Method and apparatus for operating multi-link single radio terminal in wireless LAN

Abstract

In a wireless LAN system, a first MLD may be connected to a second MLD performing multi-link communication, and the first MLD may receive an initial control frame from the second MLD. Then, the first MLD may perform communication by receiving the initial control frame. Here, the first MLD may: on the basis of an EMLSR operation and a first mode switching operation, perform a listening operation allowing only reception of an initial control frame in multiple links, on the basis of a first mode; and when the initial control frame is received during the listening operation, perform a transmission and reception operation in a link in which the initial control frame is received, on the basis of a second mode.

Description

Method and device for operating a multi-link single radio terminal in a wireless LAN

[0001] The present disclosure relates to a method and apparatus for operating a multi-link single-radio (MLSR) terminal in a wireless local area network (WLAN). Specifically, it relates to a side-channel access operation of a multi-link single-radio terminal in a wireless LAN. Furthermore, it relates to a method and apparatus for determining the time at which a side-channel transmission of a multi-link single-radio terminal in a wireless LAN ends. Additionally, it relates to a method and apparatus for supporting a dynamic power saving operation in a node that supports multi-link single-radio operation in a wireless LAN.

[0002]

[0003] With the recent expansion of mobile device adoption, Wireless Local Area Network (WLAN) technology, capable of providing fast wireless communication services to these devices, is receiving significant attention. Based on short-range wireless communication technology, WLAN technology enables mobile devices such as smartphones, smart pads, laptop computers, portable multimedia players, and embedded devices to connect to the internet wirelessly.

[0004] Standards using wireless LAN technology are primarily developed by the IEEE (Institute of Electrical and Electronics Engineers) as the IEEE 802.11 standard. As the aforementioned wireless LAN technology has been developed and disseminated, applications utilizing wireless LAN technology have diversified, and a demand has arisen for wireless LAN technology that supports higher reliability.

[0005] As applications requiring higher reliability emerge, the IEEE 802.11bn standard, an Ultra High Reliability (UHR) wireless LAN technology, is being developed for single Basic Service Set (BSS) environments and / or redundant BSS environments. The goal of the IEEE 802.11bn standard may be to support improved data transmission speeds, enhanced latency performance, and reduced data error rates. Additionally, the IEEE 802.11bn standard can support low-power operation, peer-to-peer communication, and operations designed to increase channel utilization. It can also support a TXOP sharing method, where wireless LAN terminals share communication resources (transmit opportunities) between access points (APs). Furthermore, to increase the efficiency of communication resource utilization, the wireless LAN standard can support non-primary channel access (NPCA), which uses a non-primary channel when the primary channel is occupied, and dynamic subband operation (DSO). In addition, it may be possible to support CR-TWT (coordinated-restricted target wake time) operation to protect each low-latency communication segment between multiple access points (APs).

[0006] In the following, the subchannel access operation and low-power operation method of a multi-link single-radio terminal in a wireless LAN are described as described above.

[0007] Meanwhile, the technology forming the background of the invention is written to enhance understanding of the background of the invention and may include content that is not prior art already known to a person with ordinary knowledge in the field to which this technology belongs.

[0008]

[0009] The present disclosure relates to a method and apparatus for a multi-link single radio terminal to perform a sub-channel access operation in a wireless LAN.

[0010] The present disclosure relates to a method and apparatus for a multi-link single radio terminal to perform low-power operation in a wireless LAN.

[0011] The present disclosure relates to a method and apparatus for determining the time of sub-channel transmission termination by a multi-link single radio terminal in a wireless LAN, taking into account multiple links.

[0012] The present disclosure relates to a method and apparatus for performing subband operations for efficient channel usage when a coexistence situation occurs within a device in a wireless LAN.

[0013] The present disclosure relates to a method and apparatus for supporting enhanced multi-link single radio (EMLSR) operation in a wireless LAN.

[0014] The present disclosure relates to a method and apparatus for supporting enhanced multi-link multi-radio (EMLMR) operation in a wireless LAN.

[0015] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0016]

[0017] According to one embodiment of the present specification, a method of operation of a first multi-link device (MLD) comprising a first station (STA) associated with a first link and a second STA associated with a second link in a wireless LAN system, wherein the first MLD is connected to a second MLD that performs multi-link communication, the first MLD is an MLD that simultaneously supports an enhanced multi-link single radio (EMLSR) operation and at least one mode switching operation, and the first MLD receives an initial control frame from the second MLD, wherein the initial control frame includes a padding field and the first MLD performs communication by receiving the initial control frame, wherein the first MLD performs a listening operation based on a first mode that is capable of receiving only the initial control frame in the multi-link based on the first mode switching operation among the EMLSR operation and the at least one mode switching operation, and when the initial control frame is received during the listening operation, the first MLD can perform a transmit / receive operation based on a second mode on the link where the initial control frame was received.

[0018] Additionally, according to one embodiment of the present specification, a first multi-link device (MLD) comprising a first station (STA) associated with a first link and a second STA associated with a second link in a wireless LAN system comprises at least one transceiver for transmitting and receiving signals, at least one processor for controlling the at least one transceiver, and a memory for storing instructions that cause the STA to perform a specific operation by the at least one processor, wherein the specific operation is: the first MLD is connected to a second MLD that performs multi-link communication, wherein the first MLD is an MLD that simultaneously supports an enhanced multi-link single radio (EMLSR) operation and a mode switching operation, wherein the first MLD receives an initial control frame from the second MLD, wherein the initial control frame includes a padding field, and performs communication upon receiving the initial control frame, wherein the first MLD performs a listening operation based on a first mode that is capable of receiving only the initial control frame in a multi-link based on the EMLSR operation and the mode switching operation, and when the initial control frame is received during the listening operation, the initial control frame Transmission and reception operations on the received link can be performed based on the second mode.

[0019] In addition, the following points may apply in common.

[0020] According to one embodiment of the present specification, the first MLD operates in a state where it can receive an initial control frame from multiple links during a listening operation and can perform a clear channel assessment (CCA).

[0021] According to one embodiment of the present specification, the first mode switching operation is a non-primary channel access (NPCA) operation, and when the first MLD operates based on the first mode, the first MLD performs a transmit / receive operation on the primary channel, and when the first MLD operates based on the second mode, the first MLD can perform a transmit / receive operation on the NPCA primary channel.

[0022] Additionally, according to one embodiment of the present specification, if the first link is occupied by an overlapping basic service set (OBSS) while the first MLD is performing a listening operation, the first MLD switches from the main channel to the NPCA main channel to perform the listening operation and can receive an initial control frame on the NPCA main channel.

[0023] Additionally, according to one embodiment of the present specification, the length of the padding field of the initial control frame may be determined to be a value corresponding to or longer than the EMLSR transition delay for transitioning from a listening operation to a transmit / receive operation.

[0024] Additionally, according to one embodiment of the present specification, when the first MLD switches the channel from the NPCA main channel of the first link to the main channel, the frame switching procedure in the NPCA main channel may end at a time prior to the first value from the end of the transmission opportunity of the OBSS.

[0025] Additionally, according to one embodiment of the present specification, the first value may be determined as the longer value among the NPCA switching back delay and the EMLSR switching delay.

[0026] Additionally, according to one embodiment of the present specification, the first mode switching operation is a dynamic subband operation (DSO), and when the first MLD operates based on the first mode, the first MLD performs a transmit / receive operation in the primary subband, and when the first MLD operates based on the second mode, the first MLD can perform a transmit / receive operation in the DSO subband.

[0027] Additionally, according to one embodiment of the present specification, the first MLD receives an initial control frame from the first link during a listening operation, and the initial control frame may instruct the first MLD to change its operating frequency to the DSO subband.

[0028] Additionally, according to one embodiment of the present specification, the length of the padding field of the initial control frame may be determined as the longer value between the DSO switching delay for switching the operating frequency to the DSO subband and the EMLSR switching delay for switching from a listening operation to a transmit / receive operation.

[0029] Additionally, according to one embodiment of the present specification, when the first MLD is switched from the DSO subband of the first link to the main subband, the time at which the first MLD operates in the main subband of the first link may be a time after the sum of the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of termination of the frame switching procedure of the DSO subband.

[0030] Additionally, according to one embodiment of the present specification, the first value may be determined as the longer value between the DSO switching delay and the EMLSR switching delay.

[0031] Additionally, according to one embodiment of the present specification, the first mode switching operation is a dynamic power saving (DPS) operation, and when the first MLD operates based on the first mode, the first MLD operates in a lower capability mode (LCM) in which at least one of the operating bandwidth, the number of operating space streams, and the MCS is limited or only the reception of an initial control frame is possible, and when the first MLD operates based on the second mode, the first MLD can operate in a higher capability mode (HCM).

[0032] Additionally, according to one embodiment of the present specification, the first MLD receives an initial control frame from the first link during a listening operation, and the initial control frame may indicate a DPS operation mode switch of the first MLD from the first link.

[0033] Additionally, according to one embodiment of the present specification, the first MLD can operate by switching from LCM to HCM upon receiving an initial control frame.

[0034] Additionally, according to one embodiment of the present specification, the length of the padding field of the initial control frame may be determined as the longer value between the DPS switching delay when the DPS operation mode switches and the EMLSR switching delay when switching from the listening operation to the normal transmit / receive mode.

[0035] Additionally, according to one embodiment of the present specification, when the first MLD switches from HCM to LCM, the time at which the first MLD switches from HCM to LCM may be a time after the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of termination of the frame exchange procedure according to HCM.

[0036] Additionally, according to one embodiment of the present specification, the first value may be determined as the longer value between the DPS switching delay and the EMLSR switching delay.

[0037] Additionally, according to one embodiment of the present specification, the first MLD may be a non-AP MLD and the second MLD may be an AP MLD.

[0038] Additionally, according to one embodiment of the present specification, at least one mode switching operation may include an NPCA operation, a DSO operation, and a DPS operation.

[0039] In addition, according to one embodiment of the present specification, when the mode is switched according to the NPCA operation, DSO operation and DPS operation, the integrated switching delay may be determined based on the first value.

[0040] Additionally, according to one embodiment of the present specification, the first value may be determined as the longest value among the NPCA switching back delay, DSO switching back delay, DPS switching delay, and EMLSR switching delay.

[0041] Additionally, according to one embodiment of the present specification, the first mode switching operation is an NPCA operation, and when the first MLD switches the channel from the NPCA main channel of the first link to the main channel, the frame switching procedure in the NPCA main channel may end at a time prior to the first value from the end of the transmission opportunity of the OBSS.

[0042] Additionally, according to one embodiment of the present specification, the first mode switching operation is a DSO operation, and when the first MLD is switched from the DSO subband of the first link to the main subband, the time at which the first MLD operates in the main subband of the first link and the time at which the first MLD performs a listening operation in the first link may be a time after the value obtained by adding the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of termination of the frame switching procedure of the DSO subband.

[0043] Additionally, according to one embodiment of the present specification, the first mode switching operation is a DPS operation, and when the first MLD switches from HCM to LCM, the time at which the first MLD switches from HCM to LCM and the time at which the first MLD performs a listening operation on the first link may be a time after the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of termination of the frame switching procedure according to the HCM.

[0044]

[0045] According to the present disclosure, a method can be provided for a multi-link single radio terminal in a wireless LAN to perform a sub-channel access operation.

[0046] According to the present disclosure, a method can be provided for a multi-link single radio terminal in a wireless LAN to perform low-power operation.

[0047] According to the present disclosure, a method can be provided for determining the time when a sub-channel transmission ends by considering multiple links in a multi-link single radio terminal in a wireless LAN.

[0048] According to the present disclosure, a method for performing subband operation for efficient channel usage when a coexistence situation occurs within a device in a wireless LAN can be provided.

[0049] According to the present disclosure, a method for supporting EMLSR operation in a wireless LAN can be provided.

[0050] According to the present disclosure, a method for supporting EMLMR operation in a wireless LAN can be provided.

[0051] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0052] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0053]

[0054] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0055] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0056] FIG. 3 is a diagram showing a wireless LAN network configuration to explain a wireless LAN subchannel access method applied to the present disclosure.

[0057] FIG. 4 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0058] FIG. 5 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0059] FIG. 6 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0060] FIG. 7 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0061] FIG. 8 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0062] FIG. 9 is a diagram showing a method for performing DSO operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0063] FIG. 10 is a diagram showing a wireless LAN network to which the present disclosure applies.

[0064] FIG. 11 is a diagram showing multiple links established between MLDs to which the present disclosure applies.

[0065] FIG. 12 is a diagram illustrating a dynamic power saving operation method applied to the present disclosure.

[0066] FIG. 13 is a diagram illustrating a multi-link single radio operation method applied to the present disclosure.

[0067] FIGS. 14a to 14d are drawings illustrating a dynamic power saving operation method of a wireless LAN terminal supporting multi-link single radio operation.

[0068] FIG. 15 is a diagram illustrating a wireless LAN sub-channel access operation applied to the present disclosure.

[0069] FIGS. 16a and FIGS. 16b are drawings illustrating a method for determining the time of end of sub-channel transmission considering a multi-link single radio terminal applicable to the present disclosure.

[0070] FIG. 17 is a flowchart illustrating the operation of a STA in a wireless LAN to which the present disclosure applies.

[0071]

[0072] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0073] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0074] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0075] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0076] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0077] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present disclosure, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0078] Below, a wireless communication system to which embodiments according to the present disclosure are applied will be described. The wireless communication system to which embodiments according to the present disclosure are applied is not limited to the details described below, and embodiments according to the present disclosure may be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network."

[0079] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies. Referring to FIG. 1, the communication node (100) may include at least one of a processor (110), memory (120), a transceiver (130), an input / output interface (140), a storage device (150), and a bus (160). For example, the communication node (100) may be an access point (AP), a station (STA), an access point multi-link device (MLD), or a non-AP MLD. However, the communication node may not be limited thereto and may be a node that performs communication with another node or device based on the configuration described above. For example, the operating channel bandwidth supported by the AP may be 20 MHz (megahertz), 80 MHz, 160 MHz, etc. The operating channel bandwidth supported by the station may be 20 MHz, 80 MHz, etc. However, it may not be limited thereto.

[0080] A processor (110) within a communication node (100) can control at least one of a memory (120), a transceiver (130), an input / output interface (140), and a storage device (150) for each component within the communication node. The memory (120) within the communication node (100) can store information regarding commands and instructions executed by the processor (110), and the transceiver (130) may refer to a transceiver, an RF (radio frequency) unit, an RF module, or other components that perform signal transmission and reception. The input / output interface (140) within the communication node (100) is an interface for input and output that can be linked with other interfaces and may further include a separate storage device (150). Each component within the communication node (100) can communicate with one another by being connected by a bus (160).

[0081] However, as an example, each component included in the communication node (100) may be connected via an individual interface or an individual bus centered on the processor (110), rather than via a common bus (160). The processor (1110) may also be connected via a dedicated interface to at least one of the memory (120), the transmission / reception device (130), the input / output interface device (140), and the storage device (150).

[0082] A processor (110) can execute a program command stored in at least one of a memory (120) or a storage device (150). The processor (110) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present disclosure are performed. Each of the memory (120) and the storage device (150) may be composed of at least one of a volatile storage medium or a non-volatile storage medium. e.g., the memory (120) may be composed of at least one of read-only memory (ROM) or random access memory (RAM).

[0083] In the following, the relevant operations are described based on the wireless LAN terminal as a station (STA). In accordance with the terminology usage according to IEEE 802.11, STA can refer to both AP STAs operating as access points (APs) and non-AP STAs operating in connection with an AP. However, for the convenience of explanation, APs and non-AP STAs are distinguished below; this distinction is merely for convenience of explanation, and it is self-evident that operations regarding an AP can be applied to both AP STAs and non-AP STAs. Furthermore, it is self-evident that the non-AP STA operations described below can also be applied to both non-AP STAs and AP STAs.

[0084] FIG. 2 is a diagram illustrating a wireless LAN system to which the present disclosure applies. Referring to FIG. 2, the basic service set (BSS) of the wireless LAN system may include one AP (210) and a plurality of non-AP STAs (221, 222, 223, 224), and the plurality of non-AP STAs (221, 222, 223, 224) may be controlled by the AP (210). However, the wireless LAN system is not limited to a BSS, and an environment consisting only of non-AP STAs without a fixed service set or AP may also be considered, and is not limited to a specific form. Each wireless device within the wireless LAN system may include a MAC (medium access control) layer and a physical (PHY) layer, and communication between wireless devices may be performed. For convenience of explanation, the following description focuses on the AP and non-AP STA, but is not limited thereto. For example, the following items may apply equally to other communication nodes or devices and are not limited to a specific form.

[0085]

[0086] In a wireless LAN network, wireless LAN terminals may support sub-channel access operations. In the case of sub-channel access operations, the wireless LAN terminal must perform a channel switching operation, and channel switching may take a certain amount of time. Here, it may be necessary to perform sub-channel access operations that consider support for EMLSR operations. For example, if a wireless LAN terminal supports both EMLSR operations and sub-channel access operations, the time required for channel switching may differ from that of a wireless LAN terminal that does not support EMLSR operations. Therefore, due to the difference in the timing of channel switching, frame transmission may begin before the wireless LAN terminal supporting EMLSR operations has completed channel switching, and the wireless LAN terminal supporting EMLSR operations may fail to receive the frame normally. As described above, the efficiency of sub-channel communication operations in a wireless LAN may decrease. Considering the above, the following describes a method to enable a wireless LAN terminal supporting EMLSR to successfully perform both sub-channel access operations and EMLSR operations when performing sub-channel access operations in a wireless LAN, and according to this, the efficiency and stability of sub-channel access operations in the wireless LAN may be increased.

[0087] In addition, the termination point of frame transmission by a wireless LAN terminal on a sub-channel needs to reflect the necessary delay considering EMLSR operations, and the following describes a method to achieve this. Through the above, frame transmission failures can be reduced and the performance of the wireless LAN network can be increased.

[0088] In addition, wireless LAN terminals supporting multiple links can perform dynamic low-power operation. When a wireless LAN terminal performs dynamic low-power operation, time may be required to switch from low-power mode to high-power mode, and measures for this are described below.

[0089] In addition, as an example, the following describes related operations based on EMLSR. However, the matters described below may be equally applied to EMLMR. Specifically, in this disclosure, the fact that at least one of the non-AP STA MLD and its subordinate non-AP STA performs an EMLSR operation may be replaced by at least one of the non-AP STA MLD and its subordinate non-AP STA performing an EMLMR operation that replaces the EMLSR operation, or performing both EMLSR and EMLMR operations simultaneously. For example, if the non-AP STA MLD uses an EMLMR operation instead of an EMLSR operation, the EMLSR transition delay may be an EMLMR transition delay, and the EMLSR padding delay may be replaced by an EMLMR padding delay. However, for the convenience of explanation, the following description is based on EMLSR.

[0090]

[0091] FIG. 3 is a diagram showing a wireless LAN network configuration to explain a wireless LAN subchannel access method applied to the present disclosure.

[0092] Referring to FIG. 3, a wireless LAN network may be composed of two or more basic service sets (BSS). Each BSS may be composed of an access point (AP) and multiple non-AP STAs that are connected to the AP and perform data communication. Each BSS may operate on the same channel (or frequency). Alternatively, a BSS may share all or part of the operating channel with another BSS. Alternatively, the communication ranges of the BSSs may overlap. For example, data communication performed by one of the multiple BSSs may be received by at least one other BSS. Conversely, one BSS may receive data transmitted by at least one other BSS. Alternatively, one BSS may not be able to receive data transmitted by at least one other BSS, but the data transmitted by at least one other BSS may occupy a portion of the total bandwidth in which the BSS operates. Alternatively, the data transmitted by one BSS may occupy a portion of the total bandwidth in which at least one other BSS operates.

[0093] In the following, the one BSS described above is referred to as BSS, and at least one BSS described above is referred to as OBSS (overlapping BSS). However, this is for convenience of explanation only and is not limited thereto. The operation of the BSS may be the operation of an AP or non-AP STA constituting the BSS. For example, the BSS detecting a frame transmission of the OBSS may mean that at least one of the BSS's AP and non-AP STA detects a frame transmission transmitted by at least one of the OBSS's AP and non-AP STA. Additionally, the BSS performing channel switching may mean that at least one of the BSS's AP and non-AP STA performs channel switching.

[0094] In a wireless LAN network, an access point (AP) multi-link device (MLD) 1 and a non-AP STA MLD 1 can operate. The AP MLD 1 and the non-AP STA MLD 1 can be associated with each other to perform data communication. The AP MLD 1 and the non-AP STA MLD 1 can operate on a first link and a second link. Each of the AP MLD 1 and the non-AP STA MLD 1 may have APs and non-AP STAs affiliated with it. The AP of the AP MLD 1 operating on the first link may be AP 1-1, and the AP of the AP MLD operating on the second link may be AP 1-2. Additionally, the non-AP STA of the non-AP STA MLD 1 operating on the first link may be non-AP STA 1-1, and the non-AP STA of the non-AP STA MLD 1 operating on the second link may be non-AP STA 1-2. For example, AP 1-1 of AP MLD 1 and non-AP STA 1-1 of non-AP STA MLD 1 may form a BSS in the first link, and AP 1-2 of AP MLD 1 and non-AP STA 1-1 of non-AP STA MLD 1 may form a BSS in the second link. In the following, the operation of AP MLD 1 can be interpreted as the operation of AP 1-1 and AP 1-2, and the operation of AP 1-1 and AP 1-2 can be interpreted as the operation of AP MLD 1. Additionally, the operation of non-AP STA MLD 1 can be interpreted as the operation of non-AP STA 1-1 and non-AP STA 1-2, and the operation of non-AP STA 1-1 and non-AP STA 1-2 can be interpreted as the operation of non-AP STA MLD 1.

[0095] non-AP STA MLD 1 may support enhanced multi-link single radio (EMLSR) operation. EMLSR operation may be an operation in which, while the non-AP STA MLD is performing a listening operation to receive only a specific frame from multiple links, if a specific frame is received from one of the multiple links, the non-AP STA MLD transmits and receives data frames without restriction on the link where the specific frame was received. In the present disclosure, the operation of transmitting and receiving data frames without restriction may be referred to as EMLSR mode, but is not limited to such term.

[0096] The non-AP STA MLD operates in a state where it can receive initial control frames from multiple links during a listening operation and can perform a clear channel assessment (CCA). While the non-AP STA MLD is operating in EMLSR mode on the aforementioned links, it may not be able to receive frames and may not be able to perform a clear channel assessment on links where it cannot receive the specific frame described above. For example, the specific frame may be an initial control frame (ICF) with a predetermined format. The initial control frame may be a MU-RTS (multi-user-request to send) trigger frame, a BSRP (buffer status report poll) trigger frame, or other frames, but is not limited to a specific form.

[0097] Here, regarding EMLSR operation, a transition time may be required for the non-AP STA MLD to switch from listening operation to EMLSR mode or from EMLSR mode to listening operation. This transition time may be referred to as the EMLSR transition delay (ETD), but is not limited to this term. The ETD may be set differently depending on the capability of the non-AP STA MLD. For example, the ETD may be indicated by the AP MLD to which the non-AP STA MLD is connected. That is, the AP MLD can recognize the ETD value of the connected non-AP STA MLD.

[0098] There may be two types of ETD. The time taken when a non-AP STA MLD transitions from a listening operation to EMLSR mode may be the EMLSR padding delay. When an AP MLD transmits an initial control frame to a non-AP STA MLD, the length of the padding field can be determined by the aforementioned EMLSR padding delay. The padding field may be included to secure frame transmission time for the non-AP STA MLD to respond to the initial control frame while operating in EMLSR mode during a listening operation, and may increase the frame's time length. The time taken when a non-AP STA MLD transitions from EMLSR mode to a listening operation may be the 'EMLSR transition delay'. Unless otherwise specified in the present disclosure, when a non-AP STA MLD 1 or a subordinate non-AP STA of a non-AP STA MLD 1 transitions to EMLSR mode during a listening operation, the ETD may be an EMLSR padding delay, and otherwise may be an EMLSR transition delay, but is not limited thereto.

