Method and device for performing communication on basis of beamforming matrix in wireless LAN system

Abstract

A method and a device operating in a wireless LAN system are disclosed. A method according to an embodiment of the present disclosure may comprise the steps of: obtaining, by a first station (STA), a first equivalent channel matrix on the basis of M basic service set (BSS) channel matrices and M nulling precoder matrices; obtaining, by the first STA, a second equivalent channel matrix on the basis of the first equivalent channel matrix and a first singular value decomposition (SVD) precoder matrix; and transmitting, by the first STA, a physical layer protocol data unit (PPDU) to at least one STA on the basis of the second equivalent channel matrix.

Description

Method and device for performing communication based on beamforming matrix in 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 performing communication based on a beamforming matrix 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 performing communication based on a beamforming matrix in a wireless LAN system.

[0005] The technical problem of the present disclosure is to provide a method and device for performing communication based on a multi-user (MU) MIMO beamforming matrix capable of performing full nulling and / or 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: obtaining, by a first station (STA), a first equivalent channel matrix based on M basic service set (BSS) channel matrices and M nulling precoder matrices; obtaining, by the first STA, a second equivalent channel matrix based on the first equivalent channel matrix and a first singular value decomposition (SVD) precoder matrix; And a step of transmitting a physical layer protocol data unit (PPDU) from the first STA to at least one STA based on the second equivalent channel matrix, wherein a first nulling precoder matrix among the M nulling precoder matrices is associated with a second STA among the at least one STA, and the first nulling precoder matrix can generate a null space of N interference matrices obtained based on i) a remaining BSS channel matrix excluding a first BSS channel matrix for the second STA among the M BSS channel matrices and ii) N overlapping BSS (OBSS) channel matrices.

[0008] According to various embodiments of the present disclosure, a method and device for performing communication based on a beamforming matrix in a wireless LAN system can be provided.

[0009] According to various embodiments of the present disclosure, a method and apparatus for performing communication based on an MU MIMO beamforming matrix capable of performing full nulling and / or partial nulling can be provided.

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

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

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

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

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

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

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

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

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

[0019] FIG. 8 is a flowchart illustrating a method performed by a first STA according to one embodiment of the present disclosure.

[0020] FIG. 9 is a flowchart illustrating a method performed by a second STA according to one embodiment of the present disclosure.

[0021] FIG. 10 illustrates a system to which a method for generating a precoding matrix for performing nulling is applied, according to one embodiment of the present disclosure.

[0022] FIG. 11 is a drawing for explaining experimental results according to one embodiment of the present disclosure.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Below, technical features to which examples of the present disclosure can be applied are described.

[0031] FIG. 1 illustrates a block diagram of a wireless communication device according to one embodiment of the present disclosure.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] FIG. 2 is a diagram showing an exemplary structure of a wireless LAN system to which the present disclosure can be applied.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] 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.

[0049] 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.

[0050] 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).

[0051] 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.

[0052] 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.

[0053] In addition to the structure of the DS described above, an extended service set (ESS) may be established to provide wider coverage.

[0054] 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.

[0055] 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.

[0056] FIG. 3 is a diagram for explaining a link setup process to which the present disclosure can be applied.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] For example, the association request frame may include information about various capabilities, a beacon listen interval, a service set identifier (SSID), supported rates, supported channels, an RSN, a mobility domain, supported operating classes, a Traffic Indication Map Broadcast request, interworking service capabilities, etc. For example, the association response frame may include information about various capabilities, a status code, an Association ID (AID), supported rates, an Enhanced Distributed Channel Access (EDCA) parameter set, a Received Channel Power Indicator (RCPI), a Received Signal to Noise Indicator (RSNI), a mobility domain, a timeout interval (e.g., an association comeback time), overlapping BSS scan parameters, a TIM broadcast response, a Quality of Service (QoS) map, etc. These are just some examples of information that may be included in a combined request / response frame, and may be replaced by other information or include additional information.

[0067] 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.

[0068] 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.

[0069] FIG. 4 is a diagram for explaining a backoff process to which the present disclosure can be applied.

[0070] 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.

[0071] 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).

[0072] 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, ...).

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] FIG. 5 is a diagram for explaining a CSMA / CA-based frame transmission operation to which the present disclosure can be applied.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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 are described below with reference to FIG. 7.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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).

