Method and apparatus for generating training signal by using predetermined binary sequence in wireless lan system

BACKGROUND OF THE INVENTION

Field of the invention

0001This specification relates to a method for generating a sequence for a training field in a wireless LAN system and, most particularly, to a method and apparatus for generating a short training field (STF) sequence that can be used in multiple bands in a wireless LAN system.

Related Art

0002Discussion for a next-generation wireless local area network (WLAN) is in progress. In the next-generation WLAN, an object is to 1) improve an institute of electronic and electronics engineers (IEEE) 802.11 physical (PHY) layer and a medium access control (MAC) layer in bands of 2.4 GHz and 5 GHz, 2) increase spectrum efficiency and area throughput, 3) improve performance in actual indoor and outdoor environments such as an environment in which an interference source exists, a dense heterogeneous network environment, and an environment in which a high user load exists, and the like.

0003An environment which is primarily considered in the next-generation WLAN is a dense environment in which access points (APs) and stations (STAs) are a lot and under the dense environment, improvement of the spectrum efficiency and the area throughput is discussed. Further, in the next-generation WLAN, in addition to the indoor environment, in the outdoor environment which is not considerably considered in the existing WLAN, substantial performance improvement is concerned.

0004In detail, scenarios such as wireless office, smart home, stadium, Hotspot, and building/apartment are largely concerned in the next-generation WLAN and discussion about improvement of system performance in a dense environment in which the APs and the STAs are a lot is performed based on the corresponding scenarios.

0005In the next-generation WLAN, improvement of system performance in an overlapping basic service set (OBSS) environment and improvement of outdoor environment performance, and cellular offloading are anticipated to be actively discussed rather than improvement of single link performance in one basic service set (BSS). Directionality of the next-generation means that the next-generation WLAN gradually has a technical scope similar to mobile communication. When a situation is considered, in which the mobile communication and the WLAN technology have been discussed in a small cell and a direct-to-direct (D2D) communication area in recent years, technical and business convergence of the next-generation WLAN and the mobile communication is predicted to be further active.

0006Background prior art is disclosed, for example, in <nplcit id="ncit0001" npl-type="s"><text>Yakun Sun (Marvell), "HE-STF Proposal; 11-15-0381-01-00ax-he-stf-proposal", IEEE draft, vol. 802.11ax, no.1, 11 May 2015</text></nplcit>; as well as <patcit id="pcit0001" dnum="US2011013583A1"><text>US 2011/013583 A1</text></patcit> and <patcit id="pcit0002" dnum="US2013242963A"><text>US 2013/242963</text></patcit>.

SUMMARY OF THE INVENTION

Technical Objects

0007This specification proposes a method and apparatus improving configuration of a sequence that is used for a training field in a wireless LAN system.

0008An example of this specification proposes a solution for enhancing the problems in the sequence for the STF field that is presented in the related art.

Technical Solutions

0009An example of this specification proposes a transmission method that can be applied to a wireless LAN system and, most particularly, to a method and apparatus for configuring a STF signal supporting at least any one of multiple frequency bands supported by the wireless LAN system, according to claims 1 and 5, respectively.

0010A transmitting apparatus according to the present invention comprises: a memory, and a processor coupled to the memory and configured to generate a short training field (STF) signal, and transmit a physical protocol data unit (PPDU) including the STF signal to a receiving apparatus via 80 MHz band.

0011The STF signal is generated based on a STF sequence.

0012The STF sequence is defined as: {M, 1, -M, 0, -M, 1, -M}^∗(1+j)/sqrt(2).

0013The M sequence is defined as: {-1, -1, -1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, -1, 1}, wherein the M sequence is positioned at intervals of 16 towns starting from the lowest stone having a town index of -496 and ending at the highest stone having a town index of +496.

EFFECTS OF THE INVENTION

0014According to an example of this specification, a method for generating a STF signal that can be used in the wireless LAN system is proposed herein.

0015The method for generating a STF signal that is proposed in the example of this specification resolves the problems presented in the related art.

BRIEF DESCRIPTION OF THE DRAWINGS

0016<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a conceptual view illustrating the structure of a wireless local area network (WLAN).</li><li><figref idref="f0002">FIG. 2</figref> is a diagram illustrating an example of a PPDU used in an IEEE standard.</li><li><figref idref="f0003">FIG. 3</figref> is a diagram illustrating an example of an HE PDDU.</li><li><figref idref="f0004">FIG. 4</figref> is a diagram illustrating a layout of resource units (RUs) used in a band of 20 MHz.</li><li><figref idref="f0005">FIG. 5</figref> is a diagram illustrating a layout of resource units (RUs) used in a band of 40MHz.</li><li><figref idref="f0006">FIG. 6</figref> is a diagram illustrating a layout of resource units (RUs) used in a band of 80MHz.</li><li><figref idref="f0007">FIG. 7</figref> is a diagram illustrating another example of the HE PPDU.</li><li><figref idref="f0008">FIG. 8</figref> is a block diagram illustrating one example of HE-SIG-B according to an embodiment.</li><li><figref idref="f0009">FIG. 9</figref> illustrates an example of a trigger frame.</li><li><figref idref="f0010">FIG. 10</figref> illustrates an example of a common information field.</li><li><figref idref="f0011">FIG. 11</figref> illustrates an example of a sub-field being included in a per user information field.</li><li><figref idref="f0012">FIG. 12</figref> is a block diagram illustrating an example of an uplink MU PPDU.</li><li><figref idref="f0013">FIG. 13</figref> illustrates a 1x HE-STF tone in a per-channel PPDU transmission according to an exemplary embodiment of the present invention.</li><li><figref idref="f0014">FIG. 14</figref> illustrates a 2x HE-STF tone in a per-channel PPDU transmission according to an exemplary embodiment of the present invention.</li><li><figref idref="f0015">FIG. 15</figref> illustrates an example of repeating an M sequence.</li><li><figref idref="f0016">FIG. 16</figref> is an example specifying the repeated structure of <figref idref="f0015">FIG. 15</figref> in more detail.</li><li><figref idref="f0017">FIG. 17</figref> illustrates an example of repeating an M sequence.</li><li><figref idref="f0018">FIG. 18</figref> is an example specifying the repeated structure of <figref idref="f0017">FIG. 17</figref> in more detail.</li><li><figref idref="f0019">FIG. 19</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 20MHz band.</li><li><figref idref="f0020">FIG. 20</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 40MHz band.</li><li><figref idref="f0021">FIG. 21</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a left side band of a 80MHz band.</li><li><figref idref="f0022">FIG. 22</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a right side band of a 80MHz band.</li><li><figref idref="f0023">FIG. 23</figref> illustrates an example of repeating an M sequence.</li><li><figref idref="f0024">FIG. 24</figref> is an example specifying the repeated structure of <figref idref="f0023">FIG. 23</figref> in more detail.</li><li><figref idref="f0025">FIG. 25</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 20MHz band.</li><li><figref idref="f0026">FIG. 26</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 40MHz band.</li><li><figref idref="f0027">FIG. 27</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a left side band of a 80MHz band.</li><li><figref idref="f0028">FIG. 28</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a right side band of a 80MHz band.</li><li><figref idref="f0029">FIG. 29</figref> is a procedure flow chart to which the above-described example can be applied.</li><li><figref idref="f0030">FIG. 30</figref> is a drawing showing a PAPR for RUs that are used in a 20MHz band.</li><li><figref idref="f0031">FIG. 31</figref> is a drawing showing a PAPR for RUs that are used in a 40MHz band.</li><li><figref idref="f0032">FIG. 32</figref> and <figref idref="f0033">FIG. 33</figref> are drawings respectively showing a PAPR for RUs that are used in a 80MHz band.</li><li><figref idref="f0034">FIG. 34</figref> is a block diagram showing a wireless device to which the exemplary embodiment of the present invention can be applied.</li></ul>

DESCRIPTION OF EXEMPLARY EMBODIMENTS

0017<figref idref="f0001">FIG. 1</figref> is a conceptual view illustrating the structure of a wireless local area network (WLAN).

0018An upper part of <figref idref="f0001">FIG. 1</figref> illustrates the structure of an infrastructure basic service set (BSS) of institute of electrical and electronic engineers (IEEE) 802.11.

0019Referring the upper part of <figref idref="f0001">FIG. 1</figref>, the wireless LAN system may include one or more infrastructure BSSs 100 and 105 (hereinafter, referred to as BSS). The BSSs 100 and 105 as a set of an AP and an STA such as an access point (AP) 125 and a station (STA1) 100-1 which are successfully synchronized to communicate with each other are not concepts indicating a specific region. The BSS 105 may include one or more STAs 105-1 and 105-2 which may be joined to one AP 130.

0020The BSS may include at least one STA, APs providing a distribution service, and a distribution system (DS) 110 connecting multiple APs.

0021The distribution system 110 may implement an extended service set (ESS) 140 extended by connecting the multiple BSSs 100 and 105. The ESS 140 may be used as a term indicating one network configured by connecting one or more APs 125 or 230 through the distribution system 110. The AP included in one ESS 140 may have the same service set identification (SSID).

0022A portal 120 may serve as a bridge which connects the wireless LAN network (IEEE 802.11) and another network (e.g., 802.X).

0023In the BSS illustrated in the upper part of <figref idref="f0001">FIG. 1</figref>, a network between the APs 125 and 130 and a network between the APs 125 and 130 and the STAs 100-1, 105-1, and 105-2 may be implemented. However, the network is configured even between the STAs without the APs 125 and 130 to perform communication. A network in which the communication is performed by configuring the network even between the STAs without the APs 125 and 130 is defined as an Ad-Hoc network or an independent basic service set (IBSS).

0024A lower part of <figref idref="f0001">FIG. 1</figref> illustrates a conceptual view illustrating the IBSS.

0025Referring to the lower part of <figref idref="f0001">FIG. 1</figref>, 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 150-1, 150-2, 150-3, 155-4, and 155-5 are managed by a distributed manner. In the IBSS, all STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may be constituted by movable STAs and are not permitted to access the DS to constitute a self-contained network.

0026The STA as a predetermined functional medium that includes a medium access control (MAC) that follows a regulation of an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard and a physical layer interface for a radio medium may be used as a meaning including all of the APs and the non-AP stations (STAs).

0027The STA may be called various a name such as a mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), user equipment (UE), a mobile station (MS), a mobile subscriber unit, or just a user.

0028Meanwhile, the term user may be used in diverse meanings, for example, in wireless LAN communication, this term may be used to signify a STA participating in uplink MU MIMO and/or uplink OFDMA transmission. However, the meaning of this term will not be limited only to this.

0029<figref idref="f0002">FIG. 2</figref> is a diagram illustrating an example of a PPDU used in an IEEE standard.

0030As illustrated in <figref idref="f0002">FIG. 2</figref>, various types of PHY protocol data units (PPDUs) may be used in a standard such as IEEE a/g/n/ac, etc. In detail, LTF and STF fields include a training signal, SIG-A and SIG-B include control information for a receiving station, and a data field includes user data corresponding to a PSDU.

