performing carrier sensing before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be busy, and the terminal delays access to that channel. This process is called Clear Channel Assessment (CCA), and the level at which the detection of the relevant signal is determined is called the CCA threshold. If a wireless signal received by the terminal is above the CCA threshold and the terminal is the recipient, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel, or if a wireless signal with an intensity lower than the CCA threshold is detected, the channel is determined to be idle.

[0050] When a channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after a time period corresponding to the status of each terminal, such as an IFS (Inter Frame Space), AIFS (Arbitration IFS), PIFS (PCF IFS), etc. Depending on the embodiment, the AIFS may be used as a replacement for the conventional DIFS (DCF IFS). Each terminal waits, decreasing its slot time by a random number determined for that terminal during the interval of the channel's idle state, and the terminal that has exhausted all of its slot time attempts to access the channel. The period in which each terminal performs the backoff procedure in this manner is called the conflict window period. At this time, the random number can be called the backoff counter. That is, the initial value of the backoff counter is set by an integer, which is a random number acquired by the terminal. If a terminal senses that the channel is idle during the slot time, the terminal can decrease the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be allowed to access the channel. Therefore, terminal transmission may be permitted when the channel is idle during the AIFS time and the backoff counter slot time.

[0051] If a specific terminal successfully accesses the channel, it transmits data through the channel. However, if the terminal attempting access collides with another terminal, the colliding terminals are each assigned a new random number and perform a further backoff procedure. In one embodiment, the random number newly assigned to each terminal is determined within a range twice that of the range of the random number previously assigned to that terminal (conflict window, CW) (2*CW). Meanwhile, each terminal attempts access again in the next conflict window interval by performing a further backoff procedure, but this time, each terminal performs the backoff procedure from the slot time remaining in the previous conflict window interval. In this way, each terminal performing wireless LAN communication can avoid collisions with each other for a specific channel.

[0052] <Examples of various PPDU formats>

[0053] Figure 7 shows examples of various standard generational PPDU (PLCP Protocol Data Unit) formats. More specifically, Figure 7(a) shows one example of a legacy PPDU format based on 802.11a / g, Figure 7(b) shows one example of an HE PPDU format based on 802.11ax, and Figure 7(c) shows one example of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Figure 7(d) shows the detailed field configuration of L-SIG and RL-SIG commonly used in the aforementioned PPDU formats.

[0054] Referring to Figure 7(a), the legacy PPDU preamble includes L-STF (Legacy Short Training field), L-LTF (Legacy Long Training field), and L-SIG (Legacy Signal field). In embodiments of the present invention, the L-STF, L-LTF, and L-SIG can be referred to as the legacy preamble.

[0055] Referring to Figure 7(b), the HE PPDU preamble further includes RL-SIG (Repeated Legacy Short Training field), HE-SIG-A (High Efficiency Signal A field), HE-SIG-B (High Efficiency Signal B field), HE-STF (High Efficiency Short Training field), and HE-LTF (High Efficiency Long Training field) in addition to the legacy preamble. In embodiments of the present invention, RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as the HE preamble. The specific configuration of the HE preamble may be modified according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0056] Referring to Figure 7(c), the EHT PPDU preamble further includes RL-SIG (Repeated Legacy Short Training field), U-SIG (Universal Signal field), EHT-SIG-A (Extremely High Throughput Signal A field), EHT-SIG-A (Extremely High Throughput Signal B field), EHT-STF (Extremely High Throughput Short Training field), and EHT-LTF (Extremely High Throughput Long Training field) in addition to the legacy preamble. In embodiments of the present invention, RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as the EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used in only some of the EHT PPDU formats.

[0057] The L-SIG field included in the PPDU preamble is configured with 64 FFT OFDM and consists of a total of 64 subcarriers. Of these, 48 subcarriers, excluding the guard subcarrier, DC subcarrier, and pilot subcarrier, are used for L-SIG data transmission. Since BPSK and a Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information configuration of the L-SIG.

[0058] Referring to Figure 7(d), L-SIG includes the L_RATE field and the L_LENGTH field. The L_RATE field consists of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of a modulation scheme such as BPSK / QPSK / 16-QAM / 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. Combining the information from the L_RATE and L_LENGTH fields allows us to determine the total length of the PPDU. In non-legacy PPDU formats, the L_RATE field is set to the minimum speed of 6 Mbps.

[0059] The L_LENGTH field is measured in bytes, with a total of 12 bits allocated to allow signals up to 4095. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. Legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0060] First, the method by which legacy or non-legacy terminals interpret the length of the PPDU using the L_LENGTH field is as follows: When the value of the L_RATE field is set to indicate 6Mbps, 3 bytes (i.e., 24 bits) may be transmitted during the 4us symbol duration of one 64FFT. Therefore, by adding the 3 bytes corresponding to the SVC and Tail fields to the L_LENGTH field value and dividing this by the 3 bytes transmitted for one symbol, the number of 64FFT reference symbols after L-SIG is obtained. After multiplying the obtained number of symbols by the 4us symbol duration, and then adding the 20us required for L-STF, L-LTF, and L-SIG transmissions, the length of the PPDU, i.e., the reception time (RXTIME), is obtained. This can be expressed mathematically as shown in Equation 1 below.

[0061]

number

[0062] At this time,

number

[0063]

number

[0064] Here, TXTIME is the total transmission time that constitutes the PPDU, as shown in Equation 3 below. In this case, TX represents the transmission time of X.

[0065]

number

[0066] Referring to the above formula, the length of the PPDU is calculated based on the rounded-up value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​L_LENGTH = {3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0067] Referring to Figure 7(e), the U-SIG (Universal SIG) field persists in EHT PPDUs and subsequent generations of wireless LAN PPDUs, playing a role in distinguishing which generation of PPDU it is, including 11be. The U-SIG is a 64FFT-based OFDM with two symbols, capable of transmitting a total of 52 bits of information. Of these, 43 bits, excluding the 9 bits of CRC / tail, are broadly divided into the VI (Version Independent) field and the VD (Version Dependent) field.

[0068] The VI bit maintains its current bit configuration, allowing current 11be terminals to obtain information about a PPDU from its VI field even when subsequent generations of PPDUs are defined. To this end, the VI field consists of the PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits and is responsible for sequentially distinguishing 11be and subsequent generations of wireless LAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the PPDU is an uplink or downlink PPDU. The BSS color represents the BSS identifier defined in 11ax and has a value of 6 bits or more. The TXOP represents the Transmit Opportunity Duration, which was transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP containing the PPDU can be inferred without decoding the PPDU, and it has a value of 7 bits or more.

[0069] The VD field may consist of the PPDU format as signaling information useful only for the 11be version of PPDU, fields that are common to any PPDU format such as BW, and fields that are defined differently depending on the PPDU format. The PPDU format is a divisor that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDU, etc. The BW field broadly signals five basic PPDU BW options of 20, 40, 80, 160 (80+80), and 320 (160+160) MHz (BW that can be expressed in the form of a power of 20*2 can be called a basic BW), and various remaining PPDU BWs composed of preamble puncturing. In addition, after being signaled at 320 MHz, some 80 MHz may be punctured and then signaled. Furthermore, the punctured and deformed channel shape may be signaled directly in the BW field, or it may be signaled using both the BW field and fields appearing after the BW field (for example, fields within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0070] Fields located after the BW field vary depending on the form and format of the PPDU. MU PPDUs and SU PPDUs may be signaled in the same PPDU format. A field to distinguish between MU PPDUs and SU PPDUs may be located before the EHT-SIG field, and additional signaling may be performed for this purpose. Both SU PPDUs and MU PPDUs include an EHT-SIG field, but some fields unnecessary for the SU PPDU may be compressed. In this case, the information of the compressed fields may be omitted or have a reduced size compared to the original fields included in the MU PPDU. For example, in the case of a SU PPDU, the common fields of the EHT-SIG may be omitted or replaced, or user-specific fields may be replaced or reduced to one, resulting in a different configuration.

[0071] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (e.g., the RA field) may be omitted depending on the value of the compression field.

[0072] If a portion of the EHT-SIG field of an SU PPDU is compressed, the information contained in the compressed field may be signaled together with the uncompressed field (e.g., a common field). In the case of MU PPDUs, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of information signaled may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must know the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether or not the transmitted MU PPDU was sent to them. Therefore, the AP must transmit the EHT-SIG field with the above information included. To this end, the U-SIG field signals information for efficient transmission of the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the modulation method, MCS. The EHT-SIG field may include size and location information of the RU assigned to each user.

[0073] In the case of an SU PPDU, multiple RUs may be assigned to the STA, and these RUs may be consecutive or discontinuous. If the RUs assigned to the STA are not consecutive, the STA can efficiently receive the SU PPDU only if it recognizes the punctured RU in the middle. Therefore, the AP can transmit the SU PPDU including information about the punctured RUs among the RUs assigned to the STA (e.g., the puncturing pattern of the RUs). That is, in the case of an SU PPDU, the EHT-SIG field may contain a puncturing mode field that includes information on whether a puncturing mode was applied and the puncturing pattern shown in bitmap format or similar, and the puncturing mode field can signal the form of discontinuous channels appearing within the bandwidth.

[0074] The form of the signaled discontinuous channels is limited and, in combination with the value of the BW field, indicates the BW and discontinuous channel information of the SU PPDU. For example, in the case of an SU PPDU, since it is a PPDU transmitted to only one terminal, the STA can recognize the bandwidth allocated to it from the BW field included in the PPDU, and can recognize the punctured resources within the allocated bandwidth from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the terminal can receive the PPDU with the remaining resource units excluding the specific channel of the punctured resource unit. At this time, the multiple RUs allocated to the STA may consist of different frequency bands or tones.

[0075] The reason only restricted forms of discontinuous channel configurations are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed on each 20MHz subchannel, when puncturing is performed on a bandwidth with multiple 20MHz subchannels, such as 80, 160, and 320MHz, in the case of 320MHz, the usage status of the remaining 15 20MHz subchannels (excluding the primary channel) must be represented, and the discontinuous channel configuration (if a configuration where only the end 20MHz is punctured is also considered discontinuous) must be signaled. Using 15 bits to signal the discontinuous channel configuration for single-user transmission in this way can result in excessive signaling overhead when considering the low transmission speed of the signaling portion.

[0076] This invention proposes a method for signaling the discontinuous channel configuration of SU PPDU and shows the discontinuous channel configuration determined by the proposed method. Furthermore, it proposes a method for signaling the primary 160MHz and secondary 160MHz puncturing configurations of SU PPDU in a 320MHz BW configuration.

[0077] Furthermore, in one embodiment of the present invention, a method is proposed to vary the configuration of the PPDU indicated by the preamble puncturing BW value according to the PPDU format signaled in the PPDU format field. Assuming that the length of the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, one symbol of EHT-SIG-A may be further signaled after U-SIG, or EHT-SIG-A may not be signaled at all. Considering this, it is necessary to signal all up to 11 puncturing modes using only the BW field of U-SIG. However, in the case of an EHT MU PPDU, EHT-SIG-B is further signaled after U-SIG, so up to 11 puncturing modes may be signaled in a different way than in an SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether it is a PPDU using a bandwidth of 20 MHz or 10 MHz.

[0078] Figure 7(f) shows the format-specific fields of the VD field when EHT MU PPDU is indicated in the U-SIG PPDU format field. In the case of MU PPDU, SIG-B, which is a signaling field for simultaneous reception by multiple users, is required, and SIG-B may be transmitted after U-SIG without a separate SIG-A. For this purpose, U-SIG must signal information for decoding SIG-B. Such fields include SIG-B MCS, SIG-B DCM, Number of SIG-B Symbols, SIG-B Compression, and Number of EHT-LTF Symbols fields.

[0079] Figure 8 shows examples of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats and methods for specifying them according to embodiments of the present invention.

[0080] Referring to Figure 8, a PPDU may consist of a preamble and a data portion, and one type of format, EHT PPDU, may be distinguished by a U-SIG field included in the preamble. Specifically, whether or not the PPDU format is an EHT PPDU may be indicated based on the PPDU format field included in the U-SIG field.

[0081] Figure 8(a) shows an example of the EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single-user (SU) transmission between an AP and a single STA, and may have an EHT-SIG-A field for additional signaling after the U-SIG field.

[0082] Figure 8(b) shows an example of an EHT trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. An EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame and is an uplink PPDU used as a response to a trigger frame. Unlike an EHT SU PPDU, an EHT PPDU does not have an EHT-SIG-A field after the U-SIG field.

[0083] Figure 8(c) shows an example of the EHT MU PPDU format, which is an EHT PPDU for multiple users. An EHT MU PPDU is a PPDU used to send a PPDU to one or more STAs. In the EHT MU PPDU format, the HE-SIG-B field may be located after the U-SIG field.

[0084] Figure 8(d) shows an example of the EHT ER SU PPDU format used for single-user transmissions with STAs in an extended range. EHT ER SU PPDU may be used for single-user transmissions with STAs in a wider range than EHT SU PPDU described in Figure 8(a), and the U-SIG field may be repeatedly positioned on the time axis.

[0085] The EHT MU PPDU described in Figure 8(c) can be used by an AP to transmit downlink data to multiple STAs. In this case, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive PPDUs transmitted from the AP. The EHT MU PPDU can transmit the AID information of the recipient and / or sender of the PPDU transmitted through the user-specific field of EHT-SIG-B to the STAs. Therefore, multiple terminals that receive the EHT MU PPDU can perform spatial reuse operations based on the AID information in the user-specific field included in the preamble of the received PPDU.

[0086] Specifically, the resource unit allocation (RA) field in the HE-SIG-B field included in the HE MU PPDU may contain information about the configuration of resource units (e.g., resource unit division configuration) within a specific bandwidth on the frequency axis (e.g., 20 MHz). That is, the RA field can instruct the STA on the configuration of resource units divided by the bandwidth for transmitting the HE MU PPDU in order to receive the PPDU. Information about the STA allocated (or specified) to each divided resource unit may be included in the user-specific field of EHT-SIG-B and transmitted to the STA. That is, the user-specific field may contain one or more user fields corresponding to each divided resource unit.

[0087] For example, among the multiple divided resource units, the user field corresponding to at least one resource unit used for data transmission may contain the recipient's or sender's AID, while the user fields corresponding to the remaining resource units not used for data transmission may contain a previously set Null STA ID.

[0088] For the sake of clarity, the terms frame or MAC frame may be used interchangeably with MPDU in this specification.

[0089] When a single wireless communication device communicates using multiple links, the communication efficiency of the wireless communication device can be increased. In this case, a link is a physical path and may be configured as a single wireless medium that can be used to transmit an MSDU (MAC service data unit). For example, if the frequency band of one link is being used by another wireless communication device, the wireless communication device can continue to communicate using another link. In this way, the wireless communication device can make effective use of multiple channels. Furthermore, when the wireless communication device communicates simultaneously using multiple links, the overall throughput can be increased. However, existing wireless LANs are defined on the premise that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using multiple links is necessary. Referring to Figures 9 to 26, the wireless communication method for a wireless communication device using multiple links will be explained. First, Figure 9 will be used to explain a specific form of a wireless communication device using multiple links.

[0090] Figure 9 shows a multi-link device according to an embodiment of the present invention.

[0091] A multi-link device (MLD) may be defined for the wireless communication method using the multiple links described above. A multi-link device can represent a device having one or more affiliated stations. In specific embodiments, a multi-link device can represent a device having two or more affiliated stations. A multi-link device can also have interchangeable multi-link elements. A multi-link element contains information about one or more stations or one or more links. A multi-link element may include the multi-link setup element described later. In this case, the multi-link device may be a logical entity. Specifically, a multi-link device may have multiple affiliated stations. A multi-link device can be called an MLLE (multi-link logical entity) or an MLE (multi-link entity). A multi-link device may have one medium access control service access point (SAP) up to logical link control (LLC). An MLD may also have one MAC data service.

[0092] Multiple stations included in a multilink system can operate on multiple links. Furthermore, multiple stations included in a multilink system can operate on multiple channels. Specifically, multiple stations included in a multilink system can operate on different links or different channels. For example, multiple stations included in a multilink system can operate on different channels of 2.4GHz, 5GHz, and 6GHz.

[0093] The operation of a multilink device can be called multilink operation, MLD operation, or multi-band operation. Furthermore, if the station paired with the multilink device is an AP (Application Platform), the multilink device can be called an AP MLD (Application Platform Multilink). Conversely, if the station paired with the multilink device is a non-AP station, the multilink device can be called a non-AP MLD (Application Platform Multilink).

[0094] Figure 9 illustrates the communication operation between a non-AP MLD and an AP-MLD. Specifically, the non-AP MLD and AP-MLD communicate using three links each. The AP MLD includes the first AP (AP1), the second AP (AP2), and the third AP (AP3). The non-AP MLD includes the first non-AP STA (non-AP STA1), the second non-AP STA (non-AP STA2), and the third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate via the first link (Link1). The second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via the second link (Link2). The third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via the third link (Link3).

[0095] Multilink operation may include a multilink setup operation. Multilink setup corresponds to the association operation of the single-link operation described above and must be performed before frame exchange in multilink. A multilink device can obtain the information necessary for multilink setup from a multilink setup element. Specifically, the multilink setup element may include capability information related to multilink. In this case, the capability information may include information indicating whether one of the multiple devices included in the multilink device can transmit and the other devices can receive simultaneously. The capability information may also include information about the links available to each station included in the MLD. Furthermore, the capability information may include information about the channels available to each station included in the MLD.

[0096] Multilink configuration may be established through negotiations between peer stations. Specifically, multilink configuration may be performed through communication between stations without communication with the AP. Furthermore, multilink configuration may be established through any one of the links. For example, even if links 1 through 3 are configured via a multilink, the multilink configuration may be performed through link 1.

[0097] Furthermore, a mapping between TIDs (traffic identifiers) and links may be configured. Specifically, frames corresponding to a specific TID value may be exchanged only through pre-specified links. The mapping between TIDs and links may be configured in a directional-based manner. For example, if multiple links are configured between a first multilink device and a second multilink device, the first multilink device may be configured to send frames with a first TID to multiple first links, and the second multilink device may be configured to send frames with a second TID to the first links. Additionally, a default setting may exist for the mapping between TIDs and links. Specifically, if there are no additional settings in the multilink configuration, the multilink device can exchange frames corresponding to TIDs on each link according to the default setting. In this case, the default setting may be such that all TIDs are exchanged on any one link.

[0098] Let's explain TID in detail. TID is an ID used to classify traffic and data to support QoS (Quality of Service). TID may be used and assigned at layers higher than the MAC layer. TID can also indicate traffic category (TC) and traffic stream (TS). There may be 16 distinct TID values. For example, a TID may be specified as any one of 0 to 15. Different TID values ​​may be specified depending on the access policy, channel access, or medium access method. For example, when EDCA (enhanced distributed channel access) or HCAF (hybrid coordination function contention based channel access) is used, the TID value may be assigned in the range of 0 to 7. When EDCA is used, TID can indicate user priority (UP). In this case, UP may be specified by TC or TS. UP may be assigned at layers higher than MAC. Furthermore, when HCCA (HCF controlled channel access) or SPCA is used, the TID value may be assigned in the range of 8 to 15. When HCCA or SPCA is used, TID can represent TSID. Furthermore, when HEMM or SEMM is used, the TID value may be assigned in the range of 8 to 15. When HEMM or SEMM is used, TID can represent TSID.

[0099] UP and AC (access category) may be mapped. AC may be a label for providing QoS in EDCA. AC may be a label for indicating an EDCA parameter set. EDCA parameters or EDCA parameter sets are parameters used in EDCA channel contention. QoS stations can guarantee QoS using AC. AC may also include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO can indicate background, best effort, video, and voice, respectively. AC_BK, AC_BE, AC_VI, and AC_VO may also be classified into sub-ACs. For example, AC_VI can be subdivided into AC_VI primary and AC_VI alternate. Similarly, AC_VO can be subdivided into AC_VO primary and AC_VO alternate. UP or TID may also be mapped to AC. For example, each of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Also, each of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, and AC_VO alternate, respectively. Furthermore, the priority of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be in that order from highest to lowest. That is, 1 may have a lower priority and 7 may have a higher priority. Therefore, the priority may be in the order of AC_BK, AC_BE, AC_VI, and AC_VO, from highest to lowest. Furthermore, AC_BK, AC_BE, AC_VI, and AC_VO can each correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to these characteristics of TIDs, the mapping between TIDs and links can represent the mapping between ACs and links.Furthermore, the mapping between links and ACs can represent the mapping between TIDs and links.

[0100] As mentioned above, a TID may be mapped to each of multiple links. The mapping may specify which links can exchange traffic corresponding to a particular TID or AC. Additionally, TIDs or ACs that can be transmitted in different transmission directions within a link may be specified. As mentioned above, a default setting may exist for the mapping between TIDs and links. Specifically, in a multilink configuration where no additional settings are made, the multilink device can exchange frames corresponding to TIDs on each link according to the default setting. In this case, the default setting may be that all TIDs are exchanged on any one link. At any given time, any TID or AC may always be mapped to at least one link. Management frames and control frames may be transmitted on all links.

[0101] When a link is mapped to a TID or AC, only data frames corresponding to the TID or AC mapped to that link may be transmitted on that link. Therefore, when a link is mapped to a TID or AC, frames that do not correspond to a TID or AC not mapped to that link do not need to be transmitted on that link. When a link is mapped to a TID or AC, the ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a block ACK agreement may be determined based on the mapping between TIDs and links. Furthermore, in other specific embodiments, the mapping between TIDs and links may be determined based on a block ACK agreement. Specifically, a block ACK agreement may be set for a TID mapped to a particular link.

[0102] The aforementioned mapping of TIDs to links may ensure QoS. Specifically, a relatively small number of stations may be operational, or higher-priority ACs or TIDs may be mapped to links with good channel conditions. Furthermore, the aforementioned mapping of TIDs to links may enable stations to maintain a power-saving state for longer periods.

[0103] Figure 10 shows that, according to an embodiment of the present invention, transmissions on different links are performed simultaneously in multilink operation.

[0104] The implementation of multilink devices does not always support simultaneous operation on multiple links. For example, a multilink device may support simultaneous transmission on multiple links, simultaneous reception on multiple links, or transmission on one link while receiving on another. Reception or transmission on one link may affect reception or transmission on other links. Specifically, transmission on one link may act as interference on other links. Interference from one link of a multilink device affecting other links can be called internal leakage. The smaller the frequency spacing between links, the greater the internal leakage may be. If the internal leakage is not too great, transmission on one link can occur while transmission is occurring on other links. If the internal leakage is large, transmission on one link cannot occur while transmission is occurring on other links. Thus, the simultaneous operation of a multilink device on multiple links can be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, when a multilink device transmits on multiple links simultaneously, transmits on one link while receiving on another, or receives on multiple links simultaneously, this can be called STR (Simultaneous Transmission / Reception).

[0105] On the other hand, when STR is not supported due to interference between multiple stations constituting the MLD, the STA can be described as having a non-STR relationship or an NSTR relationship (a relationship where STR is not supported).

[0106] In this case, whether or not the two STAs (STA1 and STA2) of the MLD support the STR may depend on the distance between the link pairs in which the STAs are operated (Link1 in which STA1 is operated and Link2 in which STA2 is operated).

[0107] Therefore, when an MLD operates STAs on each specific link pair, and STR is supported between the two STAs operating on the specific link pair, the specific link pair may be considered as an STR link pair by the MLD. On the other hand, when an MLD operates STAs on each individual link pair, and STR is not supported between the two STAs operating on the individual link pair, the other link pair may be considered as an NSTR link pair by the MLD.

[0108] Thus, whether or not STR is supported between the STAs of an MLD is determined by whether the link pair on which these STAs operate is an STR link pair or an NSTR link pair. However, as mentioned above, since the characteristics of each MLD (such as shielding performance) may differ from one another, a particular link pair may be considered as an STR-supported link pair for a particular MLD, and as an NSTR link pair that is not supported for other MLDs.

[0109] In one embodiment of the present invention described later, for the sake of explanation, an STA operated with an MLD STR link pair will be named (explicitly referred to) as the STA of STR MLD, and an STA operated with an MLD NSTR link pair will be named (explicitly referred to) as the STA of NSTR (and non-STR) MLD. That is, in the embodiments described below, when "STA of non-STR MLD" is mentioned, it can be interpreted as referring to one of the two STAs operated with an MLD NSTR link pair, and when "STA of STR MLD" is mentioned, it can be interpreted as referring to one of the two STAs operated with an MLD STR link pair.

[0110] Furthermore, NSTR MLD can refer to MLDs that, in relation to the presence or absence of STR support mentioned above, lose the ability to receive signals from a specific MLD's STA, as well as MLDs whose hardware configuration itself does not support simultaneous transmission / reception.

[0111] In other words, the hardware configuration of a Multi-link device (MLD) may have a configuration in which the hardware resources available to other STAs of the MLD are limited when a particular STA of the MLD is transmitting or receiving. For example, if a particular MLD has a hardware configuration that supports processing for only one PPDU, then when a particular STA of the MLD is performing an Rx, the MLD cannot support Tx and Rx to other STAs within the MLD. Similarly, when a particular STA of the MLD is performing a Tx, the MLD cannot support Tx and Rx to other STAs within the MLD.