[0095] FIG. 7 is a diagram illustrating examples of PPDUs defined in the IEEE 802.11 standard to which the present disclosure can be applied.

[0096] 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)).

[0097] 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).

[0098] 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)).

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The L-STF, L-LTF, L-SIG, RL-SIG, U-SIG (Universal SIGNAL), and EHT-SIG fields can be encoded and modulated so that even legacy STAs can attempt demodulation and decoding, and can be 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 so that they can be demodulated and decoded by an STA that has successfully decoded a non-legacy SIG (e.g., U-SIG and / or EHT-SIG) and obtained the information contained in the corresponding field, and can be mapped based on a predetermined subcarrier frequency interval (e.g., 78.125 kHz). These can be referred to as EHT modulated fields.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.).

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.).

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] Beamforming-based procedures

[0126] 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.

[0127] 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.

[0128] To design a precoding matrix for C-BF, interference information may be required in addition to channel information between intended STAs. For example, when performing multi-user (MU) MIMO transmission in a BSS, the interference that a specific STA must consider may include inter-user interference (IUI) within the same BSS and inter-BSS interference (IBI) received from an OBSS AP.

[0129] In basic wireless LAN systems, precoding techniques were applied to maximize system performance by considering only the IUI. C-BF, which will be applied to next-generation wireless LAN systems, can utilize a precoding matrix design that considers the influence of both the IUI and the IBI.

[0130] To control IUI and IBI, a full nulling method that removes all interference and a partial nulling method that removes some interference can be used. Here, nulling can be a general term for a technique for steering a transmission signal so that the reception intensity of the signal passing through the channel becomes 0 or below a threshold. In other words, the nulling technique is a technique that adjusts the phase and amplitude of the antenna array so that the signal reaching a specific reception point undergoes destructive interference.

[0131] When a full nulling scheme is applied, all interference can be eliminated, but this can lead to a loss in beamforming gain as many transmission dimensions are consumed by nulling. When a partial nulling scheme is applied, residual interference still exists, but only a relatively small number of transmission dimensions can be used for nulling, potentially benefiting beamforming gain.

[0132] Therefore, considering the trade-off between the full nulling method and the partial nulling method, the full nulling method can be used when the amount of interference is large (e.g., when the amount of interference exceeds the threshold value), and the partial nulling method can be used when the amount of interference is moderate (e.g., when the amount of interference is below the threshold value).

[0133] Below, we describe a method for designing a precoder that can remove all interference that may occur from the receiving STA's perspective (e.g., a precoding matrix that can remove both IUI and IBI) and a method for designing a precoder that can remove some interference (e.g., a precoder for nulling only some of the interference among IUI and IBI).

[0134] Here, if a precoder capable of removing all interference is applied, and even after all interference is removed, a transmission dimension remains, this dimension can be utilized to obtain eigenvalue selection gains through singular value decomposition (SVD) precoding. Furthermore, if a precoder capable of removing some interference is applied, the remaining transmission dimension can be used to obtain beamforming gains through SVD precoding.

[0135] FIG. 8 is a flowchart illustrating a method performed by a first STA according to one embodiment of the present disclosure. In FIGS. 8 and 9 , the first STA may be an AP, and at least one STA may be a non-AP STA, but is not limited thereto. Each of the first STA and the second STA may be either an AP or a non-AP STA.

[0136] As an example of the present disclosure, FIGS. 8 and 9 illustrate that when a first STA is an AP (e.g., a first AP), at least one STA may be associated with the first STA. At this time, the number of at least one STA may be M (e.g., M is a natural number greater than or equal to 1). In addition, a second AP and other non-AP STA(s) associated with the second AP may exist, and the number of other non-AP STA(s) may be N (e.g., N is a natural number greater than or equal to 1).

[0137] Accordingly, the first STA may generate a precoder matrix, etc., taking into account interference within the BSS (e.g., interference between at least one STA) and OBSS interference (e.g., interference due to the second AP and / or other STA(s) associated with the second AP).

[0138] The first STA can obtain a first equivalent channel matrix based on M BSS channel matrices and M nulling precoder matrices (S810).

