Method and device for performing TXOP sharing accompanied with DSO 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, the method comprising the steps in which: a first AP transmits, to a second AP, a first frame for notifying the second AP of an intention to share a TXOP; the first AP transmits, to the second AP, a second frame for initiating sharing of the TXOP; the first AP transmits, to an STA associated with the first AP, a third frame for triggering a DSO; and the first AP exchanges frames on an SCH within the TXOP on the basis of the DSO.

Description

Method and apparatus for performing TXOP sharing accompanied by DSO 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 performing transmission opportunity (TXOP) sharing accompanied by dynamic subband operation (DSO) 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 TXOP sharing (TXS) through (or accompanied by) dynamic subband operation (DSO) in a wireless LAN system. In particular, the present disclosure proposes a method and apparatus for effectively performing TXS in a coordinated time division multiple access (C-TDMA) situation, and proposes measures to increase the utilization efficiency and throughput of wireless resources when performing TXS (or C-TDMA). In addition, the present disclosure also proposes a procedure and frame structure for performing TXS accompanied by DSO 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 first access point (AP) of a wireless LAN system comprises: transmitting a first frame to a second AP to announce an intention to share a transmission opportunity (TXOP); transmitting a second frame to the second AP to initiate the sharing of the TXOP; transmitting a third frame to a station (STA) coupled with the first AP to trigger a dynamic subband operation (DSO); and exchanging frames on a secondary channel (SCH) within the TXOP based on the DSO.

[0008] According to one embodiment of the present disclosure, a method performed by a second AP of a wireless LAN system comprises: receiving a first frame from a first AP to announce an intention to share a transmission opportunity (TXOP); receiving a second frame from the first AP to initiate the sharing of the TXOP; transmitting a third frame to a station (STA) coupled with the second AP to trigger a dynamic subband operation (DSO); and exchanging frames on a secondary channel (SCH) within the TXOP based on the DSO.

[0009] According to one embodiment of the present disclosure, a first AP of a wireless LAN system comprises: at least one transceiver; at least one processor communicatively coupled to the at least one transceiver; and at least one memory communicatively coupled to the at least one processor for storing instructions, wherein the instructions are executed individually or in any combination by the at least one processor so that the first AP: transmits a first frame to a second AP to announce an intention to share a transmission opportunity (TXOP); transmits a second frame to the second AP to initiate the sharing of the transmission opportunity; transmits a third frame to a station (STA) coupled to the first AP to trigger a dynamic subband operation (DSO); and causes frames to be exchanged on a secondary channel (SCH) within the transmission opportunity based on the DSO.

[0010] According to one embodiment of the present disclosure, a second AP of a wireless LAN system comprises: at least one transceiver; at least one processor communicatively coupled to the at least one transceiver; and at least one memory communicatively coupled to the at least one processor for storing instructions, wherein the instructions are executed individually or in any combination by the at least one processor so that the second AP: receives a first frame from the first AP to announce an intention to share a transmission opportunity (TXOP); receives a second frame from the first AP to initiate the sharing of the transmission opportunity; transmits a third frame to a station (STA) coupled to the second AP to trigger a dynamic subband operation (DSO); and exchanges frames on a secondary channel (SCH) within the transmission opportunity based on the DSO.

[0011] According to the various embodiments proposed in this disclosure, when TXS or C-TDMA is performed in a wireless LAN system, the sharing AP and the shared AP can each use the PCH (primary channel) or SCH (secondary channel) within the TXOP. Through this, the utilization efficiency and throughput of wireless resources within the TXOP can be increased. In addition, by proposing a signaling procedure and frame structure for performing TXS or C-TDMA together with the aforementioned DSO, the increase in signaling overhead can be minimized.

[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 of a wireless LAN system related to the present disclosure.

[0021] FIG. 10 is a diagram illustrating C-TDMA or TXS operation related to the present disclosure.

[0022] FIG. 11 is a drawing illustrating the structure of a frame related to C-TDMA or TXS operation related to the present disclosure.

[0023] FIG. 12 is a diagram illustrating a DSO operation related to the present disclosure.

[0024] FIG. 13 is a diagram illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0025] FIG. 14 is a diagram illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0026] FIG. 15 is a diagram illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0027] FIG. 16 is a diagram illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0028] FIG. 17 is a drawing illustrating a frame format structure according to one embodiment proposed in the present disclosure.

[0029] FIG. 18 is a drawing illustrating a frame format structure according to one embodiment proposed in the present disclosure.

[0030] FIG. 19 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0031] FIG. 20 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0032] FIG. 21 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0033] FIG. 22 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 instruction means 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).

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] FIG. 1 illustrates the configuration of a device for wireless communication according to one embodiment of the present disclosure.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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).

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 be composed 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.

[0056] 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.

[0057] 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.).

[0058] 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.

[0059] 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.

[0060] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0061] 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.

[0062] 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.

[0063] 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).

[0064] 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.

[0065] 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.

[0066] 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).

[0067] 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.

[0068] 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.

[0069] In addition to the structure of the aforementioned DS, an Extended Service Set (ESS) may be configured to provide wider coverage.

[0070] 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.

[0071] 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.

[0072] FIG. 3 illustrates a link setup process related to the present disclosure.

[0073] 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.

[0074] 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.

[0075] 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).

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0086] 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.

[0087] 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).

[0088] 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, ...).

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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).

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0117] 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.

[0118] 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.

[0119] FIG. 9 is a diagram illustrating exemplary operations of C-TDMA of a wireless LAN system related to the present disclosure.

[0120] 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 a specific AP to share a TXOP with another AP.

[0121] An AP that shares (or transfers) a TXOP it has acquired to another AP in C-TDMA or TXS may 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 may be a frame for polling the interest of the target APs to which the sharing AP will share the TXOP, and an AP that receives (or transfers) a portion of the TXOP acquired by the sharing AP in this way may 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.

[0122] 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).

[0123] Meanwhile, as 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 these TXS (or 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 the TXS (or 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 MU-RTS TXS TF (930) described earlier. The STA2 may send 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, can perform a separate transmission and reception procedure by sending a basic TF within its own TXOP (960). The TXS described in FIG. 9 is distinguished from the procedure of sharing TXOPs between an existing AP and a non-AP STA in that it shares TXOPs between APs.

[0124] FIG. 10 is a diagram illustrating C-TDMA or TXS operation related to the present disclosure.

[0125] FIG. 10 shows that a sharing AP (associated with BSS1) transmits an ICF for polling C-TDMA (or TXS) to a non-AP STA (associated with BSS1) and a shared AP (associated with BSS2) associated with it (1005), and this ICF may be intended to announce the intention of the sharing AP to share some of its TXOP time resources with the shared AP and / or STA, and the ICF may include a BSRP (buffer status report poll) trigger frame. Subsequently, the non-AP STA and the shared AP that receive the ICF may transmit an ICR to the sharing AP (1010, 1015) to announce whether the non-AP STA and the shared AP will each participate in C-TDMA (or TXS), and the ICR may include a multi-STA block ACK frame.

[0126] Meanwhile, the time interval indicated by the duration field of the ICF transmitted by the sharing AP may be equal to the sum of the lengths of the frame for SIFS and ICR transmission. In this case, after the ICF / ICR exchange, the sharing AP may receive the ICR (1015) to occupy a time interval including a time interval for frame exchange (1035) to communicate with the STA in its BSS (BSS1) and a time interval to transfer to the shared AP, and transmit a MU-RTS (1020) frame after the SIFS time. The Sharing AP can signal that a frame exchange (1035) in BSS1 follows by sending a MU-RTS (1020) and the STA in BSS1 sends a CTS (1025), and optionally, the Sharing AP can protect the Sharing AP's frame exchange (1035) by sending a CTS (1030) to additionally set NAV for the STAs in the Shared AP's BSS2. After the frame exchange (1035) in its BSS is finished, the Sharing AP sends a MU-RTS TXS TF (1040) to the shared AP to signal the start (or initiation) of a TXS (or C-TDMA) in a TXOP, and the shared AP sends a CTS frame (1045) to the sharing AP in response. Through MU-RTS TXS TF (1040), the sharing AP can specify the time interval in which TXS (or C-TDMA) is to be performed within the TXOP, and then the shared AP can perform frame exchange according to TXS (or C-TDMA) (1050).

