Method and device for performing time division multiple access in wireless LAN

Abstract

An operation method performed by a first AP for adjusting time division multiple access in a wireless LAN system comprises: a step in which the first AP transmits a first frame; a step for transmitting a second frame in a first communication time slot set by means of a first frame, wherein the first AP allocates, through the second frame, a second communication time slot to a second AP on the basis of the time division multiple access within the first communication time slot; and a step for receiving, in response to the second frame, a third frame from each of one or more APs including the second AP, wherein the third frame is a frame for setting a second NAV to at least one wireless LAN terminal for receiving the third frame, and communication performed by the second AP in the second communication time slot may be performed regardless of the NAV.

Description

Method and device for performing time-division communication in wireless LAN

[0001] The present disclosure relates to a method and device for performing time-division communication in a Wireless Local Area Network (WLAN). Specifically, the present disclosure relates to a method and device for protecting a communication section when performing communication by time-division between users in a WLAN.

[0002]

[0003] With the recent proliferation of mobile devices, Wireless Local Area Network (WLAN) technology, which can provide fast wireless communication services to these devices, is attracting significant attention. WLAN technology utilizes short-range wireless communication technology to enable mobile devices such as smartphones, tablets, laptops, portable multimedia players, and embedded devices to wirelessly access the Internet.

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

[0005] As applications requiring higher reliability arise, the IEEE 802.11bn standard, an ultra-high reliability (UHR) wireless LAN technology, is being developed in a single Basic Service Set (BSS) environment and / or redundant BSS environments. The goals of the IEEE 802.11bn standard may support increased data transmission rates, improved delay performance, and improved data error rates. In addition, the IEEE 802.11bn standard may support low-power operation, peer-to-peer communication, operation for increased channel utilization, and coordinated time division multiple access (C-TDMA) operation of multiple APs.

[0006] However, when communicating using a coordinated time-division communication interval, the time-division communication interval may not be protected. For example, the time-division communication interval may be invaded by another communication terminal. Therefore, communication operations may not be performed within the time-division communication interval, and coordinated time-division communication operations may not be utilized.

[0007] Meanwhile, the technology that serves as the background for the invention is written to promote understanding of the background for the invention, and may include content that is not a prior art already known to a person with ordinary skill in the field to which the technology belongs.

[0008]

[0009] The present disclosure relates to a method and device for protecting a communication section when performing time-division communication in a wireless LAN.

[0010] The present disclosure relates to a method and device for preventing interference in a communication section caused by a wireless LAN terminal in a hidden node relationship when performing time-division communication in a wireless LAN.

[0011] The present disclosure relates to a method and device for transmitting a CTS frame by at least one AP based on a MU-RTS (multi user-request to send) frame transmitted by an AP (access point) that controls time division communication in a wireless LAN.

[0012] The present disclosure relates to a method and device for distinguishing a CTS frame received in response to an MU-RTS frame transmission by an AP controlling time-division communication in a wireless LAN.

[0013] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0014]

[0015] According to one example of the present disclosure, a method of operating a first access point (AP) for coordinating time division communication in a wireless LAN system includes a step of transmitting a first CTS (clear to send) frame by a first AP, wherein the first frame is a frame for setting a first network allocation vector (NAV) to at least one wireless LAN terminal receiving the first frame, and a step of transmitting a second frame in a first communication section set by the first frame, wherein the first AP allocates a second communication section to a second AP based on time division communication within the first communication section through the second frame, and receiving a third frame from each of at least one AP including the second AP in response to the second frame, wherein the third frame is a frame for setting a second NAV to at least one wireless LAN terminal receiving the third frame, and communication by the second AP within the second communication section can be performed regardless of the NAV.

[0016] Additionally, according to one embodiment of the present disclosure, a first access point (AP) may include at least one transceiver, at least one processor controlling the at least one transceiver, and a memory storing instructions for causing a wireless user device to perform a specific operation by the at least one processor. Here, the specific operation is that the first AP transmits a first CTS (clear to send) frame, the first frame is a frame that sets a first NAV (network allocation vector) to at least one wireless LAN terminal receiving the first frame, transmits a second frame in a first communication section set by the first frame, the first AP allocates a second communication section to the second AP based on time division communication within the first communication section through the second frame, and receives a third frame from each of at least one AP including the second AP in response to the second frame, the third frame is a frame that sets a second NAV to at least one wireless LAN terminal receiving the third frame, and communication by the second AP within the second communication section can be performed regardless of the NAV.

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

[0018] According to one embodiment of the present disclosure, the second frame includes user information of a second AP to which a second communication section is allocated and user information of a third AP to which a second communication section is not allocated, and the second frame may further include at least one of an indicator indicating that the second AP is allocated a second communication section and an indicator indicating that the third AP is not allocated a second communication section.

[0019] Additionally, according to one embodiment of the present disclosure, the second frame includes a group identifier of at least one AP that can be assigned a second communication segment based on time division communication, and the first AP can receive a third frame from each of the at least one AP, including the second AP, based on the group identifier.

[0020] Additionally, according to one embodiment of the present disclosure, if the second frame includes the first parameter together with the group identifier, the first AP may receive a third frame from each of at least one AP including the second AP.

[0021] Additionally, according to one embodiment of the present disclosure, a first NAV may be set to a time length indicated by a duration field of a MAC (medium access control) header included in a first frame, and a second NAV may be set to a time length indicated by a duration field of a MAC header included in a third frame.

[0022] Additionally, according to one embodiment of the present disclosure, a receiver address (RA) field in a third frame transmitted by a third AP to which a second communication section is not allocated based on a second frame may be set to the first AP, and a second NAV set to at least one wireless LAN terminal through the third frame transmitted by the third AP may be set to a basic NAV.

[0023] Additionally, according to one embodiment of the present disclosure, the third frame received by the first AP from each of at least one of the APs including the second AP may be a simultaneous CTS (S-CTS) frame, such that the first AP may simultaneously receive the third frame from each of at least one of the APs including the second AP.

[0024] Additionally, according to one embodiment of the present disclosure, the first AP may receive the third frame and detect communication of a second AP allocated a second communication section for a preset period of time, and if communication of the second AP is not detected, the second communication section may be reassigned.

[0025] Additionally, according to one embodiment of the present disclosure, a third frame transmitted by a second AP allocated a second communication section and a third frame transmitted by a third AP not allocated a second communication section are set to different bandwidths, and the first AP can identify an AP transmitting the third frame based on bandwidth information for each of the third frames simultaneously received.

[0026] Additionally, according to one embodiment of the present disclosure, the second frame further includes frequency information on which the CTS frame is transmitted, and the band on which the CTS frame is received may be set differently for each AP based on the frequency information on which the CTS frame is transmitted.

[0027] Additionally, according to one embodiment of the present disclosure, the first AP can receive a third frame in a different band from each of at least one AP, including the second AP, based on frequency information at which the CTS frame is transmitted.

[0028] Additionally, according to one embodiment of the present disclosure, the first AP may receive a third frame transmitted simultaneously from each of at least one AP including the second AP over the entire band based on the second frame, and then receive a fourth frame in a different band from each of at least one AP including the second AP based on frequency information at which the CTS frame is transmitted.

[0029] Additionally, according to one embodiment of the present disclosure, the first AP may transmit an NFRP (NDP (null data PPDU) Feedback Report Poll) trigger frame to at least one AP including the second AP after transmitting the first frame, and may transmit the second frame after receiving an NDP feedback frame from each of the at least one AP including the second AP.

[0030] Additionally, according to one embodiment of the present disclosure, the NFRP trigger frame includes identification information that identifies each of at least one AP including the second AP, and an NDP feedback frame transmitted from each of the at least one AP including the second AP can be received in a band corresponding to the identification information.

[0031] Additionally, according to one embodiment of the present disclosure, the first AP may transmit a Buffer Status Report Poll (BSRP) trigger frame to at least one AP including the second AP after transmitting the first frame, and may transmit the second frame after receiving a buffer status report from each of the at least one AP including the second AP.

[0032] Additionally, according to one embodiment of the present disclosure, the BSRP trigger frame indicates a band over which a buffer status report is transmitted, and the buffer status report transmitted from each of at least one AP including the second AP can be received in the band indicated by the BSRP trigger frame.

[0033]

[0034] According to the present disclosure, a method for protecting a communication section when performing time-division communication in a wireless LAN can be provided.

[0035] According to the present disclosure, a method for preventing interference in a communication section by a wireless LAN terminal in a hidden node relationship can be provided when performing time-division communication in a wireless LAN.

[0036] According to the present disclosure, a method can be provided in which at least one AP transmits a CTS frame based on an MU-RTS frame transmitted by an AP controlling time division communication in a wireless LAN.

[0037] According to the present disclosure, a method can be provided for an AP controlling time-division communication in a wireless LAN to distinguish a CTS frame received in response to an MU-RTS frame transmission.

[0038] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0039]

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

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

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

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

[0044] FIG. 5 is a diagram illustrating a problem that may occur when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0045] FIG. 6 is a diagram illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0046] FIG. 7 is a diagram illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0047] FIG. 8a and FIG. 8b are diagrams illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0048] FIG. 9a and FIG. 9b are diagrams illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0049] FIG. 10 is a flowchart illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN applied to the present disclosure.

[0050]

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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."

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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).

[0068] 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 through a dedicated bus or interface centered around the processor (110) of the communication node (100), but may not be limited to the above embodiment.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] 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.

[0073] FIG. 5 is a diagram illustrating a problem that may occur when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0074] Referring to FIG. 5, multiple access points (APs) may operate in a wireless LAN. For example, AP 1 to AP 3 (520, 530, 540) may operate in the wireless LAN. Here, AP 2 (530) may be a coordinating AP for coordinated time division multiple access (C-TDMA). AP 2 (530) may set a transmit opportunity (TXOP) on a channel to use C-TDMA. Here, the TXOP is a time period during which multiple frames can be transmitted. The TXOP may be set through a CTS frame (e.g., a CTS-to-Self frame in which the receiver address is set to the MAC address of AP 2). As another example, the TXOP may also be set by transmitting a multi-user-request to send (MU-RTS) frame or a data frame. The following description assumes that TXOP is set using a CTS-to-Self frame, but may not be limited thereto.

[0075] Referring to FIG. 5, AP 1 (520) and AP 3 (540) can receive the CTS-to-Self frame (or CTS frame) transmitted by AP 2 (530) and set a network allocation vector (NAV) based on the time length indicated by the duration field included in the MAC header of the CTS-to-Self frame. The NAV can be set to correspond to the length of the TXOP set by AP 2 (530). Here, STA 1 (510) connected to AP 1 (520) may be a hidden node in its relationship with AP 2 (530), and STA 1 (510) may not receive the CTS-to-Self frame transmitted by AP 2 (530). Therefore, STA 1 (510) may not be able to set a NAV.

