Method and apparatus for efficient multiple data transmission in dynamic low-power operation in wireless LAN system

Abstract

The present disclosure relates to a wireless LAN system. Disclosed are a method and an apparatus for transmitting, to a plurality of devices, an initial control frame (ICF) indicating a transition from a lower capability mode (LCM) to a higher capability mode (HCM) in order for a transmitter and a plurality of receivers to which a dynamic low-power operation is applied to effectively perform data transmission and reception when the dynamic low-power operation is applied, and transmitting a data frame to the plurality of devices when at least one ICR therefor is received.

Description

Efficient multiple data transmission method and device in dynamic low-power operation in a wireless LAN system

[0001] The present disclosure relates to a method and apparatus for transmitting signals in a wireless LAN network system, and more specifically, to a method and apparatus for efficiently transmitting multiple data when a dynamic power saving operation is performed.

[0002] A Wireless Local Area Network (WLAN), also known as Wi-Fi, is a network that enables internet access via mobile devices or laptops within a certain distance from an access point (AP). WLAN technology continues to evolve in line with the rise of the internet and the expansion of the smartphone market, and is being utilized to provide high-speed data services throughout the city, including in schools, airports, hotels, and offices.

[0003] The WiFi Alliance defines WiFi as a wireless local area network (WLAN) product based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. IEEE 802.11a and b, published in 1997 and 1999 respectively, are standards utilizing unlicensed bands at 2.4 GHz or 5 GHz; IEEE 802.11b (also known as WiFi 2) provides a transmission speed of 11 Mbps, while IEEE 802.11a provides a transmission speed of 54 Mbps. IEEE 802.11g (also known as WiFi 3) provides a transmission speed of 54 Mbps by applying orthogonal frequency-division multiplexing (OFDM) at 2.4 GHz. IEEE 802.11n (also known as Wi-Fi 4 or High Throughput, HT) utilizes multiple input multiple output OFDM (MIMO-OFDM) to provide a transmission speed of 300 Mbps using four spatial streams. IEEE 802.11n supports channel bandwidths up to 40 MHz, in which case it provides a transmission speed of 600 Mbps.

[0004] Subsequently, the IEEE 802.11ac standard (also known as Wi-Fi 5 or Very High Throughput, VHT), which uses a maximum bandwidth of 160 MHz and supports 8 spatial streams to support speeds of up to 1 Gbit / s, and the IEEE 802.11ax standard (also known as Wi-Fi 6 or High Efficiency, HE), which provides multi-user MIMO (MU-MIMO) in the uplink and downlink and supports spatial frequency reuse, dynamic fragmentation, etc., were introduced. Subsequently, 802.11be (also known as Wi-Fi 7 or Extremely High Throughput, EHT) was introduced to theoretically achieve a speed of 46Gbps by supporting up to 320 ultra-wide channels, multi-link operation, and 4kQAM, and 802.11bn (also known as Wi-Fi 8, Ultra High Reliability, UHR) is being researched to introduce technologies that optimize spectrum usage and reduce interference by strengthening collaboration among multiple APs, power management technologies to reduce energy consumption, and technologies to optimize spectrum allocation.

[0005] In 802.11, low-power (or power-saving) operations were introduced to reduce power consumption of APs and STAs. Furthermore, research is being conducted on technologies to reduce terminal power consumption by applying various capability modes supported by STAs in addition to conventional low-power operations. However, when low-power operations are applied to STAs, delays may increase and power consumption may rise due to STA mode transitions. Additionally, 802.11 supports multiple data transmission, which allows data to be sent to multiple users. In this case, methods and devices are required to effectively perform multiple data transmission when low-power operations are possible.

[0006] The present invention for solving the above-mentioned problems is characterized in that, in a method performed by a first device in a wireless LAN (WLAN) system, the method comprises the steps of: transmitting an initial control frame (ICF) to a plurality of second devices, wherein the ICF includes an instruction for the second device to switch from a lower capability mode (LCM) to a higher capability mode (HCM); checking whether at least one initial control frame response (ICR) has been received from at least one second device; and, if the at least one ICR has been received, transmitting a data frame to the plurality of second devices.

[0007] In addition, a method performed by a first device in a wireless LAN (WLAN) system comprises the steps of: transmitting an initial control frame (ICF) to a plurality of second devices, wherein the ICF includes instructions for the second devices to switch from a lower capability mode (LCM) to a higher capability mode (HCM); checking whether at least one initial control frame response (ICR) has been received from at least one second device; and, if the at least one ICR has been received, transmitting the ICF to other second devices among the plurality of second devices, excluding the at least one second device.

[0008] In addition, a method performed by a second device in a wireless LAN (WLAN) system comprises the steps of: receiving an initial control frame (ICF) from a first device, wherein the ICF includes instructions for the second device to switch from a lower capability mode (LCM) to a higher capability mode (HCM); switching from the LCM to the HCM and transmitting an initial control frame response (ICR) to the first device; and receiving a data frame from the first device.

[0009] In addition, a method performed by a second device in a wireless LAN (WLAN) system comprises the step of receiving an initial control frame (ICF) from a first device, wherein the ICF includes instructions for the second device to switch from a lower capability mode (LCM) to a higher capability mode (HCM); the step of switching from the LCM to the HCM and transmitting an initial control frame response (ICR) to the first device; and the step of determining whether a data frame has been received from the first device, wherein if the data frame has not been received, the HCM is maintained for a certain period of time after the end of the transmission of the ICR.

[0010] In addition, a first device in a wireless LAN (WLAN) system comprises: a transceiver; and a control unit configured to transmit an initial control frame (ICF) to a plurality of second devices, wherein the ICF includes an instruction for the second devices to switch from a lower capability mode (LCM) to a higher capability mode (HCM), check whether at least one initial control frame response (ICR) has been received from at least one second device, and, if the at least one ICR has been received, transmit a data frame to the plurality of second devices.

[0011] In addition, in a wireless LAN (WLAN) system, a first device comprises: a transceiver; and a control unit configured to transmit an initial control frame (ICF) to a plurality of second devices, wherein the ICF includes an instruction for the second device to switch from a lower capability mode (LCM) to a higher capability mode (HCM), check whether at least one initial control frame response (ICR) has been received from at least one second device, and, if the at least one ICR has been received, transmit the ICF to another second device among the plurality of second devices excluding the at least one second device.

[0012] In addition, in a wireless LAN (WLAN) system, a second device comprises: a transceiver; and a control unit configured to receive an ICF (initial control frame) from a first device, wherein the ICF includes an instruction for the second device to switch from a lower capability mode (LCM) to a higher capability mode (HCM), switch from the LCM to the HCM, transmit an ICR (initial control frame response) to the first device, and receive a data frame from the first device.

[0013] In addition, in a wireless LAN (WLAN) system, a second device comprises: a transceiver; and a control unit configured to receive an ICF (initial control frame) from a first device, wherein the ICF includes an instruction for the second device to switch from a LCM (lower capability mode) to a HCM (higher capability mode), switch from the LCM to the HCM, transmit an ICR (initial control frame response) to the first device, and determine whether a data frame has been received from the first device, and wherein, if the data frame has not been received, the HCM is maintained for a certain period of time after the ICR transmission ends.

[0014] According to a method according to at least one embodiment of the present disclosure, power consumption can be reduced and packet transmission delay can be reduced through efficient mode switching.

[0015] Figure 1 is a diagram illustrating an example of a wireless communication network.

[0016] Figure 2 is a diagram illustrating an example of the structure of an electronic device that performs WLAN connection.

[0017] Figure 3 is a diagram illustrating an example of a link setup process for a typical wireless LAN.

[0018] Figure 4 is a diagram illustrating an example of a hidden node and an exposed node, and an example of an RTS and CTS for solving the problem of a hidden node and an exposed node.

[0019] Figure 5 is a diagram illustrating an example of a frame structure used in an IEEE 802.11 system.

[0020] Figure 6 is a diagram illustrating an example of a NAV setting.

[0021] Figure 7 is a diagram illustrating an example of TXOP.

[0022] Figure 8 is a diagram illustrating an example of low-power operation that can be applied to a WLAN system.

[0023] Figure 9 is a diagram illustrating an example of dynamic power saving to reduce power consumption.

[0024] FIG. 10 is a diagram illustrating an example of an operation in which a transmitter transmits data to a receiver receiving a single DPS.

[0025] FIG. 11 is a diagram illustrating an example of a problem that may occur in the operation of a transmitter transmitting data to a receiver that supports multiple DPS.

[0026] FIG. 12 is a diagram illustrating an example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS.

[0027] FIG. 13 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS.

[0028] FIG. 14 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS.

[0029] FIG. 15 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS.

[0030] FIG. 16 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS.

[0031] FIG. 17 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS.

[0032] FIG. 18 is a drawing illustrating an example of the operation of a transmitter according to at least one embodiment of the present disclosure.

[0033] FIG. 19 is a diagram illustrating an example of the operation of a transmitter transmitting a MU-ICF according to at least one embodiment of the present disclosure.

[0034] FIG. 20 is a drawing illustrating an example of the operation of a receiver according to at least one embodiment of the present disclosure.

[0035] FIG. 21 is a drawing illustrating an example of the operation of a receiver receiving a MU ICF according to at least one embodiment of the present disclosure.

[0036] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

[0037] In describing the embodiments, technical details that are well known in the art to which this disclosure belongs and are not directly related to this disclosure are omitted. This is intended to convey the essence of this disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0038] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the size of each component does not entirely reflect its actual dimensions. Identical or corresponding components in each drawing have been assigned the same reference number.

[0039] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. The embodiments of the present disclosure are provided merely to make the present disclosure complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Throughout the specification, like reference numerals refer to like components.

[0040] At this point, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flow diagram block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing means of instruction to perform the function described in the flow diagram block(s).

[0041] Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that execute a computer or other programmable data processing equipment by performing a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer may also provide steps for executing the functions described in the flowchart block(s).

[0042] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For instance, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order depending on the corresponding function.

[0043] In this embodiment, the term "part" as used refers to a software or hardware component such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or may be configured to run one or more processors. Accordingly, according to some embodiments, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." In addition, the components and 'parts' may be implemented to utilize one or more CPUs within the device or secure multimedia card. Also, according to some embodiments, the 'parts' may include one or more processors.

