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

Abstract

To provide a wireless communication method that efficiently uses multi-links, and a wireless communication terminal that uses the method.SOLUTION: In a wireless communication system, a first multi-link device (MLD) including a plurality of stations each operating on a plurality of 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 through a first station among a first plurality of stations included in the first multi-link device, and receives a response frame as a response to the request frame from the second station through the first station. At this time, the request frame may include information of the other stations included in the first MLD, and the response frame may include information of the other stations included in the second MLD.SELECTED DRAWING: Figure 33

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method using multilinks and a wireless communication terminal using the same. [Background technology]

[0002] Recently, as the popularity of mobile devices has increased, wireless LAN technology, which can provide them with high-speed wireless Internet services, has been gaining attention. Wireless LAN technology is a technology that uses short-range wireless communication technology to enable mobile devices such as smartphones, smart pads, laptop PCs, portable multimedia players, embedded devices, etc. to connect to the Internet wirelessly at home, in business, or in specific service areas.

[0003] Since supporting early wireless LAN technology using the 2.4 GHz frequency band, IEEE (Institute of Electronics Engineers) 802.11 has since implemented or is currently developing various other technology standards. IEEE 802.11b uses the 2.4 GHz frequency band and supports a maximum communication speed of 11 Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5 GHz frequency band instead of the 2.4 GHz band, reducing the impact of interference compared to the significantly more congested 2.4 GHz frequency band, and uses OFDM technology to improve communication speeds to a maximum of 54 Mbps. However, IEEE 802.11a has the disadvantage of a shorter communication distance than IEEE 802.11b. IEEE 802.11g, like IEEE 802.11b, uses the 2.4GHz band and achieves a maximum transmission speed of 54Mbps, and has attracted considerable attention for its backward compatibility, but it also has an advantage over IEEE 802.11a in terms of communication distance.

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been identified as a weakness of wireless LANs. IEEE 802.11n aims to increase network speed and reliability and extend the operating distance of wireless networks. Specifically, IEEE 802.11n supports high throughput (HT) of up to 540 Mbps and is based on MIMO (Multiple Inputs and Multiple Outputs) technology, which uses multiple antennas on both the transmitting and receiving ends to minimize transmission errors and optimize data speed. This standard also uses a coding method that transmits multiple duplicate copies to increase data reliability.

[0005] As WLAN adoption continues to grow and applications become more diverse, the need for new WLAN systems is emerging to support data throughput rates (Very High Throughput, VHT) higher than those supported by IEEE 802.11n. Among these, IEEE 802.11ac supports wide bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard is defined only in the 5GHz band, initial 802.11ac chipsets are expected to support operation in the 2.4GHz band as well for backward compatibility with existing 2.4GHz products. Theoretically, this standard enables multi-station WLAN speeds of at least 1Gbps and maximum single-link speeds of at least 500Mbps. This is achieved by expanding the air interface concepts adopted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and denser modulation (up to 256QAM). Additionally, there is IEEE 802.11ad, a method of transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz. 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 and can only be used between devices in close proximity.

[0006] Meanwhile, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard is being developed and is nearing completion as the successor to 802.11ac and 802.11ad in order to provide high-efficiency and high-performance WLAN communication technology in high-density environments where APs and terminals are densely packed. In an 802.11ax-based WLAN environment, high-frequency-efficient communication must be provided both indoors and outdoors in the presence of a high density of stations and APs (Access Points), and various technologies are being developed to achieve this.

[0007] Additionally, development of a new WLAN standard has begun to increase maximum transmission speeds to support new multimedia applications such as high-definition video and real-time gaming. IEEE 802.11be (Extremely High Throughput, EHT), the seventh generation WLAN standard, is currently being developed with the goal of supporting transmission rates of up to 30Gbps in the 2.4 / 5 / 6GHz bands through wider bandwidth, increased spatial streams, and multi-AP cooperation. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of one embodiment of the present invention is to provide a wireless communication method using multiple links and a wireless communication terminal using the same.

[0009] The technical problems to be solved by the present specification are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0010] According to the present invention, a first multi-link device (MLD) including a plurality of stations operating on a plurality of links respectively includes a processor, the processor 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 the first plurality of stations included in the first multi-link device, the second station and the first station operating in a specific band, receiving a response frame from the second station via the first station in response to the request frame, the second station transmitting the response frame including capability elements and operation elements of the second station for the specific band excluding capability elements and / or operation elements of the second station in a specific legacy format for other bands, the response frame including multi-link information for association 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.

[0011] Also, in the present invention, the multilink information includes a capability element and / or an operation element of each of the second at least one station in a legacy format corresponding to each of the other bands.

[0012] Further, in the present invention, each capability element and / or operation 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 operation element, a VHT operation element, or an HE (High Efficiency) operation element including VHT operation information.

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

[0014] In addition, in the present invention, the processor determines that the request frame includes a Multi-Link element including Per-STA profile subelements corresponding to each of the second at least one station, and the Per-STA profile subelements include a Complete Profile subfield indicating whether the request frame is for all information for the corresponding station among the second at least one station.

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

[0016] Also, in the present invention, the processor performs a multilink setup procedure for setting up links between a second MLD and the first at least one station and the second at least one station based on the multilink information.

[0017] In addition, in the present invention, the request frame includes a Multi-Link element including at least one Per-STA profile sub-element corresponding to each of the first at least one stations, and each of the at least one Per-STA profile sub-element of the Multi-Link element includes a capability element and / or an operation element of a legacy format for a corresponding specific station among the first at least one station.

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

[0019] In the present invention, the response frame is one of an association request frame, an association response frame, and a multi-link (ML) probe response frame.

[0020] The present invention also provides a method, including the steps 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 the first plurality of stations included in the first multilink device, the first station and the second station operating in a specific band; and receiving a response frame from the second station via the first station in response to the request frame, the second station including capability elements and operation elements of the second station for the specific band excluding capability elements and / or operation elements of the second station for other bands in a radio frame and transmitting the radio frame, the radio frame including multilink information for association 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. [Effects of the Invention]

[0021] An embodiment of the present invention provides a wireless communication method that efficiently uses multilinks and a wireless communication terminal that uses the same.

[0022] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a configuration of an access point according to an embodiment of the present invention. [Figure 5] 1 is a diagram illustrating a process in which a STA establishes a link with an AP. [Figure 6] FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] 1A and 1B are diagrams illustrating examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8] 1A and 1B are diagrams illustrating examples of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats and methods for indicating the same according to an embodiment of the present invention. [Figure 9] 1 is a diagram showing a multi-link device according to an embodiment of the present invention; [Figure 10] 10 is a diagram illustrating simultaneous transmission of different links in a multi-link operation according to an embodiment of the present invention; [Figure 11] 10A and 10B are diagrams illustrating the operation of a multi-link device when a link is changed according to one embodiment of the present invention. [Figure 12] 10 is a diagram showing that, according to one embodiment of the present invention, when one station of a non-STR multi-link device is receiving, other stations of the non-STR multi-link device are prohibited from accessing the channel. [Figure 13] FIG. 10 is a diagram illustrating the operation of lifting channel access prohibition when it is confirmed that the intended recipient of a PPDU received by a station in a non-STR multi-link device is not a station, according to an embodiment of the present invention. [Figure 14] FIG. 10 is a diagram illustrating a station accessing a channel after channel access prohibition is lifted according to an embodiment of the present invention. [Figure 15] 10A and 10B are diagrams illustrating operations of a station transmitting after channel access prohibition is lifted according to one embodiment of the present invention. [Figure 16] FIG. 10 is a diagram illustrating transmissions based on the status of stations in a non-STR multilink device according to an embodiment of the present invention. [Figure 17] FIG. 1 illustrates a situation in which interference or collision between links may occur. [Figure 18] 10 is a diagram illustrating an operation in which an STR multilink device stops transmission to a non-STR multilink device according to one embodiment of the present invention. [Figure 19] 10 is a diagram illustrating how the STR multi-link device processes the value of CW when it recognizes a transmission collision between links according to an embodiment of the present invention. FIG. [Figure 20] 1 is a diagram illustrating an example of a transmission management method for a non-AP multilink device according to an embodiment of the present invention. [Figure 21]FIG. 10 is a diagram illustrating an example of the contents of a beacon frame transmitted by an AP in AP MLD and an example of a TBTT (target beacon transmission time) information field format included in an RNR (Reduced Neighbor Report) element according to one embodiment of the present invention. [Figure 22] FIG. 10 is a diagram illustrating yet another example of a TBTT information field format according to one embodiment of the present invention. [Figure 23] 10 is a diagram illustrating an example of a TBTT information length subfield indicating a TBTT information field including an MLD AP TBTT offset subfield according to one embodiment of the present invention. FIG. [Figure 24] FIG. 10 is a diagram illustrating an example of a Per-STA Profile subelement format according to one embodiment of the present invention. [Figure 25] FIG. 10 is a diagram illustrating an example of a process in which a non-AP MLD set up with an NSTR (Non-Simultaneous Transmission and Reception) Soft AP MLD updates information on a non-primary link, according to one embodiment of the present invention. [Figure 26] 10 is a flowchart illustrating an example of a procedure in which a non-AP STA MLD associated with an NSTR AP MLD updates parameters of a non-primary link according to an embodiment of the present invention. [Figure 27] FIG. 10 is a diagram illustrating an example of an element format according to an embodiment of the present invention. [Figure 28] 10 is a diagram illustrating an example of a process in which an NSTR AP MLD sets (defines) a quiet interval for a non-primary according to an embodiment of the present invention. FIG. [Figure 29] FIG. 10 is a diagram illustrating an example of a method in which an NSTR AP MLD performs a non-primary channel switch according to an embodiment of the present invention. [Figure 30] 1A and 1B are diagrams illustrating examples of a probe request frame, an association request frame, and an association response frame transmitted by a station operating in a specific bandwidth. [Figure 31] FIG. 10 is a diagram showing 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 are not of a specific bandwidth, in accordance with one embodiment of the present invention. [Figure 32] FIG. 10 is a diagram illustrating a portion of the configuration of a management frame for explaining a method of inheriting a complete Per-STA profile according to one embodiment of the present invention. [Figure 33] 10 is a flowchart illustrating an example of an operation of non-AP MLD according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of engineers in the relevant technical field, customs, or the emergence of new technologies. In addition, in certain cases, the applicant may have arbitrarily selected terms, and in such cases, the meanings thereof will be described in the relevant description of the invention. Therefore, it is made clear that the terms used in this specification should be interpreted not simply as names of terms, but based on the substantive meanings of the terms and the overall content of this specification.

[0025] Throughout this specification, when a component is referred to as being "connected" to another component, this includes not only when the component is "directly connected" to another component, but also when the component is "electrically connected" to another component via another component in between. Furthermore, when a component is referred to as "comprising" a specific component, this does not mean that the component may exclude the other component, but may further include the other component, unless otherwise specified. In addition, limitations such as "greater than" or "less than" based on a specific critical value may be appropriately substituted with "exceeds" or "less than," respectively, depending on the embodiment.

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

[0027] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0028] A wireless LAN system includes one or more Basic Service Sets (BSSs), which are a set of devices that can synchronize and 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 FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 that are stations providing distribution services, and a distribution system DS that connects multiple access points AP-1 and AP-2.

[0030] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium according to the IEEE 802.11 standard. In a broad sense, the term "station" encompasses not only non-AP stations but also APs. In this specification, the term "terminal" refers to either a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface and a display unit, depending on the embodiment. The processor generates frames to be transmitted over a wireless network, processes frames received over the wireless network, and performs various other processes for controlling the station. The communication unit is functionally connected to the processor and transmits and receives frames over the wireless network for the station. In this specification, the term "terminal" encompasses user equipment (UE).

[0031] An access point (AP) is an entity that provides a connection to a distribution system (DS) via a wireless medium for associated stations. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP. However, if a direct link is established, direct communication is also possible between non-AP stations. Meanwhile, in the present invention, the term AP is used as a concept including a personal BSS coordination point (PCP), but in a broader sense, it also includes concepts such as a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a site controller. In the present invention, an AP is also referred to as a base wireless communication terminal, but in a broader sense, the term base wireless communication terminal is used as a term including an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal includes various types of wireless communication terminals that allocate communication medium resources and perform scheduling for communication with multiple wireless communication terminals.

[0032] A plurality of infrastructure BSSs are connected to each other via a distribution system DS, and the plurality of BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0033] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, the same or corresponding parts as those in the embodiment of FIG. 1 will not be described again.

[0034] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so none of the stations (STA6, STA7) are connected to an AP. 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 each other.

[0035] 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention. As shown, the 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 WLAN packets and may be incorporated into or external to the station 100. According to an 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 using different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with an AP or an external station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 120 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be provided independently, or multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit 120 may represent a radio frequency (RF) communication module that processes RF signals.

[0037] Next, the user interface 140 includes various types of input / output means provided in the station 100. That is, 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. Also, the user interface unit 140 performs output based on instructions from the processor 110 using various output means.

[0038] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as a user interface, based on the contents processed by the processor 110 or the control commands of the processor 110. The memory 160 also stores control programs and various data used by the station 100. The control programs include a connection program required for the station 100 to connect to an AP or an external station.

[0039] The processor 110 of the present invention executes various commands or programs to process 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 the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information about the station 100's preferences contained in the communication setup message and requests connection to the AP based on the information about the station 100's preferences. The processor 110 of the present invention may refer to a main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling some components of the station 100, such as the communication unit 120. That is, the processor 110 may be a modem that modulates and demodulates wireless signals transmitted and received by the communication unit 120, or a modulator and / or demodulator. The processor 110 controls various operations for transmitting and receiving wireless signals in the station 100 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0040] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be implemented on a single chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated into a single chip or may be implemented on separate chips. Furthermore, in embodiments 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 included in the station 100.

[0041] 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention. As shown, the AP 200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, duplicated descriptions of parts of the configuration of the AP 200 that are the same as or correspond to the configuration of the station 100 in FIG. 3 will be omitted.

[0042] Referring to FIG. 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 FIG. 3, the communication unit 220 of the AP 200 may also include multiple communication modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention may 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 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with a station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 220 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 may represent an RF (Radio Frequency) communication module that processes RF signals.

[0043] The memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a connection program that manages station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. The communication setup message includes information about connection preferences for each station. The processor 210 also performs connection setup in response to a station connection request. According to an embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates wireless signals transmitted and received by the communication unit 220. The processor 210 controls various operations for transmitting and receiving wireless signals by the AP 200 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0044] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0045] 5, a link between the STA 100 and the AP 200 is established through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information for the BSS operated by the AP 200. There are two scanning methods: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires connection information.

[0046] The STA 100 that successfully receives wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200, and performs the authentication step (S107b). After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs the association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited to this, and association in a broad sense includes both wireless association and wired association.

[0047] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In Fig. 5, server 300 is a server that processes 802.1X-based authentication with STA 100, and may be physically connected to AP 200 or may exist as a separate server.

[0048] FIG. 6 is a diagram showing a Carrier Sense Multiple Access (CSMA) / Collision Avoidance (CA) method used in wireless LAN communication.

[0049] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether a channel is occupied. If a wireless signal above a certain strength is detected, the channel is determined to be occupied, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not a signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold received by a terminal is intended for the terminal as a receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel or a wireless signal with a strength 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 having data to transmit performs a backoff procedure after an Inter Frame Space (IFS), such as an Arbitration IFS (AIFS) or a PCF IFS (PIFS), depending on the status of each terminal. Depending on the embodiment, the AIFS may be used as a configuration replacing the conventional DCF IFS (DIFS). Each terminal waits while decrementing a slot time equal to a random number determined for the terminal during the idle interval of the channel. A terminal that has exhausted all of its slot time attempts to access the channel. The period during which each terminal performs the backoff procedure is called a contention window period. Here, the random number may be called a backoff counter. The initial value of the backoff counter is set by an integer, which is a random number obtained by the terminal. If a terminal detects that the channel is idle during the slot time, the terminal may decrement the backoff counter by 1. Furthermore, if the backoff counter reaches 0, the terminal may be allowed to perform channel access on the channel. Therefore, if the channel is idle during the AIFS time and the backoff counter slot time, the terminal may be allowed to transmit.

[0051] If a specific terminal successfully accesses the channel, it transmits data over the channel. However, if the terminal attempting access collides with another terminal, the colliding terminals are assigned new random numbers and perform a backoff procedure again. According to one embodiment, the new random numbers assigned to each terminal are determined within a range (2*CW) twice the range of the random numbers previously assigned to the terminal (contention window, CW). Meanwhile, each terminal attempts access by performing a backoff procedure again in the next contention window period. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this way, terminals communicating over a wireless LAN can avoid collisions with each other on a specific channel.

[0052] <Examples of various PPDU formats>

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

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

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

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

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

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

[0059] The unit of the L_LENGTH field is bytes, and a total of 12 bits are allocated, allowing a maximum of 4095 to be signaled. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. In this case, legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0060] First, a legacy or non-legacy terminal interprets the length of the corresponding PPDU using the L_LENGTH field as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted during 4 us, which is one symbol duration of the 64FFT. Therefore, by adding the 3 bytes corresponding to the SVC field and Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of 64FFT reference symbols after the L-SIG is obtained. The obtained number of symbols is multiplied by 4 us, which is one symbol duration, and then 20 us, which is required to transmit the L-STF, L-LTF, and L-SIG, to obtain the length of the corresponding PPDU, i.e., the reception time (RXTIME). 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 constituting the PPDU, and is expressed as the following equation 3. 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 ​​of 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 remains in the EHT PPDU and subsequent generation WLAN PPDUs, and serves to distinguish which generation of PPDU it is, including 11be. The U-SIG is two 64FFT-based OFDM symbols and can transmit a total of 52 bits of information. Of these, 43 bits excluding 9 bits of CRC / tail are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0068] The VI bit will maintain its current bit configuration, so even if a subsequent generation PPDU is defined, current 11be UEs can obtain information about the PPDU from the VI field of the PPDU. 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 long and serves to sequentially distinguish between 11be and subsequent generations of WLAN standards. 11be has a value of 000b. The UL / DL field identifies whether the PPDU is an uplink or downlink PPDU. The BSS color represents a BSS identifier defined in 11ax and has a value of 6 or more bits. The TXOP represents the transmit opportunity duration (Transmit Opportunity Duration) transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP containing the PPDU can be inferred without decoding the MPDU, and has a value of 7 or more bits.

[0069] The VD field, which is signaling information useful only for 11be version PPDUs, may consist of fields commonly used in any PPDU format, such as the PPDU format and BW, as well as fields defined differently for each PPDU format. The PPDU format is a separator that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs. The BW field broadly signals five basic PPDU BW options: 20, 40, 80, 160 (80 + 80), and 320 (160 + 160) MHz (BWs that can be expressed in the form of a power of 20 * 2 can be called basic BWs), as well as various remaining PPDU BWs formed by preamble puncturing. After signaling at 320 MHz, a portion of 80 MHz may be punctured. In addition, the punctured and modified channel shape may be signaled directly in the BW field, or may be signaled using both the BW field and a field that appears after the BW field (for example, a field in 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] The fields located after the BW field vary depending on the type and format of the PPDU. MU PPDUs and SU PPDUs may be signaled in the same PPDU format, and a field for distinguishing 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 not required for the SU PPDU may be compressed. In this case, the information of the compressed fields may be omitted or may have a reduced size compared to the size of the original fields included in the MU PPDU. For example, the SU PPDU may have a different configuration, such as the common fields of the EHT-SIG being omitted or replaced, or the user-specific fields being replaced or reduced to one.

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

[0072] When a portion of the EHT-SIG field of the SU PPDU is compressed, the information included in the compressed field may be signaled together in an uncompressed field (e.g., a common field). In the case of an MU PPDU, 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 recognize the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU was sent to it. Therefore, the AP must transmit the above information in the EHT-SIG field. To this end, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the MCS, which is the modulation method. The EHT-SIG field may include information on the size and location of the RU assigned to each user.

[0073] In the case of an SU PPDU, multiple RUs may be allocated to a STA, and the multiple RUs may be contiguous or discontinuous. If the RUs allocated to a STA are not contiguous, the STA can efficiently receive the SU PPDU only by recognizing punctured RUs in between. Therefore, the AP can transmit the SU PPDU including information on punctured RUs among the RUs allocated to the STA (e.g., puncturing pattern of the RUs). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether a puncturing mode is applied and the puncturing pattern in a bitmap format, etc., may be included in the EHT-SIG field, and the puncturing mode field can signal the type of discontinuous channels appearing within the bandwidth.

