Method and apparatus for transmitting response frame in non-primary channel access operation of wireless LAN

Abstract

In this operating method of an STA in a wireless LAN system, the STA can: detect transmission 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; receive a first frame on the NPCA primary channel; and determine, on the basis of whether the first frame is an NPCA ICF, whether to transmit a response frame to the first frame.

Description

Method and device for transmitting response frames in side-channel access operation of wireless LAN

[0001] The present disclosure relates to a method and apparatus for transmitting a response frame 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 a wireless LAN where wireless LAN terminals support side-channel access operations, some wireless LAN terminals may operate on the side-channel while others operate on the main channel. In the aforementioned case, a method for transmitting response frames may be required, and 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 transmitting a response frame in an NPCA operation of a wireless local area network (WLAN).

[0010] The present disclosure relates to a method and apparatus for transmitting a response frame in a case where some wireless LAN terminals operate on the NPCA main channel and other wireless LAN terminals operate on the main channel, in a case where NPCA operation is supported in a wireless LAN.

[0011] The present disclosure relates to a method and apparatus for determining whether a frame received by a wireless LAN terminal is transmitted using the main channel when performing NPCA operation in a wireless LAN, and determining the transmission of a response frame for the received frame.

[0012] The present disclosure relates to a method and apparatus for identifying a frame transmitted including a main channel by a wireless LAN terminal in a wireless LAN, confirming the existence of a wireless LAN terminal operating on the main channel, and determining the transmission of a response frame for a wireless LAN terminal operating on the main channel.

[0013] 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.

[0014]

[0015] According to one embodiment of the present specification, a method of operation of a first station (STA) in a wireless LAN system may include the steps of: the first STA detecting the transmission of an overlapping basic service set (OBSS) on a main channel; the first STA switching an operating channel from a main channel to an NPCA main channel based on a non-primary channel access (NPCA) switching condition; the first STA receiving a first frame on an NPCA main channel; and the first STA determining whether to transmit a response frame for the first frame based on whether the first frame is an initial control frame (NPCA ICF).

[0016] 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 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: detecting the transmission of an overlapping basic service set (OBSS) on a main channel, switching the operating channel from a main channel to an NPCA main channel based on a non-primary channel access (NPCA) switching condition, receiving a first frame on the NPCA main channel, and determining whether to transmit a response frame for the first frame based on whether the first frame is an initial control frame (NPCA ICF).

[0017] Additionally, according to one embodiment of the present specification, if the first frame is an NPCA ICF, the first STA may transmit an initial control response (ICR) as a response frame to the first frame.

[0018] Additionally, according to one embodiment of the present specification, the NPCA ICF may be a trigger frame including an NPCA main channel indicator that indicates that a trigger frame is transmitted in the NPCA main channel.

[0019] Additionally, according to one embodiment of the present specification, if the first frame is a frame other than the NPCA ICF, the first STA may not transmit a response frame for the first frame.

[0020] Additionally, according to one embodiment of the present specification, the first STA may not transmit a response frame for the first frame regardless of whether the first frame is a frame that immediately requires a response frame.

[0021] Additionally, according to one embodiment of the present specification, when the first STA receives the first frame from the second STA associated with the first STA in the NPCA main channel as a frame other than the NPCA ICF, the first STA may determine that the second STA is operating in the main channel.

[0022] Additionally, according to one embodiment of the present specification, the first STA can switch the operating channel from the NPCA main channel to the main channel based on the second STA operating in the main channel.

[0023] Additionally, according to one embodiment of the present specification, if the first STA receives a non-HT duplicate PPDU (physical layer protocol data unit) that does not include a control frame or includes a request to send (RTS) frame in the NPCA main channel, it may determine the first frame as a frame other than the NPCA ICF and not transmit a response frame for the first frame.

[0024] Additionally, according to one embodiment of the present specification, when the first STA receives a first frame occupying the main channel from a second STA associated with the first STA, the first STA may not transmit a response frame to the second STA.

[0025] Additionally, according to one embodiment of the present specification, when a first STA receives a first frame occupying a main channel from a second STA associated with the first STA, the first STA may transmit a response frame to the second STA through the NPCA main channel.

[0026] Additionally, according to one embodiment of the present specification, the response frame may be a frame that instructs the second STA to switch the operating channel to the NPCA main channel.

[0027] Additionally, according to one embodiment of the present specification, when a first STA receives a first frame occupying a main channel from a second STA associated with the first STA, the first STA may transmit a response frame to the second STA through the NPCA main channel and the main channel.

[0028] Additionally, according to one embodiment of the present specification, the response frame may be a frame that instructs the second STA to switch the operating channel to the NPCA main channel.

[0029] In addition, according to one embodiment of the present specification, when the first STA operates on the NPCA main channel, the STAs associated with the first STA can transmit uplink frames only by the trigger frame transmitted by the first STA, and when the first STA receives an uplink frame from the second STA among the STAs associated with the first STA, it can be determined that the second STA operates on the main channel.

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

[0031]

[0032] According to the present disclosure, a method for transmitting a response frame in an NPCA operation of a WLAN can be provided.

[0033] According to the present disclosure, a method for transmitting a response frame can be provided in cases where some wireless LAN terminals operate on the NPCA main channel and other wireless LAN terminals operate on the main channel, in cases where NPCA operation is supported in a wireless LAN.

[0034] According to the present disclosure, when performing NPCA operations in a wireless LAN, a method can be provided to determine whether a frame received by a wireless LAN terminal is transmitted using the main channel and to determine the transmission of a response frame for the received frame.

[0035] According to the present disclosure, a method can be provided for a wireless LAN terminal to identify a frame transmitted including a main channel in a wireless LAN, and to determine the transmission of a response frame to a wireless LAN terminal operating in the main channel by confirming that there is a wireless LAN terminal operating in the main channel.

[0036] 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.

[0037] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0038]

[0039] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0040] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0041] FIG. 3 is a diagram showing a wireless LAN network to which the present disclosure applies.

[0042] 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.

[0043] FIGS. 5a to 5c are drawings illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0044] FIGS. 6a to 6c are drawings illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0045] FIGS. 7a to 7c are drawings illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0046] FIG. 8 is a diagram illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0047] FIGS. 9a and 9b are diagrams illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0048] FIGS. 10a and FIGS. 10b are diagrams illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0049] FIG. 11 is a flowchart showing the operation of an STA in a wireless LAN to which the present disclosure applies.

[0050]

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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."

[0058] 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.

[0059] 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).

[0060] 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).

[0061] 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).

[0062] 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.

[0063] 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.

[0064] The present disclosure may relate to a method for transmitting a response frame in a wireless LAN network where wireless LAN terminals support NPCA operation, and where some of the multiple wireless LAN terminals included in the wireless LAN network operate on a sub-channel and some operate on a main channel. In the above-described case, if a wireless LAN terminal operates on the NPCA main channel, it may successfully exchange data with a wireless LAN terminal operating on the NPCA main channel, but it may fail to successfully exchange data with a wireless LAN terminal operating on the main channel, and a solution for this may be required. If appropriate operation is not performed in the above-described case, the wireless LAN terminal operating on the main channel may fail to transmit a data frame, and consequently, the transmission efficiency of the wireless LAN network may decrease and wireless resources may be wasted. Considering the above, the following describes a method for efficiently performing NPCA operation by having a wireless LAN terminal identify a frame transmitted including the main channel, confirm the existence of a wireless LAN terminal operating on the main channel, and determine the transmission of a response frame based thereon.

[0065] 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.

[0066] 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.

[0067] 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 in which Basic NAV is set). 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 a control frame, 401) and an initial response frame that is a response frame to the control frame (e.g., a PPDU containing an initial response frame, 402), and if they satisfy the condition of [NPCA Switching Condition - Control Frame] below, they can switch the operating channel to the NPCA main channel and operate.

[0068] [NPCA Transition Condition - Control Frame]

[0069] - When receiving a control frame and an initial response frame for the control frame, all of the following conditions must be satisfied

[0070] ■ Received PPDU determined to be inter-BSS PPDU

[0071] ◆ For example, at least one of the control frame and the initial response frame is determined to be an inter-BSS PPDU

[0072] ■ 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

[0073] In this case, the length of the TXOP can be referred to as the 'communication interval of the OBSS'.

[0074] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA Primary channel

[0075]

[0076] 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.

[0077] 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).

[0078] 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.

[0079] [NPCA Transition Conditions - HE Frame]

[0080] - The received PPDU is an HE / EHT / UHR PPDU and satisfies all of the following conditions

[0081] ■ PPDU is determined to be an inter-BSS PPDU

[0082] ■ The length of the PPDU is greater than the NPCA minimum duration

[0083] Here, the time length of the PPDU can be considered the 'communication interval of the OBSS'.

[0084] ◆ The time length of the PPDU described above may be one of the following.

[0085] ● 1. Length of PPDU transmission time identified from the PPDU preamble

[0086] □ Transmission time length of the PPDU identified from the value of the LENGTH field included in the L_SIG of the preamble

[0087] ◇ RXTIME time calculated from the value of the LENGTH field

[0088] ◇ ((LENGTH + 3) / 3) * 4 + 20 + SignalExtension (us)

[0089] ● 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

[0090] The value of the TXOP field can be set to the TXOP_DURATION value of the RXVECTOR obtained from the received frame.

[0091] ● 3. Other value(s) for the transmission length of OBSS found in the PPDU preamble

[0092] ● 4. The longest value among 1. to 3.

[0093] ● 5. Sum of 1. and 2.

[0094] ■ When bandwidth information occupied by the PPDU is identified and the PPDU does not occupy the NPCA Primary channel

[0095]

[0096] 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.

[0097] Referring to FIGS. 4a and 4b, a frame can be transmitted instructing the AP of BSS 1 and the STAs connected to the AP to perform NPCA operations. The UHR operation information element of the management frame (e.g., beacon frame, probe response frame) transmitted by the AP 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 separately included in the AP's management frame, may indicate the NPCA main channel, the AP's NPCA switching delay, and the NPCA switch back delay.

[0098] FIGS. 5a to 5c are drawings illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0099] Referring to FIGS. 5a to 5c, the configuration of a wireless LAN network can be considered as described above. Specifically, the wireless LAN network configuration and NPCA operation may be as follows.

[0100] [Wireless LAN Network Configuration - Network and NPCA Operation]

[0101] Consider a case where AP 1 (310) and non-AP STA 1 (320) and non-AP STA 2 (330) connected to AP 1 (310) operate in a wireless LAN network. Here, AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) can form a basic service set (BSS), as described above. For example, the operating bandwidth of AP 1 (310) is 160 MHz, but it may be any other operating bandwidth and is not limited to a specific form. The operating bandwidth of AP 1 (310) may be composed of multiple 20 MHz channels. As a specific example, if the operating bandwidth of AP 1 (310) is 160 MHz, the main 20 MHz channel may be the 20 MHz channel that AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) must occupy when performing channel access operations and transmitting data frames among the 160 MHz channels of AP 1 (310). Alternatively, among the 160 MHz channels of the operating bandwidth of AP 1 (310), the channel containing the main 20 MHz channel may be referred to as the main 80 MHz channel, and the remaining 80 MHz channel may be referred to as the secondary 80 MHz channel. Additionally, some 20 MHz channels among the secondary 80 MHz channels may be designated as the NPCA main channel, but are not limited thereto. When at least one of AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) detects a communication interval of an overlapping BSS (OBSS) occupying the main 20 MHz channel, it can perform a channel access operation (e.g., an enhanced distributed channel access (EDCA) backoff and a transmit opportunity (TXOP) acquisition procedure) on the NPCA main channel and perform a frame transmission operation.OBSS may be a BSS that is not a BSS configured by AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330). That is, it may be a wireless LAN network different from the wireless LAN network configured by AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330). Here, a hidden node problem may be considered in the wireless LAN network configuration, which may be as follows.

[0102]

[0103] [Wireless LAN Network Configuration - Hidden Node Problem]

[0104] Some wireless LAN terminals among AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) may not be able to detect the communication segment of OBSS. For example, some wireless LAN terminals in a hidden node relationship may not be able to detect the communication segment of OBSS. As a specific example, AP 1 (310) and non-AP STA 1 (320) can detect the frame of OBSS. That is, AP 1 (310) and non-AP STA 1 (320) can detect the communication segment of OBSS. On the other hand, non-AP STA 2 (330) may be in a hidden node relationship with respect to OBSS, and accordingly, may not be able to receive the frame of OBSS. In the above case, a problem may arise in which the operating channel of non-AP STA 2 (330) differs due to the hidden node problem, and may be as follows.

