WO2020009389A1 - Method and device for transmitting ppdu in wireless lan system - Google Patents

Abstract

A method and device for transmitting a PPDU in a wireless LAN system is proposed. Specifically, a transmission device generates a PPDU including an A-MPDU and transmits the PPDU to a reception device. The A-MPDU is generated by aggregating a first MPDU, a second MPDU, and a third MPDU. The first MPDU includes a first delimiter field, a first MAC header, and a first data field. The second MPDU includes a second delimiter field and a second data field. The third MPDU includes a third delimiter field and a third data field. The second delimiter field includes information on whether the second MPDU includes a second MAC header. The third delimiter field includes information on whether the third MPDU includes a third MAC header.

Description

Method and apparatus for transmitting PPDU in WLAN system

The present disclosure relates to a technique for transmitting a PPDU in a WLAN system, and more particularly, to a method and apparatus for aggregating data supporting NGV in a WLAN system.

Discussion is underway for the next generation wireless local area network (WLAN). In next-generation WLANs, 1) enhancements to the Institute of Electronics and Electronics Engineers (IEEE) 802.11 physical physical access (PHY) and medium access control (MAC) layers in the 2.4 GHz and 5 GHz bands, and 2) spectral efficiency and area throughput. aims to improve performance in real indoor and outdoor environments, such as in environments where interference sources exist, dense heterogeneous network environments, and high user loads.

The environment mainly considered in the next-generation WLAN is a dense environment having many access points (APs) and a station (STA), and improvements in spectral efficiency and area throughput are discussed in such a dense environment. In addition, in the next generation WLAN, there is an interest in improving practical performance not only in an indoor environment but also in an outdoor environment, which is not much considered in a conventional WLAN.

Specifically, in the next-generation WLAN, there is a great interest in scenarios such as wireless office, smart home, stadium, hotspot, building / apartment, and AP based on the scenario. And STA are discussing about improving system performance in a dense environment with many STAs.

In addition, in the next-generation WLAN, there will be more discussion about improving system performance in outdoor overlapping basic service set (OBSS) environment, improving outdoor environment performance, and cellular offloading, rather than improving single link performance in one basic service set (BSS). It is expected. The directionality of these next-generation WLANs means that next-generation WLANs will increasingly have a technology range similar to that of mobile communications. Considering the recent situation in which mobile communication and WLAN technology are discussed together in the small cell and direct-to-direct (D2D) communication area, the technical and business convergence of next-generation WLAN and mobile communication is expected to become more active.

The present specification proposes a method and apparatus for transmitting a PPDU in a WLAN system.

An example of the present specification proposes a method of transmitting a PPDU.

This embodiment may be performed in a network environment in which a next generation WLAN system is supported. The next generation WLAN system is a WLAN system that improves the 802.11p system and may satisfy backward compatibility with the 802.11p system. The next generation WLAN system may be referred to as NGV (Next Generation V2X) or 802.11be.

This embodiment is performed in a transmitter, and the transmitter may correspond to an AP supporting an NGV or 802.11be WLAN system. The receiving device of this embodiment may correspond to an STA supporting an NGV or 802.11be WLAN system.

The transmitting apparatus generates a PPDU including an Aggregated-MAC Protocol Data Unit (A-MPDU).

The transmitter transmits the PPDU to a receiver.

The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU. This is just one embodiment, and the A-MPDU may be aggregated with a plurality of MPDUs.

The first MPDU includes a first delimiter field, a first MAC header, and a first data field. The second MPDU includes a second delimiter field and a second data field. The third MPDU includes a third delimiter field and a third data field. The first MPDU may be transmitted first of the MPDUs included in the A-MPDU. That is, the first MPDU transmitted may always include a MAC header.

The second delegate field includes information on whether a second MAC header is included in the second MPDU. The third delimiter field includes information on whether a third MAC header is included in the third MPDU. It may be assumed that the second MPDU is transmitted after the first MPDU, and the third MPDU is transmitted after the second MPDU. That is, the MPDUs other than the first transmitted MPDU may or may not include the MAC header based on the delimiter field.

For example, when the reserved bit of the second delimiter field is 1, the second MAC header may be included in the second MPDU. If the reserved bit of the third delimiter field is 0, the third MAC header may not be included in the third MPDU. As a result, by removing some MAC headers from the existing A-MPDU, the aggregated amount of data can reduce the length of the packet compared to the existing A-MPDU.

In addition, when the reserved bit of the third delimiter field is 0, the third MAC header may not include the third MAC header and the first MAC header may be included.

Hereinafter, the second MPDU including the MAC header will be described.

The second MAC header may be configured as a partial field of the first MAC header. The first MAC header may include a frame control field, a duration / ID field, an address 1 field, an address 2 field, an address 3 field, a sequence control field, a QoS control field, an HT control field, a frame body field, and an FCS field. . The second MAC header may consist of only some of the fields constituting the first MAC header.

For example, the second MAC header may include a Quality of Service (QoS) control field, a sequence control field, and a Next Generation Vehicle-to-Everything (NGV) control field.

The QoS control field may include information on a traffic identification (TID) of the second MPDU. The sequence control field may include information about a sequence number of the second MPDU. The NGV control field may include information that the second MPDU supports NGV.

The PPDU may further include an NGV-SIG (signal) field.

The NGV-SIG field may include a start symbol offset, an end symbol offset, and MCS (Modulation and Coding Scheme) information.

The start symbol offset may include information about a symbol at which the first and second MPDUs start. The end symbol offset may include information about a symbol at which the first and second MPDUs are terminated. The MCS information may include MCSs for the first and second MPDUs.

For robust transmission of MPDUs with MAC headers, MPDUs with MAC headers and MPDUs without MAC headers can be encoded with different MCS adjustments. The symbol offset and MCS of the MPDU including the MAC header may be indicated in the NGV-SIG field. However, the NGV-SIG field may not include information on a symbol at which the first MPDU starts.

In addition, the MCS for the first and second MPDU may be negotiated in advance between the transmitter and the receiver.

The PPDU may further include a legacy preamble, a Short Training Field (NGV-STF) field, and a Long Training Field (NGV-LTF) field. The legacy preamble may be supported by an 802.11p WLAN system. The NGV-SIG field, the NGV-STF field, and the NGV-LTF field may be supported by an 802.11be WLAN system.

The PPDU may be transmitted through a 10 MHz or 20 MHz band. When the PPDU is transmitted through the 20 MHz band, the legacy preamble and the NGV-SIG field may be duplicated in units of 10 MHz band.

According to an embodiment proposed herein, by removing the MAC header in some of the aggregated MPDU, it is possible to reduce the length of the packet compared to the existing A-MPDU and improve the throughput of the next-generation V2X broadcasting service.

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

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

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

4 is a diagram illustrating an arrangement of resource units (RUs) used on a 20 MHz band.

5 is a diagram illustrating an arrangement of resource units (RUs) used on a 40 MHz band.

6 is a diagram illustrating an arrangement of resource units (RUs) used on an 80 MHz band.

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

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

9 shows an example of a trigger frame.

10 illustrates an example of subfields included in a per user information field.

11 is a block diagram showing an example of a control field and a data field constructed according to the present embodiment.

12 is a diagram illustrating an example of a HE TB PPDU.

13 illustrates a MAC frame format used in a WLAN system.

14 shows an A-MPDU format used in a WLAN system.

15 shows a band plan of 5.9 GHz DSRC.

16 illustrates a 10 MHz / 20 MHz NGV PPDU format including an A-MPDU according to this embodiment.

17 shows an example of a format in which an A-MPDU is changed in the manner of Embodiment 1).

18 shows an example of a format in which A-MPDU is changed in the manner of Embodiment 2).

Fig. 19 shows an example of a format in which A-MPDU is changed in the manner of Example 3).

20 is a flowchart illustrating a procedure of transmitting a PPDU in the transmitting apparatus according to the present embodiment.

21 is a flowchart illustrating a procedure of receiving a PPDU in the receiving apparatus according to the present embodiment.

FIG. 22 is a diagram for describing an apparatus for implementing the method as described above.

23 illustrates a more detailed wireless device implementing an embodiment of the present invention.

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

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

Referring to the top of FIG. 1, the WLAN system may include one or more infrastructure BSSs 100 and 105 (hereinafter, BSS). The BSSs 100 and 105 are a set of APs and STAs such as an access point 125 and a STA1 (station 100-1) capable of successfully synchronizing and communicating with each other, and do not indicate a specific area. The BSS 105 may include one or more joinable STAs 105-1 and 105-2 to one AP 130.

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

The distributed system 110 may connect several BSSs 100 and 105 to implement an extended service set (ESS) 140 which is an extended service set. The ESS 140 may be used as a term indicating one network in which one or several APs 125 and 230 are connected through the distributed system 110. APs included in one ESS 140 may have the same service set identification (SSID).

The portal 120 may serve as a bridge for connecting the WLAN network (IEEE 802.11) with another network (for example, 802.X).

