Power saving method and apparatus for multi-link device in wireless LAN system

Abstract

Disclosed are power saving method and apparatus for a multi-link device in a wireless LAN system. The method according to an embodiment of the present disclosure may comprise the steps of: receiving, by means of a first STA in a first MLD, a beacon frame from a first AP in a second MLD through a first link, the beacon frame including information indicating that there is data to be transmitted to the first MLD; and transmitting, by means of the first STA, a first frame to the first AP through the first link.

Description

Method and device for power saving of multi-link devices in wireless LAN systems

[0001] The present disclosure relates to a method and device for power saving (PS) of a multi-link device (MLD) 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 power saving (PS) of a multi-link device (MLD).

[0005] In addition, an additional technical problem of the present disclosure is to provide a method and a device for transmitting and receiving information about a PS state for one or more stations (e.g., devices operating in another band (e.g., millimeter wave (mmWave) band) belonging to a non-access point station MLD).

[0006] 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 will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0007] A method according to one aspect of the present disclosure may include: receiving, by a first station (STA) belonging to a first multi-link device (MLD), a beacon frame from a first access point (AP) belonging to a second MLD via a first link, the beacon frame including information indicating that there is data to be transmitted to the first MLD; and transmitting, by the first STA, a first frame to the first AP via the first link. The first frame may include information indicating whether one or more STAs belonging to the first MLD are in an awake state.

[0008] A method according to an additional aspect of the present disclosure may include: transmitting, by a first access point (AP) belonging to a second multi-link device (MLD), a beacon frame to a first station (STA) belonging to a first MLD via a first link, the beacon frame including information indicating that there is data to be transmitted to the first MLD; and receiving, by the first AP, a first frame from the first STA via the first link. The first frame may include information indicating whether one or more STAs belonging to the first MLD are in an awake state.

[0009] According to the present disclosure, signaling overhead can be reduced and communication efficiency can be improved by recognizing the PS status of one or more STAs belonging to a non-AP STA MLD, thereby enabling appropriate frame exchange.

[0010] In addition, according to the present disclosure, wireless transmission and reception efficiency can be improved because association (i.e., multi-link setup) and frame exchange can be performed with an access point or non-access point station operating in a different band (e.g., millimeter wave (mmWave) band).

[0011] 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.

[0012] 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.

[0013] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0014] FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0015] FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0016] FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0017] FIG. 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0018] 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.

[0019] FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0020] Figure 8 exemplarily shows the structure of an ML element to which the present disclosure can be applied.

[0021] FIG. 9 is a diagram illustrating an example of a broadcast TWT operation to which the present disclosure can be applied.

[0022] Figure 10 exemplarily shows the structure of an ML element to which the present disclosure can be applied.

[0023] FIG. 11 illustrates an AP MLD and a non-AP MLD supporting the mmWave band according to one embodiment of the present disclosure.

[0024] FIG. 12 illustrates a multi-link power saving operation in a wireless communication system to which the present disclosure can be applied.

[0025] FIG. 13 illustrates a method for multi-link power saving using a multi-link power saving Poll frame according to one embodiment of the present disclosure.

[0026] FIG. 14 illustrates a method for multi-link power saving using a multi-link power saving Poll frame according to one embodiment of the present disclosure.

[0027] FIG. 15 illustrates a method for multi-link power saving using a multi-link power saving control field according to one embodiment of the present disclosure.

[0028] FIG. 16 is a diagram illustrating a block ACK frame to which the present disclosure can be applied.

[0029] FIG. 17 illustrates a method for multi-link power saving using a BA frame according to one embodiment of the present disclosure.

[0030] FIG. 18 illustrates the operation of a multi-link device for a method for power saving for a multi-link device according to one embodiment of the present disclosure.

[0031] FIG. 19 illustrates the operation of a multi-link device for a method for power saving for a multi-link device according to one embodiment of the present disclosure.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Below, technical features to which examples of the present disclosure can be applied are described.

[0039] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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 operation 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 operation 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0053] 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.

[0054] 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.

[0055] 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).

[0056] 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.

[0057] 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.

[0058] 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).

[0059] 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.

[0060] Data transmitted from one of the STA(s) associated with an AP to the STA address of that AP may always be received on an uncontrolled port and processed by an IEEE 802.1X port access entity. In addition, if the controlled port is authenticated, the transmitted data (or frame) may be forwarded to the DS.

[0061] In addition to the structure of the DS described above, an extended service set (ESS) may be established to provide wider coverage.

[0062] 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.

[0063] 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.

[0064] FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0078] 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.

[0079] 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).

[0080] 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, ...).

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] FIG. 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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).

[0103] FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0104] 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)).

[0105] 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).

[0106] 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)).

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.).

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.).

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] Target wake time (TWT)

[0134] TWT is a power saving technology that can improve the energy efficiency of non-AP STAs by defining a service period (SP) between an AP and non-AP STAs and sharing information about the SP to reduce contention of the medium. In the TWT setup phase, an STA that performs requests / suggestions / demands, etc., can be called a TWT requesting STA. In addition, an AP that responds to the request with an acceptance / rejection, etc., can be called a TWT responding STA. The setup phase can include a process of determining / defining a TWT request from an STA to the AP, the type of TWT operation to be performed, and the type of frames to be transmitted and received. TWT operations can be divided into individual TWT and broadcast TWT.

[0135] FIG. 8 is a drawing illustrating an example of an individual TWT operation to which the present disclosure can be applied.

[0136] Individual TWT is a mechanism in which an AP and a non-AP STA negotiate the awake / doze status of a non-AP STA by sending and receiving TWT request / response frames, and then exchange data. In the example of Fig. 8, the AP and STA1 can form a trigger-enabled TWT agreement through a TWT request frame and a TWT response frame. Here, the method used by STA1 is a solicited TWT method, in which STA1 transmits a TWT request frame to the AP, and STA1 receives information for TWT operation from the AP through a TWT response frame. On the other hand, STA2, which performs the unsolicited TWT method, can receive information about the trigger-enabled TWT agreement setup from the AP through the unsolicited TWT response. Specifically, STA2 can calculate the next TWT by adding a specific number to the current TWT value. During the trigger-enabled TWT SP, the AP can transmit a trigger frame to the STAs. The trigger frame can inform the STAs that the AP has buffered data. In response, STA1 can inform the AP of its awake state by transmitting a PS-Poll frame. Additionally, STA2 can inform the AP of its activated state by transmitting a QoS Null frame. Here, the data frames transmitted by STA1 and STA2 can be frames in the TB PPDU format. The AP, which has checked the status of STA1 and STA2, can transmit DL MU PPDU to the activated STAs.When the corresponding TWT SP expires, STA1 and STA2 can enter doze state.

[0137] FIG. 9 is a diagram illustrating an example of a broadcast TWT operation to which the present disclosure can be applied.

