Method and device for performing NPCA in consideration of TXOP sharing in wireless LAN system

Abstract

The present disclosure relates to an improved wireless LAN system. The present disclosure proposes a method and a device considering NPCA in an improved wireless LAN system. Specifically, the present disclosure provides a method and a device for: receiving, from a first AP, a first frame for notifying TXOP sharing of the first AP; transmitting, to the first AP, a second frame for responding to a TXS; and performing NPCA in a time interval determined on the basis of at least one of the first frame and the second frame.

Description

Method and apparatus for performing NPCA considering TXOP sharing in a wireless LAN system

[0001] The present disclosure relates to a wireless local area network (WLAN) system. Specifically, the present disclosure relates to a method and apparatus for non-primary channel access (NPCA) operation in a wireless LAN system.

[0002] Wireless LAN (WLAN) systems are evolving for various purposes, such as improving transmission rates, increasing bandwidth, enhancing reliability, reducing errors, and reducing latency. The Institute of Electrical and Electronics Engineers (IEEE) publishes the 802.11 standard specification for wireless LAN systems, and the technology described in the 802.11 standard specification can be referred to as WiFi (or Wi-Fi, Wireless Fidelity).

[0003] Wi-Fi technology has evolved through several generations of 802.11 standards. For example, the 802.11ac standard covers improvements for VHT (very high throughput), the 802.11ax standard covers improvements for HE (high efficiency), and the 802.11be standard covers improvements for EHT (extreme high throughput).

[0004] Meanwhile, technologies to provide an improved wireless communication environment in wireless LAN systems are being discussed, and various technologies are being proposed and researched in response to the demand to further enhance the reliability of wireless LAN systems.

[0005] The present disclosure proposes a method and apparatus for performing non-primary channel access (NPCA) through a non-primary channel in a wireless LAN system. In particular, the present disclosure proposes a method and apparatus for effectively performing NPCA by considering TXS when TXOP sharing (TXOP sharing) is performed in a coordinated time division multiple access (C-TDMA) situation. Furthermore, the present disclosure also proposes a procedure and a frame structure for performing NPCA considering TXS according to the proposed embodiment.

[0006] The technical objectives to be achieved in this disclosure are not limited to those mentioned above, and other unmentioned technical problems may be considered by those skilled in the art from the embodiments of the present invention described below.

[0007] According to one embodiment of the present disclosure, a method performed by a second AP (access point) of a wireless LAN system comprises: receiving a first frame from a first AP to notify the first AP of a transmission opportunity (TXOP) sharing (TXS) of the first AP; transmitting a second frame to the first AP to respond to the TXS; and performing an NPCA in a time interval based on information indicating the use of a non-primary channel access (NPCA) included in the second frame, wherein the second frame includes information regarding at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

[0008] According to one embodiment of the present disclosure, a method performed by a STA (station) of a wireless LAN system comprises: receiving a first frame from a first AP to notify a TXOP sharing (TXS) of the first AP to a second AP; receiving a second frame from the second AP to respond to the TXS; and performing an NPCA in a time interval based on information indicating the use of a non-primary channel access (NPCA) included in the second frame, wherein the second frame includes information regarding at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

[0009] According to one embodiment of the present disclosure, a second AP of a wireless LAN system comprises: a transceiver; and at least one processor connected to the transceiver, wherein the at least one processor: receives a first frame for notifying the sharing of a TXOP (TXS) of the first AP from the first AP, transmits a second frame to the first AP for responding to the TXS, and is configured to perform an NPCA in a time interval based on information indicating the use of a non-primary channel access (NPCA) included in the second frame, and the second frame includes information regarding at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

[0010] According to one embodiment of the present disclosure, a STA (station) of a wireless LAN system comprises: a transceiver; and at least one processor connected to the transceiver, wherein the at least one processor: receives a first frame for notifying a TXOP sharing (TXS) of the first AP to a second AP from a first AP, receives a second frame for responding to the TXS from the second AP, and is configured to perform an NPCA in a time interval based on information indicating the use of a non-primary channel access (NPCA) included in the second frame, and the second frame includes information regarding at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

[0011] According to the various embodiments proposed in this disclosure, NPCA between an AP and a STA can be effectively performed in a situation where C-TDMA is applied in a wireless LAN system. In addition, by improving the signaling procedure and frame structure for performing NPCA, signaling overhead can be reduced, and the utilization efficiency of wireless resources can be increased.

[0012] FIG. 1 illustrates the configuration of a device for wireless communication according to one embodiment of the present disclosure.

[0013] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0014] FIG. 3 illustrates a link setup process related to the present disclosure.

[0015] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0016] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0017] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0018] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0019] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0020] FIG. 9 is a diagram illustrating exemplary operations of C-TDMA (coordinated time division multiple access) of a wireless LAN system related to the present disclosure.

[0021] FIG. 10 illustrates an exemplary structure of a frame for TXOP (transmission opportunity) sharing (TXOP sharing, TXS) related to the present disclosure.

[0022] FIG. 11 is a drawing illustrating the meaning represented by a specific field included in a frame for TXOP sharing related to the present disclosure.

[0023] FIG. 12 illustrates an exemplary format structure of a specific field included in a frame for TXOP sharing related to the present disclosure.

[0024] FIG. 13 illustrates an exemplary format structure of a frame for responding to a TXOP sharing related to the present disclosure.

[0025] FIG. 14 is a diagram illustrating the meaning represented by a specific field included in a frame for responding to a TXOP sharing related to the present disclosure.

[0026] FIG. 15 illustrates the configuration of a primary channel and a secondary channel of a wireless LAN system related to the present disclosure.

[0027] FIG. 16 illustrates the configuration of a primary channel and a secondary channel of a wireless LAN system related to the present disclosure.

[0028] FIG. 17 is a diagram illustrating non-primary channel access (NPCA) in a wireless LAN system related to the present disclosure.

[0029] FIG. 18 is a diagram illustrating an NPCA in a wireless LAN system related to the present disclosure.

[0030] FIG. 19 illustrates an exemplary structure of the format of a specific field included in a frame for TXOP sharing related to the present disclosure.

[0031] FIG. 20 illustrates an exemplary structure of the format of a specific field included in a frame for responding to a TXOP sharing related to the present disclosure.

[0032] FIG. 21 illustrates an exemplary structure of the format of a specific field included in a frame for responding to a TXOP sharing related to the present disclosure.

[0033] FIG. 22 illustrates an exemplary structure of the format of a specific field included in a frame for responding to a TXOP sharing related to the present disclosure.

[0034] FIG. 23 is a diagram illustrating an example of a procedure of NPCA considering TXOP sharing related to the present disclosure.

[0035] FIG. 24 is a diagram illustrating another example of an NPCA procedure considering TXOP sharing related to the present disclosure.

[0036] FIG. 25 illustrates a flowchart of operations related to TXOP sharing of a first AP in a wireless LAN system according to one embodiment of the present disclosure.

[0037] FIG. 26 illustrates a flowchart of operations related to TXOP sharing and NPCA of a second AP in a wireless LAN system according to one embodiment of the present disclosure.

[0038] FIG. 27 illustrates a flowchart of operations related to TXOP sharing and NPCA of a STA in a wireless LAN system according to one embodiment of the present disclosure.

[0039] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that identical components in the accompanying drawings are represented by the same reference numerals whenever possible. Furthermore, detailed descriptions of known functions and configurations that may obscure the essence of the present disclosure will be omitted.

[0040] In describing the embodiments in this specification, technical details that are well known in the technical field to which this disclosure belongs and are not directly related to this disclosure are omitted. This is intended to convey the essence of this disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0041] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the size of each component does not entirely reflect its actual dimensions.

[0042] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. The embodiments provided are merely to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims.

[0043] At this time, it will be understood that each block of the flowcharts and combinations of the flowcharts can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a specialized computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flowchart block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing the means of instruction to perform the function described in the flowchart block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0044] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specified logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For instance, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order according to their corresponding functions.

[0045] In this embodiment, the term "part" refers to a software or hardware component, such as an FPGA or ASIC, and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or configured to operate one or more processors. Accordingly, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." Furthermore, the components and "parts" may be implemented to operate one or more CPUs within a device or secure multimedia card.

[0046] In the present disclosure, when a component is described as being “connected,” “combined,” or “joined” with another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, in the present disclosure, the terms “comprising” or “having” specify the presence of the mentioned features, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, actions, elements, components, and / or groups thereof.

[0047] In the present disclosure, terms such as "first," "second," etc. are used solely for the purpose of distinguishing one component from another and are not used to limit the components, nor do they limit the order or importance of the components unless specifically stated otherwise. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and likewise, a second component in one embodiment may be referred to as a first component in another embodiment.

[0048] The terms used in this disclosure are for the description of specific embodiments and are not intended to limit the claims. As used in the description of embodiments and in the appended claims, the singular form is intended to include the plural form unless the context clearly indicates otherwise. The term "and / or" as used in this disclosure may refer to any one of the related enumerated items, or refers to and includes any and all possible combinations of two or more of them. Additionally, the " / " between words in this disclosure has the same meaning as "and / or" unless otherwise noted.

[0049] The embodiments of the present disclosure may be applied to various wireless communication systems. For example, the embodiments of the present disclosure may be applied to wireless LAN systems. For example, the embodiments of the present disclosure may be applied to wireless LAN systems based on IEEE 802.11a / g / n / ac / ax / be standards. Furthermore, the embodiments of the present disclosure may be applied to wireless LAN systems based on the newly discussed IEEE 802.11bn (or UHR (ultra high reliability)) standards. Additionally, the embodiments of the present disclosure may be applied to next-generation wireless LAN systems based on standards after IEEE 802.11bn.

[0050] In addition, the examples of the present disclosure may be applied to cellular wireless communication systems. For example, the examples of the present disclosure may be applied to cellular wireless communication systems based on LTE (Long Term Evolution), LTE-A (LTE advanced), and NR (New Radio) technologies based on 3GPP (3rd Generation Partnership Project) standard documents.

[0051] FIG. 1 illustrates the configuration of a device for wireless communication according to one embodiment of the present disclosure.

[0052] The first device (100) and the second device (200) of FIG. 1 may be replaced with various terms such as terminal, wireless device, WTRU (Wireless Transmit and Receive Unit), UE (User Equipment), MS (Mobile Station), UT (user terminal), MSS (Mobile Subscriber Station), MSS (Mobile Subscriber Unit), SS (Subscriber Station), AMS (Advanced Mobile Station), WT (Wireless terminal), client terminal, or simply user.

[0053] In addition, the first device (100) and the second device (200) can be replaced with various terms such as Access Point (AP), Base Station (BS), fixed station, Node B, base transceiver system (BTS), network, Artificial Intelligence (AI) system, road side unit (RSU), repeater, router, relay, gateway, etc.

[0054] The device (100, 200) exemplified in FIG. 1 may be referred to as a station (STA). For example, the device (100, 200) exemplified in FIG. 1 may be referred to by various terms such as a transmitting device, a receiving device, a transmitting STA, or a receiving STA. For example, the STA (110, 200) may perform the role of an access point (AP) or a non-AP. That is, in the present disclosure, the STA (110, 200) may perform the functions of an AP and / or a non-AP. If the STA (110, 200) performs the AP function, it may simply be referred to as an AP, and if the STA (110, 200) performs the non-AP function, it may simply be referred to as a STA. Additionally, in the present disclosure, the AP may also be indicated as an AP STA.

[0055] Referring to FIG. 1, the first device (100) and the second device (200) can transmit and / or receive wireless signals through various wireless LAN technologies (e.g., technologies based on the IEEE 802.11 standard). The first device (100) and the second device (200) may include interfaces for the MAC (medium access control) layer and the PHY (physical) layer that comply with the specifications of the IEEE 802.11 standard.

[0056] In addition, the first device (100) and the second device (200) may additionally support various wireless communication technologies other than wireless LAN technology (e.g., 3GPP LTE, LTE-A, or technologies based on NR standard documents). In addition, the device of the present disclosure may be implemented as various devices such as mobile phones, vehicles, personal computers, AR (Augmented Reality) equipment, VR (Virtual Reality) equipment, etc. Furthermore, the STA of the present specification may support various communication services such as voice calls, video calls, data communication, autonomous driving, MTC (Machine-Type Communication), M2M (Machine-to-Machine), D2D (Device-to-Device), and IoT (Internet-of-Things).