[0099] In the first link, non-AP STA 1-1 of non-AP STA MLD 1 and AP 1-1 of AP MLD 1, as well as AP 2 and non-AP STA 2, can operate. non-AP STA 2 can connect to AP 2 (330) to form a BSS. The operating frequency of the BSS formed by AP 2 (330) and non-AP STA 2 may overlap with the primary 20 MHz operating frequency of the BSS formed by AP 1-1 and non-AP STA 1-1. In the above case, AP 2 (330) and non-AP STA 2 may be an overlapping BSS with respect to the BSS formed by AP 1-1 and non-AP STA 1-1. AP 2 (330) or non-AP STA 2 can perform channel access operations (e.g., enhanced distributed channel access (EDCA)) in the first link. If the channel access operation is successful, AP 2 (330) or non-AP STA 2 can acquire a TXOP capable of transmitting multiple frames on the first link. The aforementioned TXOP can occupy the main 20 MHz channel of the BSS configured by AP 1-1 and non-AP STA 1-1. AP 1-1 and non-AP STA 1-1 can check the communication interval of the OBSS (e.g., time interval according to the transmission length of the PPDU, TXOP interval). For example, AP 1-1 and non-AP STA 1-1 can check the duration field included in the MAC header of the frame transmitted in the OBSS or a field indicating information of the PPDU (PHY (physical layer) protocol data unit) included in the PHY preamble (e.g.By checking at least one of the HE-SIG field, U-SIG field, EHT-SIG field, UHR-SIG field, and SERVICE field, and at least one of the time length of the PPDU indicated by L-SIG, it is possible to recognize whether the main 20 MHz channel is occupied and the information on the time interval of the main 20 MHz channel occupancy, but is not limited thereto. AP 1-1 and non-AP STA 1-1 can set a network allocation vector (NAV) for a period corresponding to the communication interval of the OBSS. Here, the NAV may be a basic NAV. Alternatively, even if AP 1-1 and non-AP STA 1-1 do not set a basic NAV, since they support non-primary channel access (NPCA) operation, they can set a timer for the time interval to perform NPCA operation for a period corresponding to the communication interval of the OBSS. In the above-described case, AP 1-1 and non-AP STA 1-1 can switch the operating channel to a non-primary channel access (NPCA) main channel, which is a separate channel that allows channel access. AP 1-1 and non-AP STA 1-1 can operate on the main channel again at the time when the communication period of the OBSS ends. The above-described matters may be applied in the same way to FIGS. 4 through 9 below. However, some operations may differ depending on the operation of each figure and are not limited to a specific form.

[0100] FIG. 4 is a diagram illustrating a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applicable to the present disclosure. Referring to FIG. 4, an NPCA switching delay (NSD) may be required for AP 1-1 (310-1) and non-AP STA 1-1 (320-1) to switch the operation channel to the NPCA main channel. The NSD may be different from each other in AP 1-1 (310-1) and non-AP STA 1-1 (320-1). The NSD of AP 1-1 (310-1) and the NSD of non-AP STA 1-1 (320-1) may be negotiated with each other. For example, AP 1-1 (310-1) can recognize the NSD of non-AP STA 1-1 (320-1), and non-AP STA 1-1 (320-1) can recognize the NSD of AP 1-1 (310-1).

[0101] Since non-AP STA 1-1 (320-1) has not received an initial control frame from AP 1-1 (310-1) on the first link, it can perform a listening operation on the first link. When non-AP STA 1-1 (320-1) switches the operating channel to the NPCA main channel, non-AP STA 1-1 (320-1) can operate in EMLSR mode on the NPCA main channel. Therefore, during the period when non-AP STA 1-1 (320-1) is operating on the NPCA main channel, non-AP STA 1-2 (320-2) cannot perform frame transmission / reception and channel detection operations. Here, when non-AP STA 1-1 (320-1) switches the operating channel to the NPCA main channel, no additional time may be required to transition from the listening operation to EMLSR mode. Alternatively, an ETD may be included within the NSD. AP 1-1 (310-1) can perform a channel access operation to transmit a frame to non-AP STA 1-1 (320-1) after switching the operating channel to the NPCA main channel. If the NSD of AP 1-1 (310-1) is shorter than the NSD of non-AP STA 1-1 (320-1) and the channel access operation of AP 1-1 (310-1) succeeds (e.g., the backoff counter reaches 0) before the NSD of non-AP STA 1-1 (320-1) is completed, AP 1-1 (310-1) can keep the backoff counter at 0 and transmit a frame to non-AP STA 1-1 (320-1) once the NSD of non-AP STA 1-1 (320-1) is completed. Alternatively, AP 1-1 (310-1) may repeat channel access operations until the NSD of non-AP STA 1-1 (320-1) is completed. In the above case, the CW[AC] and QSRC[AC] parameters of AP 1-1 (310-1) may be performed without being changed.When AP 1-1 (310-1) initiates frame transmission to non-AP STA 1-1 (320-1), AP 1-1 (310-1) can acquire a TXOP capable of transmitting multiple frames. Since non-AP STA 1-1 (320-1) operates in EMLSR mode rather than listening mode on the NPCA main channel, AP 1-1 (310-1) can immediately transmit a data frame and a trigger frame for allocating uplink resources without needing to transmit an initial control frame to non-AP STA 1-1 (320-1) as the first frame of the TXOP. non-AP STA 1-1 (320-1) can receive the data frame (401) from AP 1-1 (310-1) and transmit an acknowledgment frame (BlockAck frame, 402). The non-AP STA 1-1 (320-1) can receive a trigger frame (403) from the AP 1-1 (310-1) and transmit an uplink data frame (404) to the AP 1-1 (310-1). The above-described process can be performed even if the non-AP STA 1-1 (320-1) does not receive an initial control frame on the NPCA main channel. Since communication between the AP 1-1 (310-1) and the non-AP STA 1-1 (320-1) is possible without an initial control frame on the NPCA main channel, the time efficiency of the NPCA operation can be increased. In relation to the above-described operation, it may also be possible for the AP 1 to transmit at least one of the data frame and the trigger frame for allocating uplink resources to the non-AP STA 1-1 (320-1). Additionally, AP 1-1 (310-1) may also transmit frames other than data frames and trigger frames for allocating uplink resources to non-AP STA 1-1 (320-1), and are not limited to a specific form.

[0102] If the NSD of AP 1-1 (310-1) is the same as or longer than the NSD of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the time of the NSD of AP 1-1 (310-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0103] If the NSD of AP 1-1 (310-1) is shorter than the NSD of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the NSD time of non-AP STA 1-1 (320-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0104] non-AP STA 1-1 (320-1) and AP 1-1 (310-1) can operate on the main channel again at the end of the communication period of the OBSS occupying the main channel. Here, non-AP STA 1-1 (320-1) can perform a listening operation on the main channel. When non-AP STA 1-1 (320-1) performs a listening operation on the first link, non-AP STA 1-2 (320-2) can also perform a listening operation on the second link. If AP 1-1 (310-1) intends to transmit a data frame to non-AP STA 1-1 (320-1) on the main channel, it may need to transmit an initial control frame to non-AP STA 1-1 (320-1) after the end of the communication period of the OBSS.

[0105] For example, at the time of switching from the NPCA main channel to the main channel, NSD may be the NPCA switching back delay, which is the time required to switch the operating channel from the NPCA main channel to the main channel. ETD may be the EMLSR switching delay. As another example, ETD may be the EMLSR switching delay plus the time 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. The time 'aSIFSTime + aSlotTime + aRxPHYStartDelay' may be the waiting time required before an EMLSR STA (e.g., non-AP STA 1-1) begins to switch its operating mode from EMLSR mode (e.g., a state where normal frame transmission and reception are possible) to listening mode.

[0106] FIG. 5 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0107] Referring to FIG. 5, an NPCA switching delay (NSD) may be required for AP 1-1 (310-1) to switch the operating channel to the NPCA main channel. Here, the longer of the NSD or ETD may be required for non-AP STA 1-1 (320-1) to switch the operating channel to the NPCA main channel. When operating on the NPCA main channel, non-AP STA 1-1 (320-1) may operate in EMLSR mode without a separate time delay.

[0108] For example, the ETD may be longer than the NSD, and the NSD may differ from each other in AP 1-1 (310-1) and non-AP STA 1-1 (320-1). The NSD of AP 1-1 (310-1) and the NSD of non-AP STA 1-1 (320-1) may have been negotiated with each other. Thus, AP 1-1 (310-1) may recognize the NSD of non-AP STA 1-1 (320-1), and non-AP STA 1-1 (320-1) may recognize the NSD of AP 1-1 (310-1).

[0109] Since non-AP STA 1-1 (320-1) has not received an initial control frame from AP 1-1 (310-1) on the first link, it can perform a listening operation on the first link. When non-AP STA 1-1 (320-1) switches the operating channel to the NPCA main channel, non-AP STA 1-1 (320-1) can operate in EMLSR mode on the NPCA main channel. Therefore, during the period when non-AP STA 1-1 (320-1) is operating on the NPCA main channel, non-AP STA 1-2 (320-2) cannot perform frame transmission / reception and channel detection operations.

[0110] AP 1-1 (310-1) can perform a channel access operation to transmit a frame to non-AP STA 1-1 (320-1) after switching the operating channel to the NPCA main channel. If the NSD of AP 1-1 (310-1) is shorter than the ETD of non-AP STA 1-1 (320-1) and the channel access operation of AP 1-1 (310-1) succeeds (e.g., the backoff counter reaches 0) before the ETD of non-AP STA 1-1 (320-1) is completed, AP 1-1 (310-1) keeps the backoff counter at 0, and can transmit a frame to non-AP STA 1-1 (320-1) when the ETD of non-AP STA 1-1 (320-1) is completed. Alternatively, AP 1-1 (310-1) may repeat channel access operations until the ETD of non-AP STA 1-1 (320-1) is completed. In the above case, the CW[AC] and QSRC[AC] parameters of AP 1-1 (310-1) may be performed without being changed. When AP 1-1 (310-1) initiates frame transmission to non-AP STA 1-1 (320-1), AP 1-1 (310-1) may acquire a TXOP capable of transmitting multiple frames. Since AP 1-1 (310-1) operates in EMLSR mode rather than listening mode on the NPCA main channel, it is not necessary to send an initial control frame to non-AP STA 1-1 (320-1) as the first frame of the TXOP, and can immediately send a data frame and a trigger frame for allocating uplink resources. non-AP STA 1-1 (320-1) can receive a data frame (401) from AP 1-1 (310-1) and send an acknowledgment frame (BlockAck frame, 402). non-AP STA 1-1 (320-1) can receive a trigger frame (403) from AP 1-1 (310-1) and send an uplink data frame (404) to AP 1-1 (310-1).The above-described process can be performed even if the non-AP STA 1-1 (320-1) does not receive an initial control frame on the NPCA main channel. Since communication between AP 1-1 (310-1) and the non-AP STA 1-1 (320-1) is possible without an initial control frame on the NPCA main channel, the time efficiency of the NPCA operation can be increased. In the above-described operation, AP 1-1 (310-1) may also transmit at least one of a data frame and a trigger frame for allocating uplink resources to the non-AP STA 1-1 (320-1). Additionally, AP 1-1 (310-1) may also transmit a frame other than the data frame and the trigger frame for allocating uplink resources to the non-AP STA 1-1 (320-1), and is not limited to a specific form.

[0111] If the NSD of AP 1-1 (310-1) is equal to or longer than the ETD of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the time of the NSD of AP 1-1 (310-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0112] If the NSD of AP 1-1 (310-1) is shorter than the ETD of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the ETD time of non-AP STA 1-1 (320-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0113] non-AP STA 1-1 (320-1) and AP 1-1 (310-1) can operate on the main channel again at the end of the communication period of the OBSS occupying the main channel. Here, non-AP STA 1-1 (320-1) can perform a listening operation on the main channel. When non-AP STA 1-1 (320-1) performs a listening operation on the first link, non-AP STA 1-2 (320-2) can also perform a listening operation on the second link. If AP 1-1 (310-1) intends to transmit a data frame to non-AP STA 1-1 (320-1) on the main channel, it must transmit an initial control frame to non-AP STA 1-1 (320-1) after the end of the communication period of the OBSS.

[0114] For example, at the time of switching from the NPCA main channel to the main channel, NSD may be the NPCA switching back delay, which is the time required to switch the operating channel from the NPCA main channel to the main channel. ETD may be the EMLSR switching delay. As another example, ETD may be the EMLSR switching delay plus the time 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. The time 'aSIFSTime + aSlotTime + aRxPHYStartDelay' may be the waiting time required before an EMLSR STA (e.g., non-AP STA 1-1) begins to switch its operating mode from EMLSR mode (e.g., a state where normal frame transmission and reception are possible) to listening mode.

[0115] FIG. 6 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0116] Referring to FIG. 6, an NPCA switching delay (NSD) may be required for AP 1-1 (310-1) to switch the operating channel to the NPCA main channel. Additionally, an NSD may be required for non-AP STA 1-1 (320-1) to switch the operating channel to the NPCA main channel. Subsequently, an additional ETD may be required for non-AP STA 1-1 (320-1) to operate in EMLSR mode on the NPCA main channel. That is, the time required for non-AP STA 1-1 (320-1) to be able to transmit and receive frames on the NPCA main channel may be 'NSD + ETD' time. The NSD may differ for AP 1-1 (310-1) and non-AP STA 1-1 (320-1), respectively. The NSD of AP 1-1 (310-1) and the NSD of non-AP STA 1-1 (320-1) may have been negotiated with each other. Therefore, AP 1-1 (310-1) can recognize the NSD of non-AP STA 1-1 (320-1), and non-AP STA 1-1 (320-1) can recognize the NSD of AP 1-1 (310-1).

[0117] Since non-AP STA 1-1 (320-1) has not received an initial control frame from AP 1-1 (310-1) on the first link, it can perform a listening operation on the first link. When non-AP STA 1-1 (320-1) switches the operating channel to the NPCA main channel, non-AP STA 1-1 (320-1) can operate in EMLSR mode on the NPCA main channel. Therefore, during the period when non-AP STA 1-1 (320-1) is operating on the NPCA main channel, non-AP STA 1-2 (320-2) cannot perform frame transmission / reception and channel detection operations.

[0118] AP 1-1 (310-1) can perform a channel access operation to transmit a frame to non-AP STA 1-1 (320-1) after switching the operating channel to the NPCA main channel. If the NSD of AP 1-1 (310-1) is shorter than the 'NSD + ETD' of non-AP STA 1-1 (320-1), and the channel access operation of AP 1-1 (310-1) succeeds (e.g., the backoff counter reaches 0) before the 'NSD + ETD' of non-AP STA 1-1 (320-1) is completed, AP 1-1 (310-1) can keep the backoff counter at 0 and transmit a frame to non-AP STA 1-1 (320-1) once the 'NSD + ETD' of non-AP STA 1-1 (320-1) is completed. Alternatively, AP 1-1 (310-1) may repeat channel access operations until the 'NSD + ETD' of non-AP STA 1-1 (320-1) is completed. In the above case, the CW[AC] and QSRC[AC] parameters of AP 1-1 (310-1) may be performed without being changed. When AP 1-1 (310-1) initiates frame transmission to non-AP STA 1-1 (320-1), AP 1-1 (310-1) may acquire a TXOP capable of transmitting multiple frames. Since AP 1-1 (310-1) is operating in EMLSR mode rather than listening mode on the NPCA main channel, it is not necessary to send an initial control frame to non-AP STA 1-1 (320-1) as the first frame of the TXOP, and can immediately send a data frame and a trigger frame for allocating uplink resources. non-AP STA 1-1 (320-1) can receive a data frame (401) from AP 1-1 (310-1) and send an acknowledgment frame (BlockAck frame, 402).The non-AP STA 1-1 (320-1) can receive a trigger frame (403) from the AP 1-1 (310-1) and transmit an uplink data frame (404) to the AP 1-1 (310-1). The above-described process can be performed even if the non-AP STA 1-1 (320-1) does not receive an initial control frame on the NPCA main channel. Since communication between the AP 1-1 (310-1) and the non-AP STA 1-1 (320-1) is possible without an initial control frame on the NPCA main channel, the time efficiency of the NPCA operation can be increased. In the above-described operation, the AP 1-1 (310-1) may also transmit at least one of a data frame and a trigger frame for allocating uplink resources to the non-AP STA 1-1 (320-1). Additionally, AP 1-1 (310-1) may also transmit frames other than data frames and trigger frames for allocating uplink resources to non-AP STA 1-1 (320-1), and are not limited to a specific form.

[0119] If the NSD of AP 1-1 (310-1) is equal to or longer than the 'NSD + ETD' of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the time of the NSD of AP 1-1 (310-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0120] If the NSD of AP 1-1 (310-1) is shorter than the 'NSD + ETD' of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the NSD time of non-AP STA 1-1 (320-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0121] non-AP STA 1-1 (320-1) and AP 1-1 (310-1) can operate on the main channel again at the end of the communication period of the OBSS occupying the main channel. non-AP STA 1-1 (320-1) can perform a listening operation on the main channel. When non-AP STA 1-1 (320-1) performs a listening operation on the first link, non-AP STA 1-2 (320-2) can also perform a listening operation on the second link. If AP 1-1 (310-1) intends to transmit a data frame to non-AP STA 1-1 (320-1) on the main channel, it may need to transmit an initial control frame to non-AP STA 1-1 (320-1) after the end of the communication period of the OBSS.

[0122] For example, at the time of switching from the NPCA main channel to the main channel, NSD may be the NPCA switching back delay, which is the time required to switch the operating channel from the NPCA main channel to the main channel. ETD may be the EMLSR switching delay. As another example, ETD may be the EMLSR switching delay plus the time 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. The time 'aSIFSTime + aSlotTime + aRxPHYStartDelay' may be the waiting time required before an EMLSR STA (e.g., non-AP STA 1-1) begins to switch its operating mode from EMLSR mode (e.g., a state where normal frame transmission and reception are possible) to listening mode.

[0123] FIG. 7 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0124] Referring to FIG. 7, an NPCA switching delay (NSD) may be required for AP 1-1 (310-1) to switch its operating channel to the NPCA main channel. Additionally, an NSD may be required for non-AP STA 1-1 (320-1) to switch its operating channel to the NPCA main channel. Subsequently, an additional ETD may be required for non-AP STA 1-1 (320-1) to operate in EMLSR mode on the NPCA main channel. That is, the time required until non-AP STA 1-1 (320-1) can transmit and receive frames on the NPCA main channel may be 'NSD + ETD' time. The NSD may differ for AP 1-1 (310-1) and non-AP STA 1-1 (320-1), respectively. The NSD of AP 1-1 (310-1) and the NSD of non-AP STA 1-1 (320-1) may have been negotiated with each other. Therefore, AP 1-1 (310-1) can recognize the NSD of non-AP STA 1-1 (320-1), and non-AP STA 1-1 (320-1) can recognize the NSD of AP 1-1 (310-1).

[0125] Since non-AP STA 1-1 (320-1) has not received an initial control frame from AP 1-1 (310-1) on the first link, it can perform a listening operation on the first link. When non-AP STA 1-1 (320-1) switches the operating channel to the NPCA main channel, non-AP STA 1-1 (320-1) can operate in EMLSR mode on the NPCA main channel. Therefore, during the period when non-AP STA 1-1 (320-1) is operating on the NPCA main channel, non-AP STA 1-2 (320-2) cannot perform frame transmission / reception and channel detection operations.

[0126] AP 1-1 (310-1) can perform a channel access operation to transmit a frame to non-AP STA 1-1 (320-1) after switching the operating channel to the NPCA main channel. If the NSD of AP 1-1 (310-1) is shorter than the 'NSD + ETD' of non-AP STA 1-1 (320-1), and the channel access operation of AP 1-1 (310-1) succeeds (e.g., the backoff counter reaches 0) before the 'NSD + ETD' of non-AP STA 1-1 (320-1) is completed, AP 1-1 (310-1) can keep the backoff counter at 0 and transmit a frame to non-AP STA 1-1 (320-1) once the 'NSD + ETD' of non-AP STA 1-1 (320-1) is completed. Alternatively, AP 1-1 (310-1) may repeat channel access operations until the 'NSD + ETD' of non-AP STA 1-1 (320-1) is completed. In the above case, the CW[AC] and QSRC[AC] parameters of AP 1-1 (310-1) may be performed without being changed. When AP 1-1 (310-1) initiates frame transmission to non-AP STA 1-1 (320-1), AP 1-1 (310-1) may acquire a TXOP capable of transmitting multiple frames. Since AP 1-1 (310-1) is operating in EMLSR mode rather than listening mode on the NPCA main channel, it is not necessary to send an initial control frame to non-AP STA 1-1 (320-1) as the first frame of the TXOP, and can immediately send a data frame and a trigger frame for allocating uplink resources. non-AP STA 1-1 (320-1) can receive a data frame (401) from AP 1-1 (310-1) and send an acknowledgment frame (BlockAck frame, 402).The non-AP STA 1-1 (320-1) can receive a trigger frame (403) from the AP 1-1 (310-1) and transmit an uplink data frame (404) to the AP 1-1 (310-1). The above-described process can be performed even if the non-AP STA 1-1 (320-1) does not receive an initial control frame on the NPCA main channel. Since communication between the AP 1-1 (310-1) and the non-AP STA 1-1 (320-1) is possible without an initial control frame on the NPCA main channel, the time efficiency of the NPCA operation can be increased. In the above-described operation, the AP 1-1 (310-1) may also transmit at least one of a data frame and a trigger frame for allocating uplink resources to the non-AP STA 1-1 (320-1). Additionally, AP 1-1 (310-1) may also transmit frames other than data frames and trigger frames for allocating uplink resources to non-AP STA 1-1 (320-1), and are not limited to a specific form.

[0127] The point in time when non-AP STA 1-1 (320-1) can communicate on the NPCA main channel may be before the NSD of non-AP STA 1-1 (320-1) from the end of the communication period of the OBSS. If the NSD of AP 1-1 (310-1) is the same as or longer than the NSD of non-AP STA 1-1 (320-1), the end of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) may be before the NSD of AP 1-1 (310-1) from the end of the TXOP occupied by the OBSS on the main channel.

[0128] If the NSD of AP 1-1 (310-1) is shorter than the NSD of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the NSD time of non-AP STA 1-1 (320-1) from the end time of the TXOP occupied by the OBSS on the main channel.

[0129] non-AP STA 1-1 (320-1) and AP 1-1 (310-1) can operate on the main channel again at the end of the communication period of the OBSS occupying the main channel. non-AP STA 1-1 (320-1) can perform a listening operation on the main channel after the ETD time following the end of the communication period of the OBSS. When non-AP STA 1-1 (320-1) performs a listening operation on the first link, non-AP STA 1-2 (320-2) can also perform a listening operation on the second link. If AP 1-1 (310-1) intends to transmit a data frame to non-AP STA 1-1 (320-1) on the main channel, it may need to transmit an initial control frame to non-AP STA 1-1 (320-1) after the ETD following the end of the communication period of the OBSS.

[0130] For example, at the time of switching from the NPCA main channel to the main channel, NSD may be the NPCA switching back delay, which is the time required to switch the operating channel from the NPCA main channel to the main channel. ETD may be the EMLSR switching delay. As another example, ETD may be the EMLSR switching delay plus the time 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. The time 'aSIFSTime + aSlotTime + aRxPHYStartDelay' may be the waiting time required before an EMLSR STA (e.g., non-AP STA 1-1) begins to switch its operating mode from EMLSR mode (e.g., a state where normal frame transmission and reception are possible) to listening mode.

