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

Abstract

In an operation method of an STA in a wireless LAN system, the STA may: receive a first PPDU of an OBSS on a primary channel; switch an operation channel from the primary channel to an NPCA primary channel on the basis of an NPCA switching condition, wherein the NPCA switching condition includes the condition that the first PPDU is a PPDU of an inter-BSS and the condition that an NPCA operation period is greater than an NPCA minimum duration; after switching to the NPCA primary channel, operate on the NPCA primary channel from the end time point of the NPCA operation period to a time point earlier by a channel switching back delay; and switch the operation channel at a channel switching back delay time and operate on the primary channel at the end time point of the NPCA operation period.

Description

Method and device for operating channel transition in sub-channel access operation of wireless LAN

[0001] The present disclosure relates to a method and apparatus for transitioning the operating channel in a non-primary channel access (NPCA) operation of a wireless local area network (WLAN).

[0002]

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

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

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

[0006] In wireless LANs where wireless LAN terminals support side-channel access operations, specific conditions may be required for a wireless LAN terminal operating on the main channel to switch its operating channel to a side-channel; the following describes a method for this purpose.

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

[0008]

[0009] The present disclosure relates to a method and apparatus for transitioning an operating channel in an NPCA operation of a wireless local area network (WLAN).

[0010] The present disclosure relates to a method and apparatus for setting conditions for switching an operating channel to a sub-channel when NPCA operation is supported in a wireless LAN.

[0011] The present disclosure relates to a method and apparatus for determining the time interval during operation in a subchannel when switching the operating channel to a subchannel in a wireless LAN.

[0012] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0013]

[0014] According to one embodiment of the present specification, a method of operation of a station (STA) in a wireless LAN system may include the steps of: the STA receiving a first PPDU (physical layer protocol data unit) of an OBSS (overlapping basic service set) in a main channel; switching an operation channel from a main channel to an NPCA main channel based on a non-primary channel access (NPCA) switching condition, wherein the NPCA switching condition includes a condition that the first PPDU is a PPDU of an inter-BSS and a condition that the NPCA operation period is greater than the NPCA minimum duration; and the step of the STA operating in the NPCA main channel from the end of the NPCA operation period until a point in time preceding the channel switching back delay after switching to the NPCA main channel; and switching the operation channel at the channel switching back delay time to operate in the main channel at the end of the NPCA operation period.

[0015] Additionally, according to one embodiment of the present specification, a station (STA) in a wireless LAN system comprises at least one transceiver for transmitting and receiving signals, at least one processor for controlling the at least one transceiver, and a memory for storing instructions that cause a non-AP STA to perform a specific operation by the at least one processor, wherein the specific operation is: receiving a first PPDU (physical layer protocol data unit) of an OBSS (overlapping basic service set) on a primary channel, and switching the operating channel from the primary channel to an NPCA primary channel based on a non-primary channel access (NPCA) switching condition, wherein the NPCA switching condition includes a condition that the first PPDU is a PPDU of an inter-BSS and a condition that the NPCA operating period is greater than the NPCA minimum duration, and after switching to the NPCA primary channel, operating on the NPCA primary channel from the end of the NPCA operating period until a point in time preceding the channel switching back delay, and switching the operating channel during the channel switching back delay time to operate on the primary channel at the end of the NPCA operating period. there is.

[0016] In addition, the following matters may apply equally.

[0017] According to one embodiment of the present specification, an STA identifies a PPDU sequence composed of a plurality of PPDUs including a first PPDU in a main channel, and if the first PPDU includes an initial control frame, the NPCA operation interval can be determined based on the MAC header duration value of the initial control frame included in the first PPDU and compared with the NPCA minimum duration.

[0018] Additionally, according to one embodiment of the present specification, the time at which the STA initiates operation on the NPCA main channel may be later than the time at which the completion of reception of the second PPDU following the first PPDU is confirmed or inferred.

[0019] Additionally, according to one embodiment of the present specification, the time at which the completion of reception of the second PPDU is confirmed is the time at which the STA generates the reception-related primitive of the second PPDU, and the time at which the STA initiates operation on the NPCA main channel may be after a preset time interval has elapsed from the time at which the STA generates the reception-related primitive of the second PPDU.

[0020] In addition, according to one embodiment of the present specification, the NPCA operation interval corresponds to 'NPCA_CFRAME_TXOP_REM_DUR', and 'NPCA_CFRAME_TXOP_REM_DUR' may be a MAC variable.

[0021] In addition, according to one embodiment of the present specification, the STA operates on the NPCA main channel based on the NPCA timer, wherein the NPCA timer may expire at a time preceding the end of the time interval indicated by 'NPCA_CFRAME_TXOP_REM_DUR' by a channel switching back delay.

[0022] In addition, according to one embodiment of the present specification, if the first PPDU is at least one of HE (high efficiency) PPDU, EHT (extremely high throughput) PPDU and UHR (ultra high reliability) PPDU, the NPCA operation interval may be determined based on the 'RXTIME' value, which is the time length value of the first PPDU.

[0023] Additionally, according to one embodiment of the present specification, the NPCA operation interval may be determined at the time when the MAC of the first STA receives the reception-related primitive of the first PPDU based on the 'RXTIME' value of the first PPDU.

[0024] Additionally, according to one embodiment of the present specification, the 'RXTIME' value can be calculated from the length field value within the preamble of the first PPDU.

[0025] In addition, according to one embodiment of the present specification, the NPCA operation interval may correspond to 'NPCA_PPDU_REM_DUR'.

[0026] In addition, according to one embodiment of the present specification, the NPCA operation interval may be determined at the time when the MAC of the first STA receives the reception-related primitive of the first PPDU based on the sum of the 'RXTIME' value of the first PPDU and the 'TXOP DURATION' value of the RXVECTOR of the first PPDU.

[0027] Additionally, according to one embodiment of the present specification, the 'TXOP DURATION' value may be the value indicated by the TXOP field in the preamble of the first PPDU.

[0028] In addition, according to one embodiment of the present specification, the NPCA operation interval may correspond to 'NPCA_PHY_TXOP_REM_DUR'.

[0029] In addition, according to one embodiment of the present specification, if the first PPDU is at least one of a high efficiency (HE) PPDU, an extremely high throughput (EHT) PPDU, and an ultra high reliability (UHR) PPDU, the NPCA operation interval may be determined through the transmission time length of the first PPDU, which is determined based on the length field value, number of symbols, symbol length, and signal extension within the preamble of the first PPDU.

[0030] Additionally, according to one embodiment of the present specification, the STA may be an AP STA or a non-AP STA.

[0031]

[0032] According to the present disclosure, a method for transitioning the operating channel in the NPCA operation of a WLAN can be provided.

[0033] According to the present disclosure, a method for setting conditions for switching the operating channel to a sub-channel when NPCA operation is supported in a wireless LAN can be provided.

[0034] According to the present disclosure, a method for determining the time interval during operation in a subchannel can be provided when switching the operating channel to a subchannel in a wireless LAN.

[0035] The technical problems to be solved by the present disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0036] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0037]

[0038] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0039] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0040] FIG. 3 is a diagram showing a wireless LAN network to which the present disclosure applies.

[0041] FIGS. 4a and 4b are drawings illustrating a wireless LAN sub-channel access operation method and a sub-channel access operation applied to the present disclosure.

[0042] FIG. 5 is a diagram showing a method for switching the operating channel during wireless LAN sub-channel access operation applied to the present disclosure.

[0043] FIG. 6 is a diagram illustrating a method for switching the operating channel during wireless LAN sub-channel access operation applied to the present disclosure.

[0044] FIG. 7 is a diagram illustrating a method for switching the operating channel during wireless LAN sub-channel access operation applicable to the present disclosure.

[0045] FIG. 8 is a flowchart showing the operation of a STA in a wireless LAN to which the present disclosure applies.

