Method and device for transmitting frame on basis of prioritized channel access operation of wireless LAN

Abstract

This operation method of an STA in a wireless LAN system may comprise the steps of: identifying, by the STA, that a channel transitions from a busy state to an idle state and the channel is in the idle state for a first preset time; transmitting, by the STA, a defer signal (DS) in order to start a P-EDCA contention after the first preset time when it is identified that the channel is in the idle state for the first preset time; and performing, by the STA, the P-EDCA contention after transmitting the DS, wherein, in the P-EDCA contention, frame transmission may be performed at a slot boundary where a backoff counter reaches 0 on the basis of a channel access operation including a backoff procedure.

Description

Frame transmission method and device based on priority channel access operation of wireless LAN

[0001] The present disclosure relates to a method and apparatus for transmitting frames based on priority channel access operations in a wireless local area network (WLAN). Specifically, it relates to a method and apparatus for transmitting urgent frames during low-latency channel access operations in a wireless LAN. Furthermore, it relates to an internal channel access method and apparatus for efficient low-latency frame transmission during priority channel access operations in a wireless LAN.

[0002]

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

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

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

[0006] Meanwhile, the technology forming the background of the invention is written to enhance understanding of the background of the invention and may include content that is not prior art already known to a person with ordinary knowledge in the field to which this technology belongs.

[0007]

[0008] The present disclosure relates to a method and apparatus for transmitting frames based on priority channel access operations in a wireless local area network (WLAN).

[0009] The present disclosure relates to a method and apparatus for transmitting an emergency frame during a low-latency channel access operation in a wireless LAN.

[0010] The present disclosure relates to a method and apparatus for preventing delay when transmitting an emergency frame based on the priority channel access operation of a wireless LAN.

[0011] The present disclosure relates to an internal channel access method and apparatus for efficient low-latency frame transmission during priority channel access operation of a wireless LAN.

[0012] The present disclosure relates to a method and apparatus for transmitting low-latency frames in consideration of internal competition of wireless LAN terminals in a priority channel access operation of a wireless LAN.

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

[0014]

[0015] According to one embodiment of the present specification, a method of operation of a station (STA) in a wireless LAN system comprises: a step in which the STA confirms that the channel is in an idle state after 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 time; a step in which, if the STA confirms that the channel is in an idle state for the first set time, the STA transmits a DS (defer signal) to start a P-EDCA (prioritized enhanced distributed channel access) competition after the first set time; and a step in which the STA performs a P-EDCA competition after transmitting the DS, and performs frame transmission at a slot boundary where the backoff counter reaches 0 based on a channel access operation including a backoff procedure, wherein while the P-EDCA competition is performed in the STA, channel access related to the transmission of a VO (voice) among a plurality of access categories (AC) is granted, and channel access related to the transmission of other ACs excluding the VO among the plurality of ACs may not be granted.

[0016] 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 the 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: confirming that a 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; and if it is confirmed that the channel is in an idle state for the first predetermined time, transmitting a defer signal (DS) to start a prioritized enhanced distributed channel access (P-EDCA) competition after the first predetermined time; and performing a P-EDCA competition after transmitting the DS, wherein the P-EDCA competition performs frame transmission at a slot boundary where a backoff counter reaches 0 based on a channel access operation including a backoff procedure, wherein while the P-EDCA competition is performed in the STA, channel access related to voice (VO) transmission among a plurality of access categories (AC) is granted, and channel access related to transmission of other ACs excluding the voice among the plurality of ACs is granted. Channel access may not be granted.

[0017] In addition, the following points may apply in common.

[0018] According to one embodiment of the present specification, the first set time may be an AIFS (arbitration interframe space) related to P-EDCA competition.

[0019] In addition, according to one embodiment of the present specification, while the STA performs P-EDCA competition, a channel access operation is granted based on the operation of the STA's VO transmission-related EDCAF (enhanced distributed channel access function), wherein the VO transmission-related EDCAF can perform channel access based on the VO transmission-related AIFS corresponding to a second previously set time.

[0020] Additionally, according to one embodiment of the present specification, a plurality of ACs of the STA perform channel access operations based on each AC-related EDCAF operation, but while the STA performs P-EDCA competition, other AC transmission-related EDCAF operations, excluding the VO transmission-related EDCAF, may be deferred and channel access operations may not be permitted.

[0021] Additionally, according to one embodiment of the present specification, when another deferred AC transmission-related EDCAF operation is resumed, the other AC transmission-related EDCAF may perform channel access based on AIFS according to a preset time corresponding to each of the ACs.

[0022] Additionally, according to one embodiment of the present specification, other AC transmission-related EDCAFs may include VI (video)-related EDCAFs, BE (best effort)-related EDCAFs, and BK (background)-related EDCAFs.

[0023] In addition, according to one embodiment of the present specification, if the STA completes frame transmission after channel occupation based on P-EDCA contention, the STA may not perform P-EDCA contention until the P-EDCA constraint is resolved.

[0024] In addition, according to one embodiment of the present specification, when the P-EDCA constraint is satisfied, the STA can update the VO transmission-related parameters and perform a channel access operation through the VO transmission-related AIFS corresponding to the updated parameters based on the VO transmission-related EDCAF operation.

[0025] Additionally, according to one embodiment of the present specification, when the P-EDCA constraint is satisfied, the STA resumes the EDCAF operation related to another AC transmission, and the EDCAF related to another AC transmission can perform channel access based on the AIFS according to each preset time corresponding to each AC.

[0026] Additionally, according to one embodiment of the present specification, the DS includes a MAC (medium access control) header, and the duration field of the MAC header indicates the length of time the medium is occupied after the DS is transmitted, wherein the length of time the medium is occupied may be a length of time corresponding to the time required for P-EDCA contention.

[0027] Additionally, according to one embodiment of the present specification, a TXNAV timer is set based on the time length indicated by the duration field after transmission of DS, and the TXNAV timer is a timer shared by multiple EDCAFs of STA, and if the value of the TXNAV timer is not 0, multiple EDCAFs of STA determine that the medium is in an occupied state and delay channel access operation, but the EDCAF related to VO transmission performs P-EDCA competition and may not consider the value of the TXNAV timer that is not 0 in determining the occupied state of the medium.

[0028] Additionally, according to one embodiment of the present specification, when the value of the TXNAV timer reaches 0, the plurality of EDCAFs of the STA do not consider the value of the TXNAV timer in determining the occupancy status of the medium, and the plurality of EDCAFs of the STA can resume the channel access operation deferred by the TXNAV timer.

[0029] Additionally, according to one embodiment of the present specification, a control variable indicating the medium occupancy state within the STA is set based on the time length indicated by the duration field after transmission of the DS, and the control variable is shared by a plurality of EDCAFs of the STA, and when the control variable indicates a first state, the plurality of EDCAFs of the STA determine the medium to be in an occupied state and delay channel access operations, wherein the EDCAF related to VO transmission performs P-EDCA competition and may not consider the state of the control variable in determining the medium occupancy state.

[0030] Additionally, according to one embodiment of the present specification, when the control variable is switched to a second state as the time length indicated by the duration field elapses, a plurality of EDCAFs of the STA can resume the channel access operation deferred by the control variable.

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

[0032]

[0033] According to the present disclosure, a method for transmitting frames based on priority channel access operations in a WLAN can be provided.

[0034] According to the present disclosure, a method for transmitting an emergency frame during a low-latency channel access operation in a wireless LAN can be provided.

[0035] According to the present disclosure, a method for preventing delay when transmitting an emergency frame based on the priority channel access operation of a wireless LAN can be provided.

[0036] According to the present disclosure, an internal channel access method for efficient low-latency frame transmission during priority channel access operation of a wireless LAN can be provided.

[0037] According to the present disclosure, a method for transmitting low-latency frames can be provided by taking into account internal competition of wireless LAN terminals in a priority channel access operation of a wireless LAN.

[0038] The technical problems to be solved by the present disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0039] 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.

[0040]

[0041] FIG. 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure applies.

[0042] FIG. 2 is a drawing showing a wireless LAN system to which the present disclosure is applied.

[0043] FIG. 3 is a diagram illustrating a method for indicating P-EDCA and channel access parameters when using Priority Enhanced Distributed Channel Access (P-EDCA) for wireless LANs applicable to the present disclosure.

[0044] FIG. 4 is a diagram illustrating an emergency frame transmission method when using P-EDCA applicable to the present disclosure.

[0045] FIGS. 5A and FIGS. 5B are drawings illustrating a collision prevention method when using P-EDCA applicable to the present disclosure.

[0046] FIG. 6 is a diagram showing the method of using P-EDCA when applying the MU EDCA timer applied to the present disclosure.

[0047] FIG. 7 is a diagram illustrating a method for limiting the use of P-EDCA applicable to the present disclosure.

[0048] FIG. 8 is a diagram illustrating a P-EDCA channel access method applied to the present disclosure.

[0049] FIG. 9 is a diagram illustrating a method for stopping internal competition when using P-EDCA applicable to the present disclosure.

[0050] FIG. 10 is a diagram illustrating a method for stopping internal competition when using P-EDCA applicable to the present disclosure.

[0051] FIG. 11 is a diagram illustrating a method for stopping internal competition when using P-EDCA applicable to the present disclosure.

[0052] FIGS. 12a and FIGS. 12b are diagrams illustrating a method for interrupting P-EDCA channel access during the transmission of control frames and management frames applicable to the present disclosure.

[0053] FIGS. 13a and FIGS. 13b are drawings illustrating a transmission queue management method when using P-EDCA applicable to the present disclosure.

[0054] FIG. 14 is a flowchart showing the operation of a STA in a wireless LAN to which the present disclosure applies.

[0055]

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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."

[0063] 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.

[0064] 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).

[0065] 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).

[0066] 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).

[0067] 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.

[0068] 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.

[0069] FIG. 3 is a diagram illustrating a method for indicating P-EDCA and channel access parameters when using Priority Enhanced Distributed Channel Access (P-EDCA) for wireless LANs applicable to the present disclosure.

[0070] Referring to FIG. 3, an AP (310) and multiple STAs connected to the AP (310) (e.g., non-AP STA 1 (320), non-AP STA 2 (330), non-AP STA 3 (340)) may operate in a wireless LAN network. The AP (310) and the multiple STAs connected to the AP (310) may form a basic service set (BSS). Here, the AP (310) may instruct the use of high-priority P-EDCA within the BSS. The AP (310) may include and transmit P-EDCA usage instruction information in a beacon or probe response frame to convey instruction information regarding P-EDCA usage to all STAs connected to the AP (310). As another example, P-EDCA may also be performed by individual STAs without instruction from the AP (310) and is not limited to a specific form.

[0071] When STAs using P-EDCA perform channel access using P-EDCA, the STAs using P-EDCA may perform the following P-EDCA channel access operations. For example, DSAIFS[AC_VO] may be applied at regular time intervals in relation to the following [P-EDCA channel access operations]. Here, DSAIFS[AC_VO] may be referred to as AIFS(arbitration inter frame space)[P-EDCA] or any other name, and is not limited to a specific term or name.

[0072]

[0073] [P-EDCA Channel Access Operation]

[0074] Step 1: Verify that the medium is not in a busy state for DSAIFS[AC_VO] hours since the last detected busy (physical CS (carrier sense), virtual CS).