0031In the embodiment, an improved technique is provided, which is associated with a signal (alternatively, a control information field) used for the data field of the PPDU. The signal provided in the embodiment may be applied onto high efficiency PPDU (HE PPDU) according to an IEEE 802.11ax standard. That is, the signal improved in the embodiment may be HE-SIG-A and/or HE-SIG-B included in the HE PPDU. The HE-SIG-A and the HE-SIG-B may be represented even as the SIG-A and SIG-B, respectively. However, the improved signal proposed in the embodiment is not particularly limited to an HE-SIG-A and/or HE-SIG-B standard and may be applied to control/data fields having various names, which include the control information in a wireless communication system transferring the user data.

0032<figref idref="f0003">FIG. 3</figref> is a diagram illustrating an example of an HE PDDU.

0033The control information field provided in the embodiment may be the HE-SIG-B included in the HE PPDU. The HE PPDU according to <figref idref="f0003">FIG. 3</figref> is one example of the PPDU for multiple users and only the PPDU for the multiple users may include the HE-SIG-B and the corresponding HE SIG-B may be omitted in a PPDU for a single user.

0034As illustrated in <figref idref="f0003">FIG. 3</figref>, 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 during an illustrated time period (that is, 4 or 8 <i>µ</i>s).

0035More detailed description of the respective fields of <figref idref="f0003">FIG. 3</figref> will be made below.

0036<figref idref="f0004">FIG. 4</figref> is a diagram illustrating a layout of resource units (RUs) used in a band of 20 MHz.

0037As illustrated in <figref idref="f0004">FIG. 4</figref>, resource units (RUs) corresponding to tone (that is, subcarriers) of different numbers are used to constitute some fields of the HE-PPDU. For example, the resources may be allocated by the unit of the RU illustrated for the HE-STF, the HE-LTF, and the data field.

0038As illustrated in an uppermost part of <figref idref="f0004">FIG. 4</figref>, <figref idref="f0026">26</figref> units (that is, units corresponding to 26 tones). 6 tones may be used as a guard band in a leftmost band of the 20 MHz band and 5 tones may be used as the guard band in a rightmost band of the 20 MHz band. Further, 7 DC tones may be inserted into a center band, that is, a DC band and a 26-unit corresponding to each 13 tones may be present at left and right sides of the DC band. The 26-unit, a 52-unit, and a 106-unit may be allocated to other bands. Each unit may be allocated for a receiving station, that is, a user.

0039Meanwhile, the RU layout of <figref idref="f0004">FIG. 4</figref> may be used even in a situation for a single user (SU) in addition to the multiple users (MUs) and in this case, as illustrated in a lowermost part of <figref idref="f0004">FIG. 4</figref>, one 242-unit may be used and in this case, three DC tones may be inserted.

0040In one example of <figref idref="f0004">FIG. 4</figref>, RUs having various sizes, that is, a 26-RU, a 52-RU, a 106-RU, a 242-RU, and the like are proposed, and as a result, since detailed sizes of the RUs may extend or increase, the embodiment is not limited to a detailed size (that is, the number of corresponding tones) of each RU.

0041<figref idref="f0005">FIG. 5</figref> is a diagram illustrating a layout of resource units (RUs) used in a band of 40MHz.

0042Similarly to a case in which the RUs having various RUs are used in one example of <figref idref="f0004">FIG. 4</figref>, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and the like may be used even in one example of <figref idref="f0005">FIG. 5</figref>. Further, 5 DC tones may be inserted into a center frequency, 12 tones may be used as the guard band in the leftmost band of the 40 MHz band and 11 tones may be used as the guard band in the rightmost band of the 40MHz band.

0043In addition, as illustrated in <figref idref="f0005">FIG. 5</figref>, when the RU layout is used for the single user, the 484-RU may be used. That is, the detailed number of RUs may be modified similarly to one example of <figref idref="f0004">FIG. 4</figref>.

0044<figref idref="f0006">FIG. 6</figref> is a diagram illustrating a layout of resource units (RUs) used in a band of 80MHz.

0045Similarly to a case in which the RUs having various RUs are used in one example of each of <figref idref="f0004">FIG. 4</figref> or <figref idref="f0005">5</figref>, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and the like may be used even in one example of <figref idref="f0006">FIG. 6</figref>. Further, 7 DC tones may be inserted into the center frequency, 12 tones may be used as the guard band in the leftmost band of the 80MHz band and 11 tones may be used as the guard band in the rightmost band of the 80MHz band. In addition, the 26-RU may be used, which uses 13 tones positioned at each of left and right sides of the DC band.

0046Moreover, as illustrated in <figref idref="f0006">FIG. 6</figref>, when the RU layout is used for the single user, 996-RU may be used and in this case, 5 DC tones may be inserted. Meanwhile, the detailed number of RUs may be modified similarly to one example of each of <figref idref="f0004">FIG. 4</figref> or <figref idref="f0005">5</figref>.

0047<figref idref="f0007">FIG. 7</figref> is a diagram illustrating another example of the HE PPDU.

0048A block illustrated in <figref idref="f0007">FIG. 7</figref> is another example of describing the HE-PPDU block of <figref idref="f0003">FIG. 3</figref> in terms of a frequency.

0049An illustrated L-STF 700 may include a short training orthogonal frequency division multiplexing (OFDM) symbol. The L-STF 700 may be used for frame detection, automatic gain control (AGC), diversity detection, and coarse frequency/time synchronization.

0050An L-LTF 710 may include a long training orthogonal frequency division multiplexing (OFDM) symbol. The L-LTF 710 may be used for fine frequency/time synchronization and channel prediction.

0051An L-SIG 720 may be used for transmitting control information. The L-SIG 720 may include information regarding a data rate and a data length. Further, the L-SIG 720 may be repeatedly transmitted. That is, a new format, in which the L-SIG 720 is repeated (for example, may be referred to as R-LSIG) may be configured.

0052An HE-SIG-A 730 may include the control information common to the receiving station.

0053In detail, the HE-SIG-A 730 may include information on 1) a DL/UL indicator, 2) a BSS color field indicating an identify of a BSS, 3) a field indicating a remaining time of a current TXOP period, 4) a bandwidth field indicating at least one of 20, 40, 80, 160 and 80+80 MHz, 5) a field indicating an MCS technique applied to the HE-SIG-B, 6) an indication field regarding whether the HE-SIG-B is modulated by a dual subcarrier modulation technique for MCS, 7) a field indicating the number of symbols used for the HE-SIG-B, 8) a field indicating whether the HE-SIG-B is configured for a full bandwidth MIMO transmission, 9) a field indicating the number of symbols of the HE-LTF, 10) a field indicating the length of the HE-LTF and a CP length, 11) a field indicating whether an OFDM symbol is present for LDPC coding, 12) a field indicating control information regarding packet extension (PE), 13) a field indicating information on a CRC field of the HE-SIG-A, and the like. A detailed field of the HE-SIG-A may be added or partially omitted. Further, some fields of the HE-SIG-A may be partially added or omitted in other environments other than a multi-user (MU) environment.

0054An HE-SIG-B 740 may be included only in the case of the PPDU for the multiple users (MUs) as described above. Principally, an HE-SIG-A 750 or an HE-SIG-B 760 may include resource allocation information (alternatively, virtual resource allocation information) for at least one receiving STA.

0055<figref idref="f0008">FIG. 8</figref> is a block diagram illustrating one example of HE-SIG-B according to an embodiment.

0056As illustrated in <figref idref="f0008">FIG. 8</figref>, the HE-SIG-B field includes a common field at a frontmost part and the corresponding common field is separated from a field which follows therebehind to be encoded. That is, as illustrated in <figref idref="f0008">FIG. 8</figref>, the HE-SIG-B field may include a common field including the common control information and a user-specific field including user-specific control information. In this case, the common field may include a CRC field corresponding to the common field, and the like and may be coded to be one BCC block. The user-specific field subsequent thereafter may be coded to be one BCC block including the "user-specific field" for 2 users and a CRC field corresponding thereto as illustrated in <figref idref="f0008">FIG. 8</figref>.

0057A previous field of the HE-SIG-B 740 may be transmitted in a duplicated form on an MU PPDU. In the case of the HE-SIG-B 740, the HE-SIG-B 740 transmitted in some frequency band (e.g., a fourth frequency band) may even include control information for a data field corresponding to a corresponding frequency band (that is, the fourth frequency band) and a data field of another frequency band (e.g., a second frequency band) other than the corresponding frequency band. Further, a format may be provided, in which the HE-SIG-B 740 in a specific frequency band (e.g., the second frequency band) is duplicated with the HE-SIG-B 740 of another frequency band (e.g., the fourth frequency band). Alternatively, the HE-SIG B 740 may be transmitted in an encoded form on all transmission resources. A field after the HE-SIG B 740 may include individual information for respective receiving STAs receiving the PPDU.

0058The HE-STF 750 may be used for improving automatic gain control estimation in a multiple input multiple output (MIMO) environment or an OFDMA environment.

0059The HE-LTF 760 may be used for estimating a channel in the MIMO environment or the OFDMA environment.

0060The size of fast Fourier transform (FFT)/inverse fast Fourier transform (IFFT) applied to the HE-STF 750 and the field after the HE-STF 750, and the size of the FFT/IFFT applied to the field before the HE-STF 750 may be different from each other. For example, the size of the FFT/IFFT applied to the HE-STF 750 and the field after the HE-STF 750 may be four times larger than the size of the FFT/IFFT applied to the field before the HE-STF 750.

0061For example, when at least one field of the L-STF 700, the L-LTF 710, the L-SIG 720, the HE-SIG-A 730, and the HE-SIG-B 740 on the PPDU of <figref idref="f0007">FIG. 7</figref> is referred to as a first field, at least one of the data field 770, the HE-STF 750, and the HE-LTF 760 may be referred to as a second field. The first field may include a field associated with a legacy system and the second field may include a field associated with an HE system. In this case, the fast Fourier transform (FFT) size and the inverse fast Fourier transform (IFFT) size may be defined as a size which is N (N is a natural number, e.g., N = 1, 2, and 4) times larger than the FFT/IFFT size used in the legacy wireless LAN system. That is, the FFT/IFFT having the size may be applied, which is N (=4) times larger than the first field of the HE PPDU. For example, 256 FFT/IFFT may be applied to a bandwidth of 20 MHz, 512 FFT/IFFT may be applied to a bandwidth of 40 MHz, 1024 FFT/IFFT may be applied to a bandwidth of 80 MHz, and 2048 FFT/IFFT may be applied to a bandwidth of continuous 160 MHz or discontinuous 160 MHz.

0062In other words, a subcarrier space/subcarrier spacing may have a size which is 1/N times (N is the natural number, e.g., N = 4, the subcarrier spacing is set to 78.125 kHz) the subcarrier space used in the legacy wireless LAN system. That is, subcarrier spacing having a size of 312.5 kHz, which is legacy subcarrier spacing may be applied to the first field of the HE PPDU and a subcarrier space having a size of 78.125 kHz may be applied to the second field of the HE PPDU.

0063Alternatively, an IDFT/DFT period applied to each symbol of the first field may be expressed to be N (=4) times shorter than the IDFT/DFT period applied to each data symbol of the second field. That is, the IDFT/DFT length applied to each symbol of the first field of the HE PPDU may be expressed as 3.2 µs and the IDFT/DFT length applied to each symbol of the second field of the HE PPDU may be expressed as 3.2 µs ^∗ 4 (= 12.8µs). The length of the OFDM symbol may be a value acquired by adding the length of a guard interval (GI) to the IDFT/DFT length. The length of the GI may have various values such as 0.4 µs, 0.8 µs, 1.6 µs, 2.4 µs, and 3.2 µs.

