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

Abstract

To disclose a method and a device for transmitting / receiving data performed by a multi-link device (MLD) including a plurality of stations each operating on multiple links in a wireless communication system.SOLUTION: Specifically, an MLD of the present invention receives a frame transmitted from a first station (STA) or a first access point (AP) operating on a first link, via a second STA operating on a second link, and if a medium sync delay timer for applying a medium sync delay is not '0', can reset the medium sync delay timer of the second STA based on the received frame.SELECTED DRAWING: Figure 34

Description

[Technical Field]

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

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

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

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

[0005] As WLAN adoption continues to grow and applications become more diverse, the need for new WLAN systems is emerging to support data throughput rates (Very High Throughput, VHT) higher than those supported by IEEE 802.11n. Among these, IEEE 802.11ac supports wide bandwidth (80MHz-160MHz) in the 5GHz frequency band. While the IEEE 802.11ac standard is defined only in the 5GHz band, initial 802.11ac chipsets are expected to support operation in the 2.4GHz band as well for backward compatibility with existing 2.4GHz products. Theoretically, this standard enables multi-station WLAN speeds of at least 1Gbps and maximum single-link speeds of at least 500Mbps. This is achieved by expanding the air interface concepts adopted in 802.11n, including wider radio frequency bandwidth (up to 160MHz), more MIMO spatial streams (up to 8), multi-user MIMO, and denser modulation (up to 256QAM). Additionally, IEEE 802.11ad is a method of transmitting data using the 60GHz band instead of the conventional 24GHz / 5GHz band. IEEE 802.11ad is a transmission standard that uses beamforming technology to provide speeds of up to 7Gbps, making it suitable for streaming large amounts of data and high-bitrate video, such as uncompressed HD video. However, the 60GHz frequency band has the disadvantage of being difficult to pass through obstacles and can only be used between devices in close proximity.

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

[0007] Additionally, development of new WLAN standards has begun to increase maximum transmission speeds to support new multimedia applications such as high-definition video and real-time gaming. IEEE 802.11be (Extremely High Throughput, EHT), the 7th generation WLAN standard, is currently being developed with the goal of supporting transmission rates of up to 30 Gbps through wider bandwidth in the 2.4 / 5 / 6 GHz bands, increased spatial streams, and multi-AP cooperation. IEEE 802.11be proposes technologies such as a 320 MHz bandwidth, multi-link operation, multi-AP (multi-access point) operation, and hybrid automatic repeat request (HARQ) retransmission. Summary of the Invention [Problem to be solved by the invention]

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

[0009] Another object of an embodiment of the present invention is to provide a sink recovery method for a station using multilink.

[0010] The technical problems to be solved by the present specification are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0011] According to the present invention, a multi-link device (MLD) including a plurality of stations operating on a plurality of links including a first link and a second link includes a processor, wherein the processor receives a frame transmitted from one of one or more stations (STAs) via a second STA operating on the second link, and if a media synchronization delay timer is not '0', resets a media synchronization delay timer for applying a media synchronization delay (Medium Sync Delay) of the second STA based on the received frame, the media synchronization delay indicating an interval for restricting data transmission / reception on the second link after transmitting / receiving data of the first STA on the first link, and the media synchronization delay timer is reset if the frame is a frame for a valid MPDU other than an RTS (request to send) frame.

[0012] In addition, 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 the other link and does not support simultaneous transmission / reception within the same MLD.

[0013] In addition, in the present invention, the media synchronization delay timer starts when the transmission on the first link ends.

[0014] In addition, in the present invention, when the MLD operates in single radio mode, the media synchronization delay timer starts when a specific delay time has elapsed since the end of transmission on the first link.

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

[0016] In addition, in the present invention, the media synchronization delay timer is reset if the frame is a frame transmitted from an AP associated with the second STA or an AP included in the same multiple BSSID set as the associated AP. [Effects of the Invention]

[0017] An embodiment of the present invention provides a wireless communication method that efficiently uses multilinks and a wireless communication terminal that uses the same.

[0018] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing a wireless LAN system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram showing a wireless LAN system according to another embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the configuration of a station according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a configuration of an access point according to an embodiment of the present invention. [Figure 5] 1 is a diagram illustrating a process in which a STA establishes a link with an AP. [Figure 6] FIG. 1 is a diagram illustrating a CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method used in wireless LAN communication. [Figure 7] 1A and 1B are diagrams illustrating examples of various standard generation PPDU (PLCP Protocol Data Unit) formats. [Figure 8]1A and 1B are diagrams showing examples of various EHT (Extremely High Throughput) PPDU (Physical Protocol Data Unit) formats and methods for indicating the same according to an embodiment of the present invention. [Figure 9] 1 is a diagram illustrating a multi-link device according to an embodiment of the present invention. [Figure 10] FIG. 10 is a diagram illustrating an example of a TID-to-link mapping method according to one embodiment of the present invention. [Figure 11] FIG. 10 is a diagram illustrating an example of a multi-link NAV setting operation according to one embodiment of the present invention. [Figure 12] FIG. 10 is a diagram illustrating yet another example of a multi-link NAV setting operation according to one embodiment of the present invention. [Figure 13] FIG. 1 is a diagram illustrating an example of BSS classification and operations based thereon according to an embodiment of the present invention. [Figure 14] FIG. 2 is a diagram illustrating a wireless LAN function according to an embodiment of the present invention. [Figure 15] FIG. 2 is a diagram illustrating an uplink (UL) multi-user (MU) operation according to one embodiment of the present invention. [Figure 16] FIG. 1 is a diagram illustrating a trigger frame format according to one embodiment of the present invention. [Figure 17] A diagram showing a method for indicating a trigger-based PPDU format according to one embodiment of the present invention. [Figure 18] FIG. 10 is a diagram illustrating an example of UL MU operation according to one embodiment of the present invention. [Figure 19] FIG. 10 illustrates end time alignment of a high priority frame according to one embodiment of the present invention. [Figure 20] FIG. 10 is a diagram illustrating yet another example of end time alignment of high priority frames according to one embodiment of the present invention. [Figure 21]FIG. 10 is a diagram illustrating yet another example of end time alignment of high priority frames according to one embodiment of the present invention. [Figure 22] FIG. 2 is a diagram illustrating an example of a medium access recovery procedure according to an embodiment of the present invention. [Figure 23] FIG. 10 is a diagram illustrating an example of signaling related to a multi-link element and MediumSyncDelay according to one embodiment of the present invention. [Figure 24] FIG. 10 is a diagram illustrating an example of a MediumSyncDelay timer reset operation according to an embodiment of the present invention. [Figure 25] FIG. 10 is a diagram illustrating an example of a MediumSyncDelay timer reset operation according to an embodiment of the present invention. [Figure 26] FIG. 2 is a diagram illustrating an example of Medium Synchronization OFDM ED Threshold subfield encoding according to an embodiment of the present invention. [Figure 27] FIG. 10 is a diagram illustrating an example of a transmission operation when a MediumSyncDelay timer is not 0 according to an embodiment of the present invention. [Figure 28] FIG. 10 is a diagram illustrating yet another example of a transmission operation when the MediumSyncDelay timer is not 0 according to an embodiment of the present invention. [Figure 29] FIG. 10 is a diagram illustrating yet another example of a MediumSyncDelay timer reset operation according to an embodiment of the present invention. [Figure 30] FIG. 10 is a diagram illustrating an example of a MediumSyncDelay timer reset according to an embodiment of the present invention. [Figure 31] FIG. 10 is a diagram illustrating yet another example of MediumSyncDelay timer reset according to an embodiment of the present invention. [Figure 32] FIG. 10 is a diagram illustrating yet another example of MediumSyncDelay timer reset according to an embodiment of the present invention. [Figure 33] FIG. 10 is a diagram illustrating yet another example of MediumSyncDelay timer reset according to an embodiment of the present invention. [Figure 34] 10 is a flowchart illustrating an example of an operation of non-AP MLD according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of engineers in the relevant technical field, customs, or the emergence of new technologies. In addition, in certain cases, the applicant may have arbitrarily selected terms, and in such cases, the meanings thereof will be described in the relevant description of the invention. Therefore, it is made clear that the terms used in this specification should be interpreted not simply as names of terms, but based on the substantive meanings of the terms and the overall content of this specification.

[0021] Throughout this specification, when a component is referred to as being "coupled" to another component, this includes not only when it is "directly coupled" to another component, but also when it is "electrically coupled" with another component interposed therebetween. Furthermore, when a component "includes" a specific component, this does not mean that it excludes the other component, but that it may further include the other component, unless otherwise specified. In addition, limitations such as "greater than" or "less than" a specific threshold value may be appropriately substituted with "exceed" or "less than," respectively, depending on the embodiment. Hereinafter, in the present invention, the terms "field" and "subfield" may be used interchangeably.

[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), which are a set of devices that can synchronize and communicate with each other. Generally, BSSs are classified into infrastructure BSSs and independent BSSs (IBSSs), and Figure 1 shows an infrastructure BSS.

[0024] As shown in FIG. 1, infrastructure BSSs BSS1 and BSS2 include one or more stations STA1, STA2, STA3, STA4, and STA5, access points AP-1 and AP-2 that are stations providing distribution services, and a distribution system DS that connects multiple access points AP-1 and AP-2.

[0025] A station (STA) is any device that includes a medium access control (MAC) and a physical layer interface for a wireless medium according to the IEEE 802.11 standard. In a broad sense, the term "station" encompasses not only non-AP stations but also APs. In this specification, the term "terminal" refers to either a non-AP or an AP, or both. A station for wireless communication includes a processor and a communication unit, and may further include a user interface and a display unit, depending on the embodiment. The processor generates frames to be transmitted over a wireless network, processes frames received over the wireless network, and performs various other processes for controlling the station. The communication unit is functionally connected to the processor and transmits and receives frames over the wireless network for the station. In this specification, the term "terminal" encompasses user equipment (UE).

[0026] An access point (AP) is an entity that provides a connection to a distribution system (DS) via a wireless medium for associated stations. In an infrastructure BSS, communication between non-AP stations is generally performed via the AP. However, if a direct link is established, direct communication is also possible between non-AP stations. Meanwhile, in the present invention, the term AP is used as a concept including a personal BSS coordination point (PCP), but in a broader sense, it also includes concepts such as a central controller, a base station (BS), a node B, a base transceiver system (BTS), or a site controller. In the present invention, an AP is also referred to as a base wireless communication terminal, but in a broader sense, the term base wireless communication terminal is used as a term including an AP, a base station, an eNodeB (eNB), and a transmission point (TP). In addition, the base wireless communication terminal includes various types of wireless communication terminals that allocate communication medium resources and perform scheduling for communication with multiple wireless communication terminals.

[0027] A plurality of infrastructure BSSs are connected to each other via a distribution system DS, and the plurality of BSSs connected via the distribution system are called an Extended Service Set (ESS).

[0028] 2 is a diagram showing an independent BSS, which is a wireless LAN system according to another embodiment of the present invention. In the embodiment of FIG. 2, the same or corresponding parts as those in the embodiment of FIG. 1 will not be described again.

[0029] BSS3 shown in Figure 2 is an independent BSS and does not include an AP, so none of the stations (STA6, STA7) are connected to an AP. An independent BSS is not allowed to connect to a distribution system and forms a self-contained network. In an independent BSS, each station (STA6, STA7) is directly connected to each other.

[0030] 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 WLAN packets and may be incorporated into or external to the station 100. According to an embodiment, the communication unit 120 may include at least one communication module using different frequency bands. For example, the communication unit 120 may include communication modules using different frequency bands such as 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. According to an embodiment, the station 100 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with an AP or an external station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 120 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the station 100. When the station 100 includes multiple communication modules, each communication module may be provided independently, or multiple modules may be integrated into a single chip. In the embodiment of the present invention, the communication unit 120 may represent a radio frequency (RF) communication module that processes RF signals.

[0032] Next, the user interface 140 includes various types of input / output means provided in the station 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the station 100 based on the received user input. Also, the user interface unit 140 performs output based on instructions from the processor 110 using various output means.

[0033] Next, the display unit 150 outputs an image on a display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or a user interface based on a control command from the processor 110. The memory 160 also stores control programs and various data used by the station 100. Such control programs include a connection program required for the station 100 to connect to an AP or an external station.

[0034] The processor 110 of the present invention executes various commands or programs to process data within the station 100. The processor 110 also controls each unit of the station 100 and controls the transmission and reception of data between the units. According to an embodiment of the present invention, the processor 110 executes a program for connection with an AP stored in the memory 160 and receives a communication setup message transmitted by the AP. The processor 110 also reads information about the station 100's preferences contained in the communication setup message and requests connection to the AP based on the information about the station 100's preferences. The processor 110 of the present invention may refer to a main control unit of the station 100, or, depending on the embodiment, may refer to a control unit for individually controlling some components of the station 100, such as the communication unit 120. That is, the processor 110 may be a modem that modulates and demodulates wireless signals transmitted and received by the communication unit 120, or a modulator and / or demodulator. The processor 110 controls various operations for transmitting and receiving wireless signals in the station 100 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0035] The station 100 shown in FIG. 3 is a block diagram according to an embodiment of the present invention, and the separate blocks indicate the logically separated elements of the device. Therefore, the above-described device elements may be mounted on a single chip or multiple chips depending on the device design. For example, the processor 110 and the communication unit 120 may be integrated into a single chip or may be mounted on separate chips. Furthermore, in embodiments of the present invention, some components of the station 100, such as the user interface unit 140 and the display unit 150, may be selectively provided in the station 100.

[0036] 4 is a block diagram showing the configuration of an AP 200 according to an embodiment of the present invention. As shown, the AP 200 according to the embodiment of the present invention includes a processor 210, a communication unit 220, and a memory 260. In FIG. 4, duplicated descriptions of parts of the configuration of the AP 200 that are the same as or correspond to the configuration of the station 100 in FIG. 3 will be omitted.

[0037] Referring to FIG. 4, the AP 200 according to the present invention includes a communication unit 220 for operating a BSS in at least one frequency band. As described above in the embodiment of FIG. 3, the communication unit 220 of the AP 200 may also include multiple communication modules using different frequency bands. That is, the AP 200 according to the embodiment of the present invention may include two or more communication modules using different frequency bands, for example, 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Preferably, the AP 200 may include a communication module using a frequency band above 7.125 GHz and a communication module using a frequency band below 7.125 GHz. Each communication module may perform wireless communication with a station based on the WLAN standard of the frequency band supported by the communication module. The communication unit 220 may operate only one communication module at a time or multiple communication modules simultaneously, depending on the performance and requirements of the AP 200. In the embodiment of the present invention, the communication unit 220 may represent an RF (Radio Frequency) communication module that processes RF signals.

[0038] The memory 260 stores control programs used by the AP 200 and various data associated therewith. These control programs include a connection program that manages station connections. The processor 210 also controls each unit of the AP 200 and controls data transmission and reception between the units. According to an embodiment of the present invention, the processor 210 executes a program for connecting with a station stored in the memory 260 and transmits a communication setup message to one or more stations. The communication setup message includes information about connection preferences for each station. The processor 210 also performs connection setup in response to a station connection request. According to an embodiment, the processor 210 is a modem or a modulator / demodulator that modulates and demodulates wireless signals transmitted and received by the communication unit 220. The processor 210 controls various operations for transmitting and receiving wireless signals by the AP 200 according to an embodiment of the present invention. A detailed embodiment of this will be described later.

[0039] FIG. 5 is a diagram illustrating a process in which a STA establishes a link with an AP.

[0040] 5, a link between the STA 100 and the AP 200 is established through three steps: scanning, authentication, and association. First, the scanning step is a step in which the STA 100 acquires connection information for the BSS operated by the AP 200. There are two scanning methods: a passive scanning method in which the STA 100 acquires information using only a beacon message S101 periodically transmitted by the AP 200, and an active scanning method in which the STA 100 transmits a probe request to the AP S103, receives a probe response from the AP S105, and acquires connection information.

[0041] The STA 100 that successfully receives wireless connection information in the scanning step transmits an authentication request (S107a), receives an authentication response from the AP 200, and performs the authentication step (S107b). After the authentication step is performed, the STA 100 transmits an association request (S109a), receives an association response from the AP 200, and performs the association step (S109b). In this specification, association basically means wireless association, but the present invention is not limited to this, and association in a broad sense includes both wireless association and wired association.

[0042] Meanwhile, an 802.1X-based authentication step S111 and an IP address acquisition step S113 via DHCP are additionally performed. In Fig. 5, server 300 is a server that processes 802.1X-based authentication with STA 100, and may be physically connected to AP 200 or may exist as a separate server.

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

[0044] A terminal performing WLAN communication performs carrier sensing to check whether a channel is occupied before transmitting data. If a wireless signal above a certain strength is detected, the channel is determined to be occupied, and the terminal delays access to the channel. This process is called Clear Channel Assessment (CCA), and the level that determines whether or not a signal is detected is called the CCA threshold. If a wireless signal above the CCA threshold received by a terminal is identified as the receiver, the terminal processes the received wireless signal. On the other hand, if no wireless signal is detected from the channel or a wireless signal with strength below the CCA threshold is detected, the channel is determined to be idle.

[0045] If the channel is determined to be idle, each terminal with data to transmit performs a backoff procedure after an Inter Frame Space (IFS), such as an Arbitration IFS (AIFS) or a PCF IFS (PIFS), depending on the status of each terminal. In some embodiments, the AIFS is used as a configuration replacing the conventional DCF IFS (DIFS). Each terminal waits while decreasing a slot time by a random number determined for the corresponding terminal during the idle interval of the channel, and a terminal that has exhausted all slot times attempts to access the corresponding channel. The period during which each terminal performs the backoff procedure is called a contention window period.

[0046] If a specific terminal successfully accesses the channel, it transmits data over the channel. However, if the terminal attempting access collides with another terminal, the colliding terminals are assigned new random numbers and perform a backoff procedure again. According to one embodiment, the new random numbers assigned to each terminal are determined within a range (2*CW) twice the range of the random numbers previously assigned to the terminal (contention window, CW). Meanwhile, each terminal attempts access by performing a backoff procedure again in the next contention window period. At this time, each terminal performs the backoff procedure from the slot time remaining in the previous contention window period. In this way, terminals communicating over a wireless LAN can avoid collisions with each other on a specific channel.

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

[0048] <Examples of various PPDU formats>

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

[0050] 7(a), the preamble of the legacy PPDU includes a Legacy Short Training field (L-STF), a Legacy Long Training field (L-LTF), and a Legacy Signal field (L-SIG). In an embodiment of the present invention, the L-STF, L-LTF, and L-SIG may be referred to as a legacy preamble.

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

[0052] Referring to FIG. 7(c), the preamble of the EHT PPDU further includes a Repeated Legacy Short Training field (RL-SIG), a Universal Signal field (U-SIG), an Extremely High Throughput Signal A field (EHT-SIG-A), an Extremely High Throughput Signal B field (EHT-SIG-A), an Extremely High Throughput Short Training field (EHT-STF), and an Extremely High Throughput Long Training field (EHT-LTF) in addition to the legacy preamble. In an embodiment of the present invention, the RL-SIG, EHT-SIG-A, EHT-SIG-B, EHT-STF, and EHT-LTF may be referred to as an EHT preamble. The specific configuration of the non-legacy preamble may vary depending on the EHT PPDU format. For example, EHT-SIG-A and EHT-SIG-B may be used only in some EHT PPDU formats.

[0053] The L-SIG field included in the PPDU preamble is configured with a total of 64 subcarriers using 64 FFT OFDM. Of these, 48 subcarriers, excluding guard subcarriers, DC subcarriers, and pilot subcarriers, are used for L-SIG data transmission. BPSK and Rate=1 / 2 MCS (Modulation and Coding Scheme) are applied to the L-SIG, so it can contain a total of 24 bits of information. Figure 7(d) shows the 24-bit information structure of the L-SIG.

[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 rates of 6, 9, 12, 18, 24, 36, 48, or 54 Mbps, which is a combination of a modulation scheme such as BPSK, QPSK, 16-QAM, or 64-QAM and a code rate such as 1 / 2, 2 / 3, or 3 / 4. The combined information in the L_RATE and L_LENGTH fields indicates the total length of the PPDU. In a non-legacy PPDU format, the L_RATE field is set to the minimum rate of 6 Mbps.

[0055] The L_LENGTH field is in bytes, and a total of 12 bits are allocated, allowing a maximum of 4095 to be signaled. In combination with the L_RATE field, it can indicate the length of the corresponding PPDU. In this case, legacy and non-legacy terminals can interpret the L_LENGTH field in different ways.

[0056] First, a legacy or non-legacy terminal analyzes the length of the corresponding PPDU using the L_LENGTH field as follows. When the value of the L_RATE field is set to indicate 6 Mbps, 3 bytes (i.e., 24 bits) may be transmitted during 4 us, which is the duration of one 64 FFT symbol. Therefore, by adding the 3 bytes corresponding to the SVC field and Tail field to the L_LENGTH field value and dividing this by 3 bytes, which is the transmission amount of one symbol, the number of 64 FFT reference symbols after the L-SIG is obtained. The obtained number of symbols is multiplied by 4 us, which is the duration of one symbol, and then 20 us, which is required to transmit the L-STF, L-LTF, and L-SIG, to obtain the length of the corresponding PPDU, i.e., the reception time (RXTIME). This can be expressed mathematically as shown in Equation 1 below.

