Method and apparatus for time synchronization in wireless LAN system

Abstract

A method and an apparatus for time synchronization in a wireless LAN system are disclosed. The method according to one embodiment of the present disclosure may comprise steps in which a first STA: receives a first beacon frame from an AP, the first beacon frame including a first timestamp value for a timer of the AP; and transmits a first frame to a second STA.

Description

Method and device for time synchronization in a wireless LAN system

[0001] The present disclosure relates to a method and device for time synchronization for relay operation in a wireless local area network (WLAN) system.

[0002] New technologies have been introduced for wireless local area networks (WLANs) to improve transmission rates, increase bandwidth, enhance reliability, reduce errors, and reduce latency. Among WLAN technologies, the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards can be referred to as Wi-Fi. For example, recently introduced technologies for WLANs include enhancements for Very High Throughput (VHT) in the 802.11ac standard and enhancements for High Efficiency (HE) in the IEEE 802.11ax standard.

[0003] To provide a more advanced wireless communication environment, improved technologies for Extremely High Throughput (EHT) are being discussed. For example, technologies for Multiple Input Multiple Output (MIMO), which supports increased bandwidth, efficient utilization of multiple bands, and increased spatial streams, and for coordination of multiple access points (APs), are being studied. In particular, various technologies are being studied to support low latency or real-time traffic. Furthermore, new technologies are being discussed to support ultra-high reliability (UHR), including improvements or extensions of EHT technology.

[0004] The technical problem of the present disclosure is to provide a method and device for time synchronization between an access point (AP) and a station (STA) outside the coverage area of ​​the AP that transmits and receives signals through relay transmission.

[0005] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0006] A method according to one aspect of the present disclosure may include: receiving, by a first station (STA), a first beacon frame from an access point (AP), wherein the first beacon frame includes a first timestamp value for a timer of the AP; and transmitting, by the first STA, a first frame to a second STA. The first frame may include time information for time synchronization between the second STA and the AP, the time information being generated based on the first timestamp value.

[0007] A method according to an additional aspect of the present disclosure may include: receiving, by a second station (STA), a first frame from a first STA, the first frame including time information for time synchronization between the second STA and the access point (AP), the time information being generated based on a first timestamp value for a timer of the AP received from the AP; and updating, by the second STA, the timer of the second STA based on the time information.

[0008] According to the present disclosure, time alignment for signal transmission and reception can be maintained by aligning time synchronization between STAs outside the coverage area of ​​the AP that transmit and receive signals through relay transmission.

[0009] In addition, according to the present disclosure, wireless communication efficiency can be improved as the coverage of the AP is expanded through relay operation.

[0010] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0011] The accompanying drawings, which are incorporated in and are part of the detailed description to aid in understanding the present disclosure, provide embodiments of the present disclosure and, together with the detailed description, describe the technical features of the present disclosure.

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

[0013] FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0014] FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0015] FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0016] FIG. 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0017] FIG. 6 is a drawing for explaining an example of a frame structure used in a wireless LAN system to which the present disclosure can be applied.

[0018] FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0019] FIG. 8 is a diagram illustrating range expansion using a relay in a wireless LAN system to which the present disclosure can be applied.

[0020] FIG. 9 illustrates a procedure for transmitting a beacon frame and transmitting time information according to one embodiment of the present disclosure.

[0021] FIG. 10 illustrates a transmission procedure of a beacon frame including time information according to one embodiment of the present disclosure.

[0022] FIG. 11 illustrates the format of a time information element according to one embodiment of the present disclosure.

[0023] FIG. 12 illustrates a transmission procedure of a frame including beacon information and time information according to one embodiment of the present disclosure.

[0024] FIG. 13 illustrates the operation of a first station for a time synchronization method according to one embodiment of the present disclosure.

[0025] FIG. 14 illustrates the operation of a second station for a time synchronization method according to one embodiment of the present disclosure.

[0026] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description set forth below, together with the accompanying drawings, is intended to explain exemplary embodiments of the present disclosure and is not intended to represent the only embodiments in which the present disclosure may be practiced. The following detailed description includes specific details to provide a thorough understanding of the present disclosure. However, one of ordinary skill in the art will appreciate that the present disclosure may be practiced without these specific details.

[0027] In some cases, to avoid obscuring the concepts of the present disclosure, known structures and devices may be omitted or illustrated in block diagram form focusing on the core functions of each structure and device.

[0028] In the present disclosure, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, the terms "comprises" or "has" in the present disclosure specify the presence of the mentioned features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0029] In this disclosure, terms such as "first," "second," etc. are used only to distinguish one component from another, are not used to limit the components, and do not limit the order or importance of components unless specifically stated otherwise. Accordingly, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0030] The terminology used herein is for the purpose of describing particular embodiments and is not intended to limit the scope of the claims. As used in the description of the embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. The term "and / or" as used herein may refer to any one of the associated enumerated items, or is meant to refer to and encompass any and all possible combinations of two or more of them. Furthermore, the use of " / " between words in this disclosure has the same meaning as "and / or" unless otherwise stated.

[0031] The examples of the present disclosure can be applied to various wireless communication systems. For example, the examples of the present disclosure can be applied to a wireless LAN system. For example, the examples of the present disclosure can be applied to a wireless LAN based on the IEEE 802.11a / g / n / ac / ax / be standards. Furthermore, the examples of the present disclosure can be applied to a wireless LAN based on the newly proposed IEEE 802.11bn (or UHR) standard. Additionally, the examples of the present disclosure can be applied to a wireless LAN based on the next-generation standard after IEEE 802.11bn. Furthermore, the examples of the present disclosure can be applied to a cellular wireless communication system. For example, the examples of the present disclosure can be applied to a cellular wireless communication system based on the LTE (Long Term Evolution) series of technologies and the 5G NR (New Radio) series of technologies of the 3rd Generation Partnership Project (3GPP) standard.

[0032] Below, technical features to which examples of the present disclosure can be applied are described.

[0033] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0034] The first device (100) and the second device (200) illustrated in FIG. 1 may be replaced with various terms such as a terminal, a wireless device, a WTRU (Wireless Transmit Receive Unit), a UE (User Equipment), an MS (Mobile Station), a UT (user terminal), an MSS (Mobile Subscriber Station), an MSS (Mobile Subscriber Unit), an SS (Subscriber Station), an AMS (Advanced Mobile Station), a WT (Wireless terminal), or simply a user. In addition, the first device (100) and the second device (200) may be replaced with various terms such as an access point (AP), a BS (Base Station), a fixed station, a Node B, a BTS (Base Transceiver System), a network, an AI (Artificial Intelligence) system, an RSU (road side unit), a repeater, a router, a relay, a gateway, etc.

[0035] The devices (100, 200) illustrated in FIG. 1 may also be referred to as stations (STAs). For example, the devices (100, 200) illustrated in FIG. 1 may be referred to by various terms such as transmitting device, receiving device, transmitting STA, and receiving STA. For example, the STAs (110, 200) may perform an AP (access point) role or a non-AP role. That is, in the present disclosure, the STAs (110, 200) may perform the functions of an AP and / or a non-AP. When the STAs (110, 200) perform an AP function, they may simply be referred to as APs, and when the STAs (110, 200) perform a non-AP function, they may simply be referred to as STAs. In addition, in the present disclosure, the APs may also be referred to as AP STAs.

[0036] Referring to FIG. 1, the first device (100) and the second device (200) can transmit and receive wireless signals through various wireless LAN technologies (e.g., IEEE 802.11 series). The first device (100) and the second device (200) can include interfaces for a medium access control (MAC) layer and a physical layer (PHY) that follow the provisions of the IEEE 802.11 standard.

[0037] In addition, the first device (100) and the second device (200) may additionally support various communication standards (e.g., 3GPP LTE series, 5G NR series standards, etc.) other than wireless LAN technology. In addition, the device of the present disclosure may be implemented as various devices such as a mobile phone, a vehicle, a personal computer, an AR (Augmented Reality) device, a VR (Virtual Reality) device, etc. In addition, the STA of the present specification may support various communication services such as voice calls, video calls, data communications, autonomous driving, MTC (Machine-Type Communication), M2M (Machine-to-Machine), D2D (Device-to-Device), and IoT (Internet-of-Things).

[0038] A first device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (106) and / or one or more antennas (108). The processor (102) controls the memories (104) and / or the transceivers (106), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in the present disclosure. For example, the processor (102) may process information in the memory (104) to generate first information / signal, and then transmit a wireless signal including the first information / signal via the transceiver (106). In addition, the processor (102) may receive a wireless signal including second information / signal via the transceiver (106), and then store information obtained from signal processing of the second information / signal in the memory (104). The memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, the memory (104) may perform some or all of the processes controlled by the processor (102), or may store software code including instructions for performing the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in the present disclosure. Here, the processor (102) and the memory (104) may be part of a communication modem / circuit / chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). The transceiver (106) may be connected to the processor (102) and may transmit and / or receive wireless signals via one or more antennas (108). The transceiver (106) may include a transmitter and / or a receiver. The transceiver (106) may be used interchangeably with an RF (Radio Frequency) unit. In the present disclosure, a device may also mean a communication modem / circuit / chip.

[0039] The second device (200) includes one or more processors (202), one or more memories (204), and may further include one or more transceivers (206) and / or one or more antennas (208). The processor (202) controls the memories (204) and / or the transceivers (206), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in the present disclosure. For example, the processor (202) may process information in the memory (204) to generate third information / signals, and then transmit a wireless signal including the third information / signals via the transceivers (206). In addition, the processor (202) may receive a wireless signal including fourth information / signals via the transceivers (206), and then store information obtained from signal processing of the fourth information / signals in the memory (204). The memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, the memory (204) may perform some or all of the processes controlled by the processor (202), or may store software code including instructions for performing the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in the present disclosure. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). The transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals via one or more antennas (208). The transceiver (206) may include a transmitter and / or a receiver. The transceiver (206) may be used interchangeably with an RF unit. In the present disclosure, a device may also mean a communication modem / circuit / chip.

