Method and apparatus for performing priority transmission using subchannel access in wireless LAN

Abstract

The operation method of an STA in a wireless LAN system may comprise the steps of: transmitting a first frame related to priority transmission after a first predetermined time from a time point at which a medium switches from an occupied state to an idle state; performing a random backoff procedure after the transmission of the first frame is completed; and occupying the medium on the basis of the random backoff procedure and transmitting a second frame related to first type traffic.

Description

Method and device for performing priority transmission using side-channel access in wireless LAN

[0001] The present disclosure relates to a method and apparatus for performing priority transmission using side-channel access to perform low-latency communication in a wireless local area network (WLAN) when the main channel is occupied by another wireless LAN terminal.

[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 called TXOPs (transmit opportunities) between access points (APs). Furthermore, to increase the efficiency of communication resource utilization, the wireless LAN standard can support non-primary channel access (NPCA) operations, which use a channel other than the primary channel when the primary channel is occupied, and dynamic subchannel operation (DSO). The following describes a method for performing priority transmission using side-channel access in a wireless LAN as described above.

[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 priority transmission using sub-channel access in a wireless LAN.

[0009] The present disclosure relates to a method and apparatus for performing priority transmission using sub-channel access due to channel occupation by another wireless LAN terminal in a wireless LAN.

[0010] The present disclosure relates to a method and apparatus for performing priority transmission for low latency (LL) traffic using a side-channel access method to improve channel efficiency and latency performance when the total bandwidth of a channel occupied by a non-AP STA is narrower than the operating bandwidth of an access point (AP) and the side-channel is idle.

[0011] 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.

[0012]

[0013] According to one embodiment of the present specification, a method of operation of a station (STA) in a wireless LAN system may include the steps of: transmitting a first frame related to priority transmission after a first predetermined time from the point in time when the medium is switched from an occupied state to an idle state; performing a random backoff procedure after the transmission of the first frame is completed; and occupying the medium based on the random backoff procedure and transmitting a second frame related to a first type of traffic.

[0014] According to one embodiment of the present specification, a station (STA) in a wireless LAN system comprises at least one transceiver for transmitting and receiving signals, at least one processor for controlling at least one transceiver, and a memory for storing instructions that cause the STA to perform a specific operation by the at least one processor, wherein the specific operation is: transmitting a first frame related to priority transmission after a first predetermined time from the point in time when the medium is switched from an occupied state to an idle state, performing a random backoff procedure after the transmission of the first frame is completed, and, based on the random backoff procedure, occupying the medium to transmit a second frame related to a first type of traffic.

[0015] In addition, the following points may apply in common.

[0016] According to one embodiment of the present specification, the random backoff procedure may be a random backoff procedure in which STAs associated with a first type of traffic transmission transmitting a first frame participate.

[0017] Additionally, according to one embodiment of the present specification, the first frame may be transmitted at the slot boundary at the time when the medium is in an idle state for a first predetermined time from the time when the medium switches from an occupied state to an idle state.

[0018] Additionally, according to one embodiment of the present specification, the STA performs channel sensing in a plurality of 20 MHz channels including a main 20 MHz channel within the STA's bandwidth for a second preset time before transmitting the first frame, and according to the channel sensing result, transmits the first frame through at least one channel including an idle main 20 MHz channel among the plurality of 20 MHz channels including a main 20 MHz channel.

[0019] Additionally, according to one embodiment of the present specification, the STA may duplicate and transmit the first frame in 20 MHz increments on at least one channel including an idle main 20 MHz channel.

[0020] In addition, according to one embodiment of the present specification, the STA can transmit the first frame on a main 20 MHz channel.

[0021] Additionally, according to one embodiment of the present specification, the STA can confirm that the medium is idle for a second set time in the main 20 MHz channel after the first frame transmission is completed, and can transmit a third frame by occupying the medium based on a backoff counter at the slot boundary at the time when the medium is idle.

[0022] Additionally, according to one embodiment of the present specification, the STA may perform channel sensing on a plurality of 20 MHz channels including a main 20 MHz channel within the STA's bandwidth for a third preset time before occupying the medium to transmit the third frame, and transmit the third frame through at least one channel including an idle main 20 MHz channel among the plurality of 20 MHz channels including a main 20 MHz channel according to the channel sensing result.

[0023] Additionally, according to one embodiment of the present specification, the third frame is an RTS (request to send) frame, and after transmitting the RTS frame and receiving a CTS (clear to send) frame, a second frame associated with the first type of traffic can be transmitted.

[0024] Additionally, according to one embodiment of the present specification, the first frame may be a CTS (clear to send) frame in which the recipient address is a specific address.

[0025] Additionally, according to one embodiment of the present specification, the first type of traffic may be low-latency traffic.

[0026] In addition, according to one embodiment of the present specification, low-latency traffic may be traffic corresponding to a VO (voice) of a channel access category (AC).

[0027] Additionally, according to one embodiment of the present specification, the first frame may be a preemption request (PR) frame.

[0028] Additionally, according to one embodiment of the present specification, the STA transmits a first frame and receives a third frame instructing the transmission of a first type of traffic associated with priority transmission, wherein the third frame may be a frame transmitted by the AP to at least one STA in the basic service set (BSS).

[0029] Additionally, according to one embodiment of the present specification, the STA can transmit a fourth frame indicating that first type traffic exists in response to a third frame, receive a resource from the AP via a fifth frame based on the fourth frame, and transmit a second frame related to the first type traffic through the allocated resource.

[0030] Additionally, according to one embodiment of the present specification, the STA is allocated a random access resource based on a third frame and can transmit a second frame associated with a first type of traffic on a channel occupied based on channel contention.

[0031] Additionally, according to one embodiment of the present specification, the STA may be a non-AP STA or an AP STA.

[0032]

[0033] According to the present disclosure, a method for performing priority transmission using side-channel access in a wireless LAN can be provided.

[0034] According to the present disclosure, a method for performing priority transmission using sub-channel access by channel occupation by another wireless LAN terminal in a wireless LAN can be provided.

[0035] According to the present disclosure, a method can be provided to perform priority transmission for low latency (LL) traffic using a side-channel access method to improve channel efficiency and latency performance when the total bandwidth of the channel occupied by the non-AP STA is narrower than the operating bandwidth of the AP and the side-channel is idle.

[0036] 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.

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

[0038]

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

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

[0041] FIGS. 3a to 3c are drawings illustrating an EDCA backoff procedure in a priority transmission method using wireless LAN side-channel access applicable to the present disclosure.

[0042] FIGS. 4a and FIGS. 4b are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0043] FIGS. 5A and 5B are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0044] FIGS. 6a and 6b are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0045] FIG. 7 is a diagram illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0046] FIGS. 8a to 8f are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0047] FIGS. 9a and 9b are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0048] FIGS. 10a to 10c are diagrams illustrating a situation in which a subchannel is occupied during a priority transmission method using wireless LAN subchannel access.

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

[0050]

[0051] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0052] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0053] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0054] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0055] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0056] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present disclosure, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0057] Below, a wireless communication system to which embodiments according to the present disclosure are applied will be described. The wireless communication system to which embodiments according to the present disclosure are applied is not limited to the details described below, and embodiments according to the present disclosure may be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network."

[0058] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies. Referring to FIG. 1, the communication node (100) may include at least one of a processor (110), memory (120), a transceiver (130), an input / output interface (140), a storage device (150), and a bus (160). For example, the communication node (100) may be an access point (AP), a station (STA), an access point multi-link device (MLD), or a non-AP MLD. However, the communication node may not be limited thereto and may be a node that performs communication with another node or device based on the configuration described above. For example, the operating channel bandwidth supported by the AP may be 20 MHz (megahertz), 80 MHz, 160 MHz, etc. The operating channel bandwidth supported by the station may be 20 MHz, 80 MHz, etc. However, it may not be limited thereto.

[0059] A processor (110) within a communication node (100) can control at least one of a memory (120), a transceiver (130), an input / output interface (140), and a storage device (150) for each component within the communication node. The memory (120) within the communication node (100) can store information regarding commands and instructions executed by the processor (110), and the transceiver (130) may refer to a transceiver, an RF (radio frequency) unit, an RF module, or other components that perform signal transmission and reception. The input / output interface (140) within the communication node (100) is an interface for input and output that can be linked with other interfaces and may further include a separate storage device (150). Each component within the communication node (100) can communicate with one another by being connected by a bus (160).

[0060] However, as an example, each component included in the communication node (100) may be connected via an individual interface or an individual bus centered on the processor (110), rather than via a common bus (160). The processor (1110) may also be connected via a dedicated interface to at least one of the memory (120), the transmission / reception device (130), the input / output interface device (140), and the storage device (150).

[0061] A processor (110) can execute a program command stored in at least one of a memory (120) or a storage device (150). The processor (110) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present disclosure are performed. Each of the memory (120) and the storage device (150) may be composed of at least one of a volatile storage medium or a non-volatile storage medium. e.g., the memory (120) may be composed of at least one of read-only memory (ROM) or random access memory (RAM).

[0062] In the following, the relevant operations are described based on the wireless LAN terminal as a station (STA). In accordance with the terminology usage according to IEEE 802.11, STA can refer to both AP STAs operating as access points (APs) and non-AP STAs operating in connection with an AP. However, for the convenience of explanation, APs and non-AP STAs are distinguished below; this distinction is merely for convenience of explanation, and it is self-evident that operations regarding an AP can be applied to both AP STAs and non-AP STAs. Furthermore, it is self-evident that the non-AP STA operations described below can also be applied to both non-AP STAs and AP STAs.

[0063] FIG. 2 is a diagram illustrating a wireless LAN system to which the present disclosure applies. Referring to FIG. 2, the basic service set (BSS) of the wireless LAN system may include one AP (210) and a plurality of non-AP STAs (221, 222, 223, 224), and the plurality of non-AP STAs (221, 222, 223, 224) may be controlled by the AP (210). However, the wireless LAN system is not limited to a BSS, and an environment consisting only of non-AP STAs without a fixed service set or AP may also be considered, and is not limited to a specific form. Each wireless device within the wireless LAN system may include a MAC (medium access control) layer and a physical (PHY) layer, and communication between wireless devices may be performed. For convenience of explanation, the following description focuses on the AP and non-AP STA, but is not limited thereto. For example, the following items may apply equally to other communication nodes or devices and are not limited to a specific form.

[0064] In the following, we describe the preemption operation to support low-latency (LL) traffic transmission in consideration of latency performance. In a wireless LAN network, a non-AP STA, acting as a single wireless LAN terminal, can occupy the wireless LAN main channel by performing an enhanced distributed channel access (EDCA) operation, thereby acquiring a transmit opportunity (TXOP). Here, the non-AP STA occupying the main channel may be a TXOP holder. The total bandwidth of the channel occupied by the TXOP holder may be narrower than the total bandwidth in which the AP connected to the non-AP STA, currently the TXOP holder, operates. Therefore, bandwidth other than the bandwidth including the main channel occupied by the non-AP STA as the TXOP holder (i.e., the sub-channel) may be unused and wasted. Here, a non-AP STA as a TXOP holder can support a priority transmission method for transmitting low-latency (LL) traffic to another non-AP STA or AP from the TXOP it has acquired.

[0065] Here, a non-AP STA acting as a TXOP holder can notify other non-AP STAs or APs that it is a TXOP capable of transmitting a preemption request (PR) within a defined time interval during its frame exchange process. However, the preemption transmission method can only be performed using the channels occupied by the non-AP STA acting as the TXOP holder, including the main channel. Therefore, when preemption transmission is performed, the transmission of the non-AP STA acting as the TXOP holder may be interrupted, and high latency may be experienced. Considering the above, a method for performing preemption transmission using sub-channel access in a wireless LAN is described below.

[0066] According to the present disclosure, when an AP receives a preemption allowed TXOP indicator, it can perform an EDCA random backoff procedure on a wireless LAN subchannel. A non-AP STA can obtain a priority transmission opportunity by transmitting a PR to the AP if there is low-latency traffic requiring priority transmission. When the AP receives a PR transmitted by a non-AP STA, the AP can transmit a trigger frame (TF) containing the subchannel through an EDCA backoff procedure to allocate at least one of a designated resource unit (RU) and a random access-resource unit (RA-RU) to STAs requiring priority transmission. Accordingly, a non-AP STA with low-latency traffic requiring priority transmission can perform priority transmission using a wireless LAN subchannel, and the channel efficiency and effective throughput of the network can be increased. Specific methods for this are described below.

[0067] Access points (APs) constituting a basic service set (BSS) and wireless LAN terminals (non-AP stations, non-AP STAs) connected to the AP (e.g., non-AP STA 1, non-AP STA 2, non-AP STA 3, non-AP STA x) can perform communication. For example, non-AP STA 1 may be a non-AP STA that performs communication using only a bandwidth (or channel) narrower than the maximum operating bandwidth of the AP. non-AP STA 1 may access the channel through an enhanced distributed channel access (EDCA) operation on a primary 20 MHz channel. Specifically, the EDCA operation may be a channel access operation performed by an EDCA function (EDCA function) within the non-AP STA. As another example, the EDCA operation may be an operation performed by the non-AP STA itself, but is not limited to the above.

[0068] A non-AP STA 1 can perform a Clear Channel Assessment (CCA) operation on the main 20 MHz channel. CCA can be an operation to determine whether the channel is idle or busy (i.e., an operation to check the channel's occupancy). CCA can be divided into Energy Detection (ED), which detects energy above a certain level, and Packet Detection (PD), which detects a valid PHY preamble. As another example, Carrier Sensing (CS) can be performed as an operation to check the channel's occupancy. CS can be a Physical CS that detects carriers transmitted on the channel. Here, Physical CS can refer to the channel occupancy status indicated by CCA. Additionally, CS can be a Virtual CS that verifies the Network Allocation Vector (NAV) established through a successful frame exchange.

