Method and device for transmitting and receiving PPDU for cooperative beamforming in wireless LAN system

Abstract

Disclosed are a method and device for transmitting and receiving a PPDU for cooperative beamforming in a wireless LAN system. A method performed by a first AP in a wireless LAN system, according to one aspect of the present disclosure, may comprise the steps of: transmitting, to a second AP, a first frame including information on the number of UHR-LTF symbols for Co-BF transmission; and transmitting a first PPDU for Co-BF transmission to one or more first STAs associated with the first AP.

Description

PPDU transmission and reception method and device for cooperative beamforming in a wireless LAN system

[0001] The present disclosure relates to a method and apparatus for transmitting and receiving a physical protocol data unit (PPDU) for coordinated beamforming (Co-BF) in a Wireless Local Area Network (WLAN) system.

[0002] New technologies have been introduced for wireless LANs (WLANs) to improve transmission rates, increase bandwidth, enhance reliability, reduce errors, and reduce latency. Among wireless LAN technologies, the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards can be referred to as Wi-Fi. For example, technologies recently introduced to wireless LANs 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 an improved wireless communication environment, advanced technologies for Extremely High Throughput (EHT) are being discussed. For example, technologies for Multiple Input Multiple Output (MIMO) supporting increased bandwidth, efficient utilization of multiple bands, and increased spatial streams, as well as technologies for multiple access points (AP) coordination, are being researched. In particular, various technologies are being studied to support traffic with low latency or real-time characteristics. Furthermore, new technologies to support ultra-high reliability (UHR), including improvements or extensions of EHT technology, are being discussed.

[0004] The technical problem of the present disclosure is to provide a method and apparatus for transmitting and receiving PPDUs for coordinated beamforming (Co-BF).

[0005] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0006] A method performed by a first access point (AP) in a wireless LAN system according to one aspect of the present disclosure may include: transmitting a first frame to a second AP, wherein the first frame includes information regarding the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission; and transmitting a first physical protocol data unit (PPDU) for Co-BF transmission to one or more first stations (STA) associated with the first AP. The first PPDU may include first UHR-LTF symbols corresponding to the number of UHR-LTF symbols.

[0007] A method performed by a second access point (AP) in a wireless LAN system according to a further aspect of the present disclosure may include: receiving a first frame from a first AP, wherein the first frame includes information regarding the number of ultra-high reliability-long training field (UHR-LTF) symbols for coordinated beamforming (Co-BF) transmission; and transmitting a second physical protocol data unit (PPDU) for Co-BF transmission to one or more second stations (STAs) associated with the second AP. The second PPDU may include second UHR-LTF symbols corresponding to the number of UHR-LTF symbols.

[0008] According to the present disclosure, as multiple APs perform coordinated beamforming (Co-BF), throughput can be improved and latency reduced, thereby increasing wireless communication efficiency.

[0009] According to the present disclosure, when multiple APs perform coordinated beamforming (Co-BF), each AP can use an LTF that does not interfere with each other, allowing the STAs associated with each AP to smoothly perform channel estimation.

[0010] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

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

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

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

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

[0015] FIG. 4 is a drawing illustrating a backoff process to which the present disclosure may be applied.

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

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

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

[0019] FIG. 8 is a diagram showing an exemplary arrangement of resource units (RU) used in the 20 MHz band.

[0020] FIG. 9 is a diagram showing an exemplary arrangement of resource units (RU) used in the 40 MHz band.

[0021] FIG. 10 is a diagram showing an exemplary arrangement of resource units (RU) used in the 80 MHz band.

[0022] FIG. 11 illustrates the generation of EHT-LTF symbols within an EHT MU PPDU and an EHT TB PPDU in a wireless LAN system to which the present disclosure may be applied.

[0023] FIG. 12 is a drawing illustrating a PPDU format according to one embodiment of the present disclosure.

[0024] FIG. 13 illustrates the operation of a first AP for a PPDU transmission and reception method for cooperative beamforming according to one embodiment of the present disclosure.

[0025] FIG. 14 illustrates the operation of a second AP for a PPDU transmission and reception method for cooperative beamforming according to one embodiment of the present disclosure.

[0026] Hereinafter, preferred embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description disclosed below, together with the accompanying drawings, is intended to describe exemplary embodiments of the present disclosure and is not intended to represent the only embodiment in which the present disclosure may be practiced. The following detailed description includes specific details to provide a complete understanding of the present disclosure. However, those skilled in the art will know that the present disclosure may be practiced without such specific details.

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

[0028] In the present disclosure, when a component is described as being “connected,” “combined,” or “joined” with another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, in the present disclosure, the terms “comprising” or “having” specify the presence of the mentioned features, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, actions, elements, components, and / or groups thereof.

[0029] In the present disclosure, terms such as "first," "second," etc. are used solely for the purpose of distinguishing one component from another and are not used to limit the components, nor do they limit the order or importance of the components unless specifically stated otherwise. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and likewise, a second component in one embodiment may be referred to as a first component in another embodiment.

[0030] The terms used in this disclosure are for the description of specific embodiments and are not intended to limit the claims. As used in the description of embodiments and in the appended claims, the singular form is intended to include the plural form unless the context clearly indicates otherwise. The term "and / or" as used in this disclosure may refer to any one of the related enumerated items, or refers to and includes any and all possible combinations of two or more of them. Additionally, the " / " between words in this disclosure has the same meaning as "and / or" unless otherwise noted.

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

[0032] The following describes the technical features to which the examples of the present disclosure may be applied.

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

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

[0035] The device (100, 200) exemplified in FIG. 1 may be referred to as a station (STA). For example, the device (100, 200) exemplified in FIG. 1 may be referred to by various terms such as a transmitting device, a receiving device, a transmitting STA, or a receiving STA. For example, the STA (110, 200) may perform the role of an access point (AP) or a non-AP. That is, in the present disclosure, the STA (110, 200) may perform the functions of an AP and / or a non-AP. If the STA (110, 200) performs the AP function, it may simply be referred to as an AP, and if the STA (110, 200) performs the non-AP function, it may simply be referred to as a STA. Additionally, in the present disclosure, the AP may also be indicated as an AP STA.

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

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

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

[0039] The second device (200) includes one or more processors (202) and one or more memories (204), and may additionally include one or more transceivers (206) and / or one or more antennas (208). The processor (202) controls the memory (204) and / or transceivers (206) and may be configured to implement the descriptions, functions, procedures, proposals, methods and / or sequences of operation disclosed in this disclosure. For example, the processor (202) may process information within the memory (204) to generate a third information / signal and then transmit a wireless signal containing the third information / signal through the transceiver (206). Additionally, the processor (202) may receive a wireless signal containing a fourth information / signal through the transceiver (206) and then store information obtained from the signal processing of the fourth information / signal 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 store software code containing instructions for performing some or all of the processes controlled by the processor (202) or for performing the descriptions, functions, procedures, proposals, methods, and / or sequences of operation disclosed in this disclosure. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement 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 through one or more antennas (208). The transceiver (206) may include a transmitter and / or receiver. The transceiver (206) may be used in combination with an RF unit. In the present disclosure, the device may refer to a communication modem / circuit / chip.

[0040] Hereinafter, 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 Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts of operation disclosed in this disclosure. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts of operation disclosed in this disclosure. One or more processors (102, 202) may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this disclosure and provide it to one or more transceivers (106, 206). One or more processors (102, 202) may receive a signal (e.g., a baseband signal) from one or more transceivers (106, 206) and may obtain a PDU, SDU, message, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this disclosure.

[0041] One or more processors (102, 202) may be referred to as a controller, microcontroller, microprocessor, or 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 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. Firmware or software configured to perform the descriptions, functions, procedures, proposals, methods, and / or operation sequences disclosed in this disclosure may be included in 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 sequences disclosed in this disclosure may be implemented using firmware or software in the form of code, instructions, and / or sets of instructions.

[0042] One or more memories (104, 204) may be connected to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. One or more memories (104, 204) may be composed of ROM, RAM, EPROM, flash memory, hard drive, registers, cache memory, computer read storage media, and / or combinations thereof. One or more memories (104, 204) may be located inside and / or outside of one or more processors (102, 202). Additionally, one or more memories (104, 204) may be connected to one or more processors (102, 202) through various technologies such as wired or wireless connections.