[0112] Thus, a device that is an MLD and can operate STAs on two or more links, but can only support transmission / reception for one STA at a given time, can be called a Multi-link Single Radio MLD (MLSR MLD). Alternatively, an operating mode in which an MLD supports transmission / reception for only one STA can be called an Enhanced Multi-Link Single Radio (EMLSR) mode. In this case, an MLD operating in EMLSR mode may be a Multi-radio MLD or an Enhanced Single-radio MLD. An Enhanced Single-Radio MLD supports data transmission / reception for only one link at a time, but by having a configuration that includes separate hardware (such as a low-cost PHY front-end), it can be said to be a device that supports CCA and low-speed data rate (e.g., encoded at 6MHz or 24MHz or less) PPDU transmission / reception for two or more links.

[0113] Furthermore, as a variation of EMLSR mode, EMLMR (Enhance Multi-Link Multi-Radio) may be defined in which the MLD supports transmission / reception for each STA, but utilizes a portion of the RF chain used by a specific STA for transmission / reception of other STAs. EMLMR may have the same transmission / reception limiting characteristics as EMLSR when the entire RF chain used by the specific STA is utilized for transmission / reception of the other STAs. That is, an MLD operating in EMLMR mode can support transmission / reception for only one link (STA) at a given time, regardless of whether or not STR support is available for the link, and this can be understood as operation similar to that of an MLD operating in EMLSR mode.

[0114] In other words, MLD links operating in EMLSR / EMLMR mode may be considered as NSTR link pairs.

[0115] In this context, the terms "send / receive" include both "send / send" and "receive / receive," and are unrelated to whether or not STR / NSTR support is available on either link.

[0116] For the sake of explanation, the terms EMLSR / EMLMR MLD will be used below to include both MLDs that can only support transmission / reception to one STA at a given time due to hardware limitations, and MLDs that, despite being capable of supporting transmission / reception to two or more STAs (processing capability unrelated to STR), support only high-speed data frame transmission / reception to one STA at a given time as a type of operating mode.

[0117] The operation of the STR MLD considering the performance limitations of the NSTR MLD, as provided by the embodiment of the present invention described above, can be directly applied as the operation of the STR MLD for the MLSR MLD. For example, the STA of the STR MLD can cancel the transmission it is performing or about to perform if, after transmitting to the STA of the multilink single radio MLD, it determines or predicts that the transmission has failed due to the limited performance of the multilink single radio MLD STA. In this case, the procedure for confirming whether the transmission failed due to the limited performance of the EMLSR / EMLMR MLD may be similar to the procedure for confirming whether a transmission made to the STA of the NSTR MLD failed due to the limited performance of the NSTR MLD STA.

[0118] As mentioned earlier, multilink devices can support STR (Stroke Response) both fully and with limitations. Specifically, multilink devices can only support STR under certain conditions. For example, a multilink device may not be able to perform STR when operating as a single radio. Similarly, a multilink device may not be able to perform STR when operating as a single antenna. Furthermore, a multilink device may not be able to perform STR if internal leakage is detected to be above a predetermined level.

[0119] A station can exchange information with other stations regarding its STR capability. Specifically, a station can exchange information with other stations regarding whether there are limitations on its ability to transmit or receive on multiple links simultaneously. Specifically, information regarding limitations on the ability to transmit or receive on multiple links may indicate whether transmission or reception occurs simultaneously on multiple links, or whether transmission and reception occur simultaneously. Furthermore, information regarding limitations on the ability to transmit or receive on multiple links may be indicated in stages. Specifically, information regarding limitations on the ability to transmit or receive on multiple links may be information indicating stages indicating the magnitude of internal leakage. In a specific embodiment, information indicating stages indicating the magnitude of internal leakage may be information indicating stages indicating the magnitude of interference caused by internal leakage. In yet another specific embodiment, it may be information indicating stages indicating the frequency spacing between links that may affect internal leakage. Furthermore, information indicating stages indicating the magnitude of internal leakage may be information indicating the relationship between the frequency spacing between links and the magnitude of internal leakage in stages.

[0120] In Figure 10, the first station (STA1) and the second station (STA2) are affiliated to a single non-AP multilink device. Alternatively, the first AP (AP1) and the second AP (AP2) may also be affiliated to a single non-AP multilink device. A first link (link1) is established between the first AP (AP1) and the first station (STA1), and a second link (link2) is established between the second AP (AP2) and the second station (STA2). In Figure 10, the non-AP multilink device can perform STR (Signal Transmitting) to a limited extent. When the second station (STA2) transmits on the second link (Link2), reception by the first station (STA1) on the first link (Link1) may be interfered with by transmission on the second link (Link2). For example, in the following case, reception by the first station (STA1) on the first link (Link1) may be interfered with by transmission on the second link (Link2). On the second link (Link2), the second station (STA2) transmits the first data (Data1), and the first access point (AP1) transmits an acknowledgment (Ack for Data1) to the first station (STA1). On the second link (Link2), the second station (STA2) transmits the second data (Data2). At this time, the transmission timing of the second data (Data2) and the transmission timing of the acknowledgment (Ack for Data1) may overlap. In this case, the transmission to the second station (STA2) on the second link (Link2) may cause interference on the first link (Link1). Therefore, the first station (STA1) may not receive the acknowledgment (Ack for Data1) for the first data (Data1).

[0121] This section describes how a multilink device performs channel access. For multilink operations not specifically described, the channel access procedure shown in Figure 6 can be followed.

[0122] A multilink device can access channels independently from multiple links. In this case, the channel access may be backoff-based channel access. When a multilink device accesses channels independently from multiple links and the backoff counters reach zero on multiple links, the multilink device can start transmitting on multiple links simultaneously. In a specific embodiment, when the backoff counter of any one of the links in the multilink reaches zero and a predetermined condition is met, the multilink device can access channels on other links where the backoff counter has not reached zero, in addition to the link where the backoff counter reached zero. Specifically, when the backoff counter of any one of the links in the multilink reaches zero, the multilink device can sense energy on other links where the backoff counter has not reached zero. In this case, if no energy greater than a predetermined amount is sensed, the multilink device can access channels on the link where energy sensing was performed, in addition to the link where the backoff counter reached zero. This allows the multilink device to start transmitting on multiple links simultaneously. The size of the threshold used for energy sensing may be smaller than the size of the threshold used to determine whether to decrease the backoff counter. Furthermore, when deciding whether to reduce the backoff counter, the multilink device can sense any form of signal, not just the Wi-Fi signal. Also, in the energy sensing described above, the multilink device can sense any form of signal, not just the Wi-Fi signal. Internal leakage may not be detected as a Wi-Fi signal. In such cases, the multilink device can detect the signal detected by internal leakage through energy sensing. Also, as mentioned above, the size of the threshold used for energy sensing can be smaller than the size of the threshold used when deciding whether or not to reduce the backoff counter. Therefore, even when transmission is taking place on one link, the multilink device can reduce the backoff counter on other links.

[0123] The degree of interference between links used by the multilink device may determine whether the stations operating on each link can operate independently. In this case, the degree of interference between links may be the magnitude of interference perceived by other stations of the multilink device when any one station of the multilink device transmits on any one link. If the transmission of the first station of the multilink device on the first link causes interference exceeding a predetermined magnitude to the second station of the multilink device operating on the second link, the operation of the second station may be restricted. Specifically, the reception or channel access of the second station may be restricted. When interference occurs, the second station may fail to decode the received signal due to the interference. Also, when interference occurs, the second station may determine that the channel is in use when using backoff for channel access.

[0124] Furthermore, if the transmission from the first station of a multilink device on the first link causes interference below a predetermined magnitude to the second station of the multilink device operating on the second link, the first and second stations can operate independently. Specifically, if the transmission from the first station of a multilink device on the first link causes interference below a predetermined magnitude to the second station of the multilink device operating on the second link, the first and second stations can independently access the channel. Also, if the transmission from the first station of a multilink device on the first link causes interference below a predetermined magnitude to the second station of the multilink device operating on the second link, the first and second stations can independently transmit or receive. When interference below a predetermined magnitude occurs, the second station can successfully decode the received signal even in the presence of interference. Also, when interference below a predetermined magnitude occurs, the second station can determine that the channel is idle when using backoff for channel access.

[0125] The degree of interference between stations in a multilink system can vary not only depending on the interval between the frequency bands of the links on which the stations operate, but also on the hardware characteristics of the multilink system. For example, internal interference in a multilink system that includes high-RF (radio frequency) equipment may be less than internal interference in a multilink system that includes low-RF equipment. Therefore, the degree of interference between stations in a multilink system may be determined based on the characteristics of the multilink system.

[0126] Figure 10 shows that the magnitude of interference varies depending on the interval between the frequency bands of the links and the characteristics of the multilink device. In the embodiment shown in Figure 10, the first multilink device (MLD#1) includes a first station (STA1)-1 operating on the first link (Link1) and a second station (STA1)-2 operating on the second link (Link2). The second multilink device (MLD#2) includes a first station (STA2)-1 operating on the first link (Link1) and a second station (STA2)-2 operating on the second link (Link2). The frequency interval between the first link (Link1) and the second link (Link2) in which the first multilink device (MLD#1) operates is the same as the frequency interval between the first link (Link1) and the second link (Link2) in which the second multilink device (MLD#2) operates. However, the magnitude of interference differs due to the difference between the characteristics of the first multilink device (MLD#1) and the characteristics of the second multilink device (MLD#2). Specifically, the magnitude of interference generated by the second multilink device (MLD#2) may be greater than the magnitude of interference generated by the first multilink device (MLD#1). Considering that the magnitude of interference may differ depending on the characteristics of the multilink devices, and that the availability of STR support may vary for each multilink device, it is necessary to exchange information regarding whether or not STR support is provided.

[0127] A multilink device can signal whether or not a station it includes provides STR support. Specifically, an AP multilink device and a non-AP multilink device can exchange the status of whether or not an AP included in the AP multilink device provides STR support with the status of an STA included in the non-AP multilink device providing STR support. In such an embodiment, an element indicating the presence or absence of STR support may be used. This element can be called an STR support element. The STR support element can indicate the presence or absence of STR support of a station in the multilink device that transmitted the STR support element using one bit. Specifically, the STR support element can indicate the presence or absence of STR support for each station included in the multilink device that transmitted the STR support element, one bit at a time. In this case, the bit value may be 1 when the station provides STR support, and 0 when the station does not provide STR support. If the multilink device that transmits the STR support element includes a first station (STA1), a second station (STA2), and a third station (STA3), and the first station (STA1) and the third station (STA3) support the STR, but the second station (STA2) does not, then the STR support element is 101 1b The STR support element may include a field containing the following: It is assumed that stations operating in different frequency bands support each other, and the STR support element may omit signaling for the presence or absence of STR support between stations operating in different frequency bands. For example, suppose the first station (STA1) operates on the 2.4GHz first link, and the second station (STA2) and the third station (STA3) operate on the 5GHz second and third links, respectively. In this case, the STR support element can indicate with one bit that STR support is provided between the second station (STA2) and the third station (STA3). The STR support element may also include only one bit if there are two stations to which the STR support element signals.

[0128] In specific embodiments, the relationship between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz in a multilink device may always be considered a STR (Structured Link). Therefore, signaling for the presence or absence of a STR between the 2.4 GHz link and the 5 GHz or 6 GHz link may be omitted.

[0129] In the embodiments described above, what is described as the operation of a station in a multilink device may be replaced with the operation of the multilink device itself. Also, in the embodiments described above, the operation of the AP may be replaced with the operation of a non-AP station, and the operation of a non-AP station may be replaced with the operation of the AP. Therefore, the operation of the AP in a non-STR multilink device may be replaced with the operation of a non-AP station in a non-STR multilink device, and the operation of a non-AP station in an STR multilink device may be replaced with the operation of the AP in an STR multilink device. Furthermore, the operation of a non-AP station in a non-STR multilink device may be replaced with the operation of the AP in a non-STR multilink device, and the operation of the AP in an STR multilink device may be replaced with the operation of a non-AP station in an STR multilink device.

[0130] Figure 11 shows the operation of a multilink device when the link is changed according to one embodiment of the present invention.

[0131] The STR support element may be replaced when the link frequency bandwidth is changed. As mentioned above, the availability of STR support for a station may depend on the distance between the link frequency bandwidths, and the availability of STR support for a station may change when the link frequency bandwidth is changed. When the link frequency bandwidth is changed, this may include at least one of the following: a change in the link center frequency, a change in the bandwidth of the frequency band, and a change in the 20MHz main channel. The AP and the station can exchange the STR support element upon request and response. Furthermore, in other specific embodiments, the STR support element may be replaced without further request when the link frequency bandwidth is changed. Also, in the embodiments described above, when the link frequency bandwidth is changed, this may include a change in the operating channel of the station.

[0132] If a station of a non-AP multilink device is unable to perform a STR (Stroke Response), the station may request a link change from the AP (Application Platform). Specifically, the station of the non-AP multilink device may request at least one of the following: a change in center frequency, a change in frequency band bandwidth, and a change in the 20 MHz main channel. The link change request may be sent to the AP on the link to which the change is requested. In yet another specific embodiment, the link change request may be sent to the AP on a link to which no change is requested. In this case, the link change request may include information indicating which link is to be changed. The information indicating the link may be a number that identifies the link. In such an embodiment, the link change may be a change in the operating channel within a single frequency band. The link change may also include information on how the link is changed. Specifically, the link change request may indicate whether to move the center frequency of the link to a higher frequency than the current center frequency, or to move the center frequency of the link to a lower frequency than the current center frequency. In yet another specific embodiment, the link change request may implicitly indicate a change to a frequency band that moves away from adjacent links. Furthermore, a link change request may indicate a reduction in link bandwidth. A link change request may also request a change in the location of the primary channel. Specifically, a link change request may indicate a change in the primary channel's location to a channel in a lower or higher frequency band than the current primary channel's location. An AP receiving a link change request may change the link in response to the request. In a specific embodiment, an AP receiving a link change request may also ignore it.

[0133] In the embodiment shown in Figure 11, the second station (STA2) and third station (STA3) of the non-AP multilink device are unable to support the STR. The non-AP multilink device requests the AP multilink device to change the third link (Link3). Upon receiving the link change request, the AP multilink device changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the third link (link3) to be changed can send a change request to the third AP (AP3). Furthermore, in other specific embodiments, a station that does not operate on the third link (link3) can send a change request to an AP that does not operate on the third link (link3).

[0134] When an AP changes links, it can broadcast information about the link change using a beacon frame. This information may include information about the link frequency. This information may include at least one of the following: the link's center frequency, operating bandwidth, and primary channel. The information may also include information about the timing of the link change. Furthermore, the link change may be completed when the beacon containing the link change information is transmitted.

[0135] In Figure 11, the link on which the third station (STA3) operates has been changed, and both the third station (STA3) and the second station (STA2) are now capable of supporting the STR. As mentioned earlier, the non-AP multilink device can transmit an STR support element to the AP multilink device and signal whether the changed STR support is available.

[0136] As mentioned above, link changes may not be permitted, or STR may not be supported even after the change. Furthermore, as shown in the embodiment in Figure 11, AP multilink devices may support STR, while non-AP multilink devices may not. This is because AP multilink devices generally use relatively expensive equipment, while non-AP multilink devices use relatively inexpensive equipment. Therefore, a method is needed to enable efficient communication between multilink devices even when one of the multilink devices does not support STR. In this case, STR can indicate that transmission and reception occur simultaneously. This will be explained using Figure 12.

[0137] Figure 12 shows that, according to one embodiment of the present invention, when one station of a non-STR multilink device is receiving, channel access for other stations of the non-STR multilink device is prohibited.

[0138] When transmission occurs on one link of a non-STR multilink device while reception occurs on the other links, both reception and transmission may fail. To resolve this, channel access may be prohibited on the other links of the non-STR multilink device when reception is occurring on one link. Specifically, when reception is occurring on one link of the non-STR multilink device, backoff of channel access may be prohibited on the other links. This prevents transmission from starting on the other links of the non-STR multilink device when reception is occurring on one link. In a specific embodiment, backoff of channel access may be prohibited on the other links of the non-STR multilink device when reception begins on one link. This may be set using a specific bit in memory, such as a channel access prohibition flag. That is, whether or not channel access is prohibited may be shared by the memory inside the multilink device. With such an embodiment, channel access prohibition can be implemented without separate frame exchange. For the sake of clarity, as used herein, "channel access prohibition" means prohibiting channel access or transmission in order to protect the transmission or reception of non-STR multilink equipment, unless otherwise specified.

[0139] When channel access is prohibited, stations operating on the prohibited link cannot perform the backoff procedure regardless of the NAV and CCA results. Furthermore, when channel access is prohibited, stations operating on the prohibited link cannot transmit regardless of the NAV and CCA results. However, even when channel access is prohibited, stations operating on the prohibited link can still receive. Additionally, a channel access prohibition on the second link due to reception on the first link may be lifted based on the completion of reception on the first link. Specifically, a channel access prohibition on the second link due to reception on the first link may be lifted when reception on the first link is completed. Furthermore, in other specific embodiments, a channel access prohibition on the second link due to reception on the first link may be lifted based on the point in time when an ACK is sent after reception on the first link is completed. Specifically, a channel access prohibition on the second link due to reception on the first link may be lifted at the point in time when an ACK is sent after reception on the first link is completed. In yet another specific embodiment, channel access prohibition on the second link due to reception on the first link may be lifted when the ACK transmission is completed after reception is completed on the first link. Also, immediately after the channel access prohibition is lifted, the station can immediately decrement the backoff counter without additional sensing. In this case, the additional sensing may refer to sensing performed in DIFS (DCF Interframe Space). In yet another specific embodiment, if the channel is idle for a predetermined time immediately before the channel access prohibition is lifted, the station can immediately decrement the backoff counter without additional sensing. In this case, the predetermined time may be any one of PIFS (PCF Interframe Space), DIFS, SIFS (Short Interframe Space), and AIFS (Arbitration Interframe Space).

[0140] In the embodiment of FIG. 12, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) is receiving, in-device interference occurs. As described above, while the first station (STA1) operating on the first link (Link1) is receiving, channel access by the second station (STA2) on the second link (Link2) is prohibited. After the reception of the first station (STA1) on the first link (Link1) is completed, the channel access prohibition is released. Immediately after the channel access prohibition is released, the second station (STA2) can decrease the previous backoff counter value from 3 to 2 without additional sensing.

[0141] For the sake of expression convenience, in FIG. 12, when representing Rx and Tx, a single block (Tx solid line, Rx dotted line) is used, and it may be understood that the single block represents an operation including Tx / Ack reception and Rx / Ack transmission without separately illustrating an Ack block. This may be equally applicable to the drawings described below.

[0142] When a station confirms that it is not the intended recipient of the PPDU it receives, the station can interrupt the reception of the PPDU. In this case, the operation of releasing the channel access prohibition in the multi-link device becomes a problem. In this specification, the intended recipient is used in the same meaning as the destination station.

[0143] FIG. 13 shows the operation of releasing the channel access prohibition when a station of a non-STR multi-link device confirms that the intended recipient of the PPDU it receives is not the station, according to an embodiment of the present invention.

[0144] If a station confirms that it is not the intended recipient based on the received PPDU, the station may lift the channel access ban. The station can determine whether it is the intended recipient of the PPDU based on the information indicating the recipient address in the PPDU's signaling field. In this case, the information indicating the recipient address in the PPDU's signaling field may be the value of the STA-ID field in the EHT-SIG field as described above. Specifically, the station can determine whether the STA-ID field in the EHT-SIG field points to the station. The station can also determine whether it is the intended recipient of the PPDU based on the value of the RA field in the MAC frame contained in the PPDU. Specifically, the station can determine whether the RA field in the MAC frame contained in the PPDU points to the station. In Figure 13, the non-STR multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The first station (STA1) receives the PPDU. The first station (STA1) determines that the intended recipient of the received PPDU is not the first station (STA1) and interrupts the reception of the PPDU. At this time, the first station (STA1) can lift the channel access ban on the second station (STA2). Even after the channel access ban on the second station (STA2) is lifted, channel access on the second station (STA2) may be delayed by the NAV set on the second station (STA2).

[0145] As shown in Figure 13, even after channel access restrictions are lifted, stations included in non-STR multilink devices often have fewer channel access opportunities compared to stations not included in multilink devices or stations included in STR multilink devices. Therefore, to ensure fair competition with other stations, a method may be needed to compensate for the channel access opportunities of stations included in non-STR multilink devices. For example, immediately after the channel access restriction is lifted, it may be permissible for the station whose channel access restriction has been lifted to decrease its backoff counter by 2 or more. This will be explained using Figure 14.

[0146] Figure 14 shows an embodiment of the present invention in which a station performs channel access after the channel access ban is lifted.

[0147] A station whose channel access ban has been lifted can reduce its backoff counter by 2 or more immediately after the ban is lifted. This is to ensure fairness in channel access opportunities among stations, as other stations performed the backoff procedure while the station's channel access was banned.

[0148] In further specific embodiments, a station whose channel access is prohibited can perform a channel access procedure to reduce the CCA (CSMA) and backoff counter while channel access is prohibited. In Figure 14, a non-STR multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). In Figure 14, while the first station (STA1) is receiving, channel access for the second station (STA2) is prohibited. In Figure 14(a), while channel access for the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure to reduce the CCA (CSMA) and backoff counter. In Figure 14(a), while channel access for the second station (STA2) is prohibited, the channel on the second link (Link2) is idle, so the second station (STA2) reduces the backoff counter.

[0149] Furthermore, a station whose channel access is prohibited can delay transmission without starting transmission even if the backoff counter reaches 0 while channel access is prohibited. In this case, the station can maintain the value of the backoff counter at 0. Also, even if the station delays transmission, the station can maintain the CW value as is. Therefore, this is differentiated from the station doubling the CW value because the channel the station is accessing is busy. This is because the reason for the delay in transmission is not that the channel was determined to be busy. In Figure 14(b), while channel access for the second station (STA2) is prohibited, the second station (STA2) can perform channel access procedures to decrease the CCA (CSMA) and the backoff counter. In Figure 14(b), while channel access for the second station (STA2) is prohibited, the channel on the second link (Link2) is idle, so the second station (STA2) decreases the backoff counter. While channel access for Station 2 (STA2) is prohibited, Station 2 (STA2)'s backoff counter reaches 0. Station 2 (STA2) delays transmission and begins transmitting after the channel access prohibition is lifted.

[0150] As mentioned above, channel access prohibition may include prohibiting transmission to the second station when the first station of a non-STR multilink device is transmitting. Furthermore, channel access prohibition may also include prohibiting transmission by the second station when the first station of a non-STR multilink device is receiving.

[0151] In Figure 14(b), if multiple stations have channel access prohibited in the embodiment, there is a high probability that the channel access prohibition will be lifted simultaneously for multiple stations, and multiple stations will attempt to transmit at the same time. Therefore, a method is needed to reduce the probability of transmission collisions. This will be explained using Figure 15.

[0152] Figure 15 shows the operation of a station according to one embodiment of the present invention, which transmits after the channel access ban is lifted.

[0153] As mentioned above, transmission may occur on the first link of a non-STR multilink device while transmission is prohibited on the second link. If the transmission is completed on the first link, transmission on the second link may begin with RTS / CTS frame exchange. Therefore, when transmission occurs on the first link of a non-STR multilink device, the non-STR multilink device can begin RTS / CTS frame exchange on the second link. After the channel access prohibition is lifted for a station whose transmission has been delayed due to channel access prohibition, the station can begin RTS / CTS (request to send / clear to send) frame exchange before starting the delayed transmission. In this case, if the station fails to receive a CTS frame, it may not be able to start the delayed transmission. In the embodiment shown in Figure 15(a), the station whose transmission has been delayed due to channel access prohibition sends an RTS frame before starting the delayed transmission. After the station receives a CTS frame as a response to the RTS frame, it starts the delayed transmission.

[0154] In another specific embodiment, after a channel access ban is lifted for a station whose transmission has been delayed due to a channel access ban, the station can transmit a frame containing only a portion of the delayed transmission. At this time, after the station receives a response, such as an ACK, to the frame containing only a portion of the delayed transmission, the station can transmit the untransmitted portion of the delayed transmission. If the station does not receive a response to the frame containing only a portion of the delayed transmission, the station does not need to transmit the untransmitted portion of the delayed transmission. Thus, the reason why stations can start RTS / CTS exchange or transmit only a portion of the delayed transmission after the channel access ban is lifted is that the probability of transmission collisions after a channel access ban is higher than that of a normal transmission. Therefore, the above-described embodiment may be mandatory for transmissions made after the channel access ban is lifted. In existing wireless LAN operations, RTS / CTS frames are used to solve the hidden node problem and could be used based on the size of the transmitted data. In the embodiment described above, the RTS / CTS frame is intended to protect the transmission or reception of non-STR multilink equipment by preventing transmission collisions with stations attempting to perform delayed transmissions.

[0155] As mentioned above, when one station of a non-STR multilink device is receiving, transmission by other stations of the non-STR multilink device may be restricted. Also, when one station of a non-STR multilink device is transmitting, other stations of the non-STR multilink device may not be able to accurately sense the channel status of the link on which the station is operating. Specifically, when the first station of a non-STR multilink device is transmitting, the second station of the non-STR multilink device may always determine that the channel status of the link on which the second station is operating is busy. Therefore, even when the channel on the link on which the second station is operating is idle, the second station may determine that the channel is in use due to internal interference. In this way, when a station cannot determine the channel status due to internal interference, or when one station of the non-STR multilink device is continuing to transmit, the other stations of the non-STR multilink device are considered to be in a blind state. Due to the circumstances described above, a station in a blind state may find it difficult to attempt transmission by performing a backoff procedure. Furthermore, stations in a blind state due to the aforementioned circumstances may have difficulty in initiating or successfully decoding PPDUs. Therefore, a transmission method that takes blind stations into consideration is necessary. This will be explained using Figure 16.