[0074] The type of signaled discontinuous channel is limited, and indicates the BW and discontinuous channel information of the SU PPDU in combination with the value of the BW field. For example, since the SU PPDU is a PPDU transmitted only to a single UE, the STA can recognize its allocated bandwidth from the BW field included in the PPDU and can recognize 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 UE can receive the PPDU in the remaining resource units excluding specific channels of the punctured resource units. In this case, multiple RUs allocated to the STA may be configured with different frequency bands or tones.

[0075] The reason why only limited discontinuous channel types are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed for each 20 MHz subchannel, if puncturing is performed on a BW having multiple 20 MHz subchannels, such as 80, 160, or 320 MHz, in the case of 320 MHz, the discontinuous channel type (when only the end 20 MHz is punctured and considered discontinuous) must be signaled by expressing whether or not each of the remaining 15 20 MHz subchannels excluding the primary channel is in use. Using 15 bits to signal the discontinuous channel type for single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

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

[0077] In addition, one embodiment of the present invention proposes a method of varying the PPDU configuration indicated by the preamble puncturing BW value according to the PPDU format signaled in the PPDU format field. Assuming the length of the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, an EHT-SIG-A symbol of one symbol may be further signaled after the U-SIG, or no EHT-SIG-A may be signaled at all. Taking this into consideration, up to 11 puncturing modes must be signaled using only the BW field of the U-SIG. However, in the case of an EHT MU PPDU, an EHT-SIG-B symbol is further signaled after the U-SIG, so up to 11 puncturing modes may be signaled in a different manner than in the SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether the PPDU uses a 20 MHz or 10 MHz bandwidth.

[0078] Figure 7(f) shows the format-specific field configuration of the VD field when the PPDU format field of the U-SIG indicates an EHT MU PPDU. For an MU PPDU, SIG-B, a signaling field for simultaneous reception by multiple users, is required. SIG-B may be transmitted after the U-SIG without a separate SIG-A. For this purpose, the U-SIG must signal information for decoding SIG-B. These fields include the SIG-B MCS, SIG-B DCM, number of SIG-B symbols, SIG-B compression, and number of EHT-LTF symbols.

[0079] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention.

[0080] 8, a PPDU may be configured with a preamble and a data portion, and the format of one type, EHT PPDU, may be distinguished by a U-SIG field included in the preamble. Specifically, whether the format of the PPDU is EHT PPDU may be indicated based on a PPDU format field included in the U-SIG field.

[0081] 8(a) shows an example of an 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 an EHT-SIG-A field for additional signaling may be located after the U-SIG field.

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

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

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

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

[0086] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU may include information regarding the configuration of resource units (e.g., the division type of resource units) in a specific bandwidth (e.g., 20 MHz) on the frequency axis. That is, the RA field may indicate the configuration of resource units divided by the bandwidth for transmitting the HE MU PPDU so that the STA can receive the PPDU. Information about the STA allocated (or designated) to each divided resource unit may be included in a user specific field of the EHT-SIG-B and transmitted to the STA. That is, the user specific field may include 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 include the AID of the receiver or sender, and the user field corresponding to the remaining resource units not used for data transmission may include a previously set null STA ID.

[0088] For ease of explanation, the term 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 improved. 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, when the frequency band of one link is being used by another wireless communication device, the wireless communication device can continue communication using another link. In this way, the wireless communication device can effectively use multiple channels. Furthermore, when a wireless communication device simultaneously communicates using multiple links, the overall throughput can be improved. However, existing wireless LANs are specified on the assumption that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using multiple links is required. A wireless communication method for a wireless communication device using multiple links will be described with reference to FIGS. 9 to 26. First, a specific embodiment of a wireless communication device using multiple links will be described with reference to FIG. 9.

[0090] FIG. 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 multiple links described above. The multi-link device may represent a device having one or more affiliated stations. Depending on a specific embodiment, the multi-link device may represent a device having two or more affiliated stations. The multi-link device may also exchange multi-link elements. The multi-link element includes information about one or more stations or one or more links. The multi-link element may include a multi-link setup element, which will be described later. In this case, the multi-link device may be a logical entity. Specifically, the multi-link device may have multiple affiliated stations. The multi-link device may be referred to as a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device may have one medium access control service access point (SAP) up to a logical link control (LLC). The MLD may also have one MAC data service.

[0092] Multiple stations included in a multilink device can operate on multiple links. Also, multiple stations included in a multilink device can operate on multiple channels. Specifically, multiple stations included in a multilink device can operate on different links or different channels. For example, multiple stations included in a multilink device can operate on different channels, such as 2.4 GHz, 5 GHz, and 6 GHz.

[0093] The operation of the multilink device can be referred to as multilink operation, MLD operation, or multi-band operation. If the station associated with the multilink device is an AP, the multilink device can be referred to as AP MLD. If the station associated with the multilink device is a non-AP station, the multilink device can be referred to as non-AP MLD.

[0094] FIG. 9 shows the operation of communication between non-AP MLD and AP-MLD. Specifically, non-AP MLD and AP-MLD each communicate using three links. AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). Non-AP MLD includes a first non-AP STA (non-AP STA1), a second non-AP STA (non-AP STA2), and a third non-AP STA (non-AP STA3). The first AP (AP1) and the first non-AP STA (non-AP STA1) communicate via a first link (Link1). The second AP (AP2) and the second non-AP STA (non-AP STA2) communicate via a second link (Link2). The third AP (AP3) and the third non-AP STA (non-AP STA3) communicate via a 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 preceded by frame exchange in the multilink. A multilink device can obtain information required for multilink setup from a multi-link setup element. Specifically, the multi-link setup element may include capability information related to the multilink. In this case, the capability information may include information indicating whether one of multiple devices included in the multilink device can transmit and the other devices can receive at the same time. The capability information may also include information about links available to each station included in the MLD. The capability information may also include information about channels available to each station included in the MLD.

[0096] Multilink configuration may be established through negotiation between peer stations. Specifically, multilink configuration may be established through communication between stations without communication with an AP. Multilink configuration may also be established through any one of the links. For example, even if the first to third links are established through multilink, multilink configuration may be established through the first link.

[0097] In addition, a mapping between a traffic identifier (TID) and a link may be configured. Specifically, frames corresponding to a specific TID value may be exchanged only through a pre-specified link. The mapping between a TID and a link may be configured on a directional basis. For example, when multiple links are configured between a first multilink device and a second multilink device, the first multilink device may be configured to transmit frames of the first TID to the multiple first links, and the second multilink device may be configured to transmit frames of the second TID to the first link. In addition, a default setting may exist for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device may exchange frames corresponding to TIDs on each link according to a default setting. In this case, the default setting may be that all TIDs are exchanged on any one link.

[0098] The TID will be described in detail. The TID is an ID for classifying traffic and data to support quality of service (QoS). The TID may be used and assigned in a layer higher than the MAC layer. The TID may indicate a traffic category (TC) or a traffic stream (TS). There may be 16 distinct TIDs. For example, the TID may be designated as any one of 0 to 15. Different TID values ​​may be designated depending on an access policy, a channel access method, or a medium access method. For example, when enhanced distributed channel access (EDCA) or hybrid coordination function contention-based channel access (HCAF) is used, the TID may be assigned a value ranging from 0 to 7. When EDCA is used, the TID may indicate a user priority (UP). In this case, the UP may be designated by the TC or the TS. The UP may be assigned in a layer higher than the MAC. Furthermore, when HCCA (HCF controlled channel access) or SPCA is used, the TID may be assigned a value in the range of 8 to 15. When HCCA or SPCA is used, the TID may indicate a TSID. Furthermore, when HEMM or SEMM is used, the TID may be assigned a value in the range of 8 to 15. When HEMM or SEMM is used, the TID may indicate a 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 ACs. ACs may include AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may indicate background, best effort, video, and voice, respectively. AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower-level ACs. For example, AC_VI can be further subdivided into AC_VI primary and AC_VI alternate. AC_VO can be further subdivided into AC_VO primary and AC_VO alternate. UP or TID may be mapped to an AC. For example, 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, 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. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may have decreasing priority in that order. That is, 1 may have a lower priority, and 7 may have a higher priority. Therefore, the order of priority may be AC_BK, AC_BE, AC_VI, and AC_VO. Also, AC_BK, AC_BE, AC_VI, and AC_VO can correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to the characteristics of TID, the mapping between TID and link can represent the mapping between AC and link.The mapping between links and ACs can also represent the mapping between TIDs and links.

[0100] As described above, a TID may be mapped to each of multiple links. The mapping may specify the links through which traffic corresponding to a specific TID or AC can be exchanged. Furthermore, the TID or AC that can be transmitted for each transmission direction within a link may be specified. As described above, a default setting may exist for the mapping between TIDs and links. Specifically, if no additional settings are configured in the multilink configuration, the multilink device may exchange frames corresponding to the TID 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 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 the link may be transmitted on the link. Therefore, when a link is mapped to a TID or AC, frames not corresponding to a TID or AC not mapped to the link may not be transmitted on the link. When a link is mapped to a TID or AC, an 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 the TID and the link. In yet another specific embodiment, the mapping between the TID and the link may be determined based on the Block ACK agreement. Specifically, a Block ACK agreement may be set for a TID mapped to a specific link.

[0102] The above-described TID-to-link mapping may ensure QoS. Specifically, a high-priority AC or TID may be mapped to a link where a relatively small number of stations are active or where channel conditions are good. The above-described TID-to-link mapping may also allow stations to remain in a power-saving state for a longer period of time.

[0103] FIG. 10 illustrates simultaneous transmission of different links in multi-link operation according to an embodiment of the present invention.

[0104] Depending on the implementation of the multi-link device, simultaneous operation of the multi-links may not be supported. For example, a multi-link device may support simultaneous transmission on multiple links, simultaneous reception on multiple links, or transmission on one link while receiving on another link. Reception or transmission on one link may affect reception or transmission on another link. Specifically, transmission on one link may interfere with interference on another link. Interference from one link of a multi-link device affecting another link may be called internal leakage. The smaller the frequency spacing between links, the greater the internal leakage. If the internal leakage is not too large, transmission on one link can occur when transmission on another link. If the internal leakage is too large, transmission on one link cannot occur when transmission on another link. This simultaneous operation of the multi-link device on multiple links may be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, a multilink device transmitting on multiple links simultaneously, transmitting on one link while receiving on another link, or receiving on multiple links simultaneously can be referred to as STR.

[0105] On the other hand, if STR is not supported due to interference between multiple stations constituting an MLD, the STAs may be said to be in a non-STR relationship or NSTR relationship (a relationship in which STR is not supported).

[0106] In this case, whether two STAs (STA1 and STA2) in the MLD support STR may depend on the distance between the link pair on which the STAs operate (Link1 on which STA1 operates and Link2 on which STA2 operates).

[0107] Therefore, when an MLD operates STAs in a specific link pair, if STR is supported between the STAs operated in 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 in separate link pairs, if STR is not supported between the STAs operated in the separate link pair, the other link pair may be considered as an NSTR link pair by the MLD.

[0108] In this way, whether STR is supported between 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 described above, since the characteristics (such as shielding performance) of each MLD may differ from one another, a specific link pair may be considered as a link pair in which STR is supported for a specific MLD and as an NSTR link pair in which STR is not supported for another MLD.

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

[0110] In addition, in relation to the presence or absence of STR support as described above, NSTR MLD can refer to an MLD in which the STA of a specific MLD loses its receiving capability, as well as an MLD in which the hardware configuration of the MLD itself does not support simultaneous transmission / reception.

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

[0112] An MLD that can operate STAs on two or more links but can support transmission / reception for only one STA at a time may be called a Multi-link Single Radio MLD (MLSR MLD). Alternatively, an MLD operation mode that supports transmission / reception for only one STA may be called an Enhanced Multi-Link Single Radio (EMLSR) mode. 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 may refer to a device that supports CCA and low-data-rate (e.g., encoded at 6 MHz or 24 MHz or less) PPDU transmission / reception for two or more links by including additional hardware (e.g., a low-cost PHY front end).

[0113] In addition, as a variation of the EMLSR mode, Enhanced Multi-Link Multi-Radio (EMLMR) may be defined in which the MLD supports transmission / reception for each STA, but utilizes part of the RF chain used by a specific STA for transmission / reception for other STAs. EMLMR may have the same transmission / reception restriction characteristics as EMLSR when all of the RF chains used by the specific STA are utilized for transmission / reception for the other STAs. In other words, an MLD operating in EMLMR mode can operate to support transmission / reception for only one link (STA) at a specific time, regardless of whether STR is supported for the link, and this may be understood as an operation similar to that of an MLD operating in the EMLSR mode.

[0114] That is, the link of an MLD operating in EMLSR / EMLMR mode may be considered as an NSTR link pair.

[0115] In this case, the above-mentioned transmission / reception includes transmission / transmission and reception / reception, that is, it is not related to whether or not both links support STR / NSTR.

[0116] For ease of explanation, hereinafter, EMLSR / EMLMR MLD is used to mean an MLD that can only support transmission / reception for one STA at a specific time due to hardware constraints, and an MLD that can support transmission / reception for two or more STAs (processing capability unrelated to STR) but only supports high-speed data frame transmission / reception for one STA at a specific time as a type of operating mode.

[0117] The STR MLD operation that takes into account the performance limitations of the NSTR MLD provided by the above-described embodiment of the present invention can be directly utilized as the STR MLD operation for the MLSR MLD. For example, after an STR MLD STA transmits to a multi-link single radio MLD STA, if the STA determines that the transmission has failed or is predicted to fail due to the limited performance of the multi-link single radio MLD STA, the STA can cancel the transmission that is currently being performed or is about to be performed. In this case, the procedure for determining whether the transmission has failed due to the limited performance of the EMLSR / EMLMR MLD may be similar to the procedure for determining whether a transmission to an NSTR MLD STA has failed due to the limited performance of the NSTR MLD STA.

[0118] As mentioned above, the multilink device can support STR, or can support it with limitations. Specifically, the multilink device can support STR only under certain conditions. For example, if the multilink device operates with a single radio, the multilink device may not be able to perform STR. Also, if the multilink device operates with a single antenna, the multilink device may not be able to perform STR. Also, if an internal leak is detected to be greater than a predetermined magnitude, the multilink device may not be able to perform STR.

[0119] A station can exchange information about its STR capability with other stations. Specifically, a station can exchange information about whether or not the station has a limitation on its ability to simultaneously transmit on multiple links or simultaneously receive on multiple links. Specifically, the information about whether or not the station has a limitation on its ability to transmit or receive on multiple links can indicate whether or not the station will simultaneously transmit, receive, or transmit and receive on multiple links. Furthermore, the information about whether or not the station has a limitation on its ability to transmit or receive on multiple links can be information indicated in stages. Specifically, the information about whether or not the station has a limitation on its ability to transmit or receive on multiple links can be information indicating a stage indicating the magnitude of internal leakage. In a specific embodiment, the information indicating a stage indicating the magnitude of internal leakage can be information indicating a stage indicating the magnitude of interference caused by internal leakage. In yet another specific embodiment, the information indicating a stage indicating the frequency spacing between links that may affect internal leakage can be information indicating a stage indicating the relationship between the frequency spacing between links and the magnitude of internal leakage.

[0120] In FIG. 10, a first station (STA1) and a second station (STA2) are affiliated with one non-AP multilink device. A first AP (AP1) and a second AP (AP2) may also be affiliated with one 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 FIG. 10, the non-AP multilink device can perform limited STR. When the second station (STA2) transmits on the second link (Link2), the first station (STA1)'s reception on the first link (Link1) may be interrupted by the transmission on the second link (Link2). For example, in the following case, the first station (STA1)'s reception on the first link (Link1) may be interrupted by the transmission on the second link (Link2). The second station (STA2) transmits the first data (Data1) over the second link (Link2), and the first AP (AP1) transmits a response (Ack for Data1) to the first station (STA1). The second station (STA2) transmits the second data (Data2) over the second link (Link2). At this time, the transmission of the second data (Data2) and the transmission of the response (Ack for Data1) to the first data (Data1) may overlap. In this case, the transmission to the second station (STA2) over the second link (Link2) may cause interference to the first link (Link1). As a result, the first station (STA1) may not receive the response (Ack for Data1) to the first data (Data1).

[0121] The operation of the multilink device for channel access will be described below. The multilink operation without a specific description can follow the channel access procedure described in FIG.

[0122] A multilink device can perform channel access independently from multiple links. In this case, the channel access may be backoff-based channel access. When a multilink device performs channel access independently from multiple links and the backoff counters for multiple links reach zero, the multilink device can start transmission simultaneously from multiple links. In a specific embodiment, when one of the backoff counters for multiple links reaches zero and a predetermined condition is met, the multilink device can perform channel access not only for the link whose backoff counter has reached zero but also for other links whose backoff counters have not reached zero. Specifically, when one of the backoff counters for multiple links reaches zero, the multilink device can perform energy sensing on other links whose backoff counters have not reached zero. In this case, if energy greater than or equal to a predetermined magnitude is not detected, the multilink device can perform channel access not only for the link whose backoff counter has reached zero but also for the link for which energy sensing has been performed. This allows the multilink device to start transmission simultaneously from multiple links. The threshold used for energy sensing may be smaller than the threshold used to determine whether to decrement the backoff counter. Furthermore, when determining whether to decrement the backoff counter, the multilink device can sense any type of signal, not just a WLAN signal. Furthermore, in the energy sensing described above, the multilink device can sense any type of signal, not just a WLAN signal. Internal leakage may not be detected as a WLAN signal. In such a case, the multilink device can detect signals detected due to internal leakage through energy sensing. Furthermore, as described above, the threshold used for energy sensing may be smaller than the threshold used when determining whether to decrement the backoff counter. Therefore, even while transmission is occurring on one link, the multilink device can decrement the backoff counter on another link.

[0123] Depending on the degree of interference between links used by the multilink device, the multilink device may determine whether 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 in the multilink device when one station in the multilink device transmits on one of the links. If transmission on the first link of a first station in the multilink device causes interference of a predetermined magnitude or greater to a second station in the multilink device operating on the second link, the operation of the second station may be restricted. Specifically, reception or channel access of the second station may be restricted. If interference occurs, the second station may fail to decode a received signal due to the interference. Furthermore, if interference occurs, the second station may determine that the channel is in use when accessing the channel using backoff.

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

[0125] The degree of interference occurring between stations of a multilink device may vary depending on the interval between the frequency bands of the links on which the stations operate as well as the hardware characteristics of the multilink device. For example, the internal interference occurring in a multilink device including a high RF (radio frequency) device may be smaller than the internal interference occurring in a multilink device including a low RF device. Therefore, the degree of interference occurring between stations of a multilink device may be determined based on the characteristics of the multilink device.

[0126] FIG. 10 shows how the magnitude of interference varies depending on the spacing between link frequency bands and the characteristics of the multilink devices. In the example of FIG. 10, a first multilink device (MLD#1) includes a first station (STA1)-1 operating on a first link (Link1) and a second station (STA1)-2 operating on a second link (Link2). A second multilink device (MLD#2) includes a first station (STA2)-1 operating on a first link (Link1) and a second station (STA2)-2 operating on a second link (Link2). The frequency spacing between the first link (Link1) and the second link (Link2) on which the first multilink device (MLD#1) operates is the same as the frequency spacing between the first link (Link1) and the second link (Link2) on which the second multilink device (MLD#2) operates. However, the magnitude of interference varies depending on the difference between the characteristics of the first multilink device (MLD#1) and the second multilink device (MLD#2). Specifically, the magnitude of interference generated in the second multilink device (MLD#2) may be greater than the magnitude of interference generated in the first multilink device (MLD#1). Considering that the magnitude of interference generated may differ depending on the characteristics of the multilink devices and that the presence or absence of STR support may differ depending on the multilink device, information regarding whether STR is supported or not needs to be exchanged.

[0127] A multilink device can signal whether or not a station included in the multilink device supports STR. Specifically, an AP multilink device and a non-AP multilink device can exchange whether or not an AP included in the AP multilink device supports STR with whether or not a STA included in the non-AP multilink device supports STR. In this embodiment, an element indicating whether or not an STR is supported can be used. The element indicating whether or not an STR is supported can be called an STR support element. The STR support element can indicate, with one bit, whether or not a station in the multilink device that transmitted the STR support element supports STR. Specifically, the STR support element can indicate, with one bit, whether or not each station included in the multilink device that transmitted the STR support element supports STR. In this case, if a station supports STR, the bit value can be 1, and if a station does not support STR, the bit value can be 0. If the multilink device that transmitted 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 STR, and the second station (STA2) does not support STR, the STR support element is 101. 1b The STR support element may include a field having the following information: Stations operating in different frequency bands are assumed to support STR, and the STR support element may omit signaling regarding the presence or absence of STR support between stations operating in different frequency bands. For example, a first station (STA1) operates on a first link of 2.4 GHz, and a second station (STA2) and a third station (STA3) operate on a second link of 5 GHz and a third link of 5 GHz, respectively. In this case, the STR support element may indicate with one bit that STR is supported between the second station (STA2) and the third station (STA3). Alternatively, the STR support element may include only one bit if the STR support element signals two stations.