[0057]

number

[0058] At this time,

number

[0059]

number

[0060] Here, TXTIME is the total transmission time constituting the PPDU, and is expressed as the following equation 3. In this case, TX represents the transmission time of X.

[0061]

number

[0062] Referring to the above formula, the length of the PPDU is calculated based on the rounded up value of L_LENGTH / 3. Therefore, for any value of k, three different values ​​of L_LENGTH={3k+1, 3k+2, 3(k+1)} indicate the same PPDU length.

[0063] Referring to Figure 7(e), the U-SIG (Universal SIG) field remains in the EHT PPDU and subsequent generation WLAN PPDUs, and serves to distinguish which generation of PPDU it is, including 11be. The U-SIG is two 64FFT-based OFDM symbols and can transmit a total of 52 bits of information. Of these, 43 bits excluding 9 bits of CRC / tail are roughly divided into a VI (Version Independent) field and a VD (Version Dependent) field.

[0064] The VI bit will maintain its current bit configuration, so even if a subsequent generation PPDU is defined, current 11be UEs can obtain information about the PPDU from the VI field of the PPDU. To this end, the VI field consists of the PHY version, UL / DL, BSS color, TXOP, and Reserved fields. The PHY version field is 3 bits long and serves to sequentially distinguish between 11be and subsequent generations of WLAN standards. 11be has a value of 000b. The UL / DL field identifies whether the PPDU is an uplink or downlink PPDU. The BSS color represents a BSS identifier defined in 11ax and has a value of 6 or more bits. The TXOP represents the transmit opportunity duration (Transmit Opportunity Duration) transmitted in the MAC header. By adding it to the PHY header, the length of the TXOP containing the PPDU can be inferred without decoding the MPDU, and has a value of 7 or more bits.

[0065] The VD field, which is signaling information useful only for 11be version PPDUs, may consist of fields commonly used in any PPDU format, such as the PPDU format and BW, as well as fields defined differently for each PPDU format. The PPDU format is a separator that distinguishes between EHT SU (Single User), EHT MU (Multiple User), EHT TB (Trigger-based), and EHT ER (Extended Range) PPDUs. The BW field broadly signals five basic PPDU BW options: 20, 40, 80, 160 (80 + 80), and 320 (160 + 160) MHz (BWs that can be expressed in the form of a power of 20 * 2 can be called basic BWs), as well as various remaining PPDU BWs formed by preamble puncturing. After signaling at 320 MHz, a portion of 80 MHz may be punctured. In addition, the punctured and modified channel shape may be signaled directly in the BW field, or may be signaled using both the BW field and a field that appears after the BW field (for example, a field in the EHT-SIG field). If the BW field is 3 bits, a total of 8 BW signalings are possible, so a maximum of 3 puncturing modes can be signaled. If the BW field is 4 bits, a total of 16 BW signalings are possible, so a maximum of 11 puncturing modes can be signaled.

[0066] The fields located after the BW field vary depending on the type and format of the PPDU. MU PPDUs and SU PPDUs may be signaled in the same PPDU format, and a field for distinguishing between MU PPDUs and SU PPDUs may be located before the EHT-SIG field, and additional signaling may be performed for this purpose. Both SU PPDUs and MU PPDUs include an EHT-SIG field, but some fields not required for the SU PPDU may be compressed. In this case, the information of the compressed fields may be omitted or may have a reduced size compared to the size of the original fields included in the MU PPDU. For example, the SU PPDU may have a different configuration, such as the common fields of the EHT-SIG being omitted or replaced, or the user-specific fields being replaced or reduced to one.

[0067] Alternatively, the SU PPDU may further include a compression field indicating whether or not it is compressed, and some fields (such as the RA field) may be omitted depending on the value of the compression field.

[0068] When a portion of the EHT-SIG field of the SU PPDU is compressed, the information included in the compressed field may be signaled together in an uncompressed field (e.g., a common field). In the case of an MU PPDU, since it is a PPDU format for simultaneous reception by multiple users, the EHT-SIG field must be transmitted after the U-SIG field, and the amount of information signaled may be variable. That is, since multiple MU PPDUs are transmitted to multiple STAs, each STA must recognize the location of the RU to which the MU PPDU is transmitted, the STA to which each RU is assigned, and whether the transmitted MU PPDU was sent to it. Therefore, the AP must transmit the above information in the EHT-SIG field. To this end, the U-SIG field signals information for efficiently transmitting the EHT-SIG field, which may be the number of symbols in the EHT-SIG field and / or the MCS, which is the modulation method. The EHT-SIG field may include information on the size and location of the RU assigned to each user.

[0069] In the case of an SU PPDU, a STA may be assigned multiple RUs, and the multiple RUs may be contiguous or discontinuous. If the RUs assigned to the STA are not contiguous, the STA can efficiently receive the SU PPDU only by recognizing punctured RUs in between. Therefore, the AP can transmit the SU PPDU including information on punctured RUs among the RUs assigned to the STA (e.g., puncturing pattern of the RUs). That is, in the case of an SU PPDU, a puncturing mode field including information indicating whether a puncturing mode is applied and the puncturing pattern in a bitmap format, etc., may be included in the EHT-SIG field, and the puncturing mode field can signal the type of discontinuous channels appearing within the bandwidth.

[0070] The type of signaled discontinuous channel is limited, and indicates the BW and discontinuous channel information of the SU PPDU in combination with the value of the BW field. For example, since the SU PPDU is a PPDU transmitted only to a single UE, the STA can recognize its allocated bandwidth from the BW field included in the PPDU and can recognize punctured resources within the allocated bandwidth from the puncturing mode field of the U-SIG field or EHT-SIG field included in the PPDU. In this case, the UE can receive the PPDU in the remaining resource units excluding specific channels of the punctured resource units. In this case, multiple RUs allocated to the STA may be configured with different frequency bands or tones.

[0071] The reason why only limited discontinuous channel types are signaled is to reduce the signaling overhead of the SU PPDU. Since puncturing can be performed for each 20 MHz subchannel, if puncturing is performed on a BW having multiple 20 MHz subchannels, such as 80, 160, or 320 MHz, in the case of 320 MHz, the discontinuous channel type (when only the end 20 MHz is punctured and considered discontinuous) must be signaled by expressing whether or not each of the remaining 15 20 MHz subchannels excluding the primary channel is in use. Using 15 bits to signal the discontinuous channel type for single-user transmission can result in excessive signaling overhead when considering the low transmission rate of the signaling part.

[0072] This invention proposes a method for signaling the discontinuous channel type of the SU PPDU, shows the discontinuous channel type determined by the proposed method, and proposes a method for signaling the primary 160 MHz and secondary 160 MHz puncturing types in the 320 MHz BW configuration of the SU PPDU.

[0073] In addition, one embodiment of the present invention proposes a method of varying the PPDU configuration indicated by the preamble puncturing BW value according to the PPDU format signaled in the PPDU format field. Assuming the length of the BW field is 4 bits, in the case of an EHT SU PPDU or TB PPDU, an EHT-SIG-A symbol of one symbol may be further signaled after the U-SIG, or no EHT-SIG-A may be signaled at all. Taking this into consideration, up to 11 puncturing modes must be signaled using only the BW field of the U-SIG. However, in the case of an EHT MU PPDU, an EHT-SIG-B symbol is further signaled after the U-SIG, so up to 11 puncturing modes may be signaled in a different manner than in the SU PPDU. In the case of an EHT ER PPDU, the BW field can be set to 1 bit to signal whether the PPDU uses a 20 MHz or 10 MHz bandwidth.

[0074] Figure 7(f) shows the format-specific field configuration of the VD field when the PPDU format field of the U-SIG indicates an EHT MU PPDU. For an MU PPDU, SIG-B, a signaling field for simultaneous reception by multiple users, is required. SIG-B may be transmitted after the U-SIG without a separate SIG-A. For this purpose, the U-SIG must signal information for decoding SIG-B. These fields include the SIG-B MCS, SIG-B DCM, number of SIG-B symbols, SIG-B compression, and number of EHT-LTF symbols.

[0075] FIG. 8 illustrates an example of various Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) formats and methods for indicating the same according to an embodiment of the present invention.

[0076] 8, a PPDU may be configured with a preamble and a data portion, and the format of one type, EHT PPDU, may be distinguished by a U-SIG field included in the preamble. Specifically, whether the format of the PPDU is EHT PPDU may be indicated based on a PPDU format field included in the U-SIG field.

[0077] 8(a) shows an example of an EHT SU PPDU format for a single STA. The EHT SU PPDU is a PPDU used for single user (SU) transmission between an AP and a single STA, and an EHT-SIG-A field for additional signaling may be located after the U-SIG field.

[0078] 8(b) shows an example of an EHT trigger-based PPDU format, which is an EHT PPDU transmitted based on a trigger frame. The EHT trigger-based PPDU is an EHT PPDU transmitted based on a trigger frame and is an uplink PPDU used for responding to the trigger frame. Unlike the EHT SU PPDU, the EHT PPDU does not have an EHT-SIG-A field after the U-SIG field.

[0079] 8(c) shows an example of an EHT MU PPDU format, which is an EHT PPDU for multiple users. The EHT MU PPDU is a PPDU used to transmit a PPDU to one or more STAs. In the EHT MU PPDU format, an HE-SIG-B field may be located after the U-SIG field.

[0080] 8(d) shows an example of an EHT ER SU PPDU format used for single-user transmission with STAs in an extended range. The EHT ER SU PPDU may be used for single-user transmission with STAs in a wider range than the EHT SU PPDU described in FIG. 8(a), and the U-SIG field may be repeated on the time axis.

[0081] The EHT MU PPDU described in (c) of Figure 8 can be used by the AP for downlink transmission to multiple STAs. In this case, the EHT MU PPDU can include scheduling information so that multiple STAs can simultaneously receive the PPDU transmitted from the AP. The EHT MU PPDU can convey AID information of the receiver and / or sender of the transmitted PPDU to the STA through the user specific field of the EHT-SIG-B. Therefore, multiple terminals receiving the EHT MU PPDU can perform spatial reuse based on the AID information of the user specific field included in the preamble of the received PPDU.

[0082] Specifically, the resource unit allocation (RA) field of the HE-SIG-B field included in the HE MU PPDU may include information regarding the configuration of resource units (e.g., the division type of resource units) in a specific bandwidth (e.g., 20 MHz) on the frequency axis. That is, the RA field may indicate the configuration of resource units divided by the bandwidth for transmitting the HE MU PPDU so that the STA can receive the PPDU. Information about the STA allocated (or designated) to each divided resource unit may be included in a user specific field of the EHT-SIG-B and transmitted to the STA. That is, the user specific field may include one or more user fields corresponding to each divided resource unit.

[0083] For example, among the multiple divided resource units, the user field corresponding to at least one resource unit used for data transmission may include the AID of the receiver or sender, and the user field corresponding to the remaining resource units not used for data transmission may include a previously set null STA ID.

[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 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. In this case, the EHT SU PPDU and the EHT MU PPDU can be distinguished depending on 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 can receive the PPDU, 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] In addition, some of the fields or some information of the fields shown in Figure 8 may be omitted, and such a case where some of the fields or some information of the fields is omitted can be defined as a compression mode or a compressed mode.

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

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

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

[0089] A STA included in an MLD can operate on one or more links or channels. That is, a STA included in an MLD can operate on multiple different channels. For example, a STA included in an MLD can operate using channels in different frequency bands, such as 2.4 GHz, 5 GHz, and 6 GHz. This allows MLD to gain benefits in channel access and improve overall network performance. While existing WLANs operate on a single link, MLD operation can use multiple links to obtain more channel access opportunities or allow STAs to operate efficiently on multiple links taking into account channel conditions.

[0090] Also, if the STA affiliated with the MLD is an AP, the MLD to which the AP is affiliated may be an AP MLD, but if the STA affiliated with the MLD is a non-AP STA, the MLD to which the non-AP is affiliated may be a non-AP MLD.

[0091] An AP MLD (Multi-link Device) may be a device including one or more wireless access points (APs) and connected to a higher layer via one interface. That is, the AP MLD may be connected to the LLC (Logical Link Control) layer via one interface. Multiple APs included in the AP MLD may share some functions in the MAC layer. Each AP in the AP MLD may operate on a separate link. An STA MLD may be a device including one or more non-AP STAs and connected to a higher layer via one interface.

[0092] That is, the STA MLD may be connected to the LLC layer via a single interface. Multiple STAs included in the STA MLD may share some functions at the MAC layer. The STA MLD may also be called a non-AP MLD. The AP MLD and STA MLD can perform multi-link operations, communicating using multiple individual links. That is, if the AP MLD includes multiple APs, each AP can configure a separate link and transmit and receive frames using multiple links with each UE included in the STA MLD. Each link can operate in the 2.4 GHz, 5 GHz, or 6 GHz band, and each link can perform bandwidth extension. For example, if the AP MLD configures one link in the 2.4 GHz band and two links in the 5 GHz band, the 2.4 GHz band can transmit frames at a bandwidth of 40 MHz using a bandwidth extension scheme, and each link using the 5 GHz band can transmit frames at a maximum bandwidth of 320 MHz using discontinuous bandwidths.

[0093] Meanwhile, due to interference issues within the device, the AP MLD or STA MLD may prevent one terminal in the MLD from receiving while another terminal is transmitting. This operation, in which one AP or terminal in the MLD receives while another AP or terminal in the MLD is transmitting, is called STR (Simultaneous Transmit and Receive). The AP MLD is capable of STR operation for all links. Alternatively, STR operation is not possible for some links of the AP MLD. An STR-capable terminal MLD may be connected to an AP MLD, or an STR-incapable MLD may be connected to some or all links. Furthermore, terminals (e.g., IEEE 802.11a / b / g / n / ac / ax terminals) that do not belong to the MLD may also be connected to an AP included in the AP MLD.

[0094] The AP MLD and the STA MLD may perform a negotiation process for a multiple link usage operation during the scanning and connection process described in FIG. 5. For example, during the scanning process described in FIG. 5, an AP included in the AP MLD may transmit a beacon frame including an indicator indicating that a multiple link operation is available, the number of available links, and information on the number of available links. Alternatively, a terminal belonging to the STA MLD may transmit a probe request frame including an indicator indicating that a multiple link operation is available, and an AP belonging to the AP MLD may transmit a probe response frame including an indicator indicating that a multiple link operation is available. In this case, the AP may further transmit the number of available links, link information, etc. during the multiple link operation.

[0095] The STA MLD, which has confirmed whether the AP MLD is to operate multiple links and the link information to be used during the scanning process, 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 the multiple link operation. At this time, the negotiation process for the multiple link operation can be performed during the connection process between an AP belonging to the AP MLD and a terminal belonging to the STA MLD. That is, a terminal (e.g., STA1) belonging to the STA MLD can send a connection request frame to an AP (e.g., AP1) belonging to the AP MLD, and can send an indicator indicating that the terminal's multiple link operation is available and a request indicator requesting the terminal to perform the multiple link operation. The AP receiving the connection request frame from the terminal can check the indicator requesting the multiple link operation, and if the AP is capable of the multiple link operation, can send a connection response frame to the terminal that allows the multiple link operation, including link information to be used for the multiple link operation and parameters used for each link. The parameters for the multi-link operation may include one or more of the bandwidth of each link to be used, a bandwidth expansion direction, a Target Beacon Transmission Time (TBTT), and whether or not to perform STR operation. After the connection process, the AP MLD and the STA MLD, which have confirmed the use of the multi-link operation by exchanging the connection request frame and the response frame, can perform a frame transmission operation on multiple links via multiple APs included in the AP MLD and multiple UEs included in the STA MLD.

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

[0097] According to an embodiment of the present invention, a multi-link operation may include a multi-link setup operation. The multi-link setup operation may be an operation corresponding to association performed in a single-link operation. In order to exchange frames over multiple links, multi-link setup must precede the multi-link setup. 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 multiple links. The capability information may include information on whether a STA included in the MLD can receive frames over one link while another STA included in the MLD can transmit frames over another link. That is, the capability information may include information on whether a STA (non-AP STA) and / or an AP (or AP STA) can simultaneously transmit / receive frames in different transmission directions through links included in the MLD. The capability information may also include information on available links or operating channels. The multi-link setup may be set up through negotiation between peer STAs, and a multi-link operation may be set up over a single link.

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

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

[0100] Referring to Figure 10, there may be a mapping relationship between TIDs and links as described in Figure 9. In addition, in the present invention, the mapping relationship between TIDs and links may be referred to as TID-to-link mapping, TID-to-link mapping, TID mapping, link mapping, etc. The TID may be a traffic identifier. The TID may also be an ID (identifier) ​​that classifies traffic, data, etc. to support quality of service (QoS).

[0101] The TID may be an ID used or assigned in a layer higher than the MAC layer. The TID may indicate traffic categories (TC) or traffic streams (TS). The TID may have 16 possible values, for example, values ​​from 0 to 15. Individual TID values ​​may be used depending on an access policy, channel access, or medium access method. For example, when EDCA (HCF (hybrid coordination function) connection-based channel access, enhanced distributed channel access) is used, the possible TID values ​​may be 0 to 7. When EDCA is used, the TID value may indicate user priority (UP), and the UP may be related to TC or TS. The UP may be a value assigned in a layer higher than the MAC. When HCCA (HCF controlled channel access) or SPCA is used, the possible TID values ​​may be 8 to 15. When HCCA or SPCA is used, the TID may indicate TSID. Furthermore, when HEMM or SEMM is used, the possible TID value may be 8 to 15. Furthermore, when HEMM or SEMM is used, TID may indicate TSID.

[0102] There may also be a mapping relationship between UP and access category (AC). An AC may be a label for providing QoS in EDCA or a label indicating a set of EDCA parameters. The EDCA parameters or a set of EDCA parameters may be used for channel association. An AC may be used in a QoS STA.

[0103] The AC value 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 indicate background, best effort, video, and voice, respectively. Furthermore, AC_BK, AC_BE, AC_VI, and AC_VO may be further subdivided. For example, AC_VI may be further subdivided into AC_VI primary and AC_VI alternate. Furthermore, AC_VO may be further subdivided into AC_VO primary and AC_VO alternate. Furthermore, UP values ​​or TID values ​​may be mapped to AC values. For example, UP values ​​or TID values ​​of 1, 2, 0, 3, 4, 5, 6, and 7 may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI, AC_VI, AC_VO, and AC_VO, respectively. Alternatively, UP values ​​or TID values ​​1, 2, 0, 3, 4, 5, 6, and 7 may be mapped to AC_BK, AC_BK, AC_BE, AC_BE, AC_VI alternate, AC_VI primary, AC_VO primary, and AC_VO alternate, respectively. UP values ​​or TID values ​​1, 2, 0, 3, 4, 5, 6, and 7 may have increasing priorities. That is, 1 may be a lower priority and 7 may be a higher priority. Therefore, the order of increasing priorities may be AC_BK, AC_BE, AC_VI, and AC_VO. AC_BK, AC_BE, AC_VI, and AC_VO may correspond to ACI (AC index) 0, 1, 2, and 3, respectively.

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

[0105] According to one embodiment of the present invention, a TID may be mapped to each link of a multi-link. For example, there may be a mapping of which link among multiple links a specific TID or a specific AC is allowed to transmit or receive on. Such mapping may be defined separately for each direction of the link. As described above, a default setting may exist for the mapping between TIDs and links. For example, the mapping between TIDs and links may basically map all TIDs to a certain link. According to one embodiment, at a specific time, a certain TID or a certain AC may be mapped to at least one link. Furthermore, management frames or control frames may be transmitted on all links.

[0106] In the present invention, data frames corresponding to TIDs or ACs that are mapped to either direction of the link may be transmitted, and data frames corresponding to TIDs or ACs that are not mapped to either direction of the link may not be transmitted.

[0107] According to one 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. Alternatively, the TID-to-link mapping may be based on the block ack agreement. For example, a block ack agreement may exist for a TID-to-link mapped TID.

[0108] TID-to-link mapping can provide QoS services. For example, by mapping a high-priority AC and TID to a link with good channel conditions or few STAs, data for that AC and TID can be transmitted quickly. Alternatively, TID-to-link mapping can help STAs on a specific link save power (or enter a doze state).

[0109] 10, there may be an AP MLD including AP1 and AP2. There may also be a Non-AP MLD including STA1 and STA2. The AP MLD may also include multiple links, Link1 and Link2. AP1 and STA1 may be associated via Link1, and AP2 and STA2 may be associated via Link2.

[0110] Thus, Link1 may include a link transmitting from AP1 to STA1 and / or a link transmitting from STA1 to AP1, and Link2 may include a link transmitting from AP2 to STA2 and / or a link transmitting from STA2 to AP2, where each link may be mapped with a TID and / or AC.