[0076] For example, when NAV is set in a wireless LAN terminal, wireless LAN terminals including AP and non-AP STA (i.e., STA) may detect the channel as busy based on virtual carrier sensing and may not be able to transmit frames. That is, when NAV is set in a wireless LAN terminal, the wireless LAN terminal may wait without transmitting frames. In FIG. 5, NAVs may be set in AP 1 (520) and AP 3 (540) by a CTS-to-Self frame, so that the TXOP of AP 2 (530) may be guaranteed. AP 2 (530) may transmit an MU-RTS frame to allocate a C-TDMA communication section in the TXOP. The MU-RTS frame may include a user info field including information on AP 3 (540), which is the allocation target of the C-TDMA communication section (e.g., AID (association identifier) ​​of AP 3). AP 3 (540) may be allocated a C-TDMA communication section and may transmit a CTS frame in response to an MU-RTS frame. For example, the CTS frame transmitted in response to the MU-RTS frame may be a simultaneous CTS frame. That is, the CTS frame may be a CTS frame that multiple STAs may transmit simultaneously, but is not limited thereto. Since the CTS frame is an immediate response frame to the MU-RTS frame, it may be transmitted in response even when a NAV is set. AP 3 (540) may communicate with other wireless LAN terminals in the allocated C-TDMA communication section (or shared TXOP). That is, AP 3 (540) may ignore the NAV set in the C-TDMA communication section and communicate with an STA (e.g., STA 2 (550)) connected to AP 3 (540).

[0077] Here, STA 1 (510) may not receive the MU-RTS frame of AP 2 (520). For example, STA 1 (510) may be a hidden node from the perspective of AP 2 (520). If STA 1 (510) and AP 2 (520) have a hidden node relationship, STA 1 (510) may not detect the transmission of AP 2 (520), and AP 2 (520) may not detect the transmission of STA 1 (510). As another example, STA 1 (510) may receive the MU-RTS frame of AP 2 (520) but may not receive the response frame (CTS frame) of AP 3 (540). In the above-described case, STA 1 (510) may not set a NAV, and STA 1 (510) may transmit a data frame to AP 1 (520). For example, AP 1 (520) may set a NAV based on a frame transmitted from AP 2 (530). Here, if the data frame transmitted by STA 1 (510) requests an immediate response, AP 1 (520) may transmit an immediate response frame regardless of the NAV. However, in the above-described situation, the immediate response frame transmitted by AP 1 (520) may act as interference to AP 3 (540). Therefore, there is a need to prevent AP 1 (520) from transmitting an immediate response frame, and interference may not occur if AP 1 (520) does not transmit an immediate response frame to STA 1 (510). However, in the above-described situation, the backoff contention window (EDCA (Enhanced Distributed Channel Access) backoff contention window) of STA 1 (510) may increase, and the communication efficiency of STA 1 (510) may decrease. In addition, if there is no separate method to prevent AP 1 (520) from transmitting an immediate response frame, the immediate response frame transmitted by AP 1 (520) may act as interference to AP 3 (540).Therefore, the communication efficiency of not only AP 1 (520) and STA 1 (510) but also AP 3 (540) and STA 2 (550) may decrease.

[0078] FIG. 6 is a diagram illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0079] Referring to FIG. 6, multiple access points (APs) may operate in a wireless LAN. For example, AP 1 to AP 3 (620, 630, 640) may operate in the wireless LAN. Here, AP 2 (630) may be a coordinating AP for coordinated time division multiple access (C-TDMA). AP 2 (630) may set a transmit opportunity (TXOP) on a channel to use C-TDMA. Here, the TXOP is a time period during which multiple frames can be transmitted. The TXOP may be set through a CTS frame (e.g., a CTS-to-Self frame in which the receiver address is set to the MAC address of AP 2). As another example, the TXOP may also be set by transmitting a multi-user-request to send (MU-RTS) frame or a data frame. The following description assumes that TXOP is set using a CTS-to-Self frame, but may not be limited thereto.

[0080] Referring to FIG. 6, AP 1 (620) and AP 3 (640) can receive the CTS-to-Self frame (or CTS frame, 601) transmitted by AP 2 (630), and set a network allocation vector (NAV) based on the time length indicated by the duration field included in the MAC header of the CTS-to-Self frame (601). The NAV can be set to correspond to the length of the TXOP set by AP 2 (630). Here, STA 1 (610) connected to AP 1 (620) may be a hidden node in its relationship with AP 2 (630), and STA 1 (610) may not receive the CTS-to-Self frame (601) transmitted by AP 2 (630). Therefore, STA 1 (610) may not be able to set a NAV.

[0081] For example, when NAV is set in a wireless LAN terminal, wireless LAN terminals including AP and non-AP STA (i.e., STA) may detect the channel as busy based on virtual carrier sensing and may not be able to perform frame transmission. That is, when NAV is set in a wireless LAN terminal, the wireless LAN terminal may wait without performing frame transmission. In FIG. 6, NAV is set in AP 1 (620) and AP 3 (640) by CTS-to-Self frame (601), so that TXOP of AP 2 (630) may be guaranteed. AP 2 (630) may transmit MU-RTS frame (602) to allocate C-TDMA communication section in TXOP. The MU-RTS frame (602) may include a user info field including information of AP 3 (640) to which a C-TDMA communication section is allocated (e.g., AID (association identifier) ​​of AP 3). AP 3 (640) may be allocated a C-TDMA communication section and may transmit a CTS frame in response to the MU-RTS frame (602). For example, the CTS frame transmitted in response to the MU-RTS frame (602) may be a simultaneous CTS frame. That is, the CTS frame may be a CTS frame that may be transmitted simultaneously by multiple wireless LAN terminals, but may not be limited thereto.

[0082] In addition, AP 1 (620) may also transmit a CTS frame (603-1) in response to the MU-RTS frame (602) of AP 2 (630). Here, AP 1 (620) may be an AP that can perform C-TDMA communication but has not been allocated a communication section. More specifically, the MU-RTS frame (602) transmitted by AP 2 (630) may include information about AP 1 (620) that can perform C-TDMA communication but has not been allocated a communication section (e.g., a user info field including the AID of AP 1). The information in the MU-RTS frame (602) transmitted by AP 2 (630) may include information about at least one of an indicator indicating that AP 3 (640) is allocated a C-TDMA communication section and an indicator indicating that AP 1 (620) is not allocated a C-TDMA communication section.

[0083] As another example, when the MU-RTS frame (602) transmitted by AP 2 (630) allocates a C-TDMA communication section, AP 1 (620) may transmit a CTS frame (603-1) in response. Here, the MU-RTS frame (602) may include an indicator indicating that a C-TDMA communication section is allocated.

[0084] As another example, the MU-RTS frame (602) transmitted by AP 2 (630) may include a group identifier of APs that may be targets of C-TDMA operation. The group identifier of APs may be referred to as a MAP (Multiple-AP) ID, but may not be limited to that name. For example, the MAP ID may be an unused (or reserved) one among the AIDs. Alternatively, the MAP ID may be designated through prior negotiation between APs. Alternatively, the MAP ID may be used as a pre-determined value and is not limited to a specific form. Here, AP 1 (620) may recognize the MAP ID of the group to which AP 1 (620) is included. Therefore, if the AID corresponding to the MAP ID is included in the user information of the MU-RTS frame (602), AP 1 (620) may immediately transmit a simultaneous CTS frame (603-1) in response. Additionally, AP 3 (640) can also recognize the MAP ID of the group that includes AP 3 (640). Therefore, if the AID corresponding to the MAP ID is included in the user information in the MU-RTS frame (602), AP 3 (640) can immediately transmit a simultaneous CTS frame (603-2) in response.

[0085] As another example, based on whether the MU-RTS frame (602) transmitted by AP 2 (630) includes "SCRAMBLER_INITIAL_VALUE", AP 1 (620) can transmit a simultaneous CTS frame (603-1). Since the "SCRAMBLER_INITIAL_VALUE" of the transmit vector (TXVECTOR) parameter present in the PHY preamble of the simultaneous CTS frame (603-1) must be set to be the same as the "SCRAMBLER_INITIAL_VALUE" of the receive vector (RXVECTOR) parameter present in the MU-RTS frame (602) and transmitted, AP 1 (620) can perform transmission setup using the "SCRAMBLER_INITIAL_VALUE" value included in the MU-RTS frame (602) and then transmit the simultaneous CTS frame (603-1).

[0086] For example, the above-described operations may be combined and used, and may not be limited to one method. As a specific example, even if "SCRAMBLER_INITIAL_VALUE" is included in the MU-RTS frame (602), if the MAP ID is not the AID of the group to which the AP belongs, the simultaneous CTS frame (603-1) may not be transmitted. As another example, even if the MAP ID is the AID of the group to which the AP belongs, if "SCRAMBLER_INITIAL_VALUE" is not included, AP 1 (620) may not transmit the simultaneous CTS frame (603-1). As another example, if the MU-RTS frame (602) includes allocation information of AP 1 (620), AP 1 (620) may have to transmit the simultaneous CTS frame (603-1) without any other conditions.

[0087] For example, AP 3 (640) may ignore the NAV set in the C-TDMA communication section based on the allocated C-TDMA communication section (or shared TXOP) and communicate with an STA (e.g., STA 2 (650)) connected to AP 3 (640). AP 3 (640) may transmit a downlink frame to STA 2 (650) or trigger uplink frame transmission. AP 3 (640) may transmit a trigger frame to STA 2 (650) to trigger uplink frame transmission of STA 2 (650). For example, the trigger frame transmitted to STA 2 (650) may have the CS required field set to 0. Accordingly, when STA 2 (650) receives a trigger frame, STA 2 (650) can transmit an uplink frame (e.g., UL (uplink) TB (trigger based) PPDU (physical layer protocol data unit)) to AP 3 (640) regardless of whether the state of the channel detected by NAV (i.e., virtual carrier sensing) or physical carrier sensing is idle or busy. Here, since AP 3 (640) has been allocated a communication section from AP 2 (630), it can transmit a trigger frame with the CS required bit set to 0 to STA 2 (650).

[0088] For example, STA 1 (610) may not receive the MU-RTS frame (602) of AP 2 (630), but may receive the CTS frame (603-1) of AP 1 (620). That is, AP 1 (620), which has not been allocated a C-TDMA communication section (or shared TXOP) from AP 2 (630) as described above, may transmit the CTS frame (603-1), and STA 1 (610) may receive the CTS frame (603-1) transmitted by AP 1 (620). Accordingly, STA 1 (610) may set the NAV for the length of time indicated by the duration field included in the MAC header of the CTS frame (603-1) of AP 1 (620). That is, STA 1 (610) may not transmit a data frame to AP 1 (620) for the length of time indicated by the duration field, thereby preventing interference of C-TDMA communication due to frame transmission by STA 1 (610).

[0089] For example, since the CTS frame (603-1) transmitted by AP 1 (620) is transmitted to AP 2 (630), the RA field may be set to AP 2 (630). The RA field of the CTS frame (603-1) received by STA 1 (610) from AP 1 (620) may be AP 2 (630), and accordingly, a basic NAV may be set to STA 1 (610). That is, STA 1 (610) may set the basic NAV even though the frame is transmitted by AP 1 (620) within the same BSS.