[0128] In a specific embodiment, the relationship between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz among the links of a multi-link device may always be determined as STR, and therefore, signaling regarding the presence or absence of STR between a link located at 2.4 GHz and a link located at 5 GHz or 6 GHz may be omitted.

[0129] In the above-described embodiments, the operation of a station in a multilink device may be replaced by the operation of the multilink device. Also, in the above-described embodiments, the operation of an AP may be replaced by the operation of a non-AP station, and the operation of a non-AP station may be replaced by the operation of an AP. Thus, the operation of an AP in a non-STR multilink device may be replaced by 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 by the operation of an AP in the STR multilink device. Also, the operation of a non-AP station in a non-STR multilink device may be replaced by the operation of an AP in a non-STR multilink device, and the operation of an AP in an STR multilink device may be replaced by the operation of a non-AP station in an STR multilink device.

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

[0131] When the frequency band of a link is changed, the STR support element may be exchanged. As described above, whether a station can support STR may depend on the distance between the frequency bands of the link, and whether a station can support STR may be changed when the frequency band of the link is changed. When the frequency band of the link is changed, at least one of a change in the center frequency of the link, a change in the bandwidth of the frequency band, and a change in the 20 MHz primary channel may be included. The AP and the station may exchange the STR support element through a request and a response. In another specific embodiment, when the frequency band of the link is changed, the STR support element may be exchanged without a separate request. Furthermore, in the above embodiment, when the frequency band of the link is changed, a change in the operating channel of the station may be included.

[0132] If a station in a non-AP multilink device cannot perform STR, the station in the non-AP multilink device can request a link change from the AP. Specifically, the station in the non-AP multilink device can request at least one of a center frequency change, a frequency band bandwidth change, and a 20 MHz primary channel change. The link change request may be transmitted to the AP for the link for which the change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP for the link for which the change is not requested. In this case, the link change request may include information indicating the link for which the change is requested. The information indicating the link may be a number identifying the link. In this embodiment, the link change may be a change of an operating channel within a frequency band. The link change may also include information about a method for changing the link. Specifically, the link change request may indicate whether the center frequency of the link is to be moved to a frequency higher than the current center frequency or to a frequency lower than the current center frequency. In yet another specific embodiment, the link change request may implicitly indicate a change to a frequency band away from an adjacent link. The link change request may also indicate a reduction in link bandwidth. The link change request may also indicate a change in the position of the primary channel. Specifically, the link change request may indicate a change in the position of the primary channel to a channel in a lower frequency band or a channel in a higher frequency band than the current position of the primary channel. An AP that receives the link change request may change the link in response to the link change request. In a specific embodiment, an AP that receives the link change request may ignore the link change request.

[0133] In the embodiment of FIG. 11, the second station (STA2) and the third station (STA3) of the non-AP multilink device are in a state where they cannot support STR. The non-AP multilink device requests the AP multilink device to change the third link (Link3). The AP multilink device, upon receiving the link change request, changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the changed third link (Link3) can send a change request to the third AP (AP3). In yet another specific embodiment, a station not operating on the third link (Link3) can send a change request to the AP not operating on the third link (Link3).

[0134] When an AP changes a link, the AP may broadcast information about the link change using a beacon frame. In this case, the information about the link change may include information about the link frequency. The information about the link frequency may include at least one of a change in the link center frequency, operating bandwidth, and primary channel. The information about the link change may also include information about the time of the link change. The link change may also be completed when a beacon including information about the link change is transmitted.

[0135] In Figure 11, the link on which the third station (STA3) operates has changed, and the third station (STA3) and the second station (STA2) can now support STR. As described above, the non-AP multilink device can signal whether it supports the changed STR by sending an STR support element to the AP multilink device.

[0136] The above-mentioned link change may not be allowed, or even if the change occurs, STR may not be supported. Also, as in the embodiment of FIG. 11, the AP multilink device may support STR, but the non-AP multilink device may not support STR. This is because relatively expensive devices are typically used for AP multilink devices, and relatively inexpensive devices are typically used for non-AP multilink devices. 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 are performed simultaneously. This will be described with reference to FIG. 12.

[0137] FIG. 12 shows that, according to one embodiment of the present invention, when any one station of a non-STR multilink device is receiving, other stations of the non-STR multilink device are prohibited from accessing the channel.

[0138] When transmission is performed on one link of a non-STR multilink device and reception is performed on another link of the non-STR multilink device, reception and transmission of the non-STR multilink device may fail. To solve this problem, when reception is performed on one link of the non-STR multilink device, channel access may be prohibited on the other links of the non-STR multilink device. Specifically, when reception is performed on one link of the non-STR multilink device, channel access backoff may be prohibited on the other links of the non-STR multilink device. This prevents transmission from starting on the other links of the non-STR multilink device when reception is performed on one link of the non-STR multilink device. In a specific embodiment, when reception begins on one link of the non-STR multilink device, channel access backoff may be prohibited on the other links of the non-STR multilink device. This may be set using a specific bit in memory, such as a channel access prohibition flag. In other words, whether channel access is prohibited may be shared by memory within the multilink device. This embodiment allows channel access prohibition to be implemented without a separate frame exchange. For ease of explanation, "channel access prohibition" as used herein means prohibiting channel access or transmission to protect the transmission or reception of non-STR multilink devices, unless otherwise specified.

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

[0140] In the embodiment of FIG. 12, a 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) receives, intra-device interference occurs. As described above, while the first station (STA1) operating on the first link (Link1) receives, the second station (STA2) is prohibited from accessing the channel on the second link (Link2). After the first station (STA1) completes reception on the first link (Link1), the channel access prohibition is lifted. Immediately after the channel access prohibition is lifted, the second station (STA2) can decrement its previous backoff counter value from 3 to 2 without additional sensing.

[0141] For convenience of illustration, a single block (Tx solid line, Rx dotted line) is used to represent Rx and Tx in Figure 12, and the single block may be understood to represent an operation including Tx / Ack reception and Rx / Ack transmission even if a separate Ack block is not shown. This may be equally applied to the drawings described below.

[0142] If a station determines that it is not the intended recipient of a received PPDU, it may discontinue receiving the PPDU. In this case, channel access unblocking operations in the multilink device become an issue. In this specification, the term intended recipient is used synonymously with the term destination station.

[0143] FIG. 13 illustrates an operation of lifting channel access prohibition when it is determined that the intended recipient of a PPDU received by a station in a non-STR multilink device is not a station, according to an embodiment of the present invention.

[0144] If the station determines that it is not the intended recipient of the received PPDU, it may cancel the channel access prohibition. The station can determine whether it is the intended recipient of the PPDU based on information indicating the recipient address in the signaling field of the PPDU. In this case, the information indicating the recipient address in the signaling field of the PPDU may be the value of the STA-ID field in the EHT-SIG field described above. Specifically, the station can determine whether the STA-ID field in the EHT-SIG field indicates 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 included in the PPDU. Specifically, the station can determine whether the RA field in the MAC frame included in the PPDU indicates the station. In FIG. 13, 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). The first station (STA1) receives a PPDU. The first station (STA1) determines that it is not the intended recipient of the received PPDU and halts reception of the PPDU. At this time, the first station (STA1) can lift the channel access prohibition for the second station (STA2). Even if the channel access prohibition for the second station (STA2) is lifted, the second station (STA2)'s channel access may be delayed depending on the NAV set for the second station (STA2).

[0145] As shown in FIG. 13, even after channel access prohibition is lifted, stations included in a non-STR multilink device often do not have a channel access opportunity compared to stations not included in the multilink device or stations included in the STR multilink device. Therefore, to ensure fair competition with other stations, a method for compensating stations included in a non-STR multilink device for channel access opportunities may be necessary. For example, immediately after channel access prohibition is lifted, a station whose channel access prohibition has been lifted may be allowed to decrement its backoff counter by 2 or more. This will be described with reference to FIG. 14.

[0146] FIG. 14 illustrates a station accessing a channel after the channel access prohibition is lifted according to an embodiment of the present invention.

[0147] A station whose channel access prohibition has been lifted can decrement its backoff counter by 2 or more immediately after the channel access prohibition is lifted. This is to ensure fairness in channel access opportunities with other stations, since other stations have performed backoff procedures while the station's channel access was prohibited.

[0148] In yet another specific embodiment, a station whose channel access is prohibited can perform a channel access procedure to decrement a CCA (CSMA) and backoff counter while its channel access is prohibited. In FIG. 14, a 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). In FIG. 14, while the first station (STA1) is receiving, the second station (STA2) is prohibited from accessing the channel. In FIG. 14(a), while the second station (STA2) is prohibited from accessing the channel, the second station (STA2) can perform a channel access procedure to decrement a CCA (CSMA) and backoff counter. In FIG. 14(a), while the second station (STA2) is prohibited from accessing the channel, the second station (STA2) decrements its backoff counter because the channel of the second link (Link2) is idle.

[0149] In addition, a station whose channel access is prohibited can delay transmission without initiating transmission even if its backoff counter reaches 0 while channel access is prohibited. In this case, the station can maintain the backoff counter value at 0. Furthermore, even if the station delays transmission, the station can maintain the CW value as it is. This is different from the station doubling the CW value because the channel it accesses is busy. This is because the reason for delaying transmission is not because the channel is determined to be busy. In FIG. 14(b), while channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure to decrement the CCA (CSMA) and backoff counter. In FIG. 14(b), while channel access of the second station (STA2) is prohibited, the channel of the second link (Link2) is idle, so the second station (STA2) decrements the backoff counter. While the second station (STA2) is prohibited from accessing the channel, the backoff counter of the second station (STA2) reaches 0. The second station (STA2) delays transmission and resumes transmission after the channel access prohibition is lifted.

[0150] As previously mentioned, the channel access denial may include denial of transmission to a second station when a first station in a non-STR multilink device is transmitting, and may also include denial of transmission to a second station when a first station in a non-STR multilink device is receiving.

[0151] In Fig. 14(b), when multiple stations are prohibited from channel access in the embodiment, the channel access prohibition for multiple stations is released at the same time, and there is a high possibility that multiple stations will attempt to transmit simultaneously. Therefore, a method that can reduce the probability of transmission collision is required. This will be explained using Fig. 15.

[0152] FIG. 15 illustrates an operation of a station transmitting after channel access prohibition is lifted according to an embodiment of the present invention.

[0153] As described above, a non-STR multilink device may transmit on a first link among multiple links operated by the device, and prohibit transmission on a second link. When the transmission on the first link is completed, transmission on the second link may begin by exchanging RTS / CTS frames. Therefore, when transmission on the first link among multiple links operated by the device, the non-STR multilink device may begin exchanging RTS / CTS frames on the second link. After the channel access prohibition of a station whose transmission has been delayed due to channel access prohibition is lifted, the station may begin exchanging RTS / CTS (request to send / clear to send) frames before starting the delayed transmission. If the station fails to receive a CTS frame, it may not be able to start the delayed transmission. In the embodiment of FIG. 15(a), a station whose transmission has been delayed due to channel access prohibition transmits an RTS frame before starting the delayed transmission. The station begins the delayed transmission after receiving a CTS frame in response to the RTS frame.

[0154] In yet another specific embodiment, after the channel access prohibition of a station whose transmission has been delayed due to channel access prohibition is lifted, the station can transmit a frame including only a portion of the delayed transmission. In this case, after the station receives a response, e.g., an ACK, to the frame including only a portion of the delayed transmission, the station can transmit the portion of the delayed transmission that has not been transmitted. If the station does not receive a response to the frame including only a portion of the delayed transmission, the station may not transmit the portion of the delayed transmission that has not been transmitted. In this manner, the reason why a station initiates an RTS / CTS exchange or transmits only a portion of a delayed transmission after channel access prohibition is lifted is because the probability of transmission collisions is higher after channel access prohibition than in general transmissions. Therefore, the above-described embodiment may be mandatory for transmissions performed after channel access prohibition is lifted. In existing WLAN operations, the RTS / CTS frame is used to solve the hidden node problem and can be used based on the size of the transmission data. In the above-described embodiment, the RTS / CTS frame is used to prevent transmission collisions with stations attempting delayed transmissions in order to protect the transmission or reception of non-STR multilink devices.

[0155] As described above, when one station in a non-STR multilink device receives, the transmission of other stations in the non-STR multilink device may be restricted. Furthermore, when one station in a non-STR multilink device transmits, other stations in 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 a first station in a non-STR multilink device transmits, a second station in the non-STR multilink device may always determine the channel status of the link on which the second station is operating as busy. Therefore, even when the channel of the link on which the second station is operating is idle, the second station may determine that the channel is busy due to intra-device interference. In this way, when a station whose channel status cannot be determined due to intra-device interference or a station in the non-STR multilink device is continuing to transmit, the other stations in the non-STR multilink device are considered to be in a blind state. Due to the above-described situation, it may be difficult for a blind station to perform a backoff procedure and attempt to transmit. In addition, due to the above-mentioned circumstances, it may be difficult for a station in a blind state to start receiving or successfully decode a PPDU. Therefore, a transmission method that takes into account stations in a blind state is required. This will be described with reference to FIG. 16.

[0156] On the other hand, when a PPDU is being transmitted / received via a STA of another link, a STA in an EMLSR / EMLMR MLD cannot confirm or receive the presence of the PPDU transmitted to it. Therefore, a STA in an MLD operating in EMLSR / EMLMR mode may have the same performance constraints as a blinded STA in an NSTR MLD while other STAs in the MLD are transmitting / receiving data frames. Therefore, in the following embodiments, an operation taking into account the state of a blinded STA may be understood to be the same as considering whether a STA in an MLD operating in EMLSR / EMLMR mode is in a state where it is constrained by the operation (transmission / reception) of other STAs in the MLD.

[0157] In this case, a mode in which a multilink device uses a single radio of a single link during a specific time period can be referred to as EMLSR mode. While the multilink device exchanges frames over the first link of the EMLSR link, which is a set of multiple links to which EMLSR mode is applied, the multilink device does not transmit or receive over the second link of the EMLSR link. Furthermore, when a specific station in the multilink device transmits or receives using part of the RF chains used by another station in the multilink device during a specific time period of the specific mode, the specific mode can be referred to as EMLMR (enhanced multi-link multi-radio) mode. Specifically, when one station in the multilink device transmits or receives using all of the RF chains of another station in the multilink device in EMLMR mode, the operation of the multilink device may be the same as the operation of the multilink device in EMLSR mode. Furthermore, even when the 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 the EMLSR mode is applied may be only a portion of the links on which the multilink device operates. For example, when the multilink device operates on links 1 to 3, the EMLSR mode or the EMLMR mode may be applied only to links 1 and 2. Therefore, when the multilink device transmits or receives on link 1 during a specific time period 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 the EMLSR mode can be applied, such as links 1 and 2, are referred to as EMLSR links, and links to which the EMLMR mode can be applied are referred to as EMLMR links. Transmitting or receiving using the RF chain of a specific station in EMLSR mode and EMLMR mode results in a change in the transmit, receive, or monitoring capabilities of the link on which the specific station operates.Therefore, embodiments of the present invention that are applied in connection with the EMLSR mode in the following description may be equally applied in connection with the EMLMR mode unless otherwise specified.

[0158] FIG. 16 illustrates transmissions based on the state of stations in a non-STR multilink system according to an embodiment of the present invention.

[0159] A station attempting to transmit to a station in a non-STR multilink device can determine whether to transmit based on whether the station in the non-STR multilink device is in a blind state. In this case, the station attempting to transmit to a station in a non-STR multilink device may be a station included in the STR multilink device. Alternatively, the station attempting to transmit to a station in a non-STR multilink device may be an AP included in the 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 the station in the non-STR multilink device is in a blind state as follows: The station attempting to transmit can determine whether other stations in the multilink device in which the station is included are transmitting to the non-STR multilink device. If other stations in the multilink device in which the station is included are receiving from the non-STR multilink device, the station can determine that the station in the non-STR multilink device receiving the station's transmission is in a blind state. In the embodiment of FIG. 16, the STR AP multilink 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 multilink 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 currently 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 second station (STA2) is the subject of transmission to the second AP (AP2). 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 in the multi-link device may be operated by a common MAC, so the information exchange between the first AP (AP1) and the second AP (AP2) does not need to be performed explicitly.

[0161] A station does not need to transmit to a station in a blind state because if it transmits to a station in a blind state, there is a high possibility that the station in the blind state 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 station in the blind state and transmit to another station.

[0162] When an STR multilink device transmits to a non-STR multilink device, the STR multilink device may transmit to the non-STR multilink device over multiple links. Specifically, when the STR multilink device transmits to the non-STR multilink device over a first link, the STR multilink device may begin transmitting to the non-STR multilink device over a second link. In this case, the STR multilink device may determine the length of the transmission over the second link based on the transmission to the non-STR multilink device. Specifically, the STR multilink device may determine the length of the transmission over the second link to the non-STR multilink device based on the length of the transmission over the first link to the non-STR multilink device. In a specific embodiment, the STR multilink device may simultaneously complete transmissions over the first and second links. This is to prevent transmissions to other stations in the non-STR multilink device from occurring until transmission to one of the stations in the non-STR multilink device has finished first and one of the stations in the non-STR multilink device has sent a response to the transmission, e.g., an ACK. The above-described embodiment allows multiple stations in a non-STR multilink device to simultaneously transmit responses to transmissions intended for multiple stations.

[0163] An STR multilink device cannot determine the status of stations included in a non-STR multilink device in real time. Therefore, even if an STR multilink device operates according to the embodiment described in FIG. 16, interference or transmission collisions may occur between links operated by the non-STR multilink device. For example, in the embodiment of FIG. 16, the first AP (AP1) may begin transmitting to the first station (STA1) before recognizing that the second station (STA2) 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 described in more detail using FIG. 17.

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

[0165] When a second station in a non-STR station multilink device starts transmitting to a second AP in the STR AP multilink device at the same time as a first AP in the STR AP multilink device starts transmitting to a first station in the non-STR station multilink device, a transmission collision can occur between the links. This is shown in Figure 17(a). As mentioned above, this can occur because the STR multilink device cannot determine the status of the stations included in the non-STR multilink device in real time.

[0166] In addition, a transmission collision between links can occur when a second station in a non-STR station multilink device starts transmitting to a second AP in the STR AP multilink device before a first AP in the STR AP multilink device starts transmitting to a first station in the non-STR station multilink device. This is shown in FIG. 17(b). This is because it may take time for the second AP (AP2) to inform the first AP (AP1) that the second station (STA2) is transmitting. Since a transmission collision can occur between stations that start transmitting at different times, inter-link interference or transmission collisions can occur with a higher probability than intra-link interference or collisions. Furthermore, the longer the time it takes for the AP in the STR multilink device to identify the sender of the PPDU it receives, the greater the probability of inter-link interference or transmission collisions. Therefore, a method to resolve this issue is needed. While one station in the STR multilink device is receiving, other stations in the STR multilink device may not be allowed to access the channel. However, if channel access is prohibited in this way, the implementation of the STR function may be meaningless. Therefore, a method for operating an STR multilink device without prohibiting channel access is needed. This will be explained with reference to FIG.

[0167] As described above, it may be important for the multilink device to quickly determine the station transmitting to the multilink device. The User field of the EHT-SIG of the EHT UL PPDU may indicate the identifier (STA-ID) of the station transmitting the EHT UL PPDU. Specifically, when the DL / UL field of the signaling field of the EHT PPDU indicates that the EHT PPDU is a UL PPDU, the User field of the EHT-SIG of the EHT PPDU may 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 of the EHT UL PPDU. This allows the AP multilink device to determine the station transmitting the EHT UL PPDU and determine the destination device of the transmission. Specifically, the AP multilink device can determine whether there is a high possibility that the attempted transmission will fail due to inter-link collision. Furthermore, if there is a high possibility that a transmission that the AP multilink device is attempting to perform will fail, the AP multilink device can delay the attempted transmission and perform another transmission.

[0168] FIG. 18 illustrates an operation in which an STR multilink device stops transmission to a non-STR multilink device according to one embodiment of the present invention.

