Method and apparatus for performing multi-link relay operation in wireless LAN

Abstract

This operation method of a relay AP, which is connected to a master AP by a first link and is connected to a first STA by a second link so as to operate on the basis of NSTR in a wireless LAN system, may comprise steps in which a relay AP: receives a first frame from a first STA through a second link in a first section; transmits, as a response to the first frame, a first response frame to the first STA through the second link in the first section; occupies a first link through a channel access operation in the first section, and transmits, to a master AP, a first frame received from the first STA in the occupied first link, the relay AP receiving a second response frame from the master AP; and, after receiving the second response frame, occupies the second link on the basis of a channel access operation in the second link, and transmits a second frame in the occupied second link.

Description

Method and device for performing multi-link relay operation in wireless LAN

[0001] The present disclosure relates to a method and device for performing multi-link relay operation in a wireless local area network (WLAN). Specifically, the present disclosure relates to a scheduling method and device for smooth transmission and reception when a multi-link wireless LAN access point (AP) that cannot perform simultaneous transmission and reception (NSTR) in a WLAN performs relay operation.

[0002] In addition, the present disclosure relates to a method and device for a wireless LAN terminal to protect an R-TWT (Restricted Target Wake Time) schedule of an OBSS (Overlapping Basic Service Set).

[0003]

[0004] With the recent proliferation of mobile devices, Wireless Local Area Network (WLAN) technology, which can provide fast wireless communication services to these devices, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly access the Internet.

[0005] Standards for wireless LAN technology are primarily being developed by the Institute of Electrical and Electronics Engineers (IEEE) as the IEEE 802.11 standard. As the aforementioned wireless LAN technology has developed and become widespread, applications utilizing it have diversified, creating a demand for wireless LAN technology that supports higher reliability.

[0006] 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) and / or redundant BSS environments. The goals of the IEEE 802.11bn standard may include supporting increased data transmission rates, improved latency performance, and lower data error rates. Furthermore, the IEEE 802.11bn standard can support low-power operation and peer-to-peer communication.

[0007] In a wireless LAN, multiple APs can exist, and wireless LAN terminals can move between APs. Each time a wireless LAN terminal moves between APs, it must perform a roaming operation. However, roaming may require parameter changes, and if parameter changes are delayed, communication efficiency may decrease and latency may increase. Consequently, the reliability of the wireless LAN network is compromised.

[0008] Meanwhile, the technology that serves as the background of the invention is written to promote understanding of the background of the invention, and may include content that is not a prior art already known to a person with ordinary skill in the field to which the technology belongs, and may not be limited to a specific form.

[0009]

[0010] The present disclosure relates to a method and device for performing multi-link relay operation in a wireless LAN.

[0011] The present disclosure relates to a method and device for supporting low latency (LL) traffic through multi-link scheduling of an NSTR Relay AP in a wireless LAN.

[0012] The present disclosure relates to a method and device for protecting an OBSS R-TWT schedule through a terminal in a wireless LAN.

[0013] The present disclosure relates to a method and device for protecting an R-TWT SP of an OBSS terminal by reducing the TXOP of a terminal that has detected an R-TWT operation of an OBSS terminal and has acquired a TXOP (Transmit Opportunity) of a length that cannot protect the start time of an OBSS R-TWT SP by a channel access operation of a terminal that does not have information about an R-TWT operation of an OBSS terminal and starts transmission.

[0014] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0015]

[0016] According to one example of the present disclosure, in a wireless LAN system, a method for operating a relay AP connected to a master access point (AP) through a first link and connected to a first station (STA) through a second link and operating based on NSTR (Non-simultaneous Transmit and Receive) comprises: a step in which the relay AP receives a first frame from a first STA through a second link in a first section; a step in which the relay AP transmits a first response frame to the first STA in response to the first frame through the second link in the first section; a step in which the relay AP occupies the first link through a channel access operation in the first section and transmits the first frame received from the first STA on the occupied first link to the master AP; a step in which the relay AP is absent from the second link during the first link operation time of the relay AP and the relay AP receives a second response frame from the master AP; and a step in which the relay AP, after receiving the second response frame, occupies the second link based on the channel access operation on the second link and transmits the second frame on the occupied second link. Including a step, the second frame may be a frame indicating that the relay AP is present on the second link.

[0017] In addition, according to an example of the present disclosure, a relay access point (AP) operating based on NSTR includes at least one transceiver for transmitting and receiving a signal, at least one processor for controlling the at least one transceiver, and a memory for storing instructions for causing the relay to perform a specific operation by the at least one processor, wherein the specific operation of the relay AP, which is connected to a master access point (AP) through a first link and connected to a first station (STA) through a second link, is: receiving a first frame from a first STA through the second link in a first period, transmitting a first response frame to the first STA in response to the first frame through the second link in the first period, and the relay AP occupies the first link through a channel access operation in the first period, and forwards the first frame received from the first STA through the occupied first link to the master AP, wherein the relay AP is absent from the second link during a preset time period during which the relay AP operates on the first link, and receives a second response frame from the master AP, and After receiving the second response frame, the second link is occupied based on a channel access operation on the second link, and a second frame is transmitted on the occupied second link, wherein the second frame may be a frame indicating that a relay AP exists on the second link.

[0018] Additionally, the following may be commonly applied:

[0019] According to one example of the present disclosure, a relay AP operating based on NSTR may not be able to perform reception on one of the first link and the second link when transmitting on the other link.

[0020] In addition, according to one example of the present disclosure, the relay AP performs a relay schedule negotiation procedure with the master AP, and determines relay schedule information consisting of at least one of information on a start time and a time period during which frame transmission can be performed through the relay schedule negotiation procedure, and based on the relay schedule information, a first period during which the relay AP performs communication with the first STA on the second link and a second period during which the relay AP performs communication with the master AP on the first link can be determined.

[0021] Additionally, according to an example of the present disclosure, the first link operation time of the relay AP may be determined from the time when the relay AP starts a channel access operation on the first link to the time when the second response frame is received.

[0022] Additionally, according to an example of the present disclosure, the first frame may be a low-latency frame transmitted from the first STA to the master AP.

[0023] Here, according to one example of the present disclosure, the first response frame, which is a response to the first frame, includes an indicator indicating that the relay AP is absent from the second link after transmitting the first response frame, and the channel access operation performed on the second link is interrupted by the indicator, and the interrupted channel access operation can be resumed by the second frame.

[0024] Additionally, according to one example of the present disclosure, the relay AP may transmit a third frame on the second link after transmitting a first response frame in response to the first frame, wherein the third frame may be a frame indicating that the relay AP is absent from the second link after transmitting the third frame.

[0025] Additionally, according to one example of the present disclosure, the first frame includes an indicator for allocating a transmission section of the first STA to a relay AP, and the relay AP can transmit a third frame on the second link based on the indicator.

[0026] Additionally, according to an example of the present disclosure, the third frame may be transmitted on the second link in a broadcast manner or a multicast manner.

[0027] Additionally, according to one example of the present disclosure, the relay AP transmits a fourth frame to the master AP over the first link, wherein the fourth frame may be a short control frame requesting that the relay AP transmit the first frame received from the first STA over the first link.

[0028] Additionally, according to an example of the present disclosure, the relay AP may transmit the first frame received from the first STA to the master AP over the first link after a preset time after receiving the third response frame from the master AP in response to the fourth frame.

[0029] Additionally, according to one example of the present disclosure, the fourth frame transmitted on the first link may be transmitted simultaneously with the third frame transmitted on the second link.

[0030] Additionally, according to an example of the present disclosure, the second link is a low-latency operation support link that enables reception operation of the master AP, and the relay AP can transmit the first frame received from the first STA to the master AP through the second link instead of the first link after a preset time from the time of completion of transmission of the first response frame to the first STA.

[0031] Additionally, according to an example of the present disclosure, the first frame includes an indicator for allocating a transmission section of the first STA to a relay AP, and the relay AP can forward the first frame received from the first STA to the master AP on the second link based on the indicator.

[0032] Additionally, according to an example of the present disclosure, the first frame transmitted by the relay AP to the master AP may further include a transmission interval extension indicator indicating an extension for the transmission interval allocated to the relay AP.

[0033]

[0034] According to the present disclosure, a method for performing a multi-link relay operation in a wireless LAN can be provided.

[0035] According to the present disclosure, a method for supporting LL traffic through multi-link scheduling of an NSTR Relay AP in a wireless LAN can be provided.

[0036] According to the present disclosure, a method for protecting an OBSS R-TWT schedule through a terminal in a wireless LAN can be provided.

[0037] According to the present disclosure, when a terminal without information on an R-TWT operation of an OBSS terminal acquires a TXOP of a length that cannot protect the start time of an OBSS R-TWT SP with a channel access operation and starts transmission, a method can be provided in which a terminal that detects an R-TWT operation of an OBSS terminal reduces the TXOP of the terminal that acquired the TXOP to protect the R-TWT SP of the OBSS terminal.

[0038] According to the present disclosure, a method for improving the robustness of multi-link transmission and reception operations using an NSTR Relay AP can be provided by an artificial intelligence-based scheduling procedure for transmission and reception of a multi-link NSTR Relay AP.

[0039] According to the present disclosure, a method for protecting transmission of low-latency traffic in a wireless LAN network by protecting an OBSS R-TWT SP can be provided.

[0040] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0041]

[0042] Figure 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure is applied.

[0043] Figure 2 is a diagram showing a wireless LAN system to which the present disclosure is applied.

[0044] FIG. 3 is a diagram illustrating a machine learning unit to which the present disclosure is applied.

[0045] FIG. 4 is a flowchart illustrating a method for performing communication based on a machine learning unit to which the present disclosure is applied.

[0046] FIG. 5 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0047] FIG. 6 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0048] FIG. 7 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0049] FIG. 8 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0050] FIG. 9 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0051] FIG. 10 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0052] FIG. 11 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0053] FIG. 12 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0054] FIG. 13 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0055] FIG. 14 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0056] FIG. 15 is a flowchart illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0057]

[0058] This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

[0059] While terms such as first, second, etc. may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a 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.

[0060] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0061] The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0062] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0063] 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 in describing the present disclosure, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0064] 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 description below, and the embodiments according to the present disclosure can be applied to various wireless communication systems. The wireless communication system may be referred to as a "wireless communication network."

[0065] FIG. 1 is a diagram illustrating a communication node within a wireless LAN system to which the present disclosure applies. Referring to FIG. 1, a communication node (100) may include at least one of a processor (110), a 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 (AP) 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 other nodes or devices based on the above-described configuration. For example, the operating channel width supported by the AP may be 20 MHz (megahertz), 80 MHz, 160 MHz, etc. The operating channel width supported by the station may be 20 MHz, 80 MHz, etc. However, the present invention may not be limited thereto.

[0066] The processor (110) within the 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) as each component within the communication node. The memory (120) within the communication node (100) can store information on commands and instructions executed by the processor (110), and the transceiver (130) can refer to a transceiver, a radio frequency (RF) 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, can be linked with other interfaces, and can further include a separate storage device (150). Each component within the communication node (100) can be connected by a bus (160) to communicate with each other.

[0067] However, as an example, each component included in the communication node (100) may be connected through an individual interface or individual bus centered around the processor (110), rather than a common bus (160). The processor (1110) may be connected to at least one of the memory (120), the transmission / reception device (130), the input / output interface device (140), and the storage device (150) through a dedicated interface.

[0068] The processor (110) can execute program commands stored in at least one of the memory (120) and the storage device (150). The processor (110) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to embodiments of the present disclosure are performed. Each of the memory (120) and the storage device (150) may be configured with at least one of a volatile storage medium or a non-volatile storage medium. For example, the memory (120) may be configured with at least one of a read-only memory (ROM) or a random access memory (RAM).

[0069] FIG. 2 is a diagram illustrating a wireless LAN system to which the present disclosure applies. Referring to FIG. 2, a basic service set (BSS) of the wireless LAN system may include one AP (210) and multiple STAs (221, 222, 223, 224), and the multiple STAs (221, 222, 223, 224) may be controlled by the AP (210). However, the wireless LAN system is not limited to the BSS, and an environment consisting only of STAs without a defined 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 medium access control (MAC) layer and a physical (PHY) layer, and communication may be performed between the wireless devices. For the convenience of explanation, the following description focuses on APs and STAs, but may not be limited thereto. For example, the following may equally apply to other communication nodes or devices and are not limited to a specific form.

[0070] Figure 3 is a diagram illustrating a machine learning unit to which the present disclosure applies. Each wireless device within a wireless LAN system may be connected to a machine learning unit (300). However, this may not be limited to this, and wireless devices not connected to the machine learning unit (300) may also operate.

[0071] For example, the processor (110) of the communication node (100) of FIG. 1 may be connected to the machine learning unit (300). The machine learning unit (900) may be connected to the processor (110) through the input / output interface device (140) of the communication node (100) to communicate. As another example, the machine learning unit (300) may be connected to the processor (110) through the bus (160) of the communication node (100) to communicate. As another example, the machine learning unit (300) may be connected to the processor (110) of the communication node (100) through a separate interface or a dedicated bus to communicate. The machine learning unit (300) may be connected to the memory (120), the transceiver (130), and the storage device (140) through the input / output interface device (140), the bus (160), or the dedicated bus to communicate, but may not be limited to a specific form.

[0072] For example, the machine learning unit (300) may include at least one ML (Machine Learning) processor (310), ML memory (320), ML input / output interface (330), and ML bus (340). The ML processor (310), ML memory (320), and ML input / output interface (330) may be connected to and communicate with each other through the ML bus (340). As another example, the ML processor (310) may be connected to and communicate with at least one of the ML memory (320) and the ML input / output interface (330) through a dedicated bus or interface. The ML processor (310) may be a central processing unit, a graphics processing unit, a dedicated processor on which methods according to embodiments of the present disclosure are performed, or a processor in which at least one of the central processing unit and the dedicated processor is combined. The ML processor (310) may include at least one of a training unit (311), a verification unit (312), a performance unit (313), and an updating unit (313). The training unit (311), the verification unit (312), the performance unit (313), and the updating unit (313) may be logical entities configured by software or hardware processing devices. For example, the ML processor (310) may perform at least one of training, verification, execution, and updating of a machine learning model. The machine learning model may be in the form of a plurality of matrices or vectors. As a specific example, the machine learning model may include weights, a transition matrix, and hyperparameters that implement and learn a single or multiple combined machine learning algorithms (e.g., a deep neural network (DNN), a convolutional neural network (CNN), a recurrent neural network (RNN), and a deep reinforcement learning (DRL) algorithm).A machine learning model may include an input layer, at least one hidden layer, and an output layer to implement a deep neural network (DNN) algorithm. Each of the input layer, hidden layer, and output layer may include at least one perceptron (e.g., an artificial neuron). The perceptron includes an activation function, input weights, and a bias. Multiple perceptrons may have inputs and outputs connected to form an input layer, a hidden layer, and an output layer. The machine learning model may include a convolution algorithm and the DNN algorithm to implement a CNN algorithm. The convolution algorithm convolves a kernel matrix with input data in matrix form and may be performed at least once on the input data. When the convolution algorithm is performed on the input data, the size of the data may be increased through concatenation or reduced through pooling. The input data on which the convolution algorithm has been performed at least once is used as input data for the DNN algorithm. For example, a machine learning model may include a DNN algorithm and a cell structure to implement an RNN algorithm. The cell structure may be a structure that remembers previous input data and inputs it on its own, and may be used in at least one perceptron of the DNN algorithm. A machine learning model may include an agent, an environment structure, and a DNN algorithm to implement a DRL algorithm. In a DRL algorithm, an agent can observe the environment and perform an optimal action based on the observed data. The environment can provide feedback as a reward to the agent based on the agent's action. Based on the above, the agent can learn a policy for taking an optimal action.Agents can use DNN algorithms to learn optimal actions.

[0073] As another example, the machine learning unit (300) may be designed to additionally implement other machine learning algorithms in addition to the aforementioned machine learning algorithms (e.g., DNN, CNN, RNN, and DRL). To this end, the machine learning unit (300) may include additional components for implementing other machine learning algorithms. The ML memory (320) within the machine learning unit (300) may store machine learning models and machine learning algorithms. The implementation of the machine learning algorithms may be performed by the ML processor (310) based on the machine learning models.

[0074] As another example, all or part of the functions of the machine learning unit (300) may be integrated into the processor (110) and memory (120) of the communication node (100). That is, the processor (110) of the communication node (100) may perform all or part of the functions of the ML processor (310), and the memory (120) may perform all or part of the functions of the ML memory (320). When the processor (110) and memory (120) of the communication node (100) perform all of the functions of the machine learning unit (300), the machine learning unit (300) may not be connected by the input / output interface (140), and the processor (110) and memory (120) may operate as the machine learning unit (300).

[0075] As another example, the machine learning unit (300) may be connected not through the input / output interface (140) of the communication node (100), but through a bus (160) or a dedicated bus or interface centered around the processor (110) of the communication node (100), but may not be limited to the above embodiment.

[0076] FIG. 4 is a flowchart illustrating a method for performing communication based on a machine learning unit to which the present disclosure is applied. Referring to FIG. 4, the machine learning unit (300) is connected to a communication node (100), collects communication data, and can perform prediction based on a machine learning model (S410). As an example, the above-described prediction may be performed by the execution unit (313) of the machine learning unit (300), but is not limited thereto. Here, the communication data collected by the machine learning unit (300) may include at least one of channel noise status, channel congestion, reception strength, collision frequency, and other information obtained from a physical layer. In addition, the communication data may include information obtained from a MAC layer, and is not limited to a specific form. The communication data collected by the machine learning unit (300) may be provided as input to the machine learning model itself. As another example, the communication data collected by the machine learning unit (300) may be provided as input to the machine learning model after being operated or processed. For example, the prediction result of the machine learning unit (300) may be at least one of a physical layer and MAC parameter (e.g., MCS (modulation and coding scheme) parameter, beamforming parameter, EDCA (enhanced distributed channel access) parameter, etc.). As another example, the prediction result of the machine learning unit (300) may be information for packet scheduling, multi-AP operation scheduling, and other scheduling, but is not limited to a specific form. As another example, the communication node (100) may receive all or part of the machine learning model from another communication node. All or part of the machine learning model may be collected by the machine learning unit (300) and is not limited to a specific form. As an example, the communication node (100) may perform communication based on the prediction of the machine learning unit (300).(S420) In addition, the machine learning unit (300) can collect communication data based on the performed communication, and based on this, machine learning model verification can be performed (S430) or machine learning model training (S440) can be performed. In addition, as an example, the machine learning model can be exchanged with other communication nodes (S450), and the exchanged machine learning model information can be used for machine learning model verification or machine learning model training. As an example, when machine learning model verification is performed, it can be verified whether the communication operation performed by the prediction of the machine learning unit (300) is appropriate. As a specific example, the machine learning model verification can be performed based on at least one of the frame collision frequency, transmission error frequency, and packet transmission delay of the communication node (100), and an operation of determining whether the communication performance of the communication node (100) has been improved can be performed.

[0077] In addition, for example, if it is determined that training of a machine learning model is necessary (e.g., if communication performance has not improved, if it is determined that the performance of a machine learning model of another communication node (e.g., all or part of the machine learning model) is superior to that of the current communication node (100), the communication node (100) may perform machine learning model training. In another example, the communication node (100) may exchange the machine learning model with other communication nodes without performing machine learning model verification or machine learning model training. In addition, for example, if it is determined that training of a machine learning model is not necessary, the communication node (100) may exchange the machine learning model with other communication nodes without performing machine learning model training.

[0078] Here, the machine learning model may be trained (or learned) based on at least one of the collected communication data and all or part of the machine learning model of another communication node. The training of the machine learning model may be performed by the training unit (311) and may be performed based on at least one of the collected communication data and the output of the machine learning model of another communication node and the machine learning model of the communication node (100).

[0079] As another example, part or all of the machine learning model of the communication node (1000) may be replaced with part or all of the machine learning model of another communication node by the updating unit (314) of the machine learning unit (300). As another example, the machine learning model (e.g., part or all of the machine learning model) of the communication node (100) may be shared with another communication node. Alternatively, the communication node (100) may operate only based on machine learning model verification and training without exchanging the machine learning model with other communication nodes, and is not limited to a specific form. As an example, in the present disclosure, at least one of changing the order, adding or removing steps, and repeating specific steps may be performed in the steps of the flowchart. In other words, the flowchart is an example describing the operation of the machine learning unit (300) of the wireless communication node (100), and the procedures and operations thereof may be modified in various ways. For example, after training a machine learning model, it may be possible to perform a machine learning model validation step again to validate the trained machine learning model, and it may not be limited to a specific form.

[0080] The following FIGS. 5 to 8 and FIG. 15 describe operations of a Master AP, a Relay AP connected to the Master AP, and a non-AP STA connected to the Relay AP. That is, the following operations of the present disclosure are described based on a case where the Master AP and the Relay AP connected to the Master AP form a first link, and the Relay AP and the non-AP STA connected to the Relay AP establish a second link. However, this is for convenience of explanation and is not limited to the embodiment. For example, the operations of the present disclosure below can be equally applied even when the entities and transmission directions are different. As a specific example, the following disclosures can be equally applied even when the Master AP, the Relay AP, and the non-AP STA are all APs. That is, the present disclosure can be equally applied to a wireless LAN terminal in which links are established between APs and which operates on different links to perform a relay function. As another example, the present disclosure can be equally applied even when the Master AP, the Relay AP, and the non-AP STA are all non-AP STAs. That is, the same can be applied to a wireless LAN terminal that establishes a link between STAs and operates on different links to perform a relay function. Alternatively, the following disclosures can be equally applied even when only the Master AP is an AP and both the Relay AP and the non-AP STA are non-AP STAs. That is, the operations of the following disclosure may not be limited to the operations of a specific entity, but for the convenience of explanation, the following description is based on the operations of the Master AP, the Relay AP connected to the Master AP, and the non-AP STA connected to the Relay AP.

