Method and device for performing operation based on coordinated time division multiple access in wireless LAN

Abstract

This operation method of a STA in a wireless LAN system may comprise the steps of: a first STA acquiring a TXOP; the first STA transmitting a polling frame in the TXOP on the basis of Co-TDMA, and receiving a response frame for the polling frame; transmitting an allocation frame after receiving the response frame for the polling frame, and receiving a response frame for the allocation frame; and sharing, with a second STA, an allocated duration in the TXOP.

Description

Method and device for performing operations based on cooperative time-division multiple access in a wireless LAN

[0001] The present disclosure relates to a method and apparatus for setting a frame transmission interval and preventing frame transmission failure when Coordinated Time Division Multiple Access (Co-TDMA) is supported in a wireless local area network (WLAN). Additionally, the present disclosure relates to a method and apparatus for determining an allocated bandwidth according to a dynamic bandwidth expansion (DBE) operation in a wireless LAN network that supports Co-TDMA. Furthermore, the present disclosure relates to a method and apparatus for performing non-primary channel access (NPCA) or dynamic subband operation (DSO) during time division multiple access in a wireless LAN.

[0002]

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

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

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

[0006] In addition, it can support Co-TDMA operation for time resource sharing among multiple access points (APs). It can also support DBE operation, which is a bandwidth expansion operation method.

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

[0008]

[0009] The present disclosure relates to a method and apparatus for performing operations based on cooperative time-sharing multiple access.

[0010] The present disclosure relates to a method and apparatus for preventing frame transmission failure when Co-TDMA is supported in a wireless LAN.

[0011] The present disclosure relates to a method and apparatus for setting a time interval for frame transmission when Co-TDMA is supported in a wireless LAN.

[0012] The present disclosure relates to a method and apparatus for setting a network allocation vector (NAV) timer for a Transmit (TX) frame transmission when Co-TDMA is supported in a wireless LAN.

[0013] The present disclosure relates to a method and apparatus for setting a section where frame transmission is prohibited based on information of a frame allocating time resources in Co-TDMA operation of a wireless LAN.

[0014] The present disclosure relates to a method and apparatus for determining allocated bandwidth according to a dynamic bandwidth expansion (DBE) operation in a wireless LAN network supporting Co-TDMA.

[0015] The present disclosure relates to a method and apparatus for determining the bandwidth of frequency resources allocated in Co-TDMA operation by negotiating operating bandwidth information of a counterpart AP during time and frequency resource allocation.

[0016] The present disclosure relates to a method and apparatus for performing NPCA or DSO during time-division multiple access in a wireless LAN.

[0017] 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.

[0018]

[0019] 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 acquiring a transmission opportunity (TXOP); the first STA transmitting a polling frame in the TXOP based on coordinated time division multiple access (Co-TDMA) and receiving a response frame for the polling frame; transmitting an allocation frame after receiving a response frame for the polling frame and receiving a response frame for the allocation frame; and sharing the allocated duration in the TXOP with a second STA.

[0020] Additionally, according to one embodiment of the present specification, a first 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: acquiring a transmission opportunity (TXOP), transmitting a polling frame from the TXOP based on coordinated time division multiple access (Co-TDMA), receiving a response frame to the polling frame, transmitting an allocation frame after receiving the response frame to the polling frame, receiving a response frame to the allocation frame, and sharing the allocated duration within the TXOP with a second STA.

[0021] In addition, the following points may apply in common.

[0022] According to one embodiment of the present specification, the allocated duration is a transmission opportunity granted to the second STA, and the first STA may receive a TXOP return frame within the allocated duration or may not perform frame transmission or reception within the allocated duration until the allocated duration ends.

[0023] In addition, according to one embodiment of the present specification, when the first STA shares the allocated duration with the second STA and the third STA, the duration allocated to the second STA can be shared based on the main channel.

[0024] In addition, according to one embodiment of the present specification, when the first STA shares the allocated duration with the second STA, the first STA and the third STA connected to the first STA can perform frame exchange in the non-primary channel access (NPCA) primary channel during the allocated duration interval.

[0025] Additionally, according to one embodiment of the present specification, when the first STA receives a TXOP return frame from the second STA within the allocated duration, the sharing for the allocated duration may be terminated.

[0026] Additionally, according to one embodiment of the present specification, when the first STA performs frame exchange with the third STA through the NPCA channel at the allocated duration, the transmission of the TXOP return frame may be prohibited.

[0027] In addition, according to one embodiment of the present specification, the first STA and the third STA may operate based on at least one of a first type NPCA operation that supports NPCA operation based on TXOP length and a second type NPCA operation that supports NPCA operation based on PPDU (physical layer protocol data unit).

[0028] Additionally, according to one embodiment of the present specification, when the first STA and the third STA perform an NPCA operation in the allocated duration, only the second type NPCA operation is allowed, and the transmission of a TXOP return frame by the second STA in the allocated duration may be allowed.

[0029] Additionally, according to one embodiment of the present specification, when the first STA and the third STA perform an NPCA operation in the allocated duration, both the first type NPCA operation and the second type NPCA operation are allowed, provided that the first STA transmits an indicator prohibiting the transmission of a TXOP return frame in the allocated duration to the second STA, and based on the indicator prohibiting the transmission of a TXOP return frame, the transmission of a TXOP return frame by the second STA in the allocated duration may be prohibited.

[0030] Additionally, according to one embodiment of the present specification, at least one of the polling frame and the allocation frame includes an NPCA interruption indicator, and based on the NPCA interruption indicator, the first STA and the third STA connected to the first STA may be prohibited from performing NPCA operations for an allocated duration.

[0031] Additionally, according to one embodiment of the present specification, an allocation frame transmitted by a first STA includes an indicator sharing the allocated duration and information about the allocated duration, and the allocation frame is transmitted to a third STA connected to the first STA so that the allocated duration in the third STA can be set as a transmission prohibition period.

[0032] Additionally, according to one embodiment of the present specification, the allocated duration information is included in a user information field associated with an identifier of the second STA within the allocation frame, and when an indicator sharing the allocated duration of the allocation frame is set, the allocated duration can be identified in the third STA regardless of the identifier associated with the user information field based on Co-TDMA.

[0033] Additionally, according to one embodiment of the present specification, the first STA receives a response frame for a polling frame, performs frame exchange with the third STA, and then transmits an allocation frame, wherein the third STA may be a STA connected to the first STA.

[0034] Additionally, according to one embodiment of the present specification, the MAC (medium access control) header duration field of a frame transmitted by the first STA may be set to indicate the time required for frame exchange or to indicate the length of time until the end of the TXOP used by the first STA.

[0035] Additionally, according to one embodiment of the present specification, if the MAC header duration field of a frame transmitted by the first STA is set to indicate the time required for frame exchange, the TX(transmit)NAV(network allocation vector) is set by the MAC header duration field, and the first STA can perform at least one frame transmission for the first EDCAF of the first STA until the TXNAV expires.

[0036] Additionally, according to one embodiment of the present specification, if the first STA shares the duration allocated within the TXOP based on Co-TDMA with the second STA, the first STA can perform at least one frame transmission within the TXOP even after the TXNAV expires.

[0037] In addition, according to one embodiment of the present specification, the MAC header duration field of the allocation frame and the TXNAV set based on the allocation frame may be set to a time corresponding to the allocated duration.

[0038] Additionally, according to one embodiment of the present specification, the MAC header duration field of the polling frame transmitted by the first STA from the TXOP to the first frame indicates the time required for frame exchange of the polling frame, and the TXNAV set based on the polling frame is set to a value corresponding to the time length from the time of completion of transmission of the polling frame to the remaining TXOP of the first STA, and the first STA can perform at least one frame transmission before the TXNAV expires.

[0039] Additionally, according to one embodiment of the present specification, if the MAC header duration field of a frame transmitted by the first STA is set to indicate the time length until the end of the TXOP used by the first STA, the MAC header duration field of a polling frame transmitted by the first STA from the TXOP to the first frame indicates the time length from the time of completion of transmission of the polling frame until the remaining TXOP of the first STA, and TXNAV is set to a value corresponding to the MAC header duration field, and the first STA can perform at least one frame transmission before TXNAV expires.

[0040] Additionally, according to one embodiment of the present specification, the MAC header duration field of the response frame to the allocation frame is set to 0, and the TXNAV of the second STA is not set based on the MAC header duration field, but at least one frame transmission and reception of the second STA may be allowed during the allocated duration.

[0041] Additionally, according to one embodiment of the present specification, the MAC header duration field of the response frame for the allocation frame is set to the remaining allocated duration within the allocated duration after the completion of the transmission of the response frame, and the TXNAV is set to the remaining allocated duration within the allocated duration based on the MAC header duration field, and at least one frame transmission and reception of the second STA may be permitted during the allocated duration.

[0042] Additionally, according to one embodiment of the present specification, when the duration allocated within the TXOP is shared with the second STA, frame transmission is performed by the first EDCAF of the second STA, and if frame transmission by the first EDCAF fails, frame retransmission may be performed by the first EDCAF or an EDCAF having a higher priority than the first EDCAF within the allocated duration.

[0043] Additionally, according to one embodiment of the present specification, if the second STA is a STA that supports dynamic bandwidth expansion (DBE), the first STA may obtain operational bandwidth information based on DBE from the second STA before transmitting a polling frame that provides the duration allocated based on Co-TDMA to the second STA, and may share the duration allocated to the second STA based on the obtained operational bandwidth information.

[0044] Additionally, according to one embodiment of the present specification, if the second STA is a STA that supports DBE, the first STA can obtain operational bandwidth information based on DBE from the second STA through a response frame to a polling frame that provides the duration allocated based on Co-TDMA to the second STA, and can share the duration allocated to the second STA based on the obtained operational bandwidth information.

[0045] Additionally, according to one embodiment of the present specification, the first STA and the second STA may each be a non-AP STA or an AP STA.

[0046]

[0047] According to the present disclosure, a method for performing operations based on cooperative time-sharing multiple access can be provided.

[0048] According to the present disclosure, a method for preventing frame transmission failure can be provided when Co-TDMA is supported in a wireless LAN.

[0049] According to the present disclosure, a method for setting a time interval for frame transmission can be provided when Co-TDMA is supported in a wireless LAN.

[0050] According to the present disclosure, a method for setting a TX NAV timer according to frame transmission can be provided when Co-TDMA is supported in a wireless LAN.

[0051] According to the present disclosure, a method can be provided for setting a section where frame transmission is prohibited based on information of a frame that allocates time resources in the Co-TDMA operation of a wireless LAN.

[0052] According to the present disclosure, a method for determining allocated bandwidth based on DBE operation in a wireless LAN network supporting Co-TDMA can be provided.

[0053] According to the present disclosure, a method can be provided to determine the bandwidth of frequency resources allocated in Co-TDMA operation by negotiating operating bandwidth information of a counterpart AP when allocating time and frequency resources.

[0054] According to the present disclosure, a method for performing NPCA or DSO during time-division multiple access in a wireless LAN can be provided.

[0055] 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.

[0056] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0057]

[0058] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0059] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0060] FIGS. 3a and 3b are diagrams illustrating a DSO operation method during Co-TDMA operation applicable to the present disclosure.

[0061] FIGS. 4a and 4b are diagrams illustrating an NPCA operation method during Co-TDMA operation applicable to the present disclosure.

[0062] FIG. 5 is a diagram showing the DSO and NPCA operation methods during Co-TDMA operation applied to the present disclosure.

[0063] FIGS. 6a and 6b are diagrams illustrating an NPCA operation method during Co-TDMA operation applicable to the present disclosure.

[0064] FIG. 7 is a diagram showing a wireless LAN network to which the present disclosure applies.

[0065] FIG. 8 is a diagram showing the wireless LAN Co-TDMA operation method and problems applied to the present disclosure.

[0066] FIG. 9 is a diagram showing a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applied to the present disclosure.

[0067] FIG. 10 is a diagram showing a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applied to the present disclosure.

[0068] FIG. 11 is a diagram illustrating a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0069] FIG. 12 is a diagram illustrating a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0070] FIG. 13 is a diagram illustrating a method for performing retransmission after an initial control frame failure during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0071] FIG. 14 is a diagram illustrating a wireless LAN Co-TDMA operation method applied to the present disclosure.

[0072] FIGS. 15a to 15d are drawings illustrating a method for setting a frame transmission interval of a coordinating AP during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0073] FIGS. 16a and FIGS. 16b are diagrams illustrating a method for setting the frame transmission interval of a coordinated AP during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0074] FIG. 17 is a diagram illustrating a wireless LAN DBE operation method applied to the present disclosure.

[0075] FIG. 18 is a diagram showing bandwidth information of Coordinated APs exchanged in the MAPC procedure to which the present disclosure applies.

[0076] FIG. 19 is a diagram illustrating a Co-TDMA operation method based on DBE operation applied to the present disclosure.

[0077] FIG. 20 is a flowchart illustrating the operation of a STA in a wireless LAN to which the present disclosure applies.

[0078]

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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."

[0086] 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.

[0087] 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).

[0088] 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).

[0089] 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).

[0090] 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.

[0091] 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.

[0092] The following describes an operation in which an AP acquires a TXOP, which is a time interval during which multiple frames can be transmitted, and shares part or all of the acquired TXOP interval with another AP. For example, the TXOP acquired by the AP may be acquired on the main channel, and the AP may increase wireless resource usage efficiency by transmitting and receiving frames on a sub-channel rather than the main channel during the shared TXOP interval, and a method for doing so is described.

[0093] Furthermore, when an AP shares time resources with another AP, a hidden node problem may occur, which may lead to attempts to transmit frames that cannot be received during Co-TDMA operation. If the aforementioned operation is performed, wireless resources may be wasted, and frame transmission failures may result in increased channel access parameters and frame discarding. The following describes an operation designed to prevent the performance of Co-TDMA operations supported by wireless LAN networks from being reduced as described above. Through this, frame transmission failures caused by the hidden node problem can be prevented, and the performance of Co-TDMA operations can be enhanced.

[0094] Furthermore, when an AP shares time resources with multiple APs, continuous frame transmission may become impossible depending on the method used to execute the frame time interval instructions, and polling and allocation operations, which are essential for Co-TDMA operation, may not be performed. As described above, wireless resources may be wasted and the performance of the wireless LAN network may be reduced due to the failure of Co-TDMA operation; therefore, measures to prevent this are described below.

[0095] Furthermore, while the operating bandwidth of a wireless LAN network can be dynamically expanded by DBE operation, this expansion may not be reflected in the determination of bandwidth allocated during Co-TDMA operation. In the aforementioned case, efficient allocation of wireless LAN frequency resources based on the wireless LAN network's operating bandwidth cannot be performed during Co-TDMA operation. Consequently, the performance of Co-TDMA operation may be reduced, and measures to prevent this are described below.

[0096] Consider a case where three basic service sets (BSS) operate in a wireless LAN network. BSS 1 may be a BSS configured by AP 1 and STA 1, BSS 2 may be a BSS configured by AP 2 and STA 2, and BSS 3 may be a BSS configured by AP 3 and non-AP STA 3 (320-3). However, this is merely for the convenience of explanation and may not be limited to cases where three BSSs operate. Here, AP 1 and AP 3 may form a MAP group capable of performing Multi-AP coordination. MAP coordination may be an operation in which multiple APs perform coordination by performing at least one of the following: prior information exchange among multiple APs, sharing of transmission resources among APs, protection of transmission segments, and other operations for cooperation among multiple APs. Co-(coordinated)-TDMA (time division multiple access) operations may be included in MAP coordination. Co-TDMA may be an operation in which, when one of multiple APs in a MAP group acquires a transmit opportunity (TXOP) capable of transmitting multiple frames, that AP shares or allocates the TXOP to the remaining AP(s) of the MAP group. That is, all or part of the TXOP acquired by one AP may be shared with the remaining AP(s) of the MAP group. The remaining AP(s) of the MAP group can perform data transmission and reception with connected STAs during the shared TXOP interval.

[0097] For example, AP 1 can acquire a TXOP (or EDCA TXOP) through a channel access operation (e.g., EDCA (enhanced distributed channel access) operation, EDCA backoff operation). As described above, the TXOP may be a time interval capable of transmitting multiple frames. AP 1 may want to perform Co-TDMA operations with AP 2 and AP 3 included in the MAP group. That is, AP 1 may want to share the TXOP with the AP(s) included in the MAP group. AP 1 may transmit a polling frame to AP 2 and AP 3 within the TXOP. Since the AP to which the polling frame was transmitted is not itself, AP 2 and AP 3 may, after receiving AP 1's polling frame, set a basic NAV (network allocation vector) based on the time length indicated in the duration field of the polling frame. Here, the duration field of the polling frame may be a value corresponding to the remaining TXOP length of AP 1 after the polling frame transmission ends.

[0098] As another example, the duration field of the polling frame may be a value corresponding to the TXOP length of AP 1. Therefore, the default NAV end time of AP 2 and AP 3 may be the same as the TXOP end time of AP 1. When the default NAV is set on AP 2 and AP 3, AP 2 and AP 3 may determine the channel state to be busy based on the virtual CS (carrier sense). That is, AP 2 and AP 3 cannot transmit frames during the period in which the default NAV is set. However, AP 2 and AP 3 may be able to transmit response frames (e.g., an immediate response frame that must be transmitted after receiving a frame and the SIFS (short interframe space)) during the period in which the default NAV is set. Here, although AP 2 and AP 3 set the default NAV based on the polling frame, if there is a frame to be transmitted within the TXOP of AP 1 through the Co-TDMA procedure, they can transmit a response frame to the polling frame. AP 1 can determine whether AP 2 and AP 3 require frame transmission via Co-TDMA through polling frames and response frames to polling frames. However, if AP 1, AP 2, and AP 3 belonging to the MAP group have completed the procedure to determine whether frame transmission via Co-TDMA is required using a communication method other than wireless LAN communication (e.g., Ethernet communication), the above-described procedure may not be performed. Here, the other communication method may be an over-the-DS method.

[0099] If AP 1 requires data communication with a connected STA (e.g., STA 1) within a TXOP, AP 1 can transmit a frame containing a data frame from the acquired TXOP to STA 1 connected to and operating with AP 1. If AP 1 does not require data communication with a connected STA within a TXOP, AP 1 can immediately perform a TXOP sharing operation for Co-TDMA operation. The above-described details can be applied in the same way to FIGS. 3a through 6b below, and different operations may be performed depending on the specific operation of each figure.

[0100] The DSO channel of the present disclosure may be referred to as a DSO subband, the NPCA (Non-primary channel access) channel may be referred to as an NPCA primary channel, and the primary channel may be referred to as a BSS (basic service set) primary channel and a primary subband.

[0101] FIGS. 3a and 3b are diagrams illustrating a DSO operation method during Co-TDMA operation applicable to the present disclosure.

[0102] If AP 2 (310-2) and AP 3 (310-2), which are included in the MAP group of AP 1 (310-1), determine that frame transmission via Co-TDMA is required, AP 1 (310-1) may share TXOPs with AP 2 (310-2) and AP 3 (310-2). Here, the operating bandwidth of AP 2 (310-2) and AP 3 (310-2) may be narrower than that of AP 1 (310-1). For example, if the operating bandwidth of AP 1 (310-1) is 320 MHz, the operating bandwidth of AP 2 (310-2) and AP 3 (310-2) may be 160 MHz or 80 MHz. However, the above description is merely an example for convenience of explanation regarding the case where the operating bandwidth of AP 2 (310-2) and AP 3 (310-2) is narrower than the operating bandwidth of AP 1 (310-1), and is not limited thereto, and various other situations with narrower operating bandwidths may occur. As described above, when the operating bandwidth of AP 2 (310-2) and AP 3 (310-2) is narrower than that of AP 1 (310-1), AP 1 (310-1) may allocate channels to AP 2 (310-2) and AP 3 (310-2) so that the entire TXOP can be used when sharing acquired TXOPs. As another example, even if AP 2 (310-2) and AP 3 (310-2) have operating bandwidths equal to or wider than that of AP 1 (310-1), channels can be allocated to AP 2 (310-2) and AP 3 (310-2) to allocate Co-TDMA transmission resources through the limited bandwidth of AP 1 (310-1). Specifically, if AP 1 (310-1) needs to share TXOPs by dividing the operating bandwidth of AP 1 (310-1) among AP 2 (310-2) and AP 3 (310-2), AP 1 (310-1) can share TXOPs with AP 2 (310-2) and AP 3 (310-2) by utilizing dynamic subband operation (DSO).AP 2 (310-2) and AP 3 (310-2) can perform frame transmission and reception with non-AP STA 2 (320-2) and non-AP STA 3 (320-3), respectively, during a TXOP shared in a subband. The DSO operation may be an operation in which a portion of the operation bandwidth (i.e., operation channel) of AP 1 (310-1) is designated as the primary channel, and the remaining channel is designated as the DSO channel. AP 1 (310-1) may transmit a frame for TXOP sharing, and the frame may include an indicator instructing a specific STA or AP to change the operation channel to the DSO channel. A specific STA or AP that receives the above-mentioned frame may change the operation channel to the DSO channel.

[0103] Referring to FIG. 3a, AP 1 (310-1) can transmit a TXS frame for TXOP sharing. The TXS frame can be duplicated and transmitted in 20 MHz units. For example, the TXS frame may be a Non-HT (high throughput) 20 MHz duplicated PPDU (physical layer protocol data unit). For another example, the TXS frame may be a MU (multi-user)-RTS (request to send) trigger frame (401).

[0104] For example, the TXS frame (401) may include information that enables AP 2 (310-2) to communicate on the main channel of AP 1 (310-1) and information that enables AP 3 (310-2) to switch channels to the DSO channel of AP 1 (310-1) and operate. That is, the TXS frame (401) may be an initial control frame (ICF) that enables AP 3 (310-2) to switch channels to the DSO channel and operate. AP 1 (310-1) may indicate a time interval (i.e., a shared TXOP interval) during which AP 2 (310-2) and AP 3 (310-2) can communicate on the main channel and the DSO channel, respectively. For example, AP 1 (310-1) may indicate the identifiers (e.g., AP ID) of AP 2 (310-2) and AP 3 (310-2) and the time interval during which AP 2 (310-2) and AP 3 (310-2) can communicate in the user info field of the TXS frame (401). Accordingly, AP 2 (310-2) and AP 3 (310-2) can perform data frame transmission and reception within the time interval indicated by AP 1 (310-1). Here, AP 2 (310-2) can perform frame transmission and reception on the main channel, and AP 3 (310-2) can perform frame transmission and reception on the DSO channel. When AP 2 (310-2) and AP 3 (310-2) receive a TXS frame (401), they may perform an action to release the default NAV or ignore the default NAV during the shared TXOP interval. AP 2 (310-2) may transmit an ICR (initial control response, 402), which is a response frame to the TXS frame (401), to AP 1 (310-1) on the main channel. AP 3 (310-2) may transmit an ICR (initial control response, 403), which is a response frame to the TXS frame (401), to AP 1 (310-1) on the main channel and the DSO channel.For example, the ICR (402, 403) of AP 2 (310-2) and AP 3 (310-2) may be frames containing the same content (e.g., S (Simultaneous) - CTS (clear to send) frames), but are not limited thereto.

[0105] Here, the RA (receiver address) of the ICR (402) transmitted by AP 2 (310-2) can be set to the address of AP 2 (310-2). AP 3 (310-2) can identify the address of AP 2 (310-2) where no DSO operation is indicated in the TXS frame (401) and set the RA of the ICR (402) transmitted by AP 3 (310-2) to the address of AP 2 (310-2). Therefore, the contents of the ICRs (402, 403) transmitted simultaneously on the main channel can be identical. AP 2 (310-2) can ignore the default NAV in the shared TXOP. When RA transmits an ICR (402) which is the address of AP 2 (310-2) and non-AP STA 2 (320-2) receives the ICR (402), non-AP STA 2 (320-2) can set up an intra-BSS NAV. That is, the shared TXOP interval can be recognized as being by the BSS 2 configured by AP 2 (310-2) and non-AP STA 2 (320-2). On the other hand, when RA transmits an ICR (403) which is the address of AP 2 and non-AP STA 3 (320-3) receives the ICR (403), non-AP STA 3 (320-3) can set up a basic NAV. That is, the shared TXOP interval may be recognized as not being due to the BSS 3 configured by the AP 3 (310-2) and the non-AP STA 3 (320-3). The non-AP STA 3 (320-3) may move the operating channel to the NPCA (non-primary channel access) channel (or NPCA primary channel) when the basic NAV is set. For example, the NPCA channel and NPCA primary channel are described interchangeably below, but the channel may be the same channel and is not limited to a specific name.The NPCA channel may be a channel that AP 3 (310-2) and non-AP STA 3 (320-3) switch to operate when a basic NAV is set on AP 3 (310-2) and non-AP STA 3 (320-3). That is, AP 3 (310-2) and non-AP STA 3 (320-3) switch their operating channel to the NPCA channel, which is a channel other than the main channel (e.g., BSS main channel) where they normally operate. The NPCA channel may be the same channel as the DSO channel of AP 1 (310-1). Here, the duration of the ICR (402, 403) of AP 2 (310-2) and AP 3 (310-2) (e.g., the value of the duration field of the MAC header) may be a duration corresponding to the shared TXOP interval. That is, the length of the intra-BSS NAV set by non-AP STA 2 (320-2) and the basic NAV set by non-AP STA 3 (320-3) may be a length corresponding to the shared TXOP interval. As another example, the length of the intra-BSS NAV set by non-AP STA 2 (320-2) and the basic NAV set by non-AP STA 3 (320-3) may be set based on the duration of the TXS frame (401) transmitted by AP 1 (310-1) (e.g., the value of the duration field in the MAC header or one of the assigned duration values ​​included in the user info field). non-AP STA 3 (320-3) may operate on the NPCA channel during the interval in which the basic NAV is set and then return to the main channel. That is, non-AP STA 3 (320-3) may operate on the NPCA channel for the duration of the shared TXOP interval.