[0127] According to the above-described embodiment, the sharing AP may separately transmit a frame (i.e., a MU-RTS trigger frame) for transmitting scheduling information for a TXOP to be performed on a TXS (or C-TDMA) and a frame (MU-RTS TXS TF) for indicating that the TXS (or C-TDMA) has actually started (or started). According to the proposed embodiment, by the sharing AP transmitting a MU-RTS trigger frame and the shared AP receiving it transmitting a CTS frame for response, the sharing AP can not only transmit TXOP scheduling information for the TXS (or C-TDMA) but also resolve the hidden node problem located between the sharing AP and the shared AP. Meanwhile, according to another embodiment, in order to resolve the over-protection problem, the shared AP receiving a MU-RTS trigger frame from the sharing AP may not transmit a response frame such as a CTS. In FIG. 10, the time interval for sending the ICF (1005) and ICR (1010), and the MU-RTS (1020), CTS (1025), frame exchange (1035), MU-RTS TXS TF (1040), CTS (1045), and frame exchange (1050) may be composed of a single TXOP. In this case, the interval indicated by the duration field in the ICF (1005) may be the sum of the frame lengths for SIFS and ICF transmission, but the TXOP length may be extended according to the duration field of the frame transmitted in the subsequent MU-RTS (1020) and Frame exchange (1035).

[0128] FIG. 11 is a diagram illustrating the structure of a frame related to C-TDMA or TXS operation in relation to the present disclosure. FIG. 11 specifically describes an ICF transmitted by a sharing AP to a shared AP according to the embodiments described above.

[0129] FIG. 11 is a diagram illustrating the structure of an ICF according to one embodiment proposed in the present disclosure. FIG. 11 explains the format structure of an ICF that a sharing AP transmits to a shared AP to indicate its intention to share a portion of the time resources of its TXOP according to the embodiment described above.

[0130] According to one embodiment, the allocation duration field included in the User Info list field of the ICF transmitted by the sharing AP may indicate the length of the time interval of the TXOP that the sharing AP intends to allocate to the shared AP. The User Info field included in the ICF transmitted by the sharing AP may include an AID12 field, and the AID12 field may indicate the AID of the shared AP to receive the ICF. The fact that the AID12 field includes the AID of the shared AP may mean that an AID that enables the sharing AP to distinguish the shared AP is known in advance between the sharing AP and the shared AP.

[0131] Meanwhile, according to one embodiment, the ICF transmitted by the sharing AP may include a BSRP trigger frame, but it is obvious that other trigger frames may be used for the ICF.

[0132] FIG. 12 is a diagram illustrating a DSO operation related to the present disclosure.

[0133] Dynamic subband operation (DSO) is a procedure for an AP having an operation bandwidth of a predetermined amount (e.g., 320 MHz) including a primary channel (PCH) and a secondary channel (SCH) to dynamically direct a non-AP STA having a smaller operation bandwidth (e.g., 160 MHz) to transmit and / or receive opportunities on the SCH. Although the case where the operation bandwidths of the AP and non-AP STA performing DSO are 320 MHz and 160 MHz, respectively, has been described, this is merely one example, and the operation bandwidths of the AP and non-AP STA are not limited to the above example. That is, DSO can be applied in all cases where the bandwidth supported by the AP is higher than that of the non-AP STA.

[0134] Additionally, transmission and reception of DL or trigger-based UL may be performed within transmission and / or reception opportunities dynamically allocated through DSO. When performing DSO, the AP may dynamically allocate SCH bandwidth to at least some of the combined non-AP STAs whenever it acquires channel access (i.e., per TXOP). Furthermore, the AP may dynamically determine whether to allocate non-AP STAs to the PCH or SCH and which non-AP STAs to allocate based on bandwidth capability or bandwidth availability, channel condition, and QoS requirements.

[0135] Referring to FIG. 12, the AP transmits an ICF to allocate SCH bandwidth to a non-AP STA operating as a DSO (hereinafter referred to as DSO STA) and a non-AP STA not operating as a DSO (hereinafter referred to as non-DSO STA). The ICF transmitted to allocate SCH bandwidth may be called a DSO trigger frame, and a DSO STA that receives the DSO trigger frame (i.e., ICF) can switch the channel to SCH. A DSO STA that receives the DSO trigger frame from the AP can operate at the remaining SCH 160 MHz (hereinafter referred to as 160S), excluding the PCH 160 MHz (hereinafter referred to as 160P) which includes a primary 20 MHz for backoff among the AP's operating bandwidth (e.g., 320 MHz).

[0136] The AP transmits a first control frame (1210), i.e., an ICF, to non-AP STAs to trigger a DSO (i.e., to instruct them to change the operating band). Through the ICF (i.e., the DSO trigger frame), the AP may instruct some non-AP STAs to operate within an operating band (e.g., 160S), and a non-AP STA that has been allocated an SCH from the AP may be a DSO STA. In this case, the ICF may further include an intermediate FCS (I-FCS) and padding bits to account for the time required for the DSO STA receiving the ICF to change the operating band. DSO STAs and non-DSO STAs may receive the ICF (1220) at 160P, which is the operating band of the non-AP STAs. A DSO STA receiving the ICF may change the operating band to the band allocated by the AP (e.g., 160S) after SIFS.

[0137] The AP can transmit a second control frame to the DSO STA and the non-DSO STA (1230). The DSO STA operating under the DSO receives the second control frame in the changed band (e.g., 160S) (1240), and the non-DSO STA not instructed to perform the DSO receives the second control frame in the existing band (e.g., 160P) (1250). The DSO STA can transmit a response frame for the second control frame to the AP in the changed band (e.g., 160S) (1260). The non-DSO STA can transmit a response frame for the second control frame to the AP in the existing band (e.g., 160P) (1270). Meanwhile, the first control frame (1210) and the second control frame (1230) can be transmitted across the entire operating band of the AP (e.g., 160P+160S). Additionally, the DSO STA may transmit only a response frame (e.g., ICR) for the first control frame (1210) without receiving the second control frame (1230). Through the process described above, the AP and non-AP STAs can perform the transmission and reception of frames using the entire operating band of the AP. Afterward, when the TXOP acquired by the AP ends, the DSO STA can return to the original band (e.g., 160P) (1280).

[0138] FIG. 13 is a diagram illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0139] Before describing the TXS operation accompanied by DSO according to the embodiment proposed in this disclosure, the TXS operation and the NP (non-primary)-TXS operation are first described. The TXS operation described in FIGS. 9 and 10 includes the process of the sharing AP sharing the PCH (or PCH and SCH) in at least a portion of the TXOP to the shared AP in a situation where the sharing AP and the shared AP have the same PCH (or the same PCH and SCH). The NP-TXS operation includes the process of the sharing AP sharing the SCH in at least a portion of the TXOP to the shared AP in a situation where the SCH of the sharing AP and the PCH of the shared AP are the same (i.e., a situation where the PCH of the sharing AP and the PCH of the shared AP are different).

[0140] Unlike the TXS and NP-TXS described above, the TXS operation involving a DSO according to the proposed embodiment includes, in a situation where the sharing AP and the shared AP have the same PCH (or the same PCH and SCH), the sharing AP shares the SCH with the shared AP in at least a part of the TXOP or the sharing AP shares the PCH with the shared AP in at least a part of the TXOP. That is, the TXS operation involving a DSO includes the process of dividing and occupying the PCH and SCH in a portion of the TXOP between the sharing AP and the shared AP having the same PCH and SCH.

