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

Abstract

The present invention discloses a method and device for transmitting and receiving a frame performed by a first multi-link device (MLD) including a plurality of stations each operating on a plurality of links in a wireless communication system. Specifically, the first MLD according to the present invention can transmit 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 the first plurality of stations included in the first multi-link device, and receive a response frame as a response to the request frame from the second station through the first station. In this case, the request frame can include information of other stations included in the first MLD, and the response frame can include information of other stations included in the second MLD.

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 use of mobile devices has become more widespread, wireless LAN technology that can provide them with high-speed wireless Internet services has been attracting attention. Wireless LAN technology is a technology that enables mobile devices such as smartphones, smart pads, laptop PCs, portable multimedia players, embedded devices, etc. to wirelessly connect to the Internet at home, in business, or in specific service areas based on short-distance wireless communication technology.

[0003] Since IEEE (Institute of Electronics Engineers) 802.11 supported the initial wireless LAN technology using the 2.4GHz frequency band, it has put into practical use or is currently developing various technology standards. First, IEEE 802.11b uses the 2.4GHz frequency band and supports a maximum communication speed of 11Mbps. IEEE 802.11a, which was commercialized after IEEE 802.11b, uses the 5GHz frequency band instead of the 2.4GHz band, reducing the impact of interference compared to the significantly more congested 2.4GHz frequency band, and uses OFDM technology to increase communication speeds to a maximum of 54Mbps. 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 satisfies backward compatibility, which has attracted considerable attention, but it also has an advantage over IEEE 802.11a in communication distance.

[0004] IEEE 802.11n is a technical standard established to overcome the communication speed limitations that have been pointed out as a weakness of wireless LAN. The purpose of IEEE 802.11n is to increase the speed and reliability of the network and to extend the operating distance of wireless networks. In detail, IEEE 802.11n supports high throughput (HT) with a data processing speed of up to 540Mbps or more, and is based on MIMO (Multiple Inputs and Multiple Outputs) technology that 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 the use of wireless LANs becomes more widespread and applications using them become more diverse, the need for new wireless LAN systems to support data throughput rates (Very High Throughput, VHT) higher than those supported by IEEE 802.11n is emerging. Among them, IEEE 802.11ac supports wide bandwidth (80MHz~160MHz) at 5GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5GHz band, it is expected that initial 11ac chipsets will also support operation in the 2.4GHz band for backward compatibility with existing 2.4GHz band products. Theoretically, this standard allows multi-station wireless LAN speeds of at least 1Gbps and maximum single link speeds of at least 500Mbps. This is done by extending the air interface concepts accepted by 802.11n, such as wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high density modulation (up to 256QAM). Also, 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, and is suitable for streaming large amounts of data and high bitrate videos such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage that it is 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 in the final stages as the WLAN standard after 802.11ac and 802.11ad 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, it is necessary to provide high-frequency efficient communication indoors / outdoors in the presence of high density stations and APs (Access Points), and various technologies are being developed to realize this.

[0007] In addition, new WLAN standards have begun to be developed to increase maximum transmission speeds to support new multimedia applications such as high-definition video and real-time games. IEEE 802.11be (Extremely High Throughput, EHT), the 7th 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 multiple 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 problem to be achieved in the specification is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill 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 each operating on a plurality of links includes a processor, the processor 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, the first station and the second station operate in a specific band, and receives a response frame from the second station via the first station as a response to the request frame, the second station transmits 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 another band, and the response frame includes multi-link information for association between at least a first station among the first plurality of stations excluding the first station and at least a second station among the second plurality of stations excluding the second station.

[0011] 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] In addition, 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 further includes 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 include a Complete Profile subfield indicating whether the request frame is a request for all information for a corresponding station among the at least one second 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 a 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 multi-link 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 multi-link information.

[0017] In addition, in the present invention, the 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 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 operating 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, comprising the steps of: transmitting a request frame to a second station among a second plurality of stations included in a second MLD, each operating in 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 transmitting a wireless 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 for other bands, the wireless frame including multilink information for association between at least a first station among the first plurality of stations excluding the first station and at least a second station among the second plurality of stations excluding the second station. Effect of the Invention

[0021] An embodiment of the present invention provides a wireless communication method that efficiently uses multiple links 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 description of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing the configuration of an access point according to an embodiment of the present invention. [Diagram 5] 1 is a diagram illustrating a process in which a STA sets up 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] FIG. 1 is a diagram showing an example of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8] 1 is a diagram showing an example of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats and a method for indicating the same according to an embodiment of the present invention. [Figure 9] FIG. 1 illustrates a multi-link device according to an embodiment of the present invention. [Figure 10] 1 is a diagram illustrating simultaneous transmission of different links in a multi-link operation according to an embodiment of the present invention; [Figure 11] 4 is a diagram illustrating the operation of a multi-link device when a link is changed according to one embodiment of the present invention. FIG. [Figure 12] 13 is a diagram showing that, according to one embodiment of the present invention, when any one station of a non-STR multi-link device is receiving, other stations of the non-STR multi-link device are prohibited from channel access. [Figure 13] 13 is a diagram showing the 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 multi-link device is not a station according to an embodiment of the present invention. [Figure 14] 1 is a diagram showing a station performing channel access after channel access prohibition is lifted according to an embodiment of the present invention; FIG. [Figure 15] 11 is a diagram showing an operation of a station transmitting after channel access prohibition is lifted according to one embodiment of the present invention. FIG. [Figure 16] FIG. 13 is a diagram showing transmission based on the state of a station in a non-STR multilink device according to an embodiment of the present invention. [Figure 17] FIG. 2 illustrates a situation in which interference or collision between links may occur. [Figure 18] 11 is a diagram illustrating an operation of an STR multilink device ceasing transmission to a non-STR multilink device according to one embodiment of the present invention. [Figure 19] 11 is a diagram illustrating 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. 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. 11 is a diagram showing 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 in accordance with one embodiment of the present invention. [Figure 22] A figure showing yet another example of a TBTT information field format in one embodiment of the present invention. [Figure 23] FIG. 13 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 an embodiment of the present invention. [Figure 24] FIG. 2 is a diagram showing an example of a Per-STA Profile subelement format according to one embodiment of the present invention. [Diagram 25] FIG. 11 is a diagram showing 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 in one embodiment of the present invention. [Figure 26] 11 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. 11 is a diagram showing an example of an element format according to an embodiment of the present invention. [Figure 28] 11 is a diagram illustrating an example of a process in which an NSTR AP MLD sets (defines) a quiet interval for a non-primary in one embodiment of the present invention. [Figure 29] FIG. 13 is a diagram illustrating an example of a method in which an NSTR AP MLD performs a non-primary channel switch in accordance with one embodiment of the present invention. [Diagram 30] 1A and 1B are diagrams illustrating 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. [Diagram 31] FIG. 11 is a diagram showing an example of a method for exchanging HT (High Throughput) / VHT (Very High Throughput) related element information over other links that are not of a specific bandwidth to set up multiple links in accordance with one embodiment of the present invention. [Diagram 32] 1 is a diagram illustrating a portion of the configuration of a management frame to explain a method of inheritance of a complete Per-STA profile in one embodiment of the present invention. FIG. [Diagram 33] 11 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 PREFERRED EMBODIMENTS

[0024] The terms used in this specification are selected as general terms that are currently widely used as much as possible in consideration of the functions of the present invention, but this may vary depending on the intentions, customs, or the emergence of new technologies of the engineers in the relevant technical field. In addition, in certain cases, the applicant may arbitrarily select terms, and in such cases, the meanings of the terms will be described in the description of the relevant invention. Therefore, it is clear that the terms used in this specification should be interpreted not simply as terms, but based on the substantial meanings of the terms and the contents of this specification as a whole.

[0025] Throughout the specification, when a component is "connected" to another component, this includes not only when it is "directly connected" to another component, but also when it is "electrically connected" with another component in between. Furthermore, when a component "includes" a specific component, this means that it may further include the other component, not excluding the other component, unless otherwise specified to the contrary. In addition, limitations such as "greater than" or "less than" based on a specific critical value may be appropriately replaced with "more than" or "less than" 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 (BSS), which are a set of devices that can successfully 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, infrastructure BSS BSS1, BSS2 includes one or more stations STA1, STA2, STA3, STA4, STA5, access points AP-1, AP-2 which are stations providing a distribution service, and a distribution system DS which connects multiple access points AP-1, AP-2.

[0030] A station (STA) is any device including a medium access control (MAC) and a physical layer interface for a wireless medium according to the IEEE 802.11 standard, and in a broad sense includes not only non-AP stations but also APs. In this specification, the term "terminal" refers to either a non-AP or an AP, or to both. A station for wireless communication includes a processor and a communication unit, and further includes a user interface unit and a display unit, etc., depending on the embodiment. The processor generates frames to be transmitted through a wireless network, processes frames received through 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 through the wireless network for the station. In the present invention, the term "terminal" is used to include a 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 a station associated therewith. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP, but when a direct link is set up, direct communication is possible between non-AP stations. Meanwhile, in the present invention, AP is used as a concept including a personal BSS coordination point (PCP), but in a broad sense, AP includes all 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, AP is also referred to as a base wireless communication terminal, but in a broad sense, the 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 in communication with a plurality of wireless communication terminals.

[0032] A plurality of infrastructure BSSs are connected to each other via a distribution system DS. In this case, a plurality of BSSs connected to each other via the distribution system is 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 which the same or corresponding parts in the embodiment of FIG. 2 are the same as or correspond to the embodiment of FIG.

[0034] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so all stations (STA6, STA7) are not 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 a configuration of a station 100 according to an embodiment of the present invention. As shown in the figure, 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 wireless LAN packets, and may be built into or externally provided in 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 of 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 of 7.125 GHz or more and a communication module using a frequency band of 7.125 GHz or less. Each communication module may perform wireless communication with an AP or an external station based on the wireless LAN standard of the frequency band supported by the communication module. The communication unit 120 may operate only one communication module at a time or operate multiple communication modules simultaneously according to the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be provided in an independent form, or multiple modules may be integrated into one chip. In an 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 a command from the processor 110 using various output means.

[0038] Then, 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 performed by the processor 110 or a control command of the processor 110. The memory 160 also stores control programs used by the station 100 and various data associated therewith. Such control programs include connection programs 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 transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection to an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information on the priority conditions of the station 100 included in the communication setup message and requests a connection to the AP based on the information on the priority conditions of the station 100. The processor 110 of the present invention may refer to a main control unit of the station 100, or may refer to a control unit for individually controlling some components of the station 100, for example, the communication unit 120, depending on the embodiment. That is, the processor 110 may be a modem that modulates and demodulates a wireless signal transmitted and received from the communication unit 120, or a modulator and / or demodulator. The processor 110 controls various operations of transmitting and receiving wireless signals of the station 100 according to an embodiment of the present invention. A detailed embodiment of the present invention 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 are used to logically distinguish between elements of the device. Thus, the above-mentioned device elements may be mounted on one chip or multiple chips depending on the design of the device. For example, the processor 110 and the communication unit 120 may be integrated and embodied on one chip, or may be embodied on separate chips. In addition, in an embodiment of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively provided in the station 100.

[0041] 4 is a block diagram showing a configuration of an AP 200 according to an embodiment of the present invention. As shown in the figure, 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, a duplicated description 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 a plurality of 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, any of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 may include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module 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 operate multiple communication modules simultaneously according to the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 may represent an RF communication module that processes RF (Radio Frequency) signals.

[0043] Next, the memory 260 stores control programs used in the AP 200 and various data associated therewith. Such control programs include a connection program for managing station connections. Also, the processor 210 controls each unit of the AP 200 and controls transmission and reception of data between the units. According to an embodiment of the present invention, the processor 210 executes a program for connection with a station stored in the memory 260 and transmits a communication setting message to one or more stations. At this time, the communication setting message includes information regarding connection priority conditions of each station. Also, the processor 210 performs connection setting in response to a connection request of a station. According to an embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates wireless signals transmitted and received from the communication unit 220. The processor 210 controls various operations of transmitting and receiving wireless signals of the AP 200 according to an embodiment of the present invention. A detailed embodiment thereof 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, the link between the STA 100 and the AP 200 is set up through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information of the BSS operated by the AP 200. There are two methods for performing scanning: a passive scanning method in which the AP 200 acquires information only by using a beacon message S101 periodically transmitted by the AP, 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 has successfully received wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200 (S107b), and performs an authentication step. After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs an association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited thereto, 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, the server 300 is a server that processes 802.1X-based authentication with the STA 100, and may be physically connected to the 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 or not. If a wireless signal of a certain strength or more is detected, the channel is determined to be in an occupied state, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not the corresponding signal is detected is called a CCA threshold. If a wireless signal of a strength greater than 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 of a strength less than the CCA threshold is detected, the channel is determined to be in an idle state.

[0050] When the channel is determined to be in an idle state, each terminal having data to transmit performs a backoff procedure after an IFS (Inter Frame Space) according to the status of each terminal, for example, an AIFS (Arbitration IFS) or a PIFS (PCF IFS). In some embodiments, the AIFS may be used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while decreasing a slot time of a random number determined for the terminal during an interval of the idle state of the channel, and a terminal that has exhausted all of the slot time attempts to access the channel. In this manner, a section in which each terminal performs a backoff procedure is called a contention window section. At this time, the random number can be called a backoff counter. That is, an initial value of the backoff counter is set by an integer that is a random number obtained by the terminal. When the terminal detects that the channel is idle during the slot time, the terminal may decrease the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be allowed to perform channel access on the channel. Thus, a terminal may be allowed to transmit if the channel is idle during the AIFS time and the backoff counter slot time.

[0051] If a specific terminal succeeds in accessing the channel, the terminal transmits data through 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 random numbers newly 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, and at this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this manner, each terminal performing wireless LAN communication can avoid collision with each other on a specific channel.

[0052] <Examples of various PPDU formats>

[0053] FIG 7 shows an example of various standard generation PPDU (PLCP Protocol Data Unit) formats. More specifically, FIG 7(a) shows an example of a legacy PPDU format based on 802.11a / g, FIG 7(b) shows an example of a HE PPDU format based on 802.11ax, and FIG 7(c) shows an example of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Also, FIG 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 RL-SIG (Repeated Legacy Short Training field), a HE-SIG-A (High Efficiency Signal A field), a HE-SIG-B (High Efficiency Signal B field), a HE-STF (High Efficiency Short Training field), and a HE-LTF (High Efficiency Long Training field) 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 be modified according to the HE PPDU format. For example, the 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 RL-SIG (Repeated Legacy Short Training field), a U-SIG (Universal Signal field), an EHT-SIG-A (Extremely High Throughput Signal A field), an EHT-SIG-A (Extremely High Throughput Signal B field), an EHT-STF (Extremely High Throughput Short Training field), and an EHT-LTF (Extremely High Throughput Long Training field) 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 can be called an EHT preamble. The specific configuration of the non-legacy preamble may be modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some formats of the EHT PPDU format.

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

[0058] Referring to 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 speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of a modulation method such as BPSK / QPSK / 16-QAM / 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. The total length of the PPDU can be indicated by combining the information in the L_RATE field and the L_LENGTH field. In the non-legacy PPDU format, the L_RATE field is set to the minimum speed of 6 Mbps.

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

[0060] First, the method in which a legacy or non-legacy terminal interprets the length of the corresponding PPDU using the L_LENGTH field is 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 64 FFT. Therefore, the number of 64 FFT reference symbols after the L-SIG is obtained by adding 3 bytes corresponding to the SVC field and the Tail field to the L_LENGTH field value and dividing it by 3 bytes, which is the transmission amount of one symbol. The length of the corresponding PPDU, i.e., the reception time (RXTIME), is obtained by multiplying the number of symbols obtained by 4 us, which is one symbol duration, and then adding 20 us for transmitting the L-STF, L-LTF, and L-SIG. This can be expressed as the following Equation 1.