[0139] For example, a first nulling precoder matrix among the M nulling precoder matrices may be associated with a second STA among at least one STA. In addition, the first nulling precoder matrix may generate a null space of N interference matrices obtained based on i) the remaining BSS channel matrices excluding the first BSS channel matrix for the second STA among the M BSS channel matrices and ii) N OBSS channel matrices.

[0140] Here, the first STA can perform SVD on N OBSS channel matrices. The first STA can obtain N interference matrices based on the first right singular vector matrix of the SVD performance results of the N OBSS channel matrices. At this time, the N interference matrices can include a column vector of the number of null streams extracted from the first right singular vector matrix.

[0141] The first STA can generate M nulling precoders by generating at least one nulling precoder for each STA. The first STA can obtain a first equivalent channel matrix through a product operation of the M BSS channel matrices and the M nulling precoder matrices. Except for the diagonal elements of the first equivalent channel matrix, the remaining elements can be set to 0 by the M nulling precoder matrices.

[0142] The first STA can obtain a second equivalent channel matrix based on the first equivalent channel matrix and the first SVD precoder matrix (S820).

[0143] Specifically, the first STA can perform SVD on the first equivalent channel matrix. The first STA can obtain the first SVD precoder matrix based on the second right singular vector matrix of the SVD result of the first equivalent channel matrix. The first STA can obtain the second equivalent channel matrix through a product operation of the first equivalent channel matrix and the first SVD precoder matrix. At this time, the remaining elements except for the diagonal elements of the second equivalent channel matrix can be set to 0 by M nulling precoder matrices.

[0144] The first STA can transmit a physical layer protocol data unit (PPDU) to at least one STA based on the second equivalent channel matrix (S830).

[0145] Specifically, the first STA may generate a PPDU including the result of a product operation of a second equivalent channel matrix and a data vector. The first STA may transmit the generated PPDU to at least one STA.

[0146] The method described in the example of FIG. 8 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 obtain a first equivalent channel matrix based on M BSS channel matrices and M nulling precoder matrices. The one or more processors (102) may obtain a second equivalent channel matrix based on the first equivalent channel matrix and the first SVD precoder matrix. The one or more processors (102) may transmit a PPDU to at least one STA through one or more transceivers (106) based on the second equivalent channel matrix.

[0147] Furthermore, one or more memories (104) of the first device (100) may store commands for performing the method described in the example of FIG. 8 or the examples described below when executed by one or more processors (102).

[0148] FIG. 9 is a flowchart illustrating a method performed by a second STA according to one embodiment of the present disclosure.

[0149] The second STA can receive a PPDU from the first STA (S910). Then, the second STA can decode the PPDU (S920).

[0150] The description of the matrix applied to PPDU has been described with reference to Fig. 8, so any redundant description will be omitted.

[0151] The method described in the example of FIG. 9 can be performed by the second device (200) of FIG. 1. For example, one or more processors (202) of the second device (200) of FIG. 1 can receive a PPDU from the first STA via one or more transceivers (206). In addition, the one or more processors (202) can decode the PPDU.

[0152] Furthermore, one or more memories (204) of the second device (200) 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 (202).

[0153] Below, a method for generating a precoding matrix for performing partial nulling and full nulling, respectively, and a method for performing communication based on the precoding matrix are described in more detail.

[0154] Example 1

[0155] Example 1 relates to a system model to which various embodiments of the present disclosure can be applied. As an example of the present disclosure, as illustrated in FIG. 10, a system model in which two APs cooperate is assumed, but the present disclosure is not limited thereto, and the number of APs may be two or more.

[0156] For example, STA 1 to STA M (M is a natural number greater than or equal to 1) may be associated with AP 1, and STA M+1 to STA M+N (N is a natural number greater than or equal to 1) may be associated with AP 2. In addition, the downlink channel from AP 1 to STA i may be H i is expressed as , and the number of antennas of the AP is N AP is expressed as , and the number of antennas of STA i is N STAi , and the number of spatial streams to be transmitted to STA i is N SSi can be expressed as N. In addition, the number of null streams to be performed / applied for STA i is N. NSi can be expressed as

[0157] In the system model, the received signal y can be modeled as in Equation 1. Equation 1 represents the concatenation of the signal vectors received by all STAs.

