Method and apparatus for performing non-primary channel access operation in wireless LAN

Abstract

This operation method of a station (STA) in a wireless LAN system may comprise steps in which: an STA receives at least one frame from an overlapping basic service set (OBSS) while operating on a primary channel; whether to perform a non-primary channel access (NPCA) operation is determined on the basis of the received at least one frame; and, when performing the NPCA operation, the STA switches a channel from the primary channel of the STA to an NPCA primary channel.

Description

Method and device for performing side channel access operation in wireless LAN

[0001] The present disclosure relates to a method and device for performing communication based on a non-primary channel (subchannel) in a wireless local area network (WLAN). Specifically, the present disclosure relates to a method and device for using a subchannel based on coordination between multiple access points (APs) in a WLAN. Furthermore, the present disclosure relates to a method and device for performing a non-primary channel access (NPCA) operation in a WLAN, taking into account a hidden node environment.

[0002]

[0003] With the recent proliferation of mobile devices, wireless local area network (WLAN) technology, which can provide fast wireless communication services to these devices, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly access the Internet.

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

[0005] As applications requiring higher reliability arise, the IEEE 802.11bn standard, an Ultra High Reliability (UHR) wireless LAN technology, is being developed in a single Basic Service Set (BSS) environment and / or redundant BSS environments. The goals of the IEEE 802.11bn standard may support increased data transmission speed, improved latency performance, and improved data error rate. In addition, the IEEE 802.11bn standard may support low-power operation, peer-to-peer communication, and operations for increased channel utilization. In addition, the IEEE 802.11bn standard may support a TXOP sharing method in which wireless LAN terminals share a communication resource, a TXOP, between APs. In addition, the wireless LAN standard may support non-primary channel access (NPCA) operation and dynamic subchannel operation (DSO), which use a channel other than the primary channel when the primary channel is occupied, to increase the efficiency of communication resource utilization.

[0006] Below, we describe a multi-AP-based, coordinated side-channel access operation and a side-channel access operation that considers a hidden node environment, as described above. The background technology of the invention was written to enhance understanding of the background of the invention, and may include content that is not already known to those skilled in the art.

[0007]

[0008] The present disclosure relates to a method and device for performing a side-channel access operation in a wireless LAN.

[0009] The present disclosure relates to a method and device for using a subchannel based on coordination between multiple APs in a wireless LAN.

[0010] The present disclosure relates to a method and device for providing an opportunity for an AP that has not yet started transmission to perform an NPCA operation instruction to an AP that has started transmission when one of the APs starts transmission through coordination among the APs that constitute a basic service set (BSS) in relation to side-channel communication in a wireless LAN.

[0011] The present disclosure relates to a method and device for performing NPCA operation in consideration of a hidden node environment in a wireless LAN.

[0012] The present disclosure relates to a method and device for enabling a hidden node that does not receive a frame to efficiently perform a side-channel access operation when performing a side-channel access in a wireless LAN.

[0013] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0014]

[0015] According to one embodiment of the present specification, a method for operating a station (STA) in a wireless LAN system may include a step of receiving at least one frame from an overlapping basic service set (OBSS) while the STA operates on a primary channel, a step of determining whether to perform a non-primary channel access (NPCA) operation based on the received at least one frame, and a step of switching a channel from the STA's primary channel to an NPCA primary channel when the NPCA operation is performed.

[0016] In addition, according to one embodiment of the present specification, in a wireless LAN system, a station (STA) includes at least one transceiver for transmitting and receiving a signal, at least one processor for controlling the at least one transceiver, and a memory for storing instructions for causing the STA to perform a specific operation by the at least one processor, wherein the specific operation is: the STA receives at least one frame from an overlapping basic service set (OBSS) while operating on a primary channel, determines whether to perform a non-primary channel access (NPCA) operation based on the received at least one frame, and when performing the NPCA operation, the STA can switch a channel from the primary channel of the STA to an NPCA primary channel.

[0017] Additionally, the following may be commonly applied:

[0018] According to one embodiment of the present specification, an STA determines whether to perform an NPCA operation based on a sequence of physical layer protocol data units (PPDUs) exchanged at short interframe space (SIFS) intervals, wherein the sequence of PPDUs may include a first PPDU including an initial control frame (ICF), a second PPDU including an initial control response (ICR), and a third PPDU following the second PPDU.

[0019] Additionally, according to one embodiment of the present specification, if the STA receives a third PPDU within a preset time after receiving a first PPDU including an ICF, the STA may initiate channel switching to an NPCA channel based on an NPCA operation.

[0020] Additionally, according to one embodiment of the present specification, when the STA acquires a primitive based on reception of the first PPDU and acquires a primitive based on reception of the third PPDU within a preset time from the time of acquiring the primitive based on reception of the first PPDU, the STA may initiate channel switching to the NPCA channel based on the NPCA operation.

[0021] Additionally, according to one embodiment of the present specification, when the ICF is a request to send (RTS) frame or a multi-user (MU)-RTS trigger frame, the preset time may be '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + CTS_Time', and CTS_Time may be an expected transmission time of the CTS frame calculated based on the ICF.

[0022] In addition, according to one embodiment of the present specification, when the ICF is a BSRP (buffer status report poll) trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + the length indicated by the uplink length field', and the length of the frame indicated by the uplink length field can be set based on the value of the uplink length field included in the ICF.

[0023] In addition, according to one embodiment of the present specification, when an STA receives an RTS frame as an ICF acquired from an OBSS and does not receive a CTS frame as an ICR, the STA may set a default NAV (network allocation vector) when acquiring an RTS frame, maintain the default NAV when receiving a third PPDU transmitted from the OBSS within a preset time, and initiate channel switching to an NPCA channel based on an NPCA operation.

[0024] Additionally, according to one embodiment of the present specification, the third PPDU may include a data frame or an NPCA indication frame.

[0025] In addition, according to one embodiment of the present specification, when an STA receives an RTS frame or an MU-RTS trigger frame as an ICF from an OBSS, the STA sets a default NAV and transmits a CTS frame including the same content as a CTS frame transmitted from the OBSS as an ICR within a BSS including the STA, wherein the transmission time of the CTS frame transmitted by the STA within the BSS may be the same as the transmission time of the CTS frame by the OBSS.

[0026] In addition, according to one embodiment of the present specification, when an STA receives an MU-RTS trigger frame indicating simultaneous transmission of a CTS frame, a CTS frame including the same content as a CTS frame transmitted from an OBSS as an ICR is transmitted at the same time as the CTS frame is transmitted by the OBSS within the BSS including the STA, and the MU-RTS trigger frame may include an AID (association ID) of the STA.

[0027] Additionally, according to one embodiment of the present specification, when an STA receives an RTS frame or an MU-RTS trigger frame as an ICF from an OBSS, the STA sets a default NAV, and when the STA receives a CTS frame transmitted from the OBSS as an ICR, the STA duplicates the CTS frame and transmits the CTS frame within the BSS in which the STA is included after SIFS, but the data frame transmission by the OBSS can be performed after the CTS frame transmission by the STA.

[0028] Additionally, according to one embodiment of the present specification, a CTS frame may be transmitted once more in an OBSS at the same time that a STA transmits a CTS frame within a BSS in which the STA is included.

[0029] In addition, according to one embodiment of the present specification, when the ICF included in the first PPDU is an RTS (request to send) frame or an MU-RTS trigger frame, the third PPDU is transmitted '2x SIFS (short interframe space) + CTS_Time' after the transmission completion time of the ICF, and the CTS_Time is an expected transmission time of the CTS frame calculated based on the ICF included in the first PPDU, and when the STA acquires a primitive based on reception of the third PPDU within a preset time, the STA can start channel switching to an NPCA channel based on an NPCA operation.

[0030] In addition, according to one embodiment of the present specification, when the ICF included in the first PPDU is a BSRP trigger frame, the preset time is '2x SIFS (short interframe space) + the length indicated by the uplink length field', the length indicated by the uplink length field is set based on the value of the uplink length field included in the trigger frame, and when a primitive based on reception of the third PPDU is acquired after the preset time, channel switching to an NPCA channel can be started based on the NPCA operation.

[0031] Additionally, according to one embodiment of the present specification, at least one of the first PPDU and the second PPDU may include an NPCA preemption, and the third PPDU may include an NPCA indication frame indicating channel movement to an NPCA channel.

[0032] Additionally, according to one embodiment of the present specification, the STA receives at least one of a first PPDU including an initial control frame (ICF) and a second PPDU including an initial control response (ICR) exchanged at a short interframe space (SIFS) interval, wherein at least one of the first PPDU and the second PPDU includes an NPCA preemption, and the STA transmits a third PPDU subsequent to the second PPDU, wherein the third PPDU may include an NPCA indication frame based on the NPCA preemption.

[0033] Additionally, according to one embodiment of the present specification, if the STA does not receive the first PPDU including the ICF and receives the second PPDU including the ICR, the STA may transmit the third PPDU including the NPCA indication frame based on the second PPDU.

[0034] Additionally, according to one embodiment of the present specification, when the STA receives a first PPDU including an ICF and does not receive a second PPDU including an ICR, the STA may transmit a third PPDU including an NPCA indication frame based on the first PPDU.

[0035] Additionally, according to one embodiment of the present specification, the STA may be an AP STA or a non-AP STA.

[0036]

[0037] According to the present disclosure, a method for performing a side-channel access operation in a wireless LAN can be provided.

[0038] According to the present disclosure, a method for using a subchannel based on coordination between multiple APs in a wireless LAN can be provided.

[0039] According to the present disclosure, a method can be provided in which, when one of a plurality of APs constituting a BSS starts transmission through coordination between a plurality of APs in relation to side-channel communication in a wireless LAN, the AP that started transmission can perform an NPCA operation instruction to an AP that has not started transmission.

[0040] According to the present disclosure, a method for performing NPCA operation by taking into account a hidden node environment in a wireless LAN can be provided.

[0041] According to the present disclosure, when performing a side-channel access in a wireless LAN, a method can be provided for enabling a hidden node that does not receive a frame to efficiently perform a side-channel access operation.

[0042] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0043] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0044]

[0045] Figure 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure is applied.

[0046] Figure 2 is a diagram showing a wireless LAN system to which the present disclosure is applied.

[0047] Figure 3 is a diagram showing a wireless LAN network configuration applied to the present disclosure.

[0048] FIGS. 4A to 4C are diagrams illustrating a wireless LAN subchannel communication instruction method based on AP adjustment applied to the present disclosure.

[0049] FIG. 5 is a diagram illustrating a wireless LAN subchannel communication instruction method based on AP adjustment applied to the present disclosure.

[0050] FIG. 6 is a diagram illustrating a wireless LAN frame configuration method for performing NPCA operation in a hidden node environment applied to the present disclosure.

[0051] FIG. 7a and FIG. 7b are diagrams showing an NPCA operation method in a hidden node environment applied to the present disclosure.

[0052] FIG. 8a and FIG. 8b are diagrams showing an NPCA operation method in a hidden node environment applied to the present disclosure.

[0053] Figure 9 is a flowchart showing the operation of a non-AP STA in a wireless LAN applied to the present disclosure.

[0054] Figure 10 is a flowchart showing the operation of an AP STA in a wireless LAN applied to the present disclosure.

[0055]

[0056] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0057] While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component may be referred to as a "second component," and similarly, a second component may also be referred to as a "first component." The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein.

[0058] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0059] The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0060] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0061] 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 in describing the present disclosure, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0062] 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 description below, and the embodiments according to the present disclosure can be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network."

[0063] FIG. 1 is a diagram illustrating a communication node within a wireless LAN system to which the present disclosure applies. Referring to FIG. 1, a communication node (100) may include at least one of a processor (110), a 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 (AP) 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 other nodes or devices based on the above-described configuration. 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, the present invention may not be limited thereto.

[0064] The processor (110) within the 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) as each component within the communication node. The memory (120) within the communication node (100) can store information on commands and instructions executed by the processor (110), and the transceiver (130) can refer to a transceiver, a radio frequency (RF) 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, can be linked with other interfaces, and can further include a separate storage device (150). Each component within the communication node (100) can be connected by a bus (160) to communicate with each other.

[0065] However, as an example, each component included in the communication node (100) may be connected through an individual interface or individual bus centered around the processor (110), rather than a common bus (160). The processor (1110) may be connected to at least one of the memory (120), the transmission / reception device (130), the input / output interface device (140), and the storage device (150) through a dedicated interface.

[0066] The processor (110) can execute program commands stored in at least one of the memory (120) and the storage device (150). The processor (110) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to embodiments of the present disclosure are performed. Each of the memory (120) and the storage device (150) may be configured with at least one of a volatile storage medium or a non-volatile storage medium. For example, the memory (120) may be configured with at least one of a read-only memory (ROM) or a random access memory (RAM).

[0067] Below, the related operations are described based on a station (STA) as a wireless LAN terminal. STA can refer to both an AP STA that operates as an access point (AP) and a non-AP STA that operates while connected to an AP, in the same manner as the terminology used in IEEE 802.11. However, for the convenience of explanation, APs and non-AP STAs are distinguished below, but this may be a distinction for the convenience of explanation, and it is self-evident that the operations for an AP can be applied to both AP STAs and non-AP STAs. In addition, it is self-evident that the non-AP STA operations described below can also be applied to both non-AP STAs and AP STAs.

[0068] FIG. 2 is a diagram illustrating a wireless LAN system to which the present disclosure is applied. Referring to FIG. 2, a basic service set (BSS) of the wireless LAN system may include one AP (210) and multiple non-AP STAs (221, 222, 223, 224), and the multiple non-AP STAs (221, 222, 223, 224) may be controlled by the AP (210). However, the wireless LAN system is not limited to the BSS, and an environment composed only of non-AP STAs without a defined 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 medium access control (MAC) layer and a physical (PHY) layer, and communication may be performed between the wireless devices. For the convenience of explanation, the following description focuses on APs and non-AP STAs, but may not be limited thereto. For example, the following may equally apply to other communication nodes or devices and are not limited to a specific form.

[0069] In a wireless LAN network, wireless LAN terminals can support subchannel access operations. In subchannel access operations, the channel occupancy of the primary channel may differ from that of the AP depending on the location of the non-AP STA. As described above, this can lead to inefficiencies in subchannel communication. For example, a specific non-AP STA may determine that the primary channel is idle, while the AP may determine that the primary channel is occupied and switch to the subchannel. Here, a specific non-AP STA may attempt to transmit a data frame in a band that includes both the primary channel and the subchannel, but the AP cannot respond because the primary channel is occupied. Therefore, subchannel communication operations in a wireless LAN can be inefficient. Considering the above, an AP that has initiated transmission based on multiple APs can provide an opportunity to instruct an AP that has not initiated transmission to initiate NPCA operation. The AP that has not initiated transmission can instruct its subordinate non-AP STAs to perform NPCA operation, as will be described later.

[0070] In addition, in order to perform a side-channel access operation, it may be necessary to check the transmission section of other wireless LAN networks configured by other wireless LAN terminals. For example, some wireless LAN terminals may not be able to receive frames from other wireless LAN networks. Therefore, some wireless LAN terminals may not be able to check the transmission section of other wireless LAN networks and may not be able to perform the side-channel access operation. In other words, the efficiency of the side-channel access operation of the wireless LAN network may be reduced. Considering the above, a method may be required to efficiently perform the side-channel access operation even when there is a hidden node that does not receive the frame during the side-channel access operation in the wireless LAN, and this will be described later.