[0044] Exemplary embodiments are described below in relation to wireless LAN systems solely for the sake of simplicity. It should be understood that the exemplary embodiments are equally applicable to systems using signals of one or more wired standards or protocols (e.g., Ethernet and / or HomePlug, PLC standards), as well as other wireless networks (e.g., cellular networks, pico networks, femto networks, satellite networks). As used herein, the terms WLAN and Wi-Fi® may include communications controlled by the IEEE 802.11 family of standards, BLUETOOTH®, HiperLAN (a set of wireless standards comparable to IEEE 802.11 standards, mainly used in Europe), and other technologies having a relatively short wireless propagation range. Accordingly, the terms WLAN and Wi-Fi may be used interchangeably herein. Additionally, although the following describes an infrastructure WLAN system including one or more APs and multiple wireless stations (STAs), exemplary embodiments are equally applicable to other WLAN systems including, for example, multiple WLANs, peer-to-peer (or independent basic service set) systems, Wi-Fi Direct systems and / or hotspots.

[0045] Additionally, while this specification describes the exchange of data frames between wireless devices, exemplary embodiments may be applied to the exchange of any data unit, packet, and / or frame between wireless devices. Accordingly, the term "frame" may include any frame, packet, or data unit such as, for example, protocol data units (PDUs), MAC (media access control) protocol data units (MPDUs), and PHY protocol data units (PPDUs). The term "A-MPDU" may mean aggregated MPDUs. In the following, a wireless LAN, or WLAN network, may be a network implementing at least one of the IEEE 802.11 wireless communication protocol standard family, such as as defined by the IEEE 802.11-2016 standard or its amendments (including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be).

[0046] In the following description, many specific details, such as examples of specific components, circuits, and processes, are presented to provide a thorough understanding of the present disclosure. As used herein, the term “connected” means being directly connected or being connected through one or more intervening components or circuits. The term “connected AP” means an access point to which a given wireless station is currently associated and / or connected (e.g., there exists a communication channel or link established between the access point and the given wireless station). Additionally, in the following description and for illustrative purposes, specific nomenclature is presented to provide a thorough understanding of exemplary embodiments. However, it will be apparent to those skilled in the art that these specific details may not be necessary to carry out the exemplary embodiments. In other cases, well-known circuits and devices are depicted in block diagram form to avoid obscuring the present disclosure. Also, the description of A / B means A or / and B, or at least one of A or B.

[0047] The operating principles of the present disclosure will be described in detail below with reference to the attached drawings. In describing the present disclosure below, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the present disclosure. Furthermore, the terms described below are defined in consideration of their functions in the present disclosure, and these may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0048] FIG. 1 is a diagram illustrating an example of a wireless communication network. The wireless communication network (100) may be an example of a wireless LAN, such as a Wi-Fi network. The wireless communication network (100) may include a number of wireless communication devices, such as an access point (AP, t102) and a number of stations (STA, 104). Although only one AP (102) is illustrated, the wireless communication network (100) may also include a number of APs (102).

[0049] A STA is a logical entity that includes a physical layer interface for a MAC and a wireless medium, and includes APs and non-AP STAs (Non-AP stations). Among the STAs, a portable terminal operated by a user is a Non-AP STA, and when simply referred to as STA, it may also refer to a Non-AP STA. Hereinafter, STA may refer to a non-AP STA. Each of the STAs (104) may be referred to as a terminal or a device. The terms 'terminal' or 'device' used in this specification may be referred to as a mobile station (MS), user equipment (UE), user terminal (UT), wireless terminal, access terminal (AT), terminal, subscriber unit, subscriber station (SS), wireless device, wireless communication device, wireless transmit / receive unit (WTRU), mobile node, mobile, or other terms. Various embodiments of the terminal may include cellular telephones, smartphones with wireless communication capabilities, personal handheld terminals (PDAs) with wireless communication capabilities, wireless modems, portable computers with wireless communication capabilities, imaging devices such as digital cameras with wireless communication capabilities, gaming devices with wireless communication capabilities, music storage and playback appliances with wireless communication capabilities, internet appliances capable of wireless internet access and browsing, as well as portable units or terminals integrating combinations of such functions. Additionally, the terminal may include machine-to-machine (M2M) terminals and machine-type communication (MTC) terminals / devices, but is not limited thereto. In this specification, the terminal may be referred to as an electronic device or simply a device.

[0050] An AP (102) is an entity that provides access to a distribution system (DS) via a wireless medium to an associated STA (STA) connected to it. The AP may also be called a central controller, a base station (BS), a Node-B, a base transceiver system (BTS), or a site controller.

[0051] An exemplary coverage area (106) of an AP (102) capable of representing the basic service area (BSA) of a wireless communication network (100) is illustrated. The AP (102) periodically broadcasts beacon frames (beacon frames may be interchangeable with beacons) containing a basic service set identifier (BSSID) to enable any STA (104) within the wireless range of the AP (102) to be associated with or re-associated with the AP (102) to establish or maintain individual communication links (108) (or may be referred to as Wi-Fi links) with the AP (102). The AP (102) can provide access to external networks for various STAs (104) within the WLAN through individual communication links (108).

[0052] A single AP (102) and an associated set of STAs (104) may be referred to as a basic service set (BSS) managed by the individual AP (102). The BSS may be identified to users by a service set identifier (SSID), as well as to other devices by a BSSID, which may be the MAC address of the AP (102).

[0053] BSS can be classified into infrastructure BSS and independent BSS (IBSS). The BSS shown in Fig. 1 is an IBSS, and it is also possible to establish an infrastructure BSS (not shown). An infrastructure BSS includes one or more STAs and APs, and in principle, communication between non-AP STAs in an infrastructure BSS is carried out via an AP, but if a direct link is established between non-AP STAs, direct communication between non-AP STAs is also possible.

[0054] Multiple infrastructure BSSs can be interconnected via DS. Multiple BSSs connected via DS are called an extended service set (ESS). STAs included in an ESS can communicate with each other, and within the same ESS, STAs can move from one BSS to another while communicating seamlessly.

[0055] A DS is a mechanism that connects multiple APs; it does not necessarily have to be a network, and there are no restrictions on its form as long as it can provide a specified distribution service. For example, a DS can be a wireless network such as a mesh network, or it can be a physical structure that connects APs to each other.

[0056] Additionally, AP (102) and STA (104) may be referred to as AP-MLD (access point multi-link device) and STA-MDL, respectively. This may mean that AP and STA can support multi-link operation.

[0057] Below, an example of a hierarchical structure according to the 802.11 standard is described.

[0058] The 802.11 standard document develops MAC and PHY protocols corresponding to Wi-Fi wireless access technology. The Data Link Layer (DLL) includes the MAC sublayer, which is responsible for media access control. It receives packets from the upper layer, 802.1X Port Filtering, via the MAC_SAP interface, constructs them into IEEE 802.11 MAC frames, and transmits them to the physical layer. The physical layer includes the PLCP (Physical Layer Convergence Procedure) sublayer and the PDM (Physical Medium Dependent) sublayer. The PLCP sublayer is responsible for converting the IEEE 802.11 MAC frames constructed by the MAC sublayer into PLCP frames. The PLCP frames are then transmitted to the target terminal through the PMD sublayer.

[0059] Various management frames that manage Wi-Fi wireless access are not transmitted at the upper layers of 802.1X. Instead, these management frames are transmitted as requests and responses between Station Management Entities (SMEs) located within each terminal. An SME is a layer-independent entity that may exist within a separate management plane or appear to be off-the-side. For example, if an AP wants to configure a BSS, it instructs the transmission of beacons via the MLME_SAP interface, specifically the MLME-START.request and MLME-START.confirm primitives. If an STA wants to establish an association with the corresponding AP, it instructs the transmission of association Request / Response frames via the MLME-ASSOCIATE.request, MLME-ASSOCIATE.response, MLME-ASSOCIATE.confirm, and MLME-ASSOCIATE.indication primitives. Meanwhile, if you wish to set operational parameter values ​​related to the physical layer, the SME can set various physical layer parameter values ​​through the PLCP_SAP interface.

[0060] FIG. 2 is a diagram illustrating an example of the structure of an electronic device performing a WLAN connection. Referring to FIG. 2, the electronic device (200) may be connected to an AP (210), and the electronic device (200) may include a processor (230) and a communication module (220). The electronic device (200) may be the STA (104) of FIG. 1, in which case the electronic device (200) may be connected to the AP (210) as illustrated. Alternatively, the electronic device (200) may be the AP (102) of FIG. 1, in which case the electronic device may be connected to the STA (104) and / or another AP as illustrated in FIG. 1.

[0061] The communication module (220) can receive a communication signal from the outside or transmit a communication signal to the outside based on a Wi-Fi communication method (e.g., IEEE Std 802.11™). For example, the communication module (220) can operate based on Wi-Fi communication methods such as IEEE 802.11ac, 802.11ax, 802.11be, or 802.11bn, and in particular, IEEE 802.11be or 802.11bn supports a wider bandwidth, higher data throughput, and shorter latency compared to IEEE 802.11ax, thereby improving performance.

[0062] The communication module (220) may include a transceiver (224) for transmitting and receiving data with an external device and a communication processor (222) (e.g., a communication processor (not shown), or a short-range wireless communication module (e.g., a Wi-Fi chipset)). Depending on various embodiments, the communication module (220) may further include memory.

[0063] According to various embodiments, the transceiver (224) can convert a baseband transmission signal into a wireless signal or convert a received wireless signal into a baseband reception signal.

[0064] According to various embodiments, the communication module (220) may further include, in addition to the transceiver (224) and the communication processor (222), components for OFDM or OFDMA (orthogonal frequency division multiple access), such as a modulator, a digital-analog converter, a frequency converter, an A / D converter, an amplifier, and / or a demodulator.

[0065] According to various embodiments not shown, the electronic device (200) may be electrically connected to a communication module of the AP (210) and may include at least one antenna module that supports a communication protocol and / or frequency band supported by the communication module of the AP (210).