[0075] A. DSAIFS(defer signal arbitration inter frame space)[AC_VO] may be identical to DIFS(DCF(distributed coordinated function) IFS). Alternatively, DSAIFS[AC_VO] may be identical to AIFS(arbitration inter frame space)[VO]. Alternatively, DSAIFS[AC_VO] may have a time length selected each time during a P-EDCA channel access operation. In the above case, DSAIFS[AC_VO] may have a time length equal to or different from AIFS[VO] selected at the start of the P-EDCA channel access operation (i.e., at the start of Step 1), and that time length may be set. For example, the above different time length may be set to a time longer than AIFS[VO] by N multiples of aSlotTime (N is an integer greater than or equal to 1). Alternatively, the above different time length may be determined and set at each start of DSAIFS[AC_VO]. For example, the time length of DSAIFS[AC_VO] can be set to increase by DSr * aSlotTime, and DSr can be an integer determined based on a uniform probability distribution whenever DSAIFS[AC_VO] starts within an integer window (e.g., [0, CWds[AC_VO]]) specified by AP. If the value of CWds[AC_VO] is specified as 1, DSr can have an integer value of 0 or 1 at the start of each DSAIFS[AC_VO], and the time length of DSAIFS[AC_VO] can change based on this. If the value of CWds[AC_VO] is specified as 0, DSr can be fixed to a value of 0 at the start of each DSAIFS[AC_VO].

[0076]

[0077] Step 2: In Step 1, if the medium is not occupied (i.e., idle), transmit a DS (defer signal).

[0078] A. A Defer Signal can be a frame such as a CTS (clear to send) frame or an RTS (request to send) frame. If the Defer Signal is a CTS frame, it may be referred to as DS-CTS.

[0079] i. If the Defer Signal is a CTS frame or an RTS frame, the CTS frame and the RTS frame may be frames 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. Meanwhile, the CTS frame and the RTS frame are MAC frames and may have a MAC header. The MAC header may include a duration field, and the duration field may be a field indicating the remaining time related to the exchange or transmission of the frame. In the above case, the value of the Duration field of the Defer Signal may indicate a value for the time interval (length) from the time the transmission of the Defer Signal is completed until the time the maximum allowed time of the channel access operation defined in Step 3 is completed. That is, the value of the duration field may be set to a value corresponding to or similar to the maximum time required for the short backoff operation (P-EDCA contention) of Step 3. The duration field of the Defer Signal (i.e., the duration field of the MAC header) may be used to temporarily suspend the transmission of STAs that are not performing the P-EDCA operation. Specifically, STAs that do not perform P-EDCA operations and receive the Defer Signal can set a Network Allocation Vector (NAV) based on the time interval information specified in the duration field of the MAC header of the Defer Signal. When the NAV is set, STAs that do not perform P-EDCA operations detect the medium as busy. STAs that perform P-EDCA operations perform channel access operations within the NAV interval.

[0080]

[0081] Step 3: The STAs that transmitted the DS may 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). This may be referred to as a short backoff operation in this disclosure. The short backoff operation may be a P-EDCA contention operation. The short backoff operation (P-EDCA contention) operation is initiated by the transmission of the DS.

[0082] A. The random backoff operation is an operation that selects a random backoff counter, decrements the backoff counter for each slot time (e.g., each of AIFS[VO] and multiple aSlotTimes may be a slot, or each of multiple aSlotTimes may be a slot), and transmits a frame at the slot boundary where the backoff counter reaches 0.

[0083] B. The random backoff counter selection may be an integer selected through a uniform random method in the interval [0, CW[P-EDCA]].

[0084] Meanwhile, referring to steps 3A and B, the maximum backoff length (time length) that P-EDCA STAs can perform after DS transmission may be the sum of AIFS time (e.g., AIFS[VO] time. However, the AIFS[VO] time that starts after DS transmission may be composed of 'aSIFSTime + P-EDCA AIFSN * aSlotTime', and the P-EDCA AIFSN value is 2 by default but may be replaced with a value indicated by AP (310)) and CW[P-EDCA] * aSlotTime. CW[P-EDCA] may be a value indicated by AP (310), but may be a pre-specified value (e.g., 7). The aforementioned pre-specified value may be equal to or based on the P-EDCA CWmax value, which is the largest value among the range of backoff counters that can be selected after DS transmission. For example, the maximum CW[P-EDCA] value for calculating the maximum backoff length that the above-described P-EDCA STAs can perform after DS transmission may need to be considered, and in this case, the P-EDCA CWmax value, which is the maximum value among the minimum and maximum values ​​of CW[P-EDCA], should be used. The above-described P-EDCA CWmax value and the above-described P-EDCA CWmin value are values ​​that can be set and indicated as integers greater than or equal to 1. The above-described CW[P-EDCA] is intended to refer to the value of a contention window for selecting a backoff counter performed after DS transmission, and its name may vary and is not limited to a specific form.

[0085]

[0086] Step 4: The STA that has completed the random backoff operation transmits a frame at the slot boundary where the backoff counter reaches 0.

[0087] A. The random backoff operation of steps 3 and 4 may be the same or similar to the EDCA backoff operation and EDCA TXOP acquisition procedure performed after DS transmission. The random backoff procedure of steps 3 and 4 may be performed by a designated channel access function (function) capable of performing the backoff operation after DS transmission. This may be AC_VO EDCAF (which may be referred to as EDCAF[AC_VO], EDCAF[VO], VO EDCAF, etc.) or P-EDCAF (which may be referred to as PEDCAF).

[0088] B. Frame transmission according to the EDCA TXOP acquisition procedure can be performed using the same procedure as the example described in the diagram below. The P-EDCA STA may decrement the backoff counter after DS-CTS transmission. The backoff counter may be an integer selected based on the CW[P-EDCA] described above. For example, the P-EDCA STA may select 3 as the initial backoff counter value. The P-EDCA STA waits for the first slot of length AIFS[VO], and if the medium is idle in the first slot, decrements the backoff counter by 1 at the end point of the slot (slot boundary). Subsequently, the backoff counter may be decremented by 1 at slot boundaries occurring in slots of length aSlotTime as described above. The P-EDCA STA may transmit a frame at the slot boundary if the medium is idle in the slot where the backoff counter is 0 (indicated by * in Table 1). This may be an action of transmitting a frame at the slot boundary where the backoff counter reaches 0, and refer to Table 1 below.

[0089] [Table 1]

[0090]

[0091]

[0092] The aforementioned P-EDCA 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) rather than P-EDCA channel access operations. While exceptional situations may arise where urgent frames must be transmitted continuously using P-EDCA operations, a specific method for transmitting urgent frames may be required when using P-EDCA operations. That is, to prioritize the transmission of urgent frames, attempts to transmit non-urgent frames (e.g., AC frames with a lower priority than the highest priority AC_VO QoS category) may need to be prevented during the execution of the P-EDCA channel access procedure of the P-EDCA STA. In other words, attempts to perform channel access operations for the transmission of non-urgent frames within the P-EDCA STA may need to be prevented during the backoff operations described in Steps 3 and 4 above. Additionally, once the transmission of urgent frames via P-EDCA is completed, the use of P-EDCA may need to be restricted for the sake of fairness. The following describes a method for P-EDCA channel access operation to preserve the performance of a wireless LAN network and ensure fairness when using the aforementioned P-EDCA channel access operation.

[0093] FIG. 4 is a diagram illustrating an emergency frame transmission method when using P-EDCA applicable to the present disclosure.

[0094] Referring to FIG. 4, in a wireless LAN network, an AP (310) and non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) connected to the AP (310) can operate. Here, a plurality of STAs including the AP (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can form a BSS. The AP (310) can instruct the STAs to use P-EDCA based on the method described above in FIG. 3 or a similar method. The STAs can perform P-EDCA operations based on instructions received from the AP (310). That is, the STAs can perform a [P-EDCA channel access operation] to perform channel access operations first. Meanwhile, non-AP STA 1 (320) to non-AP STA 3 (340) may be able to perform P-EDCA operations, and other STAs may be unable to perform or not perform P-EDCA operations. However, this is for convenience of explanation only and is not limited thereto.

[0095] non-AP STA 1 (320) to non-AP STA 3 (340) can transmit DS (401-1, 401-2, 401-3) through [P-EDCA channel access operation]. Specifically, non-AP STA 1 (320) to non-AP STA 3 (340) can perform a channel sensing operation for DSAIFS[AC_VO] time when the medium is last switched from a busy state to an idle state due to frame reception (or transmission). If the medium is idle for DSAIFS[AC_VO] time, non-AP STA 1 (320) to non-AP STA 3 (340) can transmit DS (401-1, 401-2, 401-3) and perform step 3 (channel access operation) of the [P-EDCA channel access operation] described above. For example, non-AP STA 2 (330) can select the shortest backoff counter value and complete the channel access operation as quickly as possible to transmit a request to send (RTS) frame (402). However, this is for convenience of explanation only and is not limited thereto. After transmitting DS (401-2), non-AP STA 2 (330) can transmit the RTS frame (402) to AP (310). When AP (310) receives the RTS frame (402) from non-AP STA 2 (330), it can transmit a CTS frame (403) to non-AP STA 2 (330). Subsequently, non-AP STA 2 (330) can transmit a data frame (uplink data frame, 404) to AP (310) and receive a response frame (405) for the data frame (404) from AP (310). Here, the P-EDCA operation of non-AP STA 2 (330) may be restricted from the time when non-AP STA 2 (330) successfully transmits DS or completes the transmission of a data frame. For example, non-AP STA 2 (330) cannot transmit additional DS according to the following [P-EDCA constraints].That is, non-AP STA 2 (330) cannot use [P-EDCA channel access operation] if at least one of [P-EDCA constraints] is satisfied.

[0096] [P-EDCA Constraints]

[0097] - If the STA occupies X ms of the time interval (observation interval) from the current operation point up to a certain time (e.g., 0 ms) prior to it for DS transmission

[0098] - If the STA has transmitted DS Y or more times during the time interval (observation interval) prior to the current operation point (e.g., 0 ms)

[0099] - When the STA successfully transmits the DS or when the STA finishes exchanging data frames with the AP after transmitting the DS

[0100] ■ In the above case, the STA cannot use [P-EDCA channel access operation] during the first fixed time interval after the condition is satisfied.

[0101]

[0102] Here, the non-AP STA 2 (330) may need to transmit an urgent frame even if the condition for not using P-EDCA operation occurs due to the [P-EDCA constraints] described above. For example, an urgent frame may be a frame in which the delay bound, which is the lifespan of the MSDU (MAC service data unit) included in the frame, is less than or equal to a certain value, and this may not be restricted by the access categories (AC) of the MSDU. As a specific example, P-EDCA operation may generally be used to transmit a frame that is AC_VO (voice), but an urgent frame may occur in any type of AC (e.g., VO, VI (video), BE (best effort), BK (background)) including AC_VO. As another example, an urgent frame may be a frame that requires retransmission due to an error but could not be retransmitted due to the TXOP (transmit opportunity) limit for each AC of the non-AP STA 2 (330). However, the urgent frame may not be limited to a specific form.

