Patent Application
20240179744
The present disclosure relates to a target wake time (TWT) operation in a wireless local area network (WLAN) system, and more particularly, to a priority-based transmission method and device related to a restricted-TWT operation in a next-generation WLAN system.
New technologies for improving transmission rates, increasing bandwidth, improving reliability, reducing errors, and reducing latency have been introduced for a wireless LAN (WLAN). Among WLAN technologies, an Institute of Electrical and Electronics Engineers (IEEE) 802.11 series standard may be referred to as Wi-Fi. For example, technologies recently introduced to WLAN include enhancements for Very High-Throughput (VHT) of the 802.11ac standard, and enhancements for High Efficiency (HE) of the IEEE 802.11 ax standard.
In order to provide a more improved wireless communication environment, an enhancement technologies for EHT (Extremely High Throughput) are being discussed. For example, technologies for multiple access point (AP) coordination and multiple input multiple output (MIMO) supporting an increased bandwidth, efficient utilization of multiple bands and increased spatial streams are being studied, and, in particular, various technologies for supporting low latency or real-time traffic are being studied.
A technical problem of the present disclosure is to provide a method and a device for transmitting latency sensitive traffic in a WLAN system.
An additional technical problem of the present disclosure is to provide a priority-based transmission method and device related to a restricted TWT operation in a WLAN system.
An additional technical problem of the present disclosure is to provide a method and a device for a restricted TWT operation based on a TWT element including traffic identifier (TID) information related to a priority in a WLAN system.
The technical objects to be achieved by the present disclosure are not limited to the above-described technical objects, and other technical objects which are not described herein will be clearly understood by those skilled in the pertinent art from the following description.
A method of performing frame exchange by a station (STA) in a WLAN system according to an aspect of the present disclosure may include receiving restricted target wake time (r-TWT)-related information from an access point (AP); and performing the frame exchange before a start time of the r-TWT service period (SP). The r-TWT-related information may be included in a TWT element including a TWT parameter set field format, the TWT parameter set field format may include a TWT information field and the TWT information field may include a TID subfield for traffic related to the r-TWT.
A method of performing frame exchange by an access point (AP) in a WLAN system according to an additional aspect of the present disclosure may include transmitting restricted target wake time (r-TWT)-related information to a first station (STA) and a second STA; and performing frame exchange with the second STA before a start time of the r-TWT service period (SP). The r-TWT-related information may be included in a TWT element including a TWT parameter set field format, the TWT parameter set field format may include a TWT information field and the TWT information field may include a TID subfield for traffic related to the r-TWT. At least one of the first STA or the second STA may be a member for a schedule of the r-TWT.
According to the present disclosure, a method and a device for transmitting latency sensitive traffic in a WLAN system may be provided.
According to the present disclosure, a priority-based transmission method and device related to a restricted TWT operation in a WLAN system may be provided.
According to the present disclosure, a method and a device for a restricted TWT operation based on a TWT element including traffic identifier (TID) information related to a priority in a WLAN system may be provided.
Effects achievable by the present disclosure are not limited to the above-described effects, and other effects which are not described herein may be clearly understood by those skilled in the pertinent art from the following description.
The accompanying drawings, which are included as part of the detailed description to aid understanding of the present disclosure, provide embodiments of the present disclosure and together with the detailed description describe technical features of the present disclosure.
Hereinafter, embodiments according to the present disclosure will be described in detail by referring to accompanying drawings. Detailed description to be disclosed with accompanying drawings is to describe exemplary embodiments of the present disclosure and is not to represent the only embodiment that the present disclosure may be implemented. The following detailed description includes specific details to provide complete understanding of the present disclosure. However, those skilled in the pertinent art knows that the present disclosure may be implemented without such specific details.
In some cases, known structures and devices may be omitted or may be shown in a form of a block diagram based on a core function of each structure and device in order to prevent a concept of the present disclosure from being ambiguous.
In the present disclosure, when an element is referred to as being “connected”, “combined” or “linked” to another element, it may include an indirect connection relation that yet another element presents therebetween as well as a direct connection relation. In addition, in the present disclosure, a term, “include” or “have”, specifies the presence of a mentioned feature, step, operation, component and/or element, but it does not exclude the presence or addition of one or more other features, stages, operations, components, elements and/or their groups.
In the present disclosure, a term such as “first”, “second”, etc, is used only to distinguish one element from other element and is not used to limit elements, and unless otherwise specified, it does not limit an order or importance, etc. between elements. Accordingly, within a scope of the present disclosure, a first element in an embodiment may be referred to as a second element in another embodiment and likewise, a second element in an embodiment may be referred to as a first element in another embodiment.
A term used in the present disclosure is to describe a specific embodiment, and is not to limit a claim. As used in a described and attached claim of an embodiment, a singular form is intended to include a plural form, unless the context clearly indicates otherwise. A term used in the present disclosure, “and/or”, may refer to one of related enumerated items or it means that it refers to and includes any and all possible combinations of two or more of them. In addition, “/” between words in the present disclosure has the same meaning as “and/or”, unless otherwise described.
Examples of the present disclosure may be applied to various wireless communication systems. For example, examples of the present disclosure may be applied to a wireless LAN system. For example, examples of the present disclosure may be applied to an IEEE 802.11a/g/n/ac/ax standards-based wireless LAN. Furthermore, examples of the present disclosure may be applied to a wireless LAN based on the newly proposed IEEE 802.11be (or EHT) standard. Examples of the present disclosure may be applied to an IEEE 802.11be Release-2 standard-based wireless LAN corresponding to an additional enhancement technology of the IEEE 802.11be Release-1 standard. Additionally, examples of the present disclosure may be applied to a next-generation standards-based wireless LAN after IEEE 802.11be. Further, examples of this disclosure may be applied to a cellular wireless communication system. For example, it may be applied to a cellular wireless communication system based on Long Term Evolution (LTE)-based technology and 5G New Radio (NR)-based technology of the 3rd Generation Partnership Project (3GPP) standard.
Hereinafter, technical features to which examples of the present disclosure may be applied will be described.
The first device 100 and the second device 200 illustrated in
The devices 100 and 200 illustrated in
Referring to
In addition, the first device 100 and the second device 200 may additionally support various communication standards (e.g., 3GPP LTE series, 5G NR series standards, etc.) technologies other than wireless LAN technology. In addition, the device of the present disclosure may be implemented in various devices such as a mobile phone, a vehicle, a personal computer, augmented reality (AR) equipment, and virtual reality (VR) equipment, etc. In addition, the STA of the present specification may support various communication services such as a voice call, a video call, data communication, autonomous-driving, machine-type communication (MTC), machine-to-machine (M2M), device-to-device (D2D), IoT (Internet-of-Things), etc.
A first device 100 may include one or more processors 102 and one or more memories 104 and may additionally include one or more transceivers 106 and/or one or more antennas 108. A processor 102 may control a memory 104 and/or a transceiver 106 and may be configured to implement description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure. For example, a processor 102 may transmit a wireless signal including first information/signal through a transceiver 106 after generating first information/signal by processing information in a memory 104. In addition, a processor 102 may receive a wireless signal including second information/signal through a transceiver 106 and then store information obtained by signal processing of second information/signal in a memory 104. A memory 104 may be connected to a processor 102 and may store a variety of information related to an operation of a processor 102. For example, a memory 104 may store a software code including instructions for performing all or part of processes controlled by a processor 102 or for performing description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure. Here, a processor 102 and a memory 104 may be part of a communication modem/circuit/chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). A transceiver 106 may be connected to a processor 102 and may transmit and/or receive a wireless signal through one or more antennas 108. A transceiver 106 may include a transmitter and/or a receiver. A transceiver 106 may be used together with a RF (Radio Frequency) unit. In the present disclosure, a device may mean a communication modem/circuit/chip.
A second device 200 may include one or more processors 202 and one or more memories 204 and may additionally include one or more transceivers 206 and/or one or more antennas 208. A processor 202 may control a memory 204 and/or a transceiver 206 and may be configured to implement description, functions, procedures, proposals, methods and/or operation flows charts disclosed in the present disclosure. For example, a processor 202 may generate third information/signal by processing information in a memory 204, and then transmit a wireless signal including third information/signal through a transceiver 206. In addition, a processor 202 may receive a wireless signal including fourth information/signal through a transceiver 206, and then store information obtained by signal processing of fourth information/signal in a memory 204. A memory 204 may be connected to a processor 202 and may store a variety of information related to an operation of a processor 202. For example, a memory 204 may store a software code including instructions for performing all or part of processes controlled by a processor 202 or for performing description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure. Here, a processor 202 and a memory 204 may be part of a communication modem/circuit/chip designed to implement a wireless LAN technology (e.g., IEEE 802.11 series). A transceiver 206 may be connected to a processor 202 and may transmit and/or receive a wireless signal through one or more antennas 208. A transceiver 206 may include a transmitter and/or a receiver. A transceiver 206 may be used together with a RF unit. In the present disclosure, a device may mean a communication modem/circuit/chip.
