Method and apparatus for retransmission of DSO icf in wireless LAN system

Abstract

The present disclosure relates to an improved wireless LAN system. The present disclosure proposes a method and an apparatus that consider NPCA in an improved wireless LAN system. Specifically, the present disclosure relates to a method performed by an AP of a wireless LAN system, the method comprising the steps of: transmitting, to a first STA and a second STA, a first frame for initiating a DSO; and transmitting, to a plurality of STAs including the second STA, a second frame associated with the DSO.

Description

Method and apparatus for retransmitting DSO ICF 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 retransmitting an initial control frame (ICF) of a dynamic sub-band 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 retransmitting an initial control frame (ICF) of a dynamic subband operation (DSO) in a wireless LAN system. In particular, the present disclosure proposes procedures for an access point (AP) to retransmit an ICF to a non-AP station when the AP fails to receive an initial control response (ICR) for the transmission of the ICF from the non-AP station in the case of a DSO. Additionally, the present disclosure proposes a method for transmitting a buffer status report poll (BSRP) trigger frame or a multi-user request-to-send (MU-RTS) trigger frame as an ICF.

[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 an access point (AP) of a wireless local area network (WLAN) system comprises the steps of: transmitting a first frame to initiate a dynamic subband operation (DSO) to a first station (STA) and a second station (STA); and transmitting a second frame associated with the DSO to a plurality of stations including the second station (STA), wherein the operating band of the second station (STA) may be changed from the primary channel of the AP to the secondary channel of the AP based on the first frame.

[0008] According to one embodiment of the present disclosure, an access point (AP) of a wireless local area network (WLAN) system comprises a transceiver and at least one processor connected to the transceiver, wherein the at least one processor is configured to transmit a first frame to initiate a dynamic subband operation (DSO) to a first station (STA) and a second station (STA), and to transmit a second frame associated with the DSO to a plurality of stations including the second station, and the operating band of the second station may be changed from the primary channel of the AP to the secondary channel of the AP based on the first frame.

[0009] According to the various embodiments proposed in this disclosure, a transmission opportunity (TXOP) can be exceptionally maintained even in a situation where an AP in a wireless LAN system does not receive a response to a DSO ICF transmission. In addition, the DSO can be smoothly maintained even when a response from some non-AP STAs is received on a secondary channel.

[0010] FIG. 1 illustrates the configuration of a device for wireless communication according to one embodiment of the present disclosure.

[0011] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0012] FIG. 3 illustrates a link setup process related to the present disclosure.

[0013] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0014] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0015] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0016] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0017] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0018] FIG. 9 illustrates a method for transmitting a BSRP (buffer status report poll) trigger frame of a wireless LAN system related to the present disclosure.

[0019] FIG. 10 illustrates the concept of dynamic sub-band operation (DSO) in a wireless LAN system related to the present disclosure.

[0020] FIG. 11 illustrates a method in a wireless LAN system according to one embodiment of the present disclosure when an access point (AP) fails to receive a response frame.

[0021] FIG. 12 illustrates a method in a wireless LAN system according to one embodiment of the present disclosure when an AP fails to receive a portion of a response frame.

[0022] FIG. 13 illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0023] FIG. 14a illustrates a method in a wireless LAN system according to one embodiment of the present disclosure when an AP fails to receive a portion of a response frame.

[0024] FIG. 14b illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0025] FIG. 15a illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in the case where the AP fails to receive part of the response frame.

[0026] FIG. 15b illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0027] FIG. 16a illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in the case where the AP fails to receive part of the response frame.

[0028] FIG. 16b illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0029] FIG. 17a illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0030] FIG. 17b illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0031] FIG. 18 illustrates a flowchart of an operation for transmitting NPCA feedback information in a wireless LAN system according to one embodiment of the present disclosure.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] At this time, it will be understood that each block of the flowcharts and combinations of the flowcharts can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a specialized computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flowchart block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing the means of instruction to perform the function described in the flowchart block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] FIG. 1 illustrates the configuration of a device for wireless communication according to one embodiment of the present disclosure.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.).

[0056] 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.

[0057] 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.

[0058] FIG. 2 illustrates an exemplary structure of a wireless LAN system related to the present disclosure.

[0059] 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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] 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.

[0064] 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).

[0065] 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.

[0066] 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.

[0067] In addition to the structure of the aforementioned DS, an Extended Service Set (ESS) may be configured to provide wider coverage.

[0068] 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.

[0069] 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.

[0070] FIG. 3 illustrates a link setup process related to the present disclosure.

[0071] 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.

[0072] 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.

[0073] 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).

[0074] 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 and 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] FIG. 4 illustrates a backoff operation related to the present disclosure.

[0084] 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.

[0085] 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).

[0086] 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, ...).

[0087] 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.

[0088] 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.

[0089] 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.

[0090] A QoS STA can transmit a frame after a backoff, which is performed after the passage of an 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 frame for which AIFS[i] can be used can be a data frame or a management frame, and can also be a control frame rather than a response frame.

[0091] FIG. 5 illustrates a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) based frame transmission operation related to the present disclosure.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] FIG. 6 illustrates an exemplary format of a frame used in a wireless LAN system related to the present disclosure.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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).

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] FIG. 7 illustrates an exemplary format of a PPDU (physical layer protocol data unit) of a wireless LAN system related to the present disclosure.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] FIG. 8 illustrates another exemplary format of a PPDU of a wireless LAN system related to the present disclosure.