[0156] On the other hand, an STA in an EMLSR / EMLMR MLD cannot confirm or receive whether a PPDU has been sent to it if a PPDU is being sent / received via an STA on another link. Therefore, an STA in an MLD operating in EMLSR / EMLMR mode may have the same performance constraints as an NSTR MLD STA being blinded while other STAs within the MLD are sending / receiving data frames. Accordingly, in the embodiments described later, the operation considering the state of a blinded STA may be understood in the same way as considering whether an STA in an MLD operating in EMLSR / EMLMR mode is constrained by the operation (sending / receiving) of other STAs within the MLD.

[0157] In this case, a mode in which a multilink device uses a single radio on a single link for a specific time interval can be called EMLSR mode. While the multilink device performs frame exchange on the first link of an EMLSR link, which is one of several links to which EMLSR mode is applied, the multilink device does not transmit or receive on the second link of the EMLSR link. Furthermore, when other stations of the multilink device transmit or receive using a portion of the RF chain used by a specific station of the multilink device for a specific time interval in a specific mode, the specific mode can be called ELMMR (enhanced multi-link multi-radio) mode. Specifically, when one station of the multilink device transmits or receives using all of the RF chains of the other stations of the multilink device in ELMMR mode, the operation of the multilink device may be the same as the operation of the multilink in EMLSR mode. Also, even when a multilink device operates in EMLSR mode, some of the multiple links on which the multilink device operates can operate without the restrictions imposed by EMLSR mode. When a multilink device operates in EMLSR mode, the links to which EMLSR mode applies may be only a portion of the links on which the multilink device operates. For example, when a multilink device operates on links 1 through 3, EMLSR mode or ELMMR mode may be applied only to links 1 and 2. Therefore, when a multilink device transmits or receives on link 1 during a specific time interval in EMLSR mode, the multilink device cannot transmit or receive on link 2. In this case, the multilink device can transmit or receive on link 3 without the restrictions imposed by EMLSR mode. For convenience of explanation, links to which EMLSR mode can be applied, such as links 1 and 2, will be referred to as EMLSR links, and links to which ELMMR mode can be applied will be referred to as ELMMR links. Transmitting or receiving using the RF chain of a specific station in EMLSR mode and ELMMR mode results in a change in the transmission, reception, or monitoring capabilities on the links on which the specific station operates.Therefore, the embodiments of the present invention applied in the following description in relation to the EMLMR mode may be applied identically in relation to the EMLMR mode without special mention.

[0158] Figure 16 shows a transmission performed based on the status of a station in a non-STR multilink device according to an embodiment of the present invention.

[0159] A station attempting to transmit to a station in a non-STR multilink device can decide whether or not to transmit based on whether or not the non-STR multilink device station is blinded. In this case, the station attempting to transmit to a station in a non-STR multilink device may be a station included in an STR multilink device. Alternatively, the station attempting to transmit to a station in a non-STR multilink device may be an AP included in an AP multilink device, and the non-STR multilink device may be a non-AP multilink device. A station attempting to transmit to a station in a non-STR multilink device can determine whether or not the non-STR multilink device station is blinded as follows: The station attempting to transmit can determine whether or not other stations in the multilink device included in the station are transmitting to the non-STR multilink device. If other stations in the multilink device included in the station are receiving from the non-STR multilink device, the station can determine that the non-STR multilink device station receiving the station's transmission is blinded. In the embodiment shown in Figure 16, the STR AP multilink device includes a first AP (AP1) operating on the first link (Link1) and a second AP (AP2) operating on the second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). Therefore, the second AP (AP2) can inform the first AP (AP1) that it is receiving from the second station (STA2). Specifically, the second AP (AP2) can inform the first AP (AP1) that the entity transmitting to the second AP (AP2) is the second station (STA2). In yet another specific embodiment, the second AP (AP2) can inform the first AP (AP1) that the second station (STA2) is currently transmitting.Based on this, the first AP (AP1) can determine that the first station (STA1) is in a blind state.

[0160] The stations within the multilink device may be operated by a common MAC. Therefore, the information exchange between the first AP (AP1) and the second AP (AP2) mentioned above does not need to be explicitly performed.

[0161] A station does not need to transmit to a station that is blind. This is because even if a station transmits to a blind station, there is a high probability that the blind station will not be able to start receiving or will not be able to decode the PPDU. In this case, the station can cancel the transmission to the blind station and transmit to another station.

[0162] When an STR multilink device transmits to a non-STR multilink device, the STR multilink device can transmit to the non-STR multilink device on multiple links. Specifically, when the STR multilink device transmits to a non-STR multilink device on the first link, the STR multilink device can start transmitting to the non-STR multilink device on the second link. At this time, the STR multilink device can determine the length of the transmission on the second link based on the fact that it is a transmission to a non-STR multilink device. Specifically, the STR multilink device can determine the length of the transmission to the non-STR multilink device on the second link based on the length of the transmission to the non-STR multilink device on the first link. In a specific embodiment, the STR multilink device may terminate the transmission on the first link and the transmission on the second link simultaneously. This is to prevent transmission to other stations of the non-STR multilink device from occurring before the transmission to one of the non-STR multilink device stations is completed and before that station sends a response to the transmission, such as an ACK. As described above, multiple stations of a non-STR multilink device can simultaneously transmit responses to transmissions to multiple stations.

[0163] The STR multilink device cannot determine the status of stations included in the non-STR multilink device in real time. Therefore, even if the STR multilink device operates according to the embodiment described in Figure 16, interference or transmission collisions may occur between the links on which the non-STR multilink device operates. For example, in the embodiment of Figure 16, the first AP (AP1) may start transmitting to the first station (STA1) before the second station (STA2) recognizes that it is transmitting to the second AP (AP2). In this way, interference or collisions between links may occur with a higher probability than interference or transmission collisions within a link. This will be explained in more detail using Figure 17.

[0164] Figure 17 shows a situation in which interference or collision between links may occur.

[0165] A transmission collision can occur between links if the transmission from the second station of a non-STR station multilink device to the second AP of an STR AP multilink device begins simultaneously with the transmission from the first AP of an STR AP multilink device to the first station of a non-STR station multilink device. This is shown in Figure 17(a). This can occur because, as mentioned above, the STR multilink device cannot determine the status of stations included in the non-STR multilink device in real time.

[0166] Furthermore, a transmission collision can occur between links if the transmission from the second station of a non-STR station multilink device to the second AP of an STR AP multilink device begins earlier than the transmission from the first AP of an STR AP multilink device to the first station of a non-STR station multilink device. This is shown in Figure 17(b). This is because it may take time for the second AP (AP2) to notify the first AP (AP1) that the second station (STA2) is transmitting. Thus, since transmission collisions can occur between stations that start transmitting at different times, the probability of interference or transmission collisions between links may be higher than that of interference or collisions within a link. Also, the longer the time it takes for an AP of an STR multilink device to identify the sender of the PPDU it receives, the higher the probability of interference or transmission collisions between links may be. Therefore, a method to resolve this is needed. When one of the stations of an STR multilink device is receiving, other stations of the STR multilink device do not need to access the channel. However, if channel access is prohibited in this way, the meaning of the STR function may be lost. Therefore, an operating method that does not prohibit channel access of the STR multilink device is needed. This will be explained using Figure 18.

[0167] As mentioned above, it can be important for a multilink device to quickly determine which station is transmitting to the multilink device. The User field of the EHT-SIG in the EHT UL PPDU can indicate the identifier (STA-ID) of the station transmitting the EHT UL PPDU. Specifically, if the DL / UL field in the signaling field of the EHT PPDU indicates that the EHT PPDU is a UL PPDU, the User field of the EHT-SIG in the EHT PPDU can indicate the identifier of the station transmitting the EHT UL PPDU. The multilink device receiving the EHT PPDU can identify the station transmitting the EHT PPDU based on the User field of the EHT-SIG in the EHT UL PPDU. This allows the AP multilink device to determine which station is transmitting the EHT UL PPDU and decide which device is the target of the transmission. Specifically, the AP multilink device can determine whether there is a high probability that the attempted transmission will fail due to an inter-link collision. Furthermore, if there is a high probability that the transmission attempted by the AP multilink device will fail, the AP multilink device may delay the attempted transmission and perform another transmission.

[0168] Figure 18 shows an example of how an STR multilink device stops transmitting to a non-STR multilink device according to one embodiment of the present invention.

[0169] If a station of an STR multilink device is transmitting to a station of a non-STR multilink device, and the non-STR multilink device is determined to be in a blind state, the STR multilink device can interrupt transmission to the blind non-STR multilink device station. Specifically, the STR multilink device can determine whether a station of a non-STR multilink device is in a blind state based on the value indicated by the STA(AID)-ID in the signaling field of the received PPDU or the TA (transmitting address) field of the MAC frame contained in the received PPDU. In this case, the STA-ID may be a value that indicates the station transmitting the UL PPDU in the UL PPDU. In a specific embodiment, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state if the value indicated by the STA(AID)-ID in the signaling field of the received PPDU indicates a first station included in the non-STR multilink device. Furthermore, the STR multilink device can determine that a second station in the non-STR multilink device is blind if the TA field of the MAC frame contained in the received PPDU indicates a first station in the non-STR multilink device. Specifically, the STR multilink device can determine that a second station in the non-STR multilink device is blind if the station that transmitted the PPDU indicated by the PPDU's signaling field is the first station, or if the TA field of the MAC frame contained in the PPDU indicates the first station. In this way, the STR multilink device can confirm that one station in the non-STR multilink device is transmitting and determine that the other stations in the non-STR multilink device are blind. First, we will explain the operation of a station after transmission cancellation.

[0170] If a TXOP remains set on a station of a non-STR multilink device, a station that has canceled a transmission to that non-STR multilink device station may attempt to transmit to a different station. In this case, the station that canceled the transmission to the non-STR multilink device station can transmit to a different station without a separate backoff procedure. In a specific embodiment, if, after canceling a transmission to a non-STR multilink device station, the channel is detected as idle for a predetermined time interval without a separate backoff procedure, the station that canceled the transmission to the non-STR multilink device station can transmit to a different station. In this case, the predetermined time interval may be any one of SIFS, PDIF, and DIFS.

[0171] A station that has canceled a transmission to a non-STR multilink device station can, when transmitting to a different station, transmit traffic with the same priority as the canceled transmission or traffic with a higher priority. This is because it would be unfair to transmit traffic with a lower priority than the traffic used for channel access for the canceled transmission. In the embodiment described above, the STR multilink device station may be an AP.

[0172] A station that has canceled a transmission to a non-STR multilink station can initialize its configured TXOP. Specifically, a station that has canceled a transmission to a non-STR multilink station can send a CF-End frame after the transmission cancellation. This may allow other stations operating on the link where the transmission was scheduled to take place to use the link.

[0173] In Figure 18, the STR AP multilink device includes a first AP (AP1) operating on the first link (Link1) and a second AP (AP2) operating on the second link (Link2). The non-STR non-AP multilink device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). While transmitting to the first station (STA1), the first AP (AP1) determines that the first station (STA1) is in a blind state. Therefore, the first AP (AP1) interrupts the transmission to the first station (STA1). In Figure 18(a), after interrupting the transmission to the first station (STA1), the first AP (AP1) first transmits to a station different from the first station (STA1), as in the embodiment described above. In Figure 18(b), after interrupting transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame as described in the embodiment later.

[0174] When a station interrupts transmission, it does not need to send the next fragment after sending the fragment that was being transmitted. In yet another specific embodiment, the station can immediately stop transmitting the packet that was being transmitted.

[0175] Furthermore, the STA of an STR MLD that has transmitted to the STA of an MLD operating in EMLSR or ELMMR mode can also cancel the transmission it was performing or was about to perform, just as the STR MLD that transmitted to the STA in the aforementioned BLIND state. This is because the STA of an MLD operating in EMLSR / EMLMR mode may have performance constraints similar to those in the BLIND state, as mentioned above.

[0176] In other words, an STA of an STR MLD can abort its transmission if it receives a PPDU from another STA of the EMLSR / EMLMR MLD (e.g., EMLSR STA2) via an STA operating on another link while it is transmitting to an STA of an MLD in EMLSR / EMLMR mode (e.g., EMLSR STA1). Also, if it has not yet started transmitting, it can transmit other traffic of the same AC (Access Category) without transmitting the transmission it intended to send to the EMLSR / EMLMR MLD STA (e.g., EMLSR STA1).

[0177] Thus, the transmission management method for an EMLSR / EMLMR mode MLD to an STA may be managed in a similar / identical manner to the transmission management method for an NSTR MLD to an STA. Therefore, even if a separate explanation of EMLSR / EMLMR mode MLD is not provided in the present invention, the operations performed based on whether or not a specific STA in an NSTR MLD is in a BLIND state may be performed in the same / similar manner based on whether or not the performance of a specific STA in an EMLSR / EMLMR mode MLD is limited by transmission / reception of other STAs.

[0178] In the embodiment described above, when an STR multilink device interrupts transmission to a non-STR multilink device station that is in a blind state and transmits to a different station from the blind non-STR multilink device station, it is necessary to inform the other station that transmission to another station may be taking place in order to ensure stable reception. The method for doing so will be described below. For the sake of explanation, the station that is different from the blind non-STR multilink device station will be referred to as "the other station".

[0179] A station in an STR multilink device can insert the address of another station into a MAC frame. Specifically, a station in an STR multilink device can insert the address of the intended recipient of the MAC frame into the RA (receiving address) of the MAC frame and the address of another station into a separate field. In yet another specific embodiment, a station in an STR multilink device can insert the address of another station into the EHT-SIG. Specifically, a station in an STR multilink device can insert the address of the intended recipient of the PPDU and the address of another station into the User field of the PPDU's signaling field. In this case, the address of the other station may be inserted after the address of the intended recipient of the PPDU in the User field of the PPDU's signaling field.

[0180] In another specific embodiment, the station can monitor PPDU reception for a predetermined time even after recognizing that the intended recipient of the received PPDU is not the station. Specifically, the station can monitor whether PPDU reception continues for a predetermined time even after recognizing that the intended recipient of the received PPDU is not the station. This allows the station to determine whether PPDU transmission has been interrupted and whether transmission to the station can begin again. In such an embodiment, if it is determined that PPDU transmission will continue for a predetermined time, the station can enter a doze state. If it is determined that PPDU transmission will not continue for a predetermined time, the station can remain in a wake-up state. At this time, if a new PPDU is received by the station, the station can decode the PPDU.

[0181] In another specific embodiment, a station transmitting a PPDU may insert information into the PPDU that signals that the transmission of the PPDU may be interrupted. This information may be a 1-bit subfield. For example, if the value of the subfield that signals that the transmission of the PPDU may be interrupted is 1, a station receiving the PPDU can determine that the transmission of the PPDU may be interrupted before the time indicated by the Length field of the PPDU's signaling field and the Duration field of the MAC frame. If a station determines that the transmission of the PPDU may be interrupted before the time indicated by the Length field of the PPDU's signaling field and the Duration field of the MAC frame, the station may delay entering a power-saving state. Alternatively, a station transmitting a PPDU may insert information into the PPDU's reserved field that signals that the transmission may be interrupted.

[0182] In this way, it is possible to prevent the channel from being unnecessarily occupied by using transmission cancellation or transmission interruption.

[0183] When a transmission is interrupted or delayed due to a link-to-link transmit collision, the CW value used for channel access may be doubled, similar to a typical transmit failure. However, when a transmission is interrupted or delayed due to a link-to-link transmit collision, unlike a typical channel access failure or transmit failure, the CW value used for channel access may not be doubled. In other words, the station can maintain the same CW value used for channel access. Doubling the CW value reduces the probability of a transmit collision by increasing the range of numbers that can be used for the backoff counter. This is less necessary if the station can clearly recognize that it is a link-to-link transmit collision. Also, doubling the CW value when a transmission is interrupted or delayed due to a link-to-link transmit collision can lead to a transmission delay. However, if an intra-link collision occurs simultaneously with a link-to-link transmit collision, the station needs to double the CW value. This will be explained using Figure 19.

[0184] Figure 19 shows how, according to an embodiment of the present invention, the STR multilink device processes the CW value when it detects a transmission collision between links.

[0185] If a station cancels a transmission due to a transmission from a non-STR multilink device, as in the embodiment described above, the station can sense the channel status after canceling the transmission. If the channel is sensed to be active, the station can double the CW value. In this case, the doubling can follow the embodiment described in Figure 6. Also, if the channel is sensed to be active, the station can maintain the CW value. Such embodiments are used because even if the channel is sensed to be active, the likelihood of a transmission collision occurring in the link is low, so it is treated differently from when a transmission is successful. Specifically, if the AP of an AP multilink device fails to transmit to a station of a non-STR multilink device, the AP of the AP multilink device can acquire a backoff counter within CW without increasing CW. In this case, if the non-STR multilink device of the AP multilink device fails to transmit to the first station, and the second station of the non-STR multilink device transmits, the AP of the AP multilink device can acquire a backoff counter within CW without increasing CW. As described above, the AP multilink device can determine whether the second station of the non-STR multilink device transmits based on the transmitting station of the PPDU indicated by the PPDU's signaling field or the station indicated by the TA field of the MAC frame contained in the PPDU. In the embodiment described above, when EDCA is applied, the procedures for CW adjustment and backoff counter generation may be performed separately for each AC.

[0186] In further specific embodiments, the STR multilink device can determine whether it failed to transmit a PPDU based on whether it received a response to the PPDU. In this case, the STR multilink device does not need to consider whether the station receiving the PPDU is included in a non-STR multilink device. For example, even if the first station receiving the PPDU is included in a non-STR multilink device, and the second station of that non-STR multilink device is transmitting, preventing the first station from sending a response to the PPDU, the STR multilink device can still determine that it failed to transmit the PPDU. Furthermore, if the STR multilink device fails to transmit a PPDU, it can increase the CW value to the next largest possible value for the CW value. In this case, if the CW value is at its maximum value, the STR multilink device can maintain the CW value at the same value.

[0187] In another specific embodiment, if a channel is sensed to be idle, the station can set the CW value to the minimum CW value of the traffic (CW_min). This embodiment is used because when a channel is sensed to be idle, the likelihood of a transmit collision in the link is low, and therefore it is treated the same as when a transmit is successful. The station can apply the above embodiment to the CW of the AC of the traffic included in the canceled transmit.

[0188] Furthermore, if the station cancels a transmission as described in the above embodiment, it does not need to increment the retry counter. In this case, the retry counter may include at least one of a long retry counter and a short retry counter.

[0189] In the previous embodiment, canceling a transmission may include at least one of the following: interrupting the transmission or delaying the transmission before initiating it.

[0190] If the station cancels the transmission after sending a CTS-to-Self frame before attempting to send, the station does not have to initiate an RTS / CTS frame exchange before attempting to send after the cancellation. This is because the NAV has already been set by the CTS-to-Self frame. Also, if there is a remaining TXOP when the station attempts to send again after canceling the transmission, the station can attempt to send without a backoff procedure.

[0191] In FIG. 19, the STR AP multi-link device includes a first AP (AP1) operating on a first link (Link1) and a second AP (AP2) operating on a second link (Link2). The non-STR non-AP multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). The second station (STA2) is transmitting to the second AP (AP2). The first AP (AP1) determines that the first station (STA1) is in a blind state during the transmission to the first station (STA1). Therefore, the first AP (AP1) interrupts the transmission to the first station (STA1). In FIG. 19(a), the first AP (AP1) determines that the channel of the first link (Link1) is idle. At this time, since there is no remaining TXOP, the first AP (AP1) accesses the channel by a backoff procedure. In FIG. 19(b), the first AP (AP1) determines that the channel of the first link (Link1) is not idle. At this time, since there is a remaining TXOP, the first AP (AP1) attempts to send without a backoff procedure.

[0192] <Transmission method of MLD considering a pair of non-STR links>

[0193] The foregoing embodiments have described an operation restriction method for an MLD that takes into account the influence (e.g., interference) on the PPDU transmission / reception and / or channel connection of other STAs in the same MLD when an STA that constitutes the MLD for assisting NSTR performs transmission / reception. Hereinafter, embodiments of the present invention described later will describe a channel connection management method for each STA of the MLD when such an operation restriction method for the MLD that assists NSTR is applied.

[0194] <AP Transmission Management Method>

[0195] When a specific AP among at least one AP that constitutes an AP MLD has completed channel access to a specific AC and obtained the right to start transmitting traffic to the specific AC, the specific AP does not have to transmit the frames stored in the transmission queue for the specific AC.

[0196] In this case, even though the specific AP has obtained the right to start transmission to the specific AC, the specific AP may recognize that the frames in the transmission queue of the specific AC must be transmitted to an STA in the BLIND state and decide not to start transmission. At this time, the specific AP may also recognize that the frames in the transmission queue of the specific AC must be transmitted to an STA in an EMLSR / EMLMR mode MLD having performance constraints similar to BLIND and decide not to start transmission (hereinafter, the description regarding the EMLSR / EMLMR mode MLD is omitted).

[0197] Furthermore, if a frame in the transmission queue of an AC that has acquired transmission initiation authority is a frame that must be sent to an NSTR MLD STA that is in a BLIND state (i.e., another STA operating on the NSTR link pair of the NSTR MLD is currently transmitting), the AP can decide not to transmit the frame because the NSTR MLD STA will not be able to receive it even if the AP transmits it. If, however, there is a frame in the transmission queue of an AC that has acquired transmission initiation authority that needs to be sent to another STA that is not in a BLIND state, the AP can transmit the frame in the AC's transmission queue to the other STA.

[0198] If the AP decides not to initiate transmission to an AC that has acquired the authority to initiate transmission, the AP can perform / invoke a new backoff procedure with the AC. In this case, when the AP performs a new backoff procedure with the AC, it can generate a new backoff counter while maintaining the CW (contention window). That is, the CW[AC] and QSRC[AC] (QoS STA short retry counter) remain unchanged, only the backoff counter is regenerated, and a new backoff procedure may be performed with the AC that has acquired the authority to initiate transmission.

[0199] On the other hand, if the AP has acquired the authority to initiate transmission and there are frames to be sent to an STA that is in a BLIND state in the transmission queue, the AP may consider that such frames do not exist in the transmission queue. For example, if the transmission queue contains only frames to be sent to an STA that is in a BLIND state, the AP may consider that there are no frames in the transmission queue, maintain the BO (backoff counter) of the AC that has acquired the authority to initiate transmission at 0, and decide (act) not to start transmission. In this case, when the BLIND state of the STA is released, the AP may consider that frames to be sent to the STA have been generated in the transmission queue and immediately begin transmission. In this case, "immediately" can mean transmission performed without a separate backoff procedure in accordance with the EDCA rules. That is, when the BLIND state of the STA is released, if it is determined (considered) that the medium was idle for a time already set before the release of the BLIND state (e.g., DIFS, SIFS, PIFS, AIFSN[AC], etc.), the AP may start transmission to the STA at the next slot boundary.

[0200] Furthermore, an MLD AP does not need to retransmit a trigger frame if it has not received a response to a trigger frame it has sent (for example, a frame that prompts a TB PPDU or CTS response), i.e., if it has failed to send the trigger frame. Also, if an Ack (Ack frame and Block Ack frame) response is not received after sending a frame that requests an Ack response, the AP does not need to retransmit the frame.

[0201] Generally, APs (AP STAs, non-AP STAs), including AP MLDs, must retransmit frames when they believe that the transmission of a frame they sent has failed. However, AP MLDs do not need to retransmit a frame if they determine that the reason the frame they sent to an MLD STA failed was due to the operation of another STA that has an NSTR relationship with the AP. This is because even if the AP retransmits a failed frame, it is unlikely that the receiving STA will respond to the retransmitted frame unless the operation of the other STA that has an NSTR relationship with the receiving STA (intended recipient) changes.

[0202] When an AP determines that a transmission has failed due to the actions of another STA that has an NSTR relationship with the receiving STA, it can generate a new backoff counter while maintaining CW[AC] when performing the backoff procedure to transmit another frame of the same AC (Access category) as the failed frame. In other words, an STA (AP and non-AP STA) that performed a failed transmission due to the actions of another STA that has an NSTR relationship with the receiving STA can generate a new backoff counter without increasing CW[AC] by the failed transmission when performing the next backoff procedure. At this time, the STA that performed the failed transmission does not need to change QSRC[AC] in addition to CW[AC].

[0203] If, after the STA (AP STA and non-AP STA) of the MLD transmits a frame to the receiving STA on a specific link and no Ack response is received on the specific link, and an Ack for the frame is received (responded to) via the STA of another link (of the same MLD as the receiving STA), the STA of the MLD can set CW[AC] and QSRC[AC] to CW_min and 0 respectively. That is, even when the STA of the MLD does not directly receive an Ack response from the receiving STA after transmitting a frame to the receiving STA, if an Ack response is implemented (received) from another STA of the same MLD as the receiving STA, it can be considered (judged) that the transmission of the frame was successful. At this time, the STA of the MLD may maintain CW[AC] and QSRC[AC] without changing them even if an Ack is responded from another STA of the same MLD as the receiving STA. That is, at least the STA of the MLD can consider that the transmission of the frame has not failed if a response to the frame is received from another STA of the same MLD as the receiving STA even when an Ack for the frame transmitted by itself is not responded by the receiving STA.

