Method and apparatus for feeding back channel information on basis of beamforming in wireless LAN system

Abstract

A method for operating in a wireless LAN system, of the present disclosure, comprises the steps of: receiving, by a first STA, a null data physical layer protocol data unit (NDP) announcement frame from a second STA; receiving an NDP on the basis of the NDP announcement frame; and transmitting a report frame comprising a first channel feedback matrix based on the NDP, wherein the NDP announcement frame comprises a first subfield related to whether a partial overlapping basic service set (OBSS) channel feedback matrix is requested and a second subfield related to the number of columns of the partial OBSS channel feedback matrix.

Description

Method and device for feeding back channel information based on beamforming in a wireless LAN system

[0001] The present disclosure relates to a communication operation in a wireless local area network (WLAN) system, and more particularly, to a method and device for feeding back channel information based on beamforming in a next-generation wireless LAN system.

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

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

[0004] The technical problem of the present disclosure is to provide a method and device for feeding back channel information based on beamforming in a wireless LAN system.

[0005] The technical problem of the present disclosure is to provide a method and device for sounding a part of a channel vector for partial nulling.

[0006] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0007] A method according to one embodiment of the present disclosure comprises the steps of: receiving, by a first station (STA), a null data physical layer protocol data unit (NDP) announcement frame from a second STA; receiving, by the first STA, an NDP from the second STA based on the NDP announcement frame; and transmitting, by the first STA, to the second STA, a report frame including a first channel feedback matrix based on the NDP, wherein the NDP announcement frame may include a first subfield related to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested and a second subfield related to the number of columns of the partial OBSS channel feedback matrix.

[0008] According to another embodiment of the present disclosure, a method includes the steps of: transmitting a null data physical layer protocol data unit (NDP) announcement frame by a second station (STA) to a first STA; transmitting an NDP by the second STA to the first STA based on the NDP announcement frame; and receiving, by the second STA, a report frame including a first channel feedback matrix based on the NDP from the first STA, wherein the NDP announcement frame may include a first subfield related to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested and a second subfield related to the number of columns of the partial OBSS channel feedback matrix.

[0009] According to various embodiments of the present disclosure, a method and device for feeding back channel information based on beamforming in a wireless LAN system can be provided.

[0010] According to various embodiments of the present disclosure, a method and apparatus for sounding a portion of a channel vector for partial nulling may be provided.

[0011] According to various embodiments of the present disclosure, resource efficiency can be improved by performing sounding on required channel column vectors.

[0012] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0013] The accompanying drawings, which are incorporated in and are part of the detailed description to aid in understanding the present disclosure, provide embodiments of the present disclosure and, together with the detailed description, describe the technical features of the present disclosure.

[0014] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0015] FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0016] FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0017] FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0018] FIG. 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0019] FIG. 6 is a drawing for explaining an example of a frame structure used in a wireless LAN system to which the present disclosure can be applied.

[0020] FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0021] Figure 8 is a drawing for explaining the configuration of an NDP notice frame to which the present disclosure can be applied.

[0022] FIG. 9 is a flowchart illustrating a method performed by a first STA according to one embodiment of the present disclosure.

[0023] FIG. 10 is a flowchart illustrating a method performed by a second STA according to one embodiment of the present disclosure.

[0024] FIG. 11 is a diagram for explaining an STA information field and a MIMO control field of an NDP announcement frame according to one embodiment of the present disclosure.

[0025] FIG. 12 is a diagram for explaining a PPDU transmission and reception procedure between a transmitting STA and a receiving STA according to one embodiment of the present disclosure.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0048] If we do not consider the DS illustrated in Figure 2, the most basic type of BSS in a wireless LAN is an Independent BSS (IBSS). For example, an IBSS can have a minimal form consisting of only two STAs. For example, assuming other components are omitted, BSS1 consisting of only STA1 and STA2, or BSS2 consisting of only STA3 and STA4, can be representative examples of an IBSS, respectively. Such a configuration is possible when the STAs can communicate directly without an AP. Furthermore, in this type of WLAN, a LAN can be configured when needed rather than being planned in advance, and this can be called an ad-hoc network. Since an IBSS does not include an AP, there is no centralized management entity. That is, in an IBSS, STAs are managed in a distributed manner. In IBSS, all STAs can be mobile STAs, and access to distributed systems (DS) is not permitted, forming a self-contained network.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0092] The SIG field may include various information related to PPDU transmission and reception. For example, the L-SIG field may consist of 24 bits and may include a 4-bit Rate field, a 1-bit Reserved bit, a 12-bit Length field, a 1-bit Parity field, and a 6-bit Tail field. The RATE field may include information about the modulation and coding rate of data. For example, the 12-bit Length field may include information about the length or time duration of the PPDU. For example, the value of the 12-bit Length field may be determined based on the type of the PPDU. For example, for a non-HT, HT, VHT, or EHT PPDU, the value of the Length field may be determined as a multiple of 3. For example, for HE PPDU, the value of the Length field can be determined as a multiple of 3 + 1 or a multiple of 3 + 2.

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

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

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

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

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

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

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

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

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

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

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

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

[0105] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated to allow legacy STAs to attempt demodulation and decoding, and mapped based on a predetermined subcarrier frequency interval (e.g., 312.5 kHz). These can be referred to as pre-EHT modulated fields. Next, the EHT-STF, EHT-LTF, Data, and PE fields can be encoded and modulated to allow STAs that have successfully decoded non-legacy SIGs (e.g., U-SIG and / or EHT-SIG) and obtained the information contained in the fields, and mapped based on a predetermined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

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

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

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

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

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

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

[0112] For example, the version-independent bits of the U-SIG may include a 3-bit PHY version identifier, which may indicate the PHY version (e.g., EHT, UHR, etc.) of the transmitted and received PPDUs. The version-independent bits of the U-SIG may include a 1-bit UL / DL flag field. The first value of the 1-bit UL / DL flag field relates to UL communication, and the second value of the UL / DL flag field relates to DL communication. The version-independent bits of the U-SIG may include information about the length of a transmission opportunity (TXOP) and information about a BSS color ID.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0127] NDP Notice Frame

[0128] In a wireless LAN system, a sounding procedure / protocol is used to determine channel state information. A beamformer STA requesting channel state information can transmit a training signal to beamformee STA(s). The beamformee STA can measure the channel using the training signal (e.g., sounding NDP) and feed back an estimate of the channel state to the beamformer STA. The beamformer STA can derive a steering matrix or beamforming matrix using the received estimate.

