WO2019132390A1 - Method and device for configuring frame format using nbt method in wireless lan system - Google Patents

Abstract

Suggested are a method and a device for transmitting an NBT frame in a wireless LAN system. A transmitting device generates an NBT frame including a first field and a second field, and transmits same to a receiving device. The first field is transmitted in a first bandwidth. The second field is transmitted in a second bandwidth smaller than the first bandwidth. The first field includes an L-LTF sequence. The second field includes an NB-LTF sequence. Based on the tone index spacing of a first tone for which a coefficient is configured from the L-LTF sequence, the tone index spacing of a second tone for which a coefficient is configured from the NB-LTF sequence is determined. The NB-LTF sequence is transmitted through the second tone.

Description

Method and apparatus for configuring frame format using NBT scheme in wireless LAN system

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a technique for constructing a frame format in a wireless LAN system, and more particularly, to a method and apparatus for generating an NBT frame format usable in a narrow band in a wireless LAN system.

Discussions are under way for the next generation wireless local area network (WLAN). In the next generation WLAN, 1) enhancement of IEEE 802.11 PHY (physical) layer and MAC (medium access control) layer in the 2.4GHz and 5GHz bands, 2) improvement of spectrum efficiency and area throughput throughput, and 3) to improve performance in real indoor and outdoor environments, such as environments where interference sources exist, dense heterogeneous networks, and environments with high user loads.

The environment that is considered mainly in the next generation WLAN is a dense environment with AP (access point) and STA (station), and improvement in spectrum efficiency and area throughput is discussed in this dense environment. In addition, the next generation WLAN is concerned not only with the indoor environment but also with the actual performance improvement in the outdoor environment which is not considered much in the existing WLAN.

Specifically, the next-generation WLAN is interested in scenarios such as wireless office, smart home, stadium, hotspot, and building / apartment, And STA in a dense environment.

In addition, in the next generation WLAN, improvement of system performance in an overlapping basic service set (OBSS) environment, improvement of outdoor environment performance, and cellular offloading will be actively discussed rather than improvement of single link performance in one basic service set (BSS) It is expected. The directionality of this next generation WLAN means that the next generation WLAN will have a technology range similar to that of mobile communication. Considering the recent discussions of mobile communication and WLAN technology in the area of small cell and D2D (direct-to-direct) communication, it is expected that the technological and business convergence of next generation WLAN and mobile communication will become more active.

This specification proposes a method and apparatus for configuring an NBT frame format usable in a narrow band in a wireless LAN system.

One example of this specification proposes a technique for constructing a frame format using the NBT scheme.

An example of the present invention proposes a method and apparatus for transmitting an NBT (Narrow Band Transmission) frame in a wireless LAN system.

In order to solve the problem that the gain is reduced in terms of coverage expansion and coverage holes of the signal compared to the existing 20 MHz band transmission according to the reduced bandwidth in the NBT transmission, the present embodiment generates a new frame called NBT frame Method.

In addition, NB (Narrow Band) can have various bandwidths (for example, 1 MHz, 2 MHz, or 4 MHz) and can have FFT sizes (32 FFT, 64 FFT, 128 FFT, 256 FFT) , 15.625 KHz), and the like.

First, in summary terms, the transmitting apparatus may be an AP, and the receiving apparatus may be an STA. The NB-LTF sequence can correspond to the LTF sequence proposed in the present embodiment in consideration of the channel change due to the NBT transmission. The HE-LTF sequence may correspond to the LTF sequence used in an 802.11ax system. The tone may correspond to a subcarrier.

The transmitting apparatus generates an NBT frame including a first field and a second field. The first field may correspond to a legacy part, and the second field may correspond to an NBT part. That is, in this embodiment, a frame having a leg part attached to the NBT part is proposed for backward compatibility or coexistence with the existing Wi-Fi device.

The transmitting apparatus transmits the NBT frame to the receiving apparatus.

The first field is transmitted with 64 IFFT (Inverse Fast Fourier Transform) in a first bandwidth, and the second field is transmitted in a second bandwidth smaller than the first bandwidth. The first bandwidth is 20 MHz, the second bandwidth is included in the first bandwidth, and may be 1 MHz, 2 MHz, or 4 MHz. That is, the first field may be transmitted in the existing 20 MHz band, and the second field may be transmitted in the narrow band using the NBT.

The second field includes an NB-LTF (Narrow Band-Long Training Field) sequence. Because the NBT frame is transmitted over a narrow bandwidth, the change in channel in terms of frequency is smaller than the 20 MHz band. Therefore, the NB-LTF sequence can be used in order to reduce unnecessary overhead when the channel is frequency flat with a sequence configured in an NBT part. In the following, how the NB-LTF sequence is constructed will be described.

A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined. The NB-LTF sequence may be transmitted on the second tone. That is, the tone on which the NB-LTF sequence is transmitted may be determined based on the tone on which the HE-LTF sequence is transmitted.

For example, the tone interval of the NB-LTF sequence may be 15.625 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be five times larger than the tone index interval of the first tone. Thus, the tone spacing of the second tone may be equal to the tone spacing of the first tone.

The size of the tone interval of the NB-LTF sequence is 1/5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficients of the NB-LTF sequence are set is 5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFT (Inverse Fast Fourier Transform). If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. If the tone index interval of the first tone is 2, the tone index of the second tone may be [± 10 ± 20]. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 31.25 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be set to be 2.5 times larger than the tone index interval of the first tone. The tone spacing of the second tone may be the same as the tone spacing of the first tone.

Therefore, the size of the tone interval of the NB-LTF sequence is 1 / 2.5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficient of the NB-LTF sequence is set is 2.5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 15.626 KHz or 31.25 KHz, and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be four times larger than the tone index interval of the first tone to maintain commonality with the first tone index. Therefore, the tone interval of the NBT-LTF sequence may be 4/8/16 tone depending on the FFT size, and the coefficient of the NB-LTF sequence may be a coefficient of the HE-LTF sequence set in the same tone as the tone index of the second tone Can be set.

In this embodiment, the HE-LTF sequence may be used in an 802.11ax system. In particular, the HE-LTF sequence may be defined as follows in the 20 MHz band.

First, when the tone index interval of the first tone in which coefficients are set in the HE-LTF sequence is 4 (1x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 2 (2x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 1 (4x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

The first field includes an L-STF (Legacy-Short Training Field) field, an L-LTF (Legacy-Long Training Field) field, an L-SIG (Legacy-Signal) field, and a BPSK . The L-SIG field may be located after the L-STF field and the L-LTF field. The second field may further include a narrow band short training field (NB-STF) field, a narrow band signal (NB-SIG) field, and a data field. The NB-SIG field may be located after the NB-LTF field including the NB-STF field and the NB-LTF sequence.

The L-SIG field may include information on the first bandwidth and the second bandwidth. On the other hand, the NB-SIG field may not include information on the first bandwidth and the second bandwidth.

The receiving apparatus can receive the NBT frame generated by the transmitting apparatus through the second bandwidth within the first bandwidth. However, if a third party device in the same cell receives an NBT frame, it performs a constellation check on a second field received via the second bandwidth, and performs a constellation check on the second field using an imaginary symbol And recognize it as a different frame format. The BPSK symbol may be added to the first field to reduce false detection.

According to an example of the present specification, a method of generating an NBT frame using an NBT scheme in a wireless LAN system is proposed.

The use of the proposed NBT frame in one example of the present specification solves the problem of reduced coverage in terms of coverage extension and coverage hole removal compared to 20 MHz transmission.

1 is a conceptual diagram illustrating a structure of a wireless local area network (WLAN).

2 is a diagram showing an example of a PPDU used in the IEEE standard.

3 is a diagram showing an example of an HE PPDU.

4 is a diagram showing the arrangement of resource units (RU) used on the 20 MHz band.

5 is a diagram showing the arrangement of resource units (RU) used on the 40 MHz band.

6 is a diagram showing the arrangement of resource units (RU) used on the 80 MHz band.

7 is a diagram showing another example of the HE-PPDU.

8 is a block diagram showing an example of the HE-SIG-B according to the present embodiment.

9 shows an example of a trigger frame.

10 shows an example of a common information field.

11 shows an example of a sub-field included in the per user information field.

12 is a block diagram showing an example of an uplink MU PPDU.

13 is a graph showing an SINR value of a signal transmitted using the NBT scheme.

FIG. 14 is a graph showing SINR values according to distances of signals transmitted using the NBT scheme.

15 shows an example of transmitting NBT frames over 26 RUs using RU allocation defined in 802.11ax OFDMA.

16 shows an example of transmitting NBT frames over 52 RUs using RU assignments defined in 802.11ax OFDMA.

Figure 17 shows another example of transmitting an NBT frame over 52 RUs using an RU assignment defined in 802.11ax OFDMA.

18 shows an example of loading power to 26 RUs allocated for transmitting NBT frames in 802.11ax OFDMA.

FIG. 19 shows an example of putting power at center 26 RU and center 52 RU allocated for transmitting NBT frames in 802.11ax OFDMA.

20 shows an example of an NBT frame composed of legacy parts and NBT parts for performing NBT.

21 shows an example of an NBT frame composed only of NBT parts for performing NBT.

22 is a flowchart of a procedure for generating and transmitting an NBT (Narrow Band Transmission) frame according to the present embodiment.

23 shows a transmitting apparatus for implementing this embodiment.

24 shows a procedure for receiving an NBT frame generated according to the present embodiment.

25 shows a receiving apparatus for implementing the present embodiment.

1 is a conceptual diagram illustrating a structure of a wireless local area network (WLAN).

The upper part of FIG. 1 shows the structure of an infrastructure basic service set (BSS) of Institute of Electrical and Electronic Engineers (IEEE) 802.11.