0064The characteristic that the size of the FFT/IFFT being applied to the HE-STF 750 and the fields after the HE-STF 750 can be diversely configured may be applied to a downlink PPDU and/or an uplink PPDU. More specifically, such characteristic may be applied to the PPDU shown in <figref idref="f0007">FIG. 7</figref> or to an uplink MU PPDU, which will be described later on.

0065For simplicity in the description, in <figref idref="f0007">FIG. 7</figref>, it is expressed that a frequency band used by the first field and a frequency band used by the second field accurately coincide with each other, but both frequency bands may not completely coincide with each other, in actual. For example, a primary band of the first field (L-STF, L-LTF, L-SIG, HE-SIG-A, and HE-SIG-B) corresponding to the first frequency band may be the same as the most portions of a frequency band of the second field (HE-STF, HE-LTF, and Data), but boundary surfaces of the respective frequency bands may not coincide with each other. As illustrated in <figref idref="f0004 f0005 f0006">FIGS. 4 to 6</figref>, since multiple null subcarriers, DC tones, guard tones, and the like are inserted during arranging the RUs, it may be difficult to accurately adjust the boundary surfaces.

0066The user (e.g., a receiving station) may receive the HE-SIG-A 730 and may be instructed to receive the downlink PPDU based on the HE-SIG-A 730. In this case, the STA may perform decoding based on the FFT size changed from the HE-STF 750 and the field after the HE-STF 750. On the contrary, when the STA may not be instructed to receive the downlink PPDU based on the HE-SIG-A 730, the STA may stop the decoding and configure a network allocation vector (NAV). A cyclic prefix (CP) of the HE-STF 750 may have a larger size than the CP of another field and the during the CP period, the STA may perform the decoding for the downlink PPDU by changing the FFT size.

0067Hereinafter, in the embodiment of the present invention, data (alternatively, or a frame) which the AP transmits to the STA may be expressed as a terms called downlink data (alternatively, a downlink frame) and data (alternatively, a frame) which the STA transmits to the AP may be expressed as a term called uplink data (alternatively, an uplink frame). Further, transmission from the AP to the STA may be expressed as downlink transmission and transmission from the STA to the AP may be expressed as a term called uplink transmission.

0068In addition, a PHY protocol data unit (PPDU), a frame, and data transmitted through the downlink transmission may be expressed as terms such as a downlink PPDU, a downlink frame, and downlink data, respectively. The PPDU may be a data unit including a PPDU header and a physical layer service data unit (PSDU) (alternatively, a MAC protocol data unit (MPDU)). The PPDU header may include a PHY header and a PHY preamble and the PSDU (alternatively, MPDU) may include the frame or indicate the frame (alternatively, an information unit of the MAC layer) or be a data unit indicating the frame. The PHY header may be expressed as a physical layer convergence protocol (PLCP) header as another term and the PHY preamble may be expressed as a PLCP preamble as another term.

0069Further, a PPDU, a frame, and data transmitted through the uplink transmission may be expressed as terms such as an uplink PPDU, an uplink frame, and uplink data, respectively.

0070In the wireless LAN system to which the embodiment of the present description is applied, the whole bandwidth may be used for downlink transmission to one STA and uplink transmission to one STA. Further, in the wireless LAN system to which the embodiment of the present description is applied, the AP may perform downlink (DL) multi-user (MU) transmission based on multiple input multiple output (MU MIMO) and the transmission may be expressed as a term called DL MU MIMO transmission.

0071In addition, in the wireless LAN system according to the embodiment, an orthogonal frequency division multiple access (OFDMA) based transmission method is preferably supported for the uplink transmission and/or downlink transmission. That is, data units (e.g., RUs) corresponding to different frequency resources are allocated to the user to perform uplink/downlink communication. In detail, in the wireless LAN system according to the embodiment, the AP may perform the DL MU transmission based on the OFDMA and the transmission may be expressed as a term called DL MU OFDMA transmission. When the DL MU OFDMA transmission is performed, the AP may transmit the downlink data (alternatively, the downlink frame and the downlink PPDU) to the plurality of respective STAs through the plurality of respective frequency resources on an overlapped time resource. The plurality of frequency resources may be a plurality of subbands (alternatively, sub channels) or a plurality of resource units (RUs). The DL MU OFDMA transmission may be used together with the DL MU MIMO transmission. For example, the DL MU MIMO transmission based on a plurality of space-time streams (alternatively, spatial streams) may be performed on a specific subband (alternatively, sub channel) allocated for the DL MU OFDMA transmission.

0072Further, in the wireless LAN system according to the embodiment, uplink multi-user (UL MU) transmission in which the plurality of STAs transmits data to the AP on the same time resource may be supported. Uplink transmission on the overlapped time resource by the plurality of respective STAs may be performed on a frequency domain or a spatial domain.

0073When the uplink transmission by the plurality of respective STAs is performed on the frequency domain, different frequency resources may be allocated to the plurality of respective STAs as uplink transmission resources based on the OFDMA. The different frequency resources may be different subbands (alternatively, sub channels) or different resources units (RUs). The plurality of respective STAs may transmit uplink data to the AP through different frequency resources. The transmission method through the different frequency resources may be expressed as a term called a UL MU OFDMA transmission method.

0074When the uplink transmission by the plurality of respective STAs is performed on the spatial domain, different time-space streams (alternatively, spatial streams) may be allocated to the plurality of respective STAs and the plurality of respective STAs may transmit the uplink data to the AP through the different time-space streams. The transmission method through the different spatial streams may be expressed as a term called a UL MU MIMO transmission method.

0075The UL MU OFDMA transmission and the UL MU MIMO transmission may be used together with each other. For example, the UL MU MIMO transmission based on the plurality of space-time streams (alternatively, spatial streams) may be performed on a specific subband (alternatively, sub channel) allocated for the UL MU OFDMA transmission.

0076In the legacy wireless LAN system which does not support the MU OFDMA transmission, a multi-channel allocation method is used for allocating a wider bandwidth (e.g., a 20 MHz excess bandwidth) to one terminal. When a channel unit is 20 MHz, multiple channels may include a plurality of 20 MHz-channels. In the multi-channel allocation method, a primary channel rule is used to allocate the wider bandwidth to the terminal. When the primary channel rule is used, there is a limit for allocating the wider bandwidth to the terminal. In detail, according to the primary channel rule, when a secondary channel adjacent to a primary channel is used in an overlapped BSS (OBSS) and is thus busy, the STA may use remaining channels other than the primary channel. Therefore, since the STA may transmit the frame only to the primary channel, the STA receives a limit for transmission of the frame through the multiple channels. That is, in the legacy wireless LAN system, the primary channel rule used for allocating the multiple channels may be a large limit in obtaining a high throughput by operating the wider bandwidth in a current wireless LAN environment in which the OBSS is not small.

0077In order to solve the problem, in the embodiment, a wireless LAN system is disclosed, which supports the OFDMA technology. That is, the OFDMA technique may be applied to at least one of downlink and uplink. Further, the MU-MIMO technique may be additionally applied to at least one of downlink and uplink. When the OFDMA technique is used, the multiple channels may be simultaneously used by not one terminal but multiple terminals without the limit by the primary channel rule. Therefore, the wider bandwidth may be operated to improve efficiency of operating a wireless resource.

0078As described above, in case the uplink transmission performed by each of the multiple STAs (e.g., non-AP STAs) is performed within the frequency domain, the AP may allocate different frequency resources respective to each of the multiple STAs as uplink transmission resources based on OFDMA. Additionally, as described above, the frequency resources each being different from one another may correspond to different subbands (or sub-channels) or different resource units (RUs).

0079The different frequency resources respective to each of the multiple STAs are indicated through a trigger frame.

0080<figref idref="f0009">FIG. 9</figref> illustrates an example of a trigger frame. The trigger frame of <figref idref="f0009">FIG. 9</figref> allocates resources for Uplink Multiple-User (MU) transmission and may be transmitted from the AP. The trigger frame may be configured as a MAC frame and may be included in the PPDU. For example, the trigger frame may be transmitted through the PPDU shown in <figref idref="f0003">FIG. 3</figref>, through the legacy PPDU shown in <figref idref="f0002">FIG. 2</figref>, or through a certain PPDU, which is newly designed for the corresponding trigger frame. In case the trigger frame is transmitted through the PPDU of <figref idref="f0003">FIG. 3</figref>, the trigger frame may be included in the data field shown in the drawing.

0081Each of the fields shown in <figref idref="f0009">FIG. 9</figref> may be partially omitted, or other fields may be added. Moreover, the length of each field may be varied differently as shown in the drawing.

0082A Frame Control field 910 shown in <figref idref="f0009">FIG. 9</figref> may include information related to a version of the MAC protocol and other additional control information, and a Duration field 920 may include time information for configuring a NAV or information related to an identifier (e.g., AID) of the user equipment.

0083Additionally, a RA field 930 may include address information of a receiving STA of the corresponding trigger frame, and this field may also be omitted as required. A TA field 940 may include address information of the STA (e.g., AP) transmitting the corresponding trigger frame, and a common information field 950 may include common control information that is applied to the receiving STA receiving the corresponding trigger frame.

0084<figref idref="f0010">FIG. 10</figref> illustrates an example of a common information field. Among the sub-fields of <figref idref="f0010">FIG. 10</figref>, some maybe omitted, and other additional sub-fields may also be added. Additionally, the length of each of the sub-fields shown in the drawing may be varied.

0085As shown in the drawing, the Length field1010 may be given that same value as the Length field of the L-SIG field of the uplink PPDU, which is transmitted in response to the corresponding trigger frame, and the Length field of the L-SIG field of the uplink PPDU indicates the length of the uplink PPDU. As a result, the Length field 1010 of the trigger frame may be used for indicating the length of its respective uplink PPDU.

0086Additionally, a Cascade Indicator field 1020 indicates whether or not a cascade operation is performed. The cascade operation refers to a downlink MU transmission and an uplink MU transmission being performed simultaneously within the same TXOP. More specifically, this refers to a case when a downlink MU transmission is first performed, and, then, after a predetermined period of time (e.g., SIFS), an uplink MU transmission is performed. During the cascade operation, only one transmitting device performing downlink communication (e.g., AP) may exist, and multiple transmitting devices performing uplink communication (e.g., non-AP) may exist.

0087A CS Request field 1030 indicates whether or not the status or NAV of a wireless medium is required to be considered in a situation where a receiving device that has received the corresponding trigger frame transmits the respective uplink PPDU.

0088A HE-SIG-A information field 1040 may include information controlling the content of a SIG-A field (i.e., HE-SIG-A field) of an uplink PPDU, which is being transmitted in response to the corresponding trigger frame.

0089A CP and LTF type field 1050 may include information on a LTF length and a CP length of the uplink PPDU being transmitted in response to the corresponding trigger frame. A trigger type field 1060 may indicate a purpose for which the corresponding trigger frame is being used, e.g., general triggering, triggering for beamforming, and so on, a request for a Block ACK/NACK, and so on.

0090Meanwhile, the remaining description on <figref idref="f0009">FIG. 9</figref> will be additionally provided as described below.

