Low-latency channel access operation method and device in wireless LAN

Abstract

An STA in a wireless LAN system confirms that a channel is switched from an occupied state to an idle state and the channel is in the idle state for a first preset time, wherein the STA can: perform channel access through P-EDCA; transmit a DS after the first preset time; perform a backoff procedure after transmitting the DS; and perform frame transmission at a slot boundary where a backoff counter reaches 0.

Description

Wireless LAN Low-Latency Channel Access Operation Method and Device

[0001] The present disclosure relates to a method and apparatus for low-latency channel access operations of a wireless local area network (WLAN). Specifically, it relates to a method and apparatus for setting a transmission interval during low-latency channel access of a wireless LAN. Furthermore, the present disclosure relates to a method and apparatus for preventing frame transmission collisions caused by low-latency channel access when performing low-latency channel access operations of a wireless LAN. Additionally, the present disclosure relates to a method and apparatus for ensuring channel contention fairness during priority channel access operations of a wireless LAN.

[0002]

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

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

[0005] As applications requiring higher reliability emerge, the IEEE 802.11bn standard, an Ultra High Reliability (UHR) wireless LAN technology, is being developed for single Basic Service Set (BSS) environments and / or redundant BSS environments. The goal of the IEEE 802.11bn standard may be to support improved data transmission speeds, enhanced latency performance, and reduced data error rates. Additionally, the IEEE 802.11bn standard can support low-power operation, peer-to-peer communication, and operations designed to increase channel utilization. It can also support a TXOP sharing method, where wireless LAN terminals share communication resources 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). In addition, wireless LAN standards can support a high-priority channel access method that performs channel access preferentially for low-latency frame transmission.

[0006] However, when using the high-priority channel access method, the fairness of the high-priority channel access operation may decrease depending on the transmission interval included in the frame, and low-latency communication performance may decrease due to the enhancement of high-priority channel access. The following describes an operation method that takes the above into consideration.

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

[0008]

[0009] The present disclosure relates to a method and apparatus for low-latency channel access operation of a wireless LAN.

[0010] The present disclosure relates to a method and apparatus for setting a transmission interval in low-latency channel access of a wireless LAN.

[0011] The present disclosure relates to a method and apparatus for setting a frame transmission interval when using a high-priority channel access method.

[0012] The present disclosure relates to a method and apparatus for preventing frame transmission collisions caused by low-latency channel access when performing a low-latency channel access operation of a wireless LAN.

[0013] The present disclosure relates to a method and apparatus for setting channel access parameters differently to prevent frame transmission collisions when using a high-priority channel access method.

[0014] The present disclosure relates to a method and apparatus for ensuring channel contention fairness during priority channel access operations of a wireless LAN.

[0015] The present disclosure relates to a method and apparatus for releasing a timer for virtual media detection when certain conditions are satisfied after a successful transmission of a data frame based on a high-priority channel access operation.

[0016] 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.

[0017]

[0018] According to one embodiment of the present specification, a method of operation of a station (STA) in a wireless LAN system may include the step of the STA confirming that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first predetermined time, wherein the STA performs channel access through P-EDCA (prioritized enhanced distributed channel access), transmits a DS (defer signal) after the first predetermined time, performs a backoff procedure after transmitting the DS, and performs frame transmission at the slot boundary where the backoff counter reaches 0.

[0019] Additionally, according to one embodiment of the present specification, a station (STA) in a wireless LAN system comprises at least one transceiver for transmitting and receiving signals, at least one processor for controlling at least one transceiver, and a memory for storing instructions that cause a non-AP STA to perform a specific operation by the at least one processor, wherein the specific operation is: the STA confirms that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first predetermined time, wherein the STA performs channel access via P-EDCA (prioritized enhanced distributed channel access), transmits a DS (defer signal) after the first predetermined time, and performs a backoff procedure after the DS transmission, and can perform frame transmission at the slot boundary where the backoff counter reaches 0.

[0020] In addition, according to one embodiment of the present specification, a method of operation of a station (STA) in a wireless LAN system may include the step of confirming that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first predetermined time, wherein the STA performs channel access through P-EDCA (prioritized enhanced distributed channel access), the step of detecting a DS (defer signal) transmitted from another STA within the first predetermined time, the step of performing a backoff procedure when the STA detects the DS, wherein the backoff procedure is performed based on the DS transmitted to another STA, and the step of performing frame transmission at a slot boundary where the backoff counter reaches 0 when the STA occupies the channel based on channel occupancy competition with another STA.

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

[0022] Additionally, according to one embodiment of the present specification, the first set time may be determined based on P-EDCA related parameters.

[0023] In addition, according to one embodiment of the present specification, when P-EDCA is used in a basic service set (BSS) that includes STA, P-EDCA related parameters may be determined based on at least one of basic parameter values ​​and modified parameter values.

[0024] Additionally, according to one embodiment of the present specification, the first set time may be determined based on the change parameter value.

[0025] Additionally, according to one embodiment of the present specification, the first set time is an AIFS (arbitrary interframe space) associated with the transmission of DS, the AIFS is a time set based on the sum of aSIFSTime and N*aSlotTime, and N can be determined based on at least one of a basic parameter value and a change parameter value.

[0026] In addition, according to one embodiment of the present specification, the first set time is a time set based on EIFS (extended interframe space), wherein EIFS is a time set based on at least one of failure to detect a frame transmitted by another STA in a channel occupancy state or occurrence of a reception error, and EIFS may be a time set as the sum of 2*aSIFSTime, N*aSlotTime, and AckTxTime.

[0027] Additionally, according to one embodiment of the present specification, if an error occurs in the last detected frame while the channel is occupied, the STA may transmit a DS for P-EDCA competition based on at least one of a first set time, a response waiting time of the frame, and a NAV waiting time associated with the frame.

[0028] Additionally, according to one embodiment of the present specification, DS may be transmitted at the first slot boundary by a first set time elapsed after the frame in which an error occurred while the channel is occupied.

[0029] Additionally, according to one embodiment of the present specification, the STA may transmit a frame at the slot boundary where the backoff counter reaches 0 by occupying the channel based on a backoff procedure after DS transmission, and if a response frame for the frame is not detected within the response waiting time, the DS may be retransmitted after a second set time from the time when the frame transmission is completed or from the time when the response waiting time has elapsed from the time when the frame transmission is completed.

[0030] In addition, according to one embodiment of the present specification, a NAV is set in at least one STA that performs channel access via P-EDCA based on a frame transmitted by the STA, wherein the NAV set in the at least one STA is released if a response frame for the frame is not detected within a response waiting time, and a DS transmission by the at least one STA may also be performed together with the DS transmission of the STA after a second set time from the time when the frame transmission is completed.

[0031] Additionally, according to one embodiment of the present specification, the second set time may be determined based on P-EDCA related parameters.

[0032] In addition, according to one embodiment of the present specification, the second set time is AIFS or EIFS, and NAV is set in at least one STA that performs channel access through P-EDCA based on a frame transmitted by the STA, and the NAV set in the at least one STA is released after the second set time from the time when frame transmission is completed, so that DS transmission by at least one STA can also be performed together with DS transmission of the STA.

[0033] Additionally, according to one embodiment of the present specification, a STA is a TXOP responder for a transmit opportunity (TXOP) set by another STA, and a network allocation vector (NAV) may be set for at least one STA that performs channel access via P-EDCA by frame exchange between the STA and another STA within the TXOP.

[0034] In addition, according to one embodiment of the present specification, when a NAV is not set on a STA that is a TXOP responder and the channel is switched from an occupied state to an idle state due to the early termination of frame exchange between the STA and another STA within the TXOP, the STA may wait until the time of termination of the NAV set on at least one STA that performs channel access through P-EDCA, and transmit a DS after a first set time.

[0035] In addition, according to one embodiment of the present specification, NAV is set in the STA, which is a TXOP responder, and the channel is detected to be in an occupied state until the end of NAV, and when NAV is released, DS can be transmitted after a first set time.

[0036] In addition, according to one embodiment of the present specification, if the frame exchange between the STA and another STA within the TXOP is terminated early, the NAV set in at least one STA performing channel access via P-EDCA is terminated at the time of receiving the CF (contention free)-end frame, and the STA transmits the DS after a first set time at the time of receiving the CF-end frame, and the DS transmitted by at least one STA performing channel access via P-EDCA may also be transmitted together after a first set time at the time of receiving the CF-end frame.

[0037] In addition, according to one embodiment of the present specification, when a STA performs a backoff procedure after transmitting a DS, a backoff procedure is also performed at another STA that received the DS, and if the channel is occupied by another STA based on the other backoff procedure, the STA may retransmit the DS after a first set time from the time when the channel occupation by the other STA ends.

[0038] Additionally, according to one embodiment of the present specification, the STA may be a non-AP STA or an AP STA.

[0039]

[0040] According to the present disclosure, a method for low-latency channel access operation of a wireless LAN can be provided.

[0041] According to the present disclosure, a method for setting a transmission interval in low-latency channel access of a wireless LAN can be provided.

[0042] According to the present disclosure, a method for setting a frame transmission interval when using a high-priority channel access method can be provided.

[0043] According to the present disclosure, a method can be provided to prevent frame transmission collisions caused by low-latency channel access when performing a low-latency channel access operation of a wireless LAN.

[0044] According to the present disclosure, a method for setting channel access parameters differently to prevent frame transmission collisions when using a high-priority channel access method can be provided.

[0045] According to the present disclosure, a method can be provided to ensure channel contention fairness during priority channel access operations of a wireless LAN.

[0046] According to the present disclosure, a method for releasing a timer for virtual media detection can be provided when certain conditions are satisfied after a successful transmission of a data frame based on a high-priority channel access operation.

[0047] 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.

[0048] 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.

[0049]

[0050] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0051] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0052] FIG. 3 is a diagram illustrating a method for indicating HiP EDCA and channel access parameters when using High Priority (HiP) Enhanced Distributed Channel Access (EDCA) wireless LAN applicable to the present disclosure.

[0053] FIGS. 4a and 4b are drawings illustrating a frame collision prevention method when using a wireless LAN HiP EDCA applied to the present disclosure.

[0054] FIGS. 5a to 5d are drawings illustrating a method for preventing frame collisions when using a wireless LAN HiP EDCA according to the present disclosure.

[0055] FIG. 6 is a diagram illustrating a low-latency operation method when a difference in the reception time of a Defer Signal occurs when using a wireless LAN HiP EDCA applied to the present disclosure.

[0056] FIG. 7 is a diagram illustrating a method for indicating PEDCA and channel access parameters when using Prioritized Enhanced Distributed Channel Access (PEDCA) for wireless LANs applicable to the present disclosure.

[0057] FIG. 8 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0058] FIG. 9 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0059] FIG. 10 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0060] FIG. 11 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0061] FIG. 12 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0062] FIG. 13 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0063] FIG. 14 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0064] FIG. 15 is a diagram illustrating a method for indicating PEDCA and channel access parameters when using wireless LAN PEDCA applicable to the present disclosure.

[0065] FIG. 16 is a diagram illustrating a PEDCA channel access method applied to the present disclosure.

[0066] FIG. 17 is a diagram illustrating the DS transmission method of PEDCA when a frame reception error occurs, applicable to the present disclosure.

[0067] FIGS. 18a and FIGS. 18b are diagrams illustrating the problem of transmission collision occurring in PEDCA applicable to the present disclosure and the channel access method when transmission collision occurs in PEDCA.

[0068] FIGS. 19a to 19c are drawings illustrating problems that occur when RTS transmission fails in PEDCA applicable to the present disclosure, and methods for media detection and channel access when RTS transmission fails in PEDCA.

[0069] FIGS. 20a and 20b are diagrams illustrating problems that occur during RTS transmission collisions in PEDCA applicable to the present disclosure and methods for media detection and channel access when RTS transmission fails in PEDCA.

[0070] FIG. 21 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies.

[0071]

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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."

[0079] 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.

[0080] 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).

[0081] 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).

[0082] 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).

[0083] 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.

[0084] 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.

[0085] The following describes a method for fairly performing high-priority channel access operations when using a high-priority channel access method, even when the actual frame transmission completion time differs from the frame transmission completion time pre-set based on the transmission interval information included in the frame. Through the above, the low-latency performance of a wireless LAN network can be enhanced.

[0086] In addition, the following describes a method to differentiate channel access parameters from those used in general channel access when using a high-priority channel access method. Through the above, frame transmission collisions during channel access can be prevented.

[0087] Furthermore, the following describes a method for wireless LAN terminals to fairly re-access the channel using high-priority channel access operations even when a collision occurs during the use of high-priority channel access operations. Through the above, the high-priority channel access method can be used while maintaining fairness among wireless LAN terminals, and the performance of the wireless LAN network can be improved.

[0088] FIG. 3 is a diagram illustrating a method for indicating HiP EDCA and channel access parameters when using High Priority (HiP) Enhanced Distributed Channel Access (EDCA) wireless LAN applicable to the present disclosure.

[0089] Referring to FIG. 3, a case can be considered in which an AP (310) and multiple non-AP STAs (e.g., STA 1, STA 2, STA 3) connected to the AP (310) operate in a wireless LAN network. Here, the AP (310) and the multiple STAs connected to the AP (310) can form a basic service set (BSS). The AP (310) can instruct the use of High Priority (HiP) EDCA within the BSS. The AP (310) can instruct the use of HiP EDCA within the BSS through at least one of a beacon and a probe response frame. For example, whether HiP EDCA is used can be indicated through a HiP EDCA Enabled bit included in the frame. If HiP EDCA is not used, the HiP EDCA Enabled bit can be set to 0. As another example, if HiP EDCA is not used, the HiP EDCA Enabled bit may not be included in the frame. On the other hand, if HiP EDCA is used, the HiP EDCA Enabled bit may be set to 1.

[0090] Additionally, if the STA intends to use HiP EDCA, the STA may transmit a frame requesting the HiP EDCA Enabled instruction to the AP (310). For example, the STA may transmit to the AP (310) a management frame with the HiP EDCA Enabled indicator set to 1, using at least one of a link reconfiguration request frame, an action frame, and other frames. Through the above description, the STA may request the HiP EDCA Enabled instruction from the AP (310). Subsequently, when the STA obtains at least one of a beacon, a probe response, an action frame, and other frames with the HiP EDCA Enabled indicator set to 1 from the AP (310), the STA may use the HiP EDCA operation from the time the frame is received.

[0091] When the HiP Enabled bit is set to 1 to indicate the use of HiP within the BSS, additional channel access parameters to prevent frame collisions when using HiP may be included and indicated. For example, channel access parameters for an STA using HiP (i.e., EDCA channel access parameters) may be provided by including them in the frame. The aforementioned parameters may be HiP EDCA parameters, but are not limited to those names.

[0092] The HiP EDCA parameter may include at least one of CWmin[HiP], CWmax[HiP], and AIFSN[HiP]. CWmin[HiP] and CWmax[HiP] may indicate the minimum and maximum values ​​of the contention window (CW) for selecting the backoff counter for the short backoff operation performed when using HiP. AIFSN[HiP] may be a parameter for determining the length of the arbitrary interframe space (AIFS), which is the time during which channel sensing must be performed before transmitting a defer signal (DS), which is a special frame or signal. The above-mentioned parameter may be a parameter for preventing transmission by STAs other than the STA that must transmit low-latency frames during HiP operation. For example, if AIFSN[HiP] is 2, AIFS[HiP] is 'aSIFS(short interframe space)Time + 2 * aSlotTime'. Or, if AIFSN[HiP] is 3, AIFS[HiP] is 'aSIFS(short interframe space)Time + 3 * aSlotTime'. For example, if AIFSN[HiP] is 2, AIFS[HiP] can be equal to DIFS(DCF(distributed coordinated function) interframe space).

[0093] Here, when HiP is used within BSS, default HiP EDCA parameters may be used. Here, the default HiP EDCA parameters may be values ​​determined in advance or values ​​set by default. For example, AIFSN[HiP] may be determined based on the default HiP EDCA parameters.

[0094] Alternatively, if the HiP is used within the BSS, EDCA parameters modified from the default values ​​may be specified. The modified EDCA parameters may be included in an EDCA parameter element. The EDCA parameter element may be included in a beacon frame or a probe response frame. If the HiP is used within the BSS, a non-AP STA 1 (320) using the HiP may use a low-latency channel access operation because low-latency frame transmission is required.

