Patent Publication Number: US-2022231788-A1

Title: Repeated transmission of control fields for robust transmission

Description:
BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present specification relates to a method for extended range transmission and robust transmission in a wireless local area network (WLAN) system. 
     Related Art 
     Wireless network technologies may include various types of wireless local area networks (WLAN). WLAN may be used for interconnecting neighboring devices by adopting networking protocols that are extensively used. The various technical features that are described in this specification may be applied to a random communication standard, such as Wi-Fi, or more generally, any one of the IEEE 802.11 wireless protocol group. 
     The present specification either enhances the conventional (or existing) IEEE 802.11p specification or proposes technical characteristics that can be used in a new communication standard. The new communication standard may be a Next Generation V2X (NGV) standard, which is currently being discussed. 
     Meanwhile, in the IEEE standard, various types or formats of Physical Protocol Data Units (PPDUs) are defined. Transmitting and receiving stations (STA) may be configured to use an auto-detection rule to identify the type/format of the PPDU being transmitted and received. 
     SUMMARY OF THE DISCLOSURE 
     Technical Objects 
     A method performed by a station (STA) in a wireless local area network (WLAN) system according to various embodiments is a method of repeatedly transmitting a control field (e.g., an NGV-SIG field) for robust transmission. The STA may generate a next generation V2X (NGV) physical protocol data unit (PPDU). The NGV PPDU may comprise a first legacy control field, a second legacy control field in which the first legacy control field is repeated, a first NGV control field, a second NGV control field in which the first NGV control field is repeated, an NGV short training field (STF), and an NGV long training field (LTF). The second legacy control field is contiguous to the first legacy control field, the first NGV control field is contiguous to the second legacy control field, and the second NGV control field is contiguous to the first NGV control field, the NGV-STF is continuous to the second NGV control field, and the NGV-LTF is continuous to the NGV-STF. The first and second NGV control fields may comprise control information required for interpreting the NGV PPDU. The control information includes 1-bit information related to the NGV-LTF. The STA may transmit the NGV PPDU. 
     According to an example of the present specification, the control field of the NGV PPDU may be repeatedly transmitted. Accordingly, more robust transmission can be performed, and the transmission range can be extended. Since the control field is repeated in the time domain, it is easy to implement the repeated transmission, and a gain can be obtained when a channel changes over time. 
     According to an example of the present specification, power boosting may be applied to the legacy training field when a specific condition is satisfied. Through power boosting, more robust transmission and the effect of extending the transmission distance can be obtained. 
    
    
     
       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  shows an example of various types of PPDUs. 
         FIG. 21  is a diagram for distinguishing between BPSK and QBPSK. 
         FIG. 22  shows a band plan of 5.9 GHz DSRC. 
         FIG. 23  shows a frame format of a frame according to the 802.11p standard. 
         FIGS. 24 to 26  show an embodiment of a PPDU format. 
         FIG. 27  is a diagram illustrating an example of DCM. 
         FIG. 28  shows an example which four extra tones are used in a frame structure. 
         FIGS. 29 and 30  are diagrams illustrating an embodiment of a PPDU format. 
         FIG. 31  is a diagram illustrating an embodiment of a PPDU. 
         FIG. 32  is a flowchart illustrating an embodiment of an operation of a transmitting station. 
         FIG. 33  is a flowchart illustrating an embodiment of an operation of a receiving station. 
         FIG. 34  shows a vehicle or an autonomous driving vehicle applied to the present specification. 
         FIG. 35  shows an example of a vehicle that is applied to the present specification. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     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 mean 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 3 rd  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. 
     In the meantime, the fact that the specific number of RUs can be changed is the same as those of  FIGS. 5 and 6 . 
     The RU arrangement (i.e., RU location) shown in  FIGS. 5 to 7  can be applied to a new wireless LAN system (e.g. EHT system) as it is. Meanwhile, for the 160 MHz band supported by the new WLAN system, the RU arrangement for 80 MHz (i.e., an example of  FIG. 7 ) may be repeated twice, or the RU arrangement for the 40 MHz (i.e., an example of  FIG. 6 ) may be repeated 4 times. In addition, when the EHT PPDU is configured for the 320 MHz band, the arrangement of the RU for 80 MHz (i.e., an example of  FIG. 7 ) may be repeated 4 times or the arrangement of the RU for 40 MHz (i.e., an example of  FIG. 6 ) may be repeated 8 times. 
     One RU of the present specification may be allocated for a single STA (e.g., a single non-AP STA). Alternatively, a plurality of RUs may be allocated for one STA (e.g., a non-AP STA). 
     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 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 (B7 B6 B5 B4 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Number 
               
               
                 B3 B2 B1 B0) 
                 #1 
                 #2 
                 #3 
                 #4 
                 #5 
                 #6 
                 #7 
                 #8 
                 #9 
                 of 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 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 (B7 B6 B5 B4 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Number 
               
               
                 B3 B2 B1 B0) 
                 #1 
                 #2 
                 #3 
                 #4 
                 #5 
                 #6 
                 #7 
                 #8 
                 #9 
                 of 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 
               
               
                   
                 0100-0110 
                 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 
                   
                   
                   
                   
                   
                 7-8 
               
               
                   
