Method and device for performing dynamic sub-channel operation in wireless LAN

Abstract

A first STA in a wireless LAN system according to the present invention: transmits an ICF, wherein the ICF indicates a channel switching operation for one or more STAs performing DSO; after transmitting the ICF, receives an ICR from the one or more STAs; and performs at least one of data transmission and reception with the one or more STAs, wherein the ICF may indicate that a second STA among the one or more STAs is to operate on a primary channel and that a third STA among the one or more STAs is to operate on a DSO channel.

Description

Method and device for performing dynamic sub-channel operation of a wireless LAN

[0001] The present disclosure relates to a method and apparatus for performing a dynamic subchannel operation (DSO) in a wireless local area network (WLAN). Specifically, it relates to a method and apparatus for preventing the main channel from being punctured in a DSO. Additionally, the present disclosure relates to a method and apparatus for restoring media synchronization in a wireless LAN that supports DSO.

[0002]

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

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

[0005] As applications requiring higher reliability emerge, the IEEE 802.11bn standard, an Ultra High Reliability (UHR) wireless LAN technology, is being developed for single Basic Service Set (BSS) environments and / or redundant BSS environments. The goal of the IEEE 802.11bn standard may be to support improved data transmission speeds, enhanced latency performance, and reduced data error rates. Additionally, the IEEE 802.11bn standard can support low-power operation, peer-to-peer communication, and operations designed to increase channel utilization. It can also support a TXOP sharing method, where wireless LAN terminals share communication resources (transmit opportunities) between access points (APs). Furthermore, to increase the efficiency of communication resource utilization, the wireless LAN standard can support non-primary channel access (NPCA), which involves using a channel other than the primary channel when the primary channel is occupied. Furthermore, to increase the efficiency of communication resource utilization, wireless LAN standards can support Dynamic Subchannel Operation (DSO), a method in which an AP can identify wireless LAN terminals that support only an operating bandwidth narrower than that of the AP within its BSS, and allocate a portion of the operating bandwidth to a subchannel (DSO channel) rather than the primary channel used for channel access to enable simultaneous transmission. The following describes a method to prevent primary channel puncture based on DSO and a media synchronization method based on DSO.

[0006] 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.

[0007]

[0008] The present disclosure relates to a method and apparatus for performing a dynamic subchannel operation (DSO) in a wireless LAN.

[0009] The present disclosure relates to a method and apparatus for preventing the main channel from being punctured in a DSO.

[0010] The present disclosure relates to a method and apparatus for assigning a non-AP STA with little data to be transmitted and received by an access point (AP) in a wireless LAN to a sub-channel by performing a DSO operation.

[0011] The present disclosure relates to a method and apparatus for restoring media synchronization in a wireless LAN that supports DSO.

[0012] The present disclosure relates to a method and apparatus for performing an operation for restoring media synchronization when a wireless LAN terminal supporting DSO operation changes its operating state.

[0013] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0014]

[0015] According to one embodiment of the present specification, a method of operation of a first station (STA) in a wireless LAN system comprises the step of the first STA transmitting an initial control frame (ICF), wherein the ICF indicates a channel switching operation of at least one STA performing a dynamic subchannel operation (DSO); the first STA transmitting the ICF and receiving an initial control response (ICR) from at least one STA; and the first STA performing at least one of data transmission and reception with at least one STA, wherein the ICF may indicate that a second STA among the at least one STA operates on a main channel and that a third STA among the at least one STA operates on a DSO channel.

[0016] 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: transmitting an initial control frame (ICF), wherein the ICF instructs at least one STA to perform a channel switching operation of a dynamic subchannel operation (DSO); transmitting the ICF and receiving an initial control response (ICR) from at least one STA; and wherein the first STA performs at least one of data transmission and reception with at least one STA, wherein the ICF instructs a second STA among the at least one STA to operate on a main channel and instructs a third STA among the at least one STA to operate on a DSO channel.

[0017] Additionally, 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 step of the first STA transmitting an initial control frame (ICF), wherein the ICF instructs the channel switching operation of at least one STA performing a dynamic subchannel operation (DSO) and the allocation of transmission resources in the main channel and the DSO channel; the step of the first STA transmitting the ICF and receiving an initial control response (ICR), which is a response frame to the ICF, from at least one STA; and the step of, when the ICR is received through the DSO channel and not through the main channel, the first STA performing at least one of data transmission and reception in the DSO channel with at least one STA only while the main channel occupancy is maintained.

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

[0019] According to one embodiment of the present specification, when a first STA transmits downlink data to a second STA and a third STA, the first STA can check the amount of downlink data of the second STA and the amount of downlink data of the third STA, and transmit an ICF that assigns the second STA, which has a larger amount of downlink data, to the main channel and assigns the third STA, which has a smaller amount of downlink data, to the DSO channel.

[0020] Additionally, according to one embodiment of the present specification, when a first STA receives uplink data from a second STA and a third STA, the first STA can check the amount of uplink data of the second STA and the amount of uplink data of the third STA, and transmit an ICF that assigns the second STA, which has a larger amount of uplink data, to the main channel and assigns the third STA, which has a smaller amount of uplink data, to the DSO channel.

[0021] In addition, according to one embodiment of the present specification, the first STA transmits a buffer status report request frame to the second STA and the third STA, and receives buffer status report frames from the second STA and the third STA to check the amount of uplink data of the second STA and the amount of uplink data of the third STA.

[0022] Additionally, according to one embodiment of the present specification, the first STA may, after receiving an ICR from at least one STA, transmit a trigger frame for allocating uplink resources to allocate a second STA with a larger amount of uplink data to a resource within the main channel and allocate a third STA with a smaller amount of uplink data to a resource within the DSO channel.

[0023] Additionally, according to one embodiment of the present specification, when a first STA transmits a downlink frame on a DSO channel to a third STA with a downlink data amount less than that of a second STA and receives a response frame for the last downlink frame, the operating channel of the third STA is switched from the DSO channel to the main channel when the transmission of the response frame is completed, and when the first STA receives an uplink frame on a DSO channel from a third STA with an uplink data amount less than that of a second STA and transmits a response frame for the last uplink frame, the operating channel of the third STA is switched from the DSO channel to the main channel when the reception of the response frame is completed.

[0024] Additionally, according to one embodiment of the present specification, the operation mode of the third STA is maintained in an awake mode until the operation channel is switched from the DSO channel to the main channel, and after the operation channel switching is completed and the operation channel of the third STA is switched to the main channel, the operation mode of the third STA is switched to a doze mode, and when the first STA receives a response frame for the last data frame transmitted from the main channel to the second STA or transmits a response frame for the last data frame received from the second STA on the main channel, the operation mode of the third STA may be switched from a doze mode to an awake mode.

[0025] Additionally, according to one embodiment of the present specification, the operating mode of the third STA in the DSO channel is maintained as a higher capability mode (HCM), and after the operating channel switching is completed and the operating channel of the third STA is switched to the main channel, the operating mode of the third STA may be switched from HCM to a lower capability mode (LCM) and maintained.

[0026] In addition, according to one embodiment of the present specification, a third STA operating in a DSO channel switches its operating channel to a main channel when a switching condition is satisfied for a first set time from a first time point, and if the switching time for the third STA to switch its operating channel to the main channel exceeds a threshold value, a media synchronization timer may be operated in the third STA at the time it switches to the main channel.

[0027] Additionally, according to one embodiment of the present specification, the first time point may include at least one of the time point when the third STA completes transmitting a response frame for a frame received from the first STA, the time point when the third STA completes receiving a frame that does not require an immediate response, and the time point when the third STA completes transmitting a frame that does not require an immediate response.

[0028] In addition, according to one embodiment of the present specification, if the third STA does not detect frame reception for a first set time from a first time point, does not perform frame transmission, does not have a nonempty transmit queue, and does not schedule frame transmission, the switching condition is satisfied and the operating channel can be switched from the DSO channel to the main channel.

[0029] Additionally, according to one embodiment of the present specification, the first STA completes receiving a response frame for a frame transmitted to the third STA and transmits a padding frame on the main channel after the short inter frame space (SIFS), and the first STA can transmit a first frame that releases the media synchronization timer when the third STA completes operating channel switching to the main channel.

[0030] Additionally, according to one embodiment of the present specification, the first STA transmits a response frame for a frame received from the third STA, wherein the response frame includes padding corresponding to a first preset time and a transition time when the third STA switches the operating channel from the DSO channel to the main channel, and the first STA can transmit a first frame that releases the media synchronization timer when the third STA completes the operation channel switching to the main channel.

[0031] Additionally, according to one embodiment of the present specification, if the first STA fails to receive an ICR from the second STA operating on the main channel and receives an ICR from the third STA operating on the DSO channel, the first STA transmits an ICF and, when the acknowledgment time elapses, performs a channel access operation on the main channel, and the third STA transmits an ICR on the DSO channel and, when the switching condition is satisfied for a first preset time, the operating channel is switched to the main channel, and if the switching time for the third STA to switch the operating channel to the main channel exceeds a threshold value, a media synchronization timer may be operated on the third STA at the time of switching to the main channel.

[0032] Additionally, according to one embodiment of the present specification, the first STA may transmit a first frame that releases the media synchronization timer when the third STA completes the operation channel switching to the main channel.

[0033] Additionally, according to one embodiment of the present specification, if the first STA fails to receive an ICR from the second STA operating on the main channel and receives an ICR from the third STA operating on the DSO channel, the first STA transmits an ICF and, when the acknowledgment time elapses, retransmits an ICF to switch the third STA to the main channel, and the operating channel of the third STA may be switched from the DSO channel to the main channel based on the ICF.

[0034] Additionally, according to one embodiment of the present specification, the retransmitted ICF may include padding corresponding to the transition time when the operating channel of the third STA switches from the DSO channel to the main channel.

[0035] Additionally, according to one embodiment of the present specification, at least one of the first STA, the second STA, and the third STA may be a non-AP STA or an AP STA.

[0036]

[0037] According to the present disclosure, the present disclosure may provide a method for performing a dynamic subchannel operation (DSO) in a wireless LAN.

[0038] According to the present disclosure, a method can be provided to prevent the main channel in a DSO from being punctured.

[0039] According to the present disclosure, a method can be provided for assigning a non-AP STA with little data to be transmitted and received by an access point (AP) in a wireless LAN to a sub-channel by performing a DSO operation.

[0040] According to the present disclosure, a method for restoring media synchronization in a wireless LAN that supports DSO can be provided.

[0041] According to the present disclosure, a method for performing an operation for restoring media synchronization can be provided when a wireless LAN terminal supporting DSO operation changes its operating state.

[0042] 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.

[0043] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0044]

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

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

[0047] FIGS. 3a and 3b are drawings illustrating a method for preventing main channel puncture in a wireless LAN dynamic sub-channel operation applied to the present disclosure.

[0048] FIGS. 4a and 4b are drawings illustrating a method for preventing main channel puncture in a wireless LAN dynamic sub-channel operation applied to the present disclosure.

[0049] FIGS. 5A and 5B are drawings illustrating a method for preventing main channel puncture in a wireless LAN dynamic sub-channel operation applied to the present disclosure.

[0050] FIG. 6 is a diagram showing a wireless LAN network to which the present disclosure applies.

[0051] FIG. 7 is a diagram illustrating a dynamic power saving operation method applied to the present disclosure.

[0052] FIGS. 8A and FIGS. 8B are drawings illustrating a media synchronization method during dynamic subchannel operation applicable to the present disclosure.

[0053] FIGS. 9a and 9b are drawings illustrating a media synchronization method in case of dynamic subchannel operation failure applicable to the present disclosure.

[0054] FIG. 10 is a diagram illustrating a media synchronization method in case of dynamic subchannel operation failure applicable to the present disclosure.

[0055] FIG. 11 is a flowchart showing the operation of an STA in a wireless LAN to which the present disclosure applies.

[0056]

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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."

[0064] 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.

[0065] 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).

[0066] 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).

[0067] 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).

[0068] 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.

[0069] 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.

[0070] In a wireless LAN network, a non-AP STA may operate using only a bandwidth narrower than the operating bandwidth of the AP. In the above case, the AP may assign the non-AP STA to a sub-channel (DSO channel) based on DSO. Here, when the non-AP STA performs DSO operation, a problem may occur where the main channel is punctured. For example, the AP may instruct the non-AP STA to switch its operating channel to the sub-channel (DSO channel) and assign another non-AP STA to the main channel; in the above case, the non-AP STA with a small amount of data may be assigned to the sub-channel (DSO channel), and a method for doing so is described below. For example, if the amount of data that the non-AP STA assigned to the main channel needs to transmit and receive with the AP is less than the amount of data that the non-AP STA assigned to the sub-channel needs to transmit and receive with the AP, the data transmitted and received by the AP and the non-AP STAs may be transmitted excluding the main channel. Therefore, in the aforementioned case, the main channel may be breached during the data transmission and reception process, and a problem may arise where the data transmission and reception process with the said AP is compromised by transmission by other wireless LAN terminals that do not participate in the data transmission and reception process with the AP; the following describes a solution to address this.

[0071] Furthermore, depending on the capabilities of the terminal, there may be periods during low-power operation in which the DSO fails to detect the medium, or problems may arise where media synchronization is lost. In the aforementioned cases, operations to restore media synchronization may be required, and the following describes a method for this purpose.

[0072] In the following, a wireless LAN network configuration may be considered, but this is not intended to limit the scope of the present disclosure and may be a configuration for operations to be described later. For convenience of explanation, the term "wireless LAN network configuration" is used below, but it is not limited thereto.

[0073] In a wireless LAN network, at least one wireless LAN terminal capable of performing wireless LAN communication may operate. Here, the wireless LAN terminal may perform various roles. For example, the wireless LAN terminal may act as a wireless access point, and in the above-described case, the wireless LAN terminal may be referred to as an access point (AP). Alternatively, the wireless LAN terminal may be connected (associated) with an AP to perform wireless LAN communication, and in the above-described case, the wireless LAN terminal may be referred to as a non-AP STA. In this disclosure, AP 1 and non-AP STA are described based on STA 1 and STA 2, but this is merely a configuration for convenience of explanation and is not limited thereto.

[0074] An AP can configure a basic service set (BSS). A BSS may be a transmission range or communication area where an AP connects with a non-AP STA to perform communication. An AP can select a primary channel to use for channel access within the BSS and may specify the primary channel in frames transmitted by the AP (e.g., Beacon frames, Probe Response frames, etc.). A non-AP STA can establish a connection with the AP and access the channel by using the primary channel specified in the frames transmitted by the AP.

[0075] A wireless LAN terminal may have various operating bandwidths. For example, a wireless LAN terminal may have at least one of 320 MHz, 160 MHz, 80 MHz, 40 MHz, and 20 MHz, but is not limited thereto. The operating bandwidths of STA 1 and STA 2 may be more limited than those of AP 1. For example, AP 1 may have an operating bandwidth of 320 MHz, and STA 1 and STA 2 may have an operating bandwidth of 160 MHz. That is, STA 1 and STA 2 may be operating at half the operating bandwidth of AP 1, but this is for convenience of explanation only and is not limited thereto.

[0076] In addition, wireless LAN terminals can perform EDCA (enhanced distributed channel access) operations. For example, for the convenience of explanation, the following description is based on the EDCA operation of a wireless LAN terminal, but it may not be limited to such terms or names.

[0077] Wireless LAN terminals (e.g., AP 1, non-AP STA 1, non-AP STA 2) can perform an enhanced distributed channel access (EDCA) operation. The EDCA operation may include at least one of a clear channel assessment (CCA) operation and an EDCA backoff procedure (hereinafter referred to as the backoff procedure). Specifically, wireless LAN terminals (e.g., AP 1, non-AP STA 1, non-AP STA 2) can perform a CCA operation (hereinafter referred to as CCA) on a primary 20 MHz channel. CCA may be an operation to determine whether the channel is idle or busy. As a detailed operation of CCA, physical channel sensing (CS) may be an operation to detect carriers transmitted on the channel. Additionally, virtual CS may be an operation to verify a network allocation vector (NAV) established through a successful frame exchange. A wireless LAN terminal can perform CCA for a predetermined IFS (inter-frame space) length (e.g., AIFS (Arbitration IFS)[AC], etc.) depending on the type of frame to be transmitted (e.g., a frame with access category (AC) of VO, VI, BE, BO).

[0078] A wireless LAN terminal (e.g., AP 1, non-AP STA 1, non-AP STA 2) may initiate an EDCA backoff procedure (hereinafter referred to as the backoff procedure). The backoff procedure may be a procedure performed to reduce the probability of collision between wireless LAN terminals. The backoff procedure may be a procedure performed by an EDCAF (EDCA function) corresponding to the type of frame to be transmitted (e.g., AC) within the wireless LAN terminal. The EDCAF of the wireless LAN terminal may initiate the backoff procedure when traffic to be transmitted occurs (e.g., when data is entered into the transmit queue of the AC corresponding to the EDCAF) and the channel is occupied. As another example, the EDCAF of the wireless LAN terminal may initiate the backoff procedure if there is a separate instruction (e.g., when it receives an indicator instructing to start the backoff procedure via frame exchange).

[0079] The EDCAF of the wireless LAN terminal initiating the backoff procedure may randomly select a backoff counter (BC) within [0, CW (Contention Window)[AC]] determined by the associated AC. The BC value selected by the EDCAF associated with each AC may be the number of slots for which the EDCAF must perform CCA. If the channel is occupied as a result of the CCA operation performed by the EDCAF on a slot-by-slot basis, the EDCAF may perform a BC reduction operation in each slot. The slot length of the wireless LAN terminal used in the above-described operation may vary. For example, the slot length may consist of one or more AIFS[AC] times, EIFS[AC] times (EIFS - DIFS - AIFSN[AC] Х aSlotTime + aSIFSTime - aRxTxTurnaroundTime) times, or aSlotTime (e.g., 9us), but is not limited thereto. EDCAF can perform CCA according to the backoff procedure in slots corresponding to the selected BC value, and if the channel resulting from the CCA performed in one slot is idle, it can decrease BC by 1. If the channel resulting from the CCA performed when BC becomes 0 is idle, EDCAF can occupy the channel and perform frame transmission. For example, if the channel resulting from the CCA according to the backoff procedure is in an occupied state, the wireless LAN terminal can maintain its BC at the current value for use in the next backoff procedure. When the channel transitions from an occupied state to an idle state, the wireless LAN terminal (or the wireless LAN terminal's EDCAF) can perform the BC decrease procedure according to the EDCAF operation again.

