Patent Publication Number: US-2022239425-A1

Title: Technique for forming midamble in wireless communication system

Description:
BACKGROUND 
     Field of the disclosure 
     The present specification relates to a technique for configuring a midamble in a wireless LAN system, and more particularly, to a method for configuring a midamble of an NGV PPDU in a wireless LAN system and an apparatus supporting the same. 
     Related Art 
     Wireless network technologies may include various types of wireless local area networks (WLANs). WLAN employs widely used networking protocols and can be used to interconnect nearby devices together. The various technical features described in the present specification can be applied to any communication standard, such as WiFi or, more generally, any one of the IEEE 802.11 radio protocol family 
     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 Vehicular or Next Generation V2X Communication (NGV) standard, which is currently being discussed. 
     More specifically, in order to support 2× throughput enhancement, coverage extension, and high speed in comparison with the 802.11p standard system (e.g., DSRC system) in a 5.9 GHz band, the development of the NGV standard (i.e., 802.11bd standard) is being carried out. 
     SUMMARY 
     In the NGV standard (i.e., 802.11bd standard), wide bandwidth (20 MHz) transmission is being considered instead of the conventional 10 MHz transmission to achieve 2× throughput. In addition, the NGV standard must support operations such as interoperability/backward compatibility/coexistence with the existing 802.11p standard. 
     A signal according to the NGV standard may be transmitted in a high-speed environment. Accordingly, the reception performance may be deteriorated due to the influence of Doppler (or Doppler shift). Accordingly, an STA supporting the NGV standard (i.e., an NGV STA) may use a midamble for channel estimation. To reduce the overhead caused by the midamble, the use of a compressed midamble may be considered. Accordingly, technical features regarding the composition and transmission method of the compressed midamble can be proposed. 
     The receiving STA according to various embodiments may receive a Next Generation V2X Physical Protocol Data Unit (NGV PPDU). 
     According to various embodiments, the NGV PPDU may include a preamble, a data field continuous to the preamble, and a midamble continuous to the data field. 
     According to various embodiments, the preamble may include a legacy signal field, a repetitive signal field in which the legacy signal field is repeated, and an NGV signal field including control information for the NGV PPDU. 
     According to various embodiments, the NGV signal field may include 1-bit information related to the format of the midamble. 
     According to various embodiments, the midamble may be configured based on any one of a long training field (LTF) sequence of a first interval and an LTF sequence of a second interval. 
     According to various embodiments, the format of the midamble may be determined as one of a first format related to the LTF sequence of the first interval and a second format related to the LTF sequence of the second interval. 
     According to various embodiments, the symbol of the midamble of the first format may include an LTF signal configured based on the LTF sequence of the first interval and a guard interval (GI) related to the LTF signal. 
     According to various embodiments, the (symbol) duration of the LTF signal may be 3.2 μs, the (symbol) duration of the GI may be 1.6 μs, and the (symbol) duration of the midamble of the first format may be 4.8 μs. 
     According to various embodiments, the receiving STA may decode the NGV PPDU based on the NGV signal field. 
     TECHNICAL EFFECTS OF THE DISCLOSURE 
     The present specification proposes technical features supporting a situation in which the 5.9 GHz band is used in various WLAN systems (e.g., IEEE 802.11bd systems). Based on various examples of the present specification, throughput improvement and high speed of Dedicated Short Range Communication (DSRC) (802.11p) may be supported for smooth V2X support in the 5.9 GHz band. 
     According to an example of the present specification, there is an effect of preventing performance degradation due to Doppler movement through the configuration of the midamble in a high speed situation. 
     Specifically, according to an example of the present specification, the midamble of the NGV PPDU may be composed of various LTF sequences. Also, the format of the midamble symbol may be determined based on various LTF sequences. Based on the midamble symbol, the GI and duration of the midamble symbol may be set differently. Accordingly, different midamble formats are used according to channel conditions, so that the NGV PPDU can be transmitted even in various channel conditions. 
    
    
     