[0057] The first device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (or transceivers, transceivers) (106) and / or one or more antennas (108). The processor (102) controls the memory (104) and / or transceivers (106) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (102) may process information within the memory (104) to generate first information and / or a first signal, and then transmit a wireless signal including the first information and / or the first signal through the transceiver (106). Additionally, the processor (102) may receive a wireless signal including second information and / or a second signal through a transceiver (106) and then store the information obtained through signal processing of the second information and / or the second signal in the memory (104). The memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, the memory (104) may store software code including instructions for performing some or all of the processes controlled by the processor (102) or for performing the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure. Here, the processor (102) and the memory (104) may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., technology based on the IEEE 802.11 document). The transceiver (106) may be connected to the processor (102) and may transmit and / or receive wireless signals through one or more antennas (108). The transceiver (106) may include a transmitter and / or receiver. The transceiver (106) may be used in combination with an RF (Radio Frequency) unit.

[0058] The second device (200) includes one or more processors (202) and one or more memories (204), and may further include one or more transceivers (or transceivers) (206) and / or one or more antennas (208). The processor (202) controls the memory (204) and / or transceivers (206) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (202) may process information within the memory (204) to generate third information and / or a third signal, and then transmit a wireless signal including the third information and / or the third signal through the transceiver (206). Additionally, the processor (202) may receive a wireless signal including fourth information and / or a fourth signal through the transceiver (206), and then store information obtained through signal processing of the fourth information and / or the fourth signal in the memory (204). Memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, memory (204) may store software code including instructions for performing some or all of the processes controlled by the processor (202) or for performing the descriptions, functions, procedures, proposals, methods, and / or sequences of operation disclosed in this disclosure. Here, the processor (202) and memory (204) may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., technology based on the IEEE 802.11 document). A transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals through one or more antennas (208). The transceiver (206) may include a transmitter and / or receiver. The transceiver (206) may be used interchangeably with an RF unit.

[0059] Hereinafter, the hardware elements of the device (100, 200) will be described in more detail. Although not limited to the following, the operation of one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement the operation of one or more layers (e.g., functional layers such as PHY, MAC). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and / or Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure. One or more processors (102, 202) may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, traffic, or information according to the functions, procedures, proposals, and / or methods disclosed in this disclosure and provide it to one or more transceivers (106, 206). One or more processors (102, 202) may receive a signal (e.g., a baseband signal) from one or more transceivers (106, 206) and may obtain a PDU, SDU, message, control information, data, traffic, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this disclosure.

[0060] One or more memories (104, 204) may be connected to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. One or more memories (104, 204) may consist of ROM (read-only memory), RAM (random access memory), EPROM (erasable programmable ROM), EEPROM (electronically EPROM), flash memory, hard drive, registers, cache memory, computer-readable storage media, and / or combinations thereof. One or more memories (104, 204) may be located inside and / or outside of one or more processors (102, 202). Additionally, one or more memories (104, 204) may be connected to one or more processors (102, 202) through various technologies such as wired or wireless connections.

[0061] One or more transceivers (106, 206) may transmit user data, control information, data, traffic, wireless signals, and / or channels, etc., as mentioned in the methods and / or operation flowcharts, etc., of the present disclosure to one or more other devices. One or more transceivers (106, 206) may receive user data, control information, data, traffic, wireless signals, and / or channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts, etc., disclosed in the present disclosure from one or more other devices. For example, one or more transceivers (106, 206) may be connected to one or more processors (102, 202) and may transmit and receive wireless signals. For example, one or more processors (102, 202) may control one or more transceivers (106, 206) to transmit user data, control information, traffic, wireless signals, and / or channels to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, traffic, wireless signals and / or channels from one or more other devices. Additionally, one or more transceivers (106, 206) may be connected to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, traffic, wireless signals and / or channels, etc., as described in the descriptions, functions, procedures, proposals, methods and / or flowcharts, etc. disclosed in this disclosure through one or more antennas (108, 208). In this disclosure, one or more antennas (108, 208) may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).One or more transceivers (106, 206) can convert received wireless signals / channels, etc. from RF band signals to baseband signals in order to process received user data, control information, wireless signals / channels, etc. using one or more processors (102, 202). One or more transceivers (106, 206) can convert processed user data, control information, wireless signals / channels, etc. from baseband signals to RF band signals using one or more processors (102, 202). To this end, one or more transceivers (106, 206) may include (analog) oscillators and / or filters.

[0062] According to one example, one of the devices (100, 200) may perform the intended operation of an AP, and the other of the devices (100, 200) may perform the intended operation of a non-AP STA. As another example, the transceiver (106, 206) of FIG. 1 may perform the transmission and / or reception operation of a signal (e.g., a packet or PPDU (physical layer protocol data unit) according to IEEE 802.11a / b / g / n / ac / ax / be / bn, etc.).

[0063] In addition, in the present disclosure, the operation of generating transmission and reception signals or performing data processing or calculations in advance for transmission and reception signals by various STAs can be performed in the processor (102, 202) of FIG. 1. For example, examples of operations for generating transmit / receive signals or performing data processing or operations in advance for transmit / receive signals include: 1) operations for determining / acquiring / configuring / operating / decoding / encoding bit information of fields included in the PPDU (e.g., SIG (signal), STF (short training field), LTF (long training field), Data, etc.); 2) operations for determining / configuring / acquiring time resources or frequency resources (e.g., subcarrier resources) used for fields included in the PPDU (e.g., SIG, STF, LTF, Data, etc.); 3) operations for determining / configuring / acquiring specific sequences (e.g., pilot sequence, STF / LTF sequence, extra sequence applied to SIG) used for fields included in the PPDU (e.g., SIG, STF, LTF, Data, etc.); 4) power control operations and / or power saving operations applied to the STA; and 5) of the ACK (acknowledgement) signal. It may include operations related to determination / acquisition / configuration / operation / decoding / encoding, etc. In addition, in the following example, various information (e.g., information related to fields / subfields / control fields / parameters / power, etc.) used by various STAs for determination / acquisition / configuration / operation / decoding / encoding of transmission and reception signals may be stored in the memory (104, 204) of FIG. 1.

[0064] In the following, the downlink (DL) refers to a link for communication from an AP STA to a non-AP STA, and downlink PPDUs, packets, signals, etc., can be transmitted and received through the downlink. In downlink communication, the transmitter may be part of the AP STA, and the receiver may be part of the non-AP STA. The uplink (UL) refers to a link for communication from a non-AP STA to an AP STA, and uplink PPDUs, packets, signals, etc., can be transmitted and received through the uplink. In uplink communication, the transmitter may be part of the non-AP STA, and the receiver may be part of the AP STA.

[0065] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0066] A wireless LAN system may have a structure composed of multiple components. Through the interaction of these multiple components, the wireless LAN system can support transparent STA mobility relative to the upper layer. A Basic Service Set (BSS) corresponds to the basic building block of a wireless LAN. Figure 2 exemplarily illustrates the existence of two BSSs (BSS 1 and BSS 2), each containing two STAs as members (STA 1 and STA 2 are included in BSS 1, and STA 3 and STA 4 are included in BSS 2). In Figure 2, the ellipse representing the BSS can also be understood as representing the coverage area where the STAs included in the corresponding BSS maintain communication. This area can be referred to as a Basic Service Area (BSA). If a STA moves outside the BSA, it cannot communicate directly with other STAs within that BSA.

[0067] Excluding the distributed system (DS) illustrated in Fig. 2, the most basic type of BSS in a wireless LAN is the Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For instance, assuming other components are omitted, a BSS 1 composed of only STA 1 and STA 2, or a BSS 2 composed of only STA 3 and STA 4, can each be considered a representative example of an IBSS. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, this type of wireless LAN is not configured through pre-planning but can be established when a LAN (local area network) is required, and it may also be referred to as an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. In other words, in an IBSS, STAs are managed in a distributed manner. In IBSS, all STAs can be mobile STAs, and since connections to DS are not allowed, they form a self-contained network.

[0068] The membership of an STA in a BSS can be dynamically changed by the STA being turned on or off, or by the STA entering or leaving the BSS area. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services of the BSS infrastructure, an STA must be associated with the BSS. This association can be configured dynamically and may include the use of a Distribution System Service (DSS).

[0069] In a wireless LAN, the direct STA-to-STA distance can be limited by PHY performance. In some cases, this distance limit may be sufficient, but in others, communication between STAs over longer distances may be required. A DS can be configured to support extended coverage.

[0070] DS refers to a structure in which BSSs are interconnected. Specifically, as shown in FIG. 2, a BSS may exist as a component in an extended form of a network composed of multiple BSSs. DS is a logical concept and can be specified by the characteristics of the Distributed System Medium (DSM, DS medium). In this regard, the Wireless Medium (WM) and the DSM can be logically distinguished. Each logical medium is used for a different purpose and is utilized by different components. These media are not limited to being identical or different. The flexibility of the wireless LAN structure (DS structure or other network structure) can be explained by the fact that multiple media are logically distinct in this way. That is, the wireless LAN structure can be implemented in various ways, and the corresponding wireless LAN structure can be independently specified by the physical characteristics of each implementation.

[0071] DS can support mobile devices by providing seamless integration of multiple BSSs and providing logical services necessary for handling addresses to destinations. Additionally, DS may include a component called a portal that acts as a bridge for connecting the wireless LAN with other networks (e.g., IEEE 802.X).

[0072] An AP enables access to the DS via the WM for non-AP STAs coupled with it. An AP can refer to an entity that also possesses the functionality of an STA, and data movement between the BSS and the DS can be performed through the AP. For example, STA 2 and STA 3 shown in FIG. 2 possess the functionality of an STA and provide the function of enabling coupled non-AP STAs (STA 1 and STA 4) to access the DS. Furthermore, since all APs fundamentally correspond to STAs, all APs are addressable entities. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM do not necessarily have to be the same. A BSS composed of an AP and one or more STAs can be referred to as an infrastructure BSS.

[0073] Data transmitted from one of the STA(s) coupled to the AP to the STA address of the AP can always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity. Additionally, if the controlled port is authenticated, the transmitted data (or frame) can be forwarded to the DS.

[0074] In addition to the structure of the aforementioned DS, an Extended Service Set (ESS) may be configured to provide wider coverage.

[0075] An ESS is a network of arbitrary size and complexity that can correspond to a set of BSSs connected to a single DS. However, an ESS does not contain a DS. An ESS network is characterized by appearing as an IBSS at the Logical Link Control (LLC) layer. STAs included in an ESS can communicate with each other, and mobile STAs can move from one BSS to another (i.e., within the same ESS) transparently to the LLC. APs included in a single ESS can have the same Service Set Identifier (SSID). The SSID is distinguished from the BSSID (BSS SSID), which is the identifier of the BSS.

[0076] In wireless LAN systems, no assumptions are made regarding the relative physical locations of BSSs, and all of the following forms are possible. BSSs may partially overlap, which is a form commonly used to provide continuous coverage. Additionally, BSSs may not be physically connected, and logically, there is no limit to the distance between BSSs. Furthermore, BSSs may be located in the same physical location, which can be used to provide redundancy. Additionally, one or more IBSS or ESS networks may physically exist in the same space as one (or more) ESS networks. This may apply to ESS network configurations where an ad-hoc network operates at a location where an ESS network exists, where wireless networks are physically overlapping by different organizations, or where two or more different access and security policies are required at the same location.

[0077] FIG. 3 illustrates a link setup process related to the present disclosure.

[0078] In order for an STA to set up links and transmit and receive data on a network, it must discover the network through an AP, perform authentication, establish an association, and set up security. The link setup process can also be referred to as the session initiation process or the session setup process. Additionally, the processes of discovery, authentication, association, and security setup within the link setup process can be collectively referred to as the association process.

[0079] In step 310, the STA can perform a network discovery operation. The network discovery operation may include the STA's scanning operation. That is, in order for the STA to access a network, it must find a network it can join. Before joining a wireless network, the STA must identify a compatible network, and the process of identifying networks existing in a specific area is called scanning.

[0080] Scanning methods include active scanning and passive scanning. Figure 3 illustrates a network discovery operation that includes an active scanning process as an example. In active scanning, the STA performing the scanning moves between channels to search for nearby APs, transmits a probe request frame, and waits for a response. The responder transmits a probe response frame as a response to the probe request frame to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted a beacon frame from the BSS of the channel being scanned. In a BSS, the AP becomes the responder because it transmits the beacon frame; however, in an IBSS, the responder is not constant because STAs within the IBSS take turns transmitting the beacon frame. For example, an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 can store BSS-related information included in the received probe response frame and move to the next channel (e.g., channel 2) to perform scanning in the same way (i.e., transmit and receive probe request / response on channel 2).

