WO2019147057A1 - Method for allowing communication in wireless lan system on basis of nbt packet, and wireless terminal using same - Google Patents

Abstract

A method for allowing communication in a wireless LAN system on the basis of a NBT packet, according to the present embodiment, comprises the steps of: allowing a first wireless terminal in a non-NBT mode to transmit, to a second wireless terminal, a NBT mode request frame for requesting a NBT mode; allowing the first wireless terminal to receive, from a second wireless terminal, a first ACK frame for notifying of the successful reception of the NBT mode request frame; allowing the first wireless terminal to receive an NBT mode response frame from a second wireless terminal after receiving the first ACK frame; allowing the first wireless terminal to transmit, to the second wireless terminal, a second ACK frame for notifying of the successful reception of the NBT mode response frame; allowing the first wireless terminal to switch the non-NBT mode to the NBT mode after transmitting the second ACK frame; allowing the first wireless terminal in the NBT mode to receive, from the second wireless terminal, a NBT trigger frame for uplink data buffered by the first wireless terminal; and allowing the first wireless terminal in the NBT mode to transmit, to the second wireless terminal, a NBT data frame including uplink data in response to the NBT trigger frame.

Description

A method for performing communication based on an NBT packet in a wireless LAN system and a wireless terminal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a method for performing communication based on NBT packets in a wireless LAN system and a wireless terminal using the same.

Generally, when a wireless LAN (WLAN) is used in an apartment or a home, it is often difficult to smoothly use a service through a wireless LAN due to the influence of an interference signal and an obstacle depending on the location of the home. In order to smoothly support services such as smart home, home coverage needs to be fully supported. In order to increase the transmission distance of a wireless signal, narrow band transmission (NBT) technology using a bandwidth narrower than the conventional 20 MHz bandwidth for the wireless LAN can be used.

It is an object of the present invention to provide a method for performing communication based on an NBT packet in a wireless LAN system having improved performance and a wireless terminal using the same.

A method for performing communication based on an NBT packet in a wireless local area network (WLAN) system according to an exemplary embodiment of the present invention includes: transmitting, by a first wireless terminal in a non-NBT mode, an NBT mode request frame for requesting an NBT mode to a second wireless terminal ; Receiving, by the first wireless terminal, a first ACK frame from a second wireless terminal to inform successful reception of an NBT mode request frame; The first wireless terminal receiving an NBT mode response frame from a second wireless terminal after receiving the first ACK frame; The first wireless terminal transmitting a second ACK frame to the second wireless terminal to inform successful reception of the NBT mode response frame; The first wireless terminal alternating from the non-NBT mode to the NBT mode after transmission of the second ACK frame; And a first wireless terminal in NBT mode receiving an NBT trigger frame for uplink data buffered by the first wireless terminal from a second wireless terminal; And a first wireless terminal in NBT mode transmitting an NBT data frame including uplink data to a second wireless terminal in response to the NBT trigger frame.

According to an embodiment of the present invention, a method for performing communication based on an NBT packet in a wireless LAN system with improved performance and a wireless terminal using the method are provided.

1 is a conceptual diagram showing a structure of a wireless LAN system.

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 used on the 20 MHz band.

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

6 is a diagram showing the arrangement of resource units 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 HE-SIG-B.

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 user information field.

12 is a diagram illustrating an EDCA-based channel access method in a wireless LAN system.

13 is a conceptual diagram showing a backoff procedure of the EDCA.

14 is a diagram for explaining a frame transmission procedure in a wireless LAN system.

FIG. 15 shows a format of an NBT packet for NBT communication according to the present embodiment.

16 is a diagram illustrating a procedure for transmitting an uplink data frame based on an NBT trigger frame according to the present embodiment.

17 is a conceptual diagram related to a method of transmitting an NBT frame based on the NBT mode in the wireless LAN system according to the present embodiment.

18 is a flowchart illustrating a method of performing communication based on an NBT packet in a wireless LAN system according to an embodiment of the present invention.

19 is a conceptual diagram related to a method of transmitting an NBT frame based on an NBT mode in a wireless LAN system according to another embodiment of the present invention.

20 and 21 are conceptual diagrams related to a method of transmitting an NBT frame based on an NBT mode in a wireless LAN system according to yet another embodiment.

FIGS. 22 and 23 are diagrams illustrating a procedure for transmitting an uplink data frame based on the CCA operation according to another embodiment of the present invention.

24 is a flowchart illustrating a method of performing communication based on an NBT packet in a wireless LAN system according to another embodiment of the present invention.

25 is a block diagram illustrating a wireless device to which the present embodiment is applicable.

26 is a block diagram showing an example of an apparatus included in the processor.

The foregoing features and the following detailed description are exemplary only in order to facilitate explanation and understanding of the specification. That is, the present disclosure is not limited to these embodiments, but may be embodied in other forms. The following embodiments are merely illustrative of the complete disclosure of the present disclosure and are intended to be illustrative of the present disclosure to those of ordinary skill in the art to which this disclosure belongs. Thus, where there are several ways to implement the components of the present disclosure, it is necessary to make it clear that the implementation of the present specification is possible in any of these methods, or any equivalent thereof.

It is to be understood that, in the context of this specification, when reference is made to a configuration including certain elements, or when it is mentioned that a process includes certain steps, other elements or other steps may be included. In other words, the terms used herein are for the purpose of describing particular embodiments only, and are not intended to limit the concepts of the present specification. Further, the illustrative examples set forth to facilitate understanding of the invention include its complementary embodiments.

The terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Commonly used terms should be construed in a manner consistent with the context of this specification. Also, terms used in the specification should not be construed as being excessively ideal or formal in nature unless the meaning is clearly defined. BRIEF DESCRIPTION OF THE DRAWINGS Fig.

1 is a conceptual diagram showing a structure of a wireless LAN system. FIG. 1 (A) shows the structure of an infrastructure network of an Institute of Electrical and Electronic Engineers (IEEE) 802.11.

Referring to FIG. 1A, the WLAN system 10 of FIG. 1A includes at least one Basic Service Set (hereinafter referred to as 'BSS', 100, and 105). A BSS is a set of access points (APs) and stations (hereinafter, referred to as 'STAs') that can successfully communicate with each other and communicate with each other.

For example, the first BSS 100 may include a first AP 110 and a first STA 100-1 combined with the first AP 110. [ The second BSS 105 may include one or more STAs 105-1 and 105-2 coupled with the second AP 130 and the second AP 130. [

The infrastructure BSSs 100 and 105 may include at least one STA, APs 110 and 130 providing a distribution service, and a distribution system (DS) 120 connecting a plurality of APs. have.

The distributed system 110 may implement an extended service set 140 (hereinafter referred to as 'ESS') 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 at least one AP 110, 130 is connected through distributed system 120. [ At least one AP included in one ESS 140 may have the same service set identification (SSID).

The portal 150 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 110 and 130 and a network between the APs 110 and 130 and the STAs 100-1, 105-1 and 105-2 in the wireless LAN having the structure shown in FIG. 1 (A) .

1 (B) is a conceptual diagram showing an independent BSS. 1 (B), the wireless LAN system 15 of FIG. 1 (B) is different from FIG. 1 (A) in that a network is set up between STAs without APs 110 and 130 to perform communication . 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 110 and 130.

Referring to FIG. 1 (B), the IBSS 15 is a BSS operating in an ad-hoc mode. Since IBSS does not include APs, there is no centralized management entity. Therefore, in the IBSS 15, the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 are managed in a distributed manner.