       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 a band plan of 5.9 GHz DSRC. 
         FIG. 21  shows a format of an 11p PPDU. 
         FIG. 22  shows a format of an NGV PPDU. 
         FIG. 23  shows another format of an NGV PPDU. 
         FIG. 24  shows a format of an NGV PPDU for performing 10 MHz transmission. 
         FIG. 25  shows a format of an NGV PPDU for performing 20 MHz transmission. 
         FIG. 26  shows a midamble configuration in an NGV PPDU. 
         FIG. 27  shows an example of a 2×-compressed midamble. 
         FIG. 28  shows an example of a midamble symbol. 
         FIG. 29  shows an example of an NGV PPDU according to the first embodiment. 
         FIG. 30  shows another example of an NGV PPDU according to the first embodiment. 
         FIG. 31  shows another example of a midamble symbol. 
         FIG. 32  shows an example of an NGV PPDU according to the second embodiment. 
         FIG. 33  shows another example of an NGV PPDU according to the second embodiment. 
         FIG. 34  shows another example of a midamble symbol. 
         FIG. 35  shows another example of a midamble symbol. 
         FIG. 36  is a flowchart illustrating an operation of a transmitting STA. 
         FIG. 37  is a flowchart illustrating an operation of a receiving STA. 
         FIG. 38  shows a vehicle or an autonomous driving vehicle applied to the present specification 
         FIG. 39  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 STA 1 , a STA 2 , an AP, a first AP, a second AP, an AP 1 , an AP 2 , 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 STA 1 , the STA 2 , the AP, the first AP, the second AP, the AN, the AP 2 , 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®, HELIOTM 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 (STA 1 )  200 - 1  which are successfully synchronized to communicate with each other are not concepts indicating a specific region. The BSS  205  may include one or more STAs  205 - 1  and  205 - 2  which may be joined to one AP  230 . 
     The BSS may include at least one STA, APs providing a distribution service, and a distribution system (DS)  210  connecting multiple APs. 
     The distribution system  210  may implement an extended service set (ESS)  240  extended by connecting the multiple BSSs  200  and  205 . The ESS  240  may be used as a term indicating one network configured by connecting one or more APs  225  or  230  through the distribution system  210 . The AP included in one ESS  240  may have the same service set identification (SSID). 
     A portal  220  may serve as a bridge which connects the wireless LAN network (IEEE 802.11) and another network (e.g., 802.X). 
     In the BSS illustrated in the upper part of  FIG. 2 , a network between the APs  225  and  230  and a network between the APs  225  and  230  and the STAs  200 - 1 ,  205 - 1 , and  205 - 2  may be implemented. However, the network is configured even between the STAs without the APs  225  and  230  to perform communication. A network in which the communication is performed by configuring the network even between the STAs without the APs  225  and  230  is defined as an Ad-Hoc network or an independent basic service set (IBSS). 
     A lower part of  FIG. 2  illustrates a conceptual view illustrating the IBSS. 
     Referring to the lower part of  FIG. 2 , the IBSS is a BSS that operates in an Ad-Hoc mode. Since the IBSS does not include the access point (AP), a centralized management entity that performs a management function at the center does not exist. That is, in the IBSS, STAs  250 - 1 ,  250 - 2 ,  250 - 3 ,  255 - 4 , and  255 - 5  are managed by a distributed manner. In the IBSS, all STAs  250 - 1 ,  250 - 2 ,  250 - 3 ,  255 - 4 , and  255 - 5  may be constituted by movable STAs and are not permitted to access the DS to constitute a self-contained network. 
       FIG. 3  illustrates a general link setup process. 
     In S 310 , a STA may perform a network discovery operation. The network discovery operation may include a scanning operation of the STA. That is, to access a network, the STA needs to discover a participating network. The STA needs to identify a compatible network before participating in a wireless network, and a process of identifying a network present in a particular area is referred to as scanning Scanning methods include active scanning and passive scanning 
       FIG. 3  illustrates a network discovery operation including an active scanning process. In active scanning, a STA performing scanning transmits a probe request frame and waits for a response to the probe request frame in order to identify which AP is present around while moving to channels. A responder transmits a probe response frame as a response to the probe request frame to the STA having transmitted the probe request frame. Here, the responder may be a STA that transmits the last beacon frame in a BSS of a channel being scanned. In the BSS, since an AP transmits a beacon frame, the AP is the responder. In an IBSS, since STAs in the IBSS transmit a beacon frame in turns, the responder is not fixed. For example, when the STA transmits a probe request frame via channel  1  and receives a probe response frame via channel  1 , the STA may store BSS-related information included in the received probe response frame, may move to the next channel (e g , channel  2 ), and may perform scanning (e.g., transmits a probe request and receives a probe response via channel  2 ) by the same method. 
     Although not shown in  FIG. 3 , scanning may be performed by a passive scanning method. In passive scanning, a STA performing scanning may wait for a beacon frame while moving to channels. A beacon frame is one of management frames in IEEE 802.11 and is periodically transmitted to indicate the presence of a wireless network and to enable the STA performing scanning to find the wireless network and to participate in the wireless network. In a BSS, an AP serves to periodically transmit a beacon frame. In an IBSS, STAs in the IBSS transmit a beacon frame in turns. Upon receiving the beacon frame, the STA performing scanning stores information related to a BSS included in the beacon frame and records beacon frame information in each channel while moving to another channel. The STA having received the beacon frame may store BSS-related information included in the received beacon frame, may move to the next channel, and may perform scanning in the next channel by the same method. 
     After discovering the network, the STA may perform an authentication process in S 320 . The authentication process may be referred to as a first authentication process to be clearly distinguished from the following security setup operation in S 340 . The authentication process in S 320  may include a process in which the STA transmits an authentication request frame to the AP and the AP transmits an authentication response frame to the STA in response. The authentication frames used for an authentication request/response are management frames. 
     The authentication frames may include information related to an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a robust security network (RSN), and a finite cyclic group. 
     The STA may transmit the authentication request frame to the AP. The AP may determine whether to allow the authentication of the STA based on the information included in the received authentication request frame. The AP may provide the authentication processing result to the STA via the authentication response frame. 
     When the STA is successfully authenticated, the STA may perform an association process in S 330 . The association process includes a process in which the STA transmits an association request frame to the AP and the AP transmits an association response frame to the STA in response. The association request frame may include, for example, information related to various capabilities, a beacon listen interval, a service set identifier (SSID), a supported rate, a supported channel, RSN, a mobility domain, a supported operating class, a traffic indication map (TIM) broadcast request, and an interworking service capability. The association response frame may include, for example, information related to various capabilities, a status code, an association ID (AID), a supported rate, an enhanced distributed channel access (EDCA) parameter set, a received channel power indicator (RCPI), a received signal-to-noise indicator (RSNI), a mobility domain, a timeout interval (association comeback time), an overlapping BSS scanning parameter, a TIM broadcast response, and a QoS map. 
     In S 340 , the STA may perform a security setup process. The security setup process in S 340  may include a process of setting up a private key through four-way handshaking, for example, through an extensible authentication protocol over LAN (EAPOL) frame. 
       FIG. 4  illustrates an example of a PPDU used in an IEEE standard. 
     As illustrated, various types of PHY protocol data units (PPDUs) are used in IEEE a/g/n/ac standards. Specifically, an LTF and a STF include a training signal, a SIG-A and a SIG-B include control information for a receiving STA, and a data field includes user data corresponding to a PSDU (MAC PDU/aggregated MAC PDU). 
       FIG. 4  also includes an example of an HE PPDU according to IEEE 802.11ax. The HE PPDU according to  FIG. 4  is an illustrative PPDU for multiple users. An HE-SIG-B may be included only in a PPDU for multiple users, and an HE-SIG-B may be omitted in a PPDU for a single user. 
     As illustrated in  FIG. 4 , the HE-PPDU for multiple users (MUs) may include a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A (HE-SIG A), a high efficiency-signal-B (HE-SIG B), a high efficiency-short training field (HE-STF), a high efficiency-long training field (HE-LTF), a data field (alternatively, an MAC payload), and a packet extension (PE) field. The respective fields may be transmitted for illustrated time periods (i.e., 4 or 8 μs). 
     Hereinafter, a resource unit (RU) used for a PPDU is described. An RU may include a plurality of subcarriers (or tones). An RU may be used to transmit a signal to a plurality of STAs according to OFDMA. Further, an RU may also be defined to transmit a signal to one STA. An RU may be used for an STF, an LTF, a data field, or the like. 
       FIG. 5  illustrates a layout of resource units (RUs) used in a band of 20 MHz. 
     As illustrated in  FIG. 5 , resource units (RUs) corresponding to different numbers of tones (i.e., subcarriers) may be used to form some fields of an HE-PPDU. For example, resources may be allocated in illustrated RUs for an HE-STF, an HE-LTF, and a data field. 
     As illustrated in the uppermost part of  FIG. 5 , a 26-unit (i.e., a unit corresponding to 26 tones) may be disposed. Six tones may be used for a guard band in the leftmost band of the 20 MHz band, and five tones may be used for a guard band in the rightmost band of the 20 MHz band. Further, seven DC tones may be inserted in a center band, that is, a DC band, and a 26-unit corresponding to 13 tones on each of the left and right sides of the DC band may be disposed. A 26-unit, a 52-unit, and a 106-unit may be allocated to other bands. Each unit may be allocated for a receiving STA, that is, a user. 
     The layout of the RUs in  FIG. 5  may be used not only for a multiple users (MUs) but also for a single user (SU), in which case one 242-unit may be used and three DC tones may be inserted as illustrated in the lowermost part of  FIG. 5 . 
     Although  FIG. 5  proposes RUs having various sizes, that is, a 26-RU, a 52-RU, a 106-RU, and a 242-RU, specific sizes of RUs may be extended or increased. Therefore, the present embodiment is not limited to the specific size of each RU (i.e., the number of corresponding tones). 
       FIG. 6  illustrates a layout of RUs used in a band of 40 MHz. 
     Similarly to  FIG. 5  in which RUs having various sizes are used, a 26-RU, a 52-RU, a 106-RU, a 242-RU, a 484-RU, and the like may be used in an example of  FIG. 6 . Further, five DC tones may be inserted in a center frequency, 12 tones may be used for a guard band in the leftmost band of the 40 MHz band, and 11 tones may be used for a guard band in the rightmost band of the 40 MHz band. 
     As illustrated in  FIG. 6 , when the layout of the RUs is used for a single user, a 484-RU may be used. The specific number of RUs may be changed similarly to  FIG. 5 . 
       FIG. 7  illustrates a layout of RUs used in a band of 80 MHz. 
     Similarly to  FIG. 5  and  FIG. 6  in which RUs having various sizes are used, a 26-RU, a 52-RU, a 106-RU, a 242-RU, a 484-RU, a 996-RU, and the like may be used in an example of  FIG. 7 . Further, seven DC tones may be inserted in the center frequency, 12 tones may be used for a guard band in the leftmost band of the 80 MHz band, and 11 tones may be used for a guard band in the rightmost band of the 80 MHz band. In addition, a 26-RU corresponding to 13 tones on each of the left and right sides of the DC band may be used. 
     As illustrated in  FIG. 7 , when the layout of the RUs is used for a single user, a 996-RU may be used, in which case five DC tones may be inserted. 
     The RU described in the present specification may be used in uplink (UL) communication and downlink (DL) communication. For example, when UL-MU communication which is solicited by a trigger frame is performed, a transmitting STA (e.g., an AP) may allocate a first RU (e.g., 26/52/106/242-RU, etc.) to a first STA through the trigger frame, and may allocate a second RU (e.g., 26/52/106/242-RU, etc.) to a second STA. Thereafter, the first STA may transmit a first trigger-based PPDU based on the first RU, and the second STA may transmit a second trigger-based PPDU based on the second RU. The first/second trigger-based PPDU is transmitted to the AP at the same (or overlapped) time period. 
     For example, when a DL MU PPDU is configured, the transmitting STA (e.g., AP) may allocate the first RU (e.g., 26/52/106/242-RU. etc.) to the first STA, and may allocate the second RU (e.g., 26/52/106/242-RU, etc.) to the second STA. That is, the transmitting STA (e.g., AP) may transmit HE-STF, HE-LTF, and Data fields for the first STA through the first RU in one MU PPDU, and may transmit HE-STF, HE-LTF, and Data fields for the second STA through the second RU. 
     Information related to a layout of the RU may be signaled through HE-SIG-B. 
       FIG. 8  illustrates a structure of an HE-SIG-B field. 
     As illustrated, an HE-SIG-B field  810  includes a common field  820  and a user-specific field  830 . The common field  820  may include information commonly applied to all users (i.e., user STAs) which receive SIG-B. The user-specific field  830  may be called a user-specific control field. When the SIG-B is transferred to a plurality of users, the user-specific field  830  may be applied only any one of the plurality of users. 
     As illustrated in  FIG. 8 , the common field  820  and the user-specific field  830  may be separately encoded. 
     The common field  820  may include RU allocation information of N*8 bits. For example, the RU allocation information may include information related to a location of an RU. For example, when a 20 MHz channel is used as shown in  FIG. 5 , the RU allocation information may include information related to a specific frequency band to which a specific RU (26-RU/52-RU/106-RU) is arranged. 
     An example of a case in which the RU allocation information consists of 8 bits is as follows. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 8 bits indices 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 (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., B 0 -B 10 ) 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., B 11 -B 14 ) 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., B 11 -B 14 ) 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 
                 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., B 11 -B 14 ) 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 (B 11 -B 14 ) 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, B 11 -B 14 ) 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, B 11 -B 14 ) 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, B 11 -B 14 ) 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., B 15 - 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., ½, ⅔, ¾, ⅚e, 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., B 19 ) in the user field (i.e., 21 bits) may be a reserved field. 
     In addition, a fifth bit (i.e., B 20 ) 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., B 20 ) 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., B 0 -B 10 ) in the user field of the second format may include identification information of a user STA. In addition, a second bit (e.g., B 11 -B 13 ) 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., B 14 ) 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., B 15 -B 18 ) in the user field of the second format may include modulation and coding scheme (MCS) information. In addition, a fifth bit (e.g., B 19 ) 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., B 20 ) in the user field of the second format may include information related to a coding type (e.g., BCC or LDPC). 
       FIG. 10  illustrates an operation based on UL-MU. As illustrated, a transmitting STA (e.g., an AP) may perform channel access through contending (e.g., a backoff operation), and may transmit a trigger frame  1030 . That is, the transmitting STA may transmit a PPDU including the trigger frame  1030 . Upon receiving the PPDU including the trigger frame, a trigger-based (TB) PPDU is transmitted after a delay corresponding to SIFS. 
     TB PPDUs  1041  and  1042  may be transmitted at the same time period, and may be transmitted from a plurality of STAs (e.g., user STAs) having AIDs indicated in the trigger frame  1030 . An ACK frame  1050  for the TB PPDU may be implemented in various forms. 
     A specific feature of the trigger frame is described with reference to  FIG. 11  to  FIG. 13 . Even if UL-MU communication is used, an orthogonal frequency division multiple access (OFDMA) scheme or a MU MIMO scheme may be used, and the OFDMA and MU-MIMO schemes may be simultaneously used. 
       FIG. 11  illustrates an example of a trigger frame. The trigger frame of  FIG. 11  allocates a resource for uplink multiple-user (MU) transmission, and may be transmitted, for example, from an AP. The trigger frame may be configured of a MAC frame, and may be included in a PPDU. 
     Each field shown in  FIG. 11  may be partially omitted, and another field may be added. In addition, a length of each field may be changed to be different from that shown in the figure. 
     A frame control field  1110  of  FIG. 11  may include information related to a MAC protocol version and extra additional control information. A duration field  1120  may include time information for NAV configuration or information related to an identifier (e.g., AID) of a STA. 
     In addition, an RA field  1130  may include address information of a receiving STA of a corresponding trigger frame, and may be optionally omitted. A TA field  1140  may include address information of a STA (e.g., an AP) which transmits the corresponding trigger frame. A common information field  1150  includes common control information applied to the receiving STA which receives the corresponding trigger frame. For example, a field indicating a length of an L-SIG field of an uplink PPDU transmitted in response to the corresponding trigger frame or information for controlling content of a SIG-A field (i.e., HE-SIG-A field) of the uplink PPDU transmitted in response to the corresponding trigger frame may be included. In addition, as common control information, information related to a length of a CP of the uplink PPDU transmitted in response to the corresponding trigger frame or information related to a length of an LTF field may be included. 
     In addition, per user information fields  1160 # 1  to  1160 #N corresponding to the number of receiving STAs which receive the trigger frame of  FIG. 11  are preferably included. The per user information field may also be called an “allocation field”. 
     In addition, the trigger frame of  FIG. 11  may include a padding field  1170  and a frame check sequence field  1180 . 
     Each of the per user information fields  1160 # 1  to  1160 #N shown in  FIG. 11  may include a plurality of subfields. 
       FIG. 12  illustrates an example of a common information field of a trigger frame. A subfield of  FIG. 12  may be partially omitted, and an extra subfield may be added. In addition, a length of each subfield illustrated may be changed. 
     A length field  1210  illustrated has the same value as a length field of an L-SIG field of an uplink PPDU transmitted in response to a corresponding trigger frame, and a length field of the L-SIG field of the uplink PPDU indicates a length of the uplink PPDU. As a result, the length field  1210  of the trigger frame may be used to indicate the length of the corresponding uplink PPDU. 
     In addition, a cascade identifier field  1220  indicates whether a cascade operation is performed. The cascade operation implies that downlink MU transmission and uplink MU transmission are performed together in the same TXOP. That is, it implies that downlink MU transmission is performed and thereafter uplink MU transmission is performed after a pre-set time (e.g., SIFS). During the cascade operation, only one transmitting device (e.g., AP) may perform downlink communication, and a plurality of transmitting devices (e.g., non-APs) may perform uplink communication. 
     A CS request field  1230  indicates whether a wireless medium state or a NAV or the like is necessarily considered in a situation where a receiving device which has received a corresponding trigger frame transmits a corresponding uplink PPDU. 
     An HE-SIG-A information field  1240  may include information for controlling content of a SIG-A field (i.e., HE-SIG-A field) of the uplink PPDU in response to the corresponding trigger frame. 
     A CP and LTF type field  1250  may include information related to a CP length and LTF length of the uplink PPDU transmitted in response to the corresponding trigger frame. A trigger type field  1260  may indicate a purpose of using the corresponding trigger frame, for example, typical triggering, triggering for beamforming, a request for block ACK/NACK, or the like. 
     It may be assumed that the trigger type field  1260  of the trigger frame in the present specification indicates a trigger frame of a basic type for typical triggering. For example, the trigger frame of the basic type may be referred to as a basic trigger frame. 
       FIG. 13  illustrates an example of a subfield included in a per user information field. A user information field  1300  of  FIG. 13  may be understood as any one of the per user information fields  1160 # 1  to  1160 #N mentioned above with reference to  FIG. 11 . A subfield included in the user information field  1300  of  FIG. 13  may be partially omitted, and an extra subfield may be added. In addition, a length of each subfield illustrated may be changed. 
     A user identifier field  1310  of  FIG. 13  indicates an identifier of a STA (i.e., receiving STA) corresponding to per user information. An example of the identifier may be the entirety or part of an association identifier (AID) value of the receiving STA. 
     In addition, an RU allocation field  1320  may be included. That is, when the receiving STA identified through the user identifier field  1310  transmits a TB PPDU in response to the trigger frame, the TB PPDU is transmitted through an RU indicated by the RU allocation field  1320 . In this case, the RU indicated by the RU allocation field  1320  may be an RU shown in  FIG. 5 ,  FIG. 6 , and  FIG. 7 . 
     The subfield of  FIG. 13  may include a coding type field  1330 . The coding type field  1330  may indicate a coding type of the TB PPDU. For example, when BCC coding is applied to the TB PPDU, the coding type field  1330  may be set to ‘1’, and when LDPC coding is applied, the coding type field  1330  may be set to ‘0’. 
     In addition, the subfield of  FIG. 13  may include an MCS field  1340 . The MCS field  1340  may indicate an MCS scheme applied to the TB PPDU. For example, when BCC coding is applied to the TB PPDU, the coding type field  1330  may be set to ‘1’, and when LDPC coding is applied, the coding type field  1330  may be set to ‘0’. 
     Hereinafter, a UL OFDMA-based random access (UORA) scheme will be described. 
       FIG. 14  describes a technical feature of the UORA scheme. 
     A transmitting STA (e.g., an AP) may allocate six RU resources through a trigger frame as shown in  FIG. 14 . Specifically, the AP may allocate a 1st RU resource (AID  0 , RU  1 ), a 2nd RU resource (AID  0 , RU  2 ), a 3rd RU resource (AID  0 , RU  3 ), a 4th RU resource (AID  2045 , RU  4 ), a 5th RU resource (AID  2045 , RU  5 ), and a 6th RU resource (AID  3 , RU  6 ). Information related to the AID  0 , AID  3 , or AID  2045  may be included, for example, in the user identifier field  1310  of  FIG. 13 . Information related to the RU  1  to RU  6  may be included, for example, in the RU allocation field  1320  of  FIG. 13 . AID=0 may imply a UORA resource for an associated STA, and AID=2045 may imply a UORA resource for an un-associated STA. Accordingly, the 1st to 3rd RU resources of  FIG. 14  may be used as a UORA resource for the associated STA, the 4th and 5th RU resources of  FIG. 14  may be used as a UORA resource for the un-associated STA, and the 6th RU resource of  FIG. 14  may be used as a typical resource for UL MU. 
     In the example of  FIG. 14 , an OFDMA random access backoff (OBO) of a STA 1  is decreased to 0, and the STA 1  randomly selects the 2nd RU resource (AID  0 , RU  2 ). In addition, since an OBO counter of a STA 2 / 3  is greater than 0, an uplink resource is not allocated to the STA 2 / 3 . In addition, regarding a STA 4  in  FIG. 14 , since an AID (e.g., AID=3) of the STA 4  is included in a trigger frame, a resource of the RU  6  is allocated without backoff. 
     Specifically, since the STA 1  of  FIG. 14  is an associated STA, the total number of eligible RA RUs for the STA 1  is 3 (RU  1 , RU  2 , and RU  3 ), and thus the STA 1  decreases an OBO counter by 3 so that the OBO counter becomes 0. In addition, since the STA 2  of  FIG. 14  is an associated STA, the total number of eligible RA RUs for the STA 2  is 3 (RU  1 , RU  2 , and RU  3 ), and thus the STA 2  decreases the OBO counter by 3 but the OBO counter is greater than 0. In addition, since the STA 3  of  FIG. 14  is an un-associated STA, the total number of eligible RA RUs for the STA 3  is 2 (RU  4 , RU  5 ), and thus the STA 3  decreases the OBO counter by 2 but the OBO counter is greater than 0. 
       FIG. 15  illustrates an example of a channel used/supported/defined within a 2.4 GHz band. 
     The 2.4 GHz band may be called in other terms such as a first band. In addition, the 2.4 GHz band may imply a frequency domain in which channels of which a center frequency is close to 2.4 GHz (e.g., channels of which a center frequency is located within 2.4 to 2.5 GHz) are used/supported/defined. 
     A plurality of 20 MHz channels may be included in the 2.4 GHz band. 20 MHz within the 2.4 GHz may have a plurality of channel indices (e.g., an index 1 to an index 14). For example, a center frequency of a 20 MHz channel to which a channel index 1 is allocated may be 2.412 GHz, a center frequency of a 20 MHz channel to which a channel index 2 is allocated may be 2.417 GHz, and a center frequency of a 20 MHz channel to which a channel index N is allocated may be (2.407+0.005*N) GHz. The channel index may be called in various terms such as a channel number or the like. Specific numerical values of the channel index and center frequency may be changed. 
       FIG. 15  exemplifies 4 channels within a 2.4 GHz band. Each of 1st to 4th frequency domains  1510  to  1540  shown herein may include one channel For example, the 1st frequency domain  1510  may include a channel  1  (a 20 MHz channel having an index 1). In this case, a center frequency of the channel  1  may be set to 2412 MHz. The 2nd frequency domain  1520  may include a channel  6 . In this case, a center frequency of the channel  6  may be set to 2437 MHz. The 3rd frequency domain  1530  may include a channel  11 . In this case, a center frequency of the channel  11  may be set to 2462 MHz. The 4th frequency domain  1540  may include a channel  14 . In this case, a center frequency of the channel  14  may be set to 2484 MHz. 
       FIG. 16  illustrates an example of a channel used/supported/defined within a 5 GHz band. 
     The 5 GHz band may be called in other terms such as a second band or the like. The 5 GHz band may imply a frequency domain in which channels of which a center frequency is greater than or equal to 5 GHz and less than 6 GHz (or less than 5.9 GHz) are used/supported/defined. Alternatively, the 5 GHz band may include a plurality of channels between 4.5 GHz and 5.5 GHz. A specific numerical value shown in  FIG. 16  may be changed. 
     A plurality of channels within the 5 GHz band include an unlicensed national information infrastructure (UNII)- 1 , a UNII- 2 , a UNII- 3 , and an ISM. The INII- 1  may be called UNII Low. The UNII- 2  may include a frequency domain called UNII Mid and UNII- 2 Extended. The UNII- 3  may be called UNII-Upper. 
     A plurality of channels may be configured within the 5 GHz band, and a bandwidth of each channel may be variously set to, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz, or the like. For example, 5170 MHz to 5330 MHz frequency domains/ranges within the UNII- 1  and UNII- 2  may be divided into eight 20 MHz channels. The 5170 MHz to 5330 MHz frequency domains/ranges may be divided into four channels through a 40 MHz frequency domain. The 5170 MHz to 5330 MHz frequency domains/ranges may be divided into two channels through an 80 MHz frequency domain. Alternatively, the 5170 MHz to 5330 MHz frequency domains/ranges may be divided into one channel through a 160 MHz frequency domain. 
       FIG. 17  illustrates an example of a channel used/supported/defined within a 6 GHz band. 
     The 6 GHz band may be called in other terms such as a third band or the like. The 6 GHz band may imply a frequency domain in which channels of which a center frequency is greater than or equal to 5.9 GHz are used/supported/defined. A specific numerical value shown in  FIG. 17  may be changed. 
     For example, the 20 MHz channel of  FIG. 17  may be defined starting from 5.940 GHz. Specifically, among 20 MHz channels of  FIG. 17 , the leftmost channel may have an index 1 (or a channel index, a channel number, etc.), and 5.945 GHz may be assigned as a center frequency. That is, a center frequency of a channel of an index N may be determined as (5.940+0.005*N) GHz. 
     Accordingly, an index (or channel number) of the 2 MHz channel of  FIG. 17  may be 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61, 65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125, 129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 169, 173, 177, 181, 185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 233. In addition, according to the aforementioned (5.940+0.005*N)GHz rule, an index of the 40 MHz channel of  FIG. 17  may be 3, 11, 19, 27, 35, 43, 51, 59, 67, 75, 83, 91, 99, 107, 115, 123, 131, 139, 147, 155, 163, 171, 179, 187, 195, 203, 211, 219, 227. 
     Although 20, 40, 80, and 160 MHz channels are illustrated in the example of  FIG. 17 , a  240  MHz channel or a 320 MHz channel may be additionally added. 
     Hereinafter, a PPDU transmitted/received in a STA of the present specification will be described. 
       FIG. 18  illustrates an example of a PPDU used in the present specification. 
     The PPDU of  FIG. 18  may be called in various terms such as an EHT PPDU, a TX PPDU, an RX PPDU, a first type or N-th type PPDU, or the like. For example, in the present specification, the PPDU or the EHT PPDU may be called in various terms such as a TX PPDU, a RX PPDU, a first type or N-th type PPDU, or the like. In addition, the EHT PPDU may be used in an EHT system and/or a new WLAN system enhanced from the EHT system. 
     The PPDU of  FIG. 18  may represent some or all of the PPDU types used in the EHT system. For example, the example of  FIG. 18  may be used for both a single-user (SU) mode and a multi-user (MU) mode, or may be used only for the SU mode, or may be used only for the MU mode. For example, a trigger-based PPDU (TB) on the EHT system may be separately defined or configured based on the example of  FIG. 18 . The trigger frame described through at least one of  FIGS. 10 to 14  and the UL-MU operation (e.g., the TB PPDU transmission operation) started by the trigger frame may be directly applied to the EHT system. 
     In  FIG. 18 , an L-STF to an EHT-LTF may be called a preamble or a physical preamble, and may be generated/transmitted/received/obtained/decoded in a physical layer. 
     A subcarrier spacing of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields of  FIG. 18  may be determined as 312.5 kHz, and a subcarrier spacing of the EHT-STF, EHT-LTF, and Data fields may be determined as 78.125 kHz. That is, a tone index (or subcarrier index) of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may be expressed in unit of 312.5 kHz, and a tone index (or subcarrier index) of the EHT-STF, EHT-LTF, and Data fields may be expressed in unit of 78.125 kHz. 
     In the PPDU of  FIG. 18 , the L-LTF and the L-STF may be the same as those in the conventional fields. 
     The L-SIG field of  FIG. 18  may include, for example, bit information of 24 bits. For example, the 24-bit information may include a rate field of 4 bits, a reserved bit of 1 bit, a length field of 12 bits, a parity bit of 1 bit, and a tail bit of 6 bits. For example, the length field of 12 bits may include information related to a length or time duration of a PPDU. For example, the length field of 12 bits may be determined based on a type of the PPDU. For example, when the PPDU is a non-HT, HT, VHT PPDU or an EHT PPDU, a value of the length field may be determined as a multiple of 3. For example, when the PPDU is an HE PPDU, the value of the length field may be determined as “a multiple of 3”+1 or “a multiple of 3”+2. In other words, for the non-HT, HT, VHT PPDI or the EHT PPDU, the value of the length field may be determined as a multiple of 3, and for the HE PPDU, the value of the length field may be determined as “a multiple of 3”+1 or “a multiple of 3”+2. 
     For example, the transmitting STA may apply BCC encoding based on a ½ 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} 0  and a DC subcarrier {subcarrier index 0}. As a result, the 48 BPSK symbols may be mapped to subcarrier indices −26 to −22, −20 to −8, −6 to −1, +1 to +6, +8 to +20, and +22 to +26. The transmitting STA may additionally map a signal of {−1, −1, −1, 1} to a subcarrier index {−28, −27, +27, +28}. The aforementioned signal may be used for channel estimation on a frequency domain corresponding to {−28, −27, +27, +28}. 
     The transmitting STA may generate an RL-SIG generated in the same manner as the L-SIG. BPSK modulation may be applied to the RL-SIG. The receiving STA may know that the RX PPDU is the HE PPDU or the EHT PPDU, based on the presence of the RL-SIG. 
     A universal SIG (U-SIG) may be inserted after the RL-SIG of  FIG. 18 . The U-SIG may be called in various terms such as a first SIG field, a first SIG, a first type SIG, a control signal, a control signal field, a first (type) control signal, or the like. 
     The U-SIG may include information of N bits, and may include information for identifying a type of the EHT PPDU. For example, the U-SIG may be configured based on two symbols (e.g., two contiguous OFDM symbols). Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of 4 μs. Each symbol of the U-SIG may be used to transmit the 26-bit information. For example, each symbol of the U-SIG may be transmitted/received based on 52 data tomes and 4 pilot tones. 
     Through the U-SIG (or U-SIG field), for example, A-bit information (e.g., 52 un-coded bits) may be transmitted. A first symbol of the U-SIG may transmit first X-bit information (e.g., 26 un-coded bits) of the A-bit information, and a second symbol of the U-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=½ to generate 52-coded bits, and may perform interleaving on the 52-coded bits. The transmitting STA may perform BPSK modulation on the interleaved 52-coded bits to generate 52 BPSK symbols to be allocated to each U-SIG symbol. One U-SIG symbol may be transmitted based on 65 tones (subcarriers) from a subcarrier index −28 to a subcarrier index +28, except for a DC index 0. The 52 BPSK symbols generated by the transmitting STA may be transmitted based on the remaining tones (subcarriers) except for pilot tones, i.e., tones −21, −7, +7, +21. 
     For example, the A-bit information (e.g., 52 un-coded bits) generated by the U-SIG may include a CRC field (e.g., a field having a length of 4 bits) and a tail field (e.g., a field having a length of 6 bits). The CRC field and the tail field may be transmitted through the second symbol of the U-SIG. The CRC field may be generated based on 26 bits allocated to the first symbol of the U-SIG and the remaining 16 bits except for the CRC/tail fields in the second symbol, and may be generated based on the conventional CRC calculation algorithm. In addition, the tail field may be used to terminate trellis of a convolutional decoder, and may be set to, for example, “000000”. 
     The A-bit information (e.g., 52 un-coded bits) transmitted by the U-SIG (or U-SIG field) may be divided into version-independent bits and version-dependent bits. For example, the version-independent bits may have a fixed or variable size. For example, the version-independent bits may be allocated only to the first symbol of the U-SIG, or the version-independent bits may be allocated to both of the first and second symbols of the U-SIG. For example, the version-independent bits and the version-dependent bits may be called in various terms such as a first control bit, a second control bit, or the like. 
     For example, the version-independent bits of the U-SIG may include a PHY version identifier of 3 bits. For example, the PHY version identifier of 3 bits may include information related to a PHY version of a TX/RX PPDU. For example, a first value of the PHY version identifier of 3 bits may indicate that the TX/RX PPDU is an EHT PPDU. In other words, when the transmitting STA transmits the EHT PPDU, the PHY version identifier of 3 bits may be set to a first value. In other words, the receiving STA may determine that the RX PPDU is the EHT PPDU, based on the PHY version identifier having the first value. 
     For example, the version-independent bits of the U-SIG may include a UL/DL flag field of 1 bit. A first value of the UL/DL flag field of 1 bit relates to UL communication, and a second value of the UL/DL flag field relates to DL communication. 
     For example, the version-independent bits of the U-SIG may include information related to a TXOP length and information related to a BSS color ID. 
     For example, when the EHT PPDU is divided into various types (e.g., various types such as an EHT PPDU related to an SU mode, an EHT PPDU related to a MU mode, an EHT PPDU related to a TB mode, an EHT PPDU related to extended range transmission, or the like), information related to the type of the EHT PPDU may be included in the version-dependent bits of the U-SIG. 
     For example, the U-SIG may include: 1) a bandwidth field including information related to a bandwidth; 2) a field including information related to an MCS scheme applied to EHT-SIG; 3) an indication field including information regarding whether a dual subcarrier modulation (DCM) scheme is applied to EHT-SIG; 4) a field including information related to the number of symbol used for EHT-SIG; 5) a field including information regarding whether the EHT-SIG is generated across a full band; 6) a field including information related to a type of EHT-LTF/STF; and 7) information related to a field indicating an EHT-LTF length and a CP length. 
     Preamble puncturing may be applied to the PPDU of  FIG. 18 . The preamble puncturing implies that puncturing is applied to part (e.g., a secondary 20 MHz band) of the full band. For example, when an 80 MHz PPDU is transmitted, a STA may apply puncturing to the secondary 20 MHz band out of the 80 MHz band, and may transmit a PPDU only through a primary 20 MHz band and a secondary 40 MHz band. 
     For example, a pattern of the preamble puncturing may be configured in advance. For example, when a first puncturing pattern is applied, puncturing may be applied only to the secondary 20 MHz band within the 80 MHz band. For example, when a second puncturing pattern is applied, puncturing may be applied to only any one of two secondary 20 MHz bands included in the secondary 40 MHz band within the 80 MHz band. For example, when a third puncturing pattern is applied, puncturing may be applied to only the secondary 20 MHz band included in the primary 80 MHz band within the 160 MHz band (or 80+80 MHz band). For example, when a fourth puncturing is applied, puncturing may be applied to at least one 20 MHz channel not belonging to a primary 40 MHz band in the presence of the primary 40 MHz band included in the 80MHaz band within the 160 MHz band (or 80+80 MHz band). 
     Information related to the preamble puncturing applied to the PPDU may be included in U-SIG and/or EHT-SIG. For example, a first field of the U-SIG may include information related to a contiguous bandwidth, and second field of the U-SIG may include information related to the preamble puncturing applied to the PPDU. 
     For example, the U-SIG and the EHT-SIG may include the information related to the preamble puncturing, based on the following method. When a bandwidth of the PPDU exceeds 80 MHz, the U-SIG may be configured individually in unit of 80 MHz. For example, when the bandwidth of the PPDU is 160 MHz, the PPDU may include a first U-SIG for a first 80 MHz band and a second U-SIG for a second 80 MHz band. In this case, a first field of the first U-SIG may include information related to a 160 MHz bandwidth, and a second field of the first U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) applied to the first 80 MHz band. In addition, a first field of the second U-SIG may include information related to a 160 MHz bandwidth, and a second field of the second U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) applied to the second 80 MHz band. Meanwhile, an EHT-SIG contiguous to the first U-SIG may include information related to a preamble puncturing applied to the second 80 MHz band (i.e., information related to a preamble puncturing pattern), and an EHT-SIG contiguous to the second U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) applied to the first 80 MHz band. 
     Additionally or alternatively, the U-SIG and the EHT-SIG may include the information related to the preamble puncturing, based on the following method. The U-SIG may include information related to a preamble puncturing (i.e., information related to a preamble puncturing pattern) for all bands. That is, the EHT-SIG may not include the information related to the preamble puncturing, and only the U-SIG may include the information related to the preamble puncturing (i.e., the information related to the preamble puncturing pattern). 
     The U-SIG may be configured in unit of 20 MHz. For example, when an 80 MHz PPDU is configured, the U-SIG may be duplicated. That is, four identical U-SIGs may be included in the 80 MHz PPDU. PPDUs exceeding an 80 MHz bandwidth may include different U-SIGs. 
     The EHT-SIG of  FIG. 18  may include the technical feature of the HE-SIG-B shown in the examples of  FIGS. 8 to 9  as it is. The EHT-SIG may be referred to by various names such as a second SIG field, a second SIG, a second type SIG, a control signal, a control signal field, and a second (type) control signal. 
     The EHT-SIG may include N-bit information (e.g., 1-bit information) regarding whether the EHT-PPDU supports the SU mode or the MU mode. 
     The EHT-SIG may be configured based on various MCS schemes. As described above, information related to an MCS scheme applied to the EHT-SIG may be included in U-SIG. The EHT-SIG may be configured based on a DCM scheme. For example, among N data tones (e.g., 52 data tones) allocated for the EHT-SIG, a first modulation scheme may be applied to half of consecutive tones, and a second modulation scheme may be applied to the remaining half of the consecutive tones. That is, a transmitting STA may use the first modulation scheme to modulate specific control information through a first symbol and allocate it to half of the consecutive tones, and may use the second modulation scheme to modulate the same control information by using a second symbol and allocate it to the remaining half of the consecutive tones. As described above, information (e.g., a 1-bit field) regarding whether the DCM scheme is applied to the EHT-SIG may be included in the U-SIG. An HE-STF of  FIG. 18  may be used for improving automatic gain control estimation in a multiple input multiple output (MIMO) environment or an OFDMA environment. An HE-LTF of  FIG. 18  may be used for estimating a channel in the MIMO environment or the OFDMA environment. 
     The EHT-STF of  FIG. 18  may be set in various types. For example, a first type of STF (e.g., 1× 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 μs may be repeated 5 times to become a first type STF having a length of 4 μs. For example, a second type of STF (e.g., 2× STF) may be generated based on a second type STF sequence in which a non-zero coefficient is arranged with an interval of 8 subcarriers. An STF signal generated based on the second type STF sequence may have a period of 1.6 μs, and a periodicity signal of 1.6 μs may be repeated 5 times to become a second type STF having a length of 8 μs. Hereinafter, an example of a sequence for configuring an EHT-STF (i.e., an EHT-STF sequence) is proposed. The following sequence may be modified in various ways. 
     The EHT-STF may be configured based on the following sequence M. 
     