[0040] Hereinafter, the hardware elements of the device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as PHY, MAC). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and / or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in the present disclosure. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in the present disclosure. One or more processors (102, 202) can generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, procedures, proposals and / or methods disclosed in the present disclosure, and provide the signals to one or more transceivers (106, 206). One or more processors (102, 202) can receive signals (e.g., baseband signals) from one or more transceivers (106, 206) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed in the present disclosure.

[0041] One or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this disclosure may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, proposals, methods and / or operation flowcharts disclosed in this disclosure may be implemented using firmware or software configured to perform one or more processors (102, 202) or stored in one or more memories (104, 204) and driven by one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods and / or operation flowcharts disclosed in this disclosure may be implemented using firmware or software in the form of codes, instructions and / or sets of instructions.

[0042] One or more memories (104, 204) may be coupled to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. The one or more memories (104, 204) may be configured as ROM, RAM, EPROM, flash memory, hard drives, registers, cache memory, computer-readable storage media, and / or combinations thereof. The one or more memories (104, 204) may be located internally and / or externally to the one or more processors (102, 202). Additionally, the one or more memories (104, 204) may be coupled to the one or more processors (102, 202) via various technologies, such as wired or wireless connections.

[0043] One or more transceivers (106, 206) can transmit user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or flowcharts of the present disclosure, to one or more other devices. One or more transceivers (106, 206) can receive user data, control information, wireless signals / channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and / or flowcharts of the present disclosure, from one or more other devices. For example, one or more transceivers (106, 206) can be coupled 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) may 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 coupled 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, or the like, as referred to in the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in the present disclosure, via one or more antennas (108, 208). In the present disclosure, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) can convert received user data, control information, wireless signals / channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals / channels, etc. using one or more processors (102, 202).One or more transceivers (106, 206) may convert user data, control information, wireless signals / channels, etc. processed by one or more processors (102, 202) from baseband signals to RF band signals. For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and / or filter.

[0044] For example, one of the STAs (100, 200) may perform the intended operation of an AP, and the other of the STAs (100, 200) may perform the intended operation of a non-AP STA. For example, the transceivers (106, 206) of FIG. 1 may perform transmission and reception operations of signals (e.g., packets or PPDUs (Physical layer Protocol Data Units) according to IEEE 802.11a / b / g / n / ac / ax / be / bn, etc.). In addition, in the present disclosure, operations in which various STAs generate transmission and reception signals or perform data processing or calculations in advance for transmission and reception signals may be performed in the processors (102, 202) of FIG. 1. For example, an example of an operation for generating a transmission / reception signal or performing data processing or operation in advance for a transmission / reception signal may include 1) an operation for determining / obtaining / configuring / computing / decoding / encoding bit information of a field (SIG (signal), STF (short training field), LTF (long training field), Data, etc.) included in a PPDU, 2) an operation for determining / configuring / obtaining time resources or frequency resources (e.g., subcarrier resources) used for a field (SIG, STF, LTF, Data, etc.) included in a PPDU, 3) an operation for determining / configuring / obtaining a specific sequence (e.g., a pilot sequence, an STF / LTF sequence, an extra sequence applied to SIG) used for a field (SIG, STF, LTF, Data, etc.) included in a PPDU, 4) a power control operation and / or a power saving operation applied to an STA, 5) an operation related to determining / obtaining / configuring / computing / decoding / encoding an ACK signal, etc. Additionally, in the examples below, various information (e.g., information related to fields / subfields / control fields / parameters / power, etc.) used by various STAs for determining / acquiring / configuring / computing / decoding / encoding transmission / reception signals can be stored in the memory (104, 204) of FIG. 1.

[0045] Hereinafter, downlink (DL) refers to a link for communication from an AP STA to a non-AP STA, and downlink PPDUs / packets / signals, etc. can be transmitted and received through the downlink. In downlink communication, the transmitter may be part of an AP STA, and the receiver may be part of a non-AP STA. Uplink (UL) refers to a link for communication from a non-AP STA to an AP STA, and uplink PPDUs / packets / signals, etc. can be transmitted and received through the uplink. In uplink communication, the transmitter may be part of a non-AP STA, and the receiver may be part of an AP STA.

[0046] FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0047] The structure of a wireless LAN system can be composed of multiple components. Through the interaction of multiple components, a wireless LAN that supports transparent STA mobility to the upper layer can be provided. A Basic Service Set (BSS) corresponds to a basic building block of a wireless LAN. FIG. 2 illustrates, by way of example, the existence of two BSSs (BSS1 and BSS2) and the inclusion of two STAs as members of each BSS (STA1 and STA2 are included in BSS1, and STA3 and STA4 are included in BSS2). The oval representing a BSS in FIG. 2 can also be understood as representing a coverage area in which STAs included in the corresponding BSS maintain communication. This area can be referred to as a Basic Service Area (BSA). When an STA moves outside of a BSA, it cannot directly communicate with other STAs within the BSA.

[0048] If we do not consider the DS illustrated in Figure 2, the most basic type of BSS in a wireless LAN is an Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For example, assuming other components are omitted, BSS1 consisting of only STA1 and STA2, or BSS2 consisting of only STA3 and STA4, can be representative examples of an IBSS, respectively. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, in this type of WLAN, a LAN can be configured when needed rather than being planned in advance, 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 IBSS, all STAs can be mobile STAs, and access to distributed systems (DS) is not permitted, forming a self-contained network.

[0049] An STA's membership in a BSS can dynamically change, for example, when an STA is turned on or off, or when an STA enters or leaves a BSS area. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services in the BSS infrastructure, an STA must be associated with the BSS. This association can be dynamically established and may involve the use of a Distribution System Service (DSS).

[0050] In a wireless LAN, the direct STA-to-STA distance can be limited by PHY performance. While this distance limit may be sufficient in some cases, communication between STAs over longer distances may be required in other cases. To support extended coverage, a distributed system (DS) can be configured.

[0051] DS refers to a structure in which BSSs are interconnected. Specifically, a BSS may exist as an extended component of a network composed of multiple BSSs, as illustrated in Figure 2. DS is a logical concept and can be specified by the characteristics of a distributed system medium (DSM). In this regard, the Wireless Medium (WM) and DSM can be logically distinguished. Each logical medium is used for a different purpose and by different components. These media are neither limited to being identical nor limited to being different. This logical difference between multiple media explains the flexibility of the WLAN architecture (DS architecture or other network architectures). In other words, the WLAN architecture can be implemented in various ways, and the physical characteristics of each implementation can independently specify the WLAN architecture.

[0052] A DS can support mobile devices by providing seamless integration of multiple BSSs and the logical services necessary to handle addresses to destinations. Additionally, a DS may further include a component called a portal, which acts as a bridge for connecting wireless LANs to other networks (e.g., IEEE 802.X).

[0053] An AP is an entity that enables access to a DS through a WM for associated non-AP STAs and also has the functionality of an STA. Data movement between a BSS and a DS can be performed through an AP. For example, STA2 and STA3 illustrated in FIG. 2 have the functionality of an STA and provide the function of allowing associated non-AP STAs (STA1 and STA4) to access the DS. In addition, since all APs are basically STAs, all APs are addressable entities. The address used by an AP for communication on a WM and the address used by an AP for communication on a DSM do not necessarily have to be the same. A BSS consisting of an AP and one or more STAs can be referred to as an infrastructure BSS.

[0054] Data transmitted from one of the STA(s) associated with an AP to the STA address of that AP is always received on an uncontrolled port and can be processed by an IEEE 802.1X port access entity. In addition, if the controlled port is authenticated, the transmitted data (or frame) can be forwarded to the DS.

[0055] In addition to the structure of the DS described above, an extended service set (ESS) may be established to provide wider coverage.

[0056] An ESS is a network of arbitrary size and complexity, consisting of DSs and BSSs. An ESS may correspond to a set of BSSs connected to a DS. However, an ESS does not include a DS. An ESS network is characterized by appearing as an IBSS at the Logical Link Control (LLC) layer. STAs within an ESS can communicate with each other, and mobile STAs can move from one BSS to another (within the same ESS) transparently to the LLC. APs within an ESS may have the same SSID (service set identification). The SSID is distinct from the BSSID, which is the identifier of the BSS.

[0057] In a wireless LAN system, no assumptions are made about the relative physical locations of BSSs, and all of the following configurations are possible: BSSs can be partially overlapping, which is commonly used to provide continuous coverage. BSSs can also be physically disconnected, and there is no logical distance limit between them. BSSs can also be physically co-located, which can be used to provide redundancy. Furthermore, one (or more) IBSS or ESS networks can physically co-exist with one (or more) ESS networks. This can occur in cases where an ad-hoc network operates at the same location as an ESS network, where physically overlapping wireless networks are configured by different organizations, or where two or more different access and security policies are required at the same location.

[0058] FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0059] For an STA to set up a link and transmit and receive data on a network, it must first discover the network, perform authentication, establish an association, and complete security authentication procedures. The link setup process can also be referred to as the session initiation process or session setup process. Furthermore, the discovery, authentication, association, and security setup processes of the link setup process can be collectively referred to as the association process.

[0060] In step S310, the STA may perform a network discovery operation. This network discovery operation may include scanning operations by the STA. That is, for the STA to access a network, it must search for available networks. Before joining a wireless network, the STA must identify compatible networks. The process of identifying networks in a specific area is called scanning.