[0204] That is, even if the frame transmitted by the AP of the AP MLD fails, when the destination device is a STA of the MLD and it is determined that the STA did not respond due to the operating state of other STAs operating in the NSTR link pair, the AP of the AP MLD does not need to retransmit to the STA. At this time, when the AP of the AP MLD recognizes that the operating state of other STAs operating in the NSTR link pair of the STA has changed, it can retransmit the failed frame. At this time, the reason why the STA did not respond due to the operating state of other STAs may be that it became BLIND and did not respond / could not respond due to the transmission operation of other STAs, or it could only respond to protect the reception operation of other STAs.

[0205] <Transmission Management Method of STA>

[0206] When a specific STA of a Non-AP MLD completes the channel access procedure for a specific AC, that is, when it acquires the authority to begin transmitting traffic for the specific AC, the specific STA does not need to transmit frames in the transmission queue for the specific AC.

[0207] In this case, even though the specific STA has acquired the authority to initiate transmission to the specific AC, it may decide not to initiate transmission, taking into consideration the operation of STAs operating on other links that have an NSTR relationship with the link on which it operates (i.e., NSTR link pairs).

[0208] Furthermore, even though the specific STA has acquired the right to initiate transmission to the specific AC, it may decide not to transmit frames in the transmission queue of the specific AC, taking into consideration that the other STA is performing a PPDU reception operation. In other words, when the non-AP MLD is an NSTR MLD, an STA operating on an NSTR link pair may relinquish the acquired right to initiate transmission, taking into consideration the operating status of the other STAs on the NSTR link pair. In this case, "relinquishing the acquired right to initiate transmission" can mean either performing (calling) the backoff procedure again without attempting to transmit, or delaying transmission while keeping the backoff counter at 0.

[0209] If the STA decides not to initiate transmission to an AC for which transmission initiation authority has been acquired, the STA can perform / invoke a new backoff procedure for the AC. In this case, when the STA performs a new backoff procedure for the AC, it can generate a new backoff counter while maintaining the CW (contention window). That is, CW[AC] and QSRC[AC] (QoS STA short retry counter) remain unchanged, only the backoff counter is regenerated, and a new backoff procedure may be performed for the AC for which transmission initiation authority has been acquired.

[0210] On the other hand, an STA can maintain its BO (backoff counter) at 0 without performing a new backoff procedure, and thus can consider it as if there are no frames in its transmit queue when other STAs in the NSTR link pair are receiving. For example, an STA operating in an NSTR link pair may maintain the BO (backoff counter) of an AC that has acquired transmit initiation rights at 0 by considering it as if there are no frames in its transmit queue when other STAs operating in the NSTR link pair are receiving PPDUs, and may decide (act) not to start transmitting.

[0211] In this case, when the other STA completes receiving the PPDU, the STA can immediately begin transmitting, assuming that a frame has been generated again in the transmit queue. Here, "immediately" can mean transmitting without a separate backoff procedure in accordance with the EDCA rules. That is, when the other STA completes receiving the PPDU, if it is determined (considered) that the medium was idle for a time already set before the completion of the PPDU reception (e.g., DIFS, SIFS, PIFS, AIFSN[AC], etc.), the STA can begin transmitting at the next slot boundary.

[0212] At this time, the time when the other STA completes PPDU reception may be the time when a PHY-RXEND.indication primitive related to a PPDU including an MPDU targeted at the other STA occurs. Alternatively, the time when the other STA completes PPDU reception may be the time when a PHY-TXSTART.request primitive related to an Ack frame (including the PPDU containing the Ack frame) that responds to a PPDU including an MPDU targeted at the other STA occurs. Alternatively, the time when the other STA completes PPDU reception may be the time when a PHY-TXEND.confirm primitive related to an Ack frame (including the PPDU containing the Ack frame) that responds to a PPDU including an MPDU targeted at the other STA occurs. Alternatively, the time when the other STA completes PPDU reception may be the time when the corresponding TXOP for a PPDU including an MPDU targeted at the other STA ends. At this time, the end time of the TXOP can mean the time when the NAV corresponding to the TXOP is released.

[0213] <Transmission Management Restriction of STA>

[0214] According to an embodiment of the present invention described above, a non-AP MLD STA maintains the backoff counter (BO) at 0 by considering whether there is a frame in the transmission queue when another STA in the NSTR link pair is receiving a PPDU. However, when the PPDU reception of the other STA is completed, transmission can be started immediately without a new backoff procedure.

[0215] Thus, the reason for the non-AP MLD STA to perform transmission management considering the operating state of other STAs can be understood to be to minimize negative effects (such as interference and channel access delay) that may occur due to the constraint of the NSTR link pair and to ensure the channel access ability of each STA as much as possible.

[0216] However, in the process of ensuring channel accessibility to each STA of a non-AP MLD as much as possible, the probability of transmission collisions between STAs of different non-AP MLDs may increase. For example, as considered in one embodiment of the present invention, if a particular STA of a particular non-AP MLD starts transmitting while maintaining its backoff counter at 0, a transmission collision may occur with other STAs of other non-AP MLDs that are also maintaining their backoff counters at 0.

[0217] This can be a problem that occurs when the specific STA and other STAs maintain their backoff counters at 0 through receiving operations for the same PPDU. Furthermore, when an AP transmits an MU PPDU on a specific link, multiple non-AP MLDs receiving the MU PPDU can maintain the backoff counters at 0 for STAs operating on other links that are NSTR link pairs with the specific link, and multiple non-AP MLDs that have finished receiving the MU PPDU can start transmitting via the STAs on the other links.

[0218] In other words, as considered in one embodiment of the present invention, a non-AP MLD STA that starts transmitting while maintaining a backoff counter of 0 may have to start the channel access procedure considering that other non-AP MLD STAs may start transmitting at the same time. To this end, a non-AP MLD STA can manage the channel access procedure by checking whether a PPDU being received by another STA in the NSTR link pair is a PPDU that multiple STAs should receive. More specifically, a non-AP MLD STA can decide to maintain a backoff counter of 0 only if the PPDU being received by another STA in the NSTR link pair is a PPDU intended only for that other STA. In other words, a non-AP MLD STA can consider it as if there are no frames in its transmit queue (for a particular AC) only if the PPDU being received by another STA in the NSTR link pair is a PPDU intended only for that other STA. In other words, a non-AP MLD STA cannot consider a PPDU that another STA in the NSTR link pair is receiving as if it had no frames in its transmit queue if that PPDU is intended for multiple STAs, and must perform a new backoff procedure when the backoff counter becomes zero.

[0219] In this case, the method by which the STA of the non-AP MLD confirms that the PPDU being received by the other STA of the NSTR link pair is a PPDU whose target device is only the other STA may be at least one of the following methods.

[0220] 1. When the received PPDU is an EHT MU PPDU, contains only one User field, and the STA-ID of the User field is set to a value that points to the other STA.

[0221] 2. When the RA of the PPDU being received is an individual address (same meaning as direct address or unicast address), and the individual address is an individual (MAC) address assigned to the other STA. In this case, the individual address can be said to have a MAC address with a group bit of 0.

[0222] 3. When the Address 1 field of the MAC frame included in the received PPDU is set to the individual address assigned to the other STA.

[0223] 4. If the MAC frame included in the PPDU being received is a frame that has been individually addressed to the other STA.

[0224] 5. When the destination address (DA) of the MSDU included in the PPDU being received is the MAC address of the other STA mentioned above.

[0225] 6. If the Address 1 field of the MPDU contained in the PPDU being received is the MAC address of the other STA.

[0226] In other words, a non-AP MLD STA can maintain its backoff counter at 0 only if the PPDU being received by another STA in the NSTR link pair is a PPDU that is individually transmitted to the other STA. In this case, the non-AP MLD STA may maintain its backoff counter at 0 by considering the transmit queue to be empty, even though there are frames in the transmit queue.

[0227] However, the STA of the non-AP MLD can maintain the backoff counter at 0 if the other STA is implicitly or explicitly instructed by the AP.

[0228] For example, if the PPDU being received by the other STA is an EHT MU PPDU, and the first User field in the EHT MU PPDU indicates the other STA (information related to the other STA's STA-ID is indicated), then it may be analyzed that the other STA has received an implicit instruction from the AP. In this case, even if the other STA is receiving the EHT MU PPDU, the STA of the non-AP MLD can maintain its backoff counter at 0. At this time, if the first User field in the EHT MU PPDU indicates the other STA, it may be analyzed that the same implicit instruction as described above has been given.

[0229] As another example, if the value of a specific subfield in the User field, which indicates information related to the STA-ID of the other STA, is set to 1, it can be interpreted that the other STA was explicitly instructed by the AP. In this case, even if the other STA is receiving the EHT MU PPDU, the STA of the non-AP MLD can maintain its backoff counter at 0.

[0230] On the other hand, a non-AP MLD STA may need to execute (call) a new backoff procedure while maintaining CW[AC] and QSRC[AC] when the backoff counter becomes 0 if the PPDU being received by another STA in the NSTR link pair is not a PPDU targeting the other STA, or is a PPDU targeting multiple STAs including the other STA. In other words, in this case, the non-AP MLD STA cannot maintain the backoff counter at 0.

[0231] In other words, if the STA of the non-AP MLD is unable to maintain the backoff counter at 0 and must generate a new backoff counter, the STA of the non-AP MLD may need to generate a new backoff counter when the backoff counter reaches 0. That is, in at least one of the following situations, the STA of the non-AP MLD cannot maintain the backoff counter at 0 and must generate a new backoff counter.

[0232] 1. If the PPDU being received by the other STA in the NSTR link pair is an EHT MU PPDU containing two or more User fields.

[0233] 2. If the PPDU being received by the other STA in the NSTR link pair is HE MU PPDU

[0234] 3. When the RA of a PPDU being received by another STA in an NSTR link pair is a group address. That is, when the group bit is 1 in the MAC address indicated in the RA field of the MAC frame contained in the PPPDU being received.

[0235] 4. If the Address 1 field of a MAC frame contained in a PPDU being received by another STA in an NSTR link pair is not a frame individually addressed to the other STA.

[0236] 5. When the destination address (DA) of the MSDU contained in the PPDU being received by the other STA in the NSTR link pair is not the MAC address of the other STA.

[0237] 6. If the Address 1 field of the MPDU contained in the PPDU being received by the other STA in the NSTR link pair is not the MAC address of the other STA.

[0238] 7. If the format of the PPDU being received by the other STA in the NSTR link pair is not confirmed

[0239] 8. If the target device of the PPDU being received by another STA in the NSTR link pair is not identified.

[0240] Alternatively, a non-AP MLD STA may maintain its backoff counter at 0 regardless of the type of PPDU being received by the other STA in the NSTR link pair. However, if the non-AP MLD STA maintains its backoff counter at 0 but begins transmitting when the other STA in the NSTR link pair has finished receiving the PPDU (or after a predetermined time has elapsed since completion), the non-AP MLD STA must transmit the RTS frame as its first frame. This restriction that the RTS frame must be transmitted as the first frame may only apply if the PPDU being received by the other STA is not a PPDU intended solely for that other STA. In other words, if the PPDU being received by the other STA is a PPDU intended solely for that other STA, the non-AP MLD STA is not obligated to transmit the RTS frame as its first frame.

[0241] In other words, an STA that has kept its backoff counter at 0 in consideration of other STA operations operating on an NSTR link pair (e.g., PPDU reception) may have to start its first transmission to obtain a TXOP in an RTS frame. This may be a sequence that takes into account that there may be many non-AP MLD STAs that have kept their backoff counter at 0, so that any attempts to obtain a TXOP while the backoff counter is being kept at 0 are initiated (attempted) by an RTS / CTS frame exchange.

[0242] Alternatively, a non-AP MLD STA does not need to decrement its backoff counter when another STA in the NSTR link pair is receiving a PPDU. This may be an operation performed by the non-AP MLD STA considering its medium state as busy (virtual busy) when the other STA is receiving a PPDU. In other words, a non-AP MLD STA may have to consider its medium state as busy when another STA in the NSTR link pair is receiving a PPDU. In this case, the medium busy state may be released when an RXEND.indication associated with the PPDU occurs.

[0243] Figure 20 shows an example of a transmission management method for a non-AP multilink device according to an embodiment of the present invention.

[0244] Referring to Figure 20(a), while the non-AP MLD is receiving an SU (Single User) PPDU (which is an EHT MU PPDU and contains only one User field if it is an EHT PPDU) on Link 1 via STA1, the backoff counter of STA2 operated by the non-AP MLD on Link 2 reaches 0, and Link 1 and Link 2 may be an NSTR link pair.

[0245] In this case, STA2, a non-AP MLD, can recognize, based on the information that the PPDU received via STA1 is a PPDU whose intended device is only STA1, that there are no other non-AP MLD STAs that will postpone transmission while maintaining the backoff counter at 0 in order to receive the PPDU. Therefore, STA2 can choose not to start transmission even though the backoff counter has reached 0, as shown in Figure 20(a), and postpone transmission while maintaining the backoff counter at 0.

[0246] Thus, if STA1's (SU)PPDU reception procedure is completed while STA2 maintains the backoff counter at 0, STA2 can start transmitting without performing a separate backoff procedure. At this time, STA2 can internally operate as if a frame to be transmitted has been generated in the transmission queue of the AC (Access category) for which the backoff procedure has been completed (the backoff counter has been maintained at 0), coinciding with the completion of STA1's PPDU reception procedure. In other words, STA2 considers that there are no frames to be transmitted in the transmission queue of the specific AC while STA1's PPDU reception procedure is in progress, even though the backoff procedure for that AC has been completed. However, at the time STA1's PPDU reception procedure is completed, STA2 can start PPDU transmission on Link2, considering that a frame to be transmitted has been generated in the transmission queue of the specific AC. However, STA2 can only start PPDU transmission if the medium has remained in an idle state for a certain period of time or longer (considered as SIFS in Figure 20(a)) at the time PPDU transmission is initiated.

[0247] Furthermore, when transmitting without a separate backoff procedure while maintaining the backoff counter at 0, the restriction that the medium state (Link2 CCA result) has not changed to busy while the backoff counter was being maintained at 0 may apply. In other words, if STA2, which was maintaining the backoff counter at 0 while STA1 was receiving the PPDU, is found to have changed the medium state to busy, it must execute (call) a new backoff procedure after the medium state has changed back to idle.

[0248] Alternatively, STA2 may choose to execute (invoke) a new backoff procedure instead of keeping the backoff counter at 0. In this case, when STA2 invokes the new backoff procedure, it does so without changing CW[AC] and QSRC[AC].

[0249] Referring to Figure 20(b), while the non-AP MLD is receiving the MU (Multi-user) PPDU on Link 1 via STA1, the backoff counter of STA2, which the non-AP MLD is operating on Link 2, reaches 0, and Link 1 and Link 2 may be an NSTR link pair.

[0250] In this case, STA2, a non-AP MLD, can recognize that the PPDU being received by STA1 is an MU PPDU (or group (non-individual) address frame) that is intended for other STAs as well as STA1, and that other non-AP MLDs may also postpone transmission in order to receive the PPDU. Therefore, when the backoff counter reaches 0, as shown in Figure 20(b), STA2 can decide to perform (call) the backoff procedure again without maintaining the backoff counter at 0 or starting transmission. When STA2 calls the new backoff procedure, it does so without changing CW[AC] and QSRC[AC].

[0251] As shown in Figure 20(b), the backoff counter of STA2 (for a specific AC) reached 0 twice while STA1 was receiving the PPDU, and STA2 called a new backoff procedure twice. At this time, when STA2 maintained CW[AC] and called a new backoff procedure, 5 was generated as the first backoff counter (New counter #1 in Figure 20(b)), and when the backoff procedure was called again after the backoff counter reached 0, 7 was generated as the second backoff counter (New counter #2 in Figure 20(b)). After the second backoff counter reached 0, STA2 began transmitting a PPDU because STA1 was no longer receiving PPDUs.

[0252] Figure 21 shows an example of the content of a beacon frame transmitted by an AP of an AP MLD according to one embodiment of the present invention, and an example of the TBTT (target beacon transmission time) information field format included in the RNR (Reduced Neighbor Report) element.

[0253] Referring to Figure 21(a), the beacon frame may include the same parameters and elements in its Legacy IEs as those included in the beacon frame disclosed in conventional Wi-Fi 802.11ax. For example, legacy IEs in a beacon frame may include elements such as a Timestamp field, a Beacon Interval field indicating the interval at which the beacon is transmitted, TIM, DSSS parameter set, IBSS parameter set, Country, channel switch announcement, extended channel switch announcement, Wide Bandwidth channel switch, transmit power envelope, supported operating classes, IBSS DFS, ERP information, HT capabilities, HT operation, VHT capabilities, VHT operation, S1G beacon compatibility, short beacon interval, S1G capabilities, S1G operation, HE capabilities, HE 6GHz band capabilities, HE operation, BSS color change announcement, and spatial reuse parameter set.

[0254] In this case, the setting method and meaning of the fields and elements included in the legacy IEs field are the same as the setting and meaning of the fields and elements with the same names included in the beacon frame disclosed up to Wi-Fi 802.11ax.

[0255] Furthermore, the beacon frame may include an RNR (Reduced Neighbor Report) element to indicate information about neighboring APs. The RNR element may be used to inform the station of information about neighboring APs, and the station can recognize the neighboring AP by receiving the beacon frame and using the RNR element included in the beacon frame.

[0256] Specifically, an RNR element may include an element ID field, a length field, and a neighboring AP information field. Each of the neighboring AP information fields may include a TBTT information header (2 octets), an operation class (1 octet), a channel number (1 octet), and a TBTT information set (variable length) field. In this case, an RNR element transmitted by an AP included in an AP MLD may include a TBTT information field format, as shown in Figure 21(b), to indicate basic information for other APs included in the same MLD. Unlike the TBTT information field of an RNR element transmitted by an AP in conventional Wi-Fi 802.11ax, an RNR element transmitted by an AP included in an EHT AP MLD may include an MLD parameter field.

[0257] The MLD parameter field may include an MLD ID, a link ID, and a Change Sequence subfield, as shown in Figure 21(c). In this case, when an AP MLD indicates other AP information in the same MLD by the specific neighboring AP information field of the RNR element, the MLD ID subfield included in the specific neighboring AP information field can be set to 0. That is, an AP can set the MLD ID subfield to a specific value to inform a station that the neighboring AP information field is an AP included in the same AP MLD, and a station that receives the neighboring AP information field can recognize from the value of the MLD ID subfield that the AP corresponding to the neighboring AP information field is included in the same MLD as the AP that sent the neighboring AP information field.

[0258] The Link ID subfield may be a subfield that indicates the index determined by the AP MLD to indicate the link on which another AP is operating, using neighboring AP information. The Change Sequence subfield may be a subfield used to indicate information related to updates (e.g., Critical Updates) associated with links of other APs. For example, if the value of the Change Sequence subfield is changed, a station receiving this can recognize that a parameter related to the AP's BSS (or link) has been updated, and can request the updated parameter from the AP to update that parameter. In this case, if the AP MLD is an NSTR AP MLD that does not support simultaneous transmission and reception (for example, if the AP MLD is an NSTR mobile AP MLD or an NSTR soft AP MLD, i.e., if a mobile terminal operates as a soft AP MLD for tethering, etc.), the STA included in the STA MLD can only perform the procedure to update the parameter on the primary link. In other words, to update the parameters of other links to neighboring APs (e.g., non-primary links) rather than the primary link of an AP MLD, parameter update frames can only be sent and received on the primary link.

[0259] Hereinafter, in the present invention, NSTR AP MLD may be referred to as NSTR soft AP MLD or NSTR mobile AP MLD.

[0260] Furthermore, if the AP is an NSTR AP MLD that does not support simultaneous transmission and reception (for example, an NSTR mobile AP MLD or an NSTR soft AP MLD, i.e., when a mobile device operates as a soft AP MLD for tethering, etc.), the NSTR AP MLD can include information in the beacon frame indicating that it is an NSTR AP MLD. For example, an NSTR AP MLD can set the value of a specific subfield included in the beacon frame to a specific value (e.g., "0" or "1"), and a non-AP STA MLD that receives the beacon frame can recognize that the AP MLD that sent the beacon frame is an NSTR AP MLD. Therefore, the specific subfield for indicating that it is an NSTR AP MLD may be set to a different value (e.g., "1" or "0") if it does not indicate that it is an NSTR AP MLD (e.g., an STR AP MLD or another AP MLD).

[0261] A specific subfield indicating that an AP is an NSTR AP MLD may be indicated together with a Capability-related subfield in the beacon frame (e.g., MLD level capability) or transmitted in the neighboring AP information field associated with the AP of the non-primary link of the NSTR AP MLD. For example, a specific subfield indicating that an AP is an NSTR AP MLD may be encoded and indicated together with a Frequency Separation For STR / AP MLD Type Indication, which is a Capability-related subfield. That is, the specific subfield may be encoded together with a Frequency Separation For STR / AP MLD Type Indication indicating the distance to support the STR and indicated in the beacon frame. In this case, if the indicator indicates the type of AP MLD, the set value can indicate whether the AP MLD that sent the beacon frame is an NSTR AP MLD or not (for example, setting it to "0" indicates it is not an NSTR AP MLD, and setting it to "1" indicates it is an NSTR AP MLD).

[0262] The way in which a subfield indicating whether or not it is an NSTR AP MLD is utilized may be any method that explicitly indicates whether or not an AP MLD is an NSTR AP MLD.

[0263] As another example, an NSTR AP MLD can indicate that it is an NSTR AP MLD in an implicit way, rather than directly indicating it through a specific subfield. Specifically, an NSTR AP MLD can implicitly indicate that it is an NSTR AP MLD by indicating that it has two supportable links and simultaneously indicating that it has an NSTR link pair. In this case, the NSTR AP MLD can set the Maximum Number Of Simultaneous Links subfield included in the beacon frame to 1 (or a pre-promised value meaning 2) to indicate that it has two supportable links. In this case, the NSTR AP MLD can set the NSTR Link Pair Present subfield included in the beacon frame to 1 or 0 to indicate that it has an NSTR link pair.

[0264] An AP MLD can inform a Non-AP STA MLD that it is an NSTR AP MLD by transmitting a beacon frame in the manner described above, either explicitly or implicitly. A Non-AP STA MLD can implicitly or explicitly determine from the received beacon frame whether the AP MLD that sent the beacon frame is an NSTR AP MLD. If the AP MLD that sent the beacon frame is an NSTR AP MLD (i.e., the beacon frame indicates, either explicitly or implicitly, that the AP MLD is an NSTR AP MLD), then the Non-AP STA MLD can perform the association or setup procedure with the NSTR AP MLD only on the link where the beacon frame was received. In other words, a non-AP STA MLD can send and receive frames for association or setup with the NSTR AP MLD on the link where the beacon frame was received (e.g., the primary link). For example, sending and receiving frames for joining or configuring an AP connected via a link other than the primary link included in the NSTR AP MLD may only occur on the primary link. In this case, the (ML)(re)joining request frame sent by the Non-AP STA MLD may also be sent on a link other than the primary link (non-primary link).

[0265] At this time, in order to prevent the non-AP STA MLD from attempting the setup procedure on a non-primary link, the NSTR AP MLD does not need to indicate information regarding the AP of the non-primary link in the RNR element of the beacon frame (transmitted on the primary link). That is, the beacon frame transmitted by the AP of the NSTR AP MLD does not need to include / indicate the neighbor AP information field for the AP of another link (of the same MLD). In this case, after receiving the beacon frame, the non-AP STA MLD does not need to attempt to set up the NSTR AP MLD on the non-primary link because it cannot confirm the information regarding the AP of the non-primary link. At this time, the non-AP STA MLD that has received a beacon frame from the NSTR AP MLD without the neighbor AP information field for the AP of the non-primary link can implicitly recognize that the peer AP is the NSTR AP MLD based on the fact that the number of co-supporting links of the AP that transmitted the beacon frame is two and no information regarding other APs of the same MLD is indicated, as described above.

[0266] On the other hand, a general AP MLD must transmit an (ML) association response frame on the link where the (ML) association request frame was received when it receives an (ML) association request frame from a STA (MLD). However, the NSTR AP MLD may be allowed to respond to an (ML) association request frame received on a non-primary link on the primary link (that is, to be able to respond with an (ML) association response frame on the primary link).

[0267] As described above, this may be an acceptable operation because the operation of the NSTR AP MLD to perform transmission on a non-primary link is somewhat restricted compared to a general AP. Further, the NSTR AP MLD has an operation restriction that when a response to an (ML) association response frame is transmitted on a non-primary link, it must start transmission together on the primary link. This may be an operation restriction considered to prevent the AP on the primary link from entering the BLIND state, similar to what was considered in other embodiments of the present invention.

[0268] Therefore, when the NSTR AP MLD receives an (ML) (re) association request frame on a non-primary link, it can respond with an (ML) (re) association response frame on the primary link, or can respond with an (ML) (re) association response frame simultaneously on the primary link and the non-primary link. That is, the STA MLD that transmitted the (ML) (re) association request frame on the non-primary link of the NSTR AP MLD can recognize that the response to the request frame it transmitted is responded to on the primary link and can wait for the reception of the (ML) (re) association response frame on the primary link.