[0081] Additionally, as an example, the following disclosure describes an operation in which a frame is transmitted from a non-AP STA to a Master AP, but this may not be limited thereto. Specifically, the present disclosure may also be applied to a case in which a frame is to be transmitted from a Master AP to a non-AP STA. In the above-described cases, the operating section information may differ, but may not be limited to a specific form.

[0082] That is, the following disclosures may not be limited to a specific entity or a specific frame transmission direction, and may be equally applied to various entities and frame transmission directions. However, for convenience of explanation, the operation of the present disclosure is described below based on a Master AP, a Relay AP, and a non-AP STA.

[0083] FIG. 5 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0084] Referring to FIG. 5, a Master AP (e.g., Master) and a Relay AP (e.g., Relay) associated with the Master AP may operate. In addition, STA 1 associated with the Relay AP may operate. The Relay AP may be a wireless LAN terminal that performs a relay operation to extend the transmission / reception range of the Master AP. For example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation from an SME (Station Management Entity). As a specific example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation when a charging state and other conditions are satisfied, but may not be limited thereto.

[0085] When a wireless LAN terminal supporting relay operation obtains an instruction to trigger a relay operation from an SME, the wireless LAN terminal supporting relay operation can change its operation mode from a non-AP STA to a relay AP through an onboarding process. Here, the relay AP may be a non-simultaneous transmit and receive (NSTR) relay AP that cannot perform simultaneous transmission and reception operations on multiple links. For example, an NSTR relay AP may not be able to perform a reception operation on another link when transmitting on one link. Here, the link on which the NSTR relay AP cannot perform simultaneous transmission and reception may be an NSTR link pair.

[0086] As a specific example, in FIG. 5, the first link (510) and the second link (520) may operate, and the Master AP, the Relay AP, and STA 1 may perform at least one of transmission and reception operations on the first link (510) and the second link (520). Here, the first link (510) may be a link that operates only as a backhaul link, and the second link (520) may be a link that operates only as a fronthaul link. The fronthaul link may be a link used for transmission and reception between a non-AP STA and an AP (e.g., STA 1 and a Relay AP), and the backhaul link may be a link used for transmission and reception between one AP and another AP (e.g., between a Master AP and a Relay AP). However, this is for convenience of explanation and may not be limited to the embodiment.

[0087] When a relay AP uses a specific link as a fronthaul, the relay AP may transmit a beacon or a probe response to a non-AP STA on the link. Here, the beacon or the probe response may include an indicator that specifies that the relay AP is a relay AP. The master AP or the relay AP may perform relay scheduling negotiation for transmission and reception scheduling on at least one of the fronthaul link (e.g., the second link (520)) and the backhaul link (e.g., the first link (510)). The relay scheduling negotiation may be an operation to protect transmission and reception operations on at least one of the first link (510) and the second link (520) by using at least one of a restricted-target wake time (r-TWT) and a quiet time period (QTP) (e.g., protecting a frame transmission start time, stopping a backoff counter decrement of a non-AP STA). Here, r-TWT may be an operation that sets TWT only for a specific group, so that terminals outside the specific group terminate ongoing transmissions before the TWT start time, and TWT may be an operation that causes a wireless LAN terminal to wake up at a specific time and perform communication. In addition, QTP may be a period that limits wireless communication for a specific time to reduce interference or perform a specific operation.

[0088] As another example, relay scheduling may be an operation that protects the start time of frame transmission using ML (Multi Link) r-TWT. ML r-TWT may be an operation in which a Relay AP replicates at least one piece of r-TWT information negotiated with a Master AP in a backhaul link and instructs non-AP STAs in a fronthaul link to copy the information. The Master AP may instruct the Relay AP operating in the backhaul link (e.g., the first link (510)) about r-TWT operation information using at least one of a field (e.g., a TWT Parameter Set field, etc.) and an indicator (e.g., a TWT element) in a frame (e.g., a Management frame) used for r-TWT operation. The r-TWT operation information may include at least one of a start time (offset) and a time period (duration) during which the Relay AP can perform frame transmission to the Master AP as a service period (SP) in the backhaul link (e.g., the first link (510)). For example, STAs or relay APs that are members of an r-TWT SP can perform transmission and reception during the time period from the SP start time. On the other hand, STAs or relay APs that are not members of an r-TWT SP must terminate all communication at the SP start time and may not perform transmission operations during the SP time period. Here, since the Relay AP is an NSTR terminal, if the Relay AP transmits to the Master AP during the r-TWT SP of the first link (510), the signal may not be received on the second link (520). Therefore, if the Relay AP transmits during the r-TWT SP of the first link (510), the Relay AP needs to instruct STAs on the second link (520) not to transmit during the period corresponding to the r-TWT SP of the first link (510).

[0089] For example, the Relay AP may copy information indicating a section corresponding to the r-TWT SP of the first link (510) among the r-TWT information instructed by the Master AP (e.g., at least one of the start time (offset) and the time period (duration)) so that all STAs complete transmission before the start time of the r-TWT SP of the first link (510) in the second link (520) and instruct non-AP STAs connected to the Relay AP through the front hall (e.g., the second link (520)).

[0090] As another example, STAs may be excluded from being members of the r-TWT SP to prevent transmission during the r-TWT SP period of the second link (520). As another example, the Relay AP may transmit an indicator to the STAs that restricts channel access via EDCA. As another example, the Relay AP may activate a trigger-enabled setting that only allows channel access via a trigger frame.

[0091] When a Relay AP applies an r-TWT schedule whose settings are copied from a first link (510) to a second link (520), there may be another TWT schedule within the second link (520) and the copied r-TWT schedule applied to the second link (520). Here, the Relay AP may modify an existing TWT schedule so that there is no overlapping section between the copied r-TWT schedule applied to the second link (520) and the other TWT schedule within the second link (520). As another example, when a Relay AP sets a new TWT schedule after an r-TWT schedule whose settings are copied from a first link (510) is created in a second link (520), the Relay AP may need to set the new TWT schedule so that there is no overlapping section with the r-TWT schedule whose settings are copied from a first link (510).

[0092] For example, the Master AP may also transmit r-TWT information (e.g., at least one of the start time (offset) and the time duration) indicating a section corresponding to the r-TWT SP of the first link (510) that is transmitted to the second link (520). The Master AP may use the r-TWT information transmitted to the first link (510) to indicate a section transmitted by the Relay AP (e.g., transmit r-TWT information in which a member of the r-TWT SP is a Relay AP). Accordingly, the communication of all STAs may be terminated before the start time of the r-TWT SP, and transmission may not be performed during the r-TWT SP time period. Through this, the transmission section of the Relay AP may be protected. At least one of the Relay AP and the Master AP can use the r-TWT information transmitted to the second link (520) (e.g., r-TWT information in which a member of the r-TWT SP is a Relay AP) to prohibit STAs from transmitting to the Relay AP during the same time period as the time period in which the Relay AP transmits on the first link (510). That is, at least one of the Relay AP and the Master AP can indicate that the Relay AP is absent and prevent STAs from communicating during the corresponding time period.

[0093] STAs may not transmit to the Relay AP in the SP section indicated by the r-TWT information transmitted by the Relay AP on the second link (520). However, STAs may transmit to other STAs or the Master AP. As another example, STAs may not transmit to the Relay AP in the SP section indicated by the r-TWT information transmitted by the Master AP to indicate the absence of the Relay AP on the second link (520), but may transmit to other STAs or the Master AP.

[0094] At least one of the Master AP and the Relay AP can instruct non-AP STAs (e.g., STA 1) operating on at least one of the first link (510) and the second link (520) about the above-described relay scheduling information (e.g., at least one of the start time and time interval of transmission and reception operations on the first link (510) and the start time and time interval of absence of the Relay AP on the second link (520). At least one of the Master AP and the Relay AP can instruct using at least one of the fields and indicators (e.g., TWT element, QTP element, etc.) within a frame in which the above-described relay scheduling information is transmitted (e.g., Beacon frame, Probe Response frame, TWT request / response frame, QTP Action frame, etc.).

[0095] While the Relay AP performs transmission and reception operations on the first link (510), the r-TWT scheduling can be used to restrict transmissions by non-AP STAs of the second link (520). Here, since the STAs wait without performing transmissions even though the channel is idle, the backoff counter can continue to decrease. Therefore, after the r-TWT SP ends, there may be many STAs whose backoff counters reach 0, and thus the probability of collision due to channel access by the STAs immediately after the r-TWT SP ends may increase. For example, in order to prevent the above-described collision, a QTP schedule of a section identical to or including the SP section of the r-TWT schedule whose settings are copied from the first link (510) can be set on the second link (520). In the above-described case, the STAs of the second link (520) stop decreasing the backoff counter, thereby suppressing the occurrence of the above-described collision problem.

[0096] The Master AP and the Relay AP can recognize the time when the first link (510) and the second link (520) operate as a fronthaul link or a backhaul link through negotiated relay scheduling. Non-AP STAs (e.g., STA1) connected to the Master AP or the Relay AP can transmit frames to the Master AP or the Relay AP from a link (e.g., the second link (510)) operating as a fronthaul link at the time negotiated through relay scheduling. When the Master AP or the Relay AP receives a frame from a non-AP STA, the Master AP or the Relay AP can transmit the received frame from a link (e.g., the first link (510)) operating as a backhaul link at the time negotiated through relay scheduling.

[0097] For example, STA 1 may want to transmit an uplink (UL) frame (e.g., PPDU (PHY layer protocol data unit), MPDU (MAC layer protocol data unit), A-MPDU (aggregated-MPDU)) to the Master AP. STA 1 may be connected to a Relay AP on a fronthaul link (e.g., a second link (510)), and STA 1 may want to transmit the uplink frame to the Master AP via the Relay AP. Here, STA 1 may perform a channel access operation. The channel access operation may be an EDCA backoff. STA 1 may perform transmission at a slot boundary where a backoff counter reaches 0. The frame that STA 1 wants to transmit to the Master AP via the Relay AP may be a low latency (LL) frame (501) that requires priority transmission. The LL frame (501) may be a frame whose delay bound of the frame is less than or equal to a specific threshold. Whether the frame to be transmitted is an LL frame may be indicated by a specific indicator in the preamble of the frame to be transmitted or a specific indicator in the MAC header. The LL frame (501) transmitted by STA 1 may be a frame that must be transmitted to the Master AP before the delay bound is reached even though the link connected to the Relay AP (e.g., the second link (520)) operates as a fronthaul link. For example, when the Relay AP and the Master AP support LL frame transmission through the relay, and the Relay AP transmits an LL frame received from an STA in the fronthaul link transmission section in the backhaul link transmission section, a case may occur where the delay bound of the LL frame is not satisfied.Here, the Relay AP may attempt immediate relay transmission by moving to the first link (510) in the fronthaul section. In the above-described case, the Relay AP may be absent from the fronthaul link (e.g., the second link (520)) during the LL frame transmission period to the Master AP by the NSTR link pair. Therefore, the Relay AP may need to indicate to non-AP STAs operating on the fronthaul link that the Relay AP will be absent. For example, the existing r-TWT and QTP scheduling information may be transmitted during the beacon and probe processes. However, since an immediate or temporary r-TWT and QTP section must be set when the above-described situation occurs, there may be limitations in indicating it through the beacon and probe response frames.

[0098] Considering the above, there is a need to define a separate method for indicating a temporary absence period of a Relay AP. For example, the Relay AP may respond with a response frame (502) after a Short Interframe Space (SIFS) after receiving the LL frame (501) transmitted by STA 1 on the second link (520). The response frame (502) transmitted by the Relay AP to STA 1 on the second link (520) may be a Block Acknowledgement (BA) frame within the frame. The Relay AP may use at least one of the fields and indicators (e.g., a Power Management bit (PM) bit, a specific bit of a quality of service (QoS) Control field) included in the response frame (502) transmitted to STA 1 to indicate that the Relay AP will be absent on the second link (520) after transmitting the response frame.

[0099] As another example, the response frame (502) that the Relay AP transmits to STA 1 on the second link (520) may be a frame composed of an A-MPDU in which a Block Acknowledgement (BA) frame and a Quality of Service (QoS) Null frame exist together within the frame. The Relay AP may use at least one of the fields and indicators (e.g., PM bit, specific bits of the QoS Control field) included in the Quality of Service (QoS) Null frame transmitted to STA 1 to indicate that the Relay AP will be absent on the second link (520) after transmitting the response frame (502). In the above case, the response policy (Ack Policy) of the Quality of Service (QoS) Null frame may be No Ack, which does not request an additional response. The response frame (502) transmitted by the Relay AP to STA 1 can be received by other non-AP STAs (e.g., non-AP STAs other than STA 1 connected to the Relay AP) operating on the second link (520), and the other non-AP STAs can receive a frame in which the Transmitter Address (TA) is set to the identifier of the Relay AP on the second link (520), and decode at least one of a field and an indicator indicating that the Relay AP will be absent in the frame. The non-AP STAs operating on the second link (520) can stop the backoff counter decrement operation for channel access after the point in time when the Relay AP is absent. When the non-AP STAs operating on the second link (520) receive an uplink frame including an indicator indicating that it is an LL frame, an additional indicator related to the absence of the AP can be transmitted, so that a condition of receiving the downlink response frame of the AP within the same TXOP can be added.As another example, an AP may specify that it is a Relay AP and perform that action when it receives an uplink frame that includes an indicator indicating that it is an LL frame.

[0100] The Relay AP can transmit the LL frame (501) of STA 1 received on the fronthaul link (e.g., the second link (520)) to the Master AP through a channel access operation or a priority transmission operation (e.g., preemption) on the backhaul link (e.g., the first link (510)). The Master AP can respond with a response frame (e.g., a BA frame, 504) after SIFS after receiving the LL frame (503) transmitted by the Relay AP. If the Relay AP sets a temporary absence interval on the second link (520) for backhaul transmission of the LL frame (503), it may be impossible for the Relay AP to predict the total transmission time including channel access during backhaul transmission of the LL frame (503) on the first link (510). Therefore, it may be impossible for the Relay AP to indicate the length of the absence interval in advance. In consideration of the above, the STAs of the second link (520) may be restricted from transmitting to the Relay AP and reducing backoff operations until a separate indicator is transmitted after the temporary absence interval for LL frame backhaul transmission is indicated by the Relay AP. The Relay AP may transmit a frame (505) notifying the presence of the Relay AP through a channel access operation on the second link (520) that indicated the absence of the Relay AP after receiving the response frame (504) transmitted by the Master AP. For example, the frame (505) notifying the presence of the Relay AP on the second link (520) may be an Absence end frame. The Absence end frame (505) may be a short control frame (e.g., CTS (Clear To Send)-to-Self, RTS (Request To Send), MU (Multi User)-RTS, etc.) including an indicator notifying the presence of the Relay AP on the second link (520). Transmission of the Absence end frame (505) is performed in a conventional channel access operation (e.g.EDCA, etc.) can be followed. In the above case, the Relay AP may not have been able to maintain the channel status detection of the second link (520) due to the characteristics of the NSTR link pair while performing transmission and reception operations on the first link (510). Therefore, the Relay AP may wait for a certain period of time (e.g., MediumSyncDelay value) for medium synchronization and then attempt channel access through EDCA. As another example, when transmitting a short control frame as an Absence end frame (505), transmission may be permitted regardless of the procedure or backoff condition for medium synchronization in multiple links.

[0101] Non-AP STAs (e.g., STA 1) operating on the second link (520) can resume the backoff counter decrement operation for channel access on the second link (520) after receiving the Absence end frame (505). As another example, non-AP STAs (e.g., STA 1) operating on the second link (520) can recognize the presence of a Relay AP when the Relay AP starts transmitting any frame through a channel access operation, and can resume the backoff counter decrement operation for channel access on the second link (520).

[0102] At least one of the Relay AP and the Master AP may initiate a backhaul link operation (e.g., an operation to initiate an r-TWT Service Period (r-TWT SP) or an operation to terminate a QTP) by referring to the previously negotiated relay scheduling information. The Relay AP may be absent from a link other than the backhaul link (e.g., a link that is an r-TWT SP) by an NSTR link pair. The Relay AP or the Master AP may trigger a Trigger Based PPDU (TB PPDU) by transmitting a trigger frame (506) on a link (e.g., the first link) where the Relay AP is not absent. The Relay AP or the Master AP receiving the trigger frame may respond with a BA frame.

[0103] Although the above description is based on a Master AP, a Relay AP, and a non-AP STA, it may not be limited thereto. For example, the same may be applied even if both the Master AP and the Relay AP are non-AP STAs. As another example, the same may be applied even if the Master AP is an AP and the Relay AP is a non-AP STA. As a specific example, the first STA (Master AP of FIG. 5) and the second STA (Relay AP of FIG. 5) may communicate through the first link (510) described above, and the second STA (Relay AP of FIG. 5) may communicate with the third STA (STA 1 of FIG. 5) through the second link (520). Here, when the second STA is absent from the second link (520) for communication with the first STA, the second STA may indicate to the third STA that the second link (520) is absent, and may communicate with the first STA over the first link (510) during that period. In addition, other frames may be equally applied when STAs coexist as described above, and may not be limited to a specific form.

[0104] As another example, the same can be applied even when the Master AP, Relay AP, and non-AP STA are all APs. That is, the Relay AP can communicate with the first AP (Master AP of FIG. 5) through the first link (510), and communicate with the second AP (non-AP STA of FIG. 5) through the second link (520), and the same can be applied to the above-described operations.

[0105] FIG. 6 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0106] Referring to FIG. 6, a Master AP (e.g., Master) and a Relay AP (e.g., Relay) associated with the Master AP may operate. In addition, STA 1 associated with the Relay AP may operate. The Relay AP may be a wireless LAN terminal that performs a relay operation to extend the transmission / reception range of the Master AP. For example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation from an SME (Station Management Entity). As a specific example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation when a charging state and other conditions are satisfied, but may not be limited thereto.

[0107] When a wireless LAN terminal supporting relay operation obtains an instruction to trigger a relay operation from an SME, the wireless LAN terminal supporting relay operation can change its operation mode from a non-AP STA to a relay AP through an onboarding process. Here, the relay AP may be a non-simultaneous transmit and receive (NSTR) relay AP that cannot perform simultaneous transmission and reception operations on multiple links. For example, an NSTR relay AP may not be able to perform a reception operation on another link when transmitting on one link. Here, the link on which the NSTR relay AP cannot perform simultaneous transmission and reception may be an NSTR link pair.

[0108] As a specific example, in FIG. 6, the first link (610) and the second link (620) may operate, and the Master AP, the Relay AP, and STA 1 may perform at least one of transmission and reception operations on the first link (610) and the second link (620). Here, the first link (610) may be a link that operates only as a backhaul link, and the second link (620) may be a link that operates only as a fronthaul link. The fronthaul link may be a link used for transmission and reception between a non-AP STA and an AP (e.g., STA 1 and a Relay AP), and the backhaul link may be a link used for transmission and reception between one AP and another AP (e.g., between a Master AP and a Relay AP). However, this is for convenience of explanation and may not be limited to the embodiment.

[0109] When a relay AP uses a specific link as a fronthaul, the relay AP may transmit a beacon or a probe response to a non-AP STA on the link. Here, the beacon or the probe response may include an indicator that specifies that the relay AP is a relay AP. The master AP or the relay AP may perform relay scheduling negotiation for transmission and reception scheduling on at least one of the fronthaul link (e.g., the second link (620)) and the backhaul link (e.g., the first link (610)). The relay scheduling negotiation may be an operation to protect transmission and reception operations on at least one of the first link (610) and the second link (620) by using at least one of a restricted-target wake time (r-TWT) and a quiet time period (QTP) (e.g., protecting a frame transmission start time, stopping a backoff counter decrement of a non-AP STA). Here, r-TWT may be an operation that sets TWT only for a specific group, so that terminals outside the specific group terminate ongoing transmissions before the TWT start time. TWT may be an operation that causes a wireless LAN terminal to wake up at a specific time and perform communication. In addition, QTP may be an interval that limits wireless communication for a specific time to reduce interference or perform a specific operation.

[0110] As another example, relay scheduling may be an operation that protects the start point of frame transmission using ML (Multi Link) r-TWT. ML r-TWT may be an operation in which a Relay AP replicates at least one or more of the r-TWT information negotiated with a Master AP in a backhaul link and instructs non-AP STAs in a fronthaul. The Master AP may instruct a Relay AP operating in a backhaul link (e.g., the first link (510)) of r-TWT operation information using at least one of a field (e.g., a TWT Parameter Set field, etc.) and an indicator (e.g., a TWT element) in a frame (e.g., a Management frame) used for r-TWT operation.

[0111] The r-TWT operation information may be the start time of frame transmission on the backhaul link (e.g., the first link (610)). The relay AP may replicate at least one or more of the r-TWT information indicated by the master AP and instruct non-AP STAs connected to the relay AP via the front link (e.g., the second link (620)). The relay AP may use the r-TWT information to protect the start time of frame transmission on the first link (610) and the second link (620).

