Wireless communication method using multi-link and wireless communication terminal using the same

Abstract

The present invention discloses a method and apparatus for transmitting / receiving data by a Multi-Link Device (MLD) including a plurality of stations each operating on a plurality of links in a wireless communication system. Specifically, the MLD of the present invention receives a frame transmitted from a first Station (STA) or a first Access Point (AP) operating on the first link through a second STA operating on the second link, and resets a medium sync delay timer of the second STA based on the received frame if the medium sync delay timer for applying a medium sync delay is not '0'.

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, with the spread of mobile devices, wireless LAN 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 specific service-providing areas based on wireless communication technology.

[0003] Since IEEE (Institute of 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 using OFDM 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 implement a maximum communication speed of 54 Mbps and satisfies backward compatibility, attracting considerable attention, but it 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. In addition, this standard uses a coding method that transmits multiple copies of the data to increase the reliability of the data.

[0005] As the popularity of wireless LANs has been activated and the applications using them have diversified, there is 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 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 the 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 the wireless interface 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, 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 that it is difficult for obstacles to pass through and it can be used 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 for realizing this have been developed.

[0007] In order to support new multimedia applications such as high-definition 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 up to 30 Gbps through a wider bandwidth, increased spatial streams, and multi-AP cooperation in the 2.4 / 5 / 6 GHz bands. In IEEE 802.11be, technologies such as a 320 MHz bandwidth, multi-link operation, multi-AP (Multi-Access Point) operation, and hybrid automatic repeat request (HARQ) have been proposed.

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 multi-link and a wireless communication terminal using the same.

[0009] Another embodiment of the present invention aims to provide a sink recovery method for a station using multi-link.

[0010] 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

[0011] A multi-link device (MLD) including a plurality of stations each operating with a plurality of links including a first link and a second link according to the present invention includes a processor, and the processor receives a frame transmitted from one STA among one or more stations (STA) via a second STA operating on the second link, Media if the synchronization delay timer is not "0", based on the received frame, the Media synchronization delay (Medium Sync Delay) for the application of Media synchronization delay timer (Medium Sync Delay timer) is reset, and the Media synchronization delay indicates a section for restricting data transmission / reception on the second link after transmitting / receiving the data of the first STA on the first link, and the Media synchronization delay timer is reset when the frame is a frame for a valid MPDU other than an RTS (request to send) frame.

[0012] Also, in the present invention, the first link and the second link are an NSTR (Non-Simultaneous Transmission and Reception) link pair in which transmission / reception on each link causes interference on other links and does not support simultaneous transmission / reception within the same MLD.

[0013] Also, in the present invention, the Media synchronization delay timer starts when the transmission on the first link ends.

[0014] Also, in the present invention, when the MLD operates with a single radio (Single Radio), the Media synchronization delay timer starts when a specific delay time has passed after the transmission on the first link ends.

[0015] Also, in the present invention, the specific delay time is a delay time for link switching.

[0016] Also, in the present invention, the Media synchronization delay timer is reset when the frame is a frame transmitted from an AP associated with the second STA or an AP included in the same multi-BSSID set as the associated AP.

Advantages of the Invention

[0017] One embodiment of the present invention provides a wireless communication method that efficiently uses multi-link and a wireless communication terminal using the same.

[0018] 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

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BEST MODE FOR CARRYING OUT THE INVENTION

[0020] The terms used in this specification are, as much as possible, general terms currently widely used in consideration of the functions in the present invention. However, this may vary depending on the intentions, conventions, or the emergence of new technologies of those skilled in the relevant technical field. In addition, in certain cases, there are terms arbitrarily selected by the applicant. In such cases, the meaning thereof will be described in the description 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.

[0021] Throughout the specification, if a certain configuration is "connected" to another configuration, this includes not only the case where it is "directly connected", but also the case where it is "electrically connected" with other components interposed therebetween. In addition, if a certain component "includes" a specific component, this means that it can further include other components without excluding other components unless otherwise stated to the contrary. In addition, the limiting terms "above" or "below" based on a specific threshold value can be appropriately replaced by "exceeding" or "less than" respectively according to the embodiments. Hereinafter, in the present invention, a field and a subfield may be used in the same meaning.

[0022] FIG. 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention.

[0023] A 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). Figure 1 shows an infrastructure BSS among them.

[0024] As shown in Figure 1, 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 multiple access points AP-1 and AP-2.

[0025] A station (STA) is any device that includes a Medium Access Control (MAC) compliant with the IEEE 802.11 standard and a Physical Layer interface for a wireless medium, and in a broad sense 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 a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and in some embodiments further includes a user interface unit, a display unit, etc. 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 user equipment (UE).

[0026] 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. However, if a direct link is set up, direct communication is also possible between non-AP stations. 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. The base wireless communication terminal is used as a term that includes, in a broad sense, the 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.

[0027] 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).

[0028] 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 those in the embodiment of FIG. 1 are not described repeatedly.

[0029] Since the 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 is not allowed to connect to the distribution system and forms a self - contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0030] FIG. 3 is a block diagram showing the configuration of a station 100 according to an embodiment of the present invention. As shown, the station 100 according to the embodiment of the present invention includes a processor 110, a communication unit 120, a user interface unit 140, a display unit 150, and a memory 160.

[0031] 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 of different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 can be provided with 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 the embodiment of the present invention, the communication unit 120 can represent an RF (Radio Frequency) communication module that processes RF signals.

[0032] 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 output based on the instructions of the processor 110 using various output means.

[0033] 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 instructions of the processor 110. Also, the memory 160 stores control programs used in the station 100 and various data thereby. Such control programs include connection programs necessary for the station 100 to connect to an AP or an external station.

[0034] The processor 110 of the present invention executes various instructions or programs and processes data within 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 a part of the configuration 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 a radio signal 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.

[0035] 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.

[0036] FIG. 4 is a block diagram showing the configuration of AP200 according to an embodiment of the present invention. As shown, AP200 according to an embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, redundant explanations are omitted for parts of the configuration of AP200 that are the same as or corresponding to the configuration of station 100 in FIG. 3.

[0037] Referring to FIG. 4, 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, AP 200 according to an embodiment of the present invention can include two or more communication modules using different frequency bands, for example, any of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, 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 together simultaneously according to the performance and requirements of AP 200. In an embodiment of the present invention, the communication unit 220 can represent an RF (Radio Frequency) communication module that processes RF (Radio Frequency) signals.

[0038] Next, the memory 260 stores the control program used in the AP200 and various data thereby. Such control programs include connection programs for managing the connection of stations. Further, the processor 210 controls each unit of the AP200 and controls the transmission and reception of data between units. According to an embodiment of the present invention, the processor 210 executes a program for connection to a station stored in the memory 260 and transmits a communication setting message for one or more stations. At this time, the communication setting message includes information regarding the connection priority conditions of each station. Further, the processor 210 performs connection setting in response to a connection request from a station. According to one embodiment, the processor 210 is a modem or a modulation / demodulation unit that modulates and demodulates radio signals transmitted and received from the communication unit 220. The processor 210 controls various operations of wireless signal transmission and reception of the AP200 according to an embodiment of the present invention. Detailed embodiments thereof will be described later.

[0039] FIG. 5 is a diagram schematically showing the process by which a STA sets a link with an AP.

[0040] Referring to FIG. 5, the link between the STA100 and the AP200 is set through three major steps: scanning, authentication, and association. First, the scanning step is a step in which the STA100 acquires connection information of the BSS operated by the AP200. As a method for performing scanning, there are a passive scanning method of acquiring 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 acquires connection information.

[0041] The STA100 that has successfully received the wireless connection information in the scanning step transmits an authentication request to S107a, receives an authentication response from the AP200 to S107b, and performs an authentication step. After the authentication step is performed, the STA100 transmits an association request to S109a, receives an association response from the AP200 to S109b, and performs an association step. In this specification, association basically means a wireless connection, but the present invention is not limited to this, and the association in a broad sense includes all wireless connections and wired connections.

[0042] 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.

[0043] FIG. 6 is a diagram showing the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication.

[0044] A terminal performing wireless LAN communication checks whether a channel is in a busy state by performing carrier sensing before transmitting data. If a wireless signal with a certain intensity or higher is detected, the corresponding channel is determined to be in a busy state, and the terminal delays access to the corresponding channel. Such a process is called Clear Channel Assessment (CCA), and the level for determining the presence or absence of detection 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 receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the corresponding 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.

[0045] If 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) depending on the situation of each terminal, for example, a time such as AIFS (Arbitration IFS) or PIFS (PCF IFS). According to an embodiment, the AIFS is 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 corresponding terminal during the interval of the idle state of the channel, and the terminal that has exhausted all the slot times attempts access to the corresponding channel. Thus, the section in which each terminal performs the backoff procedure is called a contention window section.

[0046] If a specific terminal successfully accesses the channel, the corresponding terminal transmits data via the channel. However, if the terminals attempting access collide with other terminals, the colliding 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.

[0047] Hereinafter, in the present invention, a terminal can be referred to as a non-AP STA, AP STA, AP, STA, receiving device, or transmitting device, and the present invention is not limited thereto. Also, in the present invention, an AP STA can be referred to as an AP.

[0048] <Examples of various PPDU formats>

[0049] FIG. 7 shows an example of various standard-generation PPDU (PLCP Protocol Data Unit) formats. More specifically, FIG. 7(a) shows an embodiment of a legacy PPDU format based on 802.11a / g, FIG. 7(b) shows an embodiment of a HE PPDU format based on 802.11ax, and FIG. 7(c) shows an embodiment of a non-legacy PPDU (i.e., EHT PPDU) format based on 802.11be. Also, FIG. 7(d) shows the detailed field configurations of L-SIG and RL-SIG commonly used in the PPDU formats.

[0050] 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.

[0051] Referring to FIG. 7(b), the preamble of the HE PPDU further includes, in addition to the legacy preamble, an RL-SIG (Repeated Legacy Short Training field), an HE-SIG-A (High Efficiency Signal A field), an HE-SIG-B (High Efficiency Signal B field), an HE-STF (High Efficiency Short Training field), and an HE-LTF (High Efficiency Long Training field). In an embodiment of the present invention, the RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and HE-LTF can be referred to as an HE preamble. The specific configuration of the HE preamble may be deformed according to the HE PPDU format. For example, HE-SIG-B may be used only in the HE MU PPDU format.

[0052] 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 modified according to the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some formats of the EHT PPDU format.

[0053] 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 transmitting L-SIG data. Since BPSK and MCS (Modulation and Coding Scheme) with a rate of 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 configuration of L-SIG.

[0054] Referring to FIG. 7(d), the L-SIG includes an L_RATE field and an L_LENGTH field. The L_RATE field is composed of 4 bits and indicates the MCS used for data transmission. Specifically, the L_RATE field indicates one of the transmission speeds of 6 / 9 / 12 / 18 / 24 / 36 / 48 / 54 Mbps by combining modulation methods such as BPSK / QPSK / 16-QAM / 64-QAM and coding 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 PPDU. In the non-legacy PPDU format, the L_RATE field is set to the minimum speed of 6 Mbps.

[0055] The unit of the L_LENGTH field is byte, and 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, the legacy terminal and the non-legacy terminal can analyze the L_LENGTH field in different ways.

[0056] First, the method for a legacy terminal or a non-legacy terminal to analyze the length of the corresponding PPDU using the L_LENGTH field is as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted during the 4 us of one symbol duration of 64 FFT. Therefore, adding the 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 duration of one symbol, and then adding the 20 us required for the transmission of L-STF, L-LTF, and L-SIG, the length of the corresponding PPDU, that is, the reception time (RXTIME) is obtained. Expressing this in a mathematical formula is as shown in Equation 1 below.

[0057]

Number

[0058] At this time, [Number] represents the smallest natural number greater than or equal to x. Since the maximum value of the L_LENGTH field is 4095, the length of the PPDU may be set up to a maximum of 5.484 ms. The non-legacy terminal that transmits the PPDU must set the L_LENGTH field as shown in Equation 2 below.

[0059] [Number]

[0060] Here, TXTIME is the total transmission time that constitutes the PPDU, as shown in Equation 3 below. At this time, TX represents the transmission time of X.

[0061] [Number]

[0062] Referring to the above equations, 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.

[0063] Referring to FIG. 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 these, 43 bits excluding the CRC / Tail 9 bits are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0064] The VI bits continue to maintain the current bit configuration later. 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 field. The PHY version field is 3 bits and is responsible for sequentially distinguishing 11be and subsequent generations of wireless LAN standards by version. 11be has a value of 000b. The UL / DL field distinguishes whether the PPDU is an uplink / downlink PPDU. The BSS color means the BSS identifier defined in 11ax and has a value of 6 bits or more. The TXOP means the transmit opportunity duration transmitted in the MAC header. 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.

[0065] The VD field may be composed of signaling information that is only useful for PPDUs in the 11be version, fields that are commonly used in any PPDU format such as PPDU format and BW, and fields that are defined differently for each PPDU format. The PPDU format is a discriminator that distinguishes 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 (BW that can be expressed in the form of 20 * power of 2 can be called the basic BW), and various remaining PPDU BWs formed by preamble puncturing. Also, after being signaled at 320 MHz, some 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 fields that appear after the BW field (for example, fields within the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so 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.

[0066] The fields located after the BW field vary depending on the form and format of the PPDU. The MU PPDU and the SU PPDU may be signaled in the same PPDU format. Before the EHT-SIG field, a field for distinguishing between the MU PPDU and the SU PPDU may be located, and additional signaling for that purpose may be performed. 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.

[0067] Alternatively, the SU PPDU may 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.

[0068] When a part of the EHT-SIG field of an 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 an 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 EHT-SIG field including the above information. 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 RUs assigned to each user.

[0069] In the case of an SU PPDU, a plurality of RUs may be assigned to an 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 punctured in the middle. 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 an 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.

[0070] 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.

[0071] 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, the availability of each of the remaining 15 20 MHz subchannels excluding the primary channel must be expressed to signal the discontinuous channel form (including the form in which only the end 20 MHz is punctured as discontinuous). Using 15 bits to signal the discontinuous channel form of single-user transmission can result in excessive signaling overhead considering the low transmission rate of the signaling part.

[0072] The present invention proposes a method for signaling the discontinuous channel form of an 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.

[0073] 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 1 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 considering 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.

[0074] FIG. 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 a 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.

[0075] FIG. 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.

[0076] 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.

[0077] 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.

[0078] 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 response 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.

[0079] 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.

[0080] (d) of FIG. 8 shows an example of the EHT ER SU PPDU format used for single-user transmission to STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission to 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.

[0081] 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 transmit the AID information of the recipient and / or transmitter of the PPDU transmitted through the user specific field of the EHT-SIG-B to the STA. Therefore, multiple terminals that have received 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.

[0082] 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 form of division 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. 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.

[0083] For example, among a plurality of divided resource units, the user field corresponding to at least one resource unit used for data transmission can include the AID of the recipient or the sender, and the user field corresponding to the remaining resource units not used for data transmission can include the already set Null STA ID.

[0084] Two or more PPDUs shown in FIG. 8 can be indicated by a value indicating the same PPDU format. That is, two or more PPDUs can be indicated as having the same PPDU format by the same value. For example, an EHT SU PPDU and an EHT MU PPDU can be indicated by the same value using the U-SIG PPDU format subfield. At this time, the EHT SU PPDU and the EHT MU PPDU may be distinguished by the number of STAs receiving the PPDU. For example, a PPDU received by only one STA may be identified as an EHT SU PPDU, and when the number of STAs is set so that two or more STAs receive it, it may be identified as an EHT MU PPDU. In other words, two or more PPDU formats shown in FIG. 8 can be indicated using the same subfield value.

[0085] Also, some of the fields shown in FIG. 8 or some of the information of the fields may be omitted, and the case where some of the fields or some of the information of the fields are omitted can be defined as the compression mode or the compressed mode.

[0086] FIG. 9 is a diagram showing a multi-link device according to an embodiment of the present invention.

[0087] Referring to FIG. 9, the concept of a device with one or more STAs affiliated may be defined. As yet another example, according to one embodiment of the present invention, a device with more than one (i.e., two or more) STAs affiliated may be defined. At this time, the device may be a logical concept. Therefore, a device with one or more or more than one such concept of STAs affiliated may be referred to as a multi-link device (MLD), a multi-band device, or a multi-link logical entity (MLLE).

[0088] Alternatively, a device of the above concept may be referred to as a multi-link entity (MLE). Also, an MLD may have one MAC SAP (medium access control service access point) up to LLC (logical link control), and an MLD may have one MAC data service.

[0089] The STAs included in the MLD are capable of operating on one or more links or channels. That is, the STAs included in the MLD are capable of operating on a plurality of different channels from each other. For example, the STAs included in the MLD can operate using channels in different frequency bands of 2.4 GHz, 5 GHz, and 6 GHz. Thereby, the MLD can obtain a gain in channel access and improve the performance of the entire network. Existing wireless LANs operated on a single link, but MLD operation can obtain more channel access opportunities using a plurality of links, or the STAs can operate efficiently on a plurality of links considering the channel situation.

[0090] Also, when the STA affiliated with the MLD is an AP, the MLD affiliated with the AP may be an AP MLD. However, when the STA affiliated with the MLD is a non-AP STA, the MLD affiliated with the non-AP may be a non-AP MLD.

[0091] Also, an AP MLD (Multi-link Device) may be a device including one or more wireless access points (APs), or may be a device connected to an upper layer via one interface. That is, the AP MLD may be connected to an LLC (Logical Link Control) layer via one interface. A plurality of APs included in the AP MLD may share some functions at the MAC layer. Each AP within the AP MLD may operate on an individual link. A STA MLD may be a device including one or more non-AP STAs, or may be a device connected to an upper layer via one interface.

[0092] That is, the STA MLD may be connected to an LLC layer via one interface. A plurality of STAs included in the STA MLD may share some functions at the MAC layer. Also, the STA MLD can be called a non-AP MLD. At this time, the AP MLD and the STA MLD can perform a multi-link operation of communicating using a plurality of individual links. That is, when the AP MLD includes a plurality of APs, each AP constitutes a separate link and can perform frame transmission and reception operations using a plurality of links with each terminal included in the STA MLD. At this time, each link can operate in a 2.4 GHz, 5 GHz, or 6 GHz band, and bandwidth expansion operations can be performed on each link. For example, when the AP MLD sets one link in the 2.4 GHz band and two links in the 5 GHz band, frame transmission can be performed with a bandwidth of 40 MHz using a bandwidth expansion method in the 2.4 GHz band, and frame transmission can be performed with a maximum bandwidth of 320 MHz using discontinuous bandwidths on each link using the 5 GHz band.

[0093] On the one hand, due to interference problems within the device, it may be that while one terminal within the MLD is performing a transmission operation, other terminals cannot perform a reception operation. When one AP or terminal within the MLD performs a transmission operation in this way, the operation of other APs or terminals within the MLD receiving during this process is called STR (Simultaneous Transmit and Receive). The AP MLD is capable of performing the STR operation for all links. Alternatively, the STR operation is not possible for some links of the AP MLD. The AP MLD may be connected to a terminal MLD capable of performing the STR operation, or may be connected to an MLD that is not capable of performing the STR operation for some or all links. In addition, terminals that do not belong to the MLD (for example, IEEE 802.11a / b / g / n / ac / ax terminals) may be further connected to the APs included in the AP MLD.

[0094] The AP MLD and the STA MLD can perform a negotiation process for multi-link utilization operations during the scanning and connection processes described in FIG. 5. For example, during the scanning process described in FIG. 5, the AP included in the AP MLD can transmit by including in the beacon frame an indicator indicating that the multi-link operation is available, the number of available links, and information on a plurality of available links. Alternatively, the terminal belonging to the STA MLD can transmit by including in the probe request frame an indicator indicating that the multi-link operation is available, and the AP belonging to the AP MLD can include in the probe response frame an indicator indicating that the multi-link operation is available. At this time, the AP can further transmit by including the number of available links, link information, etc. during the multi-link operation.

[0095] The STA MLD that has confirmed whether the AP MLD performs multi-link operation during the scanning process and the link information to be used can perform a connection process with the AP MLD. At this time, the AP MLD and the STA MLD can start a negotiation process for multi-link operation. At this time, the negotiation process for the multi-link operation may be performed during the connection process between the AP belonging to the AP MLD and the terminal belonging to the STA MLD. That is, while an arbitrary terminal (for example, STA1) belonging to the STA MLD sends a connection request frame to an arbitrary AP (for example, AP1) belonging to the AP MLD, an indicator indicating that the multi-link operation of the terminal is available and a request indicator requesting to perform the multi-link operation can be sent. The AP that has received the connection request frame from the terminal can confirm the indicator requesting the multi-link operation, and when the AP is capable of multi-link operation, can send a connection response frame allowing the multi-link operation including the link information used for the multi-link operation and the parameters used for each link to the terminal. The parameters for the multi-link operation may include one or more of the bandwidth of each link used, the bandwidth expansion direction, the Target Beacon Transmission Time (TBTT), and the presence or absence of the STR operation. After the connection process, the AP MLD and the STA MLD for which the use of the multi-link operation has been confirmed by exchanging the connection request frame and the response frame can perform a frame transmission operation on a plurality of links via the plurality of APs included in the AP MLD and the plurality of terminals included in the STA MLD.

[0096] Referring to FIG. 9, there may be an MLD including a plurality of STAs, and the plurality of STAs included in the MLD may operate on a plurality of links. In FIG. 9, an MLD including APs AP1, AP2, and AP3 can be called an AP MLD, and an MLD including non-AP STAs non-AP STA1, non-AP STA2, and non-AP STA3 can be called a non-AP MLD. The STAs included in the MLD can operate on Link 1 (Link1), Link 2 (Link2), Link 3 (Link3), or some of Links 1 to 3.

[0097] According to an embodiment of the present invention, the multi-link operation may include a multi-link setup operation. The multi-link setup operation may be an operation corresponding to an association performed in a single-link operation. In order to exchange frames over multiple links, a multi-link setup is required to precede. The multi-link setup operation may be performed using a multi-link setup element. Here, the multi-link setup element may include capability information related to the multi-link, and the capability information may include information regarding whether a STA included in the MLD can receive a frame over one link while another STA included in the MLD can transmit a frame over another link at the same time. That is, the capability information may include information regarding whether STAs (non-AP STAs and / or APs (or, AP STAs) included in the MLD can transmit / receive frames in different transmission directions simultaneously over the links included in the MLD. Further, the capability information may further include information regarding available links or operating channels. The multi-link setup may be set by negotiation between peer STAs, and the multi-link operation may be set through one link.

[0098] According to an embodiment of the present invention, a mapping relationship may exist between a TID and a link of the MLD. For example, when a TID and a link are mapped, the TID may be transmitted over the mapped link. The mapping between the TID and the link may be made based on the transmission direction. For example, the mapping may be made for each direction in both directions between MLD1 and MLD2. Also, a default setting may exist for the mapping between the TID and the link. For example, the mapping between the TID and the link may basically be that all TIDs are mapped to a certain link.

[0099] FIG. 10 is a diagram showing an example of a TID-to-link mapping method according to an embodiment of the present invention.

[0100] Referring to FIG. 10, there may be a mapping relationship between the TID and the link as described in FIG. 9. Also, in the present invention, the mapping relationship between the TID and the link can be referred to as TID-to-link mapping, TID-to-link mapping, TID mapping, link mapping, etc. The TID may be a traffic identifier. Also, the TID may be an ID (identifier) for classifying traffic, data, etc. to support QoS (quality of service).

[0101] Also, the TID may be an ID used or assigned at a layer higher than the MAC layer. The TID can indicate TC (traffic categories) and TS (traffic streams). Also, the TID can have 16 values, for example, it can be indicated by values from 0 to 15. Also, individual TID values can be used according to an access policy or a channel connection or medium access method. For example, when using EDCA (HCF (hybrid coordination function)-based channel connection, extended distributed channel connection), the possible TID values may be 0 to 7. Also, when using EDCA, the TID value may indicate UP (user priority), and the UP may be related to TC or TS. Also, the UP may be a value assigned to a layer higher than the MAC. Also, when using HCCA (HCF controlled channel access) or SPCA, the possible TID values may be 8 to 15. Also, when using HCCA or SPCA, the TID may indicate TSID. Also, when using HEMM or SEMM, the possible TID values may be 8 to 15. Also, when using HEMM or SEMM, the TID may indicate TSID.

[0102] In addition, there may be a mapping relationship between the UP and the access category (AC). The AC may be a label for providing QoS in EDCA or a label indicating a set of EDCA parameters. The EDCA parameters or the set of EDCA parameters may be those used for channel bonding. The AC may be used in a QoS STA.