[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 FIG. 7(e), the U-SIG (Universal SIG) field remains in the EHT PPDU and the PPDU of the succeeding generation of WLAN, and plays a role in identifying which generation of PPDU it is, including 11be. The U-SIG is two symbols of 64FFT-based OFDM and can transmit a total of 52 bits of information. Of these, 43 bits excluding the CRC / tail 9 bits are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0068] The VI bit will maintain the current bit configuration, and even if a subsequent generation PPDU is defined, a current 11be terminal can obtain information about the PPDU from the VI field of the PPDU. To this end, the VI field is composed of PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits, and serves to sequentially distinguish 11be and subsequent generation WLAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the corresponding PPDU is an uplink / downlink PPDU. The BSS color means a BSS-specific identifier defined in 11ax, and has a value of 6 bits or more. The TXOP means a transmit opportunity duration that was transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP containing the corresponding PPDU can be inferred without decoding the MPDU, and has a value of 7 bits or more.

[0069] The VD field may be composed of fields commonly used in any PPDU format, such as PPDU format and BW, which are signaling information useful only for PPDUs of the 11be version, and fields defined differently for each PPDU format. The PPDU format is a division factor that distinguishes EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDU, etc. The BW field mainly signals five basic PPDU BW options of 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), and various remaining PPDU BWs formed by preamble puncturing. After being signaled at 320 MHz, some 80 MHz may be signaled in a punctured form. Also, the punctured and modified channel shape may be directly signaled in the BW field, or may be signaled using both the BW field and a field that appears after the BW field (e.g., 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. The MU PPDU and the SU PPDU may be signaled in the same PPDU format, and a field for distinguishing the MU PPDU from the SU PPDU may be located before the EHT-SIG field, and additional signaling may be performed for this purpose. Both the SU PPDU and the MU PPDU include an EHT-SIG field, but some fields that are not necessary in the SU PPDU may be compressed. In this case, the information of the compressed field may be omitted or may have a reduced size compared to the size of the original field included in the MU PPDU. For example, in the case of the SU PPDU, the common field of the EHT-SIG may be omitted or replaced, or the user-specific field may be replaced or reduced to one, and may have a different configuration.

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

[0072] When a part 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, etc.). In the case of the 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 transmitted to itself. 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 of the EHT-SIG field and / or MCS, which is a modulation method. The EHT-SIG field may include the size and location information of the RU assigned to each user.

[0073] In the case of a SU PPDU, a plurality of RUs may be allocated to a STA, and the plurality of 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 if it recognizes the punctured RUs in between. Therefore, the AP can transmit the SU PPDU including information on the punctured RUs among the RUs allocated to the STA (e.g., the puncturing pattern of the RUs, etc.). That is, in the case of a 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 may signal the type of discontinuous channels that appear within the bandwidth.

[0074] The form of the 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, in the case of a SU PPDU, since it is a PPDU transmitted only to a single UE, the STA can recognize the bandwidth allocated to itself from the BW field included in the PPDU, and can recognize the punctured resources of 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 except for the specific channel of the punctured resource unit. In this case, the 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 SU PPDU. Since puncturing may be performed for each 20 MHz subchannel, if puncturing is performed for a BW having multiple 20 MHz subchannels such as 80, 160, and 320 MHz, in the case of 320 MHz, the discontinuous channel type (when only the end 20 MHz is punctured and considered as discontinuous) must be signaled by expressing whether or not the remaining 15 20 MHz subchannels except the primary channel are used. In this way, using 15 bits to signal discontinuous channel types for single user transmission may result in excessive signaling overhead when considering the low transmission speed of the signaling part.

[0076] The present 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, in one embodiment of the present invention, a method is proposed in which the configuration of the PPDU indicated by the preamble puncturing BW value is changed according to the PPDU format signaled in the PPDU format field. Assuming that the length of the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, one symbol of EHT-SIG-A may be further signaled after the U-SIG, or EHT-SIG-A may not be signaled at all. Taking this into consideration, it is necessary to signal up to 11 puncturing modes using only the BW field of the U-SIG. However, in the case of an EHT MU PPDU, since an EHT-SIG-B is further signaled after the U-SIG, up to 11 puncturing modes may be signaled in a different manner from the SU PPDU. In the case of an EHT ER PPDU, the BW field is set to 1 bit, and it is possible to signal whether the PPDU uses a bandwidth of 20 MHz or 10 MHz.

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

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

[0080] 8, a PPDU may be composed of a preamble and a data portion, and the format of an EHT PPDU, which is one type, may be distinguished by a U-SIG field included in the preamble. Specifically, whether the format of the PPDU is an 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] Fig. 8(d) shows an example of an EHT ER SU PPDU format used for single-user transmission with an STA in an extended range. The EHT ER SU PPDU may be used for single-user transmission with a STA in a wider range than the EHT SU PPDU described in Fig. 8(a), and the U-SIG field may be repeatedly positioned on the time axis.

[0085] The EHT MU PPDU described in (c) of FIG. 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 PPDU transmitted through the user specific field of the EHT-SIG-B to the STA. 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 a resource unit configuration (e.g., a resource unit division form) in a specific bandwidth (e.g., 20 MHz, etc.) on the frequency axis. That is, the RA field may indicate a resource unit configuration divided by a bandwidth for transmitting the HE MU PPDU so that the STA receives the PPDU. Information on 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, a user field corresponding to at least one resource unit used for data transmission among the multiple divided resource units may include the AID of a receiver or sender, and a user field corresponding to the remaining resource units not used for data transmission may include a null STA ID that has already been set.

[0088] For ease of explanation, the term frame or MAC frame may be used interchangeably with MPDU in this specification.

[0089] When one wireless communication device communicates using multiple links, the communication efficiency of the wireless communication device can be improved. In this case, the link is a physical path, and may be configured as one wireless medium that can be used to transmit MSDU (MAC service data unit). For example, when the frequency band of any one link is being used by another wireless communication device, the wireless communication device can continue to communicate using another link. In this way, the wireless communication device can effectively use multiple channels. Also, when the wireless communication device simultaneously communicates using multiple links, the overall throughput can be increased. However, the existing wireless LAN is specified on the premise that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using multiple links is required. A wireless communication method of a wireless communication device using multiple links will be described with reference to Figs. 9 to 26. First, a specific form 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] For the wireless communication method using the above-mentioned multiple links, a multi-link device (MLD) may be defined. The multi-link device may represent a device having one or more affiliated stations. According to a specific embodiment, the multi-link device may represent a device having two or more affiliated stations. Also, the multi-link device may exchange a multi-link element. The multi-link element includes information on 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 called a multi-link logical entity (MLLE) or a multi-link entity (MLE). The multi-link device may have one MAC service access point (SAP) up to a logical link control (LLC). Also, the MLD may have one MAC data service.

[0092] The stations included in the multilink device can operate on multiple links. Also, the stations included in the multilink device can operate on multiple channels. Specifically, the stations included in the multilink device can operate on different links or different channels. For example, the stations included in the multilink device can operate on different channels of 2.4 GHz, 5 GHz, and 6 GHz.

[0093] The operation of the multilink device may be referred to as multilink operation, MLD operation, or multi-band operation. If a station associated with the multilink device is an AP, the multilink device may be referred to as AP MLD. If a station associated with the multilink device is a non-AP station, the multilink device may 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 through a first link (Link1). Also, the second AP (AP2) and the second non-AP STA (non-AP STA2) communicate through a second link (Link2). Also, the third AP (AP3) and the third non-AP STA (non-AP STA3) communicate through a third link (Link3).

[0095] The multi-link operation may include a multi-link setup operation. The multi-link setup corresponds to the association operation of the single-link operation described above, and must be performed prior to frame exchange in the multi-link. The multi-link device may obtain information required for the multi-link setup from the multi-link setup element. Specifically, the multi-link setup element may include capability information related to the multi-link. In this case, the capability information may include information indicating whether one of the multiple devices included in the multi-link device can transmit and the other devices can receive at the same time. In addition, the capability information may include information regarding links available to each station included in the MLD. In addition, the capability information may include information regarding channels available to each station included in the MLD.

[0096] The multilink setting may be set by negotiation between peer stations. Specifically, the multilink setting may be set by communication between stations without communication with the AP. The multilink setting may be set through any one of the links. For example, even if the first link to the third link are set through the multilink, the multilink setting may be set through the first link.

[0097] Also, a mapping between a traffic identifier (TID) and a link may be set. Specifically, a frame corresponding to a specific TID value may be exchanged only through a link designated in advance. The mapping between a TID and a link may be set on a directional-based basis. For example, when a plurality of links are set between a first multilink device and a second multilink device, the first multilink device may be set to transmit a frame of a first TID to a plurality of first links, and the second multilink device may be set to transmit a frame of a second TID to the first link. Also, a default setting may exist for the mapping between a TID and a link. Specifically, when there is no additional setting in the multilink setting, the multilink device may exchange frames corresponding to a TID in each link according to a default setting. In this case, the default setting may be that all TIDs are exchanged in any one link.

[0098] The TID will be specifically described. The TID is an ID for classifying traffic and data to support QoS (quality of service). 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). The TID may be classified into 16 types. For example, the TID may be designated as one of 0 to 15. The TID value to be used may be designated differently depending on an access policy, a channel access, or a medium access method. For example, when EDCA (enhanced distributed channel access) or HCAF (hybrid coordination function contention based channel access) is used, the TID value may be assigned in the range of 0 to 7. When EDCA is used, 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 channel contention in EDCA. QoS stations can guarantee QoS using AC. AC 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 ACs. For example, AC_VI may be subdivided into AC_VI primary and AC_VI alternate. AC_VO may be subdivided into AC_VO primary and AC_VO alternate. UP or TID may be mapped to 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 a higher priority in that order. That is, 1 may have a lower priority, and 7 may have a higher priority. Therefore, the priority may be higher in the order of AC_BK, AC_BE, AC_VI, and AC_VO. Also, AC_BK, AC_BE, AC_VI, and AC_VO may correspond to ACI (AC index) 0, 1, 2, and 3, respectively. Due to the characteristics of such a TID, the mapping between a TID and a link may represent the mapping between an AC and a link.Additionally, the mapping between links and ACs can represent the mapping between TIDs and links.

[0100] As described above, a TID may be mapped to each of a plurality of links. The mapping may be a designation of a link through which traffic corresponding to a particular TID or AC may be exchanged. Also, a TID or AC that may be transmitted for each transmission direction within a link may be designated. As described above, there may be a default setting for mapping between a TID and a link. Specifically, if there is no additional setting in the multilink setting, 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 the 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-mentioned 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 operating or where channel conditions are good. The above-mentioned TID-to-link mapping may also allow stations to stay in a power saving state for a longer period of time.

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

[0104] Depending on the implementation of the multilink device, simultaneous operation in the multilink may not be supported. For example, the multilink device may support simultaneous transmission in multiple links, simultaneous reception in multiple links, or transmission in one link and reception in another link. Reception or transmission in one link may affect reception or transmission in another link. Specifically, transmission in one link may act as interference in another link. Interference from one link of a multilink device acting on another link may be called internal leakage. The smaller the frequency interval between the links, the larger the internal leakage may be. If the internal leakage is not too large, transmission can be performed in another link when transmission is performed in one link. If the internal leakage is large, transmission cannot be performed in another link when transmission is performed in one link. In this way, the multilink device operating simultaneously in multiple links may be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, a multilink device may transmit on multiple links simultaneously, transmit on one link while receiving on another link, or receive on multiple links simultaneously, all of which may be referred to as STR.

[0105] On the other hand, when STR is not supported due to interference between multiple stations constituting the MLD, the STAs may be expressed as being in a non-STR relationship or NSTR relationship (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 each STA in a specific link pair, if an STR is supported between both 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 each STA in a separate link pair, if an STR is not supported between both 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 MLDs 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 each other, 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 STA operated in the STR link pair of the MLD is named (specified) as the STA of the STR MLD, and the STA operated in the NSTR link pair of the MLD is named (specified) as the STA of the NSTR (and non-STR) MLD. That is, in the embodiment described below, when "STA of the non-STR MLD" is mentioned, it may be interpreted as referring to one of the STAs operated in the NSTR link pair of the MLD, and when "STA of the STR MLD" is mentioned, it may 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 an MLD (Multi-link device) may have a configuration that limits the hardware resources that other STAs in the MLD can utilize when a specific STA in the MLD is transmitting or receiving. For example, if a specific MLD has a hardware configuration that supports processing for only one PPDU, when a specific STA in the specific 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 specific MLD is performing Tx, the specific MLD cannot support Tx and Rx for other STAs in the MLD.

[0112] In this way, a device that is an MLD and can operate STAs on two or more links but can support transmission / reception for only one STA at a particular time can be called a multi-link single radio MLD (MLSR MLD). Alternatively, an operation mode in which an MLD supports transmission / reception for only one STA as one type of operation mode can be called an enhanced multi-link single radio (EMLSR) mode. In this case, an MLD operating in EMLSR mode can 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 can refer to a device that supports CCA and low-speed data rate (e.g., encoded at 6 MHz or 24 MHz or less) PPDU transmission / reception for two or more links by having a configuration including separate hardware (such as a low-cost PHY front end).

[0113] Also, as a modification of the EMLSR mode, EMLMR (Enhance Multi-Link Multi-Radio) 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. That is, the MLD operating in the EMLMR mode can operate to support only 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 the MLD operating in the EMLSR mode.

[0114] That is, the links of an MLD operated 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 has nothing to do with the presence or absence of STR / NSTR support for both links.

[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 particular 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 particular time as a type of operating mode.

[0117] The operation of the STR MLD considering the performance limitations of the NSTR MLD provided by the above-mentioned embodiment of the present invention can be directly used as the operation of the STR MLD for the MLSR MLD. For example, after a STA of the STR MLD transmits to a STA of the multi-link single radio MLD, if the STA determines that the transmission has failed or is expected to fail due to the limited performance of the multi-link single radio MLD STA, the STA can cancel the transmission that is being performed or is about to be performed. In this case, the procedure of checking whether the transmission has failed due to the limited performance of the EMLSR / EMLMR MLD can be similar to the procedure of checking whether a transmission to a STA of the NSTR MLD 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 in a limited manner. 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 equal to or greater than a pre-specified magnitude, the multilink device may not be able to perform STR.

[0119] A station can exchange information on the STR capability of the station with other stations. Specifically, a station can exchange information on the presence or absence of a restriction on the capability of the station to simultaneously transmit on multiple links or simultaneously receive on multiple links with other stations. Specifically, the information on the presence or absence of a restriction on the capability of transmitting or receiving on multiple links can indicate whether the station transmits on multiple links simultaneously, receives on multiple links simultaneously, or transmits and receives simultaneously. In addition, the information on the presence or absence of a restriction on the capability of transmitting or receiving on multiple links may be information indicated in stages. Specifically, the information on the presence or absence of a restriction on the capability of transmitting or receiving on multiple links may be information indicating a stage indicating the magnitude of the internal leakage. In a specific embodiment, the information indicating a stage indicating the magnitude of the internal leakage may be information indicating a stage indicating the magnitude of interference generated by the internal leakage. In yet another specific embodiment, the information indicating a stage indicating a frequency interval between links that may affect the internal leakage may be information indicating a stage indicating the magnitude of the internal leakage. In addition, the information indicating a stage indicating the magnitude of the internal leakage may be information indicating a relationship between the frequency interval between links and the magnitude of the internal leakage in stages.

