Method and apparatus for performing tunneling relay communication in wireless LAN

Abstract

This operating method of a relay in a wireless LAN system may comprise steps in which a relay: receives a first frame from an AP, the first frame MAC header including a first indicator indicating that the first frame is transmitted through the relay; transmits a second frame to an STA on the basis of the received first frame; receives, from the STA, a first response frame generated on the basis of the first frame, the first response frame MAC header including a second indicator indicating that the first response frame is transmitted through the relay; and transmits, to the AP, a second response frame on the basis of the first response frame.

Description

Method and device for performing tunneling relay communication in a wireless LAN

[0001] The present disclosure relates to wireless local area network (WLAN) communication technology, and relates to a method and device for increasing the communication range of a wireless LAN terminal through the operation of a wireless LAN relay terminal.

[0002]

[0003] 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.

[0004] 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.

[0005] As applications requiring higher reliability emerge, the IEEE 802.11bn standard, an Ultra High Reliability (UHR) wireless LAN technology, is being developed for single Basic Service Set (BSS) and / or redundant BSS environments. The goals of the IEEE 802.11bn standard may include supporting increased data transmission speeds, improved latency performance, and lower data error rates. Furthermore, the IEEE 802.11bn standard may support low-power operation, peer-to-peer communication, and relay communication for extended communication range.

[0006] However, when performing a relay communication operation, it is possible to consider cases where the relay communication operation is not performed smoothly. For example, a relay terminal may have limitations in recording and managing the status of packets transmitted between other wireless LAN terminals, which may increase the complexity of the relay terminal operation. Therefore, the relay terminal may not be able to relay packets correctly, and the performance of the communication range expansion operation of the wireless LAN network may be reduced. In the following, a method for performing tunneling relay communication in a wireless LAN is described, taking this into account.

[0007] Meanwhile, the technology that serves as the background for the invention is written to promote understanding of the background for 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.

[0008]

[0009] The present disclosure relates to a method and device for performing tunneling relay communication in a wireless LAN.

[0010] The present disclosure relates to a method and device for generating a tunneled packet for a relay terminal performing a relay communication operation.

[0011] The present disclosure relates to a method and device for a relay terminal performing a relay communication operation to receive a frame from a wireless LAN terminal and transmit the frame to another wireless LAN terminal.

[0012] The present disclosure relates to a method and device for determining a relay terminal to which transmission is to be made based on an artificial intelligence algorithm.

[0013] 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 can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0014]

[0015] According to one example of the present disclosure, a method for operating a relay in a wireless LAN system may include a step in which the relay receives a first frame from an access point (AP), a medium access control (MAC) header of the first frame includes a first indicator indicating that the first frame is transmitted through the relay, and a step in which the relay transmits a second frame to a station (STA) based on the first frame received, and a step in which the relay receives a first response frame generated based on the first frame from the STA, the MAC header of the first response frame includes a second indicator indicating that the first response frame is transmitted through the relay, and a step in which the relay transmits a second response frame to the AP based on the first response frame.

[0016] In addition, according to one example of the present disclosure, a relay 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 is: receiving a first frame from an access point (AP), wherein a medium access control (MAC) header of the first frame includes a first indicator indicating that the first frame is transmitted through the relay, transmitting a second frame to a station (STA) based on the received first frame, and the relay receiving a first response frame generated based on the first frame from the STA, wherein the MAC header of the first response frame includes a second indicator indicating that the first response frame is transmitted through the relay, and the relay can transmit a second response frame to the AP based on the first response frame.

[0017] Additionally, the following may be commonly applied:

[0018] According to one example of the present disclosure, when the relay performs a relay operation setup procedure with the AP and the STA before transmitting the first frame, and performs the relay operation based on the relay operation setup procedure, the MAC header of the first frame may not include the first indicator, and the MAC header of the first response frame may not include the second indicator.

[0019] Additionally, according to an example of the present disclosure, the first indicator indicating that the first frame is transmitted through a relay may be a relay address in an address field included in a MAC header of the first frame or a subfield or bit included in the MAC header of the first frame, and the second indicator indicating that the first response frame is transmitted through a relay may be a relay address in an address field included in a MAC header of the first response frame or a subfield or bit included in the MAC header of the first response frame.

[0020] Additionally, according to an example of the present disclosure, the sender address of the first frame is the address of the AP, the receiver address of the first frame is the address of the STA, the relay receives the first frame and generates a second frame, wherein the payload of the second frame includes the first frame, and the MAC header of the second frame may include a third indicator indicating that the first frame is encapsulated.

[0021] Additionally, according to an example of the present disclosure, a sender address of the first response frame is an address of an STA, a receiver address of the first response frame is an address of an AP, a relay receives the first response frame and generates a second response frame, wherein a payload of the second response frame includes the first response frame, and a MAC header of the second response frame may include a fourth indicator indicating that the first response frame is encapsulated.

[0022] Additionally, according to one example of the present disclosure, the relay may transmit the second frame after a preset time from the time of reception of the first frame.

[0023] Additionally, according to an example of the present disclosure, when the relay receives the first frame, the relay transmits a response frame for the first frame to the AP after a preset time from the time of reception of the first frame, and the relay performs a channel access operation after transmitting the response frame for the first frame to transmit the second frame in the allocated TXOP (transmit opportunity).

[0024] Additionally, according to one example of the present disclosure, the relay is a relay multi link device (MLD) including a first relay associated with a first link and a second relay associated with a second link, wherein the relay MLD can receive a first frame from an AP MLD on a first link for the first relay, and the relay MLD can transmit a second frame to a STA MLD on a second link for the second relay.

[0025] Additionally, according to an example of the present disclosure, if the relay MLD successfully decodes the first frame or the relay MLD detects the transmission of the first frame on the first link for the first relay, the relay MLD may perform a channel access operation on the second link for the second relay to transmit the second frame in the allocated transmit opportunity (TXOP).

[0026] Additionally, according to one example of the present disclosure, the TXOP allocated in the second link may be set to a time equal to or longer than the time at which the relay MLD transmits one or more second frames, the time at which the first response frame is received from the STA MLD, the time at which the second response frame is transmitted to the AP MLD, and the interval time between frame transmissions.

[0027] Additionally, according to an example of the present disclosure, the sender address of the first frame received by the relay may be the address of the AP, the receiver address of the first frame may be the address of the relay, and the relay may receive the first frame to generate a second frame, wherein the sender address of the second frame may be the address of the AP, and the receiver address of the second frame may be the address of the STA.

[0028] Additionally, according to one example of the present disclosure, the relay generates a second frame through an original frame of the AP included in the payload of the first frame, the second frame being a frame with a modified MAC header from the original frame of the AP, wherein the MAC header of the second frame may include a fifth indicator indicating that the original frame of the AP is transmitted through the relay.

[0029] Additionally, according to an example of the present disclosure, the sender address of the first response frame received by the relay may be the address of the STA, the receiver address of the first frame may be the address of the relay, and the relay may receive the first response frame and generate a second response frame, wherein the sender address of the second response frame may be the address of the STA, and the receiver address of the second frame may be the address of the AP.

[0030] Additionally, according to one example of the present disclosure, the relay generates a second response frame through an original response frame of the STA included in the payload of the first response frame, and the second response frame is a frame in which a MAC header is modified from the original response frame of the STA, and the MAC header of the second response frame may include a sixth indicator indicating that the original response frame of the STA is transmitted through the relay.

[0031] Additionally, according to an example of the present disclosure, the relay may generate a second frame identical to the first frame based on bits obtained through decoding and error correction after receiving the first frame and transmit the second frame to the STA, and the relay may generate a second response frame identical to the first response frame based on bits obtained through decoding and error correction after receiving the first response frame and transmit the second response frame to the AP.

[0032] Additionally, according to an example of the present disclosure, the relay may wait for a preset time from the end time of retransmission of the first frame after receiving the first frame, and may then generate a second frame identical to the first frame based on bits obtained through decoding and error correction of the first frame and transmit the second frame to the STA without performing a relay operation negotiation procedure with the AP and the STA.

[0033]

[0034] According to the present disclosure, a method for performing tunneling relay communication in a wireless LAN can be provided.

[0035] According to the present disclosure, a method for generating a tunneled packet for a relay terminal performing a relay communication operation can be provided.

[0036] According to the present disclosure, a method can be provided in which a relay terminal performing a relay communication operation receives a frame from a wireless LAN terminal and transmits the frame to another wireless LAN terminal.

[0037] According to the present disclosure, a method for determining a relay terminal to which transmission is to be made based on an artificial intelligence algorithm can be provided.

[0038] 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.

[0039]

[0040] Figure 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure is applied.

[0041] Figure 2 is a diagram showing a wireless LAN system to which the present disclosure is applied.

[0042] FIG. 3 is a diagram illustrating a machine learning unit to which the present disclosure is applied.

[0043] FIG. 4 is a flowchart illustrating a method for performing communication based on a machine learning unit to which the present disclosure is applied.

[0044] FIGS. 5A to 5C are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied.

[0045] FIG. 6a and FIG. 6b are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied.

[0046] FIG. 7a and FIG. 7b are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied.

[0047] FIG. 8a and FIG. 8b are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied.

[0048] Figure 9 is a flowchart of a method for performing a relay communication operation to which the present disclosure applies.

[0049]

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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."

[0057] 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 megahertz (MHz), 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.

[0058] 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.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] As another example, the machine learning unit (300) may be designed to additionally implement other machine learning algorithms in addition to the above-described 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 algorithm may be performed by the ML processor (310) based on the machine learning model.

[0066] 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).

[0067] 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.

[0068] 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 coordination function) 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.

[0069] 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.

[0070] 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).

[0071] 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.

[0072] In the disclosures of FIGS. 5A to 9 below, a case where a frame to be transmitted from an AP (access point) to a STA (station) is generated and relayed via a relay is described based on the case. That is, although the description is based on the case where transmission is performed from an AP to a STA, this is for the convenience of explanation and is not limited to the embodiment. For example, the operations of the present disclosure below may be equally applied even when the entities and link directions are different. As a specific example, even when a frame to be transmitted from an STA to an AP is generated and relayed via a relay, the present disclosure below may be equally applied. As another example, it may be obvious that the present disclosure below may equally apply when a frame to be transmitted between APs as different entities is relayed via a relay, or when a frame to be transmitted between STAs is generated and relayed via a relay. That is, the operations described below may be for the convenience of explanation of the relay communication to which the present disclosure is applied, and may not be limited thereto.

[0073] FIGS. 5A to 5C are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied. Referring to FIGS. 5A to 5C, wireless LAN terminals (e.g., AP (access point), Relay (Relay STA), STA (station)) may operate in a wireless LAN network. For example, in FIGS. 5A and 5B , a case may be considered where AP 1-1 (510), Relay 1-1 (520), and STA 1-1 (530) operate in a wireless LAN network, but this is for convenience of explanation and may not be limited thereto. In addition, in FIG. 5C, the AP, Relay, and STA may be referred to as an MLD (multi-link device) supporting multi-link operation, and may be referred to as an AP MLD, a Relay MLD, and a STA MLD. An MLD may be a wireless LAN terminal having a separate MAC layer (MLD lower MAC sublayer) and a PHY layer for each link (e.g., a first link, a second link, etc.). Above the link-specific MAC layer of the MLD, there may be a MAC layer (MLD upper MAC sublayer) that integrates the link-specific MAC layers. Here, the link-specific AP or STA may operate below the AP MLD, STA MLD, and Relay MLD. For example, the AP of AP MLD 1 operating in the first link may be referred to as AP 1-1 of AP MLD 1, and the AP of AP MLD 1 operating in the second link may be referred to as AP 1-2 of AP MLD 1. In addition, the STA of STA MLD 1 operating in the first link may be referred to as STA 1-1 of STA MLD 1, and the STA of STA MLD 1 operating in the second link may be referred to as STA 1-2 of STA MLD 1. Additionally, the Relay of Relay MLD 1 operating on the first link may be referred to as Relay 1-1 of Relay MLD 1, and the Relay of Relay MLD 1 operating on the second link may be referred to as Relay 1-2 of Relay MLD 1.The operations of APs or STAs under the MLD may be operations of the MLD, and the operations of the MLD may be operations of the lower APs or STAs. Fig. 5c is merely an example for convenience of explanation and may not be limited to the corresponding operations.

[0074] Referring to FIGS. 5A and 5B, AP 1-1 (510), Relay 1-1 (520), and STA 1-1 (530) can perform settings for relay communication operation in advance. That is, in FIGS. 5A and 5B, AP 1-1 (510), Relay 1-1 (520), and STA 1-1 (530) can complete settings for relay communication operation in advance. AP 1-1 (510), Relay 1-1 (520), and STA 1-1 (530) can recognize that they are performing relay communication operation through the above-described settings.

[0075] Also, referring to FIG. 5c, AP MLD 1, Relay MLD 1, and STA MLD 1 can perform settings for relay communication operation in advance. That is, in FIG. 5c, AP MLD 1, Relay MLD 1, and STA MLD 1 can complete settings for relay communication operation in advance. AP MLD 1, Relay MLD 1, and STA MLD 1 can recognize that they perform relay communication operation through the above-described settings. However, FIGS. 5a to 5c are only for convenience of explanation and are not limited to the embodiment, and can be equally applied to other cases.

[0076] Referring to FIG. 5a, AP 1-1 (510) may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (530). The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (510) may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation, and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (510) may want to transmit a frame to STA 1-1 (530) within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance. The duration of the MAC header corresponding to the TXOP set by AP 1-1 (510) may be set to a time equal to or greater than the sum of the data frame transmission time from AP 1-1 (510) to Relay 1-1 (520), the encapsulated frame transmission time from Relay 1-1 (520) to STA 1-1 (530), the response frame (BlockAck) transmission time of STA 1-1 (530), the encapsulated response frame transmission time of Relay 1-1 (520), and the interval between transmissions of each frame (e.g. SIFS time).

[0077] The transmitter address of the MAC header included in the frame transmitted by AP 1-1 (510) may be set to the MAC address of AP 1-1 (510), and the receiver address may be set to the MAC address of STA 1-1 (530). The MAC header included in the frame transmitted by AP 1-1 (510) may include an indicator indicating that the frame is transmitted (eg, relayed) through Relay 1-1 (520). The indicator indicating that the frame is relayed through Relay 1-1 (520) may be the MAC address of the Relay included in the address field of the MAC header (eg, the MAC address of Relay 1-1 (520) included in the Address 4 field). That is, when the MAC address of the Relay is included in the address field of the MAC header, the frame may be indicated to be relayed through Relay 1-1 (520). Alternatively, the indicator indicating that the frame is to be relayed through Relay 1-1 (520) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field), and whether the frame is to be relayed through Relay 1-1 (520) may be indicated through that subfield or bit.

[0078] As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) have preset relay communication operations, Relay 1-1 (520) can recognize that the frame transmitted by AP 1-1 (510) to STA 1-1 (530) should be relayed. Considering the above, since an indicator indicating that the frame is relayed is unnecessary, the MAC header of the frame transmitted by AP 1-1 (510) may not include the indicator.

[0079] Referring to FIG. 5A, the payload of the frame (501-1) transmitted by AP 1-1 (510) may be MSDU 1. Here, Relay 1-1 (520) may receive the frame (501-1) including MSDU 1 from AP 1-1 (510). Relay 1-1 (520) may add a MAC header in which the transmitter address is the MAC address of Relay 1-1 (520) and the receiver address is STA 1-1 (530) to the received frame (501-1). That is, the payload of the frame (501-2) generated by Relay 1-1 (520) may be the frame transmitted by AP 1-1 (510) (the entire frame including the MAC header, 501-1). For example, the operation of Relay 1-1 (520) adding a MAC header to the frame (501-1) of AP 1-1 (510) is an encapsulation operation, and the frame to which Relay 1-1 (520) adds a MAC header may be an encapsulated frame (501-2), but may not be limited to that name.

[0080] Relay 1-1 (520) can transmit an encapsulated frame (501-2) to STA 1-1 (530) after a short interframe space (SIFS) from the time of completion of reception of the frame (501-1) transmitted by AP 1-1 (510). Since Relay 1-1 (520) transmits the encapsulated frame (501-2) after a SIFS, AP 1-1 (510) can regard the encapsulated frame (501-2) of Relay 1-1 (520) as an immediate response frame.

[0081] For example, Relay 1-1 (520) may not be able to transmit a frame due to a network allocation vector (NAV) corresponding to the TXOP acquired by AP 1-1 (510). However, Relay 1-1 (520) may regard the encapsulated frame (501-2) as an immediate response frame to the frame (501-1) of AP 1-1 (510). Therefore, Relay 1-1 (520) may transmit the encapsulated frame (501-2) to STA 1-1 (530) regardless of the NAV setting. Alternatively, Relay 1-1 (520) may not set NAV when receiving a frame with receiver address STA 1-1 (530). Here, AP 1-1 (510) may not update its BlockAck scoreboard until it receives a response frame (e.g., BlockAck frame) from STA 1-1 (530). That is, the receiver of the frame does not determine that it has received the frame.

[0082] Also, as an example, the MAC header added by Relay 1-1 (520) may include an indicator indicating that the frame is encapsulated. As a specific example, the MAC address of AP 1-1 (510) may be included in the address 4 field of the MAC header added by Relay 1-1 (520) to indicate that the frame is encapsulated. Alternatively, the indicator indicating that the frame is encapsulated may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate that the frame is encapsulated. As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) set up relay communication operation in advance, STA 1-1 (530) may recognize that the frame transmitted by Relay 1-1 (520) to STA 1-1 (530) is encapsulated, and thus a separate indicator may not be necessary.

[0083] STA 1-1 (530) can receive an encapsulated frame (501-2) from Relay 1-1 (520). STA 1-1 (530) can recognize that the frame of Relay 1-1 (520) is encapsulated based on an indicator indicating that the frame is encapsulated or a configured relay communication operation. STA 1-1 (530) can receive the encapsulated frame (501-2) from Relay 1-1 (520) and decapsulate the encapsulated frame (501-2). STA 1-1 (530) can receive (decode) MSDU 1 by confirming (e.g., receiving, decoding, error checking) the frame (501-1) of AP 1-1 (510), which is the payload of the encapsulated frame (501-2) through decapsulation. STA 1-1 (530) may transmit a response frame (502-1) to AP 1-1 (510) after SIFS time from the time of completion of reception of the encapsulated frame (501-2) of Relay 1-1 (520). The response frame (502-1) may be a BlockAck (BA) frame indicating the reception status of the frame transmitted by AP 1-1 (510). STA 1-1 (530) may set the transmitter address of the MAC header of the response frame (502-1) to the MAC address of STA 1-1 (530) and set the receiver address to the MAC address of AP 1-1 (510). The MAC header included in the response frame (502-1) transmitted by STA 1-1 (530) may include an indicator indicating that the frame is transmitted (eg relayed) via Relay 1-1 (520). For example, an indicator indicating that a frame is relayed through Relay 1-1 (520) may be the MAC address of the Relay included in the address field of the MAC header (e.g., the MAC address of Relay 1-1 (520) included in the Address 4 field). That is, if the MAC address of the Relay is included in the address field of the MAC header, it may be indicated that a frame is relayed through Relay 1-1 (520).Alternatively, the indicator indicating that the frame is relayed through Relay 1-1 (520) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether or not the frame is relayed. As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) have previously set up relay communication operation, Relay 1-1 (520) can recognize that the frame that STA 1-1 (530) transmits to AP 1-1 (510) should be relayed. Considering the above, the indicator indicating that the frame is relayed may be unnecessary. Therefore, the MAC header of the frame transmitted by STA 1-1 (530) may not include the indicator indicating that the frame is relayed.

