Method and apparatus for expanding communication bandwidth in wireless LAN

Abstract

A method for operating an AP MLD including a first AP associated with a first link and a second AP associated with a second link in a wireless LAN system may comprise the steps in which: the AP MLD transmits a first PPDU in a first bandwidth in the first link for the first AP; the AP MLD detects that a part or the entirety of the entire bandwidth of the second link is in a busy state in the second link for the second AP, wherein when the part or the entirety of the entire bandwidth of the second link is detected to be in the busy state, the link associated with the second AP is switched from the second link to the first link, and the AP MLD performs a channel sensing operation and a channel access operation in a second bandwidth in the switched first link for the second AP; and the AP MLD stops transmission of the first PPDU for the first AP and transmits a second PPDU through the first bandwidth and the second bandwidth when the second bandwidth in the first link is occupied by the AP MLD on the basis of the channel sensing operation and the channel access operation.

Description

Method and device for expanding communication bandwidth in wireless LAN

[0001] The present disclosure relates to a method and device for expanding communication bandwidth in a Wireless Local Area Network (WLAN). Specifically, the present disclosure relates to a method and device for expanding communication bandwidth between users in a WLAN based on artificial intelligence, thereby enabling high-speed communication.

[0002] In addition, the present disclosure relates to a method and device for expanding communication bandwidth that can be used when performing artificial intelligence-based reverse communication in a wireless LAN.

[0003] In addition, the present disclosure relates to a method and device for performing low-latency communication using a subchannel based on artificial intelligence in a wireless LAN.

[0004]

[0005] 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.

[0006] 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.

[0007] Recently, as applications requiring higher reliability arise, the IEEE 802.11bn standard, an ultra-high reliability (UHR) wireless LAN technology, is being developed for single BSS (Basic Service Set) 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 can support low-power operation and direct communication (peer-to-peer, P2P communication).

[0008] However, actions to increase channel utilization in WLANs may be limited. For example, in a WLAN supporting multiple links, channel expansion operations may not be possible between multiple links. Therefore, channel expansion operations in WLANs may not be performed across multiple links, and WLAN channel expansion operations may be inefficient. Consequently, the effect of increasing channel utilization in WLAN networks may be limited.

[0009] Additionally, multiple terminals in a WLAN can use wireless resources. However, as the number of wireless terminals using wireless resources increases, communication delays due to channel access can occur, and inefficient wireless resource utilization can occur. When a wireless access point allocates resources for reverse communication to terminals in a WLAN, the large number of wireless terminals can lead to inefficient resource utilization. This can lead to reduced WLAN network performance, and solutions may be needed to address this issue.

[0010] Additionally, it may be necessary to define subchannel operation for low-latency communication in wireless LAN and to define low-latency communication using this.

[0011] Meanwhile, the technology that serves as the background of the invention is written to promote understanding of the background of the invention, and may include content that is not a prior art already known to a person with ordinary skill in the field to which the technology belongs, and may not be limited to a specific form.

[0012]

[0013] The present disclosure relates to a method and device for expanding communication bandwidth in a wireless LAN.

[0014] The present disclosure relates to a method and device for expanding a communication bandwidth after performing link switching when a link is busy in a multi link device (MLD).

[0015] The present disclosure relates to a method and device for switching a communication bandwidth after performing a link switch when a link is in a busy state in MLD.

[0016] The present disclosure relates to a method and device for expanding available bandwidth when performing reverse communication in a wireless LAN.

[0017] The present disclosure relates to a method and device for efficiently transmitting low-latency traffic using subchannel operation in a wireless LAN.

[0018] 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.

[0019]

[0020] According to one example of the present disclosure, in a wireless LAN system, an AP MLD including a first AP associated with a first link and a second AP associated with a second link may be provided with an operating method, the method comprising: a step of the AP MLD transmitting a first PPDU in a first bandwidth within the first link for the first AP; a step of the AP MLD detecting that a part or all of a second link total bandwidth is busy in the second link for the second AP; when a part or all of the second link total bandwidth is detected to be busy, a link associated with the second AP is switched from the second link to the first link, and the AP MLD performing a channel sensing operation and a channel access operation in the second bandwidth within the switched first link for the second AP; and a step of the AP MLD stopping the first PPDU transmission for the first AP and transmitting a second PPDU through the first bandwidth and the second bandwidth when the second bandwidth within the first link is occupied by the AP MLD based on the channel sensing operation and the channel access operation.

[0021] Also, according to one example of the present disclosure, in an AP MLD, a first AP associated with a first link of the AP MLD, a second AP associated with a second link of the AP MLD, at least one transceiver for transmitting and receiving a signal, and at least one processor for controlling at least one of the first AP, the second AP and the at least one transceiver, and a memory for storing instructions for causing the AP MLD to perform a specific operation, wherein the specific operation is: the AP MLD transmits a first PPDU in a first bandwidth within the first link for the first AP, the AP MLD detects that a part or all of the entire bandwidth of the second link is busy in the second link for the second AP, and when a part or all of the entire bandwidth of the second link is detected to be busy, the link associated with the second AP is switched from the second link to the first link, and the AP MLD performs a channel sensing operation and a channel access operation in the second bandwidth within the switched first link for the second AP, and the channel sensing operation and the channel access operation If the second bandwidth within the first link is occupied by the AP MLD based on the operation, the AP MLD may stop transmitting the first PPDU for the first AP and transmit the second PPDU through the first bandwidth and the second bandwidth.

[0022] Additionally, the following may be commonly applied:

[0023] According to one example of the present disclosure, when the AP MLD detects that part or all of the second link total bandwidth is busy for the second AP, the AP MLD may recognize the busy period along with whether part or all of the second link total bandwidth is busy for the second AP.

[0024] Additionally, according to one example of the present disclosure, the link associated with the second AP may be switched from the second link to the first link immediately upon the AP MLD detecting that some or all of the second link's total bandwidth is busy for the second AP, or after a preset amount of time from the time the AP MLD detects that some or all of the second link's total bandwidth is busy.

[0025] In addition, according to an example of the present disclosure, when a link associated with a second AP is switched from a second link to a first link, the switching from the second link to the first link is completed after a link switching time from the time when the switching from the second link to the first link starts, and the AP MLD operates on the first link for the second AP, and the link associated with the second AP is switched from the first link to the second link is started before the link switching time from the time when a busy period ends after switching to the first link, and the switching is completed at the time when the busy period ends, and the AP MLD operates on the second link from the time when the busy period ends for the second AP.

[0026] Additionally, according to one example of the present disclosure, the link associated with the second AP is maintained as the first link until the AP MLD starts transmitting the second PPDU over the first bandwidth and the second bandwidth for the first AP based on the channel sensing operation and the channel access operation after switching to the first link, and from the time of starting transmitting the second PPDU, the AP MLD can operate on the second link for the second AP.

[0027] In addition, according to one example of the present disclosure, when the AP MLD performs a channel sensing operation and a channel access operation in a second bandwidth within a first link for a second AP, and when the second bandwidth is in a busy state based on the channel sensing operation and the channel access operation, and when it detects that the second bandwidth has transitioned from the busy state to an idle state, the AP MLD decrements a backoff counter for each slot after a preset time from the time of transitioning to the idle state, and the AP MLD stops transmitting a first PPDU at a slot boundary where the backoff counter becomes 0 for the first AP, and transmits a second PPDU through the first bandwidth and the second bandwidth.

[0028] Additionally, according to an example of the present disclosure, if the third bandwidth is idle before a preset time from a slot boundary where the backoff counter becomes 0, the AP MLD may transmit a second PPDU for the first AP through the first bandwidth, the second bandwidth, and the third bandwidth at the slot boundary where the backoff counter becomes 0, and if the third bandwidth is busy before a preset time from a slot boundary where the backoff counter becomes 0, the AP MLD may transmit a second PPDU for the first AP through the first bandwidth and the second bandwidth at the slot boundary where the backoff counter becomes 0.

[0029] Additionally, according to an example of the present disclosure, the first bandwidth may be a primary 20 MHz band, the second bandwidth may be a secondary 20 MHz band, and the third bandwidth may be a secondary 40 MHz band.

[0030] Additionally, according to an example of the present disclosure, when the first bandwidth is a primary 40 MHz band and the second bandwidth is a secondary 40 MHz band, the AP MLD can perform a channel sensing operation and a channel access operation in a secondary 20 MHz band adjacent to the first bandwidth within the second bandwidth for the second AP.

[0031] In addition, according to an example of the present disclosure, when the AP MLD detects that the secondary 20 MHz band adjacent to the first bandwidth is busy for the second AP, and when the secondary 20 MHz band adjacent to the first bandwidth transitions from the busy state to the idle state, the AP MLD decrements a backoff counter for each slot after a preset time from the time of transition to the idle state for the second AP, and the AP MLD can stop transmitting the first PPDU at the slot boundary where the backoff counter becomes 0 for the first AP, and transmit the second PPDU through the first bandwidth and the second bandwidth.

[0032] In addition, according to one example of the present disclosure, the AP MLD may decrement a backoff counter at every slot after a preset time if a secondary 20 MHz band adjacent to the first bandwidth in the second bandwidth for the second AP is idle, and if the AP MLD detects that some channels in the second bandwidth are busy at a slot boundary where the backoff counter becomes 0 for the first AP, the AP MLD may maintain the backoff counter at 0 until the entire second bandwidth for the first AP transitions to an idle state, and if the entire second bandwidth transitions to an idle state, may stop transmitting the first PPDU after a preset time from the time of transitioning to an idle state, and may transmit the second PPDU over the first bandwidth and the second bandwidth.

[0033] Additionally, according to an example of the present disclosure, when the AP MLD transmits the first PPDU over the entire bandwidth of the first link for the first AP, the AP MLD may perform a channel sensing operation and a channel access operation in a third bandwidth adjacent to the entire bandwidth of the first link after switching from the second link to the first link for the second AP.

[0034] Additionally, according to an example of the present disclosure, when the AP MLD detects that the third bandwidth is idle for the second AP, the AP MLD may perform a third PPDU transmission independent of the first PPDU in the third bandwidth for the second AP.

[0035] Additionally, according to an example of the present disclosure, when the AP MLD detects that the third bandwidth is idle for the second AP, the AP MLD may stop transmitting the first PPDU for the first AP, and the AP MLD may perform the fourth PPDU transmission over the first bandwidth and the third bandwidth for the first and second APs.

[0036] Additionally, according to one example of the present disclosure, the entire bandwidth of the first link may be a primary 80 MHz band, and a third bandwidth adjacent to the entire bandwidth of the first link may be a secondary 80 MHz band.

[0037]

[0038] According to the present disclosure, a method for expanding communication bandwidth in a wireless LAN can be provided.

[0039] According to the present disclosure, a method for expanding communication bandwidth after performing link switching when a link is busy in MLD can be provided.

[0040] According to the present disclosure, a method for switching a communication bandwidth after performing a link switch when a link is in a busy state in MLD can be provided.

[0041] According to the present disclosure, a method for expanding available bandwidth when performing reverse communication in a wireless LAN can be provided.

[0042] According to the present disclosure, a method for efficiently transmitting low-latency traffic using subchannel operation in a wireless LAN can be provided.

[0043] 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.

[0044]

[0045] Figure 1 is a diagram showing a communication node within a wireless LAN system to which the present disclosure is applied.

[0046] Figure 2 is a diagram showing a wireless LAN system to which the present disclosure is applied.

[0047] FIG. 3 is a diagram illustrating a machine learning unit to which the present disclosure is applied.

[0048] FIG. 4 is a flowchart illustrating a method for performing communication based on a machine learning unit to which the present disclosure is applied.

[0049] FIGS. 5A to 5D are diagrams showing a wireless LAN communication bandwidth expansion method to which the present disclosure is applied.

[0050] FIGS. 6A to 6C are diagrams illustrating a wireless LAN communication space stream expansion method to which the present disclosure is applied.

[0051] FIGS. 7A to 7D are diagrams showing a method for extending a reverse communication period in a wireless LAN to which the present disclosure is applied.

[0052] FIGS. 8A to 8E are diagrams showing a method for extending a reverse communication period in a wireless LAN to which the present disclosure is applied.

[0053] FIGS. 9A to 9D are diagrams illustrating a wireless LAN low-latency subchannel operation method to which the present disclosure is applied.

[0054] Fig. 10 is a flowchart showing a method for expanding communication bandwidth in a wireless LAN to which the present disclosure is applied.

[0055]

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding in describing the present disclosure, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0062] Below, a wireless communication system to which embodiments according to the present disclosure are applied will be described. The wireless communication system to which embodiments according to the present disclosure are applied is not limited to the 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."

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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).

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] As another example, the machine learning unit (300) may be designed to implement not only the machine learning algorithm but also other machine learning algorithms. To this end, the machine learning unit (300) may include additional components for implementing other machine learning algorithms. The ML memory (320) within the machine learning unit (300) may store machine learning models and machine learning algorithms. The implementation of the machine learning algorithms may be performed by the ML processor (310) based on the machine learning models.

[0072] 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).

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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).

[0077] 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.

[0078] Figures 5a to 5d are diagrams showing a method for expanding communication bandwidth in a wireless LAN.

[0079] Referring to FIGS. 5A to 5D , a first link (510) and a second link (520) may exist in a wireless LAN network. For example, a multi-link device (MLD) may operate on the first link (510) and the second link (520). The communication bandwidths of the first link (510) and the second link (520) may be 320 MHz, 160 MHz, 80 MHz, 40 MHz, and 20 MHz, respectively. The first link (510) and the second link (520) may also have different communication bandwidths, and are not limited to a specific form.

[0080] For example, in the first link (510) and the second link (520), a specific 20MHz channel of the 80MHz channel may be a primary 20MHz channel, and a 20MHz channel adjacent to the primary 20MHz channel may be a secondary 20MHz channel. Here, the primary 20MHz channel and the secondary 20MHz channel may be combined to form a primary 40MHz channel. Additionally, a 40MHz channel adjacent to the primary 40MHz channel may be a secondary 40MHz channel. In a similar manner, a primary 80MHz channel and a secondary 80MHz channel may be configured, and a primary 160MHz channel and a secondary 160MHz channel may be configured. The following description is based on the case where the operating bandwidth of the first link (510) and the second link (520) is 80MHz. However, this is only for convenience of explanation and may not be limited thereto. That is, the operating bandwidth of multiple links (including the first link and the second link) may be set in various forms, and the following may be applied equally. Meanwhile, the primary 20MHz channel may be the most basic channel used for channel access and frame transmission. That is, frame transmission must be performed by occupying the primary 20MHz channel, and whether or not the frame is transmitted may be determined depending on whether the primary 20MHz channel is occupied (busy).

[0081] AP (access point) MLD and non-AP MLD can operate in the first link (510) and the second link (520). Non-AP MLD can be referred to as STA (station) MLD. A lower AP affiliated with can operate under the AP MLD. An AP operating in the first link (510) with AP MLD can be referred to as AP 1, and an AP operating in the second link (520) with AP MLD can be referred to as AP 2. For example, AP 1 and AP 2 can be entities having independent communication modules (e.g., MAC, PHY). In addition, an STA (non-AP STA) operating in the first link (510) with STA MLD can be referred to as STA 1, and an STA operating in the second link (520) with STA MLD can be referred to as STA 2. For example, STA 1 and STA 2 may be entities with independent communication modules (e.g. MAC, PHY).

[0082] Referring to FIG. 5A, AP 1 of the AP MLD can detect that the secondary 20MHz channel is busy in the first link (510). If the secondary 20MHz channel is busy in the first link (510), AP 1 of the AP MLD cannot use the secondary 20MHz channel and the secondary 40MHz channel, and can perform transmission using only the primary 20MHz channel.

[0083] AP 2 of the AP MLD can detect that the second link (520) is busy. For example, the link's busy state can be determined based on preamble detection, virtual CCA (clear channel assessment) based on the network allocation vector (NAV), and other reasons. Here, AP 2 of the AP MLD can recognize whether the link is busy and the busy period.

[0084] For example, the occupied section of the second link (520) may be a TXOP (Transmit Opportunity) established by the transmission of an OBSS (overlapping Basic Service Set) in the second link (520). That is, the occupancy of the second link (520) may be due to communication of the OBSS. As another example, the channel may be occupied due to interference by communication of the OBSS or other reasons, and may not be limited to a specific reason. The channel occupied state or channel busy state may refer to a case where the channel is not used by other communications (e.g., non-wireless LAN wireless communications using the same channel). For the convenience of explanation, the terms channel occupied state or channel busy state are referred to below, but may not be limited to those names.

[0085] AP 2 of the AP MLD can detect that part or all of the total bandwidth (e.g., 80 MHz) of the second link (520) is occupied. When AP 2 of the AP MLD detects that part or all of the total bandwidth of the second link (520) is occupied, AP 2 of the AP MLD can change the operating link or operating frequency to the first link (510). AP 2 of the AP MLD can switch the operating state to the first link (510) for a time Ts, which is a link switching time. AP 2 of the AP MLD can change the operating link to the first link (510) immediately after detecting the occupied state in the second link (520) or after a preset time (e.g., preamble and MAC header decoding time). AP 2 of the AP MLD can operate in the first link (510) only within the recognized occupied section as described above. AP 2 of AP MLD operates on the first link (510) only until Ts time from the time point when the occupied period of the second link (520) ends, and can operate on the second link (520) after the time point when the occupied period ends. As another example, if AP 2 of AP MLD succeeds in channel access based on a channel access operation on the first link (510), AP 2 of AP MLD can operate on the first link (510) until the time point when AP 1 of AP MLD initiates wider bandwidth transmission.

[0086] For example, AP 1 of AP MLD can perform an operation of performing transmission by performing bandwidth expansion with wideband transmission, as well as an operation of performing transmission by converting (or switching) the bandwidth to another bandwidth. That is, based on the channel access operation performed by AP 2 of AP MLD, AP 1 of AP MLD may also perform an operation of switching from the existing used bandwidth to another bandwidth. For the convenience of explanation, the following description is based on the operation of bandwidth expansion, but this can be equally applied to the case where the bandwidth is switched. That is, the following matters can be equally applied to bandwidth switching. This can also be equally applied to other drawings and the description below.

[0087] AP 2 of the AP MLD can perform a channel sensing operation (e.g., a Clear Channel Assessment (CCA) operation) and a channel access operation (e.g., an enhanced distributed channel access (EDCA) backoff operation) on the first link (510). More specifically, AP 2 of the AP MLD can perform a channel sensing operation and a channel access operation on a channel (e.g., a secondary 20MHz channel) other than a channel (e.g., a primary 20MHz channel) on which AP 1 of the AP MLD performs transmission on the first link (510). Since the secondary 20MHz channel is occupied, AP 1 of the AP MLD may not be able to transmit, and AP 2 of the AP MLD performs a channel sensing operation and a channel access operation on the secondary 20MHz channel to enable AP 1 of the AP MLD to transmit frames in a wideband manner.