0091It is preferable that the trigger frame includes per user information fields 960#1 to 960#N corresponding to the number of receiving STAs receiving the trigger frame of <figref idref="f0009">FIG. 9</figref>. The per user information field may also be referred to as a "RU Allocation field".

0092Additionally, the trigger frame of <figref idref="f0009">FIG. 9</figref> may include a Padding field 970 and a Sequence field 980.

0093It is preferable that each of the per user information fields 960#1 to 960#N shown in <figref idref="f0009">FIG. 9</figref> further includes multiple sub-fields.

0094<figref idref="f0011">FIG. 11</figref> illustrates an example of a sub-field being included in a per user information field. Among the sub-fields of <figref idref="f0011">FIG. 11</figref>, some may be omitted, and other additional sub-fields may also be added. Additionally, the length of each of the sub-fields shown in the drawing may be varied.

0095A User Identifier field 1110 indicates an identifier of an STA (i.e., receiving STA) to which the per user information corresponds, and an example of the identifier may correspond to all or part of the AID.

0096Additionally, a RU Allocation field 1120 may be included in the sub-field of the per user information field. More specifically, in case a receiving STA, which is identified by the User Identifier field 1110, transmits an uplink PPDU in response to the trigger frame of <figref idref="f0009">FIG. 9</figref>, the corresponding uplink PPDU is transmitted through the RU, which is indicated by the RU Allocation field 1120. In this case, it is preferable that the RU that is being indicated by the RU Allocation field 1120 corresponds to the RU shown in <figref idref="f0004">FIG. 4</figref>, <figref idref="f0005">FIG. 5</figref>, and <figref idref="f0006">FIG. 6</figref>.

0097The sub-field of <figref idref="f0011">FIG. 11</figref> may include a Coding Type field 1130. The Coding Type field 1130 may indicate a coding type of the uplink PPDU being transmitted in response to the trigger frame of <figref idref="f0009">FIG. 9</figref>. For example, in case BBC coding is applied to the uplink PPDU, the Coding Type field 1130 may be set to '1', and, in case LDPC coding is applied to the uplink PPDU, the Coding Type field 1130 may be set to '0'.

0098Additionally, the sub-field of <figref idref="f0011">FIG. 11</figref> may include a MCS field 1140. The MCS field 1140 may indicate a MCS scheme being applied to the uplink PPDU that is transmitted in response to the trigger frame of <figref idref="f0009">FIG. 9</figref>. For example, in case BBC coding is applied to the uplink PPDU, the Coding Type field 1130 may be set to '1', and, in case LDPC coding is applied to the uplink PPDU, the Coding Type field 1130 may be set to '0'.

0099<figref idref="f0012">FIG. 12</figref> is a block diagram illustrating an example of an uplink MU PPDU. The uplink MU PPDU of <figref idref="f0012">FIG. 12</figref> may be transmitted in response to the above-described trigger frame.

0100As shown in the drawing, the PPDU of <figref idref="f0012">FIG. 12</figref> includes diverse fields, and the fields included herein respectively correspond to the fields shown in <figref idref="f0002">FIG. 2</figref>, <figref idref="f0003">FIG. 3</figref>, and <figref idref="f0007">FIG. 7</figref>. Meanwhile, as shown in the drawing, the uplink PPDU of <figref idref="f0012">FIG. 12</figref> may not include a HE-SIG-B field and may only include a HE-SIG-A field.

0101<figref idref="f0013">FIG. 13</figref> illustrates a 1x HE-STF tone in a per-channel PPDU transmission according to an exemplary embodiment of the present invention. Most particularly, <figref idref="f0013">FIG. 13</figref> shows an example of a HE-STF tone (i.e., 16-tone sampling) having a periodicity of 0.8<i>µ</i>s in 20MHz/40MHz/80MHz bandwidths. Accordingly, in <figref idref="f0013">FIG. 13</figref>, the HE-STF tones for each bandwidth (or channel) may be positioned at 16 tone intervals.

0102In <figref idref="f0013">FIG. 13</figref>, the x-axis represents the frequency domain. The numbers on the x-axis represent the indexes of a tone, and the arrows represent mapping of a value that is not equal to 0 (i.e., a non-zero value) to the corresponding tone index.

0103Sub-drawing (a) of <figref idref="f0013">FIG. 13</figref> illustrates an example of a 1x HE-STF tone in a 20MHz PPDU transmission.

0104Referring to sub-drawing (a), in case a HE-STF sequence (i.e., 1x HE-STF sequence) for a periodicity of 0.8<i>µ</i>s is mapped to tones of a 20MHz channel, the 1x HE-STF sequence is mapped to tones having tone indexes that are divisible by 16 (i.e., multiples of 16), among the tones having tone indexes ranging from -112 to 112, and, then, 0 may be mapped to the remaining tones. More specifically, in a 20MHz channel, among the tones having tone indexes ranging from -112 to 112, a 1x HE-STF tone may be positioned at a tone index that is divisible by 16 excluding the DC. Accordingly, a total of 14 1x HE-STF tones having the 1x HE-STF sequence mapped thereto may exist in the 20MHz channel.

0105Sub-drawing (b) of <figref idref="f0013">FIG. 13</figref> illustrates an example of a 1x HE-STF tone in a 40MHz PPDU transmission.

0106Referring to sub-drawing (b), in case a HE-STF sequence (i.e., 1x HE-STF sequence) for a periodicity of 0.8<i>µ</i>s is mapped to tones of a 40MHz channel, the 1x HE-STF sequence is mapped to tones having tone indexes that are divisible by 16 (i.e., multiples of 16), among the tones having tone indexes ranging from -240 to 240, and, then, 0 may be mapped to the remaining tones. More specifically, in a 40MHz channel, among the tones having tone indexes ranging from -240 to 240, a 1x HE-STF tone may be positioned at a tone index that is divisible by 16 excluding the DC. Accordingly, a total of 30 1x HE-STF tones having the 1x HE-STF sequence mapped thereto may exist in the 40MHz channel.

0107Sub-drawing (c) of <figref idref="f0013">FIG. 13</figref> illustrates an example of a 1x HE-STF tone in an 80MHz PPDU transmission.

0108Referring to sub-drawing (c), in case a HE-STF sequence (i.e., 1x HE-STF sequence) for a periodicity of 0.8<i>µ</i>s is mapped to tones of a 80MHz channel, the 1x HE-STF sequence is mapped to tones having tone indexes that are divisible by 16 (i.e., multiples of 16), among the tones having tone indexes ranging from -496 to 496, and, then, 0 may be mapped to the remaining tones. More specifically, in an 80MHz channel, among the tones having tone indexes ranging from -496 to 496, a 1x HE-STF tone may be positioned at a tone index that is divisible by 16 excluding the DC. Accordingly, a total of 62 1x HE-STF tones having the 1x HE-STF sequence mapped thereto may exist in the 80MHz channel.

0109<figref idref="f0014">FIG. 14</figref> illustrates a 2x HE-STF tone in a per-channel PPDU transmission according to an exemplary embodiment of the present invention. Most particularly, <figref idref="f0014">FIG. 14</figref> shows an example of a HE-STF tone (i.e., 8-tone sampling) having a periodicity of 1.6<i>µ</i>s in 20MHz/40MHz/80MHz bandwidths. Accordingly, in <figref idref="f0014">FIG. 14</figref>, the HE-STF tones for each bandwidth (or channel) may be positioned at 8 tone intervals.

0110The 2x HE-STF signal according to <figref idref="f0014">FIG. 14</figref> may be applied to the uplink MU PPDU shown in <figref idref="f0012">FIG. 12</figref>. More specifically, the 2x HE-STF signal shown in <figref idref="f0014">FIG. 14</figref> may be included in the PPDU, which is transmitted via uplink in response to the above-described trigger frame.

0111In <figref idref="f0014">FIG. 14</figref>, the x-axis represents the frequency domain. The numbers on the x-axis represent the indexes of a tone, and the arrows represent mapping of a value that is not equal to 0 (i.e., a non-zero value) to the corresponding tone index.

0112Sub-drawing (a) of <figref idref="f0014">FIG. 14</figref> is a drawing showing an example of a 2x HE-STF tone in a 20MHz PPDU transmission.

0113Referring to sub-drawing (a), in case a HE-STF sequence (i.e., 2x HE-STF sequence) for a periodicity of 1.6<i>µ</i>s is mapped to tones of a 20MHz channel, the 2x HE-STF sequence is mapped to tones having tone indexes that are divisible by 8 (i.e., multiples of 8), among the tones having tone indexes ranging from -120 to 120, and, then, 0 may be mapped to the remaining tones. More specifically, in a 20MHz channel, among the tones having tone indexes ranging from -120 to 120, a 2x HE-STF tone may be positioned at a tone index that is divisible by 8 excluding the DC. Accordingly, a total of 30 2x HE-STF tones having the 2x HE-STF sequence mapped thereto may exist in the 20MHz channel.

0114Sub-drawing (b) of <figref idref="f0014">FIG. 14</figref> illustrates an example of a 2x HE-STF tone in a 40MHz PPDU transmission.

0115Referring to sub-drawing (b), in case a HE-STF sequence (i.e., 2x HE-STF sequence) for a periodicity of 1.6<i>µ</i>s is mapped to tones of a 40MHz channel, the 2x HE-STF sequence is mapped to tones having tone indexes that are divisible by 8 (i.e., multiples of 8), among the tones having tone indexes ranging from -248 to 248, and, then, 0 may be mapped to the remaining tones. More specifically, in a 40MHz channel, among the tones having tone indexes ranging from -248 to 248, a 2x HE-STF tone may be positioned at a tone index that is divisible by 8 excluding the DC. Herein, however, tones having tone indexes of ±248 correspond to guard tones (left and right guard tones), and such guard tones may be processed with nulling (i.e., such guard tones may have a value of 0). Accordingly, a total of 60 2x HE-STF tones having the 2x HE-STF sequence mapped thereto may exist in the 40MHz channel.

0116Sub-drawing (c) of <figref idref="f0014">FIG. 14</figref> illustrates an example of a 2x HE-STF tone in an 80MHz PPDU transmission.

0117Referring to sub-drawing (c), in case a HE-STF sequence (i.e., 2x HE-STF sequence) for a periodicity of 1.6<i>µ</i>s is mapped to tones of an 80MHz channel, the 2x HE-STF sequence is mapped to tones having tone indexes that are divisible by 8 (i.e., multiples of 8), among the tones having tone indexes ranging from -504 to 504, and, then, 0 may be mapped to the remaining tones. More specifically, in an 80MHz channel, among the tones having tone indexes ranging from -504 to 504, a 2x HE-STF tone may be positioned at a tone index that is divisible by 8 excluding the DC. Herein, however, tones having tone indexes of ±504 correspond to guard tones (left and right guard tones), and such guard tones may be processed with nulling (i.e., such guard tones may have a value of 0). Accordingly, a total of 124 2x HE-STF tones having the 2x HE-STF sequence mapped thereto may exist in the 80MHz channel.

0118Hereinafter, a sequence that can be applied to a 1x HE-STF tone (i.e., sampling at intervals of 16 tones) and a sequence that can be applied to a 2x HE-STF tone (i.e., sampling at intervals of 8 tones) will be proposed. More specifically, a basic sequence is configured, and a new sequence structure having excellent extendibility by using a nested structure in which a conventional sequence is used as a parts of a new sequence is proposed. It is preferable that the M sequence that is used in the following example corresponds to a sequence having a length of 15. It is preferable that the M sequence is configured as a binary sequence so as to decrease the level of complexity when being decoded.