[0046]

[0047] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0048] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0049] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0050] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0051] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0052] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present disclosure, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0053] Below, a wireless communication system to which embodiments according to the present disclosure are applied will be described. The wireless communication system to which embodiments according to the present disclosure are applied is not limited to the details described below, and embodiments according to the present disclosure may be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network."

[0054] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies. Referring to FIG. 1, the communication node (100) may include at least one of a processor (110), memory (120), a transceiver (130), an input / output interface (140), a storage device (150), and a bus (160). For example, the communication node (100) may be an access point (AP), a station (STA), an access point multi-link device (MLD), or a non-AP MLD. However, the communication node may not be limited thereto and may be a node that performs communication with another node or device based on the configuration described above. For example, the operating channel bandwidth supported by the AP may be 20 MHz (megahertz), 80 MHz, 160 MHz, etc. The operating channel bandwidth supported by the station may be 20 MHz, 80 MHz, etc. However, it may not be limited thereto.

[0055] A processor (110) within a communication node (100) can control at least one of a memory (120), a transceiver (130), an input / output interface (140), and a storage device (150) for each component within the communication node. The memory (120) within the communication node (100) can store information regarding commands and instructions executed by the processor (110), and the transceiver (130) may refer to a transceiver, an RF (radio frequency) unit, an RF module, or other components that perform signal transmission and reception. The input / output interface (140) within the communication node (100) is an interface for input and output that can be linked with other interfaces and may further include a separate storage device (150). Each component within the communication node (100) can communicate with one another by being connected by a bus (160).

[0056] However, as an example, each component included in the communication node (100) may be connected via an individual interface or an individual bus centered on the processor (110), rather than via a common bus (160). The processor (1110) may also be connected via a dedicated interface to at least one of the memory (120), the transmission / reception device (130), the input / output interface device (140), and the storage device (150).

[0057] A processor (110) can execute a program command stored in at least one of a memory (120) or a storage device (150). The processor (110) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present disclosure are performed. Each of the memory (120) and the storage device (150) may be composed of at least one of a volatile storage medium or a non-volatile storage medium. e.g., the memory (120) may be composed of at least one of read-only memory (ROM) or random access memory (RAM).

[0058] In the following, the relevant operations are described based on the wireless LAN terminal as a station (STA). In accordance with the terminology usage according to IEEE 802.11, STA can refer to both AP STAs operating as access points (APs) and non-AP STAs operating in connection with an AP. However, for the convenience of explanation, APs and non-AP STAs are distinguished below; this distinction is merely for convenience of explanation, and it is self-evident that operations regarding an AP can be applied to both AP STAs and non-AP STAs. Furthermore, it is self-evident that the non-AP STA operations described below can also be applied to both non-AP STAs and AP STAs.

[0059] FIG. 2 is a diagram illustrating a wireless LAN system to which the present disclosure applies. Referring to FIG. 2, the basic service set (BSS) of the wireless LAN system may include one AP (210) and a plurality of non-AP STAs (221, 222, 223, 224), and the plurality of non-AP STAs (221, 222, 223, 224) may be controlled by the AP (210). However, the wireless LAN system is not limited to a BSS, and an environment consisting only of non-AP STAs without a fixed service set or AP may also be considered, and is not limited to a specific form. Each wireless device within the wireless LAN system may include a MAC (medium access control) layer and a physical (PHY) layer, and communication between wireless devices may be performed. For convenience of explanation, the following description focuses on the AP and non-AP STA, but is not limited thereto. For example, the following items may apply equally to other communication nodes or devices and are not limited to a specific form.

[0060] In a wireless LAN network, wireless LAN terminals can support non-primary channel access (NPCA) operations. When a wireless LAN terminal performs a non-primary channel access operation, it can perform channel access and frame transmission / reception operations on a non-primary channel (or NPCA channel) rather than the primary channel. Here, specific conditions may be required for a wireless LAN terminal operating on the primary channel to switch its operating channel to the non-primary channel, and these conditions are described below. For example, there may be cases where a wireless LAN terminal operating on the primary channel fails to switch its operating channel to the non-primary channel; since this can reduce the efficiency of the wireless LAN network, a solution for this is described below. Furthermore, the following describes a method for determining the time interval during which operation must be performed on the non-primary channel based on the conditions for switching the operating channel to the non-primary channel during a non-primary channel access operation, thereby enabling effective non-primary channel access operations.

[0061] FIG. 3 is a diagram showing a wireless LAN network to which the present disclosure applies. Also, FIG. 4a and FIG. 4b are diagrams showing a wireless LAN sub-channel access operation method and a sub-channel access operation to which the present disclosure applies.

[0062] Referring to FIGS. 3, 4a, and 4b, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) may operate in a wireless LAN network. AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) may have a predetermined primary channel and an NPCA primary channel. The primary channel may be a channel including the primary 20MHz channel of BSS (basic service set) 1 configured by AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330). The primary 20MHz channel is a channel that must be occupied by all communications of BSS 1, and all frame transmission and reception of BSS 1 must be performed by occupying the primary 20MHz channel unless the NPCA operation described later is performed. The NPCA primary channel may be a predetermined channel based on a 20 MHz channel different from the primary 20 MHz channel included in the primary channel described above, which is configured within the BSS 1 configured by AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330). That is, the NPCA primary channel may have a 20 MHz channel different from the primary channel, and the 20 MHz channel is referred to as the NPCA Primary 20 MHz channel, but is not limited to that term. Additionally, the BSS configured by AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) may be referred to as BSS 1 in this disclosure, but is not limited to that term or name. Here, there may be another BSS that occupies the main 20 MHz channel of BSS 1 (i.e., occupies the main channel of BSS 1), which is referred to as the OBSS (overlapping BSS) of BSS 1, but is not limited to that term.

[0063] Referring to FIG. 4a, NPCA operation can be initiated when control frames (401, 402) are exchanged based on the wireless LAN network configuration. AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) (i.e., APs and STAs of BSS 1) can operate by switching the operating channel to the NPCA main channel when the main channel is occupied by another BSS. Here, the other BSS may be a BSS configured by AP X and STA X. That is, when the main channel is occupied by AP X or STA X, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) can operate on the NPCA main channel and perform channel access operations (e.g., EDCA (enhanced distributed channel access) backoff operation and EDCA TXOP (transmit opportunity) acquisition procedure) on the NPCA main 20 MHz channel. Here, the time during which the APs and STAs of BSS 1 can operate on the NPCA main channel may be the time corresponding to the interval during which the OBSS communicates on the main channel (i.e., the TXOP interval or the interval where Basic NAV is configured). Specifically, the APs and STAs of BSS 1 receive a control frame of the OBSS (e.g., a PPDU (physical layer protocol data unit) containing the control frame, 401) and an initial response frame (e.g., a PPDU containing the initial response frame, 402) which is a response frame to the control frame, and if they satisfy the condition of [NPCA Switching Condition - Control Frame] below, they may switch the operating channel to the NPCA main channel and operate. The control frame of the OBSS described above may be an initial control frame (ICF).

[0064] [NPCA Transition Condition - Control Frame]

[0065] - When receiving a control frame and an initial response frame for the control frame, all of the following conditions must be satisfied

[0066] ■ Received PPDU determined to be inter-BSS PPDU

[0067] ◆ For example, at least one of the control frame and the initial response frame is determined to be an inter-BSS PPDU

[0068] ■ The length of the TXOP identified from the duration field (duration / ID field) of the MAC header of the received frame is greater than the NPCA minimum duration

[0069] In this case, the length of the TXOP can be referred to as the 'communication interval of the OBSS'.