[0105]

[0106] [Wireless LAN Network Configuration - Different Operating Channels Due to Hidden Node Issues]

[0107] AP 1 (310) and non-AP STA 1 (320) may be able to receive OBSS frames. Therefore, AP 1 (310) and non-AP STA 1 (320) may switch the operating channel to the NPCA main channel if they satisfy the [NPCA switching condition - control frame] and [NPCA switching condition - HE frame] described in FIG. 4a and 4b. On the other hand, since non-AP STA 2 (330) cannot receive OBSS frames, it may not satisfy either of the [NPCA switching condition - control frame] and [NPCA switching condition - HE frame] conditions and may have to operate on the main channel. Therefore, AP 1 (310) and non-AP STA 1 (320) can move to the NPCA main channel because they can verify the communication interval of OBSS, but non-AP STA 2 (330) cannot verify the communication interval of OBSS and may operate on the main channel. non-AP STA 2 (330) cannot determine whether AP 1 (310) and non-AP STA 1 (320) are operating on the NPCA main channel. AP 1 (310) and non-AP STA 1 (320) can operate on the NPCA main channel after the NPCA switching delay (NPCA switch delay, NSD) has elapsed from time T1, which is the time when the communication interval of OBSS is detected (specifically, the time when at least one of [NPCA switching condition - control frame] and [NPCA switching condition - HE frame] is satisfied). The NSD (NPCA switch delay) is the same time as the Ts time described in FIG. 4a and FIG. 4b. AP 1 (310) and non-AP STA 1 (320) must complete frame switching on the NPCA main channel before the NPCA switch back delay (NSBD) time from time T2, which is the end time of the communication period of the OBSS, and may operate on the main channel again at time T2.Meanwhile, since the non-AP STA 2 (330) cannot receive the OBSS frame, it can detect the main channel as idle and perform a channel access operation and perform frame transmission. In the above case, there may be a problem where the main channel is used by the non-AP STA 2 (330), and this may be as follows.

[0108]

[0109] [Wireless LAN Network Configuration - Primary Channel Frame Transmission Issues]

[0110] The non-AP STA 2 (330) can successfully perform a channel access operation on the main channel and acquire a TXOP (transmit opportunity), which is a time resource for transmitting a frame. The non-AP STA 2 (330) can support the entire operating bandwidth of AP 1 (310) (e.g., if the operating bandwidth of AP 1 (310) is 160 MHz, the entire 160 MHz). If the non-AP STA 2 (330) detects that the entire 160 MHz channel is idle, the non-AP STA 1 (320) may want to transmit a frame to AP 1 (310). Here, the non-AP STA 2 (330) can recognize that AP 1 (310) is using an NPCA operation through a management frame or other frames transmitted by AP 1 (310). However, since non-AP STA 2 (330) cannot determine whether AP 1 (310) is actually present in the NPCA main channel, the first frame that non-AP STA 2 (330) transmits to AP 1 (310) may be an initial frame. Alternatively, non-AP STA 2 (330) may transmit an initial frame to AP 1 (310) regardless of whether NPCA is active. Here, the initial frame may be of various forms. For example, the initial frame may be an RTS (request to send) frame. Or, the initial frame may be a BAR (BlockAck Request) frame, but is not limited thereto. For example, the initial frame that non-AP STA 2 (330) can transmit may be a trigger frame. Also, the initial frame that only AP 1 (310) can transmit may be a variant of the trigger frame. For example, the initial frames that AP 1 (310) can transmit may be MU-RTS trigger frames, BSRP (buffer status report poll) frames and other frames, but are not limited to a specific form.The initial frame transmitted by non-AP STA 2 (330) to AP 1 (310) can be transmitted in the form of a Non-HT (high throughput) duplicated PPDU (physical layer protocol data unit). The Non-HT duplicated PPDU format may mean that the non-AP STA 2 (330) duplicates and transmits the PPDU for each 20 MHz channel. Here, the contents (e.g., MPDU) included in the duplicated PPDU for each 20 MHz channel may be identical. However, the phase of each duplicated PPDU for each 20 MHz channel may be different. For example, the phase of the PPDU transmitted in the main 20 MHz channel and the phase of the PPDU transmitted in a channel other than the main 20 MHz channel may differ by +90° or +180°, but are not limited thereto.

[0111] Some bits of the SERVICE field, which is the first field of the data field following the preamble of each 20 MHz channel-specific PPDU containing the initial frame transmitted by the non-AP STA 2 (330), may indicate the actual bandwidth information over which the frame is transmitted. The PHY layer of the non-AP STA 2 (330) may use some bits of the SERVICE field to indicate the total transmission bandwidth (e.g., CBW (channel bandwidth) 160 - 160 MHz) of the Non-HT duplicated PPDU transmitted by the non-AP STA 2 (330). The transmitter address (TA) of the MAC header of the initial frame transmitted by the non-AP STA 2 (330) may indicate that the SERVICE field of the PPDU contains information indicating the bandwidth. Alternatively, non-AP STA 2 (330) may change some bits of the MAC (medium access control) address of non-AP STA 2 (330) to indicate that bandwidth information is present in the SERVICE field of the PPDU. The aforementioned indication operation may be referred to as a bandwidth signaling TA, but is not limited thereto. AP 1 (310) may detect the PPDU of non-AP STA 2 (330) while operating on the NPCA main channel. When AP 1 (310) receives the header (including the preamble and SERVICE field) of the PPDU of non-AP STA 2 (330), it may configure an RXVECTOR. Here, the 'CH_BANDWIDTH_IN_NON_HT' parameter included in the RXVECTOR may be set by referring to the values ​​of some bits of the SERVICE field of the PPDU. Since the value of the SERVICE field was set so that non-AP STA 2 (330) indicates CBW 160, it can be set to CBW 160.The PHY layer of AP 1 (310) passes the RXVECTOR to the MAC layer of AP 1 (310), and the MAC layer of AP 1 (310) can decode the MPDU (i.e., the initial frame of STA 2) contained in the PPDU. If the TA of the MAC header of the initial frame of non-AP STA 2 (330) is a bandwidth signaling TA, the MAC layer of AP 1 (310) can verify that the 'CH_BANDWIDTH_IN_NON_HT' of the RXVECTOR parameter is CBW160. That is, the MAC layer of AP 1 (310) can recognize that non-AP STA 2 (330) is transmitting a frame using the entire operating bandwidth of AP 1 (310). The MAC layer of AP 1 (310) can confirm that non-AP STA 2 (330) is operating on the main channel and is transmitting a frame including the main 20 MHz channel. Alternatively, depending on the configuration of at least one of the main channel and the NPCA main channel and the operating bandwidth of AP 1 (310), even if 'CH_BANDWIDTH_IN_NON_HT' is not CBW 160 (e.g., CBW320, CBW80, CBW40, etc.), AP 1 (310) can confirm that non-AP STA 2 (330) has performed frame transmission using the main channel, and is not limited to a specific form.

[0112] The following describes specific operations based on the above-described wireless LAN network configuration (i.e., [Wireless LAN Network Configuration - Network and NPCA Operation], [Wireless LAN Network Configuration - Hidden Node Problem], [Wireless LAN Network Configuration - Different Operation Channels Due to Hidden Node Problem], [Wireless LAN Network Configuration - Primary Channel Use Frame Transmission Problem]), and is not limited to a specific form.

[0113] Referring to FIG. 5a, AP 1 (310) can confirm that non-AP STA 2 (330) occupies the main channel and transmits a frame (404). AP 1 (310) can confirm that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA Primary channel) and may not transmit a response frame for the initial frame (404). Meanwhile, non-AP STA 1 (320) may operate on the NPCA main channel. When non-AP STA 1 (320) transmits a frame (405) on the NPCA main channel, the transmission bandwidth of the frame may be limited to within the operating bandwidth of AP 1 (310). As a specific example, even if non-AP STA 1 (320) supports 160 MHz operation, if the NPCA main channel is configured within the secondary 80 MHz channel of AP 1 (310), the bandwidth of the maximum transmittable frame of non-AP STA 1 (320) may be limited to 80 MHz. When non-AP STA 1 (320) operates on the NPCA main channel, the first frame (405) transmitted by non-AP STA 1 (320) to AP 1 (310) may be an initial frame. The initial frame may refer to the frame transmitted first from the TXOP when the TXOP is acquired by performing channel access. If there is an uplink data frame to be transmitted to AP 1 (310) in non-AP STA 1 (320), non-AP STA 1 (320) performs a channel access operation, and if the channel access operation is successful, it can transmit an initial frame (405) to AP 1 (310). Here, the initial frame (405) may be transmitted in the format of a 'Non-HT Duplicated PPDU'. Some bits of the SERVICE field of the 20 MHz PPDU transmitted by non-AP STA 1 (320) correspond to the transmission bandwidth of non-AP STA 1 (320) (e.g.In the NPCA Primary Channel, non-AP STA 1 (320) may indicate a bandwidth less than or equal to the transmittable bandwidth. Alternatively, the TA in the initial frame MAC header may be the Bandwidth Signaling TA of non-AP STA 1 (320). Thus, AP 1 (310) detects the PPDU of non-AP STA 1 (320) in the NPCA Primary Channel and can configure an RXVECTOR upon receiving the header of the PPDU of non-AP STA 1 (320) (including the preamble and SERVICE fields). The 'CH_BANDWIDTH_IN_NON_HT' parameter included in the RXVECTOR can be set by referring to the values ​​of some bits in the SERVICE field of the PPDU, as described above. If non-AP STA 1 (320) sets the SERVICE field value to indicate CBW 80, the 'CH_BANDWIDTH_IN_NON_HT' parameter can be set to CBW80. The PHY layer of AP 1 (310) passes the RXVECTOR to the MAC layer of AP 1 (310), and the MAC layer of AP 1 (310) can decode the MPDU contained in the PPDU (i.e., the initial frame of non-AP STA 1 (320)). The MAC layer of AP 1 (310) can verify that the 'CH_BANDWIDTH_IN_NON_HT' of the RXVECTOR parameter is CBW80 if the TA of the MAC header of the initial frame of non-AP STA 1 (320) is a bandwidth signaling TA. That is, the MAC layer of AP 1 (310) can recognize that non-AP STA 1 (320) is transmitting a frame using a portion of the operating bandwidth of AP 1 (310) (e.g., within the transmission bandwidth of a frame that can be transmitted on the NPCA Primary channel). The MAC layer of AP 1 (310) can confirm that non-AP STA 1 (320) is operating on the NPCA Primary channel and can confirm that it is in a state where frame exchange with AP 1 (310) is possible.

[0114] As another example, AP 1 (310) can determine whether non-AP STA 1 (320) is operating on the NPCA primary channel by using the 'CH_BANDWIDTH RXVECTOR' parameter instead of the 'CH_BANDWIDTH_IN_NON_HT' mentioned above. The PHY layer of AP 1 (310) can set the 'CH_BANDWIDTH' parameter based on the preamble of the PPDU transmitted by non-AP STA 1 (320), and can determine that non-AP STA 1 (320) is transmitting a frame using a bandwidth that is equal to or smaller than the available bandwidth on the NPCA primary channel (e.g., within the transmission bandwidth of a frame that can be transmitted on the NPCA primary channel). In the above case, the MAC layer of AP 1 (310) can determine that non-AP STA 1 (320) is operating on the NPCA primary channel and that it is in a state where frame exchange with AP 1 (310) is possible.

[0115] AP 1 (310) can transmit an initial response frame (406) for an initial frame (405) of non-AP STA 1 (320). non-AP STA 1 (320) can receive the initial response frame (406) of AP 1 (310), and upon receiving the initial response frame (406), can transmit an uplink data frame (407) to AP 1 (310). Upon receiving the uplink frame (407) of non-AP STA 1 (320), AP 1 (310) can transmit a response frame (408) for the uplink frame (407). Here, since AP 1 (310) recognizes that non-AP STA 2 (330) is not operating on the NPCA main channel, it may not allocate uplink resources to non-AP STA 2 (330) or transmit downlink frames. Additionally, frame exchange between non-AP STA 1 (320) and AP 1 (310) may be terminated before 'T2 - NSBD'. AP 1 (310) and non-AP STA 1 (320) may operate on the main channel after time T2. non-AP STA 2 (330) may not receive a response frame for the initial frame transmitted to AP 1 (310) and may determine that the frame transmission failed. Consequently, non-AP STA 2 (330) may increase channel access parameters (e.g., QSRC (QoS STA Retry Counter) [AC] and CW (contention window) [AC], which are channel access parameters per AC (access categories) of EDCA), and as a result, unnecessary delay may occur when non-AP STA 2 (330) accesses the channel. Accordingly, AP 1 (310) can transmit an NPCA instruction frame instructing non-AP STA 2 (330) to decrease the channel access parameters (e.g., initialize the channel access parameters of STA 2) if the channel access operation is successful after time T2.When non-AP STA 2 (330) receives an NPCA instruction frame from AP 1 (310), non-AP STA 2 (330) may reduce (e.g. initialize) the channel access parameters. Alternatively, AP 1 (310) may send a trigger frame allocating uplink resources to non-AP STA 2 (330), and when non-AP STA 2 (330) receives the trigger frame from AP 1 (310), it may send an uplink frame to AP 1 (310).

[0116] Referring to FIG. 5a, AP 1 (310) may receive a frame (404) occupying the main channel from non-AP STA 2 (330) on the NPCA main channel while operating on the NPCA main channel. In the above case, AP 1 (310) may recognize that non-AP STA 2 (330) is operating on the main channel and not on the NPCA main channel. Here, AP 1 (310) may not perform frame transmission to non-AP STA 2 (330) on the NPCA main channel before the time when AP 1 (310) operates on the main channel again (time T2). That is, AP 1 (310) may not transmit a frame to non-AP STA 2 (330) on the NPCA main channel because non-AP STA 2 (330) considers that receiving the frame is impossible. Here, AP 1 (310) may consider that there is no frame (or packet) destined for non-AP STA 2 (330) in the transmission queue. Then, AP 1 (310) may consider that a frame (or packet) destined for non-AP STA 2 (330) has occurred again after time T2. The transmission queue of AP 1 (310) may be an AC-specific transmission queue.