0119Hereinafter, in a state when a detailed example of an M sequence is not proposed, a basic procedure for generating a sequence in various bandwidths will be described in detail.

Example (A): Example of a 1x HE-STF tone

0120The example of the exemplary embodiment, which will hereinafter be described in detail, may generate an STF sequence supporting diverse frequency bandwidths by using a method of repeating the M sequence, which corresponds to a binary sequence.

0121<figref idref="f0015">FIG. 15</figref> illustrates an example of repeating an M sequence.

0122It is preferable that the example shown in <figref idref="f0015">FIG. 15</figref> is applied to 1x HE-STF.

0123As shown in <figref idref="f0015">FIG. 15</figref>, when expressed in the form of an equation, the STF sequence for 20MHz may be expressed as shown in Equation 1.<maths id="math0001" num="<Equation 1>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>112</mn><mo>:</mo><mn>16</mn><mo>:</mo><mo>+</mo><mn>112</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mn>0</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0001.tif" /></maths>

0124The notation of HE_STF(A1 :A2:A3)={M}, which is used in Equation 1 and the other equations shown below is as described below. First of all, the value of A1 corresponds to a frequency tone index corresponding to the first element of the M sequence, and the value of A3 corresponds to a frequency tone index corresponding to the last element of the M sequence. The value of A2 corresponds to an interval of frequency tone indexes corresponding to each element of the M sequence being positioned based on the frequency tone interval.

0125Accordingly, in Equation 1, the first element of the M sequence corresponds to the frequency band corresponding to index "-112", the last element of the M sequence corresponds to the frequency band corresponding to index "+112", and each element of the M sequence is positioned at 16 frequency tone intervals. Additionally, the value "0" corresponds to a frequency band corresponding to index "0" More specifically, Equation 1 has a structure corresponding to sub-drawing (a) of <figref idref="f0013">FIG. 13</figref>.

0126As shown in <figref idref="f0015">FIG. 15</figref>, when expressed in the form of an equation, the STF sequence for 40MHz may be expressed as shown in Equation 2. More specifically, in order to extend the structure of Equation 1 to the 40MHz band, {M, 0, M} may be used.<maths id="math0002" num="<Equation 2>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0002.tif" /></maths>

0127Equation 2 corresponds to a structure, wherein 15 M sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "-240" and up to a frequency band corresponding to index "-16" at 16 frequency tone intervals, wherein "0" is positioned for frequency index 0, and wherein 15 M sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "+16" and up to a frequency band corresponding to index "+240" at 16 frequency tone intervals "+16".

As shown in FIG. 15, when expressed in the form of an equation, the STF sequence for 80MHz may be expressed as shown in Equation 3.More specifically, in order to extend the structure of Equation 1 to an 80MHz band, {M, 0, M, 0, M, 0, M} may be used.

0128<maths id="math0003" num="<Equation 3>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>496</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>496</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0003.tif" /></maths>

0129Equation 3 corresponds to a structure, wherein 15 M sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "-496" and up to a frequency band corresponding to index "-272" at 16 frequency tone intervals, wherein "0" (or an arbitrary additional value a1) is positioned for a frequency band corresponding to index "-256", wherein 15 M sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "-240" and up to a frequency band corresponding to index "-16" at 16 frequency tone intervals, and wherein "0" is positioned for frequency index 0. Additionally, Equation 3 also corresponds to a structure, wherein 15 M sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "+16" and up to a frequency band corresponding to index "+240" at 16 frequency tone intervals, wherein "0" (or an arbitrary additional value a2) is positioned for a frequency band corresponding to index "+256", and wherein M sequence elements are positioned from "+272" to "+496" at 16 frequency tone intervals.

0130By applying an additional coefficient to the above-described structures of Equation 1 to Equation 3, it will be possible to optimize the sequence for PAPR. In case of the related art IEEE 802.11ac system, although it may be possible to extend the predetermined 20MHz sequence for the 40MHz and 80MHz by using a gamma value, since the gamma value may not be applied in the IEEE 802.11ax or HEW system, the PAPR should be considered without considering the gamma value. Additionally, in case of considering the 1x HE-STF sequence, as shown in Equation 1 to Equation 3, the PAPR should be calculated based on the entire band (e.g., the entire band shown in <figref idref="f0004 f0005 f0006">FIG. 4 to FIG. 6</figref>), and, in case of considering the 2x HE-STF sequence, the PAPR should be calculated while considering each unit (e.g., individual units 26-RU, 52-RU, 106-RU, and so on, shown in <figref idref="f0004 f0005 f0006">FIG. 4 to FIG. 6</figref>).

0131<figref idref="f0016">FIG. 16</figref> is an example specifying the repeated structure of <figref idref="f0015">FIG. 15</figref> in more detail.

0132As shown in the drawing, coefficients c1 to c7 may be applied, or (1+j)^∗sqrt(1/2) may be applied, and additional values, such as a1 and a2, may also be applied.

0133Based on the content of <figref idref="f0016">FIG. 16</figref>, an example of the STF sequence that is optimized for the PAPR is as shown below.

0134First of all, the M sequence may be determined as shown below in Equation 4. <maths id="math0004" num="<Equation 4>"><math display="block"><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn></mfenced></math><img file="EP3668028B1_D0004.tif" /></maths>

0135In this case, the STF sequence respective to the 20MHz and 40MHz bands may be determined in accordance with the equations shown below. <maths id="math0005" num="<Equation 5>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>112</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>112</mn></mfenced><mo>=</mo><mi mathvariant="normal">M</mi><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mn>0</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0005.tif" /></maths><maths id="math0006" num="<Equation 6>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0006.tif" /></maths>

0136The definition of the variables used in the equations presented above is the same as those used in Equation 1 to Equation 3.

0137Meanwhile, the STF sequence corresponding to the 80MHz band may be determined in accordance with any one of the equations shown below. <maths id="math0007" num="<Equation 7>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>496</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>496</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0007.tif" /></maths><maths id="math0008" num="<Equation 8>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>496</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>496</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mspace width="1ex" /><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0008.tif" /></maths>

0138The definition of the variables used in the equations presented above is the same as those used in Equation 1 to Equation 3.

0139The examples shown in Equation 4 to Equation 8, which are presented above, may be modified to other examples, as shown below.

0140First of all, the M sequence that is basically used may be modified as shown in Equation 9.<maths id="math0009" num="<Equation 9>"><math display="block"><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn></mfenced></math><img file="EP3668028B1_D0009.tif" /></maths>

0141Equation 9 that is presented above may be applied to all or part of Equation 5 to Equation 8. For example, it may be possible to use the basic sequence of Equation 9 based on the structure of Equation 7.

0142The PAPR for the examples presented in the above-described equations may be calculated as shown below. As described above, in case of considering the 1x HE-STF sequence, the PAPR is calculated based on the entire band (e.g., the entire band shown in <figref idref="f0004 f0005 f0006">FIG. 4 to FIG. 6</figref>).

0143More specifically, the PAPR for the example of applying Equation 4 to the structure of Equation 5 is equal to 2.33, the PAPR for the example of applying Equation 4 to the structure of Equation 6 is equal to 4.40, and the PAPR for the example of applying Equation 4 to the structure of Equation 7 or Equation 8 is equal to 4.49. Additionally, the PAPR for the example of applying Equation 9 to the structure of Equation 5 is equal to 1.89, the PAPR for the example of applying Equation 9 to the structure of Equation 6 is equal to 4.40, and the PAPR for the example of applying Equation 9 to the structure of Equation 7 or Equation 8 is equal to 4.53. Although the STF sequences that are presented above show minute differences in the capability of the PAPR, since the corresponding STF sequences present enhanced PAPR capability as compared to the related art sequences, it will be preferable to used any one of the examples presented above for uplink and/or downlink communication.

Example (B): Example of a 2x HE-STF tone

0144It is preferable to apply the example of the exemplary embodiment, which will hereinafter be described in detail, to 2x HE-STF.

0145<figref idref="f0017">FIG. 17</figref> illustrates an example of repeating an M sequence.

0146As shown in <figref idref="f0017">FIG. 17</figref>, when expressed in the form of an equation, the STF sequence for 20MHz may be expressed as shown below in the following Equation.

0147<maths id="math0010" num="<Equation 10>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>120</mn><mo>:</mo><mn>8</mn><mo>:</mo><mo>+</mo><mn>120</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0010.tif" /></maths>

0148As shown in <figref idref="f0017">FIG. 17</figref>, when expressed in the form of an equation, the STF sequence for 40MHz may be expressed as shown below in the following Equation. <maths id="math0011" num="<Equation 11>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>248</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>248</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0011.tif" /></maths>

0149As shown in <figref idref="f0017">FIG. 17</figref>, when expressed in the form of an equation, the STF sequence for 80MHz may be expressed as shown below in the following Equation. <maths id="math0012" num="<Equation 12>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>504</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>504</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0012.tif" /></maths>

0150By applying an additional coefficient to the above-described structures of Equation 10 to Equation 12, it will be possible to optimize the sequence for PAPR. In case of the related art IEEE 802.11ac system, although it may be possible to extend the predetermined 20MHz sequence for the 40MHz and 80MHz by using a gamma value, since the gamma value may not be applied in the IEEE 802.11ax or HEW system, the PAPR should be considered without considering the gamma value.

0151<figref idref="f0018">FIG. 18</figref> is an example specifying the repeated structure of <figref idref="f0017">FIG. 17</figref> in more detail.

0152As shown in the drawing, coefficients c1 to c14 may be applied, or (1+j)^∗sqrt(1/2) may be applied, and additional values, such as a1 to a8, may also be applied.

0153Based on the content of <figref idref="f0018">FIG. 18</figref>, an example of the STF sequence that is optimized for the PAPR is as shown below.

0154First of all, the M sequence may be determined as shown below in Equation 13.<maths id="math0013" num="<Equation 13>"><math display="block"><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn></mfenced></math><img file="EP3668028B1_D0013.tif" /></maths>

0155In this case, the STF sequence respective to the 20MHz, 40MHz, and 80MHz bands may be determined in accordance with the equations shown below.<maths id="math0014" num="<Equation 14>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>120</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>120</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0014.tif" /></maths><maths id="math0015" num="<Equation 15>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>248</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>248</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>±</mo><mn>248</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0015.tif" /></maths><maths id="math0016" num="<Equation 16>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>504</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>504</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>±</mo><mn>504</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0016.tif" /></maths>

0156The definition of the variables used in the equations presented above is the same as those used in Equation 1 to Equation 3.

0157The examples shown in Equation 14 to Equation 16, which are presented above, may be modified to other examples, as shown below.

0158First of all, the M sequence that is basically used may be modified as shown in Equation 17.<maths id="math0017" num="<Equation 17>"><math display="block"><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn></mfenced></math><img file="EP3668028B1_D0017.tif" /></maths>

0159The 2x HE-STF sequence for the 20MHz band may be generated by using a method of applying Equation 17, which is presented above, to Equation 14.

