Method and apparatus for performing non-primary channel access operation in complex hidden node environment of wireless LAN

Abstract

In a wireless LAN system, a first STA: detects transmission in a first OBSS and sets a first NAV during a time interval corresponding to the transmission in the first OBSS, the first OBSS being an OBSS detected by both the first STA and a second STA, and the first NAV being also set to the second STA by the transmission in the first OBSS; switches an operating channel from a primary channel to an NPCA channel on the basis of the first NAV, the operating channel of the second STA being also switched from the primary channel to the NPCA channel on the basis of the first NAV; and performs communication on the NPCA channel, the first STA being capable of exchanging NAV information through frame exchanges with a third STA operating on the NPCA channel by a second NAV set by a second OBSS.

Description

Method and device for performing side-channel access operations in a complex hidden node environment of a wireless LAN

[0001] The present disclosure relates to a method and apparatus for performing a non-primary channel access operation in a complex hidden node environment of a wireless local area network (WLAN). Additionally, the present disclosure relates to a method and apparatus for performing a non-primary channel access (NPCA) operation in a complex hidden node environment of a wireless LAN. Furthermore, the present disclosure relates to a method and apparatus for initiating an NPCA operation in a complex hidden node environment of a wireless LAN and determining a transmission target terminal on a non-channel.

[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 called TXOPs (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) operations, which use a channel other than the primary channel when the primary channel is occupied, and dynamic subchannel operation (DSO).

[0006] In a wireless LAN network, one can consider cases where the transmission segments by other wireless LAN networks are hidden nodes, and in a communication segment of a wireless LAN network, only a portion of the network may be detected. Here, the segments for performing side-channel access operations may differ for each communication terminal constituting the wireless LAN network, and the return and start times of the side-channel access operations may also differ. Consequently, side-channel access operations may fail or their efficiency may decrease; therefore, measures to address this are described below.

[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 performing a side-channel access operation in a complex hidden node environment of a wireless LAN.

[0010] The present disclosure relates to a method and apparatus for initiating NPCA operation in a complex hidden node environment of a wireless LAN.

[0011] The present disclosure relates to a method and apparatus for determining a transmission target terminal in a sub-channel of a wireless LAN.

[0012] The present disclosure relates to a method and apparatus for performing NPCA operations in a complex hidden node environment of a wireless LAN.

[0013] The present disclosure relates to a method and apparatus for performing NPCA operations by considering the NPCA start time and return time in a complex hidden node environment of a wireless LAN.

[0014] 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.

[0015]

[0016] According to one embodiment of the present specification, a method of operation of a first station (STA) in a wireless LAN system comprises the steps of: the first STA detecting a transmission within a first overlapping basic service set (OBSS) and setting a first time interval corresponding to the transmission within the first OBSS, wherein the first OBSS is an OBSS commonly detected by the first STA and the second STA, and the first time interval is also set in the second STA by the transmission within the first OBSS, and the first STA switching the operating channel from a primary channel to a non-primary channel access (NPCA) channel based on the first time interval, wherein the operating channel of the second STA is also switched from a primary channel to an NPCA channel based on the first time interval, and the first STA performing communication in the NPCA channel, wherein the first STA can exchange time interval information through frame exchange with a third STA operating in the NPCA channel based on a second time interval set by the second OBSS.

[0017] Additionally, according to one embodiment of the present specification, a station (STA) 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 a non-AP STA to perform a specific operation by the at least one processor, wherein the specific operation is: the first STA detects a transmission within a first overlapping basic service set (OBSS) and sets a first network allocation vector (NAV) during a time interval corresponding to the transmission within the first OBSS, wherein the first OBSS is an OBSS commonly detected by the first STA and the second STA, and the first NAV is also set in the second STA by the transmission within the first OBSS, and the first STA switches the operating channel from a primary channel to a non-primary channel access (NPCA) channel based on the first NAV, and the operating channel of the second STA is also switched from a primary channel to an NPCA channel based on the first NAV, and the first STA in the NPCA channel Communication is performed, and the first STA can exchange NAV information through frame exchange with the third STA operating in the NPCA channel by the second NAV set by the second OBSS.

[0018] In addition, the following points may apply in common.

[0019] According to one embodiment of the present specification, the time at which the first STA returns to the main channel after operating in the NPCA channel and the time at which the third STA returns to the main channel after operating in the NPCA channel can be determined to be the same.

[0020] Additionally, according to one embodiment of the present specification, the first STA returns to the main channel from the NPCA channel when the first time interval expires, and the operation channel of the third STA may also be switched from the NPCA channel to the main channel together with the first STA at the time when the first time interval expires.

[0021] Additionally, according to one embodiment of the present specification, if the expiration time of the first time interval is earlier than the expiration time of the second time interval, the first STA may perform frame transmission to the third STA from the expiration time of the first time interval to the expiration time of the second time interval, but frame transmission by the third STA may not be performed from the expiration time of the first time interval to the expiration time of the second time interval.

[0022] In addition, according to one embodiment of the present specification, a media synchronization-related timer may be set in the third STA from the time of expiration of the first time interval to the time of expiration of the second time interval.

[0023] Additionally, according to one embodiment of the present specification, at the time of expiration of the first time interval, the third time interval of the third STA is released, and the first STA can perform at least one of frame transmission and reception with the third STA on the main channel from the time of expiration of the first time interval.

[0024] Additionally, according to one embodiment of the present specification, if the expiration time of the first time interval is later than the expiration time of the second time interval, the first STA operates on the NPCA main channel at the expiration time of the second time interval, and the operation channel of the third STA may be switched from the NPCA main channel to the main channel at the expiration time of the second time interval.

[0025] In addition, according to one embodiment of the present specification, the length of a transmit opportunity (TXOP) set by the first STA and the third STA in the NPCA main channel can be adjusted based on the expiration time of the second time interval.

[0026] Additionally, according to one embodiment of the present specification, the length of the TXOP may be adjusted to end at a time prior to the operation channel switching delay of the third STA from the time of expiration of the second time interval.

[0027] In addition, according to one embodiment of the present specification, communication in the main channel by the third STA may be stopped from the time of expiration of the second time interval until the first time interval expires and the first STA switches the operating channel from the NPCA main channel to the main channel.

[0028] Additionally, according to one embodiment of the present specification, if the first time interval expiration time is later than the second time interval expiration time, the length of the transmit opportunity (TXOP) set by the first STA and the third STA in the NPCA main channel is adjusted based on the first time interval expiration time, and the first STA and the third STA can switch the operating channel from the NPCA main channel to the main channel at the first time interval expiration time.

[0029] In addition, according to one embodiment of the present specification, a media synchronization-related timer may be set in the third STA from the time the operating channel is switched from the NPCA main channel to the main channel.

[0030] Additionally, according to one embodiment of the present specification, the first STA receives an initial control frame (ICF) from the third STA in an NPCA channel and transmits an initial control response (ICR) in response to the ICF, wherein the ICF includes second time interval information set in the third STA and the ICR includes first time interval information set in the first STA.

[0031] Additionally, according to one embodiment of the present specification, the first STA transmits an ICF to the third STA in an NPCA channel and receives an ICR in response to the ICF, wherein the ICF includes first time interval information set in the first STA and the ICR includes second time interval information set in the third STA.

[0032] Additionally, according to one embodiment of the present specification, the first time interval and the second time interval may be time intervals corresponding to the NAV (network allocation vector).

[0033] Additionally, according to one embodiment of the present specification, the first STA may transmit a first frame containing at least one OBSS information detected by the first STA.

[0034] Additionally, according to one embodiment of the present specification, the first STA transmits a first frame containing at least one OBSS information detected by the first STA to at least one STA including the second STA, and can receive OBSS information commonly detected by each of the at least one STA based on at least one OBSS information detected by the first STA from each of the at least one STA including the second STA.

[0035] Additionally, according to one embodiment of the present specification, OBSS information commonly detected at each of at least one STA may be transmitted to the first STA through at least one of an uplink frame transmitted to the first STA and a response frame to a frame transmitted by the first STA.

[0036] In addition, according to one embodiment of the present specification, the first STA may support NPCA operation based on OBSS information commonly detected in each of at least one STA.

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

[0038]

[0039] According to the present disclosure, a method for performing a side-channel access operation in a complex hidden node environment of a wireless LAN can be provided.

[0040] According to the present disclosure, a method for initiating NPCA operation in a complex hidden node environment of a wireless LAN can be provided.

[0041] According to the present disclosure, a method for determining a transmission target terminal in a sub-channel of a wireless LAN can be provided.

[0042] According to the present disclosure, a method for performing NPCA operations in a complex hidden node environment of a wireless LAN can be provided.

[0043] According to the present disclosure, a method for performing NPCA operations can be provided by considering the NPCA start time and return time in a complex hidden node situation of a wireless LAN.

[0044] 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.

[0045] 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.

[0046]

[0047] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0048] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0049] FIGS. 3a and 3b are drawings showing a wireless LAN network configuration for explaining a wireless LAN subchannel access method applied to the present disclosure.

[0050] FIG. 4 is a diagram illustrating a side-channel access method in a complex hidden node environment to which the present disclosure applies.

[0051] FIGS. 5a to 5c are drawings illustrating a side-channel access method in a complex hidden node environment to which the present disclosure applies.

[0052] FIGS. 6a and 6b are drawings illustrating a side-channel access method in a complex hidden node environment to which the present disclosure applies.

[0053] FIG. 7 is a diagram showing a network configuration applicable to the present disclosure.

[0054] FIGS. 8a and 8b are drawings illustrating a wireless LAN sub-channel access operation method and a problem occurring during sub-channel access operation applicable to the present disclosure.

[0055] FIG. 9 is a diagram showing a complex hidden node situation in a wireless LAN network to which the present disclosure applies.

[0056] FIG. 10 is a diagram illustrating a method for initiating a sub-channel access operation in a complex hidden node situation to which the present disclosure applies.

[0057] FIG. 11 is a diagram illustrating a method for initiating a sub-channel access operation in a complex hidden node situation to which the present disclosure applies.

[0058] FIG. 12 is a diagram illustrating a method for initiating a sub-channel access operation in a complex hidden node situation to which the present disclosure applies.

[0059] FIG. 13 is a flowchart showing the operation of a STA in a wireless LAN to which the present disclosure applies.

[0060]

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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."

[0068] 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.

[0069] 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).

[0070] 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).

[0071] 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).

[0072] 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.

[0073] 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.

[0074] In a wireless LAN network, wireless LAN terminals can support NPCA operations. To perform NPCA operations, the transmission paths of other wireless LAN networks configured by other wireless LAN terminals must be identified. Here, if multiple different wireless LAN networks exist, the transmission paths may differ for each different wireless LAN network. Furthermore, since the transmission paths of multiple different wireless LAN networks may be hidden nodes, only a portion of the communication path of a wireless LAN network may be detected. Therefore, when performing NPCA operations, the NPCA execution path may differ for each wireless LAN terminal configuring the wireless LAN network, and the return and start times of the side-channel access operation may differ. As described above, the side-channel access operation may fail and the efficiency of the side-channel access operation may decrease, so an operation method that takes this into account may be required.

[0075] Furthermore, while the AP can initiate side-channel access operations, the communication status of other wireless LAN networks received by the AP and the communication status of wireless LAN terminals connected to the AP may differ due to hidden nodes. Therefore, while the AP is operating on the side channel, wireless LAN terminals may operate on the main channel, potentially leading to data communication failure. Consequently, the efficiency of the wireless LAN network may decrease when using side-channel access operations, and operations taking this into account may be required.

[0076] FIGS. 3a and 3b are drawings showing a wireless LAN network configuration for explaining a wireless LAN subchannel access method applied to the present disclosure.