[0129] A beamforming STA can provide feedback on channel status estimates to the beamformer STA via a compressed beamforming / CQI (channel quality indication) reporting frame. The information provided may include single-user (SU) feedback, multi-user (MU) feedback, and CQI feedback.

[0130] The beamformer STA may transmit an NDP announcement and an NDP to the beamformee(s), and receive feedback information from the beamformee STA(s). Additionally or alternatively, the beamformer STA may transmit an NDP announcement and an NDP to the beamformee(s), and transmit a beamforming report poll (BFRP) or a BFRP trigger to the beamformee(s), and receive feedback information from the beamformee(s).

[0131] The NDP Announcement (NDPA) frame can have multiple types / variants. For example, the NDP Announcement frame can be composed of various formats such as the VHT NDP Announcement frame, the HE NDP Announcement frame, and the EHT NDP Announcement frame. These formats can be distinguished by the NDP Announcement Variant subfield within the Sounding Dialog Token field.

[0132] Figure 8 illustrates an exemplary format of an NDP announcement frame to which the present disclosure can be applied.

[0133] An NDP announcement frame may contain one or more STA information (Info) fields. If the NDP announcement frame contains only one STA Info field, the RA (receiver address) field may be set to the address of an STA capable of providing feedback. If the NDP announcement frame contains multiple STA Info fields, the RA field may be set to a broadcast address.

[0134] The TA (transmitter address) field may be set to the address of the STA transmitting the NDP announcement frame, or may be set to the bandwidth signaling TA of the STA transmitting the NDP announcement frame. For example, in a non-HT or non-HT duplicate format, if the scrambling sequence (or the scrambling sequence and service field) includes parameters for the channel bandwidth, the TA field may be set to the bandwidth signaling TA.

[0135] Among the eight bits (B0-B7) of the Sounding Dialog Token field, the first two bits (B0 and B1) can be used to indicate the type / variant of the NDP announcement frame. For example, for VHT or HE, B0 can have a value of 0, and if the value of B1 is 0, it can indicate a VHT NDP announcement frame, and if the value of B1 is 1, it can indicate a HE NDP announcement frame. For example, an EHT NDP announcement frame can correspond to the case where the values ​​of B0 and B1 are both set to 1. If the value of B0 is 1 and the value of B1 is 0, it can correspond to a ranging NDP announcement frame.

[0136] For VHT STA, the first two bits (B0 and B1) of the Sounding Dialog Token field are defined as reserved, so VHT STA can recognize the Sounding Dialog Token Number field of bits B2-B7 regardless of the values ​​of B0 and B1.

[0137] For VHT STAs, the first two bits (B0 and B1) of the Sounding Dialog Token field are defined as reserved. Therefore, VHT STAs can recognize the Sounding Dialog Token Number field of bits B2-B7, regardless of the values ​​of B0 and B1.

[0138] For HE STA, the first bit (B0) of the Sounding Dialog Token field is defined as reserved, and if the value of the second bit (B1) is 0, it indicates a VHT NDP announcement frame, and if the value of B1 is 1, it indicates a HE NDP announcement frame. Therefore, HE STA can recognize the Sounding Dialog Token Number field of bits B2-B7 when the value of B1 is 1, regardless of the value of B0.

[0139] The Sounding Dialog Token Number subfield (bit positions B2-B7) may contain a value to identify the NDP announcement frame selected by the beamformer.

[0140] An NDP announcement frame may contain n STA Info fields, where n is an integer greater than or equal to 1. A single STA Info field has a size of K octets, where K=2 for a VHT NDP announcement frame and K=4 for a HE NDP announcement frame or an EHT NDP announcement frame.

[0141] As in the example of Fig. 8(a), the STA Info field of the VHT NDP announcement frame may include AID12, feedback type, and Nc index subfields.

[0142] The AID12 subfield contains the 12 least significant bits (LSBs) of the AID of the STA that is expected to process the subsequent NDP and prepare sounding feedback.

[0143] The feedback type subfield indicates the type of feedback required, with a value of 0 corresponding to SU and a value of 1 corresponding to MU.

[0144] The Nc index subfield indicates the number of columns (i.e., Nc) in the compressed beamforming feedback matrix minus 1 (i.e., Nc-1) when the feedback type is MU. In the case of SU, the Nc index field is reserved.

[0145] The example in Fig. 8(b) shows the format of the STA Info field of the HE NDP announcement frame when the value of the AID11 field is not a specific value (e.g., 2047).

[0146] A value of the AID11 subfield other than a specific value (e.g., 2047) contains the 11 LSBs of the AID of the STA that is expected to process the subsequent NDP and prepare sounding feedback.

[0147] The partial bandwidth information (partial BW Info) subfield may include a 7-bit (B0-B6) RU start index and a 7-bit (B7-B13) RU end index. The RU index may be determined according to the bandwidth of the NDP announcement frame, and its unit may be a 26-tone RU. For example, to indicate a 26-tone RU index X, the value of the start / end RU index subfield may be set to X-1.

[0148] The feedback type and Ng subfield, in combination with the codebook size subfield, may indicate whether SU / MU / CQI feedback is requested, Ng=4 or 16, and quantization resolution for trigger-based (TB) sounding. For non-TB sounding, the feedback type and Ng subfield and the codebook size subfield may indicate SU or CQI.