[0081] Although not illustrated in FIG. 3, the scanning operation may be performed using a passive scanning method. In passive scanning, the STA performing the scanning waits for a beacon frame while switching between channels. A beacon frame is one of the management frames defined in IEEE 802.11, which announces the presence of a wireless network and is periodically transmitted to allow the scanning STA to find the wireless network and join it. In a BSS, the AP performs the role of periodically transmitting beacon frames, and in an IBSS, the STAs within the IBSS take turns transmitting beacon frames. When the scanning STA receives a beacon frame, it stores the information about the BSS included in the beacon frame and records the beacon frame information in each channel while moving to another channel. The STA that receives the beacon frame stores the BSS-related information included in the received beacon frame, moves to the next channel, and can perform scanning in the next channel in the same way. When comparing active scanning and passive scanning, active scanning has the advantage of lower delay and power consumption than passive scanning.

[0082] After the STA discovers the network, an authentication process can be performed in step 320. This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation in step 340 described later.

[0083] The authentication process involves the STA sending an authentication request frame to the AP, and the AP sending an authentication response frame to the STA in response. The authentication request frame and the authentication response frame used in the authentication process belong to management frames.

[0084] The authentication frame may include information regarding the authentication algorithm number, authentication transaction sequence number, status code, challenge text, Robust Security Network (RSN), Finite Cyclic Group, etc. These are some examples of information that may be included in the authentication request / response frame, and they may be replaced with other information or additional information may be included.

[0085] The STA can send an authentication request frame to the AP. Based on the information contained in the received authentication request frame, the AP can determine whether to allow authentication for the STA. The AP can provide the result of the authentication process to the STA through an authentication response frame.

[0086] After the STA is successfully authenticated, the association process can be performed in step 330. The association process includes the STA sending an association request frame to the AP, and in response, the AP sending an association response frame to the STA.

[0087] The association request frame may include information regarding various capabilities, beacon listen interval, service set identifier (SSID), supported rates, supported channels, robust security network (RSN), mobility domain, supported operating classes, Traffic Indication Map Broadcast request, interworking service capabilities, etc. For example, the association response frame may include information regarding various capabilities, status code, Association ID (AID), supported rates, Enhanced Distributed Channel Access (EDCA) parameter set, Received Channel Power Indicator (RCPI), Received Signal to Noise Indicator (RSNI), mobility domain, timeout interval (e.g., association comeback time), overlapping BSS scan parameters, TIM broadcast response, Quality of Service (QoS) map, etc. These are some examples of information that may be included in a combined request / response frame, and the combined request / response frame may include other additional information.

[0088] After the STA is successfully joined to the network through the AP, the security setup process can be performed in step 340. The security setup process in step 340 may include an authentication process through RSNA (Robust Security Network Association) requests and responses. Additionally, if the authentication process in step 320 is referred to as the first authentication process, the security setup process in step 340 may also be referred to simply as the authentication process.

[0089] The security setup process of step 340 may include, for example, a private key setup process through a 4-way handshake via an EAPOL (Extensible Authentication Protocol over LAN) frame. Additionally, the security setup process may be performed according to a security method not defined in the IEEE 802.11 standard.

[0090] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0091] In wireless LAN systems, the basic access mechanism of a MAC is the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism. The CSMA / CA mechanism is also known as the Distributed Coordination Function (DCF) of IEEE 802.11 MACs, and it basically employs a "listen before talk" access mechanism. According to this type of access mechanism, the AP and / or STA perform Clear Channel Assessment (CCA) to sense the wireless channel or medium for a predetermined time interval (e.g., DIFS (DCF Inter-Frame Space)) before starting transmission. If the sensing result determines that the medium is in an idle status, the AP and / or STA start transmitting a frame through that medium. On the other hand, if the medium is detected to be occupied or busy, the AP and / or STA may not start their own transmission but wait for a predetermined delay period for medium access (e.g., a random backoff period) before attempting to transmit a frame. By applying a random backoff period, multiple STAs attempt to transmit frames after waiting for different periods of time, thereby minimizing collisions.

[0092] In addition, the IEEE 802.11 MAC protocol provides a Hybrid Coordination Function (HCF). The HCF is based on the aforementioned Point Coordination Function (PCF). The PCF is a polling-based synchronous access method that refers to a method of periodically polling so that all receiving APs and / or STAs can receive data frames. Furthermore, the HCF includes Enhanced Distributed Channel Access (EDCA) and Controlled Channel Access (HCCA). EDCA is a contention-based access method for a provider to provide data frames to multiple users, while HCCA uses a non-contention-based channel access method utilizing a polling mechanism. Additionally, the HCF includes a media access mechanism to improve the Quality of Service (QoS) of a wireless LAN and can transmit QoS data during both the Contention Period (CP) and the Contention-Free Period (CFP).

[0093] With reference to FIG. 4, the operation based on the random backoff period is described. When a medium that was in an occupied / busy state changes to an idle state, multiple STAs may attempt to transmit data (or frames). As a measure to minimize collisions, each STA may select a random backoff count and attempt transmission after waiting for the corresponding slot time. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​in the range from 0 to CW. Here, CW is the Contention Window parameter value. The CW parameter is given an initial value of CWmin, but in the event of transmission failure (e.g., failure to receive an ACK for a transmitted frame), the STA may double the CW. When the CW parameter value reaches CWmax, the STA may attempt to transmit data while maintaining the CWmax value until data transmission is successful, and if data transmission is successful, the CW is reset to the CWmin value. The values ​​of CW, CWmin, and CWmax can be set to 2n-1 (n=0, 1, 2, ...).

[0094] When the random backoff process begins, the STA continues to monitor the media while counting down the backoff slots according to the determined backoff count value. When the media is monitored as occupied, it stops the countdown and waits, and when the media becomes idle, it resumes the remaining countdown.

[0095] In the example of Fig. 4, when a packet to be transmitted arrives at the MAC of STA3, STA3 confirms that the medium is idle for DIFS and can immediately transmit the frame. The remaining STAs monitor whether the medium is occupied or idle and wait. Meanwhile, data to be transmitted may also arise at each of STA1, STA2, and STA5, and each STA, once it confirms that the medium is idle, waits for DIFS and then performs a countdown of the backoff slot according to a random backoff count value selected by each. Assume the case where STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value. That is, it exemplifies a case where, at the point when STA2 finishes the backoff count and starts transmitting the frame, the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1. STA1 and STA5 pause the countdown briefly and wait while STA2 occupies the medium. When STA2's possession ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the paused backoff count. That is, STA1 and STA5 can start frame transmission after counting down the remaining backoff slots corresponding to the remaining backoff time. Since STA5's remaining backoff time was shorter than STA1's, STA5 starts frame transmission. Data to be transmitted may also occur in STA4 while STA2 is occupying the medium. When the medium becomes idle, STA4 waits for DIFS, performs a countdown based on a random backoff count value selected by itself, and can start frame transmission. The example in Figure 4 illustrates a case where STA5's remaining backoff time happens to match STA4's random backoff count value; in this case, a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receives an ACK, resulting in a failure of data transmission.In this case, STA4 and STA5 can double the CW value, select a random backoff count value, and perform a countdown. STA1 waits while the medium is occupied due to the transmission of STA4 and STA5, and when the medium becomes idle, it waits for DIFS, and then can start transmitting frames after the remaining backoff time has elapsed.

[0096] As shown in the example in Fig. 4, a data frame is a frame used for transmitting data to an upper layer and can be transmitted after a backoff performed after the elapsed time of DIFS from when the medium becomes idle. Additionally, a management frame is a frame used for exchanging management information without being transmitted to an upper layer, and is transmitted after a backoff performed after the elapsed time of an IFS such as DIFS or PIFS (Point coordination function IFS). A management frame may include a beacon, association request / response, re-association request / response, probe request / response, authentication request / response, etc., as a subtype frame. A control frame is a frame used to control access to the medium. A control frame is a subtype frame and may include a Request-To-Send (RTS), Clear-To-Send (CTS), Acknowledgment (ACK), Power Save-Poll (PS-Poll), Block ACK (B-ACK or BlockAck), Block ACK Request (BlockACKReq), Null Data Packet Announcement (NDP), Trigger, etc. If the control frame is not an acknowledgment frame of the previous frame, it is transmitted after a backoff performed after the elapsed DIFS; if it is an acknowledgment frame of the previous frame, it is transmitted after the short IFS (SIFS) elapsed without a backoff. The type and subtype of the frame can be identified by the type field and subtype field within the frame control (FC) field.

[0097] A QoS (Quality of Service) STA can transmit a frame after backoff, which is performed after the elapsed time of the arbitration IFS (AIFS) for the access category (AC) to which the frame belongs, i.e., AIFS[i] (where i is a value determined by the AC). Here, the frames for which AIFS[i] can be used can be data frames, management frames, and control frames rather than response frames.

[0098] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0099] As previously mentioned, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, where the STA directly senses the medium. Virtual carrier sensing is intended to mitigate problems that may occur in medium access, such as the hidden node problem. For virtual carrier sensing, the STA's MAC can utilize the Network Allocation Vector (NAV). The NAV is a value that indicates to other STAs the time remaining until the medium becomes available, provided that the STA currently using or authorized to use the medium is using it. Therefore, the value set as the NAV corresponds to the period during which the medium is scheduled to be used by the STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during that period. For example, the NAV can be set based on the value of the "duration" field in the frame's MAC header.

[0100] In the example of FIG. 5, STA1 wants to transmit data to STA2, and STA3 is in a position to overhear part or all of the frames transmitted and received between STA1 and STA2.

[0101] In order to reduce the possibility of collisions between multiple STAs in a CSMA / CA-based frame transmission operation, a mechanism utilizing RTS / CTS frames may be applied. In the example of FIG. 5, while STA1 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA1 may be a hidden node to STA3. Alternatively, in the example of FIG. 5, while STA2 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA2 may be a hidden node to STA3. By exchanging RTS / CTS frames before performing data transmission and reception between STA1 and STA2, it is possible to prevent a STA outside the transmission range of either STA1 or STA2, or a STA outside the carrier sensing range for transmission from STA1 or STA3, from attempting to occupy the channel during data transmission and reception between STA1 and STA2.

[0102] Specifically, STA1 can determine whether the channel is in use through carrier sensing. In terms of physical carrier sensing, STA1 can determine the channel occupancy idle state based on the energy magnitude or signal correlation detected in the channel. Additionally, in terms of virtual carrier sensing, STA1 can determine the channel occupancy state using a NAV timer.

[0103] If the channel is idle during DIFS, STA1 can send an RTS frame to STA2 after performing backoff. If STA2 receives the RTS frame, it can send a CTS frame to STA1 as a response to the RTS frame after SIFS.

[0104] If STA3 cannot overhear a CTS frame from STA2 but can overhear an RTS frame from STA1, STA3 can set a NAV timer for the duration of subsequent consecutive frame transmissions (e.g., SIFS + CTS frame + SIFS + data frame + SIFS + ACK frame) using the duration information included in the RTS frame. Alternatively, if STA3 cannot overhear an RTS frame from STA1 but can overhear a CTS frame from STA2, STA3 can set a NAV timer for the duration of subsequent consecutive frame transmissions (e.g., SIFS + data frame + SIFS + ACK frame) using the duration information included in the CTS frame. That is, if STA3 can overhear one or more of the RTS or CTS frames from one or more of STA1 or STA2, it can set a NAV accordingly. If STA3 receives a new frame before the NAV timer expires, it can update the NAV timer using the duration information contained in the new frame. STA3 does not attempt channel access until the NAV timer expires.

[0105] If STA1 receives a CTS frame from STA2, it may transmit a data frame to STA2 after SIFS from the time the reception of the CTS frame is completed. If STA2 successfully receives the data frame, it may transmit an ACK frame, which is an acknowledgment of the data frame, to STA1 after SIFS. STA3 may determine whether the channel is in use through carrier sensing when the NAV timer expires. If STA3 determines that the channel is not in use by another terminal during DIFS from the time the NAV timer expires, it may attempt channel access after a contention window (CW) based on random backoff has passed.

[0106] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0107] Based on instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare the MPDU (MAC PDU) to be transmitted. When the PHY layer receives an instruction from the MAC layer requesting the start of transmission, it switches to transmission mode and can construct the information provided by the MAC layer (e.g., data) into a frame and transmit it. Additionally, if the PHY layer detects a valid preamble of the received frame, it can monitor the preamble header and send an instruction to the MAC layer indicating the start of reception.

[0108] As such, information transmission and reception in wireless LAN systems are carried out in the form of frames, and for this purpose, the Physical Layer Protocol Data Unit (PPDU) frame format is defined.