[0061] Scanning methods include active scanning and passive scanning. Figure 3 illustrates a network discovery operation including an active scanning process as an example. In active scanning, an STA performing scanning transmits a probe request frame to discover any APs in the vicinity while moving between channels and waits for a response. The responder transmits a probe response frame in response to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted a beacon frame in the BSS of the channel being scanned. In the BSS, the AP transmits the beacon frame, so the AP becomes the responder. In the IBSS, the STAs within the IBSS take turns transmitting beacon frames, so the responder is not fixed. For example, an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 can store BSS-related information included in the received probe response frame and move to the next channel (e.g., channel 2) to perform scanning (i.e., transmitting and receiving probe requests / responses on channel 2) in the same manner.

[0062] Although not shown in Figure 3, the scanning operation can also be performed in a passive scanning manner. In passive scanning, the STA performing the scanning moves between channels and waits for a beacon frame. A beacon frame is one of the management frames defined in IEEE 802.11. It announces the existence of a wireless network and is periodically transmitted so that the STA performing the scanning can find the wireless network and participate in the wireless network. In the BSS, the AP performs the role of periodically transmitting the beacon frame, and in the IBSS, the STAs within the IBSS take turns transmitting the beacon frame. When the STA performing the scanning receives a beacon frame, it stores the information about the BSS included in the beacon frame and moves to another channel, recording the beacon frame information on each channel. The STA receiving the beacon frame stores the BSS-related information included in the received beacon frame and moves to the next channel to perform scanning on the next channel in the same manner. Comparing active scanning and passive scanning, active scanning has the advantage of lower delay and power consumption than passive scanning.

[0063] After the STA discovers the network, an authentication process may be performed in step S320. This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation of step S340 described below.

[0064] The authentication process involves the STA sending an authentication request frame to the AP, and the AP responding by sending an authentication response frame to the STA. The authentication frame used for the authentication request / response corresponds to a management frame.

[0065] The authentication frame may include information such as an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a Robust Security Network (RSN), and a Finite Cyclic Group. These are just some examples of information that may be included in an authentication request / response frame, and may be replaced with other information or include additional information.

[0066] An STA can send an authentication request frame to an AP. The AP can determine whether to grant authentication to the STA based on the information contained in the received authentication request frame. The AP can provide the result of the authentication process to the STA via an authentication response frame.

[0067] After the STA is successfully authenticated, an association process may be performed in step S330. The association process includes a process in which the STA transmits an association request frame to the AP, and in response, the AP transmits an association response frame to the STA.

[0068] For example, the association request frame may include information about various capabilities, a beacon listen interval, a service set identifier (SSID), supported rates, supported channels, an RSN, a mobility domain, supported operating classes, a Traffic Indication Map Broadcast request, interworking service capabilities, etc. For example, the association response frame may include information about various capabilities, a status code, an Association ID (AID), supported rates, an Enhanced Distributed Channel Access (EDCA) parameter set, a Received Channel Power Indicator (RCPI), a Received Signal to Noise Indicator (RSNI), a mobility domain, a timeout interval (e.g., an association comeback time), overlapping BSS scan parameters, a TIM broadcast response, a Quality of Service (QoS) map, etc. These are just some examples of information that may be included in a combined request / response frame, and may be replaced by other information or include additional information.

[0069] After the STA successfully joins the network, a security setup process may be performed in step S340. The security setup process in step S340 may be referred to as an authentication process through a Robust Security Network Association (RSNA) request / response, the authentication process in step S320 may be referred to as a first authentication process, and the security setup process in step S340 may also be referred to simply as an authentication process.

[0070] The security setup process of step S340 may include, for example, a process of establishing a private key through a four-way handshaking using an Extensible Authentication Protocol over LAN (EAPOL) frame. Furthermore, the security setup process may be performed according to a security method not defined in the IEEE 802.11 standard.

[0071] FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0072] In wireless LAN systems, the basic access mechanism of MAC (Medium Access Control) is Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA). The CSMA / CA mechanism, also known as the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC, essentially employs a "listen before talk" access mechanism. According to this type of access mechanism, the AP and / or STA may perform a Clear Channel Assessment (CCA) to sense the wireless channel or medium for a predetermined time period (e.g., a DCF Inter-Frame Space (DIFS)) before starting transmission. If the sensing result determines that the medium is in an idle state, the AP and / or STA may start transmitting frames through the medium. On the other hand, if the medium is detected to be occupied or busy, the AP and / or STA may not start its own transmission, but may wait for a delay period (e.g., a random backoff period) for medium access before attempting to transmit frames. By applying a random backoff period, multiple STAs are expected to attempt to transmit frames after waiting for different periods of time, thereby minimizing collisions.

[0073] In addition, the IEEE 802.11 MAC protocol provides the Hybrid Coordination Function (HCF). The HCF is based on the DCF and the Point Coordination Function (PCF). The PCF is a polling-based synchronous access method that periodically polls all receiving APs and / or STAs to ensure that they receive data frames. In addition, the HCF has the Enhanced Distributed Channel Access (EDCA) and the HCF Controlled Channel Access (HCCA). The EDCA is a contention-based access method for a provider to provide data frames to multiple users, while the HCCA uses a non-contention-based channel access method that utilizes a polling mechanism. In addition, the HCF includes a medium access mechanism to improve the Quality of Service (QoS) of the wireless LAN, and can transmit QoS data in both the Contention Period (CP) and the Contention Free Period (CFP).

[0074] Referring to Fig. 4, an operation based on a random backoff period is described. When a medium that was occupied / busy changes to an idle state, multiple STAs can attempt to transmit data (or frames). To minimize collisions, each STA can select a random backoff count, wait for the corresponding slot time, and then attempt transmission. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​in the range of 0 to CW. Here, CW is a contention window parameter value. The CW parameter is given an initial value of CWmin, but can take a value doubled in case of transmission failure (e.g., when an ACK for a transmitted frame is not received). When the CW parameter value becomes CWmax, data transmission can be attempted while maintaining the CWmax value until data transmission is successful, and if data transmission is successful, it is reset to the CWmin value. The CW, CWmin, and CWmax values ​​are 2. n It is desirable to set it to -1 (n=0, 1, 2, ...).

[0075] Once the random backoff process begins, the STA continues to monitor the medium while counting down the backoff slots according to the determined backoff count value. If the medium is monitored as occupied, the countdown stops and waits. When the medium becomes idle, the remaining countdown resumes.

[0076] In the example of FIG. 4, when a packet to be transmitted reaches the MAC of STA3, STA3 can immediately transmit a frame if it confirms that the medium is idle for DIFS. The remaining STAs monitor the medium for occupied / busy states and wait. In the meantime, data to be transmitted may also occur in each of STA1, STA2, and STA5, and each STA can count down the backoff slot according to a random backoff count value selected by each STA after waiting for DIFS if the medium is monitored as idle. Assume that STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value. In other words, this example shows a case where the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1 when STA2 finishes the backoff count and starts frame transmission. STA1 and STA5 briefly stop counting down and wait while STA2 occupies the medium. When STA2's occupation ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the backoff count that they had stopped. That is, they can start transmitting frames after counting down the remaining backoff slots equal to the remaining backoff time. Since STA5's remaining backoff time is shorter than STA1's, STA5 starts transmitting frames. While STA2 occupies the medium, STA4 may also have data to transmit. From STA4's perspective, when the medium becomes idle, it waits for DIFS, counts down according to its selected random backoff count value, and then starts transmitting frames. In the example of Figure 4, the remaining backoff time of STA5 coincidentally matches the random backoff count value of STA4, in which case a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 will receive an ACK, resulting in a failure in data transmission.In this case, STA4 and STA5 can select a random backoff count value and perform a countdown after doubling the CW value. STA1 waits while the medium is occupied by transmissions from STA4 and STA5, and when the medium becomes idle, it waits for DIFS and can start transmitting frames after the remaining backoff time elapses.

[0077] As in the example of Fig. 4, a data frame is a frame used for transmitting data forwarded to a higher layer, and can be transmitted after a backoff performed after DIFS elapses from when the medium becomes idle. Additionally, a management frame is a frame used for exchanging management information that is not forwarded to a higher layer, and is transmitted after a backoff performed after an IFS elapses, such as DIFS or PIFS (Point coordination function IFS). Subtype frames of a management frame include a beacon, an association request / response, a re-association request / response, a probe request / response, and an authentication request / response. A control frame is a frame used to control access to the medium. The subtype frames of the control frame include Request-To-Send (RTS), Clear-To-Send (CTS), Acknowledgment (ACK), Power Save-Poll (PS-Poll), Block ACK (BlockAck), Block ACK Request (BlockACKReq), Null Data Packet Announcement (NDP), and Trigger. If the control frame is not a response frame to the previous frame, it is transmitted after a backoff performed after the DIFS (Direct Inverse Frame Stop) has elapsed, and if it is a response frame to the previous frame, it is transmitted without a backoff performed after the SIFS (short IFS). The type and subtype of the frame can be identified by the type field and subtype field in the Frame Control (FC) field.

[0078] A QoS (Quality of Service) STA can transmit a frame after a backoff performed after the AIFS (arbitration IFS) for the access category (AC) to which the frame belongs, i.e., AIFS[i] (where i is a value determined by the AC), has elapsed. Here, the frames for which AIFS[i] can be used can be data frames, management frames, and also control frames that are not response frames.