[0090] For example, the default NAV may be set when a PPDU received by a wireless LAN terminal does not correspond to either an intra-BSS PPDU or an inter-BSS PPDU. Here, when the wireless LAN terminal receives a CTS frame, which is a control frame that only contains an RA field without a TA field, the wireless LAN terminal may determine that the PPDU does not correspond to either an intra-BSS or an inter-BSS frame if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0091] More specifically, when a wireless LAN terminal receives a PPDU, the wireless LAN terminal can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU. As a specific example, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) parameter of the received PPDU is 0 or is identical to the "BSS_COLOR" value of the currently connected BSS. In addition, with respect to a VHT (very high throughput) PPDU, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) of the received PPDU is identical to the BSSID of the currently connected BSS or is identical to the BSSID of another BSS within the same Multiple BSSID Set or Co-Hosted BSSID Set and the GROUP_ID is 0. Additionally, a wireless LAN terminal can determine that a control frame containing only RA is an intra-BSS PPDU if the RA field value in relation to the CTS frame matches the address of the previous TXOP holder, or if the RA field value matches the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0092] In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) is not 0 and is different from the BSS_COLOR value of the currently connected BSS. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) with respect to the VHT PPDU is different from the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the GROUP_ID of the reception vector (RXVECTOR) is 63 and the Partial BSS Color in the recently received HE Operation Element is 1. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the UPLINK_FLAG value of the reception vector (RXVECTOR) is 0 under the VHT MU / HE MU PPDU condition and the terminal that received the PPDU is an AP. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU transmits a frame that does not match the BSSID or is not a wildcard BSSID under the BSSID-related condition. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU does not have a BSSID field but includes both RA and TA fields and these are not the same as the BSSID of the same BSS, but may not be limited thereto.

[0093] Here, the wireless LAN terminal may set the basic NAV if the PPDU received by the wireless LAN terminal is neither an intra-BSS PPDU nor an inter-BSS PPDU. For example, in the case of a CTS frame containing only an RA field, if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, it may be regarded as not being included in either the intra-BSS or the inter-BSS, and in such a case, the basic NAV may be set.

[0094] In FIG. 6, STA 1 (610) may have a hidden node relationship with AP 2 (630), and since STA 1 (610) receives a CTS frame (603-1) with the RA field set to AP 2 (630), it does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, and thus a basic NAV can be set. That is, since the AP to which STA 1 (610) is connected is AP 1 (620), when it receives a CTS frame (603-1) with the RA field set to AP 2 (630), the CTS frame cannot be determined as an intra BSS PPDU, nor can it be determined as an inter BSS PPDU, and thus a basic NAV can be set.

[0095] As another example, AP 3 (640) may not receive the MU-RTS frame (602) of AP 2 (630), and AP 1 (620) may receive the MU-RTS frame (602) of AP 2 (630). However, this is for convenience of explanation and is not limited thereto. AP 1 (620) may receive the MU-RTS frame (602) and transmit a CTS frame (603-1) to AP 2 (630). Since the CTS frame (603-1) transmitted in response to the MU-RTS frame (602) may be an S-CTS frame, AP 2 (630) may not be able to distinguish which AP transmitted the CTS frame. Accordingly, after receiving the CTS frame, AP 2 (630) can check whether AP 3 (640) is performing communication in the communication section allocated to AP 3 (640). For example, if communication of AP 3 (640) is not detected until after the PIFS (priority interframe space) time or a time longer than the PIFS time from the time when AP 2 (630) completes receiving the CTS frame, AP 2 (630) can re-allocate the communication section. In another example, if communication of AP 3 (640) is not detected until the PIFS time from a specific time (e.g., the time when AP 2 completes receiving the CTS frame) within the communication section allocated to AP 3 (640), AP 2 (630) can retransmit an MU-RTS frame after the PIFS time from the time when reception of the CTS frame is completed. Based on the above-described operation, AP 2 (630) can re-allocate a communication section to AP 3 (640). Alternatively, AP 2 (630) can allocate a communication section to another AP (e.g., AP 1) other than AP 3 (640) that failed to allocate a communication section through an MU-RTS frame, and is not limited to a specific form.

[0096] The machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may be used to determine the AP to which AP 2 (630) is a C-TDMA communication target. For example, AP 3 (640) to which AP 2 (630) allocates a C-TDMA communication section may be determined by the machine learning unit of AP 2. In addition, the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may be used to determine that AP 1 (620) transmits a CTS frame in response to the transmission of an MU-RTS frame of AP 2 (630). For example, the machine learning unit may determine whether AP 1 (620) can receive frames from AP 2 (630) and AP 3 (640) and set a NAV by inputting parameters such as the reception power of the frame. If STA 1 (610) is determined to be capable of setting up a NAV, AP 1 (620) may decide not to transmit an unnecessary CTS frame. Conversely, if STA 1 (610) is determined to be unable to set up a NAV, AP 1 (620) may decide to transmit a CTS frame.

[0097] FIG. 7 is a diagram illustrating a method for protecting a communication section when performing a coordinated time-division communication operation to which the present disclosure applies.

[0098] Referring to FIG. 7, multiple access points (APs) may operate in a wireless LAN. For example, AP 1 to AP 3 (720, 730, 740) may operate in the wireless LAN. Here, AP 2 (730) may be a coordinating AP for coordinated time division multiple access (C-TDMA). AP 2 (730) may set a transmit opportunity (TXOP) on a channel to use C-TDMA. Here, the TXOP is a time period during which multiple frames can be transmitted. The TXOP may be set through a CTS frame (e.g., a CTS-to-Self frame in which the receiver address is set to the MAC address of AP 2). As another example, the TXOP may also be set by transmitting a multi-user-request to send (MU-RTS) frame or a data frame. The following description assumes that TXOP is set using a CTS-to-Self frame, but may not be limited thereto.

[0099] Referring to FIG. 7, AP 1 (720) and AP 3 (740) can receive the CTS-to-Self frame (or CTS frame, 701) transmitted by AP 2 (730) and set a network allocation vector (NAV) based on the time length indicated by the duration field included in the MAC header of the CTS-to-Self frame (701). The NAV can be set to correspond to the length of the TXOP set by AP 2 (730). Here, STA 1 (710) connected to AP 1 (720) may be a hidden node in its relationship with AP 2 (730), and STA 1 (710) may not receive the CTS-to-Self frame (701) transmitted by AP 2 (730). Therefore, STA 1 (710) may not be able to set a NAV.

[0100] For example, when NAV is set in a wireless LAN terminal, wireless LAN terminals including AP and non-AP STA (i.e., STA) may detect the channel as busy based on virtual carrier sensing and may not be able to perform frame transmission. That is, when NAV is set in a wireless LAN terminal, the wireless LAN terminal may wait without performing frame transmission. AP 2 (730) may transmit an MU-RTS frame (702) to allocate a C-TDMA communication section in TXOP. The MU-RTS frame (702) may include information of AP 3 (740) that is the target of allocation of the C-TDMA communication section (e.g., a user info field including the AID (association identifier) ​​of AP 3). In addition, the MU-RTS frame (702) may include information of AP 1 (720) that is capable of C-TDMA communication but is not allocated a communication section. The information of AP 3 (740) and the information of AP 1 (720) may include information indicating a frequency (e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz) at which the CTS frame (703-1, 703-2) is transmitted. For example, AP 2 (730) may enable each AP to transmit the CTS frame in a different bandwidth in order to distinguish between the CTS frame transmissions of AP 3 (740) and AP 1 (720). As a specific example, AP 3 (740) assigned a C-TDMA communication section can transmit a CTS frame (703-2) in a wide bandwidth (e.g., 80 MHz), and AP 1 (720) can transmit a CTS frame (703-1) in a relatively smaller bandwidth (e.g., 40 MHz) than AP 3 (740).

[0101] That is, the AP allocated a C-TDMA communication section can be instructed to transmit a CTS frame in a wider bandwidth. Additionally, the information in the MU-RTS frame (702) transmitted by AP 2 (730) can include at least one of an indicator indicating that AP 3 (740) is allocated a C-TDMA communication section and an indicator indicating that AP 1 (720) is not allocated a C-TDMA communication section.

[0102] AP 3 (740) may be allocated a C-TDMA communication section and may transmit a CTS frame in response to the MU-RTS frame. In addition, AP 1 (720) may not be allocated a C-TDMA communication section, but may transmit a CTS frame in response based on the AP 1 (720) information included in the MU-RTS frame (702). The CTS frame transmitted in response to the MU-RTS frame (702) may be a simultaneous CTS frame. That is, it may be a CTS frame that multiple wireless LAN terminals may transmit simultaneously. In addition, since the CTS frame is an immediate response frame to the MU-RTS frame, it may respond even if the NAV is set.

[0103] For example, AP 3 (740) may ignore the NAV set in the C-TDMA communication section based on the allocated C-TDMA communication section (or shared TXOP) and communicate with an STA (e.g., STA 2 (750)) connected to AP 3 (740). AP 3 (740) may transmit a downlink frame to STA 2 (750) or trigger uplink frame transmission. AP 3 (740) may transmit a trigger frame to STA 2 (750) to trigger uplink frame transmission of STA 2 (750). For example, the trigger frame transmitted to STA 2 (750) may have the CS required field set to 0. Accordingly, when STA 2 (750) receives a trigger frame, STA 2 (750) can transmit an uplink frame (e.g., UL (uplink) TB (trigger based) PPDU (physical layer protocol data unit)) to AP 3 (740) regardless of whether the state of the channel detected by NAV (i.e., virtual carrier sensing) or physical carrier sensing is idle or busy. Here, since AP 3 (740) has been allocated a communication section from AP 2 (730), it can transmit a trigger frame with the CS required bit set to 0 to STA 2 (750).

[0104] For example, STA 1 (710) may not receive the MU-RTS frame (702) of AP 2 (730), but may receive the CTS frame (703-1) of AP 1 (720). That is, AP 1 (720), which has not been allocated a C-TDMA communication section (or shared TXOP) from AP 2 (730) as described above, may transmit the CTS frame (703-1), and STA 1 (710) may receive the CTS frame (703-1) transmitted by AP 1 (720). Accordingly, STA 1 (710) may set the NAV for the length of time indicated by the duration field included in the MAC header of the CTS frame (703-1) of AP 1 (720). That is, STA 1 (710) may not transmit a data frame to AP 1 (720) for the length of time indicated by the duration field, thereby preventing interference of C-TDMA communication due to frame transmission by STA 1 (710).

[0105] For example, since the CTS frame (703-1) transmitted by AP 1 (720) is transmitted to AP 2 (730), the RA field may be set to AP 2 (730). The RA field of the CTS frame (703-1) received by STA 1 (710) from AP 1 (720) may be AP 2 (730), and accordingly, a basic NAV may be set to STA 1 (710). That is, STA 1 (710) may set the basic NAV even though the frame is transmitted by AP 1 (720) within the same BSS.

