Patent Publication Number: US-2023147636-A1

Title: Power state information sharing for multi-link transmission

Description:
TECHNICAL FIELD 
     The present specification relates to a method of sharing power state information of STAs for a multi-link operation in a wireless local area network (WLAN) system. 
     BACKGROUND 
     Wireless network technologies may include various types of wireless local area networks (WLANs). The WLAN employs widely used networking protocols and can be used to interconnect nearby devices together. The various technical features described herein may be applied to any communication standard, such as WiFi or, more generally, any one of the IEEE 802.11 family of wireless protocols. A wireless local area network (WLAN) has been enhanced in various ways. For example, the IEEE 802.11ax standard has proposed an enhanced communication environment by using orthogonal frequency division multiple access (OFDMA) and downlink multi-user multiple input multiple output (DL MU MIMO) schemes. 
     The present specification proposes a technical feature that can be utilized in a new communication standard. For example, the new communication standard may be an extreme high throughput (EHT) standard which is currently being discussed. The EHT standard may use an increased bandwidth, an enhanced PHY layer protocol data unit (PPDU) structure, an enhanced sequence, a hybrid automatic repeat request (HARQ) scheme, or the like, which is newly proposed. The EHT standard may be called the IEEE 802.11be standard. 
     SUMMARY 
     A method performed by a STA MLD in a wireless local area network (WLAN) system according to various embodiments may include technical features related to a method for power control in multi-link transmission. A reception multi-link device (MLD) of a wireless local area network (WLAN) system includes a plurality of stations (STAs), and each STA may operate in different links. The receiving MLD may receive a first physical protocol data unit (PPDU) from the transmitting MLD. The receiving MLD may transmit a block acknowledgment (BA) frame for the first PPDU. The BA frame may include first power state information for STAs transitioning from a doze state to an awake state. 
     According to an example of the present specification, the receiving MLD may transmit power state information of internal STAs. Accordingly, the transmitting MLD may transmit data based on the power state information of the STAs inside the receiving MLD. In data transmission between MLDs including a plurality of STAs, since the transmitting MLD can know which link STAs are in the awake state and which link STAs are in the doze state, data transmission can be efficiently performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an example of a transmitting apparatus and/or receiving apparatus of the present specification. 
         FIG.  2    is a conceptual view illustrating the structure of a wireless local area network (WLAN). 
         FIG.  3    illustrates a general link setup process. 
         FIG.  4    illustrates an example of a PPDU used in an IEEE standard. 
         FIG.  5    illustrates a layout of resource units (RUs) used in a band of 20 MHz. 
         FIG.  6    illustrates a layout of RUs used in a band of 40 MHz. 
         FIG.  7    illustrates a layout of RUs used in a band of 80 MHz. 
         FIG.  8    illustrates a structure of an HE-SIG-B field. 
         FIG.  9    illustrates an example in which a plurality of user STAs are allocated to the same RU through a MU-MIMO scheme. 
         FIG.  10    illustrates an operation based on UL-MU. 
         FIG.  11    illustrates an example of a trigger frame. 
         FIG.  12    illustrates an example of a common information field of a trigger frame. 
         FIG.  13    illustrates an example of a subfield included in a per user information field. 
         FIG.  14    describes a technical feature of the UORA scheme. 
         FIG.  15    illustrates an example of a channel used/supported/defined within a 2.4 GHz band. 
         FIG.  16    illustrates an example of a channel used/supported/defined within a 5 GHz band. 
         FIG.  17    illustrates an example of a channel used/supported/defined within a 6 GHz band. 
         FIG.  18    illustrates an example of a PPDU used in the present specification. 
         FIG.  19    illustrates an example of a modified transmission device and/or receiving device of the present specification. 
         FIG.  20    is a diagram illustrating an example of channel bonding. 
         FIG.  21    to  FIG.  25    are diagrams illustrating an embodiment of a wake-up operation. 
         FIG.  26    is a diagram illustrating an embodiment of an HT Control field. 
         FIG.  27    is a diagram illustrating an embodiment of an A-Control subfield. 
         FIG.  28    is a diagram illustrating an embodiment of a control subfield format. 
         FIG.  29    shows an example of a Non-AP BSR (NMB) Control subfield. 
         FIG.  30    is a diagram illustrating an embodiment of an NMB Control subfield. 
         FIG.  31    shows an example of ACI Bitmap subfield encoding. 
         FIG.  32    shows an example of an NMB Control Subfield. 
         FIG.  33    is a diagram illustrating an example of the format of the BSR Control subfield in the 1 lax system. 
         FIG.  34    to  FIG.  35    are diagrams illustrating an embodiment of a power state transmission method. 
         FIG.  36    is a diagram illustrating an embodiment of a method for transmitting a power state according to the Method 1). 
         FIG.  37    is a diagram illustrating an embodiment of a method for transmitting a power state according to the Method 2). 
         FIG.  38    is a diagram illustrating an example of a Block Ack frame including power state information. 
         FIG.  39    is a diagram illustrating an example of a Block Ack frame including power state information. 
         FIG.  40    is a diagram illustrating an embodiment of a receiving MLD operation method. 
         FIG.  41    is a diagram illustrating an embodiment of a method of operating a transmission MLD. 
     
    
    
     DETAILED DESCRIPTION 
     In the present specification, “A or B” may mean “only A”, “only B” or “both A and B”. In other words, in the present specification, “A or B” may be interpreted as “A and/or B”. For example, in the present specification, “A, B, or C” may mean “only A”, “only B”, “only C”, or “any combination of A, B, C”. 
     A slash (/) or comma used in the present specification may mean “and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, B, or C”. 
     In the present specification, “at least one of A and B” may mean “only A”, “only B”, or “both A and B”. In addition, in the present specification, the expression “at least one of A or B” or “at least one of A and/or B” may be interpreted as “at least one of A and B”. 
     In addition, in the present specification, “at least one of A, B, and C” may mean “only A”, “only B”, “only C”, or “any combination of A, B, and C”. In addition, “at least one of A, B, or C” or “at least one of A, B, and/or C” may mean “at least one of A, B, and C”. 
     In addition, a parenthesis used in the present specification may mean “for example”. Specifically, when indicated as “control information (EHT-signal)”, it may denote that “EHT-signal” is proposed as an example of the “control information”. In other words, the “control information” of the present specification is not limited to “EHT-signal”, and “EHT-signal” may be proposed as an example of the “control information”. In addition, when indicated as “control information (i.e., EHT-signal)”, it may also mean that “EHT-signal” is proposed as an example of the “control information”. 
     Technical features described individually in one figure in the present specification may be individually implemented, or may be simultaneously implemented. 
     The following example of the present specification may be applied to various wireless communication systems. For example, the following example of the present specification may be applied to a wireless local area network (WLAN) system. For example, the present specification may be applied to the IEEE 802.11a/g/n/ac standard or the IEEE 802.11ax standard. In addition, the present specification may also be applied to the newly proposed EHT standard or IEEE 802.11be standard. In addition, the example of the present specification may also be applied to a new WLAN standard enhanced from the EHT standard or the IEEE 802.11be standard. In addition, the example of the present specification may be applied to a mobile communication system. For example, it may be applied to a mobile communication system based on long term evolution (LTE) depending on a 3rd generation partnership project (3GPP) standard and based on evolution of the LTE. In addition, the example of the present specification may be applied to a communication system of a 5G NR standard based on the 3GPP standard. 
     Hereinafter, in order to describe a technical feature of the present specification, a technical feature applicable to the present specification will be described. 
       FIG.  1    shows an example of a transmitting apparatus and/or receiving apparatus of the present specification. 
     In the example of  FIG.  1   , various technical features described below may be performed.  FIG.  1    relates to at least one station (STA). For example, STAs  110  and  120  of the present specification may also be called in various terms such as a mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit, or simply a user. The STAs  110  and  120  of the present specification may also be called in various terms such as a network, a base station, a node-B, an access point (AP), a repeater, a router, a relay, or the like. The STAs  110  and  120  of the present specification may also be referred to as various names such as a receiving apparatus, a transmitting apparatus, a receiving STA, a transmitting STA, a receiving device, a transmitting device, or the like. 
     For example, the STAs  110  and  120  may serve as an AP or a non-AP. That is, the STAs  110  and  120  of the present specification may serve as the AP and/or the non-AP. 
     The STAs  110  and  120  of the present specification may support various communication standards together in addition to the IEEE 802.11 standard. For example, a communication standard (e.g., LTE, LTE-A, 5G NR standard) or the like based on the 3GPP standard may be supported. In addition, the STA of the present specification may be implemented as various devices such as a mobile phone, a vehicle, a personal computer, or the like. In addition, the STA of the present specification may support communication for various communication services such as voice calls, video calls, data communication, and self-driving (autonomous-driving), or the like. 
     The STAs  110  and  120  of the present specification may include a medium access control (MAC) conforming to the IEEE 802.11 standard and a physical layer interface for a radio medium. 
     The STAs  110  and  120  will be described below with reference to a sub-figure (a) of  FIG.  1   . 
     The first STA  110  may include a processor  111 , a memory  112 , and a transceiver  113 . The illustrated process, memory, and transceiver may be implemented individually as separate chips, or at least two blocks/functions may be implemented through a single chip. 
     The transceiver  113  of the first STA performs a signal transmission/reception operation. Specifically, an IEEE 802.11 packet (e.g., IEEE 802.11a/b/g/n/ac/ax/be, etc.) may be transmitted/received. 
     For example, the first STA  110  may perform an operation intended by an AP. For example, the processor  111  of the AP may receive a signal through the transceiver  113 , process a reception (RX) signal, generate a transmission (TX) signal, and provide control for signal transmission. The memory  112  of the AP may store a signal (e.g., RX signal) received through the transceiver  113 , and may store a signal (e.g., TX signal) to be transmitted through the transceiver. 
     For example, the second STA  120  may perform an operation intended by a non-AP STA. For example, a transceiver  123  of a non-AP performs a signal transmission/reception operation. Specifically, an IEEE 802.11 packet (e.g., IEEE 802.11a/b/g/n/ac/ax/be packet, etc.) may be transmitted/received. 
     For example, a processor  121  of the non-AP STA may receive a signal through the transceiver  123 , process an RX signal, generate a TX signal, and provide control for signal transmission. A memory  122  of the non-AP STA may store a signal (e.g., RX signal) received through the transceiver  123 , and may store a signal (e.g., TX signal) to be transmitted through the transceiver. 
     For example, an operation of a device indicated as an AP in the specification described below may be performed in the first STA  110  or the second STA  120 . For example, if the first STA  110  is the AP, the operation of the device indicated as the AP may be controlled by the processor  111  of the first STA  110 , and a related signal may be transmitted or received through the transceiver  113  controlled by the processor  111  of the first STA  110 . In addition, control information related to the operation of the AP or a TX/RX signal of the AP may be stored in the memory  112  of the first STA  110 . In addition, if the second STA  120  is the AP, the operation of the device indicated as the AP may be controlled by the processor  121  of the second STA  120 , and a related signal may be transmitted or received through the transceiver  123  controlled by the processor  121  of the second STA  120 . In addition, control information related to the operation of the AP or a TX/RX signal of the AP may be stored in the memory  122  of the second STA  120 . 
     For example, in the specification described below, an operation of a device indicated as a non-AP (or user-STA) may be performed in the first STA  110  or the second STA  120 . For example, if the second STA  120  is the non-AP, the operation of the device indicated as the non-AP may be controlled by the processor  121  of the second STA  120 , and a related signal may be transmitted or received through the transceiver  123  controlled by the processor  121  of the second STA  120 . In addition, control information related to the operation of the non-AP or a TX/RX signal of the non-AP may be stored in the memory  122  of the second STA  120 . For example, if the first STA  110  is the non-AP, the operation of the device indicated as the non-AP may be controlled by the processor  111  of the first STA  110 , and a related signal may be transmitted or received through the transceiver  113  controlled by the processor  111  of the first STA  110 . In addition, control information related to the operation of the non-AP or a TX/RX signal of the non-AP may be stored in the memory  112  of the first STA  110 . 
     In the specification described below, a device called a (transmitting/receiving) STA, a first STA, a second STA, a STA1, a STA2, an AP, a first AP, a second AP, an AP1, an AP2, a (transmitting/receiving) terminal, a (transmitting/receiving) device, a (transmitting/receiving) apparatus, a network, or the like may imply the STAs  110  and  120  of  FIG.  1   . For example, a device indicated as, without a specific reference numeral, the (transmitting/receiving) STA, the first STA, the second STA, the STA1, the STA2, the AP, the first AP, the second AP, the AP1, the AP2, the (transmitting/receiving) terminal, the (transmitting/receiving) device, the (transmitting/receiving) apparatus, the network, or the like may imply the STAs  110  and  120  of  FIG.  1   . For example, in the following example, an operation in which various STAs transmit/receive a signal (e.g., a PPDU) may be performed in the transceivers  113  and  123  of  FIG.  1   . In addition, in the following example, an operation in which various STAs generate a TX/RX signal or perform data processing and computation in advance for the TX/RX signal may be performed in the processors  111  and  121  of  FIG.  1   . For example, an example of an operation for generating the TX/RX signal or performing the data processing and computation in advance may include: 1) an operation of determining/obtaining/configuring/computing/decoding/encoding bit information of a sub-field (SIG, STF, LTF, Data) included in a PPDU; 2) an operation of determining/configuring/obtaining a time resource or frequency resource (e.g., a subcarrier resource) or the like used for the sub-field (SIG, STF, LTF, Data) included the PPDU; 3) an operation of determining/configuring/obtaining a specific sequence (e.g., a pilot sequence, an STF/LTF sequence, an extra sequence applied to SIG) or the like used for the sub-field (SIG, STF, LTF, Data) field included in the PPDU; 4) a power control operation and/or power saving operation applied for the STA; and 5) an operation related to determining/obtaining/configuring/decoding/encoding or the like of an ACK signal. In addition, in the following example, a variety of information used by various STAs for determining/obtaining/configuring/computing/decoding/decoding a TX/RX signal (e.g., information related to a field/subfield/control field/parameter/power or the like) may be stored in the memories  112  and  122  of  FIG.  1   . 
     The aforementioned device/STA of the sub-figure (a) of  FIG.  1    may be modified as shown in the sub-figure (b) of  FIG.  1   . Hereinafter, the STAs  110  and  120  of the present specification will be described based on the sub-figure (b) of  FIG.  1   . 
     For example, the transceivers  113  and  123  illustrated in the sub-figure (b) of  FIG.  1    may perform the same function as the aforementioned transceiver illustrated in the sub-figure (a) of  FIG.  1   . For example, processing chips  114  and  124  illustrated in the sub-figure (b) of  FIG.  1    may include the processors  111  and  121  and the memories  112  and  122 . The processors  111  and  121  and memories  112  and  122  illustrated in the sub-figure (b) of  FIG.  1    may perform the same function as the aforementioned processors  111  and  121  and memories  112  and  122  illustrated in the sub-figure (a) of  FIG.  1   . 
     A mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit, a user, a user STA, a network, a base station, a Node-B, an access point (AP), a repeater, a router, a relay, a receiving unit, a transmitting unit, a receiving STA, a transmitting STA, a receiving device, a transmitting device, a receiving apparatus, and/or a transmitting apparatus, which are described below, may imply the STAs  110  and  120  illustrated in the sub-figure (a)/(b) of  FIG.  1   , or may imply the processing chips  114  and  124  illustrated in the sub-figure (b) of  FIG.  1   . That is, a technical feature of the present specification may be performed in the STAs  110  and  120  illustrated in the sub-figure (a)/(b) of  FIG.  1   , or may be performed only in the processing chips  114  and  124  illustrated in the sub-figure (b) of  FIG.  1   . For example, a technical feature in which the transmitting STA transmits a control signal may be understood as a technical feature in which a control signal generated in the processors  111  and  121  illustrated in the sub-figure (a)/(b) of  FIG.  1    is transmitted through the transceivers  113  and  123  illustrated in the sub-figure (a)/(b) of  FIG.  1   . Alternatively, the technical feature in which the transmitting STA transmits the control signal may be understood as a technical feature in which the control signal to be transferred to the transceivers  113  and  123  is generated in the processing chips  114  and  124  illustrated in the sub-figure (b) of  FIG.  1   . 
     For example, a technical feature in which the receiving STA receives the control signal may be understood as a technical feature in which the control signal is received by means of the transceivers  113  and  123  illustrated in the sub-figure (a) of  FIG.  1   . Alternatively, the technical feature in which the receiving STA receives the control signal may be understood as the technical feature in which the control signal received in the transceivers  113  and  123  illustrated in the sub-figure (a) of  FIG.  1    is obtained by the processors  111  and  121  illustrated in the sub-figure (a) of  FIG.  1   . Alternatively, the technical feature in which the receiving STA receives the control signal may be understood as the technical feature in which the control signal received in the transceivers  113  and  123  illustrated in the sub-figure (b) of  FIG.  1    is obtained by the processing chips  114  and  124  illustrated in the sub-figure (b) of  FIG.  1   . 
     Referring to the sub-figure (b) of  FIG.  1   , software codes  115  and  125  may be included in the memories  112  and  122 . The software codes  115  and  126  may include instructions for controlling an operation of the processors  111  and  121 . The software codes  115  and  125  may be included as various programming languages. 
     The processors  111  and  121  or processing chips  114  and  124  of  FIG.  1    may include an application-specific integrated circuit (ASIC), other chipsets, a logic circuit and/or a data processing device. The processor may be an application processor (AP). For example, the processors  111  and  121  or processing chips  114  and  124  of  FIG.  1    may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), and a modulator and demodulator (modem). For example, the processors  111  and  121  or processing chips  114  and  124  of  FIG.  1    may be SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or processors enhanced from these processors. 
     In the present specification, an uplink may imply a link for communication from a non-AP STA to an SP STA, and an uplink PPDU/packet/signal or the like may be transmitted through the uplink. In addition, in the present specification, a downlink may imply a link for communication from the AP STA to the non-AP STA, and a downlink PPDU/packet/signal or the like may be transmitted through the downlink. 
       FIG.  2    is a conceptual view illustrating the structure of a wireless local area network (WLAN). 
     An upper part of  FIG.  2    illustrates the structure of an infrastructure basic service set (BSS) of institute of electrical and electronic engineers (IEEE) 802.11. 
     Referring the upper part of  FIG.  2   , the wireless LAN system may include one or more infrastructure BSSs  200  and  205  (hereinafter, referred to as BSS). The BSSs  200  and  205  as a set of an AP and a STA such as an access point (AP)  225  and a station (STA1)  200 - 1  which are successfully synchronized to communicate with each other are not concepts indicating a specific region. The BSS  205  may include one or more STAs  205 - 1  and  205 - 2  which may be joined to one AP  230 . 
     The BSS may include at least one STA, APs providing a distribution service, and a distribution system (DS)  210  connecting multiple APs. 
     The distribution system  210  may implement an extended service set (ESS)  240  extended by connecting the multiple BSSs  200  and  205 . The ESS  240  may be used as a term indicating one network configured by connecting one or more APs  225  or  230  through the distribution system  210 . The AP included in one ESS  240  may have the same service set identification (SSID). 
     A portal  220  may serve as a bridge which connects the wireless LAN network (IEEE 802.11) and another network (e.g., 802.X). 
     In the BSS illustrated in the upper part of  FIG.  2   , a network between the APs  225  and  230  and a network between the APs  225  and  230  and the STAs  200 - 1 ,  205 - 1 , and  205 - 2  may be implemented. However, the network is configured even between the STAs without the APs  225  and  230  to perform communication. A network in which the communication is performed by configuring the network even between the STAs without the APs  225  and  230  is defined as an Ad-Hoc network or an independent basic service set (IBSS). 
     A lower part of  FIG.  2    illustrates a conceptual view illustrating the IBSS. 
     Referring to the lower part of  FIG.  2   , the IBSS is a BSS that operates in an Ad-Hoc mode. Since the IBSS does not include the access point (AP), a centralized management entity that performs a management function at the center does not exist. That is, in the IBSS, STAs  250 - 1 ,  250 - 2 ,  250 - 3 ,  255 - 4 , and  255 - 5  are managed by a distributed manner. In the IBSS, all STAs  250 - 1 ,  250 - 2 ,  250 - 3 ,  255 - 4 , and  255 - 5  may be constituted by movable STAs and are not permitted to access the DS to constitute a self-contained network. 
       FIG.  3    illustrates a general link setup process. 
     In S 310 , a STA may perform a network discovery operation. The network discovery operation may include a scanning operation of the STA. That is, to access a network, the STA needs to discover a participating network. The STA needs to identify a compatible network before participating in a wireless network, and a process of identifying a network present in a particular area is referred to as scanning. Scanning methods include active scanning and passive scanning. 
       FIG.  3    illustrates a network discovery operation including an active scanning process. In active scanning, a STA performing scanning transmits a probe request frame and waits for a response to the probe request frame in order to identify which AP is present around while moving to channels. A responder transmits a probe response frame as a response to the probe request frame to the STA having transmitted the probe request frame. Here, the responder may be a STA that transmits the last beacon frame in a BSS of a channel being scanned. In the BSS, since an AP transmits a beacon frame, the AP is the responder. In an IBSS, since STAs in the IBSS transmit a beacon frame in turns, the responder is not fixed. For example, when the STA transmits a probe request frame via channel 1 and receives a probe response frame via channel 1, the STA may store BSS-related information included in the received probe response frame, may move to the next channel (e.g., channel 2), and may perform scanning (e.g., transmits a probe request and receives a probe response via channel 2) by the same method. 
     Although not shown in  FIG.  3   , scanning may be performed by a passive scanning method. In passive scanning, a STA performing scanning may wait for a beacon frame while moving to channels. A beacon frame is one of management frames in IEEE 802.11 and is periodically transmitted to indicate the presence of a wireless network and to enable the STA performing scanning to find the wireless network and to participate in the wireless network. In a BSS, an AP serves to periodically transmit a beacon frame. In an IBSS, STAs in the IBSS transmit a beacon frame in turns. Upon receiving the beacon frame, the STA performing scanning stores information related to a BSS included in the beacon frame and records beacon frame information in each channel while moving to another channel. The STA having received the beacon frame may store BSS-related information included in the received beacon frame, may move to the next channel, and may perform scanning in the next channel by the same method. 
     After discovering the network, the STA may perform an authentication process in S 320 . The authentication process may be referred to as a first authentication process to be clearly distinguished from the following security setup operation in S 340 . The authentication process in S 320  may include a process in which the STA transmits an authentication request frame to the AP and the AP transmits an authentication response frame to the STA in response. The authentication frames used for an authentication request/response are management frames. 
     The authentication frames may include information related to 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. 
     The STA may transmit the authentication request frame to the AP. The AP may determine whether to allow the authentication of the STA based on the information included in the received authentication request frame. The AP may provide the authentication processing result to the STA via the authentication response frame. 
     When the STA is successfully authenticated, the STA may perform an association process in S 330 . The association process includes a process in which the STA transmits an association request frame to the AP and the AP transmits an association response frame to the STA in response. The association request frame may include, for example, information related to various capabilities, a beacon listen interval, a service set identifier (SSID), a supported rate, a supported channel, RSN, a mobility domain, a supported operating class, a traffic indication map (TIM) broadcast request, and an interworking service capability. The association response frame may include, for example, information related to various capabilities, a status code, an association ID (AID), a supported rate, an enhanced distributed channel access (EDCA) parameter set, a received channel power indicator (RCPI), a received signal-to-noise indicator (RSNI), a mobility domain, a timeout interval (association comeback time), an overlapping BSS scanning parameter, a TIM broadcast response, and a QoS map. 
     In S 340 , the STA may perform a security setup process. The security setup process in S 340  may include a process of setting up a private key through four-way handshaking, for example, through an extensible authentication protocol over LAN (EAPOL) frame. 
       FIG.  4    illustrates an example of a PPDU used in an IEEE standard. 
     As illustrated, various types of PHY protocol data units (PPDUs) are used in IEEE a/g/n/ac standards. Specifically, an LTF and a STF include a training signal, a SIG-A and a SIG-B include control information for a receiving STA, and a data field includes user data corresponding to a PSDU (MAC PDU/aggregated MAC PDU). 
       FIG.  4    also includes an example of an HE PPDU according to IEEE 802.11ax. The HE PPDU according to  FIG.  4    is an illustrative PPDU for multiple users. An HE-SIG-B may be included only in a PPDU for multiple users, and an HE-SIG-B may be omitted in a PPDU for a single user. 
     As illustrated in  FIG.  4   , the HE-PPDU for multiple users (MUs) may include a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A (HE-SIG A), a high efficiency-signal-B (HE-SIG B), a high efficiency-short training field (HE-STF), a high efficiency-long training field (HE-LTF), a data field (alternatively, an MAC payload), and a packet extension (PE) field. The respective fields may be transmitted for illustrated time periods (i.e., 4 or 8 μs). 
     Hereinafter, a resource unit (RU) used for a PPDU is described. An RU may include a plurality of subcarriers (or tones). An RU may be used to transmit a signal to a plurality of STAs according to OFDMA. Further, an RU may also be defined to transmit a signal to one STA. An RU may be used for an STF, an LTF, a data field, or the like. 
       FIG.  5    illustrates a layout of resource units (RUs) used in a band of 20 MHz. 
     As illustrated in  FIG.  5   , resource units (RUs) corresponding to different numbers of tones (i.e., subcarriers) may be used to form some fields of an HE-PPDU. For example, resources may be allocated in illustrated RUs for an HE-STF, an HE-LTF, and a data field. 
     As illustrated in the uppermost part of  FIG.  5   , a 26-unit (i.e., a unit corresponding to 26 tones) may be disposed. Six tones may be used for a guard band in the leftmost band of the 20 MHz band, and five tones may be used for a guard band in the rightmost band of the 20 MHz band. Further, seven DC tones may be inserted in a center band, that is, a DC band, and a 26-unit corresponding to 13 tones on each of the left and right sides of the DC band may be disposed. A 26-unit, a 52-unit, and a 106-unit may be allocated to other bands. Each unit may be allocated for a receiving STA, that is, a user. 
     The layout of the RUs in  FIG.  5    may be used not only for a multiple users (MUs) but also for a single user (SU), in which case one 242-unit may be used and three DC tones may be inserted as illustrated in the lowermost part of  FIG.  5   . 
     Although  FIG.  5    proposes RUs having various sizes, that is, a 26-RU, a 52-RU, a 106-RU, and a 242-RU, specific sizes of RUs may be extended or increased. Therefore, the present embodiment is not limited to the specific size of each RU (i.e., the number of corresponding tones). 
       FIG.  6    illustrates a layout of RUs used in a band of 40 MHz. 
     Similarly to  FIG.  5    in which RUs having various sizes are used, a 26-RU, a 52-RU, a 106-RU, a 242-RU, a 484-RU, and the like may be used in an example of  FIG.  6   . Further, five DC tones may be inserted in a center frequency, 12 tones may be used for a guard band in the leftmost band of the 40 MHz band, and 11 tones may be used for a guard band in the rightmost band of the 40 MHz band. 
     As illustrated in  FIG.  6   , when the layout of the RUs is used for a single user, a 484-RU may be used. The specific number of RUs may be changed similarly to  FIG.  5   . 
       FIG.  7    illustrates a layout of RUs used in a band of 80 MHz. 
     Similarly to  FIG.  5    and  FIG.  6    in which RUs having various sizes are used, a 26-RU, a 52-RU, a 106-RU, a 242-RU, a 484-RU, a 996-RU, and the like may be used in an example of  FIG.  7   . Further, seven DC tones may be inserted in the center frequency, 12 tones may be used for a guard band in the leftmost band of the 80 MHz band, and 11 tones may be used for a guard band in the rightmost band of the 80 MHz band. In addition, a 26-RU corresponding to 13 tones on each of the left and right sides of the DC band may be used. 
     As illustrated in  FIG.  7   , when the layout of the RUs is used for a single user, a 996-RU may be used, in which case five DC tones may be inserted. 
     The RU described in the present specification may be used in uplink (UL) communication and downlink (DL) communication. For example, when UL-MU communication which is solicited by a trigger frame is performed, a transmitting STA (e.g., an AP) may allocate a first RU (e.g., 26/52/106/242-RU, etc.) to a first STA through the trigger frame, and may allocate a second RU (e.g., 26/52/106/242-RU, etc.) to a second STA. Thereafter, the first STA may transmit a first trigger-based PPDU based on the first RU, and the second STA may transmit a second trigger-based PPDU based on the second RU. The first/second trigger-based PPDU is transmitted to the AP at the same (or overlapped) time period. 
     For example, when a DL MU PPDU is configured, the transmitting STA (e.g., AP) may allocate the first RU (e.g., 26/52/106/242-RU. etc.) to the first STA, and may allocate the second RU (e.g., 26/52/106/242-RU, etc.) to the second STA. That is, the transmitting STA (e.g., AP) may transmit HE-STF, HE-LTF, and Data fields for the first STA through the first RU in one MU PPDU, and may transmit HE-STF, HE-LTF, and Data fields for the second STA through the second RU. 
     Information related to a layout of the RU may be signaled through HE-SIG-B. 
       FIG.  8    illustrates a structure of an HE-SIG-B field. 
     As illustrated, an HE-SIG-B field  810  includes a common field  820  and a user-specific field  830 . The common field  820  may include information commonly applied to all users (i.e., user STAs) which receive SIG-B. The user-specific field  830  may be called a user-specific control field. When the SIG-B is transferred to a plurality of users, the user-specific field  830  may be applied only any one of the plurality of users. 
     As illustrated in  FIG.  8   , the common field  820  and the user-specific field  830  may be separately encoded. 
     The common field  820  may include RU allocation information of N*8 bits. For example, the RU allocation information may include information related to a location of an RU. For example, when a 20 MHz channel is used as shown in  FIG.  5   , the RU allocation information may include information related to a specific frequency band to which a specific RU (26-RU/52-RU/106-RU) is arranged. 
     An example of a case in which the RU allocation information consists of 8 bits is as follows. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 8 bits indices 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Number 
               