[0084] Relay 1-1 (520) can receive a frame (response frame, BlockAck frame, 502-1) from STA 1-1 (530). Relay 1-1 (520) can add a MAC header in which the transmitter address is the MAC address of Relay 1-1 (520) and the receiver address is AP 1-1 (510) to the received frame (502-1). The payload of the frame (502-2) generated by Relay 1-1 (520) can be the response frame (the entire frame including the MAC header, 502-1) transmitted by STA 1-1 (530). That is, Relay 1-1 (520) can perform an encapsulation operation to encapsulate the response frame (502-1) of STA 1-1 (530). Relay 1-1 (520) can transmit an encapsulated response frame (502-2) to AP 1-1 (510) after SIFS time from the time when it completes receiving the frame (502-1) from STA 1-1 (530). The MAC header added by Relay 1-1 (520) may include an indicator indicating that the frame is encapsulated. For example, the MAC address of STA 1-1 (530) may be included in the address 4 field of the MAC header added by Relay 1-1 (520) to indicate that the frame is encapsulated. Alternatively, the indicator indicating that the frame is encapsulated may be indicated as a separate subfield or bit (e.g., an indicator included in the HT Control field). As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) have preset relay communication operations, AP 1-1 (510) can recognize that the frame transmitted by Relay 1-1 (520) to AP 1-1 (510) is encapsulated, and thus a separate indicator may not be necessary.

[0085] AP 1-1 (510) can receive an encapsulated frame (502-2) from Relay 1-1 (520). AP 1-1 (510) can recognize that the frame of Relay 1-1 (520) is encapsulated based on an indicator indicating that the frame is encapsulated or a configured relay communication operation. AP 1-1 (510) can decapsulate the encapsulated frame (502-2). AP 1-1 (510) can receive a frame (response frame, BlockAck frame) of STA 1-1 (530), which is the payload of the encapsulated frame (502-2), and AP 1-1 (510) can check the reception status of the frame transmitted by AP 1-1 (510) to STA 1-1 (530). AP 1-1 (510) updates the BlockAck scoreboard based on the response frame (e.g. BlockAck frame) of STA 1-1 (530) and can retransmit frames if there are frames that failed to be transmitted.

[0086] For example, a frame received by Relay 1-1 (520) from AP 1-1 (510) may contain an error. If Relay 1-1 (520) receives a frame containing an error, Relay 1-1 (520) may not encapsulate the frame containing the error. Relay 1-1 (520) may not respond to AP 1-1 (510) or may transmit a frame requesting retransmission of the frame from AP 1-1 (510) (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay 1-1 (520) may retransmit the frame containing the error from AP 1-1 (510) and transmit the frame to STA 1-1 (530) after receiving the frame without an error, or if the retransmission of the frame containing the error is not received, the frame containing the error may be discarded.

[0087] As another example, STA 1-1 (530) may be able to receive (decode) frames transmitted by AP 1-1 (510). However, if STA 1-1 (530), AP 1-1 (510), and Relay 1-1 (520) have performed relay communication operation setup, STA 1-1 (530) may not directly respond to AP 1-1 (510) even if it receives frames from AP 1-1 (510).

[0088] As another example, Relay 1-1 (520) may transmit the encapsulated frame to STA 1-1 (530) when the medium is idle for a priority interframe space (PIFS) time instead of transmitting the encapsulated frame to STA 1-1 (530) after SIFS from the time when AP 1-1 (510) completes receiving the data frame. Alternatively, Relay 1-1 (520) may transmit the encapsulated frame to STA 1-1 (530) when the medium is idle for a PIFS time + 'a' from the time when AP 1-1 (510) completes receiving the data frame. The above-described operation is to check whether the frame transmitted by AP 1-1 (510) to STA 1-1 (530) is retransmitted. If the PIFS time + 'a' time has elapsed from the time of completion of receiving the frame, Relay 1-1 (520) may consider that AP 1-1 (510) does not retransmit the frame and waits for Relay 1-1 (520) to relay the frame. Here, 'a' time may be aSlotTime or a shorter or longer time, and may not be limited to a specific form.

[0089] As another example, when AP 1-1 (510) transmits to STA 1-1 (530) via Relay 1-1 (520), AP 1-1 (510) may not perform PIFS recovery operation. That is, even if AP 1-1 (510) transmits a frame and no response frame is received until after PIFS, AP 1-1 (510) may not perform frame retransmission. The above-described operations may be operations to prevent transmission collisions with frames that Relay 1-1 (520) encapsulates and transmits to STA 1-1 (530).

[0090] As another example, consider a case where STA 1-1 (530) can receive (decode) a frame from AP 1-1 (510). If STA 1-1 (530), AP 1-1 (510), and Relay 1-1 (520) perform relay communication operation setup, STA 1-1 (530) may store the received frame in a buffer when it receives the frame from AP 1-1 (510) and may not directly respond to AP 1-1 (510). Here, STA 1-1 (530) may additionally receive a data frame transmitted through Relay 1-1 (520). STA 1-1 (530) may configure a data frame using the data frame received from AP 1-1 (510) and the data frame received from Relay 1-1 (520). For example, if the received data frame is an A-MPDU, the MPDU in which an error occurred may be different between the A-MPDU received from AP 1-1 (510) and the A-MPDU received from Relay 1-1 (520). STA 1-1 (530) can recover the data frame through MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP 1-1 (510) through Relay 1-1 (520).

[0091] Referring to FIG. 5b, AP 1-1 (510) may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (530). The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (510) may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation, and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (510) may want to transmit a frame to STA 1-1 (530) within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance. The duration of the MAC header corresponding to the TXOP set by AP 1-1 (510) may be set to a time equal to or greater than the sum of the data frame transmission time from AP 1-1 (510) to Relay 1-1 (520), the response frame (BlockAck, ACK) transmission time of Relay 1-1 (520), and the interval between transmissions of each frame (e.g. SIFS time).

[0092] The transmitter address of the MAC header included in the frame (503-1) transmitted by AP 1-1 (510) may be set to the MAC address of AP 1-1 (510), and the receiver address may be set to the MAC address of STA 1-1 (530). The MAC header included in the frame (503-1) transmitted by AP 1-1 (510) may include an indicator indicating that the frame is transmitted (eg, relayed) through Relay 1-1 (520). The indicator indicating that the frame is relayed through Relay 1-1 (520) may be the MAC address of the Relay included in the address field of the MAC header (eg, the MAC address of Relay 1-1 (520) included in the Address 4 field). That is, when the MAC address of the Relay is included in the address field of the MAC header, the frame may be indicated to be relayed through Relay 1-1 (520). Alternatively, an indicator indicating that the frame is to be relayed through Relay 1-1 (520) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field), and whether the frame is to be relayed through Relay 1-1 (520) may be indicated through that subfield or bit.

[0093] As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) have preset relay communication operations, Relay 1-1 (520) can recognize that the frame transmitted by AP 1-1 (510) to STA 1-1 (530) should be relayed. Considering the above, since an indicator indicating that the frame is relayed is unnecessary, the MAC header of the frame transmitted by AP 1-1 (510) may not include the indicator.

[0094] Referring to FIG. 5B, the payload of the frame (503-1) transmitted by AP 1-1 (510) may be MSDU 1. Here, Relay 1-1 (520) may receive the frame (503-1) including MSDU 1 from AP 1-1 (510). Relay 1-1 (520) may add a MAC header in which the transmitter address is the MAC address of Relay 1-1 (520) and the receiver address is STA 1-1 (530) to the received frame (503-1). That is, the payload of the frame (503-2) generated by Relay 1-1 (520) may be the frame transmitted by AP 1-1 (510) (the entire frame including the MAC header, 503-1). For example, the operation of Relay 1-1 (520) adding a MAC header to the frame (503-1) of AP 1-1 (510) is an encapsulation operation, and the frame to which Relay 1-1 (520) adds a MAC header may be an encapsulated frame (503-2), but may not be limited to that name.

[0095] Relay 1-1 (520) can transmit an ACK (acknowledgement) frame (504) to AP 1-1 (510) after a short interframe space (SIFS) from the time of completion of reception of the frame (503-1) transmitted by AP 1-1 (510). Since Relay 1-1 (520) transmits the ACK frame (540) after SIFS, AP 1-1 (510) can regard the ACK frame (504) of Relay 1-1 (520) as an immediate response frame. For example, Relay 1-1 (520) may be unable to transmit a frame due to a NAV corresponding to the TXOP acquired by AP 1-1 (510). However, Relay 1-1 (520) may regard the ACK frame (504) as an immediate response frame to the frame of AP 1-1 (510). Therefore, Relay 1-1 (520) may transmit the ACK frame (504) to AP 1-1 (510) regardless of the NAV setting. Alternatively, Relay 1-1 (520) may not set the NAV when receiving a frame whose receiver address is STA 1-1 (530). Here, AP 1-1 (510) may not update the BlockAck scoreboard of AP 1-1 (510) until it receives a response frame (e.g., BlockAck frame) of STA 1-1 (530). That is, the receiver of the frame does not determine that it has received the frame.

[0096] Relay 1-1 (520) can transmit the encapsulated frame (503-2) to STA 1-1 (530) based on a separate TXOP (transmit opportunity). Relay 1-1 (520) transmitting the frame based on the separate TXOP may mean that Relay 1-1 (520) transmits the frame in the TXOP acquired by performing a new channel access operation. The TXOP may be a communication section in which transmission of multiple frames is possible. Since Relay 1-1 (520) must transmit the encapsulated frame (503-2) in a separate TXOP, Relay 1-1 (520) can perform a channel access operation (e.g., EDCA backoff operation). Relay 1-1 (520) can transmit the encapsulated frame (503-2) when the channel access operation is successful (completed) and the channel is occupied.

[0097] Also, as an example, the MAC header added by Relay 1-1 (520) may include an indicator indicating that the frame is encapsulated. As a specific example, the MAC address of AP 1-1 (510) may be included in the address 4 field of the MAC header added by Relay 1-1 (520) to indicate that the frame is encapsulated. Alternatively, the indicator indicating that the frame is encapsulated may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate that the frame is encapsulated. As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) set up relay communication operation in advance, STA 1-1 (530) may recognize that the frame transmitted by Relay 1-1 (520) to STA 1-1 (530) is encapsulated, and thus a separate indicator may not be necessary.

[0098] STA 1-1 (530) can receive an encapsulated frame (503-2) from Relay 1-1 (520). STA 1-1 (530) can recognize that the frame of Relay 1-1 (520) is encapsulated based on an indicator indicating that the frame is encapsulated or a configured relay communication operation. STA 1-1 (530) can receive the encapsulated frame (503-2) from Relay 1-1 (520) and decapsulate the encapsulated frame (503-2). STA 1-1 (530) can receive (decode) MSDU 1 by confirming (e.g., receiving, decoding, error checking) the frame (503-1) of AP 1-1 (510), which is the payload of the encapsulated frame (503-2) through decapsulation. STA 1-1 (530) can transmit a response frame (505-1) to AP 1-1 (510) after SIFS time from the time of completion of reception of the encapsulated frame (503-2) of Relay 1-1 (520). The response frame (505-1) may be a BlockAck (BA) frame indicating the reception status of the frame transmitted by AP 1-1 (510). STA 1-1 (530) can set the transmitter address of the MAC header of the response frame (505-1) to the MAC address of STA 1-1 (530) and set the receiver address to the MAC address of AP 1-1 (510). The MAC header included in the response frame (505-1) transmitted by STA 1-1 (530) may include an indicator indicating that the frame is transmitted (eg relayed) via Relay 1-1 (520). For example, an indicator indicating that a frame is relayed through Relay 1-1 (520) may be the MAC address of the Relay included in the address field of the MAC header (e.g., the MAC address of Relay 1-1 (520) included in the Address 4 field). That is, if the MAC address of the Relay is included in the address field of the MAC header, it may be indicated that a frame is relayed through Relay 1-1 (520).Alternatively, the indicator indicating that the frame is to be relayed via Relay 1-1 (520) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether or not to relay.

[0099] As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) have previously set up relay communication operation, Relay 1-1 (520) can recognize that the frame transmitted by STA 1-1 (530) to AP 1-1 (510) should be relayed. Considering the above, an indicator indicating that the frame is relayed may be unnecessary. Accordingly, the MAC header of the frame transmitted by STA 1-1 (530) may not include an indicator indicating that the frame is relayed.

[0100] Relay 1-1 (520) can receive a frame (response frame, BlockAck frame, 505-1) from STA 1-1 (530). Relay 1-1 (520) can add a MAC header in which the transmitter address is the MAC address of Relay 1-1 (520) and the receiver address is AP 1-1 (510) to the received frame (505-1). The payload of the frame (505-2) generated by Relay 1-1 (520) can be the response frame (the entire frame including the MAC header, 505-1) transmitted by STA 1-1 (530). That is, Relay 1-1 (520) can perform an encapsulation operation to encapsulate the response frame of STA 1-1 (530).

[0101] Relay 1-1 (520) may transmit a frame in a separate TXOP after receiving a frame from STA 1-1 (530). Relay 1-1 (520) transmitting a frame in a separate TXOP may mean that Relay 1-1 (520) transmits a frame in a TXOP acquired by performing a new channel access operation. If Relay 1-1 (520) succeeds (completes) the channel access operation (e.g., EDCA backoff operation) and occupies the channel, Relay 1-1 (520) may transmit an encapsulated response frame (505-2) to AP 1-1 (510). The MAC header added by Relay 1-1 (520) may include an indicator indicating that the frame is encapsulated (or relayed). For example, the MAC address of STA 1-1 (530) may be included in the address 4 field of the MAC header added by Relay 1-1 (520) to indicate that the frame is encapsulated. Alternatively, the indicator indicating that the frame is encapsulated may be indicated by a separate subfield or bit (e.g., an indicator included in the HT Control field). As another example, since AP 1-1 (510), STA 1-1 (530), and Relay 1-1 (520) have preset relay communication operations, AP 1-1 (510) can recognize that the frame transmitted by Relay 1-1 (520) to AP 1-1 (510) is encapsulated, and thus, a separate indicator may be unnecessary.

[0102] AP 1-1 (510) can receive an encapsulated frame (505-2) from Relay 1-1 (520). AP 1-1 (510) can recognize that the frame of Relay 1-1 (520) is encapsulated based on an indicator indicating that the frame is encapsulated or a configured relay communication operation. AP 1-1 (510) can decapsulate the encapsulated frame (505-2). AP 1-1 (510) can receive a frame (response frame, BlockAck frame, 505-1) of STA 1-1 (530), which is the payload of the encapsulated frame (505-2), and AP 1-1 (510) can check the reception status of the frame transmitted by AP 1-1 (510) to STA 1-1 (530). AP 1-1 (510) updates the BlockAck scoreboard based on the response frame (e.g. BlockAck frame) of STA 1-1 (530) and can retransmit frames if there are frames that failed to be transmitted.

[0103] For example, a frame received by Relay 1-1 (520) from AP 1-1 (510) may contain an error. If Relay 1-1 (520) receives a frame containing an error, Relay 1-1 (520) may not encapsulate the frame containing the error. For example, Relay 1-1 (520) may not respond to AP 1-1 (510) or may transmit a frame requesting retransmission of the frame from AP 1-1 (510) (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay 1-1 (520) may retransmit the frame containing the error from AP 1-1 (510) and transmit the frame to STA 1-1 (530) after receiving the frame without an error, or if the retransmission of the frame containing the error is not received, the frame containing the error may be discarded.

[0104] As another example, STA 1-1 (530) may be able to receive (decode) frames transmitted by AP 1-1 (510). If STA 1-1 (530), AP 1-1 (510), and Relay 1-1 (520) perform relay communication operation setup, STA 1-1 (530) may not directly respond to AP 1-1 (510) even if it receives a frame from AP 1-1 (510).

[0105] As another example, Relay 1-1 (520) may detect a response frame transmitted by STA 1-1 (530) to AP 1-1 (510) while performing a channel access operation after completing reception of a data frame from AP 1-1 (510). Here, Relay 1-1 (520) may perform any one of the operations in Table 1 below.

[0106] [Table 1]

[0107]

[0108]

[0109] Specifically, Relay 1-1 (520) can transmit encapsulated frames to STA 1-1 (530). That is, frames destined for STA 1-1 (530) can be duplicated. Here, if frames transmitted to STA 1-1 (530) are duplicated, communication stability can be improved. As another example, Relay 1-1 (520) may not transmit encapsulated frames to STA 1-1 (530). That is, Relay 1-1 (520) can avoid wasting unnecessary communication resources by not transmitting encapsulated frames.

[0110] As another example, when AP 1-1 (510) transmits to STA 1-1 (530) via Relay 1-1 (520), AP 1-1 (510) may not perform PIFS recovery operation. That is, even if AP 1-1 (510) transmits a frame and no response frame is received until after PIFS, AP 1-1 (510) may not perform frame retransmission. The above-described operations may be operations to prevent transmission collisions with frames that Relay 1-1 (520) encapsulates and transmits to STA 1-1 (530).

[0111] As another example, consider a case where STA 1-1 (530) can receive (decode) a frame from AP 1-1 (510). If STA 1-1 (530), AP 1-1 (510), and Relay 1-1 (520) perform relay communication operation setup, STA 1-1 (530) may store the received frame in a buffer when it receives the frame from AP 1-1 (510) and may not directly respond to AP 1-1 (510). Here, STA 1-1 (530) may additionally receive a data frame transmitted through Relay 1-1 (520). STA 1-1 (530) may configure a data frame using the data frame received from AP 1-1 (510) and the data frame received from Relay 1-1 (520). For example, if the received data frame is an A-MPDU, the MPDU in which an error occurred may be different between the A-MPDU received from AP 1-1 (510) and the A-MPDU received from Relay 1-1 (520). STA 1-1 (530) can recover the data frame through MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP 1-1 (510) through Relay 1-1 (520).

[0112] Referring to FIG. 5c, AP 1-1 (540) of AP MLD 1 operating in the first link may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (560) of STA MLD 1. The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (540) of AP MLD 1 may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation, and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (540) of AP MLD 1 may want to transmit a frame to STA 1-1 (560) of STA MLD within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance. The duration of the MAC header corresponding to the TXOP set by AP 1-1 (540) of AP MLD 1 may be set to a time equal to or greater than the sum of the transmission time of one or more data frames transmitted from AP 1-1 (540) of AP MLD 1 to Relay 1-1 (550) of Relay MLD 1, the transmission time of a response frame (BlockAck) of Relay 1-1 (550) of Relay MLD 1, and the interval between transmissions of each frame (e.g. SIFS time).

[0113] The transmitter address of the MAC header included in the frame transmitted by AP 1-1 (540) of AP MLD 1 may be set to the MAC address of AP 1-1 (540) of AP MLD 1, and the receiver address may be set to the MAC address of STA 1-1 (560) of STA MLD 1. The MAC header included in the frame transmitted by AP 1-1 (540) of AP MLD 1 may include an indicator indicating that the frame is transmitted (eg, relayed) through Relay MLD 1. The indicator indicating that the frame is relayed through Relay MLD 1 may be the MAC address of the Relay included in the address field of the MAC header (eg, the MAC address of at least one of Relay MLD 1, Relay 1-1 of Relay MLD 1, and Relay 1-2 of Relay MLD 1 included in the Address 4 field). That is, if the address field of the MAC header contains the MAC address of Relay MLD 1, it can be indicated that the frame is relayed through Relay MLD 1. Alternatively, the indicator indicating that the frame is relayed through Relay MLD 1 can be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether the frame is relayed through Relay MLD 1.