[0131] FIG. 8 is a diagram showing a method for performing NPCA operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0132] Referring to FIG. 8, an NPCA switching delay (NSD) may be required for AP 1-1 (310-1) to switch the operating channel to the NPCA main channel. Additionally, an NSD may be required for non-AP STA 1-1 (320-1) to switch the operating channel to the NPCA main channel. After switching the operating channel to the NPCA main channel, non-AP STA 1-1 (320-1) may perform a listening operation. That is, only reception of the initial control frame may be possible. While non-AP STA 1-1 (320-1) is switching from the NPCA main channel of the first link to the NPCA main channel (i.e., while non-AP STA 1-1 (320-1) detects the communication interval of OBSS and during NSD), non-AP STA 1-1 (320-1) and non-AP STA 1-2 (320-2) may not be able to perform listening operations and may not be able to transmit or receive frames. As another example, while non-AP STA 1-1 (320-1) is switching from the main channel of the first link to the NPCA main channel, non-AP STA 1-2 (320-2) may be able to perform listening operations and non-AP STA 1-1 (320-1) may not be able to transmit or receive frames. Afterwards, while non-AP STA 1-1 (320-1) performs a listening operation on the NPCA main channel of the first link, non-AP STA 1-2 (320-2) can perform a listening operation.

[0133] AP 1-1 (310-1) can perform a channel access operation to transmit a frame to non-AP STA 1-1 (320-1) after switching the operating channel to the NPCA main channel. If the NSD of AP 1-1 (310-1) is shorter than the NSD of non-AP STA 1-1 (320-1) and the channel access operation of AP 1-1 (310-1) succeeds (e.g., the backoff counter reaches 0) before the NSD of non-AP STA 1-1 (320-1) is completed, AP 1-1 (310-1) keeps the backoff counter at 0, and can transmit a frame to non-AP STA 1-1 (320-1) when the NSD of non-AP STA 1-1 (320-1) is completed. Alternatively, AP 1-1 (310-1) may repeat channel access operations until the NSD of non-AP STA 1-1 (320-1) is completed. In the above case, the CW[AC] and QSRC[AC] parameters of AP 1-1 (310-1) may be performed without being changed. When AP 1-1 (310-1) initiates frame transmission to non-AP STA 1-1 (320-1), AP 1-1 (310-1) may acquire a TXOP capable of transmitting multiple frames.

[0134] AP 1-1 (310-1) may need to send an initial control frame to non-AP STA 1-1 (320-1) as the first frame of the TXOP, since non-AP STA 1-1 (320-1) is operating in a listening operation on the NPCA main channel. The initial control frame may be a trigger frame. For example, the trigger frame may be a MU-RTS trigger frame, a BSRP trigger frame, or other frames, and is not limited to a specific form. Here, the trigger frame may include a padding field corresponding to or greater than the ETD (specifically the length of the EMLSR padding delay time). The padding field may extend the length of the frame and provide time for the EMLSR non-AP STA to switch its operation from a listening operation to an EMLSR mode. non-AP STA 1-1 (320-1) may receive the trigger frame (405), which is the initial control frame of AP 1-1 (310-1). When non-AP STA 1-1 (320-1) receives an initial control frame (405), non-AP STA 1-1 (320-1) may transition from a listening operation to an EMLSR mode while operating on the NPCA main channel, thereby transitioning to a state where frame transmission and reception are possible. Here, non-AP STA 1-2 (320-2) may become unable to communicate. When non-AP STA 1-1 (320-1) transitions to EMLSR mode, it may transmit an initial control response frame (406) to AP 1-1 (310-1). For example, the initial control response frame may be a simultaneous CTS (S-CTS) frame, a CTS frame, a BSR frame, a multi-STA BA frame, or other frames, but is not limited to a specific form. Alternatively, the initial control response frame may be an uplink data frame.AP 1-1 (310-1) receives an initial control response frame (406) from non-AP STA 1-1 (320-1) and can transmit an additional trigger frame or downlink frame to non-AP STA 1-1 (320-1). non-AP STA 1-1 (320-1) receives a data frame and a trigger frame from AP 1-1 (310-1) and can transmit a response frame (BlockAck frame) or an uplink data frame. In the operation described above, AP 1-1 (310-1) may also transmit at least one of a data frame and a trigger frame for allocating uplink resources to non-AP STA 1-1 (320-1). Additionally, AP 1-1 (310-1) may also transmit frames other than data frames and trigger frames for allocating uplink resources to non-AP STA 1-1 (320-1), and are not limited to a specific form.

[0135] The time at which non-AP STA 1-1 (320-1) can communicate on the NPCA main channel may be before the NSD of non-AP STA 1-1 (320-1) from the end of the communication period of OBSS. If the NSD of AP 1-1 (310-1) is the same as or longer than the NSD of non-AP STA 1-1 (320-1), the end of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) may be before the NSD of AP 1-1 (310-1) from the end of the TXOP occupied by OBSS on the main channel.

[0136] If the NSD of AP 1-1 (310-1) is shorter than the NSD of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) may be before the NSD time of non-AP STA 1-1 (320-1) from the end time of the TXOP occupied by OBSS on the main channel. If an EMLSR operation transition is required (e.g., transition from EMLSR mode to listening operation), non-AP STA 1-1 (320-1) may wait for the reception of an initial control frame on the main channel after the communication period of OBSS ends and after the ETD. If EMLSR operation switching is not required, non-AP STA 1-1 (320-1) may wait for reception of an initial control frame after the end of the communication period of OBSS.

[0137] As another example, the time at which non-AP STA 1-1 (320-1) can communicate on the NPCA main channel may be before the time of 'NSD+ETD' of non-AP STA 1-1 (320-1) from the time of the end of the communication period of OBSS. If the NSD of AP 1-1 (310-1) is equal to or longer than the 'NSD+ETD' of non-AP STA 1-1 (320-1), the time of the end of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) may be before the time of the NSD of AP 1-1 (310-1) from the time of the end of the TXOP occupied by OBSS on the main channel.

[0138] If the NSD of AP 1-1 (310-1) is shorter than the 'NSD+ETD' of non-AP STA 1-1 (320-1), the end time of the TXOP acquired by AP 1-1 (310-1) or the frame switching procedure (e.g., data frame transmission - response frame reception procedure, trigger frame transmission - data frame reception - response frame transmission procedure) that AP 1-1 (310-1) can transmit to non-AP STA 1-1 (320-1) may be before the 'NSD+ETD' time of non-AP STA 1-1 (320-1) from the end time of the TXOP occupied by OBSS on the main channel. If EMLSR operation switching is not required, non-AP STA 1-1 (320-1) may wait for the reception of an initial control frame after the end time of the communication period of OBSS.

[0139] AP 1-1 (310-1) can operate on the main channel again at the end of the OBSS TXOP. In order for AP 1-1 (310-1) to transmit a data frame to non-AP STA 1-1 (320-1), it may need to transmit an initial control frame to non-AP STA 1-1 (320-1). AP 1-1 (310-1) may need to transmit an initial control frame at a time when non-AP STA 1-1 (320-1) can receive the initial control frame (e.g., when operating in EMLSR mode, when operating in listening mode).

[0140] For example, at the time of switching from the NPCA main channel to the main channel, NSD may be the NPCA switching back delay, which is the time required to switch the operating channel from the NPCA main channel to the main channel. ETD may be the EMLSR switching delay. As another example, ETD may be the EMLSR switching delay plus the time 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. The time 'aSIFSTime + aSlotTime + aRxPHYStartDelay' may be the waiting time required before an EMLSR STA (e.g., non-AP STA 1-1) begins to switch its operating mode from EMLSR mode (e.g., a state where normal frame transmission and reception are possible) to listening mode.

[0141] FIG. 9 is a diagram showing a method for performing DSO operations of a non-AP STA and an AP that support EMLSR operations applied to the present disclosure.

[0142] Referring to FIG. 9, in the first link, non-AP STA 1-1 (320-1) of non-AP STA MLD 1 and AP 1-1 (310-1) of AP MLD 1, as well as non-AP STA 2-1 (340-1) connected to AP 1-1 (310-1), can be operated. The operating frequency bandwidth of non-AP STA 1-1 (320-1) and the operating frequency bandwidth of non-AP STA 2-1 (340-1) may be smaller than the total operating frequency bandwidth of AP 1-1 (310-1). For example, the operating bandwidth of AP 1-1 (310-1) may be 320 MHz. The operating bandwidth of non-AP STA 1-1 (320-1) and non-AP STA 2-1 (340-1) may be 160 MHz, 80 MHz, 40 MHz, or other bandwidths, and is not limited to a specific form. non-AP STA 1-1 (320-1) may be a non-AP STA that supports dynamic subband operation (DSO). DSO operation may be an operation in which the non-AP STA shifts its operating frequency to a frequency other than the main 20 MHz channel within the AP's operating frequency to receive a frame from the AP. For example, if the operating bandwidth of AP 1-1 (310-1) is 320 MHz and non-AP STA 1-1 (320-1) and non-AP STA 2-1 (340-1) are non-AP STAs having an operating bandwidth of 160 MHz, non-AP STA 2-1 (340-1) can receive a frame from AP 1-1 (310-1) on a channel including a main 20 MHz channel. Additionally, non-AP STA 1-1 (320-1) can receive a frame from AP 1-1 (310-1) by changing the operating frequency to a different 160 MHz channel other than the 160 MHz channel assigned to non-AP STA 2-1 (340-1). The channel including the aforementioned 20 MHz channel is the main channel, and the remaining channels (e.g.A channel that does not include a main 20MHz channel and is not included in the operating bandwidth of a non-AP STA but is included in the operating bandwidth of an AP (operating bandwidth of a BSS) may be a DSO channel. Meanwhile, in the DSO operation of the present disclosure, the main channel may be referred to as a primary subband and the DSO channel as a DSO subband, and is not limited to specific terms.

[0143] AP 1-1 (310-1) may transmit an initial control frame to transmit frames to non-AP STA 1-1 (320-1) and non-AP STA 2-1 (340-1) using DSO operation. The initial control frame may be a frame that instructs non-AP STA 1-1 (320-1), which supports DSO operation, to change the operating frequency and to transmit a response frame to the initial control frame (407-1, 407-2) from non-AP STA 1-1 (320-1) and non-AP STA 2-1 (340-1). The initial control frame (407-1, 407-2) may be a trigger frame containing a MU-RTS frame. The initial control frame (407-1, 407-2) may be transmitted using both the main channel and the DSO channel. The non-AP STA 1-1 (320-1), upon receiving the initial control frames (407-1, 407-2), can operate in EMLSR mode by switching the operating frequency to the DSO channel. Additionally, the non-AP STA 1-1 (320-1) can transmit a response frame (e.g., simultaneous CTS, 408-1) to AP 1-1 (310-1) after SIFS time from the time the initial control frames (407-1, 407-2) are received. The non-AP STA 2-1 (340-1) can transmit a response frame (408-2) to AP 1-1 (310-1) on the main channel.

[0144] In the initial control frames (407-1, 407-2), the time required for non-AP STA 1-1 (320-1) to switch its operating frequency to the DSO channel may be taken into account. The time required for non-AP STA 1-1 (320-1) to switch its operating frequency to the DSO channel may be the DSO switching delay (DSD), but is not limited thereto. Since non-AP STA 1-1 (320-1) performs an EMLSR operation and operates in EMLSR mode on the DSO channel, the time required when switching channels may be taken into account in various ways. For example, only the DSD time may be required for non-AP STA 1-1 (320-1) to switch to the DSO channel and operate in EMLSR mode. In the above case, non-AP STA 1-1 (320-1) may operate in EMLSR mode on the DSO channel after the DSD time following the reception of the initial control frame. The padding length of the initial control frame (407-1) may be equal to or greater than the DSD time.

[0145] As another example, consider the case where non-AP STA 1-1 (320-1) requires the longer of DSD and ETD to switch to a DSO channel and operate in EMLSR mode. If ETD is longer than DSD, non-AP STA 1-1 (320-1) can operate in EMLSR mode on the DSO channel after the ETD time following the reception of the initial control frame. Here, the padding length of the initial control frame may be equal to or longer than the ETD time.

[0146] As another example, both DSD and ETD may be required for non-AP STA 1-1 (320-1) to switch to a DSO channel and operate in EMLSR mode. Non-AP STA 1-1 (320-1) receives an initial control frame and operates on a DSO channel after the DSD time, but since it cannot operate in EMLSR mode, frame transmission and reception may be impossible. Non-AP STA 1-1 (320-1) may be able to operate in EMLSR mode and frame transmission and reception may be possible after the ETD time has passed from the point in time after the DSD time from the reception of the initial control frame. Here, the padding length of the initial control frame may be equal to or greater than the 'DSD + ETD' time.

[0147] AP 1-1 (310-1) can transmit trigger frames and data frames to allocate uplink resources to non-AP STA 1-1 (320-1) and non-AP STA 2-1 (340-1) using the main channel and DSO channel. non-AP STA 1-1 (320-1) and non-AP STA 2-1 (340-1) can transmit uplink data frames in response to the trigger frame, and response frames (e.g., BlockAck frames) in response to the data frame. After the TXOP of AP 1-1 (310-1) ends, non-AP STA 1-1 (320-1) can operate again on the main channel. The condition for non-AP STA 1-1 (320-1) to operate as the main channel may be after the MAC layer receives the PHY-RXSTART.indication primitive from the PHY layer within aRXPHYDelay time from after receiving the last frame that does not require a response frame on the DSO channel or after transmitting a response frame for the last frame that requires a response frame. Alternatively, the condition for non-AP STA 1-1 (320-1) to operate as the main channel may be after the MAC layer receives the PHY-RXSTART.indication primitive from the PHY layer within aRXPHYDelay time from after transmitting a frame that does not require a response frame. Alternatively, the condition for non-AP STA 1-1 (320-1) to operate as the main channel may be after the MAC layer receives the PHY-RXSTART.indication primitive from the PHY layer within aRXPHYDelay time from after receiving a response frame after transmitting a frame that requires a response frame. After the above conditions, non-AP STA 1-1 (320-1) can operate on the main channel after DSD.In the operation described above, AP 1-1 (310-1) may also transmit at least one of a data frame and a trigger frame for allocating uplink resources to non-AP STA 1-1 (320-1). Additionally, AP 1-1 (310-1) may also transmit a frame other than a data frame and a trigger frame for allocating uplink resources to non-AP STA 1-1 (320-1), and is not limited to a specific form.

[0148] As another example, non-AP STA 1-1 (320-1) may operate on the main channel after ETD. Or, non-AP STA 1-1 (320-1) may operate on the main channel after 'ETD + DSD'. AP 1-1 (310-1) may transmit an initial control frame to transmit a data frame to non-AP STA 1-1 (320-1) after the point in time when non-AP STA 1-1 (320-1) operates as a listening operation on the main channel.

[0149] For example, the time taken for non-AP STA 1-1 (320-1) to switch the operating frequency from the DSO channel to the main channel may be the DSO switching delay (DSD). ETD may be the EMLSR switching delay. As another example, ETD may be the EMLSR switching delay plus the time 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. The time 'aSIFSTime + aSlotTime + aRxPHYStartDelay' may be the waiting time required before the EMLSR STA (e.g., non-AP STA 1-1 (320-1)) begins switching the operating mode from EMLSR mode (e.g., a state where normal transmission and reception of frames is possible) to listening mode.

[0150] The non-AP STA MLD 1 of FIGS. 4 to 9 described above may support EMLSR, but the non-AP STA MLD 1 may support EMLMR operation different from EMLSR operation. Here, EMLMR operation may have a definition similar to EMLSR operation.

[0151] The EMLMR operation may be an operation in which non-AP STAs (e.g., non-AP STA 1-1, non-AP STA 1-2) operating on each link of a non-AP STA MLD use spatial streams equal to the number of spatial streams per link, and when a non-AP STA receives an initial frame, it performs a spatial stream switching operation on another link to communicate with more spatial streams. For example, if the number of spatial streams per link of the first link of non-AP STA 1-1 (320-1) is two and the number of spatial streams per link of the second link of non-AP STA 1-2 (320-2) is two, when non-AP STA 1-1 (320-1) receives an initial control frame, the spatial stream of non-AP STA 1-2 (320-2) on the second link may be switched to operate on the first link where non-AP STA 1-1 (320-1) is operating. Subsequently, non-AP STA 1-1 (320-1) can receive frames from the AP using a number of spatial streams greater than the number of spatial streams per link (e.g., 4, provided that this may vary depending on the capabilities of each non-AP STA). non-AP STA 1-2 (320-2) cannot detect the medium while non-AP STA 1-1 (320-1) is receiving frames from the AP. Meanwhile, as described above, a delay time is required to switch the spatial streams per link and to switch the spatial streams again after receiving the frame, and this can be referred to as the EMLMR transition delay (EMTD).

[0152] For example, there may be two types of EMTD. The time it takes for a non-AP STA MLD to switch a spatial stream from another link to one link in order to receive a frame from an AP MLD on one link may be the EMLMR padding delay (EMPTD). The EMLMR padding delay can determine the length of the padding field when the AP MLD connected to the non-AP STA MLD transmits an initial control frame to the non-AP STA MLD. The initial frame may contain padding for a duration equal to or longer than the length of the EMLMR padding delay. The initial frame of the EMLMR operation may not be a frame with a fixed format, but it may be a frame that includes padding of a length corresponding to the length of the EMPTD. The EMPTD may be set differently depending on the capability of the non-AP STA MLD. Additionally, the EMPTD may be directed to the AP MLD connected to the non-AP STA MLD. That is, the AP MLD can recognize the EMLMR padding delay value of the connected non-AP STA MLD.

[0153] As another example, the delay time during which a non-AP STA MLD completes receiving a frame from an AP MLD that uses the link-specific spatial stream of another link on one link, thereby allowing the other link to use the link-specific spatial stream again, may be the 'EMLMR transition delay'. For example, the time it takes for a non-AP STA MLD 1 or a subordinate non-AP STA of non-AP STA MLD 1 to switch the spatial stream of another link to one link to receive a frame from the AP MLD may be understood as the EMLMR padding delay, and in all other cases, the EMLMR may be understood as the EMLMR transition delay.

[0154] For example, if the non-AP STA MLD 1 and the subordinate non-AP STAs non-AP STA 1-1 and non-AP STA 1-2 (320-2) of FIGS. 4 to 9 described above support EMLMR operation, the initial control frame of the EMLSR operation may be the initial frame of the EMLMR operation. Additionally, the EMLSR transition delay may be replaced with the EMLMR transition delay, and the EMLSR padding delay may be replaced with the EMLMR padding delay. However, the format of the initial frame in the EMLMR operation may be more diverse than the initial control frame of the EMLSR. Accordingly, depending on the type of frame received from the AP MLD, the non-AP STA MLD may transmit a frame other than a CTS frame.

[0155] The non-AP STA MLD 1 of FIGS. 4 to 9 described above can support EMLSR operation and EMLMR operation. When the non-AP STA 2 of the non-AP STA MLD 1 of FIGS. 4 to 9 starts transmitting a frame (e.g., starts a TXOP) on the NPCA main channel, the non-AP STA 2 can terminate the frame transmission (frame exchange, TXOP, which may include a response frame) before the NPCA switching delay time from the end time of the OBSS communication period. Alternatively, the non-AP STA 2 may terminate the frame transmission (frame exchange, TXOP, which may include a response frame) before the time of 'NPCA switching delay + (EMLSR or EMLMR) padding delay' from the end time of the OBSS communication period. Alternatively, non-AP STA 2 may terminate frame transmission (frame exchange, TXOP, which may include a response frame) before the time of 'NPCA switching delay + (EMLSR or EMLMR) padding delay + (aSIFSTime + aSlotTime + aRxPHYStartDelay)' from the time of end of the communication period of OBSS.

[0156]

[0157] FIG. 10 is a diagram showing a wireless LAN network to which the present disclosure applies, and FIG. 11 is a diagram showing multiple links established between MLDs to which the present disclosure applies.

[0158] Referring to FIGS. 10 and 11, an MLD may have a single MAC (medium access control) address. An MLD may refer to an AP MLD or a non-AP STA MLD, but is not limited thereto. The MAC address of the MLD may be used in a multi-link setup procedure between a non-AP STA MLD and an AP MLD. The MAC address of the AP MLD may be different from the MAC address of the non-AP STA MLD. The AP(s) associated with the AP MLD may have different MAC addresses, and the non-AP STA(s) associated with the non-AP STA MLD may also have different MAC addresses. APs within an AP MLD with different MAC addresses may be responsible for each link and may perform the role of an independent AP. Additionally, non-AP STAs within a non-AP STA MLD with different MAC addresses may also be responsible for each link and may perform the role of an independent non-AP STA.

[0159] For example, an MLD may support STR (simultaneous transmit and receive) operation. In the above case, the MLD may perform a transmit operation on a first link and simultaneously perform a receive operation on a second link. An MLD that supports STR operation may be referred to as an STR MLD (e.g., STR AP MLD, STR non-AP STA MLD), but is not limited to such terms. For example, a link may refer to a portion consisting of a channel, band, or other frequency range. Although the following description is based on a link, it applies equally even if the link is a channel, band, or other frequency range, and is not limited to a specific form. However, for the convenience of explanation, the description is based on a link.

[0160] Devices that do not support STR operation may be referred to as NSTR (non-STR) AP MLD or NSTR non-AP STA MLD, but are not limited to such terms.

[0161] The MLD can transmit and receive frames over multiple links by using a discontinuous bandwidth expansion method (e.g., 80 MHz + 80 MHz). Multi-link operation may include multi-band transmission. The AP MLD may include multiple APs, and the multiple APs may operate on different links. Additionally, each of the multiple APs may perform function(s) of the lower MAC layer. Each of the multiple APs may be referred to as a "communication node" or "lower entity," and the communication node (i.e., AP) may operate under the control of the upper layer (or processor).

[0162] Additionally, the non-AP STA MLD may include multiple non-AP STAs, and the multiple non-AP STAs may operate on different links. Each of the multiple non-AP STAs may be referred to as a "communication node" or a "subordinate entity," and the communication node (i.e., STA) may operate under the control of a higher layer (or processor).

[0163] The MLD can perform communication in multi-band. For example, the MLD can perform communication in the 2.4 GHz band using a 40 MHz bandwidth according to a channel expansion method (e.g., bandwidth expansion method). Additionally, the MLD can perform communication in the 5 GHz band using a 160 MHz bandwidth according to a channel expansion method. Furthermore, the MLD can perform communication in the 6 GHz band using a 160 MHz bandwidth. For example, a single frequency band (e.g., a single channel) used by the MLD can be defined as a single link. As another example, multiple links can be established within a single frequency band used by the MLD. As a specific example, the MLD can establish one link in the 2.4 GHz band and two links in the 6 GHz band. Each link may be referred to as the first link, the second link, and the third link, but this is for the convenience of explanation only and is not limited thereto. In other words, links can be established in various forms, and for the convenience of explanation below, they will be referred to as links.

[0164] An MLD (e.g., AP MLD and / or non-AP STA MLD) can establish multiple links by performing at least one of a connection procedure and a negotiation procedure for multiple link operation. When multiple links are established, the number of links and the links to be used among the multiple links can be established. A non-AP STA MLD can verify band information capable of communicating with an AP MLD. In the negotiation procedure for multiple link operation between a non-AP STA MLD and an AP MLD, a non-AP STA MLD can configure one or more links among those supported by the AP MLD to be used for multiple link operation. A STA that does not support multiple link operation (e.g., IEEE 802.11a / b / g / n / ac / ax STA) can be connected to one or more links among the multiple links supported by the AP MLD. If the band spacing between multiple links (e.g., the band spacing between a first link and a second link in the frequency domain) is sufficient, the MLD can perform an STR operation. For example, an MLD can transmit a PPDU (PHY (physical layer) protocol data unit) 1 using the first link among multiple links and receive a PPDU 2 using the second link among multiple links. On the other hand, if the bandwidth between multiple links is insufficient, in-device coexistence (IDC) interference, which is interference between multiple links, may occur if the MLD performs an STR operation. Therefore, if the bandwidth between multiple links is insufficient, the MLD may not be able to perform an STR operation.