[0071] FIG. 3 is a diagram illustrating a wireless LAN network configuration applicable to the present disclosure. Referring to FIG. 3, the wireless LAN network may be comprised of two or more basic service sets (BSSs). Each BSS may be comprised of an access point (AP) and multiple non-AP STAs that connect to the AP and perform data communications. Each BSS may operate on the same channel (or frequency). Furthermore, each BSS may share all or part of the channels on which it operates with other BSSs.

[0072] BSSs may have overlapping communication ranges. For example, data communication performed by one of multiple BSSs may be received by at least one other BSS. Conversely, one BSS may receive data transmitted by at least one other BSS. Alternatively, one BSS may not be able to receive data transmitted by at least one other BSS, but data transmission by at least one other BSS may occupy a portion of the total bandwidth in which the aforementioned one BSS operates. Alternatively, data transmission performed by one BSS may occupy a portion of the total bandwidth in which the aforementioned one BSS operates. That is, an environment in which BSSs overlap may be considered, and for convenience of description, one of the aforementioned BSSs is referred to as a BSS below, and a BSS that overlaps with at least one BSS is referred to as an OBSS (overlapping BSS). In the present disclosure, the operation of a BSS may be the operation of an AP or a non-AP STA constituting the BSS. For example, when a BSS detects a frame transmission of an OBSS, it may refer to at least one of an AP and a non-AP STA of the BSS detecting a frame transmitted by at least one of an AP and a non-AP STA of the OBSS. When a BSS performs channel switching, it may refer to an operation in which at least one of an AP and a non-AP STA constituting the BSS performs channel switching. Below, a sub-channel access method that takes different channel states into account is described.

[0073] AP 1 and AP 2 may operate in a wireless LAN network. AP 1 and at least one non-AP STA connected to AP 1 may form a BSS, and AP 2 and at least one non-AP STA connected to AP 2 may form another BSS. In the following, a BSS including AP 1 is referred to as BSS 1, and a BSS including AP 2 is referred to as BSS 2, but this is only for convenience of explanation and may not be limited to the embodiment.

[0074] The primary channel operating frequencies of BSS 1 and BSS 2 may overlap in whole or in part. For example, the total operating frequency bandwidth of BSS 2 may be 160 MHz. However, this is for convenience of explanation and may not be limited thereto. The primary 20 MHz channel of BSS 1 may exist within the operating frequency of BSS 2. Therefore, it may be considered that BSS 2 occupies the primary 20 MHz channel of BSS 1 to transmit data. For example, AP 2 of BSS 2 may occupy the primary 20 MHz channel of BSS 1 to transmit data.

[0075] When AP 1 can detect a transmission from BSS 2 (e.g., AP 2 included in BSS 2 and / or non-AP STA included in BSS 2), AP 1 can perform a non-primary channel access (NPCA) operation. The NPCA operation may be an operation performed when the non-AP STA and AP constituting BSS 2 are within the detection range of AP 1. The NPCA operation may be an operation in which, when the entirety or a portion of the primary channel of a wireless LAN terminal is occupied by another BSS, the wireless LAN terminal performs a channel access operation on a separate primary channel, the NPCA primary channel, and, if the channel access operation is successful on the NPCA channel, performs a data frame exchange.

[0076] Here, due to reasons such as signal attenuation of the wireless signal, a signal transmitted by a specific wireless LAN terminal may not be received by other wireless LAN terminals other than the specific wireless LAN terminal. In other words, a hidden node problem may occur. For example, a signal transmitted by AP 2 of OBSS may be received by AP 1, but may not be received by non-AP STA 1. In the above-described case, AP 1 may perform a frame transmission operation by switching the operating channel to the NPCA channel, but non-AP STA 1 may operate on the primary channel. In other words, the channels used by AP 1 and non-AP STA 1 may be different. Therefore, a frame transmitted by AP 1 on the NPCA primary channel cannot be received by non-AP STA 1. A frame transmitted by non-AP STA 1 on the primary channel may not be received depending on the reception capability of AP 1, and thus the NPCA operation efficiency may be reduced.

[0077] For example, consider a case where AP 1 cannot detect a transmission of BSS 2. That is, non-AP STAs and APs constituting BSS 2 may be outside the detection range of AP 1. Since AP 1 cannot detect a transmission of another BSS on the primary channel, it may perform a frame transmission operation by occupying the primary 20MHz channel instead of performing an NPCA operation. In the above case, the transmission of BSS 2 and the transmission of AP 1 may collide, and data transmission may fail. As another example, some of AP 1 of BSS 1 and non-AP STAs connected to AP 1 may be able to detect a transmission of BSS 2, while others may not be able to detect a transmission of BSS 2. As a specific example, AP 1 may detect a transmission of BSS 2, but non-AP STA 1 may not be able to detect a transmission of BSS 2. In this case, AP 1 detects transmission from another BSS, BSS 2, on the primary channel, so it switches its operating channel to the NPCA primary channel, but non-AP STA 1 operates on the primary channel. AP 1 may attempt to transmit to non-AP STA 1 on the NPCA primary channel, and non-AP STA 1 may attempt to transmit to AP 1 on the primary channel. Since AP 1 and non-AP STA operate on different channels, data transmission may fail.

[0078] As another example, neither AP 1 nor non-AP STA 1 may receive a signal transmitted by non-AP STA 2 of the OBSS. When an OBSS of the BSS exists, even if a communication operation is performed in the OBSS, the BSS does not detect the communication of the OBSS, so AP 1 and non-AP STA 1 of the BSS can perform the communication operation. Here, the communication of the BSS may cause interference with the communication of the OBSS. The NPCA operation is intended to perform a wireless LAN communication operation by operating the BSS on the NPCA primary channel in the communication section of the OBSS, but in the above-described case, AP 1 and non-AP STA 1 may not be able to perform the NPCA operation. That is, the NPCA operation may not be performed.

[0079] In a hidden node environment, the collisions, transmission failures, and non-performance of the NPCA operation described above may cause transmission delays. To prevent the collisions, transmission failures, or non-performance of the NPCA operation described above, AP 1, which is an AP constituting BSS 1, and AP 2, which is an AP constituting BSS 2, may perform NPCA coordination. When AP 1 and AP 2 perform NPCA coordination, AP 1 and AP 2 may exchange at least one of BSSID and BSS color information with each other. The BSSID is an identifier that can distinguish the BSS, and may be a MAC (medium access control) address. In addition, the BSS color may also be an identifier that can distinguish the BSS.

[0080] AP 1 and AP 2 can share operating channel information through NPCA coordination and can also recognize which channels overlap. In addition, AP 1 and AP 2 can share NPCA primary channel information for performing NPCA operations in each BSS. When NPCA coordination is established, management frames (e.g., beacon frames, association response frames, probe response frames, action frames) of AP 1 and AP 2 may include information indicating that AP 1 and AP 2 establish NPCA coordination. The NPCA coordination establishment instruction may include an identifier of the BSS where NPCA cooperation has been established (e.g., BSSID, BSS Color). In addition, the NPCA cooperation establishment instruction may include operating channel information of the BSS. When NPCA cooperation establishment between AP 1 of BSS 1 and AP 2 of BSS 2 is completed, NPCA coordination operation can be performed. The following FIGS. 4A to 4C and FIG. 5 illustrate cases in which the NPCA cooperation setup is completed as described above, and the above-described operation can be applied in the same manner. However, the following FIGS. 4A to 4C and FIG. 5 can be performed without performing the NPCA cooperation setup as described above. Meanwhile, the above-described collision or transmission failure may be a problem that the coordination-based wireless LAN sub-channel operation described in the present disclosure seeks to solve, but it should be understood that the coordination-based sub-channel operation described in the present disclosure can be performed even when the above-described problem does not occur.

[0081] Below, a basic NAV and an intra-BSS NAV can be considered as network allocation vectors (NAVs) for NPCA operation. The basic NAV can be a NAV set by a BSS when a frame referenced for setting the NAV is transmitted from an OBSS. Alternatively, the basic NAV can be set even when it is not known whether the frame referenced for setting the NAV is transmitted from an OBSS or a BSS. When the basic NAV is set, non-AP STA 1 and AP 1 of the BSS can start moving the operating channel to the NPCA primary channel. As another example, when the basic NAV is set by an RTS frame and a subsequent frame is received, non-AP STA 1 and AP 1 of the BSS can start moving the operating channel to the NPCA primary channel. On the other hand, the intra-BSS NAV can be a NAV set by a frame transmission performed within the BSS. When an intra-BSS NAV is set, AP 1 and non-AP STA 1 of the BSS may not initiate operation channel movement to the NPCA primary channel. The frame transmitted from the OBSS is an intra-BSS PPDU. The NAV transmitted from the BSS is an intra-BSS PPDU. Meanwhile, unless otherwise specified, the NAV may mean the default NAV.

[0082] Additionally, in the present disclosure, the PIFS time is aSIFSTime + aSlotTime. However, the PIFS time may also mean aSIFSTime + aSlotTime + aRxPHYStartDelay time considering the delay time for frame detection.

[0083] Additionally, although referred to as "channel movement" or "channel switching" in this disclosure, this may be channel switching. That is, the operation of a wireless LAN terminal switching from one channel to another may be described as "channel movement," "channel switching," or "channel switching," and may not be limited to a specific name.

[0084] FIGS. 4A to 4C are diagrams illustrating a wireless LAN subchannel communication instruction method based on AP adjustment applied to the present disclosure.

[0085] Referring to FIG. 4A, at least one of a non-AP STA and an AP in BSS 2 may occupy the main 20 MHz channel of AP 1 (310) constituting BSS 1 to transmit an initial control frame (ICF) 401. The ICF (401) may include an indicator (e.g., an NPCA preemption indicator) that provides a transmission opportunity (e.g., a preemption operation opportunity) to AP 1 (310). At least one of the non-AP STA and the AP in BSS 2 may transmit an initial control response (ICR) 402 in response to the ICF (401). For example, the ICR (402) may include an NPCA preemption indicator. At least one of the non-AP STA and AP of BSS 2 that has completed the ICR (402) transmission may wait for a priority interframe space (PIFS) time that is longer than a short interframe space (SIFS). The PIFS may be a time for AP 1 (310) to wait for the transmission of an NPCA indicator (403). If the frame transmission of AP 1 (310) is detected within the PIFS time, the non-AP STA or AP of BSS 2 may wait until the frame transmission of AP 1 (310) is completed. If the frame transmission of AP 1 (310) is not detected within the PIFS time, at least one of the non-AP STA and AP may perform frame transmission after the PIFS time.

[0086] AP 1 (310) can receive ICF (401) and ICR (402) transmitted by at least one of the non-AP STA and AP of BSS2. For example, AP 1 (310) can check the NPCA preemption indicator included in at least one of the ICF (401) and the ICR (402). In addition, AP 1 (310) can check whether at least one of the ICF (401) and the ICR (402) is a frame transmitted from BSS 2 that performed NPCA cooperation. Alternatively, AP 1 (310) can check whether the ICF (401) is received from any of the AP and non-AP STA of the OBSS for AP 1 (310). (That is, AP 1 can check whether the frame is received from the OBSS without NPCA cooperation.)

[0087] When AP 1 (310) receives at least one ICF (401) and ICR (402) transmitted from BSS 2 and including an NPCA preemption indicator (or, when the ICF (401) and ICR (402) are received from any one of the AP and non-AP STA of BSS 2, which is an OBSS), AP 1 (310) may receive the ICR (402) and transmit an NPCA indication frame (403) after a SIFS time. When AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) may transmit the NPCA indication frame (403) using only the main 20 MHz channel of AP 1 (310). This is to minimize interference to the remaining bands except for the bandwidth in which BSS 2 transmitted the frame by minimizing the bandwidth of the NPCA indication frame (403) of AP 1 (310). As another example, if AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (403) using the entire operating bandwidth of AP 1 (310). This is to maximize the bandwidth of the NPCA indication frame (403) of AP 1 (310) so that the AP and non-AP STA of BSS 2 can detect the NPCA indication frame (403) of AP 1 (310).

[0088] On the other hand, if AP 1 (310) can accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (403) to all or part of each 20MHz channel occupied by BSS 2. If AP 1 (310) transmits the NPCA indication frame (403) to a channel bandwidth wider than 20MHz (e.g., 40MHz, 80MHz, etc.), AP 1 (310) can also duplicate and transmit the frame for each 20MHz channel to improve the frame reception performance of BSS 2. In addition, as an additional condition for AP 1 (310) to transmit the NPCA indication frame (403), it can be considered whether the channel occupied by BSS 2 occupies the NPCA main channel on which AP 1 (310) performs the NPCA operation. That is, AP 1 (310) can transmit the NPCA indication frame (403) when the channel occupied by BSS 2 does not occupy the NPCA primary channel on which AP 1 (310) performs the NPCA operation. As another example, when performing an initial frame exchange in BSS 2, the NPCA preemption operation of AP 1 (310) can be induced only when the NPCA primary channel of BSS 1 is not occupied.

[0089] Non-AP STAs of BSS 1 can receive the NPCA indication frame (403) of AP 1 (310), and the non-AP STAs that receive the NPCA indication frame (403) can switch the operating channel to the NPCA primary channel. That is, the non-AP STAs can perform the NPCA operation. In addition, AP 1 (310) can switch the operating channel to the NPCA primary channel after transmitting the NPCA indication frame (403). That is, AP 1 (310) can also perform the NPCA operation. BSS 2 can perform data frame exchange in the TXOP, which is a time period in which multiple frames can be transmitted. AP1 and non-AP STAs of BSS 1 can perform the NPCA operation until the TXOP of BSS 2 ends.

[0090] In addition, as an example, not only AP 1 (310) but also non-AP STA 1 connected to AP 1 (310) within BSS 1 may receive ICF (401) and ICR (402) due to a difference in detection range. Here, non-AP STA 1 may receive ICF (401) and ICR (402) and may receive NPCA indication frame (403) transmitted by AP 1 (310) as described above. Here, each of ICF (401), ICR (402) and NPCA indication frame (403) may be included in each PPDU and transmitted at SIFS intervals. That is, in the above-described situation, non-AP STA 1 can receive a first PPDU including an ICF (401) for each of three PPDUs, a second PPDU including an ICR (402), and a third PPDU including an NPCA indication frame (403). In the above-described case, the MAC layer of non-AP STA 1 can obtain a primitive corresponding to the second PPDU after SIFS after obtaining a primitive corresponding to the first PPDU. Thereafter, it can obtain a primitive corresponding to the third PPDU after SIFS, and can perform a channel movement operation to the NPCA channel according to the NPCA indication frame (403) of the third PPDU (e.g., when checking NPCA movement information of the NPCA indication frame or obtaining a primitive corresponding to a PPDU including an NPCA indication frame).