[0106] AP 2 (310-2) can perform frame (404) transmission and reception with non-AP STA 2 (320-2) on the main channel, and AP 3 (310-2) can perform frame (405) transmission and reception with non-AP STA 3 (320-3) on the DSO channel. Here, when AP 2 (310-2) completes frame (404) transmission and reception, AP 2 (310-2) may want to return the shared TXOP interval. In the above case, AP 2 (310-2) may transmit a TXOP return frame (406) to AP 1 (310-1). The TXOP return frame (406) may be a QoS Null frame or a QoS Data frame in which the RDG / More PPDU bit of the CAS Control information included in the form of an A-control included in the HT Control field of the MAC header is 0. When AP 2 (310-2) of the main channel returns the shared TXOP period, AP 1 (310-1) can perform frame transmission and reception on the main channel excluding the DSO channel during the remaining TXOP period. Meanwhile, AP 3 (310-2) can also transmit a TXOP return frame to return the shared TXOP period. For example, if both AP 2 (310-2) and AP 3 (310-2) transmit TXOP return frames, AP 1 (310-1) can perform frame transmission and reception during the remaining TXOP period using both the main channel and the DSO channel.

[0107] Additionally, referring to FIG. 3b, AP 1 (310-1) can transmit a TXS frame for TXOP sharing. The TXS frame can be duplicated and transmitted in 20 MHz units. For example, the TXS frame may be a Non-HT (high throughput) 20 MHz duplicated PPDU (physical layer protocol data unit). For another example, the TXS frame may be a MU (multi-user)-RTS (request to send) trigger frame (401).

[0108] For example, the TXS frame (401) may be an ICF that instructs AP 3 (310-2) to operate on a DSO channel (or DSO subband). For example, the following description is based on a DSO channel, but is not limited thereto and can be applied in the same way to a DSO subband. However, for the convenience of explanation, the description is based on a DSO channel.

[0109] AP 1 (310-1) can indicate a time interval (i.e., a shared TXOP interval) during which AP 3 (310-2) can communicate on the DSO channel. Accordingly, AP 3 (310-2) can perform frame transmission and reception within the time interval indicated by AP 1 (310-1). AP 3 (310-2) can receive a TXS frame (401) and transmit an ICR (407) as a response frame. After transmitting the ICR (407), AP 3 (310-2) can transmit a trigger frame (408) instructing non-AP STA 3 (320-3) connected to AP 3 (310-2) to operate on the DSO channel. Here, AP 3 (310-2) must transmit a trigger frame (408) to non-AP STA 3 (320-3) so that non-AP STA 3 (320-3) can also transmit and receive frames on the DSO channel. When AP 3 (310-2) completes the transmission of the trigger frame (408), non-AP STA 3 (320-3) and AP 3 (310-2) can transmit and receive frames on the DSO channel. The duration of the MAC header of the trigger frame transmitted by AP 3 (310-2) (or the UL Length field of the common info field, the allocation duration field of the user info field) may be set to a length corresponding to the interval of the TXOP shared by AP 1 (310-1) to AP 3 (310-2).

[0110] Afterward, AP 1 (310-1) can transmit a TXS frame (409) to AP 2 (310-2) on the main channel excluding the DSO channel. The TXS frame (409) may contain information that enables AP 2 (310-2) to communicate on the main channel of AP 1 (310-1). AP 1 (310-1) can indicate a time interval (i.e., a shared TXOP interval) during which AP 2 (310-2) can communicate on the main channel. AP 2 (310-2) can perform frame transmission and reception within the time interval indicated by AP 1 (310-1), and AP 2 (310-2) can perform frame transmission and reception on the main channel. Here, when AP 2 (310-2) and AP 3 (310-2) receive a TXS frame, AP 2 (310-2) and AP 3 (310-2) may perform an action to release the default NAV or ignore the default NAV during the shared TXOP interval. Alternatively, when AP 2 (310-2) and AP 3 (310-2) receive a TXS frame and the TXS frame indicates a time interval during which AP 2 (310-2) and AP 3 (310-2) can communicate, AP 2 (310-2) and AP 3 (310-2) may be considered as receivers of the ICF (i.e., TXOP responders). Therefore, AP 2 (310-2) and AP 3 (310-2) may not set the NAV separately. As another example, when AP 2 (310-2) and AP 3 (310-2) receive a TXS frame and the TXS frame indicates a time interval during which AP 2 (310-2) and AP 3 (310-2) can communicate, AP 2 (310-2) and AP 3 (310-2) may establish an intra-BSS NAV by considering the communication to be within a shared TXOP interval. Here, the operation of ignoring the intra-BSS NAV during the shared TXOP interval may be performed.

[0111] AP 2 (310-2) can perform frame transmission and reception with non-AP STA 2 (320-2) on the main channel. Additionally, AP 3 (310-2) can perform frame transmission and reception with non-AP STA 3 (320-3) on the DSO channel. Meanwhile, AP 2 (310-2) may want to return the shared TXOP interval when data frame transmission and reception is completed. In the above case, AP 2 (310-2) may transmit a TXOP return frame to AP 1 (310-1). The TXOP return frame may be a QoS Null frame or a QoS Data frame in which the RDG / More PPDU bit of the CAS Control information included in the form of an A-control included in the HT Control field of the MAC header is 0. When AP 2 (310-2) of the main channel returns the shared TXOP interval, AP 1 (310-1) can perform frame transmission and reception on the main channel excluding the DSO channel during the remaining TXOP interval. Meanwhile, AP 3 (310-2) can also transmit a TXOP return frame to return the shared TXOP interval. For example, when both AP 2 (310-2) and AP 3 (310-2) transmit TXOP return frames, AP 1 (310-1) can perform frame transmission and reception during the remaining TXOP interval using both the main channel and the DSO channel.

[0112] FIGS. 4a and 4b are diagrams illustrating an NPCA operation method during Co-TDMA operation applicable to the present disclosure.

[0113] Referring to FIGS. 4a and 4b, AP 1 (310-1) can perform a TXOP sharing operation for Co-TDMA operation with AP 3 (310-2). Here, AP 1 (310-1) can transmit a TXS frame to AP 3 (310-2). For example, the TXS frame is a MU-RTS TXS trigger frame (410), and the MU-RTS TXS frame can be transmitted using the full bandwidth of AP 1 (310-1). The TXS frame (410) can indicate a time interval (i.e., a shared TXOP interval) during which AP 3 (310-2) can transmit and receive data. When AP 3 (310-2) receives a TXS frame (410) that shares a TXOP with AP 3 (310-2), it can disable or ignore the default NAV set during the shared TXOP interval. As another example, AP 3 (310-2) can replace the basic NAV with intra-BSS NAV. When AP 3 (310-2) receives a TXS frame (410) from AP 1 (310-1), it can respond with a CTS frame (411). The CTS frame (411) may be transmitted using the full bandwidth of AP 3 (310-2). Alternatively, if some channels are occupied, the CTS frame (411) may be transmitted using only a portion of the bandwidth of AP 3 (310-2).

[0114] Here, AP 2 (310-2) may be considered as not being a shared target of the TXOP. Therefore, AP 2 (310-2) may not release the default NAV set when receiving the first polling frame. AP 2 (310-2) may update the default NAV when receiving the TXS frame (410) and the CTS frame (411) of AP 3 (310-2). AP 2 (310-2) may not perform data frame transmission and reception while the default NAV is set, as the virtual CS is occupied. On the other hand, AP 3 (310-2) may perform frame transmission and reception with non-AP STA 3 (320-3) within the shared TXOP.

[0115] Additionally, the TXS frame (410) of AP 1 (310-1) may indicate an NPCA operation of non-AP STA 1 (320-1) connected to AP 1 (310-1). An NPCA operation may be an operation in which, when the main channel of AP 1 (310-1) and non-AP STA 1 (320-1) is occupied and the occupancy is caused by a BSS other than the BSS of AP 1 (310-1) and non-AP STA 1 (320-1) (overlapping BSS, OBSS), AP 1 (310-1) and non-AP STA 1 (320-1) change the operation channel to the mutually recognized channel (NPCA Primary channel) of AP 1 (310-1) and non-AP STA 1 (320-1) during the indicated occupancy period (i.e., during the communication period) to perform frame transmission and reception. AP 1 (310-1) and non-AP STA 1 (320-1) can operate on the main channel again when the indicated communication period ends. Here, AP 1 (310-1) indicated a shared TXOP period, and the shared TXOP period may be for communication of AP 3 (310-2) (i.e., BSS 3) rather than AP 1 (310-1). Therefore, the communication period of the main channel may be a known period, and AP 1 (310-1) and non-AP STA 1 (320-1) can operate on the NPCA main channel during the shared TXOP period. For example, when a non-AP STA 1 (320-1) connected to AP 1 (310-1) starts receiving a TXS frame (410) from AP 1 (310-1) (e.g., when the PHY preamble of the TXS frame (410) is decoded to generate a PHY-RXSTART.indication primitive), the intra-BSS NAV is 0, and then when it receives a CTS frame (411) from AP 2 (310-2), this can be confirmed by the exchange of ICF and ICR frames. Based on this, the non-AP STA 1 (320-1) can operate on the NPCA main channel during the shared TXOP interval.The TXS frame (410) of AP 1 (310-1) may instruct non-AP STA 1 (320-1) to perform NPCA operations during the shared TXOP period. Here, non-AP STA 1 (320-1) may receive the TXS frame (410), and when non-AP STA 1 (320-1) receives the TXS frame (410) from AP 1 (310-1), it may operate on the NPCA main channel. AP 1 (310-1) and non-AP STA 1 (320-1) may transmit and receive frames on the NPCA main channel during the shared TXOP period, and may operate on the main channel again when the shared TXOP period ends. A method different from the NPCA operation method through the instruction of the TXS frame (410) may be considered. Specifically, AP 1 (310-1) and non-AP STA 1 (320-1) can receive frames from AP 3 (310-2) and non-AP STA connected to AP 3 (310-2) within a shared TXOP interval, and can identify the interval during which AP 3 (310-2) and non-AP STA connected to AP 3 (310-2) actually perform communication within the shared TXOP interval. Accordingly, AP 1 (310-1) and non-AP STA 1 (320-1) identify the communication interval and can operate on the NPCA main channel during the communication interval of AP 3 (310-2) and non-AP STA connected to AP 3 (310-2).

[0116] Referring to FIG. 4a, AP 3 (310-2) can use the entire shared TXOP interval. Therefore, AP 1 (310-1) and non-AP STA 1 (320-1) can perform data frame transmission and reception on the NPCA main channel up to the shared TXOP interval, and then switch the operating channel back to the main channel. Alternatively, referring to FIG. 4b, AP 3 (310-2) may return the shared TXOP interval without using the entire shared TXOP interval. To return the shared TXOP, AP 3 (310-2) can transmit a TXOP return frame (412) to AP 1 (310-1). The TXOP return frame (412) may be a QoS Null frame or a QoS Data frame in which the RDG / More PPDU bit of the CAS Control information included in the form of an A-control included in the HT Control field of the MAC header is 0. AP 1 (310-1) can receive the TXOP return frame (412) of AP 3 (310-2). When the TXOP of AP 3 (310-2) is returned, AP 1 (310-1) can use the main channel again. Here, since AP 1 (310-1) can transmit and receive frames by successfully accessing the channel on the NPCA main channel, AP 1 (310-1) can perform frame transmission and reception using both the main channel and the NPCA channel. That is, AP 1 (310-1) can perform a channel expansion operation. For example, if the operating bandwidth of the main channel is 80 MHz and the operating bandwidth of the NPCA main channel is 80 MHz, AP 1 (310-1) may perform 80+80 MHz frame transmission.

[0117] As another example, based on the capability of AP 1 (310-1), the return of the shared TXOP interval of AP 3 (310-2) may not be allowed. That is, if AP 1 (310-1) performs an NPCA operation and operates on the NPCA main channel, AP 1 (310-1) cannot transmit or receive frames on the main channel used by AP 3 (310-2), and therefore cannot receive the TXOP return frame of AP 3 (310-2). When AP 3 completes frame transmission to non-AP STA 3 (320-3) and there are no more frames to transmit in the shared TXOP interval, AP 3 (310-2) may leave the channel empty or transmit any frame that can be occupied until the shared TXOP interval ends, but is not limited to such embodiments. For example, if AP 3 (310-2) does not transmit an ICF (e.g., CTS frame, BSRP trigger frame, MU-RTS trigger frame) in the shared TXOP interval and transmits the frame with the TXOP_DURATION field of the PPDU (physical layer protocol data unit) preamble set to UNSPECIFIED, AP 1 (310-1) may stop operating on the NPCA main channel at the time AP 3 (310-2) finishes transmitting the frame and operate on the BSS main channel again. Alternatively, AP 3 (310-2) may not transmit a frame that causes AP 1 (310-1) to switch the operating channel to the NPCA main channel. In the above-described case, AP 1 (310-1) can receive a TXOP return frame from AP 3 (310-2), and AP 3 (310-2) can send a TXOP return frame (412) to AP 1 (310-1) to return the shared TXOP to AP 1 (310-1).

[0118] FIG. 5 is a diagram showing the DSO and NPCA operation methods during Co-TDMA operation applied to the present disclosure.

[0119] Referring to FIG. 5, if AP 2 (310-2) and AP 3 (310-2), which are included in the MAP group of AP 1 (310-1), are determined to require frame transmission via Co-TDMA, AP 1 (310-1) may share TXOPs with AP 2 (310-2) and AP 3 (310-2). Here, the operating bandwidth of AP 2 (310-2) and AP 3 (310-2) may be narrower than that of AP 1 (310-1). For example, the operating bandwidth of AP 1 (310-1) may be 320 MHz, and the operating bandwidths of AP 2 (310-2) and AP 3 (310-2) may be 160 MHz and 80 MHz, respectively, but this is for convenience of explanation only and is not limited thereto, and various other situations with narrow operating bandwidths may occur. As described above, if the operating bandwidth of AP 2 (310-2) and AP 3 (310-2) is narrower than the operating bandwidth of AP 1 (310-1), AP 1 (310-1) may allocate channels to AP 2 (310-2) and AP 3 (310-2) so that the entire TXOP can be used when sharing acquired TXOPs. As another example, even if AP 2 (310-2) and AP 3 (310-2) have the same or wider operating bandwidth as AP 1 (310-1), channels may be allocated to AP 2 (310-2) and AP 3 (310-2) to allocate Co-TDMA transmission resources through the limited bandwidth of AP 1 (310-1). Specifically, when AP 1 (310-1) needs to share TXOPs by dividing the operating bandwidth of AP 1 (310-1) with AP 2 (310-2) and AP 3 (310-2), AP 1 (310-1) can share TXOPs with AP 2 (310-2) and AP 3 (310-2) by utilizing dynamic subband operation (DSO). AP 2 (310-2) and AP 3 (310-2) can perform frame transmission and reception with non-AP STA 2 (320-2) and non-AP STA 3 (320-3), respectively, during the TXOP shared in the subband.The DSO operation may be an operation in which a portion of the operation bandwidth (i.e., operation channel) of AP 1 (310-1) is designated as the primary channel, and the remaining channel is designated as the DSO channel. AP 1 (310-1) may transmit a frame for TXOP sharing, and the frame may include an indicator that a specific STA or AP changes the operation channel to the DSO channel. A specific STA or AP that receives the above-mentioned frame may change the operation channel to the DSO channel.

[0120] Here, AP 1 (310-1) can transmit a TXS frame for TXOP sharing. The TXS frame can be duplicated and transmitted in 20 MHz units. For example, the TXS frame can be a Non-HT (high throughput) 20 MHz duplicated PPDU (physical layer protocol data unit). For another example, the TXS frame can be a MU (multi-user)-RTS (request to send) trigger frame (413).

[0121] The TXS frame (413) may include information that enables AP 2 (310-2) to communicate on the main channel of AP 1 (310-1) and information that enables AP 3 (310-2) to switch to and operate on the DSO channel of AP 1 (310-1). That is, the TXS frame (413) may be an initial control frame (ICF) that enables AP 3 (310-2) to switch channels to and operate on the DSO channel. AP 1 (310-1) may indicate a time interval (i.e., a shared TXOP interval) during which AP 2 (310-2) and AP 3 (310-2) can communicate on the main channel and the DSO channel, respectively. Accordingly, AP 2 (310-2) and AP 3 (310-2) can perform frame transmission and reception within the time interval indicated by AP 1 (310-1). AP 2 (310-2) can perform frame transmission and reception on the main channel, and AP 3 (310-2) can perform frame transmission and reception on the DSO channel. Here, when AP 2 (310-2) and AP 3 (310-2) receive a TXS frame (413), they can perform an operation to release the default NAV or ignore the default NAV during the shared TXOP interval.

[0122] AP 2 (310-2) can transmit an ICR (initial control response, 414), which is a response frame to a TXS frame, to AP 1 (310-1) on the main channel. Additionally, AP 3 (310-2) can transmit an ICR (initial control response, 415), which is a response frame to a TXS frame (413), to AP 1 (310-1) on the main channel and DSO channel. Here, the ICRs (414, 415) of AP 2 (310-2) and AP 3 (310-2) may be frames containing the same content (e.g., S (Simultaneous) - CTS (clear to send) frames).

[0123] The receiver address (RA) of the ICR (414) transmitted by AP 2 (310-2) can be set to the address of AP 2 (310-2). Additionally, AP 3 (310-2) can identify the address of AP 2 (310-2) where no DSO operation is indicated in the TXS frame (413) and set the RA of the ICR (415) transmitted by AP 3 (310-2) to the address of AP 2 (310-2). Therefore, the contents of the ICRs (414, 415) transmitted simultaneously on the main channel may be identical. AP 2 (310-2) can ignore the default NAV in the shared TXOP. When RA is transmitted by AP 2 (310-2) to the address of AP 2 (310-2) and received by non-AP STA 2 (320-2), non-AP STA 2 (320-2) can set up an intra-BSS NAV. That is, the shared TXOP interval can be recognized as being by the BSS 2 configured by AP 2 (310-2) and non-AP STA 2 (320-2). On the other hand, when RA is transmitted by AP 3 (310-2) to the address of AP 2 (310-2) to the address of non-AP STA 3 (320-3), non-AP STA 3 (320-3) can set up a basic NAV. That is, the shared TXOP interval may be recognized as not being due to the BSS 3 configured by AP 3 (310-2) and non-AP STA 3 (320-3). When the primary NAV is set, the non-AP STA 3 (320-3) may move the operating channel to the NPCA (non-primary channel access) channel. The NPCA channel may be the channel where AP 3 (310-2) and non-AP STA 3 (320-3) operate when the primary NAV is set on AP 3 (310-2) and non-AP STA 3 (320-3). The NPCA channel may be the same channel as the DSO channel of AP 1 (310-1).The ICR (414, 415) durations of AP 2 (310-2) and AP 3 (310-2) may be durations corresponding to the shared TXOP interval. That is, the lengths of the intra-BSS NAV set by non-AP STA 2 (320-2) and the basic NAV set by non-AP STA 3 (320-3) may be lengths corresponding to the shared TXOP interval. non-AP STA 3 (320-3) may operate on the NPCA channel during the interval in which the basic NAV is set, and then return to the main channel. That is, non-AP STA 3 (320-3) may operate on the NPCA channel for the duration of the shared TXOP interval. AP 2 (310-2) can transmit and receive data frames with non-AP STA 2 (320-2) on the main channel, and AP 3 (310-2) can transmit and receive frames with non-AP STA 3 (320-3) on the DSO channel.

[0124] Additionally, the TXS frame (413) of AP 1 (310-1) may indicate the NPCA operation of non-AP STA 1 (320-1) connected to AP 1 (310-1). The NPCA operation may be an operation in which, when the main channel of AP 1 (310-1) and non-AP STA 1 (320-1) is occupied and the occupancy is caused by a BSS (OBSS) other than the BSS of AP 1 (310-1) and non-AP STA 1 (320-1), the operation channel is changed to a known channel (NPCA Primary channel) between AP 1 (310-1) and non-AP STA 1 (320-1) to perform frame transmission and reception, and when the known communication period ends, the operation is switched back to the main channel. AP 1 (310-1) indicated a shared TXOP interval, and the shared TXOP interval may be for communication between AP 2 (310-2) and AP 3 (310-2) (i.e., BSS 2 and BSS 3) rather than AP 1 (310-1). The communication interval of the main channel may be a known interval. Thus, AP 1 (310-1) and non-AP STA 1 (320-1) can operate on the NPCA main channel during the shared TXOP interval. The TXS frame (413) of AP 1 (310-1) instructs non-AP STA 1 (320-1) to perform NPCA operation during the shared TXOP interval, and non-AP STA 1 (320-1) can receive the TXS frame (413). non-AP STA 1 (320-1) can operate on the NPCA main channel when it receives a TXS frame (413) from AP 1 (310-1). AP 1 (310-1) and non-AP STA 1 (320-1) can transmit and receive frames on the NPCA main channel during the shared TXOP period, and can operate on the main channel again when the shared TXOP period ends.

[0125] FIGS. 6a and 6b are diagrams illustrating an NPCA operation method during Co-TDMA operation applicable to the present disclosure.

[0126] Referring to FIGS. 6a and 6b, AP 1 (310-1) can perform a TXOP sharing operation with AP 2 (310-2) according to Co-TDMA operation. AP 1 (310-1) can transmit a TXS frame to AP 2 (310-2). For example, the TXS frame may be a MU-RTS TXS trigger frame (416), but is not limited thereto. The TXS frame (416) may indicate a time interval (i.e., a shared TXOP interval) during which AP 2 (310-2) can transmit and receive data. When AP 2 (310-2) receives the TXS frame (416) from AP 1 (310-1), it may respond with a CTS frame (417). AP 2 (310-2) can transmit and receive frames with non-AP STA 2 (320-2) within a shared TXOP.

[0127] Here, AP 1 (310-1) and a non-AP STA connected to AP 1 (310-1) (e.g., non-AP STA 1 (320-1)) can perform an NPCA operation by means of a frame transmitted within a TXOP shared with AP 2 (310-2). The NPCA operations that AP 1 (310-1) and the non-AP STA can perform may be MOPLEN NPCA and PHYLEN NPCA operations. AP 1 (310-1) may include in a TXS frame (416) a method for a non-AP STA connected to AP 1 (310-1) (e.g., non-AP STA 1 (320-1)) to perform an NPCA operation within a TXOP shared with another AP (e.g., AP 2 (310-2)). As another example, AP 1 (310-1) may transmit a polling frame containing a method for performing an NPCA operation.

[0128] Referring to FIG. 6a, AP 1 (310-1) may indicate that MOPLEN NPCA is unavailable (or indicate that only PHYLEN NPCA is available) via at least one of a polling frame and a TXS frame. AP 1 (310-1) may indicate to a connected non-AP STA that both PHYLEN NPCA and MOPLEN NPCA are used via at least one of a beacon frame, an action frame, and other frames before the Co-TDMA procedure begins. AP 1 (310-1) may want to stop (suspend) the use of MOPLEN NPCA within a shared TXOP of the Co-TDMA operation. A non-AP STA 1 (320-1) connected to AP 1 (310-1) may receive an indicator indicating that MOPLEN NPCA is unavailable in a polling frame or a TXS frame of AP 1 (310-1). non-AP STA 1 (320-1) checks the time length of the shared TXOP in the TXS frame (e.g., the allocation duration field of the user info field) and stops using MOPLEN NPCA during that time interval and only uses PHYLEN NPCA.

[0129] Here, a case may be considered in which at least one of AP 1 (310-1) and non-AP STA 1 (320-1) performs an NPCA operation based on PHYLEN NPCA. AP 1 (310-1) and non-AP STA 1 (320-1) can receive a PPDU (physical layer protocol data unit) transmitted by at least one of AP 2 (310-2) and non-AP STA 2 (320-2). If the MAC variable of AP 1 (310-1) and non-AP STA 1 (320-1), which is set from the time length of the PPDU, is greater than the NPCA minimum duration threshold, AP 1 (310-1) and non-AP STA 1 (320-1) can perform channel access operations and frame transmission / reception operations on the NPCA main channel during the time interval in which the PPDU is transmitted. AP 1 (310-1) and non-AP STA 1 (320-1) can operate on the main channel again at the time when the transmission of the PPDU transmitted by at least one of AP 2 (310-2) and non-AP STA 2 (320-2) is completed.