[0115] 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.

[0116] 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.

[0117] Meanwhile, UHR defines dynamic sub-band operation (DSO) so that an AP with an operation bandwidth of 320 MHz can dynamically direct a non-AP STA with an operation bandwidth of 160 MHz to transmit and / or receive at an auxiliary or secondary 160 MHz (hereinafter referred to as secondary 160 or 160S). Meanwhile, although the above example uses an AP with an operation bandwidth of 320 MHz and a non-AP STA with an operation bandwidth of 160 MHz, this is merely an example, and the operation bandwidths of the AP and non-AP STA are not limited to the above example. Therefore, it goes without saying that the DSO described in the present disclosure can be applied to any combination of AP and non-AP STA bandwidths where the bandwidth supported by the AP is higher than that of the non-AP STA.

[0118] Additionally, within each dynamically allocated transmit and / or receive opportunity, DL or trigger-based ULs can perform transmit and / or receive. Using DSO, the AP can dynamically utilize the secondary 160 MHz bandwidth on a per-transmission opportunity (TXOP) basis whenever it acquires channel access. Furthermore, the AP can dynamically determine whether to allocate non-AP STAs to the primary 160 MHz or secondary 160 MHz, and which non-AP STAs to allocate, based on bandwidth capability / availability, channel conditions, and QoS requirements. Thus, non-AP STAs with a narrower bandwidth in the secondary 160 MHz can be adjusted to match the availability of the secondary 160 MHz bandwidth.

[0119] Hereinafter, the present disclosure proposes a method for retransmitting an initial frame when an AP operating as a DSO fails to receive a response (e.g., an initial control response (ICR)) for the transmission of an initial frame (e.g., an initial control frame (ICF)) from a non-AP STA. Herein, the ICF may be a control frame for initiating a transmission opportunity (TXOP) or sequence, and a basic NAV may be set based on the ICF. Additionally, the ICR may be a control frame for confirming a transmission opportunity or sequence.

[0120] FIG. 9 illustrates a method for transmitting a BSRP (buffer status report poll) trigger frame of a wireless LAN system related to the present disclosure.

[0121] Referring to FIG. 9, the AP can transmit a BSRP trigger frame (910) to a non-AP STA as an ICF. The BSRP trigger frame is one of the trigger frames and may be a trigger frame used to instruct the non-AP STA to report a buffer status. The AP may receive a buffer status report (BSR) in the form of a TB PPDU format in response to the BSRP trigger. The TB PPDU format may be a PPDU format that allows non-AP STAs to transmit uplinks to each allocated resource unit (RU) for OFDMA. Thus, information for pre-scheduling which non-AP STA will transmit an uplink for each RU may be included in the BSRP trigger frame.

[0122] Each non-AP STA may transmit a BSR (920) in response to a BSRP trigger frame received from the AP. In this case, the BSR (920) may include the aforementioned TB PPDU format or non-HT PPDU format. In this case, for the non-HT PPDU format, the BSRP trigger frame may include at least one field reserved to convey information in the PPDU format for UL transmission to the non-AP STA. For example, at least one field following the UL BW (bandwidth) field within the Common Info field format included in the BSRP trigger frame may be a reserved field for transmission in the non-HT PPDU format. For example, the reserved at least one field may include at least one of information regarding the location of the RU, the transmission time, the type of the transmitted signal, and the method of generating the transmitted signal. However, even if the BSRP trigger frame includes at least one reserved field, it may still include some existing fields (e.g., a field indicating the response PPDU format, Special User Info Field Flag subfield). Additionally, the response frame transmitted by each non-AP STA may include not only the BSR but also an M-BA (multi-station block Ack) frame to contain information required for the DSO.

[0123] Subsequently, the AP can send a basic trigger frame (930) to each non-AP STA based on the BSR received from each non-AP STA. The AP can request an uplink transmission to a specific non-AP STA by establishing an uplink resource through the basic trigger frame. In the example described above, a BSRP trigger frame is used as an example of an ICF, but it is not limited thereto. Therefore, a MU-RTS (multi-user request-to-send) trigger frame may be used instead of a BSRP trigger frame.

[0124] FIG. 10 illustrates the concept of a DSO in a wireless LAN system related to the present disclosure.

[0125] Referring to FIG. 10, the operation of a DSO STA switching channels is described as the AP transmits an ICF to a non-AP STA (hereinafter DSO STA) operating as a DSO and to a non-AP STA (hereinafter non DSO STA) not operating as a DSO. Here, a DSO STA may refer to a non-AP STA instructed by the AP to operate at the remaining secondary 160 MHz (160S), excluding the primary 160 MHz (hereinafter 160P) which includes the primary 20 MHz for backoff, within the AP's operating bandwidth (e.g., 320 MHz). Meanwhile, the operating bandwidth of all non-AP STAs may be 160P.

[0126] The AP can assign a DSO STA to operate in a different subchannel (e.g., 160S) within the operating bandwidth by transmitting an ICF (1010) to instruct non-AP STAs to change the operating bandwidth. At this time, the control frame may further include an intermediate FCS with padding bits to account for the time required for the DSO STA receiving it to change the operating bandwidth. The DSO STA and non-DSO STA can receive the control frame (1020) at 160P, which is the operating bandwidth of the non-AP STAs. Accordingly, the DSO STA can change the operating bandwidth to the band allocated by the AP (e.g., 160S) after the short interframe space (SIFS).