[0095] AIFS[HiP] is a competition window for random channel access. It can be determined based on parameters. For example, AP (310) indicates AIFSN[HiP] as 2, and Parameters can be specified. In the above case, 'AIFS[HiP] = aSIFSTime + (2 + CW) * aSlotTime', and CW is [0, ] It may be an integer value selected based on a uniform probability distribution in a contention window. The CW may be selected before the STA transmits the DS each time. As a specific example, AP (310) If the parameter is set to 0, CW can always be 0. For example, as the default HiP EDCA parameter value The parameter can be determined to be 0, and if AIFS[HiP] is determined based on the basic HiP EDCA parameter value, CW can be 0, but is not limited to such embodiments.

[0096] As another example, AP(310) is The parameter can be set to a non-zero integer. For example, AP (310) based on the changed EDCA parameter instruction The parameter can be set to a non-zero integer, but is not limited thereto. Here, in order to prevent collisions between the transmission of VO traffic between HiP EDCA and the existing EDCA, g can be set to an integer greater than 0. [0, If the integer value selected based on a uniform probability distribution in a competition window is 0, the STA may discard the aforementioned value and select an integer again based on a uniform probability distribution until a non-zero value is selected. Or, If is a non-zero value, the competition window is [0, [1, not ] It can be used as ], but is not limited thereto. As another example, STA is [0, ] It can be used even when the integer value selected based on a uniform probability distribution in a competition window is 0, and is not limited to a specific form.

[0097] Alternatively, the CW may be selected in a different way. The STA may record the number of DS transmission attempts using the DSRC (defer signal retry count). The STA may increment the DSRC by 1 each time the DS is transmitted. For example, the initial value of the DSRC may be 0. If the STA successfully transmits a frame to the AP (310) after the DS transmission and initializes QSRC[VO] to 0, the DSRC may also be initialized to 0. As another example, if QSRC[VO] is initialized to 0 due to multiple transmission failures, the DSRC may be initialized to 0. The STA may determine the CW based on the above-described DSRC. For example, the CW value may be [0, * ( + 1) - 1] may be an integer value selected based on a uniform probability distribution in a competition window. Or, the value of CW is [0, [+ DSRC] may be an integer value selected based on a uniform probability distribution in the contention window. That is, as the number of DS transmissions increases, the CW value increases, and DS transmission collisions can be prevented.

[0098] Next, the procedure for a low-latency channel access operation can be considered. non-AP STA 1 (320) and non-AP STA 2 (330) can perform a channel access operation when the medium is detected to be occupied due to transmission by another STA (e.g., AP, STA 3), and the medium is switched to an idle state after frame transmission is completed. non-AP STA 1 (320) can check whether the medium is idle for an AIFS[HiP] time for low-latency frame transmission. If the medium is idle for an AIFS[HiP] time, non-AP STA 1 (320) can transmit a DS. After transmitting the DS, non-AP STA 1 (320) performs a short backoff operation again (e.g., [0, Backoff counter selection and decrement can be performed from integer values ​​selected by a uniform random distribution between ]. Here, The minimum value of CWmin[HiP] and the maximum value of CWmax[HiP] may be CWmax[HiP]. Meanwhile, non-AP STA 2 (330) does not transmit low-latency frames, but there may be AC ​​(access category) VO frames that need to be transmitted. Here, the AC_VO backoff counter of non-AP STA 2 (330) may reach 0. Since the backoff counter of non-AP STA 2 (330) is 0, it performs channel access when the medium becomes idle, and can transmit a frame immediately when the medium remains idle for AIFS[VO] time. In the same way, if AIFS[VO] and AIFS[HiP] are the same, a transmission collision may occur between non-AP STA 1 (320) and non-AP STA 2 (330). Low-latency channel access by non-AP STA 1 (320) may no longer be possible because the channel becomes occupied due to the uplink frame of non-AP STA 2 (330). Additionally, the DS of non-AP STA 1 (320) may cause a collision with the uplink frame of non-AP STA 2 (330), and transmission may fail. Therefore, both low-latency frame transmission and transmission of general data of the wireless LAN may fail during HiP operation. Considering the above points, a method to prevent frame collisions when using HiP may be required.

[0099] For example, DS can be a CTS (clear to send) frame or a specific signal containing all or part of a PHY preamble. When DS is transmitted, if no frame collision occurs, access to the medium by STAs that did not transmit DS can be prevented. This allows STAs that need to transmit low-latency frames to access the medium first and transmit low-latency frames.

[0100] FIGS. 4a and 4b are drawings illustrating a frame collision prevention method when using a wireless LAN HiP EDCA applied to the present disclosure.

[0101] Referring to FIGS. 4a and 4b, HiP can be used in a wireless LAN BSS as described in FIG. 3 above, and the AP (310) can instruct the STAs connected to the AP (310) to use HiP. For example, the STAs connected to the AP (310) may include non-AP STA 1 (320), non-AP STA 2 (330), non-AP STA 3 (340), and non-AP STA 3 (350). Here, non-AP STA 1 (320) and non-AP STA 2 (330) may be STAs that support UHR (ultra high reliability). Accordingly, non-AP STA 1 (320) and non-AP STA 2 (330) can identify at least one of the HiP Enabled bit and HiP element of the AP (310) from at least one of the beacon frame, probe response frame, and other frames. Through the above description, non-AP STA 1 (320) and non-AP STA 2 (330) can identify that HiP is being used within the BSS. Here, since there is a low-latency frame to be transmitted, non-AP STA 1 (320) may want to perform a channel access operation using HiP as shown in FIG. 3. non-AP STA 2 (330) may recognize that HiP is being used in the BSS but since there is no separate low-latency frame, it may want to access the channel using a standard EDCA operation. Additionally, STA 3 may be a legacy STA that does not support UHR. Therefore, it may not be possible to recognize that HiP is being used within the BSS, and HiP may not be supported. Thus, the non-AP STA 3 (340) can access the channel using normal EDCA operation regardless of whether HiP is being used in the BSS. The above-described situation is for convenience of explanation only and is not limited thereto.

[0102] AP (310) can be configured so that AIFSN[HiP], which is a channel access parameter indicated in the HiP element indicated in FIG. 3, and AIFSN[AC], which is a channel access parameter used in general EDCA operation (specifically, AIFSN for each VO (voice), VI (video), BE (best effort), and BK (background)), do not have the same value. If AIFSN[HiP] has a value greater than the AIFSN[AC] with the smallest value among the AIFSN[AC]s for each AC, the channel access priority of the STA using HiP EDCA may be lower than that of the STA using general EDCA. On the other hand, if AIFSN[HiP] has a value smaller than the AIFSN[AC] with the smallest value among the AIFSN[AC]s for each AC, the channel access priority of the STA using HiP EDCA may be higher than that of the STA using general EDCA.

[0103] Referring to FIG. 4a, the value of AIFSN[HiP] may be smaller than AIFSN[VO], which is AIFSN[AC] for AC_VO, the AC with the highest priority. Here, the medium may be detected as occupied due to transmission by non-AP STA 3 (350), and the medium may be switched back to an idle state when transmission by non-AP STA 3 (350) is completed. non-AP STA 1 (320) may want to transmit DS (401) to transmit a low-latency frame. Additionally, non-AP STA 2 (330) and non-AP STA 3 (340) may want to transmit their uplink frames to AP (310) using standard EDCA channel access. When the medium is switched back to an idle state, non-AP STA 1 (320) through non-AP STA 3 (340) may perform channel access operations. non-AP STA 1 (320) may wait for AIFS[HiP] to transmit DS (401). Here, AIFS[HiP] may be shorter than the AIFS[VO] of other STAs. Thus, non-AP STA 1 (320) may be the first to access the channel, even if the backoff counter of non-AP STA 2 (330) or non-AP STA 3 (340) is 0, and the channel is idle for AIFS[VO] and frame transmission is possible immediately afterward. non-AP STA 1 (320) may transmit DS (401) to stop further channel access by non-AP STA 2 (330) and non-AP STA 3 (340), and non-AP STA 1 (320) may perform a short backoff operation. If the backoff operation is successful, the non-AP STA 1 (320) can send a low-latency frame (e.g., a low-latency uplink frame, 402) to the AP (310).

[0104] Referring to FIG. 4b, the value of AIFSN[HiP] may be greater than AIFSN[VO], which is AIFSN[AC] for AC_VO, the AC with the highest priority. When the transmission of non-AP STA 3 (350) is completed, the medium may be switched back to an idle state. non-AP STA 1 (320) may want to transmit DS to transmit a low-latency frame. Additionally, non-AP STA 2 (330) and non-AP STA 3 (340) may want to transmit their uplink frames to the AP (310) using standard EDCA channel access. When the medium is switched back to an idle state, non-AP STA 1 (320) through non-AP STA 3 (340) may perform channel access operations. non-AP STA 1 (320) may wait for AIFS[HiP] to transmit DS. Here, AIFS[HiP] may be a larger value than the AIFS[VO] of other STAs. Thus, if the AC_VO backoff counter of non-AP STA 2 (330) is 0, non-AP STA 2 (330) can transmit an uplink frame (403) if the channel is idle during AIFS[VO]. That is, since the AIFSN[HiP] of non-AP STA 1 (320) is longer than AIFS[VO], non-AP STA 1 (320) waits for AIFS[HiP] again after the frame transmission of non-AP STA 2 (330) is completed, and can transmit a DS if the medium is idle during the AIFS[HiP] time.

[0105] FIGS. 5a to 5d are drawings illustrating a method for preventing frame collisions when using a wireless LAN HiP EDCA according to the present disclosure.

[0106] Referring to FIGS. 5a through 5d, HiP is used in a wireless LAN BSS as in FIG. 3, and the AP (310) can instruct the STAs connected to the AP (310) to use HiP. Here, the STAs connected to the AP (310) may be non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340). Here, non-AP STA 1 (320) and non-AP STA 2 (330) may be STAs that support UHR (ultra high reliability). Accordingly, non-AP STA 1 (320) and non-AP STA 2 (330) can verify at least one of the HiP Enabled bit and HiP element of the AP (310) through at least one of a beacon frame, a probe response frame, and other frames. As described above, non-AP STA 1 (320) and non-AP STA 2 (330) can confirm that HiP is used within the BSS. Here, since there is a low-latency frame to be transmitted, non-AP STA 1 (320) may want to perform a channel access operation using HiP as shown in FIG. 3. non-AP STA 2 (330) may recognize that HiP is used in the BSS, but since there is no separate low-latency frame, it may want to access the channel using a general EDCA operation. AIFSN[HiP], which is the channel access parameter indicated by the AP (310) in the HiP element, and AIFSN[AC], which is the channel access parameter used in the general EDCA operation (specifically, AIFSN for each VO (voice), VI (video), BE (best effort), and BK (background)), may have the same value as AIFSN[HiP]. For example, AIFSN[HiP] may be set to the same value as AIFSN[VO].In the above case, AP (310) may instruct HiP EDCA to use AC_VO AIFSN instead of instructing a separate AIFSN for HiP EDCA.

[0107] Referring to FIG. 5a, the medium may be detected as occupied due to transmission by non-AP STA 3 (340), and the medium may be switched back to an idle state when transmission by non-AP STA 3 (340) is completed. non-AP STA 1 (320) may want to transmit DS to transmit a low-latency frame. Additionally, non-AP STA 2 (330) may want to transmit its uplink frame to AP (310) using standard EDCA channel access. Here, if AIFSN[HiP] and AIFSN[VO] are the same, and non-AP STA 2 (330) performs transmission using standard EDCA channel access when the backoff counter of AC_VO is 0, a collision may occur between the DS transmitted by STA 1 and the AC_VO frame of non-AP STA 2 (330), and an action may be required to reduce the possibility of the aforementioned collision.

[0108] Specifically, when non-AP STA 2 (330) waits for AIFS[VO] in a BSS where HiP enabled is enabled, with AIFSN[HiP] and AIFSN[VO] being the same and the backoff counter of AC_VO being 0, non-AP STA 2 (330) can perform frame transmission using HiP even without transmitting a low-latency frame. Here, when the medium is switched back to an idle state, non-AP STA 2 (330) and non-AP STA 1 (320) can wait for the same AIFS time (i.e., AIFS[HiP] or AIFS[VO]). In the above case, non-AP STA 1 (320) and non-AP STA 2 (330) can transmit DS (404-1, 404-2) simultaneously. The non-AP STA 2 (330) may schedule the transmission of DS (404-2) at a time prior to the end of AIFS[VO] to transmit DS (404-2). For example, the non-AP STA 2 (330) may insert DS at the very front of the transmission queue of AC_VO. Alternatively, the non-AP STA 2 (330) may transmit DS as part of a control frame transmitted before transmitting a frame of the AC_VO transmission queue. Here, the timing at which the non-AP STA 2 (330) schedules the transmission of DS can be implemented in various forms. The non-AP STA 2 (330) may decrease the backoff counter of AC_VO to 0 and then perform the DS (404-2) transmission scheduling operation when channel occupancy is detected prior to the slot boundary. The non-AP STA 1 (320) and non-AP STA 2 (330) that transmitted DS (404-1, 404-2) can perform a short backoff operation. If the backoff counter of non-AP STA 2 (330) is shorter, non-AP STA 2 (330) can transmit an uplink frame (405) to the AP (310).non-AP STA 1 (320) can transmit DS if the medium is idle again during AIFS[HiP] after the transmission of the uplink frame by non-AP STA 2 (330). For example, if non-AP STA 2 (330) does not get a transmission opportunity during a short backoff operation, non-AP STA 2 (330) can schedule the transmission of DS in the same manner as described above. That is, non-AP STA 2 (330) can perform a contention through a short backoff operation by transmitting DS after waiting for AIFS[VO] when the TXOP of non-AP STA 1 (320) is completed.

[0109] Referring to FIG. 5b, the medium may be detected as occupied due to transmission by non-AP STA 3 (340), and the medium may be switched back to an idle state when transmission by non-AP STA 3 (340) is completed. Here, non-AP STA 1 (320) may want to transmit DS to transmit a low-latency frame. non-AP STA 2 (330) may want to transmit its uplink frame to AP (310) using normal EDCA channel access. Here, if AIFSN[HiP] and AIFSN[VO] are the same, non-AP STA 2 (330) may perform frame transmission using HiP even if it does not transmit a low-latency frame when the backoff counter of AC_VO is 0.

[0110] Additionally, when the medium is switched back to an idle state, non-AP STA 2 (330) and non-AP STA 1 (320) may wait for the same AIFS time (i.e., AIFS[HiP] or AIFS[VO]). In the above case, non-AP STA 1 (320) and non-AP STA 2 (330) may transmit DS (404-1, 404-2) simultaneously. Non-AP STA 1 (320) and non-AP STA 2 (330) that have transmitted DS (404-1, 404-2) may perform a short backoff operation. If the backoff counter of non-AP STA 1 (320) is shorter, non-AP STA 1 (320) may transmit a low-latency uplink frame (406) to the AP (310). Here, non-AP STA 2 (330) transmits DS (404-2), but may not be able to occupy the channel in competition with non-AP STA 1 (320) after transmitting DS (404-2). In the above case, non-AP STA 2 (330) may keep the backoff counter for AC_VO at 0. That is, if the medium is idle for AIFS[VO] time after non-AP STA 1 (320) finishes transmitting the frame, non-AP STA 2 (330) may wait for AIFS[VO] and transmit the uplink frame (407).

[0111] Referring to FIG. 5c, the medium may be detected as occupied due to transmission by non-AP STA 3 (340), and the medium may be switched back to an idle state when transmission by non-AP STA 3 (340) is completed. Here, non-AP STA 1 (320) may want to transmit DS to transmit a low-latency frame. non-AP STA 2 (330) may want to transmit its uplink frame to AP (310) using normal EDCA channel access. Here, if AIFSN[HiP] and AIFSN[VO] are the same, non-AP STA 2 (330) may perform frame transmission using HiP even if it does not transmit a low-latency frame when the backoff counter of AC_VO is 0.