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

[0121] The operation of the multilink device performing channel access will now be described. The multilink operation not specifically described can follow the channel access procedure described in FIG.

[0122] The multilink device may perform channel access independently from a plurality of links. In this case, the channel access may be a back-off based channel access. When the multilink device performs channel access independently from a plurality of links and the back-off counters reach 0 in the plurality of links, the multilink device may start transmission simultaneously from the plurality of links. In a specific embodiment, when any one of the back-off counters of the links of the multilink reaches 0 and a pre-specified condition is satisfied, the multilink device may perform channel access not only in the link whose back-off counter reaches 0 but also in other links whose back-off counters have not reached 0. Specifically, when any one of the back-off counters of the links of the multilink reaches 0, the multilink device may perform energy sensing in other links whose back-off counters have not reached 0. In this case, when energy equal to or greater than a pre-specified magnitude is not sensed, the multilink device may perform channel access not only in the link whose back-off counter reaches 0 but also in the link whose energy sensing has been performed. In this way, the multilink device may start transmission simultaneously from the plurality of links. The threshold value used for energy sensing may be smaller than the threshold value used when determining whether to decrease the back-off counter. In addition, when determining whether to decrease the back-off counter, the multilink device can sense any type of signal, not just a WLAN signal. In addition, in the above-mentioned energy sensing, 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 sense a signal detected due to internal leakage by energy sensing. In addition, as described above, the threshold value used for energy sensing may be smaller than the threshold value used when determining whether to decrease the back-off counter. Therefore, even when transmission is being performed on one link, the multilink device can decrease the back-off counter on the other link.

[0123] Depending on the degree of interference between links used by the multilink apparatus, the multilink apparatus 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 sensed by other stations of the multilink apparatus when any one station of the multilink apparatus transmits on any one link. When the transmission of a first station of the multilink apparatus on the first link causes interference of a predetermined magnitude or more to a second station of the multilink apparatus operating on the second link, the operation of the second station may be restricted. Specifically, the reception or channel access of the second station may be restricted. When interference occurs, the second station may fail to decode a signal received due to the interference. Also, when interference occurs, the second station may determine that the channel is in use when the second station accesses the channel using backoff.

[0124] In addition, when the transmission of the first station of the multilink device at the first link causes interference of less than a pre-specified magnitude to the second station of the multilink device operating at the second link, the first station and the second station can operate independently. Specifically, when the transmission of the first station of the multilink device at the first link causes interference of less than a pre-specified magnitude to the second station of the multilink device operating at the second link, the first station and the second station can independently perform channel access. In addition, when the transmission of the first station of the multilink device at the first link causes interference of less than a pre-specified magnitude to the second station of the multilink device operating at the second link, the first station and the second station can independently perform transmission or reception. When interference of less than a pre-specified magnitude occurs, the second station can successfully decode the received signal even in the presence of interference. In addition, when interference of less than a pre-specified magnitude occurs, the second station can determine that the channel is idle when the second station accesses 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 that the magnitude of interference generated varies depending on the interval between the frequency bands of the links and the characteristics of the multilink device. In the embodiment of FIG. 10, the first multilink device (MLD#1) includes a first station (STA1)-1 operating on the first link (Link1) and a second station (STA1)-2 operating on the second link (Link2). The second multilink device (MLD#2) includes a first station (STA2)-1 operating on the first link (Link1) and a second station (STA2)-2 operating on the second link (Link2). The frequency interval between the first link (Link1) and the second link (Link2) in which the first multilink device (MLD#1) operates is the same as the frequency interval between the first link (Link1) and the second link (Link2) in which the second multilink device (MLD#2) operates. However, the magnitude of interference generated varies depending on the difference between the characteristics of the first multilink device (MLD#1) and the characteristics of the second multilink device (MLD#2). Specifically, the magnitude of interference generated in the second multilink device (MLD#2) may be greater than the magnitude of interference generated in the first multilink device (MLD#1).In this manner, 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 devices, information regarding whether STR is supported or not needs to be exchanged.

[0127] The multilink device may signal whether or not a station included in the multilink device supports STR. Specifically, the AP multilink device and the non-AP multilink device may exchange whether or not an AP included in the AP multilink device supports STR and whether or not an STA included in the non-AP multilink device supports STR. In such an embodiment, an element indicating whether or not an STR support is present may be used. The element indicating whether or not an STR support is present may be called an STR support element. The STR support element may indicate whether or not an STR support is present in a station of the multilink device that transmits the STR support element by one bit. Specifically, the STR support element may indicate whether or not an STR support is present in each station included in the multilink device that transmits the STR support element by one bit. In this case, if the station supports STR, the bit value may be 1, and if the station does not support STR, the bit value may 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 It is assumed that stations operating in different frequency bands 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 in a first link of 2.4 GHz, and a second station (STA2) and a third station (STA3) operate in 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). Also, the STR support element may include only one bit when the number of stations to be signaled by the STR support element is two.

[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 the multi-link device may always be determined as an STR, and therefore, signaling regarding the presence or absence of an STR between the link located at 2.4 GHz and the link located at 5 GHz or 6 GHz may be omitted.

[0129] In the above-mentioned embodiment, the operation of the station of the multilink device may be replaced by the operation of the multilink device. Also, in the above-mentioned embodiment, the operation of the AP may be replaced by the operation of the non-AP station, and the operation of the non-AP station may be replaced by the operation of the AP. Thus, the operation of the AP of the non-STR multilink device may be replaced by the operation of the non-AP station of the non-STR multilink device, and the operation of the non-AP station of the STR multilink device may be replaced by the operation of the AP of the STR multilink device. Also, the operation of the non-AP station of the non-STR multilink device may be replaced by the operation of the AP of the non-STR multilink device, and the operation of the AP of the STR multilink device may be replaced by the operation of the non-AP station of the 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 the link is changed, the STR support element may be exchanged. As described above, whether or not the station can support STR may vary depending on the distance between the frequency bands of the link, and whether or not the 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 main channel may be included. The AP and the station may exchange the STR support element by a request and a response. In still another specific embodiment, when the frequency band of the link is changed, the STR support element may be exchanged without a separate request. Also, in the above embodiment, when the frequency band of the link is changed, it may include a change in the operating channel of the station.

[0132] When a station of a non-AP multilink device cannot perform STR, the station of the non-AP multilink device can request a link change to the AP. Specifically, the station of 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 on a link for which a change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP on a link for which a change is not requested. In this case, the link change request may include information indicating a link for which a change is requested. The information indicating a link may be a number identifying a link. In such an embodiment, the link change may be a change in an operating channel within one frequency band. Also, the link change may include information on a method of 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 the center frequency of the link is to be moved 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 reducing the bandwidth of the link. The link change request may also request changing the position of the primary channel. Specifically, the link change request may indicate changing 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. The AP that receives the link change request may change the link in response to the link change request. In a specific embodiment, the 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 in which STR cannot be supported. The non-AP multilink device requests the AP multilink device to change the third link (Link3). The AP multilink device, having received the link change request, changes the operating link of the third AP (AP3). At this time, the third station (STA3) operating on the third link (link3) to be changed can send a change request to the third AP (AP3). In yet another specific embodiment, a station that does not operate on the third link (link3) can send a change request to an AP that does not operate on the third link (link3).

[0134] When an AP changes 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 a frequency of the link. The information about the frequency of the link may include at least one of a change in a center frequency, an operating bandwidth, and a main channel of the link. The information about the link change may also include information about a time point 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 been changed, and the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multilink device can send an STR support element to the AP multilink device to signal whether or not it supports the changed STR.

[0136] The above-mentioned link change may not be allowed, or even if the change occurs, the STR may not be supported. Also, as in the embodiment of FIG. 11, the AP multilink device may support the STR, but the non-AP multilink device may not support the STR. This is because a relatively expensive device is generally used for the AP multilink device, and a relatively inexpensive device is generally used for the non-AP multilink device. Therefore, a method is required for efficient communication even when one of the multilink devices does not support the STR during communication between the multilink devices. In this case, the STR may indicate that transmission and reception are performed simultaneously. This will be described with reference to FIG. 12.

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

[0138] When transmission is performed on one link of the 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, 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, backoff of channel access may be prohibited on the other links of the non-STR multilink device. This makes it possible to prevent 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 starts on one link of the non-STR multilink device, backoff of channel access may be prohibited on the other links of the non-STR multilink device. This may be set using a specific bit of a memory such as a channel access prohibition flag. In other words, whether channel access is prohibited or not may be shared by a memory inside the multilink device. With this embodiment, channel access prohibition may be implemented without a separate frame exchange. For ease of explanation, unless otherwise specified, "channel access prohibition" as used in this specification refers to prohibiting channel access or transmission in order to protect the transmission or reception of non-STR multilink devices.

[0139] When channel access is prohibited, a station operating on a link where channel access is prohibited cannot perform a back-off procedure regardless of the NAV and CCA results. Also, when channel access is prohibited, a station operating on a link where channel access is prohibited cannot transmit regardless of the NAV and CCA results. However, even if channel access is prohibited, a station operating on a link where channel access is prohibited can receive. Also, the channel access prohibition on the second link due to reception performed on the first link may be released based on the time when reception on the first link is completed. Specifically, the channel access prohibition on the second link due to reception performed on the first link may be released when reception on the first link is completed. In still another specific embodiment, the channel access prohibition on the second link due to reception performed on the first link may be released based on the time when an ACK is transmitted after reception on the first link is completed. Specifically, the channel access prohibition on the second link due to reception performed on the first link may be released 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 in the second link due to reception in the first link may be lifted when the transmission of an ACK is completed after the reception is completed in the first link. Also, immediately after the channel access prohibition is lifted, the station may immediately decrement the back-off 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 at a pre-specified time immediately before the channel access prohibition is lifted, the station may immediately decrement the back-off 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, the non-STR multi-link device includes a first station (STA1) operating on a first link (Link1) and a second station (STA2) operating on a second link (Link2). When the second station (STA2) transmits on the second link (Link2) while the first station (STA1) receives, interference within the device occurs. As described above, while the first station (STA1) operating on the first link (Link1) receives, the channel access of the second station (STA2) on the second link (Link2) is prohibited. 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 decrease the previous backoff counter value by 1 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 Fig. 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 illustrated. 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, which would pose a channel access unblocking problem in the multilink device. In this specification, intended recipient is used synonymously with destination station.

[0143] FIG. 13 illustrates an operation of releasing channel access inhibition when a station in a non-STR multilink device determines that the intended recipient of a PPDU it receives is not a station, according to an embodiment of the present invention.

[0144] When the station confirms that the station is not the intended recipient of the received PPDU, the station may release the channel access prohibition. The station can determine whether the station 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 of the EHT-SIG field described above. Specifically, the station can determine whether the STA-ID field of the EHT-SIG field indicates the station. Also, the station can determine whether the station is the intended recipient of the PPDU based on the value of the RA field of the MAC frame included in the PPDU. Specifically, the station can determine whether the station is the intended recipient of the PPDU. In FIG. 13, the non-STR multi-link device includes a first station (STA1) operating in a first link (Link1) and a second station (STA2) operating in 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 stops receiving the PPDU. At this time, the first station (STA1) can release the channel access prohibition for the second station (STA2). Even if the channel access prohibition for the second station (STA2) is released, the channel access of the second station (STA2) may be delayed due to the NAV set for the second station (STA2).

[0145] As shown in FIG. 13, even if 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, a method for compensating for channel access opportunities of stations included in a non-STR multilink device may be required for fair competition with other stations. 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 a channel access barring is lifted according to an embodiment of the present invention.

[0147] A station whose channel access prohibition has been released can decrement its backoff counter by 2 or more immediately after the channel access prohibition is released. 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 of CCA (CSMA) and decreasing a back-off counter while the 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 channel access of the second station (STA2) is prohibited. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure of CCA (CSMA) and decreasing a back-off counter. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, the second station (STA2) decreases a back-off counter because the channel of the second link (Link2) is idle.

[0149] Also, a station whose channel access is forbidden can delay transmission without starting transmission even if the back-off counter reaches 0 while channel access is forbidden. In this case, the station can maintain the back-off counter value at 0. Also, even if the station delays transmission, the station can maintain the CW value as it is. Therefore, this is differentiated from the station doubling the CW value because the channel that the station accesses is busy. This is because the reason for delaying transmission is not because it is determined that the channel is busy. In FIG. 14(b), while the channel access of the second station (STA2) is forbidden, the second station (STA2) can perform a channel access procedure of CCA (CSMA) and decreasing the back-off counter. In FIG. 14(b), while the channel access of the second station (STA2) is forbidden, the channel of the second link (Link2) is idle, so the second station (STA2) decreases the back-off counter. While the channel access of the second station (STA2) is prohibited, 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 prohibiting a second station from transmitting when a first station of a non-STR multilink device is transmitting, and may also include prohibiting a second station from transmitting when a first station of a non-STR multilink device is receiving.

[0151] In Fig. 14(b), when there are multiple stations that are prohibited from channel access in the embodiment, the channel access prohibition of the multiple stations is released at the same time, and there is a high possibility that the multiple stations will attempt to transmit at the same time. 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 performing transmission after channel access prohibition is lifted according to an embodiment of the present invention.

[0153] As described above, among the multiple links in which the non-STR multilink device operates, transmission may be performed on a first link, and transmission may be prohibited on a second link. When the transmission on the first link is completed, transmission on the second link may be started by exchanging RTS / CTS frames. Thus, when transmission is performed on a first link among the multiple links in which the non-STR multilink device operates, the non-STR multilink device may start 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 start exchanging RTS / CTS (request to send / clear to send) frames before starting the delayed transmission. At this time, 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), the station whose transmission has been delayed due to channel access prohibition transmits an RTS frame before starting the delayed transmission. After the station receives a CTS frame in response to the RTS frame, it starts the delayed transmission.

[0154] In yet another specific embodiment, after the channel access prohibition of a station whose transmission has been delayed due to the channel access prohibition is lifted, the station may transmit a frame including only a part of the delayed transmission. In this case, after the station receives a response, e.g., an ACK, to the frame including only a part of the delayed transmission, the station may transmit the part of the delayed transmission that has not been transmitted. If the station fails to receive a response to the frame including only a part of the delayed transmission, the station may not transmit the part of the delayed transmission that has not been transmitted. In this way, the station starts an RTS / CTS exchange after the channel access prohibition is lifted or transmits only a part of the delayed transmission because the collision probability of transmission after the channel access prohibition is higher than that of general transmission. Therefore, the above-mentioned embodiment may be mandatory for transmissions performed after the channel access prohibition is lifted. In the existing WLAN operation, 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 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 any one station of the non-STR multilink device receives, the transmission of the other station of the non-STR multilink device may be restricted. In addition, when any one station of the non-STR multilink device transmits, the other station of the non-STR multilink device may not be able to accurately sense the channel state of the link on which the station operates. Specifically, when the first station of the non-STR multilink device transmits, the second station of the non-STR multilink device may always determine the channel state of the link on which the second station operates as busy. Therefore, even if the channel of the link on which the second station operates is idle, the second station may determine that the channel is busy due to interference within the device. In this way, when the station whose channel state cannot be determined due to interference within the device or any one station of the non-STR multilink device continues to transmit, the other station of the non-STR multilink device is considered to be in a blind state. Due to the above-mentioned situation, it may be difficult for a station in a blind state to perform a backoff procedure and attempt transmission. 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.