[0070] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA Primary channel

[0071]

[0072] If the [NPCA Switching Condition - Control Frame] described above is satisfied, the APs and STAs of BSS 1 may switch their operating channels to the NPCA main channel and operate. Here, the time required to switch the operating channel to the NPCA main channel may be time Ts. The period during which the APs and STAs of BSS 1 operate on the NPCA main channel may be the 'OBSS communication period' of the [NPCA Switching Condition]. The APs and STAs of BSS 1 must operate on the main channel again when the OBSS communication period ends. Here, time Ts' may be required as the switching time for the APs and STAs of BSS 1 to switch back to the main channel from the NPCA main channel. Ts and Ts' may be values ​​mutually negotiated by the APs and STAs supporting NPCA operation during the NPCA negotiation process, and Ts and Ts' may be different times or the same time. The APs and STAs of BSS 1 must terminate transmission before time Ts' from the end of the OBSS communication period.

[0073] Referring to FIG. 4b, NPCA operation may be initiated based on at least one of the exchange of HE (high efficiency), EHT (extremely high throughput), and UHR (ultra high reliability) frames (e.g., PPDU (physical layer protocol data unit) which is a physical layer frame) based on a wireless LAN network. AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) (i.e., APs and STAs of BSS 1) may operate by switching the operating channel to the NPCA main channel when the main channel is occupied by another BSS. The other BSS may be a BSS configured by AP X and STA X. That is, when the main channel is occupied by AP X or STA X, AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) can operate on the NPCA main channel and perform channel access operations (e.g., EDCA (enhanced distributed channel access) backoff operations and EDCA TXOP (transmit opportunity) acquisition procedures) on the NPCA main 20 MHz channel. Here, the time during which the APs and STAs of BSS 1 can operate on the NPCA main channel may be the time corresponding to the period during which the OBSS communicates on the main channel (i.e., the TXOP period or the period during which Basic NAV is set).

[0074] Specifically, APs and STAs of BSS 1 receive a frame of OBSS (e.g., PPDU (physical layer protocol data unit), 403), and if the received PPDU satisfies the sub-condition of [NPCA switching condition - HE frame] below, they can switch the operating channel to the NPCA main channel and operate.

[0075] [NPCA Transition Conditions - HE Frame]

[0076] - The received PPDU is an HE / EHT / UHR PPDU and satisfies all of the following conditions

[0077] ■ PPDU is determined to be an inter-BSS PPDU

[0078] ■ The length of the PPDU is greater than the NPCA minimum duration

[0079] Here, the time length of the PPDU can be considered the 'communication interval of the OBSS'.

[0080] ◆ The time length of the PPDU described above may be one of the following.

[0081] o 1. Transmission time length of the PPDU identified from the PPDU preamble

[0082] □ Transmission time length of the PPDU identified from the value of the LENGTH field included in the L_SIG of the preamble

[0083] ◇ RXTIME time calculated from the value of the LENGTH field

[0084] ◇ ((LENGTH + 3) / 3) * 4 + 20 + SignalExtension (us)

[0085] o 2. The length of the TXOP indicated by the value of the TXOP field included in the HE-SIG or U-SIG of the PPDU preamble

[0086] The value of the TXOP field can be set to the TXOP_DURATION value of the RXVECTOR obtained from the received frame.

[0087] o 3. Other value(s) for the transmission length of OBSS found in the PPDU preamble

[0088] o 4. The longest value among 1. to 3.

[0089] o 5. Sum of 1. and 2.

[0090] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA Primary channel

[0091]

[0092] If [NPCA Switching Condition - HE Frame] is satisfied, the APs and STAs of BSS 1 may switch their operating channels to the NPCA main channel and operate. The time required to switch the operating channels to the NPCA main channel may be time Ts. The period during which the APs and STAs of BSS 1 operate on the NPCA main channel may be the 'OBSS communication period' of [NPCA Switching Condition - HE Frame]. The APs and STAs of BSS 1 must operate on the main channel again when the OBSS communication period ends. Here, time Ts' may be required as the switching time for the APs and STAs of BSS 1 to switch back to the main channel from the NPCA main channel. Therefore, the APs and STAs of BSS 1 must terminate transmission before time Ts' from the end of the OBSS communication period. Ts and Ts' may be values ​​mutually negotiated by the AP and the STA supporting NPCA operation during the NPCA negotiation process, and Ts and Ts' may be different times or the same time. The APs and STAs of BSS 1 must terminate transmission before time Ts' from the end of the communication period of OBSS.

[0093] For example, APs and STAs of BSS 1 may receive at least one of HE (high efficiency) PPDU, EHT (extremely high throughput) PPDU, and UHR (ultra high reliability) PPDU from OBSS. Here, RXTIME may be calculated based on a length field included in the preamble of the PPDU (e.g., a field indicating the transmission length of the PPDU, such as the L_LENGTH field) (e.g., based on a value obtained directly from the value of the field, or based on a value calculated by a specific formula from the value of the field), and the 'communication period of OBSS' during which the APs and STAs of BSS 1 operate on the NPCA main channel may be determined. Here, the APs and STAs of BSS 1 may operate on the NPCA main channel from the time they complete receiving the PPDU. As another example, the 'communication period of the OBSS' where the APs and STAs of BSS 1 operate on the NPCA main channel can be determined based on the RXTIME of the corresponding PPDU and the TXOP DURATION value of the RXVECTOR of the corresponding PPDU. Here, TXOP DURATION may be a value indicated by the TXOP field within the preamble of the corresponding PPDU. The LENGTH field may be indicated based on the OFDMA (orthogonal frequency division multiple access) symbol time (symbol time length, symbol length) and the number of symbols of the PPDU. Here, the transmission time length of the aforementioned PPDU can be determined based on the OFDMA symbol time and the number of symbols, but is not limited to a specific form.

[0094] Referring to FIGS. 4a and 4b, AP 1 (310) of BSS 1 can transmit a frame instructing STAs connected to AP 1 (310) to perform NPCA operations. The UHR operation information element of the management frame (e.g., beacon frame, probe response frame, OMP (operation mode and parameters) frame) transmitted by AP 1 (310) may include an indicator indicating whether NPCA is used. The NPCA operation information field included in the UHR operation information element, or the NPCA operation information field included separately in the management frame of AP 1 (310), may indicate at least one of the NPCA main channel, the NPCA switching delay of AP 1 (310), and the NPCA switch back delay. In addition, AP may include the NPCA minimum duration value (or, also referred to as the NPCA minimum duration threshold value) in the aforementioned NPCA operation information field.

[0095] Referring to FIGS. 4a and 4b, the APs and STAs of BSS 1 may use at least one of the following three MAC variables to determine whether to switch the operating channel to the NPCA main channel.

[0096] 1) NPCA_PPDU_REM_DUR :

[0097] The NPCA_PPDU_REM_DUR variable can be set to the value obtained by subtracting the time difference between when the NPCA STA's PHY layer detected the first PPDU and generated the PHY-CCA.indication(BUSY) primitive and when the PHY-RXSTART.indication primitive was generated from the total length of the PPDU that the NPCA STA can identify in the PPDU header (e.g., the length of the PPDU indicated by the RXVECTOR generated upon receiving the PPDU or calculated from the indicated value, RXTIME). The NPCA_PPDU_REM_DUR variable may indicate only the remaining PPDU length without the MAC layer's frame switching time interval information.

[0098] 2) NPCA_PHY_TXOP_REM_DUR :

[0099] The NPCA_PHY_TXOP_REM_DUR variable is set to the value obtained by subtracting the time difference between when the PHY layer of the NPCA STA detected the first PPDU and generated the PHY-CCA.indication(BUSY) primitive and when it generated the PHY-RXSTART.indication primitive from the sum of the total length of the PPDU that the NPCA STA can identify in the PPDU header (e.g., the length of the PPDU indicated by the RXVECTOR generated upon receiving the PPDU, or calculated from the indicated value, RXTIME) and the TXOP_DURATION value indicated in the PPDU header. Unless the TXOP_DURATION value is UNSPECIFIED (i.e., not indicated), the NPCA_PHY_TXOP_REM_DUR variable may indicate the remaining transmission period of the received PPDU and the subsequent frame switching time period (e.g., remaining TXOP period).

