Patent Description:
Discussion for a next-generation wireless local area network (WLAN) is in progress. In the next-generation WLAN, an object is to <NUM>) improve an institute of electronic and electronics engineers (IEEE) <NUM> physical (PHY) layer and a medium access control (MAC) layer in bands of <NUM> and <NUM>, <NUM>) increase spectrum efficiency and area throughput, <NUM>) 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.

An 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.

In 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.

In 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. Further background information may be found in the documents <CIT>, <CIT>, <CIT>, and <CIT>.

The invention is defined by a method in a wireless local area network, according to claim <NUM>, and the corresponding transmitting apparatus of claim <NUM>.

According 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.

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

<FIG> is a conceptual view illustrating the structure of a wireless local area network (WLAN).

An upper part of <FIG> illustrates the structure of an infrastructure basic service set (BSS) of institute of electrical and electronic engineers (IEEE) <NUM>.

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

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

The distribution system <NUM> may implement an extended service set (ESS) <NUM> extended by connecting the multiple BSSs <NUM> and <NUM>. The ESS <NUM> may be used as a term indicating one network configured by connecting one or more APs <NUM> or <NUM> through the distribution system <NUM>. The AP included in one ESS <NUM> may have the same service set identification (SSID).

A portal <NUM> may serve as a bridge which connects the wireless LAN network (IEEE <NUM>) and another network (e.g., <NUM>.

In the BSS illustrated in the upper part of <FIG>, a network between the APs <NUM> and <NUM> and a network between the APs <NUM> and <NUM> and the STAs <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may be implemented. However, the network is configured even between the STAs without the APs <NUM> and <NUM> to perform communication. A network in which the communication is performed by configuring the network even between the STAs without the APs <NUM> and <NUM> is defined as an Ad-Hoc network or an independent basic service set (IBSS).

A lower part of <FIG> illustrates a conceptual view illustrating the IBSS.

Referring to the lower part of <FIG>, 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 <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are managed by a distributed manner. In the IBSS, all STAs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may be constituted by movable STAs and are not permitted to access the DS to constitute a self-contained network.

The 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) <NUM> 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).

The 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.

Meanwhile, 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.

<FIG> is a diagram illustrating an example of a PPDU used in an IEEE standard.

As illustrated in <FIG>, 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.

In 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 <NUM>. 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.

<FIG> is a diagram illustrating an example of an HE PDDU.

The control information field provided in the embodiment may be the HE-SIG-B included in the HE PPDU. The HE PPDU according to <FIG> 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.

As illustrated in <FIG>, 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, <NUM> or <NUM> µs).

More detailed description of the respective fields of <FIG> will be made below.

<FIG> is a diagram illustrating a layout of resource units (RUs) used in a band of <NUM>.

As illustrated in <FIG>, 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.

As illustrated in an uppermost part of <FIG>, <FIG> units (that is, units corresponding to <NUM> tones). <NUM> tones may be used as a guard band in a leftmost band of the <NUM> band and <NUM> tones may be used as the guard band in a rightmost band of the <NUM> band. Further, <NUM> DC tones may be inserted into a center band, that is, a DC band and a <NUM>-unit corresponding to each <NUM> tones may be present at left and right sides of the DC band. The <NUM>-unit, a <NUM>-unit, and a <NUM>-unit may be allocated to other bands. Each unit may be allocated for a receiving station, that is, a user.

Meanwhile, the RU layout of <FIG> 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 <FIG>, one <NUM>-unit may be used and in this case, three DC tones may be inserted.

In one example of <FIG>, RUs having various sizes, that is, a <NUM>-RU, a <NUM>-RU, a <NUM>-RU, a <NUM>-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.

Similarly to a case in which the RUs having various RUs are used in one example of <FIG>, <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, and the like may be used even in one example of <FIG>. Further, <NUM> DC tones may be inserted into a center frequency, <NUM> tones may be used as the guard band in the leftmost band of the <NUM> band and <NUM> tones may be used as the guard band in the rightmost band of the <NUM> band.

In addition, as illustrated in <FIG>, when the RU layout is used for the single user, the <NUM>-RU may be used. That is, the detailed number of RUs may be modified similarly to one example of <FIG>.

Similarly to a case in which the RUs having various RUs are used in one example of each of <FIG> or <FIG>, <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, and the like may be used even in one example of <FIG>. Further, <NUM> DC tones may be inserted into the center frequency, <NUM> tones may be used as the guard band in the leftmost band of the <NUM> band and <NUM> tones may be used as the guard band in the rightmost band of the <NUM> band. In addition, the <NUM>-RU may be used, which uses <NUM> tones positioned at each of left and right sides of the DC band.