                 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 
                 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 STA1 is decreased to 0, and the STA1 randomly selects the 2nd RU resource (AID 0, RU 2). In addition, since an OBO counter of a STA2/3 is greater than 0, an uplink resource is not allocated to the STA2/3. In addition, regarding a STA4 in  FIG. 14 , since an AID (e.g., AID=3) of the STA4 is included in a trigger frame, a resource of the RU 6 is allocated without backoff. 
     Specifically, since the STA1 of  FIG. 14  is an associated STA, the total number of eligible RA RUs for the STA1 is 3 (RU 1, RU 2, and RU 3), and thus the STA1 decreases an OBO counter by 3 so that the OBO counter becomes 0. In addition, since the STA2 of  FIG. 14  is an associated STA, the total number of eligible RA RUs for the STA2 is 3 (RU 1, RU 2, and RU 3), and thus the STA2 decreases the OBO counter by 3 but the OBO counter is greater than 0. In addition, since the STA3 of  FIG. 14  is an un-associated STA, the total number of eligible RA RUs for the STA3 is 2 (RU 4, RU 5), and thus the STA3 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 UNII Low. The UNII-2 may include a frequency domain called UNII 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  1800  depicted in  FIG. 18  may be referred to as various terms such as an EHT PPDU, a TX PPDU, an 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 subfields  1801  to  1810  depicted in  FIG. 18  may be referred to as various terms. For example, a SIG A field  1805  may be referred to an EHT-SIG-A field, a SIG B field  1806  may be referred to an EHT-SIG-B, a STF field  1807  may be referred to an EHT-STF field, and an LTF field  1808  may be referred to an EHT-LTF. 
     The subcarrier spacing of the L-LTF, L-STF, L-SIG, and RL-SIG fields  1801 ,  1802 ,  1803 , and  1804  of  FIG. 18  can be set to 312.5 kHz, and the subcarrier spacing of the STF, LTF, and Data fields  1807 ,  1808 , and  1809  of  FIG. 18  can be set to 78.125 kHz. That is, the subcarrier index of the L-LTF, L-STF, L-SIG, and RL-SIG fields  1801 ,  1802 ,  1803 , and  1804  can be expressed in unit of 312.5 kHz, and the subcarrier index of the STF, LTF, and Data fields  1807 ,  1808 , and  1809  can be expressed in unit of 78.125 kHz. 
     The SIG A and/or SIG B fields of  FIG. 18  may include additional fields (e.g., a SIG C field or one control symbol, etc.). The subcarrier spacing of all or part of the SIG A and SIG B fields may be set to 312.5 kHz, and the subcarrier spacing of all or part of newly-defined SIG field(s) may be set to 312.5 kHz. Meanwhile, the subcarrier spacing for a part of the newly-defined SIG field(s) may be set to a pre-defined value (e.g., 312.5 kHz or 78.125 kHz). 
     In the PPDU of  FIG. 18 , the L-LTF and the L-STF may be the same as conventional L-LTF and L-STF 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 the number of octets of a corresponding Physical Service Data Unit (PSDU). 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 which is identical to the L-SIG. BPSK modulation may be applied to the RL-SIG. The receiving STA may figure out that the RX PPDU is the HE PPDU or the EHT PPDU, based on the presence of the RL-SIG. 
     After RL-SIG of  FIG. 18 , for example, an EHT-SIG-A or one control symbol may be inserted. A symbol located after the RL-SIG (i.e., the EHT-SIG-A or one control symbol in the present specification) may be referred as various names, such as a U-SIG (Universal SIG) field. 
     A symbol consecutive to the RL-SIG (e.g., U-SIG) may include information of N bits, and may include information for identifying the type of the EHT PPDU. For example, the U-SIG may be configured based on two symbols (e.g., two consecutive OFDM symbols). Each symbol (e.g., OFDM symbol) for U-SIG may have a duration of 4 us. Each symbol of the U-SIG may be used to transmit 26-bit information. For example, each symbol of the U-SIG may be transmitted/received based on 52 data tones and 4 pilot tones. 
     Through the U-SIG (or U-SIG field), for example, A-bit information (e.g., 52 un-coded bits) may be transmitted. 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-SIG 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 classified into various types (e.g., EHT PPDU supporting SU, EHT PPDU supporting MU, EHT PPDU related to Trigger Frame, EHT PPDU related to Extended Range transmission, etc.), information related to the type of the EHT PPDU may be included in version-independent bits or version-dependent bits of the U-SIG. 
     For example, the U-SIG field includes 1) a bandwidth field including information related to a bandwidth, 2) a field including information related an MCS scheme applied to the SIG-B, 3) a dual subcarrier modulation in the SIG-B (i.e., an indication field including information related to whether the dual subcarrier modulation) is applied, 4) a field including information related to the number of symbols used for the SIG-B, 5) a field including information on whether the SIG-B is generated over the entire band, 6) a field including information related to a type of the LTF/STF, and/or  7 ) information related to a field indicating a length of the LTF and the CP. 
     The SIG-B of  FIG. 18  may include the technical features of HE-SIG-B shown in the example of  FIGS. 8 to 9  as it is. 
     An STF of  FIG. 18  may be used to improve automatic gain control estimation in a multiple input multiple output (MIMO) environment or an OFDMA environment. An LTF of  FIG. 18  may be used to estimate 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×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 0.8 μs, and a periodicity signal of 0.8 us 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 1.6 μs, and a periodicity signal of 1.6 us may be repeated 5 times to become a second type STF having a length of 8 μs. For example, a third type of STF (e.g., 4×STF) may be generated based on a third type STF sequence in which a non-zero coefficient is arranged with an interval of 4 subcarriers. An STF signal generated based on the third type STF sequence may have a period of 3.2 us, and a periodicity signal of 3.2 us may be repeated 5 times to become a second type STF having a length of 16 us. Only some of the first to third type EHT-STF sequences may be used. In addition, the EHT-LTF field may also have first, second, and third types (i.e., 1×, 2×, 4×LTF). For example, the first/second/third type LTF field 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, Guard Intervals (GIs) with various lengths (e.g., 0.8/1/6/3.2 μs) may be applied to the first/second/third type LTF. 
     Information related to the type of STF and/or LTF (including information related to GI applied to the LTF) may be included in the SIG A field and/or the SIG B field of  FIG. 18 . 
     The PPDU of  FIG. 18  may support various bandwidths. For example, the PPDU of  FIG. 18  may have a bandwidth of 20/40/80/160/240/320 MHz. For example, at least one field (e.g., STF, LTF, data) of  FIG. 18  may be configured based on RUs illustrated in  FIGS. 5 to 7 , and the like. For example, when there is one receiving STA of the PPDU of  FIG. 18 , all fields of the PPDU of  FIG. 18  may occupy the entire bandwidth. For example, when there are multiple receiving STAs of the PPDU of  FIG. 18  (i.e., when MU PPDU is used), some fields (e.g., STF, LTF, data) of  FIG. 18  may be configured based on the RUs shown in  FIGS. 5 to 7 . For example, the STF, LTF, and data fields for the first receiving STA of the PPDU may be transmitted/received through a first RU, and the STF, LTF, and data fields for the second receiving STA of the PPDU may be transmitted/received through a second RU. In this case, the locations/positions of the first and second RUs may be determined based on  FIGS. 5 to 7 , and the like. 
     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 “module 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 “module 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 . 
       FIG. 20  shows an example of various types of PPDUs. 
     As shown in  FIG. 20 , examples of the type (i.e., format) of the PPDU used in the WLAN system include non-HT, HT, VHT, HE PPDU, and the like. Specifically, the illustrated first type PPDU  2010  is a non-HT PPDU defined in the IEEE 802.11a standard, and the illustrated second type PPDU  2020  and the third type PPDU  2030  are an HT PPDU defined in the IEEE 802.11n standard. In addition, the illustrated fourth type PPDU  2040  is a VHT PPDU defined in the IEEE 802.11ac standard, and the illustrated fifth type PPDU  2050  and the sixth type PPDU  2060  are HE PPDUs defined in the IEEE 802.11ax standard. 
     All types of PPDUs  2010 ,  2020 ,  2030 ,  2040 ,  2050 , and  2060  shown in  FIG. 20  may include L-STF and L-LTF fields. Each of the L-STF and L-LTF fields may be transmitted over two symbols (e.g., OFDM symbols). That is, each of the L-STF and L-LTF fields may have a transmission time of 8 μs. 
     All types of PPDUs  2010 ,  2020 ,  2030 ,  2040 ,  2050 , and  2060  shown in  FIG. 20  may include an L-SIG field or an HT-SIG1 field being continuous to the L-LTF field. The L-SIG field or the HT-SIG1 field shown in  FIG. 20  may be transmitted through one symbol. 
     As shown in  FIG. 20 , the HT-SIG1 field of the third type PPDU  2030  may be modulated based on a quadrature binary phase shift keying (QBPSK) constellation. The QBPSK constellation may be a constellation rotated by 90 degrees counterclockwise based on the BPSK constellation. 
       FIG. 21  is a diagram for distinguishing between BPSK and QBPSK. As shown, the QBPSK constellation may be a constellation rotated by 90 degrees counterclockwise based on the BPSK constellation. 
     Since QBPSK is applied to the HT-SIG1 field of the third type PPDU  2030  of  FIG. 20 , the receiving STA can identify that the received PPDU is a third type PPDU when QBPSK is applied to symbols received after the L-LTF field. In addition, when BPSK is applied to symbols received after the L-LTF field, the receiving STA may identify that the received PPDU is any one of the first, second, fourth, fifth, and sixth types of PPDUs. 
     The fifth and sixth types of PPDUs may be identified/detected by the receiving STA based on the following example. The fifth and sixth types of PPDUs may include a repeated L-SIG (RL-SIG) in which the L-SIG field is repeated. The RL-SIG is contiguous to the L-SIG field. Also, in the fifth and sixth types of PPDUs, three SIG fields should be present after the L-SIG field. The receiving STA may identify that the received PPDU is the fifth and sixth type PPDU when the L-SIG is repeated in the symbol being consecutive to the L-SIG field and there are three SIG fields after the L-SIG field. 
     In the fifth type PPDU  2050 , the BPSK can be applied to the third SIG field after the L-SIG field. Also, in the sixth type PPDU  2060 , the QBPSK can be applied to the third SIG field after the L-SIG field. Accordingly, the receiving STA may distinguish the fifth and sixth types of PPDUs from each other based on whether the constellation applied to the third SIG field after the L-SIG field is BPSK or QPBSK. 
     In addition, in the fourth type PPDU, the L-SIG is not repeated in the field being continuous to the L-SIG field, the BPSK is applied to the first symbol being consecutive to the L-SIG, and the QBPSK is applied to the second symbol being consecutive to the first symbol. Accordingly, the receiving STA may identify the fourth type PPDU based on whether the QBPSK is applied to the second symbol (and/or whether the L-SIG field is repeated). 
     In addition, since the QBPSK is applied to two symbols being consecutive to the L-SIG for the second type PPDU, the receiving STA can identify/detect the second type PPDU from other types of PPDUs. In addition, as described above, since all PPDUs of second type to sixth type have distinguishable characteristics, if PPDUs not identified/detected as PPDUs of the second type to the sixth type can be identified/detected as a PPDU having the first type. 
     The specific order of the above-described identification/detection method may be changed. That is, when the number/constellation of symbols after L-LTF is uniquely configured as shown in  FIG. 20 , the receiving STA can accurately identify the type of the received PPDU through various methods. 
       FIG. 22  shows a band plan of 5.9 GHz DSRC. 
     The 5.9 GHz DSRC is a short-to-medium-range communication service that supports both public safety and private operations in roadside vehicle and vehicle-to-vehicle communication environments. The DSRC is intended to complement cellular communication by providing very high data rates in situations where it is important to minimize the latency of the communication link and separate relatively small communication areas. Further, the PHY and MAC protocols are based on the IEEE 802.11p amendments for wireless access in the vehicle environment (WAVE). 
     &lt;IEEE 802.11p&gt; 
     The 802.11p technology uses 802.11a&#39;s PHY with 2× down clocking. That is, the signal is transmitted using 10 MHz bandwidth instead of 20 MHz bandwidth. The numerology comparing 802.11a and 802.11p is as follows. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                   
                 IEEE 802.11a 
                 IEEE 802.11p 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Symbol duration 
                 4 
                 us 
                 8 
                 us 
               