[0066] The communication processor (222) can control the transceiver (224) to form a communication connection with the AP (210). For example, the communication connection may include a Wi-Fi network. For example, the communication processor (222) can control the transceiver (224) to form a wireless connection with the AP (200) using a WLAN standard in the 2.4 GHz, 5 GHz, or 6 GHz band such as IEEE 802.11ac, 802.11ax, 802.11be, or 802.11bn. Alternatively, the communication processor (222) can control the transceiver (191) to form a wireless connection with the AP (210) using a WLAN standard in the 60 GHz band such as IEEE 802.11ad or 802.11ay. In addition, the method of communicating between the electronic device (200) and the AP (210) using a WLAN standard can be referred to as a communication method based on STA mode.

[0067] According to various embodiments, the processor (230) may include an application processor. The processor (230) may perform a specified operation of the electronic device (200) or control other hardware (e.g., a communication module (220)) to perform a specified operation.

[0068] According to various embodiments, the AP (210) may support the operation of transmitting packets to an external network and / or the operation of receiving packets from an external network based on a connection between a plurality of electronic devices (e.g., electronic device (200)) and an external network (e.g., the Internet, an external LAN, or a cellular network).

[0069] For example, the AP (210) may be a wireless router. The AP (210) may be a dedicated wireless router or a general-purpose device that supports mobile hotspot functions, and there are no limitations on its implementation. For example, the AP (210) may include the same components (e.g., a processor and / or a communication module) as the electronic device (200). Additionally, the AP (210) may transmit and receive data with an external device, such as a server. For example, the AP (210) may transmit at least some of the data received from the server to the electronic device (200).

[0070] If the electronic device (200) of FIG. 2 corresponds to the AP (102), the electronic device (200) may include a separate communication module for connection with an external network, although not shown. This communication module may be controlled by a processor (230) or by a separate processor. The separate communication module may include a transceiver and a processor, and may also include memory. Additionally, the electronic device (200) may include a separate antenna module or a wired connection device for connection with an external network.

[0071] Figure 3 is a diagram illustrating an example of a link setup process for a typical wireless LAN.

[0072] In order for an STA to set up a link and transmit and receive data on a network, it must first discover the network, perform authentication, establish an association, and go through authentication procedures for security. The link setup process can also be referred to as the session initiation process or the session setup process. Additionally, the discovery, authentication, association, and security setup processes of the link setup process can be collectively referred to as the association process.

[0073] Referring to FIG. 3, the STA (300) can perform a network discovery operation. The network discovery operation may include a scanning operation of the STA (300). That is, in order for the STA (300) to access a network, it must find a network that it can join. Before joining a wireless network, the STA (300) must identify a compatible network, and the process of identifying networks existing in a specific area is called scanning.

[0074] Scanning methods include active scanning and passive scanning. In active scanning, the STA (300) performing the scanning moves between channels and sends a probe request frame (322) to search for nearby APs and waits for a response. The responder sends a probe response frame (324) as a response to the probe request frame to the STA that sent the probe request frame. Here, the responder may be the AP or STA that last sent a beacon frame from the BSS of the channel being scanned. FIG. 3 illustrates an example of a BSS that becomes the responder because the AP (310) sends a beacon frame (320). In an IBSS, the responder is not constant because the STAs within the IBSS take turns sending beacon frames. For example, if an STA transmits a probe request frame on channel 1 and receives a probe response frame on channel 1, the STA can store the BSS-related information included in the received probe response frame and move to the next channel to perform scanning in the same way.

[0075] Scanning operations may be performed using a passive scanning method. In passive scanning, the STA performing the scanning detects beacon frames while switching between channels. A beacon frame is one of the management frames in IEEE 802.11, which announces the presence of a wireless network and is periodically transmitted to allow the scanning STA to find the wireless network and join it. Figure 3 illustrates an example of a BSS in which an AP (310) periodically transmits beacon frames (320) to an STA (300), and in an IBSS, STAs within the IBSS take turns transmitting beacon frames. When the scanning STA receives a beacon frame, it stores information about the BSS included in the beacon frame and records the beacon frame information in each channel while moving to another channel. When comparing active scanning and passive scanning, active scanning has the advantage of having less delay and power consumption than passive scanning.

[0076] After the STA (300) discovers the network, an authentication process may be performed. This authentication process may be referred to as the first authentication process to clearly distinguish it from the security setup operation (350) described later. The authentication process includes the STA (300) sending an authentication request frame (330) to the AP (310), and in response, the AP (310) sending an authentication response frame (332) to the STA (300). The authentication frame used in the authentication request / response corresponds to a management frame.

[0077] The authentication frame may include information such as the authentication algorithm number, authentication transaction sequence number, status code, challenge text, RSN (robust security network), finite cyclic group, etc. These are some examples of information that may be included in the authentication request / response frame, and may be replaced with other information or additional information may be included.

[0078] AP (310) can determine whether to allow authentication for the STA based on the information included in the received authentication request frame. AP (310) can provide the result of the authentication processing to the STA (300) through an authentication response frame.

[0079] After the STA is successfully authenticated, an association process may be performed. The association process includes the STA (300) sending an association request frame (340) to the AP (310), and in response, the AP (310) sending an association response frame (342) to the STA (300).

[0080] For example, the associated request frame may include information regarding various capabilities, beacon listen interval, SSID, supported rates, supported channels, RSN (robust security network), mobility domain, supported operating classes, traffic indication map broadcast request, interworking service capabilities, etc.

[0081] For example, an association response frame may include information related to various capabilities, status code, association ID (AID), support rate, enhanced distributed channel access (EDCA) parameter set, received channel power indicator (RCPI), received signal to noise indicator (RSNI), mobility domain, timeout interval (association comeback time), overlapping BSS scan parameters, TIM broadcast response, QoS map, etc.

[0082] This is a partial example of the information that may be included in the associated request / response frame, and it may be replaced with other information or additional information may be included.

[0083] Although not yet described, a security setup process can be performed after the STA is successfully associated with the network. The security setup process may be described as an authentication process through RSNA (robust security network association) requests / responses, and the authentication process (330) may be called the first authentication process, and the security setup process may also be called the authentication process.

[0084] The security setup process may include, for example, a process of setting up a private key through a 4-way handshake via an EAPOL (extensible authentication protocol over LAN) frame, or it may be performed according to a security method not defined in the IEEE 802.11 standard.

[0085] The following describes the Media Access Control Protocol provided by 802.11.

[0086] In wireless LAN systems based on IEEE 802.11, the basic access mechanism of a MAC is based on a distributed coordination function (DCF) utilizing the carrier sense multiple access with collision avoidance (CSMA / CA) method. There are two methods for detecting carriers in DCF: physical carrier sense and virtual carrier sense. The physical carrier sense method detects channel conditions at the physical layer and informs the MAC layer, while the virtual carrier sense method reserves a channel in advance by broadcasting the channel occupancy time to surrounding stations. An STA or AP that has secured a transmission channel records and transmits this channel occupancy time within an RTS and / or CTS or data frame; other STAs receiving this information determine that the channel is in use during this time and avoid channel occupancy contention, thereby avoiding collisions.

[0087] The physical carrier sensing method basically employs a listen before talk access mechanism, and according to this type of access mechanism, the AP and / or STA can perform a clear channel assessment (CCA) to sense the wireless channel, carrier, or medium for a predetermined time interval before starting transmission. The predetermined time interval is referred to as the inter-frame space (IFS) and may vary depending on the priority of the traffic to be transmitted. That is, priority can be determined by the length of the time interval, and packets with higher priority may have shorter time intervals.

[0088] The above IFS may include SIFS (short IFS), PIFS (PCF IFS), DIFS (DCF IFS), AIFS (arbitration IFS), etc. SIFS is the shortest time interval and can be used primarily as a waiting time for control information. PIFS is a medium-length time interval and can be for packets of medium priority (PIFS = SIFS + 1 slot time). DIFS is the longest time interval compared to SIFS and PIFS, has a low priority, and can be used primarily as a waiting time to check channel usage (DIFS = SIFS + 2 slot time). That is, for example, an STA intending to perform transmission can listen to (or detect channel) the channel usage during the DIFS period.

[0089] If sensing results determine that the medium is in an idle state, the AP and / or STA initiate frame transmission through that medium. Conversely, if the medium is detected to be in an occupied state, the AP and / or STA may attempt frame transmission after waiting for a delay period for medium access (e.g., a random backoff period) without initiating their own transmission. For instance, the AP and / or STA may randomly select a timer value within the contention window (CW) range, wait until the timer expires, and then sense the channel again. At this point, if the medium is idle, the AP and / or STA may initiate frame transmission; if the medium is occupied, the AP and / or STA doubles the size of the contention window and selects a timer value again. The size of the initially applied contention window is the minimum window size (contention window minimum, CW). min It is referred to as the maximum window size (contention window maximum, CW), and the maximum size of the contention window that can be applied is called the maximum window size (contention window maximum, CW maxIt is referred to as the ). By applying a random backoff period, collisions can be minimized because multiple STAs are expected to attempt frame transmission after waiting for different durations. For example, the relevant AP and / or STA randomly selects a timer value within the contention window (CW) range, waits until the timer expires, and then senses the channel again. At this point, if the medium is idle, the AP and / or STA can begin frame transmission; if the medium is occupied, the AP and / or STA doubles the size of the contention window and selects a timer value again. The size of the initially applied contention window is the minimum window size (contention window minimum, CW min It is referred to as the maximum window size (contention window maximum, CW), and the maximum size of the contention window that can be applied is called the maximum window size (contention window maximum, CW max It is called ).

[0090] However, since this DCF method does not consider the priority between STAs, it has the problem of being difficult to support various forms of data transmission and QoS (quality of service); therefore, HCF (hybrid coordination function) was introduced. HCF is based on the aforementioned DCF and PCF (point coordination function). PCF refers to a polling-based synchronous access method that periodically polls all receiving APs and / or STAs so that they can receive data frames. HCF includes EDCA (enhanced distributed channel access), a contention-based channel access method, and HCCA (HCF controlled channel access), a contention-based method utilizing a polling mechanism. Furthermore, HCF includes a media access mechanism to enhance the QoS of a WLAN and can transmit QoS data during both the contention period (CP) and the contention-free period (CFP).