[0141] According to the proposed embodiment, when a sharing AP shares a PCH with a shared AP in part of a TXOP, the sharing AP can exchange frames in the SCH with the STA coupled to it through a DSO, and the shared AP can exchange frames in the shared PCH. According to the proposed embodiment, when a sharing AP shares a SCH with a shared AP in part of a TXOP, the shared AP can perform a DSO to exchange frames in the SCH shared with the STA coupled to it, and the sharing AP can exchange frames in the PCH.

[0142] According to one embodiment, in a situation where a sharing AP and a shared AP each operate a restricted target wakeup time (R-TWT) to support low-latency traffic and QoS traffic, a TXS operation accompanied by a DSO according to the proposed embodiment may be performed. Specifically, in a situation in FIG. 13 where AP1 operates R-TWT 1 broadcast to the STA coupled to it (e.g., STA1) and AP2 operates R-TWT 2 broadcast to the STA coupled to it (e.g., STA2), a situation in which R-TWT 1 and R-TWT 2 overlap may be considered.

[0143] That is, according to the example in FIG. 13, AP1 initiates a TXOP based on R-TWT 1 (1320) and AP2 sets up NAV based on R-TWT 1 (1330), but the time when the service period (SP) of R-TWT 2 for AP2 to handle low-latency (or urgent) traffic begins (1310) may overlap with AP1's TXOP. In this situation, since AP1 has traffic to handle, it may be difficult for AP1 to share (or transfer) the entire TXOP to AP2, and accordingly, AP1 may share (transfer) some channels within the TXOP for AP2's R-TWT 2. Through this process, if AP1 and AP2 share and occupy the PCH and SCH within AP1's TXOP, both AP1 and AP2 will be able to perform traffic transmission, and it may be possible to efficiently utilize wireless resources (or frequency resources) within the TXOP. For example, within a TXOP, AP1 may share (or transfer) a bandwidth (bandwidth, BW) including PCH to AP2. Alternatively, within a TXOP, AP1 may share (or transfer) a bandwidth excluding PCH (or a bandwidth including SCH) to AP2.

[0144] Hereinafter, specific and various operations according to the above-described embodiment will be explained through FIGS. 14 to 16.

[0145] FIG. 14 is a diagram illustrating a TXS operation involving a DSO according to one embodiment proposed in the present disclosure. FIG. 14 describes an embodiment in which a sharing AP shares (or transfers) a PCH to a shared AP within a TXOP, and the sharing AP performs a DSO to exchange frames in a SCH within the TXOP. In this embodiment, the shared AP can exchange frames in a PCH within the TXOP.

[0146] AP1 sets up a stream classification service (SCS) and an R-TWT to guarantee QoS with the STA1 coupled to it, and AP2 also sets up an SCS and an R-TWT to guarantee QoS with the STA2 coupled to it (1405). Each of AP1 and AP2 announces the R-TWT they have set up and can negotiate parameters or information for C-TDMA (or TXS) with each other (1410).

[0147] AP1 obtains a TXOP for processing traffic, and although the TXOP (1485) obtained by AP1 in FIG. 14 is depicted as a single time interval, the operations depicted in FIG. 14 may be performed over multiple TXOPs. AP1 transmits an ICF to AP2 to indicate that a TXOP has been initiated, and this ICF may include, for example, a BSRP trigger frame (1415). As previously described in FIG. 9 through 11, the ICF may include information or parameters to indicate the intention of the sharing AP (AP1 in the illustrated example) for TXS (or C-TDMA). Upon receiving the ICF, AP2 transmits an ICR to AP1, and this ICR may include, for example, a MU-STA (multi-station) BA (block ack) frame (1420).

[0148] AP1 transmits a MU-RTS trigger frame to STA1 and AP2 for traffic processing within the TXOP (1425), and STA1 and AP2 transmit a CTS frame to AP1 in response (1430). As previously described in FIGS. 9 through 11, the MU-RTS trigger frame may include information for scheduling the time interval of the TXOP in which the TXS will be performed. Upon receiving the CTS (1430) in response to the MU-RTS trigger frame (1425), AP1 can exchange frames with STA1 on the PCH (i.e., PC) and SCH (i.e., SC) within the TXOP (1435). Meanwhile, the TXOP in which the MU-RTS trigger frame and response are transmitted and received and frame exchange takes place may be the same TXOP as the TXOP in which the ICF was previously transmitted, or it may be a separate, different TXOP.

[0149] Next, AP1 (i.e., sharing AP) sends a MU-RTS TXS trigger frame to AP2 (shared AP) to indicate that TXOP sharing (i.e., TXS or C-TDMA) is starting (1440), and AP2 sends a CTS frame to AP1 in response to the MU-RTS TXS trigger frame (1445). TXOP sharing (i.e., TXS or C-TDMA) can be started from the end of the CTS frame that AP2 sends to AP1.

[0150] Meanwhile, according to the proposed embodiment, if AP1 (i.e., sharing AP) shares (or transfers) the PCH to AP2 (i.e., shared AP) for a portion of the TXOP time interval (i.e., a portion of TXOP) within the TXOP, AP1 can exchange frames in the SCH within the transferred TXOP time interval. In order for AP1 to exchange frames in the SCH, AP1 can perform DSO together with STA1 coupled to it. To perform DSO, AP1 transmits a DSO trigger frame to STA1 (1450), and the DSO trigger frame may include I-FCS (and padding bits) considering the time required for STA1's band change. Upon receiving the DSO trigger frame, STA1 moves to the SCH and then transmits a response frame to AP1 (1455), and the time interval (1490) required for the DSO procedure may be from the end of the response frame to the point in time when SIFS is added. The time interval (1490) required for the DSO procedure may be the time required to transmit the DSO trigger frame (1450) and the time when the transmission of the response frame (1455) is completed, or it may be the time obtained by adding SIFS from the end of the response frame (1455).

[0151] According to the proposed embodiment, even if the PCH is shared with AP2 (i.e., shared AP) within the TXOP, AP2 cannot use the PCH immediately, but can occupy or use the PCH only after the point in time when the DSO procedure to AP1's SCH is completed. This is because, in order for AP1 to share the PCH with AP2 and operate on the SCH, a predetermined time interval (1490) as previously described is required for AP1 to perform the DSO procedure. Therefore, AP1 can operate on the SCH by performing DSO with STA1, and subsequently, AP1 can exchange frames on the SCH (or SC) within the TXOP (1475). When the PCH is shared with AP1, AP2 can exchange frames on the PCH within the TXOP after the time interval (1490) required for AP1's DSO procedure has passed (1480).

[0152] Meanwhile, the above description describes an embodiment in which the time interval (1490) for the sharing AP to perform DSO in relation to TXS ends at the time when the response frame for the DSO trigger frame and SIFS are added. Unlike the described embodiment, according to the embodiment illustrated in FIG. 14, AP1 changes the operating band to SCH via DSO and then transmits a MU-RTS trigger frame or an RTS trigger frame on the SCH (or SC) to STA1 (1460), and STA1 can transmit a CTS frame for response to AP1 (1470). Additionally, when AP1 transmits a MU-RTS trigger frame or an RTS trigger frame on the SCH, AP2 can transmit a MU-RTS trigger frame or an RTS trigger frame on the PCH shared from AP1 (1465), and STA2 can transmit a CTS frame for response to AP2 (1470). As described above, the time interval (1490) required for the DSO operation may include not only the time interval for the DSO trigger frame (1450) and the response frame (1455), but also the time interval for the sharing AP and the shared AP to exchange the (MU-)RTS trigger frame and the CTS frame that is the response thereto on the SCH and PCH, respectively. In the illustrated embodiment, if the time interval (1490) required for the DSO procedure includes the exchange of the RTS frame and the CTS frame, the shared AP may occupy or use the PCH shared (or transferred) via TXS from the point in time when the exchange of the RTS frame and the CTS frame is substantially completed. If, in the previously described embodiment, the time interval (1490) required for the DSO procedure includes only the exchange of the DSO trigger frame and the response frame, the shared AP may occupy or use the PCH shared (or transferred) via TXS from the point in time when the exchange of the DSO trigger frame and the response frame plus SIFS is added.In other words, the procedure for AP1 and AP2 to exchange (MU-RTS) trigger frames and CTS frames after the DSO trigger frame and response frame have been exchanged may or may not be performed, and in each case, the length of the time interval required for the DSO procedure and the start time and time interval at which the TXS actually takes place may be defined differently.