[0149] The disambiguation subfield may be set to 1 to help non-HE STAs (e.g., VHT STAs) avoid misinterpreting the field as an AID field.

[0150] The Nc subfield is set to a value of Nc-1. When the feedback type is SU or MU, Nc corresponds to the number of columns in the compressed beamforming feedback matrix, and when the feedback type is CQI, Nc may correspond to the number of STSs (space-time streams). For NDP announcement frames that have AID11 subfield values ​​other than 2047 and are individually addressed to a single STA, the Nc subfield may be reserved.

[0151] The example in Fig. 8(c) shows the format of the STA Info field of the HE NDP announcement frame when the value of the AID11 field is a specific value (e.g., 2047).

[0152] The disallowed subchannel bitmap subfield indicates the 20 MHz subchannel(s) and 242-tone RU(s) present in the sounding NDPs announced by the NDP announcement frame, and the 242-tone RU(s) to be included in the requested sounding feedback. The lowest numbered bit of the disallowed subchannel bitmap corresponds to the 20 MHz subchannel with the lowest frequency among all 20 MHz subchannels within the BSS bandwidth. Each subsequent bit in the bitmap corresponds to the next higher 20 MHz subchannel. A bit set to 1 in the bitmap may indicate that no energy is present in the sounding NDP associated with the NDP announcement frame. For each disallowed 20 MHz subchannel, the 242-tone RU that is closest in frequency to that 20 MHz subchannel may be disallowed for PPDUs using that particular tone plan. STA(s) addressed by the NDP announcement frame shall not include tones from disallowed 242-tone RUs when determining the average SNR of STS 1 through Nc in generating the requested sounding feedback. If a 20 MHz subchannel and its corresponding 242-tone RU are allowed, the corresponding bit in the bitmap shall be set to 0.

[0153] The example in Fig. 8(d) shows the format of the STA Info field of the EHT NDP announcement frame.

[0154] Basically, the AID11 subfield contains the identifier of the STA that is expected to process the subsequent NDP and prepare sounding feedback.

[0155] The partial bandwidth (BW) subfield may include a 1-bit (B0) resolution subfield and an 8-bit (B1-B8) feedback bitmap. The resolution subfield indicates the resolution bandwidth (e.g., 20 MHz or 40 MHz) for each bit of the feedback bitmap subfield. The feedback bitmap subfield may indicate a request for each resolution bandwidth from low to high frequency, with the first bit (B1) of the bitmap corresponding to the lowest resolution bandwidth. Each bit of the feedback bitmap is set to 1 if feedback is requested for the corresponding resolution bandwidth.

[0156] If the bandwidth of the EHT NDP announcement frame is less than 320 MHz, a resolution of 20 MHz can be indicated by setting the value of the resolution bit (B0) to 0.

[0157] When the bandwidth of the EHT NDP announcement frame is 20 MHz, B1 is set to 1 to indicate that feedback for a 242-tone RU is requested, and B2-B8 are reserved and can be set to 0.

[0158] When the bandwidth of the EHT NDP announcement frame is 40 MHz, B1 and B2 indicate that feedback is requested from each of the two 242-tone RUs from low to high frequency, and B3-B8 are reserved and can be set to 0.

[0159] If the bandwidth of the PPDU carrying the EHT NDP announcement frame is 80 MHz, B0 can be set to 0 to indicate a resolution of 20 MHz. If B1-B4 are all set to 1, this can indicate that feedback is requested for the 996-tone RU. Otherwise, B1-B4 can indicate that feedback is requested for each of the four 242-tone RUs from low to high frequency, and B5-B8 can be reserved and set to 0.

[0160] When the bandwidth of the PPDU carrying the EHT NDP announcement frame is 160 MHz, B0 can be set to 0 to indicate a resolution of 20 MHz. If B1-B4 are all set to 1, this can indicate that feedback is requested for the lower 996-tone RU, otherwise B1-B4 can indicate that feedback is requested for each of the four 242-tone RUs from low to high frequency in the lower 80 MHz. If B5-B8 are all set to 1, this can indicate that feedback is requested for the upper 996-tone RU, otherwise B5-B8 can indicate that feedback is requested for each of the four 242-tone RUs from low to high frequency in the upper 80 MHz.

[0161] When the bandwidth of the PPDU carrying the EHT NDP announcement frame is 320 MHz, B0 may be set to 1 to indicate a resolution of 40 MHz. If both B1 and B2 are set to 1, this may indicate that feedback is requested for the first 996-tone RU, otherwise B1 and B2 may indicate that feedback is requested for each of two 484-tone RUs from low to high frequency in the first 80 MHz. If both B3 and B4 are set to 1, this may indicate that feedback is requested for the second 996-tone RU, otherwise B3 and B4 may indicate that feedback is requested for each of two 484-tone RUs from low to high frequency in the second 80 MHz. If both B5 and B6 are set to 1, this may indicate that feedback is requested for the third 996-tone RU, otherwise B5 and B6 may indicate that feedback is requested from each of two 484-tone RUs from low to high frequency in the third 80 MHz. If both B7 and B8 are set to 1, this may indicate that feedback is requested for the fourth 996-tone RU, otherwise B7 and B8 may indicate that feedback is requested from each of two 484-tone RUs from low to high frequency in the fourth 80 MHz. The feedback tone set for each 484-tone RU may consist of the feedback tone sets of two 242-tone RUs that overlap with the 484-tone RU.

[0162] For TB sounding, the feedback type and Ng subfields and the codebook size subfield can be set according to examples such as Table 1.

[0163]

[0164] For non-TB sounding, the feedback type and Ng subfields and the codebook size subfield can be set according to examples as shown in Table 2.

[0165]

[0166] The disambiguation subfield may be set to 1 to help non-EHT STAs (e.g., VHT STAs) avoid misinterpreting the field as an AID field.