[0130] Here, AP 1 (310-1) may also receive a TXOP return frame transmitted by AP 2 (310-2) and retrieve the shared TXOP. AP 1 (310-1) and non-AP non-AP STA 1 (320-1) may reactivate MOPLEN NPCA when the shared TXOP ends (e.g., end of the shared TXOP period due to time elapsed, completion of the return of the shared TXOP, etc.).

[0131] As another example, AP 1 (310-1) may not separately include an indicator indicating that MOPLEN NPCA is unavailable through at least one of the polling frame and the TXS frame. Specifically, AP 1 (310-1) may separately indicate to the connected non-AP STA, through at least one of the beacon frame, action frame, and other frames, before the Co-TDMA procedure begins, that only PHYLEN NPCA is used during the time length of the shared TXOP. Thus, a separate indicator indicating that MOPLEN NPCA is not used during the time length of the shared TXOP may not be required.

[0132] As another example, AP 1 (310-1) may indicate to a connected non-AP STA that both PHYLEN NPCA and MOPLEN NPCA are used via at least one of a beacon frame, an action frame, and other frames prior to the start of the Co-TDMA procedure. However, if AP 1 (310-1) transmits at least one of a polling frame and a TXS frame, MOPLEN NPCA may be implicitly indicated to be discontinued without a separate indicator, and MOPLEN NPCA may be discontinued within a shared TXOP.

[0133] Referring to FIG. 6b, AP 1 (310-1) can indicate that MOPLEN NPCA is available through at least one of a polling frame and a TXS frame.

[0134] As another example, AP 1 (310-1) may have indicated to the connected non-AP STA via at least one of the beacon frame, action frame, and other frames before the Co-TDMA procedure begins that both PHYLEN NPCA and MOPLEN NPCA are used. Here, AP 1 (310-1) may want to use MOPLEN NPCA even within the shared TXOP of the Co-TDMA operation. AP 1 (310-1) may not separately include an indicator in at least one of the polling frame and TXS frame indicating that MOPLEN NPCA is unavailable. Therefore, since AP 1 (310-1) does not need to change the NPCA operation already indicated to the non-AP STA connected to AP 1 (310-1), MOPLEN NPCA can be used even within the shared TXOP.

[0135] When MOPLEN NPCA is used, AP 1 (310-1) and non-AP STA 1 (320-1) may operate on the NPCA main channel for a period relatively longer than the length of a single PPDU within the shared TXOP interval. Here, AP 1 (310-1) cannot receive the TXOP return frame from AP 2 (310-2). Therefore, a method may be required to prevent AP 2 (310-2) from performing a TXOP return. For example, AP 1 (310-1) may set the TXOP return solicited bit (or subfield) of the polling frame to 0.

[0136] As another example, AP 1 (310-1) can exchange Co-TDMA profile information when performing MAP cooperation with AP 2 (310-2) and AP 3 (310-2). AP 1 (310-1) can instruct AP 2 (310-2) and AP 3 (310-2) that reception of TXOP return frames is impossible by setting the Rx TXOP return support of AP 1 (310-1)'s Co-TDMA profile to 0.

[0137] As another example, AP 1 (310-1) may set the Rx TXOP return support of AP 1 (310-1)'s Co-TDMA profile to 1 to indicate to AP 2 (310-2) and AP 3 (310-2) that reception of TXOP return frames is possible. However, if AP 1 (310-1) indicates that the TXOP return solicited of the polling frame it transmits is 0, AP 2 (310-2) and AP 3 (310-2) may recognize that AP 1 (310-1) is unable to receive TXOP return frames. Alternatively, AP 1 (310-1) may use a separate subfield or bit of the polling frame to indicate that AP 1 (310-1) is unable to receive TXOP return frames, and this is not limited to a specific form.

[0138] As another example, the information described above may also be included in a TXS frame transmitted by AP 1 (310-1). Specifically, if the TXOP return solicited in the TXS frame transmitted by AP 1 (310-1) is indicated as 0, AP 2 (310-2) and AP 3 (310-2) may recognize that AP 1 (310-1) is unable to receive a TXOP return frame. Alternatively, AP 1 (310-1) may indicate that AP 1 (310-1) is unable to receive a TXOP return frame by using a separate subfield or bit of the TXS frame, and is not limited to a specific form.

[0139] AP 2 (310-2) can exchange polling frames and TXS frames with AP 1 (310-1). After receiving a TXS frame, AP 2 (310-2) may not send a TXOP return frame to AP 1 (310-1) in the shared TXOP interval allocated by AP 1 (310-1). AP 1 (310-1) and non-AP STA 1 (320-1) can receive a frame exchange sequence transmitted by at least one of AP 2 (310-2) and non-AP STA 2 (320-2) in the shared TXOP interval. If the MAC variable of AP 1 (310-1) and non-AP STA 1 (320-1), which is determined from the time length of the PPDU (including the TXOP_DURATION information of the PHY preamble) and the time length of the MAC header, is greater than the NPCA minimum duration threshold, AP 1 (310-1) and non-AP STA 1 (320-1) can perform channel access operations and frame transmission / reception operations on the NPCA main channel during the time interval required for the frame exchange sequence of AP 2 (310-2) and non-AP STA 2 (320-2). AP 1 (310-1) and non-AP STA 1 (320-1) can operate on the main channel again at the time when the frame exchange sequence transmitted by at least one of AP 2 (310-2) and non-AP STA 2 (320-2) is completed.

[0140] Notwithstanding the case described above, AP 2 (310-2) may also transmit a TXOP return frame to AP 1 (310-1). AP 2 (310-2) may have transmitted a frame (e.g., PPDU, MDPU) in which AP 1 (310-1) and non-AP STA 1 (320-1) do not satisfy the condition for switching the operating channel to the NPCA main channel during the shared TXOP interval, or AP 1 (310-1) and non-AP STA 1 (320-1) may have transmitted only a frame in which the MOPLEN NPCA condition is not satisfied and only the PHYLEN NPCA condition is satisfied. For example, if AP 2 (310-2) does not transmit an ICF (e.g., a CTS frame, a BSRP trigger frame, a MU-RTS trigger frame) during the shared TXOP interval and transmits the frame with the TXOP_DURATION field of the PPDU (physical layer protocol data unit) preamble set to UNSPECIFIED, AP 1 (310-1) can stop operating on the NPCA main channel at the end of transmission of the frame transmitted by AP 2 (310-2) and operate on the BSS main channel again. In the above case, AP 1 (310-1) can receive the TXOP return frame from AP 2 (310-2), and AP 3 (310-3) can transmit the TXOP return frame to AP 1 (310-1) to return the shared TXOP to AP 1 (310-1).

[0141] FIGS. 6a and 6b may be a method for maintaining NPCA operation for AP 1 (310-1) and non-AP STA 1 (320-1), which is a non-AP STA connected to AP 1 (310-1), even within the shared TXOP interval of AP 1 (310-1). When NPCA operation is performed in Co-TDMA operation, AP 1 (310-1) and non-AP STA 1 (320-1), which is a non-AP STA connected to AP 1 (310-1), may operate on the NPCA main channel for a relatively long time interval, in which case AP 1 (310-1) cannot receive the TXOP return frame. Therefore, the operation of returning the TXOP to AP 1 (310-1) may fail, and to prevent this, the TXOP return frame may not be transmitted by AP 2 (310-2). In addition, when NPCA operation is performed in Co-TDMA operation, only a limited NPCA operation (i.e., PHYLEN NPCA) compared to the existing NPCA operation (e.g., NPCA operation in which both MOPLEN NPCA and PHYLEN NPCA are used) may be required to perform the TXOP return operation normally, and the method described above may be considered. In addition, a method that does not allow NPCA operation in Co-TDMA operation may be required.

[0142] Here, at least one of the polling frame and TXS frame transmitted by AP 1 (310-1) may include an NPCA interruption indicator. As another example, the NPCA operation may be interrupted within the shared TXOP interval of AP 1 (310-1) even if it is included in at least one of the polling frame and TXS frame transmitted by AP 1 (310-1) or if a separate NPCA interruption indicator is not included. When non-AP STA 1 (320-1), a non-AP STA connected to AP 1 (310-1), receives at least one of the polling frame and TXS frame from AP 1 (310-1), it may not perform the NPCA operation within the shared TXOP interval of AP 1 (310-1). Therefore, AP 1 (310-1) may not perform the NPCA operation after transmitting a polling frame or after transmitting a TXS frame. When the shared TXOP of AP 1 (310-1) is terminated (e.g., termination of the shared TXOP interval due to the passage of time, completion of the return of the shared TXOP, etc.), AP 1 (310-1) and non-AP STA 1 (320-1) can resume NPCA operation.

[0143] Meanwhile, the NPCA operation of the present disclosure may be as follows. NPCA may be an operation in which an NPCA STA performs channel access by switching the operating channel to one of the sub-channels other than the main channel among the operating channels of the BSS when the main channel of the BSS to which it belongs is occupied by an OBSS. Specifically, an NPCA AP may designate one of the sub-channels other than the main channel among the operating channels within its BSS as the NPCA primary channel. The NPCA AP may transmit information regarding the NPCA primary channel to an NPCA non-AP STA through frames transmitted within the BSS (e.g., Beacon, Probe Response, UHR OMP (Ultra High Reliability Operation Mode and Parameters)). Additionally, the NPCA AP may negotiate the use of NPCA with an NPCA non-AP STA. The negotiation for NPCA use may be performed through frame exchange between the NPCA AP and the NPCA non-AP STA. If at least one of the NPCA AP and NPCA non-AP STA that negotiated the use of NPCA cannot access the channel because the OBSS occupies the main channel of the BSS to which it belongs, at least one of the NPCA AP and NPCA non-AP STA may perform NPCA to switch its operating channel to the NPCA main channel. At least one of the NPCA AP and NPCA non-AP STA may perform channel access on the NPCA main channel.

[0144] As another example, an NPCA AP can instruct the use of an NPCA operation by setting the value of an indicator (e.g., NPCA Operation Information Present field) included in an information element (e.g., UHR Operation Element) within a frame (e.g., Beacon, Probe response) it transmits to 1 without separate negotiation. An NPCA STA that confirms that the value of the aforementioned NPCA Operation Information Present field within the frame transmitted by the NPCA AP is 1 can perform an NPCA operation and switch the operation channel to the NPCA main channel without separate negotiation if the conditions for performing an NPCA operation are met.

[0145] In addition, it may be efficient to perform the NPCA operation only when the duration for which the OBSS occupies the main channel is sufficiently long. Therefore, a minimum duration threshold for performing the NPCA operation (e.g., NPCA minimum duration threshold) may be set. Additionally, in the NPCA operation, an NPCA switching time (e.g., NPCA switching time) may be required for the NPCA STA to switch its operation channel from the main channel to the NPCA main channel. Conversely, in the NPCA operation, an NPCA switch back time (e.g., NPCA switch back time) may be required for the NPCA STA to switch its operation channel from the NPCA main channel to the main channel. The NPCA STA may indicate information regarding at least one of the aforementioned NPCA main channel, NPCA transition time, NPCA return time, and NPCA minimum time length in the form of a field, subfield, element (e.g., UHR operation element), bit, or other form within a frame (e.g., Beacon, Probe Response, UHR OMN (Ultra High Reliability Operation Mode Notification)) exchanged during the NPCA negotiation process.

[0146] NPCA STA can switch the operation channel to the NPCA main channel if the value of the NPCA Operation Information Present field that it transmits or receives is 1 and satisfies either Condition 1 or Condition 2 below.

[0147]

[0148] Condition 1 (PHY-based NPCA, PHYLEN NPCA)

[0149] If the NPCA STA has received a PPDU on the BSS main channel and / or received a PHY-RXSTART.indication primitive for the HE / EHT / UHR PPDU, and all of the following conditions are true:

[0150] A. When the PPDU received by the above NPCA STA on the main channel of the BSS is classified as an inter-BSS PPDU

[0151] B. If at least one of the following is true:

[0152] i. A case where the NPCA AP corresponding to the BSS to which the above NPCA STA belongs has enabled only PHY Header-based NPCA, and the value of NPCA_PPDU_REM_DUR, a MAC variable of the received PPDU (or configured upon receiving the PPDU), is greater than the value indicated in the NPCA Minimum Duration Threshold field of the most recently received or transmitted NPCA for the BSS to which the above NPCA STA belongs, or

[0153] ii. When the NPCA AP of the affiliated BSS has also enabled MAC Header-based NPCA, and one or more of the NPCA_PHY_TXOP_REM_DUR or NPCA_PPDU_REM_DUR set from the received PPDU are greater than the above Threshold

[0154] C. The bandwidth of the above PPDU is determined to be 20, 40, 80, or 160 MHz by the above NPCA STA, based on the in-band channel allocation information indicated in the Bandwidth field within the PHY preamble of the above PPDU and the RXVECTOR parameter RU_ALLOCATION of PHY-RXSTART.indication() associated with the said PPDU, provided that the channel occupied by the said PPDU does not overlap with the NPCA PCH

[0155] D. When the intra BSS NAV of the above NPCA STA is 0

[0156]

[0157] Condition 2 (MAC-based NPCA, MOPLEN NPCA)

[0158] If all of the following conditions are satisfied

[0159] A. The NPCA STA receives all or part of a series of PPDUs separated by SIFS (short interframe space) in the BSS PCH, the reception of the first PPDU is the reception of a PPDU containing an Initial Control Frame (ICF), which is the start frame of the Control Frame exchange, the reception of the second PPDU is the reception of a PPDU containing an Initial Control Response Frame (ICR), which is the response frame to the said ICF (however, the second PPDU may not have been received), and the reception of the third PPDU is the reception of the preamble of a PPDU transmitted after the said Control Frame exchange, and the NPCA STA generates the PHY-RXSTART.indication or / and the PHY-RXEARLYSIG.indication. and, all subsequent conditions must be satisfied.

[0160] B. If a PHY-RXEARLYSIG.indication or PHY-RXSTART.indication primitive corresponding to the third PPDU described above is received from the PHY, and this reception occurs during the NPCA_START_TIMEOUT period starting from the time the MAC received the PHY-RXEND.indication primitive for the first PPDU

[0161] i. NPCA_START_TIMEOUT is (2 x aSIFSTime) + (2 x aSlotTime) + aRxPHYStartDelay + ICR_Timeout,

[0162] (1) ICR_Timeout is the length of the expected CTS frame when the ICF is an RTS or MU-RTS trigger frame.

[0163] (2) ICR_Timeout is the value of the UL Length field of the BSRP trigger frame if the ICF is a BSRP trigger frame

[0164] C. If one of the above PPDU sequences is classified as an inter-BSS PPDU by the above NPCA STA

[0165] D. If at least one of the following is true:

[0166] i. If the NPCA AP has enabled only PHY Header-based NPCA, and the value of the NPCA_PPDU_REM_DUR MAC variable of the third received PPDU (or configured upon receiving the PPDU) is greater than the value of the NPCA Minimum Duration Threshold field most recently received or transmitted to the BSS to which the NPCA STA belongs.

[0167] ii. If the NPCA AP has activated MAC Header-based NPCA along with PHY Header-based NPCA, and the value of the NPCA_CFRAME_TXOP_REM_DUR MAC variable of the first PPDU (including ICF) in the above PPDU sequence (or configured upon receiving the PPDU) is greater than the value of the NPCA Minimum Duration Threshold field most recently received or transmitted for the BSS to which the NPCA STA belongs

[0168] E. When the bandwidth of the received PPDUs is determined to be 20, 40, 80, or 160 MHz by the NPCA STA based on the bandwidth information indicated in the received PPDU or the CH_BANDWIDTH_IN_NON_HT value, which is an RXVECTOR parameter of the received PPDU, and the channel occupied by the PPDUs does not overlap with the NPCA primary channel

[0169] i. If the Control Frame (ICF) is an RTS (request to send) frame within a non-HT (duplicate) PPDU, the RTS frame has a transmitter address (TA) field containing bandwidth information, wherein the signaled bandwidth is one of 20, 40, 80, or 160 MHz

[0170] ii. The channel occupied by a CTS (clear to send) frame within a non-HT (duplicate) PPDU is determined through the RTS frame or MU-RTS frame that elicited the corresponding CTS response.

[0171] F. If the intra BSS NAV of the above NPCA STA is 0 at the time of occurrence of the PHY-RXSTART.indication and / or PHY-RXEARLYSIG.indication caused by the reception of the first PPDU containing the ICF

[0172]

[0173] In addition, the following three MAC variables may be used to determine whether at least one of the AP and STA switches the operating channel to the NPCA main channel.

[0174]

[0175] NPCA_PPDU_REM_DUR

[0176] NPCA_PPDU_REM_DUR is set to the total length of the PPDU (e.g., RXTIME) that the NPCA STA can identify in the PPDU header, excluding the time difference between when the NPCA STA's PHY layer detects the first PPDU and generates the PHY-CCA.indication(BUSY) primitive and when it generates the PHY-RXSTART.indication primitive.

[0177]

[0178] NPCA_PHY_TXOP_REM_DUR

[0179] The NPCA_PHY_TXOP_REM_DUR variable is set to the value obtained by subtracting the time difference between when the PHY layer of the NPCA STA detects the first PPDU and generates the PHY-CCA.indication(BUSY) primitive and when it generates the PHY-RXSTART.indication primitive from the sum of the total length of the PPDU (e.g., RXTIME) and the TXOP_DURATION value that the NPCA STA can identify in the PPDU header.

[0180]

[0181] NPCA_CFRAME_TXOP_REM_DUR

[0182] The NPCA_CFRAME_TXOP_REM_DUR variable is set to the value of the duration / ID field of the MAC header of the control frame received by the NPCA STA.

[0183]

[0184] In addition, it is necessary to define the timing and duration of switching the operating channel to the NPCA main channel, and a method for setting MAC variables listed with the REM_DUR suffix may be required.

[0185] For example, at least one of the AP and STA within the BSS receives the PPDU of the OBSS and can check the time length of the PPDU in the PPDU preamble of the OBSS. Additionally, at least one of the AP and STA within the BSS can check the time length of the communication interval of the OBSS in the PPDU preamble of the OBSS. Here, the point in time at which the time length of the OBSS PPDU can be checked may be the point in time when the PHY-RXSTART.indication primitive for the PPDU occurs. Here, at the point in time when the PHY-RXSTART.indication primitive occurs, the MAC variable value may be set as follows.

[0186] o NPCA_PPDU_REM_DUR : PPDU duration - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) caused by PPDU to the occurrence of PHY-RXSTART.indication)

[0187] o NPCA_PHY_TXOP_REM_DUR: PPDU time length + TXOP time length included in PPDU - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) by PPDU to the occurrence of PHY-RXSTART.indication)

[0188] o NPCA_CFRAME_TXOP_REM_DUR: No impact

[0189]

[0190] As another example, at least one of the AP and STA within the BSS may receive the PPDU of the OBSS. Here, if the OBSS PPDU includes an initial control frame (e.g., RTS frame, CTS frame, MU-RTS trigger frame, BSRP trigger frame), the time length of the OBSS communication interval can be determined from the duration field of the MAC header of the initial control frame included in the OBSS PPDU. The point in time at which the time length of the OBSS PPDU and the duration / ID field of the MAC header can be determined may be the point in time when the PHY-RXEND primitive for the PPDU occurs, and this point in time may be time T1. Here, at the point in time when the PHY-RXEND primitive occurs, the MAC variable value may be set as follows.

[0191]

[0192] o NPCA_PPDU_REM_DUR: PPDU duration - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) caused by PPDU to the occurrence of PHY-RXSTART.indication)

[0193] o NPCA_PHY_TXOP_REM_DUR: PPDU time length + TXOP time length included in PPDU - (Time elapsed from the occurrence of PHY-CCA.indication(BUSY) by PPDU to the occurrence of PHY-RXSTART.indication)

[0194] o NPCA_CFRAME_TXOP_REM_DUR: The value of the duration field indicated by the MAC header of the initial control frame.

[0195]

[0196] The time point when the above PHY-RXSTART.indication primitive occurs or the time point when the PHY-RXEND primitive occurs can be called time point T1.

[0197] When PHYLEN NPCA is used in BSS 1, at least one of the APs and STAs in the BSS may switch the operating channel to the NPCA main channel if, at time T1, the NPCA_PPDU_REM_DUR value is greater than the most recently transmitted NPCA minimum duration threshold value. Here, when MOPLEN NPCA is used in addition to PHYLEN NPCA in BSS 1, at least one of the APs and STAs in the BSS may switch the operating channel to the NPCA main channel if, at time T1, the NPCA_PHY_TXOP_REM_DUR value or the NPCA_CFRAME_TXOP_REM_DUR value is greater than the most recently transmitted NPCA minimum duration threshold value.

[0198] Additionally, the NPCA TIMER may be the time during which the NPCA main channel operates, and may be a timer managed by the NPCA STA (at least one of the AP and STA within the BSS). The NPCA TIMER may be set based on the value of the MAC variable described above, and when the NPCA TIMER expires (e.g., the value reaches 0), the NPCA STA may operate on the main channel again. The NPCA TIMER may decrease in a time-dependent manner from the point at which the NPCA STA switches the operating channel to the NPCA main channel. If the NPCA STA switches the operating channel immediately at time T1, or if only PHYLEN NPCA is used in BSS 1, the NPCA TIMER may be the value NPCA_PPDU_REM_DUR. As another example, if MOPLEN NPCA is used in BSS 1, the NPCA TIMER can be set to the largest value among NPCA_PPDU_REM_DUR, NPCA_PHY_TXOP_REM_DUR, and NPCA_CFRAME_TXOP_REM_DUR.

[0199] If the NPCA STA is unable to immediately switch the operating channel at time T1, the MAC variable described above may decrease the corresponding value at each time interval. Subsequently, when the NPCA STA switches the operating channel to the NPCA main channel, if only PHYLEN NPCA is used in BSS 1, the NPCA TIMER may be set to the value obtained by subtracting the NPCA switching back delay time value (the time delay value required to switch the operating channel from the NPCA main channel to the main channel for each NPCA STA) from the NPCA_PPDU_REM_DUR value. If MOPLEN NPCA is also used in BSS 1, the NPCA TIMER may be set to the value obtained by subtracting the NPCA switching back delay time value for each NPCA STA from the largest value among NPCA_PPDU_REM_DUR, 4NPCA_PHY_TXOP_REM_DUR, and NPCA_CFRAME_TXOP_REM_DUR.

[0200] FIG. 7 is a diagram showing a wireless LAN network to which the present disclosure applies, and FIG. 8 is a diagram showing a wireless LAN Co-TDMA operation method and problems to which the present disclosure applies. Referring to FIG. 7 and FIG. 8, at least one AP may operate in a wireless LAN network. A wireless LAN network for Co-TDMA may be configured in the present disclosure, but this is for convenience of explanation only and is not limited thereto.

[0201]

[0202] [Co-TDMA Wireless LAN Network Configuration]

[0203] Consider a case where AP 1 (510-1) and AP 2 (510-2) are in operation. AP 1 (510-1) may be associated with and operated by non-AP STA 1 (520-1), and AP 1 (510-1) and non-AP STA 1 (520-1) may form a single basic service set (BSS). In the same way, AP 2 (510-2) may be associated with and operated by non-AP STA 2 (520-2), and AP 2 (510-2) and non-AP STA 2 (520-2) may form a different BSS. For example, in the present disclosure, the BSS formed by AP 1 and non-AP STA 1 (520-1) may be referred to as BSS 1, and the BSS formed by AP 2 and non-AP STA 2 (520-2) may be referred to as BSS 2, but this is for convenience of explanation only and is not limited thereto. Hidden nodes may occur in a wireless LAN network. For example, non-AP STA 1 (520-1) may be unable to receive frames transmitted by AP 2 and non-AP STA 2 (520-2), and vice versa. Additionally, AP 1 may be able to receive frames from AP 2 but may be unable to receive frames from non-AP STA 2 (520-2).

[0204] Co-TDMA operation for sharing acquired time resources between APs in a wireless LAN network may be supported. For example, the time resource acquired by an AP may be a transmit opportunity (TXOP). A TXOP may be a time interval during which the AP (or the AP's channel access function (e.g., EDCA Function, EDCAF)) has the right to occupy the wireless medium and transmit a frame after the AP successfully performs a channel access operation (e.g., performing an enhanced distributed channel access (EDCA) backoff operation and channel access operation). For example, the TXOP may be an EDCA TXOP, but is not limited thereto. The Co-TDMA procedure may be performed through a multi-AP coordination (MAPC) negotiation or setup procedure involving multiple APs (e.g., AP 1 and AP 2).

[0205] The following description is based on the case where Co-TDMA operation is performed in the [Co-TDMA Wireless LAN Network Configuration] described above, but it is not limited thereto.