[0043] One or more transceivers (106, 206) may transmit user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or operation flowcharts, etc., of the present disclosure to one or more other devices. One or more transceivers (106, 206) may receive user data, control information, wireless signals / channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and / or operation flowcharts, etc., disclosed in the present disclosure from one or more other devices. For example, one or more transceivers (106, 206) may be connected to one or more processors (102, 202) and may transmit and receive wireless signals. For example, one or more processors (102, 202) may control one or more transceivers (106, 206) to transmit user data, control information, 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 connected to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, wireless signals / channels, etc., as described in the descriptions, functions, procedures, proposals, methods, and / or flowcharts of operation disclosed in this disclosure through one or more antennas (108, 208). In this disclosure, one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). One or more transceivers (106, 206) can convert the received wireless signal / channel, etc. from an RF band signal to a baseband signal in order to process the received user data, control information, wireless signal / channel, etc. using one or more processors (102, 202).One or more transceivers (106, 206) can convert user data, control information, wireless signals / channels, etc. processed using one or more processors (102, 202) from baseband signals to RF band signals. To this end, one or more transceivers (106, 206) may include (analog) oscillators and / or filters.

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

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

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

[0047] The structure of a wireless LAN system can be composed of multiple components. Through the interaction of multiple components, a wireless LAN that supports STA mobility transparent to the upper layer can be provided. A Basic Service Set (BSS) corresponds to the basic building block of a wireless LAN. Figure 2 exemplarily illustrates 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). In Figure 2, the ellipse representing the BSS can also be understood as representing the coverage area where the STAs included in the corresponding BSS maintain communication. This area can be referred to as a Basic Service Area (BSA). If a STA moves outside the BSA, it becomes unable to communicate directly with other STAs within that BSA.

[0048] Excluding the DS illustrated in Fig. 2, the most basic type of BSS in a wireless LAN is the Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For instance, assuming other components are omitted, a BSS1 composed of only STA1 and STA2, or a BSS2 composed of only STA3 and STA4, can each be considered a representative example of an IBSS. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, this type of wireless LAN is not configured through pre-planning but can be configured when a LAN is needed, and this can be referred to as an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. In other words, in an IBSS, STAs are managed in a distributed manner. In IBSS, all STAs can be mobile STAs, and since connections to distributed systems (DS) are not allowed, they form a self-contained network.

[0049] The membership of an STA in a BSS can be dynamically changed by the STA being turned on or off, or by the STA entering or leaving the BSS area. To become a member of a BSS, an STA can join the BSS using a synchronization process. To access all services of the BSS infrastructure, an STA must be associated with the BSS. This association can be configured dynamically and may include the use of a Distribution System Service (DSS).

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

[0051] DS refers to a structure in which BSSs are interconnected. Specifically, as shown in FIG. 2, a BSS may exist as a component in an extended form of a network composed of multiple BSSs. DS is a logical concept and can be specified by the characteristics of the Distributed System Medium (DSM). In this regard, the Wireless Medium (WM) and the DSM can be logically distinguished. Each logical medium is used for a different purpose and is utilized by different components. These media are not limited to being identical or different. The flexibility of the wireless LAN structure (DS structure or other network structure) can be explained by the fact that multiple media are logically distinct in this way. That is, the wireless LAN structure can be implemented in various ways, and the corresponding wireless LAN structure can be specified independently by the physical characteristics of each implementation.

[0052] DS can support mobile devices by providing seamless integration of multiple BSSs and providing logical services necessary for handling addresses to destinations. Additionally, DS may include a component called a portal that acts as a bridge for connecting the wireless LAN with another network (e.g., IEEE 802.X).

[0053] An AP refers to an entity that enables access to the DS via the WM for combined non-AP STAs and also possesses the functionality of an STA. Data movement between the BSS and the DS can be performed through the AP. For example, STA2 and STA3 shown in FIG. 2 possess the functionality of an STA and provide the ability for combined non-AP STAs (STA1 and STA4) to access the DS. Furthermore, since all APs fundamentally correspond to STAs, all APs are addressable entities. The address used by the AP for communication on the WM and the address used by the AP for communication on the DSM do not necessarily have to be the same. A BSS composed of an AP and one or more STAs can be referred to as an infrastructure BSS.

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

[0055] In addition to the structure of the aforementioned DS, an Extended Service Set (ESS) may be configured to provide wider coverage.

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

[0057] In wireless LAN systems, no assumptions are made regarding the relative physical locations of BSSs, and all of the following forms are possible. BSSs may partially overlap, which is a form commonly used to provide continuous coverage. Additionally, BSSs may not be physically connected, and logically, there is no limit to the distance between BSSs. Furthermore, BSSs may be located in the same physical location, which can be used to provide redundancy. Also, one (or more) IBSS or ESS networks may physically exist in the same space as one (or more) ESS networks. This may apply to ESS network forms such as when an ad-hoc network operates at a location where an ESS network exists, when wireless networks that physically overlap are configured by different organizations, or when two or more different access and security policies are required at the same location.

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

[0059] In order 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 go through authentication procedures for security. The link setup process can also be referred to as the session initiation process or the session setup process. Additionally, the processes of discovery, authentication, association, and security setup in the link setup process can be collectively referred to as the association process.

[0060] In step S310, the STA may perform a network discovery operation. The network discovery operation may include the STA's scanning operation. That is, in order for the STA to access a network, it must find a network it can join. Before joining a wireless network, the STA must identify a compatible network, and the process of identifying networks existing in a specific area is called scanning.

[0061] Scanning methods include active scanning and passive scanning. Figure 3 illustrates a network discovery operation that includes an active scanning process as an example. In active scanning, the STA performing the scanning moves between channels to search for nearby APs, transmits a probe request frame, and waits for a response. The responder transmits a probe response frame as a response to the probe request frame to the STA that transmitted the probe request frame. Here, the responder may be the STA that last transmitted a beacon frame from the BSS of the channel being scanned. In a BSS, the AP becomes the responder because it transmits the beacon frame; however, in an IBSS, the responder is not constant because STAs within the IBSS take turns transmitting the beacon frame. For example, an STA that transmits a probe request frame on channel 1 and receives a probe response frame on channel 1 can store BSS-related information included in the received probe response frame and move to the next channel (e.g., channel 2) to perform scanning in the same way (i.e., transmit and receive probe request / response on channel 2).

[0062] Although not illustrated in FIG. 3, the scanning operation may be performed using a passive scanning method. In passive scanning, the STA performing the scanning waits for a beacon frame while switching between channels. A beacon frame is one of the management frames defined in IEEE 802.11, which is periodically transmitted to announce the presence of a wireless network and to allow the scanning STA to find the wireless network and join it. In a BSS, the AP performs the role of periodically transmitting beacon frames, and in an IBSS, the STAs within the IBSS take turns transmitting beacon frames. When the scanning STA receives a beacon frame, it stores the information about the BSS included in the beacon frame and records the beacon frame information in each channel while moving to another channel. The STA that receives the beacon frame stores the BSS-related information included in the received beacon frame, moves to the next channel, and can perform scanning in the next channel in the same way. When comparing active scanning and passive scanning, active scanning has the advantage of lower delay and power consumption than passive scanning.

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

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

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

[0066] The STA can send an authentication request frame to the AP. Based on the information contained in the received authentication request frame, the AP can determine whether to allow authentication for the STA. The AP can provide the result of the authentication process to the STA through an authentication response frame.

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

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

[0069] After the STA is successfully joined to the network, a security setup process can be performed in step S340. The security setup process in step S340 may be described as an authentication process through RSNA (Robust Security Network Association) requests / responses, and the authentication process in step S320 may be referred to as the first authentication process, and the security setup process in step S340 may simply be referred to as the authentication process.

[0070] The security setup process of step S340 may include, for example, a private key setup process through a 4-way handshake via an EAPOL (Extensible Authentication Protocol over LAN) frame. Additionally, the security setup process may be performed according to a security method not defined in the IEEE 802.11 standard.

[0071] FIG. 4 is a drawing illustrating a backoff process to which the present disclosure may be applied.

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

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

[0074] With reference to FIG. 4, the operation based on the random backoff period is described. When a medium in an occupied / busy state changes to an idle state, multiple STAs may attempt to transmit data (or frames). As a measure to minimize collisions, each STA may select a random backoff count and attempt transmission after waiting for the corresponding slot time. The random backoff count has a pseudo-random integer value and can be determined as one of the values ​​in the range from 0 to CW. Here, CW is the Contention Window parameter value. The CW parameter is given an initial value of CWmin, but in the case of transmission failure (e.g., failure to receive an ACK for a transmitted frame), it may take a value twice that amount. When the CW parameter value becomes CWmax, data transmission may be attempted while maintaining the CWmax value until data transmission is successful; if data transmission is successful, it is reset to the CWmin value. The values ​​of CW, CWmin, and CWmax are 2 n It is desirable to set it to -1 (n=0, 1, 2, ...).