[0088] For example, AP 2 of the AP MLD can perform a channel sensing operation and a channel access operation on a secondary 20MHz channel, which is an adjacent channel to a primary 20MHz channel, which is a channel on which AP 1 of the AP MLD performs transmission. As a result of the channel sensing operation, AP 2 of the AP MLD can detect that the channel is occupied. If the channel transitions from the occupied state to the idle or idle state as a result of the channel sensing operation, AP 2 of the AP MLD can wait for the AIFS (arbitrary interframe space)[AC] time, which is the waiting time for each AC (access category), on the channel. Here, AP 2 of the AP MLD can select an EDCA backoff counter, and if the channel is detected as idle during the AIFS[AC] time, can perform an operation of decreasing the EDCA backoff counter every aSlotTime. AP 1 in AP MLD can end transmission of 20MHz PPDU (PHY layer protocol data unit, 501) at the slot boundary of the slot where the EDCA backoff counter reaches 0 and expand the transmission channel to the channel detected by AP 2 in AP MLD. In other words, AP 2 in AP MLD can perform channel sensing and channel access operations for expanding the transmission bandwidth of AP 1 in AP MLD on its behalf.

[0089] AP 1 of the AP MLD may include an end indicator at the end of the PPDU to terminate the transmission of the 20MHz PPDU (501). AP 1 of the AP MLD may terminate the transmission of the 20MHz PPDU (501) and transmit a PPDU with an extended transmission bandwidth after a preset IFS (e.g., SIFS (short interframe space), RIFS (reduced interframe space), PIFS (priority interframe space)). Alternatively, AP 1 of the AP MLD may transmit a PPDU extended to 40MHz immediately after the end of the 20MHz PPDU. The extended PPDU may include a preamble according to the extended channel bandwidth.

[0090] If, while AP 2 of the AP MLD performs channel sensing and channel access operations, the secondary 40MHz channel is detected as idle for a PIFS time before a slot boundary where the backoff counter becomes 0, AP 1 of the AP MLD can transmit an 80MHz PPDU (502) using both the primary 40MHz channel and the secondary 40MHz channel. On the other hand, if, while AP 2 of the AP MLD performs channel sensing and channel access operations, the secondary 40MHz channel is detected as channel occupied for a PIFS time before a slot boundary where the backoff counter becomes 0, AP 1 of the AP MLD can use the secondary 20MHz channel. That is, only the primary 20MHz channel and the secondary 20MHz channel are not occupied, and the primary 40MHz channel composed of the primary 20MHz channel and the secondary 20MHz channel can be used. That is, AP 1 of AP MLD can transmit PPDU of 40MHz bandwidth using primary 40MHz channel. When channel detection and channel access operations of AP 2 of AP MLD are terminated (e.g., when AP 1 of AP MLD transmits extended PPDU based on channel detection and channel access operations of AP 2 of AP MLD), AP 2 of AP MLD can operate on the second link (520), which is the original operating link, after the link switching time. Alternatively, AP 2 of AP MLD can operate on the second link (520), which is the original operating link, again at the time when the occupancy state of the second link ends (i.e., when the occupancy period ends).

[0091] Referring to FIG. 5B, AP 1 of the AP MLD can detect that the secondary 40MHz channel is occupied on the first link (510). AP 1 of the AP MLD cannot use the secondary 40MHz channel and can transmit only using the primary 40MHz channel. AP 2 of the AP MLD can detect that the channel is occupied on the second link (520). For example, the link occupancy can be set based on preamble detection, virtual CCA due to NAV, and other reasons. In addition, AP 2 of the AP MLD can recognize the busy period.

[0092] For example, the occupied period of the second link (520) may be a TXOP set by the transmission of the OBSS in the second link (520). That is, the occupancy of the second link (520) may be due to communication of the OBSS and other reasons, as shown in FIG. 5a.

[0093] AP 2 of the AP MLD can detect that part or all of the entire bandwidth (e.g., 80 MHz) of the second link (520) is occupied. AP 2 of the AP MLD can change the operating link or operating frequency to the first link (510). AP 2 of the AP MLD can switch the operating state to the first link (510) for a time Ts as a link switching time. AP 2 of the AP MLD can change the operating link to the first link (510) immediately after detecting the occupied state in the second link (520) or after a preset time (e.g., preamble and MAC header decoding time). AP 2 of the AP MLD can operate in the first link (510) only within the recognized occupied period as described above. AP 2 of AP MLD operates on the first link only until Ts time from the time when the occupied period of the second link (520) ends, and can operate on the second link (520) after the time when the occupied period ends. As another example, if AP 2 of AP MLD succeeds in the channel access operation on the first link (510), AP 2 of AP MLD can operate on the first link (510) until the time when AP 1 of AP MLD initiates wider bandwidth transmission. As an example, the same bandwidth expansion and bandwidth switching as in FIG. 5A can be applied to FIG. 5B.

[0094] AP 2 of the AP MLD can perform a channel sensing operation (e.g., a CCA operation) and a channel access operation (e.g., an EDCA backoff operation) on the first link (510). More specifically, AP 2 of the AP MLD can perform a channel sensing operation and a channel access operation on a channel (e.g., the first 20 MHz channel of the secondary 40 MHz) other than a channel on which AP 1 of the AP MLD performs transmission (e.g., a primary 40 MHz channel) on the first link (510).

[0095] For example, AP 2 of the AP MLD can perform a channel detection operation and a channel access operation on a 20MHz channel adjacent to the primary 40MHz channel among the secondary 40MHz channels, which are adjacent channels to the primary 40MHz channel, which is the channel on which AP 1 of the AP MLD performs transmission. As a result of the channel detection operation, AP 2 of the AP MLD can detect that the channel is occupied. If the channel is switched from the occupied state to the idle state as a result of the channel detection operation, AP 2 of the AP MLD can wait for the AIFS[AC] time, which is the waiting time per AC, on the corresponding channel. Here, AP 2 of the AP MLD can select an EDCA backoff counter, and if the channel is detected as idle during the AIFS[AC] time, can perform an operation of decreasing the EDCA backoff counter every aSlotTime. AP 1 in AP MLD can end transmission of 40MHz PPDU (503) at the slot boundary of the slot where the EDCA backoff counter reaches 0, and can expand the transmission channel to the channel detected by AP 2 in AP MLD. In other words, AP 2 in AP MLD can perform channel sensing and channel access operations for expanding the transmission bandwidth of AP 1 in AP MLD on its behalf.

[0096] AP 1 of the AP MLD may include an end indicator at the end of the PPDU to terminate the transmission of the 40MHz PPDU (503). AP 1 of the AP MLD may terminate the transmission of the 40MHz PPDU and transmit a PPDU with an extended transmission bandwidth after a predetermined IFS (e.g., SIFS, RIFS, PIFS). Alternatively, AP 1 of the AP MLD may transmit an extended 80MHz PPDU (504) immediately after the end of the 40MHz PPDU. The extended 80MHz PPDU (504) may include a preamble according to the extended channel bandwidth.

[0097] If, while AP 2 of the AP MLD performs a channel sensing operation and a channel access operation, the secondary 40MHz channel is detected as idle for a PIFS time before a slot boundary where the backoff counter becomes 0, AP 1 of the AP MLD may transmit an 80MHz PPDU (504) using both the primary 40MHz channel and the secondary 40MHz channel. On the other hand, if, while AP 2 of the AP MLD performs a channel sensing operation and a channel access operation, the secondary 40MHz channel is detected as occupied for a PIFS time before a slot boundary where the backoff counter becomes 0, AP 1 of the AP MLD may continue to transmit the ongoing 40MHz PPDU (503) transmission. That is, AP 1 of the AP MLD may not expand its transmission bandwidth. When the channel detection and channel access operations of AP 2 of AP MLD are terminated (e.g., when AP 1 of AP MLD transmits an extended PPDU based on the channel detection and channel access operations of AP 2 of AP MLD), AP 2 of AP MLD may operate on the second link (520), which is the original operating link, after the link switching time. Alternatively, AP 2 of AP MLD may operate on the second link (520), which is the original operating link, again at the point in time when the occupancy state of the second link ends (i.e., when the occupancy period ends).

[0098] Referring to FIG. 5c, AP 1 of the AP MLD can detect that the secondary 40 MHz channel is busy in the first link (510). AP 1 of the AP MLD cannot use the secondary 40 MHz channel and can transmit using only the primary 40 MHz channel.

[0099] AP 2 of the AP MLD can detect that the second link (520) is busy. For example, the link's busy state can be determined based on preamble detection, virtual CCA due to NAV, and other reasons. AP 2 of the AP MLD can recognize the busy period.

[0100] For example, the occupied period of the second link (520) may be a TXOP set by the transmission of the OBSS in the second link (520). That is, the occupancy of the second link (520) may be due to communication of the OBSS and other reasons, as shown in FIG. 5a.

[0101] AP 2 of the AP MLD can detect that part or all of the entire bandwidth (e.g., 80 MHz) of the second link (520) is occupied. AP 2 of the AP MLD can change the operating link or operating frequency to the first link (510). AP 2 of the AP MLD can switch the operating state to the first link (510) for a time Ts as a link switching time. AP 2 of the AP MLD can change the operating link to the first link (510) immediately after detecting the occupied state in the second link (520) or after a preset time (e.g., preamble and MAC header decoding time). Here, AP 2 of the AP MLD can operate in the first link (510) only within the occupied period. AP 2 of AP MLD operates on the first link only until Ts time from the time when the occupied period of the second link (520) ends, and can operate on the second link (520) after the time when the occupied period ends. As another example, if AP 2 of AP MLD succeeds in channel access operation on the first link (510), AP 2 of AP MLD can operate on the first link (510) until the time when AP 1 of AP MLD initiates wider bandwidth transmission. As an example, the same bandwidth expansion and bandwidth switching as in FIG. 5A can be applied to FIG. 5C as well.

[0102] AP 2 of the AP MLD can perform a channel sensing operation (e.g., a CCA operation) and a channel access operation (e.g., an EDCA backoff operation) on the first link (510). More specifically, AP 2 of the AP MLD can perform a channel sensing operation and a channel access operation on a channel (e.g., the first 20 MHz of a secondary 40 MHz channel) other than a channel on which AP 1 of the AP MLD performs transmission (e.g., a primary 40 MHz channel) on the first link (510).

[0103] For example, AP 2 of AP MLD can perform channel sensing operation and channel access operation on a 20MHz channel adjacent to the primary 40MHz channel among secondary 40MHz channels, which are adjacent channels to the primary 40MHz channel, which is the channel on which AP 1 of AP MLD performs transmission.

[0104] AP 2 of the AP MLD can detect that a channel is occupied as a result of a channel detection operation. If the channel transitions from occupied to idle as a result of the channel detection operation, AP 2 of the AP MLD can wait for the AIFS [AC] time, which is the waiting time per AC, on the corresponding channel. Here, AP 2 of the AP MLD can select an EDCA backoff counter, and if the channel is detected as idle for the AIFS [AC] time, it can perform an operation of decrementing the EDCA backoff counter every aSlotTime. AP 2 of the AP MLD can detect that some channels of the secondary 40MHz channel are occupied at the slot boundary of the slot where the EDAC backoff counter reaches 0. Therefore, AP 1 of AP MLD may not expand the transmission bandwidth, and AP 2 of AP MLD may wait with the backoff counter set to 0 until the entire secondary 40MHz channel becomes idle. This may mean that AP 1 of AP MLD wants to expand the transmission bandwidth to the entire available 80MHz bandwidth. After that, AP 2 of AP MLD may detect that the entire secondary 40MHz channel is idle for the PIFS time. In the above case, AP 1 of AP MLD may finish transmitting the 40MHz PPDU (505) and expand the transmission channel to the channel detected by AP 2 of AP MLD. As another example, AP 2 of AP MLD may perform backoff again by setting a new backoff counter if another 20MHz of secondary 40MHz is occupied after successfully backing off at 20MHz. The above described operation can continue until the entire secondary 40MHz channel is idle. That is, AP 2 of AP MLD can continue to perform the operation until the backoff is successful on the 20MHz of the secondary 40MHz and the other 20MHz channel is idle for the PIFS time before the backoff is completed.AP 2 of AP MLD can perform channel sensing and channel access operations on behalf of AP 1 of AP MLD to expand the transmission bandwidth.

[0105] AP 1 of the AP MLD may include an end indicator at the end of the PPDU to terminate transmission of the 40MHz PPDU (505). AP 1 of the AP MLD may terminate transmission of the 40MHz PPDU (505) and transmit an 80MHz PPDU (506) with an extended transmission bandwidth after a predetermined IFS (e.g., SIFS, RIFS, PIFS). As another example, AP 1 of the AP MLD may transmit the extended 80MHz PPDU (506) immediately after the end of the 40MHz PPDU (505). AP 1 of the AP MLD may transmit the 80MHz PPDU (506) using both the primary 40MHz channel and the secondary 40MHz channel. The extended 80MHz PPDU (506) may include a preamble according to the extended channel bandwidth. When the channel detection and channel access operations of AP 2 of the AP MLD are terminated (e.g., when AP 1 of the AP MLD transmits an extended PPDU based on the channel detection and channel access operations of AP 2 of the AP MLD), AP 2 of the AP MLD may operate on the second link (520), which is the original operating link, after the link switching time. Alternatively, AP 2 of the AP MLD may operate on the second link (520), which is the original operating link, again at the point in time when the occupancy state of the second link ends (i.e., when the occupancy period ends).

[0106] Referring to FIG. 5d, AP 1 of AP MLD can perform transmission using the entire bandwidth in the first link (510).

[0107] Additionally, AP 2 of the AP MLD can detect that the second link (520) is busy. For example, the link's busy state can be set based on preamble detection, virtual CCA due to NAV, and other reasons. AP 2 of the AP MLD can recognize the busy period.

[0108] For example, the occupied period of the second link (520) may be a TXOP set by the transmission of the OBSS in the second link (520). That is, the occupancy of the second link (520) may be due to communication of the OBSS and other reasons, as shown in FIG. 5a.

[0109] For example, the occupied period of the second link (520) may be a TXOP set by the transmission of the OBSS in the second link (520). That is, the occupancy of the second link (520) may be due to communication of the OBSS. AP 2 of the AP MLD may detect that some or all of the entire bandwidth (e.g., 80 MHz) of the second link (520) is occupied. Here, AP 2 of the AP MLD may change the operating link or operating frequency to the first link (510). AP 2 of the AP MLD may switch the operating state to the first link (510) for a time Ts as a link switching time. AP 2 of the AP MLD may change the operating link to the first link (510) immediately after the occupancy state is detected in the second link (520) or after a preset time (e.g., preamble and MAC header decoding time). Here, AP 2 of AP MLD can operate on the first link (510) only within the occupied period. AP 2 of AP MLD can operate on the first link only until before the time Ts from the time when the occupied period of the second link (520) ends, and can operate on the second link (520) after the time when the occupied period ends. As another example, if the channel access operation on the first link (510) is successful, AP 2 of AP MLD can operate on the first link (510) until the time when AP 1 of AP MLD initiates wider bandwidth transmission. As an example, in FIG. 5c, the same as in FIG. 5a can be applied to bandwidth expansion and bandwidth switching.

[0110] AP 2 of the AP MLD can perform a channel sensing operation (e.g., a CCA operation) and a channel access operation (e.g., an EDCA backoff operation) on the first link (510). More specifically, AP 2 of the AP MLD can perform the channel sensing operation and the channel access operation on a channel (e.g., a primary 80MHz channel) adjacent to a channel on which AP 1 of the AP MLD transmits on the first link (510) (e.g., a 20MHz channel within a secondary 80MHz channel). For example, AP 2 of the AP MLD can perform the channel sensing operation and the channel access operation on a 20MHz channel within a secondary 80MHz channel that is adjacent to the primary 80MHz channel on which AP 1 of the AP MLD transmits.

[0111] When the channel is detected as idle from occupied state as a result of channel detection operation, AP 2 of AP MLD can wait for AIFS [AC] time, which is the waiting time per AC, on the corresponding channel. Here, AP 2 of AP MLD can select an EDCA backoff counter, and when the channel is detected as idle during AIFS [AC] time, can perform an operation of decreasing the EDCA backoff counter every aSlotTime. AP 2 of AP MLD can check whether the secondary 80MHz channel is idle during PIFS time before the slot boundary of the slot where the EDCA backoff counter reaches 0.

[0112] If the secondary 80MHz channel is determined to be idle, AP 2 of the AP MLD may perform transmission on an 80MHz channel adjacent to AP 1 of the AP MLD. Here, the AP MLD (i.e., subordinate AP 1 and AP 2) may perform any one of the operations in Table 1 below. More specifically, AP 2 of the AP MLD may perform 80MHz PPDU transmission independently from AP 1 of the AP MLD on a channel adjacent to AP 1 of the AP MLD. That is, AP 1 of the AP MLD maintains 80MHz PPDU (507) transmission, and AP 2 of the AP MLD may independently perform 80MHz PPDU (508) transmission on a channel adjacent to AP 1 of the AP MLD.

[0113] Based on the above-described operation, AP 1 of AP MLD and AP 2 of AP MLD can each perform PPDU transmission. Here, the above-described operation may be an operation in which AP MLD AP 2 performs communication after switching to another link based on a link busy state. Specifically, when the second link (520) on which AP 2 of AP MLD operates is in a link occupied state or a link busy state based on OBSS communication or other reasons, AP 2 of AP MLD can switch the link from the second link (520) to the first link (510), and perform a channel access operation in a band different from the band used by AP 1 of AP MLD, and perform PPDU transmission on the channel if the channel is in an idle state. That is, AP 2 of AP MLD can switch to another link through link switching when the link of AP 2 of AP MLD is in an occupied state or a busy state, and check the channel in an idle state through a channel access operation on the switched link, and perform communication on the corresponding channel.

[0114] As another example, AP 1 in AP MLD may stop transmitting an 80MHz PPDU, and AP 1 in AP MLD and AP 2 in AP MLD may perform 160MHz PPDU transmission together.

[0115] [Table 1]

[0116]

[0117]

[0118] When the channel detection and channel access operations of AP 2 of the AP MLD are terminated, AP 2 of the AP MLD can operate on the second link (520), which is the original operating link, after the link switching time. As another example, when AP2 of the AP MLD independently performs 80MHz PPDU transmission as in Table 1 or performs 160MHz PPDU transmission together with AP1 of the AP MLD, AP2 of the AP MLD can operate on the second link (520), which is the original operating link, after performing the PPDU transmission. Alternatively, AP 2 of the AP MLD can operate on the second link (520), which is the original operating link, again at the time when the occupancy state of the second link ends (i.e., when the occupancy period ends).

[0119] In addition, as an example, even if AP 2 of AP MLD in FIGS. 5A to 5D transmits a frame by performing a channel sensing operation and a channel access operation on the first link, AP 2 of AP MLD must operate again on the second link (520), which is the original operating link, when the occupied state of the second link ends (i.e., when the occupied period ends). In this case, the PPDUs transmitted by AP 1 of AP MLD and AP 2 of AP MLD on the first link (510) may end before the Ts time from the occupied period of the second link (520). AP 1 of AP MLD may additionally transmit frames on the first link (510) during a TXOP (transmit opportunity), which is a time period in which it can transmit a plurality of frames that it initially acquired.

[0120] In addition, as an example, the AP MLD operation (AP MLD subordinate AP 1 and AP 2 operation) of FIGS. 5A to 5D may be an STA MLD operation (STA MLD subordinate STA 1 operation and STA 2 operation). That is, the same can be applied to the STA MLD operation operating in multiple links, and the above description is based on the AP MLD operation for the convenience of explanation. In addition, the channel occupancy status of the second link (520) may be due to other reasons as well as communication of the OBSS, and is not limited to the embodiment. In addition, the above description is based on the case where the bandwidth is expanded, but the same can be applied even when the bandwidth is switched.