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

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

[0113] The simultaneous transmit and receive (STR) operation of MLD may be limited, which may be related to the frequency spacing between multiple links operating in a multi-link.

[0114] Therefore, according to an embodiment of the present invention, simultaneous transmission or reception is restricted when the spacing between links is m MHz, and simultaneous transmission or reception may not be restricted when the spacing between links is n MHz for n greater than m. This embodiment may be intended to solve the problem of simultaneous transmission or reception being restricted, and redundant description may be omitted. This embodiment may also be applied to MLDs that do not support STR.

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

[0116] Furthermore, according to an embodiment of the present invention, it is possible to restrict transmission or channel access during a period based on period information shared between links. The method of restricting transmission or channel access may include setting a NAV. Alternatively, the NAV may be reset to resume transmission or channel access. In this case, 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, a STA belonging to an MLD may set its NAV based on a frame (or PPDU) directed to another STA belonging to the MLD.

[0117] According to one embodiment of the present invention, an inter-link NAV may exist. The inter-link NAV may be a NAV used by STAs of multiple links belonging to an MLD when operating with multiple links. For example, transmission on link 2 may be avoided based on the inter-link NAV set based on period information received on link 1. Also, the inter-link NAV may exist or be used for an MLD that does not support STR. For example, when an inter-link NAV is set, the MLD that set the inter-link NAV does not need to transmit or connect channels on multiple links (or all links used by the MLD).

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

[0119] Using a separate inter-link NAV may have advantages over not using an inter-link NAV in situations where the NAV setting is updated. For example, situations may arise where it is acceptable to reset the NAV set by another link. For example, if an inter-link NAV is set based on a certain frame (or PPDU), but it is determined that the frame (or PPDU) is not destined for the same MLD, it may be acceptable to reset the set inter-link NAV. Suppose there is an MLD operating on link 1 and link 2, the NAV for link 1 may be set based on a frame received on link 1. Then, the NAV for link 1 may be updated based on a frame received on link 2. If the NAV for link 2 no longer needs to be maintained, resetting the NAV for link 1 would result in the loss of the NAV information set based on the frame received on link 1. If the inter-link NAV were used together with the NAV for each link, the NAV for each link would be maintained even if the inter-link NAV was reset, thereby resolving the above problem.

[0120] Although the embodiment of the present invention focuses on setting the NAV, the embodiment of the present invention is not limited to this and can also be applied to instructing the physical layer to suspend channel connection or instructing the channel state to be busy. Furthermore, the embodiment is not limited to resetting the NAV and can also be applied to instructing the physical layer to continue channel connection or instructing the channel state to be idle. In this case, a primitive exchanged between the physical layer and the MAC layer may be used. Alternatively, a primitive exchanged between one STA and another STA in the MLD may be used. Alternatively, a primitive exchanged between one MAC layer and another MAC layer in the MLD 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 terminate their channel access. As described above, channel access may be terminated based on the received duration information. However, due to the position of the field containing the duration information or the time required for decoding, there may be a time lag between the start of PPDU reception and the acquisition of the duration information. Therefore, accessing the channel and starting transmission during this time may lead to the above-mentioned problem. Therefore, according to an embodiment of the present invention, an STA in an MLD can terminate its channel access from the time another STA in the MLD starts receiving. Furthermore, after another STA in the MLD starts receiving, it can resume its channel access if it determines that the received frame is not intended for the other STA.

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

[0123] FIG. 12 embodies the explanation of the specific method of the embodiment explained in FIG. 11, and the duplicated explanation may be omitted.

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

[0125] According to an embodiment of the present invention, when STA1 begins to receive a frame, STA2 may suspend the channel connection. Furthermore, when STA1 acquires duration information from the L-SIG, STA2 may maintain the suspended channel connection. In this case, STA2 can determine that the suspended channel connection will last until the end of the frame received by STA1. Furthermore, if STA1 cannot reliably decode the L-SIG (if the L-SIG is invalid), STA2 can resume the channel connection.

[0126] In addition, STA1 can receive the TXOP duration and BSS color from the U-SIG of the frame received. If the received BSS color indicates intra-BSS or the BSS color is the BSS color corresponding to STA1, the channel connection can be suspended. In one embodiment, the duration for suspending the channel connection may be until the end of the received frame. In this case, there is an advantage that the channel connection can be started sooner after the end of the received frame. In another embodiment, the duration for suspending the channel connection may be the TXOP duration. In this case, the duration of the suspended channel connection may be updated based on the L-SIG. 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 BSS color from the U-SIG of the received frame, but the received BSS color may indicate that it is not intra-BSS, or the BSS color may not be the BSS color corresponding to STA1. Alternatively, STA1 may not be able to successfully decode the U-SIG. In such cases, STA2 can resume channel connection.

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

[0129] Although the above description is directed to the case where U-SIG is received, the same embodiment can also be applied to the case where HE-SIG-A is received when HE PPDU is received. For example, HE-SIG-A may include TXOP duration and BSS color, and therefore the above-described operations can be performed.

[0130] Also, STA2 may receive a STA-ID from the EHT-SIG of the frame received by STA1. If the received STA-ID is an indicator that STA1 should receive, for example, if the STA-ID indicates STA1, the STA-ID indicates a group to which STA1 belongs, or the STA-ID indicates broadcast, STA2 can maintain the state in which the channel connection is suspended.

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

[0132] Although the case of receiving EHT-SIG has been described, the same embodiment can also be applied to the case of receiving HE-SIG-B when receiving HE PPDU. For example, HE-SIG-B may include STA-ID, and therefore the above-described operation can be performed.

[0133] STA2 may also receive the MAC header of a frame received by STA1. If the RA (receiver address) or DA (destination address) included in the received MAC header indicates a value that STA1 should receive, for example, if the RA or DA indicates STA1, indicates a group to which STA1 belongs, or the STA-ID indicates broadcast, STA2 can maintain the suspended channel connection. In this case, the duration of the suspended channel access may be based on the duration information included in the received MAC header. More specifically, the duration of the suspended channel access may be based on the duration information indicated by the Duration / ID field included in the received MAC header.

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

[0135] The channel connection suspension and resumption described in FIG. 12 may be performed in the decoding order as STA1 starts receiving frames (or PPDUs) and sequentially decodes them. The decoding order may be based on the PPDU format, frame format, etc. For example, the L-SIG, U-SIG, EHT-SIG, and MAC header may be decoded in this order (for EHT PPDUs). Alternatively, the L-SIG, HE-SIG-A, and MAC header may be decoded in this order (for HE SU PPDUs and HE TB PPDUs). Alternatively, the L-SIG, HE-SIG-A, HE-SIG-B, and MAC header may be decoded in this order (for HE MU PPDUs). Alternatively, the L-SIG and MAC header may be decoded in this order (for 11a / g PPDUs).

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

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

[0138] According to one 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 a BSS to which the classifying STA belongs. Alternatively, classifying a BSS may mean an operation of classifying whether a received frame or a received PPDU is transmitted from a BSS to which the classifying STA belongs. Classifying a BSS may also include an operation of classifying whether a received frame or a received PPDU corresponds to a BSS to which the classifying STA does not belong. Alternatively, classifying a BSS may also mean an operation of classifying whether a received frame or a received PPDU is transmitted from a BSS to which the classifying STA does not belong. Classifying a BSS may also include an operation of classifying to which BSS a received frame or a received PPDU belongs. Alternatively, classifying a BSS may mean an operation of classifying from which BSS a received frame or a received PPDU is transmitted. According to one embodiment of the present invention, a BSS to which a classification STA belongs may be referred to as an intra-BSS. Alternatively, a BSS including a BSS to which a classification STA belongs may be referred to as an intra-BSS. Furthermore, a BSS that is not an intra-BSS may be referred to as an inter-BSS. Alternatively, a BSS that is not an intra-BSS may be an inter-BSS or an unclassified BSS. Alternatively, an inter-BSS may include an unclassified BSS. Furthermore, a BSS to which a classification STA does not belong may be referred to as an inter-BSS.

[0139] According to an embodiment, if a received frame or a received PPDU corresponds to an intra-BSS or is determined to have been transmitted from an intra-BSS, the received frame or the received PPDU may be referred to as an intra-BSS frame or an intra-BSS PPDU, respectively. Furthermore, if a received frame or a received PPDU corresponds to an inter-BSS or is determined to have been transmitted from an inter-BSS, the received frame or the received PPDU may be referred to as an inter-BSS frame or an inter-BSS PPDU, respectively. Furthermore, a PPDU including an intra-BSS frame may be an intra-BSS PPDU. Furthermore, 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, a BSS can be classified based on whether or not at least one of the one or more BSS classification conditions is satisfied.

[0141] The BSS classification conditions may include a condition based on BSS color. BSS color may be an identifier for a BSS. Also, BSS color may be included in the preamble of a PPDU, more specifically, in the signaling field (e.g., the HE-SIG-A field, the U-SIG field, or the VHT-SIG-A field). Also, BSS color may be included in TXVECTOR, which is transmitted from the MAC layer of the sender to the PHY layer. Also, BSS color may be included in RXVECTOR, which is transmitted from the PHY layer of the receiver to the MAC layer. The parameters included in TXVECTOR and RXVECTOR may be referred to as TXVECTOR parameters and RXVECTOR parameters, respectively. Also, BSS color may be included in the TXVECTOR parameter or RXVECTOR parameter. The AP may notify the STA of the BSS color set by the AP. According to an embodiment, BSSs can be classified based on the BSS color included in the received PPDU. If the BSS color included in a PPDU received by a 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. Alternatively, if the BSS color included in a PPDU received by a 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. Furthermore, if the BSS color included in a PPDU received by a 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 conditions may include a condition based on a MAC address. The MAC address may be included in the MAC header of the frame. The MAC address may include a receiver address (RA), a transmitter address (TA), a BSSID, a source address (SA), a destination address (DA), etc. According to one embodiment, a BSS may be classified based on a MAC address included in a 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 may 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 may be classified as an inter-BSS frame. 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 may 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 may be classified as an intra-BSS frame.

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

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

[0145] Furthermore, when the Partial AID field of a received PPDU indicates a portion of a BSS color, if the value of the received Partial AID field is identical to a portion of the BSS color corresponding to the receiving STA, the received PPDU can be classified as an intra-BSS PPDU. In this case, the portion of the BSS color may be 4 LSBs of the BSS color. According to another embodiment, the Partial AID field may indicate a portion of the BSSID. For example, if the Group ID field included in the VHT-SIG-A field of the VHT PPDU has a pre-set value (e.g., the Group ID field is set to 0), the Partial AID field may indicate a portion of the BSSID. According to one embodiment, when the Partial AID field of a received PPDU indicates a portion of a BSSID, if the value of the received Partial AID field is different from a portion of the BSSID corresponding to the receiving STA, the received PPDU can be classified as an inter-BSS PPDU. Furthermore, if the Partial AID field of a received PPDU indicates a portion of a BSSID, and the received Partial AID field value is identical to a portion of the BSSID corresponding to the receiving STA, the received PPDU can be classified as an intra-BSS PPDU. In this case, the portion of the BSSID can be the 9 MSBs of the BSSID. In addition, the Partial AID field value can be included in the TXVECTOR parameter PARTIAL_AID or the RXVECTOR parameter PARTIAL_AID. In addition, the Group ID field value can be included in the TXVECTOR parameter GROUP_ID or the RXVECTOR parameter GROUP_ID.

[0146] The BSS classification conditions may include conditions under which the AP receives a PPDU of a pre-set condition. For example, the PPDU of the pre-set condition 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 signaling indicating uplink or downlink is set to a pre-set value. The signaling indicating uplink or downlink may be included in the signaling field of the HE PPDU. Alternatively, the signaling indicating uplink or downlink may be included in a U-SIG. The U-SIG may be included in the preamble of an EHT PPDU or a post-EHT standard PPDU.

[0147] In addition, there may be cases where a PPDU cannot be classified as an intra-BSS PPDU or an inter-BSS PPDU. For example, if neither the above-mentioned conditions for classification as an intra-BSS PPDU nor the conditions for classification as an inter-BSS PPDU are met, the PPDU cannot be classified as an intra-BSS PPDU or an inter-BSS PPDU.

[0148] In addition, when classifying BSSs, if the classification results based on multiple conditions do not match, the final result can be determined based on the pre-set conditions. For example, if the result based on the BSS color condition does not match the result based on the MAC address condition, the result based on the MAC address condition takes precedence, or the result based on the MAC address condition can be determined as the final result. Alternatively, if both the conditions for classification as an intra-BSS PPDU and the conditions for classification as an inter-BSS PPDU are met, the PPDU can be classified as an intra-BSS PPDU.

[0149] According to an embodiment of the present invention, a STA may perform an operation based on a classified BSS. The operation based on the classified BSS may include an intra-PPDU power save operation. The intra-PPDU power save operation may be a power save operation based on a received PPDU. The intra-PPDU power save operation can be performed when a pre-defined condition is met. The pre-defined condition may include a condition for classifying a received PPDU as an intra-BSS PPDU. The pre-defined condition may also include a condition that the intended receiver of a received PPDU is not the STA that received the PPDU. For example, if an ID or address included in a 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. The STA_ID may be included in an EHT MU PPDU or an EHT PPDU. The address may be the MAC address described above. Furthermore, if the signaling indicating uplink or downlink included in the received PPDU indicates uplink, the intended recipient of the PPDU may not be the STA that received the PPDU. Furthermore, if the configuration of the received PPDU is set to a format that the STA that received the PPDU does not support, the intended recipient of the PPDU may not be the STA that received the PPDU. The configuration of the received PPDU may include the MCS of the PPDU, the number of spatial streams, the channel width, etc. Furthermore, if the STA that received the PPDU does not support the configuration of the received PPDU, a PHY-RXEND.indication(UnsupportedRate) primitive may be received. Furthermore, if the received PPDU is in a pre-configured format, the intended recipient of the PPDU may not be the STA that received the PPDU. The pre-configured format may include a TB PPDU.The TB PPDU may include an HE TB PPDU and an EHT TB PPDU. The TB PPDU may be a PPDU transmitted in response to a triggering frame. The triggering frame may include a trigger frame. The triggering frame may include a frame including triggering information. The triggering information may be included in a MAC header, for example, an A-control field. The triggering information or information included in the trigger frame may include the length of the response PPDU, the RU to be used in the response, the PHY configuration to be used in the response, the MAC configuration, etc. The intra-PPDU power saving operation may be an operation that can enter a doze state until the end of the received PPDU. As another example, if a STA determines that the intended recipient of a received PPDU or frame is not the STA, the STA may suspend reception or decoding of the PPDU or frame.

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

[0151] The operation based on the classified BSS may include a spatial reuse operation. The operation based on the classified BSS may include a channel access operation. The spatial reuse operation may be a channel access operation. When a STA receives a PPDU or a frame, if a pre-set condition is met, the spatial reuse operation can be performed. The pre-set condition may include a condition that the received PPDU or the received frame corresponds to an inter-BSS. The pre-set condition may include a condition that the signal strength of the received PPDU or the received frame is lower than a threshold. For example, the threshold may be variable. The threshold may be a threshold for an OBSS PD-based spatial reuse operation. The threshold may be a value equal to or greater than the CCA threshold. 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. The spatial reuse operation may include an operation of resetting a PHY. For example, resetting the PHY may be issuing a PHY-CCARESET.request primitive. Spatial reuse may include not setting a NAV based on a received PPDU or frame. If a STA performs spatial reuse, the STA may be able to transmit a PPDU while a received PPDU or 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. BSS A and BSS B may correspond to inter-BSSs. That is, a PPDU or frame transmitted by a STA associated with BSS A in BSS B may be classified as an inter-BSS PPDU or an inter-BSS frame. STA1 and STA2 may belong to BSS A (or associated with the AP operating BSS A). STA3 and STA4 may belong to BSS B (or associated with the AP operating BSS B). Referring to FIG. 13, STA1 may transmit a PPDU. The PPDU transmitted by STA1 may include information about the BSS. For example, the information about the BSS may be information for classifying the BSSs described above. The PPDU transmitted by STA1 may include duration information.

[0153] STA2 receives the PPDU transmitted by STA1 and can classify the BSS for this PPDU. Since STA2 and STA1 belong to BSS A, the PPDU received by STA2 may be classified as an intra-BSS PPDU. Furthermore, the PPDU received by STA2 may be a UL PPDU or a PPDU for which the STA is not the intended recipient. Therefore, according to the above-described embodiment, STA2 can perform intra-PPDU power saving. Referring to FIG. 13, STA2 may enter a doze state until the end of the received PPDU. Furthermore, STA2 can set its NAV based on the Duration information included in the received PPDU. Since STA2 has classified the received PPDU as an intra-BSS PPDU, it can set its intra-BSS NAV.

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

[0155] STA4 receives the PPDU transmitted by STA1 and can classify the BSS for this PPDU. Furthermore, 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. Furthermore, the signal strength of the PPDU received by STA4 may be lower than a threshold. 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 lower than a threshold, STA4 can perform spatial reuse. Therefore, STA4 can perform channel access and backoff procedures and begin transmission. For example, STA4 may begin transmission before the PPDU transmitted by STA1 has finished.

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

[0157] Referring to FIG. 14 , a WLAN of one standard may include the functions of a WLAN of another standard. Or, when a WLAN of one standard is used, it may be a WLAN of another standard. Here, WLAN can refer to an STA. Furthermore, WLAN can refer to an MLD including an STA. For example, a WLAN standard may include the standard functions of a previous generation and include additional functions. For example, an HT STA can also be an OFDM PHY STA. An HT STA can also perform additional functions in addition to the functions of an OFDM PHY STA. For example, a VHT STA can also be an HT STA. A VHT STA can also perform additional functions in addition to the functions of an HT STA. For example, an HE STA can also be a VHT STA. An HE STA can also perform additional functions in addition to the functions of a VHT STA. An EHT STA can also be an HE STA. An EHT STA can also perform additional functions in addition to the functions of an HE STA. There may also be standards subsequent to the EHT standard. In the present invention, the standard subsequent to the EHT standard can be called the NEXT standard, and the STA that complies with the NEXT standard can be called the NEXT STA. The NEXT STA can also be an EHT STA. In addition, the NEXT STA can perform additional functions in addition to the functions of the EHT STA.

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

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

[0160] Referring to FIG. 15, an 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 PPDUs of the same or individual formats based on the specific frame transmitted from the AP.

[0161] Specifically, as shown in FIG. 15, a frame soliciting or triggering a multi-user (MU) transmission may be transmitted, and one or more STAs may transmit or respond to such a frame based on such a frame. In this case, when one or more STAs transmit a response to the frame, the one or more STAs may simultaneously respond immediately based on the frame, and the response to the frame may begin transmission SIFS after the end of the PPDU including the frame. For example, if the frame solicits an immediate response, one or more STAs may immediately transmit a response to the frame. A frame soliciting or triggering one or more STAs to transmit may be a trigger frame or a frame including information in its MAC header that solicits or triggers uplink transmission to one or more STAs. In this case, the frame may include information (e.g., a TRS control subfield) in its MAC header that triggers or solicits uplink transmission to only one STA.

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

[0163] A frame for instructing or triggering uplink transmission may be transmitted by an AP. If the frame for instructing or triggering uplink transmission is a trigger frame, a response thereto may be transmitted in a trigger-based PPDU (TB PPDU) format. In this case, the TB PPDDU may include the above-mentioned HE TB PPDU and EHT TB PPDU, as well as a NEXT TB PPDU that may be defined in the next standard.

[0164] The HE TB PPDU may consist of a preamble, data, and a packet extension (PE), and the preamble may include L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, HE-STF, and HE-LTF in that order.

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

[0166] A frame that instructs or triggers one or more STAs to transmit a PPDU may include information necessary for one or more STAs to transmit a TB PPDU. For example, if a frame includes a type subfield of "01" (B3 B2) and a subtype subfield of "0010" (B7 B6 B5 B4), the frame including such type and subtype subfields may be a trigger frame, which is a control frame.

[0167] If multiple STAs are instructed or triggered to respond with a TB PPDU, and the formats of the PPDUs to which the multiple STAs respond are different from each other, a problem may occur in that the AP that instructed or triggered the response has difficulty receiving the response PPDUs transmitted from the multiple STAs. Alternatively, if the information contained in the preambles of the PPDUs to which the multiple STAs respond differs depending on the format, a problem may occur in that the AP that instructed or triggered the response has difficulty receiving the response PPDUs transmitted from the multiple STAs.

[0168] Therefore, to solve this problem, when multiple STAs respond to a frame from an AP, the format of the responding PPDU and / or the type of information included in the preamble of the PPDU may be set to be the same. For example, when multiple STAs transmit HE TB PPDUs in response to a frame from an AP, 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 a convention may be defined for the information included in the HE TB PPDU, so that the AP can successfully receive the preambles transmitted by the multiple STAs. However, if the HE TB PPDU, EHT TB PPDU, and NEXT TB PPDU are simultaneously transmitted in overlapping subbands, the TB PPDU formats may be different from each other, which may make it difficult for the AP to receive them.

