Method and apparatus for performing probing procedure in wireless LAN system

Abstract

A method and apparatus for operating in a wireless LAN system are disclosed. According to one embodiment of the present disclosure, a method performed by a first station (STA) in a wireless LAN system comprises the steps of: receiving a trigger frame from a second STA; and transmitting an uplink (UL) null data physical layer protocol data unit (NDP) based on the trigger frame to the second STA, where the trigger frame includes first information indicating that the trigger frame is intended to request the UL NDP, where the first information may be indicated based on at least one of a UL length field included in a common information field of the trigger frame or a specific field associated with the UL NDP request.

Description

Technical Field

[0001] This disclosure relates to communication operations in a wireless local area network (WLAN) system, and more specifically, to a method and apparatus for performing an uplink probing process in a next-generation wireless LAN system. Background Technology

[0002] New technologies have been introduced for Wireless LANs (WLANs) to improve transmission rates, increase bandwidth, enhance reliability, reduce errors, and decrease latency. Within WLAN technology, the IEEE 802.11 series of standards can be referred to as Wi-Fi. For example, recent technologies introduced into WLAN include the Ultra High Throughput (VHT) enhancement of the 802.11ac standard and the High Efficiency (HE) enhancement of the IEEE 802.11ax standard.

[0003] To provide a more advanced wireless communication environment, improved techniques for Extremely High Throughput (EHT) are being discussed. For example, techniques for MIMO and multiple access point (AP) coordination that support increased bandwidth, efficient utilization of multiple frequency bands, and increased spatial flow are being investigated. Specifically, various techniques are being explored to support low latency or real-time traffic. Furthermore, new technologies to support Ultra-High Reliability (UHR), including improvements or extensions to EHT techniques, are being discussed. Summary of the Invention

[0004] Technical issues

[0005] The technical problem of this disclosure is to provide a method and apparatus for performing an uplink probing process in a wireless LAN system.

[0006] The technical problem of this disclosure is to provide a method and apparatus for sending and receiving trigger frames and NDP frames for uplink probe procedures.

[0007] The technical objectives to be achieved by this disclosure are not limited to those described above, and other technical objectives not described herein will be clearly understood by those skilled in the art through the following description.

[0008] Technical solution

[0009] According to one embodiment of this disclosure, a method performed by a first station (STA) in a wireless LAN system may include: receiving a trigger frame from a second STA; and sending an uplink (UL) null data physical layer protocol data unit (NDP) based on the trigger frame to the second STA, wherein the trigger frame includes first information indicating that the trigger frame can be used to request a UL NDP, and the first information may be indicated based on at least one of a UL length field included in the common information field of the trigger frame or a specific field related to the UL NDP request.

[0010] According to another embodiment of this disclosure, a method performed by a second station (STA) in a wireless LAN system may include: sending a trigger frame to a first STA; and receiving an uplink (UL) null data physical layer protocol data unit (NDP) based on the trigger frame from the first STA, wherein the trigger frame may include first information indicating that the trigger frame is for requesting the UL NDP, and the first information may be indicated based on at least one of a UL length field included in the common information field of the trigger frame or a specific field related to the UL NDP request.

[0011] Technical effect

[0012] According to various embodiments of the present disclosure, methods and apparatus for performing an uplink probing process in a wireless LAN system can be provided.

[0013] According to various embodiments of this disclosure, methods and apparatus for sending and receiving trigger frames and NDP frames for uplink probing processes can be provided.

[0014] The effects achievable by this disclosure are not limited to those described above, and those skilled in the art can clearly understand other effects not described herein through the following description. Attached Figure Description

[0015] The accompanying drawings, which are included as part of the detailed description of this disclosure, provide embodiments of the disclosure and, together with the detailed description, illustrate the technical features of the disclosure.

[0016] Figure 1 A configuration block diagram of a wireless communication device according to an embodiment of the present disclosure is illustrated.

[0017] Figure 2 This is a diagram illustrating an exemplary structure of a WLAN system to which this disclosure can be applied.

[0018] Figure 3 This is a diagram used to illustrate the link establishment process that can be applied to this disclosure.

[0019] Figure 4 This is a diagram used to illustrate the backoff processing that can be applied to this disclosure.

[0020] Figure 5 This is a diagram illustrating the CSMA / CA-based frame transmission operation that can be applied to this disclosure.

[0021] Figure 6 This is a diagram illustrating an example of a frame structure that can be used in a WLAN system to which this disclosure may be applied.

[0022] Figure 7This is a diagram illustrating an example of a PPDU as defined in the IEEE 802.11 standard of this disclosure.

[0023] Figure 8 An exemplary format of the trigger frame to which this disclosure can be applied is illustrated.

[0024] Figure 9 This is a flowchart for explaining the method performed by the first STA according to an embodiment of the present disclosure.

[0025] Figure 10 This is a flowchart for explaining the method performed by the second STA according to an embodiment of the present disclosure.

[0026] Figure 11 This is a diagram used to explain the UL detection process according to embodiments of this disclosure.

[0027] Figure 12 The structure of a trigger frame and a UL NDP for requesting a UL NDP frame according to an embodiment of the present disclosure is illustrated. Detailed Implementation

[0028] In the following, embodiments according to this disclosure will be described in detail with reference to the accompanying drawings. The detailed description disclosed with reference to the drawings is intended to describe exemplary embodiments of this disclosure and not to represent the only embodiments in which this disclosure can be implemented. The following detailed description includes specific details to provide a complete understanding of this disclosure. However, those skilled in the art will recognize that this disclosure can be implemented without these specific details.

[0029] In some cases, known structures and devices may be omitted, or they may be shown in block diagram form based on the core functions of each structure and device in order to prevent ambiguity in the concepts of this disclosure.

[0030] In this disclosure, when an element is referred to as “connected,” “combined,” or “linked” to another element, it can include both indirect and direct connections between the two elements. Furthermore, in this disclosure, the terms “comprising” or “having” specify the presence of the mentioned features, steps, operations, components, and / or elements, but do not exclude the presence or addition of one or more other features, stages, operations, components, elements, and / or groups thereof.

[0031] In this disclosure, terms such as "first" and "second" are used only to distinguish one element from another and are not used to limit the elements. Unless otherwise stated, they do not limit the order or importance of the elements. Therefore, within the scope of this disclosure, a first element in one embodiment may be referred to as a second element in another embodiment, and similarly, a second element in one embodiment may be referred to as a first element in another embodiment.

[0032] The terminology used in this disclosure is for the purpose of describing particular embodiments and not for limiting the claims. As used in the description of embodiments and 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 one of the associated enumerations, or is intended to refer to and include any and all possible combinations of two or more of them. Furthermore, unless otherwise stated, the “ / ” between words in this disclosure has the same meaning as “and / or”.

[0033] The examples disclosed herein can be applied to various wireless communication systems. For example, the examples disclosed herein can be applied to wireless LAN systems. For example, the examples disclosed herein can be applied to wireless LANs based on the IEEE 802.11a / g / n / ac / ax standards. Furthermore, the examples disclosed herein can be applied to wireless LANs based on the newly proposed IEEE 802.11be (or EHT) standard. The examples disclosed herein can be applied to wireless LANs based on the IEEE 802.11be version 2 standard, corresponding to the additional enhancements of the IEEE 802.11be version 1 standard. Additionally, the examples disclosed herein can be applied to wireless LANs based on next-generation standards following IEEE 802.11be. Furthermore, the examples disclosed herein can be applied to cellular wireless communication systems. For example, it can be applied to cellular wireless communication systems based on 3GPP standards using Long Term Evolution (LTE) technology and 5G New Radio (NR) technology.

[0034] The technical features that can be applied to examples of this disclosure will be described below.

[0035] Figure 1 A block diagram illustrating a wireless communication device according to an embodiment of the present disclosure is shown.

[0036] Figure 1 The first device 100 and the second device 200 illustrated herein can be replaced by various terms such as terminal, wireless device, wireless transceiver unit (WTRU), user equipment (UE), mobile station (MS), user terminal (UT), mobile subscriber station (MSS), mobile subscriber unit (MSU), subscriber station (SS), advanced mobile station (AMS), wireless terminal (WT), or simply user. Furthermore, the first device 100 and the second device 200 include access point (AP), base station (BS), fixed station, node B, base transceiver system (BTS), and network. It can be replaced by various terms such as artificial intelligence (AI) system, roadside unit (RSU), repeater, router, relay, and gateway.

[0037] Figure 1The devices 100 and 200 illustrated herein may be referred to as stations (STAs). For example, Figure 1 The devices 100 and 200 illustrated herein may be referred to by various terms such as transmitting device, receiving device, transmitting STA, and receiving STA. For example, STA 110 and 200 may perform an access point (AP) role or a non-AP role. That is, in this disclosure, STA 110 and 200 may perform AP and / or non-AP functions. When STA 110 and 200 perform AP functions, they may simply be referred to as APs, and when STA 110 and 200 perform non-AP functions, they may simply be referred to as STAs. Alternatively, in this disclosure, AP may also be referred to as AP STA.