[0077] Referring to FIG. 3a, a wireless LAN network may be composed of two or more BSSs. Each BSS may consist 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 (frequency) or share all or part of the operating channel. Additionally, the communication ranges of each BSS 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 the aforementioned at least one other BSS. Alternatively, the aforementioned one BSS may not be able to receive data transmitted by the at least one other BSS, but the data transmission by the at least one other BSS may occupy a portion of the total bandwidth in which the one BSS operates. Furthermore, the data transmission performed by the aforementioned one BSS may occupy a portion of the total bandwidth in which the at least one other BSS operates.

[0078] In the present disclosure, the above-described BSS is referred to as BSS, and the above-described at least one BSS 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 at least one of the AP and STA constituting the BSS. For example, the detection of a frame transmission by the BSS by the BSS may mean that at least one of the AP and non-AP STA of the BSS detects a frame transmitted by at least one of the AP and non-AP STA of the OBSS.

[0079] Additionally, the fact that the BSS performs channel switching may mean that at least one of the AP and STA constituting the BSS performs channel switching. When the BSS detects communication from the OBSS (e.g., detects communication and sets the basic NAV (network allocation vector)), it may not operate on the primary channel during the OBSS communication period (i.e., the basic NAV period set based on the OBSS communication). The BSS may have a pre-configured secondary channel, a non-primary channel access (NPCA) primary channel. The BSS may switch its operating channel to the NPCA channel during the OBSS communication period to perform operations (e.g., channel access operation, frame transmission / reception operation), and the BSS may operate on the primary channel again when the OBSS communication period ends. The operation in which the BSS switches the operating channel to the NPCA channel during the communication period of the OBSS to perform an operation (i.e., wireless communication operations such as performing frame transmission and reception, performing channel access operations, etc.) and then operates back on the main channel when the communication period of the OBSS ends may be referred to as an NPCA operation, but it may not be limited to that name. That is, operations performed identically or similarly to those described above may be referred to by other names. For the convenience of explanation, the following description refers to it as an NPCA operation.

[0080] Meanwhile, referring to FIG. 3b, an OBSS can be configured for the BSS consisting of AP 1 of the BSS, a non-AP STA 1 connected to AP 1, and AP 1 and non-AP STA 1. Here, multiple OBSSs may exist. For example, non-AP STA 1 and AP 1 can detect communication of OBSS 1, but cannot detect communication of OBSS 2 and OBSS 3. Also, non-AP STA 2 can detect communication of OBSS 2, but cannot detect communication of OBSS 1 and OBSS 3. non-AP STA 3 can detect communication of OBSS 3, but cannot detect communication of OBSS 1 and OBSS 2. That is, the communication intervals of the OBSSs may differ from one another, and accordingly, the OBSS detected by each wireless LAN terminal within the BSS may differ. However, this is for the convenience of explanation only and may not be limited to the situations described above. That is, it is not intended to be limited to situations where each of the APs and STAs detects only a single OBSS.

[0081] AP 1 and non-AP STA 1 can set a network allocation vector (NAV) based on the communication interval of OBSS 1, and non-AP STA 2 can set a NAV based on the communication interval of OBSS 2. Additionally, non-AP STA 3 can set a NAV based on the communication interval of OBSS 3. Here, the NAV set by the communication of OBSS may be a basic NAV. At least one of the start time and end time of the NAV for each of AP 1, non-AP STA 1, non-AP STA 2, and non-AP STA 3 may be different. Therefore, based on NPCA operation, the start time (i.e., the time of operation on the side channel) and end time (i.e., the time of operation on the main channel) of the side channel access operation of AP 1, non-AP STA 1, non-AP STA 2, and non-AP STA 3 may differ, and a method to efficiently perform side channel access operation in an environment where multiple OBSSs exist may be required. For example, to increase the efficiency of NPCA operation, a method may be needed to perform NPCA operation even in a hidden node environment where some of the communication nodes included in the BSS (i.e., AP 1, non-AP STA 1, non-AP STA 2, non-AP STA 3) fail to detect communication from some of the multiple OBSSs. The following describes various methods for NPCA operation in complex hidden node environments to solve the aforementioned problems.

[0082] Meanwhile, the aforementioned default NAV set by the AP and STA may be set in correspondence with the communication interval of the OBSS detected by the AP and STA (the communication interval of the OBSS identified through at least one of MAC layer information or PHY layer information). The AP and STA setting the aforementioned default NAV may mean identifying the communication interval of the OBSS detected by the AP and STA. That is, the NAV setting can be interpreted as the identification of the OBSS communication interval.

[0083] Based on the foregoing, performing NPCA operations based on the default NAV set by the APs and STAs in the present disclosure (i.e., methods including switching the operation channel to the NPCA main channel when the NAV is set, performing channel access operations and / or frame transmission and reception on the NPCA main channel, and switching the operation channel back to the main channel at the end of the NAV) may mean performing NPCA operations in the communication interval of each OBSS identified by the APs and STAs. Accordingly, performing NPCA operations based on the default NAV set by the APs and STAs should be interpreted as performing NPCA operations based on the communication interval of the OBSS identified by the APs and STAs.

[0084] In addition, the exchange of basic NAV information or the exchange of NAV information set by the APs and STAs in this disclosure should be interpreted as the exchange of communication segments of the OBSS identified by each AP and STA.

[0085] FIG. 4 is a diagram illustrating a side-channel access method in a complex hidden node environment to which the present disclosure applies.

[0086] Referring to FIG. 4, in the same manner as FIG. 3b, AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can operate in the BSS. AP 1 (310) and non-AP STA 1 (320) can detect only the communication interval of OBSS 1 (e.g., TXOP (transmit opportunity), which is a time interval during which multiple frames can be transmitted), and non-AP STA 2 (330) can detect only the communication interval of OBSS 2. Additionally, non-AP STA 3 (340) can detect only the communication interval of OBSS 3, as described above. The above description may be for cases where AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) each detect a communication section of a different OBSS, and is not intended to be limited to cases where AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) detect only one OBSS. AP 1 (310) and non-AP STA 1 (320) can decode a frame of the communication segment of OBSS 1 in the primary channel to detect BSS information (e.g., BSS color or whether the MAC (medium access control) address of the AP among the transmitting and receiving targets matches the current AP's MAC address (or BSSID (basic service set identifier))) and TXOP information (e.g., length of the preamble or TXOP information included in the PPDU (physical layer protocol data unit) or duration information of the MAC header). Based on the detection results described above, AP 1 (310) and non-AP STA 1 (320) can recognize that transmission is being performed in OBSS.When a TXOP for OBSS transmission can be detected, AP 1 (310) and non-AP STA 1 (320) can set a basic NAV, which is a busy channel section, based on the communication section of OBSS 1. Here, the operation of acting as if the busy channel section has been CSed, without physically CSing the section where the actual channel is occupied based on the information contained in the frame, can be called Virtual CS. That is, AP 1 (310) and non-AP STA 1 (320) can set a basic NAV by Virtual CS based on the communication section of OBSS 1. After that, non-AP STA 2 (330) and non-AP STA 3 (340) can each detect the communication sections of OBSS 2 and OBSS 3. Each of the non-AP STA 2 (330) and non-AP STA 3 (340) can set a basic NAV according to the Virtual CS described above based on the communication interval of the detected OBSS 2 and OBSS 3.

[0087] Here, the start time of the communication period of OBSS 1 may be earlier than the start time of the communication period of OBSS 2 and OBSS 3. Also, the end time of the communication period of OBSS 1 may be earlier than the end time of the communication period of OBSS 2. Also, the end time of the communication period of OBSS 1 may be later than the end time of the communication period of OBSS 3. However, this is for convenience of explanation only and is not limited thereto. AP 1 (310) and non-AP STA 1 (320) can switch the operating channel from the primary channel to the NPCA primary channel when the basic NAV is set. AP 1 (310) and non-AP STA 1 (320) can perform a procedure to operate on the NPCA main channel at the time when the basic NAV is set (e.g., when the communication interval of OBSS 1 is identified by receiving the frame exchange of OBSS 1 or when the communication interval of OBSS 1 is identified based on the PHY preamble of OBSS 1). Here, when switching the operating channel to the NPCA main channel, time equal to the switching delay may be required. AP 1 (310) and non-AP STA 1 (320) can operate on the main channel again at the time the basic NAV ends. In the same way, non-AP STA 2 (330) and non-AP STA 3 (340) can each perform a procedure to operate on the NPCA main channel at the time when the basic NAV is set. Here, when switching the operating channel to the NPCA main channel, time equal to the switching delay may be required. In addition, non-AP STA 2 (330) and non-AP STA 3 (340) can each switch the operating channel back to the main channel at the end of the basic NAV. To switch from the NPCA main channel to the operating channel, a switching back delay may be required.For example, the switching back delay may be the same as the switching delay, but is not limited thereto. In the present disclosure, performing an NPCA operation based on the basic NAV set by AP 1 (310) and non-AP STA 1 (320) should be interpreted as performing an NPCA operation based on the communication interval of OBSS 1 identified by AP 1 (310) and non-AP STA 1 (320).

[0088] Meanwhile, AP 1 (310) and non-AP STA 1 (320) may operate on the NPCA main channel at the same time (or at a time when there is no problem for non-AP STA 1 (320) to receive a frame from AP 1 (310) or for AP 1 (310) to receive a frame from non-AP STA 1 (320), even if there is a slight difference). However, non-AP STA 2 (330) and non-AP STA 3 (340) may operate on the NPCA main channel later than when AP 1 (310) and non-AP STA 1 (320) operate on the NPCA main channel. Therefore, frames transmitted by AP 1 (310) or non-AP STA 1 (320) may not be received by non-AP STA 2 (330) and non-AP STA 3 (340) due to the difference in operating times. For example, AP 1 (310) or non-AP STA 1 (320) may transmit a frame while non-AP STA 2 (330) and non-AP STA 3 (340) have not yet started the operation channel switch to the NPCA main channel or are in the process of the operation channel switch. After AP 1 (310) starts the operation on the NPCA main channel, it may perform channel access operations (e.g., EDCA (enhanced distributed channel access) backoff operations, EDCA TXOP acquisition procedures) to transmit the frame to the STAs. However, AP 1 (310) may not be aware of which STA the frame should be transmitted to. Therefore, when AP 1 (310) performs frame transmission on the NPCA main channel, AP 1 (310) may be required to perform a procedure to check which STA exists (hereinafter referred to as the STA check procedure, but is not limited thereto).The STA verification procedure may be a procedure in which AP 1 (310) transmits a BSRP (BSR polling) trigger frame (401) requesting the transmission of a BSR (buffer status report) to be transmitted by the STAs, and receives a response (402) to this. A STA that responds to the BSRP frame (e.g., non-AP STA 1 (320)) may be in a state where it can communicate with AP 1 (310), and a STA that does not respond to the BSRP frame (e.g., non-AP STA 2 (330) and non-AP STA 3 (340)) may be in a state where it cannot communicate with AP 1 (310). As another example, the AP may transmit an NFRP (null data physical layer protocol data unit (NDP) feedback report poll)) trigger frame to check which STA responds. However, when the STA verification procedure is performed via the transmission of an NFRP trigger frame and a response to an NDP (null data physical layer protocol data unit), the STA information may not be included in the NDP, so it may not be possible to identify which STA it is. Therefore, the STA verification procedure through the transmission of an NFRP trigger frame and a response to an NDP may additionally be performed via the transmission of a BSRP trigger frame and a response to a BSR, but it may not be limited to this. The STA verification procedure may be diverse, in addition to the method of utilizing at least one of the BSRP trigger frame and the NFRP trigger frame. That is, the STA verification procedure is not limited to the method described above, and various procedures in which AP 1 (310) sends a request to verify which STAs are capable of communication and transmits a frame verifying the response to this can serve as the STA verification procedure, and it is not limited to a specific form.