[0121] For example, in FIGS. 5A to 5D , the machine learning unit described in FIGS. 1 to 4 may be used to detect the channel occupancy status of the first link (510) and the second link (520). For example, if channel occupancy is detected in the second link (520), the machine learning unit may determine the length of the channel occupancy interval and determine whether the transmission is from an OBSS. In addition, the machine learning unit may perform a result of determining whether channel expansion is necessary, and may not be limited to a specific form.

[0122] FIGS. 6A to 6C are diagrams illustrating a method for expanding a wireless LAN communication space stream. Referring to FIGS. 6A to 6C, a first link (610) and a second link (620) may exist in a wireless LAN network, and an MLD may operate on the first link (610) and the second link (620). The communication bandwidths of the first link (610) and the second link (620) may be 320 MHz, 160 MHz, 80 MHz, 40 MHz, and 20 MHz, respectively. In addition, the first link (610) and the second link (620) may each have different communication bandwidths, and are not limited to a specific form.

[0123] For example, in the first link (610) and the second link (620), a specific 20MHz channel of the 80MHz channel may be a primary 20MHz channel, and a 20MHz channel adjacent to the primary 20MHz channel may be a secondary 20MHz channel. Here, the primary 20MHz channel and the secondary 20MHz channel may be combined to form a primary 40MHz channel. Additionally, a 40MHz channel adjacent to the primary 40MHz channel may be a secondary 40MHz channel. In a similar manner, a primary 80MHz channel and a secondary 80MHz channel may be configured, and a primary 160MHz channel and a secondary 160MHz channel may be configured. The following description is based on the case where the operating bandwidth of the first link (610) and the second link (620) is 80MHz. However, this is only for convenience of explanation and may not be limited thereto. That is, the operating bandwidth of multiple links (including the first link and the second link) may be set in various forms, and the following may be applied equally. Meanwhile, the primary 20MHz channel may be the most basic channel used for channel access and frame transmission. That is, frame transmission must be performed by occupying the primary 20MHz channel, and whether or not the frame is transmitted may be determined depending on whether the primary 20MHz channel is occupied (busy).

[0124] AP MLD and non-AP MLD can operate on the first link (610) and the second link (620). Non-AP MLD can be referred to as STA MLD. A subordinate AP affiliated with can operate under the AP MLD. An AP operating on the first link (610) with AP MLD can be referred to as AP 1, and an AP operating on the second link (620) with AP MLD can be referred to as AP 2. In addition, an STA (non-AP STA) operating on the first link (610) with STA MLD can be referred to as STA 1, and an STA operating on the second link (620) with STA MLD can be referred to as STA 2.

[0125] A multi-link device can determine a per-link transmission spatial stream in advance according to hardware and channel conditions. Here, the number of spatial streams may be referred to as Nss. For example, the AP MLD and the STA MLD may use two per-link spatial streams (i.e., Nss=2) in the first link (610) and two per-link spatial streams (Nss=2) in the second link (620). When performing transmission and reception on one of the multi-links, the enhanced multi-link multi-radio (EMLMR) operation may be an operation that performs transmission using the EMLMR spatial stream number (Nss). For example, the EMLMR Nss may have a larger number of spatial streams than the number of per-link spatial streams. In FIGS. 6A to 6C, the EMLMR Nss of the AP MLD and the STA MLD are described based on the case where they are 4, but this is only one example for the convenience of explanation and may not be limited thereto. That is, the number of spatial streams per link (Nss per link) and the number of EMLMR spatial streams (EMLMR Nss) may be configured in various ways and may not be limited to a specific form.

[0126] Referring to FIG. 6A, AP 1 of the AP MLD can perform transmission in an 80MHz channel in a first link (610). Here, AP 1 of the AP MLD can perform transmission in an 80MHz channel using two spatial streams in the first link (610). That is, Nss per link can be 2. While AP 1 of the AP MLD performs transmission in the first link (610), AP 2 of the AP MLD can detect that the second link (620) is in a link occupied state or a link busy state. For example, the link occupied state can be set based on preamble detection, virtual CCA due to NAV, and other reasons. Here, AP 2 of the AP MLD can recognize whether the link is occupied and the busy period.

[0127] For example, the occupied section of the second link (620) may be a TXOP set by the transmission of the OBSS in the second link (620). That is, the occupancy of the second link (620) may be due to communication of the OBSS. As another example, the channel may be occupied due to interference by communication of the OBSS or other reasons, and may not be limited to a specific reason. The channel occupied state or channel busy state may refer to a case where the channel is not used by other communications (e.g., non-wireless LAN wireless communications using the same channel). For the convenience of explanation, the terms channel occupied state or channel busy state are referred to below, but may not be limited to those terms.

[0128] AP 2 of the AP MLD can detect that part or all of the total bandwidth (e.g., 80 MHz) of the second link (620) is occupied. When AP 2 of the AP MLD detects that part or all of the total bandwidth of the second link (620) is occupied, AP 2 of the AP MLD can change the operating link or operating frequency to the first link (610). AP 2 of the AP MLD can switch the operating state to the first link (610) for a time Ts, which is a link switching time. AP 2 of the AP MLD can change the operating link to the first link (610) immediately after detecting the occupied state in the second link (620) or after a preset time (e.g., preamble and MAC header decoding time). AP 2 of the AP MLD can operate in the first link (610) only within the occupied period. AP 2 of AP MLD operates on the first link (610) only from the time when the occupied period of the second link (620) ends until the time Ts, and can operate on the second link (620) after the time when the occupied period ends.

[0129] When AP 2 of the AP MLD operates on the first link (610), AP 1 of the AP MLD may stop transmitting PPDU (601). At the time when AP 1 of the AP MLD stops transmitting PPDU (601) or after a predetermined IFS time (e.g., after RIFS, SIFS, PIFS time) from the time when AP 1 of the AP MLD stops transmitting PPDU (601), AP 1 of the AP MLD and AP 2 of the AP MLD may perform PPDU (602) transmission using EMLMR Nss on an 80 MHz channel. Here, EMLMR may be a method of using a pre-negotiated EMLMR Nss for a frame transmitted after a certain time after transmitting the initial frame (e.g., Initial Frame). Therefore, PPDU (602) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may be PPDUs transmitted using EMLMR Nss. That is, AP 1 of AP MLD and AP 2 of AP MLD can perform PPDU (602) transmission using four spatial streams (i.e., Nss=4) based on EMLMR. For example, in FIGS. 6A to 6C, there may be four spatial streams (i.e., Nss=4) for EMLMR, but this is only for convenience of explanation and may not be limited thereto.

[0130] Here, EMLMR can be applied to a frame transmitted after a certain time after the initial frame transmission, but in FIG. 6a, AP 1 of AP MLD can stop transmitting the PPDU (601) initially transmitted and increase the number of spatial streams in the next PPDU (602) based on EMLMR. The above-described operation may be a conditional EMLMR operation. For example, when the PPDU (601) initially transmitted by AP 1 of AP MLD is stopped, a PPDU end indicator may be included at the end of the PPDU (601), and the PPDU end indicator may include information indicating whether the Nss of the next PPDU (602) increases. That is, the PPDU end indicator may indicate whether a conditional EMLMR operation is performed. As another example, an indicator indicating whether a conditional EMLMR operation is performed may be included in the last MAC frame (e.g., MPDU (MAC layer protocol data unit)) included in the PPDU (601). STA 1 of STA MLD operating on the first link (610) can recognize whether a conditional EMLMR operation is performed through the above-described indicator. After receiving the indicator, STA 1 of STA MLD can cause STA 2 (e.g., transceivers or radios) of STA MLD operating on the second link (620) to transition to the first link (610). Here, the time required for STA 2 of STA MLD to transition to the first link (610) may be a transition delay time. The MAC frame may have a length equal to the delay time required to perform the EMLMR operation (e.g., transition delay time or EMLMR padding delay).

[0131] As another example, the first transmitted PPDU (601) may include padding bits. The padding bits may be included to ensure a transition delay time required for the STA MLD to receive the corresponding indicator and for STA 2 (e.g., transceivers) of the STA MLD to transition to the first link (610). The padding bits may be bits included to increase the time length of the frame. If the padding bits are included in a MAC frame (e.g., MPDU), they may be MAC padding, and if they are included in a PHY frame (e.g., PPDU), they may be PHY padding. At least one of the MAC padding and the PHY padding may be used.

[0132] As another example, the PPDU (602) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may include an indicator in the preamble of the PPDU indicating whether a conditional EMLMR operation is performed. Here, the PPDU (602) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may end before the channel occupancy (or channel busy) period of the second link (620). More specifically, AP 2 of the AP MLD must be able to initiate link switching from the time point at which the channel occupancy period of the second link (620) ends to before the link switching time, and operate on the second link (620) when the channel occupancy period ends. That is, AP 2 of the AP MLD may use the channel from the time point at which the channel occupancy period of the second link (620) ends to before the link switching time. Additionally, as an example, the conditional EMLMR operation described above may be performed only when the strength of the signal transmitted by the OBSS detected in the second link (620) is greater than or equal to a preset threshold, but may not be limited thereto.

[0133] Referring to FIG. 6B, AP 1 of the AP MLD can perform transmission in an 80MHz channel in a first link (610). Here, AP 1 of the AP MLD can perform transmission in an 80MHz channel using two spatial streams in the first link (610). That is, Nss per link can be 2. While AP 1 of the AP MLD performs transmission in the first link (610), AP 2 of the AP MLD can detect that the second link (620) is in a link occupied state or a link busy state. For example, the link occupied state can be set based on preamble detection, virtual CCA due to NAV, and other reasons. Here, AP 2 of the AP MLD can recognize whether the link is occupied and the busy period.

[0134] For example, the occupied period of the second link (620) may be a TXOP set by the transmission of the OBSS in the second link (620). That is, the occupancy of the second link (620) may be due to communication of the OBSS. In addition, the channel occupancy state or the channel busy state may also occur due to other reasons, such as those illustrated in FIG. 6A.

[0135] AP 2 of the AP MLD can detect that part or all of the total bandwidth (e.g., 80 MHz) of the second link (620) is occupied. When AP 2 of the AP MLD detects that part or all of the total bandwidth of the second link (620) is occupied, AP 2 of the AP MLD can change the operating link or operating frequency to the first link (610). AP 2 of the AP MLD can switch the operating state to the first link (610) for a time Ts, which is a link switching time. AP 2 of the AP MLD can change the operating link to the first link (610) immediately after detecting the occupied state in the second link (620) or after a preset time (e.g., preamble and MAC header decoding time). Here, AP 2 of the AP MLD can operate in the first link (610) only within the occupied section. AP 2 of AP MLD operates on the first link (610) only from the time when the occupied period of the second link (620) ends until the time Ts, and can operate on the second link (620) after the time when the occupied period ends.

[0136] When AP 2 of the AP MLD operates on the first link (610), AP 1 of the AP MLD may include an indicator indicating whether the conditional EMLMR operation described above in FIG. 6A is performed in the preamble of the PPDU in the initial PPDU (603) transmission. As another example, an indicator indicating whether the conditional EMLMR operation is performed may be included in a MAC frame (e.g., MPDU) included in the initial PPDU (603). STA 1 of the STA MLD operating on the first link (610) may recognize whether the conditional EMLMR operation is performed through the indicator. After receiving the indicator, the STA MLD may transition STA 2 (e.g., transceivers or radios) of the STA MLD operating on the second link (620) to the first link (610). Here, the time required for STA 2 of the STA MLD to transition to the first link (610) may be the transition delay time. The initial PPDU (603) may include padding bits equal to the EMLMR padding delay or transition delay time as the time for performing the EMLMR operation. The padding bits are bits included to increase the time length of the frame, and may be MAC padding when included in a MAC frame (e.g. MPDU), and may be PHY padding when included in a PHY frame (e.g. PPDU). At least one of the MAC padding and the PHY padding may be used. The padding bits may be allocated to ensure the transition delay time required for the STA MLD to receive the corresponding indicator and for STA 2 (e.g. transceivers) of the STA MLD to transition to the first link (610).

[0137] For example, the first PPDU (603) of AP 1 in the AP MLD may be an initial frame for EMLMR operation. After a predetermined IFS time (e.g., SIFS) from the time of completion of transmission of the first PPDU (603) of AP 1 in the AP MLD, AP 1 in the AP MLD and AP 2 in the AP MLD may perform PPDU (604) transmission using EMLMR Nss on an 80 MHz channel. For example, AP 1 in the AP MLD and AP 2 in the AP MLD may perform PPDU (604) transmission using four spatial streams (i.e., EMLMR Nss=4). The preamble of the PPDU (604) transmitted by AP 1 in the AP MLD and AP 2 in the AP MLD may include an indicator indicating whether a conditional EMLMR operation is performed.

[0138] The PPDU (604) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may end before the channel occupancy period of the second link (620). More specifically, AP 2 of the AP MLD must be able to operate on the second link (620) by initiating link switching before the link switching time from the time when the channel occupancy period of the second link (620) ends, and by the time the channel occupancy period ends. That is, AP 2 of the AP MLD can use the channel from the time when the channel occupancy period of the second link (620) ends until before the link switching time.

[0139] Referring to FIG. 6c, AP 1 of the AP MLD can transmit on an 80MHz channel in the first link (610). Here, AP 1 of the AP MLD can transmit on an 80MHz channel using two spatial streams in the first link (610). That is, Nss per link can be 2.

[0140] While AP 1 of the AP MLD is transmitting on the first link (610), AP 2 of the AP MLD can detect that the second link (620) is in a link occupied state or a link busy state. For example, the link occupied state can be set based on preamble detection, virtual CCA due to NAV, and other reasons. Here, AP 2 of the AP MLD can recognize whether the link is occupied and the busy period.

[0141] For example, the occupied period of the second link (620) may be a TXOP set by the transmission of the OBSS in the second link (620). That is, the occupancy of the second link (620) may be due to communication of the OBSS. In addition, the channel occupancy state or the channel busy state may also occur due to other reasons, such as those illustrated in FIG. 6A.

[0142] AP 2 of the AP MLD can detect that part or all of the total bandwidth (e.g., 80 MHz) of the second link (620) is occupied. When AP 2 of the AP MLD detects that part or all of the total bandwidth of the second link (620) is occupied, AP 2 of the AP MLD can change the operating link or operating frequency to the first link (610). AP 2 of the AP MLD can switch the operating state to the first link (610) for a time Ts, which is a link switching time. AP 2 of the AP MLD can change the operating link to the first link (610) immediately after detecting the occupied state in the second link (620) or after a preset time (e.g., preamble and MAC header decoding time). Here, AP 2 of the AP MLD can operate in the first link (610) only within the occupied section. AP 2 of AP MLD operates on the first link only until Ts time from the time when the occupied period of the second link (620) ends, and can operate on the second link (620) after the time when the occupied period ends.

[0143] When AP 2 of the AP MLD operates on the first link (610), AP 1 of the AP MLD may stop transmitting PPDU (605). When AP 1 of the AP MLD stops transmitting PPDU (605) or after a predetermined IFS time (e.g., after RIFS, SIFS, PIFS time), AP 1 of the AP MLD may resume transmitting PPDU (606). The number of spatial streams per link may be applied to the PPDU (606) retransmitted by AP 1 of the AP MLD. When AP 1 of the AP MLD transmits PPDU (606), the preamble of the PPDU (606) may include indicator information indicating whether the conditional EMLMR operation of FIG. 6A is performed. As another example, indicator information indicating whether the conditional EMLMR operation is performed may be included in a MAC frame (e.g., MPDU) included in the PPDU (606). Here, STA 1 of STA MLD operating in the first link (610) can know whether the conditional EMLMR operation is performed through the above-described indicator. After receiving the above-described indicator, STA MLD can cause STA 2 (e.g., transceivers or radios) of STA MLD operating in the second link (620) to transition to the first link (610). Here, the time required for STA 2 to transition to the first link (610) may be a transition delay time. PPDU (606) transmitted by AP 1 of AP MLD may include padding bits equal to the EMLMR padding delay or the transition delay time, which is the time for performing the EMLMR operation. The padding bits are bits included to increase the time length of the frame, and may be MAC padding if included in a MAC frame (e.g., MPDU), and may be PHY padding if included in a PHY frame (e.g., PPDU). At least one of MAC padding and PHY padding may be used.The padding bits may ensure a transition delay time required for the STA MLD to receive the indicator and transition the STA 2 (e.g., transceivers) to the first link (610).

[0144] The PPDU (606) transmitted by AP 1 of the AP MLD may be an initial frame for EMLMR operation, and after a predetermined IFS time (e.g., SIFS) from the time point of completion of transmission of the PPDU (606) by AP 1 of the AP MLD, AP 1 of the AP MLD and AP 2 of the AP MLD may transmit the PPDU (607) using EMLMR Nss on an 80 MHz channel. For example, the PPDU (607) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may use EMLMR Nss. As a specific example, AP 1 of the AP MLD and AP 2 of the AP MLD may transmit the PPDU (607) using four spatial streams (i.e., EMLMR Nss=4). The preamble of the PPDU (607) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may include an indicator indicating whether a conditional EMLMR operation is performed. The PPDU (607) transmitted by AP 1 of the AP MLD and AP 2 of the AP MLD may end before the channel occupancy period of the second link (620). More specifically, AP 2 of the AP MLD may use the channel from the end of the channel occupancy period of the second link (620) until before the link switching time so as to be able to operate on the second link (620).

[0145] The AP MLD operation (AP MLD subordinate AP 1 and AP 2 operation) of FIGS. 6A to 6C may be an STA MLD operation (STA MLD subordinate STA 1 operation and STA 2 operation). That is, although FIGS. 6A to 6C are described based on the AP MLD operation for convenience of explanation, the present invention is not limited thereto and the STA MLD operation may be equally applied. In addition, in FIGS. 6A to 6C, the machine learning unit described in FIGS. 1 to 4 may be used to detect the channel occupancy status of the second link (620). For example, when channel occupancy is detected in the second link (620), the machine learning unit may determine the length of the channel occupancy section and determine whether the transmission is from the OBSS. In addition, the machine learning unit may perform a result of determining whether channel extension is necessary, and may not be limited to a specific form.

[0146] In addition, in a wireless LAN network, a wireless access point can grant a reverse communication section to another terminal within a communication section established by the wireless access point, and the reverse communication section can be granted by a trigger frame. If some of the channels on which the wireless access point and the terminal operate are occupied by other terminals, the channel may not be used, and other channels that are not occupied may be used. Considering the above, the terminal needs to perform a separate channel access operation to use a channel that is not occupied during the reverse communication section. For example, an artificial intelligence (machine learning) algorithm can be used to determine the channel occupied by the terminal and determine whether to perform the channel access operation. Through this, when the terminal performs reverse communication, the terminal can use a wider bandwidth, which can increase the reverse data transmission speed and improve the performance of the wireless LAN network. Specific methods for this are described below.