1, the WLAN system may include one or more infrastructure BSSs 100 and 105 (hereinafter, BSS). The BSSs 100 and 105 are a set of APs and STAs such as an access point 125 and an STA1 (station 100-1) capable of successfully synchronizing and communicating with each other. The BSS 105 may include one or more associatable STAs 105-1 and 105-2 in one AP 130. [

The BSS may include at least one STA, APs 125 and 130 providing a distribution service, and a distribution system (DS) 110 connecting a plurality of APs.

The distributed system 110 may implement an extended service set (ESS) 140 that is an extended service set by connecting a plurality of BSSs 100 and 105. ESS 140 may be used to refer to one network in which one or more APs 125 and 230 are connected through a distributed system 110. [ An AP included in one ESS 140 may have the same service set identification (SSID).

A portal 120 may serve as a bridge for performing a connection between a wireless LAN network (IEEE 802.11) and another network (for example, 802.X).

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 in the BSS as shown in the upper part of FIG. However, it is also possible to establish a network and perform communication between the STAs without the APs 125 and 130. [ An ad-hoc network or an independent basic service set (IBSS) is defined as a network that establishes a network and establishes communication between STAs without APs 125 and 130. [

1 is a conceptual diagram showing IBSS.

1, the IBSS is a BSS operating in an ad-hoc mode. Since IBSS does not include APs, there is no centralized management entity. That is, in the IBSS, the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 are managed in a distributed manner. In the IBSS, all the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may be mobile STAs, and the access to the distributed system is not allowed, network.

The STA is an arbitrary functional medium including a medium access control (MAC) conforming to IEEE (Institute of Electrical and Electronics Engineers) IEEE 802.11 standard and a physical layer interface for a wireless medium. May be used to mean both an AP and a non-AP STA (Non-AP Station).

The STA may be a mobile terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit Mobile Subscriber Unit), or simply a user.

Meanwhile, the term 'user' may be used in various meanings. For example, the term 'user' may be used to mean an STA participating in uplink MU MIMO and / or uplink OFDMA transmission in wireless LAN communication, But is not limited thereto.

2 is a diagram showing an example of a PPDU used in the IEEE standard.

As shown, various types of PPDU (PHY protocol data unit) are used in IEEE a / g / n / ac standards. Specifically, the LTF and STF fields included training signals, SIG-A and SIG-B included control information for the receiving station, and the data field included user data corresponding to the PSDU.

This embodiment proposes an improved technique for the signal (or control information field) used for the data field of the PPDU. The signal proposed in this embodiment can be applied on the HE PPDU (high efficiency PPDU) according to the IEEE 802.11ax standard. That is, the signal to be improved in this embodiment may be HE-SIG-A and / or HE-SIG-B included in the HE PPDU. Each of HE-SIG-A and HE-SIG-B can also be expressed as SIG-A, SIG-B. However, the improved signal proposed by the present embodiment is not necessarily limited to the HE-SIG-A and / or HE-SIG-B standards, and various control and control schemes including control information in a wireless communication system, It is applicable to data fields.

3 is a diagram showing an example of an HE PPDU.

The control information field proposed in this embodiment may be HE-SIG-B included in the HE PPDU as shown in FIG. The HE PPDU according to FIG. 3 is an example of a PPDU for multiple users. The HE-SIG-B is included only for multi-user, and the corresponding HE-SIG-B can be omitted for a PPDU for a single user.

As shown, an HE-PPDU for a Multiple User (MU) includes a legacy-short training field (L-STF), a legacy-long training field (L-LTF) (HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF) , A data field (or MAC payload), and a Packet Extension (PE) field. Each field may be transmitted during the time interval shown (i.e., 4 or 8 ㎲, etc.).

A more detailed description of each field of FIG. 3 will be given later.

4 is a diagram showing the arrangement of resource units (RU) used on the 20 MHz band.

As shown in FIG. 4, a resource unit (RU) corresponding to a different number of tones (i.e., subcarriers) may be used to configure some fields of the HE-PPDU. For example, resources may be allocated in units of RU shown for the HE-STF, HE-LTF, and data fields.

As shown at the top of FIG. 4, a 26-unit (i.e., a unit corresponding to 26 tones) may be placed. Six tones are used as the guard band in the leftmost band of the 20 MHz band and five tones can be used as the guard band in the rightmost band of the 20 MHz band. Also, there may be 7 DC tones in the center band, i.e., the DC band, and a 26-unit corresponding to 13 tones to the left and right of the DC band. Also, other bands may be assigned 26-unit, 52-unit, and 106-unit. Each unit may be assigned to a receiving station, i. E. A user.

4 is utilized in a situation for a single user (SU) as well as a situation for a plurality of users (MU), in which case one 242-unit as shown at the bottom of Fig. It is possible to use three DC tones in this case.

In the example of FIG. 4, 26-RU, 52-RU, 106-RU, 242-RU, etc. of various sizes have been proposed. Since the specific size of the RU can be expanded or increased, Is not limited to the specific size of each RU (i.e., the number of corresponding tones).

5 is a diagram showing the arrangement of resource units (RU) used on the 40 MHz band.

As in the example of FIG. 4, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, Five DC tones can be inserted at the center frequency. Twelve tones are used as the guard band in the leftmost band of the 40 MHz band, and 11 tones are used as the guard band in the rightmost band of the 40 MHz band. Can be used as a guard band.

Also, as shown, when used for a single user, a 484-RU may be used. On the other hand, the specific number of RUs can be changed is the same as the example of Fig.

6 is a diagram showing the arrangement of resource units (RU) used on the 80 MHz band.

6, RU, 52-RU, 106-RU, 242-RU, 484-RU, 996-RU, etc. may be used as well as the RUs of various sizes used in the examples of FIGS. have. Seven or five DC tones can be inserted at the center frequency. Twelve tones are used as the guard band in the leftmost band of the 80 MHz band, and the rightmost band of the 80 MHz band is used as the guard band. Eleven tones can be used as a guard band. You can also use 26-RUs with 13 tones on each side of the DC band.

Also, as shown, when used for a single user, a 996-RU may be used. On the other hand, the specific number of RUs can be changed is the same as the example of Figs. 4 and 5.

7 is a diagram showing another example of the HE-PPDU.

The illustrated block of Fig. 7 is yet another example for explaining the HE-PPDU block of Fig. 3 in terms of frequency.

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

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

The L-SIG 720 may be used to transmit control information. The L-SIG 720 may include information on a data rate and a data length. Also, the L-SIG 720 may be repeatedly transmitted. That is, the L-SIG 720 may be configured in a repeating format (which may be referred to as R-LSIG, for example).

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

Specifically, the HE-SIG-A 730 includes: 1) a DL / UL indicator; 2) a BSS color field that is an identifier of the BSS; 3) a field indicating the remaining time of the current TXOP section; B is a field indicating the MCS scheme applied to HE-SIG-B; 6) a field indicating whether HE-SIB-B is a dual subcarrier modulation (MCS) a field indicating whether the HE-SIG-B is modulated by a dual subcarrier modulation scheme, 7) a field indicating the number of symbols used for HE-SIG-B, 8) Field indicating the number of symbols of the HE-LTF; 10) field indicating the length and CP length of the HE-LTF; 11) field indicating whether there is additional OFDM symbol for LDPC coding; 12) A field indicating control information on a PE (Packet Extension), 13) a field indicating information on a CRC field of HE-SIG-A, and the like The. Specific fields of this HE-SIG-A may be added or some of them may be omitted. In addition, some fields may be added or omitted in other environments where HE-SIG-A is not a multi-user (MU) environment.

The HE-SIG-B 740 may only be included if it is a PPDU for a multi-user (MU) as described above. Basically, the HE-SIG-A 750 or HE-SIG-B 760 may include resource allocation information (or virtual resource allocation information) for at least one receiving STA.

8 is a block diagram showing an example of the HE-SIG-B according to the present embodiment.

As shown, the HE-SIG-B field includes a common field at the beginning, and the common field can be encoded separately from the following field. That is, as shown in FIG. 8, the HE-SIG-B field may include a common field including common control information and a user-specific field including user-specific control information. In this case, the common field may include a corresponding CRC field or the like and be coded into one BCC block. The following user-specific fields can be coded into one BCC block, including a "user-specific field" and corresponding CRC field for two users (2 users) as shown.

The previous field of HE-SIG-B 740 on the MU PPDU may be transmitted in the duplexed form. In the case of HE-SIG-B 740, HE-SIG-B 740 transmitted in some frequency bands (for example, the fourth frequency band) Data fields, and control information for data fields of other frequency bands (e.g., the second frequency band) except for the frequency bands. In addition, the HE-SIG-B 740 in a particular frequency band (e.g., the second frequency band) may transmit the HE-SIG-B 740 in another frequency band (e.g., Lt; / RTI > Or HE-SIG-B 740 may be transmitted in encoded form over the entire transmission resource. The fields after HE-SIG-B 740 may include individual information for each of the receiving STAs receiving PPDUs.

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

The HE-LTF 760 may be used to estimate a channel in a MIMO environment or an OFDMA environment.

The size of the FFT / IFFT applied to the fields after the HE-STF 750 and 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 fields after the HE-STF 750 and the HE-STF 750 may be four times larger than the size of the IFFT applied to the field before the HE-STF 750 .

For example, at least one of the L-STF 700, L-LTF 710, L-SIG 720, HE-SIG-A 730, HE-SIG- B 740 on the PPDU of FIG. 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 related to a legacy system, and the second field may include a field related to an HE system. In this case, the FFT (fast Fourier transform) size / IFFT (inverse fast Fourier transform) size is N times larger than the FFT / IFFT size used in the existing WLAN system (N is a natural number, 4). ≪ / RTI > That is, an FFT / IFFT of size N (= 1, 2, or 4) times can be applied to the second field of the HE PPDU compared to the first field of the HE PPDU. The FFT / IFFT size can be selected from 1, 2, and 4 times, and can be selectively determined according to channel conditions or setting information from other communication apparatuses. For example, if 256 FFT / IFFT is applied to a bandwidth of 20 MHz, 512 FFT / IFFT is applied to a bandwidth of 40 MHz, 1024 FFT / IFFT is applied to a bandwidth of 80 MHz, and 2048 FFT / IFFT can be applied.