[0106] For example, the default NAV may be set when a PPDU received by a wireless LAN terminal does not correspond to either an intra-BSS PPDU or an inter-BSS PPDU. Here, when the wireless LAN terminal receives a CTS frame, which is a control frame that only contains an RA field without a TA field, the wireless LAN terminal may determine that the PPDU does not correspond to either an intra-BSS or an inter-BSS frame if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0107] More specifically, when a wireless LAN terminal receives a PPDU, the wireless LAN terminal can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU. As a specific example, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) parameter of the received PPDU is 0 or is identical to the "BSS_COLOR" value of the currently connected BSS. In addition, with respect to a VHT (very high throughput) PPDU, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) of the received PPDU is identical to the BSSID of the currently connected BSS or is identical to the BSSID of another BSS within the same Multiple BSSID Set or Co-Hosted BSSID Set and the GROUP_ID is 0. Additionally, a wireless LAN terminal can determine that a control frame containing only RA is an intra-BSS PPDU if the RA field value in relation to the CTS frame matches the address of the previous TXOP holder, or if the RA field value matches the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0108] In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) is not 0 and is different from the BSS_COLOR value of the currently connected BSS. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) with respect to the VHT PPDU is different from the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the GROUP_ID of the reception vector (RXVECTOR) is 63 and the Partial BSS Color in the recently received HE Operation Element is 1. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the UPLINK_FLAG value of the reception vector (RXVECTOR) is 0 under the VHT MU / HE MU PPDU condition and the terminal that received the PPDU is an AP. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU transmits a frame that does not match the BSSID or is not a wildcard BSSID under the BSSID-related condition. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU does not have a BSSID field but includes both RA and TA fields and these are not the same as the BSSID of the same BSS, but may not be limited thereto.

[0109] Here, the wireless LAN terminal may set the basic NAV if the PPDU received by the wireless LAN terminal is neither an intra-BSS PPDU nor an inter-BSS PPDU. For example, in the case of a CTS frame containing only an RA field, if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, it may be regarded as not being included in either the intra-BSS or the inter-BSS, and in such a case, the basic NAV may be set.

[0110] In Fig. 7, STA 1 (710) may have a hidden node relationship with AP 2 (730), and since STA 1 (710) receives a CTS frame (703-1) with the RA field set to AP 2 (730), it does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, and thus a basic NAV can be set. That is, since the AP to which STA 1 (710) is connected is AP 1 (720), when it receives a CTS frame (703-1) with the RA field set to AP 2 (730), the CTS frame cannot be determined as an intra BSS PPDU, nor can it be determined as an inter BSS PPDU, and thus a basic NAV can be set.

[0111] As another example, AP 3 (740) may not receive the MU-RTS frame (702) of AP 2 (730), and AP 1 (720) may receive the MU-RTS frame (702) of AP 2 (730). AP 1 (720) may receive the MU-RTS frame (702) and transmit a CTS frame (703-1) to AP 2 (730). The CTS frame transmitted in response to the MU-RTS frame (702) is an S-CTS frame, but since the bandwidths at which AP 1 (720) and AP 3 (740) transmit the CTS frames (703-1, 703-2) are different, AP 2 (730) may be able to distinguish which AP transmitted the CTS frame. For example, AP 2 (730) can receive a CTS frame and check the bandwidth of the CTS frame. As a specific example, AP 3 (740) may not respond to the MU-RTS frame (702) of AP 2 (730) with a CTS frame, and AP 1 (720) may respond with a CTS frame. Here, since AP 3 (740) did not respond to the MU-RTS frame (702) of AP 2 (730), AP 2 (730) may not be able to allocate a communication section to AP 3 (740). Therefore, AP 2 (730) can reallocate the communication section, for example, AP 2 (730) can retransmit the MU-RTS frame after a short interframe space (SIFS) or PIFS time in the communication section allocated to AP 3 (740) (e.g., when AP 2 (730) has completed receiving the CTS frame). Through this, AP 2 (730) can allocate the communication section to another AP (e.g., AP 1 (720)) rather than AP 3 (740) that failed to allocate the communication section.

[0112] In order for AP 2 (730) to determine a target AP for C-TDMA communication, the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may be used. For example, AP 3 (740) to which AP 2 (730) allocates a C-TDMA communication section may be determined by the machine learning unit of AP 2 (730). Determining the transmission bandwidth of the CTS frame indicated in the user info field included in the MU-RTS frame transmitted by AP 2 (730) before allocating the C-TDMA communication section may be based on the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4. As a specific example, AP 2 (730) may determine the maximum bandwidth to be used in C-TDMA communication using the machine learning unit. Based on the determined maximum bandwidth, it can be determined that the CTS frame transmitted by the STA allocated the C-TDMA communication section is transmitted using the maximum bandwidth, and the CTS frame transmitted by the STA not allocated the C-TDMA communication section is transmitted using a narrower bandwidth than the CTS frame transmitted by the STA allocated the C-TDMA communication section.

[0113] The machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may also be used in the operation of determining whether AP 1 (720) transmits a CTS frame in response to the transmission of an MU-RTS frame by AP 2 (730). For example, AP 1 (720) may determine whether 'STA 1 (710) can receive frames from AP 2 (730) and AP 3 (740) and set a NAV' by using the machine learning unit as input a parameter such as the reception power of the frame. If it is determined that STA 1 (710) can set a NAV, AP 1 (720) may decide not to transmit an unnecessary CTS frame. Conversely, if it is determined that STA 1 (710) cannot set a NAV, AP 1 (720) may decide to transmit a CTS frame.

[0114] FIG. 8a and FIG. 8b are diagrams illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0115] Referring to FIGS. 8A and 8B, multiple access points (APs) may operate in a wireless LAN. For example, AP 1 to AP 3 (820, 830, 840) may operate in the wireless LAN. Here, AP 2 (830) may be a coordinating AP for coordinated time division multiple access (C-TDMA). AP 2 (830) may set a transmit opportunity (TXOP) on a channel to use C-TDMA. Here, the TXOP is a time period during which multiple frames can be transmitted. The TXOP may be set through a CTS frame (e.g., a CTS-to-Self frame in which the receiver address is set to the MAC address of AP 2). As another example, the TXOP may also be set by transmitting a multi-user-request to send (MU-RTS) frame or transmitting a data frame. The following description assumes that TXOP is set using a CTS-to-Self frame, but may not be limited thereto.

[0116] Referring to FIGS. 8A and 8B, AP 1 (820) and AP 3 (840) can receive a CTS-to-Self frame (or CTS frame) transmitted by AP 2 (830), and set a network allocation vector (NAV) based on the time length indicated by the duration field included in the MAC header of the CTS-to-Self frame. The NAV can be set to correspond to the length of the TXOP set by AP 2 (830). Here, STA 1 (810) connected to AP 1 (820) may be a hidden node in its relationship with AP 2 (830), and STA 1 (810) connected to AP 1 (820) may not receive the CTS-to-Self frame of AP 2 (830). Therefore, STA 1 (810) may not be able to set a NAV.

[0117] For example, when NAV is set in a wireless LAN terminal, wireless LAN terminals including AP and non-AP STA (i.e., STA) may detect the channel as busy based on virtual carrier sensing and may not be able to transmit frames. That is, when NAV is set in a wireless LAN terminal, the wireless LAN terminal may wait without transmitting frames. AP 2 (830) may transmit an MU-RTS frame (801) to allocate a C-TDMA communication section in TXOP. The MU-RTS frame (801) may include information on AP 3 (840) that is the target of allocation of the C-TDMA communication section (e.g., a user info field including the AID (association identifier) ​​of AP 3) and information on AP 1 (820) that is capable of C-TDMA communication but is not allocated a communication section.

[0118] Referring to FIG. 8A, information of AP 3 (840) and information of AP 1 (820) included in the MU-RTS frame may include information indicating a frequency (e.g., OFDMA (orthogonal frequency division multiple access) RU (resource unit)) at which the CTS frame is transmitted. For example, AP 2 (830) may allow each AP to transmit the CTS frame in a different RU in order to distinguish between CTS frame transmissions of AP 3 (840) and AP 1 (820). As a specific example, AP 3 (840), which is assigned a C-TDMA communication section, may transmit the CTS frame (802-2) in RU #1, and AP 1 (820) may transmit the CTS frame (802-1) in RU #2. Additionally, the information in the MU-RTS frame (801) transmitted by AP 2 (830) may include at least one of an indicator indicating that AP 3 (840) is allocated a C-TDMA communication section and an indicator indicating that AP 1 (820) is not allocated a C-TDMA communication section.

[0119] For example, AP 3 (840) may be allocated a C-TDMA communication section and may transmit a CTS frame (802-2) to AP 2 (830) in response to the MU-RTS frame (801). AP 1 (820) is not allocated a C-TDMA communication section, but may transmit a CTS frame in response based on the AP 1 (820) information included in the MU-RTS frame (801). The CTS frames (802-1, 802-2) transmitted by AP 1 (820) and AP 3 (840) in response to the MU-RTS frame (801) may be TB (trigger based) PPDUs. Here, AP 2 (830) can recognize which AP has responded because the CTS frames (802-1, 802-2) of AP 1 (820) and AP 3 (840) are transmitted on different frequencies. Since the CTS frame is an immediate response frame to the MU-RTS frame, it can respond even if the NAV is set.

[0120] For example, AP 3 (840) may ignore the NAV set in the C-TDMA communication section based on the allocated C-TDMA communication section (or shared TXOP) and communicate with an STA (e.g., STA 2 (850)) connected to AP 3 (840). AP 3 (840) may transmit a downlink frame to STA 2 (850) or trigger uplink frame transmission. AP 3 (840) may transmit a trigger frame to STA 2 (850) to trigger uplink frame transmission of STA 2 (850). For example, the trigger frame transmitted to STA 2 (850) may have the CS required field set to 0. Accordingly, when STA 2 (850) receives a trigger frame, STA 2 (850) can transmit an uplink frame (e.g., UL (uplink) TB (trigger based) PPDU (physical layer protocol data unit)) to AP 3 (840) regardless of whether the state of the channel detected by NAV (i.e., virtual carrier sensing) or physical carrier sensing is idle or busy. Here, since AP 3 (840) has been allocated a communication section from AP 2 (830), it can transmit a trigger frame with the CS required bit set to 0 to STA 2 (850).

[0121] For example, STA 1 (810) may not receive the MU-RTS frame (801) of AP 2 (830), but may receive the CTS frame (802-1) of AP 1 (820). That is, AP 1 (820), which has not been allocated a C-TDMA communication section (or shared TXOP) from AP 2 (830) as described above, may transmit the CTS frame (802-1), and STA 1 (810) may receive the CTS frame (802-1) transmitted by AP 1 (820). Accordingly, STA 1 (810) may set the NAV for the length of time indicated by the duration field included in the MAC header of the CTS frame (802-1) of AP 1 (820). That is, STA 1 (810) may not transmit a data frame to AP 1 (820) for the length of time indicated by the duration field, thereby preventing interference of C-TDMA communication due to frame transmission by STA 1 (810).