[0091] Specifically, non-AP STAs of BSS 1 can receive the NPCA indication frame (403) of AP 1 (310), and the non-AP STAs that receive the NPCA indication frame (403) can switch the operating channel to the NPCA primary channel. That is, the non-AP STAs can perform the NPCA operation. In addition, AP 1 (310) can switch the operating channel to the NPCA primary channel after transmitting the NPCA indication frame (403). That is, AP 1 (310) can also perform the NPCA operation. BSS 2 can perform data frame exchange in the TXOP, which is a time period in which multiple frames can be transmitted. AP 1 (310) and non-AP STAs of BSS 1 can perform the NPCA operation until the TXOP of BSS 2 ends. The NPCA indication frame (403) may indicate the 'length of time during which non-AP STAs of BSS 1 can perform the NPCA operation'. For example, the 'length of time during which the NPCA operation can be performed' may be indicated through the duration field of the MAC header of the frame or another field. The 'length of time during which the NPCA operation can be performed' may be a length of time corresponding to or shorter than the remaining TXOP of BSS 2 (e.g., a length of time excluding the time required for NPCA transition from the remaining TXOP of BSS 2).

[0092] Referring to FIG. 4B, AP 1 (310) may not have received ICF (401) due to a difference in detection range, but may receive ICR (402). AP 1 (310) may check whether ICR (402) includes an NPCA preemption indicator and whether ICR (402) is a frame transmitted from BSS 2 that performed NPCA cooperation. Alternatively, AP 1 (310) may check whether ICF (401) is received from either an AP or a non-AP STA of the OBSS for AP 1 (310). (That is, AP 1 can determine whether a frame is received from the OBSS without NPCA cooperation.) If the two conditions described above are satisfied, or if the ICF (401) is received from one of the AP and non-AP STA of BSS 2, which is an OBSS, AP 1 (310) can receive the ICR (402) and transmit the NPCA indication frame (403) after SIFS time. If AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (403) using only the main 20 MHz channel of AP 1 (310). This is to minimize interference to the remaining bands except for the bandwidth in which BSS 2 transmitted the frame by minimizing the bandwidth of the NPCA indication frame (403) of AP 1 (310). As another example, if AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can perform transmission using the entire operating bandwidth of AP 1 (310). This is to maximize the bandwidth of the NPCA indication frame (403) of AP 1 (310) so that the AP and non-AP STA of BSS 2 can detect the NPCA indication frame (403) of AP 1 (310).

[0093] On the other hand, if AP 1 (310) can accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (403) to all or part of each 20MHz channel occupied by BSS 2. Here, if AP 1 (310) transmits the NPCA indication frame (403) to a channel bandwidth wider than 20MHz (e.g., 40MHz, 80MHz, etc.), AP 1 (310) can also duplicate and transmit the frame for each 20MHz channel to improve the frame reception performance of BSS 2. Non-AP STAs of BSS 1 can receive the NPCA indication frame (403) of AP 1 (310), and non-AP STAs that receive the NPCA indication frame (403) can switch the operating channel to the NPCA main channel. That is, the NPCA operation can be performed. AP 1 (310) may also switch the operating channel to the NPCA main channel after transmitting the NPCA indication frame (403). That is, the NPCA operation may be performed. BSS 2 may perform data frame exchange in the TXOP, which is a time period in which multiple frames can be transmitted. Non-AP STAs of BSS 1 may perform the NPCA operation until the TXOP of BSS 2 ends. BSS 2 may perform data frame exchange in the TXOP, which is a time period in which multiple frames can be transmitted. Non-AP STAs of BSS 1 may perform the NPCA operation until the TXOP of BSS 2 ends. Here, the range of detecting frames may be different for each wireless LAN terminal, and at least one of the AP and non-AP STA of BSS 2 that transmitted the ICF (401) may not have received the NPCA indication frame (403) of AP 1 (310). As a specific example, a case may be considered where the transmission of the ICF (401) transmitted by at least one of the AP and non-AP STA of BSS 2 fails, and thus the ICR (402) is not transmitted.Here, at least one of the AP and non-AP STA of BSS 2 that transmitted the ICF (401) may not perform frame transmission at the time when the NPCA indication frame (403) of AP 1 (310) is expected to be transmitted so as not to collide with the NPCA indication frame (403) of AP 1 (310) transmitted after the ICR (402). Alternatively, at least one of the AP and non-AP STA of BSS 2 that transmitted the ICF (401) may transmit an arbitrary frame (e.g., QoS Null frame, Multi-STA BA (block ack) frame) in accordance with the time and length when the NPCA indication frame (403) of AP 1 (310) is transmitted, or transmit a dummy frame that does not include any content so as not to overlap with the channel on which the NPCA indication frame (403) is expected to be transmitted. For example, any frame transmitted in accordance with the timing and length of the NPCA indication frame (403) may be a frame having the same length as the NPCA indication frame of AP 1 (310). If at least one of the AP and non-AP STA of BSS 2 transmits any frame in accordance with the timing and length of the NPCA indication frame (403), the medium of BSS 2 can be occupied, thereby preventing other wireless LAN terminals from invading the transmission opportunity acquired by at least one of the AP and non-AP STA of BSS 2. In addition, referring to FIG. 4c, AP 1 (310) may have received ICF (401) due to a difference in detection range, but may not receive ICR (402). Here, AP 1 (310) can check whether the ICF (401) includes an NPCA preemption indicator and whether the ICF (401) is a frame transmitted from BSS 2 that performed NPCA cooperation. Alternatively, AP 1 (310) can check whether the ICF (401) is received from either an AP or a non-AP STA of the OBSS for AP 1 (310).(That is, AP 1 can check whether a frame is received from the OBSS without NPCA cooperation.) If the two conditions described above are satisfied, or if the ICF (401) is received from one of the AP and non-AP STA of BSS 2, which is an OBSS, and if the ICF (401) is an RTS (request to send) frame, AP 1 (310) can transmit the NPCA indication frame (403) after '2*SIFS + CTS_TIME' from the time of completion of reception of the ICF (401). The CTS_TIME may be the expected transmission time of the CTS frame calculated based on the transmitted PPDU (physical layer protocol data unit) format and MCS (modulation and coding index) of the RTS frame.

[0094] As another example, if the two conditions described above are satisfied and the ICF (401) is a trigger frame (e.g., BSRP (buffer status report poll) trigger frame, MU-RTS (multi user request to send) trigger frame), AP 1 (310) can check the UL (uplink) length field included in the common info field of the ICF (401), and transmit the NPCA indication frame 2*SIFS+ (the time length of the frame indicated by the UL length field) after the transmission completion time of the ICF (401). Meanwhile, the time length of the frame indicated by the UL length field may be the value of the UL length field. Alternatively, if the UL length field has a value obtained by encoding the time length of the frame using a separate formula, the time length of the frame indicated by the UL length field is a time length based on a value obtained by decoding the value of the UL length field using a separate formula.

[0095] As another example, the ICR (402) may not have been transmitted in BSS 2. As a specific example, the transmission of the ICF (401) may have failed, preventing the ICR (402) from being transmitted. In the above-described case, at least one of the AP and non-AP STA of BSS 2 that transmitted the ICF (401) may retransmit the ICF (401) within the PIFS. AP 1 (310) may also recalculate the transmission time of the NPCA indication frame (403) from the time of completion of the transmission of the additional ICF (401). BSS 2 transmits ICF (401) and, if it does not receive ICR (402), AP 1 (310) may not transmit a frame at the time when transmission of the NPCA indication frame (403) is expected so as not to collide with the NPCA indication frame (403) of AP 1 (310) transmitted after ICF (401).

[0096] For example, AP 1 (310) may receive ICR (402) and transmit an NPCA indication frame after SIFS time. If AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) may transmit the NPCA indication frame (403) using only the main 20 MHz channel of AP 1 (310). This is so that AP 1 (310) minimizes the bandwidth of the NPCA indication frame (403) and minimizes interference on the remaining bands except for the bandwidth in which BSS 2 transmitted the frame. As another example, if AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) may transmit the NPCA indication frame (403) using the entire operating bandwidth of AP 1 (310). This is so that AP 1 (310) maximizes the bandwidth of the NPCA indication frame (403) so that the AP and non-AP STA of BSS 2 can detect the NPCA indication frame (403) of AP 1 (310).

[0097] Additionally, if AP 1 (310) can accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (403) to all or part of each 20MHz channel occupied by BSS 2. If AP 1 (310) transmits the NPCA indication frame (403) to a channel bandwidth wider than 20MHz (e.g., 40MHz, 80MHz, etc.), AP 1 (310) can also duplicate and transmit the frame for each 20MHz channel to improve the frame reception performance of BSS 2.

[0098] Also, for example, not only AP 1 (310) but also non-AP STA 1 connected to AP 1 (310) within BSS 1 may have received ICF (401) due to a difference in detection range, but may not receive ICR (402). Here, non-AP STA 1 may receive ICF (401) and receive NPCA indication frame (403) transmitted by AP 1 (310) as described above. Here, each of ICF (401), ICR (402) and NPCA indication frame (403) may be included in each PPDU and transmitted at SIFS intervals. That is, in the above-described situation, non-AP STA 1 receives the first PPDU including the ICF (401) for each of the three PPDUs, cannot receive the second PPDU including the ICR (402), and can receive the third PPDU including the NPCA indication frame (403). If the ICF (401) is an RTS frame, AP 1 (310) can transmit the NPCA indication frame (403) to non-AP STA 1 after '2*SIFS + CTS_TIME' from the time of completion of reception of the ICF (401). Alternatively, if the ICF (401) is a trigger frame, AP 1 (310) can check the UL length field of the ICF (401) and transmit the NPCA indication frame (403) after 2*SIFS + (the length indicated by the UL length field) from the time of completion of transmission of the ICF (401). In the above case, the MAC layer of non-AP STA 1 can acquire the primitive corresponding to the third PPDU after the expected time of the CTS frame or the UL length time of the trigger frame with ICR (402) after acquiring the primitive corresponding to the first PPDU, and according to the NPCA indication frame (403) of the third PPDU (e.g.A channel movement operation can be performed to an NPCA channel by checking the NPCA movement information of the NPCA indication frame or by acquiring a primitive corresponding to a PPDU including an NPCA indication frame.

[0099] That is, non-AP STA 1 can wait for 'aSIFSTime + CTS_Time (or UL length time of trigger frame)' time from the time of completion of reception of ICF (401) to the expected transmission of ICR (402), and after that time, can obtain a primitive corresponding to the third PPDU within the period of 'aSIFSTime + (2 Х aSlotTime))+ aRxPHYStartDelay', and can perform a channel movement operation to the NPCA channel according to the NPCA indication frame (403) of the third PPDU (e.g., when checking NPCA movement information of the NPCA indication frame or obtaining a primitive corresponding to a PPDU including the NPCA indication frame).

[0100] Specifically, non-AP STAs of BSS 1 can receive the NPCA indication frame (403) of AP 1 (310), and the non-AP STAs that receive the NPCA indication frame (403) can switch the operating channel to the NPCA primary channel. That is, the non-AP STAs can perform the NPCA operation. In addition, AP 1 (310) can switch the operating channel to the NPCA primary channel after transmitting the NPCA indication frame (403). That is, AP 1 (310) can also perform the NPCA operation. BSS 2 can perform data frame exchange in the TXOP, which is a time period in which multiple frames can be transmitted. AP 1 (310) and non-AP STAs of BSS 1 can perform the NPCA operation until the TXOP of BSS 2 ends. The NPCA indication frame (403) may indicate the 'length of time during which non-AP STAs of BSS 1 can perform the NPCA operation'. For example, the 'length of time during which the NPCA operation can be performed' may be indicated through the duration field of the MAC header of the frame or another field. The 'length of time during which the NPCA operation can be performed' may be a length of time corresponding to or shorter than the remaining TXOP of BSS 2 (e.g., a length of time excluding the time required for NPCA transition from the remaining TXOP of BSS 2).

[0101] Also, referring to FIGS. 4a to 4c, the combination of ICF (401) and ICR (402) may be as shown in Table 1 below.

[0102] [Table 1]

[0103]

[0104]

[0105] Referring to Table 1, when the ICF (401) and the ICR (402) are an RTS frame and a CTS frame, respectively, the two least significant bits (LSBs) of the TA (transmitter address) of the RTS frame and the reserved field of the SERVICE field in the data field following the PHY preamble of the PPDU may be used. Specifically, the first LSB of the TA of the RTS frame is an Individual / Group bit, and the corresponding bit may be set to 1. For example, the TA indicated as described above may be a bandwidth signaling TA. At least one of the AP and the non-AP STA that receives the RTS frame including the bandwidth signaling TA may check the service field in the data field of the preamble of the PPDU including the RTS frame. Some bits of the service field may be used as bits indicating an NPCA preamble. A CTS frame may be a frame that a wireless LAN terminal that has received an RTS frame transmits as a response frame. The CTS frame may re-indicate the value indicated in the TA field of the RTS frame with the RA (receiver address) field. In other words, the bandwidth signaling TA of the RTS frame may be identically included in the RA field of the CTS frame. In addition, the service field of the CTS frame may also be set identically to that of the RTS frame. In other words, the CTS frame may also include an NPCA preemption indicator.

[0106] Also, referring to Table 1, if ICF (401) and ICR (402) are MU-RTS trigger frames and CTS frames, respectively, they can be set in the same manner as described above. Specifically, the first LSB of the TA of the MU-RTS trigger frame is an Individual / Group bit, and the bit can be set to 1. In the case described above, it can also be a bandwidth signaling TA, and at least one of the AP and non-AP STA that received the MU-RTS trigger frame including the bandwidth signaling TA can check the service field. Here, some bits of the service field can be used as bits indicating NPCA preemption. As another example, the MU-RTS can be a change frame of the trigger frame. Considering the above, BW (bandwidth) information is indicated within the MAC frame of the MU-RTS trigger frame, and an NPCA preemption indicator can additionally be included. In the case described above, the bandwidth signaling TA may not be used. After that, a CTS frame can be transmitted in response to the MU-RTS trigger frame. The CTS frame can re-indicate the value indicated in the TA field of the MU-RTS trigger frame in the RA field. The service field of the CTS frame can also be set to the same as that of the MU-RTS trigger frame. Alternatively, the CTS frame can also include BW information and NPCA preemption indicator information included within the MAC frame. That is, a CTS frame including the NPCA preemption indicator can be transmitted in response.

[0107] Also, referring to Table 1, a case may be considered where the ICF (401) is a trigger frame (e.g., MU-RTS trigger frame, BSRP trigger frame). Here, NPCA preemption information may be included in the common info field or the user info field of the trigger frame. If the ICR (402) is a CTS frame, the LSB of the RA field of the CTS frame may be set to 1. The service field of the CTS frame may be set to a value indicating NPCA preemption. On the other hand, if the ICR (401) is a TB PPDU other than a CTS frame, the TB PPDU may include a separate indicator (e.g., special AID (association ID)-TID (traffic ID) field, indicator bit, information element, control field) indicating NPCA preemption. AP 1 (310) can check the NPCA preemption indicator through at least one of the combinations of ICF (401) and ICR (402) in Table 1 described above, and can transmit an NPCA indication frame (403) through the NPCA preemption indicator.