[0167] In the EHT NDP announcement frame, RA is set to a broadcast address, and the following may apply. If the Feedback Type and Ng subfield and the Codebook Size subfield indicate SU or MU, the Nc index subfield is set to a value of Nc-1, where Nc corresponds to the number of columns in the compressed beamforming feedback matrix, and values ​​greater than 7 in the Nc index subfield are reserved. If the Feedback Type and Ng subfield and the Codebook Size subfield indicate CQI, the Nc index subfield is set to a value of Nc-1, where Nc corresponds to the number of STSs (space-time streams), and values ​​greater than 7 in the Nc index subfield are reserved. There may be more than one STA Info field.

[0168] In an EHT NDP announcement frame with a single STA Info field, the RA field is set to an individual address and the Nc index subfield may be reserved.

[0169] Beamforming-based procedures

[0170] SU-MIMO and DL MU-MIMO beamforming are techniques used by STAs with multiple antennas to steer signals using channel knowledge to improve throughput. When SU-MIMO beamforming is used, all spatial streams of the transmitted signal may be intended to be received by a single STA within an RU or MRU. When DL MU-MIMO beamforming is used, separate subsets of the spatial streams may be intended to be received by multiple STAs within an RU or MRU with a size of 242 tones or greater.

[0171] Coordinated transmission technologies can be applied to improve communication quality through cooperative transmission between multiple APs in next-generation wireless LAN systems. Among various types of coordinated transmission technologies, coordinated beamforming (C-BF) technology improves transmission capacity through a cooperative procedure that applies precoding to control interference toward overlapping base station service (BSS) (OBSS) at the physical layer.

[0172] Precoding techniques that reduce or eliminate interference directed to STA(s) within an overlapping BSS (OBSS) by considering the interference channel applied to the STA(s) within the OBSS can facilitate simultaneous transmission. Therefore, sounding and feedback procedures for the downlink channel directed to OBSS STAs can be crucial for C-BF technology.

[0173] C-BF related precoding techniques may include a full nulling technique that removes all interference directed to the OBSS STA and a partial nulling technique that removes only some of the interference directed to the OBSS STA.

[0174] If all interference directed toward the OBSS is eliminated through full nulling, OBSS STAs can decode downlink packets from the OBSS AP without interference. However, interference removal consumes transmission dimensions, and removing all interference can consume a significant amount of transmission dimensions. Consequently, there may be a problem in that beamforming gain toward STAs within the BSS is not sufficiently secured.

[0175] Therefore, the partial nulling precoder can perform nulling on only a portion of the interference directed to the OBSS STA, and the remaining dimensions can be used to obtain beamforming gain within the BSS. Accordingly, OBSS interference can be reduced while sufficient beamforming gain can be obtained.

[0176] From the perspective of OBSS sounding, which is necessary for applying interference control precoding, full nulling, which eliminates all interference, requires information about the channel heading to the OBSS STA. However, partial nulling only removes some interference, so information about the entire channel is not required. Below, we describe a method for reducing feedback overhead by feeding back only a portion of the channel heading to the OBSS STA when partial nulling is applied.

[0177] Specifically, for basic wireless LAN systems, a method of sounding and feedback can be applied to some channels in the frequency domain. For improved wireless LAN systems, a method of sounding and feedback can be applied to only some channels in the spatial domain for some spatial streams. Below, a signaling method for feedback and sounding only some channels in the spatial domain will be described.

[0178] FIG. 9 is a flowchart illustrating a method performed by a first STA according to an embodiment of the present disclosure. In FIGS. 9 and 10 , each of the first STA and the second STA may be either an AP or a non-AP STA. In the following, it is assumed, but not limited to, that the second STA is an AP and the first STA is a non-AP STA associated with the AP (e.g., a non-AP STA belonging to the BSS of the second STA).

[0179] The first STA can receive a null data physical layer protocol data unit (PPDU) announcement frame from the second STA (S910).

[0180] For example, an NDP announcement frame may include a first subfield (e.g., a partial OBSS sounding subfield) that relates to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested, and a second subfield (e.g., a nulling depth subfield) that relates to the number of columns of the partial OBSS channel feedback matrix.

[0181] For example, based on the first subfield value being set to a first number (e.g., 1 or 0), this may mean that the second STA requests a partial OBSS channel feedback matrix. Accordingly, the first STA may generate a first channel feedback matrix including the partial OBSS channel feedback matrix. Based on the first subfield value being set to a second number (e.g., 0 or 1), this may mean that the second STA requests a full OBSS channel feedback matrix. Accordingly, the first STA may generate a first channel feedback matrix including the full OBSS channel feedback matrix.

[0182] For example, the number of columns in the partial OBSS channel feedback matrix may be equal to the number of columns set by the second subfield. Additionally, the NDP announcement frame may include a third subfield (e.g., an Nc index subfield) related to the number of columns in the channel feedback matrix.

[0183] For example, the number of columns of the channel feedback matrix set by the third subfield and the number of columns of the partial OBSS channel feedback matrix set by the second subfield may be different, but are not limited thereto. For example, when the number of columns of the channel feedback matrix set by the third subfield and the number of columns of the partial OBSS channel feedback matrix set by the second subfield are different, the first subfield may be omitted on the NDP announcement frame.

[0184] And, among at least one STA information field of the NDP announcement frame, the first STA information field related to the first STA may include a first subfield, a second subfield, and a third subfield. As an example, the first STA information field may include a fourth subfield (e.g., a feedback type and an Ng subfield) indicating multi-user (MU) type feedback. The fourth subfield may include a decomposition diagram of a first channel feedback matrix based on the NDP.

[0185] The first STA can receive NDP from the second STA based on the NDP announcement frame (S920).

[0186] After receiving the NDP announcement frame, the first STA may receive an NDP for a sounding procedure from the second STA. The first STA may perform a channel sounding procedure via the NDP. The first STA may generate a first channel feedback matrix by performing a measurement operation for the NDP.