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

[0170] As shown in Figure 15, when an AP transmits a frame to schedule the transmission of a TB PPDU to an HE STA and an EHT STA, and uses the frame to instruct or trigger the transmission of a TB PPDU, there may be no precise instruction or protocol for the TB PPDU format. In this case, the HE STA transmits an HE TB PPDU in response to the frame, and the EHT STA may respond with an EHT TB PPDU or an HE TB PPDU. In this case, the AP may have difficulty receiving the TB PPDUs transmitted by these STAs. This may result in the AP being unable to successfully receive TB PPDUs from multiple STAs, resulting in the medium being occupied and reducing transmission opportunities for other STAs.

[0171] Hereinafter, in the present invention, instructing an STA can mean instructing a response from the STA, and the terms "trigger" and "instruct" may be used interchangeably.

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

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

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

[0175] 16(a), as a trigger MAC header, the frame includes a Frame Control field, a Duration field, 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 designated by the trigger frame. Figure 16(b) shows an example of the common information field.

[0177] The user information list field may contain zero or more user information fields, and the user information list field of a trigger frame other than a specific type of trigger frame may contain one or more user information fields. Figure 16(c) shows an example of a user information field.

[0178] The trigger frame may additionally 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 allow time for a STA receiving the trigger frame to prepare a response to the trigger frame, and may be optionally included in the trigger frame.

[0179] Referring to (b) of Figure 16, 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 trigger frame may be indicated based on the value of the trigger frame subfield. Furthermore, the information and length included in the trigger dependent common information subfield and the trigger dependent user information subfield shown in Figure 12 may be determined based on the trigger type subfield. 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 about the length of the TB PPDU, which is a response to the trigger frame, or may include information about the length of a frame responding to the trigger frame. The UL length subfield may also indicate the value included in the length subfield of the L-SIG of the TB PPDU responding 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, a STA can transmit a TB PPDU by setting 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, which indicate the UL length subfield.

[0181] The common information field may further include an uplink bandwidth subfield (UL Bandwidth (BW) subfield). The UL BW subfield may indicate a BW value included in a signaling field (e.g., HE-SIG-A or U-SIG) of a TB PPDU responding to the trigger frame, and may indicate the maximum BW of a TB PPDU transmitted in 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 included in the signaling field of the TB PPDU, which 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. Therefore, the AID12 subfield may also serve to indicate the intended recipient of the trigger frame including the AID12 subfield or the function of the trigger frame. For example, if the value of the AID12 subfield is a pre-configured value, the user information field may indicate a Random Access Resource Unit (RA-RU). That is, the pre-configured value of the AID12 subfield may indicate that the user information field indicates an RA-RU. Specifically, if the value of the AID12 subfield is '0', the user information field may indicate an RA-RU for associated STAs. For example, if the value of the AID12 subfield is "0", the user information field can indicate an RA-RU for associated STAs, and if the value of the AID12 subfield is "2045", the user information field can indicate an RA-RU for unassociated STAs. STAs corresponding to the STA ID (e.g., AID (association ID)) indicated by the value of the AID12 subfield may be instructed to respond by a user information field including the AID12 subfield or a trigger frame including the AID subfield. For example, the AID12 subfield can indicate the AID or 12 LSBs of the AID. STAs corresponding to the value indicated by the AID12 subfield can transmit a TB PPDU in response to the received trigger frame. In this case, the value of the AID12 subfield may be in the range of "1" to "2007" (inclusive), and if the AID12 subfield is a previously set value (e.g., "2046"), the RU corresponding to the previously set value of the AID12 subfield may not be assigned to any STA.Also, if the AID subfield is already set to a value (for example, "4095"), the already set value may indicate that padding of the trigger frame begins.

[0184] Information in 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 may indicate the size and location of the RU. In this case, the value of the RU Allocation subfield in 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 in the AID12 subfield may be the RU allocated to the STA indicated by the AID12 subfield.

[0185] The user information field may also indicate the coding method (UL FEC coding type), modulation method (UL HE-MCS, UL DCM), and power (UL Target RSSI) for generating the TB PPDU to be transmitted in response to the trigger frame.

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

[0187] Referring to FIG. 17, one STA can selectively transmit PPDUs of different formats based on instructions from a triggering frame instructing the transmission of the PPDU.

[0188] Specifically, an EHT STA can selectively transmit not only a legacy PPDU (e.g., an HE TB PPDU) but also an EHT TB PPDU, and a NEXT STA can selectively transmit an HE TB PPDU, an EHT TB PPDU, and / or a NEXT TB PPDU. In this case, STAs to which multiple standards are applied can be individually scheduled using one frame or one PPDU. This method can be advantageous because STAs to which multiple standards are applied share common resources in a WLAN. For example, an HE STA (an HE STA other than an EHT STA) can respond with an HE TB PPDU using one frame. That is, a non-AP STA can transmit a triggering frame to instruct EHT STAs as well as HE STAs to transmit an HE TB PPDU.

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

[0190] Information on the format of the PPDU (TB PPDU format) which is a response to such a triggering frame may exist at the MAC level, and 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 each trigger frame may be classified into an HE TB PPDU, an EHT TB PPDU, and a NEXT TB PPDU.

[0191] In addition, classifying trigger frames into HE trigger frames, EHT trigger frames, and NEXT trigger frames may be equivalent to classifying TB PPDU formats, which are responses to trigger frames, into HE TB PPDU, EHT TB PPDU, and NEXT TB PPDU, respectively.

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

[0193] For example, if 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, it may be necessary to further use entries in the Type subfield (2 bits), the Subtype subfield (4 bits), and / or the Control Frame Extension subfield (4 bits), which are assigned limited numbers of bits, in the EHT standard and the NEXT standard.

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

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

[0196] In this case, the variant for determining the format of the PPDU may further use a user information field in addition to the common information field.

[0197] For example, a 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, if the trigger type subfield value is a previously set value, the trigger frame may be an HE trigger frame. Also, if the trigger type subfield value is a previously set value, the trigger frame may be an EHT trigger frame. If the trigger type subfield value is a previously set value, the trigger frame may be a NEXT trigger frame.

[0198] For example, if the trigger type subfield value is 0 to 7, it is an HE trigger frame, and if it is not 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 still another embodiment, a trigger frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a UL length subfield of the trigger frame. For example, a trigger frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a value obtained by modulating the UL length subfield value (remainder). That is, the value of the UL length subfield may be used to determine whether the format of a PPDU transmitted in response to a trigger frame is an HE PPDU or an EHT PPDU.

[0200] More specifically, the trigger frame can be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the value obtained by modulating the UL length subfield value modulo 3 (the remainder when the UL length subfield is divided by 3). For example, if the result of modulating the UL length subfield value modulo 3 is not 0, the trigger frame may be an HE trigger frame. Alternatively, if the result of modulating the UL length subfield value modulo 3 is 1, the trigger frame may be an HE trigger frame. Alternatively, if the result of modulating the UL length subfield value modulo 3 is 0, the trigger frame may not be an HE trigger frame. Alternatively, if the result of modulating the UL length subfield value modulo 3 is 0, the trigger frame may be an EHT trigger frame or a NEXT trigger frame.

[0201] That is, if the value modulo 3 of the UL length subfield of the trigger frame is not 0, the response to the trigger frame may be transmitted in an HE TB PPDU, and if the value modulo 3 of the UL length subfield is 1, the response to the trigger frame may be transmitted in an HE TB PPDU.

[0202] Also, when the value modulo 3 of the UL length subfield of the trigger frame is 0, the format of the PPDU transmitted in response to the trigger frame may be EHT TB PPDU.

[0203] Furthermore, an additional trigger frame classification method can be used in addition to this method to classify the HE trigger frame, EHT trigger frame, and NEXT trigger frame. For example, the classification method described in FIG. 16 can be used in addition to this method to classify the HE trigger frame, EHT trigger frame, and NEXT trigger frame.

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

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

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

[0207] In this case, in addition to the user information field, a common information field may also be used as a variant for determining the format of the PPDU.

[0208] For example, a frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on the AID12 subfield. According to one embodiment, a frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on whether or not it includes an AID12 subfield with a preset value. In this case, a question may arise as to whether a STA indicated by a certain user information field should continue to check the AID12 subfield present after the user information field to determine the trigger frame format. To solve this problem, a user information field including an AID12 subfield indicating which trigger frame it is may be located at the beginning of the user information list. In addition, to prevent HE STAs that cannot understand this signaling method from malfunctioning, a user information field including an AID12 subfield indicating which trigger frame it is may be located after the user information field corresponding to the HE STA.

[0209] In addition, since information on subfields other than the AID12 subfield included in the user information field may not be necessary for the TB PPDU response, subfields of the user information field including the AID12 subfield indicating which trigger frame it is may be omitted. That is, the length of the user information field may vary depending on the AID12 subfield. Referring to FIG. 17, the AID12 subfield may serve to indicate the format of the TB PPDU to be responded to. For example, if the AID12 subfield is a pre-set value, the response to the trigger frame including the AID12 subfield set to the pre-set value may be an EHT TB PPDU. For example, if the AID12 subfield value is 2047, the response to the trigger frame including the AID12 subfield may be an EHT TB PPDU. Furthermore, if the AID12 subfield is a pre-set value, the response to the trigger frame including the AID12 subfield set to the pre-set value may be a NEXT TB PPDU. For example, if the AID12 subfield value is 2048, the response to a trigger frame containing the AID12 subfield may be a NEXT TB PPDU.

[0210] According to another embodiment, when responding based on a user information field located at a pre-set position from the AID12 subfield of a pre-set value, the response can be made in a TB PPDU format corresponding to the pre-set value. For example, when responding based on a user information field located after the AID12 subfield of a pre-set value, the response can be made in a TB PPDU format corresponding to the pre-set value. If there are multiple values ​​indicating a TB PPDU format, when responding based on a user information field located after both the pre-set value 1 and the pre-set value 2, the response can be made in a TB PPDU format according to the pre-set priority between the TB PPDU format corresponding to the pre-set value 1 and the TB PPDU format corresponding to the pre-set value 2. Referring to FIG. 17, when responding based on a user information field located after the AID12 subfield set to 2047, the response can be made in an EHT TB PPDU. Also, when responding based on a user information field located after the AID12 subfield set to 2048, the response can be made in a NEXT TB PPDU. Also, when responding based on a user information field that exists after both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it can respond with a NEXT TB PPDU. Also, when responding based on a user information field that exists before both the AID12 subfield set to 2047 and the AID12 subfield set to 2048, it can respond with a HE TB PPDU.

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

[0212] According to an embodiment, the trigger frame may be distinguished as an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame based on a padding field of the trigger frame. For example, whether the trigger frame is an HE trigger frame, an EHT trigger frame, or a NEXT trigger frame can be determined based on whether the padding field includes a pre-set value indicating whether the trigger frame is an 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 distinguish between an HE trigger frame, an EHT trigger frame, and a NEXT trigger frame by combining a plurality of trigger frame distinction methods described in the present invention. In addition, the contents described in the present invention regarding trigger frames are not limited to the above and can also be applied to TRS.

[0214] In yet another embodiment of the present invention, the AP may not be able to use a triggering frame to instruct transmission of both the EHT PPDU and the HE PPDU, i.e., the EHT AP cannot transmit a trigger frame instructing both the HE TB PPDU and the EHT TB PPDU, and can only instruct one PPDU format.

[0215] FIG. 18 illustrates 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 a TB PPDU can also be indicated by a TRS. Also, 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 can include a TRS. The TRS can be conveyed by a TRS control subfield. The A-control field may be in the form of a series of control list fields. Also, the control list field may include a TRS.

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

[0218] The embodiment of Fig. 18 may be a method for solving the problems described in Fig. 14 and Fig. 15. Also, as described above, the above-mentioned embodiment regarding the trigger frame can also be applied to the TRS. Also, the above-mentioned content can be omitted.

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

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

[0221] According to one embodiment of the present invention, it is possible to determine the TB PPDU format in response to the TRS based on the PPDU format including the TRS. That is, when a PPDU instructing PPDU transmission includes a TRS control subfield, the PPDU format 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 HE PPDU, the format of the indicated PPDU may be HE PPDU. However, when the format of the PPDU including the TRS control subfield is EHT PPDU, the format of the indicated PPDU may be EHT PPDU.

[0222] 18, when a TRS is transmitted in an HE PPDU, a TB PPDU responding to the TRS may be an HE TB PPDU. When a TRS is transmitted in an EHT PPDU, a TB PPDU responding to the TRS may be an EHT TB PPDU. When a TRS is transmitted in a NEXT PPDU, a TB PPDU responding to the TRS may be a NEXT TB PPDU.

[0223] According to an embodiment of the present invention, a subfield included in a TRS may be interpreted differently depending on the PPDU format in which the TRS is included. For example, when a TRS is included in an HE PPDU, the UL HE-MCS subfield (or a subfield related to MCS) included in the TRS may indicate a value corresponding to the HE MCS table. When a TRS is included in an EHT PPDU, the UL HE-MCS subfield (or a subfield related to MCS) included in the TRS may indicate a value corresponding to the EHT MCS table. When a TRS is included in a NEXT PPDU, the UL HE-MCS subfield (or a subfield related to MCS) included in the TRS may indicate a value corresponding to the NEXT MCS table. In addition, the RU Allocation subfield may also be interpreted differently depending on the PPDU format in which the TRS is included.

[0224] FIG. 19 illustrates end time alignment of high priority frames according to one embodiment of the present invention.

[0225] In an embodiment of the present invention, aligning or being aligned in the transmission end times of PPDUs may be referred to as end time alignment, end time alignment, PPDU end time alignment, ending time alignment, etc.

[0226] According to one embodiment of the present invention, when an MLD transmits multiple PPDUs, it can determine whether to perform end time alignment based on whether the multiple PPDUs include a high-priority frame. Alternatively, when an MLD transmits multiple PPDUs, the end time alignment operation can differ based on whether the multiple PPDUs include a high-priority frame. Furthermore, in the present invention, end time alignment can mean that the end time difference between aligned PPDUs is less than a preset time.

[0227] In an embodiment of the present invention, the MLD can start transmitting multiple PPDUs simultaneously. This can be referred to as starting transmission simultaneously if the transmission start times of multiple PPDUs transmitted by the MLD are exactly the same or if the difference between the transmission start times is equal to or less than a preset time. The simultaneous transmission of multiple PPDUs by the MLD can also be referred to as start time sync.

[0228] Whether a frame is a high priority frame may be determined based on a traffic identifier (TID) or access category (AC) corresponding to the frame. Whether a frame is a high priority frame may also 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. Alternatively, a frame may be a high priority frame if it is transmitted within an allocated time interval. In this case, time allocation for transmitting high priority frames may be performed by the AP. According to one embodiment, whether a frame is a high priority frame may be determined based on an absolute criterion. For example, a frame corresponding to a previously set TID or a previously set AC may be a high priority frame. According to another embodiment, whether a frame is a high priority frame may be determined 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. Alternatively, whether a frame is a high priority frame may be determined by the sender.

[0229] In addition, non-STR MLD may be an MLD in which simultaneous transmission and reception is restricted on the link pair used. In this case, a link pair in which simultaneous transmission and reception is restricted can be called a non-STR link pair or an NSTR link pair. Conversely, a link pair in which simultaneous transmission and reception is not restricted can be called an STR link pair.

[0230] According to an embodiment of the present invention, when an MLD transmits multiple PPDUs, if the PPDUs to be transmitted contain high-priority frames, end time alignment need not be performed. For example, even if the multiple PPDUs are to be transmitted to STAs belonging to the same MLD, end time alignment need not be performed if the PPDUs contain high-priority frames. Furthermore, even if neither the MLD transmitting the multiple PPDUs nor the MLD receiving the multiple PPDUs operates in an STR link pair (i.e., even if at least one MLD operates in an NSTR link pair), end time alignment need not be performed if the PPDUs contain high-priority frames.

[0231] According to an embodiment of the present invention, when an MLD transmits multiple PPDUs and the PPDUs to be transmitted include a high priority frame, not performing end time alignment may be limited to the case where the PPDU including the high priority frame starts to be transmitted before the PPDU not including the high priority frame.

[0232] Referring to FIG. 19, there is an AP MLD to which AP1 and AP2 belong. There is also a non-AP MLD to which STA1 and STA2 belong. The AP MLD and non-AP MLD may be multi-link setup with link 1 and link 2. 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 multiple PPDUs. The PPDUs transmitted by AP1 and AP2 may overlap in time. The PPDUs transmitted by AP1 may not contain high-priority frames. The PPDUs transmitted by AP2 may contain high-priority frames. The start times of the PPDUs transmitted by AP1 and AP2 may be synchronized, or the PPDU transmitted by AP2 may start earlier than the PPDU transmitted by AP1. In such cases, the end times of the PPDUs transmitted by AP1 and AP2 may not be aligned. 19, the PPDU transmitted by AP2 ends later than the PPDU transmitted by AP1. If the PPDUs transmitted by AP1 and AP2 are end time aligned, AP2 may be unable to transmit all of the high priority frames it wishes to transmit in a single PPDU and may have to end the PPDU. Therefore, by not performing end time alignment on the PPDU containing the high priority frames, it is possible to transmit the high priority frames earlier.

[0233] 19, the frame transmitted by AP1 may require an immediate response, and the frame transmitted by AP2 may require an immediate response.

[0234] However, in the example of FIG. 19, STA1 may interfere with the reception of high priority frames by responding to frames transmitted by AP1.

[0235] Therefore, according to an embodiment of the present invention, an STA in an MLD does not need to respond when requested to send an immediate response if it is receiving a high priority frame on another link. In the embodiment of Figure 19, STA1 does not need to send an immediate response as required by the frame sent by AP1 because STA2 is receiving a high priority frame.

[0236] Furthermore, according to an embodiment of the present invention, when an MLD receives a frame on an NSTR link pair and the frame requests an immediate response, if a response to the frame would disrupt reception on other links, the MLD may not respond. However, according to an embodiment of the present invention, this may be limited to cases where the frame is not a high priority frame. In other words, when an MLD receives a frame on an NSTR link pair and the frame requests an immediate response, the MLD may have to respond even if a response to the frame would disrupt reception on other links.

[0237] FIG. 20 illustrates yet another example of end time alignment of high priority frames according to one embodiment of the present invention.

[0238] This embodiment may be related to end time alignment or the end time of a PPDU, and mention of related conditions such as the transmitting MLD or receiving MLD operating in an NSTR link pair, the PPDU including a frame requiring an immediate response, the PPDU including a QoS Data frame, the PPDU including a QoS Data frame requiring an immediate response, multiple PPDUs being transmitted by STAs of the same MLD, and multiple PPDUs being received by STAs of the same MLD may be omitted. The described embodiment may be performed when such conditions are met.

[0239] Referring to FIG. 20, there is an AP MLD to which AP1 and AP2 belong. There is also a non-AP MLD to which STA1 and STA2 belong. The AP MLD and non-AP MLD may be multiplexed with link 1 and link 2. For the non-AP MLD, link 1 and link 2 may be an NSTR link pair. AP1 and STA1 may operate on link 1, and AP2 and STA2 may operate on link 2. The AP MLD can transmit multiple PPDUs. The PPDUs transmitted by AP1 and AP2 may overlap in time. The PPDUs transmitted by AP1 may include a high-priority frame. The PPDUs transmitted by AP2 do not need to include a high-priority frame. The PPDUs transmitted by AP1 and AP2 may be start-time synchronized, or the PPDU transmitted by AP1 may start before the PPDU transmitted by AP2.

[0240] Case 1 shown in FIG. 20(a) and Case 2 shown in FIG. 20(b) may be embodiments in which end time alignment is not performed.

[0241] In Case 1, the PPDU transmitted by AP2 ends after the PPDU transmitted by AP1. In this case, the reception of the high priority frame is not hindered by in-device interference. However, the response to the PPDU containing the high priority frame may hinder the reception of the PPDU that does not contain the high priority frame.

[0242] In Case 2, the PPDU sent by AP2 is completed before the PPDU sent by AP1. In this case, if the PPDU sent by AP2 requires an immediate response, and STA2 sends a response, STA2's transmission may interfere with the reception of a higher priority frame on Link 1. This may prevent the higher priority frame from being successfully received early.

[0243] Case 3 shown in Figure 20(c) may be an embodiment in which end time alignment is performed. Therefore, when receiving a PPDU containing a high priority frame, interference within the device is not disrupted. This solves the problem of interference with reception of high priority frames as in Case 2.

[0244] According to an embodiment of the present invention, even when multiple PPDUs including high priority frames are transmitted, it is possible to determine whether to perform end time alignment based on a pre-set condition (Case 3). More specifically, even when multiple PPDUs including high priority frames are transmitted, end time alignment can be performed according to a pre-set condition (Case 3). In this case, at least one PPDU may include a high priority frame. The pre-set condition may include a case where one PPDU includes a high priority frame and another PPDU does not include a high priority frame. The pre-set condition may include a case where a PPDU including a high priority frame starts to be transmitted before or simultaneously with a PPDU not including a high priority frame. Furthermore, the pre-set condition 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 aforementioned pre-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 before or at the same time as PPDU 2, it is possible to perform end time alignment between PPDU 1 and PPDU 2. More specifically, when transmitting PPDU 1 including a high-priority frame and PPDU 2 not including a high-priority frame, if PPDU 1 starts before or at the same time as PPDU 2, it is possible to perform end time alignment between PPDU 1 and PPDU 2 if the frame included in PPDU 2 requests an immediate response. Furthermore, if the conditions for end time alignment are not met, end time alignment does not need to be performed.