[0169] If a station in the STR multilink device is determined to be in a blind state while transmitting to a station in the non-STR multilink device, the STR multilink device can suspend transmission to the station in the blind non-STR multilink device. Specifically, the STR multilink device can determine whether a station in the 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 included in the received PPDU. In this case, the STA-ID may be a value indicating 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 when 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. In addition, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state if the TA field of the MAC frame included in the received PPDU indicates a first station included in the non-STR multilink device. Specifically, if the station that transmitted the PPDU indicated in the signaling field of the PPDU is the first station or if the TA field of the MAC frame included in the PPDU indicates the first station, the STR multilink device can determine that a second station included in the non-STR multilink device is in a blind state. In this way, the STR multilink device can confirm that one station in the non-STR multilink device is transmitting and determine that other stations in the non-STR multilink device are in a blind state. The operation of a station after transmission cancellation will be described first.

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

[0171] When a station that has canceled a transmission for a station in a non-STR multilink device transmits to a station other than the station in the non-STR multilink device, the station that canceled the transmission for the station in the non-STR multilink device can transmit traffic with the same priority as the traffic of the canceled transmission or traffic with a higher priority. This is because it would be unfair if the station transmitted traffic had a lower priority than the priority of the traffic used when accessing the channel for the canceled transmission. In the above-described embodiment, the station in the STR multilink device may be an AP.

[0172] A station that cancels transmission to a station in a non-STR multilink device can initialize the TXOP it has set. Specifically, a station that cancels transmission to a station in a non-STR multilink device can send a CF-End frame after canceling transmission. This allows other stations operating on the link where transmission is scheduled to take place to use the link.

[0173] In FIG. 18, the STR AP multilink 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 multilink 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). 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) suspends transmission to the first station (STA1). In FIG. 18(a), after suspending transmission to the first station (STA1), the first AP (AP1) transmits to a station other than the first station (STA1), as in the previously described embodiment. In FIG. 18(b), after suspending transmission to the first station (STA1), the first AP (AP1) transmits a CF-END frame as in the embodiment described below.

[0174] When a station suspends transmission, it may not transmit the next fragment after transmitting the fragment that was in progress. In yet another specific embodiment, the station may immediately stop transmitting the packet that was in progress.

[0175] In addition, an STR MLD STA that has transmitted to an MLD STA operating in EMLSR or EMLMR mode can cancel the same transmission that it was making or was about to make as the STR MLD that transmitted to a STA in the BLIND state described above, because an MLD STA operating in EMLSR / EMLMR mode may have performance constraints similar to those in the BLIND state, as described above.

[0176] That is, while a STA in the STR MLD is transmitting to a STA in the EMLSR / EMLMR mode (e.g., EMLSR STA1), if a PPDU is received from another STA in the EMLSR / EMLMR MLD (e.g., EMLSR STA2) via a STA operating on another link, the STA can stop the transmission it is currently performing. Also, if transmission has not yet started, the STA can transmit other traffic in the same Access Category (AC) without performing the intended transmission to the STA in the EMLSR / EMLMR MLD (e.g., EMLSR STA1).

[0177] In this way, the transmission management method for STAs in the EMLSR / EMLMR mode MLD may be similar / the same as the transmission management method for STAs in the NSTR MLD. Therefore, even if a separate description regarding the EMLSR / EMLMR mode MLD is not provided in the present invention, an operation performed based on whether a specific STA in the NSTR MLD is in a BLIND state may be performed in the same / similar manner based on whether the performance of a specific STA in the EMLSR / EMLMR mode MLD is in a state limited by the transmission / reception of other STAs.

[0178] In the above-described embodiment, when the STR multilink device suspends transmission to a station of a non-STR multilink device in a blind state and transmits to a station other than the station of the non-STR multilink device in a blind state, it is necessary to notify the other station that transmission to the other station is possible for stable reception. A method for this will be described. For convenience of explanation, a station other than the station of the non-STR multilink device in a blind state 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, the station in the 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 the other station into a separate field. In yet another specific embodiment, a station in an STR multilink device can insert the address of the other station into an EHT-SIG. Specifically, the station in the STR multilink device can insert the address of the intended recipient of the PPDU and the address of the other station into the User field of the signaling field of the PPDU. In this case, the address of the other station can be inserted after the address of the intended recipient of the PPDU in the User field of the signaling field of the PPDU.

[0180] In yet another specific embodiment, a station may monitor for PPDU reception for a pre-specified time even after determining that the station is not the intended recipient of the received PPDU. Specifically, the station may monitor for continued PPDU reception for a pre-specified time even after determining that the station is not the intended recipient of the received PPDU. This allows the station to determine whether PPDU transmission should be stopped and whether transmission to the station should resume. In this embodiment, if it is determined that PPDU transmission continues for the pre-specified time, the station may enter a doze state. If it is determined that PPDU transmission does not continue for the pre-specified time, the station may remain in a wake-up state. At this time, if a new PPDU is received by the station, the station may decode the PPDU.

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

[0182] In this way, unnecessary channel occupation can be prevented by using transmission cancellation or transmission interruption.

[0183] When a transmission is interrupted or postponed due to a transmission collision between links, the CW value used for channel access may be doubled, as in the case of a general transmission failure. When a transmission is interrupted or postponed due to a transmission collision between links, unlike a general channel access failure or transmission failure, the CW value used for channel access may not be doubled. That is, the station can maintain the CW value used for channel access as it is. Doubling the CW value is intended to reduce the probability of a transmission collision by increasing the range of possible backoff counter values. This is less necessary if the station can clearly recognize a transmission collision between links. Furthermore, doubling the CW value by the station when a transmission is interrupted or postponed due to a transmission collision between links may lead to a transmission delay. However, when both an inter-link transmission collision and an intra-link collision occur simultaneously, the station needs to double the CW value. This will be explained using FIG. 19.

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

[0185] When a station cancels a transmission due to a transmission from a non-STR multilink device, as in the above-described embodiment, the station can sense the channel state after canceling the transmission. If the channel is sensed as not idle, the station can double the value of CW. In this case, the doubling can follow the embodiment described in FIG. 6. Alternatively, if the channel is sensed as idle, the station can maintain the value of CW. This embodiment is used because even if the channel is sensed as idle, the possibility of transmission collision within the link is low, so this is treated differently from when a transmission is made. Specifically, if an 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 the CW without increasing the CW. In this case, if a non-STR multilink device of the AP multilink device fails to transmit to a first station and a second station of the non-STR multilink device transmits, the AP of the AP multilink device can acquire a backoff counter within the CW without increasing the CW. As described above, the AP multilink device can determine whether the second station of the non-STR multilink device is to transmit based on the transmitting station of the PPDU indicated by the signaling field of the PPDU or the station indicated by the TA field of the MAC frame included in the PPDU. In the above-described embodiment, when EDCA is applied, the procedures for CW adjustment and backoff counter generation may be performed for each AC.

[0186] In yet another specific embodiment, the STR multilink device can determine whether the transmission of a PPDU has failed based on whether a response to the PPDU has been received. 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 a first station receiving the PPDU is included in a non-STR multilink device and the first station cannot transmit a response to the PPDU because a second station in the non-STR multilink device is transmitting, the STR multilink device can determine that the transmission of the PPDU has failed. Furthermore, if the STR multilink device's transmission of the PPDU has failed, the STR multilink device can increase the value of the CW to the next largest possible value. In this case, if the value of the CW is the maximum value, the STR multilink device can maintain the same value of the CW.

[0187] In yet another specific embodiment, when a channel is sensed as being idle, the station may set the CW value to the minimum value (CW_min) of the traffic CW. This embodiment is intended to treat a sensed channel as being idle as being the same as a successful transmission, since the possibility of a transmission collision occurring within the link is low. The station may apply the above embodiment to the CW of the AC of the traffic included in the canceled transmission.

[0188] Furthermore, when a station cancels transmission according to the above-described embodiment, the station may not increment a retry counter, which may include at least one of a long retry counter and a short retry counter.

[0189] In the above embodiments, canceling a transmission may include at least one of pausing the transmission or delaying the transmission before initiating the transmission.

[0190] If a station cancels transmission after sending a CTS-to-Self frame before attempting to transmit, the station does not have to initiate an RTS / CTS frame exchange before attempting to transmit after canceling the transmission. 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 transmit again after canceling the transmission, the station can attempt to transmit 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 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 transmit without a backoff procedure.

[0192] <Transmission Method of MLD Considering <NSTR Link Pair>

[0193] The foregoing embodiments have described an operation restriction method for an MLD that takes into account that when a STA constituting an MLD that supports NSTR performs transmission and reception, it affects (for example, interferes with) the PPDU transmission and reception and / or channel connection of other STAs in the same MLD. 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 an MLD that supports NSTR is applied.

[0194] <AP Transmission Management Method>

[0195] When a specific AP among at least one AP constituting 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 a 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 a STA of 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 start authority is a frame that must be transmitted to a STA of an NSTR MLD that is in a BLIND state (i.e., if another STA operating on the NSTR link pair of the NSTR MLD is currently transmitting), the AP may decide not to transmit the frame because the STA of the NSTR MLD cannot receive the frame even if it is transmitted. If there is a frame in the transmission queue of an AC that has acquired transmission start authority to be transmitted to another STA that is not in a BLIND state, the AP may transmit the frame in the transmission queue of the AC to the other STA.

[0198] If the AP decides not to start transmission for the AC for which the transmission start permission has been obtained, the AP may perform / invoke a new backoff procedure for the AC. In this case, when performing a new backoff procedure for the AC, the AP may generate a new backoff counter while maintaining the contention window (CW). That is, the CW[AC] and QSRC[AC] (QoS STA short retry counter) are not changed, and only the backoff counter is generated again, and a new backoff procedure for the AC for which the transmission start permission has been obtained may be performed.

[0199] Meanwhile, if a frame to be transmitted to a STA in a BLIND state exists in the transmission queue of an AC that has been granted permission to start transmission, the AP may consider the frame as if it were not present in the transmission queue. For example, if only frames to be transmitted to a STA in a BLIND state exist in the transmission queue, the AP may consider the frame as if it were not present in the transmission queue, maintain the backoff counter (BO) of the AC that has been granted permission to start transmission at 0, and decide not to start transmission. In this case, when the STA's BLIND state is released, the AP may consider the frame to be present in the transmission queue and start transmission immediately. Here, "immediately" may mean transmission performed without a separate backoff procedure according to the EDCA rules. In other words, when the STA's BLIND state is released, if it is determined that the medium was idle for a previously set time (e.g., DIFS, SIFS, PIFS, AIFSN [AC], etc.) before the BLIND state was released, the AP may start transmission to the STA at the next slot boundary.

[0200] In addition, if an MLD AP does not receive a response to a trigger frame (e.g., a frame responding with a TB PPDU or a CTS), i.e., if the transmission of the trigger frame fails, the AP does not need to retransmit the trigger frame. Also, if an Ack (Ack frame and Block Ack frame) is not received after transmitting a frame requesting a response, the AP does not need to retransmit the frame.

[0201] Generally, when an AP or other STA (AP STA, non-AP STA) in an AP MLD system determines that the transmission of a frame it sent has failed, it must retransmit the failed frame. However, when an AP in an AP MLD system determines that the reason for the failure of a frame it sent to an MLD STA is due to the behavior of another STA that has an NSTR relationship with the STA, it does not need to retransmit the failed frame. This is because even if the AP retransmits the failed frame, it is considered that the receiving STA (destination device, intended recipient) will not respond to the retransmitted frame unless the behavior of another STA that has an NSTR relationship with the receiving STA changes.

[0202] When an AP determines that a transmission has failed due to the operation of another STA that has an NSTR relationship with the receiving STA, the AP can generate a new backoff counter while maintaining the CW[AC] when performing a backoff procedure to transmit another frame in the same access category (AC) as the failed frame. In other words, the STA (AP or non-AP STA) that performed the failed transmission due to the operation of another STA that has an NSTR relationship with the receiving STA can generate a new backoff counter without increasing the CW[AC] for the failed transmission when performing the next backoff procedure. In this case, the STA that performed the failed transmission does not need to change the QSRC[AC] in addition to the 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, but 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] unchanged without modification 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 when a response to the frame is received from another STA of the same MLD as the receiving STA even if 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 target 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 had to respond only to protect the receiving operation of other STAs.

[0205] <Transmission Management Method of STA>

[0206] When a specific STA in Non-AP MLD completes the channel access procedure for a specific AC, i.e., when it acquires transmission authority to start 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 start transmission for the specific AC, it may decide not to start transmission, taking into consideration the operation of STAs operating on other links (i.e., NSTR link pairs) that have an NSTR relationship with the link on which it operates.

[0208] Furthermore, the specific STA may decide not to transmit frames in the transmission queue of the specific AC despite having acquired transmission start permission for the specific AC, considering that the other STA is performing a PPDU reception operation. That is, when the non-AP MLD is NSTR MLD, the STA operating in the NSTR link pair may give up the acquired transmission start permission, considering the operation status of the other STA in the NSTR link pair. In this case, "giving up the acquired transmission start permission" may mean not attempting transmission and re-invoking (invoking) the backoff procedure, or postponing (delaying) transmission while maintaining the backoff counter at 0.

[0209] If a STA decides not to start transmission for the AC for which it has acquired the transmission start permission, the STA may perform / invoke a new backoff procedure for the AC. In this case, when performing a new backoff procedure for the AC, the STA may generate a new backoff counter while maintaining the contention window (CW). That is, only the backoff counter is regenerated without changing the CW[AC] and QSRC[AC] (QoS STA short retry counter), and a new backoff procedure for the AC for which it has acquired the transmission start permission may be performed.

[0210] On the other hand, a STA can maintain BO at 0 without performing a new backoff procedure, and therefore can consider it as if there are no frames in its transmission queue when another STA in the NSTR link pair is receiving. As an example, a STA operating in an NSTR link pair can maintain BO (backoff counter) of an AC that has acquired permission to start transmission at 0 and make a decision (operation) not to start transmission by considering it as if there are no frames in its transmission queue when another STA operating in the NSTR link pair is receiving a PPDU.

[0211] In this case, when the STA completes reception of the PPDU from the other STA, the STA can immediately begin transmission, considering it as if a frame had been generated in the transmission queue again. Here, "immediately" may mean transmission performed without a separate backoff procedure according to the EDCA rules. That is, when the STA completes reception of the PPDU from the other STA, if it is determined (considered) that the medium was idle for a set period of time (e.g., DIFS, SIFS, PIFS, AIFSN[AC], etc.) before the completion of reception of the PPDU, the STA can begin transmission 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 with the other STA as the destination device 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 (and a PPDU including the Ack frame) that responds to a PPDU including an MPDU with the other STA as the destination device 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 (a PPDU including the Ack frame) that responds to a PPDU including an MPDU with the other STA as the destination device 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 with the other STA as the destination device 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 may be understood to minimize the negative effects (such as interference and channel access delay) that may occur due to the constraint of the NSTR link pair and to guarantee the channel access ability of each STA as much as possible.

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

[0217] This may be a problem that occurs when the specific STA and other STAs maintain their backoff counters at 0 due to reception 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 of STAs operating on other links that are NSTR link pairs with the specific link at 0, and multiple non-AP MLDs that have completed reception of the MU PPDU can start transmission through the STAs of the other links.

[0218] That is, as considered in one embodiment of the present invention, a non-AP MLD STA that starts transmission while maintaining its backoff counter at 0 may need to initiate a channel access procedure, taking into account the possibility that other non-AP MLD STAs may start transmission at the same time. To this end, the non-AP MLD STA can manage the channel access procedure by checking whether the PPDU being received by another STA in the NSTR link pair is a PPDU intended for multiple STAs. More specifically, the non-AP MLD STA can determine to maintain its backoff counter at 0 only if the PPDU being received by another STA in the NSTR link pair is a PPDU intended only for the other STA. That is, the non-AP MLD STA can consider its transmit queue (for a particular AC) to be empty only if the PPDU being received by another STA in the NSTR link pair is a PPDU intended only for the other STA. In other words, if a STA in a non-AP MLD mode is receiving a PPDU that has multiple STAs as destinations, the STA cannot consider it as if there are no frames in its transmit queue and must perform a new backoff procedure when its backoff counter reaches 0.

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

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

[0221] 2. When the RA of the PPDU being received is an individual address (same meaning as a direct address or unicast address), and the individual address is an individual (MAC) address assigned to the other STA, the individual address may mean that the group bit of the MAC address is 0.

[0222] 3. If 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 individually addressed to the other STA.

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

[0225] 6. If the Address 1 field of the MPDU included in the receiving PPDU is the MAC address of the other STA

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

[0227] However, the non-AP MLD STA can maintain the backoff counter at 0 if the other STA receives an implicit or explicit instruction from the AP.

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

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

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

[0231] That is, if the PPDU being received by the other STA of the NSTR link pair is not a PPDU intended only for the other STA, or if the PPDU being received is not a PPDU intended only for the other STA, or if the format and / or destination device of the PPDU being received is not confirmed, the non-AP MLD STA may need to generate a new backoff counter when the backoff counter reaches 0. That is, in a situation corresponding to at least one of the following cases, the non-AP MLD STA cannot maintain the backoff counter at 0 and must generate a new backoff counter.

[0232] 1. When the PPDU being received by the other STA of 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 of the NSTR link pair is a HE MU PPDU

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

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

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

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

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

[0239] 8. When the destination device of the PPDU being received by another STA on the NSTR link pair is not confirmed

[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 of the NSTR link pair. However, if a non-AP MLD STA maintains its backoff counter at 0 but starts transmission when the other STA of the NSTR link pair completes PPDU reception (or after a pre-set (promised) time has elapsed since completion), the non-AP MLD STA must transmit an RTS frame in the first frame. In this case, the restriction that the RTS frame must be transmitted in the first frame may apply only when the PPDU being received by the other STA is not a PPDU intended only for the other STA. In other words, if the PPDU being received by the other STA is a PPDU intended only for the other STA, the non-AP MLD STA may not be obligated to transmit an RTS frame in the first frame.

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

[0242] Alternatively, a non-AP MLD STA may not decrement its backoff counter when another STA in the NSTR link pair is receiving a PPDU. This may be performed by the non-AP MLD STA considering the medium state as busy (virtual busy) when the other STA is receiving a PPDU. That is, a non-AP MLD STA may have to consider the 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] FIG. 20 illustrates an example of a transmission management method for a non-AP multilink device according to an embodiment of the present invention.

[0244] Referring to FIG. 20(a), while the non-AP MLD is receiving an SU (Single User) PPDU (in the case of an EHT PPDU, a PPDU that is an EHT MU PPDU and includes only one User field) 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, based on the information that the PPDU received via STA1 is a PPDU intended only for STA1, non-AP MLD STA2 can recognize that there are no other non-AP MLD STAs that can postpone transmission while maintaining their back-off counters at 0 in order to receive the PPDU. Therefore, STA2 can choose to postpone transmission while maintaining its back-off counter at 0, rather than starting transmission even when its back-off counter reaches 0, as shown in (a) of FIG.

[0246] In this way, if STA1's (SU) PPDU reception procedure is completed while STA2 maintains its backoff counter at 0, STA2 can start transmission without performing a separate backoff procedure. In this case, STA2 internally operates 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 is maintained at 0) at the time when STA1's PPDU reception procedure is completed. That is, even if the backoff procedure for a specific AC is completed, STA2 considers that there is no frame to transmit in the transmission queue of the specific AC while STA1's PPDU reception procedure is in progress. However, STA2 can start PPDU transmission on Link 2 by considering that a frame to be transmitted has been generated in the transmission queue of the specific AC at the time when STA1's PPDU reception procedure is completed. However, STA2 can start PPDU transmission only if the medium has maintained an idle state for a certain period of time (considered to be SIFS in FIG. 20(a)) at the time of starting PPDU transmission.

[0247] In addition, when transmission is performed without a separate backoff procedure while the backoff counter is maintained at 0, a restriction may be applied that the medium state (CCA result of Link 2) has not changed to busy while the backoff counter is maintained at 0. In other words, if STA2, which maintained the backoff counter at 0 while STA1 was receiving a PPDU, determines that the medium has changed to busy, it must execute (invoke) a new backoff procedure after the medium has changed to idle again.

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

[0249] Referring to FIG. 20(b), while the non-AP MLD is receiving an MU (Multi-user) 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.

[0250] In this case, STA2 of the non-AP MLD can recognize that other non-AP MLDs can postpone transmission in order to receive the PPDU based on information that the PPDU being received by STA1 is an MU PPDU (or a group (non-individual) address frame) intended for not only STA1 but also other STAs. Therefore, when the backoff counter reaches 0 as shown in Figure 20(b), STA2 can decide to maintain the backoff counter at 0 or not start transmission and execute (invoke) the backoff procedure again. In this case, when STA2 invokes a new backoff procedure, it invokes the new backoff procedure without changing CW[AC] and QSRC[AC].