[0269] The RNR element transmitted by the AP in the beacon frame may include a specific TBTT information field including an MLD Parameters field. In this case, when the MLD ID in the MLD Parameters field is set to "0", the STA MLD can recognize that the AP corresponding to the adjacent AP information field including the MLD Parameters field is included in the AP MLD including the AP that transmitted the beacon frame. That is, it can be recognized by the STA MLD that the adjacent AP information field indicates information about other APs included in the same AP MLD as the AP that transmitted the beacon frame. In this case, the method for the STA MLD to analyze / acquire this may be the same / similar to the operation performed by a conventional STA after receiving the RNR element.

[0270] However, since NSTR Soft APs do not transmit beacon frames on non-primary links, it may be impossible to indicate information related to beacon frames of other APs (APs on non-primary links) through the RNR element. Furthermore, since NSTR Soft AP MLDs do not transmit beacon frames via APs on non-primary links, they cannot support information about beacon frames when indicating basic AP information for non-primary links in the RNR element. For example, non-primary links that do not transmit beacon frames lack information corresponding to the TBTT information count (Information Count), TBTT information length (Information Length), and neighboring AP TBTT offset subfield that should be indicated in the RNR element. Therefore, when NSTR Soft AP MLDs transmit RNR elements via APs on primary links, they may need to set the TBTT-related fields of the neighboring AP information field corresponding to the non-primary link AP to pre-configured values.

[0271] The neighboring AP TBTT offset subfield of the TBTT information field (see Figure 21(b)) is a subfield that indicates information related to the next TBTT of the other AP being indicated. That is, the neighboring AP TBTT offset subfield included in the neighboring AP information field may contain information about the next TBTT of the AP corresponding to the neighboring AP information field. For example, when AP1, which transmits a beacon frame, indicates information about AP2 using the RNR element (by the neighboring AP information field), the neighboring AP TBTT offset subfield corresponding to AP2 indicates how many TU (Time Unit, 1024us) the difference is between AP2's next TBTT and AP1's previous TBTT. In this case, the value indicated in the neighboring AP TBTT offset subfield is the value obtained by rounding down the TBTT offset to an adjacent integer. That is, if an AP indicates a value of 10 in the neighboring AP TBTT offset subfield of another AP, the next TBTT of the other AP may have a time interval of 10 TU or more but less than 11 TU based on the AP's previous TBTT.

[0272] However, when an AP on the primary link of an NSTR Soft AP MLD sets the Neighbor AP TBTT Offset subfield (1-Octet) corresponding to an AP on a non-primary link, it may be necessary to set it to a pre-set value (for example, 254 or 255). This may be because, in the case of an NSTR Soft AP, it does not send a beacon frame to the non-primary link and therefore cannot determine the TBTT (Target Beacon Transmission Time), which is the scheduled time for sending the next beacon frame. In other words, the beacon frame that an NSTR Soft AP MLD sends on the primary link may need to set the Neighbor AP TBTT Offset subfield corresponding to the AP on the non-primary link to 254 and / or 255 using the RNR element. In this case, the Neighbor AP TBTT Offset subfield corresponding to the non-primary link may be located in the TBTT information field which contains an MLD Parameters field where the MLD ID subfield is set to 0.

[0273] Therefore, after receiving a beacon frame from an NSTR Soft AP MLD, a non-AP STA MLD can recognize that the specific neighboring AP information field in the RNR element included in the beacon frame contains information about an AP (of the NSTR Soft AP MLD) operating on the non-primary link of the NSTR Soft AP MLD, if it confirms that the MLD ID subfield is 0 and the TBTT offset subfield is indicated as 254 and / or 255. Thus, a non-AP STA MLD that has received a beacon frame from an NSTR Soft AP MLD should not transmit a probe request frame and an ML probe request frame to the NSTR Soft AP MLD on the non-primary link if it has confirmed that the information concerns an AP MLD operating on the non-primary link of the NSTR Soft AP MLD.

[0274] In addition, when the non-AP STA MLD recognizes that the received beacon frame is the beacon frame transmitted by the MLD, and the Neighbor AP TBTT Offset subfield corresponding to another AP of the same MLD as the AP (Reporting AP) that transmitted the beacon frame is indicated as 254 and / or 255, the non-AP STA MLD shall not transmit a probe request frame and an ML probe request frame to other APs.

[0275] In addition, when the non-AP STA MLD recognizes that the received beacon frame is the beacon frame transmitted by the MLD, and the Neighbor AP TBTT Offset subfield corresponding to another AP of the same MLD as the AP (Reporting AP) that transmitted the beacon frame is indicated as 254 and / or 255, the non-AP STA MLD shall not transmit a probe request frame and an ML probe request frame to other APs.

[0276] <MLD AP TBTT Offset Indication>

[0277] In the embodiment of the present invention described above, it was mentioned that the beacon frame transmitted by the NSTR Soft AP MLD can specify the neighboring AP TBTT offset subfield corresponding to the non-primary link AP to a preset value (254 and / or 255). However, the neighboring AP TBTT offset subfield may be specified as 254 or 255 even if it does not correspond to the non-primary link AP of the NSTR Soft AP MLD. For example, if the TBTT offset of another AP known by the AP transmitting the beacon frame is 254 TU or greater (254 TU or more than 254 TU), the AP can specify the neighboring AP TBTT offset subfield corresponding to the other AP as 254 in the beacon frame. Also, if the AP transmitting the beacon frame cannot accurately determine the TBTT offset of another AP, the AP can specify the neighboring AP TBTT offset subfield corresponding to the other AP as 255.

[0278] However, since an AP in an MLD can always recognize the TBTT offset of other APs within the MLD, you should not specify (set) 255 when using the RNR element to specify (set) the neighboring AP TBTT offset subfield corresponding to another AP (in the same MLD).

[0279] Specifically, the neighboring AP information field included in the RNR element of a beacon frame may include a neighboring AP TBTT offset subfield that indicates the offset between the times when the beacon frames are transmitted. In this case, the neighboring AP TBTT offset subfield indicates the offset value between the time when the beacon frame was transmitted and the time when the next beacon frame is transmitted by the AP corresponding to the neighboring AP TBTT offset subfield among the multiple APs included in the AP MLD (NSTR or STR AP MLD). In this case, the neighboring AP TBTT offset subfield cannot be set to a specific value under certain conditions.

[0280] For example, if an AP is included in the same AP MLD as the AP that sent the beacon frame, the neighboring AP TBTT offset subfield will not be set to a specific value (e.g., "255"). In this case, the size of the neighboring AP TBTT offset subfield may be 8 bits, and in this case, the neighboring AP TBTT offset subfield will not be set to the maximum value that can be indicated by the neighboring AP TBTT offset subfield (since each of the 8 bits corresponds to a value from 0 to 255, the maximum offset that can be indicated by 8 bits can be 255). However, if an AP is not included in the same AP MLD as the AP that sent the beacon frame (for example, if the AP is a legacy AP), the neighboring AP TBTT offset subfield may be set to a specific value (e.g., "255").

[0281] In a similar embodiment, the adjacent AP TBTT offset subfield may be analyzed such that its value differs depending on specific conditions.

[0282] For example, if the adjacent AP TBTT offset subfield is set to a specific value (e.g., "254"), the value set by a specific condition may be analyzed differently, such as "254" or "254 or greater".

[0283] Specifically, if the AP corresponding to the neighboring AP information field containing the neighboring AP TBTT offset subfield is included in the same AP MLD or another MLD as the AP that sent the beacon frame, and the neighboring AP TBTT offset subfield is set to a specific value (e.g., "254"), the station can parse the value indicated by the neighboring AP TBTT offset subfield as 254 TU. However, if the AP is not included in the same AP MLD or another MLD as the AP that sent the beacon frame (e.g., if the AP is a legacy AP or an AP not included in an MLD), and the neighboring AP TBTT offset subfield is set to a specific value (e.g., "254"), the station can parse the value indicated by the neighboring AP TBTT offset subfield as 254 TU or higher TU.

[0284] Generally, the reason why conventional APs transmit TBTT offset information along with basic information for neighboring APs using beacon frames may be to help STAs that receive the beacon frames to quickly obtain basic information about other APs and to receive other APs' beacon frames more efficiently using the confirmed TBTT offset information.

[0285] However, the neighboring AP TBTT offset subfield included in conventional beacon frames consisted of one octet and was designed to indicate only TBTT offsets corresponding to a maximum of 254 TU. This may be a neighboring AP TBTT offset subfield design that compromises beacon frame overhead and the information that can be indicated by excluding information support for cases where the TBTT offset exceeds 254 TU, considering the maximum TBTT offset that other APs may have (2^16 or (2^16)-1 TU when considering the configurable beacon interval).

[0286] However, when an AP MLD uses a beacon frame to indicate information about other APs within the MLD, it may include an additional MLD AP TBTT offset subfield to more accurately indicate the TBTT offset of the other AP. The MLD AP TBTT offset subfield may be included in the TBTT information field corresponding to other APs in the same MLD when the AP MLD transmits the beacon frame. In this case, if both the neighboring AP TBTT offset subfield and the MLD AP TBTT offset subfield are indicated in a particular TBTT information field, the neighboring AP TBTT offset subfield may be indicated as a pre-set value (which may be 254 or 255). The MLD AP TBTT offset subfield is a 2-octet subfield and may be used to indicate the TBTT offset value when the TBTT offset between the AP that transmitted the beacon frame (Reporting AP) and other APs in the same MLD (Reported APs) exceeds 254 TU. Furthermore, the MLD AP TBTT offset subfield may be included in the TBTT information field only when an AP MLD transmits a beacon frame and the TBTT offset of another AP within the same MLD exceeds 254 TU, making it impossible to specify the exact TBTT offset using the existing neighboring AP TBTT offset subfield.

[0287] When STA MLD detects a TBTT information field containing the MLD AP TBTT offset subfield in the RNR element included in a beacon frame received from a specific AP, it can determine the TBTT offset of the AP corresponding to that TBTT information field based on the value indicated in the MLD AP TBTT offset subfield. In this case, to determine whether a TBTT information field included in a beacon frame contains the MLD AP TBTT offset subfield, STA may determine this based on the value of the TBTT information length subfield corresponding to each TBTT information field (located in the TBTT Information Header (sub) field of each neighboring AP information field). That is, if STA recognizes that a TBTT information field contains the MLD AP TBTT offset subfield based on the value of the TBTT Information Length subfield, it can determine the TBTT offset of the AP corresponding to that TBTT information field based on the value indicated in the MLD AP TBTT offset subfield. In this case, if the MLD AP TBTT offset subfield of a specific TBTT information field indicates 0 or a preset value (or a value of 254 or less), STA MLD can confirm the TBTT offset of the AP corresponding to the specific TBTT information field based on the value of the adjacent AP TBTT offset subfield.

[0288] Figure 22 shows yet another example of a TBTT information field format according to one embodiment of the present invention.

[0289] Referring to FIG. 22, the TBTT information field may have a configuration including an MLD AP TBTT offset subfield. The MLD AP TBTT offset subfield may be included only in the beacon frame transmitted by the AP of the AP MLD. Also, the MLD AP TBTT offset subfield may be included only in the TBTT information field corresponding to other APs of the same MLD as the AP transmitting the beacon frame.

[0290] As an example, in the beacon frame transmitted by a specific AP of the AP MLD, in order to indicate that the TBTT offset of other APs of the same MLD is 300 TU, the TBTT information field corresponding to the other APs can be utilized in a format including the MLD AP TBTT offset subfield. At this time, the adjacent AP TBTT offset subfield of the TBTT information field corresponding to the other APs is indicated as 254 or 255, and the MLD AP TBTT offset subfield may be indicated as a value corresponding to 300 TU (for example, 300 or 299, or (300 - 254)). At this time, the above-mentioned MLD AP TBTT offset subfield is a subfield name for illustration, and subfields for the same purpose may be defined with different names.

[0291] FIG. 23 shows an example of an information length subfield that indicates a TBTT information field including an MLD AP TBTT offset subfield according to an embodiment of the present invention. <The

[0292] Referring to Figure 23, the TBTT information length subfield may indicate the type of content contained in the TBTT information field. The TBTT information length subfield may be a subfield contained in the TBTT information header field present in the neighboring AP information field contained in the RNR element. That is, an RNR element transmitted in a beacon frame may contain multiple neighboring AP information fields, and the TBTT information fields contained in each neighboring AP information field may have a structure in which they contain different amounts and types of content. In this case, since the TBTT information fields contained in each neighboring AP information field may contain different amounts and types of content, information regarding the content (and format) indicated by each TBTT information field is indicated by the TBTT information header field.

[0293] In other words, the STA can parse each neighboring AP information field in the RNR element of the beacon frame received via the AP, based on the information indicated in the TBTT information header. At this time, each parsed neighboring AP information field may indicate information about a neighboring AP or another AP in the same MLD. At this time, if the value of the TBTT information length subfield included in the TBTT information header field means a content configuration including the MLD AP TBTT offset subfield, as shown in Figure 23, the STA can confirm the TBTT offset of the AP corresponding to that TBTT information field based on the value indicated in the MLD AP TBTT offset subfield.

[0294] <Setting up and managing non-primary links>

[0295] As mentioned above, NSTR AP MLD cannot transmit beacon frames, probe response frames, or ML (Multi-link) probe response frames on non-primary links. Therefore, an STA MLD attempting to connect with an NSTR AP MLD must transmit (ML) probe request frames only on the link on which the NSTR AP MLD transmitted the beacon frame.

[0296] The ML probe request frame transmitted by the STA of an EHT non-AP STA MLD may have a configuration that includes EHT Capability information and a Multi-Link element, in addition to the information contained in the probe request frame conventionally transmitted by an HE STA. In this case, the Multi-Link element included in the ML probe request frame can serve as a means for the MLD transmitting the ML probe request frame to request additional information from the AP MLD regarding APs on other links.

[0297] For example, when a non-AP STA MLD sends an ML probe request frame, it can use the Multi-Link element of the ML probe request frame to request an AP MLD to further respond with complete or partial information for other APs on the link. In other words, it can request an AP MLD to send all or part of the link-related parameters of other APs included in the same AP MLD to the AP receiving the ML probe request frame.

[0298] For example, if all or part of the parameters associated with an AP connected via a non-primary link are updated, a station included in the non-AP STA MLD can request the AP connected via a primary link to transmit all or part of the updated parameters in relation to other APs on the non-primary link.

[0299] In this case, the request / response of complete information means that the AP (Reported AP) of the other link is requested / responded with the same level of information as the AP (Reporting AP) that responds with an ML probe response frame. In this case, the request / response of partial information means that the AP of the other link is responded with information only in relation to the information requested by the STA.

[0300] If an AP MLD that has sent a beacon frame receives an ML probe request frame on a specific link and requests additional information about APs on other links, it can use an ML probe response frame to respond with information about the AP on the specific link, as well as the additional information about the APs on the other links that was requested.

[0301] In this case, if the STA MLD requests complete information for an AP on another link while sending an ML probe request frame on a specific link, the AP MLD must use the ML probe response frame it sends in response on the specific link to provide information about the AP on the other link at the same level as the information about the AP on the specific link. In other words, if the STA MLD receives a complete information response for an AP on another link on a specific link, it can obtain the same level of information from the AP on the other link as it would if it had received an ML probe response directly from the AP on the other link.

[0302] In this case, if the STA MLD requests partial information for an AP on another link while sending an ML probe request frame on a specific link, the AP MLD can use the ML probe response frame sent in response on the specific link to provide only the requested information (information about the requested elements) from the information about the AP on the other link. In other words, the STA MLD that receives a response of partial information for an AP on another link on a specific link can further obtain only the information it requested from the AP on the other link. In this case, the STA MLD requesting partial information for an AP on another link can send an ML probe request frame that includes the link ID corresponding to the other link, along with information indicating the further information to be obtained (which may be indicated by the Requested element IDs field). Therefore, if the ML probe request frame received on a specific link contains information indicating information about the other link (Request element IDs field), the AP MLD can further indicate the information requested for the other link in the ML probe response frame.

[0303] In this case, when STA MLD sends an ML probe request frame on a specific link, it can set the Complete Profile subfield (of the Per-STA Control field included in the Multi-Link element) corresponding to the other link to 0 or 1 to indicate whether it is requesting complete or partial information for the other link.

[0304] In this case, additional information (Complete and Partial) for the other APs may be transmitted by a Per-STA profile included in the Multi-link element of the ML probe response frame. A Per-STA profile is a field included zero or more times in the Multi-link element and may contain information about other STAs (APs and non-AP STAs) that reside in the same MLD as the STA (AP and non-AP STA) transmitting a frame containing a Multi-Link element. In this case, a Per-STA profile has a configuration that includes a Complete Profile subfield, and the complete information (the same level of information as the STA (AP and non-AP) transmitting a frame containing a Multi-Link element) of the other STA (AP and non-AP STA) corresponding to (applicable to) a Per-STA profile instructed to have a Complete Profile subfield of 1 can be obtained from that Per-STA profile. However, parameters / elements that mean the same information as the STA (AP and non-AP) that transmitted the Per-STA profile may be omitted by inheritance rules. The inheritance rule can be interpreted as meaning that, to prevent the repeated indication of the same parameter and element, if the parameter and element are not indicated, the value of the same parameter and element already indicated (indicated for other STAs (AP and non-AP)) will be inherited and utilized. In other words, if the value of parameter1 is indicated for STA1, but not for STA2, the inheritance rule can be interpreted as indicating that the value of parameter1 for STA2 is the same as the value of parameter1 for STA1.

[0305] In this case, the Per-STA profile subelement included in the Multi-link element transmitted by NSTR AP MLD may have a configuration that does not include a Beacon Interval subfield for indicating the interval at which beacons are transmitted. That is, when NSTR AP MLD specifies a Per-STA profile subelement corresponding to an AP on a non-primary link in the Multi-link element, it must set the Beacon Interval Present subfield to 0. This may be because APs operating on the non-primary link of NSTR AP MLD do not transmit beacon frames, and therefore there is no separate period for beacon frames. That is, the Per-STA profile subelement (of probe response and coupled response frames) corresponding to an AP on a non-primary link of NSTR AP MLD may have the Beacon Interval Present subfield set to 0 even if the Complete Profile subfield (of the Per-STA Control field) is specified to 1. In other words, beacon interval information for APs on non-primary links does not exist even when complete information is specified.

[0306] Similarly, DTIM information (DTIM Count and DTIM Period information) for non-primary link APs does not need to be present even when complete information is indicated. That is, the Per-STA profile for a non-primary link AP in an NSTR AP MLD may have a DTIM Info Present subfield indicated as 0 even if the Complete Profile subfield (of the Per-STA Control field) is indicated as 1.

[0307] In other words, since no beacons are transmitted on the non-primary link, even if a non-AP STA MLD requests all information (or all updated information) for other APs on the non-primary link via the AP on the primary link of the AP MLD (i.e., if the complete information is set to "1"), the ML probe response frame does not need to contain beacon interval and DTIM information for the APs on the non-primary link. In other words, the Per-STA profile sub-elements for the APs on the non-primary link included in the ML probe response frame do not need to contain beacon interval and DTIM information.

[0308] In this case, even if all information (or all updated information) for other APs on the non-primary link is requested, the AP MLD does not need to include beacon interval and DTIM information for the APs on the non-primary link in the ML probe response frame. Therefore, in this case, the AP MLD can send the beacon interval gift subfield and the DTIM information gift subfield set to a value (e.g., "0") indicating that the respective fields are not included.

[0309] Since the NSTR AP MLD does not transmit beacon frames to non-primary links, it does not need to specify DTIM information and beacon interval information when specifying information about APs on non-primary links. In other words, the NSTR AP MLD may always need to specify 0 for the DTIM information present subfield of the Per-STA profile (more precisely, the STA Control field) corresponding to the AP on a non-primary link. In other words, the NSTR AP MLD may always need to specify 0 for the Beacon Interval Present subfield in the Per-STA profile corresponding to the AP on a non-primary link. Therefore, even when the NSTR AP MLD receives an ML probe request frame requesting complete information or an (ML)(re)connection request frame from a non-AP STA MLD, the NSTR AP MLD may always need to specify 0 for the Beacon Interval Present subfield and the DTIM information present subfield of the Per-STA profile corresponding to the AP on a non-primary link.

[0310] Alternatively, since NSTR AP MLD does not send beacon frames to non-primary links, it may be necessary to set the Beacon Interval, DTIM Count, and DTIM Interval subfields in the Per-STA profile corresponding to the AP on the non-primary link to predetermined values. This may be an operation considered to maintain the same Per-STA profile configuration as a general AP MLD (e.g., STR AP MLD) when NSTR AP MLD sends (responds to) complete information for an AP on a non-primary link. That is, STA MLD can request complete information for a specific link from AP MLD using an ML probe request frame, etc., and expect the response frame to contain complete information for the AP on that specific link. In this case, if the complete information responded by NSTR AP MLD has a different Per-STA profile configuration than the complete information responded by STR AP MLD, the complexity of the process by which STA MLD obtains information via the Per-STA profile may increase. Therefore, even if the AP on the non-primary link does not transmit a beacon frame, the NSTR AP MLD can use a Per-STA profile with the same configuration as the Per-STA profile used by a typical AP MLD when responding with complete information for a non-primary link. In this case, the Per-STA profile of the NSTR AP MLD corresponding to the AP on the non-primary link may have the Beacon Interval subfield, DTIM Count subfield, and DTIM Interval subfield set to pre-defined values. For example, when the NSTR AP MLD transmits complete information to the AP on the non-primary link, it can set each bit of the Beacon Interval subfield for the non-primary link to all 0, all 1, or in a pre-determined manner.For example, when NSTR AP MLD transmits complete information to an AP on a non-primary link, it can set each bit of the DTIM Count subfield of the non-primary link to all 0s, all 1s, or in a predetermined manner. For example, when NSTR AP MLD transmits complete information to an AP on a non-primary link, it can set each bit of the DTIM Interval subfield of the non-primary link to all 0s, all 1s, or in a predetermined manner.

[0311] Alternatively, since no beacon frames are transmitted to non-primary links, the NSTR AP MLD can set the Beacon Interval, DTIM Count, and DTIM Interval subfields in the Per-STA profile corresponding to the AP on the non-primary link to values ​​associated with the beacon frames on the primary link. This may be considered in order to maintain the same Per-STA profile configuration, as described above. In this case, the Per-STA profile of the NSTR AP MLD corresponding to the AP on the non-primary link may have the Beacon Interval subfield, DTIM Count subfield, and DTIM Interval subfield set to values ​​associated with the beacon frames transmitted on the primary link. For example, when the NSTR AP MLD transmits complete information to an AP on a non-primary link, it can set the Beacon Interval subfield for the non-primary link to a value that indicates (means) the beacon interval of the primary link. For example, when the NSTR AP MLD transmits complete information to an AP on a non-primary link, it can set the DTIM Count subfield for the non-primary link to the DTIM Count value of the primary link. For example, when NSTR AP MLD sends complete information to an AP on a non-primary link, it can set the DTIM Interval subfield for the non-primary link to a value that indicates (means) the DTIM interval of the primary link.

[0312] Alternatively, since beacon frames are not transmitted to non-primary links, the NSTR AP MLD can set the Beacon Interval, DTIM Count, and DTIM Interval subfields of the Per-STA profile corresponding to APs on non-primary links to values ​​with a specific purpose. Furthermore, the Beacon Interval subfield for non-primary links may be set by the AP MLD to a value with a specific purpose (a virtual beacon interval), for example, a value for calculation. Traditionally, the Wi-Fi beacon interval has literally meant a value related to the time interval at which beacon frames are transmitted, but it has also been used as a time unit for various BSS operations. For example, the unit of primitives such as JointFailureTimeout and QueryFailureTimeout is defined as the beacon interval, and fields such as the Listen interval field, PRAW Start offset subfield, AID Request Interval field, AID Switch Count field, AID Response Interval field, Minimum Transmission Interval subfield, Channel Quality Measurement Duration, and Color Switch Countdown (of the BSS Color Change Announcement element) use the beacon interval (or TBTT) as the basic unit to specify the interval / Duration. Thus, while the beacon interval has meaning as a value related to the interval at which beacon frames are actually transmitted, it is also a value used as a unit in various primitives and fields. Therefore, even if beacon frames are not actually transmitted to a non-primary link, it may be necessary to define (specify, set) the beacon interval for non-primary links so that it can be used as a unit in the aforementioned primitives / subfields.

[0313] In other words, even if no beacon frames are transmitted to the non-primary link, the NSTR AP MLD can instruct the Beacon Interval subfield of the Per-STA profile corresponding to the AP on the non-primary link to be used as the beacon interval value for the time unit of the non-primary link. In this case, the non-AP MLD can recognize (confirm, calculate) the duration and interval of the primitives and fields (to be used as beacon interval units) mentioned above, based on the value instructed in the Beacon interval subfield of the Per-STA profile corresponding to the AP on the non-primary link. At this time, the DTIM Interval subfield and DTIM Count subfield of the Per-STA profile corresponding to the AP on the non-primary link may also be set according to the purpose of the AP MLD's BSS operation, and the non-AP MLD operating STA on the non-primary link may need to operate based on the set values ​​when operating STA on the non-primary link.