[0117] Meanwhile, as described above, the operation resulting from AP 1 (310) considering a frame (or packet) to be the destination of non-AP STA 2 (330) in the transmission queue as non-AP STA 2 (330) may be as follows and may be applied equally to other operations. When the transmission queue of AP 1 (310) considers a frame (or packet) to be the destination of non-AP STA 2 (330) as non-AP STA 2 and thus considers the transmission queue to be empty, AP 1 (310) may stop the channel access operation without transmitting the frame even if the channel access operation is completed. Specifically, the transmission queue of AP 1 (310) being empty may mean that the transmission queue of a specific AC (access category) of AP 1 (310) is empty. Frames (packets) in the transmission queue of a specific AC can be transmitted by the EDCAF (EDCA function) associated with the specific AC performing channel access. If the transmission queue is considered empty as the transmission queue considers there to be no frame (or packet) destined for non-AP STA 2 (330), there may not be any frames (available frames) that EDCAF can transmit at the slot boundary where the backoff counter is 0. In the above case, EDCAF may stop the operation (or do nothing (represented as do nothing). Additionally, if the transmission queue of AP 1 (310) considers there to be no frame (or packet) destined for non-AP STA 2 (330), but there is a frame destined for a STA other than non-AP STA 2 (330), AP 1 (310) may transmit the frame destined for the other STA when the channel access operation is completed.

[0118] Additionally, as described above, the operation resulting from AP 1 (310) deeming that a frame (or packet) to be the destination of non-AP STA 2 (330) in the transmission queue has occurred may be as follows. Specifically, when the transmission queue of AP 1 (310) is deemed empty as it deems that there is no frame (or packet) to be the destination of non-AP STA 2 (330), AP 1 (310) may stop the channel access operation without transmitting the frame even if the channel access operation is completed. When a frame to be the destination of non-AP STA 2 (330) occurs again in AP 1 (310), AP 1 (310) must initiate a backoff operation regardless of whether the medium is occupied or idle. Specifically, when the transmission queue of a specific AC of AP 1 (310) is deemed empty, the EDCAF associated with the specific AC may stop the operation while keeping the backoff counter at 0. When a frame destined for non-AP STA 2 (330) occurs again in the transmission queue of a specific AC, the EDCAF may initiate a backoff operation. Initiating a backoff operation may mean that a random backoff counter is re-selected based on the EDCAF's CW (contention window) [AC], and then a TXOP acquisition procedure is performed. Here, when the aforementioned backoff operation is initiated, the EDCAF's CW may be initiated using the same value as the value previously used by the EDCAF. As another example, when a frame destined for non-AP STA 2 (330) occurs again in AP 1 (310), the AP 1 (310) may initiate a backoff operation based on whether the medium is occupied or idle.When a frame to which non-AP STA 2 (330) is the destination is recurred, or when the medium is detected to be occupied in at least one channel access slot including or after that time, AP 1 (310) may initiate a backoff operation in the same manner as described above. Meanwhile, when a frame to which non-AP STA 2 (330) is the destination is recurred, or when the medium is detected to be idle in at least one channel access slot including or after that time, and the channel access operation is interrupted to a completed state, AP 1 (310) may immediately transmit a frame to which non-AP STA 2 (330) is the destination (or immediately at the slot boundary where the medium is detected to be idle). Specifically, when the transmission queue of a specific AC of AP 1 (310) is considered empty, the EDCAF associated with the specific AC may stop operation while keeping the backoff counter at 0. When a frame destined for non-AP STA 2 (330) is re-occurred in the transmission queue of a specific AC and the medium is detected to be idle, the EDCAF can transmit the frame destined for non-AP STA 2 (330). The channel access operation based on the transmission queue operation of AP 1 (310) described above may also be applied to the operation described below, but is not limited thereto.

[0119] AP 1 (310) can receive a PPDU that occupies the main channel and the NPCA main channel in the NPCA main channel. For example, a non-AP STA 2 (330) can occupies the main channel and the NPCA main channel and transmit a frame (404). If AP 1 (310) receives a frame in a Non-HT duplicated PPDU format, AP 1 (310) can decode the frame (404) to determine whether the PPDU is an intra-BSS PPDU. Here, the PPDU may be an intra-BSS PPDU if the PPDU is transmitted by a STA that is connected to AP 1 (310). For example, AP 1 (310) can recognize that the frame is transmitted by a non-AP STA 2 (330) connected to AP 1 (310).

[0120] As another example, AP 1 (310) may receive a frame in a format other than the 'Non-HT duplicated PPDU format' (e.g., HE (high efficiency), EHT (extremely high throughput), UHR (ultra high reliability) PPDU format). In the above case, AP 1 (310) cannot determine whether the frame was transmitted by a non-AP STA 2 (330) connected to AP 1 (310), but can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU based on the BSS Color included in the PPDU preamble. For example, if the BSS Color included in the PPDU preamble is the same as the BSS Color set by AP 1 (310), it can be confirmed that the PPDU is an intra-BSS PPDU transmitted by a STA connected to AP 1 (310).

[0121] When AP 1 (310) receives an intra-BSS PPDU on the NPCA main channel, AP 1 (310) may perform a channel access operation without setting a network allocation vector (NAV) and perform frame transmission. Alternatively, when AP 1 (310) receives an intra-BSS PPDU on the NPCA main channel, AP 1 (310) may set an intra-BSS NAV. However, AP 1 (310) may ignore the set intra-BSS NAV and perform a channel access operation on the NPCA main channel and perform frame transmission, and is not limited to a specific form.

[0122] Referring to FIG. 5b, AP 1 (310) can confirm that non-AP STA 2 (330) occupies the main channel and transmits a frame (409). AP 1 (310) can confirm that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA main channel) and can transmit an initial response frame (410) for the initial frame (409) of non-AP STA 2 (330). If the initial frame is an RTS frame or a MU-RTS trigger frame, the initial response frame may be a CTS (clear to send) frame. Or if the initial frame is a BAR frame, the initial response frame may be a BlockAck frame. Or if the initial frame is a BSRP trigger frame, the initial response frame may be a QoS Null frame or a BlockAck frame. However, the initial response frame is not limited to the above, and other types of frames may also be possible.

[0123] AP 1 (310) can confirm that non-AP STA 2 (330) occupies the main channel and transmits an initial frame (409), but may not be able to transmit an initial response frame on the main channel. Additionally, AP 1 (310) can expect to receive frames transmitted by non-AP STA 2 (330) occupying only the NPCA main channel without occupying the main channel. In the above case, AP 1 (310) can transmit an initial response frame (410) on the NPCA main channel without occupying the main channel. Also, as an example, AP 1 (310) can transmit an initial response frame to instruct non-AP STA 2 (330) operating on the main channel to operate on the NPCA main channel. The RA (receiver address) in the MAC header of the initial response frame may be set to the MAC address of AP 1 (310) or to the address (e.g., BSSID) of the OBSS of the main channel detected by AP 1 (310). The duration field of the initial response frame may indicate the time length from the time of completion of transmission of the initial response frame to the time of 'T2 - NSBD'. The initial response frame may include padding bits or at least one padding field containing padding bits, which is longer than the NSD time, which is the time for the non-AP STA 2 (330) to switch the operating channel from the main channel to the NPCA main channel. In this disclosure, padding bits or at least one padding field are referred to as 'padding', but are not limited thereto. The function of padding is to extend the time length of the frame and to provide time for switching the operating channel and operating mode of the wireless LAN terminal. For example, padding may be set to extend the frame length beyond the NSD time and to provide operation channel switching of non-AP STA 2 (330) during the NSD time.As a specific example, the initial response frame may include EOF (end of frame) padding fields of an A-MPDU, and the length of the EOF padding fields may be greater than or equal to NSD. Alternatively, the initial response frame may have a Special User Info Field (or Special AID TID Info subfield) and a BlockAck Bitmap Subfield for padding. However, the type of padding is not limited to the padding described above, and any type of bit sequence, field, or subfield that satisfies the function of padding, which is to extend the frame time length and provide time for switching the operating channel and operating mode of the wireless LAN terminal, may be padding and is not limited to a specific form. AP 1 (310) may not transmit the initial response frame if the time length from the time of transmission completion to the time of 'T2 - NSBD' is shorter than the threshold time used as a criterion for performing NPCA.

[0124] non-AP STA 2 (330) can receive an initial response frame (410) from AP 1 (310) on the NPCA main channel. If non-AP STA 2 (330) receives an initial response frame (410) from AP 1 (310) on the NPCA main channel and does not receive an initial response frame on the main channel, non-AP STA 2 (330) can recognize that AP 1 (310) is operating on the NPCA main channel. The padding length of the initial response frame may be greater than or equal to NSD. non-AP STA 2 (330) can switch the operating channel to the NPCA main channel while the padding field included in the initial response frame of AP 1 (310) is being transmitted. After switching the operating channel to the NPCA main channel, non-AP STA 2 (330) can transmit a data frame to AP 1 (310) on the NPCA main channel. Data frame exchange between AP 1 (310) and non-AP STA 2 (330) may end at time T2 before time NSBD. AP 1 (310), non-AP STA 2 (330) and non-AP STA 1 (320) may operate on the main channel again at time T2.

[0125] Referring to FIG. 5c, AP 1 (310) may have the main channel available even after switching the operating channel to the NPCA main channel. For example, AP 1 (310) may be able to transmit and receive frames on the main channel even after switching the operating channel to the NPCA main channel. AP 1 (310) may confirm that non-AP STA 2 (330) occupies the main channel and transmits a frame (410). AP 1 (310) may confirm that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA main channel) and transmit an initial response frame (411) for the initial frame (410) of non-AP STA 2 (330). If the initial frame is an RTS frame or a MU-RTS trigger frame, the initial response frame may be a CTS (clear to send) frame. Or, if the initial frame is a BAR frame, the initial response frame may be a BlockAck frame. Alternatively, if the initial frame is a BSRP trigger frame, the initial response frame may be a QoS Null frame or a BlockAck frame. However, the initial response frame is not limited to what is described above. When AP 1 (310) confirms that non-AP STA 2 (330) has occupied the main channel and transmitted the initial frame (410), it may occupy both the main channel and the NPCA main channel and transmit an initial response frame (411) which is a response frame to the initial frame (410). Here, AP 1 (310) may transmit the initial response frame (411) to instruct non-AP STA 2 (330) operating on the main channel to operate on the NPCA main channel. The RA (receiver address) of the MAC header of the initial response frame may be set to the MAC address of AP 1 (310) or to the address of the OBSS of the main channel detected by AP 1 (310) (e.g., the BSSID of the OBSS).The duration field of the initial response frame may indicate the time length from the time of completion of transmission of the initial response frame to the time of 'T2 - NSBD'. The initial response frame may include padding bits or at least one padding field containing padding bits, which is longer than the NSD time, which is the time for the non-AP STA 2 (330) to switch the operating channel from the main channel to the NPCA main channel. In this disclosure, padding bits or at least one padding field are referred to as 'padding', but are not limited thereto. The function of padding is to extend the time length of the frame and to provide time for switching the operating channel and operating mode of the wireless LAN terminal. For example, padding may be set to extend the frame length longer than the NSD time and to provide the operating channel switching of the non-AP STA 2 (330) for the NSD time. As a specific example, the initial response frame may include the EOF (end of frame) padding fields of the A-MPDU, and the length of the EOF padding fields may be longer than the NSD. Alternatively, the initial response frame may have a Special User Info Field (or Special AID TID Info subfield) and a BlockAck Bitmap Subfield for padding. However, the type of padding is not limited to the padding described above; any type of bit sequence, field, or subfield that satisfies the function of padding, which is to extend the frame's time length and provide time for switching the wireless LAN terminal's operating channel and operating mode, may be padding and is not limited to a specific form. Meanwhile, AP 1 (310) may configure the initial response frame transmitted on the main channel and the initial response frame transmitted on the NPCA main channel differently. Since AP 1 (310) can recognize that the OBSS frame exchange is in progress on the main channel, AP 1 (310) may want to minimize the impact on the OBSS frame exchange.Considering the above, the initial response frame transmitted on the main channel may not include padding, while the initial response frame transmitted on the NPCA main channel may include padding. That is, the length of the initial control frame transmitted on the main channel may be shorter than the length of the initial control frame transmitted on the NPCA main channel. Therefore, the impact of AP 1 (310) on the frame exchange of OBSS on the main channel may be minimized. However, if AP 1 (310) is unable to transmit frames of different lengths on the main channel and the NPCA main channel, AP 1 (310) may transmit an initial response frame with a padding field identically on both the main channel and the NPCA main channel. Additionally, AP 1 (310) may not transmit an initial response frame if the time length from the time of transmission completion to the time of 'T2 - NSBD' is shorter than the threshold time used as a criterion for performing NPCA.