[0251] As shown in Figure 20(b), the backoff counter of STA2 (for a particular AC) reached 0 twice while STA1 was receiving the PPDU, and STA2 invoked a new backoff procedure twice. When STA2 maintained CW[AC] and invoked a new backoff procedure, 5 was generated as the first backoff counter (New counter #1 in Figure 20(b)). When the backoff procedure was invoked 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 contents of a beacon frame transmitted by an AP in AP MLD according to one embodiment of the present invention and an example of a TBTT (target beacon transmission time) information field format included in an RNR (Reduced Neighbor Report) element.

[0253] Referring to (a) of Figure 21, the beacon frame may include the same parameters and elements in legacy IEs as those included in the beacon frame disclosed in conventional Wi-Fi 802.11ax. For example, the legacy IEs of the beacon frame may include elements such as a timestamp field, a beacon interval field indicating the interval at which beacons are 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 capability, VHT operation, S1G beacon compatibility, short beacon interval, S1G capability, S1G operation, HE capability, HE 6GHz band capability, 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 of the same names included in the beacon frame disclosed up to conventional Wi-Fi 802.11ax.

[0255] The beacon frame may also include a Reduced Neighbor Report (RNR) element for indicating information about neighbor APs. The RNR element may be used to inform a station of information about neighbor APs, and the station may receive the beacon frame and recognize the neighbor APs based on the RNR element included in the beacon frame.

[0256] Specifically, the RNR element may include an element ID field, a length field, and a neighbor AP information field. Each neighbor AP information field 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, the RNR element transmitted by the AP included in the AP MLD may include a TBTT information field format as shown in (b) of FIG. 21 to indicate basic information for other APs included in the same MLD. Unlike the TBTT information field of the RNR element transmitted by the AP in conventional Wi-Fi 802.11ax, the RNR element transmitted by the AP included in the 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 (c) of Figure 21. In this case, when an AP MLD indicates information about another AP in the same MLD through a specific Neighbor AP Information field in an RNR element, the MLD ID subfield included in the specific Neighbor AP Information field can be set to 0. That is, the AP can set the MLD ID subfield to a specific value to inform a station that the Neighbor AP Information field is an AP included in the same AP MLD, and a station receiving the Neighbor AP Information field can recognize from the value of the MLD ID subfield that the AP corresponding to the Neighbor AP Information field is included in the same MLD as the AP that transmitted the Neighbor AP Information field.

[0258] The Link ID subfield may be a subfield indicating an index determined by the AP MLD to indicate a link operated by another AP to be indicated using neighbor AP information. The Change Sequence subfield may be a subfield used to indicate information related to an update (e.g., a Critical Update) related to a link of another AP. For example, if the value of the Change Sequence subfield is changed, a station receiving this can recognize that parameters related to the BSS (or link) of the corresponding AP have been updated and can request the updated parameters from the AP to update the corresponding parameters. In this case, if the AP MLD is an NSTR AP MLD, which is an MLD that does not support simultaneous transmission and reception (e.g., 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), the STA included in the STA MLD can perform a procedure to update parameters only on the primary link. That is, in order to update parameters of other links (e.g., non-primary links) to other neighbor APs other than the primary link of the AP MLD, frames for parameter update can be transmitted and received only via the primary link.

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

[0260] Furthermore, if the AP is an NSTR AP MLD that does not support simultaneous transmission and reception (e.g., an NSTR mobile AP MLD or an NSTR soft AP MLD, i.e., a mobile terminal or the like operates as a soft AP MLD for tethering, etc.), the NSTR AP MLD can transmit a beacon frame including information indicating that it is an NSTR AP MLD. For example, the 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 transmitted the beacon frame is the NSTR AP MLD. Therefore, the specific subfield for indicating an NSTR AP MLD may be set to a value different from the specific value (e.g., '1' or '0') when not indicating an NSTR AP MLD (e.g., an STR AP MLD or another AP MLD, etc.).

[0261] A specific subfield for indicating NSTR AP MLD may be indicated together with a capability-related subfield (e.g., MLD level capability) in a beacon frame, or may be included in and transmitted in a neighbor AP information field associated with an AP of a non-primary link of the NSTR AP MLD. For example, a specific subfield for indicating NSTR AP MLD may be encoded and indicated together with a frequency separation for STR / AP MLD type indicator, which is a capability-related subfield. That is, the specific subfield may be encoded together with a frequency separation for STA / AP MLD type indicator indicating the distance for supporting STR, and indicated in a beacon frame. In this case, if the corresponding indicator indicates the type of AP MLD, a set value may indicate whether the AP MLD that transmitted the beacon frame is NSTR AP MLD or not (e.g., a value of '0' indicates not NSTR AP MLD, and a value of '1' indicates NSTR AP MLD).

[0262] The method of utilizing the subfield indicating whether or not the AP MLD is an NSTR AP MLD may be a method of explicitly indicating whether or not the AP MLD is an NSTR AP MLD.

[0263] As another example, the NSTR AP MLD may indicate that it is an NSTR AP MLD in an implicit manner rather than directly indicating that it is an NSTR AP MLD using a specific subfield. Specifically, the NSTR AP MLD may indicate that it is an NSTR AP MLD by indicating that it has two supportable links and at the same time indicating that it has an NSTR link pair. In this case, the NSTR AP MLD may set the Maximum Number Of Simultaneous Links subfield included in the beacon frame to 1 (or a predetermined value meaning 2) to indicate that it has two supportable links. In this case, the NSTR AP MLD may 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] The AP MLD can explicitly or implicitly inform the non-AP STA MLD that it is the NSTR AP MLD by transmitting a beacon frame according to the above-described method. The non-AP STA MLD can implicitly or explicitly determine from the received beacon frame whether the AP MLD that transmitted the beacon frame is the NSTR AP MLD. If the AP MLD that transmitted the beacon frame is the NSTR AP MLD (i.e., if the beacon frame indicates that the AP MLD is the NSTR AP MLD by an explicit or implicit method), the non-AP STA MLD can perform the procedure for association or setup with the NSTR AP MLD only on the link on which the beacon frame was received. In other words, the non-AP STA MLD can send and receive frames for association or setup with the NSTR AP MLD on the link on which the beacon frame was received (e.g., the primary link). For example, frames for association or configuration with an AP connected via a link other than the primary link included in the NSTR AP MLD may be transmitted only via the primary link. In this case, an (ML) (re)association request frame transmitted by the Non-AP STA MLD may be transmitted via a link other than the primary link (non-primary link).

[0265] In this case, the NSTR AP MLD may not indicate information about the AP of the non-primary link in the RNR element of the beacon frame (transmitted on the primary link) to prevent the non-AP STA MLD from attempting a setup procedure on the non-primary link. That is, the beacon frame transmitted by the AP of the NSTR AP MLD may not include / indicate a neighbor AP information field for the AP of another link (in the same MLD). In this case, the non-AP STA MLD does not attempt to set up the NSTR AP MLD on the non-primary link after receiving the beacon frame because it cannot confirm information about the AP of the non-primary link. In this case, a non-AP STA MLD that receives a beacon frame from the NSTR AP MLD that does not include a neighbor AP information field for the AP of the non-primary link can implicitly recognize that the other AP is an NSTR AP MLD based on the fact that the number of simultaneously supported links of the AP that transmitted the beacon frame is two and information about other APs in the same MLD is not indicated, as described above.

[0266] Meanwhile, when a typical AP MLD receives an (ML) (re)association request frame from a STA (MLD), it must transmit an (ML) association response frame over the link on which the (ML) association request frame was received. However, the NSTR AP MLD may be allowed to respond to an (ML) association request frame received over a non-primary link over the primary link (i.e., to send an (ML) association response frame over the primary link).

[0267] This may be an acceptable operation because, as described above, the NSTR AP MLD operation of transmitting on a non-primary link is somewhat limited compared to a general AP. Furthermore, 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 also start transmitting on the primary link. This may be an operation restriction considered to prevent the AP of the primary link from entering a BLIND state, as considered in other embodiments of the present invention.

[0268] Therefore, when an NSTR AP MLD receives an (ML) (re)association request frame over a non-primary link, it can respond with an (ML) (re)association response frame over the primary link, or it can respond with an (ML) (re)association response frame over both the primary and non-primary links simultaneously. In other words, a STA MLD that sends an (ML) (re)association request frame over the non-primary link of the NSTR AP MLD recognizes that the response to its request frame will be sent over the primary link, and can wait to receive an (ML) (re)association response frame over 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, if the MLD ID in the MLD Parameters field is set to '0', the STA MLD can recognize that the AP corresponding to the Neighbor AP Information field including the MLD Parameters field is included in the AP MLD that includes the AP that transmitted the beacon frame. In other words, the STA MLD can recognize that the Neighbor 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 by which the STA MLD analyzes / acquires this information may be the same as or similar to the operation performed by a conventional STA after receiving an RNR element.

[0270] However, because an NSTR Soft AP does not transmit beacon frames via a non-primary link, it may be impossible to indicate information related to beacon frames of other APs (non-primary link APs) via the RNR element. Furthermore, because the NSTR Soft AP MLD does not transmit beacon frames via a non-primary link AP, it cannot support information related to beacon frames when indicating basic information about a non-primary link AP via the RNR element. For example, a non-primary link that does not transmit beacon frames does not have information corresponding to the TBTT information count, TBTT information length, and neighbor AP TBTT offset subfields that should be indicated in the RNR element. Therefore, when the NSTR Soft AP MLD transmits an RNR element via the primary link AP, it may be necessary to set the TBTT-related fields of the neighbor AP information field corresponding to the non-primary link AP to predetermined values.

[0271] The Neighbor AP TBTT Offset subfield of the TBTT Information field (see (b) of FIG. 21) indicates information related to the next TBTT of another AP to be indicated. That is, the Neighbor AP TBTT Offset subfield included in the Neighbor AP Information field may include information about the next TBTT of the AP corresponding to the Neighbor AP Information field. For example, when AP1 transmitting a beacon frame indicates information about AP2 using the RNR element (through the Neighbor AP Information field), the Neighbor AP TBTT Offset subfield corresponding to AP2 indicates how many TUs (Time Units, 1024 us) the next TBTT of AP2 differs from the previous TBTT of AP1. In this case, the value indicated in the Neighbor AP TBTT Offset subfield is a value obtained by rounding down the TBTT offset to the nearest integer. That is, when an AP indicates a value of 10 in the Neighbor AP TBTT Offset subfield of another AP, the next TBTT of the other AP may have a time interval of 10 TUs to less than 11 TUs based on the previous TBTT of the AP.

[0272] However, when an AP of a primary link of an NSTR Soft AP MLD sets a neighbor AP TBTT offset subfield (1-octet) corresponding to an AP of a non-primary link, it may need to set it to a preset value (e.g., 254 or 255). This may be because an NSTR Soft AP does not transmit a beacon frame on a non-primary link and is therefore unable to determine a target beacon transmission time (TBTT), which is a scheduled time for transmitting the next beacon frame. That is, a beacon frame transmitted by an NSTR Soft AP MLD on a primary link may need to set a neighbor AP TBTT offset subfield corresponding to an AP of a non-primary link to 254 and / or 255 using an RNR element. In this case, the neighbor AP TBTT offset subfield corresponding to the non-primary link may be present in a TBTT information field including an MLD parameters field in which the MLD ID subfield is set to 0.

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

[0274] Also, 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] Also, 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 above-described embodiment of the present invention, it has been mentioned that a beacon frame transmitted by the NSTR Soft AP MLD may indicate a neighbor AP TBTT offset subfield corresponding to an AP of a non-primary link as a preset value (254 and / or 255). However, the neighbor AP TBTT offset subfield may be indicated as 254 or 255 even when the beacon frame does not correspond to an AP of a non-primary link of the NSTR Soft AP MLD. For example, if the TBTT offset of another AP recognized by the AP transmitting the beacon frame is 254 TU or more (254 TU or more than 254 TU), the AP may indicate the neighbor AP TBTT offset subfield corresponding to the other AP in the beacon frame as 254. Also, if the AP transmitting the beacon frame cannot accurately recognize the TBTT offset of the other AP, the AP may indicate the neighbor 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 in the MLD, when using the RNR element to indicate (set) the neighbor AP TBTT offset subfield corresponding to another AP (in the same MLD), it must not indicate (set) it to 255.

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

[0280] For example, when the AP is included in the same AP MLD as the AP that transmitted the beacon frame, the neighbor AP TBTT offset subfield is not set to a specific value (e.g., "255"). In this case, the size of the neighbor AP TBTT offset subfield may be 8 bits, and in this case, the neighbor AP TBTT offset subfield is not set to the maximum value that can be indicated by the neighbor AP TBTT offset subfield (in the case of 8 bits, values ​​from 0 to 255 are respectively corresponding, and therefore the maximum offset that can be indicated by 8 bits may be 255). However, when the AP is not included in the same AP MLD as the AP that transmitted the beacon frame (for example, when the AP is a legacy AP), the neighbor AP TBTT offset subfield may be set to a specific value (e.g., "255").

[0281] In a similar embodiment, the neighbor AP TBTT offset subfield may be analyzed so that the set value varies depending on specific conditions.

[0282] For example, when the neighbor AP TBTT offset subfield is set to a specific value (eg, '254'), the set value may be analyzed to be different, such as '254' or greater than '254', depending on a specific condition.

[0283] Specifically, if the AP corresponding to the neighbor AP information field including the neighbor AP TBTT offset subfield is included in the same AP MLD as the AP that transmitted the beacon frame or in another MLD, and the neighbor AP TBTT offset subfield is set to a specific value (e.g., "254"), the station can interpret the value indicated by the neighbor AP TBTT offset subfield as 254 TUs. However, if the AP is not included in the same AP MLD as the AP that transmitted the beacon frame or in another MLD (e.g., if the AP is a legacy AP or an AP not included in the MLD), and the neighbor AP TBTT offset subfield is set to a specific value (e.g., "254"), the station can interpret the value indicated by the neighbor AP TBTT offset subfield as 254 TUs or more.

[0284] Generally, the reason why a conventional AP transmits TBTT offset information along with basic information about neighboring APs using a beacon frame may be to help a STA receiving a beacon frame quickly obtain basic information about other APs and receive beacon frames from other APs more efficiently using the confirmed TBTT offset information.

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

[0286] However, when an AP MLD indicates information about other APs in the MLD using a beacon frame, it may include and transmit 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 a beacon frame. In this case, if both the neighbor AP TBTT offset subfield and the MLD AP TBTT offset subfield are indicated in a specific TBTT information field, the neighbor AP TBTT offset subfield may be indicated with a preset value (which may be 254 or 255). The MLD AP TBTT offset subfield is a two-octet subfield and may be used to indicate the TBTT offset value when the TBTT offset between the AP (reporting AP) that transmitted the beacon frame and another AP (reported AP) in the same MLD exceeds 254TU. Furthermore, the MLD AP TBTT offset subfield may be included in the TBTT information field only when the TBTT offset of another AP in the same MLD exceeds 254 TU when the AP MLD transmits a beacon frame and the exact TBTT offset cannot be indicated in the existing neighbor AP TBTT offset subfield.

[0287] When the STA MLD checks a TBTT information field including an MLD AP TBTT offset subfield in an RNR element included in a beacon frame received from a specific AP, the STA can check the TBTT offset of the AP corresponding to the TBTT information field based on the value indicated in the MLD AP TBTT offset subfield. In this case, to determine whether the TBTT information field included in the beacon frame includes an MLD AP TBTT offset subfield, the STA may check based on the value of the TBTT information length subfield (located in the TBTT Information Header (sub) field of each neighbor AP information field) corresponding to each TBTT information field. That is, when the STA recognizes that the TBTT information field includes an MLD AP TBTT offset subfield based on the value of the TBTT Information Length subfield, the STA can check the TBTT offset of the AP corresponding to the TBTT information field based on the value indicated in the MLD AP TBTT offset subfield. In this case, when the MLD AP TBTT offset subfield of a specific TBTT information field indicates 0 or a preset value (or a value less than 254), the STA MLD can confirm the TBTT offset of the AP corresponding to the specific TBTT information field based on the value of the neighbor AP TBTT offset subfield.

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

[0289] 22, the TBTT information field may include an MLD AP TBTT offset subfield. The MLD AP TBTT offset subfield may be included only in beacon frames transmitted by APs of the AP MLD. Furthermore, the MLD AP TBTT offset subfield may be included only in TBTT information fields corresponding to other APs of the same MLD as the AP transmitting the beacon frame.

[0290] As an example, in a beacon frame transmitted by a specific AP in an AP MLD, to indicate that the TBTT offset of another AP in the same MLD is 300TU, the TBTT information field corresponding to the other AP may be used as a format including an MLD AP TBTT offset subfield. In this case, the neighboring AP TBTT offset subfield of the TBTT information field corresponding to the other AP may be indicated as 254 or 255, and the MLD AP TBTT offset subfield may be indicated as a value corresponding to 300TU (e.g., 300, 299, or (300-254)). In this case, the above-mentioned MLD AP TBTT offset subfield is a subfield name for illustrative purposes, and subfields with the same purpose may be defined with different names.

[0291] FIG. 23 illustrates an example of a TBTT information length subfield indicating a TBTT information field including an MLD AP TBTT offset subfield according to an embodiment of the present invention.

[0292] 23, the type of content included in the TBTT information field may be indicated by the TBTT information length subfield. The TBTT information length subfield may be a subfield included in a TBTT information header field present in a neighbor AP information field included in an RNR element. That is, the RNR element transmitted in a beacon frame may include multiple neighbor AP information fields, and the TBTT information fields included in each neighbor AP information field may have a structure including different amounts and types of content. In this case, since the TBTT information fields included in each neighbor AP information field may include 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] That is, the STA can parse each neighbor 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 neighbor AP information field may indicate information about a neighbor AP or another AP of the same MLD. At this time, if the value of the TBTT information length subfield included in the TBTT information header field indicates a content configuration including an MLD AP TBTT offset subfield as shown in FIG. 23, the STA can determine the TBTT offset of the AP corresponding to the 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, the NSTR AP MLD cannot transmit beacon frames, probe response frames, or ML (Multi-link) probe response frames on non-primary links. Therefore, a STA MLD that wishes to connect to the NSTR AP MLD must transmit ML probe request frames only on the link on which the NSTR AP MLD transmitted beacon frames.

[0296] The ML probe request frame transmitted by the STA of the EHT non-AP STA MLD may include EHT Capability information and a Multi-Link element in addition to the information included in the probe request frame transmitted by the conventional HE STA. In this case, the Multi-Link element included in the ML probe request frame can serve as a way for the MLD transmitting the ML probe request frame to request additional information about the AP of another link from the AP MLD.

[0297] For example, when transmitting an ML probe request frame, the non-AP STA MLD can request the AP MLD to further respond with complete or partial information about the APs of other links using the Multi-Link element of the ML probe request frame. That is, the non-AP STA MLD can request the AP MLD to transmit all or part of the parameters related to the links 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 related to 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 related to other APs of the non-primary link.

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

[0300] If the AP MLD that sent the beacon frame requests additional information about the AP of another link in the ML probe request frame received on a specific link, it can respond using an ML probe response frame to not only provide information about the AP of the specific link, but also the requested additional information about the AP of the other link.

[0301] In this case, when the STA MLD requests complete information about the AP of another link by transmitting an ML probe request frame on a specific link, the AP MLD must provide information about the AP of the other link at the same level as the information about the AP of the specific link using an ML probe response frame that responds on the specific link. In other words, the STA MLD that receives complete information about the AP of another link on a specific link can obtain the same level of information about the AP of the other link as when it directly receives an ML probe response from the AP of the other link.

[0302] In this case, if the STA MLD transmits an ML probe request frame over a specific link and requests partial information about the AP of another link, the AP MLD can provide only the requested information (requested element information) among the information about the AP of the other link using an ML probe response frame that responds over the specific link. In other words, the STA MLD that receives partial information about the AP of another link over a specific link can further obtain only the information it requested from the AP of the other link. In this case, the STA MLD that requests partial information about the AP of the other link can transmit an ML probe request frame including information indicating further information to be obtained (which may be indicated by the Requested element IDs field) together with the link ID corresponding to the other link. Therefore, if the ML probe request frame received over a specific link includes information indicating information about the other link (Request element IDs field), the AP MLD can further indicate the indicated information about the other link in the ML probe response frame.