[0108] Additionally, as an example, the ICF (401) and ICR (402) frames including the NPCA pre-amnesia indicator transmitted within BSS 2 may be transmitted when specific conditions are satisfied. As a specific example, the ICF (401) and ICR (402) frames including the NPCA pre-amnesia indicator may be transmitted in BSS 2 only when the transmission of BSS 2 occupies the main 20MHz channel of BSS 1. Additionally, the ICF (401) and ICR (402) frames including the NPCA pre-amnesia indicator may be transmitted in BSS 2 only when the transmission of BSS 2 is longer than a certain length.

[0109] In addition, non-AP STAs in BSS 2 that do not detect a frame of an AP (AP 1) of BSS 1 that has performed NPCA cooperation with BSS 2 may not transmit an ICF (401) including an NPCA preemption indicator. For example, non-AP STAs in BSS 2 may check the NPCA cooperation setting in a management frame (e.g., beacon frame, association response frame, probe response frame, action frame) of AP 2 (320). The management frame transmitted from AP 2 (320) of BSS 2 to non-AP STAs may include an identifier of BSS 1 (e.g., BSSID, BSS Color) and an operating channel of BSS 1. Non-AP STAs may search for BSS 1 in the operating channel of BSS 1. If non-AP STAs detect communication of BSS 1 (e.g., communication of AP 1 of BSS 1, non-AP STAs of BSS 1), the non-AP STAs may transmit an ICF (401) including an NPCA preemption indicator. On the other hand, non-AP STAs that do not detect communication of BSS 1 may not transmit an ICF (401) including an NPCA preemption indicator.

[0110] Also, referring to FIGS. 4A to 4C, a frame indicating NPCA transmitted by AP 1 (310) may be a CTS frame. The RA of the CTS frame may be set to the BSSID of BSS 2. The duration field of the CTS frame may be indicated as 0. As another example, the RA of the CTS frame may be set to the MAC address of AP 1 (310). The LSB of the MAC address of AP 1 (310) may be set to 1 and may be set as a bandwidth signaling TA. In addition, a signal (SIGNAL) field present in the PPDU data field of the CTS frame may indicate NPCA operation of non-AP STAs belonging to BSS 1.

[0111] Alternatively, the frame indicating NPCA transmitted by AP 1 (310) may be a QoS (quality of service) Null frame, and an indicator included in the A-Control subfield of the QoS Null frame may indicate NPCA operation of non-AP STAs belonging to BSS 1.

[0112] Alternatively, the frame indicating NPCA transmitted by AP 1 (310) may be a Multi-STA BA frame, and an indicator included in the A-Control subfield of the QoS Null frame may indicate NPCA operation of non-AP STAs belonging to BSS 1, but may not be limited to the embodiment.

[0113] FIG. 5 is a diagram illustrating a wireless LAN subchannel communication instruction method based on AP adjustment applied to the present disclosure.

[0114] Referring to FIG. 5, at least one of an AP (AP 2) and a non-AP STA of BSS 2 may transmit an ICF (404) as the first frame of each TXOP. The ICF (404) may include an NPCA preemption indicator. For example, the ICF (404) may be an RTS frame. When the ICF (404) is an RTS frame, the TA of the RTS frame may be set to the address of at least one of the AP and the non-AP STA of BSS 2, and the RA may be set to the BSSID of AP 1 (310) (i.e., the MAC address of AP 1). In the above case, AP 1 (310) may receive the ICF (404) and transmit an NPCA indication frame. The NPCA indication frame (405) may be a CTS frame in which the RA is equal to the TA of the ICF (404).

[0115] As another example, the ICF (404) may be an MU-RTS trigger frame. If the ICF (404) is an MU-RTS trigger frame, the user info field of the MU-RTS trigger frame may indicate an AID reserved exclusively for AP 1 (310). That is, an identifier indicating AP 1 (310) may be included in the MU-RTS trigger frame. The TA of the MU-RTS trigger frame may be set to the address of at least one of the AP and non-AP STA of BSS 2. In the above case, the AP 1 (310) may receive the ICF (404) and transmit an NPCA indication frame (405). The NPCA indication frame (405) may be a CTS frame in which the RA is the same as the TA of the MU-RTS trigger frame.

[0116] As another example, the ICF (404) may be a BSRP trigger frame. If the ICF (404) is a BSRP trigger frame, the user information field of the BSRP trigger frame may indicate an AID reserved exclusively for AP 1. That is, an identifier indicating AP 1 (310) may be included in the BSRP trigger frame. In the above case, AP 1 (310) may receive the ICF (404) and transmit a TB PPDU. The TB PPDU may include a QoS Null frame or a Multi-STA BlockAck, and the QoS Null frame or the Multi-STA BlockAck may be an NPCA indication frame (405).

[0117] As another example, the ICF (404) may be an MU-RTS TXS trigger frame, which is a modified form of the MU-RTS trigger frame. If the ICF (404) is an MU-RTS TXS trigger frame, the user information field of the MU-RTS trigger frame may indicate an AID reserved exclusively for AP 1. That is, an identifier indicating AP 1 (310) may be included in the MU-RTS trigger frame. The allocated time of the MU-RTS TXS frame may be set to 0. Here, the allocated time being set to 0 allows transmission of only the NPCA indication frame (405). As another example, the allocated time of the MU-RTS TXS frame may be set to a value greater than or equal to 0. Setting the allocated time to a non-zero value may indicate that transmission of NPCA indication frames and transmission of response frames from non-AP STAs belonging to BSS 1 to the NPCA indication frames are permitted.

[0118] AP 1 (310) can receive ICF (404) and transmit an NPCA indication frame (405). The NPCA indication frame (405) can be a CTS frame in which RA is the same as TA of an MU-RTS trigger frame. If the allocated time of the MU-RTS TXS trigger frame is not 0, AP 1 (310) can transmit the NPCA indication frame (405) to non-AP STAs in BSS 1 and receive a response frame if a response frame is required. Here, the frame indicating NPCA transmitted by AP 1 (310) can be a QoS Null frame, and an indicator included in the A-Control subfield of the QoS Null frame can indicate NPCA operation of non-AP STAs belonging to BSS 1. Alternatively, the frame indicating NPCA transmitted by AP 1 (310) may be a Multi-STA BA frame, and an indicator included in the A-Control subfield of the Multi-STA BA frame may indicate NPCA operation of non-AP STAs belonging to BSS 1.

[0119] Since the NPCA indication frame (405) of AP 1 (310) is transmitted in response to the ICF (404), the NPCA indication frame (405) may be an ICR. Here, in response to the ICF (404), not only AP 1 (310) but also other non-AP STAs (non-AP STAs belonging to BSS 2) may transmit other ICRs (405).

[0120] If AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (405) using only the main 20 MHz channel of AP 1 (310). As another example, even if AP 1 (310) cannot accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame (405) using the entire operating bandwidth of AP 1 (310).

[0121] Additionally, if AP 1 (310) can accurately recognize the channel bandwidth occupied by BSS 2, AP 1 (310) can transmit the NPCA indication frame to all or part of each 20MHz channel occupied by BSS 2. If AP 1 (310) transmits the NPCA indication frame to a channel bandwidth wider than 20MHz (e.g., 40MHz, 80MHz, etc.), AP 1 (310) can duplicate and transmit the frame for each 20MHz channel to improve the frame reception performance of BSS 2.

[0122] When resources (e.g. resource units) are allocated from ICF (404) to AP 1 (310), AP 1 (310) can transmit an NPCA indication frame through the resources allocated from ICF (404). Non-AP STAs of BSS 1 can receive the NPCA indication frame (405) of AP 1 (310), and non-AP STAs that receive the NPCA indication frame (405) can switch the operating channel to the NPCA primary channel. That is, the NPCA operation can be performed. AP 1 (310) can switch the operating channel to the NPCA primary channel after transmitting the NPCA indication frame. That is, the NPCA operation can be performed.

[0123] BSS 2 can perform data frame exchange in TXOP, which is a time period in which multiple frames can be transmitted. AP1 and non-AP STAs of BSS 1 can perform NPCA operation until TXOP of BSS 2 ends. The NPCA indication frame (405) may indicate the 'length of time in which non-AP STAs of BSS 1 can perform NPCA operation'. For example, the 'length of time in which NPCA operation can be performed' may be indicated through a duration field of the MAC header of the frame or another field. The 'length of time in which NPCA operation can be performed' may be a time length corresponding to or shorter than the remaining TXOP of BSS 2 (e.g., a time length excluding the time required for NPCA transition in the remaining TXOP of BSS 2).

[0124] An ICF (404) containing an NPCA pre-amnesia indicator transmitted within BSS 2 may be transmitted when certain conditions are met. For example, an ICF (404) containing an NPCA pre-amnesia indicator may be transmitted in BSS 2 only when a transmission of BSS 2 occupies the main 20MHz channel of BSS 1. In addition, an ICF (404) and an ICR (405) containing an NPCA pre-amnesia indicator may be transmitted in BSS 2 only when a transmission of BSS 2 is longer than a certain length.

[0125] In addition, non-AP STAs in BSS 2 that do not detect a frame of an AP (AP 1) of BSS 1 that has performed NPCA cooperation with BSS 2 may not transmit an ICF (404) including an NPCA preemption indicator. For example, non-AP STAs in BSS 2 may check the NPCA cooperation setting in a management frame (e.g., a beacon frame, an association response frame, a probe response frame, an action frame) of AP 2 (320). Specifically, the management frame transmitted from AP 2 (320) of BSS 2 to non-AP STAs may include an identifier of BSS 1 (e.g., BSSID, BSS Color) and an operating channel of BSS 1. Non-AP STAs may search for BSS 1 in the operating channel of BSS 1. If non-AP STAs detect communication of BSS 1 (e.g., communication of AP 1 of BSS 1, non-AP STAs of BSS 1), the non-AP STAs may transmit an ICF (404) including an NPCA preemption indicator. On the other hand, non-AP STAs that do not detect communication of BSS 1 may not transmit an ICF (404) including an NPCA preemption indicator.

[0126]

[0127] In the following, a basic NAV and an intra-BSS NAV may be considered as network allocation vectors (NAVs) for NPCA operation. The basic NAV may be a NAV set by a BSS when a frame referenced for setting the NAV is transmitted from an OBSS. Alternatively, the basic NAV may be set even when it is not known whether the frame referenced for setting the NAV is transmitted from an OBSS or a BSS. When the basic NAV is set, non-AP STA 1 and AP 1 (310) of the BSS may start moving the operating channel to the NPCA primary channel. As another example, when the basic NAV is set by an RTS frame and a subsequent frame is received, non-AP STA 1 and AP 1 (310) of the BSS may start moving the operating channel to the NPCA primary channel. On the other hand, the intra-BSS NAV may be a NAV set by a frame transmission performed within the BSS. When the intra-BSS NAV is set, AP 1 (310) and non-AP STA 1 of the BSS may not start operating channel movement to the NPCA primary channel. The frame transmitted in the OBSS is an intra-BSS PPDU. The NAV transmitted in the BSS is an intra-BSS PPDU. Meanwhile, unless otherwise specified in the present disclosure, the NAV may mean a basic NAV.

[0128]

[0129] FIG. 6 is a diagram illustrating a method for configuring a wireless LAN frame for performing an NPCA operation in a hidden node environment applied to the present disclosure. The format of a non-HT PPDU transmitted in a wireless LAN may be as shown in FIG. 6. For example, a non-HT PPDU may be referred to as an OFDM (orthogonal frequency division multiplexing) PPDU, but may not be limited to a specific name. The basic transmission unit of a non-HT PPDU is 20 MHz, and when transmitting on a wideband channel, the PPDU may be transmitted by being duplicated in 20-MHz units (i.e., configured in a non-HT duplicate format). That is, a 20-MHz PPDU may be duplicated and transmitted on a wideband channel (e.g., 40 MHz, 80 MHz, 160 MHz, 320 MHz) as a non-HT PPDU having the same content. For example, the RTS (request to send) frame and the CTS (clear to send) frame described below may be configured based on a non-HT PPDU format or a non-HT duplicate format, but may not be limited thereto. Unless otherwise specified, a PPDU transmitted in a non-HT PPDU format may be a PPDU transmitted in a non-HT duplicate format depending on its transmission bandwidth (e.g., the transmission bandwidth of a PPDU transmitted with a bandwidth of 40 MHz or more).

[0130] In Fig. 6, the transmission direction of PPDU bits (or symbols) may be from left to right. When a PPDU is transmitted, the PHY preamble (601) of the PPDU may be transmitted first. The PHY preamble (601) may be a field that synchronizes and trains the receivers of APs and non-AP STAs. Afterwards, a signal (SIGNAL) field (602) may be transmitted, and then a data field (603) may be transmitted. Here, the first 16 bits of the data bits (603) may be a service (SERVICE) field. The service field may be composed of bits 0 to 15, and a total of 7 bits from 0 to 6 may be 'SCRAMBLER INITIALIZATION' bits. The bits may be a seed for dispersing the data bits within the data field. When AP and non-AP STAs transmit frames with the same data field or the same physical layer service data unit (PSDU) using the same 'SCRAMBLER INITIALIZATION' parameter (e.g., RTS frame with fixed MAC frame format, CTS frame, etc.), AP and non-AP STAs may compose frames that can be transmitted simultaneously (i.e., PPDUs with identical symbols). Next, bits 7 through 15 are reserved bits and may be indicated as all 0s. However, the reserved bits may be set to indicate a specific meaning. For example, bit 7 may be a bit to indicate a 320MHz channel bandwidth. When bit 7 is set to 1, it may indicate that the bandwidth over which non-HT PPDUs are transmitted is a total of 320MHz. In addition, as an example, two bits among the reserved bits may be used for NPCA operation.As a specific example, bits 8 and 9 may be used for NPCA operation, but this is not limited to this and other bits may also be used.