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

[0076] In the example of Fig. 4, when a packet to be transmitted arrives at the MAC of STA3, STA3 confirms that the medium is idle for DIFS and can immediately transmit the frame. The remaining STAs monitor whether the medium is occupied or busy and wait. Meanwhile, data to be transmitted may also arise from each of STA1, STA2, and STA5, and each STA can perform a countdown of the backoff slot according to a random backoff count value selected by each after waiting for DIFS when the medium is monitored to be idle. Assume the case where STA2 selects the smallest backoff count value and STA1 selects the largest backoff count value. That is, this exemplifies a case where, at the point when STA2 finishes the backoff count and starts transmitting the frame, the remaining backoff time of STA5 is shorter than the remaining backoff time of STA1. STA1 and STA5 pause the countdown briefly and wait while STA2 occupies the medium. When STA2's possession ends and the medium becomes idle again, STA1 and STA5 wait for DIFS and then resume the paused backoff count. That is, they can start transmitting a frame after counting down the remaining backoff slots corresponding to the remaining backoff time. Since STA5's remaining backoff time was shorter than STA1's, STA5 starts transmitting the frame. While STA2 is occupying the medium, data to be transmitted may also be generated by STA4. From STA4's perspective, when the medium becomes idle, it waits for DIFS, performs a countdown based on a random backoff count value selected by itself, and can start transmitting a frame. The example in Figure 4 illustrates a case where STA5's remaining backoff time happens to match STA4's random backoff count value; in this case, a collision may occur between STA4 and STA5. If a collision occurs, neither STA4 nor STA5 receives an ACK, resulting in a failure to transmit data.In this case, STA4 and STA5 can double the CW value, select a random backoff count value, and perform a countdown. STA1 waits while the medium is occupied due to transmission by STA4 and STA5, and when the medium becomes idle, it waits for DIFS, and then can start transmitting frames after the remaining backoff time has passed.

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

[0078] A QoS (Quality of Service) STA can transmit a frame after backoff, which is performed after the passage of the arbitration IFS (AIFS) for the access category (AC) to which the frame belongs, i.e., AIFS[i] (where i is a value determined by the AC). Here, the frame for which AIFS[i] can be used can be a data frame or a management frame, and can also be a control frame rather than a response frame.

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

[0080] As previously mentioned, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, where the STA directly senses the medium. Virtual carrier sensing is intended to mitigate problems that may occur in medium access, such as the hidden node problem. For virtual carrier sensing, the STA's MAC can utilize the Network Allocation Vector (NAV). The NAV is a value that indicates to other STAs the time remaining until the medium becomes available, provided that the STA currently using or authorized to use the medium is using it. Therefore, the value set as the NAV corresponds to the period during which the medium is scheduled to be used by the STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during that period. For example, the NAV can be set based on the value of the "duration" field in the frame's MAC header.

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

[0082] In order to reduce the possibility of collisions between multiple STAs in a CSMA / CA-based frame transmission operation, a mechanism utilizing RTS / CTS frames may be applied. In the example of FIG. 5, while STA1 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA1 may be a hidden node to STA3. Alternatively, in the example of FIG. 5, while STA2 is transmitting, the medium may be determined to be idle based on the carrier sensing result of STA3. That is, STA2 may be a hidden node to STA3. By exchanging RTS / CTS frames before performing data transmission and reception between STA1 and STA2, it is possible to prevent a STA outside the transmission range of either STA1 or STA2, or a STA outside the carrier sensing range for transmission from STA1 or STA3, from attempting to occupy the channel during data transmission and reception between STA1 and STA2.

[0083] Specifically, STA1 can determine whether the channel is in use through carrier sensing. In terms of physical carrier sensing, STA1 can determine the channel occupancy idle state based on the energy magnitude or signal correlation detected in the channel. Additionally, in terms of virtual carrier sensing, STA1 can determine the channel occupancy state using a NAV (network allocation vector) timer.

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

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

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

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

[0088] Based on instructions or primitives (meaning a set of instructions or parameters) from the MAC layer, the PHY layer can prepare the MPDU (MAC PDU) to be transmitted. For example, upon receiving an instruction from the MAC layer requesting the start of transmission, the PHY layer switches to transmit mode and can construct the information provided by the MAC layer (e.g., data) into a frame for transmission. Additionally, if the PHY layer detects a valid preamble of a received frame, it monitors the preamble header and sends an instruction to the MAC layer indicating the start of reception.

[0089] As such, information transmission and reception in wireless LAN systems are carried out in the form of frames, and for this purpose, the Physical Layer Protocol Data Unit (PPDU) format is defined.

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

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

[0092] The SIG field may contain various information related to the transmission and reception of the PPDU. For example, the L-SIG field consists 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 contain information regarding the modulation and coding rates of the data. For example, the 12-bit Length field may contain information regarding 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 non-HT, HT, VHT, or EHT PPDUs, the value of the Length field may be determined as a multiple of 3. For example, for HE PPDUs, the value of the Length field may be determined as a multiple of 3 + 1 or a multiple of 3 + 2.

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

[0094] A MAC PDU is defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a Frame Check Sequence (FCS). A MAC frame is composed of a MAC PDU and can be transmitted or received through the PSDU of the data portion in the PPDU format.

[0095] The MAC header includes a Frame Control field, a Duration / ID field, an Address field, etc. The Frame Control field may contain control information necessary for transmitting or receiving frames. The Duration / ID field may be set as the time for transmitting the corresponding frame. Address subfields may indicate the frame's receiver address, transmitter address, destination address, and source address, and some address subfields may be omitted. Specific details regarding each subfield of the MAC header, including Sequence Control, QoS Control, and HT Control subfields, can be found in the IEEE 802.11 standard document.

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

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

[0098] Various forms of PPDU have been used in standards such as IEEE 802.11a / g / n / ac / ax. The basic PPDU format (IEEE 802.11a / g) includes L-LTF, L-STF, L-SIG, and Data fields. The basic PPDU format may also be referred to as the non-HT PPDU format (Fig. 7(a)).

[0099] The HT PPDU format (IEEE 802.11n) additionally includes HT-SIG, HT-STF, and HT-LFT(s) fields in addition to the basic PPDU format. The HT PPDU format illustrated in FIG. 7(b) may be referred to as the HT-mixed format. Additionally, an HT-greenfield format PPDU may be defined, which corresponds to a format consisting of HT-GF-STF, HT-LTF1, HT-SIG, one or more HT-LTFs, and a Data field, without including L-STF, L-LTF, and L-SIG (not shown).

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

[0101] An example of the HE PPDU format (IEEE 802.11ax) includes the RL-SIG (Repeated L-SIG), HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF(s), and PE (Packet Extension) fields in addition to the basic PPDU format (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 multiple users (MU), but is not included in the HE PPDU format for single users (SU). Additionally, the HE trigger-based (TB) PPDU format does not include HE-SIG-B, and the length of the HE-STF field may vary to 8 µs. The HE ER (Extended Range) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16 µs. For example, RL-SIG can be configured identically to L-SIG. Based on the presence of RL-SIG, the receiving STA can determine that the received PPDU is a HE PPDU or the EHT PPDU described later.

[0102] The EHT PPDU format may include the EHT MU (multi-user) 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 RL-SIG following L-SIG, but it may include U (universal)-SIG, EHT-SIG, EHT-STF, and EHT-LTF following RL-SIG.

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

[0104] The EHT-SIG is omitted in the EHT TB PPDU of FIG. 7(f) compared to the EHT MU PPDU. A STA that receives a trigger for UL MU transmission (e.g., a trigger frame or TRS (triggered response scheduling)) can perform UL transmission based on the EHT TB PPDU format.

[0105] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated so that demodulation and decoding can be attempted even on legacy STAs, and mapped based on a defined 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 so that they can be demodulated and decoded by a STA that has successfully decoded a non-legacy SIG (e.g., U-SIG and / or EHT-SIG) to obtain the information contained in the corresponding fields, and mapped based on a defined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

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

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

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

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

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

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

[0112] For example, the version-independent bits of U-SIG may include a 3-bit physical layer version identifier (PHY version identifier), and this information may indicate the PHY version of the transmitted / received PPDU (e.g., EHT, UHR, etc.). The version-independent bits of 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 U-SIG may include information regarding the length of the TXOP (transmission opportunity) and information regarding the BSS color ID.

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

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

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

[0116] Preamble puncturing may refer to the transmission of a PPDU in which a signal is not present in one or more frequency units within the PPDU bandwidth. For example, the size of the frequency unit (or the resolution of preamble puncturing) may be defined as 20 MHz, 40 MHz, etc. For example, preamble puncturing may be applied to a PPDU bandwidth of a predetermined size or larger.

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

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

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

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

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

[0122] An RU may include multiple subcarriers (or tones). An RU may be used when transmitting signals to multiple STAs based on the OFDMA technique. Additionally, an RU may be defined when transmitting signals to a single STA. Resources may be allocated on an RU basis for non-legacy STF, non-legacy LTF, and Data fields.