               
                 (B7 B6 B5 B4 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 of  
               
               
                 B3 B2 B1 B0) 
                 #1 
                 #2 
                 #3 
                 #4 
                 #5 
                 #6 
                 #7 
                 #8 
                 #9 
                 entries 
               
               
                   
               
             
            
               
                 00000000 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 00000001 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 00000010 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 00000011 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 00000100 
                 26 
                 26 
                 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 00000101 
                 26 
                 26 
                 52 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 00000110 
                 26 
                 26 
                 52 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 00000111 
                 26 
                 26 
                 52 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 00001000 
                 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
               
                   
               
            
           
         
       
     
     As shown the example of  FIG.  5   , up to nine 26-RUs may be allocated to the 20 MHz channel. When the RU allocation information of the common field  820  is set to “00000000” as shown in Table 1, the nine 26-RUs may be allocated to a corresponding channel (i.e., 20 MHz). In addition, when the RU allocation information of the common field  820  is set to “00000001” as shown in Table 1, seven 26-RUs and one 52-RU are arranged in a corresponding channel. That is, in the example of  FIG.  5   , the 52-RU may be allocated to the rightmost side, and the seven 26-RUs may be allocated to the left thereof. 
     The example of Table 1 shows only some of RU locations capable of displaying the RU allocation information. 
     For example, the RU allocation information may include an example of Table 2 below. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 8 bits indices 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Number 
               
               
                 (B7 B6 B5 B4 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 of  
               
               
                 B3 B2 B1 B0) 
                 #1 
                 #2 
                 #3 
                 #4 
                 #5 
                 #6 
                 #7 
                 #8 
                 #9 
                 entries 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 01000y 2 y 1 y 0   
                 106 
                 26 
                 26 
                 26 
                 26 
                 26 
                 8 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 01001y 2 y 1 y 0   
                 106 
                 26 
                 26 
                 26 
                 52 
                 8 
               
               
                   
               
            
           
         
       
     
     “01000y2y1y0” relates to an example in which a 106-RU is allocated to the leftmost side of the 20 MHz channel, and five 26-RUs are allocated to the right side thereof. In this case, a plurality of STAs (e.g., user-STAs) may be allocated to the 106-RU, based on a MU-MIMO scheme. Specifically, up to 8 STAs (e.g., user-STAs) may be allocated to the 106-RU, and the number of STAs (e.g., user-STAs) allocated to the 106-RU is determined based on 3-bit information (y2y1y0). For example, when the 3-bit information (y2y1y0) is set to N, the number of STAs (e.g., user-STAs) allocated to the 106-RU based on the MU-MIMO scheme may be N+1. 
     In general, a plurality of STAs (e.g., user STAs) different from each other may be allocated to a plurality of RUs. However, the plurality of STAs (e.g., user STAs) may be allocated to one or more RUs having at least a specific size (e.g., 106 subcarriers), based on the MU-MIMO scheme. 
     As shown in  FIG.  8   , the user-specific field  830  may include a plurality of user fields. As described above, the number of STAs (e.g., user STAs) allocated to a specific channel may be determined based on the RU allocation information of the common field  820 . For example, when the RU allocation information of the common field  820  is “00000000”, one user STA may be allocated to each of nine 26-RUs (e.g., nine user STAs may be allocated). That is, up to 9 user STAs may be allocated to a specific channel through an OFDMA scheme. In other words, up to 9 user STAs may be allocated to a specific channel through a non-MU-MIMO scheme. 
     For example, when RU allocation is set to “01000y2y1y0”, a plurality of STAs may be allocated to the 106-RU arranged at the leftmost side through the MU-MIMO scheme, and five user STAs may be allocated to five 26-RUs arranged to the right side thereof through the non-MU MIMO scheme. This case is specified through an example of  FIG.  9   . 
       FIG.  9    illustrates an example in which a plurality of user STAs are allocated to the same RU through a MU-MIMO scheme. 
     For example, when RU allocation is set to “01000010” as shown in  FIG.  9   , a 106-RU may be allocated to the leftmost side of a specific channel, and five 26-RUs may be allocated to the right side thereof. In addition, three user STAs may be allocated to the 106-RU through the MU-MIMO scheme. As a result, since eight user STAs are allocated, the user-specific field  830  of HE-SIG-B may include eight user fields. 
     The eight user fields may be expressed in the order shown in  FIG.  9   . In addition, as shown in  FIG.  8   , two user fields may be implemented with one user block field. 
     The user fields shown in  FIG.  8    and  FIG.  9    may be configured based on two formats. That is, a user field related to a MU-MIMO scheme may be configured in a first format, and a user field related to a non-MIMO scheme may be configured in a second format. Referring to the example of  FIG.  9   , a user field  1  to a user field  3  may be based on the first format, and a user field  4  to a user field  8  may be based on the second format. The first format or the second format may include bit information of the same length (e.g., 21 bits). 
     Each user field may have the same size (e.g., 21 bits). For example, the user field of the first format (the first of the MU-MIMO scheme) may be configured as follows. 
     For example, a first bit (i.e., B0-B10) in the user field (i.e., 21 bits) may include identification information (e.g., STA-ID, partial AID, etc.) of a user STA to which a corresponding user field is allocated. In addition, a second bit (i.e., B11-B14) in the user field (i.e., 21 bits) may include information related to a spatial configuration. Specifically, an example of the second bit (i.e., B11-B14) may be as shown in Table 3 and Table 4 below. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 Total 
                 Number 
               
               
                 N user   
                 B3 . . . B0 
                 [1] 
                 [2] 
                 [3] 
                 [4] 
                 [5] 
                 [6] 
                 [7] 
                 [8] 
                 N STS   
                 of entries 
               
               
                   
               
             
            
               
                 2 
                 0000-0011 
                 1-4 
                 1 
                   
                   
                   
                   
                   
                   
                 2-5 
                 10 
               
               
                   
                 9100-0110 
                 2-4 
                 2 
                   
                   
                   
                   
                   
                   
                 4-6 
                   
               
               
                   
                 0111-1000 
                 3-4 
                 3 
                   
                   
                   
                   
                   
                   
                 6-7 
                   
               
               
                   
                 1001 
                 4 
                 4 
                   
                   
                   
                   
                   
                   
                 8 
                   
               
               
                 3 
                 0000-0011 
                 1-4 
                 1 
                 1 
                   
                   
                   
                   
                   
                 3-6 
                 13 
               
               
                   
                 0100-0110 
                 2-4 
                 2 
                 1 
                   
                   
                   