[0079] FIG. 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0080] As mentioned above, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, in which STAs directly sense the medium. Virtual carrier sensing is intended to address potential issues in medium access, such as the hidden node problem. For virtual carrier sensing, the MAC of an STA can utilize a Network Allocation Vector (NAV). The NAV is a value that an STA that is currently using or has the right to use the medium indicates to other STAs the remaining time until the medium becomes available. Therefore, the value set as NAV corresponds to the period during which the STA transmitting the frame is scheduled to use the medium, and an STA receiving the NAV value is prohibited from accessing the medium during that period. For example, the NAV can be set based on the value of the "duration" field in the MAC header of the frame.

[0081] In the example of FIG. 5, it is assumed that STA1 wants to transmit data to STA2, and STA3 is in a position to overhear some or all of the frames transmitted and received between STA1 and STA2.

[0082] In order to reduce the possibility of collisions in transmissions of multiple STAs in a CSMA / CA-based frame transmission operation, a mechanism using RTS / CTS frames may be applied. In the example of FIG. 5, while STA1 is transmitting, STA3 may determine that the medium is idle based on carrier sensing results. That is, STA1 may correspond to a hidden node for STA3. Alternatively, in the example of FIG. 5, while STA2 is transmitting, STA3 may determine that the medium is idle based on carrier sensing results. That is, STA2 may correspond to a hidden node for 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 for transmissions from STA1 or STA3, may not attempt to occupy the channel during data transmission and reception between STA1 and STA2.

[0083] Specifically, STA1 can determine whether a channel is occupied through carrier sensing. In terms of physical carrier sensing, STA1 can determine channel occupancy idleness based on the energy level or signal correlation detected in the channel. Furthermore, in terms of virtual carrier sensing, STA1 can determine the channel occupancy status using a network allocation vector (NAV) timer.

[0084] STA1 can transmit an RTS frame to STA2 after performing a backoff if the channel is idle during the DIFS. STA2 can transmit a CTS frame, which is a response to the RTS frame, to STA1 after an SIFS if it receives the RTS frame.

[0085] If STA3 cannot overhear a CTS frame from STA2 but can overhear an RTS frame from STA1, STA3 can use the duration information contained in the RTS frame to set a NAV timer for the subsequent consecutively transmitted frame transmission period (e.g., SIFS + CTS frame + SIFS + data frame + SIFS + ACK frame). Alternatively, if STA3 cannot overhear an RTS frame from STA1 but can overhear a CTS frame from STA2, STA3 can use the duration information contained in the CTS frame to set a NAV timer for the subsequent consecutively transmitted frame transmission period (e.g., SIFS + data frame + SIFS + ACK frame). That is, if STA3 can overhear one or more of the RTS or CTS frames from one or more of STA1 or STA2, it can set a NAV accordingly. If STA3 receives a new frame before the NAV timer expires, it can update the NAV timer using the duration information contained in the new frame. STA3 does not attempt channel access until the NAV timer expires.

[0086] If STA1 receives a CTS frame from STA2, it can transmit a data frame to STA2 after SIFS from the time when the CTS frame is completely received. If STA2 successfully receives the data frame, it can transmit an ACK frame in response to the data frame to STA1 after SIFS. STA3 can determine whether the channel is in use through carrier sensing if the NAV timer expires. If STA3 determines that the channel is not in use by another terminal during the DIFS after the NAV timer expires, it can attempt channel access after a contention window (CW) based on a random backoff has elapsed.

[0087] FIG. 6 is a drawing for explaining an example of a frame structure used in a wireless LAN system to which the present disclosure can be applied.

[0088] The PHY layer can prepare an MPDU (MAC PDU) to be transmitted based on an instruction or primitive (meaning a set of instructions or parameters) from the MAC layer. For example, when a command requesting the start of transmission of the PHY layer is received from the MAC layer, the PHY layer can switch to transmission mode and transmit the information (e.g., data) provided by the MAC layer in the form of a frame. In addition, when the PHY layer detects a valid preamble of the received frame, it monitors the header of the preamble and sends a command to the MAC layer notifying the start of reception of the PHY layer.

[0089] In this way, information transmission / reception in a wireless LAN system is done in the form of frames, and for this purpose, the PHY layer Protocol Data Unit (PPDU) format is defined.

[0090] A basic PPDU may include a Short Training Field (STF), a Long Training Field (LTF), a SIGNAL (SIG) field, and a Data field. The most basic (e.g., non-HT (High Throughput) as illustrated in FIG. 7) PPDU format may consist of only the Legacy-STF (L-STF), Legacy-LTF (L-LTF), Legacy-SIG (L-SIG) fields, and a Data field. Additionally, depending on the type of PPDU format (e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (Very High Throughput) PPDU, etc.), additional (or different types of) RL-SIG, U-SIG, non-legacy SIG field, non-legacy STF, non-legacy LTF, (i.e., xx-SIG, xx-STF, xx-LTF (e.g., xx is HT, VHT, HE, EHT, etc.)) may be included between the L-SIG field and the data field. More specific details will be described later with reference to FIG. 7.

[0091] STF is a signal for signal detection, AGC (Automatic Gain Control), diversity selection, and precise time synchronization, while LTF is a signal for channel estimation, frequency error estimation, etc. STF and LTF can be said to be signals for synchronization and channel estimation of the OFDM physical layer.

[0092] The SIG field may include various information related to PPDU transmission and reception. For example, the L-SIG field may consist of 24 bits and may 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 may include information about the modulation and coding rate of data. For example, the 12-bit Length field may include information about the length or time duration of the PPDU. For example, the value of the 12-bit Length field may be determined based on the type of the PPDU. For example, for a non-HT, HT, VHT, or EHT PPDU, the value of the Length field may be determined as a multiple of 3. For example, for HE PPDU, the value of the Length field can be determined as a multiple of 3 + 1 or a multiple of 3 + 2.

[0093] The data field may include a SERVICE field, a Physical layer Service Data Unit (PSDU), a PPDU TAIL bit, and, if necessary, padding bits. Some bits of the SERVICE field may be used to synchronize the descrambler at the receiving end. The PSDU corresponds to a MAC PDU defined at the MAC layer and may contain data generated / used by upper layers. The PPDU TAIL bit may be used to return the encoder to a 0 state. The padding bit may be used to adjust the length of the data field to a predetermined unit.

[0094] 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). A MAC frame is composed of MAC PDUs and can be transmitted / received through the PSDU in the data portion of the PPDU format.

[0095] The MAC header includes a Frame Control field, a Duration / ID field, an Address field, etc. The Frame Control field may include control information required for frame transmission / reception. The Duration / ID field may be set to a time for transmitting the corresponding frame, etc. The Address subfields may indicate the receiver address, transmitter address, destination address, and source address of the frame, and some Address subfields may be omitted. For specific details of each subfield of the MAC header, including the Sequence Control, QoS Control, and HT Control subfields, refer to the IEEE 802.11 standard document.

[0096] The Null-Data PPDU (NDP) format refers to a PPDU format that does not include a data field. In other words, NDP refers to a frame format that includes a PPDU preamble (i.e., L-STF, L-LTF, L-SIG fields, and, if additionally present, non-legacy SIG, non-legacy STF, and non-legacy LTF) in the general PPDU format, and does not include the remaining part (i.e., data field).

[0097] FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0098] Standards such as IEEE 802.11a / g / n / ac / ax use various PPDU formats. The basic PPDU format (IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and Data fields. The basic PPDU format can also be referred to as the non-HT PPDU format (Fig. 7(a)).

[0099] The HT PPDU format (IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT(s) fields in addition to the basic PPDU format. The HT PPDU format illustrated in Fig. 7(b) may be referred to as an HT-mixed format. Additionally, an HT-greenfield format PPDU may be defined, which corresponds to a format that does not include L-STF, L-LTF, and L-SIG, but consists of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTF, and Data fields (not illustrated).

[0100] An example of the VHT PPDU format (IEEE 802.11ac) includes VHT SIG-A, VHT-STF, VHT-LTF, and VHT-SIG-B fields in addition to the basic PPDU format (Fig. 7(c)).

[0101] An example of a HE PPDU format (IEEE 802.11ax) additionally includes RL-SIG (Repeated L-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF(s), and PE (Packet Extension) fields in addition to the basic PPDU format (Fig. 7(d)). Depending on specific examples of the HE PPDU format, some fields may be excluded or their lengths may vary. For example, the HE-SIG-B field is included in the HE PPDU format for multi-users (MUs), but the HE PPDU format for single users (SUs) does not include the HE-SIG-B. In addition, the HE trigger-based (TB) PPDU format does not include the HE-SIG-B, and the length of the HE-STF field may vary to 8us. The HE ER (Extended Range) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16us. For example, RL-SIG can be configured identically to L-SIG. The receiving STA can determine that the received PPDU is a HE PPDU or an EHT PPDU, described later, based on the presence of RL-SIG.

[0102] The EHT PPDU format may include the EHT MU (multi-user) PPDU of FIG. 7(e) and the EHT TB (trigger-based) PPDU of FIG. 7(f). The EHT PPDU format is similar to the HE PPDU format in that it includes an RL-SIG following an L-SIG, but may include a U (universal)-SIG, an EHT-SIG, an EHT-STF, and an EHT-LTF following the RL-SIG.

[0103] The EHT MU PPDU in FIG. 7(e) corresponds to a PPDU that carries one or more data (or PSDUs) for one or more users. That is, the EHT MU PPDU can be used for both SU transmission and MU transmission. For example, the EHT MU PPDU can correspond to a PPDU for one receiving STA or multiple receiving STAs.

[0104] The EHT TB PPDU of Fig. 7(f) omits the EHT-SIG compared to the EHT MU PPDU. An STA that has received a trigger for UL MU transmission (e.g., a trigger frame or TRS (triggered response scheduling)) can perform UL transmission based on the EHT TB PPDU format.

