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

Abstract

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

Description

Technical Field

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

Background Art

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

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

[0004] And, as a technical standard established to overcome the limitations regarding communication speed pointed out as vulnerabilities in Wi-Fi, there is IEEE 802.11n. The purpose of IEEE 802.11n is to increase the speed and reliability of the network and extend the operating distance of the wireless network. Specifically, IEEE 802.11n supports a high throughput (HT) with a maximum data processing speed of 540 Mbps or more, and is based on the MIMO (Multiple Inputs and Multiple Outputs) technology that uses multiple antennas at both the transmitting and receiving ends to minimize transmission errors and optimize the data speed. Also, this standard uses a coding method that transmits multiple copies of overlapping transcripts to increase the reliability of the data.

[0005] As the popularity of wireless LANs has been activated and the applications using them have become diversified, there has been a growing need for a new wireless LAN system that supports a processing rate (Very High Throughput, VHT) higher than the data processing speed supported by IEEE 802.11n. Among them, IEEE 802.11ac supports a wide bandwidth (80 MHz to 160 MHz) at the 5 GHz frequency. Although the IEEE 802.11ac standard is defined only in the 5 GHz band, it is considered that the initial 11ac chipset supports operation in the 2.4 GHz band for backward compatibility with conventional 2.4 GHz band products. Theoretically, according to this standard, the speed of a wireless LAN with multiple stations can be up to a minimum of 1 Gbps, and the maximum single-link speed can be up to a minimum of 500 Mbps. This is achieved by expanding the concepts of wireless interfaces accepted in 802.11n, such as a wider wireless frequency bandwidth (up to 160 MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and high-density modulation (up to 256QAM). Also, as a method of transmitting data using the 60 GHz band instead of the conventional 2.4 GHz / 5 GHz bands, there is IEEE 802.11ad. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide a speed of up to 7 Gbps and is suitable for streaming high-bitrate videos such as large-capacity data and uncompressed HD videos. However, the 60 GHz frequency band has the disadvantage of being difficult for obstacles to pass through and being available only between devices in a short-distance space.

[0006] On the other hand, as a wireless LAN standard after 802.11ac and 802.11ad, the IEEE 802.11ax (High Efficiency WLAN, HEW) standard has been developed and is in the completion stage to provide high-efficiency and high-performance wireless LAN communication technology in a high-density environment where APs and terminals are concentrated. In an 802.11ax-based wireless LAN environment, it is necessary to provide high-frequency efficiency communication indoors / outdoors in the presence of a high density of stations and APs (Access Points), and various technologies have been developed to implement this.

[0007] In addition, in order to support new multimedia applications such as high-quality videos and real-time games, a new Wi-Fi standard for increasing the maximum transmission speed has been started to be developed. In the 7th generation Wi-Fi standard, IEEE 802.11be (Extremely High Throughput, EHT), the standard development is in progress with the goal of supporting a maximum transmission rate of 30 Gbps by using a wider bandwidth, increased spatial streams, and multi-AP cooperation in the 2.4 / 5 / 6 GHz bands.

Summary of the Invention

Problems to be Solved by the Invention

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

[0009] The technical problems to be achieved in the specification are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those with ordinary knowledge in the technical field to which the present invention belongs from the following description.

Means for Solving the Problems

[0010] A first Multi-link Device (MLD) including a plurality of stations each operating on a plurality of links according to the present invention includes a processor. The processor transmits a request frame to a second station among a second plurality of stations 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. The first station receives a response frame as a response to the request frame from the second station via the first station. The second station includes, in the response frame, capability elements and operation elements of the second station for the specific band, excluding capability elements and operation elements of the second station in a specific legacy format for another band. The response frame includes multi-link information for coupling a first at least one station excluding the first station among the first plurality of stations and a second at least one station excluding the second station among the second plurality of stations.

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

[0012] Also, in the present invention, each of the capability elements and / or operation elements of the second at least one station includes 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 VHT operation information.

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

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

[0015] Also, in the present invention, when the Complete Profile subfield indicates the request for all information, the multi-link information of the response frame includes the capability element and / or operation element of the station corresponding to the Complete Profile subfield indicating the request for all information among the second at least one station.

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

[0017] Also, 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 station, and each of the at least one Per-STA profile subelements of the Multi-Link element includes a legacy format capability element and / or operation element for the corresponding specific station among the first at least one station.

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

[0019] Also, 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] Also, the present invention provides a method including: transmitting a request frame from a first station among the first plurality of stations included in the first multi-link device to a second station among the second plurality of stations each operating on at least one link via the first station, where the first station and the second station operate in a specific band; and receiving, via the first station, a response frame as a response to the request frame from the second station, where the second station includes, in the wireless frame, the capability element and / or operation element of the second station for the specific band excluding the capability element and / or operation element of the second station for the other bands, and the wireless frame includes multi-link information for association between at least one first station other than the first station among the first plurality of stations and at least one second station other than the second station among the second plurality of stations.

Advantages of the Invention

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

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

Brief Description of the Drawings

[0023]

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DETAILED DESCRIPTION OF THE INVENTION

[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 in the present invention, but these may vary depending on the intentions, customs, or the emergence of new technologies of those skilled in the relevant technical field. In addition, there are also terms arbitrarily selected by the applicant in specific cases, and in such cases, the meaning thereof will be described in the explanatory part of the corresponding invention. Therefore, it is clarified that the terms used in this specification should not be merely the names of the terms, but should be interpreted based on the substantial meanings of the terms and the content throughout this specification.

[0025] Throughout the specification, if a component is "connected" to another component, this includes not only cases where it is "directly connected", but also cases where it is "electrically connected" with other components interposed therebetween. Also, if a component "includes" a specific component, this means that, unless otherwise stated to the contrary, it can further include other components rather than excluding other components. In addition, limitations such as "above" or "below" based on a specific threshold value can be appropriately replaced by "exceeding" or "less than", respectively, depending on the embodiment.

[0026] Hereinafter, in the present invention, a field and a subfield may be used in the same meaning.

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

[0028] The wireless LAN system includes one or more basic service sets (BSSs), where a BSS represents a set of devices that have successfully synchronized and can communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and FIG. 1 shows an infrastructure BSS among them.

[0029] As shown in FIG. 1, the infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, STA5, access points AP-1 and AP-2 that are stations providing a distribution service, and a distribution system DS that connects the plurality of access points AP-1 and AP-2.

[0030] A station (STA) is any device that includes a Medium Access Control (MAC) and a Physical Layer interface for a wireless medium in accordance with the provisions of the IEEE 802.11 standard. In a broad sense, it includes not only non-access point non-AP stations but also all access points AP. Also, in this specification, the term "terminal" is used to refer to either a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface unit, a display unit, etc. according to embodiments. The processor generates frames to be transmitted via a wireless network, or processes frames received via the wireless network, and performs various other processes for controlling the station. And the communication unit is functionally connected to the processor and transmits and receives frames via a 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 stations associated with it. In an infrastructure BSS, in principle, communication between non-AP stations is carried out via the AP, but direct communication is also possible between non-AP stations if a direct link is set up. On the other hand, in the present invention, the AP is used as a concept including a PCP (Personal BSS Coordination Point), but in a broad sense, it includes concepts such as a centralized controller, a base station (BS), a Node B, a BTS (Base Transceiver System), or a site controller. In the present invention, the AP is also referred to as a base wireless communication terminal, but the base wireless communication terminal is used as a term that includes, in a broad sense, an AP, a base station, an eNB (eNodeB), and a transmission point TP. Moreover, the base wireless communication terminal includes various forms 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. At this time, a plurality of BSSs connected via the distribution system are called an extended service set (ESS).

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

[0034] Since BSS3 shown in FIG. 2 is an independent BSS and does not include an AP, all stations (STA6, STA7) are not connected to the AP. An independent BSS does not allow connection 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] FIG. 3 is a block diagram showing the configuration of station 100 according to an embodiment of the present invention. As shown, station 100 according to an embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

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

[0037] Next, the user interface 140 includes various forms of input / output means provided in the station 100. 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 an output based on the instruction of the processor 110 using various output means.

[0038] Next, the display unit 150 outputs an image on the display screen. The display unit 150 outputs various display objects such as content performed by the processor 110 or a user interface based on the control instruction of the processor 110. Also, the memory 160 stores a control program used in the station 100 and various data thereby. Such a control program includes a connection program necessary for the station 100 to connect to an AP or an external station.

[0039] The processor 110 of the present invention executes various instructions or programs and processes data inside the station 100. Further, the processor 110 controls each unit of the station 100 described above and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with the AP stored in the memory 160 and receives a communication setting message transmitted by the AP. Further, the processor 110 reads information regarding the priority conditions of the station 100 included in the communication setting message and requests a connection regarding the AP based on the information regarding the priority conditions of the station 100. The processor 110 of the present invention may refer to the main control unit of the station 100, or may refer to a control unit for individually controlling some configurations of the station 100, for example, the communication unit 120, etc. according to an embodiment. That is, the processor 110 may be a modem, or a modulator and / or demodulator that modulates and demodulates radio signals transmitted and received from the communication unit 120. The processor 110 controls various operations of wireless signal transmission and reception of the station 100 according to an embodiment of the present invention. Detailed embodiments thereof 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 separately shown blocks logically distinguish the elements of the device. Therefore, the above-described elements of the device are attached to one chip or a plurality of chips according to the design of the device. For example, the processor 110 and the communication unit 120 may be integrated and implemented on one chip, or may be implemented on separate chips. Further, in an embodiment of the present invention, some configurations of the station 100, for example, the user interface unit 140 and the display unit 150, etc. may be selectively provided in the station 100.

[0041] FIG. 4 is a block diagram showing the configuration of the AP 200 according to an embodiment of the present invention. As shown, the AP 200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, redundant descriptions are omitted for the 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.

[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 can also include a plurality of communication modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention can include two or more communication modules using different frequency bands, for example, any one of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 can include a communication module using a frequency band of 7.125 GHz or higher and a communication module using a frequency band of 7.125 GHz or lower. Each communication module can perform wireless communication with a station based on the wireless LAN standard of the frequency band supported by the communication module. The communication unit 220 can operate only one communication module at a time or operate a plurality of communication modules simultaneously according to the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0043] Next, the memory 260 stores the control program used in the AP200 and various data thereby. Such a control program includes a connection program for managing the connection of the stations. Further, the processor 210 controls each unit of the AP200 and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 210 executes a program for connection to the stations stored in the memory 260 and transmits communication setting messages for one or more stations. At this time, the communication setting messages include information regarding the connection priority conditions of each station. Further, the processor 210 performs connection setting in response to a connection request from the station. According to one embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates the radio signals transmitted and received by the communication unit 220. The processor 210 controls various operations of the radio signal transmission and reception of the AP200 according to an embodiment of the present invention. Detailed embodiments thereof will be described later.

[0044] FIG. 5 is a diagram schematically showing the process in which the STA sets a link with the AP.

[0045] Referring to FIG. 5, the link between the STA100 and the AP200 is set through three major steps of scanning, authentication, and association. First, the scanning step is a step in which the STA100 obtains the connection information of the BSS operated by the AP200. As a method for performing scanning, there are a passive scanning method of obtaining information by utilizing only the beacon message S101 periodically transmitted by the AP200, and an active scanning method in which the STA100 transmits a probe request to the AP at S103, receives a probe response from the AP at S105, and obtains connection information.

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

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

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

[0049] A terminal performing wireless LAN communication performs carrier sensing before transmitting data to check whether the channel is in a busy state. If a wireless signal with a certain intensity or higher is detected, the channel is determined to be in a busy state, and the terminal delays access to the channel. Such a process is called Clear Channel Assessment (CCA), and the level for determining the presence or absence of sensing of the corresponding signal is called the CCA threshold. If a wireless signal equal to or higher than the CCA threshold received by the terminal has the terminal as the recipient, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel or a wireless signal with an intensity lower 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 situation of each terminal, for example, a time such as AIFS (Arbitration IFS) or PIFS (PCF IFS). According to an embodiment, the AIFS may be used as a configuration to replace the conventional DIFS (DCF IFS). Each terminal waits while reducing the slot time by the random number determined for the terminal during the idle interval of the channel, and the terminal that has exhausted all the slot times attempts access to the channel. Thus, the section in which each terminal performs the backoff procedure is called a contention window section. At this time, the random number can be called a backoff counter. That is, the initial value of the backoff counter is set by the integer that is the random number obtained by the terminal. When the terminal senses that the channel is idle during the slot time, the terminal can decrement the backoff counter by 1. Also, when the backoff counter reaches 0, the terminal may be permitted to perform channel access on the channel. Therefore, transmission of the terminal may be permitted when the channel is idle during the AIFS time and the slot time of the backoff counter.

[0051] If a specific terminal successfully accesses the channel, the corresponding terminal transmits data via the channel. However, if a terminal that attempts access collides with other terminals, the collided terminals are each assigned a new random number and further perform a backoff procedure. According to one embodiment, the new random number newly assigned to each terminal is determined within a range (2*CW) that is twice the range (contention window, CW) of the random number previously assigned to the corresponding terminal. On the other hand, each terminal attempts access by performing a further backoff procedure in the next contention window period. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this way, each terminal performing wireless LAN communication can avoid mutual collisions with respect to 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. Further, FIG. 7(d) shows the detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

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

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

[0056] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes RL-SIG (Repeated Legacy Short Training field), U-SIG (Universal Signal field), EHT-SIG-A (Extremely High Throughput Signal A field), EHT-SIG-A (Extremely High Throughput Signal B field), EHT-STF (Extremely High Throughput Short Training field), and EHT-LTF (Extremely High Throughput Long Training field) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF can be referred to as the EHT preamble. The specific configuration of the non-legacy preamble may be deformed 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 applies 64 FFT OFDM and is composed of a total of 64 subcarriers. Among these, 48 subcarriers excluding the guard subcarriers, DC subcarriers, and pilot subcarriers are used for data transmission of L-SIG. Since BPSK and MCS (Modulation and Coding Scheme) with Rate = 1 / 2 are applied to L-SIG, it can contain a total of 24 bits of information. Fig. 7(d) shows the 24-bit information composition of L-SIG.

[0058] Referring to Fig. 7(d), 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 value among the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps, which is a combination of modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and code rates such as 1 / 2, 2 / 3, 3 / 4. Combining the information of the L_RATE field and the L_LENGTH field can indicate the total length of the corresponding PPDU. 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 bytes. A total of 12 bits are allocated and can signal up to 4095, and in combination with the L_RATE field, it can indicate the length of the corresponding PPDU. At this time, legacy terminals and non-legacy terminals can interpret the L_LENGTH field in different ways.

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

[0061]

Number

[0062] At this time,

Number

[0063]

Number

[0064] Here, TXTIME is the total transmission time that constitutes the said PPDU and is as shown in Equation 3 below. At this time, 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 ceiling value of L_LENGTH / 3. Therefore, for any k value, three different values of L_LENGTH = {3k + 1, 3k + 2, 3(k + 1)} indicate the same PPDU length.

[0067] Referring to Figure 7(e), the U-SIG (Universal SIG) field persists in EHT PPDUs and PPDUs of subsequent generations of wireless LANs and serves to distinguish which generation of PPDU it is, including 11be. U-SIG is two symbols of 64FFT-based OFDM and can transmit a total of 52 bits of information. Of this, 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 bits continue to maintain the current bit configuration in the future, and even if subsequent generations of PPDUs are defined, current 11be terminals can obtain information about the PPDU from the VI field of the PPDU. For this purpose, the VI field is composed of a PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits and serves to sequentially distinguish the 11be and subsequent generations of wireless LAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. BSS color means the BSS identifier defined in 11ax and has a value of 6 bits or more. TXOP means the transmit opportunity duration transmitted in the MAC header, but by adding it to the PHY header, the length of the TXOP included in the 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 signaling information that is only useful for the 11be version of the PPDU, fields that are commonly used in any PPDU format such as the PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a discriminator that differentiates between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), EHT ER (Extended Range) PPDUs, etc. The BW field mainly signals five basic PPDU BW options of 20, 40, 80, 160 (80 + 80), 320 (160 + 160) MHz (the BW that can be expressed in the form of 20 * 2 to the power of n can be called the basic BW), and various remaining PPDU BWs constituted by preamble puncturing. Also, after being signaled at 320 MHz, a part of 80 MHz may be signaled in a punctured form. Also, the channel form that has been punctured and deformed 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 (for example, a field within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so the puncturing mode can signal a maximum of 3. If the BW field is 4 bits, a total of 16 BW signalings are possible, so the puncturing mode can signal a maximum of 11.

[0070] The fields located after the BW field vary depending on the form and format of the PPDU. The MU PPDU and SU PPDU may be signaled in the same PPDU format. Before the EHT-SIG field, there may be a field for distinguishing between the MU PPDU and the SU PPDU, and additional signaling may be performed for that purpose. Both the SU PPDU and the MU PPDU contain the EHT-SIG field, but some fields that are unnecessary in the SU PPDU may be compressed. At this time, the information of the fields to which compression is applied may be omitted or may have a size smaller than the size of the original fields included in the MU PPDU. For example, in the case of the SU PPDU, the common fields of the EHT-SIG may be omitted or replaced, the user-specific fields may be replaced, or it may have different configurations such as being reduced to one.

[0071] Alternatively, the SU PPDU can further include a compression field indicating whether it is compressed, and some fields (e.g., 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 contained in the compressed field may be signaled together with uncompressed fields (such as common fields). In the case of MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted obligatorily after the U-SIG field, and the amount of information to be signaled may be variable. That is, since a plurality of MU PPDUs are transmitted to a plurality of STAs, each STA must recognize the position of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU is transmitted to itself. Therefore, the AP must transmit the above information in the EHT-SIG field. For this purpose, 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 the MCS which is the modulation method. The EHT-SIG field can include the size and position information of the RU assigned to each user.

[0073] In the case of SU PPDU, a plurality of RUs may be assigned to the STA, and the plurality of RUs may be continuous or discontinuous. When the RUs assigned to the STA are not continuous, the STA can efficiently receive the SU PPDU only by recognizing the RUs with punctures in between. Therefore, the AP can transmit the SU PPDU including information on the punctured RUs among the RUs assigned to the STA (such as the RU puncturing pattern). That is, in the case of SU PPDU, a puncturing mode field including information indicating whether the puncturing mode is applied and the puncturing pattern in a bitmap format or the like may be included in the EHT-SIG field, and the puncturing mode field can signal the form of discontinuous channels appearing within the bandwidth.

[0074] The form of the discontinuous channel signaled is restricted and indicates the BW of the SU PPDU and the discontinuous channel information in combination with the value of the BW field. For example, in the case of an SU PPDU, which is a PPDU transmitted only to a single terminal, the STA can recognize the bandwidth assigned to itself from the BW field included in the PPDU, and can recognize the punctured resources among the assigned bandwidths from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the terminal can receive the PPDU with the resource units other than the specific channels of the punctured resource units. At this time, the plurality of RUs assigned to the STA may be composed of different frequency bands or tones.

[0075] The reason why only the restricted form of the discontinuous channel form is signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing may be performed for each 20 MHz subchannel, when puncturing is performed for a BW having a plurality of 20 MHz subchannels such as 80, 160, and 320 MHz, in the case of 320 MHz, it is necessary to signal the form of the discontinuous channel (including the case where only the end 20 MHz is punctured as a discontinuous form) by expressing the use or non-use of each of the remaining 15 20 MHz subchannels excluding the primary channel. Using 15 bits to signal the discontinuous channel form of single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

[0076] The present invention proposes a method for signaling the discontinuous channel form of the SU PPDU and shows the discontinuous channel form determined by the proposed method. In addition, a method for signaling the puncturing forms of the primary 160 MHz and secondary 160 MHz in the 320 MHz BW configuration of the SU PPDU is proposed.

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

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

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

[0080] Referring to FIG. 8, the PPDU may be composed of a preamble and a data part, and the format of one type of EHT PPDU may be distinguished by the U-SIG field included in the preamble. Specifically, based on the PPDU format field included in the U-SIG field, whether the format of the PPDU is an EHT PPDU may be indicated.