[0165] For example, multiple links including a first link, a second link, and a third link may be established between an AP MLD and a non-AP STA MLD 1. If the bandwidth between the first link and link 3 is sufficient, the AP MLD can perform an STR operation using the first link and the third link. That is, the AP MLD can transmit a frame using the first link while simultaneously receiving a frame using the third link. On the other hand, if the bandwidth between the first link and the second link is insufficient, the AP MLD may not be able to perform an STR operation using the first link and the second link. Alternatively, if the bandwidth between the second link and the third link is insufficient, the AP MLD may not be able to perform an STR operation using the second link and the third link.

[0166] FIG. 12 is a diagram illustrating a dynamic power saving operation method applied to the present disclosure.

[0167] In a wireless LAN network, AP 1 (510) and non-AP STA 1, which is associated with AP 1 (510), may operate. In a wireless LAN network, at least one of AP 1 (510) and non-AP STA 1 (520) may perform dynamic power saving (DPS). Here, dynamic low-power operation may be determined through negotiation between AP 1 (510) and non-AP STA 1 (520). During the association procedure between AP 1 (510) and non-AP STA 1 (520), capability information of AP 1 (510) and non-AP STA 1 (520) may be exchanged. AP 1 (510) and non-AP STA 1 (520) may perform negotiation regarding whether to use DPS operation based on the exchanged capability information. For example, AP 1 (510) can perform operations to support non-AP STA 1 (520) when it uses DPS (e.g., an initial control frame (ICF) transmission operation, a frame transmission operation according to the capability mode (low capability mode / high capability mode) of non-AP STA 1 (520). In the above case, AP 1 (510) sets the DPS assisting support bit of the UHR MAC Capabilities Information field of the UHR (ultra high reliability) capabilities element included in at least one frame among the frames exchanged in the connection procedure with non-AP STA 1 (520) to 1.

[0168] For example, non-AP STA 1 (520) can perform a transition between low capability mode and high capability mode based on DPS operation. Additionally, non-AP STA 1 (520) can respond with an initial control response (ICR) to the AP's ICF based on DPS operation. Additionally, non-AP STA 1 (520) can perform other operations based on DPS, but is not limited to a specific form. In the above case, non-AP STA 1 (520) sets the DPS support bit of the UHR MAC Capabilities Information field of the UHR capabilities element included in at least one frame among the frames exchanged during the connection procedure with AP 1 (510) to 1.

[0169] When the information described above is exchanged, non-AP STA 1 (520) can recognize that AP 1 (510) supports the DPS of non-AP STA 1 (520). Additionally, AP 1 (510) can recognize that non-AP STA 1 (520) is capable of performing DPS operations. That is, AP 1 (510) and non-AP STA 1 (520) can negotiate for DPS support.

[0170] After the negotiation process described above, non-AP STA 1 (520) may want to perform a DPS operation. If non-AP STA 1 (520) wants to perform a DPS operation, non-AP STA 1 (520) may send a UHR OMN (operating mode notification) frame (601) to AP 1 (510). The UHR OMN frame (601) may contain parameters for non-AP STA 1 (520) to perform a DPS operation. Specifically, the UHR OMN frame (601) may include a UHR control field and a DPS Operation Parameters field. The UHR control field may indicate whether the DPS is enabled (or disabled). The DPS operation parameters may include a DPS padding delay, which is the time involved in the non-AP STA 1 (520) performing the DPS operation switching from LCM (lower capability mode) to HCM (higher capability mode), and a DPS switching delay, which is the time involved in the non-AP STA 1 (520) switching from HCM to LCM. The DPS operation may be initiated after the non-AP STA 1 (520) transmits a UHR OMN frame (601) to AP 1 (510) and a certain amount of time has passed. As another example, the DPS operation may be initiated when the non-AP STA 1 (520) transmits a UHR OMN frame to AP 1 (510) and then receives a UHR OMN frame (602) from AP 1 (510).

[0171] For example, non-AP STA 1 (520) may operate as LCM when it initiates DPS operation. For another example, when non-AP STA 1 (520) initiates DPS operation, it may operate as HCM until it receives a frame from AP 1 (510), and then operate as LCM after it has finished receiving a frame from AP 1 (510). For a specific example, if non-AP STA 1 (520) receives a frame that requires an acknowledgment frame transmission according to the acknowledgment policy (Ack policy) of the frame received from the AP, non-AP STA 1 (520) may switch from HCM to LCM after waiting for time Tt after the transmission of the acknowledgment frame is completed (or after the reception of the frame is completed if it receives a frame that does not require an acknowledgment frame transmission).

[0172] DPS operation may be referred to as dynamic low-power operation. The power saving mode available during dynamic power saving operation may be a lower capability mode (LCM) with fewer restrictions than Dose mode. In LCM, the AP and STA may be limited in at least one of the operating bandwidth, the number of spatial streams (Nss), and the modulation and coding scheme (MCS). Alternatively, in LCM, the AP and STA may be able to receive only frames of a specific format. For example, a frame of a specific format may be an initial control frame (ICF), but is not limited thereto. The initial control frame may be a BlockAck request (BAR) frame, a multi-user request to send (MU) trigger frame, or a buffer status report poll (BSRP) trigger frame, but is not limited thereto. In the LCM, as described above, frame transmission and reception may be possible in which constraints according to at least one of the limited operating bandwidth, the number of operating space streams, and the MCS are satisfied.

[0173] Another power saving mode available during dynamic power saving operation may be Higher Capability Mode (HCM). When operating in HCM, the wireless LAN terminal can perform normal data transmission and reception, and the operating bandwidth and operating spatial stream may not be limited. Based on the above, power consumption may be lower when operating in LCM than when operating in HCM. Additionally, the following description is based on non-AP STA, but this applies equally to AP STA. However, for the convenience of explanation, the description is based on non-AP STA.

[0174] An AP or non-AP STA operating in DPS mode may receive an ICF (603) in LCM mode. When an AP or non-AP STA receives an ICF (603), the AP or non-AP STA may operate in HCM mode. Here, a separate transition time or switch time may be required for the AP or non-AP STA to switch from LCM mode to HCM mode. For example, a padding field present in the ICF (603) may be included corresponding to the time described above. That is, the padding field may be a field intended to extend the time length of the frame and ensure a transition time or switch time. Thus, the length of the padding field may be a time corresponding to or greater than the transition time (or switch time). Here, a DPS padding delay field included in the UHR OMN frames (601, 602) exchanged between non-AP STA 1 (520) and AP 1 (510) may indicate the transition time (or switch time). Upon receiving the ICF (603), the AP or non-AP STA operating in HCM can transmit an ICR (initial control response) frame (604) (which may be abbreviated as ICR). After the ICF and ICR exchange procedure is completed, the AP or non-AP STA operating in HCM can complete frame transmission and reception. When frame transmission and reception is completed, the AP or non-AP STA can switch from HCM to LCM and operate. A separate transition time (or switching time) may be required for the AP or non-AP STA to switch from HCM to LCM and operate. A DPS switching delay field included in the UHR OMN frame exchanged between non-AP STA 1 (520) and AP 1 (510) may indicate the aforementioned transition time (or switching time). For example, the AP or non-AP STA may have at least one of the operating bandwidth and the operating space stream limited during the corresponding transition time (or switching time).As another example, an AP or non-AP STA may be able to receive only frames of a specific format during the corresponding transition time (or switching time). As another example, an AP or non-AP STA may be able to receive only frames of a specific format during the corresponding transition time (or switching time). Alternatively, an AP or non-AP STA may be able to transmit only frames of a specific format during the corresponding transition time (or switching time).

[0175] Referring to FIG. 12, non-AP STA 1 (520) can perform a DPS operation. In the above case, AP 1 (510) can perform a channel access operation. The channel access operation may be an enhanced distributed channel access (EDCA) operation, and if the channel access operation is successful, a transmit opportunity (TXOP) can be obtained, which is a time interval for transmitting a frame. The TXOP can be obtained from the entire bandwidth available to AP 1 (510) (e.g., 40 MHz, 80 MHz, 160 MHz, 320 MHz, etc.). For example, since non-AP STA 1 (520) operates as an LCM based on the DPS operation, the receiving bandwidth of non-AP STA 1 (520) may be limited (e.g., limited to 20 MHz). AP 1 (510) can transmit an ICF duplicated in 20 MHz increments to non-AP STA 1 (520) to occupy the entire bandwidth of the TXOP acquired by AP 1 (510) while enabling non-AP STA 1 (520) to receive frames. The ICF duplicated in 20 MHz increments can be transmitted duplicated for the bandwidth of the TXOP acquired by the AP. Here, the ICF can instruct non-AP STA 1 (520) on bandwidth information. The bandwidth information may be instructed by a Bandwidth Signaling TA set in the transmitter address (TA) of the MAC header included in the ICF, or by the L-SIG field of the PHY preamble and other fields. Alternatively, the bandwidth information may be instructed through a combination of the Bandwidth Signaling TA set and the L-SIG field of the PHY preamble.

[0176] The format of the ICF may be a Non-HT (high throughput) Duplicat PPDU format, and the ICF may be a trigger frame (e.g., a BSRP (buffer status report poll) trigger frame, a MU-RTS (multi-user request to send) trigger frame). The ICF may include a padding field that guarantees a transition time that allows non-AP STA 1 (520) to operate from LCM to HCM, and the transition time may be a DPS padding delay. Upon receiving the ICF, non-AP STA 1 (520) may switch the operation mode from LCM to HCM, and non-AP STA 1 (520) that has switched the operation mode to HCM may send an ICR to AP 1 (510). After that, AP 1 (510) may send a data frame to non-AP STA 1 (520). Since non-AP STA 1 (520) operates as an HCM, AP 1 (510) can transmit data frames in the full bandwidth, full spatial stream, and full frame format supported by non-AP STA 1 (520). That is, the AP can perform normal data transmission and reception, and the operating bandwidth and operating spatial stream are not limited. non-AP STA 1 (520) can receive data frames from AP 1 (510) and can also transmit a response frame (BlockAck frame). When non-AP STA 1 (520) completes receiving a frame from AP 1 (510) and the frame is a frame that does not require a response frame (or when non-AP STA 1 (520) completes receiving a frame from AP 1 (510) and completes sending a response frame by requesting a response frame), non-AP STA 1 (520) may wait for the next frame received from AP 1 (510) for a certain period of time (e.g., aSIFSTime + aSlotTime + aRxPHYStartDelay time).The above time may be referred to as Tw time. If no frame is detected during the Tw time (e.g., if no PHY-RXSTART.indication primitive occurs), non-AP STA 1 (520) may switch the operation mode from HCM to LCM, which may be the end of HCM operation, but is not limited to that term.

[0177] When non-AP STA 1 (520) switches from HCM to LCM, a separate switching time may occur. The separate switching time may be a DPS switching delay, which may be referred to as Tt. non-AP STA 1 (520) may operate in LCM after the switching time Tt. During the switching time that occurs when non-AP STA 1 (520) switches from HCM to LCM, non-AP STA 1 (520) may receive frames that are receivable in LCM (e.g., frames in which at least one of bandwidth, spatial stream, or format is limited or fixed). The above-described operation may be applied in the same or similar way to non-AP STA 1 (520) AP 1 (510) (i.e., when the STA transmits to the AP).

[0178] Also, Tw time is the following<Tw 조건 1> ,<Tw 조건 2> and<Tw 조건 3> It can start if one of the cases is satisfied.

[0179]

[0180] <Tw 조건 1>

[0181] If the PPDU transmitted by the STA is a response to the most recently received frame from the AP, it starts at the time the transmission of the PPDU is completed.

[0182]

[0183] <Tw 조건 2>

[0184] If the PPDU received from an AP or another STA contains a frame that does not require an immediate response, start at the time the reception of the PPDU is complete.

[0185]

[0186] <Tw 조건 3>

[0187] If the PPDU transmitted by the STA includes a frame that does not require an immediate response, it starts at the time the transmission of the PPDU is completed.

[0188]

[0189] non-AP STA 1 (520) performs the following for the duration of Tw when Tw is initiated after the completion of reception of the initial control frame<LCM 전환> When the conditions are met, it no longer operates as an HCM and switches to an LCM.

[0190]

[0191] <LCM 전환>

[0192] - The MAC layer of STA 1 does not receive the PHY-RXSTART.indication primitive from the PHY layer and does not send the PHY-TXSTART.request primitive.

[0193] - The MAC layer of STA 1 does not receive the PHY-TXSTART.confirm primitive from the PHY layer.

[0194] - There is no nonempty transmit queue in STA 1.

[0195] - STA 1 does not intend to transmit a frame or schedule transmission

[0196]

[0197] <LCM 전환>In the conditions, the MAC layer of non-AP STA 1 (520) receiving the PHY-RXSTART.indication primitive from the PHY layer may mean that non-AP STA 1 (520) detects a frame being received. Additionally, the MAC layer of non-AP STA 1 (520) sending the PHY-TXSTART.request primitive to the PHY layer, and the MAC layer of non-AP STA 1 (520) receiving the PHY-TXSTART.confirm primitive from the PHY layer may mean that non-AP STA 1 (520) intends to start transmitting a frame.

[0198] Also, as an example, non-AP STA 1 (520) receives the PHY-RXSTART.indication primitive within Tw time.<LCM 전환> Even if the conditions are not met, the following<LCM 전환 - 수신> If the conditions are met, it may need to operate as an LCM instead of an HCM.<LCM 전환> Without satisfying the conditions<LCM 전환 - 수신> If the conditions are not met, non-AP STA 1 (520) may have to operate as HCM without switching to LCM.

[0199]

[0200] <LCM 전환 - 수신>

[0201] - If the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer, and the recipient of the received frame is not STA 1

[0202] - The case where the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer, and the received frame is a trigger frame, and the received trigger frame does not allocate a resource unit (RU) for STA 1

[0203] - When the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer and the received frame is a CTS (clear to send) frame

[0204] - If the receiver address (RA) of the CTS frame is not the address of the AP connected to STA 1 (i.e., the address of AP 1)

[0205]

[0206] The aforementioned<LCM 전환> and<LCM 전환 - 수신> The PPDU defined in the conditions may be a PHY layer frame (physical layer frame), and the physical layer frame may include an MPDU (MAC protocol data unit), which is a MAC layer frame.

[0207] Referring to FIG. 12, the non-AP STA MLD 1 operating on the first link may be non-AP STA 1 (520), the non-AP STA operating on the second link may be non-AP STA 2 (540), and the non-AP STA operating on the third link may be non-AP STA 3. The AP MLD 1 operating on the first link may be AP 1 (510), the AP operating on the second link may be AP 2 (530), and the AP operating on the third link may be AP 3.

[0208] Here, non-AP STA MLD 1 may perform different DPS operations depending on the link. For example, if the STA MLD has a first link, a second link, and a third link, non-AP STA 1 (520) and non-AP STA 2 (540) may perform DPS operations, while STA 3 may not perform DPS operations. DPS settings for multiple links may be set by the exchange of UHR OMN frames between MLDs. For example, the exchange of UHR OMN frames between non-AP STA MLD 1 and AP MLD 1 may be performed between non-AP STA 1 (520) and AP 1 (510) of the first link. Alternatively, the exchange of UHR OMN frames between non-AP STA MLD 1 and AP MLD 1 may involve the non-AP STA 1 (520) of the first link transmitting a UHR OMN frame to AP 1 (510), and AP 2 (530) of AP MLD 1 responding to non-AP STA 2 (540) of non-AP STA MLD 1.

[0209] When DPS settings for multiple links are configured via UHR OMN frame exchange between MLDs, the UHR control field of the UHR OMN frame may include a link identifier (e.g., a link ID bitmap) that performs the DPS operation. The link ID bitmap may indicate a first link and a second link, which are the links where the DPS operation is performed. Additionally, DPS operation parameters may be configured differently by multiple link operations. For example, if the DPS operation parameters (e.g., DPS padding delay and DPS switching delay) are the same in the first link and the second link, only one DPS operation parameter field may be included in the UHR OMN frame. On the other hand, if the DPS operation parameters (e.g., DPS padding delay and DPS switching delay) are different in the first link and the second link, a number of DPS operation parameter fields corresponding to the links using the DPS (e.g., two if the links using the DPS operation are the first link and the second link) may be included in the UHR OMN frame. Alternatively, even if the DPS operation parameters (e.g., DPS padding delay and DPS switching delay) are the same in the first link and the second link, the DPS operation parameter field may be included in the UHR OMN frame with a number corresponding to the link using DPS (e.g., two links where the link using DPS operation is the first link and the second link).

[0210] As another example, DPS configuration for multiple links can be performed individually for each link. If non-AP STA MLD 1 intends to perform DPS operations on the first link and the second link, non-AP STA 1 (520) and AP 1 (510) of the first link may exchange UHR OMN frames, and non-AP STA 2 (540) and AP 2 (530) of the second link may exchange UHR OMN frames. As an example, the above-described matters may be applied in FIGS. 13 to 14d below and may be modified according to each operation.

[0211] As another example, in addition to the LCM and HCM modes described above, there may be an MCM (middle capability mode) mode. MCM may be a mode with lower operational capability than HCM and higher operational capability than LCM. Here, when a mode switch is performed from LCM to MCM, a mode switch delay may not be required or may be less. When switching the operating mode from LCM to MCM, an MCM padding delay may be required during the mode switch operation. Here, the MCM padding delay may be 0 or smaller than the value of the DPS padding delay required when switching from LCM to HCM. As an example, non-AP STA 2 (540) communicates through the band used in LCM (e.g., 20 MHz band) in MCM, but may use physical parameters available in normal EMLSR transmit / receive mode (e.g., MCS (modulation and coding scheme), PPDU format, etc.), but is not limited thereto.

[0212]

[0213] FIG. 13 is a diagram illustrating a multi-link single radio operation method applied to the present disclosure.

[0214] A wireless LAN network can support the multi-link operation described above. AP MLD 1 and non-AP STA MLD 1 can operate in a wireless LAN network. Here, the AP of the AP MLD 1 operating on the first link may be AP 1 (510), and the AP of the AP MLD 1 operating on the second link may be AP 2 (530). Additionally, the non-AP STA of the non-AP STA MLD 1 operating on the first link may be non-AP STA 1 (520), and the non-AP STA of the non-AP STA MLD 1 operating on the second link may be non-AP STA 2 (540). The non-AP STA MLD 1 can support multi-link single-radio operation.

[0215] In a wireless LAN network, a non-AP STA MLD 1 can perform Enhanced Multi-Link Single Radio (EMLSR) operation. The EMLSR operation can be performed by negotiation between the AP MLD 1 and the non-AP STA MLD 1. Alternatively, the EMLSR operation can be performed by negotiation between the AP 1 (510) and the non-AP STA 1 (520). In the association procedure between the AP MLD 1 and the non-AP STA MLD 1, capability information of each of the AP MLD 1 and the non-AP STA MLD 1 can be exchanged. Here, whether the AP MLD 1 and the non-AP STA MLD 1 can use the EMLSR operation can be negotiated. For example, if non-AP STA MLD 1 uses EMLSR, AP MLD 1 can perform operations to support EMLSR (e.g., an initial control frame (ICF) transmission operation, a frame transmission operation according to the listening mode and normal transmission / reception mode of non-AP STA MLD 1). In the above case, AP MLD 1 can set the EMLSR Support bit of the EML Capabilities subfield of a multi-link element included in at least one frame among the frames exchanged in the association procedure with non-AP STA MLD 1 to 1. Additionally, non-AP STA 1 (520) and non-AP STA 2 (540) of non-AP STA MLD 1 can perform operation switching between listening operation and normal transmission / reception operation, and perform operations such as responding with an initial control response (ICR) to the ICF of AP MLD 1 and other operations.In the above-described case, non-AP STA MLD 1 may set the EMLSR Support bit of the EML Capabilities subfield of a multi-link element included in at least one frame among the frames exchanged in the association procedure with AP MLD 1 to 1. Additionally, the EML Capabilities subfield may include an EMLSR padding delay, which is the time related to the transition from a listening operation to a normal transmit / receive operation by the non-AP STA MLD 1 performing the EMLSR operation, and an EMLSR switching delay, which is the time related to the transition from a normal transmit / receive operation to a listening operation by the non-AP STA MLD 1.

[0216] When the information described above is exchanged, non-AP STA MLD 1 can recognize that AP MLD 1 supports the EMLSR operation of non-AP STA MLD 1. Additionally, AP MLD 1 can know that non-AP STA MLD 1 is capable of performing the EMLSR operation. That is, AP MLD 1 and non-AP STA MLD 1 can negotiate with each other regarding support for the EMLSR operation. After the negotiation process described above, non-AP STA MLD 1 may intend to perform the EMLSR operation. If non-AP STA MLD 1 intends to perform the EMLSR operation, non-AP STA MLD 1 may transmit an EML (enhanced multi-link) OMN (operating mode notification) frame (605) to AP MLD 1. The EML OMN frame (605) may include parameters for non-AP STA 1 (520) to perform the EMLSR operation. Specifically, the EML OMN frame (605) may include an EML control field. The EML control field indicates a link that performs an EMLSR operation (e.g., a first link and a second link where non-AP STA MLD 1 operates) and may indicate Nss (number of spatial streams) - MCS (modulation and coding index) set parameters and other parameters used during the EMLSR operation, but is not limited to such parameters and may include additional parameters.

[0217] After non-AP STA MLD 1 transmits an EML OMN frame (605) to AP MLD 1 and a certain amount of time has passed (or, after non-AP STA MLD 1 transmits an EML OMN frame to AP MLD 1 and then receives an EML OMN frame (606) from AP MLD 1 again), an EMLSR operation may be initiated. Here, when the EMLSR operation is initiated, non-AP STA 1 (520) may perform a listening operation.

[0218] In EMLSR operations, there may be listening operations and normal transmit / receive operations. A listening operation may be a mode in which non-AP STA MLD 1 waits for frame reception on a first link and a second link operating on an EMLSR link. That is, non-AP STA 1 (520) and non-AP STA 2 (540) of non-AP STA MLD 1 may wait for frame reception. In the listening operation, non-AP STA 1 (520) and non-AP STA 2 (540) may only receive an initial control frame (initial control frame, ICF) that is limited to a frame of a specific format. For example, the initial control frame may have a limited number of spatial streams (Nss) or a limited modulation and coding index (MCS). In addition, the ICF may be a MU (multi-user)-RTS (request to send) trigger frame, a BSRP (buffer status report poll) trigger frame, or another frame, and is not limited to a specific form.

[0219] When performing normal transmit and receive operations on an EMLSR link, non-AP STA 1 (520) and non-AP STA 2 (540) are capable of normal data transmission and reception and the operational space stream may not be restricted. (This means that there is no restriction on frame transmission and reception based on the maximum capability of non-AP STA MLD 1 by the Nss and MCS exchanged in the Nss-MCS set parameters of non-AP STA MLD 1 included in the EML OMN frame.)