               
                   
                 Guard period 
                 0.8 
                 us 
                 1.6 
                 us 
               
               
                   
                 Subcarrier spacing 
                 312.5 
                 KHz 
                 156.25 
                 KHz 
               
            
           
           
               
               
               
               
            
               
                   
                 OFDM subcarrier 
                 52 
                 52 
               
               
                   
                 Number of pilot 
                  4 
                  4 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Default BW 
                 20 
                 MHz 
                 10 
                 MHz 
               
            
           
           
               
               
               
               
            
               
                   
                 Data rate (Mbps) 
                 6, 9, 12, 18, 24, 
                 3, 4.5, 6, 9, 12, 
               
               
                   
                   
                 36, 48, 54 Mbps 
                 18, 24, 27 Mbps 
               
               
                   
                 Frequency band 
                 5 GHz ISM 
                 5.9 GHz dedicated 
               
               
                   
                   
               
            
           
         
       
     
     The DSRC band includes a control channel and a service channel, and data transmissions of 3, 4.5, 6, 9, 12, 18, 24, and 27 Mbps are available through each of the channels. In the case that the DSRC band includes an optional channel of 20 MHz, transmissions of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps are available. Transmissions of 6, 9, 12 Mbps need to be supported for all services and channels. In the case of the control channel, a preamble has 3 Mbps, but a message itself has 6 Mbps. Channels 174 and 176 and channels 180 and 182 become channels 175 and 181 of 20 MHz, respectively, in the case that the channels are approved by a frequency regulation organization. The remainder is left for future use. Through the control channel, a short message, an alarm data, and a public safety warning data are broadcasted to all OBUs (On Board Units). The reason for separation of the control from the service channel is for efficiency, and to maximize a service quality and to reduce interference between service. 
     Channel 178 is the control channel, and all OBUs automatically search the control channel and receive an alarm, a data transmission, and a warning message from an RSU (Road Side Unit). All data of the control channel need to be transmitted within 200 ms and are repeated in a predefined period. In the control channel, the public safety data is prior to all private messages. The private message greater than 200 ms is transmitted through the service channel. 
     Through the service channel, a private message or a long public safety message is transmitted. To prevent a collision, the technique of detecting a channel state before a transmission (Carrier Sense Multiple Access: CSMA) is used. 
       FIG. 23  shows a frame format of a frame according to the 802.11p standard. 
     Referring to  FIG. 23 , a frame (or packet) according to the 802.11p standard (hereinafter, an 11p frame  2300 ) may support inter-vehicle communication in a 5.9 GHz band. The 11p frame  2300  may include an STF  2310  for sync and Automatic Gain Control (AGC), an LTF  2300  for channel estimation, and/or a signal field (or SIG field)  2330  including information related to the data field  2340 . The data field  2340  may be configured including 16 bits constituting the service field. 
     The 11p frame  2300  may be configured by applying the same OFDM numerology as the 802.11a standard for a 10 MHz bandwidth. For example, the 802.11p standard can be applied by 2× down clocking OFDM numerology for a 20 MHz bandwidth according to the 802.11a standard. Accordingly, the symbol of the 11p frame  2300  may be set longer than the symbol of the frame according to the 802.11a standard. The symbol of the 11p frame  2300  may have a symbol duration of 8 μs. The 11p frame  2300  may have a length twice that of a frame according to the 802.11a standard in terms of time. 
       FIG. 24  shows an embodiment of a PPDU format. 
     Referring to  FIG. 24 , the PPDU  2400  may be configured in a 10 MHz bandwidth. For example, the PPDU  2400  may be a frame being configured based on the IEEE802.11bd standard. For backward compatibility and/or interoperability with the IEEE802.11p standard using the 5.9 GHz band, the PPDU  2400  may include a preamble part of the IEEE802.11p frame. For example, the PPDU  2400  may include an L-STF  2410 , an L-LTF  2420 , or an L-SIG (or L-SIG field)  2430 . Following the L-SIG  2430 , the PPDU  2400  may include NGV-SIG (or NGV-SIG field)  2440 , NGV-STF  2450 , NGV-LTF  2460 , and NGV Data (or NGV-Data field) including control information for NGV  2470 . 
     The NGV-SIG  2440  may be related to transmission information. For example, the NGV-SIG  2440  may include transmission information. For example, the NGV-SIG  2440  may include information related to bandwidth, MCS, Nss, Midamble periodicity, LDPC Extra symbol, LTF format, or tail bit. BCC encoding with a coding rate of 1/2 may be applied to the NGV-SIG  2440 . 
     The NGV-STF  2450  may be configured by 2× downclocking a 20 MHz VHT-STF being configured based on the IEEE802.11ac standard. The NGV-LTF  2460  may be configured by 2× downclocking a 20 MHz VHT-LTF being configured based on the IEEE802.11ac standard. When only a single stream is supported, since automatic gain control (AGC) does not need to be performed, the NGV-STF  2450  may be omitted. 
       FIGS. 25 and 26  are diagrams illustrating an embodiment of a PPDU format. 
     As shown in  FIGS. 25 and 26 , PPDUs  2500  and  2600  may include L-STF, L-LTF, L-SIG, RL-SIG, NGV-STF, NGV-LTF, and NGV-data fields. For example, the PPDUs  2500  and  2600  may be 11bd frames supporting IEEE802.11bd. 
     The PPDU  2500  of  FIG. 25  may be configured for a 10 MHz bandwidth. The PPDU  2600  of  FIG. 26  may be configured for a 20 MHz bandwidth. The PPDUs  2500  and  2600  may be configured to operate in a 5.9 GHz Intelligent Transportation Systems (ITS) band to be interoperable with the IEEE802.11p standard. 
     A device (or an apparatus) supporting the IEEE802.11bd standard (hereinafter referred to as an 11bd device) may determine whether there is a device supporting the IEEE802.11p standard (hereinafter referred to as an 11p device) in the vicinity through preamble detection, probe request/response, or transmission/reception of a CTS/RTS signal. An 11bd device may transmit an 11bd frame (or an 11bd PPDU) when there is no 11p device nearby. In other words, the 11bd device may transmit an 11bd frame (or an 11bd PPDU) based on the presence or absence of an 11p device around the 11bd device. The 11bd device may transmit the PPDUs  2500  and  2600  shown in  FIGS. 25 and/or 26  in order to reduce the effect on the hidden node. 
     The PPDUs  2500  and  2600  may include an RL-SIG contiguous to the L-SIG for robust transmission. The RL-SIG can be a repeated field of the L-SIG, and it can be the same field as the L-SIG. The RL-SIG can be continuous to the L-SIG in the time domain. 
     The NGV-LTF can be configured based on at least one LTF format. For example, NGV-LTF can be configured based on one of NGV-LTF-1× format, NGV-LTF-2× format, or repeated NGV-LTF-2× format. Information related to the LTF format used for the NGV-LTF can be included in the NGV-SIG. 
     For example, the NGV-LTF-2× format may be set as the default format. As another example, the NGV-LTF-1× format may be used for high-efficiency transmission of one spatial stream. As yet another example, the repeated NGV-LTF-2× format may be used for extended range transmissions. The repeated NGV-LTF-2× format may be configured by repeating the NGV-LTF-2× format from which 1.6 μs of one pre-appended cyclic prefix (CP) and guard interval (GI) are excluded. The repeated NGV-LTF-2× format may be used when dual carrier modulation (DCM) and BPSK modulation are applied to the NGV data. For example, when the DCM and BPSK modulation are applied to the NGV data, regardless of the information related to the LTF format included in the NGV-SIG, the repeated NGV-LTF-2× format may be used in/applied to the NGV-LTF. 
     For example, in the 10 MHz transmission, a sequence of the NGV-LTF-1× format may be configured as shown below in Equation 1. 
         NGV - LTF -1× sequence={1,0,1,0,−1,0,1,0,−1,0,−1,0,1,0,1,0,1,0,−1,0,1,0,1,0,1,0,1,0,0,0,−1,0,1,0,−1,0,−1,0,−1,0,−1,0,−1,0,1,0,−1,0,−1,0,−1,0,1,0,1,0,−1}  [Equation 1]
 