[0131] Bit 8 may be the 'COPY_SCRAMBLER_INITIAL_VALUE' bit. A transmitting STA may set this bit to 1 to transmit a PPDU, and a receiving STA may receive the PPDU. The receiving STA may need to copy the values ​​of the 'SCRAMBLER INITIALIZATION' bits of a response frame transmitted as a subsequent PPDU to the PPDU transmitted by the transmitting STA and use them as is in the PPDU transmitted by the transmitting STA. Specifically, a TXVECTOR may exist, which is a set of parameters that the transmitting STA sets to transmit a PPDU. In TXVECTOR, 'COPY_SCRAMBLER_INITIAL_VALUE' may be set to 1, and 'SCRAMBLER_INITIAL_VALUE' may be set to a specific value. The transmitting STA may construct and transmit a PPDU based on the TXVECTOR. That is, the 'SCRAMBLER INITIALIZATION' bits of the PPDU service field transmitted by the transmitting STA may be configured with the 'SCRAMBLER_INITIAL_VALUE' value of TXVECTOR, and the 'COPY_SCRAMBLER_INITIAL_VALUE' bits of the PPDU service field may be set to the 'COPY_SCRAMBLER_INITIAL_VALUE' value of TXVECTOR. TXVECTOR may be included in the PHY-TXSTART.request primitive, which is used by the MAC layer of the transmitting STA to request frame transmission to the PHY layer. When the receiving STA receives the PPDU, the PHY layer of the receiving STA may obtain the RXVECTOR from the PPDU. The RXVECTOR may be included in the PHY-RXSTART.indication primitive, which is a primitive generated by the PHY layer of the receiving STA. The parameters included in the RXVECTOR may be obtained from the preamble and header of the PPDU.In RXVECTOR, 'COPY_SCRAMBLER_INITIAL_VALUE' can be set to 1, and 'SCRAMBLER_INITIAL_VALUE' can be set to a specific value set by the transmitter. In addition, 'SCRAMBLER_INITIAL_VALUE' of RXVECTOR can be set to the value of the 'SCRAMBLER INITIALIZATION' bits of the PPDU service field transmitted by the transmitting STA. 'COPY_SCRAMBLER_INITIAL_VALUE' of RXVECTOR can be set to the value of the 'COPY_SCRAMBLER_INITIAL_VALUE' bits of the PPDU service field transmitted by the transmitting STA. When a receiving STA needs to transmit a response PPDU (response frame) to a PPDU received from a transmitting STA, the receiving STA can copy the 'SCRAMBLER_INITIAL_VALUE' of the RXVECTOR to the 'SCRAMBLER_INITIAL_VALUE' of the TXVECTOR of the receiving STA for transmitting the response PPDU since it has confirmed that 'COPY_SCRAMBLER_INITIAL_VALUE' is set to 1 in the RXVECTOR. The receiving STA can configure and transmit a PPDU based on the configured TXVECTOR. In addition, since the value of the 'SCRAMBLER INITIALIZATION' bits of the response PPDU transmitted by the receiving STA is set to the 'SCRAMBLER_INITIAL_VALUE' value of the TXVECTOR of the receiving STA, the value of the 'SCRAMBLER INITIALIZATION' bits of the service field of the response PPDU transmitted by the receiving STA to the transmitting STA may be the same as the value of the SCRAMBLER INITIALIZATION bits of the service field of the PPDU of the transmitting STA.When a transmitting STA transmits an RTS frame (MAC layer frame) and the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the service field of a PPDU (PHY layer frame) containing the RTS frame is set to 1, a receiving STA may set the 'SCRAMBLER INITIALIZATION' bits of a PPDU containing a CTS frame that must be transmitted in response to the RTS frame to be the same as those of the PPDU containing the RTS frame.

[0132] In addition, bit 9 among the bits described above may be the 'COPY_FRAME' bit. The 'COPY_FRAME' bit may be included in the PPDU service field including the CTS frame. The transmitting STA may transmit a PPDU including the RTS frame to the receiving STA, and the receiving STA may transmit a PPDU including the CTS frame. Here, the 'COPY_FRAME' bit of the PPDU service field of the receiving STA may be set to 1. When the transmitting STA receives the PPDU of the receiving STA, the PHY layer of the transmitting STA may obtain the RXVECTOR. The 'COPY_FRAME' value of the RXVECTOR of the PHY layer of the transmitting STA may be set to the 'COPY_FRAME' bit value of the PPDU service field of the receiving STA. For example, when the 'COPY_FRAME' value is 1, the transmitting STA may transmit a subsequent PPDU after a certain period of time (e.g., aSIFSTime + CTS_Time + aSIFSTime). Here, a listening STA, which is another STA capable of receiving a PPDU of a receiving STA, may be considered. The listening STA receives the PPDU of the receiving STA, and the PHY layer of the listening STA may acquire an RXVECTOR. The 'COPY_FRAME' value of the RXVECTOR of the PHY layer of the listening STA may be set to the value of the 'COPY_FRAME' bit of the PPDU service field of the receiving STA. In the above case, the listening STA may copy a PPDU including a CTS frame of the receiving STA, receive a PPDU including the CTS frame of the receiving STA, and perform transmission after an SIFS time.

[0133] Here, the positions of the bits used for the above-described NPCA operation may be changed. For example, in the above-described case, the bits in the PPDU service field indicate the NPCA operation, but the bits used for the NPCA operation are not fixed to a specific position in the service field, and other bits may be used. In other words, the above-described matter is only one example and may not be limited to the embodiment. In addition, for the convenience of explanation, in the following, a PPDU including an RTS frame, a PPDU including a CTS frame, a PPDU including a data frame, and a PPDU including a BlockAck frame are expressed as an RTS frame, a CTS frame, a data frame, and a BlockAck frame, respectively. However, the expression may refer to a PPDU including a specific frame, and may include the meaning of both a MAC layer frame and a PHY layer frame.

[0134] In a wireless LAN network, AP 1 and non-AP STA 1 can operate. AP 1 and non-AP STA 1 can be associated with each other and perform data communication. Other non-AP STAs other than non-AP STA 1 can also access AP 1 and perform data communication. Multiple non-AP STAs, including AP 1 and non-AP STA 1, can form a basic service set (BSS), which is a communication area that uses the same primary 20MHz channel. For example, in the following, a BSS formed by AP 1 and multiple non-AP STAs may be referred to as BSS 1. In addition, a set of channels including a primary 20MHz may be referred to as a primary channel. However, the foregoing names may not be limited thereto.

[0135] In a wireless LAN network, there may be another BSS occupying the primary 20MHz channel of BSS 1, which may be the OBSS described above. Communications of the OBSS (e.g., communication of AP 2 of the OBSS, communication of non-AP STA 2 of the OBSS) may occupy the primary 20MHz channel of BSS 1. BSS 1 may have a preset non-primary channel. The non-primary channel may be referred to as an NPCA primary channel or a sub-channel, and may not be limited to a specific name. The non-primary channel access (NPCA) may be a sub-channel access, which may be as described above. APs and non-AP STAs within a BSS can perform channel access operations and frame transmission operations by switching their operating channel to the NPCA primary channel when the primary 20MHz channel is occupied by an OBSS and the OBSS's communication section (e.g., the section where the default NAV set by the OBSS's transmission is set) is identified.

[0136] If the channel access operation of at least one of the AP and non-AP STA of the OBSS is successful, at least one of the AP and non-AP STA can obtain a TXOP capable of transmitting multiple frames. Here, the channel used in the OBSS can occupy the main 20MHz channel of BSS 1 configured by AP 1 and non-AP STA 1. However, as in FIG. 6, the communication (i.e., frame transmission) of at least one of the AP 2 and non-AP STA 2 may not be received by at least one of the AP 1 and non-AP STA 1.

[0137] For example, among AP 1 and non-AP STA 1 of BSS 1, only AP 1 can detect that the main 20MHz channel is occupied by the OBSS, and only AP 1 can switch its operating channel to the NPCA main channel. In the above case, if non-AP STA 1 transmits to AP 1 using the main channel, frame transmission may fail because AP 1 operates on the NPCA main channel.

[0138] As another example, both AP 1 and non-AP STA 1 of BSS 1 may not detect the communication of BSS 2. In the above-described case, the frame transmission and reception operations of non-AP STA 1 and AP 1 may cause interference to the communication of at least one of AP 2 and non-AP STA 2 of BSS 2. The above-described situations and problems may be equally applied to FIGS. 7A and 7B and 8A and 8B, and the following describes operations based on the above-described description.

[0139] FIG. 7a and FIG. 7b are diagrams showing an NPCA operation method in a hidden node environment applied to the present disclosure.

[0140] Referring to FIG. 7a, when the time length of a data frame transmitted by AP 2 (520) or the length of a TXOP (transmit opportunity), which is a time interval in which multiple frames can be transmitted, is greater than a certain threshold, AP 2 (520) may transmit an RTS (request to send) frame (604) that occupies the primary channel. The receiver of the RTS frame (604) transmitted by AP 2 (520) (i.e., receiver address (RA) of the MAC header) may be non-AP STA 2 (540), and non-AP STA 2 (540) may respond to the RTS frame (604) transmitted by AP 2 (520) with a CTS (clear to send) frame (605). When AP 2 (520) receives a CTS frame (605) of non-AP STA 2 (540), it can transmit a data frame (606) to non-AP STA 2 (540), and when non-AP STA 2 (540) receives a data frame (606) of AP 2 (520), it can receive a response frame (e.g., BlockAck frame, 607).

[0141] Here, the RTS frame (604) of AP 2 (520) may be received by AP 1 (510), but may not be received by non-AP STA 1 (530). On the other hand, the CTS frame (605) of non-AP STA 2 (540) may not be received by both non-AP STA 1 (530) and AP 1 (510). As another example, a case in which the CTS frame (605) of non-AP STA 2 (540) can be received by both non-AP STA 1 (530) and AP 1 (510) may also be considered. When AP 1 (510) receives frames of AP 2 (520) and non-AP STA 2 (540), it may set the basic NAV. Specifically, AP 1 (510) may set the basic NAV according to the following [Basic NAV Setting].

[0142]

[0143] [Basic NAV Settings]

[0144] AP 1 (510) may receive the RTS frame (604) of AP 2 (520) and check the duration field of the MAC header of the RTS frame (604) to set a default NAV for a period corresponding to the duration field. If the PHY-RXSTART.indication primitive occurs in the PHY layer of AP 1 (510) within the NAVTimeout ((2 × aSIFSTime) + (CTS_Time) + aRxPHYStartDelay + (2 Х aSlotTime)) period after AP 1 (510) completes receiving the RTS frame (604), AP 1 (510) may maintain the set default NAV. For example, if AP 1 (510) receives the RTS frame (604) and does not obtain the CTS frame (605), but obtains the primitive corresponding to the data frame (606) within the NAVTimeout period, the default NAV may be maintained. On the other hand, if the PHY-RXSTART.indication primitive does not occur in the PHY layer of AP 1 (510) within the NAVTimeout ((2 × aSIFSTime) + (CTS_Time) + aRxPHYStartDelay + (2 Х aSlotTime)) period after AP 1 (510) completes receiving the RTS frame (604), AP 1 (510) may release (e.g., initialize) the set default NAV. Here, CTS_Time may be an expected time required for CTS frame transmission. For example, CTS_TIME may be an expected time required for CTS frame transmission calculated based on the transmitted PPDU (physical layer protocol data unit) format and MCS (modulation and coding index) of the RTS frame.

[0145] Specifically, AP 1 (510) may not receive the CTS frame (605) of non-AP STA 2 (540), but may be able to receive the subsequent data frame (606) of AP 2 (520). Since the subsequent data frame (606) of AP 2 (520) starts transmitting SIFS time after the completion time of the CTS frame (605) transmitted by non-AP STA 2 (540), the PHY-RXSTART.indication primitive may be generated in the PHY layer of AP 1 (510) within the NAVTimeout period. Therefore, AP 1 (510) may not release (or initialize) the default NAV set as described above.

[0146] That is, after AP 1 (510) completes receiving the RTS frame (604), it may wait for the time period of "aSIFSTime + CTS_Time" in anticipation of transmitting the CTS frame (605), and after that time, the PHY-RXSTART.indication primitive may occur within the period of "aSIFSTime + (2 Х aSlotTime))+ aRxPHYStartDelay", and AP 1 (510) may not release (or initialize) the default NAV set as described above.

[0147] If a PHY-RXSTART.indication primitive is generated in the PHY layer of AP 1 (510) within the NAVTimeout period, AP 1 (510) may initiate channel movement to the NPCA primary channel. For example, if AP 1 (510) receives an RTS frame (604) and fails to acquire a CTS frame (605), but acquires a primitive corresponding to a data frame (606) within the NAVTimeout period, AP 1 (510) may maintain the default NAV and initiate channel movement to the NPCA primary channel.

[0148] The above PHY-RXSTART.indication primitive may be an example of a primitive that occurs when a PPDU is detected, and the PHY-RXSTART.indication primitive may be replaced by various primitives that occur when a PPDU is detected. As a specific example, the PHY-RXSTART.indication primitive may be replaced by the PHY-RXEARLYSIG.indication primitive.

[0149] AP 1 (510) may receive an RTS frame (604) as an ICF of the OBSS, but may not receive a CTS frame (605) as an ICR. Afterwards, AP 1 (510) may receive a data frame (606) following the CTS frame (605). Here, the RTS frame (604) as an ICF, the CTS frame (605) as an ICR, and the data frame (606) may be included in their respective PPDUs and transmitted at SIFS intervals. That is, in the above-described situation, AP 1 (510) may receive the first PPDU including the RTS frame (604) as an ICF for each of the three PPDUs, may not receive the second PPDU including the CTS frame (605) as an ICR, and may receive the third PPDU including the data frame (606). For example, AP 1 (510) may receive an RTS frame (604) of AP 2 (520), check the duration field of the MAC header of the RTS frame (604), and set a default NAV for a period corresponding to the duration field. After AP 1 (510) completes receiving the RTS frame (604), AP 1 (510) may receive a third PPDU including a data frame (606) within a NAVTimeout ((2 × aSIFSTime) + (CTS_Time) + aRxPHYStartDelay + (2 Х aSlotTime)) period, and thus AP 1 (510) may maintain the set default NAV.

[0150] That is, after AP 1 (510) completes receiving the RTS frame (604), it can wait for the time "aSIFSTime + CTS_Time" in anticipation of transmitting the CTS frame (605), and after that time, it can receive the third PPDU including the data frame (606) within the period "aSIFSTime + (2 Х aSlotTime)) + aRxPHYStartDelay", so that AP 1 (510) can maintain the default NAV that it has set.

[0151] In addition, AP 1 (510) can initiate channel movement to the NPCA channel. That is, the MAC layer of AP 1 (510) can acquire a primitive corresponding to the third PPDU including a data frame (606) within the NAVTimeout period after acquiring a primitive corresponding to the first PPDU including an RTS frame (604), and upon acquiring the primitive of the third PPDU, maintain the basic NAV and initiate channel movement to the NPCA channel.

[0152]

[0153] In addition, when AP 1 (510) receives the CTS frame (604) of non-AP STA 2 (540), AP 1 (510) may not release (or initialize) the default NAV set as described above. AP 1 (510) may start moving to the NPCA primary channel after completing the reception of the CTS frame (604) of non-AP STA 2 (540). The time point at which AP 1 (510) starts moving the operating channel to the NPCA primary channel may be either the time point at which a subsequent data frame is received without receiving the CTS frame or the time point at which the CTS frame is received. That is, the time point at which AP 1 (510) moves the operating channel to the NPCA primary channel may be the time point at which the default NAV of AP 1 (510) is not initialized (confirmed).

[0154] Likewise, the point in time when non-AP STA 1 (530) moves its operating channel to the NPCA primary channel may be the point in time when the default NAV of non-AP STA 1 (530) is not initialized (confirmed). Here, AP 1 (510) may recognize that non-AP STA 1 (530) has not received the RTS frame (604) and the CTS frame (605) of AP 2 (520) and non-AP STA 2 (540). Alternatively, AP 1 (510) may recognize that non-AP STA 1 (530) is unable to move to the NPCA primary channel due to a hidden node problem.

[0155] Here, AP 2 (520) may recognize that a hidden node problem may occur in AP 1 (510), which is a neighboring AP, and a non-AP STA (e.g., non-AP STA 1) connected to AP 1 (510). Specifically, AP 2 (520) may recognize the above-described information through information exchange (or channel measurement procedure) with AP 1 (510). Alternatively, AP 2 (520) may not recognize the existence of AP 1 (510) and a non-AP STA connected to AP 1 (510), but may want to prevent the neighboring AP and the non-AP STA connected to the neighboring AP from not being able to smoothly perform the NPCA operation due to the hidden node problem.