[0220] A non-AP STA 1 (520) of a non-AP STA MLD 1 operating on the first link can perform a transition from a listening operation to a normal transmit / receive operation upon receiving an ICF (607) from AP 1 (510). A separate transition time (or transition time) may be required for the non-AP STA 1 (520) to transition from a listening operation to a normal transmit / receive operation. The transition time (or transition time) may correspond to a padding field included in the ICF (607) transmitted by AP 1 (510) of the AP MLD 1. The padding field may be a field that extends the time length of the frame and ensures the aforementioned transition time (or transition time). Accordingly, the length of the padding field may correspond to the aforementioned transition time (or transition time) or be longer. For example, the EML Capabilities subfield included in the multi-link element exchanged between non-AP STA MLD 1 and AP MLD 1 may indicate the transition time (or switching time) described above. The non-AP STA 1 (520) of the non-AP STA MLD 1, which receives the ICF (607) and performs normal transmission and reception operations, may transmit an ICR (initial control response) frame (abbreviated as ICR, 608). The ICR frame (608) may be a CTS (clear to send) frame, a BSR frame (QoS Null frame), a Multi-STA BA frame, or other frames, and is not limited to a specific form.

[0221] After the ICF (607) and ICR (608) exchange procedures are completed, AP 1 (510) can transmit a downlink data frame (609) to non-AP STA 1 (520). When frame transmission and reception are completed, non-AP STA 1 (520) can switch back from normal transmission / reception operation to listening operation. Here, a separate transition time (or switching time) may be required to switch from normal transmission / reception operation to listening operation. The EML Capabilities subfield included in the multilink element exchanged between non-AP STA MLD 1 and AP MLD 1 may indicate the aforementioned transition time (or switching time).

[0222] The non-AP STA 2 (540) of the non-AP STA MLD 1 can perform a listening operation when the non-AP STA 1 (520) performs a listening operation. When the non-AP STA 1 (520) switches from a listening operation to a normal transmission / reception operation or switches from a normal transmission / reception operation to a listening operation (or when the non-AP STA 1 (520) performs a normal transmission / reception operation), a blindness period in which frames cannot be received may occur in the non-AP STA 2 (540) of the non-AP STA MLD 1. Likewise, the non-AP STA 1 (520) of the non-AP STA MLD 1 can perform a listening operation when the non-AP STA 2 (540) performs a listening operation. Additionally, when non-AP STA 2 (540) switches from a listening operation to a normal transmission / reception operation or switches from a normal transmission / reception operation to a listening operation (or when non-AP STA 2 (540) performs a normal transmission / reception operation), a blindness period may occur in which frames cannot be received in non-AP STA 1 (520) of non-AP STA MLD 1.

[0223] For example, non-AP STA MLD 1 may include a first link and a second link, which are EMLSR links that perform an EMLSR operation. AP MLD 1 may recognize the EMLSR links of non-AP STA MLD 1, and AP MLD 1 may want to transmit a frame using the first link, which is one of the EMLSR links of non-AP STA MLD 1. AP 1 (510) of AP MLD 1 operating on the first link may perform a channel access operation. The channel access operation may be an enhanced distributed channel access (EDCA) operation, and AP 1 (510) of AP MLD 1 may acquire a transmit opportunity (TXOP), which is a time interval during which a frame can be transmitted if the channel access operation is successful. The TXOP may be acquired from the entire bandwidth available to the AP (e.g., 40 MHz, 80 MHz, 160 MHz, 320 MHz, etc.). AP 1 (510) can transmit an ICF to non-AP STA 1 (520). The ICF can be duplicated and transmitted in 20 MHz increments. The ICF duplicated in 20 MHz increments can be duplicated and transmitted for a bandwidth equal to the TXOP acquired by the AP. The ICF may include a padding field to ensure a transition time for non-AP STA 1 (520) to operate from a listening operation to a normal transmit / receive mode. The aforementioned transition time may be referred to as an EMLSR padding delay. Upon receiving the ICF, non-AP STA 1 (520) can switch its operation mode from a listening operation to a normal transmit / receive operation. Once non-AP STA 1 (520) has switched its operation mode to a normal transmit / receive operation, it can transmit an ICR to AP 1 (510). AP 1 (510) can transmit a data frame to non-AP STA 1 (520).Since non-AP STA 1 (520) operates in normal transmit / receive mode, AP 1 (510) can transmit data frames in the full bandwidth, full spatial stream, and full frame format supported by non-AP STA 1 (520). non-AP STA 1 (520) can receive data frames from AP 1 (510) and can also transmit a response frame (e.g., BlockAck frame). When non-AP STA 1 (520) completes receiving a frame from AP 1 (510) and the frame is a frame that does not require a response frame (or, when non-AP STA 1 (520) completes receiving a frame from AP 1 (510) and completes transmitting a response frame by requesting a response frame), non-AP STA 1 (520) may wait for the next frame received from AP 1 (510) for a certain waiting time (e.g., aSIFSTime + aSlotTime + aRxPHYStartDelay time). Here, the certain waiting time may be referred to as Tw time. If no frame is detected during the Tw time (e.g., if no PHY-RXSTART.indication primitive occurs), non-AP STA 1 (520) may switch the operation mode from normal transmit / receive operation to listening operation. A separate transition time may occur when non-AP STA 1 (520) switches from normal transmit / receive operation to listening operation. The above separate switching time is referred to as the EMLSR switching delay. Also, in FIG. 13, the EMLSR switching delay is referred to as Tt, but is not limited to that term. The non-AP STA 1 (520) can operate as a listening operation after the switching time Tt.

[0224] In addition, the Tw time is as described in detail in FIG. 12<Tw 조건 1> ,<Tw 조건 2> and<Tw 조건 3> It can be started when one of the following cases is satisfied. When Tw is initiated after the completion of receiving the initial control frame, non-AP STA 1 (520) can be switched to a listening operation if the condition <switch to listening operation> is satisfied during the Tw time. It can no longer operate in normal transmission and reception operation.

[0225]

[0226] <Switch listening action>

[0227] - The MAC layer of STA 1 does not receive the PHY-RXSTART.indication primitive from the PHY layer and does not send the PHY-TXSTART.request primitive.

[0228] - The MAC layer of STA 1 does not receive the PHY-TXSTART.confirm primitive from the PHY layer.

[0229] - There is no nonempty transmit queue in STA 1.

[0230] - STA 1 does not intend to transmit a frame or schedule transmission

[0231]

[0232] Among the conditions for <listening operation transition>, the MAC layer of STA 1 receiving the PHY-RXSTART.indication primitive from the PHY layer may mean that STA 1 detects a receiving frame. Additionally, the MAC layer of STA 1 sending the PHY-TXSTART.request primitive to the PHY layer and the MAC layer of STA 1 receiving the PHY-TXSTART.confirm primitive from the PHY layer may mean that STA 1 intends to start transmitting a frame.

[0233] STA 1 receives the PHY-RXSTART.indication primitive within the Tw time and<LCM 전환> Even if the conditions are not met, if the <Listen Operation Switch - Receive> condition is satisfied, it may operate in listening mode instead of normal transmit / receive mode. If the <Listen Operation Switch> condition is not satisfied and the <Listen Operation Switch - Receive> condition is not satisfied, STA 1 must operate in normal transmit / receive mode without switching to listening mode.

[0234]

[0235] <Listening Action Switch - Receive>

[0236] - If the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer, and the recipient of the received frame is not STA 1

[0237] - The case where the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer, and the received frame is a trigger frame, and the received trigger frame does not allocate a resource unit (RU) for STA 1

[0238] - When the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer and the received frame is a CTS (clear to send) frame

[0239] - If the receiver address (RA) of the CTS frame is not the address of the AP connected to STA 1 (i.e., the address of AP 1)

[0240]

[0241] In the aforementioned <listen operation switching> and <listen operation switching - receive> conditions, the PPDU may be a PHY layer frame (physical layer frame). Additionally, the physical layer frame may include an MPDU (MAC protocol data unit), which is a MAC layer frame.

[0242] Since the above-described EML OMN frame is a frame exchanged between AP MLD 1 and STA MLD 1, AP 1 (510) receives the EML OMN frame transmitted by STA 1 of STA MLD 1, and AP MLD 1 can transmit the EML OMN frame to STA 2 using AP 2 (530) operating on the second link.

[0243] Both the DPS operation initiation procedure of FIG. 12 and the EMLSR operation initiation procedure of FIG. 13 can be initiated with a single UHR OMN frame exchange. For example, STA MLD 1 may transmit a UHR OMN frame containing information to initiate DPS and EMLSR operations on the first and second links to AP MLD 1. Accordingly, AP MLD 1 can know that DPS and EMLSR operations are initiated on the first and second links of STA MLD 1. For example, in this disclosure, the UHR OMN frame may be referred to as a UHR OMP frame. That is, an operation performed based on a UHR OMN frame may be interpreted as an operation performed based on a UHR OMP frame, but is not limited thereto.

[0244]

[0245] FIGS. 14a to 14d are drawings illustrating a dynamic power saving operation method of a wireless LAN terminal supporting multi-link single radio operation.

[0246] Referring to FIGS. 14a through 14d, the non-AP STA of the non-AP STA MLD 1 operating on the first link may be non-AP STA 1 (520), and the AP of the AP MLD 1 operating on the first link may be AP 1 (510). Here, the DPS setup procedure described above in FIG. 12 may be initiated through the exchange of UHR OMN frames. By the non-AP STA 1 (520) transmitting a UHR OMN frame to AP 1 (510) and AP 1 (510) transmitting a UHR OMN frame back to the non-AP STA 1 (520), the non-AP STA 1 (520) on the first link may initiate a DPS operation, and AP 1 (510) may support the DPS operation of the non-AP STA 1 (520). non-AP STA 1 (520) is a DPS non-AP STA, and AP 1 (510) may be a DPS Assisting AP. According to the DPS setup procedure, AP 1 (510) can recognize the DPS padding delay and DPS switching delay information of non-AP STA 1 (520). Additionally, the EMLSR setup procedure described above in FIG. 13 may be initiated through the exchange of EML OMN frames. For example, non-AP STA 1 (520) transmits an EML OMN frame to AP 1 (510), and AP 1 (510) transmits the EML OMN frame back to non-AP STA 1 (520), thereby allowing non-AP STA MLD 1 to perform EMLSR operations on the first link and the second link, non-AP STA 1 (520) and non-AP STA 2 (540). Additionally, AP MLD 1 can support ICF transmission and ICR reception to support EMLSR operations of non-AP STA 1 (520) and non-AP STA 2 (540) on the first link and the second link.

[0247] For example, the order of the exchange procedure for UHR OMN frames for DPS setting and EML OMN frames for EMLSR setting described above may be changed. Referring to FIG. 14a, the EMLSR setting procedure may be performed first, and the DPS setting procedure may be performed afterward. As another example, referring to FIG. 14b, the DPS setting procedure may be performed first, and the EMLSR setting procedure may be performed. As yet another example, the exchange procedure for UHR OMN frames for DPS setting and EML OMN frames for EMLSR setting may be performed simultaneously and is not limited to a specific form. For example, EMLSR setting may be performed using UHR OMN frames. In the above case, DPS and EMLSR settings may be performed simultaneously based on a single UHR OMN frame exchange.

[0248] Referring to FIG. 14a, if the EMLSR operation setting between non-AP STA MLD 1 and AP MLD 1 takes precedence over the DPS operation setting, a channel access operation (e.g., EDCA backoff operation, EDCA TXOP acquisition procedure) may be performed by non-AP STA 1 (520) to transmit an EML OMN frame. Here, non-AP STA 1 (520) may perform normal transmit / receive operations before transmitting a UHR OMN frame. When non-AP STA 1 (520) transmits a UHR OMN frame to AP 1 (510), AP 1 (510) may transmit an acknowledgment frame (Ack frame) to non-AP STA 1 (520). After the transmission of the acknowledgment frame is complete, non-AP STA 1 (520) may start the Tw time described in FIG. 13. For example, the Tw time described above<Tw 조건 2> It may be due to... If the <listening operation switch> condition is satisfied during the Tw time (or, if the <listening operation switch> condition is not satisfied and the <listening operation switch - receive> condition is satisfied), non-AP STA 1 (520) can perform a listening operation.

[0249] Here, AP 1 (510) may need to transmit a UHR OMN frame to non-AP STA 1 (520). A channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) is performed for AP 1 (510) to transmit a UHR OMN frame to non-AP STA 1 (520), and if the channel access operation is successful, AP 1 (510) may need to transmit an ICF before transmitting a UHR OMN frame to non-AP STA 1 (520) operating on an EMLSR link. When non-AP STA 1 (520) receives the ICF, it may respond with an ICR. When AP 1 (510) receives the ICR from non-AP STA 1 (520), AP 1 (510) may transmit a UHR OMN frame to non-AP STA 1 (520). non-AP STA 1 (520) can send an acknowledgment frame (e.g., Ack frame) to AP 1 (510). After non-AP STA 1 (520) sends the acknowledgment frame<Tw 조건 1> Tw time can be started according to the above. If the <listening operation switch> condition is satisfied during Tw time (or if the <listening operation switch> condition is not satisfied and the <listening operation switch - receive> condition is satisfied), non-AP STA 1 (520) can perform a listening operation. If non-AP STA 1 (520) performs a listening operation, non-AP STA 2 (540) can also perform a listening operation.

[0250] As described above, non-AP STA MLD 1 can set both DPS operation and EMLSR operation with AP MLD 1. Since the exchange of EML OMN frames and UHR OMN frames is completed, non-AP STA 1 (520) and non-AP STA 2 (540) can combine HCM and LCM in the DPS operation state and normal transmit / receive operation and listening operation in the EMLSR operation state. For example, when non-AP STA 1 (520) and non-AP STA 2 (540) perform a listening operation, non-AP STA 1 (520) and non-AP STA 2 (540) can perform an LCM operation. This operation may be referred to as L(listening)-LCM, but is not limited to that term. The normal transmit / receive operation of the EMLSR operation may be the same as the HCM of the DPS operation. When normal transmission and reception operations are performed during EMLSR operation, it may be an HCM of DPS operation.

[0251] Referring to FIGS. 14a and 14b, the exchange of EML OMN frames between AP MLD 1 and non-AP STA MLD 1 and the frame transmission operation after the exchange of UHR OMN frames can be performed. The ICF (610) for switching the EMLSR operation of non-AP STA MLD 1 from a listening operation to a normal transmit / receive operation may be the same. That is, AP MLD 1 can perform the EMLSR operation mode switching and DPS operation mode switching using a single ICF (610).

[0252] Here, AP MLD 1 may want to send a frame to non-AP STA 2 (540) of non-AP STA MLD 1. Since AP MLD 1 and non-AP STA MLD 1 have completed exchanging UHR OMN frames and EML OMN frames with each other, AP MLD 1 may recognize that non-AP STA 2 (540) of non-AP STA MLD 1 is operating in L-LCM, which is a state of performing LCM and listening operations, before transmitting ICF (610). AP 2 (530) of AP MLD 1 may transmit ICF (610) to switch the operating state of non-AP STA 2 (540) from L-LCM to HCM. ICF (610) may include a padding field for the time required for non-AP STA 2 (540) to switch its operating state from L-LCM to HCM.

[0253] If the EMLSR padding delay and DPS padding delay of non-AP STA MLD 1 are the same, the length of the padding field can be determined using either the EMLSR padding delay or the DPS padding delay. Alternatively, the length of the padding field can be set to the longer of the EMLSR padding delay and the DPS padding delay. As another example, the length of the padding field can be set to the sum of the EMLSR padding delay and the DPS padding delay. Meanwhile, it is also possible to set the length of the padding field to a value greater than or equal to the value described above.

[0254] non-AP STA 2 (540) receives the ICF (610) of AP 2 (530) and can operate in the EMLSR normal transmission / reception mode and DPS HCM mode. AP 2 (530) can transmit an ICF (610) to non-AP STA 2 (540) instructing it to transition to MCM (middle capability mode) in order to reduce the time it takes for non-AP STA 2 (540) to transition from DPS LCM to another mode. The ICF (610) can be set using one of the methods described above, taking into account the DPS padding delay. When the DPS padding delay is 0, the padding length corresponding to the EMLSR padding delay value can be set as padding.

[0255] The non-AP STA 2 (540) may respond with an ICR (611) after SIFS time from the time of completion of reception of the ICF (610) including padding. The AP 2 (530) transmits a downlink frame (612) to the non-AP STA 2 (540), and the non-AP STA 2 (540) may not transmit a response frame if the AP's downlink frame (612) is a frame that does not require an immediate response frame, and transmit an immediate response frame if the frame requires an immediate response frame. Here,<Tw 조건 1> or<Tw 조건 2> Accordingly, a waiting time Tw may be initiated for non-AP STA 2 (540) to switch from HCM to L-LCM. The Tw waiting time may be used commonly in DPS and EMLSR. As described above<LCM 전환> and the <listening action toggle> condition is the same, and<LCM 전환 - 수신> and the <Listening Action Switch - Receive> condition can be identical. For example, each pair of identical conditions<L-LCM 전환> and<L-LCM 전환 - 수신> It is referred to as, but is not limited to, the Tw waiting time.<L-LCM 전환> When the condition is satisfied, or<L-LCM 전환> The conversion conditions are not satisfied and<L-LCM 전환 - 수신> If the condition is satisfied, non-AP STA 2 (540) may begin transitioning to L-LCM. The time for non-AP STA 2 (540) to transition from HCM to L-LCM may be the longer of the EMLSR transition delay and the DPS transition delay, or the sum of the EMLSR transition delay and the DPS transition delay. non-AP STA 2 (540) may operate in L-LCM after the Tw time ends, and after the longer of the EMLSR transition delay and the DPS transition delay, or the sum of the EMLSR transition delay and the DPS transition delay. When non-AP STA 2 (540) transitions from operating in MCM to LCM, the DPS transition delay may be 0.When AP MLD 1 transmits a frame back to non-AP STA MLD 1, it may be possible to transmit an ICF to non-AP STA 1 (520) or non-AP STA 2 (540) of non-AP STA MLD 1 after the point in time when non-AP STA 2 (540) of non-AP STA MLD 1 operates as L-LCM again.

[0256] Referring to FIG. 14c, frame transmission operations can be performed after EML OMN frame exchange and UHR OMN frame exchange between AP MLD 1 and non-AP STA MLD 1. The ICF (613) for switching the EMLSR operation of non-AP STA MLD 1 from a listening operation to a normal transmit / receive operation may be the same. That is, AP MLD 1 can perform EMLSR operation mode switching and DPS operation mode switching using a single ICF (613). Here, AP MLD 1 may want to transmit a downlink frame (615) to non-AP STA 2 (540) of non-AP STA MLD 1. Since AP MLD 1 and non-AP STA MLD 1 have completed exchanging UHR OMN frames and EML OMN frames with each other, AP MLD 1 can recognize that non-AP STA 2 (540) of non-AP STA MLD 1 is operating as an L-LCM, which is in a state of performing LCM and listening operations, before transmitting the ICF (613).

[0257] AP 2 (530) of AP MLD 1 can transmit an ICF (613) to switch the operating state of non-AP STA 2 (540) from an L-LCM state to an EMLSR transmit / receive state while maintaining DPS LCM. The aforementioned state is referred to as EMLSR-LCM, but is not limited thereto. The ICF (613) may include a padding field for the time required for non-AP STA 2 (540) to switch its operating state from an L-LCM state to an EMLSR-LCM state. The length of the padding field may correspond to the EMLSR padding delay of non-AP STA MLD 1. non-AP STA 2 (540) receives the ICF (613) of AP 2 (530) and can operate in an EMLSR normal transmit / receive mode. The EMLSR-LCM may be the MCM described in FIG. 12, 14a, and 14b. That is, it uses the same band as LCM (e.g., 20 MHz band) and can use physical parameters available in the normal transmission and reception mode of EMLSR.

[0258] The non-AP STA 2 (540) may respond with an ICR (614) after SIFS time from the time the ICF (613) is received. The AP 2 (530) sends a downlink frame (615) to the non-AP STA 2 (540), and the non-AP STA 2 (540) does not send a response frame if the AP's downlink frame is a frame that does not require an immediate response frame, and sends an immediate response frame if the frame requires an immediate response frame.<Tw 조건 1> or<Tw 조건 2> According to this, a waiting time Tw may be initiated for non-AP STA 2 (540) to switch from EMLSR-LCM to L-LCM. The Tw waiting time may be used commonly in DPS and EMLSR. As described above<LCM 전환> and the <listening action toggle> condition is the same, and<LCM 전환 - 수신> and the <Listening Action Switch - Receive> condition can be identical. For example, each pair of identical conditions<L-LCM 전환> ,<L-LCM 전환 - 수신> It can be referred to as. During the Tw waiting time<L-LCM 전환> When the condition is satisfied, or<L-LCM 전환> The conversion conditions are not satisfied and<L-LCM 전환 - 수신> When the condition is satisfied, non-AP STA 2 (540) may begin transitioning to L-LCM. The time for non-AP STA 2 (540) to transition from HCM to L-LCM may be the EMLSR transition delay time. non-AP STA 2 (540) may operate in L-LCM after the Tw time ends and the EMLSR transition delay time. When AP MLD 1 transmits a frame again to non-AP STA MLD 1, it may be possible to transmit an ICF to non-AP STA 1 (520) or non-AP STA 2 (540) of non-AP STA MLD 1 after the point in time when non-AP STA 2 (540) of non-AP STA MLD 1 operates in L-LCM again.

[0259] Additionally, referring to FIG. 14d, frame transmission operations can be performed after the exchange of EML OMN frames and UHR OMN frames between AP MLD 1 and non-AP STA MLD 1. ICFs (616, 618) for performing the switching of EMLSR operation and DPS operation modes of non-AP STA MLD 1 can be transmitted separately. That is, when non-AP STA 2 (540) of non-AP STA MLD 1 is operating in the EMLSR listening operation state and DPS LCM state (i.e., L-LCM state), AP 2 (530) of AP MLD 1 can switch the operation state of non-AP STA 2 (540) to two stages by sequentially transmitting two ICFs (616, 618) to non-AP STA 2 (540). For example, AP MLD 1 may transmit an ICF (618) to switch the DPS operation mode after transmitting an ICF (616) to switch the EMLSR operation mode of non-AP STA MLD 1. When non-AP STA 2 (540) of non-AP STA MLD 1 is operating in an EMLSR listening operation state and a DPS LCM state (i.e., L-LCM state), AP 2 (530) of AP MLD 1 may switch the operation state of non-AP STA 2 (540) to two stages by sequentially transmitting two ICFs (616, 618) to non-AP STA 2 (540).

[0260] First, AP 2 (530) recognizes that non-AP STA 2 (540) is currently performing an EMLSR listening operation and can send a first ICF (616) to non-AP STA 2 (540) to transition to a normal EMLSR transmission / reception operation. The ICF (616) is an ICF for switching the EMLSR operation mode and can cause non-AP STA 2 (540) to transition from a listening operation to a state where frame transmission / reception is possible. Here, the ICF (616) may include a padding field with a duration corresponding to or longer than the EMLSR padding delay. During that time, non-AP STA 2 (540) can perform a transition of the operation mode from a listening operation to a normal transmission / reception operation. Additionally, the bandwidth of the ICF (616) transmitted by AP 2 (530) can be set in the UL BW field within the common info field of the EMLSR ICF (616). However, apart from the above, the bandwidth of the ICR (617) that the non-AP STA 2 (540) must transmit to the ICF (616) can be indicated by AP 2 (530) through the user info field of the ICF (616). The transmission bandwidth of the response frame of the non-AP STA 2 (540) may be limited in LCM mode. Therefore, AP 2 (530) may need to set the bandwidth indicated in the user info field so as not to exceed the bandwidth of the communication parameters available in the LCM operating state of the non-AP STA 2 (540). For example, the bandwidth may be 20 MHz. The bandwidth may be determined by prior negotiation between non-AP STA 2 (540) and AP 2 (530) (e.g., UHR OMN frame exchange between non-AP STA 2 and AP 2 (530)). non-AP STA 2 (540) may respond with an ICR (617) after SIFS time from the time it completes receiving the first ICF (616) from AP 2 (530).The non-AP STA 2 (540) can switch the EMLSR operation mode from listening mode to normal transmission / reception mode while the padding field of the first ICF (616) is being transmitted.