[0158] [Mathematical Formula 1]

[0159]

[0160] AP to STA channel matrix H in Equation 1 i (i = 1, 2, ..., M) is "N STAi by N AP matrix", and the transmission symbol vector xi (i = 1, 2, ..., M) transmitted to each STA is "N SSi It can be a by 1" matrix.

[0161] Example 1-1

[0162] Example 1-1 relates to an IUI removal precoder used in MU-MIMO. A C-BF precoder can be designed based on the design method / principle of the IUI removal precoder.

[0163] Precoder P to remove IUI null_IUI can be configured as a precoding matrix for each user (e.g., STA)(s) as in mathematical expression 2.

[0164] [Equation 2]

[0165]

[0166] And, the equivalent channel with precoding applied is the channel matrix and P null_IUI Through the operation between the two, it can be expressed as in mathematical formula 3.

[0167] [Equation 3]

[0168]

[0169] All matrices except the diagonal elements of the equivalent channel in Equation 3 can be IUI. The precoding matrix P null_IUI To remove IUI through , make the rest except the diagonal components 0. (i = 1, 2, ..., M) matrices can be applied. The matrix can be generated through the Null matrix for the channel matrices of all STAs except its own channel matrix. That is, A matrix (e.g., a nulling precoding matrix) can be derived using Equation 4.

[0170] [Equation 4]

[0171]

[0172] When user-to-user interference is removed through a nulling precoding matrix, an (equivalent) channel matrix can be derived as in Equation 5.

[0173] [Equation 5]

[0174]

[0175] A new equivalent channel matrix for each user can be located on the diagonal of the equivalent channel matrix, and a matrix that can act as inter-user interference can be located on the off-diagonal positions. In this case, if a 0 is set on the off-diagonal positions, this can mean that all inter-user interference is controlled to 0.

[0176] Therefore, the residual precoding design problem can be simplified into a precoding matrix design problem for each user. The physical meaning of the column dimension of a matrix can refer to the number of remaining transmission (TX) dimensions that the ith STA can utilize. Various types of precoder designs that can utilize the remaining TX dimensions are possible, and the SVD precoder is described below.

[0177] The SVD precoder to be applied to user i is equivalent to the channel matrix (H) as in Equation 6. i ) can be obtained from.

[0178] [Equation 6]

[0179]

[0180] In Equation 6, the SVD precoder can be configured by obtaining the column vector to be used for data transmission of STA i among the entire V matrix. At this time, the eigenvalues ​​are sorted in descending order, and the SVD precoder W of the i-th user is as shown in Equation 7. i can be designed.

[0181] [Equation 7]

[0182] W i = V i (:1:N SSi )

[0183] The (final) equivalent channel matrix to which both the above-described interference removal precoding and SVD precoding are applied can be constructed as in mathematical expression 8.

[0184] [Equation 8]

[0185]

[0186] Example 2

[0187] Embodiment 2 relates to a precoder for partial nulling and full nulling for IUI and IBI in C-BF based on Embodiment 1 and / or Embodiment 1-1.

[0188] In the single AP MU-MIMO system described in Embodiment 1 and / or Embodiment 1-1, the precoder was designed to only consider interference between users within the BSS. Embodiment 2 relates to a precoder that considers not only interference between users within the BSS but also interference between BSSs to OBSS STAs in a multi-AP C-BF MU-MIMO system. It may be necessary to design a precoder that can obtain beamforming gain while effectively controlling both IUI and IBI.

[0189] As an example of the present disclosure, precoding for interference removal may be applied first, followed by a precoder for beamforming gain. The interference removal precoder applied to single-AP MU-MIMO may be different from the interference removal precoder applied to multi-AP MU-MIMO.

[0190] Additionally, a full nulling C-BF precoder, which eliminates all inter-user interference, may differ from a partial nulling C-BF precoder, which eliminates only some of the existing interference. With the partial nulling C-BF precoder, the remaining dimensions can be used to obtain beamforming gain.

[0191] The precoder Pnull for removing IBI and IUI in a multi-AP MU-MIMO system can be defined as in Equation 9.

[0192] [Equation 9]

[0193]

[0194] Through the operation of the mathematical expression 9 and the STA-specific channel matrix, an equivalent channel matrix can be derived as in mathematical expression 10.