       
         
           
             
               
                 
                   
                     M 
                   
                   = 
                   
                     { 
                     
                       
                         - 
                         1 
                       
                       , 
                         
                       
                         - 
                         1 
                       
                       , 
                         
                       
                         - 
                         1 
                       
                       , 
                       1 
                       , 
                       1 
                       , 
                       1 
                       , 
                         
                       
                         - 
                         1 
                       
                       , 
                         
                       1 
                       , 
                         
                       1 
                       , 
                         
                       1 
                       , 
                         
                       
                         - 
                         1 
                       
                       , 
                       1 
                       , 
                       1 
                       , 
                         
                       
                         - 
                         1 
                       
                       , 
                       1 
                     
                     } 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     1 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 20 MHz PPDU may be configured based on the following equation. The following example may be a first type (i.e., 1× STF) sequence. For example, the first type sequence may be included in not a trigger-based (TB) PPDU but an EHT-PPDU. In the following equation, (a:b:c) may imply a duration defined as b tone intervals (i.e., a subcarrier interval) from a tone index (i.e., subcarrier index) ‘a’ to a tone index ‘c’. For example, the equation 2 below may represent a sequence defined as 16 tone intervals from a tone index −112 to a tone index 112. Since a subcarrier spacing of 78.125 kHz is applied to the EHT-STR, the 16 tone intervals may imply that an EHT-STF coefficient (or element) is arranged with an interval of 78.125*16=1250 kHz. In addition, * implies multiplication, and sqrt( ) implies a square root. In addition, j implies an imaginary number. 
     
       
         
           
             
               
                 
                   
                     
                       
                         EHT 
                         - 
                         STF 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             - 
                             11 
                           
                           ⁢ 
                           
                             2:1 
                           
                           ⁢ 
                           
                             6:1 
                           
                           ⁢ 
                           12 
                         
                         ) 
                       
                     
                     = 
                     
                       
                         
                           { 
                           M 
                           } 
                         
                         * 
                       
                       ⁢ 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         s 
                       
                       ⁢ 
                       q 
                       ⁢ 
                       r 
                       ⁢ 
                       
                         t 
                         ⁡ 
                         
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                   ⁢ 
                   
                     
 
                   
                   ⁢ 
                   
                     
                       
                         EHT 
                         - 
                         STF 
                       
                       ⁢ 
                       
                         ( 
                         0 
                         ) 
                       
                     
                     = 
                     0 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 40 MHz PPDU may be configured based on the following equation. The following example may be the first type (i.e., 1× STF) sequence. 
     
       
         
           
             
               
                 
                   EHT 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     
                       STF 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           240 
                         
                         : 
                         16 
                         : 
                         240 
                       
                       ) 
                     
                     = 
                     
                       
                         { 
                         
                           M 
                           , 
                             
                           0 
                           , 
                             
                           
                             - 
                             M 
                           
                         
                         } 
                       
                       * 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         
                           sqrt 
                           ⁡ 
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     3 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 80 MHz PPDU may be configured based on the following equation. The following example may be the first type (i.e., 1× STF) sequence. 
     
       
         
           
             
               
                 
                   EHT 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     
                       STF 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           496 
                         
                         : 
                         16 
                         : 
                         496 
                       
                       ) 
                     
                     = 
                     
                       
                         { 
                         
                           M 
                           , 
                             
                           1 
                           , 
                             
                           
                             - 
                             M 
                           
                           , 
                             
                           0 
                           , 
                             
                           
                             - 
                             M 
                           
                           , 
                             
                           1 
                           , 
                             
                           
                             - 
                             M 
                           
                         
                         } 
                       
                       * 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         
                           sqrt 
                           ⁡ 
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     4 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 160 MHz PPDU may be configured based on the following equation. The following example may be the first type (i.e., 1× STF) sequence. 
     