[0127] Additionally, the AP may transmit a second control frame to the DSO STA and the non-DSO STA (1030). Accordingly, the DSO STA may receive the second control frame in the changed operating band (e.g., 160S), and the non-DSO STA may receive the second control frame in the existing operating band (e.g., 160P) without changing the operating band (1050). Then, the DSO STA may transmit a response frame for the second control frame to the AP in the changed operating band (e.g., 160S) (1060). The non-DSO STA may transmit a response frame for the second control frame to the AP in the operating band (e.g., 160P) (1070). Meanwhile, the ICF (1010) and the second control frame (1020) for instructing the aforementioned change of operating band can be transmitted over the entire operating band of the AP (e.g., 160P+160S). Additionally, the DSO STA may transmit an initial response frame (ICR) to the ICF without transmitting a separate additional control frame (1030) to the ICF. This allows the AP and non-AP STAs to perform the transmission and / or reception of frames using the entire operating band of the AP. Subsequently, when the TXOP initiated by the ICF is terminated, the DSO STA can return to the original operating band (e.g., 160P) (1080).

[0128] Meanwhile, if the AP fails to receive an acknowledgment frame (ICR) for the ICF in the resource (e.g., primary channel) allocated to the primary 20 MHz (hereinafter P20) where contention is performed (including cases where the AP fails to receive even a portion of the ICR in the primary channel), the AP may perform the following actions. For example, the AP may terminate the frame exchange sequence for all non-AP STAs. Alternatively, the AP may continue the frame exchange sequence assuming that P20 is occupied by at least one non-AP STA. Alternatively, the AP may retransmit the ICF until it receives an ICR transmitted by at least one non-AP STA in P20. However, specific actions of the AP and non-AP STA for each case are described below in the present disclosure.

[0129] FIG. 11 illustrates a method in a wireless LAN system according to one embodiment of the present disclosure when an AP fails to receive a response frame.

[0130] Referring to FIG. 11, a method is described for cases where an AP does not receive any response frame (ICR) from a non-AP STA when transmitting a DSO ICF (e.g., a BSRP trigger frame). In this disclosure, a DSO ICF may refer to an ICF indicating a DSO, and may be a concept that includes the ICF when the DSO is initiated by the ICF. Specifically, the AP may initiate a TXOP (1120) using a DSO ICF (e.g., a BSRP trigger frame including an intermediate FCS and padding bits) (1110). In this case, the operating bandwidth of the non-AP STAs associated with the AP (e.g., 80 MHz) may be smaller than the operating bandwidth of the AP (e.g., 160 MHz). In this case, the Duration / ID field included in the MAC header of the BSRP trigger frame may contain the estimated time value of the TXOP end. However, if the AP does not receive any response frame (ICR) for an ICF transmitted from multiple non-AP STAs, the AP may determine or identify that the ICF transmission failed (or determine or identify that the TXOP was not initiated) and call a backoff procedure.

[0131] In one embodiment, the AP may operate as follows in the case described above. After transmitting a CF-End (contention-free end) frame (1130) following the PIFS, the AP may perform a backoff procedure to reset the NAV set by the BSRP trigger frame. This is because the surrounding non-AP STA may unnecessarily maintain the NAV set by the BSRP trigger frame despite the AP's TXOP termination due to the previously transmitted BSRP trigger frame (1110). Therefore, the surrounding non-AP STA that receives the CF-End frame (1130) may reset the NAV. For example, the surrounding non-AP STA may participate in contention by setting the NAV to 0.

[0132] FIG. 12 illustrates a method in a wireless LAN system according to one embodiment of the present disclosure when an AP fails to receive a portion of a response frame.

[0133] Referring to FIG. 12, the operation of an AP is described in the case where the AP receives at least one response frame for a DSO ICF (e.g., a BSRP trigger frame), but does not receive any response frames on the primary channel. For example, if the AP transmits an ICF to a non-AP STA to change the operating band to the secondary channel band for DSO, servicing a non-AP STA (DSO STA) that transmitted the ICR only on the secondary channel because it did not receive the ICR on the primary channel may be contrary to the purpose of DSO, which is for the AP to service non-AP STAs using the entire operating band. Furthermore, the AP cannot identify which non-AP STA will request a TB PPDU transmission or receive a DL(MU) PPDU on the primary channel in a subsequent step within the TXOP. Therefore, since the AP cannot vacate the primary channel when performing DSO, an additional procedure may be required to find non-AP STAs that can transmit and receive on the primary channel.

[0134] In one embodiment, the AP may transmit a BSRP trigger frame (1210) as a DSO ICF to non-AP STA 1 and non-AP STA 2 having an operating bandwidth smaller than that of the AP (e.g., 80 MHz). In this case, the BSRP trigger frame (1210) may be transmitted over the entire operating bandwidth of the AP (e.g., 160 MHz). Additionally, a TXOP (1220) may be initiated according to the BSRP trigger frame (1210). However, for smooth DSO operation, after the transmission of the BSRP trigger frame (1210) (e.g., after SIFS has elapsed), the AP may receive a response frame (ICR, 1230) (e.g., TB PPDU format or non-HT PPDU format) from each of the non-AP STAs (e.g., non-AP STA 1 and non-AP STA 2). However, the AP may receive an ICR from non-AP STA 2 (hereinafter, DSO STA) but may not receive any response from non-AP STA 1 (hereinafter, non DSO STA). For example, this may occur when the non DSO STA is in a doze state for power saving, when the channel (e.g., primary 80 MHz) is in poor condition, when the non DSO STA is set to NAV by another AP, or when the AP fails to receive transmission from the non DSO STA. In this case, the AP may retransmit a BSRP trigger frame until it finds an active non-AP STA on the primary channel. Additionally, the AP that has successfully received a response frame on the secondary channel may allow the DSO STA that transmitted the response frame to remain operating on the secondary channel. Therefore, the retransmitted BSRP trigger frame (1240) may be transmitted for a shorter period of time compared to the BSRP trigger frame (1210) as an ICF.For example, the BSRP trigger frame (1240) may not include intermediate FCS and additional padding bits because the DSO STA has already changed the operating band.