[0080] The frame transmission procedure through EDCA operation may be a procedure in which a CCA is performed for AIFS[AC] on a primary 20 MHz channel, then a frame is transmitted at the slot boundary where BC becomes 0 after waiting for an additional slot time. The value indicated by AIFS[AC] may be the number of slots for performing CCA. Specifically, AIFS[AC] may be a time length of 'aSIFS(Short Inter-Frame Space)Time + AIFSN[AC](number specified per AC)* aSlotTime'.

[0081] EDCAF may want to access a wider bandwidth channel (broadband channel) including the main 20 MHz channel. To access the broadband channel, EDCAF may perform CCA on the main 20 MHz channel during AIFS[AC], wait for an additional slot time until BC becomes 0, and then transmit a frame including the broadband channel where the result of the CCA operation performed for a period equal to the PIFS (priority interframe space) time prior to the slot boundary where BC becomes 0 is idle. Alternatively, EDCAF may want to transmit a frame using only the main 20 MHz channel regardless of the CCA result of the broadband channel. In the above case, EDCAF may transmit a frame using only the main 20 MHz channel.

[0082] For example, the EDCA operation performed by an EDCAF within a wireless LAN terminal may be an EDCA operation performed by a wireless LAN terminal (e.g., AP 1, non-AP STA 1, non-AP STA 2). The EDCAF may be a logical entity that performs the aforementioned operation within the wireless LAN terminal, and the EDCA operation may be interpreted as an operation of the wireless LAN terminal. However, it is not limited thereto.

[0083] In the aforementioned EDCA operation, the main 20 MHz channel may be a channel configured by the AP during the BSS configuration process. That is, it may be a channel indicated in a frame transmitted by the AP (e.g., Beacon frame, Probe Response frame, etc.). If the EDCAF within the wireless LAN terminal succeeds in accessing the channel as a result of performing an EDCA operation on the main 20 MHz channel, the EDCAF may transmit a frame of the corresponding access category (AC) using the successfully accessed channel (or bandwidth). The EDCAF within the wireless LAN terminal that transmitted the aforementioned frame may acquire a transmit opportunity (TXOP). The TXOP acquired by the EDCAF within the wireless LAN terminal may be a TXOP acquired by the wireless LAN terminal to which the EDCAF belongs, but is not limited thereto. The time length of the TXOP can be set to the time length from the time when the wireless LAN terminal (or the EDCAF of the corresponding AC within the wireless LAN terminal) completes the transmission of the first frame transmitted by the wireless LAN terminal until the time indicated by the duration / ID field of the MAC header within the frame. That is, the wireless LAN terminal (or the EDCAF of the corresponding AC within the wireless LAN terminal) that transmitted the first frame described above can perform transmit and receive operations from the time when the first frame transmission is completed until the time indicated by the duration / ID field of the MAC header within the first frame.

[0084] Next, the wireless LAN terminal can perform a dynamic power save (DPS) operation. The following description is based on the DPS operation of the wireless LAN terminal, but it may not be limited to these terms or names.

[0085] A wireless LAN terminal (e.g., AP, non-AP STA) within a wireless LAN network may be a wireless LAN terminal capable of dynamically switching its operational capabilities (e.g., number of spatial streams, operational bandwidth or channels, modulation coding scheme (MCS), etc.) between a lower capability mode (LCM) and a higher capability mode (HCM). That is, AP 1 and non-AP STA 1 may be DPS (dynamic power save) supported terminals (or DPS STAs). LCM may be an operational mode in which a wireless LAN terminal performs or waits to transmit or receive using an operational capability smaller than at least one of its maximum operational capabilities (e.g., operational bandwidth of 320 MHz or higher, all available spatial streams, highest MCS value, etc.). For example, a DPS STA operating in LCM mode (e.g., AP 1, non-AP STA 1) may only use a bandwidth (e.g., primary 20 MHz channel) narrower than its maximum operational bandwidth of 320 MHz. As another example, a DPS STA operating in LCM (e.g., AP 1, non-AP STA 1) may use only one number of spatial streams (NSS). As another example, a DPS STA operating in LCM (e.g., AP 1, non-AP STA 1) may perform or wait for transmit and receive operations using the lowest modulation and coding scheme (MCS). Additionally, a DPS STA operating in LCM (e.g., AP 1, non-AP STA 1) may operate based on the combination described above. That is, a DPS STA operating in LCM (e.g., AP 1, non-AP STA 1) may operate using a capability smaller than the operating capability of the wireless LAN terminal in LCM.

[0086] HCM may be an operating mode in which a wireless LAN terminal performs or waits for transmission and reception using its maximum operating capability. In other words, it is an operating mode in which the wireless LAN terminal uses the maximum operating capability available when not using DPS operation. For example, a DPS STA (e.g., AP 1, non-AP STA 1) operating in HCM may operate at its maximum operating bandwidth of 320 MHz, use the maximum number of spatial streams (NSS) available, and perform or wait for transmission and reception using the highest modulation and coding scheme (MCS).

[0087] When a DPS STA dynamically switches its operating mode, the operation mode switching may require operation mode switching time. The operation mode switching time may include the mode switching time required for the mode switching operation from LCM to HCM and the mode switching back time required for the mode switching back operation from HCM to LCM. The aforementioned operation mode switching times (mode switching time and mode switching back time) may vary depending on the performance or operational capability of the DPS STA. Here, the DPS STA can exchange information regarding its maximum operational capability and operation mode switching time with other DPS STAs. For example, non-AP STA 1, which is a DPS-supported terminal, can exchange information regarding its maximum operational capability (e.g., 320 MHz operating bandwidth) and operation mode switching time with AP 1, which is a DPS STA. Here, non-AP STA 1 and AP 1 can be aware of each other's information regarding their maximum operational capability and operation mode switching time. Meanwhile, the above mode switching time may be referred to as DPS padding delay or padding delay, and the above mode switching back time may be referred to as DPS transition delay or transition delay, but is not limited to these names.

[0088] A DPS STA may be unable to perform transmit and receive operations during the operation mode switching time. That is, a DPS STA cannot perform frame transmit and receive operations during the mode switching time. Additionally, a DPS STA may not be able to perform operations for channel access (e.g., CCA) during the mode switching time. As another example, a DPS STA may perform frame transmit and receive operations using only the operational capabilities used by the LCM during the operation mode switching time, but is not limited to this.

[0089] For example, the mode switching operation described above may also be performed upon receiving a separate indicator. Here, the separate indicator may be a mode switching indicator or a mode switching back indicator that indicates mode switching. The AP may recognize a non-AP STA operating in LCM mode and may include and transmit a mode switching indicator within the ICF sent to the non-AP STA. Upon receiving the mode switching indicator, the non-AP STA may switch its operating mode from LCM to HCM.

[0090] Next, the wireless LAN terminal can perform dynamic subchannel operation (DSO). For the sake of convenience, the following description is based on the DSO operation of the wireless LAN terminal, but it may not be limited to these specific terms or names.

[0091] Dynamic subchannel operation (DSO) is an operation that an AP may use to increase channel efficiency. Specifically, the AP can identify non-AP STAs connected to the AP within the BSS and exchange information regarding the maximum operating bandwidth of the non-AP STAs during the connection process. For example, if the maximum operating bandwidth of the non-AP STAs is limited to the maximum operating bandwidth of the AP (e.g., the AP's maximum operating bandwidth is 320 MHz and the non-AP STA's maximum operating bandwidth is 80 MHz), the transmission bandwidth may be limited to the non-AP STA's maximum operating bandwidth (e.g., 80 MHz) when the AP transmits and receives data with the non-AP STA. In the above case, the remaining channels within the AP's maximum operating bandwidth (e.g., 320 MHz), excluding the 80 MHz bandwidth that includes the main channel (e.g., the main 20 MHz channel), may not be used. Consequently, channel efficiency may be reduced.

[0092] An AP may use DSO operations to increase channel efficiency in the aforementioned situation. An AP using DSO operations may transmit an initial control frame (ICF) to non-AP STAs that have a more limited operational bandwidth than the AP within the BSS. The aforementioned ICF may include an operational channel switching indicator that instructs some of the non-AP STAs receiving the ICF to switch their operational channels to a subchannel (or DSO channel). The operational channel switching indicator may be an indicator that indicates the target subchannel (DSO channel) to which the non-AP STA receiving the ICF must switch. Additionally, the operational channel switching indicator may be an indicator that indicates the operational bandwidth used by the subchannel (DSO channel). A non-AP STA receiving the operational channel switching indicator may switch its operational channel to the subchannel (DSO channel) instructed by the AP. The aforementioned operating channel may refer to a channel used by a wireless LAN terminal to perform channel access, and may refer to at least one of a channel and bandwidth for transmitting and receiving data. Here, the ICF may be a frame of various forms. For example, the ICF may be at least one of a MU RTS (multi-user request-to-send), a BSRP (buffer status report poll), and other frames. Additionally, the ICF may be a frame that is redundantly transmitted in 20 MHz increments across the entire channel or bandwidth where the ICF is transmitted. As another example, the ICF may be a frame transmitted to match at least one of the operating channel and operating bandwidth expected to be used by the receiving wireless LAN terminal.When performing DSO operation, the main channel is an operating channel including the main 20 MHz channel of the non-AP STA, and the DSO channel may refer to a channel within the operating bandwidth of the AP but outside the main channel range of the non-AP STA.

[0093] For example, a wireless LAN terminal (e.g., AP, non-AP STA) that supports and participates in the aforementioned DSO operation may be referred to as a DSO-supported wireless LAN terminal (DSO STA). A DSO STA may require an operation channel switching time to switch its operation channel to a sub-channel (DSO channel). Here, the operation channel switching time may be the channel switching time required for a channel switching operation to switch from the main channel to the sub-channel (DSO channel) and the channel switching back time required for a channel switch back operation to switch from the sub-channel (DSO channel) to the main channel. The operation mode switching time (at least one of the channel switching time and the channel switch back time) may vary depending on the performance of the DSO STA and the operation channel to be switched. Here, the DSO STA may exchange information regarding its maximum operation bandwidth and operation channel switching time with other DSO STAs. For example, a non-AP STA that is a DSO STA can exchange information about its maximum operating bandwidth (e.g., 80 MHz operating bandwidth) and operating channel switching time with another DSO STA, an AP. The AP that is a DSO STA and the non-AP STA that is a DSO STA can recognize each other's information about maximum operating bandwidth and operating capability switching time.

[0094] A DSO STA may be unable to perform transmit and receive operations during the operation channel switching time. That is, a DSO STA may not be able to perform frame transmit and receive during at least one of the channel switching time and the channel switching back time. Additionally, a DSO STA may not be able to perform operations for channel access (e.g., clear channel assessment (CCA)) during at least one of the channel switching time and the channel switching back time.

[0095] The AP may add padding to the transmitted ICF to guarantee the operating channel switching time of the aforementioned DSO STA. The padding may be used to extend the transmission time of the frame. For example, the padding may be included in at least one of the forms of a field, a subfield, a bit, or other forms within the frame. The AP may add an Intermediate FCS to extend the padding length or to advance the start time of operation of the recipient wireless LAN terminal (e.g., the time when the DSO STA begins switching the operating channel). An Intermediate FCS may mean that all or part of the FCS (frame check sequence) field, which is a frame error detection code included at the end of the frame, is inserted in the middle of the frame in the form of a field or a subfield. A wireless LAN terminal that receives an Intermediate FCS can confirm the normal reception of the frame even in the middle of receiving the frame and can start subsequent operations (e.g., the operation of the DSO STA switching the operating channel).

[0096] The length of the padding within the ICF transmitted by the aforementioned AP to the non-AP STA may vary. For example, the padding length may be set to a time length equal to or longer than the time elapsed from the time the MAC header of the ICF is received to the time elapsed from the non-AP STA's channel switching time. As another example, the padding length may be set to a time length equal to or longer than the time elapsed from the time the intermediate FCS is received to the time elapsed from the time the non-AP STA's channel switching time is received.

[0097] A non-AP STA that is a DSO STA receives an ICF transmitted by the AP and can identify the operation channel switching indicator within the received ICF. Through the above, the non-AP STA can successfully switch the operation channel to a sub-channel (DSO channel). In the above case, the non-AP STA can transmit an initial control response frame (ICR) to the AP after a short interframe space (SIFS) time from the time the ICF reception ends. The ICR may be a frame transmitted by the non-AP STA using the bandwidth (e.g., 80 MHz) specified in the operation channel (e.g., main channel, sub-channel (DSO channel)) specified by the operation channel switching indicator. Here, the ICR may be a frame of various forms. For example, the ICR may be at least one of Simultaneous Clear-to-Send (S-CTS), Buffer Status Report (BSR), Multi-STA BlockAck, and other frames, and is not limited to a specific form. The above-described ICR may be a frame that is redundantly transmitted in 20 MHz increments across the entire channel or bandwidth where the ICR is transmitted. As another example, the ICR may be a frame that is transmitted in accordance with at least one of the operating channel and operating bandwidth currently used by the wireless LAN terminal transmitting the ICR.

[0098] The AP can receive an ICR transmitted by a non-AP STA that has successfully switched the operating channel on the channel indicated by the operating channel switching indicator. The AP can identify the non-AP STA that transmitted the ICR. The AP can receive the ICR using at least one of the channel and bandwidth where the ICR was transmitted and transmit a frame (e.g., a Data frame) to the non-AP STA that transmitted the ICR after the SIFS time. The non-AP STA that received the frame transmitted by the AP can transmit an acknowledgment frame (e.g., an acknowledgment (ACK) frame, a Block Acknowledgement (BA) frame) to the AP using the operating channel indicated by the operating channel switching indicator and the indicated bandwidth.

[0099] The DSO operation described above may be performed for a duration indicated by the duration field of the ICF initially transmitted by the AP. That is, the DSO operation described above may be performed for the length of the TXOP obtained by the AP successfully accessing the channel through the EDCA operation. The DSO STA that has switched the operating channel in accordance with the end time of the TXOP obtained by the AP may perform a channel switching back operation to switch its operating channel from the sub-channel (DSO channel) to the main channel. Meanwhile, the main channel and the DSO channel may be referred to as the main subband and the DSO subband, respectively, and may not be limited to specific terms or names. Furthermore, the above-described matters may be applied identically to FIGS. 3a through 10 below, and may be modified and operated according to the operation of each figure.

[0100] FIGS. 3a and 3b are drawings illustrating a method for preventing main channel puncture in a wireless LAN dynamic sub-channel operation applied to the present disclosure.

[0101] Referring to FIGS. 3a and 3b, the wireless LAN network configuration of FIGS. 3a and 3b may be as described above. A wireless LAN terminal can obtain a TXOP if it successfully accesses a channel by performing the EDCA operation described above. Additionally, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330), which are wireless LAN terminals within the wireless LAN network in FIGS. 3a and 3b, may be DSO STAs that follow the DSO operation of the terminal described above. Here, AP 1 (310) can recognize that non-AP STA 1 (320) and non-AP STA 2 (330) are operating with a more limited operating bandwidth than AP 1 (310). For example, AP 1 (310) has an operating bandwidth of up to 80 MHz, and non-AP STA 1 (320) and non-AP STA 2 (330) each have an operating bandwidth of up to 40 MHz, but this is for convenience of explanation only and is not limited thereto.

[0102] Referring to FIG. 3a, AP 1 (310) may decide to perform simultaneous transmission and reception using different frequency bands (channels) that do not overlap with non-AP STA 1 (320) and non-AP STA 2 (330) by using the aforementioned DSO operation to increase channel efficiency. Specifically, AP 1 (310) may perform an EDCA operation to successfully access the channel and obtain a TXOP. AP 1 (310) may obtain the TXOP and transmit an ICF (initial control frame) (401) to non-AP STA 1 (320) and non-AP STA 2 (330). AP 1 (310) may include an operation channel switching indicator in the ICF (401) to instruct non-AP STA 1 (320) or non-AP STA 2 (330) to switch the operation channel to a sub-channel (DSO channel). AP 1 (310) can redundantly transmit the same ICF (401) in 20 MHz channel units to the full bandwidth channels to be used by non-AP STA 1 (320) and non-AP STA 2 (330) based on DSO operation. non-AP STA 1 (320) and non-AP STA 2 (330) can receive the ICF (401) transmitted to the primary 20 MHz channel. non-AP STA 1 (320) and non-AP STA 2 (330) can switch the operation channel to the channel indicated by the operation channel switch indicator within the ICF (401) (or wait for ICR transmission on the primary channel if the indicated channel is the primary channel). non-AP STA 1 (320) and non-AP STA 2 (330) can receive ICF (401) and, after a short interframe space (SIFS) time, send ICR (402-1, 402-2) to AP 1 (310) to indicate that channel switching is complete.

[0103] Here, non-AP STA 1 (320) may be instructed to switch to a secondary channel (DSO channel). Thus, non-AP STA 1 (320) can transmit an ICR (402-1) on the DSO channel, and non-AP STA 2 (330) can transmit an ICR (402-2) on the primary channel. When AP 1 (310) receives the ICR (402-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330), AP 1 (310) can recognize that non-AP STA 1 (320) and non-AP STA 2 (330) are ready to receive data on the channel specified in the ICF (401). AP 1 (310) receives ICR (402-1, 402-2) and can start transmitting downlink (DL) data (403-1, 403-2) to non-AP STA 1 (320) and non-AP STA 2 (330) after SIFS time.

[0104] For example, consider a case where the amount of downlink data (403-2) to be transmitted by AP 1 (310) to non-AP STA 2 (330) operating on the main channel is less than the amount of downlink data (403-1) to be transmitted to non-AP STA 1 (320) operating on the sub-channel (DSO channel). In the above case, the downlink data frame initially transmitted by AP 1 (310) to non-AP STA 1 (320) and non-AP STA 2 (330) can be transmitted across the entire band (channel) where non-AP STA 1 (320) and non-AP STA 2 (330) are operating. That is, the initial downlink data frame transmitted by AP 1 (310) can be transmitted including the main channel. However, subsequent data frames transmitted after the initial downlink data frame transmitted by AP 1 (310) may only contain data destined for non-AP STA 1 (320) assigned to a sub-channel. In the above case, AP 1 (310) may transmit subsequent data frames only on the sub-channel (DSO channel) where non-AP STA 1 (320) operates. That is, subsequent data frames may be transmitted using only the sub-channel (DSO channel) without including the main channel.