                   
                   
                 5-7 
                   
               
               
                   
                 0111-1000 
                 3-4 
                 3 
                 1 
                   
                   
                   
                   
                   
                 7-9 
                   
               
               
                   
                 1001-1011 
                 2-4 
                 2 
                 2 
                   
                   
                   
                   
                   
                 6-8 
                   
               
               
                   
                 1100 
                 3 
                 3 
                 2 
                   
                   
                   
                   
                   
                 8 
                   
               
               
                 4 
                 0000-0011 
                 1-4 
                 1 
                 1 
                 1 
                   
                   
                   
                   
                 4-7 
                 11 
               
               
                   
                 0100-0110 
                 2-4 
                 2 
                 1 
                 1 
                   
                   
                   
                   
                 6-8 
                   
               
               
                   
                 0111 
                 3 
                 3 
                 1 
                 1 
                   
                   
                   
                   
                 8 
                   
               
               
                   
                 1000-1001 
                 2-3 
                 2 
                 2 
                 1 
                   
                   
                   
                   
                 7-8 
                   
               
               
                   
                 1010 
                 2 
                 2 
                 2 
                 2 
                   
                   
                   
                   
                 8 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 N STS   
                 Total 
                 Number 
               
               
                 N user   
                 B3 . . . B0 
                 [1] 
                 [2] 
                 [3] 
                 [4] 
                 [5] 
                 [6] 
                 [7] 
                 [8] 
                 N STS   
                 of entries 
               
               
                   
               
             
            
               
                 5 
                 0000-0011 
                 1-4 
                 1 
                 1 
                 1 
                   
                   
                   
                   
                 5-8 
                 7 
               
               
                   
                 0100-0101 
                 2-3 
                 2 
                 1 
                 1 
                 1 
                   
                   
                   
                 7-8 
                   
               
               
                   
                 0110 
                 2 
                 2 
                 2 
                 1 
                 1 
                   
                   
                   
                 8 
                   
               
               
                 6 
                 0000-0010 
                 1-3 
                 1 
                 1 
                 1 
                 1 
                 1 
                   
                   
                 6-8 
                 4 
               
               
                   
                 0011 
                 2 
                 2 
                 1 
                 1 
                 1 
                 1 
                   
                   
                 8 
                   
               
               
                 7 
                 0000-0001 
                 1-2 
                 1 
                 1 
                 1 
                 1 
                 1 
                 1 
                   
                 7-8 
                 2 
               
               
                 8 
                 0000 
                 1 
                 1 
                 1 
                 1 
                 1 
                 1 
                 1 
                 1 
                 8 
                 1 
               
               
                   
               
            
           
         
       
     
     As shown in Table 3 and/or Table 4, the second bit (e.g., B11-B14) may include information related to the number of spatial streams allocated to the plurality of user STAs which are allocated based on the MU-MIMO scheme. For example, when three user STAs are allocated to the 106-RU based on the MU-MIMO scheme as shown in  FIG.  9   , N_user is set to “3”. Therefore, values of N_STS[1], N_STS[2], and N_STS[3] may be determined as shown in Table 3. For example, when a value of the second bit (B11-B14) is “0011”, it may be set to N_STS[1]=4, N_STS[2]=1, N_STS[3]=1. That is, in the example of  FIG.  9   , four spatial streams may be allocated to the user field  1 , one spatial stream may be allocated to the user field  1 , and one spatial stream may be allocated to the user field  3 . 
     As shown in the example of Table 3 and/or Table 4, information (i.e., the second bit, B11-B14) related to the number of spatial streams for the user STA may consist of 4 bits. In addition, the information (i.e., the second bit, B11-B14) on the number of spatial streams for the user STA may support up to eight spatial streams. In addition, the information (i.e., the second bit, B11-B14) on the number of spatial streams for the user STA may support up to four spatial streams for one user STA. 
     In addition, a third bit (i.e., B15-18) in the user field (i.e., 21 bits) may include modulation and coding scheme (MCS) information. The MCS information may be applied to a data field in a PPDU including corresponding SIG-B. 
     An MCS, MCS information, an MCS index, an MCS field, or the like used in the present specification may be indicated by an index value. For example, the MCS information may be indicated by an index 0 to an index 11. The MCS information may include information related to a constellation modulation type (e.g., BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, etc.) and information related to a coding rate (e.g., 1/2, 2/3, 3/4, 5/6e, etc.). Information related to a channel coding type (e.g., LCC or LDPC) may be excluded in the MCS information. 
     In addition, a fourth bit (i.e., B19) in the user field (i.e., 21 bits) may be a reserved field. 
     In addition, a fifth bit (i.e., B20) in the user field (i.e., 21 bits) may include information related to a coding type (e.g., BCC or LDPC). That is, the fifth bit (i.e., B20) may include information related to a type (e.g., BCC or LDPC) of channel coding applied to the data field in the PPDU including the corresponding SIG-B. 
     The aforementioned example relates to the user field of the first format (the format of the MU-MIMO scheme). An example of the user field of the second format (the format of the non-MU-MIMO scheme) is as follows. 
     A first bit (e.g., B0-B10) in the user field of the second format may include identification information of a user STA. In addition, a second bit (e.g., B11-B13) in the user field of the second format may include information related to the number of spatial streams applied to a corresponding RU. In addition, a third bit (e.g., B14) in the user field of the second format may include information related to whether a beamforming steering matrix is applied. A fourth bit (e.g., B15-B18) in the user field of the second format may include modulation and coding scheme (MCS) information. In addition, a fifth bit (e.g., B19) in the user field of the second format may include information related to whether dual carrier modulation (DCM) is applied. In addition, a sixth bit (i.e., B20) in the user field of the second format may include information related to a coding type (e.g., BCC or LDPC). 
       FIG.  10    illustrates an operation based on UL-MU. As illustrated, a transmitting STA (e.g., an AP) may perform channel access through contending (e.g., a backoff operation), and may transmit a trigger frame  1030 . That is, the transmitting STA may transmit a PPDU including the trigger frame  1030 . Upon receiving the PPDU including the trigger frame, a trigger-based (TB) PPDU is transmitted after a delay corresponding to SIFS. 
     TB PPDUs  1041  and  1042  may be transmitted at the same time period, and may be transmitted from a plurality of STAs (e.g., user STAs) having AIDs indicated in the trigger frame  1030 . An ACK frame  1050  for the TB PPDU may be implemented in various forms. 
     A specific feature of the trigger frame is described with reference to  FIG.  11    to  FIG.  13   . Even if UL-MU communication is used, an orthogonal frequency division multiple access (OFDMA) scheme or a MU MIMO scheme may be used, and the OFDMA and MU-MIMO schemes may be simultaneously used. 
       FIG.  11    illustrates an example of a trigger frame. The trigger frame of  FIG.  11    allocates a resource for uplink multiple-user (MU) transmission, and may be transmitted, for example, from an AP. The trigger frame may be configured of a MAC frame, and may be included in a PPDU. 
     Each field shown in  FIG.  11    may be partially omitted, and another field may be added. In addition, a length of each field may be changed to be different from that shown in the figure. 
     A frame control field  1110  of  FIG.  11    may include information related to a MAC protocol version and extra additional control information. A duration field  1120  may include time information for NAV configuration or information related to an identifier (e.g., AID) of a STA. 
     In addition, an RA field  1130  may include address information of a receiving STA of a corresponding trigger frame, and may be optionally omitted. A TA field  1140  may include address information of a STA (e.g., an AP) which transmits the corresponding trigger frame. A common information field  1150  includes common control information applied to the receiving STA which receives the corresponding trigger frame. For example, a field indicating a length of an L-SIG field of an uplink PPDU transmitted in response to the corresponding trigger frame or information for controlling content of a SIG-A field (i.e., HE-SIG-A field) of the uplink PPDU transmitted in response to the corresponding trigger frame may be included. In addition, as common control information, information related to a length of a CP of the uplink PPDU transmitted in response to the corresponding trigger frame or information related to a length of an LTF field may be included. 
     In addition, per user information fields  1160  # 1  to  1160  #N corresponding to the number of receiving STAs which receive the trigger frame of  FIG.  11    are preferably included. The per user information field may also be called an “allocation field”. 
     In addition, the trigger frame of  FIG.  11    may include a padding field  1170  and a frame check sequence field  1180 . 
     Each of the per user information fields  1160  # 1  to  1160  #N shown in  FIG.  11    may include a plurality of subfields. 
       FIG.  12    illustrates an example of a common information field of a trigger frame. A subfield of  FIG.  12    may be partially omitted, and an extra subfield may be added. In addition, a length of each subfield illustrated may be changed. 
     A length field  1210  illustrated has the same value as a length field of an L-SIG field of an uplink PPDU transmitted in response to a corresponding trigger frame, and a length field of the L-SIG field of the uplink PPDU indicates a length of the uplink PPDU. As a result, the length field  1210  of the trigger frame may be used to indicate the length of the corresponding uplink PPDU. 
     In addition, a cascade identifier field  1220  indicates whether a cascade operation is performed. The cascade operation implies that downlink MU transmission and uplink MU transmission are performed together in the same TXOP. That is, it implies that downlink MU transmission is performed and thereafter uplink MU transmission is performed after a pre-set time (e.g., SIFS). During the cascade operation, only one transmitting device (e.g., AP) may perform downlink communication, and a plurality of transmitting devices (e.g., non-APs) may perform uplink communication. 
     A CS request field  1230  indicates whether a wireless medium state or a NAV or the like is necessarily considered in a situation where a receiving device which has received a corresponding trigger frame transmits a corresponding uplink PPDU. 
     An HE-SIG-A information field  1240  may include information for controlling content of a SIG-A field (i.e., HE-SIG-A field) of the uplink PPDU in response to the corresponding trigger frame. 
     A CP and LTF type field  1250  may include information related to a CP length and LTF length of the uplink PPDU transmitted in response to the corresponding trigger frame. A trigger type field  1260  may indicate a purpose of using the corresponding trigger frame, for example, typical triggering, triggering for beamforming, a request for block ACK/NACK, or the like. 
     It may be assumed that the trigger type field  1260  of the trigger frame in the present specification indicates a trigger frame of a basic type for typical triggering. For example, the trigger frame of the basic type may be referred to as a basic trigger frame. 
       FIG.  13    illustrates an example of a subfield included in a per user information field. A user information field  1300  of  FIG.  13    may be understood as any one of the per user information fields  1160  # 1  to  1160  #N mentioned above with reference to  FIG.  11   . A subfield included in the user information field  1300  of  FIG.  13    may be partially omitted, and an extra subfield may be added. In addition, a length of each subfield illustrated may be changed. 
     A user identifier field  1310  of  FIG.  13    indicates an identifier of a STA (i.e., receiving STA) corresponding to per user information. An example of the identifier may be the entirety or part of an association identifier (AID) value of the receiving STA. 
     In addition, an RU allocation field  1320  may be included. That is, when the receiving STA identified through the user identifier field  1310  transmits a TB PPDU in response to the trigger frame, the TB PPDU is transmitted through an RU indicated by the RU allocation field  1320 . In this case, the RU indicated by the RU allocation field  1320  may be an RU shown in  FIG.  5   ,  FIG.  6   , and  FIG.  7   . 
     The subfield of  FIG.  13    may include a coding type field  1330 . The coding type field  1330  may indicate a coding type of the TB PPDU. For example, when BCC coding is applied to the TB PPDU, the coding type field  1330  may be set to ‘1’, and when LDPC coding is applied, the coding type field  1330  may be set to ‘0’. 
     In addition, the subfield of  FIG.  13    may include an MCS field  1340 . The MCS field  1340  may indicate an MCS scheme applied to the TB PPDU. For example, when BCC coding is applied to the TB PPDU, the coding type field  1330  may be set to ‘1’, and when LDPC coding is applied, the coding type field  1330  may be set to ‘0’. 
     Hereinafter, a UL OFDMA-based random access (UORA) scheme will be described. 
       FIG.  14    describes a technical feature of the UORA scheme. 
     A transmitting STA (e.g., an AP) may allocate six RU resources through a trigger frame as shown in  FIG.  14   . Specifically, the AP may allocate a 1st RU resource (AID 0, RU 1), a 2nd RU resource (AID 0, RU 2), a 3rd RU resource (AID 0, RU 3), a 4th RU resource (AID 2045, RU 4), a 5th RU resource (AID 2045, RU 5), and a 6th RU resource (AID 3, RU 6). Information related to the AID 0, AID 3, or AID 2045 may be included, for example, in the user identifier field  1310  of  FIG.  13   . Information related to the RU 1 to RU 6 may be included, for example, in the RU allocation field  1320  of  FIG.  13   . AID=0 may imply a UORA resource for an associated STA, and AID=2045 may imply a UORA resource for an un-associated STA. Accordingly, the 1st to 3rd RU resources of  FIG.  14    may be used as a UORA resource for the associated STA, the 4th and 5th RU resources of  FIG.  14    may be used as a UORA resource for the un-associated STA, and the 6th RU resource of  FIG.  14    may be used as a typical resource for UL MU. 
     In the example of  FIG.  14   , an OFDMA random access backoff (OBO) of a STA 1  is decreased to 0, and the STA 1  randomly selects the 2nd RU resource (AID 0, RU 2). In addition, since an OBO counter of a STA 2 / 3  is greater than 0, an uplink resource is not allocated to the STA 2 / 3 . In addition, regarding a STA 4  in  FIG.  14   , since an AID (e.g., AID=3) of the STA 4  is included in a trigger frame, a resource of the RU 6 is allocated without backoff. 
     Specifically, since the STA 1  of  FIG.  14    is an associated STA, the total number of eligible RA RUs for the STA 1  is 3 (RU 1, RU 2, and RU 3), and thus the STA 1  decreases an OBO counter by 3 so that the OBO counter becomes 0. In addition, since the STA 2  of  FIG.  14    is an associated STA, the total number of eligible RA RUs for the STA 2  is 3 (RU 1, RU 2, and RU 3), and thus the STA 2  decreases the OBO counter by 3 but the OBO counter is greater than 0. In addition, since the STA 3  of  FIG.  14    is an un-associated STA, the total number of eligible RA RUs for the STA 3  is 2 (RU 4, RU 5), and thus the STA 3  decreases the OBO counter by 2 but the OBO counter is greater than 0. 
       FIG.  15    illustrates an example of a channel used/supported/defined within a 2.4 GHz band. 
     The 2.4 GHz band may be called in other terms such as a first band. In addition, the 2.4 GHz band may imply a frequency domain in which channels of which a center frequency is close to 2.4 GHz (e.g., channels of which a center frequency is located within 2.4 to 2.5 GHz) are used/supported/defined. 
     A plurality of 20 MHz channels may be included in the 2.4 GHz band. 20 MHz within the 2.4 GHz may have a plurality of channel indices (e.g., an index 1 to an index 14). For example, a center frequency of a 20 MHz channel to which a channel index 1 is allocated may be 2.412 GHz, a center frequency of a 20 MHz channel to which a channel index 2 is allocated may be 2.417 GHz, and a center frequency of a 20 MHz channel to which a channel index N is allocated may be (2.407+0.005*N) GHz. The channel index may be called in various terms such as a channel number or the like. Specific numerical values of the channel index and center frequency may be changed. 
       FIG.  15    exemplifies  4  channels within a 2.4 GHz band. Each of 1st to 4th frequency domains  1510  to  1540  shown herein may include one channel. For example, the 1st frequency domain  1510  may include a channel 1 (a 20 MHz channel having an index 1). In this case, a center frequency of the channel 1 may be set to 2412 MHz. The 2nd frequency domain  1520  may include a channel 6. In this case, a center frequency of the channel 6 may be set to 2437 MHz. The 3rd frequency domain  1530  may include a channel 11. In this case, a center frequency of the channel 11 may be set to 2462 MHz. The 4th frequency domain  1540  may include a channel 14. In this case, a center frequency of the channel 14 may be set to 2484 MHz. 
       FIG.  16    illustrates an example of a channel used/supported/defined within a 5 GHz band. 
     The 5 GHz band may be called in other terms such as a second band or the like. The 5 GHz band may imply a frequency domain in which channels of which a center frequency is greater than or equal to 5 GHz and less than 6 GHz (or less than 5.9 GHz) are used/supported/defined. Alternatively, the 5 GHz band may include a plurality of channels between 4.5 GHz and 5.5 GHz. A specific numerical value shown in  FIG.  16    may be changed. 
     A plurality of channels within the 5 GHz band include an unlicensed national information infrastructure (UNII)-1, a UNII-2, a UNII-3, and an ISM. The INII-1 may be called UNIT Low. The UNII-2 may include a frequency domain called UNIT Mid and UNII-2Extended. The UNII-3 may be called UNII-Upper. 
     A plurality of channels may be configured within the 5 GHz band, and a bandwidth of each channel may be variously set to, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, or the like. For example, 5170 MHz to 5330 MHz frequency domains/ranges within the UNII-1 and UNII-2 may be divided into eight 20 MHz channels. The 5170 MHz to 5330 MHz frequency domains/ranges may be divided into four channels through a 40 MHz frequency domain. The 5170 MHz to 5330 MHz frequency domains/ranges may be divided into two channels through an 80 MHz frequency domain. Alternatively, the 5170 MHz to 5330 MHz frequency domains/ranges may be divided into one channel through a 160 MHz frequency domain. 
       FIG.  17    illustrates an example of a channel used/supported/defined within a 6 GHz band. 
     The 6 GHz band may be called in other terms such as a third band or the like. The 6 GHz band may imply a frequency domain in which channels of which a center frequency is greater than or equal to 5.9 GHz are used/supported/defined. A specific numerical value shown in  FIG.  17    may be changed. 
     For example, the 20 MHz channel of  FIG.  17    may be defined starting from 5.940 GHz. Specifically, among 20 MHz channels of  FIG.  17   , the leftmost channel may have an index 1 (or a channel index, a channel number, etc.), and 5.945 GHz may be assigned as a center frequency. That is, a center frequency of a channel of an index N may be determined as (5.940+0.005*N) GHz. 
     Accordingly, an index (or channel number) of the 2 MHz channel of  FIG.  17    may be 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61, 65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125, 129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 169, 173, 177, 181, 185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 233. In addition, according to the aforementioned (5.940+0.005*N)GHz rule, an index of the 40 MHz channel of  FIG.  17    may be 3, 11, 19, 27, 35, 43, 51, 59, 67, 75, 83, 91, 99, 107, 115, 123, 131, 139, 147, 155, 163, 171, 179, 187, 195, 203, 211, 219, 227. 
     Although 20, 40, 80, and 160 MHz channels are illustrated in the example of  FIG.  17   , a 240 MHz channel or a 320 MHz channel may be additionally added. 
     Hereinafter, a PPDU transmitted/received in a STA of the present specification will be described. 
       FIG.  18    illustrates an example of a PPDU used in the present specification. 
     The PPDU of  FIG.  18    may be called in various terms such as an EHT PPDU, a TX PPDU, an RX PPDU, a first type or N-th type PPDU, or the like. For example, in the present specification, the PPDU or the EHT PPDU may be called in various terms such as a TX PPDU, a RX PPDU, a first type or N-th type PPDU, or the like. In addition, the EHT PPDU may be used in an EHT system and/or a new WLAN system enhanced from the EHT system. 
     The PPDU of  FIG.  18    may indicate the entirety or part of a PPDU type used in the EHT system. For example, the example of  FIG.  18    may be used for both of a single-user (SU) mode and a multi-user (MU) mode. In other words, the PPDU of  FIG.  18    may be a PPDU for one receiving STA or a plurality of receiving STAs. When the PPDU of  FIG.  18    is used for a trigger-based (TB) mode, the EHT-SIG of  FIG.  18    may be omitted. In other words, a STA which has received a trigger frame for uplink-MU (UL-MU) may transmit the PPDU in which the EHT-SIG is omitted in the example of  FIG.  18   . 
     In  FIG.  18   , an L-STF to an EHT-LTF may be called a preamble or a physical preamble, and may be generated/transmitted/received/obtained/decoded in a physical layer. 
     A subcarrier spacing of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields of  FIG.  18    may be determined as 312.5 kHz, and a subcarrier spacing of the EHT-STF, EHT-LTF, and Data fields may be determined as 78.125 kHz. That is, a tone index (or subcarrier index) of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may be expressed in unit of 312.5 kHz, and a tone index (or subcarrier index) of the EHT-STF, EHT-LTF, and Data fields may be expressed in unit of 78.125 kHz. 
     In the PPDU of  FIG.  18   , the L-LTE and the L-STF may be the same as those in the conventional fields. 
     The L-SIG field of  FIG.  18    may include, for example, bit information of 24 bits. For example, the 24-bit information may include a rate field of 4 bits, a reserved bit of 1 bit, a length field of 12 bits, a parity bit of 1 bit, and a tail bit of 6 bits. For example, the length field of 12 bits may include information related to a length or time duration of a PPDU. For example, the length field of 12 bits may be determined based on a type of the PPDU. For example, when the PPDU is a non-HT, HT, VHT PPDU or an EHT PPDU, a value of the length field may be determined as a multiple of 3. For example, when the PPDU is an HE PPDU, the value of the length field may be determined as “a multiple of 3”+1 or “a multiple of 3”+2. In other words, for the non-HT, HT, VHT PPDI or the EHT PPDU, the value of the length field may be determined as a multiple of 3, and for the HE PPDU, the value of the length field may be determined as “a multiple of 3”+1 or “a multiple of 3”+2. 
     For example, the transmitting STA may apply BCC encoding based on a 1/2 coding rate to the 24-bit information of the L-SIG field. Thereafter, the transmitting STA may obtain a BCC coding bit of 48 bits. BPSK modulation may be applied to the 48-bit coding bit, thereby generating 48 BPSK symbols. The transmitting STA may map the 48 BPSK symbols to positions except for a pilot subcarrier{subcarrier index −21, −7, +7, +21} and a DC subcarrier{subcarrier index 0}. As a result, the 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 a signal of {−1, −1, −1, 1} to a subcarrier index{−28, −27, +27, +28}. The aforementioned signal may be used for channel estimation on a frequency domain corresponding to {−28, −27, +27, +28}. 
     The transmitting STA may generate an RL-SIG generated in the same manner as the L-SIG. BPSK modulation may be applied to the RL-SIG. The receiving STA may know that the RX PPDU is the HE PPDU or the EHT PPDU, based on the presence of the RL-SIG. 
     A universal SIG (U-SIG) may be inserted after the RL-SIG of  FIG.  18   . The U-SIB may be called in various terms such as a first SIG field, a first SIG, a first type SIG, a control signal, a control signal field, a first (type) control signal, or the like. 
     The U-SIG may include information of N bits, and may include information for identifying a type of the EHT PPDU. For example, the U-SIG may be configured based on two symbols (e.g., two contiguous OFDM symbols). Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of 4 us. Each symbol of the U-SIG may be used to transmit the 26-bit information. For example, each symbol of the U-SIG may be transmitted/received based on 52 data tomes 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. A first symbol of the U-SIG may transmit first X-bit information (e.g., 26 un-coded bits) of the A-bit information, and a second symbol of the U-SIB may transmit the remaining Y-bit information (e.g., 26 un-coded bits) of the A-bit information. For example, the transmitting STA may obtain 26 un-coded bits included in each U-SIG symbol. The transmitting STA may perform convolutional encoding (i.e., BCC encoding) based on a rate of R=1/2 to generate 52-coded bits, and may perform interleaving on the 52-coded bits. The transmitting STA may perform BPSK modulation on the interleaved 52-coded bits to generate 52 BPSK symbols to be allocated to each U-SIG symbol. One U-SIG symbol may be transmitted based on 65 tones (subcarriers) from a subcarrier index −28 to a subcarrier index +28, except for a DC index 0. The 52 BPSK symbols generated by the transmitting STA may be transmitted based on the remaining tones (subcarriers) except for pilot tones, i.e., tones −21, −7, +7, +21. 
     For example, the A-bit information (e.g., 52 un-coded bits) generated by the U-SIG may include a CRC field (e.g., a field having a length of 4 bits) and a tail field (e.g., a field having a length of 6 bits). The CRC field and the tail field may be transmitted through the second symbol of the U-SIG. The CRC field may be generated based on 26 bits allocated to the first symbol of the U-SIG and the remaining 16 bits except for the CRC/tail fields in the second symbol, and may be generated based on the conventional CRC calculation algorithm. In addition, the tail field may be used to terminate trellis of a convolutional decoder, and may be set to, for example, “000000”. 
     The A-bit information (e.g., 52 un-coded bits) transmitted by the U-SIG (or U-SIG field) may be divided into version-independent bits and version-dependent bits. For example, the version-independent bits may have a fixed or variable size. For example, the version-independent bits may be allocated only to the first symbol of the U-SIG, or the version-independent bits may be allocated to both of the first and second symbols of the U-SIG. For example, the version-independent bits and the version-dependent bits may be called in various terms such as a first control bit, a second control bit, or the like. 
     For example, the version-independent bits of the U-SIG may include a PHY version identifier of 3 bits. For example, the PHY version identifier of 3 bits may include information related to a PHY version of a TX/RX PPDU. For example, a first value of the PHY version identifier of 3 bits may indicate that the TX/RX PPDU is an EHT PPDU. In other words, when the transmitting STA transmits the EHT PPDU, the PHY version identifier of 3 bits may be set to a first value. In other words, the receiving STA may determine that the RX PPDU is the EHT PPDU, based on the PHY version identifier having the first value. 
     For example, the version-independent bits of the U-SIG may include a UL/DL flag field of 1 bit. A first value of the UL/DL flag field of 1 bit relates to UL communication, and a second value of the UL/DL flag field relates to DL communication. 
     For example, the version-independent bits of the U-SIG may include information related to a TXOP length and information related to a BSS color ID. 
     For example, when the EHT PPDU is divided into various types (e.g., various types such as an EHT PPDU related to an SU mode, an EHT PPDU related to a MU mode, an EHT PPDU related to a TB mode, an EHT PPDU related to extended range transmission, or the like), information related to the type of the EHT PPDU may be included in the version-dependent bits of the U-SIG. 
     For example, the U-SIG may include: 1) a bandwidth field including information related to a bandwidth; 2) a field including information related to an MCS scheme applied to EHT-SIG; 3) an indication field including information regarding whether a dual subcarrier modulation (DCM) scheme is applied to EHT-SIG; 4) a field including information related to the number of symbol used for EHT-SIG; 5) a field including information regarding whether the EHT-SIG is generated across a full band; 6) a field including information related to a type of EHT-LTF/STF; and 7) information related to a field indicating an EHT-LTF length and a CP length. 
     Preamble puncturing may be applied to the PPDU of  FIG.  18   . The preamble puncturing implies that puncturing is applied to part (e.g., a secondary 20 MHz band) of the full band. For example, when an 80 MHz PPDU is transmitted, a STA may apply puncturing to the secondary 20 MHz band out of the 80 MHz band, and may transmit a PPDU only through a primary 20 MHz band and a secondary 40 MHz band. 
     For example, a pattern of the preamble puncturing may be configured in advance. For example, when a first puncturing pattern is applied, puncturing may be applied only to the secondary 20 MHz band within the 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 the secondary 40 MHz band within the 80 MHz band. For example, when a third puncturing pattern is applied, puncturing may be applied to only the secondary 20 MHz band included in the primary 80 MHz band within the 160 MHz band (or 80+80 MHz band). For example, when a fourth puncturing is applied, puncturing may be applied to at least one 20 MHz channel not belonging to a primary 40 MHz band in the presence of the primary 40 MHz band included in the 80 MHaz band within the 160 MHz band (or 80+80 MHz band). 
     Information related to the preamble puncturing applied to the PPDU may be included in U-SIG and/or EHT-SIG. For example, a first field of the U-SIG may include information related to a contiguous bandwidth, and second field of the U-SIG may include information related to the preamble puncturing applied to the PPDU. 
     For example, the U-SIG and the EHT-SIG may include the information related to the preamble puncturing, based on the following method. When a bandwidth of the PPDU exceeds 80 MHz, the U-SIG may be configured individually in unit of 80 MHz. For example, when 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, a first field of the first U-SIG may include information related to a 160 MHz bandwidth, and a second field of the first U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) applied to the first 80 MHz band. In addition, a first field of the second U-SIG may include information related to a 160 MHz bandwidth, and a second field of the second U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) applied to the second 80 MHz band. Meanwhile, an EHT-SIG contiguous to the first U-SIG may include information related to a preamble puncturing applied to the second 80 MHz band (i.e., information related to a preamble puncturing pattern), and an EHT-SIG contiguous to the second U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) applied to the first 80 MHz band. 
     Additionally or alternatively, the U-SIG and the EHT-SIG may include the information related to the preamble puncturing, based on the following method. The U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) for all bands. That is, the EHT-SIG may not include the information related to the preamble puncturing, and only the U-SIG may include the information related to the preamble puncturing (i.e., the information related to the preamble puncturing pattern). 
     The U-SIG may be configured in unit of 20 MHz. For example, when an 80 MHz PPDU is configured, the U-SIG may be duplicated. That is, four identical U-SIGs may be included in the 80 MHz PPDU. PPDUs exceeding an 80 MHz bandwidth may include different U-SIGs. 
     The EHT-SIG of  FIG.  18    may include control information for the receiving STA. The EHT-SIG may be transmitted through at least one symbol, and one symbol may have a length of 4 us. Information related to the number of symbols used for the EHT-SIG may be included in the U-SIG. 
     The EHT-SIG may include a technical feature of the HE-SIG-B described with reference to  FIG.  8    and  FIG.  9   . For example, the EHT-SIG may include a common field and a user-specific field as in the example of  FIG.  8   . The common field of the EHT-SIG may be omitted, and the number of user-specific fields may be determined based on the number of users. 
     As in the example of  FIG.  8   , the common field of the EHT-SIG and the user-specific field of the EHT-SIG may be individually coded. One user block field included in the user-specific field may include information for two users, but a last user block field included in the user-specific field may include information for one user. That is, one user block field of the EHT-SIG may include up to two user fields. As in the example of  FIG.  9   , each user field may be related to MU-MIMO allocation, or may be related to non-MU-MIMO allocation. 
     As in the example of  FIG.  8   , the common field of the EHT-SIG may include a CRC bit and a tail bit. A length of the CRC bit may be determined as 4 bits. A length of the tail bit may be determined as 6 bits, and may be set to ‘000000’. 
     As in the example of  FIG.  8   , the common field of the EHT-SIG may include RU allocation information. The RU allocation information may imply information related to a location of an RU to which a plurality of users (i.e., a plurality of receiving STAs) are allocated. The RU allocation information may be configured in unit of 8 bits (or N bits), as in Table 1. 
     The example of Table 5 to Table 7 is an example of 8-bit (or N-bit) information for various RU allocations. An index shown in each table may be modified, and some entries in Table 5 to Table 7 may be omitted, and entries (not shown) may be added. 
     The example of Table 5 to Table 7 relates to information related to a location of an RU allocated to a 20 MHz band. For example, ‘an index 0’ of Table 5 may be used in a situation where nine 26-RUs are individually allocated (e.g., in a situation where nine 26-RUs shown in  FIG.  5    are individually allocated). 
     Meanwhile, a plurality or RUs may be allocated to one STA in the EHT system. For example, regarding ‘an index 60’ of Table 6, one 26-RU may be allocated for one user (i.e., receiving STA) to the leftmost side of the 20 MHz band, one 26-RU and one 52-RU may be allocated to the right side thereof, and five 26-RUs may be individually allocated to the right side thereof. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Number 
               