[0126] non-AP STA 2 (330) can receive an initial response frame from AP 1 (310) on the main channel and the NPCA main channel. non-AP STA 2 (330) can check the RA of the received initial response frame. If the RA of the initial response frame, which is a response to the initial frame transmitted by non-AP STA 2 (330), is not non-AP STA 2 (330) (e.g., the MAC address of the AP or the BSSID of the OBSS), non-AP STA 2 (330) can recognize that AP 1 (310) is operating on the NPCA main channel. If the initial response frame received by non-AP STA 2 (330) on the main channel does not contain padding, non-AP STA 2 (330) can operate on the NPCA main channel after NSD time from the time the initial response frame is received. Alternatively, if padding is included in the initial response frame, non-AP STA 2 (330) may switch the operating channel to the NPCA main channel while the padding field included in the initial response frame of AP 1 (310) is being transmitted. After switching the operating channel to the NPCA main channel, non-AP STA 2 (330) may transmit data frames to AP 1 (310) on the NPCA main channel. The exchange of data frames between AP 1 (310) and non-AP STA 2 (330) may end at time T2 before time NSBD. AP 1 (310), non-AP STA 2 (330), and non-AP STA 1 (320) may operate on the main channel again at time T2.

[0127] Additionally, with reference to FIGS. 5b and 5c, non-AP STA 2 (330) may receive a frame indicating (directly or indirectly) that it is operating on the NPCA main channel from another STA (e.g., AP 1) in the BSS containing non-AP STA 2 (330) while it is operating on the main channel. non-AP STA 2 (330) may switch the operating channel to the NPCA main channel by checking the operating channel information of the other STA in the BSS containing non-AP STA 2 (330). That is, if the current operating channel and the operating channel information of the other STA included in the BSS are different, non-AP STA 2 (330) may perform an operation to switch the operating channel based on the operating channel of the other STA. Additionally, while non-AP STA 2 (330) is operating on the NPCA main channel and another STA (e.g., AP 1) is operating on the main channel, it may transmit a frame indicating that another STA is operating on the main channel. Additionally, even if non-AP STA 2 (330) receives a frame from another STA indicating that it is operating on the main channel while on the NPCA main channel, non-AP STA 2 (330) may check the operating channel information of the other STA and switch the operating channel to the main channel, but is not limited thereto.

[0128] FIGS. 6a to 6c are drawings illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0129] Referring to FIGS. 6a to 6c, the operation may be based on the configuration of the wireless LAN network described in FIGS. 5a to 5c ([Configuration of wireless LAN network - Network and NPCA operation], [Configuration of wireless LAN network - Hidden node problem], [Configuration of wireless LAN network - Different operation channel due to hidden node problem], [Configuration of wireless LAN network - Main channel usage frame transmission problem]), but is not limited to a specific form.

[0130] When AP 1 (310) uses NPCA operation, non-AP STA 1 (320) and non-AP STA 2 (330), which are STAs other than AP 1 (310) (i.e., non-AP 1 (310) STAs), may be configured so that they cannot perform uplink frame transmission without receiving a trigger frame from AP 1 (310). The above configuration may be indicated by a UHR operation information element of a management frame transmitted by AP 1 (310). For example, the indicator may be a Triggered UL indicator, but is not limited to that name. AP 1 (310) may transmit a frame instructing STAs connected to AP 1 (310) to perform NPCA operation. Specifically, the UHR operation information element of a management frame (e.g., beacon frame, probe response frame) transmitted by AP 1 (310) may include an indicator indicating whether NPCA is being 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 the NPCA main channel, the NPCA switching delay of AP 1 (310), and the NPCA switching back delay of AP 1 (310), and additionally may include the aforementioned Triggered UL indicator. When a Triggered UL indicator is indicated on a non-AP STA (e.g., STA 1, STA 2), the non-AP STA (e.g., STA 1, STA 2) cannot transmit an uplink frame to AP 1 (310) through a channel access operation after switching the operating channel to the NPCA main channel.non-AP STA 1 (320) and non-AP STA 2 (330) can transmit uplink frames to AP 1 (310) when they receive a trigger frame from AP 1 (310) and are allocated uplink resources. As another example, an uplink trigger operation performed by AP 1 (310) (a triggered UL operation that receives uplink frames from non-AP STAs using a trigger frame (or a data frame containing triggered response scheduling information)) can initialize the AC-specific MU (multi-user) EDCA Timer values ​​of non-AP STAs (e.g., non-AP STA 1 (320), non-AP STA 2 (330)) connected to AP 1 (310) to a non-zero value. If the MU EDCA Timer value of the non-AP STAs is not 0, the non-AP STAs must be able to perform channel access using the MU EDCA parameter set (EDCA parameter set) indicated by AP 1 (310). AP 1 (310) may indicate the AC-specific AIFSN in the MU EDCA parameter set to 0. In the above case, if the MU EDCA Timer value of the non-AP STAs is not 0, the operation of the EDCAF with the AC-specific AIFSN being 0 must be stopped. That is, if the AC-specific AIFSN being 0 is indicated, the channel access operation for frame transmission of the corresponding AC is stopped, and frame transmission may be impossible. The above-mentioned MU EDCA Timer may be a timer variable used identically in both the NPCA main channel and the main channel. By using the operation described above in the NPCA main channel, AP 1 (310) can instruct non-AP STAs connected to AP 1 (310) not to perform uplink transmissions in the NPCA main channel.

[0131] Referring to FIG. 6a, AP 1 (310) and non-AP STA 1 (320) can operate on the NPCA main channel by detecting the communication interval of OBSS on the main channel, and non-AP STA 2 (330) can operate on the main channel. non-AP STA 1 (320) may not be able to perform uplink frame transmission to AP 1 (310) on the NPCA main channel. Here, non-AP STA 2 (330) can transmit an initial frame (412) to AP 1 (310) on the main channel. AP 1 (310) can expect that STAs operating on the NPCA main channel will not transmit uplink frames containing an initial frame to AP 1 (310) because it has transmitted a management frame containing a Triggered UL indicator, which is an indicator that prevents STAs from performing uplink transmissions on the NPCA main channel, or has set the value of the MU EDCA Timer of non-AP STAs to a non-zero value and indicated at least one AC-specific AIFSN value to zero. That is, when AP 1 (310) receives uplink frames from STAs connected to AP 1 (310) while operating on the NPCA main channel, AP 1 (310) can recognize that the STA that transmitted the uplink frame is operating on the main channel. Here, since AP 1 (310) receives an initial frame (412) from non-AP STA 2 (330) while operating on the NPCA main channel, AP 1 (310) can recognize that non-AP STA 2 (330) is operating on the main channel. AP 1 (310) confirms that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA main channel) and may not perform frame transmission for the initial frame (412) (e.g., initial response frame transmission). Afterward, AP 1 (310) may perform a channel access operation on the NPCA main channel.If AP 1 (310) succeeds in the channel access operation, AP 1 (310) can receive an uplink frame from non-AP STA 1 (320) or transmit a downlink frame to non-AP STA 1 (320) by sending a trigger frame (413) that allocates uplink resources to non-AP STA 1 (320). Meanwhile, since AP 1 (310) recognizes that non-AP STA 2 (330) is not operating on the NPCA main channel, AP 1 (310) may not allocate uplink resources to non-AP STA 2 (330) or transmit a downlink frame. Additionally, the frame exchange between non-AP STA 1 (320) and AP 1 (310) ends before 'T2 - NSBD', and AP 1 (310) and non-AP STA 1 (320) can operate on the main channel after time T2. non-AP STA 2 (330) may not receive a response frame for the initial frame (412) transmitted to AP 1 (310), and based on this, may determine that the frame transmission failed. Therefore, non-AP STA 2 (330) may increase the channel access parameters (e.g., QSRC (QoS STA Retry Counter) [AC] and CW (contention window) [AC], which are channel access parameters for each AC (access categories) of EDCA), and accordingly, unnecessary delay may occur in non-AP STA 2 (330) during channel access. AP 1 (310) may transmit an NPCA instruction frame instructing non-AP STA 2 (330) to decrease the channel access parameters (e.g., initialize the channel access parameters of STA 2) if the channel access operation is successful after time T2. When non-AP STA 2 (330) receives an NPCA instruction frame from AP 1 (310), non-AP STA 2 (330) can reduce (e.g. initialize) the channel access parameters.Alternatively, AP 1 (310) may send a trigger frame to allocate uplink resources to non-AP STA 2 (330), and when non-AP STA 2 (330) receives the trigger frame from AP 1 (310), it may send an uplink frame to AP 1 (310).

[0132] Referring to FIG. 6b, AP 1 (310) and non-AP STA 1 (320) can operate on the NPCA main channel by detecting the communication interval of OBSS on the main channel, and non-AP STA 2 (330) can operate on the main channel. Here, as described above, non-AP STA 1 (320) can transmit an uplink frame to AP 1 (310) only after receiving a trigger frame, and accordingly, it may not be able to transmit an uplink frame to AP 1 (310) on the NPCA main channel. On the other hand, non-AP STA 2 (330) can transmit an initial frame (414) to AP 1 (310) on the main channel. AP 1 (310) has transmitted a management frame containing a Triggered UL indicator, which is an indicator to prevent STAs from transmitting uplinks on the NPCA main channel, or has set the value of the MU EDCA Timer of non-AP STAs to a non-zero value and indicated at least one AC-specific AIFSN value to zero, so it can be expected that STAs operating on the NPCA main channel will not transmit uplink frames containing an initial frame to AP 1 (310). That is, when AP 1 (310) receives uplink frames from STAs connected to AP 1 (310) while operating on the NPCA main channel, AP 1 (310) can recognize that the STA that transmitted the uplink frame is operating on the main channel. Since AP 1 (310) receives an initial frame (414) from non-AP STA 2 (330) while operating on the NPCA main channel, AP 1 (310) can recognize that non-AP STA 2 (330) is operating on the main channel. AP 1 (310) can confirm that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA main channel) and transmit an initial response frame, which is a response frame to the initial frame.Here, if the initial frame is an RTS frame or a MU-RTS trigger frame, the initial response frame may be a CTS (clear to send) frame. Or, if the initial frame is a BAR frame, the initial response frame may be a BlockAck frame. Or, if the initial frame is a BSRP trigger frame, the initial response frame may be a QoS Null frame or a BlockAck frame. However, the initial response frame may not be limited to those described above.

[0133] For example, the initial response frame may be a trigger frame. AP 1 (310) may confirm that non-AP STA 2 (330) occupies the main channel and transmits the initial frame, but may not be able to transmit the initial response frame on the main channel. Additionally, AP 1 (310) may expect to receive frames transmitted by non-AP STA 2 (330) occupying only the NPCA main channel without occupying the main channel. In the above case, AP 1 (310) may transmit the initial response frame (415) on the NPCA main channel without occupying the main channel. Meanwhile, AP 1 (310) may transmit the initial response frame (415) to instruct non-AP STA 2 (330) operating on the main channel to operate on the NPCA main channel. The RA (receiver address) in the MAC header of the initial response frame may be set to the MAC address of AP 1 (310) or to the address (e.g., BSSID) of the OBSS of the main channel detected by AP 1 (310). The duration field of the initial response frame may indicate the length of time from the time of completion of transmission of the initial response frame to the time of 'T2 - NSBD'. The initial response frame may include at least one padding field containing padding bits or padding bits longer than the NSD time, which is the time for non-AP STA 2 (330) to switch the operating channel from the main channel to the NPCA main channel. That is, padding may be included, and the padding may be intended to extend the frame length longer than the NSD time and to provide the operating channel switching of non-AP STA 2 (330) during the NSD time.

[0134] For example, padding may be configured to extend the frame length beyond the NSD time and to provide the operation channel switching of the non-AP STA 2 (330) during the NSD time. As a specific example, the initial response frame may include the EOF (end of frame) padding fields of the A-MPDU, and the length of the EOF padding fields may be longer than the NSD. Alternatively, the initial response frame may have a Special User Info Field (or Special AID TID Info subfield) and a BlockAck Bitmap Subfield for padding. However, the type of padding is not limited to the padding described above, and any type of bit sequence, field, or subfield that satisfies the function of padding, which is to extend the frame time length and provide time for switching the operation channel and operation mode of the wireless LAN terminal, may be padding and is not limited to a specific form.

[0135] The non-AP STA 2 (330) can receive an initial response frame (415) of AP 1 (310) on the NPCA main channel. The non-AP STA 2 (330) can recognize that AP 1 (310) is operating on the NPCA main channel if it receives an initial response frame (415) of AP 1 (310) on the NPCA main channel and does not receive an initial response frame on the main channel. The padding length of the initial response frame may be greater than or equal to NSD. The non-AP STA 2 (330) can switch the operating channel to the NPCA main channel while the padding field included in the initial response frame of AP 1 (310) is being transmitted. AP 1 (310) can allocate uplink resources to non-AP STA 2 (330) by sending a trigger frame to non-AP STA 2 (330) when non-AP STA 2 (330) is operating on the NPCA main channel. non-AP STA 2 (330) can send uplink frames to AP 1 (310) using the uplink resources allocated by AP 1 (310).