[0105] Here, in wireless LAN transmission, since it is permitted to extend the channel for transmission when the main channel is occupied, it may not be possible to transmit using only the sub-channel while leaving the main channel empty. For example, in a case where transmission using only the sub-channel is permitted while leaving the main channel empty (i.e., as described above, when a data frame is transmitted using only the sub-channel (DSO channel)), a STA or OBSS (overlapping BSS) STA or AP connected to AP 1 (310) that did not receive the initial ICF can transmit a frame if it performs channel access on the main channel and succeeds in channel access. In the above case, since AP 1 (310) performs transmission on the sub-channel, it may not be able to decode the frame transmitted on the main channel and thus cannot receive it. Therefore, AP 1 (310) cannot set the basic NAV based on the frame transmitted by the STA or AP of the OBSS (overlapping BSS). Additionally, at the moment AP 1 (310) is waiting for a block ack (BA) to be received, it may be impossible to receive a complete frame because even if it receives a frame on the main channel, it is not synchronized with the frame being transmitted and received on the sub-channel. For example, AP 1 (310) may transmit an initial control frame (ICF) to at least one STA. Here, the ICF may instruct the channel switching operation of at least one STA performing the DSO operation and the allocation of transmission resources on the main channel and the DSO channel. After that, AP 1 (310) may transmit the ICF and receive an initial control response (ICR) from at least one STA. Here, if the initial control response is received through the DSO channel and not through the main channel, AP 1 (310) may perform at least one of data transmission and reception on the DSO channel with at least one STA only while the main channel occupancy is maintained.

[0106] As another example, AP 1 (310) may combine and transmit data frames to non-AP STA 2 (330). Here, if the data length allocated to the main channel is shorter than the data length allocated to the sub-channel, AP 1 (310) may add padding to the data transmitted on the main channel to match the length of the data transmitted on the sub-channel. That is, the end time of transmission of the data frames can be synchronized.

[0107] As another example, AP 1 (310) may divide the data frame to be transmitted to non-AP STA 2 (330) into multiple frames. If the amount of downlink data to be transmitted by AP 1 (310) to non-AP STA 2 (330) operating on the main channel is less than the amount of downlink data to be transmitted to non-AP STA 1 (320) operating on the sub-channel (DSO channel), AP 1 (310) may divide the initial transmission data frame of non-AP STA 1 (320) to match the length of the downlink data of non-AP STA 2 (330). That is, the data frame to be transmitted to non-AP STA 1 (320) may be divided to match the length of the short downlink data frame to be transmitted to non-AP STA 2 (330). Here, the length of the data frames transmitted to non-AP STA 1 (320) and non-AP STA 2 (330) can be set to be the same. Then, AP 1 (310) can receive response frames from non-AP STA 1 (320) and non-AP STA 2 (330). If AP 1 (310) needs to transmit additional data to non-AP STA 1 (320) on the DSO channel, there may be no or few data frames to be transmitted to non-AP STA 2 (330) on the main channel. To align the length of the frame transmitted to non-AP STA 2 (330) on the main channel with the length of the data frame transmitted to non-AP STA 1 (320) on the DSO channel, padding bits to adjust the length of the frame may be included in the frame transmitted to non-AP STA 2 (330). Through this, the lengths of frames transmitted to non-AP STA 1 (320) and non-AP STA 2 (330) can be aligned and transmitted.Alternatively, AP 1 (310) may divide and transmit multiple frames of equal length to non-AP STA 1 (320) and non-AP STA 2 (330) in the main channel and DSO channel, and if the length of the last frame does not match, padding may be added to make the length of the shorter frame equal to the length of the longer frame in order to synchronize the end time of transmission. Through the above, AP 1 (310) can set the start time and end time of transmission of frames to be the same in the DSO channel and the main channel.

[0108] As another example, AP 1 (310) transmits ICF (401) to non-AP STA 1 (320) and non-AP STA 2 (330), but can receive ICR (402-1) only from non-AP STA 1 (320) operating on the sub-channel (DSO channel). In the above case, AP 1 (310) can transmit downlink data only to non-AP STA 1 (320) operating on the sub-channel and may not be able to transmit downlink data to non-AP STA 2 (330) operating on the main channel. In the above case, AP 1 (310) can transmit a padded frame on the main channel (e.g., a frame containing padding bits of the same length as the frame transmitted on the sub-channel) to match the length of the data transmitted on the sub-channel. Accordingly, the transmission start and end times of frames transmitted on the main channel and sub-channel can be synchronized (end time alignment), and the main channel can maintain an occupied state as described above.

[0109] Referring to FIG. 3a, AP 1 (310) can assign a non-AP STA with a small amount of downlink data to a sub-channel. Specifically, AP 1 (310) can recognize that there is downlink data (403-1, 403-2) to be transmitted to non-AP STA 1 (320) and non-AP STA 2 (330). AP 1 (310) can recognize that the amount of downlink data (403-1) to be transmitted to non-AP STA 1 (320) is less than the amount of downlink data (403-2) to be transmitted to non-AP STA 2 (330). Here, AP 1 (310) can assign non-AP STA 1 (320), which has a small amount of downlink data to be transmitted based on DSO operation, to a sub-channel (DSO channel), and assign non-AP STA 2 (330), which has a relatively larger amount of downlink data than non-AP STA 1 (320), to a main channel. That is, the main channel can assign a terminal with a small amount of data to a DSO channel so that a frame to be transmitted during the TXOP can exist.

[0110] The operation channel allocation procedure of AP 1 (310) can be performed by AP 1 (310) transmitting an ICF (401) to non-AP STA 1 (320) and non-AP STA 2 (330). Additionally, the ICF (401) transmitted by AP 1 (310) to non-AP STA 1 (320) and non-AP STA 2 (330) may include padding to ensure channel switching time that may occur based on DSO operation. The length of the padding included in the ICF (401) may be set such that 'padding transmission time + SIFS time' is greater than or equal to the channel switching time, taking into account the channel switching time value of non-AP STA 1 (320).

[0111] non-AP STA 1 (320) and non-AP STA 2 (330) can transmit ICR (402-1, 402-2) to AP 1 (310) after switching the operating channel to the channel assigned based on the DSO operation. That is, AP 1 (310) can receive the ICR (402-1, 402-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) to the primary 40MHz channel and the secondary 40MHz channel (DSO channel). The ICRs (402-1, 402-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) may be transmitted redundantly in 20 MHz channel units or transmitted as a single ICR (402-1, 402-2) using the entire operating bandwidth (e.g., 40 MHz). AP 1 (310) receives the ICRs (402-1, 402-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) and, after SIFS time, can simultaneously transmit data frames (Data 1 to non-AP STA 1 (320), Data 2 to non-AP STA 2 (330), 403-1, 403-2) to non-AP STA 1 (320) and non-AP STA 2 (330). The data frame transmitted by AP 1 (310) may be a frame transmitted using the operating channel and operating bandwidth used by non-AP STA 1 (320) and non-AP STA 2 (330). non-AP STA 1 (320) and non-AP STA 2 (330) may receive the data frame transmitted by AP 1 (310) within their own operating channel and operating bandwidth, and may send a reception acknowledgment frame (e.g., BA frame) to AP 1 (310) after receiving the data frame and after SIFS time.

[0112] An indicator (e.g., More PPDU bit = 0) indicating that there is no additional transmission data can be set in the MAC header of data 1 that AP 1 (310) transmits to non-AP STA 1 (320) operating on a sub-channel (DSO channel). The setting of an indicator (e.g., More PPDU bit = 0) indicating that there is no additional transmission data in the MAC header of data 1 can mean that data 1 is transmitted and there is no PPDU transmitted to non-AP STA 1 (320). non-AP STA 1 (320) can receive data 1 and recognize that there are no more downlink data frames to receive. Accordingly, non-AP STA 1 (320) can receive data 1 (403-1) and send a response frame (404-1) to AP 1 (310) after SIFS time, and after sending the response frame, it can switch its operating channel back to the main channel. For example, the response frame (404-1) may include an indicator to switch to the main channel, or it may be transmitted in combination with a frame containing the indicator and the response frame. That is, the indicator indicating that there is no additional transmission data as described above is an indicator that causes AP 1 (310) to switch the non-AP STA 1 (320) operating on the DSO channel back to the main channel.

[0113] non-AP STA 2 (330) can receive data 2 (403-2) transmitted by AP 1 (310) and, after SIFS time, transmit a response frame (404-2) to AP 1 (310). An indicator (e.g., More PPDU bit = 1) indicating the existence of additional transmission data within the MAC header of data 2 (403-2) may be set. The setting of an indicator (e.g., More PPDU bit = 1) indicating the existence of additional transmission data may mean that a PPDU exists after the transmission of data 2 (403-2) of the aforementioned downlink data frame. Therefore, non-AP STA 2 (330) can transmit the aforementioned response frame (404-2) and wait for the transmission of the downlink data frame by AP 1 (310). AP 1 (310) receives a response frame transmitted by non-AP STA 2 (330) and can transmit data 3 (405) as a subsequent downlink data frame to non-AP STA 2 (330) after SIFS time. non-AP STA 2 (330) receives data 3 (405) transmitted by AP 1 (310) and can respond with a response frame after SIFS time. Here, the response frame (406) transmitted by non-AP STA 2 (330) in response to data 3 (405) can be transmitted redundantly in 20 MHz increments across the bandwidth of the data frame transmitted by AP 1 (310), including the main channel, or transmitted as a single frame. As another example, the response frame transmitted by non-AP STA 2 (330) in response to data 3 (405) can be transmitted redundantly in 20 MHz increments or as a single frame using the maximum operating bandwidth of non-AP STA 2 (330), including the main channel.

[0114] Referring to FIG. 3b, AP 1 (310) can assign non-AP STAs with a small amount of uplink (UL) data to a subchannel. Specifically, AP 1 (310) can recognize that there is uplink data that needs to be transmitted to AP 1 (310) from non-AP STA 1 (320) and non-AP STA 2 (330). There may be various ways for AP 1 (310) to check for the existence of uplink data. For example, AP 1 (310) can send a BSRP (buffer status report poll) frame to non-AP STA 1 (320) and non-AP STA 2 (330). Non-AP STA 1 (320) and non-AP STA 2 (330) can receive the BSRP frame and send a BSR (buffer status report) frame to AP 1 (310) after SIFS time. The BSR transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) may include an indicator indicating the amount of uplink data as information about the uplink data existing in the transmission queue of non-AP STA 1 (320) and non-AP STA 2 (330). That is, AP 1 (310) can recognize the approximate amount of uplink data of non-AP STA 1 (320) and non-AP STA 2 (330). As another example, non-AP STAs (e.g., non-AP STA 1 (320), non-AP STA 2 (330)) may indicate the amount of uplink data existing in the transmission queue using the queue size subfield within the QoS control field in the MAC header of the frame they transmit. AP 1 (310) can recognize the approximate amount of uplink data present in the transmission queues of non-AP STA 1 (320) and non-AP STA 2 (330) based on at least one of the methods described above.

[0115] For example, AP 1 (310) may recognize that the amount of uplink data to be transmitted to non-AP STA 1 (320) is less than the amount of uplink data to be transmitted to non-AP STA 2 (330). Here, based on the DSO operation, AP 1 (310) may assign non-AP STA 1 (320), which has a smaller amount of uplink data to be transmitted, to a sub-channel (DSO channel), and assign non-AP STA 2 (330), which has a relatively larger amount of uplink data than non-AP STA 1 (320), to a main channel. That is, AP 1 (310) may assign the terminal with a smaller amount of data to the DSO channel so that there is a frame received during the TXOP on the main channel. The above-described channel assignment can be performed by AP 1 (310) transmitting an ICF to non-AP STA 1 (320) and non-AP STA 2 (330). That is, AP 1 (310) may transmit an ICF including an operation channel switching indicator. The ICF transmitted by AP 1 (310) may have padding added to ensure channel switching time based on DSO operation. After performing the operation channel allocation procedure, AP 1 (310) may transmit a trigger frame to non-AP STA 1 (320) and non-AP STA 2 (330) to allocate wireless resources capable of transmitting uplink data. In the above case, AP 1 (310) may not include padding for operation channel switching in the trigger frame transmitted.

[0116] As another example, AP 1 (310) can perform an operation channel allocation procedure by sending a trigger frame (407) to non-AP STA 1 (320) and non-AP STA 2 (330). Accordingly, the trigger frame (407) sent by AP 1 (310) to non-AP STA 1 (320) and non-AP STA 2 (330) may include padding to ensure a channel switching time based on the DSO. The length of the padding included in the trigger frame (407) may be set so that 'padding transmission time + SIFS time' is greater than or equal to the channel switching time based on the channel switching time of non-AP STA 1 (320).

[0117] non-AP STA 1 (320) and non-AP STA 2 (330) can transmit uplink data frames (Data 1 of non-AP STA 1 (320), Data 2 of non-AP STA 2 (330)) (408-1, 408-2) to AP 1 (310) through resources allocated to the trigger frame (407) after switching the operating channel to the channel allocated based on the DSO. That is, AP 1 (310) can receive Data 1 (408-1) and Data 2 (408-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) to the main 40 MHz channel and the secondary 40 MHz channel (DSO channel). Data 1 (408-1) and Data 2 (408-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) may be data frames transmitted redundantly in 20 MHz channel units or transmitted as a single PPDU using the entire operating bandwidth (e.g., 40 MHz). AP 1 (310) may receive Data 1 (408-1) and Data 2 (408-2) transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) and, after SIFS time, simultaneously transmit response frames (e.g., BA) (409-1, 409-2) to non-AP STA 1 (320) and non-AP STA 2 (330). The response frames (409-1, 409-2) transmitted by AP 1 (310) may be frames transmitted using the operating channels and operating bandwidths used by non-AP STA 1 (320) and non-AP STA 2 (330). non-AP STA 1 (320) and non-AP STA 2 (330) may receive the response frames (409-1, 409-2) transmitted by AP 1 (310) within their own operating channels and operating bandwidths.

[0118] A non-AP STA 1 (320) can set an indicator (e.g., More PPDU bit = 0) in the MAC header of data 1 (408-1) that it transmits to AP 1 (310) on a sub-channel (DSO channel) to indicate that there is no additional transmission data. The setting of an indicator (e.g., More PPDU bit = 0) in the MAC header of the aforementioned data 1 (408-1) to indicate that there is no additional transmission data to transmit to AP 1 (310) after the transmission of data 1 (408-1) may mean that there is no PPDU for the non-AP STA 1 (320) to transmit to AP 1 (310). AP 1 (310) receives the aforementioned data 1 (408-1) and can recognize that there are no more uplink data frames to receive from the non-AP STA 1 (320). Additionally, non-AP STA 1 (320) can switch its operating channel back to the main channel after transmitting data 1 (408-1).

[0119] Meanwhile, within the MAC header of data 2 (408-2) transmitted by non-AP STA 2 (330) to AP 1 (310), an indicator (e.g., More PPDU bit = 1) indicating the existence of additional transmission data may be set. Here, the setting of an indicator (e.g., More PPDU bit = 1) indicating the existence of additional transmission data may mean that there is a subsequent PPDU after the transmission of data 2 (408-2). Accordingly, AP 1 (310) may transmit a trigger frame that performs resource allocation that can be used to transmit additional data frames, along with an acknowledgment frame (409-2) for data 2 (408-2). After transmitting the acknowledgment frame and the trigger frame, AP 1 (310) may wait for the transmission of an uplink data frame from non-AP STA 2 (330). non-AP STA 2 (330) may receive the response frame and trigger frame transmitted by AP 1 (310) and transmit data 3 as a subsequent data frame to AP 1 (310) after SIFS time. AP 1 (310) may receive data 3 transmitted by non-AP STA 2 (330) and respond with a response frame after SIFS time. The response frame transmitted by AP 1 (310) in response to data 3 may be transmitted redundantly in 20 MHz increments across the bandwidth of the data frame transmitted by non-AP STA 2 (330), including the main channel, or transmitted as a single frame. As another example, the response frame transmitted by AP 1 (310) in response to data 3 may be transmitted redundantly in 20 MHz increments across the bandwidth of the TXOP acquired by the original AP 1 (310), including the main channel, or transmitted as a single frame.

[0120] In the case where AP 1 (310) assigns a terminal with a small amount of data to the DSO channel in the DSO operation, the resource allocation in the trigger frame is of the same length, and the terminal assigned to the DSO channel with a small amount of data to transmit can fill padding bits to match the allocated length and transmit.

[0121] Additionally, when allocating resources to divide and transmit into multiple frames, there may be cases where there are no frames to transmit in the resources allocated to the main channel as trigger frames. In the aforementioned cases, a QoS Null frame with the data portion filled with padding bits may be transmitted, but is not limited thereto.

[0122] FIGS. 4a and 4b are drawings illustrating a method for preventing main channel puncture in a wireless LAN dynamic sub-channel operation applied to the present disclosure.

[0123] The wireless LAN network configuration of FIGS. 4a and 4b may be as described above. Here, the wireless LAN terminal can acquire a TXOP if it succeeds in accessing the channel by performing the EDCA operation described above. Additionally, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330), which are wireless LAN terminals within the wireless LAN network in FIGS. 4a and 4b, may be DSO STAs that follow the DSO operation of the terminal described above. Here, AP 1 (310) can recognize that non-AP STA 1 (320) and non-AP STA 2 (330) are operating with a more limited operating bandwidth than AP 1 (310). For example, AP 1 (310) has an operating bandwidth of up to 80 MHz, and non-AP STA 1 (320) and non-AP STA 2 (330) each have an operating bandwidth of up to 40 MHz, but this is for convenience of explanation only and is not limited thereto.