[0147] Figures 7a to 7d are diagrams illustrating a method for extending a reverse communication period. Referring to Figures 7a to 7d, an access point (AP) and a station (STA, non-AP STA) may operate in a wireless LAN network. For example, there may be multiple STAs, and STA 1 and STA 2 may operate. STAs may associate with an AP and operate. The AP and STAs may operate in an 80 MHz channel. A specific 20 MHz channel among the 80 MHz channels is designated as a primary 20 MHz channel. A 40 MHz channel including the primary 20 MHz channel is designated as a primary 40 MHz channel. The remaining 40 MHz channels other than the primary 40 MHz channel are designated as secondary 40 MHz channels. In wireless LAN, frame transmission can be performed in units of 20MHz, 40MHz, 80MHz, 160MHz, and 320MHz.

[0148] The AP performs channel access operations on the primary 20MHz channel. The channel access operation is EDCA (enhanced distributed channel access). The AP's EDCAF (EDCA function) does not decrement the backoff counter when the channel is busy, but can decrement the backoff counter when the channel is idle. In other words, the AP performs the backoff operation based on CCA (clear channel assessment). The AP's EDCAF starts transmission at the slot boundary where the backoff counter reaches 0. Before transmitting on the primary 20MHz channel, the AP checks whether the secondary 20MHz channel and the secondary 40MHz channel are idle or busy during the PIFS (priority interframe space). In other words, the AP performs CCA during the PIFS. The AP can determine that the secondary 20MHz channel is busy. Alternatively, the AP may detect that the secondary 20MHz channel is busy through virtual carrier sensing. Virtual carrier sensing may be performed by decoding the header of a received frame and using a network allocation vector (NAV) that prohibits transmission during the transmission time of that frame. Therefore, the AP can transmit only using the primary 20MHz channel. The busy state of the AP's secondary 20MHz channel may be due to interference. Interference may be caused by an overlapping BSS (OBSS) or other communications. Furthermore, the causes of interference may vary and may not be limited to a specific type.

[0149] When the EDCAF of the AP decides to transmit, a transmit opportunity (TXOP) is granted to the EDCAF of the AP. In other words, the AP has acquired the TXOP, and the AP can be said to be a TXOP holder. The AP acquires the TXOP in the primary 20MHz channel. The AP can transmit data frames to STAs (e.g., STA 1) within the TXOP, and then transmit an MU-RTS (multi-user request to send) TXS (TXOP sharing) trigger frame within the same TXOP. As another example, the AP can transmit an MU-RTS TXS trigger frame as the first frame of the TXOP, or can set the TXOP by transmitting the MU-RTS TXS trigger frame. The MU-RTS TXS trigger frame may be referred to as an MU-RTS TXS frame (701) in the present disclosure. The MU-RTS TXS trigger frame may be a frame for allocating a reverse transmission (reverse direction) interval. Reverse transmission is an operation in which a terminal that is not a TXOP holder transmits a data frame. Reverse transmission may also be referred to as TXOP sharing. The AP may allocate a reverse transmission interval or a TXOP sharing interval to STA 1 using the MU-RTS TXS frame (701). There may be two modes for allocating a reverse transmission interval. The first mode, Mode 1, is an operation in which the STA can transmit data only to the AP within the allocated reverse transmission interval. The second mode, Mode 2, is an operation in which the STA can transmit data to the AP and also allows data to be transmitted to other STAs within the allocated reverse transmission interval. The operation of transmitting to other STAs may be referred to as Peer-to-Peer (P2P) transmission or direct communication.

[0150] The AP can transmit the MU-RTS TXS frame (701) transmitted by the AP by indicating the reverse transmission mode. The MU-RTS TXS frame (701) transmitted by the AP includes information on the STA allocated the reverse transmission section and information on the reverse communication section. The reverse communication section and the reverse transmission section are sections that play the same role and the terms may be used interchangeably. For example, the MU-RTS TXS frame includes information such as all or part of the STA's AID, all or part of the STA's MAC address, the length of the reverse communication section, and the bandwidth of the reverse communication section. The reverse communication section may also be referred to as the time allocated by the MU-RTS TXS trigger frame in the present disclosure.

[0151] Referring to FIG. 7A, the AP can allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (701). The reverse communication section allocated by the AP to STA 1 is by Mode 2. STA 1 can receive the MU-RTS TXS frame of the AP received on the primary 20MHz channel, and STA 1 can perform communication within the reverse communication section. STA 1 can detect not only the primary 20MHz channel but also the secondary 20MHz channel and the secondary 40MHz channel as idle. That is, the channel detection of the AP and STA 1 may differ depending on the location or channel environment. STA 1 can determine that it can transmit using both the secondary 20MHz channel and the secondary 40MHz channel, and therefore, STA 1 can transmit a CTS frame using the primary 20MHz channel, the secondary 20MHz channel, and the secondary 40MHz channel, a total of 80MHz channels, after a short interframe space (SIFS) time from the time of completion of reception of the MU-RTS TXS frame (701) in response to the MU-RTS TXS frame (701) of the AP. The CTS frame is duplicated and transmitted for each 20MHz channel. STA 1 transmits a P2P data frame to STA 2 on the 80MHz channel within the reverse communication section, and STA 2 can transmit a response frame (e.g., BlockAck (BA) frame, ACK frame) when it receives the P2P data frame of STA 1. As another example, STA 1 may transmit an RTS frame to STA 2 again using an 80MHz channel after transmitting a CTS frame in response to the AP's MU-RTS TXS frame (701). The RTS frame transmitted to STA 2 is duplicated and transmitted for each 20MHz channel. STA 2 may respond by transmitting a CTS frame to STA 1.If the CTS frame of STA 2 is transmitted through the primary 20MHz channel, STA 1 transmits a P2P data frame using the primary 20MHz channel. If the CTS frame of STA 2 is transmitted through the primary 40MHz channel, STA 1 transmits a P2P data frame through the primary 40MHz channel. If the CTS frame of STA 2 is transmitted through the 80MHz channel, STA 1 transmits a P2P data frame through the 80MHz channel. STA 1 transmits a P2P data frame to STA 2, and when STA 2 receives the P2P data frame of STA 1, it transmits a response frame to STA 1. STA 1 can transmit a data frame to the AP within the reverse communication section. However, since the MU-RTS TXS frame (701) of the AP is transmitted using only the primary 20MHz channel, STA 1 can transmit the data frame using only the primary 20MHz channel.

[0152] When STA 1 transmits a data frame using the secondary 20MHz channel, the AP cannot receive the frame because it detects the channel as busy. STA 1 must return the reverse communication segment when the reverse communication is terminated. In the case of mode 1, the reverse communication segment can be returned by the AP by not transmitting for the PIFS segment after the last transmission. In the case of mode 2, the reverse communication segment can be returned by not transmitting for the PIFS segment as described above, or by transmitting the HE variant HT Control field with the CAS Control subfield with the RDG / More PPDU subfield set to 0 in the QoS Data or QoS Null frame transmitted to the AP. Alternatively, in the case of mode 2, the frame can be returned by setting the RDG / More PPDU subfield to 0 in the HT Control field of the MAC header of the frame transmitted to the AP.

[0153] Referring to FIG. 7b, the AP can allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (701). The reverse communication section allocated by the AP to STA 1 is according to Mode 2. STA 1 can receive the MU-RTS TXS frame (701) of the AP received on the primary 20MHz channel, and STA 1 can perform communication within the reverse communication section. STA 1 transmits a CTS frame to the AP on the primary 20MHz channel. STA 1 can detect not only the primary 20MHz channel but also the secondary 20MHz channel and the secondary 40MHz channel as idle. That is, the channel detection of the AP and STA 1 may be different. STA 1 can perform a channel access operation to transmit using both the secondary 20MHz channel and the secondary 40MHz channel, and the channel access operation can be successful on the primary 20MHz channel. The success of the channel access operation may mean that the EDCAF of STA 1 has decided to transmit. STA 1 can perform a channel cancellation algorithm (CCA) on the secondary 20MHz channel and the secondary 40MHz channel during the PIFS time before the channel access operation is successful. The result of the CCA of STA 1 may be idle. Therefore, STA 1 transmits the frame using the 80MHz channel.

[0154] When STA 1 performs channel access within the reverse communication section allocated by the AP and transmits using a channel wider than the channel bandwidth allocated by the AP, the set TXOP must be equal to or less than the time allocated by the AP in the MU-RTS TXS trigger frame. The TXOP limit is determined by the AC of the EDCAF in the channel access performed by STA 1. If the TXOP limit of the AC that succeeded in channel access is greater than the time allocated by the AP in the MU-RTS TXS trigger frame, the AP sets the TXOP to the time allocated by the MU-RTS TXS trigger frame. If the TXOP limit of the AC that succeeded in channel access is less than the time allocated by the AP in the MU-RTS TXS trigger frame, the AP sets the TXOP to a smaller time and must return the allocated reverse communication section after frame transmission and reception are terminated.

[0155] In the case of Mode 1, the reverse communication section is returned by the AP by not transmitting during the PIFS section after the last transmission. In the case of Mode 2, as described above, the return may be made by not transmitting during the PIFS section, or by transmitting a "HE variant HT Control field" with the "CAS Control subfield with the RDG / More PPDU subfield" set to 0 in the "QoS Data" or "QoS Null frame" transmitted to the AP. Alternatively, in the case of Mode 2, the return may be made by setting the RDG / More PPDU subfield to 0 in the HT Control field of the MAC header of the frame transmitted to the AP. STA 1 transmits a P2P data frame to STA 2 on an 80 MHz channel within the reverse communication section, and STA 2 may transmit a response frame (e.g., BlockAck (BA) frame, ACK frame) when it receives the P2P data frame of STA 1.

[0156] As another example, after a successful channel access operation, STA 1 may transmit an RTS frame to STA 2 using an 80MHz channel. The RTS frame transmitted to STA 2 is duplicated and transmitted for each 20MHz channel. STA 2 may respond by transmitting a CTS frame to STA 1. If STA 2's CTS frame is transmitted through the primary 20MHz channel, STA 1 transmits a P2P data frame using the primary 20MHz channel. If STA 2's CTS frame is transmitted through the primary 40MHz channel, STA 1 transmits a P2P data frame through the primary 40MHz channel. If STA 2's CTS frame is transmitted through the 80MHz channel, STA 1 transmits a P2P data frame through the 80MHz channel. STA 1 transmits a P2P data frame to STA 2, and STA 2 transmits a response frame to STA 1 when it receives the P2P data frame from STA 1. STA 1 can transmit a data frame to the AP within the reverse communication section. However, since the MU-RTS TXS frame of the AP is transmitted using only the primary 20MHz channel, STA 1 can transmit the data frame using only the primary 20MHz channel. If STA 1 transmits the data frame using the secondary 20MHz channel, the AP detects the channel as busy and cannot receive the frame.

[0157] Referring to FIG. 7c, the AP can allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (701). The reverse communication section allocated by the AP to STA 1 is according to Mode 2. STA 1 can receive the MU-RTS TXS frame of the AP received on the primary 20MHz channel and confirm that the bandwidth allocated in the MU-RTS TXS frame is the primary 20MHz, and STA 1 can perform communication within the reverse communication section. STA 1 transmits a CTS frame to the AP on the primary 20MHz channel. STA 1 can perform a separate channel access operation on the secondary 20MHz channel to which AP 1 has not transmitted an MU-RTS frame. The separate channel access operation can be performed by transitioning to another radio operating on another link or operating for another interface (e.g., Bluetooth). The separate channel on which the channel access operation is performed can be a channel that is sufficiently separated in frequency such that the transmit power of the CTS frame transmitted on the primary 20MHz channel is not affected. As a result of the channel access operation, the backoff counter can reach 0 and can remain at 0. That is, STA 1 can wait for the success of the channel access operation on a separate channel (e.g., the secondary 20MHz channel or a sufficiently separated channel) without transmitting a frame. STA 1 can detect not only the primary 20MHz channel but also the secondary 20MHz channel and the secondary 40MHz channel as idle, and STA 1 transmits on the 80MHz channel using all channels detected as idle (e.g., the secondary 20MHz channel and the secondary 40MHz channel). The time from detecting a channel to detecting it as idle must be at least the PIFS time.If the channel performing the separate channel access is a different channel than the secondary 20MHz channel due to the CTS transmitted on the secondary 20MHz channel and the CTS is still being transmitted at the moment the backoff counter reaches 0, transmission on the 80MHz channel can only be performed if all channels including the secondary 20MHz channel are idle for the PIFS time after the CTS transmission ends.

[0158] For example, if the channel access procedure is not completed before the CTS transmission and CCA cannot be performed during the PIFS time, STA 1 can perform communication only using the primary 20MHz allocated by the AP. The channel access operation performed by STA 1 on a separate channel (e.g., secondary 20MHz) may succeed at another time, or the backoff counter may reach 0.

[0159] For example, a channel access operation may occur when the backoff counter reaches 0 before transmitting a CTS frame and all channels are idle for a PIFS period before transmitting the CTS frame. In this case, STA 1 may transmit a CTS frame on an 80MHz channel. A channel access operation may occur when the backoff counter reaches 0 during the transmission of a CTS frame. After the backoff counter reaches 0, all channels must be idle for at least a PIFS period before transmitting a data frame on an 80MHz channel. If CCA of the channel is not possible during a CTS transmission, a data frame is transmitted if the channel is idle for a PIFS period after the CTS transmission. A channel access operation may reach 0 after transmitting a CTS frame. In this case, STA 1 transmits data using the primary 20MHz channel until channel access on a separate channel (e.g., secondary 20MHz channel or a spaced channel) in the reverse communication section is successful, and if channel access on a separate channel (e.g., secondary 20MHz channel or a spaced channel) is successful and all other channels except the primary 20MHz are idle, data is transmitted using the 80MHz channel. In this case, if CCA is not possible on an adjacent channel to the channel transmitting data, only the primary 20MHz is used for transmission.

[0160] STA 1 transmits a P2P data frame to STA 2 on an 80MHz channel within a reverse communication section, and STA 2 can transmit a response frame (e.g., BlockAck (BA) frame, ACK frame) when it receives the P2P data frame of STA 1. As another example, STA 1 can transmit an RTS frame to STA 2 using an 80MHz channel after a successful channel access operation. The RTS frame transmitted to STA 2 is duplicated and transmitted for each 20MHz channel. STA 2 can respond by transmitting a CTS frame to STA 1. If the CTS frame of STA 2 is transmitted through the primary 20MHz channel, STA 1 transmits the P2P data frame using the primary 20MHz channel. If the CTS frame of STA 2 is transmitted through the primary 40MHz channel, STA 1 transmits the P2P data frame through the primary 40MHz channel. If STA 2's CTS frame is transmitted through an 80MHz channel, STA 1 transmits a P2P data frame through the 80MHz channel. STA 1 transmits a P2P data frame to STA 2, and if STA 2 receives the P2P data frame of STA 1, it transmits a response frame to STA 1. STA 1 can transmit a data frame to the AP within the reverse communication section. However, since the AP's MU-RTS TXS frame was transmitted using only the primary 20MHz channel, STA 1 can transmit the data frame using only the primary 20MHz channel. If STA 1 transmits the data frame using the secondary 20MHz channel, the AP detects the channel as busy and cannot receive the frame. Since STA 1 performed a separate channel access operation on the secondary 20MHz channel, it obtained the TXOP on the secondary 20MHz channel.STA 1 can set the length of the TXOP obtained through channel access on the secondary 20MHz channel to match the reverse communication interval allocated by the AP. In this case, STA 1 cannot independently use the secondary 20MHz channel for transmission after the reverse communication interval ends.

[0161] As another example, STA 1 can set the length of the TXOP acquired through channel access on the secondary 20MHz channel to end later than the end time of the reverse communication section allocated by the AP (e.g., TXOP limit, which is the maximum TXOP length for each AC (access category)). In this case, STA 1 can transmit even after the end of the reverse communication section allocated by the AP on the secondary 20MHz channel. In order for STA 1 to use the TXOP acquired on the secondary 20MHz channel, STA 1 can transmit a data frame on the secondary 20MHz channel instead of transmitting on the primary 20MHz channel when the reverse communication section ends. STA 1 can perform the channel access operation by making the AC used for the secondary 20MHz channel access operation identical to the AC of the data to be transmitted on the reverse communication section allocated by the AP. That is, STA 1 performs a channel access operation using EDCAF related to AC of data to be transmitted in the reverse communication section.

[0162] As another example, STA 1 may not place restrictions on the AC used for secondary 20MHz channel access operations. That is, STA 1 performs channel access operations using EDCAFs associated with all ACs. In FIG. 7b described above, STA 1 may perform channel access operations on the secondary 40MHz channel instead of performing channel access operations on the secondary 20MHz channel. If STA 1 performs channel access operations on the secondary 40MHz channel and the channel access operations are successful, STA 1 may obtain a TXOP on the secondary 40MHz channel. STA 1 may transmit P2P data frames on the reverse communication section allocated by the AP using both the secondary 40MHz channel and the primary 40MHz channel. When the reverse communication interval allocated by the AP has ended and the length of the TXOP acquired by STA 1 from the 40MHz channel is later than the end time of the reverse communication interval allocated by the AP, STA 1 can transmit a data frame in the remaining communication interval of the secondary 40MHz channel. When STA 1 performs channel access within the reverse communication interval allocated by the AP and transmits using a channel wider than the channel bandwidth allocated by the AP, the TXOP set may be set to be less than or equal to the time set by the AP by the MU-RTS TXS trigger frame. The TXOP limit is determined by the AC of the EDCAF in the channel access performed by STA 1. If the TXOP limit of the AC that succeeded in channel access is greater than the time allocated by the AP in the MU-RTS TXS trigger frame, STA 1 sets the TXOP to the time allocated by the AP in the MU-RTS TXS trigger frame. If the TXOP limit of the AC that succeeded in channel access is less than the time allocated by the AP in the MU-RTS TXS trigger frame, STA 1 sets the TXOP to a smaller time and returns the allocated reverse communication section after the frame transmission and reception is terminated.Alternatively, STA 1 must return the reverse communication interval when the reverse communication is terminated. In the case of Mode 1, the reverse communication interval may be returned by having the AP return it by not transmitting during the PIFS interval after the last transmission, and in the case of Mode 2, the AP may return it by not transmitting during the PIFS interval as described above, or may return it by transmitting the "HE variant HT Control field" with the "CAS Control subfield with the RDG / More PPDU subfield" set to 0 in the "QoS Data" or "QoS Null frame" transmitted to the AP. Alternatively, in the case of Mode 2, the RDG / More PPDU subfield may be set to 0 in the HT Control field of the MAC header of the frame transmitted to the AP and returned.

[0163] Referring to FIG. 7d, the AP can allocate a reverse communication section to STA 1 through the MU-RTS TXS frame (701). The reverse communication section that the AP allocates to STA 1 is according to Mode 2. AP 1 may also know when the busy state of the secondary 20MHz channel ends. In this case, the MU-RTS TXS frame (701) may be transmitted including the busy end time of AP 1 and busy channel information (e.g., secondary 20MHz channel). This may be referred to as interference information. The interference information of AP 1 may be included in the user info field of the MU-RTS TXS frame.

[0164] STA 1 can receive the MU-RTS TXS frame (701) of the AP received on the primary 20MHz channel, and STA 1 can perform communication within the reverse communication section. STA 1 transmits a CTS frame to the AP on the primary 20MHz channel. STA 1 can detect not only the primary 20MHz channel but also the secondary 20MHz channel and the secondary 40MHz channel as idle. That is, the channel detection of the AP and STA 1 may be different. STA 1 performs a channel access operation to transmit using both the secondary 20MHz channel and the secondary 40MHz channel, and if the channel access operation is successful, transmits a frame on the 80MHz channel in the reverse communication section. The channel access operation time is the time including the backoff operation time and the PIFS time for identifying the idle states of channels other than the primary 20MHz.