[0114] As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have preset relay communication operations, Relay 1-1 (550) of Relay MLD 1 can recognize that the frame transmitted by AP 1-1 (540) of AP MLD 1 to STA 1-1 (560) of STA MLD 1 should be relayed. Considering the above, since an indicator indicating that the frame is relayed is unnecessary, the MAC header of the frame transmitted by AP 1-1 (540) of AP MLD 1 may not include the indicator.

[0115] Referring to FIG. 5c, the payload of a frame transmitted by AP 1-1 (540) of AP MLD 1 may be MSDU 1. Here, Relay 1-1 (550) of Relay MLD 1 may receive a frame including MSDU 1 from AP 1-1 (540) of AP MLD 1. Relay MLD 1 may want to transmit the received frame to STA MLD 1 on the second link. That is, Relay MLD 1 may want to transmit the frame received on the first link to STA 1-2 (590) of STA MLD 1 through Relay 1-2 (580) of Relay MLD 1 on the second link.

[0116] As another example, consider a case where Relay MLD 1 receives a frame transmitted from AP MLD 1 to STA MLD 1 on the first link, and then the first link is busy. Relay MLD 1 may know that among the available first and second links, the second link is idle, or the busy state of the second link ends sooner among the first and second links. Therefore, Relay MLD 1 may not transmit the encapsulated frame from the first link to STA 1-1 (560) of STA MLD 1 through Relay 1-1 (550) of Relay MLD 1. In the above-described situation, Relay MLD 1 may want to transmit an encapsulated frame to STA 1-2 (590) of STA MLD 1 on the second link via Relay 1-2 (580) of Relay MLD 1, but may not be limited to the embodiment.

[0117] If Relay MLD 1 successfully decodes MSDU 1, Relay 1-2 (580) of Relay MLD 1 can immediately perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the second link. If the channel access operation of Relay 1-2 (580) of Relay MLD 1 is successful, EDCA TXOP, which is a communication section, can be acquired on the second link. Alternatively, if Relay MLD 1 detects a frame transmitted on the first link, Relay 1-2 (580) of Relay MLD 1 can immediately perform a channel access operation. Relay 1-2 (580) of Relay MLD 1 can wait for transmission without transmitting a frame until decoding of MSDU 1 is successfully performed. The duration of the MAC header corresponding to the TXOP set by Relay 1-2 (580) of Relay MLD 1 may be set to a time equal to or greater than the sum of the transmission time of one or more encapsulated data frames transmitted from Relay 1-2 (580) of Relay MLD 1 to STA 1-2 (590) of STA MLD 1, the transmission time of a response frame (BlockAck) of STA 1-2 (590) of STA MLD 1, the transmission time of the response frame of STA 1-2 (590) of STA MLD 1 encapsulated by Relay 1-2 (580) of Relay MLD 1, and the interval between transmissions of each frame (e.g. SIFS time). EDCA TXOP of Relay 1-2 (580) of Relay MLD 1 can be used by Relay 1-2 (580) of Relay MLD 1 to transmit frames of AP MLD 1 to STA MLD 1.Relay 1-2 (580) of Relay MLD 1 can add a MAC header whose transmitter address is the MAC address of Relay 1-2 of Relay MLD 1 and whose receiver address is STA 1-2 of STA MLD 1 to a frame received from AP 1-1 (540) of AP MLD 1. The payload of the frame generated by Relay 1-2 (580) of Relay MLD 1 may be a frame (the entire frame including the MAC header) transmitted by AP 1-1 (540) of AP MLD 1. The operation of Relay 1-2 (580) of Relay MLD 1 adding a MAC header to the frame of AP 1-1 (540) of AP MLD 1 is an encapsulation operation, and the frame to which Relay 1-2 (580) of Relay MLD 1 adds a MAC header may be an encapsulated frame. However, it may not be limited to that name.

[0118] When Relay MLD 1 completes receiving a frame transmitted by AP 1-1 (540) of AP MLD 1 in the first link, Relay MLD 1 can transmit the encapsulated frame in the TXOP of the second link to STA 1-2 (590) of STA MLD 1. The MAC header added by Relay 1-2 (580) of Relay MLD 1 may include an indicator indicating that the frame is encapsulated (or relayed). For example, the MAC address of at least one of AP MLD 1, AP 1-1 of AP MLD 1, and AP 1-2 of AP MLD 1 may be included in the address 4 field of the MAC header added by Relay 1-2 (580) of Relay MLD 1. That is, if the address 4 field of the MAC header added by Relay 1-2 (580) of Relay MLD 1 contains the MAC address of at least one of AP MLD 1, AP 1-1 of AP MLD 1, and AP 1-2 of AP MLD 1, it may be indicated that the frame is encapsulated. Alternatively, the indicator indicating that the frame is encapsulated may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field).

[0119] As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have previously set up relay communication operation, STA 1-2 (590) of STA MLD 1 can recognize that the frame transmitted by Relay 1-2 (580) of Relay MLD 1 to STA 1-2 (590) of STA MLD 1 is encapsulated. Therefore, a separate indicator may be unnecessary.

[0120] STA 1-2 (590) of STA MLD 1 can receive an encapsulated frame from Relay 1-2 (580) of Relay MLD 1. STA 1-2 (590) of STA MLD 1 can recognize that the frame of Relay 1-2 (580) of Relay MLD 1 is encapsulated based on an indicator indicating that the frame is encapsulated or a configured relay communication operation. STA 1-2 (590) of STA MLD 1 can decapsulate the encapsulated frame. STA 1-2 (590) of STA MLD 1 can receive (decode) MSDU 1, which is the payload of the frame of AP 1-1 (540) of AP MLD 1, by checking (e.g., receiving, decoding, error checking) the frame of AP 1-1 (540) of AP MLD 1, which is the payload of the encapsulated frame.

[0121] For example, AP 1-1 (540) of AP MLD 1 of the first link can transmit one frame or multiple frames at regular time intervals within a TXOP as shown in Table 2 below.

[0122] [Table 2]

[0123]

[0124]

[0125] When AP 1-1 (540) of AP MLD 1 transmits a frame, Relay 1-1 (550) of Relay MLD 1 can receive the frame (a frame whose receiver address is STA 1-1 of STA MLD 1) from AP 1-1 (540) of AP MLD 1. In response to the frame transmitted by AP 1-1 (540) of AP MLD 1 to STA 1-1 (560) of STA MLD 1, Relay 1-1 (550) of Relay MLD 1 can transmit an ACK frame to AP 1-1 (540) of AP MLD 1. AP 1-1 (540) of AP MLD 1 considers the ACK frame of Relay 1-1 (550) of Relay MLD 1 as an immediate response frame, but may not update the BlockAck scoreboard. That is, the receiver of the frame does not determine that it has received the frame. For example, Relay 1-1 (550) of Relay MLD 1 cannot transmit the frame due to the NAV corresponding to the TXOP acquired by AP 1-1 (540) of AP MLD 1. However, Relay 1-1 (550) of Relay MLD can regard the ACK frame as an immediate response frame to the frame of AP 1-1 (540) of AP MLD 1. Therefore, Relay 1-1 (550) of Relay MLD can transmit the ACK frame to AP 1-1 (540) of AP MLD 1 regardless of the NAV setting. Alternatively, Relay 1-1 (550) of Relay MLD may not set the NAV if it receives a frame whose receiver address is STA 1-2 (590) of STA MLD 1.

[0126] Relay 1-2 (580) of Relay MLD 1 can encapsulate a frame transmitted by AP 1-1 (540) of AP MLD 1 and transmit it to STA 1-2 (590) of STA MLD 1. STA 1-2 (590) of STA MLD 1 can decapsulate the encapsulated frame and receive the payload (e.g. MSDU 1). STA 1-2 (590) of STA MLD 1 can transmit a response frame (e.g. BlockAck frame) to Relay 1-2 (580) of Relay MLD 1.

[0127] As another example, consider a case where AP 1-1 (540) of AP MLD 1 transmits multiple frames at regular intervals. Relay 1-1 (550) of Relay MLD 1 can receive multiple frames (506-1, 506-2, 506-3) whose receiver address is STA 1-1 (560) of STA MLD 1 from AP MLD 1 at regular time intervals. Relay 1-1 (550) of Relay MLD 1 can encapsulate multiple frames (506-1, 506-2, 506-3) received from AP 1-1 (540) of AP MLD 1. When a frame of AP 1-1 (540) of AP MLD 1 is transmitted at a PIFS interval longer than SIFS by aSlotTime, Relay 1-1 (550) of Relay MLD 1 can transmit an ACK frame to AP 1-1 (540) of AP MLD 1 after SIFS time from the time when frame reception is completed. Alternatively, the transmission method of the response frame transmitted by Relay 1-1 (550) of Relay MLD 1 to AP 1-1 (540) of AP MLD 1 may be different depending on the setting of the Ack Policy of the frame transmitted by AP MLD 1 to Relay 1-1 (550) of Relay MLD 1. The Ack Policy of a frame other than the last frame transmitted by AP 1-1 (540) of AP MLD 1 to Relay 1-1 (550) of Relay MLD 1 may be set to BlockAck, which does not require immediate transmission of a response frame, or may be set to No Ack Policy, etc. The interval between frames other than the last frame transmitted by AP 1-1 (540) of AP MLD 1 to Relay 1-1 (550) of Relay MLD 1 may be SIFS. The Ack Policy of the last frame transmitted by AP 1-1 (540) of AP MLD 1 to Relay 1-1 (550) of Relay MLD 1 may be set to Implicit BAR.When Relay 1-1 (550) of Relay MLD 1 receives the last frame from AP 1-1 (540) of AP MLD 1, Relay 1-1 (550) of Relay MLD 1 must transmit a response frame (BlockAck frame, Ack frame) to AP 1-1 (540) of AP MLD 1 after SIFS.

[0128] As another example, referring to FIG. 5c, AP 1-1 (540) of AP MLD 1 may include an indicator indicating a last frame in the last transmitted frame (506-3) among multiple frames (506-1, 506-2, 506-3). The indicator indicating a last frame may be by setting the value of the More Data subfield of the Frame Control field to 0. Relay 1-1 (550) of Relay MLD 1, which has received a frame including an indicator indicating a last frame, may transmit an ACK frame (507) to AP 1-1 (540) of AP MLD 1 SIFS after the time of completion of reception of the last frame (506-3). AP 1-1 (540) of AP MLD 1 may consider the ACK frame of Relay 1-1 (550) of Relay MLD 1 as an immediate response frame, but may not update the BlockAck scoreboard. That is, the receiver of the frame does not consider that it has received the frame.

[0129] Here, Relay 1-1 (550) of Relay MLD 1 may not be able to transmit a frame due to the NAV corresponding to the TXOP acquired by AP 1-1 (540) of AP MLD 1. However, the ACK frame transmitted by Relay 1-1 (550) of Relay MLD 1 may be regarded as an immediate response frame to the frame of AP 1-1 (540) of AP MLD 1. Therefore, Relay 1-1 (550) of Relay MLD 1 can transmit an ACK frame regardless of the NAV setting.

[0130] Referring to FIG. 5c, Relay 1-2 (580) of Relay MLD 1 of the second link can transmit encapsulated frames (508-1, 508-2, 508-3) to STA 1-2 (590) of STA MLD 1. For example, STA 1-2 (590) of STA MLD 1 can individually transmit response frames (e.g., BlockAck frames) to encapsulated frames (508-1, 508-2, 508-3) transmitted by Relay 1-2 (580) of Relay MLD 1. The Ack Policy of each of the encapsulated frames (508-1, 508-2, 508-3) can be set to Implicit BAR requesting a BlockAck frame. As another example, after Relay 1-2 (580) of Relay MLD 1 transmits multiple encapsulated frames (508-1, 508-2, 508-3), STA 1-2 (590) of STA MLD 1 may transmit a single response frame for multiple encapsulated frames (508-1, 508-2, 508-3). The Ack Policy of some of the encapsulated frames (508-1, 508-2) may be set to BlockAck, which does not immediately request a BlockAck frame, and the Ack Policy of the last encapsulated frame, 508-3, may be set to Implicit BAR, which requests a BlockAck frame.

[0131] Based on the operation of Table 2 described above, STA 1-2 (590) of STA MLD 1 can transmit a response frame to Relay 1-2 (580) of Relay MLD 1. The response frame may be a BlockAck (BA) frame indicating the reception status of the frame transmitted by AP 1-1 (540) of AP MLD 1. STA 1-2 (590) of STA MLD 1 may set the transmitter address of the MAC header of the response frame to the MAC address of STA 1-2 (590) of STA MLD 1, and may set the receiver address to the MAC address of at least one of AP 1-1 (540) of AP MLD 1, AP 1-2 of AP MLD 1, and AP MLD 1. The MAC header included in the response frame transmitted by STA 1-2 (590) of STA MLD 1 may include an indicator indicating that the frame is transmitted (e.g., relayed) through Relay 1-2 (580) of Relay MLD 1 (i.e., Relay MLD 1). The indicator indicating that the frame is relayed through Relay MLD 1 may be the MAC address of the Relay included in the address field of the MAC header (e.g., the MAC address of at least one of Relay MLD 1 included in the Address 4 field, Relay 1-1 of Relay MLD 1, and Relay 1-2 of Relay MLD 1). Alternatively, the indicator indicating that the frame is relayed through Relay MLD 1 may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field).

[0132] As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have previously set up relay communication operation, Relay MLD 1 can recognize that the frame transmitted by STA MLD 1 to AP MLD 1 should be relayed. Therefore, an indicator indicating that the frame is relayed may be unnecessary. Accordingly, the MAC header transmitted by STA 1-2 (590) of STA MLD 1 may not include an indicator indicating that the frame is relayed. Relay 1-2 (580) of Relay MLD 1 can receive a frame (response frame, BlockAck frame) from STA 1-2 (590) of STA MLD 1. Relay MLD 1 can transmit the response frame of STA 1-2 (590) of STA MLD 1 to AP 1-1 (540) of AP MLD 1 using Relay 1-1 (550) of Relay MLD 1 of the first link. Alternatively, Relay MLD 1 can transmit the response frame to AP 1-2 (570) of AP MLD 1 via Relay 1-2 (580) of Relay MLD 1 of the second link. When a response frame of STA 1-2 (590) of STA MLD 1 is transmitted by Relay 1-1 (550) of Relay MLD 1 of the first link, Relay 1-1 (550) of Relay MLD 1 may add a MAC header, in which a transmitter address is the MAC address of Relay 1-1 (550) of Relay MLD 1 and a receiver address is the MAC address of AP 1-1 (540) of AP MLD 1, to the received frame. The payload of the frame generated by Relay 1-1 (550) of Relay MLD 1 may be a response frame (the entire frame including the MAC header) transmitted by STA 1-2 (590) of STA MLD 1. That is, Relay 1-1 (550) of Relay MLD 1 may perform an encapsulation operation to encapsulate the response frame of STA 1-2 (590) of STA MLD 1.Relay 1-1 (550) of Relay MLD 1 can perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the first link after completing frame reception from STA 1-2 (590) of STA MLD 1. After completing the channel access operation, Relay 1-1 (550) of Relay MLD 1 can transmit an encapsulated response frame to AP 1-1 (540) of AP MLD 1.

[0133] As another example, when a response frame of STA 1-2 (590) of STA MLD 1 is transmitted by Relay 1-2 (580) of Relay MLD 1 of the second link, Relay 1-2 (580) of Relay MLD 1 may add a MAC header, in which a transmitter address is the MAC address of Relay 1-2 (580) of Relay MLD 1 and a receiver address is the MAC address of AP 1-2 of AP MLD 1, to the received frame. The payload of the frame generated by Relay 1-2 (580) of Relay MLD 1 may be the response frame (the entire frame including the MAC header) transmitted by STA 1-2 (590) of STA MLD 1. That is, Relay 1-2 (580) of Relay MLD 1 can perform an encapsulation operation to encapsulate the response frame of STA 1-2 (590) of STA MLD 1. Relay 1-2 (580) of Relay MLD 1 can transmit the encapsulated response frame to AP 1-2 (570) of AP MLD 1 after SIFS after completing frame reception from STA 1-2 (590) of STA MLD 1. Alternatively, Relay 1-2 (580) of Relay MLD 1 can perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the second link, and when the channel access operation is completed, transmit the encapsulated response frame to AP 1-2 (570) of AP MLD 1.

[0134] The MAC header added by Relay MLD 1 (i.e., Relay 1-1 (550) of Relay MLD 1 and Relay 1-2 (580) of Relay MLD 1) may include an indicator indicating that the frame is encapsulated. For example, the MAC address of STA 1-2 (590) of STA MLD 1 may be included in the address 4 field of the MAC header added by Relay MLD 1, thereby indicating that the frame is encapsulated. Alternatively, the indicator indicating that the frame is encapsulated may be indicated by a separate subfield or bit (e.g., an indicator included in the HT Control field).

[0135] As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have previously set up relay communication operation, AP MLD 1 can recognize that the frame transmitted by Relay MLD 1 to AP MLD 1 is encapsulated, and a separate indicator may not be necessary.

[0136] AP MLD 1 can receive an encapsulated frame from Relay MLD 1. AP MLD 1 can recognize that the frame of Relay MLD 1 is encapsulated based on an indicator indicating that the frame is encapsulated or a configured relay communication operation. AP MLD 1 can decapsulate the encapsulated frame. AP MLD 1 can receive a frame (response frame, BlockAck frame) of STA 1-2 (590) of STA MLD 1 (i.e., STA MLD 1), which is a payload of the encapsulated frame, and AP MLD 1 can check the reception status of the frame transmitted by AP MLD 1 to STA MLD 1. AP MLD 1 can update the BlockAck scoreboard based on the response frame (e.g., BlockAck frame) of STA MLD 1, and can retransmit the frame if there is a frame that failed to be transmitted.

[0137] Also, for example, a frame received by Relay MLD 1 (i.e., Relay 1-1 (550) of Relay MLD 1) from AP MLD 1 (i.e., AP 1-1 (540) of AP MLD 1) may contain an error. Relay MLD 1 may not encapsulate the frame containing an error, may not respond to AP MLD 1, or may transmit a frame requesting retransmission of the frame from AP MLD 1 (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay MLD 1 may retransmit the frame containing an error from AP 1-1 (540) of AP MLD 1, and may transmit the frame to STA MLD 1 after receiving the frame without an error, or may discard the frame containing an error if the retransmission of the frame containing an error is not received.

[0138] STA MLD 1 (i.e., STA 1-1 (560) of STA MLD 1) may be able to receive (decode) frames of AP MLD 1 (i.e., AP 1-1 (540) of AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (560) of STA MLD 1 may not directly respond to AP 1-1 (540) of AP MLD 1 even if it receives frames of AP 1-1 (540) of AP MLD 1.

[0139] As another example, STA 1-1 (560) of STA MLD 1 (i.e., STA MLD 1) may be able to receive (decode) a frame of AP 1-1 (540) of AP MLD 1 (i.e., AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (560) of STA MLD 1 may store the frame of AP 1-1 (540) of AP MLD 1 in a buffer and may not directly respond to AP MLD 1. STA 1-1 (560) of STA MLD 1 may additionally receive a data frame transmitted via Relay MLD 1. STA MLD 1 can construct a data frame using a data frame received from AP 1-1 (540) of AP MLD 1 and a data frame received from Relay 1-2 (580) of Relay MLD 1. Here, if the received data frame is an A-MPDU, an MPDU in which an error occurred in the A-MPDU received from AP 1-1 (540) of AP MLD 1 and an A-MPDU received from Relay 1-2 (580) of Relay MLD 1 may be different. STA MLD 1 can recover the data frame using MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP MLD 1 through Relay MLD 1.