[0091] According to EDCA, data has priorities ranging from 0 to 7 based on traffic type, and data arriving at the MAC layer is mapped to four access categories (ACs) according to these priorities. Higher priorities correspond to higher priority, and since each AC has its own parameters and backoff is performed using differently configured AC parameter values, data has different channel access priorities depending on the AC. The AC parameters include AIFS and CW. min , CW max , TXOP limits, etc. may exist. AIFS and CW minThe smaller the value, the higher the priority, and accordingly, the channel access delay is shortened, allowing data to use more bandwidth in a given traffic environment. The backoff process of EDCA, which generates a new backoff counter when a collision occurs between STAs during frame transmission, is similar to the existing DCF, and transmission based on traffic priority is guaranteed through EDCA parameters that include priority per AC.

[0092] Figure 4 is a diagram illustrating an example of a hidden node and an exposed node, and an example of an RTS and CTS for solving the problem of a hidden node and an exposed node.

[0093] Figure 4 (a) (400) is an example of a hidden node. When STA A and STA B are communicating and STA C has information to transmit, STA A is transmitting information to STA B, but when STA C performs carrier sensing before sending data to STA B, it can be determined that the medium is idle. This is because STA C may not be able to sense STA A's transmission (i.e., medium occupancy) at its location. In this case, a collision occurs because STA B receives information from STA A and STA C simultaneously. At this time, STA A can be considered a hidden node of STA C.

[0094] (b)(410) is an example of an exposed node. In a situation where STA B is transmitting data to STA A, STA C may have information to transmit to STA D. In this case, if STA C performs carrier sensing, it can determine that the medium is occupied due to the transmission by STA B. Accordingly, STA C must wait until the medium becomes idle, even if it has information to transmit to STA D. However, in reality, since STA A is outside the transmission range of STA C, the transmission from STA C and the transmission from STA B may not conflict from STA A's perspective, so STA C ends up waiting unnecessarily until STA B stops transmitting. In this case, STA C can be referred to as the exposed node of STA B.

[0095] In order to efficiently utilize the collision avoidance mechanism in the above situation, short signaling packets such as RTS (request to send) and CTS (clear to send) may be used. An STA intending to transmit data transmits an RTS to a STA intending to receive data, and the receiving STA that receives the RTS responds to the transmitting STA with a CTS frame. The RTS and / or CTS between the two STAs may cause surrounding STA(s) to overhear, thereby causing the surrounding STA(s) to consider whether to transmit information between the two STAs.

[0096] (c)(420) is an example of how to solve the hidden node problem. Assume that both STA A and STA C intend to transmit data to STA B. When STA A transmits an RTS to STA B, STA B transmits a CTS to STA A. STA C, which overhears the RTS and CTS, delays its media access until the data transmission of STA A and STA B is finished, thereby avoiding collisions.

[0097] (d)(430) is an example of a method for solving the exposed node problem. STA B, which intends to send data to STA A, sends an RTS, and STA A, which is to receive the data, sends a CTS to respond to the RTS. In this case, if STA C receives only the RTS sent by STA B and does not receive the CTS sent by STA A, STA C can determine that STA A is outside the carrier sensing area of ​​STC C. In this case, STA C can determine that no collision will occur even if it sends data to another STA (e.g., STA D) and can send the data.

[0098] Figure 5 is a diagram illustrating an example of a frame structure used in an IEEE 802.11 system.

[0099] The PPDU (physical layer protocol data unit) format can be configured to include the STF (short training field), LTF (long training field), SIG (signal) field, and data field. The most basic (e.g., non-HT (high throughput)) PPDU frame format can be configured to include only the L-STF (legacy-STF), L-LTF (legacy-LTF), SIG field, and data field.

[0100] STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization. LTF can be used for fine frequency / time synchronization and channel estimation. STF and LTF together can be referred to as the PHY preamble, and the PHY preamble is a signal for synchronization and channel estimation in the OFDM physical layer.

[0101] The SIG field can be used to transmit control information for demodulation and decoding of the data field. The SIG field may include information regarding the data rate and data length. Additionally, the SIG field may include a parity bit, a SIG TAIL bit, etc.

[0102] The data field may include a SERVICE field, a PSDU (physical layer service data unit), and PPDU TAIL bits, and may also include padding bits if necessary. Some bits of the SERVICE field may be used for the descrambler at the receiver. The PSDU corresponds to the MPDU (MAC protocol data unit) defined at the MAC layer and may contain data generated or used by the upper layer. The PPDU TAIL bits may be used to return the encoder to a state of 0. Padding bits may be used to adjust the length of the data field to a predetermined unit.

[0103] MPDUs 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 an MPDU and can be transmitted or received through the PSDU of the data portion in the PPDU format.

[0104] The MAC header is defined as an area containing the frame control field, duration / ID field, address 1 field, address 2 field, address 3 field, sequence control field, address 4 field, QoS control field, and HT control field.

[0105] The frame control field contains information about the corresponding MAC frame characteristics. The interval / identifier field can be implemented to have different values ​​depending on the type and subtype of the corresponding MAC frame.

[0106] Fields 1 through 4 of the address are used to indicate the BSSID, source address (SA), destination address (DA), transmitting address (TA) representing the transmitting STA address, and receiving address (RA) representing the receiving STA address.

[0107] The sequence control field is configured to include a sequence number and a fragment number. The sequence number may indicate the sequence number assigned to the corresponding MAC frame. The fragment number may indicate the number of each fragment of the corresponding MAC frame.

[0108] The QoS control field contains information related to QoS. The QoS control field may be included if the Subtype subfield indicates a QoS data frame. The HT control field contains control information related to HT and / or VHT transmission and reception techniques.

[0109] The frame body is defined as the MAC payload, contains the data to be transmitted from the upper layer, and has a variable size. For example, the maximum MPDU size can be 11,454 octets, and the maximum PPDU size can be 5.484 ms.

[0110] FCS is defined as the MAC footer and is used for error detection in MAC frames.

[0111] The first three fields (frame control field, interval / identifier field, and address 1 field) and the very last field (FCS field) constitute the minimum frame format and are present in all frames. Other fields may exist only in specific frame types.

[0112] The following describes the network allocation vector (NAV) used in wireless LAN networks.

[0113] As previously mentioned, the CSMA / CA mechanism includes virtual carrier sensing in addition to physical carrier sensing, where the AP and / or STA directly senses the medium. Virtual carrier sensing is intended to compensate for problems that may occur in medium access, such as hidden node issues. For virtual carrier sensing, the MAC of a wireless LAN system may utilize NAV. NAV is a value that indicates to other APs and / or STAs the time remaining until the medium becomes available, provided that the AP and / or STA currently using or authorized to use the medium is using the medium. Therefore, the value set as NAV corresponds to the period during which the medium is scheduled to be used by the AP and / or STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during that period. NAV can be set, for example, based on the value of the duration field in the MAC header of the frame.

[0114] Figure 6 is a diagram illustrating an example of a NAV setting.

[0115] Referring to FIG. 6, the source STA (source STA, 600) transmits an RTS frame after DIFS, and the destination (610) transmits a CTS frame after SIFS. The destination STA designated as the recipient via the RTS frame does not set the NAV. Some of the remaining STAs (620) receive the RTS frame and set the NAV (630), while others receive the CTS frame and set the NAV (640).

[0116] If a CTS frame (e.g., PHY-RXSTART.indication primitive) is not received within a certain period from the time an RTS frame is received (e.g., when a MAC receives the PHY-RXEND.indication primitive corresponding to the RTS frame), STAs that set or updated the NAV via the RTS frame may reset the NAV (e.g., to 0) (or this case may be referred to as NAVtimeout). The certain period may be (2*aSIFSTime + CTS_Time + aRxPHYStartDelay + 2*aSlotTime), which may be referred to as the NAVtimeout period. CTS_Time may be calculated based on the length and data rate of the CTS frame indicated by the RTS frame.

[0117] In FIG. 6, for convenience, NAV setting or updating is exemplified through an RTS frame or a CTS frame, but NAV setting / resetting / updating may also be performed based on the interval field of various other frames, such as non-HT PPDU, HT PPDU, VHT PPDU, or HE PPDU (for example, the interval field within the MAC header of a MAC frame).

[0118] In addition, 802.11ax introduced basic NAV and intra-BSS NAV. Basic NAV is always set (mandatory) to NAV based on frames transmitted by APs or STAs other than itself, while intra-BSS NAV can be optionally set to NAV based on frames transmitted by the BSS to which it belongs. An AP or STA can access the medium when both NAV timers have expired (or after the NAV time interval has elapsed).

[0119] The following describes TXOP. TXOP (transmission opportunity) was newly introduced in 802.11e MACs to guarantee QoS and increase channel utilization. To guarantee QoS, TXOP can be used to allocate an opportunity for priority transmission when two or more packets belong to the same AC (access category).

[0120] Figure 7 illustrates an example of a TXOP. An STA participating in QoS transmission can obtain a TXOP that allows it to transmit traffic for a certain period using two channel access methods, such as EDCA and HCCA. TXOP acquisition is possible by succeeding in EDCA contention or by receiving a QoS CF-Poll frame from an AP; the former is referred to as an EDCA TXOP, and the latter as a Polled TXOP. In this way, the concept of a TXOP can be used to grant a certain amount of time to any STA to transmit a frame, or to forcibly limit the transmission time.

[0121] The transmission start time and maximum transmission time of a TXOP are determined by the AP, and this is notified to the STA by a beacon frame in the case of an EDCA TXOP, and by a QoS CF-Poll frame in the case of a Polled TXOP.

[0122] NAV can be understood as a type of timer designed to protect the TXOP of a transmitting STA (e.g., a TXOP holder). An STA can protect the TXOPs of other STAs by not performing channel access during the period when the NAV set for it is valid. In current wireless LAN systems, the TXOP duration is set via the duration field of the MAC header. That is, the TXOP holder and the TXOP responder (e.g., an Rx STA) include all the TXOP information necessary for transmitting and receiving frames in the duration field of the frames being exchanged between them. Third-party STAs that are not the TXOP holder or TXOP responder (e.g., third-party STAs) check the duration field of the frames exchanged between the TXOP holder and the TXOP responder, and delay channel usage until the NAV period expires by setting or updating the NAV.