All STAs 150-1, 150-2, 150-3, 155-4, and 155-5 of the IBSS may be mobile STAs, and connection to a distributed system is not allowed. All STAs in an IBSS form a self-contained network.

The STA referred to herein includes a Medium Access Control (MAC) layer and a Physical Layer interface to a wireless medium in accordance with the IEEE 802.11 standard. As a functional medium, the optical path may be used to include both an AP and a non-AP STA (Non-AP Station).

The STA referred to herein 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, or simply a user.

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 占 퐏, 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 the HE-SIG-B; 6) a field indicating whether the 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 730 or the HE-SIG-B 740 may include resource allocation information (or virtual resource allocation information) for at least one receiving STA. The HE-SIG-B 740 will be described in more detail with reference to FIG.

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 send 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 orthogonal frequency-division multiple access (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, the FFT / IFFT of size N (= 4) times can be applied to the second field of the HE PPDU compared to the first field of the HE PPDU. 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 can be applied to the subcarriers of 312.5 kHz size, which is the conventional subcarrier spacing, and the second field of the HE PPDUs can be applied to the subcarriers of the size 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 GI can be various values such as 0.4 μs, 0.8 μs, 1.6 μs, 2.4 μs, and 3.2 μs.

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, each of the PHY protocol data unit (PPDU), frame and data transmitted through downlink transmission may be represented by terms of a downlink PPDU, a downlink frame, and downlink data. 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 downlink transmission. That is, the user can perform uplink / downlink communication by allocating data units (e.g., RU) corresponding to different frequency resources to the user. Specifically, in the wireless LAN system according to the present embodiment, , And this transmission can be represented 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 overlapping time resource by each of the plurality of STAs can be performed in the frequency domain or the 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 may be indicated via a trigger frame.

8 is a block diagram showing an example of HE-SIG-B.

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.

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. The duration field 920 includes time information for setting the NAV, (E. G., AID) < / RTI >

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 Contains control information

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.

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.

In this specification, it can be assumed that the trigger type field 1060 of the trigger frame indicates a trigger frame of a basic type for normal triggering. For example, a basic type trigger frame can be referred to as a basic trigger frame.

11 shows an example of a sub-field included in a user information (per user information) field. The user information field 1100 of FIG. 11 can be understood as any one of the individual user information fields 960 # 1 to 960 # N mentioned in FIG. Some of the subfields included in the user information field 1100 of 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 a STA (i.e., a receiving STA) corresponding to individual user information (per user information). An example of the identifier is an association identifier (AID) May be all or part of a value.

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 the MCS scheme applied 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' .

The basic trigger frame in this specification can be understood as a variant of the trigger frame. The basic trigger frame may further include a Trigger Dependent User Info field 1150 in the individual user information fields 960 # 1 to 960 # N.

The trigger-dependent user information field 1150 is described in more detail below with reference to FIG.

12 is a diagram illustrating an EDCA-based channel access method in a wireless LAN system. In a WLAN system, the STA (or AP) may perform channel access according to a plurality of user priorities defined for enhanced distributed channel access (EDCA).

Specifically, for transmission of a quality of service (QoS) data frame based on a plurality of user priorities, four access categories (AC) (AC_BK (background), AC_BE (best effort), AC_VI AC_VO (voice)) can be defined.

The STA may receive traffic data (e.g., a MAC service data unit (MSDU)) having a predetermined user priority from an upper layer (e.g., logical link control (LLC) layer).

For example, to determine the transmission order of MAC frames to be transmitted by the STA, a user may be assigned a differential value for each traffic data. The user priority may be mapped to each access category (AC) in which the traffic data is buffered in the manner shown in Table 1 below.

In this specification, the user priority may be understood as a traffic identifier (TID) representing the characteristics of the traffic data.

Referring to Table 1, traffic data with a user priority (i.e., TID) of '1' or '2' may be buffered into a transmission queue 1250 of AC_BK type. Traffic data with a user priority (i.e., TID) of '0' or '3' may be buffered into a transmission queue 1240 of AC_BE type.

Traffic data with a user priority (i.e., TID) of '4' or '5' may be buffered into a transmission queue 1230 of AC_VI type. Traffic data with a user priority (i.e., TID) of '6' or '7' may be buffered with a transmission queue 1220 of AC_VO type.

Instead of the DIFS (DCF interframe space), CWmin, and CWmax, which are parameters for the backoff procedure based on the existing distributed coordination function (DCF), an EDCA parameter set AIFS (arbitration interframe space [AC], CWmin [AC], CWmax [AC], and TXOP limit [AC] can be used.

The difference in AC-to-AC transmission priority can be implemented based on a set of differential EDCA parameters. The default values of the EDCA parameter sets corresponding to each AC (i.e., AIFS [AC], CWmin [AC], CWmax [AC], TXOP limit [AC]) are illustratively shown in Table 2 below.

The set of EDCA parameters for each AC may be set to the default value or passed from the AP to each STA in a beacon frame. The lower the values of AIFS [AC] and CWmin [AC] are, the higher the priority is, and the channel access delay is shortened so that more bandwidth can be used in a given traffic environment.

The EDCA parameter set may include information about channel access parameters (e.g., AIFS [AC], CWmin [AC], CWmax [AC]) for each AC.

The backoff procedure for EDCA can be performed based on a set of EDCA parameters individually set for the four ACs included in each STA. Proper setting of EDCA parameter values that define different channel access parameters for each AC can increase the transmission effect by traffic priority while optimizing network performance.

Therefore, the AP of the WLAN system must perform overall management and coordination functions on the EDCA parameters in order to guarantee fair access to all STAs participating in the network.

12, one STA (or AP) 1200 may include a virtual mapper 1210, a plurality of transmission queues 1220-1250, and a virtual collision processor 1260. The virtual mapper 1210 of FIG. 12 may perform mapping of MSDUs received from an LLC (logical link control) layer to a transmission queue corresponding to each AC according to Table 1 above.

The plurality of transmission queues 1220-1250 of FIG. 12 can serve as separate EDCA contention entities for wireless media access within a single STA (or AP). For example, the transmission queue 1220 of the AC VO type of FIG. 12 may include one frame 1221 for a second STA (not shown).

 AC VI type transmission queue 1230 includes three frames 1231 to 1233 for a first STA (not shown) and one frame 1234 for a third STA in order to be transmitted to the physical layer .

The AC BE type transmission queue 1240 of FIG. 12 includes one frame 1241 for a second STA (not shown), one frame 1241 for a third STA (not shown) according to the order to be transmitted to the physical layer 1242) and one frame 1243 for a second STA (not shown).

By way of example, the transmission queue 1250 of the AC BK type of FIG. 12 may not include a frame to be transmitted to the physical layer.

For example, a frame 1221 included in a transmission queue 1220 of the AC VO type of FIG. 12 is concatenated with a plurality of traffic data (i.e., MSDUs) received from an upper layer (i.e., LLC layer) It can be understood as one MPDU (MAC Protocol Data Unit).

Also, the frame 1221 included in the transmission queue 1220 of the AC VO type is one having a plurality of pieces of traffic data (i.e., MSDU) having a traffic identifier (TID) of either '6' or '7' Lt; / RTI > MPDU.

A frame 1231 included in an AC VI type transmission queue 1230 of FIG. 12 includes one MPDU (concatenated) with a plurality of traffic data (i.e., MSDUs) received from an upper layer MAC Protocol Data Unit).