[0165] As another example, STA 1 can transmit a CTS frame on the 80MHz channel immediately after SIFS from the end of reception of the MU-RTS TXS frame without a separate channel access procedure in response to the MU-RTS TXS frame of the AP, or after performing CCA during the PIFS time and if all 80MHz channels are idle during the PIFS time, and can transmit a data frame on the 80MHz channel during the reverse communication section. STA 1 transmits a P2P data frame to STA 2, and STA 2 transmits a response frame to STA 1 when it receives the P2P data frame of STA 1. STA 1 can transmit a data frame to the AP within the reverse communication section. The AP can indicate and transmit information on the duration of interference by using a part targeting the identifier of the AP, for example, the MAC address, in the user info of the MU-RTS TXS frame. STA 1 can know the interference information (e.g., time information) that the AP is receiving in the MU-RTS TXS frame, and can know when the AP can receive frames on the secondary 20MHz (i.e., when it is idle and not busy).

[0166] For example, if interference on the secondary 20MHz channel of the AP is not terminated, STA 1 transmits data frames to the AP using only the primary 20MHz channel, or performs preamble puncturing while excluding the secondary 20MHz channel. If STA 1 performs preamble puncturing, the CH_BANDWIDTH field included in the L-SIG of the PPDU (physical layer protocol data unit) preamble, which is a physical layer frame transmitted by STA 1, is set to the bandwidth for performing preamble puncturing. That is, it can be set to a predetermined parameter (e.g., CBW-PUNC80-PRI for puncturing the secondary 20MHz channel in an 80MHz channel). If preamble puncturing is used, the secondary 20MHz channel is not used, and STA 1 can transmit data frames to the AP using a total bandwidth of 60MHz. When the interference of the secondary 20MHz channel of the AP is terminated, STA 1 transmits data frames to the AP using the entire 80MHz channel. STA 1 must return the reverse communication interval when the reverse communication is terminated. In the case of mode 1, the reverse communication interval can be returned by the AP by not transmitting for the PIFS interval after the last transmission. In the case of mode 2, the reverse communication interval can be returned by not transmitting for the PIFS interval as described above, or the QoS Data or QoS Null frame transmitted to the AP can be returned by including the HE variant HT Control field with the CAS Control subfield with the RDG / More PPDU subfield set to 0.

[0167] In FIGS. 7A to 7D , the machine learning unit and machine learning algorithm of FIGS. 1 to 4 may be used to determine whether STA 1 requires secondary 20MHz extended operation. For example, STA 1 may determine whether the secondary 20MHz channel is capable of transmission by inputting the received power for each channel.

[0168] As another example, STA 1 may use a machine learning unit and algorithm to determine whether the secondary 20MHz channel of the AP is receivable. In this case, if STA 1 predicts that the AP cannot use the secondary 20MHz channel, it transmits a data frame without using the secondary 20MHz channel, and if STA 1 predicts that the AP can use the secondary 20MHz channel, it transmits a data frame using the secondary 20MHz channel. The AP may use a machine learning unit and a machine learning algorithm to determine whether there is interference on the channel. AP 1 can use the received power for each channel as input to predict which channel has interference and how long the interference will last. Based on this information, AP 1 may include interference information in the MU-RTS TXS frame (701) of FIG. 7d.

[0169] In FIGS. 7A to 7D , AP 1 and STA 1 can operate in various bandwidths as well as the 80MHz channel. That is, the descriptions made above are merely for convenience of explanation and are not limited thereto and may be applied to various bandwidths. For example, AP 1 and STA 1 may operate in a 40MHz bandwidth, which is narrower than the 80MHz bandwidth, or may operate in 160MHz and 320MHz bandwidths, which are wider than the 80MHz bandwidth. In FIGS. 7A to 7D , the channel on which AP 1 experiences interference may include not only the secondary 20MHz channel but also other channels (for example, all or part of the secondary 40MHz channel, all or part of the secondary 80MHz channel, all or part of the secondary 160MHz channel).

[0170] Figures 8a to 8e are drawings showing a method for extending a reverse communication period.

[0171] Referring to FIGS. 8A to 8E, an access point (AP) and a station (STA, non-AP STA) may operate in a wireless LAN network. There may be multiple STAs, and although FIGS. 8A to 8E describe cases where STA 1 and STA 2 operate, this is for convenience of explanation and may not be limited thereto. STAs may operate by associating with an AP. APs and STAs may operate in an 80 MHz channel. A specific 20 MHz channel among the 80 MHz channels is designated as a primary 20 MHz channel. A 40 MHz channel including the primary 20 MHz channel is designated as a primary 40 MHz channel. The remaining 40 MHz channels other than the primary 40 MHz channel are designated as secondary 40 MHz channels. In a wireless LAN, frame transmission may be performed in units of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz. As another example, it may be possible for different bandwidths to be used in a wireless LAN, and it is not limited to a specific form.

[0172] The AP performs a channel access operation on the primary 20MHz channel. The channel access operation is an enhanced distributed channel access (EDCA) operation. The AP's EDCAF (EDCA function) does not decrement the backoff counter when the channel is busy, but can decrement the backoff counter when the channel is idle. In other words, the AP performs a backoff operation based on a clear channel assessment (CCA). The AP's EDCAF starts transmission at a slot boundary where the backoff counter reaches 0. Before performing transmission on the primary 20MHz channel, the AP checks whether the secondary 20MHz channel and the secondary 40MHz channel are idle or busy during the priority interframe space (PIFS). In other words, the AP performs a CCA during the PIFS. The AP can determine that the secondary 20MHz channel is busy.

[0173] Alternatively, the AP can detect that the secondary 20MHz channel is busy by virtual carrier sensing (VCS). VCS may be based on the network allocation vector (NAV). Therefore, the AP can only transmit on the primary 20MHz channel. STAs (STA 1 and STA 2) also detect the secondary 20MHz channel as busy. The busy state of the secondary 20MHz channel for the AP and STAs may be due to interference. Interference may be caused by an overlapping BSS (OBSS) or other communications. When the EDCAF of the AP determines to transmit, a transmit opportunity (TXOP) is granted to the EDCAF of the AP. That is, the AP acquires a TXOP and becomes a TXOP holder. The AP acquires a TXOP on the primary 20MHz channel. The AP can transmit a data frame to STAs (e.g., STA 1) within a TXOP, and then transmit a MU-RTS (multi-user request to send) TXS (TXOP sharing) trigger frame. As another example, the AP can also transmit the MU-RTS TXS trigger frame as the first frame of the TXOP. The MU-RTS TXS trigger frame may be referred to as an MU-RTS TXS frame (801) in the present disclosure. The MU-RTS TXS trigger frame may be a frame for reverse transmission (reverse direction) interval allocation. Reverse transmission is an operation in which a terminal that is not a TXOP holder transmits a data frame. The AP can allocate a reverse transmission interval to STA 1 using the MU-RTS TXS frame. There may be two modes for reverse transmission interval allocation.The first mode, Mode 1, is an operation in which an STA can transmit data only to an AP. The second mode, Mode 2, is an operation in which an STA can transmit data to the AP and also allows data to be transmitted to other STAs. The operation of transmitting to other STAs may be referred to as Peer-to-Peer (P2P) transmission or direct communication. The AP may transmit by indicating a reverse transmission mode in the MU-RTS TXS frame (801) transmitted by the AP. The MU-RTS TXS frame (801) transmitted by the AP includes information on an STA allocated a reverse transmission section and information on the reverse communication section. For example, the MU-RTS TXS frame (801) includes information such as all or part of the STA's AID (association ID), all or part of the STA's MAC address, the length of the reverse communication section, and the bandwidth of the reverse communication section. The reverse communication period may also be referred to as the time allocated by the MU-RTS TXS trigger frame (801) in the present disclosure.

[0174] Referring to FIG. 8A, an AP may allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (801). The reverse communication section allocated by the AP to STA 1 is by mode 1 or mode 2. STA 1 may receive the MU-RTS TXS frame (801) of the AP received on the primary 20MHz channel, and STA 1 may perform communication within the reverse communication section. STA 1 may detect a secondary 20MHz channel as busy and perform a channel access operation on the secondary 40MHz channel. The channel access operation may be performed immediately or after a certain period of time (e.g., radio switching time) after the secondary 20MHz channel is detected as busy. The radio switching time may be the time taken for STA 1 to switch the radio to enable channel access. The channel access operation can be performed in advance before the AP transmits the MU-RTS TXS frame (801) to STA 1. Accordingly, STA 1 can maintain the backoff counter as 0 in the secondary 40MHz channel. This means waiting for the success of the channel access operation. STA 1 can transmit a CTS frame using the primary 20MHz channel and the secondary 40MHz channel after a short interframe space (SIFS) time from the time of the end of reception of the MU-RTS TXS frame in response to the MU-RTS TXS frame (801) of the AP. In order to transmit a CTS frame using the secondary 40MHz channel, the secondary 40MHz channel must be idle for a PIFS time before transmitting the CTS frame. The CTS frame can be duplicated and transmitted in 20MHz units, and the CTS frame is not transmitted on the secondary 20MHz channel that is busy.

[0175] As another example, STA 1 may transmit a CTS frame only on the primary 20MHz channel and not transmit a CTS frame on the secondary 40MHz channel. In this case, STA 1 may transmit a data frame on the primary 20MHz channel using the secondary 40MHz channel. When transmitting a data frame using the secondary 40MHz channel, the secondary 40MHz channel must be idle for at least the PIFS time before transmitting the data frame. The TXOP allocated on the primary 20MHz channel and the TXOP set on the secondary 40MHz channel are set to match the smaller TXOP of the two. For example, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is longer than the time period allocated by the MU-RTS received from the primary 20MHz, transmission can be made on the secondary 40MHz only during the time period allocated by the MU-RTS.

[0176] As another example, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is shorter than the time period allocated by the MU-RTS received on the primary 20MHz, transmission must be performed on the primary 20MHz and secondary 40MHz only during the TXOP limit of the AC that has successfully accessed the channel, and the period allocated on the primary 20MHz must be returned to the AP. STA 1 can transmit data frames to the AP if the reverse transmission period is by mode 1 or mode 2. If the reverse transmission period is by mode 2, it can transmit P2P data frames to another STA (e.g., STA 2). STA 1 transmits data frames except for the secondary 20MHz channel that is busy. STA 1's operation of transmitting data frames except for the secondary 20MHz channel may be due to preamble puncturing. That is, STA 1 transmits a frame by performing preamble puncturing except for the secondary 20MHz channel. When STA 1 performs preamble puncturing, the CH_BANDWIDTH field included in the L-SIG of the PPDU (physical layer protocol data unit) preamble, which is a physical layer frame transmitted by STA 1, is set to a bandwidth for performing preamble puncturing. That is, it can be set to a predetermined parameter (e.g., CBW-PUNC80-PRI for puncturing the secondary 20MHz channel in an 80MHz channel) for performing preamble puncturing. When STA 1 transmits a data frame to the AP and the AP receives the frame of STA 1, the AP can transmit a response frame (BA frame, ACK frame) an SIFS time after the time when STA 1 completes receiving the data frame.

[0177] If STA 1 transmits a P2P data frame to STA 2 and STA 2 receives the frame from STA 1, STA 2 can transmit a response frame after SIFS time from the time of completion of reception of STA 1's data frame. If the secondary 20MHz channel changes to an idle state (i.e., interference disappears) in the reverse communication section allocated to STA 1 from the AP, STA 1 can transmit a data frame (P2P data frame) to the AP and STA 2 using the entire bandwidth (e.g., 80MHz). Even if the interference of the secondary 20MHz channel disappears, STA 1 may need a separate channel access operation to use the secondary 20MHz channel. Since STA 1 performed a separate channel access operation on the secondary 40MHz channel, STA 1 obtained a TXOP on the secondary 40MHz channel.

[0178] When STA 1 acquires a TXOP in a secondary 40 MHz channel, STA 1 may perform an operation identical to or similar to the operation of FIG. 8e, which will be described later.

[0179] STA 1 must return the reverse communication interval when reverse communication is terminated. In the case of mode 1, the reverse communication interval can be returned by having the AP return it by not transmitting during the PIFS interval after the last transmission. In the case of mode 2, it can be returned by not transmitting during the PIFS interval as described above, or it can be returned by transmitting a HE variant HT Control field with the CAS Control subfield with the RDG / More PPDU subfield set to 0 in the QoS Data or QoS Null frame transmitted to the AP.

[0180] Referring to FIG. 8B, the AP can allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (801). The reverse communication section that the AP allocates to STA 1 is by mode 2. STA 1 can receive the MU-RTS TXS frame (801) of the AP received on the primary 20MHz channel, and STA 1 can perform communication within the reverse communication section. STA 1 can detect the secondary 20MHz channel as busy. STA 1 can transmit a CTS frame using the primary 20MHz channel after a short interframe space (SIFS) time from the time point of ending reception of the MU-RTS TXS frame in response to the MU-RTS TXS frame (801) of the AP. STA 1 performs a channel access operation on a secondary 40 MHz channel upon completion of receiving the MU-RTS TXS frame (801). Alternatively, STA 1 performs a channel access operation on a secondary 40 MHz channel from the time point at which it transmits a CTS frame on the primary 20 MHz channel in response to the MU-RTS TXS frame (801).

[0181] The channel access operation performed by STA 1 on the secondary 40MHz channel may not be performed immediately. For example, a radio switching time may be required before STA 1 performs the channel access operation on the secondary 40MHz channel. The radio switching time may be the time required for STA 1 to switch the radio to enable channel access. STA 1 transmits a CTS frame on the primary 20MHz channel and then waits until the channel access operation on the secondary 40MHz channel is successful. If STA 1 succeeds in the channel access operation on the secondary 40MHz channel and the primary 20MHz channel remains idle until then, STA 1 can transmit data frames on the primary 20MHz channel using the secondary 40MHz channel. The TXOP allocated on the primary 20MHz channel and the TXOP set on the secondary 40MHz channel are set to match the smaller TXOP of the two.

[0182] For example, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is longer than the time interval allocated by the MU-RTS received on the primary 20MHz, transmission on the secondary 40MHz can be performed only during the time interval allocated by the MU-RTS. Alternatively, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is shorter than the time interval allocated by the MU-RTS received on the primary 20MHz, transmission must be performed on the primary 20MHz and secondary 40MHz only during the TXOP limit of the AC that has successfully accessed the channel, and the interval allocated on the primary 20MHz must be returned to the AP. STA 1 can transmit data frames (P2P data frames) to the AP and other STAs (e.g., STA 2) within the reverse transmission interval. STA 1 transmits data frames except for the secondary 20MHz channel that is in a busy state. STA 1's operation of transmitting a data frame except for the secondary 20MHz channel may be due to preamble puncturing. That is, STA 1 transmits a frame by performing preamble puncturing except for the secondary 20MHz channel. When STA 1 performs preamble puncturing, the CH_BANDWIDTH field included in the L-SIG of the PPDU (physical layer protocol data unit) preamble, which is a physical layer frame transmitted by STA 1, is set to the bandwidth for performing preamble puncturing. That is, it can be set to a predetermined parameter (e.g., CBW-PUNC80-PRI for puncturing the secondary 20MHz channel in an 80MHz channel) to perform preamble puncturing. After STA 1 transmits a data frame to the AP and the AP receives the frame of STA 1, the AP sends a response frame (e.g., SIFS) after the time of completion of reception of the data frame of STA 1.STA 1 can transmit a P2P data frame to STA 2, and STA 2 receives the frame of STA 1, STA 2 can transmit a response frame after SIFS time from the time of completion of reception of the data frame of STA 1. If the secondary 20MHz channel changes to an idle state (i.e., interference disappears) in the reverse communication section allocated to STA 1 from the AP, STA 1 can transmit a data frame (P2P data frame) to the AP and STA 2 using the entire bandwidth (e.g., 80MHz). Since STA 1 performed a separate channel access operation on the secondary 40MHz channel, STA 1 obtained a TXOP on the secondary 40MHz channel. When STA 1 acquires a TXOP in a secondary 40 MHz channel, STA 1 may perform an operation identical to or similar to the operation of FIG. 8e described below.

[0183] STA 1 must return the reverse communication interval when reverse communication is terminated. In the case of mode 1, the reverse communication interval can be returned by having the AP return it by not transmitting during the PIFS interval after the last transmission. In the case of mode 2, it can be returned by not transmitting during the PIFS interval as described above, or it can be returned by transmitting a HE variant HT Control field with the CAS Control subfield with the RDG / More PPDU subfield set to 0 in the QoS Data or QoS Null frame transmitted to the AP.

[0184] Referring to FIG. 8C, the AP can allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (801). The reverse communication section that the AP allocates to STA 1 is by mode 1 or mode 2. STA 1 can receive the MU-RTS TXS frame (801) of the AP received on the primary 20MHz channel, and STA 1 can perform communication within the reverse communication section. STA 1 can detect the secondary 20MHz channel as busy. STA 1 can transmit a CTS frame using the primary 20MHz channel after a short interframe space (SIFS) time from the time point of ending reception of the MU-RTS TXS frame in response to the MU-RTS TXS frame (801) of the AP. STA 1 performs a channel access operation on the secondary 40 MHz channel upon completion of reception of the MU-RTS TXS frame (801).

[0185] As another example, STA 1 performs a channel access operation on a secondary 40MHz channel from the time point when it transmits a CTS frame on the primary 20MHz channel in response to the MU-RTS TXS frame (801). The channel access operation that STA 1 performs on the secondary 40MHz channel may not be performed immediately. For example, a radio switching time may be required before STA 1 performs the channel access operation on the secondary 40MHz channel. The radio switching time may be the time it takes for STA 1 to switch the radio to enable channel access. STA 1 waits until the channel access operation on the secondary 40MHz channel is successful after transmitting the CTS frame on the primary 20MHz. Even after STA 1 transmits the CTS frame, STA 1 may not have completed the channel access operation on the secondary 40MHz channel. Therefore, STA 1 transmits a data frame to the AP using the primary 20MHz channel after SIFS after transmitting the CTS frame.

[0186] If the reverse transmission section allocated to STA 1 from the AP is by Mode 2, STA 1 may transmit a P2P data frame to STA 2. STA 1 may stop transmitting the data frame being transmitted on the primary 20MHz channel at the time of completion of the channel access operation on the secondary 40MHz channel, and may restart data transmission by synchronizing from the time of completion of the secondary 40MHz channel access operation.

[0187] In order to interrupt transmission of a data frame, the data frame can be divided into arbitrarily small sizes and transmitted, or the data frame can be divided and transmitted by considering the remaining backoff counter value. If the transmission of the divided transmission frame is not completed, it waits after the secondary 40MHz channel access operation is completed and then transmits in synchronization with the transmission time of the primary 20MHz data frame. The time point at which frame transmission on the primary 20MHz of STA 1 is interrupted is before the SIFS time from the time point at which the secondary 40MHz channel access operation is completed. If the channel access operation of STA 1 on the secondary 40MHz channel is successful, STA 1 can transmit using the secondary 40MHz channel when transmitting a data frame on the primary 20MHz channel. The remaining time of the TXOP allocated on the primary 20MHz and the TXOP set on the secondary 40MHz are set to match the smaller TXOP of the two. For example, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is longer than the remaining time for data transmission within the time interval allocated by the MU-RTS received from the primary 20MHz, transmission can be made to the secondary 40MHz only for the time corresponding to the remaining time interval in the primary 20MHz.