[0069] non-AP STA 1 may perform at least one of CCA and CS for a length of inter-frame space (IFS) (e.g., AIFS (Arbitration IFS), etc.) determined by the type of channel access category (e.g., a frame with access category (AC) of VO, VI, BE, or BK) of the frame to be transmitted. If the channel is idle as a result of non-AP STA 1 performing at least one of CCA and CS according to the frame type, non-AP STA 1 may perform a random backoff procedure. The random backoff procedure may be a procedure to reduce the probability of collision between wireless LAN terminals. The non-AP STA 1 (or EDCAF) initiating the random backoff procedure may randomly select a backoff counter (BC) within a contention window (CW) determined by the type of AC of the frame to be transmitted. The backoff counter value selected by non-AP STA 1 may be the number of slots (e.g., 9 μs) in which non-AP STA 1 must perform at least one of CCA and CS. non-AP STA 1 may perform at least one of CCA and CS according to a random backoff procedure in slots equal to the selected backoff counter value. If, as a result of non-AP STA 1 performing at least one of CCA and CS in a slot, the channel is idle, non-AP STA 1 may decrease the backoff counter by one. If, when the backoff counter becomes 0, the result of performing at least one of CCA and CS performed by non-AP STA 1 indicates that the channel is idle, non-AP STA 1 (or EDCAF) may acquire a TXOP (transmit opportunity) and perform frame transmission within the TXOP acquired by non-AP STA 1.For example, if the result of performing at least one of the CCA and CS according to the random backoff procedure indicates that the channel is busy, non-AP STA 1 may keep the backoff counter at its current value and use it for the next random backoff procedure. Additionally, non-AP STA 1 may stop accessing the channel until the result of performing at least one of the CCA and CS indicates that the channel is idle.

[0070] non-AP STA 1 can perform the aforementioned EDCA operation to access the main 20 MHz channel. If the result of the EDCA operation performed on the main 20 MHz channel is ultimately a channel idle state, non-AP STA 1 can perform frame transmission using the channel (or bandwidth) including the main 20 MHz channel. Here, the frame initially transmitted by non-AP STA 1 may be an initial control frame (ICF). The ICF transmitted by non-AP STA 1 may be an RTS (request to send) frame or a MU (multi-user)-RTS frame. non-AP STA 1 can obtain a TXOP (transmit opportunity) by transmitting the ICF to the AP.

[0071] Here, non-AP STA 1 may support low-latency (LL) traffic transmission, and preemption operations may be performed as a method to support LL traffic transmission. For example, at least one of the PHY preamble (e.g., UHR-SIG, etc.) and MAC header (e.g., user info field, etc.) of the ICF initially transmitted by non-AP STA 1 may include an indicator (e.g., preemption allowed TXOP indicator) indicating that the TXOP acquired by non-AP STA 1 is a TXOP for which a preemption request is possible (e.g., preemption allowed TXOP). Preemption may be a method in which a wireless LAN terminal with low-latency traffic data reserves a channel (or medium) by transmitting an instruction frame indicating that it will perform low-latency transmission, and performs a low-latency transmission procedure after transmitting the instruction frame.

[0072] As a specific example, preemption may be a method in which a wireless LAN terminal with low-latency traffic data within a TXOP acquired by a non-AP STA 1 transmits a directive frame instructing the wireless LAN terminal to perform low-latency transmission, thereby reserving a channel (or medium) and performing a low-latency frame transmission procedure. Here, the ICF may include a duration indicating the time of the entire TXOP. Additionally, the ICF may include a preemption-allowed TXOP indicator, and other wireless LAN terminals (e.g., AP, STA other than non-AP STA 1) that receive the ICF containing the preemption-allowed TXOP indicator can recognize that the TXOP acquired by STA 1 is a preemption-allowed TXOP. Furthermore, the length of the TXOP acquired by the wireless LAN terminal can also be recognized through the duration included in the ICF.

[0073] For example, non-AP STA 1 can divide the total traffic to be transmitted to the AP into multiple data frames to support pre-amplification by other wireless LAN terminals. The data frames transmitted by non-AP STA 1 can be transmitted at intervals equal to XIFS (e.g., Priority IFS (PIFS)), which is a time length that provides other wireless LAN terminals with an opportunity to transmit PRs. Wireless LAN terminals that need to transmit other low-latency traffic can initiate the priority transmission procedure by transmitting a PR after the SIFS time following the transmission of non-AP STA 1's data frames. Here, the SIFS time may be shorter than the XIFS time.

[0074] Preemption may refer to a series of procedures for securing a channel (or medium) and performing transmission by transmitting an instruction frame that instructs the reserving of a channel (or medium) and the execution of a rapid transmission procedure to transmit low-latency traffic. PR is an instruction frame for reserving a channel (or medium) to initiate LL (low-latency) traffic transmission procedures (e.g., preemption transmission, prioritized EDCA, etc.), and may be a CTS frame (e.g., a CTS-to-Self frame where the frame's receiver address (RA) is itself, or a CTS frame where the receiver address is a specific address). Since CTS frames have the same structure, wireless LAN terminals intending to transmit low-latency traffic can simultaneously transmit CTS frames at the same time to reserve a channel (or medium) for low-latency transmission.

[0075] Additionally, if the TXOP acquired by non-AP STA 1 is a pre-amplified TXOP, the AP may use non-primary channel access (NPCA) to occupy a non-channel not occupied by non-AP STA 1. If the main 20 MHz channel is occupied, the AP may designate (or configure) a channel to perform a channel access operation on a channel other than the occupied channel, and such channel may be referred to as a non-channel (e.g., NPCA primary channel), but is not limited to that name. For example, if a wireless LAN terminal successfully performs a channel access operation on a non-channel (e.g., a random backoff procedure of an EDCA operation), the wireless LAN terminal may occupy channels including the non-channel to communicate. As described above, the operation of transmitting data on channels including the non-channel based on NPCA may be an NPCA operation, but is not limited to that name.

[0076] For example, an NPCA operation may be performed to transmit low-latency traffic using bandwidth not occupied by other wireless LAN terminals within the maximum bandwidth available to the wireless LAN terminal. When performing an NPCA as described above, channel access may be performed on the channel that transmitted the instruction frame described above. The AP may transmit a trigger frame (TF) using the subchannel occupied by performing an NPCA operation to enable non-AP STAs connected to the AP (e.g., non-AP STA 2, non-AP STA 3, non-AP STA X (340), etc.) to transmit data to the AP. When using a subchannel access method intended to maximize bandwidth usage, the TF may be transmitted including the channel that performed the channel access after performing channel access on the channel that transmitted the instruction frame. For example, TF may be at least one of a basic TF frame, an uplink OFDMA (orthogonal frequency division multiple access) random access (UORA) TF frame, a BSRP (buffer status report poll) frame, an NFRP (non-data PPDU (PHY packet data Unit) (NDP) feedback report poll) frame, and other frames, and is not limited to a specific form.

[0077] For example, a non-AP STA transmitting low-latency traffic may be a non-AP STA capable of using the entire bandwidth supported by the AP, including side channels. A non-AP STA that receives a TF transmitted by the AP using a side channel may transmit a response frame using the resource unit (RU) allocated to it. Alternatively, the non-AP STA may transmit a response frame (e.g., a buffer status report (BSR) frame, an NDP feedback report (NFR) frame, or an uplink data frame) after performing channel access contention within the RU designated to use the UORA method. The operations described above may be applied identically to the following Figures 3a through 10c, and some operations may differ depending on the detailed operations of each figure, but they may be applied identically and are not limited to a specific form. However, regarding matters that can be applied commonly, the matters described above may be applied mutatis mutandis.

[0078] FIGS. 3a to 3c are drawings illustrating an EDCA backoff procedure in a priority transmission method using wireless LAN side-channel access applicable to the present disclosure.

[0079] When the AP (310) performs an NPCA operation, the timing of the start of the channel access operation of the AP (310) on the subchannel may vary. Referring to FIG. 3a, the AP (310) can successfully decode the ICF (401) transmitted by the non-AP STA 1 (320) (e.g., if it is a normally received frame as a result of checking at least one of the FCS field in the MAC header and the Intermediate FCS field in the user info field in the MAC header, etc.). Here, the ICF (401) transmitted by the non-AP STA 1 (320) may contain a preemption allowed TXOP indicator. The AP (310) can receive the ICF (401) containing the preemption allowed TXOP indicator and start a channel access operation on the subchannel.

[0080] As another example, AP (310) may start a channel access operation on a subchannel simultaneously with transmitting an initial control response frame (ICR, 402) as a response frame to the ICF (401) transmitted by non-AP STA 1 (320). Alternatively, AP (310) may start a channel access operation on a subchannel at the time when the transmission of the ICR (402) transmitted by AP (310) ends. Alternatively, AP (310) may start a channel access operation on a subchannel at the time when the ICF (401) and ICR (402) are exchanged and the data frame (403) transmitted by non-AP STA 1 (320) is successfully decoded. Alternatively, AP (310) may start a channel access operation on a subchannel at the time when the reception of the data frame (403) transmitted by non-AP STA 1 (320) ends. Alternatively, a channel access operation on the subchannel may be initiated when a preemption request (PR) frame transmitted by a non-AP STA other than non-AP STA 1 (320) (e.g., non-AP STA X (340), etc.) is successfully decoded. The PR is a directive frame to initiate an LL traffic transmission procedure (e.g., preemption transmission, prioritized EDCA, etc.) and may be a CTS frame (e.g., a CTS-to-Self frame in which the frame's receiver address (RA) is itself, or a CTS frame in which the receiver address is a specific address). Alternatively, if the AP (310) transmits a frame for a preemption request (e.g., a BSRP frame, 404) to a non-AP STA other than non-AP STA 1 (320), a channel access operation on the subchannel may be initiated simultaneously with the transmission of the frame. Or, AP (310) may send a frame for a pre-amplification request to a non-AP STA other than non-AP STA 1 (320) (e.g.After transmitting a BSRP frame (404), a channel access operation can be initiated on the subchannel at the time when the response frame (e.g., BSR frame, 405) transmitted by the counterpart non-AP STA (e.g., non-AP STA 2) is successfully decoded.

[0081] Here, the point at which a channel access operation is performed on the subchannel may be the point at which it is determined that a frame to be transmitted has been entered into the transmission queue. When a channel access operation is performed on the subchannel, the backoff counter used for the subchannel channel access operation may be used independently of the backoff counter used on the main channel (e.g., the main 20 MHz channel or the channel (or bandwidth) containing the main 20 MHz channel). That is, the backoff counter of the main channel and the backoff counter of the subchannel may be used separately. In addition, EDCA parameters such as CWmin, CWmax, QSRC (QoS short retry count), QLRC (QoS long retry count), and other parameters used when reselecting backoff counter values ​​may also be operated independently on the main channel and the subchannel, and may be individually indicated via beacon frames. For example, since an increase in the channel access probability of the subchannel may increase the impact on OBSS, the EDCA parameters of the subchannel may be operated in a manner that depends on some EDCA parameters of the main channel. Specifically, when successful channel access is performed on the subchannel and the CW value is reset, the CW value may be set to the larger of the CW value of the main channel's current state and the CWmin value of the subchannel. As another example, channel access by other non-AP STAs other than the AP (310) may not be allowed on the subchannel. Therefore, the EDCA parameters of the subchannel are not separately indicated via beacons, etc., and the AP (310) may set the CWmin of the subchannel based on the current CW value of the main channel, but is not limited to such embodiments.

[0082] As another example, if the AP (310) can constantly check the channel occupancy / idle status of the subchannel, the AP (310) may perform channel access operations on the subchannel at all times regardless of the ICF and ICR. Here, the channel synchronization of the subchannel may be lost due to internal terminal interference caused by transmission including adjacent channels of the subchannel. In the above case, the AP (310) may apply a timer (e.g., MediumSyncDelay, NAVSyncDelay timer) and resume channel access operations when the timer expires. The AP (310) may perform channel access operations on the subchannel by considering one or more of the start times of the random backoff procedure described above. When the backoff counter becomes 0 as a result of the channel access operation, the AP (310) may transmit TF.

[0083] Referring to FIG. 3a, AP (310) may transmit a PR to non-AP STA 2 (330) to reserve a medium. For example, the PR (Priority Transmission Instruction Frame) may be a BSRP frame (404). When there is a possibility that AP (310) will transmit a PR (e.g., when there is scheduled UL LL traffic on a non-AP STA other than non-AP STA 1 (320), etc.), AP (310) may instruct non-AP STAs in the BSS to provide information indicating at least one of the time and length of time at which AP (310) will transmit a PR in order to protect the transmission of AP (310)'s BSRP frame (404). For example, AP (310) may transmit including an indicator within a beacon that indicates the possibility of AP (310)'s PR until the next beacon transmission. As another example, the AP (310) may transmit a (re)association response frame or a probe response frame containing an indicator indicating the possibility of the AP (310) transmitting a PR. Through the above, the AP (310) in the BSS may recognize at least one of the information regarding the time and duration at which the AP (310) is likely to transmit a PR. Here, if the ICF (401) initially transmitted by the non-AP STA that acquired the TXOP contains a pre-amplification allowance TXOP indicator, the ICF (401) initially transmitted may contain an indicator prohibiting the transmission of PR by non-AP STAs other than the AP (310). If a non-AP STA other than non-AP STA 1 (320) identifies an indicator prohibiting non-AP STAs other than AP (310) from transmitting PR within the ICF (401) transmitted by non-AP STA 1 (320), the other non-AP STA may not transmit PR within the TXOP obtained by non-AP STA 1 (320).A non-AP STA 2 (330) that receives a BSRP frame (404) from an AP (310) can send a BSR frame (405) in response. After that, the AP (310) can send a TF (406) to the non-AP STA 2 (330).

[0084] When AP (310) performs a channel access operation on a subchannel by considering one or more of the start times of the random backoff procedure described above, and the backoff counter of AP (310) becomes 0, AP (310) can maintain the backoff counter at 0 until the time when TF (406) transmission is possible on the subchannel. That is, AP (310) can wait for transmission with the backoff counter at 0. When AP (310) maintains the backoff counter at 0 and then performs TF (406) transmission, it may mean that the transmission queue is assumed to be empty when the backoff counter is 0, and then is re-enqueued at the time of performing TF (406) transmission. Afterwards, when TF (406) transmission can start, AP (310) can transmit TF (406) to a non-AP STA connected to AP (310).