[0153] For the embodiment described in FIG. 14 above, the ICF (e.g., BSRP trigger frame) transmitted by AP1 (sharing AP) to AP2 (shared AP) may include various information or parameters for TXS. For example, the ICF may include not only information regarding the time when the MU-RTS TXS trigger frame is transmitted, but also information regarding which AP among the sharing AP and the shared AP will perform DSO after the transmission of the MU-RTS TXS trigger frame, information regarding the channel or band to be changed via DSO after the transmission of the MU-RTS TXS trigger frame, or information indicating whether the AP performing DSO to operate in the SCH when the PCH is shared will transmit and receive a DSO trigger frame and a response frame. The various information or parameters included in the ICF will be explained in detail later in FIGs. 17 and 18.

[0154] FIG. 15 is a diagram illustrating a TXS operation involving a DSO according to one embodiment proposed in the present disclosure. FIG. 15 describes an embodiment in which a sharing AP shares (or transfers) a SCH to a shared AP within a TXOP, and the shared AP performs a DSO to exchange frames in the SCH within the TXOP. In this embodiment, the sharing AP can exchange frames in the PCH within the TXOP.

[0155] FIG. 15 describes an embodiment in which, unlike the embodiment described in FIG. 14, AP1 (sharing AP) occupies and operates the PCH within the TXOP while sharing the SCH with AP2 (shared AP). In the embodiment of FIG. 15, AP2 (shared AP) can perform DSO and exchange frames in the SCH as the SCH is shared within the TXOP.

[0156] AP1 sets up SCS and R-TWT for QoS guarantee with STA1 coupled to itself, and AP2 also sets up SCS and R-TWT for QoS guarantee with STA2 coupled to itself (1505). Each of AP1 and AP2 informs the R-TWT they have set up and can negotiate parameters or information for C-TDMA (or TXS) with each other (1510).

[0157] AP1 obtains a TXOP for processing traffic, and although the TXOP (1585) obtained by AP1 in FIG. 15 is depicted as a single time interval, the operations depicted in FIG. 15 may be performed over multiple TXOPs. AP1 transmits an ICF to AP2 to indicate that a TXOP has been initiated, and this ICF may include, for example, a BSRP trigger frame (1515). As previously described in FIG. 9 through 11, the ICF may include information or parameters to indicate the intention of the sharing AP (AP1 in the illustrated example) for TXS (or C-TDMA). Upon receiving the ICF, AP2 transmits an ICR to AP1, and this ICR may include, for example, a MU-STA (multi-station) BA (block ack) frame (1520).

[0158] AP1 transmits a MU-RTS trigger frame to STA1 and AP2 for traffic processing within the TXOP (1525), and STA1 and AP2 transmit a CTS frame to AP1 in response (1530). According to one embodiment, the CTS response (1530) from AP2 may be performed optionally. As previously described in FIGS. 9 through 11, the MU-RTS trigger frame may include information for additionally occupying or scheduling the time interval of the TXOP where the TXS is to be performed. Upon receiving the CTS (1530) in response to the MU-RTS trigger frame (1525), AP1 may exchange frames with STA1 on the PCH (i.e., PC) and SCH (i.e., SC) within the TXOP (1535). Meanwhile, the TXOP in which the MU-RTS trigger frame and response are transmitted and received and frame exchange takes place may be the same TXOP as the TXOP in which the ICF was previously transmitted, or it may be a separate TXOP.

[0159] Next, AP1 (i.e., sharing AP) sends a MU-RTS TXS trigger frame to AP2 (shared AP) to indicate that TXOP sharing (i.e., TXS or C-TDMA) is starting (1540), and AP2 sends a CTS frame to AP1 in response to the MU-RTS TXS trigger frame (1545). TXOP sharing (i.e., TXS or C-TDMA) can be started from the end of the CTS frame that AP2 sends to AP1.

[0160] According to the proposed embodiment, when AP1 (i.e., sharing AP) shares (or transfers) SCH to AP2 (i.e., shared AP) within a TXOP, AP2 can exchange frames on SCH within the TXOP. In order for AP2 to exchange frames on SCH, AP2 can perform DSO with STA2 coupled to it. To perform DSO, AP2 transmits a DSO trigger frame to STA2 (1550), and the DSO trigger frame may include I-FCS (and padding bits) to account for the time required for the band change of STA2. Upon receiving the DSO trigger frame, STA2 transmits a response frame to AP2 on SCH (1555), and the time interval (1590) required for the DSO procedure may be from the end of the response frame to the point in time when SIFS is added. According to the proposed embodiment, even if SCH is shared with AP2 (i.e., shared AP) within the TXOP, AP2 cannot use SCH immediately, but can occupy or use SCH only after the DSO procedure to SCH is completed together with STA2. After the DSO procedure is completed, AP2 can exchange frames on SCH (or SC) within the TXOP (1580). Meanwhile, AP1, which has shared SCH with AP2, can exchange frames on PCH during the remaining time interval of the TXOP (1575).

[0161] Meanwhile, regarding TXS, an embodiment has been described above in which the time interval (1590) for the sharing AP to perform DSO ends at the time of adding the response frame (1555) for the DSO trigger frame (1550) and SIFS. Unlike the described embodiment, according to the embodiment illustrated in FIG. 15, AP2 changes the operating band to SCH via DSO and then transmits a MU-RTS trigger frame or an RTS trigger frame to STA2 on SCH (or SC) (1565), and STA2 can transmit a CTS frame for response to AP2 (1570). Additionally, when AP2 transmits a MU-RTS trigger frame or an RTS trigger frame on SCH, AP1 can transmit a MU-RTS trigger frame or an RTS trigger frame on PCH (1560), and STA1 can transmit a CTS frame for response to AP1 (1570). As described above, the time interval (1590) required for the DSO operation may include not only the time interval for the DSO trigger frame (1550) and the response frame (1555), but also the time interval for the sharing AP and the shared AP to exchange the (MU-)RTS trigger frame and the CTS frame that is the response thereto on the PCH and SCH, respectively. In the illustrated embodiment, if the time interval (1590) required for the DSO procedure includes the exchange of the RTS frame and the CTS frame, the shared AP may occupy or use the SCH shared (or transferred) via TXS from the point in time when the exchange of the RTS frame and the CTS frame is substantially completed. If, in the embodiment described above, the time interval (1590) required for the DSO procedure includes only the exchange of the DSO trigger frame and the response frame, the shared AP may occupy or use the SCH shared (or transferred) via TXS from the point in time when the exchange of the DSO trigger frame and the response frame plus SIFS is added.In other words, the procedure for AP1 and AP2 to exchange (MU-RTS) trigger frames and CTS frames after the DSO trigger frame and response frame have been exchanged may or may not be performed, and in each case, the length of the time interval required for the DSO procedure and the start time and time interval at which the TXS actually takes place may be defined differently.