In other words, the subcarrier spacing is 1 / N times as large as the subcarrier space used in the existing WLAN system (N is a natural number, for example, 78.125 kHz when N = 4) Lt; / RTI > That is, the first field of the HE PPDU may be subcarrier spacing of 312.5 kHz, which is the conventional subcarrier spacing, and the second field of the HE PPDU may be a subcarrier space of 78.125 kHz.

Alternatively, the IDFT / DFT period (IDFT / DFT period) applied to each symbol of the first field may be expressed as 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 is 3.2 μs, and the IDFT / DFT length applied to each symbol of the second field of the HE PPDU is 3.2 μs * 4 (= 12.8 μs ). The length of the OFDM symbol may be the length of the IDFT / DFT plus the length of the guard interval (GI). The length of the GI may be various values such as 0.4 μs, 0.8 μs, 1.6 μs, 2.4 μs, 3.2 μs.

The feature that the size of the FFT / IFFT applied to the fields after the HE-STF 750 and the HE-STF 750 can be variously set can be applied to the downlink PPDU and / or the uplink PPDU. That is, it can be applied to the PPDU shown in FIG. 7 or the uplink MU PPDU described later.

For convenience of explanation, in FIG. 7, it is expressed that the frequency band used by the first field and the frequency band used by the second field are exactly the same, but they may not completely coincide with each other. For example, if the main band of the first field (L-STF, L-LTF, L-SIG, HE-SIG-A, HE- , HE-LTF, Data), but the boundary surfaces may be inconsistent in each frequency band. As shown in FIGS. 4 to 6, since a plurality of null subcarriers, a DC tone, a guard tone, and the like are inserted in the process of disposing the RU, it is difficult to precisely align the boundary.

A user, i.e., the receiving station, may receive the HE-SIG-A 730 and be instructed to receive the downlink PPDU based on the HE-SIG-A 730. In this case, the STA can perform decoding based on the changed FFT size from the fields after the HE-STF 750 and the HE-STF 750. On the other hand, if the STA can not receive the downlink PPDU based on the HE-SIG-A (730), the STA can stop the decoding and set the NAV (network allocation vector). The cyclic prefix (CP) of the HE-STF 750 may have a size larger than the CP of the other fields. During this CP interval, the STA may perform decoding on the downlink PPDU by changing the FFT size.

Hereinafter, in this embodiment, the data (or frame) transmitted from the AP to the STA is referred to as downlink data (or downlink frame), and the data (or frame) transmitted from the STA to the AP is referred to as uplink data It can be expressed in terms. In addition, the transmission from the AP to the STA can be represented by the term downlink transmission, and the transmission from the STA to the AP can be expressed by the term " uplink transmission ".

Also, the PHY protocol data unit (PPDU), frame, and data transmitted through the downlink transmission may be represented by terms of 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) (or a MAC protocol data unit (MPDU)). The PPDU header may include a PHY header and a PHY preamble, and the PSDU (or MPDU) may include a frame (or an information unit of the MAC layer) or a data unit indicating a frame. The PHY header may be expressed in other terms as a physical layer convergence protocol (PLCP) header and a PHY preamble in other terms as a PLCP preamble.

Also, each of the PPDU, frame, and data transmitted through the uplink transmission may be represented by terms of uplink PPDU, uplink frame, and uplink data.

In the WLAN system to which this embodiment is applied, it is possible to use the entire bandwidth for downlink transmission to one STA and uplink transmission of one STA based on transmission of SU (single) -OFDM (orthogonal frequency division multiplexing) Do. Also, in the wireless LAN system to which the present embodiment is applied, the AP can perform DL (downlink) multi-user transmission based on MU MIMO (Multiple Input Multiple Output), and this transmission is referred to as DL MU MIMO transmission . ≪ / RTI >

Also, in the wireless LAN system according to the present embodiment, it is preferable that a transmission method based on OFDMA (orthogonal frequency division multiple access) is supported for uplink transmission and / or downlink transmission. That is, it is possible to perform uplink / downlink communication by allocating data units (for example, RUs) corresponding to different frequency resources to a user. Specifically, in the wireless LAN system according to the present embodiment, the AP can perform DL MU transmission based on OFDMA, and this transmission can be expressed by the term DL MU OFDMA transmission. When DL MU OFDMA transmission is performed, the AP can transmit downlink data (or downlink frame, downlink PPDU) to each of a plurality of STAs through each of a plurality of frequency resources on an overlapping time resource. The plurality of frequency resources may be a plurality of subbands (or subchannels) or a plurality of resource units (RUs). DL MU OFDMA transmission can be used with DL MU MIMO transmission. For example, a DL MU MIMO transmission based on a plurality of space-time streams (or spatial streams) on a specific subband (or subchannel) allocated for DL MU OFDMA transmission is performed .

In the wireless LAN system according to the present embodiment, UL MU transmission (uplink multi-user transmission) can be supported in that a plurality of STAs transmit data to APs on the same time resource. The uplink transmission on the overlapped time resource by each of the plurality of STAs can be performed in a frequency domain or a spatial domain.

When uplink transmission by each of a plurality of STAs is performed in the frequency domain, different frequency resources may be allocated to uplink transmission resources for each of a plurality of STAs based on OFDMA. Different frequency resources may be different subbands (or subchannels) or different RUs (resource units)). Each of the plurality of STAs can transmit uplink data to the AP through different allocated frequency resources. The transmission method through these different frequency resources may be expressed by the term UL MU OFDMA transmission method.

When uplink transmission by each of the plurality of STAs is performed in the spatial domain, different STAs are assigned to different STAs, and each of STAs transmits uplink data through different STAs AP. The transmission method through these different spatial streams may be represented by the term UL MU MIMO transmission method.

UL MU OFDMA transmission and UL MU MIMO transmission can be performed together. For example, UL MU MIMO transmission based on a plurality of space-time streams (or spatial streams) may be performed on a specific subband (or subchannel) allocated for UL MU OFDMA transmission.

In a conventional WLAN system that did not support MU OFDMA transmission, a multi-channel allocation method was used to allocate a wider bandwidth (for example, a bandwidth exceeding 20 MHz) to one terminal. A multi-channel may include a plurality of 20 MHz channels when one channel unit is 20 MHz. In the multi-channel allocation method, a primary channel rule is used to allocate a wide bandwidth to the UE. When the primary channel rule is used, there is a restriction to allocate a wide bandwidth to the terminal. Specifically, according to the primary channel rule, when a secondary channel adjacent to a primary channel is used in an OBSS (overlapped BSS) and is 'busy', the STA uses the remaining channels except for the primary channel I can not. Therefore, the STA can transmit frames only on the primary channel, which is restricted by the transmission of frames over multi-channels. In other words, the primary channel rule used for multi-channel allocation in a conventional WLAN system may be a great limitation in obtaining a high throughput by operating a wide bandwidth in a current wireless LAN environment where the OBSS is not small.

In order to solve such a problem, a wireless LAN system supporting OFDMA technology is disclosed in this embodiment. That is, the above-described OFDMA technique is applicable to at least one of the downlink and the uplink. Further, the MU-MIMO scheme described above for at least one of the downlink and the uplink may be further applied. When the OFDMA technique is used, a plurality of terminals, not a single terminal, can simultaneously use multi-channels without restriction by a primary channel rule. Therefore, wide bandwidth operation is possible, and the efficiency of operation of radio resources can be improved.

As described above, when uplink transmission by each of a plurality of STAs (for example, non-AP STA) is performed in the frequency domain, the AP increases the different frequency resources for each of the plurality of STAs based on OFDMA And can be assigned as a link transmission resource. Also, as described above, different frequency resources may be different subbands (or subchannels) or different RUs (resource units)).

Different frequency resources for each of a plurality of STAs are indicated through a trigger frame.

9 shows an example of a trigger frame. The trigger frame of FIG. 9 may allocate resources for uplink MU transmission (Uplink Multiple-User transmission) and may be transmitted from the AP. The trigger frame may consist of a MAC frame and may be included in a PPDU. For example, transmitted via the PPDU shown in FIG. 3, transmitted via the legacy PPDU shown in FIG. 2, or transmitted via a PPDU specifically designed for the trigger frame. If transmitted via the PPDU of FIG. 3, the trigger frame may be included in the data field shown.

Each of the fields shown in FIG. 9 may be partially omitted, and another field may be added. The lengths of the respective fields may be varied as shown.

The frame control field 910 of FIG. 9 includes information on the version of the MAC protocol and other additional control information, and the duration field 920 includes time information for setting the NAV Information about the identifier (e.g., AID) of the terminal may be included.

In addition, the RA field 930 includes address information of the receiving STA of the trigger frame, and may be omitted if necessary. The TA field 940 includes address information of an STA (e.g., an AP) that transmits the trigger frame, and a common information field 950 includes common information Control information.

10 shows an example of a common information field. Some of the subfields in FIG. 10 may be omitted, and other subfields may be added. Also, the length of each of the illustrated subfields can be varied.

The illustrated length field 1010 has the same value as the length field of the L-SIG field of the uplink PPDU transmitted corresponding to the 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 to indicate the length of the corresponding uplink PPDU.

In addition, the cascade indicator field 1020 indicates whether a cascade operation is performed. The cascade operation means that the downlink MU transmission and the uplink MU transmission are performed together in the same TXOP. That is, uplink MU transmission is performed after a predetermined time (for example, SIFS) after the downlink MU transmission is performed. During the cascade operation, there is only one transmitting apparatus (for example, AP) for performing downlink communication, and a plurality of transmitting apparatuses (for example, non-APs) performing uplink communication may exist.