[0112] Additionally, when the medium is switched back to an idle state, non-AP STA 2 (330) and non-AP STA 1 (320) may wait for the same AIFS time (i.e., AIFS[HiP] or AIFS[VO]). In the above case, non-AP STA 1 (320) and non-AP STA 2 (330) may transmit DS (404-1, 404-2) simultaneously. Non-AP STA 1 (320) and non-AP STA 2 (330) that have transmitted DS (404-1, 404-2) may perform a short backoff operation. If the backoff counter of non-AP STA 1 (320) is shorter, non-AP STA 1 (320) may transmit a low-latency uplink frame (406) to the AP (310). Here, non-AP STA 2 (330) transmits DS (404-2) but may not occupy the channel in contention with non-AP STA 1 (320) after transmitting DS (404-2). In the above case, non-AP STA 2 (330) may re-select the backoff counter for AC_VO. The re-selected backoff counter may be set based on the CW for the increased AC_VO (e.g., a backoff counter selected in the range [0, CW] by a CW increased by 2 times or up to the upper limit). The above action may occur when non-AP STA 2 (330) is considered to have failed to transmit the frame. As another example, non-AP STA 2 (330) may not be considered to have failed to transmit the frame because it succeeded in transmitting DS (404-2) but failed to occupy the channel in contention after transmitting DS (404-2). Here, the selected backoff counter can be set based on the CW for AC_VO of the existing non-AP STA 2 (330). (e.g.(Backoff counter selected in the range [0, CW] by an unchanging CW) As another example, since non-AP STA 2 (330) has transmitted DS (404-2), the selected backoff counter can be set based on the CW for AC_VO of the initialized non-AP STA 2 (330). (e.g., backoff counter selected in the range [0, CW] by a CW initialized to CWmin[VO]) non-AP STA 2 (330) can decrement one backoff slot, AIFS[VO], and the remaining backoff counters in each backoff slot after non-AP STA 1 (320) completes frame transmission, and can transmit an uplink frame (407) to AP (310) at the slot boundary where the backoff counter is 0.

[0113] Referring to FIG. 5d, the medium may be detected as occupied due to transmission by non-AP STA 3 (340), and the medium may be switched back to an idle state when transmission by non-AP STA 3 (340) is completed. Here, non-AP STA 1 (320) may want to transmit DS to transmit a low-latency frame. non-AP STA 2 (330) may want to transmit its uplink frame to AP (310) using normal EDCA channel access. Here, if AIFSN[HiP] and AIFSN[VO] are the same, non-AP STA 2 (330) may perform frame transmission using HiP even if it does not transmit a low-latency frame when the backoff counter of AC_VO is 0.

[0114] Additionally, when the medium is switched back to an idle state, non-AP STA 2 (330) and non-AP STA 1 (320) may wait for the same AIFS time (i.e., AIFS[HiP] or AIFS[VO]). In the above case, non-AP STA 1 (320) and non-AP STA 2 (330) may transmit DS (404-1, 404-2) simultaneously. Non-AP STA 1 (320) and non-AP STA 2 (330) that have transmitted DS (404-1, 404-2) may perform a short backoff operation. If the backoff counter of non-AP STA 1 (320) is shorter, non-AP STA 1 (320) may transmit a low-latency uplink frame (406) to the AP (310). Here, non-AP STA 2 (330) transmits DS (404-2), but may not be able to occupy the channel in competition with non-AP STA 1 (320) after transmitting DS (404-2). In the above case, non-AP STA 2 (330) may re-select the backoff counter for AC_VO. Here, the backoff counter for AC_VO may be set as the residual backoff counter during a short backoff operation performed after transmitting DS (404-2). After non-AP STA 1 (320) completes the frame transmission, non-AP STA 2 (330) may decrease the remaining backoff counters in one backoff slot, AIFS[VO], and each backoff slot, and transmit an uplink frame (407) to the AP (310) at the slot boundary where the backoff counter is 0.

[0115] In FIGS. 5a through 5d described above, non-AP STA 2 (330) confirms that HiP EDCA is used in BSS, and if AIFSN[VO] for AC_VO is the same as AIFSN[HiP] (i.e., if AIFS[AC] and AIFS[HiP] are the same), non-AP STA 2 (330) can insert a frame so that DS can be transmitted first from the VO queue of non-AP STA 2 (330) when the AC_VO backoff counter of non-AP STA 2 (330) reaches 0. The EDCAF associated with AC_VO can transmit DS first over other frames waiting in the queue.

[0116] The above-described DS frame collision prevention method can be applied to all ACs capable of transmitting frames at the same time as the DS, in addition to AC_VO. Specifically, all ACs capable of accessing the channel after the channel transitions from an occupied state to an idle state, at a time 'aSIFSTime + (2 + CWds) * aSlotTime', or at a time 'aSIFSTime + 2 * aSlotTime', when the CWds parameter is 0, can be made to perform the above-described DS collision prevention operation.

[0117] Here, the above-described DS frame collision prevention method can be enabled by the settings of the AP (310). For example, if the AP (310) includes an indicator (e.g., a DS Protection indicator set to 1) that instructs the activation of the DS frame collision prevention function in a management frame, which is at least one of the beacon, probe response frame, action frame, and other frames in which HiP EDCA enabled is set to 1, the above-described DS frame collision prevention method can be performed.

[0118] Additionally, when the STA requests the AP (310) to use HiP EDCA through at least one of a link reconstruction request frame, an action frame, and other frames, the STA may additionally transmit by enabling the DS Protection indicator to request a DS frame collision prevention function. In the above case, the STA may perform the DS frame collision prevention method after receiving at least one of a beacon, a probe response frame, and other frames in which HiP EDCA enabled is set to 1 and the DS Protection indicator is set to 1, or after receiving an action frame. Additionally, the above operation may be indicated through frames of other forms, not just beacons, probe request / response frames, and action frames, and is not limited to a specific form.

[0119] FIG. 6 is a diagram illustrating a low-latency operation method when a difference in the reception time of a Defer Signal occurs when using a wireless LAN HiP EDCA applied to the present disclosure.

[0120] Referring to FIG. 6, HiP is used in a wireless LAN BSS as in FIG. 3, and the AP (310) can instruct the STAs connected to the AP (310) to use HiP. The STAs connected to the AP (310) may be non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340). Here, non-AP STA 1 (320) and non-AP STA 2 (330) may be STAs that support UHR (ultra high reliability). non-AP STA 1 (320) and non-AP STA 2 (330) may identify at least one of the HiP Enabled bit and HiP element of the AP (310) from at least one of a beacon frame and a probe response frame. As described above, non-AP STA 1 (320) and non-AP STA 2 (330) can confirm that HiP is used within the BSS. Here, since there is a low-latency frame that needs to be transmitted, non-AP STA 1 (320) and non-AP STA 2 (330) may want to perform channel access operations using HiP as shown in FIG. 3.

[0121] Here, a NAV may be established due to communication between non-AP STA 3 (340) and another communication node (e.g., the AP to which STA 3 is connected). For example, non-AP STA 1 (320) may wait for an AIFS [HiP] to transmit a DS (408) if the channel is idle based on the time when the actual frame transmission of non-AP STA 3 (340) is completed (i.e., Physical CS (carrier sense)). non-AP STA 2 (330) may wait until the Virtual CS becomes idle if the Virtual CS (i.e., NAV (network allocation vector)) is occupied even when the Physical CS is idle. non-AP STA 2 (330) may wait for an AIFS [HiP] time to transmit a DS if both the Virtual CS and the Physical CS are idle. That is, there may be a difference in the start time of the operation for non-AP STA 1 (320) and non-AP STA 2 (330) to transmit DS, and non-AP STA 1 (320) may transmit DS (408) first. For example, as described above, the difference in the timing of the DS transmission operation due to the difference in the end time of virtual CS and physical CS was described based on the difference in the timing of the DS transmission operation, but the difference in the timing of the DS transmission operation may be based on other reasons and is not limited to a specific form. non-AP STA 2 (330) can receive the DS (408) transmitted by non-AP STA 1 (320) because non-AP STA 1 (320) transmits DS (408) first. Since non-AP STA 2 (330) is waiting to transmit DS, non-AP STA 2 (330) that has received DS (408) from non-AP STA 1 (320) can perform a short backoff operation for low-latency frame transmission from the time when DS reception is complete.Additionally, non-AP STA 1 (320) can also perform a short backoff operation for low-latency frame transmission from the time the transmission of the DS is completed. That is, if non-AP STA 2 (330) receives the DS of another STA while waiting for the low-latency frame transmission operation, it can perform a contention operation for low-latency frame transmission without transmitting the DS itself. That is, non-AP STA 2 (330) can perform a short backoff procedure from the time it completes receiving the DS of another STA (e.g., non-AP STA 1 (320)). When non-AP STA 2 (330) occupies the channel through the short backoff procedure, non-AP STA 2 (330) can transmit a low-latency frame (409) to the AP (310). The AP (310) can transmit a response frame to non-AP STA 2 (330). non-AP STA 1 (320) can wait for the AIFS[HiP] time again after the AP (310) sends a response frame for the transmission of a low-latency frame (411), and then transmit the DS (410). After transmitting the DS (410), the non-AP STA 1 (320) can perform a short backoff operation and transmit it to the AP (310).

[0122] As another example, if there is a difference between the start and end times of the transmission of DS, non-AP STA 1 (320) and non-AP STA 2 (330) may both transmit DS. Here, if non-AP STA 1 (320) transmits DS first and non-AP STA 2 (330) does not detect non-AP STA 1 (320)'s DS (e.g., impossible to detect due to propagation delay and difference in Rx and Tx switching times), non-AP STA 2 (330) may also transmit DS. After non-AP STA 1 (320) completes the transmission of DS, the channel may become occupied due to the transmission of DS by non-AP STA 2 (330). Here, if the channel occupancy state resulting from the DS transmission of non-AP STA 2 (330) ends within a preset time (e.g., 8us or aSIFSTime) after the completion of the DS transmission of non-AP STA 1 (320), non-AP STA 1 (320) may continue to perform a short backoff operation without performing a separate wait operation. On the other hand, if the channel occupancy state resulting from the DS transmission of non-AP STA 2 (330) does not end within a preset time (e.g., 8us or aSIFSTime) after the completion of the DS transmission of non-AP STA 1 (320), non-AP STA 1 (320) may perform a short backoff operation after the channel occupancy state ends. Alternatively, non-AP STA 1 (320) may need to wait for an AIFS[HiP] time after the occupancy state ends in order to perform the DS transmission again. Alternatively, non-AP STA 1 (320) may need to wait for the extended interframe space (EIFS) because a frame detection error has occurred. Meanwhile, the EIFS time can be calculated based on the AIFS[HiP] time. For example, the EIFS time may be 'AIFS[HiP] + aSIFSTime + AckTxTime' time.That is, the EIFS time is a time interval that includes the length of the expected response frame that may be received when a channel detection error occurs, and the IFSs. If a frame detection error occurs in non-AP STA 1 (320), non-AP STA 1 (320) may need to use the EIFS time to protect the response frame that may occur after the end of the detected frame. That is, non-AP STA 1 (320) uses the EIFS time as the first slot boundary and can transmit a frame if the medium is idle during the EIFS time. If the medium is idle during the AIFS[HiP] time after the last medium occupancy or during the EIFS time used due to a frame error, non-AP STA 1 (320) can transmit a DS.

[0123] As another example, there may be a difference in the timing of DS transmission depending on whether non-AP STA 1 (320) and non-AP STA 2 (330) can decode the frame without error. non-AP STA 1 (320) can receive the frame from non-AP STA 3 (340) without error and accurately set the NAV. That is, non-AP STA 1 (320) can determine the time when the actual frame transmission of non-AP STA 3 (340) ends or the time when the NAV set by the frame of non-AP STA 3 (340) ends. non-AP STA 1 (320) can wait for an AIFS[HiP] time to transmit the DS after the frame transmission of non-AP STA 3 (340) is completed or after the NAV ends. However, non-AP STA 2 (330) may encounter errors when decoding the frame of non-AP STA 3 (340). Alternatively, non-AP STA 2 (330) may detect that the medium is occupied by detecting only energy and failing to detect the frame. In the above case, non-AP STA 2 (330) may not be able to determine the actual frame transmission end time of non-AP STA 3 (340) and may have to wait longer than AIFS[HiP] to transmit DS. For example, the above time may be 'AIFS[HiP] + aSIFSTime + AckTxTime'. Here, 'AIFS[HiP] + aSIFSTime + AckTxTime' may be the EIFS time. That is, there may be a difference in the start time of the operation for non-AP STA 1 (320) and non-AP STA 2 (330) to transmit DS, and non-AP STA 1 (320) may transmit DS first. non-AP STA 2 (330) can receive the DS because non-AP STA 1 (320) transmits it first.Since non-AP STA 2 (330) is waiting to transmit a DS, non-AP STA 2 (330), having received the DS from non-AP STA 1 (320), can perform a short backoff operation for low-latency frame transmission from the time the DS is received. Additionally, non-AP STA 1 (320) can also perform a short backoff operation for low-latency frame transmission from the time the DS is transmitted. That is, if non-AP STA 2 (330) receives a DS from another STA while waiting for a low-latency frame transmission operation, it can perform a contention operation for low-latency frame transmission without transmitting the DS itself. non-AP STA 2 (330) can occupy the channel during the short backoff procedure and transmit a low-latency frame to AP (310). AP (310) can transmit a response frame to non-AP STA 2 (330). non-AP STA 1 (320) can wait for the AIFS[HiP] time again after the AP (310) sends a response frame for low-latency frame transmission and then send the DS. After sending the DS, non-AP STA 1 (320) can perform a short backoff operation and send it to the AP (310).

[0124] Meanwhile, if non-AP STA 1 (320) does not perform DS transmission, non-AP STA 2 (330) can transmit DS after the media occupancy state ends (e.g., after the NAV (NAV timer), which is the period for setting the Virtual CS to channel occupancy, ends, and after the physical CS is switched to an idle state) and after the EIFS time. non-AP STA 2 (330) can perform a short backoff operation for low-latency frame transmission from the time the DS transmission is completed.

[0125] In FIGS. 3 through 6 described above (operation using HiP EDCA), the short backoff operation may be an EDCA backoff operation and an EDCA TXOP acquisition procedure. The short backoff operation may be a backoff procedure performed by at least one STA after DS frame transmission. In the short backoff operation, the first slot after DS transmission may be AIFS. AIFS in the short backoff operation may be equal to AIFS[HiP] or defined as a separate time (e.g., AIFS[VO], AIFS[HiP_2]). Subsequently, the slot may be determined by aSlotTime or other units. For example, as described above, since the medium is idle for AIFS[HiP] time after the last channel occupancy state of the STA, the backoff counter may be set to 2 after DS transmission. The first backoff slot is AIFS time, and if the medium is idle for AIFS time, the backoff counter may be decreased by 1 to 1. After the first backoff slot, the second backoff slot can be aSlotTime. Here, if the medium is idle during aSlotTime, the backoff counter can be decremented by 1 to 0. The third backoff slot is aSlotTime, and if the medium is idle during aSlotTime, a low-latency frame can be transmitted.

[0126] As another example, low-latency frame transmission may not be transmitted immediately upon successful short backoff, but may be preceded by an exchange of RTS (request to send) frames and CTS (clear to send) frames. As a specific example, if the STA succeeds in short backoff after DS transmission, the STA may transmit an RTS frame to the AP (310). The AP (310) may respond to the STA's RTS frame with a CTS frame. After receiving the CTS frame from the AP (310), the STA may transmit a low-latency frame to the AP (310).

[0127] Additionally, in FIGS. 3 to 6 described above, the DS may be a specific control frame (e.g., a CTS (clear to send) frame) that multiple STAs can transmit simultaneously. However, there may be a difference in the transmission timing of the DS, and in the case described above, the short backoff operation may be as in FIG. 6. For example, the DS may include an identifier to distinguish that it is a DS. As a specific example, the address field of the DS (e.g., RA (receiver address)) may be set to the address of the AP (310) (e.g., BSS (basic service set) ID (identifier)). Alternatively, the address field of the DS may be set with a partially modified address of the AP (310). Alternatively, bits indicating that it is a DS may be additionally included in the PPDU service field of the DS, but it may not be limited to such embodiments. The DS may include specific information that can be distinguished from a general control frame, but it may not be limited thereto.

[0128] The HiP or HiP EDCA used in FIGS. 3 to 6 described above may be a Prioritized EDCA (P-EDCA) operation, and DS may be referred to as DS-CTS. That is, the HiP EDCA operation used in FIGS. 3 to 6 may be the same operation as the P-EDCA used in FIGS. 7 to 20b, but is not limited thereto.

[0129] FIG. 7 is a diagram illustrating a method for indicating PEDCA and channel access parameters when using Prioritized Enhanced Distributed Channel Access (PEDCA) for wireless LANs applicable to the present disclosure.

[0130] Referring to FIG. 7, an AP (510) and a plurality of STAs (e.g., STA 1, STA 2, STA 3) connected to the AP (510) can operate in a wireless LAN network. The AP (510) and the plurality of STAs connected to the AP (510) can form a basic service set (BSS). The AP (510) can instruct the use of a high-priority PEDCA within the BSS. The AP (510) can instruct the use of PEDCA through at least one of a beacon, a probe response frame, and other frames. Alternatively, PEDCA may be performed by individual STAs without instruction from the AP (510). When STAs using PEDCA need to perform channel access using PEDCA, they must perform the following PEDCA channel access operations.