[0140] In FIGS. 5A to 5C, the operation of encapsulating a frame of an AP (eg, AP 1-1 (540) of AP MLD 1) by a Relay (eg, Relay 1-1 (550) of Relay MLD 1) and transmitting it to an STA (eg, STA 1-1 (560) of STA MLD) or encapsulating a frame of an STA by a Relay and transmitting it to an AP may be referred to as a tunneling operation, but is not limited to that name. In addition, although FIGS. 5A to 5C are described based on an AP, a Relay, and an STA, it may not be limited thereto. For example, the same may be applied when frame transmission is relayed through a Relay in communication between STAs. As another example, the same may be applied when frame transmission is relayed through a Relay in communication between APs. As another example, the same may be applied when an STA performs uplink transmission to an AP through a Relay, and may not be limited to a specific form.

[0141] In FIGS. 5A to 5C, the setting of the relay communication operation by the AP 1-1 (540) of the AP MLD 1 (or, AP MLD 1, AP), the STA 1-1 of the STA MLD 1 (or, STA MLD 1, STA), and the Relay 1-1 (550) of the Relay MLD 1 (or, Relay MLD 1, STA) of the Relay MLD 1 may be performed based on the determination of the machine learning unit described in FIGS. 1 to 4. For example, the machine learning unit may determine that at least one of the AP, the Relay, and the STA requires a relay communication operation, and the procedure of determining the Relay that performs the relay communication operation may be performed by the machine learning unit. As another example, when multiple Relays exist in a wireless LAN network, the machine learning unit of the AP or the STA may determine that the relay communication operation is required by using signal strength, etc. as input. Once it is determined that a relay communication operation is required, the machine learning unit can input the signal strengths of multiple relays and select the most appropriate relay for the relay communication operation. After setting the relay communication operation with the most appropriate relay, the relay communication operation(s) described in FIGS. 5A through 5C can be performed.

[0142] FIG. 6a and FIG. 6b are diagrams illustrating a method for performing a relay communication operation applied to the present disclosure.

[0143] Referring to FIGS. 6A and 6B, wireless LAN terminals (e.g., AP (access point), Relay (Relay STA), STA (station)) may operate in a wireless LAN network. For example, in FIG. 6A, a case may be considered where AP 1-1 (610), Relay 1-1 (620), and STA 1-1 (630) operate in a wireless LAN network, but this is for convenience of explanation and may not be limited thereto. In addition, in FIG. 6B, the AP, Relay, and STA may be referred to as an AP MLD, a Relay MLD, and a STA MLD as a multi-link device (MLD) that supports multi-link operation. The MLD may be a wireless LAN terminal having a separate MAC layer (MLD lower MAC sublayer) and a PHY layer for each link (e.g., first link, second link, etc.). A MAC layer (MLD upper MAC sublayer) that integrates the link-specific MAC layers may exist above the link-specific MAC layers of the MLD. Here, APs or STAs for each link may operate under the AP MLD, STA MLD, and Relay MLD. For example, an AP of AP MLD 1 operating in the first link may be referred to as AP 1-1 of AP MLD 1, and an AP of AP MLD 1 operating in the second link may be referred to as AP 1-2 of AP MLD 1. In addition, an STA of STA MLD 1 operating in the first link may be referred to as STA 1-1 of STA MLD 1, and an STA of STA MLD 1 operating in the second link may be referred to as STA 1-2 of STA MLD 1. In addition, a Relay of Relay MLD 1 operating in the first link may be referred to as Relay 1-1 of Relay MLD 1, and a Relay of Relay MLD 1 operating in the second link may be referred to as Relay 1-2 of Relay MLD 1.The operations of APs or STAs under the MLD may be operations of the MLD, and the operations of the MLD may be operations of the lower APs or STAs. Fig. 6b is merely an example for convenience of explanation and may not be limited to the corresponding operations.

[0144] Referring to FIG. 6a, AP 1-1 (610), Relay 1-1 (620), and STA 1-1 (630) can perform settings for relay communication operation in advance. That is, in FIG. 6a, AP 1-1 (610), Relay 1-1 (620), and STA 1-1 (630) can complete settings for relay communication operation in advance. AP 1-1 (610), Relay 1-1 (620), and STA 1-1 (630) can recognize that they are performing relay communication operation through the above-described settings. In addition, referring to FIG. 6b, AP MLD 1, Relay MLD 1, and STA MLD 1 can perform settings for relay communication operation in advance. That is, in FIG. 6b, AP MLD 1, Relay MLD 1, and STA MLD 1 can complete settings for relay communication operation in advance. AP MLD 1, Relay MLD 1, and STA MLD 1 can recognize that they are performing relay communication operations through the above-described settings. However, FIGS. 6a and 6b are only for convenience of explanation and are not limited to the corresponding embodiment, and the same can be applied to other cases.

[0145] Referring to FIG. 6a, AP 1-1 (610) may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (630). The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (610) may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation, and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (610) may want to transmit a frame to STA 1-1 (630) within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance. The duration of the MAC header corresponding to the TXOP set by AP 1-1 (610) may be set to a time equal to or greater than the sum of the encapsulated data frame transmission time from AP 1-1 (610) to Relay 1-1 (620), the frame transmission time from Relay 1-1 (620) to STA 1-1 (630), the encapsulated response frame (BlockAck) transmission time of STA 1-1 (630), the response frame transmission time of Relay 1-1 (520), and the interval between transmissions of each frame (e.g. SIFS time).

[0146] The transmitter address of the MAC header included in the original frame transmitted by AP 1-1 (610) may be set to the MAC address of AP 1-1 (610), and the receiver address may be set to the MAC address of STA 1-1 (630). That is, AP 1-1 (610) may want to transmit the original frame whose payload is an MSDU (e.g., MSDU 1) of which STA 1-1 (630) is the recipient. Here, AP 1-1 (610) may not transmit the original frame as is, but may add a new MAC header to the frame. The transmitter address of the new MAC header may be set to the MAC address of AP 1-1 (610), and the receiver address may be set to the MAC address of Relay 1-1 (620). That is, AP 1-1 (610) may encapsulate the frame to generate an encapsulated frame (601-1). The payload of the encapsulated frame (601-1) is the original frame of AP 1-1 (610). Encapsulating the frame by AP 1-1 (610) may be an action performed to relay the frame to STA 1-1 (630) via Relay 1-1 (620).

[0147] A new MAC header of an encapsulated frame (601-1) transmitted by AP 1-1 (610) may include an indicator indicating that the frame is transmitted (e.g., relayed) via Relay 1-1 (620). The indicator indicating that the frame is relayed via Relay 1-1 (620) may be a MAC address of an STA (e.g., of STA 1-1) included in an address field of the MAC header (e.g., the MAC address of STA 1-1 (630) included in an Address 4 field). That is, when the address field of the MAC header includes a MAC address of an STA, it may be indicated that the frame is relayed to STA 1-1 via Relay 1-1 (620). Alternatively, the indicator indicating that the frame is to be relayed via Relay 1-1 (620) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether the frame is to be relayed via Relay 1-1 (620).

[0148] As another example, since AP 1-1 (610), STA 1-1 (630), and Relay 1-1 (620) have preset relay communication operations, Relay 1-1 (620) can recognize that the frame transmitted by AP 1-1 (610) should be relayed to STA 1-1 (630). Considering the above, since an indicator indicating that the frame is relayed is unnecessary, the MAC header of the frame transmitted by AP 1-1 (610) may not include the indicator.

[0149] Relay 1-1 (620) can receive a frame (601-1) from AP 1-1 (610). Relay 1-1 (620) can remove the MAC header added by AP 1-1 (610) and transmit the original frame (601-2) (i.e., the payload of the encapsulated frame) of AP 1-1 (610) after SIFS time from the time of completion of reception of the frame transmitted by AP 1-1 (610). The operation of Relay 1-1 (620) removing the MAC header added by AP 1-1 (610) may be a decapsulation operation. For example, Relay 1-1 (620) may perform an action to modify the MAC header of the original frame (601-2) of AP 1-1 (610) to include an indicator indicating that the frame is to be relayed and transmitted by Relay 1-1 (620) after removing the MAC header added by AP 1-1 (610). Since Relay 1-1 (620) transmits the decapsulated frame (601-2) after SIFS, AP 1-1 (610) may regard the decapsulated frame (601-2) of Relay 1-1 (620) as an immediate response frame. For example, Relay 1-1 (620) may be prevented from transmitting frames due to a NAV corresponding to a TXOP acquired by AP 1-1 (610). However, Relay 1-1 (620) may regard the decapsulated frame (601-2) as an immediate response frame to the frame of AP 1-1 (610). Alternatively, since Relay 1-1 (620) is a receiver that receives frames from AP 1-1 (610), it may not be necessary to set NAV. That is, Relay 1-1 (620) may be a TXOP responder. Therefore, Relay 1-1 (620) may transmit the decapsulated frame (601-2) to STA 1-1 (630) regardless of the NAV setting. AP 1-1 (610) may consider the response frame (e.g.The BlockAck scoreboard of AP 1-1 (610) may not be updated until a BlockAck frame is received. That is, the receiver of the frame does not consider that the frame has been received.

[0150] STA 1-1 (630) can receive the original frame (601-2) of AP 1-1 (610) from Relay 1-1 (620). STA 1-1 (630) can recognize that the frame is received from AP 1-1 (610) through Relay 1-1 (620) based on an indicator indicating that the frame is relayed and transmitted or a configured relay communication operation. STA 1-1 (630) can transmit a response frame (e.g., BlockAck frame) after a SIFS time from the time when Relay 1-1 (620) completes receiving the frame. The response frame transmitted by STA 1-1 (630) can be encapsulated similarly to the frame transmitted by AP 1-1 (610). For example, the transmitter address of the original BlockAck frame transmitted by STA 1-1 (630) may be set to the MAC address of STA 1-1 (630), and the receiver address may be set to the MAC address of AP 1-1 (610). STA 1-1 (630) may add a new MAC header to the original BlockAck frame. The transmitter address of the MAC header added by STA 1-1 (630) may be set to STA 1-1 (630), and the receiver address may be set to Relay 1-1 (620). That is, STA 1-1 (630) may encapsulate the response frame, and the payload of the encapsulated response frame (602-1) may be the original BlockAck frame. A new MAC header of an encapsulated response frame (602-1) of STA 1-1 (630) may include an indicator indicating that the response frame is transmitted (e.g. relayed) via Relay 1-1 (620). The indicator indicating that the frame is relayed via Relay 1-1 (620) may be an AP included in an address field of the MAC header (e.g. the MAC address of AP 1-1 included in the Address 4 field).That is, if the MAC address of the AP is included in the address field of the MAC header, it can be indicated that the frame is relayed through Relay 1-1 (620). Alternatively, the indicator indicating that the frame is relayed through Relay 1-1 (620) can be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether or not to relay.

[0151] As another example, since AP 1-1 (610), STA 1-1 (630), and Relay 1-1 (620) have previously set up relay communication operation, Relay 1-1 (620) can recognize that the response frame transmitted by STA 1-1 (630) should be relayed to AP 1-1 (610). Considering the above, an indicator indicating that the frame is relayed may be unnecessary. Accordingly, the MAC header of the frame transmitted by STA 1-1 (630) may not include an indicator indicating that the frame is relayed.

[0152] Relay 1-1 (620) may receive the encapsulated response frame (602-1) of STA 1-1 (630) and remove the MAC header added by STA 1-1 (630) from the encapsulated response frame (602-1) transmitted by STA 1-1 (630). Relay 1-1 (620) may transmit the original frame (602-2) of STA 1-1 (630) (i.e., the payload of the encapsulated frame) after SIFS time from the time point of completion of reception of the frame transmitted by STA 1-1 (630). The operation of Relay 1-1 (620) removing the MAC header added by STA 1-1 (630) may be a decapsulation operation. Relay 1-1 (620) may perform an operation of removing the MAC header added by STA 1-1 (630) and then modifying the MAC header of the original response frame of STA 1-1 (630) to include an indicator indicating that the response frame is relayed and transmitted by Relay 1-1 (620). AP 1-1 (610) can receive the response frame (602-2) of STA 1-1 (630) through Relay 1-1 (620). AP 1-1 (610) can check the reception status of the frame transmitted by AP 1-1 (610) to STA 1-1 (630) and update the BlockAck scoreboard based on the response frame (e.g. BlockAck frame) of STA 1-1 (630). Additionally, AP 1-1 (610) can retransmit frames if there are frames that failed to be transmitted.

[0153] For example, a frame received by Relay 1-1 (620) from AP 1-1 (610) may contain an error. Relay 1-1 (620) may not transmit the frame with the error to STA 1-1 (630), but may not respond to AP 1-1 (610) or transmit a frame requesting retransmission of the frame from AP 1-1 (610) (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay 1-1 (620) may retransmit the frame with the error from AP 1-1 (610), and transmit the frame to STA 1-1 (630) after receiving the frame without an error, or may discard the frame with the error if the retransmission of the frame with the error is not received.

[0154] As another example, STA 1-1 (630) may be able to receive (decode) a frame transmitted by AP 1-1 (610). However, since the receiver address of the MAC header of the frame transmitted by AP 1-1 (610) is Relay 1-1 (620), STA 1-1 (630) may not respond to the frame transmitted by AP 1-1.

[0155] As another example, STA 1-1 (630) may be able to receive (decode) a frame transmitted by AP 1-1 (610). If STA 1-1 (630), AP 1-1 (610), and Relay 1-1 (620) perform relay communication operation setup, STA 1-1 (630) may store the frame in a buffer when it receives the frame from AP 1-1 (610) and may not directly respond to AP 1-1 (610). STA 1-1 (630) may additionally receive a data frame transmitted via Relay 1-1 (620). STA 1-1 (630) may construct a data frame using the data frame received from AP 1-1 (610) and the data frame received from Relay 1-1 (620). For example, if the received data frame is an A-MPDU, the MPDU in which an error occurred may be different between the A-MPDU received from AP 1-1 (610) and the A-MPDU received from Relay 1-1 (620). STA 1-1 (630) can recover the data frame through MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP 1-1 (610) through Relay 1-1 (620).

[0156] Referring to FIG. 6b, AP MLD 1, Relay MLD 1, and STA MLD 1 can perform settings for relay communication operations in advance. AP MLD 1, Relay MLD 1, and STA MLD 1 can recognize in advance that they are performing relay communication operations through the settings for relay communication operations.

[0157] AP 1-1 (640) of AP MLD 1 operating on the first link may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (660) of STA MLD 1. The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (640) of AP MLD 1 may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation, and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (640) of AP MLD 1 may want to transmit a frame to STA 1-1 (660) of STA MLD within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance. The duration of the MAC header corresponding to the TXOP set by AP 1-1 (640) of AP MLD 1 may be set to a time equal to or greater than the sum of the transmission times of one or more data frames transmitted from AP 1-1 (640) of AP MLD 1 to Relay 1-1 (650) of Relay MLD, the transmission time of a response frame (BlockAck) of Relay 1-1 (650), and the interval between transmissions of each frame (e.g. SIFS time).

[0158] The transmitter address of the MAC header included in the original frame to be transmitted by AP 1-1 (640) of AP MLD 1 may be set to the MAC address of AP 1-1 (640) of AP MLD 1, and the receiver address may be set to the MAC address of STA 1-1 (660) of STA MLD 1. The payload included in the original frame to be transmitted by AP 1-1 (640) of AP MLD 1 may be an MSDU of which STA 1-1 (660) of STA MLD 1 is the recipient. AP 1-1 (640) of AP MLD 1 may not transmit the original frame as is, but may add a new MAC header to the frame. The transmitter address of the new MAC header may be set to the MAC address of AP 1-1 (640) of AP MLD 1, and the receiver address may be set to the MAC address of Relay 1-1 (650) of Relay MLD 1. That is, AP 1-1 (640) of AP MLD 1 may encapsulate a frame to generate an encapsulated frame. The payload of the encapsulated frame is the original frame of AP 1-1 (640) of AP MLD 1. Encapsulating the frame by AP 1-1 (640) of AP MLD 1 (i.e., AP MLD 1) may be an action performed to relay the frame through Relay 1-1 (650) of Relay MLD 1 (i.e., Relay MLD 1). The new MAC header of the encapsulated frame of AP 1-1 (640) of AP MLD 1 may include an indicator indicating that the frame is transmitted (e.g., relayed) through Relay MLD 1. The indicator that indicates that the frame is relayed through Relay MLD 1 is the MAC address of the STA (e.g. STA MLD 1 and subordinate STAs) included in the address field of the MAC header (e.g.The Address 4 field may contain the MAC address of at least one of STA MLD 1, STA 1-1 (660) of STA MLD 1, and STA 1-2 (690) of STA MLD 1. That is, if the Address field of the MAC header contains the MAC address of STA MLD 1, it may be indicated that the frame is relayed to STA MLD 1 via Relay MLD 1. Alternatively, the indicator indicating that the frame is relayed via Relay MLD 1 may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field).

[0159] As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have preset relay communication operations, Relay MLD 1 can recognize that the frame transmitted by AP MLD 1 should be relayed to STA MLD 1. Therefore, an indicator indicating that the frame is relayed may not be necessary in the MAC header of the frame transmitted by AP 1-1 (640) of AP MLD 1.

[0160] Relay 1-1 (650) of Relay MLD 1 may receive a frame from AP 1-1 (640) of AP MLD 1. Relay MLD 1 may want to transmit the received frame to STA MLD 1 through the second link. That is, Relay MLD 1 may want to transmit the frame received on the first link to STA 1-2 (690) of STA MLD 1 through Relay 1-2 of the second link. As another example, a case may be considered where the first link is busy after Relay MLD 1 receives a frame transmitted from AP MLD 1 to STA MLD 1 on the first link. Relay MLD 1 may know that among the available first link and second link, the second link is idle, or the busy state of the second link ends sooner than that of the first link and the second link. Therefore, Relay MLD 1 may not be able to transmit the encapsulated frame to STA 1-1 (660) of STA MLD 1 in the first link via Relay 1-1 (650) of Relay MLD 1. In the above-described situation, Relay MLD 1 may want to transmit the encapsulated frame to STA 1-2 (690) of STA MLD 1 in the second link via Relay 1-2 (680) of Relay MLD 1, but the present invention may not be limited to the above-described embodiment.

[0161] When Relay 1-2 (680) of Relay MLD 1 successfully decodes MSDU 1, it can immediately perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the second link. When Relay 1-2 (680) of Relay MLD 1 successfully performs the channel access operation, it can acquire EDCA TXOP, which is a communication section, on the second link. Alternatively, when Relay MLD 1 detects a frame transmitted on the first link, Relay 1-2 (680) of Relay MLD 1 can immediately perform a channel access operation. Relay 1-2 (680) of Relay MLD 1 can wait for transmission without transmitting a frame until decoding of MSDU 1 is successfully performed. The duration of the MAC header corresponding to the TXOP set by Relay 1-2 (680) of Relay MLD 1 may be set to a time equal to or greater than the sum of the transmission time of one or more data frames transmitted from Relay 1-2 (680) of Relay MLD 1 to STA 1-2 (690) of STA MLD 1, the transmission time of an encapsulated response frame (BlockAck) of STA 1-2 (690) of STA MLD 1, the time for Relay 1-2 (680) of Relay MLD 1 to transmit the response frame of STA 1-2 (690) of STA MLD 1, and the interval between transmissions of each frame (e.g. SIFS time).