Hereinafter, a hardware element of a device 100, 200 will be described in more detail. It is not limited thereto, but one or more protocol layers may be implemented by one or more processors 102, 202. For example, one or more processors 102, 202 may implement one or more layers (e.g., a functional layer such as PHY, MAC). One or more processors 102, 202 may generate one or more PDUs (Protocol Data Unit) and/or one or more SDUs (Service Data Unit) according to description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure. One or more processors 102, 202 may generate a message, control information, data or information according to description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure. One or more processors 102, 202 may generate a signal (e.g., a baseband signal) including a PDU, a SDU, a message, control information, data or information according to functions, procedures, proposals and/or methods disclosed in the present disclosure to provide it to one or more transceivers 106, 206. One or more processors 102, 202 may receive a signal (e.g., a baseband signal) from one or more transceivers 106, 206 and obtain a PDU, a SDU, a message, control information, data or information according to description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure.
One or more processors 102, 202 may be referred to as a controller, a micro controller, a micro processor or a micro computer. One or more processors 102, 202 may be implemented by a hardware, a firmware, a software, or their combination. In an example, one or more ASICs (Application Specific Integrated Circuit), one or more DSPs (Digital Signal Processor), one or more DSPDs (Digital Signal Processing Device), one or more PLDs (Programmable Logic Device) or one or more FPGAs (Field Programmable Gate Arrays) may be included in one or more processors 102, 202. Description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure may be implemented by using a firmware or a software and a firmware or a software may be implemented to include a module, a procedure, a function, etc. A firmware or a software configured to perform description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure may be included in one or more processors 102, 202 or may be stored in one or more memories 104, 204 and driven by one or more processors 102, 202. Description, functions, procedures, proposals, methods and/or operation flow charts disclosed in the present disclosure may be implemented by using a firmware or a software in a form of a code, an instruction and/or a set of instructions.
One or more memories 104, 204 may be connected to one or more processors 102, 202 and may store data, a signal, a message, information, a program, a code, an indication and/or an instruction in various forms. One or more memories 104, 204 may be configured with ROM, RAM, EPROM, a flash memory, a hard drive, a register, a cash memory, a computer readable storage medium and/or their combination. One or more memories 104, 204 may be positioned inside and/or outside one or more processors 102, 202. In addition, one or more memories 104, 204 may be connected to one or more processors 102, 202 through a variety of technologies such as a wire or wireless connection.
One or more transceivers 106, 206 may transmit user data, control information, a wireless signal/channel, etc. mentioned in methods and/or operation flow charts, etc. of the present disclosure to one or more other devices. One or more transceivers 106, 206 may receiver user data, control information, a wireless signal/channel, etc. mentioned in description, functions, procedures, proposals, methods and/or operation flow charts, etc. disclosed in the present disclosure from one or more other devices. For example, one or more transceivers 106, 206 may be connected to one or more processors 102, 202 and may transmit and receive a wireless signal. For example, one or more processors 102, 202 may control one or more transceivers 106, 206 to transmit user data, control information or a wireless signal to one or more other devices. In addition, one or more processors 102, 202 may control one or more transceivers 106, 206 to receive user data, control information or a wireless signal from one or more other devices. In addition, one or more transceivers 106, 206 may be connected to one or more antennas 108, 208 and one or more transceivers 106, 206 may be configured to transmit and receive user data, control information, a wireless signal/channel, etc. mentioned in description, functions, procedures, proposals, methods and/or operation flow charts, etc. disclosed in the present disclosure through one or more antennas 108, 208. In the present disclosure, one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., an antenna port). One or more transceivers 106, 206 may convert a received wireless signal/channel, etc, into a baseband signal from a RF band signal to process received user data, control information, wireless signal/channel, etc. by using one or more processors 102, 202. One or more transceivers 106, 206 may convert user data, control information, a wireless signal/channel, etc, which are processed by using one or more processors 102, 202 from a baseband signal to a RF band signal. Therefor, one or more transceivers 106, 206 may include an (analogue) oscillator and/or a filter.
For example, one of the STAs 100 and 200 may perform an intended operation of an AP, and the other of the STAs 100 and 200 may perform an intended operation of a non-AP STA. For example, the transceivers 106 and 206 of
Hereinafter, downlink (DL) may mean a link for communication from an AP STA to a non-AP STA, and a DL PPDU/packet/signal may be transmitted and received through the DL. In DL communication, a transmitter may be part of an AP STA, and a receiver may be part of a non-AP STA. Uplink (UL) may mean a link for communication from non-AP STAs to AP STAs, and a UL PPDU/packet/signal may be transmitted and received through the UL. In UL communication, a transmitter may be part of a non-AP STA, and a receiver may be part of an AP STA.
The structure of the wireless LAN system may consist of be composed of a plurality of components. A wireless LAN supporting STA mobility transparent to an upper layer may be provided by interaction of a plurality of components. A Basic Service Set (BSS) corresponds to a basic construction block of a wireless LAN.
If the DS shown in
Membership of an STA in the BSS may be dynamically changed by turning on or off the STA, entering or exiting the BSS area, and the like. To become a member of the BSS, the STA may join the BSS using a synchronization process. In order to access all services of the BSS infrastructure, the STA shall be associated with the BSS. This association may be dynamically established and may include the use of a Distribution System Service (DSS).
A direct STA-to-STA distance in a wireless LAN may be limited by PHY performance. In some cases, this distance limit may be sufficient, but in some cases, communication between STAs at a longer distance may be required. A distributed system (DS) may be configured to support extended coverage.
DS means a structure in which BSSs are interconnected. Specifically, as shown in
A DS may support a mobile device by providing seamless integration of a plurality of BSSs and providing logical services necessary to address an address to a destination. In addition, the DS may further include a component called a portal that serves as a bridge for connection between the wireless LAN and other networks (e.g., IEEE 802.X).
The AP enables access to the DS through the WM for the associated non-AP STAs, and means an entity that also has the functionality of an STA. Data movement between the BSS and the DS may be performed through the AP. For example, STA2 and STA3 shown in
Data transmitted from one of the STA(s) associated with an AP to a STA address of the corresponding AP may be always received on an uncontrolled port and may be processed by an IEEE 802.1X port access entity. In addition, when a controlled port is authenticated, transmission data (or frames) may be delivered to the DS.
In addition to the structure of the DS described above, an extended service set (ESS) may be configured to provide wide coverage.
An ESS means a network in which a network having an arbitrary size and complexity is composed of DSs and BSSs. The ESS may correspond to a set of BSSs connected to one DS. However, the ESS does not include the DS. An ESS network is characterized by being seen as an IBSS in the Logical Link Control (LLC) layer. STAs included in the ESS may communicate with each other, and mobile STAs may move from one BSS to another BSS (within the same ESS) transparently to the LLC. APs included in one ESS may have the same service set identification (SSID). The SSID is distinguished from the BSSID, which is an identifier of the BSS.
The wireless LAN system does not assume anything about the relative physical locations of BSSs, and all of the following forms are possible. BSSs may partially overlap, which is a form commonly used to provide continuous coverage. In addition, BSSs may not be physically connected, and logically there is no limit on the distance between BSSs. In addition, the BSSs may be physically located in the same location, which may be used to provide redundancy. In addition, one (or more than one) IBSS or ESS networks may physically exist in the same space as one (or more than one) ESS network. When an ad-hoc network operates in a location where an ESS network exists, when physically overlapping wireless networks are configured by different organizations, or when two or more different access and security policies are required in the same location, this may correspond to the form of an ESS network in the like.
In order for an STA to set up a link with respect to a network and transmit/receive data, it first discovers a network, performs authentication, establishes an association, and need to perform the authentication process for security. The link setup process may also be referred to as a session initiation process or a session setup process. In addition, the processes of discovery, authentication, association, and security setting of the link setup process may be collectively referred to as an association process.
In step S310, the STA may perform a network discovery operation. The network discovery operation may include a scanning operation of the STA. That is, in order for the STA to access the network, it needs to find a network in which it can participate. The STA shall identify a compatible network before participating in a wireless network, and the process of identifying a network existing in a specific area is called scanning.
Scanning schemes include active scanning and passive scanning.
Although not shown in
After the STA discovers the network, an authentication process may be performed in step S320. This authentication process may be referred to as a first authentication process in order to be clearly distinguished from the security setup operation of step S340 to be described later.
The authentication process includes a process in which the STA transmits an authentication request frame to the AP, and in response to this, the AP transmits an authentication response frame to the STA. An authentication frame used for authentication request/response corresponds to a management frame.
The authentication frame includes an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a robust security network (RSN), and a Finite Cyclic Group, etc. This corresponds to 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 further included.
The STA may transmit an authentication request frame to the AP. The AP may determine whether to allow authentication of the corresponding STA based on information included in the received authentication request frame. The AP may provide the result of the authentication process to the STA through an authentication response frame.
After the STA is successfully authenticated, an association process may be performed in step S330. The association process includes a process in which the STA transmits an association request frame to the AP, and in response, the AP transmits an association response frame to the STA.
For example, the association request frame may include information related to various capabilities, a beacon listen interval, a service set identifier (SSID), supported rates, supported channels, RSN, mobility domain, supported operating classes, Traffic Indication Map Broadcast request (TIM broadcast request), interworking service capability, etc. For example, the association response frame may include information related to various capabilities, status code, association ID (AID), supported rates, enhanced distributed channel access (EDCA) parameter set, received channel power indicator (RCPI), received signal to noise indicator (RSNI), mobility domain, timeout interval (e.g., association comeback time), overlapping BSS scan parameters, TIM broadcast response, Quality of Service (QOS) map, etc. This corresponds to some examples of information that may be included in the association request/response frame, and may be replaced with other information or additional information may be further included.