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

[0082] FIG. 8(b) shows an example of the 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. Different from the EHT SU PPDU, the EHT-SIG-A field is not located after the U-SIG field in the EHT PPDU.

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

[0084] (d) of FIG. 8 shows an example of an EHT ER SU PPDU format used for single-user transmission with STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission with a wider range of STAs than the EHT SU PPDU described in (a) of FIG. 8, 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. At this time, the EHT MU PPDU can include scheduling information so that multiple STAs can receive the PPDU transmitted from the AP simultaneously. The EHT MU PPDU can convey to the STA the AID information of the receiver and / or transmitter of the PPDU transmitted through the user specific field of the EHT-SIG-B. Therefore, multiple terminals that receive the EHT MU PPDU can perform a spatial reuse operation based on the AID information in the user specific field included in the preamble of the received PPDU.

[0086] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU can include information regarding the configuration of resource units (e.g., the division form of resource units) in a specific bandwidth (e.g., 20 MHz, etc.) on the frequency axis. That is, the RA field can indicate the configuration of resource units divided by the bandwidth for the transmission of the HE MU PPDU for the STA to receive the PPDU. The information of the STA assigned (or designated) to each divided resource unit may be included in the user specific field of the EHT-SIG-B and transmitted to the STA. That is, the user specific field can include one or more user fields corresponding to each divided resource unit.

[0087] For example, among a plurality of divided resource units, a user field corresponding to at least one resource unit used for data transmission may include the AID of the recipient or the sender, and a user field corresponding to the remaining resource units not used for data transmission may include a pre-set Null STA ID.

[0088] For the sake of convenience of explanation, in this specification, a frame or a MAC frame may be used in the same meaning as an MPDU.

[0089] When a wireless communication device communicates using a plurality of links, the communication efficiency of the wireless communication device can be improved. At this time, a link is a physical path and may be configured as one wireless medium available for transmitting an MSDU (MAC service data unit). For example, when the frequency band of any one link is in use by another wireless communication device, the wireless communication device can continue to communicate on other links. In this way, the wireless communication device can usefully use a plurality of channels. Also, when the wireless communication device communicates simultaneously using a plurality of links, the overall throughput can be increased. However, existing wireless LANs are defined on the premise that one wireless communication device uses one link. Therefore, a wireless LAN operation method for using a plurality of links is required. With reference to FIGS. 9 to 26, a wireless communication method of a wireless communication device using a plurality of links will be described. First, with reference to FIG. 9, a specific form of a wireless communication device using a plurality of links will be described.

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

[0091] A multi-link device (MLD) may be defined for the wireless communication method using the plurality of links described above. 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 multi-link elements. The multi-link element may include information regarding one or more stations or one or more links. The multi-link element may include a multi-link setup element to be described later. At this time, the multi-link device may be a logical entity. Specifically, the multi-link device may have a plurality of affiliated stations. The multi-link device may be referred to as an MLLE (multi-link logical entity) or an MLE (multi-link entity). The multi-link device may have one MAC service access point (medium access control service access point, SAP) up to logical link control (LLC). Also, the MLD may have one MAC data service.

[0092] The plurality of stations included in the multi-link device can operate on a plurality of links. Also, the plurality of stations included in the multi-link device can operate on a plurality of channels. Specifically, the plurality of stations included in the multi-link device can operate on different plural links or different plural channels. For example, the plurality of stations included in the multi-link device can operate on different plural channels of 2.4 GHz, 5 GHz, and 6 GHz.

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

[0094] Figure 9 shows the operation in which the non-AP MLD and the AP-MLD communicate. Specifically, the non-AP MLD and the AP-MLD communicate using three links each. The AP MLD includes a first AP (AP1), a second AP (AP2), and a third AP (AP3). The 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] 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 needs to precede frame exchange in the multi-link. The multi-link device can obtain the information necessary 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. At this time, the capability information may include information indicating whether any one of the plurality of devices included in the multi-link device can transmit while another device can receive. Also, the capability information may include information regarding the links available to each station included in the MLD. Also, the capability information may include information regarding the channels available to each station included in the MLD.

[0096] The multi-link setup may be set by negotiation between peer stations. Specifically, the multi-link setup may be performed by communication between stations without communication with the AP. Also, the multi-link setup may be set through any one of the links. For example, even when the first to third links are set through the multi-link, the multi-link setup may be performed through the first link.

[0097] Also, the mapping between a TID (traffic identifier) and a link may be set. Specifically, frames corresponding to a specific value of the TID may be exchanged only through a pre-specified link. The mapping between the TID and the link may be set in a directional-based manner. For example, when a plurality of links are set between a first multi-link device and a second multi-link device, the first multi-link device may be set to transmit frames of a first TID to a plurality of first links, and the second multi-link device may be set to transmit frames of a second TID to the first link. Also, there may be a basic setting for the mapping between the TID and the link. Specifically, when there is no additional setting in the multi-link setting, the multi-link device can exchange frames corresponding to the TID on each link according to the basic (default) setting. At this time, the basic setting may be such that all TIDs are exchanged on any one link.

[0098] Specifically describe the TID. The TID is an ID for classifying traffic and data to support QoS (Quality of Service). Also, the TID may be allocated and used in a layer higher than the MAC layer. Further, the TID can indicate a traffic category (TC) and a traffic stream (TS). Also, the TID may be distinguished into 16 types. For example, the TID may be designated as any one of 0 to 15. It may be specified that the TID values used are different depending on the access policy, channel access, or medium access method. For example, when EDCA (Enhanced Distributed Channel Access) or HCAF (Hybrid Coordination Function Contention Based Channel Access) is used, the value of the TID may be allocated in the range of 0 to 7. When EDCA is used, the TID can indicate the user priority (UP). At this time, the UP may be specified by the TC or TS. The UP may be allocated in a layer higher than the MAC. Also, when HCCA (HCF Controlled Channel Access) or SPCA is used, the value of the TID may be allocated in the range of 8 to 15. When HCCA or SPCA is used, the TID can indicate the TSID. Also, when HEMM or SEMM is used, the value of the TID may be allocated in the range of 8 to 15. When HEMM or SEMM is used, the TID can indicate the 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. The EDCA parameter or EDCA parameter set is a parameter used in the channel contention of EDCA. The QoS station can guarantee QoS using AC. Also, AC may include AC_BK, AC_BE, AC_VI, and AC_VO. Each of AC_BK, AC_BE, AC_VI, and AC_VO can indicate background, best effort, video, and voice. Also, AC_BK, AC_BE, AC_VI, and AC_VO may be classified into lower-level ACs. For example, AC_VI can be subdivided into AC_VI primary and AC_VI alternate. Also, AC_VO can be subdivided into AC_VO primary and AC_VO alternate. Also, UP or TID may be mapped to AC. For example, each of 1, 2, 0, 3, 4, 5, 6, 7 in UP or TID may be mapped to each of AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, AC_VO. Also, each of 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be mapped to each of AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, AC_VO alternate. Also, 1, 2, 0, 3, 4, 5, 6, and 7 in UP or TID may be in descending order of priority. That is, 1 may have a lower priority and 7 may have a higher priority. Therefore, the priority may increase in the order of AC_BK, AC_BE, AC_VI, AC_VO. Also, each of AC_BK, AC_BE, AC_VI, and AC_VO may correspond to each of ACI (AC index) 0, 1, 2, 3. Due to such characteristics of TID, the mapping between TID and the link can represent the mapping between AC and the link.Also, the mapping between a link and an AC can represent the mapping between a TID and a link.

[0100] As described above, a TID may be mapped to each of a plurality of links. The mapping may be that a link through which traffic corresponding to a specific TID or AC can be exchanged is specified. Also, a TID or AC that can be transmitted in the link for each transmission direction may be specified. As described above, there may be a basic setting for the mapping between a TID and a link. Specifically, when there is no additional setting in the multi-link setting, the multi-link device can exchange frames corresponding to the TID on each link according to the basic (default) setting. At this time, the basic setting may be such that all TIDs are exchanged on any one link. Always, at a certain point in time, any TID or AC may be mapped to at least one link. The management frame and the control frame may be transmitted on all links.

[0101] When a link is mapped to a TID or AC, only the data frame corresponding to the TID or AC mapped to the link on that link may be transmitted. Therefore, when a link is mapped to a TID or AC, a frame that does not correspond to the TID or AC not mapped to the link on that link may not be transmitted. When a link is mapped to a TID or AC, the ACK may also be transmitted based on the link to which the TID or AC is mapped. For example, a block ACK agreement may be determined based on the mapping between a TID and a link. In still other specific embodiments, the mapping between a TID and a link may be determined based on a block ACK agreement. Specifically, a block ACK agreement may be set for the TID mapped to a specific link.

[0102] Through the mapping between the aforementioned TID and the link, QoS may be guaranteed. Specifically, a relatively small number of stations may operate, or a high-priority AC or TID may be mapped to a link with a good channel state. Also, through the mapping between the aforementioned TID and the link, a station can be made to maintain a power-saving state for a longer time.

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

[0104] Due to the implementation of a multi-link device, simultaneous operation on multiple links may not be supported. For example, it may be supported that a multi-link device simultaneously transmits on multiple links, simultaneously receives on multiple links, or transmits on one link while receiving on another link. It is possible that reception or transmission performed on any one link may affect reception or transmission performed on another link. Specifically, transmission on one link may act as interference to another link. The interference that one link of a multi-link device exerts on another link can be called internal leakage. The smaller the frequency interval between links, the greater the internal leakage may be. If the internal leakage is not too large, transmission can be performed on another link when transmission is performed on any one link. If the internal leakage is large, transmission cannot be performed on another link when transmission is performed on any one link. Thus, the multi-link device's simultaneous operation on multiple links can be called STR (simultaneous transmit and receive, simultaneous transmission and reception). For example, a multi-link device simultaneously transmitting on multiple links, transmitting on one link while receiving on another link, or simultaneously receiving on multiple links can be called STR.

[0105] On one hand, when STR is not supported due to interference among a plurality of stations constituting the MLD, the STA may be expressed as being in a non-STR relationship or an NSTR relationship (a relationship in which STR is not supported).

[0106] At this time, whether two STAs (STA1 and STA2) of the MLD support STR may vary depending on the separation distance of the link pairs (Link1 used by STA1 and Link2 used by STA2) in which the STAs operate.

[0107] Therefore, when the MLD operates STAs for specific link pairs respectively, if STR is supported between both STAs operating in the specific link pair, the specific link pair may be considered as an STR link pair for the MLD. On the other hand, when the MLD operates STAs for individual link pairs respectively, if STR is not supported between both STAs operating in the individual link pair, the other link pair may be considered as an NSTR link pair for the MLD.

[0108] Thus, whether STR is supported between STAs of the MLD is determined by whether the link pairs in which these STAs operate are STR link pairs or NSTR link pairs. However, as described above, since the characteristics (such as shielding performance) of each MLD may be different from each other, a specific link pair may be considered as a link pair with STR supported for a specific MLD and as an NSTR link pair with STR not supported for other MLDs.

[0109] In one embodiment of the present invention described below, for the sake of convenience of explanation, the STA used in the STR link pair of the MLD is named (designated) as the STA of the STR MLD, and the STA used in the NSTR link pair of the MLD is named (designated) as the STA of the NSTR (and non-STR) MLD. That is, when referring to the "STA of the non-STR MLD" in the embodiments described below, it may be analyzed to refer to one of the two STAs used in the NSTR link pair of the MLD, and when referring to the "STA of the STR MLD", it may be analyzed to refer to one of the two STAs used in the STR link pair of the MLD.

[0110] Also, the NSTR MLD can mean, in relation to the presence or absence of the above-described STR support, not only the MLD in which the STA of a specific MLD loses its reception ability, but also the MLD in which the hardware configuration of the MLD itself does not support simultaneous transmission / reception.

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

[0112] Thus, an apparatus that is MLD and can operate an STA on two or more links but can support transmission / reception only for one STA at a specific time can be called a multi-link single radio MLD (MLSR MLD). Alternatively, an operation mode in which MLD supports transmission / reception only for one STA as a kind of operation mode can be called an enhanced multi-link single radio (EMLSR) mode. At this time, the MLD operating in the EMLSR mode may be a multi-radio MLD or an enhanced single-radio MLD. The enhanced single-radio MLD supports data transmission / reception only for one link at a time, but by having a configuration including separate hardware (such as a low-cost PHY front end), it can be meant a device that supports CCA for two or more links and transmission / reception of PPDUs with a low data rate (for example, encoded at 6 MHz or 24 MHz or less).

[0113] Also, as a variation of the EMLSR mode, an EMLMR (Enhance Multi-Link Multi-Radio) may be defined in which MLD supports transmission / reception for each STA, but a part of the RF chain used by a specific STA is utilized for transmission / reception of other STAs. The EMLMR may have the same transmission / reception limitation characteristics as the EMLSR when all of the RF chains used by the specific STA are utilized for transmission / reception of the other STAs. That is, the MLD operating in the EMLMR mode can operate to support transmission / reception only for one link (STA) at a specific time regardless of the presence or absence of STR support 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 the MLD operated in the EMLSR / EMLMR mode may be considered as NSTR link pairs.

[0115] At this time, the above-described transmission / reception means 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 the sake of convenience of explanation, hereinafter, EMLSR / EMLMR MLD is used in the sense that it includes an MLD that can support only transmission / reception for one STA at a specific time due to hardware constraints, and an MLD that can support transmission / reception (processing capability not related to STR) for two or more STAs, but as a type of operation mode, it supports only high-speed data frame transmission / reception for one STA at a specific time.

[0117] The operation of the STR MLD considering the performance limitation of the NSTR MLD provided by the above-described embodiment of the present invention can be directly utilized as the operation of the STR MLD with respect to the MLSR MLD. For example, after the STA of the STR MLD has transmitted to the STA of the multi-link single-radio MLD, if it is determined that the performed transmission has failed or is predicted to fail due to the limited performance of the multi-link single-radio MLD STA, the ongoing or intended transmission can be cancelled. At this time, the procedure for confirming whether the transmission has failed due to the limited performance of the EMLSR / EMLMR MLD may be similar to the procedure for confirming whether the transmission performed by the STA of the NSTR MLD has failed due to the limited performance of the NSTR MLD STA.

[0118] As mentioned above, the multi-link device can support STR or support it in a limited way. Specifically, the multi-link device can support STR only under specific conditions. For example, when the multi-link device operates with a single radio, the multi-link device may not be able to perform STR. Also, when the multi-link device operates with a single antenna, the multi-link device may not be able to perform STR. Also, when internal leakage is detected to be greater than a specified magnitude, the multi-link device may not be able to perform STR.

[0119] A station can exchange information regarding the STR capabilities of the station with other stations. Specifically, the station can exchange with other stations information regarding the presence or absence of restrictions on the ability of the station to transmit simultaneously over multiple links or to receive simultaneously over multiple links. Specifically, the information regarding the presence or absence of restrictions on the ability to transmit or receive over multiple links can indicate whether to transmit simultaneously over multiple links, receive simultaneously, or perform transmission and reception simultaneously. Also, the information regarding the presence or absence of restrictions on the ability to transmit or receive over multiple links can be information that is instructed step by step. Specifically, the information regarding the presence or absence of restrictions on the ability to transmit or receive over multiple links can be information that instructs a step indicating the magnitude of internal leakage. In a specific embodiment, the information that instructs a step indicating the magnitude of internal leakage can be information that instructs a step indicating the magnitude of interference generated by the internal leakage. In yet another specific embodiment, it can be information that instructs a step indicating the frequency interval between links that can affect the internal leakage. Also, the information that instructs a step indicating the magnitude of internal leakage can be information that instructs step by step the relationship between the frequency interval between links and the magnitude of internal leakage.

[0120] In FIG. 10, the first station (STA1) and the second station (STA2) are affiliated with one non-AP multi-link device. Also, the first AP (AP1) and the second AP (AP2) may be affiliated with one non-AP multi-link device. A first link (link1) is set between the first AP (AP1) and the first station (STA1), and a second link (link2) is set between the second AP (AP2) and the second station (STA2). In FIG. 10, the non-AP multi-link device can perform STR in a limited manner. When the second station (STA2) transmits on the second link (Link2), the reception of the first station (STA1) on the first link (Link1) may be interfered with by the transmission performed on the second link (Link2). For example, in the following cases, the reception of the first station (STA1) on the first link (Link1) may be interfered with by the transmission performed on the second link (Link2). The second station (STA2) transmits the first data (Data1) on the second link (Link2), and the first AP (AP1) transmits an acknowledgment for the first data (Ack for Data1) to the first station (STA1). The second station (STA2) transmits the second data (Data2) on the second link (Link2). At this time, the transmission timing of the second data (Data2) and the transmission timing of the acknowledgment for the first data (Ack for Data1) may overlap. At this time, interference may occur on the first link (Link1) due to the transmission to the second station (STA2) on the second link (Link2). Therefore, the first station (STA1) may not be able to receive the acknowledgment for the first data (Ack for Data1).

[0121] The operation of the multi-link device for channel access will be described. The multi-link operations without specific descriptions can follow the channel access procedure described in FIG. 6.

[0122] A multi-link device can perform channel access independently from a plurality of links. At this time, the channel access may be backoff-based channel access. When the multi-link device performs channel access independently from a plurality of links and the backoff counters reach 0 on the plurality of links, the multi-link device can start transmission simultaneously on the plurality of links. In a specific embodiment, when any one of the backoff counters of the multi-links reaches 0 and meets a specified condition, the multi-link device can perform channel access not only on the link where the backoff counter reaches 0 but also on other links where the backoff counters do not reach 0. Specifically, when any one of the backoff counters of the multi-links reaches 0, the multi-link device can perform energy sensing on other links where the backoff counters do not reach 0. At this time, when energy greater than or equal to a specified magnitude is not sensed, the multi-link device can perform channel access not only on the link where the backoff counter reaches 0 but also on the link where energy sensing is performed. Thereby, the multi-link device can start transmission simultaneously on the plurality of links. The magnitude of the threshold value used for energy sensing may be smaller than the magnitude of the threshold value used when determining whether to decrease the backoff counter. Also, when determining whether to decrease the backoff counter, the multi-link device can sense not only wireless LAN signals but also signals in any form. Also, in the above-described energy sensing, the multi-link device can sense not only wireless LAN signals but also signals in any form. Internal leakage may not be sensed as a wireless LAN signal. In such a case, the multi-link device can sense the signal sensed by internal leakage by energy sensing. Also, as described above, the magnitude of the threshold value used for energy sensing may be smaller than the magnitude of the threshold value used when determining whether to decrease the backoff counter. Therefore, even while transmission is being performed on any one link, the multi-link device can decrease the backoff counter on other links.

[0123] Depending on the degree of interference between the links used by the multi-link device, it may be determined whether the stations operating on each link can operate independently. At this time, the degree of interference between the links may be the magnitude of the interference sensed by other stations of the multi-link device when any one station of the multi-link device performs transmission on any one link. When the transmission on the first link of the first station of the multi-link device causes interference greater than or equal to a specified magnitude in the second station of the multi-link device operating on the second link, the operation of the second station may be restricted. Specifically, the reception or channel access of the second station may be restricted. When interference occurs, the second station may fail to decode the signal received due to the interference. Also, when interference occurs, when the second station uses backoff for channel access, the second station may determine that the channel is in use.

[0124] Also, when the transmission on the first link of the first station of the multi-link device causes interference less than a specified magnitude at the second station of the multi-link device operating on the second link, the first station and the second station can operate independently. Specifically, when the transmission on the first link of the first station of the multi-link device causes interference less than a specified magnitude at the second station of the multi-link device operating on the second link, the first station and the second station can perform channel access independently. Also, when the transmission on the first link of the first station of the multi-link device causes interference less than a specified magnitude at the second station of the multi-link device operating on the second link, the first station and the second station can transmit or receive independently. When interference less than the specified magnitude occurs, the second station can succeed in decoding the received signal even when interference exists. Also, when interference less than the specified magnitude occurs, when the second station uses backoff for channel access, the second station can determine that the channel is idle.