[0206] [Co-TDMA Operation Steps]

[0207] Referring to FIG. 8, AP 1 (510-1) may acquire a TXOP and want to share the TXOP with AP 2 (510-2). The Co-TDMA operation may be performed in two stages. The first stage may be a polling stage that searches for an AP that wishes to share the TXOP through the Co-TDMA operation. AP 1 (510-1) may transmit a polling initial control frame during the polling stage. The polling initial control frame may be, but is not limited to, a BSRP (buffer status report poll) trigger frame (601). The BSRP trigger frame (601) may contain information that AP 1 (510-1) wishes to share the TXOP through the Co-TDMA operation. An AP that wishes to share the TXOP of AP 1 (510-1) may respond to the polling frame of AP 1 (510-1). For example, AP 2 (510-2) may want to share a TXOP from AP 1 (510-1), send a polling frame in response to a polling frame from AP 1 (510-1), and send a polling response frame (e.g., Multi-STA BlockAck frame, 602) after SIFS. AP 1 (510-1) may recognize that AP 2 (510-2) wants to participate in Co-TDMA operation. The value of the duration field in the MAC header of the polling frame may be set to 'length of the polling response frame + aSIFSTime' which is sent by the other AP (e.g., AP 2 (510-2)) after the completion of the transmission of the polling frame.

[0208] Subsequently, the second step, the TXOP allocation step, may proceed. AP 1 (510-1) may send a MU-RTS (multi-user request to send) trigger frame (603) to the STA that wishes to share the TXOP during the TXOP allocation step. Specifically, the MU-RTS trigger frame (or MU-RTS TXS trigger frame, 603) used during the TXOP allocation step may be a MU-RTS TXS (TXOP sharing) variant trigger frame, but is not limited thereto. The user info field of the MU-RTS trigger frame (603) may include the AP ID (identifier) ​​of AP 2 (510-2). The AP ID of AP 2 (510-2) may be an identifier of AP 2 (510-2) that is different from the MAC address of AP 2 (510-2). For example, the AP ID of AP 2 (510-2) may be an identifier that AP 1 (510-1) and AP 2 (510-2) negotiate with each other, but is not limited thereto. For example, the AP ID of AP 2 (510-2) may be set (assigned) by AP 1 (510-1) and AP 2 (510-2) in a MAPC negotiation or setup procedure. The AP ID is an identifier for identifying each AP, and AP 1 (510-1) and AP 2 (510-2) may have different AP IDs.

[0209] The allocation duration field of the user info field of the MU-RTS trigger frame (603) may indicate the time length of the TXOP allocated by AP 1 (510-1) to AP 2 (510-2). The value of the MAC header duration field of the MU-RTS trigger frame (603) may be set to 'length of the CTS (clear to send) frame + aSIFSTime' transmitted by another AP (e.g., AP 2 (510-2)). AP 2 (510-2) receives the MU-RTS trigger frame (603) from AP 1 (510-1) and may transmit a CTS frame (604), which is a response frame to the MU-RTS trigger frame (603). The CTS frame (604), which is a response frame, may be transmitted after SIFS time from the time of completion of transmission of the MU-RTS trigger frame (603). Here, the point in time when AP 1 (510-1) starts assigning TXOP to AP 2 (510-2) may be from the point of completion of transmission of the MU-RTS trigger frame (603). After transmitting the CTS frame (604), AP 2 (510-2) can perform frame exchange with non-AP STA 2 (520-2) connected to AP 2 (510-2). For example, AP 2 (510-2) can transmit a downlink data frame (605) to non-AP STA 2 (520-2).

[0210] For example, the polling trigger frame used in the polling step described above may be referred to as a polling frame in this disclosure, and the MU-RTS trigger frame used in the TXOP allocation step may be referred to as an allocation frame in this disclosure, but this is for convenience of explanation only and is not limited to such terms.

[0211] AP 1 (510-1) is a coordinating AP that shares TXOPs with other APs as a TXOP holder, and AP 2 (510-2) may be a coordinated AP that shares TXOPs from AP 1 (510-1), which is the coordinating AP. When AP 1 (510-1) performs a polling phase and an allocation phase within an acquired TXOP, AP 1 (510-1) may be required to use a portion of its TXOP (e.g., 33 percent, but not limited thereto) for frame exchange with at least one non-AP STA (e.g., non-AP STA 1 (520-1)) connected to AP 1 (510-1). Here, the corresponding phase may be a data communication phase. The acquired TXOP may be a time interval that includes all periods during which Co-TDMA operates (i.e., a time interval that includes all of the polling phase, data communication phase, and allocation phase). For example, AP 1 (510-1) may not be allowed to proceed to an allocation step immediately after the polling step (e.g., immediately after the SIFS time, which is the shortest inter-frame time interval used within the TXOP, after receiving an ICR, which is a response frame to a BSRP trigger frame from AP 2 (510-2)). AP 1 (510-1) may be allowed to proceed to an allocation step after the polling step, after AP 1 (510-1) performs frame exchange with non-AP STA 1 (520-1) using part of the TXOP, and then share the TXOP with AP 2 (510-2). If AP 1 (510-1) performs Co-TDMA operation, the first frame transmitted within the TXOP acquired by AP 1 (510-1) may be a polling ICF for performing the polling step. The duration field of the polling ICF can only indicate the SIFS time and the length of the ICR for the polling ICF.

[0212] When a non-AP STA 1 (520-1) connected to AP 1 (510-1) receives a polling frame (601) transmitted by AP 1 (510-1) during the polling phase, it can set the NAV based on the MAC header duration field. Here, although the non-AP STA 1 (520-1) cannot detect the polling response frame of AP 2 (510-2) due to the hidden node problem, the NAV can be set until the time when the transmission of the polling response frame of AP 2 (510-2) is completed. The non-AP STA 1 (520-1) can release the NAV after the time when the transmission of the polling response frame of AP 2 (510-2) is completed has elapsed. Additionally, when the non-AP STA 1 (520-1) receives an allocation frame (603) of AP 1 (510-1), it can set the NAV based on the MAC header duration field. Here, non-AP STA 1 (520-1) cannot detect the CTS frame of AP 2 (510-2) due to a hidden node problem, but can set NAV until the transmission of the CTS frame of AP 2 (510-2) is complete. non-AP STA 1 (520-1) can release NAV once the transmission of the CTS frame of AP 2 (510-2) is complete.

[0213] Here, NAV may be a NAV timer. That is, NAV is a timer whose value can decrease over time. For example, NAV being set may mean setting a NAV that previously had a value of 0 to a non-zero value. NAV is used for virtual carrier sense operations, and if NAV is not 0, the medium is considered occupied and channel access operations may not be performed. Here, NAV may be released when NAV becomes 0. A non-AP STA 1 (520-1) can manage a single NAV, but it is also possible to manage two NAVs: an intra-BSS NAV and a Basic NAV. When non-AP STA 1 (520-1) receives a frame (intra-BSS PPDU) from its own BSS (e.g., a BSS configured by AP 1 (510-1), which is the AP to which non-AP STA 1 (520-1) is connected), it updates the intra-BSS NAV, and when it receives a frame (inter-BSS PPDU) from a BSS other than its own BSS or cannot determine the BSS from which the frame was transmitted, it updates the Basic NAV. In this case, when non-AP STA 1 (520-1) manages a single NAV, it manages only the Basic NAV.

[0214] AP 1 (510-1) may not transmit a frame until it receives a frame from AP 2 (510-2) that requires an immediate acknowledgment frame within the allocated time. non-AP STA 1 (520-1) cannot receive data frames from AP 2 (510-2). Therefore, when the NAV is released because AP 1 (510-1) does not transmit a frame, non-AP STA 1 (520-1) can detect the medium as idle, and non-AP STA 1 (520-1) can perform a channel access operation. If the channel access operation is successful, non-AP STA 1 (520-1) can transmit a frame (e.g., an uplink data frame) to AP 1 (510-1). The uplink data frame may be a frame that requires an immediate acknowledgment frame. However, AP 1 (510-1) may not be able to transmit a response frame for the uplink data frame (606) of non-AP STA 1 (520-1) according to Co-TDMA operation. Alternatively, AP 1 (510-1) may not be able to transmit a response frame for the uplink data frame (606) of non-AP STA 1 (520-1) because it is impossible to receive the uplink data frame (606) of non-AP STA 1 (520-1) while AP 1 (510-1) is receiving a data frame transmitted by AP 2 (510-2) (i.e., a collision occurs). In the above case, non-AP STA 1 (520-1) can determine that frame transmission has failed, and non-AP STA 1 (520-1) can increase the channel access parameter (e.g., QSRC (QoS STA Retry Counter) [AC]). Additionally, non-AP STA 1 (520-1) can increase the CW (contention window) [AC] as QSRC increases, and the retransmission counter of the MSDU (MAC service data unit) can also increase.An increase in QSRC and the resulting increase in CW can reduce the channel access priority of non-AP STA 1 (520-1). Additionally, an increase in the MSDU retransmission counter can cause MSDUs to be discarded. For example, if the MSDU retransmission counter reaches a certain threshold, the MSDU may be discarded. That is, MSDUs associated with frames transmitted by non-AP STA 1 (520-1) may be unnecessarily discarded. In the above case, non-AP STA 1 (520-1) may experience reduced transmission performance in the Co-TDMA procedure, and non-AP STA 1 (520-1) may unnecessarily lower the modulation and coding scheme (MCS) if the transmission of a frame to AP 1 (510-1) fails. Accordingly, the time required for frame transmission of non-AP STA 1 (520-1) may increase, and measures may be needed to reduce the channel access delay of non-AP STA 1 (520-1) and prevent the MCS from being lowered. AP 1 (510-1) may receive a frame requiring an immediate response frame from non-AP STA 1 (520-1) without receiving a frame from AP 2 (510-2) or a frame from a non-AP STA connected to AP 2 (510-2) (e.g., non-AP STA 2 (520-2)) within the allocated time. The same problem as above may occur even if AP 1 (510-1) does not transmit an immediate response frame to non-AP STA 1 (520-1) in order to avoid causing interference with the communication of AP 2 (510-2). If AP 1 (510-1) transmits an immediate response frame to non-AP STA 1 (520-1), the immediate response frame of AP 1 (510-1) may cause interference with the communication of AP 2 (510-2), and the transmission of data frames by AP 2 (510-2) and non-AP STA 2 (520-2) connected to AP 2 (510-2) may fail.Accordingly, a method is also required to ensure that the transmission of data frames from AP 2 (510-2) and non-AP STA 2 (520-2) connected to AP 2 (510-2) does not fail. In FIGS. 9 to 19 below, the wireless LAN network configuration and Co-TMDA operation described above may be applied identically, and some operations may be performed differently depending on the operation of each figure.

[0215] FIG. 9 is a diagram showing a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applied to the present disclosure.

[0216] Referring to FIG. 9, FIG. 9 can use a wireless LAN network that follows the [Co-TDMA wireless LAN network configuration], which is the same wireless LAN network configuration as FIG. 8. AP 1 (510-1) can acquire a TXOP in the [Co-TDMA operation step] described above and exchange a polling frame (601) and a response frame (602) with AP 2 (510-2). After that, AP 1 (510-1) can exchange an allocation frame (603) and a CTS frame, which is a response frame (604) to the allocation frame. Here, non-AP STA 1 (520-1) can set a transmission prohibition period when receiving the allocation frame (603).

[0217] For example, non-AP STA 1 (520-1) can check the allocation frame (603) transmitted by AP 1 (510-1). The transmitter address (TA) of the allocation frame may be the MAC address of AP 1 (510-1). The receiver address (RA) of the MAC header of the allocation frame may be a broadcast address. non-AP STA 1 (520-1) can check the user info field of the allocation frame. For example, non-AP STA 1 (520-1) can check the user info field even if the association identifier (AID) of the user info field of the allocation frame is not set to its own AID. Additionally, non-AP STA 1 (520-1) can check the user info field even if the AID of the user info field is not set to its own AID when AP 1 (510-1) transmitted a polling frame prior to transmitting the allocation frame. Alternatively, non-AP STA 1 (520-1) can check the user info field when the value of the MAC header duration field of the allocated frame of AP 1 (510-1) is set to 'length of CTS frame + aSIFSTime'. Alternatively, non-AP STA 1 (520-1) can check all user info fields even if they are not set to its own AID, regardless of the above.

[0218] AP 1 (510-1) may have indicated the AP ID of a Co-TDMA target AP (e.g., AP 2 (510-2)) to non-AP STA 1 (520-1). non-AP STA 1 (520-1) can check the user info field corresponding to the AP ID of AP 2 (510-2). As another example, the common info field of an allocation frame may include an indicator indicating that the allocation frame is a variant of a MU-RTS TXS trigger frame. This indicator is a TXS mode subfield, and in the case of an allocation frame, the value may be indicated as 2. For example, non-AP STA 1 (520-1) can receive an allocation frame and check all user info fields even if they are not set as its own AID when the value of the TXS mode subfield is 2. The user info field of the allocation frame includes an allocation duration field, which may be the length of time during which the target AP allocated by the allocation frame can actually perform communication (length of the shared (allocated) TXOP interval). The non-AP STA 1 (520-1) checks the allocated duration and may set a period (transmission prohibition period) during which transmission to AP 1 (510-1) is prohibited for the allocated duration from the time the allocation frame is received. For example, the transmission prohibition period may be an NAV (more specifically, an update of the NAV timer corresponding to the transmission prohibition period), but is not limited thereto. In cases where the transmission ban period is not an operation by NAV, non-AP STA 1 (520-1) may have an operation in which the transmission queues of channel access functions (e.g., EDCAFs for each AC (access categories)) are considered empty during the transmission ban period, or the operation of channel access functions is suspended, or channel access functions are made to repeatedly perform channel access operations without transmitting frames.If the transmission prohibition period is an operation by NAV and non-AP STA 1 (520-1) manages the basic NAV and the intra-BSS NAV, non-AP STA 1 (520-1) can update the intra-BSS NAV. That is, the intra-BSS NAV is set. Alternatively, even if non-AP STA 1 (520-1) manages both the basic NAV and the intra-BSS NAV, non-AP STA 1 (520-1) can update the basic NAV. Alternatively, if non-AP STA 1 (520-1) manages only the basic NAV, non-AP STA 1 (520-1) can update the basic NAV. Until the NAV timer expires (the NAV timer reaches 0), non-AP STA 1 (520-1) can detect the medium in an occupied state. When a transmission prohibition period is set, non-AP STA 1 (520-1) may not perform the operation of transmitting a frame to AP 1 (510-1) even after AP 1 (510-1) has allocated a TXOP to AP 2 (510-2). When the transmission prohibition period ends, non-AP STA 1 (520-1) may perform channel access and transmit a frame to AP 1 (510-1). If the AID of the user info field of the allocated frame of AP 1 (510-1) is the AID of non-AP STA 1 (520-1), non-AP STA 1 (520-1) may not set the transmission prohibition period described above. Here, a frame in which the AID of the aforementioned user info field is non-AP STA 1 (520-1) is a frame indicating that AP 1 (510-1) shares a TXOP with non-AP STA 1 (520-1). Alternatively, even if a transmission prohibition period is set, that transmission prohibition period may be ignored. In addition to the aforementioned basic NAV and intra-BSS NAV, non-AP STA 1 (520-1) includes channel access functions within non-AP STA 1 (520-1) (e.g.The TXNAV timer (or TXNAV) can be updated to stop channel access of the EDCAFs. That is, the non-AP STA 1 (520-1) updates the TXNAV to set a transmission prohibition period. When the TXNAV of the non-AP STA 1 (520-1) is updated, the channel access functions within the non-AP STA 1 (520-1) can detect that the medium is occupied and stop operation until the timer expires (i.e., the TXNAV reaches 0). The non-AP STA 1 (520-1) may also update all of the above-mentioned basic NAV, intra-BSS NAV, and TXNAV.

[0219] The transmission ban period may end when AP 1 (510-1) has an allocated time. Alternatively, the transmission ban period may end early. For example, if non-AP STA 1 (520-1) receives a frame transmitted by the AP before the transmission ban period has ended, the transmission ban period may end. For another example, if non-AP STA 1 (520-1) receives a frame transmitted by AP 1 (510-1) to protect Co-TDMA operation, the transmission ban period may not end. If the transmission prohibition period is NAV and the recipient of the frame received by non-AP STA 1 (520-1) from AP 1 (510-1) is non-AP STA 1 (520-1) (e.g., the RA of the received frame indicates the MAC address of non-AP STA 1 (520-1) or / and the received frame is a trigger frame, and the identifier of non-AP STA 1 (520-1) (e.g., AID (association identifier)) in the trigger frame indicates the uplink resource), non-AP STA 1 (520-1) does not update the NAV by the frame received from AP 1 (510-1). Additionally, the frame transmitted by AP 1 (510-1) to non-AP STA 1 (520-1) may be a frame requesting the transmission of an immediate response frame (including the transmission of an uplink frame that non-AP STA 1 (520-1) must transmit based on the uplink resources allocated in the trigger frame). non-AP STA 1 (520-1) may transmit a response frame for a frame received by AP 1 (510-1) even if a transmission prohibition period is set. Specifically, if the transmission prohibition period set by non-AP STA 1 (520-1) is an intra-BSS NAV, non-AP STA 1 (520-1) may ignore the NAV and transmit a response frame to AP 1 (510-1) regardless of what frame is received from AP 1 (510-1).Alternatively, if the transmission prohibition period set by non-AP STA 1 (520-1) is the default NAV, non-AP STA 1 (520-1) may send a response frame to AP 1 (510-1) when the frame received from AP 1 (510-1) is not a trigger frame. Exceptionally, if non-AP STA 1 (520-1) updates the default NAV timer by the allocation frame of AP 1 (510-1), non-AP STA 1 (520-1) may be able to ignore the NAV and send a response frame to AP 1 (510-1) regardless of the frame received from AP 1 (510-1). If the transmission ban period is NAV and the recipient of the frame received by non-AP STA 1 (520-1) from AP 1 (510-1) is not non-AP STA 1 (520-1), and the MAC header duration field value of the received frame is longer than the end time of the transmission ban period, non-AP STA 1 (520-1) can update the transmission ban period to the value of the MAC header duration field received from AP 1 (510-1).

[0220] For example, AP 2 (510-2) may want to return the TXOP allocated from AP 1 (510-1) early and may send a TXOP return frame (607) denoted as 'R' to AP 1 (510-1). Upon receiving the TXOP return frame (607), AP 1 (510-1) may send an acknowledgment frame (e.g., Ack frame, BlockAck frame) and subsequently send another frame from its TXOP (e.g., downlink data frame, trigger frame, or polling frame / assignment frame that assigns the TXOP to another AP other than AP 2 (510-2)). That is, in the above case, AP 1 (510-1) may send a frame from its remaining TXOP. When AP 1 (510-1) transmits a frame within the transmission prohibition period of non-AP STA 1 (520-1), non-AP STA 1 (520-1) can receive the frame transmitted by AP 1 (510-1) and non-AP STA 1 (520-1) can release the transmission prohibition period described above. As another example, when AP 1 (510-1) transmits a frame within the transmission prohibition period of non-AP STA 1 (520-1), non-AP STA 1 (520-1) can transmit an immediate response frame (including the transmission of an uplink frame that non-AP STA 1 (520-1) must transmit based on the uplink resources allocated in the trigger frame) without releasing the transmission prohibition period described above, or perform a transmission prohibition period update.

[0221] FIG. 10 is a diagram showing a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applied to the present disclosure.

[0222] FIG. 10 may use a wireless LAN network that follows the [Co-TDMA wireless LAN network configuration], which is the same wireless LAN network configuration as FIG. 8. AP 1 (510-1) can acquire a TXOP in the [Co-TDMA operation step] described above and exchange a polling frame (601) and a response frame (602) with AP 2 (510-2). Subsequently, AP 1 (510-1) can exchange an allocation frame (603) and a CTS frame, which is a response frame to the allocation frame (604), with AP 2 (510-2). STA 1 can transmit a frame to AP 1 (510-1) within the TXOP of AP 1 (510-1) as described above in FIG. 8, and QSRC[AC] and CW[AC] may increase depending on the transmission failure. In addition, the MCS of non-AP STA 1 (520-1) may be lowered as described above due to transmission failure, and the time required for frame transmission may increase accordingly.

[0223] AP 1 (510-1) may transmit an unavailability indication frame (608) indicating that frame transmission was impossible due to Co-TDMA of AP 1 (510-1) after the termination of the TXOP assigned to AP 2 (510-2). The unavailability indication frame (608) may be a BlockAck frame in which an unavailable indication bit is set in the BlockAck frame. The BlockAck frame may be a standard BlockAck frame, a Multi-STA BlockAck frame variant, and is not limited to a specific form. If AP 1 (510-1) recognizes that it has received a frame from non-AP STA 1 (520-1) while assigning a TXOP to AP 2 (510-2), AP 1 (510-1) may transmit the unavailability indication frame (608) to non-AP STA 1 (520-1). Alternatively, AP 1 (510-1) may not recognize that it has received a frame from non-AP STA 1 (520-1) or may consider other STAs other than non-AP STA 1 (520-1). Here, the recipient address of the unavailable indication frame (608) may be set to a broadcast address and transmitted. A STA (e.g., non-AP STA 1 (520-1)) that receives the unavailable indication frame (608) from AP 1 (510-1) may decrease the increased QSRC (or set it to an initial value). Additionally, a STA (e.g., non-AP STA 1 (520-1)) that receives the unavailable indication frame (608) from AP 1 (510-1) may increase the MCS that was decreased due to the frame transmission failure (e.g., increase to a maximum value or increase to the value prior to the consecutive frame failure) and may decrease the retry counter of the MSDU.

[0224] FIG. 11 is a diagram illustrating a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0225] FIG. 11 may use a wireless LAN network that follows the [Co-TDMA wireless LAN network configuration], which is the same wireless LAN network configuration as FIG. 10 and FIG. 8. AP 1 (510-1) can acquire a TXOP in the [Co-TDMA operation step] described above and exchange a polling frame (601) and a response frame (602) with AP 2 (510-2). Subsequently, AP 1 (510-1) can exchange an allocation frame (603) and a CTS frame, which is a response frame (604) to the allocation frame, with AP 2 (510-2). Here, AP 1 (510-1) may indicate communication unavailability information that can be verified by non-AP STA 1 (520-1) in the polling frame transmitted during the polling step. The communication unavailability information may be DUO (dynamic unavailability) information, but is not limited thereto. DUO information may be unavailability information where communication is impossible in the TXOP acquired by AP 1 (510-1). Here, the unavailability information may indicate the start time and duration of the unavailability of AP 1 (510-1), and may be an unavailability period. AP 1 (510-1) may set the unavailability period to the expected start time of the TXOP period shared by AP 1 (510-1) and set the duration of the unavailability period to the expected duration of the TXOP period shared by AP 1 (510-1), or it may set the duration of the unavailability period to indefinite.

[0226] The recipient address (RA) of the MAC header of the polling frame (601) of AP 1 (510-1) containing DUO information can be set as a broadcast address, and can be received by non-AP STA 1 (520-1) connected to AP 1 (510-1). Alternatively, non-AP STA 1 (520-1) can receive the polling frame (601) transmitted by AP 1 (510-1) even if the recipient address is not the MAC address of non-AP STA 1 (520-1). In the above case, the recipient address (RA) of the MAC header of the polling frame of AP 1 (510-1) containing DUO information can be set as either a broadcast address or a unicast address. When non-AP STA 1 (520-1) receives a polling frame (601) from AP 1 (510-1), it can recognize that AP 1 (510-1) is unavailable in the TXOP of AP 1 (510-1). Therefore, non-AP STA 1 (520-1) may not perform the operation of transmitting a frame to AP 1 (510-1) within the TXOP of AP 1 (510-1). When the unavailable period of AP 1 (510-1) ends, non-AP STA 1 (520-1) can perform channel access and transmit a frame to AP 1 (510-1). AP 1 (510-1) can transmit a frame to non-AP STA 1 (520-1) if the shared TXOP period is returned early by AP 2 (510-2) or if the shared TXOP period is completed. AP 1 (510-1) may also transmit a frame that directs information to release an unavailable section directed by AP 1 (510-1) by setting it to the MAC address of non-AP STA 1 (520-1), the MAC address of multiple STAs including non-AP STA 1 (520-1), or a broadcast MAC address.

[0227] FIG. 12 is a diagram illustrating a method for preventing frame transmission failure during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0228] FIG. 12 can use a wireless LAN network that follows the [Co-TDMA wireless LAN network configuration], which is the same wireless LAN network configuration as FIG. 8. AP 1 (510-1) can share the TXOP of AP 1 (510-1) with AP 2 (510-2) based on the [Co-TDMA operation steps] described above.

[0229] AP 1 (510-1) may set a time interval during which non-AP STA 1 (520-1) does not transmit frames to AP 1 (510-1) separately before performing the [Co-TDMA operation step] for sharing TXOPs with AP 2 (510-2). For example, AP 1 (510-1) may transmit a beacon frame (609). The beacon frame (609) transmitted by AP 1 (510-1) may include at least one of a quiet element and a quiet channel element. For convenience of explanation, the quiet element and the quiet channel element are described in this disclosure based on the quiet element, but the same may apply to the quiet channel element. The silence element may include information that causes STAs connected to AP 1 (510-1) to set NAV for a certain period of time after receiving the beacon frame (609) of AP 1 (510-1). That is, the silence element may set a transmission prohibition period. The silence element may indicate the start time information of the transmission prohibition period and the length of the transmission prohibition period, and AP 1 (510-1) may transmit a beacon frame indicating the transmission prohibition period before performing Co-TDMA operation. Even if AP 1 (510-1) sets the transmission prohibition period by transmitting the aforementioned beacon frame (609), it may not set the transmission prohibition period itself. That is, AP 1 (510-1) may not set NAV, and may freely perform channel access operations within the transmission prohibition period to acquire TXOP and perform frame transmission.