[0156] Considering the above, an exchange procedure of RTS frames and CTS frames of AP 2 (520), non-AP STA 2 (540), and AP 1 (510) may be performed. The RTS frame (604) of AP 2 (520) may be a frame in which the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the SERVICE field of the PPDU illustrated in FIG. 7 is set to 1. In the above-described case, non-AP STA 2 (540) and AP 1 (510) may receive the RTS frame (604) in which the corresponding bit is set to 1. Non-AP STA 2 (540) and AP 1 (510) may receive the RTS frame (604) of AP 2 (520) and obtain an RXVECTOR. The RXVECTOR may include 'SCRAMBLER_INITIAL_VALUE'. Non-AP STA 2 (540) and AP 1 (510) may include 'SCRAMBLER_INITIAL_VALUE' acquired from RXVECTOR in TXVECTOR to cause the PHY layer to transmit a CTS frame (605, 608). Accordingly, the RTS frame (604) of AP 2 (520) and the CTS frames (605, 608) of non-AP STA 2 (540) and AP 1 (510) may have 'SCRAMBLER_INITIALIZATION' bits of the same service field.

[0157] For example, the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the service field of the CTS frames (605, 608) of AP 1 (510) and non-AP STA 2 (540) may be set to 0. The RA (receiver address) of the MAC header of the CTS frames (605, 608) of non-AP STA 2 (540) and AP 1 (510) may be the same as the address of AP 2 (520) (i.e., the BSSID address of AP 2). The CTS frames (605, 608) of non-AP STA 2 (540) and AP 1 (510) may have the 'SCRAMBLER_INITIALIZATION' bits of the same service field. In addition, since the two CTS frames (605, 608) have the same content (e.g., same MPDU content, PSDU content), the two frames can be transmitted simultaneously. That is, even if non-AP STA 2 (540) and AP 1 (510) transmit CTS frames (605, 608) simultaneously, a collision between the two frames may not occur. Meanwhile, the CTS frame (608) of AP 1 (510) may be received by non-AP STA 1 (530) connected to AP 1 (510). The non-AP STA 1 (530) may receive the CTS frame (608) of AP 1 (510) and confirm that the RA indicates the address of AP 2 (520) rather than the address of AP 1 (510) (i.e., not the address of AP 1 to which non-AP STA 1 is connected). Accordingly, non-AP STA 1 (530) can set a default NAV corresponding to the duration field of the MAC header of the CTS frame (608). Since non-AP STA 1 (530) receives the CTS frame (608) and sets the default NAV, the default NAV may not be released. If non-AP STA 1 (530) sets the default NAV, non-AP STA 1 (530) can move the operating channel to the NPCA primary channel.When the above-described operation is performed, the time at which AP 1 (510) transmits the CTS frame (608) may correspond to the time at which non-AP STA 2 (540) transmits the CTS frame (608). Therefore, the time at which AP 1 (510) starts to move the operating channel to the NPCA primary channel may be the time at which the CTS frame is transmitted. This may mean that when AP 1 (510) transmits the CTS frame (608), the basic NAV set by AP 1 (510) based on the RTS frame (604) is confirmed. Alternatively, the time at which AP 1 (510) starts to move the operating channel to the NPCA primary channel may be considered as a time at which the basic NAV is not confirmed because AP 1 (510) has transmitted the CTS frame (608) but has not received the CTS frame. In the above-described case, the time point at which AP 1 (510) starts to move its operating channel to the NPCA primary channel may be the time point at which a subsequent data frame is received. That is, AP 1 (510) may start to move its operating channel to the NPCA primary channel from the time point at which it receives the preamble of a data frame (606) transmitted after a subsequent CTS frame that it did not receive. The time point at which non-AP STA 1 (530) starts to move its operating channel to the NPCA primary channel may be the time point corresponding to the time point at which it receives a subsequent data frame.

[0158] AP 2 (520) and non-AP STA 2 (540) can perform frame transmission and reception operations on the primary channel. AP 1 (510) and non-AP STA 1 (530) can operate (e.g., perform channel access operations and frame transmission and reception operations) on the NPCA primary channel for a period corresponding to the basic NAV set based on the RTS frame (604) and CTS frame (605) of at least one of AP 2 (520) and non-AP STA 2 (540), and can operate on the primary channel again when the basic NAV ends. The time at which AP 1 (510) and non-AP STA 1 (530) start operating on the NPCA primary channel may be a time at which the end of the switching delay between AP 1 (510) and non-AP STA 1 (530) (or other non-AP STAs associated with AP 1 (510)) becomes late.

[0159] AP 1 (510) and AP 2 (520) may share some of their BSS information through a pre-established pre-tuning process. For example, at least one of the operating channel and operating channel bandwidth information of each BSS, NPCA primary channel information, TXOP length threshold for NPCA operation, and other information may be pre-shared. In the above-described case, a condition may be added that AP 2 (520) transmits an RTS frame (604) with the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the service field of the PPDU illustrated in FIG. 7 set to 1 when a specific condition is satisfied for neighboring APs with which content including the above-described information is shared. For example, if the channel band transmitting the RTS frame (604) does not occupy the entire operating channel of AP 1 (510), or if it occupies the primary channel of AP 1 (510) but does not occupy the NPCA primary channel, AP 2 (520) may transmit the RTS frame (604) with the 'COPY_SCRAMBLER_INITIAL_VALUE' bit set to 1.

[0160] As another example, the 'COPY_SCRAMBLER_INITIAL_VALUE' bit may be set to 1 so that AP 1 (510) can perform the NPCA operation even when the length of the transmitted TXOP does not exceed the TXOP length threshold for the NPCA operation of AP 1 (510). As another example, the 'COPY_SCRAMBLER_INITIAL_VALUE' bit may be set to 1 so that AP 1 (510) can perform the NPCA operation when the length of the transmitted TXOP exceeds the TXOP length threshold for the NPCA operation of AP 1 (510). Here, the above conditions may be conditions that must be satisfied in part or in whole at the same time.

[0161] For example, when multiple APs exist around AP 2 (520), if there is at least one AP that satisfies the above condition, the 'COPY_SCRAMBLER_INITIAL_VALUE' bit can be set to 1. If the APs around AP 2 (520), including AP 1 (510), have previously shared BSS information with AP 2 (520), they can receive an RTS frame (604) with the 'COPY_SCRAMBLER_INITIAL_VALUE' bit set to 1. The APs around AP 2 (520), including AP 1 (510), can use the TXOP length threshold, the BW information of the service field of the RTS, and the operating channel information of AP 2 (520) to determine whether their NPCA primary channel is occupied. Here, if TXOP does not exceed the TXOP length threshold and the NPCA primary channel is not occupied, APs surrounding AP 2 (520), including AP 1 (510), can transmit a CTS frame (605).

[0162] Referring to FIG. 7b, an exchange procedure of RTS frames and CTS frames among AP 2 (520), non-AP STA 2 (540), and AP 1 (510) may be performed, which may be the same as described above. Here, when the time length of a data frame transmitted by AP 2 (520) or the length of a TXOP (transmit opportunity), which is a time interval in which multiple frames can be transmitted, is greater than a certain threshold, AP 2 (520) may transmit an MU (multi-user)-RTS (request to send) trigger frame that occupies the primary channel. The RA of the MAC header of the MU-RTS trigger frame (608) transmitted by AP 2 (520) may be a broadcast address. That is, all terminals to which the MU-RTS trigger frame (608) reaches may be recipients of the MU-RTS trigger frame (608). The MU-RTS trigger frame (608) may be receivable by multiple terminals including non-AP STA 2 (540) and AP 1 (510). The user information (user info) field of the MU-RTS trigger frame (608) may instruct non-AP STA 2 (540) and AP 1 (510) to transmit S (simultaneous)-CTS frames (609, 612) in response to the MU-RTS trigger frame (608). The S-CTS frames (609, 612) may be a method in which multiple non-AP STAs transmit CTS frames with the same content. Specifically, the AID (association identifier) ​​of non-AP STA 2 (540), the bandwidth over which non-AP STA 2 (540) must transmit an S-CTS frame, the AID of AP 1 (510), and the bandwidth over which AP 1 (510) must transmit an S-CTS frame may be included in each user field. The AID of AP 1 (510) may be an AID dedicated to AP 1 (510) (i.e., it can identify only AP 1) or may be an AID for multiple APs (e.g.,It may be an AID that indicates APs performing NPCA operations. The AID may be an identifier (or identification number) that can be used to distinguish and identify non-AP STAs and surrounding APs connected to AP 2 (520).

[0163] Non-AP STA 2 (540) and AP 1 (510) may receive the MU-RTS trigger frame (608) and acquire an RXVECTOR. The RXVECTOR may include 'SCRAMBLER_INITIAL_VALUE'. Non-AP STA 2 (540) and AP 1 (510) may include the 'SCRAMBLER_INITIAL_VALUE' obtained from the RXVECTOR in the TXVECTOR so that the PHY layer may transmit a CTS frame (609, 612). As a result, the RTS frame (608) of AP 2 (520) and the CTS frames (609, 612) of non-AP STA 2 (540) and AP 1 (510) may have 'SCRAMBLER_INITIALIZATION' bits of the same service field. The RA (receiver address) of the MAC header of the CTS frames (609, 611) of non-AP STA 2 (540) and AP 1 (510) may be the same as the address of AP 2 (520) (i.e., the BSSID address of AP 2). In addition, the CTS frames (609, 612) of non-AP STA 2 (540) and AP 1 (510) may have the 'SCRAMBLER_INITIALIZATION' bits of the same service field. Since the two CTS frames (609, 612) have the same contents (same MPDU contents, PSDU contents), the two frames may be transmitted simultaneously. That is, even if non-AP STA 2 (540) and AP 1 (510) transmit the CTS frames (609, 612) simultaneously, a collision between the two frames may not occur. Meanwhile, the CTS frame (612) of AP 1 (510) can be received by non-AP STA 1 (530) connected to AP 1 (510).

[0164] Non-AP STA 1 (530) can receive the CTS frame (612) of AP 1 (510) and recognize that the RA indicates the address of AP 2 (520) rather than the address of AP 1 (510) (i.e., not the address of AP 1 to which non-AP STA 1 is connected). Therefore, non-AP STA 1 (530) can set a default NAV corresponding to the duration field of the MAC header of the CTS frame (612). Since non-AP STA 1 (530) sets the default NAV by receiving the CTS frame (612), the default NAV may not be released. Specifically, non-AP STA 1 (530) may not receive the RTS frame (608) transmitted prior to the CTS frame (612). Here, non-AP STA 1 (530) can recognize whether the CTS frame (612) with only the subsequent RA field is an intra-BSS PPDU transmitted within its own BSS or an inter-BSS PPDU transmitted from an external OBSS by receiving an RTS frame (608) having both RA and TA fields. However, since non-AP STA 1 (530) did not receive the RTS frame (608), it can determine that the CTS frame (612) in which the RA is the address of AP 2 (520) (i.e., not the address of AP 1 to which non-AP STA 1 is connected) is a PPDU that is neither an intra-BSS PPDU nor an inter-BSS PPDU.

[0165] If non-AP STA 1 (530) determines that the CTS frame (612) is neither an intra-BSS PPDU nor an inter-BSS PPDU, non-AP STA 1 (530) may set a default NAV based on the CTS frame (612). Here, if non-AP STA 1 (530) sets the default NAV, it may move the operating channel to the NPCA primary channel. When moving the operating channel to the NPCA primary channel, the time at which AP 1 (510) transmits the CTS frame (612) may correspond to the time at which non-AP STA 2 (540) transmits the CTS frame (609). Therefore, the time at which AP 1 (510) starts moving the operating channel to the NPCA primary channel may be the time at which it transmits the CTS frame. That is, when AP 1 (510) transmits the CTS frame (612), the basic NAV set by AP 1 (510) based on the MU-RTS trigger frame (608) can be confirmed. Alternatively, the point in time when AP 1 (510) starts to move the operating channel to the NPCA primary channel may be considered as not being able to confirm the basic NAV because AP 1 (510) transmitted the CTS frame (612) but did not receive the CTS frame. Accordingly, the point in time when AP 1 (510) starts to move the operating channel to the NPCA primary channel may be the point in time when the subsequent data frame (610) is received. That is, the operating channel can start to move to the NPCA primary channel from the point in time when AP 1 (510) receives the preamble of the data frame (610) transmitted after the subsequent CTS frame (609) that AP 1 (510) did not receive. The point in time when non-AP STA 1 (530) starts to move the operating channel to the NPCA primary channel may also correspond to the point in time when the subsequent data frame (610) is received.

[0166] AP 2 (520) and non-AP STA 2 (540) can perform frame transmission and reception operations on the primary channel. AP 1 (510) and non-AP STA 1 (530) can operate (e.g., perform channel access operations and frame transmission and reception operations) on the NPCA primary channel for a period corresponding to a basic NAV set based on an RTS frame (608) and a CTS frame (609) of at least one of AP 2 (520) and non-AP STA 2 (540), and can operate on the primary channel again when the basic NAV ends. The time at which AP 1 (510) and non-AP STA 1 (530) start operating on the NPCA primary channel may be a time at which the switching delay ends later among AP 1 (510) and non-AP STA 1 (530) (or other non-AP STAs connected to AP 1). For example, AP 1 (510) and AP 2 (520) may share some of their BSS information through a preset pre-tuning process. Specifically, AP 1 (510) and AP 2 (520) may pre-share at least one of the operating channel information of each BSS, NPCA primary channel information, TXOP length threshold for NPCA operation, and other information. In the above case, AP 2 (520) may add a condition to transmit an MU-RTS trigger frame (608) that triggers AP 1 (510) only when a specific condition is satisfied for neighboring APs with which content including the above-described information is shared.

[0167] As a specific example, the MU-RTS trigger frame (608) that triggers AP 1 (510) may be transmitted only when the channel band transmitting the MU-RTS trigger frame (608) does not occupy the entire operating channel of AP 1 (510) or occupies the primary channel of AP 1 (510) but does not occupy the NPCA primary channel. Alternatively, the MU-RTS trigger frame (608) that triggers AP 1 (510) may be transmitted only when the length of the transmitted TXOP does not exceed the TXOP length threshold for the NPCA operation of AP 1 (510). Alternatively, the above-described conditions may be conditions that must be satisfied in part or in whole at the same time. For example, when multiple APs exist around AP 2 (520), the MU-RTS trigger frame (608) that triggers the corresponding AP may be transmitted if there is at least one AP that satisfies the above-described condition.

[0168] In FIGS. 7A and 7B, AP 1 (510) can transmit a CTS frame for NPCA operation even if the basic NAV has been set by the RTS frame transmitted by AP 2 (520). Since the CTS frame transmitted by AP 1 (510) can be regarded as an immediate response frame to the RTS frame transmitted by AP 2 (520), the CTS frame for NPCA operation can be transmitted as described above. Here, the immediate response frame can be transmitted ignoring the basic NAV.

[0169] FIG. 8a and FIG. 8b are diagrams showing an NPCA operation method in a hidden node environment applied to the present disclosure.