[0125] The degree of interference occurring between stations of a multi-link device may vary not only depending on the interval between the frequency bands of the links on which the stations operate, but also depending on the hardware characteristics of the multi-link device. For example, the internal interference occurring in a multi-link device including a high RF (radio frequency) device may be smaller than the internal interference occurring in a multi-link device including a low RF device. Therefore, the degree of interference occurring between stations of a multi-link device may be determined based on the characteristics of the multi-link 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 multi-link device. In the embodiment of FIG. 10, the first multi-link device (MLD#1) includes a first station (STA1)-1 operating on a first link (Link1) and a second station (STA1)-2 operating on a second link (Link2). The second multi-link 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) on which the first multi-link device (MLD#1) operates is the same as the frequency interval between the first link (Link1) and the second link (Link2) on which the second multi-link device (MLD#2) operates. However, the magnitude of interference generated differs due to the difference between the characteristics of the first multi-link device (MLD#1) and the characteristics of the second multi-link device (MLD#2). Specifically, the magnitude of interference generated in the second multi-link device (MLD#2) may be greater than the magnitude of interference generated in the first multi-link device (MLD#1). Thus, considering that the magnitude of interference generated may differ depending on the characteristics of the multi-link device and that the presence or absence of STR support may differ for each multi-link device, it is necessary to exchange information regarding whether STR is supported or not.

[0127] The multi-link device can signal the presence or absence of STR support for the stations included in the multi-link device. Specifically, the AP multi-link device and the non-AP multi-link device can exchange the presence or absence of AP STR support included in the AP multi-link device and the presence or absence of STA STR support included in the non-AP multi-link device. In such an embodiment, an element indicating the presence or absence of STR support may be used. The element indicating the presence or absence of STR support can be referred to as an STR support element. The STR support element can indicate, by 1 bit, the presence or absence of STR support for the stations of the multi-link device that transmitted the STR support element. Specifically, the STR support element can indicate, separately by 1 bit, the presence or absence of STR support for each of the stations included in the multi-link device that transmits the STR support element. At this time, when a station supports STR, the value of the bit may be 1, and when a station does not support STR, the value of the bit may be 0. When the multi-link 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 may include a field having 101 1b It may include a field having. Stations operating in different frequency bands are assumed to support STR, and the STR support element may omit signaling for the presence or absence of STR support between stations operating in different frequency bands. For example, the first station (STA1) operates on a first link at 2.4 GHz, and each of the second station (STA2) and the third station (STA3) operates on a second link and a third link at 5 GHz. At this time, the STR support element can indicate by 1 bit that STR is supported between the second station (STA2) and the third station (STA3). Also, the STR support element may include only 1 bit when there are two stations for which the STR support element signals.

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

[0129] In the foregoing embodiments, what was described as the operation of the station of the multi-link device may be replaced with the operation of the multi-link device. Also, in the foregoing embodiments, the operation of the AP may be replaced with the operation of the non-AP station, and the operation of the non-AP station may be replaced with the operation of the AP. Therefore, the operation of the AP of the non-STR multi-link device may be replaced with the operation of the non-AP station of the non-STR multi-link device, and the operation of the non-AP station of the STR multi-link device may be replaced with the operation of the AP of the STR multi-link device. Also, the operation of the non-AP station of the non-STR multi-link device may be replaced with the operation of the AP of the non-STR multi-link device, and the operation of the AP of the STR multi-link device may be replaced with the operation of the non-AP station of the STR multi-link device.

[0130] FIG. 11 shows the operation of the multi-link device when the link is changed according to an embodiment of the present invention.

[0131] When the frequency band of a link is changed, the STR support element may be exchanged. As described above, the availability of STR support at a station may vary depending on the distance between the frequency bands of the link, because when the frequency band of the link is changed, the availability of STR support at the station may change. When the frequency band of the link is changed, it may include at least one of a change in the center frequency of the link, a change in the bandwidth of the frequency band, and a change in the 20 MHz primary channel. The AP and the station can exchange the STR support element by request and response. In yet other specific embodiments, when the frequency band of the link is changed, the STR support element may be exchanged without a separate request. Also, in the embodiments described above, when the frequency band of the link is changed, it may include a change in the operating channel of the station.

[0132] When the station of the non-AP multi-link device cannot perform STR, the station of the non-AP multi-link device can request the AP to change the link. Specifically, the station of the non-AP multi-link device can request at least one of a center frequency change, a bandwidth change of the frequency band, and a 20 MHz primary channel change. The link change request may be transmitted to the AP on the link for which the change is requested. In yet another specific embodiment, the link change request may be transmitted to the AP on a link for which the change is not requested. At this time, the link change request may include information indicating the link for which the change is requested. The information indicating the link may be a number for identifying the link. In such an embodiment, the change of the link may be that the operating channel is changed within one frequency band. Also, the change of the link may include information regarding the method of changing the link. Specifically, the link change request can indicate whether to move the center frequency of the link to a frequency higher than the current center frequency or to a frequency lower than the current center frequency. In yet another specific embodiment, the link change request can implicitly indicate a change to a frequency band away from an adjacent link. Also, the link change request can indicate reducing the bandwidth of the link. Also, the link change request can request a change in the position of the primary channel. Specifically, the link change request can indicate changing the position of the primary channel to a channel in a lower frequency band or a higher frequency band than the position of the current primary channel. The AP that has received the link change request can change the link in response to the link change request. Also, in a specific embodiment, the AP that has received the link change request can 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 multi-link device are in a state where they cannot support STR. The non-AP multi-link device requests the AP multi-link device to change the third link (Link3). The AP multi-link device that receives 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 still other specific embodiments, a station that does not operate on the third link (link3) can send a change request to an AP that does not operate on the third link (link3).

[0134] When the AP changes the link, the AP can broadcast information regarding the link change using a beacon frame. At this time, the information regarding the link change may include information regarding the frequency of the link. The information regarding the frequency of the link may include at least one of the center frequency of the link, the operating bandwidth, and the change of the primary channel. Also, the information regarding the link change may include information regarding the time point of the link change. Also, the link change may be completed when the beacon is transmitted including the information regarding the link change.

[0135] In FIG. 11, the link on which the third station (STA3) operates is changed, and the third station (STA3) and the second station (STA2) can support STR. As described above, the non-AP multi-link device can send an STR support element to the AP multi-link device and signal the availability of the changed STR support.

[0136] The above-described link change may not be allowed, or the STR may not be supported even by the change. Also, as in the embodiment of FIG. 11, the AP multi-link device supports the STR, but the non-AP multi-link device may not support the STR. This is because relatively expensive devices are generally used for the AP multi-link device and relatively inexpensive devices are generally used for the non-AP multi-link device. Therefore, when communicating between multi-link devices, a method is required that can perform efficient communication even when any one of the multi-link devices does not support the STR. At this time, the STR can represent that transmission and reception are performed simultaneously. This will be described with reference to FIG. 12.

[0137] FIG. 12 shows that, according to an embodiment of the present invention, when any one station of the non-STR multi-link device is performing reception, channel access of other stations of the non-STR multi-link device is prohibited.

[0138] When transmission is performed on any one link of the non-STR multi-link device and reception is performed on another link of the non-STR multi-link device, reception and transmission of the non-STR multi-link device may fail. To solve this problem, when reception is being performed on any one link of the non-STR multi-link device, channel access may be prohibited on other links of the non-STR multi-link device. Specifically, when reception is being performed on any one link of the non-STR multi-link device, backoff of channel access may be prohibited on other links of the non-STR multi-link device. Thereby, when reception is being performed on any one link of the non-STR multi-link device, it is possible to prevent transmission from starting on other links of the non-STR multi-link device. In a specific embodiment, when reception starts on any one link of the non-STR multi-link device, backoff of channel access may be prohibited on other links of the non-STR multi-link device. This may be set using a specific bit of memory such as a channel access prohibition flag. That is, whether channel access is prohibited or not may be shared by the memory inside the multi-link device. By such an embodiment, channel access prohibition can be realized without separate frame exchange. For convenience of explanation, "channel access prohibition" used in this specification represents prohibiting channel access or transmission to protect transmission or reception of the non-STR multi-link device unless otherwise specified.

[0139] When channel access is prohibited, a station operating on a link where channel access is prohibited cannot perform a backoff 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 perform transmission 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 perform reception. Also, the prohibition of channel access on the second link due to reception on the first link may be released based on the completion of reception on the first link. Specifically, the prohibition of channel access on the second link due to reception on the first link may be released when the reception on the first link is completed. In yet another specific embodiment, the prohibition of channel access on the second link due to reception on the first link may be released based on the point in time when an ACK is transmitted after the reception on the first link is completed. Specifically, the prohibition of channel access on the second link due to reception on the first link may be released at the point in time when an ACK is transmitted after the reception on the first link is completed. In yet another specific embodiment, the prohibition of channel access on the second link due to reception on the first link may be released at the point in time when the transmission of the ACK is completed after the reception on the first link is completed. Also, immediately after the channel access prohibition is released, the station can immediately decrease the backoff counter without additional sensing. At this time, the additional sensing can indicate the sensing performed with DIFS (DCF Interframe Space). In yet another specific embodiment, when the channel is idle at a specified time immediately before the channel access prohibition is released, the station can immediately decrease the backoff counter without additional sensing. At this time, the specified time may be any one of PIFS (PCF Interframe Sapce), DIFS, SIFS (Short Interframe Sapce), and AIFS (Arbitration Interframe Space).

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

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

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

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

[0144] If the station determines that it is not the intended recipient in the received PPDU, the station may release the channel access prohibition. The station can determine whether it is the intended recipient of the PPDU based on the information indicating the recipient address in the signaling field of the PPDU. At this time, the information indicating the recipient address in the signaling field of the PPDU may be the value of the STA-ID field in the EHT-SIG field described above. Specifically, the station can determine whether the STA-ID field in the EHT-SIG field indicates the station. Also, the station can determine whether it is the intended recipient of the PPDU based on the value of the RA field in the MAC frame included in the PPDU. Specifically, the station can determine whether the RA field in the MAC frame included in the PPDU indicates the station. In FIG. 13, the non-STR multi-link device includes a first station (STA1) operating on the first link (Link1) and a second station (STA2) operating on the second link (Link2). The first station (STA1) receives the PPDU. The first station (STA1) determines that the intended recipient of the received PPDU is not the first station (STA1) and interrupts the reception of the PPDU. At this time, the first station (STA1) can 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 by the NAV set for the second station (STA2).

[0145] As shown in FIG. 13, even after the channel access prohibition is lifted, stations included in non-STR multi-link devices often do not have channel access opportunities compared to stations not included in multi-link devices or stations included in STR multi-link devices. Therefore, a method may be needed to compensate for the channel access opportunities of stations included in non-STR multi-link devices for fair competition with other stations. For example, immediately after the channel access prohibition is lifted, it may be allowed for a station whose channel access prohibition has been lifted to decrease the backoff counter by more than 2 when decreasing it. This will be described with reference to FIG. 14.

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

[0147] A station whose channel access prohibition has been lifted can decrease the backoff counter by more than 2 immediately after the channel access prohibition is lifted. This is to ensure fairness in channel access opportunities with other stations because other stations have performed the backoff procedure while the station's channel access was prohibited.

[0148] In yet other specific embodiments, a station whose channel access is prohibited can perform channel access procedures that reduce CCA (CSMA) and the backoff counter while the channel access is prohibited. In FIG. 14, 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). 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 channel access procedures that reduce CCA (CSMA) and the backoff counter. In FIG. 14(a), while the channel access of the second station (STA2) is prohibited, since the channel of the second link (Link2) is idle, the second station (STA2) reduces the backoff counter.

[0149] Also, a station whose channel access is prohibited can delay transmission without starting transmission even if the backoff counter reaches 0 while the channel access is prohibited. At this time, the station can maintain the value of the backoff counter at 0. Also, even if the station delays transmission, the station can maintain the value of CW as it is. Therefore, it is differentiated from the case where the station doubles the value of CW because the channel accessed by the station is busy. This is because the reason for the transmission delay is not determined to be that the channel is busy. In FIG. 14(b), while the channel access of the second station (STA2) is prohibited, the second station (STA2) can perform a channel access procedure that reduces CCA (CSMA) and the backoff counter. In FIG. 14(b), while the channel access of the second station (STA2) is prohibited, since the channel of the second link (Link2) is idle, the second station (STA2) reduces the backoff 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 starts transmission after the channel access prohibition is released.

[0150] As described above, channel access prohibition may include prohibiting transmission to the second station when the first station of the non-STR multi-link device performs transmission. Also, channel access prohibition may include prohibiting the transmission of the second station when the first station of the non-STR multi-link device performs reception.

[0151] In FIG. 14(b), when there are a plurality of stations whose channel access is prohibited in the embodiment, the channel access prohibitions of the plurality of stations are released simultaneously, and there is a high possibility that the plurality of stations will attempt to transmit simultaneously. Therefore, a method for reducing the transmission collision probability is required. This will be described with reference to FIG. 15.

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

[0153] As described above, transmission may be performed on a first link among a plurality of links on which a non-STR multi-link device operates, and transmission may be prohibited on a second link. When the transmission on the first link is completed, the transmission on the second link may start by RTS / CTS frame exchange. Therefore, when transmission is performed on a first link among a plurality of links on which a non-STR multi-link device operates, the non-STR multi-link device can start RTS / CTS frame exchange 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 can start the exchange of RTS (request to send) / CTS (clear to send) frames before starting the delayed transmission. At this time, if the station cannot receive the CTS frame, it may not be able to start the delayed transmission. In the embodiment of FIG. 15(a), a station whose transmission has been delayed due to channel access prohibition transmits an RTS frame before starting the delayed transmission. The station starts the delayed transmission after receiving a CTS frame as a response to the RTS frame.

[0154] In yet another specific embodiment, after the channel access prohibition of a station whose transmission has been delayed due to the channel access prohibition is released, the station can transmit a frame including only a part of the delayed transmission. At this time, after the station receives a response, such as an ACK, to the frame including only a part of the delayed transmission, the station can transmit the non-transmitted part of the delayed transmission. If the station fails to receive a response to the frame including only a part of the delayed transmission, the station does not have to transmit the non-transmitted part of the delayed transmission. Thus, the fact that the station starts an RTS / CTS exchange or transmits only a part of the delayed transmission after the channel access prohibition is released means that the probability of transmission collision after the channel access prohibition is higher than that of general transmission. Therefore, the above-described embodiments may be obligatorily applied to transmissions performed after the channel access prohibition is released. In existing wireless LAN operations, RTS / CTS frames are used to solve the hidden node problem and can be used based on the size of the transmitted data. In the above-described embodiments, the RTS / CTS frame is for preventing a transmission collision with a station attempting to perform a delayed transmission in order to protect the transmission or reception of a non-STR multi-link device.

[0155] As described above, when any one of the stations of the non-STR multi-link device receives, the transmission of other stations of the non-STR multi-link device may be restricted. Also, when any one of the stations of the non-STR multi-link device transmits, other stations of the non-STR multi-link 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 multi-link device transmits, the second station of the non-STR multi-link device may always determine that the channel state of the link on which the second station operates is busy. For this reason, even when the channel of the link on which the second station operates is idle, the second station may determine that the channel is in use due to in-device interference. When the transmission of any one of the stations of the non-STR multi-link device whose channel state cannot be determined due to in-device interference or is in progress, other stations of the non-STR multi-link device are considered to be in a blind state. A station in a blind state due to the above-described situation may have difficulty performing a backoff procedure and attempting transmission. Also, a station in a blind state due to the above-described situation may have difficulty starting to receive a PPDU or succeeding in decoding it. Therefore, a transmission method that takes into account stations in a blind state is necessary. This will be described with reference to FIG. 16.

[0156] On the one hand, when a PPDU is being transmitted or received via an STA of another link, the STA of the EMLSR / EMLMR MLD cannot confirm or receive the presence or absence of the PPDU even if the PPDU is transmitted to itself. Therefore, the STA of the MLD operating in the EMLSR / EMLSR mode may have the same performance constraints as those of the STA of the NSTR MLD being blindly inserted while other STAs in the MLD are transmitting or receiving data frames. Therefore, in the embodiments 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 restricted by the operations (transmissions / receptions) of other STAs in the MLD.

[0157] At this time, the mode in which the multi-link device uses a single radio of a single link in a specific time interval can be called the EMLSR mode. While the multi-link device performs frame switching on the first link of the EMLSR links, which are a plurality of links to which the EMLSR mode is applied, the multi-link device does not transmit or receive on the second link of the EMLSR links. Also, when another station of the multi-link device transmits or receives using a part of the RF chains used by a specific station of the multi-link device in a specific time interval of a specific mode, the specific mode can be called the EMLMR (enhanced multi-link multi-radio) mode. Specifically, when any one station of the multi-link device transmits or receives using all of the RF chains of another station of the multi-link device in the EMLMR mode, the operation of the multi-link device may be the same as the operation of the multi-link in the EMLSR mode. Also, even when the multi-link device operates in the EMLSR mode, some of the plurality of links on which the multi-link device operates can operate without the restrictions of the EMLSR mode. When the multi-link 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 multi-link device operates. For example, when the multi-link device operates on the first link to the third link, the EMLSR mode or the EMLMR mode may be applied only to the first link and the second link. Therefore, when the multi-link device transmits or receives on the first link in the specific time interval of the EMSLR mode, the multi-link device cannot transmit or receive on the second link. At this time, the multi-link device can transmit or receive on the third link without the restrictions of the EMLSR mode. For the sake of convenience of explanation, links to which the EMLSR mode can be applied, such as the first link and the second link, are referred to as EMLSR links, and links to which the EMLMR mode can be applied are referred to as EMLMR links. Transmitting or receiving using the RF chain of a specific station in the EMLSR mode and the EMLMR mode results in a conversion of the transmission, reception, or monitoring capabilities on the links on which the specific station operates.Therefore, embodiments of the present invention applied in connection with the EMLSR mode in the following description may be equally applied in connection with the EMLMR mode without special mention.

[0158] FIG. 16 shows transmissions performed based on the state of stations within a non-STR multi-link device according to an embodiment of the present invention.

[0159] A station attempting to transmit to a station of a non-STR multi-link device can determine whether to transmit based on whether the station of the non-STR multi-link device is in a blind state. At this time, the station attempting to transmit to a station of the non-STR multi-link device may be a station included in the STR multi-link device. Also, the station attempting to transmit to a station of the non-STR multi-link device is an AP included in the AP multi-link device, and the non-STR multi-link device may be a non-AP multi-link device. The station attempting to transmit to a station of the non-STR multi-link device can determine whether the station of the non-STR multi-link device is in a blind state as follows. The transmitting station can determine whether other stations of the multi-link device containing the station are transmitting to the non-STR multi-link device. When other stations of the multi-link device containing the station are receiving from the non-STR multi-link device, the station can determine that the station of the non-STR multi-link device receiving the transmission from the station is in a blind state. In the embodiment of FIG. 16, 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). Therefore, the second AP (AP2) can notify the first AP (AP1) that it is receiving from the second station (STA2). Specifically, the second AP (AP2) can notify the first AP (AP1) that the entity transmitting to the second AP (AP2) is the second station (STA2). In yet another specific embodiment, the second AP (AP2) can notify 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] Stations within a multi-link device may be operated by a common MAC. Therefore, the information exchange between the aforementioned first AP (AP1) and second AP (AP2) may not be explicitly performed.

[0161] A station may not send data to a station in a blind state. This is because even if data is sent to a station in a blind state, it is highly likely that the station in the blind state cannot start receiving or decode the PPDU. At this time, the station can cancel the transmission to the station in the blind state and perform transmission to other stations.

[0162] When the STR multi-link device sends data to the non-STR multi-link device, the STR multi-link device can send data to the non-STR multi-link device over multiple links. Specifically, when the STR multi-link device sends data to the non-STR multi-link device over the first link, the STR multi-link device can start sending data to the non-STR multi-link device over the second link. At this time, based on the data transmission to the non-STR multi-link device, the STR multi-link device can determine the length of the data transmission over the second link. Specifically, the STR multi-link device can determine the length of the data transmission over the second link based on the length of the data transmission to the non-STR multi-link device over the first link. In a specific embodiment, the STR multi-link device may end the data transmission over the first link and the data transmission over the second link simultaneously. This is to prevent the data transmission to any one of the stations of the non-STR multi-link device from ending first, and before any one of the stations of the non-STR multi-link device sends a response to the data transmission, such as an ACK, the data transmission to other stations of the non-STR multi-link device is carried out. According to the above-described embodiment, multiple stations of the non-STR multi-link device can simultaneously send responses to the data transmission to multiple stations.