The CS request field 1030 indicates whether the receiving apparatus receiving the trigger frame should consider the state of the wireless medium or the NAV in a state of transmitting the corresponding uplink PPDU.

The HE-SIG-A information field 1040 may include information for controlling the content of the SIG-A field (i.e., the HE-SIG-A field) of the upstream PPDU transmitted corresponding to the trigger frame.

The CP and LTF type field 1050 may include information about the length of the LTF and the CP length of the upstream PPDU transmitted corresponding to the trigger frame. The trigger type field 1060 may indicate the purpose for which the trigger frame is used, for example, normal triggering, triggering for beamforming, request for Block ACK / NACK, and the like.

On the other hand, the remaining description of FIG. 9 is added as follows.

It is preferable to include individual user information fields 960 # 1 to 960 # N corresponding to the number of receiving STAs receiving the trigger frame of FIG. The individual user information field may be referred to as an " assignment field ".

9 may include a padding field 970 and a frame check sequence field 980. [

Each of the per user information fields 960 # 1 to 960 # N shown in FIG. 9 preferably includes a plurality of subfields.

11 shows an example of a sub-field included in the per user information field. Some of the subfields in FIG. 11 may be omitted, and other subfields may be added. Also, the length of each of the illustrated subfields can be varied.

The user identifier field 1110 of FIG. 11 indicates an identifier of the STA (i.e., the receiving STA) to which the individual user information (per user information) corresponds, and an example of the identifier may be all or part of the AID have.

Also, an RU allocation (RU allocation) field 1120 may be included. That is, when the receiving STA identified by the user identifier field 1110 transmits the uplink PPDU corresponding to the trigger frame of FIG. 9, the RU allocation (RU allocation) field 1120 transmits the uplink PPDU . In this case, it is preferable that the RU indicated by the RU allocation (RU allocation) field 1120 indicates the RUs shown in Figs. 4, 5 and 6.

The subfields of FIG. 11 may include a coding type field 1130. The coding type field 1130 can indicate the coding type of the uplink PPDU transmitted corresponding to the trigger frame of FIG. For example, when BCC coding is applied to the uplink PPDU, the coding type field 1130 is set to '1', and when the LDPC coding is applied, the coding type field 1130 is set to '0' .

In addition, the subfield of FIG. 11 may include an MCS field 1140. The MCS field 1140 may indicate an MCS scheme to be written to the uplink PPDU transmitted in response to the trigger frame of FIG. For example, when BCC coding is applied to the uplink PPDU, the coding type field 1130 is set to '1', and when the LDPC coding is applied, the coding type field 1130 is set to '0' .

12 is a block diagram showing an example of an uplink MU PPDU. The uplink MU PPDU of FIG. 12 can be transmitted corresponding to the above-described trigger frame.

As shown, the PPDU of FIG. 12 includes various fields, and each field corresponds to the fields shown in FIGS. 2, 3, and 7. Meanwhile, as shown in FIG. 12, the uplink PPDU of FIG. 12 does not include the HE-SIG-B field but may include only the HE-SIG-A field.

The present specification proposes a Narrow Band Transmission (NBT) scheme for transmitting a signal using a narrow band in order to fully support the coverage of WiFi. Specifically, this specification proposes a method of designing a coefficient of the STF to compensate for the influence by the CFO (Center Frequency Offset) using the NBT scheme.

The signal using the extended range single user (ERSU) supported by 802.11ax has a problem in that the signal coverage can not be fully supported even if the range of the signal satisfies the long range. Therefore, in the next generation WiFi system, we propose a method to satisfy the signal range and signal coverage simultaneously by using the NBT method.

13 is a graph showing an SINR value of a signal transmitted using the NBT scheme.

Referring to FIG. 13, a signal having a narrow bandwidth 1310 has a Signal to Interference Noise Ratio (SINR) value higher than that of a signal having a wide bandwidth 1320 (assuming 20 MHz is supported). Alternatively, if the same bandwidth is considered, the number of pilots in the frame may be reduced. Since the length of the symbol increases as the bandwidth of the signal is reduced, robustness against inter symbol interference (ISI) and delay spread can be obtained. Also, the sharp peak response of the signal 1310 with a narrow bandwidth requires a high performance filter that is precisely tuned so as not to attenuate the active signal.

FIG. 14 is a graph showing SINR values according to distances of signals transmitted using the NBT scheme.

Referring to FIG. 14, assuming that the SNIR value is 10, the signal can be transmitted up to 100m when transmitted in the 20MHz band, and can be transmitted up to 160m when the signal is transmitted in the 5MHz band. It can be transmitted up to 260m. The graph of FIG. 14 shows a rate at which the transmission distance varies depending on the transmission band of a signal having a specific SINR value.

In the wireless LAN system, the Center Frequency Offset (CFO) is estimated and compensated using the STF field of the PPDU. The CFO value can indicate the degree to which the subcarrier frequency shakes from the center frequency. When a signal is transmitted in the NBT scheme, the bandwidth is reduced and the subcarrier spacing is also reduced. In the OFDM system, the CFO value varies depending on the subcarrier interval. In general, even if the CFO value is large, the influence on the OFDM system in which the subcarrier interval is sufficiently large is relatively small. Conversely, even with a small CFO value, the effect on the OFDM system is relatively large if the subcarrier interval is narrow (the system is sensitive to the influence even on small CFO values).

At this time, the STF is configured such that the same training sequence is repeatedly transmitted for CFO measurement. For example, the L-STF has a structure in which four time sequences are repeated in one symbol period. As described above, the CFO that can be measured when the same training sequence is repeatedly transmitted in one symbol is expressed as follows.

(D = number of repetitions of training sequence in one symbol), < RTI ID = 0.0 &gt;

_{ε = N * f offset / BW} , ( the size (or the size of N = IFFT / FFT), f offset = carrier frequency offset, BW = bandwidth)

f _offset = ± BW / N * D / 2

In the above equation,? Represents a value at which the frequency fluctuates, and BW is preset. Also, when the CFO is measured using the same training sequence as in the above equation, the frequency offset can be determined by the number of repeated subcarrier intervals and the training sequence. Therefore, Δf = 312.5 KHz * 4/2 = ± 625 KHz, which can be measured using L-STF transmitted over BW = 20 MHz, which satisfies the frequency tolerance required in each band. (CFO is compensated to 20 PPM (± 100 kHz) at 5 GHz and CFO is compensated to 25 PPM (± 60 KHz) at 2.4 GHz.)

Generally, when using a wireless LAN (WLAN) in an apartment or a home, it is difficult to smoothly use the service through the WLAN depending on the position of the house due to the influence of interference signals and obstacles. Therefore, to smoothly support services such as smart home service, a signal can be transmitted using narrow band transmission (NBT) to fully support home coverage. Accordingly, the present invention proposes a method of constructing a frame format for transmitting a WiFi signal through NBT transmission.

The NBT used for coverage extension or full coverage support of the WLAN has a narrow bandwidth (for example, 1/2/4/5/10 MHz), unlike the existing Wi-Fi transmitting signals using the 20- The transmission power can be concentrated in a narrow band, and the influence on the noise can be reduced, so that the signal can be transmitted farther. The NBT frame transmitted for coverage extension or cell edge support can be configured as follows.

1. When using the NBT frame format using the frame format of 802.11ax

A. The frame for NBT transmission consists of two parts. In this case, the part transmitted through the 20MHz bandwidth is composed of L-STF / L-LTF / L-SIG / RL-SIG as in 11ax.

i. At this time, L-SIG and RL-SIG may be transmitted using extra tone to reduce Peak-to-Average Power Radio (PAPR), and the legacy part may be transmitted to a third party device, the NBT receiver does not need to detect the legacy part.

ii. To extend and protect the NBT's coverage, the L-STF and L-LTF can be transmitted with power boosting of 3 dB, where the extra tone also has the same tone power as L-STF and L-LTF I have.

B. An NBT part transmitted using an NB (Narrow Band) may be configured in a frame format such as NB-STF / NB-LTF / NB-SIG / NB-DATA.

i. The NB-SIG transmitted with the control information can be repeatedly transmitted in order to transmit the NB-SIG robustly.

ii. The NBT frame may be transmitted using RU size and RU allocation defined in 11ax OFDMA. At this time, the RU size that can be used for the NBT is 26 RU or 52 RU, and accordingly, the available band size is 2 MHz or 4 MHz.

ii-1. Information such as bandwidth information / RU size / RU location for NBT transmission may be received when the STA associates with the AP or when capability negotiation is performed. Or may be received through a trigger frame transmitted from the AP before the NBT transmission or via a poll response frame.

ii-2. Using 26 tone RU (2 MHz)

ii-2-A. The number of 26 RUs defined in the 11ax OFDMA 20MHz transmission is 9, and 26 RUs used for the NBT can be selected from 9 26 RUs (consisting of 26 tones). For example, in order to reduce the influence of interference on adjacent channels, the NBT may be performed using a 26 RU centered at 26 RU, i.e., RU index = 5. 15 shows an example of transmitting NBT frames over 26 RUs using RU allocation defined in 802.11ax OFDMA.

ii-3. When using 52 tone RU (4MHz)

ii-3-A. The number of 52 tone RUs defined in the 11ax OFDMA tone allocation is 4, and in case of performing NBT, one of RUs can be selected to perform NB (Narrow band) transmission. However, it is desirable to use one of the two 52 tone RUs centered on the center frequency in consideration of adjacent channel interference. Therefore, the 52 tone RU (index 2 or 3) used for NBT is shown in FIG. 16 and FIG.