[0112] At least one of the Master AP and the Relay AP can instruct non-AP STAs (e.g., STA 1) operating on at least one of the first link (610) and the second link (620) about the above-described relay scheduling information (e.g., a start time of transmission / reception operation on at least one of the first link (610) and the second link (620), a time of absence of the AP on at least one of the first link (610) and the second link (620). At least one of the Master AP and the Relay AP can instruct using at least one of the fields and indicators (e.g., TWT element, QTP element, etc.) within a frame in which the above-described relay scheduling information is transmitted (e.g., Beacon frame, Probe Response frame, TWT request / response frame, QTP Action frame, etc.).

[0113] The Master AP and the Relay AP can recognize the time when the first link (610) and the second link (620) operate as a fronthaul link or a backhaul link through negotiated relay scheduling. Non-AP STAs (e.g., STA1) connected to the Master AP or the Relay AP can transmit frames to the Master AP or the Relay AP from a link (e.g., the second link (610)) operating as a fronthaul link at the time negotiated through relay scheduling. When the Master AP or the Relay AP receives a frame from a non-AP STA, the Master AP or the Relay AP can transmit the received frame from a link (e.g., the first link (610)) operating as a backhaul link at the time negotiated through relay scheduling.

[0114] For example, STA 1 may want to transmit an uplink (UL) frame (e.g., PPDU (PHY layer protocol data unit), MPDU (MAC layer protocol data unit), A-MPDU (aggregated-MPDU)) to the Master AP. STA 1 may be connected to a Relay AP on a fronthaul link (e.g., second link (610)), and STA 1 may want to transmit the uplink frame to the Master AP via the Relay AP.

[0115] Here, STA 1 can perform a channel access operation. The channel access operation may be EDCA backoff. STA 1 can perform transmission at a slot boundary where the backoff counter reaches 0. The frame that STA 1 wants to transmit to the Master AP via the Relay AP may be a low latency (LL) frame (601) that requires priority transmission. The LL frame (601) may be a frame whose delay bound of the frame is less than or equal to a specific threshold. Whether the frame to be transmitted is an LL frame may be indicated through a specific indicator in the preamble of the frame to be transmitted or a specific indicator in the MAC header. The LL frame (601) transmitted by STA 1 may be a frame that must be transmitted to the Master AP even though the link connected to the Relay AP (e.g., the second link (620)) is operating as a fronthaul link. In the above-described case, the Relay AP may be absent from the fronthaul link (e.g., the second link (620)) during the LL frame transmission period to the Master AP via the NSTR link pair. Therefore, the Relay AP may need to indicate to the non-AP STAs operating on the fronthaul link that the Relay AP will be absent.

[0116] For example, if a field and indicator (e.g., a PM bit in the frame or a specific bit of the QoS Control field, etc.) indicating that the Relay AP will be absent from the second link (620) as in FIG. 5 is a specific field of at least one of the response frames (BA frames) or is transmitted in a single PPDU in the form of a BA frame and an A-MPDU, it cannot be guaranteed that all non-AP STAs within the BSS (basic service set) of the Relay AP can decode the absence information. Therefore, the Relay AP may need to configure the frame as a separate PPDU that all non-AP STAs within the BSS can decode, and include information indicating that the Relay AP will be absent. To this end, STA 1 may use a method (e.g., RD ​​(Reverse Direction) protocol) that allows the Relay AP to transmit a separate downlink PPDU including the above-described indicator within its TXOP.

[0117] The condition for STA 1 to use the RD protocol may be that the AP to which STA 1 is connected is a relay AP or that an LL uplink frame is transmitted in a fronthaul link operation section negotiated by relay scheduling. If at least one of the above conditions is met, STA 1 may grant RD to the relay AP. If STA 1 decides to use the RD protocol for LL frame transmission, the length of the TXOP (Transmission Opportunity) acquired by STA 1 with the LL frame may include the length from the time of transmitting the LL frame to the time of receiving a response frame for the LL frame and the time when the relay AP transmits the above-described separate downlink PPDU using the RD protocol.

[0118] A frame that STA 1 intends to transmit to the Master AP via the Relay AP may be a frame in which the RDG (Reverse Direction Grant) / More PPDU bit in the HT Control field is set to 1. STA 1 transmitting a frame in which the RDG / More PPDU bit in the HT Control field is set to 1 may be an RD initiator, and the Relay AP receiving the frame may be an RD responder. The Relay AP may respond with a response frame (602) after a SIFS (Short Interframe Space) after receiving the LL frame (601) transmitted by STA 1 on the second link (620). The response frame (602) that the Relay AP transmits to STA 1 on the second link (620) may be a BA (Block Acknowledgement) frame. As another example, the frame may be composed of an A-MPDU in which a BA frame and a QoS (Quality of Service) Null frame exist together within the frame. The Relay AP may set the RDG / More PPDU bit in the HT Control field of a response frame (e.g., BA frame) transmitted to STA 1 on the second link (620) to 1 to indicate that another frame will be transmitted subsequently.

[0119] The frame (603) that the Relay AP transmits to STA 1 following the response frame (602) may be an Absence Notification frame (603). The Absence Notification frame (603) may indicate that the Relay AP will be absent in the second link (620) by using fields and indicators within the frame (e.g., PM bit, specific bits of the QoS Control field). The Absence Notification frame may be a frame transmitted via broadcast or multicast so that it can be received by non-AP STAs (e.g., STA 1) operating in the second link (620). The Relay AP may set the RDG / More PPDU bit in the HT Control field of the Absence Notification frame (603) to 0 to indicate that there will be no more frame transmissions. Non-AP STAs that receive the Absence Notification frame (603) can decode the fields and indicators indicating that the Relay AP will be absent on the second link (620). Non-AP STAs operating on the second link (620) can stop decreasing the backoff counter for channel access or postpone uplink transmission attempts to the Relay AP until a separate instruction is given after the Relay AP is absent.

[0120] The Relay AP can transmit the LL frame (601) of STA 1 received on the fronthaul link (e.g., the second link (620)) to the Master AP through a channel access operation or a priority transmission operation (e.g., preemption) on the backhaul link (e.g., the first link (610)). The Master AP can respond with a response frame (e.g., a BA frame, 605) after SIFS after receiving the LL frame (604) transmitted by the Relay AP.

[0121] After receiving the response frame (605) transmitted by the Master AP, the Relay AP can transmit a frame (606) notifying the presence of the Relay AP through a channel access operation on the second link (620) that indicated the absence of the Relay AP. For example, the frame (605) notifying the presence of the Relay AP on the second link (620) may be an Absence end frame. The Absence end frame (605) may be a short control frame (e.g., CTS (Clear To Send)-to-Self, RTS (Request To Send), MU (Multi User)-RTS, etc.) that includes an indicator notifying the presence of the Relay AP on the second link (620). Transmission of the Absence end frame (605) may follow a conventional channel access operation (e.g., EDCA, etc.). In the above-described case, the Relay AP may not have been able to maintain the channel status detection of the second link (620) due to the characteristics of the NSTR link pair while performing transmission and reception operations on the first link (610). Therefore, the Relay AP may wait for a certain period of time (e.g., MediumSyncDelay value) for medium synchronization and then attempt channel access through EDCA. As another example, when transmitting a short control frame as an Absence end frame (605), transmission may be permitted regardless of the procedure or backoff condition for medium synchronization in multiple links.

[0122] Non-AP STAs (e.g., STA 1) operating on the second link (620) can resume the backoff counter decrement operation for channel access on the second link (620) after receiving the Absence end frame (605). As another example, non-AP STAs (e.g., STA 1) operating on the second link (620) can recognize the presence of a Relay AP when the Relay AP starts transmitting any frame through a channel access operation, and can resume the backoff counter decrement operation for channel access on the second link (620).

[0123] At least one of the Relay AP and the Master AP may initiate a backhaul link operation (e.g., an operation to initiate an r-TWT Service Period (r-TWT SP) or an operation to terminate a QTP) by referring to the previously negotiated relay scheduling information. The Relay AP may be absent from a link other than the backhaul link (e.g., a link that is an r-TWT SP) by an NSTR link pair. The Relay AP or the Master AP may trigger a Trigger Based PPDU (TB PPDU) by transmitting a trigger frame (606) on a link where the Relay AP is not absent (e.g., the first link). The Relay AP or the Master AP receiving the trigger frame may respond with a BA frame.

[0124] In FIG. 6, the r-TWT operation and QTP operation of the Relay AP and the Master AP can be performed based on the operation of the machine learning unit illustrated in FIGS. 1 to 4. For example, the Relay AP can predict for how long the Relay AP will be absent from the fronthaul link on the second link (620) by taking as input the length of the frame transmitted by STA 1 and the congestion rate of the first link (610). The Relay AP can indicate this prediction in an absence notification frame. STAs connected to the Relay AP can transmit a frame to the Relay AP at a time when the Relay AP is predicted to operate on the fronthaul link again, thereby allowing the Relay AP to quickly access the channel. The machine learning unit of the Master AP can calculate the communication section required for the Relay AP by taking as input the input and output traffic, and can allocate an appropriate R-TWT SP communication section to the Relay AP based on the length of the frame transmitted by STA 1 and the congestion rate of the first link (610).

[0125] Although the above description is based on a Master AP, a Relay AP, and a non-AP STA, it may not be limited thereto. For example, the same may be applied even if both the Master AP and the Relay AP are non-AP STAs. As another example, the same may be applied even if the Master AP is an AP and the Relay AP is a non-AP STA. As a specific example, the first STA (Master AP of FIG. 6) and the second STA (Relay AP of FIG. 6) may communicate through the first link (610) described above, and the second STA (Relay AP of FIG. 6) may communicate with the third STA (STA 1 of FIG. 6) through the second link (620). Here, when the second STA is absent from the second link (620) for communication with the first STA, the second STA may indicate to the third STA that it is absent from the second link (620), and may perform communication with the first STA on the first link (610) during that period. In addition, other frames may be equally applied when STAs coexist as described above, and may not be limited to a specific form.

[0126] As another example, the same can be applied even when the Master AP, Relay AP, and non-AP STA are all APs. That is, the Relay AP can communicate with the first AP (Master AP of FIG. 5) through the first link (510), and communicate with the second AP (non-AP STA of FIG. 5) through the second link (520), and the same can be applied to the above-described operations.

[0127] FIG. 7 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0128] Referring to FIG. 7, a Master AP (e.g., Master) and a Relay AP (e.g., Relay) associated with the Master AP may operate. In addition, STA 1 associated with the Relay AP may operate. The Relay AP may be a wireless LAN terminal that performs a relay operation to extend the transmission / reception range of the Master AP. For example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation from an SME (Station Management Entity). As a specific example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation when a charging state and other conditions are satisfied, but may not be limited thereto.

[0129] When a wireless LAN terminal supporting relay operation obtains an instruction to trigger a relay operation from an SME, the wireless LAN terminal supporting relay operation can change its operation mode from a non-AP STA to a relay AP through an onboarding process. Here, the relay AP may be a non-simultaneous transmit and receive (NSTR) relay AP that cannot perform simultaneous transmission and reception operations on multiple links. For example, an NSTR relay AP may not be able to perform a reception operation on another link when transmitting on one link. Here, the link on which the NSTR relay AP cannot perform simultaneous transmission and reception may be an NSTR link pair.

[0130] As a specific example, in FIG. 7, the first link (710) and the second link (720) may operate, and the Master AP, the Relay AP, and STA 1 may perform at least one of transmission and reception operations on the first link (710) and the second link (720). Here, the first link (710) may be a link that operates only as a backhaul link, and the second link (720) may be a link that operates only as a fronthaul link. The fronthaul link may be a link used for transmission and reception between a non-AP STA and an AP (e.g., STA 1 and a Relay AP), and the backhaul link may be a link used for transmission and reception between one AP and another AP (e.g., between a Master AP and a Relay AP). However, this is for convenience of explanation and may not be limited to the embodiment.

[0131] When a relay AP uses a specific link as a fronthaul, the relay AP may transmit a beacon or a probe response to a non-AP STA on the link. Here, the beacon or the probe response may include an indicator that specifies that the relay AP is a relay AP. The master AP or the relay AP may perform relay scheduling negotiation for transmission and reception scheduling on at least one of the fronthaul link (e.g., the second link (720)) and the backhaul link (e.g., the first link (710)). The relay scheduling negotiation may be an operation to protect transmission and reception operations on at least one of the first link (710) and the second link (720) by using at least one of a restricted-target wake time (r-TWT) and a quiet time period (QTP) (e.g., protecting a frame transmission start time, stopping a backoff counter decrement of a non-AP STA). Here, r-TWT may be an operation that sets TWT only for a specific group, so that terminals outside the specific group terminate ongoing transmissions before the TWT start time. TWT may be an operation that causes a wireless LAN terminal to wake up at a specific time and perform communication. In addition, QTP may be an interval that limits wireless communication for a specific time to reduce interference or perform a specific operation.

[0132] As another example, relay scheduling may be an operation that protects the start point of frame transmission using ML (Multi Link) r-TWT. ML r-TWT may be an operation in which a Relay AP replicates at least one or more of the r-TWT information negotiated with a Master AP in a backhaul link and instructs non-AP STAs in a fronthaul. The Master AP may instruct a Relay AP operating in a backhaul link (e.g., the first link (510)) of r-TWT operation information using at least one of a field (e.g., a TWT Parameter Set field, etc.) and an indicator (e.g., a TWT element) in a frame (e.g., a Management frame) used for r-TWT operation.

[0133] The r-TWT operation information may be the start time of frame transmission on the backhaul link (e.g., the first link (710)). The relay AP may replicate at least one or more pieces of r-TWT information indicated by the master AP and instruct non-AP STAs connected to the relay AP via the front link (e.g., the second link (720)). The relay AP may use the r-TWT information to protect the start time of frame transmission on the first link (710) and the second link (720).

[0134] At least one of the Master AP and the Relay AP can instruct non-AP STAs (e.g., STA 1) operating on at least one of the first link (710) and the second link (720) about the above-described relay scheduling information (e.g., a start time of transmission / reception operation on at least one of the first link (710) and the second link (720), a time of absence of the AP on at least one of the first link (710) and the second link (720). At least one of the Master AP and the Relay AP can instruct using at least one of the fields and indicators (e.g., TWT element, QTP element, etc.) within a frame in which the above-described relay scheduling information is transmitted (e.g., Beacon frame, Probe Response frame, TWT request / response frame, QTP Action frame, etc.).

[0135] The Master AP and the Relay AP can recognize the time when the first link (710) and the second link (720) operate as a fronthaul link or a backhaul link through negotiated relay scheduling. Non-AP STAs (e.g., STA1) connected to the Master AP or the Relay AP can transmit frames to the Master AP or the Relay AP from a link (e.g., the second link (710)) operating as a fronthaul link at the time negotiated through relay scheduling. When the Master AP or the Relay AP receives a frame from a non-AP STA, the Master AP or the Relay AP can transmit the received frame from a link (e.g., the first link (710)) operating as a backhaul link at the time negotiated through relay scheduling.

[0136] For example, STA 1 may want to transmit an uplink (UL) frame (e.g., PPDU (PHY layer protocol data unit), MPDU (MAC layer protocol data unit), A-MPDU (aggregated-MPDU)) to the Master AP. STA 1 may be connected to a Relay AP on a fronthaul link (e.g., second link (710)), and STA 1 may want to transmit the uplink frame to the Master AP via the Relay AP.

[0137] Here, STA 1 can perform a channel access operation. The channel access operation may be EDCA backoff. STA 1 can perform transmission at a slot boundary where the backoff counter reaches 0. The frame that STA 1 wants to transmit to the Master AP via the Relay AP may be a low latency (LL) frame (701) that requires priority transmission. The LL frame (701) may be a frame whose delay bound of the frame is less than or equal to a specific threshold. Whether the frame to be transmitted is an LL frame may be indicated through a specific indicator in the preamble of the frame to be transmitted or a specific indicator in the MAC header. The LL frame (701) transmitted by STA 1 may be a frame that must be transmitted to the Master AP even though the link connected to the Relay AP (e.g., the second link (720)) is operating as a fronthaul link. In the above-described case, the Relay AP may be absent from the fronthaul link (e.g., the second link (720)) during the LL frame transmission period to the Master AP via the NSTR link pair. Therefore, the Relay AP may need to indicate to the non-AP STAs operating on the fronthaul link that the Relay AP will be absent.

[0138] For example, at least one of the fields and indicators (e.g., the PM bit in the frame or a specific bit in the QoS Control field) indicating that the Relay AP will be absent may not be decodable by all non-AP STAs within the BSS of the Relay AP. Therefore, the Relay AP may need to frame a separate PPDU that all non-AP STAs within the BSS can decode, including information indicating that the Relay AP will be absent. To this end, STA 1 may use a method that allows the Relay AP to transmit downlink frames (e.g., the RD (Reverse Direction) protocol).

[0139] The condition for STA 1 to use the RD protocol may be that the AP to which STA 1 is connected is a relay AP or that an LL uplink frame is transmitted in a fronthaul link operation section negotiated by relay scheduling. If at least one of the above conditions is met, STA 1 may grant RD to the relay AP. If STA 1 decides to use the RD protocol for LL frame transmission, the length of the TXOP (Transmission Opportunity) acquired by STA 1 with the LL frame may have to be sufficient from the time of transmitting the LL frame to the time of receiving a response frame for the LL frame and the time when the relay AP transmits a downlink frame using the RD protocol.

[0140] A frame that STA 1 intends to transmit to the Master AP via the Relay AP may be a frame in which the RDG (Reverse Direction Grant) / More PPDU bit in the HT Control field is set to 1. STA 1 transmitting a frame in which the RDG / More PPDU bit in the HT Control field is set to 1 may be an RD initiator, and the Relay AP receiving the frame may be an RD responder. The Relay AP may respond with a response frame (702) after a SIFS (Short Interframe Space) after receiving the LL frame (701) transmitted by STA 1 on the second link (720). The response frame (702) that the Relay AP transmits to STA 1 on the second link (720) may be a BA (Block Acknowledgement) frame. As another example, the frame may be composed of an A-MPDU in which a BA frame and a QoS (Quality of Service) Null frame exist together. The Relay AP may set the RDG / More PPDU bit in the HT Control field of a response frame (e.g., BA frame) transmitted to STA 1 on the second link (720) to 1 to indicate that another frame will be transmitted subsequently.

[0141] The frame (703) that the Relay AP transmits to STA 1 following the response frame (702) may be an Absence Notification frame (703). The Absence Notification frame (703) may use fields and indicators within the frame (e.g., PM bit, specific bits of the QoS Control field) to indicate that the Relay AP will be absent in the second link (720). The Absence Notification frame may be a frame transmitted via broadcast or multicast so that it can be received by non-AP STAs (e.g., STA 1) operating in the second link (720). The Relay AP may set the RDG / More PPDU bit in the HT Control field of the Absence Notification frame (703) to 0 to indicate that there will be no more frame transmissions. Non-AP STAs that receive the Absence Notification frame (703) can decode the fields and indicators indicating that the Relay AP will be absent on the second link (720). Non-AP STAs operating on the second link (720) can stop decreasing the backoff counter for channel access or postpone uplink transmission attempts to the Relay AP until a separate instruction is given after the Relay AP is absent.

[0142] For example, according to the existing channel access method, the Relay AP may perform EDCA channel access or utilize a preemption method after medium synchronization is completed on the first link (710) to transmit the LL frame (701) of STA 1 received on the fronthaul link (e.g., the second link (720)) on the backhaul link (e.g., the first link (710)). However, the above-described methods may not be suitable for immediate relay transmission of the LL frame because the time required for channel access may be long.

[0143] Considering the above, the Relay AP may transmit a short control frame to the Master AP on the first link (710). The short control frame transmitted by the Relay AP on the first link (710) may be an LL request (704) frame requesting transmission of an LL frame. Transmission of the LL request frame (704) may be performed through a conventional channel access operation (e.g., EDCA, etc.). Here, when the Relay AP transmits a short control frame as the LL request frame (704), the LL request frame (704) may be allowed to be transmitted regardless of a procedure for medium synchronization or a backoff condition in multiple links. When a Relay AP transmits an LL request frame (704) to a Master AP on a first link (710), the Master AP can check whether the Relay AP is capable of receiving an LL frame on the first link (710) even though it is expected that the Relay AP will perform a fronthaul link operation through the LL request frame (704). The LL request frame (704) that the Relay AP transmits to the Master AP on the first link (710) can be transmitted simultaneously with an absence notification frame (703) that the Relay AP transmits on the second link (720), thereby minimizing transmission delay.

[0144] If the Relay AP successfully transmits the LL request frame (704) to the Master AP on the first link (710), the Master AP can respond with a response frame (e.g., ACK frame, BA frame, 705)) after SIFS after receiving the LL request frame (704). The Relay AP can transmit the LL frame (706) of STA 1 received on the second link (720) to the Master AP on the first link (710) after SIFS after receiving the response frame transmitted by the Master AP. The Master AP can respond with a response frame (e.g., BA frame, 707) after SIFS after receiving the LL frame (706) transmitted by the Relay AP. If the Relay AP fails to transmit an LL request frame (704) from the first link (710) to the Master AP, the Relay AP can transmit an LL frame (706) to the Master AP after the medium synchronization of the first link (710) is satisfied.