[0109] A basic PPDU frame may include a short training field (STF), a long training field (LTF), a signal field (SIG), and a data field. The most basic (e.g., non-HT (high throughput)) PPDU frame format may consist only of a legacy-STF (Legacy-STF), a greenfield field (Legacy-LTF), a signal field, and a data field. Additionally, depending on the type of PPDU frame format (e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (very high throughput) PPDU, etc.), additional (or different types of) STF, LTF, and signal fields may be included between the signal field and the data field. Specific types of frame formats will be described later in FIG. 7.

[0110] STF is a signal for signal detection, AGC (automatic gain control), diversity selection, and precise time synchronization, while LTF is a signal for channel estimation and frequency error estimation. STF and LTF are signals for synchronization and channel estimation in the physical layer of OFDM (orthogonal frequency division multiplexing).

[0111] The SIG field may include a RATE field and a LENGTH field, etc. The RATE field may include information regarding the modulation and coding rates of the data. The LENGTH field may include information regarding the length of the data. Additionally, the SIG field may include a parity bit, a SIG TAIL bit, etc.

[0112] The data field may include a SERVICE field, a PSDU (physical layer service data unit), and PPDU TAIL bits, and may also include padding bits if necessary. Some bits of the SERVICE field may be used for synchronization of the descrambler at the receiver. The PSDU corresponds to a MAC PDU defined at the MAC layer and may contain data generated or used by the upper layer. The PPDU TAIL bits may be used to return the encoder to a 0 state. Padding bits may be used to adjust the length of the data field to a predetermined unit.

[0113] A MAC PDU is defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a frame check sequence (FCS). A MAC frame is composed of a MAC PDU and can be transmitted or received through the PSDU of the data portion of the PPDU frame format.

[0114] The MAC header includes a frame control field, a duration / ID field, an address field, etc. The frame control field may contain control information necessary for frame transmission / reception. The duration / ID field may be set as the time for transmitting the corresponding frame, etc. The specific details of the Sequence Control, QoS Control, and HT Control subfields of the MAC header are omitted.

[0115] Although not illustrated in Fig. 6, the null-data packet (NDP) frame format refers to a frame format that does not include data packets. That is, an NDP frame refers to a frame format that includes the PLCP (physical layer convergence procedure) header portion (i.e., STF, LTF, and SIG fields) in a standard PPDU frame format, but excludes the remaining portion (i.e., data fields). An NDP frame may also be referred to as a short frame format.

[0116] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0117] Various forms of PPDU are used in standards such as IEEE 802.11a / g / n / ac / ax / be. The basic PPDU format (the format of IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and Data fields. The basic PPDU format may also be referred to as the non-HT PPDU format.

[0118] The HT PPDU format (the format of IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT(s) fields in addition to the basic PPDU format. The HT PPDU format illustrated in Fig. 7 can be referred to as the HT-mixed format. Although not illustrated, an HT-greenfield format PPDU may be defined, which is a format that does not include L-STF, L-LTF, and L-SIG, but consists of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTFs, and Data fields.

[0119] The VHT PPDU format (the format of IEEE 802.11ac) additionally includes VHT SIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields in addition to the basic PPDU format.

[0120] The HE PPDU format (the format of IEEE 802.11ax) additionally includes the RL-SIG (Repeated L-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF(s), and PE (Packet Extension) fields in addition to the basic PPDU format. Depending on specific examples of the HE PPDU format, some fields may be excluded or their lengths may vary. For example, the HE-SIG-B field is included in the HE PPDU format for multi-user (MU), but is not included in the HE PPDU format for single-user (SU). Additionally, the HE trigger-based (TB) PPDU format does not include HE-SIG-B, and the length of the HE-STF field may vary to 8 μs. The HE ER (Extended Range) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16 μs.

[0121] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0122] The EHT PPDU format of FIG. 8 (format of IEEE 802.11be) may include the EHT MU PPDU format and the EHT TB PPDU format. The EHT MU PPDU format corresponds to a PPDU that carries one or more data (or PSDU) for one or more users. The EHT MU PPDU may be used for both SU transmission and MU transmission, and the EHT MU PPDU may correspond to a PPDU for one receiving STA or multiple receiving STAs. The EHT-SIG is omitted in the EHT TB PPDU compared to the EHT MU PPDU. A STA that receives a trigger for UL MU transmission (e.g., a trigger frame or an RTS frame) may perform UL transmission based on the EHT TB PPDU format.

[0123] The EHT PPDU format additionally includes RL-SIG, U-SIG (Universal SIG), EHT-SIG, EHT-STF, EHT-LTF(s), and PE fields in addition to the basic PPDU format. Depending on the specific examples of the EHT PPDU format, some fields may be excluded or their lengths may vary. For example, depending on the previously described EHT MU PPDU format and EHT TB PPDU format, some fields of the EHT PPDU format may be included or excluded, or the length of specific fields may vary.

[0124] FIG. 9 is a diagram illustrating exemplary operations of C-TDMA (coordinated time division multiple access) of a wireless LAN system related to the present disclosure.

[0125] As discussions on the 802.11bn standard progress, various proposals to improve C-TDMA are being discussed. C-TDMA refers to a procedure for a specific AP to share the time resources of a TXOP it has acquired with a set of other APs, and it may also be called TXS (TXOP sharing) in that it is a procedure for sharing TXOPs.

[0126] An AP that shares a TXOP it has acquired with another AP in C-TDMA or TXS can be called a sharing AP. A sharing AP announces its intention to share at least a portion of the time resources of the TXOP it has acquired, and this process can be accomplished by transmitting an initial control frame (ICF) at the beginning of the TXOP (905). The ICF transmitted by the sharing AP can poll the interest of the target APs to which the sharing AP will share the TXOP, and an AP that shares a portion of the TXOP acquired by the sharing AP in this way can be called a shared AP or a polled AP. The names Sharing AP, shared AP, and polled AP are merely exemplary names for APs participating in C-TDMA and TXS, and it is obvious that they may be called by other names instead of the ones mentioned.

[0127] The ICF (905) transmitted by the Sharing AP may include a duration field, and the duration field of the ICF (905) may be set to a value representing the time length of the time plus SIFS for transmitting an ICR (initial control response) which is a response to the ICF (905). The ICF (905) transmitted by the Sharing AP may be delivered to STA1, which is the associated STA of the Sharing AP, and to a shared AP adjacent to the sharing AP, and STA1, upon receiving the ICF (905), may transmit an ICR (initial control response) to the sharing AP in response to the ICF (910). The shared AP, upon receiving the ICF (905) from the Sharing AP, may also transmit an ICR (915) to the sharing AP in response to the ICF (905). The sharing AP sends a DL PPDU or a DL MU (multi-user) PPDU to STA1 within its TXOP (955) (920), and STA1 can send a BA (block ack) to the sharing AP in response to the reception of the DL PPDU (925).

[0128] Meanwhile, as previously explained, when the sharing AP decides to share at least some of its TXOPs with the shared AP, the sharing AP may transmit a MU-RTS TXS TF (trigger frame) to the shared AP to indicate the start (or initiation) of C-TDMA (930). Although FIG. 9 illustrates an embodiment in which the sharing AP transmits the MU-RTS TXS TF to one shared AP, the sharing AP may transmit the MU-RTS TXS TF to one or more shared APs (i.e., a set of APs). Upon receiving the MU-RTS TXS TF, the shared AP may transmit a CTS frame to the sharing AP to indicate that it has confirmed the start (or initiation) of C-TDMA (935), and may transmit a DL (MU) PPDU to STA2, a non-AP STA coupled to it, within the time resources (960) allocated to it (940). Meanwhile, the time resource (960) allocated to the Shared AP may be indicated by the allocation duration field of the previously described MU-RTS TXS TF (930). The STA2 may transmit a BA to the shared AP in response to the received DL (MU) PPDU (945). The Sharing AP monitors the TXOP and, upon confirming that there is no data transmission or reception during the PIFS, can reclaim the TXOP that was shared with the shared AP, and accordingly, transmit a basic TF within its own TXOP (960) to perform a separate transmission and reception procedure. The C-TDMA described in FIG. 9 is distinguished from the existing procedure of sharing TXOPs between an AP and a non-AP STA in that it shares TXOPs between APs.

[0129] FIG. 10 illustrates an exemplary structure of a frame for TXOP (transmission opportunity) sharing (TXOP sharing, TXS) related to the present disclosure.

[0130] Figure 10 illustrates an exemplary format structure of the MU-RTS TXS TF described in Figure 9. The MU-RTS TXS TF may indicate a MU-RTS frame where the value of the trigger type subfield (1010) of the trigger frame is 3, and the B20-B21 bits of the HE or EHT variant Common Info field are used as the TXS mode subfield.

[0131] FIG. 11 is a drawing illustrating the meaning represented by a specific field included in a frame for TXOP sharing related to the present disclosure.

[0132] The table shown in FIG. 11 indicates the meaning represented by the value of the TXS mode subfield described in FIG. 10, where the value of the TXS mode subfield is 0, it indicates that the MU-RTS frame does not initiate the TXS procedure; where the value of the TXS mode subfield is 1, it indicates that the MU-RTS frame initiates the TXS procedure and the scheduled STA can transmit the MPDU only to the AP connected to it; where the value of the TXS mode subfield is 2, it indicates that the MU-RTS frame initiates the TXS procedure and the scheduled STA can transmit the MPDU to the AP connected to it and to other STAs; and where the value of the TXS mode subfield is 3, it may be reserved.

[0133] FIG. 12 illustrates an exemplary format structure of a specific field included in a frame for TXOP sharing related to the present disclosure.

[0134] FIG. 12 illustrates an exemplary structure of a User Info field included in a MU-RTS TXS TF, FIG. 12 (a) illustrates the format structure of a HE variant User Info field included in a MU-RTS TXS TF, and FIG. 12 (b) illustrates the format structure of an EHT variant User Info field included in a MU-RTS TXS TF.

[0135] The User Info field of the MU-RTS TXS TF may include an AID12 field to indicate the AID of the AP or non-AP STA to which the MU-RTS TXS TF will be transmitted, a RU allocation field to indicate the radio resource to which the CTS will be transmitted in response to the MU-RTS TXS TF, an allocation duration field to indicate the length of the time resource to be shared within the TXOP, reserved bits, and a PS160 field.

[0136] FIG. 13 illustrates an exemplary format structure of a frame for responding to a TXOP sharing related to the present disclosure.

[0137] Figure 13 describes the detailed format structure of a multi-STA block ack (M-BA) frame. An M-BA frame may be a type of control frame and may include a frame control field, a duration field, a receiving address (RA) field, a transmitter address (TA) field, a block ack control field, a BA information field, and a frame check sequence (FCS) field. The BA information field includes a per AID TID information field<AID, TID> It may be included in each tuple. A single Per AID TID information field may include an AID TID information field, a Block ack starting sequence control field, and a Block ack bitmap field. The AID TID information field may include an AID11 field, an Ack Type field, and a TID field.

[0138] FIG. 14 is a diagram illustrating the meaning represented by a specific field included in a frame for responding to a TXOP sharing related to the present disclosure.

[0139] According to one embodiment, a specific value of the AID11 field included in the M-BA frame illustrated in FIG. 13 may be pre-specified for control extension. Values ​​of 1 to 2006 may be used for the AID11 field to indicate the AID, and values ​​of 2008 to 2042 may be reserved. Meanwhile, by assigning a specific value to the TID field of the Ack Type field (for example, by assigning the value of the Ack Type field to 0 or 1 and the value of the TID field to 8 to 13, as in 1410 of FIG. 14), the M-BA frame may be utilized for a specific purpose within the control extension.

[0140] FIG. 15 illustrates the configuration of a primary channel and a secondary channel of a wireless LAN system related to the present disclosure.

[0141] In standard specifications such as IEEE 802.11a / g / n / ac / ax / be, channels for transmission can be configured with various bandwidths (e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 320 MHz). FIG. 15 illustrates an exemplary configuration of a channel in which the operating bandwidth of an AP is 80 MHz. In the illustrated example, the operating bandwidth may include a primary 20 MHz (1510), a secondary 20 MHz (1520) adjacent to the primary 20 MHz (1510), and a secondary 40 MHz (1530). At this time, if the primary 20 MHz (1516) for accessing a broadband channel (e.g., a channel with a bandwidth greater than 20 MHz) is idle and the primary channel is being used by another AP, the AP cannot transmit using the idle secondary channel.