[0162] The EDCA TXOP of Relay 1-2 (680) of Relay MLD 1 can be used by Relay 1-2 (680) of Relay MLD 1 to transmit the frame of AP MLD 1 to STA MLD 1. Relay MLD 1 can remove the MAC header added by AP 1-1 (640) of AP MLD 1 from the frame received from AP 1-1 (640) of AP MLD 1. That is, Relay MLD 1 can decapsulate the frame. Relay MLD 1 can complete reception of the frame transmitted by AP 1-1 (640) of AP MLD 1 in the first link and transmit the original frame of AP 1-1 (640) of AP MLD 1 that has been decapsulated to STA 1-2 (690) of STA MLD 1 in the TXOP of the second link. Relay 1-2 (680) of Relay MLD 1 may further perform the action of decapsulating the frame and adding an indicator to the MAC header of the original frame transmitted by AP 1-1 (640) of AP MLD 1 indicating that the frame is encapsulated.

[0163] As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have previously set up relay communication operation, STA 1-2 (690) of STA MLD 1 can recognize that the frame transmitted by Relay 1-2 (680) of Relay MLD 1 to STA 1-2 (690) of STA MLD 1 is encapsulated, and a separate indicator may not be necessary.

[0164] STA 1-2 (690) of STA MLD 1 can receive a frame from Relay 1-2 (680) of Relay MLD 1. STA 1-2 (690) of STA MLD 1 can recognize that the frame was transmitted from AP 1-1 (640) of AP MLD 1 through Relay MLD 1 based on the configured relay communication operation. STA 1-2 (690) of STA MLD 1 can receive (decode) MSDU 1, which is the payload of the frame from AP 1-1 (640) of AP MLD 1.

[0165] Additionally, as an example, AP 1-1 (640) of AP MLD 1 may perform any one of the operations in Table 3 below within the TXOP of the first link.

[0166] [Table 3]

[0167]

[0168]

[0169] When AP 1-1 (640) of AP MLD 1 transmits a frame, Relay 1-1 (650) of Relay MLD 1 can receive an encapsulated frame (a frame in which the receiver address is Relay 1-1 (650) of Relay MLD 1 and the receiver address of the MAC header of the payload is the address of STA MLD 1 or lower STAs) from AP 1-1 (640) of AP MLD 1. In response to the frame transmitted by AP 1-1 (640) of AP MLD 1 to STA 1-1 (660) of STA MLD 1, Relay 1-1 (650) of Relay MLD 1 can transmit an ACK frame to AP 1-1 (640) of AP MLD 1. AP 1-1 (640) of AP MLD 1 may consider the ACK frame of Relay 1-1 (650) of Relay MLD 1 as an immediate response frame, but may not update the BlockAck scoreboard. That is, the receiver of the frame does not determine that the frame has been received. For example, Relay 1-1 (650) of Relay MLD 1 may not be able to transmit the frame due to the NAV corresponding to the TXOP acquired by AP 1-1 (640) of AP MLD 1. However, Relay 1-1 (650) of Relay MLD 1 may consider the ACK frame as an immediate response frame to the frame of AP 1-1 (640) of AP MLD 1. Therefore, Relay 1-1 (650) of Relay MLD 1 can transmit the ACK frame to AP 1-1 (640) of AP MLD 1 regardless of the NAV setting. Alternatively, since Relay 1-1 (650) is a receiver that receives frames from AP 1-1, it may not be necessary to set NAV. That is, Relay 1-1 (650) may be a TXOP responder.Relay 1-2 (680) of Relay MLD 1 can decapsulate the frame transmitted by AP 1-1 (640) of AP MLD 1 and transmit the frame to STA 1-2 (690) of STA MLD 1. STA 1-2 (690) of STA MLD 1 can receive the frame of AP 1-1 (640) of AP MLD 1 and receive the payload (e.g. MSDU 1). STA 1-2 (690) of STA MLD 1 can encapsulate and transmit a response frame (e.g. BlockAck frame) to Relay 1-2 (680) of Relay MLD 1.

[0170] On the other hand, AP 1-1 (640) of AP MLD 1 can transmit multiple frames at regular time intervals. When AP 1-1 (640) of AP MLD 1 transmits multiple frames at regular time intervals, Relay 1-1 (650) of Relay MLD 1 can receive encapsulated frames from AP MLD 1 (frames in which the receiver address is Relay 1-1 (650) of Relay MLD 1 and the receiver address of the MAC header of the payload is the address of STA MLD 1 or lower STAs). Relay 1-1 (650) of Relay MLD 1 can decapsulate multiple frames (603-1, 603-2) received from AP 1-1 (640) of AP MLD 1. Relay 1-1 (650) of Relay MLD 1 can transmit an ACK frame to AP 1-1 (640) of AP MLD 1 after a SIFS time from the time when frame reception is completed when the frame of AP 1-1 (640) of AP MLD 1 is transmitted at a PIFS interval longer than SIFS by aSlotTime. Alternatively, the transmission method of the response frame transmitted by Relay 1-1 (650) of Relay MLD 1 to AP 1-1 (640) of AP MLD 1 may vary depending on the setting of the Ack Policy of the frame transmitted by AP MLD 1 to Relay 1-1 (650) of Relay MLD 1. The Ack Policy of frames other than the last frame transmitted by AP 1-1 (640) of AP MLD 1 to Relay 1-1 (650) of Relay MLD 1 may be set to BlockAck, which does not require immediate transmission of a response frame, or may be set to No Ack Policy, etc. The interval between frames other than the last frame transmitted by AP 1-1 (640) of AP MLD 1 to Relay 1-1 (650) of Relay MLD 1 may be SIFS.The Ack Policy of the last frame transmitted by AP 1-1 (640) of AP MLD 1 to Relay 1-1 (650) of Relay MLD 1 can be set to Implicit BAR. When Relay 1-1 (650) of Relay MLD 1 receives the last frame from AP 1-1 (640) of AP MLD 1, Relay 1-1 (650) of Relay MLD 1 must transmit a response frame (BlockAck frame, Ack frame) to AP 1-1 after SIFS.

[0171] As another example, referring to FIG. 6B, AP 1-1 (640) of AP MLD 1 may include an indicator indicating a last frame in the last transmitted frame among multiple frames (603-1, 603-2). The indicator indicating a last frame may be by setting the value of the More Data subfield of the Frame Control field to 0. Relay 1-1 (650) of Relay MLD 1, which receives a frame including an indicator indicating a last frame, may transmit an ACK frame (604) to AP 1-1 (640) of AP MLD 1 after a SIFS time from the time of completion of frame reception. AP 1-1 (640) of AP MLD 1 may immediately regard the ACK frame (604) of Relay 1-1 (650) of Relay MLD 1 as a response frame, but may not update the BlockAck scoreboard. That is, the receiver of the frame does not determine that the frame has been received. For example, Relay 1-1 (650) of Relay MLD 1 may not be able to transmit a frame due to NAV corresponding to the TXOP acquired by AP 1-1 (640) of AP MLD 1. However, Relay 1-1 (650) of Relay MLD 1 may regard the ACK frame as an immediate response frame to the frame of AP 1-1 (640) of AP MLD 1. Therefore, Relay 1-1 (650) of Relay MLD 1 may transmit the ACK frame to AP 1-1 (640) of AP MLD 1 regardless of the NAV setting. Alternatively, since Relay 1-1 (650) is a receiver that receives frames from AP 1-1 (640), it may not be necessary to set the NAV. That is, Relay 1-1 (650) may be a TXOP responder.

[0172] Relay 1-2 (680) of Relay MLD 1 can transmit decapsulated frames (605-1, 605-2) to STA 1-2 (690) of STA MLD 1 on the second link. For example, STA 1-2 (690) of STA MLD 1 can individually transmit a response frame (e.g., BlockAck frame, 606-1, 606-2) for each frame transmitted by Relay 1-2 (680) of Relay MLD 1. The Ack Policy of each of the encapsulated frames (605-1, 605-2) can be set to Implicit BAR requesting a BlockAck frame. As another example, after Relay 1-2 (680) of Relay MLD 1 transmits multiple frames, STA 1-2 (690) of STA MLD 1 may transmit a single response frame for multiple frames, and is not limited to a specific form. The Ack Policy of some of the encapsulated frames (605-1) may be set to BlockAck, which does not immediately request a BlockAck frame, and the Ack Policy of the last encapsulated frame, 605-2, may be set to Implicit BAR, which requests a BlockAck frame.

[0173] Based on at least one operation of Table 3 described above, STA 1-2 (690) of STA MLD 1 may transmit a response frame to Relay 1-2 (680) of Relay MLD 1. The response frame may be a BlockAck (BA) frame indicating the reception status of the frame transmitted by AP 1-1 (640) of AP MLD 1 (i.e., AP MLD 1). The response frame transmitted by STA 1-2 (690) of STA MLD 1 may be encapsulated similarly to the frame transmitted by AP 1-1 (640) of AP MLD 1. For example, the transmitter address of the original BlockAck frame transmitted by STA 1-2 (690) of STA MLD 1 may be set to the MAC address of STA 1-2 (690) of STA MLD 1, and the receiver address may be indicated as the MAC address of AP MLD or APs under AP MLD (e.g., at least one of AP 1-1 (640) of AP MLD 1 and AP 1-2 (670) of AP MLD 1). STA 1-2 (690) of STA MLD 1 may add a new MAC header to the original BlockAck frame. The transmitter address of the MAC header added by STA 1-2 (690) of STA MLD 1 may be set to STA 1-2 (690) of STA MLD 1, and the receiver address may be set to Relay 1-2 (680) of Relay MLD 1. That is, STA 1-2 (690) of STA MLD 1 can encapsulate the response frame, and the payload of the encapsulated response frame can be the original BlockAck frame. The new MAC header of the encapsulated response frame of STA 1-2 (690) of STA MLD 1 can include an indicator indicating that the response frame is transmitted (e.g. relayed) through Relay 1-2 (680) of Relay MLD 1 (i.e., Relay MLD 1). The indicator indicating that the frame is relayed through Relay MLD 1 can be an AP (e.g.,The MAC address (e.g., MAC address included in the Address 4 field) of at least one of AP MLD 1, AP 1-1 (640) of AP MLD 1, and AP 1-2 (670) of AP MLD 1 may be set. Alternatively, an indicator indicating that the frame is relayed through Relay MLD 1 may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field). As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have preset relay communication operations, Relay MLD 1 may recognize that the response frame transmitted by STA MLD 1 (i.e., STA 1-2) should be relayed to AP MLD 1. Therefore, an indicator indicating that the frame is relayed may not be necessary in the MAC header transmitted by STA 1-2 (690) of STA MLD 1. Relay 1-2 (680) of Relay MLD 1 may receive a response frame of STA 1-2 (690) of STA MLD 1, and remove the MAC header added by STA 1-2 (690) of STA MLD 1 from the encapsulated response frame transmitted by STA 1-2 (690) of STA MLD 1. Relay MLD 1 may transmit the response frame of STA 1-2 (690) of STA MLD 1 to AP 1-1 (640) of AP MLD 1 through Relay 1-1 (650) of Relay MLD 1 of the first link. As another example, Relay MLD 1 can transmit a response frame of STA 1-2 (690) of STA MLD 1 to AP 1-2 (670) of AP MLD 1 through Relay 1-2 (680) of Relay MLD 1 of the second link.

[0174] Relay MLD 1 removing the MAC header added by STA 1-2 (690) of STA MLD 1 may be a decapsulation operation. Relay MLD 1 may also perform an operation to remove the MAC header added by STA 1-2 (690) of STA MLD 1 and then modify the MAC header of the original response frame of STA 1-2 (690) of STA MLD 1 to include an indicator indicating that the response frame is relayed and transmitted by Relay MLD 1. Relay MLD 1 may transmit the original response frame to AP 1-2 (670) of AP MLD 1 SIFS after the time of completion of frame reception from STA 1-2 (690) of STA MLD 1. As another example, Relay MLD 1 may perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the second link, and upon completion of the channel access operation, transmit the original response frame to AP 1-2 (670) of AP MLD 1.

[0175] AP MLD 1 can receive a response frame from STA MLD 1 via Relay MLD 1. AP MLD 1 can check the reception status of the frame transmitted to STA MLD 1. AP MLD 1 can update the BlockAck scoreboard based on the response frame (e.g. BlockAck frame) from STA MLD 1, and can retransmit frames if there are frames that failed to be transmitted.

[0176] Also, for example, a frame received by Relay MLD 1 (i.e., Relay 1-1 (650) of Relay MLD 1) from AP MLD 1 (i.e., AP 1-1 (540) of AP MLD 1) may contain an error. Relay MLD 1 may not transmit the frame containing the error to STA MLD 1. Relay MLD 1 may not respond to AP MLD 1, or transmit a frame requesting retransmission of the frame from AP MLD 1 (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay MLD 1 may retransmit the frame containing the error from AP 1-1 (640) of AP MLD 1, and transmit the frame to STA MLD 1 after receiving the frame without an error, or if the retransmission of the frame containing the error is not received, the frame containing the error may be discarded.

[0177] STA MLD 1 (i.e., STA 1-1 (660) of STA MLD 1) may be able to receive (decode) frames from AP MLD 1 (i.e., AP 1-1 (640) of AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (660) of STA MLD 1 may not directly respond to AP 1-1 (640) of AP MLD 1 even if it receives frames from AP 1-1 (640) of AP MLD 1.

[0178] As another example, STA 1-1 (660) of STA MLD 1 (i.e., STA MLD 1) may be able to receive (decode) a frame of AP 1-1 (640) of AP MLD 1 (i.e., AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (660) of STA MLD 1 may store the frame of AP 1-1 (640) of AP MLD 1 in a buffer and may not directly respond to AP MLD 1. STA 1-1 (660) of STA MLD 1 may additionally receive a data frame transmitted via Relay MLD 1. STA MLD 1 can construct a data frame using a data frame received from AP 1-1 (640) of AP MLD 1 and a data frame received from Relay 1-2 (680) of Relay MLD 1. Here, if the received data frame is an A-MPDU, an MPDU in which an error occurred in the A-MPDU received from AP 1-1 (540) of AP MLD 1 and an A-MPDU received from Relay 1-2 (580) of Relay MLD 1 may be different. STA MLD 1 can recover the data frame using MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP MLD 1 through Relay MLD 1.

[0179] In FIGS. 6A and 6B, the operation in which an AP (eg, AP 1-1 (640) of AP MLD 1) encapsulates a frame and transmits it to an STA (eg, STA 1-1 (560) of STA MLD) through a Relay (eg, Relay 1-1 (650) of Relay MLD 1) or an STA encapsulates a frame and transmits it to an AP through a Relay may be referred to as a tunneling operation, but is not limited to that name. In addition, although FIGS. 6A and 6B are described based on an AP, a Relay, and an STA, the present invention may not be limited thereto. For example, the same may be applied when frame transmission is relayed through a Relay in communication between STAs. As another example, the same may be applied when frame transmission is relayed through a Relay in communication between APs. As another example, the same may apply when an STA performs uplink transmission to an AP via a relay, and may not be limited to a specific form.

[0180] In FIGS. 6A and 6B, the setting of the relay communication operation by the AP 1-1 (640) of the AP MLD 1 (or, AP MLD 1, AP), the STA 1-1 of the STA MLD 1 (or, STA MLD 1, STA), and the Relay 1-1 (650) of the Relay MLD 1 (or, Relay MLD 1, STA) of the Relay MLD 1 may be performed based on the determination of the machine learning unit described in FIGS. 1 to 4. For example, the machine learning unit may determine that at least one of the AP, the Relay, and the STA requires a relay communication operation, and the procedure of determining the Relay that performs the relay communication operation may be performed by the machine learning unit. As another example, when multiple Relays exist in a wireless LAN network, the machine learning unit of the AP or the STA may determine that the relay communication operation is required by using signal strength, etc. as input. Once it is determined that a relay communication operation is required, the machine learning unit can input the signal strengths of multiple relays and select the most appropriate relay for the relay communication operation. After setting the relay communication operation with the most appropriate relay, the relay communication operation(s) described in FIGS. 6A and 6B can be performed.

[0181] FIG. 7A and FIG. 7B are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied. Referring to FIG. 7A and FIG. 7B, wireless LAN terminals (e.g., AP (access point), Relay (Relay STA), STA (station)) may operate in a wireless LAN network. For example, in FIG. 7A, a case may be considered in which AP 1-1 (710), Relay 1-1 (720), and STA 1-1 (730) operate in a wireless LAN network, but this is for convenience of explanation and may not be limited thereto. In addition, in FIG. 7B, the AP, Relay, and STA may be referred to as an MLD (multi-link device) supporting multi-link operation, and may be referred to as an AP MLD, a Relay MLD, and a STA MLD. An MLD may be a wireless LAN terminal having a separate MAC layer (MLD lower MAC sublayer) and a PHY layer for each link (e.g., a first link, a second link, etc.). Above the link-specific MAC layer of the MLD, there may be a MAC layer (MLD upper MAC sublayer) that integrates the link-specific MAC layers. Here, the link-specific AP or STA may operate below the AP MLD, STA MLD, and Relay MLD. For example, the AP of AP MLD 1 operating in the first link may be referred to as AP 1-1 of AP MLD 1, and the AP of AP MLD 1 operating in the second link may be referred to as AP 1-2 of AP MLD 1. In addition, the STA of STA MLD 1 operating in the first link may be referred to as STA 1-1 of STA MLD 1, and the STA of STA MLD 1 operating in the second link may be referred to as STA 1-2 of STA MLD 1. Additionally, the Relay of Relay MLD 1 operating on the first link may be referred to as Relay 1-1 of Relay MLD 1, and the Relay of Relay MLD 1 operating on the second link may be referred to as Relay 1-2 of Relay MLD 1.The operations of APs or STAs under the MLD may be operations of the MLD, and the operations of the MLD may be operations of the lower APs or STAs. Fig. 7b is merely an example for convenience of explanation and may not be limited to the corresponding operations.

[0182] Referring to FIG. 7A, AP 1-1 (710), Relay 1-1 (720), and STA 1-1 (730) can perform settings for relay communication operation in advance. That is, in FIG. 7A, AP 1-1 (710), Relay 1-1 (720), and STA 1-1 (730) can complete settings for relay communication operation in advance. AP 1-1 (710), Relay 1-1 (720), and STA 1-1 (730) can recognize that they are performing relay communication operation through the above-described settings. AP 1-1 (710) may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (730). The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (710) may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation, and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (710) may want to transmit a frame to STA 1-1 (730) within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance.The duration of the MAC header corresponding to the TXOP set by AP 1-1 (710) may be set to a time equal to or greater than the sum of the data frame transmission time from AP 1-1 (710) to Relay 1-1 (720), the frame transmission time from Relay 1-1 (720) to STA 1-1 (730), the response frame (BlockAck) transmission time of STA 1-1 (730), the response frame transmission time of Relay 1-1 (720), and the interval between transmissions of each frame (e.g. SIFS time).

[0183] The transmitter address of the MAC header included in the frame transmitted by AP 1-1 (710) may be set to the MAC address of AP 1-1 (710), and the receiver address may be set to the MAC address of STA 1-1 (730). AP 1-1 (710) may transmit a frame whose payload is an MSDU (e.g., MSDU 1) to which STA 1-1 (730) is the recipient.

[0184] The MAC header included in the frame transmitted by AP 1-1 (710) may include an indicator indicating that the frame is transmitted (e.g., relayed) via Relay 1-1 (720). The indicator indicating that the frame is relayed via Relay 1-1 (720) may be the MAC address of the Relay included in the address field of the MAC header (e.g., the MAC address of Relay 1-1 (720) included in the Address 4 field). That is, if the MAC address of the Relay is included in the address field of the MAC header, it may be indicated that the frame is relayed via Relay 1-1 (720). Alternatively, the indicator indicating that the frame is relayed via Relay 1-1 (720) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether the frame is relayed via Relay 1-1 (720).