[0123] Applicable RU sizes can be defined according to the PPDU bandwidth. RUs 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 80 MHz PPDU, the RU placement for HE PPDU and EHT PPDU may differ. The applicable RU sizes, number of RUs, RU locations, DC (direct current) subcarrier locations and numbers, null subcarrier locations and numbers, and guard subcarrier locations and numbers for each PPDU bandwidth can be referred to as a tone-plan. For example, a tone-plan for a wide bandwidth may be defined as a multiple repetition of a tone-plan for a low bandwidth.

[0124] RUs of various sizes can be defined as 26-ton RUs, 52-ton RUs, 106-ton RUs, 242-ton RUs, 484-ton RUs, 996-ton RUs, 2x996-ton RUs, 3x996-ton RUs, etc. An MRU (multiple RU) is distinguished from multiple individual RUs and corresponds to a group of subcarriers composed 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. In addition, multiple RUs constituting a single MRU may be continuous or non-continuous in the frequency domain.

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

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

[0127] Resource Units (RU) and Resource Allocation

[0128] FIGS. 8 to 10 are drawings for illustrating examples of resource units of a wireless LAN system to which the present disclosure may be applied.

[0129] With reference to FIGS. 8 to 10, a resource unit (RU) defined in a wireless LAN system will be described. The RU may include multiple subcarriers (or tones). The RU may be used when transmitting signals to multiple STAs based on the OFDMA technique. Additionally, the RU may be defined when transmitting signals to a single STA. The RU may be used for the STF, LTF, data fields, etc., of a PPDU.

[0130] As illustrated in FIGS. 8 to 10, RUs corresponding to different numbers of tones (i.e., subcarriers) can be used to form some fields of a 20 MHz, 40 MHz, or 80 MHz X-PPDU (X is HE, EHT, etc.). For example, resources can be allocated in units of the illustrated RUs for the X-STF, X-LTF, and Data fields.

[0131] FIG. 8 is a diagram showing an exemplary arrangement of resource units (RU) used in the 20 MHz band.

[0132] As shown at the top of FIG. 8, 26 units (i.e., units corresponding to 26 tones) may be allocated. Six tones may be used as a guard band in the leftmost band of the 20 MHz band, and five tones may be used as a guard band in the rightmost band of the 20 MHz band. Additionally, seven DC tones may be inserted in the center band, i.e., the DC band, and 26 units corresponding to 13 tones may exist on the left and right sides of the DC band. Furthermore, 26, 52, and 106 units may be allocated to other bands. Each unit may be allocated for an STA or a user.

[0133] The RU arrangement of FIG. 8 is utilized not only for situations involving multiple users (MU) but also for situations involving a single user (SU), in which case it is possible to use one 242-unit as shown at the bottom of FIG. 8. In this case, three DC tones can be inserted.

[0134] In the example of FIG. 8, various sizes of RUs, namely 26-RU, 52-RU, 106-RU, 242-RU, etc., are exemplified, but the specific size of these RUs may be reduced or expanded. Accordingly, in the present disclosure, the specific size of each RU (i.e., the number of corresponding tones) is not limited and is exemplary. Furthermore, in the present disclosure, within a predetermined bandwidth (e.g., 20, 40, 80, 160, 320 MHz, ...), the number of RUs may vary depending on the RU size. The fact that the size and / or number of RUs may be changed in the examples of FIG. 9 and / or FIG. 10 described below is the same as in the example of FIG. 9.

[0135] FIG. 9 is a diagram showing an exemplary arrangement of resource units (RU) used in the 40 MHz band.

[0136] Just as various sizes of RUs were used in the example of FIG. 8, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, etc., may also be used in the example of FIG. 9. Additionally, 5 DC tones may be inserted at the center frequency, 12 tones may be used as guard bands in the leftmost band of the 40 MHz band, and 11 tones may be used as guard bands in the rightmost band of the 40 MHz band.

[0137] In addition, as described, when used for a single user, the 484-RU can be used.

[0138] FIG. 10 is a diagram showing an exemplary arrangement of resource units (RU) used in the 80 MHz band.

[0139] Just as various sizes of RUs were used in the examples of FIGS. 8 and 9, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, 996-RU, etc., may also be used in the example of FIG. 10. Additionally, in the case of an 80MHz PPDU, the RU arrangement of the HE PPDU and the EHT PPDU may differ, and the example of FIG. 10 shows an example of the RU arrangement for an 80MHz EHT PPDU. In the example of FIG. 10, 12 tones are used as guard bands in the leftmost band of the 80MHz band, and 11 tones are used as guard bands in the rightmost band of the 80MHz band, which is the same for the HE PPDU and the EHT PPDU. Unlike the HE PPDU, where 7 DC tones are inserted into the DC band and there is one 26-RU corresponding to 13 tones on each side of the DC band, the EHT PPDU has 23 DC tones inserted into the DC band and one 26-RU on each side of the DC band. Unlike the HE PPDU, where there is one null subcarrier between 242-RUs outside the center band, there are 5 null subcarriers in the EHT PPDU. In the HE PPDU, one 484-RU does not contain a null subcarrier, but in the EHT PPDU, one 484-RU contains 5 null subcarriers.

[0140] In addition, as described, when used for a single user, the 996-RU can be used, and in this case, the insertion of 5 DC tones is common to both the HE PPDU and the EHT PPDU.

[0141] EHT PPDUs of 160 MHz or higher can be configured as multiple 80 MHz subblocks of FIG. 10. The RU arrangement for each 80 MHz subblock may be the same as the RU arrangement of the 80 MHz EHT PPDU of FIG. 10. When the 80 MHz subblock of a 160 MHz or 320 MHz EHT PPDU is not punctured and the entire 80 MHz subblock is used as part of an RU or MRU (Multiple RU), the 80 MHz subblock may use the 996-RU of FIG. 10.

[0142] Here, an MRU corresponds to a group of subcarriers (or tons) composed of multiple RUs, wherein the multiple RUs constituting the MRU may be RUs of the same size or RUs of different sizes. For example, a single MRU may be defined as 52+26-tons, 106+26-tons, 484+242-tons, 996+484-tons, 996+484+242-tons, 2×996+484-tons, 3×996-tons, or 3×996+484-tons. Here, the multiple RUs constituting a single MRU may correspond to RUs of small size (e.g., 26, 52, 106) or RUs of large size (e.g., 242, 484, 996, etc.). That is, a single MRU containing both small-size RUs and large-size RUs may not be set / defined. In addition, multiple RUs constituting a single MRU may be continuous or non-continuous in the frequency domain.

[0143] If the 80 MHz subblock contains RUs smaller than 996 ton, or if parts of the 80 MHz subblock are punctured, the 80 MHz subblock may use RU batches excluding the 996-ton RU.

[0144] The positions of the RUs can be fixed according to their respective PPDU bandwidths as defined in Tables 1 to 5 below.

[0145] Table 1 illustrates the indices of the RUs within the 20 MHz PPDU, the data for each RU, and the pilot subcarrier indices (ranges).

[0146]

[0147] Table 2 illustrates the indices of the RUs within the 40 MHz PPDU, the data for each RU, and the pilot subcarrier indices (ranges).

[0148]

[0149] Table 3 illustrates the indices of the RUs within the 80MHz PPDU, the data for each RU, and the pilot subcarrier indices (ranges).

[0150]

[0151] Table 4 illustrates the indices of the RUs within the 160 MHz PPDU, the data for each RU, and the pilot subcarrier indices (ranges).

[0152]

[0153]

[0154] Table 5 illustrates the indices of the RUs within the 320 MHz PPDU, the data for each RU, and the pilot subcarrier indices (ranges).

[0155]

[0156]

[0157]

[0158]

[0159] In Table 1, RU 5 corresponds to a middle 26-ton RU.

[0160] Referring to Tables 1 through 5, subcarrier index 0 corresponds to the DC tone. Negative subcarrier indices correspond to subcarriers having frequencies lower than the DC tone. Positive subcarrier indices correspond to subcarriers having frequencies higher than the DC tone. DC subcarriers may refer to subcarriers having zero energy that include the DC tone and subcarrier indices adjacent to subcarrier index 0 (i.e., the DC tone). Guard subcarriers may refer to subcarriers having zero energy that are located at the edge of an OFDM symbol in the frequency domain. Null subcarriers are located near the DC or edge tone to protect against transmission center frequency leakage, receiver DC offset, and interference from adjacent RU(s) or MRU(s), and have zero energy.

[0161] Referring to FIGS. 8 to 10 and Tables 1 to 5, for each RU, RU indices can be assigned in order from low frequency to high frequency.