Also, the frame 1231 included in the transmission queue 1230 of the AC VI type is a frame 1231 connected to a plurality of traffic data (i.e., MSDU) having a traffic identifier (TID) of either '4' Lt; / RTI > MPDU.

Similarly, each of the other frames 1232, 1233, and 1234 included in the transmission queue 1230 of the AC VI type includes a plurality of traffic data having a traffic identifier (TID) of '4' and '5' MSDU) may be understood as one MPDU concatenated.

In addition, the frame 1241 included in the transmission queue 1240 of the AC BE type is one having a plurality of pieces of traffic data (i.e., MSDUs) having traffic identifiers (TID) of '0' Lt; / RTI > MPDU.

Similarly, each of the other frames 1242 and 1243 included in the transmission queue 1240 of the AC BE type includes a plurality of traffic data (i.e., MSDUs) having a traffic identifier (TID) of '0' Can be understood as one MPDU concatenated.

Each frame 1221, 1231 to 1234, 1241 to 1243 can be understood as a frame that does not exceed a predetermined traffic size.

If there is more than one AC that has been backed off at the same time, collisions between ACs may be adjusted according to the function (EDCA function, EDCAF) included in the virtual collision handler 1260.

Specifically, a collision problem in an STA can be solved by first transmitting a frame included in AC having a higher priority among collided ACs. In this case, the other AC may increase the contention window and update the backoff counter with the again selected backoff value based on the increased contention window.

A transmission opportunity (TXOP) can be initiated when a channel is accessed in accordance with EDCA rules. If more than one frame is stacked on one AC and the EDCA TXOP is acquired, the AC of the EDCA MAC layer may attempt to transmit multiple frames. If the STA has already transmitted one frame and can receive up to the next frame in the same AC and ACK for the remaining TXOP time, the STA may attempt to transmit the frame after the SIFS time interval.

The TXOP limit value may be set to a default value for the AP and the STA, or a frame associated with the TXOP limit value from the AP may be delivered to the STA.

If the size of the data frame to be transmitted exceeds the TXOP limit value, the AP may fragment the frame into several small frames. Subsequently, the segmented frame may be transmitted in a range not exceeding the TXOP limit value.

13 is a conceptual diagram showing a backoff procedure of the EDCA.

A plurality of STAs may share a wireless medium based on a contention-based distributed coordination function (DCF). DCF can use carrier sense multiple access / collision avoidance (CSMA / CA) as an access protocol to coordinate collisions between STAs.

The channel access scheme using the DCF can transmit the MPDU internally determined if the medium is not used during the DIFS (DCF inter frame space) (i.e., the channel is idle).

If the STA determines that the wireless medium is being used by another STA (i.e., the channel is busy) by the carrier sensing mechanism, the STA determines the size of the contention window (CW) Off procedure.

To perform the backoff procedure, each STA may set a backoff value arbitrarily selected in the contention window CW to the backoff counter. In this specification, the time in which the backoff value selected by each STA is expressed in slot time units can be understood as the backoff window of FIG.

Each STA can perform a backoff procedure for channel access by counting down the backoff window in slot time units. The STA selecting the shortest backoff window in a plurality of STAs can acquire a transmission opportunity (hereinafter referred to as 'TXOP') which is an authority to occupy the medium.

During the time interval for the transmission opportunity (TXOP), the remaining STAs may stop the countdown operation. The remaining STAs may wait until the time interval for the transmission opportunity (TXOP) has expired. After the time interval for the transmission opportunity (TXOP) expires, the remaining STAs may resume the paused countdown operation to occupy the wireless medium.

According to the DCF-based transmission method, a collision phenomenon that may occur when a plurality of STAs simultaneously transmit frames can be prevented. However, the channel access scheme using DCF has no concept of transmission priority (i.e., user priority). That is, when the DCF is used, the quality of service (QoS) of the traffic to be transmitted by the STA can not be guaranteed.

In order to solve this problem, a new coordination function, a hybrid coordination function (HCF) is defined in 802.11e. The newly defined HCF has better performance than the channel access performance of the existing DCF. HCF can utilize two channel access schemes, HCF controlled channel access (HCCA) and enhanced distributed channel access (EDCA), for QoS enhancement purposes.

Referring to FIG. 13, it is assumed that the STA performs the EDCA to transmit the buffered traffic data to the STA. Referring to Table 1, the user priority set for each traffic data may be differentiated into eight levels.

Each STA may include an output queue of four types (AC_BK, AC_BE, AC_VI, AC_VO) mapped to the user priority in step 8 of Table 1.

The STA according to the present embodiment can transmit traffic data based on AIFS (Arbitration Interframe Space) corresponding to the user priority in place of the DIFS (DCF Interframe Space) used in the past.

Hereinafter, in an embodiment of the present invention, a terminal may be a device capable of supporting both a wireless LAN system and a cellular system. That is, the UE may be interpreted as a UE supporting a cellular system or an STA supporting a WLAN system.

Inter-Frame Spacing referred to in 802.11 is described for the sake of brevity. For example, the interframe interval (IFS) may include a reduced interframe space (RIFS), a short interframe space (SIFS), a PCF interframe space (PIFS) : DCF interframe space, arbitration interframe space (AIFS), or extended interframe space (EIFS).

The inter-frame interval (IFS) can be determined according to the attributes specified by the physical layer of the STA regardless of the bit rate of the STA. The rest of the interframe interval (IFS) except for AIFS can be understood as a fixed value for each physical layer.

The AIFS can be set to a value corresponding to the user priority and the four types of transmission queues mapped as shown in Table 2. [

SIFS has the shortest time gap among the above-mentioned IFSs. Accordingly, the STA occupying the wireless medium can be used when it is necessary to maintain occupancy of the medium without disturbance by another STA in a period in which a frame exchange sequence is performed.

That is, by using the smallest gap between transmissions in the frame exchange sequence, priority can be given to completion of the ongoing frame exchange sequence. In addition, an STA accessing a wireless medium using SIFS may initiate transmission directly at the SIFS boundary without determining whether the medium is Busy.

The duration of SIFS for a particular physical (PHY) layer can be defined by the aSIFSTime parameter. For example, the SIFS value in the physical layer (PHY) of IEEE 802.11a, IEEE 802.11g, IEEE 802.11n, and IEEE 802.11ac standards is 16 μs.

PIFS may be used to provide the STA with a higher priority next to the SIFS. That is, the PIFS may be used to obtain priority for accessing the wireless medium.

DIFS can be used by the STA to transmit data frames (MPDUs) and management protocol (Mac Protocol Data Units (MPDUs)) based on the DCF. After the received frame and the backoff time have expired, if the medium is determined to be idle via a carrier sense mechanism (CS), the STA may transmit the frame.

14 is a diagram for explaining a frame transmission procedure in a wireless LAN system.

As described above, each STA 1410, 1420, 1430, 1440, 1450 according to the present embodiment can individually select a backoff value for the backoff procedure.

Then, each of the STAs 1410, 1420, 1430, 1440, and 1450 may wait for a time corresponding to the selected backoff value in terms of slot time (i.e., the backoff window of FIG. 13) have.

Also, each STA 1410, 1420, 1430, 1440, 1450 may count down the backoff window in slot time units. The countdown operation for channel access to the wireless medium may be performed separately by each STA.