[0122] For example, since the CTS frame (803-1) transmitted by AP 1 (820) is transmitted to AP 2 (830), the RA field may be set to AP 2 (830). The RA field of the CTS frame (802-1) received by STA 1 (810) from AP 1 (820) may be AP 2 (830), and accordingly, a basic NAV may be set to STA 1 (810). That is, STA 1 (810) may set the basic NAV even though the frame is transmitted by AP 1 (820) within the same BSS.

[0123] For example, the default NAV may be set when a PPDU received by a wireless LAN terminal does not correspond to either an intra-BSS PPDU or an inter-BSS PPDU. Here, when the wireless LAN terminal receives a CTS frame, which is a control frame that only contains an RA field without a TA field, the wireless LAN terminal may determine that the PPDU does not correspond to either an intra-BSS or an inter-BSS frame if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0124] More specifically, when a wireless LAN terminal receives a PPDU, the wireless LAN terminal can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU. As a specific example, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) parameter of the received PPDU is 0 or is identical to the "BSS_COLOR" value of the currently connected BSS. In addition, with respect to a VHT (very high throughput) PPDU, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) of the received PPDU is identical to the BSSID of the currently connected BSS or is identical to the BSSID of another BSS within the same Multiple BSSID Set or Co-Hosted BSSID Set and the GROUP_ID is 0. Additionally, a wireless LAN terminal can determine that a control frame containing only RA is an intra-BSS PPDU if the RA field value in relation to the CTS frame matches the address of the previous TXOP holder, or if the RA field value matches the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0125] In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) is not 0 and is different from the BSS_COLOR value of the currently connected BSS. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) with respect to the VHT PPDU is different from the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the GROUP_ID of the reception vector (RXVECTOR) is 63 and the Partial BSS Color in the recently received HE Operation Element is 1. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the UPLINK_FLAG value of the reception vector (RXVECTOR) is 0 under the VHT MU / HE MU PPDU condition and the terminal that received the PPDU is an AP. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU transmits a frame that does not match the BSSID or is not a wildcard BSSID under the BSSID-related condition. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU does not have a BSSID field but includes both RA and TA fields and these are not the same as the BSSID of the same BSS, but may not be limited thereto.

[0126] Here, the wireless LAN terminal may set the basic NAV if the PPDU received by the wireless LAN terminal is neither an intra-BSS PPDU nor an inter-BSS PPDU. For example, in the case of a CTS frame containing only an RA field, if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, it may be regarded as not being included in either the intra-BSS or the inter-BSS, and in such a case, the basic NAV may be set.

[0127] In FIG. 8a, STA 1 (810) may have a hidden node relationship with AP 2 (830), and since STA 1 (810) receives a CTS frame (802-1) with the RA field set to AP 2 (830), it does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, and thus a basic NAV can be set. That is, since the AP to which STA 1 (810) is connected is AP 1 (820), when it receives a CTS frame (803-1) with the RA field set to AP 2 (830), the CTS frame cannot be determined as an intra BSS PPDU, nor can it be determined as an inter BSS PPDU, and thus a basic NAV can be set.

[0128] As another example, AP 3 (840) may not receive the MU-RTS frame (801) of AP 2 (830), and AP 1 (820) may receive the MU-RTS frame (801) of AP 2 (830). AP 1 (820) may receive the MU-RTS frame (801) and transmit a CTS frame (802-1) to AP 2 (830). AP 1 (820) and AP 3 (840) may transmit the CTS frames (802-1, 802-2) in response to the MU-RTS frame (801) using different frequencies (e.g., different RUs). Therefore, AP 2 (830) may be able to distinguish which AP transmitted the CTS frame.

[0129] For example, AP 2 (830) can receive a CTS frame and determine that AP 1 (820) transmitted a CTS frame (802-1) and AP 3 (840) did not transmit a CTS frame (802-2) based on the frequency at which the CTS frame is transmitted. Here, since AP 3 (840) did not respond to the MU-RTS frame (802) of AP 2 (830), AP 2 (830) may not be able to allocate a communication section to AP 3 (840). Therefore, AP 2 (830) can re-allocate a communication section. For example, AP 2 (830) can retransmit an MU-RTS frame after a short interframe space (SIFS) or PIFS time in the communication section allocated to AP 3 (840) (e.g., at the time when AP 2 (730) completes receiving the CTS frame). Through this, AP 2 (830) can allocate a communication section to another AP (e.g. AP 1 (820)) rather than AP 3 (840) that failed to allocate a communication section.

[0130] Referring to FIG. 8B, the information of AP 3 (840) and the information of AP 1 (820) included in the MU-RTS frame (803) may include information indicating a frequency (e.g., OFDMA (orthogonal frequency division multiple access) RU (resource unit)) at which the CTS frame is transmitted. For example, AP 2 (830) may allow each AP to transmit the CTS frame in a different RU in order to distinguish between the CTS frame transmissions of AP 3 (840) and AP 1 (820). As a specific example, AP 3 (840), which is assigned a C-TDMA communication section, may transmit the CTS frame (805-2) in RU #1, and AP 1 (820) may transmit the CTS frame (805-1) in RU #2. Additionally, the information in the MU-RTS frame (803) transmitted by AP 2 (830) may include at least one of an indicator indicating that AP 3 (840) is allocated a C-TDMA communication section and an indicator indicating that AP 1 (820) is not allocated a C-TDMA communication section.

[0131] For example, AP 3 (840) may be allocated a C-TDMA communication segment and may transmit a CTS frame to AP 2 (830) in response to the MU-RTS frame (803). AP 1 (820) is not allocated a C-TDMA communication segment, but may transmit a CTS frame in response based on the AP 1 (820) information included in the MU-RTS frame (803).

[0132] AP 1 (820) and AP 3 (840) can transmit S-CTS frames (804-1, 804-2) in response to MU-RTS frame (803). That is, AP 1 (820) and AP 3 (840) can be the first to transmit CTS frames (804-1, 804-2) using wide bandwidth. After AP 1 (820) and AP 3 (840) complete transmitting CTS frames (804-1, 804-2), AP 1 (820) and AP 3 (840) can retransmit CTS frames (805-1, 805-2) using RUs allocated by AP 2 (830). The CTS frames of AP 1 (820) and AP 3 (840) can be TB (trigger based) PPDUs. Here, AP 2 (830) can recognize which AP has responded because the CTS frames (805-1, 805-2) transmitted by AP 1 (820) and AP 3 (840) are transmitted on different frequencies. Since the CTS frame is an immediate response frame to the MU-RTS frame, it can respond even if the NAV is set.

[0133] As another example, AP 1 (820) and AP 3 (840) can transmit QoS (quality of service) Null frames instead of CTS frames transmitted in TB PPDUs. AP 2 (830) can determine which AP has responded by looking at the sender address and RU position of the QoS Null frame.

[0134] For example, AP 3 (840) may ignore the NAV set in the C-TDMA communication section based on the allocated C-TDMA communication section (or shared TXOP) and communicate with an STA (e.g., STA 2 (850)) connected to AP 3 (840). AP 3 (840) may transmit a downlink frame to STA 2 (850) or trigger uplink frame transmission. AP 3 (840) may transmit a trigger frame to STA 2 (850) to trigger uplink frame transmission of STA 2 (850). For example, the trigger frame transmitted to STA 2 (850) may have the CS required field set to 0. Accordingly, when STA 2 (850) receives a trigger frame, STA 2 (850) can transmit an uplink frame (e.g., UL (uplink) TB (trigger based) PPDU (physical layer protocol data unit)) to AP 3 (840) regardless of whether the state of the channel detected by NAV (i.e., virtual carrier sensing) or physical carrier sensing is idle or busy. Here, since AP 3 (840) has been allocated a communication section from AP 2 (830), it can transmit a trigger frame with the CS required bit set to 0 to STA 2 (850).

[0135] For example, STA 1 (810) may not receive the MU-RTS frame (803) of AP 2 (830), but may receive the CTS frame of AP 1 (820). That is, AP 1 (820), which has not been allocated a C-TDMA communication section (or shared TXOP) from AP 2 (830) as described above, may transmit a CTS frame, and STA 1 (810) may receive the CTS frame transmitted by AP 1 (820). Accordingly, STA 1 (810) may set the NAV for the length of time indicated by the duration field included in the MAC header of the CTS frame of AP 1 (820). That is, STA 1 (810) may not transmit a data frame to AP 1 (820) for the length of time indicated by the duration field, thereby preventing interference of C-TDMA communication due to frame transmission by STA 1 (810).

[0136] For example, since the CTS frame transmitted by AP 1 (820) is transmitted to AP 2 (830), the RA field may be set to AP 2 (830). The RA field of the CTS frame received by STA 1 (810) from AP 1 (820) may be AP 2 (830), and accordingly, a basic NAV may be set to STA 1 (810). That is, STA 1 (810) may set the basic NAV even though the frame is transmitted by AP 1 (820) within the same BSS.

[0137] For example, the default NAV may be set when a PPDU received by a wireless LAN terminal does not correspond to either an intra-BSS PPDU or an inter-BSS PPDU. Here, when the wireless LAN terminal receives a CTS frame, which is a control frame that only contains an RA field without a TA field, the wireless LAN terminal may determine that the PPDU does not correspond to either an intra-BSS or an inter-BSS frame if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0138] More specifically, when a wireless LAN terminal receives a PPDU, the wireless LAN terminal can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU. As a specific example, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) parameter of the received PPDU is 0 or is identical to the "BSS_COLOR" value of the currently connected BSS. In addition, with respect to a VHT (very high throughput) PPDU, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) of the received PPDU is identical to the BSSID of the currently connected BSS or is identical to the BSSID of another BSS within the same Multiple BSSID Set or Co-Hosted BSSID Set and the GROUP_ID is 0. Additionally, a wireless LAN terminal can determine that a control frame containing only RA is an intra-BSS PPDU if the RA field value in relation to the CTS frame matches the address of the previous TXOP holder, or if the RA field value matches the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0139] In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) is not 0 and is different from the BSS_COLOR value of the currently connected BSS. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) with respect to the VHT PPDU is different from the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the GROUP_ID of the reception vector (RXVECTOR) is 63 and the Partial BSS Color in the recently received HE Operation Element is 1. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the UPLINK_FLAG value of the reception vector (RXVECTOR) is 0 under the VHT MU / HE MU PPDU condition and the terminal that received the PPDU is an AP. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU transmits a frame that does not match the BSSID or is not a wildcard BSSID under the BSSID-related condition. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU does not have a BSSID field but includes both RA and TA fields and these are not the same as the BSSID of the same BSS, but may not be limited thereto.

[0140] Here, the wireless LAN terminal may set the basic NAV if the PPDU received by the wireless LAN terminal is neither an intra-BSS PPDU nor an inter-BSS PPDU. For example, in the case of a CTS frame containing only an RA field, if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, it may be regarded as not being included in either the intra-BSS or the inter-BSS, and in such a case, the basic NAV may be set.