     For example, in the 10 MHz transmission, a sequence of the NGV-LTF-2× format may be configured as shown below in Equation 2. 
         NGV - LTF -2× sequence={1,1, LTF   left ,0, LTF   right ,−1,−1}  [Equation 2]
 
     Referring to Equation 2, LTF_left and LTF_right may be configured as shown below in Equation 3. 
         LTF   left ={1,1,−1,−1,1,1,−1,1,−1,1,1,1,1,1,1,−1,−1,1,1,−1,1,1,1,1}
 
         LTF   right ={1,−1,−1,1,1,−1,1,−1,1,−1,−1,−1,−1,−1,1,1,−1,−1,1,−1,1,−1,1,1,1,}  [Equation 3]
 
     For example, in the 20 MHz transmission, a sequence of the NGV-LTF-1× format may be set as shown in Equation (4). 
         NGV - LTF -1× sequence={1,0,−1,0,1,0,−1,0,−1,0,1.0,1,0,1,0,−1,0,1,0,1,0,1,0,1,0,1,0,−1,0,−1,0,−1,0,−1,0,−1,0,−1,0,−1,0,1,0,−1,0,−1,0,−1,0,1,0,1,0,−1,0,1,0,0,0,−1,0,1,0,1,0,−1,0,1,0,−1,0,−1,0,1,0,1,0,1,0, −1,0,1,0,1,0,1,0,1,0,1,0,−1,0,1,0,−1,0,−1,0,−1,0,−1,0,−1,0,1,0,−1,0,−1,0,−1,0,1,0,1}  [Equation 4]
 
     For example, in the 20 MHz transmission, a sequence of the NGV-LTF-2× format may be set as in Equation 5. 
         NGV - LTF -2× sequence={ LTF   left ,1, LTF   right ,−1,−1,−,1,0,0,0,−1,1,1,−1, LTF   left ,1, LTF   right }  [Equation 5]
 
     In Equation 5, LTF_left and LTF_right may refer to Equation 3. 
     NGV data may include a service field, PHY pad bits, and/or PSDU. 
     The NGV-SIG may be transmitted in the following method for robust transmission. 
     For example, for robust transmission of the NGV-SIG, dual carrier modulation (DCM) may be applied to the NGV-SIG. For example, a same symbol to be modulated in the frequency domain may be repeatedly mapped to subcarriers with different constellation mapping schemes.  FIG. 27  is a diagram illustrating an example of the DCM. Referring to  FIG. 27 , the same (original) signal may be mapped to different subcarriers based on the DCM. 
     For example, for robust transmission of the NGV-SIG, the NGV-SIG signal may be transmitted based on 2-tone intervals in the frequency domain without using the DCM. For example, a tone carrying a signal and a null tone not carrying a signal may be alternately mapped. When the signal of NGV-SIG is transmitted at 2-tone intervals, two repeated time sequences can be generated in one symbol. Thus, the NGV-SIG can be transmitted robustly. 
     The receiving STA may receive the NGV-SIG, and may improve reception performance by combining the repeated NGV-SIG in the frequency/time domain. 
     The NGV-SIG can use the same number of available tones as the L-SIG. That is, the NGV-SIG may be transmitted through 48 subcarriers. When the NGV-SIG is transmitted through 48 subcarriers (e.g., excluding 4 pilots from 52 available subcarriers), the NGV-SIG field may be configured as shown in Table 6. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 Contents 
                 Bits 
               
               
                   
                   
               
             
            
               
                   
                 BW 
                 1 bit 
               
               
                   
                 MCS 
                 4 bit 
               
               
                   
                 Tail bit 
                 6 bit 
               
               
                   
                 Parity bit 
                 1 bit 
               
               
                   
                 Total 
                 12 bit  
               
               
                   
                   
               
            
           
         
       
     
     For example, the NGV-SIG field may include 12-bit information including a bandwidth (BW) field, a modulation and coding scheme (MCS) field, a tail bit field, and a parity bit field. The BW field may have a size of 1 bit, the MCS field may have a size of 4 bits, the Tail Bit field may have a size of 6 bits, and the Parity bit field may have a size of 1 bit. The MCS field may include information related to modulation and information related to a code rate. The MCS field may not include information related to a type of channel coding (e.g., low density parity check (LDPC) and/or binary convolutional coding (BCC)). 
     To transmit more information in the NGV-SIG field, four extra tones of L-SIG and RL-SIG may be used. The four extra tones in each of the L-SIG and RL-SIG may be used for channel estimation. If four extra tones in each of the L-SIG and RL-SIG are used, four extra tones of NGV-SIG field may also be used. For example, the four extra tones of the NGV-SIG may include control information. For example, the frame structure in the case where the four extra tones are used may be as shown in  FIG. 28 . 
     Referring to  FIG. 28 , the NGV-SIG may further include 2-bit information. That is, the NGV-SIG may be transmitted using four more subcarriers. For example, four extra tones (e.g., subcarrier indices 27, 28, −27, −28) may be further used. For example, in general, 48 subcarriers (i.e., excluding 4 pilot subcarriers from a total of 52 available subcarriers ranging from subcarrier index −26 to subcarrier index 26) may be used. For example, if the four extra tones are used, 52 subcarriers excluding the 4 pilot subcarriers from a total of 56 available subcarriers (i.e., ranging from subcarrier index −28 to subcarrier index 28) may be used. If the NGV-SIG is configured based on the DCM or the method of transmitting a signal at 2-tone intervals described above, the NGV-SIG may include 1 additional bit compared to the 12 bits shown in Table 6. When using the four extra tones, the NGV-SIG may be configured as shown in Table 7 to Table 10. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 Contents 
                 Bits 
               
               
                   
                   
               
             
            
               
                   
                 BW 
                 1 bit 
               
               
                   
                 MCS 
                 4 bit 
               
               
                   
                 LTF type 
                 1 bit 
               
               
                   
                 Parity bit 
                 1 bit 
               
               
                   
                 Tail bit 
                 6 bit 
               
               
                   
                 Total 
                 13 bit  
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
               
                   
                 Contents 
                 Bits 
               
               
                   
                   
               
             
            
               
                   
                 BW 
                 1 bit 
               
               
                   
                 MCS 
                 4 bit 
               
               
                   
                 Midamble period 
                 1 bit 
               
               
                   
                 Parity bit 
                 1 bit 
               
               
                   
                 Tail bit 
                 6 bit 
               
               
                   
                 Total 
                 13 bit  
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 9 
               
               
                   
                   
               
               
                   
                 Contents 
                 Bits 
               
               
                   
                   
               
             
            
               
                   
                 BW 
                 1 bit 
               
               
                   
                 MCS 
                 4 bit 
               
               
                   
                 Tail bit 
                 6 bit 
               
               
                   
                 CRC 
                 2 bit 
               
               
                   
                 Total 
                 13 bit  
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 10 
               
               
                   
                   
               
               
                   
                 Contents 
                 Bits 
               
               
                   
                   
               
             
            
               
                   
                 BW 
                 1 bit 
               
               
                   
                 MCS 
                 4 bit 
               
               
                   
                 Reserved bit 
                 1 bit 
               
               
                   
                 Parity bit 
                 1 bit 
               
               
                   
                 Tail bit 
                 6 bit 
               
               
                   
                 Total 
                 13 bit  
               
               
                   
                   
               
            
           
         
       