               
                 Indices 
                 #1 
                 #2 
                 #3 
                 #4 
                 #5 
                 #6 
                 #7 
                 #8 
                 #9 
                 of entries 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 0 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 2 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 3 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 4 
                 26 
                 26 
                 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 5 
                 26 
                 26 
                 52 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 6 
                 26 
                 26 
                 52 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 7 
                 26 
                 26 
                 52 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 8 
                 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 9 
                 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 10 
                 52 
                 26 
                 26 
                 26 
                 52 
                 26 
                 26 
                 I 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 11 
                 52 
                 26 
                 26 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 12 
                 52 
                 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 13 
                 52 
                 52 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 14 
                 52 
                 52 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 15 
                 52 
                 53 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 16 
                 26 
                 26 
                 26 
                 26 
                 26 
                 106 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 17 
                 26 
                 26 
                 52 
                 26 
                 106 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 18 
                 52 
                 26 
                 26 
                 26 
                 106 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 19 
                 52 
                 52 
                 26 
                 106 
                 1 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Number 
               
               
                 Indices 
                 #1 
                 #2 
                 #3 
                 #4 
                 #5 
                 #6 
                 #7 
                 #8 
                 #9 
                 of entries 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 20 
                 106 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 21 
                 106 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 22 
                 106 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 23 
                 106 
                 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 24 
                 52 
                 52 
                 — 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
            
               
                 25 
                 242-tone RU empty (with zero users) 
                 1 
               
            
           
           
               
               
               
               
               
            
               
                 26 
                 106 
                 26 
                 106 
                 1 
               
            
           
           
               
               
               
            
               
                 27-34 
                 242 
                 8 
               
               
                 35-42 
                 484 
                 8 
               
               
                 43-50 
                 996 
                 8 
               
               
                 51-58 
                 2*996 
                 8 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 59 
                 26 
                 26 
                 26 
                 26 
                 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 60 
                 26 
                 26 + 52 
                 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 61 
                 26 
                 26 + 52 
                 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 62 
                 26 
                 26 + 52 
                 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 63 
                 26 
                 26 
                 52 
                 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 64 
                 26 
                 26 + 52 
                 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 65 
                 26 
                 26 + 52 
                 26 
                 52 
                 52 
                 1 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 7 
               
               
                   
               
             
            
               
                 66 
                 52 
                 26 
                 26 
                 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 67 
                 52 
                 52 
                 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 68 
                 52 
                 52 + 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 69 
                 26 
                 26 
                 26 
                 26 
                 26 + 106 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 70 
                 26 
                 26 + 52 
                 26 
                 106 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 71 
                 26 
                 26 
                 52 
                 26 + 106 
                 1 
               
            
           
           
               
               
               
               
               
            
               
                 72 
                 26 
                 26 + 52 
                 26 + 106 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 73 
                 52 
                 26 
                 26 
                 26 + 106 
                 1 
               
            
           
           
               
               
               
               
               
            
               
                 74 
                 52 
                 52 
                 26 + 106 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 75 
                 106 + 26 
                 26 
                 26 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 76 
                 106 + 26 
                 26 
                 26 
                 52 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 77 
                 106 + 26 
                 52 
                 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
               
            
               
                 78 
                 106 
                 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
            
               
                 79 
                 106 + 26 
                 52 + 26 
                 26 
                 1 
               
            
           
           
               
               
               
               
               
            
               
                 80 
                 106 + 26 
                 52 
                 52 
                 1 
               
            
           
           
               
               
               
               
            
               
                 81 
                 106 + 26 
                 106 
                 1 
               
            
           
           
               
               
               
               
            
               
                 82 
                 106 
                 26 + 106 
                 1 
               
               
                   
               
            
           
         
       
     