[0123] The primary channel and secondary channel are described below. The primary channel is a common channel operated by all STAs that are members of the BSS. For example, in a 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 80 + 80 MHz BSS, the primary channel may be the primary 20 MHz channel. In this case, the 40 and 80 MHz channels containing the primary 20 MHz channel may be referred to as the primary 40 and 80 MHz channels, respectively, and the primary channel may generally be referred to as the primary 20 MHz channel.

[0124] A secondary channel is a channel associated with a primary channel and is used to create a channel wider than the primary channel. For example, in a 40 MHz, 80 MHz, and 160 MHz BSS, the 40 MHz channel may be the sum of the primary 20 MHz channel and the secondary 20 MHz channel, the 80 MHz channel may be the sum of the primary 40 MHz channel and the secondary 40 MHz channel, and the 160 MHz channel may be the sum of the primary 80 MHz channel and the secondary 80 MHz channel.

[0125] Currently, it is common for multiple APs to operate in specific areas, and in such cases, wireless LAN network performance degradation occurs due to coverage overlap between APs. This is because the APs of each BSS and the STAs connected to them are affected by signals from adjacent BSSs, leading to interference and a reduction in transmission rates caused by collisions between signals transmitted simultaneously. BSSs that can affect signal transmission in this way (or have overlapping coverage) can be referred to as overlapping BSSs (OBSS). To address this problem, interference avoidance techniques are being researched, such as dividing the bandwidth available to each user so that it does not overlap or performing channel switching to unused channels, as well as interference alignment techniques that minimize the impact of interference even when using the same bandwidth.

[0126] The 802.11be standard is described below. Also known as EHT (extremely high throughput), 802.11be operates across the 2.4, 5, and 6 GHz bands. It is being developed to provide low latency and high network throughput by introducing a 320 MHz wide bandwidth, 4096QAM, multiple resource units (RUs), and multi-link operation (MLO), offering speeds up to 46 Gbps—4.8 times faster than WiFi 6. Specifically, 802.11be provides a 320 MHz wide bandwidth in the 6 GHz band and can transmit data via MU-MIMO, which offers 16 spatial streams in both uplink and downlink. It also achieves high transmission efficiency by adopting 4096QAM. Furthermore, it features enhanced spectrum efficiency by flexibly performing spectrum resource scheduling through multiple RUs, and the ability to simultaneously transmit and receive data across various frequency bands and channels through multi-link operation.

[0127] FIG. 8 illustrates an example of low-power operation applicable to a WLAN system. Conventional power saving mechanisms are based on a low-power state in which the RF cannot transmit or receive signals. In power management mode, the AP and STA may be in active mode or power save mode (PS mode). When PS mode is applied, the RF may correspond to one of two states: a doze state, in which the RF cannot transmit or receive signals, or an awake state, in which power is supplied to the RF and signals can be transmitted or received. In the case of active mode, the AP or STA may always be in the awake state. The AP can change the power management mode of the STAs through instructions in the power management subfield included in the frame control field transmitted to the STAs. For example, if the power management subfield is 0, the STA may be in active mode, and if the power management subfield is 1, the STA may be in PS mode.

[0128] According to FIG. 8, a STA (810) with PS mode applied can receive a beacon containing its own AID in a TIM (traffic indication map) element transmitted by an AP (800), for example, in a doze state (820) (830). At this time, the STA (810) transmits a PS-poll control frame (832) and transitions to an awake state (822). Upon receiving the PS-poll control frame, the AP (800) can transmit an ACK to the STA (834) and then transmit buffered data to the STA (836). At this time, the frame control field of the MAC header of the frame for data transmission contains a more data field, and if there is more buffered data for the AP (800) to transmit to the STA (810), the more data field can be set to 1. Afterward, the STA (810), having checked the more data field, sends an ACK for the data and then re-transmits the PS-poll control frame (838, 840). Upon receiving the PS-poll frame, the AP (800) sends an ACK and transmits data for the STA (810) (844). If the AP (800) has no more data to transmit, the AP (800) sets the more data field of the frame control field of the MAC header of the data to 0 and transmits it. The STA (810) sends an ACK for the second data and can switch from awake mode (822) to doze state (820) (846). Alternatively, although not shown, the AP may set the end of service period (EOSP) subfield of the frame control field of the MAC header of the frame to 1 to notify the STA that the SP has ended, and the STA can switch to doze state. The STA can expect the above awake mode to be applied to the SP.

[0129] Figure 9 is a diagram illustrating an example of dynamic power saving (hereinafter referred to as DPS) to reduce power consumption.

[0130] A low capability mode (which can be used interchangeably with lower capability mode (LCM) or low power mode, etc.) and a high capability mode (which can be used interchangeably with higher capability mode (HCM), full capability mode, high power mode, etc.) may be applied to the AP or / and STA. Although an example in which LCM and HCM exist is illustrated in this disclosure, it is also possible for LCM and HCM to each have multiple modes that support multiple different capabilities. LCM may correspond to at least one of a mode that supports a 20 MHz bandwidth, one secondary channel, a limited data rate, or a limited PPDU format (e.g., only reception of older versions of PPDU such as Non-HT PPDU, Pre-HE PPDU, etc. is supported), or a mode in which frame transmission is limited and only frame reception is possible, and is not limited by the above description. In the case of HCM, the supported operating bandwidth may be wide, and it may correspond to a mode that supports higher capabilities compared to LCM in supported NSS (number of spatial streams) and / or MCS, etc.

[0131] According to FIG. 9, LCM and HCM may be applied to the AP (910) (940). The STA (900) transmits an ICF (initial control frame) to the AP (910) (910), and the ICF may include padding (922). The ICF is a control frame that initiates a specific operation; for example, in this example, the frame that initiates the TXOP (930) may correspond to this. Upon receiving the ICF, the AP (910) switches from the LCM (942) to the HCM (946) (944), and the padding (922) may correspond to the time for switching from the LCM to the HCM within the TXOP. After the ICF, the AP transmits an ICR (initial control frame response) as a response to the ICF (924), and the STA (900) upon receiving the ICR may transmit a PPDU containing data (926). The AP (910) that receives the above data PPDU transmits a block ACK (BA), which is acknowledgment of receipt for the above data PPDU (928). An example of FIG. 9 is also applicable when the STA and AP are applied in reverse.

[0132] The AP can instruct the STA via a beacon or probe response frame the requirements of the ICF and the required padding duration for the operation as shown in FIG. 9. The STA can transmit the ICF in a non-HT duplicate format, and the AP can determine the appropriate transmission data rate of the ICR to be transmitted to the STA through the ICF received signal strength indication (RSSI) and signal-to-noise ratio (SNR), etc. In the operation of FIG. 9, the STA can continue the TXOP only when it receives the ICR from the AP. If the STA does not receive the ICR, the TXOP may be terminated.

[0133] Dynamic low-power operation as shown in FIG. 9 includes switching between LCM and HCM. In this case, if unnecessary switching between modes occurs, frame transmission and reception cannot be performed during the time the switching takes place, resulting in data transmission latency and unnecessary power consumption due to the switching. For example, power consumption of the transmitter and receiver may occur, such as switching back to HCM and transmitting ICF and ICR due to the switching. In the present disclosure, the transmitter and receiver may be AP and STA, respectively, or vice versa. Additionally, the transmitter and receiver may be referred to as terminals.

[0134] FIG. 10 is a diagram illustrating an example of an operation in which a transmitter transmits data to a receiver receiving a single DPS. According to FIG. 10, when data to be transmitted to a receiver (RX, 1010) occurs, the transmitter (TX, 1000) transmits an ICF (1020) containing padding. Upon receiving the ICF (1020), the receiver switches from an LCM (1040) to an HCM (1044) (1042) and transmits an ICR (1022) in response, but the transmitter (1000) may fail to receive the ICR. In this case, since there is no data transmission from the transmitter (1000), the receiver (1010) switches back to an LCM (1046). A transmitter (1000) that has not received the ICR transmits the ICF (1024) again to the receiver (1010), and the receiver (1010) that has received the ICF (1024) switches back to HCM (1048) and transmits the ICR (1026) as a response. Afterwards, the transmitter (1000) that has received the ICR (1026) transmits a data frame (1028), and the receiver (1010) transmits the BA (1030), thereby completing the transmitter's data transmission. As described above, if the transmitter fails to receive the ICR, which is a response to the ICF, the receiver switches back to LCM, and the transmitter must perform ICF retransmission, so the delay becomes longer.

[0135] A transmitter to which DPS is applied can trigger a mode switch of the receiver by transmitting an ICF to transmit data to the receiver immediately without delay when buffered data occurs. However, in situations where data transmission is not possible when buffered data occurs, such as when the transmitter is transmitting a frame to another receiver or when the medium is busy for a certain period due to being occupied by OBSS frame transmission, the data to be transmitted by the transmitter to multiple receivers supporting DPS may be stored in a buffer. In this case, the transmitter may perform multi-data transmission to multiple receivers supporting DPS. The multi-data transmission may include data for each of the multiple receivers or may include transmitting a single data to multiple receivers.

[0136] FIG. 11 illustrates an example of a problem that may occur in the operation of a transmitter transmitting data to a receiver that supports multiple DPS. According to FIG. 11, a transmitter (TX, 1100) transmits an ICF (1130) including padding to receiver 1 (RX1, 1110) and receiver 2 (RX2, 1120). The ICF may include information that allocates resources that multiple receivers can use to transmit an ICR. At this time, receiver 1 (1110) succeeds in receiving the ICF, but receiver 2 (1120) may fail to receive the ICF. Receiver 1 (1110), having successfully received the ICF, switches from the LCM (1150) to the HCM (1154) (1152) and transmits an ICR (1132) in response to the ICF (1130). In contrast, receiver 2 (1120), which failed to receive the ICF, continues to maintain the LCM (1156). The transmitter (1110), having received the ICR (1132) transmitted by receiver 1 (1110), transmits a data frame (1134). Upon receiving the data frame (1134), receiver 1 (1110) transmits a BA (1136) to the transmitter (1100) and can switch to the LCM (1160).