16 shows an example of transmitting NBT frames over 52 RUs using RU assignments defined in 802.11ax OFDMA. That is, FIG. 16 shows an example of transmitting NBT frames through 52 RUs nearest to the center frequency. Figure 17 shows another example of transmitting an NBT frame over 52 RUs using an RU assignment defined in 802.11ax OFDMA. That is, FIG. 17 shows an example of transmitting an NBT frame through 52 RUs nearest to the center frequency.

ii-3-B. As shown in FIG. 16 and FIG. 17, by performing NB transmission using the 11x OFDMA defined RU, it is possible to have backward compatibility with 11ax and support coexistence with 11ax. Also, the RU index for the NBT can be selected according to the interference caused by the adjacent band and the channel condition, thereby reducing the influence due to the channel and interference.

iii. The NB-STF / NB-LTF / NB-SIG transmitted using the NB when the NBT is performed using the 11ax tone allocation is transmitted using the same tone as the RU tone allocated for data transmission. For example, if 26 RU is used, only the 26 RUs allocated for the NBT are transmitted with the NB signal, and no signal is transmitted to the remaining tones. At this time, the power of the available tone can be boosted considering the power of the unused tone. 18 shows an example of loading power to 26 RUs allocated for transmitting NBT frames in 802.11ax OFDMA.

C. Unlike the case of using the same RU allocation in NB transmission in the above, the tone of RU size allocated for NBT is always centered on the center frequency. Only the tone assigned to the NBT will be signaled and no signal will be transmitted to the remaining tones. The available tone can be power boosted considering the available tonnage relative to the total tonnage. FIG. 19 shows an example of putting power at center 26 RU and center 52 RU allocated for transmitting NBT frames in 802.11ax OFDMA.

i. Referring to the upper part of FIG. 19, for example, when NBT is performed using 26 tone RU, a center RU (for example, RU index = 5) among nine 26 tone RUs defined at 20 MHz can be used. It can also have a commonality with the 11ax frame format by using the same tone allocation as the existing 11ax tone allocation.

As described above, when transmitting signals using NB, it has been proposed to perform NB using hardware and tone allocation defined in 11ax for hardware implementation and backward compatibility. However, The receiving device supporting the NBT basically receives the signal at 20 MHz, and at this time, it decodes the allocated RU, so it should always receive in the 20 MHz band. In addition, the data rate is much lower than that of the existing signal transmission, which limits the service. Thus, the transmission may be less gain in terms of coverage extension and coverage hole removal compared to 20 MHz transmission. Accordingly, the following frame format can be used for the NB, unlike the above-described conventional frame format.

2. For NBT, frame format can be set by using bandwidth of 1/2 / 4MHz and applying numerology according to NB (narrow band).

A. Unlike method 1, in order to reduce the loss of data rate when NBT is performed, the NBT can be transmitted using one of a variety of different manners.

Bandwidth	One	One	2	2	4	4
FFT size	32	64	64	128	128	256
서브 캐리어 주파수 공간	31.25KHz	15.625KHz	31.25KHz	15.625KHz	31.25KHz	15.625KHz
Number of available tones	26	56	56	114	114	242

ii. When a signal is transmitted using the above-described NMR, the length of one symbol becomes longer (since the bandwidth is reduced), and the ISI (inter symbol interference) characteristic is obtained. Therefore, the length of CP (Cyclic Prefix) can be reduced in NB transmission, and throughput can be improved in NB transmission.

1. In the Indoor situation, since the channel change is not large compared to the outdoor, it is not necessary to use the CP of a specific length in proportion to the length of the symbol. For example, the CP length of the data part can be selected from one of 2.4us / 3.2us / 4us regardless of the symbol length without using the 1/4 part of the IDFT / DFT period. That is, it is possible to reduce the portion of CP in one symbol, thereby improving data throughput. When the NBT is transmitted using the above-described NMR, the NBT preamble part can transmit a signal using a fixed CP value. For example, the length of the CP of the preamble used for NBT performance can be set to 3.2us length defined for robust transmission at 11ax.

iii. The above described NMR is one embodiment, and NBT can be performed using a frequency tone having a smaller carrier interval for data transmission efficiency.

B. The frame format of the NBT transmitted using the above-mentioned nummerology is as follows.

i. For backward compatibility or coexistence with existing Wi-Fi devices, if you configure a frame by attaching a leg part (L-part) in front of the NBT frame

20 shows an example of an NBT frame composed of legacy parts and NBT parts for performing NBT.

1. An L-part is added in front of an NBT frame. In this case, one or two BPSK symbols are added to the L-part to form a frame for packet classification for the NBT.

1-A. 20 MHz, the third-party devices in the same cell perform a constellation check on a symbol transmitted through the NB after the L-SIG symbol when receiving the corresponding frame This can be recognized as an imaginary symbol (ie, Q symbol) and recognized as a different frame format. To reduce this false detection, a BPSK symbol is added to the L-part. In this case, the BPSK symbol may be an L-SIG symbol repeated symbol or a L-LTF repeated symbol.

2. The rate field of L-SIG can be used for early indication for packet classification.

2-A. The rate field (R1-R4) of the current L-SIG is composed of 4 bits and indicates information on 8 data rates as shown in the table below, and the rest is not used. Therefore, it is possible to instruct the transmission of the NBT frame using the remaining bits of the rate field.

R1-R4	Rate (Mb / s) (20MHz channel spacing)	Rate (Mb / s) (10MHz channel spacing)	Rate (Mb / s) (5MHz channel spacing)
1101	6	3	1.5
1111	9	4.5	2.25
0101	12	6	3
0111	18	9	4.5
1001	24	12	6
1011	36	18	9
0001	48	24	12
0011	54	27	13.5

B. For example, if the value of the rate field is 0000 or 1111, the packet is set to indicate that the packet includes the NBT frame, and the transmitting apparatus transmits the value of the rate field. This allows 20 MHz operating devices in the vicinity to perform detection on the packet type through receipt of the rate information. The rate field value is an example and can be indicated using values of other fields that are not used.

 ii. If you configure only frames for NBT without L-part

21 shows an example of an NBT frame composed only of NBT parts for performing NBT.

1. Unlike the embodiment of FIG. 20, since the L-Part is not included in the NBT packet (or the NBT PPDU), the following protection scheme is required to use the frame format shown in FIG.

1-A. Method 1

1-A-i. The AP sets an interval for the NBT and transmits an NBT frame composed only of the NBT part using a broadcast frame such as a beacon frame or the like.

1-A-ii. A receiver receiving a beacon frame or a broadcast frame including information on an NBT transmission interval may support NBT or NBT depending on the device capability. A receiving device supporting NBT performs NBT in the NBT transmission interval and a receiving device not supporting NBT may enter idle state during the NBT transmission interval and may not perform channel access.

1-B. Method 2

1-B-i. The NBT request / response frame can be used to transmit information about the NBT cycle. For example, in order to perform NBT, the receiving device transmits an NBT request frame, and transmits NBT information including NBT information (for example, NBT period information) to the NBT request frame. The NBT information can be received from the AP upon association or capability negotiation. The receiving device receives the information on the NBT period, thereby avoiding the channel access in the corresponding period. In addition, a third party device that has not received the NBT response message, i.e., a receiver device located a long distance from the NBT receiver device, can prevent the channel access to the NBT section by receiving the NBT response frame transmitted by the AP.

1-C. A device (for example, AP or STA) that wants to transmit a signal through the NBT can perform protection for the NBT interval using the existing CTS to self or CTS to AP.

C. Since the NBT transmitted using the frame structure of FIG. 20 and FIG. 21 is transmitted through a very small bandwidth, the change of the channel in terms of frequency is less than 20 MHz. In other words, since the frequency of the channel is higher, the LTF of the NBT frame can transmit signals with only a part of the tones, instead of using all the available tones in order to reduce the overhead.

i. The tone interval at which the LTF sequence is transmitted may be defined as the NBT subcarrier interval relative to the subcarrier interval of 11ax / 11ac. For example, if the subcarrier interval of 11ax is 78.125KHz and the NBT subcarrier interval is 15.625KHz or 31.25KHz, the LTF sequence transmitted through the NBT frame is a frequency tone having a subcarrier interval of 5x or 2.5x smaller than 11ax Lt; / RTI &gt; Thus, for channel conditions where the LTF sequence is transmitted at 1, 2, or 4 tone intervals at 11ax, the NBT-LTF can transmit NBT LTF sequences at 5x or 2.5x tone intervals at 11ax intervals, respectively.

For example, if the tone interval of the LTF sequence of 11ax is 78.125 KHz, then the tone interval is 78.125 KHz when the LTF sequence is transmitted at one tone interval, the tone interval is 156.25 KHz when the LTF sequence is transmitted at two tone interval, If the LTF sequence is transmitted at 4 tone intervals, the tone interval may be 312.5 KHz.

i-1. In case of subcarrier interval = 15.625KHz, NB-LTF is transmitted using interval (5/10/20) which is 5 times larger than 11ax.

i-1-A. 64 Tone index for NB-LTF in FFT

5 tone interval (when the LTF sequence of 11ax is 1 ton interval), [± 5 ± 10 ± 15 ± 20 ± 25]. (The tone interval of the NB-LTF sequence is 78.125 KHz)

10 tone intervals (when the LTF sequence of 11ax is at two tone intervals), [± 10 ± 20]. (The tone interval of the NB-LTF sequence is 156.25 KHz)

i-1-B. 128 Tone index for NB-LTF in FFT

5 tone interval (when the LTF sequence of 11ax is one tone interval), [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55]. (The tone interval of the NB-LTF sequence is 78.125 KHz)

10 tone intervals (when the LTF sequence of 11ax is at two-tone intervals), [± 10 ± 20 ± 30 ± 40 ± 50]. (The tone interval of the NB-LTF sequence is 156.25 KHz)

i-1-C. Tone index for NB-LTF in 256 FFT

5 tone interval (when the LTF sequence of 11ax is 1 ton interval), [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. (The tone interval of the NB-LTF sequence is 78.125 KHz)