[0100] 3) NPCA_CFRAME_TXOP_REM_DUR :

[0101] The NPCA_CFRAME_TXOP_REM_DUR variable can be set to the value of the duration / ID field of the MAC header of a control frame received by the NPCA STA. The NPCA_CFRAME_TXOP_REM_DUR variable can indicate a frame exchange time interval (e.g., remaining TXOP interval) that is performed after the completion of transmission of the received frame (MAC frame) (e.g., completion of transmission of the PPDU containing the MAC frame).

[0102]

[0103] The APs and STAs of BSS 1 receive the PPDU of OBSS and can determine the time length of the PPDU from the preamble of the OBSS PPDU. Additionally, the APs and STAs of BSS 1 can determine the time length of the TXOP of OBSS from the preamble of the OBSS PPDU. The point in time when the APs and STAs of BSS 1 can determine the time length of the OBSS PPDU may be the point in time when the PHY-RXSTART.indication primitive for the PPDU occurs. For example, this point in time may be T1, but it may not be limited to that point. At time T1, at least one of the MAC variable values ​​may be set as follows.

[0104] - NPCA_PPDU_REM_DUR: PPDU time length - 'Time elapsed from the occurrence of PHY-CCA.indication(BUSY) caused by PPDU to the occurrence of PHY-RXSTART.indication'

[0105] - NPCA_PHY_TXOP_REM_DUR : Time length of PPDU + Time length of TXOP included in PPDU - 'Time elapsed from the occurrence of PHY-CCA.indication(BUSY) by PPDU to the occurrence of PHY-RXSTART.indication'

[0106] - NPCA_CFRAME_TXOP_REM_DUR : No effect

[0107]

[0108] Alternatively, the OBSS PPDU received by the APs and STAs of BSS 1 may include an Initial Control Frame (ICF) (e.g., RTS frame, CTS frame, MU-RTS trigger frame, BSRP trigger frame). The APs and STAs of BSS 1 can determine the time length of the OBSS TXOP from the duration field of the MAC header of the Initial Control Frame included in the OBSS PPDU. The point in time at which the time length of the OBSS PPDU can be determined may be the point in time when the PHY-RXEND primitive for the PPDU occurs; this point in time may be time T1, but is not limited to that point. At time T1, at least one of the same MAC variables may be set as follows.

[0109] - NPCA_PPDU_REM_DUR: PPDU time length - 'Time elapsed from the occurrence of PHY-CCA.indication(BUSY) caused by PPDU to the occurrence of PHY-RXSTART.indication'

[0110] - NPCA_PHY_TXOP_REM_DUR: Time length of PPDU + Time length of TXOP included in PPDU - 'Time elapsed from the occurrence of PHY-CCA.indication(BUSY) by PPDU to the occurrence of PHY-RXSTART.indication'

[0111] - NPCA_CFRAME_TXOP_REM_DUR: The value of the duration field indicated by the MAC header of the initial control frame

[0112]

[0113] When PHYLEN NPCA is used in BSS 1, the APs and STAs of BSS 1 can compare at least one of the NPCA_PPDU_REM_DUR value, NPCA_PHY_TXOP_REM_DUR value, and NPCA_CFRAME_TXOP_REM_DUR value with the NPCA minimum duration threshold value most recently transmitted or received by the APs and STAs of BSS 1 at time T1. Here, if the above value is greater than the NPCA minimum duration threshold value most recently transmitted or received by the APs and STAs of BSS 1, the operating channel can be switched to the NPCA main channel. That is, the values ​​of the MAC variables can be set to correspond to the communication interval of the OBSS identified by the NPCA STA.

[0114] In addition, the NPCA timer (NPCA TIMER) may be a timer (timer variable) for the time of operation on the NPCA main channel. That is, the NPCA timer may be a timer that determines the NPCA operation interval determined based on the communication interval of the OBSS.

[0115] The NPCA timer may be a timer managed by an NPCA STA (an AP and STA of BSS 1). The NPCA timer may be set based on the value of the MAC variable described above. When the NPCA timer expires (i.e., when the timer value reaches 0), the NPCA STA must operate on the main channel again.

[0116] If the NPCA STA cannot immediately switch the operating channel at time T1, the MAC variable described above may decrease the corresponding value at each time interval. Subsequently, when the NPCA STA switches the operating channel to the NPCA main channel, the NPCA timer may be set to the value obtained by subtracting the NPCA switching back delay time value for each NPCA STA from the largest value among NPCA_PPDU_REM_DUR, NPCA_PHY_TXOP_REM_DUR, and NPCA_CFRAME_TXOP_REM_DUR. According to the method of setting the value of the NPCA timer described above, the NPCA STAs of FIG. 4a and FIG. 4b may operate on the NPCA main channel within the communication interval of OBSS.

[0117] FIG. 5 is a diagram showing a method for switching the operating channel during wireless LAN sub-channel access operation applied to the present disclosure.

[0118] Referring to FIG. 5, AP 1 (310) of BSS 1 according to FIG. 3, 4a, and 4b and a plurality of STAs connected to AP 1 (310) may operate. AP 1 (310) of BSS 1 and non-AP STA 1 (320) may receive a trigger frame (404) of OBSS. Here, the trigger frame (404) may be a control frame. The response frame (405) to the trigger frame (404) may be a trigger-based PPDU (physical layer protocol data unit). Here, operations may be considered for the case where AP 1 (310) of BSS 1 and non-AP STA 1 (320) receive the trigger frame (404) of OBSS. For example, the trigger frame (404) of OBSS may not be included in a PPDU for at least one of HE, EHT, and UHR. Alternatively, the trigger frame (404) of the OBSS may be included in the PPDU for at least one of HE, EHT, and UHR, but the TXOP_DURATION parameter of the RXVECTOR obtained by the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 receiving the preamble of the PPDU containing the trigger frame (404) may be 'UNSEPCIFIED'. In the above case, even if the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 receive the trigger frame (404), the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 cannot satisfy the above [NPCA transition condition - HE frame].

[0119] AP 1 (310) of BSS 1 receives a trigger frame (404) of OBSS and can receive a TB PPDU (405), which is a response frame to the trigger frame (404) of OBSS. AP 1 (310) may receive the trigger frame (404) but may not satisfy the [NPCA transition condition - control frame] condition before decoding the MAC frame to check the MAC (medium access control) header included in the TB PPDU (405). However, the TB PPDU (405) may satisfy the [NPCA transition condition - HE frame]. In the above case, AP 1 (310) can operate by switching the operating channel to the NPCA main channel.

[0120] Meanwhile, non-AP STA 1 (320) may receive the trigger frame (404) of OBSS, but may not receive the TB PPDU (405) of OBSS. In the above case, non-AP STA 1 (320) may not satisfy both [NPCA switching condition - control frame] and [NPCA switching condition - HE frame]. Therefore, non-AP STA 1 (320) cannot switch the operating channel to the NPCA main channel. Here, AP 1 (310) switches the operating channel to the NPCA main channel, but since non-AP STA 1 (320) cannot switch the operating channel to the NPCA main channel, the NPCA operation may not be performed smoothly. Therefore, the [NPCA switching condition - trigger frame] may be required as the operating channel change condition when receiving the trigger frame.

[0121] [NPCA Transition Condition - Trigger Frame]

[0122] - The received PPDU contains a trigger frame and satisfies all of the following conditions

[0123] ■ PPDU is determined to be an inter-BSS PPDU

[0124] ■ No errors related to PPDU reception occur, and all of the following must be satisfied

[0125] ◆ PHY-RXEND.indication(NOERROR) Occurrence of primitive

[0126] ◆ Trigger frames included in the PPDU do not cause FCS errors

[0127] o No errors in the trigger frame verified via the trigger frame's FCS field, or / and the intermediate FCS field of the user info field.