Hereinafter, the time corresponding to the backoff window may be referred to as a backoff time (Tb [i]). In other words, each STA can individually set the backoff time Tb [i] at the backoff counter of each STA.

Specifically, the backoff time Tb [i] is a pseudo-random integer value and can be calculated based on the following equation (1).

Random (i) in Equation (1) is a function that uses a uniform distribution and generates an arbitrary integer between 0 and CW [i]. CW [i] can be understood as a contention window selected between the minimum contention window CWmin [i] and the maximum contention window CWmax [i]. The minimum contention window CWmin [i] and the maximum contention window CWmax [i] may correspond to the default values CWmin [AC] and CWmax [AC] in Table 2.

In the initial channel access, the STA can select any integer between O and CWmin [i] via Random (i) with CW [i] as CWmin [i]. In this embodiment, any selected integer may be referred to as a backoff value.

i can be understood as the user priority of the traffic data. It can be understood that i in Equation (1) corresponds to either AC_VO, AC_VI, AC_BE or AC_BK in accordance with Table 1.

The SlotTime of Equation (1) can be used to provide enough time for the preamble of the transmitting STA to be sufficiently detected by the neighboring STA. The slot time (SlotTime) in Equation (1) can be used to define the above-mentioned PIFS and DIFS. For example. The slot time (SlotTime) may be 9 [micro] s.

For example, if the user priority (i) is '7', then the initial backoff time Tb [AC_VO] for the transmission queue of AC_VO type is set to a value between 0 and CWmin [AC_VO] And may be expressed in units of time (SlotTime).

The STA calculates an increased backoff time Tb [i] 'based on the following equation (2): " (2) " Can be calculated.

Referring to Equation (2), a new contention window CWnew [i] can be computed based on the previous window CWold [i]. The PF value of Equation (2) can be calculated according to the procedure defined in the IEEE 802.11e standard. For example, the PF value of Equation 2 may be set to '2'.

In this embodiment, the increased backoff time Tb [i] ') is set to any arbitrary integer (i.e., backoff value) selected between 0 and the new contention window CWnew [i] ≪ / RTI >

The CWmin [i], CWmax [i], AIFS [i] and PF values mentioned in FIG. 14 can be signaled from the AP through a QoS parameter set element which is a management frame. The CWmin [i], CWmax [i], AIFS [i], and PF values may be preset values by the AP and the STA.

Referring to FIG. 14, the horizontal axes t1 to t5 for the first to fifth STAs 1410 to 1450 may represent a time axis. In addition, the vertical axis for the first to fifth STAs 1410 to 1450 may indicate the backoff time.

13 and 14, when a specific medium is changed from an occupy or busy state to an idle state, a plurality of STAs may attempt to transmit data (or frames).

In order to minimize collision between STAs, each STA selects a backoff time Tb [i] of Equation (1), waits for a corresponding slot time, You can try.

When the backoff procedure is initiated, each STA may count down the individually selected backoff counter time in slot time units. Each STA can continuously monitor the media during the countdown.

If the wireless medium is monitored in an occupied state, the STA can stop and wait for the countdown. If the wireless medium is monitored in an idle state, the STA may resume the countdown.

Referring to FIG. 14, when the frame for the third STA 1430 reaches the MAC layer of the third STA 1430, the third STA 1430 can check whether the medium is idle during DIFS. Then, if the medium is determined to be idle during the DIFS, the third STA 1430 may transmit the frame to the AP (not shown). However, the inter frame space (IFS) in FIG. 14 is shown as DIFS, but it will be understood that the present invention is not limited thereto.

While the frame is being transmitted from the third STA 1430, the remaining STAs can check the occupancy state of the medium and wait for the transmission period of the frame. The frame can reach the MAC layer of each of the first STA 1410, the second STA 1420 and the fifth STA 1450. If the medium is identified as idle, each STA can wait for the DIFS and count down the individual backoff times selected by each STA.

Referring to FIG. 14, the second STA 1420 selects the smallest backoff time, and the first STA 1410 selects the largest backoff time. The remaining backoff time of the fifth STA 1450 at the time point (T1) when the backoff procedure for the backoff time selected by the second STA 1420 is completed and the frame transmission is started is the remaining backoff time of the first STA 1410 Off time.

When the medium is occupied by the second STA 1420, the first STA 1410 and the fifth STA 1450 can suspend and wait for the backoff procedure. Then, when the media occupation of the second STA 1420 is terminated (that is, when the media is idle again), the first STA 1410 and the fifth STA 1450 can wait for DIFS.

The first STA 1410 and the fifth STA 1450 may then resume the backoff procedure based on the paused remaining backoff time. In this case, since the residual backoff time of the fifth STA 1450 is shorter than the remaining backoff time of the first STA 1410, the fifth STA 1450 completes the backoff procedure before the first STA 1410 .

14, when the medium is occupied by the second STA 1420, the frame for the fourth STA 1440 can reach the MAC layer of the fourth STA 1440. [ When the medium becomes idle, fourth STA 1440 may wait for DIFS. The fourth STA 1440 may then count down the backoff time selected by the fourth STA 1440.

Referring to FIG. 14, the remaining backoff time of the fifth STA 1450 may coincide with the backoff time of the fourth STA 1440. In this case, a collision may occur between the fourth STA 1440 and the fifth STA 1450. If a collision between STAs occurs, the fourth STA 1440 and the fifth STA 1450 do not receive an ACK and may fail to transmit data.

Accordingly, the fourth STA 1440 and the fifth STA 1450 can separately compute a new contention window CWnew [i] according to Equation (2) above. The fourth STA 1440 and the fifth STA 1450 can individually perform the countdown of the newly calculated backoff time according to Equation (2).

On the other hand, when the medium is occupied due to the transmission of the fourth STA 1440 and the fifth STA 1450, the first STA 1410 can wait. Then, when the medium becomes idle, the first STA 1410 may wait for DIFS and resume back-off counting. When the remaining backoff time of the first STA 1410 elapses, the first STA 1410 can transmit the frame.

The CSMA / CA mechanism may also include virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly senses the media.

Virtual carrier sensing is intended to compensate for problems that may arise from media access, such as hidden node problems. For virtual carrier sensing, the MAC of the WLAN system uses a network allocation vector (NAV). The NAV is a value indicating to another AP and / or the STA that the AP and / or the STA that is currently using or authorized to use the medium has remaining time until the media becomes available.

Therefore, the value set to NAV corresponds to the period in which the medium is scheduled to be used by the AP and / or the STA that transmits the frame, and the STA receiving the NAV value is prohibited from accessing the medium during the corresponding period. The NAV may be set according to the value of the duration field of the MAC header of the frame, for example.

FIG. 15 shows a format of an NBT packet for NBT communication according to the present embodiment.

Referring to FIG. 15, an NBT (Narrow Band Transmission) packet 1500 may include a legacy part (L-part) and an NBT part (NBT part).

The legacy part (L-part) of FIG. 15 can be configured based on the 20 MHz band. The L-part of FIG. 15 may be used to protect the NBT part of the NBT packet 1500 from the surrounding legacy terminal. Depending on the communication environment, the legacy part (L-part) can be omitted.

For example, a legacy part (L-part) may include one or more BPSK symbols for packet classification of L-STF, L-LTF, L-SIG and legacy part and NBT part.

In particular, one or two BPSK symbols may be used to reduce false detection by third party devices. In one example, one or more BPSK symbols may be symbols in which the L-SIG symbols are repeated or symbols in which the L-LTF symbols are repeated.