[0162] For the embodiment described in FIG. 15 above, the ICF (e.g., BSRP trigger frame) transmitted by AP1 (sharing AP) to AP2 (shared AP) may include various information or parameters for TXS. For example, the ICF may include not only information regarding the time when the MU-RTS TXS trigger frame is transmitted, but also information regarding which AP among the sharing AP and the shared AP will perform DSO after the transmission of the MU-RTS TXS trigger frame, information regarding the channel or band to be changed via DSO after the transmission of the MU-RTS TXS trigger frame, or information indicating whether the AP performing DSO to operate in the SCH when the PCH is shared will transmit and receive a DSO trigger frame and a response frame. The various information or parameters included in the ICF will be explained in detail later in FIGs. 17 and 18.

[0163] FIG. 16 is a diagram illustrating a TXS operation involving a DSO according to one embodiment proposed in the present disclosure. FIG. 16 describes an embodiment in which a sharing AP shares (or transfers) a PCH to a shared AP within a TXOP, and the sharing AP performs a DSO to exchange frames in a SCH within the TXOP. In this embodiment, the shared AP can exchange frames in a PCH within the TXOP.

[0164] FIG. 16 describes an embodiment in which AP1 (sharing AP) performs DSO while sharing PCH with AP2 (shared AP) within TXOP and operates in SCH, similar to the embodiment described in FIG. 14. In the embodiment of FIG. 15, AP2 (shared AP) can exchange frames on PCH within TXOP.

[0165] AP1 sets up a stream classification service (SCS) and an R-TWT to guarantee QoS with the STA1 coupled to it, and AP2 also sets up an SCS and an R-TWT to guarantee QoS with the STA2 coupled to it (1605). Each of AP1 and AP2 announces the R-TWT they have set up and can negotiate parameters or information for C-TDMA (or TXS) with each other (1610).

[0166] AP1 obtains a TXOP for processing traffic, and although the TXOP (1660) obtained by AP1 in FIG. 16 is depicted as a single time interval, the operations depicted in FIG. 16 may be performed over multiple TXOPs. AP1 transmits an ICF to AP2 to indicate that a TXOP has been initiated, and this ICF may include, for example, a BSRP trigger frame (1615). As previously described in FIG. 9 through 11, the ICF may include information or parameters to indicate the intention of the sharing AP (AP1 in the illustrated example) for TXS (or C-TDMA). Upon receiving the ICF, AP2 transmits an ICR to AP1, and this ICR may include, for example, a MU-STA (multi-station) BA (block ack) frame (1620).

[0167] AP1 transmits a MU-RTS trigger frame to STA1 and AP2 for traffic processing within the TXOP (1625), and STA1 and AP2 transmit a CTS frame to AP1 in response (1630). As previously described in FIGS. 9 through 11, the MU-RTS trigger frame may include information for additionally occupying or scheduling the time interval of the TXOP where the TXS is to be performed. Upon receiving the CTS (1630) in response to the MU-RTS trigger frame (1625), AP1 can exchange frames with STA1 on the PCH (i.e., PC) and SCH (i.e., SC) within the TXOP (1635). Meanwhile, the TXOP in which the MU-RTS trigger frame and response are transmitted and received and frame exchange takes place may be the same TXOP as the TXOP in which the ICF was previously transmitted, or it may be a separate, different TXOP.

[0168] Subsequently, AP1 (i.e., the sharing AP) transmits a MU-RTS TXS trigger frame to AP2 (the shared AP) to indicate that TXOP sharing (i.e., TXS or C-TDMA) has started. Meanwhile, since AP1 needs to perform DSO to exchange frames in SCH with STA1 separately from sharing PCH with AP2, it needs to transmit a DSO trigger frame to STA1. Accordingly, according to one embodiment of the proposed embodiment, AP1 (the sharing AP) can generate and transmit a DSO trigger frame (transmitted to STA1) and a MU-RTS TXS trigger frame (transmitted to AP2) as a single frame (1640). In this case, the BSRP trigger frame (1615), which is an ICF transmitted by the AP, may include a list of STAs to perform DSO at the time of transmitting the MU-RTS TXS trigger frame (1640) and information about the SCH to move to. In this way, if the BSRP trigger frame (1615) contains a list of STAs to perform DSO at the time of transmitting the MU-RTS TXS trigger frame (1640), the STAs included in the list can perform DSO with the SCH after receiving the MU-RTS TXS trigger frame (1640) to be transmitted later by receiving the ICF (i.e., the BSRP trigger frame (1615). To this end, AP1 includes additional padding in the MU-RTS TXS trigger frame (1640) transmitted to transfer the TXOP to AP2, and the STAs of AP1 can perform DSO by utilizing the padding time in the MU-RTS TXS trigger frame (1640).After transmitting the MU-RTS TXS trigger frame (1640), AP2, which is a shared AP, confirms the positive number of the TXOP by transmitting the CTS (1645) in the PCH, and the STA of AP1, which has moved to the SCH, can send a response to AP1 as an Intermediate Response to the MU-RTS TXS trigger frame (1640), which is also used as a DSO trigger frame in the SCH (1645). Through this, signaling overhead can be reduced compared to the process in which the DSO trigger frame and the MU-RTS TXS trigger frame are transmitted separately according to the embodiment described in FIG. 14 and 15, and the time interval required to perform the DSO procedure is reduced, thereby securing a longer length of the time interval that can be utilized within the TXOP.

[0169] STA1, having received a DSO trigger frame from AP1, transmits a response frame to AP1 (1645), and when DSO is performed through this frame exchange process, AP1 and STA1 can exchange frames on the SCH (or SC) (1650). AP2, having received a MU-RTS TXS trigger frame from AP1, transmits a CTS frame to AP1 for response (1645), and subsequently, AP2 can exchange frames with STA2 on the PCH shared within the TXOP (1655).

[0170] FIG. 17 is a diagram illustrating a frame format structure according to one embodiment proposed in the present disclosure. FIG. 17 describes the format structure of a BSRP trigger frame used as an ICF for TXS and specific fields / subfields.

[0171] FIG. 17(a) illustrates the format structure of a basic BSRP trigger frame, and FIG. 17(b) illustrates the format structure of a BSRP trigger frame according to a proposed embodiment. The BSRP trigger frame according to the embodiment shown in FIG. 17(b) may include a Common information for C-TDMA field (1710) instead of a Common information field in the structure of the BSRP trigger frame shown in FIG. 17(a), may include an AP-specific information for C-TDMA field (1720) instead of a User information list field, and may additionally include a DSO-specific information field (1730). According to another embodiment, the common information field (1710) for C-TDMA, the AP-specific information field (1720) for C-TDMA, and the DSO-specific information field (1730) shown in FIG. 17 (b) may be included at a position immediately after the common information field of the BSRP trigger frame shown in FIG. 17 (a).In the present disclosure, when the existing common information field and user information list field transmitted for the purpose of a Buffer Status Report within a BSRP trigger frame used by the sharing AP as an ICF are included, the common information for C-TDMA field (1710), the AP-specific information for C-TDMA field (1720), and the DSO-specific information field (1730) may be located after the existing common information field and user information list field transmitted for the purpose of a Buffer Status Report.

[0172] Specific embodiments of the common information field (1710) for C-TDMA, the AP-specific information field (1720) for C-TDMA, and the DSO-specific information field (1730) shown in FIG. 17 are described below in FIG. 18.

[0173] FIG. 18 is a drawing illustrating a frame format structure according to one embodiment proposed in the present disclosure.

[0174] FIG. 18(a) illustrates an exemplary structure of a common information field for C-TDMA included in a BSRP trigger frame. The common information field for C-TDMA according to the proposed embodiment may include a special AID subfield (1812), an information type subfield (1814), an information fields for C-TDMA subfield (1816), and reserved bits (1818).