[0138] Broadcast TWT is a TWT in which a non-AP STA (or TWT scheduling STA) obtains information such as target beacon transmission time (TBTT) and listen interval by transmitting and receiving TWT request / response frames with the AP (or TWT scheduled STA). Here, a negotiation operation for TBTT may be performed. Based on this, the AP can define a frame to include TWT scheduling information through a beacon frame. In Fig. 9, STA1 performs a requested TWT operation, and STA2 performs an unsolicited TWT operation. The AP can transmit a DL MU PPDU after checking the awake status of the STAs through the trigger it transmitted. This may be the same as the process of an individual TWT. In broadcast TWT, a trigger-enabled TWT SP including a beacon frame may be repeated multiple times at a regular cycle.

[0139] Transmission of TWT information can be accomplished through a TWT information frame and a TWT information element. The TWT information frame is transmitted by an STA to request or transmit information about a TWT agreement, and is transmitted by one of the STAs of an existing TWT agreement. The action frame of the TWT Information frame includes a TWT information field. The TWT Information field can include a 3-bit TWT flow identifier subfield, a 1-bit response requested subfield, a 1-bit next TWT request subfield, a 2-bit next TWT subfield size subfield, a 1-bit all TWT subfield, and a 0 / 32 / 48 / 64-bit next TWT subfield.

[0140] multi-link operation (MLO)

[0141] Below, the multi-link (ML) operation supported by the STA according to the present disclosure is described.

[0142] The STA (AP STA and / or non-AP STA) described in the present disclosure can support multi-link (ML) communication. ML communication may refer to communication that supports multiple links. Links related to ML communication may include channels (e.g., 20 / 40 / 80 / 160 / 240 / 320MHz channels) of a frequency band (e.g., 2.4GHz band, 5GHz band, 6GHz band, etc.) in which the STA operates. The multiple links used for ML communication may be configured in various ways. For example, the multiple links supported for one STA for ML communication may belong to the same frequency band or may belong to different frequency bands. In addition, each link may correspond to a frequency unit of a predetermined size (e.g., a channel, a subchannel, an RU, etc.). In addition, some or all of the multiple links may be frequency units of the same size or may be frequency units of different sizes.

[0143] When one STA supports multiple links, the transmitting and receiving devices supporting each link can operate as one logical STA. That is, a multi-link device (MLD) is a device that has one or more affiliated STAs as a logical entity and a single MAC service access point (SAP) for one MAC data service and logical link control (LLC). A non-AP MLD refers to an MLD in which each STA affiliated with the MLD is a non-AP STA. A multi-radio non-AP MLD refers to a non-AP MLD that supports receiving or exchanging frames on more than one link at a time. An AP MLD refers to an MLD in which each STA affiliated with the MLD is an AP STA.

[0144] Multi-link operation (MLO) can enable a non-AP MLD to discover, authenticate, associate, and set up multiple links with an AP MLD. Based on the supported capabilities exchanged during the association procedure, each link can enable channel access and frame exchange between the non-AP MLD and the AP MLD. An STA affiliated with an MLD can select and manage its capabilities and operating parameters independently from other STA(s) affiliated with the same MLD.

[0145] Through the multi-link setup process, the AP MLD and / or the non-AP MLD can transmit and receive link-related information that the MLD can support. The link-related information may include one or more of information about whether the MLD supports simultaneous transmit and receive (STR) operation or non-simultaneous transmit and receive (NSTR) operation on multiple links, information about the number / upper limit of UL / DL links, information about the location / bandwidth / resource of UL / DL links, information about frame types (e.g., management, control, data, etc.) that are available or preferred on at least one UL / DL link, information about an ACK policy that is available or preferred on at least one UL / DL link, or information about a traffic identifier (TID) that is available on at least one UL / DL link.

[0146] An AP MLD (e.g., NSTR mobile AP MLD) can set one of the multiple links as the primary link. The AP MLD may transmit beacon frames, probe response frames, and group-addressed data frames only on the primary link. The remaining link(s) of the multiple links may be referred to as non-primary links. An AP MLD operating on a non-primary link may operate so as not to transmit beacon frames or probe response frames. In addition, a non-AP MLD may perform frame exchanges during authentication, (re)association, and 4-way handshaking only on the primary link.

[0147] A setup link is defined as enabled if at least one traffic identifier (TID) is mapped to the link through the multi-link setup process, and a setup link can be defined as disabled if no TID is mapped to the link. A TID must always be mapped to at least one setup link unless admission control is used. By default, a TID is mapped to all setup links, so all setup links can be enabled.

[0148] When a link is activated, it can be used for frame exchange, depending on the power state of the non-AP STAs operating on that link. Only MSDUs or A-MSDUs with TIDs mapped to the activated link can be transmitted on that link. Management frames and control frames can only be transmitted on the activated link.

[0149] When a link is disabled, that link may not be used for frame exchange, including management frames for both DL and UL.

[0150] During a multi-link setup, activation / deactivation of individual links can be directed through TID-to-Link mapping. TID-to-Link mapping can be performed in default mapping mode or / and negotiation mapping mode.

[0151] Among the STAs belonging to the MLD, one STA may provide information about one or more links other than the link on which it is located, for multi-link discovery (e.g., obtaining information about multiple links including the corresponding link on one link) or multi-link setup (e.g., simultaneously associating on multiple links by exchanging association request / response frames on one link). A multi-link (ML) element may be defined to provide such information.

[0152] Figure 10 exemplarily shows the structure of an ML element to which the present disclosure can be applied.

[0153] In an ML element, the element ID field and the element ID extension field may have specific values ​​(e.g., 255 and 107) indicating that it is an ML element, and the length field may have a value indicating the length (e.g., in octet units) of the remaining fields excluding the element ID field and the length field.

[0154] The multi-link control field is defined as 2 octets in size and may include a 3-bit type subfield, a 1-bit reserved bit, and a 12-bit presence bitmap subfield. The type subfield may have a value indicating one of the following types: basic, probe request, reconfiguration, tunneled direct-link setup (TDLS), and priority access. The presence bitmap subfield indicates the presence or absence of various subfield(s) within the common info field, and may be defined in different formats depending on the various variants (or types) of the ML element.

[0155] The common info field is defined to be of variable size and may include a 6-octet MLD MAC address subfield, which may have a value specifying the MAC address of the MLD to which the STA transmitting the basic ML element belongs. In addition, a link ID info subfield, a BSS parameter change count subfield, a medium synchronization delay information subfield, an enhanced multi-link (EML) capability subfield, and an MLD capability subfield may or may not be included in the common info field.

[0156] The link info field is defined as having a variable size, can contain link-specific information, and can be optionally present. If the link info field exists, it can contain one or more subelements. The format and order of the subelements can be defined in various ways. As an example of optional subelement IDs for the basic variant ML element, the value 0 of the subelement ID corresponds to the name of the per-STA profile and is extensible, the value 221 corresponds to the name of the vendor-specific name and the extensibility can be determined by the vendor, and the remaining values ​​1-220 and 222-255 can be reserved.