In the BSS as shown in the upper part of FIG. 1, a network between the APs 125 and 130 and a network between the APs 125 and 130 and the STAs 100-1, 105-1 and 105-2 may be implemented. However, it may be possible to perform communication by setting up a network even between STAs without the APs 125 and 130. A network that performs communication by establishing a network even between STAs without APs 125 and 130 is defined as an ad-hoc network or an independent basic service set (BSS).

1 is a conceptual diagram illustrating an IBSS.

Referring to the bottom of FIG. 1, the IBSS is a BSS operating in an ad-hoc mode. Since IBSS does not contain an AP, there is no centralized management entity. That is, in the IBSS, the STAs 150-1, 150-2, 150-3, 155-4, and 155-5 are managed in a distributed manner. In the IBSS, all STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may be mobile STAs, and access to a distributed system is not allowed, thus making a self-contained network. network).

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

The STA may include a mobile terminal, a wireless device, a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit ( It may also be called various names such as a mobile subscriber unit or simply a user.

On the other hand, the term "user" may be used in various meanings, for example, may also be used to mean an STA participating in uplink MU MIMO and / or uplink OFDMA transmission in wireless LAN communication. It is not limited to this.

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

As shown, various types of PHY protocol data units (PPDUs) have been used in the IEEE a / g / n / ac standard. Specifically, the LTF and STF fields included training signals, the SIG-A and SIG-B included control information for the receiving station, and the data fields 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 may be applied on a high efficiency PPDU (HE PPDU) according to the IEEE 802.11ax standard. That is, the signals to be improved in the present 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 may also be represented as SIG-A or SIG-B. However, the improved signal proposed by this embodiment is not necessarily limited to the HE-SIG-A and / or HE-SIG-B standard, and controls / control of various names including control information in a wireless communication system for transmitting user data. Applicable to data fields.

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

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

As shown, a HE-PPDU for a multiple user (MU) includes a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), High efficiency-signal A (HE-SIG-A), high efficiency-signal-B (HE-SIG-B), high efficiency-short training field (HE-STF), high efficiency-long training field (HE-LTF) It may include a data field (or MAC payload) and a PE (Packet Extension) field. Each field may be transmitted during the time period shown (ie, 4 or 8 ms, etc.).

Detailed description of each field of FIG. 3 will be described later.

4 is a diagram illustrating an arrangement of resource units (RUs) used on a 20 MHz band.

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

As shown at the top of FIG. 4, 26-units (ie, units corresponding to 26 tones) may be arranged. Six tones may be used as the guard band in the leftmost band of the 20 MHz band, and five tones may be used as the guard band in the rightmost band of the 20 MHz band. In addition, seven DC tones are inserted into the center band, that is, the DC band, and 26-units corresponding to each of the 13 tones may exist to the left and right of the DC band. In addition, other bands may be allocated 26-unit, 52-unit, 106-unit. Each unit can be assigned for a receiving station, i. E. A user.

On the other hand, the RU arrangement of FIG. 4 is utilized not only for the situation for a plurality of users (MU), but also for the situation for a single user (SU), in which case one 242-unit is shown as shown at the bottom of FIG. It is possible to use and in this case three DC tones can be inserted.

In the example of FIG. 4, various sizes of RUs have been proposed, that is, 26-RU, 52-RU, 106-RU, 242-RU, and the like. Since the specific sizes of these RUs can be expanded or increased, the present embodiment Is not limited to the specific size of each RU (ie, the number of corresponding tones).

5 is a diagram illustrating an arrangement of resource units (RUs) used on a 40 MHz band.

Just as RUs of various sizes are used in the example of FIG. 4, the example of FIG. 5 may also use 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and the like. In addition, five DC tones can be inserted at the center frequency, 12 tones are used as the guard band in the leftmost band of the 40 MHz band, and 11 tones are in the rightmost band of the 40 MHz band. This guard band can be used.

Also, as shown, the 484-RU may be used when used for a single user. Meanwhile, the specific number of RUs may be changed as in the example of FIG. 4.

6 is a diagram illustrating an arrangement of resource units (RUs) used on an 80 MHz band.

Just as RUs of various sizes are used in the example of FIGS. 4 and 5, the example of FIG. 6 may also use 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, 996-RU, and the like. have. In addition, seven DC tones can be inserted in the center frequency, 12 tones are used as the guard band in the leftmost band of the 80 MHz band, and 11 tones in the rightmost band of the 80 MHz band. This guard band can be used. Also available is a 26-RU with 13 tones each located to the left and right of the DC band.

Also, as shown, when used for a single user, a 996-RU may be used, in which case five DC tones may be inserted.

Meanwhile, the specific number of RUs may be changed as in the example of FIGS. 4 and 5.

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

7 is another example illustrating 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 include a long training orthogonal frequency division multiplexing symbol. The L-LTF 710 may be used for fine frequency / time synchronization and channel prediction.

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

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

Specifically, the HE-SIG-A 730 may include 1) a DL / UL indicator, 2) a BSS color field which is an identifier of a BSS, 3) a field indicating a remaining time of a current TXOP interval, 4) 20, Bandwidth field indicating whether 40, 80, 160, 80 + 80 MHz, 5) field indicating the MCS scheme applied to HE-SIG-B, 6) dual subcarrier modulation for HE-SIG-B field indicating whether it is modulated by dual subcarrier modulation), 7) field indicating the number of symbols used for HE-SIG-B, and 8) indicating whether HE-SIG-B is generated over the entire band. Field, 9) 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 additional OFDM symbols exist for LDPC coding, 12) A field indicating control information about a packet extension (PE), and 13) a field indicating information on a CRC field of the HE-SIG-A. have. Specific fields of the HE-SIG-A may be added or omitted. In addition, some fields may be added or omitted in other environments where the HE-SIG-A is not a multi-user (MU) environment.

In addition, the HE-SIG-A 730 may be composed of two parts, HE-SIG-A1 and HE-SIG-A2. HE-SIG-A1 and HE-SIG-A2 included in the HE-SIG-A may be defined in the following format structure (field) according to the PPDU. First, the HE-SIG-A field of the HE SU PPDU may be defined as follows.

In addition, the HE-SIG-A field of the HE MU PPDU may be defined as follows.

In addition, the HE-SIG-A field of the HE TB PPDU may be defined as follows.

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

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

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

The previous field of HE-SIG-B 740 on the MU PPDU may be transmitted in duplicated form. In the case of the HE-SIG-B 740, the HE-SIG-B 740 transmitted in a part of the frequency band (for example, the fourth frequency band) is the frequency band of the corresponding frequency band (ie, the fourth frequency band). Control information for a data field and a data field of another frequency band (eg, the second frequency band) except for the corresponding frequency band may be included. In addition, the HE-SIG-B 740 of a specific frequency band (eg, the second frequency band) duplicates the HE-SIG-B 740 of another frequency band (eg, the fourth frequency band). It can be one format. Alternatively, the HE-SIG-B 740 may be transmitted in encoded form on all transmission resources. The field after the HE-SIG-B 740 may include individual information for each receiving STA that receives the PPDU.

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

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

The size of the FFT / IFFT applied to the field after the HE-STF 750 and the HE-STF 750 may be different from the size of the FFT / IFFT applied to the field before the HE-STF 750. 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 L-STF 700, L-LTF 710, L-SIG 720, HE-SIG-A 730, HE-SIG-B 740 on the PPDU of FIG. When a field of s is called a first field, at least one of the data field 770, the HE-STF 750, and the HE-LTF 760 may be referred to as a second field. The first field may include a field related to a legacy system, and the second field may include a field related to a HE system. In this case, FFT (fast Fourier transform) size / inverse fast Fourier transform (IFFT) size is N times the FFT / IFFT size used in the conventional wireless LAN system (N is a natural number, for example, N = 1, 2, 4) can be defined. That is, an FFT / IFFT of N (= 4) times size may be applied to the second field of the HE PPDU compared to the first field of the HE PPDU. For example, 256 FFT / IFFT is applied for a bandwidth of 20 MHz, 512 FFT / IFFT is applied for a bandwidth of 40 MHz, 1024 FFT / IFFT is applied for a bandwidth of 80 MHz, and 2048 FFT for a bandwidth of 160 MHz continuous or discontinuous 160 MHz. / IFFT can be applied.

In other words, the subcarrier spacing / subcarrier spacing is 1 / N times the size of the subcarrier space used in the conventional WLAN system (N is a natural number, for example, 78.125 kHz when N = 4). Can be. That is, a subcarrier spacing of 312.5 kHz, which is a conventional subcarrier spacing, may be applied to a first field of the HE PPDU, and a subcarrier space of 78.125 kHz may be applied to a second field of the HE PPDU.

Alternatively, the 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 Can be expressed as The length of an OFDM symbol may be a value obtained by adding a length of a guard interval (GI) to an IDFT / DFT length. The length of the GI can be various values such as 0.4 μs, 0.8 μs, 1.6 μs, 2.4 μs, 3.2 μs.