[0103] In the above-described case, non-AP STA 2 (330) may exceptionally continue to perform the P-EDCA operation. non-AP STA 2 (330) may perform the P-EDCA operation again after the reception of the acknowledgment frame received from the AP (310) is complete. non-AP STA 1 (320) to non-AP STA 3 (340) may transmit DS (406-1, 406-2, 406-3) through the [P-EDCA channel access operation]. For example, non-AP STA 2 (330) may select the shortest backoff counter value and complete the channel access operation as quickly as possible to transmit the RTS frame (407). However, this is for convenience of explanation only and is not limited thereto. non-AP STA 2 (330) may transmit the RTS frame (407) to the AP (310) after transmitting the DS (406-2). When the AP (310) receives an RTS frame (407) from the non-AP STA 2 (330), it can send a CTS frame (408) to the non-AP STA 2 (330). Afterwards, the non-AP STA 2 (330) can send a data frame (uplink data frame, 409) to the AP (310) and receive a response frame (410) for the data frame (409) from the AP (310).

[0104] Here, since non-AP STA 2 (330) exceptionally transmitted an urgent frame despite the [P-EDCA constraint] described above being satisfied, subsequent P-EDCA operations must be restricted. For example, non-AP STA 2 (330) (and non-AP STA 1 (320), non-AP STA 3 (340)) using P-EDCA may transmit DS for exceptionally transmitting urgent frames a certain number of times even when the [P-EDCA constraint] is satisfied. As a specific example, non-AP STA 2 (330) may transmit DS for transmitting urgent frames up to 3 times. After that, non-AP STA 2 (330) may be unable to transmit DS until the [P-EDCA constraint] is released. However, this is only one example, and other numbers may be possible. Additionally, if non-AP STA 2 (330) succeeds in transmitting an urgent frame when [P-EDCA constraint] is satisfied, non-AP STA 2 (330) may apply the following [P-EDCA constraint - exception]. non-AP STA 2 (330) cannot transmit DS even exceptionally until [P-EDCA constraint - exception] is released.

[0105] [P-EDCA Constraint - Exception]

[0106] - When the STA occupies X' ms of the time interval (observation interval) from the current operation point up to a certain time (e.g., O' ms) prior to it for DS transmission

[0107] - If the STA has transmitted DS Y' or more times during the time interval (observation interval) prior to the current operation point (e.g., 0'ms)

[0108] - When the STA successfully transmits the DS or when the STA finishes exchanging data frames with the AP after transmitting the DS

[0109] ■ In the above case, the STA cannot use [P-EDCA channel access operation] during a second fixed time interval after the condition is satisfied.

[0110]

[0111] The [P-EDCA Constraint - Exception] applied to non-AP STA 2 (330) may be the same condition as the [P-EDCA Constraint], but may also be an action intended to further restrict the P-EDCA operation of non-AP STA 2 (330). For example, O' of the [P-EDCA Constraint - Exception] may be a longer value than O of the [P-EDCA Constraint]. Also, for example, X' of the [P-EDCA Constraint - Exception] may be a shorter value than X. Also, for example, the second fixed time interval of the [P-EDCA Constraint - Exception] may be a longer value than the first fixed time interval of the [P-EDCA Constraint]. The non-AP STA 2 (330) can perform the P-EDCA operation again when the [P-EDCA Constraint - Exception] is released.

[0112] FIGS. 5A and FIGS. 5B are drawings illustrating a collision prevention method when using P-EDCA applicable to the present disclosure.

[0113] Referring to FIGS. 5a and 5b, an AP (310) and non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) connected to the AP (310) can operate in a wireless LAN network. Here, a plurality of STAs including the AP (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can form a BSS. The AP (310) can instruct the STAs to use P-EDCA based on the method described above in FIG. 3 or a similar method. The STAs can perform P-EDCA operations based on instructions received from the AP (310). That is, the STAs can perform a [P-EDCA channel access operation] to perform channel access operations first. Meanwhile, non-AP STA 1 (320) to non-AP STA 3 (340) may be able to perform P-EDCA operations, and other STAs may be unable to perform or not perform P-EDCA operations. However, this is for convenience of explanation only and is not limited thereto.

[0114] non-AP STA 1 (320) to non-AP STA 3 (340) can transmit DS (401-1, 401-2, 401-3) through [P-EDCA channel access operation]. Specifically, non-AP STA 1 (320) to non-AP STA 3 (340) can perform a channel sensing operation for DSAIFS[AC_VO] time when the medium is last switched from a busy state to an idle state due to frame reception (or transmission). If the medium is idle for DSAIFS[AC_VO] time, non-AP STA 1 (320) to non-AP STA 3 (340) can transmit DS (401-1, 401-2, 401-3) and perform step 3 (channel access operation) of the [P-EDCA channel access operation] described above. For example, non-AP STA 2 (330) can select the shortest backoff counter value and complete the channel access operation as quickly as possible to transmit an RTS frame (402). However, this is for convenience of explanation only and is not limited thereto. After transmitting DS (401-2), non-AP STA 2 (330) can transmit the RTS frame (402) to AP (310). When AP (310) receives the RTS frame (402) from non-AP STA 2 (330), it can transmit a CTS frame (403) to non-AP STA 2 (330). Subsequently, non-AP STA 2 (330) can transmit a data frame (uplink data frame, 404) to AP (310) and receive a response frame (405) for the data frame (404) from AP (310).

[0115] Referring to FIG. 5a, the P-EDCA operation of non-AP STA 2 (330) may be restricted from the time when non-AP STA 2 (330) successfully transmits DS or completes the transmission of a data frame. For example, non-AP STA 2 (330) cannot transmit additional DS according to the following [P-EDCA constraints]. That is, if non-AP STA 2 (330) satisfies at least one of the [P-EDCA constraints], it cannot use the [P-EDCA channel access operation].

[0116] [P-EDCA Constraints]

[0117] - If the STA occupies X ms of the time interval (observation interval) from the current operation point up to a certain time (e.g., 0 ms) prior to it for DS transmission

[0118] - If the STA has transmitted DS Y or more times during the time interval (observation interval) prior to the current operation point (e.g., 0 ms)

[0119] - When the STA successfully transmits the DS or when the STA finishes exchanging data frames with the AP after transmitting the DS

[0120] ■ In the above case, the STA cannot use [P-EDCA channel access operation] during the first fixed time interval after the condition is satisfied.

[0121] ■ Alternatively, STA cannot use [P-EDCA channel access operation] until the QSRC (QoS STA Retry Counter) [AC_VO] of VO EDCAF reaches or exceeds a certain threshold value after the corresponding condition is satisfied.

[0122]

[0123] The non-AP STA 2 (330) may transmit AC_VO frames using AIFS[VO] instead of DSAIFS[AC_VO] while the [P-EDCA constraint] is satisfied (i.e., while the P-EDCA operation is not available). That is, the non-AP STA 2 (330) may use the AIFS[VO] slot boundary, which is the slot boundary used in the general EDCA channel access operation, instead of DSAIFS[AC_VO], which is the slot boundary used for DS transmission in the P-EDCA operation. More specifically, this may mean that the non-AP STA 2 (330) uses the general EDCA operation rather than the P-EDCA operation while the P-EDCA constraint is satisfied. Additionally, the non-AP STA 2 (330) may transmit AC_VI frames using AIFS[VI] instead of DSAIFS[AC_VO] while the [P-EDCA constraint] is satisfied (i.e., while the P-EDCA operation is not available). That is, non-AP STA 2 (330) may use at least one of AIFS[VO] and AIFS[VI] instead of using DSAIFS[AC_VO]. The above-described operation may also apply to other ACs other than AC_VO and AC_VI. That is, non-AP STA 2 (330) may use the normal EDCA operation for other ACs other than AC_VO (e.g., AC_VI, AC_BE, AC_BK) as long as the P-EDCA constraint is satisfied.

[0124] Meanwhile, non-AP STA 1 (320) and non-AP STA 3 (340) can transmit DS (411-1, 411-2) using DSAIFS[AC_VO] according to [P-EDCA channel access operation]. Here, if at least one of DSAIFS[AC_VO], AIFS[VO], and AIFS[VI] is the same, a transmission collision may occur between non-AP STA 1 (320) and non-AP STA 3 (340) using [P-EDCA channel access operation] and non-AP STA 2 (330) not using [P-EDCA channel access operation]. In particular, when non-AP STA 2 (330) transmits a normal data frame after AIFS[VO] or AIFS[VI] time, and non-AP STA 1 (320) and non-AP STA 3 (340) transmit DS, the normal data frame of non-AP STA 2 (330) may collide and be unavailable to AP (310).

[0125] Considering the problem described above, non-AP STA 2 (330) may set AIFS[VO] and AIFS[VI] longer than DSAIFS[AC_VO]. For example, if DSAIFS[AC_VO] is 'aSIFSTime+aSlotTime*AIFSN[P-EDCA]', AIFS[VO] is 'aSIFSTime+aSlotTime*AIFSN[VO]', and AIFS[VI] is 'aSIFSTime+aSlotTime*AIFSN[VI]', then AIFSN[P-EDCA] may be smaller than AIFSN[VO] and AIFSN[VI]. In the above case, a conflict due to the same AIFS length between non-AP STA 1 (320) and non-AP STA 3 (340) using P-EDCA and non-AP STA 2 (330) not using P-EDCA can be prevented.

[0126] Referring to FIG. 5b, the length of P-EDCA[AC] of non-AP STA 2 (330) can be increased from the time when non-AP STA 2 (330) successfully transmits DS or completes the transmission of a data frame. Specifically, when DSAIFS[AC_VO] is 'aSIFSTime+aSlotTime*AIFSN[P-EDCA]', the value of AIFSN[P-EDCA] can be increased (e.g., by 1) from the time when non-AP STA 2 (330) successfully transmits DS or completes the transmission of a data frame. That is, DSAIFS[AC_VO] of non-AP STA 2 (330) can be increased. Here, the minimum value of AIFSN[P-EDCA] is 2 and the maximum value is 7, but is not limited thereto. If DSAIFS[AC_VO] of non-AP STA 2 (330) increases, the channel access priority of non-AP STA 2 (330) may decrease, and non-AP STA 1 (320) and non-AP STA 3 (340) that failed to transmit DS may access the channel more preferentially using P-EDCA channel access operation.

[0127] For example, after non-AP STA 2 (330) transmits a data frame (404) to AP (310) after transmitting DS (401-2), the next DSAIFS[AC_VO] that non-AP STA 2 (330) must use to transmit DS may be increased by aSlotTime time compared to the existing DSAIFS[AC_VO]. Here, non-AP STA 1 (320) to non-AP STA 3 (340) may wait for DSAIFS[AC_VO] to transmit DS (411-1, 411-2), but the DSAIFS[AC_VO] of non-AP STA 2 (330) may be longer than that of non-AP STA 1 (320) and non-AP STA 3 (340) that transmitted a data frame after transmitting DS. Therefore, non-AP STA 1 (320) and non-AP STA 3 (340) can transmit DS before non-AP STA 2 (330). If non-AP STA 1 (320) and non-AP STA 3 (340) transmit DS (411-1, 411-2) before non-AP STA 2 (330), and non-AP STA 2 (330) fails to transmit DS, non-AP STA 2 (330) cannot perform a short backoff operation for low-latency frame transmission. non-AP STA 1 (320) and non-AP STA 3 (340) perform a short backoff operation, and non-AP STA 1 (320) completes the short backoff operation first so that it can exchange RTS frames (412), CTS frames (413), data frames (414) and response frames (BlockAck frames, 415) with AP (310). Meanwhile, the increased AIFSN [P-EDCA] of non-AP STA 2 (330) can be decreased at regular intervals.For example, if non-AP STA 2 (330) fails to transmit a data frame after transmitting DS for a certain period of time, the increased AIFSN[P-EDCA] of non-AP STA 2 (330) may be decreased sequentially by a certain amount or set to 2, which is the minimum value of AIFSN[P-EDCA].