     
     Referring to Table 7, the NGV-SIG may include BW, the MCS, LTF type (type), Parity bit, and Tail bit fields. The BW field may include 1-bit information, the MCS field may include 4-bit information, the LTF type field may include 1-bit information, the Parity bit field may include 1-bit information, the Tail bit field may include 6-bit information, and the NGV-SIG may include 13-bit information. 
     Referring to Table 8, the NGV-SIG may include the BW, MCS, midamble period, Parity bit, and Tail bit fields. The BW field may include 1-bit information, the MCS field may include 4-bit information, the midamble period field may include 1-bit information, the Parity bit field may include 1-bit information, the Tail bit field may include 6-bit information, and the NGV-SIG may include 13-bit information. The midamble may denote a channel estimation field (e.g., LTF) inserted in the middle of the data field. 
     Referring to Table 9, the NGV-SIG may include the BW, MCS, Tail bit, and CRC fields. The BW field may include 1-bit information, the MCS field may include 4-bit information, the Tail bit field may include 6-bit information, and the CRC field may include 2-bit information, and the NGV-SIG may include 13-bit information. The midamble may denote a channel estimation field (e.g., LTF) inserted in the middle of the data field. In order to increase reliability of the control field (i.e., the NGV-SIG field), the NGV-SIG may include a 2-bit CRC field instead of a 1-bit Parity bit field. 
     Referring to Table 10, the NGV-SIG may include the BW, MCS, reserved field (or reserved bit), parity bit, and tail bit fields. The BW field may include 1-bit information, the MCS field may include 4-bit information, the spare field may include 1-bit information, the Parity bit field may include 1-bit information, the Tail bit field may include 6-bit information, and the NGV-SIG may include 13-bit information. A SIG field with 1 bit reserved for future extension can be configured. For example, the 1 bit may be reserved for a spare field in consideration of further extension of the SIG field. 
       FIGS. 29 and 30  are diagrams illustrating an embodiment of a PPDU format. 
     Referring to  FIGS. 29 and 30 , the NGV-SIG field can be 24-bit information or 26-bit information. For example, when four extra tones are used, the NGV-SIG may include information having a length of 26 bits. When the extra 4 tones are not used, the NGV-SIG may include information having a length of 24 bits. The NGV-SIG field may include control information required to interpret the NGV PPDU. 
     The PPDU  2900  of  FIG. 29  may be configured for a 10 MHz bandwidth. The PPDU  3000  of  FIG. 30  may be configured for a 20 MHz bandwidth. The PPDU may be configured to operate in a 5.9 GHz Intelligent Transportation Systems (ITS) band to be interoperable with the IEEE802.11p standard. 
     The NGV-SIG field may include a 1-bit BW field. For example, the BW field may include 1-bit information related to whether the bandwidth is 10 MHz or 20 MHz. 
     The NGV-SIG field may include a 4-bit MCS field. For example, the MCS field may include information related to modulation and information related to a code rate. For example, the MCS field may not include information related to a type of channel coding (e.g., low density parity check (LDPC) and/or binary convolutional coding (BCC)). For example, code rate information included in the MCS field may or may not include whether the DCM is applied. 
     The NGV-SIG field may include a 1-bit LTF size field. The LTF size field may be a field related to NGV-LTF. For example, the LTF size field may include information related to whether the NGV-LTF is configured based on the NGV-LTF-2× format or the NGV-LTF-1× format. 
     The NGV-SIG field may include a 1-bit midamble periodicity field. The midamble period field may include information related to how many symbols the midamble is repeated/inserted. 
     The NGV-SIG field may include a 1-bit coding field. The coding field may include information related to whether the BCC scheme or the LDPC scheme is used for channel coding. 
     The NGV-SIG field may include an LDPC extra symbol field having a length of 1 bit. 
     The NGV-SIG field may include a spatial-time-stream (NSTS) field having a length of 1 bit. For example, the NSTS field may include information related to an NSTS or a number of spatial stream (NSS). That is, the NSTS field may include information related to the number of streams. 
     The NGV-SIG field may include a 1-bit STBC field, a 1-bit DCM field, a 4-bit CRC field, and a 6-bit tail bit field. 
     In addition, the NGV-SIG field may include a field including other information. The NGV-SIG field may include all or part of the fields described above. 
     The PPDUs  2900  and  3000  may include the L-STF, L-LTF, L-SIG, RL-SIG, NGV-SIG, RNGV-SIG, NGV-STF, NGV-LTF, and NGV-data. The L-LTF may be contiguous to L-STF, the L-SIG may be contiguous to the L-SIG, the RL-SIG may be contiguous to the L-SIG, and the NGV-SIG may be contiguous to the RL-SIG, the RNGV-SIG may be contiguous to the NGV-SIG, the NGV-STF may be contiguous to the RNGV-SIG, the NGV-LTF may be contiguous to the NGV-STF, and the NGV-data may be contiguous to the NGV-LTF. 
     The PPDUs  2900  and  3000  may include an RL-SIG being contiguous to the L-SIG for robust transmission. The RL-SIG can be a repeated field of the L-SIG, and may be the same field as the L-SIG. The RL-SIG can be continuous to the L-SIG in the time domain. The L-SIG and RL-SIG may include control information. 
     The NGV-SIG may be configured as one symbol (8 μs). For robust transmission and/or range extension transmission, the NGV-SIG symbol may be repeatedly transmitted once more (i.e., the RNGV-SIG symbol is transmitted). Alternatively, for example, the DCM may be applied to NGV-SIG to transmit two symbols. 
     The RNGV-SIG is a repeated field of the NGV-SIG, and may be the same field as the NGV-SIG. The RNGV-SIG can be continuous to the NGV-SIG in the time domain. 
     For example, the same encoding, interleaving, and modulation can be applied to both the NGV-SIG and the RNGV-SIG. That is, the RNGV-SIG may be configured in the same manner as the NGV-SIG. That is, in the RNGV-SIG, the same field as the NGV-SIG may be repeated. 
     For example, the RNGV-SIG may have the same encoding and modulation applied to the NGV-SIG, but may bypass the interleaver. That is, in the RNGV-SIG, modulation may be performed without using an interleaver after encoding. 
     The NGV-SIG may be repeated in units of symbols. That is, after the NGV-SIG symbol is transmitted, the RNGV-SIG symbol may be transmitted. Accordingly, the receiving STA may perform decoding of the NGV-SIG and the RNGV-SIG in units of symbols. The receiving STA may improve the performance of the NGV-SIG through aggregation using the NGV SIG and the RNGV-SIG (e.g., repeated NGV-SIG). As a result, the effect of the range extension can be obtained. For example, the receiving STA may combine the NGV-SIG and the RNGV-SIG, and may obtain a gain through the repeated reception of the control field. 
     As in the RL-SIG, the NGV-SIG may not require a separate indication because the same symbol can be repeatedly transmitted. Accordingly, an effect of reducing signaling overhead can be obtained. Since the L-SIG symbol is also repeatedly transmitted and the NGV-SIG symbol is also repeatedly transmitted, consistency can be maintained, thereby facilitating implementation. 
     Since the NGV-SIG is repeated in the time domain, it is possible to obtain an effect of increasing a gain in an environment in which a channel change is large. The NGV-SIG symbol has a length of 8 μs and may have a GI (guard interval) of 1.6 μs, so that the inter-symbol interference (e.g., delay spread) can be reduced compared to the case where the symbol length is 4 μs with a GI having a 0.8 μs symbol length. 
     As another example, the encoded NGV-SIG may be divided into two symbols and transmitted by applying DCM. The receiving STA (e.g., NGV device) may perform decoding in units of two symbols when receiving NGV-SIG. 
       FIG. 31  is a diagram illustrating an embodiment of a PPDU. 
     Referring to  FIG. 31 , the PPDU may be configured in a 10 MHz bandwidth. For example, the PPDU may be a frame being configured based on the IEEE802.11bd standard. For backward compatibility and/or interoperability with the IEEE802.11p standard using the 5.9 GHz band, the PPDU  2400  may include a preamble part of the IEEE802.11p frame. For example, the PPDU may include L-STF, L-LTF or L-SIG, and RL-SIG. In addition, following the RL-SIG, the PPDU further include NGV-SIG containing control information for NGV, a repeated field of the NGV-SIG (e.g., RNGV-SIG), NGV-STF, NGV-LTF, and NGV Data. 
     In order to reduce additional signaling overhead when configuring the NGV-SIG for robust transmission and/or range extension, the configuration of the NGV-SIG may be indicated by using the MCS. That is, the MCS may include information related to the configuration of the NGV-SIG. 
     For example, in the case of 11bd transmission, when MCS is set to MCSO, MCSO with the DCM, or lower rate than the MCSO, the NGV-SIG may be configured repeatedly or configured with the DCM being applied. For example, the above setting may be applied only when BW is set to 10 MHz. For example, when MCS different from the above or BW is set to 20 MHz, the NGV-SIG is configured by applying the MCSO, and in this case, repetition configuration of NGV-SIG or DCM may not be applied. 