After the STA is successfully associated with the network, a security setup process may be performed in step S340. The security setup process of step S340 may be referred to as an authentication process through Robust Security Network Association (RSNA) request/response, and the authentication process of step S320 is referred to as a first authentication process, and the security setup process of step S340 may also simply be referred to as an authentication process.
The security setup process of step S340 may include, for example, a process of setting up a private key through 4-way handshaking through an Extensible Authentication Protocol over LAN (EAPOL) frame. In addition, the security setup process may be performed according to a security scheme not defined in the IEEE 802.11 standard.
In the wireless LAN system, a basic access mechanism of medium access control (MAC) is a carrier sense multiple access with collision avoidance (CSMA/CA) mechanism. The CSMA/CA mechanism is also called Distributed Coordination Function (DCF) of IEEE 802.11 MAC, and basically adopts a “listen before talk” access mechanism. According to this type of access mechanism, the AP and/or STA may perform Clear Channel Assessment (CCA) sensing a radio channel or medium during a predetermined time interval (e.g., DCF Inter-Frame Space (DIFS)), prior to starting transmission. As a result of the sensing, if it is determined that the medium is in an idle state, frame transmission is started through the corresponding medium. On the other hand, if it is detected that the medium is occupied or busy, the corresponding AP and/or STA does not start its own transmission and may set a delay period for medium access (e.g., a random backoff period) and attempt frame transmission after waiting. By applying the random backoff period, since it is expected that several STAs attempt frame transmission after waiting for different periods of time, collision may be minimized.
In addition, the IEEE 802.11 MAC protocol provides a Hybrid Coordination Function (HCF). HCF is based on the DCF and Point Coordination Function (PCF). PCF is a polling-based synchronous access method and refers to a method in which all receiving APs and/or STAs periodically poll to receive data frames. In addition, HCF has Enhanced Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA). EDCA is a contention-based access method for a provider to provide data frames to multiple users, and HCCA uses a non-contention-based channel access method using a polling mechanism. In addition, the HCF includes a medium access mechanism for improving QoS (Quality of Service) of the wireless LAN, and may transmit QoS data in both a Contention Period (CP) and a Contention Free Period (CFP).
Referring to
When the random backoff process starts, the STA continuously monitors the medium while counting down the backoff slots according to the determined backoff count value. When the medium is monitored for occupancy, it stops counting down and waits, and resumes the rest of the countdown when the medium becomes idle.
In the example of
As in the example of
A Quality of Service (QOS) STA may perform the backoff that is performed after an arbitration IFS (AIFS) for an access category (AC) to which the frame belongs, that is. AIFS[i] (where i is a value determined by AC), and then may transmit the frame. Here, the frame in which AIFS[i] can be used may be a data frame, a management frame, or a control frame other than a response frame.
As described above, the CSMA/CA mechanism includes virtual carrier sensing in addition to physical carrier sensing in which a STA directly senses a medium. Virtual carrier sensing is intended to compensate for problems that may occur in medium access, such as a hidden node problem. For virtual carrier sensing, the MAC of the STA may use a Network Allocation Vector (NAV). The NAV is a value indicating, to other STAs, the remaining time until the medium is available for use by an STA currently using or having the right to use the medium. Therefore, the value set as NAV corresponds to a period in which the medium is scheduled to be used by the STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during the corresponding period. For example, the NAV may be configured based on the value of the “duration” field of the MAC header of the frame.
In the example of
In order to reduce the possibility of collision of transmissions of multiple STAs in CSMA/CA based frame transmission operation, a mechanism using RTS/CTS frames may be applied. In the example of
Specifically, the STA1 may determine whether a channel is being used through carrier sensing. In terms of physical carrier sensing, the STA1 may determine a channel occupation idle state based on an energy level or signal correlation detected in a channel. In addition, in terms of virtual carrier sensing, the STA1 may determine a channel occupancy state using a network allocation vector (NAV) timer.
The STA1 may transmit an RTS frame to the STA2 after performing a backoff when the channel is in an idle state during DIFS. When the STA2 receives the RTS frame, the STA2 may transmit a CTS frame as a response to the RTS frame to the STA1 after SIFS.
If the STA3 cannot overhear the CTS frame from the STA2 but can overhear the RTS frame from the STA1, the STA3 may set a NAV timer for a frame transmission period (e.g., SIFS+CTS frame+SIFS+data frame+SIFS+ACK frame) that is continuously transmitted thereafter, using the duration information included in the RTS frame.
Alternatively, if the STA3 can overhear a CTS frame from the STA2 although the STA3 cannot overhear an RTS frame from the STA1, the STA3 may set a NAV timer for a frame transmission period (e.g., SIFS+data frame+SIFS+ACK frame) that is continuously transmitted thereafter, using the duration information included in the CTS frame. That is, if the STA3 can overhear one or more of the RTS or CTS frames from one or more of the STA1 or the STA2, the STA3 may set the NAV accordingly. When the STA3 receives a new frame before the NAV timer expires, the STA3 may update the NAV timer using duration information included in the new frame. The STA3 does not attempt channel access until the NAV timer expires.
When the STA1 receives the CTS frame from the the STA2, the STA1 may transmit the data frame to the STA2 after SIFS from the time point when the reception of the CTS frame is completed. When the STA2 successfully receives the data frame, the STA2 may transmit an ACK frame as a response to the data frame to the STA1 after SIFS. The STA3 may determine whether the channel is being used through carrier sensing when the NAV timer expires. When the STA3 determines that the channel is not used by other terminals during DIFS after expiration of the NAV timer, the STA3 may attempt channel access after a contention window (CW) according to a random backoff has passed.
By means of an instruction or primitive (meaning a set of instructions or parameters) from the MAC layer, the PHY layer may prepare a MAC PDU (MPDU) to be transmitted. For example, when a command requesting transmission start of the PHY layer is received from the MAC layer, the PHY layer switches to the transmission mode and configures information (e.g., data) provided from the MAC layer in the form of a frame and transmits it. In addition, when the PHY layer detects a valid preamble of the received frame, the PHY layer monitors the header of the preamble and sends a command notifying the start of reception of the PHY layer to the MAC layer.
In this way, information transmission/reception in a wireless LAN system is performed in the form of a frame, and for this purpose, a PHY layer protocol data unit (PPDU) frame format is defined.
A basic PPDU frame may include a Short Training Field (STF), a Long Training Field (LTF), a SIGNAL (SIG) field, and a Data field. The most basic (e.g., non-High Throughput (HT)) PPDU frame format may consist of only L-STF (Legacy-STF), L-LTF (Legacy-LTF), SIG field, and data field. In addition, depending on the type of PPDU frame format (e.g., HT-mixed format PPDU, HT-greenfield format PPDU, VHT (Very High Throughput) PPDU, etc.), an additional (or different type) STF, LTF, and SIG fields may be included between the SIG field and the data field (this will be described later with reference to
The STF is a signal for signal detection, automatic gain control (AGC), diversity selection, precise time synchronization, and the like, and the LTF is a signal for channel estimation and frequency error estimation. The STF and LTF may be referred to as signals for synchronization and channel estimation of the OFDM physical layer.
The SIG field may include a RATE field and a LENGTH field. The RATE field may include information on modulation and coding rates of data. The LENGTH field may include information on the length of data. Additionally, the SIG field may include a parity bit, a SIG TAIL bit, and the like.
The data field may include a SERVICE field, a physical layer service data unit (PSDU), and a PPDU TAIL bit, and may also include padding bits if necessary. Some bits of the SERVICE field may be used for synchronization of the descrambler at the receiving end. The PSDU corresponds to the MAC PDU defined in the MAC layer, and may include data generated/used in the upper layer. The PPDU TAIL bit may be used to return the encoder to a 0 state. Padding bits may be used to adjust the length of a data field in a predetermined unit.
A MAC PDU is defined according to various MAC frame formats, and a basic MAC frame consists of a MAC header, a frame body, and a Frame Check Sequence (FCS). The MAC frame may consist of MAC PDUs and be transmitted/received through the PSDU of the data part of the PPDU frame format.
The MAC header includes a Frame Control field, a Duration/ID field, an Address field, and the like. The frame control field may include control information required for frame transmission/reception. The duration/ID field may be set to a time for transmitting a corresponding frame or the like. For details of the Sequence Control, QoS Control, and HT Control subfields of the MAC header, refer to the IEEE 802.11 standard document.
A null-data packet (NDP) frame format means a frame format that does not include a data packet. That is, the NDP frame refers to a frame format that includes a physical layer convergence procedure (PLCP) header part (i.e., STF. LTF, and SIG fields) in a general PPDU frame format and does not include the remaining parts (i.e., data field). A NDP frame may also be referred to as a short frame format.
In standards such as IEEE 802.11a/g/n/ac/ax, various types of PPDUs have been used. The basic PPDU format (IEEE 802.11a/g) includes L-LTF. L-STF. L-SIG and Data fields. The basic PPDU format may also be referred to as a non-HT PPDU format.
The HT PPDU format (IEEE 802.11n) additionally includes HT-SIG. HT-STF, and HT-LFT(s) fields to the basic PPDU format. The HT PPDU format shown in
An example of the VHT PPDU format (IEEE 802.11ac) additionally includes VHT SIG-A. VHT-STF. VHT-LTF, and VHT-SIG-B fields to the basic PPDU format.