[0145] After receiving the response frame transmitted by the Master AP, the Relay AP may transmit a frame notifying the presence of the Relay AP through a channel access operation on the second link (720) that indicated the absence of the Relay AP. The frame notifying the presence of the Relay AP on the second link may be an Absence end frame (708). The Absence end frame (708) may be a short control frame (e.g., CTS (Clear To Send)-to-Self, RTS (Request To Send), MU (Multi User)-RTS, etc.) that includes an indicator notifying the presence of the Relay AP on the second link (720). Transmission of the Absence end frame (708) may follow a conventional channel access operation (e.g., EDCA, etc.). In the above-described case, the Relay AP may not have maintained the channel state detection of the second link (720) while performing transmission and reception operations on the first link (710) due to the characteristics of the NSTR link pair. Accordingly, the relay AP may wait for a certain period of time (e.g., MediumSyncDelay value) for medium synchronization and then attempt to connect to the channel via EDCA. As another example, when transmitting a short control frame as an Absence end frame (705), transmission may be permitted regardless of the procedure or backoff condition for medium synchronization in multiple links.

[0146] Non-AP STAs (e.g., STA 1) operating on the second link (720) can resume the backoff counter decrement operation for channel access on the second link (720) after receiving the Absence end frame (705). As another example, non-AP STAs (e.g., STA 1) operating on the second link (720) can recognize the presence of a Relay AP when the Relay AP starts transmitting any frame through a channel access operation, and can resume the backoff counter decrement operation for channel access on the second link (720).

[0147] At least one of the Relay AP and the Master AP can initiate a backhaul link operation (e.g., an operation to initiate an r-TWT Service Period (r-TWT SP) or an operation to terminate a QTP) by referring to the previously negotiated relay scheduling information. The Relay AP may be absent from a link other than the backhaul link (e.g., a link that is an r-TWT SP) by an NSTR link pair. The Relay AP or the Master AP can trigger a Trigger Based PPDU (TB PPDU) by transmitting a trigger frame (709) on a link where the Relay AP is not absent (e.g., the first link). The Relay AP or the Master AP receiving the trigger frame can respond with a BA frame.

[0148] In FIG. 7, the r-TWT operation and QTP operation of the Relay AP and the Master AP can be performed based on the operation of the machine learning unit illustrated in FIGS. 1 to 4. For example, the Relay AP can predict for how long the Relay AP will be absent from the fronthaul link on the second link (720) by taking as input the length of the frame transmitted by STA 1 and the congestion rate of the first link (710). The Relay AP can indicate this prediction in an absence notification frame. STAs connected to the Relay AP can transmit a frame to the Relay AP at a time when the Relay AP is predicted to operate on the fronthaul link again, thereby allowing the Relay AP to quickly access the channel. The machine learning unit of the Master AP can calculate the communication section required for the Relay AP by taking as input the input and output traffic, and can allocate an appropriate R-TWT SP communication section to the Relay AP based on the length of the frame transmitted by STA 1 and the congestion rate of the first link (710).

[0149] Although the above description is based on a Master AP, a Relay AP, and a non-AP STA, it may not be limited thereto. For example, the same may be applied even if both the Master AP and the Relay AP are non-AP STAs. As another example, the same may be applied even if the Master AP is an AP and the Relay AP is a non-AP STA. As a specific example, the first STA (Master AP of FIG. 7) and the second STA (Relay AP of FIG. 7) may communicate through the first link (710) described above, and the second STA (Relay AP of FIG. 7) may communicate with the third STA (STA 1 of FIG. 7) through the second link (720). Here, when the second STA is absent from the second link (720) for communication with the first STA, the second STA may indicate to the third STA that it is absent from the second link (720), and may perform communication with the first STA on the first link (710) during that period. In addition, other frames may be equally applied when STAs coexist as described above, and may not be limited to a specific form.

[0150] As another example, the same can be applied even when the Master AP, Relay AP, and non-AP STA are all APs. That is, the Relay AP can communicate with the first AP (Master AP of FIG. 5) through the first link (510), and communicate with the second AP (non-AP STA of FIG. 5) through the second link (520), and the same can be applied to the above-described operations.

[0151] FIG. 8 is a diagram illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied.

[0152] Referring to FIG. 8, a Master AP (e.g., Master) and a Relay AP (e.g., Relay) associated with the Master AP may operate. In addition, STA 1 associated with the Relay AP may operate. The Relay AP may be a wireless LAN terminal that performs a relay operation to extend the transmission / reception range of the Master AP. For example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation from an SME (Station Management Entity). As a specific example, a wireless LAN terminal that supports the relay operation may obtain an instruction to trigger the relay operation when a charging state and other conditions are satisfied, but may not be limited thereto.

[0153] When a wireless LAN terminal supporting relay operation obtains an instruction to trigger a relay operation from an SME, the wireless LAN terminal supporting relay operation can change its operation mode from a non-AP STA to a relay AP through an onboarding process. Here, the relay AP may be a non-simultaneous transmit and receive (NSTR) relay AP that cannot perform simultaneous transmission and reception operations on multiple links. For example, an NSTR relay AP may not be able to perform a reception operation on another link when transmitting on one link. Here, the link on which the NSTR relay AP cannot perform simultaneous transmission and reception may be an NSTR link pair.

[0154] As a specific example, in FIG. 8, the first link (810) and the second link (820) can operate, and the Master AP, the Relay AP, and STA 1 can perform at least one of transmission and reception operations on the first link (810) and the second link (820). Here, the second link (820) may be a link that supports a low latency (LL) operation. If the link supports the LL operation, the link may simultaneously support a fronthaul link and a backhaul link. Accordingly, the Master AP may be able to receive on the second link (820). The fronthaul link may be a link used for transmission and reception between a non-AP STA and an AP (e.g., STA 1 and a Relay AP), and the backhaul link may be a link used for transmission and reception between one AP and another AP (e.g., between a Master AP and a Relay AP). When a relay AP uses a specific link as a front-haul, the relay AP may transmit a beacon or probe response to non-AP STAs on that link. The beacon or probe response may include an indicator that the relay AP is a relay AP.

[0155] A Master AP or a Relay AP may negotiate relay scheduling for transmission and reception scheduling on the second link (820). The relay scheduling may be an operation that protects transmission and reception operations on the second link (820) by using at least one of a restricted-Target Wake Time (r-TWT) and a Quiet Time Period (QTP) (e.g., protecting a time when the second link (820) operates as a fronthaul link and protecting a time when the second link (820) operates as a backhaul link). At least one of the Master AP and the Relay AP may indicate the negotiated relay scheduling information (e.g., when the second link (820) operates as a fronthaul link and when the second link (820) operates as a backhaul link, etc.) to non-AP STAs (e.g., STA 1) on at least one of the first link (810) and the second link (820). At least one of the Master AP and the Relay AP may indicate using at least one of the fields and indicators (e.g. TWT element, QTP element, etc.) within a frame in which negotiated relay scheduling information is transmitted (e.g. Beacon frame, Probe Response frame, TWT request / response frame, QTP Action frame, etc.).

[0156] The Master AP and the Relay AP can recognize the time when the first link (810) and the second link (820) operate as a fronthaul link or a backhaul link through negotiated relay scheduling. Non-AP STAs (e.g., STA1) connected to the Master AP or the Relay AP can transmit frames to the Master AP or the Relay AP from a link (e.g., the second link (810)) operating as a fronthaul link at the time negotiated through relay scheduling. When the Master AP or the Relay AP receives a frame from a non-AP STA, the Master AP or the Relay AP can transmit the received frame from a link (e.g., the first link (810)) operating as a backhaul link at the time negotiated through relay scheduling.

[0157] For example, STA 1 may want to transmit an uplink (UL) frame (e.g., PPDU (PHY layer protocol data unit), MPDU (MAC layer protocol data unit), A-MPDU (aggregated-MPDU)) to the Master AP. STA 1 may be connected to a Relay AP on a fronthaul link (e.g., the second link (810)), and STA 1 may want to transmit the uplink frame to the Master AP via the Relay AP.

[0158] Here, STA 1 can perform a channel access operation. The channel access operation may be EDCA backoff. STA 1 can perform transmission at a slot boundary where the backoff counter reaches 0. The frame that STA 1 wants to transmit to the Master AP via the Relay AP may be a low latency (LL) frame (801) that requires priority transmission. The LL frame (801) may be a frame whose delay bound of the frame is less than or equal to a specific threshold. Whether the frame to be transmitted is an LL frame may be indicated through a specific indicator in the preamble of the frame to be transmitted or a specific indicator in the MAC header. The LL frame (801) transmitted by STA 1 may be a frame that must be transmitted to the Master AP even though the link connected to the Relay AP (e.g., the second link (820)) is operating as a fronthaul link. To this end, STA 1 may use a method (e.g., RD ​​(Reverse Direction) protocol) that allows the Relay AP to transmit an LL frame to the Master AP within the TXOP it acquired to transmit the LL frame (801) to the Relay AP.

[0159] The conditions for STA 1 to use the RD protocol may be that the AP to which STA 1 is connected is a relay AP, or that STA 1 transmits an LL uplink frame during the fronthaul link operation period negotiated through relay scheduling. If at least one of the above conditions is met, STA 1 may grant RD to the relay AP.

[0160] For example, in FIG. 8, the Master AP can maintain a receivable state during the minimum fronthaul link transmission period on the second link (820) that supports LL frame transmission. Accordingly, as soon as the Relay AP receives the LL frame (801) from STA 1, it can attempt relay transmission to the Master AP on the same link. If STA 1 decides to use the RD protocol to transmit the LL frame (801), the length of the TXOP (Transmission Opportunity) acquired by STA 1 with the LL frame (801) may have a sufficient length from the time of transmitting the LL frame to the time of receiving a response frame for the LL frame and the time until the Relay AP transmits the LL frame to the Master AP using the RD protocol and receives the response frame. However, in the above-described case, the time for uplink transmission of the LL frame (801) of STA 1 may be significantly limited according to the TXOP limit regulation. Therefore, there is a need for an exceptionally different application of TXOP for use of the RD protocol.

[0161] More specifically, STA 1 can set TXOP based on the time expected to take from uplink transmission of LL frame (801) including RD grant indicator to reception of alternative response frame (BA frame, 802). As another example, STA 1 can determine TXOP length based on the time expected to take from SIFS after reception of the above-described response frame (802) until AP transmits short control frame (e.g. absence notification, CTS (Clear To Send)-to-Self, RTS (Request To Send), MU (Multi User)-RTS). In the above-described case, Relay AP using RD protocol can extend TXOP using duration field or indicator of LL frame (803) transmitted to Master AP. Through the above-described, Relay AP can secure time to receive response frame (804) from Master AP after SIFS after transmission of LL frame (803).

[0162] The Relay AP can normally receive an LL frame (801) including an RD grant indicator for LL frame relay from STA 1 and transmit an Ack. Here, if the duration specified by STA 1 has already expired or there is not enough time to transmit the LL frame to the Master AP and receive a response frame thereto, the Relay AP can extend the TXOP length for RD. In the above case, the duration of the LL frame (803) transmitted by the Relay AP to the Master AP can be set to the time required to transmit the LL frame (803) to the Master AP and receive a response frame (804) thereto.

[0163] A frame that STA 1 intends to transmit to a Master AP via a Relay AP may be a frame in which the RDG (Reverse Direction Grant) / More PPDU bit in the HT Control field is set to 1. STA 1 transmitting a frame in which the RDG / More PPDU bit in the HT Control field is set to 1 may be an RD initiator, and the Relay AP receiving the frame may be an RD responder. The Relay AP may respond with a response frame (802) after a SIFS (Short Interframe Space) after receiving the LL frame (801) transmitted by STA 1 on the second link (820). The response frame (802) that the Relay AP transmits to STA 1 on the second link (820) may be a BA (Block Acknowledgement) frame. As another example, the frame may be composed of an A-MPDU in which a BA frame and a QoS (Quality of Service) Null frame exist together. The Relay AP may set the RDG / More PPDU bit in the HT Control field of a response frame (e.g., BA frame) transmitted to STA 1 on the second link (820) to 1 to indicate that another frame will be transmitted subsequently.

[0164] The Relay AP may transmit the LL frame (801) of STA 1 received on the second link (820) to the Master AP on the same second link (820). The Master AP may respond with a response frame (e.g., BA frame, 804) after SIFS after receiving the LL frame (803). The Relay AP may extend the TXOP using the LL frame as described above to receive the response frame (804) from the Master AP.

[0165] In FIG. 8, TXOP allocation of STA 1 connected to the Relay AP may be performed based on the operations of the machine learning unit illustrated in FIGS. 1 to 4. For example, the machine learning unit of STA 1 may predict in advance how long a TXOP is required when performing a Reverse Direction grant operation to the Relay AP. The input of the machine learning unit of STA 1 may be the size of the LL MPDU of STA 1. The length of the TXOP predicted by the machine learning unit may be longer than the length originally required by STA 1, and the Relay AP may receive the LL MPDU from STA 1 within the longer TXOP. Alternatively, when the Relay AP receives an RDG from STA 1, the decision to extend the TXOP may be performed by the machine learning unit of the Relay AP. The machine learning unit of the Relay AP may determine the length of the extended TXOP based on the sizes of LL MPDUs previously transmitted by STA 1. TXOP can be appropriately extended by the operation of the machine learning unit, and the Relay AP can smoothly receive the LL MPDU of STA 1.

[0166] Actions to improve latency performance in wireless LANs may be limited. For example, when multiple terminals exist within the same BSS (Basic Service Set), the time required for channel access procedures may increase due to competition between terminals. Therefore, the requirements of traffic that must meet low latency performance (e.g., Low Latency (LL) traffic) may not be met. Here, the Restricted Target Wake Time (R-TWT) method may be used to transmit LL traffic in a wireless LAN. The R-TWT method may be a method to protect traffic transmission at the start of an R-TWT SP (Service Period) negotiated between terminals within a BSS (e.g., between an AP and an STA connected to the AP). Terminals that have not negotiated R-TWT within the same BSS may receive R-TWT information from other terminals that have negotiated R-TWT and may not perform channel access procedures (e.g., decrementing a backoff counter, assessing channel clearance, etc.) at the start of an R-TWT SP. However, if there is another terminal that is not included in the same BSS in the wireless LAN, that is, an OBSS (Overlapping BSS) terminal, the OBSS terminal may not be aware of information about R-TWT negotiation between terminals in the other BSS. Therefore, transmission at the R-TWT SP start point of the negotiated terminal may not be guaranteed. Considering the above, traffic transmission using the wireless LAN R-TWT may not be performed, and the effect of improving the wireless LAN delay performance may be small. The following describes a method to solve this problem.

[0167] FIG. 9 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0168] Referring to FIG. 9, AP 1 (920) and AP 2 (930) can operate, and STA 1 (910) associated with AP 1 (920) and STA 2 (940) associated with AP 2 (930) can operate. AP 1 (920) and AP 2 (930) can configure BSS (Basic Service Set) 1 and BSS 2, respectively, and STA 1 (910) and STA 2 (940) can operate in BSS 1 and BSS 2, respectively. BSS 1 and BSS 2 can use the same primary channel, i.e., the same frequency, so that APs and STAs can operate. AP 1 (920) and AP 2 (930) can exist within a range where they can transmit and receive to each other. STA 1 (910) may not be able to detect transmission and reception between wireless LAN terminals in BSS 2, and STA 2 (940) may not be able to detect transmission and reception between wireless LAN terminals in BSS 1. For STA 1 (910), BSS 2 may be an OBSS (Overlapping BSS), and for STS 2, BSS 1 may be an OBSS. Interference may occur because the OBSS and BSS use the same channel within a BSS within a distance range where the OBSS's signal can be received while transmission and reception between terminals is performed in the OBSS. Similarly, interference may occur because the OBSS and BSS use the same channel within an OBSS within a distance range where the BSS's signal can be received while transmission and reception between terminals is performed in the BSS. That is, in Fig. 9, AP 2 (930) may not be able to perform channel access operations and transmit and receive frames at the start of R-TWT SP because its NAV is set by the CTS and BA transmitted by AP 1 (920) of BSS 1, which is an OBSS. R-TWT can be used for transmitting and receiving low-latency traffic, and the transmission and reception of such low-latency traffic may be delayed due to interference from the OBSS.Therefore, a method to prevent R-TWT SP from being compromised by OBSS or a method to protect R-TWT SP of OBSS will be described later.

[0169] An AP within a BSS can negotiate an R-TWT (Restricted Target Wake Time) SP (service period) through a membership setup process with connected terminals within the same BSS. The R-TWT SP setup process (membership setup process) can be based on the broadcast TWT method. In the broadcast TWT method, the AP can include a TWT element in the Beacon frame and the Probe response frame to indicate (e.g., announce, broadcast) TWT setup. The TWT setup includes the TWT SP scheduling process. The TWT element can include a TWT ID (identifier) ​​that distinguishes the TWT setup, and a TWT setup command subfield that indicates, changes, or cancels the TWT setup. The TWT element includes scheduling information (start time, interval, etc.) of the TWT SP. The Beacon frame and the Probe response frame that include the TWT element include a TSF (time synchronization field) for time synchronization, and the scheduling of the TWT SP can be performed based on the TSF information. In the Broadcast TWT method, in order for a terminal to participate in the TWT configuration of an AP, the terminal can transmit a TWT request frame containing a TWT element to the AP. Through the TWT element included in the TWT request frame, the terminal can request a new TWT configuration or indicate participation in an existing TWT configuration (e.g., a TWT configuration indicated in the AP's Beacon and Probe response frames). The AP can accept the terminal's request, instruct to modify it, or reject it. If the AP accepts the terminal's request, a new TWT configuration is created at the terminal's request and the terminal participates in the new TWT configuration, or the terminal participates in the existing TWT configuration.If the AP changes the request of the terminal and instructs, the AP rejects the terminal's participation in the TWT configuration and instructs another (e.g., alternative) TWT configuration or TWT configuration parameters in which the terminal can participate. The terminal can send a TWT request frame to the AP again, including the parameters changed by the AP in the TWT element. If the AP rejects the terminal's request, the terminal cannot participate in the AP's TWT configuration. If the terminal participates in the AP's TWT configuration, the terminal is a member of the STA's TWT configuration. That is, membership is established. This can be said to have negotiated the TWT SP. The R-TWT SP is negotiated through a method the same as or similar to the above method. The terminal that negotiated the R-TWT SP may have received or may receive again (i.e., additionally receive) information about the R-TWT schedule (e.g., Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing Synchronization Function) information), TWT elements, etc.) from the AP through a Beacon, Probe Response frame, etc. A terminal that has negotiated an R-TWT SP can receive information about the R-TWT schedule included in the Beacon and Probe Response frames transmitted by the AP, and can perform channel access operations and frame transmission and reception processes with the AP in accordance with the R-TWT SP start time. Terminals that have not participated in the R-TWT negotiation process within the same BSS can receive information about the R-TWT schedule included in the Beacon and Probe Response frames exchanged during the R-TWT SP negotiation process. Terminals that have not participated in the R-TWT SP negotiation process can recognize that the information about the received R-TWT schedule is not information about their own R-TWT schedule, and can end the TXOP (transmit opportunity) before the R-TWT SP start time.Terminating a TXOP may mean terminating a frame transmission or a frame exchange. A frame exchange is a process that includes transmitting a frame and receiving a response frame to the transmitted frame. The AP additionally includes a quiet channel element or a quiet channel element in the Beacon frame and the Probe response frame, which instructs to set a network allocation vector (NAV) that prohibits transmission for 1 TU (time unit) from the start time of the R-TWT SP, so that terminals that do not support R-TWT operation and do not know the R-TWT schedule also terminate transmission before the start time of the R-TWT SP, and do not perform channel access operations (e.g., DCF (distributed coordination function) operation and EDCA (enhanced distributed channel access) operation) for 1 TU from the start time of the R-TWT SP, and do not transmit frames. The 1 TU is 1024 us. Therefore, the R-TWT SP start time of terminals that have negotiated the R-TWT SP can be protected.

[0170] Terminals (e.g., AP 2 (930) and STA 2 (940)) within one OBSS (e.g., BSS 2) can negotiate an R-TWT SP. AP 1 (920) can receive at least one of the frames exchanged between the terminals in the OBSS R-TWT negotiation procedure, and can decode the received frame to check information about the OBSS R-TWT SP (hereinafter, OBSS R-TWT information). The OBSS R-TWT information can include BSS Color, Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc. AP 1 (920) may include an indicator (OR-TWT present) notifying that an OBSS R-TWT SP to be protected exists during the Beacon period, in a Beacon frame including the OBSS R-TWT SP start time during the Beacon period with the immediately next TBTT (Target Beacon Transmission Time) of BSS 1, using the received OBSS R-TWT information. Alternatively, the OR-TWT present may be included in a frame that is aperiodically transmitted to a specific terminal or all terminals. Specifically, it may be included in a Probe Response frame or an Action (Management) frame including a TWT element conveying information about the TWT. A terminal that receives the OR-TWT present information may perform an operation to protect the OBSS R-TWT SP until the next Beacon reception or at least until the next TBTT. If the OR-TWT present indicator is transmitted in a frame other than a Beacon, it may include information that can infer the period during which protection operation for the OBSS R-TWT SP is performed.As another example, OR-TWT present may be an indicator specifically notifying the possibility of TXOP length reduction by the TXOP responder (hereinafter, TXOP reduction possibility indicator). The OR-TWT present indicator may be transmitted including information indicating the Duration Setting (Single Protection, Multiple Protection) method of the transmitted frame, the maximum transmission time of a single PPDU (PHY Protocol Data Unit) for uplink transmission within the TXOP, the length of IFS (Interframe Space) (PIFS, etc.) between PPDU transmissions within the TXOP, and the frame Duration Setting rule within the TXOP (e.g., a method of setting the Duration of a subsequent frame to an earlier time when the time indicated by the Duration / ID field of a response frame is earlier than the time indicated by the Duration / ID field of the initially transmitted frame, etc.). An STA that has received information on the maximum transmission time of a single PPDU for uplink transmission within a TXOP from an AP may configure and transmit the length of the PPDU it transmits so as not to exceed the length indicated by the information.