[0105] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated to allow legacy STAs to attempt demodulation and decoding, and mapped based on a predetermined 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 allow STAs that have successfully decoded non-legacy SIGs (e.g., U-SIG and / or EHT-SIG) and obtained the information contained in the fields, and mapped based on a predetermined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

[0106] Similarly, in the HE PPDU format, the L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, and HE-SIG-B fields may be referred to as pre-HE modulation fields, and the HE-STF, HE-LTF, Data, and PE fields may 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 may be referred to as pre-VHT modulation fields, and the VHT STF, VHT-LTF, VHT-SIG-B, and Data fields may be referred to as VHT modulation fields.

[0107] The U-SIG included in the EHT PPDU format of FIG. 7 can be configured based on, for example, two symbols (e.g., two consecutive OFDM symbols). Each symbol (e.g., OFDM symbol) for the U-SIG can have a duration of 4 us, and the U-SIG can have a total duration of 8 us. Each symbol of the U-SIG can be used to transmit 26 bits of information. For example, each symbol of the U-SIG can be transmitted and received based on 52 data tones and 4 pilot tones.

[0108] U-SIGs can be configured in 20MHz units. For example, when an 80MHz PPDU is configured, the same U-SIG can be duplicated in 20MHz units. That is, four identical U-SIGs can be included in an 80MHz PPDU. When the bandwidth exceeds 80MHz, for example, for a 160MHz PPDU, the U-SIGs in the first 80MHz unit and the U-SIGs in the second 80MHz unit can be different.

[0109] For example, A uncoded bits may be transmitted via U-SIG, and a first symbol of U-SIG (e.g., a U-SIG-1 symbol) may transmit the first X bits of information out of a total A bits of information, and a second symbol of U-SIG (e.g., a U-SIG-2 symbol) may transmit the remaining Y bits of information out of a total A bits of information. The A bits of information (e.g., 52 uncoded bits) may include a CRC field (e.g., a field of 4 bits in length) and a tail field (e.g., a field of 6 bits in length). The tail field may be used to terminate the trellis of the convolutional decoder and may be set to 0, for example.

[0110] The A bit information transmitted by U-SIG can be divided into version-independent bits and version-dependent bits. For example, U-SIG can be included in a new PPDU format (e.g., UHR PPDU format) not shown in FIG. 7, and 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-dependent bits can be different.

[0111] For example, the size of the version-independent bits of U-SIG can be fixed or variable. The version-independent bits can be assigned only to U-SIG-1 symbols, or to both U-SIG-1 symbols and U-SIG-2 symbols. The version-independent bits and the version-dependent bits can be called by various names, such as the first control bit and the second control bit.

[0112] For example, the version-independent bits of the U-SIG may include a 3-bit PHY version identifier, which may indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted and received PPDUs. 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 relates to UL communication, and the second value of the UL / DL flag field relates to DL communication. The version-independent bits of the U-SIG may include information about the length of a transmission opportunity (TXOP) and information about a BSS color ID.

[0113] For example, the version-dependent bits of the U-SIG may contain information that directly or indirectly indicates the type of PPDU (e.g., SU PPDU, MU PPDU, TB PPDU, etc.).

[0114] Information required for PPDU transmission and reception may be included in the U-SIG. For example, the U-SIG may further include information about bandwidth, information about the MCS technique applied to the non-legacy SIG (e.g., EHT-SIG or UHR-SIG), information indicating whether a dual carrier modulation (DCM) technique (e.g., a technique to achieve an effect similar to frequency diversity by reusing the same signal on two subcarriers) is applied to the non-legacy SIG, information about the number of symbols used for the non-legacy SIG, information about whether the non-legacy SIG is generated across the entire band, etc.

[0115] Some of the information required for transmitting and receiving a PPDU may be included in the U-SIG and / or the non-legacy SIG (e.g., EHT-SIG or UHR-SIG, etc.). For example, information about the type of the non-legacy LTF / STF (e.g., EHT-LTF / EHT-STF or UHR-LTF / UHR-STF, etc.), information about the length of the non-legacy LTF and the cyclic prefix (CP) length, information about the guard interval (GI) applicable to the non-legacy LTF, information about preamble puncturing applicable to the PPDU, information about resource unit (RU) allocation, etc. may be included only in the U-SIG, may be included only in the non-legacy SIG, or may be indicated by a combination of the information included in the U-SIG and the information included in the non-legacy SIG.

[0116] Preamble puncturing may refer to the transmission of a PPDU in which no signal is present in one or more frequency units within the PPDU's bandwidth. For example, the size of the frequency unit (or the resolution of the preamble puncturing) may be defined as 20 MHz, 40 MHz, etc. For example, preamble puncturing may be applied to a PPDU bandwidth greater than a certain size.

[0117] In the example of FIG. 7, non-legacy SIGs such as HE-SIG-B and EHT-SIG may include control information for the receiving STA. The non-legacy SIG may be transmitted over at least one symbol, and each symbol may have a length of 4 us. Information regarding the number of symbols used for the EHT-SIG may be included in a previous SIG (e.g., HE-SIG-A, U-SIG, etc.).

[0118] Non-legacy SIGs, such as HE-SIG-B and EHT-SIG, may contain common fields and user-specific fields. Common and user-specific fields may be coded separately.

[0119] In some cases, common fields may be omitted. For example, in a compressed mode where non-OFDMA (orthogonal frequency multiple access) is applied, common fields may be omitted, and multiple STAs may receive PPDUs (e.g., data fields of PPDUs) over the same frequency band. In a non-compressed mode where OFDMA is applied, multiple users may receive PPDUs (e.g., data fields of PPDUs) over different frequency bands.

[0120] The number of user-specific fields can be determined based on the number of users. A single user block field can contain up to two user fields. Each user field can be associated with either MU-MIMO allocation or non-MU-MIMO allocation.

[0121] The common field may include CRC bits and Tail bits, the length of the CRC bits may be determined as 4 bits, and the length of the Tail bits may be determined as 6 bits and set to 000000. The common field may include RU allocation information. The RU allocation information may include information about the location of RUs to which multiple users (i.e., multiple receiving STAs) are allocated.

[0122] An RU can contain multiple subcarriers (or tones). RUs can be used when transmitting signals to multiple STAs based on OFDMA techniques. RUs can also be defined when transmitting signals to a single STA. Resources can be allocated on an RU basis for non-legacy STFs, non-legacy LTFs, and data fields.

[0123] Depending on the PPDU bandwidth, an applicable RU size can be defined. The RU may be defined identically or differently for the applicable PPDU format (e.g., HE PPDU, EHT PPDU, UHR PPDU, etc.). For example, in the case of an 80MHz PPDU, the RU arrangements of HE PPDU and EHT PPDU may be different. The applicable RU size, RU number, RU position, DC (direct current) subcarrier position and number, null subcarrier position and number, guard subcarrier position and number, etc. for each PPDU bandwidth can be referred to as a tone plan. For example, a tone plan for a wide bandwidth can be defined in the form of multiple repetitions of a low bandwidth tone plan.

[0124] RUs of different sizes can be defined, such as 26-ton RU, 52-ton RU, 106-ton RU, 242-ton RU, 484-ton RU, 996-ton RU, 2X996-ton RU, 3X996-ton RU, etc. A multiple RU (MRU) is distinguished from multiple individual RUs and corresponds to a group of subcarriers consisting of multiple RUs. For example, one MRU can be defined as 52+26-tons, 106+26-tons, 484+242-tons, 996+484-tons, 996+484+242-tons, 2X996+484-tons, 3X996-tons, or 3X996+484-tons. Additionally, multiple RUs constituting one MRU may or may not be consecutive in the frequency domain.

[0125] The specific size of an RU may be reduced or expanded. Therefore, the specific size of each RU (i.e., the number of corresponding tones) in the present disclosure is not limited and is exemplary. Furthermore, within a given bandwidth (e.g., 20, 40, 80, 160, 320 MHz, etc.) in the present disclosure, the number of RUs may vary depending on the RU size.

[0126] The names of each field in the PPDU formats of FIG. 7 are exemplary and the scope of the present disclosure is not limited by those names. Furthermore, the examples of the present disclosure can be applied not only to the PPDU format exemplified in FIG. 7, but also to a new PPDU format in which some fields are excluded and / or some fields are added based on the PPDU formats of FIG. 7.

[0127] Synchronization

[0128] STAs within a single infrastructure BSS (BSS), personal BSS (PBSS), or independent BSS (IBSS) synchronize to a common clock using a defined mechanism. STAs within a mesh BSS (BSS) use a synchronization method that is part of an extensible synchronization framework.

[0129] The timing synchronization function (TSF) keeps the timers for all STAs within the same BSS synchronized.

[0130] Devices with multi-band capability must maintain a local TSF timer for each channel on which the STA operates.

[0131] Below, the TSF for the infrastructure BSS and PBSS is described.

[0132] In an infrastructure BSS or PBSS, an AP within the infrastructure BSS or a PBSS Control Point (PCP) within the PBSS acts as the timing master of the TSF.

[0133] An AP or PCP periodically transmits a beacon frame and / or an announce frame. The beacon frame and / or the announce frame include the value of the TSF timer of the AP or PCP for synchronizing the TSF timers of other STAs within the BSS. A receiving STA accepts the timing information of the Beacon, S1G Beacon, DMG Beacon, or announce frame sent by the AP or PCP serving the BSS. That is, the STA updates the TSF timer based on the value of the TSF timer of the AP or PCP. In other words, if the TSF timer of the STA is different from the timestamp of the received beacon or announce frame, the receiving STA sets the local TSF timer to the received timestamp value.