     A mode in which the common field of the EHT-SIG is omitted may be supported. The mode in which the common field of the EHT-SIG is omitted may be called a compressed mode. When the compressed mode is used, a plurality of users (i.e., a plurality of receiving STAs) may decode the PPDU (e.g., the data field of the PPDU), based on non-OFDMA. That is, the plurality of users of the EHT PPDU may decode the PPDU (e.g., the data field of the PPDU) received through the same frequency band. Meanwhile, when a non-compressed mode is used, the plurality of users of the EHT PPDU may decode the PPDU (e.g., the data field of the PPDU), based on OFDMA. That is, the plurality of users of the EHT PPDU may receive the PPDU (e.g., the data field of the PPDU) through different frequency bands. 
     The EHT-SIG may be configured based on various MCS schemes. As described above, information related to an MCS scheme applied to the EHT-SIG may be included in U-SIG. The EHT-SIG may be configured based on a DCM scheme. For example, among N data tones (e.g., 52 data tones) allocated for the EHT-SIG, a first modulation scheme may be applied to half of contiguous tones, and a second modulation scheme may be applied to the remaining half of the contiguous tones. That is, a transmitting STA may use the first modulation scheme to modulate specific control information through a first symbol and allocate it to half of the contiguous tones, and may use the second modulation scheme to modulate the same control information by using a second symbol and allocate it to the remaining half of the contiguous tones. As described above, information (e.g., a 1-bit field) regarding whether the DCM scheme is applied to the EHT-SIG may be included in the U-SIG. 
     An HE-STF of  FIG.  18    may be used for improving automatic gain control estimation in a multiple input multiple output (MIMO) environment or an OFDMA environment. An HE-LTF of  FIG.  18    may be used for estimating a channel in the MIMO environment or the OFDMA environment. 
     The EHT-STF of  FIG.  18    may be set in various types. For example, a first type of STF (e.g.,  1   x  STF) may be generated based on a first type STF sequence in which a non-zero coefficient is arranged with an interval of 16 subcarriers. An STF signal generated based on the first type STF sequence may have a period of 0.8p, and a periodicity signal of 0.8 μs may be repeated 5 times to become a first type STF having a length of 4 μs. For example, a second type of STF (e.g., 2×STF) may be generated based on a second type STF sequence in which a non-zero coefficient is arranged with an interval of 8 subcarriers. An STF signal generated based on the second type STF sequence may have a period of 1.6p, and a periodicity signal of 1.6 μs may be repeated 5 times to become a second type STF having a length of 8 μs. Hereinafter, an example of a sequence for configuring an EHT-STF (i.e., an EHT-STF sequence) is proposed. The following sequence may be modified in various ways. 
     The EHT-STF may be configured based on the following sequence M. 
         M={ 1−1,−1,−1,1,1,1,−1,1,1,1,−1,1,1,−1,1}  &lt;Equation 1&gt;
 
     The EHT-STF for the 20 MHz PPDU may be configured based on the following equation. The following example may be a first type (i.e.,  1   x  STF) sequence. For example, the first type sequence may be included in not a trigger-based (TB) PPDU but an EHT-PPDU. In the following equation, (a:b:c) may imply a duration defined as b tone intervals (i.e., a subcarrier interval) from a tone index (i.e., subcarrier index) ‘a’ to a tone index ‘c’. For example, the equation 2 below may represent a sequence defined as 16 tone intervals from a tone index − 112  to a tone index  112 . Since a subcarrier spacing of 78.125 kHz is applied to the EHT-STR, the 16 tone intervals may imply that an EHT-STF coefficient (or element) is arranged with an interval of 78.125*16=1250 kHz. In addition, * implies multiplication, and sqrt( )implies a square root. In addition, j implies an imaginary number. 
         EHT−STF (−112:16:112)={ M }*(1+ j )/sqrt(2)
 
         EHT−STF (0)=0  &lt;Equation 2&gt;
 
     The EHT-STF for the 40 MHz PPDU may be configured based on the following equation. The following example may be the first type (i.e.,  1   x  STF) sequence. 
         EHT - STF (−240:16:240)={ M, 0,− M }*(1+ j )/sqrt(2)  &lt;Equation 3&gt;
 
     The EHT-STF for the 80 MHz PPDU may be configured based on the following equation. The following example may be the first type (i.e.,  1 × STF) sequence. 
         EHT - STF (−496:16:496)={ M, 1,− M, 0,− M, 1,− M }*(1+ j )/sqrt(2)  &lt;Equation 4&gt;
 
     The EHT-STF for the 160 MHz PPDU may be configured based on the following equation. The following example may be the first type (i.e.,  1 × STF) sequence. 
         EHT - STF (−1008:16:1008)={ M, 1,− M, 0,− M, 1,− M, 0,− M,— 1, M, 0,− M, 1,− M }*(1 +j )/sqrt(2)  &lt;Equation 5&gt;
 
     In the EHT-STF for the 80+80 MHz PPDU, a sequence for lower 80 MHz may be identical to Equation 4. In the EHT-STF for the 80+80 MHz PPDU, a sequence for upper 80 MHz may be configured based on the following equation. 
         EHT - STF (−496:16:496)={- M,− 1, M, 0,− M, 1,− M }*(1+ j )/sqrt(2)  &lt;Equation 6&gt;
 
     Equation 7 to Equation 11 below relate to an example of a second type (i.e., 2×STF) sequence. 
         EHT - STF (−120:8:120)={ M, 0,− M }*(1+ j )/sqrt(2)  &lt;Equation 7&gt;
 
     The EHT-STF for the 40 MHz PPDU may be configured based on the following equation. 
         EHT−STF (−248:8:248)={ M,− 1,− M, 0, M,− 1, M }*(1+ j )/sqrt(2)
 
         EHT−STF (−248)=0
 
         EHT - STF (248)=0  &lt;Equation 8&gt;
 
     The EHT-STF for the 80 MHz PPDU may be configured based on the following equation. 
         EHT - STF (−504:8:504)={ M,− 1, M,− 1,− M,− 1, M, 0,− M, 1, M, 1,− M, 1,− M }*(1+ j )/sqrt(2)&lt;Equation9&gt;
 
     The EHT-STF for the 160 MHz PPDU may be configured based on the following equation. 
         EHT - STF (−1016:16:1016)={ M,− 1, M,− 1,− M,− 1, M, 0,− M, 1, M, 1,− M, 1,− M, 0,− M, 1,− M, 1, M, 1,− M, 0,− M, 1, M, 1,− M, 1,− M }*(1+ j )/sqrt(2)&lt;Equation10&gt;
 
     EHT-STF(−8)=0, EHT-STF(8)=0, 
     EHT-STF(−1016)=0, EHT-STF(1016)=0 
     In the EHT-STF for the 80+80 MHz PPDU, a sequence for lower 80 MHz may be identical to Equation 9. In the EHT-STF for the 80+80 MHz PPDU, a sequence for upper 80 MHz may be configured based on the following equation. 
         EHT - STF (−504:8:504)={− M, 1,− M, 1, M, 1,− M, 0,− M, 1, M, 1,− M, 1,− M }*(1+ j )/sqrt(2)&lt;Equation11&gt;
 