[0038] Reference Figure 1 The first device 100 and the second device 200 can transmit and receive radio signals via various wireless LAN technologies (e.g., IEEE 802.11 series). The first device 100 and the second device 200 may include interfaces for the Media Access Control (MAC) layer and Physical Layer (PHY) conforming to the IEEE 802.11 standard.

[0039] In addition to wireless LAN technology, the first device 100 and the second device 200 can also support various communication standards (e.g., 3GPP LTE series, 5G NR series standards, etc.). Furthermore, the devices disclosed herein can be implemented in various devices such as mobile phones, vehicles, personal computers, augmented reality (AR) devices, and virtual reality (VR) devices. Additionally, the STA of this specification can support various communication services such as voice calls, video calls, data communication, autonomous driving, machine-type communication (MTC), machine-to-machine (M2M), device-to-device (D2D), and IoT (Internet of Things).

[0040] The first device 100 may include one or more processors 102 and one or more memories 104, and may additionally include one or more transceivers 106 and / or one or more antennas 108. The processors 102 may control the memories 104 and / or the transceivers 106, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. For example, the processor 102 may transmit a wireless signal including the first information / signal via the transceivers 106 after generating first information / signal by processing information in the memories 104. Additionally, the processor 102 may receive a wireless signal including second information / signal via the transceivers 106, and then store information obtained through signal processing of the second information / signal in the memories 104. The memories 104 may be connected to the processor 102 and may store various information related to the operation of the processor 102. For example, the memories 104 may store software code including instructions for performing all or part of the processing controlled by the processor 102 or for performing the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. Here, processor 102 and memory 104 may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). Transceiver 106 may be connected to processor 102 and may transmit and / or receive wireless signals via one or more antennas 108. Transceiver 106 may include a transmitter and / or a receiver. Transceiver 106 may be used with an RF (radio frequency) unit. In this disclosure, wireless device may refer to a communication modem / circuit / chip.

[0041] The second device 200 may include one or more processors 202 and one or more memories 204, and may additionally include one or more transceivers 206 and / or one or more antennas 208. The processors 202 may control the memories 204 and / or the transceivers 206, and may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. For example, the processors 202 may generate third information / signals by processing information in the memories 204, and then transmit a wireless signal including the third information / signals via the transceivers 206. Additionally, the processors 202 may receive wireless signals including fourth information / signals via the transceivers 206, and then store information obtained through signal processing of the fourth information / signals in the memories 204. The memories 204 may be connected to the processors 202 and may store various information related to the operation of the processors 202. For example, the memories 204 may store software code including instructions for performing all or part of the processing controlled by the processors 202 or for performing the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure. Here, processor 202 and memory 204 may be part of a communication modem / circuit / chip designed to implement wireless LAN technology (e.g., IEEE 802.11 series). Transceiver 206 may be connected to processor 202 and may transmit and / or receive wireless signals via one or more antennas 208. Transceiver 206 may include a transmitter and / or a receiver. Transceiver 206 may be used with an RF unit. In this disclosure, apparatus may refer to a communication modem / circuit / chip.

[0042] The hardware elements of devices 100 and 200 will be described in more detail below. Not limited thereto, one or more protocol layers may be implemented by one or more processors 102 and 202. For example, one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as PHY and MAC). One or more processors 102 and 202 may generate one or more PDUs (Protocol Data Units) and / or one or more SDUs (Service Data Units) according to the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 202 may generate messages, control information, data, or information according to the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the functions, processes, suggestions, and / or methods disclosed in this disclosure to provide them to one or more transceivers 106 and 206. One or more processors 102, 202 may receive signals (e.g., baseband signals) from one or more transceivers 106, 206 and obtain PDUs, SDUs, messages, control information, data or information, in accordance with the description, functions, processes, suggestions, methods and / or operation flowcharts included in this disclosure.

[0043] One or more processors 102, 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. One or more processors 102, 202 may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more ASICs (Application-Specific Integrated Circuits), one or more DSPs (Digital Signal Processors), one or more DSPDs (Digital Signal Processing Devices), one or more PLDs (Programmable Logic Devices), or one or more FPGAs (Field-Programmable Gate Arrays) may be included in one or more processors 102, 202. The descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, processes, functions, etc. Firmware or software configured to execute the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure may be included in one or more processors 102, 202, or may be stored in one or more memories 104, 204 and driven by one or more processors 102, 202. The descriptions, functions, processes, suggestions, methods and / or operation flowcharts included in this disclosure may be implemented using firmware or software in the form of code, instructions and / or instruction sets.

[0044] One or more memories 104, 204 may be connected to one or more processors 102, 202 and may store data, signals, messages, information, programs, code, instructions, and / or commands in various forms. One or more memories 104, 204 may be configured with ROM, RAM, EPROM, flash memory, hard disk drive, registers, cache memory, computer-readable storage media, and / or combinations thereof. One or more memories 104, 204 may be located internally and / or externally to one or more processors 102, 202. Furthermore, one or more memories 104, 204 may be connected to one or more processors 102, 202 via various technologies such as wired or wireless connections.

[0045] One or more transceivers 106, 206 can transmit user data, control information, wireless signals / channels, etc., mentioned in the methods and / or operation flowcharts of this disclosure to one or more other devices. One or more transceivers 106, 206 can receive user data, control information, wireless signals / channels, etc., mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure from one or more other devices. For example, one or more transceivers 106, 206 can be connected to one or more processors 102, 202 and can transmit and receive wireless signals. For example, one or more processors 102, 202 can control one or more transceivers 106, 206 to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors 102, 202 can control one or more transceivers 106, 206 to receive user data, control information, or wireless signals 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, wireless signals / channels, etc., mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts included in this disclosure, via one or more antennas 108, 208. In this disclosure, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers 106, 206 may convert received wireless signals / channels, etc., from RF band signals into baseband signals for processing using one or more processors 102, 202. One or more transceivers 106, 206 may convert user data, control information, wireless signals / channels, etc., processed using one or more processors 102, 202, from baseband signals into RF band signals. Therefore, one or more transceivers 106, 206 may include (analog) oscillators and / or filters.

[0046] For example, one of STA100 and 200 can perform the expected operation of an AP, and the other of STA100 and 200 can perform the expected operation of a non-AP STA. For example, Figure 1 Transceivers 106 and 206 can perform transmission and reception operations of signals (e.g., packet or physical layer protocol data units (PPDUs) conforming to IEEE 802.11a / b / g / n / ac / ax / be / bn). Additionally, in this disclosure, the various STAs can generate transmission / reception signals or perform data processing or calculations on the transmission / reception signals in advance by [the relevant entity / component]. Figure 1Processors 102 and 202 perform the following operations: For example, examples of generating transmit / receive signals or performing data processing or computations on transmit / receive signals in advance may include: 1) determining / acquiring / configuring / computing / decoding / encoding bit information of fields (signals (SIG), short training field (STF), long training field (LTF), data, etc.) included in the PPDU; 2) determining / configuring / acquiring time or frequency resources (e.g., subcarrier resources) for the fields (SIG, STF, LTF, data, etc.) included in the PPDU; 3) determining / configuring / acquiring a specific sequence (e.g., pilot sequence, STF / LTF sequence, additional sequence applied to SIG) for the fields (SIG, STF, LTF, data, etc.) included in the PPDU action; 4) power control operations and / or power saving operations applied to the STA; 5) operations related to determining / acquiring / configuring / computing / decoding / encoding of the ACK signal. Additionally, in the example below, various information used by different STAs to determine / acquire / configure / calculate / decode / encode transmitted and received signals (e.g., information related to fields / subfields / control fields / parameters / power, etc.) can be stored. Figure 1 In memory 104 and 204.

[0047] In the following text, downlink (DL) can refer to a link used for communication from an AP STA to a non-AP STA, and DL PPDUs / packets / signals can be sent and received via DL. In DL communication, the transmitter can be part of an AP STA, and the receiver can be part of a non-AP STA. Uplink (UL) can refer to a link used for communication from a non-AP STA to an AP STA, and UL PPDUs / packets / signals can be sent and received via UL. In UL communication, the transmitter can be part of a non-AP STA, and the receiver can be part of an AP STA.

[0048] Figure 2 This is a diagram illustrating an exemplary structure of a wireless LAN system to which this disclosure can be applied.

[0049] A wireless LAN system can be structured by multiple components. These components interact to provide STA mobility support that is transparent to upper layers. The Basic Service Set (BSS) corresponds to the basic building blocks of a wireless LAN. Figure 2 An example is shown where there are two BSSs (BSS1 and BSS2), and two STAs (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2) are included as members of each BSS. Figure 2The ellipse representing the BSS can also be interpreted as representing the coverage area within the corresponding BSS where STAs maintain communication. This area can be called the Basic Service Area (BSA). When a STA moves outside the BSA, it cannot communicate directly with other STAs within the BSA.

[0050] If we do not consider Figure 2 The DS shown in the diagram represents the most basic BSS type in a wireless LAN: the Independent BSS (IBSS). For example, an IBSS can have a minimal form containing only two STAs. For instance, assuming other components are omitted, BSS1 containing only STA1 and STA2, or BSS2 containing only STA3 and STA4, can respectively correspond to representative examples of IBSS. This configuration is possible when STAs can communicate directly without an AP. Furthermore, in this type of wireless LAN, it is not pre-configured but can be configured as needed, and this can be called an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. That is, in an IBSS, STAs are managed in a distributed manner. In an IBSS, all STAs can consist of mobile STAs and are not allowed to access the Distributed System (DS), thus forming a self-contained network.