[0156] On the other hand, when a PPDU is transmitted / received through a STA of another link, the STA of the EMLSR / EMLMR MLD cannot confirm or receive the presence of the PPDU transmitted to itself. Therefore, the STA of the MLD operating in the EMLSR / EMLSR mode may have the same performance constraints as the STA of the NSTR MLD being blinded while other STAs in the MLD are transmitting / receiving data frames. Therefore, in the embodiment described below, the operation considering the state of the blinded STA may be understood to be the same as considering whether the STA of the MLD operating in the EMLSR / EMLMR mode is in a state having constraints due to the operation (transmission / reception) of other STAs in the MLD.

[0157] In this case, a mode in which the multilink device uses a single radio of a single link in a specific time period may be called an EMLSR mode. While the multilink device exchanges frames in a first link of the EMLSR link, which is a plurality of links to which the EMLSR mode is applied, the multilink device does not transmit or receive in a second link of the EMLSR link. In addition, when a specific station of the multilink device transmits or receives using a part of the RF chain used by the other station of the multilink device in a specific time period of the specific mode, the specific mode may be called an EMLMR (enhanced multi-link multi-radio) mode. Specifically, when any one station of the multilink device transmits or receives using all of the RF chains of the other station of the multilink device in the EMLMR mode, the operation of the multilink device may be the same as the operation of the multilink device in the EMLSR mode. In addition, even if the multilink device operates in the EMLSR mode, some of the multiple links in which the multilink device operates may operate without restrictions due to the EMLSR mode. When the multilink device operates in the EMLSR mode, the links to which the EMLSR mode is applied may be a part of the links on which the multilink device operates. For example, when the multilink device operates in the first to third links, the EMLSR mode or the EMLMR mode may be applied only to the first and second links. Therefore, when the multilink device transmits or receives in the first link during a specific time period in the EMSLR mode, the multilink device cannot transmit or receive in the second link. At this time, the multilink device can transmit or receive in the third link without any restriction due to the EMLSR mode. For convenience of explanation, a link to which the EMLSR mode can be applied, such as the first and second links, is called an EMLSR link, and a link to which the EMLMR mode can be applied is called an EMLMR link. Transmitting or receiving using the RF chain of a specific station in the EMLSR mode and the EMLMR mode results in a change in the transmission, reception, or monitoring capability 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 specifically stated otherwise.

[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 that is about to transmit to a station of a non-STR multilink device can determine whether to transmit depending on whether the station of the non-STR multilink device is in a blind state. In this case, the station that is about to transmit to a station of a non-STR multilink device may be a station included in the STR multilink device. Also, the station that is about to transmit to a station of 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 that is about to transmit to a station of a non-STR multilink device can determine whether the station of the non-STR multilink device is in a blind state as follows. The station that is about to transmit can determine whether another station of the multilink device in which the station is included is transmitting to the non-STR multilink device. If another station of the multilink device in which the station is included is receiving from the non-STR multilink device, the station can determine that the station of 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 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 above-mentioned 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 the STR multilink device transmits to the non-STR multilink device, the STR multilink device can transmit to the non-STR multilink device via multiple links. Specifically, when the STR multilink device transmits to the non-STR multilink device via a first link, the STR multilink device can begin transmitting to the non-STR multilink device via a second link. At this time, the STR multilink device can determine the length of the transmission to be performed on the second link based on the fact that it is a transmission to the non-STR multilink device. Specifically, the STR multilink device can determine the length of the transmission to the non-STR multilink device via the second link based on the length of the transmission to the non-STR multilink device via the first link. In a specific embodiment, the STR multilink device can simultaneously end the transmission on the first link and the transmission on the second link. This is to prevent the non-STR multilink device from transmitting to other stations until the transmission to one of the stations of the non-STR multilink device is completed first and one of the stations of the non-STR multilink device transmits a response to the transmission, such as an ACK. The above-described embodiment allows multiple stations in a non-STR multilink system to simultaneously transmit responses to transmissions intended for multiple stations.

[0163] An STR multilink device cannot determine the state of a station 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 collision may occur between links operated by the non-STR multilink device. For example, in the embodiment of FIG. 16, the first AP (AP1) may start 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 collision between links may occur with a higher probability than interference or transmission collision within a link. This will be described in more detail with reference to FIG. 17.

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

[0165] When a transmission of a second station of a non-STR station multilink device to a second AP of the STR AP multilink device begins at the same time as a transmission of a first AP of the STR AP multilink device to a first station of the non-STR station multilink device, a transmission collision may occur between the links. This is shown in Figure 17(a). As mentioned above, this may 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, if the transmission of the second station of the non-STR station multilink device to the second AP of the STR AP multilink device starts earlier than the transmission of the first AP of the STR AP multilink device to the first station of the non-STR station multilink device, a transmission collision may occur between the links. 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. In this way, since a transmission collision occurs between stations that start transmitting at different times, interference or transmission collision between links may occur with a higher probability than interference or collision within a link. In addition, the probability of interference or transmission collision between links may increase as the time for identifying the sender of the PPDU received by the AP of the STR multilink device is delayed. Therefore, a method for solving this is required. When one of the stations of the STR multilink device is receiving, it is not necessary to perform channel access of the other stations of the STR multilink device. However, if channel access is prohibited in this way, the meaning of implementing the STR function may be lost. Therefore, a method for operating the STR multilink device without prohibiting channel access is required. 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 that transmits 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 that transmits 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 that transmits the EHT UL PPDU. The multilink device that receives the EHT PPDU may identify the station that transmits 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 that transmits the EHT UL PPDU and determine the destination device of the transmission. Specifically, the AP multilink device may determine whether or not there is a high possibility that the transmission that is attempted to be performed will fail due to inter-link collision. Also, 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 of an STR multilink device ceasing transmission to a non-STR multilink device according to one embodiment of the present invention.

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

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

[0171] When a station that has cancelled a transmission to 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 has cancelled a transmission to the station in the non-STR multilink device can transmit traffic having the same priority as the traffic of the cancelled transmission or traffic having a higher priority. This is because it would be unfair to transmit traffic having a lower priority than the priority of the traffic used when accessing the channel for the cancelled transmission. In the above 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 may initialize the TXOP that it has set. Specifically, a station that cancels transmission to a station in a non-STR multilink device may transmit a CF-End frame after canceling transmission. This may allow other stations operating on the link on which the 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). The first AP (AP1) determines that the first station (STA1) is in a blind state while transmitting to the first station (STA1). 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 first embodiment described above. 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 pauses 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] Also, an STR MLD STA that has sent to an MLD STA operating in EMLSR or EMLMR mode can cancel the same transmission that it has made or was about to make as the STR MLD that sent to a STA in the BLIND state described above, because an MLD STA operating in EMLSR / EMLMR mode may have similar performance constraints as the BLIND state, as described above.

[0176] That is, while a STA in the STR MLD is transmitting to a STA in the MLD in 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 the transmission has not yet started, the STA can transmit other traffic of the same AC (Access Category) without performing the transmission it was intending to perform to the STA in the EMLSR / EMLMR MLD (e.g., EMLSR STA1).

[0177] In this way, the transmission management method for the STAs in the EMLSR / EMLMR mode MLD may be managed in a similar / similar manner to the transmission management method for the STAs in the NSTR MLD. Therefore, even if a description regarding the EMLSR / EMLMR mode MLD is not separately 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 embodiment, when the STR multilink device stops transmission to a station of the non-STR multilink device in the blind state and transmits to a station other than the station of the non-STR multilink device in the blind state, it is necessary to inform the other station that transmission to the other station may be performed in order to ensure 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 the blind state will be referred to as the other station.

[0179] A station of the STR multilink device can insert the address of another station into a MAC frame. Specifically, the station of 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 can insert the address of the other station into a separate field. In yet another specific embodiment, the station of the STR multilink device can insert the address of the other station into the EHT-SIG. Specifically, the station of 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 may 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, the station may monitor for reception of the PPDU for a pre-specified time even after it has determined that the intended recipient of the received PPDU is not the station. Specifically, the station may monitor for continued reception of the PPDU for a pre-specified time even after it has determined that the intended recipient of the received PPDU is not the station. This allows the station to determine whether transmission of the PPDU is to be interrupted and transmission to the station may begin. In this embodiment, if it is determined that transmission of the PPDU is to continue for a pre-specified time, the station may enter a doze state. If it is determined that transmission of the PPDU is not to continue for a pre-specified time, the station may remain in a wake-up state. At this time, if a new PPDU is received at 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 the power saving state. Also, a station transmitting a PPDU may insert information into the PPDU, signaling that the transmission may be interrupted, into a reserved field of the PPDU.

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

[0183] When transmission is interrupted or postponed due to a transmission collision between links, the value of the CW used for channel access may be doubled as in the case of a general transmission failure. When transmission is interrupted or postponed due to a transmission collision between links, unlike a general channel access failure or transmission failure, the value of the CW used for channel access may not be doubled. That is, the station can maintain the value of the CW used for channel access as it is. The purpose of doubling the value of the CW is to increase the range of numbers that can be the value of the backoff counter, thereby reducing the probability of a transmission collision. If the station can clearly recognize that there is a transmission collision between links, this need is less. Also, when transmission is interrupted or postponed due to a transmission collision between links, the doubling of the value of the CW by the station may lead to a delay in transmission. However, when a transmission collision between links occurs simultaneously with a collision within a link, the station needs to double the value of the CW. This will be described with reference to FIG. 19.

[0184] FIG. 19 illustrates how an 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 embodiment, the station can sense the channel state after canceling the transmission. When the channel is sensed not to be idle, the station can double the value of the CW. In this case, the doubling can follow the embodiment described in FIG. 6. Also, when the channel is sensed to be idle, the station can maintain the value of the CW. This embodiment is for treating the channel as being idle differently from when a transmission is made because the possibility of a transmission collision occurring within the link is low even if the channel is sensed to be idle. Specifically, when the AP of the AP multilink device fails to transmit to a station of the non-STR multilink device, the AP of the AP multilink device can acquire a back-off counter in the CW without increasing the CW. In this case, when the 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 back-off counter in 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 embodiment, when EDCA is applied, the procedure for CW adjustment and backoff counter generation may be performed for each AC.

[0186] In yet another specific embodiment, the STR multilink device may determine whether the transmission of the PPDU has failed based on whether a response to the PPDU has been received. At this time, the STR multilink device may not need to consider whether the station receiving the PPDU is included in the non-STR multilink device. For example, even if a first station receiving the PPDU is included in the non-STR multilink device and the first station cannot transmit a response to the PPDU because a second station of the non-STR multilink device is transmitting, the STR multilink device may determine that the transmission of the PPDU has failed. In addition, when the transmission of the PPDU of the STR multilink device has failed, the STR multilink device may increase the value of the CW to the next largest value among the values ​​that the CW value can have. At this time, when the value of the CW is the maximum value, the STR multilink device may maintain the value of the CW at the same value.

[0187] In yet another specific embodiment, when a channel is sensed as being idle, the station may set the value of the CW to the minimum value (CW_min) of the traffic CW. This embodiment is for treating a channel sensed 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 traffic AC included in the canceled transmission.

[0188] In addition, when the 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 interrupting the transmission or delaying the transmission before initiating the transmission.

[0190] After a station sends a CTS-to-Self frame and then cancels the transmission before attempting to transmit, the station does not have to initiate an RTS / CTS frame exchange before attempting to transmit after the cancellation. This is because the NAV has already been set by the CTS-to-Self frame. Also, if there is a remaining TXOP when the station attempts to 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 a pair of non-STR links>

[0193] The foregoing embodiments described an operation restriction method of an MLD considering that when an STA constituting the 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 of 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 of the MLD that supports NSTR is applied.

[0194] <AP Transmission Management Method>

[0195] When a specific AP among at least one AP constituting the AP MLD completes channel access to a specific AC and acquires 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, although the specific AP has acquired the right to start transmission to the specific AC, it may recognize that the frames in the transmission queue of the specific AC must be transmitted to an STA in the BLIND state and decide not to start transmission. At this time, the specific AP may also recognize that the frames in the transmission queue of the specific AC must be transmitted to an STA of the 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., another STA operating on the NSTR link pair of the NSTR MLD is transmitting), the AP can 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 to be transmitted to another STA that is not in a BLIND state in the transmission queue of an AC that has acquired transmission start authority, the AP can 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 acquired, the AP may perform / invoke a new backoff procedure for the AC. In this case, when the AP performs a new backoff procedure for the AC, it may generate a new backoff counter while maintaining the CW (contention window). 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 acquired may be performed.

[0199] Meanwhile, when a frame to be transmitted to a STA in a BLIND state exists in the transmission queue of an AC that has acquired the transmission start permission, the AP may consider the frame as if the frame does not exist in the transmission queue. For example, when only a frame to be transmitted to a STA in a BLIND state exists in the transmission queue, the AP may decide (operate) not to start transmission by considering the frame as if no frame exists in the transmission queue and maintaining the BO (backoff counter) of the AC that has acquired the transmission start permission at 0. In this case, the AP may immediately start transmission when the BLIND state of the STA is released, considering the frame to be transmitted to the STA as if it was generated in the transmission queue. Here, the "immediately" may mean transmission performed without a separate backoff procedure according to the EDCA rules. That is, when the BLIND state of the STA is released, if it is determined (considered) that the medium was IDLE for a time (e.g., DIFS, SIFS, PIFS, AIFSN [AC], etc.) already set before the release of the BLIND state, the AP may start transmission to the STA at the next slot boundary.

[0200] In addition, an MLD AP may not retransmit a trigger frame it has transmitted (e.g., a frame responding with a TB PPDU or CTS) if it has not received a response to the trigger frame it transmitted, i.e., if the transmission of the trigger frame has failed. Also, if an Ack (Ack frame and Block Ack frame) is not responded to after a frame requesting a response is transmitted, the MLD AP may not retransmit the frame.

[0201] In general, when a STA (AP STA, non-AP STA) including an AP in an AP MLD is considered to have failed in transmission of a frame it has sent, it must retransmit the failed frame. However, when an AP in an AP MLD determines that the reason for the failure of a frame it sent to an STA in the MLD is due to the operation 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 an AP retransmits a failed frame, it is considered that the receiving STA (destination device, intended recipient) will not respond to the retransmitted frame unless the operation of another STA that has an NSTR relationship with the receiving STA is changed.

[0202] When the AP determines that a transmission has failed due to the operation of another STA having 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 of the same AC (Access Category) as the failed frame. In other words, the STA (AP and non-AP STA) that performed the failed transmission due to the operation of another STA having an NSTR relationship with the receiving STA can generate a new backoff counter without increasing the CW[AC] due to 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, and an Ack for the frame is received (responded to) via the STA of another link (of the same MLD as the receiving STA), the STA of the MLD can set CW[AC] and QSRC[AC] to CW_min and 0 respectively. That is, even when the STA of the MLD does not directly receive an Ack response from the receiving STA after transmitting a frame to the receiving STA, if an Ack response is implemented (received) from another STA of the same MLD as the receiving STA, it can be considered (judged) that the transmission of the frame was successful. At this time, the STA of the MLD may maintain CW[AC] and QSRC[AC] without changing them even if an Ack is responded to 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 to by the receiving STA.

[0204] That is, even if a frame transmitted by the AP of the AP MLD fails, when the destination device is an 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 have 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 that it had to respond only to protect the reception operation of other STAs.