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

[0164] FIG. 17 shows a situation where interference or collision between links may occur.

[0165] When the transmission from the second station of the non-STR station multi-link device to the second AP of the STR AP multi-link device starts simultaneously with the transmission from the first AP of the STR AP multi-link device to the first station of the non-STR station multi-link device, a transmission collision may occur between the links. This is shown in FIG. 17(a). This may occur because, as described above, the STR multi-link device cannot determine in real time the state of the stations included in the non-STR multi-link device.

[0166] Also, a transmission collision may occur between the links when the transmission from the second station of the non-STR station multi-link device to the second AP of the STR AP multi-link device starts earlier than the transmission from the first AP of the STR AP multi-link device to the first station of the non-STR station multi-link device. This is shown in FIG. 17(b). This is because it may take time for the second AP (AP2) to notify the first AP (AP1) that the second station (STA2) is transmitting. Thus, since a transmission collision occurs even between stations that start transmissions at different times, interference or transmission collision between links may occur with a higher probability than interference or collision within a link. Also, the probability of interference or transmission collision between links may increase as the time for the AP of the STR multi-link device to identify the transmitter of the PPDU it receives is delayed. Therefore, a method for solving this is necessary. When one of the stations of the STR multi-link device is receiving, the other stations of the STR multi-link device do not need to access the channel. However, when the channel access is prohibited in this way, the meaning of implementing the STR function may be lost. Therefore, an operation method that does not prohibit the channel access of the STR multi-link device is necessary. This will be described with reference to FIG. 18.

[0167] As described above, it may be important for a multi-link device to quickly determine a station that transmits to the multi-link device. The User field of the EHT-SIG of the EHT UL PPDU can 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 can indicate the identifier of the station that transmits the EHT UL PPDU. A multi-link device that receives the EHT PPDU can identify the station that transmits the EHT PPDU based on the User field of the EHT-SIG of the EHT UL PPDU. Thereby, the AP multi-link device can determine the station that transmits the EHT UL PPDU and determine the destination device of the transmission. Specifically, the AP multi-link device can determine whether there is a high possibility of failure in the transmission attempted due to an inter-link collision. Also, when there is a high possibility of failure in the transmission attempted by the AP multi-link device, the AP multi-link device can delay the transmission attempted and perform other transmissions.

[0168] FIG. 18 shows an operation in which an STR multi-link device cancels transmission to a non-STR multi-link device according to an embodiment of the present invention.

[0169] When the station of the STR multi-link device determines that the station of the non-STR multi-link device is in a blind state during transmission to the station of the non-STR multi-link device, the STR multi-link device can interrupt the transmission to the station of the non-STR multi-link device in the blind state. Specifically, the STR multi-link device can determine whether the station of the non-STR multi-link device is in a blind state based on the value indicated by the signaling field of the received PPDU with STA(AID)-ID or the TA (transmitting address) field of the MAC frame included in the received PPDU. At this time, the STA-ID may be a value indicating the station that transmits the UL PPDU in the UL PPDU. In a specific embodiment, when the value indicated by the signaling field of the received PPDU with STA(AID)-ID indicates the first station included in the non-STR multi-link device, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in a blind state. Also, when the TA field of the MAC frame included in the received PPDU indicates the first station included in the non-STR multi-link device, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in a blind state. Specifically, when the station that transmits 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 is the first station, the STR multi-link device can determine that the second station included in the non-STR multi-link device is in a blind state. In this way, the STR multi-link device can confirm that any one station of the non-STR multi-link device is performing transmission and determine that the other stations of the non-STR multi-link device are in a blind state. First, the operation of the station after canceling the transmission will be described.

[0170] When there is a remaining TXOP set for a station of the non-STR multi-link device, a station that has canceled the transmission to the station of the non-STR multi-link device can attempt to transmit to a station different from the station of the non-STR multi-link device. At this time, the station that has canceled the transmission to the station of the non-STR multi-link device can transmit to a station different from the station of the non-STR multi-link device without a separate backoff procedure. In a specific embodiment, after canceling the transmission to the station of the non-STR multi-link device, when it is sensed that the channel is idle in a pre-specified time interval without a separate backoff procedure, the station that has canceled the transmission to the station of the non-STR multi-link device can transmit to a station different from the station of the non-STR multi-link device. At this time, the pre-specified time interval may be any one of SIFS, PDIF, and DIFS.

[0171] When the station that has canceled the transmission to the station of the non-STR multi-link device transmits to a station different from the station of the non-STR multi-link device, the station that has canceled the transmission to the station of the non-STR multi-link device can transmit traffic having the same priority as the traffic of the canceled transmission or traffic having a higher priority. This is because it is not fair to transmit traffic corresponding to a priority lower than the priority of the traffic used at the time of channel access for the canceled transmission. In the above-described embodiment, the station of the STR multi-link device may be an AP.

[0172] A station that has canceled the transmission to the station of the non-STR multi-link device can initialize the set TXOP. Specifically, a station that has canceled the transmission to the station of the non-STR multi-link device can transmit a CF-End frame after canceling the transmission. This may allow other stations operating on the link where transmission is scheduled to use the link.

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

[0174] When a station interrupts transmission, after transmitting the fragment that was being transmitted, it does not have to transmit the next fragment. In yet another specific embodiment, the station can immediately abort the transmission of the packet that was being transmitted.

[0175] Also, the STA of the STR MLD that has transmitted to the STA of the MLD operating in the EMLSR or EMLMR mode can cancel the transmission that was being performed or was about to be performed in the same manner as the STR MLD that has transmitted to the STA in the BLIND state described above. This is because the STA of the MLD operating in the EMLSR / EMLMR mode may have performance constraints similar to those in the BLIND state as described above.

[0176] That is, while the STA of the STR MLD is transmitting to the STA of the MLD in the EMLSR / EMLMR mode (e.g., EMLSR STA1), if a PPDU is received from another STA of the EMLSR / EMLMR MLD (e.g., EMLSR STA2) via a STA operating on another link, the transmission being performed can be aborted. Also, if the transmission has not yet started, instead of performing the transmission that was about to be made to the STA of the EMLSR / EMLMR MLD (e.g., EMLSR STA1), other traffic in the same AC (Access Category) can be transmitted.

[0177] In this way, the transmission management method for the STA of the EMLSR / EMLMR mode MLD may be managed in a manner similar to / identical to the transmission management method for the STA of the NSTR MLD. Therefore, even if no separate description of the EMLSR / EMLMR mode MLD is provided in the present invention, the operations performed based on whether a specific STA of the NSTR MLD is in the BLIND state may be performed identically / similarly based on whether the performance of a specific STA of the EMLSR / EMLMR mode MLD is restricted by the transmission / reception of other STAs.

[0178] In the foregoing embodiments, when the STR multi-link device interrupts the transmission to the station of the non-STR multi-link device in the blind state and performs transmission to a station different from the station of the non-STR multi-link device in the blind state, in order to ensure stable reception, it is necessary to notify other stations that transmission to other stations can be performed. A method therefor will be described. For the sake of convenience of explanation, a station different from the station of the non-STR multi-link device in the blind state is referred to as another station.

[0179] The station of the STR multi-link device can insert the address of another station into the MAC frame. Specifically, the station of the STR multi-link device can insert the address of the intended recipient of the MAC frame into the RA (receiving address) of the MAC frame and insert the address of another station into a separate field. In yet another specific embodiment, the station of the STR multi-link device can insert the address of another station into the EHT-SIG. Specifically, the station of the STR multi-link device can insert the address of the intended recipient of the PPDU and the address of another station into the User field of the signaling field of the PPDU. At this time, the address of another 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, even after the station recognizes that the intended recipient of the received PPDU is not the station, the station can monitor the reception of the PPDU for a specified time in advance. Specifically, even after the station recognizes that the intended recipient of the received PPDU is not the station, the station can monitor whether the reception of the PPDU continues at the specified time in advance. Thereby, the station can determine whether the transmission of the PPDU is interrupted and whether it is okay to start the transmission to the station for the first time. In such an embodiment, when it is determined that the transmission of the PPDU continues at the specified time in advance, the station can enter the doze state. When it is determined that the transmission of the PPDU does not continue at the specified time in advance, the station can maintain the wake-up state. At this time, when a new PPDU is received by the station, the station can decode the PPDU.

[0181] In yet another specific embodiment, the station transmitting the PPDU can insert information signaling that the transmission of the PPDU can be interrupted into the PPDU. The information signaling that the transmission of the PPDU can be interrupted may be a 1-bit subfield. For example, when the value of the subfield signaling that the transmission of the PPDU can be interrupted is 1, the station receiving the PPDU can determine that the transmission of the PPDU can 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. When the station determines that the transmission of the PPDU can 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 can defer entering the power-saving state. Also, the station transmitting the PPDU can insert information signaling that the transmission can be interrupted into the reserved field of the PPDU.

[0182] In this way, it is possible to prevent the unnecessary occupation of channels by using transmission cancellation or transmission interruption.

[0183] When transmission is interrupted or postponed due to a transmission collision between links, the value of CW used for channel access may be doubled like a general transmission failure. When transmission is interrupted or postponed due to a transmission collision between links, different from a general channel access failure or transmission failure, the value of CW used for channel access may not need to be doubled (doubling). That is, the station can maintain the value of CW used for channel access as it is. Doubling the value of CW is to reduce the probability of transmission collision by increasing the range of numbers that can be the value of the backoff counter. If the station can clearly recognize that it is a transmission collision between links, such a need is less. Also, when transmission is interrupted or postponed due to a transmission collision between links, doubling the value of CW by the station may lead to a delay in transmission. However, when a collision within the link also occurs simultaneously in addition to the transmission collision between links, the station needs to double the value of CW. This will be described with reference to FIG. 19.

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

[0185] When the station cancels the transmission by the transmission from the non-STR multi-link device as in the above-described 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 CW. At this time, 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 CW. Such an embodiment is for handling differently from the case of successful transmission because there is a low possibility of transmission collision occurring in the link even when the channel is sensed to be idle. Specifically, when the AP of the AP multi-link device fails to transmit to the station of the non-STR multi-link device, the AP of the AP multi-link device can acquire a backoff counter within CW without increasing CW. At this time, when the non-STR multi-link device of the AP multi-link device fails to transmit to the first station and the second station of the non-STR multi-link device performs transmission, the AP of the AP multi-link device can acquire a backoff counter within CW without increasing CW. As described above, the AP multi-link device can determine whether the second station of the non-STR multi-link device performs transmission based on the transmission station of the PPDU indicated by the signaling field of the PPDU or the station indicated by the TA field of the MAC frame included in the PPDU. In the above-described embodiment, when EDCA is applied, the procedures regarding CW adjustment and backoff counter generation may be performed separately for each AC.

[0186] In yet another specific embodiment, the STR multi-link device can determine whether the transmission of the PPDU has failed based on whether it has received a response to the PPDU. At this time, the STR multi-link device does not need to consider whether the station receiving the PPDU is included in the non-STR multi-link device. For example, if the first station receiving the PPDU is included in the non-STR multi-link device and the second station of the non-STR multi-link device is performing transmission, even if the first station cannot send a response to the PPDU, the STR multi-link device can determine that the transmission of the PPDU has failed. Also, when the transmission of the PPDU by the STR multi-link device fails, the STR multi-link device can increase the value of CW to the next larger value among the values that the CW value can have. At this time, when the value of CW is the maximum value, the STR multi-link device can maintain the value of CW at the same value.

[0187] In yet another specific embodiment, when the channel is sensed to be idle, the station can set the value of CW to the minimum value (CW_min) of the CW for traffic. Such an embodiment is because when the channel is sensed to be idle, the possibility of transmission collisions occurring within the link is low, so it is treated the same as when transmission is successful. The station can apply the above-described embodiment to the CW of the AC of the traffic included in the cancelled transmission.

[0188] Also, when the station cancels the transmission according to the above-described embodiment, it does not need to increase the retry counter. At this time, the retry counter may include at least one of a long retry counter and a short try counter.

[0189] Canceling the transmission in the previous embodiment may include at least one of interrupting the transmission or delaying the transmission before starting the transmission.

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

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

[0192] <Transmission method of MLD considering <NSTR link pair>

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

[0194] <AP Transmission Management Method>

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

[0196] In this case, although the specific AP has obtained 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 an EMLSR / EMLMR mode MLD having performance constraints similar to BLIND and decide not to start transmission (hereinafter, the description regarding the EMLSR / EMLMR mode MLD is omitted).

[0197] Furthermore, when a frame in the transmission queue of an AC that has obtained the transmission start permission needs to be transmitted to the STA of an NSTR MLD in the BLIND state (i.e., when another STA operating in the NSTR link pair of the NSTR MLD is transmitting), since the STA of the NSTR MLD cannot receive the frame even if it is transmitted, the AP can determine not to transmit the frame. If there are frames in the transmission queue of the AC that have obtained the transmission start permission and are to be transmitted to other STAs that are not in the BLIND state, the AP can transmit the frames in the transmission queue of the AC to the other STAs.

[0198] If the AP determines not to start transmission for the AC that has obtained the transmission start permission, the AP can perform / call a new backoff procedure for the AC. At this time, when performing a new backoff procedure for the AC, the AP can generate a new backoff counter while maintaining the CW (contention window). That is, CW[AC] and QSRC[AC] (QoS STA short retry counter) are not changed and only the backoff counter is regenerated again, and a new backoff procedure for the AC that has obtained the transmission start permission may be performed.

[0199] On the one hand, when there is a frame to be transmitted to a STA in the BLIND state in the transmission queue of an AC for which the transmission start permission has been obtained, the AP can consider it as if there is no such frame in the transmission queue. For example, when only the frame to be transmitted to the STA in the BLIND state exists in the transmission queue, the AP can consider it as if there is no frame in the transmission queue, maintain the BO (Backoff Counter) of the AC for which the transmission start permission has been obtained at 0, and make a decision (operation) not to start transmission. In this case, when the BLIND state of the STA is released, the AP can immediately start transmission considering as if a frame to be transmitted to the STA has been generated in the transmission queue. At this time, the "immediately" can mean transmission without an additional backoff procedure according to the EDCA rule. That is, when it is determined (considered) that the medium is IDLE at the time when the BLIND state of the STA is released at the time (e.g., DIFS, SIFS, PIFS, AIFSN[AC], etc.) that was already set before the release of the BLIND state, the AP can start transmitting to the STA at the next slot boundary.

[0200] Also, the AP of the MLD does not have to retransmit the transmitted trigger frame (e.g., a frame that elicits a response such as a TB PPDU or a CTS) when a response to the transmitted trigger frame has not been received, that is, when the transmission of the transmitted trigger frame has failed. Also, when an Ack has not been responded after transmitting a frame that requests an Ack (Ack frame and Block Ack frame) response, the frame does not have to be retransmitted.

[0201] Generally, STAs (AP STAs, non-AP STAs) including the AP of AP MLD must retransmit a frame that is considered to have failed to be transmitted. However, the AP of AP MLD does not have to retransmit the failed frame when it is determined that the reason for the failure of the frame transmitted to the STA of MLD is due to the operation of other STAs in the NSTR relationship with the STA. This is because it is considered that, unless the operation of other STAs in the NSTR relationship with the receiving STA (destination device, intended recipient) is changed, a response to the retransmitted frame will not be made by the receiving STA even if the AP retransmits the failed frame.

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

[0203] If, after the STA (AP STA and non-AP STA) of the MLD transmits a frame to the receiving STA on a specific link and no Ack response is received on the specific link, and an Ack for the frame is received (responded to) via the STA of another link (of the same MLD as the receiving STA), the STA of the MLD can set CW[AC] and QSRC[AC] to CW_min and 0 respectively. That is, when the STA of the MLD transmits a frame to the receiving STA and does not directly receive an Ack response from the receiving STA, but 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 change 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, the AP of the AP MLD does not have to retransmit to the STA when it is determined that, even if the frame transmitted by itself fails, the destination device is an STA of the MLD and the STA did not respond due to the operating states of other STAs operating in the NSTR link pair. 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 states of other STAs may be that the other STAs became BLIND and did not respond / could not respond due to their own transmission operations, or that they had to respond only to protect the receiving operations of other STAs.

[0205] <Transmission Management Method for STA>

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

[0207] At this time, although the specific STA has obtained the transmission start permission for the specific AC, it may decide not to start transmitting considering the operations of the STAs operating in other links (i.e., NSTR link pairs) that are in an NSTR relationship with the link it operates on.

[0208] Furthermore, even though the specific STA has obtained the transmission start permission for the specific AC, it may decide not to transmit the frames in the transmission queue for the specific AC considering that the other STA is performing a PPDU reception operation. That is, when non-AP MLD is NSTR MLD, the STA operating in the NSTR link pair can give up the obtained transmission start permission considering the operation states of the other STAs in the NSTR link pair. At this time, "giving up the obtained transmission start permission" can mean performing (calling) the backoff procedure again without attempting to transmit or delaying the transmission while maintaining the backoff counter at 0.

[0209] If the STA decides not to start transmitting for the AC for which the transmission start permission has been obtained, the STA can perform / call a new backoff procedure for the AC. At this time, when performing a new backoff procedure for the AC, the STA can generate a new backoff counter while maintaining the CW (contention window). That is, CW[AC] and QSRC[AC] (QoS STA short retry counter) are not changed and only the backoff counter is generated again, and a new backoff procedure for the AC for which the transmission start permission has been obtained may be performed.

[0210] On the one hand, the STA can maintain the BO at 0 without performing a new backoff procedure. For this purpose, when another STA in the NSTR link pair is receiving, it can be considered as if there is no frame in its transmission queue. As an example, the STA operating in the NSTR link pair can consider whether there is no frame in its transmission queue when another STA operating in the NSTR link pair is receiving a PPDU, and thus maintain the BO (backoff counter) of the AC that has obtained the transmission start authority at 0 and decide (operate) not to start transmission.

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

[0213] <STA Transmission Management Restriction>

[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 is understood to be to minimize the negative effects (such as interference and channel access delay) that may occur due to the constraint of the NSTR link pair and to ensure the channel access ability of each STA as much as possible.

[0216] However, in the process of ensuring the channel access ability for each STA of non-AP MLD as much as possible, the transmission collision probability may increase among STAs of different non-AP MLDs. For example, as considered in an 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 other STAs of other non-AP MLDs that maintain their backoff counters at 0.

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

[0218] That is, as considered in one embodiment of the present invention, a non-AP MLD STA that starts transmission while maintaining the backoff counter at 0 may have to start the channel access procedure considering that other non-AP MLD STAs may start transmission simultaneously. For this purpose, the non-AP MLD STA can manage the channel access procedure by checking whether the PPDU being received by the other STA in 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 the backoff counter at 0 only when the PPDU being received by the other STA in the NSTR link pair is a PPDU that has only the other STA as the intended recipient. That is, the non-AP MLD STA can consider as if there is no frame in its own transmission queue (for a specific AC) only when the PPDU being received by the other STA in the NSTR link pair is a PPDU that has only the other STA as the intended recipient. In other words, when the PPDU being received by the other STA in the NSTR link pair is a PPDU that has multiple STAs as the intended recipients, the non-AP MLD STA cannot consider as if there is no frame in its own transmission queue and must perform a new backoff procedure when the backoff counter reaches 0.

[0219] At this time, the method for the non-AP MLD STA to confirm that the PPDU being received by the other STA in the NSTR link pair is a PPDU that has only the other STA as the intended recipient may be at least one of the following methods.

[0220] 1. When the received PPDU is an EHT MU PPDU, includes only one User field, and the STA-ID in 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 (the same meaning as direct address or unicast address), and the individual address is the individual (MAC) address assigned to the other STA. At this time, the individual address can mean that the group bit in the MAC address is 0.