Moreover, as illustrated in <FIG>, when the RU layout is used for the single user, <NUM>-RU may be used and in this case, <NUM> DC tones may be inserted. Meanwhile, the detailed number of RUs may be modified similarly to one example of each of <FIG> or <FIG>.

<FIG> is a diagram illustrating another example of the HE PPDU.

A block illustrated in <FIG> is another example of describing the HE-PPDU block of <FIG> in terms of a frequency.

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

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

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

An HE-SIG-A <NUM> may include the control information common to the receiving station.

In detail, the HE-SIG-A <NUM> may include information on <NUM>) a DL/UL indicator, <NUM>) a BSS color field indicating an identify of a BSS, <NUM>) a field indicating a remaining time of a current TXOP period, <NUM>) a bandwidth field indicating at least one of <NUM>, <NUM>, <NUM>, <NUM> and <NUM>+<NUM>, <NUM>) a field indicating an MCS technique applied to the HE-SIG-B, <NUM>) an indication field regarding whether the HE-SIG-B is modulated by a dual subcarrier modulation technique for MCS, <NUM>) a field indicating the number of symbols used for the HE-SIG-B, <NUM>) a field indicating whether the HE-SIG-B is configured for a full bandwidth MIMO transmission, <NUM>) a field indicating the number of symbols of the HE-LTF, <NUM>) a field indicating the length of the HE-LTF and a CP length, <NUM>) a field indicating whether an OFDM symbol is present for LDPC coding, <NUM>) a field indicating control information regarding packet extension (PE), <NUM>) 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.

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

<FIG> is a block diagram illustrating one example of HE-SIG-B according to an embodiment.

As illustrated in <FIG>, 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 <FIG>, 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 <NUM> users and a CRC field corresponding thereto as illustrated in <FIG>.

A previous field of the HE-SIG-B <NUM> may be transmitted in a duplicated form on an MU PPDU. In the case of the HE-SIG-B <NUM>, the HE-SIG-B <NUM> 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 <NUM> in a specific frequency band (e.g., the second frequency band) is duplicated with the HE-SIG-B <NUM> of another frequency band (e.g., the fourth frequency band). Alternatively, the HE-SIG B <NUM> may be transmitted in an encoded form on all transmission resources. A field after the HE-SIG B <NUM> may include individual information for respective receiving STAs receiving the PPDU.

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

The HE-LTF <NUM> may be used for estimating a channel in the MIMO environment or the OFDMA environment.

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

For example, when at least one field of the L-STF <NUM>, the L-LTF <NUM>, the L-SIG <NUM>, the HE-SIG-A <NUM>, and the HE-SIG-B <NUM> on the PPDU of <FIG> is referred to as a first field, at least one of the data field <NUM>, the HE-STF <NUM>, and the HE-LTF <NUM> 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 = <NUM>, <NUM>, and <NUM>) 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 (=<NUM>) times larger than the first field of the HE PPDU. For example, <NUM> FFT/IFFT may be applied to a bandwidth of <NUM>, <NUM> FFT/IFFT may be applied to a bandwidth of <NUM>, <NUM> FFT/IFFT may be applied to a bandwidth of <NUM>, and <NUM> FFT/IFFT may be applied to a bandwidth of continuous <NUM> or discontinuous <NUM>.

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

Alternatively, an IDFT/DFT period applied to each symbol of the first field may be expressed to be N (=<NUM>) 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 <NUM> and the IDFT/DFT length applied to each symbol of the second field of the HE PPDU may be expressed as <NUM> * <NUM> (= <NUM>). 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 <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

The characteristic that the size of the FFT/IFFT being applied to the HE-STF <NUM> and the fields after the HE-STF <NUM> 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 <FIG> or to an uplink MU PPDU, which will be described later on.

For simplicity in the description, in <FIG>, 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 <FIG>, 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.

The user (e.g., a receiving station) may receive the HE-SIG-A <NUM> and may be instructed to receive the downlink PPDU based on the HE-SIG-A <NUM>. In this case, the STA may perform decoding based on the FFT size changed from the HE-STF <NUM> and the field after the HE-STF <NUM>. On the contrary, when the STA may not be instructed to receive the downlink PPDU based on the HE-SIG-A <NUM>, the STA may stop the decoding and configure a network allocation vector (NAV). A cyclic prefix (CP) of the HE-STF <NUM> 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.

Hereinafter, 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.

In 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.

Further, 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.

In 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.

In 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.

Further, 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.

When 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.

When 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.

The 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.