0160Meanwhile, 2x HE-STF sequence for the 40MHz band may be generated by using a method of applying Equation 17, which is presented above, to the Equation shown below.<maths id="math0018" num="<Equation 18>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>248</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>248</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>±</mo><mn>248</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0018.tif" /></maths>

0161Additionally, 2x HE-STF sequence for the 80MHz band may be generated by using a method of applying Equation 17, which is presented above, to the Equation shown below.<maths id="math0019" num="<Equation 19>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>504</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>504</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>±</mo><mn>504</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0019.tif" /></maths>

0162<figref idref="f0019">FIG. 19</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 20MHz band.

0163Each block shown in <figref idref="f0019">FIG. 19</figref> respectively indicates 26-RU, 52-RU, 106-RU, and 242-RU, which are shown in <figref idref="f0004">FIG. 4</figref>. For example, a first block 1910 indicates a leftmost 26-RU, which is shown in <figref idref="f0004">FIG. 4</figref>, a second block 1920 indicates a central 26-RU, which is shown in <figref idref="f0004">FIG. 4</figref>, a third block 1930 indicates a 52-RU, a fourth block 1940 indicates a 106-RU, and a fifth block 1950 indicates a 242-RU.

0164The example of the above-described Equation 13 to Equation 16 may be indicated as example (B-1), and the example of the above-described Equation 17 to Equation 19 may be indicated as example (B-2). In this case, the values indicated in each block represent the PAPRs for example (B-1) and example (B-2), respectively.

0165<figref idref="f0020">FIG. 20</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 40MHz band. More specifically, each block shown in <figref idref="f0020">FIG. 20</figref> respectively indicates 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU, which are shown in <figref idref="f0005">FIG. 5</figref>.

0166<figref idref="f0021">FIG. 21</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a left side band of a 80MHz band. And, <figref idref="f0022">FIG. 22</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a right side band of a 80MHz band. More specifically, each block shown in <figref idref="f0021">FIG. 21</figref> and <figref idref="f0022">FIG. 22</figref> respectively indicates 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and 996-RU, which are shown in <figref idref="f0006">FIG. 6</figref>. In the examples shown in <figref idref="f0021">FIG. 21</figref> and <figref idref="f0022">FIG. 22</figref>, in case of the 26-RU (i.e., central 26-RU) that is positioned in the DC band, the PAPR of example (B-1) is equal to 1.94, and the PAPR of example (B-2) is equal to 1.94. Additionally, for the entire band, the PAPR of example (B-1) is equal to 4.97, and the PAPR of example (B-2) is equal to 5.77.

Example (C): Example of a 2x HE-STF tone

0167In case of the 2x HE-STF according to the above-described example (B), due to a collision with a guard band in the 40MHz band and the 80MHz band, nulling is required in the tone index "±248" and the tone index "±504". The following example (C) proposes a STF sequence that does not require any nulling to be performed.

0168<figref idref="f0023">FIG. 23</figref> illustrates an example of repeating an M sequence.

0169As shown in <figref idref="f0023">FIG. 23</figref>, when expressed in the form of an equation, the STF sequence for 20MHz may be expressed as shown below in the following Equation.

0170<maths id="math0020" num="<Equation 20>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>120</mn><mo>:</mo><mn>8</mn><mo>:</mo><mo>+</mo><mn>120</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0020.tif" /></maths>

0171As shown in <figref idref="f0023">FIG. 23</figref>, when expressed in the form of an equation, the STF sequence for 40MHz may be expressed as shown below in the following Equation. <maths id="math0021" num="<Equation 21>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0021.tif" /></maths>

0172As shown in <figref idref="f0023">FIG. 23</figref>, when expressed in the form of an equation, the STF sequence for 80MHz may be expressed as shown below in the following Equation. <maths id="math0022" num="<Equation 22>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>496</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>496</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mi mathvariant="normal">M</mi><mn>0</mn><mi mathvariant="normal">M</mi><mi mathvariant="normal">M</mi></mfenced></math><img file="EP3668028B1_D0022.tif" /></maths>

0173By applying an additional coefficient to the above-described structures of Equation 20 to Equation 22, it will be possible to optimize the sequence for PAPR. In case of the related art IEEE 802.11ac system, although it may be possible to extend the predetermined 20MHz sequence for the 40MHz and 80MHz by using a gamma value, since the gamma value may not be applied in the IEEE 802.11ax or HEW system, the PAPR should be considered without considering the gamma value.

0174<figref idref="f0024">FIG. 24</figref> is an example specifying the repeated structure of <figref idref="f0023">FIG. 23</figref> in more detail.

0175As shown in the drawing, coefficients c1 to c14 may be applied, or (1+j)^∗sqrt(1/2) may be applied, and additional values, such as a1 to a4, may also be applied.

0176Based on the content of <figref idref="f0024">FIG. 24</figref>, an example of the STF sequence that is optimized for the PAPR is as shown below.

0177First of all, the M sequence may be determined as shown below in Equation 23. <maths id="math0023" num="<Equation 23>"><math display="block"><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn></mfenced></math><img file="EP3668028B1_D0023.tif" /></maths>

0178In this case, the STF sequence respective to the 40MHz and 80MHz bands may be determined in accordance with the equations shown below. Since the STF sequence for the 20MHz band is the same as example (B) (i.e., the same as Equation 14), the indication of the same will be omitted. <maths id="math0024" num="<Equation 24>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi><mspace width="1ex" /><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0024.tif" /></maths><maths id="math0025" num="<Equation 25>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mspace width="1ex" /><mn>0</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0025.tif" /></maths><maths id="math0026" num="<Equation 26>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>496</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>496</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mn>0,1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0026.tif" /></maths>

0179The definition of the variables used in the equations presented above is the same as those used in Equation 1 to Equation 3.

0180The examples shown in Equation 24 to Equation 26, which are presented above, may be modified to other examples, as shown below.

0181First of all, the M sequence that is basically used may be modified as shown in Equation 27.<maths id="math0027" num="<Equation 27>"><math display="block"><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn></mfenced></math><img file="EP3668028B1_D0027.tif" /></maths>

0182The 2x HE-STF sequences for the 40MHz band and the 80MHz band may be generated by using a method of applying Equation 27, which is presented above, to the equation shown below. Since the STF sequence for the 20MHz band is the same as example (B), the indication of the same will be omitted.<maths id="math0028" num="<Equation 28>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0028.tif" /></maths><maths id="math0029" num="<Equation 29>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>240</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>240</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0029.tif" /></maths><maths id="math0030" num="<Equation 30>"><math display="block"><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>496</mn><mo>:</mo><mn>16</mn><mo>:</mo><mn>496</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1,0</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></math><img file="EP3668028B1_D0030.tif" /></maths>

0183<figref idref="f0025">FIG. 25</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 20MHz band.

0184Each block shown in <figref idref="f0025">FIG. 25</figref> respectively indicates 26-RU, 52-RU, 106-RU, and 242-RU, which are shown in <figref idref="f0004">FIG. 4</figref>.

0185The example of the above-described Equation 23 to Equation 26 may be indicated as example (C-1), and the example of the above-described Equation 27 to Equation 30 may be indicated as example (C-2). In this case, the values indicated in each block represent the PAPRs for example (C-1) and example (C-2), respectively.

0186<figref idref="f0026">FIG. 26</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a 40MHz band. More specifically, each block shown in <figref idref="f0026">FIG. 26</figref> respectively indicates 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU, which are shown in <figref idref="f0005">FIG. 5</figref>.

0187<figref idref="f0027">FIG. 27</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a left side band of a 80MHz band. And, <figref idref="f0028">FIG. 28</figref> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a right side band of a 80MHz band. More specifically, each block shown in <figref idref="f0027">FIG. 27</figref> and <figref idref="f0028">FIG. 28</figref> respectively indicates 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and 996-RU, which are shown in <figref idref="f0006">FIG. 6</figref>. In the examples shown in <figref idref="f0027">FIG. 27</figref> and <figref idref="f0028">FIG. 28</figref>, in case of the 26-RU (i.e., central 26-RU) that is positioned in the DC band, the PAPR of example (C-1) is equal to 1.94, and the PAPR of example (C-2) is equal to 6.02. Additionally, for the entire band, the PAPR of example (C-1) is equal to 4.99, and the PAPR of example (C-2) is equal to 5.42.

0188<figref idref="f0029">FIG. 29</figref> is a procedure flow chart to which the above-described example can be applied.

0189The example of <figref idref="f0029">FIG. 29</figref> may be applied to various transmitting apparatuses, for example, the corresponding example may be applied to user equipments (i.e., non-AP STA).

0190In step S2910, the transmitting apparatus determines whether to transmit a 1x HE-STF signal or to transmit a 2x HE STF signal. For example, in response to the trigger frame shown in <figref idref="f0009">FIG. 9</figref>, in case of transmitting the uplink PPDU shown in <figref idref="f0012">FIG. 12</figref>, the transmitting apparatus may transmit a 2x HE STF signal, and, otherwise, the transmitting apparatus may transmit a 1x HE STF signal.

0191In case of transmitting the 2X HE-STF, a 2X HE-STF signal may be generated in accordance with step S2920. For example, in case of generating a short training field (STF) signal corresponding to the first frequency band (e.g., a 40MHz band), the STF signal corresponding to the first frequency band may be generated based on a sequence in which a predetermined M sequence is repeated. In this case, the repeated sequence may be defined as {M, -1, -M 0, M, -1, M}^∗(1+j)/sqrt(2). The M sequence may correspond to M={-1, -1, -1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, -1, 11. The {M, -1, -M 0, M, -1, M}^∗(1+j)/sqrt(2) sequence is positioned at intervals of 8 tones within a range of a lowest tone having a tone index of -248 and a highest tone having a tone index of +248. And, in the {M, -1, -M 0, M, -1, M}v(1+j)/sqrt(2), elements corresponding to each of the tone indexes -248 and +248 may be processed with nulling. Additionally, in case of generating a STF signal corresponding to a second frequency band, a {M, -1, M, -1, -M, -1, M, 0, -M, 1, M, 1, -M, 1, -M}^∗(1+j)/sqrt(2) sequence may be used.

0192In other words, in step S2920, at least any one of the 2x HE-STF signals proposed in the above-described Example (B) or Example (C) may be used.

0193In case of transmitting the IX HE-STF, a IX HE-STF signal may be generated in accordance with step S2930. In this case, at least any one of the 1x HE-STF signals proposed in the above-described Example (A) may be used.

0194In step S2940, the generated HE-STF signal is transmitted to a receiving device.

0195Example (D): Selecting a STF sequence in accordance with the PAPR

0196Example (D), which will hereinafter be described in detail, proposes an example for configuring an uplink PPDU by using some of sequences presented in the above-described examples.