[0051] Membership of an STA in a BSS can be dynamically changed by opening or closing an STA, or by entering or leaving a BSS zone. 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 dynamically established and may include the use of Distributed System Services (DSS).

[0052] Direct STA-to-STA distance in a wireless LAN may be limited by PHY performance. In some cases, this distance limitation may be sufficient, but in others, longer distances between STAs may be required for communication. Distributed systems (DS) can be configured to support extended coverage.

[0053] DS refers to the structure of BSS interconnection. Specifically, such as... Figure 2As shown, a BSS can exist as an extension of a network composed of multiple BSSs. A DS is a logical concept and can be specified through the characteristics of the Distributed System Medium (DSM). At this point, the Wireless Medium (WM) and the DSM can be logically separated. Each logical medium is used for a different purpose and by different components. These media are not limited to being the same, nor are they limited to being different. In this way, the flexibility of a wireless LAN architecture (DS architecture or other network architectures) can be interpreted as multiple media being logically different. That is, a wireless LAN architecture can be implemented in various ways, and the corresponding wireless LAN architecture can be independently specified by the physical characteristics of each implementation.

[0054] The DS can support mobile devices by providing seamless integration of multiple BSSs and offering the logical services necessary for addressing to the destination. Additionally, the DS may include a component called a portal, which acts as a bridge between the wireless LAN and other networks (e.g., IEEE 802.X).

[0055] AP enables access to DS via WM for associated non-AP STAs, and refers to entities that also have STA functionality. Data movement between BSS and DS can be performed through AP. For example, Figure 2 STA2 and STA3, shown in the diagram, have the functionality of STAs and provide the ability for associated non-AP STAs (STA1 and STA4) to access the DS. Furthermore, since all APs essentially correspond to STAs, all APs are addressable entities. The address used by an AP for communication on the WM is not necessarily the same as the address used by the AP for communication on the DSM. A BSS consisting of APs and one or more STAs can be referred to as an infrastructure BSS.

[0056] Data sent from one of the STAs associated with the AP to the corresponding STA address of the AP can always be received on an uncontrolled port and can be processed by the IEEE 802.1X port access entity. Alternatively, when the controlled port is authenticated, the transmitted data (or frames) can be delivered to the DS.

[0057] In addition to the DS structure described above, Extended Service Sets (ESS) can also be configured to provide wide coverage.

[0058] An ESS (Service Set Identity) refers to a network of arbitrary size and complexity consisting of DS (Service Controller) and BSS (Service Set Service). An ESS can correspond to a set of BSSs connected to a DS. However, an ESS does not include the DS. An ESS network is characterized as an IBSS (Integrated Service Set Service) within the Logical Link Control (LLC) layer. STAs included in an ESS can communicate with each other, and a moving STA can transparently move from one BSS to another (within the same ESS) to the LLC. APs included in an ESS can have the same Service Set Identity (SSID). The SSID is distinguished from the BSSID, which serves as the identifier for the BSS.

[0059] Wireless LAN systems make no assumptions about the relative physical locations of BSSs, and all of the following forms are possible: BSSs can partially overlap, which is 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 can be physically located in the same location, which can be used to provide redundancy. Additionally, one (or more) IBSS or ESS networks can physically exist in the same space as one (or more) ESS networks. This can correspond to the form of ESS networks when an ad hoc network operates in a location where an ESS network exists, when physically overlapping wireless networks are configured by different organizations, or when two or more different access and security policies are required in the same location, etc.

[0060] Figure 3 This is a diagram illustrating the link establishment process that can be applied to this disclosure.

[0061] In order for a STA to establish a link with the network and send / receive data, it first discovers the network, performs authentication, establishes an association, and performs authentication processing for security. The link establishment process can also be called session initiation processing or session establishment processing. Furthermore, the discovery, authentication, association, and security establishment processes of the link establishment process can be collectively referred to as association processing.

[0062] In step S310, the STA can perform a network discovery operation. The network discovery operation may include a scanning operation by the STA. That is, in order for the STA to access a network, it needs to find networks it can participate in. The STA should identify compatible networks before participating in a wireless network, and the process of identifying networks existing in a specific area is called scanning.

[0063] Scanning schemes include active scanning and passive scanning. Figure 3An exemplary network discovery operation including active scanning is illustrated. In active scanning, the STA performing the scan sends a probe request frame to discover which APs are present around it as the channel moves and awaits a response. The responder sends a probe response frame as a response to the probe request frame to the STA that sent the probe request frame. Here, the responder may be the STA that last sent a beacon frame in the BSS of the channel being scanned. In the BSS, the AP becomes the responder because it sends a beacon frame, and in the IBSS, the STAs in the IBSS rotate to send beacon frames, so the responder is not constant. For example, an STA that sends a probe request frame on channel 1 and receives a probe response frame on channel 1 may store the BSS-related information included in the received probe response frame and may move to the next channel (e.g., channel 2) and perform a scan in the same manner (i.e., sending and receiving probe requests / responses on channel 2).

[0064] Although not in Figure 3 As shown, scanning can be performed passively. In passive scanning, the STA performing the scan waits for beacon frames while moving through the channel. Beacon frames are one of the management frames defined in IEEE 802.11 and are sent periodically to notify of the existence of a wireless network and allow the STA performing the scan to find and participate in the wireless network. In the BSS, the AP periodically sends beacon frames, and in the IBSS, the STA within the IBSS rotates to send beacon frames. When the STA performing the scan receives a beacon frame, it stores the BSS information included in the beacon frame and records the beacon frame information for each channel while moving to another channel. The STA receiving the beacon frame can store the BSS-related information included in the received beacon frame, move to the next channel, and perform scanning in the next channel in the same manner. Comparing active and passive scanning, active scanning has the advantages of less latency and less power consumption.

[0065] After the STA discovers the network, an authentication process can be performed in step S320. To clearly distinguish it from the security establishment operation in step S340, which will be described later, this authentication process can be referred to as the first authentication process.

[0066] The authentication process includes the following steps: the STA sends an authentication request frame to the AP, and in response, the AP sends an authentication response frame to the STA. The authentication frame used for the authentication request / response corresponds to the management frame.

[0067] An authentication frame includes the authentication algorithm number, authentication transaction sequence number, status code, challenge text, robust security network (RSN), and finite circular group. These correspond to some examples of information that can be included in the authentication request / response frame and can be replaced with other information, or additional information may be included.

[0068] A STA can send an authentication request frame to an AP. The AP can determine whether to allow the corresponding STA's authentication based on the information included in the received authentication request frame. The AP can then provide the STA with the authentication processing result via an authentication response frame.

[0069] After the STA is successfully authenticated, the association process can be performed in step S330. The association process includes the following steps: the STA sends an association request frame to the AP, and in response, the AP sends an association response frame to the STA.

[0070] For example, an association request frame may include information related to various capabilities, beacon listening intervals, service set identifiers (SSIDs), supported rates, supported channels, RSNs, mobile domains, supported operation classes, traffic indication mapping broadcast requests (TIM broadcast requests), interoperability capabilities, etc. Similarly, an association response frame may include information related to various capabilities, status codes, association IDs (AIDs), supported rates, enhanced distributed channel access (EDCA) parameter sets, received channel power indicators (RCPIs), received signal-to-noise ratio indicators (RSNIs), mobile domains, timeout intervals (e.g., association recovery time), overlapping BSS scan parameters, TIM broadcast responses, quality of service (QoS) mappings, etc. These correspond to some examples of information that can be included in association request / response frames and may be replaced with other information, or additional information may be included.

[0071] After the STA successfully associates with the network, a security establishment process can be performed in step S340. The security establishment process in step S340 can be referred to as the authentication process via a Robust Secure Network Association (RSNA) request / response, the authentication process in step S320 is referred to as the first authentication process, and the security establishment process in step S340 can also be simply referred to as the authentication process.

[0072] The secure establishment process in step S340 may include, for example, the process of establishing a private key using a four-way handshake via Extensible Authentication Protocol (EAPOL) frames over the LAN. Alternatively, the secure establishment process may be performed according to a security scheme not defined in the IEEE 802.11 standard.

[0073] Figure 4 This is a diagram illustrating the fallback process that can be applied to this disclosure.

[0074] In wireless LAN systems, the basic access mechanism for Media Access Control (MAC) is Carrier Sensing Multiple Access with Collision Avoidance (CSMA / CA). Also known as the Distributed Coordination Function (DCF) of IEEE 802.11 MAC, CSMA / CA essentially employs a "listen-before-talk" access mechanism. Under this type of access mechanism, before commencing transmission, the AP and / or STA can perform explicit channel assessment (CCA) of the sensing radio channel or medium during a predetermined time interval (e.g., the DCF inter-frame interval (DIFS)). As a result of the sensing, if it is determined that the medium is idle, frame transmission begins via the corresponding medium. Conversely, if the medium is detected to be occupied or busy, the corresponding AP and / or STA does not begin its own transmission and can set a delay period for medium access (e.g., a random backoff period) and attempt frame transmission after waiting. By applying a random backoff period, collisions can be minimized because multiple STAs are expected to attempt frame transmission after waiting for different time periods.