[0187] The first STA can transmit a report frame including a first channel feedback matrix based on NDP to the second STA (S930).

[0188] For example, the first STA may generate a first channel feedback matrix based on the first subfield, the second subfield, the third subfield, and / or the fourth subfield of the NDP announcement frame.

[0189] For example, the reporting frame may include a MIMO (Multiple Input Multiple Output) control field. The MIMO control field may include a fifth subfield (e.g., a partial OBSS sounding subfield) related to whether a first channel feedback matrix included in the reporting frame is a partial OBSS channel feedback matrix, and a sixth subfield (e.g., a nulling depth subfield) related to the number of columns of the first channel feedback matrix.

[0190] Additionally or alternatively, the report frame may include a compressed beamforming report field, and the compressed beamforming report field may include a first channel feedback matrix including per-subcarrier channel information.

[0191] Additionally, the reporting frame may include an MU-exclusive beamforming reporting field, and the MU-exclusive beamforming reporting field may include an eigenvalue matrix containing eigenvalues ​​of each stream for each subcarrier. In this case, the number of streams for each subcarrier may be equal to the number of columns indicated by the sixth subfield.

[0192] The method described in the example of FIG. 9 may be performed by the first device (100) of FIG. 1. For example, one or more processors (102) of the first device (100) of FIG. 1 may receive an NDP announcement frame from a second STA through one or more transceivers (106). The one or more processors (102) may receive an NDP from the second STA through one or more transceivers (106) based on the NDP announcement frame. The one or more processors (102) may transmit a report frame including a first channel feedback matrix based on the NDP to the second STA through one or more transceivers (106).

[0193] Furthermore, one or more memories (104) of the first device (100) may store commands for performing the method described in the example of FIG. 9 or the examples described below when executed by one or more processors (102).

[0194] FIG. 10 is a flowchart illustrating a method performed by a second STA according to one embodiment of the present disclosure.

[0195] The second STA may transmit an NDP announcement frame to the first STA (S1010). For example, the second STA may transmit an NDP announcement frame to the first STA within the BSS for a sounding procedure. The second STA may transmit to the first STA whether to request a partial OBSS channel feedback matrix and / or information related to the OBSS channel feedback matrix via the NDP announcement frame. The configuration of the NDP announcement frame has been described with reference to FIG. 9, so a duplicate description will be omitted.

[0196] The second STA can transmit NDP to the first STA based on the NDP announcement frame (S1020).

[0197] In addition, the second STA can receive a report frame including a first channel feedback matrix based on NDP from the first STA (S1030). The configuration of the report frame has been described with reference to FIG. 9, so a redundant description will be omitted.

[0198] The method described in the example of FIG. 10 may be performed by the second device (200) of FIG. 1. For example, one or more processors (202) of the second device (200) of FIG. 1 may transmit an NDP announcement frame to a first STA via one or more transceivers (206). The one or more processors (202) may transmit an NDP to the first STA via one or more transceivers (206) based on the NDP announcement frame. The one or more processors (202) may receive a report frame including a first channel feedback matrix based on the NDP from the first STA via one or more transceivers (206).

[0199] Furthermore, one or more memories (204) of the second device (200) may store instructions for performing the method described in the example of FIG. 10 or the examples described below when executed by one or more processors (202).

[0200] In the following, we specifically describe an explicit signaling method (Example 1) and an implicit method (Example 2) for providing feedback and sounding for only some channels in the spatial domain.

[0201] Example 1

[0202] Example 1 relates to an explicit signaling method for feedback and sounding only some channels in the spatial domain.

[0203] As an example of the present disclosure, as illustrated in (a) of FIG. 11, in a situation where OBSS sounding is performed to apply partial nulling, the STA information field of the UHR NDP announcement frame may include a partial OBSS sounding (sub)field and a nulling depth (sub)field. However, this is only one embodiment, and the names of the above-described (sub)fields may be changed.

[0204] The Partial OBSS Sounding subfield is a field that indicates that the NDP announcement frame directed to the STA requests information about only some columns of the OBSS channel matrix for the purpose of partial nulling.

[0205] As described above, the partial OBSS sounding subfield may explicitly request information about only some columns of the OBSS channel matrix, but is not limited thereto. For example, if the Nc value and the nulling depth value in the same STA information field are the same, this may indicate a basic sounding procedure, and if the Nc value and the nulling depth value in the same STA information field are different, this may indicate that partial sounding (e.g., a method of sounding and feeding back channels for only some spatial streams in the spatial domain) is performed. Here, the Nc value may be indicated by the Nc index subfield of the corresponding STA information field.

[0206] The nulling depth subfield may indicate a value of a dimension to be used for nulling purposes among the OBSS channel matrices. For example, assume that the channel matrix is ​​2 by 8 and the beamforming feedback matrix corresponding to the channel matrix is ​​8 by 2. In this case, if the nulling depth value is set to 1, this may mean that the first column of the beamforming feedback matrix is ​​requested. In other words, this may mean that the STA (e.g., AP) that transmitted the NDP announcement frame requests an 8 by 1 beamforming feedback matrix.

[0207] For example, the nulling depth subfield can be set to 3 bits to indicate a value of one of 1 to 8. If the nulling depth subfield value is set to n, this can request that only the first n column vectors of the beamforming feedback matrix be fed back.

[0208] Example 1-1

[0209] The target STA(s) that receive the NDP announcement frame described in Example 1 can generate a channel feedback matrix based on the Nc value and the nulling depth value. After generating the channel feedback matrix, the target STA(s) can transmit a UHR compressed beamforming / CQI action frame (including the channel feedback matrix) to the AP. The following describes the configuration of the (action) frame transmitted by the target STA(s).

[0210] As an example of the present disclosure, the (action) frame transmitted by the target STA(s) may include a MIMO control field, a UHR compressed beamforming report field, a UHR MU exclusive beamforming report field, and a UHR CQI report field.