In 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 <NUM> excess bandwidth) to one terminal. When a channel unit is <NUM>, multiple channels may include a plurality of <NUM>-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.

In 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.

As 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).

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

<FIG> illustrates an example of a trigger frame. The trigger frame of <FIG> 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 <FIG>, through the legacy PPDU shown in <FIG>, 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 <FIG>, the trigger frame may be included in the data field shown in the drawing.

Each of the fields shown in <FIG> 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.

A Frame Control field <NUM> shown in <FIG> may include information related to a version of the MAC protocol and other additional control information, and a Duration field <NUM> may include time information for configuring a NAV or information related to an identifier (e.g., AID) of the user equipment.

Additionally, a RA field <NUM> 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 <NUM> may include address information of the STA (e.g., AP) transmitting the corresponding trigger frame, and a common information field <NUM> may include common control information that is applied to the receiving STA receiving the corresponding trigger frame.

<FIG> illustrates an example of a common information field. Among the sub-fields of <FIG>, 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.

As 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 <NUM> of the trigger frame may be used for indicating the length of its respective uplink PPDU.

Additionally, a Cascade Indicator field <NUM> 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.

A CS Request field <NUM> 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.

A HE-SIG-A information field <NUM> 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.

A CP and LTF type field <NUM> 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 <NUM> 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.

Meanwhile, the remaining description on <FIG> will be additionally provided as described below.

It is preferable that the trigger frame includes per user information fields <NUM>#<NUM> to <NUM>#N corresponding to the number of receiving STAs receiving the trigger frame of <FIG>. The per user information field may also be referred to as a "RU Allocation field".

Additionally, the trigger frame of <FIG> may include a Padding field <NUM> and a Sequence field <NUM>.

It is preferable that each of the per user information fields <NUM>#<NUM> to <NUM>#N shown in <FIG> further includes multiple sub-fields.

<FIG> illustrates an example of a sub-field being included in a per user information field. Among the sub-fields of <FIG>, 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.

A User Identifier field <NUM> 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.

Additionally, a RU Allocation field <NUM> 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 <NUM>, transmits an uplink PPDU in response to the trigger frame of <FIG>, the corresponding uplink PPDU is transmitted through the RU, which is indicated by the RU Allocation field <NUM>. In this case, it is preferable that the RU that is being indicated by the RU Allocation field <NUM> corresponds to the RU shown in <FIG>, <FIG>, and <FIG>.

The sub-field of <FIG> may include a Coding Type field <NUM>. The Coding Type field <NUM> may indicate a coding type of the uplink PPDU being transmitted in response to the trigger frame of <FIG>. For example, in case BBC coding is applied to the uplink PPDU, the Coding Type field <NUM> may be set to '<NUM>', and, in case LDPC coding is applied to the uplink PPDU, the Coding Type field <NUM> may be set to '<NUM>'.

Additionally, the sub-field of <FIG> may include a MCS field <NUM>. The MCS field <NUM> may indicate a MCS scheme being applied to the uplink PPDU that is transmitted in response to the trigger frame of <FIG>. For example, in case BBC coding is applied to the uplink PPDU, the Coding Type field <NUM> may be set to '<NUM>', and, in case LDPC coding is applied to the uplink PPDU, the Coding Type field <NUM> may be set to '<NUM>'.

<FIG> is a block diagram illustrating an example of an uplink MU PPDU. The uplink MU PPDU of <FIG> may be transmitted in response to the above-described trigger frame.

As shown in the drawing, the PPDU of <FIG> includes diverse fields, and the fields included herein respectively correspond to the fields shown in <FIG>, <FIG>, and <FIG>. Meanwhile, as shown in the drawing, the uplink PPDU of <FIG> may not include a HE-SIG-B field and may only include a HE-SIG-A field.

<FIG> illustrates a 1x HE-STF tone in a per-channel PPDU transmission according to an exemplary embodiment of the present invention. Most particularly, <FIG> shows an example of a HE-STF tone (i.e., <NUM>-tone sampling) having a periodicity of <NUM>µs in <NUM>/<NUM>/<NUM> bandwidths. Accordingly, in <FIG>, the HE-STF tones for each bandwidth (or channel) may be positioned at <NUM> tone intervals.

In <FIG>, 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 <NUM> (i.e., a non-zero value) to the corresponding tone index.

Sub-drawing (a) of <FIG> illustrates an example of a 1x HE-STF tone in a <NUM> PPDU transmission.

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

Sub-drawing (b) of <FIG> illustrates an example of a 1x HE-STF tone in a <NUM> PPDU transmission.

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

Sub-drawing (c) of <FIG> illustrates an example of a 1x HE-STF tone in an <NUM> PPDU transmission.