[0171] The AP can transmit the OR-TWT present indicator with the Duration Setting set to multiple protection. If there is no Duration setting information, it may mean that it is multiple protection by default. An STA (e.g., STA 1 (910)) that has received the OR-TWT present indicator from the AP can use multiple protection with the Duration setting in the TXOP it has acquired. Multiple protection may be a method used in EDCA (Enhanced Distributed Channel Access) to protect transmission and reception from hidden nodes. An STA using multiple protection can transmit the frame by setting the Duration / ID field of the transmitted frame to a length that can protect until the expected end time of the subsequent frame exchange sequence. Another STA that has received the frame transmitted by the STA using the multiple protection can set the NAV (Network Allocation Vector) if the terminal indicated by the receiver address field (e.g., RA (Receiver Address) subfield, DA (Destination Address) subfield, etc.) of the frame is not itself. When STA 1 (910) uses Multiple protection, the terminal can set TXOP within the TXOP limit length allowed for the AC to be transmitted by default and set the Duration / ID value based on that length.

[0172] STA 1 (910) can acquire TXOP by transmitting an RTS frame to AP 1 (920) through a channel access operation using EDCA. In this embodiment, since it is assumed that only AP 1 (920) has the R-TWT SP information of the OBSS, the Duration / ID field of the RTS frame transmitted by STA 1 (910) may be set to a length including the start time of the R-TWT SP of the OBSS (e.g., BSS 2) detected by AP 1 (920). AP 1 (920), which receives the RTS frame transmitted by STA 1 (910), can determine that the value of the Duration / ID field of the RTS frame includes the start time of the OBSS R-TWT SP. AP 1 (920) may transmit a CTS (Clear to Send) frame to STA 1 (910) after a SIFS (Short Interframe Space) time after receiving the RTS frame transmitted by STA 1 (910). AP 1 (920) may have decided to protect the starting point of the OBSS R-TWT SP. AP 1 (920) that has decided to protect the OBSS R-TWT SP may transmit the CTS frame transmitted to STA 1 (910) by setting the Duration / ID field to a length that does not include the starting point of the OBSS R-TWT SP. In other words, it may transmit the CTS frame by setting it to the length of time until the starting point of the OBSS R-TWT SP. After receiving the CTS frame transmitted by AP 1 (920), STA 1 (910) can determine that the Duration / ID field of the CTS frame is shorter than the time indicated by the Duration / ID field of the RTS frame transmitted by STA 1 (910).STA 1 (910), which has received a Beacon frame, Probe Response frame, Action frame, etc. including an OR-TWT present indicator, may reduce its TXOP length by considering the transmission time of the data frame to be transmitted before the time indicated by the Duration / ID field of the CTS frame transmitted by AP 1 (920) and the BA frame transmission time according to the reconstructed data frame (number of MPDUs) in order to protect the OBSS R-TWT SP. STA 1 (910), which has reduced the TXOP length, may transmit the Data frame to AP 1 (920) after SIFS after receiving the CTS frame by setting the Duration / ID field to before the time indicated by the Duration / ID field of the CTS frame. AP 1 (920) may respond with a BA frame after SIFS after receiving the Data frame transmitted by STA 1 (910). If there is not enough time to reconstruct and transmit a data frame at the time indicated by the Duration / ID field of the CTS frame transmitted by AP 1 (920), a QoS Null frame is transmitted with Duration / ID set to 0, or if there is not enough time to transmit the QoS Null frame, no data frame is transmitted. AP 2 (930), which negotiated the R-TWT SP with STA 2 (940), can only receive the CTS frame and BA frame transmitted by AP 1 (920) to STA 1 (910). Therefore, the NAV set in AP 2 (930) by AP 1 (920) can be released before the R-TWT SP start time, and AP 2 (930) can start the channel access operation according to the R-TWT SP start time. In other words, the start time of the R-TWT SP of OBSS (e.g. AP 2 (930)) can be protected.

[0173] The CTS transmitted by AP 1 (920) and / or the data frame transmitted by STA 1 (910) may include an OBSS R-TWT SP information inclusion indicator. The OBSS R-TWT SP information inclusion indicator may be included in the MAC header in the form of A-control. When the OBSS R-TWT SP information inclusion indicator is included, Duration / ID may be transmitted with the OBSS R-TWT SP start time set to the OBSS R-TWT SP start time even if data and BA transmission and reception may end before the OBSS R-TWT SP. Other STAs that receive this may have their NAVs set until the OBSS R-TWT SP start time, so that the start time of the R-TWT SP may be protected.

[0174] As another example, the AP can transmit the OR-TWT present indicator with the Duration Setting set to single protection. An STA (e.g., STA 1 (910)) that receives the OR-TWT present indicator from the AP may only use single protection with the Duration setting in the TXOP it has acquired. Single protection may be a method used in EDCA (Enhanced Distributed Channel Access) to protect transmission and reception from hidden nodes. An STA using single protection may set the Duration / ID field of the transmitted frame to a length that can protect subsequent data frames, Management frames, response frames, or additional frames (e.g., frames with the RDG / More PPDU subfield set to 1), and may set the NAV (Network Allocation Vector) to STAs that receive the frame but are not terminals indicated by the receiver address field (e.g., RA (Receiver Address) subfield, DA (Destination Address) subfield, etc.).

[0175] STA 1 (910) can acquire TXOP by transmitting an RTS frame to AP 1 (920) through a channel access operation using EDCA. The Duration / ID field of the RTS frame transmitted by STA 1 (910) can be set to a length that protects the transmission of a subsequent CTS frame. That is, the Duration value can be set to a value of SIFS + CTS frame transmission time. AP 1 (920) can transmit a CTS (Clear to Send) frame to STA 1 (910) after a SIFS (Short Interframe Space) time after receiving the RTS frame transmitted by STA 1 (910).

[0176] Since AP 1 (920) uses single protection, it transmits the CTS frame with the Duration value set to 0. STA 1 (910), which has received the OR-TWT present indicator and been instructed to use single protection, must fragment the subsequent transmitted Data frame into smaller units and transmit them. Assuming that the Data frame is fragmented into three and transmitted as Data1, Data2, and Data3, the transmission must be performed in the following order: Data1 transmission, reception of a reception response, Data2 transmission, reception of a reception response, Data3 transmission, and reception of a reception response at SIFS intervals. STA 1 (910) transmits the Data1 frame SIFS after receiving the CTS frame. The Duration value that STA1 sets when transmitting Data1 is set to SIFS + the transmission time of a reception response frame (e.g., ACK or BlockAck frame). AP 1 (920) must transmit the reception response frame with the Duration value set to 0. However, after AP 1 (920) checks whether it can exchange another Data frame + reception response frame until the OBSS R-TWT SP start time to protect the OBSS R-TWT SP, if there is enough time left, it transmits the reception response frame with the More PPDU (e.g. MorePPDU) indicator set to 1 in the header. STA 1 (910) transmits the Data2 frame after an SIFS time after receiving the reception response frame if the More PPDU of the received response frame is set to 1. The Duration value set when STA1 transmits Data2 is set to the SIFS + the transmission time of the reception response frame (e.g. ACK or BlockAck frame). AP 1 (920) must transmit the reception response frame with the Duration value set to 0.If AP 1 (920) does not have enough time left to exchange another Data frame + Receive Response frame until the OBSS R-TWT SP start time, it transmits the More PPDU (e.g. MorePPDU) indicator in the header of the Receive Response frame with it set to 0. STA 1 (910) does not transmit an additional Data frame if it has received the OR-TWT present indicator and the More PPDU indicator of the Receive Response frame is set to 0.

[0177] As another example, although single protection is used, the Duration value of the CTS frame may not be set to 0 in order to protect the start time of the OBSS R-TWT SP. AP 1 (920) that has decided to protect the OBSS R-TWT SP may transmit the CTS frame to STA 1 (910) by setting the Duration / ID field to a length that does not include the start time of the OBSS R-TWT SP. In other words, it may transmit the CTS frame by setting it to the length of time until the start time of the OBSS R-TWT SP. STA 1 (910) that has received a Beacon frame, Probe Response frame, Action frame, etc. including the OR-TWT present indicator may reconstruct the data frame to be transmitted by referring to the time indicated by the Duration / ID field of the CTS frame transmitted by AP 1 (920) in order to protect the OBSS R-TWT SP, or may set the value of the Duration / ID field of the data frame to be transmitted. There are cases where the transmission time of the data frame to be transmitted and the time required for receiving the BA frame are shorter or longer than the OBSS R-TWT SP start time (the time indicated by the Duration / ID field of the CTS frame). If the transmission time of the data frame and the time required for receiving the BA frame are shorter than the OBSS R-TWT SP start time (the time indicated by the Duration / ID field of the CTS frame), the Duration / ID field of the data frame to be transmitted to AP 1 (920) after SIFS time after receiving the CTS frame can be set to the time indicated by the Duration / ID field of the CTS frame.Although data and BA transmission and reception end before OBSS R-TWT SP, the Duration / ID fields of data and BA indicate up to the OBSS R-TWT SP point in time, so other STAs that receive it can have their NAV set until the start of OBSS R-TWT SP, so the start of R-TWT SP can be protected. In order to protect legacy terminals (Legacy STAs), the transmitted data frame and BA frame can be transmitted in the form of Non-HT PPDU, which is a legacy frame format. If the data frame transmission time and the time required to receive the BA frame are longer than the OBSS R-TWT SP start time (the time indicated by the Duration / ID field of the CTS frame), the STA can reduce its own TXOP length by considering the transmission time of the data frame reconstructed from the data frame to be transmitted before the OBSS R-TWT SP start time and the BA frame transmission time according to the reconstructed data frame (number of MPDUs). STA 1 (910) with a reduced TXOP length can transmit a Data frame to AP 1 (920) after SIFS after receiving a CTS frame, setting the Duration / ID field to a time before the point in time indicated by the Duration / ID field of the CTS frame. AP 1 (920) can respond with a BA frame after SIFS after receiving the Data frame transmitted by STA 1 (910). In order to protect legacy terminals, the transmitted Data frame and BA frame can be configured and transmitted in the form of a Non-HT PPDU, which is a legacy frame format.

[0178] If there is not enough time to reconstruct and transmit a data frame at the time indicated by the Duration / ID field of the CTS frame transmitted by AP 1 (920), a QoS Null frame is transmitted with the Duration / ID set to 0 or the time indicated by the Duration / ID field of the CTS frame, or if there is not enough time to transmit a QoS Null frame, no data frame is transmitted. AP 2 (930), which negotiated the R-TWT SP with STA 2 (940), can only receive the CTS frame and BA frame transmitted by AP 1 (920) to STA 1 (910). Therefore, the NAV set in AP 2 (930) by AP 1 (920) can be released before the R-TWT SP start time, and AP 2 (930) can start a channel access operation in accordance with the R-TWT SP start time. That is, the starting point of the R-TWT SP of OBSS (e.g. AP 2 (930)) can be protected.

[0179] The CTS transmitted by AP 1 (920) and / or the data frame transmitted by STA 1 (910) may include an OBSS R-TWT SP information inclusion indicator. The OBSS R-TWT SP information inclusion indicator may be included in the MAC header in the form of A-control. When the OBSS R-TWT SP information inclusion indicator is included, Duration / ID may be transmitted with the OBSS R-TWT SP start time set to the OBSS R-TWT SP start time even if data and BA transmission and reception may end before the OBSS R-TWT SP. Other STAs that receive this may have their NAVs set until the OBSS R-TWT SP start time, so that the start time of the R-TWT SP may be protected.

[0180] FIG. 10 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0181] Referring to FIG. 10, AP 1 (1020) and AP 2 (1030) can operate, and STA 1 (1010) associated with AP 1 (1020) and STA 2 (940) associated with AP 2 (1030) can operate. AP 1 (1020) and AP 2 (1030) can configure BSS (Basic Service Set) 1 and BSS 2, respectively, and STA 1 (1010) and STA 2 (1040) can operate in BSS 1 and BSS 2, respectively. BSS 1 and BSS 2 can use the same primary channel, i.e., the same frequency, so that APs and STAs can operate. AP 1 (1020) and AP 2 (1030) can exist within a range where they can transmit and receive to each other. STA 1 (1010) may not be able to detect transmission and reception between wireless LAN terminals in BSS 2, and STA 2 (1040) may not be able to detect transmission and reception between wireless LAN terminals in BSS 1. For STA 1 (1010), BSS 2 may be an OBSS (Overlapping BSS), and for STS 2, BSS 1 may be an OBSS. Interference may occur because the OBSS and BSS use the same channel within a BSS within a distance range where the OBSS's signal can be received while transmission and reception between terminals is performed in the OBSS. Similarly, interference may occur because the OBSS and BSS use the same channel within an OBSS within a distance range where the BSS's signal can be received while transmission and reception between terminals is performed in the BSS. That is, in Fig. 10, AP 2 (1030) may not be able to perform channel access operations and transmit and receive frames at the start of R-TWT SP because its NAV is set by the BA transmitted by AP 1 (1020) of BSS 1, which is an OBSS. R-TWT can be used to transmit and receive low-latency traffic, and the transmission and reception of such low-latency traffic may be delayed due to interference from the OBSS.Therefore, a method to prevent R-TWT SP from being compromised by OBSS or a method to protect R-TWT SP of OBSS will be described later.

[0182] An AP within a BSS can negotiate an R-TWT (Restricted Target Wake Time) SP (service period) through a membership setup process with connected terminals within the same BSS. The R-TWT SP setup process (membership setup process) can be based on the broadcast TWT method. In the broadcast TWT method, the AP can include a TWT element in the Beacon frame and the Probe response frame to indicate (e.g., announce, broadcast) TWT setup. The TWT setup includes the TWT SP scheduling process. The TWT element can include a TWT ID (identifier) ​​that distinguishes the TWT setup, and a TWT setup command subfield that indicates, changes, or cancels the TWT setup. The TWT element includes scheduling information (start time, interval, etc.) of the TWT SP. The Beacon frame and the Probe response frame that include the TWT element include a TSF (time synchronization field) for time synchronization, and the scheduling of the TWT SP can be performed based on the TSF information. In the Broadcast TWT method, in order for a terminal to participate in the TWT configuration of an AP, the terminal can transmit a TWT request frame containing a TWT element to the AP. Through the TWT element included in the TWT request frame, the terminal can request a new TWT configuration or indicate participation in an existing TWT configuration (e.g., a TWT configuration indicated in the AP's Beacon and Probe response frames). The AP can accept the terminal's request, instruct to modify it, or reject it. If the AP accepts the terminal's request, a new TWT configuration is created at the terminal's request and the terminal participates in the new TWT configuration, or the terminal participates in the existing TWT configuration.If the AP changes the request of the terminal and instructs, the AP rejects the terminal's participation in the TWT configuration and instructs another (e.g., alternative) TWT configuration or TWT configuration parameters in which the terminal can participate. The terminal can send a TWT request frame to the AP again, including the parameters changed by the AP in the TWT element. If the AP rejects the terminal's request, the terminal cannot participate in the AP's TWT configuration. If the terminal participates in the AP's TWT configuration, the terminal is a member of the STA's TWT configuration. That is, membership is established. This can be said to have negotiated the TWT SP. The R-TWT SP is negotiated through a method the same as or similar to the above method. The terminal that negotiated the R-TWT SP may have received or may receive again (i.e., additionally receive) information about the R-TWT schedule (e.g., Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing Synchronization Function) information), TWT elements, etc.) from the AP through a Beacon, Probe Response frame, etc. A terminal that has negotiated an R-TWT SP can receive information about the R-TWT schedule included in the Beacon and Probe Response frames transmitted by the AP, and can perform channel access operations and frame transmission and reception processes with the AP in accordance with the R-TWT SP start time. Terminals that have not participated in the R-TWT negotiation process within the same BSS can receive information about the R-TWT schedule included in the Beacon and Probe Response frames exchanged during the R-TWT SP negotiation process. Terminals that have not participated in the R-TWT SP negotiation process can recognize that the information about the received R-TWT schedule is not information about their own R-TWT schedule, and can end the TXOP (transmit opportunity) before the R-TWT SP start time.Terminating a TXOP may mean terminating a frame transmission or a frame exchange. A frame exchange is a process that includes transmitting a frame and receiving a response frame to the transmitted frame. The AP additionally includes a quiet channel element or a quiet channel element in the Beacon frame and the Probe response frame, which instructs to set a network allocation vector (NAV) that prohibits transmission for 1 TU (time unit) from the start time of the R-TWT SP, so that terminals that do not support R-TWT operation and do not know the R-TWT schedule also terminate transmission before the start time of the R-TWT SP, and do not perform channel access operations (e.g., DCF (distributed coordination function) operation and EDCA (enhanced distributed channel access) operation) for 1 TU from the start time of the R-TWT SP, and do not transmit frames. The 1 TU is 1024 us. Therefore, the R-TWT SP start time of terminals that have negotiated the R-TWT SP can be protected.

[0183] Terminals (e.g., AP 2 (1030) and STA 2 (1040)) within one OBSS (e.g., BSS 2) can negotiate an R-TWT SP. AP 1 (1020) can receive at least one of the frames exchanged between the terminals in the OBSS R-TWT negotiation procedure, and can decode the received frame to check information about the OBSS R-TWT SP (hereinafter, OBSS R-TWT information). The OBSS R-TWT information can include BSS Color, Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc. AP 1 (1020) may include an indicator (OR-TWT present) notifying that an OBSS R-TWT SP to be protected exists during the Beacon period, in a Beacon frame including the OBSS R-TWT SP start time during the Beacon period with the immediately next TBTT (Target Beacon Transmission Time) of BSS 1, using the received OBSS R-TWT information. Alternatively, the OR-TWT present may be included in a frame that is aperiodically transmitted to a specific terminal or all terminals. Specifically, it may be included in a Probe Response frame or an Action (Management) frame including a TWT element conveying information about the TWT. A terminal that receives the OR-TWT present information may perform an operation to protect the OBSS R-TWT SP until the next Beacon reception or at least until the next TBTT time. If the OR-TWT present indicator is transmitted in a frame other than a Beacon, it may include information that can infer the period during which protection operation for the OBSS R-TWT SP is performed.As another example, OR-TWT present may be an indicator specifically notifying the possibility of TXOP length reduction by the TXOP responder (hereinafter, TXOP reduction possibility indicator). The OR-TWT present indicator may be transmitted including information indicating the Duration Setting (Single Protection, Multiple Protection) method of the transmitted frame, the maximum transmission time of a single PPDU (PHY Protocol Data Unit) for uplink transmission within the TXOP, the length of IFS (Interframe Space) (PIFS, etc.) between Data PPDU transmissions within the TXOP, and the frame Duration Setting rule within the TXOP (e.g., a method of setting the Duration of a subsequent frame to an earlier time when the time indicated by the Duration / ID field of a response frame is earlier than the time indicated by the Duration / ID field of the initially transmitted frame, etc.). An STA that has received information on the maximum transmission time of a single PPDU for uplink transmission within a TXOP from an AP may configure and transmit the length of the PPDU it transmits so as not to exceed the length indicated by the information.

[0184] The AP can transmit the OR-TWT present indicator with the Duration Setting set to multiple protection. If there is no Duration setting information, it may mean that multiple protection is used by default. An STA (e.g., STA 1 (1010)) that has received the OR-TWT present indicator from the AP can use multiple protection with the Duration setting in the TXOP it has acquired. Multiple protection may be a method used in EDCA (Enhanced Distributed Channel Access) to protect transmission and reception from hidden nodes. An STA using multiple protection can transmit the frame by setting the Duration / ID field of the transmitted frame to a length that can protect until the expected end time of the subsequent frame exchange sequence. Another STA that has received the frame transmitted by the STA using the multiple protection can set the NAV (Network Allocation Vector) if the terminal indicated by the receiver address field (e.g., RA (Receiver Address) subfield, DA (Destination Address) subfield, etc.) of the frame is not itself. When STA 1 (1010) uses Multiple protection, the terminal can set the TXOP within the TXOP limit length allowed for the AC being transmitted by default and set the Duration / ID value based on that length. AP 1 (1020) can transmit a Beacon frame including an OR-TWT present indicator. STA 1 (1010) receiving this can recognize that there is an OBSS R-TWT SP start point, so it divides the data frame into several parts and transmits them.Alternatively, the Data frame may be divided into at least two and transmitted, and the length of the first Data frame may be made short so that a response can be received from the BA immediately. STA 1 (1010) may acquire a TXOP by transmitting a Data frame to AP 1 (1020) through a channel access operation using EDCA. In this embodiment, since it is assumed that only AP 1 (1020) has the R-TWT SP information of the OBSS, the Duration / ID field of the Data frame (Data 1 of FIG. 10) initially transmitted by STA 1 (1010) may be set to a length including the start time of the R-TWT SP of the OBSS (e.g., BSS 2) detected by AP 1 (1020). AP 1 (1020), which receives the Data frame initially transmitted by STA 1 (1010), may determine that the value of the Duration / ID field of the Data frame includes the start time of the OBSS R-TWT SP. AP 1 (1020) may transmit a BA (Block ACK (Acknowledgement)) frame to STA 1 (1010) after a SIFS (Short Interframe Space) time after receiving the Data frame initially transmitted by STA 1 (1010). AP 1 (1020) may have decided to protect the start time of the OBSS R-TWT SP. AP 1 (1020) that has decided to protect the OBSS R-TWT SP may transmit the BA frame transmitted to STA 1 (1010) by setting the Duration / ID field to a length that does not include the start time of the OBSS R-TWT SP. In other words, it may transmit the BA frame by setting it to the length of time until the start time of the OBSS R-TWT SP. After receiving the BA frame transmitted by AP 1 (1020), STA 1 (1010) can determine that the Duration / ID field of the BA frame is shorter than the time indicated by the Duration / ID field of the Data frame transmitted by STA 1 (1010).STA 1 (1010), which has received a Beacon frame, Probe Response frame, Action frame, etc. including an OR-TWT present indicator, may reduce its TXOP length to the time indicated by the Duration / ID field of the BA frame transmitted by AP 1 (1020) in order to protect the OBSS R-TWT SP. STA 1 (1010), which has reduced the TXOP length, may transmit a Data frame (Data 2 of FIG. 10) to AP 1 (1020) after SIFS after receiving the BA frame, setting the Duration / ID field to the time indicated by the Duration / ID field of the BA frame. AP 1 (1020) may respond with a BA frame after SIFS after receiving the Data frame transmitted by STA 1 (1010). AP 2 (1030), which negotiated the R-TWT SP with STA 2 (1040), can only receive the BA frame transmitted by AP 1 (1020) to STA 1 (1010). Therefore, the NAV set in AP 2 (1030) by AP 1 (1020) can be released before the R-TWT SP start time, and AP 2 (1030) can start the channel access operation in accordance with the R-TWT SP start time. In other words, the start time of the R-TWT SP of the OBSS (e.g. AP 2 (1030)) can be protected.