[0089] At least one of the BSRP trigger frame and the NFRP trigger frame may include NAV information (i.e., time information when the STA is operating on the NPCA main channel) in the main channel of AP 1 (310). The NAV information (Basic NAV information) included in at least one of the BSRP trigger frame and the NFRP trigger frame may be information included in the MAC header duration of at least one of the BSRP trigger frame and the NFRP trigger frame. As a response frame, at least one of the BSR frame and the NDP response may include NAV information (i.e., time information when the STA is operating on the NPCA main channel) in the main channel of the STA. The NAV information (Basic NAV information) included in at least one of the BSR frame and the NDP may be MAC header duration information or message content of at least one of the BSR frame and the NDP. In cases where an NFRP trigger frame is transmitted and a BSRP trigger frame and a BSR response are transmitted after an NDP response, NAV information in the main channel included in the BSRP trigger frame transmission and the BSR response can be used.

[0090] AP 1 (310) can determine, as a result of the STA verification procedure of AP 1 (310), that non-AP STA 1 (320) is able to communicate with AP 1 (310) and for what time intervals NPCA operations can be performed. AP 1 (310) can transmit a downlink frame to non-AP STA 1 (320) or transmit a trigger frame requesting an uplink frame to non-AP STA 1 (320). non-AP STA 1 (320) can receive a downlink frame from AP 1 (310) or transmit an uplink frame to AP 1 (310) based on the uplink resources allocated by AP 1 (310) in the trigger frame. As another example, AP 1 (310) can also verify in the STA verification procedure that multiple STAs are able to communicate with AP 1 (310). Therefore, AP 1 (310) may transmit downlink frames and trigger frames to multiple STAs.

[0091] For example, AP 1 (310) may not transmit downlink frames or trigger frames to non-AP STA 2 (330) and non-AP STA 3 (340) that are unable to communicate. Here, if AP 1 (310) transmits the first frame of the TXOP to STAs that are unable to communicate, the TXOP of AP 1 (310) fails (e.g., frame transmission is impossible after the failure of the first frame of the TXOP), and AP 1 (310) may have to re-access the channel using increased CW[AC] and QSRC[AC] EDCA channel access parameters to transmit frames on the NPCA main channel. Consequently, time spent operating on the NPCA main channel is wasted, and NPCA operation efficiency may be reduced. However, if AP 1 (310) transmits frames to STAs that are capable of communicating after performing the STA verification procedure, the above-mentioned problem is resolved, and NPCA operation efficiency may be increased. As another example, AP 1 (310) can transmit a BSRP trigger frame again after performing a frame exchange with non-AP STA 1 (320), and additional frame exchange may be performed on the NPCA main channel for the STA that responded to the BSRP trigger frame of AP 1 (310).

[0092] FIGS. 5a to 5c are drawings illustrating a side-channel access method in a complex hidden node environment to which the present disclosure applies.

[0093] Referring to FIGS. 5a through 5c, AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can operate in the BSS, just as in FIG. 3b. AP 1 (310) and non-AP STA 1 (320) can detect only the communication interval of OBSS 1 (e.g., TXOP (transmit opportunity), which is a time interval during which multiple frames can be transmitted), and non-AP STA 2 (330) can detect only the communication interval of OBSS 2. Additionally, non-AP STA 3 (340) can detect only the communication interval of OBSS 3, as described above. The above-described situation is for cases where AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) each detect a communication section of a different OBSS, and is not intended to be limited to cases where AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) detect only a single OBSS.

[0094] AP 1 (310) and non-AP STA 1 (320) detect the communication interval of OBSS 1 in the main channel and can set a basic NAV for the interval occupied by Virtual CS (carrier sensing) based on the communication interval of OBSS 1. Subsequently, non-AP STA 2 (330) and non-AP STA 3 (340) each detect the communication intervals of OBSS 2 and OBSS 3 and can set a basic NAV based on the detected communication intervals of OBSS 2 and OBSS 3, respectively. Here, the start time of the communication interval of OBSS 1 may be earlier than the start time of the communication intervals of OBSS 2 and OBSS 3. The end time of the communication interval of OBSS 1 may be earlier than the end time of the communication interval of OBSS 2. On the other hand, the end time of the communication interval of OBSS 1 may be later than the end time of the communication interval of OBSS 3. AP 1 (310) and non-AP STA 1 (320) can switch the operating channel from the main channel to the NPCA main channel when the basic NAV is set. AP 1 (310) and non-AP STA 1 (320) can perform a procedure to operate on the NPCA main channel at the time when the basic NAV is set (e.g., when the communication interval of OBSS 1 is identified by receiving the frame exchange of OBSS 1 or when the communication interval of OBSS 1 is identified based on the PHY preamble of OBSS 1), and a switching delay may be required for the operating channel switching. AP 1 (310) and non-AP STA 1 (320) can operate on the main channel again at the time when the basic NAV ends. Likewise, non-AP STA 2 (330) and non-AP STA 3 (340) each also at the time when the basic NAV is set (e.g.A procedure to operate as the NPCA main channel can be performed at the point in time when the communication interval of OBSS 2 and OBSS 3 is identified by receiving the frame exchange of OBSS 2 and OBSS 3 or when the communication interval of OBSS 2 and OBSS 3 is identified based on the PHY preamble of OBSS 2 and OBSS 3, and a switching delay may be required for the operation channel switching. In addition, non-AP STA 2 (330) and non-AP STA 3 (340) can each switch the operation channel back to the main channel at the end of the basic NAV.

[0095] In the present disclosure, performing an NPCA operation based on a basic NAV or NAV set by AP 1 (310) and non-AP STA 1 (320) should be interpreted as performing an NPCA operation based on the communication interval of OBSS 1 identified by AP 1 (310) and non-AP STA 1 (320). Likewise, performing an NPCA operation based on a basic NAV set by non-AP STA 2 (330) and non-AP STA 3 (340) should be interpreted as performing an NPCA operation based on the communication interval of OBSS 2 and OBSS 3 detected by each STA. In the present disclosure, APs (e.g., AP 1 (310)) and STAs (e.g., non-AP STA 2 (330), non-AP STA 3 (340)) may exchange frames containing NAV information. The NAV information of each AP and STA may be communication interval information of the OBSS identified by the AP and STA. Therefore, exchanging frames containing NAV information means that each AP and STA exchanges communication segment information of the OBSS identified by each other. Since the AP and STA must operate on the main channel again when the communication segment of the identified OBSS ends, the NAV information exchanged by the AP and STA indicates the time or segment of operation on the NPCA main channel of each AP and STA.

[0096] Meanwhile, non-AP STA 2 (330) may switch its operating channel to the NPCA main channel and operate. AP 1 (310) may already be operating on the NPCA main channel before the time when non-AP STA 2 (330) operates on the NPCA main channel. That is, AP 1 (310) may be able to receive frames transmitted by non-AP STA 2 (330). Alternatively, if AP 1 (310) transmits a frame to non-AP STA 2 (330) after the time when non-AP STA 2 (330) starts operating on the NPCA main channel, non-AP STA 2 (330) may be able to receive frames from AP 1 (310).

[0097] Additionally, when non-AP STA 2 (330) acquires a TXOP through a channel access operation (e.g., EDCA backoff procedure, EDCA TXOP acquisition procedure), the first frame that non-AP STA 2 (330) transmits from the TXOP to AP 1 (310) may be an initial control frame (ICF, 403). When AP 1 (310) receives the ICF (403) from non-AP STA 2 (330), it may transmit an initial control response (ICR, 404) (frame). The ICF (403) may contain NAV information on the main channel of non-AP STA 2 (330) (i.e., time information on when non-AP STA 2 (330) is operating on the NPCA main channel). NAV information (e.g., basic NAV information) included in ICF (403) may be MAC header duration information of ICF (403). ICR (404) may include main channel NAV information of AP 1 (310) (i.e., information on the time AP 1 (310) operates on the NPCA main channel). NAV information (e.g., basic NAV information) included in ICR (404) may be MAC header duration information of ICR (404). Through the exchange procedure of ICF (403) and ICR (404), AP 1 (310) and non-AP STA 2 (330) can each check the operating time on different NPCA main channels. As another example, in the TXOP of AP 1 (310), the first frame transmitted by AP 1 (310) to non-AP STA 2 (330) may be an ICF, and the frame in which non-AP STA 2 (330) responds to AP 1 (310) may be an ICR. Here, the ICF and ICR may each contain NAV information (e.g., basic NAV information) recognized by AP 1 (310) and non-AP STA 2 (330).Through the ICF and ICR exchange procedure, AP 1 (310) and non-AP STA 2 (330) can each check the operation time in different NPCA main channels.

[0098] Referring to FIG. 5a, non-AP STA 2 (330) can perform channel access operations (e.g., EDCA backoff operation, EDCA TXOP acquisition procedure). If the channel access operation is successful, non-AP STA 2 (330) can acquire a TXOP. non-AP STA 2 (330) can transmit an ICF (403) to AP 1 (310), and AP 1 (310) can transmit an ICR (404) to non-AP STA 2 (330). non-AP STA 2 (330) can determine from the ICR (404) the period during which AP 1 (310) is operating on the NPCA main channel. As another example, AP 1 (310) can transmit ICF to non-AP STA 2 (330) and non-AP STA 2 (330) can transmit ICR to AP 1 (310). That is, AP 1 (310) and non-AP STA 2 (330) can exchange time interval information operating on each other's NPCA main channels.

[0099] Here, non-AP STA 2 (330) can operate on the NPCA main channel in the same way as AP 1 (310) operates on the NPCA main channel. That is, the time when AP 1 (310) resumes operation on the main channel and the time when non-AP STA 2 (330) resumes operation on the main channel may be the same or similar. Since the basic NAV of the main channel of non-AP STA 2 (330) ends later than that of AP 1 (310), the basic NAV of non-AP STA 2 (330) may remain at the time non-AP STA 2 (330) resumes operation on the main channel. non-AP STA 2 (330) may not perform frame transmission due to the remaining basic NAV. However, since non-AP STA 2 (330) resumed operation on the main channel at the same or similar time as AP 1 (310) resumed operation on the main channel, it may be possible to receive frames from AP 1 (310). Although the default NAV is set, if non-AP STA 2 (330) receives a frame that requires an immediate response from AP 1 (310) (e.g., a data frame with the Ack Policy set to Normal ACK or Implicit BAR), it may send a response frame (e.g., BlockAck frame, Ack frame).

[0100] Referring to FIG. 5b, non-AP STA 2 (330) can perform channel access operations (e.g., EDCA backoff operation, EDCA TXOP acquisition procedure). If the channel access operation is successful, non-AP STA 2 (330) can acquire a TXOP. non-AP STA 2 (330) can transmit an ICF (403) to AP 1 (310), and AP 1 (310) can transmit an ICR (404) to non-AP STA 2 (330). non-AP STA 2 (330) can determine from the ICR (404) the period in which AP 1 (310) is operating on the NPCA main channel. As another example, AP 1 (310) can transmit an ICF to non-AP STA 2 (330), and non-AP STA 2 (330) can transmit an ICR to AP 1 (310). That is, AP 1 (310) and non-AP STA 2 (330) can exchange time interval information operating on each other's NPCA main channels.