[0175] According to one embodiment, the special AID subfield (1812) may contain a value that is not assigned to the STA (e.g., a value greater than 2007). The value indicated by the special AID subfield (1812) may indicate that the corresponding BSRP trigger frame contains information or parameters related to a specific feature introduced in the UHR, for example, the value of the special AID subfield (1812) may be 2024 to indicate the previously described C-TDMA (or TXS).

[0176] According to one embodiment, the information type subfield (1814) may include a bitmap for indicating a specific function related to UHR, for example, if the bitmap of the information type subfield (1814) indicates 0000, it may indicate that the BSRP trigger frame is a container carrying common information for C-TDMA (or TXS), and if the bitmap of the information type subfield (1814) indicates 0001, it may indicate that the BSRP trigger frame is a container carrying common information for C-BF (coordinated beamforming).

[0177] According to one embodiment, the information type subfield (1814) may include a multi-AP (M-AP) management ID (identifier) ​​or an M-AP agreement ID. According to this embodiment, the M-AP management ID or M-AP agreement ID for an M-AP operation determined in advance between APs through an M-AP association, negotiation, or agreement procedure may be included in the information type subfield (1814), and such M-AP management ID or M-AP agreement ID may simply be referred to as M-ID. The above-mentioned M-AP management ID or M-AP agreement ID may be a representative value for identifying parameters for an M-AP operation (e.g., C-TDMA (or TXS) operation) agreed upon / consensed between APs or for identifying participating devices.

[0178] The information field subfield (1816) for C-TDMA according to one embodiment may include detailed information or parameters related to C-TDMA (or TXS), for example, information or parameters regarding the expected time for TXOP allocation or the expected duration of a shared TXOP portion.

[0179] The reserved bits (1818) according to one embodiment may include bits for matching the length of the common information field for the C-TDMA described above to 40 bits. If the bits for constituting the fields illustrated in FIG. 18 (a) exceed 40 bits, the bits exceeding 40 bits may be appended into the BSRP trigger frame as new common information fields for the C-TDMA.

[0180] FIG. 18(b) illustrates an exemplary structure of an AP-specific information field for C-TDMA included in a BSRP trigger frame. The AP-specific information field for C-TDMA according to the proposed embodiment may include a Shared AP AID subfield (1822), an information type subfield (1824), a RU allocation subfield (1826), and reserved bits (1828).

[0181] According to one embodiment, the Shared AP AID subfield (1822) may include a value for identifying the AID of the shared AP in relation to C-TDMA (or TXS).

[0182] According to one embodiment, the information type subfield (1824) may include a bitmap for representing specific information for C-TDMA operation. In one embodiment, the information type subfield (1824) included in the AP-specific information field for C-TDMA may have the same value as the information type subfield (1814) included in the common information field for C-TDMA described above.

[0183] According to one embodiment, the RU allocation subfield (1826) may include a value for representing allocated RUs for a shared AP identified by an AP ID to respond to a BSRP trigger frame that acts as a schedule announcement trigger.

[0184] The reserved bits (1828) according to one embodiment may include bits for adjusting the length of the AP-specific information field for the C-TDMA described above to 40 bits.

[0185] FIG. 18(c) illustrates an exemplary structure of a DSO-specific information field included in a BSRP trigger frame. The DSO-specific information field according to the proposed embodiment may include a shared AP AID subfield (1832), an information type subfield (1834), a DSO information subfield (1836), and reserved bits (1838).

[0186] According to one embodiment, the shared AP AID subfield (1832) may include a value for identifying the AID of the shared AP in relation to C-TDMA (or TXS). Alternatively, according to one embodiment, the shared AP AID subfield (1832) may include a specific value (or AID value) to indicate that the BSRP trigger frame contains DSO-related information or parameters performed within the C-TDMA operation for the TXS involving the DSO. If the shared AP AID subfield (1832) refers to a specific value (or AID value) to indicate that the BSRP trigger frame contains DSO-related information or parameters performed within the C-TDMA operation for the TXS involving the DSO, the AID value must be a value that is not assigned by the AP to another AP performing STA or Multi-AP operations within its BSS, and both the sharing AP transmitting the BSRP trigger frame containing the field and the shared AP receiving it must use the same value.

[0187] According to one embodiment, the information type subfield (1834) may include a bitmap for indicating specific information for C-TDMA operation. In one embodiment, the information type subfield (1834) included in the DSO specific information field may have the same value as the information type subfield (1814, 1824) included in the common information field for C-TDMA or the AP specific information field for C-TDMA described above. Alternatively, according to one embodiment, the information type subfield (1834) may include a value to indicate that the 24 bits following the subfield contain additional information or parameters related to DSO operation.

[0188] According to one embodiment, the DSO information subfield (1836) may include information or parameters for performing DSO within a TXOP as described above. The DSO information subfield (1836) may include information regarding the channel and band for the DSO operation, and may include the AID of the AP performing the DSO (or signaling the DSO trigger frame). That is, the DSO information subfield (1836) may indicate whether the AP performing the DSO for a TXS operation involving DSO is a sharing AP or a shared AP, and may indicate which channel and band the AP performing the DSO uses to perform the DSO.

[0189] According to the proposed embodiment, if a DSO-specific information field is included in the BSRP trigger frame, the shared AP can perform a DSO within the TXOP to determine whether the AID of the AP changing the band to the SCH is the AID of the sharing AP or the AID of the shared AP. When the sharing AP performs the DSO, according to the embodiment described in FIG. 14 above, the shared AP can wait for the time interval for the sharing AP (and the STA combined with the sharing AP) to perform the DSO and exchange frames in the PCH within the TXOP. When the shared AP performs the DSO, according to the embodiment described in FIG. 15 above, the shared AP can perform the DSO and exchange frames in the SCH within the TXOP.

[0190] The reserved bits (1838) according to one embodiment may include bits for adjusting the length of the DSO specific information field described above to 40 bits.

[0191] FIG. 18(d) illustrates another exemplary structure of a DSO-specific information field included in a BSRP trigger frame. The DSO-specific information field according to the proposed embodiment may include a C-TDMA with DSO AID subfield (1842), a C-TDMA with DSO information subfield (1846), and reserved bits (1848).

[0192] According to one embodiment, the C-TDMA with DSO AID subfield (1842) may include a specific value (or AID value) to indicate that the BSRP trigger frame contains DSO-related information or parameters performed within the C-TDMA operation for a TXS accompanied by a DSO. If the C-TDMA with DSO AID subfield (1842) refers to the specific value (or AID value) described above, the AID value must be a value that is not assigned by the AP to another AP performing a STA or Multi-AP operation within its BSS, and both the Sharing AP transmitting the BSRP trigger frame containing the field and the Shared AP receiving it must use the same value.

[0193] According to one embodiment, the C-TDMA with DSO information subfield (1846) may include information or parameters for performing DSO within a TXOP as described above. The C-TDMA with DSO information subfield (1846) may include information regarding the channel and band for the DSO operation, and may include the AID of the AP performing the DSO (or signaling a DSO trigger frame). That is, the C-TDMA with DSO information subfield (1846) may indicate whether the AP performing the DSO for a TXS operation involving DSO is a sharing AP or a shared AP, and may indicate which channel and band the AP performing the DSO performs the DSO on.

[0194] According to the proposed embodiment, if a DSO-specific information field is included in the BSRP trigger frame, the shared AP can perform a DSO within the TXOP and, based on the information within the C-TDMA with DSO information subfield (1846), determine whether the AID of the AP changing the band to the SCH is the AID of the sharing AP or the AID of the shared AP. If the sharing AP performs the DSO, according to the embodiment described in FIG. 14 above, the shared AP can wait for the time interval for the sharing AP (and the STA combined with the sharing AP) to perform the DSO and exchange frames in the PCH within the TXOP. If the shared AP performs the DSO, according to the embodiment described in FIG. 15 above, the shared AP can perform the DSO and exchange frames in the SCH within the TXOP.