[0188] As another example, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is shorter than the remaining time after data transmission within the time period allocated by the MU-RTS received from the primary 20MHz, transmission must be performed on the primary 20MHz and secondary 40MHz only during the TXOP limit of the AC that has successfully accessed the channel, and the period allocated from the primary 20MHz must be returned to the AP. If the reverse transmission period is by mode 1, STA 1 can transmit data frames only to the AP within the reverse transmission period. If the reverse transmission period is by mode 2, STA 1 can transmit data frames (P2P data frames) to the AP and other STAs (e.g., STA 2) within the reverse transmission period. STA 1 transmits data frames except for the secondary 20MHz channel that is in a busy state. STA 1's transmission of a data frame except for the secondary 20MHz channel may be due to preamble puncturing. That is, STA 1 transmits a frame by performing preamble puncturing except for the secondary 20MHz channel. When STA 1 performs preamble puncturing, the CH_BANDWIDTH field included in the L-SIG of the PPDU (physical layer protocol data unit) preamble, which is a physical layer frame transmitted by STA 1, is set to the bandwidth for performing preamble puncturing. That is, it can be set to a predetermined parameter (e.g., CBW-PUNC80-PRI for puncturing the secondary 20MHz channel in an 80MHz channel) for performing preamble puncturing. When STA 1 transmits a data frame to the AP and the AP receives the frame of STA 1, the AP can transmit a response frame (BA frame, ACK frame) after an SIFS time from the time when STA 1 completes receiving the data frame.When STA 1 transmits a P2P data frame to STA 2 and STA 2 receives the frame of STA 1, STA 2 can transmit a response frame after SIFS time from the time point of completion of reception of the data frame of STA 1. In the reverse communication section allocated to STA 1 from the AP, when the secondary 20MHz channel changes to an idle state (i.e., interference disappears), STA 1 can transmit a data frame (P2P data frame) to the AP and STA 2 using the entire bandwidth (e.g., 80MHz). STA 1 obtained a TXOP in the secondary 40MHz channel because it performed a separate channel access operation in the secondary 40MHz channel. When STA 1 obtains a TXOP in the secondary 40MHz channel, STA 1 can perform an operation identical to or similar to the operation of FIG. 8e described below. STA 1 must return the reverse communication interval when reverse communication is terminated. In the case of Mode 1, the reverse communication interval can be returned by the AP by not transmitting during the PIFS interval after the last transmission. In the case of Mode 2, the reverse communication interval can be returned by not transmitting during the PIFS interval as described above, or by transmitting a HE variant HT Control field with the CAS Control subfield with the RDG / More PPDU subfield set to 0 in the QoS Data or QoS Null frame transmitted to the AP.

[0189] Referring to FIG. 8d, the AP can allocate a reverse communication section to STA 1 through an MU-RTS TXS frame (801). The reverse communication section that the AP allocates to STA 1 is by mode 1 or mode 2. STA 1 can receive the MU-RTS TXS frame (801) of the AP received on the primary 20MHz channel, and STA 1 can perform communication within the reverse communication section. STA 1 can detect the secondary 20MHz channel as busy. STA 1 can transmit a CTS frame using the primary 20MHz channel after a short interframe space (SIFS) time from the time point of ending reception of the MU-RTS TXS frame in response to the MU-RTS TXS frame (801) of the AP. STA 1 performs a channel access operation on a secondary 40MHz channel after receiving the MU-RTS TXS frame (801). As another example, STA 1 performs a channel access operation on a secondary 40MHz channel from the time point at which it transmits a CTS frame on a primary 20MHz channel in response to the MU-RTS TXS frame (801). The channel access operation performed by STA 1 on the secondary 40MHz channel may not be performed immediately. For example, a radio switching time may be required before STA 1 performs the channel access operation on the secondary 40MHz channel. The radio switching time may be the time required for STA 1 to switch the radio to enable channel access. STA 1 waits until the channel access operation on the secondary 40MHz channel is successful after transmitting the CTS frame on the primary 20MHz. Even after STA 1 transmits the CTS frame, STA 1 may not have completed channel access operations on the secondary 40 MHz channel. Therefore, STA 1 transmits a data frame to the AP using the primary 20 MHz channel after SIFS after transmitting the CTS frame.If the reverse transmission section allocated to STA 1 from the AP is by Mode 2, STA 1 may transmit a P2P data frame to STA 2. If STA 1 succeeds in channel access operation on the secondary 40MHz channel, STA 1 can transmit data frames on the primary 20MHz channel using the secondary 40MHz channel. When the channel access operation on the secondary 40MHz channel is completed, STA 1 stops frame transmission on the primary 20MHz channel and immediately adds a physical layer frame header (preamble) and transmits it. STA 1 can configure the physical layer frame or the medium access control layer frame in a form that is easy to truncate in order to perform an operation of suspending and resuming frame transmission.

[0190] For example, a physical layer frame PPDU (physical layer protocol data unit) can be divided into smaller units and transmitted, or a medium access control layer frame MPDU (MAC layer protocol data unit) can be divided into smaller units and transmitted. Both configuration methods can be used simultaneously. For simultaneous transmission, frames transmitted on the primary 20MHz channel can be divided into smaller units, each frame with a physical layer frame header added is concatenated and transmitted, and then, when channel access is successful on the secondary 40MHz, they can be transmitted in synchronization. For synchronous transmission, after channel access is successful on the secondary 40MHz, simultaneous transmission can be performed after waiting. Synchronous transmission can mean that frame transmission on the secondary 40MHz channel starts at the same time as the primary 20MHz starts transmitting the preamble. The remaining time of the TXOP allocated on the primary 20MHz and the TXOP set on the secondary 40MHz are set to match the smaller of the two TXOPs.

[0191] For example, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is longer than the remaining time after data transmission within the time interval allocated by the MU-RTS received on the primary 20MHz, transmission can be performed on the secondary 40MHz only for the time corresponding to the remaining time interval on the primary 20MHz. Alternatively, if the TXOP limit of an AC that has successfully accessed the secondary 40MHz channel is shorter than the remaining time after data transmission within the time interval allocated by the MU-RTS received on the primary 20MHz, transmission must be performed on the primary 20MHz and secondary 40MHz only during the TXOP limit of the AC that has successfully accessed the channel, and the interval allocated on the primary 20MHz must be returned to the AP. STA 1 can transmit data frames to the AP only within the reverse transmission interval if the reverse transmission interval is by mode 1. STA 1 can transmit a data frame (P2P data frame) to the AP and other STAs (e.g. STA 2) within the reverse transmission section when the reverse transmission section is by mode 2. STA 1 transmits the data frame except for the secondary 20MHz channel that is busy. The operation of STA 1 transmitting the data frame except for the secondary 20MHz channel may be due to preamble puncturing. That is, STA 1 transmits the frame by performing preamble puncturing except for the secondary 20MHz channel. When STA 1 performs preamble puncturing, the CH_BANDWIDTH field included in the L-SIG of the PPDU (physical layer protocol data unit) preamble, which is a physical layer frame transmitted by STA 1, is set to the bandwidth for performing preamble puncturing. That is, to perform preamble puncturing, a predetermined parameter (e.g.In an 80MHz channel, the secondary 20MHz channel can be set to puncturing (CBW-PUNC80-PRI).

[0192] If STA 1 transmits a data frame to AP and AP receives STA 1's frame, AP can transmit a response frame (BA frame, ACK frame) SIFS after the time when STA 1 completes receiving the data frame. If STA 1 transmits a P2P data frame to STA 2 and STA 2 receives STA 1's frame, STA 2 can transmit a response frame SIFS after the time when STA 1 completes receiving the data frame. In the reverse communication section allocated to STA 1 by AP, when the secondary 20MHz channel changes to an idle state (i.e., interference disappears), STA 1 can transmit a data frame (P2P data frame) to AP and STA 2 using all bandwidth (e.g., 80MHz). Since STA 1 performed a separate channel access operation on the secondary 40MHz channel, STA 1 obtained a TXOP on the secondary 40MHz channel. When STA 1 acquires a TXOP on a secondary 40MHz channel, STA 1 may perform an operation identical to or similar to the operation of FIG. 8e described below. STA 1 must return the reverse communication segment when reverse communication is terminated. In the case of mode 1, the reverse communication segment may be returned by having the AP return it by not transmitting during the PIFS segment after the last transmission, and in the case of mode 2, the reverse communication segment may be returned by not transmitting during the PIFS segment as described above, or the reverse communication segment may be returned by including a HE variant HT Control field with the CAS Control subfield with the RDG / More PPDU subfield set to 0 in the QoS Data or QoS Null frame transmitted to the AP.

[0193] Referring to FIG. 8E, STA 1 acquired a TXOP on the secondary 40MHz channel because it performed a separate channel access operation on the secondary 40MHz channel. The acquisition time of the TXOP on the secondary 40MHz channel may be at least one of the start time of the CTS transmission on the primary 20MHz channel of STA 1, the completion time of the CTS transmission on the primary 20MHz channel of STA 1, the start time of the data frame or P2P data frame transmission of STA 1, or the time during the data frame or P2P data frame transmission of STA 1. That is, STA 1 can acquire a TXOP on the secondary 40MHz channel at the start or middle time of the reverse communication section allocated by the AP. STA 1 can set the length of the TXOP acquired through the channel access performed on the secondary 40MHz channel to match the reverse communication section allocated by the AP. In this case, STA 1 cannot independently use the secondary 40 MHz channel to transmit after the end of the reverse communication section.

[0194] As another example, STA 1 can set the length of the TXOP acquired through channel access on the secondary 40MHz channel to end later than the end time of the reverse communication section allocated by the AP (e.g., by the TXOP limit, which is the maximum TXOP length for each AC (access category)). In this case, STA 1 can transmit even after the end time of the reverse communication section allocated by the AP on the secondary 40MHz channel. Depending on the different TXOP limits for each AC, the TXOP limit may be shorter than or equal to the end time of the reverse communication section allocated by the AP. STA 1 can use the secondary 40MHz channel only up to the TXOP limit of the secondary 40MHz channel. In other cases (i.e., when the TXOP acquired by STA 1 on the secondary 40MHz channel is longer than the end time of the reverse communication section), in order for STA 1 to use the TXOP acquired by STA 1 on the secondary 40MHz channel, STA 1 may transmit a data frame on the secondary 40MHz channel instead of transmitting on the primary 20MHz channel when the reverse communication section ends. STA 1 may perform a channel access operation by making the AC used for the secondary 40MHz channel access operation identical to the AC of the data to be transmitted in the reverse communication section allocated by the AP. That is, STA 1 performs the channel access operation using the EDCAF associated with the AC of the data to be transmitted in the reverse communication section. Alternatively, STA 1 may not place restrictions on the AC used for the secondary 40MHz channel access operation. That is, STA 1 performs the channel access operation using the EDCAF associated with all ACs.

[0195] In the embodiments of FIGS. 8A to 8E, the machine learning unit and the machine learning algorithm of FIGS. 1 to 4 may be used for STA 1 to determine whether a secondary 20MHz extension operation is necessary. For example, STA 1 may determine whether a secondary 20MHz channel is transmittable by inputting reception power for each channel. As another example, STA 1 may use the machine learning unit and the algorithm to determine whether the secondary 20MHz channel of an AP is receiveable. In this case, if STA 1 predicts that the AP cannot use the secondary 20MHz channel, it transmits a data frame without using the secondary 20MHz channel, and if it predicts that the AP can use the secondary 20MHz channel, it transmits a data frame using the secondary 20MHz channel. The AP may use the machine learning unit and the machine learning algorithm to determine whether there is interference in the channel. AP 1 can use the received power per channel as input to predict which channel has interference and how long the interference will last. Based on this information, AP 1 can also include interference information in the MU-RTS TXS frame of the embodiments of FIGS. 8a to 8e.

[0196] In the embodiments of FIGS. 8A to 8E, AP 1 and STA 1 may operate in various bandwidths as well as the 80MHz channel, and FIGS. 8A to 8E are merely examples for convenience of explanation and may not be limited thereto. For example, AP 1 and STA 1 may operate in a 40MHz bandwidth, which is narrower than the 80MHz bandwidth, or may operate in 160MHz and 320MHz channels, which are wider than the 80MHz bandwidth. For example, the channel on which AP 1 experiences interference may include not only the secondary 20MHz channel but also other channels (for example, all or part of the secondary 40MHz channel, all or part of the secondary 80MHz channel, all or part of the secondary 160MHz channel), and may not be limited to the embodiments described above.

[0197] Figures 9a to 9d are diagrams illustrating a wireless LAN low-latency subchannel operation method. Referring to Figure 9a, in a wireless LAN network, an AP and non-AP STAs, which are wireless LAN terminals associated with the AP, can operate. Non-AP STAs may be referred to as STAs. STA 1 and STA 2 may be connected to an AP to perform data communication, and the AP, STA 1, and STA 2 may configure a BSS (basic service set), which is a wireless LAN communication area that uses the same primary channel. A channel including a primary 20MHz channel among the entire frequency (e.g., 320MHz) of the BSS configured by the AP and STAs may be referred to as a primary channel. A channel not including the primary 20MHz channel among the entire channels may be referred to as a subchannel. A subchannel may be referred to as a non-primary channel access (NPCA) channel or a dynamic subchannel operation (DSO) channel. Information such as the frequency and bandwidth of a subchannel may be known to APs and STAs within the BSS. The available frequency bandwidth may vary depending on the capabilities of the APs and STAs.

[0198] For example, an AP may support 320MHz communication. STA 2 may support communication in a narrower bandwidth (e.g., 80MHz, 160MHz, etc.). When STA 2 performs communication, since STA 2 does not use the entire bandwidth that the AP can communicate, STA 2 uses the primary channel, or when transmitting data to STA 2, the subchannel is not used by the AP and STA 2. In other words, subchannel communication may be possible during the data communication section between the AP and STA 2. STA 1 may use the entire bandwidth available to the AP, or may have a narrower operating bandwidth than the AP but support channel switching operations (e.g., NPCA operation that changes the operating channel to a subchannel, DSO operation). Data transmission and reception may be possible on the subchannel when STA 1 can use the entire bandwidth available to the AP, or even when STA 1 detects the primary channel as busy. If STA 1 can use the entire bandwidth available to the AP, channel switching time for channel access operation on the subchannel may not be required, but channel switching time may be required depending on the capability of STA 1. If STA 1 supports channel switching operation, STA 1 can switch the operating channel to the subchannel even if it detects the primary channel as busy, and channel access operation and data transmission / reception operation may be possible on the switched channel. STA 1 may be required to have a channel switching time to switch the operating channel to the subchannel.

[0199] A wireless LAN terminal or AP other than STA 1 can perform data transmission on the primary channel (referred to as 'Primary' in the drawing). STA 1 can detect the primary channel as busy. While STA 1 detects the channel as busy, a low-latency packet to be transmitted can be entered into the queue of STA 1. When the channel transitions from the busy state to the idle state, STA 1 can check whether the channel is idle during a DIFS (data interframe space) or AIFS (arbitrary interframe space) period. That is, a CCA (clear channel assessment) operation is performed. If the channel is idle during the CCA period, STA 1 can perform a backoff operation (e.g., DCF (distributed channel access) backoff, EDCA (enhanced distributed channel access) backoff). STA 1 can select 6 as the backoff counter. STA 1 can perform CCA during the aSlotTime period to decrease the backoff counter by 1 when the channel is idle, and transmit at the slot boundary where the backoff counter reaches 0.

[0200] Before STA 1's backoff counter reaches 0, i.e., during a channel access operation for transmitting a frame (e.g., a low-latency frame), another STA (STA 2) can start transmitting a frame on the primary channel. The frame can be a physical layer protocol data unit (PPDU), a MAC protocol data unit (MPDU), an aggregated (A)-MPDU, etc. STA 1 can check the preamble of the PPDU transmitted by STA 2. By reading the BSS color information of the preamble, STA 1 can check whether the BSS to which STA 1 belongs (i.e., the BSS configured by the AP, STA 1, and STA 2) is transmitting, check the end time of the PPDU transmitted by STA 2, and check the remaining length of the TXOP of STA 2. In addition, STA 1 can know the bandwidth on which STA 2 transmits the frame. Meanwhile, STA 1 may not be able to identify the sender of the PPDU transmitted by STA 2 based only on the preamble of the PPDU. In this case, STA 1 can check the MPDU included in the PPDU. The MPDU may be an A-MPDU. When decoding the MAC header in the MPDU, STA 1 can check the sender of the frame, STA 2, and the remaining TXOP length. If STA 1 confirms that STA 2, which is another STA other than STA 1, is the sender of the frame, checks the remaining PPDU length, and confirms that the transmission of STA 2 does not use a subchannel, STA 1 can switch the operating channel to a subchannel (referred to as 'NPCA' in the drawing) to perform a channel access operation for frame transmission.

[0201] When STA 1 switches the operating channel to a subchannel, a channel switching time (referred to as 'switching time' in the drawing) may be required. STA 1 can determine whether the AP is a receiver or a transmitter through the UL / DL indicator, such as the SIG field in the preamble. If the UL / DL indicator is 1, the PPDU is a PPDU to which the AP is the receiver, and if it is 0, the STA is the receiver. Alternatively, STA 1 can determine whether the AP is transmitting or receiving on the main channel by specifying the transmission power of the preamble. If the transmission power of the AP measured by a beacon, etc. is smaller or larger, STA 1 can determine that the AP is in a receiving state due to transmission by another terminal. Even when STA 1 cannot determine the sender or receiver of the PPDU by preamble decoding, it can perform a channel access operation for frame transmission by switching the operating channel to a subchannel.

[0202] The channel switching start point can be when the AP knows whether it is the receiver by decoding the preamble, or when the receiver knows that it is the AP by decoding the MPDU. STA 1 can perform a channel access operation (e.g., EDCA channel access operation) on the subchannel. The transmit power of STA 2 can be input to the subchannel, and STA 1 can take this into account and increase the threshold for detecting the channel as busy during the channel sensing operation (i.e., CCA operation). That is, STA 1 can determine the subchannel as idle even if higher energy than the normal state is detected in the subchannel. STA 1 can perform a backoff operation (EDCA backoff operation according to the EDCA channel access operation) on the subchannel and transmit a frame to the AP at the slot boundary when the backoff counter reaches 0. That is, STA 1 can quickly transmit a low-latency frame to the AP without having to wait for the end of transmission on the primary channel even when the primary channel is busy. Since STA 1 knows the end time of STA 2's frame transmission, STA 1 must match the end time of the frame transmitted on the subchannel with the end time of the frame transmitted by STA 2. To achieve this, the transmitted frames can be padded to match the end times of the transmissions.