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

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

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

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

[0226] That is, the STA of non-AP MLD can perform the operation of maintaining the backoff counter at 0 only when the PPDU being received by the other STA in the NSTR link pair is a PPDU sent individually to the other STA. At this time, the STA of non-AP MLD can maintain the backoff counter at 0 considering that the transmission queue is in an empty state even though there are frames in the transmission queue.

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

[0228] As an example, when the PPDU being received by the other STA is an EHT MU PPDU, and the other STA is indicated (information related to the STA-ID of the other STA is indicated) in the first User field among the User fields included in the EHT MU PPDU, it may be analyzed that the other STA has received an implicit indication from the AP. In this case, even when the other STA is receiving the EHT MU PPDU, the STA of the non-AP MLD can perform an operation of maintaining the backoff counter at 0. At this time, when the other STA is indicated in the first User field among the User fields included in the HE MU PPDU, it may be analyzed that the same implicit indication as described above has been given.

[0229] As another example, when the value of a specific subfield is indicated as 1 in a User field that indicates information related to the STA-ID of the other STA, it can be analyzed that the other STA has been explicitly indicated by the AP. In this case, even when the other STA is receiving the EHT MU PPDU, the STA of the non-AP MLD can perform an operation of maintaining the backoff counter at 0.

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

[0231] That is, when the STA of the non-AP MLD determines that the PPDU being received by another STA in the NSTR link pair is not a PPDU targeted only at the other STA, or when the PPDU being received is not a PPDU targeted at the other STA, or when the format and / or the target device of the PPDU being received cannot be confirmed, it may be necessary 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 STA of the non-AP MLD cannot maintain the backoff counter at 0 and must generate a new backoff counter.

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

[0233] 2. When the PPDU being received by another STA in the NSTR link pair is an HE MU PPDU

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

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

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

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

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

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

[0240] As another method, the STA of the non-AP MLD can perform an operation of maintaining the backoff counter at 0 regardless of the type of the PPDU being received by another STA in the NSTR link pair. However, when the STA of the non-AP MLD maintains the backoff counter at 0 and starts transmission when the other STA in the NSTR link pair has completed PPDU reception (or after a preset (agreed) time has passed since the completion), the STA of the non-AP MLD must transmit the RTS frame as the first frame. At this time, the restriction that the RTS frame must be transmitted as the first frame may be applied only when the PPDU being received by the said other STA is not a PPDU that targets only the said other STA. That is, when the PPDU being received by the said other STA is a PPDU that targets only the said other STA, the STA of the non-AP MLD does not have to be obliged to transmit the RTS frame as the first frame.

[0241] In other words, a STA that has been maintaining its backoff counter at 0 considering other STA operations (e.g., PPDU reception) operating on the NSTR link pair may have to always start its first transmission to obtain a TXOP with an RTS frame. This may be a sequence considered such that an attempt to obtain a TXOP during the period when the backoff counter is maintained at 0 is initiated (attempted) by an RTS / CTS frame exchange, considering that there may be a large number of STAs of non-AP MLDs that have been maintaining their backoff counters at 0.

[0242] Alternatively, a non-AP MLD STA may not have to decrease its backoff counter when another STA on the NSTR link pair is receiving a PPDU. This may be an operation performed considering that the non-AP MLD STA considers 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 on the NSTR link pair is receiving a PPDU. At this time, the medium busy state may be released when an RXEND.indication related to the PPDU occurs.

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

[0244] Referring to FIG. 20(a), while a non-AP MLD is receiving a SU (Single User) PPDU (if it is an EHT PPDU, it is an EHT MU PPDU and a PPDU including only one User field) on Link1 via STA1, the backoff counter of STA2 operating on Link2 by the non-AP MLD reaches 0, and Link1 and Link2 may be an NSTR link pair.

[0245] In this case, the non-AP MLD's STA2 can recognize that there is no other non-AP MLD's STA that defers transmission while maintaining the backoff counter at 0 to receive the PPDU based on the information that the PPDU received via STA1 is a PPDU targeted only at STA1. Therefore, STA2 can choose to defer transmission while maintaining the backoff counter at 0 without starting transmission even though the backoff 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, internally, STA2 can 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 has been maintained at 0) has been generated in accordance with the completion time of the PPDU reception procedure of STA1. That is, STA2 considers that there is no frame to be transmitted to the transmission queue of the specific AC while the PPDU reception procedure of STA1 is in progress, even though the backoff procedure for the specific AC has been completed. However, at the time when the PPDU reception procedure of STA1 is completed, STA2 can start transmitting the PPDU on Link2 considering that a frame to be transmitted to the transmission queue of the specific AC has been generated. However, STA2 can start transmitting the PPDU only when the medium has been in an idle state for a certain period or longer (considered as SIFS in Fig. 20(a)) at the time of starting the PPDU transmission.

[0247] Also, when transmission is performed without a separate backoff procedure while maintaining the backoff counter at 0, a restriction may be applied that the medium (CCA result of Link2) has not been changed to busy while the backoff counter is maintained at 0. In other words, if the medium is confirmed to have been changed to busy while STA2 was maintaining the backoff counter at 0 while STA1 was receiving a PPDU, STA2 must execute (invoke) a new backoff procedure after the medium is changed back to idle.

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

[0249] Referring to FIG. 20(b), while non-AP MLD is receiving a MU (Multi user) PPDU on Link1 via STA1, the backoff counter of STA2 operating on Link2 by non-AP MLD reaches 0, and Link1 and Link2 may be an NSTR link pair.

[0250] In this case, STA2 of non-AP MLD can recognize that other non-AP MLDs may also defer transmission to receive the PPDU based on the information that the PPDU being received by STA1 is a MU PPDU (or a group (non-individual) address frame) destined not only for STA1 but also for other STAs. Therefore, when the backoff counter reaches 0 as shown in FIG. 20(b), STA2 can decide to execute (invoke) the backoff procedure again without maintaining the backoff counter at 0 or starting transmission. At this time, 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 of STA2 (for a specific AC) reached 0 twice while STA1 was receiving a PPDU, and STA2 called a new backoff procedure twice. At this time, when STA2 maintained CW[AC] and called a new backoff procedure, 5 was generated as the first backoff counter (New counter#1 in FIG. 20(b)), and 7 was generated as the second backoff counter (New counter#2 in FIG. 20(b)) in the backoff procedure called again after the backoff counter reached 0. After the second backoff counter reached 0, since STA1 was no longer receiving a PPDU, STA2 started transmitting a PPDU.

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

[0253] Referring to FIG. 21(a), the beacon frame may include the same parameters and elements as those included in the beacon frame disclosed in the conventional Wi-Fi 802.11ax in the Legacy IEs. For example, the Legacy IEs of the beacon frame may include elements such as a Timestamp field, a Beacon Interval field indicating the interval at which the beacon is transmitted, TIM, a DSSS parameter set, an IBSS parameter set, Country, a channel switch announcement, an extended channel switch announcement, a Wide Bandwidth channel switch, a transmit power envelop, supported operating classes, IBSS DFS, ERP information, HT capabilities, HT operation, VHT capabilities, VHT operation, S1G beacon compatibility, a short beacon interval, S1G capabilities, S1G operation, HE capabilities, HE6GHz band capabilities, HE operation, a BSS color change announcement, and a spatial reuse parameter set.

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

[0255] In addition, the beacon frame may include an RNR (Reduced Neighbor Report) element for indicating information of neighboring APs. The RNR element may be used to notify a station of information of neighboring APs. The station can receive the beacon frame and recognize neighboring 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 neighboring AP information field. Each of the neighboring AP information fields may include a TBTT information header (2 octets), an operating class (1 octet), a channel number (1 octet), and a TBTT information set (variable length) field. At this time, the RNR element transmitted by an AP included in an AP MLD may include a TBTT information field format as shown in (b) of FIG. 21 in order to indicate basic information about other APs included in the same MLD. Different from the TBTT information field of the RNR element transmitted by an AP in conventional Wi-Fi 802.11ax, the RNR element transmitted by an AP included in an EHT AP MLD may include an MLD parameter field.

[0257] The MLD parameter field may include an MLD ID, a link ID, and a change sequence subfield as shown in (c) of FIG. 21. At this time, when an AP MLD indicates information of other APs in the same MLD by a specific neighboring AP information field of the RNR element, the MLD ID subfield included in the specific neighboring AP information field can be set to 0. That is, the AP can set the MLD ID subfield to a specific value to notify the station that the neighboring AP information field is an AP included in the same AP MLD. The station that receives the neighboring AP information field can recognize from the value of the MLD ID subfield that the AP corresponding to the neighboring AP information field is included in the same MLD as the AP that transmitted the neighboring AP information field.

[0258] The Link ID subfield may be a subfield to which the index determined by the AP MLD for indicating the link on which another AP to be indicated using the neighboring AP information operates is indicated. The Change Sequence subfield may be a subfield used to indicate information related to an update (e.g., Critical Update) related to the link of another AP. For example, when the value of the Change Sequence subfield is changed, the station that receives this can recognize that the parameters related to the BSS (or link) of the corresponding AP have been updated, and in order to update the corresponding parameters, the updated parameters can be requested from the AP. At this time, if the AP MLD is an NSTR AP MLD that is an MLD that does not support simultaneous transmission and reception (for example, when the AP MLD is an NSTR mobile AP MLD or an NSTR soft AP MLD, that is, when a mobile terminal or the like operates as a soft AP MLD for tethering or the like), the STA included in the STA MLD can perform the procedure for updating the parameters only on the primary link. That is, in order to update the parameters of another link (e.g., a non-Primary Link) to another neighboring AP instead of the primary link of the AP MLD, the frame for parameter update can be transmitted and received only on 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, in the case where the AP is a NSTR AP MLD that does not support simultaneous transmission and reception (for example, in the case of a NSTR mobile AP MLD or a NSTR soft AP MLD, that is, when a mobile terminal or the like operates as a soft AP MLD for tethering or the like), the NSTR AP MLD can transmit a beacon frame including information indicating that it is a 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 (for example, "0" or "1"), and a non-AP STA MLD that has received the beacon frame can recognize that the AP MLD that transmitted the beacon frame is a NSTR AP MLD. Therefore, the specific subfield for indicating that it is a NSTR AP MLD may be set to a value different from the specific value (for example, "1" or "0") when it does not indicate a NSTR AP MLD (for example, a STR AP MLD or another AP MLD).

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

[0262] The method of using the subfield indicating whether it is an NSTR AP MLD in this way may be a method of explicitly indicating whether the AP MLD is an NSTR AP MLD or not.

[0263] As another example, NSTR AP MLD can indicate that it is NSTR AP MLD in an implicit way without directly indicating so by a specific subfield. Specifically, NSTR AP MLD can implicitly indicate that it is NSTR AP MLD by indicating that it has two supportable links and at the same time indicating that it has an NSTR link pair. At this time, in order to indicate that it has two supportable links, NSTR AP MLD can set the Maximum Number Of Simultaneous Links subfield included in the beacon frame to 1 (or a pre-agreed value meaning two). In this case, in order to indicate that it has an NSTR link pair, NSTR AP MLD can set the NSTR Link Pair Present subfield included in the beacon frame to 1 or 0.

[0264] The AP MLD can inform the Non-AP STA MLD that it is the NSTR AP MLD in an explicit or implicit way by transmitting a beacon frame by the method described above. The Non-AP STA MLD can implicitly or explicitly recognize whether the AP MLD that transmitted the received 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., when it is indicated in the beacon frame by an explicit or implicit method that the AP MLD is the NSTR AP MLD), the Non-AP STA MLD can perform the procedure for association or setup with the NSTR AP MLD only on the link where 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 where the beacon frame was received (e.g., the Priamry link). For example, the transmission and reception of frames for association or setup with an AP connected by a link other than the primary link included in the NSTR AP MLD may be performed only on the primary link. In this case, the (re)association request frame (association request frame) transmitted by the Non-AP STA MLD may also be transmitted on a link other than the primary link (non-primary link).

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

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

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

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

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

[0270] However, since NSTR Soft AP does not transmit beacon frames on non-primary links, it may not be possible to instruct, by means of the RNR element, information related to the beacon frames of other APs (APs on non-primary links). Further, since NSTR Soft AP MLD does not transmit beacon frames via APs on non-primary links, it cannot support information regarding beacon frames when instructing, by means of the RNR element, the basic information of APs on non-primary links. For example, a non-primary link that does not transmit beacon frames has no information corresponding to the TBTT information count, TBTT information length, and neighbor AP TBTT offset subfield that should be instructed by the RNR element. Therefore, when transmitting the RNR element via the AP on the primary link, NSTR Soft AP MLD may need to set the TBTT-related fields of the neighbor AP information field corresponding to the AP on the non-primary link to preset values.

[0271] The neighboring AP TBTT offset subfield of the TBTT information field (see (b) of FIG. 21) is a subfield that indicates information related to the next TBTT of another AP to be indicated. That is, the neighboring AP TBTT offset subfield included in the neighboring AP information field may include information regarding the next TBTT of the AP corresponding to the neighboring AP information field. As an example, when AP1 that transmits a beacon frame indicates information regarding AP2 using an RNR element (by the neighboring AP information field), the neighboring AP TBTT offset subfield corresponding to AP2 indicates the difference in terms of how many TUs (Time Unit, 1024 us) the next TBTT of AP2 has compared to the immediate previous TBTT of AP1. At this time, the value indicated by the neighboring AP TBTT offset subfield is a value obtained by rounding down the TBTT offset to the adjacent integer. That is, when an AP indicates a value of 10 in the neighboring AP TBTT offset subfield of another AP, the next TBTT of the said other AP may have a time interval of 10 TU or more and less than 11 TU based on the previous TBTT of the said AP.

[0272] However, when the AP of the primary link of NSTR Soft AP MLD sets the neighbor AP TBTT offset sub-field (1-Octet) corresponding to the AP of the non-primary link, it may be necessary to set it to a preset value (for example, 254 or 255). This may be because in the case of NSTR Soft AP, it is not possible to determine the Target Beacon Transmission Time (TBTT), which is the scheduled time to send the next beacon frame, without sending a beacon frame on the non-primary link. That is, the beacon frame transmitted by NSTR Soft AP MLD on the primary link may need to set the neighbor AP TBTT Offset sub-field corresponding to the AP of the non-primary link to 254 and / or 255 using the RNR element. At this time, the neighbor AP TBTT offset sub-field corresponding to the non-primary link may exist in the TBTT information field including the MLD Parameters field with the MLD ID sub-field set to 0.

[0273] Therefore, after receiving the beacon frame of NSTR Soft AP MLD, when the non-AP STA MLD checks the TBTT information field in which the MLD ID sub-field is 0 and the TBTT offset sub-field is indicated as 254 and / or 255 in the specific neighbor AP information field of the RNR element included in the beacon frame, it can recognize that the specific neighbor AP information field is information regarding the AP (of NSTR Soft AP MLD) operating on the non-primary link of NSTR Soft AP MLD. In this way, when the non-AP STA MLD that has received the beacon frame of NSTR Soft AP MLD checks the information regarding the AP MLD operating on the non-primary link of the NSTR AP MLD, it shall not send a probe request frame and an ML probe request frame to the NSTR Soft AP MLD on the non-primary link.

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

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

[0276] <MLD AP TBTT Offset Indication>

[0277] In one embodiment of the present invention described above, it was mentioned that the beacon frame transmitted by NSTR Soft AP MLD can indicate a neighbor AP TBTT offset subfield corresponding to an AP of a non-primary link with a preset value (254 and / or 255). However, the neighbor AP TBTT offset subfield may be indicated as 254 or 255 even when it does not correspond to an AP of a non-primary link of NSTR Soft AP MLD. As an example, when the TBTT offset of another AP grasped by the AP transmitting the beacon frame is 254 TU or more (254 TU or exceeding 254 TU), the said AP can indicate the neighbor AP TBTT offset subfield corresponding to the said other AP in the beacon frame as 254. Also, when the AP transmitting the beacon frame cannot accurately grasp the TBTT offset of another AP, the said AP can indicate the neighbor AP TBTT offset subfield corresponding to the said other AP as 255.

[0278] However, since the AP of MLD can always recognize the TBTT offset of other APs within the MLD, it shall not be indicated (set) as 255 when indicating (setting) the neighbor AP TBTT offset subfield corresponding to other APs (of 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 that indicates the offset between the times when the beacon frames are transmitted. At this time, the neighbor AP TBTT offset subfield indicates the 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 plurality of APs included in the AP MLD (NSTR or STR AP MLD). In this case, in the case of the neighbor AP TBTT offset subfield, it cannot be set to a specific value under specific conditions.

[0280] For example, when 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"). At this time, 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 (when it is 8 bits, since it corresponds to values from 0 to 255 respectively, the maximum value of the offset that can be indicated by 8 bits can be 255). However, when not included in the same AP MLD as the AP that transmitted the beacon frame (e.g., when the AP is a legacy AP, etc.), the neighbor AP TBTT offset subfield may be set to a specific value (e.g., "255").

[0281] As a similar example, the neighbor AP TBTT offset subfield may be analyzed such that the values set under specific conditions are different.

[0282] For example, when the neighbor AP TBTT offset subfield is set to a specific value (e.g., "254"), it may be analyzed such that the value set under specific conditions is different from "254" or "254" or more.

[0283] Specifically, when the AP corresponding to the neighboring AP information field including the neighboring AP TBTT offset subfield is included in the same AP MLD or another MLD as the AP that transmitted the beacon frame, and the neighboring AP TBTT offset subfield is set to a specific value (for example, "254"), the station can analyze the value indicated by the neighboring AP TBTT offset subfield as 254 TU. However, when it is not included in the same AP MLD or another MLD as the AP that transmitted the beacon frame (for example, when the AP is a legacy AP or an AP not included in the MLD), and the neighboring AP TBTT offset subfield is set to a specific value (for example, "254"), the station can analyze the value indicated by the neighboring AP TBTT offset subfield as 254 TU or more TU.

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

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

[0286] However, when the AP MLD uses a beacon frame to indicate information about other APs within the MLD, an additional MLD AP TBTT offset subfield can be included in the transmission to more accurately inform 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 present in the same MLD when the AP MLD transmits a beacon frame. At this time, when both the neighboring AP TBTT offset subfield and the MLD AP TBTT offset subfield are indicated in a specific TBTT information field, the neighboring AP TBTT offset subfield may be indicated with a preset value (which may be 254 or 255). The MLD AP TBTT offset subfield is a 2-octet-sized subfield and may be utilized to indicate the TBTT offset value when the TBTT offset between the AP (Reporting AP) that transmitted the beacon frame and another AP (Reported AP) in the same MLD exceeds 254 TU. Further, the MLD AP TBTT offset subfield may be included in the TBTT information field only when the TBTT offset of other APs within the same MLD exceeds 254 TU and the existing neighboring AP TBTT offset subfield cannot accurately indicate the TBTT offset when the AP MLD transmits a beacon frame.

[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, it can check the TBTT offset of the AP corresponding to the TBTT information field based on the value indicated by the MLD AP TBTT offset subfield. At this time, in order to determine whether the TBTT information field included in the beacon frame includes the MLD AP TBTT offset subfield, the STA may be checked based on the value of the TBTT information length subfield corresponding to each TBTT information field (in the TBTT Information Header (sub) field of each adjacent AP information field). That is, when the STA recognizes that the MLD AP TBTT offset subfield is included in the TBTT information field based on the value of the TBTT Information Length subfield, it can check the TBTT offset of the AP corresponding to the TBTT information field based on the value indicated by the MLD AP TBTT offset subfield. At this time, when 0 or a preset value (or a value of 254 or less) is indicated by the MLD AP TBTT offset subfield of a specific TBTT information field, the STA MLD can check the TBTT offset of the AP corresponding to the specific TBTT information field based on the value of the adjacent AP TBTT offset subfield.

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

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

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

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

[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 present in the neighboring AP information field included in the RNR element. That is, the RNR element transmitted in the beacon frame may include a plurality of neighboring AP information fields, and the TBTT information fields included in each neighboring AP information field may have structures including different amounts and types of content. At this time, since the TBTT information fields included in each neighboring 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 neighboring AP information field in the RNR element of the beacon frame received via the AP based on the information indicated by the TBTT information header. At this time, each parsed neighboring AP information field may indicate information regarding a neighboring AP or another AP of the same MLD. At this time, when the value of the TBTT information length subfield included in the TBTT information header field means a content configuration including the MLD AP TBTT offset subfield as shown in FIG. 23, the STA can confirm the TBTT offset of the AP corresponding to the TBTT information field based on the value indicated by the MLD AP TBTT offset subfield.