For convenience of description, although the frequency band used by the first field and the frequency band used by the second field are represented in FIG. 7, they may not exactly coincide with each other. For example, the main bands of the first fields L-STF, L-LTF, L-SIG, HE-SIG-A, and HE-SIG-B corresponding to the first frequency band are the second field HE-STF. , HE-LTF, Data) is the same as the main band, but in each frequency band may be inconsistent interface. 4 to 6, since a plurality of null subcarriers, DC tones, guard tones, etc. are inserted in the process of arranging the RU, it may be difficult to accurately match the interface.

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

Hereinafter, in the present embodiment, data (or frame) transmitted from the AP to the STA is called downlink data (or downlink frame), and data (or frame) transmitted from the STA to the AP is called uplink data (or uplink frame). Can be expressed in terms. In addition, the transmission from the AP to the STA may be expressed in terms of downlink transmission, and the transmission from the STA to the AP may be expressed in terms of uplink transmission.

In addition, each of the PHY protocol data units (PPDUs), frames, and data transmitted through downlink transmission may be expressed in 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 MAC protocol data unit (MPDU)). The PPDU header may include a PHY header and a PHY preamble, and the PSDU (or MPDU) may be a data unit including a frame (or an information unit of a MAC layer) or indicating a frame. The PHY header may be referred to as a physical layer convergence protocol (PLCP) header in another term, and the PHY preamble may be expressed as a PLCP preamble in another term.

In addition, each of the PPDUs, frames, and data transmitted through the uplink transmission may be expressed by the term uplink PPDU, uplink frame, and uplink data.

In a WLAN system to which the present embodiment is applied, the entire bandwidth may be used for downlink transmission to one STA and uplink transmission to one STA based on single (or single) -orthogonal frequency division multiplexing (SUDM) transmission. Do. In addition, in the WLAN system to which the present embodiment is applied, the AP may perform downlink (DL) multi-user (MU) transmission based on multiple input multiple output (MU MIMO), and such transmission is referred to as DL MU MIMO transmission. It can be expressed as.

In addition, in the WLAN system according to the present embodiment, an orthogonal frequency division multiple access (OFDMA) based transmission method is preferably supported for uplink transmission and / or downlink transmission. That is, uplink / downlink communication may be performed by allocating data units (eg, RUs) corresponding to different frequency resources to the user. In more detail, in the WLAN system according to the present embodiment, the AP may perform DL MU transmission based on OFDMA, and such transmission may be expressed by the term DL MU OFDMA transmission. When DL MU OFDMA transmission is performed, the AP may transmit downlink data (or downlink frame, downlink PPDU) to each of the plurality of STAs through each of the plurality of frequency resources on the overlapped time resources. The plurality of frequency resources may be a plurality of subbands (or subchannels) or a plurality of resource units (RUs). DL MU OFDMA transmission may be used with DL MU MIMO transmission. For example, 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. Can be.

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

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

When uplink transmission by each of the plurality of STAs is performed on the spatial domain, different space-time streams (or spatial streams) are allocated to each of the plurality of STAs, and each of the plurality of STAs transmits uplink data through different space-time streams. Can transmit to the AP. The transmission method through these different spatial streams may be represented by the term UL MU MIMO transmission method.

The UL MU OFDMA transmission and the UL MU MIMO transmission may 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 has been used to allocate a wider bandwidth (for example, a bandwidth exceeding 20 MHz) to one UE. The 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 terminal. If the primary channel rule is used, there is a constraint for allocating a wide bandwidth to the terminal. Specifically, according to the primary channel rule, when a secondary channel adjacent to the primary channel is used in an overlapped BSS (OBSS) and 'busy', the STA may use the remaining channels except the primary channel. Can't. Accordingly, the STA can transmit the frame only through the primary channel, thereby being limited to the transmission of the frame through the multi-channel. That is, the primary channel rule used for multi-channel allocation in the existing WLAN system may be a big limitation in obtaining high throughput by operating a wide bandwidth in the current WLAN environment where there are not many OBSS.

In the present embodiment to solve this problem is disclosed a WLAN system supporting the OFDMA technology. That is, the above-described OFDMA technique is applicable to at least one of downlink and uplink. In addition, the above-described MU-MIMO technique may be additionally applied to at least one of downlink and uplink. When OFDMA technology is used, a plurality of terminals may be used simultaneously instead of one terminal without using a primary channel rule. Therefore, wide bandwidth operation is possible, and the efficiency of the operation of radio resources can be improved.

As described above, when uplink transmission by each of a plurality of STAs (eg, non-AP STAs) is performed in the frequency domain, the AP has different frequency resources for each of the plurality of STAs based on OFDMA. It may be allocated as a link transmission resource. In addition, as described above, different frequency resources may be different subbands (or subchannels) or different resource units (RUs).

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

9 shows an example of a trigger frame. The trigger frame of FIG. 9 allocates resources for 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, it may be transmitted through the PPDU shown in FIG. 3, through the legacy PPDU shown in FIG. 2, or through a PPDU specifically designed for the trigger frame. If transmitted through the PPDU of FIG. 3, the trigger frame may be included in the illustrated data field.

Each field shown in FIG. 9 may be partially omitted, and another field may be added. In addition, the length of each field may be varied as shown.

The frame control field 910 of FIG. 9 includes information about the version of the MAC protocol and other additional control information, and the duration field 920 may include time information for NAV setting or an identifier of a terminal (eg, For example, information about AID may be included.

In addition, the RA field 930 includes address information of the receiving STA of the corresponding trigger frame and may be omitted as necessary. The TA field 940 includes address information of an STA (for example, an AP) that transmits a corresponding trigger frame, and the common information field 950 is common to be applied to a receiving STA that receives the corresponding trigger frame. Contains control information. For example, a field indicating the length of the L-SIG field of the uplink PPDU transmitted in response to the trigger frame, or the SIG-A field of the uplink PPDU transmitted in response to the trigger frame (that is, HE-SIG-A). Information to control the content of the field). In addition, the common control information may include information about the length of the CP of the uplink PPDU transmitted in response to the trigger frame or information about the length of the LTF field.

In addition, it is preferable to include the per user information field (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 called an "assignment field".

In addition, the trigger frame of FIG. 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 subfield included in a common information field. Some of the subfields of FIG. 10 may be omitted, and other subfields may be added. In addition, the length of each illustrated subfield may be modified.

The trigger type field 1010 of FIG. 10 may indicate the trigger frame variant and the encoding of the trigger frame variant. The trigger type field 1010 may be defined as follows.

The UL BW field 1020 of FIG. 10 indicates a bandwidth in the HE-SIG-A field of a HE trigger based (TB) PPDU. The UL BW field 1020 may be defined as follows.

The Guard Interval (GI) and LTF Type fields 1030 of FIG. 10 indicate the GI and HE-LTF types of the HE TB PPDU response. The GI and LTF type fields 1030 may be defined as follows.

In addition, when the GI and LTF type field 1030 has a value of 2 or 3, the MU-MIMO LTF mode field 1040 of FIG. 10 indicates an LTF mode of a UL MU-MIMO HE TB PPDU response. In this case, the MU-MIMO LTF mode field 1040 may be defined as follows.

If the trigger frame allocates an RU that occupies the entire HE TB PPDU bandwidth and the RU is assigned to one or more STAs, the MU-MIMO LTF mode field 1040 may indicate a HE single stream pilot HE-LTF mode or a HE masked HE-LTF sequence mode. It is directed to either.

If the trigger frame does not allocate an RU occupying the entire HE TB PPDU bandwidth and the RU is not allocated to one or more STAs, the MU-MIMO LTF mode field 1040 is indicated in the HE single stream pilot HE-LTF mode. The MU-MIMO LTF mode field 1040 may be defined as follows.

11 illustrates an example of subfields included in an individual user information field. Some of the subfields of FIG. 11 may be omitted, and other subfields may be added. In addition, the length of each illustrated subfield may be modified.

The User Identifier field (or AID12 field, 1110) of FIG. 11 indicates an identifier of an STA (ie, a receiving STA) to which per user information corresponds. An example of the identifier is all or the AID. It can be part of it.

In addition, the RU Allocation field 1120 may be included. That is, when the receiving STA identified by the user identifier field 1110 transmits an uplink PPDU in response to the trigger frame of FIG. 9, the corresponding uplink PPDU through the RU indicated by the RU Allocation field 1120. Send. In this case, the RU indicated by the RU Allocation field 1120 preferably indicates the RUs shown in FIGS. 4, 5, and 6. The configuration of the specific RU allocation field 1120 will be described later.

The subfield of FIG. 11 may include a (UL FEC) coding type field 1130. The coding type field 1130 may indicate a coding type of an uplink PPDU transmitted in response to the trigger frame of FIG. 9. For example, when BCC coding is applied to the uplink PPDU, the coding type field 1130 is set to '1', and when LDPC coding is applied, the coding type field 1130 is set to '0'. Can be.