[0136] As another example, the initial response frame may be a trigger frame. The trigger frame may indicate frequency resource information to which the non-AP STA 2 (330) must transmit an uplink frame. The aforementioned frequency resource information may indicate all or part of the available frequency resources in the NPCA main channel. Additionally, the trigger frame may include padding using a 'Special User Info Field'. The non-AP STA 2 (330) may receive the trigger frame and, upon checking the uplink resource information indicated in the trigger frame, switch the operating channel to the NPCA main channel. Additionally, the non-AP STA 2 (330) may transmit an uplink frame to AP 1 (310) using the uplink resources allocated by AP 1 (310). AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) must terminate frame exchange on the NPCA main channel before time 'T2 - NSBD' and operate on the main channel at time T2.

[0137] Referring to FIG. 6c, AP 1 (310) may be able to use the main channel even after switching the operating channel to the NPCA main channel. For example, AP 1 (310) may be able to perform frame transmission and reception on the main channel even after switching the operating channel to the NPCA main channel. AP 1 (310) and non-AP STA 1 (320) detect the communication interval of OBSS on the main channel and operate on the NPCA main channel, but non-AP STA 2 (330) may operate on the main channel. Here, non-AP STA 1 (320) may not be able to transmit uplink frames to AP 1 (310) on the NPCA main channel, and non-AP STA 2 (330) may transmit an initial frame (416) to AP 1 (310) on the main channel. AP 1 (310) has transmitted a management frame containing a Triggered UL indicator, which is an indicator that prevents STAs from performing uplink transmissions on the NPCA main channel, or has set the value of the MU EDCA Timer of non-AP STAs to a non-zero value and indicated at least one AC-specific AIFSN value to zero, so it can be expected that STAs operating on the NPCA main channel will not transmit uplink frames containing an initial frame to AP 1 (310). That is, when AP 1 (310) receives uplink frames from STAs connected to AP 1 (310) while operating on the NPCA main channel, AP 1 (310) can recognize that the STA that transmitted the uplink frame is operating on the main channel. When AP 1 (310) receives an initial frame (416) from non-AP STA 2 (330) while operating on the NPCA main channel, AP 1 (310) can recognize that non-AP STA 2 (330) is operating on the main channel.AP 1 (310) can confirm that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA main channel) and transmit an initial response frame, which is a response frame, to the initial frame of non-AP STA 2 (330). Here, if the initial frame is an RTS frame or a MU-RTS trigger frame, the initial response frame may be a CTS (clear to send) frame. Or, if the initial frame is a BAR frame, the initial response frame may be a BlockAck frame. Or, if the initial frame is a BSRP trigger frame, the initial response frame may be a QoS Null frame or a BlockAck frame. However, the initial response frame may not be limited to those described above. When AP 1 (310) confirms that non-AP STA 2 (330) has occupied the main channel and transmitted an initial frame, it may occupy both the main channel and the NPCA main channel to transmit an initial response frame (417), which is a response frame to the initial frame. Meanwhile, AP 1 (310) may transmit an initial response frame to instruct non-AP STA 2 (330), which is operating on the main channel, to operate on the NPCA main channel. The RA (receiver address) of the MAC header of the initial response frame may be set to the MAC address of AP 1 (310) or to the address of the OBSS of the main channel detected by AP 1 (310) (e.g., the BSSID of the OBSS). The duration field of the initial response frame may indicate the length of time from the time of completion of transmission of the initial response frame to the time of 'T2 - NSBD'. The initial response frame may include at least one padding field containing padding bits or padding bits longer than the NSD time, which is the time for non-AP STA 2 (330) to switch the operating channel from the main channel to the NPCA main channel.For example, padding may be configured to extend the frame length beyond the NSD time and to provide the operation channel switching of the non-AP STA 2 (330) during the NSD time. As a specific example, the initial response frame may include the EOF (end of frame) padding fields of the A-MPDU, and the length of the EOF padding fields may be longer than the NSD. Alternatively, the initial response frame may have a Special User Info Field (or Special AID TID Info subfield) and a BlockAck Bitmap Subfield for padding. However, the type of padding is not limited to the padding described above, and any type of bit sequence, field, or subfield that satisfies the function of padding, which is to extend the frame time length and provide time for switching the operation channel and operation mode of the wireless LAN terminal, may be padding and is not limited to a specific form.

[0138] Meanwhile, AP 1 (310) may configure the initial response frame transmitted on the main channel and the initial response frame transmitted on the NPCA main channel differently. Since AP 1 (310) is aware that frame exchange of the OBSS is in progress on the main channel, AP 1 (310) may want to minimize its impact on the frame exchange of the OBSS. To this end, the initial response frame transmitted on the main channel may not contain padding, while the initial response frame transmitted on the NPCA main channel may contain padding. That is, the length of the initial control frame transmitted on the main channel may be shorter than the length of the initial control frame transmitted on the NPCA main channel. Therefore, the impact of AP 1 (310) on the frame exchange of the OBSS on the main channel may be minimized. If AP 1 (310) is unable to transmit frames of different lengths on the main channel and the NPCA main channel, AP 1 (310) may transmit an initial response frame with a padding field identically on both the main channel and the NPCA main channel. non-AP STA 2 (330) can receive an initial response frame from AP 1 (310) on the main channel and the NPCA main channel. non-AP STA 2 (330) can identify the RA of the received initial response frame. If the RA of the initial response frame, which is a response to the initial frame transmitted by non-AP STA 2 (330), is not non-AP STA 2 (330) (e.g., the MAC address of AP 1 (310) or the BSSID of OBSS), non-AP STA 2 (330) can recognize that AP 1 (310) is operating on the NPCA main channel. If the initial response frame received on the main channel does not contain padding, non-AP STA 2 (330) can operate on the NPCA main channel after NSD time from the time the initial response frame is received.Alternatively, if padding is included in the initial response frame, non-AP STA 2 (330) may switch the operating channel to the NPCA main channel while the padding field included in the initial response frame of AP 1 (310) is being transmitted. When non-AP STA 2 (330) is operating on the NPCA main channel, AP 1 (310) may send a trigger frame to non-AP STA 2 (330) to allocate uplink resources to non-AP STA 2 (330). non-AP STA 2 (330) may use the uplink resources allocated by AP 1 (310) to transmit uplink frames to AP 1 (310).

[0139] As another example, the initial response frame may be a trigger frame. The trigger frame may indicate frequency resource information to which the non-AP STA 2 (330) must transmit an uplink frame. The aforementioned frequency resource information may indicate all or part of the available frequency resources in the NPCA main channel. Additionally, the trigger frame may include padding using a 'Special User Info Field'. The non-AP STA 2 (330) may receive the trigger frame and, upon checking the uplink resource information indicated in the trigger frame, switch the operating channel to the NPCA main channel. Additionally, the non-AP STA 2 (330) may transmit an uplink frame to AP 1 (310) using the uplink resources allocated by AP 1 (310). Additionally, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) must terminate frame exchange on the NPCA main channel before the time of 'T2 - NSBD', and must operate on the main channel at the time of T2. In FIGS. 6a to 6c described above, AP 1 (310) 1 may instruct a Triggered UL-only operation on the NPCA main channel so that when a non-AP STA detects a frame occupying the NPCA main channel, it does not transmit a response frame.

[0140] As another example, AP 1 (310) may determine that only frame switching sequences starting with an NPCA ICF (e.g., a BSRP TF, MU-RTS TF) excluding RTS in the NPCA main channel are normal frame switching sequences. For example, the NPCA ICF may indicate a BSRP TF. AP 1 (310) may detect a non-HT PPDU (e.g., a non-HT duplicate PPDU) in the NPCA main channel and determine that the PPDU was transmitted by a non-AP STA connected to AP 1 (310). The PPDU may not be an NPCA ICF. In the above case, AP 1 (310) may not respond to the PPDU transmitted by the non-AP STA. That is, AP 1 (310) may not transmit an immediate response frame even if the PPDU is a frame that requires an immediate response frame. Meanwhile, if a frame other than an NPCA ICF is received from a non-AP STA connected to AP 1 (310) on the NPCA main channel, and the receiving STA is AP 1 (310), AP 1 (310) can recognize that the non-AP STA connected to AP 1 (310) is operating on the main channel. For example, in the case described above, AP 1 (310) can perform an operation to switch the operating channel from the NPCA main channel to the main channel.

[0141] Additionally, AP 1 (310) may use the response frame non-transmission operation based on the NPCA ICF condition described above and the response frame non-transmission operation based on the Triggered UL only condition as a substitute or in parallel, and is not limited to a specific form. Additionally, the operation described above may also be applied by a non-AP STA. For example, there may be a non-AP STA (e.g., STA 1) operating on the NPCA main channel, and AP 1 (310) may operate on the main channel differently from the above. The non-AP STA 1 (320) may detect a non-HT PPDU (e.g., Non-HT duplicate PPDU) on the NPCA main channel and determine that the PPDU is transmitted by AP 1 (310) and that the non-AP STA 1 (320) is the recipient. Here, the frame received by the non-AP STA 1 (320) from AP 1 (310) may not be the NPCA ICF described above. In the above-described case, even if the frame received by non-AP STA 1 (320) from AP 1 (310) requires an immediate response frame, non-AP STA 1 (320) may not transmit an immediate response frame. Additionally, if a frame that is not an NPCA ICF is received from AP 1 (310) to which non-AP STA 1 (320) is connected on the NPCA main channel, and the receiving STA is non-AP STA 1 (320), non-AP STA 1 (320) may recognize that the connected AP 1 (310) is operating on the main channel. For example, in the above-described case, non-AP STA 1 (320) may perform an operation to switch the operating channel from the NPCA main channel to the main channel.

[0142] In addition, as an example, the above-described NPCA ICF may be a trigger frame that is not restricted to a BSRP TF. That is, among all types of trigger frames including a BSRP TF in an NPCA main channel, any type of trigger frame that includes an NPCA main channel indicator, which is an indicator indicating that a trigger frame is transmitted in an NPCA main channel, may correspond to an NPCA ICF. Alternatively, an NPCA ICF may be a BSRP TF, and may include an NPCA main channel indicator, which is an indicator indicating that a trigger frame is transmitted in the BSRP TF, but is not limited thereto.

[0143] Additionally, the case where a frame corresponding to the above-described NPCA ICF is received on the NPCA main channel can be further considered. For example, both AP 1 (310) and non-AP STA 1 (320) can operate on the NPCA main channel. AP 1 (310) can receive an NPCA ICF from non-AP STA 1 (320). AP 1 (310) can respond to non-AP STA 1 (320) with an ICR, and non-AP STA 1 (320) can confirm that AP 1 (310) is present on the NPCA main channel. Here, AP 1 (310) can respond to the NPCA ICF only when it is operating on the NPCA main channel. Therefore, the fact that non-AP STA 1 (320) receives an ICR, which is a response frame for an NPCA ICF, from AP 1 (310) may indicate that AP 1 (310) is operating on the NPCA main channel.

[0144] As another example, the ICR of AP 1 (310) may include an indicator (e.g., an indicator indicated by a specific bit, or whether a specific (sub)field, or (information) element is included) indicating that AP 1 (310) is operating on the NPCA main channel. When non-AP STA 1 (320) receives the ICR, it can recognize that AP 1 (310) is operating on the NPCA main channel. When non-AP STA 1 (320) receives the ICR from AP 1 (310), it can perform a frame switching procedure. Since AP 1 (310) has received the NPCA ICF from non-AP STA 1 (320), it can recognize that non-AP STA 1 (320) is operating on the NPCA main channel. When AP 1 (310) receives a valid NPCA ICF from non-AP STA 1 (320), AP 1 (310) receives a frame that is not an NPCA ICF (e.g., a data frame, a control frame that is not an NPCA ICF, etc.) from non-AP STA 1 (320) during the NPCA operation period of AP 1 (310), and if the frame requires an immediate response frame, AP 1 (310) can transmit an immediate response frame for the received frame.

[0145] As another example, AP 1 (310) may not separately remember whether non-AP STA 1 (320) has received the NPCA ICF. That is, in order to transmit a frame to AP 1 (310) again after non-AP STA 1 (320) has transmitted the aforementioned NPCA ICF to AP 1 (310) and finished frame exchange (e.g., after the completion of a TXOP, or after a certain time from the end of the last received or transmitted frame (e.g., after aSIFSTime + aSlotTime + aRxPHYStartDelay time)), the NPCA ICF may need to be retransmitted. The above operation may also be performed when non-AP STA and AP 1 (310) are exchanged with each other. In the above situation, there may be another non-AP STA, non-AP STA 2 (330), connected to AP 1 (310). non-AP STA 2 (330) can also operate on the NPCA main channel. non-AP STA 2 (330) can receive the NPCA ICF of AP 1 (310) on the NPCA main channel or receive the ICR that AP 1 (310) transmits in response to the NPCA ICF. non-AP STA 2 (330) can know that AP 1 (310) is operating on the NPCA main channel, and if non-AP STA 2 (330) receives a frame other than the NPCA ICF (e.g., a data frame, a control frame other than the NPCA ICF, etc.) from AP 1 (310) on the NPCA main channel and the frame requires an immediate response frame, it can transmit an immediate response frame for the received frame.