[0211] For example, as illustrated in (b) of FIG. 11, the MIMO control field may include an Nc index subfield, an Nr index subfield, a BW subfield, a grouping subfield, a feedback type subfield, a remaining feedback segment subfield, a first feedback segment subfield, a partial BW information subfield, a sounding dialog token number field, a codebook information subfield, a partial OBSS sounding subfield, a nulling depth subfield, etc.

[0212] Here, the BW subfield may indicate the bandwidth of a sounding NDP (e.g., an NDP transmitted to the target STA(s) for sounding operation after transmitting an NDP announcement frame). That is, the bit value of the BW subfield may correspond to the bandwidth of the sounding NDP. For example, bit values ​​0, 1, 2, 3, or 4 in the BW subfield may each represent 20, 40, 80, 160, or 320 MHz as the bandwidth of the sounding NDP, respectively. As described above, a partial BW information subfield may also be added to the MIMO control field.

[0213] The feedback type subfield can indicate the feedback type. For example, if the bit value of the feedback type subfield is 0, the feedback type is indicated as SU, if the bit value of the feedback type subfield is 1, the feedback type is indicated as MU, and if the bit value of the feedback type subfield is 2, the feedback type can be indicated as CQI.

[0214] The Nc index subfield indicates the number of columns (i.e., Nc) in the compressed beamforming feedback matrix minus 1 (i.e., Nc-1) when the feedback type is SU or MU. The Nc index subfield indicates the number of spatial streams in the CQI report when the feedback type is CQI and may be set to Nc-1. Nc index subfield values ​​greater than or equal to 7 may be reserved.

[0215] The Nr index subfield indicates the number of rows (i.e., Nr) in the compressed beamforming feedback matrix minus 1 (i.e., Nr-1) when the feedback type is SU or MU. The Nr index subfield may be reserved when the feedback type is CQI.

[0216] The grouping subfield may indicate a subcarrier group (Ng) used in a compressed beamforming feedback matrix when the feedback type is SU or MU. For example, when the bit value of the grouping subfield is 0, Ng may be set to 4, and when the bit value of the grouping subfield is 1, Ng may be set to 16. The grouping subfield may be reserved when the feedback type is CQI.

[0217] The codebook information subfield may indicate the size of codebook entries when the feedback type is SU or MU. The codebook information subfield may be reserved when the feedback type is CQI.

[0218] The Residual Feedback Segment subfield may indicate the number of residual feedback segments for the associated compressed beamforming / CQI frame. The First Feedback Segment subfield may indicate characteristics for the first feedback segment.

[0219] The Sounding Dialog Token Number subfield may be set to the same value as the Sounding Dialog Token Number subfield of the corresponding NDP Announcement Frame.

[0220] The Partial OBSS Sounding subfield may be a field that indicates whether the corresponding action frame is conveying a partial OBSS channel matrix (or partial feedback matrix) or a full OBSS channel matrix (or full feedback matrix).

[0221] As another example, if the Nc value and the nulling depth value are the same, this may mean that the corresponding action frame carries the full OBSS channel matrix (or the full feedback matrix). If the Nc value and the nulling depth value are different, this may mean that the corresponding action frame carries the partial OBSS channel matrix (or the partial feedback matrix). In this case, the partial OBSS sounding subfield on the MIMO control channel may be omitted.

[0222] The nulling depth subfield may indicate the number of columns of the beamforming feedback matrix that the corresponding action frame is conveying. In other words, the nulling depth subfield may indicate the dimension of the channel to be nulled among the channels between the AP and the corresponding STA.

[0223] The UHR compressed beamforming report field may include a matrix V (e.g., a beamforming feedback matrix) for each subcarrier. When partial nulling is indicated by the UHR MIMO control field (e.g., when the Partial OBSS Sounding subfield value is set to 1 (or 0) and / or the nulling depth value is the same as the value indicated by the Nc index field), the dimension of the matrix V may be "Nr by nulling value" instead of "Nr by Nc".

[0224] Specifically, based on the "Nr by Nc" matrix H, which is the full channel feedback, the matrix V having the dimension of "Nr by nulling value" can include column vectors (e.g., submatrix) from column 1 to column (nulling value). For example, when the Nr value is 4, the Nc value is 2, and the nulling depth value is 1, the dimension of the matrix V can be "4 by 1", and the feedback parameters corresponding to the matrix V can include {φ11, φ21, φ31, ψ21, ψ31, ψ41}.

[0225] The UHR MU-specific beamforming report field may include an eigenvalue matrix (e.g., matrix ∧) of each subcarrier. For example, the UHR MU-specific beamforming report field may convey, as an eigenvalue, the difference (e.g., delta value) between the SNR value for each subcarrier and the average SNR value conveyed through the UHR compressed beamforming report. In this case, the eigenvalues ​​from stream 1 to stream Nc are not conveyed for each subcarrier, but the eigenvalues ​​from stream 1 to stream (nulling depth value) may be conveyed through the UHR MU-specific beamforming report field.

[0226] The UHR CQI reporting field may include an average SNR value per stream for each subcarrier. In this case, the average SNR from stream 1 to stream Nc is not transmitted for each subcarrier, but the average SNR from stream 1 to stream (nulling depth value) may be transmitted through the UHR MU-specific beamforming reporting field.

[0227] Example 2

[0228] Example 2 relates to an implicit signaling method for feedback and sounding only some channels in the spatial domain.

[0229] As an example of the present disclosure, when performing OBSS sounding to apply partial nulling, as illustrated in (c) of FIG. 11, the UHR NDP announcement frame may include a partial OBSS sounding field. The partial OBSS sounding field may indicate that the corresponding NDP announcement frame is transmitted for partial nulling, and may be set to 1 bit, but is not limited thereto.