[0142] For example, if a PPDU is transmitted on the primary 20 MHz (1510) by another AP (e.g., an AP in another BSS), the AP in the BSS cannot transmit using the remaining secondary channels (e.g., secondary 20 MHz (1520) and secondary 40 MHz (1530)). In this case, the situation where the primary channel (e.g., primary 20 MHz (1510)) is used by the transmission of PPDUs from another AP or a STA associated with another AP may be referred to as interference or overlapping basic service set (OBSS) transmission. Additionally, PPDUs from another AP or a STA associated with another AP on the primary channel may be referred to as OBSS PPDUs. As another example, if a PPDU from another AP is transmitted on the 40 MHz including the primary 20 MHz (1510), the AP cannot transmit using the secondary 40 MHz (1530). That is, APs and non-AP STAs within the BSS can transmit and / or receive PPDUs only in the time domain of the primary channel where the OBSS does not exist.

[0143] FIG. 16 illustrates the configuration of a primary channel and a secondary channel of a wireless LAN system related to the present disclosure.

[0144] Referring to FIG. 16, when a primary channel (e.g., primary 20 MHz (1610)) is in use by another AP as in FIG. 15 and a secondary channel (e.g., secondary 20 MHz (1620) and / or secondary 40 MHz (1630)) is available, the AP and non-AP STA can perform transmission and / or reception on the available secondary channel. For example, if an OBSS PPDU of 20 MHz exists on the primary channel, the AP and non-AP STA can transmit and / or receive the PPDU on the secondary channel (e.g., secondary 20 MHz (1620) and secondary 40 MHz (1630)). Additionally, even when an OBSS PPDU of 40 MHz exists on the primary channel, the AP and non-AP STA may transmit and / or receive the PPDU on the secondary channel (e.g., secondary 40 MHz (1630)). In this case, the AP and non-AP STA may be allowed to transmit and / or receive the PPDU using the secondary channel only in the time region occupied by the OBSS PPDU, based on the time information occupied by the OBSS PPDU.

[0145] As such, the transmission and / or reception process using a secondary channel can be referred to as NPCA (non-primary channel access). For example, NPCA may refer to the transmission and reception of data on a continuous secondary channel (or NPC (non-primary channel)) excluding the bandwidth used by OBSS from the AP's operating bandwidth.

[0146] FIG. 17 is a drawing that specifically describes the NPCA in a wireless LAN system related to the present disclosure.

[0147] Referring to FIG. 17, when the operating bandwidth of the AP is 160 MHz, the operating bandwidth may include a primary 80 MHz (hereinafter P80) and a secondary 80 MHz (hereinafter S80). In this case, when OBSS transmission (e.g., OBSS PPDU by another AP) uses P80, NPCA may be performed. For example, a non-AP STA or AP may receive an RTS frame from an OBSS AP or an OBSS non-AP STA while participating in contention on a primary channel of 20 MHz (P20). The OBSS non-AP STA or OBSS AP that receives the RTS frame may transmit a CTS frame in response to the RTS frame, and the non-AP STA or AP that receives the CTS frame may set a Basic NAV by referring to the duration field of the RTS frame and / or the CTS frame. In this case, the basic NAV may be the time required for virtual carrier sensing to protect the transmission of the PPDU of the STA that has secured the TXOP. A non-AP STA or AP may determine the NPCA duration based on the basic NAV. The NPCA duration may be set to be shorter than the basic NAV by the switching delay (or switching latency). The switching delay may refer to the time taken to change channels to perform contention on a transmittable secondary channel during the process of performing NPCA. Meanwhile, the RTS frame and CTS frame associated with the OBSS non-AP STA or OBSS AP described above may be referred to as the OBSS RTS frame and the OBSS CTS frame, respectively.

[0148] As described, when the NPCA duration is established based on the transmission of OBSS RTS and / or CTS frames, the AP performing NPCA (hereinafter referred to as NPCA AP) and the non-AP STA performing NPCA (hereinafter referred to as NPCA non-AP STA) may have the same basic NAV. The NPCA AP may refer to an AP capable of performing NPCA or an AP currently performing NPCA. The NPCA non-AP STA or NPCA STA may refer to a non-AP STA capable of performing NPCA or a non-AP STA currently performing NPCA. Within the NPCA duration, data between the NPCA AP and the NPCA non-AP STA may be transmitted and / or received through a secondary channel. On the other hand, if OBSS transmission uses the entire operating bandwidth of the NPCA AP, data transmission and reception via NPCA may not be performed during the OBSS transmission period because there is no secondary channel for transmitting and receiving data.

[0149] FIG. 18 is a diagram illustrating an NPCA in a wireless LAN system related to the present disclosure.

[0150] Referring to FIG. 18, specific operations of an NPCA AP and an NPCA non-AP STA (or NPCA STA) for transmitting and receiving data by performing NPCA are described in chronological order. For example, the NPCA AP below may have an operating bandwidth of 160 MHz (e.g., including P80 and S80), and the NPCA STA(s) may have an operating bandwidth of 80 MHz or 160 MHz.

[0151] In the embodiment of FIG. 18, NPCA non-AP STAs may participate in contention and attempt to access the primary channel (e.g., P80). While participating in contention on the primary channel 80 MHz (P80), the NPCA non-AP STAs or NPCA AP may receive (or detect) an ICF (e.g., OBSS ICF (1805)) from the OBSS AP or OBSS STA. In this case, the ICF may be a control frame for initiating a TXOP or sequence. A basic NAV may be established based on the ICF. Additionally, the OBSS non-AP STA or OBSS AP that received the ICF may transmit an ICR (e.g., OBSS ICR (1810)) to the OBSS AP or OBSS non-AP in response to the ICF. At this time, the ICR may be a control frame for confirming a TXOP or sequence or for transmitting a response required by the ICF. As the OBSS AP or OBSS non-AP STA transmits the ICR, the previously set Basic NAV may be maintained. Accordingly, the NPCA AP and NPCA non-AP STA may determine the NPCA duration based on the Basic NAV. At this time, the NPCA duration associated with the NPCA AP may be set shorter than the Basic NAV by the switching delay (or switching latency). This is because the NPCA AP that has returned to the primary channel may require time (1860) to rejoin the contention after the OBSS ends. Additionally, the NPCA duration associated with the NPCA non-AP STA may be set shorter than the Basic NAV by the switching delay. This is because NPCA non-AP STAs may require time (1855) to switch from a secondary channel (e.g., S80) to a primary channel (e.g., P80).However, when the NPCA non-AP STAs have an operating bandwidth of 80 MHz, the NPCA duration may require a larger switching delay (1855) than in the case of an operating bandwidth of 160 MHz. This may be because the bandwidth in which the NPCA non-AP STAs perform NPCA is not the operating bandwidth (80 MHz) of the NPCA non-AP STAs, and therefore more time is required for the NPCA non-AP STAs to return to the primary channel after the NPCA is terminated.

[0152] The NPCA AP can receive the preamble (1815) of the OBSS PPDU. Additionally, the NPCA AP can set the duration of the NPC TXOP (1800) through the preamble to the end of the OBSS PPDU. In the following, the NPC TXOP (1800) may refer to a TXOP in which NPCA is performed. The NPCA AP can perform EDCA contention on an anchor channel (1820). At this time, the anchor channel in which EDCA contention is performed may be included in a non-primary channel (NPCH). An NPCH may refer to all channels capable of performing NPCA among secondary channels that do not overlap with OBSS transmission, and the anchor channel may include a 20 MHz channel among the NPCH that participates in contention for transmission. And the NPCA AP can send a trigger frame (1825) to NPCA non-AP STAs, and the NPCA non-AP STA(s) can send a response frame (1830) to the NPCA AP for the trigger frame. At this time, the NPCA AP can identify the NPCA non-AP STA(s) to perform NPCA based on the response frame (1830). Accordingly, the NPCA AP can perform scheduling to perform downlink transmission including a MU (multi-user) PPDU (1835) (e.g., NPCA MU PPDU) within an NPC TXOP (1800) based on the response frame (1830), but can also perform scheduling to have the NPCA non-AP STA(s) transmit uplink data. And the NPCA non-AP STA(s) can send a block ACK (block-ACK, BA) (1840) for the transmission of downlink data (1835) of the NPCA AP to the NPCA AP. Afterwards, multiple data exchanges (1845) between the NPCA AP and the NPCA non-AP STA(s) can continue within the NPC TXOP (1800).Accordingly, the NPCA AP may transmit a BA (1850) for the uplink transmission of the NPCA non-AP STA(s) to the NPCA non-AP STA(s). Afterwards, there may be an OBSS BA transmission for the OBSS PPDU transmission on the primary channel (e.g., P80). Then, at the time when the OBSS BA's primary channel occupation ends, the NPCA AP and the NPCA non-AP STA(s) may return to the primary channel.

[0153] Meanwhile, in order for the operations related to the aforementioned NPCA to be performed smoothly, the NPCA AP needs to obtain information regarding NPCA non-AP STAs to perform NPCA (e.g., NPCA feedback information). For example, the NPCA feedback information may include capability information of NPCA non-AP STAs to perform NPCA, information regarding the operating bandwidth of NPCA non-AP STAs, information regarding the band or channel (e.g., secondary channel) to perform NPCA, information regarding the NPCA duration of NPCA non-AP STAs, etc. Based on NPCA feedback from NPCA non-AP STAs, the NPCA AP can perform scheduling for transmitting and / or receiving data within an NPC TXOP.

[0154] In the following, signaling procedures and frame structures related to operations for AP and non-AP STA to perform NPCA considering TXOP sharing (TXS) according to the embodiments proposed in the present disclosure are described in detail.

[0155] FIG. 19 illustrates an exemplary structure of the format of a specific field included in a frame for TXOP sharing related to the present disclosure. FIG. 19 describes an exemplary format structure of an ICF transmitted by a sharing AP, which is an AP that shares its TXOP with another AP, to another AP, a shared AP (or polled AP), to indicate that it is sharing a portion of the time resources of the TXOP.

[0156] The ICF transmitted by the sharing AP may include information to indicate a portion of the time resources of a TXOP to be used by the shared AP (or, polled AP), and the ICF according to one embodiment may include parameters to indicate the intention of the sharing AP to share the TXOP (i.e., to poll C-TDMA) according to the process described above. In the illustrated embodiment, the ICF may include an AID12 field (1910) indicating the AID of the shared AP, a RU allocation field (1920) indicating the RU to transmit the ICR which is a response to the ICF, an allocation duration field (1930) indicating the length of the time resources to be shared via TXS, a start time field (1940) indicating the starting position of the time resources to be shared via TXS, and a PS160 field (1960) to distinguish the 160 MHz channel, and some bits of the ICF may be reserved (1950).

[0157] According to one embodiment, the Sharing AP may include the AID of the shared AP to which the TXOP is to be shared in the AID12 field (1910), which may mean that the sharing AP knows the AID of the shared AP in advance in a situation where the exchange and agreement of AIDs between APs have been made in advance.

[0158] According to one embodiment, an ICF for a sharing AP to notify the sharing of a TXOP (i.e., TXS) may include a BSRP (buffer status report poll) trigger frame. This is because, unlike when a TB PPDU is requested or solicited when a BSRP trigger frame requests or solicits a non-HT (duplicate) PPDU, various fields included in the User Info field of the BSRP trigger frame are reserved, and thus can be utilized for the purpose of sharing a TXOP as proposed in this disclosure.

[0159] According to the above-described embodiment, when a BSRP trigger frame soliciting a non-HT (duplicate) PPDU is utilized as an ICF for sharing a TXOP (or for polling for C-TDMA), the User Info field of the BSRP trigger frame may be configured to include the fields described above as illustrated in FIG. 19. The format structure illustrated in FIG. 19 differs from the format structure of the MU-RTS TXS TF described in FIG. 12 in that it includes an additional start time field (1940). Although the example in FIG. 19 illustrates an example where the start time field (1940) is 9 bits, the start time field (1940) may be configured as 10 bits including an additional reserved 1 bit.

[0160] The start time field (1940) of FIG. 19 may indicate the start time (or, start position) of a specific length of time interval indicated by the allocation duration field (1930) within the TXOP. The start time indicated by the start time field (1940) may refer to the time length from the time when the ICF ends until the time when the shared AP within the TXOP can start using the TXOP. Alternatively, the start time indicated by the start time field (1940) may refer to the time length from the time when the ICF starts (i.e., the time when the TXOP starts) until the time when the shared AP within the TXOP can start using the TXOP. Depending on the number of bits used to indicate the aforementioned time length within the start time field (1940), the resolution of the time length expressed may vary, which means that the more bits used to indicate the time length, the more detailed the start time (or, start position) can be indicated.