[0185] As another example, if the OR-TWT present indicator transmitted by AP 1 (1020) includes information on the start time of the OBSS R-TWT SP, the Duration / ID field of the Data frame (Data 1 of FIG. 10) initially transmitted by STA 1 (1010) may be set to a length within the start time of the OBSS R-TWT SP indicated by the OR-TWT present indicator. AP 1 (1020), which receives the Data frame transmitted by STA 1 (1010), may transmit a BA frame to STA 1 (1010) in response to the received Data frame. The Duration / ID field of the BA frame transmitted by AP 1 (1020) to STA 1 (1010) may be set to match the time indicated by the Duration / ID field of the Data frame. In the subsequent Data frame and BA frame exchange procedure, the Duration / ID field of each frame can be set to match the starting point of the OBSS R-TWT SP indicated by the OR-TWT present indicator. AP 2 (1030), which negotiated the R-TWT SP with STA 2 (1040), can receive only the BA frame transmitted by AP 1 (1020) to STA 1 (1010). Therefore, the NAV set in AP 2 (1030) by AP 1 (1020) can be released before the starting point of the R-TWT SP, and AP 2 (1030) can start the channel access operation according to the starting point of the R-TWT SP. In other words, the starting point of the R-TWT SP of the OBSS (e.g., AP 2 (1030)) can be protected.

[0186] As another example, the AP can transmit the OR-TWT present indicator with the Duration Setting set to single protection. An STA (e.g., STA 1 (1010)) that receives the OR-TWT present indicator from the AP may only use Single protection with the Duration setting in the TXOP it has acquired. Single protection may be a method used in EDCA (Enhanced Distributed Channel Access) to protect transmission and reception from hidden nodes. An STA using Single protection may set the Duration / ID field of the transmitted frame to a length that can protect subsequent data frames, Management frames, response frames, or additional frames (e.g., frames with the RDG / More PPDU subfield set to 1), and may set the NAV (Network Allocation Vector) for STAs that receive the frame but are not terminals indicated by the receiver address field (e.g., RA (Receiver Address) subfield, DA (Destination Address) subfield, etc.).

[0187] STA 1 (1010) can obtain TXOP by transmitting a data frame (Data 1 in FIG. 10) to AP 1 (1020) through a channel access operation using EDCA. The Duration / ID field of Data 1 transmitted by STA 1 (1010) can be set to a length that protects the transmission of a subsequent BA frame. That is, the Duration value can be set to a value of SIFS + BA frame transmission time. AP 1 (1020) can transmit a BA frame to STA 1 (1010) after a SIFS (Short Interframe Space) time after receiving Data 1 transmitted by STA 1 (1010).

[0188] Since AP 1 (1020) uses single protection, it transmits the BA frame with the Duration value set to 0. In order to efficiently explain single protection, it is assumed that the Data frame is fragmented into three and transmitted as Data1, Data2, and Data3, although it is different from the drawing. STA 1 (1010) transmits the Data2 frame after an SIFS time after receiving the BA frame. When STA1 transmits Data2, the Duration value is set to SIFS + the transmission time of the received response frame (e.g., ACK or BlockAck frame) and transmitted. AP 1 (1020) must transmit the received response frame with the Duration value set to 0. However, after AP 1 (1020) checks whether it can exchange another Data frame + reception response frame until the OBSS R-TWT SP start time to protect the OBSS R-TWT SP, if there is enough time left, it transmits the reception response frame with the More PPDU (e.g. MorePPDU) indicator set to 1 in the header, and if there is not enough time, it transmits the frame with the More PPDU indicator set to 0. STA 1 (1010) receives the OR-TWT present indicator and, after receiving the reception response frame, checks the More PPDU indicator. If it is set to 1, it transmits the Data2 frame after the SIFS time, and if it is set to 0, it does not transmit an additional Data frame.

[0189] Alternatively, although single protection is used, the Duration value of the BA frame may not be set to 0 in order to protect the start time of the OBSS R-TWT SP. AP 1 (1020) that has decided to protect the OBSS R-TWT SP may transmit the BA frame transmitted to STA 1 (1010) by setting the Duration / ID field to a length that does not include the start time of the OBSS R-TWT SP. In other words, it may transmit the BA frame by setting it to the length of time until the start time of the OBSS R-TWT SP. STA 1 (1010) that has received a Beacon frame, Probe Response frame, Action frame, etc. including the OR-TWT present indicator may reconstruct the data frame to be transmitted by referring to the time indicated by the Duration / ID field of the BA frame transmitted by AP 1 (1020) in order to protect the OBSS R-TWT SP, or may set the value of the Duration / ID field of the data frame to be transmitted. There are cases where the transmission time of the data frame to be transmitted and the time required for receiving the BA frame are shorter or longer than the OBSS R-TWT SP start time (the time indicated by the Duration / ID field of the CTS frame). In cases where the transmission time of the data frame and the time required for receiving the BA frame are shorter than the OBSS R-TWT SP start time (the time indicated by the Duration / ID field of the CTS frame), the Duration / ID field of the Data 2 frame transmitted to AP 1 (1020) SIFS after receiving the BA frame can be set to the time indicated by the Duration / ID field of the BA frame and transmitted.Although data and BA transmission and reception end before OBSS R-TWT SP, the Duration / ID fields of data and BA indicate up to the OBSS R-TWT SP point in time, so other STAs that receive it can have their NAV set until the start of OBSS R-TWT SP, so the start of R-TWT SP can be protected. In order to protect legacy terminals (Legacy STAs), the transmitted data frame and BA frame can be transmitted in the form of Non-HT PPDU, which is a legacy frame format. If the data frame transmission time and the time required to receive the BA frame are longer than the OBSS R-TWT SP start time (the time indicated by the Duration / ID field of the CTS frame), the STA can reduce its own TXOP length by considering the transmission time of the data frame reconstructed from the data frame to be transmitted before the OBSS R-TWT SP start time and the BA frame transmission time according to the reconstructed data frame (number of MPDUs). STA 1 (1010) with a reduced TXOP length can transmit a Data frame (Data 2 in FIG. 10) to AP 1 (1020) after SIFS after receiving a BA frame by setting the Duration / ID field to a time point before the Duration / ID field of the BA frame. AP 1 (1020) can respond with a BA frame after SIFS after receiving Data 2 transmitted by STA 1 (1010). In order to protect legacy terminals (Legacy STAs), the transmitted Data frame and BA frame can be configured and transmitted in the form of a Non-HT PPDU, which is a legacy frame format.

[0190] If there is not enough time to reconstruct and transmit a data frame at the time indicated by the Duration / ID field of the BA frame transmitted by AP 1 (1020), a QoS Null frame is transmitted with the Duration / ID set to 0 or the time indicated by the Duration / ID field of the BA frame, or if there is not enough time to transmit a QoS Null frame, no data frame is transmitted. AP 2 (1030), which negotiated the R-TWT SP with STA 2 (1040), can only receive the BA frame that AP 1 (1020) transmitted to STA 1 (1010). Therefore, the NAV set in AP 2 (1030) by AP 1 (1020) can be released before the R-TWT SP start time, and AP 2 (1030) can start a channel access operation in accordance with the R-TWT SP start time. That is, the starting point of the R-TWT SP of OBSS (e.g. AP 2 (1030)) can be protected.

[0191] The BA transmitted by AP 1 (1020) and / or the data frame transmitted by STA 1 (1010) may include an OBSS R-TWT SP information inclusion indicator. The OBSS R-TWT SP information inclusion indicator may be included in the MAC header in the form of A-control. When the OBSS R-TWT SP information inclusion indicator is included, Duration / ID may be transmitted with the OBSS R-TWT SP start time set to the OBSS R-TWT SP start time even if data and BA transmission and reception may end before the OBSS R-TWT SP. Other STAs that receive this may have their NAVs set until the OBSS R-TWT SP start time, so that the start time of the R-TWT SP may be protected.

[0192] FIG. 11 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0193] Referring to FIG. 11, AP 1 (1120) and AP 2 (1130) can operate, and STA 1 (1110) associated with AP 1 (1120) and STA 2 (1140) associated with AP 2 (1130) can operate. AP 1 (1120) and AP 2 (1130) can configure BSS (Basic Service Set) 1 and BSS 2, respectively, and STA 1 (1110) and STA 2 (1140) can operate in BSS 1 and BSS 2, respectively. BSS 1 and BSS 2 can use the same primary channel, i.e., the same frequency, so that APs and STAs can operate. AP 1 (1120) and AP 2 (1130) can exist within a range where they can transmit and receive to each other. STA 1 (1110) may not be able to detect transmission and reception between wireless LAN terminals in BSS 2, and STA 2 (1140) may not be able to detect transmission and reception between wireless LAN terminals in BSS 1. For STA 1 (1110), BSS 2 may be an OBSS (Overlapping BSS), and for STS 2, BSS 1 may be an OBSS. Interference may occur because the OBSS and BSS use the same channel within a BSS within a distance range where signals of the OBSS can be received while transmission and reception between terminals are performed in the OBSS. Similarly, interference may occur because the OBSS and BSS use the same channel within an OBSS within a distance range where signals of the BSS can be received while transmission and reception between terminals are performed in the BSS. That is, in Fig. 11, AP 2 (1130) may not be able to perform channel access operations and transmit and receive frames at the R-TWT SP start point because its NAV is set by the BA transmitted by AP 1 (1120) of BSS 1, which is an OBSS. R-TWT can be used to transmit and receive low-latency traffic, and the transmission and reception of such low-latency traffic may be delayed due to interference from the OBSS.Therefore, a method to prevent R-TWT SP from being compromised by OBSS or a method to protect R-TWT SP of OBSS will be described later.

[0194] An AP within a BSS can negotiate an R-TWT (Restricted Target Wake Time) SP (service period) through a membership setup process with connected terminals within the same BSS. The R-TWT SP setup process (membership setup process) can be based on the broadcast TWT method. In the broadcast TWT method, the AP can include a TWT element in the Beacon frame and the Probe response frame to indicate (e.g., announce, broadcast) TWT setup. The TWT setup includes the TWT SP scheduling process. The TWT element can include a TWT ID (identifier) ​​that distinguishes the TWT setup, and a TWT setup command subfield that indicates, changes, or cancels the TWT setup. The TWT element includes scheduling information (start time, interval, etc.) of the TWT SP. The Beacon frame and the Probe response frame that include the TWT element include a TSF (time synchronization field) for time synchronization, and the scheduling of the TWT SP can be performed based on the TSF information. In the Broadcast TWT method, in order for a terminal to participate in the TWT configuration of an AP, the terminal can transmit a TWT request frame containing a TWT element to the AP. Through the TWT element included in the TWT request frame, the terminal can request a new TWT configuration or indicate participation in an existing TWT configuration (e.g., a TWT configuration indicated in the AP's Beacon and Probe response frames). The AP can accept the terminal's request, instruct to modify it, or reject it. If the AP accepts the terminal's request, a new TWT configuration is created at the terminal's request and the terminal participates in the new TWT configuration, or the terminal participates in the existing TWT configuration.If the AP changes the request of the terminal and instructs, the AP rejects the terminal's participation in the TWT configuration and instructs another (e.g., alternative) TWT configuration or TWT configuration parameters in which the terminal can participate. The terminal can send a TWT request frame to the AP again, including the parameters changed by the AP in the TWT element. If the AP rejects the terminal's request, the terminal cannot participate in the AP's TWT configuration. If the terminal participates in the AP's TWT configuration, the terminal is a member of the STA's TWT configuration. That is, membership is established. This can be said to have negotiated the TWT SP. The R-TWT SP is negotiated through a method the same as or similar to the above method. The terminal that negotiated the R-TWT SP may have received or may receive again (i.e., additionally receive) information about the R-TWT schedule (e.g., Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing Synchronization Function) information), TWT elements, etc.) from the AP through a Beacon, Probe Response frame, etc. A terminal that has negotiated an R-TWT SP can receive information about the R-TWT schedule included in the Beacon and Probe Response frames transmitted by the AP, and can perform channel access operations and frame transmission and reception processes with the AP in accordance with the R-TWT SP start time. Terminals that have not participated in the R-TWT negotiation process within the same BSS can receive information about the R-TWT schedule included in the Beacon and Probe Response frames exchanged during the R-TWT SP negotiation process. Terminals that have not participated in the R-TWT SP negotiation process can recognize that the information about the received R-TWT schedule is not information about their own R-TWT schedule, and can end the TXOP (transmit opportunity) before the R-TWT SP start time.Terminating a TXOP may mean terminating a frame transmission or a frame exchange. A frame exchange is a process that includes transmitting a frame and receiving a response frame to the transmitted frame. The AP additionally includes a quiet channel element or a quiet channel element in the Beacon frame and the Probe response frame, which instructs to set a network allocation vector (NAV) that prohibits transmission for 1 TU (time unit) from the start time of the R-TWT SP, so that terminals that do not support R-TWT operation and do not know the R-TWT schedule also terminate transmission before the start time of the R-TWT SP, and do not perform channel access operations (e.g., DCF (distributed coordination function) operation and EDCA (enhanced distributed channel access) operation) for 1 TU from the start time of the R-TWT SP, and do not transmit frames. The 1 TU is 1024 us. Therefore, the R-TWT SP start time of terminals that have negotiated the R-TWT SP can be protected.

[0195] Terminals (e.g., AP 2 (1130) and STA 2 (1140)) within one OBSS (e.g., BSS 2) can negotiate an R-TWT SP. AP 1 (1120) can receive at least one of the frames exchanged between the terminals in the OBSS R-TWT negotiation procedure, and can decode the received frame to check information about the OBSS R-TWT SP (hereinafter, OBSS R-TWT information). The OBSS R-TWT information can include BSS Color, Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc. AP 1 (1120) may include an indicator (OR-TWT present) notifying that an OBSS R-TWT SP to be protected exists during the Beacon period, in a Beacon frame including the OBSS R-TWT SP start time during the Beacon period with the immediately next TBTT (Target Beacon Transmission Time) of BSS 1, using the received OBSS R-TWT information. Alternatively, the OR-TWT present may be included in a frame that is aperiodically transmitted to a specific terminal or all terminals. Specifically, it may be included in a Probe Response frame or an Action (Management) frame including a TWT element conveying information about the TWT. A terminal that receives the OR-TWT present information may perform an operation to protect the OBSS R-TWT SP until the next Beacon reception or at least until the next TBTT time. If the OR-TWT present indicator is transmitted in a frame other than a Beacon, it may include information that can infer the period during which protection operation for the OBSS R-TWT SP is performed.As another example, OR-TWT present can be an indicator (hereinafter, TXOP reduction possibility indicator) specifically notifying the possibility of TXOP length reduction by the TXOP responder. The OR-TWT present indicator can be transmitted including information indicating the Duration Setting (Single Protection, Multiple Protection) method of the transmitted frame, the maximum transmission time of a single PPDU (PHY Protocol Data Unit) for uplink transmission within the TXOP, the length of IFS (Interframe Space) (PIFS, etc.) between PPDU transmissions within the TXOP, and the frame Duration Setting rule within the TXOP (e.g., a method of setting the Duration of a subsequent frame to an earlier time when the time indicated by the Duration / ID field of a response frame is earlier than the time indicated by the Duration / ID field of the initially transmitted frame, etc.). An STA that has received information on the maximum transmission time of a single PPDU for uplink transmission within a TXOP from an AP can configure and transmit the length of the PPDU it transmits so as not to exceed the length indicated by the information.

[0196] The AP can transmit the OR-TWT present indicator by setting the Duration Setting to multiple protection. If there is no Duration setting information, it may mean that multiple protection is set by default. An STA (e.g., STA 1 (1110)) that has received the OR-TWT present indicator from the AP can use multiple protection with the Duration setting in the TXOP it has acquired. Multiple protection may be a method used in EDCA (Enhanced Distributed Channel Access) to protect transmission and reception from hidden nodes. An STA using multiple protection can transmit the frame by setting the Duration / ID field of the transmitted frame to a length that can protect until the expected end time of the subsequent frame exchange sequence. Another STA that has received the frame transmitted by the STA using the multiple protection can set the NAV (Network Allocation Vector) if the terminal indicated by the receiver address field (e.g., RA (Receiver Address) subfield, DA (Destination Address) subfield, etc.) of the frame is not itself. When STA 1 (1110) uses Multiple protection, the terminal can set TXOP within the TXOP limit length allowed for the AC to be transmitted by default and set the Duration / ID value based on that length.

[0197] As another example, the AP can transmit the OR-TWT present indicator with the Duration Setting set to single protection. An STA (e.g., STA 1 (1110)) that receives the OR-TWT present indicator from the AP may only use single protection with the Duration setting in the TXOP it has acquired. Single protection may be a method used in EDCA (Enhanced Distributed Channel Access) to protect transmission and reception from hidden nodes. An STA using single protection may set the Duration / ID field of the transmitted frame to a length that can protect subsequent data frames, Management frames, response frames, or additional frames (e.g., frames with the RDG / More PPDU subfield set to 1), and may set the NAV (Network Allocation Vector) for STAs that receive the frame but are not terminals indicated by the receiver address field (e.g., RA (Receiver Address) subfield, DA (Destination Address) subfield, etc.).

[0198] The AP can transmit an OR-TWT present indicator, and STA 1 (1110) can receive the OR-TWT present indicator from the AP. Since STA 1 (1110) can know that OBSS R-TWT SP exists, it transmits data using the Inter PPDU transmission method that divides the data to be transmitted and transmits PPDUs with XIFS (e.g. PIFS) spaced between them for continuous transmission. Among the PPDUs transmitted using the Inter PPDU transmission method, the RDG / More PPDU field of the MAC header of the PPDUs except for the last PPDU transmitted may be set to 1 to indicate that there is a subsequent PPDU. The Inter PPDU transmission method may be initiated after an additional frame exchange (e.g. RTS and CTS frame exchange, etc.) for channel access and TXOP acquisition prior to the initial PPDU transmission. STA 1 (1110) can acquire TXOP by transmitting the first PPDU (Data 1 in FIG. 11) to AP 1 (1120) through a channel access operation using EDCA. After transmitting Data 1, STA 1 (1110) can transmit subsequent PPDUs (Data 2 in FIG. 11) to AP 1 (1120) at a time interval of XIFS (e.g. PIFS (Priority Interframe Space)). AP 1 (1120) can receive the PPDUs transmitted by STA 1 (1110). If AP 1 (1120) determines that the start time of OBSS R-TWT SP will be exceeded while receiving PPDU transmitted by STA 1 (1110), it can transmit a BA frame to STA 1 (1110) within the XIFS time interval before the next PPDU is transmitted (e.g., after SIFS after receiving DATA).Depending on whether the Duration Setting of the OR-TWT present indicator is multiple protection or single protection, the Duration / ID value of the Data frame transmitted by STA 1 (1110) may be set differently and transmitted. In the case of multiple protection, the Duration / ID value of the Data frame transmitted by STA 1 (1110) is set to a value indicating the time required for transmitting PPDUs and receiving BA (Data PPDU transmission time + XIFS time in between + SIFS + BA transmission time point). When transmitting each Data PPDU, the value indicating the end time is calculated and set by excluding the time taken by the previous Data PPDU transmission. If the OR-TWT present indicator indicates the OBSS R-TWT SP end time, the Duration / ID value of the Data frame transmitted by STA 1 (1110) may be set to the OBSS R-TWT SP end time. In the case of single protection, the Duration / ID value of the data frame transmitted by STA 1 (1110) is set to 0 or the XIFS time value at each PPDU transmission point.