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

[0304] In this case, the 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. The Per-STA profile is a field that may be included zero or more times in the Multi-link element and may include information on other STAs (APs and non-AP STAs) that exist in the same MLD as the STA (AP and non-AP STA) that transmits the frame including the Multi-Link element. In this case, the Per-STA profile includes a Complete Profile subfield, and complete information (information at the same level as the STA (AP and non-AP) that transmits the frame including the Multi-Link element) of the other STAs (APs and non-AP STAs) corresponding to (corresponding to) the Per-STA profile whose Complete Profile subfield is indicated as 1 can be obtained from the 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 according to inheritance rules. The inheritance rule may mean that if a parameter or element is not specified, the value of the same parameter or element (specified for other STAs (AP and non-AP)) that has already been specified is inherited and utilized to prevent repeated specification of the same parameter or element. That is, if a value of parameter1 is specified for STA1 and a value of parameter1 is not specified for STA2, the inheritance rule may interpret the value of parameter1 for STA2 as being 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 the NSTR AP MLD may not include a Beacon Interval subfield for indicating the interval at which beacons are transmitted. That is, when the NSTR AP MLD indicates a Per-STA Profile subelement corresponding to an AP of a non-primary link in the Multi-link element, the Beacon Interval Present subfield must be set to 0. This may be because an AP operating on a non-primary link of the NSTR AP MLD does not transmit beacon frames, and therefore there is no separate beacon frame period. That is, even if the Complete Profile subfield (in the Per-STA Control field) of the Per-STA Profile subelement (of the Probe Response and Association Response frames) corresponding to an AP of a non-primary link of the NSTR AP MLD is set to 1, the Beacon Interval Present subfield may be set to 0. That is, beacon interval information for the AP of a non-primary link is not present even when complete information is indicated.

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

[0307] That is, because beacons are not transmitted on non-primary links, even when a non-AP STA MLD requests all information (or all updated information) for other APs on non-primary links through the AP on the primary link of the AP MLD (i.e., when complete information is set to '1'), the beacon interval and DTIM information for the AP on the non-primary link may not be present in the ML probe response frame. That is, the beacon interval and DTIM information may not be included in the Per-STA profile subelement for the AP on the non-primary link included in the ML probe response frame.

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

[0309] Because the NSTR AP MLD does not transmit beacon frames to non-primary links, it does not need to indicate DTIM information and beacon interval information when indicating information about the AP of the non-primary link. That is, the NSTR AP MLD may need to always indicate 0 in the DTIM information present subfield of the Per-STA profile (more precisely, the STA Control field) corresponding to the AP of the non-primary link. That is, the NSTR AP MLD may need to always indicate 0 in the Beacon Interval Present subfield of the Per-STA profile corresponding to the AP of the non-primary link. Therefore, even when the NSTR AP MLD receives an ML probe request frame requesting complete information or an (ML) (re)association request frame from a non-AP STA MLD, the NSTR AP MLD may need to always indicate 0 in the Beacon Interval Present subfield and the DTIM information present subfield of the Per-STA profile corresponding to the AP of the non-primary link.

[0310] Alternatively, since beacon frames are not transmitted to non-primary links, the NSTR AP MLD may need to set the Beacon Interval, DTIM Count, and DTIM Interval subfields in the Per-STA profile corresponding to the AP of 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 the NSTR AP MLD transmits (responds to) complete information for the AP of the non-primary link. That is, the STA MLD requests complete information for a specific link from the AP MLD using an ML probe request frame, and then the complete information for the AP of the specific link is expected to be returned in the response frame. In this case, if the complete information responded by the NSTR AP MLD has a different Per-STA profile configuration from the complete information responded by the STR AP MLD, the implementation complexity of the process by which the STA MLD obtains information according to the Per-STA profile may increase. Therefore, even if the AP of 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 the general AP MLD when responding with complete information for the non-primary link when responding with complete information. In this case, the Per-STA profile of the NSTR AP MLD corresponding to the AP of the non-primary link may have the Beacon Interval subfield, DTIM Count subfield, and DTIM Interval subfield set to predetermined values, respectively. For example, when transmitting complete information to the AP of the non-primary link, the NSTR AP MLD can set each bit of the Beacon Interval subfield of the non-primary link to all 0s, all 1s, or a predetermined method.For example, when the NSTR AP MLD transmits complete information for the AP of 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 a predetermined manner. For example, when the NSTR AP MLD transmits complete information for the AP of 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 a predetermined manner.

[0311] Alternatively, because beacon frames are not transmitted on the non-primary link, the NSTR AP MLD may set the Beacon Interval, DTIM Count, and DTIM Interval subfields in the Per-STA profile corresponding to the AP of the non-primary link to values ​​associated with the beacon frame of the primary link. This may be considered to maintain the same Per-STA profile configuration, as described above. In this case, the Beacon Interval subfield, DTIM Count subfield, and DTIM Interval subfield in the Per-STA profile corresponding to the AP of the non-primary link may be set to values ​​associated with the beacon frame transmitted on the primary link, respectively. For example, when transmitting complete information for the AP of the non-primary link, the NSTR AP MLD may set the Beacon Interval subfield of the non-primary link to a value indicating (meaning) the beacon interval of the primary link. For example, when transmitting complete information for the AP of the non-primary link, the NSTR AP MLD may set the DTIM Count subfield of the non-primary link to the DTIM Count value of the primary link. For example, when the NSTR AP MLD transmits complete information for the AP on the non-primary link, it can set the DTIM Interval subfield of the non-primary link to a value indicating the DTIM interval of the primary link.

[0312] Alternatively, because 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 the AP of the non-primary link to values ​​with specific purposes. Furthermore, the Beacon Interval subfield of the non-primary link may be set by the AP MLD to a value with specific purposes (a virtual beacon interval), for example, a value for calculation. Conventionally, the Wi-Fi beacon interval literally means a value related to the time interval between beacon frame transmissions, but is also used as a time unit for the operation of various BSSs. For example, the unit of a JointFailureTimeout primitive, a QueryFailureTimeout primitive, etc. is defined as a beacon interval, and the Listen Interval field, the PRAW Start Offset subfield, the AID Request Interval field, the AID Switch Count field, the AID Response Interval field, the Minimum Transmission Interval subfield, the Channel Quality Measurement Duration, the Color Switch Countdown (of the BSS Color Change Announcement element) subfield, etc. indicate their interval / duration using the beacon interval (or TBTT) as a basic unit. As such, the beacon interval has the meaning of a value related to the interval at which beacon frames are actually transmitted, and is also a value used as a unit in various primitives and fields. Therefore, even if beacon frames are not actually transmitted over non-primary links, the beacon interval for non-primary links may need to be defined (indicated, set) to be used as a unit in the above-mentioned primitives / subfields.

[0313] That is, even if a beacon frame is not transmitted over the non-primary link, the NSTR AP MLD can indicate the Beacon Interval subfield of the Per-STA profile corresponding to the AP of the non-primary link as the beacon interval value to be used as the time unit of the non-primary link. In this case, the non-AP MLD can recognize (check and calculate) the duration and interval of the above-mentioned primitives and fields (used as the beacon interval unit) based on the value indicated in the Beacon Interval subfield of the Per-STA profile corresponding to the AP of the non-primary link. In this case, the DTIM Interval subfield and DTIM Count subfield of the Per-STA profile corresponding to the AP of the non-primary link may also be set according to the BSS operation purpose of the AP MLD, and the non-AP MLD operating the STA over the non-primary link may need to operate based on the set values ​​when operating the STA over the non-primary link.

[0314] Meanwhile, the method of setting subfields (Beacon Interval, DTIM Count, DTIM Interval, etc.) related to non-primary link beacons of the NSTR AP MLD described above may be equally applied to other frames and subfields (transmitted on the primary link or non-primary link) containing information related to non-primary link beacons, as well as the Per-STA profile transmitted on the primary link.

[0315] In addition, a non-AP STA MLD attempting to associate with an NSTR AP MLD may need to use the beacon interval of the primary link of the NSTR AP MLD as the unit of the Listen Interval field transmitted while requesting setup for the primary link and non-primary links. That is, a non-AP STA MLD transmitting a Listen Interval field to an NSTR AP MLD must calculate and set the unit of the Listen Interval field as 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) at which at least one STA transitions to a wake state in order for the non-AP STA MLD performing multi-link (re)association to receive beacon frames. In this case, the Listen Interval field may indicate a value derived when the ListenInterval parameter is indicated in the MLME primitive.

[0316] In this case, when a non-AP STA MLD transmits a Listen interval field to another AP MLD (e.g., an STR AP MLD) other than the NSTR AP MLD, it may need to set the unit of the Listen interval field to the maximum value of the beacon interval of the link (AP) it is attempting to set up. For example, when a non-AP STA MLD attempts to perform multi-link setup with the AP MLD and link 1 or link 2, the non-AP STA MLD may set the unit of the Listen interval field included in the ML association request frame to the larger of the beacon interval of link 1 (AP) and the beacon interval of link 2. In other words, if the beacon interval of link 1 is 100 ms and the beacon interval of link 2 is 50 ms, the unit of the Listen interval subfield transmitted by the non-AP STA MLD may be in 100 ms units.

[0317] Generally, when an AP and a STA complete setup, the STA can learn and track (update) the AP's operating parameters and element changes by receiving a beacon frame transmitted by the AP. The beacon frame also provides information, including a timestamp field, for STAs within the BSS to synchronize their time.

[0318] However, since the NSTR AP MLD does not transmit beacon frames on non-primary links as mentioned above, the STA MLD set up with the NSTR AP MLD may need to perform separate operations to track (update) parameters / elements and maintain time synchronization for the non-primary links.

[0319] According to one embodiment of the present invention, a non-AP STA MLD combined with an NSTR AP MLD can check the change sequence (in the MLD parameter field of the RNR element) of the non-primary link after receiving a beacon frame over the primary link and transmit an ML Probe Request. In this case, the ML Probe Request frame transmitted by the non-AP STA MLD may be transmitted 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. Alternatively, the ML Probe Request frame transmitted by the STA MLD for the purpose of updating parameters / elements 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 the non-AP STA MLD and the AP MLD, frames for performing association, reassociation, and / or parameter update procedures may be transmitted only on the primary link. For example, if the STA recognizes that parameters for the AP of a non-primary link have been updated from a specific field (e.g., a change sequence or a BSS parameter change count subfield, etc.) that indicates whether the parameter update is for a link of another AP included in the neighbor AP information included in the beacon frame, the non-AP STA MLD can request transmission of the updated parameters on a primary link other than the non-primary link of the other AP. In other words, the non-AP MLD cannot transmit frames (e.g., probe request frames) for requesting updated parameters on a non-primary link.

[0321] As an example, after setting up with the NSTR AP MLD, the non-AP STA MLD requesting information for updating parameters / elements of the 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 transmitted over the primary link. If the Updated Profile subfield is set to 1 in the Per-STA profile (corresponding to the non-primary link) of the received ML Probe Request frame, the NSTR AP MLD can respond with an ML Probe Response frame including information (parameters and elements) of the changed non-primary link.

[0322] In this case, the Per-STA Profile field of the ML Probe Request frame transmitted by the non-AP STA MLD may include an Updated Profile subfield and a Recorded Change Sequence subfield. The Recorded Change Sequence subfield indicates the latest Change Sequence value maintained by the non-AP STA MLD for the non-primary link, and the AP MLD can check / 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 increasing the Change Sequence number from 101 to 102. In this case, the STA MLD can request updated information for the non-primary link by transmitting an ML probe request frame. In this case, if the non-AP STA MLD specifies the Recorded Change Sequence subfield as 100, the NSTR AP MLD can respond with an ML probe response frame that includes both Parameter 1 and Parameter 2, and if the non-AP STA MLD specifies the Recorded Change Sequence subfield as 101, the NSTR AP MLD can respond with an ML probe response frame that includes only Parameter 2.

[0324] In this case, the Non-AP STA MLD does not use a separate Updated Profile subfield to request an Updated Profile, but can indicate the Complete Profile subfield as 0. That is, the way in which the Non-AP STA MLD requests an Updated Profile is to set the Complete Profile subfield to 0, and in this case, a separate Updated Profile subfield may not be included in the Per-STA profile.

[0325] FIG. 24 illustrates an example of a format of a Per-STA Profile subelement according to an embodiment of the present invention.

[0326] Referring to FIG. 24(a), a Per-STA profile sub-element may include a STA Control field. The STA Control field (see FIG. 24(b)) indicates information for indicating the type of fields included in the STA profile (see FIG. 24(a)) of the corresponding Per-STA profile sub-element. In this case, in a specific Per-STA profile sub-element transmitted by an AP MLD other than the NSTR AP MLD, if the Complete Profile sub-field of the STA Control field is indicated as 1, 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 described above, since the NSTR AP MLD does not transmit beacon frames to non-primary links, information related to beacon frames of non-primary links may not need to be indicated in the Per-STA profile sub-element corresponding to the non-primary link. That is, a specific Per-STA profile sub-element (corresponding to an AP of a non-primary link) transmitted by the NSTR AP MLD may have the Complete Profile sub-field indicated as 1, but the Beacon Interval Present sub-field and the DTIM Information Present sub-field indicated as 0.

[0327] Also, as described in the above-described embodiment, a non-AP STA MLD transmitting 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 1 in the Updated Profile subfield of the STA Control field (included in the Per-STA Profile subelement corresponding to the non-primary link AP). In this case, the non-AP STA MLD can specify a Recorded Change Sequence value, which is information related to the time when the non-AP STA MLD updated the non-primary link AP information, using the Recorded Change Sequence subfield (see FIG. 24(c)). In this case, the Recorded Change Sequence subfield may be a subfield included in the STA profile. After receiving an ML probe request frame of the non-AP STA MLD received via the primary link, the NSTR AP MLD can determine information of the non-primary link AP responding 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 Change Sequence value of the current non-primary link AP.

[0328] FIG. 25 illustrates an example of a process in which a non-AP MLD set up with an NSTR (Non-Simultaneous Transmission and Reception) Soft AP MLD updates information about a non-primary link according to an embodiment of the present invention.

[0329] 25, after changing the parameters of AP2 operating on Link 2, which is a non-primary link, the NSTR AP MLD may indicate that the parameters of AP2 have been changed using a beacon frame transmitted by AP1 operating on Link 1, which is a primary link. In this case, the information that the parameters of AP2 have been changed may be indicated by indicating that the Change Sequence subfield value corresponding to AP2 in the RNR element included in the beacon frame transmitted by AP1 is increased by 1 from the value indicated in the immediately preceding beacon frame.

[0330] After receiving the beacon frame sent by AP1 through STA1, the non-AP STA MLD can recognize that the parameters of AP2 have been updated. The non-AP STA MLD can send an ML probe request frame through STA1 to obtain the changed parameter information of AP2.

[0331] The ML probe request frame transmitted by the non-AP STA MLD via STA1 may have a configuration in which a Per-STA profile sub-element corresponding to AP2 is included in the ML element, and the Per-STA profile sub-element may include an indicator indicating whether a complete profile or an updated profile is 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 an ML probe response frame.

[0333] The non-AP STA MLD receives the requested AP2 information in an ML probe response frame from the NSTR AP MLD, and can complete the parameter update for the non-primary link to which the beacon frame is not transmitted by updating the parameters for AP2.

[0334] <Broadcast ML Probe Response>

[0335] According to one embodiment of the present invention, the NSTR AP MLD may transmit a broadcast ML probe response frame over the primary link when information related to an AP operating over a non-primary link is changed. When the non-AP STA MLD receives a broadcast ML probe response frame transmitted by the NSTR AP MLD over the primary link, it may need to update information related to the non-primary link (AP). In this case, the broadcast ML probe response frame may not be transmitted in response to an ML probe request frame transmitted by a specific STA, but may be an ML probe request frame transmitted by the NSTR AP MLD without a separate request.

[0336] The broadcast ML probe response frame includes a Per-STA profile subelement corresponding to the AP of the non-primary link and serves to help the non-AP STA MLD update changed parameters and elements of the non-primary link. Since the (Recorded) Change Sequence of the non-primary link maintained by each non-AP STA may be different from each other, the broadcast ML probe response frame may include complete information for the AP of the non-primary link. In this case, the broadcast ML probe response frame may be transmitted together with a 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 of the non-primary link is different from the Change Sequence it maintains (recorded).

[0338] In this case, the parameter update procedure for the non-primary link using the above-mentioned broadcast ML probe response frame may be performed using a broadcast ML association response frame. In this case, the method of configuring the Per-STA profile sub-element of the broadcast ML association response frame and the procedure of updating the MLD of the receiving STA are the same as the embodiment of the above-mentioned broadcast ML probe response frame, and detailed description thereof will be omitted.

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

[0340] After receiving a beacon frame over the primary link, the non-AP STA MLD checks the non-primary link Change Sequence (in the MLD Parameter field of the RNR element). If the checked non-primary link Change Sequence value differs from the Change Sequence value it maintains (recorded), the non-AP STA MLD can transmit an ML probe request frame over the primary link. In this case, the ML probe request frame may include a subfield indicating whether to request complete information or updated information from the AP of the non-primary link. In addition, an ML probe request frame requesting updated information may also include a subfield indicating the Change Sequence value it maintains (recorded). Thereafter, the non-AP STA MLD that receives an ML probe response frame from the AP MLD updates its parameters based on the non-primary link AP information included in the received ML probe response frame.

[0341] <Time synchronization management for non-primary links>

[0342] As mentioned above, the beacon frame transmitted by the AP not only conveys various parameters and element information but also helps STAs in the BSS to achieve time synchronization. The TimeStamp field included in the beacon frame indicates the timing synchronization function (TSF) timer value at the time when the data symbol containing the first bit of the TimeStamp field appears at the transmit antenna connector. STAs that receive the TimeStamp field can synchronize their own TSF timer with the AP based on the received TimeStamp field value.

[0343] In this way, the AP and STA can operate while maintaining time synchronization based on the TimeStamp value included in the beacon frame, and perform timing-based operations. However, NSTR AP MLD cannot transmit beacon frames on non-primary links, so among STAs in Non-AP STA MLD, STAs associated with a non-primary link AP in NSTR AP MLD must use a method other than beacon frames to maintain time synchronization with the AP.

[0344] To maintain time synchronization with the AP of the non-primary link of the NSTR AP MLD, associated non-AP STAs may need to use the TimeStamp in the TIM frame transmitted by the AP. Because the TIM frame includes a TimeStamp field with the same function as a beacon frame, STAs receiving a TIM frame from an AP of the non-primary link of the NSTR AP MLD may need to manage the TFS timer using the TimeStamp field included in the TIM frame. However, because the NSTR AP MLD may be restricted from starting transmission on a non-primary link without occupying the primary link, it may be necessary to simultaneously transmit a TIM frame on the non-primary link when transmitting a beacon frame on the primary link. In other words, non-AP STA MLDs associated with the 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 in each link for multiple APs included in the NSTR AP MLD, and the TSF timer used at this time may be the TSF timer of the primary link. That is, when the AP MLD is an NSTR AP MLD, links (non-primary links) for APs affiliated with the NSTR AP MLD can use the TSF timer of the primary link.

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

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

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

[0349] In addition, when a non-AP STA MLD combined with an NSTR AP MLD receives a TIM frame over a non-primary link, it may need to receive the next beacon frame transmitted over the primary link. More specifically, when a non-AP STA MLD receives a TIM frame through a non-primary link STA and the value indicated in the Check Beacon field in the TIM frame action field is different from the Check Beacon value it maintains, it may need to receive the next beacon frame transmitted over the primary link. In this case, the next beacon frame may refer to a beacon frame transmitted corresponding to the TBTT of the primary link that exists after the time the TIM frame was received over the non-primary link. In this case, receiving the next beacon frame may involve (include) updating parameters of the non-primary link using the Per-STA profile (corresponding to the AP of the non-primary link) included in the beacon frame. In this case, the parameters to be updated may be limited to parameters associated with a critical update.

[0350] <Channel Switching and Channel Quieting Procedures for Non-Primary Links>

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

[0352] Conventional Wi-Fi can change the operating channel frequency (operating frequency band) of a BSS through a procedure previously agreed upon between the AP and STA. This can be achieved using the conventional Extended Channel Switching (ECS) operation or the newly defined channel change mechanism in 11be. When an AP decides to change the operating channel of a BSS, it transmits a beacon frame, probe response frame, Extended Channel Switch Announcement frame, etc. to inform associated STAs that they can switch to a new channel and operating class while maintaining their association. In this case, the AP transmits an Extended Channel Switch Announce element in a beacon frame, and the Channel Switch Count field of the element indicates information about the number of subsequent beacon frame transmissions required before a channel switch (operating channel change) occurs. If the AP includes a MAX Channel Switch Time element in a beacon frame along with an Extended Channel Switch Announcement element, the AP must transmit the first beacon frame on the new channel within the Switch Time field (of the Max Channel Switch Time element). That is, the beacon frame transmitted on the new channel must be transmitted at a time interval that is smaller than the time interval indicated by the Switch Time field from the last beacon frame transmitted on the current channel.