[0294] <Setup and Management of Non-Primary Links>

[0295] As described above, NSTR AP MLD cannot transmit beacon frames, probe response frames, and ML (Multi-link) probe response frames on non-primary links. Therefore, the STA MLD attempting to connect to NSTR AP MLD must send an (ML) probe request frame only on the link where NSTR AP MLD has sent a beacon frame.

[0296] The ML probe request frame transmitted by the STA of the EHT non-AP STA MLD may have a configuration that includes EHT Capability information and Multi-Link elements in addition to the information included in the probe request frame transmitted by a conventional HE STA. At this time, the Multi-Link element included in the ML probe request frame can serve to request the AP MLD that transmits the ML probe request frame to provide additional information about the APs on other links.

[0297] As an example, when transmitting an ML probe request frame, the non-AP STA MLD can use the Multi-Link element of the ML probe request frame to request the AP MLD to further respond with complete information or partial information about the APs on other links. That is, the AP MLD that receives the ML probe request frame can be requested to transmit all or part of the parameters related to the links of other APs included in the same AP MLD.

[0298] For example, when all or part of the parameters related to the AP connected by a non-primary link are updated, the stations included in the non-AP STA MLD can request the AP connected by the primary link to transmit all or part of the updated parameters related to the other APs on the non-primary link.

[0299] At this time, the fact that the complete information is requested / responded means that information at the same level as the AP (Reporting AP) that responds to the ML probe response frame is requested / responded to the AP (Reported AP) of the other link. At this time, the fact that the partial information is requested / responded means that information about the AP of the other link is only responded to the information requested by the STA.

[0300] The AP MLD that transmitted the beacon frame can, in the ML probe request frame received on a specific link, when additional information about the AP of another link is requested, use the ML probe response frame to respond not only with information about the AP of the specific link but also with the additional information about the requested AP of the other link.

[0301] At this time, when the STA MLD requests complete information about the AP of another link while transmitting an ML probe request frame on a specific link, the AP MLD must provide information about the AP of the other link at the same level as the information about the AP of the specific link using the ML probe response frame that responds on the specific link. In other words, the STA MLD that has received a response of complete information about the AP of another link on a specific link can obtain information at the same level as when directly receiving an ML probe response from the AP of the other link with respect to the AP of the other link.

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

[0303] At this time, when transmitting an ML probe request frame on a specific link, the STA MLD can set the Complete Profile subfield (included in the Per-STA Control field of the Multi-Link element) corresponding to the other link to 0 or 1 in order to indicate whether to request complete information or partial information about the other link.

[0304] At this time, the additional information (Complete and Partial) for the other APs may be transmitted by the Per-STA profile included in the Multi-link element of the ML probe response frame. The Per-STA profile is a field included zero or more times in the Multi-link element and may include information on other STAs (APs and non-AP STAs) existing in the same MLD as the STA (AP and non-AP STA) that transmits the frame including the Multi-Link element. At this time, the Per-STA profile has a configuration including a Complete Profile sub-field, and the complete information of other STAs (APs and non-AP STAs) corresponding to the Per-STA profile in which the Complete Profile sub-field is indicated as 1 (information at the same level as the STA (AP and non-AP) that transmits the frame including the Multi-Link element) can be obtained from the Per-STA profile. However, parameters / elements that mean the same information as the STA (AP and non-AP) that transmitted the Per-STA profile may be omitted according to the inheritance rule. The inheritance rule can mean that in order to prevent repetitive indication of the same parameters and elements, if the parameters and elements are not indicated, the values of the same parameters and elements (indicated for other STAs (APs and non-APs)) that have already been indicated are inherited and utilized. That is, if the value of parameter1 is indicated for STA1 and not indicated for STA2, according to the inheritance rule, the value of parameter1 for STA2 may be analyzed as if the same value as that of parameter1 of STA1 was indicated.

[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 the Beacon Interval subfield for indicating the interval at which beacons are transmitted. That is, when the NSTR AP MLD indicates the Per-STA profile subelement corresponding to the non-primary link AP in the Multi-link element, the Beacon Interval Present subfield must be set to 0. This may be because there is no separate beacon frame period since the AP operating on the non-primary link of the NSTR AP MLD does not transmit beacon frames. That is, the Per-STA profile subelement (for probe response and association response frames) corresponding to the non-primary link AP of the NSTR AP MLD may have the Beacon Interval Present subfield indicated as 0 even if the Complete Profile subfield (of the Per-STA Control field) is indicated as 1. That is, the beacon interval information for the non-primary link AP does not exist even when complete information is indicated.

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

[0307] That is, since the beacon is not transmitted on the non-primary link, even when the non-AP STA MLD requests all information (or all updated information) about other APs on the non-primary link via the AP of the primary link of the AP MLD (that is, when the complete information is set to "1"), the beacon interval and DTIM information for the AP on the non-primary link do not have to be present in the ML probe response frame. That is, the beacon interval and DTIM information do not have to be included in the per-STA profile sub-element for the AP on the non-primary link included in the ML probe response frame.

[0308] In this case, even if all information (or all updated information) about other APs on the non-primary link is requested, the AP MLD does not have to include the beacon interval and DTIM information for the AP on the non-primary link in the ML probe response frame. Therefore, in this case, the AP MLD can transmit by setting the beacon interval present sub-field and the DTIM information present sub-field to values (for example, "0") indicating that each field is not included.

[0309] Since the NSTR AP MLD does not transmit beacon frames on non-primary links, it may not be necessary 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 that 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 is 0. That is, the NSTR AP MLD may need to always indicate that the beacon interval present subfield in the Per-STA profile corresponding to the AP of the non-primary link is 0. Therefore, even when the NSTR AP MLD receives an ML probe request frame requesting complete information from a non-AP STA MLD or receives an (ML) (re) association request frame, the NSTR AP MLD may need to always indicate that the beacon interval present subfield and the DTIM information present subfield of the Per-STA profile corresponding to the AP of the non-primary link are 0.

[0310] Alternatively, since beacon frames are not transmitted on non-primary links in NSTR AP MLD, it may be necessary to set the sub-fields of Beacon Interval, DTIM Count, and DTIM Interval to pre-agreed 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 with) complete information about the AP of the non-primary link. That is, after the STA MLD requests complete information about a specific link from the AP MLD using an ML probe request frame or the like, it can be expected that the complete information about the AP of the specific link will be responded to in the response frame. At this time, 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 complexity of implementing the process of the STA MLD obtaining information according to the Per-STA profile may increase. Therefore, even if the AP of the non-primary link does not transmit a beacon frame, the NSTR AP MLD can use a Per-STA profile with the same configuration as the Per-STA profile used by a general AP MLD when responding with complete information about the non-primary link. At this time, the Per-STA profile corresponding to the AP of the non-primary link of the NSTR AP MLD may be set to the pre-set values for the Beacon Interval sub-field, the DTIM Count sub-field, and the DTIM Interval sub-field, respectively. As an example, when transmitting complete information about the AP of the non-primary link, the NSTR AP MLD can set all bits of the Beacon Interval sub-field of the non-primary link to 0 or all to 1 or in a pre-agreed manner.As an example, when transmitting complete information to the AP of a non-primary link, NSTR AP MLD can set each bit of the DTIM Count subfield of the non-primary link to all 0s or all 1s or in a pre-agreed manner. As an example, when transmitting complete information to the AP of a non-primary link, NSTR AP MLD can set each bit of the DTIM Interval subfield of the non-primary link to all 0s or all 1s or in a pre-agreed manner.

[0311] Alternatively, since no beacon frame is transmitted to the non-primary link, in the Per-STA profile corresponding to the AP of the non-primary link, NSTR AP MLD can set the subfields of Beacon Interval, DTIM Count, and DTIM Interval to the values associated with the beacon frame of the primary link. This can be an operation considered to maintain the same Per-STA profile configuration as described above. At this time, the Per-STA profile corresponding to the AP of the non-primary link of NSTR AP MLD may be set to the values associated with the beacon frame transmitted on the primary link for the Beacon Interval subfield, DTIM Count subfield, and DTIM Interval subfield, respectively. As an example, when transmitting complete information to the AP of a non-primary link, NSTR AP MLD can set the Beacon Interval subfield of the non-primary link to the value indicating (meaning) the beacon interval of the primary link. As an example, when transmitting complete information to the AP of a non-primary link, NSTR AP MLD can set the DTIM Count subfield of the non-primary link to the DTIM Count value of the primary link. As an example, when transmitting complete information to the AP of a non-primary link, NSTR AP MLD can set the DTIM Interval subfield of the non-primary link to the value indicating (meaning) the DTIM interval of the primary link.

[0312] Alternatively, since the beacon frame is not transmitted on the non-primary link, the sub-fields of the Beacon Interval, DTIM Count, and DTIM Interval in the Per-STA profile corresponding to the AP on the non-primary link can be set to values with specific purposes. Further, the Beacon Interval sub-field of the non-primary link may be set to a value with a specific purpose (virtual beacon interval), such as a value for calculation, by the AP MLD. Conventionally, the Wi-Fi beacon interval means a value related to the time interval at which the beacon frame is actually transmitted, while it is utilized as time units for the operations of various BSSs. As an example, units such as JointFailureTimeout and QueryFailureTimeout primitives are defined with the beacon interval, and fields such as the Listen interval field, PRAW Start offset sub-field, AID Request Interval field, AID Switch Count field, AID Response Interval field, Minimum Transmission Interval sub-field, Channel Quality Measurement Duration, and Color Switch Countdown (of the BSS Color Change Announcement element) sub-field utilize the beacon interval (or, TBTT) as the basic unit to indicate interval / Duration. Thus, while the beacon interval has the meaning of a value related to the interval at which the beacon frame is actually transmitted, it is a value utilized as a unit for various primitives and fields. Therefore, even if the beacon frame is not actually transmitted on the non-primary link, a beacon interval for the non-primary link may need to be defined (indicated, set) for use as a unit for the above-described primitives / sub-fields.

[0313] That is, even if a beacon frame is not transmitted on a non-primary link, NSTR AP MLD can indicate a beacon interval value for utilizing the Beacon Interval subfield of the Per-STA profile corresponding to the AP of the non-primary link as the time unit of the non-primary link. In this case, the non-AP MLD can recognize (confirm, calculate) the duration and interval of the above-described primitive and field (utilized as the beacon interval unit) based on the value indicated by the Beacon interval subfield of the Per-STA profile corresponding to the AP of the non-primary link. At this time, the DTIM Interval subfield and the 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 values when operating the STA on the non-primary link.

[0314] On the other hand, the setting method of the subfields (such as Beacon Interval, DTIM Count, DTIM Interval, etc.) related to the beacon of the non-primary link of the above-described NSTR AP MLD may be equally applicable to other frames and subfields including information related to the beacon of the non-primary link, in addition to the Per-STA profile transmitted on the primary link (transmitted on the primary link or the non-primary link).

[0315] In addition, a non-AP STA MLD attempting to associate with an NSTR AP MLD may need to utilize 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 and non-primary links. That is, a non-AP STA MLD transmitting the Listen interval field to the NSTR AP MLD must calculate and set the unit of the Listen interval field based on the beacon interval of the AP operating on the primary link of the NSTR AP MLD. At this time, the Listen interval field may be a field indicating information related to the period (time) during which at least one STA transitions to the wake state for the non-AP STA MLD performing multi-link (re)association to receive the beacon frame. At this time, the Listen interval field may indicate a value derived when the ListenInterval parameter is indicated by the MLME primitive.

[0316] At this time, when the non-AP STA MLD sends the Listen interval field to another AP MLD that is not the NSTR AP MLD (e.g., the STR AP MLD), it may be necessary to set the unit of the Listen interval field to the maximum value among the beacon intervals of the link (AP) for which it is about to perform the setup. As an example, when the non-AP STA MLD attempts to perform a multi-link setup with the AP MLD and Link 1 or Link 2, the non-AP STA MLD can set the unit of the Listen interval field included in the ML association request frame to the larger value between the beacon interval of Link 1 (AP) and the beacon interval of Link 2. That is, 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 sent by the non-AP STA MLD can be in units of 100 ms.

[0317] Generally, when the setup between the AP and the STA is completed, the STA can grasp and update the operation parameters and element change items of the AP while receiving the beacon frame sent by the AP. Also, the beacon frame, including the Timestamp field, also plays a role in providing information for the STA within the BSS to perform time synchronization.

[0318] However, since the NSTR AP MLD does not send the beacon frame on the non-primary link as described above, the STA MLD that has set up with the NSTR AP MLD may need to perform another operation for parameter / element tracking (update) and time synchronization maintenance for the non-primary link.

[0319] According to an embodiment of the present invention, after receiving a beacon frame on the primary link, the non-AP STA MLD combined with the NSTR AP MLD can check the change sequence of the non-primary link (in the MLD parameter field of the RNR element) and send an ML Probe Request. At this time, the ML probe request frame sent by the non-AP STA MLD may be sent for the purpose of requesting the changed parameters and element information of the non-primary link. At this time, the ML probe request frame may request the complete information of the non-primary link by setting the complete profile of the per-STA profile corresponding to the non-primary link (and the AP of the non-primary link) to 1 and sending it. Alternatively, the ML probe request frame sent by the STA MLD for the purpose of updating the parameters / elements of the non-primary link may request updated information that is not complete / partial information for the non-primary link.

[0320] In other words, even when a plurality of links are formed between the non-AP STA MLD and the AP MLD, the frames for performing the bonding, re-bonding, and / or parameter update procedures may be performed only on the primary link. For example, from a specific field (e.g., change sequence or BSS parameter change count subfield (such as BSS Parameter Change Count subfield, etc.)) indicating whether it is a parameter update for the link to another AP included in the neighboring AP information included in the beacon frame, when the STA recognizes that the parameters for the non-primary link AP of another AP have been updated, the non-AP STA MLD can request the transmission of the updated parameters on the primary link that is not the non-primary link of the other AP. That is, the non-AP MLD cannot send a frame (e.g., a probe request frame, etc.) for requesting the updated parameters on the non-primary link.

[0321] As an example, after setting up with the NSTR AP MLD, the non-AP STA MLD that requests information to update the Parameter / elements of the non-primary link can request the changed parameter / elements from the non-primary link's AP by setting the Updated Profile sub-field of the Per-STA profile corresponding to the non-primary link to 1 in the ML probe request frame transmitted on the primary link. The NSTR AP MLD can respond with an ML probe response frame containing the changed non-primary link information (parameters and elements) when the Updated Profile sub-field is indicated as 1 in the Per-STA profile (corresponding to the non-primary link) of the received ML probe request frame.

[0322] At this time, the Per-STA profile field of the ML probe request frame transmitted by the non-AP STA MLD may have a configuration including an Updated Profile sub-field and a Recorded Change Sequence sub-field. The Recorded Change Sequence sub-field 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 sub-field.

[0323] As an example, NSTR AP MLD may change Parameter1 while increasing the Change Sequence number of the non-primary link from 100 to 101, and further change Parameter2 while increasing the Change Sequence number from 101 to 102. At this time, STA MLD can request the Updated information of the non-primary link while transmitting the ML probe request frame. In this case, when non-AP STA MLD indicates that the Recorded Change Sequence subfield is 100, NSTR AP MLD responds with an ML probe response frame containing both Parameter1 and Parameter2, and when non-AP STA MLD indicates that the Recorded Change Sequence subfield is 101, NSTR AP MLD can respond with an ML probe response frame containing only Parameter2.

[0324] At this time, Non-AP STA MLD can indicate that the Complete Profile subfield is 0 without using another Updated Profile subfield to request the Updated Profile. That is, the method for Non-AP STA MLD to request the Updated Profile may be to set the Complete Profile subfield to 0, and in this case, another Updated Profile subfield may not be included in the Per-STA profile.

[0325] FIG. 24 shows an example of the format of the profile sub-element (Per-STA Profile subelement) of each STA 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 an STA Control field. The STA Control field (see FIG. 24(b)) indicates information for instructing the types of fields included in the STA profile (see FIG. 24(a)) of the Per-STA profile sub-element. At this time, in a specific Per-STA profile sub-element transmitted by an AP MLD other than the NSTR AP MLD, when the Complete Profile sub-field of the STA Control field is indicated as 1, it may be necessary that the MAC Address Present sub-field, the Beacon Interval Present sub-field, and the DTIM Information Present sub-field are all indicated as 1. However, as described above, since the NSTR AP MLD does not transmit beacon frames on non-primary links, information related to the beacon frames of the non-primary links does not need to be indicated in the Per-STA profile sub-element corresponding to the non-primary link. That is, for a specific Per-STA profile sub-element (corresponding to an AP on a non-primary link) transmitted by the NSTR AP MLD, even if the Complete Profile sub-field is indicated as 1, the Beacon Interval Present sub-field and the DTIM Information Present sub-field may be indicated as 0.

[0327] Also, as described in the above-described embodiment, a non-AP STA MLD that transmits an ML probe request frame to an NSTR AP MLD can request the primary-link AP for updated information of the non-primary-link AP by instructing the Updated Profile subfield of the STA Control field (included in the Per-STA profile sub-element corresponding to the non-primary-link AP) to be 1. At this time, the non-AP STA MLD can indicate the Recorded Change Sequence value, which is information related to the time when it updated the information of the non-primary-link AP, using the Recorded Change Sequence subfield (see FIG. 24(c)). At this time, 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 on the primary link, the NSTR AP MLD can determine the information of the non-primary-link AP 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 non-primary-link AP.

[0328] FIG. 25 shows 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 the information of the non-primary link according to an embodiment of the present invention.

[0329] Referring to FIG. 25, after NSTR AP MLD changes the parameters of AP2 operating on Link 2, which is a non-primary link, it can indicate that the parameters of AP2 have been changed using the beacon frame transmitted by AP1 operating on Link 1, which is the primary link. At this time, the information that the parameters of the AP2 have been changed may be indicated in the RNR element included in the beacon frame transmitted by AP1, where the Change Sequence subfield value corresponding to AP2 is increased by 1 from the value indicated in the previous beacon frame.

[0330] After receiving the beacon frame transmitted by AP1 via STA1, Non-AP STA MLD can recognize the fact that the parameters of AP2 have been updated. Non-AP STA MLD can transmit an ML probe request frame via STA1 to obtain the updated parameter information of AP2.

[0331] The ML probe request frame transmitted by Non-AP STA MLD via STA1 may have a configuration including 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 to request a Complete Profile or an Updated Profile.

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

[0333] From the NSTR AP MLD, the non-AP STA MLD that has been responded to with the information of the requested AP2 in the ML probe response frame can complete the parameter update for the non-primary link where 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 can transmit a broadcast ML probe response frame on the primary link when information related to the AP operating on the non-primary link is changed. The non-AP STA MLD may need to update the information regarding the non-primary link (AP) when it receives the broadcast ML probe response frame transmitted by the NSTR AP MLD on the primary link. At this time, the broadcast ML probe response frame may not be transmitted as a response to the ML probe request frame transmitted by a specific STA, but may be an ML probe request frame transmitted by the NSTR AP MLD without another 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 update the changed parameters and elements of the non-primary link. At this time, since the (Recorded) Change Sequences of the non-primary links maintained by each non-AP STA may be different from each other, the broadcast ML probe response frame may include complete information about the AP of the non-primary link. At this time, the broadcast ML probe response frame may be transmitted together with the DTIM beacon frame.

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

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

[0339] FIG. 26 is a flowchart showing an example of a procedure for updating parameters of a non-primary link by a non-AP STA MLD associated with an NSTR AP MLD according to an embodiment of the present invention.