[0205] <Transmission Management Method of STA>

[0206] When a specific STA of Non-AP MLD completes a channel access procedure for a specific AC, i.e., when it acquires transmission permission to start transmitting traffic for the specific AC, the specific STA does not need to transmit frames in a 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, considering that the other STA is performing a PPDU reception operation, even though the specific STA has acquired the transmission start authority for the specific AC. That is, when the non-AP MLD is the NSTR MLD, the STA operating in the NSTR link pair may give up the acquired transmission start authority, considering the operation state of the other STA in the NSTR link pair. In this case, "giving up the acquired transmission start authority" may mean performing (invoking) the backoff procedure again without attempting transmission, or postponing (delaying) transmission while maintaining the backoff counter at 0.

[0209] If the STA decides not to start transmission for the AC for which the transmission start permission has been acquired, the STA may perform / invoke a new backoff procedure for the AC. In this case, when the STA performs a new backoff procedure for the AC, the STA may generate a new backoff counter while maintaining the CW (contention window). 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 acquired may be performed.

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

[0211] In this case, when the STA completes the PPDU reception of the other STA, the STA can immediately start transmission as if a frame was generated again in the transmission queue. Here, the "immediately" can mean transmission performed without a separate backoff procedure according to the EDCA rules. That is, when the STA completes the PPDU reception of the other STA, if it is determined (considered) that the medium was IDLE for a set time (e.g., DIFS, SIFS, PIFS, AIFSN[AC], etc.) before the completion of the PPDU reception, the STA can start 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 associated with a PPDU including an MPDU targeted at the other STA occurs. Alternatively, the time when the other STA completes PPDU reception may be the time when a PHY-TXSTART.request primitive associated with an Ack frame (and a PPDU including the Ack frame) that responds to a PPDU including an MPDU targeted at the other STA occurs. Alternatively, the time when the other STA completes PPDU reception may be the time when a PHY-TXEND.confirm primitive associated with an Ack frame (a PPDU including the Ack frame) that responds to a PPDU including an MPDU targeted at the other STA occurs. Alternatively, the time when the other STA completes PPDU reception may be the time when the corresponding TXOP for a PPDU including an MPDU targeted at the other STA ends. At this time, the end time of the TXOP can mean the time when the NAV corresponding to the TXOP is released.

[0213] <Transmission Management Limitation 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 as minimizing the negative effects (such as interference and channel access delay) that may occur due to the constraint of the NSTR link pair and ensuring the channel access ability of each STA as much as possible.

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

[0217] This may be a problem that occurs when the specific STA and other STAs maintain their back-off counters at 0 due to receiving operations for the same PPDU. Furthermore, when an AP transmits an MU PPDU through a specific link, multiple non-AP MLDs receiving the MU PPDU can maintain the back-off 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 receiving the MU PPDU can start transmission through 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 a back-off counter at 0 may have to start a channel access procedure considering 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 a PPDU being received by another STA of the NSTR link pair is a PPDU that should be received by multiple STAs. More specifically, the non-AP MLD STA can determine to maintain a back-off counter at 0 only if a PPDU being received by another STA of the NSTR link pair is a PPDU whose intended recipient is only the other STA. That is, the non-AP MLD STA can consider that there is no frame in its transmission queue (of a specific AC) only if a PPDU being received by another STA of the NSTR link pair is a PPDU whose intended recipient is only the other STA. In other words, a non-AP MLD STA cannot consider a PPDU being received by another STA on an NSTR link pair as having multiple STAs as its destination PPDU as if there were 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 received PPDU 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 an individual address assigned to the other STA.

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

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

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

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

[0227] However, the non-AP MLD STAs can maintain the backoff counter at 0 if the other STAs receive 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 among User fields 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 analyzed 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 perform an operation of maintaining the back-off counter at 0. In this case, if the first User field among User fields included in the HE MU PPDU indicates the other STA, it may be analyzed that the same implicit instruction as described above has been performed.

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

[0230] On the other hand, when the PPDU being received by another STA of the NSTR link pair is not a PPDU whose destination device is the other STA, or is a PPDU whose destination device is a plurality of STAs including the other STA, the non-AP MLD STA may need to execute (invoke) a new backoff procedure while maintaining CW[AC] and QSRC[AC] when the backoff counter becomes 0. 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 whose destination device is only the other STA, or if the PPDU being received is not a PPDU whose destination device is 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. If the PPDU being received by the other STA of the NSTR link pair is an EHT MU PPDU that contains two or more User fields.

[0233] 2. If the PPDU being received by the other STA of the NSTR link pair is an 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 said 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 the other STA of the NSTR link pair is not confirmed

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

[0240] As another method, the non-AP MLD STA may maintain the back-off counter at 0 regardless of the type of PPDU being received by the other STA of the NSTR link pair. However, if the non-AP MLD STA maintains the back-off 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 from the completion point), the non-AP MLD STA must transmit the RTS frame in the first frame. In this case, the restriction that the RTS frame must be transmitted in the first frame may be applied only when the PPDU being received by the other STA is not a PPDU whose only destination is the other STA. In other words, when the PPDU being received by the other STA is a PPDU whose only destination is the other STA, the non-AP MLD STA may not be obligated to transmit the 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 the first transmission to obtain a TXOP with an RTS frame. This may be a sequence that is considered so that TXOP acquisition attempts while the backoff counter is maintained at 0 are started (attempted) by exchanging RTS / CTS frames, considering that there may be a large number of non-AP MLD STAs that have maintained their backoff counter at 0.

[0242] Alternatively, a non-AP MLD STA may not decrement a back-off counter when another STA of an NSTR link pair is receiving a PPDU. This may be an operation 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 of an NSTR link pair is receiving a PPDU. In this case, the medium busy state may be released when an RXEND.indication related to 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 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 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 destined only for STA1, non-AP MLD STA2 can recognize that there is no other non-AP MLD STA that can postpone transmission while maintaining the back-off counter at 0 in order to receive the PPDU. Therefore, STA2 can select to postpone transmission while maintaining the back-off counter at 0, rather than starting transmission even when the back-off counter has reached 0 as shown in FIG. 20(a).

[0246] In this way, if the (SU)PPDU reception procedure of STA1 is completed while STA2 maintains the backoff counter at 0, STA2 can start transmission without performing a separate backoff procedure. At this time, STA2 can internally operate as if a frame to be transmitted to the transmission queue of the AC (Access Category) for which the backoff procedure has been completed (the backoff counter is maintained at 0) has been generated at the time when the PPDU reception procedure of STA1 is completed. That is, STA2 considers that there is no frame to be transmitted to the transmission queue of the specific AC when the PPDU reception procedure of STA1 is in progress even though the backoff procedure for the specific AC has been completed, but can start PPDU transmission on Link2 by considering that a frame to be transmitted to the transmission queue of the specific AC has been generated at the time when the PPDU reception procedure of STA1 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)) or more at the time when STA2 starts PPDU transmission.

[0247] In addition, when transmission is performed without a separate backoff procedure while maintaining the backoff counter at 0, a restriction may be applied that the medium state (CCA result of Link2) has not changed to busy while the backoff counter is maintained at 0. In other words, if STA2, which has maintained the backoff counter at 0 while STA1 is 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] Also, STA2 may 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 does so without changing CW[AC] and QSRC[AC].

[0249] Referring to FIG. 20(b), while non-AP MLD is receiving MU (Multi-user) PPDU on Link 1 via STA1, the back-off counter of STA2 operated by 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 also 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) whose destination is not only STA1 but also other STAs. Therefore, when the backoff counter reaches 0 as shown in (b) of FIG. 20, STA2 can decide to maintain the backoff counter at 0 or not to start transmission and to 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 Fig. 20(b), the backoff counter (for a specific AC) of STA2 reaches 0 twice while STA1 is receiving a PPDU, and STA2 invokes a new backoff procedure twice. In this case, when STA2 maintains CW[AC] and invokes a new backoff procedure, 5 is generated as the first backoff counter (New counter #1 in Fig. 20(b)), and when the backoff procedure is invoked again after the backoff counter reaches 0, 7 is generated as the second backoff counter (New counter #2 in Fig. 20(b)). After the second backoff counter reaches 0, STA2 starts transmitting a PPDU because STA1 is not receiving any more PPDUs.

[0252] FIG. 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 FIG. 21, the beacon frame may include the same parameters and elements in the Legacy IEs as those included in the beacon frame disclosed in conventional Wi-Fi 802.11ax. For example, the legacy IEs of a beacon frame may include elements such as a timestamp field, a beacon interval field indicating the interval at which a beacon is transmitted, TIM, DSSS parameter set, IBSS parameter set, country, channel switch announcement, extended channel switch announcement, wide bandwidth channel switch, transmit power envelope, supported operating classes, IBSS DFS, ERP information, HT capabilities, HT operation, VHT capability, VHT operation, S1G beacon compatibility, short beacon interval, S1G capability, S1G operation, HE capability, HE 6 GHz 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 in conventional Wi-Fi up to 802.11ax.

[0255] In addition, the beacon frame may 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 of the neighbor AP information fields may include a TBTT information header (2 octets), an operation class (1 octet), a channel number (1 octet), and a TBTT information set (variable length) field. In this case, 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 in order 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 FIG. 21. In this case, when the AP MLD indicates other AP information of the same MLD by the specific neighbor AP information field of the 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 the station that the neighbor AP information field is an AP included in the same AP MLD, and the 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 in which an index determined by the AP MLD is indicated to indicate a link in which another AP to be indicated using the neighbor AP information is operated. 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, when the value of the change sequence subfield is changed, a station receiving it can recognize that a parameter related to the BSS (or link) of the corresponding AP has been updated, and can request the updated parameter from the AP to update the corresponding parameter. In this case, if the AP MLD is an NSTR AP 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., a mobile terminal operates as a soft AP MLD for tethering, etc.), the STA included in the STA MLD can perform a procedure for updating parameters only in a primary link. That is, in order to update parameters of other links (e.g., non-primary links) to other neighboring APs other than the primary link of the AP MLD, frames for parameter update can be transmitted and received only through 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] Also, when the AP is an NSTR AP MLD that does not support simultaneous transmission and reception (e.g., when it is an NSTR mobile AP MLD or an NSTR soft AP MLD, i.e., when a mobile terminal 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 a beacon frame can recognize that the AP MLD that transmitted the beacon frame is the NSTR AP MLD. Therefore, the specific subfield for indicating that it is an NSTR AP MLD may be set to a value different from the specific value (e.g., "1" or "0") when not indicating the NSTR AP MLD (e.g., the STR AP MLD or another AP MLD, etc.).

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

[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 by an implicit method, rather than directly indicating that it is an NSTR AP MLD by a specific subfield. Specifically, the NSTR AP MLD may indicate that it has an NSTR link pair while indicating that it has two links that it can support, thereby implicitly indicating that it is an NSTR AP MLD. 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 pre-agreed value meaning 2) to indicate that it has two links that it can support. 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 inform the non-AP STA MLD that it is the NSTR AP MLD by an explicit or implicit method by transmitting a beacon frame by the above-mentioned method. The non-AP STA MLD can implicitly or explicitly recognize whether the AP MLD that transmitted the beacon frame is the NSTR AP MLD from the received beacon frame. 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 a procedure for association or setup with the NSTR AP MLD only on the link on which the beacon frame was received. That is, the non-AP STA MLD can transmit and receive frames for association or setup with the NSTR AP MLD on the link on which the beacon frame was received (e.g., 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] At this time, 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) in order 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 the neighbor AP information field for the AP of the other link (of the same MLD). In this case, the non-AP STA MLD may 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. At this time, the non-AP STA MLD that receives a beacon frame from the NSTR AP MLD that does not include the neighbor AP information field for the AP of the non-primary link can implicitly recognize that the other AP is the 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 of the same MLD is not indicated, as described above.

[0266] Meanwhile, in a typical AP MLD, when an (ML) (re)association request frame is received from a STA (MLD), an (ML) association response frame must be transmitted on the link on which the (ML) association request frame was received. However, in the NSTR AP MLD, a response to an (ML) association request frame received on a non-primary link can be made on the primary link (i.e., an (ML) association response frame can be responded to on the primary link).

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

[0268] Therefore, when the NSTR AP MLD receives an (ML) (re)association request frame on a non-primary link, it can respond with an (ML) (re)association response frame on the primary link, or it can respond with an (ML) (re)association response frame on both the primary link and the non-primary link at the same time. In other words, the STA MLD that sent an (ML) (re)association request frame on the non-primary link of the NSTR AP MLD knows that the response to the request frame it sent will be on the primary link, and can wait to receive an (ML) (re)association response frame on the primary link.

[0269] The RNR element transmitted by the AP in the beacon frame may include a specific TBTT information field including the MLD Parameters field. In this case, when the MLD ID of 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. That is, 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 / obtains this may be the same / similar to the operation that a conventional STA performs after receiving an RNR element.

[0270] However, since the NSTR Soft AP does not transmit a beacon frame through a non-primary link, it may be impossible to indicate information related to the beacon frame of another AP (non-primary link AP) through the RNR element. Furthermore, since the NSTR Soft AP MLD does not transmit a beacon frame through the non-primary link AP, it cannot support information related to the beacon frame when indicating the non-primary link AP basic information through the RNR element. For example, a non-primary link that does not transmit a beacon frame 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 through 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 a preset value.

[0271] The neighbor AP TBTT offset subfield of the TBTT information field (see FIG. 21(b)) is a subfield indicating 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 on the next TBTT of the AP corresponding to the neighbor AP information field. As an example, when AP1 transmitting a beacon frame indicates information on AP2 using the RNR element (by 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 has compared to 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 or more and less than 11 TUs based on the previous TBTT of the AP.

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

[0273] Therefore, when a non-AP STA MLD receives a beacon frame of an NSTR Soft AP MLD and checks a TBTT information field in which the MLD ID subfield is 0 and the TBTT offset subfield is specified as 254 and / or 255 in the specific neighbor AP information field of the RNR element included in the beacon frame, the non-AP STA MLD can recognize that the specific neighbor AP information field is information about an AP (of the NSTR Soft AP MLD) operated on a non-primary link of the NSTR Soft AP MLD. In this way, when a non-AP STA MLD that receives a beacon frame of an NSTR Soft AP MLD checks information about an AP MLD operated 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] In addition, when the non-AP STA MLD recognizes that the received beacon frame is the beacon frame transmitted by the MLD, and the Neighbor AP TBTT Offset subfield corresponding to another AP of the same MLD as the AP (Reporting AP) that transmitted the beacon frame is indicated as 254 and / or 255, the non-AP STA MLD shall not transmit a probe request frame and an ML probe request frame to other APs.

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

[0276] <MLD AP TBTT Offset Indication>

[0277] In the above-mentioned embodiment of the present invention, it has been mentioned that the beacon frame transmitted by the NSTR Soft AP MLD can indicate the neighbor AP TBTT offset subfield corresponding to the AP of the non-primary link as a preset value (254 and / or 255). However, the neighbor AP TBTT offset subfield can be indicated as 254 or 255 even if it does not correspond to the AP of the non-primary link of the NSTR Soft AP MLD. As an example, when 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 can indicate the neighbor AP TBTT offset subfield corresponding to the other AP in the beacon frame as 254. Also, when the AP transmitting the beacon frame cannot accurately recognize the TBTT offset of the other AP, the AP can 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 offsets of other APs in the MLD, it should not indicate (set) 255 when indicating (setting) the neighbor AP TBTT offset subfield corresponding to another AP (in the same MLD) using the RNR element.

[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 when the beacon frame is transmitted. In this case, the neighbor AP TBTT offset subfield indicates an offset value between the time when the beacon frame is transmitted and the time when the next beacon frame is transmitted by the AP corresponding to the neighbor AP TBTT offset subfield among the 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 according to a specific condition.