       
         
           
             
               
                 
                   EHT 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   ⁠ 
                   
                     
                       STF 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           1008 
                         
                         : 
                         16 
                         : 
                         1008 
                       
                       ) 
                     
                     = 
                     
                       
                         { 
                         
                           M 
                           , 
                           1 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           0 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           1 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           0 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           
                             - 
                             1 
                           
                           , 
                           M 
                           , 
                           0 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           1 
                           , 
                           
                             - 
                             M 
                           
                         
                         } 
                       
                       * 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         sqrt 
                       
                       ⁢ 
                       
                         ( 
                         2 
                         ) 
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     5 
                   
                   &gt; 
                 
               
             
           
         
       
     
     In the EHT-STF for the 80+80 MHz PPDU, a sequence for lower 80 MHz may be identical to Equation 4. In the EHT-STF for the 80+80 MHz PPDU, a sequence for upper 80 MHz may be configured based on the following equation. 
     
       
         
           
             
               
                 
                   EHT 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     
                       STF 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           496 
                         
                         : 
                         16 
                         : 
                         496 
                       
                       ) 
                     
                     = 
                     
                       
                         { 
                         
                           
                             - 
                             M 
                           
                           , 
                             
                           
                             - 
                             1 
                           
                           , 
                             
                           M 
                           , 
                             
                           0 
                           , 
                             
                           
                             - 
                             M 
                           
                           , 
                             
                           1 
                           , 
                             
                           
                             - 
                             M 
                           
                         
                         } 
                       
                       * 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         
                           sqrt 
                           ⁡ 
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     6 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Equation 7 to Equation 11 below relate to an example of a second type (i.e., 2× STF) sequence. 
     
       
         
           
             
               
                 
                   EHT 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     
                       STF 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           120 
                         
                         : 
                         8 
                         : 
                         120 
                       
                       ) 
                     
                     = 
                     
                       
                         { 
                         
                           M 
                           , 
                           0 
                           , 
                           
                             - 
                             M 
                           
                         
                         } 
                       
                       * 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         
                           sqrt 
                           ⁡ 
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     7 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 40 MHz PPDU may be configured based on the following equation. 
     
       
         
           
             
               
                 
                   
                     
                       EHT 
                     
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         
                           STF 
                         
                         
                           ( 
                         
                         
                           
                             
                               - 
                               248 
                             
                           
                           : 
                           
                             8 
                           
                           
                             : 
                           
                           
                             248 
                           
                         
                         
                           ) 
                         
                       
                       
                         = 
                       
                       
                         
                           
                             { 
                             
                               M 
                               , 
                               
                                 - 
                                 1 
                               
                               , 
                               
                                 - 
                                 M 
                               
                               , 
                               0 
                               , 
                               M 
                               , 
                               
                                 - 
                                 1 
                               
                               , 
                               M 
                             
                             } 
                           
                           * 
                           
                             
                               ( 
                               
                                 1 
                                 + 
                                 j 
                               
                               ) 
                             
                             / 
                             
                               sqrt 
                               ⁡ 
                               ( 
                               2 
                               ) 
                             
                           
                         
                       
                     
                   
                   ⁢ 
                     
                   
                     
                       EHT 
                     
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         
                           STF 
                           ⁡ 
                           ( 
                           
                             - 
                             248 
                           
                           ) 
                         
                         = 
                         0 
                       
                     
                   
                   ⁢ 
                     
                   
                     
                       EHT 
                     
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         
                           STF 
                           ⁡ 
                           ( 
                           248 
                           ) 
                         
                         = 
                         0 
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     8 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 80 MHz PPDU may be configured based on the following equation. 
     
       
         
           
             
               
                 
                   EHT 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   ⁠ 
                   
                     
                       STF 
                       ⁡ 
                       ( 
                       
                         
                           - 
                           504 
                         
                         : 
                         8 
                         : 
                         504 
                       
                       ) 
                     
                     = 
                     
                       
                         { 
                         
                           M 
                           , 
                           
                             - 
                             1 
                           
                           , 
                           M 
                           , 
                           
                             - 
                             1 
                           
                           , 
                           
                             - 
                             M 
                           
                           , 
                           
                             - 
                             1 
                           
                           , 
                           M 
                           , 
                           0 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           1 
                           , 
                           M 
                           , 
                           1 
                           , 
                           
                             - 
                             M 
                           
                           , 
                           1 
                           , 
                           
                             - 
                             M 
                           
                         
                         } 
                       
                       * 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         
                           sqrt 
                           ⁡ 
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     9 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The EHT-STF for the 160 MHz PPDU may be configured based on the following equation. 
     
       
         
           
             
               
                 
                   
                     EHT 
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         STF 
                         ⁡ 
                         ( 
                         
                           - 
                           1016 
                           : 
                           16 
                           : 
                           1016 
                         
                         ) 
                       
                       = 
                       
                         
                           { 
                           
                             M 
                             , 
                             
                               - 
                               1 
                             
                             , 
                             M 
                             , 
                             
                               - 
                               1 
                             
                             , 
                             
                               - 
                               M 
                             
                             , 
                             
                               - 
                               1 
                             
                             , 
                             M 
                             , 
                             0 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             M 
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                               
                             0 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             M 
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             0 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             M 
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                           
                           } 
                         
                         * 
                         
                           
                             ( 
                             
                               1 
                               + 
                               j 
                             
                             ) 
                           
                           / 
                           s 
                         
                         ⁢ 
                         q 
                         ⁢ 
                         r 
                         ⁢ 
                         
                           t 
                           ⁡ 
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                   ⁢ 
                   
 
                   
                     EHT 
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         STF 
                         ⁡ 
                         ( 
                         
                           - 
                           8 
                         
                         ) 
                       
                       = 
                       0 
                     
                     , 
                     
 
                     EHT 
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         STF 
                         ⁡ 
                         ( 
                         8 
                         ) 
                       
                       = 
                       0 
                     
                     , 
                     
 
                     EHT 
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         STF 
                         ⁡ 
                         ( 
                         
                           - 
                           1016 
                         
                         ) 
                       
                       = 
                       0 
                     
                     , 
                     
 
                     EHT 
                     ⁢ 
                     ‐ 
                     ⁢ 
                     
                       
                         STF 
                         ⁡ 
                         ( 
                         1016 
                         ) 
                       
                       = 
                       0 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     10 
                   
                   &gt; 
                 
               
             
           
         
       
     
     In the EHT-STF for the 80+80 MHz PPDU, a sequence for lower 80 MHz may be identical to Equation 9. In the EHT-STF for the 80+80 MHz PPDU, a sequence for upper 80 MHz may be configured based on the following equation. 
     
       
         
           
             
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     11 
                   
                   &gt; 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         EHT 
                         - 
                         STF 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             - 
                             50 
                           
                           ⁢ 
                           
                             4:8:504 
                           
                         
                         ) 
                       
                     
                     = 
                     
                       
                         
                           { 
                           
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             M 
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             0 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             M 
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                             , 
                             1 
                             , 
                             
                               - 
                               M 
                             
                           
                           } 
                         
                         * 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         
                           ( 
                           
                             1 
                             + 
                             j 
                           
                           ) 
                         
                         / 
                         
                           sqrt 
                           ⁡ 
                           
                             ( 
                             2 
                             ) 
                           
                         
                       
                     
                   
                   ⁢ 
                   
                     
 
                   
                   ⁢ 
                   
                     
                       
                         
                           EHT 
                           - 
                           STF 
                         
                         ⁢ 
                         
                           ( 
                           
                             - 
                             504 
                           
                           ) 
                         
                       
                       = 
                       0 
                     
                     , 
                     
                       
 
                     
                     ⁢ 
                     
                       
                         
                           EHT 
                           - 
                           STF 
                         
                         ⁢ 
                         
                           ( 
                           504 
                           ) 
                         
                       
                       = 
                       0 
                     
                   
                 
               
               
                 
                     
                 
               
             
           
         
       
     
     The EHT-LTF may have first, second, and third types (i.e., 1×, 2×, 4× LTF). For example, the first/second/third type LTF may be generated based on an LTF sequence in which a non-zero coefficient is arranged with an interval of 4/2/1 subcarriers. The first/second/third type LTF may have a time length of 3.2/6.4/12.8 μs. In addition, a GI (e.g., 0.8/1/6/3.2 μs) having various lengths may be applied to the first/second/third type LTF. 
     Information related to a type of STF and/or LTF (information related to a GI applied to LTF is also included) may be included in a SIG-A field and/or SIG-B field or the like of  FIG. 18 . 
     A PPDU (e.g., EHT-PPDU) of  FIG. 18  may be configured based on the example of  FIG. 5  and  FIG. 6 . 
     For example, an EHT PPDU transmitted on a 20 MHz band, i.e., a 20 MHz EHT PPDU, may be configured based on the RU of  FIG. 5 . That is, a location of an RU of EHT-STF, EHT-LTF, and data fields included in the EHT PPDU may be determined as shown in  FIG. 5 . 
     An EHT PPDU transmitted on a 40 MHz band, i.e., a 40 MHz EHT PPDU, may be configured based on the RU of  FIG. 6 . That is, a location of an RU of EHT-STF, EHT-LTF, and data fields included in the EHT PPDU may be determined as shown in  FIG. 6 . 
     Since the RU location of  FIG. 6  corresponds to 40 MHz, a tone-plan for 80 MHz may be determined when the pattern of  FIG. 6  is repeated twice. That is, an 80 MHz EHT PPDU may be transmitted based on a new tone-plan in which not the RU of  FIG. 7  but the RU of  FIG. 6  is repeated twice. 
     When the pattern of  FIG. 6  is repeated twice, 23 tones (i.e., 11 guard tones+12 guard tones) may be configured in a DC region. That is, a tone-plan for an 80 MHz EHT PPDU allocated based on OFDMA may have 23 DC tones. Unlike this, an 80 MHz EHT PPDU allocated based on non-OFDMA (i.e., a non-OFDMA full bandwidth 80 MHz PPDU) may be configured based on a 996-RU, and may include 5 DC tones, 12 left guard tones, and 11 right guard tones. 
     A tone-plan for 160/240/320 MHz may be configured in such a manner that the pattern of  FIG. 6  is repeated several times. 
     The PPDU of  FIG. 18  may be determined (or identified) as an EHT PPDU based on the following method. 
     A receiving STA may determine a type of an RX PPDU as the EHT PPDU, based on the following aspect. For example, the RX PPDU may be determined as the EHT PPDU: 1) when a first symbol after an L-LTF signal of the RX PPDU is a BPSK symbol; 2) when RL-SIG in which the L-SIG of the RX PPDU is repeated is detected; and 3) when a result of applying “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 frames, 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 a band plan of 5.9 GHz DSRC. 
     5.9 GHz DSRC is a short to medium range communications service that supports both public safety and private operations in roadside-to-vehicle and vehicle-to-vehicle communication environments. DSRC is devised as a complement to cellular communications by providing very high data transfer rates in situations where minimizing latency in the communication link and isolating relatively small communication zones are important. Additionally, PHY and MAC protocols are based on the revision of IEEE 802.11p for wireless access in a vehicular environment (WAVE). 
     &lt;IEEE 802.11p&gt; 
     802.11p uses a PHY of 802.11a by performing 2× downclocking on the PHY. That is, 802.11p transmits a signal by using a 10 MHz bandwidth and not a 20 MHz bandwidth. The numerology comparing 802.11a to 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, 36, 
                 3, 4.5, 6, 9, 12, 18, 
               
               
                   
                 48, 54 Mbps 
                 24, 27 Mbps 
               
            
           
           
               
               
               
               
               
            
               
                 Frequency band 
                 5 
                 GHz ISM 
                 5.9 
                 GHz dedicated 
               
               
                   
               
            
           
         
       
     
     Channels of a DSRC band include a control channel and a service channel, and each channel is capable of performing data transmission at 3, 4.5, 6, 9, 12, 18, 24, and 27 Mbps. If an option channel (or optional channel) of 20 MHz exists, transmission at 6, 9, 12, 18, 24, 36, 48, and 54 Mbps may be performed. 6, 9, and 12 Mbps should be supported in all services and channels. And, in case of a control channel, although a preamble is 3 Mbps, the message itself is 6 Mbps. In case channels  174  and  176  and channels  180  and  182  are authorized by a frequency regulation organization, the channel sets may be channels  175  and  181  of 20 MHz, respectively. The remaining channel should be reserved for future usage. A short message or notification data, public safety alarm data, and so on, are broadcasted to all On Board Units (OBUs) through the control channel The control channel and the service channel have been isolated in order to maximize efficiency and quality of service and to reduce interference between services. 
     Channel number  178  is a control channel, which automatically performs search and receives notification or data transmission, warning messages, and so on, from a Road Side Unit (RSU). All data of the control channel should be transmitted within 200 ms and is repeated at a pre-defined cycle. In a control channel, public safety warnings have the highest priority over any other private messages. Private messages that are larger than 20 Oms are transmitted through a service channel. 
     Private messages or long public safety messages, and so on, are transmitted through a service channel In order to prevent collision (or conflict), a scheme for detecting channel status (i.e., Carrier Sense Multiple Access (CSMA)) is used prior to the transmission. 
     Hereinafter, EDCA parameters in an Outside Context of BSS (OCB) mode will be defined. An OCB mode denotes a state where direct communication between nodes can be performed without any procedure of association with an AP. The following shows a basic EDCA parameter set for STA operations, in case dot11OCBActivated is true. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 AC 
                 CWmin 
                 CWmax 
                 AIFSN 
                 TXOP limit 
               
               
                   
               
             
            
               
                 AC_BK 
                 aCWmin 
                 aCWmax 
                 9 
                 0 
               
               
                 AC_BE 
                 aCWmin 
                 aCWmax 
                 6 
                 0 
               
               
                 AC_VI 
                 (aCWmin + 1)/2 − 1 
                 aCWmin 
                 3 
                 0 
               
               
                 AC_VO 
                 (aCWmin + 1)/4 − 1 
                 (aCWmin + 1)/2 − 1 
                 2 
                 0 
               
               
                   
               
            
           
         
       
     
     Characteristics of the OCB mode are as follows. 
     1. In a MAC header, To/From DS fields may be set to ‘0’. 
     2. Fields related to Address
         Individual or group destination MAC address may be used.   A BSSID field may be the same as a wildcard BSSID. (BSSID field=wildcard BSSID)   In a Data/Management frame, Address 1 may be an RA, Address 2 may be a TA, and Address 3 may be a wildcard BSSID.       