[0353] Referring to the channel change operation of the conventional Wi-Fi BSS described above, the AP of the BSS can use a beacon frame transmitted on the current channel to indicate to the STA information about the new channel, information about 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 association with the AP by moving to the new channel during a predetermined time interval (the time interval indicated by the AP) based on the channel change-related information included in the beacon frame transmitted by the AP. As such, the channel change procedure of the conventional Wi-Fi BSS is performed in a manner in which information required for the channel change (e.g., channel switch mode, new operating class, new channel number, channel switch count) is provided by the beacon frame transmitted by the AP. Therefore, in the case of a BSS of a non-primary link of an NSTR AP MLD in which beacon frames are not transmitted, a channel change cannot be performed using the conventional channel change procedure.

[0354] In addition, when conventional Wi-Fi sets a quiet interval, information regarding the time period to which the quiet interval applies is indicated by elements (quiet element, quiet channel element) included in the beacon frame transmitted by the AP of the BSS, and similar to the channel change procedure, the non-primary link of the NSTR AP MLD, which does not transmit a beacon frame, cannot use the conventional quieting procedure to set the quiet interval.

[0355] According to one embodiment of the present invention, the NSTR AP MLD can indicate information required for changing the operating channel of the non-primary link (channel switching) and / or information required for setting the quiet interval through a beacon frame transmitted through the primary link. That is, the non-AP STA MLD associated with the NSTR AP MLD can operate based on information obtained through a beacon frame of the primary link to perform channel switching of the non-primary link. That is, the non-AP STA MLD associated with the NSTR AP MLD can obtain information related to the quiet interval of the non-primary link using a beacon frame of the primary link.

[0356] More specifically, the NSTR AP MLD may need to include a Per-STA profile for the non-primary link AP in the primary link beacon frame (and (ML) probe response frame) when changing channels or setting a quiet interval for the non-primary link.

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

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

[0359] The timing field of the element may need to be set based on the target beacon transmission time (TBTT) and beacon interval of the primary link.

[0360] The AP of the primary link of the 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 AP of the non-primary link based on its own beacon interval and TBTT. Here, the timing fields are used to collectively refer to time-related fields including duration-related fields (e.g., Switch Time, Quiet Duration fields) and time-point-related fields (e.g., Channel Switch Count, Quiet Count fields).

[0361] Therefore, the non-AP MLD combined with the NSTR AP MLD may receive a beacon frame from the AP of the NSTR AP MLD operating on the primary link, acquire information related to a channel change and / or a quiet interval of the non-primary link from the Per-STA profile included in the beacon frame, and then analyze the information related to a channel change and / or a quiet interval of the non-primary link based on the TBTT and Beacon interval (BI) of the primary link. Here, the Per-STA profile refers to a Per-STA profile corresponding to the AP of the non-primary link.

[0362] Meanwhile, after completing a channel change of a non-primary link using a beacon frame of the primary link (after announcement and completion of the channel change), the NSTR AP MLD may need to transmit a TIM frame (of the non-primary link) on a new channel within the time indicated by the Switch Time field (Max Channel Switch Time element). That is, after performing a channel change, the non-primary link AP of the NSTR AP MLD may need to transmit a TIM frame on a new channel. In this case, the non-primary link AP may need to transmit a TIM frame on a new channel within the time indicated by the Switch Time field after a beacon frame with a Channel Switch Count subfield set to 1 (or 0) is transmitted on the primary link. In this case, the Channel Switch Count field and the Switch Time field may be included in a Per-STA profile (corresponding to a non-primary AP) included in a beacon frame transmitted on the primary link. In this case, the TIM frame may be replaced with another frame transmitted on a new channel of the primary link or non-primary link. For example, after completing a channel change for a non-primary link, the NSTR AP MLD may transmit a beacon frame indicating information related to the completion of the channel change for the primary link. In this case, the beacon frame may be an additional beacon frame transmitted regardless of the TBTT. In this case, the beacon frame may be a beacon frame configured to include complete information for the non-primary link. For example, the beacon frame configured to include 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 of 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 from the beacon frame transmitted before the channel change began. In this case, the predetermined time may be the time indicated in the Switch Time field (of the Max Channel Switch Time element). Alternatively, the beacon frame may be a beacon frame including an indication related to the channel change of the non-primary link. For example, the primary link beacon frame transmitted after the channel change of the non-primary link is completed may include a Channel Switch Complete subfield. In this case, the Channel Switch Complete subfield may be a subfield included in the ML element. A specific Switch Complete subfield may be indicated as 1 when the channel change of the AP corresponding to the Per-STA profile including the specific subfield is completed. That is, after completing the channel change of the non-primary link, the AP may need to set the Channel Switch Complete subfield of the Per-STA profile (of the beacon frame) corresponding to the non-primary link AP to 1. In this case, the beacon frame related to the channel change may be transmitted (utilized) for the same purpose even if the AP MLD is not the NSTR AP MLD, that is, by the general AP MLD.

[0363] The non-AP MLD combined with the NSTR AP MLD can perform operations that consider the channel change of the non-primary link to be complete only when it receives a promised frame (a TIM frame or other frame of the non-primary link and / or a beacon frame indicating information related to the completion of the channel change of the primary link) from the AP MLD after performing a channel change of the non-primary link on the primary link. If it is determined that the channel change is not complete, the non-AP STA MLD may need to consider the channel change of the non-primary link to be canceled and operate (return to) the previous channel (before the channel change was performed).

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

[0365] In addition, the NSTR AP MLD cannot change the channel of a non-primary link. However, when the NSTR AP MLD attempts to change the channel of a non-primary link, it can perform the same operation as removing the non-primary link AP operating on the existing channel and adding a new non-primary link AP on the new channel.

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

[0367] 1. The Quiet Count field may be set to the number of TBTTs remaining on the primary link before the next quiet interval begins on the non-primary link.

[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 every (set to 0 if not a regular quiet interval).

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

[0370] The (Extended) Channel Switch Announcement element and Max Channel Switch Time element for the non-primary link transmitted in the beacon frame of the primary link may be set (instructed) by the 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 the number of remaining TBTTs of the primary link until a channel change of the non-primary link begins. If a channel change of the AP of the non-primary link begins in the next TBTT of the primary link, the beacon frame transmitted in this TBTT may have the Channel Switch Count field (associated with the AP of the non-primary link) set to 1 or 0.

[0372] 2. The Switch Time field (of the Max Channel Switch Time element) may be set to a value corresponding to the maximum time difference between the primary beacon frame (a beacon frame with the Channel Switch Count field set to 1 or 0 in 1 above) transmitted in the TBTT immediately before the TBTT at which the non-primary link channel change began and the TIM frame transmitted on the new channel of the non-primary link after the channel change of the non-primary link is completed. For example, if the beacon interval of the primary link is 100 ms and the Switch Time field (for the non-primary link AP) is set to 200 ms, the non-primary link AP must transmit a TIM frame on the new channel within 200 ms from the time of transmitting the primary link beacon frame at which it began the channel change.

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

[0374] Conventionally, Wi-Fi non-AP STAs can choose whether to change channels together with the AP to maintain association when the AP changes channels. However, a non-AP STA MLD associated with an NSTR AP MLD may need to change the channel of the non-primary link whenever the NSTR AP MLD changes channels on the non-primary link.

[0375] If a non-AP STA MLD that has performed ML setup with the NSTR AP MLD (i.e., 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 it to a state set up only on the primary link (by setting up or resetting after termination).

[0376] FIG. 28 illustrates an example of a process in which an NSTR Soft AP MLD sets (defines) a quiet interval for a non-primary according to an embodiment of the present invention.

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

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

[0379] The 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 (announced by the AP MLD) on the non-primary link by checking the Quiet element included in the Per-STA profile (corresponding to AP2) of the beacon frame, and that the quiet interval (Quiet interval #1 in Figure 28) begins when "x" TUs have elapsed since the TBTT corresponding to the third beacon frame.

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

[0381] When a non-AP STA MLD receives the sixth and / or seventh beacon frame on the primary link, it checks the Quiet element included in the Per-STA profile (corresponding to AP2) of the beacon frame and recognizes that a quiet interval (Quiet interval #2) has been set (announced by the AP MLD) on the non-primary link and that the quiet interval (Quiet interval #2) begins from the TBTT corresponding to the eighth beacon frame.

[0382] At this time, information regarding the length of the quiet interval is indicated in the Quiet Duration field indicated together with the Quiet element.

[0383] FIG. 29 illustrates an example of a method for an NSTR Soft AP MLD to perform a non-primary channel switch according to an embodiment of the present invention.

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

[0385] To change the non-primary link to a new channel, the NSTR AP MLD can include a Per-STA profile corresponding to AP2 (non-primary link) in a beacon frame transmitted via AP1 of the primary link. The Per-STA profile corresponding to AP2 includes an (Extended) Channel Switch Announcement element and a Max Channel Switch Time element, indicating information related to the time when a channel change begins and the time duration for transmitting a TIM frame 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 (Beacon #1 in FIG. 19) shown in FIG. 19, the Channel Switch Count field is set to 2, and in the second beacon frame (Beacon #2 in FIG. 19) it is set to 1.

[0386] A non-AP STA MLD that receives the first and / or second beacon frame on the primary link can determine by checking the (Extended) Channel Switch Announcement element included in the Per-STA profile (corresponding to AP2) of the beacon frame that a channel change (to a new channel) of the non-primary link begins after receiving the second beacon frame and that AP2's TIM frame will be received on the new channel within "x" TUs from the time the second beacon frame is 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, the "x" TUs 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 Limitations 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 enter the BLIND state. Conversely, when the AP of the non-primary link transmits, the AP of the primary link may enter the BLIND state. In this case, the AP of the NSTR AP MLD that has passed through the BLIND state may need to set the MediumSyncDelay to a pre-set 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 constraints may be applied when the STA acquires a TXOP. At this time, the additional constraints may be: (1) the first transmission attempt to obtain a TXOP must be an RTS frame; (2) only attempts to acquire a TXOP a pre-set number of times or less (until it decreases to 0) are allowed while MediumSyncDelay is applied; (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 MediumSyncDelay value has more constraints applied in TXOP acquisition compared to a STA with MediumSyncDelay equal to 0.

[0390] Therefore, even in the case of NSTR AP MLD, MediumSyncDelay must be applied when the AP enters a BLIND state, and in situations where AP channel access is restricted, it may be difficult to provide normal service to STAs in the BSS. The NSTR AP MLD determines one of the links of the NSTR link pair for which the AP operates as the primary link, thereby managing transmissions over non-primary links (links other than the primary link) in a manner that prevents the primary link from entering a BLIND state. For example, the NSTR AP MLD can manage the primary link from entering a BLIND state by transmitting over the non-primary link only when a transmission over the primary link is in progress. For this purpose, even if the NSTR AP MLD receives a frame requesting a response frame via the AP of the non-primary link, it does not need to respond with the requested response frame. In other words, the NSTR AP MLD can operate not to respond with a response frame even if it receives a frame requesting a response frame via the AP of the non-primary link. At this time, the reason why the NSTR AP MLD does not respond with a response frame via the AP of the non-primary link may be to prevent the AP of 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 link and / or non-primary links to establish a primary link and prevent the AP on the primary link from entering a BLIND state. Similarly, a non-AP STA MLD combined with the NSTR AP MLD may need to understand and operate according to the primary link management method of the NSTR AP MLD. For example, if the non-AP STA MLD determines that a response frame has not been received from the NSTR AP MLD on the non-primary link, it may not transmit a frame requesting a response on the non-primary link. Furthermore, if the non-AP STA MLD transmits a frame requesting a response on the non-primary link and then fails to receive a response from the NSTR AP MLD, it may not retransmit the frame requesting a response. For example, if the non-AP STA MLD transmits an RTS frame to the NSTR AP MLD on the non-primary link and fails to receive a CTS frame response, it may not retransmit the RTS frame. In this case, the Non-AP MLD does not need to attempt transmission to the NSTR AP MLD via the non-primary link until it receives a trigger frame via the non-primary link.

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

[0393] A non-AP STA MLD that has completed the channel access procedure on both the primary link and the non-primary link using the above method can perform simultaneous transmission (simultaneous UL PPDU transmission) on the primary link and the non-primary link. Here, "simultaneous transmission" means that the start times of each transmission are 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 can start simultaneous transmission when the channel access procedure on the non-primary link is completed. That is, when transmitting to an NSTR AP MLD, the non-AP MLD can transmit using only the primary link, or can perform simultaneous transmission using the primary link and the non-primary link. However, a non-AP MLD may not be allowed to transmit PPDUs to an NSTR AP MLD using only the non-primary link.

[0394] In addition, non-AP MLD may require NSTR AP MLD to synchronize the end points of transmissions on both links when performing UL transmissions using both the primary link and the non-primary link. In this case, synchronizing the end points of transmissions may mean that transmissions on both links end within a predetermined time interval.

[0395] In addition, when NSTR AP MLD performs UL transmission using both the primary link and the non-primary link, the non-AP MLD may need to set whether the PPDUs transmitted on both links request a response frame. Furthermore, two UL PPDUs simultaneously transmitted by non-AP MLD on the primary link and the non-primary link may require both to request a response frame, or both to request a response frame. This restriction applies because if a response frame is only sent on a specific link as a result of UL transmission by non-AP MLD using both the primary link and the non-primary link, the AP operating on the other link of the NSTR AP MLD may enter a BLIND state. However, NSTR AP MLD does not need to send a response frame for both PPDUs if only one of two PPDUs received simultaneously (received on the primary link and the non-primary link, respectively) requests a response frame.

[0396] In addition, non-AP MLD may need to configure NSTR AP MLD so that when transmission is performed using both the primary link and the non-primary link, the TXOP of the non-primary link terminates at the same time as or earlier than the TXOP of the primary link. In other words, non-AP MLD may need to configure so that the TXOP of the non-primary link terminates at the same time as or earlier than the TXOP of the primary link. However, the non-primary link TXOP of the non-AP STA MLD may be allowed to terminate later than the TXOP of the primary link by a predetermined time interval.

[0397] In addition, the non-AP STA MLD can recognize that the NSTR AP MLD has experienced a BLIND state for an AP of a specific link and assist the AP in its operation. Furthermore, when the non-AP STA MLD recognizes that transmission has occurred on only one of the primary and non-primary links, it can determine that the AP of the other link that did not transmit must have experienced a BLIND state. In this case, the non-AP STA MLD can assist the AP in releasing the MediumSyncDelay (resetting it to 0) in consideration of the fact that the AP experiencing the BLIND state is restricted in channel access due to a non-zero MediumSyncDelay. In this case, the operation performed by the non-AP STA MLD may utilize the characteristic that MediumSyncDelay can be released when a NAV-configurable PPDU (including a valid MPDU) is received.

[0398] For example, after passing through the BLIND state, the non-AP STA MLD may transmit an Assist frame (a type of PPDU) capable of NAV setting to the AP of the NSTR AP MLD that is determined to have a non-zero MediumSyncDelay. Here, the Assist frame may refer to a frame included in a valid MPDU capable of NAV setting, regardless of the frame format. The condition under which the non-AP STA MLD transmits an Assist frame to the NSTR AP MLD over a specific link may be limited to when the state of the specific link confirmed by the non-AP STA MLD is in an IDLE state. Another condition under which the non-AP STA MLD transmits an Assist frame to the 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 transmit an Assist frame.

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

[0400] Wi-Fi prior to 6-generation Wi-Fi supported operation at 2.4GHz and 5GHz, and the 6GHz band, which was recently incorporated into the ISM band, is the Wi-Fi frequency band (unlicensed band) that HE devices (AP STA, non-AP STA) first began using. The IEEE 802.11ax Task Group (TG), which promoted standardization for HE devices, took into account the lack of conventional Wi-Fi devices (devices prior to 6th generation Wi-Fi) operating in the 6GHz band and specified that HE STA (AP STA, non-AP STA) operating in the 6GHz band will not be backward compatible with previous generation Wi-Fi devices. More specifically, the standard specifies that HE STAs operating at 6 GHz should not transmit HE operation elements, including HT Capabilities element, VHT Capabilities element, HT Operation element, VHT Operation element, and / or VHT Operation Information field, thereby eliminating support for terminals prior to 6-home Wi-Fi and reducing overhead by reducing the information contained in beacon frames, etc.

[0401] That is, APs and / or non-AP STAs operating in a particular band (e.g., the 6 GHz band) cannot transmit legacy format capability elements and / or operation elements (e.g., HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, and / or HE operation elements including VHT operation 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 factors for 2.4 GHz / 5 GHz, such as an HT capability factor, a VHT capability factor, an HT operation factor, and / or a VHT operation factor, the AP and / or non-AP STA can transmit information about other APs and / or non-AP STAs included in the same MLD in addition to information about itself. In this case, the information about other APs and / or non-AP STAs may include capability factors and operation factors for bands other than the specific band (e.g., 2.4 GHz / 5 GHz). In other words, the AP and / or non-AP STA can transmit capability factors and / or operation information for bands in which each of the multiple STAs operates, but cannot transmit capability factors and / or operation information for bands in which each of the multiple STAs does not operate.

[0403] That is, beacon frames transmitted by HE APs operating in 6 GHz and association request frames transmitted by non-AP STAs setting up in 6 GHz do not include capability and operation information when operating as HT and VHT STAs (APs and non-AP STAs). HE STAs operating in 6 GHz do not need to operate as HT / VHT STAs because there are no other HT / VHT STAs operating in the 6 GHz band. Therefore, the capability and operation information for HT / VHT STA operation described above may be unnecessary. For this reason, the 11ax standard restricts HE STAs (AP STAs and non-AP STAs) operating in 6 GHz from transmitting HE operation elements, including the HT capability element, VHT capability element, HT operation element, VHT operation element, and VHT operation information field. The same restriction may also apply to EHT STAs (MLD) that inherit the operation of HE STAs.

[0404] In other words, a STA operating in the 6 GHz band cannot transmit an HT Capability element, a VHT Capability element, an HT Operation element, a VHT Operation element, or an HE Operation element that includes a VHT Operation Information field. That is, a STA operating in the 6 GHz band does not have to transmit a Capability / Operation element in a specific legacy format to provide parameters for its capabilities and operation.

[0405] However, in this case, the STA operating at 6 GHz may transmit a Basic Multi-Link element containing information about other STAs. In this case, the Basic Multi-Link element may include a STA Profile field containing capability elements and / or operation elements for the other STAs reported by the STA operating at 6 GHz. The STA reported by the STA operating at 6 GHz may operate in the 2.4 GHz or 5 GHz 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 above-described embodiment of the present invention, an EHT STA in an MLD must perform ML setup by transmitting not only information about itself but also information about other STAs (operating on other links) in the same MLD in a beacon frame and an (ML) probe response frame, an association request frame, and / or an association response frame. In other words, an AP operating in 6 GHz among APs in an AP MLD must indicate the HT / VHT capability / operation elements of the 2.4 GHz and 5 GHz APs in an (ML) probe response frame or association response frame to provide information about other APs operating in 2.4 GHz and 5 GHz. Therefore, the restriction in 11ax that 6 GHz STAs (AP STAs, non-AP STAs) cannot indicate HT / VHT-related elements needs to be amended. In this case, an (ML) probe response frame can refer to a response frame transmitted in response to an ML probe request frame.

[0407] In the description of the present invention given below, APs operating at 2.4 GHz, 5 GHz, and 6 GHz will be referred to as 2.4 GHz AP, 5 GHz AP, and 6 GHz AP, respectively, and STAs performing (attempting) ML setup at 2.4 GHz, 5 GHz, and 6 GHz will be referred to as 2.4 GHz STA, 5 GHz STA, and 6 GHz STA (non-AP STA), respectively.

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

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

[0410] More specifically, the (re)association response frame sent by a 6 GHz AP in an EHT AP MLD to perform (accept) ML setup with 2.4 GHz and / or 5 GHz APs may include HT / VHT capability / operation elements.

[0411] Similarly, a (re)association request frame sent by a 6 GHz STA in EHT non-AP MLD to perform (request, solicit) ML setup involving 2.4 GHz and / or 5 GHz STAs may include HT / VHT capability / operation elements.

[0412] That is, a 6 GHz STA (in an MLD) can transmit a (re)association request frame with HT / VHT capability / operation elements only if it is attempting an ML setup involving 2.4 GHz and / or 5 GHz STAs in the same MLD.

[0413] In other words, a 6 GHz AP (in an MLD) can send HT / VHT capability / operation elements in a re-association response frame only if it is performing an ML setup involving 2.4 GHz and / or 5 GHz APs in the same MLD.

[0414] For example, APs or non-AP STAs that make up an MLD can each operate in various bands (6 GHz, 2.4 GHz, or 5 GHz). In this case, an MLD (first MLD) including non-AP STAs can transmit and receive frames to set up multiple links with an MLD (second MLD) including an AP. In this case, a STA (first STA) operating at 6 GHz included in the first MLD can transmit an association request frame (or reassociation request frame) to set up multiple links, and an AP (first AP) operating at 6 GHz included in the second MLD can transmit an association response frame (or reassociation response frame) in response to the association request frame (or reassociation request frame).