An example of the HE PPDU format (IEEE 802.11ax) additionally includes Repeated L-SIG (RL-SIG). HE-SIG-A. HE-SIG-B. HE-STF. HE-LTF(s). Packet Extension (PE) field to the basic PPDU format. Some fields may be excluded or their length may vary according to detailed examples of the HE PPDU format. For example, the HE-SIG-B field is included in the HE PPDU format for multi-user (MU), and the HE-SIG-B is not included in the HE PPDU format for single user (SU). In addition, the HE trigger-based (TB) PPDU format does not include the HE-SIG-B, and the length of the HE-STF field may vary to 8 us. The Extended Range (HE ER) SU PPDU format does not include the HE-SIG-B field, and the length of the HE-SIG-A field may vary to 16 us.
Referring to
As shown in
As shown at the top of
The RU allocation of
In the example of
Just as RUs of various sizes are used in the example of
In addition, as shown, when used for a single user, a 484-RU may be used.
Just as RUs of various sizes are used in the example of
In addition, as shown, when used for a single user, 996-RU may be used, and in this case, 5 DC tones are inserted in common with HE PPDU and EHT PPDU.
EHT PPDUs over 160 MHz may be configured with a plurality of 80 MHZ subblocks in
Here, the MRU corresponds to a group of subcarriers (or tones) composed of a plurality of RUs, and the plurality of RUs constituting the MRU may be RUs having the same size or RUs having different sizes. For example, a single MRU may be defined as 52+26-tone, 106+26-tone, 484+242-tone, 996+484-tone, 996+484+242-tone, 2X996+484-tone, 3X996-tone, or 3X996+484-tone. Here, the plurality of RUs constituting one MRU may correspond to small size (e.g., 26, 52, or 106) RUs or large size (e.g., 242, 484, or 996) RUs. That is, one MRU including a small size RU and a large size RU may not be configured/defined. In addition, a plurality of RUs constituting one MRU may or may not be consecutive in the frequency domain.
When an 80 MHz subblock includes RUs smaller than 996 tones, or parts of the 80 MHz subblock are punctured, the 80 MHz subblock may use RU allocation other than the 996-tone RU.
The RU of the present disclosure may be used for uplink (UL) and/or downlink (DL) communication. For example, when trigger-based UL-MU communication is performed, the STA transmitting the trigger (e.g., AP) may allocate a first RU (e.g., 26/52/106/242-RU, etc.) to a first STA and allocate a second RU (e.g., 26/52/106/242-RU, etc.) to a second STA, through trigger information (e.g., trigger frame or triggered response scheduling (TRS)). Thereafter, the first STA may transmit a first trigger-based (TB) PPDU based on the first RU, and the second STA may transmit a second TB PPDU based on the second RU. The first/second TB PPDUs may be transmitted to the AP in the same time period.
For example, when a DL MU PPDU is configured, the STA transmitting the DL MU PPDU (e.g., AP) may allocate a first RU (e.g., 26/52/106/242-RU, etc.) to a first STA and allocate a second RU (e.g., 26/52/106/242-RU, etc.) to a second STA. That is, the transmitting STA (e.g., AP) may transmit HE-STF, HE-LTF, and Data field for the first STA through the first RU and transmit HE-STF, HE-LTF, and Data field for the second STA through the second RU, in one MU PPDU,
Information on the allocation of RUs may be signaled through HE-SIG-B in the HE PPDU format.
As shown, the HE-SIG-B field may include a common field and a user-specific field. If HE-SIG-B compression is applied (e.g., full-bandwidth MU-MIMO transmission), the common field may not be included in HE-SIG-B, and the HE-SIG-B content channel may include only a user-specific field. If HE-SIG-B compression is not applied, the common field may be included in HE-SIG-B.
The common field may include information on RU allocation (e.g., RU assignment, RUs allocated for MU-MIMO, the number of MU-MIMO users (STAs), etc.)
The common field may include N*8 RU allocation subfields. Here, N is the number of subfields, N=1 in the case of 20 or 40 MHZ MU PPDU, N=2 in the case of 80 MHZ MU PPDU, N=4 in the case of 160 MHz or 80+80 MHZ MU PPDU, etc. One 8-bit RU allocation subfield may indicate the size (26, 52, 106, etc.) and frequency location (or RU index) of RUs included in the 20 MHz band.
For example, if a value of the 8-bit RU allocation subfield is 00000000, it may indicate that nine 26-RUs are sequentially allocated in order from the leftmost to the rightmost in the example of
As an additional example, if the value of the 8-bit RU allocation subfield is 01000$2y1y0, it may indicate that one 106-RU and five 26-RUs are sequentially allocated from the leftmost to the rightmost in the example of
Basically, one user/STA may be allocated to each of a plurality of RUs, and different users/STAs may be allocated to different RUs. For RUs larger than a predetermined size (e.g., 106, 242, 484, 996-tones, . . . ), a plurality of users/STAs may be allocated to one RU, and MU-MIMO scheme may be applied for the plurality of users/STAs.
The set of user-specific fields includes information on how all users (STAs) of the corresponding PPDU decode their payloads. User-specific fields may contain zero or more user block fields. The non-final user block field includes two user fields (i.e., information to be used for decoding in two STAs). The final user block field contains one or two user fields. The number of user fields may be indicated by the RU allocation subfield of HE-SIG-B, the number of symbols of HE-SIG-B, or the MU-MIMO user field of HE-SIG-A. A User-specific field may be encoded separately from or independently of a common field.
In the example of
The user field may be constructed based on two formats. The user field for a MU-MIMO allocation may be constructed with a first format, and the user field for non-MU-MIMO allocation may be constructed with a second format. Referring to the example of
The user field of the first format (i.e., format for MU-MIMO allocation) may be constructed as follows. For example, out of all 21 bits of one user field, B0-B10 includes the user's identification information (e.g., STA-ID, AID, partial AID, etc.), B11-14 includes spatial configuration information such as the number of spatial streams for the corresponding user, B15-B18 includes Modulation and Coding Scheme (MCS) information applied to the Data field of the corresponding PPDU, B19 is defined as a reserved field, and B20 may include information on a coding type (e.g., binary convolutional coding (BCC) or low-density parity check (LDPC)) applied to the Data field of the corresponding PPDU.
The user field of the second format (i.e., the format for non-MU-MIMO allocation) may be constructed as follows. For example, out of all 21 bits of one user field, B0-B10) includes the user's identification information (e.g., STA-ID, AID, partial AID, etc.), B11-13 includes information on the number of spatial streams (NSTS) applied to the corresponding RU, B14 includes information indicating whether beamforming is performed (or whether a beamforming steering matrix is applied), B15-B18 includes Modulation and Coding Scheme (MCS) information applied to the Data field of the corresponding PPDU, B19 includes information indicating whether DCM (dual carrier modulation) is applied, and B20 may include information on a coding type (e.g., BCC or LDPC) applied to the Data field of the corresponding PPDU.
MCS, MCS information, MCS index, MCS field, and the like used in the present disclosure may be indicated by a specific index value. For example, MCS information may be indicated as index 0 to index 11. MCS information includes information on constellation modulation type (e.g., BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, etc.), and coding rate (e.g., 1/2, 2/3, 3/4, 5/6, etc.). Information on a channel coding type (e.g., BCC or LDPC) may be excluded from the MCS information.
The PPDU of
The EHT MU PPDU of
In the EHT TB PPDU of
In the example of the EHT PPDU format of
A Subcarrier frequency spacing of L-STF. L-LTF. L-SIG. RL-SIG. Universal SIGNAL (U-SIG). EHT-SIG field (these are referred to as pre-EHT modulated fields) may be set to 312.5 kHz. A subcarrier frequency spacing of the EHT-STF. EHT-LTF. Data, and PE field (these are referred to as EHT modulated fields) may be set to 78.125 kHz. That is, the tone/subcarrier index of L-STF. L-LTF. L-SIG. RL-SIG. U-SIG, and EHT-SIG field may be indicated in units of 312.5 kHz, and the tone/subcarrier index of EHT-STF. EHT-LTF. Data. and PE field may be indicated in units of 78.125 kHz.
The L-LTF and L-STF of
The L-SIG field of
For example, the transmitting STA may apply BCC encoding based on a coding rate of 1/2 to 24-bit information of the L-SIG field. Thereafter, the transmitting STA may obtain 48-bit BCC coded bits. BPSK modulation may be applied to 48-bit coded bits to generate 48 BPSK symbols. The transmitting STA may map 48 BPSK symbols to any location except for a pilot subcarrier (e.g., {subcarrier index −21, −7, +7, +21}) and a DC subcarrier (e.g., {subcarrier index 0)}). As a result, 48 BPSK symbols may be mapped to subcarrier indices −26 to −22, −20 to −8, −6 to −1, +1 to +6, +8 to +20, and +22 to +26. The transmitting STA may additionally map the signals of {−1, −1, −1, 1} to the subcarrier index {−28, −27, +27, +28}. The above signal may be used for channel estimation in the frequency domain corresponding to {−28, −27, +27, +28}.