[0162] PPDUs in the range of 160 MHz or higher may be composed of multiple 80 MHz frequency subblocks. The tone plan and RU allocation for each 80 MHz frequency subblock may be the same as those of the 80 MHz PPDU. If the 80 MHz frequency subblock of a 160 MHz or 320 MHz PPDU is not punctured and the entire 80 MHz frequency subblock is used as an RU or as part of an RU / MRU, the 80 MHz frequency subblock may use the 996-tone RU exemplified in FIG. 9. If the 80 MHz frequency subblock contains fewer than 996 tones of RU, or if part of the 80 MHz frequency subblock is punctured, the 80 MHz frequency subblock may use a tone plan and RU allocation excluding the 996-tone RU as exemplified in FIG. 9.

[0163] Multiple RUs (MRU) can be assigned to an STA. The subcarrier indexes of an MRU can be composed of the indexes of the corresponding RUs that make up the MRU.

[0164] The RU of the present disclosure may be used for uplink (UL) and / or downlink (DL) communication. For example, when trigger-based UL-MU communication is performed, the STA transmitting the trigger (e.g., AP) may assign a first RU (e.g., 26 / 52 / 106 / 242-RU, etc.) to a first STA and assign a second RU (e.g., 26 / 52 / 106 / 242-RU, etc.) to a second STA through trigger information (e.g., a trigger frame or TRS (triggered response scheduling)). Subsequently, the first STA may transmit a first trigger-based (TB) PPDU based on the first RU, and the second STA may transmit a second TB PPDU based on the second RU. The first and second TB PPDUs may be transmitted to the AP in the same time interval.

[0165] For example, when a DL MU PPDU is configured, the STA (e.g., AP) transmitting the DL MU PPDU may allocate a first RU (e.g., 26 / 52 / 106 / 242-RU, etc.) to the first STA and a second RU (e.g., 26 / 52 / 106 / 242-RU, etc.) to the second STA.

[0166] EHT-LTF field

[0167] The EHT-LTF field provides a means for the receiver to estimate the MIMO channel between the set of constellation mapper outputs and the receive chain. In the EHT MU PPDU, the transmitter uses N for the transmission of the PSDU (Physical Layer Service Data Unit)(s) at the r-th RU or MRU. SS,r,total Provides training for spatial streams. The transmitter of user u in the r-th RU or MRU in the EHT TB PPDU is N used for PSDU transmission. SS,r,u It provides training for spatial streams. For each subcarrier of the r-th RU or MRU, the estimable MIMO channels are N. RX × N SS,r,total It is a matrix. EHT transmission includes a preamble containing EHT-LTF symbols, and the data tone of each EHT-LTF symbol is matrix P EHT-LTF It is multiplied with the entries belonging to to enable channel estimation at the receiver. When a single-stream pilot is used in 2× or 4× EHT-LTF, the pilot subcarrier of each EHT-LTF symbol is matrix R EHT-LTFIt is multiplied with the entries of to enable the receiver to track phase and / or frequency offsets when MIMO channel estimation using EHT-LTF. A single stream pilot must be used for all spatial multiplexing modes defined in EHT (both UL and DL), except when 1× EHT-LTF is used. P EHT-LTF It is defined such that each modulated spatial stream of the RU or MRU is activated in all subcarriers where the EHT-LTF sequence of the corresponding RU or MRU has a non-zero value.

[0168] N in EHT MU PPDU EHT-LTF is indicated in the EHT-SIG field. The initial N, which is the initial number of EHT-LTF symbols in a non-OFDMA EHT MU PPDU or EHT sounding NDP. EHT-LTF is the total number of spatial streams N as shown in Table 6 below. SS It is determined by the function of.

[0169] Table 6 shows the initial number of EHT-LTF symbols required for different spatial stream numbers.

[0170]

[0171] To improve MIMO channel estimation upon reception of non-OFDMA EHT MU PPDU or EHT sounding NDP, the number of EHT-LTFs may be greater than the initial number of EHT-LTFs determined by the total number of spatial streams. If additional EHT-LTFs are used, the total number of EHT-LTFs (N SS(signaled separately from) must not exceed twice the initial number of EHT-LTFs determined by the number of spatial streams shown in Table 6 and must be selected from the set {2 4 8}. Additional EHT-LTF support for the receiver is optional and is indicated by the maximum number of supported EHT-LTFs subfield of the EHT PHY capabilities information field.

[0172] For all supported bandwidths and EHT-MCSs within the EHT Capabilities element, the highest N indicated by the STA in the beamformee SS subfield and the supported EHT-MCS and NSS set field SS Based on the value of the maximum number of supported space streams, the maximum number of supported EHT-LTFs must not be smaller than the value shown in Table 6.

[0173] In OFDMA EHT MU PPDU, N EHT-LTF can have a value greater than or equal to the maximum value of the initial EHT-LTF symbol count for each RU or MRU. Here, the initial EHT-LTF symbol count is N based on Table 6. SS,r,total It is calculated as a function of.

[0174] N in EHT TB PPDU EHT-LTF is indicated in the trigger frame that triggers the PPDU transmission. For EHT TB PPDU, N EHT-LTF may be greater than or equal to the maximum value of the initial EHT-LTF symbol count for each RU or MRU r, which is N based on Table 6 SS,r,total It is calculated as a function of.

[0175] EHT PPDU supports three EHT-LTF types: 1× EHT-LTF, 2× EHT-LTF, and 4× EHT-LTF. Table 7 defines whether a specific combination of EHT-LTF type and GI (guard interval) duration is required, optional, or unsupported for each EHT PPDU format.

[0176] Table 7 provides examples of EHT-LTF type and GI duration combinations for various EHT PPDU formats.

[0177]

[0178] In Table 7, M indicates mandatory, O indicates optional, and N / A indicates that it is not supported in the corresponding PPDU format.

[0179] In EHT MU PPDU, the combination of EHT-LTF type and GI duration is specified in the EHT-SIG field. In EHT TB PPDU, the combination of EHT-LTF type and GI duration is specified in the trigger frame that triggers the PPDU transmission. If the EHT PPDU is an EHT sounding NDP, the combination of EHT-LTF type and GI duration is predefined in the standard.

[0180] T EHT-LTF represents the duration of each OFDM symbol without GI within the EHT-LTF field, and T EHT-LTF-1X represents the duration of each 1× EHT-LTF OFDM symbol without GI, and T EHT-LTF-2X represents the duration of each 2× EHT-LTF OFDM symbol without GI, and T EHT-LTF-4X represents the duration of each 4× EHT-LTF OFDM symbol without GI.

[0181] T EHT-LTFis given as in mathematical formula 1 below.

[0182]

[0183] In the case of non-OFDMA transmission where preamble puncturing is applied, a single large size MRU spans the unpunctured portion of the PPDU bandwidth. In the case of puncturing, the values ​​of the EHT-LTF sequence are replaced with 0 for subcarriers that fall outside the aforementioned single large size MRU range.

[0184] In the case of OFDMA transmission, the values ​​of the EHT-LTF sequence are replaced with 0 for all subcarriers, including unassigned or punctured subcarriers, as well as DC tones or null subcarriers.

[0185] FIG. 11 illustrates the generation of EHT-LTF symbols within an EHT MU PPDU and an EHT TB PPDU in a wireless LAN system to which the present disclosure may be applied.

[0186] Figure 11 illustrates the generation of time-domain EHT-LTF symbols, where A EHT-LTF k is given in mathematical formula 2 below.

[0187]

[0188] K in mathematical equation 2 pilot is a set of subcarrier indices for pilot subcarriers. R EHT-LTF is N EHT-LTF × N EHT-LTF It is a matrix, and its elements are defined as shown in Equation 3 below.

[0189]

[0190] P EHT-LTF A matrix is ​​defined as shown in Equation 4 below.

[0191]

[0192] Here, P 4×4 , P6×6 , P 8×8 is defined in mathematical formulas 5, 6, and 7, respectively.

[0193]

[0194]

[0195] Here, w is exp(-j2π / 6).

[0196]

[0197] P in mathematical equation 7 4×4 is defined in mathematical formula 5.

[0198] P EHT-LTF The matrix refers to a linear mapping matrix that defines the mapping between EHT-LTF symbols and transmit streams. This matrix has a size of M×N, where M represents the number of EHT-LTF symbols and N represents the number of transmit spatial streams. Each column of the P matrix corresponds to a single spatial stream, and each row represents a specific time slot or subcarrier position on the EHT-LTF symbol. Furthermore, each element of the P matrix consists of ±1 or complex values, maintaining spatial orthogonality to minimize interference.

[0199] Here, when M=N (i.e., the number of EHT-LTF symbols is equal to the number of transmit space streams), the P matrix corresponds to a square matrix. When M>N (i.e., the number of EHT-LTF symbols is greater than the number of transmit space streams), this may refer to a case where the number of EHT-LTF symbols exceeds the number of transmit space streams due to repetition or extension. In this case, the P matrix corresponds to a rectangular matrix and can be designed to ensure orthogonality mapping. In other words, a single space stream is mapped to multiple LTF symbols, but the design ensures that orthogonality between symbols is maintained.