[0101] Here, non-AP STA 2 (330) can operate on the NPCA main channel in the same way as AP 1 (310) operates on the NPCA main channel. That is, the time when AP 1 (310) resumes operation on the main channel and the time when non-AP STA 2 (330) resumes operation on the main channel may be the same or similar. Since the basic NAV of the main channel of non-AP STA 2 (330) ends later than that of AP 1 (310), the basic NAV of non-AP STA 2 (330) may remain at the time when non-AP STA 2 (330) resumes operation on the main channel. Additionally, non-AP STA 2 (330) may detect channel detection (e.g., Physical CS, Virtual CS) in the main channel as being occupied. Therefore, non-AP STA 2 (330) may need to reacquire medium synchronization on the main channel. That is, when non-AP STA 2 (330) switches to the main channel after NPCA operation based on time information (i.e., information on the main channel occupancy period of AP 1 (310)) while operating on the NPCA main channel of AP 1 (310), non-AP STA 2 (330) may start a MediumSyncDelay timer (or NAVSyncDelay timer) to obtain medium synchronization again at the time of operation on the main channel, even if the basic NAV period remains. Non-AP STA 2 (330) may be restricted from accessing the channel during the time the timer is applied. If the energy detected in the channel after accessing the channel during the time the timer is applied is below a certain threshold, non-AP STA 2 (330) may detect the medium as idle (i.e., detect the physical CS as idle) and perform a channel access operation, and only a frame transmission procedure starting with an RTS (request to send) frame may be possible.non-AP STA 2 (330) cannot perform frame transmission if the energy detected in the channel after non-AP STA 2 (330) accesses the channel exceeds a certain threshold during the timer application period. If non-AP STA 2 (330) correctly receives a frame within the MediumSyncDelay timer (e.g., successful decoding), the timer may expire. Once the MediumSyncDelay timer expires, non-AP STA 2 (330) can perform channel access without restriction.

[0102] Additionally, non-AP STA 2 (330) may be able to receive frames from AP 1 (310). Although non-AP STA 2 (330) has a default NAV set, if it receives a frame from AP 1 (310) that requires an immediate response (e.g., a data frame with an Ack Policy set to Normal ACK or Implicit BAR), it may send a response frame (e.g., BlockAck frame, Ack frame).

[0103] Referring to FIG. 5c, non-AP STA 2 (330) can perform channel access operations (e.g., EDCA backoff operation, EDCA TXOP acquisition procedure). If the channel access operation is successful, non-AP STA 2 (330) can acquire a TXOP. non-AP STA 2 (330) can transmit an ICF (403) to AP 1 (310), and AP 1 (310) can transmit an ICR (404) to non-AP STA 2 (330). non-AP STA 2 (330) can determine from the ICR (404) the period during which AP 1 (310) is operating on the NPCA main channel. As another example, AP 1 (310) can transmit an ICF to non-AP STA 2 (330), and non-AP STA 2 (330) can transmit an ICR to AP 1 (310). That is, AP 1 (310) and non-AP STA 2 (330) can exchange time interval information operating on each other's NPCA main channels.

[0104] Here, non-AP STA 2 (330) can operate on the NPCA main channel in the same way as AP 1 (310) operates on the NPCA main channel. That is, the time when AP 1 (310) resumes operation on the main channel and the time when non-AP STA 2 (330) resumes operation on the main channel may be the same or similar. Since the basic NAV of the main channel of non-AP STA 2 (330) ends later than that of AP 1 (310), the basic NAV of non-AP STA 2 (330) may remain at the time when non-AP STA 2 (330) resumes operation on the main channel. Additionally, non-AP STA 2 (330) can detect channel detection (e.g., Physical CS, Virtual CS) in the main channel as being occupied. However, non-AP STA 2 (330) operates on the main channel in accordance with the NAV of AP 1 (310), and since the NAV of AP 1 (310) has ended at the time when AP 1 (310) and non-AP STA 2 (330) are operating on the main channel, it can be determined that non-AP STA 2 (330) has not lost media access. In the above case, non-AP STA 2 (330) can release the remaining basic NAV. At the time when non-AP STA 2 (330) is operating on the main channel, it can perform a channel access operation to transmit a frame to AP 1 (310).

[0105] Additionally, non-AP STA 2 (330) may be able to receive frames from AP 1 (310). Although the non-AP STA 2 (330) has a default NAV set, if it receives a frame from AP 1 (310) that requires an immediate response (e.g., a data frame with an Ack Policy set to Normal ACK or Implicit BAR), it may send a response frame (e.g., BlockAck frame, Ack frame). As another example, since the non-AP STA 2 (330) terminates the default NAV after the time the non-AP STA 2 (330) operates as the main channel, it may perform channel access operations after the time the non-AP STA 2 (330) terminates the default NAV.

[0106] Additionally, as an example, referring to FIGS. 5a through 5c, if the difference between the end time of the basic NAV of the non-AP STA 2 (330) that ends later and the end time of the basic NAV of AP 1 (310) that ends earlier is less than a predetermined time (e.g., 72 µs, which is the expected transmission time of a BlockAck frame), the non-AP STA 2 (330) can operate on the main channel at the end time of the basic NAV of the non-AP STA 2 (330) without referring to the basic NAV of AP 1 (310). Through the above, the non-AP STA 2 (330) can prevent frame collisions caused by frame transmission after the channel access operation by operating a timer to obtain media synchronization again after performing the NPCA operation. Alternatively, the non-AP STA 2 (330) can be made to perform the NPCA operation without losing media synchronization.

[0107] FIGS. 6a and 6b are drawings illustrating a side-channel access method in a complex hidden node environment to which the present disclosure applies.

[0108] Referring to FIGS. 6a and 6b, AP 1 (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can operate in the BSS, just as in FIG. 3b. AP 1 (310) and non-AP STA 1 (320) can detect only the communication interval of OBSS 1 (e.g., TXOP (transmit opportunity), which is a time interval during which multiple frames can be transmitted), and non-AP STA 2 (330) can detect only the communication interval of OBSS 2. Additionally, non-AP STA 3 (340) can detect only the communication interval of OBSS 3, as described above.

[0109] AP 1 (310) and non-AP STA 1 (320) detect the communication interval of OBSS 1 in the main channel and can set a basic NAV for the interval occupied by Virtual CS (carrier sensing) based on the communication interval of OBSS 1. Subsequently, non-AP STA 2 (330) and non-AP STA 3 (340) each detect the communication intervals of OBSS 2 and OBSS 3 and can set a basic NAV based on the detected communication intervals of OBSS 2 and OBSS 3, respectively. Here, the start time of the communication interval of OBSS 1 may be earlier than the start time of the communication intervals of OBSS 2 and OBSS 3. The end time of the communication interval of OBSS 1 may be earlier than the end time of the communication interval of OBSS 2. On the other hand, the end time of the communication interval of OBSS 1 may be later than the end time of the communication interval of OBSS 3. AP 1 (310) and non-AP STA 1 (320) can switch the operating channel from the main channel to the NPCA main channel when the basic NAV is set. AP 1 (310) and non-AP STA 1 (320) can perform a procedure to operate on the NPCA main channel at the time when the basic NAV is set (e.g., when the communication interval of OBSS 1 is identified by receiving the frame exchange of OBSS 1 or when the communication interval of OBSS 1 is identified based on the PHY preamble of OBSS 1), and a switching delay may be required for the operating channel switching. AP 1 (310) and non-AP STA 1 (320) can operate on the main channel again at the time when the basic NAV ends. Each of non-AP STA 2 (330) and non-AP STA 3 (340) can also operate on the main channel at the time when the basic NAV is set (e.g.A procedure to operate as the NPCA main channel can be performed at the point in time when the communication interval of OBSS 2 and OBSS 3 is identified by receiving the frame exchange of OBSS 2 and OBSS 3 or when the communication interval of OBSS 2 and OBSS 3 is identified based on the PHY preamble of OBSS 2 and OBSS 3, and a switching delay may be required for the operation channel switching. Additionally, non-AP STA 2 (330) and non-AP STA 3 (340) can each switch the operation channel back to the main channel at the end of the basic NAV. In the present disclosure, performing an NPCA operation based on the basic NAV or NAV set by AP 1 (310) and non-AP STA 1 (320) should be interpreted as performing an NPCA operation based on the communication interval of OBSS 1 identified by AP 1 (310) and non-AP STA 1 (320). Likewise, performing NPCA operations based on the default NAV set by non-AP STA 2 (330) and non-AP STA 3 (340) should be interpreted as performing NPCA operations based on the communication intervals of OBSS 2 and OBSS 3 detected by each STA. In this disclosure, APs (e.g., AP 1 (310)) and STAs (e.g., non-AP STA 2 (330), non-AP STA 3 (340)) may exchange frames containing NAV information. The NAV information of each AP and STA may be communication interval information of the OBSS identified by the AP and STA. Therefore, exchanging frames containing NAV information means exchanging communication interval information of the OBSS identified by each AP and STA. Since the AP and STA must operate on the main channel again when the communication interval of the identified OBSS ends, the NAV information exchanged by the AP and STA indicates the time or interval of operation on the NPCA main channel of each AP and STA.

[0110] Referring to FIG. 6a, non-AP STA 3 (340) can perform channel access operations (e.g., EDCA backoff operation, EDCA TXOP acquisition procedure). If non-AP STA 3 (340) succeeds in the channel access operation, it can acquire a TXOP. non-AP STA 3 (340) can transmit an ICF (405) to AP 1 (310), and AP 1 (310) can transmit an ICR (406) to non-AP STA 3 (340). The ICF (405) transmitted by non-AP STA 3 (340) may contain default NAV information set by non-AP STA 3 (340) on the main channel. Additionally, the ICR (406) transmitted by AP 1 (310) may contain default NAV information set by AP 1 (310) on the main channel. non-AP STA 3 (340) can determine the time interval during which AP 1 (310) operates on the NPCA main channel from the basic NAV information contained in the ICR (406). As another example, AP 1 (310) can transmit an ICF to non-AP STA 3 (340), and non-AP STA 3 (340) can transmit an ICR to AP 1 (310). In the above case, the ICF transmitted by AP 1 (310) contains the basic NAV information set by AP 1 (310) on the main channel. Additionally, the ICR transmitted by non-AP STA 3 (340) contains the basic NAV information set by non-AP STA 3 (340) on the main channel. That is, AP 1 (310) and non-AP STA 3 (340) can exchange information on the time interval during which they operate on the NPCA main channel.

[0111] Here, non-AP STA 3 (340) can operate on the NPCA main channel for the length of the default NAV set by non-AP STA 3 (340) on the main channel. That is, the time when non-AP STA 3 (340) resumes operation on the main channel may be earlier than the time when AP 1 (310) resumes operation on the main channel. When non-AP STA 3 (340) transmits a frame to AP 1 (310), non-AP STA 3 (340) can adjust the length of the TXOP so that it can switch channels to the main channel and operate at the time when the default NAV of non-AP STA 3 (340) ends. That is, the length of the TXOP can be adjusted so that the transmission can be terminated before the switching delay, which is the time for non-AP STA 3 (340) to switch from the NPCA main channel to the main channel, before the time when the default NAV ends. When AP 1 (310) transmits a frame to non-AP STA 3 (340), AP 1 (310) can adjust the length of the TXOP so that it can resume operation by switching the operation channel to the main channel at the end of the basic NAV of non-AP STA 3 (340). That is, the length of the TXOP can be adjusted so that the transmission can be terminated before the switching delay, which is the time for non-AP STA 3 (340) to switch the operation channel from the NPCA main channel to the main channel before the end of the basic NAV.