[0135] However, the retransmission of the AP's BSRP trigger frame may be subject to the following restrictions. In one embodiment, the BSRP trigger frame may be retransmitted only when the More TF field value in the common information field included in the BSRP trigger frame is set to 1. Therefore, if the More TF field value is set to 0, it may imply that the BSRP trigger frame will not be retransmitted further. In this case, if the More TF field value is 0, the DSO STA may terminate the DSO and return to the existing operating band if it does not receive a packet from the AP despite transmitting an ICR. Of course, the above More TF field value is merely an example and is not limited to a specific value. In one embodiment, the AP may limit the number of DSO ICFs retransmitted within the TXOP. For example, the AP may further include a parameter (e.g., anIcfMaxRetransmit) in the BSRP trigger frame that indicates the number of retransmissions of the DSO ICF. Of course, the embodiments regarding the constraints on the retransmission of BSRP trigger frames described above may not necessarily be methods performed independently, but may be performed in combination with each other.

[0136] Meanwhile, if the AP does not receive a response frame (1250) on the primary channel despite the retransmission of the BSRP trigger frame (1240), it may retransmit the BSRP trigger frame (1260) including another non-AP STA instead of the non-AP STA that did not respond.

[0137] FIG. 13 illustrates a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0138] Referring to FIG. 13, the operation of the AP is described in the case where the AP receives at least one response frame for a DSO ICF (e.g., a MU-RTS trigger frame), but does not receive any response frame on the primary channel. However, unlike FIG. 12 described above, the DSO ICF may be a MU-RTS trigger frame, and the response frame may also be a CTS frame. Therefore, descriptions that overlap with FIG. 12 may be omitted.

[0139] In one embodiment, the AP may transmit a MU-RTS trigger frame (1310) as a DSO ICF to non-AP STA 1 and non-AP STA 2 having an operating bandwidth smaller than that of the AP (e.g., 80 MHz). In this case, the MU-RTS trigger frame (1310) may be transmitted over the entire operating bandwidth of the AP (e.g., 160 MHz). Additionally, a TXOP (1320) may be initiated according to the MU-RTS trigger frame (1310). However, for smooth DSO operation, after the transmission of the MU-RTS trigger frame (1310) (e.g., after SIFS has elapsed), the AP may receive a response frame (ICR, 1330) (e.g., a CTS frame) from each of the non-AP STAs (e.g., non-AP STA 1 and non-AP STA 2). However, the AP may receive an ICR from non-AP STA 2 (hereinafter, DSO STA) but may not receive any response from non-AP STA 1 (hereinafter, non DSO STA). In this case, the AP may retransmit a MU-RTS trigger frame until it finds an active non-AP STA on the primary channel. Additionally, the AP that successfully receives a response frame on the secondary channel may maintain the DSO STA that transmitted the response frame on the secondary channel. Therefore, the retransmitted MU-RTS trigger frame (1340) may be transmitted for a shorter period of time compared to the initially transmitted MU-RTS trigger frame (1310). For example, the MU-RTS trigger frame (1340) may not include an intermediate FCS and additional padding bits because the DSO STA has already changed its operating band.

[0140] However, the retransmission of the AP's MU-RTS trigger frame may be subject to the following restrictions. In one embodiment, the MU-RTS trigger frame may be retransmitted only when the More TF field value in the common information field included in the MU-RTS trigger frame is set to 1. Therefore, if the More TF field value is set to 0, it implies that the MU-RTS trigger frame will not be retransmitted further. In this case, if the More TF field value is 0, the DSO STA may terminate the DSO and return to the existing operating band if it fails to receive a packet from the AP despite transmitting an ICR. Of course, the above More TF field value is merely an example and is not limited to a specific value. In one embodiment, the AP may limit the number of DSO ICFs retransmitted within the TXOP. For example, the AP may further include a parameter (e.g., anIcfMaxRetransmit) in the MU-RTS trigger frame that indicates the number of retransmissions of the DSO ICF. Of course, the embodiments regarding the constraints on the retransmission of the MU-RTS trigger frame described above may not necessarily be methods performed independently, but may be performed in combination with each other.

[0141] Meanwhile, if the AP does not receive a response frame (1350) on the primary channel despite the retransmission of the MU-RTS trigger frame (1340), it may retransmit the MU-RTS trigger frame (1360) including another non-AP STA instead of the non-AP STA that did not respond.

[0142] FIGS. 14a and FIGS. 14b illustrate a method in a wireless LAN system according to one embodiment of the present disclosure when an AP fails to receive a portion of a response frame.

[0143] Referring to FIGS. 14a and 14b, it can be assumed that, similar to FIGS. 12 and 13 described above, some of the ICRs of non-AP STAs (e.g., the response frame of non-AP STA 1) are not received for the transmission of the AP's BSRP trigger frame. Therefore, descriptions that overlap with FIGS. 12 and 13 may be omitted.