The subfield of FIG. 11 may include a UL MCS field 1140. The MCS field 1140 may indicate an MCS scheme applied to an uplink PPDU transmitted in response to the trigger frame of FIG. 9.

In addition, the subfield of FIG. 11 may include a trigger dependent user info field 1150. When the trigger type field 1010 of FIG. 10 indicates a basic trigger variant, the trigger dependent user information field 1150 may include an MPDU MU Spacing Factor subfield (2 bits), a TID Aggregation Limit subfield (3 bits), and a Reserved sub. Field (1 bit) and a Preferred AC subfield (2 bits).

Hereinafter, the present specification proposes an example of improving the control field included in the PPDU. The control field improved by the present specification includes a first control field including control information required for interpreting the PPDU and a second control field including control information for demodulating the data field of the PPDU. do. The first and second control fields may be various fields. For example, the first control field may be the HE-SIG-A 730 illustrated in FIG. 7, and the second control field may be the HE-SIG-B 740 illustrated in FIGS. 7 and 8. Can be.

Hereinafter, a specific example of improving the first or second control field will be described.

In the following example, a control identifier inserted into a first control field or a second control field is proposed. The size of the control identifier may vary, for example, may be implemented with 1-bit information.

The control identifier (eg, 1 bit identifier) may indicate whether 242-RU is allocated, for example when 20 MHz transmission is performed. As shown in FIGS. 4 to 6, RUs of various sizes may be used. These RUs can be broadly divided into two types of RUs. For example, all of the RUs shown in FIGS. 4 to 6 may be classified into 26-type RUs and 242-type RUs. For example, a 26-type RU may include 26-RU, 52-RU, 106-RU, and the 242-type RU may include 242-RU, 484-RU, and larger RUs.

The control identifier (eg, 1 bit identifier) may indicate that 242-type RU has been used. That is, it may indicate that 242-RU is included or 484-RU or 996-RU is included. If the transmission frequency band in which the PPDU is transmitted is a 20 MHz band, 242-RU is a single RU corresponding to the full bandwidth of the transmission frequency band (ie, 20 MHz) band. Accordingly, the control identifier (eg, 1 bit identifier) may indicate whether a single RU corresponding to the full bandwidth of the transmission frequency band is allocated.

For example, if the transmission frequency band is a 40 MHz band, the control identifier (eg, 1 bit identifier) is assigned a single RU corresponding to the entire band (ie, 40 MHz band) of the transmission frequency band. Can be indicated. That is, it may indicate whether the 484-RU has been allocated for the transmission of 40MHz.

For example, if the transmission frequency band is an 80 MHz band, the control identifier (eg, 1-bit identifier) is assigned a single RU corresponding to the entire band of the transmission frequency band (ie, 80 MHz band). Can be indicated. That is, it may indicate whether the 996-RU has been allocated for the transmission of 80MHz.

Various technical effects can be achieved through the control identifier (eg, 1 bit identifier).

First of all, when a single RU corresponding to the entire band of the transmission frequency band is allocated through the control identifier (eg, a 1-bit identifier), it is possible to omit allocation information of the RU. That is, since only one RU is allocated to all bands of the transmission frequency band instead of the plurality of RUs, it is possible to omit allocation information of the RU.

It can also be used as signaling for full-band multi-user full bandwidth MU-MIMO (MIMO). For example, when a single RU is allocated over the full bandwidth of the transmission frequency band, multiple users may be allocated to the single RU. That is, signals for each user are not spatially and spatially distinct, but other techniques (eg, spatial multiplexing) may be used to multiplex the signals for multiple users in the same single RU. Accordingly, the control identifier (eg, 1 bit identifier) may also be used to indicate whether to use the full-band multi-user MIMO as described above.

The common field included in the second control field HE-SIG-B 740 may include an RU allocation subfield. According to the PPDU bandwidth, the common field may include a plurality of RU allocation subfields (including N RU allocation subfields). The format of the common field may be defined as follows.

The RU allocation subfield included in the common field of the HE-SIG-B is configured with 8 bits, and can be indicated as follows for a 20 MHz PPDU bandwidth. The RU allocation to be used in the data portion in the frequency domain indicates the size of the RU and the placement of the RU in the frequency domain as an index. The mapping of the 8-bit RU allocation subfield for the RU allocation and the number of users per RU may be defined as follows.

The user-specific field included in the second control field HE-SIG-B 740 may include a user field, a CRC field, and a tail field. The format of the user-specific field may be defined as follows.

In addition, the user-specific field of the HE-SIG-B is composed of a plurality of user fields. Multiple user fields are located after the common field of the HE-SIG-B. The location of the RU allocation subfield of the common field and the user field of the user-specific field together identify the RU used to transmit data of the STA. Multiple RUs designated as a single STA are not allowed in the user-specific field. Thus, signaling that allows the STA to decode its data is carried in only one user field.

As an example, assume that the RU allocation subfield is indicated by 8 bits of 01000010 indicating that one 26-tone RU is followed by five 26-tone RUs, and that the 106-tone RU includes three user fields. . At this time, the 106-tone RU may support multiplexing of three users. The eight user fields contained in the user-specific fields are mapped to six RUs, the first three user fields are assigned MU-MIMO in the first 106-tone RU, and the remaining five user fields are five 26- It may indicate that it is allocated to each of the tone RU.

The user field included in the user-specific field of the HE-SIG-B may be defined as follows. First, the user field for non-MU-MIMO allocation is as follows.

User fields for MU-MIMO allocation are as follows:

12 is a diagram illustrating an example of a HE TB PPDU. The PPDU of FIG. 12 represents an uplink PPDU transmitted in response to the trigger frame of FIG. 9. At least one STA receiving the trigger frame from the AP may check the common information field and the individual user information field of the trigger frame and simultaneously transmit the HE TB PPDU with the other STA that received the trigger frame.

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

One. CSMA Carrier sense multiple access / collision avoidance (CA)

In IEEE 802.11, the communication is fundamentally different from the wired channel environment because the communication is performed on a shared wireless medium. For example, in a wired channel environment, communication was possible based on carrier sense multiple access / collision detection (CSMA / CD). For example, once a signal is transmitted in Tx, the channel environment does not change so much that Rx does not suffer significant signal attenuation. At this time, if two or more signals collided, detection was possible. This is because the power detected at the Rx stage is instantaneously larger than the power transmitted at Tx. However, in a wireless channel environment, various factors (e.g., attenuation of the signal may be large depending on the distance, or may experience deep fading momentarily), affect the channel, so whether the signal is actually transmitted in Rx or whether there is collision Tx cannot accurately sense carrier. Thus, 802.11 introduced a distributed coordination function (DCF), a carrier sense multiple access / collision avoidance (CSMA / CA) mechanism. This performs a clear channel assessment (CCA) that senses the medium for a certain duration (eg DIFS: DCF inter-frame space) before STAs with data to transmit. At this time, if the medium is idle, the STA can transmit using the medium. However, if the medium is busy, assuming that several STAs are already waiting to use the medium, data can be transmitted after waiting for an additional random backoff period in addition to DIFS. In this case, the random backoff period allows collision avoidance, because assuming that there are multiple STAs for transmitting data, each STA has a different backoff interval value and thus different transmission time. to be. When one STA starts transmission, the other STAs cannot use the medium.

Briefly, the random backoff time and procedure are as follows. When a certain medium changes from busy to idle, several STAs start preparing to send data. At this time, STAs that want to transmit data in order to minimize collision each select a random backoff count and wait for the slot time. The random backoff count is a pseudo-random integer value that selects one of the uniformly distributed values in the [0 CW] range. CW stands for contention window. The CW parameter takes the CWmin value as the initial value, but if the transmission fails, the value is doubled. For example, if an ACK response is not received for a transmitted data frame, collision can be considered. If the CW value has a CWmax value, the CWmax value is maintained until the data transmission is successful, and the data transfer succeeds and is reset to the CWmin value. At this time, CW, CWmin, CWmax is preferable to maintain 2 ⁿ -1 for convenience of implementation and operation. On the other hand, when the random backoff procedure starts, the STA selects a random backoff count in the [0 CW] range and continuously monitors the medium while the backoff slot counts down. In the meantime, if the medium is busy, it stops counting down, and when the medium becomes idle again, it resumes counting down the remaining backoff slots.

2. PHY  procedure

The PHY transmit / receive procedure in Wi-Fi may have a different packet configuration method, but is as follows. It looks like this: For simplicity, we will use only 11n and 11ax as examples, but 11g / ac follows a similar procedure.

That is, the PHY transmit procedure converts a MAC protocol data unit (MPDU) or an A-MPDU (A-MPDU) into a single PSDU (PHY service data unit) at the PHY stage, and preamble and tail bits and padding bits (if necessary). ) Is transmitted by inserting it).

The PHY receive procedure usually looks like this: When energy detection and preamble detection (L / HT / VHT / HE-preamble detection for each Wifi version), the information on PSDU configuration is obtained from PHY header (L / HT / VHT / HE-SIG) to read MAC header and data Read

3.MAC Header

13 illustrates a MAC frame format used in a WLAN system.