[0112] As a method to adjust the length of the TXOP, one can consider adjusting the TXOP during the ICF and ICR switching phases and adjusting the TXOP when transmitting the data frame. The first method, adjusting the TXOP during the ICF and ICR switching phases, may be to set the TXOP to match the short base NAV interval. When AP 1 (310) transmits an ICR as a response to the ICF transmitted by non-AP STA 3 (340), the duration of the ICR (i.e., the value of the duration field in the MAC header of the ICR) may be set to match the interval of non-AP STA 3 (340), which has a shorter base NAV of the main channel, and transmitted. Setting it to match the interval of non-AP STA 3 (340) may mean setting it to match the interval that can operate on the NPCA main channel, taking into account the switching delay. When expressing basic NAV information as MAC header duration values, ICR cannot mean the basic NAV value set by AP 1 (310) in the main channel, so the basic NAV value may need to be indicated by a separate method.

[0113] As another example, when non-AP STA 3 (340) transmits an ICR that is a response to an ICF transmitted by AP 1 (310), non-AP STA 3 (340) can transmit the ICR by truncation, since the duration value of the ICF transmitted by AP 1 (310) exceeds the basic NAV interval set by non-AP STA 3 (340) on the main channel, and adjusting it to the interval that can operate on the NPCA main channel by taking into account the switching delay.

[0114] A second method for adjusting the length of the TXOP when transmitting a data frame is to receive basic NAV information from each main channel through ICF and ICR exchanges, and then transmit the data frame by setting a duration value in the MAC header of the data frame so that the exchange between the data frame and the response frame can be completed by matching the shorter basic NAV interval when transmitting the data frame.

[0115] AP 1 (310) can operate on the NPCA main channel at the time when non-AP STA 3 (340) is operating on the main channel. That is, the time when the basic NAV of AP 1 (310)'s main channel ends may be later than the time when the basic NAV of non-AP STA 3 (340) ends. Therefore, even if non-AP STA 3 (340) transmits a frame to AP 1 (310) on the main channel, AP 1 (310) cannot receive the frame from non-AP STA 3 (340). Since non-AP STA 3 (340) is aware of the time when AP 1 (310) is operating on the main channel, it may not transmit a frame to AP 1 (310) until that time. For example, non-AP STA 3 (340) may consider that there are no frames destined for AP 1 (310) in the transmission queue (e.g., EDCA queue) of non-AP STA 3 (340) until the time when AP 1 (310) is operating on the main channel. Here, non-AP STA 3 (340) may not perform a channel access operation or may repeat a channel access operation. After the time when AP 1 (310) is operating on the main channel, it may consider that frames destined for AP 1 (310) have been entered into the transmission queue again. After the time when AP 1 (310) is operating on the main channel, non-AP STA 3 (340) may perform a channel access operation again, and if the channel access operation is successful, it may transmit frames on the main channel to AP 1 (310).

[0116] Referring to FIG. 6b, non-AP STA 3 (340) can perform channel access operations (e.g., EDCA backoff operation, EDCA TXOP acquisition procedure). If non-AP STA 3 (340) succeeds in the channel access operation, it can acquire a TXOP. non-AP STA 3 (340) can transmit an ICF (405) to AP 1 (310), and AP 1 (310) can transmit an ICR (406) to non-AP STA 3 (340). The ICF (405) transmitted by non-AP STA 3 (340) may contain default NAV information set by non-AP STA 3 (340) on the main channel. Additionally, the ICR (406) transmitted by AP 1 (310) may contain default NAV information set by AP 1 (310) on the main channel. non-AP STA 3 (340) can determine the time interval during which AP 1 (310) operates on the NPCA main channel from the basic NAV information contained in the ICR (406). As another example, AP 1 (310) can transmit an ICF to non-AP STA 3 (340), and non-AP STA 3 (340) can transmit an ICR to AP 1 (310). In the above case, the ICF transmitted by AP 1 (310) contains basic NAV information set by AP 1 (310) on the main channel.

[0117] Here, non-AP STA 3 (340) can operate on the NPCA main channel in the same way as the operating period of AP 1 (310) on the NPCA main channel. That is, the time when AP 1 (310) resumes operation on the main channel and the time when non-AP STA 3 (340) resumes operation on the main channel may be the same or similar. Additionally, the length of the TXOP can be adjusted to match the longer of the basic NAVs set on the main channels of AP 1 (310) and non-AP STA 3 (340). Methods for adjusting the length of the TXOP include adjusting it during the ICF and ICR switching phases and adjusting it when transmitting the data frame. The first method, adjusting the TXOP during the ICF and ICR switching phases, may be a method of setting the TXOP to match the longer basic NAV period. When AP 1 (310) transmits an ICR, which is a response to an ICF transmitted by non-AP STA 3 (340), the duration can be set to match the longer interval of AP 1 (310)'s default NAV on the main channel. Setting it to match the interval of AP 1 (310) may mean setting it to match the interval that can operate on the NPCA main channel, taking into account the switching delay. When non-AP STA 3 (340) transmits an ICR, which is a response to an ICF transmitted by AP 1 (310), the duration value transmitted by AP 1 (310) is longer than the default NAV interval set by non-AP STA 3 (340) on the main channel, so this interval can be set to match the interval that can operate on the NPCA main channel, taking into account the switching delay. When the default NAV information is expressed as the duration value of the MAC header, the ICR cannot mean the default NAV value set by the non-AP STA 3 (340) in the main channel, so the default NAV value may need to be indicated by a separate method.

[0118] A second method for adjusting the length of the TXOP when transmitting a data frame is to receive basic NAV information from each main channel through ICF and ICR exchanges, and then transmit the data frame by setting a duration value in the MAC header of the data frame so that the exchange between the data frame and the response frame can be completed by matching the longer basic NAV interval when transmitting the data frame.

[0119] The time when non-AP STA 3 (340) resumes operation on the main channel may be after the time when the non-AP STA 3 (340)'s basic NAV has ended. That is, since non-AP STA 3 (340) has been operating on the NPCA main channel rather than the main channel for a certain period of time after the basic NAV has ended, it may not know the NAV setting status of the main channel. If the time when non-AP STA 3 (340) operates on the main channel is after a predetermined threshold time (e.g., 72us) from the time when the non-AP STA 3 (340)'s basic NAV has ended, non-AP STA 3 (340) may lose medium synchronization. Therefore, non-AP STA 3 (340) may need to regain medium synchronization on the main channel. The non-AP STA 3 (340) may start a MediumSyncDelay timer (or NAVSyncDelay timer), which is a timer for regaining media synchronization when operating again on the main channel. The non-AP STA 3 (340) may be restricted from accessing the channel during the time the timer is applied. If the energy detected in the channel after the non-AP STA 3 (340) accesses the channel during the time the timer is applied is below a certain threshold, the non-AP STA 3 (340) may detect the medium as idle (i.e., detect the physical CS as idle) and perform a channel access operation, and only a frame transmission procedure starting with an RTS frame may be possible. If the energy detected in the channel after the non-AP STA 3 (340) accesses the channel during the time the timer is applied is above a certain threshold, the non-AP STA 3 (340) cannot transmit a frame. The non-AP STA 3 (340) can have its timer expire if it receives a frame correctly within the MediumSyncDelay timer (e.g., successful decoding).The non-AP STA 3 (340) may not be restricted when accessing the channel when the MediumSyncDelay timer expires. Through the method described above, the non-AP STA 3 (340) may have a reduced chance of failing to transmit frames to AP 1 (310). Alternatively, the non-AP STA 3 (340) may activate a timer to obtain medium synchronization again after performing the NPCA operation, thereby preventing frame collisions caused by frame transmission after the channel access operation.

[0120] FIG. 7 is a diagram showing a network configuration applicable to the present disclosure. In addition, FIG. 8a and FIG. 8b are diagrams showing a wireless LAN sub-channel access operation method applicable to the present disclosure and a problem occurring during sub-channel access operation.

[0121] Referring to FIGS. 7, 8a, and 8b, AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) may operate in a wireless LAN network. AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) may have a predetermined main channel and an NPCA main channel. The main channel may be a channel including the main 20 MHz channel of the BSS (basic service set) configured by AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530). The main 20 MHz channel may be a channel that must be occupied by all communications of BSS 1. All frame transmission and reception of BSS 1 may be performed by occupying the main 20 MHz channel unless the above-described NPCA operation is performed. The NPCA main channel is a channel configured within the BSS formed by AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530), and may be a predetermined channel set based on a 20 MHz channel different from the main 20 MHz channel included in the main channel described above. That is, the NPCA main channel may have a 20 MHz channel different from the main channel, and this may be the NPCA main 20 MHz channel. In the following, the BSS formed by AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) is referred to as BSS 1, but is not limited to this name. Here, there may be an OBSS as another BSS that occupies the main 20 MHz channel among the main channels of BSS 1 (i.e., occupies the main channel of BSS 1).

[0122] Referring to FIG. 8a, NPCA operation may be initiated when control frame exchange is performed based on the network configuration described above. AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) (i.e., APs and STAs of BSS 1) may switch their operating channels to the NPCA main channel and operate when the main channel is occupied by another BSS. The other BSS may be a BSS configured by AP X and STA X. That is, when the main channel is occupied by AP X or STA X, AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) may operate on the NPCA main channel and perform channel access operations (e.g., EDCA (enhanced distributed channel access) backoff operations and EDCA TXOP (transmit opportunity) acquisition procedures) on the NPCA main 20 MHz channel. Here, the time during which AP 1 (510) and STAs of BSS 1 can operate on the NPCA main channel may be the time corresponding to the interval during which OBSS communicates on the main channel (i.e., the TXOP interval or the interval during which the basic NAV is set). Specifically, STAs and AP 1 (510) of BSS 1 may receive a control frame of OBSS (e.g., a PPDU (physical layer protocol data unit) containing a control frame) and an initial response frame (e.g., a PPDU containing an initial response frame) which is a response frame to the control frame. Here, if the condition of [NPCA switching condition - control frame] below is satisfied, the operating channel may be switched to the NPCA main channel and operated.

[0123] [NPCA Transition Condition - Control Frame]

[0124] - When receiving a control frame and an initial response frame for the control frame, all of the following conditions must be satisfied

[0125] ■ Received PPDU determined to be inter-BSS PPDU

[0126] ■ The length of the TXOP identified from the duration field of the MAC header of the received frame is greater than the NPCA minimum duration

[0127] The length of the TXOP can be referred to as the 'communication interval of the OBSS'.

[0128] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA main channel

[0129]

[0130] [NPCA Switching Condition - Control Frame] If the condition is satisfied, the APs and STAs of BSS 1 may switch their operating channels to the NPCA main channel and operate. The time required to change the operating time to the NPCA main channel may take time Ts. The period during which the AP 1 (510) and STAs of BSS 1 operate in the NPCA main channel may be the 'communication period of OBSS' of [NPCA Switching Condition]. The APs and STAs of BSS 1 may need to operate back on the main channel when the communication period of OBSS ends. The switching time required for the APs and STAs of BSS 1 to switch back from the NPCA main channel to the main channel may be Ts'. Ts and Ts' may be values ​​mutually negotiated by the APs and STAs supporting NPCA operation during the NPCA negotiation process, and Ts and Ts' may be the same time. The APs and STAs of BSS 1 may need to terminate transmission before time Ts' from the end of the communication period of OBSS.

[0131] Referring to FIG. 8b, NPCA operation may be initiated when at least one of HE frames, EHT frames, and UHR frames is exchanged based on the network configuration. AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) (i.e., APs and STAs of BSS 1) may switch their operating channels to the NPCA main channel and operate when the main channel is occupied by another BSS. The other BSS may be a BSS configured by AP X and STA X. That is, when the main channel is occupied by AP X or STA X, AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) may operate on the NPCA main channel and perform channel access operations (e.g., EDCA (enhanced distributed channel access) backoff operations and EDCA TXOP (transmit opportunity) acquisition procedures) on the NPCA main 20 MHz channel. Here, the time during which the APs and STAs of BSS 1 can operate on the NPCA main channel may be the time corresponding to the period during which the OBSS communicates on the main channel (i.e., the TXOP period or the period during which Basic NAV is set).