[0230] Alternatively, AP 1 (510-1) may transmit a quiet time period (QTP) action frame, and the QTP action frame may contain a QTP element. The QTP element may contain information that causes STAs connected to AP 1 (510-1) (e.g., STAs including non-AP STA 1 (520-1)) to set up NAV for a certain period of time.

[0231] As another example, AP 1 (510-1) can set a restricted target wake time (R-TWT) SP. To set the R-TWT SP, a management frame containing a beacon frame (609) may include a TWT element. Here, the TWT element may include information on the start time and length of the TWT SP. Since AP 1 (510-1) sets the R-TWT SP to restrict channel access by STAs connected to AP 1 (510-1), member STAs may not exist in the R-TWT SP set by AP 1 (510-1), and only AP 1 (510-1) may be able to communicate in the R-TWT SP. As an example, the R-TWT SP may be a restricted target wake time. As another example, AP 1 (510-1) may include a TWT element in the beacon frame (609), and the TWT SP indicated by the TWT element may indicate a period in which the AP is available. Therefore, a period that is not a TWT SP may be a period in which AP 1 (510-1) is not available.

[0232] AP 1 (510-1) may perform Co-TDMA operations (e.g., at least one of the polling step and TXOP allocation step of the [Co-TDMA operation step]) within a period indicating that AP 1 (510-1) is unavailable. A management frame containing a beacon frame (609) transmitted by AP 1 (510-1) to indicate a TWT SP indicating that AP 1 (510-1) is unavailable may include a TWT element, and the TWT element may be transmitted with bit(s) set indicating that AP 1 (510-1) is unavailable. Alternatively, AP 1 (510-1) may indicate a TWT SP with a specific TWT ID indicating that AP 1 (510-1) is unavailable, but is not limited thereto. Here, the TWT SP may be a transmission prohibition period. Alternatively, a time period other than the TWT SP may be a transmission prohibition period.

[0233] AP 1 (510-1) can perform Co-TDMA operation at the time when the transmission prohibition period begins (or after it begins). AP 1 (510-1) can acquire a TXOP in the [Co-TDMA operation phase] and exchange a polling frame (601) and a response frame (602) with AP 2 (510-2). Subsequently, AP 1 (510-1) can exchange an allocation frame (603) and a CTS frame, which is a response frame (604) to the allocation frame, with AP 2 (510-2). AP 2 (510-2) and the STA connected to AP 2 (510-2) can exchange data frames (605). Meanwhile, non-AP STA 1 (520-1), which is a STA connected to AP 1 (510-1), cannot transmit frames to AP 1 (510-1) within the transmission prohibition period.

[0234] The transmission prohibition period set by AP 1 (510-1) may be longer than the actual data communication period. For example, the transmission prohibition period set by AP 1 (510-1) may be longer than the TXOP of AP 1 (510-1) due to the early termination of the TXOP of AP 1 (510-1). Alternatively, consider the case where AP 2 (510-2), which shares the TXOP with AP 1 (510-1), returns the TXOP to AP 1 (510-1) early, causing AP 1 (510-1) to terminate the TXOP. In the above case, AP 1 (510-1) can release the NAV set on non-AP STA 1 (520-1) by transmitting a CF-End (contention free end) frame (610). Alternatively, AP 1 (510-1) may transmit a frame (e.g., a TWT information frame) to terminate the R-TWT SP. Alternatively, AP 1 (510-1) may transmit a frame (e.g., a TWT information frame) to start the TWT SP or remove the TWT SP set by AP 1 (510-1).

[0235] FIG. 13 is a diagram illustrating a method for performing retransmission after an initial control frame failure during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0236] Referring to FIG. 13, the polling step, which is the first step of the [Co-TDMA operation step], may fail. For example, AP 1 (510-1) may not receive a response to the polling frame (601), which is the first frame acquired by AP 1 (510-1). That is, AP 1 (510-1) may fail to transmit the polling frame. Alternatively, other APs may receive the polling frame (601) transmitted by AP 1 (510-1) but may not transmit a polling response frame, which is a response frame to the polling frame (601), in order not to participate in the Co-TDMA operation of AP 1 (510-1). AP 1 (510-1) may determine that the transmission of the polling frame (601) failed if the first frame transmitted in the TXOP is a polling frame (601) but a response frame to the polling frame is not received until a predetermined timeout, such as an AckTimeout, after the time the transmission of the polling frame is completed. In the above-described case, even if AP 1 (510-1) acquires the TXOP, it may need to perform a new channel access operation (EDCA backoff operation and TXOP acquisition procedure) based on the increase in QSRC[AC] and the resulting increased CW[AC]. Here, while AP 1 (510-1) is performing the new channel access operation, another wireless LAN terminal may occupy the channel and acquire the TXOP.

[0237] Considering the above points, a method may be required to allow AP 1 (510-1) to maintain the TXOP even after the initial polling frame (601) transmission fails. Here, AP 1 (510-1) may transmit a CTS frame (611) before transmitting the polling frame. The recipient address of the CTS frame (611) may be set to the MAC address of AP 1 (510-1). The duration field length of the CTS frame (611) may be set to 'aSIFSTime+(length of the polling frame)' to protect the transmission of the polling frame. For example, the CTS frame may be a CTS-to-Self frame, but is not limited thereto. Since the CTS frame (611) is not a frame that requires a response frame, if AP 1 (510-1) transmits the CTS frame (611), the initial frame transmission may be successful. AP 1 (510-1) may then transmit the polling frame (601). A response frame for a polling frame (601) may not be received, but AP 1 (510-1) may perform a PIFS (priority interframe space) recovery operation without performing a new backoff. The PIFS recovery operation may be an operation to retransmit a frame after the PIFS if a response frame for the frame is not detected after the frame is transmitted. Transmitting an additional frame after the PIFS is an operation to retransmit a frame if the channel is detected to be in an idle state during the TxPIFS slot boundary. Even if AP 1 (510-1) transmits an additional frame after the PIFS after a frame transmission failure, the length of the acquired TXOP of AP 1 (510-1) and the associated timer (e.g., TXNAV timer) may not be extended. AP 1 (510-1) may transmit a new polling frame after the PIFS from the time when the first polling frame was completed.Alternatively, AP 1 (510-1) may transmit a downlink data frame to non-AP STA 1 (520-1) after PIFS from the time when the first polling frame is transmitted. AP 1 (510-1) may perform frame transmission by maintaining the TXOP without performing a new backoff through the method described above. Alternatively, if the first transmitted polling frame (601) is the first frame of the TXOP and no response frame for the polling frame (601) is received, AP 1 (510-1) may perform backoff and TXOP acquisition operations and transmit an additional frame at the slot boundary where the backoff counter reaches 0. Even if AP 1 (510-1) transmits a frame by performing backoff and TXOP acquisition operations after a frame transmission failure, the length of the acquired TXOP of AP 1 (510-1) and the associated timer (e.g., TXNAV timer) may not be extended.

[0238] As another example, if the polling frame (601) initially transmitted by AP 1 (510-1) is the first frame of the TXOP and no response frame for the polling frame (601) is received, AP 1 (510-1) may exceptionally complete the transmission of the polling frame (601) and transmit an additional frame after the PIFS. For example, the polling frame (601) may be considered a frame that does not require a response frame, and transmission may be considered successful even if no response frame is received. Transmitting an additional frame after the PIFS may be an action to retransmit the frame when it is detected that the channel is idle during the TxPIFS slot boundary. Even if AP 1 (510-1) transmits an additional frame after the PIFS following a frame transmission failure, the length of the acquired TXOP of AP 1 (510-1) and the associated timer (e.g., TXNAV timer) may not be extended. AP 1 (510-1) may transmit a new polling frame PIFS after the time when the first polling frame is completed, or transmit a downlink data frame to non-AP STA 1 (520-1) PIFS after the time when the first polling frame is completed. As described above, AP 1 (510-1) may perform frame transmission by maintaining the TXOP without performing a new backoff. Alternatively, if the first polling frame (601) transmitted is the first frame of the TXOP and no response frame for the polling frame (601) is received, AP 1 (510-1) may perform backoff and TXOP acquisition operations and transmit an additional frame at the slot boundary when the backoff counter reaches 0. Even if AP 1 (510-1) performs backoff and TXOP acquisition operations after a frame transmission failure and transmits a frame, the length of the acquired TXOP of AP 1 (510-1) and the associated timer (e.g., TXNAV timer) may not be extended.Meanwhile, the sender address (TA) and receiver address (RA) of the MAC header of the polling frame that AP 1 (510-1) first transmits within the TXOP may be set to the address of AP 1 (510-1). For example, the polling frame described above may be referred to as a BSRP-to-Self frame, but is not limited to that name. An AP other than AP 1 (510-1) (e.g., AP 2 (510-2)) can recognize that the frame is a Co-TDMA polling frame even if it receives a polling frame in which the receiver address RA of the MAC header is the address of AP 1 (510-1). Therefore, if AP 2 (510-2) wishes to participate in the Co-TDMA operation of AP 1 (510-1) and share the TXOP of AP 1 (510-1), AP 2 (510-2) can transmit a response frame to the polling frame. In the case of a BSRP-to-Self frame, AP 1 (510-1) can transmit a new polling frame after the initial polling frame transmission is completed and after PIFS, or transmit a downlink data frame to non-AP STA 1 (520-1) after the initial polling frame transmission is completed and after PIFS.

[0239] The operation described above may also be used in the transmission of allocation frames during the TXOP allocation stage of the [Co-TDMA operation stage]. For example, the polling stage and the TXOP allocation stage during the [Co-TDMA operation stage] may be performed as separate TXOPs. Alternatively, it may be possible for only the TXOP allocation stage to be performed independently. During the TXOP allocation stage, the transmission of the allocation frame may be transmitted as the first frame of the AP 1 (510-1) TXOP. Even if there is no response frame for the allocation frame, or even if the allocation frame is transmitted as the first frame of the TXOP, AP 1 (510-1) may transmit a new frame after the transmission of the allocation frame and the subsequent PIFS. That is, AP 1 (510-1) may transmit a new allocation frame after the transmission of the first allocation frame is completed and the subsequent PIFS, or transmit a downlink data frame to non-AP STA 1 (520-1) after the transmission of the first allocation frame is completed and the subsequent PIFS.

[0240] FIG. 14 is a diagram illustrating a wireless LAN Co-TDMA operation method applicable to the present disclosure. Referring to FIG. 14, the [Co-TDMA wireless LAN network configuration] and [Co-TDMA operation step] described in FIG. 7 and FIG. 8 may be performed, and the same may be applied to FIG. 14 to FIG. 19 below. However, the specific operation for each figure may be performed with modifications and is not limited to a specific form.

[0241] Referring to FIG. 14, AP 1 (710-1) is a coordinating AP that shares TXOPs with other APs as a TXOP holder, and AP 2 (710-2) may be a coordinated AP that shares TXOPs from AP 1 (710-1), which is the coordinating AP. When AP 1 (710-1) performs a polling step and an allocation step within the acquired TXOP, AP 1 (710-1) may be required to use a portion of its TXOP (e.g., 33 percent, but not limited thereto) for frame exchange with at least one non-AP STA (e.g., non-AP STA 1 (720-1)) connected to AP 1 (710-1). Here, the corresponding step may be a data communication step. The acquired TXOP may be a time interval that includes all periods during which Co-TDMA operates (i.e., a time interval that includes all of the polling step, data communication step, and allocation step). For example, AP 1 (710-1) may not be allowed to proceed to an allocation step immediately after the polling step (e.g., immediately after the SIFS time, which is the shortest inter-frame time interval used within the TXOP, after receiving an ICR, which is a response frame to a BSRP trigger frame from AP 2 (710-2)). AP 1 (710-1) may be allowed to proceed to an allocation step after the polling step, after AP 1 (710-1) performs frame exchange with non-AP STA 1 (720-1) using part of the TXOP, to share the TXOP with AP 2 (710-2). If AP 1 (710-1) performs Co-TDMA operation, the first frame transmitted within the TXOP acquired by AP 1 (710-1) may be a polling ICF for performing the polling step. The duration field of the MAC header of the polling ICF can only indicate the SIFS time and the length of the ICR for the polling ICF.

[0242] The EDCAF (or TXOP holder EDCAF, TXOP holder) of AP 1 (710-1) can transmit the polling ICF of AP 1 (710-1). In the operation between terminals of a wireless LAN network, the TXOP holder may be AP 1 (710-1), but it may also refer to the channel access function of AP 1 (710-1). That is, AP 1 (710-1) being the TXOP holder may refer to a specific channel access function within AP 1 (710-1) being the TXOP holder, but it is not limited to a specific form. Each access category (AC) (e.g., VO (voice), VI (video), BE (best effort), BK (background)) may exist in AP 1 (710-1), and an EDCAF may exist for each AC. The EDCAFs for each AC may internally manage a TXNAV timer, which is a timer shared among the EDCAFs to stop contention. The TXNAV timer may be set based on the duration / ID field of the MAC header of the most recently transmitted frame (e.g., MPDU (MAC protocol data unit)) of any of the EDCAFs. If a PPDU containing the most recently transmitted frame is successfully transmitted, the value of the TXNAV timer may be set based on the value of the duration / ID field (referred to as the duration field in this disclosure) of the MAC header of the most recently transmitted frame after the end of transmission of the PPDU containing the most recently transmitted frame (e.g., completion of transmission of the PPDU containing the most recently transmitted frame or reception of a response frame for the PPDU containing the most recently transmitted frame). Here, the TXNAV timer value may decrease over time. When the TXNAV timer value is 0, the TXNAV timer may expire.On the other hand, if the TXNAV timer value is not zero, other EDCAFs other than the TXOP holder EDCAF may consider the channel to be occupied. Additionally, if a MAC frame transmission is performed that includes a duration / ID field value indicating a longer duration than the TXNAV timer value, the TXNAV timer value may be extended based on the value of the duration / ID field indicating the longer duration.

[0243] For example, the polling ICF may be a trigger frame, and the polling ICF may be capable of transmitting the EDCAF of all ACs. As a specific example, the VO EDCAF of AP 1 (710-1) acquires a TXOP, and AP 1 (710-1) may transmit the polling ICF to AP 2 (710-2). Here, the TXNAV timer value of AP 1 (710-1) may be set to 'time length of ICR + SIFS time length', which is the MAC header duration field value of the polling ICF. AP 2 (710-2) may respond to the polling ICF of AP 1 (710-1) by transmitting an ICR, and the time when the transmission of the ICR is completed may be 'time length of ICR + SIFS time' after the time when the transmission of the ICF is completed. That is, when the transmission of the ICR is completed, the TXNAV timer value may reach 0. Here, in order for AP 1 (710-1) (or the VO EDCAF of AP 1 (710-1) that acquired the TXOP) to transmit additional frames within the TXOP (e.g., data frames to be transmitted to non-AP STA 1 (720-1) and allocation frames to start the allocation phase), the TXNAV may not expire, and if the TXNAV expires, AP 1 (710-1) may be unable to transmit additional frames, and an operation taking this into account may be required.

[0244] Here, AP 1 (710-1) can perform a polling phase, a data communication phase (a data frame exchange phase with non-AP STA 1 (720-1)), and an allocation phase, respectively. That is, AP 1 (710-1) can perform the polling phase, the data communication phase, and the allocation phase by dividing them into separate TXOPs (e.g., the polling phase, the data communication phase, and the allocation phase by dividing them into two or three TXOPs). As another example, it may also be possible for AP 1 (710-1) to perform the polling phase, the data communication phase, and the allocation phase within a single TXOP, and a method for setting TXNAV may be required considering the above-mentioned case.

[0245] Meanwhile, AP 1 (710-1) can determine the bandwidth of frames transmitted in subsequent remaining TXOPs based on the bandwidth of the polling frame transmitted in the initial polling phase or the frame transmitted in the initial TXOP acquisition phase. For example, AP 1 (710-1) can transmit the polling frame or the frame transmitted in the initial TXOP acquisition phase using the initial bandwidth of 320 MHz. Subsequently, AP 1 (710-1) can perform a data communication phase with the STA connected to AP 1 (710-1), and the exchange of data frames performed with non-AP STA 1 (720-1) can be performed using a bandwidth less than the initial bandwidth (e.g., 320 MHz) (e.g., 160 MHz, 80 MHz, etc.). Subsequently, AP 1 (710-1) can perform an allocation phase. In the allocation phase, the maximum bandwidth that AP 1 (710-1) can allocate to AP 2 (710-2) may be 320 MHz. Even if AP 1 (710-1) performs data frame exchanges with less than the initial bandwidth in the data communication phase, it may transmit an allocation frame that allocates a TXOP to AP 2 (710-2) with the initial bandwidth as the upper limit. Alternatively, if AP 1 (710-1) performs data frame exchanges with less than the initial bandwidth in the data communication phase, it may transmit an allocation frame that allocates a TXOP to AP 2 (710-2) with the bandwidth of the last frame transmitted or received by AP 1 (710-1) as the upper limit.

[0246] Additionally, while FIGS. 15a to 16b below may operate according to FIGS. 8 and FIG. 14 described above, it may also be possible to perform different operations according to each figure. When AP 2 (710-2), which is a coordinated AP, receives an allocation frame from AP 1 (710-1), it can transmit a CTS frame to share the TXOP. Here, when performing frame transmission within the allocation duration interval, which is the shared TXOP interval, a method for setting the duration field value of the frame MAC header and a method for performing retransmission in the event of a frame error may be required, and this is described below. In this disclosure, the duration field of the frame MAC header (included in the PPDU) may be the duration / ID field of the MPDU, and for convenience of explanation, it is referred to as the duration field. However, it may not be limited thereto. Additionally, the VO EDCAF of the aforementioned AP 1 (710-1) may be an example of one of the AC-specific EDCAFs that acquire a TXOP and transmit a polling ICF within the coordinating AP AP 1 (710-1). For convenience of explanation, the following description is based on this, but it is not limited to this. That is, the operation may not be limited to the case where the EDCAF for a specific AC of AP 1 (710-1) acquires a TXOP.

[0247] In addition, a Triggered TXOP sharing operation similar to the allocation stage of the [Co-TDMA operation stage] described above may be used in a wireless LAN network. The Triggered TXOP sharing operation may involve a TXOP holder STA (e.g., a non-AP STA or AP) sharing a TXOP with another STA (a non-AP STA or AP that is not the TXOP holder STA). The TXOP holder STA may transmit the MU-RTS TXS frame within the TXOP acquired during the TXOP sharing operation to the other STA. The other STA described above may be able to perform frame transmission and reception operations within the allocated duration time interval indicated by the MU-RTS TXS frame. The MU-RTS TXS frame used in the Triggered TXOP sharing operation may correspond to the allocation frame of the allocation stage of the [Co-TDMA operation stage], and may be a frame with the same or very similar purpose, but is not limited thereto.

[0248] Although the following description is based on Co-TDMA operation, if the coordinating AP is replaced by the TXOP holder STA of the TXOP sharing operation and the coordinated AP is replaced by another STA of the TXOP sharing operation, the same can be applied as a Triggered TXOP sharing operation. However, in a Triggered TXOP sharing operation, the polling step of the [Co-TDMA operation step] is unnecessary and may not be performed. Additionally, in a Triggered TXOP sharing operation, the data communication step may be unnecessary. Therefore, in a Triggered TXOP sharing operation, the first frame transmitted by the TXOP holder STA within the TXOP may not be a polling frame, and it is not necessary to use its own TXOP for the exchange of data frames with the STA it is connected to. The Triggered TXOP sharing operation may be freely initiated within the TXOP without the constraint that the allocation step of the [Co-TDMA operation step] must follow the polling step and data communication step within the TXOP of the TXOP holder STA, and it is not limited to a specific form.

[0249] FIGS. 15a to 15d are drawings illustrating a method for setting a frame transmission interval of a coordinating AP during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0250] Referring to FIGS. 15a through 15d, in the wireless LAN network environment described above, AP 1 (710-1) and non-AP STA 1 (720-1), which is a non-AP STA connected to AP 1 (710-1), can be operated. Additionally, a case can be considered in which AP 2 (710-2) and non-AP STA 2 (720-2), which is a non-AP STA connected to AP 2 (710-2), are operated. Here, AP 1 (710-1) can perform a channel access operation (e.g., a channel access operation following the EDCA TXOP acquisition procedure and the EDCA backoff procedure) as a coordinating AP and succeed to acquire a TXOP (e.g., determine the start of frame transmission at the slot boundary where the EDCAF backoff counter is 0). AP 1 (710-1) can perform the polling step, data communication step (data communication with non-AP STA 1 (720-1) and subsequent allocation step of the [Co-TDMA operation step] described in FIG. 14 in order to share TXOP with AP 2 (710-2).

[0251] For example, when the VO EDCAF of AP 1 (710-1) acquires a TXOP and becomes a TXOP holder, the VO EDCAF of AP 1 (710-1) can transmit a polling frame (801) as the first frame. Here, if AP 1 (710-1) wishes to share the TXOP with another AP, AP 2 (710-2), via Co-TDMA, the VO EDCAF of AP 1 (710-1) can transmit a polling frame (801). When the VO EDCAF of AP 1 (710-1) transmits a polling frame (801), other EDCAFs other than the VO EDCAF of AP 1 (710-1) may stop the transmission of the polling frame by the VO EDCAF of AP 1 (710-1), exchange data frames with non-AP STA 1 (720-1), transmit allocated frames to the coordinated AP AP 2 (710-2), and transmit additional frames (if necessary). That is, other EDCAFs other than the VO EDCAF of AP 1 (710-1) may stop the channel access operation (or repeat the channel access operation and not transmit frames, or perform a 'do nothing' operation). Additionally, the TXOP holder of AP 1 (710-1) may transmit multiple frames within the TXOP limit (e.g., within the TXOP limit of the AC associated with the EDCAF that transmitted the polling frame, or within the TXOP limit of the AC with the longest TXOP limit). However, this is not limited thereto, and the TXOP holder of AP 1 (710-1) may also transmit multiple frames beyond the TXOP limit.

[0252] Additionally, in a situation where AP 1 (710-1) intends to share a TXOP with another AP, AP 2 (710-2), via Co-TDMA, if the VO EDCAF is the TXOP holder as described above, a retransmission operation by the VO EDCAF of AP 1 (710-1) can be performed. Specifically, the VO EDCAF of AP 1 (710-1) can transmit a polling frame (801) to AP 2 (710-2) and receive an ICR (802) from AP 2 (710-2). When AP 1 (710-1) receives an ICR (802) from AP 2 (710-2), the VO EDCAF of AP 1 (710-1) considers the initial TXOP frame exchange to be successful, and retransmission may be possible in the event of a failure of a subsequently transmitted frame. For example, if the VO EDCAF of AP 1 (710-1) transmits a polling frame (401) to AP 2 (710-2) and receives an ICR (402), the VO EDCAF of AP 1 (710-1) may subsequently fail to transmit a frame to non-AP STA 1 (720-1) (e.g., failure to receive a response frame). Here, the VO EDCAF of AP 1 (710-1) may transmit a data frame to non-AP STA 1 (720-1) or to a non-AP STA connected to AP 1 (710-1) that is not non-AP STA 1 (720-1) at the time when the TxPIFS slot boundary is reached from the time when the transmission of the failed frame is completed after initiating a new channel access procedure or at the time when the transmission of the failed frame is completed. Here, even if VO EDCAF of AP 1 (710-1) initiates and completes a new channel access procedure, the channel access procedure may not be the start of a new TXOP. That is, VO EDCAF, the TXOP holder of AP 1 (710-1), may not extend the end time of the TXOP limit starting from the time of the TXOP initiation.In a situation where AP 1 (710-1) intends to share a TXOP with another AP, AP 2 (710-2), via Co-TDMA, the VO EDCAF of AP 1 (710-1) may have transmitted a polling frame (801) to AP 2 (710-2) but failed to receive an ICR (802) from AP 2 (710-2). For example, one may consider that AP 2 (710-2) failed to receive the polling frame (801), or that AP 2 (710-2) did not want to share the TXOP and therefore did not transmit the ICR (802). In the above case, since the polling frame (801) is the first frame of the TXOP, AP 1 (710-1) may perform a retransmission operation in the event of a failure to transmit the Co-TDMA polling frame, even though the transmission of the first frame of the TXOP has failed. Alternatively, AP 1 (710-1) may consider the transmission of the polling frame successful even if it does not receive a response frame for the Co-TDMA polling frame. That is, the VO EDCAF of AP 1 (710-1) may transmit a data frame to non-AP STA 1 (720-1) or to a non-AP STA connected to AP 1 (710-1) that is not non-AP STA 1 (720-1) at the time when the TxPIFS slot boundary is reached from the time when the transmission of the failed frame is completed after initiating a new channel access procedure. AP 1 (710-1) may retry the polling step if the polling step fails, or it may perform frame exchange with a STA connected to it (e.g., non-AP STA 1 (720-1)) within the acquired TXOP without retrying the polling step. Additionally, if AP 1 (710-1) does not receive ICR (802), the polling phase may have failed. Subsequently, the polling phase may not be retried, or if the retried polling phase fails again, the allocation phase may not be performed.Unlike the above, AP 1 (710-1) must perform a new backoff and TXOP acquisition procedure when the transmission of the first frame of the TXOP fails and a polling frame fails, and acquire a new TXOP to transmit subsequent frames.