     3. An authentication process, an association process, or data confidentiality services of the IEEE 802.11 standard may not be used (or utilized). 
     4. A TXOP limit may be set to ‘0’. 
     5. Only a TC (TID) may be used. 
     6. STAs may not be required to synchronize to a common clock or use such mechanisms.
         STAs may maintain a timing synchronization function (TSF) timer for purposes other than synchronization       

     7. The STA may send Action frames, and, if the STA maintains a TSF Timer, the STA may transmit Timing Advertisement frames. 
     8. The STA may send control frames excluding subtype PS-Poll, CF-End, and CF-End +CFAck. 
     9. The STA may send data frames of subtype Data, Null, QoS Data, and QoS Null. 
     10. An STA having dot11OCBActivated that is equal to true should not join (or participate in) or start a BSS. 
     Format of 11p PPDU 
       FIG. 21  shows a format of an 11p PPDU. 
     Referring to  FIG. 21 , a frame of the 802.11p standard (hereinafter referred to as 11p PPDU  2100 ) may support vehicle-to-vehicle (V2V) communication in a 5.9 GHz band. The 11p PPDU  2100  may include an STF  2110  for synchronization (sync) and Automatic Gain Control AGC, an LTF  2120  for channel estimation, and/or a SIG (or SIG field)  2130  including information related to a Data field  2140 . The Data field  2140  may be configured to include 16 bits configuring the service field. 
     The 11p PPDU  2100  may be configured by applying the same OFDM numerology as the IEEE 802.11a standard for a 10 MHz bandwidth. For example, the IEEE 802.11p standard may be applied by 2× down-clocking the OFDM numerology for a 20 MHz bandwidth according to the IEEE 802.11a standard. Therefore, a symbol of the 11p PPDU  2100  may be configured to be longer than a symbol of a frame (or PPDU) of the IEEE 802.11a standard. A symbol of the 11p PPDU  2100  may have a symbol duration of 8 μs. The 11p PPDU  2100  may have a length that is two times longer than a frame according to the 802.11a standard in the aspect of time. 
     Format of NGV PPDU 
     Hereinafter, a technical characteristic that can provide interoperability of multiple system will be proposed. For example, multiple systems may include a system (IEEE 802.11bd standard) that is proposed for supporting throughput enhancement, coverage extension, and/or high speed for Vehicle-to-Everything (V2X) in a 5.9 GHz band, and/or a DSRC system that is based on the existing (or conventional) IEEE 802.11p standard. 
     In order to achieve smooth V2X support in a 5.9 GHz band, a technology for NGV considering throughput enhancement and high-speed support in the DSRC is being developed.  FIG. 22  to  FIG. 25  show the format of a frame (hereinafter referred to as NGV PPDU) according to the IEEE 802.11bd standard. 
     An NGV PPDU that will hereinafter be described may include a preamble, a data field that is contiguous to the preamble, and a midamble that is contiguous to the data field. Additionally, the NGV PPDU may include an additional data field that is contiguous to the midamble. A number of symbols or a periodicity (or period or cycle period) of a midamble within an NGV PPDU may be variously configured. For example, the preamble of the NGV PPDU may include an L-STF, an L-LTF, an L-SIG, an RL-SIG, an NGV-SIG, an RNGV-SIG, an NGV-STF, and/or an NGV-LTF. An NGV midamble may be configured to have the same format as the NGV-LTF. The above-mentioned L-SIG, RL-SIG, NGV-SIG, and/or RNGV-SIG may also be referred to as an L-SIG field, an RL-SIG field, an NGV-SIG field, and/or an RNGV-SIG field, respectively. 
       FIG. 22  shows a format of an NGV PPDU. 
     Referring to  FIG. 22 , the IEEE 802.11bd standard may be proposed for throughput enhancement and coverage extension in comparison with the IEEE 802.11p standard. That is, when a PPDU of the IEEE 802.11bd standard (e.g., NGV PPDU  2200 ) is used, the effects of throughput enhancement and coverage extension are greater than when using a PPDU of the IEEE 802.11p standard (e.g., 11p PPDU  2100  of  FIG. 21 ). 
     The NGV PPDU  2200  may be configured to have a 10 MHz bandwidth. The NGV PPDU  2200  may include a preamble of an 11p PPDU (i.e., L-STF, L-LTF or L-SIG) for backward compatibility or interoperability with the IEEE 802.11p standard. For example, the NGV PPDU  2200  may include an L-STF  2210 , an L-LTF  2220  or an L-SIG  2230 . For example, the L-STF  2210 , L-LTF  2220  or L-SIG  2230  may be located in a foremost position within the NGV PPDU  2200 . In other words, when the L-STF  2210 , L-LTF  2220  or L-SIG  2230  are transmitted these fields may be the first to be transmitted/received. 
     The NGV PPDU  2200  may include symbols constituting the NGV-SIG  2240 , NGV-STF  2250  and NGV-LTF  2260  including control information for the NGV standard and NGV-data  2270 . The NGV-SIG  2240 , NGV-STF  2250 , NGV-LTF  2260 , and/or NGV-data  2270  may be positioned after L-SIG  2230 . 
     Contrary to that shown in  FIG. 22 , the NGV PPDU may be configured in various ways. 
     1) For example, when transmission of one spatial stream (or single stream) is performed, additional AGC may not be performed. In this case, NGV-STF may be omitted. Accordingly, there is an effect that it is not necessary to configure the NGV-STF individually. Therefore, when broadcasting in an Outside Context of BSS (OCB) mode, a frame format in which NGV-STF is excluded may be used. 
     2) For example, after the L-SIG for robust transmission and/or range extension of the NGV standard, the L-SIG may be repeatedly transmitted. In other words, the RL-SIG may be contiguous to the L-SIG. An example of a configuration including the RL-SIG may be described with reference to  FIG. 23 . 
       FIG. 23  shows another format of an NGV PPDU. 
     Referring to  FIG. 23 , the NGV PPDU  2300  includes an L-STF  2310 , an L-LTF  2320 , an L-SIG  2330 , an RL-SIG  2340 , an NGV-SIG  2350 , an NGV-STF  2360 , NGV-LTF  2370 , and/or NGV data  2380 . The RL-SIG  2340  may be contiguous to L-SIG  2330 . The RL-SIG  2340  may include the same information field as the L-SIG  2330  and may be modulated (e.g., BPSK) in the same manner as the L-SIG  2330 . 
     3) When transmitting the NGV PPDU, the rate field of the L-SIG may be set to 4 bits representing 3 Mbps. Also, the length field may be set based on 3 Mbps. Accordingly, the length field may set to a value satisfying the condition that the remainder is zero when (the value of) the length field is divided by 3. A specific example in which the length field is set may be described below. 
     The value of the length field may be set as in Equation 12. 
     
       
         
           
             
               
                 
                   Length 
                   = 
                   
                     
                       
                         
                           
                             T 
                             ⁢ 
                             X 
                             ⁢ 
                             T 
                             ⁢ 
                             I 
                             ⁢ 
                             M 
                             ⁢ 
                             E 
                           
                           - 
                           
                             4 
                             ⁢ 
                             0 
                           
                         
                         8 
                       
                       × 
                       3 
                     
                     - 
                     3 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     12 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 12, Length may denote a value of the length field of the L-SIG. In Equation 12, TXTIME may denote a transmission time (or duration) of the NGV PPDU. 
     1) Here, TXTIME in Equation 12 may be set as in Equation 13. 
     
       
         
           
             
               
                 
                   TXTIME 
                   = 
                   
                     
                       T 
                       
                         L 
                         - 
                         STF 
                       
                     
                     + 
                     
                       T 
                       
                         L 
                         - 
                         LTF 
                       
                     
                     + 
                     
                       T 
                       
                         L 
                         - 
                         SIG 
                       
                     
                     + 
                     
                       T 
                       
                         RL 
                         - 
                         SIG 
                       
                     
                     + 
                     
                       T 
                       
                         NGV 
                         - 
                         SIG 
                       
                     
                     + 
                     
                       T 
                       
                         NGV 
                         - 
                         STF 
                       
                     
                     + 
                     
                       T 
                       
                         NGV 
                         - 
                         LTF 
                       
                     
                     + 
                     
                       
                         T 
                         SYML 
                       
                       × 
                       
                         N 
                         SYM 
                       
                     
                     + 
                     
                       
                         T 
                         MID 
                       
                       × 
                       
                         N 
                         MID 
                       
                     
                     + 
                     alpha 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     13 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 13, TXTIME may denote a transmission time (or duration) of an NGV PPDU. TXTIME may be set as the sum of the transmission times of each field included in the NGV PPDU. T L-STF  may denote a transmission time of L-STF. T L-LTF  may denote a transmission time of L-LTF. T L-SIG  may denote a transmission time of the L-SIG. T RL-SIG  may denote a transmission time of the RL-SIG. T NGV-SIG  may denote a transmission time of NGV-SIG. T NGV-STF  may denote a transmission time of NGV-STF. T NGV-LTF  may denote a transmission time of NGV-LTF. T SYML  may denote one symbol length of NGV data. N SYM  may denote the number of symbols of NGV data. T MID  may denote the length of the midamble. N MID  may denote the number of midambles. In Equation 13, alpha may be set to a value for packet extension (PE) or signal extension added so that length can be a multiple of 3. 
       FIG. 24  shows a format of an NGV PPDU for performing 10 MHz transmission. 
     Referring to  FIG. 24 , for backward compatibility or interoperability with the IEEE 802.11p, an NGV PPDU  2400  may include fields (i.e., L-STF, L-LTF and/or L-SIG) of a frame according to the IEEE 802.11p standard (hereinafter referred to as an 11p PPDU). For example, the NGV PPDU  2400  may include an L-STF  2410 , an L-LTF  2420  or an L-SIG  2430 . Additionally, the NGV PPDU may include an RL-SIG  2440 , an NGV-SIG  2450 , an RNGV-SIG  2460 , an NGV-STF  2470 , an NGV-LTF  2480 , and/or an NGV Data  2490 . 
     The RL-SIG  2440  may be contiguous to the L-SIG  2430 . The RL-SIG  2440  may be a field in which the L-SIG  2430  is repeated. In other words, the RL-SIG  2440  may include the same information field as the L-SIG  2430  and may be modulated by using the same method as the L-SIG  2430  (e.g., BPSK). 
     The NGV-SIG  2450  may be related to transmission information. For example, the NGV-SIG  2450  may include the transmission information. For example, the NGV-SIG  2450  may be configured to be equal to 24 bits. For example, the NGV-SIG  2450  may include information related to a Physical layer (PHY) Version, information related to a bandwidth, information related to an MCS, information related to a number of spatial streams, information related to a midamble periodicity, information related to an LTF format, information related to an LDPC Extra OFDM Symbol, information related to a CRC, and/or information related to a tail bit. BCC encoding based on a ½ coding rate may be applied to the NGV-SIG  2450 . 
     The RNGV-SIG  2460  may be contiguous to the NGV-SIG  2450 . The RNGV-SIG  2460  may be a field in which the NGV-SIG  2450  is repeated. In other words, the RNGV-SIG  2460  may include the same information field as the NGV-SIG  2450  and may be modulated by using the same method as the NGV-SIG  2450  (e.g., BPSK). 
     The NGV-STF  2470  may be configured by 2× down-clocking a 20 MHz VHT-STF that is configured according to the IEEE 802.11ac standard. The NGV-LTF  2480  may be configured by 2× down-clocking a 20 MHz VHT-LTF that is configured according to the IEEE 802.11ac standard. 
     The NGV-LTF  2480  may be configured based on at least one LTF format. For example, the NGV-LTF  2480  may be configured based on at least one of an NGV-LTF-lx format, an NGV-LTF-2× format, or a repeated NGV-LTF-2× format. Information related to the LTF format that is used in the NGV-LTF  2480  may be included in the NGV-SIG  2450 . 
     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  2490 . For example, when the DCM and BPSK modulation are applied to the NGV data  2490 , regardless of the information related to the LTF format included in the NGV-SIG  2450 , the repeated NGV-LTF-2× format may be used in/applied to the NGV-LTF  2480 . 
     For example, in the 10 MHz transmission, a sequence of the NGV-LTF-1× format may be configured as shown below in Equation 14. 
     
       
         
           
             
               
                 
                   NGV 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   LTF 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     
                       1 
                       ⁢ 
                       x 
                       ⁢ 
                           
                       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 
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     14 
                   
                   &gt; 
                 
               
             
           
         
       
     
     For example, in the 10 MHz transmission, a sequence of the NGV-LTF-2× format may be configured as shown below in Equation 15. 
     
       
         
           
             
               
                 
                   NGV 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   LTF 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   ⁠ 
                   
                     
                       2 
                       ⁢ 
                       x 
                       ⁢ 
                           
                       sequence 
                     
                     = 
                     
                       [ 
                       ⁠ 
                       
                         1 
                         , 
                         1 
                         , 
                         LTF_left 
                         , 
                         0 
                         , 
                         LTF_right 
                         , 
                         
                           - 
                           1 
                         
                         , 
                         
                           - 
                           1 
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     15 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 15, 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 
                         , 
                         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 
                         , 
                         1 
                       
                       ] 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     16 
                   
                   &gt; 
                 
               
             
           
         
       
     
     The NGV data  2490  may include a service field, PHY pad bits, and/or a PSDU. 
     Although it is not shown in the drawing, the NGV PPDU  2400  may include a midamble that is contiguous to the NGV data  2490 . Additionally, the NGV PPDU  2400  may include an additional data field that is contiguous to the midamble. 
     The midamble may be used for performing additional channel estimation. That is, the midamble has an effect of reducing the effect of Doppler shift. 
     The midamble may be inserted/configured in the NGV PPDU  2400  according to a designated periodicity. Information related to the designated periodicity may be included in the NGV-SIG  2450 . For example, the NGV-SIG  2450  may include information related to the midamble periodicity. The midamble periodicity may be set to one of 4, 8 or 16. For example, when the midamble periodicity is set to 4, the NGV PPDU  2400  may include midamble(s) being inserted every 4 data symbols. 
     The midamble may be configured to have the same format as the NGV-LTF  2480 . For example, the midamble may be configured of at least one of an NGV-LTF-1× format, an NGV-LTF-2× format, or a repeated NGV-LTF-2× format. Information related to the LTF format that is used in the midamble may be included in the NGV-SIG  2450 . 
       FIG. 25  shows a format of an NGV PPDU for performing 20 MHz transmission. 
     Referring to  FIG. 25 , an NGV PPDU  2500  may be configured of 20 MHz. The NGV PPDU  2500  may include an L-STF  2510 , an L-LTF  2520 , an L-SIG  2530 , an RL-SIG  2540 , an NGV-SIG  2550 , an RNGV-SIG  2560 , an NGV-STF  2570 , an NGV-LTF  2580 , and/or an NGV Data  2590 . 
     The L-STF  2510 , L-LTF  2520  or L-SIG  2530  may be configured by being duplicated in 10 MHz units. The L-STF  2510 , L-LTF  2520  or L-SIG  2530  may be related to the L-STF  2410 , L-LTF  2420  or L-SIG  2430  of  FIG. 24 . 
     According to an embodiment, the RL-SIG  2540 , NGV-SIG  2550  or RNGV-SIG  2560  may also be configured by being duplicated in 10 MHz units. The RL-SIG  2540 , NGV-SIG  2550  or RNGV-SIG  2560  may be related to the RL-SIG  2440 , NGV-SIG  2450  or RNGV-SIG  2460  of  FIG. 24 , respectively. 
     The NGV-STF  2570  may be configured by 2× down-clocking a 40 MHz VHT-STF that is configured according to the IEEE 802.11ac standard. The NGV-LTF  2580  may be configured by 2× down-clocking a 40 MHz VHT-LTF that is configured according to the IEEE 802.11ac standard. 
     The NGV-LTF  2580  may be configured based on at least one LTF format. For example, the NGV-LTF  2580  may be configured based on at least one of an NGV-LTF-1× format, an NGV-LTF-2× format, or a repeated NGV-LTF-2× format. 
     For example, in the 20 MHz transmission, a sequence of the NGV-LTF-1× format may be configured as shown below in Equation 17. 
     
       
         
           
             
               
                 
                   
                     NGV 
                     - 
                     LTF 
                     - 
                     1 
                     ⁢ 
                     x 
                     ⁢ 
                         
                     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 
                     
                     ] 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     17 
                   
                   &gt; 
                 
               
             
           
         
       
     
     For example, in the 20 MHz transmission, a sequence of the NGV-LTF-2× format may be configured as shown below in Equation 18. 
     