     EHT-STF(−504)=0, 
     EHT-STF(504)=0 
     The EHT-LTF may have first, second, and third types (i.e., 1×, 2×, 4×LTF). For example, the first/second/third type LTF may be generated based on an LTF sequence in which a non-zero coefficient is arranged with an interval of 4/2/1 subcarriers. The first/second/third type LTF may have a time length of 3.2/6.4/12.8 μs. In addition, a GI (e.g., 0.8/1/6/3.2 μs) having various lengths may be applied to the first/second/third type LTF. 
     Information related to a type of STF and/or LTF (information related to a GI applied to LTF is also included) may be included in a SIG-A field and/or SIG-B field or the like of  FIG.  18   . 
     A PPDU (e.g., EHT-PPDU) of  FIG.  18    may be configured based on the example of  FIG.  5    and  FIG.  6   . 
     For example, an EHT PPDU transmitted on a 20 MHz band, i.e., a 20 MHz EHT PPDU, may be configured based on the RU of  FIG.  5   . That is, a location of an RU of EHT-STF, EHT-LTF, and data fields included in the EHT PPDU may be determined as shown in  FIG.  5   . 
     An EHT PPDU transmitted on a 40 MHz band, i.e., a 40 MHz EHT PPDU, may be configured based on the RU of  FIG.  6   . That is, a location of an RU of EHT-STF, EHT-LTF, and data fields included in the EHT PPDU may be determined as shown in  FIG.  6   . 
     Since the RU location of  FIG.  6    corresponds to 40 MHz, a tone-plan for 80 MHz may be determined when the pattern of  FIG.  6    is repeated twice. That is, an 80 MHz EHT PPDU may be transmitted based on a new tone-plan in which not the RU of  FIG.  7    but the RU of  FIG.  6    is repeated twice. 
     When the pattern of  FIG.  6    is repeated twice, 23 tones (i.e., 11 guard tones+12 guard tones) may be configured in a DC region. That is, a tone-plan for an 80 MHz EHT PPDU allocated based on OFDMA may have 23 DC tones. Unlike this, an 80 MHz EHT PPDU allocated based on non-OFDMA (i.e., a non-OFDMA full bandwidth 80 MHz PPDU) may be configured based on a 996-RU, and may include 5 DC tones, 12 left guard tones, and 11 right guard tones. 
     A tone-plan for 160/240/320 MHz may be configured in such a manner that the pattern of  FIG.  6    is repeated several times. 
     The PPDU of  FIG.  18    may be determined (or identified) as an EHT PPDU based on the following method. 
     A receiving STA may determine a type of an RX PPDU as the EHT PPDU, based on the following aspect. For example, the RX PPDU may be determined as the EHT PPDU: 1) when a first symbol after an L-LTF signal of the RX PPDU is a BPSK symbol; 2) when RL-SIG in which the L-SIG of the RX PPDU is repeated is detected; and 3) when a result of applying “modulo 3” to a value of a length field of the L-SIG of the RX PPDU is detected as “0”. When the RX PPDU is determined as the EHT PPDU, the receiving STA may detect a type of the EHT PPDU (e.g., an SU/MU/Trigger-based/Extended Range type), based on bit information included in a symbol after the RL-SIG of  FIG.  18   . In other words, the receiving STA may determine the RX PPDU as the EHT PPDU, based on: 1) a first symbol after an L-LTF signal, which is a BPSK symbol; 2) RL-SIG contiguous to the L-SIG field and identical to L-SIG; 3) L-SIG including a length field in which a result of applying “modulo 3” is set to “0”; and 4) a 3-bit PHY version identifier of the aforementioned U-SIG (e.g., a PHY version identifier having a first value). 
     For example, the receiving STA may determine the type of the RX PPDU as the EHT PPDU, based on the following aspect. For example, the RX PPDU may be determined as the HE PPDU: 1) when a first symbol after an L-LTF signal is a BPSK symbol; 2) when RL-SIG in which the L-SIG is repeated is detected; and 3) when a result of applying “modulo 3” to a value of a length field of the L-SIG is detected as “1” or “2”. 
     For example, the receiving STA may determine the type of the RX PPDU as a non-HT, HT, and VHT PPDU, based on the following aspect. For example, the RX PPDU may be determined as the non-HT, HT, and VHT PPDU: 1) when a first symbol after an L-LTF signal is a BPSK symbol; and 2) when RL-SIG in which L-SIG is repeated is not detected. In addition, even if the receiving STA detects that the RL-SIG is repeated, when a result of applying “modulo 3” to the length value of the L-SIG is detected as “0”, the RX PPDU may be determined as the non-HT, HT, and VHT PPDU. 
     In the following example, a signal represented as a (TX/RX/UL/DL) signal, a (TX/RX/UL/DL) frame, a (TX/RX/UL/DL) packet, a (TX/RX/UL/DL) data unit, (TX/RX/UL/DL) data, or the like may be a signal transmitted/received based on the PPDU of  FIG.  18   . The PPDU of  FIG.  18    may be used to transmit/receive frames of various types. For example, the PPDU of  FIG.  18    may be used for a control frame. An example of the control frame may include a request to send (RTS), a clear to send (CTS), a power save-poll (PS-poll), BlockACKReq, BlockAck, a null data packet (NDP) announcement, and a trigger frame. For example, the PPDU of  FIG.  18    may be used for a management frame. An example of the management frame may include a beacon frame, a (re-)association request frame, a (re-)association response frame, a probe request frame, and a probe response frame. For example, the PPDU of  FIG.  18    may be used for a data frame. For example, the PPDU of  FIG.  18    may be used to simultaneously transmit at least two or more of the control frame, the management frame, and the data frame. 
       FIG.  19    illustrates an example of a modified transmission device and/or receiving device of the present specification. 
     Each device/STA of the sub-figure (a)/(b) of  FIG.  1    may be modified as shown in  FIG.  19   . A transceiver  630  of  FIG.  19    may be identical to the transceivers  113  and  123  of  FIG.  1   . The transceiver  630  of  FIG.  19    may include a receiver and a transmitter. 
     A processor  610  of  FIG.  19    may be identical to the processors  111  and  121  of  FIG.  1   . Alternatively, the processor  610  of  FIG.  19    may be identical to the processing chips  114  and  124  of  FIG.  1   . 
     A memory  620  of  FIG.  19    may be identical to the memories  112  and  122  of  FIG.  1   . Alternatively, the memory  620  of  FIG.  19    may be a separate external memory different from the memories  112  and  122  of  FIG.  1   . 
     Referring to  FIG.  19   , a power management module  611  manages power for the processor  610  and/or the transceiver  630 . A battery  612  supplies power to the power management module  611 . A display  613  outputs a result processed by the processor  610 . A keypad  614  receives inputs to be used by the processor  610 . The keypad  614  may be displayed on the display  613 . A SIM card  615  may be an integrated circuit which is used to securely store an international mobile subscriber identity (IMSI) and its related key, which are used to identify and authenticate subscribers on mobile telephony devices such as mobile phones and computers. 
     Referring to  FIG.  19   , a speaker  640  may output a result related to a sound processed by the processor  610 . A microphone  641  may receive an input related to a sound to be used by the processor  610 . 
     Hereinafter, technical features of channel bonding supported by the STA of the present disclosure will be described. 
     For example, in an IEEE 802.11n system, 40 MHz channel bonding may be performed by combining two 20 MHz channels. In addition, 40/80/160 MHz channel bonding may be performed in the IEEE 802.11ac system. 
     For example, the STA may perform channel bonding for a primary 20 MHz channel (P20 channel) and a secondary 20 MHz channel (S20 channel). A backoff count/counter may be used in the channel bonding process. The backoff count value may be chosen as a random value and decremented during the backoff interval. In general, when the backoff count value becomes 0, the STA may attempt to access the channel. 
     During the backoff interval, when the P20 channel is determined to be in the idle state and the backoff count value for the P20 channel becomes 0, the STA, performing channel bonding, determines whether an S20 channel has maintained an idle state for a certain period of time (for example, point coordination function interframe space (PIFS)). If the S20 channel is in an idle state, the STA may perform bonding on the P20 channel and the S20 channel. That is, the STA may transmit a signal (PPDU) through a 40 MHz channel (that is, a 40 MHz bonding channel) including a P20 channel and the S20 channel. 
       FIG.  20    shows an example of channel bonding. As shown in  FIG.  20   , the primary 20 MHz channel and the secondary 20 MHz channel may make up a 40 MHz channel (primary 40 MHz channel) through channel bonding. That is, the bonded 40 MHz channel may include a primary 20 MHz channel and a secondary 20 MHz channel. 
     Channel bonding may be performed when a channel contiguous to the primary channel is in an idle state. That is, the Primary 20 MHz channel, the Secondary 20 MHz channel, the Secondary 40 MHz channel, and the Secondary 80 MHz channel can be sequentially bonded. However, if the secondary 20 MHz channel is determined to be in the busy state, channel bonding may not be performed even if all other secondary channels are in the idle state. In addition, when it is determined that the secondary 20 MHz channel is in the idle state and the secondary 40 MHz channel is in the busy state, channel bonding may be performed only on the primary 20 MHz channel and the secondary 20 MHz channel. 
     Hereinafter, preamble puncturing supported by a STA in the present disclosure will be described. 
     For example, in the example of  FIG.  20   , if the Primary 20 MHz channel, the Secondary 40 MHz channel, and the Secondary 80 MHz channel are all in the idle state, but the Secondary 20 MHz channel is in the busy state, bonding to the secondary 40 MHz channel and the secondary 80 MHz channel may not be possible. In this case, the STA may configure a 160 MHz PPDU and may perform a preamble puncturing on the preamble transmitted through the secondary 20 MHz channel (for example, L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, EHT-SIG, EHT-STF, EHT-LTF, etc.), so that the STA may transmit a signal through a channel in the idle state. In other words, the STA may perform preamble puncturing for some bands of the PPDU. Information on preamble puncturing (for example, information about 20/40/80 MHz channels/bands to which puncturing is applied) may be included in a signal field (for example, HE-SIG-A, U-SIG, EHT-SIG) of the PPDU. 
     Hereinafter, technical features of a multi-link (ML) supported by a STA of the present disclosure will be described. 
     The STA (AP and/or non-AP STA) of the present disclosure may support multi-link (ML) communication. ML communication may refer to communication supporting a plurality of links. The link related to ML communication may include channels of the 2.4 GHz band shown in  FIG.  15   , the 5 GHz band shown in  FIG.  16   , and the 6 GHz band shown in  FIG.  17    (for example, 20/40/80/160/240/320 MHz channels). 
     A plurality of links used for ML communication may be set in various ways. For example, a plurality of links supported by one STA for ML communication may be a plurality of channels in a 2.4 GHz band, a plurality of channels in a 5 GHz band, and a plurality of channels in a 6 GHz band. Alternatively, a plurality of links supported by one STA for ML communication may be a combination of at least one channel in the 2.4 GHz band (or 5 GHz/6 GHz band) and at least one channel in the 5 GHz band (or 2.4 GHz/6 GHz band). Meanwhile, at least one of the plurality of links supported by one STA for ML communication may be a channel to which preamble puncturing is applied. 
     The STA may perform an ML setup to perform ML communication. The ML setup may be performed based on a management frame or control frame such as a Beacon, a Probe Request/Response, an Association Request/Response, and the like. For example, information about ML setup may be included in an element field included in a Beacon, a Probe Request/Response, an Association Request/Response, and the like. 
     When ML setup is completed, an enabled link for ML communication may be determined. The STA may perform frame exchange through at least one of a plurality of links determined as an enabled link. For example, the enabled link may be used for at least one of a management frame, a control frame, and a data frame. 
     When one STA supports multiple links, a transceiver supporting each link may operate as one logical STA. For example, one STA supporting two links may be expressed as one Multi Link Device (MLD) including a first STA for the first link and a second STA for the second link. For example, one AP supporting two links may be expressed as one AP MLD including a first AP for a first link and a second AP for a second link. In addition, one non-AP supporting two links may be expressed as one non-AP MLD including a first STA for the first link and a second STA for the second link. 
     Hereinafter, more specific features related to the ML setup are described. 
     The MLD (AP MLD and/or non-AP MLD) may transmit, through ML setup, information on a link that the corresponding MLD can support. Link information may be configured in various ways. For example, information on the link may include at least one of 1) information on whether the MLD (or STA) supports simultaneous RX/TX operation, 2) information on the number/upper limit of uplink/downlink links supported by the MLD (or STA), 3) information on the location/band/resource of the uplink/downlink Link supported by the MLD (or STA), 4) information on the frame type (management, control, data, etc.) available or preferred in at least one uplink/downlink link, 5) information on ACK policy available or preferred in at least one uplink/downlink link, and 6) information on an available or preferred traffic identifier (TID) in at least one uplink/downlink Link. The TID is related to the priority of traffic data and is expressed as eight types of values according to the conventional wireless LAN standard. That is, eight TID values corresponding to four access categories (ACs) (AC_Background (AC_BK), AC_Best Effort (AC_BE), AC_Video (AC_VI), AC_Voice (AC_VO)) according to the conventional WLAN standard may be defined. 
     For example, it may be preset that all TIDs are mapped for uplink/downlink link. Specifically, if negotiation is not made through ML setup, if all TIDs are used for ML communication, and if the mapping between uplink/downlink link and TID is negotiated through additional ML settings, the negotiated TID may be used for ML communication. 
     Through ML setup, a plurality of links usable by the transmitting MLD and the receiving MLD related to ML communication may be set, and this may be referred to as an “enabled link”. The “enabled link” may be called differently in various expressions. For example, it may be referred to as various expressions such as a first link, a second link, a transmission link, and a reception link. 
     After the ML setup is completed, the MLD could update the ML setup. For example, the MLD may transmit information on a new link when it is necessary to update information on the link. Information on the new link may be transmitted based on at least one of a management frame, a control frame, and a data frame. 
     In extreme high throughput (EHT), a standard being discussed after IEEE802.11ax, the introduction of HARQ is being considered. When HARQ is introduced, coverage can be expanded in a low signal to noise ratio (SNR) environment, that is, in an environment where the distance between the transmitting terminal and the receiving terminal is long, and higher throughput may be obtained in a high SNR environment. 
     The device described below may be the apparatus of  FIGS.  1  and/or  19   , and the PPDU may be the PPDU of  FIG.  18   . A device may be an AP or a non-AP STA. The device described below may be an AP multi-link device (MLD) supporting multi-link or a non-AP STA MLD. 
     In extremely high throughput (EHT), a standard being discussed after 802.11ax, a multi-link environment using one or more bands at the same time is being considered. When the device supports multi-link or multi-link, the device may use one or more bands (for example, 2.4 GHz, 5 GHz, 6 GHz, 60 GHz, etc.) simultaneously or alternately. 
     Hereinafter, although described in the form of multi-link, the frequency band may be configured in various other forms. In this specification, terms such as multi-link, multi-link, and the like may be used, however, for the convenience of the description below, some embodiments may be described based on multi-link. 
     In the following specification, an MLD refers to a multi-link device. The MLD has one or more connected STAs and one MAC service access point (SAP) that connects to an upper link layer (Logical Link Control, LLC). An MLD may mean a physical device or a logical device. Hereinafter, a device may mean an MLD. 
     In the following specification, a transmitting device and a receiving device may refer to an MLD. The first link of the receiving/transmitting device may be a terminal (for example, STA or AP) that performs signal transmission/reception through the first link included in the receiving/transmitting device. The second link of the receiving/transmitting device may be a terminal (for example, STA or AP) that performs signal transmission/reception through the second link included in the receiving/transmitting device. 
     Power Saving Mechanism 
     The IEEE 802.11 standard provides a power saving mechanism to increase a lifespan of a WLAN station. For power saving, the WLAN station operates in two modes, i.e., an active mode and a sleep mode. The active mode is a state in which a normal operation such as frame transmission/reception, channel scanning, etc., is possible. On the other hand, in the sleep mode, since power consumption is decreased extremely, frame transmission/reception is impossible, and channel scanning is also impossible. A basic operation of power saving is in principle that the WLAN station is usually in a sleep mode and transitions to an active mode only when necessary. 
     The longer the operation is performed in the sleep mode, the less the power is consumed, thereby the longer the lifespan of the WLAN station. However, it is not preferable to operate in the sleep mode unconditionally since frame transmission/reception is impossible in this mode. If there is a frame to be sent, the sleep mode transitions to an active mode to transmit the frame, and thus there is no significant problem. However, if a station is in the sleep mode and an AP has a frame to be sent to the station, the station cannot receive the frame and cannot know that there is a frame to be received. Therefore, the station must occasionally transition to the active mode and operate in a reception mode to know whether there is a frame to be received by the station and, if the frame exists, to receive the frame. The AP must announce whether there is the frame to be sent to the station at a corresponding time. 
     In order to know that there is the frame to be received, the WLAN station periodically wakes up from the sleep mode and receives a beacon frame from the AP. By using a TIM element of the beacon frame, the AP reports to each station about whether there is the frame to be received. There are two types of TIM elements, i.e., TIM and DTIM. The TIM is used to indicate a unicast frame, and the DTIM is used to indicate a multicast/broadcast frame. 
     When the station knows through the TIM element of the beacon frame that there is a frame to be transmitted to the station by the AP, the station transmits a PS-poll frame through contending. Upon receiving the PS-poll frame, the AP operates by selecting either Immediate Response or Deferred Response according to a situation. In the Immediate Response, the PS-poll frame is received and then a data frame is transmitted immediately after an SIFS time. If reception is normally performed, the station transmits an ACK frame after an SIFS and returns to the sleep mode. 
     If a data frame is not prepared during an SIFS duration after receiving the PS-poll frame, the AP selects Deferred Response. When an ACK frame is first transmitted and thereafter a data frame is prepared, the data frame is transmitted to the station through contending. When the data frame is normally received, the station transmits an ACK frame and returns to the sleep mode. 
     On the other hand, in case of the DTIM, a multicast/broadcast frame is used. Thus, a beacon frame is followed directly by data frame transmission without PS-poll frame transmission/reception, and all corresponding stations receive this in an active mode. 
     The WLAN station is associated with the AP and is assigned an association ID (AID). The AID is used uniquely in one BSS, and has a value in the range of 1 to 2007 at present. Since 14 bits are assigned for the AID, up to 16383 can be used. Values in the range of 2008 to 16383 are reserved. 
     IEEE802.11be can support two types of multi-link operations. For example, simultaneous transmit and receive (STR) and non-STR operations may be considered. For example, an STR may be referred to as an asynchronous multi-link operation, and a non-STR may be referred to as a synchronous multi-link operation. A multi-link may include a multi-band. That is, the multi-link may mean links included in several frequency bands, or may mean a plurality of links included in one frequency band. 
     EHT (11be) may consider multi-link technology, where multi-link may include multi-band. That is, the multi-link may represent links of several bands and at the same time may represent several multi-links within one band. Two types of multi-link operations are being considered. The asynchronous operation that enables simultaneous TX/RX on multiple links and synchronous operation that is not possible are considered. Hereinafter, the capability that enables simultaneous reception and transmission in multiple links is called STR (simultaneous transmit and receive), a STA having STR capability is called a STR MLD (multi-link device), and a STA not having STR capability is called a non-STR MLD. 
     In 11be, the multi-link system is a system in which multiple STAs (APs/non-APs) are co-located in one device (multi-link device (MLD)), which may improve performance of a wireless network. 
     A specific TID may be mapped to specific link(s) among enabled/available links, and traffic for the TID may be transmitted/received through the link(s). Unless otherwise specified, the TID may be basically mapped to all enabled/available links. 
     An AP may transmit buffered traffic indication information for multiple links through one link, or may transmit buffered traffic indication information for different links through one link. In this case, only one link among available (or enabled) multiple links may operate in a power saving mode. When other links in a doze state receive a traffic indication related to the links through the link operating in the power saving mode, an MLD may expect to receive corresponding traffic by transitioning a corresponding link (e.g., terminal(s)) to an awake state. In this case, if it is assumed that TIDs are mapped to all available links, the terminal may awaken all available links. If a size of data to be actually transmitted from the AP is not great, instead of transitioning all available links to the awake state, the AP may transition only a specific link (or links) to the awake state and then transmit and receive a frame through the awakened links. 
     In addition, the non-AP STA in the multi-link device may notify the power state transition (e.g., transition from doze state to awake state) of other STAs in the same MLD. In the present specification, a detailed method of notifying the power state transition (e.g., transition from doze state to awake state) of other STAs in the same MLD is proposed. 
     Since a traffic indication in the existing single link operation provides only information on whether there is traffic for a corresponding terminal (i.e., link), the corresponding terminal (i.e., link) may be awakened and informs the AP that the corresponding terminal is awakened (e.g., PS-poll frame or QoS null/data frame transmission) to receive a DL frame through a corresponding single link. 
     However, when a non-AP device (e.g., MLD) with a multi-link has multiple links with respect to an associated AP MLD, there may be case where a specific TID is mapped to a specific link and the non-AP MLD in the non-AP MLD is in a power saving mode. In this case, when the AP MLD receives traffic for the non-AP MLD, a corresponding bit of a traffic indication map (TIM) bitmap may be set to 1 for STAs corresponding to a link mapped to a TID of the corresponding traffic and then it may be transmitted to the non-AP MLD. The non-AP STA/non-AP MLD may receive a TIM bitmap to know for which link the AP has traffic. 
     If TIDs of the non-AP MLD are mapped to all enabled/available links, the AP may perform transmission by setting a bit corresponding to STAs to 1 in a TIM bitmap in order to awaken non-AP STAs corresponding to all links. In this case, however, since the non-AP MLD does not know how much data the AP MLD actually has, it may be necessary to awaken all STAs mapped to the available links or it may be implemented such that only specific STAs are awakened. Although transitioning of all STAs from the doze state to the awake state has an advantage in that data can be quickly received, since the awakened STAs shall remain in the doze state for a long period of time until DL data is received, power consumption of the non-AP MLD may be increased. 
     Method 0: Upon receiving traffic for a TID mapped to all available links in the non-AP MLD, an AP reports to a non-AP MLD about corresponding all available links (or corresponding STAs) through a traffic indication bitmap, and the non-AP MLD uses this information to transition a state of a non-AP STA corresponding to each link to an awake state. 
       FIG.  21    illustrates an embodiment of a wakeup operation. 
     Referring to  FIG.  21   , APs  1 ,  2 , and  3  may be present in an AP MLD, and STAs  1 ,  2 , and  3  may be present in a non-AP MLD. The STAs  1 ,  2 , and  3  are associated respectively with the APs  1 ,  2 , and  3 . Upon receiving traffic corresponding to a TID mapped to the STAs  1 ,  2 , and  3  (i.e., links 1, 2, and 3), the AP MLD may indicate that buffer traffic is present in the STAs  1 ,  2 , and  3 . That is, even if corresponding buffer traffic is present in the STAs  1 ,  2 , and  3 , the AP (or AP MLD) may transmit a traffic indication to corresponding STAs in order to awaken some of the three STAs. The STAs  1 ,  2 , and  3  of the non-AP MLD transition to the awake state, and when transmitting a UL frame, may inform the AP MLD (or AP) that the STAs  1 ,  2 , and  3  are awakened. The AP may transmit a DL frame to two STAs (STA 1 , STA 2 ) among them. Although the STA 1  informs the AP 1  of the awake state of the STAs  1 ,  2 , and  3  in  FIG.  21   , it is obvious that each STA can inform each associated AP of the awake state thereof through a link thereof. For example, the STA 1  may inform the AP 1  of the awake state of the STA 1  through a link1, the STA 2  may inform the AP 2  of the awake state of the STA 2  through a link2, and the STA 3  may inform the AP 3  of the awake state of the STA 3  through a link3. Descriptions thereon may be equally applied throughout the present specification. 
     Method 1: An AP MLD (or AP) provides a non-AP MLD (or non-AP STA) with at least one of a buffer status report for a corresponding non-AP MLD, a buffer status report for each STA in the non-AP MLD, and a buffer status report per TID in each STA of the non-AP MLD 
     Buffer status report information of a terminal (e.g., non-AP MLD) to which the AP transfers buffer information may include at least one piece of information described below. 
     1) The total amount of the entire buffered traffic for the non-AP MLD (i.e., Queue size all of the non-AP MLD) 
     2) The total amount of buffered traffic for each STA in the non-AP MLD (i.e., Queue size all of each non-AP STA): that is, sum information of all queues for respective STAs 
     3) The amount of per-AC (access category, e.g., AC_VI, AC_VO, AC_BE, AC_BK) buffered traffic in each non-AP STA: that is, queue information corresponding to each AC is included in each STA 
     4) The amount of per-TID buffered traffic in each non-AP STA: that is, queue information corresponding to each TID is included in each STA 
     5) Report the amount of buffered traffic by distinguishing the received buffered traffic for STAs in the non-AP MLD according to an AC: that is, per-AC queue size information for a corresponding non-AP MLD is included 
     6) Report the amount of buffered traffic by distinguishing the received buffered traffic for STAs in the non-AP MLD according to a TID: that is, per-TID queue size (buffered traffic amount) information for a corresponding non-AP MLD is included 
     In addition, buffer information to be transmitted by the AP MLD may include at least one piece of information (e.g., ACI Bitmap, Delta TID, ACI High, Scaling Factor, Queue Size High, Queue Size All, etc.) included in the existing buffer status report (BSR) control field. 
     Although the amount of the entire buffer traffic of the non-AP MLD is reported in the description of the present specification, it is obvious that one or more pieces of information listed above may be included in buffer status information for the non-AP MLD, transmitted by the AP. 
     When the non-AP MLD receives BSR information (i.e., at least one of BSR information of the aforementioned non-AP MLD, BSR information for each of STAs in the non-AP MLD, per-AC queue size information in each non-AP STA of the non-AP MLD, per-TID BSR information in each non-AP STA in the non-AP MLD, per-AC BSR information in the non-AP MLD, per-TID BSR information in the non-AP MLD) corresponding to the non-AP MLD from the AP MLD, the non-AP MLD may determine how many links (i.e., STAs mapped to the links) will be awakened based on the information. The non-AP MLD (or non-AP STA) may report to an associated AP MLD (or AP) about which STAs (or links corresponding to the STAs) have been awakened. The AP MLD (or AP) may transmit a DL frame through a corresponding link, based on information transmitted by a terminal (information on which non-AP STA in the non-AP has been awakened). 
       FIG.  22    illustrates an embodiment of a wakeup operation. 
     Referring to  FIG.  22   , APs  1 ,  2 , and  3  may be present in an AP MLD, and STAs  1 ,  2 , and  3  may be present in a non-AP MLD. The STAs  1 ,  2 , and  3  of the non-AP are associated respectively with the APs  1 ,  2 , and  3 . 
     When transmitting a DL frame to the STA 1  through a link1, the AP MLD (or AP 1 ) may transmit to the STA 1  (or a non-AP MLD of the STA 1 ) a BSR (queue size or buffered traffic size) of the non-AP MLD together with an indication indicating a presence of buffered traffic. After the STA 1  (or non-AP MLD) receives BSR information from the AP, the STA 2  (i.e., link2) may be awakened, and if transmission is performed by including information indicating that the STA 1  and the STA 2  have been awakened (i.e., information indicating that it is ready to receive the DL frame) when transmitting a UL frame to the AP (e.g., AP MLD), the AP (e.g., AP MLD) may transmit the DL frame to the STA 1  and the STA 2  through the link1 and the link2. The DL frame including the indication indicating the presence of the buffered traffic is preferably a beacon frame in the present specification, but is not limited thereto. Instead of transmitting to the STA 1  a buffered traffic indication for the STA 1 , only a buffered traffic indication for the non-AP MLD of the STA 1  may be included in a TIM, and a specific STA or the specific link may not be indicated. This may be equally applied throughout the present specification. 
     Detailed transmission method: The AP MLD (or AP STA) performs transmission by including the buffer status report information defined above for the non-AP MLD (or non-AP STA) together in a corresponding frame (e.g., a DL data frame) when transmitting an individually address (e.g., unicast) frame to a terminal in an awake state. The non-AP MLD (or non-AP STA) uses the buffer status report information included in the DL frame to determine whether to transition some links (or STAs corresponding to the links) to the awake state among multiple links, and transmits an uplink frame including information on the awake links/STAs to the AP to report this. 
       FIG.  23    illustrates an embodiment of a wakeup operation. 
     Referring to  FIG.  23   , APs  1 ,  2 , and  3  are present in an AP MLD, and STAs  1 ,  2 , and  3  are present in a non-AP MLD. The STAs  1 ,  2 , and  3  are associated respectively with the APs  1 ,  2 , and  3 . It is assumed that all TID(s) for the non-AP MLD are mapped to available links through default TID-to-link mapping. 
     For example, when the AP 1  transmits a beacon through the link1, buffered traffic information for other links/other STAs may be transmitted. Since TIDs are mapped to all available links, the AP MLD may transmit a beacon frame including a TIM for awakening only a corresponding STA (e.g., STA 1 ). Even if information for awakening only the STA 1  is contained in the TIM, and even if the TIDs are mapped to all links, the non-AP MLD (or STA 1 ) transitions the STA 1  to the awake state. Thereafter, the STA 1  may transmit to the AP a UL frame (e.g., PS-poll or QoS null) for reporting that the STA 1  is awakened, and may receive an Ack frame in response thereto. When the AP 1  transmits a DL frame to the STA 1 , buffer status information (e.g., BSR or queue size) for a non-AP MLD corresponding to the STA 1  may be included and transmitted. When the STA 1  receives the DL frame, how many available links thereof will be awakened may be determined upon receiving BSR information for the non-AP MLD. Although only the BSR information for the non-AP MLD is mentioned to describe embodiments of the present specification, it may be replaced with including one or more of various types of BSRs (e.g., BSR information for each STA in the non-AP MLD, or BSR information for each of ACs (or TIDs) of the non-AP MLD).  FIG.  23    illustrates an example of transitioning the STA 2  for the link2 from the doze state to the awake state. This example shows that the STA 1  receives a DL frame and then transmits ACK/BA to the AP 1  in response thereto. A subsequent operation of the STA (non-AP MLD) and the AP (/AP MLD) may perform one or more of the following operations. 
     1) The AP 1  (or AP MLD) which has received a response frame (ACK/BA) for DL frame transmission including BSR for the non-AP MLD may transmit a DL frame also through another link (link 2). However, there is a problem in that whether the STA 2  is awakened cannot be guaranteed. 
     2) When the non-AP STA (STA 1 ) receives the BSR for the non-AP MLD, links to be awakened (or STAs to be mapped to the links) are determined based on BSR information, and information of the awakened STA is included and transmitted when a UL frame is transmitted. The AP may transmit a DL frame through multiple links, based on information of an awakened terminal, included in the UL frame. 
       FIG.  24    illustrates an embodiment of a wakeup operation. 
     Referring to  FIG.  24   , APs  1 ,  2 , and  3  are present in an AP MLD, and STAs  1 ,  2 , and  3  are present in a non-AP MLD. The STAs  1 ,  2 , and  3  are respectively associated with the APs  1 ,  2 , and  3 . 
     The STA 1  may determine to additionally transition the STA 2  (link2) to an awake state, based on BSR information for the non-AP MLD included in a first DL frame. After the STA 2  is awakened, in order to report that the STA 2  is awakened, information thereon is transmitted by being included in a UL frame when the STA 1  transmits the UL frame. Thereafter, the AP MLD may transmit the DL frame to the non-AP MLD by using the link 1 and the link 2. 
     Instead of reporting by the STA 1  to the AP MLD (or AP 1 ) that “the STA 2  has transitioned to the awake state”, the STA 2  may report through the link 2 that the STA 2  has transitioned to the awake state. An example thereof is described below with reference to  FIG.  25   . 
       FIG.  25    illustrates an embodiment of a wakeup operation. 
     Referring to  FIG.  25   , APs  1 ,  2 , and  3  are present in an AP MLD, and STAs  1 ,  2 , and  3  are present in a non-AP MLD. The STAs  1 ,  2 , and  3  are respectively associated with the APs  1 ,  2 , and  3 . 
     The STA 1  (or non-AP MLD) may determine to additionally transition the STA 2  (link2) to an awake state, based on BSR information for the non-AP MLD included in a first DL frame. After the STA 2  is awakened, in order to report that the STA 2  is awakened, the STA 2  may transmit a UL frame through the link2. The AP MLD which has received the UL frame (e.g., PS-poll/QoS null frame) from the STA 2  through the link2 may know that the STA 2  has been awakened, and may transmit the DL frame to the non-AP MLD by using the link1 and the link 2. 
     A method of transmitting information (e.g., BSR information) related to data to be transmitted by the AP MLD to the STA MLD may be roughly classified into two types as follows. 
     1. A method in which the information (e.g., BSR information) related to the data to be transmitted by the AP MLD to the STA MLD is included in a beacon frame (the method of  FIG.  21    to  FIG.  32   ). 
     2. A method in which only a TIM related to data to be transmitted by the AP MLD to the STA MLD is transmitted through a beacon frame, and the information (e.g., BSR information) related to the data to be transmitted by the AP MLD to the STA MLD is transmitted through a subsequent DL frame (e.g., a data frame) (the method of  FIG.  23    to  FIG.  25   ) 
     The AP MLD may use both of the two methods. For example, the AP MLD may determine how to transmit BSR information to the STA MLD according to a type of traffic, i.e., AC (or TID). For example, the AP MLD may transmit the BSR information to the STA MLD through the first method (or second method) upon receiving traffic of an AC requiring low latency, and may transmit the BSR information to the STA MLD through the second (or first method) upon receiving traffic of an AC not requiring relatively low latency. 
     Herein, the AC requiring low latency may be a new AC defined additionally for low-latency transmission, or may be traffic requiring relatively low latency among the existing ACs such as AC_VO, AC_VI, or the like. The AC requiring low latency may vary depending on a situation, and is not limited thereto. 
     The BSR information of the non-AP MLD, included in the DL frame, may be configured using the following methods. 
     For example, the BSR information of the non-AP MLD may be included in an HT control field. 
       FIG.  26    illustrates an embodiment of an HT control field. 
     Referring to  FIG.  26   , when B 0  and B 1  of the HT control field are both set to 1 so as to be an HE variable HT control field, the remaining bits may be constructed of an A-Control subfield. 
       FIG.  27    illustrates an embodiment of an A-Control subfield. 
     Referring to  FIG.  27   , the A-Control subfield may have a length of 30 bits, and a control list subfield may include one or more control subfields. 
       FIG.  28    illustrates an embodiment of a control subfield format. 
     Referring to  FIG.  28   , a control ID subfield indicates a type of information to be transmitted in a control information subfield, and a length of the control information subfield is fixed for each value of the control ID subfield Different control information may be configured according to a value of a control ID. 
     BSR information of a non-AP MLD may be defined with one new control subfield. 
       FIG.  29    illustrates an example of a non-AP MLD BSR (NMB) control subfield. 
     Referring to  FIG.  29   , a control ID may indicate the NMB, and a queue size may indicate total queue size information of a non-AP MLD to which a corresponding STA (a STA indicated by a receiver address) belongs. 
     The queue size information may extend an additional queue size by using a scaling factor as shown in  FIG.  30   . 
       FIG.  30    illustrates an embodiment of an NMB control subfield. 
     Referring to  FIG.  30   , a control ID may include at least one of a TID, a STA ID, and a link ID. Table 8 shows an example of scaling factor subfield encoding. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
               