[0131]

[0132] [PEDCA Channel Access Operation]

[0133] Step 1. Verify that the medium is not busy for AIFS [PEDCA] hours since the last detected busy (physical CS (carrier sense), virtual CS).

[0134] A). AIFS(arbitrary inter frame space)[PEDCA] may be the same as DIFS(DCF(distributed coordinated function) IFS). Or, AIFS[PEDCA] may be the same as AIFS[VO].

[0135] B). Alternatively, AIFS[HiP] is a competition window for random channel access. It can be determined based on parameters. For example, AP indicates AIFSN[HiP] as 2, and Parameters can be specified. In the above case, 'AIFS[HiP] = aSIFSTime + (2 + CW) * aSlotTime', and CW is [0, ] It can be an integer value selected based on a uniform probability distribution in a competition window.

[0136] Step 2. If the medium is not busy in Step 1 (i.e., idle), transmit DS (defer signal).

[0137] A). The Defer Signal is a CTS (clear to send) frame. The Defer Signal may be referred to as DS or DS-CTS.

[0138] i. The Defer Signal may be a frame whose format and content are defined in advance so that frames of the same format and content can be transmitted simultaneously from multiple STAs without collisions. In this case, the Duration field of the Defer Signal may be: 1) the time interval from the completion of transmission of the Defer Signal to the completion of the maximum allowable time of the channel access operation defined in Step 3; or 2) the time obtained by subtracting aSIFSTime + AIFSN[i] x (aSlotTime) from the completion of transmission of the Defer Signal to the completion of the maximum allowable time of the channel access operation defined in Step 3, where AIFSN[i] is the smallest AIFSN[i] value in the EDCA Parameter set of the corresponding BSS; or 3) the time obtained by subtracting aSIFSTime + (AIFSN[i]-1) x (aSlotTime) from the completion of transmission of the Defer Signal to the completion of the maximum allowable time of the channel access operation defined in Step 3. In this case, AIFSN[i] is the smallest AIFSN[i] value in the EDCA parameter set of the corresponding BSS. Or 4) it may be the time obtained by subtracting aSIFSTime + 2 x (aSlotTime) from the completion time of the maximum allowable time of the channel access operation defined in 3, starting from the time of completion of the Defer Signal transmission. In this case, AIFSN[i] is the smallest AIFSN[i] value in the EDCA parameter set of the corresponding BSS. Or 5) it may be the time obtained by subtracting aSIFSTime + aSlotTime from the completion time of the maximum allowable time of the channel access operation defined in step 3, starting from the time of completion of the Defer Signal transmission.

[0139] B. The default value of the Duration value in the MAC header of DS-CTS can be AIFS[VO] + 7*aSlotTime. This is a default value, and it can be changed by the AP instructing it in a management frame, such as a beacon frame.

[0140] Step 3. The STAs that transmitted the DS-CTS perform a channel access operation (e.g., performing a random backoff operation consisting of AIFS[VO] + multiple aSlotTime times, or performing a random backoff operation consisting of multiple aSlotTime times). Whether to wait for AIFS[VO] during the channel access operation can be determined by the AP (510) indicating the PEDCA mode via a Beacon or Probe Response, etc. For example, if the PEDCA mode is 1, the backoff operation is performed by waiting for AIFS[VO], and if the PEDCA mode is 2, the backoff operation is performed without waiting for AIFS[VO]. Alternatively, it may be used selectively depending on the type of traffic intended for low-latency transmission. For example, if the traffic type is high-priority low-latency traffic, the backoff operation is performed without waiting for AIFS[VO], and for other low-latency traffic, the backoff operation is performed by waiting for AIFS[VO]. The above-mentioned highest priority low-latency traffic may be traffic at the deadline for transmission, i.e., when the Delay bound value is below a specific threshold. Additionally, STAs that have not transmitted a DS but possess a frame corresponding to the conditions for performing a PEDCA channel access operation may perform a PEDCA channel access operation after receiving a DS transmitted by the AP (510) or another STA. The above STAs may be excluded from the operation of setting the NAV by receiving the DS after receiving the DS. Or, if the NAV is set by receiving the DS, it may be canceled. The maximum allowable time for the channel access operation is AIFS[VO] + backoff counter x aSlotTime when using AIFS[VO], and backoff counter x aSlotTime when not using AIFS[VO].

[0141] A). The random backoff operation is an operation in which a random backoff counter is selected according to B., the backoff counter is decremented for each slot time (e.g., each of AIFS[VO] and multiple aSlotTimes is a slot, or each of multiple aSlotTimes is a slot), and a frame is transmitted at the slot boundary where the backoff counter reaches 0. When the backoff counter reaches 0, the channel access operation is said to have succeeded.

[0142] B). The random backoff counter selection may be an integer selected through a uniform random method in the interval [0, CW[PEDCA]].

[0143] Step 4. The STA that has completed the random backoff operation transmits a frame at the slot boundary where the backoff counter reaches 0. The transmitted frame may be an RTS frame.

[0144]

[0145] The PEDCA channel access operation enables STAs to access the channel and transmit frames preferentially over STAs using general channel access operations (e.g., EDCA channel access operation) that are not PEDCA channel access operations. Additionally, the PEDCA channel access operation can be used to transmit AC (access categories) VO (voice) packets. Furthermore, the PEDCA channel access operation can be used to transmit frames by replacing the existing EDCA VO EDCAF. In this disclosure, DS-CTS is referred to as DS, but this is for convenience of explanation only and is not limited to this name.

[0146] STAs performing PEDCA may encounter a problem in "Step 1" of the aforementioned PEDCA channel access operation. A specific STA may detect the medium as being occupied during the time interval in which the NAV (network allocation vector), a parameter used by the Virtual CS operation to determine if the channel is in an occupied state, is set. For example, due to the difference between the NAV setting and the actual frame transmission time, a specific STA (e.g., the TXOP holder STA that is the sender of the frame setting the NAV, or the TXOP responder STA that is the destination STA of the frame setting the NAV) may not set the NAV. In this case, the DS may be transmitted first by the STA that has not set the NAV. That is, because the STA that has not set the NAV can access the channel preferentially over other STAs through the PEDCA operation, the fairness of the PEDCA operation may be reduced.

[0147] Referring to FIG. 7, a NAV (e.g., an intra-BSS NAV set by a frame transmitted within the BSS) corresponding to a TXOP (transmit opportunity) of non-AP STA 3 (540) may be set in non-AP STA 1 (520) and non-AP STA 2 (530). On the other hand, a NAV (e.g., intra-BSS NAV) may not be set in non-AP STA 3 (540). Non-AP STA 1 (520) and non-AP STA 2 (530) may detect the medium as occupied while the NAV is set. If non-AP STA 1 (520) to non-AP STA 3 (540) are all STAs using PEDCA, the time when non-AP STA 1 (520) and non-AP STA 2 (530) can transmit DS may be the time when the NAV is released. Therefore, non-AP STA 3 (540), for which NAV is not set, may be later than the time when DS can be transmitted. The above-described situation may be an operation that provides non-AP STA 3 (540) with the opportunity to transmit low-latency frames preferentially. Here, since non-AP STA 1 (520) and non-AP STA 2 (530) cannot transmit DS, the fairness of the PEDCA operation may be reduced, and methods to improve the fairness of the PEDCA operation may be required.

[0148] FIG. 8 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0149] Referring to FIG. 8, in a wireless LAN network, an AP (510) and non-AP STA 1 (520), non-AP STA 2 (530), and non-AP STA 3 (540) connected to the AP (510) can operate. The non-AP STA 1 (520) to non-AP STA 3 (540) can support the PEDCA operation described above in FIG. 7.

[0150] Here, if the channel access operation (e.g., EDCA TXOP acquisition procedure, EDCA backoff procedure) is successful, the AP (510) acquires a TXOP, which is a time interval during which multiple frames can be transmitted, and can transmit frames to non-AP STA 3 (540). Thus, the AP (510) can be a TXOP holder. For example, the AP (510) can transmit an initial RTS frame (601) to the non-AP STA 3 (540). The recipient address of the RTS frame (601) is the address of the non-AP STA 3 (540), and the duration field of the RTS frame (601) can indicate the entire time interval of the initial TXOP that the AP (510) intends to use. non-AP STA 1 (520) to non-AP STA 3 (540) can receive the RTS frame (601) of the AP (510), but non-AP STA 1 (520) and non-AP STA 2 (530) may not be recipients of the RTS frame (601). Therefore, non-AP STA 1 (520) and non-AP STA 2 (530) can set the NAV for the length of the duration field indicated in the RTS frame (601). That is, non-AP STA 1 (520) and non-AP STA 2 (530) can detect the medium in an occupied state for the length of the duration field indicated in the RTS frame (601) (i.e., during the time interval in which the NAV is set). Here, the operation of determining the occupancy status by virtually performing a CCA on the medium without physically performing a CCA (clear channel assessment) may be a Virtual CCA, but is not limited to that name.

[0151] Meanwhile, non-AP STA 3 (540) may be a receiver of the RTS frame (601), and non-AP STA 3 (540) may be a TXOP responder. Since non-AP STA 3 (540) is a receiver of the RTS frame (601), it may not set the NAV. If non-AP STA 3 (540) properly receives the RTS frame (601) of the AP (510), non-AP STA 3 (540) may transmit a CTS frame (602) to the AP (510). When the AP (510) receives the CTS frame (602) from non-AP STA 3 (540), it may transmit a data frame (603) to non-AP STA 3 (540). When non-AP STA 3 (540) receives a data frame (603) from AP (510), it may transmit a response frame (e.g., Ack frame, BlockAck frame) for the data frame (603). For example, the data frame (603) of AP (510) may be transmitted within a shorter time period than the entire TXOP time interval set by the initial AP (510). The last data frame transmitted within the TXOP may indicate the last frame transmitted within the current TXOP by setting the More Data indicator in the MAC header to 0. Alternatively, the response frame of non-AP STA 3 (540) may include only the 'All ACK' (indicating that all frames were successfully received) or 'All NACK' (indicating that all frames were not received) indicators. As described above, the response frame may be shorter than the length of the original response frame, allowing for faster transmission. Alternatively, both of the above cases may occur.

[0152] That is, the data frame exchange procedure of AP (510) and non-AP STA 3 (540) may be terminated before the NAV set by non-AP STA 1 (520) and non-AP STA 2 (530). In the above case, since the NAV is not set for non-AP STA 3 (540), the Virtual CS may be idle. non-AP STA 3 (540) may transmit DS if the medium is idle during the AIFS [PEDCA] time. Since non-AP STA 1 (520) and non-AP STA 2 (530) have the NAV set, they may not be able to perform channel access operations using PEDCA even if frame transmission is complete. Therefore, the TXOP responder non-AP STA 3 (540) may transmit DS alone. non-AP STA 3 (540) can transmit frames through the PEDCA channel access operation described above, so priority can be given to non-AP STA 3 (540), and for fairness, it is necessary to give the same priority to other STAs.

[0153] Considering the above, if the actual frame exchange ends earlier than the initially set TXOP interval, the AP (510) can transmit a CF (contention free)-end frame (604) to release the NAV corresponding to the initially set TXOP interval. That is, non-AP STA 1 (520) and non-AP STA 2 (530) can receive the CF-end frame (604) transmitted from the AP (510) and release the set NAV. After the AP (510) transmits the CF-end frame (604), the NAV is not set on non-AP STA 1 (520) to non-AP STA 3 (540), so the Virtual CS may be in an idle state.

[0154] Here, if the medium is idle during the AIFS[PEDCA] time, non-AP STA 1 (520) through non-AP STA 3 (540) can transmit DS (605-1, 605-2, 605-3). That is, all STAs that had NAV set can perform channel access operations using PEDCA after NAV is released or after the AP (510) has finished receiving the CF-End frame. For example, non-AP STA 2 (530) that had NAV set can transmit a frame (e.g., a low-latency frame) (606) through a random backoff operation after transmitting DS (605-2). Thus, all STAs can perform PEDCA operations with equal fairness. In APs (510) and all STAs that use (or support) PEDCA, if there is a difference between the length of the initial TXOP and the actual frame transmission interval, and thus the CF-end frame (604) can be transmitted within the TXOP interval, the CF-end frame (604) may be mandatory to use. Here, STAs receiving the CF-end frame (604) may disable NAV only for intra BSS NAV. For example, if the CF-end frame (604) is transmitted in a specific PPDU format (e.g., UHR PPDU format) or contains specific MAC address information, the CF-end frame (604) may disable NAV only for intra NAV. Specifically, when the STA receives a CF-End frame (604) transmitted in a specific PPDU format or a CF-end frame (604) transmitted including specific MAC address information, and checks BSS identification information such as the BSS color of the preamble or the BSSID of the MAC header to confirm that the CF-end frame (604) is transmitted from the AP (510) associated with it, the STA can release the NAV only for the intra-BSS NAV.Alternatively, if the CF-end frame (604) is transmitted from the AP (510) to which non-AP STA 1 (520) to non-AP STA 3 (540) are connected, the TA (transmitter address) of the CF-end frame (604) may be set to the address of the AP (510). In the above case, when the STA receives the CF-end frame (604), it may release the NAV only for the intra-BSS NAV.

[0155] As another example, other methods to improve fairness in PEDCA can be considered. The Virtual CS may be idle because the NAV is not set after the frame transmission is completed on non-AP STA 3 (540). Here, if the medium is idle during the AIFS[PEDCA] time, non-AP STA 3 (540) can transmit the DS. After transmitting the DS, non-AP STA 3 (540) can perform the channel access operation of the PEDCA channel access operation 'step 3' described above. Here, non-AP STA 1 (520) and non-AP STA 2 (530) may be in a state where they are waiting to transmit the DS because there is a low-latency frame. When non-AP STA 1 (520) and non-AP STA 2 (530) receive DS from non-AP STA 3 (540), they can perform the channel access operation of the PEDCA channel access operation 'step 3' described above from the time of receiving DS without transmitting DS. If the configured NAV is set by the AP (510) to which it is connected (e.g., if the configured NAV is an intra-BSS NAV set by communication performed within the BSS (basic service set)), non-AP STA 1 (520) and non-AP STA 2 (530) may ignore or release the NAV upon receiving the DS and perform a backoff operation by physical CCA (e.g., the PEDCA channel access operation 'step 3' described above). Among non-AP STA 1 (520) to non-AP STA 3 (540), the STA whose backoff counter becomes 0 by the PEDCA channel access operation 'step 3' described above and whose channel access operation is completed first may transmit a frame according to the PEDCA channel access operation 'step 4' described above.

[0156] Hereinafter, FIGS. 9 to 11 may be methods of operation for improving the processability of PEDCA other than the methods described above.

[0157] FIG. 9 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0158] Referring to FIG. 9, a frame transmission procedure by an AP (510) or a non-AP STA can be performed in the wireless LAN network described above in FIG. 8. For example, a frame transmission procedure by the AP (510) described above in FIG. 8 can be performed. That is, as described above, a NAV longer than the actual frame transmission interval is set for non-AP STA 1 (520) and non-AP STA 2 (530), and STA 3 has no NAV set, so a situation may be possible where faster frame transmission is possible than for non-AP STA 1 (520) and non-AP STA 2 (530).

[0159] Here, the AP (510) may be a TXOP holder. If the actual frame transmission is completed earlier than the initial TXOP period, the AP (510) may transmit a DS (604) in the remaining TXOP period. The last data frame transmitted within the TXOP may indicate the last frame transmitted within the current TXOP by setting the More Data indicator in the MAC header to 0. The AP (510) may transmit a DS (607) after a SIFS time from the time it receives a reception acknowledgment for the last transmitted data frame (603) within the TXOP period. Non-AP STA 1 (520) to non-AP STA 3 (540) may be in a state of waiting to transmit a DS because there is a low-latency frame. When non-AP STA 1 (520) to non-AP STA 3 (540) receive the DS (607) from the AP (510), they may perform the channel access operation of the above-described PEDCA channel access operation 'step 3'. If the set NAV is set by the AP (510) to which it is connected (e.g., if the set NAV is an intra-BSS NAV set by communication performed within the BSS (basic service set)), non-AP STA 1 (520) and non-AP STA 2 (530) may ignore or release the NAV upon receiving DS (607) and perform a backoff operation by physical CCA (e.g., the PEDCA channel access operation 3 described above). Among non-AP STA 1 (520) to non-AP STA 3 (540), the STA whose backoff counter becomes 0 by the PEDCA channel access operation 'step 3' described above and whose channel access operation is completed first may transmit a frame (e.g., a low-latency frame) (608) according to the PEDCA channel access operation 'step 4' described above.In FIG. 9, the channel access operation by the aforementioned PEDCA channel access operation 'step 3' of the non-AP STA 2 (530) may be completed first to transmit a frame, but is not limited thereto. Additionally, when the AP (510) transmits DS (607), a condition may be added that the AP (510) is excluded from the target of the PEDCA channel access operation and cannot perform PEDCA channel access, but is not limited thereto.