[0134] Time synchronization method for relay operation

[0135] The next-generation wireless LAN (beyond 802.11be) aims to support ultra-high reliability when transmitting signals to STAs, and various technologies are being considered for high throughput, low latency, and extended range support. To this end, signal transmission using a relay can be considered to extend the coverage of AP signal transmission as well as reliability within the AP coverage. In order to extend the range through relay operation, the AP's signal (e.g., management frame such as a beacon frame) can be transmitted to non-AP STAs located outside the AP coverage through the relay STA. In this way, since an STA that receives an AP signal (e.g., a beacon frame and / or a management frame) transmitted by a relay STA receives the AP signal from the relay STA, not the AP, a definition of a method for synchronizing time with the AP is necessary (since this may cause problems such as ambiguity in the timestamp value transmitted through the AP signal).

[0136] In the present disclosure, when transmitting a signal of an AP (e.g., a management frame (e.g., a beacon frame, a probe response frame, etc.)) to a non-AP STA through a relay STA, a method for a non-AP STA to synchronize time with the AP is proposed.

[0137] FIG. 8 is a diagram illustrating range expansion using a relay in a wireless LAN system to which the present disclosure can be applied.

[0138] In the next generation wireless LAN (beyond 802.11be), a relay STA can be used to ensure smooth signal transmission and reception for STAs located at the coverage boundary of the AP and to extend the coverage of the AP to transmit and receive signals.

[0139] Here, the relay STA may be an AP STA or a non-AP STA. For example, if the relay STA is an AP STA, the relay STA can only support / perform AP functions. Also, for example, if the relay STA is a non-AP STA, the relay STA can only support / perform non-AP STA functions. Also, for example, the relay STA may be an STA that can support / perform both AP functions and non-AP STA functions.

[0140] Hereinafter, in the description of the present disclosure, for convenience of explanation, the relay STA is mainly described as a non-AP STA, but the present disclosure is not limited thereto.

[0141] Through signal transmission and reception using a relay STA, the AP can transmit and receive signals with an STA that exists outside the coverage of the AP, as shown in FIG. 8.

[0142] As shown in Fig. 8, when using relay operation to transmit and receive signals to and from STAs that exist outside the coverage / range of the AP, frames / PPDUs (e.g., management frames) transmitted by the AP can be transmitted to STAs (e.g., End-STA or non-AP STAs) via the relay STA.

[0143] In addition, for example, an End-STA that exists outside the coverage / range of an AP cannot receive the beacon frame transmitted by the AP. Therefore, after the relay STA receives the beacon frame transmitted by the AP, the relay STA can broadcast the beacon frame. In this way, in order to synchronize the time with the AP using the beacon frame transmitted by the relay STA, the End-STA can use the value of the timestamp field included in the beacon frame.

[0144] Here, as another example, a probe response frame instead of a beacon frame may be used for time synchronization.

[0145] For non-AP STAs within AP coverage, non-AP STAs that receive beacon frames from the AP perform time synchronization to exchange frames with the AP. Here, the non-AP STA performs time synchronization using the value of the timestamp field included in the beacon frame or the probe response frame. Here, the non-AP STA performs time synchronization using the time measured by receiving the beacon frame or the probe response frame (when the frame is received based on the local timer of the non-AP STA (e.g., the start time or measured time of frame reception) and the TSF timer information determined by receiving the value of the timestamp field of the beacon frame or the probe response frame.

[0146] However, since non-AP STAs that exist outside the coverage of the AP cannot directly receive the beacon frame transmitted by the AP but instead receive the beacon frame transmitted by the relay STA, when performing the time synchronization process using the beacon frame received in the above manner, a time offset (because the beacon frame was rebroadcast by the relay STA) may occur, resulting in timing ambiguity.

[0147] Therefore, the following method can be defined for a non-AP STA outside the coverage of an AP that receives management frames such as beacon frames through a relay STA to perform synchronization with the TSF timer of the AP.

[0148] As described above, the AP may broadcast timestamp information (e.g., the value of the timestamp field) for the TSF timer to STAs within the AP's coverage through a frame such as a beacon frame or a probe response frame. Hereinafter, in the description of the present disclosure, for the convenience of explanation, a case in which the value of the timestamp field is transmitted through a beacon frame is mainly described, but the present disclosure is not limited thereto, and the proposed method of the present disclosure may be equally applied to a case in which timestamp information is transmitted through another frame.

[0149] Additionally, in the description of the proposed method of the present disclosure below, the timers of the AP, STA, and / or relay STA may be referred to as local timers, TSF timers, local TSF timers, etc.

[0150] Example 1: Time synchronization method

[0151] A relay STA that receives a beacon frame from an AP can perform time synchronization, thereby updating its own timer value using the value of the timestamp field of the beacon frame.

[0152] The update of the timer value of the Relay STA is performed using the following method.

[0153] The relay STA measures the reception time of the beacon frame received from the AP (e.g., the point in time when reception of the beacon frame 'starts') through a timer, and also determines the AP's timer information when the AP transmits the beacon frame through the value of the timestamp field of the received beacon frame.

[0154] Using the reception time of the beacon frame and the value of the timestamp field of the beacon frame, the relay STA measures / calculates the time offset between the AP timer and the relay STA's timer. That is, the relay STA performs time synchronization by updating the relay STA's timer using the time offset determined / measured through reception of the beacon frame (or probe response frame) transmitted by the AP.

[0155] T_offset = Time measured from the received beacon frame (T_measured from Receied_beacon frame) - Value of the timestamp field within the received beacon frame (T_timestamp field within received beacon frame)

[0156] A Relay STA that has performed time synchronization as above can update its own timer and then transmit the received beacon frame by broadcasting it.

[0157] Here, the timestamp field of the beacon frame transmitted by the relay STA may be set to the updated timer value of the relay STA and transmitted when the relay STA transmits the beacon frame after completing time synchronization. That is, the relay STA may transmit the beacon frame by updating the timestamp value to the updated timer value of the relay STA at the time when the relay STA transmits the beacon frame (e.g., the time when the transmission of the beacon frame is 'started').

[0158] In this way, after completing synchronization with the AP's timer, the relay STA can transmit a beacon frame. In this case, since the AP's timer and the relay STA's timer are aligned, ambiguity in terms of time synchronization can be reduced even if a non-AP STA receives the beacon frame through the relay STA.

[0159] According to this embodiment, since the relay STA receives the beacon frame and then forwards / retransmits it to the non-AP STA, the STA that receives the beacon frame through the relay STA receives a delayed beacon frame.

[0160] Example 2: Time synchronization method

[0161] A relay STA that receives a beacon frame from an AP can perform time synchronization with the AP's timer value using the information in the beacon frame. In addition, in order to reduce ambiguity regarding the timer due to beacon frame transmission through relaying, the relay STA can instruct non-AP STA(s) about time information for time synchronization with the AP through a separate frame transmission after transmitting the beacon frame.

[0162] Here, time synchronization means that the relay STA updates its own timer with the AP's timer value for frame exchange with the AP, and the description thereof is the same as in Embodiment 1. However, unlike Embodiment 1, the relay STA does not change or update the value of the timestamp field of the beacon frame received from the AP when broadcasting the beacon frame to non-AP STAs. In addition, the relay STA may separately transmit available time information to the non-AP STA for time synchronization of the non-AP STA with the AP.

[0163] The following description is provided in more detail with reference to the drawings.

[0164] FIG. 9 illustrates a procedure for transmitting a beacon frame and transmitting time information according to one embodiment of the present disclosure.

[0165] Referring to FIG. 9, a relay STA that receives a beacon frame from an AP can perform time synchronization using the timer value of the AP using the information in the beacon frame. In addition, after receiving a beacon frame from AP1, the relay STA can forward / retransmit (e.g., broadcast) it to non-AP STA(s) (this can be referred to as an F_beacon frame). After receiving the beacon frame, the relay STA can forward / retransmit the beacon frame after a certain period of time (e.g., processing time and SIFS from reception of the beacon frame from the AP to forward / retransmit).

[0166] Additionally, the relay STA may transmit a frame containing time information for time synchronization with the AP of the non-AP STA to the non-AP STA(s).

[0167] A frame transmitted including the above-described time information may be transmitted after a certain period of time (e.g., XIFS (X inter-frame space)) after the relay STA transmits the beacon frame. For example, the certain period of time (e.g., XIFS) may be defined as SIFS or PIFS. In FIG. 9, SIFS is illustrated for convenience of explanation, but the present disclosure is not limited thereto.

[0168] A frame transmitted including time information may be configured to include at least one of the following information.

[0169] - Time offset

[0170] A relay STA that receives a beacon frame from an AP can measure the offset values ​​of the AP's timer and the relay STA's timer using the value of the timestamp field of the beacon frame as follows.

[0171] T_offset value = local TSF timer value when receiving beacon frame - timestamp field value in beacon frame (i.e. TSF timer value of AP)

[0172] Here, as described above, when receiving a beacon frame, the timer value may represent the timer value of the relay STA when reception of the beacon frame is 'started'.

[0173] - Relay STA timestamp: Relay STA timer value

[0174] Here, the timer value of the Relay STA may mean the timestamp value when transmitting / retransmitting a beacon frame (or a frame transmitted including time information).

[0175] - Delay time (e.g., XIFS in Fig. 9): The time from receiving a beacon frame from the AP to transmitting / retransmitting the beacon frame (in the following embodiments 2 to 4, the time from receiving a beacon frame from the AP to transmitting a frame including time information)

[0176] Here, the delay time can be configured to include the processing time of the beacon frame. That is, in order to reduce the error in the specific transmission time of the AP's beacon frame, the relay STA can measure and indicate information about the time taken from reception to transmission / retransmission of the beacon frame.