     For example, a) 11bd PPDU (i.e., NGV PPDU) is configured as an NGV-SIG using the above method in order to satisfy range extension or low sensitivity; or b) when the L-STF and/or L-LTF of the legacy preamble is power boosted, it is possible to apply power boosting to the NGV-STF and the NGV-LTF. 
     For example, the MCS and/or BW field may include information related to the power boosting for the NGV-STF and/or the NGV-LTF. 
     For example, if the BW of the NGV PPDU is 10 MHz, and the MCS is set to MCSO with the DCM being applied, or is set to lower rate than MCSO, the NGV-SIG is repeatedly configured or DCM is applied. The STF and/or the NGV-LTF may be transmitted with the power boosting by a predetermined dB value. The predetermined power boosting value may be one of 1, 2, and 3 dB. For example, a power boosting value applied to NGV-STF and/or NGV-LTF may be the same as a value applied to L-STF and L-LTF. 
     The MCSO may denote that BPSK modulation is being applied. For example, when the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the power boosting is being applied to the L-STF and/or L-LTF of the NGV PPDU. For example, when the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain relevant information indicating that power boosting by 3 dB is being applied to the L-STF and/or L-LTF of the NGV PPDU. For example, if the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor as much as root 2 (i.e., the square root of 2). 
     For example, when both the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that power boosting is applied to the L-STF and/or L-LTF of the NGV PPDU. For example, when both the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that 3 dB of power boosting is applied to the L-STF and/or L-LTF of the NGV PPDU. For example, if the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor as much as root 2 (i.e., the square root of 2). 
       FIG. 32  is a flowchart illustrating an embodiment of an operation of a transmitting station (STA). 
     Referring to  FIG. 32 , the transmitting STA may generate a PPDU as shown in Step S 3210 . The PPDU may be an NGV PPDU supporting 11bd. The NGV PPDU may include a first legacy control field (e.g., L-SIG), a second legacy control field in which the first legacy control field is repeated (e.g., RL-SIG), a first NGV control field (e.g., NGV-SIG), a second NGV control field in which the first NGV control field is repeated (e.g., RNGV-SIG), a short training field (NGV-STF), and a long training field (NGV-LTF). 
     The second legacy control field can be contiguous to the first legacy control field, the first NGV control field can be contiguous to the second legacy control field, the second NGV control field can be contiguous to the first NGV control field, and the NGV-STF can be contiguous to the second NGV control field, and NGV-LTF can be contiguous to the NGV-STF. 
     The first and second NGV control fields may include control information required to interpret the NGV PPDU. The control information may include 1-bit information related to NGV-LTF (e.g., an LTF size field described below). The first and second NGV control fields may include 24-bit information. 
     The NGV-SIG field (i.e., the first and second NGV control fields) may include a 1-bit BW field. For example, the BW field may include 1-bit information related to whether the bandwidth is 10 MHz or 20 MHz. 
     The NGV-SIG field may include a 4-bit MCS field. For example, the MCS field may include information related to modulation and information related to a code rate. For example, the MCS field may not include information related to a type of channel coding (e.g., low density parity check (LDPC) and/or binary convolutional coding (BCC)). For example, code rate information included in the MCS field may or may not include whether the DCM is applied. 
     The NGV-SIG field may include a 1-bit LTF size field. The LTF size field may be a field related to NGV-LTF. For example, the LTF size field may include information related to whether the NGV-LTF is configured based on the NGV-LTF-2× format or the NGV-LTF-1× format. 
     The NGV-SIG field may include a 1-bit midamble periodicity field. The midamble period field may include information related to how many symbols the midamble is repeated/inserted. 
     The NGV-SIG field may include a 1-bit coding field. The coding field may include information related to whether the BCC scheme or the LDPC scheme is used for channel coding. 
     The NGV-SIG field may include an LDPC extra symbol field having a length of 1 bit. 
     The NGV-SIG field may include a spatial-time-stream (NSTS) field having a length of 1 bit. For example, the NSTS field may include information related to an NSTS or a number of spatial stream (NSS). That is, the NSTS field may include information related to the number of streams. 
     The NGV-SIG field may include a 1-bit STBC field, a 1-bit DCM field, a 4-bit CRC field, and a 6-bit tail bit field. 
     In addition, the NGV-SIG field may include a field including other information. The NGV-SIG field may include all or part of the fields described above. 
     The PPDU may include an RL-SIG being contiguous to the L-SIG for robust transmission. The RL-SIG can be a repeated field of the L-SIG, and may be the same field as the L-SIG. The RL-SIG can be continuous to the L-SIG in the time domain. The L-SIG and RL-SIG may include control information. 
     The NGV-SIG may be configured as one symbol (8 μs). For robust transmission and/or range extension transmission, the NGV-SIG symbol may be repeatedly transmitted once more (i.e., the RNGV-SIG symbol is transmitted). Alternatively, for example, the DCM may be applied to NGV-SIG to transmit two symbols. 
     The RNGV-SIG is a repeated field of the NGV-SIG, and may be the same field as the NGV-SIG. The RNGV-SIG can be continuous to the NGV-SIG in the time domain. 
     For example, the same encoding, interleaving, and modulation can be applied to both the NGV-SIG and the RNGV-SIG. That is, the RNGV-SIG may be configured in the same manner as the NGV-SIG. That is, in the RNGV-SIG, the same field as the NGV-SIG may be repeated. 
     The NGV-SIG may be repeated in units of symbols. That is, after the NGV-SIG symbol is transmitted, the RNGV-SIG symbol may be transmitted. Accordingly, the receiving STA may perform decoding of the NGV-SIG and the RNGV-SIG in units of symbols. The receiving STA may improve the performance of the NGV-SIG through aggregation using the NGV SIG and the RNGV-SIG (e.g., repeated NGV-SIG). As a result, the effect of the range extension can be obtained. For example, the receiving STA may combine the NGV-SIG and the RNGV-SIG, and may obtain a gain through the repeated reception of the control field. 
     As in the RL-SIG, the NGV-SIG may not require a separate indication because the same symbol can be repeatedly transmitted. Accordingly, an effect of reducing signaling overhead can be obtained. Since the L-SIG symbol is also repeatedly transmitted and the NGV-SIG symbol is also repeatedly transmitted, consistency can be maintained, thereby facilitating implementation. 
     Since the NGV-SIG is repeated in the time domain, it is possible to obtain an effect of increasing a gain in an environment in which a channel change is large. The NGV-SIG symbol has a length of 8 μs and may have a GI (guard interval) of 1.6 μs, so that the inter-symbol interference (e.g., delay spread) can be reduced compared to the case where the symbol length is 4 μs with a GI having a 0.8 μs symbol length. 
     In order to reduce additional signaling overhead when configuring the NGV-SIG for robust transmission and/or range extension, the configuration of the NGV-SIG may be indicated by using the MCS. That is, the MCS may include information related to the configuration of the NGV-SIG. 
     For example, in the case of NGV PPDU transmission, when MCS is set to MCSO, MCSO with the DCM, or lower rate than the MCSO, the NGV-SIG may be configured repeatedly or configured with the DCM being applied. For example, the above setting may be applied only when BW is set to 10 MHz. For example, when MCS different from the above or BW is set to 20 MHz, the NGV-SIG is configured by applying the MCSO, and in this case, repetition configuration of NGV-SIG or DCM may not be applied. 
     For example, a) 11bd PPDU (i.e., NGV PPDU) is configured as an NGV-SIG using the above method in order to satisfy range extension or low sensitivity; or b) when the L-STF and/or L-LTF of the legacy preamble is power boosted, it is possible to apply power boosting to the NGV-STF and the NGV-LTF. 
     For example, the MCS and/or BW field may include information related to the power boosting for the NGV-STF and/or the NGV-LTF. 
     For example, if the BW of the NGV PPDU is 10 MHz, and the MCS is set to MCSO with the DCM being applied, or is set to lower rate than MCSO, the NGV-SIG is repeatedly configured or DCM is applied. The STF and/or the NGV-LTF may be transmitted with the power boosting by a predetermined dB value. The predetermined power boosting value may be one of 1, 2, and 3 dB. For example, a power boosting value applied to NGV-STF and/or NGV-LTF may be the same as a value applied to L-STF and L-LTF. 
     The MCSO may denote that BPSK modulation is being applied. For example, when the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the power boosting is being applied to the L-STF and/or L-LTF of the NGV PPDU. For example, when the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain relevant information indicating that power boosting by 3 dB is being applied to the L-STF and/or L-LTF of the NGV PPDU. For example, if the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor as much as root 2 (i.e., the square root of 2). 