[0075] In addition, the IEEE 802.11 MAC protocol provides a Hybrid Coordination Function (HCF). HCF is based on DCF and Point Coordination Function (PCF). PCF is a polling-based synchronous access method, meaning that all receiving APs and / or STAs periodically poll to receive data frames. Furthermore, HCF includes Enhanced Distributed Channel Access (EDCA) and HCF Control Channel Access (HCCA). EDCA is a contention-based access method that provides data frames to multiple users, while HCCA uses a non-contention-based channel access method that utilizes a polling mechanism. Additionally, HCF includes a media access mechanism for improving the QoS (Quality of Service) of wireless LANs and can transmit QoS data during contention periods (CP) and contention-free periods (CFP).

[0076] Reference Figure 4This section describes the operation based on a random backoff period. When an occupied / busy medium becomes idle, multiple STAs can attempt to transmit data (or frames). As a method to minimize collisions, each STA can individually select a random backoff count and attempt to transmit after waiting for the corresponding time slot. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​ranging from 0 to CW. Here, CW is the contention window parameter value. The CW parameter is assigned an initial value of CWmin, but can take a value twice as large as in the event of transmission failure (e.g., when no ACK is received for the transmitted frame). When the CW parameter value reaches CWmax, data transmission can be attempted while maintaining the CWmax value until successful data transmission, and when successful, the CWmin value is reset. The values ​​of CW, CWmin, and CWmax are preferably set to 2n-1 (n = 0, 1, 2, ...).

[0077] When random backoff processing begins, the STA continuously monitors the medium during the backoff time slot countdown based on the determined backoff count value. When monitoring the medium for occupancy, it stops the countdown and waits, and restarts the remainder of the countdown when the medium becomes idle.

[0078] exist Figure 4 In the example, when the packet to be sent arrives at STA 3's MAC, STA 3 can send the frame immediately after confirming that the medium has been idle for up to DIFS. The remaining STAs monitor and wait for the medium to be occupied / busy. Meanwhile, the data to be sent can also occur in each of STA 1, STA 2, and STA 5, and when the medium is detected as idle, each STA waits for up to DIFS, and then performs a countdown for the backoff slot based on a random backoff count value chosen by each STA. Assume STA 2 chooses the minimum backoff count value, and STA 1 chooses the maximum backoff count value. That is, the example illustrates the case where STA 5's remaining backoff time is shorter than STA 1's remaining backoff time when STA 2 completes its backoff count and begins frame transmission. STA 1 and STA 5 temporarily stop the countdown and wait while STA 2 occupies the medium. When STA 2's occupancy ends and the medium becomes idle again, STA 1 and STA 5 wait for DIFS and restart the stopped backoff count. In other words, frame transmission can begin after a countdown for the remaining backoff slot based on the remaining backoff time. Since STA5 has a shorter remaining backoff time than STA1, STA5 begins frame transmission. Data to be transmitted can also occur in STA4 while STA2 is occupying the medium. From STA4's perspective, when the medium becomes idle, STA4 can wait for DIFS, then execute a countdown based on a random backoff count value selected by STA4, and begin transmitting frames. Figure 4The example illustrates a scenario where the remaining backoff time of STA5 accidentally conflicts with the random backoff count value of STA4. In this case, a collision may occur between STA4 and STA5. When a collision occurs, neither STA4 nor STA5 receives an ACK, so data transmission fails. In this situation, STA4 and STA5 can double the CW value, select a random backoff count value, and begin a countdown. While the medium is occupied due to the transmissions of STA4 and STA5, STA1 waits; when the medium becomes idle, STA1 waits for DIFS, and then begins frame transmission after the remaining backoff time has elapsed.

[0079] As in Figure 4 In the example, data frames are frames used to send data forwarded to higher layers and can be sent after a backoff performed after DIFS (Distributed Access Frame) from the time the medium becomes idle. Additionally, management frames are frames used to exchange management information that has not been forwarded to higher layers and are sent after a backoff performed after an IFS (Initial Point Coordination Function) such as DIFS or PIFS (Initial Point Coordination Function). Subtypes of management frames include beacons, association requests / responses, reassociation requests / responses, probe requests / responses, authentication requests / responses, etc. Control frames are frames used to control access to the medium. Subtypes of control frames include request-to-transmit (RTS), clear-to-transmit (CTS), acknowledgment (ACK), power-saving polling (PS-Poll), block ACK (BlockAck), block ACK request (BlockACKReq), null data packet advertisement (NDP advertisement), and triggers, etc. If the control frame is not a response frame to the previous frame, it is sent after backoff following the DIFS; if it is a response frame to the previous frame, it is sent without backoff following the Short IFS (SIFS). The type and subtype of a frame can be identified by the type field and subtype field in the Frame Control (FC) field.

[0080] The Quality of Service (QoS) STAR can perform a backoff following the Arbitration IFS (AIFS) for the Access Class (AC) to which the frame belongs (i.e., AIFS where i is a value determined by the AC) before the frame can be transmitted. Here, the frame that can use AIFS can be a data frame, management frame, or control frame, rather than a response frame.

[0081] Figure 5 This is a diagram illustrating the CSMA / CA-based frame transmission operation that can be applied to this disclosure.

[0082] As mentioned above, in addition to physical carrier sensing of the medium directly sensed by the STA, the CSMA / CA mechanism also includes virtual carrier sensing. Virtual carrier sensing aims to compensate for problems such as hidden node issues that may occur during medium access. For virtual carrier sensing, the STA's MAC can use the Network Allocation Vector (NAV). The NAV is a value that indicates to other STAs the remaining time until the medium is available for current use or for STAs authorized to use the medium. Therefore, a value set to NAV corresponds to the period during which the STA sending the frame plans to use the medium, and during the corresponding period, STAs receiving the NAV value are prohibited from accessing the medium. For example, the NAV can be configured based on the value of the "Duration" field in the frame's MAC header.

[0083] exist Figure 5 In the example, it is assumed that STA1 intends to send data to STA2, and STA3 is in a position that can eavesdrop on some or all of the frames sent and received between STA1 and STA2.

[0084] To reduce the likelihood of transmission conflicts among multiple STAs in CSMA / CA-based frame transmission operations, a mechanism using RTS / CTS frames can be applied. Figure 5 In the example, when STA1 is transmitting, as a result of carrier sensing by STA3, it can be determined that the medium is in an idle state. That is, STA1 can correspond to a hidden node with respect to STA3. Alternatively, in Figure 5 In the example, it can be determined that while STA2 is transmitting, the carrier sensing result medium of STA3 is in an idle state. That is, STA2 can correspond to a hidden node with respect to STA3. By exchanging RTS / CTS frames before performing data transmission and reception between STA1 and STA2, STAs outside the transmission range of either STA1 or STA2, or STAs outside the carrier sensing range of transmissions from STA1 or STA3, can avoid attempting to occupy the channel during data transmission and reception between STA1 and STA2.

[0085] Specifically, STA1 can determine whether a channel is in use through carrier sensing. Regarding physical carrier sensing, STA1 can determine the channel occupancy / idle status based on the energy level or signal correlation detected in the channel. Alternatively, regarding virtual carrier sensing, STA1 can use a Network Allocation Vector (NAV) timer to determine the channel occupancy status.

[0086] When the channel is idle during DIFS, STA1 can send an RTS frame to STA2 after performing backoff. When STA2 receives the RTS frame, STA2 can send a CTS frame to STA1 after SIFS as a response to the RTS frame.

[0087] If STA3 cannot eavesdrop on CTS frames from STA2 but can eavesdrop on RTS frames from STA1, STA3 can use the duration information included in the RTS frame to set the NAV timer for the subsequent consecutive frame transmission period (e.g., SIFS+CTS frame+SIFS+data frame+SIFS+ACK frame). Alternatively, if STA3 can eavesdrop on CTS frames from STA2, STA3 can also use the duration information included in the CTS frame to set the NAV timer for the subsequent consecutive frame transmission period (e.g., SIFS+data frame+SIFS+ACK frame), even though STA3 cannot eavesdrop on RTS frames from STA1. In other words, if STA3 can eavesdrop on one or more RTS or CTS frames from either STA1 or STA2, STA3 can set the NAV accordingly. When STA3 receives a new frame before the NAV timer expires, STA3 can update the NAV timer using the duration information included in the new frame. STA3 does not attempt channel access until the NAV timer expires.

[0088] When STA1 receives a CTS frame from STA2, STA1 can send a data frame to STA2 after the completion time of CTS frame reception, following SIFS. When STA2 successfully receives the data frame, STA2 can send an ACK frame to STA1 after SIFS as a response to the data frame. When the NAV timer expires, STA3 can determine whether the channel is in use through carrier sensing. If STA3 determines that the channel is not in use by other terminals during the DIFS period after the NAV timer expires, STA3 can attempt channel access after the contention window (CW) for random backoff has expired.