[0103] The value of the AC may be set to one of AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may respectively indicate background, best effort, video, and voice. Also, it is possible to subdivide AC_BK, AC_BE, AC_VI, and AC_VO. For example, AC_VI may be subdivided into AC_VI primary and AC_VI alternate. Also, AC_VO may be subdivided into AC_VO primary and AC_VO alternate. Also, the UP value or the TID value may be mapped to the AC value. For example, the UP value or the TID values 1, 2, 0, 3, 4, 5, 6, 7 may be respectively mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, AC_VO. Or, the UP value or the TID values 1, 2, 0, 3, 4, 5, 6, 7 may be respectively mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, AC_VO alternate. Also, the UP value or the TID values 1, 2, 0, 3, 4, 5, 6, 7 may be in order of higher 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, AC_BK, AC_BE, AC_VI, and AC_VO may respectively correspond to ACI (AC index) 0, 1, 2, 3.

[0104] Therefore, it is possible that a relationship exists between the TID and the AC. Therefore, the TID-to-link mapping of the present invention may be a mapping relationship between the AC and the link. Also, in the present invention, mapping of the TID may mean that the AC is mapped, or vice versa.

[0105] According to an embodiment of the present invention, there may be TIDs mapped to each link of the multi-link. For example, there may be a mapping for which link among a plurality of links allows transmission and reception of a specific TID or a specific AC. Also, such a mapping may be defined separately for each direction of both directions of the link. Also, as described above, there may be a basic (default) setting for the mapping between the TID and the link. For example, basically, all TIDs may be mapped to a certain link. Also, according to an embodiment, at a specific point in time, a certain TID or a certain AC may be mapped to at least one link. Also, a management frame or a control frame may be transmitted on all links.

[0106] In the present invention, a data frame corresponding to a TID or an AC mapped to any direction of the link may be transmitted. Also, a data frame corresponding to a TID or an AC not mapped to any direction of the link may not be transmitted.

[0107] According to an embodiment, the TID-to-link mapping may also be applied to the acknowledgment. For example, a block ack agreement may be based on the TID-to-link mapping. Or, the TID-to-link mapping may be based on the block ack agreement. For example, it is possible that there is a block ack agreement for the TID mapped by the TID-to-link.

[0108] It is possible to provide QoS services by performing TID-to-link mapping. For example, by mapping a high-priority AC or TID to a link with a good channel state or few STAs, it is possible to quickly transmit data of the AC or TID. Or, by performing TID-to-link mapping, it is possible to help the STA of a specific link save power (or enter the doze state).

[0109] Referring to FIG. 10, an AP MLD including AP1 and AP2 may exist. Also, a Non-AP MLD including STA1 and STA2 may exist. Also, there may be two links, Link1 and Link2, in the AP MLD. AP1 and STA1 may be associated by Link1, and AP2 and STA2 may be associated by Link2.

[0110] Therefore, Link1 may include a link for transmitting from AP1 to STA1 and / or a link for transmitting from STA1 to AP1, and Link2 may include a link for transmitting from AP2 to STA2 and / or a link for transmitting from STA2 to AP2. At this time, each link may have a TID and / or an AC mapped thereto.

[0111] For example, all TIDs and all ACs may be mapped to the link for transmitting from AP1 to STA1 on Link1 and the link for transmitting from STA1 to AP1 on Link1. Also, only AC_VO or the TID corresponding to AC_VO may be mapped to the link for transmitting from STA2 to AP2 on Link2. Also, only the data of the mapped TID and / or AC can be transmitted on the link. Also, the data of the TID or AC not mapped to the link cannot be transmitted on the link.

[0112] FIG. 11 is a diagram showing an example of a multi-link NAV setting operation according to an embodiment of the present invention.

[0113] The operation for an MLD to transmit or receive simultaneously (STR; simultaneous transmit and receive; simultaneous transmission and reception) may be restricted, which may be related to the frequency interval between a plurality of links operating in a multi-link.

[0114] Therefore, according to an embodiment of the present invention, when the interval between links is m MHz, it is restricted to transmit or receive simultaneously, and when the interval between links is n MHz for n greater than m, it may not be restricted to transmit or receive simultaneously. This embodiment may be for solving the problem that it is restricted to transmit or receive simultaneously, and repeated descriptions may be omitted. Also, this embodiment can be applied to an MLD for which STR is not possible.

[0115] According to an embodiment of the present invention, duration information may be shared between links operating as a multi-link. As an embodiment, the duration information may be TXOP duration information transmitted in a signaling field of a preamble. The signaling field may be the U-SIG field described above. Or, the signaling field may be the HE-SIG-A field described above. As yet another embodiment, the duration information may be the duration information indicated by a Duration / ID field included in a MAC header. As yet another embodiment, the duration information may be the duration information indicated by a Length field (L Length field) included in an L-SIG field. According to an embodiment, the duration information indicated by a U-SIG field or HE-SIG-A or Duration / ID field may be a value indicating a TXOP duration. According to an embodiment, the duration information indicated by an L-SIG field may be the length of a PPDU (physical layer protocol data unit) including the L-SIG field or a value indicating the end of a PPDU including the L-SIG field.

[0116] Also, according to an embodiment of the present invention, it is possible to restrict performing transmission or channel connection during a period based on period information shared between links. A method of restricting transmission or channel connection may include setting a NAV. Alternatively, the NAV can be reset to resume transmission or channel connection. At this time, the NAV may be an intra-BSS NAV. The intra-BSS NAV may be a NAV set by an intra-BSS frame (or PPDU). That is, an STA belonging to an MLD can set a NAV based on a frame (or PPDU) directed to another STA belonging to the MLD.

[0117] According to an embodiment of the present invention, an inter-link NAV may exist. The inter-link NAV may be a NAV used by STAs of a plurality of links belonging to a certain MLD when operating in a multi-link. For example, transmission on link 2 may not be required based on an inter-link NAV set based on period information received on link 1. Also, the inter-link NAV can exist or be used for an MLD that is not STR-capable. For example, when an inter-link NAV is set, the MLD that set the inter-link NAV does not have to perform transmission or channel connection on a plurality of links (or all links used by the MLD).

[0118] In addition to the intra-BSS NAV, a basic NAV may exist as a type of NAV. The basic NAV may be a NAV set by an inter-BSS frame (or PPDU), and the basic NAV may also be set by a frame (or PPDU) for which it is not determined whether it is intra-BSS or inter-BSS.

[0119] When using the inter-link NAV separately, it may have advantages in situations where the NAV setting is updated compared to the case of not using the inter-link NAV. For example, a situation may occur where it is possible to reset the NAV set by other links. For example, although the inter-link NAV is set based on a certain frame (or PPDU), it may be determined that the frame (or PPDU) is not directed to the same MLD, and the set inter-link NAV may be reset. If there is an MLD operating on Link 1 and Link 2, the NAV for Link 1 may be set based on the frame received on Link 1. Subsequently, the NAV of Link 1 may be updated based on the frame of Link 2. And when it is no longer necessary to maintain the NAV by Link 2, if the NAV of Link 1 is reset, there is a problem of losing the NAV information set based on the frame received on Link 1. If the inter-link NAV is used together with the NAV for each link, even if the inter-link NAV is reset, the NAV for each link is maintained, and the above problem can be solved.

[0120] Although setting the NAV has been taken up in the embodiments of the present invention, the embodiments of the present invention are not limited thereto, and are also applicable to instructing to interrupt the channel connection in the physical layer or instructing the channel state to be busy. Also, it is not limited to resetting the NAV, and it is also applicable to instructing to continue the channel connection in the physical layer or instructing the channel state to be idle. At this time, primitives exchanged between the physical layer and the MAC layer may be used. Or, primitives exchanged between one STA of the MLD and another STA may be used. Or, primitives exchanged between one MAC layer of the MLD and another MAC layer may be used.

[0121] According to an embodiment of the present invention, when a STA belonging to an MLD starts receiving a PPDU, other STAs belonging to the MLD may have to stop channel connection. As described above, the channel connection may be stopped based on the received period information. However, due to the position of the field including the period information or the time required for decoding or the like, there may be a time from when the PPDU starts to be received until the period information is obtained. Therefore, accessing the channel and starting transmission during this time may lead to the above-mentioned problem. For this reason, according to an embodiment of the present invention, a STA of an MLD can interrupt the channel connection from the time when other STAs of the MLD start receiving. Also, when it is confirmed that a frame received after other STAs of the MLD start receiving is not directed to the other STAs, the channel connection can be started again.

[0122] FIG. 12 is a diagram showing still another example of a multi-link NAV setting operation according to an embodiment of the present invention.

[0123] FIG. 12 embodies the description of the specific method of the embodiment described in FIG. 11, and duplicate description may be omitted.

[0124] As described above, based on the frame or PPDU received by a certain STA belonging to the MLD, other STAs belonging to the same MLD can suspend or resume channel connection or transmission. In the present invention, suspending channel connection or transmission may include operations such as setting (updating) the NAV, determining that the channel is busy, or suspending CCA. Also, resuming channel connection or transmission may include operations such as resetting the NAV, canceling the NAV setting, determining that the channel is idle, or performing CCA. Hereinafter, such operations can be instructed as suspending and resuming channel connection. Also, hereinafter, it can be described that STA1 and STA2 belong to the MLD, and STA1 and STA2 operate on Link1 and Link2, respectively. Also, the frame and the PPDU can be interchangeably instructed. Also, the NAV at this time may be an intra-BSS NAV or an inter-link NAV as described in FIG. 11.

[0125] According to an embodiment of the present invention, when STA1 starts receiving a frame, STA2 may interrupt the channel connection. Also, when STA1 obtains duration information from the L-SIG, STA2 may maintain the state of interrupting the channel connection. At this time, the state in which STA2 interrupts the channel connection can be determined until the end of the frame received by STA1. Also, when STA1 cannot surely decode the L-SIG (when it is an invalid L-SIG), STA2 can resume the channel connection.

[0126] In addition, STA1 can receive the TXOP duration and the BSS color from the U-SIG of the frame it receives. If the received BSS color indicates that it is intra-BSS or the BSS color corresponds to the BSS color of STA1, the channel connection can be interrupted. As an example, the period for interrupting the channel connection at this time may be until the end of the received frame. In this case, there is an advantage that the channel connection can be started earlier after the received frame ends. As another example, the period for interrupting the channel connection at this time may be the TXOP duration. In this case, the period of the channel connection interrupted based on the L-SIG may be updated. In this case, there is an advantage that the sequence following the received frame can be better protected.

[0127] Alternatively, STA1 may receive the TXOP duration and the BSS color from the U-SIG of the frame it receives, and the received BSS color may not indicate that it is intra-BSS or the BSS color may not correspond to the BSS color of STA1. Or, there may be a case where STA1 cannot successfully decode the U-SIG. In such a case, STA2 can resume the channel connection.

[0128] Or, when the information obtained by STA1 from the U-SIG of the received frame indicates that the frame is a frame that STA1 does not receive, STA2 can resume the channel connection. For example, when the PHY identifier obtained from the U-SIG is an ID corresponding to a future standard or an unrecognizable ID, STA2 can resume the channel connection.

[0129] Also, although the case of receiving the U-SIG has been described, the same example can also be applied when receiving the HE PPDU or when receiving the HE-SIG-A. For example, the HE-SIG-A may include the TXOP duration and the BSS color, and thus, the operations as described above can be performed.

[0130] In addition, STA1 may receive a STA-ID from the EHT-SIG of the frame it receives. If the received STA-ID is an indicator that STA1 should receive, for example, when the STA-ID indicates STA1, indicates the group to which STA1 belongs, or indicates broadcast, STA2 can maintain the state of interrupting the channel connection.

[0131] Alternatively, STA1 may receive a STA-ID from the EHT-SIG of the frame it receives. If the received STA-ID is an indicator that does not correspond to STA1, for example, when the STA-ID does not indicate an indicator corresponding to STA1, does not indicate the group to which STA1 belongs, or does not indicate broadcast, STA2 can resume the channel connection. Alternatively, STA2 can also resume the channel connection when STA1 fails to successfully decode the EHT-SIG.

[0132] In addition, although the case of receiving the EHT-SIG has been described, the same embodiment can also be applied when receiving an HE PPDU or when receiving an HE-SIG-B. For example, the HE-SIG-B may include a STA-ID, and thus, the operations as described above can be performed.

[0133] In addition, STA1 may receive the MAC header of the frame it receives. If the RA (receiver address) or DA (destination address) included in the received MAC header indicates the value that STA1 should receive, for example, when the RA or DA indicates STA1, indicates the group to which STA1 belongs, or indicates broadcast, STA2 can maintain the state of interrupting the channel connection. At this time, the period of interrupting the channel access can be obtained based on the period information included in the received MAC header. More specifically, the period of interrupting the channel access can be obtained based on the period information indicated by the Duration / ID field included in the received MAC header.

[0134] Also, STA1 may be receiving the MAC header of the frame. If the RA or DA included in the received MAC header is an indicator that does not correspond to STA1, for example, if the RA or DA does not indicate an indicator corresponding to STA1, does not indicate the group to which STA1 belongs, or does not indicate broadcast, STA2 can resume the channel connection. Or, STA1 may not be receiving all MAC headers. For example, STA1 may fail to receive all MPDUs included in an A-MPDU. In this case, STA2 can resume the channel connection.

[0135] The channel connection interruption and resumption described with reference to FIG. 12 may operate in the order in which they are decoded as STA1 starts receiving and sequentially decodes frames (or PPDUs). The decoding order may be based on the PPDU format, frame format, etc. For example, it can be decoded in the order of L-SIG, U-SIG, EHT-SIG, MAC header (in the case of an EHT PPDU). Or, it can be decoded in the order of L-SIG, HE-SIG-A, MAC header (in the case of an HE SU PPDU or HE TB PPDU). Or, it can be decoded in the order of L-SIG, HE-SIG-A, HE-SIG-B, MAC header (in the case of an HE MU PPDU). Or, it can be decoded in the order of L-SIG, MAC header (in the case of an 11a / g PPDU).

[0136] According to an embodiment of the present invention, the above-mentioned STA-ID may be a value indicating the intended recipient of a PPDU or RU (resource unit). Also, the STA-ID may be included in an EHT-SIG field or an HE-SIG-B field, etc. Also, the STA-ID can indicate a value corresponding to a single STA. For example, when multiple STAs are included in an MLD, the STA-ID can indicate a value corresponding to one of the multiple STAs. Also, the STA-ID may be a value based on the AID or MAC address of the STA.

[0137] FIG. 13 is a diagram showing an example of BSS classification according to an embodiment of the present invention and operations based thereon.

[0138] According to an embodiment of the present invention, a STA can classify (or determine) a BSS based on a received frame or a received PPDU. Classifying a BSS may include an operation of classifying whether a received frame or a received PPDU corresponds to the BSS to which the STA that classifies belongs. Or, classifying a BSS can mean an operation of classifying whether a received frame or a received PPDU is transmitted from the BSS to which the STA that classifies belongs. Further, classifying a BSS may include an operation of classifying whether a received frame or a received PPDU corresponds to a BSS to which the STA that classifies does not belong. Or, classifying a BSS can mean an operation of classifying whether a received frame or a received PPDU is transmitted from a BSS to which the STA that classifies does not belong. Also, classifying a BSS may include an operation of classifying to which BSS a received frame or a received PPDU belongs. Or, classifying a BSS can mean an operation of classifying from which BSS a received frame or a received PPDU is transmitted. According to an embodiment of the present invention, the BSS to which the STA that classifies belongs can be called an intra-BSS. Or, a BSS including the BSS to which the STA that classifies belongs can be called an intra-BSS. Also, a BSS that is not an intra-BSS can be called an inter-BSS. Or, a BSS that is not an intra-BSS may be an inter-BSS or a BSS that is not classified. Or, an inter-BSS may include a BSS that is not classified. Also, a BSS to which the STA that classifies does not belong can be called an inter-BSS.

[0139] According to an embodiment, when it is determined that the received frame or the received PPDU belongs to an intra-BSS or is transmitted from an intra-BSS, the received frame or the received PPDU can be referred to as an intra-BSS frame and an intra-BSS PPDU, respectively. Further, when it is determined that the received frame or the received PPDU belongs to an inter-BSS or is transmitted from an inter-BSS, the received frame or the received PPDU can be referred to as an inter-BSS frame and an inter-BSS PPDU, respectively. Also, a PPDU including an intra-BSS frame may be an intra-BSS PPDU. Further, a PPDU including an inter-BSS frame may be an inter-BSS PPDU.

[0140] According to an embodiment of the present invention, a BSS can be classified based on one or more BSS classification conditions. For example, the BSS can be classified according to whether or not at least one of the one or more BSS classification conditions is satisfied.

[0141] The BSS classification condition may include a condition based on BSS color. The BSS color may be an identifier for the BSS. Also, the BSS color may be included in the preamble of the PPDU, more specifically, in the signaling field (e.g., HE-SIG-A field or U-SIG field or VHT-SIG-A field). Also, the BSS color may be included in the TXVECTOR transmitted from the MAC layer of the sender to the PHY layer. Also, the BSS color may be included in the RXVECTOR transmitted from the PHY layer of the receiver to the MAC layer. The parameters included in the TXVECTOR and RXVECTOR can be called TXVECTOR parameters and RXVECTOR parameters, respectively. Also, the BSS color may be included in the TXVECTOR parameters or the RXVECTOR parameters. Also, the AP can notify the STA of the BSS color set by the AP. According to one embodiment, the BSS can be classified based on the BSS color included in the received PPDU. If the BSS color included in the PPDU received by the STA is different from the BSS color of the BSS corresponding to the STA, the received PPDU can be classified as an inter-BSS PPDU. Or, if the BSS color included in the PPDU received by the STA is different from the BSS color of the BSS corresponding to the STA and its value is not 0, the received PPDU can be classified as an inter-BSS PPDU. Also, if the BSS color included in the PPDU received by the STA is the same as the BSS color of the BSS corresponding to the STA, the received PPDU can be classified as an intra-BSS PPDU.

[0142] The BSS classification condition may include a condition based on the MAC address. The MAC address may be included in the MAC header of the frame. Also, the MAC address may include the RA (receiver address), TA (transmitter address), BSSID, SA (source address), DA (destination address), etc. According to one embodiment, the BSS can be classified based on the MAC address included in the received frame. If the MAC address included in the received frame is different from the BSSID of the BSS corresponding to the STA, the received frame can be classified as an inter-BSS frame. More specifically, if all of the MAC addresses included in the received frame are different from the BSSID of the BSS corresponding to the STA, the received frame can be classified as an inter-BSS frame. Also, if the MAC address included in the received frame is the same as the BSSID of the BSS corresponding to the STA, the received frame can be classified as an intra-BSS frame. More specifically, if at least one of the MAC addresses included in the received frame is the same as the BSSID of the BSS corresponding to the STA, the received frame can be classified as an intra-BSS frame.

[0143] The corresponding BSS may include the BSS to which the STA is associated. Also, the corresponding BSS may include the BSS included in the same multiple BSSID set as the BSS to which the STA is associated. Also, the corresponding BSS may include the BSS included in the same co-hosted BSSID set as the BSS to which the STA is associated. Also, information regarding the one or more BSSs included in the same multiple BSSID set or the same co-hosted BSSID set may be transmitted to the one or more BSSs in one frame.

[0144] The BSS classification condition may include a condition based on the Partial AID field value included in the VHT PPDU. The Partial AID field may be included in the preamble of the VHT PPDU. Also, the Partial AID field may be included in the VHT-SIG-A field included in the VHT PPDU. According to one embodiment, the Partial AID field can indicate a part of the BSS color. For example, when using the partial BSS color function, the Partial AID field can indicate a part of the BSS color. Or, when using the AID assignment rule, the Partial AID field can indicate a part of the BSS color. The AID assignment rule may be a method of assigning an AID based on the BSS color. Also, when the Group ID field included in the VHT-SIG-A field of the VHT PPDU is a set value (for example, when the Group ID field is set to 63), the Partial AID field can indicate a part of the BSS color. According to one embodiment, when the Partial AID field of the received PPDU indicates a part of the BSS color, if the received Partial AID field value is different from the part of the BSS color corresponding to the received STA, the received PPDU can be classified as an inter-BSS PPDU.

[0145] Also, when the Partial AID field of the received PPDU indicates a part of the BSS color, if the received Partial AID field value is the same as the part of the BSS color corresponding to the received STA, the received PPDU can be classified as an intra-BSS PPDU. At this time, a part of the BSS color can be the 4 LSBs of the BSS color. According to another embodiment, the Partial AID field can indicate a part of the BSSID. For example, when the Group ID field included in the VHT-SIG-A field of the VHT PPDU is a set value (for example, when the Group ID field is set to 0), the Partial AID field can indicate a part of the BSSID. According to one embodiment, when the Partial AID field of the received PPDU indicates a part of the BSSID, if the received Partial AID field value is different from the part of the BSSID corresponding to the received STA, the received PPDU can be classified as an inter-BSS PPDU. Also, when the Partial AID field of the received PPDU indicates a part of the BSSID, if the received Partial AID field value is the same as the part of the BSSID corresponding to the received STA, the received PPDU can be classified as an intra-BSS PPDU. At this time, a part of the BSSID can be the 9 MSBs of the BSSID. Also, the Partial AID field value may be included in the TXVECTOR parameter PARTIAL_AID or the RXVECTOR parameter PARTIAL_AID. Also, the Group ID field value may be included in the TXVECTOR parameter GROUP_ID or the RXVECTOR parameter GROUP_ID.

[0146] The BSS classification conditions may include the condition that the AP receives a PPDU that meets the already set conditions. For example, the PPDU that meets the already set conditions may include a downlink PPDU. According to one embodiment, the downlink PPDU may include a VHT MU PPDU. Also, the downlink PPDU may include a PPDU in which the signaling indicating whether it is an uplink or a downlink is set to a pre-set value. The signaling indicating whether it is an uplink or a downlink may be included in the signaling field of the HE PPDU. Or, the signaling indicating whether it is an uplink or a downlink may be included in the U-SIG. The U-SIG may be included in the preamble of an EHT PPDU or a PPDU after the EHT standard.

[0147] Also, there may be cases where it cannot be classified as an intra-BSS PPDU or an inter-BSS PPDU. For example, when neither the conditions for classifying as the aforementioned intra-BSS PPDU nor the conditions for classifying as the inter-BSS PPDU are satisfied, it cannot be classified as an intra-BSS PPDU or an inter-BSS PPDU.

[0148] Also, when classifying the BSS, if the classification results based on multiple conditions do not match, it is possible to determine the final result according to the already set conditions. For example, when the result based on the condition based on the BSS color and the result based on the condition based on the MAC address do not match, the result based on the condition based on the MAC address may be prioritized, or the result based on the condition based on the MAC address may be determined as the final result. Or, when both the conditions for classifying as an intra-BSS PPDU and the conditions for classifying as an inter-BSS PPDU are satisfied, it can be classified as an intra-BSS PPDU.

[0149] According to an embodiment of the present invention, the STA can perform operations based on the classified BSS. The operations based on the classified BSS may include intra-PPDU power save operations. The intra-PPDU power save operation may be a power save operation based on the received PPDU. When the already set conditions are satisfied, it is possible to perform the intra-PPDU power save operation. The already set conditions may include conditions for classifying the received PPDU as an intra-BSS PPDU. Also, the already set conditions may include the condition that the intended receiver of the received PPDU is not the STA that received the PPDU. For example, when the ID or address included in the PPDU does not correspond to the STA that received the PPDU, the intended receiver of the PPDU may not be the STA that received the PPDU. The ID may be included in the preamble of the PPDU. For example, the ID may be the STA_ID included in the preamble of the PPDU. Also, the STA_ID may be included in the HE MU PPDU or the EHT PPDU. Also, the address may be the MAC address described above. Also, when the signaling indicating whether the received PPDU is an uplink or a downlink indicates an uplink, the intended receiver of the PPDU may not be the STA that received the PPDU. Also, when the setting of the received PPDU is set to something that the STA that received the PPDU does not support, the intended receiver of the PPDU may not be the STA that received the PPDU. The setting of the received PPDU may include the MCS of the PPDU, the number of spatial streams, the channel width, etc. Also, when the setting of the received PPDU is not supported by the STA that received the PPDU, the PHY-RXEND.indication(UnsupportedRate) primitive may be received. Also, when the received PPDU is in the already set format, the intended receiver of the PPDU may not be the STA that received the PPDU. The already set format may include the TB PPDU.The TB PPDU may include an HE TB PPDU and an EHT TB PPDU. Also, the TB PPDU may be a PPDU transmitted as a response to a triggering frame. The triggering frame may include a trigger frame. The triggering frame may include a frame containing triggering information. The triggering information may be included in a MAC header, for example, an A-control field. Also, the triggering information or the information included in the trigger frame may include the length of the responding PPDU, the RU used at the time of response, the PHY configuration used at the time of response, the MAC configuration, etc. The intra-PPDU power-saving operation may be an operation that can enter the doze state until the end of the received PPDU. As another example, when it is determined that the intended recipient of the PPDU or frame received by the STA is not the STA, the reception or decoding of the PPDU or frame can be interrupted.