[0160] Additionally, for example, if no STA performs data transmission within the maximum channel connection period allowed by PEDCA from the time after the DS transmission of the AP (510), the AP (510) can resume normal EDCA operation. That is, the EDCA operation can be resumed by setting the time after aSlotTime, when the maximum channel connection period allowed by PEDCA ends, as the EDCA slot boundary.

[0161] FIG. 10 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0162] Referring to FIG. 10, a frame transmission procedure by an AP (510) or a non-AP STA can be performed in the wireless LAN network described above in FIG. 8. For example, a frame transmission procedure by the AP (510) described above in FIG. 8 can be performed. That is, as described above, a NAV longer than the actual frame transmission interval is set for non-AP STA 1 (520) and non-AP STA 2 (530), and a NAV is not set for non-AP STA 3 (540), so a situation may be possible where faster frame transmission is possible than for non-AP STA 1 (520) and non-AP STA 2 (530).

[0163] non-AP STA 1 (520) and non-AP STA 2 (530) can receive frames from AP (510). non-AP STA 1 (520) and non-AP STA 2 (530) can receive RTS frames (601) from AP (510), set NAV, and then receive data frames (603) that AP (510) transmits to non-AP STA 3 (540). The last data frame transmitted within a TXOP can indicate the last frame transmitted within the current TXOP by setting the More Data indicator in the MAC header to 0. non-AP STA 1 (520) and non-AP STA 2 (530) can check at least one of the TXOP field included in the PHY preamble of the data frame (603) and the duration field of the MAC header. AP (510) can set a time length indicated in at least one of the TXOP field and the duration field of the MAC header until the time from transmitting the last data frame to receiving the response frame, thereby shortening the TXOP length compared to the original TXOP. That is, AP (510) can indicate the end time of the shortened TXOP. Alternatively, non-AP STA 1 (520) and non-AP STA 2 (530) can check the duration field by checking the MAC header of the data frame (603) that AP (510) transmits to non-AP STA 3 (540). The duration field may indicate a transmission period shorter than the initially set TXOP period. That is, it can indicate the end time of the shortened TXOP.

[0164] If the data frame (603) of the AP (510) indicates a shortened TXOP (i.e., if it is confirmed that the actual frame transmission ends faster), non-AP STA 1 (520) and non-AP STA 2 (530) can compare the end time of the shortened TXOP with the set NAV. If the difference between the end time of the shortened TXOP and the set NAV is below a certain threshold, non-AP STA 1 (520) and non-AP STA 2 (530) can ignore the intra-BSS NAV set by communication between the AP (510) and non-AP STA 3 (540) after the completion time of the shortened TXOP indicated in the TXOP field. Here, non-AP STA 1 (520) and non-AP STA 2 (530) can transmit DS (609-1, 609-2) if the medium is idle during the AIFS [PEDCA] time. Additionally, non-AP STA 3 (540) can transmit DS (609-3) after the completion of the actual frame transmission, as the intra BSS NAV is not set as a TXOP responder.

[0165] Additionally, as an example, the AP (510) may indicate the original TXOP end time without including a modified time value to indicate the end time of the shortened TXOP in at least one of the TXOP field of the PHY preamble and the duration field of the MAC header. Here, the STAs may determine that frame transmission has ended even if the TXOP remains when they receive the last transmitted data frame (i.e., a frame in which the More Data indicator of the MAC header is set to 0) and receive a response frame. If it is determined using the More Data indicator that the actual frame transmission has ended sooner, non-AP STA 1 (520) and non-AP STA 2 (530) may compare the end time of the shortened TXOP with the set NAV. If the difference between the end time of the shortened TXOP and the time of the set NAV is below a certain threshold, non-AP STA 1 (520) and non-AP STA 2 (530) may ignore the intra-BSS NAV set by communication with AP (510) and non-AP STA 3 (540) after the completion time of the shortened TXOP indicated in the TXOP field, and transmit DS (609-1, 609-2) if the medium is idle for AIFS[PEDCA] time. Since non-AP STA 3 (540) is a TXOP responder and the intra-BSS NAV is not set, it may transmit DS (609-3) after the completion time of the actual frame transmission.

[0166] FIG. 11 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0167] Referring to FIG. 11, a frame transmission procedure by an AP (510) or a non-AP STA can be performed in the wireless LAN network described above in FIG. 8. For example, a frame transmission procedure by the AP (510) described above in FIG. 8 can be performed. That is, as described above, a NAV longer than the actual frame transmission interval is set for non-AP STA 1 (520) and non-AP STA 2 (530), and a NAV is not set for non-AP STA 3 (540), so a situation may be possible where faster frame transmission is possible than for non-AP STA 1 (520) and non-AP STA 2 (530).

[0168] Here, the AP (510) can transmit a data frame (603) to the non-AP STA 3 (540), and the non-AP STA 3 (540) can transmit a response frame (604) to the AP (510). If the response frame for the data frame can simply indicate the reception status, such as in the case of 'All ACK' or 'All NACK', the length of the response frame may be shortened compared to the original response frame. In the above case, the non-AP STA 3 (540) may add padding fields to the response frame (604) to match the TXOP interval of the AP (510). For example, the response frame may be in the Multi-STA BA format and may include multiple Per AID-TID fields. Some of the Per AID-TID fields may indicate the reception status of the data frame (603) received by the non-AP STA 3 (540) from the AP (510). Additionally, some of the Per AID-TID fields may be padding fields that extend the length of the response frame (604). The non-AP STA 3 (540) may extend the length of the response frame (604) and transmit it until the actual TXOP of the AP (510) ends.

[0169] As another example, if the actual frame transmission ends faster than the initially set TXOP interval, the AP (510) can occupy the medium for the entire TXOP interval by transmitting a frame that occupies the remaining interval of the TXOP, such as a QoS Null frame, in the remaining TXOP.

[0170] As described above, the time at which non-AP STA 1 (520) to non-AP STA 3 (540) can access the medium again can be synchronized after the initial TXOP set by the AP (510). non-AP STA 1 (520) to non-AP STA 3 (540) transmit DS (612-1, 612-2, 612-3), and among non-AP STA 1 (520) to non-AP STA 3 (540), the STA whose backoff counter becomes 0 by the above-described PEDCA channel access operation 'step 3' and whose channel access operation is completed first can transmit a frame (e.g., low-latency frame) (613) according to the above-described PEDCA channel access operation 'step 4'. In FIG. 11, the channel access operation by the aforementioned PEDCA channel access operation 3 of the non-AP STA 2 (530) is completed first so that a frame can be transmitted, but this is for convenience of explanation only and is not limited thereto.

[0171] FIG. 12 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure differs from the length of the set NAV. Referring to FIG. 12, a frame transmission procedure by an AP (510) or a non-AP STA can be performed in the wireless LAN network of FIG. 8. For example, a non-AP STA 3 (540) can transmit an uplink frame to the AP (510). When a channel access operation (e.g., EDCA TXOP acquisition procedure, EDCA backoff procedure) is successful, the non-AP STA 3 (540) acquires a TXOP, which is a time interval for transmitting multiple frames, and can transmit frames to the AP (510). Thus, the non-AP STA 3 (540) can be a TXOP holder. For example, the non-AP STA 3 (540) can transmit an initial RTS frame (614) to the AP (510). The recipient address of the RTS frame (614) is the address of the AP (510), and the duration field of the RTS frame (614) may indicate the entire time interval of the first TXOP that the non-AP STA 3 (540) intends to use. The non-AP STA 1 (520), the non-AP STA 2 (530), and the AP (510) may receive the RTS frame (614) of the non-AP STA 3 (540). Here, the non-AP STA 1 (520) and the non-AP STA 2 (530) may not be recipients of the RTS frame (614), and the non-AP STA 1 (520) and the non-AP STA 2 (530) may set the NAV for the length of the duration field indicated in the RTS frame (614). That is, non-AP STA 1 (520) and non-AP STA 2 (530) can detect the medium in an occupied state for the length of the duration field indicated in the RTS frame (614). Meanwhile, AP (510) may be a receiver of the RTS frame (614), and AP (510) may be a TXOP responder.Since the AP (510) is the receiver of the RTS frame, it may not set the NAV. If the AP (510) properly receives the RTS frame (614) of the non-AP STA 3 (540), the AP (510) can send a CTS frame (615) to the non-AP STA 3 (540). When the non-AP STA 3 (540) receives the CTS frame (615) from the AP (510), it sends a data frame (616) to the AP (510), and when the AP (510) receives the data frame (616) from the non-AP STA 3 (540), it can send an acknowledgment frame (e.g., Ack frame, BlockAck frame) (617) for the data frame. Meanwhile, the data frame (616) of the non-AP STA 3 (540) may be transmitted within a shorter time interval than the total TXOP time interval set by the initial non-AP STA 3 (540). Alternatively, the response frame (617) of the AP (510) may include only an 'All ACK' (indicating that all frames were successfully received) or 'All NACK' (indicating that all frames were not received). As described above, the response frame may be shorter than the length of the original response frame, so transmission may be completed quickly. Alternatively, both of the above cases may occur.

[0172] Therefore, that is, the data frame exchange procedure of AP (510) and non-AP STA 3 (540) may be terminated before the NAV set by non-AP STA 1 (520) and non-AP STA 2 (530). In the above case, since the NAV is not set for AP (510) and non-AP STA 3 (540), the Virtual CS may be idle. non-AP STA 3 (540) may transmit DS if the medium is idle during the AIFS [PEDCA] time. Since non-AP STA 1 (520) and non-AP STA 2 (530) have the NAV set, they may not be able to perform channel access operations using PEDCA even if frame transmission is completed. Therefore, the fairness of PEDCA may be reduced, and an action may be required to prevent this.

[0173] Referring to FIG. 12, a frame (uplink frame) (616) transmitted by non-AP STA 3 (540) to AP (510) may include a More Data indicator. If there is a subsequent frame transmitted by non-AP STA 3 (540) to AP (510), the More Data indicator may be set to 1. Otherwise (i.e., if there is no subsequent frame transmitted by non-AP STA 3 (540) to AP (510), the More Data indicator may be set to 0. That is, the More Data indicator of the last data frame transmitted within the TXOP may be set to 0. The non-AP STA 3 (540) may set the More Data indicator of the uplink frame to 0, and upon receiving the frame, the AP (510) may recognize that there is no subsequent data transmitted by non-AP STA 3 (540). That is, it may know that it is the last data frame transmitted within the TXOP.

[0174] As another example, a frame (uplink frame) transmitted by non-AP STA 3 (540) to AP (510) may include a reverse direction grant (RDG) bit. If non-AP STA 3 (540) grants part of non-AP STA 3 (540)'s TXOP to AP (510), the RDG bit may be set to 1. Otherwise, the RDG bit may be set to 0. If the RDG bit of the frame transmitted by non-AP STA 3 (540) to AP (510) is 1, AP (510) may transmit a response frame and an additional frame within non-AP STA 3 (540)'s TXOP. AP (510) may receive a data frame in which the More Data indicator is set to 0 (and / or the RDG bit is set to 1) and transmit a response frame for the uplink data frame. The AP (510) may initiate a PEDCA operation simultaneously with (or after) the transmission of a data frame. The response frame (617) of the AP (510) may be configured in the form of an A-MPDU (Aggregated-MAC Protocol Data Unit) and transmit a BlockAck frame and a DS for the PEDCA operation concatenated together.

[0175] As another example, the response frame of the AP (510) is a BlockAck frame, and the DS (618) can be transmitted after a certain time (e.g., SIFS time, PIFS time) after the response frame is transmitted. If the RDG is set to 1 in the data frame transmitted by the non-AP STA 3 (540) and the AP (510) wants to transmit a frame (DS) in the reverse direction, it may need to transmit the More PPDU indicator of the response frame (617) by setting it to 1. The AP (510) can transmit the DS in the form of an A-MPDU as in the response frame (617) or transmit the DS after SIFS time after the response frame is transmitted only when the More PPDU indicator of the response frame (617) is set to 1 and transmitted.

[0176] When non-AP STA 1 (520) to non-AP STA 3 (540) receive the DS (618) of the AP (510), they can perform the channel access operation of the PEDCA channel access operation 'step 3' described above. Among non-AP STA 1 (520) to non-AP STA 3 (540), the STA whose backoff counter becomes 0 by the PEDCA channel access operation 'step 3' described above and whose channel access operation is completed first can transmit a frame (e.g., a low-latency frame) according to the PEDCA channel access operation 'step 4' described above. In FIG. 12, the channel access operation by the PEDCA channel access operation 3 described above of non-AP STA 2 (530) may be completed first and a frame (619) may be transmitted, but this is for convenience of explanation only and is not limited thereto.

[0177] FIG. 13 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0178] Referring to FIG. 13, a frame transmission procedure by an AP (510) or a non-AP STA can be performed in the wireless LAN network of FIG. 8. For example, the AP (510) can transmit a downlink frame to a non-AP STA 3 (540). When a channel access operation (e.g., EDCA TXOP acquisition procedure, EDCA backoff procedure) is successful, the AP (510) acquires a TXOP, which is a time interval during which multiple frames can be transmitted, and can transmit frames to the non-AP STA 3 (540). Thus, the AP (510) can be a TXOP holder. For example, the AP (510) can transmit an initial RTS frame (620) to the STA. The recipient address of the RTS frame (620) is the address of non-AP STA 3 (540), and the duration field of the RTS frame (620) may indicate the entire time interval of the initial TXOP that the AP (510) intends to use. non-AP STA 1 (520), non-AP STA 2 (530), and non-AP STA 3 (540) may receive the RTS frame (620) of the AP (510). Here, non-AP STA 1 (520) and non-AP STA 2 (530) may not be recipients of the RTS frame (620), and STA 1 and non-AP STA 2 (530) may set NAV for the length of the duration field indicated in the RTS frame (620). That is, STA 1 and non-AP STA 2 (530) can detect the medium as being occupied for the length of the duration field indicated in the RTS frame (620). Meanwhile, non-AP STA 3 (540) may be a receiver of the RTS frame (620), and non-AP STA 3 (540) may be a TXOP responder. Since non-AP STA 3 (540) is a receiver of the RTS frame (620), it may not set the NAV.If non-AP STA 3 (540) properly receives the RTS frame (620) of AP (510), non-AP STA 3 (540) can transmit a CTS frame (621) to AP (510). When AP (510) receives the CTS frame (621) from non-AP STA 3 (540), it transmits a data frame (622) to non-AP STA 3 (540), and when non-AP STA 3 (540) receives the data frame from AP (510), it can transmit an acknowledgment frame (e.g., Ack frame, BlockAck frame) (623) for the data frame. Meanwhile, the transmission of the data frame (622) of AP (510) may be completed within a shorter time period than the total TXOP time interval set by the initial AP (510). Alternatively, the response frame (623) of the non-AP STA 3 (540) may contain only an 'All ACK' (indicating that all frames were successfully received) or 'All NACK' (indicating that all frames were not received). In the above description, the response frame may be shorter than the length of the original response frame, so transmission may be performed quickly. Or, both of the above cases may occur.

[0179] Therefore, the data frame exchange procedure of AP (510) and non-AP STA 3 (540) may be terminated before the NAV set by non-AP STA 1 (520) and non-AP STA 2 (530). In the above case, since the NAV is not set for AP (510) and non-AP STA 3 (540), the Virtual CS may be idle. Non-AP STA 3 (540) may transmit DS if the medium is idle during the AIFS [PEDCA] time. Since non-AP STA 1 (520) and non-AP STA 2 (530) have the NAV set, they may not be able to perform channel access operations using PEDCA even if frame transmission is completed. Therefore, the fairness of PEDCA may be reduced, and an action may be required to prevent this.