[0085] As another example, referring to FIG. 3b, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) may transmit a PR (408) to the AP (310) after SIFS time from the time of completion of the transmission of the data frame (403) of non-AP STA 1 (320) for a priority transmission request. If non-AP STA 1 (320) receives a PR (408) from another non-AP STA, non-AP STA 1 (320) may wait for subsequent data frame transmission to protect against pre-amplification. Additionally, the AP (310) may receive a PR (408) from at least one non-AP STA. The AP (310) may transmit a TF (406) to check for the presence of LL traffic from non-AP STAs other than non-AP STA 1 (320). AP (310) may perform channel access on a subchannel using an EDCA random backoff procedure prior to TF transmission. Here, if the backoff counter becomes 0 but AP (310) is unable to transmit a frame, AP (310) may assume that the transmission queue is empty and reinvoke the random backoff procedure on that subchannel. Here, the random backoff procedure may be reinvoke repeatedly until TF transmission is possible on the subchannel. Afterward, AP (310) may transmit TF (406) to a non-AP STA connected to AP (310) at the time when TF (406) transmission can begin. For example, when the random backoff procedure is reinvoke, the CW value may be selected while remaining the same as before.

[0086] Random backoff, which is performed repeatedly for the transmission of TF (406) in the side channel, may be performed until the time of receiving PR (408). If the random backoff becomes 0 at the time of receiving PR (408), the AP (310) may keep the backoff counter at 0 and wait, and then transmit TF (406) to the non-AP STA immediately after completing the reception of PR (408) and SIFS time. Alternatively, the AP (310) may perform random backoff until the time after the reception of PR (408) is completed. If there is a backoff in progress at the time of receiving PR (408), the AP (310) may transmit TF (406) to the non-AP STA when the random backoff becomes 0 after receiving PR (408) and SIFS time. Here, non-AP STAs, including non-AP STA 1 (320) that received PR (408), may wait for the AP (310) to transmit TF (406) without transmitting frames.

[0087] A non-AP STA 2 (330) that receives a TF (406) transmitted by an AP (310) may need to change its operating bandwidth to transmit an LL data frame (407). When the non-AP STA 2 (330) changes its operating bandwidth, a delay may occur, and the delay may vary depending on the implementation specifications of the non-AP STA. For example, the operating bandwidth switching delay of the non-AP STA 2 (330) may be exchanged during the (re)association process with the AP (310). Thus, the AP (310) can recognize the operating bandwidth switching delay of the non-AP STA 2 (330) and use this information to add padding to the TF (406). The AP (310) may add an Intermediate FCS to the TF (406) to support the operating bandwidth switching of the non-AP STA 2 (330). Intermediate FCS is a frame check sequence inserted in the middle of the TF (406) that allows the non-AP STA to decode only the necessary information and then perform a channel or bandwidth switching operation. As a result, the non-AP STA 2 (330) that receives the TF (406) transmitted by the AP (310) can receive the TF (406) by appropriately adjusting its operating bandwidth, and then transmit the LL data frame (407) after the SIFS time.

[0088] Referring to FIG. 3c, a wireless LAN terminal (e.g., AP 1, non-AP STA 1 (320), non-AP STA 2 (330), non-AP STA 3 (350)) may perform a P-EDCA operation as a method to support LL traffic. The P-EDCA operation may be the pre-amplification operation described above as an operation for priority transmission. In this disclosure, the priority transmission operation, the P-EDCA operation, and the pre-amplification operation may refer to the same operation for priority transmission. That is, in this disclosure, the pre-amplification operation may be interpreted as a P-EDCA operation, and the P-EDCA operation may be interpreted as a pre-amplification operation. Although each operation is described in this disclosure, this is merely for convenience of explanation, and it may be obvious that each operation can be applied to an operation with the same meaning.

[0089] For example, the P-EDCA operation may be an enhanced EDCA operation to reduce the tail of the channel access delay distribution of the EDCA voice traffic. The P-EDCA operation may be available only when the use of P-EDCA is allowed in the BSS where the wireless LAN terminal is operating. As a specific example, the AP (310) may allow the execution of P-EDCA within its BSS. The AP (310) may transmit a management frame (e.g., Beacon, Probe Response, (Re-)Association Response) transmitted by the AP (310) within the BSS that includes an indicator allowing the use of P-EDCA. The indicator allowing the use of P-EDCA may be the same indicator as the indicator indicating that a TXOP is capable of preemption requests (e.g., preemption allowed TXOP) in other embodiments of the present disclosure.

[0090] A non-AP STA (e.g., non-AP STA 1 (320), non-AP STA 2 (330)) that receives any of the frames transmitted by the AP (310) may instruct the AP (310) to perform P-EDCA, and may perform P-EDCA within the BSS configured by the AP (310). As another example, P-EDCA may be an operation performed when a wireless LAN terminal supports P-EDCA without separate permission. For example, non-AP STAs connected to the AP (310) may perform P-EDCA on their own without instructions from the AP (310). A wireless LAN terminal that supports P-EDCA (e.g., AP 1, non-AP STA 1 (320), non-AP STA 2 (330)) may manage PSRC[AC_VO] as a PSRC (P-EDCA station retry counter). The initial value of PSRC[AC_VO] may be 0. PSRC[AC_VO] can be incremented by 1 each time DS-CTS (defer signal clear to send) is transmitted, and PSRC[AC_VO] can be initialized to 0 when QSRC[AC_VO] becomes 0 as a QoS (Quality of Service) station retry counter.

[0091] A wireless LAN terminal that supports P-EDCA (e.g., AP 1, non-AP STA 1 (320), non-AP STA 2 (330)) can perform P-EDCA only when the following [P-EDCA execution conditions] are satisfied.

[0092]

[0093] [P-EDCA Execution Conditions]

[0094] 1. Where P-EDCA was permitted by the AP within the BSS and non-AP STAs instructed the AP to use P-EDCA.

[0095] 2. When a wireless LAN terminal (AP, non-AP STA) performing P-EDCA has AC_VO traffic that is pending transmission.

[0096] 3. When QSRC[AC_VO] is greater than or equal to dot11PECARetryThreshold and PSRC[AC_VO] is not greater than (equal to or less than) dot11PEDCAConsecutiveAttempt.

[0097]

[0098] A P-EDCA STA that satisfies all of the above-described [P-EDCA execution conditions] can transmit DS-CTS (409-1, 409-2, 409-3) frames at the slot boundary where the medium is in an idle state for DSAIFS[AC_VO] from the time when the medium was last switched from an occupied state to an idle state through a CS operation. The DS-CTS (409-1, 409-2, 409-3) frames may be the same frames as the instruction frames (e.g., PR frames) for initiating LL traffic transmission procedures (e.g., preemption transmission, prioritized EDCA) in other embodiments of the present disclosure. As an example, the length of DSAIFS[AC_VO] may be equal to Equation 1 below.

[0099] [Mathematical Formula 1]

[0100] DSAIFS[AC_VO] = aSIFSTime + (AIFSN + DSr) x aSlotTime

[0101]

[0102] In Equation 1, the above DSAIFS[AC_VO] may also be referred to as AIFS[PEDCA]. AIFSN may be 2. DSr may be an integer randomly selected from a uniform distribution between 0 and CWds[AC_VO]. The format of the DS-CTS(409-1, 409-2, 409-3) frames may be fixed. For example, the DS-CTS(409-1, 409-2, 409-3) frames may be in a non-HT format and / or a non-HT duplicate format, may be transmitted at a data rate of 6 Mb / s, and the SCRAMBLER_INITIAL_VALUE may use a fixed value of [0, 0, 0, 0, 0, 1, 0] (seed value = 32). Here, the above-mentioned non-HT format may be a PPDU format in which the PPDU is transmitted only on the primary 20 MHz channel. Additionally, the non-HT duplicate format may be a PPDU format in which the PPDU is duplicated and transmitted in 20 MHz units on 20 MHz channels, including the primary 20 MHz channel, where the result of at least one of CCA and CS is identified as idle. Additionally, the receiver address (RA) field of the DS-CTS (409-1, 409-2, 409-3) frame may be set to a unicast MAC address of 00:0F:AC:47:43:00. Additionally, as an example, the duration field value of the DS-CTS (409-1, 409-2, 409-3) frame may be set to the P-EDCA contention length indicated in the basic P-EDCA parameter set. As an example, the duration field value of the DS-CTS (409-1, 409-2, 409-3) frame may be set to 97 microseconds, which is the P-EDCA contention length. The above basic P-EDCA parameter set may be the basic P-EDCA parameters used when AP (310) does not separately specify the parameters that P-EDCA STAs should use in the P-EDCA competition.That is, the DS-CTS (409-1, 409-2, 409-3) frame can be set to a length that protects the P-EDCA competition time between P-EDCA STAs after the transmission (or reception) of the DS-CTS frame by the P-EDCA STA that transmitted the DS-CTS frame and the P-EDCA STA that received at least one of the DS-CTS frames and participated in the competition.

[0103] P-EDCA contention may be performed immediately after the transmission (or reception) of DS-CTS (409-1, 409-2, 409-3) frames is completed, and the random backoff procedure of EDCA (e.g., select a backoff counter, decrement a non-zero backoff counter by 1 at the slot boundary, and if the backoff counter is zero at the slot boundary, the corresponding EDCAF (EDCA Function) transmits the frame) may be applied, but the following exceptions may apply, and the variables applied below may be as shown in Table 1 below.

[0104] 1. During the P-EDCA competition period, only EDCAF[AC_VO] can compete, and other EDCAFs are suspended.

[0105] 2. EDCAF[AC_VO] must be initialized with AIFSN, CWmin, and CWmax as P-EDCA AIFSN, P-EDCA CWmin, and P-EDCA CWmax, respectively, and CW[AC_VO] is initialized with CWmin[AC_VO].

[0106] 3. EDCAF[AC_VO] must be set to a backoff counter, a randomly selected integer with a uniform distribution between 0 and CW[AC_VO].

[0107] [Table 1]

[0108]

[0109]

[0110] [Table 1] may be a set of basic P-EDCA parameters that the P-EDCA STA uses by default in P-EDCA operation. If necessary, the P-EDCA parameters may be specified as separate values ​​by AP (310).

[0111] A P-EDCA STA that has won the TXOP in a P-EDCA competition can send an RTS (request to send, 410) as the first frame to be sent from the TXOP. A P-EDCA STA that has received a response frame (CTS, 411) for the RTS (410) can send the AC_VO traffic that is pending transmission. A P-EDCA STA that has won the TXOP in a P-EDCA competition and succeeded in sending one or more MPDUs cannot start a P-EDCA competition until the P-EDCA execution conditions are satisfied. Additionally, EDCAF[AC_VO] must update AIFSN, CWmin, and CWmax to the values ​​of dot11EDCATable (or dot11QAPEDCATable for APs), and EDCAF[AC_VI], EDCAF[AC_BE], and EDCAF[AC_BK] may be resumed.

[0112] If a TXOP is not acquired in a P-EDCA competition (or if a TXOP is acquired in a P-EDCA competition and an RTS is transmitted but a CTS response is not received), the P-EDCA STA may start another P-EDCA competition by transmitting a DS-CTS frame at the slot boundary where it is determined that the medium is idle during DSAIFS[AC_VO] according to the CS mechanism of the P-EDCA STA. The above-described restart of the P-EDCA competition may be performed up to dot11PEDCAConsecutiveAttempt. When PSRC[AC_VO] reaches dot11PEDCAConsecutiveAttempt, the P-EDCA STA initializes QSRC[AC_VO] and cannot attempt a P-EDCA competition until the conditions for P-EDCA execution are satisfied. Additionally, EDCAF[AC_VO] must update AIFSN, CWmin, and CWmax to the values ​​of dot11EDCATable (dot11QAPEDCATable for AP), and EDCAF[AC_VI], EDCAF[AC_BE], and EDCAF[AC_BK] can be resumed.

[0113] FIGS. 4a and FIGS. 4b are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0114] Referring to FIGS. 4a and 4b, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) can successfully receive an ICF (401) transmitted by non-AP STA 1 (320). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) can recognize through the ICF (401) that the TXOP obtained by non-AP STA 1 (320) is a pre-amplified TXOP. Here, low-latency (LL) traffic requiring priority transmission to the AP (310) may occur in at least one of non-AP STA 2 (330) and non-AP STA 3 (350). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) may send a PR (412) to the AP (310) after SIFS time from the time the data frame (403) of non-AP STA 1 (320) is completed for a priority transmission request. If non-AP STA 1 (320) receives a PR (412) from another non-AP STA, non-AP STA 1 (320) may wait for a subsequent data frame transmission to protect against pre-amplification. Additionally, the AP (310) may receive a PR (412) from at least one non-AP STA. The AP (310) may send a TF to check for LL traffic from non-AP STAs other than non-AP STA 1 (320). AP (310) can successfully access a channel on a subchannel by using the EDCA random backoff procedure described in FIGS. 3a through 3c prior to TF transmission. AP (310) can transmit TF using channels including the subchannel on which it successfully accessed the channel, along with the channel occupied by the TXOP of non-AP STA 1 (320).

[0115] The TF transmitted by the AP (310) may be an NFRP frame (413). The receiver address (RA) field in the MAC header of the NFPR frame (413) transmitted by the AP (310) may be set to a broadcast address. The feedback type subfield in the user information field in the MAC header of the NFPR frame (413) transmitted by the AP (310) may be set to 0, and the non-AP STA (e.g., non-AP STA 2, non-AP STA 3) that transmitted the PR (412) to the AP (310) may be notified of the existence of LL traffic to be transmitted first. The non-AP STA that transmitted the PR (412) to the AP (310) may have negotiated the use of pre-amplification with the AP (310) in advance. The AP (310) may schedule the aforementioned non-AP STAs to respond to the NFRP frame (413). A non-AP STA (e.g., non-AP STA 2, non-AP STA 3) scheduled to respond to an NFRP frame (413) receives the NFRP frame (413) transmitted by the AP (310) and can respond with an NFR (NDP Feedback Request Response, 414) frame after SIFS. Thus, a non-AP STA that responds with an NFR can indicate the presence of low-latency (LL) traffic to be transmitted first.

[0116] Here, the non-AP STA that transmitted PR (413) to the AP (310) may need to change its operating bandwidth to transmit an NFR frame (414). When changing the operating bandwidth, a delay may occur, and the delay may vary depending on the implementation specifications of the non-AP STA. The operating bandwidth switching delay of the non-AP STA described above may have been exchanged during the (re)association process with the AP (310). Therefore, the AP (310) may use the delay information to add padding to the NFRP frame (413) to ensure the bandwidth switching delay. Here, the AP (310) may add an Intermediate FCS to the NFRP frame (413) to support rapid operating bandwidth switching of the non-AP STA. The Intermediate FCS is a frame check sequence inserted in the middle of the NFRP frame that allows the non-AP STA to decode only the necessary information and perform channel or bandwidth switching operations. Accordingly, a non-AP STA that has transmitted PR (412) to AP (310) and received the NFRP frame (413) transmitted by AP (310) can adjust its operating bandwidth to receive the NFPR frame (413) and transmit an NFR frame (414) after SIFS time.