[0144] However, instead of retransmitting the ICF described above (e.g., BSRP trigger frame or MU-RTS trigger frame), the AP may request a UL transmission (e.g., TB PPDU) to another non-AP STA (e.g., non-AP STA 3) (Fig. 14a) or transmit a DL transmission (e.g., MU PPDU) (Fig. 14b). In this case, non-AP STA 3 may be a non-AP STA that knows that the AP is operating on the primary channel and is in an awake state.

[0145] Referring again to FIG. 14a, the AP can initiate a TXOP (1410) by sending a BSRP trigger frame (1405) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP can receive an ICR (1415) only from the DSO STA (e.g., non-AP STA 2). At this time, if the AP identifies that another STA (e.g., non-AP STA 3) is operating on the primary channel and is awake, it can send a basic trigger frame (1420) to request UL transmission to non-AP STA 3 instead of non-AP STA 1, which has no response. Then, non-AP STA 3 can send a TB PPDU (1425) to the AP on the primary channel. Of course, the AP can also send a basic trigger frame (1420) to the DSO STA to receive a TB PPDU (1425) from the DSO STA on the secondary channel. Additionally, the AP can send an M-BA frame (1430) in response to the TB PPDU received from each non-AP STA (e.g., DSO STA and non-AP STA 3).

[0146] Referring again to FIG. 14b, the AP may initiate a TXOP (1440) by transmitting a BSRP trigger frame (1435) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP may receive an ICR (1445) only from the DSO STA (e.g., non-AP STA 2). At this time, if the AP identifies that another STA (e.g., non-AP STA 3) is operating on the primary channel and is awake, it may perform a DL transmission (1450) (e.g., MU PPDU) to non-AP STA 3 instead of non-AP STA 1, which has no response. non-AP STA 3 may transmit a BA frame (1455) to the AP on the primary channel in response to the MU PPDU. And the AP can also perform DL transmission to the DSO STA to receive a BA frame (1455) on the secondary channel in response to the MU PPDU from the DSO STA.

[0147] According to the embodiments described above, services can be provided to non-AP STAs across the entire operating bandwidth without clearing the primary channel during DSO operation. Additionally, by not performing retransmission of trigger frames to find non-AP STAs to be served on the primary channel, the AP can provide services to more surrounding non-AP STAs within a shorter time within the TXOP. Furthermore, although a BSRP trigger frame is used as an example of a DSO ICF in the embodiments described above, it is not limited thereto, and a MU-RTS trigger frame described in FIG. 13 may also be used. Moreover, in addition to non-AP STA 2 whose operating bandwidth has been changed to a secondary channel according to FIG. 14a and 14b, and non-AP STA 3 capable of transmitting and receiving on the primary channel, the AP may apply a DSO ICF retransmission technique to provide services within the TXOP to non-AP STA 1, which has not received a response to the DSO ICF, according to the method described in FIG. 12 or 13. Accordingly, in the DSO operation, the above-described embodiments (e.g., FIGS. 12 to 13, FIGS. 14a and FIGS. 14b) can be performed in combination with each other.

[0148] FIGS. 15a and 15b illustrate a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0149] Referring to FIGS. 15a and 15b, it can be assumed that, similar to FIGS. 12 to 13 and FIGS. 14a and 14b described above, some of the ICRs of non-AP STAs (e.g., response frames of non-AP STA 1) are not received for the transmission of a BSRP trigger frame of the AP. Accordingly, descriptions that overlap with FIGS. 12 to 13 and FIGS. 14a and FIGS. 14b may be omitted.

[0150] However, instead of retransmitting the ICF described above (e.g., BSRP trigger frame or MU-RTS trigger frame), the AP may request a UL transmission (e.g., TB PPDU) to a non-AT STA that has not responded (e.g., non-AP STA 1) (Fig. 15a) or transmit a DL transmission (e.g., MU PPDU) (Fig. 15b). In this case, the AP may not consider whether non-AP STA 1 has successfully received the DSO ICF or has successfully transmitted a response to the DSO ICF.

[0151] Referring again to FIG. 15a, the AP can initiate a TXOP (1510) by transmitting a BSRP trigger frame (1505) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP can receive an ICR (1515) only from the DSO STA (e.g., non-AP STA 2). Accordingly, the AP can transmit a basic trigger frame (1520) to request UL transmission to non-AP STA 1 that has not responded. Of course, depending on the changed state, such as the channel state or the state of non-AP STA 1, the AP may receive a UL (e.g., TB PPDU) (1525) on the primary channel from non-AP STA 1 that received the basic trigger frame. Meanwhile, the AP can also transmit a basic trigger frame (1520) to the DSO STA to receive a TB PPDU (1525) from the DSO STA on a secondary channel. Additionally, the AP can transmit an M-BA frame (1530) in response to the TB PPDU received from each non-AP STA (e.g., DSO STA, or DSO STA and non-AP STA 1).

[0152] Referring again to FIG. 15b, the AP can initiate a TXOP (1540) by transmitting a BSRP trigger frame (1535) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP can receive an ICR (1545) only from the DSO STA (e.g., non-AP STA 2). Therefore, the AP can perform a DL transmission (1550) (e.g., MU PPDU) on the primary channel to non-AP STA 1 that has not responded. Of course, non-AP STA 1 may receive the MU PPDU (1550) transmitted from the AP on the primary channel depending on the changed state, such as the channel state or the state of non-AP STA 1. Meanwhile, the DSO STA can transmit a BA frame (1555) to the AP on the secondary channel in response to the MU PPDU. Accordingly, the DSO STA can transmit a BA frame (1555) to the AP on the secondary channel in response to the MU PPDU.