[0177] Delay time = SIFS + beacon frame processing time (e.g. processing for RX and TX)

[0178] - Period / interval: Information about the period / interval at which time information (or the frame in which the time information is transmitted) is transmitted.

[0179] For example, within a beacon interval, the time information may be transmitted via one or more frame transmissions.

[0180] Embodiment 3: In the examples of Embodiment 2 and FIG. 9, after the relay STA transmits the beacon frame to the non-AP STAs, the relay STA transmits a separate frame to the non-AP STA(s) to indicate time information. However, in contrast, in this embodiment, the relay STA can transmit the time information through the beacon frame (e.g., through a field in the beacon frame (e.g., through an aggregated control (A-control) field).

[0181] The following description is provided in more detail with reference to the drawings.

[0182] FIG. 10 illustrates a transmission procedure of a beacon frame including time information according to one embodiment of the present disclosure.

[0183] Referring to FIG. 10, similarly to the above-described embodiment 2, the relay STA, which receives a beacon frame from the AP, can perform time synchronization using the timer value of the AP using the information in the beacon frame. In addition, the relay STA can forward / retransmit (e.g., broadcast) the beacon frame to non-AP STA(s) (this may be referred to as an F_beacon frame). The relay STA can forward / retransmit the beacon frame after a certain period of time (e.g., processing time and SIFS taken from reception of the beacon frame from the AP to forward / retransmit).

[0184] Here, the relay STA does not change or update the value of the timestamp field of the beacon frame, but may include the above time information. Here, the time information is the same information as described in the above embodiment 2, so a detailed description is omitted.

[0185] For example, time information may be transmitted within the a-control field within a beacon frame. The beacon frame represents the F_beacon frame transmitted by the relay STA in FIG. 10.

[0186] In order to transmit time information through the a-control field when transmitting a beacon frame of a relay STA, the +HTC subfield in the Frame Control field in the MAC header of the beacon frame transmitted by the relay STA may be set to 1. When the +HTC subfield is set to 1, this may indicate that the frame includes an HT (high throughput) control field. That is, the beacon frame transmitted by the relay STA may be configured to include an HT control field. Here, the HT control field included in the beacon frame may be configured as follows.

[0187] - B0 (bit 0) and B1 (bit 1) of the HT control field can be set to 1 to indicate the A-control field.

[0188] - The time information transmitted by the relay STA can be defined / transmitted using the value of the control identifier (Control ID) subfield of the A-control field transmitted and included in the beacon frame transmitted by the relay STA. That is, the A-control field can be configured by merging multiple control subfields, and each control subfield can be configured with a control identifier subfield and a control information subfield. Here, the control information included in the control information subfield can be identified by the value of the control identifier subfield.

[0189] Here, time / timing information for time synchronization can be defined using one of the control identifier values ​​7 to 14 of the control identifier subfield.

[0190] - The a-control field for time synchronization defined as above can be configured to include the time information proposed in the above embodiment 2.

[0191] As another example, time information may be transmitted within the a-control field within a beacon frame.

[0192] Additionally, the time information may be defined as a separate element or field within a beacon frame, and the time information may be transmitted by being included within the element or field.

[0193] FIG. 11 illustrates the format of a time information element according to one embodiment of the present disclosure.

[0194] Referring to FIG. 11, a time information element may be configured to include an element identifier (element ID) field, a length field, and a time information field.

[0195] The element identifier field may include an identifier to identify that it is a time information element, and the length field may indicate the total length of the time information element.

[0196] The time information field may be configured to include a time offset subfield, a timestamp of relay STA subfield, a delay time subfield, and a period / interval subfield. The description of the information included in each subfield is the same as that of the above-described embodiment 2, so a detailed description is omitted.

[0197] Example 4: Unlike the above Examples 2 and 3, a relay STA that receives a beacon frame from an AP can configure a separate frame including information included in the beacon frame and information for time synchronization with the non-AP AP, and transmit the frame to the non-AP STA.

[0198] The following description is provided in more detail with reference to the drawings.

[0199] FIG. 12 illustrates a transmission procedure of a frame including beacon information and time information according to one embodiment of the present disclosure.

[0200] Referring to FIG. 12, similarly to the above-described embodiment 2, the relay STA, which receives a beacon frame from the AP, can perform time synchronization using the timer value of the AP using the information in the beacon frame. Then, the relay STA can transmit (e.g., broadcast) a new frame including (all or part of) the information in the beacon frame and the time information to non-AP STA(s) (e.g., a relay operation action frame). The relay STA can transmit a new frame (e.g., a relay operation action frame) after a certain period of time (e.g., a processing time and SIFS taken from receiving and forwarding / retransmitting the beacon frame from the AP) after receiving the beacon frame.

[0201] Here, the relay STA can construct a new frame including the above time information together with all or part of the information in the beacon frame received from the AP.

[0202] For example, a frame composed of information included in a beacon frame received by a relay STA from an AP and information for time synchronization may be defined as an action frame. For example, the action frame is referred to as a relay operation action frame, but this designation is only an example, and the present disclosure is not limited thereto.

[0203] In this case, information for time synchronization may be defined as a separate element or field and included in the action frame (e.g., relay operation action frame).

[0204] A newly defined action frame can be defined by a new category value. For example, it can be defined as one of the reserved category values ​​of the action field (e.g., one of 33-125). For example, the category name can be defined as a relay operation, which is merely an example and the present disclosure is not limited thereto.

[0205] The newly defined relay operation action frame can be configured to include relay operation action field values ​​as shown in Table 6 below.

[0206] Relay operation action field values ​​Meaning 0 Beacon frame 1 Probe response 2 (re)-Association response 3 (re)-Authentication response 4 ~ 255 Reserved

[0207] The above relay operation action frame may be configured to include all or only part of the information included in the beacon frame received from the AP.

[0208] Additionally, the relay action frame may be transmitted more than once within a beacon frame interval, and may be transmitted at a specific period interval. In this case, information regarding the period of the relay action frame may be transmitted through the relay action frame.

[0209] FIG. 13 illustrates the operation of a first station for a time synchronization method according to one embodiment of the present disclosure.

[0210] Figure 13 illustrates the operation of a first STA device (e.g., a relay STA device) based on the previously proposed methods. The example in Figure 13 is provided for convenience of explanation and does not limit the scope of the present disclosure. Some of the step(s) illustrated in Figure 13 may be omitted depending on the circumstances and / or settings.

[0211] Referring to FIG. 13, the first STA device receives a first beacon frame from the AP (S1301).

[0212] Here, the first beacon frame includes a first timestamp value for a timer of the AP. For example, the first beacon frame may include the first timestamp value in a timestamp field, and the first timestamp value may indicate a timestamp value of a timer of the AP at the time when the AP starts transmitting the first beacon frame.

[0213] The first STA device transmits the first frame to the second STA device (S1302).

[0214] The first frame may include time information for time synchronization between the second STA device and the AP, which is generated based on the first timestamp value.

[0215] Although not shown in FIG. 13, the first STA device may transmit the first beacon frame to the second STA device. In this case, the first frame may be transmitted a short inter-frame space (SIFS) after the first beacon frame is transmitted by the first STA device.

[0216] Additionally, the first frame may be a second beacon frame that includes the same first timestamp value. Here, the time information may be included in an A-control field within the second beacon frame. For example, each control field of the A-control field includes a control identifier (control ID) subfield and a control information subfield, and based on the value of the control identifier (control ID) being one of 7 to 14, it may be indicated that the control information subfield includes the time information.

[0217] Additionally, the first frame may be an action frame that includes all or part of the information included in the first beacon frame and includes the same first timestamp value. For example, based on the category value within the action frame being one of 33 to 125, it may be indicated that the action frame includes the time information.

[0218] Here, the time information may include at least one of i) an offset value between a timer of the AP and a timer of the first STA, ii) a second timer stamp value for the timer of the first STA, iii) a time from receiving the first beacon frame from the AP to transmitting the first frame, and iv) a transmission period of the first frame.

[0219] Additionally, the first frame may be repeatedly transmitted within the transmission interval of the first beacon frame.

[0220] In step S1302, a PPDU including / carrying the first frame may be configured to include a legacy part, a SIG part (e.g., U-SIG, UHR-SIG, etc.), an STF part (e.g., UHR-STF), an LTF part (e.g., UHR-LTF), and a data part.

[0221] All or part of any part (i.e., field) may be divided into multiple sub-parts / sub-fields. Each field (and its sub-fields) may be transmitted in units of 4us * N (where N is an integer). Additionally, a guard interval (GI) may be included. A common subcarrier frequency spacing value (delta_f=312.5 kHz / N or 312.5 kHz * N, where N=integer) may be applied to all of the fields, or a first delta_f may be applied to the first part (e.g., all legacy part, all / part of SIG part), and a second delta_f (e.g., a value smaller than the first delta_f) may be applied to all / part of the remaining parts.

[0222] Some of the fields described above may be omitted, and the order of the fields may be changed in various ways. For example, the subfields of the signal part may be placed before the STF part, and the remaining subfields of the SIG part may be placed after the STF part.

[0223] The legacy portion described above may include at least one of a conventional L-STF (Non-HT Short Training Field), L-LTF (Non-HT Long Training Field), and L-SIG (Non-HT Signal Field).

[0224] The SIG portion described above (e.g., including the U-SIG field, UHR-SIG field, etc.) may include various control information for the transmitted PPDU. For example, it may include the STF portion, the LTF portion, and control information for decoding data.

[0225] The above-described STF-part may contain an STF sequence.

[0226] The above-described LTF portion may include a training field (i.e., an LTF sequence) for channel estimation.

[0227] The data-partial user data described above may include packets (e.g., MPDUs) for upper layers. For example, the first STA device may construct the first frame based on the information described above.