[0253] As another example, the VO EDCAF of AP 1 (710-1) can send a polling frame (401) to AP 2 (710-2) and receive an ICR (402) from AP 2 (710-2). In the above case, the VO EDCAF of AP 1 (710-1) can be considered to have successfully exchanged the TXOP first frame, but the VO EDCAF of AP 1 (710-1) can be considered to have successfully exchanged the first frame with AP 2 (710-2). Therefore, the VO EDCAF of AP 1 (710-1) and the STA other than AP 1 (e.g., non-AP STA 1 (720-1) connected to AP 1 (710-1) may not have successfully exchanged the first frame. If the VO EDCAF of AP 1 (710-1) fails to transmit a frame to non-AP STA 1 (720-1) for the first time, the VO EDCAF of AP 1 (710-1) may need to initiate a new channel access procedure. The VO EDCAF of AP 1 (710-1) may not allow the retransmission of the frame at the TxPIFS slot boundary after the transmission of the failed frame is completed. Additionally, when the VO EDCAF of AP 1 (710-1) initiates and completes a new channel access procedure, a new TXOP may be initiated by that channel access procedure. That is, since the VO EDCAF, which is the TXOP holder of AP 1 (710-1), initiates a new TXOP, it may be subject to the TXOP limit starting from the time the new TXOP is initiated. If the VO EDCAF of AP 1 (710-1) successfully transmits a frame to non-AP STA 1 (720-1), the VO EDCAF of AP 1 (710-1) may have successfully completed the initial frame exchange with non-AP STA 1 (720-1). Therefore, the VO EDCAF of AP 1 (710-1) subsequently fails to transmit a frame to non-AP STA 1 (720-1) (e.g.In the case of non-receipt of a response frame, the VO EDCAF may transmit a data frame to non-AP STA 1 (720-1) or to a non-AP STA connected to AP 1 (710-1) that is not non-AP STA 1 (720-1) at the time when the TxPIFS slot boundary is reached from the time when the new channel access procedure is initiated and completed or the time when the transmission of the failed frame is completed. Even if the VO EDCAF of AP 1 (710-1) initiates and completes a new channel access procedure, the channel access procedure may not be the start of a new TXOP. That is, the VO EDCAF of AP 1 (710-1), which is the TXOP holder of AP 1 (710-1), may not extend the end time of the TXOP limit starting from the time of the TXOP initiation. In the case where the TXOP holder does not initiate a new TXOP in the retransmission operation described above, the time required for the data communication step in which data communication is performed between the VO EDCAF of AP 1 (710-1) and the non-AP STA 1 (720-1) may include the exchange of retransmission frames and the channel access time and IFS time required for the exchange of retransmission frames (e.g., PIFS time used for calculating TxPIFS slot boundaries, SIFS time, etc.). Additionally, the ratio of the time required for the data communication step, excluding the allocation step and the polling step, may be at least a certain ratio (e.g., 33 percent), but is not limited thereto.

[0254] As another example, if the TXOP holder initiates a new TXOP in the retransmission operation described above, the Co-TDMA operation may be considered to be newly initiated. However, the time spent in the polling phase during the newly initiated TXOP interval is considered to be non-existent, and the ratio of the time spent in the data communication phase excluding the allocation phase among the newly acquired TXOPs may be set to be at least a certain ratio (e.g., 33 percent), but is not limited thereto.

[0255] Additionally, the retransmission operation described above is performed by the TXOP holder EDCAF of AP 1 (710-1) (e.g., the VO EDCAF of AP 1 (710-1)), but cases where the retransmission operation is not performed by the TXOP holder EDCAF can also be considered. For example, the retransmission operation of a failed frame may be performed by the EDCAF associated with the AC of the failed frame, or the retransmission operation of a failed frame may be performed by the EDCAF among all ACs that first succeeded in the channel access operation.

[0256] Additionally, for example, the operation of AP 1 (710-1) sharing a TXOP with AP 2 (710-2) via Co-TDMA can be performed in various ways. However, even if the operation of AP 1 (710-1) sharing a TXOP with AP 2 (710-2) via Co-TDMA is performed in various ways, the operations related to FIGS. 15a to 15d, which perform ‘frame transmission and reception for the polling stage of Co-TDMA within a single transmission interval of the coordinating AP during Co-TDMA operation in a wireless LAN network, transmission and reception of data frames of the coordinating AP including retransmission of frames where errors occurred, frame transmission and reception for the allocation stage of Co-TDMA of the coordinating AP, and additional frame exchange of the coordinating AP if necessary after the TXOP allocation interval,’ can be applied in the same way. In addition, the frame retransmission operation of the coordinating AP described in FIGS. 15a to 15d can be performed by the TXOP holder STA in the same or similar way in the Triggered TXOP sharing operation.

[0257] FIG. 15a may be a method in which AP 1 (710-1), a coordinating AP, transmits multiple frames even when the TXNAV has expired during frame transmission within a TXOP. Referring to FIG. 15a, AP 1 (710-1) can determine the protection method of the TXOP at the start of the initial TXOP. Here, a single protection method may be a method in which the time value indicated by the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to the time required for frame exchange. A multiple protection method is a method in which the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to indicate the time length until the end of the total TXOP length that AP 1 (710-1) intends to use. The duration field of the polling frame (801) transmitted by AP 1 (710-1) as the first frame of the TXOP may indicate the time from the completion of transmission of the polling frame (801) to the completion time of the transmission of AP 2 (710-2) ICR (i.e., the length of the ICR + SIFS). This method is a single protection setting, and AP 1 (710-1) may also set the MAC header duration field value based on the single protection method for all subsequent frames transmitted within the TXOP. After that, AP 1 (710-1) may receive the ICR (802) from AP 2 (710-2), and AP 1 (710-1)'s TXNAV may expire. If AP 1 (710-1) wishes to share a TXOP with AP 2 (710-2) via Co-TDMA even though the TXNAV has expired, AP 1 (710-1) may transmit multiple frames (e.g., SIFS or PIFS intervals, etc.) within the TXOP limit (e.g., within the TXOP limit of the AC associated with the EDCAF that transmitted the polling frame, or within the TXOP limit of the AC with the longest TXOP limit).That is, the TXOP holder EDCAF of AP 1 (710-1) can transmit multiple frames even if the TXNAV has expired. The transmission of multiple frames may include retransmission of failed frames. For example, when using Co-TDMA operation, the TXOP holder EDCAF of AP 1 (710-1) can retransmit frames within a range that does not exceed the TXOP limit of the acquired TXOP by using methods such as transmitting additional frames after the PIFS (TxPIFS slot boundary) from the time of frame transmission completion, or transmitting additional frames by performing backoff and channel access operations.

[0258] For example, if the VO EDCAF of AP 1 (710-1) transmits a polling frame (801) and AP 1 (710-1) receives an ICR (802) from AP 2 (710-2), the VO EDCAF of AP 1 (710-1) may transmit additional frames within the TXOP limit corresponding to the AC VO (or the TXOP limit of the AC with the longest TXOP limit). Meanwhile, other EDCAFs other than the VO EDCAF that did not transmit the polling frame may perform a channel access suspension (e.g., consider the medium to be occupied and stop the channel access operation, or consider the transmission queue for each AC to be empty and perform a 'do nothing' operation) until the VO EDCAF transmits the last frame (or PPDU). Alternatively, other EDCAFs other than the VO EDCAF that transmitted the polling frame may not transmit frames by repeatedly performing channel access operations (e.g., not transmitting frames at slot boundaries where the backoff counter is 0, and repeating the process of selecting a new backoff counter and acquiring a TXOP) until the VO EDCAF transmits the last frame (or PPDU). Afterward, AP 1 (710-1) may perform data frame exchange with non-AP STA 1 (720-1) (e.g., exchange of frames including at least one of a downlink data frame, a trigger frame, an uplink data frame, and a response frame). In the data frame exchange procedure, the MAC header duration value of at least one frame transmitted by AP 1 (710-1) to non-AP STA 1 (720-1) may be set from the time of completion of transmission of each frame to the time required to transmit a response frame for the frame. Alternatively, the MAC header duration value of at least one frame transmitted by AP 1 (710-1) to non-AP STA 1 (720-1) may be set to the time of completion of transmission of the MU-RTS frame (803) transmitted during the allocation phase.

[0259] After AP 1 (710-1) finishes exchanging data frames with non-AP STA 1 (720-1), it may transmit a MU-RTS TXS TF, which is an allocation frame (803), to allocate a TXOP to AP 2 (710-2). The MAC header duration field of the allocation frame (803) may be set to the value of 'length of AP 2 (710-2) CTS frame + SIFS time length'. When AP 1 (710-1) receives a CTS frame, which is a response frame (804) to the allocation frame (803) from AP 2 (710-2), AP 1 (710-1) may not perform frame transmission until the time interval allocated to AP 2 (710-2) in the allocation frame has ended. Alternatively, AP 1 (710-1) may not perform frame transmission until it receives a frame from AP 2 (710-2) instructing a TXOP return (e.g., receiving a QoS data frame or QoS Null frame from AP 2 (710-2) in which the value of the RDG / More PPDU subfield of the CAS (command and status) Control field included in the HT Control field of the frame's MAC header is 0). That is, all AC-specific EDCAFs of AP 1 (710-1), including the TXOP holder EDCAF of AP 1 (710-1), may not perform frame transmission. For example, not performing frame transmission may be to stop the channel access operation or to repeat the channel access operation so as not to transmit the frame.

[0260] Meanwhile, when AP 1 (710-1) receives a frame from AP 2 (710-2) instructing a TXOP return or when the allocated duration time interval expires, the TXOP holder EDCAF of AP 1 (710-1) may transmit a frame within the TXOP limit (e.g., if the TXOP holder is VO EDCAF, VO EDCAF is the TXOP limit corresponding to AC VO or the TXOP limit of the AC with the longest TXOP limit). Alternatively, the TXOP holder EDCAF of AP 1 (710-1) may not transmit a frame further if the TXOP limit is reached (e.g., if the frame to be transmitted cannot be transmitted within the TXOP limit or if the frame has already been transmitted beyond the TXOP limit) or if there are no more frames to transmit. Additionally, other EDCAFs other than the TXOP holder EDCAF of AP 1 (710-1) may resume channel access operations (e.g., not considering the transmission queue for each AC as empty, stopping the do nothing operation that keeps the backoff counter at 0, stopping the repeated channel access operation) if the aforementioned TXOP holder EDCAF has completed the transmission of the last frame or has not transmitted an additional frame after the allocated duration.

[0261] FIG. 15b may be a method in which AP 1 (710-1), a coordinating AP, sets the duration field of an allocated frame based on the time length indicated by the allocated duration field when transmitting a frame within a TXOP. Referring to FIG. 15b, AP 1 (710-1) can determine the protection method of the TXOP at the start of the initial TXOP. Here, a single protection method may be a method in which the time value indicated by the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to the time required for frame exchange. A multiple protection method is a method in which the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to indicate the time length until the end of the total TXOP length that AP 1 (710-1) intends to use. The duration field of the polling frame (801) transmitted by AP 1 (710-1) as the first frame of the TXOP may indicate the time from the completion of transmission of the polling frame (801) to the completion of transmission of AP 2 (710-2)'s ICR (802) (i.e., the length of the ICR + SIFS). This method is a single protection setting, and AP 1 (710-1) may also set the MAC header duration field value based on the single protection method for frames transmitted within the TXOP thereafter. However, exceptionally, the MAC header duration field value of the MU-RTS frame (803) may not use the single protection setting method, which will be described later. After that, AP 1 (710-1) may receive the ICR (802) from AP 2 (710-2), and AP 1 (710-1)'s TXNAV may expire. If AP 1 (710-1) wishes to share a TXOP with AP 2 (710-2) via Co-TDMA even though the TXNAV has expired, AP 1 (710-1) must be within the TXOP limit (e.g.Multiple frames (e.g., SIFS or PIFS intervals, etc.) may be transmitted within the TXOP limit of the AC associated with the EDCAF that transmitted the polling frame (801) or within the TXOP limit of the AC having the longest TXOP limit. That is, the TXOP holder EDCAF of AP 1 (710-1) may be able to transmit multiple frames even if the TXNAV has expired. The transmission of multiple frames may include retransmission of failed frames. For example, when using Co-TDMA operation, the TXOP holder EDCAF of AP 1 (710-1) may retransmit frames within a range that does not exceed the TXOP limit of the acquired TXOP by using methods such as additionally transmitting frames after the PIFS (TxPIFS slot boundary) from the time of frame transmission completion, or by performing backoff and channel access operations to additionally transmit frames.

[0262] For example, if the VO EDCAF of AP 1 (710-1) transmits a polling frame (801) and AP 1 (710-1) receives an ICR (802) from AP 2 (710-2), the VO EDCAF of AP 1 (710-1) may transmit additional frames within the TXOP limit corresponding to the AC VO (or the TXOP limit of the AC with the longest TXOP limit). Meanwhile, other EDCAFs other than the VO EDCAF that transmitted the polling frame may perform a channel access suspension (e.g., suspend channel access by considering the medium to be occupied, or perform a 'do nothing' operation by considering the transmission queue for each AC to be empty) until the VO EDCAF transmits the last frame (or PPDU). Alternatively, other EDCAFs other than the VO EDCAF that transmitted the polling frame may not transmit frames by repeatedly performing channel access operations (e.g., not transmitting frames at slot boundaries where the backoff counter is 0, and repeating the process of selecting a new backoff counter and acquiring a TXOP) until the VO EDCAF transmits the last frame (or PPDU). Afterward, AP 1 (710-1) may perform data frame exchange with non-AP STA 1 (720-1) (e.g., exchange of frames including at least one of a downlink data frame, a trigger frame, an uplink data frame, and a response frame). In the data frame exchange procedure, the MAC header duration value of at least one frame transmitted by AP 1 (710-1) to non-AP STA 1 (720-1) may be set from the time of completion of transmission of each frame to the time required to transmit a response frame for the frame. Alternatively, the MAC header duration value of at least one frame transmitted by AP 1 (710-1) to non-AP STA 1 (720-1) may be set to the time of completion of transmission of the MU-RTS frame (803) transmitted during the allocation phase.

[0263] After AP 1 (710-1) finishes exchanging data frames with non-AP STA 1 (720-1), it may transmit an allocation frame (803), MU-RTS TXS TF, to allocate a TXOP to AP 2 (710-2). Here, the MAC header duration field of the allocation frame may indicate a time length corresponding to the time length indicated by the value of the allocated duration field of the polling frame. Alternatively, the MAC header duration field of the allocation frame may indicate a time length corresponding to the TXOP acquired by AP 1 (710-1) (specifically, acquired by the TXOP holder EDCAF of AP 1 (710-1)). Thus, when AP 1 (710-1) transmits the allocation frame (801), the TXNAV is set for the allocated duration period after the allocation frame is transmitted, and the EDCAFs can detect the medium as being occupied until the TXNAV expires. Alternatively, the MAC header duration field of the allocation frame (801) may be set to 'time length of the CTS frame + SIFS'. However, separately, the TXNAV of AP 1 (710-1) may be set to the time length indicated by the allocated duration field of the allocation frame. When AP 1 (710-1) receives a CTS frame, which is a response frame (804) to the allocation frame (803) from AP 2 (710-2), AP 1 (710-1) may not perform frame transmission until the time interval allocated to AP 2 (710-2) in the allocation frame (801) has ended. Alternatively, AP 1 (710-1) may not perform frame transmission until it receives a frame instructing a TXOP return from AP 2 (710-2) (e.g., receiving a QoS data frame or QoS Null frame in which the value of the RDG / More PPDU subfield of the CAS (command and status) Control field included in the HT Control field of the frame's MAC header is 0 from AP 2 (710-2)).

[0264] Here, the TXOP holder EDCAF may ignore TXNAV, but as described above, in the interval where TXNAV is set, the TXOP holder EDCAF may also detect the medium as occupied if TXNAV has not expired and may not perform a channel access operation. Alternatively, the TXOP holder EDCAF may perform a 'do nothing' operation during the allocated duration regardless of TXNAV. That is, all AC-specific EDCAFs of AP 1 (710-1), including the TXOP holder EDCAF of AP 1 (710-1), may not perform frame transmission. Not performing frame transmission by all AC-specific EDCAFs of AP 1 (710-1), including the TXOP holder EDCAF of AP 1 (710-1), may be to stop the channel access operation or to repeatedly perform the channel access operation to not transmit the frame. Meanwhile, when AP 1 (710-1) receives a frame from AP 2 (710-2) instructing a TXOP return or when the allocated duration time interval expires, the TXOP holder EDCAF of AP 1 (710-1) may resume the operation for frame transmission by ignoring the TXNAV or stopping the 'do nothing' operation. The TXOP holder EDCAF of AP 1 (710-1) may transmit a frame within the TXOP limit (e.g., if the TXOP holder is VO EDCAF, VO EDCAF is the TXOP limit corresponding to AC VO or the TXOP limit of the AC having the longest TXOP limit). Alternatively, the TXOP holder EDCAF of AP 1 (710-1) may not transmit frames further if the TXOP limit is reached (e.g., when a frame to be transmitted cannot be transmitted within the TXOP limit, or when a frame has already been transmitted beyond the TXOP limit) or if there are no more frames to transmit.Additionally, other EDCAFs other than the TXOP holder EDCAF of AP 1 (710-1) may resume channel access operations (e.g., not considering the transmission queue per AC as empty, stopping the do nothing operation that keeps the backoff counter at 0, stopping the repeated channel access operation, detecting the virtual carrier detection as idle, and resuming the backoff operation and TXOP acquisition operation accordingly).

[0265] FIG. 15c may be a case where AP 1 (710-1), a coordinating AP, sets the duration field of an allocated frame based on a multiple protection method when transmitting a frame within a TXOP. Referring to FIG. 15c, AP 1 (710-1) can determine the protection method of the TXOP at the start of the initial TXOP. Here, a single protection method may be a method in which the time value indicated by the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to the time required for frame exchange. A multiple protection method is a method in which the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to indicate the time length until the end of the total TXOP length that AP 1 (710-1) intends to use.

[0266] The duration field of the polling frame (801) transmitted by AP 1 (710-1) as the first frame of the TXOP can indicate the length of time from the time the transmission of the polling frame is completed until the remaining TXOP of AP 1 (710-1). The above method is a multiple protection setting, so that AP 1 (710-1) can set the duration field value of the MAC header based on the multiple protection method for all frames transmitted within the TXOP thereafter.

[0267] The value of the TXNAV timer can be set to correspond to the total time length of the remaining TXOP interval of AP 1 (710-1). AP 1 (710-1) can receive an ICR (802) from AP 2 (710-2). The TXOP holder EDCAF of AP 1 (710-1) may be able to transmit multiple frames (e.g., multiple frames transmitted at SIFS or PIFS intervals, etc.) before the TXNAV expires. For example, if the VO EDCAF of AP 1 (710-1) transmits a polling frame (801) and AP 1 (710-1) receives an ICR (802) from AP 2 (710-2), the VO EDCAF of AP 1 (710-1) may transmit additional frames before the TXNAV expires. The transmission of multiple frames may include retransmission of failed frames. For example, the TXOP holder EDCAF of AP 1 (710-1) can retransmit frames until the TXNAV expires by using methods such as additionally transmitting frames after the PIFS (TxPIFS slot boundary) from the time the frame transmission is completed, or by performing backoff and channel access operations to additionally transmit frames. Meanwhile, other EDCAFs other than the VO EDCAF that transmitted the polling frame may stop channel access operations (e.g., stop channel access operations by considering the medium as occupied because the TXNAV has not expired) and not perform frame transmission until the VO EDCAF transmits the last frame (or PPDU). Afterwards, AP 1 (710-1) can perform data frame exchange with non-AP STA 1 (720-1) (e.g., exchange of frames including at least one of a downlink data frame, a trigger frame, an uplink data frame, and a response frame).In the data frame exchange procedure, the MAC header duration value of at least one frame transmitted by AP 1 (710-1) to non-AP STA 1 (720-1) may indicate the time length of the remaining TXOP of AP 1 (710-1) at the time the frame transmission is completed. After AP 1 (710-1) finishes the data frame exchange with non-AP STA 1 (720-1), it transmits an allocation frame, MU-RTS TXS TF, to allocate a TXOP to AP 2 (710-2). The MAC header duration field of the allocation frame (803) may indicate the time length of the remaining TXOP of AP 1 (710-1) at the time the allocation frame transmission is completed. AP 1 (710-1) transmits the allocation frame (803), and the EDCAFs may detect the medium as occupied until the TXNAV expires. When AP 1 (710-1) receives a CTS frame (804), which is a response frame to an allocation frame from AP 2 (710-2), AP 1 (710-1) may not perform frame transmission until the time interval allocated to AP 2 (710-2) in the allocation frame has ended. Alternatively, AP 1 (710-1) may not perform frame transmission until it receives a frame instructing a TXOP return from AP 2 (710-2) (e.g., receiving a QoS data frame or QoS Null frame in which the value of the RDG / More PPDU subfield of the CAS (command and status) Control field included in the HT Control field of the frame's MAC header is 0 from AP 2 (710-2)).

[0268] Here, TXNAV is a timer that can ignore TXOP holder EDCAF, but as described above, during the period when TXNAV is set, TXOP holder EDCAF may also detect the medium as occupied and may not perform channel access operations if TXNAV has not expired. Alternatively, TXOP holder EDCAF may perform a 'do nothing' operation for an allocated duration regardless of TXNAV. That is, all AC-specific EDCAFs of AP 1 (710-1), including TXOP holder EDCAF of AP 1 (710-1), may not perform frame transmission.

[0269] When AP 1 (710-1) receives a frame from AP 2 (710-2) instructing a TXOP return, or when the allocated duration time interval expires, the TXOP holder EDCAF of AP 1 (710-1) may resume the operation for frame transmission by ignoring the TXNAV or stopping the 'do nothing' operation. The TXOP holder EDCAF of AP 1 (710-1) may transmit a frame before the set TXNAV timer expires. Alternatively, the TXOP holder EDCAF of AP 1 (710-1) may not transmit any additional frames if the frames to be transmitted cannot be transmitted before the TXNAV timer expires or if the TXNAV has already expired. All EDCAFs of AP 1 (710-1) can resume channel access operations (e.g., detect virtual carrier detection as idle, and resume backoff operations and TXOP acquisition operations accordingly) without detecting the medium as occupied by TXNAV when TXNAV expires. Meanwhile, the TXOP holder EDCAF of AP 1 (710-1) can set the MAC header duration field value of the polling frame to the value obtained by subtracting the time length of the polling frame from the TXOP limit (e.g., if the TXOP holder is VO EDCAF, VO EDCAF is the TXOP limit corresponding to AC VO or the TXOP limit of the AC having the longest TXOP limit) when transmitting the first polling frame.

[0270] FIG. 15d may be a method for setting TXNAV independently of the duration field of an allocated frame when AP 1 (710-1), which is a coordinating AP, transmits a frame within a TXOP.

[0271] Referring to FIG. 15d, AP 1 (710-1) can determine the protection method for the TXOP at the start of the initial TXOP. Here, a single protection method may be a method in which the time value indicated by the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to the time required for frame exchange. A multiple protection method is a method in which the duration field of each MAC header of the MAC frames transmitted by AP 1 (710-1) is set to indicate the time length until the end of the total TXOP length that AP 1 (710-1) intends to use. The duration field of the polling frame (801) transmitted by AP 1 (710-1) as the first frame of the TXOP may indicate the length from the time of completion of transmission of the polling frame to the time of completion of transmission of AP 2 (710-2)'s ICR (801) (i.e., the length of the ICR + SIFS). In this method, with a single protection setting, AP 1 (710-1) can set the MAC header duration field value based on the single protection method for all frames transmitted within the subsequent TXOP. However, if AP 1 (710-1) intends to perform Co-TDMA operation, instead of setting the TXNAV timer based on the time length indicated by the MAC header duration field value of the frame transmitted by AP 1 (710-1), AP 1 (710-1) may set the TXNAV timer value corresponding to the remaining time length of the entire TXOP it intends to use when transmitting the polling frame (801). Alternatively, when transmitting the polling frame (801), AP 1 (710-1) may set the TXNAV timer value based on the time length indicated by the MAC header duration field value of the polling frame. Here, AP 1 (710-1) [receives] a valid response to the polling frame (801) (e.g.When an ICR for a polled frame is received after the SIFS time (or including the aRxPHYStartDelay time, which is additional overhead for SIFS and frame detection, etc., and there are no reception errors in the ICR), the value of the TXNAV timer corresponding to the remaining time length of the entire TXOP that AP 1 (710-1) intends to use can be set. The TXOP holder EDCAF of AP 1 (710-1) may be able to transmit multiple frames (e.g., multiple frames transmitted at SIFS or PIFS intervals, etc.) before the TXNAV expires. Multiple frame transmission may include retransmission of failed frames. For example, the TXOP holder EDCAF of AP 1 (710-1) may retransmit frames before the TXNAV expires by using methods such as additionally transmitting frames after the PIFS (TxPIFS slot boundary) from the time of frame transmission completion, or additionally transmitting frames by performing backoff and channel access operations.