[0146] Additionally, referring to FIGS. 5c and 6c, when AP 1 (310) receives a transmitted frame while occupying the main channel, AP 1 (310) may transmit a response frame to cause the non-AP STA to switch its operating channel to the NPCA main channel, as described above. Here, instead of transmitting a response frame to cause the non-AP STA to switch its operating channel to the NPCA main channel, AP 1 (310) may also switch its operating channel to the main channel early. That is, AP 1 (310) may switch its operating channel to the main channel to perform frame transmission and reception with the non-AP STA operating on the main channel.

[0147] FIGS. 7a to 7c are drawings illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0148] Referring to FIGS. 7a to 7c, the configuration of the wireless LAN network described in FIGS. 5a to 5c may be based on [Configuration of wireless LAN network - Network and NPCA operation], [Configuration of wireless LAN network - Hidden node problem], and [Configuration of wireless LAN network - Different operation channels due to hidden node problem]. However, regarding the matters described in FIGS. 5a to 5c, [Configuration of wireless LAN network - Main channel usage frame transmission problem] among the configurations of the wireless LAN network may not be used, but the following [Configuration of wireless LAN network - Main channel partial usage frame transmission problem] may be considered.

[0149]

[0150] [Wireless LAN Network Configuration - Frame Transmission Issues Using Part of Main Channel]

[0151] The non-AP STA 2 (330) can successfully perform a channel access operation on the main channel and acquire a TXOP, which is a time resource for transmitting a frame. The non-AP STA 2 (330) can transmit a frame using a portion of the operating bandwidth of AP 1 (310) (e.g., the main 80 MHz channel that does not include the NPCA main channel among the 160 MHz channels that are the entire operating channels of AP 1 (310), or other bandwidth that occupies the main 20 MHz channel but does not occupy the NPCA main channel).

[0152] non-AP STA 2 (330) can recognize that AP 1 (310) is using NPCA operation in management frames transmitted by AP 1 (310), etc.

[0153] However, since non-AP STA 2 (330) cannot determine whether AP 1 (310) is actually present in the NPCA main channel, the first frame that non-AP STA 2 (330) sends to AP 1 (310) may be an initial frame. Alternatively, non-AP STA 2 (330) may send an initial frame to AP 1 (310) regardless of whether NPCA is active. Here, the initial frame may be of various forms. For example, the initial frame may be an RTS (request to send) frame. Alternatively, the initial frame may be a BAR (BlockAck Request) frame, but is not limited thereto. Also, the initial frame that only AP 1 (310) can send may be a variant of a trigger frame. For example, the initial frame that AP 1 (310) can transmit may be a MU-RTS trigger frame, a BSRP (buffer status report poll) frame, and other frames, but is not limited to a specific form. The initial frame that non-AP STA 2 (330) transmits to AP 1 (310) may be transmitted in a Non-HT (high throughput) duplicated PPDU (physical layer protocol data unit) format. The Non-HT duplicated PPDU format may mean that non-AP STA 2 (330) duplicates and transmits the PPDU for each 20 MHz channel. Here, the contents (e.g., MPDU) included in the duplicated PPDU for each 20 MHz channel may be identical. However, the phase of each duplicated PPDU for each 20 MHz channel may be different. Additionally, AP 1 (310) may be able to receive frames transmitted on the main channel even when operating on the NPCA main channel. In the above case, AP 1 (310) may be able to receive frames from non-AP STA 2 (330) even while operating on the NPCA main channel.

[0154] Referring to FIG. 7a, AP 1 (310) and non-AP STA 1 (320) detect the communication interval of OBSS on the main channel and operate on the NPCA main channel, but non-AP STA 2 (330) can transmit an initial frame (418) to AP 1 (310) on the main channel. AP 1 (310) can confirm the initial frame (418) of non-AP STA 2 (330) transmitted on the main channel. While AP 1 (310) is operating on the NPCA main channel, it can receive frames from non-AP STA 2 (330) operating on the main channel, but it may not be able to perform frame transmission on the main channel. Additionally, AP 1 (310) and non-AP STA 1 (320) can perform frame exchange on the NPCA main channel, and frame exchange may be terminated before the time of 'T2 - NSBD'. AP 1 (310) and non-AP STA 1 (320) can operate on the main channel again at time T2. Therefore, non-AP STA 2 (330) may not receive a response frame for the initial frame (418) transmitted to AP 1 (310), and thus may determine that the frame transmission failed. Non-AP STA 2 (330) may increase channel access parameters (e.g., QSRC (QoS STA Retry Counter) [AC] and CW (contention window) [AC], which are channel access parameters per AC (access categories) of EDCA), and based on this, unnecessary delay may occur when non-AP STA 2 (330) performs channel access. AP 1 (310) can transmit an NPCA instruction frame instructing non-AP STA 2 (330) to decrease the channel access parameters (e.g., initialize the channel access parameters of STA 2) if the channel access operation is successful after time T2.When non-AP STA 2 (330) receives an NPCA instruction frame from AP 1 (310), non-AP STA 2 (330) may reduce (e.g. initialize) the channel access parameters. Alternatively, AP 1 (310) may send a trigger frame allocating uplink resources to non-AP STA 2 (330), and when non-AP STA 2 (330) receives the trigger frame from AP 1 (310), it may send an uplink frame to AP 1 (310).

[0155] Referring to FIG. 7b, AP 1 (310) may be able to use the main channel even after switching the operating channel to the NPCA main channel. For example, AP 1 (310) may be able to transmit and receive frames on the main channel even after switching the operating channel to the NPCA main channel. Here, AP 1 (310) can confirm that non-AP STA 2 (330) has occupied the main channel and transmitted a frame (419). AP 1 (310) can confirm that non-AP STA 2 (330) is operating on the main channel (i.e., not operating on the NPCA main channel) and transmit an initial response frame (420) to the initial frame (419) of non-AP STA 2 (330). If the initial frame is an RTS frame or a MU-RTS trigger frame, the initial response frame may be a CTS (clear to send) frame. Alternatively, if the initial frame is a BAR frame, the initial response frame may be a BlockAck frame. Alternatively, if the initial frame is a BSRP trigger frame, the initial response frame may be a QoS Null frame or a BlockAck frame. However, the initial response frame is not limited to those described above. When AP 1 (310) confirms that non-AP STA 2 (330) has occupied the main channel and transmitted the initial frame (419), it may occupy both the main channel and the NPCA main channel and transmit an initial response frame (420) which is a response frame to the initial frame. Meanwhile, AP 1 (310) may transmit the initial response frame to instruct non-AP STA 2 (330), which is operating on the main channel, to operate on the NPCA main channel. The RA (receiver address) of the MAC header of the initial response frame may be set to the MAC address of AP 1 (310) or to the address of the OBSS of the main channel detected by AP 1 (310) (e.g., the BSSID of the OBSS).The duration field of the initial response frame may indicate the time length from the time of completion of transmission of the initial response frame to the time of 'T2 - NSBD'. The initial response frame may include padding bits or at least one padding field containing padding bits, which is longer than the NSD time, which is the time for the non-AP STA 2 (330) to switch the operating channel from the main channel to the NPCA main channel. In this disclosure, padding bits or at least one padding field are referred to as 'padding', but are not limited thereto. The function of padding is to extend the time length of the frame and to provide time for switching the operating channel and operating mode of the wireless LAN terminal. For example, padding may be set to extend the frame length longer than the NSD time and to provide the operating channel switching of the non-AP STA 2 (330) for the NSD time. As a specific example, the initial response frame may include the EOF (end of frame) padding fields of the A-MPDU, and the length of the EOF padding fields may be longer than the NSD. Alternatively, the initial response frame may have a Special User Info Field (or Special AID TID Info subfield) and a BlockAck Bitmap Subfield for padding. However, the type of padding is not limited to the padding described above, and any type of bit sequence, field, or subfield that satisfies the function of padding, which is to extend the frame's time length and provide time for switching the wireless LAN terminal's operating channel and operating mode, may be padding and is not limited to a specific form.

[0156] Meanwhile, AP 1 (310) may configure the initial response frame transmitted on the main channel and the initial response frame transmitted on the NPCA main channel differently. Since AP 1 (310) can recognize that the frame exchange of the OBSS is in progress on the main channel, AP 1 (310) may want to minimize its influence on the frame exchange of the OBSS. Considering the above, the initial response frame transmitted on the main channel may not include padding, while the initial response frame transmitted on the NPCA main channel may include padding. That is, the length of the initial control frame transmitted on the main channel may be shorter than the length of the initial control frame transmitted on the NPCA main channel. Therefore, the influence of AP 1 (310) on the frame exchange of the OBSS on the main channel may be minimized.

[0157] If AP 1 (310) is unable to transmit frames of different lengths on the main channel and the NPCA main channel, AP 1 (310) may transmit an initial response frame with padding fields on both the main channel and the NPCA main channel. A non-AP STA 2 (330) may receive the initial response frame from AP 1 (310) on the main channel and the NPCA main channel. The non-AP STA 2 (330) may identify the RA of the received initial response frame. If the RA of the initial response frame, which is a response to the initial frame transmitted by the non-AP STA 2 (330), is not that of the non-AP STA 2 (330) (e.g., the MAC address of AP 1 (310) or the BSSID of the OBSS), the non-AP STA 2 (330) may recognize that AP 1 (310) is operating on the NPCA main channel. If the initial response frame received on the main channel does not contain padding, non-AP STA 2 (330) may operate on the NPCA main channel after NSD time from the time the initial response frame is received. Alternatively, if the initial response frame contains padding, non-AP STA 2 (330) may switch the operating channel to the NPCA main channel while the padding field included in the initial response frame of AP 1 (310) is being transmitted. After switching the operating channel to the NPCA main channel, non-AP STA 2 (330) may transmit data frames to AP 1 (310) on the NPCA main channel. The exchange of data frames between AP 1 (310) and non-AP STA 2 (330) may end at time T2 before NSBD time. AP 1 (310), non-AP STA 2 (330) and non-AP STA 1 (320) can operate on the main channel again at time T2.

[0158] FIG. 8 is a diagram illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0159] Referring to FIG. 8, the configuration of the wireless LAN network described in FIG. 5a to 5c may be based on [configuration of wireless LAN network - network and NPCA operation], [configuration of wireless LAN network - hidden node problem], and [configuration of wireless LAN network - operation channel difference due to hidden node problem], but is not limited to a specific form.

[0160] Referring to FIG. 8, AP 1 (310) can operate on the NPCA main channel, and non-AP STA 2 (330), which is a non-AP STA connected to AP 1 (310), can operate on the main channel. That is, the operating channels of AP 1 (310) and non-AP STA 2 (330) may be different from each other. non-AP STA 2 (330) can perform channel access operations (e.g., EDCA backoff operations and / or EDCA TXOP acquisition procedures) on the main channel and acquire a TXOP. When non-AP STA 2 (330) acquires a TXOP, it can transmit a PPDU that occupies the main channel and the NPCA main channel. Here, the PPDU (421) transmitted by non-AP STA 2 (330) may be in a Non-HT duplicate PPDU format that is duplicated and transmitted in 20 MHz channel units. Alternatively, when transmission is performed by occupying both the main channel and the NPCA main channel, other formats may be used in addition to the non-HT duplicate PPDU format so that AP 1 (310) operating on the NPCA main channel can decode the contents of the frame, and are not limited to a specific form. The PPDU transmitted by the non-AP STA 2 (330) may be a frame that is not a control frame (e.g., management frame, data frame (Non-QoS or QoS data frame, Non-QoS or QoS Null frame), etc.). That is, the non-AP STA 2 (330) may not transmit a control frame. Alternatively, the frame transmitted by the non-AP STA 2 (330) may be a control frame, but may not be an initial control frame. That is, the frame transmitted by the non-AP STA 2 (330) may be a MU-RTS trigger frame, a BSRP trigger frame, an RTS frame, and other forms of control frames, and is not limited to a specific form.Here, the control frame may be a control frame that does not include an NPCA main channel indicator indicating that a trigger frame has been transmitted in the NPCA main channel (or indicates that it has not been transmitted in the NPCA channel).

[0161] AP 1 (310) operating on the NPCA main channel can verify frames received from non-AP STA 2 (330). That is, AP 1 (310) can decode the PPDU (421) received from non-AP STA 2 (330) and decode the MAC frames (i.e., MAC management frames, data frames, control frames, etc.) included in the PPDU to verify the frame contents. Here, AP 1 (310) can verify that the frame received from non-AP STA 2 (330) is not an initial control frame. However, AP 1 (310) can verify that only frame exchanges starting with the reception of an initial control frame on the NPCA main channel are valid. For example, if AP 1 (310) successfully receives an initial control frame on the NPCA main channel while operating on the NPCA main channel, AP 1 (310) can transmit a response frame (initial control response, ICR) for the initial control frame. Here, the initial control frame in the NPCA main channel may be an ICF transmitted in the NPCA main channel (a BSRP TF containing an NPCA main channel indicator, or any type of trigger frame containing an NPCA main channel indicator that indicates that a trigger frame has been transmitted in the NPCA main channel). For example, an NPCA main channel indicator may be included within the BSRP TF, but is not limited thereto.