[0157] The STA-per-profile subfield may include a 1-octet subelement ID subfield, a 1-octet length subfield, a 2-octet STA control subfield, a variable-size STA info subfield, and a variable-size STA profile subfield. The STA control subfield may include information such as a link ID, whether a complete profile is included, whether an STA MAC address exists, etc. The STA info subfield may include information such as an STA MAC address. The STA profile subfield may include information included in a probe response or probe request frame body, information included in a (re)association response or (re)association request frame body, etc., depending on whether the reported STA is an AP STA or a non-AP STA.

[0158] The format of the ML elements in FIG. 10 is exemplary, and the order, names, sizes, etc. of the fields / subfields may be changed, additional fields / subfields may be further defined, and some fields / subfields may be excluded. In short, the common information field includes common information between STAs in the MLD, and the link information field may include specific information for each STA / link (e.g., in a per-STA profile subelement including a link ID corresponding to the STA).

[0159] MLD discovery method in the millimeter wave (mmWave) band

[0160] A multi-link device (MLD) defined in 802.11be consists of affiliated APs (or non-AP STAs) that operate on one or more different channels, and has fundamentally achieved significant improvements in terms of (aggregated / average) throughput / latency. In particular, while the existing MLD has primarily targeted the 2.4 to 7.25 GHz (sub-7 GHz) band, recently, with the growing need for millimeter wave (mmWave) that offers relatively limited coverage but powerful throughput / latency improvements, research is being conducted to enable MLD affiliated APs (or non-AP STAs) to operate in the mmWave band (i.e., unlicensed bands between 42 and 71 GHz). Therefore, the issues that arise as affiliated APs (or non-AP STAs) of MLDs operating in the mmWave band are included need to be resolved.

[0161] FIG. 11 illustrates an AP MLD and a non-AP MLD supporting the mmWave band according to one embodiment of the present disclosure.

[0162] Figure 11 illustrates an MLD supporting the mmWave band. AP 1 of the AP MLD operates a channel in the sub-7 GHz band, AP 3 operates a channel in the mmWave band, STA 1 of the non-AP MLD supports the sub-7 GHz band, and STA 2 supports the mmWave band. Therefore, the non-AP MLD can request a multi-link setup from the AP MLD so that STA 1 can associate with AP 1 (link 1) and STA 2 can associate with AP 3 (link 2).

[0163] The mmWave band requires directional transmission due to its relatively small range / coverage. This can increase the protocol / implementation complexity for beamforming, control / management, etc. Therefore, if STAs operating in the sub-7 GHz band can perform control / management tasks instead of STAs operating in the mmWave band, utilizing various protocols / features defined for MLD, the mmWave band can be utilized more efficiently. For example, to achieve high throughput, actual data frame exchanges can be performed in the mmWave band using a relatively high data rate, while most other control / management functions can be performed in the sub-7 GHz band. As another example, APs operating in the mmWave band may not transmit management frames, such as beacon / probe response frames. Therefore, an STA operating in the sub-7 GHz band can perform many control / management functions instead of an STA operating in the mmWave band belonging to the same MLD.

[0164] In particular, with respect to Power Saving (PS), AP MLD can basically use information about the traffic indication map (TIM) from one AP to another (i.e., Multi-Link Traffic Indication element (MLTI IE)) to inform Non-AP MLD on which link it should transmit / receive data (e.g., recommendation).

[0165] FIG. 12 illustrates a multi-link power saving operation in a wireless communication system to which the present disclosure can be applied.

[0166] FIG. 12 illustrates an example in which AP 1 and AP 2 belong to the AP MLD, AP 1 operates on link 1, and AP 2 operates on link 2. FIG. 12 illustrates an example in which STA 1 and STA 2 belong to the Non-AP MLD, STA 1 operates on link 1, and STA 2 operates on link 2. In addition, an example in which the AP MLD assigns AID 20 to the Non-AP MLD during a multi-link setup is illustrated.

[0167] Referring to FIG. 12, when there is downlink data for a Non-AP MLD, AP 1 sets the bit of the TIM IE (traffic indication map element) corresponding to AID 20 to 1 through a beacon frame (B in FIG. 12), and recommends that the MLTI IE solicit downlink data on link 2 (i.e., recommends that the Non-AP MLD receive downlink data through link 2).

[0168] STA 1 in power saving (PS) mode receives a beacon frame by transitioning from a doze state to an awake state before the beacon frame of AP 1 is received (i.e., before the target beacon transmission time (TBTT) of AP 1). Accordingly, STA 2 in PS mode and operating on link 2 transitions from the doze state to the awake state based on the TIM / MLTI information confirmed by STA 1, and transmits a power saving-poll (PS-Poll) frame to AP 2. Accordingly, AP 2, which receives the PS-Poll frame, can immediately transmit a data frame or an acknowledgment (ACK) frame to STA 2. Here, if AP 2 transmits an ACK frame, it can also transmit a data frame to STA 2 thereafter.

[0169] According to the example of Fig. 12, the PS-Poll frame transmitted by STA 2 serves to inform that STA 2 is awake. As described above, if the transmission of such control information in an MLD including an STA operating in the mmWave band can be performed by an STA operating in the Sub-7 GHz band as much as possible, efficient operation of the MLD including the mmWave band will be possible.

[0170] Therefore, the present disclosure proposes a more effective multi-link power saving method for MLD including mmWave band.

[0171] The names and other designations used in this disclosure are for convenience of explanation and may be replaced with equivalent names. Furthermore, unless otherwise specified in this disclosure, an STA may include an AP STA or a non-AP STA. Furthermore, an MLD may include an AP MLD or a non-AP MLD.

[0172] In addition, in the description of the present disclosure, for the convenience of explanation, a case in which a configuration includes an AP / non-AP STA operating in a sub-7 GHz band within an MLD and an AP / non-STA operating in a mmWave band is mainly explained. Here, for the convenience of explanation, an STA or AP operating in a mmWave band within the same MLD is referred to as an mSTA or mAP, and an STA or AP operating in a sub-7 GHz band is referred to as an sSTA or sAP, respectively.

[0173] However, the present disclosure is not limited thereto, and the proposed method of the present disclosure can be equally applied in a situation where multiple APs / non-STAs are included in the MLD and at least one AP / non-STA in the MLD operates in a power saving mode.

[0174] Currently, the PS-Poll frame can only be transmitted on each link, making it difficult to utilize multiple links. In other words, it's difficult for a single STA within an MLD to use the PS-Poll frame to inform other links of their awake status. Therefore, at least one of the following methods can be used to address this issue.

[0175] Example 1: Definition of a multi-link (ML) PS-Poll frame to indicate transition to the awake state of another STA within the MLD.