[0199] The Duration / ID field of the BA frame transmitted by AP 1 (1120) can be set to a value indicating the start time of OBSS R-TWT SP or 0. The More PPDU value of the BA frame can be set to 0 to indicate the start of OBSS R-TWT SP. STA 1 (1110) receives BA in Preemption, that is, after SIFS time after data transmission, and if More PPDU is set to 0, it does not transmit additional data frames after receiving the BA frame. That is, it terminates TXOP.

[0200] AP 2 (1130), which negotiated the R-TWT SP with STA 2 (1140), can only receive the BA frame transmitted by AP 1 (1120) to STA 1 (1110). Therefore, the NAV set in AP 2 (1130) by AP 1 (1120) can be released before the R-TWT SP start time, and AP 2 (1130) can start the channel access operation in accordance with the R-TWT SP start time. In other words, the start time of the R-TWT SP of the OBSS (e.g. AP 2 (1130)) can be protected.

[0201] FIG. 12 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0202] Referring to FIG. 12, AP 1 (1210) and AP 2 (1240) can operate, and STA 1 (1220) associated with AP 1 (1210) and STA 2 (1230) associated with AP 2 (1240) can operate. AP 1 (1210) and AP 2 (1240) can configure BSS (Basic Service Set) 1 and BSS 2, respectively, and STA 1 (1220) and STA 2 (1230) can operate in BSS 1 and BSS 2, respectively. BSS 1 and BSS 2 can use the same primary channel, i.e., the same frequency, so that APs and STAs can operate. STA 1 (1220) and STA 2 (1230) can exist within a range where they can transmit and receive to each other. AP 1 (1210) may not be able to detect transmission and reception between wireless LAN terminals in BSS 2, and AP 2 (1240) may not be able to detect transmission and reception between wireless LAN terminals in BSS 1. AP 1 (1210) and AP 2 (1240) may be connected by a method other than wireless LAN (e.g., wired LAN, etc.) to form an ESS (Extended Service Set) that allows data exchange regardless of the wireless LAN transmission and reception distance. BSS 2 may be an OBSS (Overlapping BSS) to STA 1 (1220), and BSS 1 may be an OBSS to STS 2. While transmission and reception between terminals is performed in the OBSS, interference may occur because the OBSS and the BSS use the same channel within the BSS within the range of the distance at which the OBSS signal can be received. Similarly, interference may occur within the OBSS within the range of distances within which the BSS's signals can be received while transmission and reception between terminals in the BSS is performed, because the OBSS and the BSS use the same channel.That is, in FIG. 12, STA 1 (1220) may not be able to respond to the TF transmitted by AP 1 (1210) at the start of the R-TWT SP because the NAV is set by the RTS and data frame transmitted by STA 2 (1230) of BSS 2, which is an OBSS. R-TWT can be used to transmit and receive low-latency traffic, and the transmission and reception of such low-latency traffic may be delayed due to interference from the OBSS. Therefore, a method for preventing the R-TWT SP from being invaded by the OBSS or a method for protecting the R-TWT SP of the OBSS will be described later.

[0203] An AP within a BSS can negotiate an R-TWT (Restricted Target Wake Time) SP (service period) through a membership setup process with connected terminals within the same BSS. The R-TWT SP setup process (membership setup process) can be based on the broadcast TWT method. In the broadcast TWT method, the AP can include a TWT element in the Beacon frame and the Probe response frame to indicate (e.g., announce, broadcast) TWT setup. The TWT setup includes the TWT SP scheduling process. The TWT element can include a TWT ID (identifier) ​​that distinguishes the TWT setup, and a TWT setup command subfield that indicates, changes, or cancels the TWT setup. The TWT element includes scheduling information (start time, interval, etc.) of the TWT SP. The Beacon frame and the Probe response frame that include the TWT element include a TSF (time synchronization field) for time synchronization, and the scheduling of the TWT SP can be performed based on the TSF information. In the Broadcast TWT method, in order for a terminal to participate in the TWT configuration of an AP, the terminal can transmit a TWT request frame containing a TWT element to the AP. Through the TWT element included in the TWT request frame, the terminal can request a new TWT configuration or indicate participation in an existing TWT configuration (e.g., a TWT configuration indicated in the AP's Beacon and Probe response frames). The AP can accept the terminal's request, instruct to modify it, or reject it. If the AP accepts the terminal's request, a new TWT configuration is created at the terminal's request and the terminal participates in the new TWT configuration, or the terminal participates in the existing TWT configuration.If the AP changes the request of the terminal and instructs, the AP rejects the terminal's participation in the TWT configuration and instructs another (e.g., alternative) TWT configuration or TWT configuration parameters in which the terminal can participate. The terminal can send a TWT request frame to the AP again, including the parameters changed by the AP in the TWT element. If the AP rejects the terminal's request, the terminal cannot participate in the AP's TWT configuration. If the terminal participates in the AP's TWT configuration, the terminal is a member of the STA's TWT configuration. That is, membership is established. This can be said to have negotiated the TWT SP. The R-TWT SP is negotiated through a method the same as or similar to the above method. The terminal that negotiated the R-TWT SP may have received or may receive again (i.e., additionally receive) information about the R-TWT schedule (e.g., Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing Synchronization Function) information), TWT elements, etc.) from the AP through a Beacon, Probe Response frame, etc. A terminal that has negotiated an R-TWT SP can receive information about the R-TWT schedule included in the Beacon and Probe Response frames transmitted by the AP, and can perform channel access operations and frame transmission and reception processes with the AP in accordance with the R-TWT SP start time. Terminals that have not participated in the R-TWT negotiation process within the same BSS can receive information about the R-TWT schedule included in the Beacon and Probe Response frames exchanged during the R-TWT SP negotiation process. Terminals that have not participated in the R-TWT SP negotiation process can recognize that the information about the received R-TWT schedule is not information about their own R-TWT schedule, and can end the TXOP (transmit opportunity) before the R-TWT SP start time.Terminating a TXOP may mean terminating a frame transmission or a frame exchange. A frame exchange is a process that includes transmitting a frame and receiving a response frame to the transmitted frame. The AP additionally includes a quiet channel element or a quiet channel element in the Beacon frame and the Probe response frame, which instructs to set a network allocation vector (NAV) that prohibits transmission for 1 TU (time unit) from the start time of the R-TWT SP, so that terminals that do not support R-TWT operation and do not know the R-TWT schedule also terminate transmission before the start time of the R-TWT SP, and do not perform channel access operations (e.g., DCF (distributed coordination function) operation and EDCA (enhanced distributed channel access) operation) for 1 TU from the start time of the R-TWT SP, and do not transmit frames. The 1 TU is 1024 us. Therefore, the R-TWT SP start time of terminals that have negotiated the R-TWT SP can be protected.

[0204] Terminals (e.g., AP 2 (1240) and STA 2 (1230)) within one BSS (e.g., BSS 2) can negotiate an R-TWT SP. STA 1 (1220) can receive at least one of the frames exchanged between the terminals in the R-TWT SP negotiation procedure of the OBSS, and can decode the received frame to check information about the OBSS R-TWT SP (hereinafter, OBSS R-TWT information). The OBSS R-TWT information can include BSS Color, Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc. AP 1 (1210) and AP 2 (1240) can exchange R-TWT SP information within the BSS they configure within the ESS by a method other than wireless LAN (e.g. wired LAN, etc.) and can perform actions to protect the R-TWT SP of the AP belonging to the ESS (e.g., actions not to perform channel access actions at the start of the OBSS R-TWT SP, etc.).

[0205] AP 1 (1210) may use the OBSS R-TWT information exchanged with AP 2 (1240) through the ESS to include an indicator (OR-TWT present) notifying the presence of an OBSS R-TWT SP to be protected during the Beacon period in a Beacon frame including the OBSS R-TWT SP start time during the Beacon period with the immediately next TBTT (Target Beacon Transmission Time) of BSS 1. Alternatively, the OR-TWT present may be included in a frame that is aperiodically transmitted to a specific terminal or all terminals. Specifically, it may be included in a Probe Response frame or an Action (Management) frame including a TWT element conveying information about the TWT. A terminal that receives the OR-TWT present information may perform an operation to protect the OBSS R-TWT SP until the next Beacon reception or at least until the next TBTT time. If the OR-TWT present indicator is transmitted in a frame other than a Beacon, it may include information that can infer the period during which a protection operation is performed for the OBSS R-TWT SP. The OR-TWT present indicator may be transmitted including information that instructs to set its NAV to the value of the Duration / ID field indicating the earliest point in time among the points in time indicated by the Duration / ID field of the received OBSS frame when the frame transmitted from the OBSS is received. STA 1 (1220) that has received the OR-TWT present indicator may set its NAV to the value of the Duration / ID field indicating the earlier point in time among the Duration / ID fields of the received frame when the frame transmitted from the OBSS (e.g. BSS 2) is received.

[0206] STA 2 (1230) can acquire TXOP by transmitting an RTS frame to AP 2 (1240) through a channel access operation using EDCA. The Duration / ID field of the RTS frame transmitted by STA 2 (1230) may be set to a length including the start time of the R-TWT SP of AP 1 (1210). STA 1 (1220), which receives the RTS frame transmitted by STA 2 (1230), can set its NAV to the value of the Duration / ID field of the RTS frame. AP 2 (1240) can transmit a CTS (Clear to Send) frame to STA 2 (1230) after a SIFS (Short Interframe Space) time after receiving the RTS frame initially transmitted by STA 2 (1230). AP 2 (1240) may decide to protect the starting point of the OBSS (e.g., AP 1 (1210)) R-TWT SP. AP 2 (1240) that decides to protect the OBSS R-TWT SP may transmit the CTS frame transmitted to STA 2 (1230) with the Duration / ID field set to a length that does not include the starting point of the OBSS R-TWT SP. STA 2 (1230) may transmit a Data frame to AP 2 (1240) after an SIFS time after receiving the CTS frame transmitted by AP 2 (1240). The Duration / ID field value of the Data frame transmitted by STA 2 (1230) to AP 2 (1240) may be set to the point in time indicated by the Duration / ID field of the CTS frame transmitted by AP 2 (1240). AP 2 (1240) may respond with a BA (Block ACK (Acknowledgement)) frame after a SIFS time after receiving the Data frame transmitted by STA 2 (1230). The Duration / ID field of the BA frame transmitted by AP 2 (1240) may be set to a value indicating a time before the start of the OBSS R-TWT SP or to 0.STA 1 (1220) can receive only the RTS frame and Data frame transmitted by STA 2 (1230) to AP 2 (1240). STA 1 (1220) may have received the OR-TWT present indicator transmitted by AP 1 (1210), and therefore may set its NAV using the value of the Duration / ID field indicating an earlier time among the Duration / ID fields of the frame transmitted by STA 2 (1230). That is, STA 1 (1220) may set its NAV using the value of the Duration / ID field of the Data frame transmitted by STA 2 (1230). The NAV set in STA 1 (1220) may be set to a length that does not include the start time of the R-TWT SP of AP 1 (1210). Therefore, the NAV set by STA 2 (1230) to STA 1 (1220) can be released before the R-TWT SP start time, and AP 1 (1210) can start channel access operation in accordance with the R-TWT SP start time. In other words, the start time of the R-TWT SP of OBSS (e.g. AP 1 (1210)) can be protected.

[0207] As another example, if STA 1 (1220) receives multiple frames transmitted by STA 2 (1230), the STA 1 (1220) may ignore the CS Required setting of the trigger frame transmitted by AP 1 (1210) only if the point in time indicated by the Duration / ID field of the received frame is earlier than the point in time indicated by the Duration / ID field of the previously received frame (i.e., the length of the NAV is shortened). Accordingly, STA 1 (1220) may transmit a response frame (e.g., Data frame) to AP 1 (1210) regardless of whether the NAV is set by STA 2 (1230). That is, the starting point of the R-TWT SP of the OBSS (e.g., AP 1 (1210)) may be protected.

[0208] FIG. 13 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0209] Referring to FIG. 13, AP 1 (1310) and AP 2 can operate, and STA 1 (1320) associated with AP 1 (1310) and STA 2 (1330) associated with AP 2 (1340) can operate. AP 1 (1310) and AP 2 (1340) can configure BSS (Basic Service Set) 1 and BSS 2, respectively, and STA 1 (1320) and STA 2 (1330) can operate in BSS 1 and BSS 2, respectively. BSS 1 and BSS 2 can use the same primary channel, i.e., the same frequency, so that APs and STAs can operate. STA 1 (1320) and STA 2 (1330) can exist within a range where they can transmit and receive to each other. AP 1 (1310) may not be able to detect transmission and reception between wireless LAN terminals in BSS 2, and AP 2 (1340) may not be able to detect transmission and reception between wireless LAN terminals in BSS 1. AP 1 (1310) and AP 2 (1340) may be connected by a method other than wireless LAN (e.g., wired LAN, etc.) to form an ESS (Extended Service Set) that allows data exchange regardless of the wireless LAN transmission and reception distance. BSS 2 may be an OBSS (Overlapping BSS) to STA 1 (1320), and BSS 1 may be an OBSS to STS 2. While transmission and reception between terminals is performed in the OBSS, interference may occur because the OBSS and the BSS use the same channel within the BSS within the range of the distance at which the OBSS signal can be received. Similarly, interference may occur because the OBSS and BSS use the same channel within the OBSS within the range of distances where the BSS's signal can be received while transmitting and receiving between terminals in the BSS. That is, in FIG. 13, STA 1 (1320) may not respond to the TF transmitted by AP 1 (1310) at the start of the R-TWT SP because its NAV is set by the data frame transmitted by STA 2 (1330) of BSS 2, which is an OBSS.R-TWT can be used to transmit and receive low-latency traffic, and the transmission and reception of such low-latency traffic may be delayed due to interference from OBSS. Therefore, a method to prevent R-TWT SP from being invaded by OBSS or a method to protect R-TWT SP of OBSS will be described below. An AP within a BSS can negotiate an R-TWT (Restricted Target Wake Time) SP (service period) through a membership setup process with a connected terminal within the same BSS. The setup process of the R-TWT SP (membership setup process) may be based on the broadcast TWT method. In the broadcast TWT method, the AP may include a TWT element in the Beacon frame and the Probe response frame to indicate (e.g., announce, broadcast) TWT setup. The TWT setup includes a scheduling process of the TWT SP. The TWT element may include a TWT ID (identifier) ​​that distinguishes the TWT setup, and a TWT setup command subfield that indicates, changes, or cancels the TWT setup. The TWT element includes scheduling information (start time, interval, etc.) of the TWT SP. The Beacon frame and Probe response frame including the TWT element include a time synchronization field (TSF) for time synchronization, and the scheduling of the TWT SP can be performed based on the TSF information. In the Broadcast TWT method, in order for the terminal to participate in the TWT configuration of the AP, the terminal can transmit a TWT request frame including the TWT element to the AP. Through the TWT element included in the TWT request frame, the terminal can request a new TWT configuration or configure an existing TWT configuration (e.g.The AP can instruct the terminal to participate in the TWT configuration (indicated in the Beacon and Probe response frames). The AP can accept, modify, or reject the terminal's request. If the AP accepts the terminal's request, a new TWT configuration is created at the terminal's request, and the terminal has participated in the new TWT configuration, or the terminal has participated in the existing TWT configuration. If the AP instructs by modifying the terminal's request, the AP rejects the terminal's participation in the TWT configuration and instructs another (e.g., alternative) TWT configuration or TWT configuration parameters in which the terminal can participate. The terminal can include the parameters changed by the AP in the TWT element and transmit a TWT request frame to the AP again. If the AP rejects the terminal's request, the terminal cannot participate in the AP's TWT configuration. If the terminal participates in the AP's TWT configuration, the terminal is a member of the STA's TWT configuration. That is, membership is established. This can be said to be a negotiated TWT SP. The R-TWT SP is negotiated through a method the same as or similar to the above method. A terminal that has negotiated an R-TWT SP can receive or re-receive (i.e., additionally receive) information about the R-TWT schedule (e.g., Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc.) from the AP through Beacon, Probe Response frames, etc. A terminal that has negotiated an R-TWT SP can receive information about the R-TWT schedule included in Beacon, Probe Response frames, etc. transmitted by the AP, and perform channel access operations and frame transmission / reception processes with the AP in accordance with the R-TWT SP start time.Terminals that have not participated in the R-TWT negotiation process within the same BSS can receive information about the R-TWT schedule included in the Beacon and Probe Response frames exchanged during the R-TWT SP negotiation process. Terminals that have not participated in the R-TWT SP negotiation process can recognize that the information about the received R-TWT schedule is not information about their own R-TWT schedule and can end the TXOP (transmit opportunity) before the start of the R-TWT SP. Ending the TXOP may mean ending frame transmission or frame exchange. Frame exchange is a process that includes frame transmission and reception of a response frame to the transmitted frame. The AP additionally includes a quiet channel element or a quiet channel element in the Beacon frame and the Probe response frame, which instructs the AP to set a network allocation vector (NAV) that prohibits transmission for 1 TU (time unit) from the start time of the R-TWT SP, so that terminals that do not support the R-TWT operation and therefore do not know the R-TWT schedule also terminate transmission before the start time of the R-TWT SP, and do not perform channel access operations (e.g., DCF (distributed coordination function) operations and EDCA (enhanced distributed channel access) operations) and do not transmit frames for 1 TU from the start time of the R-TWT SP. The 1 TU is 1024 us. Therefore, the R-TWT SP start time of terminals that have negotiated the R-TWT SP can be protected.

[0210] Terminals (e.g., AP 2 (1340) and STA 2 (1330)) within one BSS (e.g., BSS 2) can negotiate an R-TWT SP. STA 1 (1320) can receive at least one of the frames exchanged between the terminals in the R-TWT SP negotiation procedure of the OBSS, and can decode the received frame to check information about the OBSS R-TWT SP (hereinafter, OBSS R-TWT information). The OBSS R-TWT information can include BSS Color, Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc. AP 1 (1310) and AP 2 (1340) can exchange R-TWT SP information within the BSS they configure within the ESS by a method other than wireless LAN (e.g. wired LAN, etc.) and can perform actions to protect the R-TWT SP of the AP belonging to the ESS (e.g., actions not to perform channel access actions at the start of the OBSS R-TWT SP, etc.).

[0211] AP 1 (1310) may use the OBSS R-TWT information exchanged with AP 2 (1340) through the ESS to include an indicator (OR-TWT present) notifying the presence of an OBSS R-TWT SP to be protected during the Beacon period in a Beacon frame including the OBSS R-TWT SP start time during the Beacon period with the immediately next TBTT (Target Beacon Transmission Time) of BSS 1. Alternatively, the OR-TWT present may be included in a frame that is aperiodically transmitted to a specific terminal or all terminals. Specifically, it may be included in a Probe Response frame or an Action (Management) frame that includes a TWT element conveying information about the TWT. A terminal that receives the OR-TWT present information may perform an operation to protect the OBSS R-TWT SP until the next Beacon reception or at least until the next TBTT time. If the OR-TWT present indicator is transmitted in a frame other than a Beacon, it may include information that can infer the period during which a protection operation is performed for the OBSS R-TWT SP. The OR-TWT present indicator may be transmitted including information that instructs to set its NAV to the value of the Duration / ID field indicating the earliest point in time among the points in time indicated by the Duration / ID field of the received OBSS frame when the frame transmitted from the OBSS is received. STA 1 (1320) that has received the OR-TWT present indicator can set its NAV to the value of the Duration / ID field indicating the earlier point in time among the Duration / ID fields of the received frame when the frame transmitted from the OBSS (e.g. BSS 2) is received.

[0212] STA 2 (1330) can obtain TXOP by transmitting a Data frame (Data 1 in FIG. 13) to AP 2 (1340) through a channel access operation using EDCA. The Duration / ID field of the Data frame transmitted by STA 2 (1330) may be set to a length including the start time of the R-TWT SP of AP 1 (1310). STA 1 (1320), which receives Data 1 transmitted by STA 2 (1330), can set its NAV to the value of the Duration / ID field of Data 1. AP 2 (1340) can transmit a BA (Block ACK (Acknowledgement)) frame to STA 2 (1330) after a SIFS (Short Interframe Space) time after receiving Data 1 initially transmitted by STA 2 (1330). AP 2 (1340) may decide to protect the starting point of the OBSS (e.g., AP 1 (1310)) R-TWT SP. AP 2 (1340) that decides to protect the OBSS R-TWT SP may transmit the BA frame transmitted to STA 2 (1330) with the Duration / ID field set to a length that does not include the starting point of the OBSS R-TWT SP. STA 2 (1330) may transmit a Data frame (Data 2 of FIG. 13) to AP 2 (1340) after an SIFS time after receiving the BA frame transmitted by AP 2 (1340). The Duration / ID field value of Data 2 that STA 2 (1330) transmits to AP 2 (1340) may be set to the point in time indicated by the Duration / ID field of the BA frame transmitted by AP 2 (1340). AP 2 (1340) can respond with a BA frame after an SIFS time after receiving Data 2 transmitted by STA 2 (1330). The Duration / ID field of the BA frame transmitted by AP 2 (1340) can be set to a value indicating a time before the start of the OBSS R-TWT SP or to 0.STA 1 (1320) can only receive the Data frame (Data 1, Data 2 in FIG. 13) that STA 2 (1330) transmits to AP 2 (1340). STA 1 (1320) may have received the OR-TWT present indicator transmitted by AP 1 (1310), and therefore may set its NAV using the value of the Duration / ID field indicating an earlier time among the Duration / ID fields of the frames transmitted by STA 2 (1330). That is, STA 1 (1320) can set its NAV using the value of the Duration / ID field of the Data frame (Data 2 in FIG. 13) with a shorter Duration length among the Data frames transmitted by STA 2 (1330). The NAV set in STA 1 (1320) may be set to a length that does not include the start time of the R-TWT SP of AP 1 (1310). Therefore, the NAV set by STA 2 (1330) to STA 1 (1320) can be released before the R-TWT SP start time, and AP 1 (1310) can start channel access operation in accordance with the R-TWT SP start time. In other words, the start time of the R-TWT SP of OBSS (e.g. AP 1 (1310)) can be protected.