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

<FIG> illustrates a 2x HE-STF tone in a per-channel PPDU transmission according to an exemplary embodiment of the present invention. Most particularly, <FIG> shows an example of a HE-STF tone (i.e., <NUM>-tone sampling) having a periodicity of <NUM>µs in <NUM>/<NUM>/<NUM> bandwidths. Accordingly, in <FIG>, the HE-STF tones for each bandwidth (or channel) may be positioned at <NUM> tone intervals.

The 2x HE-STF signal according to <FIG> may be applied to the uplink MU PPDU shown in <FIG>. More specifically, the 2x HE-STF signal shown in <FIG> may be included in the PPDU, which is transmitted via uplink in response to the above-described trigger frame.

Sub-drawing (a) of <FIG> is a drawing showing an example of a 2x HE-STF tone in a <NUM> PPDU transmission.

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

Sub-drawing (b) of <FIG> illustrates an example of a 2x HE-STF tone in a <NUM> PPDU transmission.

Referring to sub-drawing (b), in case a HE-STF sequence (i.e., 2x HE-STF sequence) for a periodicity of <NUM>µs is mapped to tones of a <NUM> channel, the 2x HE-STF sequence is mapped to tones having tone indexes that are divisible by <NUM> (i.e., multiples of <NUM>), among the tones having tone indexes ranging from -<NUM> to <NUM>, and, then, <NUM> may be mapped to the remaining tones. More specifically, in a <NUM> channel, among the tones having tone indexes ranging from -<NUM> to <NUM>, a 2x HE-STF tone may be positioned at a tone index that is divisible by <NUM> excluding the DC. Herein, however, tones having tone indexes of ±<NUM> 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 <NUM>). Accordingly, a total of <NUM>2x HE-STF tones having the 2x HE-STF sequence mapped thereto may exist in the <NUM> channel.

Sub-drawing (c) of <FIG> illustrates an example of a 2x HE-STF tone in an <NUM> PPDU transmission.

Referring to sub-drawing (c), in case a HE-STF sequence (i.e., 2x HE-STF sequence) for a periodicity of <NUM>µs is mapped to tones of an <NUM> channel, the 2x HE-STF sequence is mapped to tones having tone indexes that are divisible by <NUM> (i.e., multiples of <NUM>), among the tones having tone indexes ranging from -<NUM> to <NUM>, and, then, <NUM> may be mapped to the remaining tones. More specifically, in an <NUM> channel, among the tones having tone indexes ranging from -<NUM> to <NUM>, a 2x HE-STF tone may be positioned at a tone index that is divisible by <NUM> excluding the DC. Herein, however, tones having tone indexes of ±<NUM> 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 <NUM>). Accordingly, a total of <NUM>2x HE-STF tones having the 2x HE-STF sequence mapped thereto may exist in the <NUM> channel.

Hereinafter, a sequence that can be applied to a 1x HE-STF tone (i.e., sampling at intervals of <NUM> tones) and a sequence that can be applied to a 2x HE-STF tone (i.e., sampling at intervals of <NUM> 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 <NUM>. It is preferable that the M sequence is configured as a binary sequence so as to decrease the level of complexity when being decoded.

Hereinafter, 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.

The 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.

<FIG> illustrates an example of repeating an M sequence.

It is preferable that the example shown in <FIG> is applied to 1x HE-STF.

As shown in <FIG>, when expressed in the form of an equation, the STF sequence for <NUM> may be expressed as shown in Equation <NUM>.

The notation of HE_STF(A1:A2:A3)={M}, which is used in Equation <NUM> 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.

Accordingly, in Equation <NUM>, the first element of the M sequence corresponds to the frequency band corresponding to index "-<NUM>"" the last element of the M sequence corresponds to the frequency band corresponding to index "+<NUM>", and each element of the M sequence is positioned at <NUM> frequency tone intervals. Additionally, the value "<NUM>" corresponds to a frequency band corresponding to index "<NUM>" More specifically, Equation <NUM> has a structure corresponding to sub-drawing (a) of <FIG>.

As shown in <FIG>, when expressed in the form of an equation, the STF sequence for <NUM> may be expressed as shown in Equation <NUM>. More specifically, in order to extend the structure of Equation <NUM> to the <NUM> band, {M, <NUM>, M} may be used.

Equation <NUM> corresponds to a structure, wherein <NUM> sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "-<NUM>" and up to a frequency band corresponding to index "-<NUM>" at <NUM> frequency tone intervals, wherein "<NUM>" is positioned for frequency index <NUM>, and wherein <NUM> sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "+<NUM>" and up to a frequency band corresponding to index "+<NUM>" at <NUM> frequency tone intervals "+<NUM>".