[0150] Operations based on the classified BSS may include the operation of setting (or updating) the NAV. According to one embodiment, a STA can operate one or more NAVs. Also, when a STA receives a PPDU or a frame, it is possible to set the NAV corresponding to the BSS classified based on the received PPDU or the received frame. For example, the intra-BSS NAV may be the NAV corresponding to the intra-BSS PPDU. Also, the basic NAV may be the NAV corresponding to a PPDU that is not an intra-BSS PPDU. Or, the basic NAV may be the NAV corresponding to an inter-BSS PPDU. Also, when setting the NAV based on the received PPDU or the received frame, it is possible to use the duration information included in the received PPDU or the received frame. The duration information may include a TXOP. The TXOP can mean the value included in the TXOP field. The TXOP field may be included in the preamble of the PPDU. For example, the TXOP field may be included in the HE-SIG-A field of the HE PPDU. Or, the TXOP field may be included in the U-SIG field of the EHT PPDU or a PPDU of a standard after EHT. Also, the duration information may be included in the MAC header. For example, the duration information may be included in the Duration / ID field included in the MAC header.

[0151] Operations based on the classified BSSs may include spatial reuse operations. Also, operations based on the classified BSSs may include channel connection operations. The spatial reuse operation may be a channel connection operation. When a STA receives a PPDU or a frame, if the already set conditions are met, it is possible to perform a spatial reuse operation. The already set conditions may include conditions where the received PPDU or the received frame corresponds to an inter-BSS. Also, the already set conditions may include conditions where the signal strength of the received PPDU or the received frame is less than a threshold. For example, the threshold may be variable. Also, the threshold may be a threshold for OBSS PD-based Spatial reuse operations. Also, the threshold may be a value equal to or greater than the CCA threshold. Also, the threshold may be a value based on the power to be transmitted. The spatial reuse operation may include an operation of transmitting a PPDU. Also, the spatial reuse operation may include an operation of resetting the PHY. For example, the operation of resetting the PHY may be an operation of issuing a PHY-CCARESET.request primitive. Also, the spatial reuse operation may include an operation of not setting the NAV based on the received PPDU or the received frame. If the STA performs a spatial reuse operation, it may be possible for the STA to transmit a PPDU while the received PPDU or the received frame is being transmitted or received.

[0152] Referring to FIG. 13, BSS A and BSS B may exist, and BSS A and BSS B may be different BSSs from each other. Also, BSS A and BSS B may correspond to each other in inter-BSS. That is, a PPDU or frame transmitted by a STA associated with BSS B in BSS A may be classified as an inter-BSS PPDU or an inter-BSS frame. Also, there may be STAs STA1 and STA2 belonging to (or associated with an AP operating BSS A). There may be STAs STA3 and STA4 belonging to (or associated with an AP operating BSS B). Referring to FIG. 13, STA1 can transmit a PPDU. Also, the PPDU transmitted by STA1 may contain information about the BSS. For example, the information about the BSS may be information for classifying the aforementioned BSS. Also, the PPDU transmitted by STA1 may contain Duration information.

[0153] STA2 can receive the PPDU transmitted by STA1 and classify the BSS for this PPDU. Also, since STA2 and STA1 belong to BSS A, the PPDU received by STA2 may be classified as an intra-BSS PPDU. Also, the PPDU received by STA2 may be a UL PPDU or a PPDU that is not the intended recipient of the STA. Therefore, according to the aforementioned embodiments, STA2 can perform intra-PPDU power saving. Referring to FIG. 13, STA2 can enter the doze state until the end time of the received PPDU. Also, STA2 can set the NAV based on the Duration information contained in the received PPDU. Since STA2 classifies the received PPDU as an intra-BSS PPDU, it is possible to set the intra-BSS NAV.

[0154] STA3 can receive the PPDU transmitted by STA1 and classify the BSS for this PPDU. Also, since STA3 and STA1 belong to BSS B and BSS A respectively, the PPDU received by STA3 may be classified as an inter-BSS PPDU. Further, STA3 can set the NAV based on the Duration information included in the received PPDU. Since STA3 classifies the received PPDU as an inter-BSS PPDU, it is possible to set the basic NAV.

[0155] STA4 can receive the PPDU transmitted by STA1 and classify the BSS for this PPDU. Also, since STA4 and STA1 belong to BSS B and BSS A respectively, the PPDU received by STA4 may be classified as an inter-BSS PPDU. Also, the signal strength of the PPDU received by STA4 may be less than the threshold value. Therefore, since the PPDU received by STA4 is classified as an inter-BSS PPDU and the signal strength of the PPDU received by STA4 is less than the threshold value, STA4 can perform a spatial reuse operation. Therefore, STA4 can perform a channel connection and a backoff procedure and start transmission. For example, it may be possible for STA4 to start transmission when the PPDU transmitted by STA1 has not ended.

[0156] FIG. 14 shows a wireless LAN function according to an embodiment of the present invention.

[0157] Referring to FIG. 14, a certain standard wireless LAN may include the functions of other standard wireless LANs. Or, when it is a certain standard wireless LAN, it may be another standard wireless LAN. Here, the wireless LAN can mean a STA. Further, here, the wireless LAN may mean an MLD including a STA. For example, the wireless LAN standard may include the functions of previous generation standards and additional functions. For example, an HT STA can also be an OFDM PHY STA. Also, in addition to the functions of an OFDM PHY STA, an HT STA can perform additional functions. For example, a VHT STA can also be an HT STA. Also, in addition to the functions of an HT STA, a VHT STA can perform additional functions. For example, a HE STA can also be a VHT STA. Also, in addition to the functions of a VHT STA, a HE STA can perform additional functions. Also, an EHT STA can also be a HE STA. Also, in addition to the functions of a HE STA, an EHT STA can perform additional functions. Also, there may be a standard after the EHT standard. In the present invention, the standard after the EHT standard can be called the NEXT standard, and a STA conforming to the NEXT standard can be called a NEXT STA. A NEXT STA can also be an EHT STA. Also, in addition to the functions of an EHT STA, a NEXT STA can perform additional functions.

[0158] FIG. 14 is a diagram showing the relationship between STAs of each standard. Referring to FIG. 14, if it is an EHT STA, it can be a HE STA, a VHT STA, an HT STA, and an OFDM PHY STA. Also, if it is a NEXT STA, it can be an EHT STA, a HE STA, a VHT STA, an HT STA, and an OFDM PHY STA.

[0159] FIG. 15 shows the uplink (UL) multi-user (MU) operation according to an embodiment of the present invention.

[0160] Referring to FIG. 15, the AP can instruct at least one STA to transmit a PPDU through a specific frame (e.g., a triggering frame), and at least one STA can simultaneously transmit a PPDU in the same or an individual format based on the specific frame transmitted from the AP.

[0161] Specifically, as shown in FIG. 15, a frame that instructs or triggers multi-user (MU) transmission may be transmitted, and based on such a frame, one or more STAs can transmit or respond to such a frame. At this time, when one or more STAs transmit a response to the frame, based on the frame, one or more STAs can simultaneously give an immediate response, and the response to the frame may start to be transmitted after SIFS from the end of the PPDU containing the frame. For example, when the frame instructs an immediate response, one or more STAs can immediately transmit a response to the frame. A frame that instructs or triggers transmission to one or more STAs may be a trigger frame or a frame included in the MAC header that contains information instructing or triggering uplink transmission to one or more STAs. At this time, the frame may include in the MAC header information (e.g., a TRS control subfield) that triggers or instructs uplink transmission only to one STA.

[0162] For example, the information instructing or triggering uplink transmission included in the MAC header may be a triggered response scheduling (TRS) or a TRS control subfield included in an HT control field, a control subfield, or an A-control subfield.

[0163] Frames for instructing or triggering uplink transmission may be transmitted by the AP. When the frame for instructing or triggering uplink transmission is a trigger frame, the response thereto may be transmitted in the trigger-based PPDU (TB PPDU) format. At this time, the TB PPDDU may include, in addition to the HE TB PPDU and EHT TB PPDU described above, the NEXT TB PPDU that may be defined by the following standard.

[0164] The HE TB PPDU may be composed of a preamble, data, and a packet extension (PE). The preamble may sequentially include L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, HE-STF, and HE-LTF.

[0165] The EHT TB PPDU and NEXT TB PPDU may also be composed of a preamble, data, PE, etc. The preambles of the EHT TB PPDU and NEXT TB PPDU may sequentially include L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, (EHT- / NEXT-)STF, and (EHT- / NEXT-)LTF.

[0166] Frames for instructing or triggering the transmission of a PPDU to one or more STAs may include information necessary for one or more STAs to transmit a TB PPDU. For example, when the type subfield included in the frame is "01" (B3 B2) and the subtype subfield is "0010" (B7 B6 B5 B4), a frame including such type and subtype subfields may be a trigger frame that is a control frame.

[0167] If, when responses to a TB PPDU are indicated or triggered for a plurality of STAs, the formats of the PPDUs to be responded to by the plurality of STAs are different from each other, there may arise a problem that it is difficult for the AP that indicated or triggered the responses to receive the PPDUs that are responses transmitted from the plurality of STAs. Or, if the information included in the preambles of the PPDUs to be responded to by the plurality of STAs is different from each other depending on the format, there may arise a problem that it is difficult for the AP that indicated or triggered the responses to receive the PPDUs that are responses transmitted from the plurality of STAs.

[0168] Therefore, in order to solve such a problem, when a plurality of STAs respond to an AP's frame, the format of the PPDU to be responded to and / or the type of information included in the preamble of the PPDU may be set to be the same. For example, when a plurality of STAs transmit a HE TB PPDU as a response to an AP's frame, the AP may transmit information so that the information included in the L-STF, L-LTF, L-SIG, RL-SIG, and HE-SIG-A is the same, or an agreement may be defined for the information included in the HE TB PPDU so that the preamble transmitted by the plurality of STAs can be successfully received by the AP. However, if the TB PPDU formats are different from each other when HE TB PPDU, EHT TB PPDU, and NEXT TB PPDU are simultaneously transmitted in an overlapping subband, there may arise a problem that it is difficult for the AP to receive them.

[0169] According to an embodiment of the present invention, a HE STA can transmit a HE TB PPDU. Also, an EHT STA can transmit an EHT TB PPDU or a HE TB PPDU. Also, a NEXT STA can transmit a NEXT TB PPDU or an EHT TB PPDU or a HE TB PPDU. This is because, as described with reference to FIG. 10, a certain standard STA may include the functions of a previous standard.

[0170] As shown in FIG. 15, when AP transmits a frame for scheduling the transmission of a TB PPDU to a HE STA and an EHT STA, and instructs or triggers the transmission of the TB PPDU using the frame, there may be no exact instruction or protocol for the TB PPDU format. In this case, the HE STA transmits a HE TB PPDU as a response to the frame, and the EHT STA can respond with an EHT TB PPDU or a HE TB PPDU. In this case, the AP may have difficulty receiving the TB PPDUs transmitted by these STAs. The AP may not be able to successfully receive TB PPDUs from multiple STAs, and although the transmission was not successful, the medium may be occupied, resulting in a problem that the transmission opportunities of other STAs are reduced.

[0171] Hereinafter, in the present invention, instructing an STA may mean instructing a response from the STA, and trigger and instruction may be used in the same meaning.

[0172] Also, the HE trigger frame, the EHT trigger frame, and the NEXT trigger frame may be trigger frames defined by the HE, EHT, and NEXT standards, respectively. Also, in the present invention, the HE TRS, the EHT TRS, and the NEXT TRS may be TRSs defined by the HE, EHT, and NEXT standards, respectively.

[0173] FIG. 16 shows a trigger frame format according to an embodiment of the present invention.

[0174] FIG. 16(a) shows the trigger frame format, and FIGS. 16(b) and 16(c) show the common information field and the user information field, which are fields included in the trigger frame, respectively.

[0175] Referring to Fig. 16(a), as a trigger MAC header, the frame includes a Frame Control field, a Duration field, and an Address field, and may include a common information field and a user information list field. The Address field may include a Resource Allocation (RA) field and a transmitter address (TA) field.

[0176] The common information field may include information that is common to all STAs indicated by the trigger frame. Fig. 16(b) shows an example of the common information field.

[0177] The user information list field may include zero or more user information fields. The user information list field of a trigger frame, except for a specific type of trigger frame, may include one or more user information fields. Fig. 16(c) shows an example of the user information field.

[0178] As an addition, the trigger frame may further include a Padding field and a Frame Check Sequence (FCS) field. The Padding field may be used to increase the length of the frame to ensure the time required for the STA receiving the trigger frame to prepare a response to the trigger frame, and may be selectively included in the trigger frame.

[0179] Referring to FIG. 16(b), the common information field may include a trigger type subfield. The trigger type subfield may be used to identify a trigger frame variant. Alternatively, the type of the trigger frame may be indicated based on the value of the trigger frame subfield. Also, based on the trigger type subfield, the information and length included in the trigger dependent common information subfield and the trigger dependent user information subfield shown in FIG. 12 may be determined. For example, the trigger type subfield may be indicated by bits B0 to B3 of the common information field.

[0180] The common information field may include an uplink (UL) length subfield. The UL length subfield may include information regarding the length of the TB PPDU that is a response to the trigger frame, and may include information regarding the length of the frame that responds to the trigger frame. Also, the UL length subfield can indicate the value included in the length subfield of the L-SIG of the TB PPDU that responds to the trigger frame. Therefore, a STA that receives a trigger frame and responds with a TB PPDU can set the value of the length subfield included in the L-SIG of the TB PPDU based on the value of the UL length subfield included in the received trigger frame. Specifically, a STA that responds with a TB PPDU can set the length subfield included in the L-SIG of the TB PPDU to the value of the UL length subfield included in the received trigger frame. For example, the STA can set the length subfield included in the L-SIG of the TB PPDU based on the value of bits B4 to B15 of the common information field indicating the UL length subfield and transmit the TB PPDU.

[0181] In addition, the common information field may further include an uplink bandwidth subfield (UL Bandwidth (BW) subfield). The UL BW subfield can indicate the BW value included in the signaling field (e.g., HE-SIG-A or U-SIG, etc.) of the TB PPDU that responds to the trigger frame, and can indicate the maximum BW of the TB PPDU transmitted as a response to the trigger frame. Therefore, the STA can set the BW value included in the signaling field of the TB PPDU based on the value of the UL BW subfield included in the trigger frame.

[0182] In addition, the common information field may further include information such as that included in the signaling field of the TB PPDU that is a response to the trigger frame. Therefore, after receiving the trigger frame, the STA can set the information included in the TB PPDU based on the information included in the trigger frame.

[0183] Referring to (c) of FIG. 16, the user information field may include an AID12 subfield. The AID12 subfield may be used to indicate the intended recipient of the user information field including the AID12 subfield or the function of the user information field. Thus, the AID12 subfield can also play a role in indicating the intended recipient of the trigger frame including the AID12 subfield or the function of the trigger frame. For example, when the value of the AID12 subfield is a preset value, the user information field can indicate a RA-RU (Random Access Resource Unit). That is, the preset value of the AID12 subfield can indicate that the user information field indicates a RA-RU. Specifically, when the value of the AID12 subfield is "0", the user information field can indicate a RA-RU for the associated STAs. For example, when the value of the AID12 subfield is "0", the user information field can indicate a RA-RU for the associated STAs, and when the value of the AID12 subfield is "2045", the user information field can indicate a RA-RU for the unassociated STAs. The STA corresponding to the STA ID (e.g., AID (association ID)) indicated by the value of the AID12 subfield may be instructed to respond by the user information field including the AID12 subfield or the trigger frame including the AID subfield. For example, the AID12 subfield can indicate an AID or the 12 LSBs of an AID. The STA corresponding to the value indicated by the AID12 subfield can transmit a TB PPDU as a response to the received trigger frame. In this case, the value of the AID12 subfield may be in the range from "1" to "2007" (including 1 and 2007), and when the AID12 subfield is a preset value (e.g., "2046", etc.), the RU corresponding to the preset value of the AID12 subfield does not have to be assigned to any STA.Also, when the value already set in the AID subfield (e.g., "4095", etc.) is present, the already set value can indicate that the padding of the trigger frame starts.

[0184] The information of the user information field including the AID12 subfield may be information corresponding to the STA indicated by the AID12 subfield. For example, the Resource Unit (RU) Allocation subfield can indicate the size and location of the RU, etc. At this time, the value of the RU allocation subfield of the user information field including the AID12 subfield may be information corresponding to the STA indicated by the AID12 subfield. That is, the RU indicated by the RU allocation subfield of the AID12 subfield may be the RU allocated to the STA indicated by the AUD12 subfield.

[0185] Also, the user information field can indicate the coding method (UL FEC coding type), modulation method (UL HE-MCS, UL DCM), and power (UL Target RSSI), etc. for generating the TB PPDU transmitted as a response to the trigger frame.

[0186] FIG. 17 shows a method for indicating a triggered-based (TB) PPDU format according to an embodiment of the present invention.

[0187] Referring to FIG. 17, one STA can selectively transmit PPDUs in different formats based on being indicated by a triggering frame that indicates the transmission of the PPDU.

[0188] Specifically, in addition to legacy PPDUs (e.g., HE TB PPDUs), the EHT STA can also selectively transmit EHT TB PPDUs, and the NEXT STA can selectively transmit HE TB PPDUs, EHT TB PPDUs, and / or NEXT TB PPDUs. In this case, STAs to which multiple standards are respectively applied in one frame or one PPDU can be individually scheduled. Since multiple standards are applied to common resources in the wireless LAN by multiple STAs, such a method can be an advantage. For example, HE STAs (HE STAs other than EHT STAs) and EHT STAs can be made to respond with HE TB PPDUs using one frame. That is, the non-AP STA can transmit a triggering frame and instruct the transmission of HE TB PPDUs not only to HE STAs but also to EHT STAs.

[0189] Also, information for selecting the TB PPDU format may be included in a trigger frame which is a triggering frame, a TRS, a PPDU including a triggering frame, or a PPDU including a TRS control subfield. That is, the AP STA includes information for selecting the format of the TB PPDU in a triggering frame and transmits it to at least one non-AP STA, and the non-AP STA can select the format of the PPDU to respond based on the information included in the received triggering frame. Thereafter, at least one non-AP STA can transmit a PPDU to the AP based on the selected format.

[0190] Information regarding the format (TB PPDU format) of the PPDU which is a response to such a triggering frame may exist at the MAC level. A trigger frame which is one of the triggering frames may be classified into an HE trigger frame, an EHT trigger frame, and a NEXT trigger frame, and responses to the respective trigger frames may be classified into HE TB PPDUs, EHT TB PPDUs, and NEXT TB PPDUs.

[0191] Also, distinguishing the trigger frame into an HE trigger frame, an EHT trigger frame, and a NEXT trigger frame may have the same meaning as distinguishing the TB PPDU format, which is a response to the trigger frame, into an HE TB PPDU, an EHT TB PPDU, and a NEXT TB PPDU, respectively.

[0192] Whether the format of the trigger frame for distinguishing the TB PPDU format is an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame may be identified based on the Frame Control field included in the MAC header. Specifically, the format of the trigger frame may be distinguished based on the Type subfield, the Subtype subfield, and / or the Control Frame Extension subfield. Also, when the values of the Type subfield, the Subtype subfield, and / or the Control Frame Extension subfield are already set values, the trigger frame may be identified as an HE trigger frame, and when they are other already set values, the trigger frame may be identified as an EHT trigger frame. Also, when the values of the Type subfield, the Subtype subfield, and / or the Control Frame Extension subfield are other already set values, the trigger frame may be identified as a NEXT trigger frame.

[0193] For example, when the Type subfield is 01 (B3 B2) and the Subtype subfield is 0010 (B7 B6 B5 B4), the format of the frame including the Type subfield and the Subtype subfield may be an HE trigger frame. In this case, entries of the Type subfield (2 bits), the Subtype subfield (4 bits), and / or the Control Frame Extension subfield (4 bits) with limited number of bits may need to be further used in the EHT standard and the NEXT standard.

[0194] Alternatively, whether the format of the trigger frame is a HE trigger frame or an EHT trigger frame may be identified based on a common information field included in the trigger frame. That is, based on the value of a specific subfield (first subfield) included in the common information field, the format of the PPDU transmitted as a response to the trigger frame may be determined. For example, depending on the value of the common information field, a non-AP STA may select a HE TB PPDU or an EHT TB PPDU and transmit it using the assigned RU. At this time, in addition to the common information field, a specific subfield (second subfield) of the user information field may also be further used to identify the format of the PPDU.

[0195] That is, based on the common information field of the trigger frame, a variant for determining the format of the PPDU that is a response to the trigger frame may be determined, and the format of the PPDU may be determined by the determined variant. For example, when the variant for determining the format of the PPDU by the common information field is determined to be a HE variant, the non-AP STA can respond with a HE TB PPDU, and when the variant for determining the format of the PPDU by the common information field is determined to be an EHT variant, the non-AP STA can respond with an EHT TB PPDU.

[0196] At this time, for the variant for determining the format of the PPDU, in addition to the common information field, the user information field may also be further used.

[0197] For example, the trigger frame may be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the trigger type subfield. For example, when the trigger type subfield value is a preset value, the trigger frame may be an HE trigger frame. Also, when the trigger type subfield value is a preset value, the trigger frame may be an EHT trigger frame. When the trigger type subfield value is a preset value, the trigger frame may be a NEXT trigger frame.

[0198] For example, when the trigger type subfield value is from 0 to 7, it may be an HE trigger frame, and when it is not from 0 to 7, it may be an EHT trigger frame or a NEXT trigger frame. The trigger type subfield indicates various trigger frame types, but in this case, there is a disadvantage that a limited trigger type subfield space must be used.

[0199] According to yet another embodiment, based on the UL length subfield of the trigger frame, it can be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. For example, based on the value obtained by performing a mod (remainder) operation on the UL length subfield value, it can be classified as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. That is, using the value of the UL length subfield, it may be determined whether the format of the PPDU transmitted as a response to the trigger frame is an HE PPDU or an EHT PPDU.

[0200] More specifically, based on the value obtained by performing a mod(remainder) 3 operation on the UL length subfield value (the remainder when the UL length subfield is divided by 3), it is possible to distinguish whether it is an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. For example, when the result of performing mod 3 on the UL length subfield value is not 0, the trigger frame may be an HE trigger frame. Or, when the result of performing mod 3 on the UL length subfield value is 1, the trigger frame may be an HE trigger frame. Or, when the result of performing mod 3 on the UL length subfield value is 0, the trigger frame may not be an HE trigger frame. Or, when the result of performing mod 3 on the UL length subfield value is 0, the trigger frame may be an EHT trigger frame or a NEXT trigger frame.

[0201] That is, when the value obtained by performing mod 3 on the value of the UL length subfield of the trigger frame is not 0, the response to the trigger frame may be transmitted as an HE TB PPDU, and when the value obtained by performing mod 3 on the value of the UL length subfield is 1, the response to the trigger frame may be transmitted as an HE TB PPDU.

[0202] Also, when the value obtained by performing mod 3 on the value of the UL length subfield of the trigger frame is 0, the format of the PPDU transmitted as a response to the trigger frame may be an EHT TB PPDU.

[0203] In addition, it is possible to distinguish HE trigger frames, EHT trigger frames, and NEXT trigger frames by using such a method together with an additional trigger frame classification method. For example, it is possible to distinguish HE trigger frames, EHT trigger frames, and NEXT trigger frames by using the classification method described in FIG. 16 together.

[0204] According to one embodiment, based on the User Info field of the trigger frame, it may be determined whether the format of the trigger frame is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame.

[0205] That is, similar to the aforementioned common information field, whether the format of the trigger frame is a HE trigger frame or an EHT trigger frame can be identified based on the user information field included in the trigger frame. That is, based on the value of a specific subfield (second subfield) included in the user information field, the format of the PPDU transmitted as a response to the trigger frame may be determined. For example, depending on the value of the user information field, the non-AP STA can select a HE TB PPDU or an EHT TB PPDU and transmit it using the allocated RU. In this case, in addition to the user information field, a specific subfield (first subfield) of the common information field may be further used to identify the format of the PPDU.

[0206] That is, based on the user information field of the trigger frame, a variant for determining the format of the PPDU that is a response to the trigger frame may be determined, and the format of the PPDU may be determined by the determined variant. For example, when the variant for determining the format of the PPDU is determined to be a HE variant by the user information field, the non-AP STA can respond with a HE TB PPDU, and when the variant for determining the format of the PPDU is determined to be an EHT variant by the user information field, the non-AP STA can respond with an EHT TB PPDU.

[0207] At this time, for the variant for determining the format of the PPDU, in addition to the user information field, the common information field may be further used.

[0208] For example, based on the AID12 subfield, it may be classified whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. According to one embodiment, whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame may be classified according to whether it includes the AID12 subfield of a pre-set value. Also, in this case, it may be a problem whether the STA indicated by a certain user information field should continuously check the AID12 subfield existing after the user information field to determine the trigger frame format. To solve such a problem, the user information field including the AID12 subfield indicating which trigger frame it is may be present in front of the user information list. Also, in order to prevent a HE STA that cannot understand such a signaling method from malfunctioning, it is possible that a user information field including the AID12 subfield indicating which trigger frame it is exists after the user information field corresponding to the HE STA.