[0195] The reserved bits (1848) according to one embodiment may include bits for matching the length of the DSO specific information field described above to 40 bits.

[0196] Hereinafter, the operations of the sharing AP and the shared AP (or polled AP) according to the various embodiments described above will be explained in chronological order. In FIGS. 19, 20, 21, and 22, the first AP may refer to the sharing AP of the embodiments described above, and the second AP may refer to the shared AP (or polled AP) of the embodiments described above.

[0197] FIGS. 19 and 20 describe an embodiment in which a sharing AP performs a DSO in relation to a TXS operation involving a DSO according to the proposed embodiment. The embodiment described in FIGS. 19 and 20 may be applied in the same or similar manner as the content previously described in FIG. 14.

[0198] FIG. 19 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0199] FIG. 19 illustrates a flowchart regarding the operation of a first AP in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 19, some or all of the various embodiments described above may be applied identically or similarly to the process of the first AP (i.e., sharing AP) transmitting and receiving parameters or information related to TXS and the process of transmitting and receiving parameters or information related to DSO.

[0200] In FIG. 19, the first AP (i.e., sharing AP) transmits a first frame to the second AP (i.e., shared AP) to notify the intention of sharing a TXOP (TXS) (1910). In one embodiment, the first frame may include a BSRP trigger frame as an ICF, and the first frame may include various information or parameters required to perform a DSO for the TXS. For example, the first frame may include information to indicate which AP, the sharing AP or the shared AP, will perform the DSO for the TXS, or information to indicate the channel and band for performing the DSO. After transmitting the first frame to the second AP, the first AP may receive a frame for a response (e.g., an ICR) from the second AP.

[0201] The first AP transmits a second frame to notify the second AP that it is starting to share a TXOP (1920). According to one embodiment, the second frame may include a MU-RTS TXS trigger frame and may notify that the sharing of a TXOP, i.e., the TXS, is started within the TXOP acquired by the sharing AP. After transmitting the second frame to the second AP, the first AP may receive a frame for a response (e.g., a CTS frame) from the second AP.

[0202] In the embodiment of FIG. 19, since the first AP performs DSO to operate in SCH (or SC), the first AP transmits a third frame for triggering the DSO to the STA coupled to it (1930). According to one embodiment, the third frame may include a DSO trigger frame, and the first AP may transmit the DSO trigger frame on the PCH. That is, the first AP may exchange frames for the DSO on the PCH in the TXOP until the required time interval for performing the DSO, and the PCH may be shared with the DSO after the DSO procedure is completed (e.g., after SIFS has passed from the response frame to the DSO trigger frame).

[0203] The first AP can share (or transfer) the PCH (or PC) to the second AP and, as it performs the DSO, exchange frames in the SCH (or SC) within the TXOP (1940). Meanwhile, when the second AP shares the PCH from the first AP, it can exchange frames on the PCH within the TXOP after the time interval for the first AP's DSO procedure has ended.

[0204] 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. 19. However, it goes without saying that the operation of the first AP (i.e., sharing AP) may vary depending on other embodiments described above.

[0205] FIG. 20 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0206] FIG. 20 illustrates a flowchart regarding the operation of a second AP in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 20, some or all of the various embodiments described above may be applied identically or similarly to the process of the second AP (i.e., shared AP) transmitting and receiving parameters or information related to TXS and the process of transmitting and receiving parameters or information related to DSO.

[0207] In FIG. 20, the second AP (i.e., shared AP) receives a first frame from the first AP (i.e., sharing AP) to indicate an intention to share a TXOP (2010). In one embodiment, the first frame may include a BSRP trigger frame as an ICF, and the first frame may include various information or parameters required to perform a DSO for a TXS. For example, the first frame may include information to indicate which AP, the sharing AP or the shared AP, will perform the DSO for a TXS, or information to indicate the channel and band for performing the DSO. After receiving the first frame from the first AP, the second AP may transmit a frame for a response (e.g., ICR) to the first AP.

[0208] The second AP receives a second frame from the first AP to indicate that TXOP sharing has started (2020). According to one embodiment, the second frame may include a MU-RTS TXS trigger frame and may indicate that the sharing of a TXOP, i.e., the TXS, has started within the TXOP acquired by the sharing AP. After receiving the second frame from the first AP, the second AP may transmit a frame for response (e.g., a CTS frame) to the first AP.

[0209] In the embodiment of FIG. 20, the first AP performs DSO to operate in SCH (or SC), and the second AP operates in PCH (or PC). When the exchange of frames for the DSO trigger of the first AP is completed (i.e., when the time interval for the DSO procedure ends, or when SIFS passes from the response frame to the DSO trigger frame), the second AP can exchange frames on the PCH (or PC) shared (or acquired) from the first AP within TXOP (2030). Meanwhile, the first AP can exchange frames on SCH (or SC) within TXOP by sharing the PCH (or PC) with the second AP and performing DSO.

[0210] Meanwhile, an example of the operation of the second AP (i.e., shared AP) has been described above based on the flowchart illustrated in FIG. 20. However, it is obvious that the operation of the second AP (i.e., shared AP) may vary depending on other embodiments described above.

[0211] FIGS. 21 and 22 describe an embodiment in which a shared AP performs a DSO in relation to a TXS operation involving a DSO according to the proposed embodiment. The embodiment described in FIGS. 21 and 22 may be applied in the same or similar manner as the content previously described in FIG. 15.

[0212] FIG. 21 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0213] FIG. 21 illustrates a flowchart regarding the operation of a first AP in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 21, some or all of the various embodiments described above may be applied identically or similarly to the process of the first AP (i.e., sharing AP) transmitting and receiving parameters or information related to TXS and the process of transmitting and receiving parameters or information related to DSO.

[0214] In FIG. 21, the first AP (i.e., sharing AP) transmits a first frame to the second AP (i.e., shared AP) to notify the intention of sharing a TXOP (TXS) (2110). In one embodiment, the first frame may include a BSRP trigger frame as an ICF, and the first frame may include various information or parameters required to perform a DSO for the TXS. For example, the first frame may include information to indicate which AP, the sharing AP or the shared AP, will perform the DSO for the TXS, or information to indicate the channel and band for performing the DSO. After transmitting the first frame to the second AP, the first AP may receive a frame for a response (e.g., an ICR) from the second AP.

[0215] The first AP transmits a second frame to notify the second AP that it is starting to share a TXOP (2120). According to one embodiment, the second frame may include a MU-RTS TXS trigger frame and may notify that the sharing of a TXOP, i.e., the TXS, is started within the TXOP acquired by the sharing AP. After transmitting the second frame to the second AP, the first AP may receive a frame for a response (e.g., a CTS frame) from the second AP.

[0216] In the embodiment of FIG. 21, the first AP shares (or transfers) the SCH (or SC) to the second AP and can exchange frames on the PCH within the TXOP. Meanwhile, the second AP transmits a DSO trigger frame on the SCH (or SC) and receives a response, and accordingly, the second AP can exchange frames on the SCH (or SC) within the TXOP.

[0217] 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. 21. However, it is obvious that the operation of the first AP (i.e., sharing AP) may vary depending on other embodiments described above.

[0218] FIG. 22 is a flowchart illustrating a TXS operation accompanied by a DSO according to one embodiment proposed in the present disclosure.

[0219] FIG. 22 illustrates a flowchart regarding the operation of a second AP in a wireless LAN system according to one embodiment of the present disclosure. In FIG. 22, some or all of the various embodiments described above may be applied identically or similarly to the process of the second AP (i.e., shared AP) transmitting and receiving parameters or information related to TXS and the process of transmitting and receiving parameters or information related to DSO.