[0124] Referring to FIG. 4a, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) can perform communication by assigning the non-AP STA, which has a small amount of downlink data to be transmitted as described above in FIG. 3a, to a sub-channel. non-AP STA 1 (320) can receive data 1 (410-1) transmitted by AP 1 (310) and recognize that there is no subsequent downlink data frame, and can switch the operating channel back to the main channel after transmitting a response frame (411-1) for data 1 (410-1). From the time non-AP STA 1 (320) completes switching the operating channel back to the main channel until the end of the TXOP obtained by AP 1 (310) during the initial ICF transmission, non-AP STA 1 (320) may not expect frame transmission and reception operations with AP 1 (310). Accordingly, when a non-AP STA (i.e., non-AP STA 1 (320)) with a small amount of downlink data to be transmitted is assigned to a sub-channel as described above, the non-AP STA 1 (320) may perform a power saving operation in a doze state until the TXOP of AP 1 (310) is terminated after switching the operating channel back to the main channel. Here, the doze state may be an operation in which no transmission or reception operation is performed with the wireless LAN transceiver module (e.g., radio frequency chain, etc.) turned off. As an example, the operation described above may be referred to as intra TXOP power saving, but it may not be limited to that name. Before performing the intra TXOP power saving operation, the non-AP STA 1 (320) may include an intra TXOP power saving indicator in the last transmitted BA (411-1) or transmit a frame containing an intra TXOP power saving indicator together with the BA.The non-AP STA 1 (320), which has performed a power saving operation in the aforementioned doze state, can switch to an awake state at the time of the TXOP termination of AP 1 (310) and perform a channel access operation. Here, the awake state may be a state in which a wireless LAN transceiver module (e.g., radio frequency chain, etc.) is turned on and performs or waits for a transceiver operation.

[0125] Referring to FIG. 4b, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) can perform communication by assigning the non-AP STA with a small amount of uplink data to be transmitted to a sub-channel based on FIG. 3b described above. When the non-AP STA with a small amount of uplink data to be transmitted is assigned to a sub-channel, non-AP STA 1 (320) transmits data 1 (412-1) and there may be no subsequent uplink data frame to be transmitted. Therefore, non-AP STA 1 (320) can switch the operating channel back to the main channel after receiving a response frame (413-1) for data 1 (412-1). non-AP STA 1 (320) may not expect frame transmission and reception operations with AP 1 (310) from the time it completes switching to the main channel until the time the TXOP acquired by AP 1 (310) when transmitting the first trigger frame ends. Therefore, if a non-AP STA with a small amount of uplink data to transmit is assigned to a sub-channel, non-AP STA 1 (320) may operate in a doze state for power saving from the time it switches the operating channel to the main channel until the time the TXOP of AP 1 (310) ends. Here, the doze state may be an operation in which no transmission or reception operations are performed with the wireless LAN transceiver module (e.g., radio frequency chain, etc.) turned off. As an example, the above-described operation may be referred to as intra TXOP power saving, but it may not be limited to that name. The non-AP STA 1 (320) may include an intra TXOP power saving indicator in the last transmitted BA (413-1) before performing the intra TXOP power saving operation, or transmit a frame including an intra TXOP power saving indicator along with the BA.The non-AP STA 1 (320), which has performed a power saving operation in the aforementioned doze state, can switch to an awake state at the time of the TXOP termination of AP 1 (310) and perform a channel access operation. Here, the awake state may be a state in which a wireless LAN transceiver module (e.g., radio frequency chain, etc.) is turned on and performs or waits for a transceiver operation.

[0126] As another example, as in FIG. 3b, when a non-AP STA with a small amount of uplink data to be transmitted is assigned to a sub-channel, AP 1 (310) may transmit an ICF as the initial frame transmitted to non-AP STA 1 (320) and non-AP STA 2 (330). The ICF transmitted by AP 1 (310) may include an indicator that directs an operation channel switching to assign non-AP STA 1 (320) to a sub-channel (DSO channel), and at the same time, AP 1 (310) may use the ICF to assign non-AP STA 2 (330) to a main channel. Here, the ICF may be transmitted with padding included. Upon receiving the ICF transmitted by AP 1 (310), non-AP STA 1 (320) and non-AP STA 2 (330) may prepare for transmit and receive operations on the assigned channel. That is, non-AP STA 1 (320) can switch to a sub-channel (DSO channel) to wait for transmission and reception, and non-AP STA 2 (330) can wait for transmission and reception on the main channel. non-AP STA 1 (320) and non-AP STA 2 (330) can transmit an ICR to AP 1 (310) after SIFS time from the time the ICF transmission is completed. AP 1 (310) receives the ICR transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) and can transmit a trigger frame after SIFS time. non-AP STA 1 (320) and non-AP STA 2 (330) receive the trigger frame transmitted by AP 1 (310) and can transmit uplink data frames (e.g., Data 1, Data 2) to AP 1 (310) after SIFS time. In the above-mentioned case, the trigger frame may not include separate padding.

[0127] For example, if AP 1 (310) recognizes that there is an additional uplink data frame to be received in addition to the uplink data frame (e.g., Data 1) received from non-AP STA 1 (320) operating on a sub-channel (DSO channel), AP 1 (310) may compose a single frame in the form of an A-MPDU containing a response frame (e.g., BA frame) for the previously received uplink data frame (e.g., data 1) and a trigger frame that triggers a subsequent uplink data frame, and transmit it to non-AP STA 1 (320). After receiving the response frame and trigger frame composed of a single frame, non-AP STA 1 (320) may transmit uplink data (e.g., data 4) to AP 1 (310) after SIFS time.

[0128] FIGS. 5A and 5B are drawings illustrating a method for preventing main channel puncture in a wireless LAN dynamic sub-channel operation applied to the present disclosure.

[0129] The wireless LAN network configuration of FIGS. 5a and 5b may be as described above. Here, the wireless LAN terminal can acquire a TXOP if it succeeds in accessing the channel by performing the EDCA operation described above. Additionally, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330), which are wireless LAN terminals within the wireless LAN network in FIGS. 5a and 5b, may be DSO STAs that follow the DSO operation of the terminal described above. Here, AP 1 (310) can recognize that non-AP STA 1 (320) and non-AP STA 2 (330) are operating with a more limited operating bandwidth than AP 1 (310). For example, AP 1 (310) has an operating bandwidth of up to 80 MHz, and non-AP STA 1 (320) and non-AP STA 2 (330) each have an operating bandwidth of up to 40 MHz, but this is for convenience of explanation only and is not limited thereto.

[0130] AP 1 (310) can recognize that non-AP STA 1 (320) is a DPS STA. In the above case, non-AP STA 1 (320) may need to perform DSO operations and DPS operations simultaneously. Here, AP 1 (310) may not allow non-AP STA 1 (320), which is a DPS STA, to participate in the DSO operation. That is, AP 1 (310) may allow non-AP STA 1 (320) to switch to only one operation mode when it is operating in two or more operation modes (e.g., DSO, DPS, EMLSR, etc.). For example, if AP 1 (310) recognizes that there is data to be exchanged with non-AP STA 1 (320) and non-AP STA 2 (330), the data exchange with non-AP STA 1 (320) may be performed by acquiring a separate TXOP to minimize additional delay time (e.g., switching time, switching delay, transition delay, etc. required for switching LCM and HCM modes) caused by non-AP STA 1 (320), which is a DPS STA, but is not limited thereto.

[0131] Referring to FIG. 5a, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) can perform communication by assigning a non-AP STA with a small amount of downlink data to a sub-channel, as described above in FIG. 3a. Here, non-AP STA 1 (320) may be a DPS STA that supports DPS operation. Therefore, DPS operation can be performed together by assigning non-AP STA 1 (320) to a sub-channel as a non-AP STA with a small amount of downlink data to transmit.

[0132] For example, non-AP STA 1 (320) may be operating as an initial LCM. When non-AP STA 1 (320) is operating as an initial LCM, AP 1 (310) may assign non-AP STA 1 (320) to a sub-channel based on DSO operation without a separate mode switching instruction. That is, AP 1 (310) may assign non-AP STA 1 (320) to a sub-channel (DSO channel) without including a separate mode switching instruction for non-AP STA 1 (320) in the ICF transmitted initially. AP 1 (310) may include the sub-channel (DSO channel) in the ICF transmitted to non-AP STA 1 (320). The ICF transmitted to non-AP STA 1 (320) may only include the identifier (e.g., association identifier (AID)) of non-AP STA 1 (320). Additionally, the ICF transmitted to non-AP STA 1 (320) may contain wireless resource information (e.g., resources corresponding to sub-channels) available to non-AP STA 1 (320). On the other hand, the ICF transmitted to non-AP STA 2 (330) may have the same ICF transmitted redundantly per 20 MHz channel to the main channel (e.g., a 40 MHz channel including the main channel, which is the bandwidth supported by the terminal). Alternatively, a single ICF may be transmitted to the main 40 MHz channel (e.g., a 40 MHz channel including the main channel). The ICF transmitted to non-AP STA 2 (330) may contain only the identifier of non-AP STA 2 (330). Additionally, the ICF may contain wireless resource information (e.g., resources corresponding to a 40 MHz channel including the main channel) available to non-AP STA 2 (330).

[0133] Here, if there is no frame to transmit in the secondary channel remaining after allocating to non-AP STA 1 (320) and non-AP STA 2 (330) (band (channel) of TXOP acquired by AP 1 (310) that is not used by non-AP STA 1 (320) and non-AP STA 2 (330)), AP 1 (310) may transmit the frame by puncturing. Alternatively, AP 1 (310) may transmit the ICF by redundantly transmitting it at 20 MHz or by padding, but is not limited thereto. As another example, the ICF may include both identifiers of non-AP STA 1 (320) and non-AP STA 2 (330), and may also include wireless resource information that non-AP STA 1 (320) and non-AP STA 2 (330) can each use. Here, the ICF can be transmitted in duplicate in 20 MHz increments across the entire bandwidth of the TXOP acquired by AP 1 (310).

[0134] Referring to FIG. 5a, another example can be considered in which a non-AP STA 1 (320) is assigned to a sub-channel and a DPS operation is performed together with a non-AP STA with a small amount of downlink data to be transmitted. Here, the non-AP STA 1 (320) may be operating as an initial LCM. AP 1 (310) may instruct the non-AP STA 1 (320) to perform a mode switching operation when it is operating as an initial LCM and may assign the non-AP STA 1 (320) to a sub-channel based on a DSO operation. That is, AP 1 (310) may transmit the initial ICF (414) including a mode switching indicator for the non-AP STA 1 (320) and an operation channel switching indicator for assigning the non-AP STA 1 (320) to a sub-channel (DSO channel). AP 1 (310) can use the indicators included in the transmitted ICF (414) (e.g., operation channel switching indicator, mode switching indicator) to instruct non-AP STA 1 (320) to perform channel switching based on DSO and mode switching based on DPS operation.

[0135] Based on the above description, non-AP STA 1 (320) can receive the ICF (414) transmitted by AP 1 (310) and switch its operating channel and operating mode. Subsequently, non-AP STA 1 (320) can communicate based on the method of assigning a non-AP STA with a small amount of downlink data to a sub-channel for communication, as described above in FIG. 3a. That is, non-AP STA 1 (320) can receive the data transmitted by AP 1 (310) and recognize that there is no subsequent downlink data frame. non-AP STA 1 (320) can transmit a response frame for data 1 and switch the operating channel back to the main channel. non-AP STA 1 (320) may not expect frame transmission and reception operations with AP 1 (310) from the time it completes switching the operating channel to the main channel until the time the TXOP obtained by AP 1 (310) during the initial ICF (414) transmission ends. Therefore, non-AP STA 1 (320) may switch its operating mode to LCM after switching the operating channel to the main channel. The operation mode switching operation of non-AP STA 1 (320) may be performed simultaneously with the operation channel switching, depending on the operation capability of non-AP STA 1 (320). Alternatively, channel switching and mode switching may be performed separately by non-AP STA 1 (320). For example, non-AP STA 1 (320) may be configured to perform mode switching after switching the operating channel to the main channel. As another example, non-AP STA 1 (320) may switch the operation mode from the sub-channel and then perform an operation channel switch to the main channel.

[0136] The LCM operation period of non-AP STA 1 (320) may be performed from the time when non-AP STA 1 (320) completes the operation mode switching operation until the time when AP 1 (310) obtains the TXOP during the initial ICF transmission or thereafter. Before performing the operation mode switching operation described above, non-AP STA 1 (320) may include a mode switch back indicator in the last transmitted BA, or transmit a frame containing a mode switch back indicator along with the BA.

[0137] Referring to FIG. 5b, AP 1 (310), non-AP STA 1 (320), and non-AP STA 2 (330) can perform communication based on the non-AP STA with less uplink data to transmit as described in FIG. 3b. Here, non-AP STA 1 (320) may be a DPS STA that supports DPS operation. Thus, DPS operation can be performed together by assigning non-AP STA 1 (320) to a sub-channel as a non-AP STA with less uplink data to transmit.

[0138] For example, non-AP STA 1 (320) may be operating as an initial LCM. When non-AP STA 1 (320) is operating as an initial LCM, AP 1 (310) may assign non-AP STA 1 (320) to a sub-channel based on DSO operation without a separate mode switching instruction. That is, AP 1 (310) may assign non-AP STA 1 (320) to a sub-channel (DSO channel) without including a separate mode switching instruction for non-AP STA 1 (320) in the trigger frame transmitted initially.

[0139] The trigger frame transmitted by AP 1 (310) to non-AP STA 1 (320) may include a sub-channel (DSO channel). The user info of the trigger frame transmitted to non-AP STA 1 (320) may include only the identifier of non-AP STA 1 (320). Additionally, the trigger frame may include wireless resource information (e.g., resources corresponding to the sub-channel) available to non-AP STA 1 (320). The trigger frame transmitted by AP 1 (310) to non-AP STA 2 (330) may have the same trigger frame transmitted redundantly per 20 MHz channel on the main channel (e.g., a 40 MHz channel including the main channel, which is the bandwidth supported by the terminal). Alternatively, the trigger frame may be transmitted as a single trigger frame on the main 40 MHz channel (e.g., a 40 MHz channel including the main channel). The user information of the trigger frame transmitted to the non-AP STA 2 (330) may include only the identifier of the non-AP STA 2 (330). Additionally, the trigger frame may include wireless resource information available to the non-AP STA 2 (330) (e.g., resources corresponding to a 40 MHz channel including the main channel).

[0140] Here, if there are no frames to transmit in the secondary channels remaining after allocating to non-AP STA 1 (320) and non-AP STA 2 (330) (bands (channels) of the TXOPs (channels) acquired by AP 1 (310) that are not used by non-AP STA 1 (320) and non-AP STA 2 (330)), the remaining secondary channels may be punctured. Alternatively, transmission may be performed by redundantly transmitting trigger frames transmitted at 20 MHz or by padding, but is not limited thereto.

[0141] Referring to FIG. 5b, another example can be considered in which a non-AP STA 1 (320) is assigned to a sub-channel and a DPS operation is performed together with a non-AP STA with a small amount of downlink data to be transmitted. Here, the non-AP STA 1 (320) may be operating as an initial LCM. AP 1 (310) may instruct the non-AP STA 1 (320) to perform a mode switching operation when it is operating as an initial LCM and may assign the non-AP STA 1 (320) to a sub-channel based on a DSO operation. That is, AP 1 (310) may transmit a mode switching indicator for the non-AP STA 1 (320) and an operation channel switching indicator for assigning the non-AP STA 1 (320) to a sub-channel (DSO channel) in the initial transmitted trigger frame (415). AP 1 (310) can use indicators (e.g., operation channel switching indicator, mode switching indicator) included in the transmitted trigger frame (415) to instruct non-AP STA 1 (320) to perform channel switching based on DSO and mode switching based on DPS operation.

[0142] Based on the above description, non-AP STA 1 (320) can receive a trigger frame transmitted by AP 1 (310) and switch its operating channel and operating mode. Subsequently, non-AP STA 1 (320) can communicate based on the method of assigning a non-AP STA with a small amount of uplink data to a sub-channel for communication, as described above in FIG. 3b. That is, non-AP STA 1 (320) can transmit data to AP 1 (310) and recognize that there is no subsequent uplink data frame. non-AP STA 1 (320) can receive a response frame for data 1 and switch the operating channel back to the main channel. From the time non-AP STA 1 (320) completes switching the operating channel back to the main channel until the end of the TXOP obtained by AP 1 (310) when the first trigger frame was transmitted, non-AP STA 1 (320) may not expect frame transmission and reception operations with AP 1 (310). Accordingly, the non-AP STA 1 (320) can switch its operating channel to the main channel and then switch its operating mode to LCM. The operation mode switching operation of the non-AP STA 1 (320) may be performed simultaneously with the operation channel switching, depending on the operation capability of the non-AP STA 1 (320). Alternatively, the channel switching and mode switching of the non-AP STA 1 (320) may be performed separately. For example, the non-AP STA 1 (320) may switch its operating channel to the main channel and then perform a mode switching. As another example, the non-AP STA 1 (320) may switch its operating mode from the sub-channel and then perform an operation channel switch to the main channel.

[0143] The LCM operation period of non-AP STA 1 (320) may be performed from the time when non-AP STA 1 (320) completes the operation mode switching operation until the time when AP 1 (310) obtains the TXOP when transmitting the first trigger frame, or thereafter. Before performing the operation mode switching operation described above, non-AP STA 1 (320) may include a mode switch back indicator in the last transmitted frame or transmit with a frame containing a mode switch back indicator.

[0144] As another example, AP 1 (310) may transmit an ICF as an initial frame to non-AP STA 1 (320) and non-AP STA 2 (330). The ICF transmitted initially by AP 1 (310) may include an indicator directing an operation channel switch to assign non-AP STA 1 (320) to a sub-channel (DSO channel). At the same time, AP 1 (310) may use the ICF to assign non-AP STA 2 (330) to a main channel. Additionally, the ICF may include an operation mode switch indicator for non-AP STA 1 (320) in addition to the operation channel switch indicator, and non-AP STA 1 (320) upon receiving the ICF may perform a mode switching operation. Here, the ICF may include padding. The padding may vary depending on the operation that non-AP STA 1 (320) and non-AP STA 2 (330) must perform and the operation capabilities of non-AP STA 1 (320) and non-AP STA 2 (330).