[0128] FIG. 6 is a diagram showing the method of using P-EDCA when applying the MU EDCA timer applied to the present disclosure.

[0129] Referring to FIG. 6, in a wireless LAN network, an AP (310) and non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) connected to the AP (310) can operate. Here, a plurality of STAs including the AP (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can form a BSS. The AP (310) can instruct the STAs to use P-EDCA based on the method described above in FIG. 3 or a similar method. The STAs can perform P-EDCA operations based on instructions received from the AP (310). That is, the STAs can perform a [P-EDCA channel access operation] to perform channel access operations first. Meanwhile, non-AP STA 1 (320) to non-AP STA 3 (340) may be able to perform P-EDCA operations, and other STAs may be unable to perform or not perform P-EDCA operations. However, this is for convenience of explanation only and is not limited thereto.

[0130] Here, non-AP STA 1 (320) to non-AP STA 3 (340) can participate in multi-user (MU) transmission of AP (310). MU transmission can be performed by non-AP STA 1 (320) to non-AP STA 3 (340) receiving a trigger frame of AP (310). The trigger frame can allocate uplink resources (e.g., RU, which is an OFDMA frequency resource, and time length) to non-AP STA 1 (320) to non-AP STA 3 (340). non-AP STA 1 (320) to non-AP STA 3 (340) can transmit uplink data frames to AP (310) from the uplink resources allocated in the trigger frame. After that, non-AP STA 1 (320) to non-AP STA 3 (340) can receive a response frame for the uplink data frame transmitted to the AP (310). However, the above-described operation may be one example of a MU transmission operation and is not limited thereto.

[0131] non-AP STA 1 (320) to non-AP STA 3 (340) may operate the MU EDCA Timer after completing the transmission of an uplink data frame in a MU transmission operation (or after receiving a response frame from the AP for the uplink data frame transmitted by non-AP STA 1 (320) to non-AP STA 3 (340). Specifically, the STA may have an EDCAF (EDCA function) for each AC. A MU EDCA Timer[AC] that determines whether to use a MU EDCA parameter set may be managed in the EDCAF for each AC. The MU EDCA Timer[AC] may be 0 before the MU transmission operation is performed. In the above case, a general EDCA parameter set, rather than a MU EDCA parameter set, may be used in the EDCAF for each AC. Alternatively, MU EDCA Timer[AC] may be a non-zero value before the MU transmission operation is performed. In the above case, the MU EDCA parameter set may be used in the EDCAF for each AC. The MU EDCA parameter set may indicate parameters (e.g., CWmin, CWmax, AIFSN) that are more disadvantageous to channel access than the general EDCA parameter set. Since the MU EDCA Timer[AC] value is a timer value, it may decrease over time. When the MU EDCA Timer[AC] of the EDCAF for each AC becomes zero, the EDCAF may stop using the MU EDCA parameter set and use the general EDCA parameter set again.

[0132] When non-AP STA 2 (330) participates in a MU transmission operation, the MU EDCA Timer[AC] of the EDCAF for each AC of the non-AP STA 2 (330) may be a non-zero value. That is, the non-AP STA 2 (330) may use an adverse channel access parameter (MU EDCA Parameter Set). Here, there may be an urgent frame that needs to be transmitted on the non-AP STA 2 (330). For example, an urgent frame may be a frame in which the delay bound, which is the lifetime of the MSDU (MAC service data unit) included in the frame, is less than or equal to a certain value, and this may not be restricted by the access categories (AC) of the MSDU. As a specific example, the P-EDCA operation may generally be used to transmit a frame that is AC_VO (voice), but an urgent frame may occur in any type of AC (e.g., VO, VI (video), BE (best effort), BK (background)), including AC_VO. As another example, an urgent frame may be a frame that needs to be retransmitted due to an error but could not be retransmitted due to the TXOP (transmit opportunity) limit for each AC of non-AP STA 2 (330). However, urgent frames may not be limited to a specific form.

[0133] If an urgent frame exists, non-AP STA 2 (330) can transmit the frame using a P-EDCA operation even if the MU EDCA Timer[AC] value is not 0. non-AP STA 2 (330) can transmit DS (416) through a [P-EDCA channel access operation]. Specifically, non-AP STA 2 (330) can perform a channel sensing operation for DSAIFS[AC_VO] time when the medium is last switched from a busy state to an idle state due to receiving (or transmitting) a frame. If the medium is idle for DSAIFS[AC_VO] time, non-AP STA 2 (330) can transmit DS (416) and perform step 3 (channel access operation) of the [P-EDCA channel access operation] described above. For example, non-AP STA 2 (330) can select the shortest backoff counter value and complete the channel access operation as quickly as possible to transmit an RTS frame (417). However, this is for convenience of explanation only and is not limited thereto. After transmitting DS, non-AP STA 2 (330) can transmit the RTS frame (417) to AP (310). When AP (310) receives the RTS frame (417) from non-AP STA 2 (330), it can transmit a CTS frame (418) to non-AP STA 2 (330). Subsequently, non-AP STA 2 (330) can transmit a data frame (uplink data frame, 419) to AP (310) and receive a response frame (420) for the data frame (419) from AP (310).

[0134] The non-AP STA 2 (330) may reapply the MU EDCA Timer[AC] at the time when it has completed the transmission of the DS (or at the time when it has completed the exchange of data frames with the AP (310) after transmitting the DS) (i.e., at the time when it has completed receiving the response frame). The EDCAF that transmitted the DS may be the EDCAF associated with AC_VO. In the above case, the MU EDCA Timer[VO] of the EDCAF associated with AC_VO may be restarted. Since the non-AP STA 2 (330) exceptionally transmitted an urgent frame at a time when the MU EDCA Timer[AC] value is not 0, the MU EDCA Timer[VO] of the EDCAF may be set longer than that of other STAs. Additionally, since non-AP STA 2 (330) exceptionally transmitted an urgent frame when the MU EDCA Timer[AC] value was not 0, a time interval during which DS transmission is restricted for non-AP STA 2 (330) (i.e., a time interval during which non-AP STA 2 (330) cannot use the P-EDCA channel access operation) may be established. Once the time interval during which non-AP STA 2 (330) cannot use the P-EDCA channel access operation ends, non-AP STA 2 (330) can use the P-EDCA channel access operation again to transmit a low-latency frame.

[0135] FIG. 7 is a diagram illustrating a method for limiting the use of P-EDCA applicable to the present disclosure.

[0136] Referring to FIG. 7, in a wireless LAN network, an AP (310) and non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) connected to the AP (310) can operate. Here, a plurality of STAs including the AP (310), non-AP STA 1 (320), non-AP STA 2 (330), and non-AP STA 3 (340) can form a BSS. The AP (310) can instruct the STAs to use P-EDCA based on the method described above in FIG. 3 or a similar method. The STAs can perform P-EDCA operations based on instructions received from the AP (310). That is, the STAs can perform a [P-EDCA channel access operation] to perform channel access operations first. Meanwhile, non-AP STA 1 (320) to non-AP STA 3 (340) may be able to perform P-EDCA operations, and other STAs may be unable to perform or not perform P-EDCA operations. However, this is for convenience of explanation only and is not limited thereto.

[0137] AP (310) can check DS transmitted by non-AP STA 1 (320) to non-AP STA 3 (340) using P-EDCA. AP (310) can set an observation interval, which is a time interval for checking DS transmitted by non-AP STA 1 (320) to non-AP STA 3 (340). Here, the observation interval may be a time interval from the time when AP (310) is currently operating to a certain time prior. For example, the certain time may be 0ms. AP (310) can check whether DS transmitted by non-AP STA 1 (320) to non-AP STA 3 (340) occupies a certain time length within the observation interval. Here, the certain time length may be Xms. Alternatively, AP (310) can check whether DS transmitted by non-AP STA 1 (320) to non-AP STA 3 (340) is transmitted more than a certain number of times within the observation interval. Here, the certain number may be Y times.

[0138] If DSs transmitted within the observation interval of the AP (310) occupy a length of Xms or longer or are transmitted more than a certain number of times, the AP (310) may stop the P-EDCA operation of non-AP STA 1 (320) to non-AP STA 3 (340). The AP (310) may transmit a beacon frame or a probe response frame containing an information element, a subfield, that indicates the cessation of P-EDCA usage. Upon receiving the beacon frame or probe response frame, non-AP STA 1 (320) to non-AP STA 3 (340) may stop the P-EDCA operation. Alternatively, the AP (310) may transmit a frame to indicate the immediate cessation (suspension) of the P-EDCA operation. The frame (421) indicating the cessation of the P-EDCA operation transmitted by the AP (310) may indicate the P-EDCA cessation / resume indicator and the P-EDCA resumption time. When AP (310) transmits a frame (421) instructing the interruption of P-EDCA operation, non-AP STA 1 (320) to non-AP STA 3 (340) cannot use the channel access method using [P-EDCA channel access operation] until they receive a frame instructing the resumption of P-EDCA operation from AP (310) or until the P-EDCA resumption time of the received frame instructing the interruption of P-EDCA operation is reached.

[0139] For a specific example, if O is 50, X is 2.5, and Y is 50, the observation interval may be 50 ms. Within the observation interval of 50 ms, the AP (310) can check whether DS occupies a time length of 2.5 ms or more, or whether DS is transmitted 50 times or more. If DS occupies a time length of 2.5 ms or more, or if DS is transmitted 50 times or more, the AP (310) can transmit a frame (421) instructing the suspension of the P-EDCA operation. The AP (310) can control the P-EDCA operation so that DS does not occupy a time length exceeding 2.5 ms and DS is not transmitted more than 50 times. If DS does not occupy a time length exceeding 2.5 ms and DS is not transmitted more than 50 times, the AP (310) can transmit a frame instructing the resumption of the P-EDCA operation. Alternatively, the AP may transmit a frame instructing the interruption of the P-EDCA operation by setting a P-EDCA resumption time so that the DS does not occupy a time length of more than 2.5ms and the DS is not transmitted more than 50 times.

[0140] FIG. 8 is a diagram illustrating a P-EDCA channel access method applicable to the present disclosure. Referring to FIG. 8, the wireless LAN network disclosed in FIG. 3 described above can be operated. non-AP STA 1 (520) and non-AP STA 2 (530) may be STAs that use P-EDCA (i.e., support P-EDCA and enable P-EDCA). Meanwhile, non-AP STA 3 (340) may be a STA that uses (general) EDCA and does not use P-EDCA. That is, non-AP STA 3 (340) may be a STA that does not support P-EDCA, or supports P-EDCA but does not enable P-EDCA (disables). non-AP STA 1 (520) and non-AP STA 2 (530) can transmit AC_VO frames according to the [P-EDCA channel access operation] described above.