[0161] Meanwhile, although an embodiment in which the AID12 field (1910) of FIG. 19 includes the AID of a shared AP has been described above, the AID12 field (1910) may also include the AID of a non-AP STA. In other words, when a BSRP trigger frame is used as an ICF to notify TXOP sharing, each of the multiple User Info fields included within a single BSRP trigger frame may include parameters for notifying TXOP sharing to a shared AP (or polled AP). Meanwhile, when the AID12 field (1910) included in the BSRP trigger frame includes the AID of a non-AP STA, the corresponding User Info field may not only include parameters for notifying TXOP sharing to a non-AP STA, but may also include parameters for the operation of a general BSRP trigger frame (i.e., BSR polling).

[0162] Although an embodiment in which a BSRP trigger frame is utilized as an ICF to notify the sharing of a TXOP (or to poll C-TDMA) has been described above, according to another embodiment, a MU-RTS trigger frame may be utilized as an ICF to notify the sharing of a TXOP. When a MU-RTS trigger frame is utilized as an ICF, some of the reserved bits of the format structure described above in FIG. 12 may be utilized as a start time field. The format structure of the MU-RTS trigger frame according to this embodiment may also be similar to the form shown in FIG. 19, provided that the number of bits in the start time field may differ from that of the illustrated embodiment.

[0163] Additionally, when a MU-RTS trigger frame is utilized as an ICF, the AID12 field of the MU-RTS trigger frame may include the AID of a combined STA (non-AP STA) instead of the AID of a shared AP (or polled AP). According to this embodiment, a single MU-RTS trigger frame may include multiple User Info fields, and each User Info field may include parameters for a combined STA or parameters for a shared AP (or polled AP). According to another embodiment, when a MU-RTS trigger frame includes parameters for a non-AP STA, these parameters may include parameters for general MU-RTS operations as well as parameters for indicating TXOP sharing.

[0164] FIGS. 20 and 21 illustrate exemplary structures of the format of specific fields included in a frame for responding to TXOP sharing related to the present disclosure. FIGS. 20 and 21 respectively describe exemplary format structures of an ICR for a shared AP (or polled AP) to respond to the sharing AP after the shared AP has obtained information about a shared TXOP.

[0165] Such an ICR may include information regarding whether the shared AP (or polled AP) will accept or reject information or a proposal received from the sharing AP to announce the sharing of a TXOP. Additionally, the ICR may include alternative information if the shared AP (or polled AP) suggests a different alternative. Furthermore, the ICR may also include information related to NPCA if the shared AP (or polled AP) and the combined STA intend to perform NPCA. Below, examples of the format structure of an ICR containing such various information or parameters are described in FIGS. 20 and FIGS. 21, respectively.

[0166] FIG. 20 illustrates a format structure in which an M-BA frame is utilized as an ICR for a shared AP (or polled AP) to respond to a sharing AP. In accordance with the embodiment described in FIG. 19, when the ICF indicates the length of the time interval and the start position of the TXOP to be shared with the AID of the shared AP (or polled AP), the shared AP (or polled AP) determines whether to accept, reject, or propose an alternative to the shared TXOP, which is the time interval identified by the combination of the time length and the start position, and can include information regarding the result in the ICR and transmit it to the sharing AP.

[0167] According to one embodiment, a shared AP (or polled AP) may decide not to accept (i.e., reject) a shared TXOP from a sharing AP. This decision may be due to various reasons, such as when the shared AP (or polled AP) has no available DL BU (bufferable unit) and the UL buffer is empty during the time interval in which the TXOP is shared by the sharing AP (e.g., when there is no UL buffer reported by a non-AP STA or when there is no scheduled UL scheduling), or when the shared AP (or polled AP) cannot participate in transmission due to power saving or in-device coexistence (IDC) during the time interval in which the TXOP is shared by the sharing AP. In such cases, the shared AP (or polled AP) may determine that the shared TXOP from the sharing AP is inappropriate and may implicitly reject the sharing AP's proposal by not transmitting an ICR. According to this embodiment, when a BSRP trigger frame is utilized as an ICF, the shared AP (or polled AP) may not transmit a BSR in response to the ICF, and when a MU-RTS trigger frame is utilized as an ICF, the shared AP (or polled AP) may not transmit a CTS in response to the ICF.

[0168] According to one embodiment, even if the shared AP (or, polled AP) decides not to accept (i.e., reject) a shared TXOP from the sharing AP, the shared AP (or, polled AP) may send an ICR to the sharing AP to explicitly notify the result of the decision.

[0169] The following describes in detail cases where a shared AP (or polled AP) transmits an ICR to reject, accept, or propose an alternative to a shared TXOP. If a BSRP trigger frame is used as an ICF, the shared AP (or polled AP) may transmit an M-BA frame as an ICR, and such an M-BA frame may contain various parameters or information described below. If a MU-RTS trigger frame is used as an ICF, the shared AP (or polled AP) may transmit a CTS frame as an ICR, and the transmission of such a CTS frame itself may signify an acceptance of the shared TXOP.

[0170] In the embodiment of FIG. 20, an embodiment in which an M-BA frame is utilized as an ICR is described. Among the various values ​​that can be indicated by the AID11 field (2040) included in the M-BA frame, a specific value may be assigned as a value to indicate a control extension. Additionally, through a combination of the value indicated by the Ack Type field (2050) included in the M-BA frame and the value indicated by the TID field (2060), it may be expressed that the Block Ack Bitmap field (2030) included in the M-BA frame contains C-TDMA related feedback information.

[0171] For a specific example, among the values ​​indicated by the AID11 field (2040), a value such as 2009 may be assigned to indicate control extension, and if the value of the Ack Type field (2050) is 0 and the value of the TID field (2060) is 12, the Block Ack Bitmap field (2030) may contain C-TDMA feedback information. For another example, if the AID11 field (2040) contains the AID11 of the sharing AP or the AID11 of the shared AP, and the value of the Ack Type field (2050) is 0 and the value of the TID field (2060) is 9, the Block Ack Bitmap field (2030) may contain C-TDMA feedback information.

[0172] According to one embodiment, the Block Ack Bitmap field (2030) may further include information related to various other wireless access technologies (e.g., NPCA, DPS (dynamic power save), IDC (in-device coexistence), etc.) along with C-TDMA feedback information. For example, if the AID11 field (2040) indicates a value for control extension (e.g., 9), and the value of the Ack Type field (2050) is 0 and the value of the TID field (2060) is 13, the Block Ack Bitmap field (2030) may further include NPCA-related information along with C-TDMA feedback information. As another example, if the AID11 field (2040) represents a value for control extension (e.g., 9), the value of the Ack Type field (2050) is 1, and the value of the TID field (2060) is 13, the Block Ack Bitmap field (2030) may additionally include DPS-related information along with C-TDMA feedback information. In this embodiment, the values ​​of each field are merely exemplary values, so any other values ​​or combinations of values ​​may be used.

[0173] Meanwhile, in FIG. 20, the Block Ack Starting Sequence Control field (2020) may include a Fragment number field (2070) and a Starting Sequence Number field (2080) to indicate the size of the Block Ack Bitmap field (2030). According to one embodiment, the Starting Sequence Number field (2080) may include AID11 or AID12 of a shared AP, or AID11 or AID12 of a sharing AP. The Block Ack Bitmap field (2030) may include C-TDMA feedback information according to the previously described embodiment, and the specific format structure of the Block Ack Bitmap field (2030) is described in detail in FIG. 22.

[0174] In the embodiment of FIG. 21, another embodiment in which an M-BA frame is utilized as an ICR is described. In the format structure according to the embodiment of FIG. 21, each field may represent information or parameters different from the format structure according to the embodiment described in FIG. 20.

[0175] In the example of FIG. 21, the AID11 field (2140) may include a partial AID of the sharing AP, which is the ICF sender, and the Starting Sequence Number field (2180) may indicate that the M-BA frame corresponds to a C-TDMA feedback type. In other words, when the AID11 field (2140) includes a partial AID of the sharing AP and the Starting Sequence Number field (2180) indicates a C-TDMA feedback type, the Block Ack Bitmap field (2130) may include C-TDMA feedback information. The specific format structure of the Block Ack Bitmap field (2130) according to this embodiment is described in detail in FIG. 22.

[0176] FIG. 22 illustrates an exemplary structure of the format of a specific field included in a frame for responding to a TXOP sharing related to the present disclosure.

[0177] The C-TDMA feedback information illustrated in FIG. 22 may be included in the Block Ack Bitmap field (2030 or 2130) of the ICR, i.e., the M-BA frame, described previously in FIG. 20 and FIG. 21. The C-TDMA feedback information may include 0, 4, 8, 16, 32, 64, or 128 bytes, and the C-TDMA feedback information includes a response field (2210), an alternate allocation duration field (2220), an alternate start time field (2230), a channel field (2240), and an NPCA field (2250), and some bytes may be reserved (2260).

[0178] If the size of the C-TDMA feedback information is 0 bytes, the Starting Sequence Number field (2080, 2180) may include only 1 bit indicating an acknowledgment for acknowledging the reception of the ICF. Meanwhile, according to another embodiment, as another method for indicating an acknowledgment for acknowledging the reception of the ICF, at least some of the 12 bits of the Starting Sequence Number field (2180) described in FIG. 21 may be utilized.

[0179] In the following, when the size of the C-TDMA feedback information is 4 bytes or more, each field included in the C-TDMA feedback information is described. The Response field (2210) may indicate the result of the response of the shared AP (or polled AP) to the TXOP shared by the sharing AP (e.g., rejection, acceptance, presentation of an alternative, etc.). For example, if the response field (2210) contains 2 bits and the value is 0, it may indicate rejection of the shared TXOP (i.e., not using the shared TXOP); if the response field (2210) contains 2 bits and the value is 1, it may indicate acceptance of the shared TXOP (i.e., using the shared TXOP); and if the response field (2210) contains 2 bits and the value is 2, it may indicate partial acceptance of the shared TXOP (or presentation of an alternative). The value of the response field (2210) and the result shown above are merely examples, and the corresponding relationship can be changed at any time.

[0180] If the value of the Response field (2210) indicates partial acceptance (or alternative proposal), at least one of the alternate allocation duration field (2220) or the alternate start time field (2230) may have a value different from at least one of the allocation duration field or the alternate start time field included in the ICF from the sharing AP. For example, if the shared AP wishes to propose a different time length instead of the time length indicated by the allocation duration field included in the ICF, the alternate allocation duration field (2220) included in the ICR may have a value different from the value of the allocation duration field included in the ICF. As another example, if the shared AP wishes to propose a different time position instead of the time position indicated by the start time field included in the ICF, the alternate start time field (2230) included in the ICR may have a value different from the value of the start time field included in the ICF. In this way, through the combination of the alternate allocation duration field (2220) and the alternate start time field (2230), a time interval of a different length and / or a different location from the time interval of the TXOP shared by the sharing AP can be proposed by the shared AP.

[0181] Meanwhile, the time interval alternatively proposed by the shared AP through at least one of the two fields (2220, 2230) may be equal to or shorter than the shared TXOP indicated by the sharing AP through the ICF. In other words, the shared AP may not be able to request a TXOP longer than the length proposed by the sharing AP. Accordingly, the value of the alternate allocation duration field (2220) transmitted by the shared AP may be equal to or smaller than the value of the allocation duration field transmitted by the sharing AP to the ICF.

[0182] According to one embodiment, if the shared AP proposes a different time interval through at least one of the two fields (2220, 2230), the sharing AP may share the TXOP in the time interval proposed by the shared AP without additional confirmation / acknowledgment. Alternatively, if the shared AP proposes a different time interval through at least one of the two fields (2220, 2230) but the sharing AP does not wish to accept the proposed time interval, the sharing AP may not transmit a MU-RTS TXS trigger frame at a time corresponding to the time interval proposed by the shared AP.

[0183] The Channel field (2240) may indicate the bandwidth that the shared AP will use within the shared TXOP. The value of the Channel field (2240) may include a value encoded based on the primary channel of the shared AP, for example, a value of 0 of the 3-bit channel field (2240) may indicate a primary 20 MHz, a value of 1 may indicate a primary 40 MHz, a value of 2 may indicate a primary 80 MHz, a value of 3 may indicate a primary 160 MHz, and a value of 7 may indicate all the bandwidth guaranteed by the sharing AP.