[0117] Referring to FIG. 4a, the AP (310) can identify non-AP STAs (e.g., non-AP STA 2, non-AP STA 3) that have LL traffic requiring priority transmission within the BSS through the exchange of NFRP frames and NFR frames described above. The AP (310) receives an NFR frame (414) but cannot identify which non-AP STA transmitted the NFR frame (414), so it can allocate uplink transmission resources to all non-AP STAs that transmitted the NFR frame (414). Here, the non-AP STAs may be non-AP STAs that have negotiated the use of pre-amplification with the AP (310) as described above, and are non-AP STAs that transmit LL traffic. AP (310) can allocate a resource unit (RU) for transmitting an uplink trigger based PPDU (UL TB PPDU) by transmitting a TF (415) to a non-AP STA where LL traffic exists. AP (310) can transmit the TF (415) using channels including the channel (or bandwidth) occupied by the TXOP initially acquired by non-AP STA 1 (320) and the channel successfully accessed through an EDCA operation performed on a sub-channel. The TF (415) transmitted by AP (310) may be a TF that allocates a RU to a non-AP STA where LL traffic exists, and AP (310) may allocate a RU within the channel (or bandwidth) to which the TF (415) was transmitted. A non-AP STA assigned a RU can use its RU to receive TF (415) and, after SIFS time, send a UL TB PPDU containing LL traffic (416-1, 416-2) to AP (310). Upon receiving the UL TB PPDU, AP (310) can perform LL data frame decoding for each RU assigned to the non-AP STA.AP (310) can send a Multi-STA BlockAck frame to non-AP STA 2 (330) and non-AP STA 3 (350) using the RU allocated per non-AP STA. Non-AP STA 2 (330) and non-AP STA 3 (350) that sent the UL TB PPDU can receive the Multi-STA BlockAck frame sent by AP (310). AP (310) can send a BlockAck frame for the data frame sent by non-AP STA 1 (320) after sending the Multi-STA BlockAck frame and after SIFS time. Non-AP STA 1 (320) can receive the BlockAck frame sent by AP (310).

[0118] As another example, referring to FIG. 4b, the AP (310) can identify non-AP STAs (e.g., non-AP STA 2, non-AP STA 3) that have LL traffic requiring priority transmission within the BSS through the exchange of NFRP frames and NFR frames described above. Since the AP (310) receives an NFR frame (414) but cannot identify which non-AP STA transmitted the NFR frame (414), it can allocate uplink transmission resources to all non-AP STAs that transmitted the NFR frame (414). Here, the non-AP STAs may be non-AP STAs that transmit LL traffic and have negotiated the use of pre-amplification with the AP (310) as described above. AP (310) can send TF (415) to non-AP STAs where LL traffic exists to allocate a resource unit (RU) for transmitting UL TB PPDU (uplink trigger based PPDU).

[0119] AP (310) can transmit TF (415) using channels including the channel (or bandwidth) occupied by the TXOP initially acquired by non-AP STA 1 (320) and the channel successfully accessed through EDCA operations performed on the sub-channel. The TF (415) transmitted by AP (310) may be a TF that allocates RU to a non-AP STA where LL traffic exists, and AP (310) may allocate RU within the channel (or bandwidth) to which TF (415) was transmitted.

[0120] Here, the AP (310) may allocate a RU in the channel (or bandwidth) occupied by the TXOP of non-AP STA 1 (320) for the transmission of data frames of non-AP STA 1 (320), and may allocate a RU to non-AP STA 2 (330), where LL traffic exists, to use a channel other than the channel occupied by the TXOP of non-AP STA 1 (320). The non-AP STA 1 (320) and non-AP STA 2 (330) that have been allocated a RU may use their RUs to receive TF (415) and, after SIFS time, transmit an UL TB PPDU containing LL data frames (417-1) and data frames (417-2) to the AP (310). An AP (310) that receives an UL TB PPDU containing a data frame (417-2) of non-AP STA 1 (320) and an LL data frame (417-1) of non-AP STA 2 (330) can decode the LL data frame (417-1) of non-AP STA 2 (330) and the data frame (417-2) of non-AP STA 1 (320) by RUs assigned to non-AP STAs. The AP (310) can send a Multi-STA BlockAck frame to non-AP STA 1 (320) and non-AP STA 2 (330) using RUs assigned to non-AP STAs. The non-AP STA 1 (320) and non-AP STA 2 (330) that transmitted the UL TB PPDU can receive the Multi-STA BlockAck frame transmitted by the AP (310).

[0121] As another example, non-AP STA 1 (320) receives an acknowledgment frame (e.g., BlockAck frame or Multi-STA BlockAck) for an LL data frame from non-AP STA 2 (330), and may perform additional data frame transmission within the remaining time length of the TXOP it initially acquired after SIFS time. If non-AP STA 1 (320) performs additional data frame transmission, AP (310) may transmit a BlockAck frame for the data frame successfully received from non-AP STA 1 (320) before the time when non-AP STA 1 (320)'s data frame transmission is completed (or the time when non-AP STA 1 (320)'s TXOP is expected to be completed). The additional data frames transmitted by non-AP STA 1 (320) may be transmitted at intervals of XIFS (e.g., PIFS) to support PR transmission. Alternatively, non-AP STA 1 (320) does not support PR transmission and can be transmitted at intervals of SIFS within the remaining time length of the TXOP it first acquired.

[0122] FIGS. 5A and 5B are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0123] Referring to FIGS. 5a and 5b, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) can successfully receive an ICF (401) transmitted by non-AP STA 1 (320). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) can recognize through the ICF (401) that the TXOP obtained by non-AP STA 1 (320) is a pre-amplified TXOP. Here, low-latency (LL) traffic requiring priority transmission to the AP (310) may occur in at least one of non-AP STA 2 (330) and non-AP STA 3 (350). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) may send a PR (412) to the AP (310) after SIFS time from the time of completion of the transmission of the data frame (403) of non-AP STA 1 (320) for a priority transmission request. If non-AP STA 1 (320) receives the transmission of the PR (412) from another non-AP STA, non-AP STA 1 (320) may wait for the transmission of a subsequent data frame to protect against pre-amplification. Additionally, the AP (310) may receive a PR (412) from at least one non-AP STA. The AP (310) may send a TF to check for the presence of LL traffic from non-AP STAs other than non-AP STA 1 (320). AP (310) can successfully access a channel on a subchannel by using the EDCA random backoff procedure described in FIGS. 3a through 3c prior to TF transmission. AP (310) can transmit TF using channels including the subchannel on which it successfully accessed the channel, along with the channel occupied by the TXOP of non-AP STA 1 (320).

[0124] Referring to FIG. 5a, the TF transmitted by the AP (310) may be a frame (hereinafter referred to as a UORA frame, 418) that allocates a random access RU (RA-RU) for the use of the UORA method. The UORA frame (418) transmitted by the AP (310) may be a frame that allocates a RU to which a designated non-AP STA can transmit a frame, and simultaneously allocates an RA-RU to which a frame can be transmitted by competing for channel access. A non-AP STA (e.g., non-AP STA 2, non-AP STA 3) that has transmitted PR (412) to the AP (310) may compete for channel access within the RA-RU to transmit low-latency (LL) traffic. That is, a non-AP STA (e.g., non-AP STA 2, non-AP STA 3) that has sent PR (412) to the AP (310) can randomly select one of the RA-RUs to perform transmission. If the RA-RU selected by the non-AP STA (e.g., non-AP STA 2, non-AP STA 3) that has sent PR (412) to the AP (310) is not selected for transmission by another non-AP STA, the UORA channel access competition may be successful. non-AP STA 2 (330) and non-AP STA 3 (350) receive the UORA frame (418) and, after SIFS, can perform transmission of LL data frames (419-1, 419-2) using a randomly selected RA-RU from among the RA-RUs allocated in the UORA frame. AP (310) can receive UL TB PPDU transmitted by non-AP STA 2 (330) and non-AP STA 3 (350) and then decode it for each RU.AP (310) receives the UL TB PPDU and, after SIFS time, can send a Multi-STA BlockAck frame to non-AP STA 2 (330) and non-AP STA 3 (350) using the RU that non-AP STA 2 (330) and non-AP STA 3 (350) sent the frame to. non-AP STA 2 (330) and non-AP STA 3 (350) can decode the Multi-STA BlockAck frame within the RU they used. AP (310) can transmit a Multi-STA BlockAck frame, and after SIFS time, can transmit a BlockAck frame for a data frame transmitted by non-AP STA 1 (320) using the channel (or bandwidth) occupied by the TXOP acquired by non-AP STA 1 (320), and non-AP STA 1 (320) can receive the BlockAck frame transmitted by AP (310).

[0125] As another example, referring to FIG. 5b, the TF transmitted by the AP (310) may be a frame (hereinafter referred to as a UORA hybrid frame, 420) in which an RA-RU is allocated for the UORA method and a RU is allocated to transmit general data, such as TB PPDU. The UORA hybrid frame (420) transmitted by the AP (310) may be a frame in which a designated non-AP STA is allocated a RU to transmit the frame and simultaneously an RA-RU is allocated to transmit the frame by competing for channel access. The transmission length of the RA-RU and the general RU may be set to be equal to the length of the data initially transmitted by the non-AP STA 1 (320). AP (310) may have allocated a RU corresponding to the channel (or bandwidth) occupied by the TXOP of non-AP STA 1 (320) within the UORA hybrid frame (420) to non-AP STA 1 (320) to ensure transmission of non-AP STA 1 (320), and an RA-RU may be allocated to the remaining channel excluding the channel (or bandwidth) allocated to non-AP STA 1 (320). The UORA hybrid frame (420) may be transmitted in the band occupied by non-AP STA 1 (320) so that non-AP STA 1 (320) using a limited band can receive the UORA hybrid frame (420). Additionally, the same UORA hybrid frame (420) may be transmitted in a subchannel. A non-AP STA (e.g., non-AP STA 2) that sent PR (412) to the AP (310) can compete for channel access within an RA-RU to transmit low-latency (LL) traffic. That is, a non-AP STA (e.g., non-AP STA 2) that sent PR (412) to the AP (310) can randomly select one of the RA-RUs to perform the transmission. Here, a non-AP STA (e.g., non-AP STA 2) that sent PR (412) to the AP (310)If the RA-RU selected by non-AP STA 2) is not selected for transmission by another non-AP STA, UORA channel access contention can succeed. non-AP STA 1 (320) and non-AP STA 2 (330) can receive a UORA hybrid frame (420) using the RU assigned to them or the RU they obtained through channel access contention, and transmit frames (421-1, 421-2) after SIFS. AP (310) can receive the UL TB PPDU transmitted by non-AP STA 1 (320) and non-AP STA 2 (330) and decode it by RU. AP (310) can send a Multi-STA BlockAck frame to non-AP STA 1 (320) and non-AP STA 2 (330) using the RU that non-AP STA 1 (320) and non-AP STA 2 (330) sent the frame to after SIFS time following the reception of the UL TB PPDU. non-AP STA 1 (320) and non-AP STA 2 (330) can decode the Multi-STA BlockAck frame within the RU they used.

[0126] As another example, non-AP STA 1 (320) may receive a response frame (e.g., BlockAck frame or Multi-STA BlockAck) for an LL data frame (421-1) from non-AP STA 2 (330) and, after SIFS time, perform additional data frame transmission within the remaining time length of the TXOP it initially acquired. If non-AP STA 1 (320) transmits additional data frames, AP (310) may transmit a BlockAck frame for the data frames successfully received from non-AP STA 1 (320) before the time when the data frame transmission by non-AP STA 1 (320) is completed (or the time when the TXOP of non-AP STA 1 (320) is expected to be completed). The additional data frames transmitted by non-AP STA 1 (320) may be transmitted at intervals of XIFS (e.g., PIFS) to support PR transmission. Alternatively, it may be transmitted at intervals of SIFS within the remaining time length of the TXOP initially acquired without supporting PR transmission.

[0127] FIGS. 6a and 6b are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0128] Referring to FIGS. 6a and 6b, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) can successfully receive an ICF (401) transmitted by non-AP STA 1 (320). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) can recognize through the ICF (401) that the TXOP obtained by non-AP STA 1 (320) is a pre-amplified TXOP. Here, low-latency (LL) traffic requiring priority transmission to the AP (310) may occur in at least one of non-AP STA 2 (330) and non-AP STA 3 (350). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) may send a PR (412) to the AP (310) after SIFS time from the time of completion of the transmission of the data frame (403) of non-AP STA 1 (320) for a priority transmission request. If non-AP STA 1 (320) receives the transmission of the PR (412) from another non-AP STA, non-AP STA 1 (320) may wait for the transmission of a subsequent data frame to protect against pre-amplification. Additionally, the AP (310) may receive a PR (412) from at least one non-AP STA. The AP (310) may send a TF to check for the presence of LL traffic from non-AP STAs other than non-AP STA 1 (320). AP (310) can successfully access a channel on a subchannel by using the EDCA random backoff procedure described in FIGS. 3a through 3c prior to TF transmission. AP (310) can transmit TF using channels including the subchannel on which it successfully accessed the channel, along with the channel occupied by the TXOP of non-AP STA 1 (320).

[0129] Here, the TF transmitted by the AP (310) may be a BSRP frame (422). The recipient address field within the MAC header of the BSRP frame (422) transmitted by the AP (310) may be set to a broadcast address. The BSRP frame (422) transmitted by the AP (310) may indicate to the AP (310) the presence of low-latency (LL) traffic to be transmitted first by the non-AP STA (e.g., at least one of non-AP STA 2 and non-AP STA 3 (350)) that transmitted the PR (412). The non-AP STA that transmitted the PR (412) to the AP (310) may have negotiated the use of pre-amplification with the AP (310) in advance. A non-AP STA (e.g., at least one of non-AP STA 2 and non-AP STA 3) that sent PR (412) to the AP (310) can receive a BSRP frame (422) and respond with a Buffer Status Report (BSR) frame (423-2) after SIFS to notify the presence of LL traffic.