[0153] According to the embodiments described above, service can be provided to at least one non-AP STA using the entire operating bandwidth without clearing the primary channel during DSO operation. Additionally, the AP can provide service to a non-AP STA that has changed its operating bandwidth to at least a secondary channel within a TXOP without performing an ICF retransmission to find a non-AP STA to provide service to on the primary channel. Furthermore, although a BSRP trigger frame is used as an example of a DSO ICF in the embodiments described above, it is not limited thereto, and a MU-RTS trigger frame described in FIG. 13 may also be used. Moreover, for non-AP STA 1 that has not received a response to the DSO ICF according to FIG. 15a and 15b, a DSO ICF retransmission technique may be applied to provide service within a TXOP according to the method described in FIG. 12 or 13. Accordingly, in the DSO operation, the above-described embodiments (e.g., FIGS. 12 to 13, FIGS. 15a and FIGS. 15b) can be performed in combination with each other.

[0154] FIGS. 16a and 16b illustrate a method in a wireless LAN system according to one embodiment of the present disclosure when an AP fails to receive a portion of a response frame.

[0155] Referring to FIGS. 16a and 16b, it can be assumed that, similar to FIGS. 12 and 13 described above, some of the ICRs of non-AP STAs (e.g., the response frame of non-AP STA 1) are not received for the transmission of the AP's BSRP trigger frame. Therefore, descriptions that overlap with FIGS. 12 and 13 may be omitted.

[0156] However, unlike the retransmission of the previously described ICF (e.g., BSRP trigger frame or MU-RTS trigger frame), the AP may not provide service within the TXOP to a non-AT STA (e.g., non-AP STA 1) that has not responded on the primary channel. Therefore, the AP may provide service within the TXOP using only the secondary channel band for a non-AT STA (e.g., non-AP STA 2) that has changed its operating band to the secondary channel according to the DSO ICF. Meanwhile, according to the methods of FIG. 16a and FIG. 16b, the following constraints may exist to resolve or reduce problems caused by the AP not using the primary channel within the TXOP.

[0157] For example, if the size of the DL buffer unit (BU) or UL BU of a DSO STA is small, or if the overhead incurred by the DSO STA returning to the primary channel is large, it may be relatively advantageous to provide service to the DSO STA rather than using the primary channel within a given TXOP. Therefore, considering the overhead incurred by the DSO STA returning to the primary channel, the AP requests UL transmission or imposes limits on data size (bytes) or transmission time (msec) during DL transmission (e.g., thresholds: bytes or (msec) can be set. In one embodiment, the AP may provide service using only a secondary channel within a given TXOP when the size of the data or the time required for transmission is smaller than (or less than or equal to) a threshold value. Meanwhile, when the size of the data to be transmitted or the time required for transmission is larger than (or greater than or equal to) a threshold value, the AP may operate according to the method described above (e.g., FIGS. 12 and 13, FIGS. 13a, 13b, 14a, 14b, 15a, or 15b).

[0158] Referring again to FIG. 16a, the AP may initiate a TXOP (1610) by transmitting a BSRP trigger frame (1605) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP may receive an ICR (1615) only from the DSO STA (e.g., non-AP STA 2). If the size of the data (e.g., TB PPDU) to be transmitted or the time required for transmission is less than (or less than or equal to) a threshold value, the AP may receive a TB PPDU (1625) from the DSO STA on the secondary channel by transmitting a basic trigger frame (1620) to the DSO STA. Additionally, the AP may transmit an M-BA frame (1630) on the secondary channel in response to the TB PPDU (1625) received from the DSO STA. Meanwhile, the AP may send a CF-end frame (1635) to the DSO STA and non-AP STA 1 to request additional UL transmission within a given TXOP, perform additional DL transmission within a given TXOP, or terminate the TXOP.

[0159] Referring again to FIG. 16b, the AP may initiate a TXOP (1645) by transmitting a BSRP trigger frame (1640) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP may receive an ICR (1650) only from the DSO STA (e.g., non-AP STA 2). If the size of the DL data (e.g., MU PPDU) or the time required for transmission is less than (or less than or equal to) a threshold value, the AP may perform a DL transmission (1655) (e.g., MU PPDU) on a secondary channel to the DSO STA. Then, the DSO STA may transmit a BA frame (1660) to the AP on a secondary channel in response to the MU PPDU (1655). Accordingly, the DSO STA may transmit a BA frame (1660) to the AP on the secondary channel in response to the MU PPDU. Meanwhile, the AP may transmit a CF-end frame (1665) to the DSO STA and non-AP STA 1 to perform additional DL transmission within a given TXOP, request additional UL transmission within a given TXOP, or terminate the TXOP.

[0160] According to the embodiments described above, the AP may provide service to a DSO STA using only a secondary channel without using the primary channel in the DSO operation within the TXOP. Additionally, the AP may provide service in the secondary channel within the TXOP already initiated by the DSO ICF, without instructing the DSO STA that has changed its operation band to the secondary channel to return to the primary channel. Furthermore, although the BSRP trigger frame is used as an example of the DSO ICF in the embodiments described above, it is not limited thereto, and the MU-RTS trigger frame described in FIG. 13 may also be used.