[0280] For example, when the neighbor AP TBTT offset subfield 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, the values ​​from 0 to 255 are respectively corresponding, so the maximum offset that can be indicated by 8 bits may be 255). However, when the neighbor AP TBTT offset subfield 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 a value set therein may differ according to a specific condition.

[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', according to a specific condition.

[0283] Specifically, if an AP corresponding to a neighbor AP information field including a 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 indicate only a TBTT offset of up to 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 the case where a TBTT offset of 254TU or more is present when considering the maximum TBTT offset that other APs may have ((2^16) or (2^16)-1TU when considering the configurable beacon interval).

[0286] However, when the AP MLD indicates information about other APs in the MLD using a beacon frame, an additional MLD AP TBTT offset subfield may be included in the transmission to more accurately notify the TBTT offset of the other APs. 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, when the neighbor AP TBTT offset subfield and the MLD AP TBTT offset subfield are both indicated in a specific TBTT information field, the neighbor AP TBTT offset subfield may be indicated as a preset value (which may be 254 or 255). The MLD AP TBTT offset subfield is a subfield with a size of 2 octets, and may be used to indicate a TBTT offset value when the TBTT offset between the AP (Reporting AP) that transmits 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 existing neighbor AP TBTT offset subfield cannot indicate an accurate TBTT offset.

[0287] When the STA MLD checks the TBTT information field including the MLD AP TBTT offset subfield in the RNR element included in the 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, in order to know whether the TBTT information field included in the beacon frame includes the MLD AP TBTT offset subfield, the STA may check based on the value of the TBTT information length subfield (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 the 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 have a configuration including an MLD AP TBTT offset subfield. The MLD AP TBTT offset subfield may be included only in a beacon frame transmitted by an AP of the AP MLD. Also, the MLD AP TBTT offset subfield may be included only in a TBTT information field corresponding to another AP of the same MLD as the AP transmitting the beacon frame.

[0290] As an example, in a beacon frame transmitted by a specific AP of an AP MLD, in order to indicate that the TBTT offset of another AP of 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 neighbor 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 an example subfield name, and subfields having 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] Referring to FIG. 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 the TBTT information header field in the neighbor AP information field included in the RNR element. That is, the RNR element transmitted in the 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 through the AP based on the information indicated in the TBTT information header. At this time, each parsed neighbor AP information field may indicate information on 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 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.

[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 be connected to the NSTR AP MLD must transmit (ML) probe request frames only on the link on which the NSTR AP MLD transmitted a beacon frame.

[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 play a role in which the MLD transmitting the ML probe request frame requests additional information on the AP of another link to the AP MLD.

[0297] For example, when a non-AP STA MLD transmits an ML probe request frame, it can request the AP MLD to further respond with complete information or partial information on the AP of another link using the Multi-Link element of the ML probe request frame. That is, it can request the AP MLD to transmit all or part of the parameters related to the link of another AP included in the same AP MLD to the AP receiving the ML probe request frame.

[0298] For example, when 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 is requested / responded to mean 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, whereas the partial information is requested / responded to mean that only the information on the AP of the other link requested by the STA is responded to.

[0300] When additional information about APs of other links is requested in the ML probe request frame received on a particular link, the AP MLD that sent the beacon frame can respond using an ML probe response frame to not only provide information about the AP of the particular link, but also the requested additional information about the AP of the other link.

[0301] In this case, when the STA MLD transmits an ML probe request frame on a specific link and requests complete information on the AP of another link, the AP MLD must provide information on the AP of the other link at the same level as the information on 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 a response of complete information on the AP of another link on a specific link can obtain the same level of information on 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, when the STA MLD transmits an ML probe request frame on a specific link and requests partial information on the AP of another link, the AP MLD can provide only requested information (requested element information) among information on the AP of the other link using an ML probe response frame that responds on the specific link. In other words, the STA MLD that receives partial information on the AP of the other link on a specific link can further obtain only the information that it requested from the AP of the other link. In this case, the STA MLD that requests partial information on 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, when the ML probe request frame received on a specific link includes information indicating information on the other link (Request element IDs field), the AP MLD can further indicate the indicated information on the other link in the ML probe response frame.

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

[0304] In this case, the additional information (Complete and Partial) for the other AP may be transmitted by a Per-STA profile included in a Multi-link element of an ML probe response frame. The Per-STA profile is a field included in the Multi-link element with 0 or more, and may include information of other STAs (AP and non-AP STAs) that exist in the same MLD as the STA (AP and non-AP STA) that transmits a frame including the Multi-Link element. In this case, the Per-STA profile has a configuration including a Complete Profile subfield, and complete information (information at the same level as the STA (AP and non-AP) that transmits a frame including the Multi-Link element) of other STAs (AP and non-AP STAs) that correspond (correspond) to a Per-STA profile in which the 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 transmits 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 analyze that the value of parameter1 for STA2 is specified to be the same as the value of parameter1 for STA1.

[0305] At this time, the Per-STA profile subelement included in the Multi-link element transmitted by the NSTR AP MLD may have a configuration that does not include a Beacon Interval subfield for indicating the interval at which a beacon is 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 the AP operated in the non-primary link of the NSTR AP MLD does not transmit a beacon frame, and therefore there is no separate period of the beacon frame. That is, even if the Complete Profile subfield (in the Per-STA Control field) is indicated as 1, the Beacon Interval Present subfield of the Per-STA profile subelement corresponding to the AP of a non-primary link of the NSTR AP MLD may be indicated as 0. That is, the beacon interval information for the AP of a non-primary link does not exist 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 be indicated as 1 in the Complete Profile subfield (in the Per-STA Control field) and 0 in the DTIM Info Present subfield.

[0307] That is, since beacons are not transmitted on non-primary links, even if a non-AP STA MLD requests all information (or all updated information) for other APs of non-primary links through the AP of the primary link of the AP MLD (i.e., completeness is set to '1'), the beacon interval and DTIM information for the AP of 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 of 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 of non-primary links is requested, the AP MLD does not need to include the beacon interval and DTIM information for the APs of 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] Since the NSTR AP MLD does not transmit a beacon frame to a non-primary link, 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 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 as 0. That is, the NSTR AP MLD may need to always indicate the Beacon Interval Present subfield in the Per-STA profile corresponding to the AP of the non-primary link as 0. Therefore, even if the NSTR AP MLD receives an ML probe request frame requesting complete information from a non-AP STA MLD or receives a (ML) (re)association request frame, the NSTR AP MLD may need to always indicate the Beacon Interval Present subfield and the DTIM information present subfield in the Per-STA profile corresponding to the AP of the non-primary link as 0.

[0310] Alternatively, since the NSTR AP MLD does not transmit a beacon frame to the non-primary link, it may be necessary to set the subfields of Beacon Interval, DTIM Count, and DTIM Interval to pre-promised values ​​in the Per-STA profile corresponding to the AP of the non-primary link. 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, etc., and then the complete information for the AP of the specific link is expected to be responded to 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 of the STA MLD acquiring 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 when the general AP MLD responds with complete information when responding with complete information of the non-primary link. In this case, the Per-STA profile corresponding to the AP of the non-primary link of the NSTR AP MLD may have the Beacon Interval subfield, the DTIM Count subfield, and the DTIM Interval subfield set to preset values, respectively. As an example, when the NSTR AP MLD transmits complete information for the AP of the non-primary link, each bit of the Beacon Interval subfield of the non-primary link can be set to all 0, all 1, or in a predetermined manner.For example, when the NSTR AP MLD transmits complete information for the AP of the non-primary link, it can set each bit of the DTIM Count subfield of the non-primary link to all 0's, all 1's, or a predetermined manner. For example, when the NSTR AP MLD transmits complete information for the AP of the non-primary link, it can set each bit of the DTIM Interval subfield of the non-primary link to all 0's, all 1's, or a predetermined manner.

[0311] Alternatively, since a beacon frame is not transmitted to 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 an operation 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 of 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. As an 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. As an 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. As an example, when the NSTR AP MLD transmits complete information for the AP of a non-primary link, it can set the DTIM Interval subfield of the non-primary link to a value indicating (meaning) the DTIM interval of the primary link.

[0312] Alternatively, since the NSTR AP MLD does not transmit a beacon frame to the non-primary link, the Beacon Interval, DTIM Count, and DTIM Interval subfields of the Per-STA profile corresponding to the AP of the non-primary link may be set to values ​​having a specific purpose by the AP MLD. Furthermore, the Beacon Interval subfield of the non-primary link may be set to a value having a specific purpose (virtual beacon interval), for example, a value for calculation. Conventionally, the beacon interval of Wi-Fi literally means a value related to the time interval at which a beacon frame is transmitted, but is also used as a time unit for the operation of various BSSs. For example, a unit such as JointFailureTimeout and QueryFailureTimeout primitives is defined as a beacon interval, and a Listen interval field, a PRAW Start offset subfield, an AID Request Interval field, an AID Switch Count field, an AID Response Interval field, a Minimum Transmission Interval subfield, a Channel Quality Measurement Duration, a Color Switch Countdown (BSS Color Change Announcement element) subfield, etc. indicate an interval / duration using the beacon interval (or TBTT) as a basic unit. As such, since the beacon interval has a meaning of a value related to an interval at which a beacon frame is actually transmitted, and is a value used as a unit for various primitives and fields, it may be necessary to define (indicate, set) a beacon interval for a non-primary link in order to be used as a unit for the above-mentioned primitives / subfields even if a beacon frame is not actually transmitted to the non-primary link.

[0313] That is, even if a beacon frame is not transmitted to 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 a beacon interval value to be used as a time unit of the non-primary link. In this case, the non-AP MLD can recognize (check, calculate) the duration and interval of the above-mentioned primitives and fields (used as a 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 on the non-primary link may need to operate based on the set value when operating the STA on the non-primary link.

[0314] Meanwhile, the method of setting subfields related to non-primary link beacons of the NSTR AP MLD described above (Beacon Interval, DTIM Count, DTIM Interval, etc.) 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 that wishes to associate with the 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 the non-primary link. That is, a non-AP STA MLD that transmits a Listen interval field to the NSTR AP MLD must calculate and set the unit of the Listen interval field as the beacon interval of an AP operating on the primary link of the NSTR AP MLD. In this case, the Listen interval field may be a field indicating information related to a period (time) at least one STA changes to a wake state in order for the non-AP STA MLD performing multi-link (re)association to receive a beacon frame. In this case, the Listen interval field may indicate a value derived when the ListenInterval parameter is indicated in the MLME primitive.

[0316] In this case, when the non-AP STA MLD transmits a Listen interval field to another AP MLD (e.g., STR AP MLD) other than the NSTR AP MLD, it may be necessary to set the unit of the Listen interval field to the maximum value of the beacon interval of the link (AP) that it is trying to set up. As an example, when the non-AP STA MLD is trying to perform a 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 value of the beacon interval of the 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 units of 100 ms.

[0317] Generally, when an AP and a STA complete the setup, the STA can learn and track (update) the operation parameters and element changes of the AP while receiving the beacon frame transmitted by the AP. The beacon frame also plays a role of providing information including the Timestamp field for the STA in the BSS to achieve time synchronization.

[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 additional operations to track (update) parameters / elements and maintain time synchronization for the non-primary links.

[0319] According to an embodiment of the present invention, the non-AP STA MLD combined with the 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 on 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 parameters and element information of the non-primary link. In this case, the ML probe request frame may request complete information of the non-primary link by setting the complete profile of the Per-STA profile corresponding to the non-primary link (and the AP of the non-primary link) to 1 and transmitting it. Alternatively, the ML probe request frame transmitted by the STA MLD for the purpose of updating the 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 performed only on the primary link. For example, when the STA recognizes that parameters for the AP of a non-primary link have been updated from a specific field (e.g., change sequence or BSS parameter change count subfield, etc.) indicating whether or not the parameter for the link of another AP included in the neighbor AP information included in the beacon frame is an update, the non-AP STA MLD can request transmission of 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 a frame (e.g., a probe request frame, etc.) 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 that requests 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 on the primary link. When the Updated Profile subfield is indicated as 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] As an 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 may further change Parameter 2 while increasing the Change Sequence number from 101 to 102. In this case, the STA MLD may request updated information of the non-primary link while transmitting an ML probe request frame. In this case, the NSTR AP MLD may respond with an ML probe response frame including both Parameter 1 and Parameter 2 when the non-AP STA MLD indicates that the Recorded Change Sequence subfield is 100, and may respond with an ML probe response frame including only Parameter 2 when the non-AP STA MLD indicates that the Recorded Change Sequence subfield is 101.

[0324] In this case, the Non-AP STA MLD does not use a separate Updated Profile subfield to request an Updated Profile, and may indicate the Complete Profile subfield as 0. That is, the way in which the Non-AP STA MLD requests an Updated Profile may be 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 Per-STA Profile subelement format according to an embodiment of the present invention.

[0326] Referring to FIG. 24(a), the Per-STA profile sub-element may have a configuration including a STA Control field. The STA Control field (see FIG. 24(b)) indicates information for indicating the type of field included in the STA profile (see FIG. 24(a)) of the Per-STA profile sub-element. In this case, in a specific Per-STA profile sub-element transmitted by another AP MLD other than the NSTR AP MLD, when the Complete Profile sub-field of the STA Control field is indicated as 1, the MAC Address Present sub-field, the Beacon Interval Present sub-field, and the 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 a beacon frame to a non-primary link, information related to a beacon frame of a non-primary link may not be indicated in the Per-STA profile sub-element corresponding to the non-primary link. That is, even if the Complete Profile subfield of a specific Per-STA profile subelement (corresponding to an AP of a non-primary link) transmitted by the NSTR AP MLD is indicated as 1, the Beacon Interval Present subfield and the DTIM Information Present subfield may be indicated as 0.

[0327] Also, as described in the above embodiment, the non-AP STA MLD that transmits the ML probe request frame to the NSTR AP MLD can request the AP of the primary link for updated information of the AP of the non-primary link by specifying the Updated Profile subfield of the STA Control field (included in the Per-STA profile subelement corresponding to the AP of the non-primary link) as 1. In this case, the non-AP STA MLD can specify the Recorded Change Sequence value, which is information related to the time when the non-primary link AP information is updated, 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 the ML probe request frame of the non-AP STA MLD received via the primary link, the NSTR AP MLD can determine the information of the AP of the non-primary link that responds 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 AP of the non-primary link.

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

[0329] 25, the NSTR AP MLD may indicate that the parameters of AP2 have been changed by using a beacon frame transmitted by AP1 operating on the primary link, link 1, after changing the parameters of AP2 operating on link 2, which is a non-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] Non-AP STA MLD can recognize the fact that the parameters of AP2 have been updated after receiving the beacon frame sent by AP1 through STA1. 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 be configured to include a Per-STA profile sub-element corresponding to AP2 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 information of AP2 (complete or updated information) in an ML probe response frame.

[0333] The non-AP STA MLD, which receives the requested information about AP2 from the NSTR AP MLD in an ML probe response frame, 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 an 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 operated 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 about 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 sub-element corresponding to the AP of the non-primary link, and plays a role in helping the non-AP STA MLD to 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 on the AP of the non-primary link. In this case, the broadcast ML probe response frame may be transmitted together with the DTIM beacon frame.

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

[0338] In this case, the parameter update procedure of 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 through the primary link, the non-AP STA MLD checks the Change Sequence (in the MLD Parameter field of the RNR element) of the non-primary link. If the checked Change Sequence value of the non-primary link is different from the Change Sequence value maintained (recorded) by the non-AP STA MLD, the non-AP STA MLD can transmit an ML probe request frame through the primary link. In this case, the ML probe request frame may include a subfield indicating whether to request complete information or updated information for the AP of the non-primary link. In addition, the ML probe request frame requesting updated information may also include a subfield indicating the Change Sequence value maintained (recorded) by the non-AP STA MLD. Thereafter, the non-AP STA MLD that has received a ML probe response frame from the AP MLD updates parameters based on the information of the AP of the non-primary link included in the responded ML probe response frame.