[0130] A non-AP STA that has transmitted PR (412) to the AP (310) may need to change its operating bandwidth to transmit a BSR frame (423-2). When changing the operating bandwidth, a delay may occur, and the delay may vary depending on the implementation specifications of the non-AP STA. The operating bandwidth switching delay of the non-AP STA described above may have been exchanged during the (re)association process with the AP (310). Therefore, the AP (310) may use the delay information to add padding to the BSRP frame (422) to ensure the bandwidth switching delay. Here, the AP (310) may add an Intermediate FCS to the BSRP frame (422) to support rapid operating bandwidth switching of the non-AP STA. The Intermediate FCS is a frame check sequence inserted in the middle of the BSRP frame that allows the non-AP STA to decode only the necessary information and perform channel or bandwidth switching operations. Therefore, a non-AP STA that has transmitted PR to AP (310) and received a BSRP frame transmitted by AP (310) can adjust its operating bandwidth to receive the BSRP frame and transmit a BSR frame after SIFS time.

[0131] Referring to FIG. 6a, the AP (310) can identify non-AP STAs (e.g., non-AP STA 2, non-AP STA 3) that have LL traffic requiring priority transmission within the BSS through the exchange of the aforementioned BSRP frame and BSR frame. The AP (310) can allocate a resource unit (RU) for transmitting an UL TB PPDU (uplink trigger based PPDU) by sending a TF (424) to the non-AP STA that has LL traffic. The AP (310) can send the TF (424) using channels including the channel (or bandwidth) occupied by the TXOP initially acquired by non-AP STA 1 (320), as well as channels successfully accessed through EDCA operations performed on sub-channels. The TF (424) transmitted by the AP (310) may be a TF (424) that allocates a RU to a non-AP STA where LL traffic exists, and the AP (310) may allocate a RU within the channel (or bandwidth) where the TF (424) was transmitted. The non-AP STA that has been allocated a RU may receive the TF (424) using its RU and, after SIFS time, send a UL TB PPDU containing LL traffic to the AP (310). Upon receiving the UL TB PPDU, the AP (310) may perform decoding of LL data frames (425-1, 425-2) for each RU allocated to the non-AP STA. The AP (310) may send a Multi-STA BlockAck frame to non-AP STA 2 (330) and non-AP STA 3 (350) using the RU allocated to each non-AP STA. The non-AP STA 2 (330) and non-AP STA 3 (350) that transmitted the UL TB PPDU can receive the Multi-STA BlockAck frame transmitted by the AP (310).AP (310) can transmit a Multi-STA BlockAck frame and, after SIFS time, transmit a BlockAck frame for a data frame transmitted by non-AP STA 1 (320). non-AP STA 1 (320) can receive the BlockAck frame transmitted by AP (310).

[0132] As another example, referring to FIG. 6b, the AP (310) can identify non-AP STAs (e.g., non-AP STA 2, non-AP STA 3) that have LL traffic requiring priority transmission within the BSS through the exchange of the aforementioned BSRP frame and BSR frame. The AP (310) can allocate a resource unit (RU) for transmitting an UL TB PPDU (uplink trigger based PPDU) by sending a TF (424) to the non-AP STA that has LL traffic. The AP (310) can send the TF (424) using channels including the channel (or bandwidth) occupied by the TXOP initially acquired by non-AP STA 1 (320), as well as channels successfully accessed through EDCA operations performed on sub-channels. The TF (424) transmitted by the AP (310) may be a TF (424) that allocates RUs to non-AP STAs where LL traffic exists, and the AP (310) may allocate RUs within the channel (or bandwidth) where the TF (424) is transmitted.

[0133] AP (310) may allocate RUs in the channel (or bandwidth) occupied by the TXOP of non-AP STA 1 (320) for the transmission of data frames of non-AP STA 1 (320), and may allocate RUs to non-AP STA 2 (330), where LL traffic exists, to use a channel other than the channel occupied by the TXOP of non-AP STA 1 (320). Non-AP STA 1 (320) and non-AP STA 2 (330) that have been allocated RUs may use their RUs to receive TF (424) and, after SIFS time, transmit UL TB PPDU containing LL data frame (426-1) and data frame (426-2) to AP (310). An AP (310) that receives an UL TB PPDU containing a data frame (426-2) of non-AP STA 1 (320) and an LL data frame (426-1) of non-AP STA 2 (330) can decode the LL data frame (426-1) of non-AP STA 2 (330) and the data frame (426-2) of non-AP STA 1 (320) by RU assigned to the non-AP STA. The AP (310) can send a Multi-STA BlockAck frame to non-AP STA 1 (320) and non-AP STA 2 (330) using the RU assigned to each non-AP STA. The non-AP STA 1 (320) and non-AP STA 2 (330) that transmitted the UL TB PPDU can receive the Multi-STA BlockAck frame transmitted by the AP (310).

[0134] As another example, non-AP STA 1 (320) receives an acknowledgment frame (e.g., BlockAck frame or Multi-STA BlockAck) for an LL data frame from non-AP STA 2 (330), and may perform additional data frame transmission within the remaining time length of the TXOP it initially acquired after SIFS time. If non-AP STA 1 (320) performs additional data frame transmission, AP (310) may transmit a BlockAck frame for the data frame successfully received from non-AP STA 1 (320) before the time when non-AP STA 1 (320)'s data frame transmission is completed (or the time when non-AP STA 1 (320)'s TXOP is expected to be completed). The additional data frames transmitted by non-AP STA 1 (320) may be transmitted at intervals of XIFS (e.g., PIFS) to support PR transmission. Alternatively, non-AP STA 1 (320) does not support PR transmission and can be transmitted at intervals of SIFS within the remaining time length of the TXOP it first acquired.

[0135] FIG. 7 is a diagram illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0136] Referring to FIG. 7, a non-AP STA (e.g., non-AP STA 2, non-AP STA 3) that transmits PR (412) to the AP (310) may compete for channel access for priority transmission using an EDCA random backoff procedure on a main 20 MHz channel to transmit low-latency (LL) traffic. The entire channel on which the aforementioned non-AP STA competes for channel access may be a channel including a wireless LAN subchannel available to the AP (310) (e.g., a main 20 MHz channel, a channel included within the operating bandwidth including the main 20 MHz channel and the subchannel, etc.).

[0137] For example, as a result of a channel access competition, non-AP STA 2 (330) may succeed in accessing the channel, and non-AP STA 2 (330) may transmit an LL data frame (427) to AP (310) using the channel (or bandwidth) that succeeded in accessing the channel. AP (310) may receive the LL data frame (427) transmitted by non-AP STA 2 (330) and transmit a BlockAck frame to non-AP STA 2 (330) after SIFS time. non-AP STA 2 (330) may receive the BlockAck frame transmitted by AP (310). AP (310) can transmit a BlockAck frame to non-AP STA 2 (330) and, after SIFS time, transmit a BlockAck frame for a data frame transmitted by non-AP STA 1 (320) using the channel (or bandwidth) occupied by the TXOP acquired by non-AP STA 1 (320), and non-AP STA 1 (320) can receive the BlockAck frame transmitted by AP (310).

[0138] As another example, non-AP STA 1 (320) receives a response frame (e.g., BlockAck frame or Multi-STA BlockAck) for an LL data frame (427) from non-AP STA 2 (330), and may perform additional data frame transmission within the remaining time length of the TXOP it initially acquired after SIFS time. If non-AP STA 1 (320) transmits additional data frames, AP (310) may transmit a BlockAck frame for the data frames successfully received from non-AP STA 1 (320) before the time when the data frame transmission by non-AP STA 1 (320) is completed (or the time when the TXOP of non-AP STA 1 (320) is expected to be completed). The additional data frames transmitted by non-AP STA 1 (320) may be transmitted at intervals of XIFS (e.g., PIFS) to support PR transmission. Alternatively, non-AP STA 1 (320) does not support PR transmission and can be transmitted at intervals of SIFS within the remaining time length of the TXOP it first acquired.

[0139] Referring to FIG. 7, all or part of the P-EDCA operation described in FIG. 3c may correspond as a method to support LL traffic. Specifically, the aforementioned non-AP STA 2 (330) and non-AP STA 3 (350) may transmit a PR (412), which is a frame that initiates LL traffic transmission, as a frame transmitted to the AP (310). Here, the PR (412) may be a CTS frame (e.g., a CTS-to-Self frame in which the receiver address (RA) of the frame is itself, or a CTS frame in which the receiver address is a specific address) as an instruction frame to initiate an LL traffic transmission procedure (e.g., preemption transmission, prioritized EDCA, etc.). Additionally, the CTS frame may be a DS-CTS frame transmitted to initiate P-EDCA competition. That is, a CTS frame (or DS-CTS frame) transmitted by at least one of non-AP STA 2 (330) and non-AP STA 3 (350) may be transmitted after a certain time interval after the medium has become idle (i.e., after the transmission of a data frame by non-AP STA 1 (320)). For example, a CTS frame (or DS-CTS frame) may be transmitted using the main 20 MHz channel of the BSS.

[0140] Alternatively, if AP (310) transmits a frame (e.g., BSRP frame, 404) for a pre-amplification request to a non-AP STA other than non-AP STA 1 (320), channel access operation on the subchannel may begin simultaneously with the transmission of said frame. Alternatively, channel access operation on the subchannel may begin at the time when AP (310) successfully decodes a response frame (e.g., BSR frame, 405) transmitted by the other non-AP STA (e.g., non-AP STA 2) after transmitting a frame (e.g., BSRP frame, 404) for a pre-amplification request to a non-AP STA other than non-AP STA 1 (320).

[0141] As another example, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) may transmit a CTS frame (or DS-CTS frame) using channels determined to be idle based on the results of performing at least one of CCA and CS among the 20 MHz channels, including the main 20 MHz channel within its operating bandwidth, during the PIFS time immediately preceding the transmission of the CTS frame (or DS-CTS frame). At least one of non-AP STA 2 (330) and non-AP STA 3 (350) may perform at least one of CCA and CS during the PIFS time from the time when the main 20 MHz channel was last occupied. Here, the channels determined to be idle during the PIFS time may be 20 MHz channels included in a total bandwidth of 320 MHz, including the main 20 MHz channel. In the above-described situation, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) can transmit a CTS frame (or DS-CTS frame) using 20 MHz channels included in a total bandwidth of 320 MHz that is identified as idle during the PIFS time. That is, the transmission bandwidth of the CTS frame (or DS-CTS frame) may be 320 MHz.

[0142] At least one of non-AP STA 2 (330) and non-AP STA 3 (350) that transmitted the CTS frame (or DS-CTS frame) may initiate the P-EDCA competition described above in the P-EDCA operation after transmitting the CTS frame (or DS-CTS frame). That is, at least one of non-AP STA 2 (330) and non-AP STA 3 (350) may transmit the CTS frame (or DS-CTS frame) and perform the P-EDCA operation, thereby performing a backoff procedure to acquire the EDCA TXOP. As an example, non-AP STA 2 (330) may select 1 as the backoff counter for the P-EDCA competition, and non-AP STA 3 (350) may select 3 as the backoff counter. However, this is for convenience of explanation only and is not limited thereto. non-AP STA 2 (330) and non-AP STA 3 (350) transmit a CTS frame (or DS-CTS frame) and confirm that the main 20 MHz channel is idle for AIFS[VO] time, and may reach the AIFS[VO] slot boundary. In the above situation, non-AP STA 2 (330) and non-AP STA 3 (350) may decrease their backoff counters by 1. Thus, the backoff counter of non-AP STA 2 (330) becomes 0, and the backoff counter of non-AP STA 3 (350) becomes 2. Subsequently, non-AP STA 2 (330) and non-AP STA 3 (350) confirm that the main 20 MHz channel is idle for aSlotTime from the AIFS[VO] slot boundary point and may reach the aSlotTime slot boundary. Here, the backoff counter of non-AP STA 2 (330) may be 0, and non-AP STA 2 (330) may win the P-EDCA competition and obtain TXOP.The non-AP STA 2 (330) (or the EDCAF[VO] of the non-AP STA 2) that has acquired the TXOP may start transmitting the frame. The non-AP STA 2 (330) that has acquired the TXOP may decide to transmit the frame using a bandwidth wider than the main 20 MHz channel. Here, the non-AP STA 2 (330) may need to perform PIFS sensing to use a bandwidth wider than the main 20 MHz channel. Specifically, the non-AP STA 2 (330) may determine the result of performing at least one of CCA and CS on the 20 MHz channels within its operating bandwidth during the PIFS time (e.g., 25 us) immediately before transmitting the frame. The non-AP STA 2 (330) may determine from the PIFS sensing result that the 20 MHz channels equal to the AP's maximum operating bandwidth (e.g., 320 MHz) are idle during the PIFS time immediately before transmitting the frame. In the above-described case, non-AP STA 2 (330) may transmit a frame to AP (310) using channels identified as idle during the PIFS time immediately preceding frame transmission by PIFS sensing (e.g., 20 MHz channels included in the 320 MHz bandwidth). The frame transmitted by non-AP STA 2 (330) may be a data frame containing LL traffic. Upon receiving the data frame transmitted by non-AP STA 2 (330), AP (310) may respond by transmitting a Block Acknowledgement (BA) frame after receiving the data frame and after the SIFS time. The transmission bandwidth of the BA frame transmitted by AP (310) may be the same as the transmission bandwidth of the data frame transmitted by non-AP STA 2 (330) (e.g., 320 MHz).

[0143] AP (310) can transmit a BlockAck frame to non-AP STA 2 (330) and, after SIFS time, transmit a BlockAck frame for a data frame transmitted by non-AP STA 1 (320) using the channel (or bandwidth) occupied by the TXOP acquired by non-AP STA 1 (320), and non-AP STA 1 (320) can receive the BlockAck frame transmitted by AP (310).

[0144] FIGS. 8a to 8f are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0145] AP (310) may have successfully received an ICF transmitted by non-AP STA 1 (320) and may recognize that the TXOP obtained by non-AP STA 1 (320) is a pre-amplified TXOP. AP (310) may recognize that there is scheduled uplink low latency (LL) traffic that non-AP STA 2 (330) needs to transmit to AP (310). AP (310) may transmit a PR to non-AP STA 2 (330) after a Short IFS (SIFS) time from the time non-AP STA 1 (320) completes transmitting the data frame to request priority transmission of non-AP STA 2 (330)'s scheduled UL LL traffic. non-AP STA 1 (320) may receive the PR transmitted by AP (310) and wait for subsequent data frame transmission for pre-amplification protection.