[0089] Figure 6 This is a diagram illustrating an example of a frame structure that can be used in a WLAN system to which this disclosure may be applied.

[0090] Using instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare the MAC PDU (MPDU) to be transmitted. For example, when the PHY layer receives a command from the MAC layer requesting the start of transmission, it switches to transmit mode, configures the information (e.g., data) provided by the MAC layer in the form of a frame, and transmits it. Additionally, when the PHY layer detects a valid preamble in a received frame, it monitors the preamble header and sends a command to the MAC layer notifying the PHY layer of the start of reception.

[0091] In this way, information transmission / reception in a wireless LAN system is performed in the form of frames, and for this purpose, the PHY layer Protocol Data Unit (PPDU) format is defined.

[0092] A basic PPDU can include a Short Training Field (STF), a Long Training Field (LTF), a Signal (SIG) field, and a Data field. The most basic PPDU format (e.g., Figure 7 The non-HT (high throughput) fields shown can consist solely of a conventional-STF (L-STF), conventional-LTF (L-LTF), conventional-SIG (L-SIG) field, and a data field. Additionally, depending on the PPDU format type (e.g., HT mixed format PPDU, HT green format PPDU, VHT (very high throughput) PPDU, etc.), additional (or different types of) RL-SIG, U-SIG, non-conventional SIG fields, non-conventional STF, non-conventional LTF (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) can be included between the L-SIG field and the data field.

[0093] STF is a signal used for signal detection, automatic gain control (AGC), diversity selection, precise time synchronization, etc., while LTF is a signal used for channel estimation and frequency error estimation. STF and LTF can be referred to as signals used for synchronization and channel estimation in the OFDM physical layer.

[0094] The SIG field can include various information related to PPDU transmission and reception. For example, the L-SIG field consists of 24 bits and can include a 4-bit rate field, a 1-bit reserved bit, a 12-bit length field, a 1-bit parity field, and a 6-bit tail field. The RATE field can include information about the modulation and coding rate of the data. For example, the 12-bit length field can include information about the length or duration of the PPDU. For example, the value of the 12-bit length field can be determined based on the type of PPDU. For example, for non-HT, HT, VHT, or EHT PPDUs, the value of the length field can be determined to be a multiple of 3. For example, for HEPPDUs, the value of the length field can be determined to be a multiple of 3+1 or 3+2.

[0095] The data field may include a service field, a physical layer service data unit (PSDU), and a PPDU tail bit, and may also include padding bits if necessary. Some bits of the service field can be used for synchronization of the descrambler at the receiver. The PSDU corresponds to the MAC PDU defined in the MAC layer and may include data generated / used in the upper layer. The PPDU tail bit can be used to return the encoder to a 0 state. Padding bits can be used to adjust the length of the data field by predetermined units.

[0096] MAC PDUs are 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). MAC frames can be composed of MAC PDUs and transmitted / received via PSDUs in the data portion of the PPDU format.

[0097] The MAC header includes a frame control field, a duration / ID field, and an address field. The frame control field can include control information required for frame transmission / reception. The duration / ID field can be set to the time used to transmit the corresponding frame, etc. For details on the sequence control, QoS control, and HT control subfields of the MAC header, refer to the IEEE 802.11 standard document.

[0098] The Empty Data PPDU (NDP) format refers to a PPDU format that does not include the data field. In other words, NDP is a frame format that includes the PPDU preamble of the general PPDU format (i.e., the L-STF, L-LTF, L-SIG fields and additional non-traditional SIG, non-traditional STF, and non-traditional LTF (if present)) and does not include the remaining part (i.e., the data field).

[0099] Figure 7 This is a diagram illustrating an example of a PPDU as defined in the IEEE 802.11 standard of this disclosure.

[0100] Various types of PPDUs have been used in standards such as IEEE 802.11a / g / n / ac / ax. The basic PPDU format (IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and a data field. The basic PPDU format can also be referred to as a non-HT PPDU format (such as...). Figure 7 (as shown in (a)).

[0101] Compared to the basic PPDU format, the HT PPDU format (IEEE 802.11n) additionally includes the HT-SIG, HT-STF, and HT-LFT fields. Figure 7The HT PPDU format shown in (b) can be referred to as the HT hybrid format. Furthermore, an HT green format PPDU can be defined, and this corresponds to a format consisting of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTFs and a data field, excluding L-STF, L-LTF, and L-SIG (not shown).

[0102] Compared to the basic PPDU format, examples of the VHT PPDU format (IEEE 802.11ac) additionally include VHTSIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields (e.g., ...). Figure 7 (as shown in (c)).

[0103] Compared to the basic PPDU format, examples of the HE PPDU format (IEEE 802.11ax) additionally include repeated L-SIG (RL-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, and Packet Extension (PE) fields (such as...). Figure 7 (as shown in (d)). Some fields can be excluded, or their lengths can vary depending on the detailed examples of the HE PPDU format. For example, the HE-SIG-B field is included in the HE PPDU format for multi-user (MU), but not in the HE PPDU format for single-user (SU). Furthermore, the HE-Trigger-Based (TB) PPDU format does not include HE-SIG-B, and the length of the HE-STF field can vary up to 8 μs. The Extended Range (HE ER) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field can vary up to 16 μs. For example, RL-SIG can be configured to be the same as L-SIG. Based on the presence of RL-SIG, the receiving STA can determine whether the received PPDU is an HE PPDU or an EHT PPDU, which will be described later.

[0104] EHT PPDU format can include Figure 7 EHT MU (Multi-user) in (e) and Figure 7 The EHT TB (trigger-based) PPDU in (f). The EHT PPDU format is similar to the HE PPDU format in that it includes RL-SIG following L-SIG, but it can include U (generic)-SIG, EHT-SIG, EHT-STF and EHT-LTF following RL-SIG.

[0105] Figure 7In (e), the EHT MU PPDU corresponds to a PPDU carrying one or more data (or PSDU) for one or more users. That is, the EHT MU PPDU can be used for both SU and MU transmissions. For example, the EHT MU PPDU can correspond to a PPDU for one or more receiving STAs.

[0106] Compared to EHT MU PPDU, Figure 7 In (f), the EHT-SIG is omitted from the EHT TB PPDU. The STA that receives the trigger for UL MU transmission (e.g., trigger frame or trigger response schedule (TRS)) can perform UL transmission based on the EHT TB PPDU format.

[0107] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (general signal), and EHT-SIG fields can be encoded and modulated so that even conventional STAs can attempt demodulation and decoding, and can be mapped based on a determined subcarrier frequency interval (e.g., 312.5 kHz). These can be referred to as pre-EHT modulated fields. Next, the EHT-STF, EHT-LTF, data, and PE fields can be encoded and modulated to be demodulated and decoded by an STA that has successfully decoded a non-conventional SIG (e.g., U-SIG and / or EHT-SIG) and obtained the information contained in that field, and can be mapped based on a determined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

[0108] Similarly, in the HE PPDU format, the L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, and HE-SIG-B fields can be referred to as pre-HE modulation fields, and the HE-STF, HE-LTF, data, and PE fields can be referred to as HE modulation fields. Additionally, in the VHT PPDU format, the L-STF, L-LTF, L-SIG, and VHT-SIG-A fields can be referred to as non-VHT modulation fields, and the VHT STF, VHT-LTF, VHT-SIG-B, and data fields can be referred to as VHT modulation fields.

[0109] Included Figure 7In the EHT PPDU format, U-SIG can be configured based on, for example, two symbols (e.g., two consecutive OFDM symbols). Each symbol used for U-SIG (e.g., an OFDM symbol) can have a duration of 4 μs, and U-SIG can have a total duration of 8 μs. Each symbol of U-SIG can be used to transmit 26 bits of information. For example, each symbol of U-SIG can be transmitted and received based on 52 data tones and 4 pilot tones.

[0110] U-SIGs can be constructed in 20MHz units. For example, if an 80MHz PPDU is constructed, U-SIGs can be replicated. That is, the same four U-SIGs can be included in an 80MHz PPDU. PPDUs with bandwidths exceeding 80MHz can include different U-SIGs.

[0111] For example, A uncoded bits can be sent via U-SIG. The first symbol of U-SIG (e.g., U-SIG-1 symbol) can send the first X bits of the total A bits, and the second symbol of U-SIG (e.g., U-SIG-2 symbol) can send the remaining Y bits of the total A bits. The A bits (e.g., 52 uncoded bits) can include a CRC field (e.g., a 4-bit field) and a tail field (e.g., a 6-bit field). For example, the tail field can be used to terminate the lattice structure of the convolutional decoder and can be set to 0.

[0112] Bit information sent via U-SIG can be divided into version-independent bits and version-dependent bits. For example, U-SIG can be included in... Figure 7 The new PPDU format (e.g., UHR PPDU format) not shown in the figure, and can be included in the format of the U-SIG field included in the EHT PPDU format and the format of the U-SIG field included in the UHR PPDU format, the version-independent bits can be the same, and some or all of the version-related bits can be different.

[0113] For example, the size of the version-independent bits in U-SIG can be fixed or variable. Version-independent bits can be assigned only to the U-SIG-1 symbol, or to both the U-SIG-1 and U-SIG-2 symbols. Version-independent and version-dependent bits can be referred to by various names, such as first control bit and second control bit.