     For example, when both the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that power boosting is applied to the L-STF and/or L-LTF of the NGV PPDU. For example, when both the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that 3 dB of power boosting is applied to the L-STF and/or L-LTF of the NGV PPDU. For example, if the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor as much as root 2 (i.e., the square root of 2). 
     The transmitting STA may transmit the NGV PPDU (S 3220 ). 
       FIG. 33  is a flowchart illustrating an embodiment of an operation of a receiving station (STA). 
     Referring to  FIG. 33 , the receiving STA may receive a PPDU as shown in Step S 3310 . The PPDU may be an NGV PPDU supporting 11bd. The NGV PPDU may include a first legacy control field (e.g., L-SIG), a second legacy control field in which the first legacy control field is repeated (e.g., RL-SIG), a first NGV control field (e.g., NGV-SIG), a second NGV control field in which the first NGV control field is repeated (e.g., RNGV-SIG), a short training field (NGV-STF), and a long training field (NGV-LTF). 
     The second legacy control field can be contiguous to the first legacy control field, the first NGV control field can be contiguous to the second legacy control field, the second NGV control field can be contiguous to the first NGV control field, and the NGV-STF can be contiguous to the second NGV control field, and NGV-LTF can be contiguous to the NGV-STF. 
     The first and second NGV control fields may include control information required to interpret the NGV PPDU. The control information may include 1-bit information related to NGV-LTF (e.g., an LTF size field described below). The first and second NGV control fields may include 24-bit information. 
     The NGV-SIG field (i.e., the first and second NGV control fields) may include a 1-bit BW field. For example, the BW field may include 1-bit information related to whether the bandwidth is 10 MHz or 20 MHz. 
     The NGV-SIG field may include a 4-bit MCS field. For example, the MCS field may include information related to modulation and information related to a code rate. For example, the MCS field may not include information related to a type of channel coding (e.g., low density parity check (LDPC) and/or binary convolutional coding (BCC)). For example, code rate information included in the MCS field may or may not include whether the DCM is applied. 
     The NGV-SIG field may include a 1-bit LTF size field. The LTF size field may be a field related to NGV-LTF. For example, the LTF size field may include information related to whether the NGV-LTF is configured based on the NGV-LTF-2× format or the NGV-LTF-1× format. 
     The NGV-SIG field may include a 1-bit midamble periodicity field. The midamble period field may include information related to how many symbols the midamble is repeated/inserted. 
     The NGV-SIG field may include a 1-bit coding field. The coding field may include information related to whether the BCC scheme or the LDPC scheme is used for channel coding. 
     The NGV-SIG field may include an LDPC extra symbol field having a length of 1 bit. 
     The NGV-SIG field may include a spatial-time-stream (NSTS) field having a length of 1 bit. For example, the NSTS field may include information related to an NSTS or a number of spatial stream (NSS). That is, the NSTS field may include information related to the number of streams. 
     The NGV-SIG field may include a 1-bit STBC field, a 1-bit DCM field, a 4-bit CRC field, and a 6-bit tail bit field. 
     In addition, the NGV-SIG field may include a field including other information. The NGV-SIG field may include all or part of the fields described above. 
     The PPDU may include an RL-SIG being contiguous to the L-SIG for robust transmission. The RL-SIG can be a repeated field of the L-SIG, and may be the same field as the L-SIG. The RL-SIG can be continuous to the L-SIG in the time domain. The L-SIG and RL-SIG may include control information. 
     The NGV-SIG may be configured as one symbol (8 μs). For robust transmission and/or range extension transmission, the NGV-SIG symbol may be repeatedly transmitted once more (i.e., the RNGV-SIG symbol is transmitted). 
     The RNGV-SIG is a repeated field of the NGV-SIG, and may be the same field as the NGV-SIG. The RNGV-SIG can be continuous to the NGV-SIG in the time domain. 
     For example, the same encoding, interleaving, and modulation can be applied to both the NGV-SIG and the RNGV-SIG. That is, the RNGV-SIG may be configured in the same manner as the NGV-SIG. That is, in the RNGV-SIG, the same field as the NGV-SIG may be repeated. 
     The NGV-SIG may be repeated in units of symbols. That is, after the NGV-SIG symbol is transmitted, the RNGV-SIG symbol may be transmitted. Accordingly, the receiving STA may perform decoding of the NGV-SIG and the RNGV-SIG in units of symbols. The receiving STA may improve the performance of the NGV-SIG through aggregation using the NGV SIG and the RNGV-SIG (e.g., repeated NGV-SIG). As a result, the effect of the range extension can be obtained. For example, the receiving STA may combine the NGV-SIG and the RNGV-SIG, and may obtain a gain through the repeated reception of the control field. 
     As in the RL-SIG, the NGV-SIG may not require a separate indication because the same symbol can be repeatedly transmitted. Accordingly, an effect of reducing signaling overhead can be obtained. Since the L-SIG symbol is also repeatedly transmitted and the NGV-SIG symbol is also repeatedly transmitted, consistency can be maintained, thereby facilitating implementation. 
     Since the NGV-SIG is repeated in the time domain, it is possible to obtain an effect of increasing a gain in an environment in which a channel change is large. The NGV-SIG symbol has a length of 8 μs and may have a GI (guard interval) of 1.6 μs, so that the inter-symbol interference (e.g., delay spread) can be reduced compared to the case where the symbol length is 4 μs with a GI having a 0.8 μs symbol length. 
     In order to reduce additional signaling overhead when configuring the NGV-SIG for robust transmission and/or range extension, the configuration of the NGV-SIG may be indicated by using the MCS. That is, the MCS may include information related to the configuration of the NGV-SIG. 
     For example, in the case of NGV PPDU transmission, when MCS is set to MCSO, MCSO with the DCM, or lower rate than the MCSO, the NGV-SIG may be configured repeatedly or configured with the DCM being applied. For example, the above setting may be applied only when BW is set to 10 MHz. For example, when MCS different from the above or BW is set to 20 MHz, the NGV-SIG is configured by applying the MCSO, and in this case, repetition configuration of NGV-SIG or DCM may not be applied. 
     For example, a) 11bd PPDU (i.e., NGV PPDU) is configured as an NGV-SIG using the above method in order to satisfy range extension or low sensitivity; or b) when the L-STF and/or L-LTF of the legacy preamble is power boosted, it is possible to apply power boosting to the NGV-STF and the NGV-LTF. 
     For example, the MCS and/or BW field may include information related to the power boosting for the NGV-STF and/or the NGV-LTF. 
     For example, if the BW of the NGV PPDU is 10 MHz, and the MCS is set to MCSO with the DCM being applied, or is set to lower rate than MCSO, the NGV-SIG is repeatedly configured or DCM is applied. The STF and/or the NGV-LTF may be transmitted with the power boosting by a predetermined dB value. The predetermined power boosting value may be one of 1, 2, and 3 dB. For example, a power boosting value applied to NGV-STF and/or NGV-LTF may be the same as a value applied to L-STF and L-LTF. 
     The MCSO may denote that BPSK modulation is being applied. For example, when the BPSK modulation is applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that the power boosting is being applied to the L-STF and/or L-LTF of the NGV PPDU. That is, by applying BPSK modulation to at least one field included in the NGV PPDU, the transmitting STA may include information related to that the power boosting is being applied to the L-STF and/or L-LTF of the NGV PPDU in the NGV PPDU. For example, the transmitting STA applies the BPSK modulation to at least one field included in the NGV PPDU, so that that information indicating that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor as much as root 2 (i.e., the square root of 2) can be included in the NGV PPDU. 
     For example, when both the BPSK modulation and the DCM are applied to at least one field included in the NGV PPDU, the receiving STA may obtain information related to that power boosting is applied to the L-STF and/or L-LTF of the NGV PPDU. That is, by applying the BPSK modulation and the DCM to at least one field included in the NGV PPDU, the transmitting STA may include information related to that power boosting is applied to the L-STF and/or L-LTF of the NGV PPDU in the NGV PPDU. For example, the transmitting STA may apply the BPSK modulation and the DCM to at least one field included in the NGV PPDU, so that information related to that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor as much as root 2 (i.e., the square root of 2) may be included in the NGV PPDU. For example, by applying the BPSK modulation and the DCM to at least one field included in the NGV PPDU, the transmitting STA may include the information related to that the L-STF and/or L-LTF of the NGV PPDU is multiplied by a scaling factor equal to root 2 (i.e., the square root of 2) in the NGV PPDU. 
     The receiving STA may decode the PPDU (S 3320 ). 