[0145] non-AP STA 1 (320) and non-AP STA 2 (330), having received the ICF transmitted by AP 1 (310), can prepare for transmit and receive operations on the assigned channel. That is, non-AP STA 1 (320) can switch to a sub-channel (DSO channel) to wait for transmit and receive, and non-AP STA 2 (330) can wait for transmit and receive on the main channel. non-AP STA 1 (320) and non-AP STA 2 (330) can transmit an ICR to AP 1 (310) after SIFS time from the time the ICF transmission is completed. AP 1 can receive an ICR transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) and transmit a trigger frame after SIFS time, and non-AP STA 1 (320) and non-AP STA 2 (330) can receive a trigger frame transmitted by AP 1 (310) and transmit uplink data frames (e.g., Data 1, Data 2) to AP 1 (310) after SIFS time. In the above case, the trigger frame may not include separate padding.

[0146] For example, if AP 1 (310) recognizes that there is an additional uplink data frame received in addition to the uplink data (e.g., Data 1) received from non-AP STA 1 (320) operating on a sub-channel (DSO channel), AP 1 (310) may compose a single frame in the form of an A-MPDU containing a response frame (e.g., BA frame) for the previously received uplink data frame (e.g., Data 1) and a trigger frame that triggers a subsequent uplink data frame, and transmit this to non-AP STA 1 (320). Upon receiving the frame in which the response frame and the trigger frame are combined into a single frame, non-AP STA 1 (320) may receive the frame and transmit a data frame (e.g., Data 4) to AP 1 (310) after SIFS time.

[0147] Additionally, referring to FIG. 5a and FIG. 5b, the length of padding included in the ICF transmitted by AP 1 (310) considering the parallel operation of the ICF and DPS based on FIG. 5a described above may vary depending on the operating capability of non-AP STA 1 (320). Alternatively, if padding is included in the trigger frame transmitted by AP 1 (310) based on the above description, the padding length may vary depending on the operating capability of non-AP STA 1 (320).

[0148] For example, if non-AP STA 1 (320) performs DSO channel switching and DPS mode switching independently, the padding length in the ICF or trigger frame transmitted by AP 1 (310) can be set to the sum of the time required for the DSO channel switching operation and the time required for the DPS mode switching by non-AP STA 1 (320). For another example, if non-AP STA 1 (320) can perform DSO channel switching and DPS mode switching simultaneously, the padding length in the ICF or trigger frame transmitted by AP 1 (310) can be set to the longer of the time required for the DSO channel switching operation and the time required for the DPS mode switching by non-AP STA 1 (320). That is, AP 1 (310) can be configured such that the padding length included in the ICF or trigger frame is equal to or longer than the sum of the 'padding transmission time + SIFS time' of the mode switching time and channel switching time of the non-AP STA 1 (320). AP 1 (310) and the non-AP STA 1 (320) can negotiate mutual capabilities during the association phase, which is a capability negotiation process. AP 1 (310) can recognize the DSO channel switching time and DPS mode switching time of the non-AP STA 1 (320), and can recognize whether they can be performed simultaneously or independently. Here, as described above, the length of the padding within the ICF or trigger frame can be adjusted.

[0149] FIG. 6 is a diagram showing a wireless LAN network to which the present disclosure applies, and FIG. 7 is a diagram showing a dynamic power saving operation method to which the present disclosure applies.

[0150] Referring to FIGS. 6 and 7, the description is based on AP 1 and non-AP STA 1 operating in association with AP 1 in a wireless LAN network, but this is for convenience of explanation only and is not limited thereto. At least one of AP 1 and non-AP STA 1 (510) in a wireless LAN network may perform the DSO operation described above, and the operation based on the DSO may be as described above.

[0151] Regarding DSO operation, the DSO padding delay time indicated by non-AP STA 1 (510) may be sufficient time for non-AP STA 1 (510) to receive AP 1's ICF (601), switch to the operation channel indicated by the ICF (601), and then transmit an ICR (602). However, the DSO padding delay time may be too short a time for non-AP STA 1 (510) to perform channel sensing (e.g., energy sensing, carrier sensing) after switching to the operation channel indicated by the ICF (601). Here, if the CS required bit of the common info field of the ICF (601) transmitted by AP 1 is set to 1, the non-AP STA 1 (510) may be required to perform channel detection and transmit an ICR (602) when the channel is in an idle state (i.e., not occupied). For example, the padding field length of the ICF (601) transmitted by AP 1 to the non-AP STA 1 (510) may be equal to the DSO padding delay time indicated by the non-AP STA 1 (510). In the above case, the non-AP STA 1 (510) may not be able to perform channel detection and may not be able to transmit an ICR (602).

[0152] Considering the aforementioned problem, the length of the padding included in the ICF (601) transmitted by AP 1 may be set to a length equal to or longer than the length of the DSO padding delay of non-AP STA 1 (510). For example, the length of the padding included in the ICF (601) transmitted by AP 1 may be set to be at least longer than the length of the padding delay of non-AP STA 1 (510) by SIFS time. In the above case, non-AP STA 1 (510) may perform a channel detection operation for a maximum SIFS time after switching the operating channel to the operating channel indicated by the ICF (601), and if the channel is not occupied, transmit a frame to AP 1. Alternatively, non-AP STA 1 (510) may set the DSO padding delay time indicated to AP 1 to the time during which channel detection is possible after switching the operating channel.

[0153] AP 1 can receive an ICR (602) transmitted by a non-AP STA 1 (510) that has successfully switched the operating channel on the channel indicated by the operating channel switching indicator. AP 1 can identify the non-AP STA 1 (510) that transmitted the ICR (602). AP 1 can receive the ICR (602) and transmit a frame (e.g., a data frame) (603) after SIFS time. Here, the data frame (603) may be transmitted based on at least one of the channel and bandwidth where the ICR (602) was transmitted. AP 1 can transmit a downlink data frame (603) to the non-AP STA 1 (510). Alternatively, AP 1 can transmit a trigger frame that allocates an uplink resource to the non-AP STA 1 (510) and receive an uplink frame of the non-AP STA 1 (510) that is transmitted based on the uplink resource allocated in the trigger frame.

[0154] A non-AP STA 1 (510) that receives a frame (603) transmitted by AP 1 can transmit an acknowledgment frame (e.g., Acknowledgement (ACK) frame, Block Acknowledgement (BA) frame) (604) to AP 1 using the bandwidth specified in the operation channel indicated by the operation channel switching indicator. A DSO STA that has switched the operation channel (i.e., non-AP STA 1 (510)) can perform a channel switching back operation to switch its operation channel from the sub-channel (DSO channel) to the main channel. After switching the operation channel to the DSO channel, AP 1 and non-AP STA 1 (510) can wait for a certain waiting time (e.g., aSIFSTime + aSlotTime + aRxPHYStartDelay time) after receiving or transmitting a frame from AP 1. Here, the certain waiting time may be referred to as Tw time, but is not limited to that name. If no frame is detected during the Tw time (e.g., if the PHY-RXSTART.indication primitive does not occur), the non-AP STA 1 (510) may switch the operating channel from the DSO channel to the main channel. For example, the operation described above may be referred to as the main channel switching operation, but is not limited to that name. When the non-AP STA 1 (510) switches from the DSO channel to the main channel, a separate switching time may occur, which may be referred to as the DSO switching delay, but is not limited to that name. For example, the DSO switching delay may be referred to as Tt. The non-AP STA 1 (510) may operate on the main channel after the switching time Tt. During the switching time that occurs when the non-AP STA 1 (510) switches from the DSO channel to the main channel, the non-AP STA 1 (510) may be unable to perform channel detection operations and frame reception.

[0155] Here, Tw time is as follows<Tw 조건 1> ,<Tw 조건 2> and<Tw 조건 3> It can start if one of the following cases is satisfied.

[0156]

[0157] <Tw 조건 1>

[0158] If the PPDU (physical protocol data unit) transmitted by the STA is a response to the most recently received frame from the AP, it starts at the time the transmission of the PPDU is completed.

[0159]

[0160] <Tw 조건 2>

[0161] If the PPDU received from an AP or another STA contains a frame that does not require an immediate response, start at the time the reception of the PPDU is complete.

[0162]

[0163] <Tw 조건 3>

[0164] If the PPDU transmitted by the STA contains a frame that does not require an immediate response, it starts at the time the transmission of the PPDU is completed.

[0165]

[0166] STA 1 is for the time Tw after Tw is initiated following the completion of reception of the initial control frame.<Primary 채널 전환> When the conditions are met, it no longer operates on the DSO channel and can switch to the main channel, and<Primary 채널 전환> The conditions may be as follows.

[0167]

[0168] <Primary 전환>

[0169] 1) The MAC layer of STA 1 does not receive the PHY-RXSTART.indication primitive from the PHY layer, 2) The MAC layer does not send the PHY-TXSTART.request primitive to the PHY layer and the MAC layer of STA 1 does not receive the PHY-TXSTART.confirm primitive from the PHY layer, 3) There is no nonempty transmit queue in STA 1, and 4) STA 1 does not intend to transmit a frame or schedule a transmission

[0170]

[0171] The aforementioned<Primary 전환> In the conditions, the MAC layer of STA 1 receiving the PHY-RXSTART.indication primitive from the PHY layer may mean that STA 1 detects a frame being received. Additionally, the MAC layer of STA 1 sending the PHY-TXSTART.request primitive to the PHY layer and the MAC layer of STA 1 receiving the PHY-TXSTART.confirm primitive from the PHY layer may mean that STA 1 intends to start transmitting a frame.

[0172] In addition, STA 1 receives the PHY-RXSTART.indication primitive within the Tw time,<Primary 전환> Even if the conditions are not met, the following<Primary 전환 - 수신> If the conditions are met, it can operate by switching the operating channel to the main channel instead of operating on the DSO channel.<Primary 전환> Without satisfying the conditions<Primary 전환 - 수신> If the conditions are not met, STA 1 must operate on the DSO channel without switching to the main channel.

[0173]

[0174] <Primary 전환 - 수신>

[0175] - When the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer, but the recipient of the received frame is not STA 1

[0176] - If the MAC layer of STA 1 receives the PHY-RXSTART.indication primitive from the PHY layer and the received frame is a trigger frame, and the received trigger frame does not allocate a resource unit (RU) for STA 1

[0177] - If the MAC layer of STA 1 receives a PHY-RXSTART.indication primitive from the PHY layer and the received frame is a CTS (clear to send) frame, and the receiver address (RA) of the CTS frame is not the address of the AP to which STA 1 is connected (i.e., the address of AP 1)

[0178]

[0179] The aforementioned<Primary 전환> and<Primary 전환 - 수신> The PPDU defined in the conditions may be a PHY layer frame (physical layer frame). A physical layer frame may include an MPDU (MAC protocol data unit) which is a MAC layer frame. For example, STA 1 receiving a CTS (clear to send) frame may mean that STA 1 receives a PPDU containing a CTS frame (i.e., an MPDU which is a MAC frame).

[0180] AP 1 may intend to operate multiple STAs (e.g., at least two STAs including STA 1) as DSO channels. In the above case, the ICF transmitted by AP 1 may contain DSO channel allocation information for multiple STAs including non-AP STA 1 (510). Here, the DSO padding delay and DSO switching delay of the multiple STAs may all be the same. The length of the padding field of the ICF transmitted by AP 1 may correspond to or have a longer time length than the time length of the DSO padding delay of the multiple STAs described above. After the multiple STAs described above have completed frame exchange on the DSO channel (i.e.,<Primary 전환> Satisfy the conditions or<Primary 전환> Although the conditions are not met<Primary 전환 - 수신> After satisfying the condition) the point at which it operates again on the main channel can be the same as after the DSO switching delay point.

[0181] Alternatively, at least one of the DSO padding delay and the DSO switching delay of the multiple STAs may differ. The length of the padding field of the ICF transmitted by AP 1 may correspond to or have a longer time length than the longest DSO padding delay among the DSO padding delay time lengths for the multiple STAs described above. That is, AP 1 may include padding in the ICF having a sufficient time length to enable all of the multiple STAs described above to operate on the DSO channel. After the multiple STAs described above have completed frame exchange on the DSO channel (i.e.,<Primary 전환> Satisfy the conditions or<Primary 전환> Although the conditions are not met<Primary 전환 - 수신> After satisfying the conditions) the timing at which each of the multiple STAs operates as the main channel again may differ.

[0182] For example, the initiation of the above-described DSO operation may be performed by non-AP STA 1 (510) and AP 1 exchanging a UHR OMN (ultra high reliability operation mode notification) frame or a UHR OMP (operation mode and parameters) frame, but is not limited thereto. As a specific example, non-AP STA 1 (510) may initiate the DSO operation by sending a UHR OMN frame to AP 1, and AP 1 sending a UHR OMN frame back to non-AP STA 1 (510). Additionally, AP 1 may support the DSO operation of non-AP STA 1 (510). non-AP STA 1 (510) may be a DSO STA, and AP 1 may be a DSO assisting AP. Here, according to the DSO setting procedure described above, AP 1 can obtain information on the DSO padding delay and DSO switching delay of non-AP STA 1 (510). In addition, the above-described items may be applied commonly in FIGS. 8a to 10 below, and may also be applied differently depending on the operation of each figure.

[0183] FIGS. 8A and FIGS. 8B are drawings illustrating a media synchronization method during dynamic subchannel operation applicable to the present disclosure.

[0184] Referring to FIGS. 8a and 8b, non-AP STA 1 (510) and AP 1 can operate in a wireless LAN. However, this is for convenience of explanation only and is not limited thereto. The non-AP STA 1 (510) and AP 1 can support the DSO operation described above. DSO operation may be a method to efficiently use the frequency resources of a wireless LAN network by changing the operating frequency of a STA with a smaller operating bandwidth than that of an AP. For example, the operating bandwidth of non-AP STA 1 (510) may be 80 MHz, the operating bandwidth of STA 2, another STA connected to AP 1, may be 80 MHz, and the operating bandwidth of AP 1 may be 160 MHz. If DSO is not used, even if the operating bandwidth of AP 1 is 160 MHz, since the operating bandwidth of non-AP STA 1 (510) and STA 2 is 80 MHz, AP 1 can perform transmission to non-AP STA 1 (510) or STA 2 using only the 80 MHz channel. That is, the remaining 80 MHz channel of AP 1 may not be used. If DSO operation is used, when non-AP STA 1 (510) receives an ICF from AP 1, non-AP STA 1 (510) can change the operating frequency (channel). For example, AP 1 can designate an 80 MHz channel including the main 20 MHz as the main channel and the remaining 80 MHz channel as the DSO channel. non-AP STA 1 (510) can operate on the main channel before receiving the ICF from AP 1. When non-AP STA 1 (510) receives the ICF of AP 1, it can switch the operating channel to the DSO channel and operate. When non-AP STA 1 (510) switches from the main channel to the DSO channel, a DSO padding delay is required, and when switching from the DSO channel to the main channel, a DSO switching delay (time Tt) may be required.During the switching delay time, non-AP STA 1 (510) may not detect the medium.

[0185] Here, non-AP STA 1 (510) can operate on the main channel, and AP 1 can transmit an ICF (601) to switch non-AP STA 1 (510) to the DSO channel. The ICF may include a padding field having a time length corresponding to or greater than the DSO padding delay for switching the non-AP STA 1 (510) from the main channel to the DSO channel. The ICF (601) may be transmitted in a Non-HT duplicate PPDU format that is duplicated and transmitted in 20 MHz increments on the main channel and the DSO channel. Additionally, as an example, the ICF may be a trigger frame.

[0186] The non-AP STA 1 (510) can receive the AP 1's ICF (601) and switch the operating channel to the DSO channel. Meanwhile, the non-AP STA 1 (510) may not be able to perform media detection during the DSO padding delay time while the non-AP STA 1 (510) switches from the main channel to the DSO channel. Not being able to perform media detection may mean that the non-AP STA 1 (510) cannot perform a frame reception operation and cannot detect the energy of the medium. For example, if the DSO padding delay exceeds the MediumSyncThreshold time length (e.g., 72us), the non-AP STA 1 (510) may lose media synchronization during that period. For example, the non-AP STA 1 (510) may lose the medium's NAV (network allocation vector) information (i.e., virtual carrier detection information). Alternatively, non-AP STA 1 (510) may have lost physical carrier detection information. Alternatively, non-AP STA 1 (510) may have lost both the media NAV information (i.e., virtual carrier detection information) and the physical carrier detection information. If non-AP STA 1 (510) loses media synchronization, non-AP STA 1 (510) may need to operate the MediumSyncDelay timer. The aforementioned timer may be a timer for non-AP STA 1 (510) to restore the correct media detection information. The MediumSyncDelay timer is a timer with a value of aPPDUMaxTime, etc., and may expire when the timer becomes 0 or when a normal frame is received (e.g., when at least one MPDU is decoded without error). non-AP STA 1 (510) may perform channel detection operations until the timer expires. The non-AP STA 1 (510) can lower the energy threshold of physical carrier detection while the medium detection timer has not expired.That is, non-AP STA 1 (510) can lower the energy level at which it detects the medium as occupied. When non-AP STA 1 (510) performs a channel access operation and the channel access operation is successful, non-AP STA 1 (510) can transmit an ICF (e.g., RTS frame) on the channel. When the energy detected on the channel is above a certain threshold, non-AP STA 1 (510) can detect the medium as occupied, and non-AP STA 1 (510) may continue to perform the channel detection operation. That is, non-AP STA 1 (510) must wait until the medium is switched to an idle state. As another example, the above-described operation may mean repeating the channel access operation of non-AP STA 1 (510) (e.g., selecting a new backoff counter) or pausing the channel access operation (e.g., keeping the backoff counter at 0).

[0187] On the other hand, if non-AP STA 1 (510) successfully receives ICF (601) from AP 1, it can check the end time of ICF (601), and it may be possible to transmit ICR (602) after SIFS time from the time AP 1 completes the transmission of ICF (601). That is, non-AP STA 1 (510) can transmit ICR (602), which is a response frame to ICF (601). At the time when non-AP STA 1 (510) transmits ICR (602) or when non-AP STA 1 (510) transmits ICR (602) and receives a frame from AP 1 (data frame or trigger frame, etc.) transmitted after SIFS, non-AP STA 1 (510) can release the aforementioned MediumSyncDelay timer. Alternatively, if non-AP STA 1 (510) successfully receives ICF (601) from AP 1, non-AP STA 1 (510) can check the end time of ICF (601). After receiving AP 1's ICF (601), non-AP STA 1 (510) can transmit ICR (602) after SIFS time from the time AP 1 completes transmitting ICF (601) without operating the MediumSyncDelay timer.