[0146] Referring to FIGS. 8a and 8b, the PR (Priority Transmission Instruction Frame) transmitted by AP (310) to non-AP STA 2 (330) to reserve a medium may be a BSRP frame (428). When there is a possibility that AP (310) will transmit a PR (e.g., when there is scheduled UL LL traffic on a non-AP STA other than non-AP STA 1 (320), etc.), AP (310) may instruct non-AP STAs in the BSS to provide information indicating at least one of the time and duration at which AP (310) is likely to transmit a PR in order to protect the transmission of AP (310)'s BSRP frame (428). For example, AP (310) may transmit including an indicator within a beacon that indicates the possibility of AP (310)'s PR until the next beacon transmission. As another example, the AP (310) may transmit a (re)association response frame or a probe response frame containing an indicator indicating the possibility of the AP (310) transmitting a PR. Through the above, the AP (310) in the BSS may recognize at least one of the information regarding the time and duration at which the AP (310) is likely to transmit a PR. Here, if the ICF (401) initially transmitted by the non-AP STA that acquired the TXOP contains a pre-amplification allowance TXOP indicator, the ICF (401) initially transmitted may contain an indicator prohibiting the transmission of PR by non-AP STAs other than the AP (310). If a non-AP STA other than non-AP STA 1 (320) identifies an indicator prohibiting non-AP STAs other than AP (310) from transmitting PR within the ICF (401) transmitted by non-AP STA 1 (320), the other non-AP STA may not transmit PR within the TXOP obtained by non-AP STA 1 (320).For example, the AP (310) can successfully access the channel on the subchannel using the EDCA random backoff procedure prior to transmitting the BSRP frame. Thus, the AP (310) can perform the transmission of the BSRP frame (428) using the subchannel it successfully accessed (e.g., channels within the operating bandwidth including the main 20 MHz channel and the subchannel) in addition to the channel occupied by the TXOP of the non-AP STA 1 (320). That is, the AP (310) can transmit the BSRP frame (428) as a PR over a wide bandwidth. Additionally, the BSRP frame (428) may be a different type of frame as the PR. The BSRP frame (428) may be a CTS frame (or DS-CTS frame) as the PR, and the above-described matters may apply equally even if it is a CTS frame (or DS-CTS frame).

[0147] A non-AP STA 2 (330) that receives a BSRP frame (428) transmitted by an AP (310) may need to change its operating bandwidth before transmitting a BSR frame (429). When changing the operating bandwidth, a delay may occur, and the delay may vary depending on the implementation specifications of the non-AP STA. The aforementioned operating bandwidth switching delay of the non-AP STA may have been exchanged during the (re)association process with the AP (310). Therefore, the AP (310) may use the delay information to add padding to the BSRP frame (428) to ensure the bandwidth switching delay. Here, the AP (310) may add an Intermediate FCS to the BSRP frame (428) to support rapid operating bandwidth switching of the non-AP STA 2 (330). Intermediate FCS is a frame check sequence inserted in the middle of a BSRP frame, which allows a non-AP STA to decode only the necessary information and perform channel or bandwidth switching operations. Thus, a non-AP STA 2 (330) that receives a BSRP frame transmitted as PR to the AP (310) can receive the BSRP frame by adjusting its operating bandwidth and transmit a BSR frame after SIFS time.

[0148] Referring to FIG. 8a, the AP (310) that receives the BSR frame (429) transmitted by the non-AP STA 2 (330) can recognize that there is UL LL traffic that requires priority transmission to the non-AP STA 2 (330). To trigger the UL LL traffic present in the non-AP STA 2 (330), the AP (310) can receive the BSR frame (429) using the channel (or bandwidth) through which the BSRP frame and BSR frame were transmitted, and then transmit a TF (430) to the non-AP STA 2 (330) after SIFS time. The non-AP STA 2 (330) can receive the TF (430) transmitted by the AP (310) for the transmission of UL LL traffic, and then transmit an LL data frame (431) to the AP (310) after SIFS time. AP (310) can receive an LL data frame (431) transmitted by non-AP STA 2 (330) and, after SIFS time, transmit a BlockAck frame to non-AP STA 2 (330). non-AP STA 2 (330) can receive a BlockAck frame transmitted by AP (310). AP (310) can transmit a BlockAck frame to non-AP STA 2 (330) and, after SIFS time, transmit a BlockAck frame as an acknowledgment frame to a data frame transmitted by non-AP STA 1 (320) using the channel (or bandwidth) occupied by the TXOP acquired by non-AP STA 1 (320), and non-AP STA 1 (320) can receive a BlockAck frame transmitted by AP (310).

[0149] As another example, referring to FIG. 8b, AP (310) can allocate a resource unit (RU) for transmitting UL TB PPDU by sending TF (432-1, 432-2) to non-AP STA 1 (320), which is a TXOP holder, and to non-AP STA 2 (330), which has UL LL traffic. Specifically, AP (310) can allocate a RU to non-AP STA 1 (320) to use the channel (or bandwidth) occupied by the TXOP of non-AP STA 1 (320), and can allocate a RU to non-AP STA 2 (330), which has UL LL traffic, to use a channel other than the channel occupied by the TXOP of non-AP STA 1 (320). non-AP STA 1 (320) and non-AP STA 2 (330), who have received the TF (432-1, 432-2) transmitted by AP (310) and have been assigned an RU, can use the assigned RU to receive the TF (432-1, 432-2) and, after SIFS time, send an UL TB PPDU containing the LL data frame (433-1) and data frame (433-2) to AP (310). An AP (310) that receives an UL TB PPDU containing a data frame (433-2) of non-AP STA 1 (320) and an LL data frame (433-1) of non-AP STA 2 (330) can decode the LL data frame (433-1) of non-AP STA 2 (330) and the data frame (433-2) of non-AP STA 1 (320) by RU assigned to the non-AP STA. The AP (310) can transmit a Multi-STA BlockAck frame to non-AP STA 1 (320) and non-AP STA 2 (330) using the RU assigned to each non-AP STA. The non-AP STA 1 (320) and non-AP STA 2 (330) that transmitted the UL TB PPDU can receive the Multi-STA BlockAck frame transmitted by the AP (310).

[0150] In FIGS. 8a and 8b described above, the PR transmitted by the AP (310) may be a frame that initiates LL traffic transmission and may be a frame in which the recipient address is set to a specific address. That is, the PR transmitted by the AP (310) may correspond to the DS-CTS frame of the P-EDCA operation described in FIG. 3c. For example, the DS-CTS frame transmitted by the AP (310) may be transmitted using a bandwidth (channels) wider than the main 20 MHz. That is, the AP (310) may transmit the DS-CTS frame over a wide bandwidth. More specifically, when the AP (310) transmits a DS-CTS frame over a broadband, the AP (310) may transmit the DS-CTS frame using channels determined to be idle based on the result of performing at least one of CCA and CS on 20 MHz channels, including a main 20 MHz channel and a secondary channel, within its operating bandwidth (e.g., 320 MHz) during the PIFS time immediately preceding the transmission of the DS-CTS frame. For example, the AP (310) may perform at least one of CCA and CS during the PIFS time from the time the main 20 MHz channel was last occupied.

[0151] For example, the AP (310) may include 20 MHz channels that are identified as idle during the PIFS time, which are included in the main 20 MHz channel, for a total operating bandwidth of 320 MHz. In the above situation, the AP (310) may transmit a DS-CTS frame using the 20 MHz channels identified as idle during the PIFS time within the 320 MHz operating bandwidth. Thus, the transmission bandwidth of the DS-CTS frame may be 320 MHz. Here, there may be no response frame for the DS-CTS frame transmitted by the AP (310). The AP (310) may transmit a TF to a subordinate non-AP STA (e.g., non-AP STA 2) after the SIFS time from the time the DS-CTS frame transmission is completed. The TF transmitted by the AP (310) may be transmitted using a bandwidth that is equal to or narrower than the transmission bandwidth of the DS-CTS frame transmitted by the AP (310).

[0152] As another example, referring to FIG. 8c and FIG. 8d, when there is a possibility that AP (310) will transmit a PR (e.g., when there is scheduled UL LL traffic on a non-AP STA other than non-AP STA 1 (320), etc.), AP (310) may instruct non-AP STAs in the BSS to provide information indicating at least one of the time and duration at which AP (310) is likely to transmit a PR in order to protect the transmission of the BSRP frame of AP (310). For example, AP (310) may transmit including an indicator within a beacon that indicates the possibility of AP (310) transmitting a PR until the next beacon transmission. As another example, AP (310) may transmit including an indicator that indicates the possibility of AP (310) transmitting a PR in a (re)association response frame or a probe response frame. Through the above description, the AP (310) in the BSS can recognize at least one of the information regarding the time point and the length of time at which the PR may be transmitted. Here, if the ICF initially transmitted by the non-AP STA that acquired the TXOP contains a pre-amplification-allowed TXOP indicator, the ICF initially transmitted may contain an indicator prohibiting the transmission of PR by non-AP STAs other than the AP (310). If a non-AP STA other than non-AP STA 1 (320) identifies an indicator prohibiting the transmission of PR by non-AP STAs other than the AP (310) within the ICF transmitted by non-AP STA 1 (320), the other non-AP STA may not transmit PR within the TXOP acquired by non-AP STA 1 (320).

[0153] For example, a BSRP frame (434) transmitted by AP (310) may be transmitted within a channel (or bandwidth) occupied by a TXOP acquired by non-AP STA 1 (320). Non-AP STA 2 (330), having received the BSRP frame (434) transmitted by AP (310), may transmit a BSR frame (435) to AP (310) using the channel (or bandwidth) through which the BSRP frame (434) was transmitted. After receiving the BSR frame (435) transmitted by non-AP STA 2 (330), AP (310) may confirm the presence of UL LL traffic that requires priority transmission to non-AP STA 2 (330).

[0154] That is, the AP (310) can transmit a BSRP frame (434) as a PR using a main 20 MHz bandwidth. Additionally, the BSRP frame (434) can be a different type of frame as a PR. The BSRP frame (434) can be a CTS frame (or DS-CTS frame) as a PR, and the above-described matters can be applied in the same way even if it is a CTS frame (or DS-CTS frame).

[0155] AP (310), upon receiving a BSR frame (435) transmitted by non-AP STA 2 (330), can transmit a TF (436) to non-AP STA 2 (330) to transmit UL LL Data data. For example, AP (310) can successfully access a channel on a subchannel using an EDCA random backoff procedure before transmitting a BSRP frame (434). Thus, AP (310) can transmit a TF frame using the subchannel it successfully accessed, along with the channel occupied by the TXOP of non-AP STA 1 (320).

[0156] A non-AP STA (e.g., at least one of non-AP STA 1 (320) and non-AP STA 2 (330)) that receives a TF (436) transmitted by the AP (310) may need to change its operating bandwidth to transmit an LL data frame. When changing the operating bandwidth, a delay may occur, and the delay may vary depending on the implementation specifications of the non-AP STA. The operating bandwidth switching delay of the non-AP STA described above may have been exchanged during the (re)association process with the AP (310). Accordingly, the AP (310) may use the delay information to add padding to the TF (436) to ensure the bandwidth switching delay. Here, the AP (310) may add an Intermediate FCS to the TF (436) to support rapid operating bandwidth switching of the non-AP STA. Intermediate FCS is a frame check sequence inserted in the middle of a TF, which allows a non-AP STA to decode only the necessary information and perform channel or bandwidth switching operations. Thus, a non-AP STA that receives a TF transmitted by the AP (310) can receive the TF by adjusting its operating bandwidth and transmit an uplink data frame (at least one of an LL Data frame and a Data frame) after a SIFS time.

[0157] Referring to FIG. 8c, a non-AP STA 2 (330) that receives a TF (436) transmitted by the AP (310) for UL LL traffic transmission can transmit an LL data frame (437) to the AP (310) after receiving the TF (436) and after SIFS time. The AP (310) can transmit a BlockAck frame to the non-AP STA 2 (330) after receiving the LL data frame (437) transmitted by the non-AP STA 2 (330) and after SIFS time. The non-AP STA 2 (330) can receive the BlockAck frame transmitted by the AP (310). AP (310) can send a BlockAck frame to non-AP STA 2 (330) and, after SIFS time, use the channel (or bandwidth) occupied by the TXOP acquired by non-AP STA 1 (320) to send a BlockAck frame as an acknowledgment frame to the data frame sent by non-AP STA 1 (320), and non-AP STA 1 (320) can receive the BlockAck frame sent by AP (310).

[0158] In another way, referring to FIG. 8d, the AP (310) can allocate a resource unit (RU) for transmitting UL TB PPDU by sending a TF (438-1, 438-2) to a non-AP STA 1 (320) that is a TXOP holder and to a non-AP STA 2 (330) that has UL LL traffic. Specifically, the AP (310) can allocate a RU to the non-AP STA 1 (320) to use the channel (or bandwidth) occupied by the TXOP of the non-AP STA 1 (320), and can allocate a RU to the non-AP STA 2 (330) that has UL LL traffic to use a channel other than the channel occupied by the TXOP of the non-AP STA 1 (320). non-AP STA 1 (320) and non-AP STA 2 (330), who have received the TF (438-1, 438-2) transmitted by AP (310) and have been assigned an RU, can use the assigned RU to receive the TF (438-1, 438-2) and, after SIFS time, send an UL TB PPDU containing the LL data frame (439-1) and data frame (439-2) to AP (310). An AP (310) that receives an UL TB PPDU containing a data frame (439-2) of non-AP STA 1 (320) and an LL data frame (439-1) of non-AP STA 2 (330) can decode the LL data frame (439-1) of non-AP STA 2 (330) and the data frame (439-2) of non-AP STA 1 (320) by RUs assigned to non-AP STAs. The AP (310) can send a Multi-STA BlockAck frame to non-AP STA 1 (320) and non-AP STA 2 (330) using RUs assigned to non-AP STAs. The non-AP STA 1 (320) and non-AP STA 2 (330) that transmitted the UL TB PPDU can receive the Multi-STA BlockAck frame transmitted by the AP (310).