[0209] Also, at this time, since the information of other sub-fields other than the AID12 sub-field included in the user information field may not be necessary for the TB PPDU response, the sub-field of the user information field including the AID12 sub-field that indicates which trigger frame it is may be omitted. That is, the length of the user information field may vary based on the AID12 sub-field. Referring to FIG. 17, the AID12 sub-field can play a role of indicating the response TB PPDU format. For example, when the AID12 sub-field has a preset value, the response to the trigger frame including the AID12 sub-field set to the preset value may be an EHT TB PPDU. For example, when the AID12 sub-field value is 2047, the response to the trigger frame including the AID12 sub-field may be an EHT TB PPDU. Also, when the AID12 sub-field has a preset value, the response to the trigger frame including the AID12 sub-field set to the preset value may be a NEXT TB PPDU. For example, when the AID12 sub-field value is 2048, the response to the trigger frame including the AID12 sub-field may be a NEXT TB PPDU.

[0210] According to still other embodiments, when responding based on the user information field existing at the already set position from the AID12 subfield of the already set value, it is possible to respond in the TB PPDU format corresponding to the already set value. For example, when responding based on the user information field existing after the AID12 subfield of the already set value, it is possible to respond in the TB PPDU format corresponding to the already set value. If there are multiple values indicating the TB PPDU format, when responding based on the user information field existing after both the already set value 1 and the already set value 2, among the TB PPDU format corresponding to the already set value 1 and the TB PPDU format corresponding to the already set value 2, it is possible to respond in the TB PPDU format according to the already set priority order. Referring to FIG. 17, when responding based on the user information field existing after the AID12 subfield set to 2047, it is possible to respond with an EHT TB PPDU. Also, when responding based on the user information field existing after the AID12 subfield set to 2048, it is possible to respond with a NEXT TB PPDU. Also, when responding based on the user information field existing after both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it is possible to respond with a NEXT TB PPDU. Also, when responding based on the user information field existing before both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it is possible to respond with a HE TB PPDU.

[0211] In this embodiment, an example where the AID12 subfield indicates the type of trigger frame is taken, but the present invention is not limited to this, and it is also possible to indicate the type of trigger frame with other subfields of the user information field.

[0212] According to one embodiment, based on the padding field of the trigger frame, it may be determined whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame. For example, it can be determined whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on whether the padding field includes a pre-set value indicating whether it is a HE trigger frame, an EHT trigger frame, or a NEXT trigger frame.

[0213] According to an embodiment of the present invention, it is possible to classify HE trigger frames, EHT trigger frames, and NEXT trigger frames by combining a plurality of trigger frame classification methods described in the present invention. Further, the content described about the trigger frame in the present invention is not limited to the above, and is also applicable to TRS.

[0214] As yet another embodiment of the present invention, the AP may not be able to instruct the transmission of both the EHT PPDU and the HE PPDU using a trigger frame. That is, the EHT AP cannot transmit a trigger frame that instructs both the HE TB PPDU and the EHT TB PPDU, and can only instruct one PPDU format.

[0215] FIG. 18 shows UL MU operation according to yet another embodiment of the present invention.

[0216] As described above, in addition to the trigger frame, the transmission of the TB PPDU can also be instructed by the TRS. Further, the TRS may be included in the HT control field as described above. For example, when the HT control field includes an A-control field, it is possible to include the TRS. The TRS can be transmitted by a TRS control subfield. The A-control field may be in a form in which the control list field continues continuously. Further, the control list field may include the TRS.

[0217] Also, the receiver of a frame including the TRS (indented receiver) can respond to the TRS. For example, a STA corresponding to the RA included in the frame including the TRS can respond to the TRS. The TRS may include information regarding the length of the PPDU or frame that responds to the TRS (UL Data Symbols), the position and size of the RU used when responding to the TRS (RU Allocation), information regarding power when responding to the TRS (AP Tx Power, UL Target RSSI), information regarding the modulation method when responding to the TRS (UL HE-MCS), and the like.

[0218] The embodiment of FIG. 18 may be a method for solving the problems described in FIGS. 14 to 15. Also, as described above, the embodiments regarding the above trigger frame are also applicable to the TRS. Also, the above-described content may be omitted.

[0219] According to an embodiment of the present invention, in addition to the TRS (HE TRS) defined by the HE standard, it is also possible to have a TRS defined by the EHT standard or the NEXT standard (EHT TRS and NEXT TRS, respectively). Therefore, depending on whether the indicated TRS is any of HE TRS, EHT TRS, and NEXT TRS, the TB PPDU that responds to the TRS may be HE TB PPDU, EHT TB PPDU, or NEXT TB PPDU, respectively. For example, it is possible to determine which standard the defined TRS belongs to by the Control ID subfield of the A-control subfield. As an additional embodiment, the TRS can be divided into two types: HE TRS and TRS other than HE TRS.

[0220] Alternatively, for example, which standard-defined TRS it is may be determined by whether the HT control field is a HE variant, an EHT variant, or a NEXT variant. Also, whether it is a HE variant, an EHT variant, or a NEXT variant may be determined by the value of the already set bits in the HT control field. For example, when B0 and B1 of the HT control field are 1 and 1, it may be a HE variant. Also, using B0, B1 of the HT control field and an additional bit (e.g., B31), whether it is a HE variant, an EHT variant, or a NEXT variant can be determined.

[0221] According to an embodiment of the present invention, based on a PPDU format including a TRS, it is possible to determine a TB PPDU format that responds to the TRS. That is, when a PPDU instructing the transmission of a PPDU includes a TRS control subfield, the format of the PPDU may be determined based on the format of the PPDU including the TRS control subfield. For example, when the format of the PPDU including the TRS control subfield is a HE PPDU, the format of the instructed PPDU may be a HE PPDU. However, when the format of the PPDU including the TRS control subfield is an EHT PPDU, the format of the instructed PPDU may be an EHT PPDU.

[0222] Referring to FIG. 18, when the TRS is transmitted by a HE PPDU, the TB PPDU that responds to the TRS may be a HE TB PPDU. Also, when the TRS is transmitted by an EHT PPDU, the TB PPDU that responds to the TRS may be an EHT TB PPDU. Also, when the TRS is transmitted by a NEXT PPDU, the TB PPDU that responds to the TRS may be a NEXT TB PPDU.

[0223] According to an embodiment of the present invention, based on the PPDU format including the TRS, the sub-fields included in the TRS can be analyzed differently. For example, when the TRS is included in the HE PPDU, the UL HE-MCS sub-field (or the sub-field related to MCS) included in the TRS can indicate a value corresponding to the HE MCS table. When the TRS is included in the EHT PPDU, the UL HE-MCS sub-field (or the sub-field related to MCS) included in the TRS can indicate a value corresponding to the EHT MCS table. When the TRS is included in the NEXT PPDU, the UL HE-MCS sub-field (or the sub-field related to MCS) included in the TRS can indicate a value corresponding to the NEXT MCS table. Also, the RU Allocation sub-field may be analyzed differently based on the PPDU format including the TRS.

[0224] FIG. 19 shows the end time alignment of a high priority frame according to an embodiment of the present invention.

[0225] In an embodiment of the present invention, aligning or having aligned the transmission end time of the PPDU can be referred to as end time alignment, PPDU end time alignment, ending time alignment, etc.

[0226] According to an embodiment of the present invention, when the MLD transmits a plurality of PPDUs, it can be determined whether to perform end time alignment based on whether the plurality of PPDUs include a high priority frame. Or, when the MLD transmits a plurality of PPDUs, the end time alignment operation may be different based on whether the plurality of PPDUs include a high priority frame. Also, in the present invention, end time alignment can mean that the end time difference of the PPDUs to be aligned is less than or equal to a preset time.

[0227] In an embodiment of the present invention, the MLD can start transmitting a plurality of PPDUs simultaneously. Also, when the transmission start times of the plurality of PPDUs transmitted by the MLD are exactly the same or the difference between the plurality of transmission start times is less than or equal to a preset time, it can be said that the transmission starts simultaneously. Also, the fact that the MLD starts transmitting a plurality of PPDUs simultaneously can be called start time sync.

[0228] Whether a frame is a high-priority frame can be determined based on the TID (traffic identifier) or AC (access category) corresponding to the frame. Also, whether a frame is a high-priority frame can be determined based on the type and subtype of the frame. The type and subtype of the frame may be indicated in the MAC header of the frame. Or, a frame can be a high-priority frame when it is transmitted within an assigned time interval. At this time, the time allocation for transmitting the high-priority frame may be made by the AP. Also, according to one embodiment, there may be an absolute criterion for whether a frame is a high-priority frame. For example, a frame corresponding to a preset TID or a preset AC may be a high-priority frame. According to another embodiment, whether a frame is a high-priority frame may be relative to other frames. For example, whether a frame is a high-priority frame may be determined based on whether the frame has a higher priority than frames transmitted on other links. Or, whether a frame is a high-priority frame may be determined by the sender.

[0229] Also, the non-STR MLD may be an MLD whose simultaneous transmission and reception are restricted for the link pair it uses. At this time, the link pair for which simultaneous transmission and reception are restricted can be called a non-STR link pair or an NSTR link pair. Conversely, a link pair for which simultaneous transmission and reception are not restricted can be called an STR link pair.

[0230] According to an embodiment of the present invention, when the MLD transmits a plurality of PPDUs and the transmitted PPDU includes a high-priority frame, end time alignment may not be performed. For example, when the plurality of PPDUs are transmitted to STAs belonging to the same MLD and also include a high-priority frame, end time alignment may not be performed. Further, even if both the MLD transmitting the plurality of PPDUs and the MLD receiving them do not operate in an STR link pair (i.e., at least one MLD operates in an NSTR link pair), when a high-priority frame is included, end time alignment may not be performed.

[0231] According to an embodiment of the present invention, the fact that end time alignment is not performed when the MLD transmits a plurality of PPDUs and the transmitted PPDU includes a high-priority frame may be limited to the case where the PPDU including the high-priority frame starts to be transmitted earlier than the PPDU not including the high-priority frame.

[0232] Referring to FIG. 19, there is an AP MLD to which AP1 and AP2 belong. Also, there is a non-AP MLD to which STA1 and STA2 belong. The AP MLD and the non-AP MLD may be multi-link setup with Link 1 and Link 2. Also, Link 1 and Link 2 may be NSTR link pairs for the non-AP MLD. AP1 and STA1 can operate on Link 1, and AP2 and STA2 can operate on Link 2. The AP MLD can transmit multiple PPDUs. The time of the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may overlap. Also, the PPDU transmitted by AP1 may not include high-priority frames. The PPDU transmitted by AP2 may include high-priority frames. Also, the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may be start time synced, or the PPDU transmitted by AP2 may start earlier than the PPDU transmitted by AP1. In such a case, it is not necessary to perform end time alignment on the PPDU transmitted by AP1 and the PPDU transmitted by AP2. Referring to FIG. 19, the PPDU transmitted by AP2 ends later than the PPDU transmitted by AP1. If the PPDU transmitted by AP1 and the PPDU transmitted by AP2 are end time aligned, AP2 may have to end the PPDU without being able to transmit all the high-priority frames it intends to transmit in one PPDU. Therefore, by not performing end time alignment on the PPDU including high-priority frames, it is possible to transmit high-priority frames faster.

[0233] Also, in the embodiment of FIG. 19, the frame transmitted by AP1 may require an immediate response. The frame transmitted by AP2 may require an immediate response.

[0234] However, in the embodiment of FIG. 19, when STA1 responds to the frame transmitted by AP1, it may interfere with the reception of high-priority frames.

[0235] Therefore, according to the embodiments of the present invention, when the STA of the MLD has received high-priority frames on other links, it does not have to respond even if it is required to send an immediate response. In the embodiment of FIG. 19, since STA2 has received high-priority frames, STA1 does not have to send the immediate response requested by the frame sent by AP1.

[0236] Also, according to the embodiments of the present invention, when the MLD receives a frame on an NSTR link pair and the frame requests an immediate response, it does not have to respond if the response to the frame interferes with reception on other links. However, according to the embodiments of the present invention, this may be limited to the case where the frame is not a high-priority frame. That is, when the MLD receives a frame on an NSTR link pair and the frame requests an immediate response, it may sometimes have to respond even if the response to the frame interferes with reception on other links.

[0237] FIG. 20 shows still another example of end time alignment of high-priority frames according to an embodiment of the present invention.

[0238] This embodiment may be related to the end time alignment or the end time of the PPDU, the transmitting MLD or the receiving MLD operating on an NSTR link pair, the PPDU including a frame that requests an immediate response, the PPDU including a QoS Data frame, the PPDU including a QoS Data frame that requests an immediate response, the STA of the same MLD transmitting a plurality of PPDUs, the STA of the same MLD receiving a plurality of PPDUs, etc. Related conditions such as these may be omitted from mention. The embodiments to be described may be made when such conditions are satisfied.

[0239] Referring to FIG. 20, there is an AP MLD to which AP1 and AP2 belong. Also, there is a non-AP MLD to which STA1 and STA2 belong. The AP MLD and the non-AP MLD may be set up with a multiple link set using Link 1 and Link 2. Also, for the non-AP MLD, Link 1 and Link 2 may be an NSTR link pair. AP1 and STA1 can operate on Link 1, and AP2 and STA2 can operate on Link 2. The AP MLD can transmit a plurality of PPDUs. The times of the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may overlap. Also, the PPDU transmitted by AP1 may include high-priority frames. The PPDU transmitted by AP2 may not include high-priority frames. Also, the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may be start time synced, or the PPDU transmitted by AP1 may start earlier than the PPDU transmitted by AP2.

[0240] Case 1 and Case 2 shown in FIGS. 20(a) and 20(b) may be embodiments that do not perform end time alignment.

[0241] In Case 1, the PPDU transmitted by AP2 ends after the PPDU transmitted by AP1. In such a case, high-priority frames are not obstructed from being received due to in-device interference. However, the response to the PPDU containing high-priority frames may obstruct the reception of the PPDU not containing high-priority frames.

[0242] In Case 2, the PPDU transmitted by AP2 ends before the PPDU transmitted by AP1. In such a case, when the PPDU transmitted by AP2 requires an immediate response and when STA2 transmits a response, the transmission of STA2 may obstruct the reception of high-priority frames on Link 1. For this reason, high-priority frames may not be able to successfully be received quickly.

[0243] Case 3 shown in FIG. 20(c) may be an example where end time alignment is performed. Therefore, when receiving a PPDU including a high-priority frame, it is not affected by in-device interference. The problem of interference with the reception of a high-priority frame as in Case 2 can be solved.

[0244] According to an embodiment of the present invention, even when transmitting a plurality of PPDUs including high-priority frames, it is possible to determine whether to perform end time alignment based on the already set conditions (Case 3). More specifically, even when transmitting a plurality of PPDUs including high-priority frames, it is possible to perform end time alignment under the already set conditions (Case 3). At this time, at least one PPDU may be a case including a high-priority frame. The already set conditions may include a case where one PPDU includes a high-priority frame and the other PPDUs do not include a high-priority frame. The already set conditions may include a case where a PPDU including a high-priority frame starts being transmitted earlier or simultaneously with a PPDU not including a high-priority frame. Further, the already set conditions may include a case where a frame of a PPDU not including a high-priority frame requests an immediate response.

[0245] Furthermore, it is possible to determine whether to perform end time alignment by combining the mentioned already set conditions. For example, when transmitting PPDU 1 including a high-priority frame and PPDU 2 not including a high-priority frame, it is possible to perform end time alignment between PPDU 1 and PPDU 2 when PPDU 1 starts earlier than or at the same time as PPDU 2. More specifically, when transmitting PPDU 1 including a high-priority frame and PPDU 2 not including a high-priority frame, when PPDU 1 starts earlier than or at the same time as PPDU 2, if the frame included in PPDU 2 requires an immediate response, it is possible to perform end time alignment between PPDU 1 and PPDU 2. Also, when the conditions for end time alignment are not satisfied, it is not necessary to perform end time alignment.

[0246] According to another embodiment of the present invention, when transmitting a plurality of PPDUs including high-priority frames, it is also possible to determine whether to perform end time alignment or when to end the PPDU based on the already set conditions (Case 1 or Case 3). More specifically, when transmitting a plurality of PPDUs including high-priority frames, it is possible to perform end time alignment or determine the end time of one PPDU under the already set conditions (Case 1 or Case 3). More specifically, when transmitting a plurality of PPDUs including high-priority frames, it is possible to perform end time alignment under the already set conditions or to end a PPDU not including a high-priority frame after a PPDU including a high-priority frame. The already set conditions may include a case where one PPDU includes a high-priority frame and the other PPDU does not include a high-priority frame. The already set conditions may include a case where a PPDU including a high-priority frame starts being transmitted earlier or simultaneously with a PPDU not including a high-priority frame. Further, the already set conditions may include a case where the frame of a PPDU not including a high-priority frame requests an immediate response.

[0247] In addition, it is possible to determine whether to perform end time alignment by combining the mentioned already set conditions. For example, when transmitting PPDU 1 including a high-priority frame and PPDU 2 not including a high-priority frame, if PPDU 1 starts earlier than or at the same time as PPDU 2, it is possible to perform end time alignment between PPDU 1 and PPDU 2, or for PPDU 2 to end after PPDU 1. More specifically, when transmitting PPDU 1 including a high-priority frame and PPDU 2 not including a high-priority frame, if PPDU 1 starts earlier than or at the same time as PPDU 2, and if the frame included in PPDU 2 requires an immediate response, it is possible to perform end time alignment between PPDU 1 and PPDU 2, or for PPDU 2 to end after PPDU 1. Also, when the condition for performing end time alignment or for one PPDU to end after another PPDU is not satisfied, there may be no constraint on the transmission end time. Or, when the condition for performing end time alignment or for one PPDU to end after another PPDU is not satisfied, end time alignment may always be performed.

[0248] FIG. 21 shows still other examples of end time alignment of high-priority frames according to an embodiment of the present invention.

[0249] In the embodiment of FIG. 21, the content described in FIG. 20 etc. may be omitted from mention. This embodiment may be related to end time alignment or the end time of the PPDU, and related conditions such as the transmitting MLD or receiving MLD operating on the NSTR link pair, the PPDU including a frame that requires an immediate response, the PPDU including a QoS Data frame, the PPDU including a QoS Data frame that requires an immediate response, the same MLD's STA transmitting a plurality of PPDUs, the same MLD's STA receiving a plurality of PPDUs, etc. may be omitted from mention. The described embodiment may be performed when such conditions are satisfied.

[0250] According to an embodiment of the present invention, when transmitting a plurality of PPDUs including high-priority frames, it is possible to determine whether to perform end time alignment or when to end the PPDU based on whether at least two PPDUs include high-priority frames. Or, when transmitting a plurality of PPDUs including high-priority frames, it is possible to determine whether to perform end time alignment based on whether at least two PPDUs include high-priority frames.

[0251] According to an embodiment, when two or more of the PPDUs transmitted by the MLD when transmitting a plurality of PPDUs include high-priority frames, there may be no constraint on the PPDU end time. For example, in such a case, even when the conditions for executing the constraints on the PPDU end time including the aforementioned end time alignment are satisfied, there may be no constraint on the PPDU end time. For example, when an MLD transmits a PPDU including a frame (e.g., a QoS Data frame) that requests an immediate response from an STA belonging to the same MLD, even if these STAs operate in an NSTR link pair, it is not necessary to perform end time alignment on the transmitted PPDU. This is because, in order to perform end time alignment, redundancy such as padding may have to be included in the PPDU, and thus the time point when the reception of the PPDU frame including the redundancy is completed may be delayed. Also, when end time alignment is not performed, reception of any one of the PPDUs may be disturbed by in-device interference. Therefore, it is possible for the transmitting MLD to determine whether to apply the constraint on the end time of the PPDU. Or, it may be possible for the receiving MLD to make a recommendation regarding the constraint on the end time of the PPDU.

[0252] According to still other embodiments, when the MLD transmits a plurality of PPDUs, if two or more of the transmitted PPDUs include high-priority frames, it is possible to perform end time alignment for the plurality of PPDUs. For example, when the MLD transmits two PPDUs, if the two transmitted PPDUs each include a high-priority frame, it is possible to perform end time alignment for the plurality of PPDUs. This is because if end time alignment is not performed, the reception of any one of the PPDUs will be interfered with by in-device interference. Also, this embodiment can be applied only when at least two PPDUs including high-priority frames all require an immediate response. For example, when the MLD transmits two PPDUs, if the two transmitted PPDUs each include a high-priority frame and require an immediate response, it is possible to perform end time alignment for the two PPDUs.

[0253] Referring to FIG. 21, there is an AP MLD to which AP1 and AP2 belong. Also, there is a non-AP MLD to which STA1 and STA2 belong. The AP MLD and the non-AP MLD may be set up as a multi-link set with Link 1 and Link 2. Also, for the non-AP MLD, Link 1 and Link 2 may be an NSTR link pair. AP1 and STA1 can operate on Link 1, and AP2 and STA2 can operate on Link 2. The AP MLD can transmit a plurality of PPDUs. The time of the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may overlap. Also, the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may include high-priority frames. Also, the PPDU transmitted by AP1 and the PPDU transmitted by AP2 may or may not be start time synced. In such a case, the PPDU transmitted by AP1 and the PPDU transmitted by AP2 can be transmitted with end time alignment. This is because the PPDU transmitted by AP1 and the PPDU transmitted by AP2 each require an immediate response. At this time, the high-priority frame included in the PPDU transmitted by AP1 may be one that requires an immediate response. Also, the high-priority frame included in the PPDU transmitted by AP2 may be one that requires an immediate response.

[0254] In the embodiments of FIGS. 19 to 21, the fact that a PPDU includes a high-priority frame can mean that the PPDU includes at least one high-priority frame. Also, the fact that a PPDU does not include a high-priority frame can mean that the PPDU does not include any high-priority frames.

[0255] FIG. 22 is a diagram showing an example of a medium access recovery procedure according to an embodiment of the present invention.

[0256] According to an embodiment of the present invention, the multi-link device (MLD) may be restricted from simultaneously transmitting and receiving on multiple links. The restriction may be an inevitable thing. Also, simultaneously transmitting and receiving may include at least transmitting on one link and receiving on at least one other link at the same time (at the same point in time). Also, whether the MLD is restricted from simultaneously transmitting and receiving on multiple links may be based on the capability of the MLD and each link. That is, there may be an MLD that is restricted from simultaneously transmitting and receiving on multiple links, or there may be an MLD that is not restricted. Also, when the MLD operates in a certain link set, the MLD may be restricted from simultaneously transmitting and receiving on multiple links, and when the MLD operates in a link set different from the certain link set, the MLD may not be restricted from simultaneously transmitting and receiving on multiple links. Also, when it is possible to simultaneously transmit / receive on multiple links, this can be called simultaneous transmit (transmission) and receive (reception) (STR). When STR is restricted, it can be called non-STR or NSTR.

[0257] That is, when each of the STAs included in the same MLD can simultaneously transmit / receive on each of multiple links, this can be called STR, and a pair of links capable of such STR operation can be called an STR link pair. However, when each of the STAs included in the same MLD performs transmit / receive operations on each link, if transmission / reception on other links becomes impossible due to interference in the transmit / receive operations, this can be called NSTR, and a pair of links for such NSTR operation can be called an NSTR link pair.

[0258] What is not restricted by STR can be called STR. Also, for a certain MLD, a link pair where STR is restricted or not restricted can be called an STR link pair or an NSTR link pair, respectively. Also, an MLD where STR is restricted or not restricted can be called an STR MLD or an NSTR MLD, respectively. An MLD can be an NSTR MLD when at least one link pair in the operating link set is an NSTR link pair. In the embodiments of the present invention, what is described for an MLD operating with an NSTR (or STR) link pair can also be read as an embodiment described for an NSTR (or STR) MLD. Conversely, what is described for an NSTR (or STR) MLD can also be read as an embodiment described for an MLD operating with an NSTR (or STR) link pair.

[0259] The fact that STR is restricted may be because the transmission on one link of the MLD acts as interference to other links. More specifically, the fact that STR is restricted may be because the transmission on one link of the MLD acts as interference to the reception performed by the MLD on other links. Such interference can be called in-device interference. Also, as yet another embodiment, the fact that STR is restricted may be because the number of radios of the MLD is restricted. For example, an MLD operating with a single radio may have restricted STR. An MLD operating with a single radio may be able to receive or transmit on only one link at a time. Or, an MLD operating with a single radio may be able to listen or monitor on multiple links simultaneously, but may be able to receive or transmit on only one link at a time. At this time, listening or monitoring can mean receiving a PPDU or frame consisting of a previously set setting.