[0176] An ML PS-Poll frame may include information about a link. In addition, when an ML PS-Poll frame indicating information about one or more specific links is transmitted, information (e.g., link indication) indicating that an STA corresponding to the indicated link has woken up (i.e., transitioned from a doze state to an awake state) may be indicated using at least one of the following methods.

[0177] That is, the ML PS-Poll frame can be transmitted including at least one of the following information.

[0178] A) Link identifier (Link ID): Link ID

[0179] The link ID can be received / acquired during discovery (e.g., receiving a beacon frame) or association.

[0180] Additionally, information about the number of link IDs (Number of Link IDs) may be included to indicate whether multiple link IDs are included.

[0181] B) Link ID Bitmap: The bitmap may have each bit set to "1" if the STA for the corresponding link has awoke (e.g., transitioned from doze state to awake state). For example, the link corresponding to bit position i (where i is an integer greater than 0) is the link with link ID i.

[0182] Also, here, a "0" in each bit may mean that the STA for that link is in doze state.

[0183] Additionally, the bitmap size can be 2 octets (i.e., indicating the status of STAs for 16 links) or more.

[0184] Additionally or alternatively, the bitmap size can be changed (or set). For example, the bitmap size (e.g., 1 octet, 2 octets) can be additionally indicated to change (or set) the bitmap size.

[0185] Additionally or alternatively, a Multi-link PS-Poll frame may be defined as a control frame or a management frame (e.g., an Action frame, see Table 1).

[0186] Table 1 illustrates the information contained in a Multi-link PS-Poll frame, which is a management frame (e.g., an action frame).

[0187] Order Information 1 Category 2 UHR Action or Protected UHR Action 3 Dialog Token 4 Link ID Bitmap (field)

[0188] FIG. 13 illustrates a method for multi-link power saving using a multi-link power saving Poll frame according to one embodiment of the present disclosure. FIG. 13 illustrates a multi-link PS Poll frame defined as an Action frame. Additionally or alternatively, the Link ID bitmap field may be replaced with a multi-link operation (MLO) link information element (MLO Link Info element).

[0189] FIG. 13 illustrates an example in which AP 1 and AP 2 belong to an AP MLD, AP 1 operates on link 1, and AP 2 operates on link 2. FIG. 13 illustrates an example in which STA 1 and STA 2 belong to a Non-AP MLD, STA 1 operates on link 1, and STA 2 operates on link 2. In addition, an example in which the AP MLD assigns AID 20 to the Non-AP MLD during a multi-link setup is illustrated.

[0190] Referring to FIG. 13, in sAP, when there is downlink data for Non-AP MLD, it is recommended to set the bit of TIM IE corresponding to AID 20 to 1 through a beacon frame (B in FIG. 13) and request downlink data on link 2 in MLTI IE (i.e., it is recommended that Non-AP MLD receive downlink data on link 2).

[0191] An sSTA in power saving (PS) mode transitions from doze to awake before receiving a beacon frame from the sAP (i.e., before the TBTT of the sAP). This allows an mSTA in PS mode and operating on link 2 to transition from doze to awake using the TIM / MLTI information confirmed by the sSTA. Here, the sSTA can use the Multi-link PS-Poll frame instead of the mSTA to inform the sAP that the mSTA is awake (or transitioned from doze to awake).

[0192] The example of Fig. 13 illustrates a case where the link ID bitmap consists of 16 bits. In this case, as shown in Fig. 13, in order to indicate that the STAs operating in link ID 1 and link ID 2 are in an awake state, only the bits corresponding to link ID 1 and link ID 2 may be set to 1, and the bits corresponding to the remaining link IDs may be set to 0. Accordingly, the AP MLD (from the sAP) that receives the multi-link PS-Poll frame can control the mAP to transmit a data frame. This can reduce the control overhead in the mmWave band, and the effect can be greater when the number of mAPs and mSTAs is large and the MLTI IE recommends links for multiple mmWave bands.

[0193] FIG. 14 illustrates a method for multi-link power saving using a multi-link power saving Poll frame according to one embodiment of the present disclosure.

[0194] Figure 14 illustrates the use of a Multi-link PS-Poll frame in an Aligned Broadcast TWT.

[0195] FIG. 14 illustrates an example in which AP 1 and AP 2 belong to an AP MLD, AP 1 operates on link 1, and AP 2 operates on link 2. FIG. 14 illustrates an example in which STA 1 and STA 2 belong to a Non-AP MLD, STA 1 operates on link 1, and STA 2 operates on link 2. In addition, an example in which the AP MLD assigns AID 20 to the Non-AP MLD during a multi-link setup is illustrated.

[0196] The sAP (and mAP) announces a broadcast TWT schedule in the beacon frame, and this schedule is aligned with the TWT on other links. Here, the sSTA (and mSTA) can wake up before receiving the beacon frame of the associated AP to receive the schedule. After that, the sSTA can exchange frames such as TWT request / response, data frames, etc., and then transition back to the doze state. Here, the sSTA can transition to the awake state before the TWT service period (SP) starts. Next, within the TWT SP, the AP may need to check whether the member STA is awake (e.g., the announced TWT).

[0197] Here, (for example, when it is difficult to determine whether mSTA is awake due to a delay in transmitting PS-Poll frames, due to some of the TWT SPs in which mAP and mSTA have membership being BUSY, or regardless of this), sSTA can instead use a Multi-link PS-Poll frame (for example, as a response to a trigger frame from AP) to inform sAP that mSTA is awake (or has transitioned from doze to awake).

[0198] The example of Fig. 14 illustrates a case where the link ID bitmap consists of 16 bits. In this case, as shown in Fig. 14, in order to indicate that the STAs operating in link ID 1 and link ID 2 are in an awake state, only the bits corresponding to link ID 1 and link ID 2 may be set to 1, and the bits corresponding to the remaining link IDs may be set to 0. Accordingly, the AP MLD (from the sAP) that receives the Multi-link PS-Poll frame can enable the mAP to transmit a data frame in the TWT SP (e.g., immediately after the Multi-link PS-Poll frame). This can reduce the control overhead in the mmWave band, and the effect can be greater as the number of mAPs and mSTAs increases.

[0199] Meanwhile, transmitting a Multi-link PS-Poll frame requires channel access, making it difficult to transmit a Multi-link PS-Poll frame when the medium is occupied, such as by exchanging other frames. In this case, a method may be required to quickly notify STAs on other links that they are awake. At least one of the following methods may be used for this purpose.

[0200] Example 2: Indicating the awake state of another STA within the MLD using an existing frame.

[0201] 1) Instructed in A-control (aggregated control) (e.g. QoS data / QoS null frame)

[0202] The HT control field is always present in the control wrapper frame, and is present in quality of service (QoS) data, QoS Null, and management frames. The HT control field includes the HT variant, VHT variant, and HE variant, and the HE variant includes the A-control subfield.