[0261] However, regardless of the EMLSR operation state, the DPS operation mode of the non-AP STA 2 (540) may still remain LCM. Subsequently, AP 2 (530) may send a second ICF (618) to the non-AP STA 2 (540) to switch the DPS operation mode of the non-AP STA 2 (540) from LCM to HCM. The non-AP STA 2 (540) may switch the DPS operation mode from LCM to HCM while the padding field of the second ICF (618) is being sent. Here, the padding time may be set to a time corresponding to the DPS padding delay (or MCM padding delay) or a longer time.

[0262] When non-AP STA 2 (540) receives the second ICF (618) from AP 2 (530), it can use the transmit / receive parameters available in HCM. These parameters may also be applied when AP 2 (530) transmits the ICF (618) to non-AP STA 2 (540). AP 2 (530) can indicate the bandwidth of the ICR (619) that non-AP STA 2 (540) must transmit for the ICF (618) through the user information field of the ICF (618). AP 2 (530) can set the bandwidth indicated in the user information field so as not to exceed the bandwidth of the communication parameters available in the HCM operating state of non-AP STA 2 (540). For example, it may be HCM communication parameters confirmed by AP 2 (530) and non-AP STA 2 (540) through the exchange of UHR OMN frames (or capability-based parameters of non-AP STA 2 (540) negotiated in the multi-link setup of AP MLD 1 or non-AP STA MLD 1) (e.g., MCS, Bandwidth, Nss).

[0263] non-AP STA 2 (540) can transmit an ICR (619) after SIFS time from the time it has received the second ICF (618) from AP 2 (530). Afterward, AP 2 (530) and non-AP STA 2 (540) can perform normal frame transmission and reception based on the HCM communication parameters of non-AP STA 2 (540). The communication parameters may include at least one of the MCS, NSS, and bandwidth available to non-AP STA 2 (540), but are not limited thereto. The above-described parameters may be HCM communication parameters performed by AP 2 (530) and non-AP STA 2 (540) through the exchange of UHR OMN frames (or capability-based parameters of non-AP STA 2 (540) negotiated in the multi-link configuration of AP MLD 1 or non-AP STA MLD 1). The non-AP STA 2 (540) is switched to the EMLSR normal transmission / reception state and the DPS HCM state, and the AP 2 (530) can send a downlink frame (620) to the non-AP STA 2 (540) after the switch.

[0264] non-AP STA 2 (540) does not send a response frame if the frame received from AP 2 (530) does not require an immediate response frame, but can send a response frame if it requires an immediate response frame.<Tw 조건 1> or<Tw 조건 2> According to this, a waiting time Tw may be initiated for non-AP STA 2 (540) to switch from EMLSR-LCM to L-LCM. The Tw waiting time may be used commonly in DPS and EMLSR. Here, the above-described<LCM 전환> and the <listening action toggle> condition is the same, and<LCM 전환 - 수신> and the <Listening Action Switch - Receive> condition is identical. Each pair of identical conditions<L-LCM 전환> ,<L-LCM 전환 - 수신> It can be referred to as.

[0265] During the Tw waiting time<L-LCM 전환> When the condition is satisfied, or<L-LCM 전환> The conversion conditions are not satisfied and<L-LCM 전환 - 수신> When the condition is satisfied, non-AP STA 2 (540) can start transitioning to L-LCM. At this time, the time for non-AP STA 2 (540) to transition from HCM to L-LCM is the EMLSR transition delay time. non-AP STA 2 (540) can operate in L-LCM after the Tw time ends and after the EMLSR transition delay time. When AP MLD 1 transmits a frame again to non-AP STA MLD 1, it may be possible to transmit an ICF to non-AP STA 1 (520) or non-AP STA 2 (540) of non-AP STA MLD 1 after the point in time when non-AP STA 2 (540) of non-AP STA MLD 1 operates in L-LCM again.

[0266] Additionally, in FIG. 14d above, AP 2 (530) may first transmit an ICF that switches the DPS operation mode of non-AP STA 2 (540) to HCM, and then transmit a second ICF that switches the EMLSR operation mode of non-AP STA 2 (540).

[0267] FIG. 15 is a diagram illustrating wireless LAN subchannel access operations applicable to the present disclosure. Referring to FIG. 15, AP 1 (510) and AP 2 (530) can operate in a wireless LAN network. AP 1 (510) and AP 2 (530) can each configure BSS (Basic Service Set) 1 and BSS 2. Additionally, non-AP STA 1 (520) and non-AP STA 2 (540) can operate in a wireless LAN network. non-AP STA 1 (520) can be connected to AP 1 (510) to operate in BSS 1, and non-AP STA 2 (540) can be connected to AP 2 (530) to operate in BSS 2. AP 1 (510) and AP 2 (530) can configure a primary channel (PCH) used for channel access in their respective BSSs. A wireless LAN terminal (e.g., AP 1 (510), AP 2 (530), non-AP STA 1 (520), non-AP STA 2 (540)) may need to access and occupy the main channel of the BSS to which it belongs in order to communicate with other wireless LAN terminals. Here, the channel access operation may vary. For example, the channel access operation may be a DCF (distributed coordination function) procedure, an EDCA (enhanced distributed channel access) procedure, a backoff procedure, or an EDCA TXOP (transmit opportunity) acquisition procedure, but may not be limited thereto.

[0268] Additionally, BSS 1 and BSS 2 may have an overlapping BSS relationship. For example, a non-AP STA 1 (520) within BSS 1 may transmit a frame by occupying the main channel, which is a channel for channel access. When the non-AP STA 1 (520) transmits a frame by occupying the main channel, the non-AP STA 1 (520) may transmit a frame including a secondary channel (SCH) within the operating bandwidth of BSS 1 in addition to the main channel of BSS 1.

[0269] In a wireless LAN network, in addition to BSS 1, there may be another BSS (BSS 2). When a frame transmitted by non-AP STA 1 (520), including the main channel and sub-channel of BSS 1, is received by a wireless LAN terminal (e.g., AP 2, non-AP STA 2) operating in BSS 2 by occupying at least one of the main channel and sub-channel of BSS 2, the channel access and frame transmission / reception operations of the wireless LAN terminal operating in BSS 2 may be affected by the transmission of BSS 1. As described above, if communication within a BSS affects communication in an adjacent other BSS (e.g., if channel access and frame transmission / reception operations of BSS 2 become impossible as a result of channel access operations performed in BSS 1, and / or if transmission by a wireless LAN terminal of BSS 1 is detected in the main channel of BSS 2), the two BSSs may recognize each other as OBSS. That is, in the above-described case, BSS 1 and BSS 2 may recognize each other as OBSS.

[0270] Additionally, in a wireless LAN network, a wireless LAN terminal (e.g., AP 1, non-AP STA 1 (520)) may support NPCA (non-primary channel access) operation. An AP that supports NPCA operation may be referred to as an NPCA AP, and a non-AP STA that supports NPCA operation may be referred to as an NPCA non-AP STA. Additionally, the term NPCA STA may be used as a general term for NPCA APs and NPCA non-AP STAs, but is not limited to that term. An NPCA STA may transmit a management frame, such as a probe request / response frame or a beacon frame, that includes capability information indicating whether NPCA operation is available. For example, a UHR capability element may be included in the management frame described above. In the UHR capability element, an indicator (e.g., an indicator bit) indicating whether NPCA is supported may indicate whether NPCA is available.

[0271] Alternatively, there may be STAs that do not support NPCA. An STA that does not support NPCA may transmit a management frame, such as a probe request / response frame or a beacon frame, containing capability information indicating whether NPCA operation is available. For example, a UHR capability element may be included in the aforementioned management frame, and the UHR capability element may include an indicator (e.g., an indicator bit) indicating NPCA support, which indicates that NPCA is not supported. Alternatively, a management frame, such as a probe request / response frame or a beacon frame, transmitted by an STA that does not support NPCA may not include an indicator indicating whether NPCA operation is available. For example, NPCA operation may be a feature supported only in a specific IEEE 802.11 version. Therefore, a wireless LAN terminal using an earlier version of a specific IEEE 802.11 standard may not have an indicator indicating whether NPCA operation is available.

[0272] NPCA may be a method for an NPCA STA to perform channel access by switching the operating channel to one of the non-primary channels among the operating channels of a BSS when the primary channel of the BSS to which it belongs is occupied by an OBSS. Specifically, an NPCA AP may designate one of the non-primary channels among the operating channels within its BSS, other than the primary channel, as the NPCA primary channel. An NPCA AP may convey information about the NPCA primary channel to NPCA non-AP STAs through frames transmitted within the BSS (e.g., Beacon, Probe Response, UHR OMN (Ultra High Reliability Operation Mode Notification)). Additionally, an NPCA AP may negotiate the use of NPCA with NPCA non-AP STAs. The negotiation for NPCA usage may be performed through frame exchange between the NPCA AP and the NPCA non-AP STA. If at least one of the NPCA AP and NPCA non-AP STA that negotiated the use of NPCA cannot access the channel because the OBSS occupies the main channel of the BSS to which it belongs, at least one of the NPCA AP and NPCA non-AP STA may perform NPCA to switch its operating channel to the NPCA main channel. At least one of the NPCA AP and NPCA non-AP STA may perform channel access on the NPCA main channel.

[0273] As another example, an NPCA AP can instruct the use of an NPCA operation by setting the value of an indicator (e.g., NPCA Operation Information Present field) included in an information element (e.g., UHR Operation Element) within a frame (e.g., Beacon, Probe response) it transmits to 1 without separate negotiation. An NPCA STA that confirms that the value of the aforementioned NPCA Operation Information Present field within the frame transmitted by the NPCA AP is 1 can perform an NPCA operation and switch the operation channel to the NPCA main channel without separate negotiation if the conditions for performing an NPCA operation are met.

[0274] In addition, it may be efficient to perform the NPCA operation only when the duration for which the OBSS occupies the main channel is sufficiently long. Therefore, a minimum duration threshold for performing the NPCA operation (e.g., NPCA minimum duration threshold) may be set. Additionally, in the NPCA operation, an NPCA switching time (e.g., NPCA switching time) may be required for the NPCA STA to switch its operation channel from the main channel to the NPCA main channel. Conversely, in the NPCA operation, an NPCA switch back time (e.g., NPCA switch back time) may be required for the NPCA STA to switch its operation channel from the NPCA main channel to the main channel. The NPCA STA may indicate information regarding at least one of the aforementioned NPCA main channel, NPCA transition time, NPCA return time, and NPCA minimum time length in the form of a field, subfield, element (e.g., UHR operation element), bit, or other form within a frame (e.g., Beacon, Probe Response, UHR OMN (Ultra High Reliability Operation Mode Notification)) exchanged during the NPCA negotiation process.

[0275] NPCA STA can switch the operation channel to the NPCA main channel if the value of the NPCA Operation Information Present field that it transmits or receives is 1 and satisfies either Condition 1 or Condition 2 below.

[0276]

[0277] Condition 1 (PHY-based NPCA, PHYLEN NPCA)

[0278] If the NPCA STA has received a PPDU on the BSS main channel and / or received a PHY-RXSTART.indication primitive for the HE / EHT / UHR PPDU, and all of the following conditions are true:

[0279] A. When the PPDU received by the above NPCA STA on the main channel of the BSS is classified as an inter-BSS PPDU.

[0280] B. If at least one of the following is true:

[0281] i. A case where the NPCA AP corresponding to the BSS to which the above NPCA STA belongs has enabled only PHY Header-based NPCA, and the value of the MAC variable NPCA_PPDU_REM_DUR of the received PPDU (or configured upon receiving the PPDU) is greater than the value indicated in the NPCA Minimum Duration Threshold field of the most recently received or transmitted NPCA for the BSS to which the above NPCA STA belongs, or

[0282] ii. When the NPCA AP of the affiliated BSS has also enabled MAC Header-based NPCA, and one or more of the NPCA_PHY_TXOP_REM_DUR or NPCA_PPDU_REM_DUR set from the received PPDU are greater than the above Threshold

[0283] C. The bandwidth of the above PPDU is determined to be 20, 40, 80, or 160 MHz by the above NPCA STA, based on the in-band channel allocation information indicated in the Bandwidth field within the PHY preamble of the above PPDU and the RXVECTOR parameter RU_ALLOCATION of PHY-RXSTART.indication() associated with the said PPDU, provided that the channel occupied by the said PPDU does not overlap with the NPCA PCH

[0284] D. When the intra BSS NAV of the above NPCA STA is 0

[0285]

[0286] Condition 2 (MAC-based NPCA, MOPLEN NPCA)

[0287] If all of the following conditions are satisfied

[0288] A. The NPCA STA receives all or part of a series of PPDUs separated by SIFS (short interframe space) in the BSS PCH, the reception of the first PPDU is the reception of a PPDU containing an Initial Control Frame (ICF), which is the start frame of the Control Frame exchange, the reception of the second PPDU is the reception of a PPDU containing an Initial Control Response Frame (ICR), which is the response frame to the said ICF (however, the second PPDU may not have been received), and the reception of the third PPDU is the reception of the preamble of a PPDU transmitted after the said Control Frame exchange, and the NPCA STA generates the PHY-RXSTART.indication or / and the PHY-RXEARLYSIG.indication. and, all subsequent conditions must be satisfied.

[0289] B. If a PHY-RXEARLYSIG.indication or PHY-RXSTART.indication primitive corresponding to the third PPDU described above is received from the PHY, and this reception occurs during the NPCA_START_TIMEOUT period starting from the time the MAC received the PHY-RXEND.indication primitive for the first PPDU

[0290] i. NPCA_START_TIMEOUT is (2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + ICR_Timeout,

[0291] (1) ICR_Timeout is the length of the expected CTS frame when the ICF is an RTS or MU-RTS trigger frame.

[0292] (2) ICR_Timeout is the value of the UL Length field of the BSRP trigger frame if the ICF is a BSRP trigger frame

[0293] C. If one of the above PPDU sequences is classified as an inter-BSS PPDU by the above NPCA STA

[0294] D. If at least one of the following is true:

[0295] i. If the NPCA AP has enabled only PHY Header-based NPCA, and the value of the NPCA_PPDU_REM_DUR MAC variable of the third received PPDU (or configured upon receiving the PPDU) is greater than the value of the NPCA Minimum Duration Threshold field most recently received or transmitted to the BSS to which the NPCA STA belongs.

[0296] ii. If the NPCA AP has activated MAC Header-based NPCA along with PHY Header-based NPCA, and the value of the NPCA_CFRAME_TXOP_REM_DUR MAC variable of the first PPDU (including ICF) in the above PPDU sequence (or configured upon receiving the PPDU) is greater than the value of the NPCA Minimum Duration Threshold field most recently received or transmitted for the BSS to which the NPCA STA belongs

[0297] E. When the bandwidth of the received PPDUs is determined to be 20, 40, 80, or 160 MHz by the NPCA STA based on the bandwidth information indicated in the received PPDU or the CH_BANDWIDTH_IN_NON_HT value, which is an RXVECTOR parameter of the received PPDU, and the channel occupied by the PPDUs does not overlap with the NPCA primary channel

[0298] i. If the Control Frame (ICF) is an RTS (request to send) frame within a non-HT (duplicate) PPDU, the RTS frame has a transmitter address (TA) field containing bandwidth information, wherein the signaled bandwidth is one of 20, 40, 80, or 160 MHz

[0299] ii. The channel occupied by a CTS (clear to send) frame within a non-HT (duplicate) PPDU is determined through the RTS frame or MU-RTS frame that elicited the corresponding CTS response.

[0300] F. When the intra BSS NAV of the above NPCA STA is 0

[0301]

[0302] In addition, the following three MAC variables may be used to determine whether at least one of the AP and STA switches the operating channel to the NPCA main channel.

[0303] NPCA_PPDU_REM_DUR

[0304] NPCA_PPDU_REM_DUR is set to the total length of the PPDU (e.g., RXTIME) that the NPCA STA can identify in the PPDU header, excluding the time difference between when the NPCA STA's PHY layer detects the first PPDU and generates the PHY-CCA.indication(BUSY) primitive and when it generates the PHY-RXSTART.indication primitive.

[0305]

[0306] NPCA_PHY_TXOP_REM_DUR

[0307] The NPCA_PHY_TXOP_REM_DUR variable is set to the value obtained by subtracting the time difference between when the PHY layer of the NPCA STA detects the first PPDU and generates the PHY-CCA.indication(BUSY) primitive and when it generates the PHY-RXSTART.indication primitive from the sum of the total length of the PPDU (e.g., RXTIME) and the TXOP_DURATION value that the NPCA STA can identify in the PPDU header.

[0308]

[0309] NPCA_CFRAME_TXOP_REM_DUR

[0310] The NPCA_CFRAME_TXOP_REM_DUR variable is set to the value of the duration / ID field of the MAC header of the control frame received by the NPCA STA.

[0311]

[0312] In addition, it is necessary to define the timing and time length for switching the operating channel to the NPCA main channel, and a method for setting MAC variables illustrated as REM_DUR in Fig. 15 may be required.

[0313] For example, at least one of the AP and STA within the BSS receives the PPDU of the OBSS and can determine the time length of the PPDU from the PPDU preamble of the OBSS. Additionally, at least one of the AP and STA within the BSS can determine the time length of the communication interval of the OBSS from the PPDU preamble of the OBSS. Here, the point in time at which the time length of the OBSS PPDU can be determined may be the point in time when the PHY-RXSTART.indication primitive for the PPDU occurs. Here, at the point in time when the PHY-RXSTART.indication primitive occurs, the MAC variable value may be set as follows.

[0314]

[0315] - NPCA_PPDU_REM_DUR: Duration of PPDU - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) caused by PPDU to the occurrence of PHY-RXSTART.indication)

[0316] - NPCA_PHY_TXOP_REM_DUR: Time length of PPDU + Time length of TXOP included in PPDU - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) by PPDU to the occurrence of PHY-RXSTART.indication)

[0317] - NPCA_CFRAME_TXOP_REM_DUR: No impact

[0318]

[0319] As another example, at least one of the AP and STA within the BSS may receive the PPDU of the OBSS. Here, if the OBSS PPDU includes an initial control frame (e.g., RTS frame, CTS frame, MU-RTS trigger frame, BSRP trigger frame), the time length of the OBSS communication interval can be determined from the duration field of the MAC header of the initial control frame included in the OBSS PPDU. The point in time at which the time length of the OBSS PPDU and the duration / ID field of the MAC header can be determined may be when the PHY-RXEND primitive for the PPDU occurs, and this point in time may be time T1. Here, at the time when the PHY-RXEND primitive occurs, the MAC variable value may be set as follows.

[0320]

[0321] - NPCA_PPDU_REM_DUR: Duration of PPDU - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) caused by PPDU to the occurrence of PHY-RXSTART.indication)

[0322] - NPCA_PHY_TXOP_REM_DUR: Time length of PPDU + Time length of TXOP included in PPDU - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) by PPDU to the occurrence of PHY-RXSTART.indication)

[0323] - NPCA_CFRAME_TXOP_REM_DUR: The value of the duration field indicated by the MAC header of the initial control frame.

[0324]

[0325] The time point when the above PHY-RXSTART.indication primitive occurs or the time point when the PHY-RXEND primitive occurs can be called time point T1.

[0326] When PHYLEN NPCA is used in BSS 1, at least one of the APs and STAs in the BSS may switch the operating channel to the NPCA main channel if, at time T1, the NPCA_PPDU_REM_DUR value is greater than the most recently transmitted NPCA minimum duration threshold value. Here, when MOPLEN NPCA is used in addition to PHYLEN NPCA in BSS 1, at least one of the APs and STAs in the BSS may switch the operating channel to the NPCA main channel if, at time T1, the NPCA_PHY_TXOP_REM_DUR value or the NPCA_CFRAME_TXOP_REM_DUR value is greater than the most recently transmitted NPCA minimum duration threshold value.

[0327] Additionally, the NPCA TIMER may be the time during which the NPCA main channel operates, and may be a timer managed by the NPCA STA (at least one of the AP and STA within the BSS). The NPCA TIMER may be set based on the value of the MAC variable described above, and when the NPCA TIMER expires (e.g., the value reaches 0), the NPCA STA may operate on the main channel again. The NPCA TIMER may decrease in a time-dependent manner from the point at which the NPCA STA switches the operating channel to the NPCA main channel. If the NPCA STA switches the operating channel immediately at time T1, or if only PHYLEN NPCA is used in BSS 1, the NPCA TIMER may be the value NPCA_PPDU_REM_DUR. As another example, if MOPLEN NPCA is used in BSS 1, the NPCA TIMER can be set to the largest value among NPCA_PPDU_REM_DUR, NPCA_PHY_TXOP_REM_DUR, and NPCA_CFRAME_TXOP_REM_DUR.

[0328] If the NPCA STA is unable to immediately switch the operating channel at time T1, the MAC variable described above may decrease the corresponding value at each time interval. Subsequently, when the NPCA STA switches the operating channel to the NPCA main channel, if only PHYLEN NPCA is used in BSS 1, the NPCA TIMER may be set to the value obtained by subtracting the NPCA switching back delay time value (the time delay value required to switch the operating channel from the NPCA main channel to the main channel for each NPCA STA) from the NPCA_PPDU_REM_DUR value. If MOPLEN NPCA is also used in BSS 1, the NPCA TIMER may be set to the value obtained by subtracting the NPCA switching back delay time value for each NPCA STA from the largest value among NPCA_PPDU_REM_DUR, 4NPCA_PHY_TXOP_REM_DUR, and NPCA_CFRAME_TXOP_REM_DUR.

[0329] FIGS. 16a and FIGS. 16b are drawings illustrating a method for determining the time of end of sub-channel transmission considering a multi-link single radio terminal applicable to the present disclosure.

[0330] Referring to FIGS. 16a and 16b, AP MLD 1 and at least one non-AP STA MLD (e.g., STA MLD 1, STA MLD 2) may operate in a wireless LAN network. The MLDs may operate on at least one link (e.g., a plurality of links including a first link and a second link). The AP of AP MLD 1 operating on the first link may be AP 1-1 (710-1), and the AP of AP MLD 1 operating on the second link may be AP 1-2 (710-2). Likewise, the non-AP STAs operating on the first link and the second link, respectively, of non-AP STA MLD 1 and non-AP STA MLD 2 may be non-AP STA 1-1 (720-1), non-AP STA 2-1 (730-1), non-AP STA 1-2 (720-2), and non-AP STA 2-2.

[0331] The first link and the second link may be EMLSR or EMLMR links. That is, non-AP STA MLD 1 may perform EMLSR or EMLMR operations on the first link and the second link. For example, for convenience of explanation, the present disclosure describes based on EMLSR operations. However, EMLSR operations may be replaced by EMLMR operations and applied in the same way. In the present disclosure, the fact that at least one of the non-AP STA MLD and its subordinate non-AP STA performs an EMLSR operation may mean that at least one of the non-AP STA MLD and its subordinate non-AP STA uses an EMLMR operation that replaces the EMLSR operation, or uses both EMLSR and EMLMR operations simultaneously. For example, if the non-AP STA MLD uses an EMLMR operation instead of an EMLSR operation, the EMLSR transition delay may be an EMLMR transition delay time, and the EMLSR padding delay may be replaced by an EMLMR padding delay time. However, for convenience of explanation, the following description is based on EMLSR.

[0332] EMLSR operation may refer to an operation in which, when a non-AP STA MLD is performing a listening operation in which it can only receive a specific frame on multiple links, and a specific frame is received on one of the multiple links, the non-AP STA MLD performs an operation in which it can transmit and receive data frames without restriction on the link where the specific frame was received. In the present disclosure, the operation in which data frames can be transmitted and received without restriction may be referred to as EMLSR mode, but is not limited thereto.