[0260] According to an embodiment of the present invention, end time alignment of a PPDU can be performed so that an MLD does not simultaneously transmit and receive on an NSTR link pair. According to one embodiment, MLD1 can transmit a plurality of PPDUs on a plurality of links to MLD2. At this time, when a link pair included in the plurality of links is an NSTR link pair with respect to MLD1 or MLD2, end time alignment of the PPDU transmitted on the NSTR link pair can be performed. The end time alignment of the PPDU may be to adjust the difference in the end times of the plurality of PPDUs to be equal to or less than a preset time. The preset time may be 8 us. Alternatively, when the PPDU includes a Trigger frame and a CS Required subfield (a subfield indicating whether to respond to the Trigger frame or to determine based on carrier sense (CS)) included in the Trigger frame is instructed to respond based on the CS result, the preset time may be 4 us. When the PPDU includes a Trigger frame and a CS Required subfield (a subfield indicating whether to respond to the Trigger frame or to determine based on CS) included in the Trigger frame is instructed to respond based on the CS result, other PPDUs end earlier than such a PPDU, and when these are end time aligned, the preset time may be 4 us. The MLD must ensure that the end time of one or more PPDUs carrying frames that require an immediate response is at most 4 us earlier than the end time of a certain PPDU including a Trigger frame in which the CS Required subfield is set to 1. Also, performing end time alignment of the PPDU may be limited to the case where at least one frame included in the PPDU requires an immediate response. Alternatively, performing end time alignment of the PPDU may be limited to the case where at least two frames included in the PPDU require an immediate response.It is possible to add padding to perform end time alignment.

[0261] According to an embodiment of the present invention, the MLD can perform start time sync when transmitting a PPDU over a plurality of links. The MLD may be an MLD operating on an NSTR link pair. The MLD can obtain a transmission opportunity based on a backoff procedure or a backoff counter on each link and transmit a PPDU. For example, it is possible to transmit a PPDU at a slot boundary when the backoff counter reaches 0. This may be the case when using DCF (distributed coordination function). Alternatively, it is possible to transmit a PPDU at the slot boundary next to the slot boundary when the backoff counter reaches 0. This may be the case when using EDCA (enhanced distributed channel access; EDCAF (EDCA function)). However, the MLD operating on the NSTR link pair may have a problem that when starting to transmit a PPDU on one link, it affects the other link and determines it as busy, making it difficult to transmit simultaneously with the PPDU on the other link. Therefore, according to an embodiment of the present invention, a STA whose backoff counter reaches 0 can keep the backoff counter 0 without transmitting. Also, a STA that keeps the backoff counter 0 can transmit when a STA belonging to the same MLD has its backoff counter reach 0.

[0262] According to an embodiment of the present invention, in the case where there are Link 1 and Link 2 that constitute an NSTR link pair, when transmitting on Link 1, it may be difficult to receive on Link 2 for an MLD operating on the NSTR link pair. Therefore, it may be difficult to receive duration information of a PPDU or frame transmitted from another STA on Link 2. When such a situation occurs on Link 2, the STA operating on Link 2 of the MLD operating on the NSTR link pair can be expressed as having lost medium synchronization. Or, when such a situation occurs on Link 2, the STA operating on Link 2 of the MLD operating on the NSTR link pair can be expressed as being blinded. In such a case, the STA operating on Link 2 of the MLD operating on the NSTR link pair may not be able to receive the transmitted duration information and may not perform an operation of deferring channel access that should be performed if the duration information is received. For this reason, it may interfere with the transmission and reception of other STAs.

[0263] Referring to FIG. 22, there may be an AP1 and an AP2 operating on Link 1 and Link 2 respectively, and AP1 and AP2 may belong to the same AP MLD which is an MLD. Also, there may be an STA1 and an STA2 operating on Link 1 and Link 2 respectively, and STA1 and STA2 may belong to the same non-AP MLD which is an MLD. Also, the AP MLD and the non-AP MLD may set up a multiple link set on Link 1 and Link 2. Also, the non-AP MLD may be an NSTR MLD. Or, for the non-AP MLD, Link 1 and Link 2 may be an NSTR link pair. STA1 can transmit Data 1. In such a case, transmitting Data 1 may act as an interference to STA2. Therefore, STA2 may be blinded during the period when Data 1 is transmitted.

[0264] According to an embodiment of the present invention, in order to alleviate the problem that occurs because the STA cannot receive the period information while the STA is blind, the channel access of the STA may be restricted at regular intervals. Such a certain period of time can be called MediumSyncDelay. Or, it can be said that applying MediumSyncDelay restricts the channel access at regular intervals. According to one embodiment, in order to apply MediumSyncDelay at regular intervals, the MediumSyncDelay timer can be set to a non-zero value, and MediumSyncDelay can be applied while the timer is a non-zero value. Also, the certain period of time may start when the blindness is lifted. Or, the certain period of time may start when the transmission that induced the blindness ends. Referring to FIG. 22, after the transmission of Data 1 ends, STA2 can set the MediumSyncDelay timer to a non-zero value. At this time, the MediumSyncDeley timer can be set to the MediumSyncDelay value. The channel access of STA2 may be restricted during MediumSyncDelay. For example, the STA that applies MediumSyncDelay may belong to the MLD operating in the NSTR link pair. Or, the STA that applies MediumSyncDelay may belong to the NSTR MLD. Also, the STA that applies MediumSyncDelay may belong to the non-AP MLD.

[0265] According to one embodiment, when the transmission period that induces blindness is shorter than a preset time, it may not be necessary to apply MediumSyncDelay.

[0266] According to one embodiment, the MediumSyncDelay value may have a base value. The base value may be the maximum duration of the PPDU. The maximum duration of the PPDU may be 5.484 ms. Also, the MediumSyncDelay value may be a value transmitted from a peer MLD (AP MLD) with multiple link sets up. If the non-AP MLD cannot receive the MediumSyncDelay value from the AP MLD, the base value can be used as the MediumSyncDelay value. If the non-AP MLD receives the MediumSyncDelay value from the AP MLD, the received value can be used as the MediumSyncDelay value.

[0267] When channel access is restricted when applying MediumSyncDelay, it may include the following operations. For example, the restriction of channel access may be related to the attempt to obtain a TXOP (transmit opportunity). The restriction of channel access may include that the type of the first frame to be transmitted when a TXOP is obtained is restricted. The type of the frame may be defined by the Type subfield or Subtype subfield indicated by the MAC header of the frame. For example, the type of the first frame may be an RTS (request to send) frame. The RTS frame may be a type of Control frame. Also, when it is a Control frame, the B3 and B2 bits of the Type subfield may be set to 0 and 1 respectively. Also, when it is an RTS frame, the B7, B6, B5, and B4 bits of the Subtype subfield may be set to 1, 0, 1, and 1 respectively. At this time, the bit index may be the bit index of the Frame Control field. B2 may be the LSB (least significant bit) of the Type subfield, and B3 may be the MSB (most significant bit) of the Type subfield. B4 may be the LSB of the Subtype subfield, and B7 may be the MSB of the Subtype subfield. Therefore, when the STA transmits an RTS frame as the first frame and cannot receive the corresponding CTS frame as a response, it may not continue the transmission. Thus, even if there is period information that the STA could not receive during the blind period, it does not have to greatly interfere with the transmissions of other STAs. Or, the restriction of channel access may include that the size or length of the first frame or PPDU to be transmitted when a TXOP is obtained is restricted. For example, the size or length of the first frame or PPDU may be smaller than a previously set value. Thus, even if there is period information that the STA could not receive during the blind period, it does not have to greatly interfere with the transmissions of other STAs.

[0268] Also, restricting channel access may include changing the CCA (clear channel assessment) threshold. More specifically, restricting channel access may include changing the CCA (clear channel assessment) threshold to be lower than the existing one. According to one embodiment, when a signal above (or exceeding) the CCA threshold is sensed, it can be determined that the channel is busy. Otherwise, it can be determined that the channel is idle. The CCA threshold may include a threshold for sensing a PPDU (Wi-Fi signal). The CCA using such a CCA threshold can be called CCA PD (preamble detection; packet detection), and at this time, the threshold can be called the CCA PD threshold or the PD threshold. The CCA threshold may include a threshold for sensing a certain signal. The CCA using such a CCA threshold can be called CCA ED (energy detection), and at this time, the threshold can be called the CCA ED threshold or the ED threshold. More specifically, restricting channel access can mean changing the ED threshold. When MediumSyncDelay is not applied, the PD threshold may be -82 dBm. When MediumSyncDelay is not applied, the ED threshold may be -62 dBm. When MediumSyncDelay is applied, the CCA threshold may have a basic value. Also, when MediumSyncDelay is applied, the CCA threshold may be a value transmitted from a peer MLD (AP MLD) with multiple link sets up. If a non-AP MLD fails to receive the CCA threshold from the AP MLD when MediumSyncDelay is applied, the basic value can be used as the CCA threshold when MediumSyncDelay is applied. If a non-AP MLD receives the CCA threshold from the AP MLD when MediumSyncDelay is applied, the received value can be used as the CCA threshold when MediumSyncDelay is applied. According to one embodiment, when MediumSyncDelay is applied, the basic value of the ED threshold may be -72 dBm.Also, when MediumSyncDelay is applied, the value that can be indicated as the ED threshold may be -72 dBm or higher. When MediumSyncDelay is applied, the ED threshold may be the dot11MSDOFDM ED threshold. Lowering the CCA threshold when MediumSyncDelay is applied compared to when it is not applied may be to perform channel access conservatively. This is because when using the existing CCA threshold, a signal that is determined to be idle may be determined to be busy when using a lower CCA threshold. Also, according to one embodiment, the CCA threshold referred to in the present invention may be a threshold corresponding to a 20 MHz subchannel.

[0269] Also, restricting channel access may include restricting the number of transmission attempts during MediumSyncDelay. For example, the STA may not need to make transmission attempts exceeding a certain number during MediumSyncDelay. That is, if the STA has a certain number of transmission failures during MediumSyncDelay, it may not need to make further transmission attempts during MediumSyncDelay. Such a certain number may be MSD_TXOP_MAX. A backoff procedure can be invoked to avoid making transmission attempts. Or, the backoff counter can be reset to avoid making transmission attempts. According to one embodiment, at this time, the contention window (CW) may be left unchanged. The CW may be a value used when resetting the backoff counter. For example, when resetting the backoff counter, an integer randomly selected from the range of 0 to the CW value may be used as the value to reset. Also, when resetting the backoff counter to avoid making transmission attempts, the retry counter may not need to be changed. If the retry counter has reached a preset value, it is possible not to make further transmission attempts for the frame for which transmission was being attempted, or to discard the frame for which transmission was being attempted. According to one embodiment, the MSD_TXOP_MAX value may have a base value. The base value may be 1. Also, the MediumSyncDelay value may be a value transmitted from a peer MLD (AP MLD) with multiple link sets up. If the non-AP MLD cannot receive the MSD_TXOP_MAX value from the AP MLD, the base value can be used as the MSD_TXOP_MAX value. If the non-AP MLD receives the MSD_TXOP_MAX value from the AP MLD, the received value can be used as the MSD_TXOP_MAX value.

[0270] FIG. 23 is a diagram showing an example of signaling related to a Multi-Link element and MediumSyncDelay according to one embodiment of the present invention.

[0271] Referring to FIG. 23, the STA of the MLD Media Information relating to the synchronization delay may be included and transmitted.

[0272] Specifically, there may be a multi-link element as shown in Fig. 23. Based on a frame including the multi-link element, multi-link discovery, setup, and operation can be performed. For example, the multi-link element may be included in a Beacon frame, a Probe Request frame, a Probe Response frame, an Authentication frame, an Association Request frame, an Association Response frame, a Reassociation Request frame, a Reassociation Response frame, etc.

[0273] The multi-link element may include an Element ID, Length, Element ID Extension, Multi-Link Control, Common Info, and Link Info fields. The Element ID or Element ID Extension can indicate what kind of element the emerald containing the Element ID or the Element ID Extension is, i.e., whether it is a multi-link element. The Length field can indicate the length of the element containing the Length field. The Multi-Link Control field may include a Type sub-field and a Presence Bitmap field. The Type sub-field can indicate the type of the multi-link element. Also, based on the type of the multi-link element, the format of the multi-link element may be determined. The Presence Bitmap field can indicate whether sub-fields that may be included in the multi-link element are included. For example, the Presence Bitmap field can indicate whether sub-fields that may be included in the Common Info field included in the multi-link element are included. The sub-fields in the Presence Bitmap field indicating whether they are included may include MLD MAC address, Link ID Info, BSS Parameters Change Count, Medium Synchronization Delay Information, EML Capabilities, and MLD Capabilities fields (sub-fields). Also, the Medium Synchronization Delay Information field may include information related to MediumSyncDelay.

[0274] The Common Info field may include information regarding multiple links or all links. The Common Info field may include information that is commonly required or identical for multiple links or all links. The Link Info field may include information for each respective link.

[0275] According to one embodiment, information related to MediumSyncDelay may have a base value. Also, information related to MediumSyncDelay may be signaled. For example, the Medium Synchronization Delay Information field shown in FIG. 23 may include information related to MediumSyncDelay. The MLD can initialize information related to MediumSyncDelay as a base value. Also, when the MLD (non-AP MLD) cannot receive information related to MediumSyncDelay from the peer MLD (AP MLD), the base value can be used as the information related to MediumSyncDelay. When the MLD (non-AP MLD) receives information related to MediumSyncDelay from the peer MLD (AP MLD), the received value can be used as the information related to MediumSyncDelay.

[0276] The Medium Synchronization Delay Information field may include a Medium Synchronization Duration subfield, a Medium Synchronization OFDM ED Threshold subfield, and a Medium Synchronization Maximum Number Of TXOPs subfield.

[0277] The Medium Synchronization Duration subfield can indicate MediumSyncDelay. That is, the Medium Synchronization Duration subfield can indicate the value for setting the MediumSyncDelay timer. For example, the Medium Synchronization Duration subfield may be 8 bits. Also, the Medium Synchronization Duration subfield can indicate a duration in units of 32 us. That is, when the Medium Synchronization Duration subfield is set to A, the time indicated by the Medium Synchronization Duration subfield may be A * 32 us.

[0278] The Medium Synchronization OFDM ED Threshold subfield can indicate the CCA threshold when MediumSyncDelay is applied. More specifically, at this time, the CCA threshold to be indicated may be the CCA ED threshold. That is, the Medium Synchronization OFDM ED Threshold subfield can indicate the dot11MSDOFDMED threshold. The Medium Synchronization OFDM ED Threshold subfield may be 4 bits. The CCA threshold indicated by the Medium Synchronization OFDM ED Threshold subfield is the value obtained by adding -72 to the Medium Synchronization OFDM ED Threshold subfield value, and its unit may be dBm. Therefore, when the Medium Synchronization OFDM ED Threshold subfield has a value of 0 or more, the CCA threshold indicated may be a value of -72 dBm or more. Also, the maximum CCA threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may be -62 dBm. In this case, the Medium Synchronization OFDM ED Threshold subfield may be set to values from 0 to 10. At this time, values from 11 to 15 may be reserved. That is, when the Medium Synchronization OFDM ED Threshold subfield value is from 0 to 10, CCA thresholds of -72 dBm to -62 dBm can be indicated respectively.

[0279] The Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX. That is, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate the maximum number of transmission attempts while the MediumSyncDelay is applied. The Medium Synchronization Maximum Number Of TXOPs subfield may be 4 bits. According to one embodiment, the Medium Synchronization Maximum Number Of TXOPs subfield value may be the MSD_TXOP_MAX value. According to other embodiments, the Medium Synchronization Maximum Number Of TXOPs subfield value may be the (MSD_TXOP_MAX + 1) value. According to other embodiments, the Medium Synchronization Maximum Number Of TXOPs subfield value may be the (MSD_TXOP_MAX - 1) value. Also, this may be limited when the Medium Synchronization Maximum Number Of TXOPs subfield value is not set to the maximum value. If the Medium Synchronization Maximum Number Of TXOPs subfield value is set to the maximum value (15 when it is 4 bits), it may indicate that there is no limit to the number of transmission attempts.

[0280] FIG. 24 is a diagram showing an example of a MediumSyncDelay timer reset operation according to an embodiment of the present invention.

[0281] Referring to FIG. 24, in the NSTR link pair included in the same MLD, if transmission is performed on one link, transmission / reception is not possible on the other link, and after transmission is completed, transmission / reception is possible after the media link delay is applied.

[0282] Specifically, there may be a method to prevent a STA to which MediumSyncDelay is applied from applying MediumSyncDelay additionally. For example, since there may be period information, a frame, or a PPDU that could not be received while a STA belonging to an MLD operating on an NSTR link was blinded, MediumSyncDelay was applied. However, in reality, there may be nothing that could not be received while blinded. Even in such a case, it may be a method to reduce the problem that channel access is restricted by applying MediumSyncDelay.

[0283] According to an embodiment, when a STA to which MediumSyncDelay is applied receives valid period information during MediumSyncDelay, the MediumSyncDelay timer can be reset (or set) to 0. In an embodiment of the present invention, a STA to which MediumSyncDelay is applied may have the same meaning as a STA whose MediumSyncDelay timer is not a value of 0. Also, for a STA or an MLD to apply MediumSyncDelay may have the same meaning as setting the MediumSyncDelay timer to a value other than 0. Also, resetting the MediumSyncDelay timer to 0 may have the same meaning as ending the application of MediumSyncDelay.

[0284] According to an embodiment of the present invention, the period information may be included in a frame. More specifically, the period information may be included in a MAC header included in the frame. More specifically, the period information may be included in a Duration / ID field included in the MAC header. Therefore, when a STA to which MediumSyncDelay is applied receives a valid frame or MPDU during MediumSyncDelay, the MediumSyncDelay timer can be reset to 0. In the present invention, a frame, an MPDU, a MAC header, a Duration / ID field, and period information may be used interchangeably.

[0285] Also, the period information may be included in the PPDU. More specifically, the period information may be included in the preamble included in the PPDU. More specifically, the period information may be included in the TXOP field included in the preamble. Also, the TXOP field may be included in the HE-SIG-A field included in the HE PPDU. Also, the TXOP field may be included in the U-SIG field included in the EHT PPDU or a PPDU of a future standard beyond EHT. When the STA receives the PPDU or the TXOP field, the RXVECTOR parameter TXOP_DURATION may be set based on the TXOP field value. The RXVECTOR parameter may be a parameter transmitted from the PHY of the STA to the MAC. Therefore, the period information may include the RXVECTOR parameter TXOP_DURATION. Also, the TXOP field or the RXVECTOR parameter TXOP_DURATION may be set to UNSPECIFIED in some cases. When the TXOP field or the RXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED, this may mean that there is no period information. When the TXOP field or the RXVECTOR parameter TXOP_DURATION is set to a value other than UNSPECIFIED, this may mean that there is period information. Therefore, when a STA to which MediumSyncDelay is applied receives a PPDU corresponding to the RXVECTOR parameter TXOP_DURATION having a value other than UNSPECIFIED during the MediumSyncDelay, the MediumSyncDelay timer can be reset to 0.

[0286] That is, in short, when a STA having a non-zero MediumSyncDelay timer receives a valid frame (or, valid MPDU) or an RXVECTOR parameter TXOP_DURATION with a value other than UNSPECIFIED, the MediumSyncDelay timer can be reset to 0.

[0287] However, according to an embodiment of the present invention, there may be a plurality of STAs with a non-zero MediumSyncDelay timer at a certain point in time. Referring to FIG. 24, Link 1 and Link 2 can form a multi-link. Also, an AP1 operating on Link 1 can transmit a trigger frame. The trigger frame can solicit responses from a plurality of STAs. Also, for each of the plurality of STAs, Link 1 and Link 2 may be an NSTR link pair. That is, when STA1, which is one of the plurality of STAs, transmits on Link 1, it may act as interference to STA2 belonging to the same MLD as STA1. Therefore, while the plurality of STAs are transmitting on Link 1, STAs belonging to the same MLD as each of the plurality of STAs may be in a blind state, and when the blindness ends, the MediumSyncDelay timer can be set to a non-zero value. That is, while a plurality of TB PPDUs are being transmitted as a response to the trigger frame, a plurality of STAs operating on Link 2 may be blind, and after the TB PPDU transmission ends, the plurality of STAs can set the MediumSyncDelay timer to a non-zero value.

[0288] Also, as yet another embodiment, while STA1 on Link 1 applies MediumSyncDelay, when STA2 on Link 1 starts to apply MediumSyncDelay, there may be a plurality of STAs with a non-zero MediumSyncDelay timer at a certain point in time.

[0289] However, according to the above-described embodiments, it is possible for the STA to transmit an RTS frame as the first frame while applying the MediumSyncDelay. Referring to FIG. 24, when the STA2 of Link 2 transmits an RTS frame as the first frame during the MediumSyncDelay, other STAs that were applying the MediumSyncDelay may have successfully received the RTS frame. In such a case, the other STAs may be able to reset the MediumSyncDelay timer. However, the CTS frame, which is a response to the RTS frame, may not be transmitted. In such a case, although there is period information that the STA of Link 2 could not actually receive, a situation may occur where the application of the MediumSyncDelay ends. Therefore, it becomes highly likely that the STA that has ended the application of the MediumSyncDelay will interfere with the reception of the frames that have already been transmitted.

[0290] Hereinafter, a method for restricting the type of frame for resetting the timer for applying the MediumSyncDelay to solve such a problem will be described.

[0291] FIG. 25 is a diagram showing an example of the MediumSyncDelay timer reset operation according to an embodiment of the present invention.

[0292] In FIG. 25, Media the STA to which the synchronization delay is applied can operate the synchronization delay timer after the blind interval ends, Media for the application of the synchronization delay Media and the synchronization delay timer can be reset to "0" when a valid PPDU other than a specific frame is received. Media

[0293] Specifically, when MediumSyncDelay is applied by transmission / reception on other links, the STA of the link to which MediumSyncDelay is applied can set the MediumSyncDelay timer to a non-zero value and operate it. At this time, the MediumSyncDelay timer may start when the transmission of other links ends. However, when MLD is in the EMLSR mode operating on a single radio, the MediumSyncDelay timer may start immediately after a specific delay. For example, the MediumSyncDelay timer may start immediately after the delay time for link switching or after returning to the listening operation.

[0294] Thereafter, when the STA of the link to which MediumSyncDelay is applied receives a PPDU for a valid frame or a valid MPDU, if the MediumSyncDelay timer is not "0", the MediumSyncDelay timer can be reset to "0". Or, when receiving a PPDU whose TXOP_Duration as the received parameter (RXVECTOR parameter) is a value other than an unspecified value, if the MediumSyncDelay timer is not "0", the MediumSyncDelay timer can be reset to "0". At this time, the valid frame may be a frame other than the RTS frame.

[0295] At this time, the valid frame may be a frame transmitted by another AP or non-AP STA that is not the STA that generated MediumSyncDelay. The valid frame transmitted by the AP includes the RTS frame, but the valid frame transmitted by the non-AP STA may be a frame other than the RTS frame.

[0296] For example, when the transmission / reception of one or more STAs at the second link, which is an NSTR link pair, is restricted by the PPDU transmitted at the first link, and the MediumSyncDelay timer operates and MediumSyncDelay is applied to one or more STAs when the transmission of the PPDU ends, one or more STAs at the second link can reset the MediumSyncDelay timer when receiving a valid frame. That is, one or more STAs to which a specific frequency band is allocated can reset the MediumSyncDelay timer when receiving a PPDU for a valid MPDU other than an RTS frame transmitted at 20 MHz of the same BSS or different BSSs. At this time, even when the PPDU or frame is transmitted from an associated AP or an AP included in the same multiple BSSID set and the received PPDU or frame is an RTS frame, one or more STAs can reset the MediumSyncDelay timer.

[0297] That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), it may be determined whether the operation of resetting the MediumSyncDelay timer to 0 is allowed based on whether this is a type of frame allowed as the first frame during MediumSyncDelay. According to an embodiment of the present invention, even when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), if this is a type of frame allowed as the first frame during MediumSyncDelay, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed. That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), if this is not a type of frame allowed as the first frame during MediumSyncDelay, the operation of resetting the MediumSyncDelay timer to 0 may be allowed. According to the above-described embodiment, the type of frame allowed as the first frame during MediumSyncDelay may be an RTS frame.

[0298] Therefore, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), it may be determined whether the operation of resetting the MediumSyncDelay timer to 0 is allowed based on whether this is an RTS frame. For example, when a STA with a non-zero MediumSyncDelay timer receives an RTS frame, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed. Also, when a STA with a non-zero MediumSyncDelay timer receives a frame that is not an RTS frame, the operation of resetting the MediumSyncDelay timer to 0 may be allowed.

[0299] Referring to FIG. 25, multiple STAs operating on Link 2 may apply MediumSyncDelay. Also, STA2 of Link 2 applying MediumSyncDelay can obtain a TXOP and transmit an RTS frame as the first frame. Further, the multiple STAs can successfully receive the RTS frame. That is, the multiple STAs can successfully receive the duration information from the RTS frame. However, since the received frame is an RTS frame, the multiple STAs do not need to reset the MediumSyncDelay timer. Therefore, when the response to the RTS frame does not continue, the multiple STAs can protect the channel of Link 2 or the transmission on Link 2 by maintaining the application of MediumSyncDelay. If a response to the RTS frame is transmitted, a CTS frame may be transmitted as the response to the RTS frame. Also, subsequently STA2 can transmit a frame (Subsequent frame in the figure). In this case, the multiple STAs can reset the MediumSyncDelay timer based on the CTS frame or the subsequent frame without resetting the MediumSyncDelay timer based on the RTS frame. Therefore, it is possible to prevent the unnecessary application of MediumSyncDelay.