The MAC frame format 1310 includes a set of fields that occur in a fixed order in every frame. 13 shows a general MAC frame format. The first three fields (frame control, duration / ID and address 1) and the last field (FCS) of FIG. 13 constitute the minimum frame format and are reserved. It exists in every frame, including types and subtypes. The Address 2, Address 3, Sequence Control, Address 4, QoS Control, HT Control, and Frame Body fields It exists only in certain frame types and subtypes.

13 illustrates a frame control field 1320 included in the MAC frame format.

The first three subfields of the frame control field 1320 are the Protocol Version, Type and Subtype. The remaining subfields of the frame control field may vary according to the settings of the Type and Subtype subfields.

If the value of the Type subfield is not 1 or the value of the Subtype subfield is not 6, the remaining subfields within the frame control field are To DS, From DS, More Fragments, Retry, Power Management, More Data, Protected Frame, and + HTC / Contains the Order subfield. In this case, the format of the frame control field is shown at the bottom of FIG. 13.

If the value of the Type subfield is 1 and the value of the Subtype subfield is 6, the remaining subfields in the frame control field include the Control Frame Extension, Power Management, More Data, Protected Frame, and + HTC / Order subfields. city).

4. A- MPDU (Aggregate MPDU )

14 shows an A-MPDU format used in a WLAN system.

The A-MPDU 1410 is composed of a sequence of one or more A-MPDU subframes and EOF padding having various sizes as shown in FIG. 14.

Figure 14 also shows the structure of the A-MPDU subframe 1420. Each A-MPDU subframe 1420 is optionally comprised of an MPDU delimiter 1440 followed by (following) an MPDU. Each non-final A-MPDU subframe in the A-MPDU added a padding octet to make the subframe a multiple of four octets long. The content of this octet has not been determined.

In the HT PPDU, the final A-MPDU subframe is not padded.

14 also shows an EOF padding field 1430. The EOF padding field is present only in the VHT PPDU.

EOF Padding Subframe The subfield includes zero or more EOF padding subframes. The EOF padding subframe is an A-MPDU subframe having 0 in the MPDU Length field and 1 in the EOF field.

The padding in the VHT PPDU may be determined according to the following rules.

0-3 octets in the padding subfield of the final A-MPDU subframe before the EOF padding subframe (see 1430 of FIG. 14). The contents of this octet are not specified.

0 or more EOF padding subframes in the EOF padding subframe subfield

0-3 octets in the EOF padding octet subfield. The contents of this octet are not specified.

A-MPDU pre-EOF padding corresponds to A-MPDU content that does not include an EOF padding field. A-MPDU pre-EOF padding includes all A-MPDU subframes with 0 in the MPDU Length field and 0 in the EOF field to meet the minimum MPDU start interval requirement.

14 also shows an MPDU delimiter 1440. The MPDU delimiter 1440 has a length of 4 octets, and the MPDU delimiter 1440 of FIG. 14 shows the structure of the MPDU delimiter transmitted by the non-DMG STA. The structure of the MPDU delimiter transmitted by the DMG STA is a structure in which the EOF subfield is removed from the MPDU delimiter transmitted by the non-DMG STA (not shown).

The contents of the MPDU delimiter (1440, non-DMG) can be defined as follows.

5. DSRC (Dedicated Short Range Communications)

The 5.9 GHz DSRC is a short-range, medium-range communications service that supports both public safety and private operations in roadside vehicles and in vehicle-to-vehicle communications. DSRC is intended to complement cellular communications by providing very high data rates in situations where it is important to minimize the latency of the communications link and to isolate relatively small communications areas. The PHY and MAC protocols are also based on the IEEE 802.11p amendment for wireless access in the vehicular environment (WAVE).

<IEEE 802.11p>

802.11p uses 2x down clocking the PHY of 802.11a. That is, the signal is transmitted using 10MHz bandwidth instead of 20MHz bandwidth. Numerology comparing 802.11a and 802.11p is as follows.

	IEEE 802.11a	IEEE 802.11p
Symbol duration	4us	8us
Guard period	0.8us	1.6us
Subcarrier spacing	312.5KHz	156.25KHz
OFDM subcarrier	52	52
Number of pilot	4	4
Default BW	20 MHz	10 MHz
Data rate (Mbps)	6,9,12,18,24,36,48,54 Mbps	3,4.5,6,9,12,18,24,27 Mbps
Frequency band	5 GHz ISM	5.9 GHz dedicated

FIG. 15 shows a band plan of a 5.9 GHz DSRC. A channel of the DSRC band includes a control channel and a service channel, and transmits data at 3, 4.5, 6, 9, 12, 18, 24, and 27 Mbps, respectively. This is possible. If there is an optional channel of 20MHz, transmission of 6,9,12,18,24,36,48,54 Mbps is possible. 6,9,12 Mbps must be supported for all services and channels. For the control channel, the preamble is 3 Mbps, but the message itself is 6 Mbps. Channels 174 and 176, and channels 180 and 182 are channels 175 and 181 at 20 MHz, respectively, when authorized by the frequency coordinator. The rest is reserved for future use. It broadcasts short messages, notification data, and public safety alarm data to all OBUs (On Board Units) via the control channel. The reason for separating the control and service channels is to maximize efficiency and quality of service and to reduce interference between services.

Channel 178 is a control channel. All OBUs automatically search the control channel and receive notifications, data transmissions, and warning messages from the RSU (Road Side Unit). All data on the control channel must be transmitted within 200ms and repeat at predefined intervals. In the control channel, public safety alarms take precedence over all private messages. Private messages larger than 200 ms are sent over the service channel.

Private messages or long public safety messages are transmitted over the service channel. Carrier Sense Multiple Access (CSMA) is used to prevent collisions before transmission.

The following defines EDCA parameters in OCB (Outside Context of BSS) mode. The OCB mode means a state in which direct communication between nodes is possible without a procedure of being associated with an AP. The following shows a set of basic EDCA parameters for STA operation when dot11OCBActivated is true.

The characteristics of the OCB mode are as follows.

In a MAC header, To / From DS fields = 0

Address

Individual or a group destination MAC address

BSSID field = wildcard BSSID

Data / Management frame => Address 1: RA, Address 2: TA, Address 3: wildcard BSSID

Not utilize IEEE 802.11 authentication, association, or data confidentiality services

TXOP limit = 0

Use only TC (TID)

A STA is not required to synchronize to a common clock or to use these mechanisms

-STAs may maintain a TSF timer for purposes other than synchronization

The STA may send Action frames and, if the STA maintains a TSF Timer, Timing Advertisement frames

The STA may send Control frames, except those of subtype PS-Poll, CF-End, and CF-End + CFAck

The STA may send Data frames of subtype Data, Null, QoS Data, and QoS Null

A STA with dot11OCBActivated equal to true shall not join or start a BSS

6. Applicable to the present invention Example

In existing vehicle networks, V2X communication, that is, vehicle-to-vehicle (V2V), which transmits data between vehicles, vehicle-to-infrastructure (V2I), which transmits data between infrastructure such as vehicles and APs, and data between vehicles and pedestrians Vehicle-to-Pedestrian (V2P) which transmits is made. In particular, unlike existing WLAN based infrastructure such as 802.11ac / ax, safety messages between STAs are exchanged through broadcasting for each other for services directly related to safety. However, unlike the service that exchanges small messages such as vehicle information, Next Generation V2X (NGV, 11be), autonomous driving or platening, which exchanges data with large-capacity sensor images / video, etc. There is a need for a method that can improve throughput not only in the PHY layer but also in the MAC layer, because such services cannot exist with the throughput that 802.11p can support. The specification proposes a transmission method that can improve throughput in the next-generation V2X broadcasting service.

As a method for improving throughput in the MAC layer, there is a method of reducing contention delay for channel access, and a method of aggregation of data is representative. This method can reduce the contention delay by reducing the average number of contention of each packet.

6.1 A- for Broadcasting Transmission MPDU

A-MPDU is one of the important WLAN technologies introduced since 802.11n and designated as mandatory from 11ac. However, only the AP can use A-MPDU during packet transmission (MPDU whose group address is RA) using broadcasting, and STAs other than the AP cannot transmit A-MPDU. However, in next-generation V2X communication, in order to support broadcasting service for large data between STAs, A-MPDU must be supported, and the following rules are required.

-In the next generation V2X communication, the STA must support A-MPDU when transmitting a packet having a group address as an RA (that is, broadcasting or multicasting).

The 10 MHz / 20 MHz NGV PPDU including the A-MPDU may be basically as shown in FIG. 16 including the NGV-SIG, the NGV-STF, and the NGV-LTF.

16 illustrates a 10 MHz / 20 MHz NGV PPDU format including an A-MPDU according to this embodiment.