[0184] The NPCA field (2250) may indicate whether the shared AP (or polled AP) performs NPCA in the interval excluding the time interval shared by the sharing AP within the TXOP. For example, if the NPCA field (2250) contains 1 bit and the value is 0, the shared AP may indicate that it does not perform NPCA within the TXOP, and if the NPCA field (2250) contains 1 bit and the value is 1, the shared AP may indicate that it can perform NPCA in the interval excluding the time interval shared by the sharing AP within the TXOP. Of course, the correspondence between the value of the NPCA field (2250) and the meaning it represents can vary.

[0185] According to one embodiment, if the NPCA field (2250) indicates that the shared AP performs NPCA, the shared AP may not be able to allocate additional time resources to the shared AP in the remaining time interval excluding the shared time interval within the TXOP (e.g., at a time earlier than the shared time interval). This is because the shared AP is scheduled to perform NPCA and transmit / receive data in the remaining time interval.

[0186] Meanwhile, if the size of the C-TDMA feedback information is less than 4 bytes, the C-TDMA feedback information may be configured to include some of the various fields described in FIG. 22. For example, if the C-TDMA feedback information is configured to be less than 4 bytes, at least one of the response field (2210), alternate allocation duration field (2220), alternate start time field (2230), Channel field (2240), and NPCA field (2250) may be omitted, or the C-TDMA feedback information may be configured in a form where some of the bits included in a specific field are reduced.

[0187] FIG. 23 is a diagram illustrating an example of a procedure of NPCA considering TXOP sharing related to the present disclosure.

[0188] According to the embodiments described above, the sharing AP and the shared AP (or polled AP) can exchange parameters and / or information regarding the TXOP to be shared through the transmission and reception process of the ICF and ICR. Through the described procedure and frame format structure, the sharing AP can share some time resources of the TXOP with the shared AP, and the shared AP can perform transmission and reception within the shared TXOP.

[0189] Meanwhile, the shared AP can determine the time interval during which it can perform NPCA as the shared TXOP provided by the sharing AP is specified. For example, the shared AP may perform NPCA in the remaining time interval excluding the shared TXOP provided by the sharing AP within the total TXOP.

[0190] According to the proposed embodiment, the conditions for triggering NPCA can be specified as follows. According to the existing NPCA triggering conditions, NPCA can be performed when the STA combined with the AP checks the TXOP of the OBSS. According to another existing NPCA triggering condition, NPCA can be performed when the STA combined with the AP checks that the duration for transmitting a predetermined packet is sufficiently long.

[0191] In addition to these NPCA triggering conditions, according to the proposed embodiment, NPCA may be performed in a time interval excluding the time during which TXS is performed within a TXOP in a C-TDMA situation. That is, since the shared AP performs channel access in a shared TXOP according to C-TDMA, it does not basically perform NPCA within the TXOP. However, the shared AP can know when and for how long the time interval of the shared TXOP provided by the sharing AP lasts by receiving an ICF. Therefore, the shared AP (or polled AP) can perform NPCA in a time interval excluding the shared TXOP within the entire TXOP.

[0192] According to one embodiment, for a Shared AP (or polled AP) to perform NPCA, the size of the total bandwidth through which the ICF is transmitted (i.e., the bandwidth used for the TXOP) may be smaller than the size of the operating bandwidth of the shared AP, and the total bandwidth through which the ICF is transmitted (i.e., the bandwidth used for the TXOP) may not overlap with the NPCA primary channel. For example, if a TXOP provided by the sharing AP uses an 80 MHz bandwidth and this 80 MHz bandwidth corresponds to the 80 MHz primary channel of the shared AP, the shared AP and the non-AP STA coupled to the shared AP can perform NPCA using the secondary channel 80 MHz. Bandwidth information for such a shared TXOP may be included in the ICF described above and transmitted to the shared AP.

[0193] The fact that a non-AP STA coupled to a shared AP can perform NPCA together with the shared AP is that the non-AP STA coupled to the shared AP can determine from the ICR transmitted to the sharing AP whether the shared AP accepts, rejects, or proposes an alternative to the shared TXOP. In other words, when the shared AP, having received an ICF from the sharing AP, transmits an ICR containing information on whether the shared TXOP is accepted and C-TDMA feedback information or parameters, the non-AP STA coupled to the shared AP can also receive the ICR to verify the shared AP's response to the shared TXOP. Accordingly, the non-AP STA coupled to the shared AP can determine the time interval and time location of the shared TXOP, and based on this, the non-AP STA coupled to the shared AP can also decide to perform NPCA within the time interval excluding the shared TXOP. Thus, among the non-AP STAs coupled to the shared AP, a non-AP STA that performs NPCA by receiving an ICR from the shared AP is referred to as an NPCA non-AP STA.

[0194] Specific embodiments related to the execution of NPCA by an NPCA non-AP STA are further explained below. As previously explained, an NPCA non-AP STA can perform NPCA by receiving an ICR from a shared AP; below, the specific operation of the NPCA non-AP STA is described according to the situations indicated by the results of the ICR from the shared AP.

[0195] First, regarding the ICF, ICR, or ICF / ICR exchange process received by the NPCA non-AP STA, if the AP coupled to it is not involved in it, the NPCA non-AP STA can perform the NPCA non-AP STA according to existing trigger conditions and procedures. That is, the NPCA non-AP STA can perform the NPCA in a manner similar to when a TXOP is detected by OBSS.

[0196] Next, if the ICF received by the NPCA non-AP STA contains C-TDMA information (or information about a shared TXOP) for the shared AP coupled to itself, but the shared AP coupled to itself has not transmitted an ICR (or if the NPCA non-AP STA has not received an ICR), the NPCA non-AP STA can perform NPCA as in the case where the sharing AP is an OBSS.

[0197] Next, if the ICF received by the NPCA non-AP STA contains C-TDMA information (or information about a shared TXOP) for the shared AP coupled to it, but the shared AP coupled to it transmits an ICR containing a response that it does not join the C-TDMA operation (or if the shared AP rejects the proposal for the shared TXOP), the NPCA non-AP STA can perform NPCA as in the case where the sharing AP is an OBSS.

[0198] Next, we describe the case where an NPCA non-AP STA receives an ICF containing C-TDMA information (or information about a shared TXOP) about the shared AP coupled to it and transmits an ICR containing a response that the shared AP coupled to it is participating in the C-TDMA operation (or the shared AP has accepted a proposal for a shared TXOP). The NPCA non-AP STA may perform an NPCA operation immediately upon receiving an ICR from the shared AP. The NPCA operation by the NPCA non-AP STA may be performed up to the moment immediately before the sharing AP transmits a MU-RTS TXS TF to notify the shared AP of the initiation of a shared TXOP.

[0199] Meanwhile, even in the case where the NPCA non-AP STA does not receive an ICF from the sharing AP and only receives an ICR transmitted by the shared AP, the NPCA non-AP STA can perform NPCA in the same manner as described above in the case where the shared AP transmits an ICR of the response participating in the C-TDMA operation.

[0200] As previously explained, in the process where an NPCA non-AP STA participates in C-TDMA (i.e., TXS), there may be cases where the time interval of a TXOP is not specified during the ICF / ICR exchange. For example, consider the case where the value of the duration / ID field in the MAC header of the ICR is set to 0. In such cases, the sharing AP can additionally specify the TXOP through a subsequent transmission process, and accordingly, the NPCA non-AP STA can determine the starting point of the time interval or the trigger point at which NPCA can be performed after receiving the subsequent transmission from the sharing AP.

[0201] The procedure illustrated in FIG. 23 will be described in detail below in chronological order. The Sharing AP indicates its intention to share a portion of the time resources within the TXOP it has secured, and this process can be accomplished by transmitting an ICF (2305) to the shared AP. As previously explained, the non-AP STA (STA2 in the figure) coupled with the shared AP may or may not transmit the ICF transmitted by the sharing AP. The non-AP STA (STA1 in the figure) coupled with the Sharing AP and the shared AP each transmit an ICR (2310, 2315) to respond to the ICF, and in particular, the shared AP transmits to the sharing AP the result of its decision on whether to participate in the TXS (i.e., C-TDMA) included in the ICR. The figure illustrates an embodiment in which the shared AP transmits the intention to participate in the TXS (i.e., the intention to approve the shared TXOP) included in the ICR. The sharing AP sends a DL (MU) PPDU to STA1 within the entire TXOP (2355) (2320), and STA1 sends a BA (2325) to the sharing AP in response to the PPDU.

[0202] Meanwhile, the shared AP can determine the time interval of the shared TXOP through ICF / ICR exchange with the sharing AP. That is, since the shared AP knows the time interval and start location of the shared TXOP, it can also determine the time interval excluding the shared TXOP for itself. Accordingly, the shared AP and the STA2 coupled to the shared AP can perform NPCA until the sharing AP actually transmits the MU-RTS TXS TF (2330) to indicate the initiation of the shared TXOP (2370).

[0203] As the C-TDMA (i.e., TXS) begins, the sharing AP transmits a MU-RTS TXS TF (2330) to the shared AP to signal the start of the shared TXOP (2360), and the shared AP transmits a CTS in response (2335). Subsequently, the shared AP transmits a DL (MU) PPDU within the shared TXOP (2360) assigned to it to the STA2 coupled to it (2340), and the STA2 can transmit a BA (2345) to the shared AP for response.

[0204] Afterward, as the shared TXOP (2360) allocated to the shared AP ends, the C-TDMA also ends, and the remaining shared TXOP allocated to the shared AP can be returned. The sharing AP can then perform additional transmission and reception during the remaining time interval of the entire TXOP (2355) by transmitting the basic TF (2350). Alternatively, the sharing AP can transmit DL MU PPDU according to the general TXOP operation during the remaining TXOP (2355) interval. Meanwhile, since the shared AP and STA2 know that a portion of the entire TXOP (2355) remains even after the shared TXOP (2360) ends, they can perform NPCA until the entire TXOP (2355) ends (2380).

[0205] FIG. 24 illustrates another example of an NPCA procedure considering TXOP sharing related to the present disclosure. Above, an embodiment in which an NPCA considering C-TDMA (i.e., TXS) is performed through an ICF / ICR exchange process between a sharing AP and a shared AP has been described. Meanwhile, FIG. 24 describes an embodiment in which an NPCA considering C-TDMA is performed through a MAP (multi AP) procedure rather than an ICF / ICR exchange.

[0206] In FIG. 24, a MAP coordination procedure may be performed between AP1, a sharing AP, and AP2 and AP3, which are shared APs (2410). The MAP coordination procedure may refer to a procedure for exchanging and coordinating settings or parameters for subsequent operations between APs in advance. According to one embodiment, through the MAP coordination procedure, whether the sharing AP can perform NPCA during C-TDMA (or TXS) operation may be determined or coordinated in advance with the shared AP. FIG. 24 illustrates a situation where the NPCA of AP2 is disabled and the NPCA of AP3 is enabled. When C-TDMA (or TXS) is performed between APs after the above-described MAP coordination (2410) process, AP2 cannot perform NPCA because the execution of NPCA in TXOP #1 (2420) and TXOP #2 (2430) is disabled, but AP3 can perform NPCA because the execution of NPCA in TXOP #1 (2420) and TXOP #2 (2430) is enabled (2470).

[0207] Meanwhile, as an additional MAP coordination (2440) process is performed thereafter, the NPCA of AP2 may be enabled and the NPCA of AP3 may be disabled during C-TDMA (or TXS) operation. Accordingly, AP2 performs NPCA because the execution of NPCA is enabled in TXOP #3 (2450) and TXOP #4 (2460) (2480), and AP3 cannot perform NPCA because the execution of NPCA is disabled in TXOP #3 (2450) and TXOP #4 (2460).

[0208] According to the embodiment of FIG. 24, since the sharing AP and the shared AP can consult and decide in advance whether to perform NPCA in the MAP coordination procedure, signaling for NPCA (e.g., ICF / ICR exchange, etc.) for each TXOP can be reduced.

[0209] Hereinafter, the operations of the sharing AP, shared AP (or polled AP), and non-AP STA according to the various embodiments described above will be explained in chronological order. In FIGS. 25, 26, and 27, the first AP may refer to the sharing AP of the embodiments described above, the second AP may refer to the shared AP (or polled AP) of the embodiments described above, and the non-AP STA may refer to the non-AP STA combined with the shared AP (or polled AP) of the embodiments described above.

[0210] FIG. 25 illustrates a flowchart of operations related to TXOP sharing of a first AP in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 25, some or all of the various embodiments described above may be applied identically or similarly to FIG. 25 regarding the process of the first AP (i.e., the sharing AP) transmitting and receiving parameters and information related to TXOP and NPCA.