[0114] For example, the version-independent bits of the U-SIG may include a 3-bit Physical Layer Version Identifier (PHY Version Identifier), which can indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted / received PPDU. The version-independent bits of the U-SIG may include a 1-bit UL / DL Flag field. The first value of the 1-bit UL / DL Flag field is related to UL communication, and the second value is related to DL communication. The version-independent bits of the U-SIG may include information about the length of the Transmission Opportunity (TXOP) and information about the BSS color ID.

[0115] For example, the version-related bits of U-SIG may include information that directly or indirectly indicates the type of PPDU (e.g., SU PPDU, MU PPDU, TB PPDU, etc.).

[0116] Information required for PPDU transmission and reception can be included in the U-SIG. For example, the U-SIG may also include information about bandwidth, information about the MCS technique applied to non-traditional SIGs (e.g., EHT-SIG or UHR-SIG), information indicating whether DCM (dual-carrier modulation) techniques (e.g., techniques used to achieve effects similar to frequency diversity by reusing the same signal on two subcarriers) are applied to non-traditional SIGs, information about the number of symbols used for non-traditional SIGs, and information about whether non-traditional SIGs are generated across the entire frequency band.

[0117] Some of the information required for PPDU transmission and reception may be included in U-SIG and / or non-traditional SIG (e.g., EHT-SIG or UHR-SIG). For example, information about the type of non-traditional LTF / STF (e.g., EHT-LTF / EHT-STF or UHR-LTF / UHR-STF), the length of the non-traditional LTF and the CP (cyclic prefix) length, the GI (guard interval) applicable to the non-traditional LTF, the preamble punching information applicable to the PPDU, and the resource unit (RU) allocation may be included only in U-SIG, only in non-traditional SIG, or may be indicated by a combination of information included in U-SIG and information included in non-traditional SIG.

[0118] Preamble puncturing can represent the transmission of a PPDU where no signal is present in one or more frequency units within the bandwidth of the PPDU. For example, the size of the frequency unit (or the resolution of the preamble puncturing) can be defined as 20MHz, 40MHz, etc. For example, preamble puncturing can be applied to PPDU bandwidths of a predetermined size or larger.

[0119] exist Figure 7In the examples, non-traditional SIGs such as HE-SIG-B and EHT-SIG can include control information for receiving STAs. Non-traditional SIGs can be transmitted on at least one symbol, and a symbol can have a length of 4 μs. Information regarding the number of symbols used for EHT-SIGs can be included in previous SIGs (e.g., HE-SIG-A, U-SIG, etc.).

[0120] Non-traditional SIGs such as HE-SIG-B and EHT-SIG can include both public and user-specific fields. These public and user-specific fields can be encoded separately.

[0121] In some cases, the common field can be omitted. For example, in compressed mode using non-OFDMA (Orthogonal Frequency Division Multiple Access), the common field can be omitted, and multiple STAs can receive PPDUs (e.g., the data field of the PPDU) through the same frequency band. In uncompressed mode using OFDMA, multiple users can receive PPDUs (e.g., the data field of the PPDU) through different frequency bands.

[0122] The number of user-specific fields can be determined based on the number of users. A user block field can include up to two user fields. Each user field can be associated with either a MU-MIMO allocation or a non-MU-MIMO allocation.

[0123] The common fields may include CRC bits and a tail bit, where the CRC bits can be 4 bits long and the tail bit can be 6 bits long and set to 000000. The common fields may also include RU allocation information. RU allocation information may include information about the locations of RUs to which multiple users (i.e., multiple receiving STAs) are assigned.

[0124] An RU can include multiple subcarriers (or tones). RUs can be used when transmitting signals to multiple STAs based on OFDMA technology. Additionally, RUs can be defined even when transmitting signals to a single STA. Resources can be allocated to non-traditional STFs, non-traditional LTFs, and data fields on a RU basis.

[0125] The appropriate RU size can be defined based on the PPDU bandwidth. RUs can be defined the same or different for the applied PPDU format (e.g., HEPPDU, EHT PPDU, UHR PPDU, etc.). For example, in the case of an 80MHz PPDU, the RU layout for HEPPDU and EHT PPDU can be different. The applicable RU size, number and location of RUs, DC (direct current) subcarrier locations and numbers, empty subcarrier locations and numbers, guard subcarrier locations and numbers, etc., for each PPDU bandwidth can be referred to as the tone scheme. For example, a tone scheme for high bandwidth can be defined as multiple iterations of a low-bandwidth tone scheme.

[0126] RUs of various sizes can be defined as 26-tone RUs, 52-tone RUs, 106-tone RUs, 242-tone RUs, 484-tone RUs, 996-tone RUs, 2×996-tone RUs, 3×996-tone RUs, etc. MRUs (Multiple RUs) differ from multiple individual RUs and correspond to a group of subcarriers composed of multiple RUs. For example, an MRU can be defined as 52+26 tones, 106+26 tones, 484+242 tones, 996+484 tones, 996+484+242 tones, 2×996+484 tones, 3×996 tones, or 3×996+484 tones. Furthermore, the multiple RUs constituting an MRU can be consecutive or non-consecutive in the frequency domain.

[0127] The specific size of the RU can be reduced or expanded. Therefore, the specific size of each RU in this disclosure (i.e., the number of corresponding tones) is not limiting but illustrative. In addition, in this disclosure, the number of RUs can vary depending on the RU size within a predetermined bandwidth (e.g., 20MHz, 40MHz, 80MHz, 160MHz, 320MHz...).

[0128] Figure 7 The names of each field in the PPDU format are exemplary, and the scope of this disclosure is not limited to these names. Furthermore, the examples in this disclosure can be applied to... Figure 7 The PPDU format shown and based on Figure 7 A new PPDU format that excludes some fields and / or adds some fields, based on the PPDU format.

[0129] Figure 8 This is a diagram illustrating an example format of the trigger frame that can be applied to this disclosure.

[0130] A trigger frame can allocate resources for the transmission of one or more TB PPDUs and request the transmission of TB PPDUs. The trigger frame may also include additional information required by the STA sending the TB PPDU in response. The trigger frame may include public information and user information list fields in the frame body.

[0131] The common info field is information typically used for the transmission of one or more TB PPDUs requested by a trigger frame, such as trigger type, UL length, presence or absence of subsequent trigger frames (e.g., more TFs), CS (channel sensing) request, UL BW (bandwidth), HE / EHT P160, special user information field flags, etc.

[0132] The 4-bit trigger type subfield can have values ​​from 0 to 15. Values ​​0, 1, 2, 3, 4, 5, 6, and 7 are defined to correspond to Basic, Beamforming Report Polling (BFRP), Multi-User Block Acknowledgment Request (MU-BAR), Multi-User Request Transmission (MU-RTS), Buffer Status Report Polling (BSRP), Multicast with Retry (GCR), MU-BAR, Bandwidth Query Report Polling (BQRP), and NDP Feedback Report Polling (NFRP), respectively. Values ​​8 through 15 are reserved.

[0133] In public information, the trigger-related public information subfields may include information that can be optionally included based on the trigger type.

[0134] Special user information fields can be included in the trigger frame. These fields do not include user-specific information, but rather extended public information not provided in the public information fields.

[0135] The user information list includes zero or more user information fields. Figure 8 An example of the EHT variant user information field format is shown.

[0136] The AID12 subfield essentially indicates that it is a user information field for a STA with the corresponding AID. Furthermore, if the AID12 field has a specific predetermined value, it can be used for other purposes, such as assigning a Random Access (RA)-RU or being configured as a special user information field. A special user information field is a user information field that does not include user-specific information but includes extended public information not provided in the public information field. For example, a special user information field can be identified by the AID12 value 2007, and the special user information field flag subfield within the public information field can indicate whether a special user information field is included.

[0137] The RU allocation subfield can indicate the size and location of the RU / MRU. For this purpose, the RU allocation subfield can be interpreted together with the PS160 (primary / secondary 160MHz) subfield of the user information field and the UL BW subfield of the public information field.

[0138] Uplink (UL) detection process

[0139] In next-generation wireless LAN systems, when sending signals to STAs, the goal is to support UHR (Universal High-Resolution Environment). To this end, technologies are being considered to support high throughput, low latency, and extended range.

[0140] To increase the throughput and reliability of UL transmission, accurate information about the UL channel is required. To obtain this accurate information, a UL probing process can be performed between the non-AP STA and the AP. The methods for configuring the trigger frame and UL NDP frame used to perform the UL probing process are described below.

[0141] Figure 9 This is a flowchart used to explain the method performed by the first STA according to embodiments of the present disclosure. Figure 9 and Figure 10 In this configuration, each of the first STA and the second STA can be implemented as either a non-AP STA or an AP. Furthermore, the first STA can operate as a beamforming agent during UL detection, and the second STA can also operate as a beamforming agent.

[0142] The first STA can receive trigger frames from the second STA (S910).

[0143] As an example of this disclosure, the trigger frame may include first information indicating that the trigger frame is used to request a UL NDP. Here, the first information may be indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the UL NDP request.