[0203] The HT control field (e.g., A-control subfield) may be utilized by the sSTA to transmit information (e.g., link ID bitmap) about the awake state (and / or doze state) of the STA for other links within the MLD that may be indicated in the Multi-link PS-Poll frame exemplified in Embodiment 1 to the sAP instead of the mSTA. For example, one new control type of A-Control may include information (e.g., link ID bitmap) about the awake state (and / or doze state) of the STA for other links within the MLD.

[0204] For convenience of explanation in this disclosure, a control field that carries information (e.g., a link ID bitmap) about an STA's awake state (and / or doze state) for other links within an MLD is referred to as a multi-link power save (MLPS) control field. However, the name of this control field is only an example, and a field with a different name may be used to convey information (e.g., a link ID bitmap) about an STA's awake state (and / or doze state) for other links within an MLD.

[0205] Additionally, the MLPS control field may be included in a QoS data frame and / or a QoS Null frame.

[0206] FIG. 15 illustrates a method for multi-link power saving using a multi-link power saving control field according to one embodiment of the present disclosure.

[0207] FIG. 15 illustrates an example in which AP 1 and AP 2 belong to an AP MLD, AP 1 operates on link 1, and AP 2 operates on link 2. FIG. 15 illustrates an example in which STA 1 and STA 2 belong to a Non-AP MLD, STA 1 operates on link 1, and STA 2 operates on link 2. In addition, an example in which the AP MLD assigns AID 20 to the Non-AP MLD during a multi-link setup is illustrated.

[0208] Referring to FIG. 15, in sAP, when there is downlink data for Non-AP MLD, it is recommended to set the bit of TIM IE corresponding to AID 20 to 1 through a beacon frame (B in FIG. 15) and request downlink data on link 2 in MLTI IE (i.e., it is recommended that Non-AP MLD receive downlink data on link 2).

[0209] An sSTA in Power Save (PS) mode transitions from doze to awake before receiving a beacon frame from the sAP (i.e., before the TBTT of the sAP). This allows an mSTA in PS mode and operating on Link 2 to transition from doze to awake using the TIM / MLTI information verified by the sSTA.

[0210] Here, when the sSTA obtains a transmission opportunity (TXOP) for uplink data transmission, the sSTA may include an MLPS control field in one or more UL QoS data frames transmitted to the sAP instead of the Multi-link PS-Poll frame described above, to inform the sAP that the mSTA is in the awake state (or transitions from the doze state to the awake state).

[0211] The example of Fig. 15 illustrates a case where the link ID bitmap consists of 16 bits. In this case, as shown in Fig. 15, in order to indicate that the STAs operating in link ID 1 and link ID 2 are in an awake state, only the bits corresponding to link ID 1 and link ID 2 may be set to 1, and the bits corresponding to the remaining link IDs may be set to 0. Accordingly, the AP MLD (from the sAP) that has received the QoS data frame and the MLPS control field can control the mAP to transmit the data frame. This can reduce the control overhead in the mmWave band, and the effect can be greater when the number of mAPs and mSTAs is large and the MLTI IE recommends links for multiple mmWave bands.

[0212] 2) Instructions in block ACK (BA: block ACK) frame

[0213] FIG. 16 is a diagram illustrating a block ACK frame to which the present disclosure can be applied.

[0214] Referring to FIG. 16, the block ACK frame is composed of a frame control field, a duration field, a receiving address (RA) field, a transmitting address (TA) field, a BA control field, a BA information field, and an FCS.

[0215] Here, the BA control field is composed of a reserved bit, a BA type subfield, a reserved bit, a No memory kept subfield, a memory configuration on tag subfield, a management ACK subfield, and a TID information (TID_INFO) subfield.

[0216] The BA type subfield indicates a variant of the BA frame.

[0217] Table 2 illustrates BA frame variants.

[0218]

[0219] The meaning / content of the BA control field depends on the BA frame variant type.

[0220] Figure 16 illustrates the BA information field when the BA frame variant is a multi-STA blockack (i.e., a multi-STA BA frame).

[0221] The BA information field of a multi-STA BA frame consists of one or more Per AID TID Info subfields.

[0222] If the AID11 subfield within the AID TID info subfield is not 2045, the Per AID TID Info subfield consists of the AID TID info subfield, the block ACK starting sequence control subfield, and the block ACK bitmap subfield.

[0223] The AID TID info subfield consists of the AID11 subfield, the ACK type subfield, and the TID subfield.

[0224] The AID11 subfield carries the 11 least significant bits (LSBs) of the AID of the non-AP STA for which the Per AID TID Info subfield is intended. The format of the Per AID TID Info subfield depends on the value of the AID11 subfield. When a multi-STA BA frame is transmitted to the AP, the AID11 subfield is set to 0. The value 2045 in the AID11 subfield is used as an identifier for all unassociated STAs. When the AID11 subfield is set to 2045, the ACK type subfield and the TID subfield are set to 0 and 15, respectively.

[0225] The context and presence of each optional subfield in the Per AID TID Info subfield of the Multi-STA BA frame when the AID11 subfield is not 2045 is as shown in Table 3 below.

[0226]

[0227] A new type of BA frame may be defined to include information (e.g., link ID bitmap) about the awake state (and / or doze state) of an STA for other links within the MLD that may be indicated in the Multi-link PS-Poll frame exemplified in Example 1, or the format of an existing type of BA frame may be utilized.

[0228] A BA frame containing information about the awake state (and / or doze state) of an STA for other links within the MLD (e.g., a link ID bitmap) can be defined in at least one of the following ways:

[0229] - A BA frame can be defined as a new type in the BA type subfield within the BA control field. Additionally, in case of a new type, information about the awake state (and / or doze state) of the STA for other links in the MLD (e.g., link ID bitmap) can be included in an additionally defined field after the BA information field or in an additionally defined field between the BA control field and the BA information field.

[0230] - A compressed BA variant may be used in the BA type subfield within the BA control field.

[0231] Additionally, for compressed BA frames, information about the awake state (and / or doze state) of the STA for other links within the MLD (e.g., link ID bitmap) may be included in an additionally defined field after the BA information field or in an additionally defined field between the BA control field and the BA information field.

[0232] Additionally or alternatively, a bit may be additionally included / defined in the BA control field to indicate the presence of an additional field such as the above. For example, a reserved bit (one of B0 (bit 0), B5 (bit 5), or B8 (bit 8)) of the BA conrol field may be utilized.

[0233] - Multi-STA BA variants can be used within the BA control field.

[0234] Here, the Per AID TID Info subfield of the BA information field of the Multi-STA BA frame can be utilized as follows.

[0235] The AID TID Info subfield of the Per AID TID Info subfield may be set to at least the following:

[0236] i) The ACK Type subfield can be set to a specific value, for example, 0 or 1.

[0237] ii) The TID subfield may be set to a specific value, for example, one of the values ​​8 to 15 (where ACK Type = 1, TID = 15 may be excluded).

[0238] Depending on the value set in the AID TID Info subfield as per the above conditions, it may contain information (e.g., link ID bitmap) about the awake state (and / or doze state) of the STA for other links within the MLD.