[0300] Also, according to an embodiment of the present invention, even if a STA with a non-zero MediumSyncDelay timer receives a valid frame, it may not be allowed to reset the MediumSyncDelay timer if this is a PS-Poll frame. This may be because the PS-Poll frame does not contain duration information. That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame that is not a PS-Poll frame, it may be allowed to reset the MediumSyncDelay timer.

[0301] Also, according to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer receives a PPDU or receives a valid frame or RXVECTOR parameter TXOP_DURATION, it may be determined whether it is allowed to reset the MediumSyncDelay timer based on whether it is intra-BSS or inter-BSS. The STA can determine whether the received frame (or PPDU) is an intra-BSS frame (or PPDU) or an inter-BSS frame (or PPDU) based on the MAC address field included in the received frame or the BSS color field included in the PPDU including the received frame. For example, the STA can determine the received frame as an intra-BSS frame when the MAC address field included in the received frame or the BSS color field included in the PPDU including the received frame is set to a value corresponding to the STA. Also, the STA can determine the received frame as an inter-BSS frame when the MAC address field included in the received frame or the BSS color field included in the PPDU including the received frame is not set to a value corresponding to the STA.

[0302] Also, according to an embodiment of the present invention, whether it is allowed to reset the MediumSyncDelay timer may be determined based on whether a frame or PPDU received by a STA with a non-zero MediumSyncDelay timer is sent by an associated AP (or an AP included in the same multi-BSSID set as the associated AP). For example, when a frame or PPDU received by a STA with a non-zero MediumSyncDelay timer is sent by an associated AP (or an AP included in the same multi-BSSID set as the associated AP), it may be allowed to reset the MediumSyncDelay timer. Also, when a frame or PPDU received by a STA with a non-zero MediumSyncDelay timer is not sent by an associated AP (or an AP included in the same multi-BSSID set as the associated AP), it may not be allowed to reset the MediumSyncDelay timer. This may be because the AP is likely to know well the channel situation of the link.

[0303] Based on the MAC address field included in the MAC header included in the received frame, it can be determined whether the frame is sent by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). For example, based on the TA (transmitter address) field included in the received frame, it can be determined whether the frame is sent by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). For example, when the TA (transmitter address) field included in the received frame is set to the address of the associated AP (or an AP included in the same multi-BSSID set as the associated AP), it may be sent by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). Also, when the TA (transmitter address) field included in the received frame is neither the address of the associated AP nor the address of an AP included in the same multi-BSSID set as the associated AP, it may not be sent by the associated AP nor by an AP included in the same multi-BSSID set as the associated AP. In this embodiment, the AP address may be rephrased as the BSSID.

[0304] Based on the MAC address field included in the MAC header included in the received frame, it can be determined whether the frame was sent to the associated AP (or an AP included in the same multi-BSSID set as the associated AP). For example, based on the RA (receiver or recipient address) field included in the received frame, it can be determined whether the frame was sent to the associated AP (or an AP included in the same multi-BSSID set as the associated AP). For example, when the RA field included in the received frame is set to the address of the associated AP (or an AP included in the same multi-BSSID set as the associated AP), it may have been sent to the associated AP (or an AP included in the same multi-BSSID set as the associated AP). Also, when the RA field included in the received frame is neither the associated AP address nor the address of an AP included in the same multi-BSSID set as the associated AP, it may not have been sent to the associated AP and may not have been sent to an AP included in the same multi-BSSID set as the associated AP. In this embodiment, the AP address may be rephrased as the BSSID.

[0305] Based on the MAC address field included in the MAC header included in the received frame, it can be determined whether the frame is sent from an inter-BSS. For example, based on the RA or TA or BSSID field included in the received frame, it can be determined whether the frame is sent from an inter-BSS. For example, when all of the RA field, TA field, and BSSID field (only included in the condition if each field exists) included in the received frame are set to values that are not the addresses of the combined APs (or APs included in the same multi-BSSID set as the combined APs), it may be sent from an inter-BSS. Also, when at least one of the RA field, TA field, or BSSID field (only included in the condition if each field exists) included in the received frame is set to the address value of the combined AP (or an AP included in the same multi-BSSID set as the combined APs), it may be sent from an intra-BSS. In this embodiment, the AP address may be rephrased as the BSSID.

[0306] The BSS color included in the preamble of the received PPDU is the same as the BSS color corresponding to the BSS of the received STA. When the preamble indicates that the preamble is a downlink, the received PPDU may be sent by the combined AP (or an AP included in the same multi-BSSID set as the combined APs). Otherwise, the received PPDU may not be sent by the combined AP nor by an AP included in the same multi-BSSID set as the combined APs.

[0307] Multiple BSSIDs may be a plurality of BSSIDs indicated by a single Beacon frame or a single Probe Response frame. At this time, it may not use a plurality of Beacon frames or a plurality of Probe Response frames corresponding to each of the plurality of BSSIDs. Also, a single TIM element included in a single Beacon frame or a single TIM frame can be used to indicate buffered frames corresponding to a plurality of BSSIDs. For example, a single Beacon frame or a single Probe Response frame may be transmitted, and such a frame may include a Multiple BSSID element. The Multiple BSSID element can indicate a plurality of BSSs or a plurality of BSSIDs. Also, the BSSID that transmitted the single Beacon frame or the single Probe Response frame can be called the transmitted BSSID. A BSSID other than the transmitted BSSID among the BSSIDs indicated by the Multiple BSSID element can be called the nontransmitted BSSID. The nontransmitted BSSID does not have to transmit a Beacon frame or a Probe Response frame. A set of BSSIDs indicated by one Multiple BSSID element can be called a multiple BSSID set. Or, the set of the transmitted BSSID and the nontransmitted BSSID described can be called a multiple BSSID set. The maximum possible number of BSSIDs as the multiple BSSID set may be 2^n. At this time, n may be a value signaled by the Multiple BSSID element. For example, n may be a value indicated by a MaxBSSID Indicator included in the Multiple BSSID element. An STA that receives a Multiple BSSID element can know the address or BSSID of the AP included in the multiple BSSID set from the received Multiple BSSID element.

[0308] In an embodiment of the present invention, it is possible to use in combination the above-described conditions under which reset is allowed or not allowed. According to one embodiment, it may be considered together whether the received frame is a type of frame (RTS frame) that is allowed as the first frame during MediumSyncDelay, and whether the transmitter or receiver of the frame is an associated AP (or an AP included in the same multi-BSSID set as the associated AP).

[0309] For example, even if a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may not be allowed when 1) this is not a type of frame that is allowed as the first frame during MediumSyncDelay, and 2) it is not a frame transmitted by an associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may be allowed when 1) this is not a type of frame that is allowed as the first frame during MediumSyncDelay, or 2) it is a frame transmitted by an associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, the operation of resetting the MediumSyncDelay timer to 0 may be allowed when receiving a type of frame that is allowed as the first frame during MediumSyncDelay transmitted by an associated AP (or an AP included in the same multi-BSSID set as the associated AP). Also, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed when receiving a type of frame that is allowed as the first frame during MediumSyncDelay transmitted to an associated AP (or an AP included in the same multi-BSSID set as the associated AP) or transmitted from inter-BSS.

[0310] According to the foregoing embodiments, the type of frame that may be allowed as the first frame during MediumSyncDelay may be an RTS frame. Therefore, even if a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 is not necessarily allowed when 1) this is not an RTS frame and 2) it is not a frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may be allowed when 1) this is not an RTS frame or 2) it is a frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, the operation of resetting the MediumSyncDelay timer to 0 may be allowed when an RTS frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP) is received. Also, the operation of resetting the MediumSyncDelay timer to 0 is not necessarily allowed when an RTS frame transmitted to the associated AP (or an AP included in the same multi-BSSID set as the associated AP) or received from inter-BSS is received.

[0311] According to another embodiment, even when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may not be allowed if 1) this is a type of frame that is allowed as the first frame during MediumSyncDelay, and 2) it is a frame to be transmitted to the associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may be allowed if 1) this is not a type of frame that is allowed as the first frame during MediumSyncDelay, or 2) it is not a frame to be transmitted to the associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, the operation of resetting the MediumSyncDelay timer to 0 may be allowed when receiving a type of frame that is allowed as the first frame during MediumSyncDelay and is transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP) or transmitted from inter-BSS. Also, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed when receiving a type of frame that is allowed as the first frame during MediumSyncDelay and is transmitted to the associated AP (or an AP included in the same multi-BSSID set as the associated AP).

[0312] According to the foregoing embodiments, the type of frame that may be allowed as the first frame during MediumSyncDelay may be an RTS frame. Therefore, even when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may not be allowed if 1) this is not an RTS frame and 2) it is not a frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may be allowed if 1) this is not an RTS frame or 2) it is a frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP). That is, the operation of resetting the MediumSyncDelay timer to 0 may be allowed when an RTS frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP) is received. That is, the operation of resetting the MediumSyncDelay timer to 0 may be allowed when an RTS frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP) or an RTS frame transmitted from inter-BSS is received. Also, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed when an RTS frame transmitted to the associated AP (or an AP included in the same multi-BSSID set as the associated AP) is received.

[0313] FIG. 26 is a diagram showing an example of Medium Synchronization OFDM ED Threshold subfield encoding according to an embodiment of the present invention.

[0314] As described with reference to FIGS. 21 to 25, the CCA threshold value changed during MediumSyncDelay can be used. Also, at this time, there is a basic value of the changed CCA threshold value, and it is possible to signal the changed CCA threshold value. Further, it is possible to signal the changed CCA threshold value using the Medium Synchronization OFDM ED Threshold subfield described above. In the embodiments of the present invention, the above-described content may be omitted.

[0315] According to an embodiment of the present invention, when MediumSyncDelay is not applied, the CCA ED threshold value may be -62 dBm. However, depending on the regulation, it is possible to use a CCA ED threshold value lower than -62 dBm. For example, it is possible to use a CCA ED threshold value of -72 dBm in a specific region such as Europe. However, since the CCA threshold value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield described in FIG. 23 is -72 dBm or higher, it may be difficult to achieve restricting channel access using a lower CCA threshold value when MediumSyncDelay is applied compared to when it is not. The embodiment of FIG. 26 may be a method for solving such a problem.

[0316] According to an embodiment of the present invention, the minimum value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield may be a value smaller than -72 dBm. For example, the minimum value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield may be -82 dBm. Or, the minimum value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield may be -77 dBm.

[0317] Also, the maximum value that the Medium Synchronization OFDM ED Threshold subfield can indicate may be -62 dBm. Or, the maximum value that the Medium Synchronization OFDM ED Threshold subfield can indicate may be -72 dBm.

[0318] Also, according to an embodiment of the present invention, the basic value of the dot11MSDOFDMED threshold may be a value smaller than -72 dBm. For example, the basic value of the dot11MSDOFDMED threshold may be the same as the minimum value that the Medium Synchronization OFDM ED Threshold subfield can indicate. Or, the basic value of the dot11MSDOFDMED threshold may be -77 dBm. Or, the basic value of the dot11MSDOFDMED threshold may be -82 dBm. Or, the basic value of the dot11MSDOFDMED threshold may be -72 dBm.

[0319] In the present invention, the Medium Synchronization OFDM ED Threshold subfield value can be referred to as Fval. Also, the Medium Synchronization OFDM ED Threshold subfield may be an integer. Also, the dot11MSDOFDMED threshold may be an integer in dBm units.

[0320] According to one embodiment, the dot11MSDOFDMED threshold may be (-77 + Fval) dBm. Also, the Medium Synchronization OFDM ED Threshold subfield may be 4 bits, and Fval may be an integer in the range of 0 to 15. Therefore, the dot11MSDOFDMED thresholds indicated by Fval from 0 to 15 may be -77 to -62 dBm, respectively. That is, in such a case, the minimum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -77 dBm. Also, the maximum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -62 dBm.

[0321] According to other embodiments, the dot11MSDOFDMED threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may not be at uniform intervals. For example, when Fval <= A, the dot11MSDOFDMED threshold may be (-82 + 2 * Fval) dBm. Also, when Fval > A, the dot11MSDOFDMED threshold may be (-82 + 5 + Fval) dBm. That is, when Fval > A, the dot11MSDOFDMED threshold may be (-77 + Fval) dBm. Also, A may be 4. Thus, referring to FIG. 23, the dot11MSDOFDMED thresholds indicated by Fval 0 to 15 may be -82, -80, -78, -76, -74, -72, -71, -70, -69, -68, -67, -66, -65, -64, -63, -62 dBm, respectively. That is, in such a case, the minimum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -82 dBm. Also, the maximum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -62 dBm. In this embodiment, the size of the Medium Synchronization OFDM ED Threshold subfield may be 4 bits.

[0322] According to other embodiments, the dot11MSDOFDMED threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may not be at uniform intervals. For example, when Fval <= B, the dot11MSDOFDMED threshold may be (-82 + Fval) dBm. Also, when Fval > B, the dot11MSDOFDMED threshold may be (-92 + 2 * Fval) dBm. Also, B may be 10. Thus, the dot11MSDOFDMED thresholds indicated by Fval 0 to 15 may be -82, -81, -80, -79, -78, -77, -76, -75, -74, -73, -72, -70, -68, -66, -64, -62 dBm respectively. That is, in such a case, the minimum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -82 dBm. Also, the maximum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -62 dBm. In this embodiment, the size of the Medium Synchronization OFDM ED Threshold subfield may be 4 bits.

[0323] According to other embodiments, the dot11MSDOFDMED threshold may be (-82 + 2 * Fval) dBm. Also, the Medium Synchronization OFDM ED Threshold subfield may be 4 bits, and Fval may be an integer in the range of 0 to 15. Therefore, the dot11MSDOFDMED thresholds indicated by Fval 0 to 10 may be -82, -80, -78, -76, -74, -72, -70, -68, -66, -64, -62 dBm, respectively. In this case, Fval 11 to 15 may be reserved. That is, in such a case, the minimum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -82 dBm. Also, the maximum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -62 dBm. In this embodiment, the size of the Medium Synchronization OFDM ED Threshold subfield may be 4 bits.

[0324] The previous embodiment shows a case including where the interval of the dot11MSDOFDMED threshold indicated by the Medium Synchronization OFDM ED Threshold subfield is 2 dBm, but other intervals are also possible.

[0325] According to an embodiment of the present invention, the size of the Medium Synchronization OFDM ED Threshold subfield may be greater than 4 bits. For example, the size of the Medium Synchronization OFDM ED Threshold subfield may be 5 bits. This may be for representing a wider range of CCA thresholds than those described in FIG. 23. When the size of the Medium Synchronization OFDM ED Threshold subfield is 5 bits, possible Fval may be from 0 to 31. Also, the dot11MSDOFDMED threshold may be (-82 + Fval) dBm. Therefore, when Fval is from 0 to 20, the dot11MSDOFDMED thresholds of -82 dBm to -62 dBm can be indicated respectively. Also, at this time, the Medium Synchronization OFDM ED Threshold subfield 21 to 31 values may be reserved.

[0326] In an embodiment where the size of the Medium Synchronization OFDM ED Threshold subfield is larger than 4 bits, in order to maintain the size of the Medium Synchronization Delay Information described in FIG. 23, it may be necessary to reduce the sizes of other subfields included in the Medium Synchronization Delay Information. For example, the Medium Synchronization Duration subfield may be less than 8 bits. For example, the Medium Synchronization Duration subfield may be 7 bits. As an example, in this case, the Medium Synchronization Duration subfield can indicate a time in units of 32 us as described above. At this time, the time indicated by the Medium Synchronization Duration subfield may be up to 32*(2^7 - 1) us. The time indicated by the Medium Synchronization Duration subfield may be from 0 to 32*(2^7 - 1) us. As another example, in this case, the Medium Synchronization Duration subfield can indicate a time in units of 64 us. At this time, the time indicated by the Medium Synchronization Duration subfield may be up to 64*(2^7 - 1) us (8128 us). The time indicated by the Medium Synchronization Duration subfield may be from 0 to 64*(2^7 - 1) us.

[0327] For example, the Medium Synchronization Maximum Number Of TXOPs subfield may be less than 4 bits. For example, the Medium Synchronization Maximum Number Of TXOPs subfield may be 3 bits. As an example, in this case, as described above, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate the number of transmission attempts in units of 1. MSD_TXOP_MAX can be indicated as an integer number of times from 0 to 6. Or, MSD_TXOP_MAX can be indicated as an integer number of times from 1 to 6. According to other embodiments, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate the number of transmission attempts in units of 2. For example, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 0, 2, 4, 6, 8, 10, 12. Or, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 2, 4, 6, 8, 10, 12, 14. The Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 1, 3, 5, 7, 9, 11, 13. The Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 0, 1, 3, 5, 7, 9, 11. When the Medium Synchronization Maximum Number Of TXOPs subfield is less than 4 bits, it can also be indicated that there is no limit to the number of transmission attempts when the Medium Synchronization Maximum Number Of TXOPs subfield is set to the maximum value (for example, 7 values with 3 bits).

[0328] According to a further embodiment, the maximum value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield may be 1 less than the maximum value that can be shown in the above-described embodiment. Also, at this time, each subfield value may be 1 less than that described above. For example, the maximum value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield may be -63 dBm. Also, when the Medium Synchronization OFDM ED Threshold subfield is 14 or 15, -64 dBm and -63 dBm can be indicated respectively.

[0329] According to an embodiment of the present invention, an MLD operating on a single radio may have a latency required to change to a state where it can listen on multiple links after transmitting or receiving on one link. Such latency can be indicated by an MLD operating on a single radio. For example, it can be indicated by the multi-link element or EML Capabilities field described in FIG. 23. Therefore, the time for setting the MediumSyncDelay timer by an MLD operating on a single radio may be different from that of an MLD operating on a multi radio. In the above-described embodiment, the MediumSyncDelay timer was set at the end of transmission. According to an embodiment, an MLD operating on a single radio can set the MediumSyncDelay timer based on the end of transmission and a time point based on the latency.

[0330] For example, when an MLD operating on a single radio transmits a PPDU including a frame that solicits an immediate response, the MediumSyncDelay timer can be set after a further latency has elapsed after receiving the PPDU including the immediate response. This may be limited to the case where the MLD operating on a single radio is a TXOP holder.

[0331] Also, when an MLD operating on a single radio transmits a PPDU that contains only frames that do not require an immediate response, the MediumSyncDelay timer can be set after additional latency has elapsed since the transmission of the PPDU. This may be limited to the case where the MLD operating on a single radio is the TXOP holder.

[0332] Also, when an MLD operating on a single radio is the TXOP responder, the MediumSyncDelay timer can be set after additional latency has elapsed since the TXOP holder stops transmitting any more frames. Or, the MLD operating on a single radio can set the MediumSyncDelay timer after additional latency has elapsed since the end of the TXOP. Also, this may be limited to the case where the MLD operating on a single radio is the TXOP responder.

[0333] That is, a STA operating on an NSTR link pair can operate by setting the MediumSyncDelay timer for applying MediumSyncDelay to a value other than "0". At this time, the MediumSyncDelay timer can be operated when the transmission of other STAs ends. However, for an MLD operating on a single radio, additional delays such as a link switching or listening operation delay to return from a single radio to multiple radios may be required. Therefore, in this case, the MediumSyncDelay timer can be operated after the transmission ends and after additional delays. For example, when the MLD operates in the EMLSR mode, the STA can operate the MediumSyncDelay timer immediately after returning to the listening operation.

[0334] FIG. 27 is a diagram showing an example of a transmission operation when the MediumSyncDelay timer according to an embodiment of the present invention is not 0.

[0335] The embodiment of FIG. 27 may be for solving the problems described in FIG. 24. Also, the above-described content may be omitted.

[0336] As described above, according to one embodiment of the present invention, a STA (STA belonging to the MLD) can reset the MediumSyncDelay timer. For example, as described in FIG. 25, it may be determined whether resetting is allowed based on the type of the received frame. For example, the type of the frame may be determined based on the value included in the MAC header of the frame. More specifically, the type of the frame may be determined based on the Frame Control field included in the MAC header. Even more specifically, the type of the frame may be determined based on the Type subfield and / or Subtype subfield included in the Frame Control field. According to one embodiment, the Type subfield may be located at bits of bit indices B2 to B3 of the Frame Control field. Also, the Subtype subfield may be located at bits of bit indices B4 to B7 of the Frame Control field. According to a further embodiment, the type of the frame may be determined based on the Type subfield and / or Subtype subfield and / or Control Frame Extension subfield included in the Frame Control field. The Control Frame Extension subfield may be located at bits of bit indices B8 to B11 of the Frame Control field.

[0337] That is, it may be determined whether it is allowed to reset the MediumSyncDelay timer based on the Type and Subtype of the frame.

[0338] According to an embodiment of the present invention, when B3 and B2 of the Type subfield are 00, 01, and 10 respectively, it can indicate that the frame including the Type subfield is a Management frame, a Control frame, or a Data frame. Also, when B3 and B2 of the Type subfield are 11,

[0339] it can indicate a Type extension.

[0340] According to an embodiment of the present invention, an RTS frame may be a frame that requests a CTS frame. Or, an RTS frame may be a frame that requests a CTS frame from a single STA. The RTS frame may include a Frame Control field, a Duration field, an RA field, a TA field, and an FCS field. The Duration field may include time information for a STA that receives the Duration field to set the NAV. Also, the RA field may include the address of an intended immediate recipient. For example, when the RA field included in the RTS frame received by a STA is the address of the STA, it is possible to respond to the RTS frame with a CTS frame. Also, whether a frame is an RTS frame may be determined based on the Frame Control field included in the frame. For example, whether a frame is an RTS frame may be determined based on the Type subfield and the Subtype subfield included in the Frame Control field included in the frame. For example, when the Type subfield is 01 (B3 B2) and the Subtype subfield is 1011 (B7 B6 B5 B4), it can indicate that the frame including the Type subfield and the Subtype subfield is an RTS frame. For example, an RTS frame may be a Control frame.

[0341] According to the embodiment described with reference to FIG. 25, it may be determined whether the MediumSyncDelay timer can be reset based on the type of frame received to solve the problem described with reference to FIG. 21. However, even if that is the case, according to the reset conditions described above, since the STA can reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION, the problem described with reference to FIG. 22 may not be completely solved. For example, there may be a plurality of STAs whose MediumSyncDelay timer is not 0. Among these, since one of the STAs has a MediumSyncDelay timer that is not 0, it can transmit a frame based on restricted channel access. At this time, the frame to be transmitted may be an RTS frame. When the PPDU format transmitted by the one STA is a PPDU format including a TXOP field, the STA that receives the PPDU transmitted by the one STA can receive a PPDU having an RXVECTOR parameter TXOP_DURATION. Therefore, the STA that receives the PPDU transmitted by the one STA can reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION without resetting the MediumSyncDelay timer based on the RTS frame. That is, since there may be a plurality of STAs that receive the PPDU transmitted by the one STA, a plurality of STAs can reset the MediumSyncDelay timer. If the sequence of the PPDU transmitted by the one STA is not continuous, the MediumSyncDelay timer will be reset unnecessarily. For example, the STA that has reset the MediumSyncDelay timer may interfere with an existing ongoing frame exchange by transmitting a frame based on unrestricted channel access.

[0342] As described with reference to FIGS. 7 and 8, various PPDU formats may exist. For example, non-HT PPDU (or non-HT duplicate PPDU), HT PPDU, VHT PPDU, HE PPDU, EHT PPDU, etc. may exist. HT can mean high throughput, the IEEE 802.11n standard. VHT can mean very high throughput, the IEEE 802.11ac standard. HE can mean high efficiency, the IEEE 802.11ax standard. EHT can mean extremely high throughput, the IEEE 802.11be standard.

[0343] According to an embodiment of the present invention, the TXOP field may be included in the preamble of the PPDU. More specifically, the TXOP field may be included in the HE-SIG-A field or the U-SIG field. Also, the HE PPDU may include the HE-SIG-A field. The EHT PPDU may include the U-SIG field. That is, the HE PPDU or the EHT PPDU may include the TXOP field. For example, the preamble of the PPDU may include the TXOP field. Also, non-HT PPDU (or non-HT duplicate PPDU), HT PPDU, VHT PPDU may not include the TXOP field.

[0344] According to an embodiment of the present invention, when the STA receives a PPDU including the TXOP field, the STA may receive a PPDU in which the RXVECTOR parameter TXOP_DURATION exists. Also, when the STA transmits a PPDU including the TXOP field, the STA may transmit a PPDU in which the TXVECTOR parameter TXOP_DURATION exists.

[0345] According to one embodiment of the present invention, there may be a restriction on the PPDU format when a STA with a non-zero MediumSyncDelay timer transmits. For example, the restriction on the PPDU format when a STA with a non-zero MediumSyncDelay timer transmits may be when transmitting the first frame in a TXOP. Also, when there is a restriction on the PPDU format, the STA may not transmit (or use) a PPDU including a TXOP field. Also, when there is a restriction on the PPDU format, the STA may transmit a PPDU not including a TXOP field. That is, when there is a restriction on the PPDU format, the STA may not transmit a HE PPDU or an EHT PPDU, but may transmit a non-HT PPDU or a non-HT duplicate PPDU or an HT PPDU or a VHT PPDU. More specifically, when there is a restriction on the PPDU format, the STA may transmit a non-HT PPDU or a non-HT duplicate PPDU.