10 tone interval (when the LTF sequence of 11ax is 2-ton interval), [± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120]. (The tone interval of the NB-LTF sequence is 156.25 KHz)

20 tone interval (when the LTF sequence of 11ax is 4 ton interval), [± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120]. (The tone interval of the NB-LTF sequence is 312.5 KHz)

i-2. If the subcarrier interval is 31.25 KHz, the NB-LTF is transmitted using an interval (3/5/10) that is about 2.5 times larger than 11ax.

i-2-A. 64 Tone index for NB-LTF in FFT

3 tone intervals (when the LTF sequence of 11ax is one tone interval), [± 3 ± 6 ± 9 ± 12 ± 15 ± 18 ± 21 ± 24 ± 27]. (The tone interval of the NB-LTF sequence is 93.75 KHz)

5 tone interval (when the LTF sequence of 11ax is 2-ton interval), [± 5 ± 10 ± 15 ± 20 ± 25]. (The tone interval of the NB-LTF sequence is 156.25 KHz)

i-2-B. 128 Tone index for NB-LTF in FFT

3 tone intervals (when the LTF sequence of 11ax is 1 tone interval), [± 3 ± 6 ± 9 ± 12 ± 15 ± 18 ± 21 ± 24 ± 27 ± 30 ± 33 ± 36 ± 39 ± 42 ± 45 ± 48 ± 51 ± 54 ± 57]. (The tone interval of the NB-LTF sequence is 93.75 KHz)

5 tone interval (when the LTF sequence of 11ax is two-tone interval), [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55]. (The tone interval of the NB-LTF sequence is 156.25 KHz)

10 tone intervals (when the LTF sequence of 11ax is 4 ton intervals), [± 10 ± 20 ± 30 ± 40 ± 50]. (The tone interval of the NB-LTF sequence is 312.5 KHz)

i-2-C. Tone index for NB-LTF in 256 FFT

3 tone intervals (when the LTF sequence of 11ax is one tone interval), [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55]. (The tone interval of the NB-LTF sequence is 93.75 KHz)

5 tone interval (when the LTF sequence of 11ax is two tone interval), [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. (The tone interval of the NB-LTF sequence is 156.25 KHz)

10 tone interval (when the LTF sequence of 11ax is 4 ton intervals), [± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120]. (The tone interval of the NB-LTF sequence is 312.5 KHz)

ii. Unlike the above, for the commonality with 11ax, NB-LTF is transmitted using a gap of about 4 times larger than the tone interval used in 11ax since the subcarrier interval of 11ax is 2.5 times or 5 times smaller than that of 11ax. Therefore, the NBT LTF is transmitted using 4, 8, or 16 tone intervals (when the LTF sequence of 11ax is 1, 2, or 4 tone intervals), the sequence used is 11ax LTF sequence corresponding to the corresponding tone And can be set to a corresponding sequence length having a minimum PAPR.

The 11ax LTF sequence in the 20MHz band is as follows.

HE-LTF _-28,28 = {1, 1, LTF _left , 0, LTF _right , -1, -1}

At this time, LTF _left and LTF _right are as follows.

LTF _left = {1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, 1, 1, -1, -1, , -1, 1, 1, 1, 1}

LTF _right = {1, -1, -1, 1, -1, -1, -1, -1, -1, -1, -1, -1, , -1, 1, -1, 1, 1, 1, 1}

D. The information transmitted through the NB-SIG in the NBT frame format transmitted through the NB may be composed of the following information and is encoded through the BCC. Also, the NB-SIG may be repeatedly transmitted for robust transmission to a channel or may be transmitted by applying dual carrier modulation to obtain diversity gain.

i. MCS - modulation and coding rate

ii. Coding - BCC or LDPC

iii. CP - CP for data part (2.4us / 3.2us / 4us)

iv. TXOP / PPDU length - TXOP / PPDU duration information

v. Beamforming

vi. STBC

vii. Number of spatial streams

viii. CRC

ix. Tail bit

E. As described above, when a signal is transmitted using the NB, the length of the symbol becomes longer and it is vulnerable to fast fading. In order to reduce the distortion of the signal due to the fast fading or Doppler effect, a midamble may be added between the payloads in the structure of the frame, and the midamble symbol may be transmitted in units of 4 symbols or 5 symbols .

i. For channel estimation, the midamble is transmitted using LTF symbols.

22 is a flowchart of a procedure for generating and transmitting an NBT (Narrow Band Transmission) frame according to the present embodiment.

In order to solve the problem that the gain is reduced in terms of coverage expansion and coverage holes of the signal compared to the existing 20 MHz band transmission according to the reduced bandwidth in the NBT transmission, the present embodiment generates a new frame called NBT frame Method.

In addition, NB (Narrow Band) can have various bandwidths (for example, 1 MHz, 2 MHz, or 4 MHz) and can have FFT sizes (32 FFT, 64 FFT, 128 FFT, 256 FFT) , 15.625 KHz), and the like.

First, in summary terms, the transmitting apparatus may be an AP, and the receiving apparatus may be an STA. The NB-LTF sequence can correspond to the LTF sequence proposed in the present embodiment in consideration of the channel change due to the NBT transmission. The HE-LTF sequence may correspond to the LTF sequence used in an 802.11ax system. The tone may correspond to a subcarrier.

In step S2210, the transmitting apparatus generates an NBT frame including a first field and a second field. The first field may correspond to a legacy part, and the second field may correspond to an NBT part. That is, in this embodiment, a frame having a leg part attached to the NBT part is proposed for backward compatibility or coexistence with the existing Wi-Fi device.

In step S2220, the transmitting apparatus transmits the NBT frame to the receiving apparatus.

The first field is transmitted with 64 IFFT (Inverse Fast Fourier Transform) in a first bandwidth, and the second field is transmitted in a second bandwidth smaller than the first bandwidth. The first bandwidth is 20 MHz, the second bandwidth is included in the first bandwidth, and may be 1 MHz, 2 MHz, or 4 MHz. That is, the first field may be transmitted in the existing 20 MHz band, and the second field may be transmitted in the narrow band using the NBT.

The second field includes an NB-LTF (Narrow Band-Long Training Field) sequence. Because the NBT frame is transmitted over a narrow bandwidth, the change in channel in terms of frequency is smaller than the 20 MHz band. Therefore, the NB-LTF sequence can be used in order to reduce unnecessary overhead when the channel is frequency flat with a sequence configured in an NBT part. In the following, how the NB-LTF sequence is constructed will be described.

A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined. The NB-LTF sequence may be transmitted on the second tone. That is, the tone on which the NB-LTF sequence is transmitted may be determined based on the tone on which the HE-LTF sequence is transmitted.

For example, the tone interval of the NB-LTF sequence may be 15.625 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be five times larger than the tone index interval of the first tone. Thus, the tone spacing of the second tone may be equal to the tone spacing of the first tone.

The size of the tone interval of the NB-LTF sequence is 1/5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficients of the NB-LTF sequence are set is 5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFT (Inverse Fast Fourier Transform). If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. If the tone index interval of the first tone is 2, the tone index of the second tone may be [± 10 ± 20]. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 31.25 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be set to be 2.5 times larger than the tone index interval of the first tone. The tone spacing of the second tone may be the same as the tone spacing of the first tone.

Therefore, the size of the tone interval of the NB-LTF sequence is 1 / 2.5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficient of the NB-LTF sequence is set is 2.5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 15.626 KHz or 31.25 KHz, and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be four times larger than the tone index interval of the first tone to maintain a commonality with the first tone index. Therefore, the tone interval of the NBT-LTF sequence may be 4/8/16 tone depending on the FFT size, and the coefficient of the NB-LTF sequence may be a coefficient of the HE-LTF sequence set in the same tone as the tone index of the second tone Can be set.

In this embodiment, the HE-LTF sequence may be used in an 802.11ax system. In particular, the HE-LTF sequence may be defined as follows in the 20 MHz band. First, when the tone index interval of the first tone in which coefficients are set in the HE-LTF sequence is 4 (1x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 2 (2x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 1 (4x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

The first field includes an L-STF (Legacy-Short Training Field) field, an L-LTF (Legacy-Long Training Field) field, an L-SIG (Legacy-Signal) field, and a BPSK . The L-SIG field may be located after the L-STF field and the L-LTF field. The second field may further include a narrow band short training field (NB-STF) field, a narrow band signal (NB-SIG) field, and a data field. The NB-SIG field may be located after the NB-LTF field including the NB-STF field and the NB-LTF sequence.

The L-SIG field may include information on the first bandwidth and the second bandwidth. On the other hand, the NB-SIG field may not include information on the first bandwidth and the second bandwidth.

The receiving apparatus can receive the NBT frame generated by the transmitting apparatus through the second bandwidth within the first bandwidth. However, if a third party device in the same cell receives an NBT frame, it performs a constellation check on a second field received via the second bandwidth, and performs a constellation check on the second field using an imaginary symbol And recognize it as a different frame format. The BPSK symbol may be added to the first field to reduce false detection.

23 shows a transmitting apparatus for implementing this embodiment.

Referring to FIG. 23, a wireless device is a transmitting device capable of implementing the above-described embodiment, and can operate as an AP. In addition, the wireless device may correspond to a transmitting device that transmits a signal to a user.

23 includes a processor 2310, a memory 2320, and a transceiver 2330 as shown. The illustrated processor 2310, the memory 2320, and the transceiver 2330 may be implemented as separate chips, or at least two blocks / functions may be implemented through a single chip.

The transceiver 2330 is a device including a transmitter and a receiver. When a specific operation is performed, only the operation of either the transmitter or the receiver is performed, or both the transmitter and the receiver are performed . The transceiver 2330 may include one or more antennas for transmitting and / or receiving wireless signals. In addition, the transceiver 2330 may include an amplifier for amplifying a received signal and / or a transmitted signal, and a band-pass filter for transmitting on a specific frequency band.