[0246] According to another embodiment of the present invention, even when multiple PPDUs including high priority frames are transmitted, it is possible to determine whether to perform end time alignment or when to end the PPDUs based on pre-set conditions (Case 1 or Case 3). More specifically, even when multiple PPDUs including high priority frames are transmitted, it is possible to perform end time alignment or determine the end point of one PPDU based on pre-set conditions (Case 1 or Case 3). More specifically, even when multiple PPDUs including high priority frames are transmitted, it is possible to perform end time alignment based on pre-set conditions or end a PPDU that does not include a high priority frame after a PPDU that does not include a high priority frame. The pre-set conditions may include a case where one PPDU includes a high priority frame and another PPDU does not include a high priority frame. The pre-set conditions may include a case where a PPDU that includes a high priority frame starts transmission before or simultaneously with a PPDU that does not include a high priority frame. Furthermore, the pre-set conditions may include a case where a frame of a PPDU that does not include a high priority frame requests an immediate response.

[0247] In addition, the aforementioned pre-defined conditions can be combined to determine whether to perform end time alignment. For example, when transmitting PPDU 1 including a high-priority frame and PPDU 2 not including a high-priority frame, if PPDU 1 starts before or at the same time as PPDU 2, PPDU 1 and PPDU 2 can be end time aligned, or PPDU 2 can 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 before or at the same time as PPDU 2, and a frame included in PPDU 2 requests an immediate response, PPDU 1 and PPDU 2 can be end time aligned, or PPDU 2 can end after PPDU 1. Furthermore, if the condition for end time alignment or ending one PPDU after another PPDU is not met, there may be no restriction on the transmission end time. Alternatively, if the condition for end time alignment or ending one PPDU after another PPDU is not met, end time alignment may be performed without fail.

[0248] FIG. 21 illustrates yet another example of end time alignment of high priority frames according to one embodiment of the present invention.

[0249] In the embodiment of Fig. 21, the contents described in Fig. 20 etc. may be omitted. This embodiment may be related to end time alignment or the end time of a PPDU, and related conditions such as the transmitting MLD or receiving MLD operating in an NSTR link pair, the PPDU including a frame requiring an immediate response, the PPDU including a QoS Data frame, the PPDU including a QoS Data frame requiring an immediate response, multiple PPDUs being transmitted by STAs of the same MLD, and multiple PPDUs being received by STAs of the same MLD may be omitted. The embodiment to be described may be performed when such conditions are met.

[0250] According to one embodiment of the present invention, when transmitting multiple PPDUs including high priority frames, it is possible to determine whether to perform end time alignment or when to end a PPDU based on whether at least two PPDUs include high priority frames. Alternatively, when transmitting multiple 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 one embodiment, when an MLD transmits multiple PPDUs, if two or more of the PPDUs to be transmitted contain high-priority frames, there may be no constraint on the PPDU end time. For example, in this case, even if the conditions for implementing the PPDU end time constraints, including the end time alignment described above, are met, there may be no constraint on the PPDU end time. For example, if an MLD transmits a PPDU containing a frame (e.g., a QoS Data frame) requesting an immediate response to STAs belonging to the same MLD, and these STAs operate in an NSTR link pair, end time alignment may not be performed on the transmitted PPDU. This is because end time alignment may require redundancy, such as padding, to be included in the PPDU, which may delay the completion of reception of the PPDU frame containing the redundancy. Also, if end time alignment is not performed, reception of one of the PPDUs may be disrupted due to intra-device interference. Therefore, the transmitting MLD can determine whether or not to apply the constraint on the PPDU end time. Alternatively, the receiving MLD may be able to make a recommendation regarding constraints on the end time of the PPDU.

[0252] According to yet another embodiment, when an MLD transmits multiple PPDUs, if two or more of the PPDUs to be transmitted contain high-priority frames, end time alignment can be performed on the multiple PPDUs. For example, when an MLD transmits two PPDUs, if each of the two PPDUs to be transmitted contains a high-priority frame, end time alignment can be performed on the multiple PPDUs. This is because, if end time alignment is not performed, reception of one of the PPDUs may be hindered due to intra-device interference. This embodiment can also be applied only when at least two PPDUs containing high-priority frames each require an immediate response. For example, when an MLD transmits two PPDUs, if each of the two PPDUs to be transmitted contains a high-priority frame and requires an immediate response, end time alignment can be performed on the two PPDUs.

[0253] Referring to FIG. 21, there is an AP MLD to which AP1 and AP2 belong. There is also a non-AP MLD to which STA1 and STA2 belong. The AP MLD and non-AP MLD may be multiplexed with link 1 and link 2. For the non-AP MLD, link 1 and link 2 may be an NSTR link pair. AP1 and STA1 may operate on link 1, and AP2 and STA2 may operate on link 2. The AP MLD can transmit multiple PPDUs. The PPDUs transmitted by AP1 and AP2 may overlap in time. The PPDUs transmitted by AP1 and AP2 may include high-priority frames. The start times of the PPDUs transmitted by AP1 and AP2 may or may not be synchronized. In this case, the PPDUs transmitted by AP1 and AP2 may be end-time aligned. This is because the PPDUs transmitted by AP1 and AP2 each require an immediate response. In this case, a high priority frame included in the PPDU transmitted by AP1 may request an immediate response, and a high priority frame included in the PPDU transmitted by AP2 may request an immediate response.

[0254] In the embodiments of Figures 19 to 21, "a PPDU includes a high priority frame" can mean that the PPDU includes at least one high priority frame, and "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 illustrating an example of a medium access recovery procedure according to an embodiment of the present invention.

[0256] According to one embodiment of the present invention, an MLD (multi-link device) may be restricted from simultaneously transmitting and receiving on multiple links. This restriction may not be necessary. Simultaneous transmission and reception may include transmitting on at least one link simultaneously (at the same time) and receiving on at least one other link. Whether simultaneous transmission and reception on multiple links is restricted may depend on the capability of the MLD and each link. That is, some MLDs may be restricted from simultaneously transmitting and receiving on multiple links, while others may not be restricted. Simultaneous transmission and reception on multiple links may be restricted when an MLD operates on a link set, but may not be restricted when the MLD operates on a link set different from the link set. Simultaneous transmission and reception on multiple links may be possible when simultaneous transmission and reception on multiple links is possible, which can be referred to as STR (simultaneous transmit (transmission) and receive (reception)). Restricted STR may be referred to as non-STR or NSTR.

[0257] That is, when each STA 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 STA included in the same MLD performs transmission / reception on each link, if transmission / reception on other links is impossible due to interference between the transmission / reception operations, this can be called NSTR, and a pair of links for such NSTR operation can be called an NSTR link pair.

[0258] An STR can be referred to as an STR when the STR is not restricted. Furthermore, a link pair in which the STR is restricted or not restricted for a certain MLD can be referred to as an STR link pair or an NSTR link pair, respectively. Furthermore, an MLD in which the STR is restricted or not restricted can be referred to as an STR MLD or an NSTR MLD, respectively. An MLD may be an NSTR MLD when at least one link pair in the operating link set is an NSTR link pair. In embodiments of the present invention, descriptions for an MLD operating with an NSTR (or STR) link pair can also be read as embodiments described for an NSTR (or STR) MLD. Conversely, descriptions for an NSTR (or STR) MLD can also be read as embodiments described for an MLD operating with an NSTR (or STR) link pair.

[0259] The STR may be limited because the MLD's transmission on one link interferes with other links. More specifically, the STR may be limited because the MLD's transmission on one link interferes with the MLD's reception on another link. This type of interference may be referred to as in-device interference. As another example, the STR may be limited because the number of radios in the MLD is limited. For example, an MLD operating with a single radio may have a limited STR. An MLD operating with a single radio may be able to receive or transmit on only one link at a time. Alternatively, an MLD operating with a single radio may be able to listen or monitor multiple links simultaneously, but may only receive or transmit on one link at a time. In this case, listening or monitoring may mean receiving a PPDU or frame configured with a pre-configured setting.

[0260] According to an embodiment of the present invention, PPDU end time alignment can be performed to prevent MLDs from simultaneously transmitting and receiving via an NSTR link pair. According to one embodiment, MLD1 can transmit multiple PPDUs to MLD2 via multiple links. In this case, if a link pair included in the multiple links for MLD1 or MLD2 is an NSTR link pair, end time alignment of PPDUs transmitted via the NSTR link pair can be performed. PPDU end time alignment may be performed by adjusting the difference in end times of multiple PPDUs to be equal to or less than a preset time. The preset time may be 8 us. Alternatively, if the PPDU includes a Trigger frame and the CS Required subfield (a subfield indicating whether to respond to the Trigger frame or to decide based on carrier sense (CS)) included in the Trigger frame indicates that the response should be based on the CS result, the preset time may be 4 us. If a PPDU includes a Trigger frame and the CS Required subfield (a subfield indicating whether to respond to the Trigger frame or to decide based on the CS) included in the Trigger frame indicates that a response should be made based on the CS result, if another PPDU ends before such a PPDU and their end time alignment is performed, the preset time may be 4 us. The MLD must ensure that the end time of one or more PPDUs carrying frames requiring an immediate response is a maximum of 4 us earlier than the end time of a PPDU including a Trigger frame whose CS Required subfield is set to 1. In addition, end time alignment of PPDUs may be performed only if a frame included in at least one of the PPDUs solicits an immediate response. Alternatively, end time alignment of PPDUs may be performed only if frames included in at least two of the PPDUs solicit an immediate response.It is possible to add padding to achieve end time alignment.

[0261] According to an embodiment of the present invention, an MLD can perform start time synchronization when transmitting a PPDU over multiple links. The MLD may be an MLD operating in an NSTR link pair. The MLD can obtain a transmission opportunity for each link based on a backoff procedure or a backoff counter, and transmit the PPDU. For example, the PPDU can be transmitted at a slot boundary where the backoff counter reaches 0. This may be the case when using a distributed coordination function (DCF). Alternatively, the PPDU can be transmitted at the slot boundary next to the slot boundary where the backoff counter reaches 0. This may be the case when using enhanced distributed channel access (EDCAF). However, when an MLD operating in an NSTR link pair starts transmitting a PPDU over one link, it may affect the other links, causing them to be determined as busy, making it difficult to simultaneously transmit the PPDU over the other links. Therefore, according to an embodiment of the present invention, a STA whose backoff counter reaches 0 can maintain the backoff counter at 0 without transmitting. Also, a STA that keeps its backoff counter at 0 can transmit when a STA belonging to the same MLD has its backoff counter reach 0.

[0262] According to one embodiment of the present invention, when an MLD operating in an NSTR link pair has Link 1 and Link 2 that constitute the NSTR link pair, when transmitting on Link 1, it may have difficulty receiving on Link 2. Therefore, it may have difficulty receiving duration information of a PPDU or frame transmitted from another STA on Link 2. When this occurs on Link 2, it can be expressed that the STA operating on Link 2 of the MLD operating in the NSTR link pair has lost media synchronization. Alternatively, when this occurs on Link 2, it can be expressed that the STA operating on Link 2 of the MLD operating in the NSTR link pair is blinded. In this case, the STA operating on Link 2 of the MLD operating in the NSTR link pair cannot receive the transmitted duration information and may not defer channel access, which it would have done if it had received the duration information. This may interfere with the transmission and reception of other STAs.

[0263] Referring to FIG. 22, AP1 and AP2 may operate on Link 1 and Link 2, respectively, and AP1 and AP2 may belong to the same MLD, AP MLD. STA1 and STA2 may operate on Link 1 and Link 2, respectively, and STA1 and STA2 may belong to the same MLD, non-AP MLD. AP MLD and non-AP MLD may be set up as multiple links for Link 1 and Link 2. Non-AP MLD may be NSTR MLD. For non-AP MLD, Link 1 and Link 2 may be an NSTR link pair. STA1 may transmit Data 1. In this case, transmitting Data 1 may cause interference to STA2. Therefore, STA2 may be blind to the section in which Data 1 is transmitted.

[0264] According to an embodiment of the present invention, in order to alleviate problems that arise from a STA being unable to receive period information while the STA is blind, the STA may be restricted from accessing the channel for a certain period of time. This certain period of time may be referred to as MediumSyncDelay. Alternatively, restricting channel access for a certain period of time may be referred to as applying MediumSyncDelay. According to one embodiment, to apply MediumSyncDelay for a certain period of time, the MediumSyncDelay timer may be set to a non-zero value, and MediumSyncDelay may be applied while the timer is non-zero. The certain period of time may also start when the blind is released. Alternatively, the certain period of time may start when the transmission that triggered the blind is completed. Referring to FIG. 22, after completing the transmission of Data 1, STA2 may set the MediumSyncDelay timer to a non-zero value. In this case, the MediumSyncDelay timer may be set to the MediumSyncDelay value. STA2 may be restricted from accessing the channel during MediumSyncDelay. For example, a STA applying MediumSyncDelay may belong to an MLD operating on an NSTR link pair. Alternatively, a STA that applies MediumSyncDelay may belong to an NSTR MLD, or a STA that applies MediumSyncDelay may belong to a non-AP MLD.

[0265] According to one embodiment, if the blind-inducing transmission period is shorter than the previously set time, MediumSyncDelay may not be applied.

[0266] According to one embodiment, the MediumSyncDelay value may have a base value. The base value may be the maximum duration of a PPDU. The maximum duration of a PPDU may be 5.484 ms. The MediumSyncDelay value may also be a value transmitted from the peer MLD (AP MLD) that set up the multiplexed link. If a non-AP MLD fails to receive a MediumSyncDelay value from the AP MLD, it can use the base value as the MediumSyncDelay value. If a non-AP MLD receives a MediumSyncDelay value from the AP MLD, it can use the received value as the MediumSyncDelay value.

[0267] Restricting channel access when MediumSyncDelay is applied may include the following operations. For example, restricting channel access may be related to attempting to obtain a transmit opportunity (TXOP). Restricting channel access may include restricting the type of the first frame to be transmitted when a TXOP is obtained. The type of frame may be defined by the Type subfield or Subtype subfield indicated in the MAC header of the frame. For example, the type of the first frame may be a request to send (RTS) frame. An RTS frame may be a type of Control frame. If it is a Control frame, the B3 and B2 bits of the Type subfield may be set to 0 and 1, respectively. If 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. In this case, the bit index may be the bit index of the Frame Control field. B2 may be the least significant bit (LSB) of the Type subfield, and B3 may be the most significant bit (MSB) of the Type subfield. B4 may be the LSB of the Subtype subfield, and B7 may be the MSB of the Subtype subfield. Therefore, if a STA transmits an RTS frame as the first frame and fails to receive a CTS frame in response to it, it does not need to continue transmitting. This prevents the STA from significantly disrupting the transmission of other STAs even if there is information about a period during which the STA was unable to receive data during the blind period. Alternatively, restricting channel access may include restricting the size or length of the first frame or PPDU to be transmitted when a TXOP is obtained. For example, the size or length of the first frame or PPDU may be set to be smaller than a preset value. This prevents the STA from significantly disrupting the transmission of other STAs even if there is information about a period during which the STA was unable to receive data during the blind period.

[0268] Furthermore, restricting channel access may include changing a clear channel assessment (CCA) threshold. More specifically, restricting channel access may include changing the clear channel assessment (CCA) threshold to a lower value. According to one embodiment, if a signal equal to or greater than (or exceeding) the CCA threshold is detected, the channel may be determined to be busy. Otherwise, the channel may be determined to be idle. The CCA threshold may include a threshold for detecting a Wi-Fi signal (PPDU). A CCA using such a CCA threshold may be referred to as CCA preamble detection (PD), and the threshold may be referred to as a CCA PD threshold or a PD threshold. The CCA threshold may include a threshold for detecting a certain signal. A CCA using such a CCA threshold may be referred to as CCA energy detection (ED), and the threshold may be referred to as a CCA ED threshold or an ED threshold. More specifically, restricting channel access may 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 be a base value. Also, when MediumSyncDelay is applied, the CCA threshold may be a value transmitted from the peer MLD (AP MLD) that set up the multiple links. If a non-AP MLD fails to receive a CCA threshold from the AP MLD when MediumSyncDelay is applied, it can use the base value as the CCA threshold when MediumSyncDelay is applied. If a non-AP MLD receives a CCA threshold from the AP MLD when MediumSyncDelay is applied, it can use the received value as the CCA threshold when MediumSyncDelay is applied. According to one embodiment, when MediumSyncDelay is applied, the base value of the ED threshold may be -72 dBm.Furthermore, when MediumSyncDelay is applied, a value that can be specified as the ED threshold may be -72 dBm or more. When MediumSyncDelay is applied, the ED threshold may be the dot11MSDOFDMED threshold. Lowering the CCA threshold when MediumSyncDelay is applied compared to when it is not applied may allow for more conservative channel access. This is because a signal that is determined to be idle when using the existing CCA threshold may be determined to be busy when a lower CCA threshold is used. Furthermore, according to one embodiment, the CCA threshold referred to in the present invention may be a threshold corresponding to a 20 MHz subchannel.

[0269] Furthermore, limiting channel access may include limiting the number of transmission attempts during MediumSyncDelay. For example, a STA may not attempt transmission more than a certain number of times during MediumSyncDelay. That is, if a STA experiences a certain number of transmission failures during MediumSyncDelay, it may not attempt transmission any more during MediumSyncDelay. This certain number may be MSD_TXOP_MAX. A backoff procedure may be invoked to prevent transmission attempts. Alternatively, a backoff counter may be reset to prevent transmission attempts. According to one embodiment, in this case, the contention window (CW) may be left unchanged. The CW may be a value used when resetting the backoff counter. For example, the value reset when resetting the backoff counter may be an integer randomly selected from the range of 0 to the CW value. Furthermore, a retry counter may not be changed when resetting the backoff counter to prevent transmission attempts. If the retry counter reaches a set value, no further transmission of the frame being attempted may be attempted, or the frame being attempted to be transmitted may be discarded. According to one embodiment, the MSD_TXOP_MAX value may have a base value. The base value may be 1. The MediumSyncDelay value may be a value transmitted from the peer MLD (AP MLD) that set up the multiplexed link. If a non-AP MLD does not receive an MSD_TXOP_MAX value from the AP MLD, it may use the base value as the MSD_TXOP_MAX value. If a non-AP MLD receives an MSD_TXOP_MAX value from the AP MLD, it may use the received value as the MSD_TXOP_MAX value.

[0270] FIG. 23 is a diagram illustrating 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, an STA in an MLD can transmit a frame including information related to media synchronization delay.

[0272] Specifically, a multi-link element may exist as shown in Figure 23. Multi-link discovery, setup, and operation can be performed based on a frame including the multi-link element. 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] A multi-link element may include an Element ID, Length, Element ID Extension, Multi-Link Control, Common Info, and Link Info field. The Element ID or Element ID Extension may indicate what type of element the emerald containing the Element ID or Element ID Extension is, i.e., whether it is a multi-link element. The Length field may indicate the length of the element containing the Length field. The Multi-Link Control field may include a Type subfield and a Presence Bitmap field. The Type subfield may indicate the type of the multi-link element. The format of the multi-link element may also be determined based on the type of the multi-link element. The Presence Bitmap field may indicate whether or not subfields that can be included in the multi-link element are included. For example, the Presence Bitmap field may indicate whether or not subfields that can be included in the Common Info field included in the multi-link element are included. The subfields indicating whether the Presence Bitmap field is included may include the MLD MAC address, Link ID Info, BSS Parameters Change Count, Medium Synchronization Delay Information, EML Capabilities, and MLD Capabilities fields (subfields). Also, the Medium Synchronization Delay Information field may include information related to MediumSyncDelay.

[0274] The Common Info field may contain information about multiple links or all links. The Common Info field may contain information commonly required or identical information for multiple links or all links. The Link Info field may contain information for each link.

[0275] According to one embodiment, the information related to MediumSyncDelay may have a base value. Furthermore, the 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 may initialize the information related to MediumSyncDelay as a base value. Furthermore, if an MLD (non-AP MLD) fails to receive information related to MediumSyncDelay from a peer MLD (AP MLD), it may use the base value as the information related to MediumSyncDelay. If an MLD (non-AP MLD) receives information related to MediumSyncDelay from a peer MLD (AP MLD), it may use the received value 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 a value to set the MediumSyncDelay timer. For example, the Medium Synchronization Duration subfield can be 8 bits. Also, the Medium Synchronization Duration subfield can indicate a duration in 32us units. That is, if the Medium Synchronization Duration subfield is set to A, the time indicated by the Medium Synchronization Duration subfield can be A*32us.