As shown in <FIG>, when expressed in the form of an equation, the STF sequence for <NUM> may be expressed as shown in Equation <NUM>. More specifically, in order to extend the structure of Equation <NUM> to an <NUM> band, {M, <NUM>, M, <NUM>, M, <NUM>, M} may be used.

Equation <NUM> corresponds to a structure, wherein <NUM> sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "-<NUM>" and up to a frequency band corresponding to index "-<NUM>" at <NUM> frequency tone intervals, wherein "<NUM>" (or an arbitrary additional value a1) is positioned for a frequency band corresponding to index "-<NUM>", wherein <NUM> sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "-<NUM>" and up to a frequency band corresponding to index "-<NUM>" at <NUM> frequency tone intervals, and wherein "<NUM>" is positioned for frequency index <NUM>. Additionally, Equation <NUM> also corresponds to a structure, wherein <NUM> sequence elements are positioned within a frequency band range starting from a frequency band corresponding to index "+<NUM>" and up to a frequency band corresponding to index "+<NUM>" at <NUM> frequency tone intervals, wherein "<NUM>" (or an arbitrary additional value a2) is positioned for a frequency band corresponding to index "+<NUM>", and wherein M sequence elements are positioned from "+<NUM>" to "+<NUM>" at <NUM> frequency tone intervals.

By applying an additional coefficient to the above-described structures of Equation <NUM> to Equation <NUM>, it will be possible to optimize the sequence for PAPR. In case of the related art IEEE <NUM>. 11ac system, although it may be possible to extend the predetermined <NUM> sequence for the <NUM> and <NUM> by using a gamma value, since the gamma value may not be applied in the IEEE <NUM>. 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 <NUM> to Equation <NUM>, the PAPR should be calculated based on the entire band (e.g., the entire band shown in <FIG>), and, in case of considering the 2x HE-STF sequence, the PAPR should be calculated while considering each unit (e.g., individual units <NUM>-RU, <NUM>-RU, <NUM>-RU, and so on, shown in <FIG>).

<FIG> is an example specifying the repeated structure of <FIG> in more detail.

As shown in the drawing, coefficients c1 to c7 may be applied, or (<NUM>+j)*sqrt(<NUM>/<NUM>) may be applied, and additional values, such as a1 and a2, may also be applied.

Based on the content of <FIG>, an example of the STF sequence that is optimized for the PAPR is as shown below.

First of all, the M sequence may be determined as shown below in Equation <NUM>.

In this case, the STF sequence respective to the <NUM> and <NUM> bands may be determined in accordance with the equations shown below. <MAT> <MAT>.

The definition of the variables used in the equations presented above is the same as those used in Equation <NUM> to Equation <NUM>.

Meanwhile, the STF sequence corresponding to the <NUM> band may be determined in accordance with any one of the equations shown below. <MAT><MAT>.

The examples shown in Equation <NUM> to Equation <NUM>, which are presented above, may be modified to other examples, as shown below.

First of all, the M sequence that is basically used may be modified as shown in Equation <NUM>.

Equation <NUM> that is presented above may be applied to all or part of Equation <NUM> to Equation <NUM>. For example, it may be possible to use the basic sequence of Equation <NUM> based on the structure of Equation <NUM>.

The 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 <FIG>).

More specifically, the PAPR for the example of applying Equation <NUM> to the structure of Equation <NUM> is equal to <NUM>, the PAPR for the example of applying Equation <NUM> to the structure of Equation <NUM> is equal to <NUM>, and the PAPR for the example of applying Equation <NUM> to the structure of Equation <NUM> or Equation <NUM> is equal to <NUM>. Additionally, the PAPR for the example of applying Equation <NUM> to the structure of Equation <NUM> is equal to <NUM>, the PAPR for the example of applying Equation <NUM> to the structure of Equation <NUM> is equal to <NUM>, and the PAPR for the example of applying Equation <NUM> to the structure of Equation <NUM> or Equation <NUM> is equal to <NUM>. 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.

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

As shown in <FIG>, when expressed in the form of an equation, the STF sequence for <NUM> may be expressed as shown below in the following Equation.

By applying an additional coefficient to the above-described structures of Equation <NUM> to Equation <NUM>, it will be possible to optimize the sequence for PAPR. In case of the related art IEEE <NUM>. 11ac system, although it may be possible to extend the predetermined <NUM> sequence for the <NUM> and <NUM> by using a gamma value, since the gamma value may not be applied in the IEEE <NUM>. 11ax or HEW system, the PAPR should be considered without considering the gamma value.