The processor 2310 may implement the functions, processes, and / or methods suggested herein. For example, the processor 2310 may perform the operations according to the embodiment described above. That is, the processor 2310 generates an NBT frame including a first field and a second field, and transmits the NBT frame to the receiving apparatus.

The first field may correspond to a legacy part, and the second field may correspond to an NBT part. That is, in this embodiment, a frame having a leg part attached to the NBT part is proposed for backward compatibility or coexistence with the existing Wi-Fi device.

The first field is transmitted with 64 IFFT (Inverse Fast Fourier Transform) in a first bandwidth, and the second field is transmitted in a second bandwidth smaller than the first bandwidth. The first bandwidth is 20 MHz, the second bandwidth is included in the first bandwidth, and may be 1 MHz, 2 MHz, or 4 MHz. That is, the first field may be transmitted in the existing 20 MHz band, and the second field may be transmitted in the narrow band using the NBT.

The second field includes an NB-LTF (Narrow Band-Long Training Field) sequence. Because the NBT frame is transmitted over a narrow bandwidth, the change in channel in terms of frequency is smaller than the 20 MHz band. Therefore, the NB-LTF sequence can be used in order to reduce unnecessary overhead when the channel is frequency flat with a sequence configured in an NBT part. In the following, how the NB-LTF sequence is constructed will be described.

 A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined. The NB-LTF sequence may be transmitted on the second tone. That is, the tone on which the NB-LTF sequence is transmitted may be determined based on the tone on which the HE-LTF sequence is transmitted.

For example, the tone interval of the NB-LTF sequence may be 15.625 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be five times larger than the tone index interval of the first tone. Thus, the tone spacing of the second tone may be equal to the tone spacing of the first tone.

The size of the tone interval of the NB-LTF sequence is 1/5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficients of the NB-LTF sequence are set is 5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFT (Inverse Fast Fourier Transform). If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. If the tone index interval of the first tone is 2, the tone index of the second tone may be [± 10 ± 20]. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 31.25 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be set to be 2.5 times larger than the tone index interval of the first tone. The tone spacing of the second tone may be the same as the tone spacing of the first tone.

Therefore, the size of the tone interval of the NB-LTF sequence is 1 / 2.5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficient of the NB-LTF sequence is set is 2.5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 15.626 KHz or 31.25 KHz, and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be four times larger than the tone index interval of the first tone to maintain a commonality with the first tone index. Therefore, the tone interval of the NBT-LTF sequence may be 4/8/16 tone depending on the FFT size, and the coefficient of the NB-LTF sequence may be a coefficient of the HE-LTF sequence set in the same tone as the tone index of the second tone Can be set.

In this embodiment, the HE-LTF sequence may be used in an 802.11ax system. In particular, the HE-LTF sequence may be defined as follows in the 20 MHz band. First, when the tone index interval of the first tone in which coefficients are set in the HE-LTF sequence is 4 (1x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 2 (2x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 1 (4x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

The first field includes an L-STF (Legacy-Short Training Field) field, an L-LTF (Legacy-Long Training Field) field, an L-SIG (Legacy-Signal) field, and a BPSK . The L-SIG field may be located after the L-STF field and the L-LTF field. The second field may further include a narrow band short training field (NB-STF) field, a narrow band signal (NB-SIG) field, and a data field. The NB-SIG field may be located after the NB-LTF field including the NB-STF field and the NB-LTF sequence.

The L-SIG field may include information on the first bandwidth and the second bandwidth. On the other hand, the NB-SIG field may not include information on the first bandwidth and the second bandwidth.

The processor 2310 may include an application-specific integrated circuit (ASIC), another chipset, logic circuitry, a data processing device, and / or a transducer to convert baseband signals and radio signals. Memory 2320 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

24 shows a procedure for receiving an NBT frame generated according to the present embodiment.

24 is performed in the transmitting apparatus and the receiving apparatus, the receiving apparatus can correspond to the STA supporting the NBT scheme, and the transmitting apparatus can correspond to the AP.

First, in summary terms, the transmitting apparatus may be an AP, and the receiving apparatus may be an STA. The NB-LTF sequence can correspond to the LTF sequence proposed in the present embodiment in consideration of the channel change due to the NBT transmission. The HE-LTF sequence may correspond to the LTF sequence used in an 802.11ax system. The tone may correspond to a subcarrier.

In step S2410, the AP generates an NBT frame including a legacy field (first field) and an NBT field (second field).

In step S2420, the STA receives the NBT frame generated from the AP.

That is, in this embodiment, a frame having a legacy field before the NBT field is proposed for backward compatibility or coexistence with existing Wi-Fi devices.

The first field is transmitted with 64 IFFT (Inverse Fast Fourier Transform) in a first bandwidth, and the second field is transmitted in a second bandwidth smaller than the first bandwidth. The first bandwidth is 20 MHz, the second bandwidth is included in the first bandwidth, and may be 1 MHz, 2 MHz, or 4 MHz. That is, the first field may be transmitted in the existing 20 MHz band, and the second field may be transmitted in the narrow band using the NBT.

The second field includes an NB-LTF (Narrow Band-Long Training Field) sequence. Because the NBT frame is transmitted over a narrow bandwidth, the change in channel in terms of frequency is smaller than the 20 MHz band. Therefore, the NB-LTF sequence can be used in order to reduce unnecessary overhead when the channel is frequency flat with a sequence configured in an NBT part. In the following, how the NB-LTF sequence is constructed will be described.

A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined. The NB-LTF sequence may be transmitted on the second tone. That is, the tone on which the NB-LTF sequence is transmitted may be determined based on the tone on which the HE-LTF sequence is transmitted.

For example, the tone interval of the NB-LTF sequence may be 15.625 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be five times larger than the tone index interval of the first tone. Thus, the tone spacing of the second tone may be equal to the tone spacing of the first tone.

The size of the tone interval of the NB-LTF sequence is 1/5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficients of the NB-LTF sequence are set is 5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFT (Inverse Fast Fourier Transform). If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. If the tone index interval of the first tone is 2, the tone index of the second tone may be [± 10 ± 20]. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 31.25 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be set to be 2.5 times larger than the tone index interval of the first tone. The tone spacing of the second tone may be the same as the tone spacing of the first tone.

Therefore, the size of the tone interval of the NB-LTF sequence is 1 / 2.5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficient of the NB-LTF sequence is set is 2.5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 15.626 KHz or 31.25 KHz, and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be four times larger than the tone index interval of the first tone to maintain commonality with the first tone index. Therefore, the tone interval of the NBT-LTF sequence may be 4/8/16 tone depending on the FFT size, and the coefficient of the NB-LTF sequence may be a coefficient of the HE-LTF sequence set in the same tone as the tone index of the second tone Can be set.

In this embodiment, the HE-LTF sequence may be used in an 802.11ax system. In particular, the HE-LTF sequence may be defined as follows in the 20 MHz band. First, when the tone index interval of the first tone in which coefficients are set in the HE-LTF sequence is 4 (1x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 2 (2x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 1 (4x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

The first field includes an L-STF (Legacy-Short Training Field) field, an L-LTF (Legacy-Long Training Field) field, an L-SIG (Legacy-Signal) field, and a BPSK . The L-SIG field may be located after the L-STF field and the L-LTF field. The second field may further include a narrow band short training field (NB-STF) field, a narrow band signal (NB-SIG) field, and a data field. The NB-SIG field may be located after the NB-LTF field including the NB-STF field and the NB-LTF sequence.

The L-SIG field may include information on the first bandwidth and the second bandwidth. On the other hand, the NB-SIG field may not include information on the first bandwidth and the second bandwidth.

The STA may receive the NBT frame generated by the transmitting apparatus through the second bandwidth within the first bandwidth. However, if a third-party STA in the same cell receives an NBT frame, it performs a constellation check on a second field received via the second bandwidth, identifies it as a virtual symbol, . The BPSK symbol may be added to the first field to reduce false detection.

25 shows a receiving apparatus for implementing the present embodiment.

Referring to FIG. 25, a wireless device is a receiving device capable of implementing the above-described embodiment, and can operate as a non-AP STA. Also, the wireless device may correspond to the above-described user.

25 includes a processor 2510, a memory 2520 and a transceiver 2530 as shown. The illustrated processor 2510, memory 2520 and transceiver 2530 may each be implemented as separate chips, or at least two blocks / functions may be implemented on a single chip.

The transceiver 2530 is a device including a transmitter and a receiver. When a specific operation is performed, only the operation of either the transmitter or the receiver is performed, or both the transmitter and the receiver are performed . The transceiver 2530 may include one or more antennas for transmitting and / or receiving wireless signals. In addition, the transceiver 2530 may include an amplifier for amplifying a received signal and / or a transmitted signal, and a band-pass filter for transmitting on a specific frequency band.

The processor 2510 may implement the functions, processes, and / or methods suggested herein. For example, the processor 2510 may perform the operations according to the embodiment described above. That is, the processor 2510 receives the NBT frame generated from the transmitting apparatus.

The first field may correspond to a legacy part, and the second field may correspond to an NBT part. That is, in this embodiment, a frame having a leg part attached to the NBT part is proposed for backward compatibility or coexistence with the existing Wi-Fi device.

The first field is transmitted with 64 IFFTs in a first bandwidth, and the second field is transmitted in a second bandwidth less than the first bandwidth. The first bandwidth is 20 MHz, the second bandwidth is included in the first bandwidth, and may be 1 MHz, 2 MHz, or 4 MHz. That is, the first field may be transmitted in the existing 20 MHz band, and the second field may be transmitted in the narrow band using the NBT.