[0185] As another example, since AP 1-1 (710), STA 1-1 (730), and Relay 1-1 (720) have preset relay communication operations, Relay 1-1 (720) can recognize that the frame transmitted by AP 1-1 (710) to STA 1-1 (730) should be relayed. Considering the above, since an indicator indicating that the frame is relayed is unnecessary, the MAC header of the frame transmitted by AP 1-1 (710) may not include the indicator.

[0186] Referring to FIG. 7A, Relay 1-1 (720) can receive a frame (701-1) from AP 1-1 (710). Relay 1-1 (720) can transmit the frame (701-2) of AP 1-1 (710) identically after a SIFS time from the time of completion of reception of the frame transmitted by AP 1-1 (710). Relay 1-1 (720) transmitting the frame of AP 1-1 (710) identically may mean that Relay 1-1 (720) transmits the bits obtained based on the result of decoding and error correction of the frame of AP 1-1 (710) identically. Alternatively, it may mean that Relay 1-1 (720) duplicates the frame of AP 1-1 (710), but is not limited thereto. Since Relay 1-1 (720) transmits the frame after SIFS, AP 1-1 (710) may regard the frame of Relay 1-1 (720) as an immediate response frame. For example, Relay 1-1 (720) may not be able to transmit the frame due to the network allocation vector (NAV) corresponding to the TXOP acquired by AP 1-1 (710). However, Relay 1-1 (720) may regard the frame as an immediate response frame to the frame of AP 1-1 (710). Alternatively, Relay 1-1 (720) may not set a NAV for a frame whose receiver address is STA 1-1 (730). Therefore, Relay 1-1 (720) may transmit the frame (701-2) to STA 1-1 (730) regardless of the NAV setting. Here, AP 1-1 (710) may not update its BlockAck scoreboard until it receives a response frame (e.g., BlockAck frame) from STA 1-1 (730). That is, the receiver of the frame does not determine that it has received the frame.

[0187] STA 1-1 (730) can receive a frame (701-2) from Relay 1-1 (720). STA 1-1 (730) can recognize that the frame is received through Relay 1-1 (720) based on an indicator indicating that the frame is relayed and transmitted or a set relay communication operation. STA 1-1 (730) can transmit a response frame (702-1) to AP 1-1 (710) after a SIFS time from the time when Relay 1-1 (720) completes receiving the frame (701-2). The response frame (702-1) may be a BlockAck (BA) frame indicating the reception status of the frame transmitted by AP 1-1 (710). STA 1-1 (730) may set the transmitter address of the MAC header of the original response frame (702-1) to the MAC address of STA 1-1 (730) and set the receiver address to the MAC address of AP 1-1 (710). The MAC header included in the original response frame (702-1) transmitted by STA 1-1 (730) may include an indicator indicating that the frame is transmitted (eg, relayed) through Relay 1-1 (720). For example, the indicator indicating that the frame is relayed through Relay 1-1 (720) may be the MAC address of the Relay included in the address field of the MAC header (eg, the MAC address of Relay 1-1 (720) included in the Address 4 field). That is, when the MAC address of the Relay is included in the address field of the MAC header, it may be indicated that the frame is relayed through Relay 1-1 (720). Alternatively, the indicator indicating that the frame is to be relayed via Relay 1-1 (720) may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether or not to relay.As another example, since AP 1-1 (710), STA 1-1 (730), and Relay 1-1 (720) have previously set up relay communication operation, Relay 1-1 (720) can recognize that the frame transmitted by STA 1-1 (730) to AP 1-1 (710) should be relayed. Considering the above, an indicator indicating that the frame is relayed may be unnecessary. Accordingly, the MAC header of the frame transmitted by STA 1-1 (730) may not include an indicator indicating that the frame is relayed.

[0188] Relay 1-1 (720) can receive a frame (response frame, BlockAck frame, 702-1) from STA 1-1 (730). Relay 1-1 (720) can transmit a response frame (702-2) to AP 1-1 (710) in the same manner after an SIFS time from the time of completion of receiving the frame (702-1) from STA 1-1 (730).

[0189] Relay 1-1 (720) may also perform an operation to modify the MAC header of the original response frame of STA 1-1 (730) to include an indicator indicating that the response frame is relayed and transmitted by Relay 1-1 (720). AP 1-1 (710) can receive the response frame of STA 1-1 (730) through Relay 1-1 (720). AP 1-1 (710) can check the reception status of the frame transmitted by AP 1-1 (710) to STA 1-1 (730). AP 1-1 (710) can update the BlockAck scoreboard through the response frame (e.g. BlockAck frame) of STA 1-1 (730) and retransmit the frame if there is a frame that failed to be transmitted.

[0190] For example, a frame received by Relay 1-1 (720) from AP 1-1 (710) may contain an error. Relay 1-1 (720) may not transmit the frame with the error to STA 1-1 (730), but may not respond to AP 1-1 (710) or transmit a frame requesting retransmission of the frame from AP 1-1 (710) (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay 1-1 (720) may retransmit the frame with the error from AP 1-1 (710), and transmit the frame to STA 1-1 (730) after receiving the frame without an error, or may discard the frame with the error if the retransmission of the frame with the error is not received.

[0191] As another example, STA 1-1 (730) may be able to receive (decode) frames transmitted by AP 1-1 (710). If STA 1-1 (730), AP 1-1 (710), and Relay 1-1 (720) perform relay communication operation setup, STA 1-1 (730) may not directly respond to AP 1-1 (710) even if it receives frames from AP 1-1 (710).

[0192] As another example, instead of transmitting the same frame to STA 1-1 (730) after SIFS from the time when the data frame of AP 1-1 (710) is received, Relay 1-1 (720) may transmit the frame to STA 1-1 (730) when the medium is idle for PIFS (priority interframe space) time. Alternatively, Relay 1-1 (720) may transmit the frame to STA 1-1 (730) when the medium is idle for PIFS time + 'a' from the time when the data frame of AP 1-1 (710) is received. The above-described operation is to check whether the frame transmitted by AP 1-1 (710) to STA 1-1 (730) is retransmitted. If the PIFS time + 'a' time has elapsed from the time of completion of receiving the frame, Relay 1-1 (720) may consider that AP 1-1 (710) does not retransmit the frame and waits for Relay 1-1 (720) to relay the frame. Here, 'a' time may be aSlotTime or a shorter or longer time, and may not be limited to a specific form.

[0193] As another example, when AP 1-1 (710) transmits to STA 1-1 (730) via Relay 1-1 (720), AP 1-1 (710) may not perform PIFS recovery. That is, even if AP 1-1 (710) transmits a frame and no response frame is received until after PIFS, AP 1-1 (710) may not perform frame retransmission. The above-described operations may be operations to prevent transmission collision with the frame transmitted by Relay 1-1 (720) to STA 1-1 (730).

[0194] As another example, consider a case where STA 1-1 (730) can receive (decode) a frame from AP 1-1 (710). If STA 1-1 (730), AP 1-1 (710), and Relay 1-1 (720) perform relay communication operation setup, STA 1-1 (730) may store the received frame in a buffer when it receives the frame from AP 1-1 (710) and may not directly respond to AP 1-1 (710). Here, STA 1-1 (730) may additionally receive a data frame transmitted through Relay 1-1 (720). STA 1-1 (730) may configure a data frame using the data frame received from AP 1-1 (710) and the data frame received from Relay 1-1 (720). For example, if the received data frame is an A-MPDU, the MPDU in which an error occurred may be different between the A-MPDU received from AP 1-1 (710) and the A-MPDU received from Relay 1-1 (720). STA 1-1 (730) can recover the data frame through MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP 1-1 (710) through Relay 1-1 (720).

[0195] Referring to FIG. 7b, AP MLD 1, Relay MLD 1, and STA MLD 1 can perform settings for relay communication operations in advance. Through this, AP MLD 1, Relay MLD 1, and STA MLD 1 can recognize that they perform relay communication operations. AP 1-1 (740) of AP MLD 1 operating on the first link can perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (760) of STA MLD 1. The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (740) of AP MLD 1 may decrement a backoff counter when the medium is detected as idle in the EDCA backoff operation and transmit a frame at a slot boundary where the backoff counter reaches 0. As another example, AP 1-1 (740) of AP MLD 1 may want to transmit a frame to STA 1-1 (760) of STA MLD within an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frames can be transmitted by successfully performing a channel access operation in advance.The duration of the MAC header corresponding to the TXOP set by AP 1-1 (740) of AP MLD 1 may be set to a time equal to or greater than the sum of the transmission time of one or more data frames transmitted from AP 1-1 (740) of AP MLD 1 to Relay 1-1 (750) of Relay MLD, the transmission time of a response frame (BlockAck) of Relay 1-1 (750) of Relay MLD, and the interval between transmissions of each frame (e.g. SIFS time).

[0196] The transmitter address of the MAC header included in the frame transmitted by AP 1-1 (740) of AP MLD 1 may be set to the MAC address of AP 1-1 (740) of AP MLD 1, and the receiver address may be set to the MAC address of STA 1-1 (760) of STA MLD 1. The payload included in the original frame that AP 1-1 (740) of AP MLD 1 intends to transmit may be an MSDU whose recipient is STA 1-1 (760) of STA MLD 1.

[0197] AP 1-1 (740) of AP MLD 1 can transmit a frame. The MAC header included in the frame transmitted by AP 1-1 (740) of AP MLD 1 may include an indicator indicating that the frame is transmitted (e.g., relayed) through Relay MLD 1. The indicator indicating that the frame is relayed through Relay MLD 1 may be the MAC address of the Relay included in the address field of the MAC header (e.g., the MAC address of at least one of Relay MLD 1, Relay 1-1 of Relay MLD 1, and Relay 1-2 of Relay MLD 1 included in the Address 4 field). That is, when the MAC address of Relay MLD 1 is included in the address field of the MAC header, it may be indicated that the frame is relayed through Relay MLD 1. Alternatively, the indicator indicating that the frame is relayed through Relay MLD 1 may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field) to indicate whether the frame is relayed through Relay MLD 1. As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have preset relay communication operations, Relay 1-1 (750) of Relay MLD 1 can recognize that the frame transmitted by AP 1-1 (740) of AP MLD 1 to STA 1-1 (760) of STA MLD 1 should be relayed. Considering the above, the indicator indicating that the frame is relayed may be unnecessary, and thus the MAC header of the frame transmitted by AP 1-1 (740) of AP MLD 1 may not include the indicator.

[0198] Relay 1-1 (750) of Relay MLD 1 can receive a frame from AP 1-1 (740) of AP MLD 1. Relay MLD 1 may want to transmit the received frame to STA MLD 1 through a second link. That is, Relay MLD 1 may want to transmit the frame received on the first link to STA 1-2 (790) of STA MLD 1 through Relay 1-2 (780) of Relay MLD 1 of the second link. As another example, a case may be considered where the first link is busy after Relay MLD 1 receives a frame transmitted from AP MLD 1 to STA MLD 1 on the first link. Among the first and second links available to Relay MLD 1, the second link may be in an idle state, or the busy state of the second link may end sooner than that of the first and second links. Therefore, Relay MLD 1 may not be able to transmit a frame from the first link to STA 1-1 (760) of STA MLD 1 via Relay 1-1 (750) of Relay MLD 1. In the above-described situation, Relay MLD 1 may want to transmit a frame from the second link to STA 1-2 (790) of STA MLD 1 via Relay 1-2 (780) of Relay MLD 1, but the present invention may not be limited to the above-described embodiment.

[0199] When Relay 1-2 (780) of Relay MLD 1 successfully decodes MSDU 1, it can immediately perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the second link. When the channel access operation is successful, Relay 1-2 (780) of Relay MLD 1 can acquire EDCA TXOP, which is a communication section, on the second link. Alternatively, when Relay MLD 1 detects a frame transmitted on the first link, Relay 1-2 (780) of Relay MLD 1 can immediately perform a channel access operation. Relay 1-2 (780) of Relay MLD 1 can wait for transmission without transmitting a frame until decoding of MSDU 1 is successfully performed. The duration of the MAC header corresponding to the TXOP set by Relay 1-2 (780) of Relay MLD 1 may be set to a time equal to or greater than the sum of the transmission time of one or more data frames transmitted from Relay 1-2 (780) of Relay MLD 1 to STA 1-2 (790) of STA MLD 1, the transmission time of a response frame (BlockAck) of STA 1-2 (790) of STA MLD 1, the time for Relay 1-2 (780) of Relay MLD 1 to transmit the response frame of STA 1-2 (790) of STA MLD 1, and the interval between transmissions of each frame (e.g. SIFS time).

[0200] The EDCA TXOP of Relay 1-2 (780) of Relay MLD 1 can be used by Relay 1-2 (780) of Relay MLD 1 to transmit the frame of AP MLD 1 to STA MLD 1. Relay MLD 1 can transmit the frame received from AP 1-1 (740) of AP MLD 1 in the same manner. This may mean that Relay MLD 1 performs decoding and error correction on the frame of AP MLD 1 and transmits the bits obtained as a result thereof in the same manner. Relay MLD 1 can complete reception of the frame transmitted by AP 1-1 (740) of AP MLD 1 in the first link and transmit the same frame as the frame of AP 1-1 (740) of AP MLD 1 to STA 1-2 (790) of STA MLD 1 in the TXOP of the second link. Relay MLD 1 may further perform the operation of adding an indicator to the MAC header of the original frame transmitted by AP 1-1 (740) of AP MLD 1, indicating that the frame was relayed and transmitted. As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have previously set up a relay communication operation, STA 1-2 (790) of STA MLD 1 can recognize the frame transmitted by Relay 1-2 (780) of Relay MLD 1 to STA 1-2 (790) of STA MLD 1. Therefore, a separate indicator may be unnecessary.

[0201] STA 1-2 (790) of STA MLD 1 can receive a frame from Relay 1-2 (780) of Relay MLD 1. STA 1-2 (790) of STA MLD 1 can recognize that the frame of Relay 1-2 (780) of Relay MLD 1 is relayed based on an indicator indicating that the frame is relayed or a configured relay communication operation. STA 1-2 (790) of STA MLD 1 can receive (decode) MSDU 1, which is the payload of the frame of AP 1-1 (740) of AP MLD 1.

[0202] For example, AP 1-1 (740) of AP MLD 1 of the first link can transmit one frame or multiple frames at regular time intervals within a TXOP as shown in Table 4 below.

[0203] [Table 4]

[0204]

[0205]

[0206] When AP 1-1 (740) of AP MLD 1 transmits a frame, Relay 1-1 (750) of Relay MLD 1 can receive the frame (a frame whose receiver address is STA 1-1 of STA MLD 1) from AP 1-1 (740) of AP MLD 1. In response to the frame transmitted by AP 1-1 (740) of AP MLD 1 to STA 1-1 (760) of STA MLD 1, Relay 1-1 (750) of Relay MLD 1 can transmit an ACK frame to AP 1-1 (740) of AP MLD 1. AP 1-1 (740) of AP MLD 1 considers the ACK frame of Relay 1-1 (750) of Relay MLD 1 as an immediate response frame, but may not update the BlockAck scoreboard. That is, the receiver of the frame does not determine that it has received the frame. For example, Relay 1-1 (750) of Relay MLD 1 cannot transmit the frame due to the NAV corresponding to the TXOP acquired by AP 1-1 (740) of AP MLD 1. However, Relay 1-1 (750) of Relay MLD can regard the ACK frame as an immediate response frame to the frame of AP 1-1 (740) of AP MLD 1. Therefore, Relay 1-1 (750) of Relay MLD can transmit the ACK frame to AP 1-1 (740) of AP MLD 1 regardless of the NAV setting.

[0207] Relay 1-2 (780) of Relay MLD 1 can decode the frame transmitted by AP 1-1 (740) of AP MLD 1 and transmit the same frame to STA 1-2 (790) of STA MLD 1. STA 1-2 (790) of STA MLD 1 can receive the frame of AP 1-1 (740) of AP MLD 1 and receive the payload (e.g. MSDU 1). STA 1-2 (790) of STA MLD 1 can transmit a response frame (e.g. BlockAck frame) to Relay 1-2 (780) of Relay MLD 1.

[0208] As another example, consider a case where AP 1-1 (740) of AP MLD 1 transmits multiple frames (703-1, 703-2) at regular intervals. Relay 1-1 (750) of Relay MLD 1 can receive multiple frames (703-1, 703-2) whose receiver address is STA 1-1 (760) of STA MLD 1 from AP MLD 1 at regular time intervals. Relay 1-1 (750) of Relay MLD 1 can decode multiple frames (703-1, 703-2) received from AP 1-1 (740) of AP MLD 1. When a frame of AP 1-1 (740) of AP MLD 1 is transmitted at a PIFS interval longer than SIFS by aSlotTime, Relay 1-1 (750) of Relay MLD 1 can transmit an ACK frame to AP 1-1 (740) of AP MLD 1 after SIFS time from the time when frame reception is completed. Alternatively, the transmission method of the response frame transmitted by Relay 1-1 (750) of Relay MLD 1 to AP 1-1 (740) of AP MLD 1 may vary depending on the setting of the Ack Policy of the frame transmitted by AP MLD 1 to Relay 1-1 (750) of Relay MLD 1. The Ack Policy of a frame other than the last frame transmitted by AP 1-1 (740) of AP MLD 1 to Relay 1-1 (750) of Relay MLD 1 may be set to BlockAck, which does not require immediate transmission of a response frame, or may be set to No Ack Policy, etc. The interval between frames other than the last frame transmitted by AP 1-1 (740) of AP MLD 1 to Relay 1-1 (750) of Relay MLD 1 may be SIFS. The Ack Policy of the last frame transmitted by AP 1-1 (740) of AP MLD 1 to Relay 1-1 (750) of Relay MLD 1 may be set to Implicit BAR.When Relay 1-1 (750) of Relay MLD 1 receives the last frame from AP 1-1 (740) of AP MLD 1, Relay 1-1 must transmit a response frame (BlockAck frame, Ack frame) to AP 1-1 (740) of AP MLD 1 after SIFS. As another example, referring to FIG. 7b, AP 1-1 (740) of AP MLD 1 may include an indicator indicating the last frame in the last transmitted frame (706-3) among multiple frames (703-1, 703-2). The indicator indicating the last frame may be setting the value of the More Data subfield of the Frame Control field to 0. Relay 1-1 (750) of Relay MLD 1, which has received a frame including an indicator indicating the last frame, may transmit an ACK frame (704) to AP 1-1 (740) of AP MLD 1 after SIFS time from the time of completion of reception of the last frame (703-2). AP 1-1 (740) of AP MLD 1 immediately regards the ACK frame (704) of Relay 1-1 (750) of Relay MLD 1 as a response frame, but may not update the BlockAck scoreboard. That is, the receiver of the frame does not determine that the frame has been received.