[0137] Afterwards, the transmitter (1100) transmits the ICF (1138) again to transmit data to the receiver 2 (1120). Upon receiving the ICF (1138), the receiver 2 (1120) switches to HCM (1158) and transmits the ICR (1140) to receive the data frame (1142).

[0138] As described above, when an ICF is transmitted to multiple DPS receivers, if the transmission of the ICF to some of the receivers fails or / and the transmitter fails to receive the ICR from some of the receivers, the transmission of data frames is performed to some of the receivers that have successfully transmitted and received the ICF and ICR. In this case, for receivers that have failed to transmit and receive the ICF or / and ICR, additional mode switching and additional transmission and reception of the ICF and ICR are required until the data frame is received, which leads to a problem of prolonged delay in data reception and increased power consumption due to switching between modes. The present disclosure proposes at least one embodiment to solve this problem. At least one of the methods described below may be used in combination.

[0139] FIG. 12 is a diagram illustrating an example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS. FIG. 12 is a diagram illustrating a method of transmitting a data frame to a specific receiver even if the transmitter has not received an ICR from the specific receiver.

[0140] Although not shown, the transmitter and receiver may be configured to perform DPS operation. The transmitter and receiver exchange capability information regarding DPS operation in advance and agree to apply dynamic low-power operation from a specific point in time. The capability information regarding DPS operation may include specific information regarding each LCM or / and HCM (at least one of the following: PPDU format receivable in each mode, supported modulation (modulation method, modulation order, etc.), supported bandwidth (bandwidth, BW) in each mode, and whether a frame can be transmitted), the transition time from LCM to HCM (or / and vice versa), and the transition time from normal transmit / receive operation to DPS operation (or / and vice versa). Additionally, whether the receiver and / or transmitter support operation for multiple DPS receivers as shown in FIG. 12 may also be included in the capability information.

[0141] According to FIG. 12, the transmitter (TX, 1200) transmits an ICF (1240) including padding to receiver 1 (RX1, 1210), receiver 2 (RX2, 1220), and receiver 3 (RX3, 1230). For example, the ICF may correspond to a multi-user (MU)-RTS, a buffer status report poll (BSRP), etc., but is not limited to such examples. The ICF (1240) may include information for allocating resources to each receiver to transmit an ICR. The ICF may follow the structure of a trigger frame, and ICR resource allocation information is transmitted to receivers 1, 2, and 3 through the RU (resource unit) allocation subfield of the user info field included in the ICF. The ICF (1240) may include padding, which may correspond to an ICF that initiates a TXOP. The above ICF (1240) may include instructions for the receiver to switch from LCM to HCM. The receiver switches from LCM to HCM if the ICF has a user info field assigned to it (in the case of a multi-user ICF).

[0142] Receiver 1 (1210) and Receiver 2 (1220) succeed in receiving the ICF (1240) and switch from LCM (1260) to HCM (1264, 1268) (1262). At this time, Receiver 3 (1230) fails to receive the ICF (1240) and maintains LCM (1270). Receiver 1 (1210) and Receiver 2 (1220), having succeeded in receiving the ICF (1240), each transmit an ICR (1242, 1244), but the transmitter (1200) succeeds in receiving the ICR (1242) of Receiver 1 (1210) but fails to receive the ICR (1244) of Receiver 2 (1220). At this time, the format of the ICR can be determined as a response message according to the ICF. For example, if the ICF is BSRP, the ICR can be BSR or BA, and if the ICF is MU-RTS, the ICR can be CTS. At this time, since the transmitter (1200) has succeeded in receiving the ICR transmitted from at least one receiver (among the receivers to which it transmitted the ICF), the transmitter (1200) transmits a data frame (1246) to all ICF receiving terminals (i.e., receiver 1 (1210), receiver 2 (1220) and receiver 3 (1230)).

[0143] Since transmission and reception between frames within a TXOP caused by an ICF are performed at short time intervals known as SIFS, the transmitter can pre-configure a data frame containing data for multiple receivers that received the ICF. This is because, even if the transmitter realizes that it failed to receive the ICR, there may not be enough time to reconfigure a data frame only for the receivers that successfully received the ICR; therefore, transmitting the configured data frame (containing data for multiple receivers that received the ICF) may be more advantageous in terms of implementation compared to constructing a new data frame. Additionally, by immediately transmitting the data frame, a receiver that receives the ICF and switches to HCM can receive the data frame (even if the transmitter fails to receive the corresponding ICR), thereby reducing the delay in data transmission and reception.

[0144] When the transmitter (1200) transmits a data frame (1246), receivers 1 (1210) and 2 (1220), which are HCMs (1264, 1268), can receive the data frame (1246) through the reception of the ICF (1240). At this time, receiver 3 (1230), which is in the LCM (1230), cannot receive the data frame (1246) because it cannot receive the ICF (1240). Subsequently, receivers 1 (1210) and 2 (1220) each transmit BA (1248, 1250), which is reception acknowledgment information for the data frame (1246), to the transmitter (1200) and switch to the LCM (1266, 1280).

[0145] The transmitter (1200) transmits an ICF (1252) to receiver 3 (1230) for data transmission to receiver 3 (1230). Upon receiving the ICF (1252), receiver 3 (1230) switches to an HCM (1274) (1272), receives a data frame (1256), transmits a BA (1258), and switches back to an LCM (1278) (1276).

[0146] Referring to FIG. 12, when a receiver receives an ICF and transmits an ICR to a transmitter, even if the transmitter fails to receive the ICR, the receiver can receive the data frame transmitted by the transmitter because it has switched to HCM. In this case, the receiver can receive the data frame without unnecessary mode switching or delay. However, if the receiver fails to receive the ICF transmitted by the transmitter, it does not switch to HCM (i.e., maintains LCM), so the receiver cannot receive the data frame transmitted by the transmitter. In this case, the transmitter must transmit the ICF again to transmit the data frame to the receiver.

[0147] Considering that a receiver may fail to receive the ICF, if the size (or length) of the data to be received by the receiver is large, there is a problem that the delay may become too large because the receiver that failed to receive the ICF must receive its own data after another receiver has received the data frame. Taking this into account, if the size (or length) of the data to be received by multiple receivers (or at least one of the multiple receivers) or the length of the data frame configured by the transmitter is long, the method shown in FIG. 12 may not be applied, and if the size (or length) of the data is short, the method shown in FIG. 12 may be applied. The transmitter may determine whether to apply the method of FIG. 12 based on capability information or / and a comparison of the size of the data with a specific threshold, or by any method, and the threshold may be predetermined, set by the transmitter or receiver, or / and included in the capability information.

[0148] FIG. 13 illustrates another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS. FIG. 13 illustrates a method in which a transmitter retransmits an ICF to a receiver that has not received the corresponding ICR, and retransmits the ICF until it receives the ICR from all receivers.

[0149] According to FIG. 13, the transmitter (TX, 1300) transmits an ICF (1340) including padding to receiver 1 (RX1, 1310), receiver 2 (RX2, 1320), and receiver 3 (RX3, 1330). The ICF (1340) may correspond to an ICF that initiates a TXOP, and the ICF (1340) may include instructions for the receiver to switch from LCM to HCM.

[0150] Receiver 1 (1310) and Receiver 2 (1320) succeed in receiving the ICF (1340) and switch from LCM (1360) to HCM (1364) (1262). At this time, Receiver 3 (1330) fails to receive the ICF (1340) and maintains LCM (1376). Receiver 1 (1310) and Receiver 2 (1320), having succeeded in receiving the ICF (1340), each transmit an ICR (1342, 1344), but the transmitter (1300) succeeds in receiving the ICR (1342) of Receiver 1 (1310) but fails to receive the ICR (1344) of Receiver 2 (1320). At this time, the transmitter (1300) transmits the ICF (1346) again to receiver 2 (1320) and receiver 3 (1330) that failed to receive the ICR. At this time, since a specific receiver may not have received the previously transmitted ICF (1340) and therefore has not switched to HCM, the ICF (1346) may include padding.

[0151] Receiver 2 (1320) and receiver 3 (1330) that receive the retransmitted ICF (1346) each transmit an ICR (1348, 1350) to the transmitter (1300), and the transmitter (1300) that receives the ICR (1348, 1350) transmits a data frame (1352) to receiver 1 (1310), receiver 2 (1320), and receiver 3 (1330), and the data frame may contain data for receiver 1 (1310), receiver 2 (1320), and receiver 3 (1330). Subsequently, receiver 1 (1310), receiver 2 (1320) and receiver 3 (1330) each transmit BA (1354, 1356, 1358) to the transmitter (1300) and switch to LCM (1368) (1366).

[0152] At this time, the transmitter can transmit data in a single data frame transmission by retransmitting the ICF to the receiver corresponding to the ICR it did not receive. At this time, the transmitter may retransmit the ICF after receiving the ICR from at least one receiver, either at SIFS or after a certain period of time. In the example of FIG. 13, an example is shown in which the ICR is received from all multiple receivers with a single ICF retransmission, but two or more ICF retransmissions are also possible. Additionally, ICF retransmissions may be limited to a maximum number, and after the maximum number of ICF retransmissions, the transmitter may transmit a data frame (as in the example of FIG. 12). The transmitter may determine whether to apply the method of FIG. 13 based on capability information, and the maximum number may be predetermined, set by the transmitter or receiver, or / and included in the capability information.

[0153] FIG. 14 illustrates another example of an operation in which a transmitter transmits data to receivers that support multiple DPS. FIG. 14 illustrates a method in which a transmitter receives an ICF but fails to receive the corresponding ICR to retransmit the ICF to receivers. According to FIG. 14, a transmitter (TX, 1400) transmits a padded ICF (1440) to receiver 1 (RX1, 1410), receiver 2 (RX2, 1420), and receiver 3 (RX3, 1430). The ICF (1440) may correspond to an ICF that initiates a TXOP, and the ICF (1440) may include instructions for the receivers to switch from LCM to HCM.