[0272] Here, AP 1 (710-1) can receive an ICR (802) from AP 2 (710-2). AP 1 (710-1) can initiate a data frame exchange procedure with non-AP STA 1 (720-1). In the data frame exchange procedure, the MAC header duration value of at least one frame transmitted by AP 1 (710-1) to non-AP STA 1 (720-1) may be set from the time of completion of transmission of each frame to the time required to transmit a response frame for the frame (or, the time of completion of transmission of a MU-RTS frame transmitted during the allocation phase). After completing the data frame exchange with non-AP STA 1 (720-1), AP 1 (710-1) can transmit a MU-RTS TXS TF, which is an allocation frame (803), to allocate a TXOP to AP 2 (710-2). The duration field of the MAC header of the allocated frame can be set to the value of 'length of AP 2 (710-2) CTS frame + SIFS time length'. Since the value of the TXNAV timer corresponds to the remaining time length of the entire TXOP that AP 1 (710-1) intends to use, it can be maintained until the TXOP of AP 1 (710-1) is terminated. Meanwhile, other EDCAFs other than the VO EDCAF that sent the polling frame may stop channel access operations (e.g., stop channel access operations by considering the medium to be occupied because the TXNAV has not expired) and not send frames until the VO EDCAF sends the last frame (or PPDU).

[0273] After AP 1 (710-1) finishes exchanging data frames with non-AP STA 1 (720-1), it may transmit a MU-RTS TXS TF, which is an allocation frame (803), to allocate a TXOP to AP 2 (710-2). Here, the duration field of the MAC header of the allocation frame may be set to 'time length of the CTS frame + SIFS'. When AP 1 (710-1) receives a CTS frame, which is a response frame (804) to the allocation frame (803) from AP 2 (710-2), AP 1 (710-1) may not perform frame transmission until the time interval allocated to AP 2 (710-2) in the allocation frame (801) has ended. Alternatively, AP 1 (710-1) may not perform frame transmission until it receives a frame instructing a TXOP return from AP 2 (710-2) (e.g., receiving a QoS data frame or QoS Null frame in which the value of the RDG / More PPDU subfield of the CAS (command and status) Control field included in the HT Control field of the frame's MAC header is 0 from AP 2 (710-2)).

[0274] Here, the TXOP holder EDCAF may ignore TXNAV, but as described above, in the period where TXNAV is set, the TXOP holder EDCAF may also detect the medium as occupied and not perform channel access operations if the TXNAV has not expired. Alternatively, the TXOP holder EDCAF may perform a 'do nothing' operation for the allocated duration regardless of TXNAV. That is, all AC-specific EDCAFs of AP 1 (710-1), including the TXOP holder EDCAF of AP 1 (710-1), may not perform frame transmission.

[0275] Here, when AP 1 (710-1) receives a frame instructing a TXOP transition from AP 2 (710-2) or when the allocated duration time interval expires, the TXOP holder EDCAF of AP 1 (710-1) may ignore the TXNAV or stop the 'do nothing' operation and resume the operation for frame transmission. This allows the TXOP holder EDCAF of AP 1 (710-1) to transmit a frame before the set TXNAV timer expires. Alternatively, if additional frames to be transmitted cannot be transmitted before the TXNAV timer expires or the TXNAV has already expired, the TXOP holder EDCAF of AP 1 (710-1) may not transmit any more frames. When TXNAV expires, all EDCAFs of AP 1 (710-1) can resume channel access operations without detecting the medium as occupied by TXNAV (e.g., detecting virtual carrier detection as idle, and consequently resuming backoff operations and TXOP acquisition operations).

[0276] As described above, AP 1 (710-1) sets the TXNAV based on the value of the remaining time length of the entire TXOP of AP 1 (710-1) when transmitting the first polling frame, but AP 1 (710-1) may also set the TXNAV based on the value of the remaining time length of the entire TXOP of AP 1 (710-1) when transmitting a frame within the TXOP.

[0277] The above-described method for setting transmission intervals for multiple frame transmissions of AP 1 (710-1), which is a coordinating AP and a TXOP holder in FIGS. 15a to 15d, may be described below. A method for setting transmission intervals for a coordinated AP to perform multiple frame transmissions is described below.

[0278] FIGS. 16a and FIGS. 16b are diagrams illustrating a method for setting the frame transmission interval of a coordinated AP during wireless LAN Co-TDMA operation applicable to the present disclosure.

[0279] Referring to FIGS. 16a and 16b, in the wireless LAN network environment described above, AP 1 (710-1) and non-AP STA 1 (720-1), which is a non-AP STA connected to AP 1 (710-1), can operate. Additionally, a case can be considered in which AP 2 (710-2) and non-AP STA 2 (720-2), which is a non-AP STA connected to AP 2 (710-2), operate. Here, AP 1 (710-1) can perform a channel access operation (e.g., a channel access operation following the EDCA TXOP acquisition procedure and the EDCA backoff procedure) as a coordinating AP and succeed to acquire a TXOP (e.g., determine the start of frame transmission at the slot boundary where the EDCAF backoff counter is 0). AP 1 (710-1) can perform the polling step and data communication step (performing data communication with non-AP STA 1 (720-1)) of the [Co-TDMA operation step] described in FIG. 14 in order to share TXOP with AP 2 (710-2), and then perform the allocation step.

[0280] AP 2 (710-2) receives an allocated frame from AP 1 (710-1) and can transmit a CTS frame, which is a response frame to the allocated frame from AP 1 (710-1), within the allocated duration time interval. Subsequently, AP 2 (710-2) can perform frame exchange (e.g., data frame exchange with non-AP STA 2 (720-2), which is a non-AP STA connected to AP 2 (710-2)) within the allocated duration time interval within the remaining TXOP. Meanwhile, AP 2 (710-2) may also act similarly to a TXOP holder within the allocated duration time interval. That is, AP 2 (710-2) may be considered to have temporarily acquired the TXOP, and once the allocated duration time interval ends, AP 2 (710-2) may no longer be considered to have acquired the TXOP. Here, if AP 2 (710-2) transmits a data frame within the allocated duration time interval, AP 2 (710-2) may fail to transmit the data frame. For example, the transmission of a frame sent by AP 2 (710-2) to non-AP STA 2 (720-2) may fail (e.g., failure to receive an acknowledgment frame within a certain time (e.g., AckTimeout time). Since AP 2 (710-2) has transmitted a CTS frame to the coordinating AP AP 1 (710-1), AP 2 (710-2) considers the initial frame exchange to have been successful within the allocated duration time interval, and may be able to retransmit the frame if a failure occurs in a subsequent transmission. For example, AP 2 (710-2) (or a specific channel access function of AP 2 (710-2)) may transmit a data frame to a non-AP STA 1 (720-1) or a non-AP STA connected to AP 1 (710-1) that is not non-AP STA 1 (720-1) at the time when the TxPIFS slot boundary is reached after the new channel access procedure has been initiated and completed or after the transmission of a failed frame has been completed.Here, a specific channel access function may perform a new channel access procedure. The specific channel access function may be one of the AC-specific EDCAFs of AP 2 (710-2). Or, the specific channel access function may be a distributed coordination function (DCF). If the specific channel access function is one of the AC-specific EDCAFs of AP 2 (710-2), then one of the AC-specific EDCAFs of AP 2 (710-2) may be an EDCAF associated with a preferred AC (or an EDCAF associated with a higher AC) included in at least one of the polling frames or allocation frames received by AP 2 (710-2) from AP 1 (710-1). As another example, one of the AC-specific EDCAFs of AP 2 (710-2) may be the EDCAF associated with the preferred AC (or EDCAF associated with a higher-priority AC) included in at least one of the polling frames or allocation frames received by AP 2 (710-2) from AP 1 (710-1), for which the channel access operation was completed first. The channel access operation may be determined by being performed internally by AP 2 (710-2), or it may be performed through a backoff and / or TXOP acquisition procedure after the transmission of the CTS frame (806), which is an ICR transmitted by AP 2 (710-2). AP 2 (710-2) (i.e., the coordinated AP) may transmit a frame of the preferred AC or a higher-priority AC indicated by AP 1 (710-1) (i.e., the coordinating AP) in the polling frame. Here, among the four ACs VO, VI, BE, and BK, the AC with the highest priority is VO, and the AC with the lowest priority is BK. For example, if the preferred AC is BE, AP 1 (710-1) can transmit frames of three ACs, VO, VI, and BE, within the allocated duration time interval.If at least one frame that AP 2 (710-2) is to transmit includes a frame in which AC is VO, the channel access function that AP 2 (710-2) transmits the frame within the allocated duration may be VO EDCAF. Additionally, retransmission operations may also be performed by VO EDCAF. That is, the EDCAF associated with the highest priority AC among the frames that AP 2 (710-2) intends to transmit within the allocated duration may (re)transmit the frame.

[0281] As another example, if AP 2 (710-2) successfully transmits the first VO frame and subsequently transmits a BE frame (i.e., a lower AC frame) but fails, the retransmission operation of the failed BE frame may be performed by the BE EDCAF. That is, the retransmission operation of the failed frame may be performed by the EDCAF associated with the AC of the failed frame. Alternatively, the retransmission operation of the failed frame may be performed by the EDCAF of all ACs that first succeeded in the channel access operation. The channel access operation may be determined by being performed internally by AP 2 (710-2), or it may be performed through a backoff or / and TXOP acquisition procedure that begins from the time AP 2 (710-2) completes the transmission of the failed frame.

[0282] Even if the specific channel access function described above initiates and completes a new channel access procedure, the specific channel access function may only be able to retransmit the frame within the range that does not exceed the allocated duration time interval allocated by AP 1 (710-1). The allocated duration time interval may not be extended. That is, frame exchange including frame retransmission may not exceed the allocated duration time interval. Although the operation for the case where AP 2 (710-2) shares a TXOP from AP 1 (710-1) and retransmits a frame has been described above, the operation described above may be performed through various methods and is not limited to a specific form.

[0283] A polling frame or allocation frame transmitted by AP 1 (710-1) to AP 2 (710-2) may include an indicator that indicates which TXOP protection method (e.g., indicating one of single protection and multiple protection) AP 2 (710-2) should use within the allocated duration. For example, AP 1 (710-1) may indicate one of single protection and multiple protection in a specific bit or subfield included in the user info field, which indicates the AP ID of AP 2 (710-2) in the allocation frame, MU-RTS TXS frame. AP 2 (710-2) may set the MAC header duration value within the allocated duration time interval according to the indicator in the allocation frame.

[0284] Here, when a coordinated AP performs the transmission and reception of data frames, including the retransmission of a frame with an error, within a shared transmission interval during Co-TDMA operation in a wireless LAN network, the exchange order of detailed frames (or the position of a specific field) may be changed in relation to the operations described below. Additionally, the frame retransmission operation of the coordinated AP described in FIGS. 16a and 16b may be performed identically or similarly within the allocated duration by a STA that has shared a TXOP from a TXOP holder STA of a Triggered TXOP sharing operation, and is not limited to a specific form.

[0285] FIG. 16a may be a method for a coordinated AP to set the MAC header duration field value based on a single protection method. Referring to FIG. 16a, AP 2 (710-2), which is a coordinated AP, receives an allocation frame (805) from AP 1 (710-1), which is a coordinating AP, and can transmit a CTS frame after SIFS as a response frame (806) to the allocation frame (805). Here, the MAC header duration field value of the CTS frame can be set to a value obtained by subtracting 'SIFS + time length of the CTS frame' from the duration field value of the allocation frame. For example, if the duration of the allocation frame is 'SIFS + time length of the CTS frame', the MAC header duration field value of the AP 2 (710-2) CTS frame can be set to 0 and transmitted. When AP 2 (710-2) receives an allocation frame (805) transmitted by AP 1 (710-1), AP 2 (710-2) can check the allocated duration time interval. AP 2 (710-2) can transmit and receive frames within the allocated duration time interval after transmitting a CTS frame. Here, since the duration field value of the frame transmitted by AP 2 (710-2) is 0, TXNAV may not be set. However, within the allocated duration time interval, only a specific channel access function of AP 2 (710-2) may be allowed to transmit frames, and other channel access functions may have their channel access operations suspended (e.g., performing a 'do nothing' operation during the allocation duration, considering the medium as busy during the allocation duration, repeating channel access operations, and not transmitting frames).Alternatively, independently of the duration field value of the frame transmitted by AP 2 (710-2), AP 2 (710-2) may set TXNAV to a time length value corresponding to the allocated duration interval when it receives an allocated frame or transmits a CTS frame for the allocated frame. In the above case, channel access functions other than the specific channel access function may detect the medium as occupied and stop channel access operations until TXNAV expires.

[0286] AP 2 (710-2) may transmit frames to non-AP STA 2 (720-2) within the allocated duration time interval. The duration field value of the frame transmitted by AP 2 (710-2) to non-AP STA 2 (720-2) may be set to the time required for the response frame to the frame. Alternatively, the duration field value of the frame transmitted by AP 2 (710-2) to non-AP STA 2 (720-2) may be set to the time required for the transmission of the response frame to the frame and the transmission of additional frames by AP 2 (710-2). AP 2 (710-2) may allow the transmission of multiple frames within the range that does not exceed the allocated duration time interval (or, until the expiration of TXNAV).

[0287] As another example, AP 2 (710-2) may allow only single frame exchanges within a range that does not exceed the allocated duration time interval. Specifically, only RTS frames, CTS frames, data frames transmitted to non-AP STA 2 (720-2), response frames received when the frame transmitted to non-AP STA 2 (720-2) is a frame requiring an immediate response frame, and QoS frames transmitted by AP 2 (710-2) to request a TXOP return (e.g., QoS Null frames or QoS Data frames in which the value of the RDG / More PPDU subfield of the CAS Control field included in the HT Control field of the MAC header is 0) may be allowed. In the above case, the duration field of the first frame transmitted by AP 2 (710-2) after transmitting a CTS frame to AP 1 (710-1) in the allocated duration may be set to a value excluding the time length of the first frame transmitted by AP 2 (710-2) after transmitting a CTS frame in the time interval required for the RTS frame exchanged with non-AP STA 2 (720-2), the CTS frame, the data frame transmitted to non-AP STA 2 (720-2), the response frame if the frame transmitted to non-AP STA 2 (720-2) is a frame requiring an immediate response frame, the QoS Null frame transmitted by AP 2 (710-2) to request a TXOP return, and at least one frame, which is the IFS time (e.g., at least one SIFS or PIFS time interval).

[0288] FIG. 16b is a diagram illustrating how a coordinated AP sets the MAC header duration field based on a multiple protection method. Referring to FIG. 16b, AP 2 (710-2), which is a coordinated AP, receives an allocation frame (805) from AP 1 (710-1), which is a coordinating AP, and can transmit a CTS frame after SIFS as a response frame (806) to the allocation frame (805). Here, the MAC header duration field value of the CTS frame (806) can be set to a value obtained by subtracting 'SIFS + time length of the CTS frame' from the duration field value of the allocation frame. For example, if the duration of the allocation frame is 'SIFS + time length of the CTS frame', the MAC header duration field value of the CTS frame of AP 2 (710-2) can be set to 0 and transmitted.

[0289] As another example, the duration field value of the CTS frame MAC header of AP 2 (710-2) may be set to indicate the remaining allocated duration time interval. When AP 2 (710-2) receives an allocated frame transmitted by AP 1 (710-1), AP 2 (710-2) can check the allocated duration time interval. After transmitting the CTS frame, AP 2 (710-2) can transmit and receive frames within the allocated duration time interval. Subsequently, the duration field value of the frame transmitted by AP 2 (710-2) may be set to indicate the remaining allocated duration time interval. That is, AP 2 (710-2), which is a coordinated AP, may want to transmit multiple frames using a multiple protection method regardless of the protection method, unless AP 1 (710-1) separately instructs AP 2 (710-2) to use a TXOP protection method.

[0290] AP 2 (710-2) can set TXNAV based on the duration field of the CTS frame and the duration field value of the frame subsequently transmitted. In the above case, channel access functions other than the specific channel access function may detect the medium as occupied and stop channel access operations until TXNAV expires. AP 2 (710-2) can transmit frames to non-AP STA 2 (720-2) within the allocated duration time interval (or before the TXNAV timer expires). If AP 2 (710-2) fails to transmit a frame to non-AP STA 2 (720-2) (including failure of the initial frame transmission by AP 2 (710-2) to non-AP STA 2 (720-2) within the allocated duration time interval), AP 2 (710-2) may retransmit the frame at the time of the TxPIFS slot boundary reached from the time of completion of transmission of the failed frame, or at the time of performing and completing a new channel access operation, provided that it does not go out of the allocated duration time interval. This may be the case where AP 2 (710-2) receives a TXOP from AP 1 (710-1) and transmits a CTS frame to AP 1 (710-1), which is considered to be the initial frame exchange of AP 2 (710-2) successful.

[0291] As another example, if the first frame transmission sent by AP 2 (710-2) to non-AP STA 2 (720-2) within the allocated duration fails, AP 2 (710-2) must perform a new channel access operation, and once the channel access operation is completed, it may perform an operation to retransmit the frame to non-AP STA 2 (720-2). That is, retransmitting the frame at the TxPIFS slot boundary may not be allowed. This may be the case where AP 2 (710-2) receives a TXOP from AP 1 (710-1) and transmits a CTS frame to AP 1 (710-1), which is not considered to be the first frame exchange of AP 2 (710-2). However, if AP 2 (710-2) fails to transmit a frame to non-AP STA 2 (720-2) within the allocated duration, but the failed frame is not the first frame transmitted by AP 2 (710-2) to non-AP STA 2 (720-2) within the allocated duration time interval, the first frame exchange of AP 2 (710-2) is considered successful, and AP 2 (710-2) may retransmit the frame at the time of the TxPIFS slot boundary reached from the time of completion of transmission of the failed frame or at the time of performing and completing a new channel access operation, provided that it does not go out of the allocated duration time interval or TXNAV.

[0292] For FIGS. 17 to 19 described below, the [Co-TDMA wireless LAN network configuration] and [Co-TDMA operation steps] described in FIGS. 7, 8, and 14 may be applied in the same way. However, the specific operation for each figure may be performed with modifications and is not limited to a specific form. The following description is based on the case where AP 2 (710-2), which is a coordinated AP, supports dynamic bandwidth expansion (DBE) operation that can dynamically expand the operating bandwidth of the basic service set (BSS), but it may not be limited to this.

[0293] FIG. 17 is a diagram illustrating a wireless LAN DBE operation method applicable to the present disclosure. Referring to FIG. 17, AP 2 (710-2) and at least one non-AP STA connected to AP 2 (710-2) may form a BSS (e.g., BSS of AP 2 (710-2), AP 2 (710-2) BSS, BSS 2). The basic operating bandwidth of BSS 2 may be indicated by AP 2 (710-2). Here, the basic operating bandwidth (non-DBE bandwidth, BSS operating bandwidth) of AP 2 (710-2) may be 20, 40, 80, or 160 MHz, but is not limited thereto. FIG. 17 describes the case where the operating bandwidth of AP 2 (710-2) is 160 MHz, but this is for convenience of explanation only and is not limited thereto.

[0294] The base operating bandwidth is the operating bandwidth of the original AP 2 (710-2) that has not been extended. If the AP 2 (710-2) supports DBE, the AP 2 (710-2) may want to operate at a bandwidth wider than the base operating bandwidth. For example, the AP 2 (710-2) may want to operate at an operating bandwidth larger than the base operating bandwidth without changing the main 20 MHz channel. As a specific example, if the AP 2 (710-2) has a base operating bandwidth of 160 MHz, the AP 2 (710-2) may use DBE to extend the operating bandwidth (referred to as DBE operating bandwidth) to 320 MHz. As another example, if the operating bandwidth of the AP 2 (710-2) is smaller, the DBE operating bandwidth may be configured in a more diverse form. For example, if the basic operating bandwidth of AP 2 (710-2) is 40 MHz, the DBE operating bandwidth of AP 2 (710-2) can be 80, 160, or 320 MHz, etc. That is, the DBE operating bandwidth can be set to a bandwidth greater than the basic operating bandwidth.

[0295] AP 2 (710-2) may have various operating bandwidth extension modes. For example, AP 2 (710-2) may extend the operating bandwidth using a specific DBE operating bandwidth. When AP 2 (710-2) extends the operating bandwidth using a specific DBE operating bandwidth, the basic operating bandwidth of AP 2 (710-2) is 40 MHz and the DBE operating bandwidth is 160 MHz, but it may also be possible to fix it to another specific DBE operating bandwidth. Here, AP 2 (710-2) may operate with only one bandwidth, either the basic bandwidth of 40 MHz or the DBE operating bandwidth of 160 MHz.

[0296] As another example, AP 2 (710-2) can pre-set multiple DBE profiles and expand the operating bandwidth based on them. When AP 2 (710-2) expands the operating bandwidth by pre-setting multiple DBE profiles, the basic operating bandwidth of AP 2 (710-2) is 40 MHz, and the maximum DBE operating bandwidth of AP 2 (710-2) can be determined to be 320 MHz or other bandwidths. AP 2 (710-2) can also freely change the operating bandwidth within a range of operating bandwidths that are equal to or greater than the basic operating bandwidth and equal to or smaller than the maximum DBE operating bandwidth.

[0297] Referring to FIG. 17, a method of indicating AP 2 (710-2) for the above-described DBE operation may be required. AP 2 (710-2) may transmit Beacon frames (807-1, 807-2, 807-3, 807-4) at a TBTT (target beacon transmission time) period. The Beacon frames (807-1, 807-2, 807-3, 807-4) may generally indicate the basic operating bandwidth of AP 2 (710-2). If AP 2 (710-2) intends to indicate an operating bandwidth expansion through DBE, AP 2 (710-2) may include a UHR parameter update element in the Beacon frames transmitted by AP 2 (710-2). The UHR parameter update element may include the DBE operating bandwidth that AP 2 (710-2) intends to use, and may include a counter (e.g., a countdown timer) that indicates when the DBE operating bandwidth is applied. For example, if the default operating bandwidth of AP 2 (710-2) is 160 MHz and the DBE operating bandwidth that AP 2 (710-2) intends to use is 320 MHz, AP 2 (710-2) may indicate the 320 MHz DBE operating bandwidth through the UHR parameter update element of the beacon frames transmitted by AP 2 (710-2). Additionally, AP 2 (710-2) may indicate when the DBE operating bandwidth is applied by decreasing the counter included in the UHR parameter update element. For example, if the counter is 2, the counter may indicate that the DBE operating bandwidth is used after two beacon cycles. As another example, if the counter is 1, the counter may indicate that the DBE operating bandwidth will be used starting from the next beacon cycle (i.e., the next beacon transmission).As another example, if the counter is 0 or 127, it may indicate that DBE operation bandwidth is being used during the current beacon period (i.e., the time of transmission of the beacon containing the UHR parameters update element). As another example, if the counter is greater than 127, it may indicate that DBE bandwidth has been in use since before the 'counter - 127' beacon period. A beacon frame indicating that AP 2 (710-2) is using DBE operation bandwidth (i.e., a beacon frame containing the UHR parameters update element with a counter of 0, 807-3) and a subsequently transmitted beacon frame (807-4) may additionally include a UHR operation element to indicate that AP 2 (710-2) is using DBE operation bandwidth (i.e., AP 2 (710-2) is using DBE). As another example, the probe request / response frame and the UHR link (re)configuration request / response frame transmitted by AP 2 (710-2) may include at least one of the UHR parameter update element and the UHR operation element described above. The probe request / response frame and the UHR link (re)configuration request / response frame may indicate at least one of the time when AP 2 (710-2) uses the DBE, whether AP 2 (710-2) is currently using the DBE, and the DBE operation bandwidth.

[0298] Additionally, AP 2 (710-2) may terminate the use of the DBE in the same or similar manner as described above. For example, the UHR parameter update element may not indicate the DBE operation bandwidth parameter or may include an indicator explicitly indicating the termination of the DBE. That is, AP 2 (710-2) transmits beacon frames containing an indicator indicating the termination of DBE use. AP 2 (710-2) may decrease the value of the counter in the UHR parameter update element by 1 while transmitting beacon frames containing an indicator indicating the termination of DBE use. Subsequently, when the counter in the UHR parameter update element of the beacon frame containing the indicator indicating the termination of DBE use transmitted by AP 2 (710-2) reaches 0 or 127, the use of the DBE may be terminated. As another example, the UHR operation element may indicate that the DBE is not being used.

[0299] As described above, when AP 2 (710-2) instructs the use of DBE and uses DBE (i.e., when AP 2 (710-2) operates from the basic operating bandwidth to an extended DBE operating bandwidth), bandwidth information exchange for Co-TDMA operation can be performed.