[0162] AP 1 (310) can determine that the exchange of frames is valid only for frames received after the transmission of the ICR (e.g., additional frames received at SIFS (short inter frame space) intervals after the completion of the ICR transmission, frames received before the duration field of the TXOP holder who transmitted the ICF expires, frames received from the STA that transmitted the ICF). AP 1 (310) can determine that a STA that has successfully exchanged ICF and ICR frames in the NPCA main channel is present in the NPCA main channel. That is, if AP 1 (310) transmits the ICF and a non-AP STA transmits the ICR, or if a non-AP STA transmits the ICF and AP 1 (310) transmits the ICR, and the exchange of ICF and ICR frames between NPCA peer STAs is completed, then that STA is determined to be present in the NPCA main channel. Therefore, AP 1 (310) may determine that it is an exchange of valid frames even if it receives a frame other than an ICF after the exchange of ICF and ICR is complete, until the operating channel is switched from the NPCA main channel to the main channel. AP 1 (310) may transmit a response frame if the received frame is a frame that requires an immediate response frame. AP 1 (310) may transmit an immediate response frame for a frame if the received frame in the exchange of valid frames requires an immediate response frame. On the other hand, if it is not an exchange of valid frames, AP 1 (310) may decide not to transmit an immediate response frame for a frame even if the received frame requires an immediate response frame.Additionally, if AP 1 (310) does not detect the exchange of a valid frame on the NPCA main channel, and the sender of the frame is connected to AP 1 (310) (i.e., received from the BSS configured (to which AP 1 (310) belongs)), and the recipient of the frame is AP 1 (310), AP 1 (310) can switch the operating channel to the main channel where the sender of the frame is operating. That is, AP 1 (310) can recognize that the sender of the frame is operating on the main channel and can switch the operating channel to the main channel.

[0163] AP 1 (310) may determine that the frame received from non-AP STA 2 (330) is not an ICF and therefore is not a valid frame exchange. Accordingly, AP 1 (310) may decide not to send an immediate response frame to non-AP STA 2 (330) even if the frame received from non-AP STA 2 (330) requests an immediate response frame. Alternatively, AP 1 (310) may send an immediate response frame to non-AP STA 2 (330), but this may be sent only on the NPCA main channel and not on the main channel which is the operating channel of non-AP STA 2 (330).

[0164] Although the above-described operation is described as an operation for AP 1 (310) and non-AP STA 2 (330) connected to AP 1 (310), the same may apply when AP 1 (310) operates on the main channel and non-AP STA 2 (330) operates on the NPCA main channel, and AP 1 (310) transmits a frame to non-AP STA 2 (330) from the main channel. That is, the above-described operation may not be dependent on the relationship between AP 1 (310) and non-AP STA, and may be an operation performed by the peer relationship of each NPCA STA. For example, if the aforementioned AP 1 (310) and non-AP STA 2 (330), which is a non-AP STA connected to AP 1 (310), are connected, AP 1 (310) and non-AP STA 2 (330) can form a BSS. That is, AP 1 (310) and non-AP STA 2 (330) can belong to the BSS. Operations can be applied to NPCA STAs (e.g., AP 1 (310) and non-AP STA 2 (330)) that have become NPCA peer STA relationships by supporting NPCA within the BSS and enabling NPCA.

[0165] FIGS. 9a and 9b are diagrams illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0166] Referring to FIGS. 9a and 9b, the configuration of the wireless LAN network described in FIGS. 5a to 5c may be based on [configuration of wireless LAN network - network and NPCA operation], [configuration of wireless LAN network - hidden node problem] and [configuration of wireless LAN network - operation channel difference due to hidden node problem], but is not limited to a specific form.

[0167] Here, AP 1 (310) can operate on the main channel, and non-AP STA 2 (330), which is a non-AP 1 (310) STA connected to AP 1 (310), can operate on the NPCA main channel. That is, the operating channels of AP 1 (310) and non-AP STA 2 (330) may be different from each other. AP 1 (310) performs channel access operations (e.g., EDCA backoff operations and / or EDCA TXOP acquisition procedures) on the main channel, and AP 1 (310) can acquire TXOPs.

[0168] When AP 1 (310) acquires a TXOP, AP 1 (310) can transmit a PPDU (422) that occupies the main channel and the NPCA main channel. Here, the PPDU (422) transmitted by AP 1 (310) may be a multi-user (MU) PPDU transmitted to multiple receivers. The MU PPDU may be transmitted per orthogonal frequency division multiple access (OFDMA) resource unit (RU). The RU may be a set of tones that are OFDMA subcarriers. That is, the RU may represent a frequency resource corresponding to the OFDMA tone set in the frequency domain. Additionally, the RU index may indicate the location of the RU in the frequency domain. In FIGS. 9a and 9b, for convenience of explanation, the RU is assigned to each 20 MHz channel, and the lowest RU index number is assigned to the lowest frequency, followed by the highest RU index number to the highest frequency in order, but this is not limited thereto. The method of RU allocation and index assignment may be one example, and RU allocation and RU index assignment may be performed in different ways.

[0169] NPCA STAs (i.e., NPCA STAs using NPCA in the BSS, such as AP 1 (310) and NPCA non-AP STAs connected to AP 1 (310)) may change the basis of the RU index number according to the operating channel. For example, in this disclosure, the RU index of the main 20 MHz channel may be assigned 0, and the RU index of the NPCA main channel may be assigned 4. Here, when the NPCA STAs move the operating channel to the NPCA main channel, the RU index based on the NPCA main channel may be used. For example, in this disclosure, the RU index in the NPCA main channel is referred to as nRU to facilitate the distinction between different RU indices in the main channel and the NPCA main channel, but is not limited thereto. The actual RU index value may be an integer value, and the values ​​of the NPCA main channel reference RU index and the main channel RU index may not be distinguished from each other by the STA including AP 1 (310). That is, the value of the RU index cannot identify the NPCA main channel-based RU index and the main channel-based RU index. However, for the convenience of explanation, it will be described based on the above.

[0170] The MU PPDU (422) transmitted by AP 1 (310) is a single PPDU, but may contain different MAC frames for each RU. The PPDU preamble of the MU PPDU may contain RU allocation information for the MU PPDU. The non-AP STA 2 (330) can determine that the start of the frame exchange received from AP 1 (310) is not an ICF. That is, if the non-AP STA 2 (330) receives a frame containing the MU PPDU (422) from AP 1 (310) without receiving an ICF (a BSRP TF containing an NPCA main channel indicator transmitted on the NPCA main channel, or any type of trigger frame containing an NPCA main channel indicator indicating that a trigger frame has been transmitted on the NPCA main channel), the non-AP STA 2 (330) can determine that the frame transmission by AP 1 (310) is invalid. That is, non-AP STA 2 (330) can recognize that AP 1 (310) is not operating on the NPCA main channel and is operating on the main channel. Alternatively, non-AP STA 2 (330) can recognize that the MU PPDU (422) is occupying the main channel and being transmitted based on bandwidth information included in the MU PPDU (422) or other information included in the preamble of the MU PPDU. Non-AP STA 2 (330) can determine that the MU PPDU (422) is invalid by considering that it is occupying the main channel and being transmitted as described above. Therefore, non-AP STA 2 (330) may determine that it is not responding to the MU PPDU (422) of AP 1 (310). That is, non-AP STA 2 (330) may not transmit a response frame for the MU PPDU (422) received on the NPCA main channel. In addition, non-AP STA 2 (330) receives frames transmitted by occupying the main channel from AP 1 (310) (e.g.In the event that an invalid frame is received, such as when receiving a MU PPDU without an ICF, or when receiving an ICF or trigger frame that is transmitted by occupying the main channel (i.e., receiving an ICF or trigger frame that does not contain an NPCA main (channel) indication), the non-AP STA 2 (330) may switch the operating channel to the main channel, which is the operating channel of AP 1 (310). On the other hand, the non-AP STA 2 (330) may also perform a procedure to transmit a response frame in response to the MU PPDU (422) of AP 1 (310).

[0171] Referring to FIG. 9a, AP 1 (310) can transmit a frame to non-AP STA 2 (330) as the destination, from RU 1, which is a RU existing in the main channel (i.e., an RU configurable only in the main channel). non-AP STA 2 (330) can perform an acknowledgment procedure to receive the MU PPDU. RU 1, the main channel reference RU index indicated by AP 1 (310), may not have a corresponding RU (nRU) in the NPCA main channel. That is, since the RU is allocated in the main channel, non-AP STA 2 (330) cannot receive the MU PPDU (422) in the NPCA main channel. Therefore, non-AP STA 2 (330) cannot receive the MU PPDU (422). Here, non-AP STA 2 (330) may not be able to send a response frame because it cannot receive the frame even if the frame sent by AP 1 (310) to non-AP STA 2 (330) is a frame that requires a response frame.

[0172] Referring to FIG. 9b, AP 1 (310) can transmit a frame to non-AP STA 2 (330) at RU 5, which is an RU present in the NPCA main channel (i.e., an RU configurable in the NPCA main channel). non-AP STA 2 (330) can perform an acknowledgment procedure to receive the MU PPDU (423). RU 5, the main channel reference RU index indicated by AP 1 (310), has a corresponding RU (nRU) in the NPCA main channel, which may be nRU 1. That is, non-AP STA 2 (330) can convert the RU index to the NPCA main channel reference RU index to receive the transmitted MU PPDU (423) by occupying the main channel, and can receive the frame at the corresponding RU. A frame transmitted by AP 1 (310) to non-AP STA 2 (330) may be a frame requesting a response frame based on a trigger frame. For example, the Ack Policy included in the MAC header of a frame transmitted by AP 1 (310) to non-AP STA 2 (330) may indicate a HETP Ack, which may indicate a request for the transmission of a response frame based on a trigger frame. AP 1 (310) may indicate a RU allocation using the trigger frame (e.g., MU-BAR trigger frame) or the TRS control information in the MAC header to transmit the response frame. Here, the RU allocation may indicate a RU index. non-AP STA 2 (330) may receive a MU PPDU (423) on the NPCA main channel. If the frame received by non-AP STA 2 (330) requests a response frame and RU allocation information that enables the transmission of the response frame is included in the trigger frame or TRS control information, non-AP STA 2 (330) can transmit a response frame (424) based on the RU allocation information.

[0173] For example, if the RU allocation information assigned to non-AP STA 2 (330) indicates RU indices 4 to 7, which are configurable RUs in the NPCA main channel (corresponding to nRU indices 0 to 3, which are RU indices based on the NPCA main channel in FIG. 9b), then non-AP STA 2 (330) can transmit a response frame from the corresponding RU (i.e., the NPCA main channel reference RU corresponding to the main channel reference RU index). On the other hand, if the RU allocation information assigned to non-AP STA 2 (330) indicates RU indices 0 to 3, which are RUs that are not configurable in the NPCA main channel, then non-AP STA 2 (330) cannot transmit a response frame to AP 1 (310). It may also be possible for non-AP STA 2 (330) to transmit a BlockAck frame to AP 1 (310) separately after switching the operating channel from the NPCA main channel to the main channel.

[0174] Additionally, referring to FIGS. 9a and 9b, the response frame transmitted by the non-AP STA 2 (330) may be transmitted with preamble puncturing performed. For example, the non-AP STA 2 (330) may transmit a frame to AP 1 (310) without using the 20 MHz subchannel corresponding to the disabled subchannel bitmap received from AP 1 (310). Alternatively, since the non-AP STA 2 (330) operates on the NPCA main channel, it may transmit a frame to AP 1 (310) without using the 20 MHz subchannel corresponding to the NPCA disabled subchannel bitmap received from AP 1 (310).

[0175] Although the above-described operation is described for AP 1 (310) and non-AP STA 2 (330) connected to AP 1 (310), it can be applied in the same way when non-AP STA 2 (330) operates on the main channel and AP 1 (310) operates on the NPCA main channel, and non-AP STA 2 (330) occupies the main channel to transmit frames to AP 1 (310).

[0176] That is, the above-described operation may not be an operation dependent on the relationship between AP 1 (310) and non-AP STA, but may be an operation performed by the peer relationship of each NPCA STA. For example, when the above-described AP 1 (310) and non-AP STA 2 (330), which is a non-AP STA connected to AP 1 (310), are connected, AP 1 (310) and non-AP STA 2 (330) may form a BSS. That is, AP 1 (310) and non-AP STA 2 (330) may belong to the BSS. The operation may be applied to NPCA STAs (e.g., AP 1 (310) and non-AP STA 2 (330)) that have become NPCA peer STA relationships by supporting NPCA within the BSS and enabling NPCA.

[0177] FIGS. 10a and FIGS. 10b are diagrams illustrating a method for determining the transmission of a response frame during a wireless LAN sub-channel access operation applicable to the present disclosure.

[0178] Referring to FIGS. 10a and 10b, the configuration of the wireless LAN network described in FIGS. 5a to 5c may be based on [configuration of wireless LAN network - network and NPCA operation], [configuration of wireless LAN network - hidden node problem] and [configuration of wireless LAN network - operation channel difference due to hidden node problem], but is not limited to a specific form.