[0128] ■ The trigger frame length information is greater than the NPCA minimum duration.

[0129] ◆ Trigger frame length information can be one of the following

[0130] o Length value of the TB PPDU subsequently transmitted for the trigger frame indicated by the UL Length subfield of the Common Info Field of the trigger frame

[0131] o The length value of the duration field indicated in the MAC header of the trigger frame

[0132] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA Primary channel

[0133]

[0134] That is, AP 1 (310) and non-AP STA 1 (320) can receive the trigger frame (404) of OBSS and perform an NPCA operation when [NPCA transition condition - trigger frame] is satisfied. Specifically, AP 1 (310) and non-AP STA 1 (320) can receive the trigger frame (404) of OBSS. Here, the trigger frame (404) of OBSS may not be included in the PPDU for at least one of HE, EHT, and UHR. Or, the trigger frame (404) of OBSS may be included in the PPDU for at least one of HE, EHT, and UHR, but the TXOP_DURATION parameter of the RXVECTOR obtained by AP 1 (310) and non-AP STA 1 (320) of BSS 1 receiving the preamble of the PPDU containing the trigger frame may be 'UNSEPCIFIED'. In the above case, AP 1 (310) and non-AP STA 1 (320) cannot satisfy both [NPCA transition condition - control frame] and [NPCA transition condition - HE frame].

[0135] Here, the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 can check the length information of the trigger frame indicated by the uplink length (UL length) subfield of the common info field included in the trigger frame (404) or the duration field of the MAC header. For example, the AP 1 (310) and non-AP STA 1 (320) may use only one identical criterion to check the length information of the trigger frame (404), but are not limited thereto. Here, the AP 1 (310) and non-AP STA 1 (320) included in the same BSS 1 may commonly use either the UL Length subfield of the common info field or the duration field of the MAC header to check the length information of the trigger frame (404). If the length information of the trigger frame is longer than the NPCA minimum duration and other conditions of [NPCA transition condition - trigger frame] are satisfied, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 can operate on the NPCA main channel according to the length information of the confirmed trigger frame (404).

[0136] Specifically, referring to FIG. 5, AP 1 (310) and non-AP STA 1 (320) can complete reception of the trigger frame (404) at time T1 and check the length information of the trigger frame (404) to switch the operating channel to the NPCA main channel. Alternatively, time T1 may be a time when SIFS (short interframe space) time has elapsed since the time when reception of the trigger frame (404) is completed. This time may be a time considering the case where another STA (e.g., non-AP STA 2 (330)) that has not received the OBSS trigger frame can receive the TB PPDU transmitted in response to the OBSS trigger frame. If another STA (e.g., STA 2) that has not received the OBSS trigger frame can receive the TB PPDU transmitted in response to the OBSS trigger frame, the other STA can switch the operating channel to the NPCA main channel by [NPCA switching condition - HE frame], so the SIFS time may be considered to minimize the difference in the time when AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) operate on the NPCA main channel.

[0137] As another example, time T1 may be the time when a UL TB PPDU, which is a response frame to a trigger frame, is detected (e.g., when the NPCA AP (e.g. AP 1) and the NPCA STA (e.g. STA 1) connected to AP 1 (310) detect the preamble of the UL TB PPDU and generate the PHY-RXEARLYSIG.indication primitive or the PHY-RXSTART.indication primitive). If time T1 is the time when a UL TB PPDU containing a frame transmitted in response to a trigger frame is detected, AP 1 (310) and non-AP STA 1 (320) cannot switch the operating channel to the NPCA main channel unless they receive the UL TB PPDU transmitted in response to the trigger frame. Additionally, AP 1 (310) and non-AP STA 1 (320) must detect a UL TB PPDU within a time window having a certain length of time (e.g., aSIFSTime, or aSIFSTime + aRxPHYStartDelay, or aSIFSTime + aRxPHYStartDelay + aSlotTime) after the completion of receiving the trigger frame of OBSS (e.g., PHY-RXEND.indication) so that AP 1 (310) and non-AP STA 1 (320) can switch the operating channel to the NPCA main channel.

[0138] AP 1 (310) and non-AP STA 1 (320) may take time Ts to switch the operating channel from the main channel to the NPCA main channel. AP 1 (310) and non-AP STA 1 (320) may perform channel access operations and frame transmission / reception operations when time Ts has elapsed from time T1. AP 1 (310) and non-AP STA 1 (320) of BSS 1 may determine time T2, which is the time of completion of transmission of the OBSS frame (e.g., TB PPDU), or the communication interval of the OBSS (e.g., OBSS TXOP or OBSS frame exchange) obtained through the length information of the trigger frame. For example, time T2 may be (time of completion of transmission of the OBSS communication interval or OBSS frame) + 72us. AP 1 (310) and non-AP STA 1 (320) of BSS 1 may need to operate on the main channel again at time T2. If the length information of the trigger frame is information confirmed based on the UL Length subfield of the common information field included in the trigger frame, AP 1 (310) and non-AP STA 1 (320) of BSS 1 may operate on the NPCA main channel during the 'NPCA operation period 1' of BSS 1. If the length information of the trigger frame is information confirmed based on the duration field of the MAC header included in the trigger frame, AP 1 (310) and non-AP STA 1 (320) of BSS 1 may operate on the NPCA main channel during the 'NPCA operation period 2' of BSS 1. Additionally, the time Ts' may be required for the AP 1 (310) and non-AP STA 1 (320) of BSS 1 to switch the operating channel from the NPCA main channel back to the main channel.Therefore, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 may stop operating on the NPCA main channel from time T2 until time Ts', and then perform an operation channel switch back to the main channel. At time T2, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 may operate on the main channel.

[0139] Meanwhile, although FIG. 5 describes the NPCA main channel switching operation of BSS 1 when receiving a trigger frame of OBSS, the case where BSS 1 receives a CTS (clear to send) frame can also be considered. For example, BSS 1 can set the basic NAV using the value of the duration field included in the MAC header of the CTS frame, and it may not be initialized even after a certain period of time. Therefore, even when BSS 1 receives a CTS frame, it may be necessary to switch the operating channel to the NPCA main channel.

[0140] Referring to FIG. 5, AP 1 (310) of BSS 1 and a plurality of STAs connected to AP 1 (310) according to FIG. 3, FIG. 4a and FIG. 4b may operate. Here, AP 1 (310) of BSS 1 and non-AP STA 1 (320) may receive a CTS frame of OBSS. Additionally, a subsequent frame for the CTS frame may be transmitted, and [NPCA transition condition - CTS frame] may be considered.

[0141] [NPCA Transition Conditions - CTS Frame]

[0142] - The received PPDU contains a CTS frame and satisfies all of the following conditions

[0143] ■ PPDU is determined to be an inter-BSS PPDU

[0144] ■ No errors related to PPDU reception occur, and all of the following must be satisfied

[0145] ◆ PHY-RXEND.indication(NOERROR) Occurrence of primitive

[0146] ◆ CTS frames included in PPDU do not cause FCS errors

[0147] ■ The length information of the CTS frame is greater than the NPCA minimum duration.

[0148] The length information of the trigger frame is the length value of the duration field specified in the MAC header.