[0278] The Medium Synchronization OFDM ED Threshold subfield may indicate a CCA threshold when MediumSyncDelay is applied. More specifically, the indicated CCA threshold may be a CCA ED threshold. That is, the Medium Synchronization OFDM ED Threshold subfield may 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 may be a value obtained by adding -72 to the Medium Synchronization OFDM ED Threshold subfield value, and the unit of the value may be dBm. Therefore, when the Medium Synchronization OFDM ED Threshold subfield has a value greater than or equal to 0, the indicated CCA threshold may be a value greater than or equal to -72 dBm. Furthermore, 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 a value between 0 and 10. In this case, values ​​between 11 and 15 may be reserved. That is, when the Medium Synchronization OFDM ED Threshold subfield value is between 0 and 10, it can indicate a CCA threshold between -72 dBm and -62 dBm, respectively.

[0279] The Medium Synchronization Maximum Number Of TXOPs subfield may indicate MSD_TXOP_MAX. That is, the Medium Synchronization Maximum Number Of TXOPs subfield may indicate the maximum number of transmission attempts during which 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 another embodiment, the Medium Synchronization Maximum Number Of TXOPs subfield value may be the (MSD_TXOP_MAX+1) value. According to another embodiment, the Medium Synchronization Maximum Number Of TXOPs subfield value may be the (MSD_TXOP_MAX-1) value. This may also be limited to the case where 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 in the case of 4 bits), it may indicate that there is no limit to the number of transmission attempts.

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

[0281] Referring to Figure 24, in an 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 once transmission is completed, transmission / reception is possible after the media link delay is applied.

[0282] Specifically, there may be a method for preventing a STA to which MediumSyncDelay is applied from applying MediumSyncDelay unnecessarily. For example, MediumSyncDelay is applied because there may be period information, frames, or PPDUs that a STA belonging to an MLD operating on an NSTR link pair may not have received while blinded. However, in reality, there may not have been anything that could not be received while blinded. In such cases, applying MediumSyncDelay may be a way to reduce the problem of channel access restriction.

[0283] According to one embodiment, if a STA to which MediumSyncDelay is applied receives valid period information during MediumSyncDelay, it can reset (or set) the MediumSyncDelay timer to 0. In an embodiment of the present invention, a STA to which MediumSyncDelay is applied may be equivalent to a STA whose MediumSyncDelay timer is a non-zero value. Furthermore, application of MediumSyncDelay by a STA or MLD may be equivalent to setting the MediumSyncDelay timer to a non-zero value. Furthermore, resetting the MediumSyncDelay timer to 0 may be equivalent to terminating application of MediumSyncDelay.

[0284] According to an embodiment of the present invention, the duration information may be included in a frame. More specifically, the duration information may be included in a MAC header included in the frame. More specifically, the duration information may be included in a Duration / ID field included in the MAC header. Therefore, if 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, the frame, MPDU, MAC header, Duration / ID field, and duration information may be used interchangeably.

[0285] The duration information may also be included in the PPDU. More specifically, the duration information may be included in the preamble included in the PPDU. More specifically, the duration information may be included in the TXOP field included in the preamble. The TXOP field may also be included in the HE-SIG-A field included in the HE PPDU. The TXOP field may also be included in the U-SIG field included in the EHT PPDU or a PPDU of a future standard than EHT. When a STA receives a PPDU or a 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 STA's PHY to the MAC. Therefore, the duration information may include the RXVECTOR parameter TXOP_DURATION. The TXOP field or the RXVECTOR parameter TXOP_DURATION may be set to UNSPECIFIED. When the TXOP field or the RXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED, this may mean that no duration information is present. If the TXOP field or the RXVECTOR parameter TXOP_DURATION is set to a value other than UNSPECIFIED, this may indicate that duration information exists. Therefore, if a STA to which MediumSyncDelay is applied receives a PPDU with an RXVECTOR parameter TXOP_DURATION other than UNSPECIFIED during MediumSyncDelay, it can reset the MediumSyncDelay timer to 0.

[0286] In other words, if a STA with a non-zero MediumSyncDelay timer receives a valid frame (or a valid MPDU) or an RXVECTOR parameter TXOP_DURATION that is a value other than UNSPECIFIED, it can reset the MediumSyncDelay timer to 0.

[0287] However, according to an embodiment of the present invention, there may be multiple STAs whose MediumSyncDelay timer is not set to 0 at a given time. Referring to FIG. 24, Link 1 and Link 2 may form multiple links. AP 1 operating on Link 1 may transmit a trigger frame. The trigger frame may solicit responses from multiple STAs. Link 1 and Link 2 may be an NSTR link pair for each of the multiple STAs. That is, transmission by STA 1, one of the multiple STAs, on Link 1 may cause interference to STA 2, which belongs to the same MLD as STA 1. Therefore, while the multiple STAs transmit on Link 1, STAs belonging to the same MLD as each of the multiple STAs may be in a blind state, and after the blinding ends, they may set the MediumSyncDelay timer to a non-zero value. That is, while multiple TB PPDUs are transmitted in response to the trigger frame, multiple STAs operating on Link 2 may be blind, and after the TB PPDU transmission ends, the multiple STAs may set the MediumSyncDelay timer to a non-zero value.

[0288] As another example, while STA1 of link 1 is applying MediumSyncDelay, STA2 of link 1 may start applying MediumSyncDelay, so that at a certain point in time there may be multiple STAs whose MediumSyncDelay timers are not set to 0.

[0289] However, according to the above-described embodiment, it is possible for a STA to transmit an RTS frame as the first frame while applying MediumSyncDelay. Referring to FIG. 24, when STA2 of link 2 transmits an RTS frame as the first frame during MediumSyncDelay, another STA that also applies MediumSyncDelay may have successfully received the RTS frame. In this case, the other STA may reset the MediumSyncDelay timer. However, a CTS frame, which is a response to the RTS frame, may not be transmitted. In this case, the application of MediumSyncDelay may be terminated even though there is information about a period during which the STA of link 2 was unable to receive the RTS frame. This increases the possibility that the STA that terminated MediumSyncDelay may interfere with the reception of frames that have already been transmitted.

[0290] In order to solve this problem, a method of limiting the type of frames for resetting the timer for applying MediumSyncDelay will be described below.

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

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

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

[0294] Thereafter, when a STA of a link to which MediumSyncDelay is applied receives a valid frame or a PPDU for a valid MPDU, it can reset the MediumSyncDelay timer to "0" if the MediumSyncDelay timer is not "0". Alternatively, when a STA receives a PPDU in which the receive parameter (RXVECTOR parameter) TXOP_Duration is a value other than an unspecified value, it can reset the MediumSyncDelay timer to "0" if the MediumSyncDelay timer is not "0". In this case, the valid frame may be a frame other than an RTS frame.

[0295] In this case, a valid frame may be a frame transmitted by another AP or a non-AP STA other than the STA that caused MediumSyncDelay, and a valid frame transmitted by an AP includes an RTS frame, but a valid frame transmitted by a non-AP STA may be a frame other than an RTS frame.

[0296] For example, if a PPDU transmitted on a first link restricts transmission / reception of one or more STAs on a second link of an NSTR link pair, and the MediumSyncDelay timer operates at the end of PPDU transmission, applying MediumSyncDelay to one or more STAs, one or more STAs on the second link can reset the MediumSyncDelay timer when they receive a valid frame. That is, one or more STAs assigned a specific frequency band can reset the MediumSyncDelay timer when they receive a PPDU for a valid MPDU other than an RTS frame transmitted at 20 MHz in the same or a different BSS. In this case, if the PPDU or frame is transmitted from an associated AP or an AP included in the same multiple BSSID set, one or more STAs can reset the MediumSyncDelay timer even if the received PPDU or frame is an RTS frame.

[0297] That is, when a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), the STA may determine whether or not to allow the operation of resetting the MediumSyncDelay timer to 0, based on whether the frame is of a type that is allowed as the first frame during MediumSyncDelay. According to one embodiment of the present invention, even if a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), if the frame is of a type that is allowed as the first frame during MediumSyncDelay, the STA may not allow the operation of resetting the MediumSyncDelay timer to 0. That is, when a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), if the frame is not of a type that is allowed as the first frame during MediumSyncDelay, the STA may allow the operation of resetting the MediumSyncDelay timer to 0. According to the above-mentioned embodiment, the type of frame that is allowed as the first frame during MediumSyncDelay may be an RTS frame.

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

[0299] Referring to FIG. 25, multiple STAs operating on link 2 may apply MediumSyncDelay. STA2 of link 2, which applies MediumSyncDelay, obtains a TXOP and can transmit an RTS frame as the first frame. The multiple STAs may also successfully receive the RTS frame. That is, the multiple STAs may successfully receive the period information from the RTS frame. However, because the received frame is an RTS frame, the multiple STAs do not need to reset the MediumSyncDelay timer. Therefore, if a response to the RTS frame does not follow, the multiple STAs can protect the channel of link 2 or transmission on link 2 by continuing to apply MediumSyncDelay. If a response to the RTS frame is transmitted, a CTS frame may be transmitted as a response to the RTS frame. STA2 may also transmit a frame (a subsequent frame in FIG. 25) following the CTS frame. In this case, the STAs can reset the MediumSyncDelay timers based on the CTS frame or the subsequent frame without resetting the MediumSyncDelay timers based on the RTS frame, thereby preventing unnecessary application of MediumSyncDelay.

[0300] Furthermore, according to an embodiment of the present invention, even if a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame, if this frame is a PS-Poll frame, it may not be allowed to reset the MediumSyncDelay timer. This may be because a PS-Poll frame does not contain period information. In other words, if a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame that is not a PS-Poll frame, it may be allowed to reset the MediumSyncDelay timer.

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

[0302] Furthermore, according to an embodiment of the present invention, whether or not to reset the MediumSyncDelay timer may be determined based on whether a frame or PPDU received by a STA whose MediumSyncDelay timer is not set to 0 was sent by the associated AP (or an AP included in the same multiple BSSID set as the associated AP). For example, if a frame or PPDU received by a STA whose MediumSyncDelay timer is not set to 0 was sent by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), the MediumSyncDelay timer may be allowed to be reset. Also, if a frame or PPDU received by a STA whose MediumSyncDelay timer is not set to 0 was not sent by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), the MediumSyncDelay timer may not be allowed to be reset. This may be because the AP is likely to have good knowledge of the channel conditions of the link.

[0303] Based on the MAC address field included in the MAC header of the received frame, it can be determined whether the frame was sent by the associated AP (or an AP included in the same multiple 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 was sent by the associated AP (or an AP included in the same multiple BSSID set as the associated AP). For example, if 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 multiple BSSID set as the associated AP), the frame may be sent by the associated AP (or an AP included in the same multiple BSSID set as the associated AP). Furthermore, if 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 multiple BSSID set as the associated AP, the frame may not have been sent by the associated AP or an AP included in the same multiple 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 of a received frame, it can be determined whether the frame was sent to the associated AP (or an AP included in the same multiple 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 multiple BSSID set as the associated AP). For example, if the RA field included in the received frame is set to the address of the associated AP (or an AP included in the same multiple BSSID set as the associated AP), the frame may be sent to the associated AP (or an AP included in the same multiple BSSID set as the associated AP). Furthermore, if the RA field included in the received frame is neither the associated AP address nor the address of an AP included in the same multiple BSSID set as the associated AP, the frame may not be sent to the associated AP or an AP included in the same multiple BSSID set as the associated AP. In this embodiment, the AP address may be rephrased as a BSSID.

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

[0306] If the BSS color included in the preamble of the received PPDU is the same as the BSS color corresponding to the BSS of the receiving STA, and the preamble indicates that the preamble is downlink, the received PPDU may be sent by the associated AP (or an AP included in the same multiple BSSID set as the associated AP). Otherwise, the received PPDU may not be sent by the associated AP or an AP included in the same multiple BSSID set as the associated AP.

[0307] Multiple BSSIDs may be multiple BSSIDs indicated in a single Beacon frame or a single Probe Response frame. In this case, multiple Beacon frames or multiple Probe Response frames corresponding to the multiple BSSIDs may not be used. Alternatively, a single TIM element included in a single Beacon frame or a single TIM frame may be used to indicate buffered frames corresponding to multiple 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. A Multiple BSSID element may indicate multiple BSSs or multiple BSSIDs. The BSSID that transmitted the single Beacon frame or the single Probe Response frame may be referred to as a transmitted BSSID. BSSIDs other than the transmitted BSSID among the BSSIDs indicated by the Multiple BSSID element may be referred to as nontransmitted BSSIDs. Beacon frames or probe response frames do not need to be transmitted for nontransmitted BSSIDs. A set of BSSIDs indicated by a single Multiple BSSID element may be referred to as a multiple BSSID set. Alternatively, the set of transmitted and nontransmitted BSSIDs described above can be called a multiple BSSID set. The maximum number of BSSIDs possible in a multiple BSSID set may be 2^n, where n may be a value signaled in the Multiple BSSID element. For example, n may be a value indicated by the MaxBSSID Indicator included in the Multiple BSSID element. A STA receiving a Multiple BSSID element can determine the addresses or BSSIDs of APs included in the multiple BSSID set from the received Multiple BSSID element.

[0308] In an embodiment of the present invention, the above-described conditions for allowing or disallowing a reset can be combined and used. According to one embodiment, whether the received frame is a type of frame (RTS frame) that is allowed as the first frame during MediumSyncDelay and whether the sender or receiver of the frame is an associated AP (or an AP included in the same multiple BSSID set as the associated AP) may be considered together.

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

[0310] According to the above-described embodiment, the type of frame permitted as the first frame during MediumSyncDelay may be an RTS frame. Therefore, even if a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), if 1) this is an RTS frame and 2) it is not a frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), resetting the MediumSyncDelay timer to 0 may not be permitted. In other words, when a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), 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 multiple BSSID set as the associated AP), resetting the MediumSyncDelay timer to 0 may be permitted. In other words, if a STA receives an RTS frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), resetting the MediumSyncDelay timer to 0 may be permitted. In addition, the operation of resetting the MediumSyncDelay timer to 0 may not be allowed when an RTS frame sent to an associated AP (or an AP included in the same multiple BSSID set as the associated AP) or sent from an inter-BSS is received.

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

[0312] According to the above-described embodiment, the type of frame permitted as the first frame during MediumSyncDelay may be an RTS frame. Therefore, even if a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), if 1) this is an RTS frame and 2) it is not a frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), resetting the MediumSyncDelay timer to 0 may not be permitted. In other words, when a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), 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 multiple BSSID set as the associated AP), resetting the MediumSyncDelay timer to 0 may be permitted. In other words, if a STA receives an RTS frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), resetting the MediumSyncDelay timer to 0 may be permitted. That is, when an RTS frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP) or transmitted from an inter-BSS is received, the MediumSyncDelay timer may be allowed to be reset to 0. Also, when an RTS frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP) is received, the MediumSyncDelay timer may not be allowed to be reset to 0.

[0313] FIG. 26 is a diagram illustrating an example of medium synchronization OFDM ED threshold subfield encoding according to an embodiment of the present invention.

[0314] As described in FIGS. 21 to 25, the modified CCA threshold may be used during MediumSyncDelay. In this case, a base value for the modified CCA threshold exists, and the modified CCA threshold may be signaled. The modified CCA threshold may be signaled using the Medium Synchronization OFDM ED Threshold subfield described above. In some embodiments of the present invention, the above content may be omitted.

[0315] According to an embodiment of the present invention, when MediumSyncDelay is not applied, the CCA ED threshold may be −62 dBm. However, regulations may allow the use of a CCA ED threshold lower than −62 dBm. For example, a CCA ED threshold of −72 dBm may be used in certain regions such as Europe. However, since the CCA thresholds indicated by the Medium Synchronization OFDM ED Threshold subfield described in FIG. 23 are −72 dBm or higher, it may be difficult to restrict channel access using a lower CCA threshold when MediumSyncDelay is applied compared to when MediumSyncDelay is not applied. The embodiment of FIG. 26 may be a method for solving this problem.

[0316] According to one embodiment of the present invention, the minimum value that the Medium Synchronization OFDM ED Threshold subfield can indicate may be a value smaller than −72 dBm. For example, the minimum value that the Medium Synchronization OFDM ED Threshold subfield can indicate may be −82 dBm. Alternatively, the minimum value that the Medium Synchronization OFDM ED Threshold subfield can indicate may be −77 dBm.

[0317] Furthermore, the maximum value that the Medium Synchronization OFDM ED Threshold subfield can indicate may be −62 dBm, or −72 dBm.

[0318] Furthermore, 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 equal to the minimum value that can be indicated by the Medium Synchronization OFDM ED Threshold subfield. Alternatively, the basic value of the dot11MSDOFDMED threshold may be −77 dBm. Alternatively, the basic value of the dot11MSDOFDMED threshold may be −82 dBm. Alternatively, 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. The Medium Synchronization OFDM ED Threshold subfield value may be an integer. The dot11MSDOFDMED threshold value may be an integer in dBm.

[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 ranging from 0 to 15. Therefore, the dot11MSDOFDMED thresholds indicated by Fval 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 another embodiment, the dot11MSDOFDMED threshold indicated by the Medium Synchronization OFDM ED Threshold subfield may not be uniformly spaced. For example, if Fval<=A, the dot11MSDOFDMED threshold may be (-82+2*Fval) dBm. If Fval>A, the dot11MSDOFDMED threshold may be (-82+5+Fval) dBm. That is, if Fval>A, the dot11MSDOFDMED threshold may be (-77+Fval) dBm. Also, A may be 4. 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, and -62 dBm, respectively. In other words, in this 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 another embodiment, the dot11MSDOFDMED thresholds indicated by the Medium Synchronization OFDM ED Threshold subfield may not be uniformly spaced. For example, if Fval<=B, the dot11MSDOFDMED threshold may be (-82+Fval) dBm. If Fval>B, the dot11MSDOFDMED threshold may be (-92+2*Fval) dBm, where B may be 10. Therefore, 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, and -62 dBm, respectively. In this case, the minimum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -82 dBm, and 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 another embodiment, the dot11MSDOFDMED threshold may be (-82+2*Fval) dBm. Furthermore, the Medium Synchronization OFDM ED Threshold subfield may be 4 bits, and Fval may be an integer ranging from 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, and -62 dBm, respectively. In this case, Fval 11 to 15 may be reserved. That is, in this case, the minimum value indicated by the Medium Synchronization OFDM ED Threshold subfield may be -82 dBm. Furthermore, 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] In the above embodiment, the dot11MSDOFDMED threshold interval 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 to represent a wider range of CCA thresholds than that described in FIG. 23. When the size of the Medium Synchronization OFDM ED Threshold subfield is 5 bits, the possible Fval values ​​may be 0 to 31. Furthermore, the dot11MSDOFDMED threshold may be (-82+Fval) dBm. Therefore, when Fval is 0 to 20, it can indicate dot11MSDOFDMED thresholds of -82 dBm to -62 dBm, respectively. Furthermore, in this case, the values ​​of Medium Synchronization OFDM ED Threshold subfields 21 to 31 may be reserved.

[0326] In an embodiment in which the size of the Medium Synchronization OFDM ED Threshold subfield is greater than 4 bits, maintaining the size of the Medium Synchronization Delay Information described in FIG. 23 may require reducing the size of other subfields included in the Medium Synchronization Delay Information. For example, the Medium Synchronization Duration subfield may be smaller than 8 bits. For example, the Medium Synchronization Duration subfield may be 7 bits. In one embodiment, the Medium Synchronization Duration subfield may indicate a time in 32 us units as described above. In this case, 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. In another embodiment, the Medium Synchronization Duration subfield may indicate a time in 64 us units. In this case, 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 smaller than 4 bits. For example, the Medium Synchronization Maximum Number Of TXOPs subfield may be 3 bits. In one embodiment, 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 from 0 to 6. Or, MSD_TXOP_MAX can be indicated as an integer number from 1 to 6. According to another embodiment, 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, or 12. Alternatively, the Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 2, 4, 6, 8, 10, 12, or 14. The Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 1, 3, 5, 7, 9, 11, or 13. The Medium Synchronization Maximum Number Of TXOPs subfield can indicate MSD_TXOP_MAX 0, 1, 3, 5, 7, 9, or 11. Even if the Medium Synchronization Maximum Number Of TXOPs subfield is smaller than 4 bits, it can indicate that there is no limit on the number of transmission attempts when the Medium Synchronization Maximum Number Of TXOPs subfield is set to the maximum value (e.g., 7 values ​​in 3 bits).

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

[0329] According to one embodiment of the present invention, an MLD operating with a single radio may experience latency required to change from transmitting or receiving on one link to being able to listen on multiple links. This latency can be indicated by the MLD operating with a single radio. For example, it can be indicated in the multiple link element or EML Capabilities field described in FIG. 23. Therefore, an MLD operating with a single radio may set the MediumSyncDelay timer at a different time than an MLD operating with multiple radios. In the above-described embodiment, the MediumSyncDelay timer was set to the end of transmission. According to one embodiment, an MLD operating with a single radio may set the MediumSyncDelay timer to a time based on the end of transmission and the latency.