[0230] For example, if the Partial OBSS Sounding field value is set to 1 (or 0), this may mean that the STA (e.g., AP) that transmitted the NDP announcement frame requests partial channel information (e.g., partial feedback matrix) from the receiving STA (e.g., target STA). If the Partial OBSS Sounding field value is set to 0 (or 1), this may mean that the STA (e.g., AP) that transmitted the NDP announcement frame requests full channel information (e.g., full feedback matrix) from the receiving STA.

[0231] The feedback type and Ng subfields may indicate whether the feedback requested from the target STA is SU type, MU type, or CQI type feedback, and the feedback resolution (e.g., Ng value).

[0232] The interpretation of the partial OBSS sounding field according to the present disclosure may vary depending on whether the feedback requested by the feedback type and the Ng subfield is SU-type, MU-type, or CQI-type feedback. Hereinafter, the interpretation of the partial OBSS sounding field depending on the feedback type and whether the feedback requested by the Ng subfield is SU-, MU-, or CQI-type feedback will be described.

[0233] Example 2-1

[0234] Example 2-1 relates to a method of interpreting a partial OBSS sounding field when MU type feedback is indicated.

[0235] When performing MU type feedback, the STA can perform channel sounding using the Nc subfield value indicated by the NDP announcement frame within the capability range, and feed back the sounding result to the AP. For example, if the AP sets a value smaller than the dimension of the actual channel (e.g., reduces the Nc value) for the purpose of partial nulling and then transmits the NDP announcement frame to the STA, the STA can feed back information about only a portion of the entire channel to the AP based on the reduced Nc value. In this process, the STA may not decode the partial OBSS sounding field, but is not limited thereto. The STA can confirm that the sounding procedure applies partial nulling through the partial OBSS sounding field.

[0236] Example 2-2

[0237] Example 2-2 relates to a method of interpreting a partial OBSS sounding field when SU ​​type feedback is indicated.

[0238] When performing SU-type feedback, the STA may not need to perform channel sounding based on the Nc subfield value transmitted through the NDP announcement frame. In the case of SU beamforming, the STA can provide feedback only considering the dimensions that it can acquire. In other words, the STA can set the Nc value it wants to receive service for and feed it back to the AP, and the AP can perform beamforming operation considering only the STA.

[0239] At this time, if the AP sets the Nc value to a specific value (e.g., a value smaller than the entire column value) for partial nulling and then transmits it to the STA as an NDP announcement frame, the STA can refer to the Nc value, but can also feed back the entire channel information to the AP.

[0240] To prevent this, in the case of SU type feedback, the STA can check the partial OBSS sounding field value. For example, if the OBSS sounding field value is set to 1, the STA can feed back OBSS channel information to the AP based on the Nc value indicated through the NDP announcement frame.

[0241] Example 2-3

[0242] Example 2-3 relates to a method of interpreting a partial OBSS sounding field when CQI type feedback is indicated.

[0243] Simply transmitting the average SNR value of each stream may not be sufficient for precoder generation for C-BF. Therefore, elements indicating CQI-type feedback may not be used during the sounding process for C-BF.

[0244] However, partial information about CQI may be requested from the target STA for other purposes. For example, if CQI type feedback is indicated and the partial OBSS sounding field value is 1, the target STA may perform a feedback procedure using the Nc value indicated by the NDP announcement frame. If CQI type feedback is indicated and the partial OBSS sounding field value is 0, the target STA may not follow the Nc value indicated by the NDP announcement frame. That is, the target STA may perform a feedback operation based on the Nc value determined by itself.

[0245] Additionally or alternatively, the target STA may perform a feedback action based on the Nc indicated by the NDP announcement frame regardless of the partial OBSS sounding field value.

[0246] FIG. 12 is a diagram illustrating a PPDU transmission and reception procedure between a transmitting STA and a receiving STA according to one embodiment of the present disclosure. Some of the steps shown in FIG. 12 may be omitted depending on circumstances and / or settings. The transmitting device and the receiving STA may be APs and / or non-AP STAs.

[0247] The transmitting STA may obtain control information related to the aforementioned tone plan (or RU / DRU) (S105). The control information related to the tone plan may include the size and location of the RU, control information related to the RU, information about the frequency band in which the RU is included, information about the STA receiving the RU, etc.

[0248] The transmitting STA may configure / generate a PPDU based on the acquired control information (S110). Configuring / generating a PPDU may mean configuring / generating each field of the PPDU. That is, the step of configuring / generating a PPDU may include a step of configuring U-SIG and UHR-SIG-A / B / C fields that contain control information regarding a tone plan.

[0249] That is, the step of configuring / generating a PPDU may include a step of configuring a field including control information (e.g., N bitmap) indicating the size / position of the RU and / or a step of configuring a field including an identifier (e.g., AID) of an STA receiving the RU.

[0250] Additionally, the step of configuring / generating a PPDU may include a step of generating an STF / LTF sequence to be transmitted via a specific RU. The STF / LTF sequence may be generated based on a preset STF generation sequence / LTF generation sequence.

[0251] Additionally, the step of constructing / generating a PPDU may include a step of generating a data field (i.e., an MPDU) to be transmitted via a specific RU.

[0252] The transmitting STA can transmit the configured / generated PPDU to the receiving STA (S115).

[0253] Specifically, the transmitting STA can perform at least one of cyclic shift diversity (CSD), spatial mapping, inverse discrete Fourier transform (IDFT) / inverse fast Fourier transform (IFFT) operation, and guard interval (GI) insertion operation.

[0254] The receiving STA can decode the PPDU and obtain control information related to the tone-plan (or RU) (S120).

[0255] Specifically, the receiving STA can decode the L-SIG and U-SIG / UHR-SIG of the PPDU based on the L-STF / LTF, and obtain information included in the L-SIG and U-SIG, UHR-SIG fields. Information about various tone plans (i.e., RUs) of the present disclosure can be included in the U-SIG / UHR-SIG (UHR-SIG-A / B / C, etc.), and the receiving STA can obtain information about the tone plan (i.e., RU) through the EHT-SIG.