The NBT part of FIG. 15 may be configured based on a narrow band (NB) channel. For example, the NB channel may be associated with a 50 kHz bandwidth, a 1 MHz bandwidth, or a 2 MHz bandwidth.

For example, an NBT part may include an NB-STF, an NB-LTF, an NB-SIG field, and an NB-data field.

For example, NB-STF, NB-LTF, and NB-SIG fields can be used for channel estimation and synchronization acquisition of NB channels. The NB-data field may contain information (i. E., Payload) necessary for the peer terminal.

It will be appreciated that, for the purpose of increasing the transmission distance of a wireless signal of a wireless terminal, an NBT packet may be transmitted based on the transmission power for an existing legacy 20MHz packet.

The NB channel of FIG. 15 is shown as being centered within 20 MHz, but it will be understood that the present disclosure is not so limited. Further, it will be appreciated that more than one NB may be utilized within 20 MHz.

To support wireless communication based on NBT packets, the AP needs to receive both legacy formatted packets and NBT packets. Accordingly, the AP may need to continuously perform reception attempts on the 20 MHz band and the NB channel.

For example, when the AP receives a packet in the 20 MHz band, the AP can transmit an ACK frame for the packet based on the 20 MHz band. In another example, if the AP receives a packet on the NB, the AP may transmit an ACK frame for that packet based on the NB channel.

In addition, the AP can maintain both the normal NAV associated with packets in the 20 MHz legacy format and the NBT_NAV associated with the NB channel.

For example, normal NAV may be understood as a NAV timer commonly used in IEEE 802.11. For example, NBT_NAV can be understood as a NAV timer that is updated based on NBT packets based on the NB channel.

In this specification, the AP can always update / check the normal NAV and the NBT_NAV. In this specification, when the non-AP STA operates based on the NBT mode, the non-AP STA can only update / check the NBT_NAV.

In addition, the AP can perform a Channel Clear Assessment (CCA) operation in both the 20 MHz band and the NB channel. As a result of the CCA operation, only when the 20 MHz band and the NB channel are determined to be idle, the state of the radio channel associated with the AP can be determined as idle.

In addition, in order to support wireless communication based on NBT packets, it is necessary that the STA continuously perform only reception attempts on the NB channel. However, according to the implementation, the STA can continuously perform reception attempts on the NB channel and the 20 MHz band.

For example, if the STA receives a packet in the 20 MHz band, the STA may transmit an ACK frame for that packet based on the 20 MHz band. In another example, if the STA receives a packet in the NB, the STA may transmit an ACK frame for that packet based on the NB channel.

In addition, the STA may transmit an ACK frame for a packet received in the 20 MHz band based on the NB channel. In this case, since the transmission time of the ACK frame can be long, it can be implemented on the assumption that the RSSI or SINR of the packet received in the 20 MHz band is below a certain level.

16 is a diagram illustrating a procedure for transmitting an uplink data frame based on an NBT trigger frame according to the present embodiment.

The STA 1610 of FIG. 16 may be understood as a wireless terminal combined with the AP 1600. The STA 1610 of FIG.

The horizontal axis of AP 1600 is associated with time domain tl and the vertical axis of AP 1600 is associated with the presence of a frame transmitted by AP 1600. [ The horizontal axis of STA 1610 is associated with time domain t2 and the vertical axis of STA 1610 is associated with the presence of frames transmitted by STA 1610. [

AP 1600 may send an NBT trigger (NBT_Trigger) frame to STA 1610. For example, an NBT trigger frame may include a legacy part (L-part) indicated by the dashed line associated with the 20 MHz bandwidth and an NBT part (NBT part) indicated by the solid line associated with the NB channel.

That is, the legacy part (L-part) of the NBT trigger frame is transmitted in units of 20 MHz, and the NBT part of the NBT trigger (NBT_Trigger) frame can be transmitted in units of NB.

For reference, a legacy part (L-part) indicated by a dotted line may be omitted depending on the wireless LAN environment.

In this specification, an NBT_Trigger frame may be a frame periodically transmitted by AP 1600 to confirm the presence of buffered uplink data by STA 1610.

In this specification, an NBT_Trigger frame may be a frame for allocating uplink resources to the STA 1610 for uplink transmission of the uplink data buffered by the STA 1610.

In this specification, an NBT_Trigger frame may be a frame for signaling the STA 1610 in an appropriate mode of operation (e.g., normal mode or NBT mode).

In this specification, an NBT_Trigger frame may include information as to whether the STA 1610 performs CCA operations for wireless media during SIFS after receipt of an NBT_Trigger frame. In this case, the CCA operation can be implemented based on an energy detection method.

For example, it may be assumed that an NBT trigger (NBT_Trigger) frame is received that indicates that the STA 1610 performs a CCA operation on the wireless medium during SIFS. Accordingly, during SIFS after receipt of the NBT Trigger (NBT_Trigger) frame, STA 1610 may perform a CCA operation on the wireless medium.

For example, if the wireless channel is determined to be idle according to the CCA operation, the STA 1610 transmits NBT data (NBT_Data) including uplink data based on the uplink resources allocated through the NBT trigger (NBT_Trigger) Frame to the AP 1600. [

In another example, if the wireless channel is determined to be busy according to the CCA operation, the STA 1610 may defer transmission of the NBT data (NBT_Data) frame including the uplink data.

For example, it may be assumed that an NBT trigger (NBT_Trigger) frame is received that indicates that STA 1610 does not perform CCA operation for wireless medium during SIFS. Accordingly, when the SIFS has elapsed since the reception of the NBT trigger (NBT_Trigger) frame, the STA 1610 can transmit the NBT data frame including the uplink data to the AP 1600 without performing a separate CCA operation.

The AP 1600 may then transmit an ACK (NBT_ACK) frame to the STA 1610 to inform successful reception of the NBT data (NBT_Data) frame. For example, the NBT_ACK frame may be transmitted based on the NB.

16 is based on the assumption that an NBT trigger (NBT_Trigger) frame is received, so that the uplink operation can be performed in a situation where a channel state of a certain level or more is guaranteed. As a result, unnecessary transmission can be suppressed in a situation where the radio channel is in a bad situation, so that interference to the adjacent BSS can be reduced.

17 is a conceptual diagram related to a method of transmitting an NBT frame based on the NBT mode in the wireless LAN system according to the present embodiment.

In this specification, when a wireless terminal communicates based on legacy packets based on the conventional 20 MHz band, the wireless terminal may be in non-NBT mode. For example, after the wireless terminal (i.e., the non-AP STA) and the AP are combined, the initial wireless terminal may be in the non-NBT mode.

In this specification, when a wireless terminal communicates based on an NBT packet based on an NB channel, the wireless terminal may be in NBT mode. For example, when certain conditions are met, the wireless terminal may alternatively operate from the initial non-NBT mode to the NBT mode.

In this specification, the AP can simultaneously perform reception attempts on the 20 MHz band and the NB channel. Also, the AP can communicate with the wireless terminal in the NBT mode based on the NBT packet.

If the channel condition between the wireless terminal and the AP is not good or the distance between the wireless terminal and the AP is sufficiently long, a legacy packet based on the 20 MHz band may be difficult to receive properly. In this case, the wireless terminal can alternately operate from the non-NBT mode to the NBT mode.