[0141] In FIG. 8b, AP 2 (830) may be in a hidden node relationship with STA 1 (810), and since STA 1 (810) receives a CTS frame with the RA field set to AP 2 (830), it does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, and thus a basic NAV can be set. That is, since the AP to which STA 1 (810) is connected is AP 1 (820), when it receives a CTS frame (803-1) with the RA field set to AP 2 (830), the CTS frame cannot be determined as an intra BSS PPDU, nor can it be determined as an inter BSS PPDU, and thus a basic NAV can be set.

[0142] As another example, AP 3 (840) may not receive the MU-RTS frame (803) of AP 2 (830), and AP 1 (820) may receive the MU-RTS frame (803) of AP 2 (830). AP 1 (820) may receive the MU-RTS frame (803) and transmit a CTS frame to AP 2 (830). AP 1 (820) and AP 3 (840) may transmit the CTS frame in response to the MU-RTS frame using different frequencies (e.g., different RUs). Therefore, AP 2 (830) may be able to distinguish which AP transmitted the CTS frame.

[0143] For example, AP 2 (830) can receive a CTS frame and determine that AP 1 (820) transmitted a CTS frame and AP 3 (840) did not transmit a CTS frame based on the frequency at which the CTS frame is transmitted. Here, since AP 3 (840) did not respond to the MU-RTS frame of AP 2 (830), AP 2 (830) may not be able to allocate a communication section to AP 3 (840). Therefore, AP 2 (830) can re-allocate a communication section. For example, AP 2 (830) can retransmit an MU-RTS frame after a short interframe space (SIFS) or PIFS time in the communication section allocated to AP 3 (840) by AP 2 (830) (e.g., at the time when AP 2 (830) completes receiving the CTS frame). Through this, AP 2 (830) can allocate a communication section to another AP (e.g. AP 1 (820)) rather than AP 3 (840) that failed to allocate a communication section.

[0144] In FIGS. 8A and 8B, in order for AP 2 (830) to determine a target AP for C-TDMA communication, the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may be used. For example, AP 3 (840) to which AP 2 (830) allocates a C-TDMA communication section may be determined as a result of the machine learning unit of AP 2 (830). Determining the transmission frequency (e.g., RU, OFDMA RU) of the CTS frame indicated in the user info field included in the MU-RTS frame transmitted by AP 2 (830) before allocating the C-TDMA communication section may be based on the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4. For example, AP 2 (830) may determine the maximum bandwidth to be used in C-TDMA communication using the machine learning unit. Based on the determined maximum bandwidth, it can be determined that the CTS frame transmitted by the STA allocated the C-TDMA communication section is transmitted using the maximum bandwidth, and the CTS frame transmitted by the STA not allocated the C-TDMA communication section is transmitted using a different frequency and bandwidth from the CTS frame transmitted by the STA allocated the C-TDMA communication section.

[0145] The machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may be used to determine whether AP 1 (820) transmits a CTS frame in response to the transmission of an MU-RTS frame by AP 2 (830). For example, AP 1 (820) may determine whether 'STA 1 can receive frames from AP 2 and AP 3 and set up a NAV' by using the machine learning unit as input a parameter such as the reception power of the frame. If it is determined that STA 1 can set up a NAV, AP 1 (820) may decide not to transmit an unnecessary CTS frame. Conversely, if it is determined that STA 1 cannot set up a NAV, AP 1 (820) may decide to transmit a CTS frame.

[0146] FIG. 9a and FIG. 9b are diagrams illustrating a method for protecting a communication section when performing a time-division communication operation adjusted in a wireless LAN to which the present disclosure is applied.

[0147] Referring to FIGS. 9A and 9B, multiple access points (APs) may operate in a wireless LAN. For example, AP 1 to AP 3 (920, 930, 940) may operate in the wireless LAN. Here, AP 2 (930) may be a coordinating AP for coordinated time division multiple access (C-TDMA). AP 2 (930) may set a transmit opportunity (TXOP) on a channel to use C-TDMA. Here, the TXOP is a time period during which multiple frames can be transmitted. The TXOP may be set through a CTS frame (e.g., a CTS-to-Self frame in which the receiver address is set to the MAC address of AP 2). As another example, the TXOP may also be set by transmitting a multi-user-request to send (MU-RTS) frame or a data frame. The following description assumes that TXOP is set using a CTS-to-Self frame, but may not be limited thereto.

[0148] Referring to FIGS. 9A and 9B, AP 1 (920) and AP 3 (940) can receive a CTS-to-Self frame (or CTS frame) transmitted by AP 2 (930), and set a network allocation vector (NAV) based on the length of time indicated by the duration field included in the MAC header of the CTS-to-Self frame. The NAV can be set to correspond to the length of the TXOP set by AP 2 (930). Here, STA 1 (910) connected to AP 1 (920) may be a hidden node in its relationship with AP 2 (930), and STA 1 (910) connected to AP 1 (920) may not receive the CTS-to-Self frame of AP 2 (930). Therefore, STA 1 (910) may not be able to set a NAV.

[0149] For example, when NAV is set in a wireless LAN terminal, wireless LAN terminals including AP and non-AP STA (i.e., STA) may detect the channel as busy based on virtual carrier sensing and may not be able to perform frame transmission. That is, when NAV is set in a wireless LAN terminal, the wireless LAN terminal may wait without performing frame transmission. AP 2 (930) may transmit an MU-RTS frame (903) to allocate a C-TDMA communication section in TXOP. The MU-RTS frame (903) may include information on AP 3 (940) that is the target of allocation of the C-TDMA communication section (e.g., a user info field including the AID (association identifier) ​​of AP 3) and information on AP 1 (920) that is capable of C-TDMA communication but is not allocated a communication section.

[0150] Referring to FIG. 9A, AP 2 (930) may transmit an NFRP (NDP (null data PPDU) Feedback Report Poll, 901) trigger frame before transmitting an MU-RTS frame (903) to allocate a C-TDMA communication section. The NFRP trigger frame (901) may be a frame requesting feedback (e.g., requesting NDP Feedback) to confirm whether a communication target AP exists. The NFRP trigger frame (901) may include a dedicated AID starting index, through which APs can be identified. When the NFRP trigger frame (901) transmitted by AP 2 (930) is received, AP 1 (920) and AP 3 (940) may transmit an NDP Feedback Report (NDP Feedback Report, 902-1, 902-2) in response. The NDP feedback report (902-1, 902-2) is a frame that only contains a PHY preamble, and can be transmitted for each OFDMA subcarrier tone. For example, dedicated AIDs are designated to identify AP 1 (920) and AP 3 (940), and AP 1 (920) and AP 3 (940) can transmit the NDP feedback report (902-1, 902-2) with the OFDMA tone corresponding to the dedicated AID. AP 2 (930) can recognize which AP has responded through the received NDP feedback report.

[0151] Here, as an example, the AP to which AP 2 (930) wishes to allocate a C-TDMA section may be AP 3 (940). However, this is for convenience of explanation and may not be limited thereto. AP 2 (930) can check whether AP 3 (940) has responded to the NFRP trigger frame (901) transmitted by AP 2 (930). If AP 3 (940) has responded, AP 2 (930) can transmit an MU-RTS frame (903) for allocating a C-TDMA communication section to AP 3 (940). AP 3 (940) allocated a C-TDMA communication section can transmit a CTS frame (904-2) in response to the MU-RTS frame (903) of AP 2 (930). Additionally, AP 1 (920), which is not allocated a C-TDMA communication section but can receive an MU-RTS frame (903), can transmit a CTS frame (904-1) in response to the MU-RTS frame (903) of AP 2 (930). Here, the CTS frames transmitted by AP 1 (920) and AP 3 (940) may be S-CTS frames. Since the CTS frame is an immediate response frame to the MU-RTS frame, it can respond even if the NAV is set.

[0152] For example, AP 3 (940) may ignore the NAV set in the C-TDMA communication section based on the allocated C-TDMA communication section (or shared TXOP) and communicate with an STA (e.g., STA 2 (950)) connected to AP 3 (940). AP 3 (940) may transmit a downlink frame to STA 2 (950) or trigger uplink frame transmission. AP 3 (940) may transmit a trigger frame to STA 2 (950) to trigger uplink frame transmission of STA 2 (950). For example, the trigger frame transmitted to STA 2 (950) may have the CS required field set to 0. Accordingly, when STA 2 (950) receives a trigger frame, STA 2 (950) can transmit an uplink frame (e.g., UL (uplink) TB (trigger based) PPDU (physical layer protocol data unit)) to AP 3 (940) regardless of whether the state of the channel detected by NAV (i.e., virtual carrier sensing) or physical carrier sensing is idle or busy. Here, since AP 3 (940) has been allocated a communication section from AP 2 (930), it can transmit a trigger frame with the CS required bit set to 0 to STA 2 (950).

[0153] For example, STA 1 (910) may not receive the MU-RTS frame (903) of AP 2 (930), but may receive the CTS frame (904-1) of AP 1 (920). That is, AP 1 (920), which has not been allocated a C-TDMA communication section (or shared TXOP) from AP 2 (930) as described above, may transmit the CTS frame (904-1), and STA 1 (910) may receive the CTS frame (904-1) transmitted by AP 1 (920). Accordingly, STA 1 (910) may set the NAV for the length of time indicated by the duration field included in the MAC header of the CTS frame (904-1) of AP 1 (920). That is, STA 1 (910) may not transmit a data frame to AP 1 (920) for the length of time indicated by the duration field, thereby preventing interference of C-TDMA communication due to frame transmission by STA 1 (910).

[0154] For example, since the CTS frame (904-1) transmitted by AP 1 (920) is transmitted to AP 2 (930), the RA field may be set to AP 2 (930). The RA field of the CTS frame (904-1) received by STA 1 (910) from AP 1 (920) may be AP 2 (930), and accordingly, a basic NAV may be set to STA 1 (910). That is, STA 1 (910) may set the basic NAV even though the frame is transmitted by AP 1 (920) within the same BSS.

[0155] For example, the default NAV may be set when a PPDU received by a wireless LAN terminal does not correspond to either an intra-BSS PPDU or an inter-BSS PPDU. Here, when the wireless LAN terminal receives a CTS frame, which is a control frame that only contains an RA field without a TA field, the wireless LAN terminal may determine that the PPDU does not correspond to either an intra-BSS or an inter-BSS frame if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0156] More specifically, when a wireless LAN terminal receives a PPDU, the wireless LAN terminal can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU. As a specific example, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) parameter of the received PPDU is 0 or is identical to the "BSS_COLOR" value of the currently connected BSS. In addition, with respect to a VHT (very high throughput) PPDU, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) of the received PPDU is identical to the BSSID of the currently connected BSS or is identical to the BSSID of another BSS within the same Multiple BSSID Set or Co-Hosted BSSID Set and the GROUP_ID is 0. Additionally, a wireless LAN terminal can determine that a control frame containing only RA is an intra-BSS PPDU if the RA field value in relation to the CTS frame matches the address of the previous TXOP holder, or if the RA field value matches the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0157] In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) is not 0 and is different from the BSS_COLOR value of the currently connected BSS. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) with respect to the VHT PPDU is different from the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the GROUP_ID of the reception vector (RXVECTOR) is 63 and the Partial BSS Color in the recently received HE Operation Element is 1. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the UPLINK_FLAG value of the reception vector (RXVECTOR) is 0 under the VHT MU / HE MU PPDU condition and the terminal that received the PPDU is an AP. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU transmits a frame that does not match the BSSID or is not a wildcard BSSID under the BSSID-related condition. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU does not have a BSSID field but includes both RA and TA fields and these are not the same as the BSSID of the same BSS, but may not be limited thereto.