[0195] [Equation 10]

[0196]

[0197] The procedure for performing full nulling based on mathematical expression 10 is explained through Example 2-1, and the procedure for performing partial nulling based on mathematical expression 10 is explained through Example 2-2.

[0198] Example 2-1

[0199] Example 2-1 relates to a design method of a precoder for full nulling of IUI and IBI in C-BF.

[0200] In the equivalent channel matrix of Equation 10, the remainder, excluding the diagonal elements, is inter-user interference and can be eliminated as 0. In other words, nulling can be applied to the channels of all users except for the BSS to eliminate IUI within the BSS.

[0201] The precoder of multi-AP can be designed considering OBSS interference. That is, the OBSS channel H M From H M+N By including the nulling vector up to , a precoder that sets / controls all interference to 0 can be derived / obtained. The null matrix (e.g., null precoder) of each user obtained according to the above-described method can be derived as in mathematical formula 11.

[0202] [Equation 11]

[0203]

[0204] An equivalent channel matrix can be produced as in Equation 12 through a multiplication operation between the null precoder and the channel matrix obtained according to Equation 11.

[0205] [Equation 12]

[0206]

[0207] According to Equations 11 and 12, interference (e.g., IBI) between IUI and OBSS channels within a BSS can be eliminated to zero. Since both IUI and IBI are eliminated, the precoder design problem can be regarded as a problem of obtaining beamforming gain for each user.

[0208] The physical meaning of the column dimension of a matrix can refer to the number of remaining transmission (TX) dimensions that the ith STA can utilize. Various types of precoder designs that can utilize the remaining TX dimensions are possible, and the SVD precoder is described below.

[0209] The SVD precoder to be applied to user i is equivalent to the channel matrix (H) as in Equation 13. i ) can be obtained from.

[0210] [Equation 13]

[0211]

[0212] In Equation 13, the SVD precoder can be configured by obtaining the column vector to be used for data transmission of STA i among the entire V matrix. At this time, the eigenvalues ​​are sorted in descending order, and the SVD precoder W of the i-th user is as in Equation 14. i can be designed.

[0213] [Equation 14]

[0214] W i = V i (:1:N SSi )

[0215] The (final) equivalent channel matrix to which both the above-described interference removal precoding and SVD precoding are applied can be constructed as in Equation 15.

[0216] [Equation 15]

[0217]

[0218] Example 2-2

[0219] Example 2-2 relates to a design method of a precoder for partial nulling of IUI and IBI in C-BF. As described above, when full nulling is applied, all IUIs are removed, but partial nulling may remove only a portion of the IUIs.

[0220] As another example, since the interference amount for IUI can be very large, if a partial nulling precoder is applied, all IUI may be removed and only a part of the OBSS IUI may be removed.

[0221] Example 2-2-1

[0222] Example 2-2-1 relates to a partial precoding method in which all IUIs in a BSS are removed and only some IUIs in an OBSS are removed.

[0223] To remove all IUIs in the BSS, the null precoder of the i-th user is is from H1 to H M Null operation can be applied to all channels except Hi, which is its own channel, among the channels within the BSS. In addition, some dimensions of the OBSS channels for which interference is to be eliminated can be specified in order to remove only some of the OBSS IUIs.

[0224] Assume that the OBSS channel with the index i value is Hi (i = M+1, M+2, ..., M+N). In this case, H i The SVD result of can be produced as N among OBSS channel dimensions NSi The stream can be nulled. For this, V i (1:N NSi ) H By reflecting the IUI component within the BSS for the interference matrix obtained, a nulling matrix as in mathematical expression 16 can be obtained.

[0225] [Equation 16]

[0226]

[0227] Example 2-2-2

[0228] Example 2-2-2 relates to a partial precoding method that removes only a portion of both the IUI in the BSS and the IUI in the OBSS.

[0229] In order to remove some of the IUI within the BSS, the large-dimensional interference can be removed from the results of applying SVD to the interference channels within the BSS. H of the interference channels within the BSS i The SVD result of (i = 1, 2, ..., M) is H i = is defined as . At this time, among the dimensions of the interference channel within the BSS, N NSi A stream of numbers can be nulled. For this, V i (1:N NSi ) H Null operations can be performed on interference produced by .