       
         
           
             
               
                 
                   NGV 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   LTF 
                   ⁢ 
                   ‐ 
                   ⁢ 
                   
                     
                       2 
                       ⁢ 
                       x 
                       ⁢ 
                           
                       sequence 
                     
                     = 
                     
                       [ 
                       
                         LTF_left 
                         , 
                         1 
                         , 
                         LTF_right 
                         , 
                         
                           - 
                           1 
                         
                         , 
                         
                           - 
                           1 
                         
                         , 
                         
                           - 
                           1 
                         
                         , 
                         1 
                         , 
                         0 
                         , 
                         0 
                         , 
                         0 
                         , 
                         
                           - 
                           1 
                         
                         , 
                         1 
                         , 
                         1 
                         , 
                         
                           - 
                           1 
                         
                         , 
                         LTF_left 
                         , 
                         1 
                         , 
                         LTF_right 
                       
                       ] 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     18 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 18, LTF_left and LTF_right may be configured as presented above in Equation 16. 
     The NGV data  2590  may include a service field, PHY pad bits, and/or a PSDU. The NGV data  2590  may be related to the NGV data  2490  of  FIG. 24 . 
     Although it is not shown in the drawing, similarly to the NGV PPDU  2400  of  FIG. 24 , the NGV PPDU  2500  may include a midamble that is contiguous to the NGV data  2590 . Additionally, the NGV PPDU  2500  may include an additional data field that is contiguous to the midamble. 
     An example of this specification is related to an NGV PPDU (or 11bd PPDU). The NGV PPDU may be used in various wireless communication systems, and, for example, the NGV PPDU may be used in an IEEE 802.11bd wireless LAN communication system. 
     The NGV PPDU may be referred to by using various terms. For example, the NGV PPDU may also be referred to as an NGV frame, an 11bd frame, an 11bd PPDU, and so on. Additionally, as another example, the NGV PPDU may also be referred to by using other various terms, such as a first type PPDU, a transmission PPDU, a reception PPDU, a WLAN PPDU, and so on. Hereinafter, for simplicity in the description, a frame of the IEEE 802.11bd standard may also be referred to as an NGV PPDU. Additionally, a PPDU according to the IEEE 802.11p standard may also be referred to as an 11p PPDU. 
     Similarly, an STA supporting the IEEE 802.11bd standard may also be referred to by using other various terms. For example, an STA supporting the IEEE 802.11bd standard may also be referred to as an 11bd STA, an NGV STA, a transmitting STA or a receiving STA. Hereinafter, for simplicity in the description, the STA supporting the IEEE 802.11bd standard may be referred to as a transmitting/receiving STA. Additionally, an STA supporting the IEEE 802.11p standard may be referred to as an 11p STA. Furthermore, the 5.9 GHz band may also be variously referred to as an NGV band, a reception band, a transmission band, and so on. 
     The development of an NGV standard for throughput enhancement and coverage extension, and so on, in comparison with the IEEE 802.11p standard is currently in process. According to the NGV standard, smooth V2X (or V2X communication) may be supported in a 5.9 GHz band. 
     Midamble Configuration of NGV PPDU 
     When a transmitting STA transmits an NGV PPDU (e.g., NGV PPDU  2400 ,  2500 ), in order to reduce the effect of Doppler shift, which is caused by high speed, the NGV STA may periodically transmit a midamble between NGV-data fields. The configuration of a midamble, which is included in an NGV PPDU, may be described in detail with reference to  FIG. 26 . 
       FIG. 26  shows a midamble configuration in an NGV PPDU. 
     Referring to  FIG. 26 , an NGV PPDU may include at least one midamble. 
     According to an embodiment, the NGV PPDU  2600  may include a first midamble  2620  that is continuous to the NGV-data  2610 . The NGV PPDU  2600  may include NGV-data  2630  continuous to the first midamble  2620 . The NGV PPDU  2600  may include a second midamble  2640  continuous to the NGV-data  2630 . 
     According to an embodiment, the midambles  2620  and  2640  may be inserted/configured in the middle of the NGV-data part at a specified period (i.e., the transmission periodicity of the midamble). For example, the NGV PPDU  2600  may include midambles  2620  and  2640  having the periodicity of M symbol following the NGV-LTF  2601 . That is, the each of the NGV-data  2610  and the NGV-data  2630  may have M symbols. 
     Structure of Midamble 
     According to an embodiment, the midamble may be configured based on NGV-LTF (e.g., 1×-LTF). According to an embodiment, the midamble may be configured based on a compressed LTF (or a compressed LTF sequence). For example, the midamble may be configured based on 2×-compressed LTF (or 2×-LTF sequence) or 4×-compressed LTF (or 4×-LTF sequence). That is, the midamble and the NGV-LTF may be configured as one of 1×-LTF, 2×-LTF, and 4×-LTF. In other words, the format of the midamble and the NGV-LTF may be set to one of 1×-LTF, 2×-LTF, and 4×-LTF. 
     According to an embodiment, the LTF signal may be generated based on the LTF sequence, and the LTF signal may constitute the midamble. The LTF signal may be called variously. For example, the LTF signal may be referred to as an LTF or an LTF symbol. Hereinafter, for convenience of description, the LTF signal (e.g., NGV-LTF signal) may be described as LTF (e.g., NGV-LTF). As an example, the 1×-LTF signal may be described as 1×-LTF. 
     For example, the midamble and the NGV-LTF may be configured with the same LTF (or LTF sequence) for transmission. For example, the midamble may be configured based on 1×-LTF (or 1×-LTF sequence), and the NGV-LTF may be configured based on the same 1×-LTF (or 1×-LTF sequence) as the midamble. 
     As another example, the midamble may be configured based on a sequence different from that of the NGV-LTF. As an example, the NGV-LTF may be configured based on 1×-LTF (or 1×-LTF sequence), and the midamble may be configured based on 2×-LTF (or 2×-LTF sequence). 
     The above-described example is only one example and is not limited thereto. The NGV-LTF and the midamble may be variously configured based on a combination of 1×/2×/4× LTF. 
     The above-described 1×/2×/4× LTF may be configured as follows. 
     1) 1×-LTF (normal LTF)—The 1×-LTF may be configured such that an LTF sequence is carried on all available tones. For example, the LTF sequence constituting the 1×-LTF may be set to non-zero in all available tones. For example, the available tones may denote tones excluding DC tone(s) and guard tone(s) from all tones within a bandwidth. The DC tone(s) and guard tone(s) may be set based on bandwidth. 
     For example, in a 10 MHz band, the DC tone(s) may consist of 1 tone. The left guard tone(s) may consist of 4 tones. The right guard tone(s) may consist of 3 tones. Therefore, the available tones in a 10 MHz band may consist of 56 tones. That is, the LTF sequence constituting the 1×-LTF of 10 MHz may have non-zero elements/values in 56 tones. In addition, the LTF sequence constituting the 1×-LTF of 10 MHz may be set to “0” (zero) in the DC tone(s) consisting of 1 tone. 
     As another example, in a 20 MHz band, the DC tone(s) may consist of 3 tones. The left guard tone(s) may consist of 6 tones. The right guard tone(s) may consist of 5 tones. Accordingly, the available tones in a 20 MHz band may consist of 114 tones. That is, the LTF sequence constituting the lx-LTF of 20 MHz may be have non-zero elements/values in 114 tones. In addition, the LTF sequence constituting the 1×-LTF of 10 MHz may be set to “0” (zero) in the DC tone(s) consisting of 3 tones. 
     According to an embodiment, the 1×-LTF may be called variously. For example, the 1×-LTF may be referred to as 1×-compressed LTF. As another example, the 1×-LTF may be referred to as a 1×-LTF symbol. 
     2) 2×-compressed LTF—The 2×-compressed LTF may be configured such that an LTF sequence is carried in an interval of 2 tones within the available tones. A 2×-compressed LTF may be configured by using only one of the two repeated signals within one symbol. Since only one of the two repeated signals is used, the length of the 2×-compressed LTF may be set to ½ of the length of the 1×-compressed LTF. For example, the LTF sequence constituting the 2×-compressed LTF may be set to non-zero at an interval of 2 tones within the available tones. For example, the available tones may denote tones excluding the DC tone(s) and guard tone(s) from all tones within a bandwidth. The DC tone(s) and guard tone(s) may be set based on bandwidth. 
     For example, in a 10 MHz band, the DC tone(s) may consist of 1 tone. Also, the available tones may consist of 56 tones. That is, the LTF sequence constituting the 2×-compressed LTF of 10 MHz may be set to ‘0’ (zero) in the DC tone(s) consisting of 1 tone. In addition, the LTF sequence constituting the 2×-compressed LTF of 10 MHz may have ‘non-zero’ elements/values at an interval of 2 tones in the available tones of 56 tones. 
     As another example, in a 20 MHz band, the DC tone(s) may consist of 3 tones. Also, the available tones may consist of 114 tones. That is, the LTF sequence constituting the 2×-compressed LTF of 20 MHz may be set to ‘0’ (zero) in the DC tone(s) consisting of 3 tones. In addition, the LTF sequence constituting the 2×-compressed LTF of 20 MHz may have ‘non-zero’ elements/values at an interval of 2 tones in the available tones of 114 tones. 
     According to an embodiment, the 2×-compressed LTF may be called variously. For example, the 2×-compressed LTF may be referred to as a 2×-LTF. As another example, the 2×-compressed LTF may be referred to as a 2×-compressed LTF symbol. 
     3) 4×-compressed LTF—The 4×-compressed LTF can be configured such that the LTF sequence is carried in 4-tone intervals within the available tones. The 4×-compressed LTF may be configured by using only one of the four repeated signals within one symbol. The length of the 4×-compressed LTF may be set to ¼ of the length of the 1×-LTF. For example, the LTF sequence constituting the 4×-compressed LTF may have non-zero elements/values at intervals of 4 tones within the available tones. For example, the available tones may denote tones excluding the DC tone(s) and the guard tone(s) from all tones within a bandwidth. The DC tone(s) and guard tone(s) may be set based on bandwidth. 
     For example, in a 10 MHz band, the DC tone(s) may consist of 1 tone. Also, the available tones may consist of 56 tones. That is, the LTF sequence constituting the 4×-compressed LTF of 10 MHz may be set to ‘0’ (zero) in the DC tone(s) consisting of 1 tone. In addition, the LTF sequence constituting the 4×-compressed LTF of 10 MHz may have ‘non-zero’ elements/values at intervals of 4 tones in the available tones of 56 tones. 
     As another example, in the 20 MHz bandwidth, the DC tone(s) may be set to 3 tones. Also, the available tones may be set to 114 tones. That is, the LTF sequence constituting the 4×-compressed LTF of 20 MHz may be set to ‘0’ (zero) in the DC tone(s) of 3 tones. In addition, the LTF sequence constituting the 4×-compressed LTF of 20 MHz may be set to ‘non-zero’ at an interval of 4 tones in the available tones of 114 tones. 
     According to an embodiment, the 4×-compressed LTF may be called variously. For example, the 4×-compressed LTF may be referred to as a 4×-LTF. As another example, the 4×-compressed LTF may be referred to as a 4×-compressed LTF symbol. 
     According to an embodiment, the NGV PPDU may be transmitted in a high speed environment having a large influence of Doppler shift. Accordingly, the transmitting STA transmitting the NGV PPDU may configure the midamble based on the receiving environment (or the transmitting environment). In other words, the transmitting STA may set the format of the midamble based on the reception environment. When the midamble is transmitted based on the reception environment, there is an effect of increasing transmission efficiency. 
     As described above, in order to reduce overhead caused by the midamble, a ‘compressed midamble’ constructed using a 2×-LTF sequence or a 4×-LTF sequence may be used. In addition, for more accurate channel estimation and Doppler tracking, a ‘compressed midamble’ may be repeatedly transmitted. A configuration in which the ‘compressed midamble’ is repeatedly transmitted may be referred to as a ‘repeated compressed midamble’. 
     According to an embodiment, the ‘compressed midamble’ and/or the ‘repeated compressed midamble’ may be set in various ways. Hereinafter, specific examples of the ‘compressed midamble’ and/or the ‘repeated compressed midamble’ may be described. Hereinafter, for convenience of description, the ‘compressed midamble’ may be described through the ‘2×-compressed midamble’ that is an example of the ‘compressed midamble’. 
       FIG. 27  shows an example of a ‘2×-compressed midamble’. 
     Referring to  FIG. 27 , a ‘2×-compressed midamble’ may be configured based on a 2×-LTF sequence. In other words, the ‘2×-compressed midamble’ may include the 2×-LTF sequence. In the frequency domain, the 2×-LTF sequence mapped at 2 tone intervals may be set in a structure in which the same sequence is repeated within one symbol in the time domain. In this case, in order to use the ‘compressed midamble’, a symbol may be configured using only one of two Training Sequences (TSs). In addition, in the case of repeated transmission, a symbol may be constructed by using all of the TSs formed in the time domain without separation. 
     For example, the transmitting STA may configure the 2×-LTF sequence with 2 tone intervals in the frequency domain. A tone in which the 2×-LTF sequence is not configured may be represented by “X” in  FIG. 27 . For example, a tone in which the 2×-LTF sequence is not configured may have a value of ‘0’. The transmitting STA may perform Inverse Fast Fourier Transform (IFFT) based on the 2×-LTF sequence. The transmitting STA may generate two TSs through the IFFT. The two TSs may be configured identically. In other words, the TS may be repeatedly configured in the time domain. Accordingly, the transmitting STA may configure a symbol through only one of the two TSs. The transmitting STA may configure a symbol through all of the two TSs during repeated transmission. That is, the ‘2×-compressed midamble’ may be configured through only one of the two TSs. The ‘repeated 2×-compressed midamble’ can be configured through all two TSs. 
     The 2×-compressed midamble (hereinafter, “2×-comp_mid”) symbol constructed using the above-described embodiment may be configured by applying various GIs for transmission through the NGV PPDU. Hereinafter, various embodiments for describing the configuration of the “2×-comp_mid” symbol may be described. 
     First Embodiment 
     According to the first embodiment, when the “2×-comp-mid” is configured with only one TS (i.e. S1), the midamble symbol may be configured using GI to match symbol boundaries. In other words, the midamble symbol may further include a GI in order to match the symbol boundary. A short GI shorter than the GI used for the NGV data may be used as the GI. An example of a midamble (or a midamble symbol) according to the first embodiment may be described with reference to  FIG. 28 . 
       FIG. 28  shows an example of a midamble symbol. 
     Referring to  FIG. 28 , when the same GI as the 802.11p standard (i.e., 1.6 μs) is used in the NGV standard, the GI used in the midamble may be set to 0.8 μs. Using the GI, a 2×-comp_mid symbol may consist of 4 μs. In other words, 2×-comp-mid (or 2×-comp-mid symbol) may include the GI and 2×-compressed LTF. For example, the transmission time (or duration) of 2×-comp-mid may be set to 4 μs. As an example, the transmission time (or duration) of the GI may be set to 0.8 μs. The transmission time (or duration) of the 2×-compressed LTF may be set to 3.2 μs. 
     A. The length transmitted through the length field of the L-SIG may be transmitted based on 8 μs symbols. Accordingly, in order to match the length indicated in the length field with the length of the PPDU transmitted including the midamble, the PPDU may be configured as follows. 
     A-1. When the number of midambles is odd 
     A-1-i) In order to match the number of Length fields and the length of the NGV PPDU, a midamble may be added to the end of the NGV PPDU by one symbol to configure the NGV PPDU. According to an embodiment, the midamble added after the last data symbol may be ignored. According to an embodiment, the midamble added after the last data symbol may be used together with the previous midambles for channel estimation. 
     A-1-ii) Unlike the above example, instead of one midamble symbol, a padding corresponding to the length may be added to configure a PPDU. In this example, decoding may be performed on the added padding. 
       FIG. 29  shows an example of an NGV PPDU according to the first embodiment. 
     Referring to  FIG. 29 , when the number of midambles of the NGV PPDU  2900  is an odd number, one more midamble symbol  2910  may be added to the end of the NGV PPDU  2900 . The midamble symbol  2910  may be used for channel estimation together with previous midambles. 
     Referring to  FIG. 30 , unlike  FIG. 29 , when the number of midambles of the NGV PPDU  3000  is an odd number, a padding  3010  may be added to the end of the NGV PPDU  3000 . 
       FIG. 30  shows another example of an NGV PPDU according to the first embodiment. 
     A-2. When the number of midambles is even, the total length of the midambles may be set to a multiple of 8 μs. Therefore, when the NGV PPDU is configured, an additional midamble or a padding may not be required. 
     A-3. Information related to an indication for the number of midambles and an additional symbol for PPDU length alignment may be transmitted through the NGV-SIG. In other words, the NGV-SIG may include information related to the number of midambles and/or information related to additional symbols for PPDU length alignment. 
     Second Embodiment 
     Unlike the first embodiment, a GI having the same length as the GI applied to the data symbol can be added to the midamble in order to reduce the influence of Inter Symbol Interference (ISI). An example of a midamble (or a midamble symbol) according to the second embodiment may be described with reference to  FIG. 31 . 
       FIG. 31  shows another example of a midamble symbol. 
     Referring to  FIG. 31 , when the same GI as the 802.11p standard (i.e., 1.6 μs) is used, a GI having a length of 1.6 μs can be added to the midamble to construct the midamble. Therefore, the length of the midamble symbol may be set to 4.8 μs. In other words, 2×-comp-mid (or 2×-comp-mid symbol) may include the GI and 2×-compressed LTF. For example, the transmission time (or duration) of the 2×-comp-mid may be set to 4.8 μs. As an example, the transmission time (or duration) of the GI may be set to 1.6 μs. The transmission time (or duration) of the 2×-compressed LTF may be set to 3.2 μs. 
     A. Since the length of one midamble symbol is 4.8 μs, the NGV PPDU can be configured as follows in order to match the length indicated through the length field and the transmission length. 
     A-1. When the number of symbols in the midamble is a multiple of 5, the transmission length of the entire midamble may be set to a multiple of 8 μs. Accordingly, when the midamble of the above-described structure is transmitted, the total length of the added symbols may be configured as follows. 
     A-1-i) The length (T add ) of the total symbols to be added may be set as in Equation 19. 
     