[0132] Specifically, the STA and AP of BSS 1 can receive frames of OBSS (e.g., PPDU (physical layer protocol data unit)). Here, if the received PPDU satisfies the conditions of the following [NPCA switching condition - control frame], the operating channel can be switched to the NPCA main channel and operated.

[0133]

[0134] [NPCA Transition Conditions - HE Frame]

[0135] - The received PPDU is an HE / EHT / UHR PPDU and satisfies all of the following conditions

[0136] ■ PPDU is determined to be an inter-BSS PPDU

[0137] ■ The length of the PPDU is greater than the NPCA minimum duration

[0138] ◆ The time length of the PPDU can be considered the 'communication interval of the OBSS'

[0139] ◆ The time length of the above PPDU may be one of the following.

[0140] ● 1. PPDU transmission time length identified from the PPDU preamble

[0141] ■ Transmission time length of the PPDU identified from the value of the LENGTH field included in the L_SIG of the preamble

[0142] ◆ RXTIME time calculated from the value of the LENGTH field

[0143] ◆ ((LENGTH + 3) / 3) * 4 + 20 + SignalExtension (us)

[0144] ● 2. The length of the TXOP indicated by the value of the TXOP field included in the HE-SIG or U-SIG of the PPDU preamble

[0145] ■ The value of the TXOP field can be set to the TXOP_DURATION value of the RXVECTOR obtained from the received frame.

[0146] ● 3. Other value(s) for the transmission length of OBSS found in the PPDU preamble

[0147] ● 4. The longest value among 1. to 3.

[0148] ● 5. Sum of 1. and 2.

[0149] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA main channel

[0150]

[0151] [NPCA Switching Condition - HE Frame] If the condition is satisfied, the APs and STAs of BSS 1 may switch their operating channels to the NPCA main channel and operate. The time required to change the operating time to the NPCA main channel may take time Ts. The period during which the APs and STAs of BSS 1 operate on the NPCA main channel may be the 'OBSS communication period' of the [NPCA Switching Condition - HE Frame]. The APs and STAs of BSS 1 may need to operate on the main channel again when the OBSS communication period ends. The switching time required for the APs and STAs of BSS 1 to switch back from the NPCA main channel to the main channel may require Ts'. The APs and STAs of BSS 1 may need to terminate transmission before time Ts' from the end of the OBSS communication period.

[0152] Referring to FIGS. 8a and 8b, AP 1 (510) of BSS 1 can transmit a frame instructing STAs connected to AP 1 (510) to perform NPCA operations. The UHR operation element of the management frame (e.g., beacon frame, probe response frame) transmitted by AP 1 (510) may include an indicator indicating whether NPCA is used. The NPCA operation information field or NPCA parameter field included in the UHR operation element, or the NPCA operation information field or NPCA parameter field included separately in the management frame of AP 1 (510), may indicate the NPCA main channel, the NPCA switching delay of AP 1 (510), and the NPCA switching back delay.

[0153] Some of the conditions of the aforementioned [NPCA transition condition - control frame] and [NPCA transition condition - HE frame] may be modified.

[0154] FIG. 9 is a diagram illustrating a composite hidden node situation in a wireless LAN network to which the present disclosure applies. Referring to FIG. 9, the AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) of the BSS can support the NPCA operation described above in FIG. 8a and FIG. 8b. Here, an OBSS can be configured for the AP 1 (510) of the BSS and the non-AP STA 1 (520) connected to the AP 1 (510). Additionally, an OBSS can be configured for the AP 1 (510) of the BSS and the non-AP STA 2 (530) connected to the AP 1 (510). That is, there may be multiple OBSSs. Referring to FIG. 9, the AP 1 (510) can detect communication from OBSS 1 and OBSS 2, but cannot detect communication from OBSS 3. Additionally, non-AP STA 1 (520) can detect communication from OBSS 1 but cannot detect communication from other OBSSs. Additionally, non-AP STA 2 (530) can detect communication from OBSS 2 but cannot detect communication from other OBSSs. Non-AP STA 3 (540) can detect communication from OBSS 3 but cannot detect communication from other OBSSs. However, this is for convenience of explanation only and may not be limited to such situations. That is, it is not intended to be limited to a situation where each AP and STA detects only a single OBSS.

[0155] As described above, if the configuration of the NPCA operation is not performed correctly in a complex hidden node situation, the NPCA operation may not be performed correctly. For example, when OBSS 3 performs communication, the AP operates on the main channel, but non-AP STA 3 (540) may operate on the NPCA main channel, and a frame transmission failure may occur. Also, when OBSS 1 performs communication, the AP and non-AP STA 1 (520) operate on the NPCA main channel, but non-AP STA 2 (530) may operate on the main channel. Therefore, if the AP performs frame transmission to non-AP STA 2 (530) from the NPCA main channel, the frame transmission may fail. Accordingly, a method for initiating the NPCA operation and a procedure for determining the frame transmission target during the NPCA operation may be required to resolve the above, and this is described below.

[0156] FIG. 10 is a diagram illustrating a method for initiating a sub-channel access operation in a complex hidden node situation to which the present disclosure applies.

[0157] Referring to FIG. 9, a wireless LAN network supporting the NPCA operation described in FIG. 8a and FIG. 8b can be considered. Additionally, the wireless LAN network may be composed of AP 1 (510) and non-AP STA 1 (520) to non-AP STA 3 (540) as described above in FIG. 9, and AP 1 (510) and non-AP STA 1 (520) to non-AP STA 3 (540) may operate in a composite hidden node environment. However, this is for convenience of explanation only and is not limited thereto.

[0158] AP 1 (510) and STAs connected to AP 1 (510) (e.g., non-AP STA 1 (520), non-AP STA 2 (530), non-AP STA 3 (540)) can recognize that OBSS(s) are operating on the main channel. Here, AP 1 (510) and STAs connected to AP 1 (510) can recognize that OBSS(s) are operating on the main channel by receiving frames transmitted from OBSS(s). AP 1 (510) may include information elements (e.g., reduced neighbor report (RNR) elements) indicating information about OBSS(s) in management frames (e.g., beacon frames, probe response frames) transmitted by AP 1 (510). For example, a management frame may include an RNR element, and the RNR element may include information about OBSS(s). Each piece of information regarding OBSSs may include the MAC address (e.g., BSS (basic service set) ID) of the OBSSs. The RNR element may indicate only the information regarding OBSSs that AP 1 (510) can detect. Alternatively, the information regarding OBSSs within the RNR element may further include an indicator indicating that it is an OBSS directly detected by AP 1 (510). Referring to FIG. 9 described above, the OBSSs detected by AP 1 (510) may be OBSS 1 and OBSS 2. AP 1 (510) may transmit a management frame containing the information regarding OBSS 1 and OBSS 2.

[0159] Meanwhile, non-AP STA 1 (520) to non-AP STA 3 (540) receive a management frame from AP 1 (510) and can recognize OBSSs (i.e., OBSS 1, OBSS 2) detected by AP 1 (510). Here, the common OBSS detected by non-AP STA 1 (520) and AP 1 (510) may be OBSS 1, and the common OBSS detected by non-AP STA 2 (530) and AP 1 (510) may be OBSS 2. There may be no OBSS detected in common by non-AP STA 3 (540) and AP 1 (510). If there is a common OBSS with AP 1 (510), the STAs may initiate NPCA operations. NPCA operation initiation can be performed by transmitting a frame to AP 1 (510) to initiate NPCA operation or by exchanging frames with AP 1 (510). The non-AP STA 1 (520) can transmit a frame (e.g., NPCA enablement frame, 601) to initiate NPCA operation. The frame (601) to initiate NPCA operation may include a UHR operation element and may indicate at least one of parameters for NPCA operation (e.g., NPCA switch delay - time Ts in FIG. 8a and 8b, NPCA Switch back delay - time Ts' in FIG. 8a and 8b, NPCA main channel information), but is not limited thereto. Additionally, the frame (601) to initiate NPCA operation may indicate information of the OBSS detected by the non-AP STA 1 (520) (e.g., information of OBSS 1). When AP 1 (510) receives a frame (601) for initiating an NPCA operation of non-AP STA 1 (520), it may transmit an NPCA operation initiation response frame (602). The response frame (602) may have the same format as the frame for initiating an NPCA operation of non-AP STA 1 (520).After that, AP 1 (510) can initiate NPCA operation. Meanwhile, non-AP STA 2 (530) can also initiate NPCA operation. non-AP STA 2 (530) can transmit a frame (e.g., NPCA enablement frame, 603) to initiate NPCA operation. The frame to initiate NPCA operation may include a UHR operation element and may indicate at least one of parameters for NPCA operation (e.g., NPCA switch delay - time Ts in FIG. 8a and 8b, NPCA Switch back delay - time Ts' in FIG. 8a and 8b, NPCA main channel information), but is not limited thereto. Additionally, the frame (603) to initiate NPCA operation may indicate information of OBSS detected by non-AP STA 2 (530) (e.g., information of OBSS 2). When AP 1 (510) receives a frame (603) for initiating NPCA operation of non-AP STA 2 (530), it can transmit an NPCA operation initiation response frame (604). AP 1 (510) can verify the OBSS information detected by non-AP STA 1 (520) and non-AP STA 2 (530) included in the NPCA operation initiation frames (601, 603) of non-AP STA 1 (520) and non-AP STA 2 (530). AP 1 (510) can verify that non-AP STA 1 (520) detects OBSS 1 in common with AP 1 (510), and that non-AP STA 2 (530) detects OBSS 2 in common with AP 1 (510). The aforementioned NPCA enablement frame may also be an UHR (ultra high reliability) OMP (operating mode and parameter) frame.

[0160] AP 1 (510) may transmit a management frame (e.g., beacon frame, probe response frame) after performing frame exchange to initiate NPCA operation with non-AP STA 1 (520) and non-AP STA 2 (530). The UHR operation element of the management frame may include an indicator indicating whether NPCA is used. The NPCA operation information field or NPCA parameter field included in the UHR operation element, or the NPCA operation information field or NPCA parameter field included separately in the management frame of AP 1 (510), may indicate the NPCA main channel, the NPCA switching delay of AP 1 (510), and the NPCA switching back delay. Since non-AP STA 3 (540) does not have an OBSS detected in common with AP 1 (510), it may not transmit an NPCA operation initiation frame to AP 1 (510). That is, non-AP STA 3 (540) may not perform NPCA operations.

[0161] Referring to FIG. 10, after non-AP STA 1 (520) and AP 1 (510) exchange a frame (601) for initiating an NPCA operation and an NPCA operation initiation response frame (602), AP 1 (510) may initiate an NPCA operation and immediately transmit a management frame (e.g., a management frame containing an indicator instructing the use of NPCA in the UHR Operation element). As another example, the NPCA operation initiation response frame transmitted by AP 1 (510) to non-AP STA 1 (520) may be a management frame containing an indicator instructing the use of NPCA. Here, other STAs other than non-AP STA 1 (520) (e.g., non-AP STA 2 (530), non-AP STA 3 (540)) may receive the management frame transmitted by AP 1 (510). Here, a non-AP STA 2 (530) that has a common OBSS with AP 1 (510) may implicitly initiate an NPCA operation. That is, the non-AP STA 2 (530) may initiate an NPCA operation without separate negotiation or frame exchange with AP 1 (510). The non-AP STA 3 (540) may not initiate an NPCA operation because it does not have a common OBSS with AP 1 (510).