[0141] Here, [P-EDCA channel access operation] allows 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 P-EDCA channel access operations. Additionally, the above-described P-EDCA channel access operation can be used to transmit AC (access categories) VO (voice) packets. AC_VO may be the AC with the highest QoS priority. Additionally, the above-described P-EDCA channel access operation may be used to transmit frames by replacing the existing EDCA VO EDCAF. Alternatively, the above-described P-EDCA channel access operation may be an operation that can be performed by setting the parameters of the existing VO EDCAF (setting to use DSAIFS[AC_VO], which is a slot for DS transmission of the P-EDCA operation, and setting to use the AIFS[VO] slot, whose length is determined based on P-EDCA AIFSN after DS transmission, and the backoff counter set based on CW[P-EDCA]). Alternatively, the DS transmission operation may be performed by a channel access function other than VO EDCAF (e.g., implemented as a service of a DCF (distributed channel access function)), and the VO EDCAF may perform the channel access operation after the DS transmission. Meanwhile, DS-CTS may be referred to as DS in this disclosure and is not limited to a specific name.

[0142] FIG. 9 is a diagram illustrating an internal contention interruption method when using P-EDCA applicable to the present disclosure. Referring to FIG. 9, an AP (510) in a wireless LAN network and a non-AP STA 1 (520) connected to the AP (510) and other STAs or a wireless LAN terminal operating in another wireless LAN network (e.g., a STA and / or AP operating in another BSS (basic service set)) may operate. The non-AP STA 1 (520) may be a STA using the P-EDCA channel access operation of FIG. 3. That is, the non-AP STA 1 (520) may use the P-EDCA channel access operation to transmit an AC_VO frame.

[0143] A non-AP STA 1 (520) may transmit DS (601) after DSAIFS[AC_VO] time when the medium transitions from a busy state to an idle state. STAs that have not transmitted DS since the transmission of DS may set a network allocation vector (NAV), which is a timer that sets the virtual carrier sense (CS) to a busy state based on the value indicated by the duration field of the DS MAC header. That is, the value indicated by the duration field of the DS MAC header may be a length of time that causes the medium to be considered a busy state after the transmission of DS. For example, the value indicated by the duration field of the DS MAC header may be 'AIFS[VO] + 7*aSlotTime' time. This time may be the sum of 'aSIFSTime + AIFSN*aSlotTime + 7*aSlotTime'. 'aSIFSTime + AIFSN*aSlotTime' may be a value representing AIFS[VO]. For example, the default value of AIFSN in AIFS[VO] may be 2. However, in the [P-EDCA channel access operation] described above, the value of AIFSN used after DS transmission may be a value specified by AP (510). '7*aSlotTime' may be a value representing the length of slot boundaries up to a maximum of 7 aSlotTime lengths after DS transmission. The aforementioned length may vary depending on the value specified by AP (510) (e.g., the value of AIFS[VO], which is the time length of the slot that must be waited for media occupancy verification after DS transmission, and the number of each slot having a subsequent aSlotTime length). That is, the aforementioned length may be a default value specified by the duration field of the DS MAC header, but it may be set to a different value and is not limited to a specific form.The value indicated by the duration field of the MAC header of the DS is the time length for performing the short backoff operation of the [P-EDCA channel access operation] described above. Meanwhile, the transmission of the DS (601) by the non-AP STA 1 (520) may be for the transmission of the AC_VO frame. Accordingly, the EDCAF (referred to as VO EDCAF in this disclosure), which is the channel access function responsible for the transmission of the AC_VO frame, may acquire a TXOP. Here, the acquisition of the TXOP by the EDCAF is for the short backoff operation corresponding to step 3 of the P-EDCA channel access operation disclosed in FIG. 3 after the transmission of the DS, and the corresponding length may be 'length of the DS + value indicated by the duration of the MAC header of the DS'. Alternatively, it may be considered that the VO EDCAF acquired the TXOP because the transmission of the DS frame is for the transmission of the subsequent AC_VO frame, even though the VO EDCAF does not transmit the DS.

[0144] The VO EDCAF of non-AP STA 1 (520) that has acquired or is considered to have acquired a TXOP may be a TXOP holder. Meanwhile, non-AP STA 1 (520) may have VI EDCAF, BE EDCAF, and BK EDCAF, which are channel access functions for transmitting VI (video), BE (best effort), and BK (background) frames that are not AC_VO. For example, within the STA, EDCAFs may engage in internal competition for transmission before transmitting the actual frame wirelessly. Internal competition may be a procedure to select the EDCAF within the STA to transmit the actual frame. Or, if different EDCAFs that have frames to transmit engage in a competition procedure for transmission, internal competition may be a procedure to select the EDCAF that wins the competition first. For example, the internal competition procedure may be a virtual competition procedure in which actual time does not flow. In the present disclosure, competition among EDCAFs within the STA is an internal competition procedure and may be a procedure for selecting an EDCAF to be transmitted in which actual physical time does not elapse.

[0145] The time mentioned above may be used to calculate the time taken for the EDCAF to perform a competition for actual transmission, but is not limited thereto. Alternatively, the internal competition procedure may actually be performed according to the decrement of the backoff counter over time. If there are at least two EDCAFs within the STA attempting to transmit at a slot boundary where the backoff counter is 0 at the same time, the EDCAF that wins the competition may be allowed to transmit the frame according to the priority of the EDCAFs. On the other hand, the EDCAF that loses the competition and is not selected may be allowed to perform a new backoff procedure. After the VO EDCAF of non-AP STA 1 (520) transmits the DS, a TXNAV timer (which may also be referred to as TXNAV) may be set, which is shared by the EDCAFs within non-AP STA 1 (520) to consider the medium as occupied. The TXNAV timer is a timer set based on the value of the duration field of the MAC header of the last frame successfully transmitted by non-AP STA 1 (520). The TXNAV timer may be set for the duration indicated by the duration field of the MAC header of the DS (601) transmitted by the non-AP STA 1 (520). The DS (601) transmitted by the non-AP STA 1 (520) may be a frame that does not require an immediate acknowledgment frame. Therefore, at the time when the DS (601) is completed (or at the time when the transmission of the PPDU containing the frame is completed), the non-AP STA 1 (520) may consider the transmission of the DS (601) to be successful and may update the TXNAV accordingly. Alternatively, the TXNAV timer may be updated at the time when the frame is completed (or at the time when the transmission of the PPDU containing the frame is completed), regardless of the reception of the acknowledgment frame, even if the frame transmitted by the non-AP STA 1 (520) is a frame that requires an immediate acknowledgment frame. Meanwhile, the TXOP holder VO EDCAF may ignore the TXNAV timer.In other words, virtual carrier sense operations are not performed based on the TXNAV timer value. Specifically, EDCAFs can use virtual carrier sense operations based on NAV and TXNAV, as well as physical carrier sense based on physical channel detection, to determine the occupancy status of the medium. Here, VO EDCAFs that are TXOP holders may not consider or use the determination of the medium occupancy status based on the virtual carrier sense operation based on TXNAV described above. VO EDCAFs that are TXOP holders can determine the medium occupancy status by considering only the other NAV and physical carrier sense. However, the remaining EDCAFs cannot detect the medium as occupied and perform channel access operations if the TXNAV timer value is not zero. That is, they can perform virtual carrier sense operations based on the TXNAV timer value. This means that channel access operations by EDCAFs other than VO EDCAF are suspended. Specifically, EDCAFs can use virtual carrier sense operations by NAV and TXNAV and physical carrier sense by physical channel detection to determine the occupancy status of the medium. If the medium is confirmed to be occupied by at least one of the aforementioned NAV, TXNAV, and physical CS medium detection operations, the medium is determined to be in an occupied state. The VO EDCAF performs a short backoff operation corresponding to step 3 of the P-EDCA channel access operation described in FIG. 3 and can transmit a frame to the AP (510) at the slot boundary where the backoff counter reaches 0. Here, the VO EDCAF may be seen as having acquired a new TXOP. Or, the VO EDCAF may be seen as extending a previously acquired TXOP.Meanwhile, if other STAs other than non-AP STA 1 (520) use a P-EDCA channel access operation to transmit DS simultaneously with non-AP STA 1 (520) but fail to transmit a frame during a short backoff operation, those STAs may be considered to have acquired a TXOP but failed to extend it. Alternatively, those STAs may be considered to have canceled the TXOP. That is, other STAs other than non-AP STA 1 (520) may not be able to transmit additional frames, and the TXNAV timer set for DS transmission may not be extended. Since the TXNAV timers of STAs other than non-AP STA 1 (520) cannot be extended, when TXNAV reaches 0 (i.e., expires), EDCAFs of ACs other than VO EDCAF, who was the TXOP holder, can also participate in channel access operations again when the medium is switched to an idle state (e.g., when the virtual CS by NAV is idle and the physical CS is also idle (where the value of TXNAV is 0, so the medium occupancy state by TXNAV is idle. When the value of TXNAV is 0, the value of TXNAV may not be considered in determining the channel occupancy state)). That is, the channel access operations of EDCAFs other than VO EDCAF, who was the TXOP holder, may not be interrupted by TXNAV, which is the timer protecting the internal transfer operation of the TXOP holder. That is, channel access operations can be resumed. Meanwhile, the expiration of TXNAV may mean the loss of TXOP holder status. In other words, as described above, when TXNAV expires, the VO EDCAF may no longer be a TXOP holder. Accordingly, EDCAFs that were previously not TXOP holders and EDCAFs that were previously TXOP holders can perform channel access operations after TXNAV expires. That is, when the medium switches to an idle state (e.g.When the virtual CS by NAV is idle and the physical CS is also idle (at this time, since the value of TXNAV is 0, the media occupancy state by TXNAV is idle. When the value of TXNAV is 0, the value of TXNAV may not be considered in determining the channel occupancy state.)), a channel access operation can be performed.

[0146] As described above, TXNAV can be implemented in the form of a concrete countdown timer. Alternatively, TXNAV can be implemented in the form of a logical control variable, such as a state flag, that is toggled depending on whether the timer expires. Specifically, the TXNAV timer can be implemented in the form of a virtual timer, counter, or logical state flag to restrict channel access by EDCAFs within the STA.

[0147] If a TXNAV timer is implemented as a virtual timer or counter to restrict channel access by EDCAFs within the STA, other EDCAFs (i.e., EDCAFs that are not TXOP holders) may suspend channel access (internal competition occurring between EDCAFs within the STA, or / and TXOP acquisition procedures) if the TXNAV value implemented as a timer or counter is not zero based on the above description. Here, other EDCAFs may resume channel access (internal competition occurring between EDCAFs within the STA, or / and TXOP acquisition procedures) when the timer or counter value becomes zero.

[0148] If the TXNAV timer is implemented in the form of a logical state flag to restrict channel access by EDCAFs within the STA, other EDCAFs (i.e., EDCAFs that are not TXOP holders) may suspend channel access operations (internal contention) when the timer implemented as a logical state flag is active based on the above description. Here, other EDCAFs may resume channel access (internal contention) when the timer is switched to an inactive state. That is, the TXNAV value is implemented in the form of a logical control variable and can indicate the state in which TXNAV is active and the state in which TXNAV is suspended in the form of a flag, and operations based on this may be possible.