       
         
           
             
               
                 
                   
                     T 
                     add 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           5 
                           × 
                           n 
                         
                         - 
                         
                           number 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           of 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           midamble 
                         
                       
                       ) 
                     
                     × 
                     4.8 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     us 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     19 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 19, a value of n may be set to a natural number (or an integer). In addition, ‘5×n’ may be set to be larger than the number of transmitted midambles, and the value of ‘n’ may be set to a value having a minimum value of ‘5×n—number of midambles’. 
     A-1-ii) According to an embodiment, the midamble symbol may be repeated by the length calculated in Equation 19 to construct an NGV PPDU. According to an embodiment, an NGV PPDU may be configured by adding a padding as much as the length calculated in Equation 19 above. 
     As described above, decoding may be performed by the receiving STA on the midamble symbol and the padding symbol added to match the length of the NGV PPDU. 
     A-1-iii) Unlike the above, the NGV PPDU may be configured by adding a padding corresponding to the minimum length for setting the length of the NGV PPDU to a multiple of 8. In this case, the added padding length may be set as in Equation 20. 
     
       
         
           
             
               
                 
                   
                     Length 
                     ⁢ 
                         
                     of 
                     ⁢ 
                         
                     padding 
                   
                   = 
                   
                     
                       8 
                       × 
                       m 
                     
                     - 
                     
                       N_SYM 
                       ⁢ 
                       _midamble 
                       × 
                       4.8 
                       us 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     20 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 20, ‘m’ may denote a minimum integer satisfying ‘8×m&gt;N_SYM_midamble×4.8’. 
       FIG. 32  shows an example of an NGV PPDU according to the second embodiment. 
     Referring to  FIG. 32 , if the number of symbols in the midamble of the NGV PPDU  3200  is not a multiple of 5, a midamble may be added at the end of the NGV PPDU  3200  so that the number of symbols in the entire midamble is set to a multiple of 5. The added midamble symbol can be used for channel estimation together with the previous midambles. 
       FIG. 33  shows another example of an NGV PPDU according to the second embodiment. 
     Referring to  FIG. 33 , unlike  FIG. 32 , when the number of symbols in the midamble of the NGV PPDU  3300  is not a multiple of 5, a padding can be added by the length of the total symbols (T add ) calculated based on Equation 19 in the NGV PPDU  3300 . According to an embodiment, a padding may be added to the NGV PPDU  3300  by the length of the padding calculated based on Equation 20. 
     B. The number of symbols of the above-described midamble and the number of added symbols may be indicated through the NGV-SIG. In other words, the NGV-SIG may include information related to the number of symbols in the midamble and the number of symbols to be added. 
     Third Embodiment 
     In the above-described embodiments (the first embodiment and the second embodiment), a symbol of the midamble is configured as a single time-sequence. In the third embodiment, unlike the above-described embodiments, the midamble may be configured using two time-sequences. In this case, the midamble may be set in various ways. Hereinafter, an embodiment in which one GI is set/added with respect to the midamble is described in the following example A, and an embodiment in which a GI is set/added for each time sequence may be described in the following example B. 
     A. An embodiment of constructing a symbol using only one GI for the entire midamble 
     A-1. A time symbol may be configured by adding one GI to the midamble configured to be repeated. An example of a midamble (or midamble symbol) according to the ‘Example A’ of the third embodiment may be described with reference to  FIG. 34 . 
       FIG. 34  shows another example of a midamble symbol. 
     Referring to  FIG. 34 , a midamble symbol may be configured to be a GI and a repeated time sequence (i.e., 2×-comp-mid). The 2×-comp-mid can be set to 3.2 μs. Also, the 2×-comp-mid may be repeated. 
     A-1-i) The length of the GI (Len_GI) in the midamble symbol may be set to 0.8 μs or 1.6 μs. Based on the length of the GI, the length of the midamble symbol may be set to 7.2 μs or 8 μs. For example, when the length of the GI (Len_GI) in the midamble symbol is set to 0.8 μs, the length of the midamble symbol may be set to 7.2 μs. As another example, when the length of the GI (Len_GI) in the midamble symbol is set to 1.6 μs, the length of the midamble symbol may be set to 8 μs. 
     Considering the PPDU length alignment, using a GI of 1.6 μs has the advantage of simple implementation because there is no need to add symbols when configuring the PPDU. In other words, when a GI of 1.6 μs is used, there is an effect of easy implementation. 
     On the other hand, when using a GI of 0.8 μs, an NGV PPDU may be configured by adding a symbol for PPDU length alignment. An example of this can be described below. 
     The symbol length of the midamble may be 7.2 μs. Therefore, in order to align with the length field having a length of 8 μs, the midamble should be composed of a total multiple of 10. Accordingly, the length (T add ) of symbols added when configuring the NGV PPDU may be set as in Equation 21. 
     
       
         
           
             
               
                 
                   
                     T 
                     add 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           10 
                           × 
                           n 
                         
                         - 
                         N_midamble 
                       
                       ) 
                     
                     × 
                     7.2 
                     u 
                     ⁢ 
                     s 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     21 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 21, ‘n’ may be set to a natural number (or an integer). In Equation 21, ‘n’ may be set to a minimum value satisfying that 10×n is greater than the total number of midambles (N_midamble). For example, when the total number of midambles is 7, the length of the added symbol when configuring the NGV PPDU may be set to (10×1−7)×7.2=21.6 μs. In this case, the added symbol may be composed of a midamble or may be composed of a padding. 
     A-1-ii) Unlike the above-described embodiment, the NGV PPDU may be configured by adding a padding corresponding to the minimum length for setting the PPDU length to a multiple of 8. In this case, the added padding length may be set as in Equation 22. 
     
       
         
           
             
               
                 
                   
                     Length 
                     ⁢ 
                         
                     of 
                     ⁢ 
                         
                     padding 
                   
                   = 
                   
                     
                       8 
                       × 
                       m 
                     
                     - 
                     
                       N_sym 
                       ⁢ 
                       _midamble 
                       × 
                       7.2 
                       us 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     22 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 22, ‘m’ may denote a minimum integer satisfying that (8×m)&gt;(N_sym_midamble×7.2). 
     A-1-iii) Unlike the above-described embodiment, a midamble symbol may be configured using a long-length GI in order to prevent inter symbol interference (ISI). For example, the length of the long GI may be set to 3.2 μs. 
     B. Example of configuring midamble symbols in consideration of individual GIs for each time sequence 
     B-1. A midamble symbol may be configured by adding a GI to each time sequence constituting the midamble. A specific example may be described with reference to  FIG. 35 . 
       FIG. 35  shows another example of a midamble symbol. 
     Referring to  FIG. 35 , in the midamble symbol, a GI may be positioned in front of a repeated time sequence (i.e., 2×-comp-mid). That is, the midamble symbol may be configured to include a GI before each time sequence. In other words, the midamble symbol may be configured such that the GI and 2×-comp-mid are repeated. The 2×-comp-mid can be set to 3.2 μs. 
     B-2. As shown in  FIG. 35 , orthogonality can be maintained for each midamble time sequence by adding a GI to each midamble time sequence. Accordingly, when the GI is added to each midamble time sequence, the effect of ISI can be reduced. 
     B-3. In  FIG. 35 , the length of the GI (Len_GI) may be set to 0.8 μs or 1.6 μs. For example, if the length of the GI is set to 0.8 μs, the length of the NGV data symbol (8 μs) and the length of the midamble symbol (0.8+3.2+0.8+3.2 μs) match. Therefore, there is no need to add a symbol to match the PPDU length with the value of the length field of the L-SIG. As another example, when the length of the GI is set to 1.6 μs, a symbol may be added to align the value of the length field with the length of the PPDU. The length of the added symbol may be variously set. 
     B-3-i) The length (T add ) of the added symbol may be set as in Equation 23. 
     
       
         
           
             
               
                 
                   
                     T 
                     add 
                   
                   = 
                   
                     
                       min 
                       ⁡ 
                       ( 
                       
                         
                           
                             5 
                             × 
                             n 
                           
                           - 
                           N_midamble 
                         
                         , 
                         
                           
                             10 
                             × 
                             m 
                           
                           - 
                           N_midamble 
                         
                       
                       ) 
                     
                     × 
                     9.6 
                     us 
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     23 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 23, ‘n’ and ‘m’ may denote integers (or natural numbers). Here, the values of n and m may denote a minimum value satisfying a value of ‘5×n’ is greater than the number of midambles (N_midamble) and a value of ‘10×m’ is greater than the number of midambles (N_midamble). That is, the value of n may be set to a minimum integer satisfying a value ‘5×n’ is greater than the midambles (N_midamble). The value of m may be set to a minimum integer satisfying a value ‘10×m’ is greater than the number of midambles (N_midamble). 
     According to an embodiment, a midamble symbol corresponding to the length (T add ) of the added symbol calculated based on Equation 23 may be added to configure the NGV PPDU. According to an embodiment, a padding corresponding to the length (T add ) of the added symbol calculated based on Equation 23 may be added to configure the NGV PPDU. 
     B-3-ii). Unlike the above-described embodiment, the NGV PPDU can be configured by adding a padding corresponding to the minimum length for setting the PPDU length to a multiple of 8. The added padding length may be set as in Equation 24. 
     
       
         
           
             
               
                 
                   
                     Length 
                     ⁢ 
                         
                     of 
                     ⁢ 
                         
                     padding 
                   
                   = 
                   
                     
                       8 
                       × 
                       m 
                     
                     - 
                     
                       N_sym 
                       ⁢ 
                       _midamble 
                       × 
                       9.6 
                     
                   
                 
               
               
                 
                   &lt; 
                   
                     Equation 
                     ⁢ 
                         
                     24 
                   
                   &gt; 
                 
               
             
           
         
       
     