In this specification, when at least one of the following first to sixth conditions is satisfied, the wireless terminal can alternate from the non-NBT mode to the NBT mode.

The first condition is that the wireless terminal does not receive a 20 MHz packet from the AP for a certain period of time. The second condition is that the wireless terminal has a lower RSSI or SINR value of a packet received from the AP than a certain level. The third condition is a case where the wireless terminal can not continuously receive the ACK for the packet transmitted by the UL by more than a predetermined number of times.

The fourth condition is a case where the AP does not successively receive ACKs for packets transmitted to the wireless terminal by DLs more than a predetermined number of times. The fifth condition is a case where the RSSI or SINR value of the packet received from the wireless terminal by the AP is lower than a certain level. The sixth condition is a case where, after the AP transmits a packet having a specific MCS value (for example, '0') to the wireless terminal, the packet error rate (PER) of the packet is higher than a certain level.

Further, when at least one of the following seventh to twelfth conditions is satisfied, the wireless terminal can alternate from the NBT mode to the non-NBT mode.

The seventh condition is a case where the RSSI or SINR value of the NBT packet received from the AP by the wireless terminal is higher than a certain level. The eighth condition is a case where the wireless terminal continuously receives the NBT packets from the AP for a predetermined time without error. The ninth condition is that the ACK for the NBT packet transmitted by the wireless terminal in the UL is received successively more than a predetermined number of times, and the bit maps included in the ACK indicate success.

The tenth condition is a case where the AP continuously receives an ACK for the NBT packet transmitted to the wireless terminal in the DL by a predetermined number of times or more. The eleventh condition is a case where the RSSI or the SINR value of the packet received from the wireless terminal by the AP is higher than a certain level. The 12th condition is a case where the PER of the packet is lower than a predetermined level after the AP transmits the NBT packet to the wireless terminal.

In this specification, the types of signaling for the NBT mode can be divided into the following two types according to the signaling direction.

First, the STA initiated signaling is performed in accordance with the first to twelfth conditions, in which the wireless terminal alternates from the non-NBT mode to the NBT mode or the NBT mode to the non-NBT mode The wireless terminal may request the AP from the AP.

Secondly, the AP initiated signaling is performed in such a manner that the wireless terminal changes from the non-NBT mode to the NBT mode or alternates from the NBT mode to the non-NBT mode according to the first to twelfth conditions May be a manner in which the AP requests the wireless terminal.

In the present specification, the types of signaling for the NBT mode can be classified into two types according to the signaling purpose.

First, the NBT mode initiation signaling may be a method in which a wireless terminal operating in a non-NBT mode is used to switch to the NBT mode according to the first through sixth conditions.

Second, the NBT mode termination signaling may be a method in which a wireless terminal operating in the NBT mode is used to switch to the non-NBT mode according to the seventh to twelfth conditions.

15 through 17, the AP 1700 in FIG. 17 corresponds to the AP 1600 in FIG. 16, and the STA 1710 in FIG. 17 corresponds to the STA 1610 in FIG. Specifically, the STA 1710 combined through the combining procedure with the AP 1700 can be understood as a wireless terminal in the non-NBT mode.

Figure 17 can be understood based on STA initiated signaling and NBT mode initiation signaling.

The STA 1710 in the non-NBT mode initially transmits the NBT mode request frame to the AP 1700 for requesting the NBT mode after being combined with the AP 1700. For example, when it is determined by the STA 1710 that at least one of the first to sixth conditions is satisfied, an NBT mode request frame may be transmitted.

Specifically, the NBT mode request frame may be used to request a plurality of pieces of information for the NBT mode from the AP 1700. Here, the plurality of pieces of information may include the following first to fourth pieces of information.

For example, the first information may be information on the frequency location of the NB channel. The second information may be information on the MCS to be used in the NBT mode. The third information may be information on whether a legacy preamble is used in the NBT packet. The fourth information may be information on the bandwidth of the frequency channel associated with the NB channel.

Note that although not shown in FIG. 17, the NBT mode request frame may be used by the STA 1710 to request the termination of the NBT mode.

The STA 1710 may then receive a first ACK frame (ACK # 1) from the AP 1700 to inform the successful reception of the NBT mode request frame.

The STA 1710 may then receive the NBT mode response frame from the AP 1700. [

Specifically, the NBT mode response frame may be used to convey a plurality of information determined for the NBT mode to the STA 1710. Here, the plurality of pieces of information may include the following first to fourth pieces of information.

For example, the first information may be information on the frequency location of the NB channel. The second information may be information on the MCS to be used in the NBT mode. The third information may be information on whether a legacy preamble is used in the NBT packet. The fourth information may be information on the bandwidth of the frequency channel associated with the NB channel.

The STA 1710 may then transmit a second ACK frame (ACK # 2) to the AP 1700 to inform successful reception of the NBT mode response frame.

17, the NBT mode request frame, the first ACK frame (ACK # 1), the NBT mode response frame, and the second ACK frame (ACK # 2) may be frames transmitted and received based on the 20 MHz band.

After transmission of the second ACK frame (ACK # 2), the STA 1710 in the non-NBT mode may alternate in the NBT mode. Upon receipt of the second ACK frame, the AP 1700 may know that the STA 1710 has switched from the non-NBT mode to the NBT mode.

The AP 1700 may periodically transmit the NBT trigger frame to confirm the presence of the uplink data buffered by the STA 1710 operating in the NBT mode. In this case, the STA 1710 can receive the NBT trigger frame based on the NB channel.

Here, the legacy part (L-part) of the NBT trigger frame may be omitted. Also, it will be appreciated that, unlike the one shown in FIG. 17, the legacy part (L-part) may be transmitted first based on the 20 MHz band prior to transmission of the NBT trigger frame.

Then, the STA 1710 may transmit an NBT data frame including the uplink data for the AP 1700 to the AP 1700 based on the uplink resources allocated by the NBT trigger frame.

Here, the legacy part (L-part) of the NBT data frame may be omitted. Also, it will be appreciated that, unlike that shown in FIG. 17, the legacy part (L-part) may be transmitted first based on the 20 MHz band prior to transmission of the NBT data frame.

In this case, the AP 1700 can receive the NBT data frame based on the NB channel.

The AP 1700 may then transmit an NBT ACK frame (NBT_ACK) to the STA 1710 to inform successful reception of the NBT data frame. In this case, the STA 1710 can receive an NBT ACK frame (NBT_ACK) based on the NB channel.

18 is a flowchart illustrating a method of performing communication based on an NBT packet in a wireless LAN system according to an embodiment of the present invention.

For the sake of a clear and concise understanding of FIG. 18, there is shown an example of an NBT mode initiation signaling (STA initiated signaling) initiated by a first wireless terminal that is a non-AP STA and an NBT mode initiation signal signaling can be assumed.

Also, the first wireless terminal of FIG. 10 may be a non-AP STA combined through a combining procedure with the second wireless terminal. In this case, the initial first wireless terminal may operate based on the non-NBT mode after the association procedure with the second wireless terminal.

For example, an initial first wireless terminal may communicate with a second wireless terminal based on a 20 MHz band based legacy PPDU after the combining procedure.

1 to 18, in step S1810, a first wireless terminal that is a non-AP STA in a non-NBT mode may transmit an NBT mode request frame for requesting an NBT mode to a second wireless terminal have.

For example, when at least one of the first through sixth conditions of FIG. 16 is satisfied, an NBT mode request frame may be transmitted.