[0180] non-AP STA 3 (540) cannot immediately transmit DS even if both Virtual CS and Physical CS are idle for AIFS[PEDCA] time after transmitting a response frame (623) to AP (510) (or after receiving a frame from AP that does not immediately request a response frame) (e.g., various frames such as a response frame). non-AP STA 3 (540) does not set NAV based on the duration field values ​​included in the MAC headers of frames received from AP (510), but can recognize the end time of the TXOP acquired by AP (510) (or the end time of the NAV of other STAs set based on frames transmitted by AP). non-AP STA 3 (540) cannot transmit DS until that time, even if both Virtual CS state and Physical CS state are idle for AIFS[PEDCA] time. Alternatively, the non-AP STA 3 (540) may exceptionally set the NAV based on the time length information of the frames received from the AP (510) (e.g., time length information based on the TXOP duration included in the preamble of the PPDU or time length information based on the duration field included in the MAC header) when using PEDCA (or when the connected BSS (i.e., AP) indicates that PEDCA is used even if the STA 3 does not use PEDCA). That is, the non-AP STA 3 (540) may set the Virtual CS busy period based on the duration field included in the MAC header of the frames received from the AP (510). The non-AP STA 3 (540) cannot transmit the DS even when the physical CS is idle for the AIFS[PEDCA] time because the Virtual CS is occupied.non-AP STA 3 (540) can release NAV when the time length indicated in the time length information value has elapsed and transmit DS when both Virtual CS and Physical CS are idle for the AIFS[PEDCA] time.

[0181] non-AP STA 1 (520) to non-AP STA 3 (540) can transmit DS (624-1, 624-2, 624-3) and perform the channel access operation of the PEDCA channel access operation 'step 3' described above. If the non-AP STA 1 (520), which is the TXOP responder, has not set the NAV, the non-AP STA 1 (520) can perform a channel detection operation for transmitting DS frames (i.e., a channel detection operation corresponding to 'step 2' of the PEDCA channel access operation) based on the duration field value included in the MAC header received from the AP (510) from the end time of the TXOP acquired by the AP (510) or the end time of the NAV of other STAs. Among non-AP STA 1 (520) to non-AP STA 3 (540), the STA whose backoff counter becomes 0 by the aforementioned PEDCA channel access operation 'step 3' and whose channel access operation is completed first can transmit a frame (e.g., low-latency frame) (625) according to the aforementioned PEDCA channel access operation 'step 4'. In FIG. 13, the channel access operation by the aforementioned PEDCA channel access operation 'step 3' of non-AP STA 2 (530) is completed first and transmits a frame, but this is for convenience of explanation only and is not limited thereto.

[0182] FIG. 14 is a diagram illustrating a PEDCA operation method when the actual frame transmission time interval applied to the present disclosure and the length of the set NAV are different.

[0183] Referring to FIG. 14, a frame transmission procedure by an AP (510) or a non-AP STA can be performed in the wireless LAN network of FIG. 8. For example, the AP (510) can transmit a downlink frame to a non-AP STA 3 (540). When a channel access operation (e.g., EDCA TXOP acquisition procedure, EDCA backoff procedure) is successful, the AP (510) acquires a TXOP, which is a time interval during which multiple frames can be transmitted, and can transmit frames to the non-AP STA 3 (540). Thus, the AP (510) can be a TXOP holder. For example, the AP (510) can transmit an initial RTS frame (620) to the STA. The recipient address of the RTS frame (620) is the address of non-AP STA 3 (540), and the duration field of the RTS frame (620) may indicate the entire time interval of the first TXOP that the AP (510) intends to use. non-AP STA 1 (520), non-AP STA 2 (530), and non-AP STA 3 (540) may receive the RTS frame (620) of the AP (510). Here, non-AP STA 1 (520) and non-AP STA 2 (530) may not be recipients of the RTS frame (620), and non-AP STA 1 (520) and non-AP STA 2 (530) may set NAV for the length of the duration field indicated in the RTS frame (620). However, the NAV set by non-AP STA 1 (520) and non-AP STA 2 (530) may be an intra-BSS NAV rather than a basic NAV. The intra-BSS NAV may be a NAV set by a frame transmitted within the BSS (e.g., a BSS configured by AP, STA 1, STA 2, and non-AP STA 3 (540)).non-AP STA 1 (520) and non-AP STA 2 (530) can update the intra-BSS NAV based on the duration field value of the MAC header of a frame transmitted by at least one of AP (510) and non-AP STA 3 (540). Additionally, non-AP STA 1 (520) and non-AP STA 2 (530) can detect the medium as occupied for the length of the duration field indicated in the RTS frame (620) based on the intra-BSS NAV. Here, non-AP STA 3 (540) is the receiver of the RTS frame (620) and may be a TXOP responder. Since non-AP STA 3 (540) is the receiver of the RTS frame (620), it may not set the NAV. If non-AP STA 3 (540) properly receives the RTS frame (620) of AP (510), non-AP STA 3 (540) can transmit a CTS frame (621) to AP (510). When AP (510) receives the CTS frame (621) from non-AP STA 3 (540), it transmits a data frame (622) to non-AP STA 3 (540), and when non-AP STA 3 (540) receives the data frame (622) of AP (510), it can transmit an acknowledgment frame (e.g., Ack frame, BlockAck frame) (623) for the data frame. Meanwhile, the transmission of the data frame (622) of AP (510) may be completed within a shorter time period than the total TXOP time interval set by the initial AP (510). Alternatively, the response frame (623) of the non-AP STA 3 (540) may contain only an 'All ACK' (indicating that all frames were successfully received) or 'All NACK' (indicating that all frames were not received). In the above description, the response frame (623) may be shorter than the length of the original response frame, so transmission may be performed quickly. Or, both of the above cases may occur.

[0184] For example, the data frame exchange procedure of AP (510) and non-AP STA 3 (540) may be terminated before the end (or expiration) of the intra BSS NAV set by non-AP STA 1 (520) and non-AP STA 2 (530). In the above case, the Virtual CS may be idle because no NAV is set for AP (510) and non-AP STA 3 (540). non-AP STA 3 (540) may transmit DS if the medium is idle for an AIFS [PEDCA] time. non-AP STA 1 (520) and non-AP STA 2 (530) may need to check whether the medium is idle for an AIFS [PEDCA] time in order to transmit DS. Here, non-AP STA 1 (520) and non-AP STA 2 (530) may ignore the intra BSS NAV value.

[0185] Referring to FIG. 14, non-AP STA 3 (540) may transmit DS after transmitting a response frame (623) to AP (510) (or after receiving a frame from AP that does not immediately request a response frame) (e.g., various frames such as a response frame) if both the Virtual CS and Physical CS are idle for an AIFS [PEDCA] time. non-AP STA 1 (520) and non-AP STA 2 (530) may detect the medium as occupied based on the physical CS when the transmission of a frame by AP (510) and non-AP STA 3 (540) is detected. When the frame exchange between non-AP STA 3 (540) and AP (510) is finished, non-AP STA 1 (520) and non-AP STA 2 (530) may detect the medium as idle based on the physical CS. If non-AP STA 1 (520) and non-AP STA 2 (530) detect the medium as idle based on the physical CS and the default NAV is not set (wherein the intra-BSS NAV is ignored during DS transmission), non-AP STA 1 (520) and non-AP STA 2 (530) can detect the medium as idle based on the virtual CS. If non-AP STA 1 (520) and non-AP STA 2 (530) detect the medium as idle based on the physical CS and virtual CS during the AIFS[PEDCA] time, non-AP STA 1 (520) and non-AP STA 2 (530) can transmit DS (624-1, 624-2, 624-3). As described above, the point in time when non-AP STA 1 (520) to non-AP STA 3 (540) can access the medium again may be the point in time when the frame exchange of AP (510) and non-AP STA 3 (540) is completed.

[0186] Among non-AP STA 1 (520) to non-AP STA 3 (540), the STA whose backoff counter becomes 0 by the above-described PEDCA channel access operation 'step 3' and whose channel access operation is completed first can transmit a frame (e.g., a low-latency frame) according to the above-described PEDCA channel access operation 'step 4'. In FIG. 14, the channel access operation by non-AP STA 2 (530) according to the above-described PEDCA channel access operation 'step 3' is completed first and transmits a frame.

[0187] FIG. 15 is a diagram illustrating a method for indicating PEDCA and channel access parameters when using wireless LAN PEDCA applicable to the present disclosure.

[0188] Referring to FIG. 15, an AP (710) and a plurality of STAs (e.g., STA 1, STA 2, STA 3) connected to the AP (710) can operate in a wireless LAN network. The AP (710) and the plurality of STAs connected to the AP (710) can form a basic service set (BSS). The AP (710) can direct the use of a high-priority PEDCA within the BSS. The AP (710) can direct the use of PEDCA through at least one of a beacon, a probe response frame, and other frames. Alternatively, PEDCA can be performed by individual STAs without directives from the AP (710). When STAs using PEDCA need to perform channel access using PEDCA, a PEDCA channel access operation such as that described in FIG. 7 above and FIG. 16 below can be performed.

[0189] FIG. 16 is a diagram illustrating a PEDCA channel access method applicable to the present disclosure. Referring to FIG. 16, an operation based on the wireless LAN network of FIG. 15 can be considered. Here, non-AP STA 1 (720) and non-AP STA 2 (730) may be STAs using PEDCA. Meanwhile, non-AP STA 3 (740) may be a STA using (general) EDCA that does not use PEDCA. As an example, non-AP STA 1 (720) and non-AP STA 2 (730) may transmit AC VO frames according to the PEDCA channel access operation described above in FIG. 7. However, the above-described situation is for convenience of explanation only and is not limited thereto.

[0190] FIG. 17 is a diagram illustrating the DS transmission method of PEDCA when a frame reception error occurs, applicable to the present disclosure.

[0191] Referring to FIG. 17, an AP (710) in a wireless LAN network and a non-AP STA 1 (720) connected to the AP (710) and other STAs, or a wireless LAN terminal operating in another wireless LAN network (e.g., a STA and / or AP (710) operating in another BSS (basic service set)) may operate. The non-AP STA 1 (720) may be a STA that supports the PEDCA channel access operation of FIG. 7 and FIG. 16 described above. When the non-AP STA 1 (720) receives a frame (801) transmitted by another wireless LAN terminal (e.g., a STA or AP other than STA 1), it may detect that the medium is occupied. Here, a reception error of the frame (801) may occur at the non-AP STA 1 (720). The reception error may occur as follows. Specifically, if a frame reception error occurs at the physical layer of non-AP STA 1 (720), a frame reception error may occur at non-AP STA 1 (720). For example, consider a case where non-AP STA 1 (720) fails to detect at least one of the physical layer (PHY) preamble and header and detects only the energy of the medium. For another example, even if the PHY layer of non-AP STA 1 (720) correctly detects at least one of the physical layer (PHY) preamble and header, it may fail to detect the frame while receiving the frame. In the above case, the PHY layer of non-AP STA 1 (720) may fail to receive the frame. Here, the PHY layer of non-AP STA 1 (720) can generate the PHY-RXEND.indication primitive, and the PHY layer of non-AP STA 1 (720) can indicate that an error occurred in the PHY-RXEND.indication primitive. That is, PHY-RXEND.If the RXERROR parameter of the indication primitive is not NoError, a frame reception error may occur in non-AP STA 1 (720).

[0192] As another example, a frame reception error may occur at the MAC layer of non-AP STA 1 (720). Even if the physical layer of non-AP STA 1 (720) detects the correct PHY preamble and the physical layer successfully receives the entire frame, a frame error may still occur at the MAC layer. The MAC layer frame contains a MAC header. The MAC header may contain a field that checks for errors in the frame using a cyclic redundancy check (CRC) as a frame check sequence (FCS) to verify the MAC frame. The non-AP STA 1 (720) can use the FCS field to check for errors in the frame at the MAC layer, and if an error exists in the frame, the MAC layer of non-AP STA 1 (720) can confirm that an error occurred in frame reception.

[0193] As described above, if an error occurs in a frame, the first slot boundary at which the non-AP STA 1 (720) performs a backoff operation (e.g., decrementing the backoff counter and transmitting the frame) may be after the EIFS time when the error occurs in receiving the frame. The EIFS time may be a time to protect against collisions with response frames that the non-AP STA 1 (720) has not detected. The EIFS time may be determined by the following Equations 1 and 2, but is not limited thereto.

[0194] [Mathematical Formula 1]

[0195] EIFS = aSIFSTime + AckTxTime + DIFS

[0196]

[0197] In mathematical formula 1, AckTxTime may be the length of time required to transmit a response frame using the lowest modulation and coding scheme (MCS).

[0198]

[0199] [Mathematical Formula 2]

[0200] EIFS = aSIFSTime + EstimatedAckTxTime + DIFS

[0201]

[0202] In mathematical formula 2, EstimatedAckTxTime may be the length of the expected response frame, which is AckTxTime that varies depending on the version of the PHY where the error occurred.

[0203] As described above, since non-AP STA 1 (720) uses PEDCA, it may be necessary to define the EIFS time for the PEDCA channel access operation, and the EIFS time for the PEDCA channel access operation may be referred to as EIFS[PEDCA], but is not limited to that name. In the PEDCA channel access operation of FIGS. 7 and FIGS. 16, non-AP STA 1 (720) may transmit DS after the AIFS[PEDCA] time after the medium is switched from an occupied state to an idle state. Here, EIFS[PEDCA] may be configured as shown in Equation 3 below, based on the EIFS determined based on Equation 1 or Equation 2.

[0204] [Mathematical Formula 3]

[0205] EIFS[PEDCA] = EIFS - DIFS + AIFS[PEDCA] - aRxTxTurnAroundTime

[0206]

[0207] In Equation 3, 'AIFS[PEDCA] = AIFSN[PEDCA] * aSlotTime + aSIFSTime'. For example, AIFSN[PEDCA] may be a parameter transmitted by AP (710) to non-AP STA 1 (720) via a broadcast frame (e.g., a beacon frame or a probe response frame) or a unicast frame. As another example, 'AIFS[PEDCA] = (AIFSN[PEDCA] + DSr) * aSlotTime + aSIFSTime', where DSr may be a parameter set as in FIG. 7. DSr of EIFS[PEDCA] may be calculated every time EIFS[PEDCA] is used. Alternatively, DSr may be ignored (e.g., considered as 0).

[0208] As another example, the one described in detail in Fig. 7 This can be set to a maximum or minimum value, and EIFS[PEDCA] may be calculated and used based on the above. Meanwhile, aRxTxTurnAroundTime may be a time that accounts for the delay used by the wireless LAN terminal to perform channel access, and may be ignored when calculating EIFS. Accordingly, Equation 3 may be replaced with Equation 4 below.

[0209] [Mathematical Formula 4]

[0210] EIFS[PEDCA] = EIFS - DIFS + AIFS[PEDCA]

[0211]

[0212] Referring to FIG. 17, non-AP STA 1 (720) may use the PEDCA channel access operation after a frame error occurs. non-AP STA 1 (720) detects that the medium has transitioned from an occupied state to an idle state, and may wait for EIFS[PEDCA] time before transmitting DS (802) if a frame error occurs in the last detected occupied state of the medium. non-AP STA 1 (720) may transmit DS (802) if the medium is idle during the EIFS[PEDCA] time. After that, non-AP STA 1 (720) transmits an RTS frame (803) to AP (710), and AP (710) may respond to non-AP STA 1 (720)'s RTS frame (803) with a CTS frame (804). When non-AP STA 1 (720) receives a CTS frame (804) from AP (710), it can transmit an uplink data frame (805) to AP (710). Depending on the acknowledgment policy (ack policy) of the uplink frame transmitted by non-AP STA 1 (720) to AP (710), non-AP STA 1 (720) may or may not receive an acknowledgment frame from AP (710). In FIG. 17, non-AP STA 1 (720) may receive a BlockAck frame, which is an acknowledgment frame, from AP (710), but is not limited thereto. Additionally, EIFS[PEDCA] described in Equation 3 may be used commonly in the present disclosure, but is not limited thereto.

[0213] FIGS. 18a and FIGS. 18b are diagrams illustrating the problem of transmission collision occurring in PEDCA applicable to the present disclosure and the channel access method when transmission collision occurs in PEDCA.

[0214] Referring to FIGS. 18a and 18b, a case can be considered in which an AP (710) and non-AP STA 1 (720) and non-AP STA 2 (730) connected to the AP (710) operate in a wireless LAN network. Here, non-AP STA 1 (720) is a STA that uses the PEDCA channel access operation described above in FIGS. 7 and 16, and non-AP STA 2 (730) may be a STA that does not use the PEDCA channel access operation. non-AP STA 1 (720) can detect that the medium has switched from an occupied state to an idle state to transmit an AC_VO frame, and transmit a DS after AIFS[PEDCA] time from the time of detection. non-AP STA 2 (730) uses EDCA channel access operation and detects when the medium is switched from an occupied state to an idle state, and after AIFS[VO] time from the time of detection, it can decrease the backoff counter or transmit a frame if the backoff counter is already 0.