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

[0342] As mentioned above, the beacon frame transmitted by the AP not only transmits various parameters and element information, but also helps the STAs in the BSS to synchronize time. The TimeStamp field included in the beacon frame indicates the TSF (timing synchronization function) timer value at the time when the data symbol containing the first bit of the TimeStamp field appears at the transmit antenna connector, and the STA that receives the TimeStamp field can synchronize its 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 that are associated with a non-primary link AP of NSTR AP MLD must use a method other than beacon frames to maintain time synchronization with the AP.

[0344] In order to maintain time synchronization with the AP of the non-primary link of the NSTR AP MLD, the associated non-AP STA may need to use the TimeStamp of the TIM frame transmitted by the AP. Since the TIM frame has a configuration including a TimeStamp field having the same function as a beacon frame, the STA that receives the TIM frame from the 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, since the NSTR AP MLD may be restricted from starting transmission on the non-primary link without occupying the primary link, it may be necessary to transmit a TIM frame on the non-primary link at the same time as transmitting a beacon frame on the primary link. In other words, the non-AP STA MLD associated with the NSTR AP MLD may need to prepare to receive a TIM frame 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, a link (non-primary link) for an AP 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 (NSTR Soft AP MLD reference) link, 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 to maintain time synchronization between APs of the NSTR AP MLD and / or between STAs of the non-AP STA MLD combined with the NSTR AP MLD to have an error less than 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 pre-promised / configured 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 pre-promised / configured value.

[0347] In other words, the TSF timer of the primary link may be maintained (or applied or used) the same for all links to APs included or affiliated in the NSTR AP MLD, and the difference between the timestamp or TSF timer of any two APs included or affiliated in 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 any two APs (e.g., an AP of a primary link and an AP of a non-primary link) included in or affiliated with the AP MLD or NSTR AP MLD may be limited to within a specific value (e.g., ±30 us), in which case the AP MLD or NSTR AP MLD can modify the timestamps or TSF timers so that the difference or clock drift of the TSF timers is within the specific value.

[0349] In addition, the non-AP STA MLD associated with the NSTR AP MLD may need to receive the next beacon frame transmitted through the primary link when it receives a TIM frame through the non-primary link. More specifically, when the non-AP STA MLD receives a TIM frame through the STA of the non-primary link 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 through the primary link. In this case, the next beacon frame may mean a beacon frame transmitted corresponding to the TBTT of the primary link that exists after the time when the TIM frame is received through the non-primary link. In this case, the meaning of receiving the next beacon frame may be an operation that accompanies (includes) updating parameters of the non-primary link using a 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 related to a critical update.

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

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

[0352] In conventional Wi-Fi, the operating channel frequency (operating frequency band) of the BSS can be changed by a procedure previously agreed between the AP and the STA. In this case, the conventional ECS (Extended channel switching) operation can be used, or the channel change mechanism newly defined in 11be can be used. When the AP decides to change the operating channel of the BSS, it can transmit a beacon frame, a probe response frame, an Extended Channel Switch Announcement frame, etc., to inform the associated STAs that they can switch to a new channel and operating class while maintaining the 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 on how many beacon frames are transmitted before a channel switch (operating channel change) is performed. If the AP includes a MAX Channel Switch Time element in a beacon frame together 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 smaller than the time interval indicated by the Switch Time field relative to 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 on the new channel, information on the time when the channel change is performed, 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 in a time period (time period indicated by the AP) determined based on the channel change related information included in the beacon frame transmitted by the AP. In this way, the channel change procedure of the conventional Wi-Fi BSS is performed in a manner in which information required for channel change (Channel Switch mode, new operating class, new channel number, channel switch count, etc.) is provided by the beacon frame transmitted by the AP, and therefore, in the case of a non-primary link BSS of the NSTR AP MLD in which a beacon frame is 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 an 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 by a beacon frame transmitted on the primary link. That is, the non-AP STA MLD associated with the NSTR AP MLD can operate based on information obtained by 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 by 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 performing a channel change or setting a quiet interval for the non-primary link.

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

[0358] Referring to FIG. 27, a (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. In this case, the timing fields are used to collectively refer to time-related fields including duration-related fields (Switch Time, Quiet Duration field, etc.) and time-related fields (Channel Switch Count, Quiet Count field, etc.).

[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 operated in the primary link, obtain 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 analyze the information related to a channel change and / or a quiet interval of the non-primary link based on the TBTT and BI (Beacon interval) of the primary link. In this case, the Per-STA profile refers to a Per-STA profile corresponding to the AP of the non-primary link.

[0362] Meanwhile, the NSTR AP MLD may need to transmit a TIM frame (of the non-primary link) on a new channel within a time period indicated by the Switch Time field (of the Max Channel Switch Time element) after completing a channel change of the non-primary link using a beacon frame of the primary link (after announcing and completing the channel change). That is, the AP of the non-primary link of the NSTR AP MLD may need to transmit a TIM frame on a new channel after performing a channel change. In this case, the AP of the non-primary link may need to transmit a TIM frame on a new channel within a time period indicated by the Switch Time field after a beacon frame with a Channel Switch Count subfield indicated as 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. As an example, the NSTR AP MLD may transmit a beacon frame indicating information related to the completion of the channel change in the primary link after completing the channel change of the non-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 having a configuration including complete information for the non-primary link. For example, the beacon frame having a configuration including 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 time period previously agreed upon with the beacon frame transmitted before the channel change is started. In this case, the previously agreed upon time may be a time indicated in a Switch Time field (of a 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. As an example, the primary link beacon frame transmitted after the channel change of the non-primary link is completed may have a configuration including a Channel Switch Complete subfield. In this case, the Channel Switch Complete subfield may be a subfield included in an ML element. The specific Switch Complete subfield may be a subfield that is indicated as 1 when the channel change of the AP corresponding to the Per-STA profile 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 AP of the non-primary link to 1. At this time, 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, according to a general AP MLD.

[0363] The non-AP MLD combined with the NSTR AP MLD can perform an operation that considers the channel change of the non-primary link to be completed only when it receives a promised frame (the 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 considered that the channel change is not completed, the non-AP STA MLD may need to consider that the channel change of the non-primary link is canceled and operate (return to the previous channel) on the previous channel (before the channel change was performed).

[0364] Alternatively, the NSTR AP MLD may be restricted so that a quiet interval cannot be set in a non-primary link. In this case, if there is a quiet interval defined (set) in the primary link, the quiet interval of the non-primary link may be defined (set) as the same time interval as the quiet interval of the primary link. In other words, when the non-AP STA MLD combined with the NSTR AP MLD recognizes the quiet interval of the primary link, it can be considered that a quiet interval is set for the same time interval in 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 tries 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 (indicated) by the NSTR AP MLD as follows.

[0367] 1. The Quiet Count field may be set to the number of TBTTs of the primary link remaining 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 TUs) 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 how many TBTTs of the primary link remain before 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 (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 begins 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. As an example, when the beacon interval of the primary link is 100 ms, if 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, the non-AP MLD combined with the NSTR AP MLD can obtain information on the quiet interval and channel change time and period of the non-primary link based on the information indicated in the Per-STA profile of the non-primary AP included in the beacon frame, the TBTT of the primary link, and the beacon interval information after receiving the beacon frame on the primary link. At this time, the non-AP MLD can set (recognize, 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 on the primary link.

[0374] Conventionally, a Wi-Fi non-AP STA can select whether or not 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 channels on 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 to a state set up only on the primary link (by setup or reset after release).

[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 associated with 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) in a non-primary link, the NSTR AP MLD can transmit a beacon frame transmitted via AP1 of the primary link including a Per-STA profile corresponding to AP2. The Per-STA profile corresponding to AP2 includes a Quiet element and indicates information related to the time when the Quiet interval (Quiet interval#1 in FIG. 18) starts in 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, 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) starts when "x" TUs have elapsed since the TBTT corresponding to the third beacon frame.

[0380] As shown in Fig. 28, the NSTR AP MLD can again include the Per-STA profile corresponding to AP2 in the beacon frame transmitted via AP1 of the primary link in order to further set (define) the next quiet interval (Quiet interval#2 in Fig. 28) in the non-primary link. The sixth beacon frame (Beacon#6 in Fig. 28) of the primary link shown in Fig. 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 Fig. 28) has the Quiet Count field set to 1.

[0381] A non-AP STA MLD that receives the sixth and / or seventh beacon frame on the primary link can recognize that a quiet interval (Quiet interval #2) is 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 #2) starts from the TBTT corresponding to the eighth beacon frame.

[0382] At this time, information regarding the length of the quiet interval is indicated by a 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 one 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 associated with STA1 and STA2 of the Non-AP STA MLD, respectively.

[0385] In order to change the non-primary link to a new channel, the NSTR AP MLD can transmit a beacon frame transmitted via the primary link AP1 including a Per-STA profile corresponding to AP2 (non-primary link). The Per-STA profile corresponding to AP2 includes an (Extended) Channel Switch Announcement element and a Max Channel Switch Time element, and indicates information related to the time when the channel change starts and the time period during which the TIM frame is transmitted on the new channel after the channel change. When the (Extended) Channel Switch Announcement element is included in the first beacon frame (Beacon#1 in FIG. 19) of the primary link 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] The non-AP STA MLD that receives the first and / or second beacon frame on the primary link can determine that the channel change (to a new channel) of the non-primary link begins after receiving the second beacon frame by checking the (Extended) Channel Switch Announcement element included in the Per-STA profile (corresponding to AP2) of the beacon frame, and that the TIM frame of AP2 on the new channel will be received within 'x' TUs from the time the second beacon frame is received. In this case, the new channel may be a 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 a time value indicated in the Switch Time field included in the Max Channel Switch Time element included in the Per-STA profile (corresponding to AP2).

[0387] Operation restrictions of non-AP STA MLD combined with NSTR AP MLD

[0388] NSTR AP MLD is an AP MLD in which 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 be in the BLIND state, and conversely, when the AP of the non-primary link transmits, the AP of the primary link may be in the BLIND state. In this case, the AP of the NSTR AP MLD that has gone through the BLIND state may need to set the MediumSyncDelay to a preset value.

[0389] MediumSyncDelay is a single timer that is commonly applied to the EDCAF (EDCA Function) of the STA. When MediumSyncDelay is not 0, additional 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 preset 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 stricter (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 a MediumSyncDelay of 0.

[0390] Therefore, in the case of NSTR AP MLD, when the AP passes through the BLIND state, MediumSyncDelay must be applied, and in a situation where the channel access of the AP is restricted, it may be difficult to provide normal service to the STA of the BSS. The NSTR AP MLD can manage transmissions on a non-primary link (a link other than the primary link) in a manner that the primary link does not enter the BLIND state by determining one of the links of the NSTR link pair in which the AP operates as a primary link. As an example, the NSTR AP MLD can manage the primary link not to enter the BLIND state by transmitting on the non-primary link only when transmission is in progress on the primary link. For this purpose, the NSTR AP MLD does not need to respond with the requested response frame even if it receives a frame requesting a response frame through the AP of the non-primary link. That is, the NSTR AP MLD can perform an operation of not responding with a response frame even if it receives a frame requesting a response frame through 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 the AP operating on the primary link and / or the non-primary link in order to set up a primary link and prevent the AP of the primary link from being in a BLIND state. Similarly, the non-AP STA MLD combined with the NSTR AP MLD may need to understand the primary link management method of the NSTR AP MLD and operate. For example, when the non-AP STA MLD recognizes that a response frame is not responded to from the NSTR AP MLD on the non-primary link, it may not transmit a frame requesting a response of the response frame on the non-primary link. Also, when the non-AP STA MLD transmits a frame requesting a response of the response frame on the non-primary link and fails to receive a response of the response frame from the NSTR AP MLD, it may not retransmit the frame requesting a response of the response frame. For example, when 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] In addition, even if the non-AP MLD completes the channel access procedure of the non-primary link to perform UL transmission, the non-primary link transmission can be postponed until the channel access procedure is completed on the primary link. In this case, the method by which the non-AP MLD postpones the non-primary link transmission may be to stop 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 stops the backoff procedure performed by the STA of the non-primary link may be to maintain the backoff counter at 0.

[0393] In the above-mentioned method, the non-AP STA MLD that has completed the channel access procedure in both the primary link and the non-primary link can perform simultaneous transmission (simultaneous UL PPDU transmission) in the primary link and the non-primary link. In this case, the "simultaneous transmission" means that the time when each transmission starts is within a preset time interval. However, if only the channel access procedure in the primary link is completed and the channel access procedure in the non-primary link is not yet completed, the non-AP MLD can start PPDU transmission only in the primary link, or can start simultaneous transmission when the channel access procedure in the non-primary link is completed. That is, when transmitting to the NSTR AP MLD, the non-AP MLD can perform transmission using only the primary link, or can perform simultaneous transmission using the primary link and the non-primary link. However, it is not necessary to allow the non-AP MLD to transmit PPDU to the 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 the transmissions on both links are completed within a preset time interval.

[0395] In addition, the non-AP MLD may need to set whether or not the PPDUs transmitted on both links request a response frame when performing UL transmission using both the primary link and the non-primary link in the NSTR AP MLD. Furthermore, the two UL PPDUs transmitted simultaneously by the non-AP MLD on the primary link and the non-primary link may both request a response frame, or both may need to request a response frame. This may be a restriction that is applied because if a response frame is only responded to on a specific link as a result of the UL transmission performed by the non-AP MLD using both the primary link and the non-primary link, the APs operating on other links of the NSTR AP MLD may be in a BLIND state. However, the NSTR AP MLD may not need to respond to all of the two PPDUs (received on the primary link and the non-primary link, respectively) that have been received simultaneously if only one of them is a PPDU that requests a response frame.

[0396] In addition, the non-AP MLD may need to configure the NSTR AP MLD so that the TXOP of the non-primary link ends at the same time as the TXOP of the primary link or ends earlier when transmitting using both the primary link and the non-primary link. In other words, the non-AP MLD may need to configure so that the TXOP of the non-primary link ends at the same time as the TXOP of the primary link or ends earlier. However, the non-primary link TXOP of the non-AP STA MLD may be allowed to end later than the TXOP of the primary link by a point within a preset time interval.

[0397] In addition, the non-AP STA MLD can recognize that the NSTR AP MLD has experienced a BLIND state in the AP of a specific link and assist the operation of the AP. Furthermore, when the non-AP STA MLD recognizes that the NSTR AP MLD has transmitted only on one of the primary link and the non-primary link, it can recognize 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 perform an operation to assist the AP to release (reset to 0) MediumSyncDelay, considering that the AP that experienced 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 be an operation using a characteristic that MediumSyncDelay can be released when a PPDU (including a valid MPDU) capable of NAV setting is received.

[0398] As an example, the non-AP STA MLD may transmit an Assist frame (a kind of PPDU) capable of NAV setting to the AP of the NSTR AP MLD that is determined to have a non-zero MediumSyncDelay after passing through the BLIND state. In this case, the Assist frame may mean a frame included in a valid MPDU capable of NAV setting, regardless of the frame format. In this case, the condition for the non-AP STA MLD to transmit an Assist frame to the NSTR AP MLD on 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. In this case, another condition for the non-AP STA MLD to transmit 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 is explicitly or implicitly requested (instructed) to transmit an Assist frame from the NSTR AP MLD.