[0314] On the other hand, the method for setting the subfields related to beacons on the non-primary link of the NSTR AP MLD described above (such as Beacon Interval, DTIM Count, and DTIM Interval) may be applied identically to other frames and subfields (sent on either the primary or non-primary link) that contain information related to beacons on the non-primary link, as well as to the Per-STA profile transmitted on the primary link.

[0315] Furthermore, a non-AP STA MLD attempting to associate with an NSTR AP MLD may need to utilize the primary link beacon interval of the NSTR AP MLD as the unit of the Listen interval field it transmits while requesting setup for the primary and non-primary links. That is, a non-AP STA MLD that transmits a Listen interval field to an NSTR AP MLD must calculate and set the unit of the Listen interval field to the beacon interval of the AP operating on the primary link of the NSTR AP MLD. In this case, the Listen interval field may indicate information related to the period (time) during which at least one STA switches to a wake state in order for a non-AP STA MLD performing Multi-Link (Re)Association to receive a beacon frame. In this case, the Listen interval field may indicate a value derived when the ListenInterval parameter is specified in the MLME primitive.

[0316] In this case, when a non-AP STA MLD sends a Listen interval field to another AP MLD (e.g., an STR AP MLD) that is not an NSTR AP MLD, it may need to set the unit of the Listen interval field to the maximum value among the beacon intervals of the link (AP) it is trying to set up. For example, when a non-AP STA MLD tries to perform a Multi-Link Setup with an AP MLD and Link 1 or Link 2, the non-AP STA MLD can set the unit of the Listen interval field included in the ML coupling request frame to the larger of the beacon interval of Link 1 (AP) and the beacon interval of Link 2. That is, if the beacon interval of Link 1 is 100ms and the beacon interval of Link 2 is 50ms, the Listen interval subfield unit sent by the non-AP STA MLD may be 100ms.

[0317] Generally, once the AP and STA have completed setup, the STA can understand and track (update) the AP's operating parameters and element changes by receiving beacon frames transmitted by the AP. The beacon frames also play a role in providing information for the STA within the BSS to perform time synchronization, including the Timestamp field.

[0318] However, as mentioned earlier, NSTR AP MLD does not transmit beacon frames over non-primary links, so STA MLD set up with NSTR AP MLD may need to perform other actions to track (update) parameters and maintain time synchronization over non-primary links.

[0319] According to one embodiment of the present invention, a non-AP STA MLD coupled with an NSTR AP MLD can, after receiving a beacon frame on the primary link, verify the Change Sequence of the non-primary link (located in the MLD parameter field of the RNR element) and send an ML Probe Request. In this case, the ML probe request frame sent by the non-AP STA MLD may be sent for the purpose of requesting changed parameter and element information of the non-primary link. In this case, the ML probe request frame may request complete information of the non-primary link by setting the complete profile of the Per-STA profile corresponding to the non-primary link (and the AP of the non-primary link) to 1 and sending it. Alternatively, an ML probe request frame sent by the STA MLD for the purpose of updating the parameter / element of the non-primary link may request Updated Information, not Complete / partial information, for the non-primary link.

[0320] In other words, even if multiple links are formed between a non-AP STA MLD and an AP MLD, frames for joining, rejoining, and / or updating parameters may only be performed on the primary link. For example, if the STA recognizes that parameters for an AP on a non-primary link have been updated based on a specific field (e.g., the change sequence or BSS parameter change count subfield) indicating whether or not the update is for a link on another AP included in the neighboring AP information included in the beacon frame, the non-AP STA MLD can request the transmission of the updated parameters on the primary link of the other AP that is not a non-primary link. That is, the non-AP MLD cannot send frames (e.g., probe request frames) to request updated parameters on a non-primary link.

[0321] For example, a non-AP STA MLD that has set up with an NSTR AP MLD and requests information to update the parameters / elements of a non-primary link can request the changed parameters / elements from the AP of the non-primary link by setting the Updated Profile subfield of the Per-STA profile corresponding to the non-primary link to 1 in the ML probe request frame sent on the primary link. If the NSTR AP MLD receives an ML probe request frame and the Updated Profile subfield is indicated as 1 in the Per-STA profile (corresponding to the non-primary link), it can respond with an ML probe response frame containing the changed non-primary link information (parameters and elements).

[0322] In this case, the Per-STA profile field of the ML probe request frame transmitted by the non-AP STA MLD may have a configuration that includes an Updated Profile subfield and a Recorded Change Sequence subfield. The Recorded Change Sequence subfield indicates the latest Change Sequence value that the non-AP STA MLD maintains for the non-primary link, and the AP MLD can verify / determine the type of Updated Information based on the value indicated by the Recorded Change Sequence subfield.

[0323] For example, the NSTR AP MLD may change Parameter 1 while increasing the Change Sequence number of the non-primary link from 100 to 101, and then change Parameter 2 while further increasing the Change Sequence number from 101 to 102. In this case, the STA MLD can request updated information for the non-primary link while sending an ML probe request frame. In this case, if the non-AP STA MLD indicates the Recorded Change Sequence subfield as 100, the NSTR AP MLD can respond with an ML probe response frame containing both Parameter 1 and Parameter 2, and if the non-AP STA MLD indicates the Recorded Change Sequence subfield as 101, the NSTR AP MLD can respond with an ML probe response frame containing only Parameter 2.

[0324] In this case, Non-AP STA MLD can specify the Complete Profile subfield as 0 without utilizing another Updated Profile subfield to request an Updated Profile. In other words, Non-AP STA MLD can request an Updated Profile by setting the Complete Profile subfield to 0, in which case another Updated Profile subfield does not need to be included in the Per-STA profile.

[0325] Figure 24 shows an example of the profile subelement (Per-STA Profile subelement) format for each STA according to one embodiment of the present invention.

[0326] Referring to Figure 24(a), a Per-STA profile sub-element may have a configuration that includes an STA Control field. The STA Control field (see Figure 24(b)) indicates the type of field included in the STA profile (see Figure 24(a)) of the Per-STA profile sub-element. In this case, if the Complete Profile sub-field of the STA Control field is indicated as 1 in a specific Per-STA profile sub-element transmitted by an AP MLD other than an NSTR AP MLD, the MAC Address Present sub-field, Beacon Interval Present sub-field, and DTIM Information Present sub-field may all need to be indicated as 1. However, as mentioned above, since an NSTR AP MLD does not transmit beacon frames to a non-primary link, the Per-STA profile sub-element corresponding to the non-primary link does not need to indicate information related to the beacon frame of the non-primary link. In other words, a specific Per-STA profile sub-element transmitted by an NSTR AP MLD (corresponding to an AP on a non-primary link) may have the Complete Profile sub-field set to 1, while the Beacon Interval Present sub-field and the DTIM Information Present sub-field set to 0.

[0327] Furthermore, as described in the embodiment above, a non-AP STA MLD that sends an ML probe request frame to an NSTR AP MLD can request updated information of the non-primary link AP from the primary link AP by specifying the Updated Profile subfield of the STA Control field (included in the Per-STA profile sub-element corresponding to the non-primary link AP) as 1. At this time, the non-AP STA MLD can specify the Recorded Change Sequence value, which is information associated with the time when it updated the information of the non-primary link AP, using the Recorded Change Sequence subfield (see Figure 24(c)). At this time, the Recorded Change Sequence subfield may be a subfield included in the STA profile. After the NSTR AP MLD receives the ML probe request frame from the non-AP STA MLD received on the primary link, it can determine the information of the non-primary link AP to respond to the non-AP STA MLD by comparing the value of the Recorded Change Sequence subfield included in the ML probe request frame with the current Change Sequence value of the non-primary link AP.

[0328] Figure 25 shows an example of the process by which a non-AP MLD, set up with an NSTR (Non-Simultaneous Transmission and Reception) Soft AP MLD according to one embodiment of the present invention, updates information on a non-primary link.

[0329] Referring to Figure 25, NSTR AP MLD can change the parameters of AP2, which is operating on Link 2, a non-primary link, and then use a beacon frame transmitted by AP1, which is operating on Link 1, a primary link, to indicate that the parameters of AP2 have been changed. In this case, the information that the parameters of AP2 have been changed may be indicated by the Change Sequence subfield value corresponding to AP2 in the RNR element included in the beacon frame transmitted by AP1, which is one value higher than the value indicated in the previous beacon frame.

[0330] A Non-AP STA MLD can recognize that AP2's parameters have been updated after receiving a beacon frame transmitted by AP1 via STA1. The Non-AP STA MLD can then send an ML probe request frame via STA1 to obtain the changed parameter information of AP2.

[0331] The ML probe request frame transmitted by Non-AP STA MLD via STA1 may have a configuration in which the ML element includes a Per-STA profile sub-element corresponding to AP2, and the Per-STA profile sub-element may include an indicator indicating whether a Complete Profile or an Updated Profile is being requested.

[0332] After receiving an ML probe request frame from STA1 on the primary link, the NSTR AP MLD can respond to STA1 by including the requested AP2 information (complete or updated information) in the ML probe response frame.

[0333] A non-AP STA MLD, having received the requested AP2 information in an ML probe response frame from an NSTR AP MLD, can complete the parameter update for non-primary links where beacon frames are not transmitted by updating the parameters for AP2.

[0334] <Broadcast ML Probe Response>

[0335] According to one embodiment of the present invention, an NSTR AP MLD can send a broadcast ML probe response frame on the primary link when information related to an AP operating on a non-primary link changes. A Non-AP STA MLD may need to update information about the non-primary link (AP) when it receives a broadcast ML probe response frame sent by an NSTR AP MLD on the primary link. In this case, the broadcast ML probe response frame may not be sent as a response to an ML probe request frame sent by a specific STA, but may be an ML probe request frame sent by an NSTR AP MLD without any further request.

[0336] The broadcast ML probe response frame includes Per-STA profile sub-elements corresponding to the AP of the non-primary link and plays a role in helping the non-AP STA MLD update the changed parameters and elements of the non-primary link. In this case, since the (Recorded) Change Sequence of the non-primary link maintained by each non-AP STA may differ from one another, the broadcast ML probe response frame may contain complete information for the AP of the non-primary link. In this case, the broadcast ML probe response frame may be transmitted together with the DTIM beacon frame.

[0337] Therefore, a non-AP STA MLD may need to receive a broadcast ML probe response frame while receiving the next DTIM frame, using a beacon frame, if the Change Sequence Number corresponding to the AP on the non-primary link differs from the (Recorded) Change Sequence it maintains.

[0338] In this case, the parameter update procedure for the non-primary link using the broadcast ML probe response frame described above may be performed using the broadcast ML coupled response frame. In this case, the method for configuring the Per-STA profile sub-elements of the broadcast ML coupled response frame and the update procedure for the received STA MLD are the same as in the embodiment of the broadcast ML probe response frame described above, and a detailed explanation thereof is omitted.

[0339] Figure 26 is a flowchart illustrating an example of a procedure in which a non-AP STA MLD, associated with an NSTR AP MLD according to one embodiment of the present invention, updates the parameters of a non-primary link.

[0340] After receiving a beacon frame on the primary link, the non-AP STA MLD checks the Change Sequence of the non-primary link (located in the MLD Parameter field of the RNR element). If the checked Change Sequence value of the non-primary link differs from the recorded Change Sequence value it maintains, the non-AP STA MLD can send an ML probe request frame on the primary link. In this case, the ML probe request frame may include a subfield indicating whether it requests complete information or updated information for the AP of the non-primary link. Furthermore, an ML probe request frame requesting updated information may also include a subfield indicating the recorded Change Sequence value it maintains. Subsequently, the non-AP STA MLD, having received an ML probe response frame from the AP MLD, performs a parameter update based on the information of the non-primary link AP included in the responded ML probe response frame.

[0341] <Time Sync Management for Non-Primary Links>

[0342] As mentioned above, the beacon frames transmitted by the AP serve to transmit various parameters and element information, as well as to help the STAs within the BSS perform time synchronization. The TimeStamp field included in the beacon frame indicates the timing synchronization function (TSF) timer value at the time the data symbol containing the first bit of the TimeStamp field appears at the transmit antenna connector. Upon receiving the TimeStamp field, the STA can synchronize its own TSF timer with the AP based on the received TimeStamp field value.

[0343] Thus, APs and STAs can operate while maintaining time synchronization based on the TimeStamp value included in the beacon frame, enabling timing-based operation. However, NSTR AP MLDs cannot transmit beacon frames on non-primary links. Therefore, among Non-AP STA MLDs, STAs that are associated with an NSTR AP MLD non-primary link AP must use methods other than beacon frames to maintain time synchronization with the AP.

[0344] To maintain time synchronization with the AP on the non-primary link of an NSTR AP MLD, an associated non-AP STA may need to use the TimeStamp of the TIM frame transmitted by the AP. Since the TIM frame has a configuration that includes a TimeStamp field with the same function as a beacon frame, an STA that receives a TIM frame from the AP on the non-primary link of an NSTR AP MLD may need to manage the TFS timer using the TimeStamp field included in the TIM frame. However, since an NSTR AP MLD may be restricted from starting transmission on the non-primary link without occupying the primary link, it may need to transmit a TIM frame on the non-primary link at the same time as transmitting a beacon frame on the primary link. In other words, a non-AP STA MLD associated with an NSTR AP MLD may need to prepare to receive TIM frames on the non-primary link in accordance with the TBTT of the primary link.

[0345] In yet another embodiment of the present invention, when the AP MLD is an NSTR AP MLD that does not support simultaneous transmission and reception, the same TSF timer may be used for each link to the multiple APs included in the NSTR AP MLD, and the TSF timer used in this case may be the TSF timer of the primary link. That is, when the AP MLD is an NSTR AP MLD, the links to APs affiliated with the NSTR AP MLD (non-primary links) can use the TSF timer of the primary link.

[0346] In other words, a non-AP STA MLD coupled with an NSTR Soft AP MLD may need to share the primary link's TSF timer with the non-primary link. To put it another way, a non-AP STA MLD coupled with an NSTR AP MLD does not need a separate TSF timer for the non-primary (NSTR Soft AP MLD-based) link, and can use the TSF timer managed using the primary link. That is, in one aspect of the present invention, NSTR AP MLDs and non-AP STA MLDs coupled with NSTR AP MLDs can use MLD-level (MLD unit, MLD common) timers. In this case, for stable operation of NSTR AP MLDs and non-AP STA MLDs coupled with NSTR AP MLDs, it may be required that the time synchronization between each AP in an NSTR AP MLD and / or between each STA in a non-AP STA MLD coupled with an NSTR AP MLD is maintained with an error below a predetermined value. For example, an NSTR AP MLD may be required to maintain a timestamp difference (or difference between timers) between the primary link AP and the non-primary link AP. For example, a non-AP STA MLD coupled with an NSTR Soft AP MLD may be required to maintain a timestamp difference between the primary link STA and the non-primary link STA.

[0347] In other words, the primary link TSF timer may be maintained (or applied / used) identically for all APs included in or affiliated with the NSTR AP MLD. Furthermore, the difference between the timestamps or TSF timers of any two APs included in or affiliated with the NSTR AP MLD may be limited to a specific value (e.g., 30us).

[0348] In other words, the TSF timers of all APs included in or affiliated with the NSTR AP MLD may be identical, and the difference or clock drift between timestamps or TSF timers between any two APs included in or affiliated with the AP MLD or NSTR AP MLD (e.g., a primary link AP and a non-primary link AP) may be limited to a specific value (e.g., ±30us), in which case the AP MLD or NSTR AP MLD can modify the timestamps or TSF timers so that the difference or clock drift between TSF timers is within the specific value.

[0349] Furthermore, a non-AP STA MLD coupled with an NSTR AP MLD may need to receive the next beacon frame transmitted on the primary link when it receives a TIM frame on the non-primary link. More specifically, if a non-AP STA MLD receives a TIM frame via the STA on the non-primary link, and the value indicated in the Check Beacon field in the TIM frame action field differs from the Check Beacon value it maintains, it may need to receive the next beacon frame transmitted on the primary link. In this case, the next beacon frame may mean a beacon frame transmitted in response to a TBTT on the primary link that exists after the time the TIM frame was received on the non-primary link. In this case, receiving the next beacon frame may involve (include) updating the parameters of the non-primary link using the Per-STA profile (corresponding to the AP on the non-primary link) contained in the beacon frame. In this case, the parameters to be updated may be limited to those associated with critical updates.

[0350] <Procedures for changing channels and channel quieting on non-primary links>

[0351] As mentioned above, NSTR AP MLD does not transmit beacon frames on non-primary links, and therefore the BSS operation, which is based on the timing of beacon frame transmission, may be performed in a different manner than the BSS operation of a typical AP MLD.

[0352] Conventional Wi-Fi allows the BSS operating channel frequency (operating frequency band) to be changed by a pre-agreed procedure between the AP and STA. In this case, the conventional ECS (Extended Channel Switching) operation may be utilized, or the channel switching mechanism newly defined in 11be may be utilized. When an AP decides to change the BSS operating channel, it can send beacon frames, probe response frames, Extended Channel Switch Announcement frames, etc., to inform the associated STA that it can switch to the new channel and operating class while maintaining the connection. At this time, the AP sends an Extended Channel Switch Announce element in the beacon frame, and the Channel Switch Count field of this element indicates how many beacon frames will be sent before the channel switch (operating channel change) occurs. If the AP includes a MAX Channel Switch Time element along with the Extended Channel Switch Announcement element in the beacon frame, the AP must send the first beacon frame on the new channel within the Switch Time field (of the Max Channel Switch Time element). In other words, beacon frames transmitted on a new channel must be transmitted at a time interval shorter than the time interval specified in the Switch Time field between the last beacon frame transmitted on the current channel and the current beacon frame.

[0353] Referring to the conventional Wi-Fi BSS channel change operation described above, the AP of the BSS can use the beacon frame transmitted on the current channel to instruct the STA (System Aid) about the new channel, the time when the channel change will occur, and information related to the time of the first beacon frame transmitted on the new channel. The STA of the BSS can complete the channel change while maintaining the connection with the AP by moving to the new channel within a time interval determined based on the channel change-related information contained in the beacon frame transmitted by the AP (the time interval instructed by the AP). Thus, the conventional Wi-Fi BSS channel change procedure is performed in a way that the information necessary for the channel change (Channel Switch mode, new operating class, new channel number, channel switch count, etc.) is provided by the beacon frame transmitted by the AP. Therefore, in the case of a BSS on a non-primary link of an NSTR AP MLD where beacon frames are not transmitted, the conventional channel change procedure cannot be used to perform a channel change.

[0354] Furthermore, when Wi-Fi conventionally sets a quiet interval, the elements (Quiet element, Quiet Channel element) included in the beacon frame transmitted by the BSS AP indicate the time interval to which the quiet interval applies. Similar to the channel change procedure, non-primary links of NSTR AP MLDs that do not transmit beacon frames cannot use the conventional quieting procedure to set a quiet interval.

[0355] According to one embodiment of the present invention, an NSTR AP MLD can instruct the primary link to provide information necessary for channel switching of a non-primary link and / or information necessary for setting a quiet interval using a beacon frame transmitted on the primary link. That is, a non-AP STA MLD coupled with an NSTR AP MLD can operate based on information obtained from the primary link's beacon frame in order to perform channel switching of a non-primary link. That is, a non-AP STA MLD coupled with an NSTR AP MLD can obtain information related to the quiet interval of a non-primary link using the primary link's beacon frame.

[0356] More specifically, when the NSTR AP MLD changes channels on a non-primary link or sets a quiet interval, it may be necessary to include the Per-STA profile for the non-primary link AP in the primary link's beacon frame (and (ML) probe response frame).

[0357] Figure 27 shows an example of the format of an element according to one embodiment of the present invention. Figure 17 shows an example of the format of each element described above.

[0358] Referring to Figure 27, the (corresponding) Per-STA profile for an AP of a non-primary link may have a configuration that includes at least one of the following elements: Channel Switch Announcement element, Extended Channel Switch Announcement element, Max Channel Switch Time element, Quiet element, and Quiet Channel element.

[0359] The timing field of the aforementioned element may need to be set based on the TBTT (Target Beacon Transmission Time) and beacon interval of the primary link.

[0360] The primary link AP of NSTR AP MLD may need to set the timing fields of the Channel Switch Announcement element, Extended Channel Switch Announcement element, Max Channel Switch Time element, Quiet element, and Quiet Channel element included in the Per-STA profile (included in the beacon frame and (ML) probe response frame) for the non-primary link AP, based on its own beacon interval and TBTT. In this case, the timing fields are used to refer collectively to time-related fields, including duration-related fields (such as Switch Time and Quiet Duration fields) and time-related fields (such as Channel Switch Count and Quiet Count fields).

[0361] Therefore, a non-AP MLD coupled with an NSTR AP MLD may need to receive a beacon frame from the AP of the NSTR AP MLD operating on the primary link, obtain information related to channel changes and / or quiet intervals on the non-primary link from the Per-STA profile contained in the beacon frame, and then analyze the information related to channel changes and / or quiet intervals on the non-primary link based on the TBTT and BI (Beacon interval) of the primary link. In this case, the Per-STA profile refers to the Per-STA profile corresponding to the AP of the non-primary link.

[0362] On the other hand, NSTR AP MLD may need to send a TIM frame on the new channel (for the non-primary link) within the time specified by the Switch Time field (of the Max Channel Switch Time element) after completing the channel change on the non-primary link using the primary link beacon frame (after announcement and completion of the channel change). In other words, the AP on the non-primary link of NSTR AP MLD may need to send a TIM frame on the new channel after performing a channel change. In this case, the AP on the non-primary link may need to send a TIM frame on the new channel within the time specified by the Switch Time field after a beacon frame with the Channel Switch Count subfield set to 1 (or 0) has been sent on the primary link. In this case, the Channel Switch Count field and Switch Time field may be those included in the Per-STA profile (corresponding to the non-primary AP) included in the beacon frame sent on the primary link. In this case, the TIM frame may be replaced by another frame sent on the new channel of the primary or non-primary link. As an example, an NSTR AP MLD may, after completing a channel change on a non-primary link, transmit a beacon frame on the primary link indicating information related to the completion of the channel change. In this case, the beacon frame may be an additional beacon frame transmitted regardless of TBTT. In this case, the beacon frame may be a beacon frame having a configuration that includes complete information for the non-primary link. For example, the beacon frame having a configuration that includes complete information for the non-primary link may be a beacon frame in which the complete information subfield of the Per-STA profile corresponding to the AP on the non-primary link is set to 1.In this case, the primary link beacon frame transmitted after the channel change of the non-primary link is completed may need to be transmitted within a predetermined time frame with respect to the beacon frame transmitted before the channel change began. In this case, the predetermined time frame may be the time indicated by the Switch Time field (of the Max Channel Switch Time element). Alternatively, the beacon frame may be a beacon frame that includes an indication related to the channel change of the non-primary link. As an example, the primary link beacon frame transmitted after the channel change is completed on the non-primary link may have a configuration that includes a Channel Switch Complete subfield. In this case, the Channel Switch Complete subfield may be a subfield included in the ML element. The specific Switch Complete subfield may be a subfield that is indicated as 1 when the channel change of the AP corresponding to the Per-STA profile that includes the specific subfield is completed. That is, after the AP completes the channel change on the non-primary link, it may need to set the Channel Switch Complete subfield of the Per-STA profile (of the beacon frame) corresponding to the AP on the non-primary link to 1. In this case, the beacon frame associated with the channel change may be transmitted (utilized) for the same purpose even if the AP MLD is not an NSTR AP MLD, i.e., by a general AP MLD.

[0363] A non-AP MLD coupled with an NSTR AP MLD can only act as if the channel change on the non-primary link is complete if it receives a promised frame (the TIM frame or other frame for the non-primary link and / or a beacon frame indicating information related to the completion of the channel change on the primary link) from the AP MLD after the channel change on the primary link has been performed. If the channel change is not considered complete, the non-AP STA MLD may consider the channel change on the non-primary link to have been canceled and may need to operate on the previous channel (the channel before the channel change occurred) (return to the previous channel).

[0364] Alternatively, the NSTR AP MLD may be restricted from setting a quiet interval on the non-primary link. In this case, the quiet interval on the non-primary link may be defined (set) as the same time interval as the quiet interval on the primary link, if a quiet interval is defined (set) on the primary link. That is, when a non-AP STA MLD coupled with the NSTR AP MLD recognizes a quiet interval on the primary link, it can consider that a quiet interval has also been set for the same time interval on the non-primary link.

[0365] Furthermore, NSTR AP MLD cannot change the channel of a non-primary link. However, if NSTR AP MLD attempts to change the channel of a non-primary link, it can perform the same action as if it were deactivating the AP of the non-primary link operating on the existing channel and adding a new AP for the new non-primary link on the new channel.

[0366] The Quiet element for non-primary links transmitted in the primary link's beacon frame may be set (instructed) by NSTR AP MLD as follows:

[0367] 1. The Quiet Count field may be set to the number of TBTTs (Track By Time To) of primary links remaining until the next quiet interval begins for non-primary links.

[0368] 2. The Quiet Period field may be set to a value (in primary link beacon interval units) related to how many primary link beacon intervals the regular (periodic) quiet interval of the non-primary link defined by the Quiet element begins. (Set to 0 if it is not a regular quiet interval.)

[0369] 3. The Quiet Offset field may be set to a time value (in TU units) related to how much offset the quiet interval of the non-primary link begins with from the TBTT of the primary link, as identified by the Quiet Count subfield.