[0213] As another example, if STA 1 (1320) receives multiple frames transmitted by STA 2 (1330), the STA 1 (1320) may ignore the CS Required setting of the trigger frame transmitted by AP 1 (1310) only if the point in time indicated by the Duration / ID field of the received frame is earlier than the point in time indicated by the Duration / ID field of the previously received frame (i.e., the length of the NAV is shortened). Accordingly, STA 1 (1320) may transmit a response frame (e.g., Data frame) to AP 1 (1310) regardless of whether the NAV is set by STA 2 (1330). That is, the R-TWT SP start point of the OBSS (e.g., AP 1 (1310)) may be protected.

[0214] FIG. 14 is a diagram illustrating a method for protecting an OBSS R-TWT schedule through a wireless LAN terminal to which the present disclosure is applied.

[0215] Referring to FIG. 14, AP 1 (1410) and AP 2 (1440) can operate, and STA 1 (1420) associated with AP 1 (1410) and STA 2 (1430) associated with AP 2 (1440) can operate. AP 1 (1410) and AP 2 (1440) can configure BSS (Basic Service Set) 1 and BSS 2, respectively, and STA 1 (1420) and STA 2 (1430) can operate in BSS 1 and BSS 2, respectively. STA 1 (1420) and STA 2 (1430) can exist within a transmission and reception range with each other. AP 1 (1410) can also be within a transmission and reception range with STA 2 (1430). AP 1 (1410) and AP 2 (1440) can be connected by a method other than wireless LAN (e.g., wired LAN, etc.) to form an ESS (Extended Service Set) that can exchange data regardless of the wireless LAN transmission and reception distance. For STA 1 (1420), BSS 2 can be an OBSS (Overlapping BSS), and for STA 2 (1430), BSS 1 can be an OBSS. Interference may occur because the OBSS and BSS use the same channel within a BSS within a distance range where the OBSS signal can be received while transmission and reception between terminals are performed in the OBSS. Similarly, interference may occur because the OBSS and BSS use the same channel within an OBSS within a distance range where the BSS signal can be received while transmission and reception between terminals are performed in the BSS. That is, in FIG. 14, STA 1 (1420) may not be able to respond to the TF transmitted by AP 1 (1410) at the start of the R-TWT SP because the NAV is set by the frame exchange process (e.g., RTS and CTS exchange, etc.) between AP 2 (1440) of BSS 2, which is an OBSS, and STA 2 (1430). R-TWT can be used for transmitting and receiving low-latency traffic, and the transmission and reception of such low-latency traffic may be delayed due to interference from the OBSS.Therefore, a method to prevent R-TWT SP from being compromised by OBSS or a method to protect R-TWT SP of OBSS will be described later.

[0216] An AP within a BSS can negotiate an R-TWT (Restricted Target Wake Time) SP (service period) through a membership setup process with connected terminals within the same BSS. The R-TWT SP setup process (membership setup process) can be based on the broadcast TWT method. In the broadcast TWT method, the AP can include a TWT element in the Beacon frame and the Probe response frame to indicate (e.g., announce, broadcast) TWT setup. The TWT setup includes the TWT SP scheduling process. The TWT element can include a TWT ID (identifier) ​​that distinguishes the TWT setup, and a TWT setup command subfield that indicates, changes, or cancels the TWT setup. The TWT element includes scheduling information (start time, interval, etc.) of the TWT SP. The Beacon frame and the Probe response frame that include the TWT element include a TSF (time synchronization field) for time synchronization, and the scheduling of the TWT SP can be performed based on the TSF information. In the Broadcast TWT method, in order for a terminal to participate in the TWT configuration of an AP, the terminal can transmit a TWT request frame containing a TWT element to the AP. Through the TWT element included in the TWT request frame, the terminal can request a new TWT configuration or indicate participation in an existing TWT configuration (e.g., a TWT configuration indicated in the AP's Beacon and Probe response frames). The AP can accept the terminal's request, instruct to modify it, or reject it. If the AP accepts the terminal's request, a new TWT configuration is created at the terminal's request and the terminal participates in the new TWT configuration, or the terminal participates in the existing TWT configuration.If the AP changes the request of the terminal and instructs, the AP rejects the terminal's participation in the TWT configuration and instructs another (e.g., alternative) TWT configuration or TWT configuration parameters in which the terminal can participate. The terminal can send a TWT request frame to the AP again, including the parameters changed by the AP in the TWT element. If the AP rejects the terminal's request, the terminal cannot participate in the AP's TWT configuration. If the terminal participates in the AP's TWT configuration, the terminal is a member of the STA's TWT configuration. That is, membership is established. This can be said to have negotiated the TWT SP. The R-TWT SP is negotiated through a method the same as or similar to the above method. The terminal that negotiated the R-TWT SP may have received or may receive again (i.e., additionally receive) information about the R-TWT schedule (e.g., Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing Synchronization Function) information), TWT elements, etc.) from the AP through a Beacon, Probe Response frame, etc. A terminal that has negotiated an R-TWT SP can receive information about the R-TWT schedule included in the Beacon and Probe Response frames transmitted by the AP, and can perform channel access operations and frame transmission and reception processes with the AP in accordance with the R-TWT SP start time. Terminals that have not participated in the R-TWT negotiation process within the same BSS can receive information about the R-TWT schedule included in the Beacon and Probe Response frames exchanged during the R-TWT SP negotiation process. Terminals that have not participated in the R-TWT SP negotiation process can recognize that the information about the received R-TWT schedule is not information about their own R-TWT schedule, and can end the TXOP (transmit opportunity) before the R-TWT SP start time.Terminating a TXOP may mean terminating a frame transmission or a frame exchange. A frame exchange is a process that includes transmitting a frame and receiving a response frame to the transmitted frame. The AP additionally includes a quiet channel element or a quiet channel element in the Beacon frame and the Probe response frame, which instructs to set a network allocation vector (NAV) that prohibits transmission for 1 TU (time unit) from the start time of the R-TWT SP, so that terminals that do not support R-TWT operation and do not know the R-TWT schedule also terminate transmission before the start time of the R-TWT SP, and do not perform channel access operations (e.g., DCF (distributed coordination function) operation and EDCA (enhanced distributed channel access) operation) for 1 TU from the start time of the R-TWT SP, and do not transmit frames. The 1 TU is 1024 us. Therefore, the R-TWT SP start time of terminals that have negotiated the R-TWT SP can be protected.

[0217] Terminals (e.g., AP 2 (1440) and STA 2 (1430)) within one BSS (e.g., BSS 2) can negotiate an R-TWT SP. STA 1 (1420) can receive at least one of the frames exchanged between the terminals in the R-TWT SP negotiation procedure of the OBSS, and can decode the received frame to check information about the OBSS R-TWT SP (hereinafter, OBSS R-TWT information). The OBSS R-TWT information can include BSS Color, Service Period (SP) scheduling information (start time, interval, etc.), time synchronization information (TSF (Timing synchronization function) information), TWT elements, etc. AP 1 (1410) and AP 2 (1440) can exchange R-TWT SP information within the BSS they configure within the ESS by a method other than wireless LAN (e.g. wired LAN, etc.) and can perform actions to protect the R-TWT SP of the AP belonging to the ESS (e.g., actions not to perform channel access actions at the start of the OBSS R-TWT SP, etc.).

[0218] AP 1 (1410) may use the OBSS R-TWT information exchanged with AP 2 (1440) through the ESS to include an indicator (OR-TWT present) notifying the presence of an OBSS R-TWT SP to be protected during the Beacon period in a Beacon frame including the OBSS R-TWT SP start time during the Beacon period with the immediately next TBTT (Target Beacon Transmission Time) of BSS 1. Alternatively, the OR-TWT present may be included in a frame that is aperiodically transmitted to a specific terminal or all terminals. Specifically, it may be included in a Probe Response frame or an Action (Management) frame that includes a TWT element conveying information about the TWT. A terminal that receives the OR-TWT present information may perform an operation to protect the OBSS R-TWT SP until the next Beacon reception or at least until the next TBTT time. If the OR-TWT present indicator is transmitted in a frame other than a Beacon, it may include information that can infer the period during which protection operation for the OBSS R-TWT SP is performed.

[0219] STA 2 (1430) can acquire TXOP by transmitting an RTS frame to AP 2 (1440) through a channel access operation using EDCA. The Duration / ID field of the RTS frame transmitted by STA 2 (1430) may be set to a length including the start time of the R-TWT SP of AP 1 (1410). STA 1 (1420), which receives the RTS frame transmitted by STA 2 (1430), can set its NAV to the value of the Duration / ID field of the RTS frame. AP 2 (1440) can transmit a CTS (Clear to Send) frame to STA 2 (1430) after a SIFS (Short Interframe Space) time after receiving the RTS frame initially transmitted by STA 2 (1430). AP 2 (1440) may have decided to protect the start time of the OBSS (e.g., AP 1 (1410)) R-TWT SP. AP 2 (1440) that has decided to protect the OBSS R-TWT SP may transmit the CTS frame to STA 2 (1430) with the Duration / ID field set to a length that does not include the start time of the OBSS R-TWT SP. The RTS / CTS may have been transmitted in a non-HT duplicate PPDU format that all legacy terminals can receive in order to set the NAV of the legacy terminals. According to the present embodiment, STA 1 (1420) is within the transmission and reception range with STA 2 (1430) and AP 2 (1440), and thus has received all of the RTS / CTS exchanges, and may not be able to transmit at the start section of the R-TWT SP by setting the NAV based on the RTS frame with a longer duration set according to the basic rule of NAV setting.

[0220] To solve the above problem, in this embodiment, a NAV truncation operation is performed using a UHR PPDU, which is a new PPDU format that only UHR terminals can receive. According to this embodiment, a UHR STA that has received an OR-TWT present indicator can transmit a UHR PPDU with an activated NAV truncation indicator included in the preamble of the UHR PPDU. The indicator is an indicator that notifies that the NAV may be shortened in the middle of a TXOP. If a terminal for which a NAV is currently set from an OBSS terminal has received a UHR PPDU with an activated NAV truncation indicator, has received the PPDU from the same OBSS as the OBSS that has set the current NAV, and has instructed that a NAV be set with a Duration of internal data of the PPDU that is shorter than the current NAV, the NAV can be updated to the shorter NAV. For the above operation, the terminal may need to temporarily store identification information of the OBSS that sets the NAV when a new NAV is set.

[0221] According to the embodiment of FIG. 14, STA 2 (1430) can transmit a Data frame to AP 2 (1440) after an SIFS time after receiving the CTS frame transmitted by AP 2 (1440). The Duration / ID field value of the Data frame transmitted by STA 2 (1430) to AP 2 (1440) can be set to the time indicated by the Duration / ID field of the CTS frame transmitted by AP 2 (1440). In this case, separately from transmitting the RTS / CTS frame as a non-HT duplicate, the Data frame can be transmitted using the UHR PPDU format, and since information about a shorter TXOP is received from the AP through the CTS frame, the Data frame can be transmitted by activating the NAV truncation indicator of the UHR PPDU preamble. Therefore, if AP 1 (1410) or STA 1 (1420) receives a data frame with the NAV truncation indicator activated, confirms that the data frame is from the same OBSS as the OBSS that exchanged RTS / CTS, and has a shorter Duration value, the NAV truncation operation can be performed to shorten the currently set NAV based on the Duration value of the data frame. Therefore, it is possible to utilize the SP without applying the NAV at the start of the R-TWT SP.

[0222] AP 2 (1440) may respond with a BA (Block ACK (Acknowledgement)) frame after a SIFS time after receiving the Data frame transmitted by STA 2 (1430). The Duration / ID field of the BA frame transmitted by AP 2 (1440) may be set to a value indicating a time before the start of the OBSS R-TWT SP or to 0.

[0223] In FIGS. 9 through 14, a machine learning unit and a machine learning algorithm may be used to determine whether AP 1 should protect the R-TWT SP start point of an OBSS. For example, AP 1 may perform information gathering operations, such as recording the frequency of transmission and reception failures due to OBSS R-TWT SPs, through the machine learning unit, and may use this information to determine the OBSS R-TWT SPs to be protected through the machine learning algorithm.

[0224] In Fig. 11, a machine learning unit and a machine learning algorithm may be used to calculate the maximum length of a data frame within a TXOP indicated by the TXOP scalability indicator. For example, if there is one or more OBSS R-TWT SPs, the AP may set the maximum length of a data frame within a TXOP to the optimal data size calculated by the machine learning unit through the machine learning algorithm to transmit a BA frame to the STA at an appropriate time to terminate the TXOP of the STA.

[0225] FIG. 15 is a flowchart illustrating a method for performing a wireless LAN multi-link relay operation to which the present disclosure is applied. In a first section, a relay AP may receive a first frame from a first STA via a second link. (S1510) Here, the first frame may be a low-latency frame transmitted from the first STA to the master AP, as described above. In addition, the relay AP may operate based on NSTR, and if transmission is performed on either of the first link and the second link, reception may not be performed on the other link. Here, the relay AP may perform a relay schedule negotiation procedure with the master AP, and determine relay schedule information comprising at least one of information on a start time and a time period during which frame transmission can be performed through the relay schedule negotiation procedure. For example, a first section in which the relay AP communicates with the first STA via the second link and a second section in which the relay AP communicates with the master AP via the first link may be determined based on the relay schedule information.

[0226] Thereafter, the relay AP can transmit a first response frame to the first STA in response to the first frame through the second link in the first section. (S1520) The relay AP can occupy the first link through a channel access operation in the first section, and transmit the first frame received from the first STA through the occupied first link to the master AP. (S1530) Here, the relay AP may be absent from the second link during the first link operation time of the relay AP. For example, the first link operation time of the relay AP may be determined from the time when the relay AP starts the channel access operation on the first link to the time when the second response frame is received.

[0227] After that, the relay AP can receive a second response frame from the master AP. (S1540) After receiving the second response frame, the relay AP can occupy the second link based on the channel access operation on the second link, and transmit the second frame on the occupied second link. (S1550) Here, the second frame may be a frame indicating that the relay AP exists on the second link.

[0228] In addition, as an example, the above-described relay AP operating based on NSTR may include 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 for causing the relay to perform a specific operation by the at least one processor. As an example, the relay AP may be connected to a master AP via a first link and to a first STA via a second link, as described above.

[0229] For example, the first response frame, which is a response to the first frame described above, may include an indicator indicating that the relay AP is absent from the second link after transmitting the first response frame. Here, the indicator causes the channel access operation performed on the second link to be interrupted, and the interrupted channel access operation may be resumed by the second frame, as illustrated in FIG. 5.

[0230] Additionally, as an example, the relay AP may transmit a third frame on the second link after transmitting a first response frame in response to the first frame. As an example, the third frame may be a frame indicating the absence of the relay AP. Here, the first frame includes an indicator for allocating the transmission section of the first STA to the relay AP, and the relay AP may transmit the third frame on the second link based on the indicator. The third frame may be transmitted on the second link in a broadcast manner or a multicast manner, thereby allowing other non-AP STAs to recognize the absence of the relay AP, as illustrated in FIG. 6.

[0231] Additionally, as an example, the relay AP may transmit a fourth frame to the master AP on the first link. Here, the fourth frame may be a short control frame that requests the relay AP to transmit the first frame received from the first STA through the first link. After receiving a third response frame from the master AP in response to the fourth frame, the relay AP may transmit the first frame received from the first STA to the master AP on the first link after a preset time, as illustrated in FIG. 7. Additionally, the fourth frame transmitted on the first link may be transmitted simultaneously with the third frame transmitted on the second link.

[0232] In addition, as an example, the second link is a low-latency operation support link that enables reception operation of the master AP, and the relay AP can transmit the first frame received from the first STA to the master AP through the second link instead of the first link after a preset time from the time of completing transmission of the first response frame to the first STA. Here, the first frame may include an indicator for allocating a transmission section of the first STA to the relay AP. The relay AP can transmit the first frame received from the first STA to the master AP through the second link based on the indicator. In addition, the first frame transmitted by the relay AP to the master AP may further include a transmission section extension indicator for indicating extension of the transmission section allocated to the relay AP, which may be as shown in FIG. 8.

[0233] The methods according to the present disclosure may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either singly or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and configured for the present disclosure or may be known and available to those skilled in the computer software art.

[0234] Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate with at least one software module to perform the operations of the present disclosure, and vice versa.

[0235] Although the present disclosure has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

[0236]

[0237] The above may also apply to other systems.

Claims

1. In a wireless LAN system, a method for operating a relay AP that is connected to a master access point (AP) through a first link and to a first station (STA) through a second link and operates based on NSTR (Non-simultaneous Transmit and Receive), A step in which the relay AP receives a first frame from the first STA through the second link in the first section; A step in which the relay AP transmits a first response frame to the first STA in response to the first frame through the second link in the first section; A step in which the relay AP occupies the first link through a channel access operation in the first section and transmits the first frame received from the first STA on the occupied first link to the master AP, wherein the relay AP is absent from the second link during the first link operation time of the relay AP; a step in which the relay AP receives a second response frame from the master AP; and An operating method of a relay AP, comprising: a step of occupying a second link based on a channel access operation on the second link after the relay AP receives the second response frame, and transmitting a second frame on the occupied second link, wherein the second frame is a frame indicating that the relay AP exists on the second link.

2. In paragraph 1, A relay AP operating method based on the above NSTR, wherein the relay AP performs transmission on one of the first link and the second link and fails to perform reception on the other link.

3. In paragraph 2, The above relay AP performs a relay schedule negotiation procedure with the master AP, and determines relay schedule information consisting of at least one of information on a start time and a time interval during which frame transmission can be performed through the relay schedule negotiation procedure, A relay AP operation method, wherein a first section in which the relay AP performs communication with the first STA over the second link and a second section in which the relay AP performs communication with the master AP over the first link are determined based on the relay schedule information.

4. In paragraph 1, A relay AP operation method, wherein the first link operation time of the relay AP is determined from the time when the relay AP starts channel access operation on the first link to the time when the second response frame is received.

5. In paragraph 1, A method for operating a relay AP, wherein the first frame is a low-latency frame transmitted from the first STA to the master AP.

6. In paragraph 5, The first response frame, which is a response to the first frame, includes an indicator indicating that the relay AP is absent from the second link after transmission of the first response frame, and the channel access operation performed on the second link is stopped by the indicator. A relay AP operation method, wherein the interrupted channel access operation is resumed by the second frame.

7. In paragraph 5, A method for operating a relay AP, wherein the relay AP transmits a third frame on the second link after transmitting the first response frame in response to the first frame, wherein the third frame is a frame indicating that the relay AP is absent from the second link after transmitting the third frame.

8. In paragraph 7, The first frame includes an instruction for allocating a transmission section of the first STA to the relay AP, A method for operating a relay AP, wherein the relay AP transmits the third frame on the second link based on the indicator.

9. In paragraph 8, A method of operating a relay AP, wherein the third frame is transmitted on the second link by broadcast or multicast.

10. In paragraph 8, A method for operating a relay AP, wherein the relay AP transmits the fourth frame to the master AP through the first link, the fourth frame being a short control frame requesting that the relay AP transmit the first frame received from the first STA through the first link.

11. In Article 10, A method for operating a relay AP, wherein the relay AP transmits the first frame received from the first STA to the master AP through the first link after a preset time after receiving a third response frame from the master AP in response to the fourth frame.

12. In paragraph 10, A method for operating a relay AP, wherein the fourth frame transmitted on the first link is transmitted simultaneously with the third frame transmitted on the second link.

13. In paragraph 1, The above second link is a low-latency operation support link that enables the master AP to perform reception operations. A relay AP operation method, wherein the relay AP transmits the first frame received from the first STA to the master AP through the second link instead of the first link after a preset time from the time when the first response frame transmission to the first STA is completed.

14. In paragraph 13, The first frame includes an instruction for allocating a transmission section of the first STA to the relay AP, A method for operating a relay AP, wherein the relay AP forwards the first frame received from the first STA to the master AP through the second link based on the indicator.

15. In paragraph 14, A relay AP operating method, wherein the first frame transmitted by the relay AP to the master AP further includes a transmission interval extension indicator indicating an extension of the transmission interval allocated to the relay AP.

16. In a relay access point (AP) that operates based on NSTR (Non-simultaneous Transmit and Receive), At least one transceiver for transmitting and receiving signals; At least one processor controlling at least one transceiver; and A memory storing instructions causing the relay to perform a specific operation by at least one processor, The specific operation of the relay AP, which is connected to a master access point (AP) through a first link and to a first station (STA) through a second link, is: In the first section, a first frame is received from the first STA through the second link, In the first section, a first response frame is transmitted to the first STA in response to the first frame through the second link, In the first section, the relay AP occupies the first link through a channel access operation, and transmits the first frame received from the first STA on the occupied first link to the master AP, but the relay AP is absent from the second link during a preset time while the relay AP operates on the first link. Receive a second response frame from the above master AP, and A relay AP, which, after receiving the second response frame, occupies the second link based on a channel access operation on the second link, and transmits a second frame on the occupied second link, wherein the second frame is a frame indicating that the relay AP exists on the second link.

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