     Some of the detailed steps shown in the example of  FIGS. 32 and 33  may be omitted, and other steps may be added. 
     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 herein may include a memory and a processor operatively coupled to the memory, wherein the processor is configured to receive a physical protocol data unit (PPDU) including a first legacy training field, a second legacy training field, a legacy control field, and a next generation vehicular network (NGV) training field, wherein the legacy control field is received through a first symbol, the NGV training field is received through a second symbol being contiguous to the first symbol, the first symbol is modulated based on a first constellation, and the second A symbol may be modulated based on a second constellation rotated based on the first constellation, and information on the type of the PPDU may be obtained based on the first constellation and the second constellation. 
     The technical features of the present specification may be implemented based on computer readable medium (CRM). For example, the CRM proposed by the present specification is an instruction based on execution by at least one processor of a shared access point (AP) of a wireless local area network system. The instructions perform operation comprising receiving a physical protocol data unit (PPDU) including a first legacy training field, a second legacy training field, a legacy control field, and a next generation vehicular network (NGV) training field, wherein the legacy control field is received through a first symbol, the NGV training field is received through a second symbol being contiguous to the first symbol, the first symbol is modulated based on a first constellation, and the second A symbol may be modulated based on a second constellation rotated based on the first constellation, and information on the type of the PPDU may be obtained based on the first constellation and the second constellation. The instructions stored in the CRM of the present specification may be executed by at least one processor. At least one processor related to CRM in the present specification may be the processors  111  and  121  or the 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 , the memory  620  of  FIG. 19 , or a separate external memory/storage medium/disk. 
     The above-described technical characteristics of the present specification may be applied to various applications or business models. For example, the UE, Terminal, STA, Transmitter, Receiver, Processor, and/or Transceiver, and so on, that are described in the present specification may be applied to vehicles that support autonomous driving or prior art vehicles that support autonomous driving. 
       FIG. 34  shows a vehicle or an autonomous driving vehicle applied to the present specification. The vehicle or autonomous driving vehicle may be implemented by a mobile robot, a car, a train, a manned/unmanned Aerial Vehicle (AV), a ship, and so on. 
     A memory unit  3430  shown in  FIG. 34  may be included in the memory(s)  112 ,  122  shown in  FIG. 1 . Additionally, a communication unit  3410  shown in  FIG. 34  may be include in the transceiver(s)  113 ,  123  and/or processor(s)  111 ,  121  shown in  FIG. 1 . Furthermore, the remaining devices that are shown in  FIG. 34  may be included in the processor(s)  111 ,  121  shown in  FIG. 1 . 
     Referring to  FIG. 34 , a vehicle or autonomous driving vehicle  3400  may include an antenna unit  3408 , a communication unit  3410 , a control unit  3420 , a memory unit  3430 , a driving unit  3440   a , a power supply unit  3440   b , a sensor unit  3440   c , and/or an autonomous driving unit  3440   d . The antenna unit  3408  may be configured as a part of the communication unit  3410 . 
     The communication unit  3410  may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles, BSs (e.g., gNBs and road side units), and servers. The control unit  3420  may perform various operations by controlling elements of the vehicle or the autonomous driving vehicle  3400 . The control unit  3420  may include an Electronic Control Unit (ECU). The driving unit  3440   a  may cause the vehicle or the autonomous driving vehicle  3400  to drive on a road. The driving unit  3440   a  may include an engine, a motor, a powertrain, a wheel, a brake, a steering device, and so on. The power supply unit  3440   b  may supply power to the vehicle or the autonomous driving vehicle  3400  and include a wired/wireless charging circuit, a battery, and so on. The sensor unit  3440   c  may acquire a vehicle state, ambient environment information, user information, and so on. The sensor unit  3440   c  may include an Inertial Measurement Unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, a slope sensor, a weight sensor, a heading sensor, a position module, a vehicle forward/backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illumination sensor, a pedal position sensor, and so on. The autonomous driving unit  3440   d  may implement technology for maintaining a lane on which a vehicle is driving, technology for automatically adjusting speed, such as adaptive cruise control, technology for autonomously driving along a determined path, technology for driving by automatically setting a path if a destination is set, and the like. 
     For example, the communication unit  3410  may receive map data, traffic information data, and so on, from an external server. The autonomous driving unit  3440   d  may generate an autonomous driving path and a driving plan from the obtained data. The control unit  3420  may control the driving unit  3440   a  such that the vehicle or the autonomous driving vehicle  3400  may move along the autonomous driving path according to the driving plan (e.g., speed/direction control). In the middle of autonomous driving, the communication unit  3410  may aperiodically/periodically acquire recent traffic information data from the external server and acquire surrounding traffic information data from neighboring vehicles. In the middle of autonomous driving, the sensor unit  3440   c  may obtain a vehicle state and/or surrounding environment information. The autonomous driving unit  3440   d  may update the autonomous driving path and the driving plan based on the newly obtained data/information. The communication unit  3410  may transfer information related to a vehicle position, the autonomous driving path, and/or the driving plan to the external server. The external server may predict traffic information data using AI technology, and so on, based on the information collected from vehicles or autonomous driving vehicles and provide the predicted traffic information data to the vehicles or the autonomous driving vehicles. 
     An example of the present specification includes an example of  FIG. 31 , which will hereinafter be described in detail. 
       FIG. 35  shows an example of a vehicle that is applied to the present specification. The vehicle may be implemented as a transport means, an aerial vehicle, a ship, and so on. 
     Referring to  FIG. 35 , a vehicle  3400  may include a communication unit  3410 , a control unit  3420 , a memory unit  3430 , an input/output (I/O) unit  3440   e , and a positioning unit  3440   f  Each block/unit/device shown in  FIG. 34  may be the same as each block/unit/device shown in  FIG. 31 , respectively. 
     The communication unit  3410  may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles or BSs. The control unit  3420  may perform various operations by controlling constituent elements of the vehicle  3400 . The memory unit  3430  may store data/parameters/programs/code/commands for supporting various functions of the vehicle  3400 . The I/O unit  3440   e  may output an AR/VR object based on information within the memory unit  3430 . The I/O unit  3440   e  may include a HUD. The positioning unit  3440   f  may acquire information related to the position of the vehicle  3400 . The position information may include information related to an absolute position of the vehicle  3400 , information related to the position of the vehicle  3400  within a traveling lane, acceleration information, and information related to the position of the vehicle  3400  from a neighboring vehicle. The positioning unit  3440   f  may include a GPS and various sensors. 
     As an example, the communication unit  3410  of the vehicle  3400  may receive map information and traffic information from an external server and store the received information in the memory unit  3430 . The positioning unit  3440   f  may obtain the vehicle position information through the GPS and various sensors and store the obtained information in the memory unit  3430 . The control unit  3420  may generate a virtual object based on the map information, traffic information, and vehicle position information and the I/O unit  3440   e  may display the generated virtual object in a window in the vehicle  3410 ,  3420 . The control unit  3420  may determine whether the vehicle  3400  normally drives within a traveling lane, based on the vehicle position information. If the vehicle  3400  abnormally exits from the traveling lane, the control unit  3420  may display a warning on the window in the vehicle through the I/O unit  3440   e . In addition, the control unit  3420  may broadcast a warning message regarding driving abnormity to neighboring vehicles through the communication unit  3410 . According to situation, the control unit  3420  may transmit the vehicle position information and the information related to driving/vehicle abnormality to related organizations. 
     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.