[0161] FIGS. 17a and 17b illustrate a method in a wireless LAN system according to one embodiment of the present disclosure in which an AP fails to receive a portion of a response frame.

[0162] Referring to FIGS. 17a and 17b, it can be assumed that, similar to FIGS. 12 and 13 described above, some of the ICRs of non-AP STAs (e.g., the response frame of non-AP STA 1) are not received for the transmission of the AP's BSRP trigger frame. Therefore, descriptions that overlap with FIGS. 12 and 13 may be omitted.

[0163] However, rather than retransmitting the ICF described above (e.g., BSRP trigger frame or MU-RTS trigger frame), the AP may terminate the DSO if there is no response from a non-AT STA (e.g., non-AP STA 1) on the primary channel. Accordingly, the AP may instruct a non-AT STA (e.g., non-AP STA 2) that has changed its operating band to the secondary channel according to the DSO ICF to return to the primary channel band. Meanwhile, according to the methods of FIG. 17a and FIG. 17b, since a delay problem may occur when the DSO STA changes its operating band again between the primary channel and the secondary channel, the following limitations may exist.

[0164] For example, if the size of the DL buffer unit (BU) or UL BU of a DSO STA is large, or if the overhead incurred by the DSO STA returning to the primary channel is small, it may be advantageous to terminate the DSO compared to the delay issues caused by changing the operating band of the DSO STA. Therefore, considering the delay and overhead incurred by the DSO STA returning to the primary channel, the AP requests UL transmission or imposes limits on data size (bytes) or transmission time (msec) during DL transmission (e.g., thresholds: bytes or (msec) can be set. In one embodiment, the AP may terminate the DSO when the size of the data or the time required for transmission is greater than (or greater than or equal to) a threshold value (e.g., when it is greater than the delay time required for the DPO STA to change the operating band back to the primary channel band). Conversely, when the size of the data to be transmitted or the time required for transmission is less than (or less than or equal to) a threshold value, the AP may operate according to the method described above (e.g., FIG. 12 to 13, FIG. 13a, 13b, 14a, 14b, 15a, 15b, 16a, or 16b).

[0165] Referring again to FIG. 17a, the AP may initiate a TXOP (1710) by transmitting a BSRP trigger frame (1705) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP may receive an ICR (1715) only from the DSO STA (e.g., non-AP STA 2). If the size of the data (e.g., TB PPDU) to be transmitted or the time required for transmission is greater than (or greater than or equal to) a threshold value, the AP may transmit a BSRP trigger frame (1720) for changing the operating band of the DSO STA (e.g., from a secondary channel to a primary channel). Accordingly, non-AP STA 2, which was operating as a DSO STA, may return to the primary channel band and then transmit a response frame (1725) to the AP on the primary channel in response to the BSRP trigger frame (1720). Subsequently, the AP can transmit a basic trigger frame (1730) to request UL transmission to non-AP STA 2 on the primary channel. Then, non-AP STA 2 can transmit a TB PPDU (1735) to the AP on the primary channel. Accordingly, the AP can transmit a BA frame (1740) on the primary channel in response to the TB PPDU (1735) received from non-AP STA 2.

[0166] Referring again to FIG. 17b, the AP may initiate a TXOP (1745) by transmitting a BSRP trigger frame (1740) as a DSO ICF to non-AP STA 1 and non-AP STA 2. However, the AP may receive an ICR (1750) only from the DSO STA (e.g., non-AP STA 2). If the size of the DL data (e.g., MU PPDU) or the time required for transmission is greater than (or greater than or equal to) a threshold value, the AP may transmit a BSRP trigger frame (1760) for changing the operating band of the DSO STA (e.g., from a secondary channel to a primary channel). Accordingly, non-AP STA 2, which was operating as a DSO STA, may return to the primary channel band and then transmit a response frame (1765) to the AP on the primary channel in response to the BSRP trigger frame (1760). The AP can perform a DL transmission (1770) (e.g., MU PPDU) on the primary channel to the non-AP STA 2. And the non-AP STA 2 can transmit a BA frame (1775) to the AP on the primary channel in response to the MU PPDU (1770).

[0167] According to the embodiments described above, the AP can terminate the DSO within a TXOP for a connected non-AP STA and provide service in the existing operating band (e.g., primary channel), even if it accepts the delay or overhead problem caused by the DSO STA changing the operating band again. Additionally, although a BSRP trigger frame is used as an example of a DSO ICF in the embodiments described above, it is not limited thereto, and a MU-RTS trigger frame described in FIG. 13 may also be used.

[0168] FIG. 18 illustrates a flowchart of AP operations for performing DSO in a wireless LAN system according to one embodiment of the present disclosure.

[0169] Referring to FIG. 18, the DSO operation proposed in the present disclosure is illustrated, and some or all of the various embodiments related to the AP described above may be applied to FIG. 18 in the same or similar manner.

[0170] In step 1810, the AP may transmit a first frame to initiate a DSO to the first non-AP STA and the second non-AP STA. At this time, the first frame may be a BSRP trigger frame or a MU-RTS trigger frame. Additionally, the first frame may initiate a TXOP as an ICF. Additionally, the first frame may instruct the second non-AP STA to change channels for the DSO and may include at least one padding bit for the intermediate FCS and the channel change of the second non-AP STA.