[0149] Additionally, the above-described matters may be applied equally to the present disclosure, but for convenience of explanation, they are described based on a TXNAV implemented in the form of a counter or timer, although they may also be applied equally when implemented as a logical status flag. Meanwhile, the STA acquiring a TXOP can be seen as the STA's EDCAF acquiring a TXOP. Here, the frame transmitted by the VO EDCAF may be an RTS frame (602). The duration field of the MAC header of the RTS frame may indicate the length of time required for subsequent transmission of a CTS frame (603), a data frame (604), and, if necessary, an expected response frame (605) for the data frame. The above-described method may be a single protection method. As another example, the duration field of the RTS frame MAC header may be set to the total time required for non-AP STA 1 (520) to transmit the entire frame (e.g., remaining TXOP time), and this method may be a multiple protection method. Meanwhile, when VO EDCAF has completed transmitting a frame (e.g., an RTS frame), the TXNAV timer may be set for the duration of the time indicated by the duration field of the MAC header of the frame transmitted by non-AP STA 1 (520). That is, the TXNAV timer may be updated. Meanwhile, the TXNAV timer may be updated when the response frame is successfully received, in the case where the frame transmitted by the aforementioned non-AP STA 1 (520) is a frame that requires an immediate response frame. Alternatively, the TXNAV timer may be updated at the time of completion of transmission of the frame (or at the time of completion of transmission of the PPDU containing the frame), regardless of the reception of the response frame, even if the frame transmitted by non-AP STA 1 (520) is a frame that requires an immediate response frame.Additionally, even if the existing TXNAV timer value is not zero, if the remaining TXNAV timer value is shorter than the time length indicated by the duration field of the MAC header of the frame transmitted by the EDCAF (VO EDCAF), the TXNAV timer value may be updated to the time length indicated by the duration field of the MAC header of the frame transmitted by the EDCAF (VO EDCAF). According to the procedure described above, channel access operations by EDCAFs other than VO EDCAF after DS transmission may be prevented (stopped) by setting the TXNAV timer value. For example, the value of the TXNAV timer may be updated to correspond to the time length of the frame that the VO EDCAF of non-AP STA 1 (520) must transmit. That is, channel access operations by EDCAFs other than VO EDCAF of non-AP STA 1 (520) are stopped because the channel is detected as occupied by TXNAV. Therefore, the transmission of the AC_VO frame resulting from the P-EDCA channel access operation may be transmitted with priority over the frames of other ACs. Meanwhile, the VO EDCAF of non-AP STA 1 (520) can complete the frame transmission. Accordingly, when the value of the TXNAV timer of non-AP STA 1 (520) reaches 0 (i.e., the TXNAV timer expires), the EDCAFs of other ACs, other than the VO EDCAF that was the TXOP holder, can also rejoin the channel access operation when the medium is switched to an idle state (e.g., when the virtual CS by NAV is idle and the physical CS is also idle). That is, the channel access operation of EDCAFs other than the VO EDCAF that was the TXOP holder is not interrupted by the TXNAV, which is a timer that protects the internal transmission operation of the TXOP holder. Meanwhile, the expiration of the TXNAV may mean the loss of the TXOP holder status. That is, as described above, when TXNAV expires, VO EDCAF may no longer be a TXOP holder.Accordingly, EDCAFs that were not previously TXOP holders and EDCAFs that were previously TXOP holders can participate in channel access after TXNAV expires.

[0150] As another example, the transmission of DS by non-AP STA 1 (520) may mean a transmission to protect the contention period for AC_VO frame transmission. Therefore, the EDCAF (VO EDCAF), which is the channel access function responsible for AC_VO frame transmission, may not be considered to have acquired the TXOP. That is, the VO EDCAF of non-AP STA 1 (520) that transmitted DS may not be a TXOP holder. During the time when the VO EDCAF of non-AP STA 1 (520) transmits DS and performs backoff, the TXNAV timer, which can be set for the time length indicated by the duration field of the transmitted DS, may not be set. Therefore, other EDCAFs may compete with the VO EDCAF that transmitted DS during the time when backoff is performed. For example, if the time when VI EDCAF transitions from a medium-occupied state to an idle state, waits for AIFS[VI], and then decrements the backoff counter to 0 is earlier than the time when VO EDCAF transitions from a medium-occupied state to an idle state, waits for DSAIFS[AC_VO], transmits DS, and then decrements the backoff counter to 0, VI EDCAF can win the internal competition and can participate in the competition for actual transmission. If the backoff counter of VO EDCAF that transmitted DS becomes 0 before the other EDCAFs, VO EDCAF has won the internal competition and can set the TXNAV timer from the time the RTS frame is transmitted.

[0151] FIG. 10 is a diagram illustrating a method for stopping internal competition when using P-EDCA applicable to the present disclosure.

[0152] Referring to FIG. 10, an AP (510) in a wireless LAN network and a non-AP STA 1 (520) connected to the AP (510) and other STAs or a wireless LAN terminal operating in another wireless LAN network (e.g., a STA and / or AP operating in another BSS (basic service set)) may operate. The non-AP STA 1 (520) may be a STA that uses the P-EDCA channel access operation of FIG. 3. That is, the non-AP STA 1 (520) may use the P-EDCA channel access operation to transmit an AC_VO frame.

[0153] A non-AP STA 1 (520) may transmit DS (606) after DSAIFS[AC_VO] time when the medium transitions from a busy state to an idle state. STAs that have not transmitted DS since the transmission of DS may set a network allocation vector (NAV), which is a timer that sets the virtual carrier sense (CS) to a busy state based on the value indicated by the duration field of the DS MAC header. That is, the value indicated by the duration field of the DS MAC header may be a length of time that causes the medium to be considered a busy state after the transmission of DS. For example, the value indicated by the duration of the DS MAC header may be 'AIFS[VO] + 7*aSlotTime' time. This time may be the sum of 'aSIFSTime + AIFSN*aSlotTime + 7*aSlotTime'. 'aSIFSTime + AIFSN*aSlotTime' may be a value representing AIFS[VO]. For example, the default value of AIFSN in AIFS[VO] may be 2. '7*aSlotTime' may be a value representing the length of slot boundaries up to a maximum of 7 aSlotTime lengths after DS transmission. The aforementioned length may vary depending on the value indicated by the AP (510) (e.g., the AIFS[VO] value and the number of slot boundaries to wait for after DS transmission). That is, the aforementioned length may be the default value indicated by the duration of the DS MAC header, but it may be set to a different value and is not limited to a specific form.

[0154] Meanwhile, after non-AP STA 1 (520) transmits DS (606), the AIFSN values ​​of the EDCAFs for each AC of non-AP STA 1 (520) (for VO, VI, BE, and BK ACs) may be set. The AIFSN value of the VO EDCAF may be set to 2, and the AIFSN values ​​of the remaining EDCAFs may be set to 0. The EDCAFs with an AIFSN value of 0 may stop operations (e.g., EDCA TXOP acquisition procedure). As another example, the AIFSN value of the VO EDCAF may be set to 2, and the AIFSN values ​​of the remaining EDCAFs may be set to configure the length of AIFS[AC] up to the value indicated by the duration field of the DS MAC header after DS transmission. For example, if the length of the duration field of the MAC header of the DS is 'aSIFSTime + 2*aSlotTime + 7*aSlotTime', the AIFSN value of the remaining EDCAFs can be set to 9. As another example, to prevent conflicts with the VO EDCAF, the AIFSN value of the remaining EDCAFs can be set to a value greater than 9. Here, the AIFSN setting of the VO EDCAF described above may be a default value and may be changed by a value indicated by the AP (510).

[0155] After DS transmission, the VO EDCAF of non-AP STA 1 (520) may perform a channel access operation (EDCA backoff operation and / or EDCA TXOP acquisition operation). When the VO EDCAF of non-AP STA 1 (520) acquires a TXOP and transmits an RTS frame (607), or when a STA other than non-AP STA 1 (520) transmits a frame while the VO EDCAF of non-AP STA 1 (520) is performing a channel access operation (or after the time length indicated by the duration field of the DS frame MAC header has elapsed), the VO EDCAF of non-AP STA 1 (520) and the remaining EDCAFs may set the AIFSN parameter to a preset default value. Alternatively, the VO EDCAF of non-AP STA 1 (520) and the remaining EDCAFs may reset the AIFSN based on the AIFSN for each AC of the EDCA parameter set indicated by the EDCA parameter set element included in the management frame (e.g., beacon frame, probe response frame, etc.) previously transmitted by the AP (510). The value indicated by the duration field of the MAC header of the above-described DS may be the maximum length for which the VO EDCAF can perform channel access operations after the DS is transmitted. Meanwhile, the TXNAV timer, which is a timer shared by the EDCAFs for each AC (for VO, VI, BE, and BK ACs), may not be set after the DS is transmitted.

[0156] FIG. 11 is a diagram illustrating a method for stopping internal competition when using P-EDCA applicable to the present disclosure.

[0157] Referring to FIG. 11, an AP (510) in a wireless LAN network and a non-AP STA 1 (520) connected to the AP (510) and other STAs or a wireless LAN terminal operating in another wireless LAN network (e.g., a STA and / or AP operating in another BSS (basic service set)) may operate. The non-AP STA 1 (520) may be a STA that uses the P-EDCA channel access operation of FIG. 3. That is, the non-AP STA 1 (520) may use the P-EDCA channel access operation to transmit an AC_VO frame.

[0158] A non-AP STA 1 (520) may transmit DS (608) after DSAIFS[AC_VO] time when the medium transitions from a busy state to an idle state. STAs that have not transmitted DS since the transmission of DS may set a network allocation vector (NAV), which is a timer that sets the virtual carrier sense (CS) to a busy state based on the value indicated by the duration field of the DS MAC header. That is, the value indicated by the duration field of the DS MAC header may be a length of time that causes the medium to be considered a busy state after the transmission of DS. For example, the value indicated by the duration of the DS MAC header may be 'AIFS[VO] + 7*aSlotTime' time. This time may be the sum of 'aSIFSTime + AIFSN*aSlotTime + 7*aSlotTime'. 'aSIFSTime + AIFSN*aSlotTime' may be a value representing AIFS[VO]. For example, the default value for AIFSN in AIFS[VO] may be 2. '7*aSlotTime' may be a value representing the length of slot boundaries up to a maximum of 7 aSlotTime lengths after DS transmission. The aforementioned length may vary depending on the value indicated by the AP (510) (e.g., the AIFS[VO] value and the number of slot boundaries to wait for after DS transmission). That is, the aforementioned length may be the default value indicated by the duration of the MAC header of the DS, but may be set to a different value and is not limited to a specific form.

[0159] After DS transmission, it may be assumed that there are no transmittable frames in the transmission queues of EDCAFs for each AC (VI, BE, BK AC) that are not VO EDCAFs. That is, in the above case, the transmission queues of EDCAFs for each AC may be assumed to be empty. For example, if the backoff counter of EDCAFs that are not VO EDCAFs reaches 0 after DS transmission, they may select a new backoff counter and perform a channel access operation. Alternatively, EDCAFs that are not VO EDCAFs may not transmit frames while keeping the backoff counter at 0.