[0211] In FIG. 25, the first AP transmits a first frame to notify the second AP of TXOP sharing (2510). The first frame may be an ICF containing the first AP's intention to share a portion of the time resources of its TXOP, and the first frame may include any one of various types of frames, such as a BSRP trigger frame or a MU-RTS trigger frame. Additionally, the first frame may include the AID of the second AP and information to indicate the time interval and start position of the shared TXOP provided by the first AP.

[0212] The first AP receives a second frame from the second AP to respond to the TXOP sharing (2520). The second frame may be an ICR transmitted by the second AP to respond to the first AP's ICF, and the second frame may include any one of various types of frames, such as an M-BA control frame or a CTS frame. Additionally, the values ​​of one or more fields included in the second frame, or combinations of values, may indicate that the second frame is C-TDMA feedback containing parameters related to whether the shared TXOP provided by the first AP is accepted. For example, the second frame may include parameters related to information regarding whether the second AP accepts, rejects, or suggests an alternative to the shared TXOP, and / or whether to perform NPCA in the interval excluding the shared TXOP.

[0213] The first AP transmits a third frame to the second AP to initiate the sharing of TXOPs (or to signal the start of C-TDMA) based on the second frame received from the second AP (2530), and this third frame may be a MU-RTS TXS TF. Subsequently, the first AP may receive a fourth frame from the second AP as a response to the third frame (2540), and this fourth frame may be a CTS frame.

[0214] Meanwhile, an example of the operation of the first AP (i.e., sharing AP) has been described above based on the flowchart illustrated in FIG. 25. However, it goes without saying that the operation of the first AP (i.e., sharing AP) may vary depending on other embodiments described above.

[0215] FIG. 26 illustrates a flowchart of operations related to TXOP sharing and NPCA of a second AP in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 26, some or all of the various embodiments described above may be applied identically or similarly to FIG. 26 regarding the process in which the second AP (i.e., a shared AP or a polled AP) transmits and receives parameters and information related to a TXOP and performs NPCA based thereon.

[0216] In FIG. 26, the second AP receives a first frame from the first AP to notify TXOP sharing (2610). The first frame may be an ICF containing the first AP's intention to share a portion of the time resources of its TXOP, and the first frame may include any one of various types of frames, such as a BSRP trigger frame or a MU-RTS trigger frame. Additionally, the first frame may include the AID of the second AP and information to indicate the time interval and start position of the shared TXOP provided by the first AP.

[0217] The second AP transmits a second frame to the first AP to respond to the TXOP sharing (2620). The second frame may be an ICR transmitted by the second AP to respond to the first AP's ICF, and the second frame may include any one of various types of frames, such as an M-BA control frame or a CTS frame. Additionally, the values ​​of one or more fields included in the second frame, or combinations of values, may indicate that the second frame is C-TDMA feedback containing parameters related to whether the shared TXOP provided by the first AP is accepted. For example, the second frame may include parameters related to information regarding whether the second AP accepts, rejects, or suggests an alternative to the shared TXOP, and / or whether to perform NPCA in the interval excluding the shared TXOP.

[0218] The second AP can determine the time interval and start position of the shared TXOP by exchanging the first frame and the second frame with the first AP. Through this, the second AP can determine the time interval excluding the shared TXOP within the entire TXOP, that is, the time interval in which NPCA can be performed. The second AP can perform NPCA in the determined time interval (the time interval excluding the shared TXOP) (2630), and the NPCA of the second AP can be performed until the transmission of the third frame to initiate the sharing of the TXOP from the first AP is made.

[0219] The second AP receives a third frame from the first AP to initiate the sharing of a TXOP (or to signal the start of C-TDMA) (2640), and this third frame may be a MU-RTS TXS TF. Subsequently, the second AP may transmit a fourth frame to the first AP as a response to the third frame (2650), and this fourth frame may be a CTS frame.

[0220] Meanwhile, an example of the operation of the second AP (i.e., shared AP or polled AP) has been described above based on the flowchart illustrated in FIG. 26. However, it goes without saying that the operation of the second AP (i.e., shared AP or polled AP) may vary depending on other embodiments described above.

[0221] FIG. 27 illustrates a flowchart of operations related to TXOP sharing and NPCA of a STA in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 27, some or all of the various embodiments described above may be applied identically or similarly to FIG. 27 regarding the process in which a non-AP STA performs NPCA based on parameters and information related to TXOP.

[0222] In FIG. 27, a non-AP STA receives a first frame from the first AP to announce the sharing of a TXOP (2710). The first frame may be an ICF containing the first AP's intention to share a portion of its TXOP time resources with the second AP, and the detailed description of the first frame may be the same or similar as that described in FIG. 25 and FIG. 26.

[0223] A non-AP STA receives a second frame to respond to a TXOP sharing from a second AP coupled to it (2720). The second frame may be an ICR transmitted by the second AP to respond to the ICF of the first AP, and a detailed description of the second frame may be applied in the same or similar way as described in FIG. 25 and FIG. 26 above. Meanwhile, a non-AP STA may not receive a first frame from the first AP and may only receive a second frame from the second AP coupled to it.

[0224] A non-AP STA can determine the time interval and start position of the shared TXOP provided by the first AP through the second frame from the second AP (or the first frame from the first AP and the second frame from the second AP). Through this, the non-AP STA can determine the time interval excluding the shared TXOP within the entire TXOP, that is, the time interval in which NPCA can be performed, in the same way as the second AP. Accordingly, the non-AP STA can perform NPCA in the determined time interval (the time interval excluding the shared TXOP) (2730), and the NPCA of the non-AP STA can be performed until the transmission of the third frame to initiate the sharing of the TXOP from the first AP is made.

[0225] Meanwhile, an example of the operation of the non-AP STA was described above based on the flowchart illustrated in FIG. 27. However, it goes without saying that the operation of the non-AP STA may vary depending on other embodiments described above.

[0226] Meanwhile, the present specification and drawings disclose preferred embodiments of the present disclosure. Although specific terms have been used, they are used merely in a general sense to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the disclosure, and are not intended to limit the scope of the present disclosure.

[0227] Furthermore, it is obvious to those skilled in the art that, in addition to the embodiments described in this disclosure, other variations based on the technical concept of this disclosure are possible. For example, some or all of the contents of one embodiment described above may be combined with some or all of one or more other embodiments, and such combination is also included in the embodiments proposed in this disclosure.

Claims

1. A method performed by a second access point (AP) of a wireless local area network (WLAN) system, A step of receiving a first frame from a first AP to notify the sharing of a TXOP (transmission opportunity) (TXOP sharing, TXS) of the first AP; The step of transmitting a second frame to the first AP to respond to the TXS; and Based on information instructing the use of non-primary channel access (NPCA) included in the second frame, the step of performing NPCA in a time interval is included. A method in which the second frame includes information about at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

2. In Paragraph 1, The first frame is an initial control frame (ICF) and includes an association identity (AID) field of the second AP, an allocation duration field for the TXS, and a starting time field for the TXS, and The second frame is an ICR (initial control response) and includes a response field related to whether the TXS is approved, and an NPCA field indicating whether to perform the NPCA in the section excluding the TXS. A method in which, if the above response field indicates partial acceptance, the second frame further includes at least one of an alternate allocation duration field or an alternate start time field.

3. In Paragraph 2, The above ICF includes either a BSRP (buffer status report poll) trigger frame or a MU-RTS (multi-user request to send) frame, and The above ICR includes either an M-BA frame or a CTS (clear to send) frame, and A method in which the first AP is a sharing AP associated with the TXS, and the second AP is a shared AP associated with the TXS.

4. In Paragraph 1, The time interval during which the above NPCA is performed is the interval excluding the interval during which the above TXS is performed within the TXOP of the first AP, and A method in which the above NPCA is performed after transmitting the above second frame and before the time of transmitting the third frame to indicate the initiation of the above TXS.

5. A method performed by a STA (station) of a wireless local area network (WLAN) system, A step of receiving a first frame from a first AP to notify the sharing of a TXOP (transmission opportunity) (TXOP sharing, TXS) of the first AP to a second AP; A step of receiving a second frame from the second AP to respond to the TXS; and Based on information instructing the use of non-primary channel access (NPCA) included in the second frame, the step of performing NPCA in a time interval is included. A method in which the second frame includes information about at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

6. In Paragraph 5, The first frame is an initial control frame (ICF) and includes an association identity (AID) field of the second AP, an allocation duration field for the TXS, and a starting time field for the TXS, and The second frame is an ICR (initial control response) and includes a response field related to whether the TXS is approved, and an NPCA field indicating whether to perform the NPCA in the section excluding the TXS. A method in which, if the above response field indicates partial acceptance, the second frame further includes at least one of an alternate allocation duration field or an alternate start time field.

7. In Paragraph 6, The above ICF includes either a BSRP (buffer status report poll) trigger frame or a MU-RTS (multi-user request to send) frame, and The above ICR includes either an M-BA frame or a CTS (clear to send) frame, and The first AP is a sharing AP associated with the TXS, and the second AP is a shared AP associated with the TXS, and The time interval during which the above NPCA is performed is the interval excluding the interval during which the above TXS is performed within the TXOP of the first AP, and A method in which the above NPCA is performed after receiving the above second frame and before the time of transmission of the third frame to indicate the initiation of the above TXS.

8. In a second access point (AP) of a wireless local area network (WLAN) system, transceiver; and It includes at least one processor connected to the above-mentioned transmitting and receiving unit, and The above at least one processor is: Receive a first frame from the first AP to notify the sharing of the first AP's TXOP (transmission opportunity) (TXOP sharing, TXS), and Transmit a second frame to the first AP to respond to the TXS, and Based on information instructing the use of non-primary channel access (NPCA) included in the second frame, it is set to perform NPCA in a time interval, and The second frame comprises information regarding at least one of a channel or bandwidth to be used within a TXOP according to the TXS, a second AP.

9. In Paragraph 8, The first frame is an initial control frame (ICF) and includes an association identity (AID) field of the second AP, an allocation duration field for the TXS, and a starting time field for the TXS, and The second frame is an ICR (initial control response) and includes a response field related to whether the TXS is approved, and an NPCA field indicating whether to perform the NPCA in the section excluding the TXS. If the above response field indicates partial acceptance, the second frame further includes at least one of an alternate allocation duration field or an alternate start time field, a second AP.

10. In Paragraph 9, The above ICF includes either a BSRP (buffer status report poll) trigger frame or a MU-RTS (multi-user request to send) frame, and The above ICR includes either an M-BA frame or a CTS (clear to send) frame, and The first AP is a sharing AP associated with the TXS, and the second AP is a shared AP associated with the TXS, wherein the second AP is a shared AP associated with the TXS.

11. In Paragraph 8, The time interval during which the above NPCA is performed is the interval excluding the interval during which the above TXS is performed within the TXOP of the first AP, and The second AP, wherein the above NPCA is performed after transmitting the above second frame and before the time of transmitting the third frame to indicate the initiation of the above TXS.

12. In a STA (station) of a wireless local area network (WLAN) system, transceiver; and It includes at least one processor connected to the above-mentioned transmitting and receiving unit, and The above at least one processor is: Receive a first frame from the first AP to notify the sharing of a TXOP (transmission opportunity) (TXOP sharing, TXS) of the first AP to the second AP, and Receive a second frame from the second AP to respond to the TXS, and Based on information instructing the use of non-primary channel access (NPCA) included in the second frame, it is set to perform NPCA in a time interval, and The second frame above is a STA that includes information about at least one of a channel or bandwidth to be used within a TXOP according to the TXS.

13. In Paragraph 12, The first frame is an initial control frame (ICF) and includes an association identity (AID) field of the second AP, an allocation duration field for the TXS, and a starting time field for the TXS, and The second frame is an ICR (initial control response) and includes a response field related to whether the TXS is approved, a channel field indicating the bandwidth in the TXS, and an NPCA field indicating whether to perform the NPCA in the interval excluding the TXS. If the above response field indicates partial acceptance, the STA further includes at least one of an alternate allocation duration field or an alternate start time field.

14. In Paragraph 13, The above ICF includes either a BSRP (buffer status report poll) trigger frame or a MU-RTS (multi-user request to send) frame, and The above ICR includes either an M-BA frame or a CTS (clear to send) frame, and STA, wherein the first AP is a sharing AP associated with the TXS, and the second AP is a shared AP associated with the TXS.

15. In Paragraph 12, The time interval during which the above NPCA is performed is the interval excluding the interval during which the above TXS is performed within the TXOP of the first AP, and The above NPCA is performed after receiving the above second frame and before the time of transmission of the third frame to indicate the initiation of the above TXS, STA.

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