[0228] The method described in the example of FIG. 13 may be performed by the first device (100) of FIG. 1. For example, one or more processors (102) of the first device (100) of FIG. 1 may be configured to perform PPDU exchange with other devices via transceiver(s) (106). Furthermore, one or more memories (104) of the first device (100) may store commands for performing the method described in the example of FIG. 13 or the examples described above when executed by one or more processors (102).

[0229] FIG. 14 illustrates the operation of a second station for a time synchronization method according to one embodiment of the present disclosure.

[0230] Figure 14 illustrates the operation of a second STA device (e.g., a non-AP STA device outside the coverage area of ​​the AP) based on the previously proposed methods. The example in Figure 14 is provided for convenience of explanation and does not limit the scope of the present disclosure. Some of the step(s) illustrated in Figure 14 may be omitted depending on the circumstances and / or settings.

[0231] Referring to FIG. 14, the second STA device receives a first frame from the first STA (S1401).

[0232] The first frame may include time information for time synchronization between the second STA and the AP, which is generated based on a first timestamp value for a timer of the AP received from the AP.

[0233] Although not shown in FIG. 14, the second STA device may receive the first beacon frame transmitted from the AP by the first STA device. In this case, the first frame may be transmitted a short inter-frame space (SIFS) after the first beacon frame is transmitted by the first STA device.

[0234] Additionally, the first frame may be a second beacon frame that includes the same first timestamp value. Here, the time information may be included in an A-control field within the second beacon frame. For example, each control field of the A-control field includes a control identifier (control ID) subfield and a control information subfield, and based on the value of the control identifier (control ID) being one of 7 to 14, it may be indicated that the control information subfield includes the time information.

[0235] Additionally, the first frame may be an action frame that includes all or part of the information included in the first beacon frame and includes the same first timestamp value. For example, based on the category value within the action frame being one of 33 to 125, it may be indicated that the action frame includes the time information.

[0236] Here, the time information may include at least one of i) an offset value between a timer of the AP and a timer of the first STA, ii) a second timer stamp value for the timer of the first STA, iii) a time from receiving the first beacon frame from the AP to transmitting the first frame, and iv) a transmission period of the first frame.

[0237] Additionally, the first frame may be repeatedly transmitted within the transmission interval of the first beacon frame.

[0238] The second STA device updates the timer of the second STA based on the time information (S1402).

[0239] That is, the second STA device can perform time synchronization with the AP by adjusting the timer of the second STA device based on the above time information.

[0240] A PPDU including / carrying the first frame in step S1401 may be configured to include a legacy part, a SIG part (e.g., U-SIG, UHR-SIG, etc.), an STF part (e.g., UHR-STF), an LTF part (e.g., UHR-LTF), and a data part.

[0241] All or part of any part (i.e., field) may be divided into multiple sub-parts / sub-fields. Each field (and its sub-fields) may be transmitted in units of 4us * N (where N is an integer). Additionally, a guard interval (GI) may be included. A common subcarrier frequency spacing value (delta_f=312.5 kHz / N or 312.5 kHz * N, where N=integer) may be applied to all of the fields, or a first delta_f may be applied to the first part (e.g., all legacy part, all / part of SIG part), and a second delta_f (e.g., a value smaller than the first delta_f) may be applied to all / part of the remaining parts.

[0242] Some of the fields described above may be omitted, and the order of the fields may be changed in various ways. For example, the subfields of the signal part may be placed before the STF part, and the remaining subfields of the SIG part may be placed after the STF part.

[0243] The legacy portion described above may include at least one of a conventional L-STF (Non-HT Short Training Field), L-LTF (Non-HT Long Training Field), and L-SIG (Non-HT Signal Field).

[0244] The SIG portion described above (e.g., including the U-SIG field, UHR-SIG field, etc.) may include various control information for the transmitted PPDU. For example, it may include the STF portion, the LTF portion, and control information for decoding data.

[0245] The above-described STF-part may contain an STF sequence.

[0246] The above-described LTF portion may include a training field (i.e., an LTF sequence) for channel estimation.

[0247] The data-part described above may include user data and may include packets (e.g., MPDUs) for upper layers. The second STA device may decode the received frame through the acquired MPDU to obtain information contained in the frame and determine whether to transmit it through a relay STA.

[0248] The method described in the example of FIG. 14 may be performed by the second device (200) of FIG. 1. For example, one or more processors (202) of the second device (200) of FIG. 1 may be configured to perform PPDU exchange with other devices via transceivers (206). Furthermore, one or more memories (204) of the second device (200) may store commands for performing the method described in the example of FIG. 14 or the examples described above when executed by one or more processors (202).

[0249] In order to support relay operation for STAs outside the coverage area of ​​an AP in a conventional wireless LAN system, a method for maintaining time synchronization between an AP and an STA outside the coverage area of ​​the AP that transmits and receives signals through relay transmission has not been defined. In contrast, according to the time synchronization method according to the examples of the present disclosure, by aligning the time between an AP and an STA outside the coverage area of ​​the AP that transmits and receives signals through relay transmission, time alignment for signal transmission and reception can be maintained, thereby achieving the effect of efficiently performing relay transmission and increasing wireless communication efficiency.

[0250] The embodiments described above are combinations of components and features of the present disclosure in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, it is also possible to form embodiments of the present disclosure by combining some components and / or features. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form embodiments or incorporated as new claims through post-application amendments.

[0251] It will be apparent to those skilled in the art that the present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present disclosure are intended to be included within the scope of the present disclosure.

[0252] The scope of the present disclosure includes software or machine-executable instructions (e.g., an operating system, an application, firmware, a program, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer. Instructions that can be used to program a processing system to perform the features described in the present disclosure can be stored on / in a storage medium or a computer-readable storage medium, and a computer program product including such a storage medium can be used to implement the features described in the present disclosure. The storage medium can include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices, and can include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. The memory optionally includes one or more storage devices remotely located from the processor(s). The memory or, alternatively, the non-volatile memory device(s) within the memory comprise a non-transitory computer-readable storage medium. The features described in this disclosure may be incorporated into software and / or firmware stored on any of the machine-readable media, which may control the hardware of the processing system and allow the processing system to interact with other mechanisms that utilize results according to embodiments of the present disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0253] The method proposed in this disclosure has been described with a focus on examples applied to IEEE 802.11-based systems, but can be applied to various wireless LANs or wireless communication systems in addition to IEEE 802.11-based systems.

Claims

1. A step of receiving a first beacon frame from an access point (AP: access point) by a first station (STA: station), wherein the first beacon frame includes a first timestamp value for a timer of the AP; and A step of transmitting a first frame to a second STA by the first STA, A method wherein the first frame includes time information for time synchronization between the second STA and the AP generated based on the first timestamp value.

2. In paragraph 1, A method further comprising the step of transmitting, by the first STA, the first beacon frame to the second STA.

3. In paragraph 2, A method wherein the first frame is transmitted a short inter frame space (SIFS) after the first beacon frame is transmitted by the first STA.

4. In paragraph 1, A method wherein the first frame is a second beacon frame that includes the same first timestamp value.

5. In paragraph 4, A method wherein the time information is included in an aggregated control (A-control) field within the second beacon frame.

6. In paragraph 5, Each control field of the above A-control field includes a control identifier (control ID) subfield and a control information subfield, A method wherein the control information subfield is indicated to include the time information based on the value of the control identifier (control ID) being one of 7 to 14.

7. In paragraph 1, A method wherein the first frame is an action frame that includes all or part of the information included in the first beacon frame and includes the same first timestamp value.

8. In paragraph 7, A method wherein the action frame is indicated to include the time information based on a category value within the action frame being one of 33 to 125.

9. In paragraph 1, A method according to claim 1, wherein the time information comprises at least one of: i) an offset value between a timer of the AP and a timer of the first STA, ii) a second timer stamp value for the timer of the first STA, iii) a time from receiving the first beacon frame from the AP to transmitting the first frame, and iv) a transmission period of the first frame.

10. In paragraph 1, A method wherein the first frame is repeatedly transmitted within the transmission interval of the first beacon frame.

11. The first station (STA: station) device is: one or more transmitters and receivers; and comprising one or more processors coupled to said one or more transceivers; One or more of the above processors: Receive a first beacon frame from an access point (AP), wherein the first beacon frame includes a first timestamp value for a timer of the AP, and To the second STA, it is set to transmit the first frame, A first STA device, wherein the first frame includes time information for time synchronization between the second STA and the AP, generated based on the first timestamp value.

12. A step of receiving a first frame from a first STA by a second station (STA: station), wherein the first frame includes time information for time synchronization between the second STA and the AP, the first frame being generated based on a first timestamp value for a timer of the AP received from an access point (AP: access point); and A method comprising the step of updating a timer of the second STA based on the time information, by the second STA.

13. The second station (STA: station) device: one or more transmitters and receivers; and comprising one or more processors coupled to said one or more transceivers; One or more of the above processors: Receiving a first frame from a first STA, wherein the first frame includes time information for time synchronization between the second STA and the AP, which is generated based on a first timestamp value for a timer of the AP received from an access point (AP), and A second STA device configured to update a timer of the second STA based on the above time information.

14. In a processing device configured to control a station (STA: station) in a wireless LAN system, the processing device: one or more processors; and A processing device comprising one or more computer memories operatively connected to said one or more processors and storing instructions that, when executed by said one or more processors, perform a method according to any one of claims 1 to 10.

15. One or more non-transitory computer-readable media storing one or more instructions, A computer-readable medium, wherein the one or more commands are executed by one or more processors to control a device in a wireless LAN system to perform a method according to any one of claims 1 to 10.

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