[0239] Additionally, the Block Ack Starting Sequence Control subfield may not be included depending on the value set in the AID TID Info subfield as per the above conditions.

[0240] Additionally, the Block Ack Bitmap subfield may not be included depending on the value set in the AID TID Info subfield as per the above conditions.

[0241] Additionally or alternatively, the size of the Block Ack Bitmap subfield may be determined by the presence of a Block Ack Starting Sequence Control subfield (e.g., 2 octets) and by setting one of the values ​​of the Fragment Number subfield in the Block Ack Starting Sequence Control subfield. In this case, the Block Ack Bitmap subfield may include information about the awake state (and / or doze state) of the STA for other links in the MLD (e.g., a link ID bitmap). For example, the size of the Block Ack Bitmap subfield may be determined to be 4 octets by setting the Fragment Number subfield to B3 = 0, B2-B1 = 3, and B0 = 0. Additionally or alternatively, a presence bit, etc. may be defined in the Starting Sequence Number subfield within the Block Ack Starting Sequence Control subfield, and the presence bit may indicate the presence or absence of information (e.g., a link ID bitmap) about the awake state (and / or doze state) of the STA for other links within the MLD.

[0242] Additionally or alternatively, a control field according to ID may be configured depending on a specific ACK type / TID value. That is, a control ID (e.g., 3 bits or 4 bits) may be defined following a specific ACK type / TID value, and information according to the control ID may be included. For example, if the control ID is 0, information about the awake state (and / or doze state) of the STA for other links in the MLD (e.g., a link ID bitmap) may be included.

[0243] FIG. 17 illustrates a method for multi-link power saving using a BA frame according to one embodiment of the present disclosure.

[0244] FIG. 17 illustrates an example in which AP 1 and AP 2 belong to an AP MLD, AP 1 operates on link 1, and AP 2 operates on link 2. FIG. 17 illustrates an example in which STA 1 and STA 2 belong to a Non-AP MLD, STA 1 operates on link 1, and STA 2 operates on link 2. In addition, an example in which the AP MLD assigns AID 20 to the Non-AP MLD during a multi-link setup is illustrated.

[0245] Referring to FIG. 17, in sAP, when there is downlink data for Non-AP MLD, it is recommended to set the bit of TIM IE corresponding to AID 20 to 1 through a beacon frame (B in FIG. 17) and solicit downlink data on links 1 and 2 in MLTI IE (i.e., it is recommended that Non-AP MLD receive downlink data on links 1 and 2).

[0246] An sSTA in Power Save (PS) mode transitions from doze to awake before receiving a beacon frame from the sAP (i.e., before the TBTT of the sAP) and receives the beacon frame. This allows the mSTA in PS mode and operating on Link 2 to transition from doze to awake using the TIM / MLTI information verified by the sSTA.

[0247] Here, when sAP first acquires TXOP for downlink data transmission to sSTA and transmits downlink data, sSTA can include a link ID bitmap field in the BA frame transmitted to sAP instead of the Multi-link PS-Poll frame described above to inform sAP that mSTA is in the awake state (or transitioned from the doze state to the awake state).

[0248] The example of Fig. 17 illustrates a case where the link ID bitmap consists of 16 bits. In this case, as shown in Fig. 17, in order to indicate that the STA operating in link ID 1 and link ID 2 is in an awake state, only the bits corresponding to link ID 1 and link ID 2 may be set to 1, and the bits corresponding to the remaining link IDs may be set to 0.

[0249] In particular, in the example of FIG. 17, in the case of a Multi-STA BA frame, the ACK type subfield of the Per AID TID Info subfield is set to 0 and the TID subfield is set to 14, thereby indicating that a link ID bitmap field is included thereafter. However, the present disclosure is not limited thereto, and a combination of the ACK type subfield and the TID subfield values ​​may indicate whether information (e.g., a link ID bitmap) about an STA's awake state (and / or doze state) for another link in the MLD in the Multi-STA BA frame exists.

[0250] Additionally, the example in FIG. 17 illustrates a case where a link ID bitmap is included following the BA Information field in a new BA type BA frame or a Compressed BA frame. Accordingly, the AP MLD (from the sAP) that received the BA frame can control the mAP to transmit a data frame. This can reduce the control overhead in the mmWave band, and the effect can be greater when the number of mAPs and mSTAs is large and the MLTI IE recommends links for multiple mmWave bands.

[0251] FIG. 18 illustrates the operation of a multi-link device for a method for power saving for a multi-link device according to one embodiment of the present disclosure.

[0252] Figure 18 illustrates the operation of a multi-link device based on the previously proposed methods. The example in Figure 18 is provided for convenience of explanation and does not limit the scope of the present disclosure. Some of the steps illustrated in Figure 18 may be omitted depending on the circumstances and / or settings.

[0253] Here, a multi-link device may refer to a device capable of multi-link operation. In addition, the multi-link device may be a non-AP MLD (hereinafter, a first MLD) in which each STA belonging to the multi-link device is a non-AP STA, or an AP MLD (hereinafter, a second MLD) in which each STA belonging to the multi-link device is an AP.

[0254] In addition, it is assumed that a first non-AP STA and a second non-AP STA belong to a first MLD, and a first AP and a second AP belong to a second MLD. Here, the first non-AP STA and the first AP may operate on a sub-7 GHz band (e.g., 2.4 to 7.25 GHz), and the second non-AP STA and the second AP may operate on a millimeter wave (mmWave) band (e.g., 42 to 71 GHz).

[0255] FIG. 18 illustrates operations related to transmitting power saving mode-related information to STAs (including APs or non-AP STAs) of a multi-link device. In particular, for convenience of explanation, FIG. 18 assumes that a first MLD, which is a non-AP MLD, transmits power saving mode-related information to a second MLD, which is an AP MLD. However, conversely, a second MLD, which is an AP MLD, may also transmit power saving mode-related information to a first MLD, which is a non-AP MLD.

[0256] Referring to FIG. 18, a first STA belonging to a first MLD receives a beacon frame from a first AP belonging to a second MLD through a first link (S1801).

[0257] Here, the beacon frame may include information indicating that there is data to be transmitted to the first MLD.

[0258] The first STA transmits the first frame to the first AP through the first link (S1802).

[0259] Here, the first frame may include information indicating whether one or more STAs belonging to the first MLD are in an awake state.

[0260] For example, information indicating whether one or more STAs belonging to the first MLD are in an awake state is configured as a link identifier (ID) bitmap for a link on which one or more STAs (e.g., including the first STA and the second STA) operate, and based on the value of each bit of the bitmap, whether an STA operating on a link of a link ID corresponding to each bit is in an awake state can be indicated.

[0261] Here, the first frame is a control frame or a management frame for a power saving (PS) poll, and the link ID bitmap can be included in the control frame or the management frame.