[0340] After receiving a beacon frame on the primary link, the Non-AP STA MLD checks the Change Sequence of the non-primary link (which is in the MLD Parameter field of the RNR element). If the Change Sequence value of the non-primary link checked is different from the (Recorded) Change Sequence value it maintains, the Non-AP STA MLD can send an ML probe request frame on the primary link. At this time, the ML probe request frame may include a subfield indicating whether to request complete information about the non-primary link's AP or updated information. Also, the ML probe request frame requesting updated information may have a configuration that includes a subfield indicating the (Recorded) Change Sequence value it maintains. Subsequently, the Non-AP STA MLD that receives an ML probe response frame from the AP MLD performs parameter update based on the information of the non-primary link's AP included in the received ML probe response frame.

[0341] <Non-primary link Time Sync management>

[0342] As described above, the beacon frame transmitted by the AP plays a role in helping STAs within the BSS to achieve time synchronization (Time Sync) while transmitting various parameters and element information. 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. The STA that receives the TimeStamp field can synchronize its 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, the NSTR AP MLD cannot transmit beacon frames on non-primary links. Therefore, among the STAs of the Non-AP STA MLD, the STAs associated with the non-primary link APs of the NSTR AP MLD must use other methods instead of beacon frames to maintain time synchronization with the AP.

[0344] In order to maintain time synchronization with the non-primary link AP 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 with the same function as the beacon frame, the STA that receives the TIM frame from the non-primary link AP 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 a non-primary link without occupying the primary link, it may be necessary to transmit the TIM frame on the non-primary link simultaneously when transmitting the beacon frame on the primary link. That is, the non-AP STA MLD associated with the NSTR AP MLD may need to prepare to receive the TIM frame on the non-primary link in accordance with the TBTT of the primary link.

[0345] As yet another embodiment of the present invention, in the case of a NSTR AP MLD that does not support simultaneous transmission and reception, the same TSF timer may be used for each link to a plurality of 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 a NSTR AP MLD, the link (non-primary link) to the 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 for use 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 (based on the NSTR Soft AP MLD) link and can use the TSF timer managed using the primary link together. 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. At this time, for the 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 the time synchronization between each pair of APs of the NSTR AP MLD and / or between each pair of STAs of the non-AP STA MLD combined with the NSTR AP MLD so as to have an error within a pre-agreed value. As an example, the 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 to be within a pre-agreed / set value. As an example, the non-AP STA MLD combined with the 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 to be within a pre-agreed / set value.

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

[0349] In addition, when the non-AP STA MLD associated with the NSTR AP MLD receives a TIM frame on the non-primary link, it may be necessary to receive the next beacon frame transmitted on the primary link. More specifically, when the non-AP STA MLD receives a TIM frame via 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 be necessary to receive the next beacon frame transmitted on the primary link. At this time, 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 on the non-primary link. At this time, the meaning of receiving the next beacon frame may be an operation (including) updating the parameters of the non-primary link using the Per-STA profile (corresponding to the AP of the non-primary link) included in the beacon frame. At this time, the parameters to be updated may be limited to the parameters related to the critical update.

[0350] <Non-primary link Channel Switching, Channel Quieting procedures>

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

[0352] Conventional Wi-Fi can change the operation channel frequency (operation frequency band) of the BSS by a procedure pre-agreed between the AP and the STA. At this time, the conventional ECS (Extended channel switching) operation may be utilized, and the channel change mechanism newly defined in 11be may be utilized. When the AP determines to change the operation channel of the BSS, it can send beacon frames, probe response frames, Extended Channel Switch Announcement frames, etc., and notify the associated STAs that they can switch to a new channel and operating class while maintaining the association. At this time, the AP sends an Extended Channel Switch Announce element in the beacon frame, and the Channel Switch Count field of the element indicates information regarding how many beacon frames will be sent later before the channel switch (operation channel change) is performed. If the AP includes the MAX Channel Switch Time element in the beacon frame together with the Extended Channel Switch Announcement element, the AP must send the first beacon frame within the Switch Time field (of the Max Channel Switch Time element) on the new channel. That is, the beacon frames transmitted on the new channel need to be transmitted at an interval smaller than the interval between the last beacon frame transmitted on the current channel and the time indicated by the Switch Time field.

[0353] Referring to the above-described conventional Wi-Fi BSS channel change operation, the AP of the BSS can instruct the STA using the beacon frame transmitted on the current channel with information regarding the new channel, information regarding the time when the channel change is to be performed, and information related to the time point of the first beacon frame transmitted on the new channel. The STA of the BSS can complete the channel change while maintaining the association with the AP by moving to the new channel during 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. Thus, the conventional Wi-Fi BSS channel change procedure is performed in such a way that information necessary 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. Therefore, in the case of a non-primary link BSS of an NSTR AP MLD where no beacon frame is transmitted, the conventional channel change procedure cannot be used to perform a channel change.

[0354] Also, when the conventional Wi-Fi sets a Quiet interval, information regarding the time period to which the Quiet interval is applied is indicated by elements (Quiet element, Quiet Channel element) included in the beacon frame transmitted by the AP of the BSS. Similar to the channel change procedure, a non-primary link of an NSTR AP MLD where no beacon frame is transmitted cannot use the conventional Quieting procedure for setting the Quiet interval.

[0355] According to an embodiment of the present invention, NSTR AP MLD can indicate, by a beacon frame transmitted on a primary link, information necessary to change an operation channel of a non-primary link (Channel switching) and / or information necessary to set a quiet interval. That is, a non-AP STA MLD associated with NSTR AP MLD can operate based on information obtained from a beacon frame of the primary link in order to perform a channel change of the non-primary link. That is, a non-AP STA MLD associated with NSTR AP MLD can obtain information related to a quiet interval of the non-primary link using a beacon frame of the primary link.

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

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

[0358] Referring to FIG. 27, the (corresponding) Per-STA profile for the non-primary link's AP 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 primary link's TBTT (Target Beacon Transmission Time) and beacon interval.

[0360] The AP of the primary link of the NSTR AP MLD needs 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. At this time, the timing field is used in the general sense to collectively refer to the time-related fields including the duration-related fields (such as Switch Time, Quiet Duration field, etc.) and the time-point-related fields (such as Channel Switch Count, Quiet Count field, etc.).

[0361] Therefore, after receiving the beacon frame from the AP of the NSTR AP MLD operating on the primary link, the non-AP MLD combined with the NSTR AP MLD needs to obtain the information related to the channel change and / or quiet interval of the non-primary link in the Per-STA profile included in the beacon frame, and then analyze the information related to the channel change and / or the information related to the quiet interval of the non-primary link based on the TBTT and BI (Beacon interval) of the primary link. At this time, the Per-STA profile means the Per-STA profile corresponding to the AP of the non-primary link.

[0362] On the one hand, after NSTR AP MLD completes the channel change of the non-primary link using the beacon frame of the primary link (after announce and completion of channel change), it may be necessary to transmit a TIM frame on the new channel (for the non-primary link) within the time indicated by the Switch Time field (of the Max Channel Switch Time element). That is, the AP of the non-primary link of NSTR AP MLD may need to transmit a TIM frame on the new channel after performing the channel change. At this time, the AP of the non-primary link may need to transmit a TIM frame on the new channel within the time indicated by the Switch Time field after the beacon frame indicating the Channel Switch Count subfield as 1 (or 0) is transmitted on the primary link. At this time, the Channel Switch Count field and the Switch Time field may be those included in the Per-STA profile (corresponding to the non-primary AP) included in the beacon frame transmitted on the primary link. At this time, the TIM frame may be replaced by other frames transmitted on the new channel of the primary link or the non-primary link. As an example, after NSTR AP MLD completes the channel change of the non-primary link, it can transmit a beacon frame indicating information related to the completion of the channel change on the primary link. At this time, the beacon frame may be an additional beacon frame transmitted regardless of the TBTT. At this time, 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.At this time, the beacon frame of the primary link transmitted after the channel change of the non-primary link is completed may need to be transmitted within a time pre-agreed with the beacon frame transmitted before the channel change starts. At this time, the pre-agreed time may be the time indicated by the Switch Time field (of the Max Channel Switch Time element). Alternatively, the beacon frame may be a beacon frame including an indication related to the channel change of the non-primary link. As an example, the beacon frame of the primary link transmitted after the channel change is completed in the non-primary link may have a configuration including a Channel Switch Complete subfield. At this time, the Channel Switch Complete subfield may be a subfield included in the ML element. The specific Switch Complete subfield may be a subfield that is indicated as 1 when the channel change of the AP corresponding to the Per-STA profile including the specific subfield is completed. That is, 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 after the channel change in the non-primary link is completed. At this time, the beacon frame related to the channel change may be transmitted (utilized) for the same purpose even when the AP MLD is not the NSTR AP MLD, that is, even by a general AP MLD.

[0363] The non-AP MLD combined with the NSTR AP MLD can perform operations considering that the channel change of the non-primary link is completed only when, after changing the channel of the non-primary link with the primary link, it receives from the AP MLD an agreed frame (the TIM frame of the non-primary link or other frames and / or a beacon frame instructing information related to the completion of the channel change of the primary link). If it is considered that the channel change is not completed, the non-AP STA MLD may need to operate (return to the previous channel) considering that the channel change of the non-primary link is canceled and operate on the previous channel (before the channel change).

[0364] Alternatively, the NSTR AP MLD may be restricted so that it cannot set a quiet interval on the non-primary link. At this time, when there is a quiet interval defined (set) for 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. That is, the non-AP STA MLD combined with the NSTR AP MLD can consider that a quiet interval is set for the same time interval on the non-primary link when it recognizes the quiet interval of the primary link.

[0365] Also, the NSTR AP MLD cannot change the channel of the non-primary link. However, if the NSTR AP MLD attempts to change the channel of the non-primary link, it can perform the same operations as when the AP of the non-primary link operating on the existing channel is released and a new AP of the non-primary link is added on the new channel.

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

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

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

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

[0370] The (Extended) Channel Switch Announcement element and the Max Channel Switch Time element for the non-primary link sent in the beacon frame of the primary link may be set (indicated) 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 until the channel change of the non-primary link starts. If the channel change of the non-primary link AP starts at the next TBTT of the primary link, the beacon frame sent at this TBTT may have the Channel Switch Count field (related to the non-primary link AP) set to 1 or 0.

[0372] 2. The Switch Time field (of the Max Channel Switch Time element) may be set to a value relative to the maximum time difference between the primary beacon frame transmitted at the TBTT immediately preceding the TBTT at which the channel change of the non-primary link starts (the beacon frame in which the Channel Switch Count field was set to 1 or 0 in 1. above) 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 and the Switch Time field (for the non-primary link AP) is set to 200 ms, the non-primary link AP must transmit the TIM frame on the new channel within 200 ms from the time of transmission of the beacon frame of the primary link at which it started the channel change.

[0373] Therefore, after receiving the beacon frame on the primary link, the non-AP MLD combined with the NSTR AP MLD can obtain information regarding the quiet interval and the channel change time and interval 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. 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 choose whether to perform a channel change together with an AP to maintain the association when the AP performs a channel change. However, a non-AP STA MLD associated with an NSTR AP MLD may necessarily need to perform a channel change on a non-primary link when the NSTR AP MLD performs a channel change on a non-primary link.

[0375] If a non-AP STA MLD that has performed an ML setup (i.e., an ML setup using primary and non-primary links) with an NSTR AP MLD decides not to perform a channel change on the non-primary link, then the non-AP STA MLD may need to terminate (release or change) the ML setup with the NSTR AP MLD and change to a setup state using only the primary link (by setting up or re-setting up after release).

[0376] FIG. 28 shows an example of a process in which an NSTR Soft AP MLD sets (defines) a non-primary quiet interval 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 the non-primary link, respectively, and is associated with STA1 and STA2 of the Non-AP STA MLD.

[0378] NSTR AP MLD can transmit a beacon frame sent via AP1 of the primary link, including the Per-STA profile corresponding to AP2, in order to set (define) a quiet interval (Quiet interval#1 in FIG. 18) for a non-primary link. The Per-STA profile corresponding to the said AP2 includes a Quiet element, and the Quiet Count and Quiet offset fields indicate information related to the time when the quiet interval (Quiet interval#1 in FIG. 18) starts. When the said Quiet element is included in the first beacon frame of the primary link shown in FIG. 18 (Beacon#1 in FIG. 28), the Quiet Count field is set to 2 and the Quiet offset field is set to a value indicating "x" TU (Time Unit, 1024 us). 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 has received the first and / or second beacon frame in the primary link can, by checking the Quiet element included in the Per-STA profile (corresponding to AP2) of the beacon frame, recognize that a quiet interval is set (announced from the AP MLD) for the non-primary link and that the said quiet interval (Quiet interval#1 in FIG. 28) starts from the time when "x" TU has elapsed from the TBTT corresponding to the third beacon frame.

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

[0381] The non-AP STA MLD that has received the sixth and / or seventh beacon frames on the primary link checks the Quiet element included in the Per-STA profile (corresponding to AP2) of the beacon frame, thereby setting (announced from the AP MLD) the quiet interval (Quiet interval#2) for the non-primary link, and can recognize that the quiet interval (Quiet interval#2) starts from the TBTT corresponding to the eighth beacon frame.

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

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

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

[0385] NSTR AP MLD can send a beacon frame transmitted via AP1 of the primary link to a new channel, including the Per-STA profile corresponding to AP2 (non-primary link), in order to change the non-primary link to a new channel. The Per-STA profile corresponding to the said AP2 includes an (Extended) Channel Switch Announcement element and a Max Channel Switch Time element, and indicates information related to the time point when the channel change starts and the time interval 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 of the primary link (Beacon#1 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 has received the first and / or second beacon frames on the primary link checks the (Extended) Channel Switch Announcement element included in the Per-STA profile (corresponding to AP2) of the beacon frame, and thus can recognize that the channel change of the non-primary link (to the new channel) starts after receiving the second beacon frame, and the TIM frame of AP2 on the new channel will be received within "x" TUs from the time when the second beacon frame is received. At this time, the said new channel may be the channel corresponding to the value indicated by the New Channel Number field included in the (Extended) Channel Switch Announcement element. At this time, the said "x" TUs may be the time value indicated by 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 become blind, and conversely, when the AP of the non-primary link transmits, the AP of the primary link may become blind. In this case, the AP of the NSTR AP MLD that has passed 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 more stringent (lower: for example, -72dBm to -62dBm) CCA ED (energy detection) threshold than when MediumSyncDelay is 0. That is, a STA with a non-zero MediumSyncDelay value is subject to more constraints in acquiring a TXOP than a STA with a MediumSyncDelay of 0.

[0390] Therefore, even in the case of NSTR AP MLD, when the AP goes through the BLIND state, MediumSyncDelay must be applied, and in a situation where the AP's channel access is restricted, it may be difficult to provide normal services to the STAs of the BSS. NSTR AP MLD can manage transmissions on non-primary links (links other than the primary link) in a way that the primary link does not enter the BLIND state by determining one of the links of the NSTR link pair for which it operates the AP as the primary link. As an example, NSTR AP MLD can manage to prevent the primary link from entering the BLIND state by performing transmissions on non-primary links only when transmissions are in progress on the primary link. For such a purpose, even if NSTR AP MLD receives a frame requesting a response (Response) frame via an AP on a non-primary link, it does not have to respond with the requested response (Response) frame. That is, NSTR AP MLD can perform an operation of not responding with a response frame even when it receives a frame requesting a response frame via an AP on a non-primary link. At this time, the reason why NSTR AP MLD does not respond with a response frame via an AP on a non-primary link may be to prevent the AP on the primary link from entering the BLIND state.

[0391] As described above, NSTR AP MLD can manage the operations (transmissions) of APs operating on the primary link and / or non-primary links in order to set up the primary link and prevent the AP on the primary link from entering the BLIND state. Similarly, the non-AP STA MLD associated with NSTR AP MLD may need to understand and operate according to the primary link management method of NSTR AP MLD. As an example, when the non-AP STA MLD recognizes that no response frame is received from NSTR AP MLD on a non-primary link, it may not be necessary to send a frame requesting a response to the response frame on the non-primary link. Also, after the non-AP STA MLD sends a frame requesting a response to the response frame on a non-primary link and fails to receive a response to the response frame from NSTR AP MLD, it may not be necessary to retransmit the frame requesting a response to the response frame. As an example, when the non-AP STA MLD sends an RTS frame to NSTR AP MLD on a non-primary link and fails to receive a CTS frame response, it may not be necessary to retransmit the RTS frame. At this time, the Non-AP MLD does not have to attempt to transmit on the non-primary link to NSTR AP MLD until it receives a Trigger frame on the non-primary link.

[0392] Also, even if the non-AP MLD completes the channel access procedure for the non-primary link to perform UL transmission, it can postpone the transmission on the non-primary link until it completes the channel access procedure on the primary link. At this time, the method for the non-AP MLD to postpone the transmission on the non-primary link may be to suspend the backoff procedure performed by the STA on the non-primary link (more precisely, the EDCAF of the STA) until the backoff procedure performed by the STA on the primary link is completed. At this time, the method for the non-AP MLD to suspend the backoff procedure performed by the STA on the non-primary link may be to maintain the backoff counter in a state where it is 0.

[0393] By the method as described above, a non-AP STA MLD that has completed the channel access procedure for both the primary link and the non-primary link can perform simultaneous transmission (simultaneous UL PPDU transmission) on the primary link and the non-primary link. At this time, the "simultaneous transmission" means that the start times of each transmission are within a preset time interval. However, if only the channel access procedure for the primary link is completed and the channel access procedure for the non-primary link is not yet completed, the non-AP MLD can start PPDU transmission only on the primary link, or start simultaneous transmission when the channel access procedure for the non-primary link is completed. That is, when the non-AP MLD performs transmission to the NSTR AP MLD, it can perform transmission using only the primary link, or perform simultaneous transmission using the primary link and the non-primary link. However, it is not necessary to allow the non-AP MLD to perform PPDU transmission to the NSTR AP MLD using only the non-primary link.

[0394] Also, when the non-AP MLD performs UL transmission to the NSTR AP MLD using both the primary link and the non-primary link, it may be necessary to make the end points of the transmissions performed on both links coincide. At this time, making the end points of the transmissions coincide can mean that the transmissions performed on both links end together within a preset time interval.

[0395] Also, when the non-AP MLD performs UL transmission using both the primary link and the non-primary link to the NSTR AP MLD, it may be necessary to set the same requirement for whether the PPDUs transmitted on both links request a response frame. Further, the two UL PPDUs simultaneously transmitted by the non-AP MLD on the primary link and the non-primary link may both need to request a response from the response frame, or neither of them may be required to request a response from the response frame. This may be a restriction applied because when the response frame is only responded 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 AP operating on the other link of the NSTR AP MLD may enter the BLIND state. However, when only one of the two PPDUs (received on the primary link and the non-primary link respectively) that have completed reception simultaneously is a PPDU that requests a response frame response, the NSTR AP MLD does not need to perform a response frame response for all of the two PPDUs.

[0396] Also, when the non-AP MLD performs transmission to the NSTR AP MLD using both the primary link and the non-primary link, it may be necessary to set the TXOP of the non-primary link to end at the same time as or earlier than the TXOP of the primary link. In other words, the non-AP MLD may need to set the TXOP of the non-primary link to end at the same time as or earlier than the TXOP of the primary link. However, the TXOP of the non-primary link of the non-AP STA MLD may be allowed to end only at a point within a preset time interval later than the TXOP of the primary link.

[0397] Also, the non-AP STA MLD can recognize that the NSTR AP MLD has experienced a BLIND state with respect to the AP of a specific link and assist the operation of the AP. Further, 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 be understood that the AP of the other link that did not transmit should have experienced the BLIND state. In this case, the non-AP STA MLD can perform an operation to assist the AP in releasing (resetting to 0) the MediumSyncDelay in consideration of the fact that the AP experiencing the BLIND state is restricted from accessing the channel by a non-zero MediumSyncDelay. At this time, the operation performed by the non-AP STA MLD may be an operation using the characteristic that the MediumSyncDelay can be released when a PPDU (including a valid MPDU) capable of NAV setting is received.