[0200] The receiver estimates the channel response for each spatial stream based on the received EHT-LTF symbols. A receiver that knows the P matrix can separate and estimate the channel characteristics of each stream by performing an inverse mapping on the received signal.

[0201] Coordinated LTF Configuration Method for Coordinated Beamforming

[0202] Multi-AP transmission technology is a new wireless transmission technology to be defined in next-generation wireless LAN systems (e.g., Wi-Fi 8, 802.11bn). Among these, Coordinated Beamforming (C-BF) is a multi-AP cooperation technology that enables simultaneous transmission by multiple APs by eliminating or reducing interference directed toward STAs of adjacent BSSs, thereby improving system performance (throughput, latency, etc.). For example, each AP can control interference by designing and applying a precoder that can reduce interference directed toward overlapping BSS (OBSS) STAs.

[0203] There are two approaches to C-BF: Full Nulling, which eliminates all interference directed toward the OBSS STA, and Partial Nulling, which eliminates only a portion of the interference. Full Nulling, which eliminates all interference for simultaneous transmission, may seem intuitive. However, fundamentally, nulling consumes the transmission dimension (TX dimension) equal to the dimension being nulled. Therefore, if too many dimensions are consumed for nulling, the Tx dimension available to obtain beamforming gain for the STA within the BSS is reduced, which can lead to performance degradation. Consequently, when Partial Nulling is applied—eliminating only a portion of the interference rather than all of it—system performance can be improved by saving dimensions through partial nulling and utilizing those dimensions for obtaining beamforming gain within the BSS.

[0204] From a data frame perspective, Partial Nulling can yield performance gains through the approach described above. However, if approached from an LTF perspective, since only a portion of the interference is removed, the residual signal of the OBSS AP may interfere with the LTF of the BSS STA during channel estimation, potentially leading to a decrease in channel estimation performance. Since a decline in channel estimation performance can have an effect similar to an increase in noise, potentially degrading the signal-to-interference plus noise ratio (SINR), it is expected that resolving this interference issue will further improve system performance.

[0205] Accordingly, the present disclosure proposes a method to solve the above-mentioned LTF contamination problem. Specifically, a method is proposed in which mutually orthogonal global LTFs are designed and non-overlapping sets of LTF indices are assigned to each AP, thereby enabling each STA to perform channel estimation using the LTFs without mutual interference. In addition, a signaling method for operating such cooperative LTFs is also proposed.

[0206] Coordinated beamforming (Co-BF) enables two APs with multiple antennas to transmit simultaneously to non-AP STAs connected to each of the two APs. Here, each AP transmits PPDU to connected non-AP STAs within its Baseline Service (BSS). Here, by using information about the channel between each AP and the receiving STA of the other AP in the Co-BF transmission, interference to the non-AP STA(s) connected to the other AP can be minimized.

[0207] Hereinafter, an AP that secures a TXOP for operation / transmission of Co-BF (coordinated beamforming) and transmits a frame / signaling for invitation / request to another AP may be referred to as a (Co-BF) coordinating AP, sharing AP, master AP, primary AP, etc., and may be referred to as the first AP (AP 1) for convenience of explanation in the description of the present disclosure below. In addition, an AP that receives a frame / signaling for invitation / request for Co-BF operation / transmission may be referred to as a (Co-BF) coordinated AP, shared AP, slave AP, secondary AP, etc., and may be referred to as the second AP (AP 2) for convenience of explanation in the description of the present disclosure below.

[0208] Additionally, in Co-BF operation, to prevent preamble collisions caused by simultaneous transmission between the first PPDU transmitted by the first AP and the second PPDU transmitted by the second AP, the first PPDU and the second PPDU may include a common preamble (i.e., the same preamble). The aforementioned global P matrix refers to an LTF included within the common preamble, and may refer to a P matrix that is equally applied to the common LTF, and may simply be referred to as a P matrix.

[0209] As described above, in an 802.11 system, mutually orthogonal (e.g., orthogonal between each stream) P matrices are applied to LTF symbols to perform antenna or stream-specific channel estimation without interference between antennas. Conventionally, P matrices are applied to LTF symbols to eliminate interference between one's own antennas (or streams) during transmission within a BSS, but in the present disclosure, a global P matrix is ​​set / designed to take into account all interference coming from an OBSS, and a set of row vectors of mutually orthogonal P matrices (i.e., row vectors of one or more P matrices) can be assigned / assigned to each AP.

[0210] For example, if AP 1 uses 4 streams for PPDU transmission and AP 2 also uses 4 streams for PPDU transmission, according to the conventional method, each AP transmits PPDU by applying the row vector of the P matrix corresponding to each stream to each of the 4 time domain LTF symbols using a 4×4 P matrix (e.g., see Equation 5).

[0211] On the other hand, according to the proposed method of the present disclosure, if the first AP uses four spatial streams for PPDU transmission and the second AP also uses four spatial streams for PPDU transmission in the same manner as above, both the first AP and the second AP can transmit a PPDU containing eight time domain LTF symbols. In this case, four row vectors of the P matrix can be assigned / assigned to the first AP, and the remaining four row vectors of the P matrix can be assigned / assigned to the second AP. For example, in this case, the P matrix can be composed of an 8×8 matrix, and four row vectors from the 1st row to the 4th row can be assigned to the first AP (i.e., a 4×8 matrix), and four row vectors from the 5th row to the 8th row can be assigned to the second AP (i.e., a 4×8 matrix). Alternatively, conversely, four row vectors from the 5th row to the 8th row may be assigned to the first AP, and four row vectors from the 1st row to the 4th row may be assigned to the second AP. However, this is merely an example for convenience of explanation, and in this disclosure, a method in which different row vectors of the P matrix are assigned to different APs may be applied in a different manner. The first AP and the second AP may each apply the assigned / assigned row vectors to generate time-domain LTF symbols in each spatial stream and transmit PPDU. For example, the first AP may apply the four row vectors assigned to it to each of the eight LTF symbols for each of the four spatial streams. That is, each element value of a specific row vector may be applied sequentially to each LTF symbol for a specific spatial stream. Likewise, the second AP may apply the four row vectors assigned to it to each of the eight LTF symbols for each of the four spatial streams. In other words, the value of each element of a specific row vector can be applied sequentially to each LTF symbol for a specific spatial stream.

[0212] For the above operation, the first AP (e.g., coordinating AP, sharing AP) may need to know how many spatial streams the second AP (e.g., coordinated AP, shared AP) intends to transmit in Co-BF transmission. This is because, when determining the size of the same P matrix (e.g., global P matrix, common P matrix) in the PPDU transmitted by the first AP and the second AP respectively in Co-BF operation / transmission, it is necessary to consider the sum of the number of spatial streams of the first AP and the number of spatial streams of the second AP. That is, the second AP can transmit to the first AP the number of spatial streams for the receiving STA(s) of the Co-BF transmission associated with it. In other words, frame exchange between the first AP and the second AP may be performed to execute Co-BF transmission, and in this process, the second AP can transmit to the first AP the number of spatial streams for the receiving STA(s) of the Co-BF transmission associated with it through a specific frame (hereinafter referred to as Frame A).

[0213] Additionally, the second AP (e.g., coordinated AP, shared AP) may also need to know how many spatial streams the first AP (e.g., coordinating AP, sharing AP) intends to transmit in Co-BF transmission. This is because the number of spatial streams of the first AP must be known in order to determine which index corresponds to the row(s) of the P matrix assigned to it. That is, the first AP can transmit the number of spatial streams for the receiving STA(s) of the Co-BF transmission associated with it to the second AP. In other words, frame exchange between the first AP and the second AP may be performed to execute Co-BF transmission, and in this process, the first AP can transmit the number of spatial streams for the receiving STA(s) of the Co-BF transmission associated with it to the second AP through a specific frame (hereinafter referred to as the B frame). Here, the B frame may be transmitted before the reception of the A frame, or it may be transmitted after the reception of the A frame. If Frame B is transmitted prior to the reception of Frame A, Frame A may be transmitted as a response to Frame B.

[0214] Additionally, the second AP (e.g., coordinated AP, shared AP) may need to know the global / common LTF size (i.e., the number of UHR-LTF symbols for Co-BF transmission) determined and announced by the first AP (e.g., coordinating AP, sharing AP) for Co-BF transmission. This is because the global LTF size must be known to determine the LTF length to be transmitted to its own STA. Alternatively, the number of global LTF symbols may be determined by summing the number of spatial streams that the first AP (e.g., coordinating AP, sharing AP) intends to transmit and the number of spatial streams that it intends to transmit (i.e., the second AP (e.g., coordinated AP, shared AP)). In this case, the global LTF size may not be signaled. If the global LTF size (i.e., the number of UHR-LTF symbols for Co-BF transmission) is signaled, it may be transmitted by being included in the aforementioned B frame, or it may be transmitted by being included in a frame separate from the B frame (hereinafter referred to as the C frame). If the above C frame is defined separately from the above B frame, the above C frame may be transmitted after the exchange of the above A frame and the above B frame.