[0171] In step 1820, the AP may transmit a second frame associated with a DSO to a plurality of STAs, including a second non-AP STA. In one embodiment, if the AP does not receive any response to the transmission of the first frame, the second frame may be a CF-End frame to terminate the TXOP initiated by the first frame. In one embodiment, if the AP receives only a partial response to the transmission of the first frame (e.g., if it does not receive a response from the first non-AP STA on the primary channel), the second frame may include a retransmission of the first frame. In this case, unlike the first frame transmitted as an ICF, the retransmitted first frame may not include at least one padding bit for intermediate FCS and channel change of the second non-AP STA. Additionally, the number of retransmissions of the first frame transmitted within the AP's TXOP may be based on at least one of the More TF field or a parameter regarding the number of retransmissions. In this case, the More TF field is included in the Common Info field of the first frame and may have a value of 1. Meanwhile, the response frame for the first frame as an ICF may include a TB PPDU format or a non-HT PPDU format. Additionally, the response frame may include a BSR and an M-BA.

[0172] Meanwhile, although an example of the operation of the AP and non-AP STA was described above based on the flowchart illustrated in FIG. 18, it is obvious that the operation of the non-AP STA and AP may differ according to other examples described above.

[0173] 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.

[0174] 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 an access point (AP) of a wireless local area network (WLAN) system, A step of transmitting a first frame to initiate a dynamic subband operation (DSO) to a first STA (station) and a second STA; and The method includes the step of transmitting a second frame associated with the DSO to a plurality of STAs including the second STA, and The operating band of the second STA is changed from the primary channel of the AP to the secondary channel of the AP based on the first frame, and A method wherein the second frame comprises a CF-End (contention-free end) frame for terminating a TXOP (transmission opportunity) initiated by the first frame or a retransmission of the first frame.

2. In Paragraph 1, A method in which, if the AP does not receive a response frame for the first frame from the first STA and the second STA, the second frame is the CF-End (contention-free end) frame.

3. In Paragraph 1, A method in which, if the AP does not receive a response frame for the first frame from the first STA on the primary channel, the second frame is the first frame being retransmitted.

4. In Paragraph 3, The first frame for initiating the above DSO is an ICF (initial control frame) including an intermediate FCS (frame check sequence) and at least one padding bit, and A method in which the first frame being retransmitted is a control frame that does not include the intermediate FCS and the at least one padding bit.

5. In Paragraph 3, The number of retransmissions of the first frame being retransmitted within the above TXOP is based on at least one of the More TF field or a parameter regarding the number of retransmissions, and A method in which the above More TF field is included in the Common Info field included in the first frame and has a value of 1.

6. In Paragraph 3, The first frame for initiating the above DSO is a BSRP (buffer status report poll) trigger frame or a MU-RTS (multi-user request-to-send) trigger frame, and If the first frame for initiating the above DSO is the BSRP trigger frame, the response frame is in TB (trigger-based) PPDU (physical layer protocol data unit) format or non-HT (high throughput) PPDU format, and A method in which, when the first frame for initiating the above DSO is the MU-RTS trigger frame, the response frame is a CTS (Clear-To-Send) frame.

7. In Paragraph 6, A method in which the above response frame includes a BSR (buffer status report) and an M-BA (multi-station block ACK).

8. In Paragraph 1, The second frame above includes a trigger frame or downlink data for requesting uplink transmission, and A method wherein the second frame is transmitted to the second STA on the secondary channel and transmitted to the STA operating on the primary channel among the plurality of STAs excluding the second STA on the primary channel.

9. In an access point (AP) of a wireless local area network (WLAN) system, transceiver; and It includes at least one processor connected to the above-mentioned transmitting and receiving unit, and The above at least one processor is: Transmit a first frame to initiate a dynamic subband operation (DSO) to the first STA (station) and the second STA, and A plurality of STAs including the second STA are configured to transmit a second frame associated with the DSO, and The operating band of the second STA is changed from the primary channel of the AP to the secondary channel of the AP based on the first frame, and AP, wherein the second frame comprises a CF-End (contention-free end) frame for terminating a TXOP (transmission opportunity) initiated by the first frame or a retransmission of the first frame.

10. In Paragraph 9, If the AP does not receive a response frame for the first frame from the first STA and the second STA, the second frame is the CF-End (contention-free end) frame, the AP.

11. In Paragraph 9, If the AP does not receive a response frame for the first frame from the first STA on the primary channel, the second frame is the retransmitted first frame, the AP.

12. In Paragraph 11, The first frame for initiating the above DSO is an ICF (initial control frame) including an intermediate FCS (frame check sequence) and at least one padding bit, and AP, wherein the first frame being retransmitted is a control frame that does not include the intermediate FCS and the at least one padding bit.

13. In Paragraph 11, The number of retransmissions of the first frame being retransmitted within the above TXOP is based on at least one of the More TF field or a parameter regarding the number of retransmissions, and The above More TF field is included in the Common Info field included in the first frame and is an AP having a value of 1.

14. In Paragraph 11, The first frame for initiating the above DSO is a BSRP (buffer status report poll) trigger frame or a MU-RTS (multi-user request-to-send) trigger frame, and If the first frame for initiating the above DSO is the BSRP trigger frame, the response frame is in TB (trigger-based) PPDU (physical layer protocol data unit) format or non-HT (high throughput) PPDU format, and AP, wherein if the first frame for initiating the above DSO is the MU-RTS trigger frame, the response frame is a CTS (Clear-To-Send) frame.

15. In Paragraph 14, The above response frame is an AP that includes a BSR (buffer status report) and an M-BA (multi-station block ACK).

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