[0346] Therefore, according to one embodiment, a STA with a non-zero MediumSyncDelay timer does not have to transmit using a PPDU format including a TXOP field. Also, a STA with a non-zero MediumSyncDelay timer may transmit using a PPDU format not including a TXOP field. Also, this may be limited to when transmitting the first frame of a TXOP. That is, a STA with a non-zero MediumSyncDelay timer does not have to transmit using a PPDU format including a TXOP field when transmitting the first frame of a TXOP. Also, a STA with a non-zero MediumSyncDelay timer may transmit using a PPDU format not including a TXOP field when transmitting the first frame of a TXOP. Also, as described above, an RTS frame may be transmitted as the first frame of a TXOP.

[0347] Referring to FIG. 27, multiple STAs operating on Link 2 may apply MediumSyncDelay. Also, STA2 of Link 2 that applies MediumSyncDelay can obtain a TXOP and transmit an RTS frame as the first frame. Also, when STA2 transmits the first frame, a PPDU that does not include a TXOP field may be used. For example, a non-HT PPDU, a non-HT duplicate PPDU, an HT PPDU, or a VHT PPDU may be used. As a result, even if an STA that applies MediumSyncDelay receives a frame or PPDU transmitted by STA2, it does not receive the TXOP field, so the RXVECTOR parameter TXOP_DURATION does not exist. That is, an STA that receives a frame or PPDU transmitted by STA2 does not have to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION. Also, according to the embodiment described in FIG. 22, it is not necessary to reset the MediumSyncDelay timer based on the type of frame transmitted by STA2. Therefore, even if an STA that applies MediumSyncDelay receives the first frame or a PPDU including the first frame transmitted by STA2, it is not necessary to reset the MediumSyncDelay timer based on the first frame or the PPDU including the first frame. Therefore, when the response to the RTS frame does not continue, the multiple STAs can protect the channel of Link 2 or the transmission on Link 2 by maintaining the application of MediumSyncDelay. If a response to the RTS frame is transmitted, a CTS frame may be transmitted as the response to the RTS frame. Also, subsequently, STA2 can transmit a frame (Subsequent frame in the figure).In such a case, the plurality of STAs may be able to reset the MediumSyncDelay timer based on the CTS frame or the subsequent frame without resetting the MediumSyncDelay timer based on the RTS frame. Therefore, it is possible to prevent the unnecessary application of MediumSyncDelay.

[0348] FIG. 28 is a diagram showing still another example of the transmission operation when the MediumSyncDelay timer according to an embodiment of the present invention is not 0.

[0349] The embodiment of FIG. 28 may be for solving the problem described with reference to FIG. 24. Also, the above-described content may be omitted.

[0350] As described with reference to FIG. 27, when a STA with a non-zero MediumSyncDelay timer transmits the first frame of a TXOP, by using a PPDU including a TXOP field, a problem may occur in that a STA receiving the PPDU resets the MediumSyncDelay timer based on the TXOP field.

[0351] Therefore, according to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer transmits, there may be a limitation in the TXVECTOR parameter TXOP_DURATION setting. When a STA with a non-zero MediumSyncDelay timer transmits, the TXVECTOR parameter TXOP_DURATION can be set to UNSPECIFIED. When the TXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED, the period information may not exist in the TXOP field. Also, this may be limited to the case where the STA transmits the first frame of the TXOP. That is, when a STA with a non-zero MediumSyncDelay timer transmits the first frame of the TXOP and uses a PPDU including the TXOP field, the TXVECTOR parameter TXOP_DURATION can be set to UNSPECIFIED. Thereby, a STA receiving such a PPDU does not have to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION because even if the RXVECTOR parameter TXOP_DURATION exists, its value is set to UNSPECIFIED.

[0352] When the TXVECTOR parameter TXOP_DURATION or the RXVECTOR parameter TXOP_DURATION is UNSPECIFIED, the TXOP field may be set to 127. That is, when the TXOP field is 7 bits, all bits set to 1 can indicate UNSPECIFIED.

[0353] Referring to FIG. 28, multiple STAs operating on Link 2 may apply MediumSyncDelay. Also, STA2 of Link 2 that applies MediumSyncDelay can obtain a TXOP and transmit an RTS frame as the first frame. At this time, when STA2 uses a PPDU including a TXOP field, the TXVECTOR parameter TXOP_DURATION can be set to UNSPECIFIED. Therefore, even if one of the multiple STAs receives the PPDU transmitted by STA2, the RXVECTOR parameter TXOP_DURATION may be set to UNSPECIFIED. Therefore, the one STA does not have to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION. Also, at this time, if both the examples of whether reset is allowed based on the frame type described in FIG. 25 are used, the one STA does not have to reset the MediumSyncDelay timer based on the first frame or PPDU of the TXOP transmitted by STA2. Also, as described in FIG. 22 or FIG. 24, the one STA can reset the MediumSyncDelay timer based on a subsequent frame or PPDU when the sequence of frames transmitted by STA2 continues.

[0354] FIG. 29 is a diagram showing still another example of the MediumSyncDelay timer reset operation according to an embodiment of the present invention.

[0355] The embodiment of FIG. 29 may be for solving the problem described in FIG. 24. Also, the above-described content may be omitted.

[0356] According to the above-described embodiments, a STA with a non-zero MediumSyncDelay timer can reset the MediumSyncDelay timer based on the received frame (or the duration information included in the frame) or PPDU (or the RXVECTOR parameter TXOP_DURATION). However, a method for solving the problem described in FIG. 24 may be required.

[0357] Therefore, according to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer has received all of the frame (or the duration information included in the frame) and the preamble of the PPDU (or the RXVECTOR parameter TXOP_DURATION), it does not have to reset the MediumSyncDelay timer based on the preamble of the PPDU (or the RXVECTOR parameter TXOP_DURATION). Also, in such a case, a STA with a non-zero MediumSyncDelay timer may be able to reset the MediumSyncDelay timer based on the frame (or the duration information included in the frame). At this time, the term "received" can mean successfully received or having received a valid one. Also, at this time, the embodiment described in FIG. 22 can be used in combination.

[0358] In the present invention, the TXOP field, the TXVECTOR parameter TXOP_DURATION, and the RXVECTOR parameter TXOP_DURATION may be used interchangeably.

[0359] Referring to FIG. 29, a plurality of STAs operating on Link 2 may apply MediumSyncDelay. Also, STA2 of Link 2 that applies MediumSyncDelay can obtain a TXOP and transmit an RTS frame as the first frame. At this time, STA2 can transmit using a PPDU including a TXOP field. Also, one STA whose MediumSyncDelay timer is not 0 can successfully receive both the TXOP field and the frame from the PPDU transmitted by STA2. At this time, according to the embodiment described in FIG. 26, the one STA may not reset the MediumSyncDelay timer based on the TXOP field. Also, according to the embodiment described in FIG. 22, the MediumSyncDelay timer may not be reset based on the RTS frame. Therefore, the problem of resetting the MediumSyncDelay timer when the sequence is not continued for the frame transmitted by STA2 can be solved. Also, as described in FIG. 25 or FIG. 27, the one STA can reset the MediumSyncDelay timer based on a subsequent frame or PPDU when the sequence of the frame transmitted by STA2 continues.

[0360] According to the embodiment described with reference to FIG. 25, whether it is permitted to reset the MediumSyncDelay timer may be determined based on whether the frame or PPDU received by a STA with a non-zero MediumSyncDelay timer belongs to intra-BSS or inter-BSS. According to a more specific embodiment, when the frame or PPDU received by a STA with a non-zero MediumSyncDelay timer belongs to intra-BSS, it may not be permitted to reset the MediumSyncDelay timer. Also, when the frame or PPDU received by a STA with a non-zero MediumSyncDelay timer belongs to inter-BSS, it may be permitted to reset the MediumSyncDelay timer. This may be for protecting intra-BSS frames or intra-BSS PPDUs.

[0361] According to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer receives a frame or PPDU, whether it is permitted to reset the MediumSyncDelay timer may be based on whether the frame or PPDU is an uplink or a downlink. According to one embodiment, when a STA with a non-zero MediumSyncDelay timer receives a frame or PPDU and it is an uplink, it may not be permitted to reset the MediumSyncDelay timer. Also, when a STA with a non-zero MediumSyncDelay timer receives a frame or PPDU and it is a downlink, it may be permitted to reset the MediumSyncDelay timer. This is because downlink frames (or, PPDUs) are transmitted by the AP, and the AP is likely to know well the overall channel situation of the BSS, while uplink frames (or, PPDUs) are transmitted by non-AP STAs, and non-AP STAs may not know well the overall channel situation of the BSS as compared with the AP.

[0362] Whether a frame or PPDU is an uplink or a downlink can be obtained based on the preamble of the PPDU containing the frame or the signaling included in the preamble of the PPDU. For example, the preamble may include a UL / DL field or an Uplink field. The UL / DL field or the Uplink field may be 1 bit and can indicate an uplink or a downlink. Alternatively, the preamble may include a Group ID field. The Group ID field may be set to a preset value depending on whether the PPDU containing the Group ID field is an uplink or a downlink. Also, whether a frame or PPDU is an uplink or a downlink can be obtained based on the MAC header included in the frame contained in the frame or the PPDU. For example, the MAC header may include a MAC address. The MAC address can indicate whether it is an uplink or a downlink. For example, when the MAC address of the AP is set in the TA (transmitter address) field, the frame containing the TA field may be a downlink. When the MAC address of the AP is set in the RA (receiver address) field, the frame containing the RA field may be an uplink. Or,

[0363] According to one embodiment, whether it is allowed to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION when a STA with a non-zero MediumSyncDelay timer receives a PPDU may be determined based on whether the PPDU is an uplink or a downlink. For example, when the UL / DL field indicates an uplink when a STA with a non-zero MediumSyncDelay timer receives a PPDU, it may not be allowed to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION. When the UL / DL field indicates a downlink when a STA with a non-zero MediumSyncDelay timer receives a PPDU, it may be allowed to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION.

[0364] According to a further embodiment, in an embodiment where it is determined whether it is allowed to reset the MediumSyncDelay timer based on whether the received frame or PPDU is an uplink or a downlink, whether it is executed may be determined according to whether the frame or the PPDU belongs to intra-BSS or inter-BSS. That is, whether it is allowed to reset the MediumSyncDelay timer may be determined based on 1) whether the received frame or PPDU is an uplink or a downlink, and 2) whether it belongs to intra-BSS or inter-BSS. For example, when the received frame or PPDU belongs to intra-BSS, according to the above-described embodiment, whether it is allowed to reset the MediumSyncDelay timer may be determined based on whether it is an uplink or a downlink. Also, when the received frame or PPDU belongs to inter-BSS, it may be allowed to reset the MediumSyncDelay timer regardless of whether it is an uplink or a downlink. For example, when the received frame or PPDU is intra-BSS and is an uplink, it may not be allowed to reset the MediumSyncDelay timer. Also, when the received frame or PPDU is intra-BSS and is a downlink, it may be allowed to reset the MediumSyncDelay timer. Also, when the received frame or PPDU is inter-BSS, it may be allowed to reset the MediumSyncDelay timer regardless of whether it is an uplink or a downlink.

[0365] FIG. 30 is a diagram showing an example of MediumSyncDelay timer reset according to an embodiment of the present invention.

[0366] As described above, there may be an operation to reset the MediumSyncDelay timer. In this embodiment, an operation to reset based on conditions different from those described above will be described, and the above-described content may be omitted.

[0367] According to an embodiment of the present invention, when a STA whose MediumSyncDelay timer is not 0 successfully receives an L preamble, it may be possible to reset the MediumSyncDelay timer.

[0368] The L preamble may be a legacy preamble or the legacy preamble described above with reference to FIG. 7 or the like. Alternatively, the L preamble may be referred to as a non-HT PHY preamble. This is because the L preamble is a preamble of the non-HT (duplicate) PPDU format. Also, the operation when the L preamble is successfully received may be the same as the operation when the L-SIG field is successfully received. This is because the L preamble includes the L-SIG field. Also, the L-SIG field may exist at the end of the L preamble. Also, when the L-SIG field is successfully received, it may be the case where a field indicating the length (duration) of the PPDU (PHY protocol data unit) including the L-SIG field is successfully received. In such a case, it is possible to determine the length of the PPDU. Also, the length of the PPDU including the L-SIG field may be determined based on the RATE field and the LENGTH field included in the L-SIG field. The RATE field and the LENGTH field may be the L_RATE field and the L_LENGTH field described above, respectively.

[0369] The L preamble may include L-STF, L-LTF, and L-SIG fields. The L-STF, L-LTF, and L-SIG fields can each occupy 8 us, 8 us, and 4 us, respectively, from the very beginning of the PPDU. That is, the L preamble may be present in the first 20 us of the PPDU.

[0370] The L-SIG field may include RATE, reserved, LENGTH, parity, and SIGNAL TAIL fields. RATE and LENGTH can be the values (Mbps) indicated by the RATE field and the value of the LENGTH field, respectively. LENGTH may be set as follows.

[0371] LENGTH = Ceil((TXTIME - SignalExtension - 20) / 4)*RATE / 8*4 - 3 - m

[0372] Here, Ceil(x) may be the smallest integer larger than or equal to x. TXTIME may be the PPDU transmission length or the PPDU length. SignalExtension may be the length of the signal extension. SignalExtension may be 0 us in the 5 GHz band or 6 GHz band. SignalExtension may be 6 us in the 2.4 GHz band. Also, m may be 1 or 2 for HE PPDUs. Also, m may be 0 for PPDUs other than HE PPDUs (i.e., non-HT (duplicate) PPDUs, HT PPDUs, VHT PPDUs, EHT PPDUs).

[0373] Also, RXTIME or the PPDU length may be calculated as follows. This may be the PPDU length indicated by L-SIG (or the LENGTH field and the RATE field).

[0374] RXTIME = Ceil((LENGTH + 3) / (RATE / 8*4))*4 + 20 + SignalExtension

[0375] Also, the values that RATE can indicate may be 6, 9, 12, 18, 24, 36, 48, 54 Mbps. This may be an example when the channel spacing is 20 MHz. Also, the RATE field values indicating the values that the mentioned RATE can indicate may be those when the values from the LSB to the MSB of the RATE field are 1101, 1111, 0101, 0111, 1001, 1011, 0001, 0011 respectively. That is, when the RATE field is 1101, the RATE indicated by the RATE field may be 6 Mbps.

[0376] If, for example, RATE is 6 Mbps, LENGTH and RXTIME may be as follows.

[0377] LENGTH = Ceil((TXTIME - SignalExtension - 20) / 4)*3 - 3 - m

[0378] RXTIME = Ceil((LENGTH + 3) / 3)*4 + 20 + SignalExtension

[0379] Resetting the MediumSyncDelay timer when the L preamble is successfully received is for successfully receiving and determining the duration of the PPDU including the L preamble. Also, when the STA successfully receives the L preamble, it may determine that the medium is busy during the duration of the PPDU including the L preamble and does not need to perform medium (channel) access. However, in such a case, compared with the embodiments of resetting based on the valid period information or valid MPDU or RXVECTOR parameter TXOP_DURATION described in FIGS. 21 to 26, it may become difficult to protect the frame exchange sequence. The above-mentioned valid period information or valid MPDU or RXVECTOR parameter TXOP_DURATION can indicate the duration of the frame sequence, which may be because the duration indicated by the L preamble is the duration of the PPDU. However, the embodiment of FIG. 27 may have a higher possibility of accessing the channel earlier after resetting the MediumSyncDelay timer compared with the embodiments described in FIGS. 21 to 26. This is because the L preamble exists in the previous part of the PPDU, and there may be cases where the L preamble is successfully received but the valid period information or valid MPDU or RXVECTOR parameter TXOP_DURATION cannot be successfully received.

[0380] Also, the embodiments for solving the problem of resetting the MediumSyncDelay timer based on the first frame or RTS frame during MediumSyncDelay described in FIGS. 24, 25, and 27 to 29 can be applied to the embodiment of FIG. 30. In the present invention, the embodiments referring to the first frame or RTS frame during MediumSyncDelay are not limited thereto, and it is also possible to apply them by replacing them with the first frame during the RTS frame or MediumSyncDelay respectively.

[0381] According to an embodiment of the present invention, as described above, when it is determined whether to reset based on whether the received frame is an RTS frame, it may be determined whether it is an RTS frame based on the duration. The duration may be the PPDU duration. According to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer successfully receives an L preamble, the MediumSyncDelay timer may be reset only when the duration of the PPDU including the L preamble is longer than the duration of the RTS frame. That is, when the duration of the PPDU including the L preamble is less than or equal to the duration of the RTS frame, it may be impossible to reset the MediumSyncDelay timer.

[0382] When the RTS frame is included in a non-HT PPDU or a non-HT duplicate PPDU, the PPDU duration may be as follows. When the value indicated by the RATE is 6, 9, 12, 18, 24, 36, 48, 54 Mbps, they may be 52, 44, 36, 32, 28, 28, 24, 24 us, respectively. Therefore, when receiving a PPDU equal to or shorter than 52 us, it may not be necessary to reset the MediumSyncDelay timer.

[0383] When a frame is included in the PPDU, the PPDU length may be calculated as follows.

[0384] PPDU duration=Ceil((FrameOctet*8+ServiceTailBits) / RATE / 4)*4+Preamble

[0385] FrameOctet may be the octet number in the MAC frame format. In an RTS frame, FrameOctet may be 20. ServiceTailBits may be the sum of the number of bits of the service field and the tail bits. For example, ServiceTailBits may be 22 bits. RATE may be the RATE mentioned above. Also, 4 may be the OFDM symbol length (us). Preamble may be the length of the L preamble when it is a Non-HT PPDU or a non-HT duplicate PPDU. That is, when it is a Non-HT PPDU or a non-HT duplicate PPDU, Preamble may be 20 us.

[0386] As an embodiment of the present invention, in an embodiment where the MediumSyncDelay timer can be reset only when the duration of the PPDU including the L preamble is longer than the duration of the RTS frame when a STA with a non-zero MediumSyncDelay timer successfully receives the L preamble, it is possible to determine the duration of the RTS frame based only on the LENGTH field. Therefore, in such a case, when a STA with a non-zero MediumSyncDelay timer successfully receives the L preamble, the MediumSyncDelay timer may be reset only when the duration of the PPDU including the L preamble is longer than 54 us.

[0387] Alternatively, as an embodiment of the present invention, in an embodiment where the MediumSyncDelay timer can be reset only when a STA with a non-zero MediumSyncDelay timer successfully receives an L preamble and the duration of the PPDU including the L preamble is longer than the duration of the RTS frame, it is possible to determine the duration of the RTS frame based on the LENGTH field and the RATE field. That is, the threshold for comparing the duration of the PPDU may change based on the received RATE field value.

[0388] In such an embodiment, the duration of the PPDU including the RTS frame may be assumed on the premise that the RTS frame is included in a non-HT PPDU or a non-HT duplicate PPDU.

[0389] According to still another embodiment, the duration of the PPDU including the RTS frame can be determined by considering the preamble length and / or the data rate of the PPDU format when determining the PPDU format including the RTS frame.

[0390] However, in such an embodiment, it may be difficult to reset the MediumSyncDelay timer when a frame with the same or smaller number of octets as the RTS frame is received. For example, a CF-End frame or a PS-Poll frame may have 20 octets and be the same as the RTS frame. Also, an Ack frame or a CTS frame may have a smaller number of octets than the RTS frame. The Ack frame or the CTS frame may be 14 octets.

[0391] Also, when receiving a PPDU using a high data rate, it may be difficult to reset the MediumSyncDelay timer accordingly. For example, even if the number of octets of a frame is larger than that of an RTS frame, it may be transmitted as a short PPDU using a high MCS. In this case, since the PPDU duration is below the threshold, it may be difficult to reset the MediumSyncDelay timer.

[0392] Referring to FIG. 30, a plurality of STAs operating on Link 2 may apply MediumSyncDelay. Also, STA2 on Link 2 that applies MediumSyncDelay can obtain a TXOP and transmit an RTS frame as the first frame. An STA3 whose MediumSyncDelay timer is not 0 (for example, one of the plurality of STAs) can determine whether to reset the MediumSyncDelay timer based on a PPDU including the RTS frame or a PPDU including a CTS frame following the RTS frame or a PPDU including a subsequent frame following the CTS frame. That is, when STA3 successfully receives an L preamble, it may be determined whether it is possible to reset the MediumSyncDelay timer based on the PPDU duration indicated by the L preamble. If the PPDU duration is larger than the PPDU duration including the RTS frame, it may be possible to reset it, and if it is smaller or the same, it may not be possible to reset it.

[0393] According to one embodiment, the PPDU duration including the RTS frame may be 52 us. According to other embodiments, the PPDU duration including the RTS frame may be 52, 44, 36, 32, 28, 28, 24, 24 us, respectively, when the RATE field indicates 6, 9, 12, 18, 24, 36, 48, 54 Mbps. This may be the case when the RTS frame is included in a non-HT PPDU or a non-HT duplicate PPDU.

[0394] Therefore, in the embodiment of FIG. 30, STA3 may not be able to reset the MediumSyncDelay timer based on the PPDU including the RTS frame and the PPDU including the CTS frame. If STA3 receives a PPDU including a subsequent frame, it can be determined whether it is possible to reset the MediumSyncDelay timer based on the above-described conditions.

[0395] That is, according to the embodiment described in FIG. 30, an STA existing in a hidden position from the STA that transmitted the RTS frame may have difficulty resetting the MediumSyncDelay timer based on the RTS frame and subsequent frame exchanges. This may disadvantageously affect the channel access by the STA.

[0396] FIG. 31 is a diagram showing still another example of MediumSyncDelay timer reset according to an embodiment of the present invention.

[0397] FIG. 31 is a diagram showing MediumSyncDelay timer reset according to an embodiment of the present invention.

[0398] The embodiment of FIG. 31 may be an embodiment for solving the problem described in FIG. 30. Also, the above-described content may be omitted.

[0399] According to an embodiment of the present invention, as described above, when it is determined whether to be reset based on whether the received frame is an RTS frame, whether it is an RTS frame may be determined based on the duration. The duration may be the PPDU duration. According to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer successfully receives an L preamble, the MediumSyncDelay timer may be reset only when the duration of the PPDU including the L preamble is different from the duration of the RTS frame. That is, when the duration of the PPDU including the L preamble is the same as the duration of the RTS frame, it may be impossible to reset the MediumSyncDelay timer. That is, compared with the embodiment described in FIG. 27, when a STA with a non-zero MediumSyncDelay timer successfully receives an L preamble, even when the duration of the PPDU including the L preamble is shorter than the duration of the RTS frame, it may be possible to reset the MediumSyncDelay timer.

[0400] The duration of the RTS frame may be the same as the description in FIG. 27.

[0401] An embodiment showing comparison between the PPDU duration and the RTS frame duration in the present invention has been described, but the present invention is not limited thereto, and it can also be applied to embodiments in which the number of octets of the received PSDU (PHY service data unit) (RXVECTOR parameter PSDU_LENGTH), the number of octets of the frame, the LENGTH field value included in the L-SIG, etc. are compared with the values corresponding to the RTS frame. For example, the above-described received comparison criteria are compared with the values corresponding to the RTS frame, and if they are the same as each other, the MediumSyncDelay timer cannot be reset, and if they are not the same as each other, it may be possible to reset the MediumSyncDelay timer.

[0402] Therefore, according to this embodiment, even when using a frame smaller or shorter than the RTS frame, or a high data rate or MCS, it may be possible to reset the MediumSyncDelay timer based on such a frame or PPDU.

[0403] Referring to FIG. 31, a plurality of STAs operating on Link 2 may apply MediumSyncDelay. Also, STA2 on Link 2 that applies MediumSyncDelay can obtain a TXOP and transmit an RTS frame as the first frame. An STA3 (for example, one of the plurality of STAs) whose MediumSyncDelay timer is not 0 can determine whether to reset the MediumSyncDelay timer based on a PPDU including the RTS frame, a PPDU including a CTS frame following the RTS frame, or a PPDU including a subsequent frame following the CTS frame. That is, when STA3 successfully receives an L preamble, it may be determined whether it is possible to reset the MediumSyncDelay timer based on the PPDU duration indicated by the L preamble. If the PPDU duration is different from the PPDU duration including the RTS frame, it may be possible to reset it, and in the same case, it may not be possible to reset it.

[0404] According to one embodiment, the PPDU duration including the RTS frame may be 52 us. According to other embodiments, the PPDU duration including the RTS frame may be 52, 44, 36, 32, 28, 28, 24, 24 us respectively when the RATE field indicates 6, 9, 12, 18, 24, 36, 48, 54 Mbps. This may be the case when the RTS frame is included in a non-HT PPDU or a non-HT duplicate PPDU.