[0330] For example, when an MLD operating with a single radio transmits a PPDU containing a frame requesting an immediate response (solicit), the MediumSyncDelay timer can be set after a certain latency has elapsed since the PPDU containing the immediate response is received. This may be limited to the case where the MLD operating with a single radio is the TXOP holder.

[0331] In addition, when an MLD operating with a single radio transmits a PPDU containing only frames that do not require an immediate response, the MediumSyncDelay timer can be set after a certain latency has elapsed since the transmission of the PPDU. This may be limited to when the MLD operating with a single radio is a TXOP holder.

[0332] Also, when an MLD operating with a single radio is a TXOP responder, it can set the MediumSyncDelay timer after a further latency has elapsed from the time when the TXOP holder no longer transmits frames. Alternatively, an MLD operating with a single radio can set the MediumSyncDelay timer after a further latency has elapsed from the time when the TXOP ends. This may also be limited to cases when an MLD operating with a single radio is a TXOP responder.

[0333] That is, a STA operating on an NSTR link pair can set the MediumSyncDelay timer to a non-zero value to apply MediumSyncDelay and operate it. In this case, the MediumSyncDelay timer can be operated when the transmission of the other STA ends. However, an MLD operating with a single radio may require additional delays, such as link switching to change from a single radio to multiple radios or a delay to return to listening operation. Therefore, in this case, the MediumSyncDelay timer can be operated after the transmission ends and an additional delay. For example, when the MLD operates in EMLSR mode, the STA can start the MediumSyncDelay timer immediately after returning to listening operation.

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

[0335] The embodiment of Fig. 27 may be intended to solve the problem described in Fig. 24. Also, the above-described content may be omitted.

[0336] As described above, according to one embodiment of the present invention, an STA (STA belonging to an MLD) can reset the MediumSyncDelay timer. For example, as described in FIG. 25, whether or not the reset is permitted may be determined based on the type of the received frame. For example, the frame type may be determined based on a value included in the MAC header of the frame. More specifically, the frame type may be determined based on a Frame Control field included in the MAC header. Even more specifically, the frame type may be determined based on a Type subfield and / or a Subtype subfield included in the Frame Control field. According to one embodiment, the Type subfield may be located in bits with bit indexes B2 to B3 of the Frame Control field. Furthermore, the Subtype subfield may be located in bits with bit indexes B4 to B7 of the Frame Control field. According to a further embodiment, the frame type may be determined based on a Type subfield and / or a Subtype subfield and / or a Control Frame Extension subfield included in the Frame Control field. The Control Frame Extension subfield may be located in bits with bit indexes B8 to B11 of the Frame Control field.

[0337] That is, whether or not it is permitted to reset the MediumSyncDelay timer may be determined based on the Type and Subtype of the frame.

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

[0339] Type extension can be specified.

[0340] According to an embodiment of the present invention, an RTS frame may be a frame requesting a CTS frame. Alternatively, an RTS frame may be a frame requesting 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 receiving the Duration field to set a NAV. The RA field may include the address of an intended immediate recipient. For example, if the RA field included in an RTS frame received by a STA is the address of the STA, the STA can respond to the RTS frame with a CTS frame. 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, if the Type subfield is 01 (B3 B2) and the Subtype subfield is 1011 (B7 B6 B5 B4), it indicates that the frame including the Type subfield and the Subtype subfield is an RTS frame. For example, the RTS frame may be a Control frame.

[0341] According to the embodiment described in FIG. 25, whether to reset the MediumSyncDelay timer may be determined based on the type of received frame to solve the problem described in FIG. 21. However, even if this is the case, the problem described in FIG. 22 may not be completely solved because the reset condition allows a STA to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION. For example, there may be multiple STAs whose MediumSyncDelay timer is not set to 0. One of these STAs may transmit a frame based on restricted channel access because its MediumSyncDelay timer is not set to 0. In this case, the transmitted frame may be an RTS frame. If the PPDU format transmitted by one STA is a PPDU format including a TXOP field, the STA receiving the PPDU transmitted by the one STA may receive a PPDU in which the RXVECTOR parameter TXOP_DURATION is present. Therefore, a STA receiving a PPDU transmitted by the single 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 multiple STAs receiving the PPDU transmitted by the single STA, multiple STAs can reset the MediumSyncDelay timer. If the sequence of PPDUs transmitted by the single STA is not continuous, the MediumSyncDelay timer will be reset unnecessarily. For example, a STA that resets the MediumSyncDelay timer may transmit a frame based on unrestricted channel access, thereby disrupting an existing frame exchange that is currently being transmitted.

[0342] As described in Figures 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 may mean high throughput, the IEEE 802.11n standard. VHT may mean very high throughput, the IEEE 802.11ac standard. HE may mean high efficiency, the IEEE 802.11ax standard. EHT may 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 a PPDU. More specifically, the TXOP field may be included in the HE-SIG-A field or the U-SIG field. Also, an HE PPDU may include the HE-SIG-A field. An EHT PPDU may include the U-SIG field. That is, an HE PPDU or an EHT PPDU may include the TXOP field. For example, the TXOP field may be included in the preamble of a PPDU. Also, a non-HT PPDU (or a non-HT duplicate PPDU), an HT PPDU, or a VHT PPDU may not include the TXOP field.

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

[0345] According to one embodiment of the present invention, when a STA whose MediumSyncDelay timer is not set to 0 transmits, there may be restrictions on the PPDU format. For example, when a STA whose MediumSyncDelay timer is not set to 0 transmits, the PPDU format may be restricted when transmitting the first frame in the TXOP. Furthermore, when there is a restriction on the PPDU format, the STA may not transmit (or use) a PPDU that includes a TXOP field. Furthermore, when there is a restriction on the PPDU format, the STA may transmit a PPDU that does not include a TXOP field. In other words, when there is a restriction on the PPDU format, the STA may not transmit an HE PPDU or an EHT PPDU, but may transmit a non-HT PPDU, a non-HT duplicate PPDU, 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 whose MediumSyncDelay timer is not set to 0 may not transmit using a PPDU format including a TXOP field. Also, a STA whose MediumSyncDelay timer is not set to 0 may transmit using a PPDU format that does not include a TXOP field. This may be limited to transmitting the first frame of a TXOP. That is, a STA whose MediumSyncDelay timer is not set to 0 may not transmit using a PPDU format that includes a TXOP field when transmitting the first frame of a TXOP. Also, a STA whose MediumSyncDelay timer is not set to 0 may transmit using a PPDU format that does not include an XOP field when transmitting the first frame of a TXOP. Also, as described above, an RTS frame can be transmitted as the first frame of a TXOP.

[0347] Referring to FIG. 27, multiple STAs operating on link 2 may apply MediumSyncDelay. Furthermore, STA2 of link 2, which applies MediumSyncDelay, may obtain a TXOP and transmit an RTS frame as the first frame. Furthermore, when STA2 transmits the first frame, it may use a PPDU that does not include a TXOP field. 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 a STA applying MediumSyncDelay receives a frame or PPDU transmitted by STA2, it does not receive a TXOP field, and therefore the RXVECTOR parameter TXOP_DURATION does not exist. In other words, a STA that receives a frame or PPDU transmitted by STA2 does not need to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION. Furthermore, 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 a STA applying MediumSyncDelay receives the first frame or a PPDU including the first frame transmitted by STA2, it does not need to reset the MediumSyncDelay timer based on the first frame or the PPDU including the first frame. Therefore, if a response to the RTS frame does not follow, the STAs can protect the channel of Link2 or transmission on Link2 by continuing to apply MediumSyncDelay. If a response to the RTS frame is transmitted, a CTS frame may be transmitted as a response to the RTS frame. STA2 can also transmit a frame (referred to as a subsequent frame in the figure) following the CTS frame.In this case, the 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, thereby preventing unnecessary application of MediumSyncDelay.

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

[0349] The embodiment of Fig. 28 may be intended to solve the problem described in Fig. 24. Also, the above-described contents may be omitted.

[0350] As described in Figure 27, when a STA whose MediumSyncDelay timer is not 0 sends the first frame of a TXOP, using a PPDU including a TXOP field can cause a problem where the 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 restrictions on the setting of the TXVECTOR parameter TXOP_DURATION. 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, duration information may not be present in the TXOP field. This may also be limited to when the STA transmits the first frame of a TXOP. That is, when a STA with a non-zero MediumSyncDelay timer transmits the first frame of a TXOP using a PPDU that includes a TXOP field, the TXVECTOR parameter TXOP_DURATION can be set to UNSPECIFIED. As a result, a STA receiving such a PPDU does not need to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION, even if it is present, because 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, if 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, which applies MediumSyncDelay, may obtain a TXOP and transmit an RTS frame as the first frame. In this case, if STA2 uses a PPDU including a TXOP field, it may set the TXVECTOR parameter TXOP_DURATION 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 need to reset the MediumSyncDelay timer based on the RXVECTOR parameter TXOP_DURATION. In this case, if the embodiment of whether or not resetting is permitted based on the frame type described in FIG. 25 is used together, the one STA does not need 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, if the sequence of frames transmitted by STA2 continues, the one STA can reset the MediumSyncDelay timer based on the subsequent frame or PPDU.

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

[0355] The embodiment of Fig. 29 may be intended to solve the problem described in Fig. 24. Also, the above-mentioned content may be omitted.

[0356] According to the above-described embodiment, a STA whose MediumSyncDelay timer is not set to 0 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 necessary.

[0357] Therefore, according to one embodiment of the present invention, a STA whose MediumSyncDelay timer is not 0 may not reset the MediumSyncDelay timer based on the PPDU preamble (or the RXVECTOR parameter TXOP_DURATION) if it receives both the frame (or the duration information included in the frame) and the PPDU preamble (or the RXVECTOR parameter TXOP_DURATION). In this case, a STA whose MediumSyncDelay timer is not 0 may reset the MediumSyncDelay timer based on the frame (or the duration information included in the frame). In this case, reception may mean successful reception or reception of a valid frame. In this case, the embodiment described in FIG. 22 may also be used.

[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, multiple STAs operating on link 2 may apply MediumSyncDelay. STA2 of link 2, which also applies MediumSyncDelay, may obtain a TXOP and transmit an RTS frame as the first frame. At this time, STA2 may transmit using a PPDU including a TXOP field. One STA whose MediumSyncDelay timer is not set to 0 may successfully receive both the TXOP field and the frame from the PPDU transmitted by STA2. In this case, according to the embodiment described in FIG. 26, the one STA does not need to reset the MediumSyncDelay timer based on the TXOP field. Also, according to the embodiment described in FIG. 22, the one STA does not need to reset the MediumSyncDelay timer based on the RTS frame. Therefore, the problem of resetting the MediumSyncDelay timer when the sequence for the frame transmitted by STA2 is not continuing can be solved. Furthermore, as described in FIG. 25 or 27, the one STA may reset the MediumSyncDelay timer based on the subsequent frame or PPDU when the sequence of frames transmitted by STA2 continues.

[0360] According to the embodiment described in FIG. 25, whether or not to reset the MediumSyncDelay timer may be determined based on whether a frame or PPDU received by a STA whose MediumSyncDelay timer is not set to 0 corresponds to intra-BSS or inter-BSS. According to a more specific embodiment, if a frame or PPDU received by a STA whose MediumSyncDelay timer is not set to 0 corresponds to intra-BSS, the MediumSyncDelay timer may not be reset. Also, if a frame or PPDU received by a STA whose MediumSyncDelay timer is not set to 0 corresponds to inter-BSS, the MediumSyncDelay timer may be reset. This may be to protect intra-BSS frames or intra-BSS PPDUs.

[0361] According to an embodiment of the present invention, whether or not a STA whose MediumSyncDelay timer is not set to 0 is allowed to reset the MediumSyncDelay timer when it receives a frame or PPDU may depend on whether the frame or PPDU is for uplink or downlink. According to one embodiment, if a STA whose MediumSyncDelay timer is not set to 0 receives a frame or PPDU and it is for uplink, it may not be allowed to reset the MediumSyncDelay timer. Also, if a STA whose MediumSyncDelay timer is not set to 0 receives a frame or PPDU and it is for downlink, it may be allowed to reset the MediumSyncDelay timer. This is because a downlink frame (or PPDU) is transmitted by an AP, and the AP is likely to have good knowledge of the overall channel conditions of the BSS, while an uplink frame (or PPDU) is transmitted by a non-AP STA, and the non-AP STA may not be as knowledgeable of the overall channel conditions of the BSS as the AP.

[0362] Whether a frame or a PPDU is uplink or downlink may be determined 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 may indicate uplink or downlink. Alternatively, the preamble may include a Group ID field. The Group ID field may be set to a pre-defined value depending on whether the PPDU containing the Group ID field is uplink or downlink. Whether a frame or a PPDU is uplink or downlink may also be determined based on the MAC header included in the frame or a frame included in the PPDU. For example, the MAC header may include a MAC address. The MAC address can indicate uplink or downlink. For example, if the MAC address of an AP is set in the TA (transmitter address) field, the frame containing the TA field may be downlink. If the MAC address of an AP is set in the RA (receiver address) field, the frame containing the RA field may be uplink. Or,

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

[0364] According to further embodiments, the embodiment in which whether or not to reset the MediumSyncDelay timer is determined based on whether a received frame or PPDU is uplink or downlink may be performed based on whether the frame or PPDU corresponds to an intra-BSS or an inter-BSS. That is, whether or not to reset the MediumSyncDelay timer may be determined based on 1) whether the received frame or PPDU is uplink or downlink, and 2) whether or not to reset the MediumSyncDelay timer is intra-BSS or inter-BSS. For example, when a received frame or PPDU corresponds to an intra-BSS, the above-described embodiment may determine whether or not to reset the MediumSyncDelay timer based on whether it is uplink or downlink. Also, when a received frame or PPDU corresponds to an inter-BSS, resetting the MediumSyncDelay timer may be permitted regardless of whether it is uplink or downlink. For example, if the received frame or PPDU is intra-BSS and uplink, resetting the MediumSyncDelay timer may not be allowed. Alternatively, if the received frame or PPDU is intra-BSS and downlink, resetting the MediumSyncDelay timer may be allowed. Alternatively, if the received frame or PPDU is inter-BSS, resetting the MediumSyncDelay timer may be allowed regardless of whether it is uplink or downlink.

[0365] FIG. 30 is a diagram illustrating 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, a reset operation based on a different condition from the above will be described, and the above content may be omitted.

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

[0368] The L preamble may be a legacy preamble or the legacy preamble described above in FIG. 7, etc. Alternatively, the L preamble may be referred to as a non-HT PHY preamble. This is because the L preamble is a preamble of a non-HT (duplicate) PPDU format. Furthermore, 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 an L-SIG field. This may be because the L-SIG field is located at the end of the L preamble. Furthermore, the successful reception of the L-SIG field may be the case when a field indicating the length of a PHY protocol data unit (PPDU) including the L-SIG field is successfully received. In this case, the length of the PPDU can be determined. The length of the PPDU including the L-SIG field may be determined based on a RATE field and a LENGTH field included in the L-SIG field. The RATE field and the LENGTH field may be the above-mentioned L_RATE field and L_LENGTH field, respectively.

[0369] The L-preamble may include the L-STF, L-LTF, and L-SIG fields. The L-STF, L-LTF, and L-SIG fields may occupy 8 us, 8 us, and 4 us from the beginning of the PPDU, respectively. In other words, the L-preamble may be present within 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 referred to as the value (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 the 6 GHz band. SignalExtension may be 6 us in the 2.4 GHz band. Also, m may be 1 or 2 for an HE PPDU. Also, m may be 0 for PPDUs other than an HE PPDU (i.e., non-HT (duplicate) PPDU, HT PPDU, VHT PPDU, EHT PPDU).

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

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

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

[0376] If the RATE is 6 Mbps, the 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] The MediumSyncDelay timer is reset when the L preamble is successfully received so that the duration of the PPDU including the L preamble can be successfully received and determined. Furthermore, when the L preamble is successfully received, the STA may determine that the medium is busy for the duration of the PPDU including the L preamble, or may not access the medium (channel). However, in this case, it may be more difficult to protect the frame exchange sequence compared to the embodiments described with reference to FIGS. 21 to 26 in which the timer is reset based on the valid duration information, a valid MPDU, or the RXVECTOR parameter TXOP_DURATION. This is because the valid duration information, a valid MPDU, or the RXVECTOR parameter TXOP_DURATION can indicate the duration of a frame sequence, but the duration indicated by the L preamble is the duration of a PPDU. However, the embodiment of FIG. 27 may be more likely to access the channel sooner after resetting the MediumSyncDelay timer compared to the embodiments described with reference to FIGS. 21 to 26. This is because the L preamble is located before the PPDU, so there may be cases where the L preamble is successfully received but valid duration information or a valid MPDU or RXVECTOR parameter TXOP_DURATION is not successfully received.

[0380] Furthermore, the embodiments for solving the problem of resetting the MediumSyncDelay timer based on the first frame or RTS frame during MediumSyncDelay described in Figures 24, 25, and 27 to 29 can be applied to the embodiment of Figure 30. In the present invention, the embodiments referring to the first frame or RTS frame during MediumSyncDelay are not limited to this, and can also be applied by replacing them with an RTS frame or the first frame during MediumSyncDelay, respectively.

[0381] According to one embodiment of the present invention, as described above, when determining whether to reset a received frame based on whether it is an RTS frame, whether it is an RTS frame may be determined based on its duration. The duration may be the PPDU duration. According to one embodiment of the present invention, when an STA whose MediumSyncDelay timer is not 0 successfully receives an L-preamble, the MediumSyncDelay timer may be reset only if the duration of the PPDU including the L-preamble is longer than the duration of the RTS frame. In other words, if the duration of the PPDU including the L-preamble is shorter than the duration of the RTS frame, the MediumSyncDelay timer may not be reset.

[0382] If the RTS frame is included in a non-HT PPDU or a non-HT duplicate PPDU, the PPDU duration may be as follows: 52, 44, 36, 32, 28, 28, 24, or 24 us when the RATE value is 6, 9, 12, 18, 24, 36, 48, or 54 Mbps. Therefore, if a PPDU shorter than or equal to 52 us is received, the MediumSyncDelay timer does not need to be reset.

[0383] If 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 number of octets in the MAC frame format. In an RTS frame, FrameOctet may be 20. ServiceTailBits may be the sum of the number of bits in 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 L preamble in the case of a non-HT PPDU or a non-HT duplicate PPDU. That is, in the case of a non-HT PPDU or a non-HT duplicate PPDU, the preamble may be 20 us.

[0386] In one embodiment of the present invention, when a STA whose MediumSyncDelay timer is not 0 successfully receives an L preamble, the MediumSyncDelay timer may be reset only if the duration of the PPDU including the L preamble is longer than the duration of the RTS frame, and the duration of the RTS frame may be determined based only on the LENGTH field. Therefore, in this case, when a STA whose MediumSyncDelay timer is not 0 successfully receives an L preamble, the MediumSyncDelay timer may be reset only if the duration of the PPDU including the L preamble is longer than 54 us.

[0387] Alternatively, in one embodiment of the present invention, when a STA whose MediumSyncDelay timer is not 0 successfully receives an L-preamble, the MediumSyncDelay timer can be reset only if the duration of the PPDU including the L-preamble is longer than the duration of the RTS frame. In this embodiment, the duration of the RTS frame can be determined based on the LENGTH field and the RATE field. That is, the threshold for comparing the duration of the PPDU can be changed based on the received RATE field value.

[0388] In such an embodiment, the duration of the PPDU containing the RTS frame may be assumed to be the duration of the PPDU containing the RTS frame if the RTS frame were contained in a non-HT PPDU or a non-HT duplicate PPDU.

[0389] According to yet another embodiment, when a PPDU format including an RTS frame is determined, the duration of the PPDU including the RTS frame can be determined by taking into account the preamble length and / or data rate of the PPDU format.

[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 the same number of octets as the RTS frame, that is, 20 octets. Also, an Ack frame or a CTS frame may have a smaller number of octets than the RTS frame. An Ack frame or a CTS frame may have 14 octets.

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

[0392] Referring to FIG. 30, multiple STAs operating on link 2 may apply MediumSyncDelay. STA2 of link 2 applying MediumSyncDelay obtains a TXOP and can transmit an RTS frame as the first frame. STA3 (e.g., one of the multiple 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 subsequent CTS frame, or a PPDU including a subsequent frame following the CTS frame. That is, when STA3 successfully receives an L preamble, it can determine whether to reset the MediumSyncDelay timer based on the PPDU duration indicated by the L preamble. If the PPDU duration is greater than the PPDU duration including the RTS frame, the MediumSyncDelay timer can be reset, and if it is smaller or the same, the MediumSyncDelay timer cannot be reset.

[0393] According to one embodiment, the duration of a PPDU including an RTS frame may be 52 us. According to other embodiments, the duration of a PPDU including an RTS frame may be 52, 44, 36, 32, 28, 28, 24, or 24 us when the RATE field indicates 6, 9, 12, 18, 24, 36, 48, or 54 Mbps, respectively. 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 Figure 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 determine whether it is possible to reset the MediumSyncDelay timer based on the above-mentioned conditions.