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

[0400] Wi-Fi prior to 6-home 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 terminals (AP STA, non-AP STA) first began using. Considering that there are no conventional Wi-Fi terminals (terminals prior to 6th generation Wi-Fi) operating in the 6GHz band, the IEEE 802.11ax Task Group (TG), which has been working on standardization for HE terminals, stipulated that HE STAs (AP STA, non-AP STA) operating in the 6GHz band should not operate in backward compatibility with previous generation Wi-Fi terminals. More specifically, the standard specifies that HE STAs operating at 6 GHz should be restricted from transmitting HE operation elements, including HT capabilities elements, VHT capabilities elements, HT operation elements, VHT operation elements, and / or VHT operation information fields, 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 capability elements and / or operation elements in legacy formats (e.g., HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, and / or HE operation elements including a VHT operation information field, etc.).

[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 2.4GHz / 5GHz, such as HT capability factor, VHT capability factor, HT operation factor, and / or 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 and operation factors for bands other than the specific band (e.g., 2.4GHz / 5GHz). In other words, the AP and / or non-AP STA can transmit capability and / or operation information for bands in which each of the multiple STAs operates, and cannot transmit capability and / or operation information for bands in which each of the multiple STAs does not operate.

[0403] That is, the beacon frame transmitted by the HE AP operating at 6 GHz and the association request frame transmitted by the non-AP STA performing setup at 6 GHz do not include the capability and operation information when operating as HT and VHT STA (AP and non-AP STA). Since there are no other HT / VHT STAs operating in the 6 GHz band, the HE STA operating at 6 GHz does not need to operate as a HT / VHT STA, and therefore the capability and operation information of the HT / VHT STA operation described above may be unnecessary information. For this reason, the 11ax standard restricts the HE STA (AP STA and non-AP STA) operating at 6 GHz from transmitting the HE operation element including the HT capability element, VHT capability element, HT operation element, VHT operation element, and VHT operation information field, and the same restriction may be applied to the EHT STA (MLD) that inherits the operation of the HE STA.

[0404] In other words, a STA operating in the 6 GHz band may not 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, i.e., a STA operating in the 6 GHz band may not 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 including information of the other STAs. In this case, the Basic Multi-Link element may include a STA Profile field including capability elements and / or operation elements for the other STAs reported by the STA operating at 6 GHz. The STAs 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-mentioned 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 (operated on other links) in the same MLD in a beacon frame and a (ML) probe response frame, an association request frame, and / or an association response frame. In other words, an AP operating at 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 in order to provide information about other APs operating at 2.4 GHz and 5 GHz, and therefore the restriction in 11ax that 6 GHz STAs (AP STAs, non-AP STAs) cannot indicate HT / VHT related elements must be amended. In this case, the (ML) probe response frame can mean a response frame transmitted in response to an ML probe request frame.

[0407] In the description of the present invention given below, APs operating at 2.4 GHz / 5 GHz / 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 / 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 an embodiment of the present invention, a 6GHz 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 2.4GHz and 5GHz STAs (reported STAs) in the same MLD. In this case, a frame in which the 6GHz AP / STA can include HT / VHT related information for the 2.4GHz and 5GHz STAs (AP STAs that are reported STAs, non-AP STAs) may be a management frame. In this case, the 6GHz AP / STA may include HT / VHT related information for the 2.4GHz and 5GHz AP / STAs in an ML IE (Multi-Link information element) in the management frame. In this case, the 6GHz AP / STA may include HT / VHT related information for the 2.4GHz and 5GHz AP / STAs in a Per-STA profile sub-element 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 with 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) may send a (re)association request frame with HT / VHT capability / action 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) may send HT / VHT capability / action 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 constituting an MLD can 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, an STA (first STA) operating at 6 GHz included in the first MLD can transmit an association request frame (or a 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 a reassociation response frame) in response to the association request frame (or a 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 (eg, multilink information (or elements), etc.).

[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., HT capability element, VHT capability element, HT operation element, VHT operation element, or 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 regarding the other STAs included in the association request message (e.g., multilink information (or elements) etc.) may include information regarding 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 etc.).

[0418] In this case, information regarding 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 subelements corresponding to each of the reported STAs, and the Per-STA profile subelement may include a Complete Profile subfield indicating whether or not the request is for all information for the corresponding station among the 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 (eg, multilink information (or elements), etc.).

[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., HT capability element, VHT capability element, HT operation element, VHT operation element, or 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 regarding the other APs included in the association request message (e.g., multilink information (or elements) etc.) may include information regarding 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 etc.).

[0424] Furthermore, the 6 GHz AP (in MLD) can transmit an ML probe response frame including an HT / VHT capability / operation element in the same manner as the above-mentioned association request frame or association response frame. At this time, 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). At this time, 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 a 6 GHz AP 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 for the purpose of indicating 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 for certain purposes.

[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 send a (re)association response frame including HT / VHT related elements only if a non-AP STA has sent a (re)association request frame in the 6 GHz band and intends to accept the ML setup request of the non-AP STA and perform setup in 2.4 GHz and / or 5 GHz as well.

[0432] As another method, there may be a method of restricting 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 including information (Per-STA Profile) of 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 transmit an ML probe request frame to the 2.4 GHz AP or 5 GHz AP to obtain additional information (included in the HT / VHT related element) for the 2.4 GHz and / or 5 GHz AP.

[0434] Considering the limitation that HT / VHT related elements cannot be transmitted / obtained in 6 GHz, a non-AP EHT MLD that intends to transmit an ML association request frame to a 6 GHz AP may need to receive an ML probe response frame including complete information (or HT / VHT related elements) of an AP that is to be set up in 2.4 GHz or 5 GHz in advance. In other words, a non-AP EHT MLD that intends to transmit an ML association request frame to a 6 GHz AP and 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] In addition, after completing ML setup in 6 GHz, the non-AP MLD may need to transmit complete information (or HT / VHT related elements) of the STAs (2.4 GHz STAs and 5 GHz STAs) operating in the 2.4 GHz link and 5 GHz link that have been set up to the AP MLD. In this case, the non-AP MLD can transmit the HT / VHT capability / operation elements of the 2.4 / 5 GHz STAs in the first PPDU transmitted after association in order to transmit the elements of the 2.4 / 5 GHz STAs that have been set up.

[0436] FIG. 31 illustrates an example of a method for exchanging HT (High Throughput) / VHT (Very High Throughput) related element information with other links that are not of a specific bandwidth to set up multiple links according to an embodiment of the present invention.

[0437] 31, the AP MLD can operate AP1 to AP3 at 2.4 GHz / 5 GHz / 6 GHz, respectively. The non-AP MLD that receives the beacon frame of the 6 GHz AP AP3 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, non-AP MLD may intend to attempt ML setup including the 2.4 GHz AP and the 5 GHz AP, and therefore 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 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 a 5 GHz AP can transmit an association request frame to the 6 GHz AP via a 6 GHz STA to request an ML setup including 2.4 GHz / 5 GHz. Generally, complete information for the STA of the link requesting the ML setup should be included in the association request frame, but the 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 a setup for 2.4 GHz and / or 5 GHz should generally include complete information for the AP of the link accepting the ML setup, but the 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 transmit HT / VHT capability / operation elements for the 2.4 / 5 GHz STA with which it has been set up to the AP MLD using the first PPDU it transmits after receiving the association response frame.

[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) in the MLD.

[0443] As discussed in the above-described embodiment of the present invention, an EHT STA (reporting STA) can transmit a management frame containing complete information of other STAs (reported STAs) within the same MLD, and considering that an MLD can operate multiple STAs, a management frame containing complete information of 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 an element of the reporting STA including the same information as an element of the reporting STA. 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 some elements may be analyzed as inheritance of information 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 mean 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 when 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 subelement 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 in the management frame. Also, an MLD receiving a management frame from a STA in an MLD can use the inheritance rule to obtain (analyze, recognize) the omitted information of reported STAs.

[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 indicated as 1. In other words, the reported STA corresponding to the Per-STA profile in which the Complete Profile subfield is indicated as 1 may be a STA for which complete information is indicated in the management frame.

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

[0448] There may be a case where a reporting STA that transmits a management frame does not have specific element information. For example, when a reporting STA is a 6 GHz STA (AP STA, non-AP STA), the 6 GHz STA that is the reporting STA may not have HT / VHT related elements. In this case, when 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 indicated to the 2.4 GHz and 5 GHz STAs cannot be indicated / analyzed using the inheritance rule. This is because the 6 GHz STA that is the reporting STA does not have HT / VHT related information, and therefore, the management frame in which the 6 GHz STA is the reporting STA cannot apply the inheritance rule to the elements indicated only to the reported STA. That is, when complete information of multiple 2.4 GHz and 5 GHz STAs is to be indicated in a management frame transmitted by a 6 GHz STA, 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 on 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 (e.g., elements) of a 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 be inherited from another element rather than an element of the reporting STA. In this case, the condition for considering the specific element as inherited from another element rather than an 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 is inherited from another element rather than an element of the reporting STA may be applied only when the reporting STA is a 6 GHz STA.

[0452] According to an embodiment of the present invention, when 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 a value of an element (having the same element ID and extended element ID) identical to 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 the specific element for the reported STA may be an element for other reported STAs. In this manner, even if the HT / VHT capability / operation element for the 6 GHz STA is not indicated in the 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 other reported STAs.

[0455] Or, the same element (having the same element ID and Extended element ID as the specific element) inherited as the specific element for the reported STA may be an additional element designated for inheritance, where the additional element designated for inheritance may refer to 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 a 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 to be not indicated in the management frame.

[0457] For example, if a specific element for STA1, for which complete information is indicated by a 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 being the same as that indicated in the specific element of STA1. In this case, STA2 may not be a reporting STA.

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

[0459] According to an embodiment of the present invention, when a specific element of a reported STA for which complete information (profile) is indicated is not indicated in a management frame, a value of an element (having the same element ID and extended element ID) identical to the specific element indicated in the management frame may be considered to be applied (indicated) to the specific element of the reported STA in the same manner. In this case, an element to be 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, when 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, when an element that is the same as the specific element is indicated for a reporting STA (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) to be inherited as a specific element for a reported STA may be determined to be the same element (in element order) that was last indicated in the management frame.

[0463] Furthermore, when 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 specified for three STAs earlier, 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] 32, the management frame includes four elements for the reporting AP (respectively elements IDA to D in FIG. 22), and includes an ML IE for indicating complete information of the reporting STA.

[0466] The ML IE (Multi-link element) is composed of an element ID subfield, a Length subfield, an element ID Extension subfield, and two Per-STA profile subelements. At this time, the Per-STA profile indicated first in the order is the Per-STA profile included to indicate complete information (profile) for the reported STA1, and the Per-STA profile indicated later in the order is the Per-STA profile included to indicate complete information (profile) for the reported STA2. That is, the Per-STA profile indicated first in the order is the Per-STA profile for the reported STA1, and the Per-STA profile indicated later is the Per-STA profile for the reported STA2.

[0467] The Per-STA profile corresponding to reported STA1 includes two elements (with 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 (with element IDs A to D), the remaining three elements (with element IDs A, B, and D, respectively) excluding the element indicated in the Non-Inheritance element (with element ID C) may be considered to be indicated identically for reported STA1. In this case, the three elements considered to be indicated identically to the reporting STA are also considered to have the same values ​​indicated by each element as 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 from the reporting STA (element IDs A, B, and D), it may 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 (of the element with element ID B) indicated for reported STA2 is different from the element value (of element ID B) indicated for the reporting STA, so the element for the reporting STA was not inherited and a new element value for reported STA2 was 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 designated the same as for reported STA2. In this case, the values ​​indicated by each of the above three elements considered to be designated the same as the reporting STA are also considered to be the same as 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 that were specified earlier in terms of 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 specified identically 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 elements with the same values ​​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 a function of explicitly indicating elements to which inheritance should not be applied after elements that are not indicated to the Reported STA. In other words, when a specific element is indicated in the Non-Inheritance element included in the Per-STA profile sub-element of a specific STA, the specific element that is not indicated to the specific STA may be explicitly indicated not to inherit the value of other elements. In this case, the MLD that receives 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 for the purpose of resolving 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 received the management frame may be aware that some elements that are 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 know in advance 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 transmits the (re)association response frame does not separately indicate 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 a Non-Inheritance element corresponding to a 6 GHz AP that is a reported STA, the element may not be inherited to the 6 GHz AP. In this case, not being listed in the Non-Inheritance element may mean 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, when a management frame (e.g., a (re)association response frame) transmitted by the 2.4 GHz AP indicates a complete profile for the 6 GHz AP, the HT capability element for the 2.4 GHz AP is not 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 a particular band via a STA operating in another 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 (eg, 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 association between at least a first station, excluding the first station, among the first plurality of stations, and at least a second station, excluding the second station, among the second plurality of stations.

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

[0488] The capability elements and / or operation elements of each of the second at least one station are at least one of a HT (High Throughput) capability element, a VHT (Very High Throughput) capability element, a HT operation element, a VHT operation element, or a HE (High Efficiency) operation element including VHT operation 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 or not this is a request for all information for a corresponding station among the at least one second station.

[0491] When a Complete Profile subfield indicates a request for all the information, the multilink information of the response frame may include capability elements and / or operation elements of the station corresponding to the Complete Profile subfield indicating the 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) may include 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 legacy format capability element and / or an operation element for a corresponding particular 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 idea or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative and not restrictive in all respects. 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 that fall within the meaning and scope of the claims and their equivalent concepts should be construed as being included 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; The second MLD includes the second STA and at least one other second STA operating on the plurality of links, The first STA and the second STA operate in a specific band, 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 the 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, MLD.

2. The MLD of claim 1, 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 a HE (High Efficiency) operation element including a VHT operation information field.

3. The specific band is 6 GHz, The MLD of claim 1 , 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 1, wherein the Per-STA profile sub-element includes a Complete Profile sub-field indicating whether a request for all information for a corresponding STA among the at least one other second STA is made.

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

6. The MLD of claim 1 , wherein the processor performs a multi-link setup procedure for setting up the plurality of links between the first MLD and the second MLD based on the response frame.

7. 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 STAs when the request frame is an association request frame; The MLD of claim 6, 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.

8. The specific STA is an STA that operates in the at least one other band, The MLD of claim 7 , wherein the request frame includes a capability element and an operation element for the at least one other band.

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

10. A method performed by 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 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, The second MLD includes the second STA and at least one other second STA operating on the plurality of links, the first STA and the second STA operate in a specific band; 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 the 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.

11. The method of claim 10, 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 a High Throughput (HT) capability element, a Very High Throughput (VHT) capability element, an HT operation element, a VHT operation element, or a High Efficiency (HE) operation element including a VHT operation information field.

12. The specific band is 6 GHz, The method of claim 10, wherein the at least one other band is 2.4 GHz or 5 GHz.

13. 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 10, wherein the Per-STA profile subelement includes a Complete Profile subfield indicating whether the request is for all information for a corresponding STA among the at least one other second STA.

14. The method described in claim 13, wherein each of the at least one other second STA corresponds to the complete profile subfield indicating the request for all of the information among the at least one other second STA when the complete profile subfield indicates the request for all of the information.

15. The method of claim 10, further comprising: performing a multi-link setup procedure for setting up the plurality of links between the first MLD and the second MLD based on the response frame.

16. The method of claim 10, wherein the response frame is one of an association response frame or a multi-link (ML) probe response frame.

17. 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 STAs when the request frame is an association request frame; The method of claim 10, 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.

18. The specific STA is an STA that operates in the at least one other band, The method of claim 17 , wherein the request frame includes a capability element and an operation element for the at least one other band.

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