[0220] In FIG. 22, the second AP (i.e., shared AP) receives a first frame from the first AP (i.e., sharing AP) to indicate an intention to share a TXOP (2210). In one embodiment, the first frame may include a BSRP trigger frame as an ICF, and the first frame may include various information or parameters required to perform a DSO for a TXS. For example, the first frame may include information to indicate which AP, the sharing AP or the shared AP, will perform the DSO for a TXS, or information to indicate the channel and band for performing the DSO. After receiving the first frame from the first AP, the second AP may transmit a frame for a response (e.g., ICR) to the first AP.

[0221] The second AP receives a second frame from the first AP to indicate that TXOP sharing has started (2220). According to one embodiment, the second frame may include a MU-RTS TXS trigger frame and may indicate that the sharing of a TXOP, i.e., the TXS, has started within the TXOP acquired by the sharing AP. After receiving the second frame from the first AP, the second AP may transmit a frame for response (e.g., a CTS frame) to the first AP.

[0222] In the embodiment of FIG. 22, since the second AP performs DSO to operate on the SCH (or SC), the second AP transmits a third frame for triggering the DSO to the STA coupled to it (2230). According to one embodiment, the third frame may include a DSO trigger frame, and the second AP may transmit the DSO trigger frame on the shared (or assigned) SCH (or SC).

[0223] The second AP can exchange frames by performing DSO on the SCH (or SC) shared (or transferred) from the first AP within the TXOP (2240). Meanwhile, the first AP can share the SCH with the second AP and exchange frames on the PCH within the TXOP.

[0224] Meanwhile, an example of the operation of the second AP (i.e., shared AP) has been described above based on the flowchart illustrated in FIG. 22. However, it goes without saying that the operation of the second AP (i.e., shared AP) may vary depending on other embodiments described above.

[0225] 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.

[0226] 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 first access point (AP) of a wireless local area network (WLAN) system, A step of transmitting a first frame to the second AP to announce the intention to share a TXOP (transmission opportunity); A step of transmitting a second frame to the second AP to initiate the sharing of the TXOP; A step of transmitting a third frame for triggering a dynamic subband operation (DSO) to a station (STA) combined with the first AP; and A method comprising the step of exchanging frames on a secondary channel (SCH) within the TXOP based on the above DSO.

2. In Paragraph 1, A method in which the PCH (primary channel) within the above TXOP is shared with the second AP, and the PCH is shared with the second AP from the point in time after the SIFS (short interframe space) has passed following the response frame for the third frame.

3. In Paragraph 1, The above first frame includes a BSRP (buffer status report poll) trigger frame, and The above BSRP trigger frame includes a common information field containing a multi-AP management ID related to the sharing of the TXOP, and a DSO-specific information field for indicating that the DSO is accompanying the sharing of the TXOP. A method wherein the above DSO-specific information field comprises at least one of information indicating that the above DSO-specific information field includes parameters for a DSO, information indicating the channel and bandwidth in which the DSO is to be performed within the TXOP, or information for identifying the AP to perform the DSO within the TXOP.

4. In Paragraph 1, A method wherein the first frame includes an ICF (initial control frame), the second frame includes a MU-RTS (multi-user request to send) TXS trigger frame, and the third frame includes a DSO trigger frame including an I-FCS (intermediate frame check sequence).

5. A method performed by a second AP of a wireless local area network (WLAN) system, A step of receiving a first frame from the first AP to announce the intention to share a TXOP (transmission opportunity); A step of receiving a second frame from the first AP to start sharing the TXOP; A step of transmitting a third frame for triggering a dynamic subband operation (DSO) to a station (STA) combined with the second AP; and A method comprising the step of exchanging frames on a secondary channel (SCH) within the TXOP based on the above DSO.

6. In Paragraph 5, In the above TXOP, the PCH (primary channel) is occupied by the first AP, and A method wherein the first frame includes an ICF (initial control frame), the second frame includes a MU-RTS (multi-user request to send) TXS trigger frame, and the third frame includes a DSO trigger frame including an I-FCS (intermediate frame check sequence).

7. In Paragraph 5, The above first frame includes a BSRP (buffer status report poll) trigger frame, and The above BSRP trigger frame includes a common information field containing a multi-AP management ID related to the sharing of the TXOP, and a DSO-specific information field for indicating that the DSO is accompanying the sharing of the TXOP. A method wherein the above DSO-specific information field comprises at least one of information indicating that the above DSO-specific information field includes parameters for a DSO, information indicating the channel and bandwidth in which the DSO is to be performed within the TXOP, or information for identifying the AP to perform the DSO within the TXOP.

8. In a first access point (AP) of a wireless local area network (WLAN) system, At least one transceiver; At least one processor communicatively coupled to the above at least one transceiver; and It includes at least one memory that is communicationally coupled to the above at least one processor and stores instructions, and The above instructions are executed individually or in any combination by the above at least one processor, and the above first AP: Transmit a first frame to the second AP to announce the intention to share a TXOP (transmission opportunity), and Transmit a second frame to the second AP to initiate sharing of the above TXOP, and Transmit a third frame for triggering a DSO (dynamic subband operation) to a STA (station) combined with the first AP above, and A first AP that exchanges frames on the SCH (secondary channel) within the TXOP based on the above DSO.

9. In Paragraph 8, A first AP in which the PCH (primary channel) within the above TXOP is shared with the second AP, and the PCH is shared with the second AP from the point in time after the SIFS (short interframe space) has passed following the response frame for the third frame.

10. In Paragraph 8, The above first frame includes a BSRP (buffer status report poll) trigger frame, and The above BSRP trigger frame includes a common information field containing a multi-AP management ID related to the sharing of the TXOP, and a DSO-specific information field for indicating that the DSO is accompanying the sharing of the TXOP. The first AP, wherein the above DSO-specific information field comprises at least one of information indicating that the DSO-specific information field includes parameters for a DSO, information indicating the channel and bandwidth in which the DSO is to be performed within the TXOP, or information for identifying the AP to perform the DSO within the TXOP.

11. In Paragraph 8, The first AP, wherein the first frame includes an ICF (initial control frame), the second frame includes a MU-RTS (multi-user request to send) TXS trigger frame, and the third frame includes a DSO trigger frame including an I-FCS (intermediate frame check sequence).

12. In a second AP of a wireless local area network (WLAN) system, At least one transceiver; At least one processor communicatively coupled to the above at least one transceiver; and It includes at least one memory that is communicationally coupled to the above at least one processor and stores instructions, and The above instructions are executed individually or in any combination by the above at least one processor, so that the second AP: Receive a first frame from the first AP to announce the intention to share a TXOP (transmission opportunity), and Receive a second frame from the first AP to start sharing the above TXOP, and Transmit a third frame for triggering a DSO (dynamic subband operation) to the STA (station) combined with the above-mentioned second AP, and A second AP that exchanges frames on the SCH (secondary channel) within the TXOP based on the above DSO.

13. In Paragraph 12, In the above TXOP, the PCH (primary channel) is the second AP, which is occupied by the first AP.

14. In Paragraph 12, The above first frame includes a BSRP (buffer status report poll) trigger frame, and The above BSRP trigger frame includes a common information field containing a multi-AP management ID related to the sharing of the TXOP, and a DSO-specific information field for indicating that the DSO is accompanying the sharing of the TXOP. The second AP, wherein the above DSO-specific information field comprises at least one of information indicating that the DSO-specific information field includes parameters for a DSO, information indicating the channel and bandwidth in which the DSO is to be performed within the TXOP, or information for identifying the AP to perform the DSO within the TXOP.

15. In Paragraph 12, The second AP, wherein the first frame includes an ICF (initial control frame), the second frame includes a MU-RTS (multi-user request to send) TXS trigger frame, and the third frame includes a DSO trigger frame including an I-FCS (intermediate frame check sequence).

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