[0395] That is, according to the embodiment described in Figure 30, a STA located 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, which may adversely affect the STA's channel access.

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

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

[0398] The embodiment of Fig. 31 may be an embodiment for solving the problem explained in Fig. 30. Also, the above-mentioned contents may be omitted.

[0399] According to an embodiment of the present invention, as described above, when determining whether to reset the received frame based on whether it is an RTS frame, whether it is an RTS frame may be determined based on its duration. The duration may be the PPDU duration. According to an embodiment of the present invention, when a STA whose MediumSyncDelay timer is not set to 0 successfully receives an L preamble, the MediumSyncDelay timer may be reset only if 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, the MediumSyncDelay timer may not be reset. That is, compared to the embodiment described in FIG. 27, when a STA whose MediumSyncDelay timer is not set to 0 successfully receives an L preamble, the MediumSyncDelay timer may be reset even if the duration of the PPDU including the L preamble is shorter than the duration of the RTS frame.

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

[0401] Although the present invention has been described with reference to an embodiment in which the duration of a PPDU and the duration of an RTS frame are compared, the present invention is not limited thereto and may be applied to an embodiment in which the number of octets of a received PSDU (PHY service data unit) (RXVECTOR parameter PSDU_LENGTH), the number of octets of a frame, the LENGTH field value included in an L-SIG, etc. are compared with a value corresponding to an RTS frame. For example, the received comparison criterion may be compared with a value corresponding to an RTS frame, and if the values ​​are identical, the MediumSyncDelay timer may not be reset, but if they are not identical, the MediumSyncDelay timer may be reset.

[0402] Therefore, this embodiment may allow resetting the MediumSyncDelay timer based on frames or PPDUs smaller than RTS frames or PPDUs with higher data rates or MCSs.

[0403] Referring to FIG. 31, multiple STAs operating on link 2 may apply MediumSyncDelay. Also, STA2 of link 2 applying MediumSyncDelay may obtain a TXOP and transmit an RTS frame as the first frame. STA3 (e.g., one of the multiple STAs) whose MediumSyncDelay timer is not 0 may determine whether to reset the MediumSyncDelay timer based on the PPDU including the RTS frame, the PPDU including the subsequent CTS frame, or the PPDU including a subsequent frame following the CTS frame. That is, when STA3 successfully receives an L preamble, it may determine whether 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, the MediumSyncDelay timer may be reset, but if they are the same, the MediumSyncDelay timer may not be reset.

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

[0405] 31, STA3 may not be able to reset the MediumSyncDelay timer based on a PPDU containing an RTS frame. Furthermore, if STA3 receives a PPDU containing a CTS frame, STA3 may be able to reset the MediumSyncDelay timer based on the PPDU containing the CTS frame. If STA3 receives a PPDU containing a subsequent frame, STA3 can 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 located in a hidden position from the STA that transmitted the RTS frame may be able to reset the MediumSyncDelay timer based on a CTS frame or a PPDU containing a CTS frame.

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

[0408] FIG. 32 is a diagram illustrating yet another example of MediumSyncDelay timer reset according to an embodiment of the present invention.

[0409] The embodiment of Fig. 32 may be an embodiment for solving the problems described in Fig. 30 and Fig. 31. Furthermore, the above-described contents may be omitted. In particular, the above-described contents regarding duration may be omitted.

[0410] According to an embodiment of the present invention, a method for determining whether to reset the MediumSyncDelay timer may differ depending on whether a frame (MAC frame) has been received. For example, a method for determining whether to reset the MediumSyncDelay timer may differ depending on whether a frame has been received or whether a frame has not been received and only a preamble has been received.

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

[0412] If a frame cannot be received from a PPDU, the MediumSyncDelay timer may be reset based on the embodiments described in Figures 30 and 31. For example, if a frame cannot be received from a PPDU, but an L preamble is successfully received from the PPDU, the MediumSyncDelay timer may be reset (embodiment of Figure 30). Alternatively, if a frame cannot be received from a PPDU, but an L preamble is successfully received from the PPDU and the duration of the PPDU is greater than the duration of a PPDU containing an RTS frame, the MediumSyncDelay timer may be reset (embodiment of Figure 30). Alternatively, if a frame cannot be received from a PPDU, but an L preamble is successfully received from the PPDU and the duration of the PPDU is different from the duration of a PPDU containing an RTS frame, the MediumSyncDelay timer may be reset (embodiment of Figure 31).

[0413] The duration of the RTS frame or the duration of the PPDU containing the RTS frame may be the same as that described in Figures 30 and 31.

[0414] Although the present invention has been described with reference to an embodiment in which the duration of a PPDU is compared with the duration of an RTS frame, the present invention is not limited thereto and may be applied to an embodiment in which the number of octets of a received PSDU (PHY service data unit) (RXVECTOR parameter PSDU_LENGTH), the number of octets of a frame, the LENGTH field value included in an L-SIG, etc. are compared with a value corresponding to an RTS frame. For example, the received comparison criterion may be compared with a value corresponding to an RTS frame, and if the values ​​are identical, the MediumSyncDelay timer may not be reset, but if they are not identical, the MediumSyncDelay timer may be reset.

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

[0416] For example, if a STA receives a frame that is not an L preamble or an RTS frame, it may be possible to reset the MediumSyncDelay timer. In this case, the STA may be an STA whose MediumSyncDelay timer value is not 0. Furthermore, reception may mean successful reception.

[0417] Alternatively, the STA may be able to reset the MediumSyncDelay timer when 1) it receives an L-preamble whose duration is longer than the duration of the RTS frame, or 2) it receives a frame that is not an RTS frame. In this case, the duration may be the duration indicated by the LENGTH field included in the L-preamble or the L-SIG field. That is, the MediumSyncDelay timer may not be reset when the STA receives an RTS frame in the received PPDU. Also, the MediumSyncDelay timer may be reset when the STA receives a CTS frame, a CF-End frame, or a PS-Poll frame in the received PPDU. Alternatively, there may be an embodiment in which the MediumSyncDelay timer can be reset under the condition 1) or 2) above, or when the STA receives an RXVECTOR parameter TXOP_DURATION that is not the UNSPECIFIED value.

[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 that of the RTS frame, or 2) it receives a frame that is not an RTS frame. In this case, the duration may be the duration indicated by the L-preamble or the L-SIG field. That is, the STA may not be able to reset the MediumSyncDelay timer when it receives an RTS frame in the received PPDU. Also, the STA may be able to reset the MediumSyncDelay timer when it receives a CTS frame, a CF-End frame, or a PS-Poll frame in the received PPDU. Alternatively, there may be an embodiment in which the MediumSyncDelay timer can be reset under the above conditions 1) or 2), or when it receives an RXVECTOR parameter TXOP_DURATION that is not the UNSPECIFIED value.

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

[0420] Referring to FIG. 32, multiple STAs operating on link 2 may apply MediumSyncDelay. Also, STA2 of link 2 applying MediumSyncDelay may obtain a TXOP and transmit an RTS frame as the first frame. STA3 (e.g., one of the multiple STAs) whose MediumSyncDelay timer is not 0 may determine whether to reset the MediumSyncDelay timer based on a PPDU including the RTS frame, a PPDU including a subsequent CTS frame, or a PPDU including a subsequent frame following the CTS frame. That is, when STA3 successfully receives an L preamble, it may determine whether to reset the MediumSyncDelay timer based on the PPDU duration indicated by the L preamble. In this case, STA3 may not be able to reset the MediumSyncDelay timer based on the L preamble of a PPDU including an RTS frame. Alternatively, STA3 may be able to reset the MediumSyncDelay timer when it receives a frame that is not an RTS frame. Therefore, even if STA3 receives an RTS frame following the L preamble of a PPDU containing an RTS frame, the MediumSyncDelay timer may not be reset. Also, even if the duration of the PPDU containing a subsequent frame received by STA3 is the same as the duration of the PPDU containing an RTS frame, the MediumSyncDelay timer may be reset when STA3 receives the subsequent frame. Or, even if STA3 receives a CTS frame, the MediumSyncDelay timer may be reset.

[0421] According to a further embodiment, in the above embodiment, when a STA having a MediumSyncDelay timer whose value is not 0 receives a PPDU or frame and determines whether the MediumSyncDelay timer can be reset, the STA may be limited to only being able to reset the received PPDU or frame corresponding to the intra-BSS. This is because there may be cases where a frame or PPDU is transmitted when only the basic NAV of the STA is configured and the intra-BSS NAV is not configured. For example, when only the basic NAV of the STA is configured and the intra-BSS NAV is not configured, if an intra-BSS AP or an associated AP transmits a triggering frame (a trigger frame or a frame including TRS Control) to the STA, the STA may be able to transmit a frame or PPDU.

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

[0423] As described in Figures 24 to 32, there may be an operation to reset the MediumSyncDelay timer. Also, as described above, whether or not to perform the reset operation may be based on the type of the received frame. Also, whether or not to perform the reset operation may be based on which STA transmitted the received frame. In the present invention, the above-described content may be omitted.

[0424] As described in FIG. 23, there may be cases where the MediumSyncDelay timer of multiple STAs is not 0. Also, according to an embodiment of the present invention, the multiple STAs may include STAs (i.e., APs) that belong to an AP MLD. For example, there may be cases where an AP MLD operates on an NSTR link pair. Such an AP MLD may be called an NSTR AP MLD, an NSTR mobile AP MLD, or an NSTR soft AP MLD.

[0425] Referring to FIG. 33, AP1 and AP2 may belong to the AP MLD, which is the NSTR mobile AP MLD. AP1 and AP2 may operate on link 1 and link 2, respectively. A non-AP MLD may exist that is associated (multiple link setup) with the NSTR mobile AP MLD. STA1 and STA2 may belong to the non-AP MLD. STA1 and STA2 may operate on link 1 and link 2, respectively. Link 1 and link 2 may be a primary link and a non-primary link, respectively. For example, there may be a case where AP1 and STA1 exchange frames. AP1 may transmit PPDU1. STA1 may also transmit PPDU2. In this case, while AP1 is transmitting PPDU1, this transmission may act as interference to AP2, and AP2 may be blinded while transmitting PPDU1. In this case, the MediumSyncDely timer may be started when AP2 leaves the blind state. Also, while STA1 is transmitting PPDU 2, the transmission may act as interference to STA2, causing STA2 to be blinded while transmitting PPDU 2. In such a case, the MediumSyncDelay timer can be started when STA2 exits the blind state. In this way, there may be cases where the MediumSyncDelay timers of multiple STAs, including the AP, are not set to 0.

[0426] In this case, if the MediumSyncDelay timer is allowed to be reset to 0 when a frame of a type that is permitted as the first frame transmitted by an associated AP or an AP belonging to the same multiple BSSID set as the associated AP is received according to the embodiment described in FIG. 25, even if no frame exchange occurs following the first frame, the MediumSyncDelay timer may be reset based on the first frame, thereby interfering with an existing frame exchange, as in the problem described in FIG. 21. That is, in FIG. 30, AP2 may transmit an RTS frame as the first frame while the MediumSyncDelay timer is not set to 0 (for example, this first frame may have been transmitted to STA3, not STA2), and STA2 receiving this frame may reset the MediumSyncDelay timer based on the first frame. In this case, STA2 may begin transmission, causing interference with the frame exchange currently being transmitted.

[0427] The NSTR mobile AP MLD can set, assign, and designate primary links and non-primary links. In addition, a non-AP MLD that has multiple link setup with the NSTR mobile AP MLD can receive information from the NSTR mobile AP MLD as to which links are primary links and which links are non-primary links and determine this information. 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 non-primary links. In addition, a non-AP MLD that has multiple link setup (or is attempting to do so) 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 that has associated with an NSTR mobile AP MLD or has set up multiple links (or is attempting to do so) may not be able to send Probe Request frames, Association Request frames, or Reassociation Request frames on the non-primary link.

[0428] In addition, NSTR mobile AP MLD or non-AP MLD combined with NSTR mobile AP MLD may require the use of a primary link to initiate a TXOP (start frame transmission) on a non-primary link. For example, to start PPDU transmission on a non-primary link, it may be necessary to start PPDU transmission on the primary link simultaneously with the non-primary link. Also, a backoff procedure may exist to start PPDU transmission on the primary link and non-primary link simultaneously. For example, a link whose backoff counter reaches 0 may maintain a backoff counter value of 0, and a link with a backoff counter of 0 may start PPDU transmission when the backoff counter on another link reaches 0.

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

[0430] Furthermore, when an NSTR mobile AP MLD transmits a Reduced Neighbor Report element, it may include only the MLD Parameters subfield in the TBTT Information field corresponding to the NSTR mobile AP MLD. Furthermore, when an AP MLD other than an NSTR mobile AP MLD transmits a Reduced Neighbor Report element, it may not include only the MLD Parameters subfield in the TBTT Information field corresponding to the AP MLD. 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 receiving a TBTT Information field can determine whether the AP MLD corresponding to the TBTT Information field is an NSTR mobile AP MLD depending on whether the TBTT Information field includes only the MLD Parameters field. Whether the TBTT Information field includes only the MLD Parameters subfield may be determined based on a field indicating the length or type of the TBTT Information field. For example, the MLD Parameters subfield may have a preset length, e.g., 3 octets. Also, if the value indicating the length of the TBTT Information field indicates the previously set length, it can be determined that the TBTT Information field includes only the MLD Parameters subfield and corresponds to the NSTR mobile AP MLD.

[0431] According to one embodiment of the present invention, when a STA whose MediumSyncDelay timer is not set to 0 receives a valid frame (or MPDU), it can determine whether or not to reset the MediumSyncDelay timer based on whether the STA is in the AP MLD to which it is associated (multiple link setup) or the NSTR mobile AP MLD. In the embodiment described with reference to FIG. 22, if the frame received by the STA is a frame of a type permitted as an initial frame and is not a frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), the operation of resetting the MediumSyncDelay timer to 0 is not permitted. Also, if the frame received by the STA is a frame of a type permitted as an initial frame or is a frame transmitted by the associated AP (or an AP included in the same multiple BSSID set as the associated AP), the operation of resetting the MediumSyncDelay timer to 0 is permitted. However, in an embodiment of the present invention, this may be limited to cases where the associated AP (or an AP included in the same multiple BSSID set as the associated AP) belongs to an AP MLD other than the NSTR mobile AP MLD.

[0432] In other words, when a STA whose MediumSyncDelay timer is not 0 receives a valid frame (or MPDU), the operation of resetting the MediumSyncDelay timer to 0 may not be permitted if the frame is 1) a type of frame that is allowed as the first frame during MediumSyncDelay, and 2) is not a frame sent by an associated AP (or an AP included in the same multiplexed BSSID set as the associated AP) that belongs to an AP MLD that is not the NSTR mobile AP MLD.

[0433] In addition, when a STA whose MediumSyncDelay timer is not 0 receives a valid frame (or MPDU), it may be allowed to reset the MediumSyncDelay timer to 0 if 1) the frame is not of a type that is allowed as the first frame during MediumSyncDelay, or 2) the frame was sent by an associated AP (or an AP included in the same multiplexed BSSID set as the associated AP) that belongs to an AP MLD that is not the NSTR mobile AP MLD.

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

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

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

[0437] In addition, if the frame received by the STA is not a type of frame that is permitted as the first frame during MediumSyncDelay (for example, an RTS frame), the STA may be permitted to reset the MediumSyncDelay timer to 0.

[0438] At this time, the STA that received the frame may be one whose MediumSyncDelay timer value is not 0.

[0439] The above embodiment, in which whether to allow a MediumSyncDelay reset based on whether the frame was transmitted by an associated AP, may be limited to when the non-AP MLD makes the determination. If the NSTR mobile AP MLD determines whether to allow a MediumSyncDelay reset, it may do so regardless of the sender of the received frame. For example, when the NSTR mobile AP MLD determines whether to allow a MediumSyncDelay reset, it may do so based solely on whether the received frame is a type of frame that is permitted as the first frame during MediumSyncDelay, regardless of who sent the frame. In other words, when a STA belonging to the NSTR mobile AP MLD receives a valid frame, if the frame is not a type of frame that is permitted as the first frame during MediumSyncDelay (e.g., an RTS frame), it may be permitted to reset the MediumSyncDelay timer to 0. Also, when a STA belonging to the NSTR mobile AP MLD receives a valid frame, if the frame is of a type that is allowed as the first frame during MediumSyncDelay (e.g., an RTS frame), 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 Figure 34, when an MLD consisting of multiple STAs operates on an NSTR link pair, the MediumSyncDelay timer for applying MediumSyncDelay can be reset to "0" in certain 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 of one or more stations (STAs) via a second STA operating on the second link (S34010).

[0443] Then, if the media synchronization delay timer is not '0', the second STA can reset the media synchronization delay timer for applying the media synchronization delay based on the received frame (S34020).

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

[0445] When a STA of a link to which media synchronization delay is applied receives a valid frame or a PPDU for a valid MPDU, the STA can reset the media synchronization delay timer to 0 if the media synchronization delay timer is not 0. Alternatively, when a STA receives a PPDU in which the TXOP_Duration, which is a receive parameter (RXVECTOR parameter), is a value other than a specific value, the STA can reset the MediumSyncDelay timer to 0 if the MediumSyncDelay timer is not 0. In this case, the valid frame may be a frame other than an RTS frame.

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

[0447] For example, if a PPDU transmitted on a first link restricts transmission / reception of one or more STAs on a second link of an NSTR link pair, and the MediumSyncDelay timer operates at the end of PPDU transmission, applying MediumSyncDelay to one or more STAs, one or more STAs on the second link can reset the MediumSyncDelay timer when they receive a valid frame. That is, one or more STAs assigned a specific frequency band can reset the MediumSyncDelay timer when they receive a PPDU for a valid MPDU other than an RTS frame transmitted at 20 MHz in the same BSS or another BSS. In this case, if the PPDU or frame is transmitted from an associated AP or an AP included in the same multiple BSSID set, one or more STAs can reset the MediumSyncDelay timer even if the received PPDU or frame is an RTS frame.

[0448] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. Therefore, the above-described embodiments should be understood as illustrative and not restrictive in any respect. For example, each component described as a single type may be implemented in a distributed manner, and similarly, Components described as being distributed 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 all modifications and variations that come within the meaning and scope of the claims and their equivalents should be construed as being within the scope of the present invention.

Claims

1. A multi-link device (MLD) including a plurality of stations each operating on a plurality of links including a first link and a second link, The processor receiving a frame transmitted from one of one or more stations (STAs) via a second STA operating on the second link; If the media synchronization delay timer is not '0', resetting a media synchronization delay timer (Medium Sync Delay timer) for applying a media synchronization delay (Medium Sync Delay) of the second STA based on the received frame; the media synchronization delay indicates a period for restricting data transmission / reception on the second link after transmitting / receiving data of the first STA on the first link; The media synchronization delay timer is reset if the frame is for a valid MPDU other than a request to send (RTS) frame.

2. The MLD according to claim 1, wherein the first link and the second link are a pair of NSTR (Non-Simultaneous Transmission and Reception) links in which transmission / reception on each link causes interference on the other link and does not support simultaneous transmission / reception within the same MLD.

3. The MLD of claim 2 , wherein the media synchronization delay timer starts when transmission on the first link ends.

4. The MLD of claim 1, wherein when the MLD operates in a single radio mode, the media synchronization delay timer starts when a specific delay time has elapsed since transmission on the first link ends.

5. The MLD according to claim 4 , wherein the specific delay time is a delay time for link switching.

6. The MLD of claim 1, wherein 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 multiple BSSID set as the associated AP.

7. A method performed by a multi-link device (MLD) including a plurality of stations operating on a plurality of links, including a first link and a second link, in a wireless communication system, comprising: The method comprises: receiving a frame transmitted from one of one or more stations (STAs) via a second STA operating on the second link; and If the media synchronization delay timer is not '0', resetting a media synchronization delay timer for applying a media synchronization delay (Medium Sync Delay) of the second STA based on the received frame; the media synchronization delay indicates a period for restricting data transmission / reception on the second link after transmitting / receiving data of the first STA on the first link; The media synchronization delay timer is reset if the frame is a frame for a valid MPDU other than a request to send (RTS) frame.

8. 8. The method of claim 7, wherein the first link and the second link are a pair of non-simultaneous transmission and reception (NSTR) links in which transmission / reception on each link causes interference on the other link and does not support simultaneous transmission / reception within the same MLD.

9. 9. The method of claim 8, wherein the media synchronization delay timer starts when transmission on the first link ends.

10. 8. The method of claim 7, wherein when the MLD operates in a single radio mode, the media synchronization delay timer starts when a specific delay time has elapsed since the end of transmission on the first link.

11. The method of claim 10 , wherein the specific delay time is a delay time for link switching.

12. 8. The method of claim 7, wherein the media synchronization delay timer is reset when the frame is transmitted from an AP associated with the second STA or an AP included in the same multiple BSSID set as the associated AP.

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