The first field is transmitted with 64 IFFT (Inverse Fast Fourier Transform) in a first bandwidth, and the second field is transmitted in a second bandwidth smaller than the first bandwidth. The first bandwidth is 20 MHz, the second bandwidth is included in the first bandwidth, and may be 1 MHz, 2 MHz, or 4 MHz. That is, the first field may be transmitted in the existing 20 MHz band, and the second field may be transmitted in the narrow band using the NBT.

The second field includes an NB-LTF (Narrow Band-Long Training Field) sequence. Because the NBT frame is transmitted over a narrow bandwidth, the change in channel in terms of frequency is smaller than the 20 MHz band. Therefore, the NB-LTF sequence can be used in order to reduce unnecessary overhead when the channel is frequency flat with a sequence configured in an NBT part. In the following, how the NB-LTF sequence is constructed will be described.

A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined. The NB-LTF sequence may be transmitted on the second tone. That is, the tone on which the NB-LTF sequence is transmitted may be determined based on the tone on which the HE-LTF sequence is transmitted.

For example, the tone interval of the NB-LTF sequence may be 15.625 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. The tone index interval of the second tone may be five times larger than the tone index interval of the first tone. Thus, the tone spacing of the second tone may be equal to the tone spacing of the first tone.

The size of the tone interval of the NB-LTF sequence is 1/5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficients of the NB-LTF sequence are set is 5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFT (Inverse Fast Fourier Transform). If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. If the tone index interval of the first tone is 2, the tone index of the second tone may be [± 10 ± 20]. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 1, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 31.25 KHz and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be set to be 2.5 times larger than the tone index interval of the first tone. The tone spacing of the second tone may be the same as the tone spacing of the first tone.

Therefore, the size of the tone interval of the NB-LTF sequence is 1 / 2.5 times the size of the HE-LTF sequence, but the tone index of the tone for which the coefficient of the NB-LTF sequence is set is 2.5 times the size of the same interval.

For example, the second field may be generated by applying 64 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 128 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone may be ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the second field may be generated by applying 256 IFFTs. If the tone index interval of the first tone is 2, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]. If the tone index interval of the first tone is 4, the tone index of the second tone may be ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120. That is, the NB-LTF sequence may be transmitted on the second tone corresponding to (or indicated by) the tone index.

As another example, the tone interval of the NB-LTF sequence may be 15.626 KHz or 31.25 KHz, and the tone interval of the HE-LTF sequence may be 78.125 KHz. In this case, the tone index interval of the second tone may be four times larger than the tone index interval of the first tone to maintain commonality with the first tone index. Therefore, the tone interval of the NBT-LTF sequence may be 4/8/16 tone depending on the FFT size, and the coefficient of the NB-LTF sequence may be a coefficient of the HE-LTF sequence set in the same tone as the tone index of the second tone Can be set.

In this embodiment, the HE-LTF sequence may be used in an 802.11ax system. In particular, the HE-LTF sequence may be defined as follows in the 20 MHz band. First, when the tone index interval of the first tone in which coefficients are set in the HE-LTF sequence is 4 (1x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 2 (2x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

First, when the tone index interval of the first tone in which the coefficient is set in the HE-LTF sequence is 1 (4x HE-LTF), the HE-LTF sequence in the 20MHz band can be defined as follows.

The first field includes an L-STF (Legacy-Short Training Field) field, an L-LTF (Legacy-Long Training Field) field, an L-SIG (Legacy-Signal) field, and a BPSK . The L-SIG field may be located after the L-STF field and the L-LTF field. The second field may further include a narrow band short training field (NB-STF) field, a narrow band signal (NB-SIG) field, and a data field. The NB-SIG field may be located after the NB-LTF field including the NB-STF field and the NB-LTF sequence.

The L-SIG field may include information on the first bandwidth and the second bandwidth. On the other hand, the NB-SIG field may not include information on the first bandwidth and the second bandwidth.

The processor 2510 may include an application-specific integrated circuit (ASIC), another chipset, logic circuitry, a data processing device, and / or a converter for converting baseband signals and radio signals. Memory 2520 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.

Claims (14)

1. A method for transmitting an NBT (Narrow Band Transmission) frame in a wireless LAN system,

   Generating, at the transmitting apparatus, an NBT frame including a first field and a second field; And

   Transmitting, at the transmitting apparatus, the NBT frame to a receiving apparatus,

   The first field is transmitted in 64 IFFT (Inverse Fast Fourier Transform) in the first bandwidth,

   Wherein the second field is transmitted in a second bandwidth smaller than the first bandwidth,

   The second field includes a NB-LTF (Narrow Band-Long Training Field) sequence,

   A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined, and

   The NB-LTF sequence is transmitted via the second tone

   Way.
2. The method according to claim 1,

   The tone interval of the NB-LTF sequence is 15.625 KHz,

   The tone interval of the HE-LTF sequence is 78.125 KHz,

   Wherein the tone index interval of the second tone is five times larger than the tone index interval of the first tone,

   Wherein the tone spacing of the second tone is equal to the tone spacing of the first tone

   Way.
3. 3. The method of claim 2,

   The second field is generated by applying 64 IFFT (Inverse Fast Fourier Transform)

   If the tone index interval of the first tone is 1, the tone index of the second tone is [± 5 ± 10 ± 15 ± 20 ± 25]

   If the tone index interval of the first tone is 2, the tone index of the second tone is [± 10 ± 20]

   Way.
4. 3. The method of claim 2,

   The second field is generated by applying 128 IFFTs,

   If the tone index interval of the first tone is 1, the tone index of the second tone is [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55]

   If the tone index interval of the first tone is 2, the tone index of the second tone is [± 10 ± 20 ± 30 ± 40 ± 50]

   Way.
5. 3. The method of claim 2,

   The second field is generated by applying 256 IFFTs,

   If the tone index interval of the first tone is 1, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 5 ± ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]

   If the tone index interval of the first tone is 2, the tone index of the second tone is ± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120,

   If the tone index interval of the first tone is 4, the tone index of the second tone is [± 20 ± 40 ± 60 ± 60 ± 80 ± 100 ± 120]

   Way.
6. The method according to claim 1,

   The tone interval of the NB-LTF sequence is 31.25 KHz,

   The tone interval of the HE-LTF sequence is 78.125 KHz,

   Wherein the tone index interval of the second tone is 2.5 times larger than the tone index interval of the first tone,

   Wherein the tone spacing of the second tone is equal to the tone spacing of the first tone

   Way.
7. The method according to claim 6,

   The second field is generated by applying 64 IFFTs,

   If the tone index interval of the first tone is 2, the tone index of the second tone is [± 5 ± 10 ± 15 ± 20 ± 25]

   Way.
8. The method according to claim 6,

   The second field is generated by applying 128 IFFTs,

   If the tone index interval of the first tone is 2, the tone index of the second tone is [± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55]

   If the tone index interval of the first tone is 4, the tone index of the second tone is [± 10 ± 20 ± 30 ± 40 ± 50]

   Way.
9. The method according to claim 6,

   The second field is generated by applying 256 IFFTs,

   If the tone index interval of the first tone is 2, the tone index of the second tone is ± 5 ± 10 ± 15 ± 20 ± 25 ± 30 ± 35 ± 40 ± 45 ± 50 ± 55 ± 60 ± 65 ± 70 ± 75 ± 80 ± 85 5 ± 90 ± 95 ± 100 ± 105 ± 110 ± 115 ± 120]

   If the tone index interval of the first tone is 4, the tone index of the second tone is [± 10 ± 20 ± 30 ± 40 ± 50 ± 60 ± 70 ± 80 ± 90 ± 100 ± 110 ± 120]

   Way.
10. The method according to claim 1,

    The tone interval of the NB-LTF sequence is 15.626 KHz or 31.25 KHz,

    The tone interval of the HE-LTF sequence is 78.125 KHz,

    Wherein the tone index interval of the second tone is four times larger than the tone index interval of the first tone,

    The coefficient of the NB-LTF sequence is set to a coefficient of the HE-LTF sequence set in the same tone as the tone index of the second tone

    Way.
11. 11. The method of claim 10,

    The HE-LTF sequence is used in an 802.11ax system

    Way.
12. The method according to claim 1,

    The first field includes an L-STF (Legacy-Short Training Field) field, an L-LTF (Legacy-Long Training Field) field, an L-SIG (Legacy-Signal) field, and a BPSK ,

    Wherein the L-SIG field is located after the L-STF field and the L-LTF field,

    The second field may further include a Narrow Band-Short Training Field (NB-STF) field, a Narrow Band-Signal (NB-SIG)

    Wherein the NB-SIG field is located after the NB-LTF field including the NB-STF field and the NB-LTF sequence,

    Wherein the L-SIG field includes information on the first bandwidth and the second bandwidth,

    Wherein the NB-SIG field does not include information on the first bandwidth and the second bandwidth

    Way.
13. The method according to claim 1,

    Wherein the first bandwidth is 20 MHz,

    Wherein the second bandwidth is included in the first bandwidth and is 1 MHz, 2 MHz, or 4 MHz

    Way.
14. A method for transmitting an NBT (Narrow Band Transmission) frame in a wireless LAN system,

    A transceiver for transmitting or receiving a wireless signal; And

    A processor for controlling the transceiver, the processor comprising:

    Generating an NBT frame including a first field and a second field; And

    And transmitting the NBT frame to a receiving apparatus,

    The first field is transmitted in 64 IFFT (Inverse Fast Fourier Transform) in the first bandwidth,

    Wherein the second field is transmitted in a second bandwidth smaller than the first bandwidth,

    The second field includes a NB-LTF (Narrow Band-Long Training Field) sequence,

    A coefficient is set in the NB-LTF sequence based on a tone index spacing of a first tone for which a coefficient is set in a HE-LTF (High Efficiency-Long Training Field) sequence. A tone index interval of two tones is determined, and

    The NB-LTF sequence is transmitted via the second tone

    Transmitting apparatus.

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