As shown in the drawing, coefficients c1 to c14 may be applied, or (<NUM>+j)*sqrt(<NUM>/<NUM>) may be applied, and additional values, such as a1 to a8, may also be applied.

In this case, the STF sequence respective to the <NUM>, <NUM>, and <NUM> bands may be determined in accordance with the equations shown below. <MAT><MAT><MAT>.

The 2x HE-STF sequence for the <NUM> band may be generated by using a method of applying Equation <NUM>, which is presented above, to Equation <NUM>.

Meanwhile, 2x HE-STF sequence for the <NUM> band may be generated by using a method of applying Equation <NUM>, which is presented above, to the Equation shown below.

Additionally, 2x HE-STF sequence for the <NUM> band may be generated by using a method of applying Equation <NUM>, which is presented above, to the Equation shown below.

<FIG> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a <NUM> band.

Each block shown in <FIG> respectively indicates <NUM>-RU, <NUM>-RU, <NUM>-RU, and <NUM>-RU, which are shown in <FIG>. For example, a first block <NUM> indicates a leftmost <NUM>-RU, which is shown in <FIG>, a second block <NUM> indicates a central <NUM>-RU, which is shown in <FIG>, a third block <NUM> indicates a <NUM>-RU, a fourth block <NUM> indicates a <NUM>-RU, and a fifth block <NUM> indicates a <NUM>-RU.

The example of the above-described Equation <NUM> to Equation <NUM> may be indicated as example (B-<NUM>), and the example of the above-described Equation <NUM> to Equation <NUM> may be indicated as example (B-<NUM>). In this case, the values indicated in each block represent the PAPRs for example (B-<NUM>) and example (B-<NUM>), respectively.

<FIG> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a <NUM> band. More specifically, each block shown in <FIG> respectively indicates <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, and <NUM>-RU, which are shown in <FIG>.

<FIG> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a left side band of a <NUM> band. And, <FIG> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a right side band of a <NUM> band. More specifically, each block shown in <FIG> and <FIG> respectively indicates <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, and <NUM>-RU, which are shown in <FIG>. In the examples shown in <FIG> and <FIG>, in case of the <NUM>-RU (i.e., central <NUM>-RU) that is positioned in the DC band, the PAPR of example (B-<NUM>) is equal to <NUM>, and the PAPR of example (B-<NUM>) is equal to <NUM>. Additionally, for the entire band, the PAPR of example (B-<NUM>) is equal to <NUM>, and the PAPR of example (B-<NUM>) is equal to <NUM>.

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

As shown in the drawing, coefficients c1 to c14 may be applied, or (<NUM>+j)*sqrt(<NUM>/<NUM>) may be applied, and additional values, such as a1 to a4, may also be applied.

In this case, the STF sequence respective to the <NUM> and <NUM> bands may be determined in accordance with the equations shown below. Since the STF sequence for the <NUM> band is the same as example (B) (i.e., the same as Equation <NUM>), the indication of the same will be omitted. <MAT><MAT> <MAT>.

The 2x HE-STF sequences for the <NUM> band and the <NUM> band may be generated by using a method of applying Equation <NUM>, which is presented above, to the equation shown below. Since the STF sequence for the <NUM> band is the same as example (B), the indication of the same will be omitted. <MAT><MAT> <MAT>.

Each block shown in <FIG> respectively indicates <NUM>-RU, <NUM>-RU, <NUM>-RU, and <NUM>-RU, which are shown in <FIG>.

The example of the above-described Equation <NUM> to Equation <NUM> may be indicated as example (C-<NUM>), and the example of the above-described Equation <NUM> to Equation <NUM> may be indicated as example (C-<NUM>). In this case, the values indicated in each block represent the PAPRs for example (C-<NUM>) and example (C-<NUM>), respectively.

<FIG> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a left side band of a <NUM> band. And, <FIG> is a drawing indicating the above-described examples of the PAPR in RU units that are used in a right side band of a <NUM> band. More specifically, each block shown in <FIG> and <FIG> respectively indicates <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, <NUM>-RU, and <NUM>-RU, which are shown in <FIG>. In the examples shown in <FIG> and <FIG>, in case of the <NUM>-RU (i.e., central <NUM>-RU) that is positioned in the DC band, the PAPR of example (C-<NUM>) is equal to <NUM>, and the PAPR of example (C-<NUM>) is equal to <NUM>. Additionally, for the entire band, the PAPR of example (C-<NUM>) is equal to <NUM>, and the PAPR of example (C-<NUM>) is equal to <NUM>.