[0170] Referring to FIGS. 8A and 8B, when the time length of a data frame transmitted by non-AP STA 2 (540) or the length of a TXOP (transmit opportunity), which is a time interval in which multiple frames can be transmitted, is greater than a certain threshold, non-AP STA 2 (540) may transmit an RTS (request to send) frame (613) that occupies the primary channel. The receiver (i.e., Receiver Address (RA) of the MAC header) of the RTS frame (613) transmitted by non-AP STA 2 (540) may be AP 2 (520), and AP 2 (520) may respond to the RTS frame (613) transmitted by non-AP STA 2 (540) with a CTS (clear to send) frame (614).

[0171] When non-AP STA 2 (540) receives a CTS frame (614) of AP 2 (520), it can transmit a data frame (616) to AP 2 (520), and when AP 2 (520) receives a data frame (616) of non-AP STA 2 (540), it can receive a response frame (e.g., BlockAck frame, 617).

[0172] For example, the RTS frame (613) of non-AP STA 2 (540) may not be received by both AP 1 (510) and non-AP STA 1 (530) as described above. On the other hand, the CTS frame (614) of AP 2 (520) may be received by AP 1 (510). AP 1 (510) may receive the CTS frame (614) of AP 2 (520) and set a default NAV, and the default NAV set by AP 1 (510) may not be released because it is based on the CTS frame (614). (That is, the default NAV may be confirmed.) However, non-AP STA 1 (530) connected to AP 1 (510) may not receive both the RTS frame (613) and the CTS frame (614) of AP 2 (520). Therefore, non-AP STA 1 (530) cannot set the default NAV. AP 1 (510) may recognize that non-AP STA 1 (530) did not receive the RTS frame (613) and CTS frame (614) of AP 2 (520) and non-AP STA 2 (540), and may want to prevent the problem of non-AP STA 1 (530) not being able to move to the NPCA main channel due to a hidden node problem. AP 2 (520) may recognize that a hidden node problem may occur in AP 1 (510), which is a neighboring AP, and a non-AP STA (e.g., non-AP STA 1) connected to AP 1 (510) through information exchange with AP 1 (510) (or channel measurement procedure). Alternatively, AP 2 (520) may be unaware of the existence of AP 1 (510) and non-AP STAs connected to AP 1 (510), but may want to prevent surrounding APs and non-AP STAs connected to surrounding APs from not being able to perform NPCA operations smoothly due to hidden node issues.Accordingly, the following exchange procedure of RTS frame (613) and CTS frame (614) of AP 2 (520), non-AP STA 2 (540), and AP 1 (510) can be performed.

[0173] Referring to FIG. 8A, the 'COPY_FRAME' bit of the service field of the CTS frame (614) of AP 2 (520) may be set to 1. The CTS frame (614) of AP 2 (520) may be received by non-AP STA 2 (540) and AP 1 (510), and non-AP STA 2 (540) and AP 1 (510) may perform different operations after receiving the CTS frame (614). Non-AP STA 2 (540) may receive the CTS frame (614) of AP 2 (520) and wait without transmitting a data frame (615) to AP 2 (520) immediately (or after SIFS time). Non-AP STA 2 (540) can wait without transmitting a frame for 'SIFS + CTS_RxTime + SIFS' time after receiving the CTS frame (614) of AP 2 (520).

[0174] CTS_RxTime may be CTS_Time, which is the expected transmission time length of the CTS frame. Alternatively, CTS_RxTime may be the transmission time length of an actual CTS frame (614) received from AP 2 (520). Non-AP STA 2 (540) may receive the CTS frame (614) of AP 2 (520) and transmit a data frame (615) to AP 2 (520) after 'SIFS + CTS_RxTime + SIFS' time. AP 1 (510) may confirm that the 'COPY_FRAME' bit of the service field of the CTS frame (614) of AP 2 (520) is set to 1. AP 1 (510) may receive the CTS frame (614) of AP 2 (520) and transmit a copy of the CTS frame (617) received from AP 2 (520) after SIFS. Here, the RA of the CTS frame (614) of AP 2 (520) may be non-AP STA 2 (540). Therefore, when AP 1 (510) duplicates and transmits the CTS frame received from AP 2 (520), the RA of the CTS frame may be non-AP STA 2 (540). Non-AP STA 1 (530) cannot receive the CTS frame (614) of AP 2 (520), but can receive the CTS frame (617) duplicated and transmitted by AP 1 (510). Non-AP STA 1 (530) can confirm that the RA of the CTS frame (617) received from AP 1 (510) is not the address of AP 1 (510), and non-AP STA 1 (530) can set the default NAV. As another example, instead of AP 1 (510) transmitting an identical copy of the CTS frame (614) of AP 2 (520), AP 1 (510) may modify the RA of the CTS frame (617) and transmit it to AP 2 (520).Even in the above-described case, non-AP STA 1 (530) can confirm that the RA of the CTS frame (617) received from AP 1 (510) is not the address of AP 1 (510), and non-AP STA 1 (530) can set the default NAV.

[0175] As a more specific example, non-AP STA 1 (530) may not receive an RTS frame transmitted before a CTS frame. When non-AP STA 1 (530) receives an RTS frame in which both RA and TA fields exist, non-AP STA 1 (530) can determine whether the subsequent CTS frame in which only the RA field exists is an intra-BSS PPDU transmitted within its own BSS or an inter-BSS PPDU transmitted from an external OBSS. However, since non-AP STA 1 (530) did not receive the RTS frame, non-AP STA 1 (530) may determine the CTS frame in which the RA is not the address of AP 1 (510) (i.e., not the address of AP 1 to which non-AP STA 1 is connected) as a PPDU that is neither an intra-BSS PPDU nor an inter-BSS PPDU. If non-AP STA 1 (530) determines that the CTS frame (617) is neither an intra-BSS PPDU nor an inter-BSS PPDU, non-AP STA 1 (530) can set a default NAV based on the CTS frame (617). AP 1 (510) can start operating channel movement to the NPCA primary channel after replicating and transmitting the CTS frame (614) of AP 2 (520). If non-AP STA 1 (530) receives the replicating CTS frame (617) of AP 1 (510) and sets a default NAV, non-AP STA 1 (530) can start operating channel movement to the NPCA primary channel. AP 2 (520) and non-AP STA 2 (540) can perform frame transmission and reception operations on the primary channel. AP 1 (510) and non-AP STA 1 (530) operate (e.g.,) on the NPCA primary channel for a period corresponding to the default NAV established based on the RTS frame and CTS frame of at least one of AP 2 (520) and non-AP STA 2 (540).(performing channel access operations and frame transmission / reception operations) and can operate on the primary channel again when the basic NAV ends. The time at which AP 1 (510) and non-AP STA 1 (530) start operating on the NPCA primary channel may be the time at which the switching delay ends later among AP 1 (510) and non-AP STA 1 (530) (or other non-AP STAs connected to AP 1). AP 1 (510) may ignore the CTS frame (614) transmitted by AP 2 (520) although the basic NAV is set. AP 1 (510) may transmit a CTS frame (617) for initiating NPCA operations of non-AP STAs within the BSS of AP 1 (510), and AP 1 (510) may perform NPCA switching initiation after transmitting the CTS frame (617). Non-AP STAs within the BSS of AP 1 (510) that receive both the RTS frame transmitted by AP 2 (520) and the CTS frame transmitted by non-AP STA 2 (540) can perform NPCH operation by switching to the NPCA primary channel with the default NAV set. Alternatively, non-AP STAs within the BSS of AP 1 (510) can wait for the CTS frame transmission of AP 1 (510) when they receive the CTS frame of AP 2 (520) with the 'COPY_FRAME' bit of the service field set to 1, and can perform NPCA operation by switching to the NPCA primary channel after receiving the CTS frame. In the above case, non-AP STAs can recognize the time at which operation starts on the NPCA primary channel of AP 1 (510) by calculating it from the time at which AP 1 (510) transmits the CTS frame.

[0176] Also, referring to FIG. 8b, the 'COPY_FRAME' bit of the service field of the CTS frame (614) of AP 2 (520) may be set to 1, and the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the service field of the CTS frame (614) may be set to 1. The CTS frame (614) of AP 2 (520) may be received by non-AP STA 2 (540) and AP 1 (510). The non-AP STA 2 (540) and AP 1 (510) may perform other operations after receiving the CTS frame (614). The non-AP STA 2 (540) may receive the CTS frame (614) of AP 2 (520) and wait without transmitting a data frame (615) to AP 2 (520) immediately (or after a SIFS time). Non-AP STA 2 (540) can wait without transmitting a frame for 'SIFS + CTS_RxTime + SIFS' time after receiving the CTS frame (614) of AP 2 (520). CTS_RxTime can be the expected time length of the CTS frame, CTS_Time, or the time length of the actual CTS frame (614) received from AP 2 (520). Non-AP STA 2 (540) can transmit a data frame (615) to AP 2 (520) after 'SIFS + CTS_RxTime + SIFS' time after receiving the CTS frame (614) of AP 2 (520). AP 1 (510) can confirm that the 'COPY_FRAME' bit of the service field of the CTS frame (614) of AP 2 (520) is set to 1. Additionally, AP 1 (510) can confirm that the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the CTS frame (614) service field is set to 1. AP 1 (510) can receive the CTS frame (614) of AP 2 (520) and, after SIFS, copy and transmit the CTS frame received from AP 2 (520).Since the 'COPY_SCRAMBLER_INITIAL_VALUE' bit of the service field of the CTS frame (614) of AP 2 (520) is set to 1, AP 1 (510) may need to use the same 'SCRAMBLER_INITIAL_VALUE' bit when copying and transmitting the CTS frame. When AP 1 (510) receives the CTS frame (614) of AP 2 (520), it can obtain RXVECTOR and obtain the 'SCRAMBLER_INITIAL_VALUE' parameter included in the RXVECTOR. When AP 1 (510) copies and transmits the CTS frame, it can include the 'SCRAMBLER_INITIAL_VALUE' parameter obtained from RXVECTOR in TXVECTOR and transmit the CTS frame using the TXVECTOR. Therefore, when AP 1 (510) duplicates and transmits the CTS frame, the 'SCRAMBLER_INITIAL_VALUE' bit of the CTS frame service field may be identical to the 'SCRAMBLER_INITIAL_VALUE' bit of the CTS frame received from AP 2 (520). AP 2 (520) may transmit the CTS frame (614) and then, after SIFS, transmit a second CTS frame (618) having the same content as the first transmitted CTS frame (614). The second CTS frame (618) may be transmitted at the same time as the CTS frame (617) transmitted by AP 1 (510). The 'SCRAMBLER_INITIAL_VALUE' bit of the second CTS frame (618) may be identical to the 'SCRAMBLER_INITIAL_VALUE' bit of the first transmitted CTS frame (614). That is, the replicated CTS frame (617) of AP 1 (510) and the second CTS frame (618) of AP 2 (520) may be identical. Therefore, even if the two frames are transmitted simultaneously, a collision may not occur. The RA of the CTS frame of AP 2 (520) may be non-AP STA 2 (540).Therefore, when AP 1 (510) duplicates and transmits the CTS received from AP 2 (520), the RA of the CTS frame may be non-AP STA 2 (540). Non-AP STA 1 (530) cannot receive the CTS frame (618) of AP 2 (520), but can receive the CTS frame (617) duplicated and transmitted by AP 1 (510). Non-AP STA 1 (530) can confirm that the RA of the CTS frame (617) received from AP 1 (510) is not the address of AP 1 (510), and non-AP STA 1 (530) can set the default NAV.

[0177] As a more specific example, non-AP STA 1 (530) may not receive an RTS frame transmitted before a CTS frame. When non-AP STA 1 (530) receives an RTS frame in which both RA and TA fields exist, non-AP STA 1 (530) can determine whether the subsequent CTS frame in which only the RA field exists is an intra-BSS PPDU transmitted within its own BSS or an inter-BSS PPDU transmitted from an external OBSS. However, since non-AP STA 1 (530) did not receive the RTS frame, non-AP STA 1 (530) may determine the CTS frame in which the RA is not the address of AP 1 (510) (i.e., not the address of AP 1 to which non-AP STA 1 is connected) as a PPDU that is neither an intra-BSS PPDU nor an inter-BSS PPDU. If non-AP STA 1 (530) determines that the CTS frame (617) is neither an intra-BSS PPDU nor an inter-BSS PPDU, non-AP STA 1 (530) can set a default NAV based on the CTS frame (617). AP 1 (510) can start operating channel movement to the NPCA primary channel after duplicating and transmitting the CTS frame (614) of AP 2 (520).

[0178] When non-AP STA 1 (530) receives the duplicated CTS frame (617) of AP 1 (510) and sets the default NAV, non-AP STA 1 (530) may start operating channel movement to the NPCA primary channel. AP 2 (520) and non-AP STA 2 may perform frame transmission and reception operations on the primary channel. AP 1 (510) and non-AP STA 1 (530) may operate (e.g., perform channel access operations and frame transmission and reception operations) on the NPCA primary channel for a period corresponding to the default NAV set based on the RTS frame and CTS frame of at least one of AP 2 (520) and non-AP STA 2, and may operate on the primary channel again when the default NAV ends. The time at which AP 1 (510) and non-AP STA 1 (530) start operation on the NPCA primary channel may be a time at which the end of the switching delay between AP 1 (510) and non-AP STA 1 (530) (or other non-AP STAs connected to AP 1) becomes later. AP 1 (510) may ignore the CTS frame (614) transmitted by AP 2 (520) although the default NAV is set. AP 1 (510) may transmit a CTS frame (617) for initiating NPCA operation of non-AP STAs within the BSS of AP 1 (510), and AP 1 (510) may perform NPCA switching initiation after transmitting the CTS frame (617). Non-AP STAs within the BSS of AP 1 (510) that have received both the RTS frame transmitted by AP 2 (520) and the CTS frame transmitted by non-AP STA 2 can perform NPCH operation by switching to the NPCA primary channel with the default NAV set.Alternatively, non-AP STAs within the BSS of AP 1 (510) may wait for the CTS frame transmission of AP 1 (510) upon receiving the CTS frame of AP 2 (520) with the 'COPY_FRAME' bit of the service field set to 1, and may perform NPCA operation by switching to the NPCA primary channel after receiving the CTS frame. In the above case, non-AP STAs may recognize the time at which operation begins on the NPCA primary channel of AP 1 (510) by calculating it from the time at which AP 1 (510) transmits the CTS frame.

[0179] FIG. 9 is a flowchart illustrating an operation of a non-AP STA in a wireless LAN applied to the present disclosure. Referring to FIG. 9, an STA may receive at least one frame from an overlapping basic service set (OBSS) while operating on a primary channel. (S910) Thereafter, the STA may determine whether to perform a non-primary channel access (NPCA) operation based on the at least one received frame. (S920) If the NPCA operation is performed, the STA may switch the channel from the primary channel of the STA to the NPCA primary channel. (S930) For example, the STA may be a non-AP STA. For example, the STA may determine whether to perform the NPCA operation based on a sequence of physical layer protocol data units (PPDUs) exchanged at short interframe space (SIFS) intervals. The sequence of PPDUs may include a first PPDU including an initial control frame (ICF), a second PPDU including an initial control response (ICR), and a third PPDU following the second PPDU. In addition, if the STA receives the third PPDU within a preset time after receiving the first PPDU including the ICF, the STA may initiate channel switching to an NPCA channel based on an NPCA operation. In addition, if the STA acquires a primitive based on reception of the first PPDU and acquires a primitive based on reception of the third PPDU within a preset time from the time of acquiring the primitive based on reception of the first PPDU, the STA may initiate channel switching to the NPCA channel based on the NPCA operation.In addition, if the ICF is an RTS (request to send) frame or an MU (multi-user)-RTS trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + CTS_Time', and CTS_Time may be the expected transmission time of the CTS frame calculated based on the ICF. In addition, if the ICF is a BSRP (buffer status report poll) trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + the length indicated by the uplink length field', and the length of the frame indicated by the uplink length field may be set based on the value of the uplink length field included in the ICF.