[0188] As another example, when non-AP STA 1 (510) receives AP 1's ICF (601), it can check the duration field value set by AP 1 in the MAC header of the ICF (601). Thus, non-AP STA 1 (510) can set the NAV (NAV timer) according to the value of the duration field of the ICF (601) transmitted by AP 1 (e.g., the duration field of the MAC header, the TXOP duration field of the PHY preamble, or a field related to the length of the PPDU, etc.) and recognize the NAV information being set. Non-AP STA 1 (510) can prevent the MediumSyncDelay timer from operating even if media detection is impossible for a certain period of time before the NAV expires (i.e., before the NAV timer reaches 0). That is, non-AP STA 1 (510) can recognize NAV information set based on the frame received from AP 1, and even if non-AP STA 1 (510) is unavailable for a certain period of time, the MediumSyncDelay timer may not operate because it can anticipate that the medium is occupied due to the frame transmitted by AP 1. As another example, if AP 1 transmits a frame that can set NAV (e.g., a frame in which a duration field value is set in the MAC header of the frame to set NAV, a CTS-to-Self frame and a (QoS) data frame, etc.) before transmitting ICF (601), there may be NAV set before receiving ICF (601) in non-AP STA 1 (510). non-AP STA 1 (510) receives the ICF (601) of AP 1, and although channel detection is not possible for a certain period of time during the DSO padding delay time, the MediumSyncDelay timer may not operate because it can know the NAV information already set by non-AP STA 1 (510).

[0189] Referring to FIG. 8a, AP 1 can transmit a data frame (603) to non-AP STA 1 (510) after performing an ICF (601) and ICR (602) frame exchange with non-AP STA 1 (510). After that, non-AP STA 1 (510) can transmit an acknowledgment frame (e.g., BlockAck frame) (604) for the data frame (603) to AP 1. Alternatively, if the frame transmitted by AP 1 to non-AP STA 1 (510) is a frame that does not require an acknowledgment frame, non-AP STA 1 (510) may not transmit an acknowledgment frame to AP 1. AP 1 can transmit a data frame (603) to a non-AP STA 1 (510) on the DSO channel, and can transmit a data frame (603) to a STA other than non-AP STA 1 (510) (e.g., STA 2) on the main channel. Meanwhile, the start and end times of the data frame (603) transmitted by AP 1 to non-AP STA 1 (510) and STA 2 may be the same. After receiving the data frame (603), non-AP STA 1 (510) [performs as described above]<Tw 조건 1> or<Tw 조건 2> The Tw time can be started according to. At the Tw time<primary 전환> or the condition is satisfied<primary 전환> Although the conditions were not met<primary 전환 - 수신> If the condition is satisfied, non-AP STA 1 (510) can switch the operating channel from the DSO channel to the main channel.

[0190] The following describes how AP 1 quickly stops the MediumSyncDelay timer of non-AP STA 1 (510). AP 1 may no longer want to transmit data frames to the DSO channel. If the data frame transmitted by AP 1 to non-AP STA 1 (510) is a frame that does not require a response frame, the time at which non-AP STA 1 (510) returns from the DSO channel to the main channel may be after 'Tw + Tt' time has elapsed since AP 1 finished transmitting the data frame to non-AP STA 1 (510). On the other hand, if the data frame transmitted by AP 1 to non-AP STA 1 (510) is a frame requesting a response frame, the time when non-AP STA 1 (510) returns to the main channel from the DSO channel may be after 'Tw + Tt' time has elapsed since non-AP STA 1 (510) finished transmitting the response frame to AP 1.

[0191] Here, AP 1 can transmit a padding frame (605) on the main channel to prevent other STAs from occupying the medium. Since AP 1 must switch non-AP STA 1 (510) to the main channel on the DSO channel, it may not transmit the padding frame on the DSO channel. For example, if the padding frame is transmitted on the DSO channel,<primary 전환> Although the conditions were not met<primary 전환> Although the conditions are satisfied<primary 전환 - 수신> Since the condition is not satisfied, non-AP STA 1 (510) cannot switch the operating channel from the DSO channel to the main channel until the padding frame is finished. If the data frame transmitted to non-AP STA 1 (510) during the Tw time is a frame that does not require a response frame, AP 1 can transmit a padding frame (605) on the main channel after SIFS time from the time it finishes transmitting the data frame to non-AP STA 1 (510). Or, if the data frame transmitted to non-AP STA 1 (510) is a frame that requires a response frame, AP 1 can transmit a padding frame (605) on the main channel after SIFS time from the time it finishes receiving the response frame received from non-AP STA 1 (510).

[0192] Meanwhile, the length of the padding frame (605) may be the time length of 'Tw + Tt - SIFS' or longer. The time length of the padding frame (605) may be for AP 1 to perform occupation of the main channel until the time when non-AP STA 1 (510) operates again on the main channel or thereafter.

[0193] As another example, AP 1 may have set a NAV during the ICF and ICR exchange process (or prior to ICF transmission). Based on the set NAV, AP 1 may be considered to be performing media occupancy even without transmitting a padding frame. In the above case, AP 1 may not need to transmit a padding frame, but may prefer to transmit a padding frame for media occupancy. The padding frame (605) may be a frame of the same or similar format as the ICF (601) transmitted by AP 1. Alternatively, the padding frame (605) may be a frame of a different format than the ICF (601). For example, the padding frame (605) may be a frame such as a QoS Null frame rather than an ICF (601). The non-AP STA 1 (510) may switch the operating channel from the DSO channel to the main channel while AP 1's padding frame is being transmitted on the main channel. For example, if the time Tt exceeds the specified time, MediumSyncThreshold (e.g., 72us), the non-AP STA 1 (510) cannot perform channel detection operations during the time Tt, so the MediumSyncDelay timer can be started when operating on the main channel. That is, the non-AP STA 1 (510) could not perform media detection during the time Tt, which is the delay time for switching the operating channel, and since the length of time during which media detection could not be performed exceeds a specified time length, the non-AP STA 1 (510) may lose media synchronization. Therefore, the non-AP STA 1 (510) can start the MediumSyncDelay timer for media synchronization recovery. AP 1 can transmit any frame (606) that can release the MediumSyncDelay timer of the non-AP STA 1 (510) on the main channel after SIFS time at the time the padding frame transmission is completed.For example, the arbitrary frame (606) may be a short QoS Null frame. For another example, the arbitrary frame (606) may be a data frame or trigger frame transmitted by AP 1 to at least one of non-AP STA 1 (510) and other STAs. When non-AP STA 1 (510) receives AP 1's frame (such as a data frame or trigger frame) without error, non-AP STA 1 (510) can obtain NAV information through correct frame decoding. When non-AP STA 1 (510) has completed receiving the frame without error, it can release the aforementioned MediumSyncDelay timer. Thus, non-AP STA 1 (510) can perform channel access operations on the main channel without restriction.

[0194] Additionally, AP 1 may set a NAV or TXOP that can ensure sufficient time to transmit any frame capable of releasing the padding frame and the MediumSyncDelay timer of non-AP STA 1 (510). That is, the duration field of the MAC header of the frame transmitted by AP 1 may indicate the length of the communication interval capable of transmitting any frame capable of releasing the padding frame and the MediumSyncDelay timer of non-AP STA 1 (510).

[0195] As another example, non-AP STA 1 (510) may anticipate that AP 1 will transmit a padding frame for media synchronization of non-AP STA 1 (510). Alternatively, AP 1 and non-AP STA 1 (510) may have negotiated in the initiation procedure of the DSO operation that when non-AP STA 1 (510) switches the operation channel from the DSO channel to the main channel, AP 1 transmits the aforementioned padding frame, and non-AP STA 1 (510) performs an operation that does not use the MediumSyncDelay timer due to AP 1's transmission of the padding frame. In the above case, non-AP STA 1 (510) may not start the MediumSyncDelay timer when operating on the main channel.

[0196] As another example, consider a case where the NAV set by non-AP STA 1 (510) based on the frame transmitted by AP 1 remains for more than 'Tw + Tt' time from the time non-AP STA 1 (510) has finished receiving a data frame on the DSO channel or has finished transmitting a response frame. AP 1 may no longer transmit frames to non-AP STA 1 (510) on the DSO channel. In the above case, non-AP STA 1 (510) during Tw time<Primary 전환> If the operation of switching the operating channel from the DSO channel to the main channel for a time Tt is performed based on conditions, the NAV of non-AP STA 1 (510) may end at the same time as when non-AP STA 1 (510) operates on the main channel. As another example, there may be a remaining NAV of non-AP STA 1 (510) at the time when non-AP STA 1 (510) operates on the main channel. In the above case, since non-AP STA 1 (510) maintains correct NAV information, the MediumSyncDelay timer may not be applied at the time when operating on the main channel. Additionally, AP 1 may transmit various frames including data frames on the main channel during the remaining NAV period set by AP 1 without transmitting the padding frame described above. AP 1 may ensure that frame exchange on the DSO channel is terminated at least before the time 'Tw + Tt' from the time of termination of the NAV (or TXOP) of AP 1 indicated by the duration field of the frame transmitted by AP 1 (e.g., the time of termination of a subsequent response frame for a data frame, or the time of termination of the data frame if the data frame does not require a response frame).

[0197] Referring to FIG. 8b, AP 1 can transmit a trigger frame (607) that allocates uplink resources to non-AP STA 1 (510) after performing an ICF (601) and ICR (602) exchange with non-AP STA 1 (510). non-AP STA 1 (510) can receive the trigger frame (607) from AP 1 and transmit an uplink TB (trigger-based) PPDU after SIFS time. That is, non-AP STA 1 (510) can transmit an uplink frame (608) from the uplink resources allocated by AP 1's trigger frame (607). AP 1 can receive the uplink frame (608) from non-AP STA 1 (510) and transmit an acknowledgment frame (e.g., BlockAck frame) (609) to non-AP STA 1 (510). non-AP STA 1 (510) receives an acknowledgment frame (609) from AP 1 on the DSO channel, and at the time when receiving the acknowledgment frame (609) is completed<Tw 조건 2> The Tw time can be started according to. At the Tw time<Primary 전환> or the condition is satisfied<Primary 전환> Although the conditions were not met<Primary 전환 - 수신> If the condition is satisfied, non-AP STA 1 (510) can switch the operating channel from the DSO channel to the main channel.

[0198] Additionally, AP 1 may perform an action to quickly stop the MediumSyncDelay timer of non-AP STA 1 (510). AP 1 may no longer want to transmit data frames to the DSO channel. The time when non-AP STA 1 (510) returns to the main channel from the DSO channel may be after 'Tw + Tt' time has elapsed from the end of the acknowledgment frame (609) transmitted by AP 1 to non-AP STA 1 (510). Here, AP 1 may prevent other STAs from occupying the medium on the main channel. When AP 1 transmits an acknowledgment frame (609) for an uplink frame (608) to non-AP STA 1 (510), the acknowledgment frame (610) transmitted on the main channel may include padding (padding field) that guarantees the Tw time and DSO switching delay (Tt time) of non-AP STA 1 (510). That is, the length of the padding field of the response frame (610) transmitted by AP 1 on the main channel may have a time length of 'Tt + Tw' or longer. The aforementioned time length of the padding field may be for AP 1 to perform occupation of the main channel until the time when non-AP STA 1 (510) operates again on the main channel or thereafter. The response frame (609) transmitted by AP 1 on the DSO channel may not include a padding field. For example, padding may be a method of extending the length of the response frame by using a Per AID-TID BlockAck Bitmap field indicated by at least one of the AID (association identifier) ​​and TID (traffic identifier) ​​for padding the BlockAck frame. Alternatively, padding may use the Packet extension field of the PHY or EOF padding that repeats the EOF (end of frame) of the A-MPDU, but may not be limited thereto.That is, padding can be performed for the purpose of increasing the length of the frame. Additionally, AP 1 may not include padding as described above in the response frame transmitted on the DSO channel. Since AP 1 must switch non-AP STA 1 (510) to the main channel on the DSO channel, it may not transmit a response frame containing padding on the DSO channel. If a response frame containing padding is transmitted on the DSO channel, the start time of the Tw time when non-AP STA 1 (510) starts on the DSO channel may be delayed to the end time of the response frame containing padding. Therefore, the time when non-AP STA 1 (510) operates again on the main channel may also be delayed. The time length of the padding included in the response frame, 'Tt + Tw' time or longer, is intended for AP 1 to occupy the main channel until non-AP STA 1 (510) operates again on the main channel.

[0199] Alternatively, AP 1 may set NAV during the ICF and ICR exchange (or prior to the ICF transmission). Here, AP 1 may be considered to be performing media occupancy even if it does not transmit a padded acknowledgment frame (610) based on the NAV. In the above case, AP 1 may not need to transmit a padded acknowledgment frame (610), but may prefer to transmit a padded acknowledgment frame (610) for media occupancy. The non-AP STA 1 (510) may switch the operating channel from the DSO channel to the main channel while AP 1's padded acknowledgment frame (610) is being transmitted on the main channel. If the non-AP STA 1 (510) exceeds the MediumSyncThreshold time (e.g., 72us), which is a specified time Tt, the non-AP STA 1 (510) may start the MediumSyncDelay timer when operating on the main channel because it failed to perform a channel sensing operation during the Tt time. AP 1 may transmit any frame (611) that can release the MediumSyncDelay timer of non-AP STA 1 (510) on the main channel after SIFS time at the time the padding-containing response frame (610) is transmitted. For example, the aforementioned arbitrary frame (611) may be a short QoS Null frame. Alternatively, the aforementioned arbitrary frame (611) may be a data frame or trigger frame transmitted by AP 1 to at least one of non-AP STA 1 (510) and another STA. non-AP STA 1 (510) can obtain NAV information through correct frame decoding when non-AP STA 1 (510) receives a frame of AP 1 (such as a data frame or a trigger frame) without error. non-AP STA 1 (510) can release the MediumSyncDelay timer when it has finished receiving the frame without error.The non-AP STA 1 (510) can perform channel access operations without restriction on the main channel. AP 1 may need to set a NAV that ensures sufficient time to transmit the padded response frame and any frame that can release the MediumSyncDelay timer of the non-AP STA 1 (510). That is, the duration field of the MAC header of the frame transmitted by AP 1 may indicate the length of the communication interval during which the padded response frame and any frame that can release the MediumSyncDelay timer of the non-AP STA 1 (510) can be transmitted.

[0200] As another example, non-AP STA 1 (510) may anticipate that AP 1 will send a padded acknowledgment frame for media synchronization of non-AP STA 1 (510). Alternatively, when non-AP STA 1 (510) switches the operating channel from the DSO channel to the main channel, AP 1 may send a padded acknowledgment frame, and non-AP STA 1 (510) may have negotiated in the initiation procedure of the DSO operation to perform an operation that does not use the MediumSyncDelay timer because AP 1's padded acknowledgment frame is sent. In the above case, non-AP STA 1 (510) may not start the MediumSyncDelay timer when operating on the main channel.

[0201] As another example, the NAV set by non-AP STA 1 (510) based on the frame transmitted by AP 1 may remain for more than 'Tw + Tt' time from the time non-AP STA 1 (510) finishes receiving the response frame on the DSO channel. AP 1 may not transmit any more frames to non-AP STA 1 (510) on the DSO channel. In the above case, non-AP STA 1 (510) for Tw time<Primary 전환> When conditions are met and an operation is performed to switch the operating channel from the DSO channel to the main channel for a time Tt, the NAV of non-AP STA 1 (510) may end at the same time as when non-AP STA 1 (510) operates on the main channel. As another example, there may be a remaining NAV of non-AP STA 1 (510) at the time when non-AP STA 1 (510) operates on the main channel. In the above case, since non-AP STA 1 (510) maintains correct NAV information, the MediumSyncDelay timer may not be applied at the time when it operates on the main channel. Additionally, in the above case, AP 1 may not transmit a response frame containing padding as described above, and may transmit various frames including data frames on the main channel during the remaining NAV period set by AP 1. For the above operation, AP 1 may ensure that the response frame transmitted on the DSO channel is terminated at least before the time 'Tw + Tt' from the time of termination of the NAV (or TXOP) of AP 1 indicated by the duration field of the frame set by AP 1.

[0202] Referring to FIGS. 8a and 8b, padding, padding fields, and padding bits may be used to extend the length of the frame and provide time for non-AP STA 1 (510) to switch the operating channel. For example, FIG. 8a may be the case where AP 1 performs a downlink transmission to non-AP STA 1 (510) in a DSO channel, and FIG. 8b may be the case where AP 1 allocates uplink resources to non-AP STA 1 (510) in a DSO channel so that non-AP STA 1 (510) performs an uplink transmission. Downlink transmission by AP 1 and uplink transmission by non-AP STA 1 (510) may be performed in a DSO channel. When frame transmission is performed continuously in a DSO channel, non-AP STA 1 (510) may operate based on the description in FIG. 8a when it receives the last downlink data frame in the DSO channel. Alternatively, if non-AP STA 1 (510) last transmitted an uplink data frame in the DSO channel based on the trigger frame of AP 1, it may operate based on the description in FIG. 8b.

[0203] Referring to FIGS. 8a and 8b, the main channel may always need to be occupied. For example, STA 2, which is a STA other than non-AP STA 1 (510), may be present on the main channel, and STA 2 may transmit or receive frames by synchronizing with the DSO channel. When AP 1 first transmits an ICF to switch non-AP STA 1 (510) to the DSO channel, the allocation of the main resource for STA 2 may be mandatory. However, if STA 2 fails to receive AP 1's ICF or if STA 2 detects that the main channel is occupied, STA 2 may not be able to respond to AP 1's ICF. In the above case, the DSO operation may not be performed smoothly, and the operation based on the above is described below.

[0204] FIGS. 9a and 9b are drawings illustrating a media synchronization method in case of dynamic subchannel operation failure applicable to the present disclosure.