[0162] AP 1 (510) may transmit a management frame containing information about OBSSs (e.g., OBSS 1, OBSS 2) detected by AP 1 (510) even after initiating the NPCA operation. STAs (non-AP STA 1 (520) to non-AP STA 3 (540)) may receive the management frame from AP 1 (510). For example, non-AP STA 3 (540) may detect at least one of OBSS 1 or OBSS 2 due to a change in location. In the above case, non-AP STA 3 (540) may perform the NPCA operation by exchanging a frame to initiate the NPCA operation and an NPCA operation initiation response frame with AP 1 (510). Alternatively, non-AP STA 3 (540) may initiate the NPCA operation without separate negotiation or frame exchange with AP 1 (510).

[0163] AP 1 (510) may transmit a management frame containing information about OBSSs (e.g., OBSS 1, OBSS 2) detected by AP 1 (510) even after initiating NPCA operation. Here, at least one STA among non-AP STA 1 (520) to non-AP STA 3 (540) may have changed location and may not be able to detect the OBSSs detected by AP 1 (510). For example, non-AP STA 2 (530) may no longer be able to detect OBSS 2. In the above case, non-AP STA 2 (530) may implicitly stop NPCA operation with AP 1 (510). Alternatively, non-AP STA 2 (530) may transmit to AP 1 (510) a frame to stop NPCA operation that has the same format as the frame to initiate NPCA operation but includes an indicator to stop NPCA operation. When AP 1 (510) receives the frame to stop NPCA operation from non-AP STA 2 (530), AP 1 (510) can confirm that non-AP STA 2 (530) does not switch the operation channel to the NPCA main channel. Although the above description is based on non-AP STA 2 (530), this is merely one example for convenience of explanation and is not limited thereto. For example, the same or similar method may be applied to non-AP STA 1 (520) and non-AP STA 3 (540).

[0164] FIG. 11 is a diagram illustrating a method for initiating a sub-channel access operation in a complex hidden node situation to which the present disclosure applies.

[0165] As described above in FIG. 10, after AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530) initiate NPCA operation, non-AP STA 1 (520) and non-AP STA 2 (530) can transmit OBSS information detected by non-AP STA 1 (520) and non-AP STA 2 (530) to AP 1 (510) in a transmitted frame. Specifically, non-AP STA 1 (520) and non-AP STA 2 (530) can recognize information of OBSSs detected by AP 1 (510) (e.g., OBSS 1, OBSS 2) included in the RNR element included in the last management frame transmitted by AP 1 (510) (e.g., beacon frame, probe response frame). At least one of non-AP STA 1 (520) and non-AP STA 2 (530) may compare the information of OBSSs detected by AP 1 (510) with the information of OBSSs detected by each of non-AP STA 1 (520) and non-AP STA 2 (530), and include common OBSS information that is commonly detected by STA (i.e., at least one of non-AP STA 1 (520) and non-AP STA 2 (530)) and AP 1 (510) in a frame transmitted to AP 1 (510), and the following method may be considered.

[0166] [Instruct common OBSS information to uplink frame]

[0167] Common OBSS information can be indicated using the MAC header of an uplink frame (605) transmitted by a STA (i.e., at least one of non-AP STA 1 (520) and non-AP STA 2 (530)) to AP 1 (510). Specifically, the MAC header of the uplink frame (605) may include a high throughput (HT) control field. The HT control field may include a bitmap. For example, if the information of two OBSSs is indicated in the order of OBSS 1 information and OBSS 2 information in the RNR element of AP 1 (510), the first bit of the bitmap may indicate whether OBSS 1 is detected, and the second bit may indicate whether OBSS 2 is detected. However, the order of the bitmap may be reversed, and the configuration of the bitmap may not be limited to a specific form. Here, the bitmap value may be set to a specific value to indicate the OBSS detected by the STA. For example, the MAC header of a data frame transmitted by non-AP STA 1 (520) to AP 1 (510) may include a bitmap indicating that OBSS 1 is detected and OBSS 2 is not detected. Additionally, the MAC header of a data frame transmitted by non-AP STA 2 (530) to AP 1 (510) may include a bitmap indicating that OBSS 1 is not detected and OBSS 2 is detected. Alternatively, the HT Control field may indicate the whole or part of the MAC address of the OBSS, thereby directly indicating whether at least one of OBSS 1 and OBSS 2 is detected. Alternatively, the uplink frame (605) transmitted by the STA may be configured in the form of an A (aggregated)-MPDU (MAC protocol data unit) in which multiple MAC frames are concatenated, and the A-MPDU may contain a frame containing information about the OBSS (e.g.A frame indicating a bitmap, a frame that may include the address of the OBSS, and a frame that includes an RNR element indicating the information of the OBSS can be transmitted by being concatenated with the original MAC frame that the STA intends to transmit.

[0168]

[0169] [Indicate common OBSS information in response frame]

[0170] As another example, when a STA (i.e., at least one of non-AP STA 1 (520) and non-AP STA 2 (530)) receives a downlink frame from AP 1 (510), common OBSS information may be indicated in a response frame (606) for the downlink frame. As an example, the response frame (606) may be a BlockAck frame. If the response frame (606) is a BlockAck frame, the BlockAck frame may include a Per AID TID Info subfield indicating whether the frame has been received, and the Per AID TID Info subfield may indicate a BlockAck bitmap per AID and TID. Here, at least one Special Per AID TID Info subfield may be included to indicate common OBSS information in the BlockAck frame. At least one Special Per AID TID Info subfield may include a bitmap. For example, if the information of two OBSSs is indicated in the order of the information of OBSS 1 and the information of OBSS 2 in the RNR element of AP 1 (510), the first bit of the bitmap may indicate whether OBSS 1 is detected and the second bit may indicate whether OBSS 2 is detected. The order of the bitmap may be reversed, or the composition of the bitmap may not be limited to this. The bitmap may indicate the OBSS detected by the STA by setting the bitmap to a specific value. For example, the MAC header of a data frame transmitted by non-AP STA 1 (520) to AP 1 (510) may include a bitmap indicating that OBSS 1 is detected and OBSS 2 is not detected, and the MAC header of a data frame transmitted by non-AP STA 2 (530) to the AP may include a bitmap indicating that OBSS 1 is not detected and OBSS 2 is detected.Alternatively, at least one Special Per AID TID Info subfield may indicate all or part of the MAC address of the OBSS to directly indicate whether at least one of OBSS 1 and OBSS 2 has been detected. Alternatively, the Special Per AID TID Info subfield may include an RNR element, and the RNR element may include OBSS information detected by the STA. Alternatively, the uplink frame transmitted by the STA may be configured in the form of an A (aggregated)-MPDU (MAC protocol data unit) in which a plurality of MAC frames are concatenated, and a frame containing information of the OBSS (e.g., a frame indicating the bitmap, a frame that may include the address of the OBSS, a frame containing an RNR element indicating information of the OBSS) may be concatenated with the original response frame (e.g., a BlockAck frame) that the STA intends to transmit and transmitted.

[0171] Meanwhile, if a non-AP STA 3 (540) that has not set up NPCA instructs the use of NPCA operation in a management frame transmitted by AP 1 (510), it may initiate NPCA operation without transmitting a frame to AP 1 (510) to initiate the aforementioned NPCA operation. The non-AP STA 3 (540) may detect a common OBSS with AP 1 (510) due to the movement of the non-AP STA 3 (540) (or other reasons). For example, the non-AP STA 3 (540) may detect at least one of OBSS 1 and OBSS 2. The non-AP STA 3 (540) may initiate NPCA operation by transmitting a frame to AP 1 (510) to initiate the NPCA operation described in FIG. 10. As another example, the non-AP STA 3 (540) can initiate the NPCA operation by instructing common OBSS information in a frame transmitted to the AP. As an example, the non-AP STA 3 (540) can instruct the AP 1 (510) to the common OBSS information detected by the non-AP STA 3 (540) using at least one of the methods described above [instructing common OBSS information in an uplink frame] and [instructing common OBSS information in a response frame].

[0172] AP 1 (510) can receive common OBSS information detected by each STA from STAs (e.g., non-AP STA 1 (520), non-AP STA 2 (530), non-AP STA 3 (540)) using at least one of [indicating common OBSS information in an uplink frame] and [indicating common OBSS information in a response frame]. That is, AP 1 (510) can recognize the OBSS detected by each STA. When the information of the common OBSS detected by the STAs (e.g., non-AP STA 1 (520), non-AP STA 2 (530), non-AP STA 3 (540)) changes (e.g., when the common OBSS of AP 1 (510) and each STA increases or decreases), the STAs (e.g., non-AP STA 1 (520), non-AP STA 2 (530), non-AP STA 3 (540)) may direct the common OBSS information to AP 1 (510) using at least one of the methods described above [directing common OBSS information in the uplink frame] and [directing common OBSS information in the response frame]. For example, if non-AP STA 1 (520) begins to detect both OBSS 1 and OBSS 2, non-AP STA 1 (520) may send a frame to AP 1 (510) to indicate that it detects both OBSS 1 and OBSS 2. For another example, if non-AP STA 2 (530) does not detect both OBSS 1 and OBSS 2, non-AP STA 2 (530) may send a frame to AP 1 (510) to indicate that it does not detect both OBSS 1 and OBSS 2. The above indication may indicate that non-AP STA 2 (530) has no common OBSS with non-AP STA 2 (530) and AP 1 (510). As another example, the above-mentioned instruction may indicate that non-AP STA 2 (530) does not perform NPCA operations.

[0173] FIG. 12 is a diagram illustrating a method for initiating a sub-channel access operation in a complex hidden node situation to which the present disclosure applies.

[0174] Referring to FIG. 12, based on the method described above in FIG. 10 and FIG. 11, AP 1 (510) can recognize whether non-AP STA 1 (520), non-AP STA 2 (530), and non-AP STA 3 (540) are each detecting any OBSS. For example, non-AP STA 1 (520) can recognize that it detects OBSS 1 in common with AP 1 (510), non-AP STA 2 (530) can recognize that it detects OBSS 2 in common with AP 1 (510), and non-AP STA 3 (540) can recognize that it does not detect any OBSS in common with AP 1 (510).

[0175] AP 1 (510) can operate on the NPCA main channel when it receives a frame of OBSS 1 (i.e., detects a communication interval, TXOP) and satisfies at least one of the [NPCA switching condition - control frame] and [NPCA switching condition - HE frame] conditions described above in FIGS. 8a and 8b. Here, the time at which the above conditions are satisfied is T1, and it can operate on the NPCA main channel from a point in time after the NSD (NPCA switch delay) time (time Ts in FIGS. 8a and 8b) after time T1. AP 1 (510) can operate on the main channel again at time T2, which is the time when the communication interval of OBSS 1 ends. AP 1 (510) may terminate frame transmission and reception on the NPCA main channel before the NSBD (NPCA switch back delay) time (time Ts' in FIGS. 8a and 8b) from time T2. AP 1 (510) can recognize that non-AP STA 1 (520) is capable of receiving frames of OBSS 1 and can expect non-AP STA 1 (520) to operate on the NPCA main channel. AP 1 (510) can recognize that non-AP STA 2 (530) and non-AP STA 3 (540) are not operating on the NPCA main channel but are operating on the main channel. Here, AP 1 (510) can send a downlink frame to non-AP STA 1 (520). Or, AP 1 (510) can send a trigger frame allocating uplink resources to non-AP STA 1 (520).