[0215] FIG. 12 is a drawing illustrating a PPDU format according to one embodiment of the present disclosure.

[0216] Referring to FIG. 12, a UHR PPDU that can be used in a UHR system may include some format features of HE TB PPDU and EHT TB PPDU. For example, a UHR PPDU (e.g., UHR TB PPDU) may be configured to include L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, UHR-STF, UHR-LTF(s), and data fields.

[0217] In addition, although not shown in FIG. 12, the UHR PPDU (e.g., UHR MU PPDU) may be configured to include an additional UHR SIG between the U-SIG and UHR-STF.

[0218] In FIG. 12, L-STF, L-LTF, and L-SIG may be referred to as legacy parts, RL-SIG, U-SIG, and UHR-SIG (if included) may be referred to as SIG parts, UHR-STF may be referred to as STF parts, and UHR-LTF may be referred to as LTF parts.

[0219] All or part of all parts (i.e., fields) of FIG. 12 may be divided into multiple subparts / subfields. Each field (and its subfields) may be transmitted in units of 4us * N (where N is an integer). Additionally, it may include a Guard Interval (GI) (or short GI) as defined in conventional wireless LAN systems. A common subcarrier frequency spacing value (delta_f = 312.5 kHz / N or 312.5 kHz * N, where N is an integer) may be applied to all of the illustrated fields, or a first delta_f may be applied to the first part (e.g., all of the legacy part, all / part of the 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.

[0220] Some of the illustrated fields may be omitted, and the order of the fields is illustrated illustratively and may be changed in various ways.

[0221] The SIG part may include various control information for the transmitted PPDU. For example, it may include an STF part, an LTF part, and control information for decoding the data. For example, it may include all or part of the information included in the previously described HE-SIG-A information, information included in the HE-SIG-B information, information included in the U-SIG information, and information included in the EHT-SIG.

[0222] The STF part may include an STF sequence.

[0223] The LTF part may include a training field (i.e., an LTF sequence) for channel estimation.

[0224] The data field contains user data and may include packets for the upper layer. That is, it may include MPDU (MAC Frame).

[0225] For Co-BF transmission, the first PPDU transmitted by the first AP to one or more STA(s) connected to it and the second PPDU transmitted by the second AP to one or more STA(s) connected to it may each be configured in the PPDU format according to FIG. 12 described above, and a common preamble may be constructed for the first PPDU and the second PPDU.

[0226] FIG. 13 illustrates the operation of a first AP for a PPDU transmission and reception method for cooperative beamforming according to one embodiment of the present disclosure.

[0227] FIG. 13 illustrates the operation of a first AP device (e.g., coordinating AP, sharing AP, etc.) based on the previously proposed methods. The example in FIG. 13 is for convenience of explanation and is not intended to limit the scope of the present disclosure. Some step(s) illustrated in FIG. 13 may be omitted depending on the situation and / or configuration.

[0228] The first AP transmits to the second AP a first frame containing information about the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission (S1301).

[0229] Although not illustrated in FIG. 13, the first AP may transmit a second frame to the second AP, and the second frame may include information regarding the number of spatial streams for the Co-BF transmission to the one or more first STAs by the first AP (e.g., information regarding the number of spatial streams for each of the one or more STAs for the Co-BF transmission associated with the first AP).

[0230] Additionally, although not illustrated in FIG. 13, the first AP may receive a third frame from the second AP, and the third frame may include information regarding the number of spatial streams for the Co-BF transmission by the second AP to one or more second STAs associated with the second AP (e.g., information regarding the number of spatial streams for each of the one or more STAs for the Co-BF transmission associated with the second AP).

[0231] Here, the third frame may be received after the second frame has been transmitted. Additionally, the first frame may be transmitted after the third frame has been received.

[0232] The first AP transmits a first PPDU for Co-BF transmission to one or more first STAs connected to the first AP (S1302).

[0233] That is, the first AP and the second AP perform concurrent transmission, and to this end, the first AP transmits a first PPDU for Co-BF transmission to one or more first STAs connected to the first AP, and the second AP transmits a second PPDU for Co-BF transmission to one or more second STAs connected to the second AP.

[0234] Here, the first PPDU may include first UHR-LTF symbols corresponding to the number of UHR-LTF symbols (i.e., information regarding the number of UHR-LTF symbols within the first frame).

[0235] Additionally, the first UHR-LTF symbols of the first PPDU and the second UHR-LTF symbols of the second PPDU for Co-BF transmission by the second AP can be generated based on the same specific P matrix. Here, the size of the specific P matrix can be determined based on the sum of the number of spatial streams for the first AP and the number of spatial streams for the second AP. For example, in the specific P matrix, row vectors equal to the number of spatial streams for the first AP may be applied for the generation of the first UHR-LTF symbols, and the remaining row vectors equal to the number of spatial streams for the second AP may be applied for the generation of the second UHR-LTF symbols.

[0236] The first AP may obtain information regarding a tone plan and / or spatial modulation in order to generate the first PPDU. As described above, information regarding the tone plan may include the size and location of the RU, control information related to the RU, information regarding the frequency band in which the RU is included, information regarding the STA receiving the RU, etc. Additionally, information regarding spatial modulation may include information regarding a combination of specific antennas. When transmitting the TB PPDU, such information may be obtained through a trigger frame.

[0237] In addition, the first AP can configure / generate a PPDU based on the acquired control information. The step of configuring / generating the PPDU may include the step of configuring / generating each field of the PPDU. That is, it may include the step of configuring one or more fields containing control information regarding the Tone Plan (e.g., U-SIG and UHR-SIG-A / B fields). For example, it may include the step of configuring a field containing control information indicating the bandwidth of the PPDU and / or the step of configuring a field containing control information indicating the size / location of the RU / MRU (e.g., N bitmap) and / or the step of configuring a field containing the identifier of the STA receiving the RU / MRU (e.g., AID). In the case of a TB PPDU, only some of the information may be included.

[0238] Additionally, it may include a step of generating an STF / LTF sequence transmitted through a specific RU / MRU. The STF / LTF sequence may be generated based on a pre-configured STF generation sequence / LTF generation sequence. Additionally, it may include a step of determining the number of symbols of the LTF according to spatial modulation information.

[0239] Additionally, it may include a step of generating a data field (i.e., MPDU) transmitted through a specific RU. Additionally, it may include a step of determining an antenna combination to transmit at each subcarrier of the data field according to spatial modulation information.

[0240] According to an embodiment of the present disclosure, the first PPDU may be configured as shown in the example of FIG. 12.

[0241] To transmit the first AP to one or more first STAs, the first AP may perform at least one of the following operations: cyclic shift diversity (CSD), spatial mapping, inverse discrete Fourier transform (IDFT) / inverse fast Fourier transform (IFFT) operation, guard interval (GI) insertion.

[0242] The method described in the example of FIG. 13 can 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 generate a PPDU and transmit the PPDU through transceiver(s) (106). Furthermore, one or more memories (104) of the first device (100) may store instructions for performing the method described in the example of FIG. 13 or the examples described above when executed by one or more processors (102).

[0243] FIG. 14 illustrates the operation of a second AP for a PPDU transmission and reception method for cooperative beamforming according to one embodiment of the present disclosure.

[0244] FIG. 14 illustrates the operation of a second AP device (e.g., coordinated AP, shared AP, etc.) based on the previously proposed methods. The example in FIG. 14 is for convenience of explanation and is not intended to limit the scope of the present disclosure. Some step(s) illustrated in FIG. 14 may be omitted depending on the situation and / or configuration.

[0245] Referring to FIG. 14, the second AP receives a first frame from the first AP containing information about the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission (S1401).

[0246] Although not illustrated in FIG. 14, the second AP may receive a second frame from the first AP, and the second frame may include information regarding the number of spatial streams for the Co-BF transmission by the first AP to one or more first STAs associated with the first AP (e.g., information regarding the number of spatial streams for each of the one or more STAs for the Co-BF transmission associated with the first AP).

[0247] Additionally, although not illustrated in FIG. 14, the second AP may transmit a third frame to the first AP, and the third frame may include information regarding the number of spatial streams for the Co-BF transmission by the second AP to one or more second STAs associated with the second AP (e.g., information regarding the number of spatial streams for each of the one or more STAs for the Co-BF transmission associated with the second AP).