[0215] Here, if the AIFS[PEDCA] time or the AIFS[VO] time is the same, non-AP STA 1 (720) and non-AP STA 2 (730) can transmit frames simultaneously. For example, non-AP STA 1 (720) can transmit DS (806), and non-AP STA 2 (730) can transmit a data frame (807) or a control frame (e.g., an RTS frame) simultaneously. Since non-AP STA 1 (720) and non-AP STA 2 (730) transmit different frames simultaneously, a frame collision may occur. The AP (710) cannot decode the frames because non-AP STA 1 (720) and non-AP STA 2 (730) transmit frames simultaneously. That is, a frame reception error may occur. Therefore, the AP (710) may not transmit any frames after the frame has been received (e.g., after the medium has transitioned from an occupied state to an idle state). The non-AP STA 1 (720) may detect that the medium is in an occupied state after the frame has been transmitted. In the above case, the non-AP STA 1 (720) may confirm that the frame transmission has failed. Additionally, the non-AP STA 2 (730) may wait for a response frame from the AP (710) after the frame transmission is completed (e.g., after the PHY layer of STA 2 has generated the PHY-TXEND.indication primitive), and the waiting time for the response frame may be the AckTimeout time. The AckTimeout time may be 'aSIFSTime + aSlotTime + aRxPHYStartDelay' time. If the non-AP STA 2 (730) does not detect a response frame during the AckTimeout time, it may confirm that the response frame has failed to be received.

[0216] Referring to FIG. 18a, if a response frame is not received correctly, the non-AP STA 2 (730) may increase the parameters for channel access of the non-AP STA 2 (730). For example, the VO EDCAF of the non-AP STA 2 (730) may attempt to transmit but fail to transmit. In the above case, CW[VO], which is an AC[VO] related EDCA parameter of the non-AP STA 2 (730), may increase by a factor of 2, and QSRC[VO] may increase by 1. Since the CW[VO] of the non-AP STA 2 (730) increases, the probability that the next backoff counter value will be larger than the previous one may increase. Therefore, the channel access priority of the non-AP STA 2 (730) may decrease. On the other hand, non-AP STA 1 (720) can transmit DS (808) again if the medium is idle for the AIFS[PEDCA] time even if a frame collision occurs. That is, non-AP STA 1 (720) can have channel access priority even if a frame collision occurs with non-AP STA 2 (730). As described above, a fairness issue may arise between non-AP STA 1 (720) using PEDCA channel access operation and non-AP STA 2 (730) not using PEDCA channel access operation, and a solution to resolve this may be required.

[0217] Referring to FIG. 18b, if a response frame is not received correctly, the non-AP STA 2 (730) may increase the parameters for channel access of the non-AP STA 2 (730). For example, if the AC_VO EDCAF of the non-AP STA 2 (730) attempts to transmit but fails to transmit, the AC[VO] related EDCA parameter CW[VO] of the non-AP STA 2 (730) may be doubled, and QSRC[VO] may be increased by 1. Since the CW[VO] of the non-AP STA 2 (730) increases, the probability that the value of the next backoff counter will be larger than before increases. Therefore, the channel access priority of the non-AP STA 2 (730) may decrease. If non-AP STA 1 (720) detects a channel occupancy state for a certain period of time (e.g., at least one aSlotTime, or at least aCCATime) after transmitting DS (806), non-AP STA 1 (720) may determine that the transmission of DS (806) has failed. If the transmission of DS (806) fails, non-AP STA 1 (720) may perform a backoff operation before transmitting the next DS. That is, non-AP STA 1 (720) may perform a backoff operation without transmitting the next DS after AIFS[PEDCA] time has elapsed from the point at which it detects that the medium has transitioned from an occupied state to an idle state, and transmit at the slot boundary where the backoff counter is 0. If non-AP STA 1 (720) determines that the transmission of DS has failed, it may double CW[VO], which is an AC[VO] related EDCA parameter, and increase QSRC[VO] by 1. non-AP STA 1 (720) can select a backoff counter based on the increased CW[VO]. Additionally, non-AP STA 2 (730) can determine that the frame transmission failed if the AckTimeout time elapses after the frame transmission is completed.If non-AP STA 2 (730) determines that frame transmission has failed, it can double CW[VO], which is an AC[VO] related EDCA parameter, and increase QSRC[VO] by 1. non-AP STA 2 (730) can select a backoff counter based on the increased CW[VO]. non-AP STA 1 (720) can perform a backoff procedure at the first AIFS[VO] time or AIFS[PEDCA] time after detecting that the medium has transitioned from an occupied state to an idle state, and can decrease the backoff counter at each slot boundary.

[0218] As another example, non-AP STA 1 (720) may detect that the medium has switched to an occupied state after transmitting DS. Since non-AP STA 1 (720) failed to decode the frame normally during the interval where it detected the medium being occupied, it may have to wait for the EIFS time. As an example, the EIFS time may be the EIFS[PEDCA] time. At the slot boundary where the backoff counter is 0, non-AP STA 1 (720) may transmit a frame (e.g., DS). The slot boundary at which non-AP STA 2 (730) decrements the backoff counter after completing the frame transmission (after detecting that the medium has switched from an occupied state to an idle state, or after the PHY layer of non-AP STA 2 (730) generates the PHY-TXEND.indication primitive) may vary. Specifically, non-AP STA 2 (730) may initiate a backoff procedure at the initial slot boundary of length AIFS[VO] after the AckTimeout time. Here, since the AIFS[VO] time is longer than the AckTimeout time, the AckTimeout time may be included within the initial slot boundary of length AIFS[VO]. If non-AP STA 1 (720) transmits DS before non-AP STA 2 (730), non-AP STA 1 (720) may perform the short backoff operation described above in FIGS. 7 and FIGS. 16 and transmit the frame to AP (710). Meanwhile, if non-AP STA 2 (730) transmits an uplink frame in priority over non-AP STA 1 (720), non-AP STA 1 (720) may have to wait until non-AP STA 2 (730) completes transmitting the frame to the AP (710) before transmitting the next DS.

[0219] As another example, if non-AP STA 1 (720) detects that the medium is occupied for a certain period of time after DS transmission and determines that DS transmission has failed, non-AP STA 1 (720) may perform channel access operations using a standard EDCA channel access operation instead of using a PEDCA channel access operation. If non-AP STA 1 (720) determines that DS transmission has failed, it may double CW[VO], an EDCA parameter related to AC[VO], and increase QSRC[VO] by 1. Additionally, non-AP STA 1 (720) may select a backoff counter based on the increased CW[VO]. Alternatively, if non-AP STA 1 (720) decides to use standard EDCA instead of PEDCA, non-AP STA 1 (720) may select a backoff counter using initial EDCA parameters (e.g., initial parameters where CW[VO] is the value of CWmin[VO] and QSRC[VO] is 0). FIG. 18b may be a case where non-AP STA 2 (730) succeeds in transmitting an uplink frame before non-AP STA 1 (720), but this is for convenience of explanation only and is not limited thereto. Even if a frame collision occurs between non-AP STA 1 (720) and non-AP STA 2 (730), fairness in frame transmission between non-AP STA 1 (720) and non-AP STA 2 (730) can be guaranteed and is not limited to a specific form.

[0220] FIGS. 19a to 19c are drawings illustrating problems that occur when RTS transmission fails in PEDCA applicable to the present disclosure, and methods for media detection and channel access when RTS transmission fails in PEDCA.

[0221] Referring to FIGS. 19a through 19c, an AP (710) and non-AP STA 1 (720) through non-AP STA 3 (740) connected to the AP (710) can operate in a wireless LAN network. The non-AP STA 1 (720) through non-AP STA 3 (740) can support the PEDCA channel access operation described above in FIGS. 7 and FIG. 16. The non-AP STA 1 (720) through non-AP STA 3 (740) can simultaneously transmit DS (809-1, 809-2, 809-3) after AIFS[PEDCA] time from the time when they detect that the medium has switched from an occupied state to an idle state. non-AP STA 1 (720) to non-AP STA 3 (740) can transmit DS (809-1, 809-2, 809-3) and perform a short backoff operation. For example, non-AP STA 1 (720) may have selected a backoff counter smaller than that of non-AP STA 2 (730) and non-AP STA 3 (740), and may have transmitted the RTS frame (810) first. Here, the transmission of the RTS frame (810) may fail. At the time when non-AP STA 1 (720) has completed the transmission of the RTS frame (810) (after the PHY layer of STA 1 has generated the PHY-TXEND.indication primitive), if a response frame is not detected within a CTSTimeout, such as the AckTimeout time described in FIG. 18a and FIG. 18b, non-AP STA 1 (720) can determine that the transmission of the RTS frame (810) has failed. Meanwhile, non-AP STA 2 (730) and non-AP STA 3 (740) receive the RTS frame (810) of non-AP STA 1 (720) and can set a NAV (network allocation vector) timer based on the value indicated in the duration field of the MAC header of the RTS frame (810). The NAV timer may be referred to as NAV and is not limited to a specific name.

[0222] When NAV is set on non-AP STA 2 (730) and non-AP STA 3 (740), non-AP STA 2 (730) and non-AP STA 3 (740) can detect the medium as being occupied based on virtual CS. When NAV is set, non-AP STA 2 (730) and non-AP STA 3 (740) may not be able to perform frame transmission because they detect the medium as being occupied even after the reception of the RTS frame (810) is complete. Meanwhile, non-AP STA 1 (720) does not set NAV for the RTS frame (810) that it has transmitted. If non-AP STA 1 (720) determines that the transmission of the RTS frame (810) has failed, non-AP STA 1 (720) can transmit DS (811) again after AIFS[PEDCA] time from the time of completion of transmission of the RTS frame (810). Alternatively, non-AP STA 1 (720) may transmit DS (810) again after AIFS[PEDCA] time has elapsed following the CTSTimeout time. Here, non-AP STA 2 (730) and non-AP STA 3 (740) may release the NAV set by the RTS frame (810) if no frame is detected during the NAVTimeout time, which is longer than the CTSTimeout time. However, if non-AP STA 1 (720) transmits DS (811) again, non-AP STA 2 (730) and non-AP STA 3 (740) may confirm the NAV without releasing it. In the above case, channel access operations and frame transmission of non-AP STA 2 (730) and non-AP STA 3 (740) are impossible due to the NAV initially set by non-AP STA 1 (720), and only non-AP STA 1 (720) can perform channel access operations.non-AP STA 1 (720) can perform a short backoff operation after DS transmission during the period when other STAs are unable to perform channel access operations, and can transmit frames to AP (710). In the above case, non-AP STA 1 (720) may exclusively perform channel access, which may cause fairness issues, and a solution may be needed to resolve this.

[0223] Referring to FIG. 19b, non-AP STA 2 (730) and non-AP STA 3 (740) may release the NAV set based on the RTS frame (810) of non-AP STA 1 (720) if no frame is detected within the CTSTimeout time after receiving the RTS frame (810) of non-AP STA 1 (720) (e.g., if the PHY-RXSTART.indication primitive is not generated in the PHY layer of each STA). Specifically, each of non-AP STA 2 (730) and non-AP STA 3 (740) may release the NAV set based on the RTS frame (810) if no frame is detected within the CTSTimeout time after non-AP STA 1 (720) transmits DS (809-1) and transmits the RTS frame (810). Here, non-AP STA 2 (730) and non-AP STA 3 (740) may start waiting to transmit DS (812-2, 812-3) at the same time as non-AP STA 1 (720). For example, non-AP STA 2 (730) and non-AP STA 3 (740) may transmit DS (812-2, 812-3) again after AIFS[PEDCA] time from the time of completion of transmission of the RTS frame (810). For another example, non-AP STA 2 (730) and non-AP STA 3 (740) may transmit DS (812-2, 812-3) again after AIFS[PEDCA] time has passed after the CTSTimeout time. Accordingly, non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously transmit DS (812-1, 812-2, 812-3), and non-AP STA 1 (720) to non-AP STA 3 (740) can perform a fairly short backoff operation.In FIG. 19b, non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously perform a short backoff operation after DS transmission. In FIG. 19b, non-AP STA 3 (740) may select the shortest backoff counter and transmit an RTS frame first to transmit an uplink frame to the AP (710), but this is for convenience of explanation only and is not limited thereto.

[0224] Referring to FIG. 19c, if the transmission of the RTS frame (810) fails, the non-AP STA 1 (720) may wait for an EIFS time (e.g., EIFS time, EIFS[PEDCA] time, EIFS[VO] time) before transmitting the next DS (813-1). The start time for the non-AP STA 1 (720) to wait for the EIFS time may be when the non-AP STA 1 (720) has completed transmitting the RTS frame (810) (or when the CTSTimeout time has passed after transmitting the RTS frame). The non-AP STA 1 (720) may transmit the DS (813-1) if the medium is detected to be idle during the EIFS time. non-AP STA 2 (730) and non-AP STA 3 (740) may set NAV when they receive an RTS frame from non-AP STA 1 (720) after DS transmission. Here, the set NAV may be released by applying EIFS time instead of applying NAVTimeout time. Specifically, non-AP STA 2 (730) and non-AP STA 3 (740) may release the set NAV based on the RTS frame (810) from non-AP STA 1 (720) after receiving the RTS frame (810) and after EIFS time (or, if no frame is detected within the time between CTSTimeout time and EIFS time after RTS frame transmission is complete) (e.g., if the PHY-RXSTART.indication primitive is not generated in the PHY layer of each STA). That is, when the NAV of non-AP STA 2 (730) and non-AP STA 3 (740) is released, EIFS may be applied instead of NAVtimeout. Additionally, non-AP STA 2 (730) and non-AP STA 3 (740) may transmit DS (813-2, 813-3) when releasing the NAV.As another example, non-AP STA 2 (730) and non-AP STA 3 (740) may receive an RTS frame (810) and release NAV if no frame is detected within NAVTimeout. Non-AP STA 2 (730) and non-AP STA 3 (740) may be able to transmit a frame after EIFS time from the time the above-mentioned NAV is released or the time the RTS frame (810) is received.

[0225] Additionally, for example, the EIFS time may be longer than the NAV timeout of the NAV set by the RTS frame (810). Non-AP STA 1 (720) can transmit the RTS frame (810) and transmit DS (813-1) if the medium is detected to be idle during the EIFS time. Additionally, non-AP STA 2 (730) and non-AP STA 3 (740) can also receive the RTS frame (810) and transmit DS (813-2, 813-3) after the EIFS time, which is longer than the NAV timeout. Here, non-AP STA 2 (730) and non-AP STA 3 (740) can initiate the EIFS slot boundary through physical medium detection rather than virtual medium detection caused by the NAV. As described above, non-AP STA 2 (730) and non-AP STA 3 (740) can transmit DS (813-2, 813-3) after the time when NAV is released by the RTS frame (810), and non-AP STA 1 (720) to non-AP STA 3 (740) can transmit DS (813-1, 813-2, 813-3) simultaneously. Meanwhile, although the NAVTimeout time is described as being longer than the EIFS time, the NAVTimeout may be shorter than the EIFS time. In this case as well, the operation described above may be performed.

[0226] Accordingly, non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously transmit DS (813-1, 813-2, 813-3), and non-AP STA 1 (720) to non-AP STA 3 (740) can perform a fairly short backoff operation. In FIG. 19c, non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously transmit DS (813-1, 813-2, 813-3) and perform a short backoff operation. In FIG. 19c, non-AP STA 3 (740) can select the shortest backoff counter and non-AP STA 3 (740) can transmit an RTS frame first to transmit an uplink frame to AP (710), but this is for convenience of explanation only and is not limited thereto.

[0227] FIGS. 20a and 20b are diagrams illustrating problems that occur during RTS transmission collisions in PEDCA applicable to the present disclosure and methods for media detection and channel access when RTS transmission fails in PEDCA.