     Referring to Equation 24, the value of m may be set to a minimum integer satisfying (8×m)&gt;(N_sym_midamble×9.6). 
     Fourth embodiment 
     As in the above-described embodiments, information related to symbols added to align the value of the length field and the length of the PPDU (e.g., NGV PPDU), or information related to ‘n’ and ‘m’ defined in the above-mentioned equation can be transmitted via the NGV signal field (or NGV-SIG). In other words, the NGV-SIG may include information related to an added symbol and/or information related to a parameter value for determining an added symbol. 
     According to an embodiment, the information (i.e., information related to added symbols or information related to n, m) may be transmitted through an NGV signal field using packet extension information. 
     According to an embodiment, information related to the midamble transmitted through the NGV-SIG may be configured in various ways. An example of information related to the midamble transmitted through the NGV-SIG may be described below. 
     i) Information Related to Periodicity 
     Information related to the (midamble) periodicity may be composed of one bit (1-bit information). For example, when information related to the periodicity is set to a first value (e.g., 0), the periodicity may be set to 4. As another example, when information related to periodicity is set to a second value (e.g., 1), the periodicity may be set to 8. 
     ii) Information Related to Mode 
     The information related to the mode may be composed of one bit (one-bit information). For example, when information related to mode is set to a first value (e.g., 0), it may be set to a normal LTF (i.e., 1× LTF). When information on mode information is set to a second value (e.g., 1), it may be set to the 2×-Compressed or the repeated 2×-compressed. 
     iii) Information Related to Symbol for Alignment 
     Information related to the symbol for alignment may consist of 4 bits (4-bit information). Based on the 4-bit information, 0 to 9 symbols may be indicated. In other words, the 4-bit information may include information representing 0 to 9 symbols. 
     In the above-described embodiments (the first to fourth embodiments), the description has been made based on the midamble using the 2×-compreseed LTF. However, the 4×-compressed LTF may be equally applied to the above-described embodiments. Accordingly, the midamble may be configured through the 4×-compressed LTF. Also, the normal LTF (i.e., 1× LTF) may be equally applied to the above-described embodiments. 
       FIG. 36  is a flowchart illustrating an operation of a transmitting STA. 
     Referring to  FIG. 36 , in step S 3610 , the transmitting STA (e.g., STA  110 ,  120  in  FIG. 1 ) may generate/configure an NGV PPDU. 
     According to an embodiment, the NGV PPDU may include a preamble, a data field continuous to the preamble, and a midamble continuous to the data field. For example, the preamble may include a legacy signal field, a repetition signal field in which the legacy signal field is repeated, and an NGV signal field including control information for an NGV PPDU. 
     As an example, the legacy signal field may include the L-SIG. 
     As an example, the repetition control field may include the same information field as the legacy signal field. Also, the repetition control field may be modulated (e.g., BPSK) in the same manner as the legacy signal field. The repetition control field may include the RL-SIG. 
     As an example, the NGV signal field may be related to transmission information. The NGV signal field may include the NGV-SIG. 
     According to an embodiment, the NGV signal field may include 1-bit information related to the format of the midamble. 
     According to an embodiment, the midamble may be configured based on one of an LTF sequence of the first interval and an LTF sequence of the second interval. For example, the first interval may be set to twice the second interval. For example, non-zero element(s) of the LTF sequence of the first interval may be positioned based on the two subcarrier index intervals. For another example, non-zero element(s) of the LTF sequence of the second interval may be positioned based on one subcarrier index interval. 
     For example, the LTF sequence of the first interval may be set based on available tones. As an example, the LTF sequence of the first interval may be configured based on the first interval in the available tones. The available tones may refer to tones excluding DC tone(s) and guard tone(s) from all tones within a bandwidth. Accordingly, in the LTF sequence of the first interval, DC tone(s) (e.g., 1 tone or 3 tones) may be set to ‘0’ (zero). Also, the available tones of the LTF sequence of the first interval may have non-zero elements/values at the first interval. 
     For example, the LTF sequence of the second interval may be set based on available tones. As an example, the LTF sequence of the second interval may be configured based on the second interval within the available tones. The available tones may refer to tones excluding DC tone(s) and guard tone(s) from all tones within a bandwidth. Accordingly, in the LTF sequence of the second interval, DC tone(s) (e.g., 1 tone or 3 tones) may be set to ‘0’ (zero). Also, the available tones of the LTF sequence of the second interval may have non-zero elements/values at the second interval. 
     According to an embodiment, the format of the midamble may be determined as one of a first format related to an LTF sequence of a first interval and a second format related to an LTF sequence of a second interval. For example, the format of the midamble may be determined as one of a first format related to an LTF sequence of a first interval and a second format related to an LTF sequence of a second interval based on 1-bit information related to the format of the midamble. 
     For example, when the 1-bit information related to the format of the midamble is set to a first value (e.g., 1), the format of the midamble may be set as the first format. As another example, when the 1-bit information related to the format of the midamble is set to a second value (e.g., 0), the format of the midamble may be set to the second format. 
     In other words, for example, when the format of the midamble is set as the first format, the transmitting STA may set the 1-bit information related to the format of the midamble as the first value. For another example, when the format of the midamble is set as the second format, the transmitting STA may set the 1-bit information related to the format of the midamble as the second value. 
     For example, the NGV PPDU may further include an NGV-LTF. The 1-bit information related to the format of the midamble may also include (indication) information related to the format of the NGV-LTF. Accordingly, the 1-bit information related to the format of the midamble may indicate the format of the midamble and the NGV-LTF together. Also, the format of the midamble and the format of the NGV-LTF may be identically set. For example, when the 1-bit information related to the format of the midamble is set to a first value (e.g., 1), the LTF sequence of the first interval may be used for the format of the midamble format and the NGV-LTF. When the 1-bit information related to the format of the midamble is set to a second value (e.g., 0), the LTF sequence of the second interval may be used for the format of the midamble format and the NGV-LTF. 
     According to an embodiment, the midamble symbol of the first format may include an LTF signal configured based on the LTF sequence of the first interval and a guard interval (GI) related to the LTF signal. The duration of the LTF signal and the GI related to the LTF signal may be variously set. For example, the duration of the LTF signal may be 3.2 μs. The duration of the GI related to the LTF signal may be 1.6 μs. Accordingly, the midamble symbol duration of the first format may be 4.8 μs. 
     According to an embodiment, the midamble symbol of the second format may include a second LTF signal configured based on the LTF sequence of the second interval and a guard interval (GI) related to the second LTF signal. The second LTF signal and the duration of the GI related to the second LTF signal may be variously set. For example, the duration of the second LTF signal may be 6.4 μs. The duration of the GI related to the LTF signal may be 1.6 μs. Accordingly, the midamble symbol duration of the second format may be set to 8 μs. 
     According to an embodiment, the LTF signal may be generated based on the LTF sequence of the first interval. The transmitting STA may perform IFFT on the LTF sequence of the first interval. The transmitting STA may generate a training sequence based on the IFFT. The training sequence can be constructed by repeating twice in the time domain. The transmitting STA may generate an LTF signal based on one of the configured training sequences repeated twice. 
     According to an embodiment, the subcarrier spacing of the NGV PPDU may be set to 156.25 kHz. Accordingly, one symbol length of the NGV PPDU may be set to 8 μs. 
     According to an embodiment, the NGV signal field may further include information related to a transmission periodicity of the midamble. For example, the NGV signal field may further include 1-bit information related to the transmission periodicity of the midamble. As another example, the NGV signal field may further include 2-bit information related to the transmission periodicity of the midamble. 
     In step S 3620 , the transmitting STA may transmit an NGV PPDU. According to an embodiment, the transmitting STA may transmit an NGV PPDU to the receiving STA. According to an embodiment, the transmitting STA may transmit the NGV PPDU through a 5.9 GHz band. 
       FIG. 37  is a flowchart illustrating an operation of a receiving STA. 
     Referring to  FIG. 37 , in step S 3710 , the receiving STA (e.g., STA  110 ,  120  in  FIG. 1 ) may receive the NGV PPDU. 
     According to an embodiment, the NGV PPDU may include a preamble, a data field contiguous to the preamble, and a midamble contiguous to the data field. For example, the preamble may include a legacy signal field, a repetition signal field in which the legacy signal field is repeated, and an NGV signal field including control information for an NGV PPDU. 
     As an example, the legacy signal field may include L-SIG. 
     As an example, the repetition control field may include the same information field as the legacy signal field. Also, the repetition control field may be modulated (e.g., BPSK) in the same manner as the legacy signal field. The repetition control field may include the RL-SIG. 
     As an example, the NGV signal field may be related to transmission information. The NGV signal field may include the NGV-SIG. 
     According to an embodiment, the NGV signal field may include 1-bit information related to the format of the midamble. 
     According to an embodiment, the midamble may be configured based on one of an LTF sequence of the first interval and an LTF sequence of the second interval. For example, the first interval may be set to twice the second interval. For example, non-zero element(s) of the LTF sequence of the first interval may be positioned based on the two subcarrier index intervals. For another example, non-zero element(s) of the LTF sequence of the second interval may be positioned based on one subcarrier index interval. 
     For example, the LTF sequence of the first interval may be set based on available tones. As an example, the LTF sequence of the first interval may be configured based on the first interval in the available tones. The available tones may refer to tones excluding DC tone(s) and guard tone(s) from all tones within a bandwidth. Accordingly, in the LTF sequence of the first interval, DC tone(s) (e.g., 1 tone or 3 tones) may be set to ‘0’ (zero). Also, the available tones of the LTF sequence of the first interval may have non-zero elements/values at the first interval. 
     For example, the LTF sequence of the second interval may be set based on available tones. As an example, the LTF sequence of the second interval may be configured based on the second interval within the available tones. The available tones may refer to tones excluding DC tone(s) and guard tone(s) from all tones within a bandwidth. Accordingly, in the LTF sequence of the second interval, DC tone(s) (e.g., 1 tone or 3 tones) may be set to ‘0’ (zero). Also, the available tones of the LTF sequence of the second interval may have non-zero elements/values at the second interval. 
     According to an embodiment, the format of the midamble may be determined as one of a first format related to an LTF sequence of a first interval and a second format related to an LTF sequence of a second interval. For example, the format of the midamble may be determined as one of a first format related to an LTF sequence of a first interval and a second format related to an LTF sequence of a second interval based on 1-bit information related to the format of the midamble. 
     For example, when the 1-bit information related to the format of the midamble is set to a first value (e.g., 1), the format of the midamble may be set as the first format. As another example, when the 1-bit information related to the format of the midamble is set to a second value (e.g., 0), the format of the midamble may be set to the second format. 
     For example, the receiving STA may confirm that the 1-bit information related to the format of the midamble is set as the first value. In this case, based on the 1-bit information related to the format of the midamble, the receiving STA may identify that the format of the midamble is the first format. 
     As another example, the receiving STA may confirm that the 1-bit information related to the format of the midamble is set as the second value. In this case, based on the 1-bit information related to the format of the midamble, the receiving STA may identify that the format of the midamble is the second format. 
     For example, the NGV PPDU may further include an NGV-LTF. The 1-bit information related to the format of the midamble may also include (indication) information related to the format of the NGV-LTF. Accordingly, the 1-bit information related to the format of the midamble may indicate the format of the midamble and the NGV-LTF together. Also, the format of the midamble and the format of the NGV-LTF may be identically set. For example, when the 1-bit information related to the format of the midamble is set to a first value (e.g., 1), the LTF sequence of the first interval may be used for the format of the midamble format and the NGV-LTF. When the 1-bit information related to the format of the midamble is set to a second value (e.g., 0), the LTF sequence of the second interval may be used for the format of the midamble format and the NGV-LTF. 
     According to an embodiment, the LTF signal may be generated based on the LTF sequence of the first interval. According to an embodiment, the midamble symbol of the first format may include an LTF signal configured/generated based on the LTF sequence of the first interval and a guard interval (GI) related to the LTF signal. The duration of the LTF signal and the GI related to the LTF signal may be variously set. For example, the duration of the LTF signal may be 3.2 μs. The duration of the GI related to the LTF signal may be 1.6 μs. Accordingly, the midamble symbol duration of the first format may be 4.8 μs. 
     According to an embodiment, the midamble symbol of the second format may include a second LTF signal configured based on the LTF sequence of the second interval and a guard interval (GI) related to the second LTF signal. The second LTF signal and the duration of the GI related to the second LTF signal may be variously set. For example, the duration of the second LTF signal may be 6.4 μs. The duration of the GI related to the LTF signal may be 1.6 μs. Accordingly, the midamble symbol duration of the second format may be set to 8 μs. 
     According to an embodiment, the subcarrier spacing of the NGV PPDU may be set to 156.25 kHz. Accordingly, one symbol length of the NGV PPDU may be set to 8 μs. 
     According to an embodiment, the NGV signal field may further include information related to a transmission periodicity of the midamble. For example, the NGV signal field may further include 1-bit information related to the transmission periodicity of the midamble. As another example, the NGV signal field may further include 2-bit information related to the transmission periodicity of the midamble. 
     In other words, the receiving STA may identify the transmission periodicity of the midamble based on 2-bit information related to the transmission periodicity of the midamble. For example, when the 2-bit information is set to a first value (e.g., ‘0’), the period of the midamble may be set to ‘4’ (or 4 symbols). When the 2-bit information is set to a second value (e.g., ‘1’), the period of the midamble may be set to ‘8’ (or 8 symbols). When the 2-bit information is set to a third value (e.g., ‘2’), the period of the midamble may be set to ‘16’ (or 16 symbols). 
     In step S 3710 , the receiving STA may decode the NGV PPDU. According to an embodiment, the receiving STA may decode the NGV PPDU based on the NGV signal field. 
     According to an embodiment, the receiving STA may identify information related to the midamble based on the NGV signal field. The receiving STA may check/confirm the format of the midamble based on the NGV signal field, and may decode the NGV PPDU based on the checked/confirmed format. In addition, the receiving STA may check/confirm the transmission periodicity of the midamble based on the NGV signal field, and decode the NGV PPDU based on the checked/confirmed transmission period. 
     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, the apparatus of the present specification includes a memory, and a processor operatively coupled to the memory, wherein the processor receives a Next Generation V2X Physical Protocol Data Unit (NGV PPDU). The NGV PPDU may include a preamble, a data field contiguous to the preamble, and a midamble contiguous to the data field. The preamble may include a legacy signal field and a repeating signal field in which the legacy signal field is repeated. The NGV signal field may include control information for the NGV PPDU. The NGV signal field may include 1-bit information related to the format of the midamble. The midamble may be configured based on any one of a long training field (LTF) sequence of a first interval and an LTF sequence of a second interval. The format of the midamble may be determined as one of a first format related to the LTF sequence of the first interval and a second format related to the LTF sequence of the second interval. The symbol of the midamble of the first format may include an LTF signal configured based on the LTF sequence of the first interval and a guard interval (GI) related to the LTF signal. The duration of the LTF signal may be 3.2 μs, the duration of the GI may be 1.6 μs, and the symbol duration of the midamble of the first format may be 4.8 μs. The processor may be configured to decode the NGV PPDU based on the NGV signal field. 
     The technical features of the present specification may be implemented based on a CRM (computer readable medium). For example, the CRM proposed by the present specification receives a Next Generation V2X Physical Protocol Data Unit (NGV PPDU). The NGV PPDU may include a preamble, a data field contiguous to the preamble, and a midamble contiguous to the data field. The preamble may include a legacy signal field and a repeating signal field in which the legacy signal field is repeated. The NGV signal field may include control information for the NGV PPDU. The NGV signal field may include 1-bit information related to the format of the midamble. The midamble may be configured based on any one of a long training field (LTF) sequence of a first interval and an LTF sequence of a second interval. The format of the midamble may be determined as one of a first format related to the LTF sequence of the first interval and a second format related to the LTF sequence of the second interval. The symbol of the midamble of the first format may include an LTF signal configured based on the LTF sequence of the first interval and a guard interval (GI) related to the LTF signal. The duration of the LTF signal may be 3.2 μs, the duration of the GI may be 1.6 μs, and the symbol duration of the midamble of the first format may be 4.8 μs. the CRM proposed by the present specification may further decode the NGV PPDU based on the NGV signal field. 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 processor  111 ,  121  or the processing chip  114 ,  124  of  FIG. 1 , or the processor  610  of  FIG. 19 . Meanwhile, the CRM of the present specification may be the memory  112 ,  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. 38  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  3830  shown in  FIG. 38  may be included in the memory(s)  112 ,  122  shown in  FIG. 1 . Additionally, a communication unit  3810  shown in  FIG. 38  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. 38  may be included in the processor(s)  111 ,  121  shown in  FIG. 1 . 
     Referring to  FIG. 38 , a vehicle or autonomous driving vehicle  3800  may include an antenna unit  3808 , a communication unit  3810 , a control unit  3820 , a memory unit  3830 , a driving unit  3840   a , a power supply unit  3840   b , a sensor unit  3840   c , and/or an autonomous driving unit  3840   d . The antenna unit  3808  may be configured as a part of the communication unit  3810 . 
     The communication unit  3810  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  3820  may perform various operations by controlling elements of the vehicle or the autonomous driving vehicle  3800 . The control unit  3820  may include an Electronic Control Unit (ECU). The driving unit  3840   a  may cause the vehicle or the autonomous driving vehicle  3800  to drive on a road. The driving unit  3840   a  may include an engine, a motor, a powertrain, a wheel, a brake, a steering device, and so on. The power supply unit  3840   b  may supply power to the vehicle or the autonomous driving vehicle  3800  and include a wired/wireless charging circuit, a battery, and so on. The sensor unit  3840   c  may acquire a vehicle state, ambient environment information, user information, and so on. The sensor unit  3840   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  3840   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  3810  may receive map data, traffic information data, and so on, from an external server. The autonomous driving unit  3840   d  may generate an autonomous driving path and a driving plan from the obtained data. The control unit  3820  may control the driving unit  3840   a  such that the vehicle or the autonomous driving vehicle  3800  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  3810  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  3840   c  may obtain a vehicle state and/or surrounding environment information. The autonomous driving unit  3840   d  may update the autonomous driving path and the driving plan based on the newly obtained data/information. The communication unit  3810  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. 39 , which will hereinafter be described in detail. 
       FIG. 39  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. 39 , a vehicle  3800  may include a communication unit  3810 , a control unit  3820 , a memory unit  3830 , an input/output (I/O) unit  3840   e , and a positioning unit  3840   f . Each block/unit/device shown in  FIG. 39  may be the same as each block/unit/device shown in  FIG. 38 , respectively. 
     The communication unit  3810  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  3820  may perform various operations by controlling constituent elements of the vehicle  3800 . The memory unit  3830  may store data/parameters/programs/code/commands for supporting various functions of the vehicle  3800 . The I/O unit  3840   e  may output an AR/VR object based on information within the memory unit  3830 . The I/O unit  3840   e  may include a HUD. The positioning unit  3840   f  may acquire information related to the position of the vehicle  3800 . The position information may include information related to an absolute position of the vehicle  3800 , information related to the position of the vehicle  3800  within a traveling lane, acceleration information, and information related to the position of the vehicle  3800  from a neighboring vehicle. The positioning unit  3840   f  may include a GPS and various sensors. 
     As an example, the communication unit  3810  of the vehicle  3800  may receive map information and traffic information from an external server and store the received information in the memory unit  3830 . The positioning unit  3840   f  may obtain the vehicle position information through the GPS and various sensors and store the obtained information in the memory unit  3830 . The control unit  3820  may generate a virtual object based on the map information, traffic information, and vehicle position information and the I/O unit  3840   e  may display the generated virtual object in a window in the vehicle  3810 ,  3820 . The control unit  3820  may determine whether the vehicle  3800  normally drives within a traveling lane, based on the vehicle position information. If the vehicle  3800  abnormally exits from the traveling lane, the control unit  3820  may display a warning on the window in the vehicle through the I/O unit  3840   e . In addition, the control unit  3820  may broadcast a warning message regarding driving abnormity to neighboring vehicles through the communication unit  3810 . According to situation, the control unit  3820  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.