[0262] Additionally, the first frame may be a QoS (quality or service) data frame or a QoS null frame including an aggregated control (A-control) subfield, and the link ID bitmap may be included in the A-control subfield.

[0263] Additionally, the first frame is a multi-STA BA frame, and whether the link ID bitmap exists in the multi-STA BA frame can be indicated by a combination of a value of an ACK type subfield and a value of a traffic identifier (TID) subfield. For example, to indicate that the link ID bitmap exists, the value of the ACK type subfield can be set to 0 or 1, and the value of the TID subfield can be set to one of 8 to 15.

[0264] In this case, the block ACK starting sequence control subfield in the multi-STA BA frame may not be included based on the presence of the link ID bitmap in the multi-STA BA frame indicated by a combination of the value of the ACK type subfield and the value of the TID subfield.

[0265] Additionally, based on the presence of the link ID bitmap within the multi-STA BA frame indicated by a combination of the value of the ACK type subfield and the value of the TID subfield, the block ACK bitmap subfield within the multi-STA BA frame may not be included.

[0266] In addition, when the presence of the link ID bitmap in the multi-STA BA frame is indicated by a combination of the value of the ACK type subfield and the value of the TID subfield, the size of the Block ACK Bitmap subfield is determined based on the presence of a block ACK starting sequence control subfield in the multi-STA BA frame and the fragment number subfield in the block ACK starting sequence control subfield being set to a specific value, and the link ID bitmap may be included in the block ACK bitmap subfield. For example, the remaining bits except for the link ID bitmap in the block ACK bitmap subfield may be reserved.

[0267] In addition, the first frame is a multi-STA BA frame, and whether the link ID bitmap exists in the multi-STA BA frame can be indicated by a starting sequence number subfield in a block ACK staring sequence control subfield in the multi-STA BA frame. In this case, based on the presence of the block ACK staring sequence control subfield in the multi-STA BA frame and the fragment number subfield in the block ACK staring sequence control subfield being set to a specific value, the size of the block ACK bitmap subfield is determined, and the link ID bitmap can be included in the block ACK bitmap subfield. For example, bits remaining except for the link ID bitmap in the block ACK bitmap subfield can be reserved.

[0268] Additionally, the first frame may be i) a new type of block ACK (BA) frame defined to include the link ID bitmap or ii) a compressed BA frame.

[0269] In this case, the link ID bitmap may be included in a field defined after the BA information field or a field defined between the BA control field and the BA information field.

[0270] For example, whether the link ID bitmap is present in the new type of BA frame or the compressed BA frame may be indicated by the bit value of one of bits 0, 5, and 8 in the BA control field.

[0271] At step S1802, the first MLD transmitting the first frame to the second MLD means transmitting a PPDU including the first frame.

[0272] Here, the PPDU 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.

[0273] 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.

[0274] 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.

[0275] 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).

[0276] 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.

[0277] The above-described STF-part (e.g., the U-STF field) may contain an STF sequence.

[0278] The above-described LTF-part (e.g., U-LTF field) may include a training field (i.e., LTF sequence) for channel estimation.

[0279] The data-part described above may include user data and may include packets for upper layers (e.g., MPDUs) (i.e., first frames).

[0280] The method described in the example of FIG. 18 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 transmit a first frame (or a PPDU including the first frame) via the 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. 18 or the examples described above when executed by one or more processors (102).

[0281] FIG. 19 illustrates the operation of a multi-link device for a method for power saving for a multi-link device according to one embodiment of the present disclosure.

[0282] Figure 19 illustrates the operation of a multi-link device based on the previously proposed methods. The example in Figure 19 is provided for convenience of explanation and does not limit the scope of the present disclosure. Some of the steps illustrated in Figure 19 may be omitted depending on the circumstances and / or settings.

[0283] Here, a multi-link device may refer to a device capable of multi-link operation. In addition, the multi-link device may be a non-AP MLD (hereinafter, a first MLD) in which each STA belonging to the multi-link device is a non-AP STA, or an AP MLD (hereinafter, a second MLD) in which each STA belonging to the multi-link device is an AP.

[0284] In addition, it is assumed that a first non-AP STA and a second non-AP STA belong to a first MLD, and a first AP and a second AP belong to a second MLD. Here, the first non-AP STA and the first AP may operate on a sub-7 GHz band (e.g., 2.4 to 7.25 GHz), and the second non-AP STA and the second AP may operate on a millimeter wave (mmWave) band (e.g., 42 to 71 GHz).

[0285] FIG. 19 illustrates operations related to receiving power saving mode-related information for an STA (including an AP or non-AP STA) of a multi-link device. In particular, for convenience of explanation, FIG. 19 assumes that a second MLD, which is an AP MLD, receives power saving mode-related information from a first MLD, which is a non-AP MLD. However, conversely, a first MLD, which is a non-AP MLD, may also receive power saving mode-related information from a second MLD, which is an AP MLD.

[0286] Referring to FIG. 19, the first AP belonging to the second MLD transmits a beacon frame to the first STA belonging to the first MLD through the first link (S1901).

[0287] Here, the beacon frame may include information indicating that there is data to be transmitted to the first MLD.

[0288] The first AP receives the first frame from the first STA through the first link (S1902).

[0289] Here, the first frame may include information indicating whether one or more STAs belonging to the first MLD are in an awake state.

[0290] For example, information indicating whether one or more STAs belonging to the first MLD are in an awake state is configured as a link identifier (ID) bitmap for a link on which one or more STAs (e.g., including the first STA and the second STA) operate, and based on the value of each bit of the bitmap, whether an STA operating on a link of a link ID corresponding to each bit is in an awake state can be indicated.

[0291] Here, the first frame is a control frame or a management frame for a power saving (PS) poll, and the link ID bitmap can be included in the control frame or the management frame.

[0292] Additionally, the first frame may be a QoS (quality or service) data frame or a QoS null frame including an aggregated control (A-control) subfield, and the link ID bitmap may be included in the A-control subfield.

[0293] Additionally, the first frame is a multi-STA BA frame, and whether the link ID bitmap exists in the multi-STA BA frame can be indicated by a combination of a value of an ACK type subfield and a value of a traffic identifier (TID) subfield. For example, to indicate that the link ID bitmap exists, the value of the ACK type subfield can be set to 0 or 1, and the value of the TID subfield can be set to one of 8 to 15.

[0294] In this case, the block ACK starting sequence control subfield in the multi-STA BA frame may not be included based on the presence of the link ID bitmap in the multi-STA BA frame indicated by a combination of the value of the ACK type subfield and the value of the TID subfield.

[0295] Additionally, based on the presence of the link ID bitmap within the multi-STA BA frame indicated by a combination of the value of the ACK type subfield and the value of the TID subfield, the block ACK bitmap subfield within the multi-STA BA frame may not be included.