<FIG> is a procedure flow chart to which the above-described example can be applied.

The example of <FIG> may be applied to various transmitting apparatuses, for example, the corresponding example may be applied to user equipments (i.e., non-AP STA).

In 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 <FIG>, in case of transmitting the uplink PPDU shown in <FIG>, the transmitting apparatus may transmit a 2x HE STF signal, and, otherwise, the transmitting apparatus may transmit a 1x HE STF signal.

In 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 <NUM> 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, -<NUM>, -M <NUM>, M, -<NUM>, M}*(<NUM>+j)/sqrt(<NUM>). The M sequence may correspond to M={-<NUM>, -<NUM>, -<NUM>, <NUM>, <NUM>, <NUM>, -<NUM>, <NUM>, <NUM>, <NUM>, -<NUM>, <NUM>, <NUM>, -<NUM>, <NUM>}. The {M, -<NUM>, -M <NUM>, M, -<NUM>, M}*(<NUM>+j)/sqrt(<NUM>) sequence is positioned at intervals of <NUM> tones within a range of a lowest tone having a tone index of -<NUM> and a highest tone having a tone index of +<NUM>. And, in the {M, -<NUM>, -M <NUM>, M, -<NUM>, M}*(<NUM>+j)/sqrt(<NUM>), elements corresponding to each of the tone indexes -<NUM> and +<NUM> may be processed with nulling. Additionally, in case of generating a STF signal corresponding to a second frequency band, a {M, -<NUM>, M, -<NUM>, -M, -<NUM>, M, <NUM>, -M, <NUM>, M, <NUM>, -M, <NUM>, - M}*(<NUM>+j)/sqrt(<NUM>) sequence may be used.

In 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.

In case of transmitting the 1X HE-STF, a 1X 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.

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

Example (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.

For example, as shown below, 2x HE-STF sequences for <NUM>, <NUM>, and <NUM> 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. <MAT><MAT><MAT>.

Meanwhile, in case of configuring an uplink PPDU in a user STA, among the RUs shown in <FIG>, it may be possible to configure the STF field only for the RUs that are allocated to the corresponding user STA.

For example, a leftmost <NUM>-RU, which is shown in <FIG>, is positioned in a section starting from frequency index "-<NUM>" to frequency index "-<NUM>". If a user STA is allocated to the leftmost <NUM>-RU, sequences may be generated based on Equation <NUM>, 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 "-<NUM>" to frequency index "-<NUM>".

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

<FIG> is a drawing showing a PAPR for RUs that are used in a <NUM> band.

The value marked on an uppermost end of <FIG> indicates the PAPR for the <NUM>-RU. More specifically, <NUM><NUM>-RUs (RU1 to RU4) exist on the left side of the central <NUM>-RU (RU5) shown in <FIG>, and <FIG> <NUM>-RUs (RU6 to RU9) exist on the right side of the central <NUM>-RU (RU5).

In this case, the range of frequency indexes for each <NUM>-RU may correspond to Table <NUM> shown below.

Additionally, as shown in <FIG> and <FIG>, in case of <NUM>-RUs that are used for the <NUM> band, <NUM><NUM>-RUs are included on the left side of the central <NUM>-RU, and <NUM><NUM>-RUs are included on the right side of the central <NUM>-RU. Herein, the range of frequency indexes for each RU may correspond to Table <NUM> shown below. Additionally, as shown in <FIG> and <FIG>, <NUM><NUM>-RUs that are used for the <NUM> band exist, and <NUM><NUM>-RU that is used for the <NUM> band exists. And, herein, the range of frequency indexes for each RU may correspond to Table <NUM> shown below.

For example, among the <NUM><NUM>-RUs shown in Table <NUM>, even if RU1 is allocated to a specific user, as shown in <FIG>, 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 <NUM> (i.e., a STF sequence corresponding to the frequency index of RU2 or RU3). In case a <NUM>-RU is allocated, it is preferable to use a STF sequence corresponding to a RU having a PAPR of <NUM>.

The value marked on an uppermost end of <FIG> indicates the PAPR for the <NUM>-RU. More specifically, <NUM><NUM>-RUs (RU1 to RU9) exist on the left side of the central <NUM>-RU (RU5) shown in <FIG>, and <FIG> <NUM>-RUs (RU10 to RU18) exist on the right side of the central <NUM>-RU (RU5).