[0203] The AP can receive signals in all available bandwidths even while receiving data frames from STA 2. That is, the AP can wait to receive frames transmitted on subchannels even while receiving frames from STA 2. While the AP is waiting to receive frames on subchannels, it can receive frames from STA 1. That is, the AP receives frames from STA 1 on subchannels and frames from STA 2 on the main channel. The frame transmission end times of STA 1 and STA 2 can be aligned. Therefore, the AP can immediately transmit response frames (e.g., BlockAck frame, Ack frame) to STA 1 and STA 2. Although frame transmission of STA 2 has ended, there may be remaining TXOPs for transmitting multiple frames of STA 2. In this case, STA 2 may transmit additional frames. STA 1 can operate on the primary channel again after receiving an immediate response frame from AP 1, and if it confirms the information of the frame transmitted by STA 2 on the primary channel (at least one of the frame transmission end time, the frame transmission bandwidth, and the remaining TXOP length), it can perform channel access on the subchannel again to transmit a low-latency frame to the AP. On the other hand, if STA 2 has no TXOPs left or STA 1 has no more low-latency frames to transmit, STA 1 can operate on the primary channel. When STA 1 returns to the primary channel from the subchannel, it does not need to wait for NAVSyncDelay for NAV synchronization. NAVSyncDelay may also be referred to as MediumSyncDelay. NAVSyncDelay is a timer. NAVSyncDelay can be released when the frame is decoded normally.

[0204] Referring to FIG. 9b, in a wireless LAN network, an AP and non-AP STAs, which are wireless LAN terminals associated with the AP, may operate. Non-AP STAs may be referred to as STAs. STA 1 and STA 2 may be connected to the AP to perform data communication, and the AP, STA 1, and STA 2 may configure a basic service set (BSS), which is a wireless LAN communication area that uses the same primary channel. A channel including a primary 20MHz channel among the entire frequency (e.g., 320MHz) of the BSS configured by the AP and STAs may be referred to as a primary channel (main channel). A channel not including the primary 20MHz channel among the entire channels may be referred to as a subchannel. The subchannel may be referred to as a non-primary channel access (NPCA) channel or a dynamic subchannel operation (DSO) channel. Information such as the frequency and bandwidth of the subchannel may be known to APs and STAs existing within the BSS. Depending on the capabilities of the AP and STAs, the frequency bandwidths that can be communicated may differ. For example, the AP can support 320MHz communication. STA 2 can support communication in a narrower bandwidth (e.g., 80MHz, 160MHz, etc.). When STA 2 performs communication, since STA 2 does not use the entire bandwidth that the AP can communicate, STA 2 uses the main channel, or when transmitting data to STA 2, the subchannel is not used by the AP and STA 2. In other words, subchannel communication may be possible during the data communication section between the AP and STA 2. STA 1 can use the entire bandwidth that the AP can use, or although its operating bandwidth is narrower than the AP, it can support channel switching operations (e.g., NPCA operation that changes the operating channel to a subchannel, DSO operation).If STA 1 can use the entire bandwidth available to the AP, data transmission and reception may be possible on the subchannel even if STA 1 detects the primary channel as busy. If STA 1 can use the entire bandwidth available to the AP, a channel switching time may not be required for channel access operations on the subchannel, but a channel switching time may be required depending on the capability of STA 1. If STA 1 supports the channel switching operation, even if STA 1 detects the primary channel as busy, the operating channel may be switched to the subchannel, and channel access operations and data transmission and reception operations may be possible on the switched channel. STA 1 may be required to have a channel switching time to switch the operating channel to the subchannel.

[0205] A wireless LAN terminal or AP other than STA 1 can perform data transmission on the primary channel (referred to as 'Primary' in the drawing). STA 1 can detect the primary channel as busy. While STA 1 detects the channel as busy, a low-latency packet to be transmitted can be entered into the queue of STA 1. When the channel transitions from the busy state to the idle state, STA 1 can check whether the channel is idle during a DIFS (data interframe space) or AIFS (arbitrary interframe space) period. That is, a CCA (clear channel assessment) operation is performed. If the channel is idle during the CCA period, STA 1 can perform a backoff operation (e.g., DCF (distributed channel access) backoff, EDCA (enhanced distributed channel access) backoff). STA 1 can select 6 as the backoff counter. STA 1 can perform CCA during the aSlotTime period to decrease the backoff counter by 1 when the channel is idle, and transmit at the slot boundary where the backoff counter reaches 0.

[0206] Before STA 1's backoff counter reaches 0, i.e., during channel access operation for frame (e.g., low-latency frame) transmission, the AP can start frame transmission on the primary channel. The frame can be a physical layer protocol data unit (PPDU), a MAC protocol data unit (MPDU), an aggregated (A)-MPDU, etc. STA 1 can check the preamble of the PPDU transmitted by the AP. By reading the BSS color information of the preamble, STA 1 can check whether the BSS to which STA 1 belongs (i.e., the BSS configured by the AP, STA 1, and STA 2) is transmitting, check the end time of the PPDU transmitted by the AP, and check the remaining length of the AP's TXOP. In addition, STA 1 can check the bandwidth over which the AP transmits the frame. Meanwhile, STA 1 may not be able to identify the sender of the PPDU transmitted by the AP based only on the preamble of the PPDU. In this case, STA 1 can check the MPDU included in the PPDU. The MPDU may be an A-MPDU. When decoding the MAC header in the MPDU, STA 1 can check the AP, which is the sender of the frame, and the remaining TXOP length. If STA 1 confirms that the AP, not STA 1, is the sender of the frame, checks the remaining PPDU length, and confirms that the AP's transmission does not use the subchannel, STA 1 can switch the operating channel to a subchannel (referred to as 'NPCA' in the drawing) to perform a channel access operation for frame transmission. When STA 1 switches the operating channel to a subchannel, a channel switching time (referred to as 'switching time' in the drawing) may be required. STA 1 can determine whether the AP is the receiver or the sender through the UL / DL indicator, such as the SIG field in the preamble. If the UL / DL indicator is 1, the PPDU is the AP's recipient PPDU, and if it is 0, the STA's recipient PPDU.As another example, STA 1 can determine whether the AP is transmitting or receiving on the main channel by specifying the transmission power of the preamble. If the transmission power of the AP measured by the beacon or the like is lower or higher, STA 1 can determine that the AP is in a receiving state due to transmission by another terminal. Even when STA 1 cannot identify the sender or receiver of the PPDU through preamble decoding, it can perform channel access operation for frame transmission by switching the operating channel to a subchannel.

[0207] The channel switching start point can be the point at which the AP knows whether the sender is the AP by decoding the preamble or the point at which the sender is the AP by decoding the MPDU. STA 1 can perform a channel access operation (e.g., EDCA channel access operation) on the subchannel. The transmit power of the AP can be input to the subchannel, and STA 1 can take this into account and increase the threshold for detecting the channel as busy during the channel sensing operation (i.e., CCA operation). That is, STA 1 can determine the subchannel to be idle even if higher energy than the normal state is detected in the subchannel. STA 1 performs a backoff operation (EDCA backoff operation according to the EDCA channel access operation) on the subchannel, and the backoff counter can reach 0. STA 1 needs to transmit a low-latency frame to the AP, but the AP cannot receive frames on the subchannel, which is a part of the same link's band, while transmitting the frame, because it uses some bands including the primary channel of the same link.

[0208] STA 1 can keep the backoff counter at 0 until the AP completes transmitting the frame. Alternatively, instead of keeping the backoff counter at 0, it can repeatedly perform a new backoff until the AP completes transmitting the data frame. When performing a repeated backoff, the parameters for the backoff (e.g., CW[AC], QSRC[AC]) are not changed. STA 1 can know the end time of the AP's frame transmission and can expect that a response frame will be transmitted to the AP after the SIFS time after the end of the AP's frame transmission. STA 1 can transmit a low-latency frame to the AP on the subchannel after the SIFS time or at the time of receiving the BA. That is, STA 1 may want to synchronize the start time of the response frame on the main channel with the start time of the frame transmitted by STA 1 on the subchannel. When performing a repeated backoff, the low-latency frame can be transmitted to the AP on the subchannel after a successful backoff after the SIFS time or at the time of receiving the BA.

[0209] If the AP needs to perform a backoff for frame transmission on the main channel while STA 1 is transmitting on a subchannel, it must wait until it needs to transmit a BA to STA 1 on the subchannel. During this wait, it can receive frame transmissions from other STAs on the main channel. If the period of receiving frames from other STAs on the main channel overlaps with the period of BA transmission, BA transmission on the subchannel may cause errors in frame reception on the main channel during BA transmission due to the transmission power of the subchannel. Alternatively, if the AP prioritizes frame reception on the main channel, the AP can continue to receive frames on the main channel instead of transmitting BA frames on the subchannel.

[0210] The AP may transmit a data frame to STA 2 on the primary channel, and STA 2 may transmit the frame with a bandwidth equal to or less than its maximum available bandwidth. Therefore, the AP may expect that the response frame from STA 2 is received only in a portion of the total bandwidth available to the AP. However, the AP may receive signals in all bandwidths available to the AP. That is, the AP may wait to receive a frame transmitted on a subchannel even while receiving a response frame from STA 2. While the AP is waiting to receive a frame on the subchannel, it may receive a frame from STA 1. That is, the AP receives the data frame of STA 1 (the low-latency frame of STA 1) on the subchannel and the response frame of STA 2 on the primary channel. The frame transmission start times of STA 1 and STA 2 may be synchronized. The AP may receive the data frame of STA 1 on the subchannel, and after receiving the data frame, transmit a reception response frame (e.g., BlockAck frame, Ack frame) to STA 1 on the subchannel. When STA 1 completes low-latency frame transmission on a subchannel and receives a response frame from the AP, STA 1 can operate on the primary channel. The AP can transmit a response frame to STA 1 including an indicator indicating whether to apply the NAVSyncDelay timer after switching to the primary channel. If the indicator indicating whether to apply the NAVSyncDelay timer is set, the NAVSyncDelay timer must be applied due to reasons such as frame exchange currently in progress on the primary channel. If the indicator indicating whether to apply the NAVSyncDelay timer is not set, STA 1 can perform normal channel access operations immediately after switching to the primary channel without applying the NAVSyncDelay timer.

[0211] If the NAVSyncDelay timer application indication is set in the response frame received from the subchannel or the NAVSyncDelay timer application indication is not set in the received response frame, STA 1 must switch to the main channel and wait for the NAVSyncDelay timer, which is the time for NAV synchronization, before transmitting the frame. If a frame is detected within the NAVSyncDelay timer and NAV synchronization is achieved, this timer is released. NAVSyncDelay may also be referred to as MediumSyncDelay. NAVSyncDelay is a timer. NAVSyncDelay can be released when the frame is decoded normally.

[0212] Referring to FIG. 9c, in a wireless LAN network, an AP and non-AP STAs, which are wireless LAN terminals associated with the AP, may operate. Non-AP STAs may be referred to as STAs. STA 1 and STA 2 may be connected to the AP to perform data communication, and the AP, STA 1, and STA 2 may form a basic service set (BSS), which is a wireless LAN communication area that uses the same primary channel. A channel including a primary 20MHz channel among the entire frequency (e.g., 320MHz) of the BSS configured by the AP and STAs may be referred to as a primary channel. A channel not including the primary 20MHz channel among the entire channels may be referred to as a subchannel. The subchannel may be referred to as an NPCA (non-primary channel access) primary channel or a DSO (dynamic subchannel operation) channel. Information such as the frequency and bandwidth of the subchannel may be known to APs and STAs existing within the BSS. Depending on the capabilities of the AP and STAs, the frequency bandwidths that can be communicated may differ. For example, the AP can support 320MHz communication. STA 2 can support communication in a narrower bandwidth (e.g., 80MHz, 160MHz, etc.). When STA 2 performs communication, STA 2 uses the main channel because it does not use the entire bandwidth that the AP can communicate, or when transmitting data to STA 2, the subchannel is not used by the AP and STA 2. In other words, subchannel communication may be possible during the data communication section between the AP and STA 2. STA 1 can use the entire bandwidth that the AP can use, or although its operating bandwidth is narrower than the AP, it can support channel switching operations (e.g., NPCA operation that changes the operating channel to a subchannel, DSO operation).If STA 1 can use the entire bandwidth available to the AP, data transmission and reception may be possible on the subchannel even if STA 1 detects the primary channel as busy. If STA 1 can use the entire bandwidth available to the AP, a channel switching time may not be required for channel access operations on the subchannel, but a channel switching time may be required depending on the capability of STA 1. If STA 1 supports the channel switching operation, even if STA 1 detects the primary channel as busy, the operating channel may be switched to the subchannel, and channel access operations and data transmission and reception operations may be possible on the switched channel. STA 1 may be required to have a channel switching time to switch the operating channel to the subchannel.

[0213] A wireless LAN terminal or AP other than STA 1 can perform data transmission on the primary channel (referred to as 'Primary' in the drawing). STA 1 can detect the primary channel as busy. While STA 1 detects the channel as busy, a low-latency packet to be transmitted can be entered into the queue of STA 1. When the channel transitions from the busy state to the idle state, STA 1 can check whether the channel is idle during a DIFS (data interframe space) or AIFS (arbitrary interframe space) period. That is, a CCA (clear channel assessment) operation is performed. If the channel is idle during the CCA period, STA 1 can perform a backoff operation (e.g., DCF (distributed channel access) backoff, EDCA (enhanced distributed channel access) backoff). STA 1 can select 6 as the backoff counter. STA 1 can perform CCA during the aSlotTime period to decrease the backoff counter by 1 when the channel is idle, and transmit at the slot boundary where the backoff counter reaches 0.

[0214] Before the backoff counter of STA 1 reaches 0, another STA (STA 2) may start transmitting a frame on the primary channel. The frame may be a physical layer protocol data unit (PPDU), a MAC protocol data unit (MPDU), an aggregated (A)-MPDU, etc. The first frame transmitted by STA 2 may be an initial control frame (ICF). An example of an initial control frame may be a request to send (RTS) frame. STA 2 may transmit the initial control frame to the AP, and the AP may transmit an initial control response (ICR) frame as a response to the initial control frame to STA 2. An example of an initial control response frame may be a clear to send (CTS) frame. The initial control frame may be referred to as an ICF. The initial control response frame may be referred to as an initial control response or ICR.

[0215] STA 1 can receive the ICF of STA 2. STA 1 can decode the ICF and check the duration field. STA 1 can confirm that STA 2 transmits a frame to the AP, check the transmission bandwidth of STA 2, and check the TXOP length of STA 2. The transmission bandwidth of STA 2 may not occupy a subchannel. STA 1 may wait for an ICR received from the AP after receiving the ICF to determine the NAV. When STA 1 detects an ICR (e.g., detects a physical layer PPDU preamble of the ICR), STA 1 can switch the operating channel to a subchannel (referred to as 'NPCA' in the drawing). When STA 1 switches the operating channel to a subchannel, a channel switching time (referred to as 'switching time' in the drawing) may be required.

[0216] STA 1 can perform a channel access operation (e.g., EDCA channel access operation) on a subchannel. The transmission power of STA 2 and the AP can be input to the subchannel, and STA 1 can take this into account and increase a threshold for detecting the channel as busy during a channel detection operation (e.g., CCA operation). That is, STA 1 can determine the subchannel as an idle state even if higher energy than a normal state is detected in the subchannel. STA 1 can perform a backoff operation (EDCA backoff operation according to the EDCA channel access operation) on the subchannel, and the backoff counter can reach 0. If the backoff counter reaches 0 and the transmission of a data frame transmitted by STA 2 to the AP on the primary channel after the ICR transmission has not started, STA 1 can maintain the backoff counter as 0 until the start time of the data frame transmission of STA 2 on the primary channel, and can transmit a data frame (low-latency frame) to the AP on the subchannel in accordance with the start time of the data frame transmission of STA 2. Alternatively, instead of keeping the backoff counter at 0, the backoff can be performed repeatedly until the start time of STA 2's data frame transmission occurs. When performing the repeated backoff, the parameters for the backoff (e.g., CW[AC], QSRC[AC]) do not change. Alternatively, STA 1 may not perform a separate channel access operation on the subchannel. STA 1 can transmit the data frame on the subchannel to the AP in accordance with the start time of the data frame transmitted by STA 2 on the primary channel. In other words, STA 1 can quickly transmit the low-latency frame to the AP without having to wait for the end of the transmission on the primary channel even when the primary channel is in use. Since STA 1 knows the end time of STA 2's TXOP, it should match the end time of the frame transmitted by STA 1 on the subchannel with the end time of the frame transmitted by STA 2.To achieve this, the transmitted frame can be padded to match the end point of transmission.

[0217] The AP can receive signals in all available bandwidths even while receiving a data frame from STA 2. That is, the AP can wait to receive a frame transmitted on a subchannel even while receiving a frame from STA 2. While the AP is waiting to receive a frame on a subchannel, it can receive a frame from STA 1. That is, the AP receives a frame from STA 1 on the subchannel and a frame from STA 2 on the main channel. The frame transmission end times of STA 1 and STA 2 can be matched. Therefore, the AP can immediately transmit a response frame (e.g., BlockAck frame, Ack frame) to STA 1 and STA 2.

[0218] STA 2's frame transmission is finished, but there may be TXOP remaining to transmit multiple frames of STA 2. In this case, STA 2 may transmit additional frames. STA 1 may operate on the primary channel again after receiving an immediate response frame from AP 1, and if it confirms information of the frame transmitted by STA 2 on the primary channel (at least one of the frame transmission end time, the frame transmission bandwidth, and the remaining TXOP length), it may perform channel access on the subchannel again to transmit a low-latency frame to the AP. On the other hand, if STA 2's TXOP is empty or STA 1 has no more low-latency frames to transmit, STA 1 may operate on the primary channel. STA 1 does not need to wait for NAVSyncDelay for NAV synchronization when it returns to the primary channel from the subchannel. NAVSyncDelay may also be referred to as MediumSyncDelay. NAVSyncDelay is a timer. NAVSyncDelay can be released if the frame is decoded normally.

[0219] Referring to FIG. 9d, in a wireless LAN network, an AP and non-AP STAs, which are wireless LAN terminals associated with the AP, may operate. Non-AP STAs may be referred to as STAs. STA 1 and STA 2 may be connected to the AP to perform data communication, and the AP, STA 1, and STA 2 may form a basic service set (BSS), which is a wireless LAN communication area that uses the same primary channel. Among the entire frequency (e.g., 320 MHz) of the BSS formed by the AP and STAs, a channel including a primary 20 MHz channel may be referred to as a primary channel. Among the entire channels, a channel that does not include the primary 20 MHz channel may be referred to as a subchannel. The subchannel may be referred to as a non-primary channel access (NPCA) channel or a dynamic subchannel operation (DSO) channel. Information such as the frequency and bandwidth of the subchannel may be known to APs and STAs existing within the BSS. Depending on the capabilities of the AP and STAs, the frequency bandwidths that can be communicated may differ. For example, the AP can support 320MHz communication. STA 2 can support communication in a narrower bandwidth (e.g., 80MHz, 160MHz, etc.). When STA 2 performs communication, STA 2 uses the main channel because it does not use the entire bandwidth that the AP can communicate, or when transmitting data to STA 2, the subchannel is not used by the AP and STA 2. In other words, subchannel communication may be possible during the data communication section between the AP and STA 2. STA 1 can use the entire bandwidth that the AP can use, or although its operating bandwidth is narrower than the AP, it can support channel switching operations (e.g., NPCA operation that changes the operating channel to a subchannel, DSO operation).