[0179] AP 1 (310) can operate on the main channel, and non-AP STA 2 (330), which is a non-AP STA connected to AP 1 (310), can operate on the NPCA main channel. That is, the operating channels of AP 1 (310) and non-AP STA 2 (330) may be different from each other. AP 1 (310) performs channel access operations (e.g., EDCA backoff operations and / or EDCA TXOP acquisition procedures) on the main channel, and AP 1 (310) can acquire TXOPs.

[0180] When AP 1 (310) acquires a TXOP, it may transmit a PPDU that occupies the main channel and the NPCA main channel. Here, the PPDU transmitted by AP 1 (310) may be a trigger frame (425). The trigger frame (425) may be a frame that allocates frequency resources and time resources (i.e., uplink resources) indicated by an OFDMA RU to non-AP STAs connected to AP 1 (310). The RU may be a set of tones that are OFDMA subcarriers. That is, the RU may represent frequency resources according to the OFDMA tone set in the frequency domain. Additionally, the RU index may indicate the location of the RU in the frequency domain. In FIGS. 9a and 9b, for convenience of explanation, the RU is allocated for each 20 MHz channel, and the lowest RU index number is assigned to the lowest frequency and the highest RU index number is assigned to the highest frequency in order, but this is not limited thereto. The method of RU allocation and index assignment may be one example, and RU allocation and RU index assignment may be performed in different ways.

[0181] NPCA STAs (i.e., NPCA STAs using NPCA in the BSS, such as AP 1 (310) and NPCA non-AP STAs connected to AP 1 (310)) may change the basis of the RU index number according to the operating channel. For example, in this disclosure, the RU index of the main 20 MHz channel may be assigned 0, and the RU index of the NPCA main channel may be assigned 4. Here, when the NPCA STAs move the operating channel to the NPCA main channel, the RU index based on the NPCA main channel may be used. For example, in this disclosure, the RU index in the NPCA main channel is referred to as nRU to facilitate the distinction between different RU indices in the main channel and the NPCA main channel, but is not limited thereto. The actual RU index value may be an integer value, and the values ​​of the NPCA main channel reference RU index and the main channel RU index may not be distinguished from each other by the STA including AP 1 (310). That is, the value of the RU index cannot identify the NPCA main channel-based RU index and the main channel-based RU index. However, for the convenience of explanation, it will be described based on the above.

[0182] non-AP STA 2 (330) can confirm that the start of the frame exchange received from AP 1 (310) is not an ICF. The trigger frame (425) transmitted by AP 1 (310) is transmitted by occupying the main channel, and the non-AP STA 2 (330) can confirm this information. That is, if non-AP STA 2 (330) receives the aforementioned trigger frame (425) without receiving an ICF (all types of trigger frames including a BSRP TF transmitted on the NPCA main channel or an NPCA main channel indicator indicating that a trigger frame has been transmitted on the NPCA main channel) from AP 1 (310), non-AP STA 2 (330) can determine that the frame transmission by AP 1 (310) is invalid. That is, the non-AP STA 2 (330) can recognize that AP 1 (310) is not operating on the NPCA main channel and is operating on the main channel. The non-AP STA 2 (330) can determine that the trigger frame (425) is invalid based on the fact that it is transmitted by occupying the main channel as described above. The non-AP STA 2 (330) may also determine that it is not responding to the trigger frame (425) of AP 1 (310). Additionally, if the non-AP STA 2 (330) receives an invalid frame (e.g., an ICF or trigger frame that does not contain an NPCA main channel indication) from AP 1 (310) that is transmitted by occupying the main channel, the operating channel can be switched to the main channel, which is the operating channel of AP 1 (310). On the other hand, non-AP STA 2 (330) may perform a procedure to transmit an uplink frame (TB (trigger based) PPDU) from an uplink resource allocated by the trigger frame of AP 1 (310).

[0183] Referring to FIG. 10a, AP 1 (310) can assign RU 1, which is a RU existing in the main channel (i.e., an RU configurable only in the main channel), to non-AP STA 2 (330). Here, non-AP STA 2 (330) can perform a verification procedure to transmit an uplink frame. RU 1, the main channel reference RU index indicated by AP 1 (310), does not have a corresponding RU (nRU) in the NPCA main channel. That is, because the RU is assigned in the main channel, non-AP STA 2 (330) cannot transmit an uplink frame in the NPCA main channel.

[0184] Referring to FIG. 10b, AP 1 (310) can assign RU 5, which is an RU existing in the NPCA main channel (i.e., an RU configurable in the NPCA main channel), to non-AP STA 2 (330). non-AP STA 2 (330) can perform a verification procedure to transmit an uplink frame. RU 5, which is the main channel reference RU index indicated by AP 1 (310), has a corresponding RU (nRU) in the NPCA main channel, which may be nRU 0. That is, non-AP STA 2 (330) can convert the RU index indicated by the main channel reference to an NPCA main channel reference RU index and transmit a frame (427) from the corresponding RU.

[0185] Referring to FIGS. 10a and 10b, the response frame transmitted by the non-AP STA 2 (330) may be transmitted with preamble puncturing performed. For example, the non-AP STA 2 (330) may transmit a frame to AP 1 (310) without using the 20 MHz subchannel corresponding to the disabled subchannel bitmap received from AP 1 (310). Alternatively, since the non-AP STA 2 (330) operates on the NPCA main channel, it may transmit a frame to AP 1 (310) without using the 20 MHz subchannel corresponding to the NPCA disabled subchannel bitmap received from AP 1 (310).

[0186] Although the above-described operation is described for AP 1 (310) and non-AP STA 2 (330) connected to AP 1 (310), it can be applied in the same way when non-AP STA 2 (330) operates on the main channel and AP 1 (310) operates on the NPCA main channel, and non-AP STA 2 (330) occupies the main channel to transmit frames to AP 1 (310).

[0187] That is, the above-described operation may not be an operation dependent on the relationship between AP 1 (310) and non-AP STA, but may be an operation performed by the peer relationship of each NPCA STA. For example, when the above-described AP 1 (310) and non-AP STA 2 (330), which is a non-AP STA connected to AP 1 (310), are connected, AP 1 (310) and non-AP STA 2 (330) may form a BSS. That is, AP 1 (310) and non-AP STA 2 (330) may belong to the BSS. The operation may be applied to NPCA STAs (e.g., AP 1 (310) and non-AP STA 2 (330)) that have become NPCA peer STA relationships by supporting NPCA within the BSS and enabling NPCA.

[0188] Meanwhile, in the present disclosure, the initial frame may be referred to as an initial control frame (ICR). In FIGS. 5a to 5c, FIGS. 6a to 6c, FIGS. 7a, and FIGS. 7b, the initial frame may be illustrated as an initial control frame, and the initial response frame may be illustrated as an initial control response frame (ICR). However, it is not limited thereto. Furthermore, although the present disclosure describes a method in which an AP and a non-AP STA do not transmit a response frame on the NPCA main channel, the AP and the non-AP involved in this operation may both be wireless LAN STAs. That is, it may be possible for the non-AP STA and the AP to operate interchangeably, and for the convenience of explanation, the method has been described as one in which an AP and a non-AP STA do not transmit a response frame on the NPCA main channel.

[0189] FIG. 11 is a flowchart showing the operation of an STA in a wireless LAN to which the present disclosure applies.

[0190] Referring to FIG. 11, the first STA can detect the transmission of OBSS on the main channel (S1110). Then, the first STA can switch the operating channel from the main channel to the NPCA main channel based on the NPCA switching condition (S1120), and the first STA can receive a first frame on the NPCA main channel (S1130). Here, the first STA can determine whether to transmit a response frame for the first frame based on whether the first frame is an NPCA ICF (S1140). For example, if the first frame is an NPCA ICF, the first STA can transmit an ICR as a response frame for the first frame. Additionally, the NPCA ICF may be a trigger frame containing an NPCA main channel indicator, which is an indicator indicating that a trigger frame is transmitted on the NPCA main channel.

[0191] As another example, if the first frame is a frame other than an NPCA ICF, the first STA may not transmit a response frame for the first frame. Here, the first STA may not transmit a response frame for the first frame regardless of whether the first frame is a frame that immediately requires a response frame. Additionally, if the first STA receives the first frame as a frame other than an NPCA ICF from a second STA associated with the first STA on the NPCA main channel, the first STA may determine that the second STA is operating on the main channel. Additionally, the first STA may switch the operating channel from the NPCA main channel to the main channel based on the fact that the second STA is operating on the main channel. As an example, if the first STA receives a non-HT duplicate PPDU (physical layer protocol data unit) on the NPCA main channel that does not contain a control frame or contains an RTS (request to send) frame, it may determine that the first frame is a frame other than an NPCA ICF and not transmit a response frame for the first frame.

[0192] Additionally, if the first STA receives a first frame occupying the main channel from the second STA associated with the first STA, the first STA may not transmit a response frame to the second STA. Alternatively, if the first STA receives a first frame occupying the main channel from the second STA associated with the first STA, the first STA may transmit a response frame to the second STA through the NPCA main channel. Here, the response frame may be a frame instructing the second STA to switch the operating channel to the NPCA main channel.

[0193] Additionally, when the first STA receives a first frame occupying the main channel from the second STA associated with the first STA, the first STA may transmit a response frame to the second STA through the NPCA main channel and the main channel. Here, the response frame may be a frame instructing the second STA to switch the operating channel to the NPCA main channel.

[0194] Additionally, when the first STA is operating on the NPCA main channel, the STAs associated with the first STA can transmit uplink frames only by trigger frames transmitted by the first STA, and if the first STA receives an uplink frame from the second STA among the STAs associated with the first STA, it can be determined that the second STA is operating on the main channel. For example, the first STA may be an AP STA or a non-AP STA, but is not limited to a specific form.

[0195] 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.

[0196]

[0197] The above-mentioned matters may also be applied to other systems.

Claims

1. In a method of operation of a first station (station, STA) in a wireless LAN system, A step in which the first STA detects the transmission of an overlapping basic service set (OBSS) on the main channel; A step in which the first STA switches the operating channel from the main channel to the NPCA main channel based on a non-primary channel access (NPCA) switching condition; The step of the first STA receiving a first frame on the NPCA main channel; and A method of operation comprising the step of determining whether to transmit a response frame for the first frame based on whether the first frame is an NPCA ICF (initial control frame) by the first STA.

2. In Paragraph 1, A method of operation in which, if the first frame is the NPCA ICF, the first STA transmits an ICR (initial control response) as a response frame to the first frame.

3. In Paragraph 2, A method of operation in which the above NPCA ICF is a trigger frame including an NPCA main channel indicator which is an indicator indicating that a trigger frame is transmitted in the above NPCA main channel.

4. In Paragraph 1, A method of operation in which, if the first frame is a frame other than the NPCA ICF, the first STA does not transmit a response frame for the first frame.

5. In Paragraph 4, The above-mentioned first STA is a method of operation in which it does not transmit a response frame for the first frame regardless of whether the first frame is a frame that requires an immediate response frame.

6. In Paragraph 4, A method of operation in which, when the first STA receives the first frame as a frame other than the NPCA ICF from a second STA associated with the first STA in the NPCA main channel, the first STA determines that the second STA is operating in the main channel.

7. In Paragraph 6, The above-mentioned first STA is a method of operation that switches the operating channel from the NPCA main channel to the main channel based on the above-mentioned second STA operating in the main channel.

8. In Paragraph 4, A method of operation in which the first STA, upon receiving a non-HT duplicate PPDU (physical layer protocol data unit) that does not include a control frame or includes an RTS (request to send) frame in the NPCA main channel, determines the first frame as a frame other than the NPCA ICF and does not transmit a response frame for the first frame.

9. In Paragraph 1, A method of operation in which, when the first STA receives the first frame occupying the main channel from the second STA associated with the first STA, the first STA does not transmit the response frame to the second STA.

10. In Paragraph 1, A method of operation in which, when the first STA receives the first frame occupying the main channel from the second STA associated with the first STA, the first STA transmits the response frame to the second STA through the NPCA main channel.

11. In Paragraph 10, A method of operation in which the above response frame is a frame that instructs the second STA to switch the operation channel to the NPCA main channel.

12. In Paragraph 1, A method of operation in which, when the first STA receives the first frame occupying the main channel from the second STA associated with the first STA, the first STA transmits the response frame to the second STA through the NPCA main channel and the main channel.

13. In Paragraph 12, A method of operation in which the above response frame is a frame that instructs the second STA to switch the operation channel to the NPCA main channel.

14. In Paragraph 1, When the first STA operates on the NPCA main channel, the STAs associated with the first STA can transmit uplink frames only by the trigger frame transmitted by the first STA, and A method of operation in which, if the first STA receives an uplink frame from the second STA among the STAs associated with the first STA, the second STA is determined to be operating on the main channel.

15. In Paragraph 1, A method of operation in which the first STA is an AP STA or a non-AP STA.

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: Detect the transmission of OBSS (overlapping basic service set) on the main channel, and Based on the NPCA (non-primary channel access) switching condition, the operating channel is switched from the main channel to the NPCA main channel, and Receive a first frame on the above NPCA main channel, and STA that determines whether to transmit a response frame for the first frame based on whether the first frame is an NPCA ICF (initial control frame).

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