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

[0150]

[0151] AP 1 (310) and non-AP STA 1 (320) included in BSS 1 can perform an NPCA operation when [NPCA transition condition - CTS frame] is satisfied. Specifically, AP 1 (310) and non-AP STA 1 (320) can receive a CTS frame of OBSS. In the above case, AP 1 (310) and non-AP STA 1 (320) cannot satisfy both [NPCA transition condition - control frame] and [NPCA transition condition - HE frame]. AP 1 (310) and non-AP STA 1 (320) of BSS 1 can check the time length information indicated by the duration field of the MAC header included in the CTS frame. Here, if the time length information of the CTS frame is longer than the NPCA minimum duration and other conditions of [NPCA switching condition - CTS frame] are satisfied, AP 1 (310) and non-AP STA 1 (320) can operate on the NPCA main channel according to the verified length information of the CTS frame. Specifically, in FIG. 5, AP 1 (310) and non-AP STA 1 (320) can complete reception of the CTS frame at time T1, verify the length information of the CTS frame, and switch the operating channel to the NPCA main channel. Alternatively, time T1 may be the time after the SIFS time has elapsed from the time of completion of reception of the CTS frame. This time may be a time considering the case where another STA (e.g., STA 2) that has not received the CTS frame of the OBSS can receive the PPDU transmitted subsequently for the CTS frame of the OBSS. Another STA that has not received the CTS frame of the OBSS (e.g.When STA 2) can receive a PPDU transmitted as a follow-up to the OBSS CTS frame, it can switch the operating channel to the NPCA main channel by [NPCA switching condition - HE frame], so the SIFST time can be considered to minimize the difference in the time when AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) operate on the NPCA main channel.

[0152] As another example, time T1 may be the time when a PPDU transmitted subsequently to the CTS frame is detected (e.g., when the NPCA AP (e.g., AP 1) and the NPCA STA connected to AP 1 (e.g., STA 1) generate the PHY-RXEARLYSIG.indication primitive or the PHY-RXSTART.indication primitive by detecting the preamble of the PPDU). If time T1 is the time when a PPDU containing a frame transmitted subsequently to the CTS frame is detected, AP 1 (310) and non-AP STA 1 (320) cannot switch the operating channel to the NPCA main channel unless they receive the PPDU transmitted subsequently to the CTS frame. Additionally, AP 1 (310) and non-AP STA 1 (320) must detect a PPDU within a time window having a certain length (e.g., aSIFSTime, or aSIFSTime + aRxPHYStartDelay, or aSIFSTime + aRxPHYStartDelay + aSlotTime) after the completion of receiving the CTS frame of the OBSS (e.g., PHY-RXEND.indication) so that AP 1 (310) and non-AP STA 1 (320) may be able to switch the operating channel to the NPCA main channel. AP 1 (310) and non-AP STA 1 (320) must not switch the operating channel to the NPCA main channel if the PPDU transmitted subsequently to the CTS frame is determined to be an intra-BSS PPDU.

[0153] AP 1 (310) and non-AP STA 1 (320) may take time Ts to switch the operating channel from the main channel to the NPCA main channel. AP 1 (310) and non-AP STA 1 (320) can perform channel access operations and frame transmission / reception operations when time Ts has elapsed at time T1. AP 1 (310) and non-AP STA 1 (320) of BSS 1 can determine the communication interval of OBSS (the Basic NAV interval set based on the TXOP of egOBSS or the frame exchange of OBSS) obtained through the length information of the CTS frame, or T2, which is the time when transmission of the OBSS frame (eg PPDU) is completed. For example, time T2 may be (the time when transmission of the OBSS communication interval or the OBSS frame is completed) + 72us. AP 1 (310) and non-AP STA 1 (320) of BSS 1 may need to operate on the main channel again at time T2. If the length information of the CTS frame is information confirmed based on the duration field of the MAC header included in the CTS frame, AP 1 (310) and non-AP STA 1 (320) of BSS 1 may operate on the NPCA main channel until the end of the time interval indicated by the CTS frame of OBSS. Here, time Ts' may be required for AP 1 (310) and non-AP STA 1 (320) of BSS 1 to switch the operating channel from the NPCA main channel back to the main channel. Therefore, AP 1 (310) and non-AP STA 1 (320) of BSS 1 must stop operating on the NPCA main channel from time T2 until time Ts', and then perform the switching of the operating channel back to the main channel. At time T2, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 can operate on the main channel.

[0154] FIG. 6 is a diagram illustrating a method for switching the operating channel during wireless LAN sub-channel access operation applied to the present disclosure.

[0155] Referring to FIG. 6, AP 1 (310) of BSS 1 according to FIG. 3, 4a, and 4b and a plurality of STAs connected to AP 1 (310) can operate. Here, AP 1 (310) of BSS 1 and non-AP STA 1 (320) can receive control frames (406, 407) of OBSS. For example, the control frames (406, 407) may be control frame 1 and control frame 2, but are not limited to these terms. AP 1 (310) of BSS 1 and non-AP STA 1 (320) can receive control frame 1 (406) and control frame 2 (407). Accordingly, AP 1 (310) and non-AP STA 1 (320) may need to check whether all [NPCA transition condition - control frame] conditions are satisfied. However, among the sub-conditions of the [NPCA transition condition - control frame] condition, a problem may occur with the condition 'the length of the TXOP identified from the duration field of the MAC header of the received frame is greater than the NPCA minimum duration'. Specifically, the length of the communication period (TXOP) of the OBSS indicated by the duration field of the MAC header of control frame 1 (406) may be longer than the NPCA Minimum Duration Threshold length. However, the length of the communication period of the OBSS indicated by the duration field of the MAC header of control frame 2 (407) may be shorter than the length indicated by the duration field of the MAC header of control frame 1 (406). Specifically, the length indicated by the duration field of the MAC header of control frame 2 (407) may be shorter than the length indicated by the duration field of control frame 1 (406) minus the length of control frame 2 (407) and the SIFS time, which is the time interval between control frame 1 (406) and control frame 2 (4067). Alternatively, the STA that transmitted control frame 2 (407) may intentionally reduce the duration field value.In the above case, the length of the communication interval indicated by the MAC header duration field of control frame 2 (407) may be shorter than the NPCA minimum duration. Therefore, control frame 1 (406) satisfies the [NPCA transition condition - control frame] condition, but control frame 2 (407) may not satisfy the [NPCA transition condition - control frame] condition.

[0156] In light of the above, the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 may need to decide whether to compare the duration field value of control frame 1 (i.e., the control frame of the OBSS transmitted first, 406) with the NPCA minimum duration or the duration field value of control frame 2 (i.e., the control frame of the OBSS transmitted later, 407) with the NPCA minimum duration. For example, the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 may prefer to compare the value of the duration field of control frame 2 (407) with the NPCA minimum duration for smooth NPCA operation. In the above case, the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 may not switch the operation channel to the NPCA main channel. After transmitting control frame 2 (407), if OBSS operates on the main channel for a length shorter than the value of the NPCA minimum duration, the period during which BSS 1 operates on the NPCA main channel may become excessively short.

[0157] Meanwhile, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 may compare the value of the duration field of control frame 1 (406) with the NPCA minimum duration for NPCA operation. The AP 1 (310) and non-AP STA 1 (320) of BSS 1 may operate on the NPCA main channel during the communication period of OBSS indicated by the value of the duration field included in control frame 1 (406) after the reception of control frame 2 (407) is completed (at time T1 and thereafter), and may operate on the main channel again at time T2, which is the time when the communication period of OBSS ends. Here, the time period excluding times Ts and Ts' in the time interval between T2 and T1 may be indicated in the drawing as 'NPCA operation period of BSS 1 (based on Control Frame 1 Duration)', but is not limited thereto. For example, the illustrated NPCA operation interval, 'NPCA operation interval of BSS 1 (based on Control Frame 1 Duration)', may be a time interval including Ts.