[0160] After DS transmission, the VO EDCAF of non-AP STA 1 (520) may perform a channel access operation (EDCA backoff operation and / or EDCA TXOP acquisition operation). When the VO EDCAF of non-AP STA 1 (520) acquires a TXOP and transmits an RTS frame (609), or when a STA other than non-AP STA 1 (520) transmits a frame while the VO EDCAF of non-AP STA 1 (520) is performing a channel access operation (or after the time length indicated by the duration field of the DS frame MAC header has elapsed), other EDCAFs other than the VO EDCAF of non-AP STA 1 (520) may perform a channel access operation for frame transmission. If frame transmission is not performed while the backoff counters of the other EDCAFs other than the VO EDCAF remain at 0, a new backoff counter value must be selected, and a channel access operation may be performed based on this. If the backoff counters of EDCAFs other than VO EDCAF have non-zero values, channel access operations may be performed based on the existing backoff counter values. If non-AP STA 1 (520) considers the transmission queues of EDCAFs for each AC (VI, BE, BK AC) other than VO EDCAF to be empty after DS transmission, the transmission queues may be considered re-entered when EDCAF[VO] successfully sets the TXOP after DS transmission. That is, the transmission queues may be considered to be entered after the contention initiated by DS transmission has ended. Meanwhile, the TXNAV timer, which is a timer shared by EDCAFs for each AC (VO, VI, BE, BK AC), may not be set even after DS is transmitted.

[0161] FIGS. 12a and FIGS. 12b are diagrams illustrating a method for interrupting P-EDCA channel access during the transmission of control frames and management frames applicable to the present disclosure.

[0162] Referring to FIGS. 12a and 12b, an AP (510) in a wireless LAN network and a non-AP STA 1 (520) connected to the AP (510) and other STAs or a wireless LAN terminal operating in another wireless LAN network (e.g., a STA and / or AP operating in another BSS (basic service set)) may operate. The non-AP STA 1 (520) may be a STA that uses the P-EDCA channel access operation of FIG. 3. That is, the non-AP STA 1 (520) may use the P-EDCA channel access operation to transmit an AC_VO frame. Meanwhile, the AP (510) may need to transmit at least one of a control frame (e.g., a trigger frame) and a management frame (e.g., an action frame, a beacon frame, a probe response, a request frame, etc.) to the connected STA (e.g., non-AP STA 1 (520)).

[0163] Referring to FIG. 12a, the AP (510) can transmit a trigger frame (610) to a non-AP STA 1 (520). The trigger frame (610) can be transmitted by the EDCAF of various ACs (VO, VI, BE, BK), and may be transmitted as a trigger frame alone or concatenated with other QoS data MPDUs (MAC protocol data units) and transmitted in the form of an A-MPDU. Meanwhile, the trigger frame (610) may be input into a VO EDCA queue and transmitted by a VO EDCAF. Alternatively, the trigger frame (610) may be allocated as an AC_VO frame by a separate scheduler and transmitted by a VO EDCAF. For the transmission of the trigger frame (610), the P-EDCA channel access operation described in FIG. 3 may be used, but is not limited thereto, and such method may not be used.

[0164] For example, if the AP (510) transmits a control frame such as a trigger frame, the AP (510) may perform an additional short backoff operation after the DS transmission, and in the above case, the RTS frame and CTS frame exchange operation may be inefficient. The AP (510) may decrement the backoff counter at the first slot boundary starting at AIFS[VO] time and subsequent slot boundaries following aSlotTime when the medium transitions from an occupied state to an idle state, as in the existing VO EDCAF operation, and transmit a control frame such as a trigger frame at the slot boundary where the backoff counter reaches 0. If the AP (510) explicitly transmits at least one of the control frame and the management frame, the AP (510) may instruct all terminals in the BSS via a beacon or other frame to use the existing VO EDCAF. Alternatively, all terminals in the BSS may be instructed via a beacon or other frame to transmit at least one of the control frame and the management frame using P-EDCA. If the transmission of at least one of the control frame and the management frame is instructed to be transmitted using P-EDCA, the rule requiring the use of the existing VO EDCA is ignored and P-EDCA may be used continuously if P-EDCA satisfies certain conditions. When P-EDCA is used, the first frame to be transmitted after contention may be an RTS frame. Here, in all cases where it must start with a frame other than an RTS frame, the existing VO EDCA may be used. As another example, the AP (510) may perform a P-EDCA channel access operation when transmitting a control frame, such as a trigger frame, to perform a short backoff operation after DS transmission. The first frame transmitted by the AP (510) after performing a short backoff operation after DS transmission is sufficient time for the transmission and reception of the control frame (e.g.If the control frame is a trigger frame, it may be a CTS-to-Self frame that indicates in the MAC header duration field value a time sufficient for the trigger frame, subsequent reception of an uplink data frame, and reception of a response frame. The AP (510) may transmit a control frame, such as the trigger frame, at the slot boundary where the backoff counter reaches 0 after transmitting the CTS-to-Self frame. Alternatively, the AP (510) may transmit a MU-RTS trigger frame after performing a short backoff operation to receive a CTS frame from at least one connected STA. Afterward, the AP (510) may transmit a control frame, such as the trigger frame. Alternatively, the AP (510) may determine that there is no hidden node problem because all connected STAs are able to receive the frame, and transmit a control frame, such as the trigger frame, immediately after performing a short backoff operation. Additionally, the AP (510) may perform additional operations after transmitting the control frame. For example, in the present disclosure, if the control frame transmitted by the AP (510) is a trigger frame that allocates uplink resources for receiving an uplink data frame (UL TB (trigger based) PPDU) from at least one connected STA (e.g., non-AP STA 1 (520)), the AP (510) may receive an uplink frame (611) in response to the trigger frame (610). Meanwhile, a non-AP STA 1 (520), which is a STA connected to the AP (510), may transmit a specific control frame, such as a trigger frame, to the AP (510). Even when the non-AP STA 1 (520) transmits a trigger frame to the AP (510), the method of the AP (510) transmitting a control frame to the STA as described above may be used.

[0165] Referring to FIG. 12b, the AP (510) can transmit a management frame (action frame, 612) to a non-AP STA 1 (520). The management frame (612) can be transmitted by the EDCAF of various ACs (VO, VI, BE, BK). The management frame (612), such as the action frame, may be classified as AC_VO and transmitted alone, or it may be concatenated with other QoS data MPDUs (MAC protocol data units) and transmitted in the form of an A-MPDU. Meanwhile, the management frame (612), such as the action frame, may be input into the VO EDCA queue and transmitted by the VO EDCAF. Alternatively, the management frame (612), such as the action frame, may be allocated as an AC_VO frame by a separate scheduler and transmitted by the VO EDCAF. For the transmission of the action frame, the P-EDCA channel access operation described in FIG. 3 may be used, but is not limited thereto, and such a method may not be used. For example, the AP (510) may additionally perform a short backoff operation after DS transmission when transmitting a management frame, such as an action frame, and in the above case, the operation of exchanging RTS frames and CTS frames may be inefficient. The AP (510) may decrement the backoff counter at the first slot boundary starting at AIFS[VO] time and subsequent slot boundaries following aSlotTime when the medium transitions from an occupied state to an idle state, as in the existing VO EDCAF operation. The AP (510) may transmit a management frame (612), such as an action frame, at the slot boundary where the backoff counter reaches 0. As another example, the AP (510) may perform a short backoff operation after DS transmission by performing a P-EDCA channel access operation when transmitting a management frame, such as an action frame. Then, the first frame transmitted by the AP (510) is sufficient time for transmitting and receiving the management frame (e.g.If the management frame is an action frame, it may be a CTS-to-Self frame that indicates in the duration field value of the MAC header a sufficient amount of time for receiving the action frame and subsequent response frame, or, if the action frame is a frame that does not require a response frame, sufficient time for transmitting the action frame. The AP (510) may transmit a management frame (612) that is the same as the action frame at the slot boundary where the backoff counter reaches 0 after transmitting the CTS-to-Self frame. Alternatively, the AP (510) may determine that there is no hidden node problem because all connected STAs can receive the frame, and may transmit a management frame (612) that is the same as the action frame immediately after performing a short backoff operation. Meanwhile, the STA may transmit a response management frame in response to the management frame transmitted by the AP (510). For example, when AP (510) transmits an action frame to non-AP STA 1 (520), non-AP STA 1 (520) may transmit a response frame (613) in response to the action frame of AP (510). Subsequently, non-AP STA 1 (520) may perform a separate channel access operation to transmit an action frame, which is a response management frame, to AP (510). Even when non-AP STA 1 (520) transmits an action frame to AP (510), the method of AP (510) transmitting a management frame to STA as described above may be used.

[0166] FIGS. 13a and FIGS. 13b are drawings illustrating a transmission queue management method when using P-EDCA applicable to the present disclosure.

[0167] Referring to FIG. 13a, an STA or AP (510) using the P-EDCA channel access operation described above in FIG. 3 may have separate transmission queues. For example, transmission queues may generally include a VO transmission queue, a VI transmission queue, a BE transmission queue, and a BK transmission queue, which are transmission queues for each AC. An STA or AP (510) using the P-EDCA channel access operation described above may have two VO transmission queues (614, 615). The two VO transmission queues (614, 615) described above may be an A(alternative)_VO transmission queue (614) and a VO transmission queue (615). Here, the A_VO (614) transmission queue may be used when the P-EDCA channel access operation is enabled. For example, the AP (510) can broadcast a P-EDCA usage activation indicator within the BSS, and STAs supporting P-EDCA that receive this can activate the P-EDCA channel access operation. An MSDU (MAC service data unit) can be input into the transmission queue at the upper layer, and a UP (user priority) associated with the MSDU can also be input. For example, if the UP is 6, it is an MSDU that must be input into the VO transmission queue (615), and if the UP is 7, it is an MSDU that must be input into the A_VO transmission queue (614). Additionally, a higher UP may mean a higher transmission priority. Alternatively, even if the UP corresponds to AC_VO, if the P-EDCA channel access operation is activated, the operation of inputting it into the A_VO transmission queue (614) can be performed while satisfying the conditions for activation and use of P-EDCA. Meanwhile, a method for switching between P-EDCA channel access operations and general EDCA channel access operations according to the transmission queue structure described above can be performed as shown in FIG. 13b.