                   
                 Scaling Factor subfield 
                 Scaling factor, SF, in octets 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 16 
               
               
                   
                 1 
                 256 
               
               
                   
                 2 
                 2048 
               
               
                   
                 3 
                 32768 
               
               
                   
                   
               
            
           
         
       
     
     Referring to Table 8, the Scaling Factor subfield may indicate the unit (SF), in octets, of the Queue size subfield. In association with an SF value of the Scaling Factor subfield, a Queue size may be used to indicate a total size of all MSDUs and A-MSDUs buffered for a corresponding non-AP MLD by the AP. When a value of the Queue size subfield is A and the Scaling Factor subfield is 1, this indicates that the total size of all MSDUs and A-MSDUs buffered for the non-AP MLD by the AP is about A*256 octets, which may be known to the non-AP MLD (or STA). 
     The AP-MLD (or AP) may perform transmission by including one or more pieces of information listed below, as well as reporting of the entire buffered information of the non-AP MLD. 
     ACI(Access Category Indication) information(e.g., 4 bits size): Information indicating an access category (AC) (e.g., AC_VO, AC_VI, AC_BE, AC_BK) of which an BSR is indicated by corresponding BSR information. When it is included in a bitmap format, bits are mapped to respective ACs, and indicate that traffic is present for an AC set to 1. 
       FIG.  31    illustrates an example of ACI bitmap subfield encoding. 
     Delta TID (e.g., 2 bits size): indicates the number of TIDs for which a buffer status is reported, together with an ACI bitmap subfield. Table 9 shows an example of delta TID subfield encoding. 
     
       
         
           
               
               
             
               
                 TABLE 9 
               
               
                   
               
               
                 Number of bits 
                   
               
               
                 in the ACI 
               
               
                 Bitmap subfield 
                 Mapping of Delta TID subfield value and number 
               
               
                 that are set to 1 
                 of TIDs, N TID   
               
               
                   
               
             
            
               
                 0 
                 Values 0 to 2 are not applicable; 
               
               
                   
                 Value 3 indicates 8 TIDs (i.e., all ACs have traffic) 
               
               
                 1 
                 Value 0 indicates 1 TID; Value 1 indicates 2 TIDs; 
               
               
                   
                 Values 2 to 3 are not applicable; 
               
               
                 2 
                 Value 0 indicates 2 TID; Value 1 indicates 3 TIDs; 
               
               
                   
                 Value 2 indicates 4 TIDs; Value 3 is not applicable; 
               
               
                 3 
                 Value 0 indicates 3 TID; Value 1 indicates 4 TIDs; 
               
               
                   
                 Value 2 indicates 5 TIDs; Value 3 indicates 6 TIDs; 
               
               
                 4 
                 Value 0 indicates 4 TID; Value 1 indicates 5 TIDs; 
               
               
                   
                 Value 2 indicates 6 TIDs; Value 3 indicates 7 TIDs; 
               
               
                   
               
               
                 NOTE 1 
               
               
                 The number of TIDs can be obtained as N TID  = N ones  + D Val , where N ones  is the number of bits set to one in the AC Bitmap subfield, and D Val  is the value of the Delta TID subfield except if N ones  is equal to 0 for which there is the N TID  = 8 case. 
               
               
                 NOTE 2 
               
               
                 The Delta TID might be used by an AP to determine the setting of the TID Aggre-gation Limit field in the User Info field addressed to the STA in a subsequent Basic Trigger frame. 
               
            
           
         
       