[0370] The (Extended) Channel Switch Announcement element and Max Channel Switch Time element for non-primary links transmitted in the primary link beacon frame may be set (instructed) by NSTR AP MLD as follows:

[0371] 1. The Channel Switch Count field (of the Channel Switch Announcement element) may be set to information related to how many TBTTs remain for the primary link before a channel change for the non-primary link begins. If a channel change for the non-primary link AP begins in the next TBTT for the primary link, the beacon frame sent in this TBTT may have its Channel Switch Count field (related to the non-primary link AP) set to 1 or 0.

[0372] 2. The Switch Time field (of the Max Channel Switch Time element) may be set to the maximum time difference between the primary beacon frame sent in the TBTT immediately preceding the TBTT in which the non-primary link channel change began (the beacon frame in 1. above where the Channel Switch Count field is set to 1 or 0) and the TIM frame sent on the new channel of the non-primary link after the channel change of the non-primary link is complete. For example, if the primary link beacon interval is 100ms and the Switch Time field (for the non-primary link AP) is set to 200ms, the non-primary link AP must send a TIM frame on the new channel within 200ms from the time it sent the primary link beacon frame initiating its channel change.

[0373] Therefore, a non-AP MLD coupled with an NSTR AP MLD can, after receiving a beacon frame on the primary link, obtain information about the quiet interval and channel change time and interval of the non-primary link based on the information indicated in the non-primary AP's Per-STA profile contained in the beacon frame, the primary link's TBTT, and beacon interval information. At this time, the Non-AP MLD can set (perceive and analyze) the start time of the quiet interval of the non-primary link based on the primary link's TBTT. At this time, the Non-AP MLD can perceive / analyze the channel change time of the non-primary link based on the reception time of the beacon frame received on the primary link.

[0374] Traditionally, Wi-Fi non-AP STAs can choose whether or not to change channels together with the AP to maintain connectivity when the AP changes channels. However, a non-AP STA MLD coupled with an NSTR AP MLD may always need to change channels on the non-primary link when the NSTR AP MLD changes channels on the non-primary link.

[0375] If a non-AP STA MLD that has performed an ML setup with an NSTR AP MLD (i.e., an ML setup using primary and non-primary links) decides not to change the channel of the non-primary link, the non-AP STA MLD may need to terminate (cancel or change) the ML setup with the NSTR AP MLD and change back to a state where it is set up only on the primary link (by canceling and then setting up or resetting).

[0376] Figure 28 shows an example of the process by which NSTR Soft AP MLD sets (defines) a quiet interval non-primarily according to one embodiment of the present invention.

[0377] Referring to Figure 28, the NSTR AP MLD operates AP1 and AP2 on the primary and non-primary links, respectively, and is coupled to STA1 and STA2 of the Non-AP STA MLD.

[0378] The NSTR AP MLD can include a Per-STA profile corresponding to AP2 in the beacon frame transmitted via AP1 on the primary link in order to set (define) a quiet interval (Quiet interval #1 in Figure 18) on the non-primary link. The Per-STA profile corresponding to AP2 includes a Quiet element, which indicates information related to when the quiet interval (Quiet interval #1 in Figure 18) begins in the Quiet Count and Quiet Offset fields. When the Quiet element is included in the first beacon frame of the primary link shown in Figure 18 (Beacon #1 in Figure 28), the Quiet Count field is set to 2 and the Quiet Offset field is set to a value indicating "x" TU (Time Unit, 1024us), and in the second beacon frame (Beacon #2 in Figure 18), the Quiet Count field is set to 1.

[0379] A non-AP STA MLD that receives the first and / or second beacon frame on the primary link can recognize that a quiet interval has been set on the non-primary link (published by the AP MLD) by checking the Quiet element included in the Per-STA profile of the beacon frame (corresponding to AP2), and that the said quiet interval (Quiet interval #1 in Figure 28) begins when "x" TU has elapsed from the TBTT corresponding to the third beacon frame.

[0380] As shown in Figure 28, the NSTR AP MLD can send a beacon frame via AP1 on the primary link, again including the Per-STA profile corresponding to AP2, in order to further set (define) the next quiet interval (Quiet interval #2 in Figure 28) on the non-primary link. The sixth beacon frame on the primary link shown in Figure 28 (Beacon #6 in Figure 28) has the Quiet Count field set to 2 and the Quiet Offset field set to 0TU (Time Unit, 1024us), while the seventh beacon frame (Beacon #7 in Figure 28) has the Quiet Count field set to 1.

[0381] A non-AP STA MLD that receives the sixth and / or seventh beacon frame on the primary link can recognize that a Quiet interval (Quiet interval #2) has been set on the non-primary link (published by the AP MLD) by checking the Quiet element included in the Per-STA profile (corresponding to AP2) of the beacon frame, and that the said Quiet interval (Quiet interval #2) will begin from the TBTT corresponding to the eighth beacon frame.

[0382] In this case, information regarding the length of the quiet interval is indicated by the Quiet Duration field, which is also specified in the Quiet element.

[0383] Figure 29 shows an example of a method by which an NSTR Soft AP MLD performs a non-primary channel switch according to one embodiment of the present invention.

[0384] Referring to Figure 29, the NSTR AP MLD operates AP1 and AP2 on the primary and non-primary links, respectively, and is coupled to STA1 and STA2 of the Non-AP STA MLD.

[0385] The NSTR AP MLD can include a Per-STA profile corresponding to AP2 (the non-primary link) in the beacon frame transmitted via AP1 on the primary link to change the non-primary link to a new channel. The Per-STA profile corresponding to AP2 includes an (Extended)Channel Switch Announcement element and a Max Channel Switch Time element, which indicate information related to when the channel change begins and the time interval during which TIM frames are transmitted on the new channel after the channel change. When the (Extended)Channel Switch Announcement element is included in the first beacon frame of the primary link shown in Figure 19 (Beacon #1 in Figure 19), the Channel Switch Count field is set to 2, and in the second beacon frame (Beacon #2 in Figure 19), it is set to 1.

[0386] A non-AP STA MLD that receives the first and / or second beacon frames on the primary link can recognize, by checking the (Extended)Channel Switch Announcement element included in the Per-STA profile (corresponding to AP2) of the beacon frame, that the channel change (to a new channel) on the non-primary link begins after receiving the second beacon frame, and that the AP2 TIM frame is received on the new channel within "x" TU from the time the second beacon frame was received. In this case, the new channel may be the channel corresponding to the value indicated in the New Channel Number field included in the (Extended)Channel Switch Announcement element. In this case, "x" TU may be the time value indicated in the Switch Time field included in the Max Channel Switch Time element included in the Per-STA profile (corresponding to AP2).

[0387] Operation Restrictions of non-AP STA MLD Combined with NSTR AP MLD

[0388] NSTR AP MLD is an AP MLD where the primary link and the non-primary link are an NSTR link pair. Therefore, during the transmission of a PPDU via the AP of the primary link, the AP of the non-primary link may become blind, and conversely, when the AP of the non-primary link transmits, the AP of the primary link may become blind. In this case, the AP of the NSTR AP MLD that has gone through the blind state may need to set the MediumSyncDelay to a preset value.

[0389] MediumSyncDelay is a single timer that is commonly applied to the EDCAF (EDCA Function) of the STA. When MediumSyncDelay is not 0, additional restrictions may be applied when the STA acquires a TXOP. At this time, the additional restrictions may be: (1) the first transmission attempt to obtain a TXOP must be an RTS frame; (2) only attempts to acquire a TXOP within a preset number of times (until it decreases to 0) while MediumSyncDelay is applied are allowed; (3) utilize a CCA ED (energy detection) threshold that is more stringent (lower: for example, -72dBm to -62dBm) than when MediumSyncDelay is 0. That is, a STA with a non-zero value of MediumSyncDelay has more restrictions applied in TXOP acquisition compared to a STA with MediumSyncDelay equal to 0.

[0390] Therefore, even in the case of NSTR AP MLD, when the AP goes through a BLIND state, MediumSyncDelay must be applied, and it may be difficult to provide normal service to the BSS STA when the AP's channel access is restricted. NSTR AP MLD can manage transmissions performed on non-primary links (links other than the primary link) in a way that prevents the primary link from going into a BLIND state by designating one of the links in the NSTR link pair on which it operates the AP as the primary link. For example, NSTR AP MLD can manage to prevent the primary link from going into a BLIND state by only transmitting on the non-primary link when it is in the process of transmitting on the primary link. For this purpose, NSTR AP MLD does not have to respond to a frame requesting a response frame even if it receives a frame requesting a response frame via the AP on the non-primary link. In other words, NSTR AP MLD can perform the operation of not responding to a response frame even if it receives a frame requesting a response frame via the AP on the non-primary link. In this case, the reason why the NSTR AP MLD does not respond with a response frame via the AP on the non-primary link may be to prevent the AP on the primary link from entering a BLIND state.

[0391] As described above, the NSTR AP MLD can manage the operation (transmission) of APs operating on the primary and / or non-primary links in order to set up the primary link and prevent the AP on the primary link from entering a BLIND state. Similarly, a non-AP STA MLD coupled with the NSTR AP MLD may need to understand and operate according to the NSTR AP MLD's primary link management method. For example, if the non-AP STA MLD recognizes that the NSTR AP MLD has not responded to a response frame on the non-primary link, it does not need to send a frame requesting a response frame on the non-primary link. Also, if the non-AP STA MLD has sent a frame requesting a response frame on the non-primary link and has not received a response frame from the NSTR AP MLD, it does not need to retransmit the frame requesting a response frame. For example, if the non-AP STA MLD sends an RTS frame to the NSTR AP MLD on the non-primary link and does not receive a CTS frame response, it does not need to retransmit the RTS frame. In this case, the Non-AP MLD does not need to attempt to send to the NSTR AP MLD via the non-primary link until it receives a trigger frame on the non-primary link.

[0392] Furthermore, even if a non-AP MLD completes the channel access procedure on the non-primary link to perform UL transmission, it may postpone transmission on the non-primary link until the channel access procedure on the primary link is completed. In this case, the method by which the non-AP MLD postpones transmission on the non-primary link may be to suspend the backoff procedure performed by the STA (more precisely, the EDCAF of the STA) on the non-primary link until the backoff procedure performed by the STA on the primary link is completed. In this case, the method by which the non-AP MLD suspends the backoff procedure performed by the STA on the non-primary link may be to maintain the backoff counter at 0.

[0393] As described above, a non-AP STA MLD that has completed the channel access procedure on both the primary and non-primary links can perform simultaneous transmission (simultaneous UL PPDU transmission) on both the primary and non-primary links. In this case, "simultaneous transmission" means that the start time of each transmission is within a predetermined time interval. However, if only the channel access procedure on the primary link is completed and the channel access procedure on the non-primary link is not yet completed, the non-AP MLD can start PPDU transmission only on the primary link, or start simultaneous transmission when the channel access procedure on the non-primary link is completed. In other words, when a non-AP MLD transmits to an NSTR AP MLD, it can transmit using only the primary link, or perform simultaneous transmission using both the primary and non-primary links. However, it is not necessary for a non-AP MLD to transmit PPDU to an NSTR AP MLD using only the non-primary link.

[0394] Furthermore, when non-AP MLD performs UL transmission using both the primary and non-primary links with NSTR AP MLD, it may be necessary to synchronize the end times of transmissions on both links. In this case, synchronizing the end times of transmissions means that transmissions on both links are completed within a predetermined time interval.

[0395] Furthermore, when a non-AP MLD performs UL transmission using both the primary and non-primary links with an NSTR AP MLD, it may be necessary to set the PPDU transmitted on both links to the same setting as whether or not it requests a response frame. Moreover, two UL PPDUs transmitted simultaneously by a non-AP MLD on the primary and non-primary links may both need to request a response frame, or both must request a response frame. This is a limitation that may apply because if a response frame is returned only on a specific link as a result of a UL transmission performed by a non-AP MLD using both the primary and non-primary links, the AP operating on the other links of the NSTR AP MLD may enter a BLIND state. However, if only one of two PPDUs that are received simultaneously (received on the primary and non-primary links, respectively) requests a response frame, the NSTR AP MLD does not need to return a response frame to both PPDUs.

[0396] Furthermore, when a non-AP MLD transmits using both the primary and non-primary links, it may be necessary to configure the non-primary link TXOP to terminate at the same time as, or earlier than, the primary link TXOP when transmitting with an NSTR AP MLD. In other words, a non-AP MLD may be necessary to configure the non-primary link TXOP to terminate at the same time as, or earlier than, the primary link TXOP. However, the non-primary link TXOP of a non-AP STA MLD may be permitted to terminate later than the primary link TXOP by a predetermined time interval.

[0397] Furthermore, a non-AP STA MLD can recognize that an NSTR AP MLD has experienced a BLIND state on a specific link and can assist the AP's operation. More specifically, when a non-AP STA MLD recognizes that an NSTR AP MLD has transmitted on only one of the primary and non-primary links, it can deduce that the AP on the other link that did not transmit must have experienced a BLIND state. In this case, the non-AP STA MLD can take action to help the AP that experienced the BLIND state to release (reset to 0) its MediumSyncDelay, considering that its channel access will be restricted by a non-zero MediumSyncDelay. The action taken by the non-AP STA MLD in this case may be an action that utilizes the characteristic that MediumSyncDelay can be released when a PPDU (including a valid MPDU) that can be configured for NAV is received.

[0398] As an example, a non-AP STA MLD can send a NAV-configurable Assist frame (a type of PPDU) to an AP of an NSTR AP MLD that, after going through a BLIND state, is determined to have a non-zero MediumSyncDelay. In this case, the Assist frame may mean a frame included in a valid MPDU that is NAV-configurable, regardless of the frame format. In this case, the condition for a non-AP STA MLD to send an Assist frame to an NSTR AP MLD on a specific link may be limited to when the state of the specific link, as confirmed by the non-AP STA MLD, is in an IDLE state. In this case, other conditions for a non-AP STA MLD to send an Assist frame to an NSTR AP MLD may be limited to when the non-AP STA MLD is a non-AP STA MLD that has been explicitly or implicitly requested (instructed) by the NSTR AP MLD to send an Assist frame.

[0399] <ML Discovery (Multi-Link Operation Discovery) and ML Setup (Association) Procedures Related to the 6GHz Band>

[0400] Prior to 6th generation Wi-Fi, Wi-Fi supported operation on 2.4GHz and 5GHz bands, and the 6GHz band, recently incorporated into the ISM band, was the first Wi-Fi frequency band (unlicensed band) used by HE terminals (AP STA, non-AP STA). The IEEE 802.11ax Task Group (TG), which advanced the standardization of HE terminals, considered that there were no conventional Wi-Fi terminals (terminals prior to 6th generation Wi-Fi) operating on the 6GHz band, and therefore specified that HE STA (AP STA, non-AP STA) operating on the 6GHz band would not perform backward compatibility with previous generation Wi-Fi terminals. More specifically, the specification aims to reduce overhead by limiting HE STAs operating at 6GHz from transmitting HT Capabilities elements, VHT Capabilities elements, HT Operation elements, VHT Operation elements, and / or HE Operation elements including VHT Operation Information fields, thereby eliminating support for terminals prior to 6-home Wi-Fi and reducing the amount of information contained in beacon frames, etc.

[0401] In other words, APs and / or non-AP STAs operating in a specific band (e.g., the 6GHz band) cannot transmit legacy format capability elements and / or operational elements (e.g., HT capability elements, VHT capability elements, HT operational elements, VHT operational elements, and / or HE operational elements including VHT operational information fields).

[0402] In yet another embodiment of the present invention, when an AP and / or non-AP STA operates in a specific band and does not transmit its own capability and operation elements for 2.4GHz / 5GHz, namely the HT capability element, VHT capability element, HT operation element, and / or VHT operation element, the AP and / or non-AP STA can transmit information about itself as well as information about other APs and / or non-AP STAs included in the same MLD. In this case, the information about other APs and / or non-AP STAs may include capability and operation elements for other bands other than the specific band (e.g., 2.4GHz / 5GHz). That is, an AP and / or non-AP STA can transmit capability and / or operation information for the band in which each of the multiple STAs operates, but cannot transmit capability and / or operation information for the band in which each of the multiple STAs does not operate.

[0403] In other words, beacon frames transmitted by HE APs operating at 6GHz and coupling request frames transmitted by non-AP STAs performing setup at 6GHz do not contain capability and operation information for when they are operating as HT and VHT STAs (APs and non-AP STAs). HE STAs operating at 6GHz do not need to operate as HT / VHT STAs because there are no other HT / VHT STAs operating in the 6GHz band, and therefore the capability and operation information for HT / VHT STA operation mentioned above may be unnecessary information. For this reason, the 11ax standard restricts HE STAs (AP STAs and non-AP STAs) operating at 6GHz from transmitting HE operation elements including HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, and VHT operation information fields, and the same restriction may apply to EHT STAs (MLDs) that inherit the operation of HE STAs.

[0404] In other words, an STA operating in the 6GHz band cannot transmit HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, or HE operation elements that include VHT operation information fields. That is, an STA operating in the 6GHz band does not need to transmit capability / operation elements in specific legacy formats to provide parameters for its capabilities and operations.

[0405] However, in this case, the STA operating at 6GHz may transmit a Basic Multi-Link element containing information about other STAs. In this case, the Basic Multi-Link element may include an STA Profile field containing capability and / or operational elements for other STAs reported by the STA operating at 6GHz. The STA reported by the STA operating at 6GHz may operate in the 2.4GHz or 5GHz band, and the STA Profile field may be included in a Per-STA profile subelement corresponding to the reported STA.

[0406] However, as considered in the embodiments of the present invention described above, an EHT STA that is an MLD must perform ML setup by transmitting not only information about itself but also information about other STAs within the same MLD (operating on other links) in the beacon frame and (ML) probe response frame, coupling request frame and / or coupling response frame. In other words, among APs in an AP MLD, an AP operating at 6 GHz must indicate the HT / VHT capability / operation elements of the 2.4 GHz and 5 GHz APs in the (ML) probe response frame and coupling response frame in order to provide information about other APs operating at 2.4 GHz and 5 GHz, and therefore the restriction that 11ax stipulates that a 6 GHz STA (AP STA, non-AP STA) cannot indicate HT / VHT related elements needs to be modified. In this case, the (ML) probe response frame can mean a response frame transmitted in response to an ML probe request frame.

[0407] In the description of the present invention, which will be described later, APs operating at 2.4GHz / 5GHz / 6GHz will be referred to as 2.4GHz AP, 5GHz AP, and 6GHz AP, respectively, and STAs that perform (attempt to perform) ML setup at 2.4GHz / 5GHz / 6GHz will be referred to as 2.4GHz STA, 5GHz STA, and 6GHz STA (non-AP STA), respectively.

[0408] According to one embodiment of the present invention, a 6GHz AP / STA (reporting STA) of an EHT MLD can transmit HE operation elements, including HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, and VHT operation information fields, for 2.4GHz and 5GHz STAs (reported STAs) of the same MLD. In this case, the frame in which the 6GHz AP / STA may include HT / VHT-related information for the 2.4GHz and 5GHz STAs (AP STAs that are reported STAs, non-AP STAs) may be a management frame. In this case, the 6GHz AP / STA may include HT / VHT-related information for the 2.4GHz and 5GHz AP / STAs in the ML IE (Multi-Link Information Element) in the management frame. In this case, the 6GHz AP / STA may include HT / VHT-related information for the 2.4GHz and 5GHz AP / STAs in the Per-STA profile sub-elements corresponding to each STA in the management frame.

[0409] Alternatively, a 6GHz AP / STA may include HT / VHT capability / operational elements for 2.4GHz and 5GHz STAs (reported STAs) as common information indicated in the ML IE of the management frame.

[0410] More specifically, the (re)combined response frame that a 6GHz AP of an EHT AP MLD transmits to perform (accept) an ML setup including 2.4GHz and / or 5GHz APs may include HT / VHT capability / operation elements.

[0411] Similarly, a (re)combination request frame transmitted by a 6GHz STA of an EHT non-AP MLD to perform (request, request) an ML setup including 2.4GHz and / or 5GHz STAs may include HT / VHT capability / operation elements.

[0412] In other words, a 6GHz STA (of the MLD) can transmit the HT / VHT capability / operational elements in the (re)combination request frame only when attempting an ML setup that includes 2.4GHz and / or 5GHz STAs of the same MLD.

[0413] In other words, a 6GHz AP (of the MLD) can transmit HT / VHT capability / operational elements in a re)combined response frame only if it is part of an ML setup that includes 2.4GHz and / or 5GHz APs of the same MLD.

[0414] For example, the APs or non-AP STAs that make up the MLD can each operate in various frequency bands (6GHz, 2.4GHz, or 5GHz). In this case, the MLD containing the non-AP STA (first MLD) can send and receive frames with the MLD containing the AP (second MLD) for multiplex link configuration. At this time, the STA operating at 6GHz included in the first MLD (first STA) can send a coupling request frame (or recouping request frame) for multiplex link configuration, and the AP operating at 6GHz included in the second MLD (first AP) can send a coupling response frame (or recouping response frame) as a response to the coupling request frame (or recouping request frame).

[0415] The first STA can send a link request message that includes information about itself and information about other STAs included in the same MLD (e.g., multilink information (or elements)).

[0416] The information about the first STA included in the coupling request message may be information related to 6GHz (e.g., HE capability information, HE operation information, EHT capability information, and / or EHT operation information). However, the coupling request message does not include information about the first STA for other bands other than the 6GHz band (e.g., 2.4GHz or 5GHz) (e.g., HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, or HE operation elements including VHT operation information fields). In other words, the first STA cannot transmit information about bands other than the band in which it operates.

[0417] Information about other STAs included in the coupling request message (e.g., multilink information (or elements)) may include information about the bandwidth in which each of the other STAs operates (e.g., 2.4 GHz or 5 GHz) (e.g., HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, or HE operation elements including VHT operation information fields).

[0418] In this case, information about other STAs may be included in the Per-STA profile sub-elements corresponding to each STA.

[0419] Furthermore, the multi-link information (or multi-link element) of the coupling request message may include a multi-link element containing a Per-STA profile subelement corresponding to each of the reported STAs, and the Per-STA profile subelement may include a Complete Profile subfield indicating whether or not the request is for all information for the corresponding station among at least one of the reported stations.

[0420] In this case, if the complete profile subfield is set to a value indicating a request for all information or a specific value (e.g., "1"), all information of the STA corresponding to the complete profile subfield may be included in the multilink element. Alternatively, the complete profile may indicate whether the corresponding Per-STA profile contains the complete information of that STA.

[0421] The first AP can send a combined response message that includes information about itself and information about other APs included in the same MLD (e.g., multilink information (or elements)).

[0422] The information about the first AP included in the coupled response message may be information related to 6GHz (e.g., HE capability information, HE operation information, EHT capability information, and / or EHT operation information). However, the coupled response message shall not include information about the first AP relating to other bands other than the 6GHz band (e.g., 2.4GHz or 5GHz) (e.g., HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, or HE operation elements including VHT operation information fields). In other words, the first AP cannot transmit information about bands other than the band in which it operates.

[0423] Information about other APs included in the coupling request message (e.g., multilink information (or elements)) may include information about the bandwidth in which each of the other STAs operates (e.g., 2.4 GHz or 5 GHz) (e.g., HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, or HE operation elements including VHT operation information fields).

[0424] Furthermore, a 6GHz AP (of MLD) can transmit the ML probe response frame including the HT / VHT capability / operation elements, identical to those in the coupling request frame or coupling response frame described above. In this case, the condition for a 6GHz AP to transmit (respond) the ML probe response frame including HT / VHT-related information is that the received probe request frame may include a multilink element (a probe request variant). In this case, a probe request frame containing a multilink element may be considered an ML probe request (frame).

[0425] More specifically, the conditions under which a 6GHz AP transmits (responds) an ML probe response frame containing HT / VHT capability elements and / or HT / VHT operation elements are that the received ML probe request frame contains multilink elements and requests complete information or HE / VHT capability / operation element information for the 2.4GHz and / or 5GHz APs.

[0426] Figure 30 shows an example of a probe request frame, association request frame, and association response frame transmitted by a station operating within a specific bandwidth.

[0427] Referring to Figure 30, the 6GHz AP can transmit HT / VHT capability elements and HT / VHT operation elements in the ML IE of the (ML) probe response frame. In this case, the HT / VHT capability / operation elements may be those for the 2.4GHz and 5GHz APs operated by the MLD to which the 6GHz AP belongs.

[0428] In other words, while the 6GHz band operating regulations restrict 6GHz APs from transmitting HT / VHT-related elements, a 6GHz AP that is an AP MLD STA can transmit (ML) probe response frames containing HT / VHT-related elements in the 6GHz band for the purpose of providing complete information to 2.4GHz and 5GHz APs.

[0429] Furthermore, non-AP MLD STAs and AP MLD APs that transmit (re)combination request / response frames in the 6GHz band can also transmit (re)combination Req / Resp frames containing HT / VHT-related elements in the 6GHz band, depending on their purpose.

[0430] A 6GHz STA may include HT / VHT-related elements in its (re)combination request frame if it intends to perform ML setup simultaneously on 6GHz and 2.4 / 5GHz using the (re)combination request frame transmitted at 6GHz.