[0205] Referring to FIG. 9a and FIG. 9b, non-AP STA 1 (510) and AP 1 can operate in a wireless LAN. However, this is for convenience of explanation only and is not limited thereto. The non-AP STA 1 (510) and AP 1 can support the DSO operation described above. DSO operation may be a method to efficiently use the frequency resources of a wireless LAN network by changing the operating frequency of a STA with a smaller operating bandwidth than that of an AP. For example, the operating bandwidth of non-AP STA 1 (510) may be 80 MHz, the operating bandwidth of STA 2, another STA connected to AP 1, may be 80 MHz, and the operating bandwidth of AP 1 may be 160 MHz. If DSO is not used, even if the operating bandwidth of AP 1 is 160 MHz, since the operating bandwidth of non-AP STA 1 (510) and STA 2 is 80 MHz, AP 1 can perform transmission to non-AP STA 1 (510) or STA 2 using only the 80 MHz channel. That is, the remaining 80 MHz channel of AP 1 may not be used. If DSO operation is used, when non-AP STA 1 (510) receives an ICF from AP 1, non-AP STA 1 (510) can change the operating frequency (channel). For example, AP 1 can designate an 80 MHz channel including the main 20 MHz as the main channel and the remaining 80 MHz channel as the DSO channel. non-AP STA 1 (510) can operate on the main channel before receiving the ICF from AP 1. When non-AP STA 1 (510) receives the ICF of AP 1, it can switch the operating channel to the DSO channel and operate. When non-AP STA 1 (510) switches from the main channel to the DSO channel, a DSO padding delay is required, and when switching from the DSO channel to the main channel, a DSO switching delay (time Tt) may be required.

[0206] Here, non-AP STA 1 (510) can operate on the main channel, and AP 1 can transmit an ICF (601) to switch non-AP STA 1 (510) to the DSO channel. The ICF (601) may include a padding field having a time length corresponding to or greater than the DSO padding delay for switching the non-AP STA 1 (510) from the main channel to the DSO channel. The ICF (601) may be transmitted in a Non-HT duplicate PPDU format that is duplicated and transmitted in 20 MHz increments on the main channel and the DSO channel. Additionally, as an example, the ICF may be a trigger frame.

[0207] STA 1 can receive the ICF (601) of AP 1 and switch the operating channel to the DSO channel. Meanwhile, during the DSO padding delay time when non-AP STA 1 (510) switches from the main channel to the DSO channel, non-AP STA 1 (510) may not be able to perform media detection. Not being able to perform media detection may mean that non-AP STA 1 (510) cannot perform frame reception operations and cannot detect the energy of the medium. For example, if the DSO padding delay exceeds the MediumSyncThreshold time length (e.g., 72us), non-AP STA 1 (510) may lose media synchronization during that period. For example, non-AP STA 1 (510) may lose the network allocation vector (NAV) information of the medium (i.e., virtual carrier detection information). Or, non-AP STA 1 (510) may lose physical carrier detection information. Alternatively, non-AP STA 1 (510) may have lost both the media NAV information (i.e., virtual carrier detection information) and the physical carrier detection information. If non-AP STA 1 (510) loses media synchronization, non-AP STA 1 (510) may operate the MediumSyncDelay timer. The aforementioned timer may be a timer for non-AP STA 1 (510) to restore the correct media detection information. The MediumSyncDelay timer is a timer with a value of aPPDUMaxTime, etc., and may expire when the timer becomes 0 or when a normal frame is received (e.g., when at least one MPDU is decoded without error). non-AP STA 1 (510) may perform channel detection operations until the timer expires. non-AP STA 1 (510) may lower the energy threshold of the physical carrier detection while the media detection timer has not expired.That is, non-AP STA 1 (510) can lower the energy level at which it detects the medium as occupied. When non-AP STA 1 (510) performs a channel access operation and the channel access operation is successful, non-AP STA 1 (510) can transmit an ICF (e.g., RTS frame) on the channel. When the energy detected on the channel is above a certain threshold, non-AP STA 1 (510) can detect the medium as occupied, and non-AP STA 1 (510) may continue to perform the channel detection operation. That is, non-AP STA 1 (510) must wait until the medium is switched to an idle state. As another example, the above-described operation may mean repeating the channel access operation of non-AP STA 1 (510) (e.g., selecting a new backoff counter) or pausing the channel access operation (e.g., keeping the backoff counter at 0).

[0208] On the other hand, if non-AP STA 1 (510) successfully receives ICF (601) from AP 1, it can check the end time of ICF (601), and it may be possible to transmit ICR (602) after SIFS time from the time AP 1 completes the transmission of ICF (601). That is, non-AP STA 1 (510) can transmit ICR (602), which is a response frame to ICF (601). At the time when non-AP STA 1 (510) transmits ICR (602) or when non-AP STA 1 (510) transmits ICR (602) and receives a frame from AP 1 (data frame or trigger frame, etc.) transmitted after SIFS, non-AP STA 1 (510) can release the aforementioned MediumSyncDelay timer. Alternatively, if non-AP STA 1 (510) successfully receives ICF (601) from AP 1, non-AP STA 1 (510) can check the end time of ICF (601). After receiving AP 1's ICF (601), non-AP STA 1 (510) can transmit ICR (602) after SIFS time from the time AP 1 completes transmitting ICF (601) without operating the MediumSyncDelay timer.

[0209] As another example, when non-AP STA 1 (510) receives AP 1's ICF (601), it can check the duration field value set by AP 1 in the MAC header of the ICF (601). Thus, non-AP STA 1 (510) can set the NAV (NAV timer) according to the value of the duration field of the ICF (601) transmitted by AP 1 (e.g., the duration field of the MAC header, the TXOP duration field of the PHY preamble, or a field related to the length of the PPDU, etc.) and recognize the NAV information being set. Non-AP STA 1 (510) can prevent the MediumSyncDelay timer from operating even if media detection is impossible for a certain period of time before the NAV expires (i.e., before the NAV timer reaches 0). That is, non-AP STA 1 (510) can recognize NAV information set based on the frame received from AP 1, and even if non-AP STA 1 (510) is unavailable for a certain period of time, the MediumSyncDelay timer may not operate because it can anticipate that the medium is occupied due to the frame transmitted by AP 1. As another example, if AP 1 transmits a frame that can set NAV (e.g., a frame in which a duration field value is set in the MAC header of the frame to set NAV, a CTS-to-Self frame and a (QoS) data frame, etc.) before transmitting ICF (601), there may be NAV set before receiving ICF (601) in non-AP STA 1 (510). non-AP STA 1 (510) receives the ICF (601) of AP 1, and although channel detection is not possible for a certain period of time during the DSO padding delay time, non-AP STA 1 (510) can already know the NAV information set by non-AP STA 1 (510), so the MediumSyncDelay timer may not be operated.

[0210] Meanwhile, the main channel of AP 1 (a channel including the main 20 MHz channel) may also always need to be occupied. AP 1 may allocate resources in the ICF (601) to allow STA 2 to transmit a frame (e.g., ICR) on the main channel. If STA 2 fails to receive AP 1's ICF (601) or if STA 2 detects that the main channel is occupied, STA 2 may not be able to respond to AP 1's ICF (601). In the above case, the ICR (602), which is a response frame to AP 1's ICF (601), may be transmitted on the DSO channel but not on the main channel including the main 20 MHz channel. Consequently, the AP may be unable to transmit a subsequent frame or may need to perform a separate procedure for transmitting a subsequent frame.

[0211] Referring to FIG. 9a, AP 1 may wait for a NAVTimeout time after transmitting the ICF (601) on the main channel and the DSO channel. The NAVTimeout time may be '(2 Х aSIFSTime) + T_PREAMBLE + T_SIGNAL + UL_Length + aRxPHYStartDelay + (2 Х aSlotTime)' time or '(2 Х aSIFSTime) + (2 Х aSlotTime) + UL_Length + aRxPHYStartDelay' time. Here, UL length is the time length indicated in the UL length field of the common info field of the ICF (601), T_PREAMBLE is the time length of the preamble in non-HT PPDU format, and T_SIGNAL is the time length of the signal field in non-HT PPDU format. Meanwhile, UL_Length may be a time length indicated in the UL length field of the common info field of the ICF (601), but it may be a time length that must be calculated (or converted) separately. AP 1 may determine that the ICF transmission has failed if the ICR is not detected within that time. Alternatively, AP 1 may determine that the ICR transmission has failed based on CTSTimeout or AckTimeout. CTSTimeout or AckTimeout is the time 'aSIFSTime+aSlotTime+aRxPHYStartDelay', and if the ICR is not detected within that time, AP 1 may determine that the ICF transmission has failed. The aforementioned NAVTimeout, AckTimeout, and CTSTimeout may be referred to as 'acknowledgment time' in this disclosure, but this is for convenience of explanation only and is not limited to such names.

[0212] AP 1 may detect the ICR (602) of non-AP STA 1 (510) on the DSO channel within the acknowledgment time, but may not detect the ICR of STA 2 on the main channel. AP 1 detecting a frame may mean that AP 1 generates a PHY-RXSTART.indication primitive or a PHY-RXEARLYSIG.indication primitive. Alternatively, it may mean that AP 1 generates at least one primitive as described above and decodes the frame in the MAC to determine whether it is a valid acknowledgment frame. AP 1 may want to switch non-AP STA 1 (510) operating on the DSO channel to the main channel because transmission failed on the main channel (i.e., failure to receive the acknowledgment frame occurred). That is, AP 1 may want to occupy the main channel to perform frame transmission and reception with non-AP STA 1 (510). AP 1 may not perform transmission for a certain period of time or longer after receiving the ICR (601) of non-AP STA 1 (510) on the DSO channel (for a period of time longer than Tw (aSIFSTime + aSIFSTime + aRxPHYStartDelay time) from the time non-AP STA 1 (510) completes receiving the ICR). After non-AP STA 1 (510) transmits the ICR (601) on the DSO channel<Tw 조건 1> or<Tw 조건 3> The Tw time is started by, but since AP 1 does not transmit frames to non-AP STA 1 (510), non-AP STA 1 (510) during the Tw time<Primary 전환> The conditions can be satisfied.

[0213] If AP 1 transmits an ICF (601) as the first frame of a TXOP, the NAV of surrounding STAs set based on AP 1's ICF (601) may be released after the NAVTimeout time from the time AP 1's ICF (601) transmission is completed. Alternatively, if AP 1 transmits a frame other than the ICF (601) in the TXOP (e.g., a frame capable of setting NAV, such as a CTS-to-Self frame or a data frame), the NAV set on surrounding STAs based on the frame transmitted by AP 1 may not be released even after the NAVTimeout time from the time AP 1's ICF (601) transmission is completed. Alternatively, the NAV set based on AP 1's reception of the ICF may not be released.

[0214] non-AP STA 1 (510) after transmitting ICR (602)<Tw 조건 1> or<Tw 조건 3> The Tw time can be started by... Here, non-AP STA 1 (510) during the Tw time<Primary 전환> The condition may be satisfied, which may be because the AP did not perform frame transmission to the DSO channel. Therefore, the non-AP STA 1 (510) may switch the operating channel from the DSO channel to the main channel for a time Tt after the time Tw. The non-AP STA 1 (510) may operate on the main channel again after the time 'Tw + Tt' of the time from the time of completion of the ICR (602) transmission, which may be the time when the operating channel switch to the main channel is completed.

[0215] If the first frame received by non-AP STA 1 (510) from AP 1's TXOP is an ICF (601) and there is no subsequent frame after transmitting an ICR (602), and non-AP STA 1 (510) switches from the DSO channel to the main channel, non-AP STA 1 (510) may consider that there is no NAV set by the STAs that received AP 1's ICF (601) based on the ICF (601) transmitted by AP 1 at the time when the NAVTimeout time has elapsed after receiving the ICF (601). That is, non-AP STA 1 (510) may determine that it has lost NAV information after switching to the main channel, which may mean that non-AP STA 1 (510) has lost media synchronization. Alternatively, non-AP STA 1 (510) may consider that it has lost media synchronization because media detection was impossible for a certain period of time regardless of NAV. non-AP STA 1 (510) may start a MediumSyncDelay timer because it has lost medium synchronization. AP 1 may perform a channel access operation at a point in time after the acknowledgment time. AP 1 may transmit any frame that can release the MediumSyncDelay timer of non-AP STA 1 (510) at or after the time when non-AP STA 1 (510) has completed switching the operating channel from the DSO channel back to the main channel. If the channel access operation of AP 1 ends before the time when non-AP STA 1 (510) has completed switching the operating channel from the DSO channel back to the main channel, AP 1 may repeat the channel access operation.Alternatively, AP 1 may keep the backoff counter of the channel access operation at 0 and transmit any frame (612) that can release the MediumSyncDelay timer of non-AP STA 1 (510) when the channel access operation is successful at or after the time when non-AP STA 1 (510) has completed switching the operating channel from the DSO channel back to the main channel. Alternatively, since the NAV resulting from the transmission of AP 1's ICF (601) has not been released, AP 1 may transmit a frame to non-AP STA 1 (510) at or after the time when non-AP STA 1 (510) has completed switching the operating channel from the DSO channel back to the main channel, instead of performing a separate channel access procedure again. For example, any frame (612) transmitted by AP 1 to non-AP STA 1 (510) may not be limited to a frame that can release the MediumSyncDelay timer of non-AP STA 1 (510). For example, AP 1 can transmit downlink data frames or trigger frames that allocate uplink resources to non-AP STA 1 (510) on the main channel, and frame exchange can be performed on the main channel.

[0216] Alternatively, the first frame received by non-AP STA 1 (510) from AP 1's TXOP may not be an ICF, and the NAV may have been set based on a frame previously transmitted by AP 1. Since there is no subsequent frame after non-AP STA 1 (510) transmits the ICR, the NAV may end or not end at the time non-AP STA 1 (510) switches from the DSO channel to the main channel, and non-AP STA 1 (510) retains the NAV information, so it may not lose media synchronization. Additionally, AP 1 may perform further frame transmissions during the remaining NAV period of AP 1. If AP 1 wants to transmit a frame to a STA other than non-AP STA 1 (510) on the main channel, AP 1 may transmit the frame on the main channel after SIFS time from the time the ICR is received on the DSO channel. Alternatively, if AP 1 wants to transmit a frame to non-AP STA 1 (510) from the main channel, AP 1 can transmit the frame to non-AP STA 1 (510) when non-AP STA 1 (510) is operating back on the main channel.

[0217] Referring to FIG. 9b, AP 1 may wait for a NAVTimeout time after transmitting an ICF (601) on the main channel and DSO channel. The NAVTimeout time is '(2 Х aSIFSTime) + T_PREAMBLE + T_SIGNAL + UL_Length + aRxPHYStartDelay + (2 Х aSlotTime)' time or '(2 Х aSIFSTime) + (2 Х aSlotTime) + UL_Length + aRxPHYStartDelay' time. Here, UL length is the time length indicated in the UL length field of the common info field of the ICF, T_PREAMBLE is the time length of the preamble in non-HT PPDU format, and T_SIGNAL is the time length of the signal field in non-HT PPDU format. Meanwhile, UL_Length is a time length indicated in the UL length field of the common info field of the ICF (601), but it may be a time length that must be calculated (or converted) separately. AP 1 may determine that the ICF transmission has failed if the ICR is not detected within that time. Alternatively, AP 1 may determine that the ICR transmission has failed based on CTSTimeout or AckTimeout. CTSTimeout or AckTimeout is the time 'aSIFSTime+aSlotTime+aRxPHYStartDelay', and if the ICR is not detected within that time, AP 1 may determine that the ICF transmission has failed. The aforementioned NAVTimeout, AckTimeout, and CTSTimeout may be referred to as 'acknowledgment time' in this disclosure, but this is for convenience of explanation only and is not limited to such names.

[0218] AP may detect the ICR (602) of non-AP STA 1 (510) on the DSO channel within the acknowledgment time, but may not detect the ICR of STA 2 on the main channel. If AP 1 detects the ICR (602) on the DSO channel but does not detect the ICR on the main channel during the acknowledgment time, AP 1 may receive the ICR (602) on the DSO channel and retransmit the ICF (613) that occupies the main channel and DSO channel after the SIFS time. The ICF (613) retransmitted by AP 1 may be transmitted within the NAVTimeout described above. That is, the ICF (613) may be transmitted before the surrounding STAs release the NAV set based on the ICF (601) initially transmitted by AP 1. The user info field included in the retransmitted ICF (613) may include resource allocation information (e.g., the association identifier (AID) and resource unit (RU) index of the non-AP STA 1 (510)) that causes the non-AP STA 1 (510) to operate on the main channel again. The RU index may indicate a RU present on the main channel. That is, it may indicate the frequency index or subchannel index of the main channel. Thus, when the non-AP STA 1 (510) receives the retransmitted ICF (613), it may switch the operating channel from the DSO channel to the main channel. For example, AP 1 detecting a frame may mean that the AP generates the PHY-RXSTART.indication primitive or the PHY-RXEARLYSIG.indication primitive. Alternatively, AP 1 detecting a frame may mean that AP 1 generates at least one of the aforementioned primitives and decodes the frame in the MAC to determine whether it is a normal response frame.

[0219] Additionally, the ICF (613) that AP 1 retransmits may include padding fields, similar to the ICF (601) that AP 1 initially transmits. The length of the padding field in the retransmitting ICF (613) may be equal to or longer than the length of the DSO padding delay time of non-AP STA 1 (510), just like the ICF (601) that AP 1 initially transmits. However, the ICF (613) that AP 1 retransmits may be intended to cause the operating channel of non-AP STA 1 (510) to operate back from the DSO channel to the main channel. Here, the DSO padding delay, which is the time for non-AP STA 1 (510) to switch from the main channel to the DSO channel, and the time for non-AP STA 1 (510) to switch from the DSO channel to the main channel may be different. Therefore, the length of the padding field of the retransmitted ICF (613) may be the same as or longer than the length of the DSO switching delay time of the non-AP STA 1 (510), which is different from the ICF (601) that AP 1 initially transmits.

[0220] As another example, if non-AP STA 1 (510) activates an operation mode that requires a separate transition time, such as EMLSR mode, the length of the padding field may be set to be greater than the longest transition time or the sum of the mode transition times of the modes that the STA activates and uses, by comparing the separate transition times (e.g., EMLSR Transition Delay, DPS Transition Delay used by the STA) and the DSO switching delay time lengths.