[0248] Here, the third frame may be transmitted after the second frame is received. Additionally, the first frame may be received after the transmission of the third frame.

[0249] The second AP transmits a second PPDU for Co-BF transmission to one or more second STAs connected to the second AP (S1402).

[0250] That is, the first AP and the second AP perform concurrent transmission, and to this end, the first AP transmits a first PPDU for Co-BF transmission to one or more first STAs connected to the first AP, and the second AP transmits a second PPDU for Co-BF transmission to one or more second STAs connected to the second AP.

[0251] Here, the second PPDU may include second UHR-LTF symbols corresponding to the number of UHR-LTF symbols (i.e., information regarding the number of UHR-LTF symbols in the first frame).

[0252] Additionally, the first UHR-LTF symbols of the first PPDU for Co-BF transmission by the first AP and the second UHR-LTF symbols of the second PPDU for Co-BF transmission by the second AP can be generated based on the same specific P matrix. Here, the size of the specific P matrix can be determined based on the sum of the number of spatial streams for the first AP and the number of spatial streams for the second AP. For example, in the specific P matrix, row vectors equal to the number of spatial streams for the first AP may be applied for the generation of the first UHR-LTF symbols, and the remaining row vectors equal to the number of spatial streams for the second AP may be applied for the generation of the second UHR-LTF symbols.

[0253] The second AP may obtain information regarding a tone plan and / or spatial modulation in order to generate the second PPDU. As described above, information regarding the tone plan may include the size and location of the RU, control information related to the RU, information regarding the frequency band in which the RU is included, information regarding the STA receiving the RU, etc. Additionally, information regarding spatial modulation may include information regarding a combination of specific antennas. When transmitting the TB PPDU, such information may be obtained through a trigger frame.

[0254] In addition, the second AP can configure / generate a PPDU based on the acquired control information. The step of configuring / generating a PPDU may include the step of configuring / generating each field of the PPDU. That is, it may include the step of configuring one or more fields containing control information regarding a Tone Plan (e.g., U-SIG and UHR-SIG-A / B fields). For example, it may include the step of configuring a field containing control information indicating the bandwidth of the PPDU and / or the step of configuring a field containing control information indicating the size / location of the RU / MRU (e.g., N bitmap) and / or the step of configuring a field containing the identifier of the STA receiving the RU / MRU (e.g., AID). In the case of a TB PPDU, only some of the information may be included.

[0255] Additionally, it may include a step of generating an STF / LTF sequence transmitted through a specific RU / MRU. The STF / LTF sequence may be generated based on a pre-configured STF generation sequence / LTF generation sequence. Additionally, it may include a step of determining the number of symbols of the LTF according to spatial modulation information.

[0256] Additionally, it may include a step of generating a data field (i.e., MPDU) transmitted through a specific RU. Additionally, it may include a step of determining an antenna combination to transmit at each subcarrier of the data field according to spatial modulation information.

[0257] According to an embodiment of the present disclosure, the second PPDU may be configured as shown in the example of FIG. 12.

[0258] To transmit the second AP to one or more second STAs, at least one of the following operations may be performed: cyclic shift diversity (CSD), spatial mapping, inverse discrete Fourier transform (IDFT) / inverse fast Fourier transform (IFFT) operation, guard interval (GI) insertion.

[0259] The method described in the example of FIG. 14 can 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 a PPDU through transceiver(s) (106) and process the PPDU. Furthermore, one or more memories (204) of the second device (200) may store instructions for performing the method described in the example of FIG. 14 or the examples described above when executed by one or more processors (202).

[0260] In existing wireless LAN systems, each AP performs transmission to the STA connected to it within its own BSS, but unlike this, according to the examples of the present disclosure, multiple APs perform Co-BF transmission (i.e., concurrent transmission by multiple APs), thereby improving throughput and reducing latency, and thus achieving the effect of increasing wireless communication efficiency.

[0261] The embodiments described above are combinations of the components and features of the present disclosure in a specific form. Each component or feature should be considered optional unless otherwise explicitly stated. Each component or feature may be implemented in a form not combined with other components or features. Additionally, it is possible to construct 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 obvious that embodiments may be constructed by combining claims that are not explicitly related in the claims, or that they may be included as new claims by amendment after filing.

[0262] It is obvious to those skilled in the art that the present disclosure may be embodied in other specific forms without departing from the essential features of the present disclosure. Accordingly, the detailed description set forth above should not be interpreted restrictively in all respects and should be considered exemplary. The scope of the present disclosure shall be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present disclosure are included within the scope of the present disclosure.

[0263] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that enable operations according to the methods of various embodiments to be executed on a device or computer, and a non-transitory computer-readable medium on which such software or instructions, etc. are stored and executable on a device or computer. Instructions that may be used to program a processing system to perform the features described in the present disclosure may be stored on or within a storage medium or a computer-readable storage medium, and the features described in the present disclosure may be implemented using a computer program product comprising such a storage medium. The storage medium may include, but is not limited to, high-speed random access memory such as DRAM, SRAM, DDR RAM, or other random access solid-state memory devices, and may 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 may optionally include one or more storage devices located remotely from the processor(s). Memory or alternatively, non-volatile memory device(s) within memory comprises a non-transient computer-readable storage medium. The features described in this disclosure may be stored in any one of the machine-readable media and integrated into software and / or firmware that can control the hardware of a processing system and allow the processing system to interact with other mechanisms utilizing results according to the embodiments of this disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0264] Although the method proposed in this disclosure has been described with an example applied to an IEEE 802.11-based system, it can be applied to various wireless LANs or wireless communication systems in addition to IEEE 802.11-based systems.

Claims

1. A method performed by a first access point (AP) in a wireless LAN system, wherein the method comprises: A step of transmitting a first frame to a second AP, wherein the first frame includes information regarding the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission; and The method includes the step of transmitting a first PPDU (physical protocol data unit) for Co-BF transmission to one or more first stations (STA) connected to the first AP. A method in which the first PPDU comprises first UHR-LTF symbols corresponding to the number of UHR-LTF symbols.

2. In Paragraph 1, It further includes the step of transmitting a second frame to the second AP, and A method in which the second frame comprises information about the number of spatial streams for the Co-BF transmission to one or more first STAs by the first AP.

3. In Paragraph 2, It further includes the step of receiving a third frame from the second AP, and A method in which the third frame comprises information on the number of spatial streams for the Co-BF transmission to one or more second STAs associated with the second AP by the second AP.

4. In Paragraph 3, A method in which the third frame is received after the second frame is transmitted.

5. In Paragraph 4, A method in which the first UHR-LTF symbols of the first PPDU and the second UHR-LTF symbols of the second PPDU for Co-BF transmission to one or more second STAs associated with the second AP by the second AP are generated based on the same specific P matrix.

6. In Paragraph 5, A method in which the size of a specific P matrix is ​​determined based on the sum of the number of spatial streams for the first AP and the number of spatial streams for the second AP.

7. In Paragraph 6, A method in which, in the aforementioned specific P matrix, row vectors equal to the number of spatial streams for the first AP are applied for the generation of the first UHR-LTF symbols, and the remaining row vectors equal to the number of spatial streams for the second AP are applied for the generation of the second UHR-LTF symbols.

8. In a first access point (AP) device in a wireless LAN system, the first AP device comprises: One or more transceivers; and It includes one or more processors connected to the above one or more transmitters and receivers, and The above one or more processors are: Transmit a first frame to a second AP, wherein the first frame includes information regarding the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission; and It is configured to transmit a first PPDU (physical protocol data unit) for Co-BF transmission to one or more first stations (STA) connected to the first AP, and The first AP device, wherein the first PPDU comprises first UHR-LTF symbols corresponding to the number of UHR-LTF symbols.

9. A method performed by a second access point (AP) in a wireless LAN system, A step of receiving a first frame from a first AP, wherein the first frame includes information regarding the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission; and The method includes the step of transmitting a second PPDU (physical protocol data unit) for Co-BF transmission to one or more second stations (STA) connected to the second AP, and A method in which the second PPDU comprises second UHR-LTF symbols corresponding to the number of UHR-LTF symbols.

10. In a second access point (AP) device in a wireless LAN system, the second AP device comprises: One or more transceivers; and It includes one or more processors connected to the above one or more transmitters and receivers, and The above one or more processors are: A first frame is received from a first AP, wherein the first frame includes information regarding the number of UHR-LTF (ultra high reliability-long training field) symbols for coordinated beamforming (Co-BF) transmission; and The second AP is configured to transmit a second PPDU (physical protocol data unit) for Co-BF transmission to one or more second stations (STA) connected to the second AP, and The second AP device, wherein the second PPDU comprises second UHR-LTF symbols corresponding to the number of UHR-LTF symbols.

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