0197For example, as shown below, 2x HE-STF sequences for 20MHz, 40MHz, and 80MHz may be configured. More specifically, in case an uplink MU PPDU is transmitted in response to a trigger frame, the STF sequence shown below may be used.<maths id="math0031" num="<Equation 31>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>20</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>120</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>120</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr></mtable></math><img file="EP3668028B1_D0031.tif" /></maths><maths id="math0032" num="<Equation 32>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>248</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>248</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mspace width="1ex" /><mn>0</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>40</mn><mi>MHz</mi><mfenced><mo>±</mo><mn>248</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0032.tif" /></maths><maths id="math0033" num="<Equation 33>"><math display="block"><mtable columnalign="left"><mtr><mtd><mi mathvariant="normal">M</mi><mo>=</mo><mfenced open="{" close="}"><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mn>1,1</mn><mo>,</mo><mo>−</mo><mn>1,1</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>−</mo><mn>504</mn><mo>:</mo><mn>8</mn><mo>:</mo><mn>504</mn></mfenced><mo>=</mo><mfenced open="{" close="}"><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mo>−</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>0</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi><mo>,</mo><mn>1</mn><mo>,</mo><mo>−</mo><mi mathvariant="normal">M</mi></mfenced><mo>∗</mo><mfenced><mn>1</mn><mo>+</mo><mi mathvariant="normal">j</mi></mfenced><mo>/</mo><mi>sqrt</mi><mfenced><mn>2</mn></mfenced></mtd></mtr><mtr><mtd><mi>HE</mi><mo>_</mo><mi>STF</mi><mo>_</mo><mn>80</mn><mi>MHz</mi><mfenced><mo>±</mo><mn>504</mn></mfenced><mo>=</mo><mn>0</mn></mtd></mtr></mtable></math><img file="EP3668028B1_D0033.tif" /></maths>

0198Meanwhile, in case of configuring an uplink PPDU in a user STA, among the RUs shown in <figref idref="f0004 f0005 f0006">FIG. 4 to FIG. 6</figref>, it may be possible to configure the STF field only for the RUs that are allocated to the corresponding user STA.

0199For example, a leftmost 26-RU, which is shown in <figref idref="f0004">FIG. 4</figref>, is positioned in a section starting from frequency index "-121" to frequency index "-96". If a user STA is allocated to the leftmost 26-RU, sequences may be generated based on Equation 31, which is presented above. In this case, however, among the generated sequences, the STF field of the uplink MU PPDU may be configured by using only the sequence corresponding to the section starting from frequency index "-121" to frequency index "-96".

0200However, in case of configuring the STF field according to the above-described method, the PAPR may be decreased.

0201<figref idref="f0030">FIG. 30</figref> is a drawing showing a PAPR for RUs that are used in a 20MHz band.

0202The value marked on an uppermost end of <figref idref="f0030">FIG. 30</figref> indicates the PAPR for the 26-RU. More specifically, 4 26-RUs (RU1 to RU4) exist on the left side of the central 26-RU (RU5) shown in <figref idref="f0030">FIG. 30</figref>, and <figref idref="f0004">4</figref> 26-RUs (RU6 to RU9) exist on the right side of the central 26-RU (RU5).

0203In this case, the range of frequency indexes for each 26-RU may correspond to Table 1 shown below. <tables id="tabl0001" num="0001"><table frame="all"><title>[Table 1]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="17mm" /><colspec colnum="2" colname="col2" colwidth="19mm" /><colspec colnum="3" colname="col3" colwidth="18mm" /><colspec colnum="4" colname="col4" colwidth="18mm" /><colspec colnum="5" colname="col5" colwidth="17mm" /><colspec colnum="6" colname="col6" colwidth="24mm" /><thead><row><entry valign="top">RU type</entry><entry namest="col2" nameend="col6" align="left" valign="top" /></row></thead><tbody><row rowsep="0"><entry morerows="3" rowsep="1">26-RU</entry><entry>RU 1</entry><entry>RU 2</entry><entry>RU 3</entry><entry>RU 4</entry><entry>RU 5</entry></row><row><entry>[-121: -96]</entry><entry>[-95: -70]</entry><entry>[-68: -43]</entry><entry>[-42: -17]</entry><entry>[-16: -4, 4: 16]</entry></row><row rowsep="0"><entry>RU 6</entry><entry>RU 7</entry><entry>RU 8</entry><entry>RU 9</entry><entry /></row><row><entry>[17: 42]</entry><entry>[43: 68]</entry><entry>[70: 95]</entry><entry>[96: 121]</entry><entry /></row></tbody></tgroup></table></tables>

0204Additionally, as shown in <figref idref="f0004">FIG. 4</figref> and <figref idref="f0030">FIG. 30</figref>, in case of 52-RUs that are used for the 20MHz band, 2 52-RUs are included on the left side of the central 26-RU, and 2 52-RUs are included on the right side of the central 26-RU. Herein, the range of frequency indexes for each RU may correspond to Table 2 shown below. Additionally, as shown in <figref idref="f0004">FIG. 4</figref> and <figref idref="f0030">FIG. 30</figref>, 2 106-RUs that are used for the 20MHz band exist, and 1 242-RU that is used for the 20MHz band exists. And, herein, the range of frequency indexes for each RU may correspond to Table 2 shown below. <tables id="tabl0002" num="0002"><table frame="all"><title>[Table 2]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="17mm" /><colspec colnum="2" colname="col2" colwidth="19mm" /><colspec colnum="3" colname="col3" colwidth="18mm" /><colspec colnum="4" colname="col4" colwidth="17mm" /><colspec colnum="5" colname="col5" colwidth="17mm" /><colspec colnum="6" colname="col6" colwidth="7mm" /><thead><row><entry valign="top">RU type</entry><entry namest="col2" nameend="col6" align="left" valign="top" /></row></thead><tbody><row rowsep="0"><entry>52-RU</entry><entry>RU 1</entry><entry>RU 2</entry><entry>RU 3</entry><entry>RU 4</entry><entry /></row><row><entry /><entry>[-121: -70]</entry><entry>[-68: -17]</entry><entry>[17: 68]</entry><entry>[70: 121]</entry><entry /></row><row rowsep="0"><entry>106-RU</entry><entry>RU 1</entry><entry /><entry>RU 2</entry><entry /><entry /></row><row><entry /><entry>[-122: -17]</entry><entry /><entry>[17: 122]</entry><entry /><entry /></row><row rowsep="0"><entry morerows="1" rowsep="1">242-RU</entry><entry namest="col2" nameend="col5" align="left">RU 1</entry><entry morerows="1" rowsep="1" /></row><row><entry namest="col2" nameend="col5" align="left">[-122: -2, 2:122]</entry></row></tbody></tgroup></table></tables>

0205For example, among the 4 52-RUs shown in Table 2, even if RU1 is allocated to a specific user, as shown in <figref idref="f0030">FIG. 30</figref>, it is apparent that the PAPR of RU2 or RU3 is lower. In this case, even if RU1 is allocated, it is preferable that the user configures the STF field by using a STF sequence corresponding to RU2 or RU3. More specifically, in case the user receives a trigger frame and configures an uplink MU PPDU corresponding to the received trigger frame, the user configures an STF field corresponding only to the RU that are allocated to the user. And, in this case, it is preferable that the STF field is configured by using a sequence having a PAPR of 4.26 (i.e., a STF sequence corresponding to the frequency index of RU2 or RU3). In case a 26-RU is allocated, it is preferable to use a STF sequence corresponding to a RU having a PAPR of 2.22.

0206<figref idref="f0031">FIG. 31</figref> is a drawing showing a PAPR for RUs that are used in a 40MHz band.

0207The value marked on an uppermost end of <figref idref="f0031">FIG. 31</figref> indicates the PAPR for the 26-RU. More specifically, 9 26-RUs (RU1 to RU9) exist on the left side of the central 26-RU (RU5) shown in <figref idref="f0031">FIG. 31</figref>, and <figref idref="f0009">9</figref> 26-RUs (RU10 to RU18) exist on the right side of the central 26-RU (RU5).

0208In this case, the range of frequency indexes for each 26-RU may correspond to Table 3 shown below. <tables id="tabl0003" num="0003"><table frame="all"><title>[Table 3]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="17mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="22mm" /><colspec colnum="5" colname="col5" colwidth="23mm" /><colspec colnum="6" colname="col6" colwidth="22mm" /><thead><row><entry valign="top">RU type</entry><entry namest="col2" nameend="col6" align="left" valign="top" /></row></thead><tbody><row rowsep="0"><entry morerows="7" rowsep="1">26-RU</entry><entry>RU 1</entry><entry>RU 2</entry><entry>RU 3</entry><entry>RU 4</entry><entry>RU 5</entry></row><row><entry>[-243: -218]</entry><entry>[-217: -192]</entry><entry>[-189: -164]</entry><entry>[-163: -1381</entry><entry>[-136: -111]</entry></row><row rowsep="0"><entry>RU 6</entry><entry>RU 7</entry><entry>RU 8</entry><entry>RU 9</entry><entry /></row><row><entry>[-109: -84]</entry><entry>[-83: -58]</entry><entry>[-55: -30]</entry><entry>[-29: -4]</entry><entry /></row><row rowsep="0"><entry>RU 10</entry><entry>RU 11</entry><entry>RU 12</entry><entry>RU 13</entry><entry>RU 14</entry></row><row><entry>[4: 29]</entry><entry>[30: 55]</entry><entry>[58: 83]</entry><entry>[84: 109]</entry><entry>[111: 136]</entry></row><row rowsep="0"><entry>RU 15</entry><entry>RU 16</entry><entry>RU 17</entry><entry>RU 18</entry><entry /></row><row><entry>[138: 163]</entry><entry>[164: 189]</entry><entry>[192: 217]</entry><entry>[218: 243]</entry><entry /></row></tbody></tgroup></table></tables>

0209Additionally, as shown in <figref idref="f0005">FIG. 5</figref> and <figref idref="f0031">FIG. 31</figref>, in case of 52-RUs that are used for the 40MHz band, 4 52-RUs are included on the left side of the central 26-RU, and 4 52-RUs are included on the right side of the central 26-RU. Herein, the range of frequency indexes for each RU may correspond to Table 4 shown below. Additionally, as shown in <figref idref="f0005">FIG. 5</figref> and <figref idref="f0031">FIG. 31</figref>, 4 106-RUs that are used for the 40MHz band exist, 2 242-RUs that are used for the 40MHz band exist, and 1 484-RU that is used for the 40MHz band exists. And, herein, the range of frequency indexes for each RU may correspond to Table 4 shown below. <tables id="tabl0004" num="0004"><table frame="all"><title>[Table 4]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="17mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><colspec colnum="3" colname="col3" colwidth="22mm" /><colspec colnum="4" colname="col4" colwidth="20mm" /><colspec colnum="5" colname="col5" colwidth="20mm" /><colspec colnum="6" colname="col6" colwidth="7mm" /><thead><row><entry valign="top">RU type</entry><entry namest="col2" nameend="col6" align="left" valign="top" /></row></thead><tbody><row rowsep="0"><entry morerows="3" rowsep="1">52-RU</entry><entry>RU 1</entry><entry>RU 2</entry><entry>RU 3</entry><entry>RU 4</entry><entry /></row><row><entry>[-243: -192]</entry><entry>[-189: -138]</entry><entry>[-109: -58]</entry><entry>[-55: -4]</entry><entry /></row><row rowsep="0"><entry>RU 5</entry><entry>RU 6</entry><entry>RU 7</entry><entry>RU 8</entry><entry /></row><row><entry>[4: 55]</entry><entry>[58: 109]</entry><entry>[138: 189]</entry><entry>[192: 243]</entry><entry /></row><row rowsep="0"><entry>106-RU</entry><entry>RU 1</entry><entry>RU 2</entry><entry>RU 3</entry><entry>RU 4</entry><entry /></row><row><entry /><entry>[-243: -138]</entry><entry>[-109: -4]</entry><entry>[4: 109]</entry><entry>[138: 243]</entry><entry /></row><row rowsep="0"><entry>242-RU</entry><entry namest="col2" nameend="col3" align="left">RU 1</entry><entry namest="col4" nameend="col5" align="left">RU2</entry><entry /></row><row><entry /><entry namest="col2" nameend="col3" align="left">[-244: -3]</entry><entry namest="col4" nameend="col5" align="left">[3: 244]</entry><entry /></row><row rowsep="0"><entry>484-RU</entry><entry namest="col2" nameend="col6" align="left">RU 1</entry></row><row><entry /><entry namest="col2" nameend="col6" align="left">[-244: -3, 3: 244]</entry></row></tbody></tgroup></table></tables>

0210For example, it is preferable that a user being allocated with 26-RUs for the 40MHz band uses a STF sequence corresponding to the RU having a PAPR of 2.22. Also, it is preferable that a user being allocated with 52-RUs uses a STF sequence corresponding to the RU having a PAPR of 2.90. Additionally, it is preferable that a user being allocated with 106-RUs uses a STF sequence corresponding to the RU having a PAPR of 4.39. Moreover, it is preferable that a user being allocated with 242-RUs uses a STF sequence corresponding to the RU having a PAPR of 5.46.