The transmitting STA may construct RL-SIG which is constructed identically to L-SIG. For RL-SIG. BPSK modulation is applied. The receiving STA may recognize that the received PPDU is a HE PPDU or an EHT PPDU based on the existence of the RL-SIG.
After the RL-SIG of
The U-SIG may include N-bit information and may include information for identifying the type of EHT PPDU. For example. U-SIG may be configured based on two symbols (e.g., two consecutive OFDM symbols). Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of 4 us, and the U-SIG may have a total 8 us duration. Each symbol of the U-SIG may be used to transmit 26 bit information. For example, each symbol of the U-SIG may be transmitted and received based on 52 data tones and 4 pilot tones.
Through the U-SIG (or U-SIG field), for example. A bit information (e.g., 52 un-coded bits) may be transmitted, the first symbol of the U-SIG (e.g., U-SIG-1) may transmit the first X bit information (e.g., 26 un-coded bits) of the total A bit information, and the second symbol of the U-SIG (e.g., U-SIG-2) may transmit the remaining Y-bit information (e.g., 26 un-coded bits) of the total A-bit information. For example, the transmitting STA may obtain 26 un-coded bits included in each U-SIG symbol. The transmitting STA may generate 52-coded bits by performing convolutional encoding (e.g., BCC encoding) based on a rate of R=1/2, and perform interleaving on the 52-coded bits. The transmitting STA may generate 52 BPSK symbols allocated to each U-SIG symbol by performing BPSK modulation on the interleaved 52-coded bits. One U-SIG symbol may be transmitted based on 56 tones (subcarriers) from subcarrier index −28 to subcarrier index +28, except for DC index 0). The 52 BPSK symbols generated by the transmitting STA may be transmitted based on the remaining tones (subcarriers) excluding pilot tones −21, −7, +7, and +21 tones.
For example, the A bit information (e.g., 52 un-coded bits) transmitted by the U-SIG includes a CRC field (e.g., a 4-bit field) and a tail field (e.g., 6 bit-length field). The CRC field and the tail field may be transmitted through the second symbol of the U-SIG. The CRC field may be constructed based on 26 bits allocated to the first symbol of U-SIG and 16 bits remaining except for the CRC/tail field in the second symbol, and may be constructed based on a conventional CRC calculation algorithm. In addition, the tail field may be used to terminate the trellis of the convolution decoder, and for example, the tail field may be set to 0).
A bit information (e.g., 52 un-coded bits) transmitted by the U-SIG (or U-SIG field) may be devided into version-independent bits and version-independent bits. For example, a size of the version-independent bits may be fixed or variable. For example, the version-independent bits may be allocated only to the first symbol of U-SIG, or the version-independent bits may be allocated to both the first symbol and the second symbol of U-SIG. For example, the version-independent bits and the version-dependent bits may be referred as various names such as a first control bit and a second control bit, etc.
For example, the version-independent bits of the U-SIG may include a 3-bit physical layer version identifier (PHY version identifier). For example, the 3-bit PHY version identifier may include information related to the PHY version of the transmitted/received PPDU. For example, the first value of the 3-bit PHY version identifier may indicate that the transmission/reception PPDU is an EHT PPDU. In other words, when transmitting the EHT PPDU, the transmitting STA may set the 3-bit PHY version identifier to a first value. In other words, the receiving STA may determine that the received PPDU is an EHT PPDU based on the PHY version identifier having the first value.
For example, the version-independent bits of U-SIG may include a 1-bit UL/DL flag field. A first value of the 1-bit UL/DL flag field is related to UL communication, and a second value of the UL/DL flag field is related to DL communication.
For example, the version-independent bits of the U-SIG may include information on the length of a transmission opportunity (TXOP) and information on a BSS color ID.
For example, if the EHT PPDU is classified into various types (e.g., EHT PPDU related to SU mode. EHT PPDU related to MU mode. EHT PPDU related to TB mode. EHT PPDU related to Extended Range transmission, etc.), information on the type of EHT PPDU may be included in the version-dependent bits of the U-SIG.
For example, the U-SIG may include information on 1) a bandwidth field containing information on a bandwidth, 2) a field containing information on a MCS scheme applied to EHT-SIG, 3) an indication field containing information related to whether the DCM technique is applied to the EHT-SIG, 4) a field containing information on the number of symbols used for EHT-SIG, 5) a field containing information on whether EHT-SIG is constructed over all bands, 6) a field containing information on the type of EHT-LTF/STF, and 7) a field indicating the length of EHT-LTF and CP length.
Preamble puncturing may be applied to the PPDU of
For example, a pattern of preamble puncturing may be configured in advance. For example, when a first puncturing pattern is applied, puncturing may be applied only to a secondary 20 MHz band within a 80 MHz band. For example, when a second puncturing pattern is applied, puncturing may be applied to only any one of two secondary 20 MHZ bands included in a secondary 40 MHz band within a 80 MHz band. For example, when a third puncturing pattern is applied, puncturing may be applied to only a secondary 20 MHZ band included in a primary 80 MHz band within a 160 MHz band (or a 80+80 MHz band). For example, when a fourth puncturing pattern is applied, a primary 40 MHz band included in a primary 80 MHz band within a 160 MHz band (or a 80+80 MHz band) is present and puncturing may be applied to at least one 20 MHz channel which does not belong to a primary 40 MHz band.
Information on preamble puncturing applied to a PPDU may be included in a U-SIG and/or a EHT-SIG. For example, the first field of the U-SIG may include information on the contiguous bandwidth of the PPDU, and the second field of the U-SIG may include information on preamble puncturing applied to the PPDU.
For example, the U-SIG and the EHT-SIG may include information on preamble puncturing based on the following method. If the bandwidth of the PPDU exceeds 80 MHZ, the U-SIG may be individually constructed in units of 80 MHZ. For example, if the bandwidth of the PPDU is 160 MHZ, the PPDU may include a first U-SIG for a first 80 MHZ band and a second U-SIG for a second 80 MHz band. In this case, the first field of the first U-SIG includes information on the 160 MHZ bandwidth, and the second field of the first U-SIG includes information on preamble puncturing applied to the first 80 MHz band (i.e., information on a preamble puncturing pattern). In addition, the first field of the second U-SIG includes information on a 160 MHZ bandwidth, and the second field of the second U-SIG includes information on preamble puncturing applied to a second 80 MHz band (i.e., information on a preamble puncturing pattern). The EHT-SIG following the first U-SIG may include information on preamble puncturing applied to the second 80 MHz band (i.e., information on a preamble puncturing pattern), and the EHT-SIG following the second U-SIG may include information on preamble puncturing applied to the first 80 MHz band (i.e., information on a preamble puncturing pattern).
Additionally or alternatively, the U-SIG and the EHT-SIG may include information on preamble puncturing based on the following method. The U-SIG may include information on preamble puncturing for all bands (i.e., information on a preamble puncturing pattern). That is. EHT-SIG does not include information on preamble puncturing, and only U-SIG may include information on preamble puncturing (ie, information on a preamble puncturing pattern).
U-SIG may be constructed in units of 20 MHZ. For example, if an 80 MHZ PPDU is constructed, the U-SIG may be duplicated. That is, the same 4 U-SIGs may be included in the 80 MHZ PPDU. PPDUs exceeding 80 MHz bandwidth may include different U-SIGs.
The EHT-SIG of
The EHT-SIG may include technical features of HE-SIG-B described through
As in the example of
In the same way as in the example of
As in the example of
A mode in which a common field of EHT-SIG is omitted may be supported. The mode in which the common field of the EHT-SIG is omitted may be referred as a compressed mode. When the compressed mode is used, a plurality of users (i.e., a plurality of receiving STAs) of the EHT PPDU may decode the PPDU (e.g., the data field of the PPDU) based on non-OFDMA. That is, a plurality of users of the EHT PPDU may decode a PPDU (e.g., a data field of the PPDU) received through the same frequency band. When a non-compressed mode is used, multiple users of the EHT PPDU may decode the PPDU (e.g., the data field of the PPDU) based on OFDMA. That is, a plurality of users of the EHT PPDU may receive the PPDU (e.g., the data field of the PPDU) through different frequency bands.
EHT-SIG may be constructed based on various MCS scheme. As described above, information related to the MCS scheme applied to the EHT-SIG may be included in the U-SIG. The EHT-SIG may be constructed based on the DCM scheme. For example, a first modulation technique may be applied to the contiguous half tones of N data tones (e.g., 52 data tones) allocated for a EHT-SIG and a second modulation technique may be applied to the remaining contiguous half tones. In other words, a transmitting STA may modulate specific control information into a first symbol based on a first modulation technique and allocate it to contiguous half tones and may modulate the same control information into a second symbol based on a second modulation technique and allocate it to the remaining contiguous half tones. As described above, information related to whether the DCM scheme is applied to the EHT-SIG (e.g., a 1-bit field) may be included in the U-SIG. The EHT-STF of
Information on the type of STF and/or LTF (including information on a guard interval (GI) applied to LTF) may be included in the U-SIG field and/or the EHT-SIG field of
The PPDU (i.e., EHT PPDU) of
For example, a EHT PPDU transmitted on a 20 MHz band, that is, a 20 MHZ EHT PPDU may be constructed based on the RU of
The EHT PPDU transmitted on the 80 MHz band, that is, the 80 MHZ EHT PPDU may be constructed based on the RU of
The tone-plan for 160/240/320 MHZ may be configured in the form of repeating the pattern of
The PPDU of
The receiving STA may determine the type of the received PPDU as the EHT PPDU based on the following. For example, when 1) the first symbol after the L-LTF signal of the received PPDU is BPSK, 2) RL-SIG in which the L-SIG of the received PPDU is repeated is detected, and 3) the result of applying the modulo 3 calculation to the value of the Length field of the L-SIG of the received PPDU (i.e., the remainder after dividing by 3) is detected as 0), the received PPDU may be determined as a EHT PPDU. When the received PPDU is determined to be an EHT PPDU, the receiving STA may determine the type of the EHT PPDU based on bit information included in symbols subsequent to the RL-SIG of
For example, the receiving STA may determine the type of the received PPDU as the HE PPDU based on the following. For example, when 1) the first symbol after the L-LTF signal is BPSK, 2) RL-SIG in which L-SIG is repeated is detected, and 3) the result of applying modulo 3 to the length value of L-SIG is detected as 1 or 2, the received PPDU may be determined as a HE PPDU.