[0230] In the case of OBSS IUI, the SVD result of OBSS interference channel Hi(i = M+1, M+2, ..., M+N) is can be defined as . At this time, N is one of the dimensions of the interference channel within the OBSS. NSi To null the stream of numbers, V i (1:N NSi ) H The interference matrix produced by can be used.

[0231] The nulling matrix for removing the IUI and IBI described above can be expressed as in mathematical expression 17.

[0232] [Equation 17]

[0233]

[0234] Example 2-2-3

[0235] Example 2-2-3 relates to a partial precoding method in which only some of the IUIs in the BSS are removed and all of the IUIs (e.g., IBIs) in the OBSS are removed.

[0236] When applying the method described in Examples 2-2-1 and 2-2-2, etc., a nulling matrix that removes only a part of the IUI in the BSS and removes all of the IUI in the OBSS can be configured as in mathematical expression 18.

[0237] [Equation 18]

[0238]

[0239] An equivalent channel matrix can be obtained as in Equation 19 through the nulling precoder matrix (e.g., Equation 16, Equation 17, and Equation 18, respectively) described in each of Embodiments 2-2-1, 2-2-2, and 2-2-3.

[0240] [Equation 19]

[0241]

[0242] Referring to mathematical expression 19, the IUI within the BSS is set / controlled to 0, and the interference of the OBSS channel can also be set / controlled to 0. In the case of the equivalent channel matrix calculated according to embodiment 2-2-2, the IUI component within the BSS may be included, and accordingly, the component included in a position other than the diagonal position may not be set to 0.

[0243] Since interference within the BSS and interference from the OBSS are eliminated / controlled, the precoding design problem can be considered as a matrix design problem to obtain beamforming gain for each user. The physical meaning of the column dimension of a matrix can refer to the number of remaining transmission (TX) dimensions that the ith STA can utilize. Various types of precoder designs that can utilize the remaining TX dimensions are possible, and the SVD precoder is described below.

[0244] The SVD precoder to be applied to user i is equivalent to the channel matrix (H) as in Equation 20. i ) can be obtained from.

[0245] [Equation 20]

[0246]

[0247] In Equation 20, the SVD precoder can be configured by obtaining the column vector to be used for data transmission of STA i among the entire V matrix. At this time, the eigenvalues ​​are sorted in descending order, and the SVD precoder W of the i-th user is as in Equation 21. i can be designed.

[0248] [Equation 21]

[0249]

[0250] The (final) equivalent channel matrix to which both the above-described interference removal precoding and SVD precoding are applied can be constructed as in Equation 22.

[0251] [Equation 22]

[0252]

[0253] Example 3

[0254] Example 3 relates to the experimental results of at least one of the above-described examples.

[0255] The system may include two APs, each of which is associated with two STAs. Each AP has eight antennas, and each STA can have two. The comparison group may include a single-AP MU-MIMO situation and a multi-AP MU-MIMO situation.

[0256] In a single AP MU-MIMO scenario, it is assumed that transmission and reception operations are performed only within a single BSS, and no transmission and reception operations are performed in other BSSs. In other words, only one AP can perform transmission and reception operations without interference. In a multi-AP MU-MIMO scenario, each AP can perform a total of six-dimensional nulling for each STA. Two-dimensional nulling can be performed to eliminate interference within the BSS, and four-dimensional nulling can be applied to eliminate interference in the OBSS. In addition, the partial nulling described in the above-described embodiment can also be applied.

[0257] As an example of the present disclosure, (a) of FIG. 11 shows the packet error rate (PER) according to each nulling method.

[0258] The X-axis represents the difference between the SNR of an STA within a BSS and the SNR of the OBSS. When X=0dB, it means that the two SNRs are the same, and when X=40dB, it means that the SNR of an STA within a BSS is 40dB higher than the SNR of the OBSS.

[0259] Referring to Figure 11(a), in the absence of interference, a single-AP transmission, capable of utilizing all dimensions for beamforming, has the best PER. However, since the data rate for single-AP transmission is half that of multi-AP transmission technologies, multi-AP transmission technologies may offer superior performance in terms of throughput.

[0260] When X=0dB, interference is strong, so a full nulling scheme that eliminates all interference may outperform a partial nulling scheme. When X=40dB, interference is not significant, so only some dimensions can be utilized for interference removal. Accordingly, a partial nulling scheme that utilizes more dimensions for beamforming within the BSS may have better PER performance.