[0431] A 6GHz AP may include HT / VHT-related elements in its (re)connection response frame only if a non-AP STA has transmitted a (re)connection request frame in the 6GHz band and accepts the non-AP STA's ML setup request, intending to also perform setup in 2.4GHz and / or 5GHz.

[0432] Another possible approach is to restrict 6GHz STAs (AP STAs, non-AP STAs) from including HT / VHT capability / operational elements in frames transmitted in the 6GHz band.

[0433] In this case, the 6GHz AP may omit the HT / VHT capability / operation elements when transmitting the ML probe response frame containing information (Per-STA Profile) of the 2.4GHz and / or 5GHz APs and the ML coupling response frame accepting the setup of the 2.4GHz and / or 5GHz APs. Therefore, a non-AP MLD attempting to perform an ML setup including 2.4GHz and 5GHz via a 6GHz AP may need to send an ML probe request frame to the 2.4GHz or 5GHz AP to obtain additional information (included in the HT / VHT related elements) for the 2.4GHz and / or 5GHz APs.

[0434] Considering the limitation that HT / VHT-related elements cannot be transmitted / acquired at 6GHz, a non-AP EHT MLD attempting to send an ML coupling request frame to a 6GHz AP may need to receive an ML probe response frame containing complete information (or HT / VHT-related elements) about the AP to be set up at 2.4GHz or 5GHz beforehand. In other words, a non-AP EHT MLD attempting to perform ML setup simultaneously with 2.4GHz and / or 5GHz APs by sending an ML coupling request frame to a 6GHz AP may need to transmit an ML probe request frame at 2.4GHz or 5GHz and acquire complete information (or HT / VHT-related elements) about the 2.4GHz and / or 5GHz APs before or after the setup is complete.

[0435] Furthermore, after completing the ML setup at 6GHz, the non-AP MLD may need to transmit complete information (or HT / VHT-related elements) of the STAs (2.4GHz STA and 5GHz STA) operating on the set-up 2.4GHz and 5GHz links to the AP MLD. In this case, the non-AP MLD can transmit the HT / VHT capability / operation elements of the 2.4 / 5GHz STA in the first PPDU transmitted after coupling in order to transmit the elements of the set-up 2.4 / 5GHz STA.

[0436] Figure 31 shows an example of a method for setting up multiple links by exchanging HT (High Throughput) / VHT (Very High Throughput) related element information over other links that do not have a specific bandwidth, according to one embodiment of the present invention.

[0437] Referring to Figure 31, the AP MLD can operate AP1 to AP3 at 2.4GHz, 5GHz, and 6GHz respectively. A non-AP MLD that receives a beacon frame from AP3, which is a 6GHz AP, may attempt to perform ML setup by exchanging (re)connection Req / Res frames with the AP MLD using the 6GHz band.

[0438] In this case, the Non-AP MLD may intend to attempt an ML setup including a 2.4GHz AP and a 5GHz AP, and to that end, it may send an ML probe request frame to the 5GHz AP at 5GHz before sending a coupling request frame at 6GHz. In this case, the ML probe request frame that the non-AP MLD sends in the 5GHz band may be an ML probe request frame requesting complete information (or HT / VHT related elements) for the 2.4GHz AP and the 5GHz AP among the APs for which it intends to perform the ML setup.

[0439] A non-AP MLD that has received an ML probe response frame from a 5GHz AP can send a coupling request frame via a 6GHz STA to the 6GHz AP requesting an ML setup including 2.4GHz / 5GHz. Generally, the coupling request frame should contain complete information for the STA of the link requesting the ML setup, however, the coupling request frame sent by the 6GHz STA may not contain HT / VHT capability / operational elements for the 2.4GHz and 5GHz STAs. Similarly, a coupling response frame sent (responded) to accept a setup for 2.4GHz and / or 5GHz generally should contain complete information for the AP of the link accepting the ML setup, however, the coupling response frame sent by the 6GHz AP may not contain HT / VHT capability / operational elements for the 2.4GHz and 5GHz APs.

[0440] Thus, a non-AP MLD that has set up with an AP MLD at 2.4GHz and / or 5GHz using a coupling request / response frame that does not contain HT / VHT elements for 2.4 / 5GHz can transmit the HT / VHT capability / operation elements for the set up 2.4 / 5GHz STA to the AP MLD using the first PPDU transmitted after receiving the coupling response frame.

[0441] <Management Frame Structure and Inheritance Rules>

[0442] EHT STAs (AP STAs, non-AP STAs) included in the same MLD are likely to have similar capabilities and operating parameters, even if they are operating on different links. Therefore, some elements of an STA that transmits management frames (beacons, (ML) probe Req / Resp, (ML) coupled Req / Resp frames, etc.) (reporting STA) may contain the same information as some elements of other STAs (reported STAs) in the MLD.

[0443] As considered in the embodiments of the present invention described above, an EHT STA (reporting STA) can transmit complete information of other STAs (reported STAs) within the same MLD in a management frame, and given that an MLD can operate multiple STAs, a management frame containing complete information for each STA can induce a lot of overhead.

[0444] Therefore, in a management frame that includes complete information for other STAs within the MLD in its Per-STA profile sub-elements, elements of the reporting STA that contain the same information as the reporting STA elements may be omitted. That is, in a management frame that includes complete information for a specific STA (reported STA), if some elements are not indicated in the Per-STA profile sub-element corresponding to the specific STA, the unindicated elements may be analyzed as having inherited the same information (the same elements as the aforementioned some elements) corresponding to the STA (reporting AP) that sent the management frame. In this case, "a management frame that includes complete information for the specific STA (reported STA)" can mean a management frame that contains the same level (same amount) of information as the STA (reporting STA) that sent the management frame. In this case, analyzing the Per-STA profile sub-elements using inheritance rules may be performed only if the Per-STA profile is a complete profile. In this context, "Per-STA profile is a complete profile" means that the Complete Profile subfield of the Per-STA profile sub-element is set to 1.

[0445] Thus, an MLD's STA can construct its management frame using inheritance rules to reduce the size of the management frame, while still including complete information about other STAs within the MLD. Furthermore, an MLD that receives a management frame from another MLD's STA can use inheritance rules to retrieve (analyze, recognize) the information of the omitted reported STA.

[0446] In this case, whether or not the management frame contains complete information for each reported STA may be indicated by whether or not the Complete Profile subfield (of the STA Control field) is set to 1 in the Per-STA profile sub-element corresponding to each reported STA. That is, a reported STA corresponding to a Per-STA profile in which the Complete Profile subfield is set to 1 may be an STA for which complete information is indicated in that management frame.

[0447] <Inheritance rules that apply to elements not designated as reporting STA elements in the management frame>

[0448] A reporting STA sending a management frame may not possess specific element information. For example, if the reporting STA is a 6GHz STA (AP STA, non-AP STA), the 6GHz STA that is the reporting STA may not have HT / VHT-related elements. In this case, if the management frame should contain complete information for the 2.4GHz and 5GHz STAs, the HT / VHT-related information (HT / VHT capability / operation elements) that should be indicated for the 2.4GHz and 5GHz STAs cannot be indicated / analyzed using inheritance rules. This is because the 6GHz STA that is the reporting STA does not possess HT / VHT-related information, and therefore, a management frame in which the 6GHz STA is the reporting STA cannot apply inheritance rules to elements that are indicated only for the reported STA. In other words, when a management frame transmitted by a 6GHz STA should indicate complete information for multiple 2.4GHz and 5GHz STAs, even if all of the reported STAs (2.4 / 5GHz STAs) have the same HT / VHT capability / operational element values, each element may need to be indicated repeatedly in the Per-STA profile corresponding to each reported STA. This means that if the reporting STA transmitting the management frame does not contain information about a particular element, the use of inheritance rules in the management frame may be restricted, which could result in an increase in the size of the management frame.

[0449] Therefore, due to the limitation that inheritance rules are not applicable to elements not specified for reporting STA, new inheritance rules may be needed to prevent the size of the management frame from becoming excessive.

[0450] According to one embodiment of the present invention, information (such as elements) of a reported STA indicated by a management frame (e.g., a beacon, (ML) probe response, (ML) coupling request, (ML) coupling response frame, etc.) can inherit other information that is not related to the reporting STA.

[0451] Furthermore, if a management frame is instructed to contain complete information for a specific reported STA, but no specific element corresponding to the said reported STA is instructed, then the said specific element may be considered to have inherited from another element rather than from an element of the reporting STA. In this case, the condition for the said specific element to be considered to have inherited from another element rather than from an element of the reporting STA is that the said specific element is not instructed (not included) for the reporting STA (in the management frame). In this case, the method of instructing / analyzing the information of the reported STA to inherit from another element rather than from an element of the reporting STA may be applied only when the reporting STA is a 6GHz STA.

[0452] According to one embodiment of the present invention, if a specific element of a reported STA that indicates complete profile information is not indicated in the management frame, the value of the same element (where the element ID and Extended element ID are the same) as the specific element indicated in the management frame may be considered to be applied (indicated) identically to the specific element of the reported STA. In this case, the identical element inherited as the specific element of the reported STA does not have to be an element for the reporting STA.

[0453] In other words, an identical element inherited as a specific element for a reported STA (having the same element ID and Extended element ID as the aforementioned specific element) does not have to be an element for a reporting STA.

[0454] In other words, the same element inherited as a specific element for a reported STA (having the same element ID and Extended element ID as the aforementioned specific element) may be an element for another reported STA. In this manner, even if the HT / VHT capability / operation elements for the 6GHz STA are not specified in the management frame where the 6GHz STA is the reporting STA, the HT / VHT elements specified in the Per-STA sub-element of the reported STA may be inherited by other reported STAs.

[0455] Alternatively, an identical element inherited as a specific element for a reported STA (having the same element ID and Extended element ID as the aforementioned specific element) may be an additional element designated for inheritance. In this case, the additional element designated for inheritance may represent a reporting STA or an element that does not directly correspond to a reporting STA.

[0456] However, if the aforementioned specific element (not included in the management frame) is indicated by the Non-Inheritance element of the Per-STA profile sub-element corresponding to the reported STA, then the aforementioned specific element for the reported STA may be considered as not inheriting any value and not being indicated in the management frame.

[0457] For example, if a specific element is not specified for STA1, which is indicated by a management frame, and the same element exists for STA2, then the value indicated by that same element may be considered (i.e., inherited) in the same way as the value indicated by the specific element of STA1. In this case, STA2 does not have to be a reporting STA.

[0458] Furthermore, any identical element inherited as a specific element of STA1 (having the same element ID and Extended element ID as the aforementioned specific element) may be an additional element designated for inheritance, not an element for reporting STA or reported STA.

[0459] According to one embodiment of the present invention, if a specific element of a reported STA that indicates complete information (profile) is not indicated in the management frame, the value of the same element (with the same element ID and Extended element ID) as the specific element indicated in the management frame may be considered to be applied (indicated) identically to the specific element of the reported STA. In this case, the element inherited as a specific element of the reported STA may be determined by inheritance rules.

[0460] As an example of a rule for selecting inherited elements, other elements inherited as specific elements for a reported STA (having the same element ID and Extended element ID as the aforementioned specific element) may be determined as the same element that was first indicated in the management frame.

[0461] Furthermore, in a management frame that should contain complete information (profile) for a reported STA, if no specific element is specified for the reported STA, the value of the element that is specified earliest (in element order) among other elements having the same element ID and Extended element ID as the specific element may be considered to have been inherited by the specific element. That is, if the same element as the specific element is specified for the reporting STA (specified in the earliest order among the same elements), the specific element may be considered to have inherited the same element value of the reporting STA.

[0462] Another example of a rule for selecting inherited elements is that other elements inherited as specific elements for a reported STA (having the same element ID and Extended element ID as the aforementioned specific element) may be determined to be the same element as the last indicated (in terms of element order) in the management frame.

[0463] Furthermore, in a management frame that should contain complete information (profile) for a reported STA, if no specific element is specified for the reported STA, it may be assumed that the value of the last element specified (in element order) among other elements having the same element ID and Extended element ID as the specific element is inherited by the specific element. That is, if the same element as the specific element is specified for three STAs beforehand, it may be assumed that the specific element inherits the same element value from the third specified element.

[0464] Figure 32 illustrates a part of the configuration of a management frame for explaining a method for inheriting a complete Per-STA profile according to one embodiment of the present invention.

[0465] Referring to Figure 32, the management frame contains four elements for the reporting AP (elements IDA to D in Figure 22), and includes an ML IE to indicate the complete information for the reporting STA.

[0466] An ML IE (Multi-link element) consists of an element ID subfield, a Length subfield, an element ID Extension subfield, and two Per-STA profile sub-elements. In this case, the Per-STA profile indicated first is the Per-STA profile included to indicate the complete information (profile) for reported STA1, and the Per-STA profile indicated later is the Per-STA profile included to indicate the complete information (profile) for reported STA2. In other words, the Per-STA profile indicated first is the Per-STA profile for reported STA1, and the Per-STA profile indicated later is the Per-STA profile for reported STA2.

[0467] The Per-STA profile corresponding to reported STA1 includes two elements (element IDs E and F, respectively) that are not indicated by the elements for reporting STA. In this case, since the Per-STA profile corresponding to reported STA1 is a complete Per-STA profile with the Complete profile subfield indicated as 1, the remaining three elements (element IDs A, B, and D, respectively) of the elements for reporting STA (element IDs A to D), excluding the element indicated by the Non-Inheritance element (element ID C), may be considered to be the same as those indicated for reported STA1. In this case, the values ​​indicated by each of these three elements, which are considered to be the same as those indicated by the elements for reporting STA, are also considered to be the same as those indicated by the elements for reporting STA.

[0468] Consequently, although the Per-STA profile for reporting STA1 has a configuration containing only two elements (element IDs E and F), it can be analyzed that five elements were indicated as the complete profile for reported STA1, considering that it inherited three elements (element IDs A, B, and D) from reporting STA.

[0469] The Per-STA profile corresponding to reported STA2 includes an element with element ID B that has been indicated as an element for reporting STA. This may be because the value of the element indicated for reported STA2 (the element with element ID B) is different from the value of the element indicated for reporting STA (element ID B), so the element of reporting STA is not inherited, and a new element value is indicated for reported STA2.

[0470] Since the Per-STA profile corresponding to reported STA2 is a complete Per-STA profile with the Complete profile subfield indicated as 1, the remaining elements for reporting STA (A, C, and D, excluding element ID B) are considered to be the same as those indicated for reported STA2. In this case, the values ​​indicated by each of the three elements considered to be the same as those for reporting STA are also considered to be the same as those for the elements for reporting STA.

[0471] Furthermore, the Per-STA profile corresponding to reported STA2 can inherit not only the elements specified for reporting STA, but also the elements of reported STA1, which were specified earlier in the sequence. That is, the two elements specified in the Per-STA profile of reported STA1 (element IDs E and F) may also be inherited by the elements of reported STA2. In other words, elements for reported STA1 may also be inherited as elements of reported STA2. That is, the two elements specified in the Per-STA profile of reported STA1 (element IDs E and F) may be considered to be the same elements specified for reported STA2.

[0472] <Implicit non-Inheritance rule>

[0473] As mentioned above, complete information (profile) for a reported STA may be indicated in a management frame sent by the reporting STA, and inheritance rules may be applied to prevent the same element with the same value from being indicated repeatedly within the management frame.

[0474] The Non-Inheritance element included in the Per-STA profile sub-element of a Reported STA has the function of explicitly indicating elements that are not specified for the Reported STA and to which inheritance should not be applied. In other words, when a specific element is specified in the Non-Inheritance element included in the Per-STA profile sub-element of a particular STA, it may be explicitly indicated that the specific element not specified for the said particular STA will not inherit the values ​​of other elements. In this case, the MLD that receives the management frame can consider (analyze) that the said specific element does not exist for the said particular STA.

[0475] In other words, Non-Inheritance elements may be used to resolve ambiguity regarding whether a particular element of a reported STA not indicated in the management frame is omitted by inheritance rules or does not exist in the first place.

[0476] However, in certain cases, the MLD that receives the management frame may recognize that some elements not indicated for the reported STA are elements that do not exist for the reported STA in the first place.

[0477] For example, a non-AP STA MLD that receives a (re)combined response frame in which a 6GHz AP is included as a reported STA may already be aware that the HT / VHT capability / operation elements for the 6GHz AP cannot be specified in the (re)combined response frame. In this case, even if the AP MLD that sends the (re)combined response frame does not separately indicate that the HT / VHT-related elements are not inherited by the Non-Inheritance element (of the Per-STA profile sub-element) corresponding to the 6GHz AP, the STA MLD does not need to analyze the HT / VHT-related elements for the 6GHz AP using inheritance rules.

[0478] According to one embodiment of the present invention, even if the HT / VHT capability / operation elements are not listed in the Non-Inheritance element corresponding to the 6GHz AP which is a reported STA, the elements do not need to be inherited by the 6GHz AP. In this case, not being listed in the Non-Inheritance element may mean either that the Non-Inheritance element is not shown (not included) in the Per-STA profile sub-element, or that it is not indicated by the Non-Inheritance element.

[0479] For example, if a management frame (e.g., a (re)connection response frame) transmitted by a 2.4GHz AP indicates a complete profile for a 6GHz AP, the HT capability elements for the 2.4GHz AP will not be inherited as HT capability elements for the 6GHz AP, even if the HT capability elements for the 6GHz AP are not indicated and the Non-Inheritance elements are not included in the Per-STA profile.

[0480] Figure 33 is a flowchart showing an example of the operation of a non-AP MLD according to one embodiment of the present invention.

[0481] Referring to Figure 33, an MLD composed of multiple STAs can transmit information about STAs operating in other bands via an STA operating in a specific band.

[0482] Specifically, a first multi-link device (MLD) including a first plurality of stations each operating on multiple links transmits a request frame to a second station among a second plurality of stations included in a second MLD, each operating on at least one link, via a first station among the first plurality of stations included in the first multi-link device (S3310).

[0483] At this time, the first and second stations can operate in a specific frequency band (for example, 6 GHz).

[0484] Subsequently, the first station can receive a response frame from the second station as a response to the request frame (S3320).

[0485] At this time, the second station can transmit the capability element and / or operation element of the second station for the specific bandwidth, excluding the capability element and / or operation element of the second station for the specific legacy format for other bandwidths, in the response frame.

[0486] The response frame may include multilink information for coupling between at least one first station among the first plurality of stations, excluding the first station, and at least one second station among the second plurality of stations, excluding the second station.

[0487] The multilink information may include capability and / or operational elements of each of the second or at least one station in a legacy format corresponding to each of the other bandwidths.

[0488] Each capability element and / or operating element of the second or at least one station is at least one of the following: an HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, an HT operating element, a VHT operating element, or an HE (High Efficiency) operating element including VHT operating information.

[0489] In this case, the specific frequency band is 6 GHz, and the other frequency bands may be 2.4 GHz and / or 5 GHz.

[0490] The request frame (for example, an ML probe request frame) includes a multi-link element containing a Per-STA profile subelement corresponding to each of the second at least one station, and the Per-STA profile subelement may include a Complete Profile subfield indicating whether or not it is a request for all information for the corresponding station among the second at least one station.

[0491] When the complete profile subfield indicates a request for all of the above information, the multilink information in the response frame may include capability and / or operational elements of the second or at least one station corresponding to the complete profile subfield indicating a request for all of the above information.

[0492] Based on the multilink information, a multilink configuration procedure can be performed to configure a link between the second MLD and the first at least one station and the second at least one station.

[0493] A request frame (e.g., a combined request frame) includes a multi-link element which includes at least one Per-STA profile subelement corresponding to each of the first at least one stations, and each of the at least one Per-STA profile subelements of the multi-link element may include legacy format capability elements and / or operational elements for a specific station among the first at least one stations.

[0494] A specific station is a station operating in at least one of the other bands, and the first station can transmit the capability element and / or operation element of the first station for the specific band, excluding the capability element and / or operation element of the first station for the other bands in a specific legacy format, in the request frame.

[0495] The response frame is one of the following: an association response frame or a multi-link (ML) probe response frame.

[0496] The above description of the present invention is illustrative, and a person with ordinary skill in the art to which the present invention belongs will understand that it can be easily modified into other specific forms without altering the technical idea or essential features of the present invention. Accordingly, the embodiments described above should be understood to be illustrative and not limiting in any respect. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

[0497] The scope of the present invention is defined more by the claims described below than by the above detailed description, and all modifications or altered forms derived from the meaning and scope of the claims and the concept of equivalents thereof should be interpreted as being included within the scope of the present invention.

Claims

1. A first multi-link device (MLD) including a plurality of first stations each operating on a plurality of links, The processor is, A request frame is transmitted from the first station among the first plurality of stations included in the first multilink device to the second station among the second plurality of stations included in the second MLD, each operating on at least one link. The first station and the second station operate in a specific frequency band. The first station receives a response frame from the second station as a response to the request frame, The second station transmits the capability element and / or operation element of the second station for the specific bandwidth, excluding the capability element and / or operation element of the second station for the specific legacy format for other bandwidths, in the response frame. The response frame includes multilink information for coupling between at least one first station among the first plurality of stations, excluding the first station, and at least one second station among the second plurality of stations, excluding the second station, in an MLD.

2. The MLD according to claim 1, wherein the multilink information includes capability and / or operational elements of each of the second or at least one station in a legacy format corresponding to each of the other bandwidths.

3. The MLD according to claim 2, wherein each capability element and / or operating element of the second at least one station is at least one of an HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, an HT operating element, a VHT operating element, or an HE (High Efficiency) operating element including VHT operating information.

4. The aforementioned specific frequency band is 6 GHz. The MLD according to claim 1, wherein the other frequency band is 2.4 GHz and / or 5 GHz.

5. The aforementioned processor, The request frame includes a multi-link element which includes a Per-STA profile sub-element corresponding to each of the second or at least one station. The MLD according to claim 1, wherein the Per-STA profile sub-element includes a Complete Profile sub-field indicating whether or not it is a request for all information for the corresponding station among the second at least one station.

6. The MLD according to claim 5, wherein when the complete profile subfield indicates a request for all of the information, the multilink information of the response frame includes capability elements and / or operational elements of the station among the second or at least one station corresponding to the complete profile subfield indicating a request for all of the information.

7. The MLD according to claim 1, wherein the processor performs a multilink setting procedure for setting up a link between the second MLD and the first at least one station and the second at least one station based on the multilink information.

8. The request frame includes a multi-link element which includes at least one Per-STA profile sub-element corresponding to each of the first at least one station, The MLD according to claim 1, wherein each of the at least one Per-STA profile sub-elements of the multilink element includes legacy format capability elements and / or operational elements for a corresponding specific station among the first at least one station.

9. The aforementioned specific station is a station that operates in at least one of the other frequency bands, The MLD according to claim 8, wherein the first station transmits the capability element and / or operation element of the first station for the specific bandwidth, excluding the capability element and / or operation element of the first station for the other bandwidth in a specific legacy format, in the request frame.

10. The MLD according to claim 1, wherein the response frame is one of an Association request frame, an Association response frame, or an ML Probe Response frame.

11. A method performed by a first multi-link device (MLD) in a wireless communication system, which includes a plurality of stations each operating on a plurality of first links, The aforementioned method, The step of transmitting a request frame to a second station among a second plurality of stations included in a second MLD, each operating on at least one link, via a first station among a first plurality of stations included in the first multilink device, The first station and the second station operate in a specific frequency band; and The step of receiving a response frame from the second station as a response to the request frame via the first station, The second station transmits the capability element and / or operation element of the second station for the specific band, excluding the capability element and / or operation element of the second station for other bands, in a wireless frame. A method comprising the steps: the wireless frame includes multilink information for coupling between at least one first station of the first plurality of stations excluding the first station and at least one second station of the second plurality of stations excluding the second station.

12. The method according to claim 11, wherein the multilink information includes the capability elements and / or operational elements of each of the second at least one station for a specific band among the other bands.

13. The method according to claim 12, wherein each capability element and / or operating element of the second at least one station is at least one of an HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, an HT operating element, a VHT operating element, or an HE (High Efficiency) operating element including VHT operating information.

14. The aforementioned specific frequency band is 6 GHz. The method according to claim 11, wherein the other frequency band is 2.4 GHz and / or 5 GHz.

15. The request frame includes a multi-link element which includes a Per-STA profile sub-element corresponding to each of the second or at least one station. The method according to claim 11, wherein the Per-STA profile sub-element includes a Complete Profile sub-field indicating whether or not the request is for all information for the corresponding station among the second at least one station.

16. The method according to claim 15, wherein the multilink information of the response frame includes capability elements and / or operational elements of a station corresponding to the Per-STA profile sub-element, which includes the complete profile sub-field indicating the request for all of the information, among the second or at least one station.

17. The method according to claim 11, wherein a multilink is established between the first at least one station and the second at least one station based on the multilink information.

18. The method according to claim 11, wherein the response frame is one of an Association request frame, an Association response frame, or an ML Probe Response frame.

19. The request frame includes a multi-link element which includes at least one Per-STA profile sub-element corresponding to each of the first at least one station, The method according to claim 11, wherein each of the at least one Per-STA profile sub-elements of the multilink element includes a legacy format capability element and / or operational element for a corresponding specific station among the first at least one station.

20. The aforementioned specific station is a station that operates in at least one of the other frequency bands, The method according to claim 19, wherein the first station transmits the capability element and / or operation element of the first station for the specific bandwidth, excluding the capability element and / or operation element of the first station for the other bandwidth in a specific legacy format, in the request frame.

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