Additionally, as shown in <FIG> and <FIG>, in case of <NUM>-RUs that are used for the <NUM> band, <NUM><NUM>-RUs are included on the left side of the central <NUM>-RU, and <NUM><NUM>-RUs are included on the right side of the central <NUM>-RU. Herein, the range of frequency indexes for each RU may correspond to Table <NUM> shown below. Additionally, as shown in <FIG> and <FIG>, <NUM><NUM>-RUs that are used for the <NUM> band exist, <NUM><NUM>-RUs that are used for the <NUM> band exist, and <NUM><NUM>-RU that is used for the <NUM> band exists. And, herein, the range of frequency indexes for each RU may correspond to Table <NUM> shown below.

For example, it is preferable that a user being allocated with <NUM>-RUs for the <NUM> band uses a STF sequence corresponding to the RU having a PAPR of <NUM>. Also, it is preferable that a user being allocated with <NUM>-RUs uses a STF sequence corresponding to the RU having a PAPR of <NUM>. Additionally, it is preferable that a user being allocated with <NUM>-RUs uses a STF sequence corresponding to the RU having a PAPR of <NUM>. Moreover, it is preferable that a user being allocated with <NUM>-RUs uses a STF sequence corresponding to the RU having a PAPR of <NUM>.

<FIG> and <FIG> are drawings respectively showing a PAPR for RUs that are used in a <NUM> band. In the <NUM> band, the PAPR of the central <NUM>-RU is equal to <NUM>, and the PAPR of the entire band is equal to <NUM>.

The values respectively marked on uppermost ends of <FIG> and <FIG> indicate the PAPR for the <NUM>-RU. More specifically, the RUs shown in <FIG> correspond to RUs positioned on the left side of the central frequency, and the RUs shown in <FIG> correspond to RUs positioned on the right side of the central frequency. The range of frequency indexes for the <NUM><NUM>-RUs (RU1 to RU18), which are shown in <FIG>, may correspond to Table <NUM> shown below. Additionally, the range of frequency indexes for the <NUM><NUM>-RUs (RU20 to RU37), which are shown in <FIG>, may correspond to Table <NUM> shown below.

Additionally, as shown in <FIG> and <FIG>, in case of the <NUM>-RUs that are used for the <NUM> band, <NUM><NUM>-RUs are included on the left side of the central <NUM>-RU. Also, as shown in <FIG> and <FIG>, in case of the <NUM>-RUs that are used for the <NUM> band, <NUM><NUM>-RUs are included on the right side of the central <NUM>-RU. Herein, the range of frequency indexes for each RU may correspond to Table <NUM> shown below. Additionally, as shown in <FIG>, <FIG>, and <FIG>, <NUM><NUM>-RUs that are used for the <NUM> band exist, <NUM><NUM>-RUs that are used for the <NUM> band exist, <NUM><NUM>-RU that are used for the <NUM> band exist, and <NUM><NUM>-RU that is used for the <NUM> band exists. And, herein, the range of frequency indexes for each RU may correspond to Table <NUM> shown below.

<FIG> is a block view showing a wireless device to which the exemplary embodiment of the present invention can be applied.

Referring to <FIG>, 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.

The AP <NUM> includes a processor <NUM>, a memory <NUM>, and a radio frequency unit (RF unit) <NUM>.

The RF unit <NUM> is connected to the processor <NUM>, thereby being capable of transmitting and/or receiving radio signals.

The processor <NUM> implements the functions, processes, and/or methods proposed in this specification. For example, the processor <NUM> may be realized to perform the operations according to the above-described exemplary embodiments of the present invention. More specifically, the processor <NUM> may perform the operations that can be performed by the AP, among the operations that are disclosed in the exemplary embodiments of <FIG>.

The non-AP STA <NUM> includes a processor <NUM>, a memory <NUM>, and a radio frequency (RF) unit <NUM>.

The processor <NUM> may implement the functions, processes, and/or methods proposed in the exemplary embodiment of the present invention. For example, the processor <NUM> 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 <FIG>.

The processor <NUM> and <NUM> 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 <NUM> and <NUM> 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 <NUM> and <NUM> may include one or more antennas transmitting and/or receiving radio signals.

Claim 1:
A method in a wireless local area network, LAN, system, comprising:
generating, by a transmitting apparatus, a short training field, STF, signal; and
transmitting, by the transmitting apparatus, the STF signal to a receiving apparatus via <NUM> band,
wherein the STF signal is generated based on an STF sequence defined as shown below: <MAT>
wherein sqrt() denotes a square root, "j" denotes an imaginary number, and "*" denotes multiplication, and
wherein the M sequence is defined as shown below: <MAT>
wherein the STF sequence is positioned at intervals of <NUM> subcarriers starting from a lowest subcarrier having a subcarrier index of -<NUM> and up to a highest subcarrier having a subcarrier index of +<NUM>.