[0158] Meanwhile, the point in time when the NPCA STAs of BSS 1 (i.e., STA 1 and AP 1) begin switching the operating channel to the NPCA main channel may be considered to be after time T1. For example, AP 1 (310) and non-AP STA 1 (320) may switch the operating channel to the NPCA main channel after a certain amount of time has elapsed since time T1. For example, the point in time after time T1 may be the time when the third frame (PPDU) of the OBSS, which begins transmission after SIFS time from the time of completion of transmission of control frame 2 (407) or the time when the PHY-RXSTART.indication and / or PHY-RXEARLYSIG.indication primitive is generated. As another example, the time after which a certain amount of time has elapsed since time T1 may be the time after three Symbol Times (e.g., OFDM symbol time, OFDMA symbol time) have elapsed since the time when the L-SIG field in the PHY preamble of the third frame of OBSS is received, but is not limited thereto. At the time after the time after which a certain amount of time has elapsed since time T1, AP 1 (310) and non-AP STA 1 (320) can complete the operation channel switching to the NPCA main channel.

[0159] Specifically, the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 may receive a first PPDU (physical layer protocol data unit) containing a control frame 1 (406) and a second PPDU containing a control frame 2 (407) as a sequence of PPDUs from the OBSS. Here, each of the first PPDU and the second PPDU may include the control frame described above. The AP 1 (310) and non-AP STA 1 (320) of the BSS 1 may operate on the NPCA main channel during the communication period of the OBSS indicated by the duration field value included in the control frame of the first PPDU among the control frame of the first PPDU and the control frame of the second PPDU received from the OBSS. Here, the AP 1 (310) and non-AP STA 1 (320) of the BSS 1 may operate on the NPCA main channel during the communication period of the OBSS indicated based on the time of reception of the second PPDU. That is, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 can compare the value of the duration field included in the MAC header of the control frame 1 (406) included in the first PPDU with the NPCA minimum duration value, and can perform NPCA operation channel switching as described above. In addition, the AP 1 (310) and non-AP STA 1 (320) of BSS 1 can store the value of the duration field of the control frame 1 (406) or control frame 2 (407) (i.e., the time length value of the communication interval of OBSS) in the NPCA_CFRAME_TXOP_REM_DUR described above in FIG. 4a and FIG. 4b. The AP 1 (310) and non-AP STA 1 (320) of BSS 1 can reduce the time length value of the corresponding variable until the time point when the operating channel is switched to the NPCA main channel (the time point T1 shown or the time point after the above time point T1 has elapsed) is reached.Here, the NPCA_CFRAME_TXOP_REM_DUR value may indicate the communication interval of the OBSS that ends at the illustrated time T2. Subsequently, when the AP 1 (310) and non-AP STA 1 (320) of BSS 1 switch their operating channels to the NPCA main channel, the NPCA TIMER may be set to a time point that is ahead of the value of NPCA_CFRAME_TXOP_REM_DUR by the respective NPCA switching back delay (Ts') of AP 1 (310) and non-AP STA 1 (320). The NPCA TIMER indicates a time interval that ends at a time Ts' prior to the time point T2, and the time interval corresponding to the NPCA TIMER is illustrated in the form of adding Ts time to the NPCA operating interval of BSS 1.

[0160] In addition, for example, the UHR operation information element of a management frame (beacon frame, probe response frame, OMP frame) transmitted by the AP 1 (310) of BSS 1 may indicate whether the NPCA minimum duration is compared with the value of the duration field of the control frame received first (i.e., the duration field of control frame 1) or whether the NPCA minimum duration is compared with the value of the duration field of the control frame received later (the duration field of control frame 2), but is not limited thereto.

[0161] FIG. 7 is a diagram illustrating a method for switching the operating channel during wireless LAN sub-channel access operation applicable to the present disclosure.

[0162] According to FIGS. 3, FIG. 4a and FIG. 4b, AP 1 (310) of BSS 1 and a plurality of STAs connected to AP 1 (310) may operate. Here, an OBSS in which the main channel and the operating channel of BSS 1 overlap may be configured such that when setting the duration field of a transmitted frame, the duration field value is set to a NAV (network allocation vector) of length corresponding to the entire TXOP that the AP or STA of the OBSS intends to use. For example, the method of setting the duration field described above may be a multiple protection method, but is not limited to such terms.

[0163] BSS 1 (or the AP of BSS 1) and OBSS (or the AP of OBSS) can exchange operation channel information and NPCA operation information with each other. The operation channels of BSS 1 and OBSS may overlap. For example, the operation channel of OBSS may overlap with the main channel of BSS 1 (e.g., main 20 MHz channel). BSS 1 can perform NPCA operations according to FIGS. 3, 4a, and 4b, and the AP 1 (310) of BSS 1 can transmit information (e.g., UHR Operation Information element) indicating that it is performing NPCA operations to the AP of OBSS. The AP of OBSS can confirm that the main channel of BSS 1 and the channel of OBSS overlap, and confirm that BSS 1 is performing NPCA operations. The AP of the OBSS can transmit a management frame (e.g., beacon frame, probe response frame) to indicate the NPCA operation information of BSS 1 (e.g., BSS 1 operation channel information, whether BSS 1 NPCA is operating) so that the STAs included in the OBSS can use the multiple protection method. Alternatively, the AP of the OBSS can transmit a directive in the management frame that instructs the STAs included in the OBSS to use the multiple protection method. Alternatively, the above methods may be combined. The AP and STAs of the OBSS can set the duration field of the MAC header of the frames transmitted using the multiple protection method.

[0164] Specifically, the TXOP of the OBSS may be from the start of transmission of control frame 1 to time T2 due to the NPCA operation of BSS 1 following the frame transmission of the OBSS using multiple protection. For example, the OBSS may transmit a total of 6 frames on the main channel. The 6 frames may include control frame 1 (406), control frame 2 (407), data frame 1 (408), response frame 1 (409), data frame 2 (410), and response frame 2 (411), and these frames may be transmitted in order. Here, the end time of the communication period of the OBSS may be T2. When a multiple protection method is used, the duration field of each of the control frame 1 (406), control frame 2 (407), data frame 1 (408), response frame 1 (409), data frame 2 (410), and response frame 2 (411) frames may indicate the time remaining until T2 after the completion of transmission of the frame.

[0165] On the other hand, when the Single protection method is used, the duration fields of control frame 1 (406) and control frame 2 (407) may indicate the time length until the completion of transmission of data frame 1 (408) or response frame 1 (409). Additionally, data frame 2 (410) may indicate the time length until the completion of transmission of response frame 2 (411). Therefore, the duration fields of control frame 1 (406) and control frame 2 (407) may not indicate the full length of the entire communication interval (TXOP) of the OBSS but may be shorter. The length excluding the lengths of control frame 1, SIFS, and control frame 2 from the total communication interval of the OBSS (or the total communication interval of the OBSS) may be longer than the NPCA minimum duration. However, the value of the duration field indicated by at least one of control frame 1 (406) and control frame 2 (407) of the OBSS may be shorter than the NPCA minimum duration. Therefore, if OBSS uses a Single Protection method, BSS 1 cannot switch the operating channel to the NPCA main channel, and the opportunity to perform NPCA channel switching may be reduced. On the other hand, if OBSS uses a Multiple Protection method, BSS 1 can switch the operating channel to the NPCA main channel.