[0159] As another example, non-AP STA 1 (320) may receive a response frame (e.g., BlockAck frame or Multi-STA BlockAck) for an LL data frame from non-AP STA 2 (330) and, after SIFS time, perform additional data frame transmission within the remaining time length of the TXOP it initially acquired. If non-AP STA 1 (320) transmits additional data frames, AP (310) may transmit a BlockAck frame for the successfully received data frame from non-AP STA 1 (320) before the time when non-AP STA 1 (320)'s data frame transmission is completed (or the time when non-AP STA 1 (320)'s TXOP is expected to be completed). The additional data frames transmitted by non-AP STA 1 (320) may be transmitted at intervals of XIFS (e.g., PIFS) to support PR transmission. Alternatively, additional data frames may be transmitted at intervals of SIFS within the remaining time length of the TXOP initially acquired, without supporting PR transmission.

[0160] In FIGS. 8c and 8d described above, the PR transmitted by the AP (310) may be a frame that initiates LL traffic transmission and may be a frame in which the recipient address is set to a specific address. That is, the PR transmitted by the AP (310) may be a DS-CTS frame of the P-EDCA operation described above in FIG. 3c. The AP (310) may transmit the DS-CTS frame using the main 20 MHz channel. That is, the transmission bandwidth of the DS-CTS frame may be 20 MHz. The AP (310) that has transmitted the DS-CTS frame may transmit the DS-CTS frame and initiate the P-EDCA competition described above in the P-EDCA operation. For example, the AP (310) may select a backoff counter for the P-EDCA competition to 1. After transmitting the DS-CTS frame, the AP (310) may determine that the main 20 MHz channel is idle for an AIFS[VO] time and may reach the AIFS[VO] slot boundary. In the above-described situation, AP (310) can recognize that its backoff counter has decreased by 1 and recognize that AP (310)'s backoff counter has become 0. AP (310) can confirm that the main 20 MHz channel has been idle for aSlotTime from the AIFS[VO] slot boundary point and may have reached the aSlotTime slot boundary. In the above-described situation, AP (310)'s backoff counter may be 0. Therefore, AP (310) can win the P-EDCA competition and acquire the TXOP. AP (310) (or AP (310)'s EDCAF[VO]) that has acquired the TXOP can start transmitting the frame.

[0161] Here, the AP (310) that acquired the TXOP may decide to transmit a frame (e.g., trigger frame) using a bandwidth wider than the main 20 MHz channel. The AP (310) may need to perform PIFS sensing to use a bandwidth wider than the main 20 MHz channel. More specifically, the AP (310) may check the results of at least one of the CCA and CS of the 20 MHz channels within its operating bandwidth during the PIFS time (e.g., 25 us) immediately before transmitting the frame. The AP (310) may check, as a result of PIFS sensing, that the 20 MHz channels corresponding to the AP (310)'s maximum operating bandwidth (e.g., 320 MHz) are idle during the PIFS time immediately before transmitting the frame. In the above-described case, the AP (310) can transmit a frame (e.g., Trigger Frame) using channels (e.g., 20 MHz channels included in the 320 MHz bandwidth) that are identified as idle during the PIFS time immediately preceding frame transmission by PIFS sensing.

[0162] Referring to FIGS. 8e and 8f, an AP (310) intending to transmit LL traffic may perform the P-EDCA operation described in FIG. 3c after the TXOP acquired by non-AP STA 1 (320) has ended. More specifically, the AP (310) may perform at least one of CCA and CS for an AIFS[PEDCA] (or DSAIFS[AC_VO]) time from the time when the medium transitions from an occupied state to an idle state as a result of performing at least one of CCA and CS on the main 20 MHz channel. If the AP (310) confirms that the main 20 MHz channel is idle for an AIFS[PEDCA] (or DSAIFS[AC_VO]) time, the AP (310) may transmit a DS-CTS frame.

[0163] Referring to FIG. 8e, the DS-CTS frame (440) transmitted by the AP (310) can be transmitted using a bandwidth (channels) that is wider than the main 20 MHz. That is, the AP (310) can transmit the DS-CTS frame (440) in a broadband manner. More specifically, when the AP (310) transmits the DS-CTS frame (440) in a broadband manner, the AP (310) can transmit the DS-CTS frame (440) using channels determined to be idle based on the result of performing at least one of CCA and CS on 20 MHz channels, including the main 20 MHz channel and the secondary channel, within its operating bandwidth (e.g., 320 MHz) during the PIFS time immediately preceding the transmission of the DS-CTS frame (440). For example, AP (310) can perform at least one of CCA and CS during the PIFS time from the time the main 20 MHz channel was last occupied.

[0164] For example, the AP (310) may include the channels identified as idle during the PIFS time as 20 MHz channels included in the main 20 MHz channel, which are included in the total operating bandwidth of 320 MHz. In the above situation, the AP (310) may transmit DS-CTS frames (440) using the 20 MHz channels identified as idle during the PIFS time within the 320 MHz operating bandwidth. Thus, the transmission bandwidth of the DS-CTS frame may be 320 MHz.

[0165] AP (310) may initiate the P-EDCA contention described above in the P-EDCA operation after transmitting the DS-CTS frame (440). For example, AP (310) may set the backoff counter for the P-EDCA contention to 1. After transmitting the DS-CTS frame (440), AP (310) may determine that the main 20 MHz channel is idle for AIFS[VO] time and reach the AIFS[VO] slot boundary. In the above situation, AP (310) may decrease the backoff counter of AP (310) by 1, and accordingly, the backoff counter of AP (310) may become 0. After that, AP (310) may determine that the main 20 MHz channel is idle for aSlotTime from the time of the AIFS[VO] slot boundary and reach the aSlotTime slot boundary, and in the above situation, the backoff counter of AP (310) may be 0. Therefore, AP (310) may have won the P-EDCA competition and acquired the TXOP. The AP (310) that acquired the TXOP (or the AP (310)'s EDCAF[VO]) can start transmitting frames. For example, AP (310) can transmit an RTS frame (441) to non-AP STA 2 (330).

[0166] The bandwidth of the RTS frame (441) transmitted by the AP (310) may be transmitted using a bandwidth that is equal to or narrower than the transmission bandwidth of the DS-CTS frame (440). The RTS frame (441) may be redundantly transmitted within the transmission bandwidth in 20 MHz channel units using a PPDU in a non-HT duplicate format. A non-AP STA 2 (330) that receives the RTS frame (441) transmitted by the AP (310) may transmit a CTS frame (442) to the AP (310) in response to the RTS frame (441). The CTS frame (442) may be transmitted using a bandwidth that is equal to or narrower than the bandwidth of the RTS frame (441) transmitted by the AP (310). As another example, the CTS frame (442) may be transmitted using a bandwidth that is equal to or narrower than the bandwidth of the DS-CTS frame (440) transmitted by the AP (310). The AP (310) that receives the CTS frame (442) transmitted by the non-AP STA 2 (330) can transmit a data frame (443) to the non-AP STA 2 (330) using the bandwidth through which the CTS frame (442) was transmitted. The non-AP STA 2 (330) that receives the data frame (443) transmitted by the AP (310) can transmit a Block Acknowledge frame to the AP (310) in response.

[0167] Referring to FIG. 8f, the DS-CTS frame (444) transmitted by the AP (310) can be transmitted using only the main 20 MHz channel. That is, the AP (310) can transmit the DS-CTS frame (444) with a 20 MHz bandwidth. After transmitting the DS-CTS frame (444), the AP (310) can initiate the P-EDCA competition described above in the P-EDCA operation. For example, the AP (310) can set the backoff counter to 1 for the P-EDCA competition. After transmitting the DS-CTS frame, the AP (310) checks that the main 20 MHz channel is idle for an AIFS[VO] time and may have reached the AIFS[VO] slot boundary. In the situation described above, the AP (310) can decrease the AP (310) backoff counter by 1, and accordingly, the AP (310) backoff counter may become 0. After this, AP (310) checks that the main 20 MHz channel is idle for aSlotTime from the AIFS[VO] slot boundary point, and may reach the aSlotTime slot boundary, and in the above situation, the backoff counter of AP (310) may be 0. Thus, AP (310) may have won the P-EDCA competition and acquired the TXOP. AP (310) (or AP (310)'s EDCAF[VO]) that acquired the TXOP may start transmitting a frame. AP (310) that acquired the TXOP may transmit a frame (e.g., RTS frame, 441) using a wider bandwidth than the main 20 MHz channel. AP (310) may need to perform PIFS sensing to use a wider bandwidth than the main 20 MHz channel. More specifically, the AP (310) can check the result of at least one of the CCA and CS of the 20 MHz channels within its operating bandwidth during the PIFS (e.g., 25 us) time immediately before transmitting the aforementioned frame (e.g., RTS frame, 441). The AP (310) can check the maximum operating bandwidth of the AP (310) (e.g., PIFS sensing result)It can be confirmed that 20 MHz channels (e.g., 320 MHz) are idle during the PIFS time immediately preceding frame transmission. In the above case, the AP (310) can transmit a frame (e.g., RTS frame, 441) using the channels (e.g., 20 MHz channels included in the 320 MHz bandwidth) that were confirmed to be idle during the PIFS time immediately preceding frame transmission by PIFS sensing.

[0168] The RTS frame (441) may be transmitted using a PPDU in a non-HT format. The PPDU format of the RTS frame (441) is not limited to a non-HT format and may be an HT, VHT, or other frame. A non-AP STA 2 (330) that receives the RTS frame (441) transmitted by the AP (310) may transmit a CTS frame (442) to the AP (310) in response to the RTS frame. The CTS frame (442) may be transmitted using a bandwidth equal to or narrower than the bandwidth of the RTS frame (441) transmitted by the AP (310). Upon receiving the CTS frame (442) transmitted by the non-AP STA 2 (330), the AP (310) may transmit a data frame (443) to the non-AP STA 2 (330) using the bandwidth in which the CTS frame (442) was transmitted. A non-AP STA 2 (330) that receives a data frame (443) transmitted by AP (310) can send a Block Acknowledge frame to AP (310) in response.

[0169] FIGS. 9a and 9b are drawings illustrating a priority transmission method using wireless LAN subchannel access applicable to the present disclosure.

[0170] AP (310) may have successfully received an ICF transmitted by non-AP STA 1 (320) and may recognize that the TXOP obtained by non-AP STA 1 (320) is a pre-amplified TXOP. AP (310) may recognize that there is scheduled uplink low latency (LL) traffic that non-AP STA 2 (330) needs to transmit to AP (310). AP (310) may transmit a PR to non-AP STA 2 (330) after a Short IFS (SIFS) time from the time non-AP STA 1 (320) completes transmitting the data frame to request priority transmission of non-AP STA 2 (330)'s scheduled UL LL traffic. non-AP STA 1 (320) may receive the PR transmitted by AP (310) and wait for subsequent data frame transmission for pre-amplification protection.

[0171] Referring to FIGS. 9a and 9b, the PR transmitted by AP (310) to non-AP STA 2 (330) may be a TF (445). If there is a possibility that AP (310) will transmit a PR (e.g., if there is scheduled UL LL traffic on a non-AP STA other than non-AP STA 1 (320), etc.), AP (310) may instruct non-AP STAs in the BSS to provide information indicating at least one of the time and duration at which AP (310) is likely to transmit a PR in order to protect the transmission of AP's TF (445). For example, AP (310) may transmit including an indicator within a beacon indicating the possibility of AP (310)'s PR until the next beacon transmission. For another example, AP (310) may transmit including an indicator indicating the possibility of AP (310)'s PR in a (re)association response frame or a probe response frame. Through the above description, the AP (310) in the BSS can recognize at least one of the information regarding the time point and the length of time at which the PR may be transmitted. Here, if the ICF (401) initially transmitted by the non-AP STA that acquired the TXOP contains a pre-amplification-allowed TXOP indicator, the ICF (401) initially transmitted may contain an indicator prohibiting the transmission of PR by non-AP STAs other than the AP (310). If a non-AP STA other than non-AP STA 1 (320) identifies an indicator prohibiting the transmission of PR by non-AP STAs other than the AP (310) within the ICF (401) transmitted by non-AP STA 1 (320), the other non-AP STA may not transmit PR within the TXOP acquired by non-AP STA 1 (320).

[0172] For example, the AP (310) may successfully access a channel on a subchannel using an EDCA random backoff procedure prior to transmitting the TF (445). Thus, the AP (310) may perform the transmission of the TF (445) using the subchannel it successfully accessed (e.g., channels within the operating bandwidth including the main 20 MHz channel and the subchannel) in addition to the channel occupied by the TXOP of the non-AP STA 1 (320). The non-AP STA 2 (330), upon receiving the TF (445) transmitted by the AP (310), may need to change its operating bandwidth to transmit the UL LL data frame. When changing the operating bandwidth, a delay may occur, and the delay may vary depending on the implementation specifications of the non-AP STA. The operating bandwidth switching delay of the non-AP STA 2 (330) described above may have been exchanged during the (re)association process with the AP (310). Accordingly, the AP (310) can use delay information to add padding to the TF (445) to ensure a bandwidth switching delay. Here, the AP (310) can add an Intermediate FCS to the TF (445) to support rapid operation bandwidth switching of the non-AP STA 2 (330). The Intermediate FCS is a frame check sequence inserted in the middle of the TF that allows the non-AP STA to decode only the necessary information and perform channel or bandwidth switching operations. Thus, the non-AP STA 2 (330) that receives the TF transmitted to the AP (310) as a PR can adjust its operation bandwidth to receive the TF and transmit an UL LL data frame after the SIFS time.

[0173] Referring to FIG. 9a, non-AP STA 2 (330), having received a TF (445) that has allocated resources for the transmission of UL LL traffic of non-AP STA 2 (330), can transmit an LL data frame (446) to AP (310) after receiving the TF (445) and SIFS time. AP (310) can receive the LL data frame (446) transmitted by non-AP STA 2 (330) and transmit a BlockAck frame to non-AP STA 2 (330) after SIFS time, and non-AP STA 2 (330) can receive the BlockAck frame transmitted by AP (310). AP (310) can send a BlockAck frame to non-AP STA 2 (330) and, after SIFS time, use the channel (or bandwidth) occupied by the TXOP acquired by non-AP STA 1 (320) to send a BlockAck frame as an acknowledgment frame to the data frame sent by non-AP STA 1 (320), and non-AP STA 1 (320) can receive the BlockAck frame sent by AP (310).