For example, the receiving STA may determine the type of the received PPDU as non-HT, HT, and VHT PPDU based on the following. For example, when 1) the first symbol after the L-LTF signal is BPSK and 2) RL-SIG in which L-SIG is repeated is not detected, the received PPDU may be determined as non-HT, HT, and VHT PPDU. In addition, although a receiving STA detects repetition of a RL-SIG, when a result of applying modulo 3 to a length value of a L-SIG is detected as 0), a received PPDU may be determined as a non-HT, a HT and a VHT PPDU.
The PPDU of
Hereinafter, a target wake time (TWT) is described.
A TWT is a power saving (PS) technology which may improve energy efficiency of non-AP STAs by defining a service period (SP) between an AP and non-AP STA and sharing information about a SP each other to reduce media contention. A STA which performs a request/a suggest/a demand, etc, in a TWT setup step may be referred to as a TWT requesting STA. In addition, an AP which responds to a corresponding request such as Accept/Reject. etc. may be referred to as a TWT responding STA. A setup step may include a TWT request for an AP of a STA, a type of a TWT operation performed and a process of determining/defining a frame type transmitted or received. A TWT operation may be divided into an individual TWT and a broadcast TWT.
An individual TWT is a mechanism that an AP and non-AP STA perform data exchange after performing negotiation for an awake/doze status of a non-AP STA through transmission or reception of a TWT request/response frame. In an example of
A broadcast TWT is a TWT that a non-AP STA (or a TWT scheduling STA) acquires information on a target beacon transmission time (TBTT) and a listen interval, etc. by transmitting or receiving a TWT request/response frame with an AP (or a TWT scheduled STA). Here, a negotiation operation for a TBTT may be performed. Based on it, an AP may define a frame which will include scheduling information of a TWT through a beacon frame. In
Delivery of TWT information may be performed through a TWT information frame and a TWT information element. A TWT information frame is transmitted by a STA to request or deliver information on a TWT agreement and is transmitted by one of STAs in an existing TWT agreement. An action frame of a TWT Information frame includes a TWT information field. A TWT Information field may include a 3-bit TWT flow identifier subfield, a 1-bit response requested subfield, a 1-bit next TWT request subfield, a 2-bit next TWT subfield size subfield, a 1-bit all TWT subfield and a 0/32/48/64-bit next TWT subfield.
A TWT information element may be transmitted or received by being included in a beacon, a probe response, a (re)association response frame, etc. A TWT information element may include an element ID field, a length field, a control field and a TWT parameter information field.
A control field of a TWT information element has the same format regardless of an individual TWT and a broadcast TWT.
A NDP paging indication subfield may have a value of 1 when a NDP paging field exists and may have a value of 0 when a NDP paging field does not exist.
A responder PM mode subfield may represent a power management (PM) mode.
A negotiation type subfield may represent whether information included in a TWT element is about a negotiation of broadcast TWT or individual TWT(s) or is about a wake TBTT interval.
For example, when a value of a negotiation type subfield is 0, a TWT subfield is about a future individual TWT SP start time and a TWT element includes one individual TWT parameter set. It may correspond to an individual TWT negotiation between a TWT requesting STA and a TWT responding STA or may correspond to an individual TWT announcement by a TWT responder.
For example, when a value of a negotiation type subfield is 1, a TWT subfield is about a next TBTT time and a TWT element includes one individual TWT parameter set. It may correspond to a wake TBTT and a wake interval negotiation between a TWT scheduled STA and a TWT scheduling AP.
For example, when a value of a negotiation type subfield is 2, a TWT subfield is about a future broadcast TWT SP start time and a TWT element includes at least one broadcast TWT parameter set. It may correspond to providing a broadcast TWT schedule to a TWT scheduled STA by including a TWT element in a broadcast management frame transmitted by a TWT scheduling AP.
For example, when a value of a negotiation type subfield is 3, a TWT subfield is about a future broadcast TWT SP start time and a TWT element includes at least one broadcast TWT parameter set. It may correspond to managing membership of a broadcast TWT schedule by including a TWT element in an individually addressed management frame transmitted by any one of a TWT scheduled STA or a TWT scheduling AP.
When a TWT information frame disabled subfield is configured as 1, it represents that reception of a TWT information frame by a STA is disabled and otherwise, it may be configured as 0.
A wake duration unit subfield represents a unit of a nominal minimum TWT wake duration field. A wake duration unit subfield may be configured as 0 when a unit is 256 us and may be configured as 1 when a unit is a TU. When it is not a HE/EHT STA, a wake duration unit subfield may be configured as 0).
A most significant bit (MSB) of a negotiation type field may correspond to a broadcast field. When the broadcast field is 1, at least one broadcast TWT parameter set may be included in a TWT element. When the broadcast field is 0, only one individual TWT parameter set may be included in a TWT element. A TWT element that the broadcast field is configured as 1 may be referred to as a broadcast TWT element.
A TWT parameter information field included in a TWT element in
For an individual TWT, a TWT parameter information field in a TWT element includes a single individual TWT parameter set field.
For a broadcast TWT, a TWT parameter information field in a TWT element includes at least one broadcast TWT parameter set field. Each broadcast TWT parameter set may include specific information on one broadcast TWT.
As shown in
A request type subfield has the same size in an individual TWT parameter set field and a broadcast TWT parameter set field, but may have a different detailed configuration. It is described later.
A target wake time subfield represents a start time of an individual/broadcast TWT SP expected in the future.
A nominal minimum TWT wake duration subfield represents the minimum unit that a TWT requesting STA is expected to be awaken in order to complete frame exchange related to a TWT flow identifier during a TWT wake interval duration. Here, a TWT wake interval may mean an average time between contiguous TWT SPs expected by a TWT requesting STA.
A TWT Wake Interval Mantissa subfield is a binary value of a TWT wake interval value, which may be indicated in microseconds.
In reference to
A TWT group assignment subfield is provided to a TWT requesting STA by including information on a TWT group to which a STA is assigned. A TWT value in a TWT group may be calculated by using corresponding information. A TWT value of a STA may be the same as a value obtained by multiplying a value of a zero offset and a value of a TWT offset by a value of a TWT unit.
A TWT channel subfield represents a bitmap representing an allowed channel. When transmitted by a TWT requesting STA, a TWT channel subfield may include a bitmap representing a channel which is requested by a STA to be used as a temporary basic channel during a TWT SP. When transmitted by a TWT response STA, a TWT channel subfield may include a bitmap representing a channel that a TWT request is allowed.
A NDP paging subfield is optional and may include an identifier of a paged STA, information related to the maximum number of TWT wake intervals between NDP paging frames, etc.
In reference to
Next, a detailed configuration of a request type subfield is described.
First, a format of a request type subfield of an individual TWT parameter set field is described by referring to
A TWT request subfield may represent whether it is a requesting STA or a response STA. When that value is 1, it may represent that it is a TWT requesting STA or a scheduling STA and when that value is 0, it may represent that it is a TWT responding STA or a scheduling AP.
A TWT setup command subfield may represent a command such as Request, Suggest, Demand, Accept, Alternate, Dictate, Reject, etc.
A trigger subfield represents whether a trigger frame will be used in a TWT SP. When that value is 1, a trigger may be used and when that value is 0, a trigger may not be used.
An implicit subfield may represent whether it is an implicit TWT or an explicit TWT. When that value is 1, it may represent an implicit TWT and when that value is 0, it may represent an explicit TWT.
A flow type subfield may represent an interaction type between a TWT requesting STA (or a TWT scheduled STA) and a TWT responding STA (or a TWT scheduling AP). When that value is 1, it may mean an announced TWT that a STA transmits a wakeup signal to an AP by transmitting a PS-Poll or automatic power save delivery (APSD) trigger frame before a frame, not a trigger frame, is transmitted from an AP to a STA. When that value is 0, it may mean an unannounced TWT.
A TWT flow identifier subfield may include a 3-bit value which uniquely identifies specific information on a corresponding TWT request in other request performed between the same TWT requesting STA and TWT responding STA pair.
A TWT wake interval exponent subfield may configure a TWT wake interval value in a binary microsecond unit. For an individual TWT, it may mean an interval between individual TWT SPs. A TWT wake interval of a requesting STA may be defined as [TWT Wake Interval Mantissa*2*TWT Wake Interval Exponent].