[0209] For example, Relay 1-1 (750) of Relay MLD 1 may not be able to transmit a frame due to NAV corresponding to TXOP acquired by AP 1-1 (740) of AP MLD 1. However, the ACK frame (704) transmitted by Relay 1-1 (750) of Relay MLD 1 may be regarded as an immediate response frame to the frame of AP 1-1 (740) of AP MLD 1. Therefore, Relay 1-1 (750) of Relay MLD 1 may transmit the ACK frame (704) regardless of the NAV setting. Referring to FIG. 7B, Relay 1-2 (780) of Relay MLD 1 of the second link may transmit frames decoded by Relay 1-1 (750) of Relay MLD 1 to STA 1-2 (790) of STA MLD 1. For example, STA 1-2 (790) of STA MLD 1 may individually transmit response frames (e.g., BlockAck frames, 706-1, 706-2) to frames (705-1, 705-2) transmitted by Relay 1-2 (780) of Relay MLD 1. The Ack Policy of each encapsulated frame (705-1, 705-2, 705-3) may be set to an Implicit BAR requesting a BlockAck frame. As another example, after Relay 1-2 (780) of Relay MLD 1 transmits multiple frames (705-1, 705-2), STA 1-2 (790) of STA MLD 1 may transmit a single response frame for the multiple frames (705-1, 705-2). The Ack Policy of some of the encapsulated frames (705-1, 705-2) may be set to BlockAck, which does not immediately request a BlockAck frame, and the Ack Policy of the last encapsulated frame (705-3) may be set to Implicit BAR, which requests a BlockAck frame.

[0210] Based on the operation of Table 4 described above, STA 1-2 (790) of STA MLD 1 can transmit a response frame to Relay 1-2 (780) of Relay MLD 1. The response frame may be a BlockAck (BA) frame indicating the reception status of the frame transmitted by AP 1-1 (740) of AP MLD 1. STA 1-2 (790) of STA MLD 1 may set the transmitter address of the MAC header of the response frame to the MAC address of STA 1-2 (790) of STA MLD 1, and set the receiver address to the MAC address of at least one of AP 1-1 (740) of AP MLD 1, AP 1-2 of AP MLD 1, and AP MLD 1. The MAC header included in the response frame transmitted by STA 1-2 (790) of STA MLD 1 may include an indicator indicating that the frame is transmitted (e.g., relayed) through Relay 1-2 (780) of Relay MLD 1 (i.e., Relay MLD 1). The indicator indicating that the frame is relayed through Relay MLD 1 may be the MAC address of the Relay included in the address field of the MAC header (e.g., the MAC address of at least one of Relay MLD 1 included in the Address 4 field, Relay 1-1 of Relay MLD 1, and Relay 1-2 of Relay MLD 1). Alternatively, the indicator indicating that the frame is relayed through Relay MLD 1 may be set as a separate subfield or bit (e.g., an indicator included in the HT Control field). As another example, since AP MLD 1, STA MLD 1, and Relay MLD 1 have previously set up relay communication operations, Relay MLD 1 can recognize that the frame transmitted by STA MLD 1 to AP MLD 1 should be relayed. Therefore, an indicator indicating that the frame is relayed may be unnecessary.Accordingly, the MAC header transmitted by STA 1-2 (790) of STA MLD 1 may not include an indicator indicating that the frame is relayed. Relay 1-2 (780) of Relay MLD 1 can receive a frame (response frame, BlockAck frame) from STA 1-2 (790) of STA MLD 1. Relay MLD 1 can transmit the response frame of STA 1-2 (790) of STA MLD 1 to AP 1-1 (740) of AP MLD 1 using Relay 1-1 (750) of Relay MLD 1 of the first link. Alternatively, Relay MLD 1 can transmit the response frame to AP 1-2 (770) of AP MLD 1 through Relay 1-2 (780) of Relay MLD 1 of the second link.

[0211] Relay 1-2 (780) of Relay MLD 1 may perform an operation to modify the MAC header of the response frame of STA 1-2 (790) of STA MLD 1 to include an indicator indicating that the response frame is relayed and transmitted by Relay MLD 1. After Relay MLD 1 completes receiving the frame from STA 1-2 (790) of STA MLD 1, it may transmit a response frame identical to the frame transmitted by STA 1-2 (790) of STA MLD 1 to AP 1-2 (770) of AP MLD 1 after SIFS. Alternatively, Relay 1-2 (780) of Relay MLD 1 may perform a channel access operation (EDCA backoff operation, EDCA TXOP acquisition procedure) on the second link, and when the channel access operation is completed, the STA 1-2 (790) of STA MLD 1 may transmit a response frame identical to the frame transmitted to AP 1-2 (770) of AP MLD 1. AP MLD 1 may receive the response frame of STA MLD 1 through Relay MLD 1. AP MLD 1 may check the reception status of the frame transmitted to STA MLD 1. AP MLD 1 may update the BlockAck scoreboard based on the response frame of STA MLD 1 (e.g. BlockAck frame), and may retransmit the frame if there is a frame that failed to be transmitted.

[0212] Also, for example, a frame received by Relay MLD 1 (i.e., Relay 1-1 (750) of Relay MLD 1) from AP MLD 1 (i.e., AP 1-1 (740) of AP MLD 1) may contain an error. Relay MLD 1 may not transmit the frame containing the error to STA MLD 1. Relay MLD 1 may not respond to AP MLD 1, or transmit a frame requesting retransmission of the frame from AP MLD 1 (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay MLD 1 may retransmit the frame containing the error from AP 1-1 (740) of AP MLD 1, and transmit the frame to STA MLD 1 after receiving the frame without an error, or if the retransmission of the frame containing the error is not received, the frame containing the error may be discarded.

[0213] STA MLD 1 (i.e., STA 1-1 (760) of STA MLD 1) may be able to receive (decode) frames from AP MLD 1 (i.e., AP 1-1 (740) of AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (760) of STA MLD 1 may not directly respond to AP 1-1 (740) of AP MLD 1 even if it receives frames from AP 1-1 (740) of AP MLD 1.

[0214] As another example, STA 1-1 (760) of STA MLD 1 (i.e., STA MLD 1) may be able to receive (decode) a frame of AP 1-1 (740) of AP MLD 1 (i.e., AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (760) of STA MLD 1 may store the frame of AP 1-1 (740) of AP MLD 1 in a buffer and may not directly respond to AP MLD 1. STA 1-1 (760) of STA MLD 1 may additionally receive a data frame transmitted via Relay MLD 1. STA MLD 1 can construct a data frame using a data frame received from AP 1-1 (740) of AP MLD 1 and a data frame received from Relay 1-2 (780) of Relay MLD 1. Here, if the received data frame is an A-MPDU, an MPDU in which an error occurred in the A-MPDU received from AP 1-1 (740) of AP MLD 1 and an A-MPDU received from Relay 1-2 (780) of Relay MLD 1 may be different. STA MLD 1 can recover the data frame using MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP MLD 1 through Relay MLD 1.

[0215] In FIGS. 7A and 7B, the setting of the relay communication operation by the AP 1-1 (740) of the AP MLD 1 (or, AP MLD 1, AP), the STA 1-1 of the STA MLD 1 (or, STA MLD 1, STA), and the Relay 1-1 (750) of the Relay MLD 1 (or, Relay MLD 1, STA) of the Relay MLD 1 may be performed based on the determination of the machine learning unit described in FIGS. 1 to 4. For example, the machine learning unit may determine that at least one of the AP, the Relay, and the STA requires a relay communication operation, and the procedure of determining the Relay that performs the relay communication operation may be performed by the machine learning unit. As another example, when multiple Relays exist in a wireless LAN network, the machine learning unit of the AP or the STA may determine that the relay communication operation is required by using signal strength, etc. as input. Once it is determined that a relay communication operation is required, the machine learning unit can input the signal strengths of multiple relays and select the most appropriate relay for the relay communication operation. After setting the relay communication operation with the most appropriate relay, the relay communication operation(s) described in Figures 7a and 7b can be performed.

[0216] FIG. 8A and FIG. 8B are diagrams illustrating a method for performing a relay communication operation to which the present disclosure is applied. Referring to FIG. 8A and FIG. 8B, wireless LAN terminals (e.g., AP (access point), Relay (Relay STA), STA (station)) may operate in a wireless LAN network. For example, in FIG. 8A, a case may be considered in which AP 1-1 (810), Relay 1-1 (820), and STA 1-1 (830) operate in a wireless LAN network, but this is for convenience of explanation and may not be limited thereto. In addition, in FIG. 8B, the AP, Relay, and STA may be referred to as an MLD (multi-link device) supporting multi-link operation, and may be referred to as an AP MLD, a Relay MLD, and a STA MLD. An MLD may be a wireless LAN terminal having a separate MAC layer (MLD lower MAC sublayer) and a PHY layer for each link (e.g., a first link, a second link, etc.). Above the link-specific MAC layer of the MLD, there may be a MAC layer (MLD upper MAC sublayer) that integrates the link-specific MAC layers. Here, the link-specific AP or STA may operate below the AP MLD, STA MLD, and Relay MLD. For example, the AP of AP MLD 1 operating in the first link may be referred to as AP 1-1 of AP MLD 1, and the AP of AP MLD 1 operating in the second link may be referred to as AP 1-2 of AP MLD 1. In addition, the STA of STA MLD 1 operating in the first link may be referred to as STA 1-1 of STA MLD 1, and the STA of STA MLD 1 operating in the second link may be referred to as STA 1-2 of STA MLD 1. Additionally, the Relay of Relay MLD 1 operating on the first link may be referred to as Relay 1-1 of Relay MLD 1, and the Relay of Relay MLD 1 operating on the second link may be referred to as Relay 1-2 of Relay MLD 1.The operations of APs or STAs under the MLD may be operations of the MLD, and the operations of the MLD may be operations of the lower APs or STAs. Fig. 8b is merely an example for convenience of explanation and may not be limited to the corresponding operations.

[0217] Referring to FIG. 8A, AP 1-1 (810), Relay 1-1 (820), and STA 1-1 (830) may not be configured for relay communication operation in advance. Relay 1-1 (820) can receive frames from AP 1-1 (810) and STA 1-1 (830), and thus can recognize that communication with AP 1-1 (810) and STA 1-1 (830) is possible. AP 1-1 (810) can perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (830), and can obtain an EDCA TXOP. AP 1-1 (810) may wish to transmit a frame to STA 1-1 (830). For example, AP 1-1 (810) may successfully transmit a frame to another STA at least once before transmitting the frame to STA 1-1 (830). Afterwards, AP 1-1 (810) may wish to transmit the frame to STA 1-1 (830) within an EDCA TXOP (transmit opportunity).

[0218] The transmitter address of the MAC header of the frame to be transmitted by AP 1-1 (810) may be set to the MAC address of AP 1-1 (810), and the receiver address may be set to the MAC address of STA 1-1 (830). AP 1-1 (810) may transmit a frame whose payload is an MSDU (e.g., MSDU 1) to which STA 1-1 (830) is the recipient. Here, STA 1-1 (830) cannot receive the frame of AP 1-1 (810), and Relay 1-1 (820) may receive the frame from AP 1-1 (810). Relay 1-1 (820) may recognize that the destination is STA 1-1 (830) after receiving the frame from AP 1-1 (810). However, Relay 1-1 (820) may not transmit the frame of AP 1-1 (810) to STA 1-1 (830) until AP 1-1 (810) retransmits the frame. The retransmission of the frame may be performed PIFS. after the transmission of the initial frame.

[0219] For example, referring to FIG. 8A, if STA 1-1 (830) does not respond to frame (801-1) of AP 1-1 (810), AP 1-1 (810) can retransmit frame (801-2) after PIFS time from the end time of transmission of frame (801-1). If AP 1-1 (810) retransmits frame (801-2) after PIFS, Relay 1-1 (820) can equally transmit frame (802) of AP 1-1 (810) to STA 1-1 (830) after SIFS time from the end time of transmission of retransmitted frame of AP 1-1 (810). Relay 1-1 (820) transmitting the frame (802) of AP 1-1 (810) identically may mean that Relay 1-1 (820) transmits the bits obtained as a result of decoding and error correction of the frame of AP 1-1 (810) identically. For example, this may mean that Relay 1-1 (820) duplicates the frame of AP 1-1 (810), but it may not be limited to this embodiment.

[0220] Relay 1-1 (820) may further include an indicator in the MAC header of the frame (802) of AP 1-1 (810) indicating that it is to be relayed and transmitted. Since Relay 1-1 (820) transmits the frame after SIFS, AP 1-1 (810) may consider the frame (802) of Relay 1-1 (820) as an immediate response frame. However, AP 1-1 (810) may not update its BlockAck scoreboard until it receives a response frame (e.g., BlockAck frame) of STA 1-1 (830). That is, the receiver of the frame does not determine that it has received the frame.

[0221] For example, Relay 1-1 (820) may not be able to transmit a frame due to a network allocation vector (NAV) corresponding to the TXOP acquired by AP 1-1 (810). However, Relay 1-1 (820) may regard frame (801-2) as an immediate response frame to frame (801-1) of AP 1-1 (810). Therefore, Relay 1-1 (820) may transmit frame (802) to STA 1-1 (830) regardless of the NAV setting. Alternatively, Relay 1-1 (820) may not set the NAV when receiving a frame whose receiver address is STA 1-1 (830).

[0222] STA 1-1 (830) can receive a frame (802) from Relay 1-1 (820). STA 1-1 (830) can recognize that the frame is received from AP 1-1 (810) through Relay 1-1 (820) based on an indicator indicating that the frame is relayed and transmitted. Alternatively, STA 1-1 (830) may not be aware of the existence of Relay 1-1 (820) and may recognize that the frame (802) of Relay 1-1 (820) is received from AP 1-1 (810). STA 1-1 (830) can transmit a response frame (e.g., BlockAck frame) after a SIFS time from the time point when Relay 1-1 (820) completes receiving the frame. The transmitter address of the BlockAck frame transmitted by STA 1-1 (830) may be set to the MAC address of STA 1-1 (830), and the receiver address may be set to the MAC address of AP 1-1 (810). Since Relay 1-1 (820) relayed the frame to STA 1-1 (830) in which AP 1-1 (810) is the transmitter and STA 1-1 (830) is the receiving destination, it can be known that the response frame transmitted by STA 1-1 (830) should be relayed to AP 1-1 (810). Relay 1-1 (820) may receive the response frame (803-1) of STA 1-1 (830) and transmit the frame (803-2) in the same manner after an SIFS time from the time of completion of reception of the response frame of STA 1-1 (830). Relay 1-1 (820) may also perform an operation to modify the MAC header of the original response frame of STA 1-1 (830) to include an indicator indicating that the response frame is relayed and transmitted by Relay 1-1 (820). AP 1-1 (810) can receive the response frame (803-2) of STA 1-1 (830) through Relay 1-1 (820). AP 1-1 (810) can check the reception status of the frame transmitted by AP 1-1 to STA 1-1 (830).AP 1-1 updates the BlockAck scoreboard based on the response frame (e.g. BlockAck frame) of STA 1-1 (830) and can retransmit frames if there are frames that failed to be transmitted.

[0223] For example, a frame received by Relay 1-1 (820) from AP 1-1 (810) may contain an error. Relay 1-1 (820) may not transmit the frame containing the error to STA 1-1 (830). Relay 1-1 (820) may not respond to AP 1-1 (810) or transmit a frame requesting retransmission of the frame from AP 1-1 (810) (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay 1-1 (820) may retransmit the frame containing the error from AP 1-1 (810) and transmit the frame to STA 1-1 (830) after receiving the frame without an error, or if the retransmission of the frame containing the error is not received, the frame containing the error may be discarded.

[0224] As another example, STA 1-1 (830) may be able to receive (decode) frames transmitted by AP 1-1 (810). If STA 1-1 (830), AP 1-1 (810), and Relay 1-1 (820) perform relay communication operation setup, STA 1-1 (830) may not directly respond to AP 1-1 (810) even if it receives frames from AP 1-1 (810).

[0225] As another example, consider a case where STA 1-1 (830) can receive (decode) a frame from AP 1-1 (810). If STA 1-1 (830), AP 1-1 (810), and Relay 1-1 (820) perform relay communication operation setup, STA 1-1 (830) may store the received frame in a buffer when it receives the frame from AP 1-1 (810) and may not directly respond to AP 1-1 (810). Here, STA 1-1 (830) may additionally receive a data frame transmitted through Relay 1-1 (820). STA 1-1 (830) may construct a data frame using the data frame received from AP 1-1 (810) and the data frame received from Relay 1-1 (820). For example, if the received data frame is an A-MPDU, the MPDU in which an error occurred may be different between the A-MPDU received from AP 1-1 (810) and the A-MPDU received from Relay 1-1 (820). STA 1-1 (830) can recover the data frame through MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP 1-1 (810) through Relay 1-1 (820).

[0226] Referring to FIG. 8B, AP MLD 1, Relay MLD 1, and STA MLD 1 may not perform configuration for relay communication operation. Here, Relay MLD 1 may recognize that it can communicate with AP MLD 1 and STA MLD 1 because it can receive frames from AP MLD 1 and STA MLD 1. AP 1-1 (840) of AP MLD 1 operating on the first link may perform a channel access operation to transmit a frame (e.g., packet, physical layer protocol data unit (PPDU), MAC layer protocol data unit (MPDU), aggregated-MPDU (A-MPDU), MAC service data unit (MSDU), aggregated-MSDU (A-MSDU)) to STA 1-1 (860) of STA MLD 1. The channel access operation may be an enhanced distributed channel access (EDCA) backoff operation and an EDCA TXOP (transmit opportunity) acquisition procedure. AP 1-1 (840) of AP MLD 1 can decrease the backoff counter when the medium is detected as idle in the EDCA backoff operation and transmit a frame at the slot boundary where the backoff counter reaches 0. That is, AP 1-1 (840) of AP MLD 1 can obtain an EDCA TXOP (transmit opportunity), which is a communication section in which multiple frame transmissions are possible. AP 1-1 (840) of AP MLD 1 may have successfully transmitted at least one frame to another STA in the EDCA TXOP.

[0227] AP 1-1 (840) of AP MLD 1 may want to transmit a frame to STA 1-1 (860) of STA MLD 1 in EDCA TXOP. A transmitter address of a MAC header of a frame that AP 1-1 (840) of AP MLD 1 wants to transmit may be set to the MAC address of AP 1-1 (840) of AP MLD 1, and a receiver address may be set to the MAC address of STA 1-1 (860) of STA MLD 1. A payload included in a frame that AP 1-1 (840) of AP MLD 1 wants to transmit may be an MSDU of which STA 1-1 (860) of STA MLD 1 is the recipient.

[0228] Referring to FIG. 8B, AP 1-1 (840) of AP MLD 1 can transmit frame (804-1). Here, it can be considered that STA 1-1 (860) of STA MLD 1 cannot receive frame (804-1). AP MLD 1 can retransmit frame (804-2) to STA 1-1 (860) of STA MLD 1 after PIFS. Relay 1-1 (850) of Relay MLD 1 can receive the frame that AP 1-1 (840) of AP MLD 1 transmits to STA 1-1 (860) of STA MLD 1. However, Relay 1-1 (850) of Relay MLD 1 may not transmit a response frame (e.g., ACK frame, 805) to AP 1-1 (840) of AP MLD 1 until AP 1-1 (840) of AP MLD 1 retransmits the frame. AP 1-1 (840) of AP MLD 1 may retransmit the frame (804-2) to STA 1-1 (860) of STA MLD 1 after PIFS time from the time of frame transmission completion if STA 1-1 (860) of STA MLD 1 does not respond. When AP 1-1 (840) of AP MLD 1 retransmits frame (804-2) after PIFS, Relay MLD 1 can transmit ACK frame (805) to AP 1-1 (840) of AP MLD 1 after SIFS after the end of transmission of retransmission frame of AP 1-1 (840) of AP MLD 1 (i.e., AP MLD 1). In addition, Relay MLD 1 can equally transmit frame (806) of AP 1-1 (840) of AP MLD 1 to STA 1-2 (890) of STA MLD 1 through Relay 1-2 (880) of Relay MLD 1 of the second link.For example, Relay MLD 1 transmitting the frame of AP MLD 1 identically may mean that Relay MLD 1 transmits the bits obtained as a result of decoding and error correction of the frame of AP 1-1 (840) of AP MLD 1 identically. Alternatively, it may mean, but is not limited to, that Relay MLD 1 duplicates the frame of AP MLD 1.