[0296] In addition, when the presence of the link ID bitmap in the multi-STA BA frame is indicated by a combination of the value of the ACK type subfield and the value of the TID subfield, the size of the Block ACK Bitmap subfield is determined based on the presence of a block ACK starting sequence control subfield in the multi-STA BA frame and the fragment number subfield in the block ACK starting sequence control subfield being set to a specific value, and the link ID bitmap may be included in the block ACK bitmap subfield. For example, the remaining bits except for the link ID bitmap in the block ACK bitmap subfield may be reserved.

[0297] In addition, the first frame is a multi-STA BA frame, and whether the link ID bitmap exists in the multi-STA BA frame can be indicated by a starting sequence number subfield in a block ACK staring sequence control subfield in the multi-STA BA frame. In this case, based on the presence of the block ACK staring sequence control subfield in the multi-STA BA frame and the fragment number subfield in the block ACK staring sequence control subfield being set to a specific value, the size of the block ACK bitmap subfield is determined, and the link ID bitmap can be included in the block ACK bitmap subfield. For example, bits remaining except for the link ID bitmap in the block ACK bitmap subfield can be reserved.

[0298] Additionally, the first frame may be i) a new type of block ACK (BA) frame defined to include the link ID bitmap or ii) a compressed BA frame.

[0299] In this case, the link ID bitmap may be included in a field defined after the BA information field or a field defined between the BA control field and the BA information field.

[0300] For example, whether the link ID bitmap is present in the new type of BA frame or the compressed BA frame may be indicated by the bit value of one of bits 0, 5, and 8 in the BA control field.

[0301] At step S1901, the second MLD receiving the first frame from the first MLD means receiving a PPDU including the first frame.

[0302] Here, the PPDU 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.

[0303] 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.

[0304] 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.

[0305] 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).

[0306] 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.

[0307] The above-described STF-part (e.g., the U-STF field) may contain an STF sequence.

[0308] The above-described LTF-part (e.g., U-LTF field) may include a training field (i.e., LTF sequence) for channel estimation.

[0309] The data-part described above may include user data and may include packets for upper layers (e.g., MPDUs) (i.e., first frames).

[0310] The method described in the example of FIG. 19 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 receive the first frame (or the PPDU including the first frame) via the transceiver(s) (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. 19 or the examples described above when executed by one or more processors (202).

[0311] While MLD operation in existing wireless LAN systems only supports operation in the sub-7 GHz band, in contrast, MLD operation according to examples of the present disclosure can discover APs or non-AP STAs operating in the mmWave band. In addition, since association (i.e., multi-link setup) and frame exchange can be performed with APs or non-AP STAs operating in the mmWave band, wireless transmission and reception efficiency can be improved. In addition, the AP MLD can appropriately perform frame exchange without separate triggering by recognizing the power saving status of one or more affiliated STAs of the STA MLD.

[0312] 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.

[0313] 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.

[0314] 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.

[0315] The method proposed in this disclosure is 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 beacon frame from a first access point (AP) belonging to a second MLD through a first link by a first station (STA) belonging to a first multi-link device (MLD), wherein the beacon frame includes information indicating that there is data to be transmitted to the first MLD; and A step of transmitting a first frame to the first AP through the first link by the first STA, A method wherein the first frame includes information indicating whether one or more STAs belonging to the first MLD are in an awake state.

2. In paragraph 1, Information indicating whether one or more STAs belonging to the first MLD are in an awake state is composed of a link identifier (ID: idnetifier) ​​bitmap for a link on which one or more STAs operate, A method in which, based on the value of each bit of the above bitmap, it is indicated whether an STA operating on a link of a link ID corresponding to each bit is in an awake state.

3. In paragraph 2, The above first frame is a control frame or management frame for a power saving (PS) poll, A method wherein the above link ID bitmap is included in the control frame or the management frame.

4. In paragraph 2, The first frame is a QoS (quality or service) data frame or QoS null frame including an aggregated control (A-control) subfield, The above link ID bitmap is included in the A-control subfield.

5. In paragraph 2, The above first frame is a multi-STA BA frame, A method in which the presence of the link ID bitmap in the multi-STA BA frame is indicated by a combination of the value of the ACK type subfield and the value of the traffic identifier (TID) subfield.

6. In paragraph 5, A method wherein the size of a Block Ack Bitmap subfield is determined based on the presence of a block ACK starting sequence control subfield in the multi-STA BA frame and the fragment number subfield in the block ACK starting sequence control subfield being set to a specific value, and the link ID bitmap is included in the block ACK bitmap subfield.

7. In paragraph 5, A method in which the value of the ACK type subfield is set to 0 or 1, and the value of the TID subfield is set to one of 8 to 15, to indicate that the link ID bitmap exists.

8. In paragraph 2, The above first frame is a multi-STA BA frame, A method wherein whether the link ID bitmap exists in the multi-STA BA frame is indicated by a starting sequence number subfield in a block ACK starting sequence control subfield in the multi-STA BA frame.

9. In paragraph 8, A method in which the size of a Block Ack Bitmap subfield is determined based on the fragment number subfield in the Block ACK Start Sequence Control subfield being set to a specific value, and the link ID bitmap is included in the Block ACK Bitmap subfield.

10. In paragraph 2, A method wherein the first frame is i) a new type of block ACK (BA) frame defined to include the link ID bitmap or ii) a compressed BA frame.

11. In paragraph 10, A method wherein the above link ID bitmap is included in a field defined after the BA information field or a field defined between the BA control field and the BA information field.

12. In paragraph 10, A method in which whether the link ID bitmap is present in the new type of BA frame or the compressed BA frame is indicated by a bit value of one of bits 0, 5, and 8 in the BA control field.

13. The first multi-link device (MLD) is: one or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: A first station (STA: station) belonging to the first MLD receives a beacon frame from a first access point (AP: access point) belonging to the second MLD through a first link, wherein the beacon frame includes information indicating that there is data to be transmitted to the first MLD, and By the first STA, the first frame is set to be transmitted to the first AP through the first link, A device wherein the first frame includes information indicating whether one or more STAs belonging to the first MLD are in an awake state.

14. A step of transmitting a beacon frame to a first station (STA) belonging to a first MLD via a first link by a first access point (AP) belonging to a second multi-link device (MLD), wherein the beacon frame includes information indicating that there is data to be transmitted to the first MLD; and A step of receiving a first frame from the first STA through the first link by the first AP, A method wherein the first frame includes information indicating whether one or more STAs belonging to the first MLD are in an awake state.

15. The second multi-link device (MLD) is: one or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: A first access point (AP) belonging to the second MLD transmits a beacon frame to a first station (STA) belonging to the first MLD through a first link, wherein the beacon frame includes information indicating that there is data to be transmitted to the first MLD, and By the first AP, a first frame is set to be received from the first STA through the first link, A device wherein the first frame includes information indicating whether one or more STAs belonging to the first MLD are in an awake state.

16. In a processing device configured to control a multi-link device (MLD) 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 11.

17. 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 11.

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