[0144] For example, when the UL length field value is set to a specific (length) value, this can mean that the UL length field value indicates first information. For example, the UL length field can be set to a specific length value calculated from the length values ​​of each of the UL NDP's L-STF field, L-LTF field, L-SIG field, R (repeating) L-SIG field, U-SIG field, and UL-STF field.

[0145] As another example, the UL length field can be set to a value calculated from the length values ​​of the UL NDP's L-STF, L-LTF, L-SIG, R (repeating) L-SIG, U-SIG, UHR-STF, UHR-LTF, and PE fields, respectively. In this case, the UHR-LTF field value can be set by assuming a maximum number of spatial flows (NSS) value (e.g., 8). Furthermore, the PE can be disregarded when setting the UL length value.

[0146] As another example, the first information can be indicated by a specific field included in the public information field of the trigger frame. The specific subfield can be set to at least one bit from the 23rd (B22), 27th (B26), 54th (B53), or 57th (B56) through 64th (B63) bits of the public information field. For example, when the specific field value is set to 1, this can indicate that the trigger frame is for requesting a UL NDP.

[0147] As another example, a specific field can indicate the type of the trigger frame. That is, the specific field can be configured as the trigger type field included in the public information fields of the trigger frame. Here, the specific field value can be set to one of 9 to 15, and thus, the specific field can indicate the first information.

[0148] As another example, the determination of whether to indicate first information can be based on a combination of a specific field and a UL length field. When the first information is indicated by a specific field (i.e., when the specific field value is set to 1), if the UL length field value is not a specific length value, the first STA can determine that the trigger frame received from the second STA is not a trigger frame requesting UL NDP.

[0149] The first STA can send a UL NDP (S920) based on a trigger frame to the second STA.

[0150] For example, the first STA can send a UL NDP to the AP using a resource or subchannel indicated by the resource allocation subfield included in the user information field of the trigger frame. Furthermore, the UL NDP may include at least one of the L-STF field, L-LTF field, L-SIG field, RL-SIG field, U-SIG field, UHR-STF field, UHR-LTF field, and PE field.

[0151] The first STA can receive a specific frame from the second STA to trigger UL data, and send UL data to the second STA based on that specific frame. Here, the specific frame may include beamforming information or MIMO (Multiple Input Multiple Output) information based on UL NDP formation.

[0152] exist Figure 9The method described in the example, executed by the first STA, can be performed by... Figure 1 The first device (100) is executed. For example, Figure 1 One or more processors (102) of the first device (100) can receive trigger frames from the second STA via one or more transceivers (106). One or more processors (102) can send UL NDP based on the trigger frames to the second STA via one or more transceivers (106).

[0153] The aforementioned memory (104) can store data for execution by one or more processors (102) in the context of... Figure 9 The instructions for the methods described in the example.

[0154] Figure 10 This is a flowchart for explaining a method performed by a second STA according to one embodiment of the present disclosure.

[0155] The second STA can send a trigger frame (S1010) to the first STA. Here, the trigger frame can request the transmission of a UL NDP frame. (See reference...) Figure 9 The configuration of the trigger frame is described, so redundant descriptions will be omitted.

[0156] The second STA can receive UL NDP based on the trigger frame from the first STA (S1020).

[0157] The second STA can form / acquire channel information (e.g., beamforming information and / or MIMO information) between the first and second STAs via UL NDP. The second STA can then send a specific frame to the first STA via the acquired channel information to trigger UL data. The second STA can then receive UL data based on the specific frame from the first STA.

[0158] exist Figure 10 The method described in the example, executed by the second STA, can be performed by... Figure 1 The second device (200) performs the operation. For example, Figure 1 One or more processors (202) of the second device (200) can send trigger frames to the first STA via one or more transceivers (206). One or more processors (202) can receive UL NDP based on the trigger frames from the first STA via one or more transceivers (206).

[0159] Furthermore, one or more memories (204) of the second device (200) may store information for execution by one or more processors (202) in order to perform the operation. Figure 10 The instructions for the methods described in the example.

[0160] The following describes the UL detection process and related parameters for increasing the output and reliability of UL transmission in next-generation wireless LAN systems.

[0161] Implementation Method 1

[0162] As an example of this disclosure, such as Figure 11 As shown, the AP (i.e., the beamforming side) can perform a UL probing procedure with a non-AP STA to measure information about the UL channel. Here, in order to request a UL-based NDP, the AP can send a trigger frame to the non-AP STA.

[0163] A non-AP STA that has received a trigger frame from the AP can send an NDP to the AP using the assigned BW / subchannel / MRU / RU based on the STA-specific information included in the trigger frame.

[0164] The AP can use the NDP received from non-AP STAs to measure the UL channel with each STA. The AP can use the measured information to form information for beamforming or MIMO transmission.

[0165] Information or beamforming matrices generated by the AP for UL beamforming, MIMO, or MU-MIMO transmission can be sent to a non-AP STA along with triggering information for requesting UL data transmission from a non-AP STA.

[0166] Trigger frames for UL data can be configured based on channel information measured by the AP. For example, a trigger frame may include a feedback matrix or beamforming matrix formed for each non-AP STA. Furthermore, a trigger frame may include a TRS control subfield. A trigger frame including a TRS control subfield can indicate trigger information for requesting UL transmission.

[0167] Additionally or alternatively, the AP may send information about the measured UL channel or beamforming matrix to a non-AP STA via a DL MU PPDU after receiving the UL NDP and SIFS. The AP may send information about the UL channel to a non-AP STA via a DL PPDU and send a trigger frame after the SIFS. The non-AP STA may send a ULPPDU to the AP based on the received trigger frame.

[0168] Implementation Method 1-1

[0169] As described in Example 1, when performing the UL detection process, the AP can use a trigger frame to request ULNDP from a non-AP STA.

[0170] As an example of this disclosure, such as Figure 12As shown in (a), the common information field of the trigger frame (e.g., EHT variant common information field or UHR variant common information field, etc.) may include a UL length field, and the UL length field may indicate that the trigger frame is a trigger frame for UL detection.

[0171] In other words, the trigger frame requesting a TB PPDU can indicate the length information of the corresponding TB PPDU through the UL length field. The AP can set the UL length field by considering that the data size included in the UL NDP is 0 (i.e., considering that there is no data field).

[0172] As an example of this disclosure, the UL length field can be set based on the length of the L-STF field, the length of the L-LTF field, the length of the L-SIG field, the length of the RL-SIG field, the length of the U-SIG field, the length of the UL-STF field, the length of the UL-LTF field, and the PE length. As an example, the UHR-STF field can be configured with a structure such as a 1x STF field of an EHT PPDU (i.e., 1.6μs * 5 = 8μs).

[0173] The UHR-LTF field used in UL NDP can be indicated via the LTF type and GI transmitted through the trigger frame. For example, it can be indicated via the trigger frame as "1x LTF+1.6μs", "2x LTF+1.6μs", and "4x LTF+3.2μs". As another example, the UHR LTF field can be used / configured with a "4x LTF+3.2μs" structure for accurate channel estimation.

[0174] Furthermore, as an example, the PE can consist of 4 μs. However, since the AP receives the UL NDP and measures the channel during UL probing, the UL NDP may not include the PE.

[0175] The number of LTF symbols can be formed based on the total number of spatial streams (NSS) allocated to all STAs in the receive trigger frame. That is, since the number of LTF symbols is variable, in order to set a fixed UL length value when triggering NDP transmission, the number of LTF symbols can be set with the assumption of a maximum NSS (i.e., 8).

[0176] As described above, the UL length of the trigger frame requesting UL NDP can consist of the length of each of the preamble (excluding the data field) and the PE (optional). Furthermore, non-AP STAs can confirm that the UL length field does not include the data field by checking the LTF and NSS information included in the trigger frame. Thus, non-AP STAs can implicitly identify that a UL NDP transmission has been requested.

[0177] As another example of this disclosure, the UL length field can be set to a specific value to explicitly indicate a request for UL NDP transmission via a trigger frame. For example, the UL length field can be set by considering only the length up to the UHR-STF and excluding the LTF, which has a variable size. In this case, the UL length can be set to 40 μs, and a UL length field set to the corresponding length can indicate that a UL NDP transmission has been requested.

[0178] As an example of this disclosure, all subfields of the data field included in the trigger frame requesting UL NDP transmission may be retained. As another example, a non-AP STA receiving the trigger frame may ignore subfields related to the data field.

[0179] For example, the LDPC extra symbol segment field and FEC pre-padding factor in the EHT variant public information field of the trigger frame can be retained. Furthermore, the UL space reuse field can be set to a value that disallows space reuse.

[0180] Additional or alternative land, such as Figure 12 As shown in (b), the UL FEC encoding type field (B20) and the UL EHT MCS field (B21 to B24) of the EHT variant user information field corresponding to the trigger frame can be retained.

[0181] Information about the resources and / or subchannels on which a non-AP STA will transmit UL NDP can be indicated through the RU allocation field of the user information field in the trigger frame. Here, the RU allocation field can be configured based on MRU and punching information.