[0333] The non-AP STA MLD may receive initial control frames from multiple links during a listening operation. Here, the non-AP STA MLD may perform a channel detection operation (clear channel assessment (CCA)). While the non-AP STA MLD is operating in EMLSR mode on the aforementioned links, it may not be able to receive frames and may not be able to perform channel detection on links where it fails to receive the specific frame described above. For example, the specific frame may be an initial control frame (ICF) with a predetermined format. The initial control frame may be a MU-RTS (multi-user-request to send) trigger frame, a BSRP (buffer status report poll) trigger frame, or other frames, but is not limited to a specific form.

[0334] In relation to EMLSR operation, a transition time may be required for a non-AP STA MLD to switch from listening operation to EMLSR mode or from EMLSR mode to listening operation. This transition time may be referred to as the EMLSR Transition Delay (ETD), but is not limited to this term. The ETD may be set differently depending on the capability of the non-AP STA MLD. For example, the ETD may be indicated by the AP MLD to which the non-AP STA MLD is connected. That is, the AP MLD can recognize the ETD value of the connected non-AP STA MLD. The time required for the non-AP STA MLD to transition from listening operation to EMLSR mode is the EMLSR padding delay, and the length of the padding field when the AP MLD to which the non-AP STA MLD is connected transmits an initial control frame to the non-AP STA MLD can be determined by the EMLSR padding delay. A padding field may be included to secure frame transmission time so that the non-AP STA MLD can respond to an initial control frame by operating in EMLSR mode during listening operation, and may increase the time length of the frame.

[0335] The EMLMR operation may be an operation in which non-AP STAs (e.g., non-AP STA 1-1, non-AP STA 1-2) operating on each link of a non-AP STA MLD use spatial streams equal to the number of spatial streams per link, and when a non-AP STA receives an initial frame, it performs a spatial stream switching operation on another link to communicate with more spatial streams. For example, if the number of spatial streams per link of the first link of non-AP STA 1-1 (720-1) is two and the number of spatial streams per link of the second link of non-AP STA 1-2 (720-2) is two, when non-AP STA 1-1 (720-1) receives an initial control frame, the spatial stream of non-AP STA 1-2 (720-2) on the second link may be switched to operate on the first link where non-AP STA 1-1 (720-1) is operating. Subsequently, non-AP STA 1-1 (720-1) can receive frames from the AP using a number of spatial streams greater than the number of spatial streams per link (e.g., 4, provided that this may vary depending on the capabilities of each STA). non-AP STA 1-2 (720-2) cannot detect the medium while non-AP STA 1-1 (720-1) is receiving frames from the AP MLD.

[0336] As described above, a delay may be required to switch spatial streams per link and to switch spatial streams again after receiving a frame, and the aforementioned delay may be referred to as the EMLMR transition delay. Additionally, the time it takes for a non-AP STA MLD to switch spatial streams from another link to one link in order to receive a frame from an AP MLD on one link may be the EMLMR padding delay. When the AP MLD connected to the non-AP STA MLD transmits an initial control frame to the non-AP STA MLD, the length of the padding field may be determined in correspondence with the EMLMR padding delay. The initial frame may include padding with a length equal to or longer than the length of the EMLMR padding delay. The initial frame of the EMLMR operation may not be a fixed-format frame and may be a frame that includes padding of a length corresponding to the EMLMR padding delay. The EMLMR padding delay can be set differently depending on the capability of the non-AP STA MLD, and the EMLMR padding delay can be indicated by the AP MLD to which the non-AP STA MLD is connected.

[0337] Additionally, an NPCA operation may be performed on at least one link among multiple links including the first link. Here, the non-AP STA MLD 1 can set the AP MLD 1 and the EMLSR operation. The non-AP STA MLD 1 can compare the NPCA switch back delay time, which is the time required to switch the operation channel from the NPCA main channel to the main channel, with the EMLSR switch delay described above. The NPCA switch back delay and the EMLSR switch delay may be determined differently depending on the capabilities of the non-AP STA MLD (or, non-AP STA). The non-AP STA MLD 1 can instruct the NPCA switch back delay time and the EMLSR switch delay, respectively, to the AP MLD 1. Here, non-AP STA MLD 1 can specify the NPCA switching back delay time via an OMP (operating mode and parameters) frame, and the EMLSR switching delay time via an EML (enhanced multi-link) OMN (operating mode and notification) frame. As another example, non-AP STA MLD 1 can specify both the NPCA switching back delay time and the EMLSR switching delay using either an OMP frame or an EML OMN frame.

[0338] If the EMLSR transition delay value is greater than or equal to the NPCA switching back delay time value, the non-AP STA MLD 1 may indicate the EMLSR transition delay value indicated by the frame described above as the original EMLSR transition delay value. On the other hand, if the EMLSR transition delay time value is smaller than the NPCA switching back delay time value, the non-AP STA MLD 1 may indicate the EMLSR transition delay value indicated by the frame described above as the longer NPCA switching back delay value. AP 1 may determine the EMLSR transition delay value and the NPCA switching back delay time value from at least one of the OMP frame and the OMN frame received from the non-AP STA 1.

[0339] AP 1-1 (710-1) of AP MLD 1 and non-AP STA 1-1 (720-1) of non-AP STA MLD 1 can detect the transmission of OBSS on the first link (e.g., setting of TXOP, which is the transmission section, transmission of PPDU). AP 1-1 (710-1) and non-AP STA 1-1 (720-1), which are NPCA STAs, can set the value of NPCA_TIMER and operate on the NPCA main channel. The NPCA STAs can operate on the NPCA main channel during the period when NPCA_TIMER has not expired (e.g., the period when the value of NPCA_TIMER is not zero). NPCA_TIMER may be a timer set to a value obtained by subtracting its own NPCA switching back delay from the communication interval of the OBSS detected by each STA (e.g., the communication interval of the OBSS identified by referring to at least one of the values ​​in the duration field of the MAC header and the TXOP_DURATION field of the PHY preamble, the transmission interval of the PPDU identified by referring to the PPDU length information of the PHY preamble, etc.). Therefore, the end time (i.e., the time length of the timer) of NPCA_TIMER may differ depending on the NPCA switching back delay value of each STA. For example, a STA with a larger NPCA switching back delay value may have an earlier end time of NPCA_TIMER than a STA with a smaller NPCA switching back delay value. That is, the time length of the timer may be shorter. Additionally, when NPCA_TIMER expires (i.e., the timer value reaches 0 over time), the NPCA STA may operate on the main channel.

[0340] Referring to FIG. 16a, consider the case where AP 1-1 (710-1) transmits a frame to non-AP STA 1-1 (720-1) performing an EMLSR operation. AP 1-1 (710-1) may want to transmit a frame to non-AP STA 1-1 (720-1) on the NPCA main channel. Since non-AP STA 1-1 (720-1) is a non-AP STA operating on the first link, which is one of the EMLSR links of non-AP STA MLD 1, AP 1-1 (710-1) may need to transmit an initial control frame (e.g., MU-RTS (multi-user request to send) trigger frame, BSRP trigger frame) when transmitting a frame to non-AP STA 1-1 (720-1). AP 1-1 (710-1) initiating the transmission of an initial control frame may mean that a frame exchange procedure between AP 1-1 (710-1) and non-AP STA 1-1 (720-1) is initiated. Such procedure may be an EML frame exchange procedure, but is not limited to such a name.

[0341] During the process of performing the EML frame exchange procedure between AP 1-1 (710-1) and non-AP STA 1-1 (720-1), non-AP STA 1-1 (720-1) may wait for a timeout (TO) from the last frame transmitted by non-AP STA 1-1 (720-1) or the last frame received by non-AP STA 1-1 (720-1). The TO time may be 'aSIFSTime + aSlotTime + aRxPHYStartDelay'. Alternatively, the TO time may be any other time and is not limited to a specific form. The TO time may be the time for non-AP STA 1-1 (720-1), which is performing the EMLSR operation, to wait for additional frame reception before switching the operation mode to listen mode. If the PHY-RXSTART.indication primitive does not occur during the TO time in non-AP STA 1-1 (720-1), the EML frame exchange procedure may be terminated.

[0342] Alternatively, if a PHY-RXSTART.indication primitive occurs during the TO time in non-AP STA 1-1 (720-1), but the recipient of a subsequently received frame is not non-AP STA 1-1 (720-1), the EML frame exchange procedure may be terminated. For example, there may be cases where the RA (receiver address) field included in the MAC (medium access control) header of the frame is not the MAC address of non-AP STA 1-1 (720-1), or where the RA field included in the MAC header of the frame is a broadcast address so that non-AP STA 1-1 (720-1) is the recipient of the frame but the frame does not allocate uplink resources to non-AP STA 1-1 (720-1) (e.g., no RA-RU corresponding to STA 1-1 is allocated separately, or no uplink resources are allocated using the AID of STA 1), or where the PHY-RXSTART.indication primitive occurred at non-AP STA 1-1 (720-1) for the TO time but the recipient of the subsequently received frame is not non-AP STA 1-1 (720-1).

[0343] non-AP STA 1-1 (720-1) can switch its operating mode from EMLSR mode to listening mode after the above-described EML frame exchange procedure ends. non-AP STA 1-1 (720-1) can operate in listening mode after or before the time following the EMLSR transition delay from the time of the end of the EML frame exchange procedure. That is, it may take a maximum EMLSR transition delay time for non-AP STA 1-1 (720-1) to switch its operating mode to listening mode. AP 1-1 (710-1) can start a new frame exchange procedure by transmitting an initial control frame to non-AP STA 1-1 (720-1) after the time following the end of the frame exchange procedure, or after the time following the time following the time following the time following the EMLSR transition delay of non-AP STA 1-1 (720-1).

[0344] The EMLSR switching delay of non-AP STA 1-1 (720-1) may be specified as the largest time length value between the EMLSR switching delay time and the NPCA switching back delay time, regardless of the actual capability of non-AP STA 1-1 (720-1). AP 1-1 (710-1) may use the EMLSR switching delay of non-AP STA 1-1 (720-1) to determine the end time of the frame switching procedure on the NPCA main channel. That AP 1-1 (710-1) uses the EMLSR switching delay value of non-AP STA 1-1 (720-1) may mean that non-AP STA 1-1 (720-1) uses the EMLSR switching delay value specified by AP 1-1 (710-1). Therefore, the EMLSR switching delay value based on the actual capability of the non-AP STA 1-1 (720-1) may be irrelevant. As another example, the EMLSR switching delay of the non-AP STA 1-1 (720-1) may not be indicated by the largest time length value between the EMLSR switching delay time and the NPCA switching back delay time, regardless of the actual capability of the non-AP STA 1-1 (720-1), but may be indicated independently by the non-AP STA 1-1 (720-1).

[0345] AP 1-1 (710-1) can compare the NPCA switching back delay of non-AP STA 1-1 (720-1) with the EMLSR switching delay of non-AP STA 1-1 (720-1). If the EMLSR switching delay of non-AP STA 1-1 (720-1) is equal to or greater than the NPCA switching back delay, AP 1-1 (710-1) can use the EMLSR switching delay of non-AP STA 1-1 (720-1) to determine the end time of frame switching on the NPCA main channel. On the other hand, if the NPCA switching back delay of AP 1-1 (710-1) is greater than the EMLSR switching delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) may need to ensure that the termination of the EML frame switching procedure occurs at or before the time when AP 1-1 (710-1)'s own NPCA_TIMER reaches 0. On the other hand, if the NPCA switching back delay of AP 1-1 (710-1) is smaller than the EMLSR switching delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) must consider the time after the termination of the EML frame switching procedure for frames transmitted to non-AP STA 1-1 (720-1) that non-AP STA 1-1 (720-1) can perform a change in EMLSR operation mode and channel switching. For example, AP 1-1 (710-1) can terminate the EML frame exchange procedure when the value of '(AP 1-1's NPCA_TIMER) + (AP 1-1's NPCA switching back delay) - (STA 1-1's EMLSR switching delay)' reaches 0 or before it reaches 0.

[0346] If the EMLSR switching delay of non-AP STA 1-1 (720-1) is smaller than the NPCA switching back delay, AP 1-1 (710-1) can determine the end time of frame switching on the NPCA main channel using the NPCA switching back delay of non-AP STA 1-1 (720-1). If the NPCA switching back delay of AP 1-1 (710-1) is larger than the NPCA switching back delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) can terminate the EML frame switching procedure at or before the NPCA_TIMER of AP 1-1 (710-1) itself reaches 0.

[0347] On the other hand, if the NPCA switching back delay of AP 1-1 (710-1) is smaller than the NPCA switching back delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) must consider the time after the end of the frame switching procedure for frames transmitted to non-AP STA 1-1 (720-1) so that non-AP STA 1-1 (720-1) can perform channel switching (switching between the NPCA main channel and the main channel) at an appropriate time. For example, AP 1-1 (710-1) may terminate the EML frame switching procedure at the point when the value of (NPCA_TIMER of AP 1-1) + (NPCA switching back delay of AP 1-1) - (NPCA switching back delay of STA 1-1) reaches 0 or before it reaches 0.

[0348] non-AP STA 1-1 (720-1) can receive frames from AP 1-1 (710-1) on the NPCA main channel. When the EML frame exchange procedure is terminated, non-AP STA 1-1 (720-1) can switch its operating mode from EMLSR mode (i.e., a state where normal transmission and reception of frames is possible) to listening mode. Additionally, non-AP STA 1-1 (720-1) can switch its operating channel from the NPCA main channel to the main channel when NPCA_TIMER reaches 0 (or reaches a value smaller than that) while operating on the NPCA main channel. Even if the termination of the EML frame exchange procedure has not occurred, non-AP STA 1-1 (720-1) may consider the termination of the EML frame exchange procedure to have occurred when NPCA_TIMER reaches 0 while operating on the NPCA main channel. The non-AP STA 1-1 (720-1) can switch the operation mode from EMLSR mode to listening mode.

[0349] If the EMLSR switching delay of non-AP STA 1-1 (720-1) is longer than the NPCA switching back delay, the setting of the NPCA_TIMER value of non-AP STA 1-1 (720-1) may be set to 'the value obtained by subtracting its own EMLSR switching delay from the communication period of the OBSS detected by non-AP STA 1-1 (720-1)' instead of 'the value obtained by subtracting its own NPCA switching back delay from the communication period of the OBSS detected by non-AP STA 1-1 (720-1)'. AP 1-1 (710-1) and non-AP STA 1-1 (720-1) can perform frame transmission and reception and channel access operations on the main channel again at the end of the communication period of the OBSS.

[0350] As another example, when AP 1-1 (710-1) intends to transmit a frame to non-AP STA 1-1 (720-1), 'termination of a general frame switching procedure' may be used instead of the termination of the EML frame switching procedure described above. In the following, 'termination of a frame switching procedure' not specified as 'EML' may be 'termination of a general frame switching procedure', but is not limited thereto.

[0351] "Termination of a general frame switching procedure" may refer to the point in time when a frame transmission is terminated within the frame switching procedure. A frame switching procedure may refer to a frame switching procedure that includes at least one of a control frame and a data frame. For example, if AP 1-1 (710-1) transmits a data frame that does not require an immediate acknowledgment frame to non-AP STA 1-1 (720-1), and AP 1-1 (710-1) does not transmit any additional frames to non-AP STA 1-1 (720-1) after that frame, the point in time when the frame switching procedure is terminated may be the point in time when the transmission of the data frame that does not require an immediate acknowledgment frame is completed. As another example, if AP 1-1 (710-1) transmits a data frame requesting an immediate response frame to non-AP STA 1-1 (720-1), and after that frame, non-AP STA 1-1 (720-1) transmits an immediate response frame to AP 1-1 (710-1), the end point of the frame switching procedure may be the time when the immediate response frame is received. As another example, the end point of the frame switching procedure may be the end point of the TXOP of AP 1-1 (710-1).

[0352] Since non-AP STA 1-1 (720-1) is a non-AP STA operating on the first link, which is one of the EMLSR links of non-AP STA MLD 1, AP 1-1 (710-1) may need to transmit an initial control frame (e.g., MU-RTS (multi-user request to send) trigger frame, BSRP trigger frame) when transmitting a frame to non-AP STA 1-1 (720-1). AP 1-1 (710-1) can compare the NPCA switching back delay of non-AP STA 1-1 (720-1) with the EMLSR switching delay of non-AP STA 1-1 (720-1). If the EMLSR switching delay of non-AP STA 1-1 (720-1) is equal to or greater than the NPCA switching back delay, AP 1-1 (710-1) can determine the end time of frame switching on the NPCA main channel using the EMLSR switching delay of non-AP STA 1-1 (720-1). On the other hand, if the NPCA switching back delay of AP 1-1 (710-1) is greater than the EMLSR switching delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) can terminate the frame switching procedure at or before the NPCA_TIMER of AP 1-1 (710-1) itself reaches 0. Additionally, if the NPCA switching back delay of AP 1-1 (710-1) is smaller than the EMLSR switching delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) may terminate the frame switching procedure when the value of '(NPCA_TIMER of AP 1-1) + (NPCA switching back delay of AP 1-1) - (EMLSR switching delay of STA 1-1)' reaches 0 or before it reaches 0.

[0353] If the EMLSR switching delay of non-AP STA 1-1 (720-1) is smaller than the NPCA switching back delay, AP 1-1 (710-1) can determine the end time of frame switching on the NPCA main channel using the NPCA switching back delay of non-AP STA 1-1 (720-1). If the NPCA switching back delay of AP 1-1 (710-1) is larger than the NPCA switching back delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) can terminate the frame switching procedure at or before the NPCA_TIMER of AP 1-1 (710-1) itself reaches 0. On the other hand, if the NPCA switching back delay of AP 1-1 (710-1) is smaller than the NPCA switching back delay of non-AP STA 1-1 (720-1), AP 1-1 (710-1) may terminate the frame switching procedure when the value of '(NPCA_TIMER of AP 1-1) + (NPCA switching back delay of AP 1-1) - (NPCA switching back delay of STA 1-1)' reaches 0 or before reaching 0.

[0354] Referring to FIG. 16a, non-AP STA 1-1 (720-1) receives an ICF (801) on the NPCA main channel and can switch the operation mode to EMLSR operation. Subsequently, non-AP STA 1-1 (720-1) can receive a frame (802) from AP 1-1 (710-1). When non-AP STA 1-1 (720-1) performs an EMLSR operation on the NPCA main channel, it can determine the end of the EML frame exchange procedure by applying the 'end of the general frame exchange procedure'. That is, the end of the general frame exchange procedure can be considered as the end of the EML frame exchange procedure. When the EML frame exchange procedure ends, non-AP STA 1-1 (720-1) can switch the operation mode from EMLSR mode (i.e., a state where normal transmission and reception of frames is possible) to listening mode. Alternatively, non-AP STA 1-1 (720-1) may switch the operating channel from the NPCA main channel to the main channel when NPCA_TIMER reaches 0 (or reaches a value smaller than that) while operating on the NPCA main channel. Alternatively, non-AP STA 1-1 (720-1) may consider the EML frame switching procedure to have ended when NPCA_TIMER reaches 0 while operating on the NPCA main channel, even if the EML frame switching procedure has not ended. non-AP STA 1-1 (720-1) may switch the operating mode from EMLSR mode to listening mode.

[0355] If the EMLSR switching delay of non-AP STA 1-1 (720-1) is longer than the NPCA switching back delay, the setting of the NPCA_TIMER value of non-AP STA 1-1 (720-1) may be set to 'the value obtained by subtracting its own EMLSR switching delay from the communication period of the OBSS detected by non-AP STA 1-1 (720-1)' instead of 'the value obtained by subtracting its own NPCA switching back delay from the communication period of the OBSS detected by non-AP STA 1-1 (720-1)'. AP 1-1 (710-1) and non-AP STA 1-1 (720-1) can perform frame transmission and reception and channel access operations on the main channel again at the end of the communication period of the OBSS.

[0356] As another example, non-AP STA 2-1 (730-1) may not perform EMLSR operations. For example, non-AP STA MLD 2 to which non-AP STA 2-1 (730-1) belongs may not use EMLSR operations, or non-AP STA 2-1 (730-1) may not operate on the EMLSR link of non-AP STA MLD 2. Consider the case where AP 1-1 (710-1) transmits a frame to non-AP STA 2-1 that does not perform EMLSR operations.

[0357] If the NPCA switching back delay of AP 1-1 (710-1) is equal to or greater than the NPCA switching back delay of non-AP STA 2-1 (730-1), AP 1-1 (710-1) may terminate the frame switching procedure at or before the time when AP 1-1 (710-1)'s own NPCA_TIMER reaches 0. On the other hand, if the NPCA switching back delay of AP 1-1 (710-1) is smaller than the NPCA switching back delay of non-AP STA 2-1 (730-1), AP 1-1 (710-1) must consider the time for non-AP STA 2-1 (730-1) to perform channel switching (switching between the NPCA main channel and the main channel) at an appropriate time after the termination of the frame switching procedure described above for frames transmitted to non-AP STA 2-1 (730-1). For example, AP 1-1 (710-1) can terminate the frame switching procedure when the value of '(AP 1-1's NPCA_TIMER) + (AP 1-1's NPCA switching back delay) - (STA 2-1's NPCA switching back delay)' reaches 0 or before reaching 0.

[0358] Referring to FIG. 16b, a non-AP STA 1-1 (720-1) performing an EMLSR operation may want to transmit a frame to AP 1-1 (710-1) on the NPCA main channel. If the EMLSR switching delay of the non-AP STA 1-1 (720-1) is smaller than the NPCA switching back delay of the non-AP STA 1-1 (720-1), the non-AP STA 1-1 (720-1) may use the NPCA switching back delay of the non-AP STA 1-1 (720-1) to determine the end time of frame exchange on the NPCA main channel when transmitting a frame to AP 1-1 (710-1).

[0359] If the NPCA switching back delay of non-AP STA 1-1 (720-1) is greater than the NPCA switching back delay of AP 1-1 (710-1), non-AP STA 1-1 (720-1) may terminate the TXOP of non-AP STA 1-1 (720-1) at or before its own NPCA_TIMER reaches 0. If the NPCA switching back delay of non-AP STA 1-1 (720-1) is smaller than the NPCA switching back delay of AP 1-1 (710-1), time may be considered for AP 1-1 (710-1) to perform channel switching (switching between NPCA main channel and main channel) at an appropriate time after the end of the frame switching procedure for the frame transmitted by non-AP STA 1-1 (720-1). For example, non-AP STA 1-1 (720-1) can terminate the TXOP of non-AP STA 1-1 (720-1) when the value of '(STA 1-1's NPCA_TIMER) + (STA 1-1's NPCA switching back delay) - (AP 1-1's NPCA switching back delay)' reaches 0 or before reaching 0.

[0360] On the other hand, if the EMLSR switching delay of non-AP STA 1-1 (720-1) is greater than the NPCA switching back delay, non-AP STA 1-1 (720-1) can determine the end time of frame switching on the NPCA main channel by using the EMLSR switching delay of non-AP STA 1-1 (720-1) when transmitting a frame to AP 1-1 (710-1). If the EMLSR switching delay of non-AP STA 1-1 (720-1) is greater than the NPCA switching back delay of AP 1-1 (710-1), non-AP STA 1-1 (720-1) can terminate the TXOP of non-AP STA 1-1 (720-1) at or before its own NPCA_TIMER reaches 0.