The 10 MHz / 20 MHz NGV PPDU format of FIG. 16 is one example, but is not limited thereto. As another example, a Repeated Non-HT SIGNAL (RL-SIG) may be inserted between the L-Part and the NGV SIG. In addition, the NGV-STF may not be included in the format, and the NGV-LTF may be periodically inserted into the PSDU of FIG. 16. In FIG. 16, L-STF is a Non-HT Short Training Field, L-LTF is a Non-HT Long Training Field, L-SIG is a non-HT SIGNAL field, D is a Delimiter, and Hdr is a Header.

In the next generation V2X communication, the format for the existing A-MPDU, that is, the A-MPDU format corresponding to the PSDU of FIG. 16 may be changed to reduce latency for A-MPDU transmission. The A-MPDU may be configured by removing all or some fields of the MAC header included in all or some MPDUs except the MAC header of the most recently transmitted MPDU.

1) When all or part of the MDPU does not include a MAC header except for the 1st MPDU (FIG. 17)

17 shows an example of a format in which an A-MPDU is changed in the manner of Embodiment 1).

-> By removing some MAC headers from the existing A-MPDU format, more data aggregation can reduce the packet length more than the existing format.

In the case of 1), the presence or absence of a MAC header must be identified in the MAC, and this indication method can use the reserved bit (Rb) of the delimiter. For example, as shown in FIG. 17, if Rb = 1, the MAC header exists. If Rb = 0, the MAC header does not exist. If the location information on the MAC header is negotiated or set in advance, Rb may not be used.

In addition, when an error occurs in the MAC header in FIG. 17, since the information on the data of all the MPDUs sequentially connected without including the MAC header is lost, the corresponding MPDU cannot be decoded. Therefore, for robust transmission of MPDU including MAC header, PCS can adjust and encode MCS for MPDU including header differently from MPDU without header. Information on this can be indicated by the NGV SIG, and the indication information and method are as follows.

Starting symbol offset: Starting point of MPDU including each MAC header (unit of symbol)

-Ending symbol offset: End point of MPDU including each MAC header (unit of symbol)

MCS: MCS information about the MPDU corresponding to each symbol offset

1-1) Indicate only Starting / Ending Symbol offset

-It can be used after negotiating encoding MCS for MPDU including header (eg MCS 0).

The starting symbol offset may not be indicated for the 1st MPDU.

1-2) Indicating Starting / Ending symbol offset and corresponding MCS information

-Depending on the situation, you can adjust the MCS for the MPDU. For example, on a fairly stable channel, you can send higher MCS.

The starting symbol offset may not be indicated for the 1st MPDU.

2) When all or part of the MDPU except for the 1st MPDU includes a P-MAC header (if not included, no header exists) (FIG. 18)

18 shows an example of a format in which A-MPDU is changed in the manner of Embodiment 2).

This partial field may consist of the following fields, but is not limited thereto.

QoS Control field: can utilize Multi-TID (Traffic ID)

-Sequence Control field: can utilize sequence number

-NGV Control field: It can be included if the technology for next generation V2X is supported and can utilize existing HT control field. Also included in MAC header

This method can be distinguished through the partial field if there is information that must be distinguished between MSDUs.

In the case of 2), the presence or absence of the P-MAC header in the MAC should be known, and this indication method may use the reserved bit (Rb) of the delimiter. For example, as shown in FIG. 18, if Rb = 1, the P-MAC header exists. If Rb = 0, the P-MAC header does not exist. If the location information on the MAC header is negotiated or set in advance, Rb may not be used.

In addition, similarly, when an error occurs in the header in FIG. 18, since the information on the data of all the MPDUs sequentially connected without including the header is lost, the corresponding MPDU cannot be decoded. Therefore, the MCS for the MPDU including the header may be adjusted and encoded differently from the MPDUs without the header for the robust transmission of the MPDU including the header. Information on this can be indicated by the NGV SIG, and the indication information and method are as follows.

Starting symbol offset: Starting point of MPDU including each header (unit of symbol)

-Ending symbol offset: End point of MPDU including each header (unit of symbol)

MCS: MCS information about the MPDU corresponding to each symbol offset

2-1) Indicating only Starting / Ending Symbol offset

-It can be used after negotiating encoding MCS for MPDU including header (eg MCS 0).

The starting symbol offset may not be indicated for the 1st MPDU.

2-2) Indication of Starting / Ending symbol offset and corresponding MCS information

-Depending on the situation, you can adjust the MCS for the MPDU. For example, on a fairly stable channel, you can send a higher MCS.

The starting symbol offset may not be indicated for the 1st MPDU.

3) When all or part of the MDPU except the 1st MPDU includes the P-MAC header, if not included, the MAC header is included (FIG. 19).

Fig. 19 shows an example of a format in which A-MPDU is changed in the manner of Example 3).

This partial field may consist of the following fields, but is not limited thereto.

QoS Control field: can utilize Multi-TID

-Sequence Control field: can utilize sequence number

-NGV Control field: It can be included if the technology for next generation V2X is supported and can utilize existing HT control field. Also included in MAC header

In the case of 3), the location of the P-MAC header in the MAC should be known, and this indication method may use the reserved bit (Rb) of the delimiter. For example, as shown in FIG. 19, if Rb = 1, a P-MAC header exists, and if Rb = 0, a MAC header exists. If the header location information is negotiated or configured in advance, Rb may not be used.

 Also, in the method of 3), 2-1) and 2-2) of the PHY can be used for robust transmission of the MAC header.

Hereinafter, the above-described embodiment will be described with reference to FIGS. 13 to 19.

20 is a flowchart illustrating a procedure of transmitting a PPDU in the transmitting apparatus according to the present embodiment.

20 may be performed in a network environment in which a next generation WLAN system is supported. The next generation WLAN system is a WLAN system that improves the 802.11p system and may satisfy backward compatibility with the 802.11p system. The next generation WLAN system may be referred to as NGV (Next Generation V2X) or 802.11be.

An example of FIG. 20 is performed by a transmitter, and the transmitter may correspond to an AP supporting an NGV or 802.11be WLAN system. The receiving device of FIG. 20 may correspond to an STA supporting an NGV or 802.11be WLAN system.

In operation S2010, the transmitting apparatus generates a PPDU including an Aggregated-MAC Protocol Data Unit (A-MPDU).

In step S2020, the transmitting device transmits the PPDU to the receiving device.

The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU. This is just one embodiment, and the A-MPDU may be aggregated with a plurality of MPDUs.

The first MPDU includes a first delimiter field, a first MAC header, and a first data field. The second MPDU includes a second delimiter field and a second data field. The third MPDU includes a third delimiter field and a third data field. The first MPDU may be transmitted first of the MPDUs included in the A-MPDU. That is, the first MPDU transmitted may always include a MAC header.

The second delegate field includes information on whether a second MAC header is included in the second MPDU. The third delimiter field includes information on whether a third MAC header is included in the third MPDU. It may be assumed that the second MPDU is transmitted after the first MPDU, and the third MPDU is transmitted after the second MPDU. That is, the MPDUs other than the first transmitted MPDU may or may not include the MAC header based on the delimiter field.

For example, when the reserved bit of the second delimiter field is 1, the second MAC header may be included in the second MPDU. If the reserved bit of the third delimiter field is 0, the third MAC header may not be included in the third MPDU. As a result, by removing some MAC headers from the existing A-MPDU, the aggregated amount of data can reduce the length of the packet compared to the existing A-MPDU.

In addition, when the reserved bit of the third delimiter field is 0, the third MAC header may not include the third MAC header and the first MAC header may be included.

Hereinafter, the second MPDU including the MAC header will be described.

The second MAC header may be configured as a partial field of the first MAC header. The first MAC header may include a frame control field, a duration / ID field, an address 1 field, an address 2 field, an address 3 field, a sequence control field, a QoS control field, an HT control field, a frame body field, and an FCS field. . The second MAC header may consist of only some of the fields constituting the first MAC header.

For example, the second MAC header may include a Quality of Service (QoS) control field, a sequence control field, and a Next Generation Vehicle-to-Everything (NGV) control field.

The QoS control field may include information on a traffic identification (TID) of the second MPDU. The sequence control field may include information about a sequence number of the second MPDU. The NGV control field may include information that the second MPDU supports NGV.

The PPDU may further include an NGV-SIG (signal) field.

The NGV-SIG field may include a start symbol offset, an end symbol offset, and MCS (Modulation and Coding Scheme) information.

The start symbol offset may include information about a symbol at which the first and second MPDUs start. The end symbol offset may include information about a symbol at which the first and second MPDUs are terminated. The MCS information may include MCSs for the first and second MPDUs.

For robust transmission of MPDUs with MAC headers, MPDUs with MAC headers and MPDUs without MAC headers can be encoded with different MCS adjustments. The symbol offset and MCS of the MPDU including the MAC header may be indicated in the NGV-SIG field. However, the NGV-SIG field may not include information on a symbol at which the first MPDU starts.

In addition, the MCS for the first and second MPDU may be negotiated in advance between the transmitter and the receiver.