[0154] Receiver 1 (1410) and Receiver 2 (1420) succeed in receiving the ICF (1440) and switch from LCM (1470) to HCM (1474, 1478) (1472). At this time, Receiver 3 (1430) fails to receive the ICF (1440) and maintains LCM (1482). Receiver 1 (1410) and Receiver 2 (1420), having succeeded in receiving the ICF (1440), each transmit an ICR (1442, 1444), but the transmitter (1300) succeeds in receiving the ICR (1442) of Receiver 1 (1410) but fails to receive the ICR (1444) of Receiver 2 (1420). At this time, the transmitter (1400) successfully receives the ICF but transmits the ICF (1446) again to receiver 2 (1420), which failed to receive the ICR. If the transmitter detects a PHY preamble in the resource (or resource unit, RU) where the specific receiver is supposed to transmit the ICR (this can be understood as a case where information is not properly received, such as when a signal is detected but fails to pass the MAC CRC check), it determines that the specific receiver has received the ICF but has not received the specific receiver's ICR, and can retransmit the ICF without padding. This is because the specific receiver has received the ICF and converted it to HCM (1478). At this time, the transmitter can retransmit the ICF after SIFS or a certain time after receiving the ICR from the receiver.

[0155] Receiver 2 (1420), having received the ICF (1446) retransmitted by the transmitter (1400), transmits an ICR (1448), and the transmitter (1400), having received this, can transmit a data frame (1450) to receiver 1 (1400) and receiver 2 (1410). The data frame may contain data for receiver 1 (1410) and receiver 2 (1420). Subsequently, receiver 1 (1410) and receiver 2 (1420) each transmit a BA (1352, 1354) to the transmitter (1400) and switch to an LCM (1476) (1474, 1480).

[0156] Subsequently, the transmitter (1400) transmits an ICF (1456) including padding to receiver 3 (1430), and receiver 3 (1430), upon receiving the ICF (1456), switches to an HCM (1486) (1484) and transmits an ICR (1458) to the transmitter (1400). Subsequently, receiver 3 (1430), upon receiving the data frame (1460) transmitted by the transmitter (1400), transmits a BA (1462) and switches back to an LCM (1490) (1488).

[0157] FIG. 15 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS. FIG. 15 is a diagram illustrating an operation in which a transmitter and multiple receivers transmit and receive data when the transmitter occupies a long TXOP capable of transmitting and receiving multiple data frames.

[0158] According to FIG. 15, the transmitter (TX, 1500) transmits an ICF (1530) including padding to receiver 1 (RX1, 1510) and receiver 2 (RX2, 1520). The ICF (1530) may correspond to an ICF that initiates a TXOP, and the ICF (1530) may include instructions for the receiver to switch from LCM to HCM. At this time, the transmitter may set the TXOP length, and sets the TXOP length to be as long as possible.

[0159] Receiver 1 (1510) succeeds in receiving the ICF (1530), switches from the LCM (1550) to the HCM (1554) (1552), and transmits the ICR (1532). At this time, Receiver 2 (1520) fails to receive the ICF (1530) and maintains the LCM (1558). The transmitter (1500) transmits a data frame (1534) to Receiver 1 (1530), and Receiver 1 (1510) transmits a BA (1534) for the data frame and switches to the LCM (1556). The data frame may contain data for Receiver 1 (1510) and Receiver 2 (1520).

[0160] At this time, since the TXOP period of the transmitter (1500) remains even after receiving the BA (1534), the transmitter (1500) transmits the ICF (1536) to receiver 2 (1510) so that receiver 2 (1520) switches from the LCM (1558) to the HCM (1562) (1560). At this time, the transmitter may retransmit the ICF to another terminal after SIFS or after a certain time interval after receiving the BA (or after the end of data transmission and reception with another receiver). This operation is possible because the ICF retransmission is performed within the TXOP period of the transmitter (1500). Subsequently, the transmitter (1500), having received the ICR (1538) from receiver 2 (1538), transmits a data frame (1540) to receiver 2 (1520). If the transmitter (1500) lacks sufficient time to construct a new second data frame (1540) containing only data for receiver 2 (1520), the transmitter (1500) may also generate the second data frame (1540) by filling the portion for receiver 1 (1510) in the first data frame (1534) with null data or padding. In this way, the method of transmitting a transmitted data frame containing null data or padding without the transmitter creating a new data frame may be applied not only to FIG. 15 but also to the examples of FIG. 12 through 17.

[0161] FIG. 16 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS. FIG. 16 is a diagram illustrating a case in which an example of the present disclosure is applied in the case of a terminal with a long transition delay and a terminal with a short transition delay.

[0162] According to FIG. 16, the transmitter (1600) transmits an ICF (1630) including padding to receiver 1 (RX1, 1610) and receiver 2 (RX2, 1620). The ICF (1630) may correspond to an ICF that initiates a TXOP, and the ICF (1630) may include instructions for the receiver to switch from LCM to HCM. In this case, receiver 1 (1610) may correspond to a terminal with a short switching delay, and receiver 2 (1610) may correspond to a terminal with a long switching delay.

[0163] At this time, receiver 1 (1610) succeeds in receiving the ICF (1630), switches from the LCM (1650) to the HCM (1654) (1652), and transmits the ICR (1632) to the transmitter (1600). The transmitter (1600) succeeds in receiving the ICR (1632). Receiver 2 (1610) also succeeds in receiving the ICF (1630), switches from the LCM (1656) to the HCM (1660) (1658), and transmits the ICR (1634) to the transmitter (1600), but the transmitter (1600) may fail to receive the ICR (1634).

[0164] At this time, the transmitter (1600) transmits a data frame (1636) to receiver 1 (1610), and receiver 1 (1610) transmits a BA (1638) for the data frame (1636) to the transmitter (1600). At this time, receiver 2 (1620) transmits the ICR (1634) for a certain period of time (for example, the certain period of time is DIFS + 2* CW). min or DIFS + CW minAlternatively, after waiting for the reception of a frame (ICF or data frame) for a specific value specified by the transmitter or receiver, if no frame is detected, the mode is switched to LCM (1662). At this time, if the transmitter (1600), having finished transmitting data to receiver 1 (1610), retransmits the ICF (1640) to receiver 2 (1620), receiver 2 (1610), which has a long switching time, switches back from LCM to HCM (1666) (1664), and after transmitting the ICR (1642), receives the data frame (1644) transmitted by the transmitter (1600) in HCM (1666).

[0165] If the switching time of a specific terminal is long, such as receiver 2 (1620) in FIG. 16, multiple mode switching operations must be performed in the event that the transmitter fails to transmit data, thereby increasing the data transmission delay compared to other terminals with short switching times. Considering this, the applicability of at least one embodiment of the present disclosure may be determined by considering the switching time of a receiver that supports DPS. The switching time of each terminal may be shared between the transmitter and the receiver through the transmission and reception of capability information, and at least one embodiment of the present disclosure may be applied if the switching time is above a specific threshold or if the capability of the terminal regarding the switching time corresponds to a specific level (or above a specific level, or below a specific level). The specific threshold or specific level may be fixed, set by the transmitter or receiver, or / and may be included in the capability information.

[0166] FIG. 17 is a diagram illustrating another example of an operation in which a transmitter transmits data to a receiver that supports multiple DPS. FIG. 17 is a diagram illustrating an example of an operation in which the transmitter transmits an ICF to multiple receivers and fails to receive an ICR from all receivers.

[0167] According to FIG. 17, the transmitter (TX, 1700) transmits an ICF (1730) including padding to receiver 1 (RX1, 1710) and receiver 2 (RX2, 1720). The ICF (1730) may correspond to an ICF that initiates a TXOP, and the ICF (1730) may include instructions for the receiver to switch from LCM to HCM. At this time, receiver 1 (1710) and receiver 2 (1720) both succeed in receiving the ICF (1730) and switch from LCM (1750) to HCM (1754) (1752), but the transmitter (1700) fails to receive the ICR (1732, 1734) transmitted by receiver 1 (1710) and receiver 2 (1720), respectively.

[0168] At this time, receiver 1 (1710) and receiver 2 (1720) may switch back to LCM (1758) after a certain time (the certain time is SIFS + PHY_preamble_length or a specific value specified by the transmitter or receiver) after transmitting their ICR, since there is no transmission of data frames after transmitting their ICR (1756). The PHY Preamble length may include only L-Parts (L-STF, L-LTF, L-SIG) according to the PPDU format, or may include U-SIG, EHT-SIG, and / or UHR-SIG (length). Since the PHY layer of the receiver must wait until the PHY Preamble length of the data frame to determine whether data is actually transmitted after SIFS, the certain time may be SIFS + PHY_preamble_length. In this case, the transmitter (1700) can perform data transmission by retransmitting the ICF (1736) to receiver 1 (1710) and receiver 2 (1720).

[0169] Alternatively, the transmitter may transmit a data frame even if no ICR is received from the receiver. In this case, if the PHY header of the data frame is detected, the receiver checks the BSS color field included in the PHY header, and if the AP (or transmitter) indicated by the BSS color field matches the transmitter that transmitted the ICF, the receiver may receive the data frame. If the AP (or transmitter) indicated by the BSS color field does not match the transmitter that transmitted the ICF, the receiver may switch to LCM. Alternatively, if the PHY header of the data frame is not detected, the receiver may also switch to LCM. In this case, the receiver may detect the data frame for the aforementioned specified period of time after transmitting the ICR.

[0170] FIG. 18 is a diagram illustrating an example of the operation of a transmitter according to at least one embodiment of the present disclosure. The transmitter may be an AP.

[0171] According to FIG. 18, the transmitter checks whether data from a DPS-enabled receiver exists in the buffer (1800). If the transmitter is an AP, the receiver corresponds to a STA, and the data may correspond to DL data. If data from a DPS-enabled receiver does not exist in the buffer, the transmitter does not perform the operation.

[0172] If data from a single receiver exists in the buffer, the transmitter transmits a single-user (SU) ICF for a single user (1810). If data from multiple receivers exists in the buffer, the transmitter transmits a multi-user (MU) ICF for multiple users (1820). In the case of the SU ICF, the receiver is designated as a single receiver, and in the case of the MU ICF, there may be a user info field indicating multiple receivers.