[0228] Referring to FIGS. 20a and 20b, an AP (710) and non-AP STA 1 (720) to non-AP STA 3 (740) connected to the AP (710) can operate in a wireless LAN network. The non-AP STA 1 (720) to non-AP STA 3 (740) can support the PEDCA channel access operation described above in FIGS. 7 and FIGS. 16. The non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously transmit DS after an AIFS[PEDCA] time from the time they detect that the medium has switched from an occupied state to an idle state. The non-AP STA 1 (720) to non-AP STA 3 (740) can perform a short backoff operation after transmitting DS (814-1, 814-2, 814-3). Here, non-AP STA 1 (720) and non-AP STA 2 (730) may have the same backoff counter, and the backoff counters of non-AP STA 1 (720) and non-AP STA 2 (730) may be smaller than the backoff counter of non-AP STA 3 (740). Thus, non-AP STA 1 (720) and non-AP STA 2 (730) may have transmitted the RTS frames (815-1, 815-2) first. However, the RTS frames (815-1, 815-2) may not be frames considered to be transmitted simultaneously, such as DS (814-1, 814-2, 814-3). Therefore, if non-AP STA 1 (720) and non-AP STA 2 (730) transmit RTS frames (815-1, 815-2) simultaneously, a collision may occur. At the time when non-AP STA 1 (720) and non-AP STA 2 (730) complete the transmission of RTS frames (815-1, 815-2) (the PHY layer of non-AP STA 1 (720) is PHY-TXEND.After generating the indication primitive, if no response frame is detected within the same CTSTimeout as the AckTimeout time described in FIG. 18a and FIG. 18b, non-AP STA 1 (720) and non-AP STA 2 (730) can determine that the transmission of RTS frames (815-1, 815-2) has failed. non-AP STA 3 (740) may be unable to decode the RTS frames (815-1, 815-2) that collided because non-AP STA 1 (720) and non-AP STA 2 (730) transmitted them simultaneously. Accordingly, non-AP STA 3 (740) may wait for EIFS time (e.g., EIFS time, EIFS[PEDCA] time, EIFS[VO] time) after detecting that the medium has switched from an occupied state to an idle state due to the crashed RTS frames (815-1, 815-2). Additionally, non-AP STA 1 (720) and non-AP STA 2 (730) may wait for AIFS[PEDCA] time, which is shorter than EIFS time, after the completion of transmission of RTS frames (815-1, 815-2), or wait for AIFS[PEDCA] time after CTSTimeout time at the time of completion of transmission of RTS frames (815-1, 815-2). non-AP STA 1 (720) and non-AP STA 2 (730) can transmit DS (816-1, 816-2) if they detect that the medium is idle during that time. In the above case, non-AP STA 3 (740), which failed to transmit DS due to the EIFS time wait operation, may not be able to perform a short backoff operation. That is, channel access opportunities may be provided to non-AP STA 1 (720) and non-AP STA 2 (730) that caused the collision, while channel access opportunities may not be provided to non-AP STA 3 (740) that did not cause the collision. Accordingly, fairness issues may arise, and a solution may be required.

[0229] Referring to FIG. 20b, non-AP STA 1 (720) and non-AP STA 2 (730) may wait for an EIFS time (e.g., EIFS time, EIFS[PEDCA] time, EIFS[VO] time) before transmitting the next DS if the transmission of RTS frames (815-1, 815-2) fails. The start time for non-AP STA 1 (720) and non-AP STA 2 (730) to wait for the EIFS time may be when non-AP STA 1 (720) and non-AP STA 2 (730) have completed transmitting the RTS frames (815-1, 815-2) (or when the CTSTimeout time has passed after the transmission of the RTS frames is complete). non-AP STA 1 (720) and non-AP STA 2 (730) can transmit DS (817-1, 817-2) when the medium is detected to be idle during the EIFS time. Meanwhile, non-AP STA 3 (740) can transmit DS (817-3) after receiving the crashed RTS frame (815-1, 815-2) and after the EIFS time (or if the medium is not detected to be occupied within the time between the CTSTimeout time and the EIFS time after the RTS frame transmission is complete). Thus, non-AP STA 1 (720) to non-AP STA 3 (740) can transmit DS (817-1, 817-2, 817-3) simultaneously, and non-AP STA 1 (720) to non-AP STA 3 (740) can perform a fairly short backoff operation. In FIG. 20b, non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously transmit DS (817-1, 817-2, 817-3) and perform a short backoff operation.In FIG. 20b, non-AP STA 3 (740) selects the shortest backoff counter and transmits an RTS frame first to transmit an uplink frame to AP (710), but this is for convenience of explanation only and is not limited thereto.

[0230] As another example, non-AP STA 1 (720), non-AP STA 2 (730), and non-AP STA 3 (740) may wait for the AIFS[PEDCA] time before transmitting the next DS if the transmission of the RTS frame (815-1, 815-2) fails. The time when non-AP STA 1 (720) and non-AP STA 2 (730) begin waiting for the AIFS[PEDCA] time may be when the transmission of the RTS frame is completed or when the transmission of the RTS frame is completed and the CTSTimeout time has passed. The time when non-AP STA 3 (740) begins waiting for the AIFS[PEDCA] time may be when the reception of the RTS frame is completed (when the reception of the frame detected as an error is completed) or when the reception of the RTS frame is completed and the CTSTimeout time has passed. Accordingly, non-AP STA 1 (720) to non-AP STA 3 (740) can simultaneously transmit DS (817-1, 817-2, 817-3), and non-AP STA 1 (720) to non-AP STA 3 (740) can perform a fairly short backoff operation.

[0231] In the above-described FIGS. 18a to 20b, if the STA using the PEDCA channel access operation fails to transmit a DS frame (or, if the transmission of an RTS frame fails after the DS transmission), the STA using the PEDCA channel access operation may update the EDCA channel access parameters. The PEDCA channel access operation can replace the operation of the EDCAF transmitting an AC VO frame. That is, it can perform an operation that replaces the VO EDCAF. If the STA using the PEDCA channel access operation fails to transmit a DS frame (or, if the transmission of an RTS frame fails after the DS transmission), the STA using the PEDCA channel access operation may update CW[VO] and QSRC[VO]. For example, the STA using the PEDCA channel access operation may increase CW[VO] by a factor of 2 using CWmax[VO] as the upper limit, and increase QSRC[VO] by 1 using Dot11RetryLimit, a parameter set per STA. If certain conditions are met (e.g., failure to transmit DS more than a certain number of times, or failure to receive response frames for RTS frames more than a certain number of times after transmitting DS, or failure to transmit RTS frames more than a certain number of times after transmitting DS), the STA using the PEDCA channel access operation may need to transmit AC VO frames using the existing VO EDCAF instead of using the PEDCA channel access operation. Here, the backoff counters for AC VO EDCAF to perform the channel access operation can be selected as the CW[VO] parameter and the QSRC[VO] parameter. Meanwhile, if the STA using the PEDCA channel access operation successfully acquires a TXOP after transmitting DS and transmits a frame, the EDCA channel access parameters CW[VO] and QSRC[VO] may be updated to their initial values.For example, CW[VO] can be set to CWmin[VO], and QSRC[VO] can be set to 0. That is, the operation described above may consider a frame transmission failure or a TXOP acquisition failure caused by the PEDCA channel access operation as a transmission failure of VO EDCAF. Additionally, a frame transmission success or a TXOP acquisition success caused by the PEDCA channel access operation may be considered a transmission success of VO EDCAF. For example, the operation described above may be applied to all wireless LAN terminals (non-AP STA and AP) using the PEDCA channel access operation described in FIG. 7 and FIG. 16, but is not limited thereto.

[0232] FIG. 21 is a flowchart illustrating the operation of an STA in a wireless LAN to which the present disclosure applies. Referring to FIG. 21, the STA can confirm that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first predetermined time (S2110). Here, the STA can perform channel access via P-EDCA (prioritized enhanced distributed channel access). Subsequently, the STA transmits a DS (defer signal) after the first predetermined time (S2120), and after transmitting the DS, performs a backoff procedure to perform frame transmission at the slot boundary where the backoff counter reaches 0 (S2130).

[0233] For example, the first set time may be determined based on P-EDCA related parameters. When P-EDCA is used in a basic service set (BSS) that includes STA, the P-EDCA related parameters may be determined based on at least one of the basic parameter values ​​and the modified parameter values. Additionally, the first set time may be determined based on the modified parameter values. The first set time is an arbitrary interframe space (AIFS) associated with DS transmission, the AIFS is a time set based on the sum of aSIFSTime and N*aSlotTime, and N may be determined based on at least one of the basic parameter values ​​and the modified parameter values.

[0234] Alternatively, the first set time may be a time set based on the EIFS (extended interframe space). The EIFS is a time set based on at least one of failure to detect a frame transmitted by another STA or occurrence of a reception error while the channel is occupied, and the EIFS may be a time set as the sum of 2*aSIFSTime, N*aSlotTime, and AckTxTime. Additionally, if an error occurs in the last detected frame while the channel is occupied, the STA may transmit a DS for P-EDCA contention based on at least one of the first set time, the frame response wait time, and the NAV wait time associated with the frame. The DS may be transmitted at the first slot boundary resulting from the elapsed first set time after the frame in which the error occurred while the channel is occupied.

[0235] Additionally, the STA may occupy the channel based on a backoff procedure after DS transmission and transmit a frame at the slot boundary where the backoff counter reaches 0. If a response frame for the frame is not detected within the response waiting time, the DS may be retransmitted after a second set time from the time the frame transmission is completed or after the response waiting time has elapsed from the time the frame transmission is completed. Additionally, NAVs are set for at least one STA that performs channel access via P-EDCA based on the frame transmitted by the STA, wherein the NAVs set for at least one STA are released if a response frame for the frame is not detected within the response waiting time, and DS transmission by at least one STA may also be performed together with the DS transmission of the STA after a second set time from the time the frame transmission is completed. The second set time may be determined based on P-EDCA related parameters. Additionally, the second set time is AIFS or EIFS, and NAV is set for at least one STA that performs channel access via P-EDCA based on a frame transmitted by the STA, and the NAV set for at least one STA is released after the second set time from the time when frame transmission is completed, so that DS transmission by at least one STA can also be performed together with the DS transmission of the STA. Additionally, the STA is a TXOP responder for a transmit opportunity (TXOP) set by another STA, and a network allocation vector (NAV) may be set for at least one STA that performs channel access via P-EDCA through frame exchange between the STA and another STA within the TXOP.In the case where the NAV is not set on the STA that is the TXOP responder and the channel is switched from an occupied state to an idle state due to the early termination of frame exchange between the STA and another STA within the TXOP, the STA may wait until the time of termination of the NAV set on at least one STA that performs channel access via P-EDCA, and transmit the DS after a first set time. Additionally, the NAV is set on the STA that is the TXOP responder, and the channel is detected to be in an occupied state until the time of termination of the NAV, and when the NAV is released, the DS may be transmitted after a first set time. In addition, if the frame exchange between the STA and another STA within the TXOP is terminated prematurely, the NAV set on at least one STA performing channel access via P-EDCA is terminated at the time of receiving the CF (contention free)-end frame, and the STA transmits the DS after a first set time from the time of receiving the CF-end frame, and the DS transmitted by at least one STA performing channel access via P-EDCA may also be transmitted together after a first set time from the time of receiving the CF-end frame. In addition, if the STA performs a backoff procedure after transmitting the DS, the backoff procedure is also performed on the other STA that received the DS, and if the channel is occupied by the other STA based on the other backoff procedure, the STA may retransmit the DS after a first set time from the time when the channel occupancy by the other STA ends. For example, the STA may be a non-AP STA or an AP STA.

[0236] In addition, as a method of operation for an STA in a wireless LAN, the STA can check that the channel has transitioned from an occupied state to an idle state and that the channel is in an idle state for a first set period of time. Here, the STA can perform channel access through P-EDCA (prioritized enhanced distributed channel access). The STA can detect a DS (defer signal) transmitted from another STA within the first set period of time, and if the STA detects the DS, it can perform a backoff procedure. Here, the other STA can also perform a backoff procedure based on the transmitted DS. That is, the STA and other STAs can compete for channel occupancy, and if the channel is occupied, frame transmission can be performed at the slot boundary where the backoff counter reaches 0.

[0237] 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.

[0238]

[0239] 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 in which the above STA confirms that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first pre-set time, wherein the STA performs channel access through P-EDCA (prioritized enhanced distributed channel access); A step of transmitting a DS (defer signal) after the first set time; and A method of operation comprising the step of performing a backoff procedure after the above DS transmission, and performing frame transmission at the slot boundary where the backoff counter reaches 0.

2. In Paragraph 1, The above-mentioned first set time is determined based on P-EDCA related parameters, in a method of operation.

3. In Paragraph 2, A method of operation in which, when the above P-EDCA is used in a BSS (basic service set) including the above STA, the P-EDCA related parameter is determined based on at least one of a basic parameter value and a modified parameter value.

4. In Paragraph 3, A method of operation in which the first set time is determined based on the change parameter value.

5. In Paragraph 3, A method of operation in which the first time set above is an AIFS (arbitrary interframe space) related to the transmission of the DS, the AIFS is a time set based on the sum of aSIFSTime and N*aSlotTime, and N is determined based on at least one of the basic parameter value and the change parameter value.

6. In Paragraph 3, A method of operation in which the first time set above is a time set based on EIFS (extended interframe space), wherein the EIFS is a time set based on at least one of failure to detect a frame transmitted by another STA or occurrence of a reception error while the channel is occupied, and the EIFS is a time set as the sum of 2*aSIFSTime, N*aSlotTime, and AckTxTime.

7. In Paragraph 6, A method of operation in which, if an error occurs in the last detected frame while the channel is occupied, the STA transmits the DS for P-EDCA competition based on at least one of the first preset time, the response waiting time of the frame, and the NAV waiting time associated with the frame.

8. In Paragraph 7, The above DS is transmitted at the first slot boundary by the elapsed time of the first set time after the above frame in which an error occurred while the above channel is occupied, in a method of operation.

9. In Paragraph 7, A method of operation in which the STA occupies the channel based on the backoff procedure after transmitting the DS, transmits the frame at the slot boundary where the backoff counter reaches 0, and if a response frame for the frame is not detected within the response waiting time, retransmits the DS after a second set time from the time when the frame transmission is completed or the time when the response waiting time has elapsed from the time when the frame transmission is completed.

10. In Paragraph 9, A method of operation in which a NAV is set in at least one STA that performs channel access through the P-EDCA based on the frame transmitted by the STA, wherein the NAV set in the at least one STA is released if the response frame for the frame is not detected within the response waiting time, and a DS transmission by the at least one STA is also performed together with the DS transmission of the STA after the second previously set time from the time when the frame transmission is completed.

11. In Paragraph 9, The above-mentioned second set time is determined based on P-EDCA related parameters, in a method of operation.

12. In Paragraph 9, A method of operation in which the second set time is AIFS or EIFS, and NAV is set in at least one STA that performs channel access through the P-EDCA based on the frame transmitted by the STA, and the NAV set in the at least one STA is released after the second set time from the time when the frame transmission is completed, so that DS transmission by the at least one STA is also performed together with the DS transmission of the STA.

13. In Paragraph 1, A method of operation in which the above STA is a TXOP responder to a transmit opportunity (TXOP) set by another STA, and a network allocation vector (NAV) is set for at least one STA that performs channel access through the P-EDCA by frame exchange between the STA and the other STA within the TXOP.

14. In Paragraph 13, A method of operation in which, when the NAV is not set on the STA that is the TXOP responder and the channel is switched from an occupied state to an idle state due to the early termination of frame exchange between the STA and the other STA within the TXOP, the STA waits until the termination point of the NAV set on the at least one STA performing channel access through the P-EDCA, and transmits the DS after the first set time.

15. In Paragraph 13, A method of operation in which the NAV is set in the STA, which is the TXOP responder, the channel is detected to be in an occupied state until the end of the NAV, and the DS is transmitted after the first set time when the NAV is released.

16. In Paragraph 6, A method of operation in which, if the frame exchange between the STA and the other STA within the above TXOP is terminated early, the NAV set in the at least one STA performing channel access through the P-EDCA is terminated at the time of receiving the CF (contention free)-end frame, and the STA transmits the DS after the first set time at the time of receiving the CF-end frame, wherein the DS transmitted by the at least one STA performing channel access through the P-EDCA is also transmitted together after the first set time at the time of receiving the CF-end frame.

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

18. In the method of operation of a station (STA) in a wireless LAN system, A step in which the above STA confirms that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first pre-set time, wherein the STA performs channel access through P-EDCA (prioritized enhanced distributed channel access); A step in which the above STA detects a DS (defer signal) transmitted from another STA within the first set time; A step of performing a backoff procedure when the STA detects the DS, wherein the backoff procedure is performed based on the DS transmitted to the other STA; and A method of operation comprising the step of performing frame transmission at a slot boundary where a backoff counter reaches 0 when the STA occupies the channel based on channel occupancy competition with the other STA.

19. In a wireless LAN system, regarding a station (STA), At least one transceiver for transmitting and receiving signals; At least one processor controlling the above-mentioned at least one transmitting and receiving unit; and It includes a memory that stores instructions for the non-AP STA to perform a specific operation by the above at least one processor, and The above specific operation is: The above STA confirms that the channel is switched from an occupied state to an idle state and that the channel is in an idle state for a first set period of time, and the above STA performs channel access through P-EDCA (prioritized enhanced distributed channel access). After the first set time mentioned above, transmit DS (defer signal), and STA that performs a backoff procedure after the above DS transmission and performs frame transmission at the slot boundary where the backoff counter reaches 0.

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