For example, when a frame based on the 20 MHz band is not received from the second wireless terminal for a predetermined time period, the NBT mode request frame may be transmitted by the first wireless terminal to the second wireless terminal.

The first wireless terminal may then receive a first acknowledgment (ACK) frame from the second wireless terminal to signal the successful reception of the NBT mode request frame.

In step S1820, the first wireless terminal may receive the NBT mode response frame from the second wireless terminal after receiving the first ACK frame.

For example, the NBT mode response frame may include information on the frequency position of the NB channel and information on the bandwidth of the NB channel. That is, based on the received NBT mode response frame, the second wireless terminal can acquire information on the NB channel for the NBT mode.

The first wireless terminal may then transmit a second ACK frame to the second wireless terminal to inform successful reception of the NBT mode response frame.

The NBT mode request frame, the first ACK frame, the NBT mode response frame, and the second ACK frame mentioned in steps S1810 and S1820 may be implemented as a legacy PPDU based on a 20 MHz channel.

In step S1830, after the transmission of the second ACK frame, the first wireless terminal may alternate from the non-NBT mode to the NBT mode. The first wireless terminal alternating in the NBT mode may perform an attempt to receive an NB channel based on previously acquired information.

In other words, if the second ACK frame is received at the second wireless terminal, the second wireless terminal can know that the first wireless terminal is in the NBT mode since the reception of the second ACK frame.

In step S1840, the first wireless terminal in the NBT mode may receive the NBT trigger frame for the uplink data buffered by the first wireless terminal from the second wireless terminal.

For example, the NBT trigger frame may be a frame periodically transmitted by the second wireless terminal to confirm the existence of the uplink data buffered by the first wireless terminal.

In step S1850, the first wireless terminal may transmit an NBT data frame including uplink data to the second wireless terminal in response to the NBT trigger frame.

In step S1860, the first wireless terminal may receive an NBT_ACK frame from the second wireless terminal to notify the successful reception of the NBT data frame.

The NBT trigger frame and the NBT data frame mentioned in steps S1840 to S1860 can be implemented as a new type of PPDU based on a NB (narrow band) channel formed in a 20 MHz channel.

19 is a conceptual diagram related to a method of transmitting an NBT frame based on an NBT mode in a wireless LAN system according to another embodiment of the present invention.

Figure 19 can be understood based on STA initiated signaling and NBT mode initiation signaling.

17-19, AP 1900 in FIG. 19 corresponds to AP 1700 in FIG. 17, and STA 1910 in FIG. 19 may correspond to STA 1710 in FIG. Specifically, the STA 1910 combined with the AP 1900 through the combining procedure can be understood as a wireless terminal in the non-NBT mode.

However, if an ACK frame for the NBT mode request frame is received from the AP 1900, the STA 1900 can alternate from the non-NBT mode to the NBT mode without transmitting a separate NBT mode response frame.

In other words, after transmission of the ACK frame for the NBT mode request frame, the AP 1900 may expect the STA 1900 to operate in the NBT mode. Accordingly, after transmitting the ACK frame for the NBT mode request frame, the AP 1900 can communicate with the STA 1910 based on the NB channel.

20 and 21 are conceptual diagrams related to a method of transmitting an NBT frame based on an NBT mode in a wireless LAN system according to yet another embodiment.

20 and 21 can be understood based on AP initiated signaling and NBT mode initiation signaling.

Referring to FIG. 20, a first ACK frame (ACK # 1) for an NBT mode request frame may be received from the STA 2010. The AP 2000 may then transmit a second ACK frame (ACK # 2) to inform successful reception of the NBT mode response frame.

After transmitting the second ACK frame (ACK # 2), the AP 2000 can expect the STA 2110 to operate in the NBT mode. Accordingly, after transmitting the second ACK frame (ACK # 2), the AP 2000 can communicate with the STA 2010 based on the NB channel.

Referring to FIG. 21, when an ACK frame for an NBT mode request frame is received from the STA 2110, the AP 2100 expects the STA 2110 to operate in the NBT mode without transmitting a separate NBT mode response frame .

Accordingly, after receiving the ACK frame for the NBT mode request frame, the AP 2100 can communicate with the STA 2110 based on the NB channel.

FIGS. 22 and 23 are diagrams illustrating a procedure for transmitting an uplink data frame based on the CCA operation according to another embodiment of the present invention.

Referring to FIG. 22, transmission of an uplink data frame may be performed according to a state of a wireless channel based on a CCA operation according to a conventional operation without receiving an NBT trigger frame.

For example, it may be assumed that the buffer of the STA 2210 includes uplink data for the AP 2200. In this case, the STA 2210 can perform the CCA operation for the wireless channel. The STA 2210 can transmit uplink data only when the state of the wireless channel is determined to be idle.

Referring to FIG. 23, the wireless terminal in the NBT mode can perform only the CCA operation for the NBT band. In other words, the wireless terminal in the NBT mode may not perform the CCA operation for the 20 MHz band. In this case, the wireless terminal in the NBT mode can only maintain NBT_NAV.

As shown in FIG. 23, in order to perform the minimum protection function for the frame being transmitted, the wireless terminal in the NBT mode performs the CCA operation for the 20 MHz band during the PIFS interval immediately before the expected transmission time according to the backoff operation .

24 is a flowchart illustrating a method of performing communication based on an NBT packet in a wireless LAN system according to another embodiment of the present invention.

18 and 24, a method of performing communication based on an NBT packet according to another embodiment of the present invention can be understood as a reinterpretation of the contents mentioned in the point of view of the non-AP STA in FIG. 18 from the viewpoint of the AP .

Referring to FIG. 24, the first wireless terminal referred to in FIG. 24 is an AP, and the second wireless terminal referred to in FIG. 24 can be understood as a non-AP STA.

In step S2410, the first wireless terminal can receive the NBT mode request frame from the second wireless terminal. The first wireless terminal may then transmit a first acknowledgment (ACK) frame to inform the second wireless terminal of successful reception of the NBT mode request frame.

In step S2420, after the transmission of the first ACK frame, the first wireless terminal may transmit the NBT mode response frame to the second wireless terminal. Here, the NBT mode response frame may include information on the frequency position of the NB channel and information on the bandwidth of the NB channel. The first wireless terminal may then receive a second ACK frame from the second wireless terminal to inform successful reception of the NBT mode response frame.

In this case, after the second ACK frame is received, the first wireless terminal can know that the second wireless terminal operates in the NBT mode.

Accordingly, in step S2430, the first wireless terminal may transmit an NBT trigger frame for uplink data buffered by the second wireless terminal to the second wireless terminal.

In step S2440, the first wireless terminal may receive the NBT data frame including the uplink data from the second wireless terminal in response to the NBT trigger frame.

In step S2450, the first wireless terminal may transmit an NBT_ACK frame to notify the successful reception of the NBT data frame to the second wireless terminal.

Here, the NBT mode request frame, the first ACK frame, the NBT mode response frame, and the second ACK frame are transmitted based on the PPDU based on the existing 20 MHz channel. In addition, the NBT trigger frame and the NBT data frame may be delivered based on PPDUs based on NB (narrow band) channels formed in a 20 MHz channel.

25 is a block diagram illustrating a wireless device to which the present embodiment is applicable.

Referring to FIG. 25, a wireless device is an STA capable of implementing the above-described embodiment, and can operate as an AP or a non-AP STA. Further, the wireless device may correspond to the above-described user, or may correspond to a transmitting device that transmits a signal to the 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.