[0158] Here, the wireless LAN terminal may set the basic NAV if the PPDU received by the wireless LAN terminal is neither an intra-BSS PPDU nor an inter-BSS PPDU. For example, in the case of a CTS frame containing only an RA field, if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, it may be regarded as not being included in either the intra-BSS or the inter-BSS, and in such a case, the basic NAV may be set.

[0159] In Fig. 9a, STA 1 (910) may have a hidden node relationship with AP 2 (930), and since STA 1 (910) receives a CTS frame (904-1) with the RA field set to AP 2 (930), it does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, and thus a basic NAV can be set. That is, since the AP to which STA 1 (910) is connected is AP 1 (920), when it receives a CTS frame (903-1) with the RA field set to AP 2 (930), the CTS frame cannot be determined as an intra BSS PPDU, nor can it be determined as an inter BSS PPDU, and thus a basic NAV can be set.

[0160] As another example, AP 3 (940) may not receive the NFRP trigger frame (901) of AP 2 (930), and AP 1 (920) may receive the NFRP trigger frame (901) of AP 2 (930). In the above-described situation, only AP 1 (920) may transmit the NDP feedback report (902-1). AP 2 (930) may not allocate a C-TDMA communication section to AP 3 (940), but may allocate a C-TDMA communication section to AP 1 (920) that is determined to be capable of communication (i.e., for which an NDP feedback report has been received), but this may not be limited to the embodiment.

[0161] Referring to FIG. 9B, AP 2 (930) may transmit a BSRP (Buffer Status Report Poll) trigger frame (905) before transmitting an MU-RTS frame to allocate a C-TDMA communication section. The BSRP trigger frame (905) may be a frame requesting a buffer status (e.g., Buffer Status Report) of a communication target AP. In addition, the BSRP trigger frame (905) may be a frame transmitted to check whether an AP to which a C-TDMA communication section is to be allocated exists. The BSRP trigger frame (905) may include information indicating an OFDMA RU to which APs (e.g., AP 1 (920) and AP 2 (930)) may transmit a BSR.

[0162] When AP 1 (920) and AP 3 (940) receive the BSRP trigger frame (905) transmitted by AP 2 (930), AP 1 (920) and AP 3 (940) may transmit a Buffer Status Report (906-1, 906-2) in response at the RU (i.e., frequency) indicated by the BSRP trigger frame (905). The Buffer Status Report (906-1, 906-2) may be a frame indicating the transmission buffer status of the APs. AP 2 (930) may recognize whether an AP has responded based on the received Buffer Status Report (906-1, 906-2).

[0163] Here, as an example, the AP to which AP 2 (930) wants to allocate a C-TDMA section may be AP 3 (940). However, this is for convenience of explanation and may not be limited thereto. AP 2 (930) can check whether AP 3 (940) has responded to the BSRP trigger frame (905) transmitted by AP 2 (930). If AP 3 (940) has responded, AP 2 (930) can transmit an MU-RTS frame (907) for allocating a C-TDMA communication section to AP 3 (940). AP 3 (940) allocated a C-TDMA communication section can transmit a CTS frame (908-2) in response to the MU-RTS frame (907) of AP 2 (930). Additionally, AP 1 (920), which is not allocated a C-TDMA communication section but can receive an MU-RTS frame (907), can transmit a CTS frame (908-1) in response to the MU-RTS frame (907) of AP 2 (930). Here, the CTS frames transmitted by AP 1 (920) and AP 3 (940) may be S-CTS frames. Since the CTS frame is an immediate response frame to the MU-RTS frame, it can respond even if the NAV is set.

[0164] For example, AP 3 (940) may ignore the NAV set in the C-TDMA communication section based on the allocated C-TDMA communication section (or shared TXOP) and communicate with an STA (e.g., STA 2 (950)) connected to AP 3 (940). AP 3 (940) may transmit a downlink frame to STA 2 (950) or trigger uplink frame transmission. AP 3 (940) may transmit a trigger frame to STA 2 (950) to trigger uplink frame transmission of STA 2 (950). For example, the trigger frame transmitted to STA 2 (950) may have the CS required field set to 0. Accordingly, when STA 2 (950) receives a trigger frame, STA 2 (950) can transmit an uplink frame (e.g., UL (uplink) TB (trigger based) PPDU (physical layer protocol data unit)) to AP 3 (940) regardless of whether the state of the channel detected by NAV (i.e., virtual carrier sensing) or physical carrier sensing is idle or busy. Here, since AP 3 (940) has been allocated a communication section from AP 2 (930), it can transmit a trigger frame with the CS required bit set to 0 to STA 2 (950).

[0165] For example, STA 1 (910) may not receive the MU-RTS frame (907) of AP 2 (930), but may receive the CTS frame (908-1) of AP 1 (920). That is, AP 1 (920), which has not been allocated a C-TDMA communication section (or shared TXOP) from AP 2 (930) as described above, may transmit the CTS frame (908-1), and STA 1 (910) may receive the CTS frame (908-1) transmitted by AP 1 (920). Accordingly, STA 1 (910) may set the NAV for the length of time indicated by the duration field included in the MAC header of the CTS frame (908-1) of AP 1 (920). That is, STA 1 (910) may not transmit a data frame to AP 1 (920) for the length of time indicated by the duration field, thereby preventing interference of C-TDMA communication due to frame transmission by STA 1 (910).

[0166] For example, since the CTS frame (908-1) transmitted by AP 1 (920) is transmitted to AP 2 (930), the RA field may be set to AP 2 (930). The RA field of the CTS frame (908-1) received by STA 1 (910) from AP 1 (920) may be AP 2 (930), and accordingly, a basic NAV may be set to STA 1 (910). That is, STA 1 (910) may set the basic NAV even though the frame is transmitted by AP 1 (920) within the same BSS.

[0167] For example, the default NAV may be set when a PPDU received by a wireless LAN terminal does not correspond to either an intra-BSS PPDU or an inter-BSS PPDU. Here, when the wireless LAN terminal receives a CTS frame, which is a control frame that only contains an RA field without a TA field, the wireless LAN terminal may determine that the PPDU does not correspond to either an intra-BSS or an inter-BSS frame if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0168] More specifically, when a wireless LAN terminal receives a PPDU, the wireless LAN terminal can determine whether the PPDU is an intra-BSS PPDU or an inter-BSS PPDU. As a specific example, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) parameter of the received PPDU is 0 or is identical to the "BSS_COLOR" value of the currently connected BSS. In addition, with respect to a VHT (very high throughput) PPDU, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) of the received PPDU is identical to the BSSID of the currently connected BSS or is identical to the BSSID of another BSS within the same Multiple BSSID Set or Co-Hosted BSSID Set and the GROUP_ID is 0. Additionally, a wireless LAN terminal can determine that a control frame containing only RA is an intra-BSS PPDU if the RA field value in relation to the CTS frame matches the address of the previous TXOP holder, or if the RA field value matches the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set.

[0169] In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the "BSS_COLOR" value of the reception vector (RXVECTOR) is not 0 and is different from the BSS_COLOR value of the currently connected BSS. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the partial AID (PARTIAL_AID) value of the reception vector (RXVECTOR) with respect to the VHT PPDU is different from the BSSID of the currently connected BSS or the BSSID of another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set. In addition, the wireless LAN terminal can determine that it is an inter-BSS PPDU if the GROUP_ID of the reception vector (RXVECTOR) is 63 and the Partial BSS Color in the recently received HE Operation Element is 1. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS PPDU if the UPLINK_FLAG value of the reception vector (RXVECTOR) is 0 under the VHT MU / HE MU PPDU condition and the terminal that received the PPDU is an AP. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU transmits a frame that does not match the BSSID or is not a wildcard BSSID under the BSSID-related condition. In addition, the wireless LAN terminal can determine that the PPDU is an inter-BSS if the PPDU does not have a BSSID field but includes both RA and TA fields and these are not the same as the BSSID of the same BSS, but may not be limited thereto.

[0170] Here, the wireless LAN terminal may set the basic NAV if the PPDU received by the wireless LAN terminal is neither an intra-BSS PPDU nor an inter-BSS PPDU. For example, in the case of a CTS frame containing only an RA field, if the RA field does not match the address of the previous TXOP holder or does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, it may be regarded as not being included in either the intra-BSS or the inter-BSS, and in such a case, the basic NAV may be set.

[0171] In FIG. 9b, STA 1 (910) may have a hidden node relationship with AP 2 (930), and since STA 1 (910) receives a CTS frame (908-1) with the RA field set to AP 2 (930), it does not match the address of the currently connected BSS or another BSS within the same Multiple BSSID Set / Co-Hosted BSSID Set, and thus a basic NAV can be set. That is, since the AP to which STA 1 (910) is connected is AP 1 (920), when it receives a CTS frame (903-1) with the RA field set to AP 2 (930), the CTS frame cannot be determined as an intra BSS PPDU, nor can it be determined as an inter BSS PPDU, and thus a basic NAV can be set.

[0172] As another example, AP 3 (940) may not receive the BSRP trigger frame (905) of AP 2 (930), and AP 1 (920) may receive the BSRP trigger frame (905) of AP 2 (930). In the above-described situation, only AP 1 (920) may transmit the buffer status report (906-1). AP 2 (930) may not allocate a C-TDMA communication section to AP 3 (940), but may allocate a C-TDMA communication section to AP 1 (920) that is determined to be capable of communication (i.e., for which a buffer status report has been received), but this may not be limited to the embodiment.

[0173] In FIGS. 9A and 9B, in order for AP 2 (930) to determine a C-TDMA communication target AP, the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 may be used. For example, AP 3 (940) to which AP 2 (930) allocates a C-TDMA communication section may be determined by the machine learning unit of AP 2 (930). Determining the transmission frequency (e.g., Tone, RU, OFDMA RU) of the NDP Feedback Report or Buffer Status Report indicated in the user info field included in the NFRP and BSRP frames transmitted by AP 2 (930) before allocating the C-TDMA communication section may be based on the machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4.

[0174] For example, AP 2 (930) can use a machine learning unit to determine the maximum bandwidth to be used in C-TDMA communication. Based on the determined maximum bandwidth, it can be determined that a CTS frame transmitted by an STA allocated a C-TDMA communication section is transmitted using the maximum bandwidth, and a CTS frame transmitted by an STA not allocated a C-TDMA communication section is transmitted using a different frequency and bandwidth from the CTS frame transmitted by an STA allocated a C-TDMA communication section. The machine learning algorithm and the operation of the machine learning unit illustrated in FIGS. 1 to 4 can be used to determine whether AP 1 (920) transmits a CTS frame in response to the transmission of an MU-RTS frame by AP 2 (930). For example, AP 1 (920) can determine whether 'STA 1 can receive frames from AP 2 (930) and AP 3 (940) and set up a NAV' by using a machine learning unit as input a parameter such as the reception power of the frame. If STA 1 (910) is determined to be able to set up a NAV, AP 1 (920) can decide not to transmit an unnecessary CTS frame. Conversely, if STA 1 is determined not to be able to set up a NAV, AP 1 (920) can decide to transmit a CTS frame.