[0405] Therefore, in the embodiment of FIG. 31, STA3 may not be able to reset the MediumSyncDelay timer based on the PPDU including the RTS frame. Also, when STA3 receives a PPDU including a CTS frame, it may be possible to reset the MediumSyncDelay timer based on the PPDU including the CTS frame. If STA3 receives a PPDU including a subsequent frame, it is possible to determine whether it is possible to reset the MediumSyncDelay timer based on the above-described conditions.

[0406] That is, according to the embodiment described in FIG. 31, a STA existing in a hidden position from the STA that transmitted the RTS frame may be able to reset the MediumSyncDelay timer based on the CTS frame or the PPDU including the CTS frame.

[0407] However, even in the case of the embodiment of FIG. 31, it may be difficult to reset the MediumSyncDelay timer based on a frame having the same length as the RTS frame or a PPDU including such a frame. For example, as described above, since the CF-End frame or the PS-Poll frame has the same number of octets as the RTS frame, it may be difficult to reset the MediumSyncDleay timer based on a PPDU including such a frame. Also, when receiving a PPDU using a high data rate, it may be difficult to reset the MediumSyncDelay timer accordingly. For example, even if the number of octets of a frame is different from that of the RTS frame, it may be transmitted in a PPDU having the same length as the case where the RTS frame is included using a high MCS. In such a case, since the PPDU duration is the same as the threshold value, it may be difficult to reset the MediumSyncDelay timer. For example, a PPDU other than a non-HT PPDU or a non-HT duplicate PPDU (HT PPDU, VHT PPDU, HE PPDU, EHT PPDU) can always set the RATE field included in the L-SIG field to a pre-set value, for example, a value indicating 6 Mbps. And the actually used rate may be included in fields after the L-SIG field (for example, HT-SIG, VHT-SIG-A, HE-SIG-A, U-SIG, EHT-SIG fields, etc.). Therefore, when determining the PPDU duration based on the RATE field included in the L-SIG field, even when it is not a PPDU including the RTS frame, it may be calculated as having the same duration as a PPDU including the RTS frame.

[0408] FIG. 32 is a diagram showing still another example of resetting the MediumSyncDelay timer according to an embodiment of the present invention.

[0409] The embodiment of FIG. 32 may be an embodiment for solving the problems described with reference to FIGS. 30 and 31. Also, the above-described content may be omitted. In particular, the content described above regarding the duration may be omitted.

[0410] According to an embodiment of the present invention, a method for determining whether it is possible to reset a MediumSyncDelay timer may differ depending on whether a frame (MAC frame) is received. For example, the method for determining whether it is possible to reset the MediumSyncDelay timer may differ depending on whether a frame is received or whether only a preamble is received without being able to receive the frame.

[0411] According to an embodiment, when receiving a frame from a PPDU, it may be possible to reset the MediumSyncDelay timer based on the embodiments described with reference to FIGS. 25 and 27 to 29. For example, when receiving a frame from a PPDU, if the frame is not an RTS frame, it may be possible to reset the MediumSyncDelay timer. Alternatively, when receiving a frame from a PPDU, if the frame is not an RTS frame and not a PS-Poll frame, it may be possible to reset the MediumSyncDelay timer.

[0412] If it is not possible to receive a frame from the PPDU, it may be possible to reset the MediumSyncDelay timer based on the embodiments described with reference to FIGS. 30 and 31. For example, if it is not possible to receive a frame from the PPDU, and the L preamble is successfully received from the PPDU, it may be possible to reset the MediumSyncDelay timer (the embodiment of FIG. 30). Alternatively, if it is not possible to receive a frame from the PPDU, and the L preamble is successfully received from the PPDU, and the duration of the PPDU is greater than the duration of a PPDU that includes an RTS frame, it may be possible to reset the MediumSyncDelay timer (the embodiment of FIG. 30). Alternatively, if it is not possible to receive a frame from the PPDU, and the L preamble is successfully received from the PPDU, and the duration of the PPDU is different from the duration of a PPDU that includes an RTS frame, it may be possible to reset the MediumSyncDelay timer (the embodiment of FIG. 31).

[0413] The duration of the RTS frame or the duration of a PPDU that includes an RTS frame may be the same as the description in FIGS. 30 and 31.

[0414] The present invention shows an embodiment in which the duration of the PPDU is compared with the duration of the RTS frame, but the present invention is not limited thereto, and the present invention is also applicable to an embodiment in which the number of octets of the received PSDU (PHY service data unit) (RXVECTOR parameter PSDU_LENGTH), the number of octets of the frame, the LENGTH field value included in the L-SIG, etc. are compared with the value corresponding to the RTS frame. For example, the above-described received comparison criteria are compared with the value corresponding to the RTS frame, and if they are the same, it may not be possible to reset the MediumSyncDelay timer, and if they are not the same, it may be possible to reset the MediumSyncDelay timer.

[0415] The above-described embodiments can also be described as follows.

[0416] For example, when the STA receives a frame that is not an L preamble or an RTS frame, it may be possible to reset the MediumSyncDelay timer. At this time, the STA may be a STA whose MediumSyncDelay timer value is not 0. Also, receiving may mean successfully receiving.

[0417] Or, when the STA has received 1) an L preamble and the duration is longer than the duration of the RTS frame, or 2) a frame that is not an RTS frame, it may be possible to reset the MediumSyncDelay timer. At this time, the duration may be the duration indicated by the LENGTH field included in the L preamble or the L-SIG field. That is, when the STA receives an RTS frame in the received PPDU, it may not be possible to reset the MediumSyncDelay timer. Also, when the STA receives a CTS frame or a CF-End frame or a PS-Poll frame in the received PPDU, it may be possible to reset the MediumSyncDelay timer. Or, there may be an embodiment in which the MediumSyncDelay timer can be reset when the conditions of the above 1) or 2) are met, or 3) when an RXVECTOR parameter TXOP_DURATION that is not an UNSPECIFIED value is received.

[0418] Alternatively, the STA may be able to reset the MediumSyncDelay timer when 1) it receives an L preamble and the duration is different from the duration of the RTS frame, or 2) it receives a frame other than the RTS frame. At this time, the duration may be the duration indicated by the LENGTH field included in the L preamble or L-SIG field. That is, when the STA receives an RTS frame in the received PPDU, it may not be possible to reset the MediumSyncDelay timer. Also, when the STA receives a CTS frame or a CF-End frame or a PS-Poll frame in the received PPDU, it may be able to reset the MediumSyncDelay timer. Or, there may be an embodiment where the MediumSyncDelay timer can be reset when the above 1) or 2) conditions are met, or 3) an RXVECTOR parameter TXOP_DURATION other than the UNSPECIFIED value is received.

[0419] Also, in an embodiment of the present invention, the above-described embodiments can be used in combination for the condition of resetting when a frame other than the RTS frame is received. For example, not only when a frame other than the RTS frame is received, but also when an RTS frame is received, if it is an RTS frame transmitted by an AP corresponding to the BSSID included in the combined AP or the same multi-BSSID set as the combined AP, it may be possible to reset. Or, an embodiment of determining whether to reset based on whether it is an uplink or a downlink can be used in combination.

[0420] Referring to FIG. 32, a plurality of STAs operating on link 2 may apply MediumSyncDelay. Also, STA2 of link 2 that applies MediumSyncDelay obtains a TXOP and can transmit an RTS frame as the first frame. An STA3 whose MediumSyncDelay timer is not 0 (for example, one of the plurality of STAs) can determine whether to reset the MediumSyncDelay timer based on a PPDU including the RTS frame or a PPDU including a CTS frame following the RTS frame or a PPDU including a subsequent frame following the CTS frame. That is, when STA3 successfully receives an L preamble, it may be determined whether it is possible to reset the MediumSyncDelay timer based on the PPDU duration indicated by the L preamble. In such a case, STA3 may not be able to reset the MediumSyncDelay timer based on the L preamble of the PPDU including the RTS frame. Or, when STA3 receives a frame that is not an RTS frame, it may be possible to reset the MediumSyncDelay timer. Therefore, even if STA3 receives an RTS frame following the L preamble of the PPDU including the RTS frame, it may not be possible to reset the MediumSyncDelay timer. Also, even if the duration of the PPDU including the subsequent frame received by STA3 is the same as the PPDU duration including the RTS frame, when STA3 receives the subsequent frame, it may be possible to reset the MediumSyncDelay timer. Or, even when STA3 receives a CTS frame, it may be possible to reset the MediumSyncDelay timer.

[0421] According to a further embodiment, in the foregoing embodiment, in the case where a STA having a timer with a non-zero MediumSyncDelay timer value receives a PPDU or a frame and determines whether the MediumSyncDelay timer can be reset, it may be limited that the received PPDU or frame can be reset only when it belongs to an intra-BSS. This is because there may be a case where a frame or a PPDU is transmitted when only the basic NAV of the STA is set and the intra-BSS NAV is not set. For example, when only the basic NAV of the STA is set and the intra-BSS NAV is not set, if an intra-BSS AP or an associated AP transmits a triggering frame (a frame including a trigger frame or a TRS Control) to the STA, the STA may be able to transmit a frame or a PPDU.

[0422] FIG. 33 is a diagram showing still another example of MediumSyncDelay timer reset according to an embodiment of the present invention.

[0423] As described with reference to FIGS. 24 to 32, there may be an operation of resetting the MediumSyncDelay timer. Also, as described above, at this time, whether to perform the reset operation may be based on the type of the received frame. Also, whether to perform the reset operation may be based on which STA transmitted the received frame. The content described above in the present invention may be omitted.

[0424] As described with reference to FIG. 23, there may be a case where a plurality of STAs have a non-zero MediumSyncDelay timer. Also, according to an embodiment of the present invention, the plurality of STAs may include a STA (i.e., an AP) belonging to an AP MLD. For example, there may be a case where an AP MLD operates in an NSTR link pair. Such an AP MLD can be referred to as an NSTR AP MLD or an NSTR mobile AP MLD or an NSTR soft AP MLD.

[0425] Referring to FIG. 33, AP1 and AP2 may belong to an AP MLD which is an NSTR mobile AP MLD. Also, AP1 and AP2 can each operate on Link 1 and Link 2. There may be a non-AP MLD associated (multi-link set-up) with the NSTR mobile AP MLD. STA1 and STA2 may belong to the non-AP MLD. Also, STA1 and STA2 can each operate on Link 1 and Link 2. Link 1 and Link 2 can each be a primary link and a non-primary link. For example, there may be a case where AP1 and STA1 perform frame exchange. AP1 can transmit PPDU 1. Also, STA1 can transmit PPDU 2. In such a case, during the transmission of PPDU 1 by AP1, the transmission may act as interference to AP2, and AP2 may be blinded during the transmission of PPDU 1. In such a case, when AP2 gets out of the blind, it can start the MediumSyncDely timer. Also, during the transmission of PPDU 2 by STA1, the transmission may act as interference to STA2, and STA2 may be blinded during the transmission of PPDU 2. In such a case, when STA2 gets out of the blind, it can start the MediumSyncDely timer. Thus, there may be a case where the MediumSyncDelay timers of a plurality of STAs including an AP are not zero.

[0426] At this time, according to an embodiment described with reference to FIG. 25, when receiving a type of frame that is allowed as the first frame transmitted by the combined AP or an AP belonging to the same multi-BSSID set as the combined AP, if it is allowed to reset the MediumSyncDelay timer to 0, even when no frame exchange is made following the first frame as in the problem described with reference to FIG. 21, resetting the MediumSyncDelay timer based on the first frame may interfere with the existing frame exchange. That is, in FIG. 30, AP2 can transmit an RTS frame as the first frame while the MediumSyncDelay timer is not 0 (for example, this first frame may be transmitted to STA3 instead of STA2). However, STA2 that receives this may reset the MediumSyncDelay timer based on the first frame. In such a case, STA2 may start transmitting and induce interference in the ongoing frame exchange.

[0427] The NSTR mobile AP MLD can set, allocate, and designate primary and non-primary links. Also, a non-AP MLD set up with multiple links with the NSTR mobile AP MLD can receive information from the NSTR mobile AP MLD regarding which link is the primary link and which link is the non-primary link, and make a determination. The NSTR mobile AP MLD may be able to transmit Beacon frames, Probe Response frames, Association Response frames, and Reassociation Response frames only on the primary link. The NSTR mobile AP MLD may be unable to transmit Beacon frames, Probe Response frames, Association Response frames, and Reassociation Response frames on the non-primary link. Also, a non-AP MLD set up (or to be set up) with multiple links with the NSTR mobile AP MLD may be able to transmit Probe Request frames, Association Request frames, and Reassociation Request frames only on the primary link. A non-AP MLD associated or set up (or to be set up) with multiple links with the NSTR mobile AP MLD may be unable to transmit Probe Request frames, Association Request frames, and Reassociation Request frames on the non-primary link.

[0428] Also, the NSTR mobile AP MLD or the non-AP MLD combined with the NSTR mobile AP MLD may need to use the primary link together to start a TXOP (start frame transmission) on a non-primary link. For example, to start transmitting a PPDU on a non-primary link, it may be necessary to start transmitting the PPDU on the primary link simultaneously with the non-primary link. Also, there may be a backoff procedure for starting PPDU transmission simultaneously on the primary link and the non-primary link. For example, maintain the backoff counter 0 value on the link where the backoff counter has reached 0, and on the link with a backoff counter of 0, start transmitting the PPDU when the backoff counter reaches 0 on other links.

[0429] Also, the AP MLD can indicate whether it is an NSTR mobile AP MLD or an AP MLD that is not an NSTR mobile AP MLD (AP MLD operating in an STR link pair). For example, the multi-link element described in FIG. 20 may include the indication. More specifically, the MLD Capabilities field in the Common Info field included in the multi-link element may include the indication. More specifically, bit B7 in the MLD Capabilities field can indicate the indication. The indication may exist when the AP MLD transmits a multi-link element. For example, when the NSTR mobile AP MLD transmits a multi-link element, the bit value may be set to 1. When an AP MLD that is not an NSTR mobile AP MLD transmits a multi-link element, the bit value may be set to 0. The non-AP MLD that receives the bit can determine whether the multi-link element including the bit is an NSTR mobile AP MLD based on the bit.

[0430] Also, when the NSTR mobile AP MLD sends a Reduced Neighbor Report element, the TBTT Information field corresponding to the NSTR mobile AP MLD may contain only the MLD Parameters subfield. Also, an AP MLD that is not an NSTR mobile AP MLD does not necessarily have to contain only the MLD Parameters subfield in the TBTT Information field corresponding to the AP MLD when sending a Reduced Neighbor Report element. The Reduced Neighbor Report element may be included in a Beacon frame, a Probe Response frame, an Association Response frame, or a Reassociation Response frame. Therefore, a non-AP MLD that receives a TBTT Information field can determine whether the AP MLD corresponding to the TBTT Information field is an NSTR mobile AP MLD based on whether the TBTT Information field contains only the MLD Parameters field. Whether the TBTT Information field contains only the MLD Parameters subfield may be determined based on a field that indicates the length or type of the TBTT Information field. For example, the MLD Parameters subfield may have a pre-set length, such as 3 octets. Also, when the value indicating the length of the TBTT Information field indicates the pre-set length, it can be determined that the TBTT Information field contains only the MLD Parameters subfield and that the TBTT Information field corresponds to an NSTR mobile AP MLD.

[0431] According to an embodiment of the present invention, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), it is possible to determine whether it is allowed to reset the MediumSyncDelay timer based on whether the STA is an AP MLD to which it is associated (multi-link setup) or an NSTR mobile AP MLD. In the embodiment described in FIG. 22, when the frame received by the STA is a type of frame allowed as the first frame and is not a frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP), the operation of resetting the MediumSyncDelay timer to 0 is not allowed. Also, when the frame received by the STA is not a type of frame allowed as the first frame or is a frame transmitted by the associated AP (or an AP included in the same multi-BSSID set as the associated AP), the operation of resetting the MediumSyncDelay timer to 0 is allowed. However, in an embodiment of the present invention, this may be limited to the case where the associated AP (or an AP included in the same multi-BSSID set as the associated AP) belongs to an AP MLD that is not an NSTR mobile AP MLD.

[0432] That is, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may not be allowed if 1) the frame is a type of frame allowed as the first frame during MediumSyncDelay and 2) it is not a frame transmitted by the associated AP belonging to an AP MLD that is not an NSTR mobile AP MLD (or an AP included in the same multi-BSSID set as the associated AP).

[0433] Also, when a STA with a non-zero MediumSyncDelay timer receives a valid frame (or MPDU), an operation of resetting the MediumSyncDelay timer to 0 may be allowed if 1) the frame is not of a type allowed as the first frame during MediumSyncDelay, or 2) the frame is transmitted by an associated AP that belongs to an AP MLD that is not an NSTR mobile AP MLD (or an AP included in the same multi-BSSID set as the associated AP).

[0434] That is, when the frame received by the STA is a type of frame allowed as the first frame during MediumSyncDelay (e.g., an RTS frame), the associated AP belongs to an NSTR mobile AP MLD, and the received frame is transmitted by the associated AP, an operation of resetting the MediumSyncDelay timer to 0 may not be allowed.

[0435] Also, when the frame received by the STA is a type of frame allowed as the first frame during MediumSyncDelay (e.g., an RTS frame), the associated AP belongs to an AP MLD that is not an NSTR mobile AP MLD, and the received frame is transmitted by the associated AP, an operation of resetting the MediumSyncDelay timer to 0 may be allowed.

[0436] Also, when the frame received by the STA is a type of frame allowed as the first frame during MediumSyncDelay (e.g., an RTS frame), and the received frame is not transmitted by the associated AP, an operation of resetting the MediumSyncDelay timer to 0 may not be allowed.

[0437] Also, when the frame received by the STA is not a type of frame allowed as the first frame during MediumSyncDelay (e.g., an RTS frame), an operation of resetting the MediumSyncDelay timer to 0 may be allowed.

[0438] At this time, the STA that has received the frame may be a STA in a state where the MediumSyncDelay timer value is not 0.

[0439] The above embodiment of determining whether to allow MediumSyncDelay reset based on whether the frame is sent by the combined AP may be limited to when the non-AP MLD determines. If the NSTR mobile AP MLD determines whether to allow MediumSyncDelay reset, it can be determined regardless of the sender of the received frame. For example, when the NSTR mobile AP MLD determines whether to allow MediumSyncDelay reset, it can be determined only based on whether the received frame is a type of frame allowed as the first frame during MediumSyncDelay, regardless of who sent the received frame. That is, when a STA belonging to the NSTR mobile AP MLD receives a valid frame, if the frame is not a type of frame (such as an RTS frame) allowed as the first frame during MediumSyncDelay, the operation of resetting the MediumSyncDelay timer to 0 may be allowed. Also, when a STA belonging to the NSTR mobile AP MLD receives a valid frame, if the frame is a type of frame (such as an RTS frame) allowed as the first frame during MediumSyncDelay, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed.

[0440] FIG. 34 is a flowchart showing an example of the operation of non-AP MLD according to an embodiment of the present invention.

[0441] Referring to FIG. 34, when an MLD composed of a plurality of STAs operates in an NSTR link pair, it can reset the MediumSyncDelay timer for applying MediumSyncDelay to "0" in specific cases.

[0442] Specifically, a multi-link device (MLD) including a plurality of stations each operating on a plurality of links including a first link and a second link can receive a frame transmitted from one STA among one or more stations (Station: STA) via a second STA operating on the second link (S34010).

[0443] After that, Media if the synchronization delay timer is not "0", based on the received frame, the Media synchronization delay (Medium Sync Delay) application Media synchronization delay timer (Medium Sync Delay timer) can be reset (S34020).

[0444] At this time, the STA operating in the NSTR link pair can Media set the synchronization delay timer to a non-zero value and operate it. Media The synchronization delay timer can be operated when the transmission of other STAs ends. However, an MLD operating on a single radio may require additional delays such as a delay to return to a link switching or listening operation for changing from a single radio to multiple radios. Therefore, in this case, the MediumSyncDelay timer can be operated after an additional delay after the transmission ends. For example, when the MLD operates in the EMLSR mode, the STA can operate the MediumSyncDelay timer immediately after returning to the listening operation.

[0445] MediaWhen the STA of a link to which the synchronization delay is applied receives a PPDU for a valid frame or a valid MPDU, Media if the synchronization delay timer is not "0", Media the synchronization delay timer can be reset to "0". Or, when receiving a PPDU whose TXOP_Duration, which is a received parameter (RXVECTOR parameter), is a value other than a specific value, if the MediumSyncDelay timer is not "0", the MediumSyncDelay timer can be reset to "0". At this time, the valid frame may be a frame other than the RTS frame.

[0446] At this time, the first link and the second link may be a pair of NSTR (Non-Simultaneous Transmission and Reception) links where transmission / reception in each link causes interference in other links and does not support simultaneous transmission / reception within the same MLD.

[0447] For example, when the transmission of a PPDU in the first link restricts the transmission / reception of one or more STAs in the second link, which is a pair of NSTR links, and the MediumSyncDelay timer operates and MediumSyncDelay is applied to one or more STAs when the transmission of the PPDU ends, when one or more STAs in the second link receive a valid frame, the MediumSyncDelay timer can be reset. That is, one or more STAs to which a specific frequency band is allocated can reset the MediumSyncDelay timer when receiving a PPDU for a valid MPDU excluding the RTS frame transmitted at 20 MHz in the same BSS or another BSS. At this time, even when the PPDU or frame is transmitted from an associated AP or an AP included in the same multiple BSSID set and the received PPDU or frame is an RTS frame, one or more STAs can reset the MediumSyncDelay timer.

[0448] As described above, the description of the present invention is for illustrative purposes, and those with ordinary knowledge in the technical field to which the present invention pertains can understand that it can be easily deformed into other specific forms without changing the technical idea or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative and non-limiting in any aspect. For example, each component described as a single type may be implemented dispersedly, and similarly, components described as being dispersed may also be implemented in a combined form.

[0449] The scope of the present invention is defined by the appended claims rather than the above detailed description, and any changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included within the scope of the present invention.

Claims

1. A multi-link device (MLD) including a first station (STA) operating on a first link and a second STA operating on a second link, a communication module, and a processor configured to control the communication module, wherein the processor receives a frame transmitted from one of the one or more STAs via the second STA operating on the second link, and when the frame is a specific frame, is configured to reset a medium sync delay timer to "0" for application of the medium sync delay of the second STA based on the received frame, wherein the medium sync delay indicates a period for restricting data transmission on the second link after transmitting data of the first STA on the first link, and when the second STA loses medium sync due to the data transmission by the first STA, the medium sync delay timer starts to be set after the second STA returns to the listening operation. MLD

2. The MLD according to claim 1, wherein the first link and the second link are a pair of non-simultaneous transmission and reception (NSTR) links that do not support simultaneous transmission and reception within the same MLD.

3. The MLD according to claim 1, wherein the specific frame is a medium access control protocol data unit (MPDU) or a physical layer protocol data unit (PPDU) in which a transmission opportunity (TXOP) period is not unspecified.

4. The MLD according to claim 1, wherein the second STA returns to the listening operation after a specific delay time from the end of the data transmission by the first STA or the end of the TXOP.

5. The MLD according to claim 4, wherein the specific delay time is a delay switching from a frame exchange related to the data transmission to the listening operation. **Claim 6**: The MLD according to claim 1, wherein the MLD operates in an Enhanced Multi-Link Single Radio (EMLSR) mode / an Enhanced Multi-Link Multi-Radio (EMLMR) mode. **Claim 7**: A method performed by a Multi-Link Device (MLD) including a first Station (STA) operating on a first link and a second STA operating on a second link, wherein the method comprises: receiving, via the second STA operating on the second link, a frame transmitted from one of the one or more STAs; and when the frame is a specific frame, resetting a Medium Sync Delay timer for applying a medium synchronization delay of the second STA to "0" based on the received frame, wherein the medium synchronization delay indicates a period for restricting data transmission on the second link after transmitting data of the first STA on the first link, wherein when the second STA loses medium synchronization due to the data transmission by the first STA, after the second STA returns to a listening operation, the medium synchronization delay timer is set and starts. **Claim 8** The method according to claim 7, wherein the first link and the second link are a Non-Simultaneous Transmission and Reception (NSTR) link pair that does not support simultaneous transmission within the same MLD. **Claim 9**: The method according to claim 7, wherein the specific frame is a Medium Access Control Protocol Data Unit (MPDU) or a Physical layer Protocol Data Unit (PPDU) in which a Transmission Opportunity (TXOP) period is not unspecified. **Claim 10**: The method according to claim 7, wherein the second STA returns to a listening operation after a specific delay time from the end of the data transmission by the first STA or the end of the TXOP.

11. The method according to claim 10, wherein the specific delay time is a delay switching from a frame exchange related to the data transmission to the listening operation.

12. The method according to claim 7, wherein the MLD operates in an Enhanced Multi-Link Single Radio (EMLSR) mode / an Enhanced Multi-Link Multi-Radio (EMLMR) mode.

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