[0180] In addition, when the STA receives an RTS frame as an ICF acquired from the OBSS and does not receive a CTS frame as an ICR, the STA may set a default NAV (network allocation vector) when acquiring the RTS frame, maintain the default NAV when receiving a third PPDU transmitted from the OBSS within a preset time, and initiate channel switching to an NPCA channel based on an NPCA operation. In addition, the third PPDU may include a data frame or an NPCA indication frame. In addition, when the STA receives an RTS frame or an MU-RTS trigger frame as an ICF from the OBSS, the STA may set the default NAV, and transmit a CTS frame including the same content as the CTS frame transmitted from the OBSS as an ICR within the BSS including the STA, wherein the transmission time of the CTS frame transmitted by the STA within the BSS may be the same as the transmission time of the CTS frame by the OBSS.

[0181] In addition, when the STA receives an MU-RTS trigger frame indicating simultaneous transmission of a CTS frame, the STA may transmit a CTS frame having the same content as a CTS frame transmitted from the OBSS as an ICR at the same time as the CTS frame is transmitted by the OBSS within the BSS including the STA. Here, the MU-RTS trigger frame may include the AID (association ID) of the STA. In addition, when the STA receives an RTS frame or an MU-RTS trigger frame as an ICF from the OBSS, the STA may set a default NAV, and when the STA receives a CTS frame transmitted from the OBSS as an ICR, the STA may duplicate the CTS frame and transmit the CTS frame within the BSS including the STA after SIFS. Here, the transmission of a data frame by the OBSS may be performed after the transmission of the CTS frame by the STA. In addition, the OBSS may transmit a CTS frame again at the same time as the STA transmits the CTS frame within the BSS including the STA.

[0182] In addition, if the ICF included in the first PPDU is an RTS (request to send) frame or an MU-RTS trigger frame, the third PPDU is transmitted '2x SIFS (short interframe space) + CTS_Time' after the transmission completion time of the ICF, and the CTS_Time may be the expected transmission time of the CTS frame calculated based on the ICF included in the first PPDU. Here, if the STA acquires a primitive based on reception of the third PPDU within a preset time, the STA may start channel switching to the NPCA channel based on the NPCA operation.

[0183] In addition, when the ICF included in the first PPDU is a BSRP trigger frame, the preset time is '2x SIFS (short interframe space) + the length indicated by the uplink length field', and the length indicated by the uplink length field can be set based on the uplink length field value included in the trigger frame. If a primitive based on reception of the third PPDU is acquired after the preset time, channel switching to the NPCA channel can be started based on the NPCA operation. In addition, at least one of the first PPDU and the second PPDU can include an NPCA preemption. Here, the third PPDU can include an NPCA indication frame that indicates channel switching to the NPCA channel. In addition, the STA receives at least one of a first PPDU including an initial control frame (ICF) and a second PPDU including an initial control response (ICR) that are exchanged at a short interframe space (SIFS) interval, wherein at least one of the first PPDU and the second PPDU includes an NPCA preemption, and the STA can transmit a third PPDU following the second PPDU. Here, the third PPDU can include an NPCA indication frame based on the NPCA preemption. In addition, when the STA does not receive the first PPDU including the ICF and receives the second PPDU including the ICR, the STA can transmit the third PPDU including the NPCA indication frame based on the second PPDU. Additionally, if the STA receives a first PPDU including an ICF and does not receive a second PPDU including an ICR, the STA may transmit a third PPDU including an NPCA indication frame based on the first PPDU.

[0184] Figure 10 is a flowchart showing the operation of an AP STA in a wireless LAN applied to the present disclosure.

[0185] Referring to FIG. 10, an AP may receive at least one frame from an overlapping basic service set (OBSS) while operating on a primary channel (S1010). Thereafter, the AP may determine whether to perform a non-primary channel access (NPCA) operation based on the at least one received frame (S1020). If the NPCA operation is performed, the AP may switch the channel from the AP's primary channel to the NPCA primary channel (1030). For example, the AP may be an AP STA. For example, the AP may determine whether to perform the NPCA operation based on a sequence of physical layer protocol data units (PPDUs) exchanged at short interframe space (SIFS) intervals. The sequence of PPDUs may include a first PPDU including an initial control frame (ICF), a second PPDU including an initial control response (ICR), and a third PPDU following the second PPDU. In addition, if the AP receives a third PPDU within a preset time after receiving a first PPDU including an ICF, the AP may initiate channel switching to an NPCA channel based on the NPCA operation. In addition, if the AP acquires a primitive based on reception of the first PPDU and acquires a primitive based on reception of the third PPDU within a preset time from the time of acquiring the primitive based on reception of the first PPDU, the AP may initiate channel switching to an NPCA channel based on the NPCA operation.In addition, if the ICF is an RTS (request to send) frame or an MU (multi-user)-RTS trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + CTS_Time', and CTS_Time may be the expected transmission time of the CTS frame calculated based on the ICF. In addition, if the ICF is a BSRP (buffer status report poll) trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + the length indicated by the uplink length field', and the length of the frame indicated by the uplink length field may be set based on the value of the uplink length field included in the ICF.

[0186] In addition, when the AP receives an RTS frame as an ICF acquired from the OBSS and does not receive a CTS frame as an ICR, the AP may set a default NAV (network allocation vector) when acquiring the RTS frame, maintain the default NAV when receiving a third PPDU transmitted from the OBSS within a preset time, and initiate channel switching to an NPCA channel based on an NPCA operation. In addition, the third PPDU may include a data frame or an NPCA indication frame. In addition, when the AP receives an RTS frame or an MU-RTS trigger frame as an ICF from the OBSS, the AP may set the default NAV, and transmit a CTS frame including the same content as the CTS frame transmitted from the OBSS as an ICR within the BSS including the AP, wherein the transmission time of the CTS frame transmitted by the AP within the BSS may be the same as the transmission time of the CTS frame by the OBSS.

[0187] In addition, when the AP receives an MU-RTS trigger frame indicating simultaneous transmission of a CTS frame, the AP may transmit a CTS frame having the same content as a CTS frame transmitted from the OBSS as an ICR at the same time when the CTS frame is transmitted by the OBSS within the BSS including the AP. Here, the MU-RTS trigger frame may include the AID (association ID) of the AP. In addition, when the AP receives an RTS frame or an MU-RTS trigger frame as an ICF from the OBSS, the AP may set a default NAV, and when the AP receives a CTS frame transmitted from the OBSS as an ICR, the AP may duplicate the CTS frame and transmit the CTS frame within the BSS including the AP after SIFS. Here, the transmission of a data frame by the OBSS may be performed after the transmission of the CTS frame by the AP. In addition, the OBSS may transmit a CTS frame again at the same time when the AP transmits the CTS frame within the BSS including the AP.

[0188] In addition, if the ICF included in the first PPDU is an RTS (request to send) frame or an MU-RTS trigger frame, the third PPDU is transmitted '2x SIFS (short interframe space) + CTS_Time' after the transmission completion time of the ICF, and the CTS_Time may be the expected transmission time of the CTS frame calculated based on the ICF included in the first PPDU. Here, if the AP acquires a primitive based on reception of the third PPDU within a preset time, it may start channel switching to the NPCA channel based on the NPCA operation.

[0189] In addition, when the ICF included in the first PPDU is a BSRP trigger frame, the preset time is '2x SIFS (short interframe space) + the length indicated by the uplink length field', and the length indicated by the uplink length field can be set based on the uplink length field value included in the trigger frame. If a primitive based on reception of the third PPDU is acquired after the preset time, channel switching to the NPCA channel can be started based on the NPCA operation. In addition, at least one of the first PPDU and the second PPDU can include an NPCA preemption. Here, the third PPDU can include an NPCA indication frame that indicates channel switching to the NPCA channel. In addition, the AP receives at least one of a first PPDU including an initial control frame (ICF) and a second PPDU including an initial control response (ICR) that are exchanged at a short interframe space (SIFS) interval, wherein at least one of the first PPDU and the second PPDU includes an NPCA preemption, and the AP can transmit a third PPDU subsequent to the second PPDU. Here, the third PPDU can include an NPCA indication frame based on the NPCA preemption. In addition, when the AP does not receive the first PPDU including the ICF and receives the second PPDU including the ICR, the AP can transmit the third PPDU including the NPCA indication frame based on the second PPDU. In addition, when the AP receives the first PPDU including the ICF and does not receive the second PPDU including the ICR, the AP can transmit the third PPDU including the NPCA indication frame based on the first PPDU.

[0190] The methods according to the present disclosure may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., 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 may be known and available to those skilled in the art of computer software. Examples of the computer-readable medium include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The above-described hardware devices 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 disclosure has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

[0191]

[0192] The above may also apply to other systems.

Claims

1. In the operation method of a station (STA) in a wireless LAN system, A step of receiving at least one frame from an overlapping basic service set (OBSS) while the STA is operating on a primary channel; A step of determining whether to perform a non-primary channel access (NPCA) operation based on at least one received frame; and An operating method, comprising a step of the STA switching a channel from the primary channel of the STA to an NPCA primary channel when performing the above NPCA operation.

2. In paragraph 1, An operating method in which the STA determines whether to perform the NPCA operation based on a sequence of physical layer protocol data units (PPDUs) exchanged at a short interframe space (SIFS) interval, wherein the sequence of PPDUs includes a first PPDU including an initial control frame (ICF), a second PPDU including an initial control response (ICR), and a third PPDU following the second PPDU.

3. In paragraph 2, An operating method in which, if the STA receives the third PPDU within a preset time after receiving the first PPDU including the ICF, the STA starts channel switching to an NPCA channel based on the NPCA operation.

4. In paragraph 3, An operating method in which the STA acquires a primitive based on reception of the first PPDU, and acquires a primitive based on reception of the third PPDU within the preset time from the time of acquiring the primitive based on reception of the first PPDU, and starts channel switching to the NPCA channel based on the NPCA operation.

5. In paragraph 3, An operating method, wherein when the above ICF is an RTS (request to send) frame or an MU (multi-user)-RTS trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + CTS_Time', and CTS_Time is the expected transmission time of the CTS frame calculated based on the ICF.

6. In paragraph 3, An operating method in which, when the above ICF is a BSRP (buffer status report poll) trigger frame, the preset time is '(2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + the length indicated by the uplink length field', and the length of the frame indicated by the uplink length field is set based on the value of the uplink length field included in the ICF.

7. In paragraph 3, An operating method in which, when the STA receives an RTS frame as the ICF acquired from the OBSS and does not receive a CTS frame as the ICR, the STA sets a default NAV (network allocation vector) when acquiring the RTS frame, maintains the default NAV when receiving the third PPDU transmitted from the OBSS within the preset time, and starts channel switching to an NPCA channel based on the NPCA operation.

8. In the 7th paragraph, the operating method, wherein the third PPDU includes a data frame or an NPCA indication frame.

9. In paragraph 3, An operating method in which, when the STA receives an RTS frame or an MU-RTS trigger frame as the ICF from the OBSS, the STA sets a basic NAV and transmits a CTS frame including the same content as a CTS frame transmitted from the OBSS as the ICR within a BSS including the STA, wherein the transmission time of the CTS frame transmitted by the STA within the BSS is the same as the transmission time of the CTS frame by the OBSS.

10. In paragraph 9, An operating method in which, when the STA receives the MU-RTS trigger frame indicating simultaneous transmission of the CTS frame, a CTS frame including the same content as the CTS frame transmitted from the OBSS as the ICR is transmitted at the same time as the CTS frame is transmitted by the OBSS within the BSS including the STA, the MU-RTS trigger frame includes the AID (association ID) of the STA.

11. In paragraph 3, When the STA receives an RTS frame or an MU-RTS trigger frame as the ICF from the OBSS, the STA sets a default NAV, and when the STA receives a CTS frame transmitted from the OBSS as the ICR, the STA duplicates the CTS frame and transmits the CTS frame within the BSS in which the STA is included after SIFS. An operating method in which data frame transmission by the above OBSS is performed after CTS frame transmission by the above STA.

12. In paragraph 11, An operating method in which the CTS frame is transmitted once more in the OBSS at the same time as the STA transmits the CTS frame within the BSS in which the STA is included.

13. In paragraph 3, An operating method in which, when the ICF included in the first PPDU is an RTS (request to send) frame or an MU-RTS trigger frame, the third PPDU is transmitted '2x SIFS (short interframe space) + CTS_Time' after the transmission completion time of the ICF, CTS_Time is an expected transmission time of a CTS frame calculated based on the ICF included in the first PPDU, and when the STA acquires a primitive based on reception of the third PPDU within the preset time, the STA starts channel switching to the NPCA channel based on the NPCA operation.

14. In paragraph 4, If the ICF included in the first PPDU is a BSRP trigger frame, the preset time is '2x SIFS (short interframe space) + the length indicated by the uplink length field', and the length indicated by the uplink length field is set based on the value of the uplink length field included in the trigger frame. An operating method for starting channel switching to the NPCA channel based on the NPCA operation when a primitive based on reception of the third PPDU is acquired after the above-described preset time.

15. In paragraph 3, An operating method, wherein at least one of the first PPDU and the second PPDU includes an NPCA preemption, and the third PPDU includes an NPCA indication frame that indicates channel movement to an NPCA channel.

16. In paragraph 1, The STA receives at least one of a first PPDU including an initial control frame (ICF) and a second PPDU including an initial control response (ICR) exchanged at a short interframe space (SIFS) interval, wherein at least one of the first PPDU and the second PPDU includes an NPCA preemption, An operating method wherein the STA transmits a third PPDU subsequent to the second PPDU, wherein the third PPDU includes an NPCA indication frame based on the NPCA preemption.

17. In paragraph 16, An operating method in which, when the STA fails to receive the first PPDU including the ICF and receives the second PPDU including the ICR, the STA transmits the third PPDU including the NPCA indication frame based on the second PPDU.

18. In paragraph 16, An operating method in which, when the STA receives the first PPDU including the ICF and fails to receive the second PPDU including the ICR, the STA transmits the third PPDU including the NPCA indication frame based on the first PPDU.

19. In paragraph 1, An operating method wherein the above STA is an AP STA or a non-AP STA.

20. In a wireless LAN system, at a station (STA), At least one transceiver for transmitting and receiving signals; At least one processor controlling at least one transceiver; and A memory storing instructions that cause the STA to perform a specific operation by at least one processor, The above specific actions are: The STA receives at least one frame from an overlapping basic service set (OBSS) while operating on a primary channel, Determine whether to perform a non-primary channel access (NPCA) operation based on at least one received frame, and When performing the above NPCA operation, the STA switches the channel from the primary channel of the STA to the NPCA primary channel.

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