[0175] FIG. 10 is a flowchart illustrating a method for protecting a communication section when performing a coordinated time-division communication operation in a wireless LAN applied to the present disclosure. A first AP may transmit a first frame (S1010). For example, the first frame may be a CTS frame, but may not be limited to the embodiment. Here, the first AP may be an AP that coordinates time-division communication with AP 2 described above in FIGS. 5 to 9B. The first frame may be a frame that sets a first NAV for at least one wireless LAN terminal that receives the first frame. That is, the first AP transmits the first frame to at least one wireless LAN terminal, and at least one wireless LAN terminal that receives the first frame sets the first NAV described above and waits without performing frame transmission. Thereafter, the first AP can transmit the second frame in the first communication section set by the first frame. (S1020) As an example, the second frame may be, but is not limited to, an MU-RTS frame. The first AP may assign the second communication section to the second AP based on time division communication within the first communication section through the second frame. Here, the second AP may be AP 3 described above with reference to FIGS. 5 to 9B. That is, it may be an AP that is assigned a communication section from the first AP. Thereafter, the first AP may receive a third frame from each of at least one AP including the second AP in response to the second frame. (S1030) As an example, the third frame may be, but is not limited to, a CTS frame. Here, the third frame may be a frame that sets a second NAV to at least one wireless LAN terminal that receives the third frame. Additionally, the third frame is an S-CTS frame, and the first AP can receive the third frame simultaneously from multiple wireless LAN terminals.For example, a second AP assigned a second communication section can perform communication within the second communication section regardless of the NAV setting, as described above. For example, a first access point (AP) may include at least one transceiver, at least one processor controlling the at least one transceiver, and a memory storing instructions that cause a wireless user device to perform a specific operation by the at least one processor. Here, the specific operation may be as described above.

[0176] Additionally, as an example, the second frame may include user information of a second AP to which a second communication section is allocated and user information of a third AP to which a second communication section is not allocated. As an example, the third AP may be AP 1 described above in FIGS. 5 to 9B. The second frame may further include at least one of an indicator indicating that the second AP is allocated a second communication section and an indicator indicating that the third AP is not allocated a second communication section, as described above.

[0177] As another example, the second frame may include a group identifier of at least one AP that may be allocated a second communication segment based on time division communication, and the first AP may receive a third frame from each of the at least one AP including the second AP based on the group identifier. Here, if the second frame includes a first parameter (e.g., SCRAMBLER_INITIAL_VALUE) together with the group identifier, the first AP may receive a third frame from each of the at least one AP including the second AP, as described above. In addition, the first NAV may be set to a time length indicated by a duration field of a MAC header included in the first frame, and the second NAV may be set to a time length indicated by a duration field of a MAC header included in the third frame.

[0178] The receiver address (RA) field in the third frame transmitted by the third AP, to which the second communication section is not allocated based on the second frame, may be set to the first AP. Here, the second NAV set to at least one wireless LAN terminal through the third frame transmitted by the third AP may be set to a basic NAV. That is, as described above, the RA field of the CTS frame transmitted by AP 1 in response to the second frame transmission may be set to AP 2, and STA 1, which receives the CTS frame transmitted by AP 1, may set the basic NAV.

[0179] In addition, the third frame received by the first AP from each of at least one of the APs including the second AP may be a simultaneous CTS (S-CTS) frame, and the third frame may be simultaneously received from each of at least one of the APs including the second AP. Here, the first AP may receive the third frame and detect communication from the second AP allocated the second communication section for a preset period of time, and may re-allocate the second communication section if communication from the second AP is not detected.

[0180] As another example, the third frame transmitted by the second AP assigned to the second communication section and the third frame transmitted by the third AP not assigned to the second communication section may be set to different bandwidths. For example, the transmission bandwidth of the third frame transmitted by the second AP assigned to the second communication section may be wider than the transmission bandwidth of the third frame transmitted by the third AP not assigned to the second communication section.

[0181] In another embodiment, the second frame may further include information on the frequency at which the CTS frame is transmitted, and the band at which the CTS frame is received may be set differently for each AP based on the frequency information at which the CTS frame is transmitted. Furthermore, the first AP may receive the third frame in a different band from each of at least one AP, including the second AP, based on the frequency information at which the CTS frame is transmitted.

[0182] As another example, the first AP may receive a third frame transmitted simultaneously from each of at least one AP, including the second AP, across the entire band based on the second frame, and then receive a fourth frame in a different band from each of at least one AP, including the second AP, based on frequency information at which the CTS frame is transmitted. As an example, the fourth frame may be a CTS frame, but is not limited thereto.

[0183] Additionally, the first AP may transmit an NFRP trigger frame to at least one AP including the second AP after transmitting the first frame, and may transmit the second frame after receiving an NDP feedback frame from each of the at least one AP including the second AP. Here, the NFRP trigger frame may include identification information identifying each of the at least one AP including the second AP. The NDP feedback frame transmitted from each of the at least one AP including the second AP may be received in a band corresponding to the identification information.

[0184] As another example, the first AP may transmit a BSRP trigger frame to at least one AP including the second AP after transmitting the first frame, and may transmit the second frame after receiving a buffer status report from each of the at least one AP including the second AP. Here, the BSRP trigger frame may indicate a band over which the buffer status report is transmitted, and the buffer status report transmitted from each of the at least one AP including the second AP may be received in the band indicated by the BSRP trigger frame.

[0185] 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.

[0186] 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.

[0187] 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.

[0188]

[0189] The above may also apply to other systems.

Claims

1. In a method of operating a first access point (AP) that coordinates time division communication in a wireless LAN system, As a step of the first AP transmitting a first frame, the first frame is a frame that sets a first NAV (network allocation vector) to at least one wireless LAN terminal receiving the first frame; A step of transmitting a second frame in a first communication section established by the first frame, wherein the first AP allocates a second communication section to the second AP based on the time division communication within the first communication section through the second frame; and An operating method of a first AP, comprising: receiving a third frame from each of at least one AP including the second AP in response to the second frame, wherein the third frame is a frame that sets a second NAV to at least one wireless LAN terminal receiving the third frame, and communication by the second AP within the second communication section is performed regardless of the NAV.

2. In paragraph 1, The second frame includes user information of the second AP to which the second communication section is allocated and user information of the third AP to which the second communication section is not allocated. A method of operating a first AP, wherein the second frame further includes at least one of an instruction indicating that the second AP is allocated the second communication section and an instruction indicating that the third AP is not allocated the second communication section.

3. In paragraph 1, The second frame includes a group identifier of at least one AP that can be assigned the second communication section based on the time division communication, A method of operating a first AP, wherein the first AP receives the third frame from each of at least one AP including the second AP based on the group identifier.

4. In paragraph 3, A method of operating a first AP, wherein the first AP receives the third frame from each of at least one AP including the second AP, if the second frame includes a first parameter together with the group identifier.

5. In paragraph 1, The first NAV is set to a time length indicated by the duration field of the MAC (medium access control) header included in the first frame, An operating method of a first AP, wherein the second NAV is set to a time length indicated by a duration field of a MAC header included in the third frame.

6. In paragraph 1, The receiver address (RA) field in the third frame transmitted by the third AP to which the second communication section is not allocated based on the second frame is set to the first AP, An operating method of a first AP, wherein the second NAV set to at least one wireless LAN terminal through a third frame transmitted by the third AP is set as a basic NAV.

7. In paragraph 1, A method of operating a first AP, wherein the first AP simultaneously receives the third frame from each of at least one AP including the second AP as a simultaneous CTS (S-CTS) frame.

8. In paragraph 7, The first AP receives the third frame and detects communication of the second AP allocated the second communication section for a preset period of time, An operating method of a first AP, wherein the second communication section is re-allocated if communication of the second AP is not detected.

9. In paragraph 7, The third frame transmitted by the second AP allocated to the second communication section and the third frame transmitted by the third AP not allocated to the second communication section are set to different bandwidths. A method of operating a first AP, wherein the first AP identifies an AP transmitting the third frame based on bandwidth information for each of the third frames simultaneously received.

10. In paragraph 7, An operating method of a first AP, wherein the second frame further includes frequency information at which a CTS frame is transmitted, and a band at which the CTS frame is received is set differently for each AP based on the frequency information at which the CTS frame is transmitted.

11. In clause 10, A method of operating a first AP, wherein the first AP receives the third frame in a different band from each of at least one AP including the second AP based on frequency information at which the CTS frame is transmitted.

12. In paragraph 10, A method of operating a first AP, wherein the first AP receives a third frame transmitted simultaneously from each of at least one AP including the second AP over the entire band based on the second frame, and then receives a fourth frame in a different band from each of at least one AP including the second AP based on frequency information at which the CTS frame is transmitted.

13. In paragraph 7, An operating method of a first AP, wherein the first AP transmits an NFRP (NDP (null data PPDU) Feedback Report Poll) trigger frame to at least one AP including the second AP after transmitting the first frame, and transmits the second frame after receiving an NDP feedback frame from each of the at least one AP including the second AP.

14. In paragraph 13, A method of operating a first AP, wherein the NFRP trigger frame includes identification information that identifies each of at least one AP including the second AP, and the NDP feedback frame transmitted from each of at least one AP including the second AP is received in a band corresponding to the identification information.

15. In paragraph 7, An operating method of a first AP, wherein the first AP transmits a BSRP (Buffer Status Report Poll) trigger frame to at least one AP including the second AP after transmitting the first frame, and transmits the second frame after receiving a buffer status report from each of the at least one AP including the second AP.

16. In paragraph 13, The operating method of the first AP, wherein the BSRP trigger frame indicates a band over which the buffer status report is transmitted, and the buffer status report transmitted from each of at least one AP including the second AP is received in the band indicated by the BSRP trigger frame.

17. At the first access point (AP), At least one transceiver; At least one processor controlling at least one transceiver; and A memory storing instructions that cause the wireless user device to perform a specific operation by the at least one processor, The above specific actions are: The first AP transmits a first frame, wherein the first frame is a frame that sets a first NAV (network allocation vector) to at least one wireless LAN terminal receiving the first frame, Transmitting a second frame in a first communication section established by the first frame, wherein the first AP allocates a second communication section to the second AP based on the time division communication within the first communication section through the second frame, and A first AP, which receives a third frame from each of at least one AP including the second AP in response to the second frame, wherein the third frame is a frame that sets a second NAV to at least one wireless LAN terminal receiving the third frame, and wherein communication by the second AP within the second communication section is performed regardless of the NAV.

Images