[0261] As an example of the present disclosure, (b) of FIG. 11 shows the output amount according to each nulling method.

[0262] Referring to Figure 11(b), C-BF-based technologies exhibit superior throughput compared to single-AP-based transmission technologies. This can be interpreted as a performance improvement effect resulting from allowing simultaneous transmissions.

[0263] In addition, when the X value is 40 dB, the performance of the partial nulling technique according to the present disclosure is superior to the control group in most sections. This can be interpreted as the high performance of the method designed to remove only part of the interference and increase the BSS beamforming gain. On the other hand, when the X value is 0 dB, the performance of the partial nulling technique may be relatively poor. Therefore, when the interference is strong (e.g., when the interference exceeds the threshold), it may be desirable to utilize many dimensions for interference removal (e.g., full nulling, etc.).

[0264] 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.

[0265] 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.

[0266] 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.

[0267] 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.

[0268] 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.

[0269] 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.

[0270] The transmitting STA can transmit the configured / generated PPDU to the receiving STA (S115).

[0271] 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.

[0272] The receiving STA can decode the PPDU and obtain control information related to the tone-plan (or RU) (S120).

[0273] 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.

[0274] 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.

[0275] 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.

[0276] 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.

[0277] 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.

[0278] 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.

[0279] 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

A step of obtaining a first equivalent channel matrix by a first station (STA) based on M basic service set (BSS) channel matrices and M nulling precoder matrices; A step of obtaining a second equivalent channel matrix by the first STA based on the first equivalent channel matrix and the first singular value decomposition (SVD) precoder matrix; and A step of transmitting a physical layer protocol data unit (PPDU) to at least one STA by the first STA based on the second equivalent channel matrix, A first nulling precoder matrix among the M nulling precoder matrices is associated with a second STA among the at least one STA, A method in which the first nulling precoder matrix generates a null space of N interference matrices obtained based on i) the remaining BSS channel matrices excluding the first BSS channel matrix for the second STA among the M BSS channel matrices and ii) N overlapping BSS (OBSS) channel matrices. In the first paragraph, SVD is performed by the first STA for the N OBSS channel matrices, A method in which the N interference matrices are obtained by the first STA based on the first right singular vector matrix of the SVD results of the N OBSS channel matrices. In the second paragraph, A method wherein the N interference matrices include a column vector of the number of null streams extracted from the first right singular vector matrix. In the first paragraph, A method in which the remaining elements except the diagonal elements of the first equivalent channel matrix are set to 0 by the M nulling precoder matrices. In the first paragraph, SVD is performed by the first STA for the first equivalent channel matrix, A method wherein the first SVD precoder matrix is ​​obtained by the first STA based on a second right singular vector matrix of the SVD result of the first equivalent channel matrix. In paragraph 5, A method in which the second equivalent channel matrix is ​​obtained by the first STA through a product operation of the first equivalent channel matrix and the first SVD precoder matrix. In the first paragraph, A method in which the remaining elements except the diagonal elements of the second equivalent channel matrix are set to 0 by the M nulling precoder matrices. In the first paragraph, A method wherein the PPDU includes the result of a product operation of the second equivalent channel matrix and the data vector. In the first paragraph, The above first STA is an access point (AP), wherein at least one STA is a non-AP STA, A method wherein the number of at least one STA is M. 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: Obtain a first equivalent channel matrix based on M basic service set (BSS) channel matrices and M nulling precoder matrices; Obtaining a second equivalent channel matrix based on the first equivalent channel matrix and the first singular value decomposition (SVD) precoder matrix; and It is configured to transmit a physical layer protocol data unit (PPDU) to at least one STA through the one or more transceivers based on the second equivalent channel matrix, A first nulling precoder matrix among the M nulling precoder matrices is associated with a second STA among the at least one STA, The first nulling precoder matrix generates a null space of N interference matrices obtained based on i) the remaining BSS channel matrices excluding the first BSS channel matrix for the second STA among the M BSS channel matrices and ii) N overlapping BSS (OBSS) channel matrices. A processing device configured to control a station (STA) in a wireless local area network (WLAN) system, wherein 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 9. 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 9.

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