[0229] Relay MLD 1 may further include an indicator in the MAC header of the frame of AP 1-1 (840) of AP MLD 1 indicating that it is to be relayed and transmitted, and may transmit the frame (806) to the second link. Relay 1-2 (880) of Relay MLD 1 may perform a channel access procedure on the second link. Since Relay 1-1 (850) of Relay MLD 1 transmits the ACK frame (805) after SIFS, AP 1-1 (840) of AP MLD 1 (i.e., AP MLD 1) may regard the frame of Relay 1-1 (850) of Relay MLD 1 as an immediate response frame. However, AP MLD 1 may not update the BlockAck scoreboard of AP MLD 1 until it receives a response frame (e.g., BlockAck frame) from STA 1-1 (860) of STA MLD 1 (i.e., STA MLD 1). That is, the receiver of the frame does not determine that it has received the frame.

[0230] For example, Relay 1-1 (850) of Relay MLD 1 may not be able to transmit a frame due to the NAV corresponding to the TXOP acquired by AP 1-1 (840) of AP MLD 1. However, Relay 1-1 (850) of Relay MLD 1 may regard the ACK frame (805) as an immediate response frame to the frame of AP 1-1 (840) of AP MLD 1. Alternatively, Relay 1-1 (850) may not set a NAV for a frame whose receiver address is STA 1-1 (860). Therefore, Relay 1-1 (850) of Relay MLD 1 may transmit the ACK frame (805) to AP 1-1 (840) of AP MLD 1 regardless of the NAV setting.

[0231] When Relay 1-2 (880) of Relay MLD 1 completes the channel access procedure on the second link, Relay 1-2 (880) of Relay MLD 1 can transmit the frame (806) received from AP 1-1 (840) of AP MLD 1 to STA 1-2 (890) of STA MLD 1. Here, Relay 1-2 (880) of Relay MLD 1 can obtain EDCA TXOP. The duration of the MAC header corresponding to the TXOP set by Relay 1-2 (880) of Relay MLD 1 can be set to a time equal to or greater than the sum of the transmission time of one or more data frames transmitted from Relay 1-2 (880) of Relay MLD 1 to STA 1-2 (890) of STA MLD 1, the transmission time of a response frame (BlockAck) of STA 1-2 (890) of STA MLD 1, the time for Relay 1-2 (880) of Relay MLD 1 to transmit the response frame of STA 1-2 (890) of STA MLD 1, and the interval between transmissions of each frame (e.g. SIFS time).

[0232] STA 1-2 (890) of STA MLD 1 can receive a frame (806) from Relay 1-1 (850) of Relay MLD 1. STA 1-2 (890) of STA MLD 1 can recognize that the frame is received from AP MLD 1 through Relay MLD 1 based on an indicator indicating that the frame is relayed and transmitted. Alternatively, since the sender of the MAC header of the frame transmitted by Relay 1-2 (880) of Relay MLD 1 is the MAC address of AP 1-1 (840) of AP MLD 1, not AP 1-2, Relay 1-2 (880) of Relay MLD 1 can recognize that the frame is received through Relay MLD 1. Alternatively, STA 1-2 (890) of STA MLD 1 may not be aware of the existence of Relay MLD 1 and may recognize that the frame of Relay MLD 1 is received from AP MLD 1. STA 1-2 (890) of STA MLD 1 may transmit a response frame (e.g., BlockAck frame, 807-1) after SIFS time from the time of completion of frame reception of Relay 1-2 (880) of Relay MLD 1. The transmitter address of the BlockAck frame transmitted by STA 1-2 (890) of STA MLD 1 may be set to the MAC address of STA 1-2 (890) of STA MLD 1, and the receiver address may be indicated as the MAC address of AP MLD 1 or an AP below AP MLD 1 (e.g., AP 1-2 of AP MLD 1). Relay MLD 1 can recognize that the response frame transmitted by STA 1-2 (890) of STA MLD 1 must be relayed to AP MLD 1 because the lower AP of AP MLD 1 is the transmitter and the lower STA of STA MLD 1 relayed the frame to STA MLD 1 as the receiving destination.

[0233] Relay MLD 1 may receive a response frame (807-1) of STA 1-2 (890) of STA MLD 1 on the second link, and transmit the same frame (807-2) to AP 1-2 (870) of AP MLD 1 after SIFS time from the time of completion of reception of the response frame of STA 1-2 (890) of STA MLD 1 on the second link. Alternatively, Relay MLD 1 may receive a response frame (807-1) of STA 1-2 (890) of STA MLD 1 on the second link, perform a channel access procedure on the first link, and transmit the response frame of STA MLD 1 to AP 1-1 (840) of AP MLD 1 when the channel access procedure is completed.

[0234] AP MLD 1 can receive a response frame from STA MLD 1 through Relay MLD 1. AP MLD 1 can check the reception status of the frame transmitted from AP MLD 1 to STA MLD 1. AP MLD 1 can update the BlockAck scoreboard based on the response frame (e.g. BlockAck frame) from STA MLD 1, and can retransmit a frame if there is a frame that failed to be transmitted.

[0235] Also, for example, a frame received by Relay MLD 1 (i.e., Relay 1-1 (850) of Relay MLD 1) from AP MLD 1 (i.e., AP 1-1 (840) of AP MLD 1) may contain an error. Relay MLD 1 may not transmit the frame containing the error to STA MLD 1, may not respond to AP MLD 1, or may transmit a frame requesting retransmission of the frame from AP MLD 1 (e.g., an ACK frame indicating NACK, a BlockAck frame). In this case, Relay MLD 1 may retransmit the frame containing the error from AP 1-1 (840) of AP MLD 1, and may transmit the frame to STA MLD 1 after receiving the frame without an error, or may discard the frame containing the error if the retransmission of the frame containing the error is not received.

[0236] STA MLD 1 (i.e., STA 1-1 (860) of STA MLD 1) may be able to receive (decode) frames from AP MLD 1 (i.e., AP 1-1 (840) of AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (860) of STA MLD 1 may not directly respond to AP 1-1 (840) of AP MLD 1 even if it receives frames from AP 1-1 (840) of AP MLD 1.

[0237] As another example, STA 1-1 (860) of STA MLD 1 (i.e., STA MLD 1) may be able to receive (decode) a frame of AP 1-1 (840) of AP MLD 1 (i.e., AP MLD 1). If STA MLD 1, AP MLD 1, and Relay MLD 1 perform relay communication operation setup, STA 1-1 (860) of STA MLD 1 may store the frame of AP 1-1 (840) of AP MLD 1 in a buffer and may not directly respond to AP MLD 1. STA 1-1 (860) of STA MLD 1 may additionally receive a data frame transmitted via Relay MLD 1. STA MLD 1 can construct a data frame using a data frame received from AP 1-1 (840) of AP MLD 1 and a data frame received from Relay 1-2 (880) of Relay MLD 1. Here, if the received data frame is an A-MPDU, an MPDU in which an error occurred in the A-MPDU received from AP 1-1 (840) of AP MLD 1 and an A-MPDU received from Relay 1-2 (880) of Relay MLD 1 may be different. STA MLD 1 can recover the data frame using MPDUs without errors, and can generate a response frame (BlockAck) based on the recovered data frame and transmit it to AP MLD 1 through Relay MLD 1.

[0238] In FIGS. 8A and 8B, the setting of the relay communication operation by the AP 1-1 (840) of the AP MLD 1 (or, AP MLD 1, AP), the STA 1-1 of the STA MLD 1 (or, STA MLD 1, STA), and the Relay 1-1 (850) of the Relay MLD 1 (or, Relay MLD 1, STA) of the Relay MLD 1 may be performed based on the determination of the machine learning unit described in FIGS. 1 to 4. For example, the machine learning unit may determine that at least one of the AP, the Relay, and the STA requires a relay communication operation, and the procedure of determining the Relay that performs the relay communication operation may be performed by the machine learning unit. As another example, when multiple Relays exist in a wireless LAN network, the machine learning unit of the AP or the STA may determine that the relay communication operation is required by using signal strength, etc. as input. Once it is determined that a relay communication operation is required, the machine learning unit can input the signal strengths of multiple relays and select the most appropriate relay for the relay communication operation. After setting the relay communication operation with the most appropriate relay, the relay communication operation(s) described in FIGS. 8A and 8B can be performed.

[0239] FIG. 9 is a flowchart illustrating a method for performing a relay communication operation to which the present disclosure applies. Referring to FIG. 9, a relay may receive a first frame from an AP (S910). Here, the first frame may be a frame transmitted from the AP to an STA through the relay, and may not be limited to a specific form. For example, the MAC header of the first frame may include a first indicator indicating that the first frame is transmitted through the relay. Thereafter, the relay may transmit a second frame to the STA based on the received first frame (920). For example, the second frame may be a frame generated by the relay through a frame received from the AP, and is not limited to a specific form.

[0240] Thereafter, the relay may receive a first response frame generated by the STA based on the first frame from the STA. (S930) Here, the MAC header of the first response frame may include a second indicator indicating that the first response frame is transmitted through the relay. Thereafter, the relay may transmit a second response frame to the AP based on the first response frame. (S940) As an example, the relay may include 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, and the specific operation may be as described above.

[0241] The relay may perform a relay operation setup procedure with the AP and STA before transmitting the first frame. For example, if the relay has established relay operation by performing a relay operation setup procedure with the AP and STA, an indicator indicating the relay may not be necessary. Accordingly, the MAC header of the first frame may not include the first indicator, and the MAC header of the first response frame may not include the second indicator.

[0242] For example, the first indicator indicating that the first frame is transmitted through a relay may be a relay address within an address field included in the MAC header of the first frame, or a subfield or bit included in the MAC header of the first frame. In addition, the second indicator indicating that the first response frame is transmitted through a relay may be a relay address within an address field included in the MAC header of the first response frame, or a subfield or bit included in the MAC header of the first response frame, as described above.

[0243] In addition, the sender address of the first frame may be the address of the AP, and the receiver address of the first frame may be the address of the STA. The relay may receive the first frame and generate a second frame, and the payload of the second frame may include the first frame. That is, the relay may encapsulate the received first frame to generate the second frame, which may be as shown in FIGS. 5A to 5C. For example, the MAC header of the second frame may include a third indicator indicating that the first frame is encapsulated.

[0244] In addition, the sender address of the first response frame may be the address of the STA, and the receiver address of the first response frame may be the address of the AP. The relay may receive the first response frame and generate a second response frame, and the payload of the second response frame may include the first response frame. That is, the relay may encapsulate the received first response frame to generate the second response frame, which may be as shown in FIGS. 5A to 5C. For example, the MAC header of the second response frame may include a fourth indicator indicating that the first response frame is encapsulated. In addition, the relay may transmit the second frame after a preset time from the time of receiving the first frame. In addition, for example, when the relay receives the first frame, it may transmit a response frame for the first frame to the AP after a preset time from the time of receiving the first frame. After transmitting a response frame to the first frame, the relay may perform a channel access operation to transmit the second frame in the allocated transmit opportunity (TXOP), as described above.

[0245] Additionally, the relay may be a relay MLD including a first relay associated with a first link and a second relay associated with a second link, as illustrated in FIGS. 5C, 6B, 7B, and 8B. The relay MLD may receive a first frame from the AP MLD on a first link for a first relay (Relay 1-1 of the Relay MLD), and the relay MLD may transmit a second frame to the STA MLD on a second link for a second relay (Relay 1-2 of the Relay MLD), as described above. For example, if the relay MLD successfully decodes the first frame or if the relay MLD detects a first frame transmission on the first link for the first relay, the relay MLD may perform a channel access operation on the second link for the second relay to transmit the second frame on the assigned TXOP. Here, the TXOP allocated in the second link can be set to a time equal to or longer than the time at which the relay MLD transmits one or more second frames, the time at which the first response frame is received from the STA MLD, the time at which the second response frame is transmitted to the AP MLD, and the interval time between frame transmissions, as described above.

[0246] Also, as an example, the sender address of the first frame received by the relay may be the address of the AP, and the receiver address of the first frame may be the address of the relay. That is, the relay may receive a frame encapsulated by the AP. The relay may receive the first frame and generate a second frame, which may be the decapsulation described above. Here, the sender address of the second frame may be the address of the AP, and the receiver address of the second frame may be the address of the STA. The relay may generate the second frame through the original frame of the AP included in the payload of the first frame. Here, the second frame may be a frame in which the MAC header is modified from the original frame of the AP, and the MAC header of the second frame may include a fifth indicator indicating that the original frame of the AP is transmitted through the relay.

[0247] In addition, the sender address of the first response frame received by the relay may be the address of the STA, and the receiver address of the first frame may be the address of the relay. That is, the relay may receive the response frame encapsulated by the STA. The relay may receive the first response frame and generate a second response frame, which may be the decapsulation described above. The sender address of the second response frame may be the address of the STA, and the receiver address of the second frame may be the address of the AP. Here, the relay may generate the second response frame through the original response frame of the STA included in the payload of the first response frame. For example, the second response frame may be a frame in which the MAC header is modified from the original response frame of the STA, and the MAC header of the second response frame may include a sixth indicator indicating that the original response frame of the STA is transmitted through the relay.

[0248] Additionally, the relay may generate a second frame identical to the first frame based on bits obtained through decoding and error correction after receiving the first frame and transmit the second frame to the STA. Additionally, the relay may generate a second response frame identical to the first response frame based on bits obtained through decoding and error correction after receiving the first response frame and transmit the second response frame to the AP, which may be as shown in FIGS. 7A and 7B .

[0249] In addition, the relay may not perform a relay operation negotiation procedure with the AP and the STA, and after receiving the first frame, the relay may wait for a preset time from the end time of retransmission of the first frame, and then generate a second frame identical to the first frame based on bits obtained through decoding and error correction of the first frame and transmit the second frame to the STA, which may be as shown in FIGS. 8A and 8B.

[0250] 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.

[0251] 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.

[0252] 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.

[0253]

[0254] The above may also apply to other systems.

Claims

1. In the method of operating a relay in a wireless LAN system, A step in which the above relay receives a first frame from an access point (AP), wherein a medium access control (MAC) header of the first frame includes a first indicator indicating that the first frame is transmitted through the relay; A step of transmitting a second frame to a station (STA) based on the first frame received by the relay; A step in which the relay receives a first response frame generated based on the first frame from the STA, wherein the MAC header of the first response frame includes a second indicator indicating that the first response frame is transmitted through the relay; and A relay operation method, comprising a step of the relay transmitting a second response frame to the AP based on the first response frame.

2. In paragraph 1, The above relay performs a relay operation setup procedure with the AP and the STA before transmitting the first frame, A relay operation method, wherein when performing a relay operation based on the above relay operation setting procedure, the MAC header of the first frame does not include the first indicator, and the MAC header of the first response frame does not include the second indicator.

3. In paragraph 2, The first indicator indicating that the first frame is transmitted through the relay is a relay address in an address field included in the MAC header of the first frame or a subfield or bit included in the MAC header of the first frame, A relay operation method, wherein the second indicator indicating that the first response frame is transmitted through the relay is a relay address in an address field included in a MAC header of the first response frame or a subfield or bit included in a MAC header of the first response frame.

4. In paragraph 1, The sender address of the first frame is the address of the AP, and the receiver address of the first frame is the address of the STA. A method of operating a relay, wherein the relay receives the first frame and generates the second frame, wherein the payload of the second frame includes the first frame, and the MAC header of the second frame includes a third indicator indicating that the first frame is encapsulated.

5. In paragraph 1, The sender address of the first response frame is the address of the STA, and the receiver address of the first response frame is the address of the AP. A relay operating method, wherein the relay receives the first response frame and generates the second response frame, wherein the payload of the second response frame includes the first response frame, and the MAC header of the second response frame includes a fourth indicator indicating that the first response frame is encapsulated.

6. In paragraph 1, A relay operation method, wherein the relay transmits the second frame after a preset time from the time of receiving the first frame.

7. In paragraph 1, A relay operation method, wherein the relay transmits a response frame for the first frame to the AP after a preset time from the time of reception of the first frame when the first frame is received, and the relay performs a channel access operation after transmitting the response frame for the first frame to transmit the second frame in the allocated TXOP (transmit opportunity).

8. In paragraph 1, The above relay is a relay multi link device (MLD) including a first relay associated with a first link and a second relay associated with a second link, The above relay MLD receives the first frame from the AP MLD on the first link for the first relay, A relay operation method, wherein the above relay MLD transmits the second frame to the STA MLD on the second link for the second relay.

9. In paragraph 8, A method of relay operation, wherein if the relay MLD successfully decodes the first frame or the relay MLD detects transmission of the first frame on the first link for the first relay, the relay MLD performs a channel access operation on the second link for the second relay to transmit the second frame in an allocated transmit opportunity (TXOP).

10. In paragraph 9, A relay operation method, wherein the TXOP allocated in the second link is set to a time that is equal to or longer than a time at which the relay MLD transmits one or more of the second frames, a time at which the relay MLD receives the first response frame from the STA MLD, a time at which the second response frame is transmitted to the AP MLD, and an interval time between frame transmissions.

11. In paragraph 1, The sender address of the first frame received by the above relay is the address of the AP, and the receiver address of the first frame is the address of the relay. A relay operation method, wherein the relay receives the first frame and generates the second frame, wherein the transmitter address of the second frame is the address of the AP, and the receiver address of the second frame is the address of the STA.

12. In paragraph 11, A relay operation method, wherein the relay generates the second frame through the original frame of the AP included in the payload of the first frame, the second frame being a frame with a modified MAC header from the original frame of the AP, and the MAC header of the second frame includes a fifth indicator indicating that the original frame of the AP is transmitted through the relay.

13. In paragraph 1, The sender address of the first response frame received by the above relay is the address of the STA, and the receiver address of the first frame is the address of the relay, A relay operation method, wherein the relay receives the first response frame and generates the second response frame, wherein the sender address of the second response frame is the address of the STA, and the receiver address of the second frame is the address of the AP.

14. In paragraph 13, A relay operation method, wherein the relay generates the second response frame through the original response frame of the STA included in the payload of the first response frame, the second response frame being a frame in which the MAC header is modified from the original response frame of the STA, and the MAC header of the second response frame includes a sixth indicator indicating that the original response frame of the STA is transmitted through the relay.

15. In paragraph 1, A relay operation method, wherein the relay generates a second frame identical to the first frame based on bits obtained through decoding and error correction after receiving the first frame and transmits the second frame to the STA, and the relay generates a second response frame identical to the first response frame based on bits obtained through decoding and error correction after receiving the first response frame and transmits the second response frame to the AP.

16. In paragraph 1, The above relay does not perform relay operation negotiation procedures with the above AP and the above STA, A relay operation method in which, after receiving the first frame, the relay waits for a preset time from the end time of retransmission of the first frame, and then generates a second frame identical to the first frame based on bits obtained through decoding and error correction of the first frame and transmits the second frame to the STA.

17. In relay, 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 above specific actions are: Receiving a first frame from an access point (AP), wherein the medium access control (MAC) header of the first frame includes a first indicator indicating that the first frame is transmitted through the relay, Transmitting a second frame to a station (STA) based on the received first frame, The relay receives from the STA a first response frame generated based on the first frame, wherein the MAC header of the first response frame includes a second indicator indicating that the first response frame is transmitted through the relay, and A relay, wherein the relay transmits a second response frame to the AP based on the first response frame.

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