A TWT protection subfield may represent whether to use a TWT protection mechanism. When that value is 1, a TXOP in a TWT SP may be started with a NAV protection mechanism such as a (MU)RTS/CTS or a CTS-to-self frame and when that value is 0, a NAV protection mechanism may not be applied.
In reference to
A last broadcast parameter set subfield represents whether it is a last broadcast TWT parameter set. When that value is 1, it may represent that it is a last broadcast TWT parameter set and when that value is 0, it may represent that a next broadcast TWT parameter set exists.
A broadcast TWT recommendation subfield may represent recommendations for a frame type transmitted by an AP during a broadcast TWT SP as a value of 1-7.
A last 1 bit of a request type subfield of a broadcast TWT parameter set field may be reserved.
Hereinafter, a low latency transmission method according to the present disclosure for supporting traffic sensitive to latency is described.
As wired/wireless traffic has recently exploded, traffic sensitive to latency has also increased significantly. Traffic sensitive to latency includes real-time audio/video transmission, and with the spread of multimedia devices, the need to support it in a wireless environment has increased. However, compared to a wired environment, there are many things to consider in a wireless environment to support traffic sensitive to latency. It is because transmission speed in a wireless environment is lower than that in a wired environment and interference issues from the surroundings should be also considered. In particular, in a WLAN system, multiple STAs should compete equally for occupying the medium in an Industry-Science-Medical (ISM) band, so compared to a cellular communication network based on radio resource scheduling by a central base station, it is relatively more difficult to support traffic sensitive to latency. The present disclosure describes a new method for supporting traffic sensitive to latency in a WLAN system.
In the present disclosure, latency may mean latency defined in a IEEE 802.11 series standard. For example, it may mean a time until, after a frame to be transmitted is entered to a queue of a MAC layer of a transmitting STA, a transmission of the transmitting STA successfully ends in a PHY layer, the transmitting STA receives ACK/block ACK, etc. from a receiving STA and a corresponding frame is deleted from the queue of the MAC layer of the transmitting STA. In addition, in the present disclosure, a non-AP STA which supports transmission of latency sensitive data may be referred to as a low latency STA. And, data other than latency sensitive data may be referred to as regular data.
Hereinafter, a restricted TWT is described.
A restricted TWT (r-TWT) may support preferentially securing a data transmission possibility for a low latency STA compared to other STAs by making an AP configure a special broadcast TWT for a low latency STA transmitting latency sensitive data. A STA may establish membership for at least one r-TWT schedule for an AP. Here, a r-TWT agreement may be established by the same process as a broadcast TWT agreement and a broadcast TWT element for it may be defined to include a r-TWT parameter set field. For example, a r-TWT parameter set may refer to a specific broadcast TWT parameter set field which is distinct from other broadcast TWT parameter set fields. In other words, a r-TWT parameter set field may correspond to a special case of a broadcast TWT parameter set field. In addition, an AP may announce a r-TWT SP.
Basically, when other STA which supports a r-TWT operation is a TXOP holder, the TXOP should be ended before a start time of a r-TWT SP advertised in a combined AP. Accordingly, a STA related to a corresponding r-TWT (i.e., a low latency STA) may transmit or receive traffic preferentially compared to the other STAs in a r-TWT SP.
In the present disclosure, as described above, a low latency STA related to a specific r-TWT is referred to as a member r-TWT scheduled STA and other STAs are referred to as a non-member STA. A non-member STA may be a STA which has a capability to support a r-TWT operation, but is not a member of any r-TWT or which supports a r-TWT operation and is a member of other r-TWT or which has no capability to support a r-TWT operation.
A STA (e.g., a low latency STA) which supports a restricted SP (or r-TWT SP) operation of a broadcast TWT may inform an AP that latency sensitive data should be transmitted based on a r-TWT operation. If an AP supports a r-TWT operation/mode, an AP may transmit a frame including scheduling information of TWTs requested by each STA to a low latency STA and other STA(s). For example, in order to perform an operation for a r-TWT, non-AP STAs may acquire r-TWT-related information from an AP through a beacon frame, a probe response frame, a (re)association response frame or other frames in a non-defined format (e.g., a frame for broadcast, advertisement and announcement).
According to a restricted TWT operation, a NAV such as a (MU) RTS/CTS or CTS-to-self or a quiet interval. etc. may be used to secure a separate TXOP (i.e., access of other STAs is restricted) in a r-TWT SP. Before a specific r-TWT SP starts, if there is a TXOP of other STA (i.e., a non-member STA) other than a STA having a membership for the specific r-TWT schedule, it should be stopped. And, a TXOP of the other STA (i.e., a non-member STA) may be additionally performed after the specific r-TWT SP ends. It may be referred to as a TXOP rule-based operation for a r-TWT SP of a non-member STA.
In the present disclosure, latency sensitive data may be data to which a specific traffic identifier (TID) value is allocated. A TID may identify a traffic category (TC), a traffic stream (TS), etc. A TC may correspond to a priority. In other words, a TID value may represent at least a priority of corresponding data.
When an AP announces r-TWT information to non-AP STAs, TID information may be included in a TWT element. For example, in order to support a priority-based conditional operation for a TXOP rule for a r-TWT SP of a non-AP STA (or a non-member STA) transmitting data before a r-TWT SP starts, TID information of data to be transmitted during a r-TWT SP may be provided to a non-member STA. Data being transmitted in a TXOP held by a non-member STA may be latency sensitive data or not.
In S1910, a STA may receive restricted TWT (r-TWT)-related information from an AP. For example, r-TWT-related information may be included in a TWT element of a predetermined frame (e.g., a beacon frame, a probe response frame, a (re)association response frame, etc.). Specifically, r-TWT-related information may be included in a r-TWT parameter set field in a TWT element. More specifically, r-TWT-related information may include a first TID subfield of a 3-bit size in a TWT information (e.g., broadcast TWT information or r-TWT information) subfield of a r-TWT parameter set field. Detailed examples of a TWT element including a first TID subfield are described later.
In S1920, a STA may exchange a frame with the AP. The frame exchange may start before a start time of a service period (SP) for the r-TWT. The maximum duration of the frame exchange may be after the r-TWT SP start time.
In S1930, a STA may maintain or stop the frame exchange based on a priority between the first TID and a second TID of data to be exchanged with the AP during the frame exchange duration.
A STA may be a member STA for the r-TWT schedule or may be a non-member STA.
In S2010, an AP may transmit restricted-TWT (r-TWT)-related information to a first and second STA. For example, r-TWT-related information may be included in a TWT element of a predetermined frame (e.g., a beacon frame, a probe response frame, a (re)association response frame, etc.). Specifically, r-TWT-related information may be included in a r-TWT parameter set field in a TWT element. More specifically, r-TWT-related information may include a first TID subfield of a 3-bit size in a TWT information (e.g., broadcast TWT information or r-TWT information) subfield of a r-TWT parameter set field. Detailed examples of a TWT element including a first TID subfield are described later.
In S2020, an AP may exchange a frame with a second STA. The frame exchange may start before a start time of a service period (SP) for the r-TWT. The maximum duration of the frame exchange may be after the r-TWT SP start time.
In S2030, an AP may maintain or stop the frame exchange based on a priority between the first TID and a second TID of data to be exchanged with the second STA during the frame exchange duration.
When frame exchange with the second STA is maintained, an AP may postpone a start time of the r-TWT SP by a first predetermined time length after a time when frame exchange with the second STA is completed. In addition, an end time of the r-TWT SP may be extended by a second predetermined time length. A second predetermined length may be the same as a first predetermined length or may have a length less than a first predetermined length. Additionally or alternatively, a first predetermined length may correspond to the maximum value of a second predetermined length.
An AP may indicate to a first STA information on whether a start/end time of a r-TWT SP is postponed/extended and/or a postponed/extended time, etc, through a variety of means. For example, the information on whether postponement/extension is performed and/or a time changed according to postponement/extension may be implicitly indicated through a frame exchanged between an AP and a second STA or may be explicitly indicated from an AP to a first STA.
A first STA may correspond to a member STA for a specific restricted-TWT (r-TWT) schedule. A second STA may be a member STA for the specific r-TWT schedule or may be a non-member STA.
Hereinafter, specific examples of the present disclosure for a TID included in r-TWT-related information are described.
A TID field has a 4-bit size and is defined to use a value from 0) to 7 in EDCA. A value from 8 to 15 of a TID field is defined to be used for HCCA, SPCA (service period channel access), HEMM (HCCA, EDCA mixed mode) and SEMM (SEMM SPCA-EDCA mixed mode), but conventionally (e.g., according to a IEEE 802.11ax standard), corresponding values are defined as reserved values that are not used.
In the present disclosure, distinguishing latency sensitive data/traffic from other data/traffic by using a value from 8 to 15 of a TID field is defined. For example, based on a TID of latency sensitive data, it may be distinguished from data of other ACs. Furthermore, based on a TID, latency sensitive data/traffic may be distinguished per transmission priority of a data/traffic type.
Accordingly, a transmission priority of first data to be transmitted during a r-TWT SP and second data being transmitted before a start time of a r-TWT SP may be determined by comparing it each other based on a TID value of each of first and second data. According to a priority determination, whether a TXOP of a STA transmitting data before the start of a r-TWT SP is ended may be terminated.