[0256] The receiving STA can decode the remaining portion of the PPDU based on the information about the acquired tone plan (i.e., RU) (S125). For example, the receiving STA can decode the STF / LTF field of the PPDU based on the information about the tone plan (i.e., RU). In addition, the receiving STA can decode the data field of the PPDU based on the information about the tone plan (i.e., RU) and obtain the MPDU included in the data field.

[0257] Additionally, the receiving STA may perform a processing operation to forward the decoded data to a higher layer (e.g., the MAC layer). Furthermore, if the higher layer instructs the PHY layer to generate a signal in response to the data forwarded to the higher layer, the receiving STA may perform a subsequent operation.

[0258] The embodiments described above are combinations of components and features of the present disclosure in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, it is also possible to form embodiments of the present disclosure by combining some components and / or features. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form embodiments or incorporated as new claims through post-application amendments.

[0259] It will be apparent to those skilled in the art that the present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present disclosure are intended to be included within the scope of the present disclosure.

[0260] The scope of the present disclosure includes software or machine-executable instructions (e.g., an operating system, an application, firmware, a program, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer. Instructions that can be used to program a processing system to perform the features described in the present disclosure can be stored on / in a storage medium or a computer-readable storage medium, and a computer program product including such a storage medium can be used to implement the features described in the present disclosure. The storage medium can include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices, and can include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. The memory optionally includes one or more storage devices remotely located from the processor(s). The memory or, alternatively, the non-volatile memory device(s) within the memory comprise a non-transitory computer-readable storage medium. The features described in this disclosure may be incorporated into software and / or firmware stored on any of the machine-readable media, which may control the hardware of the processing system and allow the processing system to interact with other mechanisms that utilize results according to embodiments of the present disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0261] The method proposed in this disclosure has been described with a focus on examples applied to IEEE 802.11-based systems, but can be applied to various wireless LANs or wireless communication systems in addition to IEEE 802.11-based systems.

Claims

1. A step of receiving a null data physical layer protocol data unit (NDP) announcement frame from a second STA by a first station (STA); A step of receiving an NDP from the second STA by the first STA based on the NDP notification frame; and A step of transmitting a report frame including a first channel feedback matrix based on the NDP to the second STA by the first STA, A method wherein the NDP announcement frame includes a first subfield related to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested and a second subfield related to the number of columns of the partial OBSS channel feedback matrix.

2. In paragraph 1, Based on the first subfield value being set to the first number, the first channel feedback matrix includes the partial OBSS channel feedback matrix, A method wherein the first channel feedback matrix includes the entire OBSS channel feedback matrix based on the first subfield value being set to the second number.

3. In paragraph 1, A method wherein the number of columns of the above partial OBSS channel feedback matrix is ​​equal to the number of columns set by the second subfield.

4. In paragraph 1, The above NDP announcement frame includes a third subfield related to the number of columns of the channel feedback matrix, A method wherein the number of columns of the channel feedback matrix set by the third subfield and the number of columns of the partial OBSS channel feedback matrix set by the second subfield are different.

5. In paragraph 4, A method, wherein the first STA information field related to the first STA among at least one STA information field of the NDP announcement frame includes the first subfield, the second subfield, and the third subfield.

6. In paragraph 5, The above first STA information field includes a fourth subfield indicating multi-user (MU) type feedback, A method wherein the fourth subfield includes a decomposition diagram of the first channel feedback matrix.

7. In paragraph 1, The above report frame includes a MIMO (Multiple Input Multiple Output) control field, A method wherein the MIMO control field includes a fifth subfield related to whether the first channel feedback matrix is ​​the partial OBSS channel feedback matrix and a sixth subfield related to the number of columns of the first channel feedback matrix.

8. In paragraph 7, The above report frame includes a compressed beamforming report field, A method wherein the compressed beamforming report field includes the first channel feedback matrix containing channel information per subcarrier.

9. In paragraph 7, The above reporting frame includes an MU exclusive beamforming reporting field, The above MU-only beamforming report field includes an eigenvalue matrix containing the eigenvalues ​​of each stream for each subcarrier, A method in which the number of streams per subcarrier is equal to the number of columns indicated by the sixth subfield.

10. In paragraph 1, The above first STA is a non-access point (AP) STA, The above second STA is an AP.

11. In the first station (STA), the first STA: one or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: Receiving a null data physical layer protocol data unit (NDP) announcement frame from a second STA through the one or more transceivers; Receiving an NDP from the second STA through the one or more transceivers based on the NDP notification frame; and A report frame including a first channel feedback matrix based on the NDP is set to be transmitted to the second STA through the one or more transceivers, The NDP announcement frame comprises a first subfield related to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested and a second subfield related to the number of columns of the partial OBSS channel feedback matrix, wherein the first STA.

12. A step of transmitting a null data physical layer protocol data unit (NDP) announcement frame from a second station (STA) to a first STA; A step of transmitting NDP to the first STA by the second STA based on the NDP notification frame; and A step of receiving a report frame including a first channel feedback matrix based on the NDP from the first STA by the second STA, A method wherein the NDP announcement frame includes a first subfield related to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested and a second subfield related to the number of columns of the partial OBSS channel feedback matrix.

13. In the second station (STA), the second STA: one or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: Transmitting a null data physical layer protocol data unit (NDP) announcement frame to the first STA via the one or more transceivers; Transmitting NDP to the first STA through the one or more transceivers based on the NDP notification frame; and A report frame including a first channel feedback matrix based on the NDP is set to be received from the first STA through the one or more transceivers, The NDP announcement frame comprises a second STA, wherein the first subfield relates to whether a partial overlapping basic service set (OBSS) channel feedback matrix is ​​requested and a second subfield relates to the number of columns of the partial OBSS channel feedback matrix.

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

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

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