[0220] If STA 1 can use the entire bandwidth available to the AP, data transmission and reception may be possible on the subchannel even if STA 1 detects the primary channel as busy. If STA 1 can use the entire bandwidth available to the AP, a channel switching time may not be required for channel access operations on the subchannel, but a channel switching time may be required depending on the capability of STA 1. If STA 1 supports the channel switching operation, even if STA 1 detects the primary channel as busy, the operating channel may be switched to the subchannel, and channel access operations and data transmission and reception operations may be possible on the switched channel. STA 1 may be required to have a channel switching time to switch the operating channel to the subchannel.

[0221] A wireless LAN terminal or AP other than STA 1 can perform data transmission on the primary channel (referred to as 'Primary' in the drawing). STA 1 can detect the primary channel as busy. While STA 1 detects the channel as busy, a low-latency packet to be transmitted can be entered into the queue of STA 1. When the channel transitions from the busy state to the idle state, STA 1 can check whether the channel is idle during a DIFS (data interframe space) or AIFS (arbitrary interframe space) period. That is, a CCA (clear channel assessment) operation is performed. If the channel is idle during the CCA period, STA 1 can perform a backoff operation (e.g., DCF (distributed channel access) backoff, EDCA (enhanced distributed channel access) backoff). STA 1 can select 6 as the backoff counter. STA 1 can perform CCA during the aSlotTime period to decrease the backoff counter by 1 when the channel is idle, and transmit at the slot boundary where the backoff counter reaches 0.

[0222] Before STA 1's backoff counter reaches 0, another STA (STA 2) may start transmitting a frame on the primary channel. The frame may be a physical layer protocol data unit (PPDU), a MAC protocol data unit (MPDU), an aggregated MPDU, etc. The first frame transmitted by STA 2 may be an initial control frame (ICF). An example of an initial control frame may be a request to send (RTS) frame. STA 2 may transmit the initial control frame to the AP, and the AP may transmit an initial control response (ICR) frame as a response to the initial control frame to STA 2. An example of an initial control response frame may be a clear to send (CTS) frame. The initial control frame may be referred to as an ICF. The initial control response frame may be referred to as an initial control response or ICR.

[0223] STA 1 can receive the ICF of STA 2. STA 1 can decode the ICF and check the duration field. STA 1 can confirm that STA 2 transmits a frame to the AP, check the transmission bandwidth of STA 2, and check the TXOP length of STA 2. The transmission bandwidth of STA 2 may not occupy a subchannel. When STA 1 receives the ICF, STA 1 can switch the operating channel to a subchannel (referred to as 'NPCA' in the drawing). When STA 1 switches the operating channel to a subchannel, a channel switching time (referred to as 'switching time' in the drawing) may be required.

[0224] STA 1 can perform a channel access operation (e.g., EDCA channel access operation) on a subchannel. The transmission power of STA 2 and the AP can be input to the subchannel, and STA 1 can take this into account and raise the threshold for detecting the channel as busy during a channel detection operation (i.e., CCA operation). That is, STA 1 can determine the subchannel as idle even if higher energy than the normal state is detected in the subchannel. STA 1 can perform a backoff operation (EDCA backoff operation according to the EDCA channel access operation) on the subchannel, and the backoff counter can reach 0. If the backoff counter reaches 0 and the transmission of the data frame transmitted by STA 2 to the AP on the primary channel after the ICR transmission has not started, STA 1 may keep the backoff counter at 0 until the time when STA 2 starts transmitting the data frame on the primary channel, and may transmit the data frame (low-latency frame) to the AP on the subchannel in accordance with the time when STA 2 starts transmitting the data frame. Alternatively, instead of keeping the backoff counter at 0, the backoff may be repeatedly performed until the time when STA 2 starts transmitting the data frame. When performing the repeated backoff, the parameters for the backoff (e.g., CW[AC], QSRC[AC]) are not changed. Alternatively, STA 1 may not perform a separate channel access operation on the subchannel. STA 1 may transmit the data frame to the AP on the subchannel in accordance with the time when STA 2 starts transmitting the data frame on the primary channel. That is, STA 1 can quickly transmit a low-latency frame to the AP without having to wait for the end of transmission on the primary channel even when the primary channel is in use. Since STA 1 knows the end time of STA 2's TXOP, it must match the end time of the frame transmitted by STA 1 on the subchannel with the end time of the frame transmitted by STA 2.To achieve this, the transmitted frame can be padded to match the end point of transmission.

[0225] In a different method from the above method, STA 1 can perform a backoff operation (EDCA backoff operation according to EDCA channel access operation) on a subchannel and transmit a CTS frame at a slot boundary where a backoff counter reaches 0. The CTS frame transmitted by STA 1 may be a CTS frame whose receiver address of the MAC header is STA 1's own address for setting NAV. After transmitting the CTS frame, STA 1 can transmit a data frame to the AP on the subchannel at the start time of a data frame transmitted by STA 2 on the main channel without a separate channel access operation. The CTS frame may be transmitted by padding it so that the interval between the completion time of the CTS frame transmission and the start time of the data frame transmitted by STA 2 becomes SIFS. Instead of the CTS frame, a QoS Null frame may be transmitted in the same manner as the above method.

[0226] Referring to FIGS. 9A to 9D , STA 1 may use the machine learning unit and machine learning algorithm illustrated in FIGS. 1 to 4 to determine whether to transmit on a subchannel. STA 1 may input a received frame into the machine learning algorithm, and the machine learning algorithm may determine whether transmission is possible on a subchannel and the transmittable frequency band. STA 1 may transmit the frame on the subchannel using the determined transmittable status and transmittable frequency band.

[0227] FIG. 10 is a flowchart illustrating a method for expanding communication bandwidth in a wireless LAN to which the present disclosure applies. Referring to FIG. 10, a method for operating an AP MLD including a first AP associated with a first link and a second AP associated with a second link may be provided. Here, the first AP associated with the first link may be AP 1 of the aforementioned AP MLD, and the second AP associated with the second link may be AP 2 of the aforementioned AP MLD.

[0228] For example, the AP MLD may transmit the first PPDU in the first bandwidth within the first link for the first AP (S1010). That is, AP 1 of the AP MLD may transmit the first PPDU in the first bandwidth within the first link. Thereafter, the AP MLD may detect whether a part or all of the entire bandwidth of the second link is busy in the second link for the second AP (S1020). That is, AP 2 of the AP MLD may detect whether a part or all of the entire bandwidth of the second link is occupied by another entity in the second link, as described above. Here, if a part or all of the entire bandwidth of the second link is detected to be busy, the link associated with the second AP may be switched from the second link to the first link. Thereafter, the AP MLD may perform a channel detection operation and a channel access operation in the second bandwidth within the first link to which the second AP has been switched (S1030). That is, AP 2 of the AP MLD may perform a channel detection operation and a channel access operation in the second bandwidth within the first link to which the second AP has been switched. Here, if the second bandwidth within the first link is occupied by the AP MLD based on the channel detection operation and the channel access operation, the AP MLD may stop transmitting the first PPDU for the first AP and transmit the second PPDU through the first bandwidth and the second bandwidth (S1040). That is, AP 1 of the AP MLD may stop transmitting the first PPDU and transmit the second PPDU through the first bandwidth and the second bandwidth. For example, the operation performed by the AP MLD for the first AP or the second AP may be the operation of AP 1 of the AP MLD and AP 2 of the AP MLD described above, but may not be limited thereto.

[0229] For example, if the AP MLD detects that part or all of the second link's total bandwidth is busy for the second AP, the AP MLD can recognize the busy interval along with whether part or all of the second link's total bandwidth is busy for the second AP. In other words, the AP MLD can recognize whether part or all of the second link's total bandwidth for the second AP is occupied by another entity and the occupied interval information.

[0230] In addition, the link associated with the second AP may be switched from the second link to the first link immediately after the AP MLD detects that part or all of the second link's total bandwidth is busy for the second AP, or after a preset time from the time the AP MLD detects that part or all of the second link's total bandwidth is busy, as described above. In addition, when the link associated with the second AP is switched from the second link to the first link, the switching from the second link to the first link is completed after a link switching time from the time the switching from the second link to the first link is initiated, so that the AP MLD may operate on the first link for the second AP. Thereafter, the AP MLD may operate on the first link for the second AP. Here, the link associated with the second AP starts switching from the first link to the second link before the link switching time from the point in time when the busy period ends after switching to the first link, and the switching is completed at the point in time when the busy period ends, and the AP MLD can operate on the second link from the point in time when the busy period ends for the second AP.

[0231] Additionally, the link associated with the second AP may be maintained as the first link until the AP MLD starts transmitting the second PPDU over the first bandwidth and the second bandwidth for the first AP based on channel sensing operations and channel access operations after switching to the first link. Here, the AP MLD may operate on the second link from the time the second PPDU is transmitted for the second AP.

[0232] In addition, when the AP MLD performs a channel detection operation and a channel access operation in a second bandwidth within the first link for the second AP, and the second bandwidth is in a busy state based on the channel detection operation and the channel access operation, and when it detects that the second bandwidth has transitioned from the busy state to an idle state, the AP MLD can decrement a backoff counter for each slot after a preset time from the time of transitioning to the idle state. The AP MLD can stop transmitting a first PPDU at a slot boundary where the backoff counter becomes 0 for the first AP, and transmit a second PPDU through the first bandwidth and the second bandwidth.

[0233] In addition, if the third bandwidth is idle before a preset time from a slot boundary where the backoff counter becomes 0, the AP MLD can transmit the second PPDU for the first AP through the first bandwidth, the second bandwidth, and the third bandwidth at the slot boundary where the backoff counter becomes 0. On the other hand, if the third bandwidth is busy before a preset time from a slot boundary where the backoff counter becomes 0, the AP MLD can transmit the second PPDU for the first AP through the first bandwidth and the second bandwidth at the slot boundary where the backoff counter becomes 0. Here, the first bandwidth may be a primary 20 MHz band, the second bandwidth may be a secondary 20 MHz band, and the third bandwidth may be a secondary 40 MHz, but is not limited thereto.

[0234] As another example, if the first bandwidth is a primary 40 MHz band and the second bandwidth is a secondary 40 MHz band, the AP MLD can perform a channel sensing operation and a channel access operation in a secondary 20 MHz band adjacent to the first bandwidth within the second bandwidth for the second AP. Here, if the AP MLD detects that the secondary 20 MHz band adjacent to the first bandwidth is busy for the second AP, and if the secondary 20 MHz band adjacent to the first bandwidth transitions from the busy state to the idle state, the AP MLD can decrement a backoff counter for each slot after a preset time from the time of transition to the idle state for the second AP. The AP MLD can stop transmitting the first PPDU at the slot boundary where the backoff counter becomes 0 for the first AP, and transmit the second PPDU through the first bandwidth and the second bandwidth.

[0235] Additionally, the AP MLD may decrement the backoff counter at each slot after a preset time if the secondary 20 MHz band adjacent to the first bandwidth in the second bandwidth for the second AP is idle. Additionally, if the AP MLD detects that some channels in the second bandwidth are busy at a slot boundary where the backoff counter becomes 0 for the first AP, the AP MLD may maintain the backoff counter at 0 until the entire second bandwidth for the first AP transitions to an idle state, and when the entire second bandwidth transitions to an idle state, may stop transmitting the first PPDU after a preset time from the time of transitioning to an idle state, and may transmit the second PPDU through the first bandwidth and the second bandwidth.

[0236] Additionally, when the AP MLD transmits the first PPDU over the entire bandwidth of the first link for the first AP, the AP MLD may perform channel sensing operations and channel access operations in a third bandwidth adjacent to the entire bandwidth of the first link after switching from the second link to the first link for the second AP. Additionally, when the AP MLD detects that the third bandwidth for the second AP is idle, the AP MLD may perform a third PPDU transmission independent of the first PPDU in the third bandwidth for the second AP.

[0237] Additionally, if the AP MLD detects that the third bandwidth is idle for the second AP, the AP MLD may stop transmitting the first PPDU for the first AP, and the AP MLD may perform the fourth PPDU transmission through the first bandwidth and the third bandwidth for the first and second APs. Here, the entire bandwidth of the first link may be a primary 80 MHz band, and the third bandwidth adjacent to the entire bandwidth of the first link may be a secondary 80 MHz band, but may not be limited thereto.

[0238] 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.

[0239] 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.

[0240] 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.

[0241]

[0242] The above may also apply to other systems.

Claims

1. In a wireless LAN system, a method for operating an AP multi-link device (MLD) including a first access point (AP) associated with a first link and a second AP associated with a second link, A step in which the AP MLD transmits a first PPDU (PHY layer protocol data unit) in a first bandwidth within the first link for the first AP; A step for the above AP MLD to detect that a part or all of the second link total bandwidth is busy for the second AP, wherein if a part or all of the second link total bandwidth is detected to be busy, the link associated with the second AP is switched from the second link to the first link; The step of the AP MLD performing a channel sensing operation and a channel access operation in the second bandwidth within the first link switched for the second AP; and An AP MLD operating method, comprising: a step of the AP MLD stopping transmission of the first PPDU for the first AP and transmitting a second PPDU through the first bandwidth and the second bandwidth when the second bandwidth in the first link is occupied by the AP MLD based on the channel sensing operation and the channel access operation.

2. In paragraph 1, An AP MLD operating method, wherein when the AP MLD detects that a part or all of the entire bandwidth of the second link is busy for the second AP, the AP MLD recognizes a busy period along with whether a part or all of the entire bandwidth of the second link is busy for the second AP.

3. In paragraph 2, An AP MLD operating method, wherein the link associated with the second AP is switched from the second link to the first link immediately after the AP MLD detects that part or all of the total bandwidth of the second link is busy for the second AP, or after a preset time from the time when the AP MLD detects that part or all of the total bandwidth of the second link is busy.

4. In paragraph 3, When the link associated with the second AP switches from the second link to the first link, the switching from the second link to the first link is completed after a link switching time from the time when the switching from the second link to the first link starts, and the AP MLD operates on the first link for the second AP. An AP MLD operating method, wherein the link associated with the second AP starts switching from the first link to the second link before the link switching time from the point in time at which the busy interval ends after switching to the first link, and the switching is completed at the point in time at which the busy interval ends, and the AP MLD operates on the second link from the point in time at which the busy interval ends for the second AP.

5. In paragraph 2, The link associated with the second AP is maintained as the first link until the AP MLD starts transmitting the second PPDU over the first bandwidth and the second bandwidth for the first AP based on the channel sensing operation and the channel access operation after switching to the first link, An AP MLD operating method, wherein the AP MLD operates on the second link for the second AP from the time point at which the second PPDU is transmitted.

6. In paragraph 1, The above AP MLD performs the channel sensing operation and the channel access operation in the second bandwidth within the first link for the second AP, If the second bandwidth is in a busy state based on the channel detection operation and the channel access operation, and if it is detected that the second bandwidth has transitioned from the busy state to the idle state, a backoff counter is decremented for each slot after a preset time from the time of transition to the idle state. An AP MLD operation method in which the above AP MLD stops transmitting the first PPDU at a slot boundary where the backoff counter becomes 0 for the first AP, and transmits the second PPDU through the first bandwidth and the second bandwidth.

7. In paragraph 6, If the third bandwidth is idle before a preset time from the slot boundary where the backoff counter becomes 0, the AP MLD transmits the second PPDU through the first bandwidth, the second bandwidth, and the third bandwidth for the first AP at the slot boundary where the backoff counter becomes 0, An AP MLD operation method in which, if the third bandwidth is busy before a preset time from the slot boundary where the backoff counter becomes 0, the AP MLD transmits the second PPDU through the first bandwidth and the second bandwidth for the first AP at the slot boundary where the backoff counter becomes 0.

8. In paragraph 7, An AP MLD operating method, wherein the first bandwidth is a primary 20 MHz band, the second bandwidth is a secondary 20 MHz band, and the third bandwidth is the secondary 40 MHz.

9. In paragraph 1, An AP MLD operating method, wherein when the first bandwidth is a primary 40 MHz band and the second bandwidth is a secondary 40 MHz band, the AP MLD performs the channel sensing operation and the channel access operation in a secondary 20 MHz band adjacent to the first bandwidth within the second bandwidth for the second AP.

10. In paragraph 9, When the AP MLD detects that the secondary 20MHz band adjacent to the first bandwidth is busy for the second AP, and when the secondary 20MHz band adjacent to the first bandwidth transitions from the busy state to the idle state, the AP MLD decrements a backoff counter for each slot after a preset time from the time of transition to the idle state for the second AP, An AP MLD operation method in which the above AP MLD stops transmitting the first PPDU at a slot boundary where the backoff counter becomes 0 for the first AP, and transmits the second PPDU through the first bandwidth and the second bandwidth.

11. In paragraph 9, The above AP MLD decrements the backoff counter at every slot after a preset time if the secondary 20MHz band adjacent to the first bandwidth in the second bandwidth for the second AP is idle, An AP MLD operating method, wherein, when the AP MLD detects that a part of a channel of the second bandwidth is busy at a slot boundary where the backoff counter becomes 0 for the first AP, the AP MLD maintains the backoff counter as 0 until the entire second bandwidth transitions to an idle state for the first AP, and when the entire second bandwidth transitions to an idle state, stops transmitting the first PPDU after a preset time from the time of transitioning to the idle state, and transmits the second PPDU through the first bandwidth and the second bandwidth.

12. In paragraph 1, An AP MLD operating method, wherein when the AP MLD transmits the first PPDU over the entire bandwidth of the first link for the first AP, the AP MLD performs the channel sensing operation and the channel access operation in a third bandwidth adjacent to the entire bandwidth of the first link after switching from the second link to the first link for the second AP.

13. In paragraph 12, An AP MLD operating method, wherein when the AP MLD detects that the third bandwidth is idle for the second AP, the AP MLD performs a third PPDU transmission independent of the first PPDU in the third bandwidth for the second AP.

14. In paragraph 12, An AP MLD operating method, wherein when the AP MLD detects that the third bandwidth is idle for the second AP, the AP MLD stops transmitting the first PPDU for the first AP, and the AP MLD performs transmitting a fourth PPDU through the first bandwidth and the third bandwidth for the first AP and the second AP.

15. In paragraph 12, An AP MLD operating method, wherein the entire bandwidth of the first link is a primary 80 MHz band, and the third bandwidth adjacent to the entire bandwidth of the first link is a secondary 80 MHz band.

16. In an access point (AP) multi link device (MLD), A first AP associated with the first link of the AP MLD; A second AP associated with the second link of the AP MLD; At least one transceiver for transmitting and receiving signals; At least one processor controlling at least one of the first AP, the second AP and the at least one transceiver; and A memory storing instructions that cause the AP MLD to perform a specific operation by at least one processor, The above specific actions are: The above AP MLD transmits a first PPDU (PHY layer protocol data unit) in a first bandwidth within the first link for the first AP, The above AP MLD detects that a part or all of the second link total bandwidth is busy for the second AP, and if a part or all of the second link total bandwidth is detected to be busy, the link associated with the second AP is switched from the second link to the first link, The above AP MLD performs a channel sensing operation and a channel access operation in a second bandwidth within the first link switched for the second AP, and An AP MLD, wherein if the second bandwidth within the first link is occupied by the AP MLD based on the channel sensing operation and the channel access operation, the AP MLD stops transmitting the first PPDU for the first AP and transmits a second PPDU through the first bandwidth and the second bandwidth.

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