[0221] non-AP STA 1 (510) may switch the operating channel from the DSO channel back to the main channel while the padding field of the ICF (613) being retransmitted is being transmitted. Afterward, non-AP STA 1 (510) may transmit an ICR, which is a response frame for the ICF, to AP 1 on the main channel after the transmission of the ICF is complete. AP 1 may perform downlink frame exchange (e.g., exchange of a downlink frame and a response frame for the downlink frame) or uplink frame exchange (e.g., exchange of a trigger frame allocating uplink resources to non-AP STA 1 (510), an uplink frame for the trigger frame, and a response frame for the uplink frame). Alternatively, non-AP STA 1 (510) may perform both of the aforementioned downlink frame exchange and uplink frame exchange.

[0222] FIG. 10 is a diagram illustrating a media synchronization method in case of dynamic subchannel operation failure applicable to the present disclosure.

[0223] Referring to FIG. 10, non-AP STA 1 (510) and AP 1 may operate in a wireless LAN. However, this is for convenience of explanation only and is not limited thereto. The non-AP STA 1 (510) and AP 1 may support the DSO operation described above. The DSO operation may be a method that enables efficient use of frequency resources in a wireless LAN network by changing the operating frequency of a STA with a smaller operating bandwidth than that of an AP. For example, the operating bandwidth of non-AP STA 1 (510), non-AP STA 2 (520), non-AP STA 3 (530), and non-AP STA 4 (540) may be 80 MHz, 160 MHz, or other bandwidths. The operating bandwidth of AP 1 may be 320 MHz, which is wider than that of the STAs connected to AP 1. AP 1 may have two DSO channels (or subbands). Each of the two DSO subbands can be configured from two 80MHz channels out of the 320MHz channels. For example, each of the two DSO subbands can be two 80MHz channels from the secondary 160MHz channels out of the 320MHz channels. However, the two DSO subbands described above are merely one example, and the configuration of DSO subbands can be more diverse. Nevertheless, for the convenience of explanation, the following description is based on the case where two DSO subbands are configured.

[0224] AP 1 may transmit an ICF (615-1, 615-2, 615-3) instructing to assign non-AP STA 1 (510) to non-AP STA 3 (530) to each channel (e.g., main channel (or subband), DSO subband 1, DSO subband 2). For example, AP 1 may transmit an ICF (615-1, 615-2, 615-3) instructing to assign non-AP STA 1 (510) to the main subband, assign non-AP STA 2 (520) to DSO subband 1, and assign non-AP STA 3 (530) to DSO subband 2. The padding field of the ICF (615-1, 615-2, 615-3) may be set to a time length greater than or equal to the DSO padding delay of the STA with the longest DSO padding delay among non-AP STA 2 (520) and non-AP STA 3 (530). The non-AP STA 2 (520) may switch its operating channel to DSO subband 2, and the non-AP STA 3 (530) may switch its operating channel to DSO subband 3, so that the ICR (616-2, 616-3) can be transmitted in the DSO subband where each STA operates. Here, the non-AP STA 1 (510) may not be able to transmit the ICR in the main subband. In the above case, AP 1 may need to perform an action to avoid emptying the main subband. That is, AP 1 may need to reoccupy the main channel after transmitting ICR in the main subband before the NAVTimeout time elapses.

[0225] AP 1 receives the ICR (616-2, 616-3) of non-AP STA 2 (520) and non-AP STA 3 (530) and can transmit the ICF (617-1, 617-2) and downlink frame (618) again after the SIFS time. For example, AP 1 can transmit the downlink frame (618) to non-AP STA 3 (530) operating in DSO subband 2, and transmit the ICF (617-1, 617-2) instructing non-AP STA 2 (520) to operate on the main channel again in DSO subband 1 and the main subband, and instructing non-AP STA 4 (540) to operate in DSO subband 1. Here, the length of the padding field of the ICF (617-1, 617-2) may be set to a length greater than or equal to the longest time length between the DSO switching delay time length of the non-AP STA 2 (520) and the DSO padding delay of the non-AP STA 4 (540). The total length of the frame of the ICF (617-1, 617-2) and the total length of the downlink frame (618) transmitted to the non-AP STA 3 (530) may be the same. Additionally, the start and end times of the frame may be the same. The total length of the frame of the ICF (617-1, 617-2) and the PPDU format of the downlink frame (618) transmitted to the non-AP STA 3 (530) may be the same (e.g., non-HT format, etc.). Alternatively, the entire length of the frame of the ICF (617-1, 617-2) and the downlink frame (618) transmitted to the non-AP STA 3 (530) may be transmitted in the DL MU format (e.g., HE, EHT, UHR MU PPDU using the DL OFDMA method), but may not be restricted to the frame format described above.In the above-described case, non-AP STA 2 (520) can operate again on the main channel, non-AP STA 4 (540) can operate on DSO subband 1, and non-AP STA 3 (530) can receive downlink data (618) frames on DSO subband 2. AP 1 may include information in the MAC header of the downlink frame (618) transmitted to non-AP STA 3 (530) that instructs the length of the response frame to be matched. Here, such information may be included in the HT control field. Additionally, such information may be single response scheduling (SRS) information. The length of the response frame indicated by the SRS information may be set to be equal to the length of the ICR (619-1, 619-2) transmitted by non-AP STA 2 (520) and non-AP STA 4 (540) in the main subband and DSO subband.

[0226] Additionally, non-AP STA 3 (530) can transmit a response frame (e.g., BA frame) (620) for a received data frame (618). non-AP STA 3 (530) can adjust the length of the response frame (620) based on the SRS information directed by AP 1. (e.g., padding can be used to extend the length of the response frame.) non-AP STA 2 (520) and non-AP STA 4 (540) can transmit ICR (619-1, 619-2). Frames transmitted by non-AP STA 2 (520), non-AP STA 3 (530), and non-AP STA 4 (540) to AP 1 can be synchronized (e.g., the start time and end time are synchronized). Here, AP 1 can perform uplink frame transmission and downlink frame transmission operations with non-AP STA 2 (520), non-AP STA 3 (530) and non-AP STA 4 (540) in the main subband, DSO subband 1 and DSO subband 2.

[0227] FIG. 11 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies. A first STA may transmit an initial control frame (ICF) (S1110). Here, the ICF may indicate a channel switching operation of at least one STA that performs a dynamic subchannel operation (DSO). Subsequently, the first STA transmits the ICF and receives an initial control response (ICR) from at least one STA (S1120), and the first STA may perform at least one of data transmission and reception with at least one STA. Here, the ICF may indicate that a second STA among the at least one STA operates on the main channel, and that a third STA among the at least one STA operates on the DSO channel. Additionally, when the first STA transmits downlink data to the second STA and the third STA, the first STA can check the amount of downlink data of the second STA and the amount of downlink data of the third STA, and transmit an ICF that assigns the second STA, which has a larger amount of downlink data, to the main channel and assigns the third STA, which has a smaller amount of downlink data, to the DSO channel. When the first STA receives uplink data from the second STA and the third STA, the first STA can check the amount of uplink data of the second STA and the amount of uplink data of the third STA, and transmit an ICF that assigns the second STA, which has a larger amount of uplink data, to the main channel and assigns the third STA, which has a smaller amount of uplink data, to the DSO channel. In addition, the first STA can send a buffer status report request frame to the second STA and the third STA, and receive buffer status report frames from the second STA and the third STA to check the amount of uplink data of the second STA and the amount of uplink data of the third STA.Additionally, the first STA may, after receiving an ICR from at least one STA, transmit a trigger frame for allocating uplink resources to allocate the second STA, which has a larger amount of uplink data, to resources within the main channel, and the third STA, which has a smaller amount of uplink data, to resources within the DSO channel. Additionally, when the first STA transmits a downlink frame in the DSO channel to the third STA, which has a smaller amount of downlink data than the second STA, and receives a response frame for the last downlink frame, the operating channel of the third STA may be switched from the DSO channel to the main channel when the transmission of the response frame is completed; and when the first STA receives an uplink frame in the DSO channel from the third STA, which has a smaller amount of uplink data than the second STA, and transmits a response frame for the last uplink frame, the operating channel of the third STA may be switched from the DSO channel to the main channel when the reception of the response frame is completed. Additionally, the operating mode of the third STA is maintained in Awake mode until the operating channel is switched from the DSO channel to the main channel, and after the operating channel switching is completed and the operating channel of the third STA is switched to the main channel, the operating mode of the third STA is switched to Doze mode, and when the first STA receives a response frame for the last data frame transmitted to the second STA on the main channel or transmits a response frame for the last data frame received from the second STA on the main channel, the operating mode of the third STA may be switched from Doze mode to Awake mode. Additionally, the operating mode of the third STA is maintained in Higher Capability Mode (HCM) on the DSO channel, and after the operating channel switching is completed and the operating channel of the third STA is switched to the main channel, the operating mode of the third STA may be switched from HCM to Lower Capability Mode (LCM) and maintained.Additionally, the third STA operating on the DSO channel switches its operating channel to the main channel when the switching condition is satisfied for a first set time from the first time point, provided that if the switching time for the third STA to switch its operating channel to the main channel exceeds a threshold value, a media synchronization timer may be operated on the third STA at the time it switches to the main channel. Additionally, the first time point may include at least one of the time when the third STA completes transmitting a response frame for a frame received from the first STA, the time when the third STA completes receiving a frame that does not require an immediate response, and the time when the third STA completes transmitting a frame that does not require an immediate response. Additionally, if the third STA does not detect frame reception, does not perform frame transmission, does not have a nonempty transmit queue, and does not schedule frame transmission for a first set time from the first time point, the switching condition is satisfied and the operating channel may be switched from the DSO channel to the main channel. Additionally, the first STA may complete receiving a response frame for a frame transmitted to the third STA and transmit a padding frame on the main channel after the short inter frame space (SIFS), and the first STA may transmit a first frame that releases the media synchronization timer when the third STA completes switching the operating channel to the main channel. Additionally, the first STA may transmit a response frame for a frame received from the third STA, wherein the response frame includes padding corresponding to a first preset time and the switching time when the third STA switches the operating channel from the DSO channel to the main channel, and the first STA may transmit a first frame that releases the media synchronization timer when the third STA completes switching the operating channel to the main channel.In addition, if the first STA fails to receive an ICR from the second STA operating on the main channel and receives an ICR from the third STA operating on the DSO channel, the first STA transmits an ICF and, when the acknowledgment time elapses, performs a channel access operation on the main channel, and the third STA transmits an ICR on the DSO channel and, if the switching condition is satisfied for a first preset time, the operating channel is switched to the main channel, but if the switching time for the third STA to switch the operating channel to the main channel exceeds a threshold value, a media synchronization timer may be operated on the third STA at the time of switching to the main channel. In addition, the first STA may transmit a first frame that releases the media synchronization timer when the third STA completes the switching of the operating channel to the main channel. Additionally, if the first STA fails to receive an ICR from the second STA operating on the main channel and receives an ICR from the third STA operating on the DSO channel, the first STA transmits an ICF, and when the acknowledgment time elapses, it retransmits an ICF that switches the third STA to the main channel, and the operating channel of the third STA can be switched from the DSO channel to the main channel based on the ICF. Additionally, the retransmitted ICF may include padding corresponding to the switching time when the operating channel of the third STA is switched from the DSO channel to the main channel. Additionally, at least one of the first STA, the second STA, and the third STA may be a non-AP STA or an AP STA.

[0228] Additionally, as an example, the first STA may transmit an initial control frame (ICF). Here, the ICF may direct the channel switching operation of at least one STA performing a dynamic subchannel operation (DSO) and the allocation of transmission resources on the main channel and the DSO channel. Subsequently, the first STA may transmit the ICF and receive an initial control response (ICR), which is a response frame to the ICF, from at least one STA. Here, if the ICR is received through the DSO channel but not through the main channel, the first STA may perform at least one of data transmission and reception on the DSO channel with at least one STA only while the main channel occupancy is maintained.

[0229] 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.

[0230]

[0231] 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 transmits an initial control frame (ICF), wherein the ICF directs a channel switching operation of at least one STA performing a dynamic subchannel operation (DSO); The first STA transmits the ICF and receives an initial control response (ICR) from at least one STA; and A method of operation comprising the step of the first STA performing at least one of data transmission and reception with the at least one STA, wherein the ICF indicates that the second STA among the at least one STA operates on a main channel and that the third STA among the at least one STA operates on a DSO channel.

2. In Paragraph 1, A method of operation in which, when the first STA transmits downlink data to the second STA and the third STA, the first STA checks the amount of downlink data of the second STA and the amount of downlink data of the third STA, assigns the second STA with a larger amount of downlink data to the main channel, and assigns the third STA with a smaller amount of downlink data to the DSO channel, and transmits the ICF.

3. In Paragraph 1, A method of operation in which, when the first STA receives uplink data from the second STA and the third STA, the first STA checks the amount of uplink data of the second STA and the amount of uplink data of the third STA, assigns the second STA with a larger amount of uplink data to the main channel, and assigns the third STA with a smaller amount of uplink data to the DSO channel, and transmits the ICF.

4. In Paragraph 3, A method of operation in which the first STA transmits a buffer status report request frame to the second STA and the third STA, and receives a buffer status report frame from the second STA and the third STA to check the amount of uplink data of the second STA and the amount of uplink data of the third STA.

5. In Paragraph 4, A method of operation in which the first STA receives the ICR from the at least one STA and then transmits a trigger frame for allocating uplink resources to allocate the second STA, which has a larger amount of uplink data, to a resource within the main channel, and allocate the third STA, which has a smaller amount of uplink data, to a resource within the DSO channel.

6. In Paragraph 1, When the first STA transmits a downlink frame on the DSO channel to the third STA, which has less downlink data than the second STA, and receives a response frame for the last downlink frame, the operating channel of the third STA switches from the DSO channel to the main channel at the time when the transmission of the response frame is completed, and When the first STA receives an uplink frame on the DSO channel from the third STA, which has less uplink data than the second STA, and transmits a response frame for the last uplink frame, the operating channel of the third STA is switched from the DSO channel to the main channel at the time when the reception of the response frame is completed, and the method of operation.

7. In Paragraph 6, Until the operation channel is switched from the DSO channel to the main channel, the operation mode of the third STA is maintained in Awake mode, and after the operation channel switching is completed and the operation channel of the third STA is switched to the main channel, the operation mode of the third STA is switched to Dose mode, and A method of operation in which, when the first STA receives a response frame for the last data frame transmitted to the second STA on the main channel or transmits a response frame for the last data frame received from the second STA on the main channel, the operation mode of the third STA is switched from the doze mode to the awake mode.

8. In Paragraph 6, A method of operation in which the operating mode of the third STA in the above DSO channel is maintained as a higher capability mode (HCM), and after the operating channel switching is completed and the operating channel of the third STA is switched to the main channel, the operating mode of the third STA is switched from HCM to a lower capability mode (LCM) and maintained.

9. In Paragraph 1, A method of operation in which the third STA operating on the DSO channel switches its operating channel to the main channel when a switching condition is satisfied for a first set time from a first point in time, wherein if the switching time for the third STA to switch its operating channel to the main channel exceeds a threshold value, a media synchronization timer is operated on the third STA at the time it switches to the main channel.

10. In Paragraph 9, A method of operation comprising at least one of the following: the first time point, which includes the time point when the third STA completes transmitting a response frame for a frame received from the first STA, the time point when the third STA completes receiving a frame that does not require an immediate response, and the time point when the third STA completes transmitting a frame that does not require an immediate response.

11. In Paragraph 10, A method of operation in which the third STA does not detect frame reception, does not perform frame transmission, does not have a nonempty transmit queue, and does not schedule frame transmission, thereby satisfying the switching condition and switching the operating channel from the DSO channel to the main channel.

12. In Paragraph 10, A method of operation in which the first STA completes receiving a response frame for a frame transmitted to the third STA and transmits a padding frame on the main channel after the short inter frame space (SIFS), and the first STA transmits a first frame that releases the media synchronization timer when the third STA completes switching the operating channel to the main channel.

13. In Paragraph 10, A method of operation in which the first STA transmits a response frame for a frame received from the third STA, wherein the response frame includes padding corresponding to the first preset time and the transition time when the third STA switches the operating channel from the DSO channel to the main channel, and the first STA transmits a first frame that releases the media synchronization timer when the third STA completes the operation channel transition to the main channel.

14. In Paragraph 1, A method of operation in which, if the first STA fails to receive the ICR from the second STA operating on the main channel and receives the ICR from the third STA operating on the DSO channel, the first STA transmits the ICF and, when the acknowledgment time elapses, performs a channel access operation on the main channel, wherein the third STA transmits the ICR on the DSO channel and, when a switching condition is satisfied for a first preset time, the operating channel is switched to the main channel, and if the switching time for the third STA to switch the operating channel to the main channel exceeds a threshold value, a media synchronization timer is operated on the third STA at the time of switching to the main channel.

15. In Paragraph 14, A method of operation in which the first STA transmits a first frame that releases the media synchronization timer when the third STA completes the operation channel switching to the main channel.

16. In Paragraph 1, A method of operation in which, if the first STA fails to receive the ICR from the second STA operating on the main channel and receives the ICR from the third STA operating on the DSO channel, the first STA transmits the ICF and, when the acknowledgment time elapses, retransmits the ICF to switch the third STA to the main channel, and the operating channel of the third STA is switched from the DSO channel to the main channel based on the ICF.

17. In Paragraph 16, A method of operation in which the retransmitted ICF includes padding corresponding to the transition time when the operating channel of the third STA switches from the DSO channel to the main channel.

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

19. 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: Transmit an initial control frame (ICF), wherein the ICF instructs the channel switching operation of at least one STA performing a dynamic subchannel operation (DSO), and Transmitting the above ICF and receiving an initial control response (ICR) from at least one STA, and The first STA performs at least one of data transmission and reception with the at least one STA, wherein the ICF indicates that the second STA among the at least one STA operates on the main channel and that the third STA among the at least one STA operates on the DSO channel.

20. A method of operation of a first station (station, STA) in a wireless LAN system, A step in which the first STA transmits an initial control frame (ICF), wherein the ICF directs the channel switching operation of at least one STA performing a dynamic subchannel operation (DSO) and the allocation of transmission resources in the main channel and the DSO channel; The first STA transmits the ICF and receives an initial control response (ICR), which is a response frame for the ICF, from at least one STA; and A method of operation comprising the step of performing at least one of data transmission and reception on the at least one STA and the DSO channel only when the first STA maintains the occupation of the main channel, when the above ICR is received through the DSO channel and not through the main channel.

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