The PPDU may further include a legacy preamble, a Short Training Field (NGV-STF) field, and a Long Training Field (NGV-LTF) field. The legacy preamble may be supported by an 802.11p WLAN system. The NGV-SIG field, the NGV-STF field, and the NGV-LTF field may be supported by an 802.11be WLAN system.

The PPDU may be transmitted through a 10 MHz or 20 MHz band. When the PPDU is transmitted through the 20 MHz band, the legacy preamble and the NGV-SIG field may be duplicated in units of 10 MHz band.

21 is a flowchart illustrating a procedure of receiving a PPDU in the receiving apparatus according to the present embodiment.

21 may be performed in a network environment in which a next generation WLAN system is supported. The next generation WLAN system is a WLAN system that improves the 802.11p system and may satisfy backward compatibility with the 802.11p system. The next generation WLAN system may be referred to as NGV (Next Generation V2X) or 802.11be.

An example of FIG. 21 is performed in a receiving apparatus, and the receiving apparatus may correspond to an STA supporting an NGV or 802.11be WLAN system. The transmitter of FIG. 20 may correspond to an AP supporting an NGV or 802.11be WLAN system.

In step S2110, the receiving device receives a PPDU including an Aggregated-MAC Protocol Data Unit (A-MPDU) from the transmitting device.

In step S2120, the receiver decodes the PPDU.

The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU. This is just one embodiment, and the A-MPDU may be aggregated with a plurality of MPDUs.

The first MPDU includes a first delimiter field, a first MAC header, and a first data field. The second MPDU includes a second delimiter field and a second data field. The third MPDU includes a third delimiter field and a third data field. The first MPDU may be transmitted first of the MPDUs included in the A-MPDU. That is, the first MPDU transmitted may always include a MAC header.

The second delegate field includes information on whether a second MAC header is included in the second MPDU. The third delimiter field includes information on whether a third MAC header is included in the third MPDU. It may be assumed that the second MPDU is transmitted after the first MPDU, and the third MPDU is transmitted after the second MPDU. That is, the MPDUs other than the first transmitted MPDU may or may not include the MAC header based on the delimiter field.

For example, when the reserved bit of the second delimiter field is 1, the second MAC header may be included in the second MPDU. If the reserved bit of the third delimiter field is 0, the third MAC header may not be included in the third MPDU. As a result, by removing some MAC headers from the existing A-MPDU, the aggregated amount of data can reduce the length of the packet compared to the existing A-MPDU.

In addition, when the reserved bit of the third delimiter field is 0, the third MAC header may not include the third MAC header and the first MAC header may be included.

Hereinafter, the second MPDU including the MAC header will be described.

The second MAC header may be configured as a partial field of the first MAC header. The first MAC header may include a frame control field, a duration / ID field, an address 1 field, an address 2 field, an address 3 field, a sequence control field, a QoS control field, an HT control field, a frame body field, and an FCS field. . The second MAC header may consist of only some of the fields constituting the first MAC header.

For example, the second MAC header may include a Quality of Service (QoS) control field, a sequence control field, and a Next Generation Vehicle-to-Everything (NGV) control field.

The QoS control field may include information on a traffic identification (TID) of the second MPDU. The sequence control field may include information about a sequence number of the second MPDU. The NGV control field may include information that the second MPDU supports NGV.

The PPDU may further include an NGV-SIG (signal) field.

The NGV-SIG field may include a start symbol offset, an end symbol offset, and MCS (Modulation and Coding Scheme) information.

The start symbol offset may include information about a symbol at which the first and second MPDUs start. The end symbol offset may include information about a symbol at which the first and second MPDUs are terminated. The MCS information may include MCSs for the first and second MPDUs.

For robust transmission of MPDUs with MAC headers, MPDUs with MAC headers and MPDUs without MAC headers can be encoded with different MCS adjustments. The symbol offset and MCS of the MPDU including the MAC header may be indicated in the NGV-SIG field. However, the NGV-SIG field may not include information on a symbol at which the first MPDU starts.

In addition, the MCS for the first and second MPDU may be negotiated in advance between the transmitter and the receiver.

The PPDU may further include a legacy preamble, a Short Training Field (NGV-STF) field, and a Long Training Field (NGV-LTF) field. The legacy preamble may be supported by an 802.11p WLAN system. The NGV-SIG field, the NGV-STF field, and the NGV-LTF field may be supported by an 802.11be WLAN system.

The PPDU may be transmitted through a 10 MHz or 20 MHz band. When the PPDU is transmitted through the 20 MHz band, the legacy preamble and the NGV-SIG field may be duplicated in units of 10 MHz band.

6. Device Configuration

FIG. 22 is a diagram for describing an apparatus for implementing the method as described above.

The wireless device 100 of FIG. 22 is a transmission device capable of implementing the above-described embodiment and may operate as an AP STA. The wireless device 150 of FIG. 21 is a receiving device capable of implementing the above-described embodiment and may operate as a non-AP STA.

The transmitter 100 may include a processor 110, a memory 120, and a transceiver 130, and the receiver device 150 may include a processor 160, a memory 170, and a transceiver 180. can do. The transceiver 130 and 180 may transmit / receive a radio signal and may be executed in a physical layer such as IEEE 802.11 / 3GPP. The processors 110 and 160 are executed in the physical layer and / or the MAC layer and are connected to the transceivers 130 and 180.

The processors 110 and 160 and / or the transceivers 130 and 180 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processors. The memory 120, 170 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage unit. When an embodiment is executed by software, the method described above can be executed as a module (eg, process, function) that performs the functions described above. The module may be stored in the memories 120 and 170 and may be executed by the processors 110 and 160. The memories 120 and 170 may be disposed inside or outside the processes 110 and 160, and may be connected to the processes 110 and 160 by well-known means.

The processors 110 and 160 may implement the functions, processes, and / or methods proposed herein. For example, the processors 110 and 160 may perform operations according to the above-described embodiment.

The operation of the processor 110 of the transmitter is specifically as follows. The processor 110 of the transmitting device generates a PPDU including the A-MPDU and transmits the PPDU to the receiving device.

The operation of the processor 160 of the receiving apparatus is as follows. The processor 160 of the receiving device receives the PPDU including the A-MPDU and decodes the PPDU.

23 illustrates a more detailed wireless device implementing an embodiment of the present invention. The present invention described above with respect to the transmitting apparatus or the receiving apparatus can be applied to this embodiment.

The wireless device includes a processor 610, a power management module 611, a battery 612, a display 613, a keypad 614, a subscriber identification module (SIM) card 615, a memory 620, a transceiver 630. ), One or more antennas 631, speakers 640, and microphones 641.

Processor 610 may be configured to implement the proposed functions, procedures, and / or methods described herein. Layers of the air interface protocol may be implemented in the processor 610. The processor 610 may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and / or a data processing device. The processor may be an application processor (AP). The processor 610 may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), and a modem (modulator and demodulator). Examples of processor 610 include SNAPDRAGONTM series processors manufactured by Qualcomm®, EXYNOSTM series processors manufactured by Samsung®, A Series processors manufactured by Apple®, HELIOTM series processors manufactured by MediaTek®, INTEL® It may be an ATOMTM series processor or a corresponding next generation processor manufactured by.

The power management module 611 manages power of the processor 610 and / or the transceiver 630. The battery 612 supplies power to the power management module 611. The display 613 outputs the result processed by the processor 610. Keypad 614 receives input to be used by processor 610. Keypad 614 may be displayed on display 613. SIM card 615 is an integrated circuit used to securely store an international mobile subscriber identity (IMSI) and its associated keys used to identify and authenticate subscribers in mobile phone devices such as mobile phones and computers. You can also store contact information on many SIM cards.

The memory 620 is operatively coupled with the processor 610 and stores various information for operating the processor 610. The memory 620 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and / or other storage device. When an embodiment is implemented in software, the techniques described herein may be implemented as modules (eg, procedures, functions, etc.) that perform the functions described herein. The module may be stored in the memory 620 and executed by the processor 610. The memory 620 may be implemented inside the processor 610. Alternatively, the memory 620 may be implemented outside the processor 610 and communicatively connected to the processor 610 through various means known in the art.

The transceiver 630 is operatively coupled with the processor 610 and transmits and / or receives a radio signal. The transceiver 630 includes a transmitter and a receiver. The transceiver 630 may include a baseband circuit for processing radio frequency signals. The transceiver controls one or more antennas 631 to transmit and / or receive wireless signals.

The speaker 640 outputs a sound related result processed by the processor 610. The microphone 641 receives a sound related input to be used by the processor 610.

In the case of a transmitter, the processor 610 generates a PPDU including an A-MPDU and transmits the PPDU to a receiver.

In the case of a receiving device, the processor 610 of the receiving device receives a PPDU including an A-MPDU and decodes the PPDU.

The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU. This is just one embodiment, and the A-MPDU may be aggregated with a plurality of MPDUs.

The first MPDU includes a first delimiter field, a first MAC header, and a first data field. The second MPDU includes a second delimiter field and a second data field. The third MPDU includes a third delimiter field and a third data field. The first MPDU may be transmitted first of the MPDUs included in the A-MPDU. That is, the first MPDU transmitted may always include a MAC header.