A transceiver 2530 is a device that includes a transmitter and a receiver, and when a specific operation is performed, only the operation of either the transmitter or the receiver is performed, or both the transmitter and receiver operations are performed have. 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, processor 2510 may perform the operations disclosed in the embodiments of Figs. 1-24.

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.

26 is a block diagram showing an example of an apparatus included in the processor.

26 is described with reference to a block for a transmission signal, it is obvious that a received signal can be processed using the block.

The illustrated data processing unit 2610 generates transmission data (control data and / or user data) corresponding to a transmission signal. The output of the data processing unit 2610 may be input to the encoder 2620. The encoder 2620 can perform coding through BCC (binary convolutional code) or LDPC (low-density parity-check) techniques. At least one encoder 2620 may be included, and the number of encoders 2620 may be determined according to various information (e.g., the number of data streams).

The output of the encoder 2620 may be input to an interleaver 2630. Interleaver 2630 performs operations to spread successive bit signals over radio resources (e.g., time and / or frequency) to prevent burst errors due to fading or the like. At least one interleaver 2630 may be included, and the number of interleavers 2630 may be determined according to various information (e.g., the number of spatial streams).

The output of the interleaver 2630 may be input to a constellation mapper 2640. The constellation mapper 2640 performs constellation mapping such as biphase shift keying (BPSK), quadrature phase shift keying (QPSK), and quadrature amplitude modulation (n-QAM).

The output of the constellation mapper 2640 may be input to a spatial stream encoder 2650. The spatial stream encoder 2650 performs data processing to transmit the transmission signal through at least one spatial stream. For example, the spatial stream encoder 2650 may perform at least one of space-time block coding (STBC), cyclic shift diversity (CSD) insertion, and spatial mapping for a transmission signal.

The output of spatial stream encoder 2650 may be input to an IDFT 2660 block. The IDFT 2660 block performs inverse discrete Fourier transform (IDFT) or inverse fast Fourier transform (IFFT).

The output of the IDFT 2660 block is input to the GI (Guard Interval) inserter 2670, and the output of the GI inserter 2670 is input to the transceiver 2530 of FIG.

Although a detailed description of the present invention has been provided for specific embodiments, various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present specification should not be construed as being limited to the above-described embodiments, and should be defined by equivalents to the claims of the present invention as well as the following claims.

Claims (15)

1. A method for performing communication based on narrowband transmission (NBT) packets in a wireless LAN system,

   the first wireless terminal in the non-NBT mode transmitting an NBT mode request frame to request the NBT mode to the second wireless terminal;

   Receiving, by the first wireless terminal, a first ACK (acknowledgment) frame for notifying successful reception of the NBT mode request frame from the second wireless terminal;

   Receiving, by the first wireless terminal, an NBT mode response frame from the second wireless terminal after receiving the first ACK frame;

   Transmitting, by the first wireless terminal, a second ACK frame to inform the second wireless terminal of successful reception of the NBT mode response frame;

   The first wireless terminal alternating from the non-NBT mode to the NBT mode after transmission of the second ACK frame; And

   The first wireless terminal in the NBT mode receiving an NBT trigger frame for uplink data buffered by the first wireless terminal from the second wireless terminal; And

   And the first wireless terminal in the NBT mode transmitting an NBT data frame including the uplink data to the second wireless terminal in response to the NBT trigger frame.
2. The method according to claim 1,

   Wherein the NBT mode request frame, the first ACK frame, the NBT mode response frame, and the second ACK frame are based on a 20 MHz channel,

   Wherein the NBT trigger frame and the NBT data frame are based on narrow band channels formed in the 20 MHz channel.
3. 3. The method of claim 2,

   Wherein the NBT mode response frame includes information on a frequency location of the NB channel and information on a bandwidth of the NB channel.
4. The method according to claim 1,

   Further comprising the step of the first wireless terminal receiving an NBT ACK frame to inform successful reception of the NBT data frame.
5. The method according to claim 1,

   Wherein the NBT mode request frame is transmitted by the first wireless terminal when a frame based on the 20 MHz band is not received from the second wireless terminal for a predetermined time period.
6. The method according to claim 1,

   Wherein the NBT trigger frame is transmitted periodically by a second wireless terminal.
7. A first wireless terminal for performing communication based on a narrow band transmission (NBT) packet in a wireless LAN system,

   A transceiver for transmitting or receiving a radio signal; And

   And a processor for controlling the transceiver,

   And transmit an NBT mode request frame for requesting an NBT mode to a second wireless terminal,

   And to receive from the second wireless terminal a first acknowledgment (ACK) frame for informing the successful reception of the NBT mode request frame,

   And to receive an NBT mode response frame from the second wireless terminal after receiving the first ACK frame,

   And transmit a second ACK frame to inform the second wireless terminal of successful reception of the NBT mode response frame,

   And to alternate from the non-NBT mode to the NBT mode after transmission of the second ACK frame,

   And receive an NBT trigger frame for uplink data buffered by the first wireless terminal from the second wireless terminal based on the NBT mode, and

   And transmit the NBT data frame including the uplink data to the second wireless terminal based on the NBT mode in response to the NBT trigger frame.
8. 8. The method of claim 7,

   Wherein the NBT mode request frame, the first ACK frame, the NBT mode response frame, and the second ACK frame are based on a 20 MHz channel,

   Wherein the NBT trigger frame and the NBT data frame are based on a NB (narrow band) channel formed in the 20 MHz channel.
9. 9. The method of claim 8,

   Wherein the NBT mode response frame includes information on a frequency location of the NB channel and information on a bandwidth of the NB channel.
10. 8. The method of claim 7,

    Wherein the processor is further adapted to receive an NBT ACK frame to signal successful reception of an NBT data frame.
11. 8. The method of claim 7,

    Wherein the NBT mode request frame is transmitted by the first wireless terminal when a frame based on the 20 MHz band is not received from the second wireless terminal for a predetermined time period.
12. 8. The method of claim 7,

    Wherein the NBT trigger frame is periodically transmitted by the second wireless terminal.
13. A wireless terminal for performing communication based on narrow band transmission (NBT) packets in a wireless LAN system,

    A transceiver for transmitting or receiving a radio signal; And

    And a processor for controlling the transceiver,

    And to receive an NBT mode request frame from the second wireless terminal for requesting an NBT mode,

    And transmit a first acknowledgment (ACK) frame to inform the second wireless terminal of successful reception of the NBT mode request frame,

    And to transmit an NBT mode response frame to the second wireless terminal after transmission of the first ACK frame,

    And to receive from the second wireless terminal a second ACK frame to inform successful reception of the NBT mode response frame,

    And transmit an NBT trigger frame for uplink data buffered by the second wireless terminal to the second wireless terminal based on the NBT mode after transmission of the second ACK frame,

    And receives an NBT data frame including the uplink data from the second wireless terminal based on the NBT mode in response to the NBT trigger frame.
14. 14. The method of claim 13,

    Wherein the NBT mode request frame, the first ACK frame, the NBT mode response frame, and the second ACK frame are based on a 20 MHz channel,

    Wherein the NBT trigger frame and the NBT data frame are based on a NB (narrow band) channel formed in the 20 MHz channel.
15. 15. The method of claim 14,

    Wherein the NBT mode response frame includes information on a frequency location of the NB channel and information on a bandwidth of the NB channel.

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