[0174] In another way, referring to FIG. 9b, a TF (447) can be sent to a non-AP STA 1 (320) that is a TXOP holder and to a non-AP STA 2 (330) that has UL LL traffic to allocate a resource unit (RU) for UL TB PPDU transmission. Specifically, the AP (310) can allocate a RU to the non-AP STA 1 (320) to use the channel (or bandwidth) occupied by the TXOP of the non-AP STA 1 (320), and the non-AP STA 2 (330) that has UL LL traffic can allocate a RU to use a channel other than the channel occupied by the TXOP of the non-AP STA 1 (320). Non-AP STA 1 (320) and non-AP STA 2 (330), who have been assigned RUs upon receiving the TF (447) transmitted by AP (310), can use the assigned RUs to receive the TF (447) and, after SIFS time, send a UL TB PPDU containing LL data frame (448-1) and data frame (448-2) to AP (310). Upon receiving the UL TB PPDU containing the data frame (448-2) of non-AP STA 1 (320) and the LL data frame (448-1) of non-AP STA 2 (330), AP (310) can decode the LL data frame (448-1) of non-AP STA 2 (330) and the data frame (448-2) of non-AP STA 1 (320) according to the RUs assigned to the non-AP STAs. AP (310) can send Multi-STA BlockAck frames to non-AP STA 1 (320) and non-AP STA 2 (330) using RUs allocated per non-AP STA. Non-AP STA 1 (320) and non-AP STA 2 (330) that sent UL TB PPDU can receive Multi-STA BlockAck frames sent by AP (310).

[0175] As another example, non-AP STA 1 (320) may receive a response frame (e.g., BlockAck frame or Multi-STA BlockAck) for an LL data frame from non-AP STA 2 (330) and, after SIFS time, perform additional data frame transmission within the remaining time length of the TXOP it initially acquired. If non-AP STA 1 (320) transmits additional data frames, AP (310) may transmit a BlockAck frame for the successfully received data frame from non-AP STA 1 (320) before the time when non-AP STA 1 (320)'s data frame transmission is completed (or the time when non-AP STA 1 (320)'s TXOP is expected to be completed). The additional data frames transmitted by non-AP STA 1 (320) may be transmitted at intervals of XIFS (e.g., PIFS) to support PR transmission. Alternatively, non-AP STA 1 (320) does not support PR transmission and can be transmitted at intervals of SIFS within the remaining time length of the TXOP it first acquired.

[0176] FIGS. 10a to 10c are diagrams illustrating a situation in which a subchannel is occupied during a priority transmission method using wireless LAN subchannel access.

[0177] Referring to FIG. 10a, the AP (310) may attempt to access the channel on the subchannel using an EDCA random backoff procedure. However, the result of the EDCA random backoff procedure performed on the subchannel may be busy. The EDCA random backoff of the main channel may keep the backoff counter at 0 when the backoff counter reaches 0 while the transmission queue is empty, and may keep the backoff counter at 0 when the channel is occupied by another terminal while the backoff counter is maintained at 0.

[0178] However, i) if data occurs in the transmission queue while the channel is in a state of occupancy, the probability of a channel collision may increase immediately after the state of occupancy, so backoff may be resumed (or reinvoke) immediately after data occurs in the transmission queue. Here, in the case of a subchannel, if the AP (310) determines that the subchannel is in a state of occupancy as a result of CCA and that time is before the TF transmission within a TXOP that allows PR, it can be considered a situation similar to the condition in i), so the EDCA random backoff procedure may be resumed (or reinvoke) at the time the subchannel becomes in a state of occupancy. The AP (310) that has resumed (or reinvoke) the EDCA random backoff procedure may update the maximum value of the CW (hereinafter NPCA_CW) used in the subchannel to double.

[0179] As another example, if the current NPCA_CW value is at its maximum value (e.g., NPCA_CWmax), AP (310) may maintain NPCA_CW at NPCA_CWmax. Alternatively, AP (310) may maintain NPCA_CW without change. AP (310) may select a new backoff counter to use in the subchannel within the updated or maintained NPCA_CW. Alternatively, AP (310) may resume (or reinvoke) the EDCA random backoff procedure when the subchannel changes from an occupied state to an idle state.

[0180] As described above, if the result of the EDCA random backoff procedure performed on the main channel is occupied, non-AP STA 1 (320) can perform communication for priority transmission using only the channel (or bandwidth) occupied by the TXOP initially acquired. AP (310) can transmit TF (450) to non-AP STAs (e.g., non-AP STA 1, non-AP STA 2, non-AP STA 3, non-AP STA x) connected to AP (310) to allocate resources for transmitting UL LL traffic that requires priority transmission. However, AP (310) may perform the EDCA random backoff procedure on the main 20 MHz channel before transmitting TF (450). When the result of the EDCA random backoff procedure on the main 20 MHz channel is idle, the AP (310) may transmit a TF (450) to a non-AP STA connected to the AP (310). The TF (450) transmitted by the AP (310) may include a RU assigned to a non-AP STA where UL LL traffic exists, or a RU assigned to non-AP STA 1 together with a non-AP STA where UL LL traffic exists. A non-AP STA that receives the TF (450) transmitted by the AP (310) may use the RU assigned to the non-AP STA to transmit a UL TB PPDU (451) containing at least one of a UL LL data frame and a data frame to the AP (310). The AP (310) that receives the UL TB PPDU (451) transmitted by the non-AP STAs may decode the frames by RU. AP (310) can send Multi-STA BlockAck frames to non-AP STAs that have sent frames within the UL TB PPDU (451), and non-AP STAs that have sent frames within the UL TB PPDU can receive Multi-STA BlockAck.

[0181] Referring to FIG. 10b, a case can be considered in which the result of the EDCA random backoff procedure performed on the side channel as described above is in a occupied state. However, the occupied state may be temporary. Specifically, the occupied state of the NPCA side channel may change to an idle state before the transmission of the PR (449) of the non-AP STA (or before the AP (310) transmits the TF after receiving the PR transmitted by the non-AP STA). In the case described above, the AP (310) may resume (or reinvoke) the EDCA random backoff procedure at the time when the side channel transitions from the occupied state to the idle state. If the result of the reinvoked EDCA random backoff procedure is idle, the AP (310) may succeed in accessing the channel on the subchannel and may send TF (452) to the non-AP STA that sent PR (449) using the channel (or bandwidth) that succeeded in accessing, along with the channel occupied by the TXOP of non-AP STA 1.

[0182] Referring to FIG. 10c, the AP (310) may be aware of the presence of scheduled UL LL traffic on non-AP STA 2 (330). Therefore, the AP (310) may want to transmit PR (453) during the TXOP of non-AP STA 1. The AP (310) may attempt to access the channel on the subchannel using the EDCA random backoff procedure described above in order to use a wider channel (or bandwidth) resource if possible. However, the result of the EDCA random backoff procedure performed on the subchannel before the AP (310) transmits PR (453) may be occupied. Accordingly, the AP (310) can transmit PR (453) to non-AP STAs (e.g., non-AP STA 2 alone, non-AP STA 1 including non-AP STA 2, non-AP STA 3 including non-AP STA 3, non-AP STA x including non-AP STA 2, etc.) using only the channel (or bandwidth) occupied by the TXOP initially acquired by non-AP STA 1. After transmitting PR (453), the AP (310) can allocate resources so that only non-AP STAs with UL LL traffic can transmit for UL LL data priority transmission. Alternatively, the AP (310) can perform the priority transmission procedure by allocating resources for transmission to other non-AP STAs, including non-AP STAs with UL LL traffic.

[0183] FIG. 11 is a flowchart showing the operation of an STA in a wireless LAN to which the present disclosure applies.

[0184] Referring to FIG. 11, the STA can transmit a first frame related to priority transmission after a first predetermined time from the point when the medium transitions from an occupied state to an idle state (S1110). After that, the STA performs a random backoff procedure after the transmission of the first frame is completed (S1120), and based on the random backoff procedure, can occupy the medium and transmit a second frame related to a first type of traffic (S1130). Here, the random backoff procedure may be a random backoff procedure in which STAs related to the transmission of the first type of traffic that transmits the first frame participate. Additionally, the first frame may be transmitted at the slot boundary of the point when the medium is in an idle state for a first predetermined time from the point when the medium transitions from an occupied state to an idle state. Additionally, the STA may perform channel sensing on a plurality of 20 MHz channels, including a main 20 MHz channel within the STA's bandwidth, for a second pre-set time before transmitting the first frame, and transmit the first frame through at least one channel including an idle main 20 MHz channel among the plurality of 20 MHz channels including a main 20 MHz channel, based on the channel sensing result. Here, the STA may transmit the first frame by duplicating it in 20 MHz units on at least one channel including an idle main 20 MHz channel.

[0185] Additionally, the STA can transmit the first frame on the main 20 MHz channel. After the transmission of the first frame is completed, the STA checks that the medium is idle for a second set time on the main 20 MHz channel, and can transmit the third frame by occupying the medium based on a backoff counter at the slot boundary at the time when the medium is idle.

[0186] Additionally, the STA may occupy the medium and perform channel sensing on a plurality of 20 MHz channels, including a main 20 MHz channel within the STA's bandwidth, for a third pre-set time before transmitting the third frame, and, based on the channel sensing result, transmit the third frame through at least one channel including an idle main 20 MHz channel among the plurality of 20 MHz channels including a main 20 MHz channel. Here, the third frame is a request to send (RTS) frame, and after transmitting the RTS frame and receiving a clear to send (CTS) frame, the STA may transmit a second frame associated with the first type of traffic. Additionally, the first frame may be a clear to send (CTS) frame in which the recipient address is a specific address.

[0187] Additionally, the first type of traffic may be low-latency traffic. Here, the low-latency traffic may be traffic corresponding to the VO (voice) of the channel access category (AC). Additionally, the first frame may be a preemption request (PR) frame.

[0188] Additionally, the STA transmits a first frame and receives a third frame instructing the transmission of first-type traffic related to priority transmission, wherein the third frame may be a frame transmitted by the AP to at least one STA within the basic service set (BSS). Additionally, the STA transmits a fourth frame in response to the third frame indicating the presence of first-type traffic, receives resource allocation from the AP via a fifth frame based on the fourth frame, and can transmit a second frame related to first-type traffic through the allocated resource. Additionally, the STA receives random access resource allocation based on the third frame and can transmit a second frame related to first-type traffic on a channel occupied based on channel contention. Additionally, the STA may be a non-AP STA or an AP STA.

[0189] 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.

[0190]

[0191] The above-mentioned matters may also be applied to other systems.

Claims

1. In the method of operation of a station (STA) in a wireless LAN system, A step of transmitting a first frame related to priority transmission after a first set time from the point in time when the medium switches from an occupied state to an idle state; A step of performing a random backoff procedure after the completion of the first frame transmission; and A method of operation comprising the step of occupying the medium based on the above random backoff procedure and transmitting a second frame associated with a first type of traffic.

2. In Paragraph 1, The above random backoff procedure is a method of operation in which STAs associated with the first type of traffic transmission transmitting the above first frame participate in the random backoff procedure.

3. In Paragraph 1, A method of operation in which the first frame is transmitted at the slot boundary of the time when the medium is in an idle state for the first set time from the time when the medium switches from an occupied state to an idle state.

4. In Paragraph 3, A method of operation in which the STA performs channel sensing in a plurality of 20 MHz channels including a main 20 MHz channel within the bandwidth of the STA for a second preset time before transmitting the first frame, and transmits the first frame through at least one channel including the main 20 MHz channel that is idle among the plurality of 20 MHz channels including the main 20 MHz channel according to the channel sensing result.

5. In Paragraph 4, A method of operation in which the above STA duplicates and transmits the above first frame in 20 MHz units on at least one channel including the idle main 20 MHz channel.

6. In Paragraph 3, The above STA is a method of operation in which the above STA transmits the above first frame on a main 20 MHz channel.

7. In Paragraph 1, A method of operation in which the above STA confirms that the medium is idle for a second set time in a main 20 MHz channel after the first frame transmission is completed, and occupies the medium based on a backoff counter at the slot boundary at the time when the medium is idle to transmit a third frame.

8. In Paragraph 7, A method of operation in which the STA occupies the medium and performs channel sensing in a plurality of 20 MHz channels including a main 20 MHz channel within the bandwidth of the STA for a third preset time before transmitting the third frame, and transmits the third frame through at least one channel including the main 20 MHz channel that is idle among the plurality of 20 MHz channels including the main 20 MHz channel according to the channel sensing result.

9. In Paragraph 8, A method of operation in which the third frame is an RTS (request to send) frame, transmits the RTS frame, receives a CTS (clear to send) frame, and then transmits the second frame associated with the first type of traffic.

10. In Paragraph 1, The above first frame is a CTS (clear to send) frame in which the recipient address is a specific address, a method of operation.

11. In Paragraph 1, The above-mentioned first type of traffic is a low-latency traffic, a method of operation.

12. In Paragraph 11, The above low-latency traffic is a method of operation in which the traffic corresponds to the VO (voice) of the channel access category (AC).

13. In Paragraph 1, A method of operation in which the first frame above is a preemption request (PR) frame.

14. In Paragraph 11, A method of operation in which the STA transmits the first frame and receives the third frame instructing the transmission of the first type of traffic associated with priority transmission, wherein the third frame is a frame transmitted by the AP to at least one STA in the basic service set (BSS).

15. In Paragraph 14, A method of operation in which the STA transmits a fourth frame indicating the existence of the first type of traffic in response to the third frame, allocates resources from the AP via a fifth frame based on the fourth frame, and transmits the second frame related to the first type of traffic through the allocated resources.

16. In Paragraph 14, A method of operation in which the above STA is allocated a random access resource based on the above third frame and transmits the above second frame associated with the above first type traffic on a channel occupied based on channel contention.

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

18. In a wireless LAN system, regarding a station (STA), At least one transceiver for transmitting and receiving signals; At least one processor controlling the above-mentioned at least one transmitting and receiving unit; and It includes a memory that stores instructions for the STA to perform a specific operation by the at least one processor, and The above specific operation is: After a first set time from the point in time when the medium switches from an occupied state to an idle state, a first frame related to priority transmission is transmitted, and After the completion of the transmission of the first frame above, a random backoff procedure is performed, and STA that occupies the medium based on the above random backoff procedure and transmits a second frame associated with the first type of traffic.

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