The second delegate field includes information on whether a second MAC header is included in the second MPDU. The third delimiter field includes information on whether a third MAC header is included in the third MPDU. It may be assumed that the second MPDU is transmitted after the first MPDU, and the third MPDU is transmitted after the second MPDU. That is, the MPDUs other than the first transmitted MPDU may or may not include the MAC header based on the delimiter field.

For example, when the reserved bit of the second delimiter field is 1, the second MAC header may be included in the second MPDU. If the reserved bit of the third delimiter field is 0, the third MAC header may not be included in the third MPDU. As a result, by removing some MAC headers from the existing A-MPDU, the aggregated amount of data can reduce the length of the packet compared to the existing A-MPDU.

In addition, when the reserved bit of the third delimiter field is 0, the third MAC header may not include the third MAC header and the first MAC header may be included.

Hereinafter, the second MPDU including the MAC header will be described.

The second MAC header may be configured as a partial field of the first MAC header. The first MAC header may include a frame control field, a duration / ID field, an address 1 field, an address 2 field, an address 3 field, a sequence control field, a QoS control field, an HT control field, a frame body field, and an FCS field. . The second MAC header may consist of only some of the fields constituting the first MAC header.

For example, the second MAC header may include a Quality of Service (QoS) control field, a sequence control field, and a Next Generation Vehicle-to-Everything (NGV) control field.

The QoS control field may include information on a traffic identification (TID) of the second MPDU. The sequence control field may include information about a sequence number of the second MPDU. The NGV control field may include information that the second MPDU supports NGV.

The PPDU may further include an NGV-SIG (signal) field.

The NGV-SIG field may include a start symbol offset, an end symbol offset, and MCS (Modulation and Coding Scheme) information.

The start symbol offset may include information about a symbol at which the first and second MPDUs start. The end symbol offset may include information about a symbol at which the first and second MPDUs are terminated. The MCS information may include MCSs for the first and second MPDUs.

For robust transmission of MPDUs with MAC headers, MPDUs with MAC headers and MPDUs without MAC headers can be encoded with different MCS adjustments. The symbol offset and MCS of the MPDU including the MAC header may be indicated in the NGV-SIG field. However, the NGV-SIG field may not include information on a symbol at which the first MPDU starts.

In addition, the MCS for the first and second MPDU may be negotiated in advance between the transmitter and the receiver.

The PPDU may further include a legacy preamble, a Short Training Field (NGV-STF) field, and a Long Training Field (NGV-LTF) field. The legacy preamble may be supported by an 802.11p WLAN system. The NGV-SIG field, the NGV-STF field, and the NGV-LTF field may be supported by an 802.11be WLAN system.

The PPDU may be transmitted through a 10 MHz or 20 MHz band. When the PPDU is transmitted through the 20 MHz band, the legacy preamble and the NGV-SIG field may be duplicated in units of 10 MHz band.

Claims (15)

1. In the method for transmitting a PHY protocol data unit (PPDU) in a WLAN system,

   Generating, by the transmitting device, a PPDU including an Aggregated-MAC Protocol Data Unit (A-MPDU); And

   Transmitting, by the transmitter, the PPDU to a receiver;

   The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU.

   The first MPDU includes a first delimiter field, a first MAC header and a first data field.

   The second MPDU includes a second delimiter field and a second data field,

   The third MPDU includes a third delimiter field and a third data field,

   The second delegate field includes information about whether a second MAC header is included in the second MPDU, and

   The third delimiter field includes information on whether a third MAC header is included in the third MPDU.

   Way.
2. The method of claim 1,

   If the reserved bit of the second delimiter field is 1, the second MPDU includes the second MAC header,

   If the reserved bit of the third delimiter field is 0, the third MPDU does not include the third MAC header.

   Way.
3. The method of claim 2,

   If the reserved bit of the third delimiter field is 0, the third MPDU does not include the third MAC header and the first MAC header is included.

   Way.
4. The method of claim 2,

   The second MAC header is composed of a partial field of the first MAC header,

   The second MAC header includes a Quality of Service (QoS) control field, a sequence control field, and a Next Generation Vehicle-to-Everything (NGV) control field.

   The QoS control field includes information about a traffic identification (TID) of the second MPDU,

   The sequence control field includes information about a sequence number of the second MPDU,

   The NGV control field includes information indicating that the second MPDU supports NGV.

   Way.
5. The method of claim 2,

   The PPDU further includes an NGV-SIG (signal) field.

   The NGV-SIG field includes a start symbol offset, an end symbol offset, and modulation and coding scheme (MCS) information.

   The start symbol offset includes information on a symbol at which the first and second MPDUs begin;

   The end symbol offset includes information on a symbol at which the first and second MPDUs end;

   The MCS information includes MCSs for the first and second MPDUs.

   Way.
6. The method of claim 5,

   The MCS for the first and second MPDUs is negotiated in advance between the transmitter and the receiver.

   Way.
7. The method of claim 5,

   The PPDU further includes a legacy preamble, a Short Training Field (NGV-STF) field, and a Long Training Field (NGV-LTF) field,

   The legacy preamble is supported 802.11p WLAN system,

   The NGV-SIG field, the NGV-STF field and the NGV-LTF field are supported by an 802.11be WLAN system,

   The PPDU is transmitted through a 10 MHz or 20 MHz band,

   When the PPDU is transmitted through a 20 MHz band, the legacy preamble and the NGV-SIG field are duplicated in units of 10 MHz band.

   Way.
8. In the transmitter for transmitting a PHY protocol data unit (PPDU) in a wireless LAN system, the transmitter,

   Memory;

   Transceiver; And

   A processor operatively coupled with the memory and the transceiver, the processor comprising:

   Generate a PPDU including an Aggregated-MAC Protocol Data Unit (A-MPDU); And

   Transmit the PPDU to a receiving device;

   The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU.

   The first MPDU includes a first delimiter field, a first MAC header and a first data field.

   The second MPDU includes a second delimiter field and a second data field,

   The third MPDU includes a third delimiter field and a third data field,

   The second delegate field includes information about whether a second MAC header is included in the second MPDU, and

   The third delimiter field includes information on whether a third MAC header is included in the third MPDU.

   Transmitter.
9. The method of claim 8,

   If the reserved bit of the second delimiter field is 1, the second MPDU includes the second MAC header,

   If the reserved bit of the third delimiter field is 0, the third MPDU does not include the third MAC header.

   Transmitter.
10. The method of claim 9,

    If the reserved bit of the third delimiter field is 0, the third MPDU does not include the third MAC header and the first MAC header is included.

    Transmitter.
11. The method of claim 9,

    The second MAC header is composed of a partial field of the first MAC header,

    The second MAC header includes a Quality of Service (QoS) control field, a sequence control field, and a Next Generation Vehicle-to-Everything (NGV) control field.

    The QoS control field includes information about a traffic identification (TID) of the second MPDU,

    The sequence control field includes information about a sequence number of the second MPDU,

    The NGV control field includes information indicating that the second MPDU supports NGV.

    Transmitter.
12. The method of claim 9,

    The PPDU further includes an NGV-SIG (signal) field.

    The NGV-SIG field includes a start symbol offset, an end symbol offset, and modulation and coding scheme (MCS) information.

    The start symbol offset includes information on a symbol at which the first and second MPDUs begin;

    The end symbol offset includes information on a symbol at which the first and second MPDUs end;

    The MCS information includes MCSs for the first and second MPDUs.

    Transmitter.
13. The method of claim 12,

    The MCS for the first and second MPDUs is negotiated in advance between the transmitter and the receiver.

    Transmitter.
14. The method of claim 12,

    The PPDU further includes a legacy preamble, a Short Training Field (NGV-STF) field, and a Long Training Field (NGV-LTF) field,

    The legacy preamble is supported 802.11p WLAN system,

    The NGV-SIG field, the NGV-STF field and the NGV-LTF field are supported by an 802.11be WLAN system,

    The PPDU is transmitted through a 10 MHz or 20 MHz band,

    When the PPDU is transmitted through a 20 MHz band, the legacy preamble and the NGV-SIG field are duplicated in units of 10 MHz band.

    Transmitter.
15. In the method for receiving a PHY protocol data unit (PPDU) in a WLAN system,

    Receiving, by the receiving device, a PPDU including an Aggregated-MAC Protocol Data Unit (A-MPDU) from the transmitting device; And

    Decoding, by the receiving device, the PPDU;

    The A-MPDU is generated by aggregating a first MAC Protocol Data Unit (MPDU), a second MPDU, and a third MPDU.

    The first MPDU includes a first delimiter field, a first MAC header and a first data field.

    The second MPDU includes a second delimiter field and a second data field,

    The third MPDU includes a third delimiter field and a third data field,

    The second delegate field includes information about whether a second MAC header is included in the second MPDU, and

    The third delimiter field includes information on whether a third MAC header is included in the third MPDU.

    Way.

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