[0166] FIG. 8 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies. Referring to FIG. 8, the STA can receive a first PPDU (physical layer protocol data unit) of an OBSS (overlapping basic service set) on the main channel (S810). After that, the STA can switch the operating channel from the main channel to the NPCA main channel based on a non-primary channel access (NPCA) switching condition (S820). Here, the NPCA switching condition may include a condition that the first PPDU is an inter-BSS PPDU and a condition that the NPCA operating period is greater than the NPCA minimum duration. After that, the STA can operate on the NPCA main channel from the end of the NPCA operation period until a point in time preceding the channel switching back delay after the STA has switched to the NPCA main channel (S830). The STA can switch the operation channel during the channel switching back delay time to operate on the main channel at the end of the NPCA operation period (S840). Here, the STA identifies a PPDU sequence consisting of a plurality of PPDUs including a first PPDU in the main channel, and if the first PPDU includes an initial control frame, the NPCA operation period can be determined based on the MAC header duration value of the initial control frame included in the first PPDU and compared with the NPCA minimum duration. Additionally, the time at which the STA starts operation on the NPCA main channel may be later than the time at which the reception completion of the second PPDU following the first PPDU is confirmed or inferred. Alternatively, the point in time when the completion of reception of the second PPDU is confirmed is the point in time when the STA generates the primitive related to reception of the second PPDU, and the point in time when the STA initiates operation on the NPCA main channel may be after a preset time interval has elapsed from the point in time when the STA generates the primitive related to reception of the second PPDU.Additionally, the NPCA operation interval corresponds to 'NPCA_CFRAME_TXOP_REM_DUR', and 'NPCA_CFRAME_TXOP_REM_DUR' may be a MAC variable. Additionally, the STA operates on the NPCA main channel based on the NPCA timer, and the NPCA timer may expire at a point that is ahead of the end of the time interval indicated by 'NPCA_CFRAME_TXOP_REM_DUR' by a channel switching back delay. Additionally, if the first PPDU is at least one of HE (high efficiency) PPDU, EHT (extremely high throughput) PPDU, and UHR (ultra high reliability) PPDU, the NPCA operation interval may be determined based on the 'RXTIME' value, which is the time length value of the first PPDU. Additionally, the NPCA operation interval may be determined based on the 'RXTIME' value of the first PPDU at the time when the MAC of the first STA receives the reception-related primitive of the first PPDU. Additionally, the 'RXTIME' value can be calculated from the length field value within the preamble of the first PPDU. Additionally, the NPCA operation interval can correspond to 'NPCA_PPDU_REM_DUR'. Additionally, the NPCA operation interval can be determined at the time when the MAC of the first STA receives the reception-related primitive of the first PPDU based on the sum of the 'RXTIME' value of the first PPDU and the 'TXOP DURATION' value of the RXVECTOR of the first PPDU. Additionally, the 'TXOP DURATION' value may be the value indicated by the TXOP field within the preamble of the first PPDU. Additionally, the NPCA operation interval can correspond to 'NPCA_PHY_TXOP_REM_DUR'.In addition, if the first PPDU is at least one of a high efficiency (HE) PPDU, an extremely high throughput (EHT) PPDU, and an ultra high reliability (UHR) PPDU, the NPCA operation interval can be determined through the transmission time length of the first PPDU, which is determined based on the length field value, number of symbols, symbol length, and signal extension within the preamble of the first PPDU. In addition, as an example, the STA may be an AP STA or a non-AP STA.

[0167] The methods according to the present disclosure may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and configured for the present disclosure, or they may be those known and available to those skilled in the art of computer software. Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as at least one software module to perform the operations of the present disclosure, and vice versa. Although the present invention has been described with reference to the embodiments above, those skilled in the art will understand that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the disclosure as set forth in the following claims.

[0168]

[0169] The above-mentioned matters may also be applied to other systems.

Claims

1. In the method of operation of a station (STA) in a wireless LAN system, The step of the above STA receiving a first PPDU (physical layer protocol data unit) of the OBSS (overlapping basic service set) on the main channel; A step of switching an operating channel from the main channel to an NPCA main channel based on a non-primary channel access (NPCA) switching condition, wherein the NPCA switching condition includes a condition that the first PPDU is an inter-BSS PPDU and a condition that the NPCA operating interval is greater than the NPCA minimum duration; A step of operating on the NPCA main channel from the end point of the NPCA operation period until a point preceding the channel switching back delay after the STA is switched to the NPCA main channel; and A method of operation comprising the step of switching the operation channel during the channel switching back delay time and operating on the main channel at the end of the NPCA operation period.

2. In Paragraph 1, A method of operation in which the STA identifies a PPDU sequence composed of a plurality of PPDUs including the first PPDU in the main channel, and if the first PPDU includes an initial control frame, the NPCA operation interval is determined based on the MAC header duration value of the initial control frame included in the first PPDU and compared with the NPCA minimum duration.

3. In Paragraph 2, A method of operation in which the time at which the STA initiates operation on the NPCA main channel is later than the time at which the completion of reception of the second PPDU following the first PPDU is confirmed or inferred.

4. In Paragraph 3, A method of operation in which the point in time when the completion of reception of the second PPDU is confirmed is the point in time when the STA generates the primitive related to reception of the second PPDU, and the point in time when the STA initiates operation on the NPCA main channel is after a preset time interval has elapsed from the point in time when the STA generates the primitive related to reception of the second PPDU.

5. In Paragraph 3, The above NPCA operation interval corresponds to 'NPCA_CFRAME_TXOP_REM_DUR', and the above 'NPCA_CFRAME_TXOP_REM_DUR' is a MAC variable, operation method.

6. In Paragraph 5, A method of operation in which the above STA operates on the above NPCA main channel based on the NPCA timer, wherein the above NPCA timer expires at a point preceding the end of the time interval indicated by the above 'NPCA_CFRAME_TXOP_REM_DUR' by the above channel switching back delay.

7. In Paragraph 1, A method of operation in which, when the first PPDU is at least one of HE (high efficiency) PPDU, EHT (extremely high throughput) PPDU, and UHR (ultra high reliability) PPDU, the NPCA operation interval is determined based on the 'RXTIME' value, which is the time length value of the first PPDU.

8. In Paragraph 7, A method of operation in which the above NPCA operation interval is determined at the time when the MAC of the first STA receives the reception-related primitive of the first PPDU based on the 'RXTIME' value of the first PPDU.

9. In Paragraph 8, A method of operation in which the above 'RXTIME' value is calculated from the length field value within the preamble of the first PPDU.

10. In Paragraph 8, The above NPCA operation section is an operation method corresponding to 'NPCA_PPDU_REM_DUR'.

11. In Paragraph 7, A method of operation in which the above NPCA operation interval is determined at the time when the MAC of the first STA receives a reception-related primitive of the first PPDU based on the sum of the 'RXTIME' value of the first PPDU and the 'TXOP DURATION' value of the RXVECTOR of the first PPDU.

12. In Paragraph 11, A method of operation in which the above 'TXOP DURATION' value is the value indicated by the TXOP field in the preamble of the first PPDU.

13. In Paragraph 11, The above NPCA operation section is an operation method corresponding to 'NPCA_PHY_TXOP_REM_DUR'.

14. In Paragraph 1, A method of operation in which, when the first PPDU is at least one of HE (high efficiency) PPDU, EHT (extremely high throughput) PPDU, and UHR (ultra high reliability) PPDU, the NPCA operation interval is determined through the transmission time length of the first PPDU, which is determined based on the length field value, number of symbols, symbol length, and signal extension within the preamble of the first PPDU.

15. In Paragraph 1, The above STA is an AP STA or a non-AP STA, a method of operation.

16. In a wireless LAN system, regarding a station (STA), At least one transceiver for transmitting and receiving signals; At least one processor controlling the above-mentioned at least one transmitting and receiving unit; and It includes a memory that stores instructions for the non-AP STA to perform a specific operation by the above at least one processor, and The above specific operation is: Receive the first PPDU (physical layer protocol data unit) of the OBSS (overlapping basic service set) on the main channel, and Based on NPCA (non-primary channel access) switching conditions, the operating channel is switched from the main channel to the NPCA main channel, wherein the NPCA switching conditions include the condition that the first PPDU is an Inter-BSS PPDU and the condition that the NPCA operating interval is greater than the NPCA minimum duration; After switching to the above NPCA main channel, it operates on the above NPCA main channel from the end point of the above NPCA operation period until a point preceding by the channel switching back delay, and STA that operates on the main channel at the end of the NPCA operation period by switching the operation channel during the channel switching back delay time.

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