0211<figref idref="f0032">FIG. 32</figref> and <figref idref="f0033">FIG. 33</figref> are drawings respectively showing a PAPR for RUs that are used in a 80MHz band. In the 80MHz band, the PAPR of the central 26-RU is equal to 1.94, and the PAPR of the entire band is equal to 5.77.

0212The values respectively marked on uppermost ends of <figref idref="f0032">FIG. 32</figref> and <figref idref="f0033">FIG. 33</figref> indicate the PAPR for the 26-RU. More specifically, the RUs shown in <figref idref="f0032">FIG. 32</figref> correspond to RUs positioned on the left side of the central frequency, and the RUs shown in <figref idref="f0033">FIG. 33</figref> correspond to RUs positioned on the right side of the central frequency. The range of frequency indexes for the 18 26-RUs (RU1 to RU18), which are shown in <figref idref="f0032">FIG. 32</figref>, may correspond to Table 5 shown below. Additionally, the range of frequency indexes for the 18 26-RUs (RU20 to RU37), which are shown in <figref idref="f0033">FIG. 33</figref>, may correspond to Table 5 shown below. <tables id="tabl0005" num="0005"><table frame="all"><title>[Table 5]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="16mm" /><colspec colnum="2" colname="col2" colwidth="30mm" /><colspec colnum="3" colname="col3" colwidth="30mm" /><colspec colnum="4" colname="col4" colwidth="30mm" /><colspec colnum="5" colname="col5" colwidth="29mm" /><colspec colnum="6" colname="col6" colwidth="32mm" /><thead><row><entry valign="top">RU type</entry><entry namest="col2" nameend="col6" align="left" valign="top" /></row></thead><tbody><row><entry>26-RU</entry><entry>RU 1 [-499: -474]</entry><entry>RU 2 [-473: -448]</entry><entry>RU 3 [-445: -420]</entry><entry>RU 4 [-419: -394]</entry><entry>RU 5 [-392: -367]</entry></row><row><entry /><entry>RU 6 [-365: -340]</entry><entry>RU 7 [-339: -314]</entry><entry>RU 8 [-311: -286]</entry><entry>RU 9 [-285: -260]</entry><entry /></row><row><entry /><entry>RU 10 [-257: -232]</entry><entry>RU 11 [-231: -206]</entry><entry>RU 12 [-203: -178]</entry><entry>RU 13 [-177: -152]</entry><entry>RU 14 [-150: -125]</entry></row><row><entry /><entry>RU 15 [-123: -98]</entry><entry>RU 16 [-97: -72]</entry><entry>RU 17 [-69: -44]</entry><entry>RU 18 [-43: -18]</entry><entry>RU 19 [-16: -4. 4: 16]</entry></row><row><entry /><entry>RU 20 [18: 43]</entry><entry>RU 21 [44: 69]</entry><entry>RU 22 [72: 971</entry><entry>RU 23 [98: 123]</entry><entry>RU 24 [125: 150]</entry></row><row><entry /><entry>RU 25 [152: 177]</entry><entry>RU 26 [178: 203]</entry><entry>RU 27 [206: 231]</entry><entry>RU28 [232: 257]</entry><entry /></row><row><entry /><entry>RU 29 [260: 285]</entry><entry>RU 30 [286: 311]</entry><entry>RU 31 [314: 339]</entry><entry>RU 32 [340: 365]</entry><entry>RU 33 [367: 392]</entry></row><row><entry /><entry>RU 34 [394: 419]</entry><entry>RU 35 [420: 445]</entry><entry>RU 36 [448: 473]</entry><entry>RU37 [474: 499]</entry><entry /></row></tbody></tgroup></table></tables>

0213Additionally, as shown in <figref idref="f0006">FIG. 6</figref> and <figref idref="f0032">FIG. 32</figref>, in case of the 52-RUs that are used for the 80MHz band, 8 52-RUs are included on the left side of the central 26-RU. Also, as shown in <figref idref="f0006">FIG. 6</figref> and <figref idref="f0033">FIG. 33</figref>, in case of the 52-RUs that are used for the 80MHz band, 8 52-RUs are included on the right side of the central 26-RU. Herein, the range of frequency indexes for each RU may correspond to Table 6 shown below. Additionally, as shown in <figref idref="f0006">FIG. 6</figref>, <figref idref="f0032">FIG. 32</figref>, and <figref idref="f0033">FIG. 33</figref>, 8 106-RUs that are used for the 80MHz band exist, 4 242-RUs that are used for the 80MHz band exist, 2 484-RU that are used for the 40MHz band exist, and 1 996-RU that is used for the 80MHz band exists. And, herein, the range of frequency indexes for each RU may correspond to Table 6 shown below. <tables id="tabl0006" num="0006"><table frame="all"><title>[Table 6]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="17mm" /><colspec colnum="2" colname="col2" colwidth="29mm" /><colspec colnum="3" colname="col3" colwidth="29mm" /><colspec colnum="4" colname="col4" colwidth="29mm" /><colspec colnum="5" colname="col5" colwidth="29mm" /><colspec colnum="6" colname="col6" colwidth="7mm" /><thead><row><entry valign="top">RU type</entry><entry namest="col2" nameend="col6" align="left" valign="top" /></row></thead><tbody><row><entry morerows="3">52-RU</entry><entry>RU 1 [-499: -448]</entry><entry>RU 2 [-445: -394]</entry><entry>RU 3 [-365: -314]</entry><entry>RU 4 [-311: -260]</entry><entry /></row><row><entry>RU 5 [-257: -206]</entry><entry>RU 6 [-203: -152]</entry><entry>RU 7 [-123: -72]</entry><entry>RU 8 [-69: -18]</entry><entry /></row><row><entry>RU 9 [18: 69]</entry><entry>RU 10 [72: 123]</entry><entry>RU 11 [152: 203]</entry><entry>RU 12 [206: 257]</entry><entry /></row><row><entry>RU 13 [260: 3111</entry><entry>RU 14 [314: 365]</entry><entry>RU 15 [394: 445]</entry><entry>RU 16 [448: 499]</entry><entry /></row><row><entry morerows="1">106-RU</entry><entry>RU 1 [-499: -394]</entry><entry>RU 2 [-365: -260]</entry><entry>RU 3 [-257: -152]</entry><entry>RU 4 [-123: -18]</entry><entry /></row><row><entry>RU 5 [18: 123]</entry><entry>RU 6 [152: 257]</entry><entry>RU 7 [260: 365]</entry><entry>RU 8 [394: 499]</entry><entry /></row><row><entry>242-RU</entry><entry>RU 1 [-500: -259]</entry><entry>RU 2 [-258: -17]</entry><entry>RU 3 [17: 258]</entry><entry>RU 4 [259: 500]</entry><entry /></row><row rowsep="0"><entry>484-RU</entry><entry namest="col2" nameend="col3" align="left">RU 1</entry><entry namest="col4" nameend="col5" align="left">RU 2</entry><entry /></row><row><entry /><entry namest="col2" nameend="col3" align="left">[-500: -17]</entry><entry namest="col4" nameend="col5" align="left">[17: 500]</entry><entry /></row><row rowsep="0"><entry>996-RU</entry><entry namest="col2" nameend="col5" align="left">RU 1</entry><entry /></row><row><entry /><entry namest="col2" nameend="col5" align="left">[-500: -3. 3: 500]</entry><entry /></row></tbody></tgroup></table></tables>

0214For example, it is preferable that a user being allocated with 26-RUs for the 40MHz band uses a STF sequence corresponding to the RU having a PAPR of 2.22. Also, it is preferable that a user being allocated with 52-RUs uses a STF sequence corresponding to the RU having a PAPR of 2.90. Additionally, it is preferable that a user being allocated with 106-RUs uses a STF sequence corresponding to the RU having a PAPR of 4.39. Moreover, it is preferable that a user being allocated with 242-RUs uses a STF sequence corresponding to the RU having a PAPR of 5.50.

0215<figref idref="f0034">FIG. 34</figref> is a block view showing a wireless device to which the exemplary embodiment of the present invention can be applied.

0216Referring to <figref idref="f0034">FIG. 34</figref>, as a station (STA) that can implement the above-described exemplary embodiment, the wireless device may correspond to an AP or a non-AP station (non-AP STA). The wireless device may correspond to the above-described user or may correspond to a transmitting device transmitting a signal to the user.

0217The AP 3400 includes a processor 3410, a memory 3420, and a radio frequency unit (RF unit) 3430.

0218The RF unit 3430 is connected to the processor 3410, thereby being capable of transmitting and/or receiving radio signals.

0219The processor 3410 implements the functions, processes, and/or methods proposed in this specification. For example, the processor 3410 may be realized to perform the operations according to the above-described exemplary embodiments of the present invention. More specifically, the processor 3410 may perform the operations that can be performed by the AP, among the operations that are disclosed in the exemplary embodiments of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032 f0033">FIG. 1 to FIG. 33</figref>.

0220The non-AP STA 3450 includes a processor 3460, a memory 3470, and a radio frequency (RF) unit 3480.

0221The RF unit 3480 is connected to the processor 3460, thereby being capable of transmitting and/or receiving radio signals.

0222The processor 3460 may implement the functions, processes, and/or methods proposed in the exemplary embodiment of the present invention. For example, the processor 3460 may be realized to perform the non-AP STA operations according to the above-described exemplary embodiments of the present invention. The processor may perform the operations of the non-AP STA, which are disclosed in the exemplary embodiments of <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032 f0033">FIG. 1 to FIG. 33</figref>.

0223The processor 3410 and 3460 may include an application-specific integrated circuit (ASIC), another chip set, a logical circuit, a data processing device, and/or a converter converting a baseband signal and a radio signal to and from one another. The memory 3420 and 3470 may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and/or another storage device. The RF unit 3430 and 3480 may include one or more antennas transmitting and/or receiving radio signals.

0224When the exemplary embodiment is implemented as software, the above-described method may be implemented as a module (process, function, and so on) performing the above-described functions. The module may be stored in the memory 3420 and 3470 and may be executed by the processor 3410 and 3460. The memory 3420 and 3470 may be located inside or outside of the processor 3410 and 3460 and may be connected to the processor 3410 and 3460 through a diversity of well-known means.