[0182] As another example of this disclosure, the information requesting UL NDP can be sent during data transmission via the Triggered Response Scheduling (TRS) control subfield instead of via a trigger frame. As stated above, even when trigger information is sent via the TRS control field, UL NDP transmission can still be requested from a non-AP STA via the UL length and related information.

[0183] Implementation Methods 1-2

[0184] Implementation methods 1-2 involve the configuration of trigger frames including instructions for UL NDP transmission and related processes.

[0185] The trigger frame can be configured based on the EHT variant common information field. The trigger frame may include a specific subfield indicating that the trigger frame is for a UL NDP transmission, and the specific subfield may be set to at least one of bits 23 (B22), 27 (B26), 54 (B53), and 57 (B56) through 64 (B63) of the common information field. In the following, the specific subfield indicating that the trigger frame is for a UL NDP transmission is referred to as the UL NDP subfield, but is not limited thereto.

[0186] For example, the UL NDP subfield can consist of 1 bit. If the UL NDP subfield value is set to 1 (or 0), this indicates that the corresponding trigger frame requests UL NDP transmission. If the UL NDP subfield value is set to 0 (or 1), this indicates that the corresponding trigger frame does not request UL NDP transmission.

[0187] Non-AP STAs that receive the trigger frame can confirm the AP's request for ULNDP transmission through the UL NDP subfield included in the trigger frame.

[0188] Additionally or alternatively, the UL NDP subfield and UL length field can indicate that a trigger frame requests UL NDP transmission, thereby preventing false detection.

[0189] For example, if the UL length field is not set to a specific value (i.e., the value defined / set in implementation 1-1), the relay STA can determine that it has not requested UL NDP even if the UL NDP subfield is set, thus improving reliability.

[0190] Implementation methods 1-3

[0191] Implementation methods 1-3 relate to new trigger frames for UL detection. Since the trigger frame for UL detection requests UL NDP frame transmission, the trigger frame can be newly defined via the trigger type subfield. For example, the trigger subfield value of a trigger frame requesting UL NDP frame transmission can be set to one of 9 to 15.

[0192] Additionally, the trigger frame for requesting the transmission of UL NDP frames can be configured based on the EHT trigger variant frame. Furthermore, since the trigger frame is used to request NDP transmission from non-AP STAs, subfields related to the data fields within the trigger frame can be retained or ignored.

[0193] Implementation methods 1-4

[0194] Implementation methods 1-4 relate to the configuration of UL DNP frames for UL detection. Since UL NDP frames are requested via trigger frames, UL NDP frames can be configured based on the TB frame format.

[0195] As an example of this disclosure, such as Figure 12 As shown in (c), a UL NDP frame may include the L-STF field, L-LTF field, L-SIG field, RL-SIG field, U-SIG field, UHR-STF field, UHR-LTF field, and PE. Unlike DL NDP frames, UL NDP frames may not include the EHT-SIG field, UHR-SIG field, and SIG field for next-generation wireless LAN systems based on UHR or later.

[0196] The UHR-STF field can be configured as a 1x STF structure (i.e., 8-tone intervals) (i.e., 1.6μs*5). The UHR-LTF can be set to one of "1x LTF+1.6μs" or "4x LTF+3.2μs". Considering processing time, the PE can be set to 4μs, but is not limited to this. The UL NDP frame may not include the PE.

[0197] The above embodiments combine the elements and features of this disclosure in a predetermined form. Unless otherwise expressly stated, each element or feature should be considered optional. Each element or feature may be implemented without being combined with other elements or features. Furthermore, embodiments of this disclosure may include combinations of some elements and / or features. The order of operations described in embodiments of this disclosure may be changed. Some elements or features of one embodiment may be included in other embodiments, or may be replaced by corresponding elements or features of other embodiments. Obviously, embodiments may include claims that are not explicitly referenced in the claims, or may be included as new claims after the application has been amended.

[0198] It will be apparent to those skilled in the art that this disclosure may be implemented in other specific forms without departing from its essential characteristics. Therefore, the above detailed description should not be construed as restrictive in every respect, but rather as illustrative. The scope of this disclosure should be determined by a reasonable interpretation of the appended claims, and all variations within the equivalent scope of this disclosure are included within its scope.

[0199] The scope of this disclosure includes software or machine-executable commands (e.g., operating systems, applications, firmware, programs, etc.) that operate in a device or computer according to methods of various embodiments, and non-transitory computer-readable media that cause software or commands to be stored and executable in a device or computer. Commands that can be used to program a processing system to perform the features described in this disclosure can be stored in a storage medium or a computer-readable storage medium, and the features described in this disclosure can be implemented by using a computer program product including such a storage medium. The storage medium may include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid-state storage devices, and may include non-volatile memory, such as one or more disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory may optionally include one or more storage devices located remotely from the processor. The memory, or alternatively, the non-volatile memory devices in the memory include non-transitory computer-readable storage media. The features described in this disclosure can be stored in any machine-readable medium to control the hardware of a processing system and can be integrated into software and / or firmware that allows the processing system to interact with other mechanisms using the results of embodiments of this disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0200] Industrial applicability

[0201] The method proposed in this disclosure has been described in reference to examples applied to IEEE 802.11-based systems, but the method can also be applied to various wireless LAN or wireless communication systems other than IEEE 802.11-based systems.

Claims

1. A method performed by a first station (STA) in a wireless LAN system, the method comprising the following steps: Receive trigger frames from the second STA; as well as Send the uplink UL null data physical layer protocol data unit (NDP) based on the trigger frame to the second STA. The trigger frame includes first information indicating that the trigger frame is used to request the UL NDP, and The first information is indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the ULNDP request.

2. The method according to claim 1, wherein, The UL NDP frame includes an ultra-high reliability UHR short training field (STF) and a UHR long training field (LTF).

3. The method according to claim 1, wherein, The UL length field is set to a specific length value calculated from the length values ​​of each of the conventional L-STF field, L-LTF field, L-SIG field, repeating L-SIG field, general U-SIG field, and UHR-STF field of the UL NDP.

4. The method according to claim 1, wherein, The specific field is set to at least one of the following: the 23rd bit B22, the 27th bit B26, the 54th bit B53, or the 57th bit B56 to the 64th bit B63 of the public information field.

5. The method according to claim 3, wherein, Based on the first information, indicated by the specific field: Based on the fact that the UL length field value is not the specific length value, the first STA determines that the trigger frame is not a trigger frame requesting the UL NDP.

6. The method according to claim 1, wherein, The resource or subchannel used to transmit the UL NDP is indicated by the resource allocation subfield included in the user information field of the trigger frame.

7. The method according to claim 1, wherein, The type of the trigger frame is indicated by the specific field, and The specific field is set to one of the values ​​9 to 15.

8. The method according to claim 1, wherein, Receive a specific frame from the AP to trigger UL data, and The specific frame includes beamforming information or multiple-input multiple-output (MIMO) information based on the UL NDP.

9. A first STA operating in a wireless LAN system, the first STA comprising: At least one transceiver; as well as At least one processor connected to the at least one transceiver Wherein, the at least one processor is configured to: The trigger frame is received from the second STA via the at least one transceiver; and The at least one transceiver sends an uplink UL (Uniform Logic) null data physical layer protocol data unit (NDP) based on the trigger frame to the second STA. The trigger frame includes first information indicating that the trigger frame is used to request the UL NDP, and The first information is indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the ULNDP request.

10. A method performed by a second station (STA) in a wireless LAN system, the method comprising the following steps: Send a trigger frame to the first STA; as well as Receive uplink UL null data physical layer protocol data unit (NDP) based on the trigger frame from the first STA. The trigger frame includes first information indicating that the trigger frame is used to request the UL NDP, and The first information is indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the ULNDP request.

11. A second STA operating in a wireless LAN system, the second STA comprising: At least one transceiver; as well as At least one processor connected to the at least one transceiver Wherein, the at least one processor is configured to: A trigger frame is sent to the first STA via the at least one transceiver; and The at least one transceiver receives uplink UL null data physical layer protocol data unit (NDP) based on the trigger frame from the first STA. The trigger frame includes first information indicating that the trigger frame is used to request the UL NDP, and The first information is indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the ULNDP request.

12. A processing apparatus configured to control a first STA in a wireless LAN system, the processing apparatus comprising: At least one processor; as well as At least one computer memory, operatively coupled to the at least one processor and storing instructions for performing operations when executed by the at least one processor. The operation includes: Receive trigger frames from the second STA; and Send the uplink UL null data physical layer protocol data unit (NDP) based on the trigger frame to the second STA. The trigger frame includes first information indicating that the trigger frame is used to request the UL NDP, and The first information is indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the ULNDP request.

13. At least one non-transitory computer-readable medium, said at least one non-transitory computer-readable medium storing at least one instruction, Based on the at least one instruction executed by at least one processor, a device for performing communication in a wireless LAN system is controlled to: Receive trigger frames from the second STA; and Send the uplink UL null data physical layer protocol data unit (NDP) based on the trigger frame to the second STA. in, The trigger frame includes first information indicating that the trigger frame is used to request the UL NDP, and The first information is indicated based on at least one of the UL length field included in the public information field of the trigger frame or a specific field related to the ULNDP request.

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