[0398] As an example, after experiencing the BLIND state, the non-AP STA MLD can transmit an Assist frame (a type of PPDU) capable of NAV setting to the AP of the NSTR AP MLD that is determined to have a non-zero MediumSyncDelay. At this time, the Assist frame may mean a frame included in a valid MPDU capable of NAV setting regardless of the frame format. At this time, the condition for the non-AP STA MLD to transmit the Assist frame to the NSTR AP MLD on a specific link may be restricted to when the state of the specific link confirmed by the non-AP STA MLD is the IDLE state. At this time, another condition for the non-AP STA MLD to transmit the Assist frame to the NSTR AP MLD may be restricted to the case where the non-AP STA MLD has been explicitly or implicitly requested (instructed) by the NSTR AP MLD to transmit the Assist frame.

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

[0400] Prior to 6th generation Wi-Fi, Wi-Fi supported operation in the 2.4 GHz and 5 GHz bands. The recently incorporated 6 GHz band into the ISM band is a Wi-Fi frequency band (unlicensed band) that HE devices (AP STAs, non-AP STAs) first started using. Considering that there are no legacy Wi-Fi devices (devices prior to 6th generation Wi-Fi) operating in the 6 GHz band, the IEEE 802.11ax TG (Task Group) that has been standardizing for HE devices stipulated that HE STAs (AP STAs, non-AP STAs) operating in the 6 GHz band do not perform backward compatibility operations with previous generation Wi-Fi devices. More specifically, by restricting HE STAs operating at 6 GHz from transmitting HE operation elements including HT capabilities element, VHT capabilities element, HT operation element, VHT operation element, and / or VHT operation information field, support for devices prior to 6th generation Wi-Fi was excluded, and it was stipulated to reduce overhead by reducing the information included in beacon frames and the like.

[0401] That is, an AP and / or non-AP STA operating in a specific band (e.g., 6 GHz band) cannot transmit legacy format capabilities elements and / or operation elements (e.g., HE operation elements including HT capabilities element, VHT capabilities element, HT operation element, VHT operation element, and / or VHT operation information field, etc.).

[0402] In still other embodiments of the present invention, when an AP and / or a non-AP STA operates in a specific band and does not transmit HT capability elements, VHT capability elements, HT operation elements, and / or VHT operation elements, which are capability elements and operation elements for its own 2.4 GHz / 5 GHz, the AP and / or the non-AP STA can transmit, in addition to information about itself, information about other APs and / or non-AP STAs included in the same MLD. At this time, the information about other APs and / or non-AP STAs may include capability elements and operation elements for bands other than the specific band (e.g., 2.4 GHz / 5 GHz). That is, the AP and / or the non-AP STA can transmit capability elements and / or operation information for the bands in which each of a plurality of STAs operates, and cannot transmit capability elements and / or operation information for bands in which each of the plurality of STAs does not operate.

[0403] That is, beacon frames transmitted by HE APs operating in 6 GHz and association request frames transmitted by non-AP STAs performing setup in 6 GHz do not include the capabilities and operation information when operating as HT and VHT STAs (APs and non-AP STAs). Since there are no other HT / VHT STAs operating in the 6 GHz band, HE STAs operating in 6 GHz do not need to operate as HT / VHT STAs, and therefore, the above-described capabilities and operation information of HT / VHT STA operation may be unnecessary information. For these reasons, in the 11ax standard, HE STAs (AP STAs and non-AP STAs) operating in 6 GHz are restricted from transmitting HE operation elements including HT capability elements, VHT capability elements, HT operation elements, VHT operation elements, and VHT operation information fields, and the same restriction may be applied to EHT STAs (MLDs) that inherit the operation of HE STAs.

[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 to be described later, the APs operating at 2.4 GHz / 5 GHz / 6 GHz are respectively described as 2.4 GHz AP, 5 GHz AP, and 6 GHz AP, and the STAs that perform (attempt) ML setup at 2.4 GHz / 5 GHz / 6 GHz are respectively described as 2.4 GHz STA, 5 GHz STA, and 6 GHz STA (non-AP STA).

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

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

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

[0412] That is, a 6 GHz STA (of the MLD) can include HT / VHT capability / operation elements in the (re) association request frame and send it only when attempting an ML setup that includes 2.4 GHz and / or 5 GHz STAs of the same MLD.

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

[0414] For example, each of the APs or non-AP STAs that make up the MLD can operate in various bands (6 GHz, 2.4 GHz, or 5 GHz). At this time, the MLD (the first MLD) including the non-AP STA can send and receive frames for a multi-link setup with the MLD (the second MLD) including the AP. At this time, the STA (the first STA) operating at 6 GHz included in the first MLD can send an association request frame (or, a re-association request frame) for the multi-link setup, and the AP (the first AP) operating at 6 GHz included in the second MLD can send an association response frame (or, a re-association response frame) as a response to the association request frame (or, the re-association request frame).

[0415] The first STA can include information about itself and information about other STAs included in the same MLD (e.g., multi-link information (or, elements), etc.) in the association request message and send it.

[0416] The information about the first STA included in the association request message may be information regarding 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 for other bands that are not in 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 the VHT operation information field, etc.). That is, the first STA cannot transmit information regarding bands other than the band in which it operates.

[0417] The information about other STAs included in the association request message (e.g., multi-link information (or, element), etc.) may include information regarding the bands in which each of the other STAs operates (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 the VHT operation information field, etc.).

[0418] At this time, the information about other STAs may be included in the Per-STA profile sub-element corresponding to each STA.

[0419] Also, the multi-link information (or, multi-link element) of the association request message may include a multi-link element that includes Per-STA profile sub-elements corresponding to each of the reported STAs, and the Per-STA profile sub-element may include a complete profile sub-field indicating whether it is a request for all information regarding the corresponding station among at least one of the reported stations.

[0420] At this time, when the complete profile subfield is set to a value or a specific value (e.g., "1") indicating the request for all information, all information of the STA corresponding to the complete profile subfield may be included in the multi-link element. Or, the complete profile can indicate whether the corresponding Per-STA profile contains the complete information of the STA.

[0421] The first AP can include information about itself and information about other APs included in the same MLD (e.g., multi-link information (or, element), etc.) in the association response message.

[0422] The information about the first AP included in the association response message may be information related to 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 related to other bands that are not in 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 VHT operation information field, etc.). That is, the first AP cannot send information related to bands other than the band in which it operates.

[0423] The information about other APs included in the association request message (e.g., multi-link information (or, element), etc.) may include information related to the bands in which each of the other STAs operates (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 VHT operation information field, etc.).

[0424] Furthermore, a 6 GHz AP (of the MLD) can transmit an ML probe response frame with the same HT / VHT capabilities / operation elements as the above-mentioned association request frame or association response frame. At this time, the condition for the 6 GHz AP to transmit (respond) with HT / VHT-related information included in the ML probe response frame may be that the received probe request frame includes a multi-link element (probe request variant). At this time, the probe request frame including the multi-link element may be considered an ML probe request (frame).

[0425] A more specific condition for the 6 GHz AP to transmit (respond) an ML probe response frame including HT / VHT capability elements and / or HT / VHT operation elements is that the received ML probe request frame includes a multi-link element and requests complete information or HE / VHT capabilities / operation element information for 2.4 GHz and / or 5 GHz APs.

[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 at a specific bandwidth.

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

[0428] That is, although the operation regulations in the 6 GHz band restrict 6 GHz APs from transmitting HT / VHT-related elements, a 6 GHz AP that is an STA of an AP MLD can transmit an (ML) probe response frame containing HT / VHT-related elements in the 6 GHz band for the purpose of instructing complete information for 2.4 GHz APs and 5 GHz APs.

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

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

[0431] A 6 GHz AP may include HT / VHT-related elements in a transmitted (re)association response frame only when a non-AP STA has transmitted a (re)association request frame in the 6 GHz band and the AP has accepted the ML setup request of the non-AP STA and intends to perform a setup also at 2.4 GHz and / or 5 GHz.

[0432] As another method, there may be a method of restricting so that 6 GHz STAs (AP STAs, non-AP STAs) cannot include HT / VHT capabilities / operation elements in frames transmitted in the 6 GHz band.

[0433] In this case, when the 6GHz AP sends an ML probe response frame containing information (Per-STA Profile) of the 2.4GHz and / or 5GHz AP and an ML association response frame that acknowledges the setup of the 2.4GHz and / or 5GHz AP, it is possible not to include the HT / VHT capabilities / operation elements. Therefore, a non-AP MLD attempting to perform an ML setup including 2.4GHz and 5GHz via the 6GHz AP may need to send an ML probe request frame to the 2.4GHz AP or 5GHz AP in order to obtain additional information (contained in the HT / VHT-related elements) for the 2.4GHz and / or 5GHz AP.

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

[0435] Also, after completing the ML setup at 6GHz, the non-AP MLD may need to send complete information (or HT / VHT-related elements) of the STAs (2.4GHz STA and 5GHz STA) operating on the 2.4GHz link and 5GHz link where the setup was performed to the AP MLD. At this time, the non-AP MLD can transmit the HT / VHT capabilities / operation elements of the 2.4 / 5GHz STA in the PPDU transmitted for the first time after association in order to transmit the elements of the 2.4 / 5GHz STA where the setup was performed.

[0436] Figure 31 shows an example of a method for performing a multi-link setup by exchanging HT (High Throughput) / VHT (Very High Throughput) related element information on other links that are not of a specific bandwidth according to an embodiment of the present invention.

[0437] Referring to Figure 31, the AP MLD can operate AP1 to AP3 at 2.4 GHz / 5 GHz / 6 GHz respectively. The non-AP MLD that has received the beacon frame of the 6 GHz AP, AP3, may attempt to perform an ML setup by exchanging (re) association Req / Res frames with the AP MLD using the 6 GHz band.

[0438] In this case, the Non-AP MLD can intend to attempt an ML setup including the 2.4 GHz AP and the 5 GHz AP. To this end, it can transmit an ML probe request frame at 5 GHz to the 5 GHz AP before transmitting an association request frame at 6 GHz. At this time, the ML probe request frame transmitted by the non-AP MLD in the 5 GHz band can be an ML probe request frame that requests complete information (or HT / VHT related elements) for the 2.4 GHz AP and the 5 GHz AP among the APs for which an ML setup is to be performed.

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

[0440] In this way, a non-AP MLD that sets up with an AP MLD at 2.4GHz and / or 5GHz using a combined request / response frame without HT / VHT elements for 2.4 / 5GHz can use the first PPDU sent after receiving the combined response frame to send HT / VHT capabilities / operation elements for the 2.4 / 5GHz STA with which the setup was performed to the AP MLD.

[0441] <Configuration and Inheritance Rules of Management Frames>

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

[0443] As considered in the foregoing embodiments of the present invention, the EHT STA (reporting STA) can include complete information of other STAs (reported STAs) within the same MLD in the management frame. Considering that the MLD can operate multiple STAs, the management frame containing complete information of each STA may induce a lot of overhead.

[0444] Therefore, in the management frame including complete information for other STAs within the MLD in the Per-STA profile sub-element, the element of the reporting STA including the same information as that of the reporting STA element may be omitted. That is, in the management frame including complete information for a specific STA (reported STA), when some elements are not indicated in the Per-STA profile sub-element corresponding to the specific STA, the unindicated some elements may be analyzed as those in which the information of the same elements (the same elements as the some elements) corresponding to the STA (reporting AP) that transmitted the management frame is directly inherited. At this time, the "management frame including complete information for the specific STA (reported STA)" can mean a management frame including the same level (the same amount) of information as that of the STA (reporting STA) that transmitted the management frame. At this time, analyzing the Per-STA profile sub-element using the inheritance rule may be performed only when the Per-STA profile is a complete profile. At this time, "the Per-STA profile is a complete profile" can mean that the Complete Profile sub-field of the Per-STA profile sub-element is indicated as 1.

[0445] In this way, the STA of the MLD can configure the management frame using inheritance rules for the purpose of reducing the size of the management frame while including complete information about other STAs in the MLD in the management frame. Also, the MLD that has received the management frame from the STA of the MLD can obtain (analyze, recognize) the information of the reported STA that has been omitted using the inheritance rules.

[0446] At this time, whether or not the complete information of each reported STA is included in the management frame may be indicated by whether or not the Complete Profile subfield (in the STA Control field) corresponding to each reported STA is indicated as 1 in the Per-STA profile sub-element corresponding to each reported STA. That is, the reported STA corresponding to the Per-STA profile in which the Complete Profile subfield is indicated as 1 may be the STA for which complete information is indicated in the management frame.

[0447] <Inheritance rules applied to elements not indicated as elements of the reporting STA in the management frame>

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

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

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

[0451] Furthermore, when the management frame is instructed to include complete information for a specific reported STA, but the specific element corresponding to the specific reported STA is not instructed, the specific element may be considered to inherit elements other than those of the reporting STA. At this time, the condition for considering that the specific element inherits elements other than those of the reporting STA may be that the specific element is not instructed (not included) for the reporting STA (in the management frame). At this time, the method of instructing / analyzing that the information of the reported STA inherits elements other than those 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 instructed is not instructed in the management frame, it may be considered that the value of the same element (the element ID and the Extended element ID are the same) as the specific element instructed in the management frame is identically applied (instructed) to the specific element of the reported STA. At this time, 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) inherited as the specific element for the reported STA may not be an element for the reporting STA.

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

[0455] Alternatively, the same element inherited as a specific element for a reported STA (having the same element ID and Extended element ID as the specific element) may be an additional element indicated for inheritance. At this time, the additional element indicated for inheritance may mean an element corresponding directly to the reporting STA or an element not corresponding directly to the reporting STA.

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

[0457] As an example, when no specific element for STA1 is indicated by the management frame and there is the same element indicated for STA2, the value indicated by the same element may be considered (i.e., inherited) to be the same as that indicated by the specific element of STA1. At this time, the STA2 does not have to be the reporting STA.

[0458] Also, the same element inherited as a specific element of STA1 (having the same element ID and Extended element ID as the specific element) may be an additional element indicated 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 a complete profile is indicated is not indicated in a management frame, the value of an element (the element ID and the Extended element ID are the same) that is the same as the specific element indicated in the management frame may be considered to be identically applied (indicated) to the specific element of the reported STA. At this time, the element inherited as the specific element of the reported STA may be determined by inheritance rules.

[0460] As an example of a rule for selecting an inherited element, another 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 determined as the same element indicated earliest in the management frame.

[0461] Furthermore, in a management frame in which a complete profile for the reported STA should be included, when a specific element for the reported STA is not indicated, among other elements having the same element ID and Extended element ID as the specific element, the value of the element indicated earliest (in the element order) may be considered to be inherited by the specific element. That is, when the same element as the specific element is indicated for the reporting STA (among the same elements, it is indicated in the earliest order), 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) inherited as the specific element for the reported STA may be determined as the same element indicated last (in the order of elements) in the management frame.

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

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

[0465] Referring to FIG. 32, the management frame includes four elements for the reporting AP (the elements are element IDA to D in FIG. 22), and includes an ML IE for indicating the 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 sub-elements. At this time, in terms of order, the Per-STA profile indicated first is the Per-STA profile included for indicating the complete information (profile) for reported STA1, and the Per-STA profile indicated later in terms of order is the Per-STA profile included for indicating the complete information (profile) for reported STA2. That is, in terms of order, the Per-STA profile indicated first is the Per-STA profile for reported STA1, and the Per-STA profile indicated later is the Per-STA profile for reported STA2.

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

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

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

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

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

[0472] <Implied non-Inheritance rule>

[0473] As described above, the complete information (profile) for the reported STA may be indicated in the management frame sent 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 elements included in the Per-STA profile sub-elements of the Reported STA have the function of explicitly indicating elements to which inheritance is not applied among the elements not instructed for the Reported STA. In other words, when a specific element is indicated by a Non-Inheritance element included in the Per-STA profile sub-element of a specific STA, it may be explicitly indicated that a specific element not instructed for the specific STA does not inherit the values of other elements. In this case, the MLD that has received the management frame can consider (analyze) that the specific element for the specific STA does not exist.

[0475] That is, the Non-Inheritance element may be used for the purpose of resolving the ambiguity as to whether a specific element of the reported STA not instructed in the management frame has been omitted by the inheritance rule or does not exist in the first place.

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

[0477] For example, a non-AP STA MLD that has received a (re)association response frame including a 6GHz AP as the Reported STA may have previously recognized that the HT / VHT capability / operation elements for the 6GHz AP are not instructable 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 sub-element) corresponding to the 6GHz AP, the STA MLD does not have to analyze the HT / VHT-related elements for the 6GHz AP according to the inheritance rule.

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

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

[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 composed of a plurality of STAs can transmit information regarding STAs operating in another band via an STA operating in a specific band.

[0482] Specifically, a first multi-link device (MLD) including a first plurality of stations each operating on 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 the first station among the first plurality of stations included in the first multi-link device (S3310).

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

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

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

[0486] The response frame may include multi-link information for the combination of at least one first station other than the first station among the first plurality of stations and at least one second station other than the second station among the second plurality of stations.

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

[0488] Each of the capability elements and / or operation elements of the at least one second 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.

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

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

[0491] When the Complete Profile subfield indicates the request for all the information, the multi-link information in the response frame may include the capability element and / or operation element of the station corresponding to the Complete Profile subfield indicating the request for all the information among the at least one second station.

[0492] Based on the multi-link information, a multi-link setup procedure for setting up links between the second MLD and the at least one first station and the at least one second station can be performed.

[0493] The request frame (e.g., association request frame) includes a Multi-Link element that includes at least one Per-STA profile subelement corresponding to each of the at least one first station, and each of the at least one Per-STA profile subelements of the Multi-Link element may include a legacy format capability element and / or operation element regarding the corresponding specific station among the at least one first station.

[0494] The specific station is a station operating in at least one of the other bands, and the first station can include and transmit, in the request frame, 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 for the 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, and it should be...

Claims

1. A first multi-link device (MLD) including a first plurality of stations each operating on a plurality of links, The processor transmitting a request frame to a second station among a second plurality of stations included in a second MLD, each of which operates on at least one link, through a first station among the first plurality of stations included in the first multilink device; The first station and the second station operate in a particular band; receiving a response frame from a second station via the first station as a response to the request frame; The second station transmits, in the response frame, capability elements and operation elements of the second station for the specific band, excluding capability elements and / or operation elements of the second station in a specific legacy format for other bands; The response frame includes 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.

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

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

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

5. The processor, The request frame includes a multi-link element including Per-STA profile subelements corresponding to each of the second at least one stations; 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 station among the second at least one station is received.

6. The MLD of claim 5, wherein when the Complete Profile subfield indicates a request for all the information, the multilink information of the response frame includes a capability element and / or an operation element of a station corresponding to the Complete Profile subfield indicating the request for all the information, among the second at least one station.

7. The MLD of claim 1 , wherein 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.

8. 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; The MLD of claim 1 , wherein each of the at least one Per-STA profile sub-elements of the multilink element includes a legacy format capability element and / or an operation element for a corresponding particular station of the first at least one station.

9. the specific station is a station that operates in at least one of the other bands, The MLD of claim 8, wherein the first station transmits the request frame including capability elements and operation elements of the first station for the specific band, excluding capability elements and / or operation elements of the first station in a specific legacy format for the other band.

10. The MLD of claim 1, wherein the response frame is one of an association request frame, an association response frame, and a Multi-link (ML) probe response frame.

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

12. The method of claim 11 , wherein the multilink information includes a capability element and / or an operational element of each of the second at least one station for a particular one of the other bands.

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

14. The specific band is 6 GHz, The method of claim 11 , wherein the other bands are 2.4 GHz and / or 5 GHz.

15. The request frame includes a multi-link element including Per-STA profile subelements corresponding to each of the second at least one stations; The method of claim 11, wherein the Per-STA profile subelement includes a Complete Profile subfield indicating whether a request for all information for a corresponding station of the second at least one station is received.

16. The method of claim 15, wherein the multilink information of the response frame includes a capability element and / or an operation element of a station corresponding to the Per-STA profile sub-element including the Complete Profile subfield indicating a request for all the information among the second at least one station.

17. The method of claim 11 , further comprising: establishing a multilink connection between the first at least one station and the second at least one station based on the multilink information.

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

19. 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; The method of claim 11 , wherein each of the at least one Per-STA profile sub-elements of the multilink element includes a legacy format capability element and / or an operation element for a corresponding particular one of the first at least one stations.

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

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