[0168] Referring to FIG. 13b, non-AP STA 1 (520) may be a STA that uses a P-EDCA channel access operation. The non-AP STA 1 (520) may transmit a VO frame (616) using a P-EDCA channel access operation when the medium is switched from an occupied state to an idle state. Here, the VO frame (616) being transmitted may be a frame from the A_VO transmission queue described above. If there are no frames to transmit in the A_VO transmission queue, a frame from the VO transmission queue may be transmitted. Alternatively, if the non-AP STA 1 (520) has an available TXOP that transmits all frames from the A_VO transmission queue and then also transmits frames from the VO transmission queue, the non-AP STA 1 (520) may also transmit frames from the VO transmission queue. For example, when performing internal contention, both the EDCAF of A_VO and the EDCAF of VO may participate in the internal contention. Here, A_VO EDCAF can perform internal contention using P-EDCA and VO EDCAF can perform internal contention using the existing VO EDCAF. non-AP STA 1 (520) can disable the P-EDCA channel access operation. For example, this may be when non-AP STA 1 (520) has used the P-EDCA channel access operation more than a certain frequency, or when the use of the P-EDCA channel access operation is prohibited for a certain period after transmitting a data frame through the P-EDCA channel access operation. non-AP STA 1 (520) can transmit a frame using the normal EDCA operation. non-AP STA 1 (520) can wait for the first slot boundary where the medium is idle for AIFS[VO] time to transmit the AC_VO frame, and then decrement the backoff counter at slot boundaries of length aSlotTime. When the backoff counter of non-AP STA 1 (520) reaches 0, non-AP STA 1 (520) can transmit an AC_VO frame.Here, non-AP STA 1 (520) may transmit frames from the VO transmission queue first, and then transmit frames from the A_VO transmission queue. Alternatively, since frames from the A_VO transmission queue have a higher transmission priority, non-AP STA 1 (520) may transmit frames from the A_VO transmission queue first, and then transmit frames from the VO transmission queue. Alternatively, if the P-EDCA channel access operation is disabled, non-AP STA 1 (520) may transmit frames currently in the A_VO transmission queue but disable additional input of frames (MSDU) into the A_VO transmission queue. If non-AP STA 1 (520) does not input MSDU into the A_VO transmission queue, it may input MSDU into the VO transmission queue. Alternatively, if the P-EDCA channel access operation is disabled, non-AP STA 1 (520) can disable the A_VO transmission queue and move the MSDUs from the A_VO transmission queue to the VO transmission queue. Since the MSDUs in the A_VO transmission queue have a higher UP than the MSDUs in the VO transmission queue, non-AP STA 1 (520) can move the MSDUs in the A_VO transmission queue to be transmitted with priority over the MSDUs in the existing VO transmission queue. Meanwhile, non-AP STA 1 (520) can then enable the P-EDCA channel access operation again. non-AP STA 1 (520) can move frames from the VO transmission queue that are nearing a delay bound to the A_VO transmission queue and transmit them using the P-EDCA channel access operation.

[0169] The P-EDCA operation of the present disclosure can be performed by both a non-AP STA and an AP (AP STA). For example, an AP can transmit a frame to a non-AP STA connected to the AP using the [P-EDCA channel access operation] described above. Although it has been described above as being performed by a non-AP STA for ease of explanation, it should be understood that an AP can also perform the operations according to the present disclosure in the same or similar manner as a non-AP STA.

[0170] Additionally, the interruption and suspension of channel access operations of the present disclosure may be referred to as suspend operations.

[0171] FIG. 14 is a flowchart showing the operation of a STA in a wireless LAN to which the present disclosure applies.

[0172] Referring to FIG. 14, the STA can confirm that the channel has transitioned from an occupied state to an idle state and that the channel has been in an idle state for a first set time (S1410). When the STA confirms that the channel has been in an idle state for the first set time, it can transmit DS to start a P-EDCA competition after the first set time (S1420). After that, the STA performs a P-EDCA competition after transmitting DS, and the P-EDCA competition can perform frame transmission at the slot boundary where the backoff counter reaches 0 based on a channel access operation including a backoff procedure (S1430). Here, while the P-EDCA competition is being performed in the STA, channel access related to the transmission of VO (voice) among a plurality of access categories (AC) may be granted, and channel access related to the transmission of other ACs excluding VO among the plurality of ACs may not be granted.

[0173] For example, the first pre-set time may be the arbitration interframe space (AIFS) related to P-EDCA competition. Additionally, while the STA is performing P-EDCA competition, channel access operations are granted based on the enhanced distributed channel access function (EDCAF) operation related to the STA's VO transmission, and the VO transmission-related EDCAF may perform channel access based on the VO transmission-related AIFS corresponding to the second pre-set time. Additionally, multiple ACs of the STA may perform channel access operations based on their respective AC-related EDCAF operations. While the STA is performing P-EDCA competition, other AC transmission-related EDCAF operations, excluding the VO transmission-related EDCAF, may be deferred and channel access operations may not be granted. Here, when the deferred other AC transmission-related EDCAF operations are resumed, the other AC transmission-related EDCAFs may perform channel access based on the AIFS corresponding to the respective pre-set time corresponding to each AC. Additionally, other AC transmission-related EDCAFs may include VI (video) related EDCAF, BE (best effort) related EDCAF, and BK (background) related EDCAF. Additionally, if the STA completes frame transmission after channel occupation based on P-EDCA contention, the STA may not perform P-EDCA contention until the P-EDCA constraint is resolved. When the P-EDCA constraint is satisfied, the STA updates the VO transmission-related parameters and may perform channel access operations through the VO transmission-related AIFS corresponding to the updated parameters based on the VO transmission-related EDCAF operation.Additionally, if the P-EDCA constraint is satisfied, the STA resumes the EDCAF operation related to other AC transmissions, and the EDCAF related to other AC transmissions may perform channel access based on the AIFS according to the respective pre-configured times corresponding to each AC. Additionally, the DS includes a MAC (medium access control) header, and the duration field of the MAC header indicates the length of time the medium is occupied after the DS is transmitted, and the length of time the medium is occupied may be a length corresponding to the time required for P-EDCA contention. Additionally, a TXNAV timer is set based on the length of time indicated by the duration field after the DS is transmitted, and the TXNAV timer may be a timer shared by multiple EDCAFs of the STA. If the value of the TXNAV timer is not zero, the multiple EDCAFs of the STA may determine that the medium is occupied and postpone channel access operations. The EDCAF related to the VO transmission performs P-EDCA contention and may not consider the non-zero value of the TXNAV timer in determining the medium's occupied state. Additionally, when the value of the TXNAV timer reaches 0, multiple EDCAFs of the STA do not consider the value of the TXNAV timer in determining the medium occupancy status, and multiple EDCAFs of the STA can resume the channel access operation deferred by the TXNAV timer. Additionally, a control variable indicating the medium occupancy status within the STA is set based on the time length indicated by the duration field after transmission of the DS, and the control variable can be shared by multiple EDCAFs of the STA. When the control variable indicates a first state, multiple EDCAFs of the STA can determine the medium to be in an occupancy state and defer the channel access operation. The EDCAF related to VO transmission performs P-EDCA competition and may not consider the state of the control variable in determining the medium occupancy status.Additionally, when the control variable transitions to a second state as the time length indicated by the duration field elapses, multiple EDCAFs of the STA may resume channel access operations deferred by the control variable. For example, the STA may be an AP STA or a non-AP STA, but is not limited thereto.

[0174] 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.

[0175]

[0176] 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 set period of time; If the STA confirms that the channel is idle for the first set time, the step of transmitting a DS (defer signal) to start a P-EDCA (prioritized enhanced distributed channel access) competition after the first set time; and The above STA performs the P-EDCA competition after the DS transmission, and the P-EDCA competition includes the step of performing frame transmission at the slot boundary where the backoff counter reaches 0 based on a channel access operation including a backoff procedure, wherein A method of operation in which, while the P-EDCA competition is performed in the above STA, channel access related to the transmission of VO (voice) among a plurality of access categories (AC) is granted, and channel access related to the transmission of other ACs excluding VO among the plurality of ACs is not granted.

2. In Paragraph 1, The above-mentioned first set time is an operation method in which the AIFS (arbitration interframe space) related to the above-mentioned P-EDCA competition.

3. In Paragraph 2, A method of operation in which, while the STA performs the P-EDCA competition, the channel access operation is permitted based on the operation of the STA's VO transmission-related EDCAF (enhanced distributed channel access function), wherein the VO transmission-related EDCAF performs the channel access based on the VO transmission-related AIFS corresponding to a second previously set time.

4. In Paragraph 3, A method of operation in which the plurality of ACs of the STA perform the channel access operation based on each AC-related EDCAF operation, wherein while the STA performs the P-EDCA competition, other AC transmission-related EDCAF operations, excluding the VO transmission-related EDCAF, are deferred and the channel access operation is not permitted.

5. In Paragraph 4, A method of operation in which, when the above-mentioned postponed EDCAF operation related to another AC transmission is resumed, the above-mentioned EDCAF related to another AC transmission performs the channel access based on AIFS according to each preset time corresponding to each AC.

6. In Paragraph 5, A method of operation in which the above other AC transmission-related EDCAF includes VI (video) related EDCAF, BE (best effort) related EDCAF, and BK (background) related EDCAF.

7. In Paragraph 1, A method of operation in which, when the STA completes frame transmission after channel occupation based on the P-EDCA competition, the STA does not perform the P-EDCA competition until the P-EDCA constraint is resolved.

8. In Paragraph 7, A method of operation in which, when the above P-EDCA constraint is satisfied, the STA updates the VO transmission-related parameters and performs the channel access operation through the VO transmission-related AIFS corresponding to the updated parameters based on the VO transmission-related EDCAF operation.

9. In Paragraph 7, A method of operation in which, when the above P-EDCA constraint is satisfied, the STA resumes the other AC transmission-related EDCAF operation, and the other AC transmission-related EDCAF performs the channel access based on the AIFS according to a preset time corresponding to each AC.

10. In Paragraph 1, A method of operation in which the above DS includes a MAC (medium access control) header, and the duration field of the MAC header indicates the length of time the medium is occupied after the transmission of the above DS, wherein the length of time the medium is occupied corresponds to the time required for the P-EDCA competition.

11. In Paragraph 10, A method of operation in which, after the transmission of the above DS, a TXNAV timer is set based on the time length indicated by the duration field, the TXNAV timer is a timer shared and used by a plurality of EDCAFs of the above STA, and if the value of the TXNAV timer is not zero, the plurality of EDCAFs of the above STA determine that the medium is in an occupied state and postpone channel access operation, wherein the EDCAF related to VO transmission performs the P-EDCA competition and does not consider the value of the TXNAV timer that is not zero in determining the occupied state of the medium.

12. In Paragraph 11, A method of operation in which, when the value of the TXNAV timer reaches 0, the plurality of EDCAFs of the STA do not consider the value of the TXNAV timer in determining the occupancy status of the medium, and the plurality of EDCAFs of the STA resume the channel access operation deferred by the TXNAV timer.

13. In Paragraph 10, A method of operation in which, after the transmission of the above DS, a control variable indicating the medium occupancy state within the STA is set based on the time length indicated by the duration field, the control variable is shared by a plurality of EDCAFs of the STA, and when the control variable indicates a first state, the plurality of EDCAFs of the STA determine the medium to be in an occupied state and postpone channel access operation, wherein the EDCAF related to the VO transmission performs the P-EDCA competition and does not consider the state of the control variable in determining the medium occupancy state.

14. In Paragraph 13, A method of operation in which, as the time length indicated by the duration field elapses, the control variable switches to a second state, the plurality of EDCAFs of the STA resume the channel access operation deferred by the control variable.

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

16. In a wireless LAN system, regarding a station (STA), At least one transceiver for transmitting and receiving signals; At least one processor controlling the above-mentioned at least one transmitting and receiving unit; and It includes a memory that stores instructions for the non-AP STA to perform a specific operation by the at least one processor, and The above specific operation is: The channel is switched from an occupied state to an idle state, and it is confirmed that the channel is in an idle state for a first set period of time, and If it is confirmed that the channel is idle during the first set time, a DS (defer signal) is transmitted to initiate P-EDCA (prioritized enhanced distributed channel access) competition after the first set time, and A STA that performs the P-EDCA competition after the DS transmission, wherein the P-EDCA competition performs frame transmission at the slot boundary where the backoff counter reaches 0 based on a channel access operation including a backoff procedure, and wherein, while the P-EDCA competition is performed in the STA, channel access related to the transmission of VO (voice) among a plurality of access categories (AC) is granted, and channel access related to the transmission of other ACs excluding VO among the plurality of ACs is not granted.

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