For a broadcast TWT, at least one broadcast TWT parameter set field is included in a TWT parameter information field of a TWT element format (refer to
As in
A subfield including a TID value in a TWT element is referred to as LLD (Low Latency Data)_TID or Restricted TWT (r-TWT)_TID. A scope of the present disclosure is not limited to a name of a corresponding subfield and includes various examples in which a 3-bit TID for a specific r-TWT or data/traffic transmitted in a specific r-TWT is included in a TWT element.
As in
An example in
Accordingly, a LLD_TID subfield may represent a TID value (e.g., one value of 8 to 15) of latency sensitive data/traffic related to a r-TWT.
Whether a TWT parameter set field is related to a broadcast TWT or is related to a restricted TWT may be determined based on whether a corresponding STA supports a restricted TWT operation (e.g., a capability of a STA). If a corresponding STA supports a r-TWT, a restricted TWT parameter set field that part of the existing broadcast TWT parameter set field is modified may be defined and used.
For example, a 1-bit (a reserved bit in an example of
Although information indicating whether it is a broadcast TWT or a restricted TWT is not included in a broadcast/restricted TWT parameter set field, interpretation of a STA for a broadcast/restricted TWT parameter set field may be different according to whether a terminal supports a restricted TWT operation as described above.
Hereinafter, examples of a mapping relationship between a LLD_TID value and a TID value indicating latency sensitive data/traffic are described. As a LLD_TID subfield described above has a 3-bit size, it may have one value of 0) to 7. Meanwhile, a priority of latency sensitive data/traffic may be represented through a value of 8 to 15 of a TID field. Accordingly, it is necessary to define a mapping relationship between a value of LLD_TID and a value of a TID field.
An example in Table 1 is one example of a method in which one TID is mapped to one LLD_TID and a TID and a LLD_TID may be mapped one-to-one in different order. In an example in Table 1, a scope of a TID value corresponding to a LLD_TID value corresponds to 8 to 15. Here, a transmission priority refers to a priority in data transmission. For example, data with a LLD_TID value of 3 may correspond to data which should be transmitted with priority than data with a LLD_TID value of 0).
In Table 1 and examples below, it may be defined that as a value of at least one of a LLD_TID or a TID is larger, a transmission priority is higher and conversely, it may be defined that as a value of at least one of a LLD_TID or a TID is smaller, a transmission priority is higher.
In Table 2, a scope of a TID value corresponding to a LID_TID value corresponds to part of 8 to 15. In addition, at least one TID value may be mapped to one LLD_TID value. For example, Table 2 shows a case in which only 8 to 10 of a TID value is used. Here, some of values from 8 to 10 of a TID may be mapped one-to-one to each value of 0 to 7 of a LLD_TID and some may be mapped one-to-many. Some of TID values may be 8 to 10 or may be 13 to 15 or less than 8 TID values which are contiguous or not may be used.
As Table 3 is an additional example similar to Table 2, a scope of a TID value corresponding to a LID_TID value corresponds to part of 8 to 15. In addition, at least one TID value may be mapped to one LLD_TID value. For example, Table 3 shows a case in which 8 to 11 of a TID value is used. When 12 or higher is used as a TID value, some LID_TID values may be mapped to one TID value and other LID_TID values may be mapped to a plurality of TID values.
Table 4 corresponds to an example in which a scope of a TID value mapped to a LLD_TID value is mapped to 0 to 15, not 8 to 15 (i.e., the entire value of a TID field). For example, when a value of a LLD_TID is 0, a TID value from 0 to 7 may be matched. In other words, when a LLD_TID value is 0, it may mean regular data, not latency sensitive data, and regular data may have the lowest transmission priority. When TXOP sharing is supported in a restricted TWT SP, it is necessary to distinguish between latency sensitive data and other data, so representing regular data allowed for transmission in a r-TWT SP through a LLD_TID value may be supported. Table 4 shows that 1 to 7 of a LLD_TID value corresponds to 8 to 15 of a TID value. Alternatively, when a TID value from 8 to 15 does not mean latency sensitive data/traffic, as shown in an example of Table 2 and Table 3, some LLD_TID values may be reserved or some LLD_TID values may be mapped to a plurality of TID values.
As an additional example, at least one some value of a LLD_TID may be mapped to a value of 0-7 of a TID and at least one other value of a LLD_TID may be mapped to a value of 8-15 of a TID or some values of 8-15. In the present disclosure, an AP provides non-AP STAs with information on a TID of data to be transmitted during a r-TWT SP, supporting a priority-based conditional operation for a TXOP rule for a r-TWT SP for a r-TWT of a non-AP STA. For example, a non-AP STA which is transmitting data before a r-TWT SP may receive a TWT element including TID information through a predetermined frame (e.g., a beacon frame, a probe response frame, a (re)association response frame or a newly defined frame) from an AP.
A transmission priority between data may be determined based on TID information of each data. In the present disclosure, it is assumed that as a TID value is larger, a data transmission priority is higher and as a TID value is smaller, a data transmission priority is lower. In addition, it is assumed that as a LLD_TID value corresponding to a TID value is larger, a data transmission priority is higher and as a LLD_TID value corresponding to a TID value is smaller, a data transmission priority is lower. However, it is just an example for clarity of a description, and it may be defined that as a value of at least one of a TID or a LID_TID is larger, a priority is higher or as a value of at least one of a TID or a LID_TID is smaller, a priority is higher.
As such, when TID information is included in information related to a r-TWT (i.e., a TWT element), a non-AP STA which is transmitting data before a r-TWT SP may determine whether to maintain its TXOP by comparing a TID value of r-TWT-related data and a TID value of data being transmitted or received by it as in examples described later.
In an example of
In an example of
In an example of
In this case, a start time of a r-TWT SP may be postponed to continuously transmit data without ending a TXOP of STA2 which is transmitting data before a r-TWT SP. Additionally, an end time of a r-TWT SP may be also extended by a time length based on (or less than) a time length that a start time is postponed. Here, a postponed end time may be defined in a TWT wake interval. In other words, although an end time is postponed, it may be configured not to be after a next TWT wake interval.
In an example of
In this case, a TXOP of STA2 which is transmitting data before a r-TWT SP may be stopped or suspended. In other words, frame exchange may be completed (e.g., data transmission and ACK reception) before the maximum duration of a TXOP secured by STA2 for frame exchange. In this case, a start time and an end time of a r-TWT SP are not postponed/extended. In this case, a stopped or suspended TXOP may be resumed after a r-TWT SP ends.
According to the present disclosure, a new method of clearly providing a TID of data related to a specific r-TWT to multiple STAs may be provided. Accordingly, an operation that a STA which is a member of the specific r-TWT as well as other STAs maintains or stops a TXOP being performed before the start of the specific r-TWT SP by comparing a TID-based priority may be performed more efficiently.
Embodiments described above are that elements and features of the present disclosure are combined in a predetermined form. Each element or feature should be considered to be optional unless otherwise explicitly mentioned. Each element or feature may be implemented in a form that it is not combined with other element or feature. In addition, an embodiment of the present disclosure may include combining a part of elements and/or features. An order of operations described in embodiments of the present disclosure may be changed. Some elements or features of one embodiment may be included in other embodiment or may be substituted with a corresponding element or a feature of other embodiment. It is clear that an embodiment may include combining claims without an explicit dependency relationship in claims or may be included as a new claim by amendment after application.
It is clear to a person skilled in the pertinent art that the present disclosure may be implemented in other specific form in a scope not going beyond an essential feature of the present disclosure. Accordingly, the above-described detailed description should not be restrictively construed in every aspect and should be considered to be illustrative. A scope of the present disclosure should be determined by reasonable construction of an attached claim and all changes within an equivalent scope of the present disclosure are included in a scope of the present disclosure.
A scope of the present disclosure includes software or machine-executable commands (e.g., an operating system, an application, a firmware, a program, etc.) which execute an operation according to a method of various embodiments in a device or a computer and a non-transitory computer-readable medium that such a software or a command, etc, are stored and are executable in a device or a computer. A command which may be used to program a processing system performing a feature described in the present disclosure may be stored in a storage medium or a computer-readable storage medium and a feature described in the present disclosure may be implemented by using a computer program product including such a storage medium. A storage medium may include a high-speed random-access memory such as DRAM, SRAM, DDR RAM or other random-access solid state memory device, but it is not limited thereto, and it may include a nonvolatile memory such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices or other nonvolatile solid state storage devices. A memory optionally includes one or more storage devices positioned remotely from processor(s). A memory or alternatively, nonvolatile memory device(s) in a memory include a non-transitory computer-readable storage medium. A feature described in the present disclosure may be stored in any one of machine-readable mediums to control a hardware of a processing system and may be integrated into a software and/or a firmware which allows a processing system to interact with other mechanism utilizing a result from an embodiment of the present disclosure. Such a software or a firmware may include an application code, a device driver, an operating system and an execution environment/container, but it is not limited thereto.
A method proposed by the present disclosure is mainly described based on an example applied to an IEEE 802.11-based system, 5G system, but may be applied to various WLAN or wireless communication systems other than the IEEE 802.11-based system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0039862 | Mar 2021 | KR | national |
This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2022/004117, filed on Mar. 24, 2022, which claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2021-0039862, filed on Mar. 26, 2021, the contents of which are all incorporated by reference herein in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/004117 | 3/24/2022 | WO |