[0300] FIG. 18 is a diagram showing bandwidth information of Coordinated APs exchanged in the MAPC procedure to which the present disclosure applies.

[0301] Referring to FIG. 18, AP 2 (710-2), which is a coordinated AP, can transmit a frame containing a multi-AP coordination (MAPC) element to AP 1 (710-1), which is a coordinating AP, to perform co-TDMA operation bandwidth information exchange. For example, AP 2 (710-2) can negotiate with AP 1 (710-1) in advance regarding DBE operation possibility through a MAPC frame containing a MAPC element. For another example, AP 2 (710-2) may not perform a separate negotiation with AP 1 (710-1), and it may be possible for DBE operation possibility to be indicated at the folding stage.

[0302] FIG. 18 may be the highest layer block as a MAPC element. The MAPC Schemes Info of the MAPC element may include one or more subelements, each of which may indicate the respective operation parameters required for Co-TDMA. AP 2 (710-2) may include two or more subelements in the MAPC Schemes Info to indicate the basic operation bandwidth and DBE operation bandwidth, respectively, as described in FIG. 17. The block of the second layer may represent two Co-TDMA subelements. The MAPC scheme parameter set of one of the two subelements (the left subelement of the second layer block) may include the basic operation bandwidth information of AP 2 (710-2) when performing Co-TDMA operation. Referring to the third and fourth layers, the bandwidth control subfield within the MAPC scheme parameter set may indicate the BW info header and the CCFS (channel center frequency). The BW info header may include an indicator indicating that DBE operation is disabled. Thus, the bandwidth indicated by the bandwidth control subfield may be the default operating bandwidth of AP 2 (710-2). Accordingly, the remainder of the BW info header may include the default operating bandwidth of AP 2 (710-2) and a disabled subchannel bitmap that is disabled at the default operating bandwidth. Additionally, if the BW info header includes an indicator indicating that DBE operation is disabled, the CCFS indicator subfield of the bandwidth control subfield may indicate channel center frequency information when AP 2 (710-2) is operating at the default operating bandwidth.

[0303] The MAPC scheme parameter set of the remaining of the two sub-elements (the right sub-element of the second layer block) may contain DBE bandwidth information of AP 2 (710-2) when performing Co-TDMA operation. Referring to the third and fourth layers, the bandwidth control subfield within the MAPC scheme parameter set may indicate a BW info header and a channel center frequency (CCFS). The BW info header contains a DBE usage indicator, and the bandwidth indicated by the bandwidth control subfield may be the DBE operation bandwidth of AP 2 (710-2). Accordingly, the remainder of the BW info header may contain the DBE bandwidth of AP 2 (710-2) and a disabled subchannel bitmap in the DBE bandwidth. Additionally, if the BW info header includes an indicator indicating DBE usage, the CCFS indicator subfield of the bandwidth control subfield may indicate channel center frequency information when AP 2 (710-2) is operating in the DBE bandwidth. Additionally, the DBE usage indicator in the BW info header may be extended to a DBE profile. For example, if there are three possible DBE bandwidths for AP 2 (710-2), namely 80, 160, and 320 MHz, the BW info header may include an identifier to distinguish each DBE bandwidth. As another example, even if there are two or more possible DBE bandwidths for AP 2 (710-2), the DBE usage indicator in the BW info header may not be extended to a DBE profile. The DBE usage indicator or DBE profile information may further indicate whether AP 2 (710-2) is currently operating using the corresponding DBE bandwidth.

[0304] As another example, as described above, when AP 2 (710-2) has multiple usable DBE bandwidths, such as when there are three possible DBE bandwidths of AP 2 (710-2) at 80, 160, and 320 MHz, the MAPC Schemes Info may include a sub-element indicating one basic operating bandwidth and additional sub-elements indicating DBE bandwidths equal to the number of usable DBE bandwidths of AP 2 (710-2). In the description above, AP 2 (710-2) indicated the basic operating bandwidth and DBE operating bandwidths using sub-elements indicating two or more Co-TDMA operating bandwidths using DBE, but AP 2 (710-2) may also indicate the information described above using a different method. For example, if AP 2 (710-2) does not use DBE (or, if DBE use is discontinued), AP 2 (710-2) may include a sub-element indicating a Co-TDMA operating bandwidth in the MAPC Schemes Info of the MAPC element transmitted to AP 1 (710-1). The sub-element indicating a Co-TDMA operating bandwidth may indicate the default operating bandwidth of AP 2 (710-2) (and CCFS, disabled subchannel bitmap). Additionally, if AP 2 (710-2) uses DBE, the MAPC Schemes Info of the MAPC element transmitted to AP 1 (710-1) may include a sub-element indicating a Co-TDMA operating bandwidth. The sub-element indicating a Co-TDMA operating bandwidth may indicate the DBE bandwidth of AP 1 (710-1) (and CCFS, disabled subchannel bitmap). That is, whenever AP 2 (710-2) uses and discontinues the DBE, it can transmit a frame containing a MAPC element that indicates the DBE bandwidth or the basic operating bandwidth as described above to AP 1 (710-1).

[0305] When AP 1 (710-1) receives a frame from AP 2 (710-2) containing a MAPC element identical or similar to the MAPC element described above, AP 1 (710-1) can recognize that AP 2 (710-2) supports DBE operation (i.e., supports an operation bandwidth other than the basic operation bandwidth of AP 2 (710-2)). Accordingly, AP 1 (710-1) can perform at least one of a Co-TDMA polling step and an allocation step according to the basic operation bandwidth and DBE bandwidth of AP 2 (710-2).

[0306] FIG. 19 is a diagram illustrating a Co-TDMA operation method based on DBE operation applicable to the present disclosure. AP 1 (710-1) can perform a polling step and an allocation step to share time resources with AP 2 (710-2) within a TXOP acquired by AP 1 (710-1). Through the polling step, AP 1 (710-1) can determine whether AP 2 (710-2) wishes to be allocated time resources during the allocation step.

[0307] Referring to FIG. 19, AP 1 (710-1) sends polling frames (808-1, 808-2) to AP 2 (710-2), and AP 2 (710-2) can send an ICR (initial control response, 809-1, 809-2) in response to the polling frames of AP 1 (710-1). Here, the ICR (809-1, 809-2) may be a Multi-STA BlockAck (M-BA) frame. AP 2 (710-2) may want to be allocated time resources from AP 1 (710-1). In the case where AP 2 (710-2) indicates the current operating bandwidth of AP 2 (710-2) in FIG. 17 described above (e.g., AP 2 (710-2) transmits a MAPC element containing sub-elements indicating two or more Co-TDMA operating bandwidths, and the MAPC Scheme Parameter Set containing DBE bandwidth information includes an indicator that AP 2 (710-2) is currently operating using the corresponding DBE bandwidth, or if AP 2 (710-2) uses DBE operation, it includes a MAPC element containing a sub-element indicating Co-TDMA operating bandwidth containing DBE bandwidth information, and if AP 2 (710-2) does not use DBE operation, AP 2 (710-2) transmits a MAPC element containing a sub-element indicating Co-TDMA operating bandwidth containing basic operating bandwidth information), the ICR (809-1) transmitted by AP 2 (710-2) indicates whether AP 2 (710-2) participates in the polling phase. It can only include indicators.

[0308] As another example, if AP 2 (710-2) does not specify the operating bandwidth of AP 2 (710-2) to AP 1 (710-1), AP 2 (710-2) may transmit the ICR (809-1, 809-2) including the current operating bandwidth information of AP 2 (710-2) (e.g., default operating bandwidth information (default operating bandwidth, disabled subchannel bitmap, CCFS) or DBE bandwidth information (DBE bandwidth, disabled subchannel bitmap, CCFS)) according to the current operating bandwidth of AP 2 (710-2). As an example, if AP 2 (710-2) operates at the default operating bandwidth, the ICR (809-1) transmitted by AP 2 (710-2) may not need to include the default operating bandwidth information.

[0309] As another example, if AP 2 (710-2) specifies each DBE profile as in FIG. 18, AP 2 (710-2) may include DBE profile information (identifier) ​​in the ICR (809-2) and transmit it. AP 1 (710-1) may transmit an allocation frame (810-2) to AP 2 (710-2) using the bandwidth information included in the ICR received from AP 2 (710-2), the bandwidth information included in the MAPC element received from AP 2 (710-2) as described in FIG. 18, or the operational bandwidth information of AP 2 (710-2) that AP 1 (710-1) has received and verified (e.g., reception of a frame according to the procedure in which AP 2 (710-2) instructs AP 2 (710-2) to use / stop using the DBE as in FIG. 17). AP 1 (710-1) can send allocation frames to AP 2 (710-2) using the DBE operation bandwidth information (default operation bandwidth, disabled subchannel bitmap, CCFS) of AP 2 (710-2) when AP 2 (710-2) is currently using DBE operation. For example, when AP 1 (710-1) is operating at 320 MHz and AP 2 (710-2) has stopped using DBE and is operating at the default operation bandwidth of 160 MHz, AP 1 (710-1) can send allocation frames and polling frames to allocate resources to AP 2 (710-2) within a maximum bandwidth of 160 MHz. On the other hand, if AP 2 (710-2) uses DBE and operates at a DBE bandwidth of 320 MHz, AP 1 (710-1) can transmit allocation frames and polling frames to allocate resources to AP 2 (710-2) within a maximum bandwidth of 320 MHz.Specifically, if AP 1 (710-1) includes AP 2 (710-2) among the candidates for AP to share a TXOP using Co-TDMA operation, and AP 2 (710-2) is expected to perform a DBE operation based on the exchange of MAPC elements through the MAPC procedure, AP 1 (710-1) may transmit a polling frame or the first frame of the TXOP to which the polling frame is transmitted with a bandwidth within the upper limit of the maximum DBE bandwidth of AP 2 (710-2). If the bandwidth of the polling frame transmitted by AP 1 (710-1) or the first frame of the TXOP to which the polling frame is transmitted is within the basic bandwidth of AP 2 (710-2), AP 1 (710-1) directs the bandwidth of the response frame to the polling frame to be within the bandwidth of the polling frame. However, if the bandwidth of the polling frame transmitted by AP 1 (710-1) or the first frame of the TXOP in which the polling frame is transmitted exceeds the basic bandwidth of AP 2 (710-2) and is within the maximum DBE bandwidth of AP 2 (710-2), AP 1 (710-1) needs a method to indicate the bandwidth of the response frame to the polling frame. AP 1 (710-1) may indicate the bandwidth of the response frame to the polling frame to be within the basic bandwidth of AP 2 (710-2). AP 2 (710-2) may receive the polling frame of AP 1 (710-1) and transmit the response frame to the polling frame at the basic bandwidth of AP 2 (710-2). Alternatively, if AP 2 (710-2) receives a polling frame in a DBE bandwidth wider than the base bandwidth of AP 2 (710-2), it may transmit a response frame to the polling frame using the bandwidth in which the polling frame was transmitted, ignoring the bandwidth indication of AP 1 (710-1). Alternatively, AP 1 (710-1) may indicate the bandwidth of the response frame to the polling frame using the bandwidth of the polling frame that is greater than or equal to the base bandwidth of AP 2 (710-2).AP 1 (710-1) may transmit an allocation frame to AP 2 (710-2) with the upper limit of the operating bandwidth of AP 2 (710-2) indicated in the response frame transmitted by AP 2 (710-2) or / and the bandwidth of the polling frame transmitted by AP 1 (710-1) or the initial frame of the TXOP in which the polling frame is transmitted. AP 2 (710-2) may receive a polling frame from AP 1 (710-1) and transmit a response frame for the polling frame using the bandwidth of the polling frame that is within the DBE bandwidth of AP 2 (710-2). Alternatively, AP 2 (710-2) may use DBE operation but the operating DBE operating bandwidth may be smaller than the bandwidth of the polling frame, or AP 2 (710-2) may stop using DBE and operate at the default operating bandwidth. AP 2 (710-2) can transmit a response frame to a polling frame by ignoring the bandwidth indication of AP 1 (710-1) and setting the operating bandwidth of AP 2 (710-2) as the upper limit. AP 1 (710-1) can transmit an allocation frame to AP 2 (710-2) by setting the operating bandwidth of AP 2 (710-2) indicated in the response frame transmitted by AP 2 (710-2) as the upper limit.

[0310] FIG. 20 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies. Referring to FIG. 20, a first STA in a wireless LAN system may acquire a transmission opportunity (TXOP) (S2010). After that, the first STA may transmit a polling frame in the TXOP based on coordinated time division multiple access (Co-TDMA) and receive a response frame for the polling frame (S2020). After that, the first STA may transmit an allocation frame after receiving the response frame for the polling frame and receive a response frame for the allocation frame (S2030), and may share the allocated duration within the TXOP with the second STA.

[0311] Here, the allocated duration is a transmission opportunity granted to the second STA, and the first STA may receive a TXOP return frame within the allocated duration or may not perform frame transmission or reception within the allocated duration until the allocated duration ends. Additionally, according to one embodiment of the present specification, when the first STA shares the allocated duration with the second STA and the third STA, the allocated duration to the second STA may be shared based on the main channel.

[0312] In addition, for example, when the first STA shares the allocated duration with the second STA, the first STA and the third STA connected to the first STA can perform frame exchange on the non-primary channel access (NPCA) primary channel during the allocated duration period. When the first STA receives a TXOP return frame from the second STA within the allocated duration, it can terminate the sharing of the allocated duration. In addition, when the first STA performs frame exchange with the third STA through the NPCA channel during the allocated duration, the transmission of the TXOP return frame may be prohibited. In addition, the first STA and the third STA can operate based on at least one of a first type NPCA operation that supports NPCA operation based on TXOP length and a second type NPCA operation that supports NPCA operation based on PPDU (physical layer protocol data unit).

[0313] When the first STA and the third STA perform an NPCA operation in the allocated duration, only the second type NPCA operation is allowed, and transmission of a TXOP return frame by the second STA in the allocated duration may be allowed. Additionally, when the first STA and the third STA perform an NPCA operation in the allocated duration, both the first type NPCA operation and the second type NPCA operation are allowed, provided that the first STA transmits an indicator prohibiting transmission of a TXOP return frame in the allocated duration to the second STA, and based on the indicator prohibiting transmission of a TXOP return frame, transmission of a TXOP return frame by the second STA in the allocated duration may be prohibited.

[0314] Additionally, at least one of the polling frame and the allocation frame includes an NPCA interruption indicator, and based on the NPCA interruption indicator, the first STA and the third STA connected to the first STA may be prohibited from performing NPCA operations during the allocated duration. Additionally, the allocation frame transmitted by the first STA includes an indicator sharing the allocated duration and information regarding the allocated duration, and the allocation frame is transmitted to the third STA connected to the first STA, so that the allocated duration in the third STA may be set as a transmission prohibition period. Additionally, the allocated duration information is included in a user information field associated with the identifier of the second STA within the allocation frame, but when an indicator sharing the allocated duration of the allocation frame is set, the allocated duration may be identified in the third STA based on Co-TDMA regardless of the identifier associated with the user information field.

[0315] Additionally, the first STA receives a response frame for a polling frame, performs frame exchange with the third STA, and then transmits an allocated frame, wherein the third STA may be a STA connected to the first STA. The MAC (medium access control) header duration field of the frame transmitted by the first STA may be set to indicate the time required for frame exchange or to indicate the length of time until the end of the TXOP used by the first STA. Additionally, if the MAC header duration field of the frame transmitted by the first STA is set to indicate the time required for frame exchange, the TX (transmit)NAV (network allocation vector) is set by the MAC header duration field, and the first STA may perform at least one frame transmission for the first STA's first EDCAF before the TXNAV expires. Additionally, if the first STA shares the duration allocated within the TXOP with the second STA based on Co-TDMA, the first STA may perform at least one frame transmission within the TXOP even after the TXNAV expires. Additionally, the MAC header duration field of the allocated frame and the TXNAV set based on the allocated frame can be set to a time corresponding to the allocated duration. Additionally, the MAC header duration field of the polling frame transmitted by the first STA from the TXOP to the first frame indicates the time required for frame exchange of the polling frame, and the TXNAV set based on the polling frame is set to a value corresponding to the time length from the time of completion of transmission of the polling frame to the remaining TXOP of the first STA, and the first STA can perform at least one frame transmission before the TXNAV expires.Additionally, if the MAC header duration field of a frame transmitted by the first STA is set to indicate the time length until the end of the TXOP used by the first STA, the MAC header duration field of a polling frame transmitted by the first STA from the TXOP to the first frame indicates the time length from the time of completion of transmission of the polling frame until the remaining TXOP of the first STA, and the TXNAV is set to a value corresponding to the MAC header duration field, and the first STA can perform at least one frame transmission before the TXNAV expires. Additionally, the MAC header duration field of a response frame to an allocation frame is set to 0, and the TXNAV of the second STA is not set based on the MAC header duration field, but at least one frame transmission and reception by the second STA may be permitted during the allocated duration.

[0316] The MAC header duration field of the response frame for the allocation frame is set to the remaining allocated duration within the allocated duration after the completion of the response frame transmission, and the TXNAV is set to the remaining allocated duration within the allocated duration based on the MAC header duration field, and at least one frame transmission and reception of the second STA may be permitted within the allocated duration. Additionally, if the allocated duration within the TXOP is shared with the second STA, frame transmission is performed by the first EDCAF of the second STA, and if frame transmission by the first EDCAF fails, frame retransmission may be performed by the first EDCAF or an EDCAF having a higher priority than the first EDCAF within the allocated duration. Additionally, if the second STA is a STA that supports dynamic bandwidth expansion (DBE), the first STA may obtain operational bandwidth information based on DBE from the second STA before transmitting a polling frame that provides the duration allocated based on Co-TDMA to the second STA, and may share the duration allocated to the second STA based on the obtained operational bandwidth information. Additionally, if the second STA is a STA that supports DBE, the first STA may obtain operational bandwidth information based on DBE from the second STA through a response frame to a polling frame that provides the duration allocated based on Co-TDMA to the second STA, and may share the duration allocated to the second STA based on the obtained operational bandwidth information.

[0317] For example, the first STA and the second STA may each be a non-AP STA or an AP STA.

[0318] 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.

[0319]

[0320] 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 acquires a transmission opportunity (TXOP); The first STA transmits a polling frame at a TXOP based on coordinated time division multiple access (Co-TDMA) and receives a response frame for the polling frame; The step of transmitting an allocation frame after receiving a response frame for the above polling frame, and receiving a response frame for the allocation frame; and A method of operation comprising the step of sharing the duration allocated within the above TXOP with a second STA.

2. In Paragraph 1, A method of operation in which the allocated duration is a transmission opportunity granted to the second STA, and the first STA receives a TXOP return frame within the allocated duration or does not perform frame transmission or reception within the allocated duration until the allocated duration ends.

3. In Paragraph 2, A method of operation in which, when the first STA shares the allocated duration with the second STA and the third STA, the allocated duration is shared with the second STA based on the main channel.

4. In Paragraph 2, A method of operation in which, when the first STA shares the allocated duration with the second STA, the first STA and the third STA connected to the first STA perform frame exchange in the non-primary channel access (NPCA) primary channel during the allocated duration interval.

5. In Paragraph 4, A method of operation in which the first STA terminates sharing for the allocated duration when it receives the TXOP return frame from the second STA within the allocated duration.

6. In Paragraph 4, A method of operation in which, when the first STA performs the frame exchange with the third STA through the NPCA channel at the allocated duration, the transmission of the TXOP return frame is prohibited.

7. In Paragraph 4, A method of operation in which the first STA and the third STA operate based on at least one of a first type NPCA operation supporting NPCA operation based on TXOP length and a second type NPCA operation supporting NPCA operation based on PPDU (physical layer protocol data unit).

8. In Paragraph 7, A method of operation in which, when the first STA and the third STA perform an NPCA operation in the allocated duration, only a second type NPCA operation is allowed, and the transmission of the TXOP return frame by the second STA in the allocated duration is allowed.

9. In Paragraph 7, A method of operation in which, when the first STA and the third STA perform an NPCA operation in the allocated duration, both a first type NPCA operation and a second type NPCA operation are allowed, wherein the first STA transmits an indicator prohibiting the transmission of a TXOP return frame in the allocated duration to the second STA, and based on the indicator prohibiting the transmission of a TXOP return frame, the transmission of the TXOP return frame by the second STA in the allocated duration is prohibited.

10. In Paragraph 2, A method of operation in which at least one of the polling frame and the allocation frame includes an NPCA interruption indicator, and based on the NPCA interruption indicator, the first STA and the third STA connected to the first STA are prohibited from performing an NPCA operation at the allocated duration.

11. In Paragraph 2, A method of operation in which the allocation frame transmitted by the first STA includes an indicator sharing the allocated duration and information about the allocated duration, and the allocation frame is transmitted to a third STA connected to the first STA, and the allocated duration is set as a transmission prohibition period in the third STA.

12. In Paragraph 11, A method of operation in which the allocated duration information is included in a user information field associated with an identifier of a second STA within the allocation frame, wherein, when an indicator sharing the allocated duration of the allocation frame is set, the allocated duration is identified in the third STA regardless of the identifier associated with the user information field based on the Co-TDMA.

13. In Paragraph 2, A method of operation in which the first STA receives a response frame for the polling frame, performs frame exchange with the third STA, and then transmits the allocation frame, wherein the third STA is a STA connected to the first STA.

14. In Paragraph 13, A method of operation in which the MAC (medium access control) header duration field of a frame transmitted by the first STA is set to indicate the time required for frame exchange or to indicate the length of time until the end of the TXOP used by the first STA.

15. In Paragraph 14, A method of operation in which, when the MAC header duration field of a frame transmitted by the first STA is set to indicate the time required for frame exchange, the TX(transmit)NAV(network allocation vector) is set by the MAC header duration field, and the first STA performs at least one frame transmission for the first EDCAF of the first STA until the TXNAV expires.

16. In Paragraph 15, A method of operation in which, when the first STA shares the allocated duration within the TXOP with the second STA based on the Co-TDMA, the first STA performs at least one frame transmission within the TXOP even after the TXNAV expires.

17. In Paragraph 15, A method of operation in which the MAC header duration field of the allocation frame and the TXNAV set based on the allocation frame are set to a time corresponding to the allocated duration.

18. In Paragraph 15, A method of operation in which the MAC header duration field of the polling frame transmitted by the first STA as the first frame at the TXOP indicates the time required for frame exchange of the polling frame, wherein the TXNAV set based on the polling frame is set to a value corresponding to the time length from the time of completion of transmission of the polling frame to the remaining TXOP of the first STA, and the first STA performs at least one frame transmission before the TXNAV expires.

19. In Paragraph 14, A method of operation in which, when the MAC header duration field of a frame transmitted by the first STA is set to indicate the time length until the end of the TXOP used by the first STA, the MAC header duration field of the polling frame transmitted by the first STA from the TXOP to the first frame indicates the time length from the time of completion of transmission of the polling frame until the remaining TXOP of the first STA, TXNAV is set to a value corresponding to the MAC header duration field, and the first STA performs at least one frame transmission until the TXNAV expires.

20. In Paragraph 13, A method of operation in which the MAC header duration field of a response frame for the above-mentioned allocation frame is set to 0, and the TXNAV of the second STA is not set based on the MAC header duration field, but at least one frame transmission and reception of the second STA is permitted during the above-mentioned allocation duration.

21. In Paragraph 13, A method of operation in which the MAC header duration field of a response frame for the above-mentioned allocation frame is set to the remaining allocated duration within the above-mentioned allocation duration after the completion of the transmission of the above-mentioned response frame, TXNAV is set to the remaining allocated duration within the above-mentioned allocation duration based on the MAC header duration field, and at least one frame transmission and reception of the second STA is permitted during the above-mentioned allocation duration.

22. In Paragraph 2, A method of operation in which, when the allocated duration within the above TXOP is shared with the second STA, frame transmission is performed by the first EDCAF of the second STA, and when the frame transmission by the first EDCAF fails, frame retransmission is performed by the first EDCAF or an EDCAF having a higher priority than the first EDCAF within the allocated duration.

23. In Paragraph 2, A method of operation in which, if the second STA is a STA that supports dynamic bandwidth expansion (DBE), the first STA obtains operational bandwidth information based on the DBE from the second STA before transmitting the polling frame that provides the allocated duration to the second STA based on the Co-TDMA, and shares the allocated duration with the second STA based on the obtained operational bandwidth information.

24. In Paragraph 2, A method of operation in which, if the second STA is a STA that supports DBE, the first STA obtains operational bandwidth information based on the DBE from the second STA through a response frame to a polling frame that provides the allocated duration to the second STA based on the Co-TDMA, and shares the allocated duration with the second STA based on the obtained operational bandwidth information.

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

26. In a wireless LAN system, in a first station (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: Acquire a transmission opportunity (TXOP), and Based on Coordinated Time Division Multiple Access (Co-TDMA), a polling frame is transmitted at the TXOP, and a response frame to the polling frame is received, After receiving a response frame for the above polling frame, transmit an allocation frame, receive a response frame for the allocation frame, and A first STA that shares the duration allocated within the above TXOP with a second STA.

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