[0176] AP 1 (510) can operate on the NPCA main channel when it receives a frame of OBSS 2 (i.e., detects a communication interval, TXOP) and satisfies at least one of the [NPCA transition condition - control frame] and [NPCA transition condition - HE frame] conditions described in FIGS. 8a and 8b. The time at which the condition is satisfied is T3, and it can operate on the NPCA main channel from the time after the NSD time (time Ts in FIGS. 8a and 8b) after time T3. AP 1 (510) may need to operate on the main channel again at time T4, which is the time when the communication interval of OBSS 2 ends. AP 1 (510) may need to terminate frame transmission and reception on the NPCA main channel from time T4 before the NSBD (time Ts' in FIGS. 8a and 8b). AP 1 (510) can recognize that non-AP STA 2 (530) is capable of receiving frames from OBSS 2 and can expect non-AP STA 2 (530) to operate on the NPCA main channel. AP 1 (510) can recognize that non-AP STA 1 (520) and non-AP STA 3 (540) are not operating on the NPCA main channel but are operating on the main channel. AP 1 (510) can send a downlink frame to non-AP STA 2 (530). Alternatively, AP 1 (510) can send a trigger frame allocating uplink resources to non-AP STA 2 (530).

[0177] As described above, AP 1 (510) has described the transmission of downlink frames and the allocation of uplink resources to one STA, but is not limited thereto. For example, there exists an OBSS 4 that can be detected by AP 1 (510), non-AP STA 1 (520), and non-AP STA 2 (530), and if AP 1 (510) can confirm that non-AP STA 1 (520) and non-AP STA 2 (530) detect the OBSS 4, AP 1 (510) can operate on the NPCA main channel when it detects a frame of OBSS 4 and transmit a downlink frame to at least one of non-AP STA 1 (520) and non-AP STA 2 (530), or allocate uplink resources to at least one of non-AP STA 1 (520) and non-AP STA 2 (530).

[0178] FIG. 13 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies. Referring to FIG. 13, a first STA detects a transmission within a first overlapping basic service set (OBSS) and can set a first time interval corresponding to the transmission within the first OBSS (S1310). Here, the first OBSS is an OBSS that is commonly detected by both the first STA and the second STA, and a first time interval can also be set for the second STA by the transmission within the first OBSS. After that, the first STA can switch the operating channel from the main channel to a non-primary channel access (NPCA) channel based on the first time interval (S1320). Here, the operating channel of the second STA can also be switched from the main channel to the NPCA channel based on the first time interval. After that, the first STA can perform communication on the NPCA channel (S1330). The first STA can exchange time interval information with the third STA operating on the NPCA channel through frame exchange by the second time interval set by the second OBSS.

[0179] Additionally, the time at which the first STA returns to the main channel after operating on the NPCA channel and the time at which the third STA returns to the main channel after operating on the NPCA channel can be determined to be the same. Here, the first STA returns from the NPCA channel to the main channel when the first time interval expires, but the operating channel of the third STA may also switch from the NPCA channel to the main channel together with the first STA when the first time interval expires. Additionally, if the time at which the first time interval expires is earlier than the time at which the second time interval expires, the first STA performs frame transmission to the third STA from the time at which the first time interval expires to the time at which the second time interval expires, but frame transmission by the third STA may not be performed from the time at which the first time interval expires to the time at which the second time interval expires. Additionally, a media synchronization timer may be set on the third STA from the time at which the first time interval expires to the time at which the second time interval expires. Additionally, at the time of expiration of the first time interval, the third time interval of the third STA is released, and the first STA can perform at least one of frame transmission and reception with the third STA on the main channel from the time of expiration of the first time interval. Additionally, if the time of expiration of the first time interval is later than the time of expiration of the second time interval, the first STA operates on the NPCA main channel at the time of expiration of the second time interval, and the operating channel of the third STA can be switched from the NPCA main channel to the main channel at the time of expiration of the second time interval. Additionally, the length of the transmit opportunity (TXOP) set by the first STA and the third STA on the NPCA main channel can be adjusted based on the time of expiration of the second time interval. Additionally, the length of the TXOP can be adjusted to end at a time prior to the time of the delay in switching the operating channel of the third STA from the time of expiration of the second time interval.Additionally, communication on the main channel by the third STA may be stopped from the time the second time interval expires until the first time interval expires and the first STA switches the operating channel from the NPCA main channel to the main channel. Additionally, if the time the first time interval expires is later than the time the second time interval expires, the length of the transmit opportunity (TXOP) set by the first STA and the third STA on the NPCA main channel is adjusted based on the time the first time interval expires, and the first STA and the third STA may switch the operating channel from the NPCA main channel to the main channel at the time the first time interval expires. Additionally, a media synchronization timer may be set on the third STA from the time the operating channel is switched from the NPCA main channel to the main channel. Additionally, the first STA receives an initial control frame (ICF) from the third STA in an NPCA channel and transmits an initial control response (ICR) in response to the ICF, wherein the ICF may include second time interval information set in the third STA and the ICR may include first time interval information set in the first STA. Additionally, the first STA transmits the ICF to the third STA in an NPCA channel and receives an ICR in response to the ICF, wherein the ICF may include first time interval information set in the first STA and the ICR may include second time interval information set in the third STA. Additionally, the first time interval and the second time interval may be time intervals corresponding to a network allocation vector (NAV). Additionally, the first STA may transmit a first frame containing at least one OBSS information detected by the first STA.Additionally, the first STA transmits a first frame containing at least one OBSS information detected by the first STA to at least one STA including the second STA, and can receive OBSS information commonly detected by each of the at least one STA from each of the at least one STA including the second STA based on the at least one OBSS information detected by the first STA. Additionally, the OBSS information commonly detected by each of the at least one STA can be transmitted to the first STA through at least one of an uplink frame transmitted to the first STA and a response frame for a frame transmitted by the first STA. Additionally, the first STA can support NPCA operation based on the OBSS information commonly detected by each of the at least one STA. Additionally, at least one of the first STA and the second STA may be a non-AP STA or an AP STA.

[0180] 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.

[0181]

[0182] The above-mentioned matters may also be applied to other systems.

Claims

1. In a method of operation of a first station (station, STA) in a wireless LAN system, A step in which the first STA detects a transmission within a first OBSS (overlapping basic service set) and sets a first time interval corresponding to the transmission within the first OBSS, wherein the first OBSS is an OBSS commonly detected by the first STA and the second STA, and the first time interval is also set in the second STA by the transmission within the first OBSS; A step in which the first STA switches the operating channel from the main channel to the NPCA (non-primary channel access) channel based on the first time interval, wherein the operating channel of the second STA is also switched from the main channel to the NPCA channel based on the first time interval; and The above first STA includes the step of performing communication on the NPCA channel, wherein A method of operation in which the first STA exchanges time interval information with a third STA operating in the NPCA channel through frame exchange by means of a second time interval set by the second OBSS.

2. In Paragraph 1, A method of operation in which the time at which the first STA returns to the main channel after operating in the NPCA channel and the time at which the third STA returns to the main channel after operating in the NPCA channel are determined to be the same.

3. In Paragraph 2, A method of operation in which the first STA returns to the main channel from the NPCA channel when the first time interval expires, and the operation channel of the third STA also switches from the NPCA channel to the main channel together with the first STA at the time when the first time interval expires.

4. In Paragraph 3, A method of operation in which, if the expiration time of the first time interval is earlier than the expiration time of the second time interval, the first STA performs frame transmission to the third STA from the expiration time of the first time interval to the expiration time of the second time interval, but frame transmission by the third STA is not performed from the expiration time of the first time interval to the expiration time of the second time interval.

5. In Paragraph 3, A method of operation in which a media synchronization-related timer is set in the third STA from the expiration time of the first time interval to the expiration time of the second time interval.

6. In Paragraph 3, A method of operation in which, at the time of expiration of the first time interval, the third time interval of the third STA is released, and the first STA performs at least one of frame transmission and reception with the third STA on the main channel from the time of expiration of the first time interval.

7. In Paragraph 1, A method of operation in which, if the expiration time of the first time interval is later than the expiration time of the second time interval, the first STA operates on the NPCA main channel at the expiration time of the second time interval, and the operation channel of the third STA switches from the NPCA main channel to the main channel at the expiration time of the second time interval.

8. In Paragraph 7, A method of operation in which the length of a transmit opportunity (TXOP) set by the first STA and the third STA in the above NPCA main channel is adjusted based on the expiration time of the second time interval.

9. In Paragraph 7, A method of operation in which the length of the above TXOP is adjusted to end at a time prior to the operation channel switching delay of the above 3 STA from the time of expiration of the above 2 time interval.

10. In Paragraph 7, A method of operation in which communication in the main channel by the third STA is stopped from the time of expiration of the second time interval until the first time interval expires and the first STA switches the operating channel from the NPCA main channel to the main channel.

11. In Paragraph 1, If the expiration time of the first time interval is later than the expiration time of the second time interval, the length of the transmit opportunity (TXOP) set by the first STA and the third STA in the NPCA main channel is adjusted based on the expiration time of the first time interval, and A method of operation in which the first STA and the third STA switch the operating channel from the NPCA main channel to the main channel at the time of expiration of the first time interval.

12. In Paragraph 11, A method of operation in which a media synchronization-related timer is set in the third STA from the time the operating channel is switched from the NPCA main channel to the main channel.

13. In Paragraph 1, The first STA receives an initial control frame (ICF) from the third STA in the NPCA channel and transmits an initial control response (ICR) in response to the ICF, wherein A method of operation in which the above ICF includes the second time interval information set in the above third STA, and the above ICR includes the first time interval information set in the above first STA.

14. In Paragraph 1, The first STA transmits an ICF to the third STA over an NPCA channel and receives an ICR in response to the ICF, A method of operation in which the above ICF includes the first time interval information set in the above first STA, and the above ICR includes the second time interval information set in the above third STA.

15. In Paragraph 1, A method of operation in which the first time interval and the second time interval are time intervals corresponding to the NAV (network allocation vector).

16. In Paragraph 1, A method of operation in which the first STA transmits a first frame containing at least one OBSS information detected by the first STA.

17. In Paragraph 16, The first STA transmits the first frame, which includes at least one OBSS information detected by the first STA, to at least one STA including the second STA, and A method of operation for receiving OBSS information commonly detected in each of the at least one STA based on at least one OBSS information detected by the first STA from each of the at least one STA including the second STA.

18. In Paragraph 17, A method of operation in which OBSS information commonly detected in each of the at least one STA is transmitted to the first STA through at least one of an uplink frame transmitted to the first STA and a response frame to a frame transmitted by the first STA.

19. In Paragraph 17, A method of operation in which the first STA supports NPCA operation based on OBSS information commonly detected in each of the at least one STA.

20. In Paragraph 1, A method of operation in which at least one of the first STA and the second STA is a non-AP STA or an AP STA.

21. In a wireless LAN system, regarding a station (STA), 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 non-AP STA to perform a specific operation by the above at least one processor, and The above specific operation is: The first STA detects a transmission within the first overlapping basic service set (OBSS) and sets a first network allocation vector (NAV) during a time interval corresponding to the transmission within the first OBSS, wherein the first OBSS is an OBSS commonly detected by the first STA and the second STA, and the first NAV is also set in the second STA by the transmission within the first OBSS. The first STA switches the operating channel from the main channel to the NPCA (non-primary channel access) channel based on the first NAV, and the operating channel of the second STA also switches from the main channel to the NPCA channel based on the first NAV, and The first STA performs communication on the NPCA channel, The above-mentioned first STA exchanges NAV information through frame exchange with a third STA operating in the NPCA channel by a second NAV set by the second OBSS.

Images