[0361] If the EMLSR switching delay of non-AP STA 1-1 (720-1) is smaller than the NPCA switching back delay of AP 1-1 (710-1), a time may be considered during which AP 1-1 (710-1) can perform channel switching (switching between the NPCA main channel and the main channel) at an appropriate time after the end of the frame switching procedure for frames transmitted by non-AP STA 1-1 (720-1). For example, non-AP STA 1-1 (720-1) must ensure that the TXOP of non-AP STA 1-1 (720-1) terminates at or before the value of '(STA 1-1's NPCA_TIMER) + (STA 1-1's EMLSR switching delay) - (AP 1-1's NPCA switching back delay)' reaches 0. If the EMLSR switching delay of non-AP STA 1-1 is longer than the NPCA switching back delay, the NPCA_TIMER value of STA 1-1 may be set to 'the value obtained by subtracting its own EMLSR switching delay from the communication interval of the OBSS detected by STA 1-1' instead of 'the value obtained by subtracting its own NPCA switching back delay from the communication interval of the OBSS detected by STA 1-1'.

[0362]

[0363] In the aforementioned FIGS. 4 to 8 and FIGS. 15 to 16b, the execution of the NPCA operation of a non-AP STA MLD performing an EMLSR operation and a non-AP STA connected to the non-AP STA MLD is described. Additionally, in the aforementioned FIG. 9, the execution of the DSO operation of a non-AP STA MLD performing an EMLSR operation and a non-AP STA connected to the non-AP STA MLD is described. Furthermore, in FIGS. 12 to 14d, the execution of the DPS operation of a non-AP STA MLD performing an EMLSR operation and a non-AP STA connected to the non-AP STA MLD is described.

[0364] Here, a non-AP STA MLD performing EMLSR operation and a non-AP STA associated with the non-AP STA MLD may be able to enable two or more modes among the NPCA, DSO, and DPS operation modes described above. In the above case, the time it takes for the non-AP STA MLD and the non-AP STA associated with the non-AP STA MLD to complete the switching of the operation mode from normal transmit / receive operation (or EMLSR mode) back to listening mode may be determined by the time delay values ​​according to two or more modes. In the above case, the non-AP STA can identify the largest value among the EMLSR transition delay value after the completion of frame switching and the delay time value of the mode enabled by the non-AP STA (e.g., NPCA switching delay (or NPCA switchback delay), DSO switching delay (or DSO switchback delay), DPS switching delay (or DPS transition delay)).

[0365] The non-AP STA, in frame exchange with the connected AP, as described above<Tw 조건 1> or<Tw 조건 2> Accordingly, a waiting time Tw may be started to switch the operation mode of the EMLSR operation from normal transmit / receive operation to listen mode. If the <Listen Operation Switch> condition is satisfied within the Tw time, or if the <Listen Operation Switch> condition is not satisfied but the <Listen Operation Switch - Receive> condition is satisfied (which means completion of EML frame exchange, or completion of frame exchange), the non-AP STA may operate in listen mode after the time corresponding to the longest time delay value among the EMLSR switch delay value and the delay time value of the mode enabled by the non-AP STA has elapsed. Meanwhile, the AP to which the non-AP STA is connected may terminate the frame exchange procedure with the non-AP STA according to the EMLSR switch delay value of the non-AP STA and the delay time value of the mode enabled by the non-AP STA as described above. The AP can terminate the frame switching procedure with the non-AP STA and recognize whether the non-AP STA and other non-AP STAs of the non-AP STA MLD associated with the non-AP STA can perform a listening operation.

[0366] Here, the above-described matters may be cases considering FIGS. 4 to 8, FIG. 9, FIGS. 12 to 14d, and FIGS. 15 to 16b together, and the following cases may be considered. Here, for convenience of explanation, time units are omitted. Also, the time values ​​described in the following cases are configurations arbitrarily described for convenience of explanation and are not limited thereto.

[0367] As a specific example, consider the case where a non-AP STA enables all modes of NPCA, DSO, and DPS, and this case may be Case 1. As another example, consider the case where a non-AP STA enables some modes of NPCA, DSO, and DPS, and this may be Case 2.

[0368]

[0369] [Case 1]

[0370] EMLSR transition delay of non-AP STA: 16

[0371] NPCA switching delay of non-AP STA: 32

[0372] DSO switching delay of non-AP STA: 64

[0373] DPS switching delay of non-AP STA: 16

[0374]

[0375] [Case 2]

[0376] EMLSR transition delay of non-AP STA: 16

[0377] NPCA switching delay of non-AP STA: 32

[0378] DSO switching delay for non-AP STA: (None - non-AP STA is disabled)

[0379] DPS switching delay of non-AP STA: 16

[0380]

[0381] In Case 1, the non-AP STA may operate in listening mode after 64 hours have elapsed, which is the longest inter-mode delay value since the completion of frame switching. In Case 2, the non-AP STA may operate in listening mode after 32 hours have elapsed, which is the longest inter-mode delay value since the completion of frame switching. Meanwhile, while the non-AP STA may enable two modes simultaneously, two operating modes may not be used simultaneously. For example, if the non-AP STA is operating on the NPCA main channel, DSO operation may not be possible, and vice versa. However, the non-AP STA may use DPS operation while performing either NPCA or DSO operation. Here, the non-AP STA may consider only the switching delay of the available modes. Cases 3 and 4 below may be cases that take into account the above-described matters, and are provided for convenience of explanation only and are not limited thereto. Case 3 is a transition delay case that can be considered when a non-AP STA performs NPCA operation, and Case 4 is a transition delay case that can be considered when a non-AP STA performs DSO operation.

[0382]

[0383] [Case 3]

[0384] EMLSR transition delay of non-AP STA: 16

[0385] NPCA switching delay of non-AP STA: 32

[0386] DSO switching delay for non-AP STA: 64 (Not considered - NPCA in operation)

[0387] DPS switching delay of non-AP STA: 16

[0388]

[0389] [Case 4]

[0390] EMLSR transition delay of non-AP STA: 16

[0391] NPCA switching delay for non-AP STA: 32 (Not considered - DSO in operation)

[0392] DSO switching delay of non-AP STA: 64

[0393] DPS switching delay of non-AP STA: 16

[0394]

[0395] In Case 3, the non-AP STA can operate in listening mode after 32 hours have elapsed, which is the longest inter-mode delay value excluding the DSO switching delay after the completion of frame exchange. Additionally, in Case 4, the non-AP STA can operate in listening mode after 64 hours have elapsed, which is the longest inter-mode delay value excluding the NPCA switching delay after the completion of frame exchange.

[0396] Meanwhile, when a non-AP STA enables NPCA operation and operates on an NPCA main channel, the non-AP STA and AP may consider the longest inter-mode delay value described above at the time of termination of frame transmission on the NPCA main channel. The longest inter-mode delay value described above may be referred to as the aggregation switching delay value, but is not limited thereto.

[0397] Here, referring to FIG. 16a, consider the case where AP 1-1 transmits a frame to STA 1-1, which performs an EMLSR operation. AP 1-1 can check the aggregate switching delay value of STA 1-1. If the NPCA switching back delay of AP 1-1 is smaller than the aggregate switching delay of STA 1-1, AP 1-1 can use the aggregate switching delay of STA 1-1 to determine the time to end frame switching on the NPCA main channel.

[0398] On the other hand, if the NPCA switching back delay of AP 1-1 is greater than the aggregation switching delay of STA 1-1, AP 1-1 may cause the EML frame switching procedure to terminate when AP 1-1's own NPCA_TIMER reaches 0 or before it reaches 0. On the other hand, if the NPCA switching back delay of AP 1-1 is smaller than the aggregation switching delay of STA 1-1, AP 1-1 must consider the time after the frame switching procedure for frames transmitted to STA 1-1 that allows STA 1-1 to perform a change in EMLSR operation mode and channel switching. For example, AP 1-1 may terminate the frame switching procedure when the value of '(AP 1-1's NPCA_TIMER) + (AP 1-1's NPCA switching back delay) - (STA 1-1's aggregation switching delay)' reaches 0 or before it reaches 0.

[0399] STA 1-1 can receive frames from AP 1-1 on the NPCA main channel. Additionally, STA 1-1 can switch the operating channel from the NPCA main channel to the main channel when NPCA_TIMER reaches 0 (or a value less than that) while operating on the NPCA main channel. STA 1-1 may consider the frame switching procedure to have ended when NPCA_TIMER reaches 0 while operating on the NPCA main channel, even if the frame switching procedure has not ended.

[0400] The NPCA_TIMER value of STA 1-1 may be set to 'a value excluding its own integrated switching delay from the communication period of the OBSS detected by STA 1-1'. AP 1-1 and STA 1-1 may perform frame transmission and reception and channel access operations on the main channel again at the end of the communication period of the OBSS.

[0401] Since STA 1-1 is a STA operating on the first link, which is one of the EMLSR links of STA MLD 1, AP 1-1 may need to transmit an initial control frame (e.g., MU-RTS (multi-user request to send) trigger frame, BSRP trigger frame) when transmitting a frame to STA 1-1. AP 1-1 can determine the end time of frame switching on the NPCA main channel using the aggregation switching delay of STA 1-1. On the other hand, if the NPCA switching back delay of AP 1-1 is greater than the aggregation switching delay of STA 1-1, AP 1-1 may terminate the frame switching procedure when or before its own NPCA_TIMER reaches 0. Additionally, if the NPCA switching back delay of AP 1-1 is smaller than the integrated switching delay of STA 1-1, AP 1-1 may terminate the frame switching procedure when the value of '(NPCA_TIMER of AP 1-1) + (NPCA switching back delay of AP 1-1) - (integrated switching delay of STA 1-1)' reaches 0 or before it reaches 0.

[0402] Additionally, referring to FIG. 16b, STA 1-1, which performs the EMLSR operation, may want to transmit a frame to AP 1-1 on the NPCA main channel. If the aggregation switching delay of STA 1-1 is smaller than the NPCA switching back delay of STA 1-1, STA 1-1 may use the NPCA switching back delay of STA 1-1 to determine the end time of frame switching on the NPCA main channel when transmitting a frame to AP 1-1.

[0403] If the aggregation switching delay of STA 1-1 is greater than the NPCA switching back delay of AP 1-1, STA 1-1 may terminate STA 1-1's TXOP at or before STA 1-1's own NPCA_TIMER reaches 0. If the aggregation switching delay of STA 1-1 is less than the NPCA switching back delay of AP 1-1, time may be considered for AP 1-1 to perform channel switching (switching between NPCA main channel and main channel) at an appropriate time after the end of the frame switching procedure for the frame transmitted by STA 1-1. For example, STA 1-1 may terminate STA 1-1's TXOP at or before the value of '(STA 1-1's NPCA_TIMER) + (STA 1-1's aggregation switching delay) - (AP 1-1's NPCA switching back delay)' reaches 0.

[0404] If the integrated switching delay of STA 1-1 is smaller than the NPCA switching back delay of AP 1-1, a time may be considered during which AP 1-1 can perform channel switching (switching between the NPCA main channel and the main channel) at an appropriate time after the end of the frame switching procedure for the frame transmitted by STA 1-1. For example, STA 1-1 must ensure that the TXOP of STA 1-1 terminates at or before the value of '(STA 1-1's NPCA_TIMER) + (STA 1-1's integrated switching delay) - (AP 1-1's NPCA switching back delay)' reaches 0.

[0405] FIG. 17 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies. Referring to FIG. 17, a method of operation of a first multi-link device (MLD) comprising a first station (STA) associated with a first link and a second STA associated with a second link in a wireless LAN system may be provided. Specifically, the first MLD may be connected to a second MLD that performs multi-link communication (S1710). Here, the first MLD may be an MLD that simultaneously supports EMLSR operation and at least one mode switching operation. Subsequently, the first MLD may receive an initial control frame from the second MLD (S1720). The initial control frame may include a padding field. Subsequently, the first MLD may perform communication by receiving the initial control frame. (S1730) The first MLD performs a listening operation based on the first mode, which is capable of receiving only an initial control frame on multiple links, based on the first mode switching operation among the EMLSR operation and at least one mode switching operation, and when an initial control frame is received during the listening operation, it can perform a transmit / receive operation based on the second mode on the link where the initial control frame was received.

[0406] Here, the first MLD operates in a state where it can receive an initial control frame from multiple links during a listening operation, and can perform a channel detection operation.

[0407] For example, the first mode switching operation described above may be a non-primary channel access (NPCA) operation. When the first MLD operates based on the first mode, the first MLD performs a transmit / receive operation on the primary channel, and when the first MLD operates based on the second mode, the first MLD may perform a transmit / receive operation on the NPCA primary channel. Additionally, if the first link is occupied by an overlapping basic service set (OBSS) while the first MLD is performing a listening operation, the first MLD may switch from the primary channel to the NPCA primary channel to perform a listening operation and receive an initial control frame on the NPCA primary channel. Additionally, the length of the padding field of the initial control frame may be determined to correspond to the EMLSR switching delay for switching from a listening operation to a transmit / receive operation, or to be a value longer than the EMLSR switching delay. In addition, when the first MLD switches the channel from the NPCA main channel of the first link to the main channel, the frame switching procedure in the NPCA main channel may end at a time prior to the first value from the end of the transmission opportunity of the OBSS. In addition, the first value may be determined as the longer value between the NPCA switching back delay and the EMLSR switching delay.

[0408] As another example, the first mode switching operation may be a dynamic subband operation (DSO). Here, if the first MLD operates based on the first mode, the first MLD can perform transmit and receive operations in the primary subband. Conversely, if the first MLD operates based on the second mode, the first MLD can perform transmit and receive operations in the DSO subband. Here, the first MLD receives an initial control frame from the first link during a listening operation, and the initial control frame may instruct the first MLD to change its operating frequency to the DSO subband from the first link. Additionally, the length of the padding field of the initial control frame may be determined by the longer value between the DSO switching delay for switching the operating frequency to the DSO subband and the EMLSR switching delay for switching from a listening operation to a transmit and receive operation. Additionally, when the first MLD switches from the DSO subband of the first link to the main subband, the time at which the first MLD operates in the main subband of the first link may be a time after the sum of the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the end time of the frame switching procedure of the DSO subband. Additionally, the first value may be determined as the longer value between the DSO switching delay and the EMLSR switching delay.

[0409] As another example, the first mode switching operation may be a dynamic power saving (DPS) operation. Here, when the first MLD operates based on the first mode, the first MLD operates in a lower capability mode (LCM) where at least one of the operating bandwidth, the number of operating space streams, and the MCS is limited or only the reception of an initial control frame is possible, and when the first MLD operates based on the second mode, the first MLD may operate in a higher capability mode (HCM). Additionally, the first MLD receives an initial control frame from the first link during a listening operation, and the initial control frame may instruct the first MLD to switch to the DPS operation mode from the first link. Additionally, upon receiving the initial control frame, the first MLD may switch from LCM to HCM and operate. Furthermore, the length of the padding field of the initial control frame may be determined by the longer value between the DPS switching delay when the DPS operation mode switches and the EMLSR switching delay when switching from the listening operation to the normal transmit / receive mode. Additionally, when the first MLD switches from HCM to LCM, the time at which the first MLD switches from HCM to LCM may be a time after the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of completion of the frame exchange procedure according to HCM. Additionally, the first value may be determined as the longer value between the DPS switching delay and the EMLSR switching delay.

[0410] As another example, at least one mode switching operation may include an NPCA operation, a DSO operation, and a DPS operation. Here, when the mode is switched according to the NPCA operation, the DSO operation, and the DPS operation, the integrated switching delay may be determined based on a first value. Additionally, the first value may be determined as the longest value among the NPCA switching back delay, the DSO switching back delay, the DPS switching delay, and the EMLSR switching delay.

[0411] For example, the first mode switching operation is an NPCA operation, and when the first MLD switches the channel from the NPCA main channel of the first link to the main channel, the frame switching procedure in the NPCA main channel may end at a time prior to the first value from the end of the transmission opportunity of the OBSS.

[0412] As another example, the first mode switching operation is a DSO operation, and when the first MLD switches from the DSO subband of the first link to the main subband, the time when the first MLD operates in the main subband of the first link and the time when the first MLD performs a listening operation in the first link may be a time after the sum of the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time when the frame switching procedure of the DSO subband ends.

[0413] As another example, the first mode switching operation is a DPS operation, and when the first MLD switches from HCM to LCM, the time at which the first MLD switches from HCM to LCM and the time at which the first MLD performs a listening operation on the first link may be a time after the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of termination of the frame switching procedure according to the HCM.

[0414] In addition, the first MLD may be a non-AP MLD and the second MLD may be an AP MLD, or the first MLD may be an AP MLD and the second MLD may be a non-AP MLD, and is not limited to a specific form.

[0415]

[0416] The methods according to the present disclosure may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and configured for the present disclosure, or they may be those known and available to those skilled in the art of computer software. Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as at least one software module to perform the operations of the present disclosure, and vice versa. Although the present invention has been described with reference to the embodiments above, those skilled in the art will understand that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the disclosure as set forth in the following claims.

[0417]

[0418] The above-mentioned matters may also be applied to other systems.

Claims

1. A method of operation of a first multi-link device (MLD) comprising a first station (STA) associated with a first link and a second STA associated with a second link in a wireless LAN system, A step in which the first MLD is connected to a second MLD that performs multi-link communication, wherein the first MLD is an MLD that simultaneously supports EMLSR (enhanced multi-link single radio) operation and at least one mode switching operation; The step of the first MLD receiving an initial control frame from the second MLD, wherein the initial control frame includes a padding field; and The method includes the step of receiving the above initial control frame and performing communication, A method of operation in which the first MLD performs a listening operation based on a first mode, which is capable of receiving only the initial control frame in the multiple links based on the first mode switching operation among the EMLSR operation and the at least one mode switching operation, and when the initial control frame is received during the listening operation, performs a transmit / receive operation based on a second mode in the link where the initial control frame was received.

2. In Paragraph 1, A method of operation in which the first MLD operates in a state where the initial control frame is received from the multiple links during the listening operation, and performs a clear channel assessment (CCA).

3. In Paragraph 1, The above first mode switching operation is a non-primary channel access (NPCA) operation, and when the first MLD operates based on the first mode, the first MLD performs a transmit / receive operation on the primary channel, and A method of operation in which, when the first MLD operates based on the second mode, the first MLD performs a transmission and reception operation on the NPCA main channel.

4. In Paragraph 3, A method of operation in which, when the first link is occupied by an overlapping basic service set (OBSS) while the first MLD is performing the listening operation, the first MLD switches from the main channel to the NPCA main channel to perform the listening operation and receives the initial control frame on the NPCA main channel.

5. In Paragraph 4, A method of operation in which the length of the padding field of the above initial control frame is determined to be a value corresponding to or longer than the EMLSR switching delay for switching from the listening operation to the transmitting / receiving operation.

6. In Paragraph 4, A method of operation in which, when the first MLD switches the channel from the NPCA main channel of the first link to the main channel, the frame switching procedure in the NPCA main channel ends at a time prior to the first value from the time of end of the transmission opportunity of the OBSS.

7. In Paragraph 6, A method of operation in which the first value is determined as the longer value among the NPCA switching back delay and the EMLSR switching delay.

8. In Paragraph 1, The above first mode switching operation is a DSO (dynamic subband operation), and when the first MLD operates based on the first mode, the first MLD performs a transmit / receive operation in the primary subband, and A method of operation in which, when the first MLD operates based on the second mode, the first MLD performs a transmission and reception operation in the DSO subband.

9. In Paragraph 8, A method of operation in which the first MLD receives the initial control frame from the first link during the listening operation, wherein the initial control frame instructs the first link to change the operating frequency of the first MLD to a DSO subband.

10. In Paragraph 9, A method of operation in which the length of the padding field of the above initial control frame is determined by the longer value between the DSO switching delay for switching the operating frequency to the DSO subband and the EMLSR switching delay for switching from the listening operation to the transmit / receive operation.

11. In Paragraph 10, A method of operation in which, when the first MLD is switched from the DSO subband of the first link to the main subband, the time at which the first MLD operates in the main subband of the first link and the time at which the first MLD performs a listening operation in the first link are at a time after the sum of the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay from the time of termination of the frame switching procedure of the DSO subband.

12. In Paragraph 11, A method of operation in which the first value is determined as the longer value between the DSO switching delay and the EMLSR switching delay.

13. In Paragraph 1, The above first mode switching operation is a dynamic power saving (DPS) operation, and when the first MLD operates based on the first mode, the first MLD operates in a lower capability mode (LCM) in which at least one of the operation bandwidth, the number of operation space streams, and the MCS is limited or only the reception of the initial control frame is possible. A method of operation in which, when the first MLD operates based on the second mode, the first MLD operates in HCM (higher capability mode).

14. In Paragraph 13, A method of operation in which the first MLD receives the initial control frame from the first link during the listening operation, wherein the initial control frame instructs the first MLD to switch to a DPS operation mode at the first link.

15. In Paragraph 14, The above first MLD is a method of operation in which, upon receiving the above initial control frame, it switches from the LCM to the HCM and operates.

16. In Paragraph 15, A method of operation in which the length of the padding field of the above initial control frame is determined by the longer value between the DPS switching delay when the DPS operation mode switches and the EMLSR switching delay when switching to the normal transmission / reception mode in the above listening operation.

17. In Paragraph 16, A method of operation in which, when the first MLD switches from the HCM to the LCM, the time at which the first MLD switches from the HCM to the LCM and the time at which the first MLD performs a listening operation on the first link are after the time at which the frame exchange procedure according to the HCM ends, a first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay.

18. In Paragraph 17, A method of operation in which the first value is determined as the longer value between the DPS switching delay and the EMLSR switching delay.

19. In Paragraph 1, The above-mentioned at least one mode switching operation is a method of operation including an NPCA operation, a DSO operation, and a DPS operation.

20. In Paragraph 19, A method of operation in which, when a mode is switched according to the above NPCA operation, the above DSO operation and the above DPS operation, the integrated switching delay is determined based on a first value.

21. In Paragraph 20, A method of operation in which the first value is determined as the longest value among the NPCA switching back delay, DSO switching back delay, DPS switching delay, and the EMLSR switching delay.

22. In Article 21, A method of operation in which, when the first mode switching operation is an NPCA operation and the first MLD switches the channel from the NPCA main channel of the first link to the main channel, the frame switching procedure in the NPCA main channel ends at a time prior to the first value from the time of end of the transmission opportunity of the OBSS.

23. In Article 21, A method of operation in which the first mode switching operation is a DSO operation, and when the first MLD is switched from the DSO subband of the first link to the main subband, the time at which the first MLD operates in the main subband of the first link and the time at which the first MLD performs a listening operation in the first link are after the time at which the value obtained by adding the first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay is obtained from the time at which the frame switching procedure of the DSO subband ends.

24. In Paragraph 21, A method of operation in which the first mode switching operation is a DPS operation, and when the first MLD switches from the HCM to the LCM, the time at which the first MLD switches from the HCM to the LCM and the time at which the first MLD performs a listening operation on the first link are after the time at which the frame switching procedure according to the HCM ends, a first value, aSIFSTime, aSlotTime, and aRxPHYStartDelay.

25. In Paragraph 1, A method of operation in which the first MLD is a non-AP MLD and the second MLD is an AP MLD.

26. In a first multi-link device (MLD) comprising a first station (STA) associated with a first link and a second STA associated with a second link in a wireless LAN system, At least one transceiver for transmitting and receiving signals; At least one processor controlling the above-mentioned at least one transmitting and receiving unit; and It includes a memory that stores instructions for the STA to perform a specific operation by the at least one processor, and The above specific operation is: The first MLD is connected to a second MLD that performs multi-link communication, wherein the first MLD is an MLD that simultaneously supports EMLSR (enhanced multi-link single radio) operation and at least one mode switching operation, and The first MLD receives an initial control frame from the second MLD, wherein the initial control frame includes a padding field, and Receive the above initial control frame and perform communication, The first MLD performs a listening operation based on a first mode, which is capable of receiving only the initial control frame on the multiple links, based on the first mode switching operation among the EMLSR operation and the at least one mode switching operation, and when the initial control frame is received during the listening operation, performs a transmit / receive operation based on a second mode on the link where the initial control frame was received.

Images