[0173] The transmitter that transmitted the ICF determines whether the ICR is received (1830). If the ICR is received, the transmitter may transmit a data frame (1840). In this case, if the SU ICF is transmitted, the transmitter receives the ICR from a single receiver, and if the MU ICF is transmitted, the transmitter may transmit a data frame if the ICR is received from at least one of multiple receivers. In this case, the data frame may include all data for multiple receivers or may include data from the receiver that transmitted the received ICR. FIG. 18 describes an example in which the transmitter transmits a data frame, but the transmitter may also transmit the ICF again. If the transmitter does not receive the ICR, the transmitter returns to steps 1810 and 1820 and transmits the ICF again. After transmitting the data frame, the transmitter determines whether it has received an ACK (which may be a BA) for the data frame (1850). If an ACK is received, the operation is terminated, and if an ACK is not received, the transmitter transmits the ICF again to the receiver to retransmit the data frame.

[0174] The flowcharts described above illustrate exemplary methods that may be implemented in accordance with the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of this specification. For example, although they are illustrated as a series of steps, the various steps in each figure may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, steps may be omitted or replaced with other steps. The values ​​described above are merely examples, and it is fully possible to apply other values.

[0175] FIG. 19 is a diagram illustrating an example of the operation of a transmitter transmitting a MU-ICF according to at least one embodiment of the present disclosure. The transmitter may be an AP.

[0176] According to FIG. 19, the transmitter checks that data from multiple DPS-supported receivers exists in the buffer (1900). If the transmitter is an AP, the receiver corresponds to a STA, and the data may correspond to DL data. The transmitter transmits a MU (multi-user) ICF for the multiple receivers (1910). The MU ICF may contain a user info field indicating the multiple receivers. The transmitter that transmitted the MU ICF determines whether an ICR has been received (1920).

[0177] If at least one ICR is received from multiple receivers, the transmitter may transmit a data frame (1930). At this time, the data frame may include all data for multiple receivers or data from the receiver that transmitted the received ICR. FIG. 19 describes an example in which the transmitter transmits a data frame, but the transmitter may also transmit an ICF again. If the transmitter does not receive an ICR, the transmitter returns to step 1910 and transmits the MU ICF again. The transmitter that transmitted the data frame determines whether it has received an ACK (which may be a BA) for the data frame (1940). If the transmitter receives an ACK, the operation ends, and if the transmitter does not receive an ACK, the transmitter returns to step 1910 and transmits the ICF again to the receiver for data frame retransmission.

[0178] Although not described, if the transmitter transmits an ICF instead of a data frame in step 1930 above, the transmitter may wait for ICR reception. After receiving ICR, the transmitter may transmit a data frame to the receiver(s).

[0179] The flowcharts described above illustrate exemplary methods that may be implemented in accordance with the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of this specification. For example, although they are illustrated as a series of steps, the various steps in each figure may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, steps may be omitted or replaced with other steps. The values ​​described above are merely examples, and it is fully possible to apply other values.

[0180] FIG. 20 is a drawing illustrating an example of the operation of a receiver according to at least one embodiment of the present disclosure. The receiver may be a STA.

[0181] The receiver checks whether an ICF related to DPS operation has been received (2000). The ICF may be an SU ICF for a single user or a MU ICF for multiple users; in the case of an SU ICF, the receiver is designated as a single receiver, and in the case of a MU ICF, there may be a user info field indicating multiple receivers. Upon receiving the ICF, the receiver switches to HCM (2010) and transmits an ICR to the transmitter (2020). If the ICF has not been received, the receiver continues to check whether the ICF has been received.

[0182] Subsequently, the receiver checks whether a data frame has been received from the transmitter (2030). If a data frame has not been received, or if the receiver has received the SU ICF, the receiver waits for a certain period of time from the time the ICR transmission ended (for example, the certain period of time is DIFS + CW). minThe receiver maintains HCM for a period of time that can be * 2 or a value set by the AP or STA (2050). When the receiver receives the MU ICF, the receiver maintains HCM for a certain period of time from the time the ICR transmission ends (for example, the said certain period of time can be SIFS + PHY_preamble_length or a value set by the AP or STA) (2060). If a data frame is received, the receiver sends an ACK for the data frame to the transmitter (2080).

[0183] The receiver checks whether the ICF is received again during the HCM maintenance period described above (2070). If the ICF is received, the receiver returns to step 2020 and transmits the ICR, and if the ICF is not received, the receiver switches to LCM and returns to step 2000.

[0184] The flowcharts described above illustrate exemplary methods that may be implemented in accordance with the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of this specification. For example, although they are illustrated as a series of steps, the various steps in each figure may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, steps may be omitted or replaced with other steps. The values ​​described above are merely examples, and it is fully possible to apply other values.

[0185] FIG. 21 is a diagram illustrating an example of the operation of a receiver receiving a MU ICF according to at least one embodiment of the present disclosure. The receiver may be a STA.

[0186] The receiver checks whether a MU ICF related to DPS operation has been received (2100). In the case of the MU ICF, there may be a user info field indicating multiple receivers. Upon receiving the ICF, the receiver switches to HCM and transmits an ICR to the transmitter (2110). If the ICF has not been received, the receiver continues to check whether the ICF has been received.

[0187] Subsequently, the receiver checks whether a data frame has been received from the transmitter (2120). If a data frame has not been received, the receiver maintains HCM for a certain period of time from the time the ICR transmission ends (for example, the certain period of time may be SIFS + PHY_preamble_length, or a value set by the AP or STA) (2130). If a data frame has been received, the receiver sends an ACK for the data frame to the transmitter (2160).

[0188] The receiver checks whether the ICF is received again during the HCM maintenance period described above (2140). If the ICF is received, the receiver returns to step 2110 and transmits the ICR, and if the ICF is not received, the receiver switches to LCM and returns to step 2100.

[0189] Although not described, it is also possible for the receiver to receive an ICF instead of a data frame at step 2120. In this case, the receiver can send an ICR to the transmitter and wait again for the reception of a data frame.

[0190] The flowcharts described above illustrate exemplary methods that may be implemented in accordance with the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of this specification. For example, although they are illustrated as a series of steps, the various steps in each figure may overlap, occur in parallel, occur in a different order, or occur multiple times. In other examples, steps may be omitted or replaced with other steps. The values ​​described above are merely examples, and it is fully possible to apply other values.

[0191] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present disclosure are possible. Furthermore, each of the above embodiments may be combined and operated together as needed. For example, parts of one embodiment of the present disclosure and another embodiment may be combined to operate AP and STA.

[0192] Meanwhile, the order of description in the drawings explaining the method of the present invention does not necessarily correspond to the order of execution, and the order of precedence may be changed or executed in parallel. Alternatively, the drawings explaining the method of the present invention may omit some components and include only some components to the extent that the essence of the present invention is not compromised.

Claims

1. A method performed by a first device in a wireless LAN (WLAN) system, A step of transmitting an ICF (initial control frame) to a plurality of second devices, wherein the ICF includes an instruction for the second devices to switch from an LCM (lower capability mode) to an HCM (higher capability mode); A step of checking whether at least one ICR (initial control frame response) has been received from at least one second device; A method characterized by including the step of, when at least one ICR is received, transmitting a data frame to the plurality of second devices or transmitting an ICF to another second device excluding the at least one second device among the plurality of second devices.

2. In Paragraph 1, A method characterized by further including the step of receiving acknowledgment information for the data frame from at least one second device.

3. In Paragraph 1, A method characterized in that the above data frame includes data for each of the plurality of second devices.

4. In Paragraph 1, A method characterized in that the above ICF is transmitted after SIFS (short inter frame space) after at least one ICR is received.

5. A method performed by a second device in a wireless LAN (WLAN) system, A step of receiving an ICF (initial control frame) from a first device, wherein the ICF includes an instruction for the second device to switch from an LCM (lower capability mode) to an HCM (higher capability mode); A step of switching from the LCM to the HCM and transmitting an ICR (initial control frame response) to the first device; and A method characterized by including the step of maintaining the HCM for a certain period of time after the termination of the ICR transmission when a data frame is received from the first device or when the data frame is not received.

6. In Paragraph 5, A method characterized by further including the step of transmitting acknowledgment information for the data frame to the first device.

7. In the case of maintaining the above HCM in Paragraph 5, A step of checking whether an ICF has been received during the above specified time period; When the above ICF is received, the step of transmitting an ICR to the first device; and A method characterized by further including the step of receiving a data frame from the first device.

8. In Paragraph 7, A method characterized by further including the step of switching to the LCM when the above ICF is not received.

9. In a first device of a wireless LAN (WLAN) system, Transmitter / receiver; and Transmit an ICF (initial control frame) to a plurality of second devices, and the ICF includes an instruction for the second devices to switch from LCM (lower capability mode) to HCM (higher capability mode), Check whether at least one ICR (initial control frame response) has been received from at least one second device, and A first device characterized by including a control unit configured to transmit a data frame to the plurality of second devices or to transmit an ICF to another second device excluding the at least one second device among the plurality of second devices when the at least one ICR is received.

10. In Paragraph 9, A first device characterized in that the control unit is further configured to receive acknowledgment information for the data frame from at least one second device.

11. In Paragraph 9, A first device characterized in that the above data frame includes data for each of the plurality of second devices.

12. In Paragraph 9, A first device characterized in that the above ICF is transmitted after SIFS (short inter frame space) after the above at least one ICR is received.

13. In a second device of a wireless LAN (WLAN) system, Transmitter / receiver; and A step of receiving an ICF (initial control frame) from a first device, wherein the ICF includes an instruction for the second device to switch from an LCM (lower capability mode) to an HCM (higher capability mode), and Switching from the above LCM to the above HCM, transmitting an ICR (initial control frame response) to the above first device, and A second device characterized by including a control unit configured to maintain the HCM for a certain period of time after the termination of the ICR transmission when a data frame is received from the first device or when the data frame is not received.

14. In Paragraph 13, A method characterized in that the control unit is configured to transmit acknowledgment information for the data frame to the first device.

15. In the case of Paragraph 13, when maintaining the above HCM, The above control unit is, Check whether ICF was received during the above period of time, and When the above ICF is received, transmit the ICR to the first device, and Receive a data frame from the first device, and A second device characterized by being set to switch to the LCM when the above ICF is not received.

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