     
     ACI High subfield (e.g., 2 bits size): used together with a queue size high subfield, and indicates ACI of an AC for which a BSR is indicated in a queue size high subfield. An example of ACI to AC coding is shown in the table below. 
     Queue Size High subfield (e.g., 8 bits size): indicates an amount of buffered traffic for an AC indicated by the ACI High subfield, by using an SF unit. 
     The Queue Size All subfield: indicates an amount of buffered traffic for all ACs indicated by the ACI Bitmap subfield, in units of SF octets of the Scaling Factor subfield. 
     In addition, a value of 254 in the Queue Size High and Queue Size All subfields indicates that the amount of buffered traffic is greater than 254×SF octets, and a value of 255 in the Queue Size High and Queue Size All subfields indicates that the amount of buffered traffic is an unspecified or unknown. 
       FIG.  32    illustrates an example of an NMB control subfield including every information described above. 
     As described above, a value indicated by a scaling factor is applied to both Queue Size High and Queue Size All. ACI Bitmap and Delta TID values are applied to Queue Size All. ACI High is applied to Queue Size High. 
     It is exemplified that an AP (or AP MLD) newly defines and uses a control subfield to report a BSR of a specific non-AP MLD. Hereinafter, a method of using the existing BSR control subfield is described. 
       FIG.  33    illustrates an example of a BSR control subfield in an flax system. 
     Referring to  FIG.  33   , the BSR control subfield is an HT control field used when a terminal transmits a buffer status thereof to an AP. For a simple definition in the present specification, when an AP MLD transfers to a corresponding non-AP STA an amount of buffered traffic for a specific non-AP MLD in a BSR thereof, the existing BSR control subfield may be used. However, to use this, the BSR transmitted by the AP needs to be redefined to indicate not a buffer status of a specific non-AP STA (i.e., a STA indicated by a receiver address of a frame including the BSR control field) but an amount of traffic to be transmitted to a non-AP MLD to which the non-AP STA belongs. In this case, there may be a constraint in that the BSR information for the specific non-AP STA cannot be transferred. 
     That is, when the AP transmits the BSR control field, information included in the BSR control field indicates BSR information of an MLD to which the STA indicated by the receiver address of the frame including the BSR control field belongs. 
     If an address is set to a broadcast address, the AP indicates TID count information and AC information related to queue size information for high AC and a total buffered traffic amount of the AP. 
     The information defined above may be transmitted by being defined in different formats described below. 
     1) The amount of per-AC (access category, e.g., AC_VI, AC_VO, AC_BE, AC_BK) buffered traffic in each non-AP STA: that is, queue information corresponding to each AC is included in each STA 
     2) The amount of per-TID buffered traffic in each non-AP STA: that is, queue information corresponding to each TID is included in each STA 
     3) Report the amount of buffered traffic by distinguishing the received buffered traffic for STAs in the non-AP MLD according to an AC: that is, per-AC queue size information for a corresponding non-AP MLD is included 
     4) Report the amount of buffered traffic by distinguishing the received buffered traffic for STAs in the non-AP MLD according to a TID: that is, per-TID queue size (buffered traffic amount) information for a corresponding non-AP MLD is included 
     Hereinafter, a method in which the MLD (e.g., non-AP MLD) transmits information related to the power state (e.g., doze state or awake state) of STAs included in the MLD will be described. For convenience of description, a method in which a non-AP MLD that has received buffer information from the AP MLD transmits power state information based on the buffer information is described, but a method in which the MLD transmits power state information is not limited thereto. 
       FIG.  34    is a diagram illustrating an embodiment of a method for transmitting a power state. 
     Referring to  FIG.  34   , the AP  1 , AP  2 , and AP  3  are configured in the AP MLD, and the STA  1 , STA  2 , and STA  3  are configured in the Non-AP MLD. The STA  1 , STA  2 , and STA  3  are associated with the AP  1 , AP  2 , and AP  3 , respectively. 
     The AP MLD (or AP 1 ) may transmit a DL frame to the STA MLD (or STA 1 ). The DL frame is not limited to a beacon frame or a PPDU including data. When the STA MLD receives a DL frame from the AP MLD, the STA MLD may transmit power state information of STAs included in the STA MLD. The power state information may include information related to whether STAs included in the STA MLD are in a doze state or an awake state. 
     For example, the DL frame may include information requesting power state information of STAs of the STA MLD. In this case, since the STA MLD has been requested for the power state information through the DL frame, the STA MLD may transmit the power state information of the STAs to the AP MLD. 
     For example, the DL frame may include buffer information on the amount of data to be transmitted from the AP MLD to the STA MLD. In this case, the STA MLD may determine STAs to be transitioned from the doze state to the awake state or from the awake state to the doze state based on the buffer information, and may transmit power state information of the STAs to the AP MLD. 
     The above embodiments are examples of information that may be included in the DL frame, and the information included in the DL frame is not limited thereto. 
     When the AP MLD receives the power state information from the STA MLD, the AP MLD may transmit data through at least one link (e.g., the first link and the second link) based on the received power state information. 
     For example, the non-AP MLD that has received the BSR of the non-AP MLD included in the DL frame may determine which STAs to awake and then transmit the awake STA information in the UL data frame. However, since the AP MLD does not know the information of the awake STA of the non-AP MLD until the UL frame is received by the AP MLD, the DL frame transmission may be possible through only one STA. 
     In order to transmit fast power state transition information, when the non-AP MLD transmits an immediate response frame (e.g., acknowledgement/block ACK (ACK/BA)) upon receiving a DL frame including its BSR information, the non-AP MLD, the non-AP MLD can quickly inform the AP MLD by transmitting power state transition information in the corresponding frame. 
       FIG.  35    is a diagram illustrating an embodiment of a method for transmitting a power state. 
     Referring to  FIG.  35   , the AP (or AP MLD) may wake up the STA 1  through the TIM. For example, the AP may transmit TIM information to the STA 1 , and the STA 1  may transition to an awake state based on the TIM information. The STA 1  may transmit a PS-Poll including information that the STA 1  is in the awake state to the AP. When the AP transmits the DL frame after receiving the PS-Poll, the DL frame may include BSR information for the non-AP MLD and transmit it. After awake of the STA 2  based on the received BSR, the non-AP MLD of STA 1  may include and transmit information on the awake STA when transmitting a response frame (ACK/BA) for a DL frame. A method in which power state information (i.e., information indicating which STA has transitioned to an awake state (or doze state)) is transmitted together with a response frame may be transmitted using one of the following methods. 
     Method 1): A MAC frame (e.g., QoS data frame or QoS Null frame) including power state transition information (e.g., information indicating which STAs have transitioned to an awake state (or to a doze state))may be aggregated into a response frame (Ack frame or Block Ack frame) and one A-MPDU and transmitted.  FIG.  36    is a diagram illustrating an embodiment of a method for transmitting a power state according to the Method 1). 
     2) Power state transition information (e.g., information indicating which STAs have transitioned to an awake state (or to a doze state)) is transmitted by being included in the Block Ack frame or Ack frame or the Multi-STA BlockAck frame.  FIG.  37    is a diagram illustrating an embodiment of a method for transmitting a power state according to the Method 2). 
       FIG.  38    is a diagram illustrating an example of a Block Ack frame including power state information. 
     Referring to  FIG.  38   , when the BA Type field includes new Type-related information, the BA Control field includes a power state bitmap, and each bit in the bitmap may indicate the power state of STAs for a link corresponding to each bit. The bit set to 1 may mean that the STA corresponding to the link to the bit set to 1 is in an awake state. 
     Instead of putting the power state link bitmap in the BA Control field, it can be included in the BA Information (e.g., the front part or the last part). 
       FIG.  39    is a diagram illustrating an example of a Block Ack frame including power state information. 
     Referring to  FIG.  39   , at least a part of the Reserved fields of the BA Control field may be used to indicate the size of the power state bitmap. For example, the power state bitmap size field may have a size of 2 bits. If the size of the power state bitmap field can be changed according to definition, an example of this is shown below. 
     Power state bitmap size field (1 bit): 
     0: Indicates that a power state bitmap having a size of 8 bits (1 byte) is included in BA Information 
     1: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     Power state bitmap size field (2 bits): 
     0: Indicates that a power state bitmap having a size of 4 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 12 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     Power state bitmap size field (2 bits): 
     0: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 24 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 32 bits is included in BA Information 
     Power state bitmap size field (3 bit): 
     0: Indicates that a power state bitmap having a size of 4 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 12 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     4: Indicates that a power state bitmap having a size of 20 bits is included in BA Information 
     5: Indicates that a power state bitmap having a size of 24 bits is included in BA Information 
     6: Indicates that a power state bitmap having a size of 28 bits is included in BA Information 
     7: Indicates that a power state bitmap having a size of 32 bits is included in BA Information 
     The above size is an example, and if the bitmap can have different sizes, it can have a different value for each size, and the location can also be located in a different place than the front. 
     The BA Type may be newly defined, the existing BA Type (e.g., Compressed BA, Multi-STA BA, Multi-TID BA, etc.) may be used, and some bits of the Reserved bits of the BA Control field may contain information indicating whether or not the above information is included. 
       FIG.  40    is a diagram illustrating an embodiment of a receiving MLD operation method. 
     Referring to  FIG.  40   , the receiving MLD includes a plurality of stations (STAs), and each STA may operate on different links. 
     The receiving MLD may receive a beacon frame (S4010). For example, the receiving MLD may receive a beacon frame from the transmitting MLD. For example, the beacon frame may include traffic indication map (TIM) information. 
     The receiving MLD may transmit second power state information (S4020). For example, the receiving MLD may transmit to the transmitting MLD a frame including second power state information for a STA that has transitioned from a doze state to an awake state based on the TIM information. 
     The receiving MLD may receive the first PPDU (S4030). For example, the receiving MLD may receive a first physical protocol data unit (PPDU) from the transmitting MLD. 
     For example, the first PPDU may include buffer information related to the amount of data to be transmitted by the transmitting MLD to the receiving MLD. 
     For example, the first PPDU may include buffer information related to an amount of data to be transmitted from the transmitting MLD to the receiving MLD, and the first power state information may be determined based on the buffer information. 
     For example, the first power state information may be included in a BA control subfield of the BA frame, and may include information related to whether STAs operating in each link are in an awake state or a doze state. 
     The receiving MLD may transmit the first power state information (S4040). For example, the receiving MLD transmits a block ACK (acknowledgement) (BA) frame for the first PPDU, and the BA frame may include first power state information for STAs transitioning from a doze state to an awake state. 
     For example, the first power state information may be determined based on the buffer information. 
     For example, the BA frame may further include a size field related to the size of the first power state information. 
     The receiving MLD may receive data (S4050). For example, the receiving MLD may receive the second PPDU from the transmitting MLD through a link related to the first power state information. For example, the second PPDU may include data. 
     The AP MLD may transmit a DL frame to the STA MLD. The DL frame is not limited to a beacon frame or a PPDU including data. When the STA MLD receives a DL frame from the AP MLD, the STA MLD may transmit power state information of STAs included in the STA MLD. The power state information may include information related to whether STAs included in the STA MLD are in a doze state or an awake state. 
     For example, the DL frame may include information requesting power state information of STAs of the STA MLD. In this case, since the STA MLD has been requested for the power state information through the DL frame, the STA MLD may transmit the power state information of the STAs to the AP MLD. 
     For example, the DL frame may include buffer information on the amount of data to be transmitted from the AP MLD to the STA MLD. In this case, the STA MLD may determine STAs to be transitioned from the doze state to the awake state or from the awake state to the doze state based on the buffer information, and may transmit power state information of the STAs to the AP MLD. 
     The above embodiments are examples of information that may be included in the DL frame, and the information included in the DL frame is not limited thereto. 
     When the AP MLD receives the power state information from the STA MLD, the AP MLD may transmit data through at least one link (e.g., the first link and the second link) based on the received power state information. 
     For example, the non-AP MLD that has received the BSR of the non-AP MLD included in the DL frame may determine which STAs to awake and then transmit the awake STA information in the UL data frame. However, since the AP MLD does not know the information of the awake STA of the non-AP MLD until the UL frame is received by the AP MLD, the DL frame transmission may be possible through only one STA. 
     In order to transmit fast power state transition information, when the non-AP MLD transmits an immediate response frame (e.g., acknowledgement/block ACK (ACK/BA)) upon receiving a DL frame including its BSR information, the non-AP MLD, the non-AP MLD can quickly inform the AP MLD by transmitting power state transition information in the corresponding frame. 
     The AP (or AP MLD) may wake up the STA 1  through the TIM. For example, the AP may transmit TIM information to the STA 1 , and the STA 1  may transition to an awake state based on the TIM information. The STA 1  may transmit a PS-Poll including information that the STA 1  is in the awake state to the AP. When the AP transmits the DL frame after receiving the PS-Poll, the DL frame may include BSR information for the non-AP MLD and transmit it. After awake of the STA 2  based on the received BSR, the non-AP MLD of STA 1  may include and transmit information on the awake STA when transmitting a response frame (ACK/BA) for a DL frame. A method in which power state information (i.e., information indicating which STA has transitioned to an awake state (or doze state)) is transmitted together with a response frame may be transmitted using one of the following methods. 
     Method 1): A MAC frame (e.g., QoS data frame or QoS Null frame) including power state transition information (e.g., information indicating which STAs have transitioned to an awake state (or to a doze state))may be aggregated into a response frame (Ack frame or Block Ack frame) and one A-MPDU and transmitted. 
     Method 2): Power state transition information (e.g., information indicating whether certain STAs have transitioned to an awake state (or to a doze state)) is transmitted in a Block Ack frame or Ack frame or a Multi-STA BlockAck frame. 
     When the BA Type field includes new Type-related information, the BA Control field includes a power state bitmap, and each bit in the bitmap may indicate the power state of STAs for a link corresponding to each bit. The bit set to 1 may mean that the STA corresponding to the link to the bit set to 1 is in an awake state. 
     Instead of putting the power state link bitmap in the BA Control field, it can be included in the BA Information (e.g., the front part or the last part). 
     At least a part of the Reserved fields of the BA Control field may be used to indicate the size of the power state bitmap. For example, the power state bitmap size field may have a size of 2 bits. If the size of the power state bitmap field can be changed according to definition, an example of this is shown below. 
     Power state bitmap size field (1 bit): 
     0: Indicates that a power state bitmap having a size of 8 bits (1 byte) is included in BA Information 
     1: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     Power state bitmap size field (2 bits): 
     0: Indicates that a power state bitmap having a size of 4 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 12 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     Power state bitmap size field (2 bits): 
     0: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 24 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 32 bits is included in BA Information 
     Power state bitmap size field (3 bit): 
     0: Indicates that a power state bitmap having a size of 4 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 12 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     4: Indicates that a power state bitmap having a size of 20 bits is included in BA Information 
     5: Indicates that a power state bitmap having a size of 24 bits is included in BA Information 
     6: Indicates that a power state bitmap having a size of 28 bits is included in BA Information 
     7: Indicates that a power state bitmap having a size of 32 bits is included in BA Information 
     The above size is an example, and if the bitmap can have different sizes, it can have a different value for each size, and the location can also be located in a different place than the front. 
     The BA Type may be newly defined, the existing BA Type (e.g., Compressed BA, Multi-STA BA, Multi-TID BA, etc.) may be used, and some bits of the Reserved bits of the BA Control field may contain information indicating whether or not the above information is included. 
       FIG.  41    is a diagram illustrating an embodiment of a method of operating a transmitting STA. 
     Referring to  FIG.  41   , a transmitting MLD includes a plurality of stations (STA), and each STA may operate on a different link. 
     The transmitting MLD may transmit a beacon frame (S4110). For example, the transmitting MLD may transmit a beacon frame to the receiving MLD. For example, the beacon frame may include traffic indication map (TIM) information. 
     The transmitting MLD may receive the second power state information (S4120). For example, the transmitting MLD may receive, from the receiving MLD, a frame including second power state information on the STA that has transitioned from the doze state to the awake state based on the TIM information. 
     The transmitting MLD may transmit the first PPDU (S4130). For example, the transmitting MLD may transmit a first physical protocol data unit (PPDU) to the receiving MLD. 
     For example, the first PPDU may include buffer information related to the amount of data to be transmitted by the transmitting MLD to the receiving MLD. 
     For example, the first PPDU may include buffer information related to an amount of data to be transmitted from the transmitting MLD to the receiving MLD, and the first power state information may be determined based on the buffer information. 
     For example, the first power state information may be included in a BA control subfield of the BA frame, and may include information related to whether STAs operating in each link are in an awake state or a doze state. 
     The transmitting MLD may receive the first power state information (S4140). For example, the transmitting MLD receives a block acknowledgement (BA) frame for the first PPDU, and the BA frame may include first power state information for STAs transitioning from a doze state to an awake state. 
     For example, the first power state information may be determined based on the buffer information. 
     For example, the BA frame may further include a size field related to the size of the first power state information. 
     The transmitting MLD may transmit data (S4150). For example, the transmitting MLD may transmit a second PPDU to the receiving MLD through a link related to the first power state information. For example, the second PPDU may include data. 
     The AP MLD may transmit a DL frame to the STA MLD. The DL frame is not limited to a beacon frame or a PPDU including data. When the STA MLD receives a DL frame from the AP MLD, the STA MLD may transmit power state information of STAs included in the STA MLD. The power state information may include information related to whether STAs included in the STA MLD are in a doze state or an awake state. 
     For example, the DL frame may include information requesting power state information of STAs of the STA MLD. In this case, since the STA MLD has been requested for the power state information through the DL frame, the STA MLD may transmit the power state information of the STAs to the AP MLD. 
     For example, the DL frame may include buffer information on the amount of data to be transmitted from the AP MLD to the STA MLD. In this case, the STA MLD may determine STAs to be transitioned from the doze state to the awake state or from the awake state to the doze state based on the buffer information, and may transmit power state information of the STAs to the AP MLD. 
     The above embodiments are examples of information that may be included in the DL frame, and the information included in the DL frame is not limited thereto. 
     When the AP MLD receives the power state information from the STA MLD, the AP MLD may transmit data through at least one link (e.g., the first link and the second link) based on the received power state information. 
     For example, the non-AP MLD that has received the BSR of the non-AP MLD included in the DL frame may determine which STAs to awake and then transmit the awake STA information in the UL data frame. However, since the AP MLD does not know the information of the awake STA of the non-AP MLD until the UL frame is received by the AP MLD, the DL frame transmission may be possible through only one STA. 
     In order to transmit fast power state transition information, when the non-AP MLD transmits an immediate response frame (e.g., acknowledgement/block ACK (ACK/BA)) upon receiving a DL frame including its BSR information, the non-AP MLD, the non-AP MLD can quickly inform the AP MLD by transmitting power state transition information in the corresponding frame. 
     The AP (or AP MLD) may wake up the STA 1  through the TIM. For example, the AP may transmit TIM information to the STA 1 , and the STA 1  may transition to an awake state based on the TIM information. The STA 1  may transmit a PS-Poll including information that the STA 1  is in the awake state to the AP. When the AP transmits the DL frame after receiving the PS-Poll, the DL frame may include BSR information for the non-AP MLD and transmit it. After awake of the STA 2  based on the received BSR, the non-AP MLD of STA 1  may include and transmit information on the awake STA when transmitting a response frame (ACK/BA) for a DL frame. A method in which power state information (i.e., information indicating which STA has transitioned to an awake state (or doze state)) is transmitted together with a response frame may be transmitted using one of the following methods. 
     Method 1): A MAC frame (e.g., QoS data frame or QoS Null frame) including power state transition information (e.g., information indicating which STAs have transitioned to an awake state (or to a doze state))may be aggregated into a response frame (Ack frame or Block Ack frame) and one A-MPDU and transmitted. 
     Method 2): Power state transition information (e.g., information indicating whether certain STAs have transitioned to an awake state (or to a doze state)) is transmitted in a Block Ack frame or Ack frame or a Multi-STA BlockAck frame. 
     When the BA Type field includes new Type-related information, the BA Control field includes a power state bitmap, and each bit in the bitmap may indicate the power state of STAs for a link corresponding to each bit. The bit set to 1 may mean that the STA corresponding to the link to the bit set to 1 is in an awake state. 
     Instead of putting the power state link bitmap in the BA Control field, it can be included in the BA Information (e.g., the front part or the last part). 
     At least a part of the Reserved fields of the BA Control field may be used to indicate the size of the power state bitmap. For example, the power state bitmap size field may have a size of 2 bits. If the size of the power state bitmap field can be changed according to definition, an example of this is shown below. 
     Power state bitmap size field (1 bit): 
     0: Indicates that a power state bitmap having a size of 8 bits (1 byte) is included in BA Information 
     1: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     Power state bitmap size field (2 bits): 
     0: Indicates that a power state bitmap having a size of 4 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 12 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     Power state bitmap size field (2 bits): 
     0: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 24 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 32 bits is included in BA Information 
     Power state bitmap size field (3 bit): 
     0: Indicates that a power state bitmap having a size of 4 bits is included in BA Information 
     1: Indicates that a power state bitmap having a size of 8 bits is included in BA Information 
     2: Indicates that a power state bitmap having a size of 12 bits is included in BA Information 
     3: Indicates that a power state bitmap having a size of 16 bits is included in BA Information 
     4: Indicates that a power state bitmap having a size of 20 bits is included in BA Information 
     5: Indicates that a power state bitmap having a size of 24 bits is included in BA Information 
     6: Indicates that a power state bitmap having a size of 28 bits is included in BA Information 
     7: Indicates that a power state bitmap having a size of 32 bits is included in BA Information 
     The above size is an example, and if the bitmap can have different sizes, it can have a different value for each size, and the location can also be located in a different place than the front. 
     The BA Type may be newly defined, the existing BA Type (e.g., Compressed BA, Multi-STA BA, Multi-TID BA, etc.) may be used, and some bits of the Reserved bits of the BA Control field may contain information indicating whether or not the above information is included. 
     Some of the detailed steps shown in the example of  FIGS.  40  and  41    may not be essential steps and may be omitted. For example, steps S 4010 , S 4020 , and S 4050  of  FIG.  40    may be omitted. In addition to the steps shown in  FIGS.  40  and  41   , other steps may be added, and the order of the steps may vary. Some of the above steps may have their own technical meaning. 
     The technical features of the present specification described above may be applied to various devices and methods. For example, the above-described technical features of the present specification may be performed/supported through the apparatus of  FIGS.  1  and/or  19   . For example, the technical features of the present specification described above may be applied only to a part of  FIGS.  1  and/or  19   . For example, the technical features of the present specification described above are implemented based on the processing chips  114  and  124  of  FIG.  1   , or implemented based on the processors  111  and  121  and the memories  112  and  122  of  FIG.  1   , or may be implemented based on the processor  610  and the memory  620  of  FIG.  19   . For example, an apparatus of the present specification may be included in a receiving multi-link device (MLD) in a wireless local area network (WLAN) system, the apparatus comprising: wherein the receiving MLD includes a plurality of stations (STAs), each STA operating on different links, wherein the apparatus comprises: a memory; and a processor operatively coupled to the memory, wherein the processor is further configured for: receiving a first physical protocol data unit (PPDU) from a transmitting MLD; and transmitting a block acknowledgment (BA) frame for the first PPDU, wherein the BA frame includes first power state information for STAs transitioning from a doze state to an awake state. 
     Technical features of the present specification may be implemented based on a computer readable medium (CRM). The CRM proposed by the present specification may be at least one computer readable medium (CRM) storing instructions that, based on being executed by at least one processor of a receiving multi-link device (MLD) in a Wireless Local Area Network (WLAN) system, perform operations comprising: wherein the receiving MLD includes a plurality of stations (STAs), each STA operating on different links, receiving a first physical protocol data unit (PPDU) from a transmitting MLD; and transmitting a block acknowledgment (BA) frame for the first PPDU, wherein the BA frame includes first power state information for STAs transitioning from a doze state to an awake state. 
     Instructions stored in a CRM of the present specification may be executed by at least one processor. The at least one processor related to the CRM of the present specification may be the processors  111  and  121  or processing chips  114  and  124  of  FIG.  1    or the processor  610  of  FIG.  19   . Meanwhile, the CRM of the present specification may be the memories  112  and  122  of  FIG.  1    or the memory  620  of  FIG.  19    or a separate external memory/storage medium/disk or the like. 
     The foregoing technical features of this specification are applicable to various applications or business models. For example, the foregoing technical features may be applied for wireless communication of a device supporting artificial intelligence (AI). 
     Artificial intelligence refers to a field of study on artificial intelligence or methodologies for creating artificial intelligence, and machine learning refers to a field of study on methodologies for defining and solving various issues in the area of artificial intelligence. Machine learning is also defined as an algorithm for improving the performance of an operation through steady experiences of the operation. 
     An artificial neural network (ANN) is a model used in machine learning and may refer to an overall problem-solving model that includes artificial neurons (nodes) forming a network by combining synapses. The artificial neural network may be defined by a pattern of connection between neurons of different layers, a learning process of updating a model parameter, and an activation function generating an output value. 
     The artificial neural network may include an input layer, an output layer, and optionally one or more hidden layers. Each layer includes one or more neurons, and the artificial neural network may include synapses that connect neurons. In the artificial neural network, each neuron may output a function value of an activation function of input signals input through a synapse, weights, and deviations. 
     A model parameter refers to a parameter determined through learning and includes a weight of synapse connection and a deviation of a neuron. A hyper-parameter refers to a parameter to be set before learning in a machine learning algorithm and includes a learning rate, the number of iterations, a mini-batch size, and an initialization function. 
     Learning an artificial neural network may be intended to determine a model parameter for minimizing a loss function. The loss function may be used as an index for determining an optimal model parameter in a process of learning the artificial neural network. 
     Machine learning may be classified into supervised learning, unsupervised learning, and reinforcement learning. 
     Supervised learning refers to a method of training an artificial neural network with a label given for training data, wherein the label may indicate a correct answer (or result value) that the artificial neural network needs to infer when the training data is input to the artificial neural network. Unsupervised learning may refer to a method of training an artificial neural network without a label given for training data. Reinforcement learning may refer to a training method for training an agent defined in an environment to choose an action or a sequence of actions to maximize a cumulative reward in each state. 
     Machine learning implemented with a deep neural network (DNN) including a plurality of hidden layers among artificial neural networks is referred to as deep learning, and deep learning is part of machine learning. Hereinafter, machine learning is construed as including deep learning. 
     The foregoing technical features may be applied to wireless communication of a robot. 
     Robots may refer to machinery that automatically process or operate a given task with own ability thereof. In particular, a robot having a function of recognizing an environment and autonomously making a judgment to perform an operation may be referred to as an intelligent robot. 
     Robots may be classified into industrial, medical, household, military robots and the like according uses or fields. A robot may include an actuator or a driver including a motor to perform various physical operations, such as moving a robot joint. In addition, a movable robot may include a wheel, a brake, a propeller, and the like in a driver to run on the ground or fly in the air through the driver. 
     The foregoing technical features may be applied to a device supporting extended reality. 
     Extended reality collectively refers to virtual reality (VR), augmented reality (AR), and mixed reality (MR). VR technology is a computer graphic technology of providing a real-world object and background only in a CG image, AR technology is a computer graphic technology of providing a virtual CG image on a real object image, and MR technology is a computer graphic technology of providing virtual objects mixed and combined with the real world. 
     MR technology is similar to AR technology in that a real object and a virtual object are displayed together. However, a virtual object is used as a supplement to a real object in AR technology, whereas a virtual object and a real object are used as equal statuses in MR technology. 
     XR technology may be applied to a head-mount display (HMD), a head-up display (HUD), a mobile phone, a tablet PC, a laptop computer, a desktop computer, a TV, digital signage, and the like. A device to which XR technology is applied may be referred to as an XR device. 
     The claims recited in the present specification may be combined in a variety of ways. For example, the technical features of the method claims of the present specification may be combined to be implemented as a device, and the technical features of the device claims of the present specification may be combined to be implemented by a method. In addition, the technical characteristics of the method claim of the present specification and the technical characteristics of the device claim may be combined to be implemented as a device, and the technical characteristics of the method claim of the present specification and the technical characteristics of the device claim may be combined to be implemented by a method.