[0415] The first STA can transmit an association request message including information about itself and information about other STAs included in the same MLD (for example, multilink information (or elements)).

[0416] The information about the first STA included in the association request message may be information about 6 GHz (e.g., HE capability information, HE operation information, EHT capability information, and / or EHT operation information). However, the association request message does not include information about the first STA about bands other than the 6 GHz band (e.g., 2.4 GHz or 5 GHz) (e.g., an HT capability element, a VHT capability element, an HT operation element, a VHT operation element, or an HE operation element including a VHT operation information field). That is, the first STA cannot transmit information about bands other than the band in which it operates.

[0417] The information about the other STAs included in the association request message (e.g., multilink information (or elements)) may include information about the band (e.g., 2.4 GHz or 5 GHz) in which each of the other STAs operates (e.g., an HT capability element, a VHT capability element, an HT operation element, a VHT operation element, or an HE operation element including a VHT operation information field).

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

[0419] In addition, the multi-link information (or multi-link element) of the association request message may include a multi-link element including per-STA profile sub-elements corresponding to each of the reported STAs, and the per-STA profile sub-element may include a complete profile sub-field indicating whether the request is for all information for the corresponding station among at least one reported station.

[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 includes complete information of the STA.

[0421] The first AP can transmit an association response message including information about itself and information about other APs included in the same MLD (for example, multilink information (or elements)).

[0422] The information about the first AP included in the association response message may be information about 6 GHz (e.g., HE capability information, HE operation information, EHT capability information, and / or EHT operation information). However, the association response message does not include information about the first AP about bands other than the 6 GHz band (e.g., 2.4 GHz or 5 GHz) (e.g., an HT capability element, a VHT capability element, an HT operation element, a VHT operation element, or an HE operation element including a VHT operation information field). That is, the first AP cannot transmit information about bands other than the band in which it operates.

[0423] The information about other APs included in the association request message (e.g., multilink information (or elements)) may include information about the band (e.g., 2.4 GHz or 5 GHz) in which each of the other STAs operates (e.g., an HT capability element, a VHT capability element, an HT operation element, a VHT operation element, or an HE operation element including a VHT operation information field).

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

[0425] A more specific condition for the 6 GHz AP to send (respond) an ML probe response frame including an HT / VHT capability element and / or an HT / VHT operation element may be that the received ML probe request frame includes a multilink element and requests complete information or HE / VHT capability / operation element information from the 2.4 GHz and / or 5 GHz AP.

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

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

[0428] That is, although the 6 GHz band operating regulations restrict 6 GHz APs from transmitting HT / VHT-related elements, a 6 GHz AP that is an AP MLD STA can transmit (ML) probe response frames containing HT / VHT-related elements in the 6 GHz band in order to indicate complete information to the 2.4 GHz AP and the 5 GHz AP.

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

[0430] A 6 GHz STA may transmit a (re)association request frame including HT / VHT related elements if it intends to perform ML setup simultaneously in 6 GHz and 2.4 / 5 GHz using the (re)association request frame transmitted in 6 GHz.

[0431] The 6 GHz AP may transmit a (re)association response frame including HT / VHT related elements only if a non-AP STA has transmitted a (re)association request frame in the 6 GHz band, has accepted the non-AP STA's ML setup request, and intends to set up in 2.4 GHz and / or 5 GHz as well.

[0432] Another possible method is to restrict the inclusion of HT / VHT capability / operation elements in frames transmitted by 6 GHz STAs (AP STAs, non-AP STAs) in the 6 GHz band.

[0433] In this case, the 6 GHz AP may not include the HT / VHT capability / operation element when transmitting an ML probe response frame containing information (Per-STA Profile) about the 2.4 GHz and / or 5 GHz AP and an ML association response frame accepting the setup of the 2.4 GHz and / or 5 GHz AP. Therefore, a non-AP MLD attempting to perform ML setup including 2.4 GHz and 5 GHz via the 6 GHz AP may need to send an ML probe request frame to the 2.4 GHz AP or 5 GHz AP to obtain additional information about the 2.4 GHz and / or 5 GHz AP (included in the HT / VHT related element).

[0434] Considering the limitation that HT / VHT-related elements cannot be transmitted / obtained in 6 GHz, a non-AP EHT MLD intending to transmit an ML association request frame to a 6 GHz AP may need to receive an ML probe response frame containing complete information (or HT / VHT-related elements) of the AP to be set up in 2.4 GHz or 5 GHz in advance. In other words, a non-AP EHT MLD intending to transmit an ML association request frame to a 6 GHz AP to perform ML setup simultaneously with a 2.4 GHz and / or 5 GHz AP may need to transmit an ML probe request frame in 2.4 GHz or 5 GHz and obtain complete information (or HT / VHT-related elements) for the 2.4 GHz and / or 5 GHz AP before or after completing the setup.

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

[0436] FIG. 31 illustrates an example of a method for establishing 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 an embodiment of the present invention.

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

[0438] In this case, the non-AP MLD may intend to attempt ML setup including the 2.4 GHz AP and the 5 GHz AP, and to do so, may transmit an ML probe request frame to the 5 GHz AP in 5 GHz before transmitting an association request frame in 6 GHz. In this case, the ML probe request frame transmitted by the non-AP MLD in the 5 GHz band may be an ML probe request frame requesting complete information (or HT / VHT-related elements) for the 2.4 GHz AP and the 5 GHz AP among the APs attempting ML setup.

[0439] A non-AP MLD that receives an ML probe response frame from the 5 GHz AP can transmit an association request frame to the 6 GHz AP via the 6 GHz STA to request ML setup, including 2.4 GHz and 5 GHz. While complete information for the STA of the link requesting ML setup should generally be included in the association request frame, an association request frame transmitted by the 6 GHz STA may not include HT / VHT capability / operation elements for the 2.4 GHz and 5 GHz STAs. Similarly, an association response frame transmitted (responding) to accept setup for 2.4 GHz and / or 5 GHz should generally include complete information for the AP of the link accepting ML setup, but an association response frame transmitted by the 6 GHz AP may not include HT / VHT capability / operation elements for the 2.4 GHz and 5 GHz APs.

[0440] In this way, a non-AP MLD that has set up with an AP MLD in 2.4 GHz and / or 5 GHz using an association request / response frame that does not include HT / VHT elements for 2.4 / 5 GHz can use the first PPDU it transmits after receiving the association response frame to transmit the HT / VHT capability / operation elements for the 2.4 / 5 GHz STA with which it has set up to the AP MLD.

[0441] <Management frame configuration 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 operate on different links. Therefore, some elements of a STA (reporting STA) that transmits management frames (beacons, (ML) Probe Req / Resp, (ML) Association Req / Resp frames, etc.) may contain the same information as some elements of other STAs (reported STAs) within the MLD.

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

[0444] Therefore, a management frame including complete information for other STAs in the MLD in a Per-STA profile sub-element may omit a reporting STA element that includes the same information as the reporting STA element. That is, in a management frame including complete information for a specific STA (reported STA), if some elements are not specified in the Per-STA profile sub-element corresponding to the specific STA, the unspecified elements may be interpreted as inheritance of the same elements (the same elements as the some elements) corresponding to the STA (reporting AP) that transmitted the management frame. In this case, a "management frame including complete information for the specific STA (reported STA)" may refer to a management frame including the same level (the same amount) of information as the STA (reporting STA) that transmitted the management frame. In this case, analyzing the Per-STA profile sub-element using the inheritance rule may be performed only if the per-STA profile is a complete profile. In this case, "the Per-STA profile is a complete profile" may mean that the Complete Profile subfield of the Per-STA profile sub-element is indicated as 1.

[0445] In this way, a STA in an MLD can use the inheritance rule to construct a management frame in order to reduce the size of the management frame while still including complete information for other STAs in the MLD. Also, an MLD that receives a management frame from a STA in an MLD can use the inheritance rule to obtain (analyze and recognize) the omitted information of the reported STA.

[0446] In this case, whether or not the management frame includes complete information for each reported STA may be indicated by whether or not the Complete Profile subfield (in the STA Control field) in the Per-STA profile subelement corresponding to each reported STA is set to 1. In other words, the reported STA corresponding to the Per-STA profile for which the Complete Profile subfield is set to 1 may be the STA for which complete information is indicated in the management frame.

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

[0448] There may be cases where a reporting STA transmitting a management frame does not have specific element information. For example, if the reporting STA is a 6 GHz STA (AP STA, non-AP STA), the 6 GHz reporting STA may not have HT / VHT-related elements. In this case, if complete information for the 2.4 GHz and 5 GHz STAs should be included in the management frame, the HT / VHT-related information (HT / VHT capability / operation elements) that should be instructed to the 2.4 GHz and 5 GHz STAs cannot be instructed / analyzed using the inheritance rules. This is because the 6 GHz reporting STA does not have HT / VHT-related information. Therefore, the management frame in which the 6 GHz STA is the reporting STA cannot apply the inheritance rules to elements instructed only to the reported STA. That is, when a management frame transmitted by a 6 GHz STA needs to indicate complete information of multiple 2.4 GHz and 5 GHz STAs, even if the multiple reported STAs (2.4 / 5 GHz STAs) have the same HT / VHT capability / operation element values, each element may need to be repeatedly indicated in the Per-STA profile corresponding to each reported STA. This means that if a reporting STA transmitting a management frame does not include information about a specific element, the use of inheritance rules in the management frame may be limited, which may result in an increase in the size of the management frame.

[0449] Therefore, a new inheritance rule may be necessary to prevent the size of the management frame from increasing due to the limitation that the inheritance rule cannot be applied to elements that are not indicated to the reporting STA.

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

[0451] Furthermore, if a management frame is indicated as including complete information for a specific reported STA, but a specific element corresponding to the specific reported STA is not indicated, the specific element may be considered to have inherited another element rather than the element of the reporting STA. In this case, the condition for considering the specific element as having inherited another element rather than the element of the reporting STA may be that the specific element is not indicated (included) for the reporting STA (in the management frame). In this case, the method of indicating / analyzing that the information of the reported STA inherits another element rather than the element of the reporting STA may be applied only when the reporting STA is a 6 GHz STA.

[0452] According to one embodiment of the present invention, if a specific element of a reported STA for which complete information (profile) is indicated is not indicated in a management frame, it may be considered that the value of the same element (having the same element ID and extended element ID) as the specific element indicated in the management frame is applied (indicated) to the specific element of the reported STA. In this case, the same element inherited as the specific element of the reported STA may not be an element for the reporting STA.

[0453] That is, the same element (having the same element ID and Extended element ID as the specific element) that is inherited as a specific element for a reported STA may not be an element for a reporting STA.

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

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

[0456] However, if the 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, the specific element for the reported STA does not inherit any value and may be considered not to be indicated in the management frame.

[0457] For example, if a specific element for STA1, whose complete information is indicated by the management frame, is not indicated, and there is an identical element indicated for STA2, the value indicated in the identical element may be considered (i.e., inherited) as the same as that indicated in the specific element of STA1. In this case, STA2 may not be the reporting STA.

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

[0459] According to one embodiment of the present invention, if a specific element of a reported STA for which complete information (profile) is indicated is not indicated in a management frame, the value of the same element (having the same element ID and extended element ID) as the specific element indicated in the management frame may be considered to be applied (indicated) to the specific element of the reported STA. In this case, the element inherited as the specific element of the reported STA may be determined according to an inheritance rule.

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

[0461] Furthermore, if a specific element for a reported STA is not indicated in a management frame that should include complete information (profile) for the reported STA, the value of the element that is indicated earliest (in element order) among other elements having the same element ID and Extended element ID as the specific element may be considered to be inherited by the specific element. That is, if an element identical to the specific element is indicated for a reporting STA (the element indicated earliest in order among the same elements), the specific element may be considered to inherit the same element value of the reporting STA.

[0462] As another example of a rule for selecting an inherited element, another element (having the same element ID and Extended element ID as the specific element) that is inherited as a specific element for the reported STA may be determined to be the same element (in element order) that was last indicated in the management frame.

[0463] Furthermore, if a specific element for a reported STA is not specified in a management frame that should include complete information (profile) for the reported STA, the value of the last specified element (in element order) among other elements having the same element ID and Extended element ID as the specific element may be considered to be inherited by the specific element. That is, if the same element as the specific element is previously specified for three STAs, the specific element may be considered to inherit the same element value specified third.

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

[0465] Referring to FIG. 32, the management frame includes four elements for the reporting AP (elements IDA to ID in FIG. 22), and includes an ML IE for indicating complete information of the reporting STA.

[0466] The ML IE (Multi-link element) consists of an element ID subfield, a length subfield, an element ID extension subfield, and two per-STA profile subelements. In this case, the per-STA profile indicated first in the order is the per-STA profile included to indicate complete information (profile) for reported STA1, and the per-STA profile indicated last in the order is the per-STA profile included to indicate complete information (profile) for reported STA2. In other words, the per-STA profile indicated first in the order is the per-STA profile for reported STA1, and the per-STA profile indicated last 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 in the elements for the 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, among the elements for the reporting STA (element IDs A to D), the remaining three elements (element IDs A, B, and D, respectively) excluding the element indicated in the Non-Inheritance element (element ID C) may be considered to be indicated identically for reported STA1. In this case, the values ​​indicated by each of the three elements considered to be indicated identically to the reporting STA are also considered to be identical to the elements for the reporting STA.

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

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

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

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

[0472] <Implicit non-Inheritance rule>

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

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

[0475] In other words, the Non-Inheritance element may be used to resolve ambiguity as to whether a specific element of the reported STA that is not indicated in the management frame has been 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 specified 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)association response frame that includes a 6 GHz AP as a reported STA may already know that the HT / VHT capability / operation elements for the 6 GHz AP cannot be specified in the (re)association response frame. In this case, even if the AP MLD that sends the (re)association response frame does not separately specify the fact that the HT / VHT-related elements are not inherited by the Non-Inheritance element (of the Per-STA profile subelement) corresponding to the 6 GHz AP, the STA MLD does not need to analyze the HT / VHT-related elements for the 6 GHz AP according to the inheritance rules.

[0478] According to one embodiment of the present invention, even if an HT / VHT capability / operation element is not listed in the Non-Inheritance element corresponding to the 6 GHz AP that is the reported STA, the element may not be inherited to the 6 GHz AP. In this case, "not listed in the Non-Inheritance element" may mean either that the Non-Inheritance element is not indicated (included) in the Per-STA profile subelement or that the Non-Inheritance element is not listed.

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

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

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

[0482] Specifically, a first multi-link device (MLD) including a first plurality of stations each operating on a plurality of 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] In this case, the first station and the second station can operate in a specific band (for example, 6 GHz).

[0484] Thereafter, the first station may receive a response frame from the second station in response to the request frame (S3320).

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

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

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

[0488] The capability element and / or operational element of each of the second at least one station is at least one of a HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, a HT operational element, a VHT operational element, or a HE (High Efficiency) operational element including VHT operational information.

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

[0490] The request frame (e.g., an ML probe request frame) may include a Multi-Link element including Per-STA profile subelements corresponding to each of the at least one second station, and the Per-STA profile subelements may include a Complete Profile subfield indicating whether the request is for all information for the corresponding station among the at least one second station.

[0491] If the Complete Profile subfield indicates a request for all the information, the multilink information of the response frame may include a capability element and / or an operation element of the station corresponding to the Complete Profile subfield indicating a request for all the information, among the second at least one station.

[0492] Based on the multilink information, a multilink setup procedure can be performed to set up links between a second MLD and the first at least one station and the second at least one station.

[0493] The request frame (e.g., an association request frame) includes a Multi-Link element including 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 subelement of the Multi-Link element may include a capability element and / or an operation element of a legacy format for a corresponding specific station among the first at least one stations.

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

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

[0496] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed form, and similarly, each component described as a distributed type may be implemented in a combined form.

[0497] The scope of the present invention is indicated by the claims set forth below rather than by the above detailed description, and all modifications and variations derived from the meaning and scope of the claims and their equivalents should be construed as being within the scope of the present invention.

Claims

1. A first multi-link device (MLD) including a first station (STA) and at least one other first STA, each of which operates on a plurality of links, The processor A request frame is transmitted to a second STA included in a second MLD via the first STA included in the first MLD; receiving a response frame from the second STA via the first STA as a response to the request frame; The response frame includes: i) capability parameters and operation parameters of the second STA, excluding capability elements and operation elements of a legacy format for a specific band; and ii) a first multilink element; The first multilink element includes at least one of i) at least one capability element, or ii) at least one operation element for the at least one other second STA operating in at least one other band other than the specific band in which the first STA and the second STA operate.

2. The second MLD includes the second STA and at least one other second STA operating on the plurality of links; The MLD of claim 1 , wherein the first STA and the second STA operate in a specific band.

3. The specific band is 6 GHz, The MLD according to claim 2 , wherein the at least one other band is 2.4 GHz or 5 GHz.

4. The request frame includes a second multi-link element including Per-STA profile subelements corresponding to each of the at least one other second STA; The MLD of claim 2, wherein the Per-STA profile sub-element includes a complete profile sub-field indicating whether the request is for all information for a corresponding STA among the at least one other second STA.

5. An MLD as described in claim 4, wherein each of the at least one other second STA corresponds to the complete profile subfield indicating a request for all of the information among the at least one other second STA when the complete profile subfield indicates a request for all of the information.

6. The MLD of claim 2, wherein each of the at least one capability element and the at least one operation element for the at least one other second STA is at least one of an HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, an HT operation element, a VHT operation element, or an HE (High Efficiency) operation element including a VHT operation information field.

7. The MLD described in claim 1, wherein the processor performs a multi-link setting procedure for setting up the multiple links between the first MLD and the second MLD based on the response frame.

8. When the request frame is an association request frame, the request frame includes a second multi-link element including at least one Per-STA profile subelement corresponding to each of the at least one other first STA; The MLD of claim 7, wherein each of the at least one Per-STA profile sub-element of the second multilink element includes a capability element or an operation element of the legacy format for a corresponding specific STA among the at least one other first STA.

9. The specific STA is a STA that operates in the at least one other band, The MLD of claim 8 , wherein the request frame includes a capability element and an operation element for the at least one other band.

10. The MLD according to claim 1, wherein the response frame is one of an association response frame or a multi-link (ML) probe response frame.

11. A method performed by a first multi-link device (MLD) including a first station (STA) and at least one other first STA, each operating on a plurality of links in a wireless communication system, comprising: The method comprises: transmitting a request frame to a second STA included in a second MLD via the first STA included in the first MLD; and receiving a response frame from the second STA via the first STA as a response to the request frame, The response frame includes: i) capability parameters and operation parameters of the second STA, excluding capability elements and operation elements of a legacy format for a specific band; and ii) a first multilink element; The method includes a step in which the first multilink element includes at least one of i) at least one capability element, or ii) at least one operation element for the at least one other second STA operating in at least one other band other than the specific band in which the first STA and the second STA operate.

12. The second MLD includes the second STA and at least one other second STA operating on the plurality of links; The method of claim 11 , wherein the first STA and the second STA operate in a specific band.

13. The specific band is 6 GHz, The method of claim 12 , wherein the at least one other band is 2.4 GHz or 5 GHz.

14. The request frame includes a second multi-link element including Per-STA profile subelements corresponding to each of the at least one other second STA; The method of claim 12, wherein the Per-STA profile sub-element includes a Complete Profile sub-field indicating whether the request is for all information for a corresponding STA among the at least one other second STA.

15. The method described in claim 14, wherein each of the at least one other second STA corresponds to the complete profile subfield indicating a request for all of the information among the at least one other second STA when the complete profile subfield indicates a request for all of the information.

16. The method of claim 12, wherein each of the at least one capability element and the at least one operation element for the at least one other second STA is at least one of an HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, an HT operation element, a VHT operation element, or an HE (High Efficiency) operation element including a VHT operation information field.

17. The method of claim 11, wherein a multi-link setup procedure is performed to set up the plurality of links between the first MLD and the second MLD based on the response frame.

18. The method of claim 11, wherein the response frame is one of an association response frame or a multi-link (ML) probe response frame.

19. When the request frame is an association request frame, the request frame includes a second multi-link element including at least one Per-STA profile subelement corresponding to each of the at least one other first STA; The method of claim 17, wherein each of the at least one Per-STA profile sub-element of the second multilink element includes a capability element or an operation element of the legacy format for a corresponding specific STA among the at least one other first STA.

20. The specific STA is a STA operating in the at least one other band, 20. The method of claim 19, wherein the request frame includes a capability element and an operation element for the at least one other band.

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