WO2020032431A1 - Method and device for transmitting ppdu in wireless lan system - Google Patents

Abstract

A method and a device for transmitting a PPDU in a wireless LAN system are presented. Specifically, a transmitter generates a first PPDU and transmits the first PPDU to a receiver. The first PPDU includes a plurality of second PPDUs. An NDP and an NGV-SIG are additionally transmitted after a third PPDU, which is the first PPDU transmitted from among the plurality of second PPDUs. The first PPDU supports an NGV or an 802.11bd system. The plurality of second PPDUs support an 802.11p system.

Description

Method and apparatus for transmitting PPDU in WLAN system

The present specification relates to a technique for transmitting a PPDU in a WLAN system, and more particularly, to a method and apparatus for configuring an NGV PPDU to allow 802.11p and NGV to interoperate 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 Electronic and Electronics Engineers (IEEE) 802.11 physical 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 next-generation WLAN is a dense environment with many access points and STAs, 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 technologies 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.

One 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 802.11bd.

This embodiment may be performed in a transmitter, and the transmitter may correspond to an AP. The receiving apparatus of this embodiment may correspond to an NGV STA supporting an NGV or 802.11bd system or an 11p STA supporting an 802.11p system.

This embodiment proposes a method for satisfying interoperability between a newly proposed NGV or 802.11bd WLAN system and a legacy 802.11p system. Specifically, the present embodiment proposes a method of configuring an NGV PPDU that can be decoded by both the NGV STA and the 11p STA.

The transmitter generates a first PPDU.

The transmitter transmits the first PPDU to a receiver.

The first PPDU includes a plurality of second PPDUs. The plurality of second PPDUs may be connected continuously or at a predetermined interval. That is, the first PPDU may be defined as an A-MPDU format in which the plurality of second PPDUs are aggregated. The predetermined interval may be a short inter frame space (SIFS).

In addition, the first PPDU supports an NGV or 802.11bd system, and the plurality of second PPDUs supports an 802.11p system. That is, the first PPDU is defined in the NGV PPDU format, and the plurality of second PPDUs are defined in the 802.11p PPDU format.

NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added after the third PPDU transmitted first of the plurality of second PPDUs. An embodiment of adding an NDP and an NGV-SIG to the first PPDU (NGV PPDU format) in order to satisfy an interoperability between an NGV system and an 802.11p system is provided. When receiving the first PPDU, the receiver may regard the NGV-SIG as a BUSY signal and may decode again when it finds the STF of the second 11p PPDU that is transmitted after the NGV-SIG. .

The NDP may include a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), and a first Legacy-Signal (L-SIG). The L-STF and the L-LTF may be used to perform channel estimation of the channel through which the third PPDU is transmitted.

When the receiving device is an NGV STA, the receiving device may check information to be described later by decoding the NGV-SIG. The reason for adding the NDP to the first PPDU is as follows. If only the NGV-SIG is added to the first PPDU without the NDP, if the receiver fails to receive the third PPDU, the NGV-SIG may not be decoded. However, when the NDP is added to the first PPDU, the reception apparatus decodes the NGV-SIG based on the estimated channel by decoding the NDP and estimating a channel even if the reception of the third PPDU fails. can do.

The first L-SIG may include a first LEGNTH field. The first LENGTH field may include information on the length from a point at which transmission of the first PPDU starts to a point at which transmission of the NGV-SIG ends. That is, the receiving device can decode the first L-SIG of the NDP to know the length from the start of the first PPDU to the NGV-SIG.

The NDP may be connected to the third PPDU continuously or at predetermined intervals. That is, the NDP may be continuously aggregated to the 11p PPDU transmitted first of the plurality of second PPDUs or may be aggregated at a predetermined interval. The predetermined interval may be SIFS.

Information included in the NGV-SIG is as follows.

The NGV-SIG may include a Number of PPDUs (NP) field and a Different Data Present (DDP) field.

The NP field may include information on the number of the plurality of second PPDUs, and the DDP field may include a bitmap indicating whether data included in each of the plurality of second PPDUs is the same. The bitmap may be determined based on the number of the plurality of second PPDUs. For example, if the number of the plurality of second PPDUs is a total of six, whether the data included in each of the plurality of second PPDUs is equal to each other is determined as a 5-bit bitmap since information on the first 11p PPDU is unnecessary. Can be set. Specifically, when the NP field is set to 101, it can be seen that the total number of second PPDUs is six. If the DDP field is set to 01010, the second 11p PPDU has the same data as the first 11p PPDU (set to 0), and the third 11p PPDU has different data from the second 11p PPDU (set to 1). Can be indicated. Similarly, the fourth, fifth, and sixth PPDUs may be identified by the DDP field whether they have the same data as the previous 11p PPDU or other data.

The plurality of second PPDUs may each include a second legacy-signal (L-SIG) and data. The second L-SIG may include a second LENGTH field including information on the length of each of the plurality of PPDUs.

When the NGV-SIG is added and transmitted after some of the plurality of second PPDUs, the NGV-SIG may include a Next Different Data Location (NDDL) field and an End of PPDU (EoP) field. Data included in the some PPDUs may be different.

The NDDL field may include information on the location of the partial PPDU. The EoP field may include information on the existence of the last PPDU of the partial PPDUs.

When the NGV-SIG is added to the remaining PPDUs except for the last PPDU among the plurality of second PPDUs and transmitted, respectively, the NGV-SIG may include a Next Different Data Present (NDDP) field and an EoP field.

The NDDP field may include information on whether data included in adjacent PPDUs among the plurality of second PPDUs are the same. The EoP field may include information on the presence of the last PPDU among the plurality of second PPDUs.

The NGV-SIG field includes bandwidth, Modulation and Coding Scheme (MCS), Dual Carrier Modulation (DCM), Number of Space Time Streams (NSTS), midamble, doppler, and Space Time Block Coding (STBC). The information may further include information about coding, a low density parity check (LDPC) additional symbol, a cyclonic redundancy check (CRC), and a tail bit.

The bandwidth information may include information that the WLAN system supports a 10 MHz or 20 MHz band. The information on the MCS may include information supported by the WLAN system up to 256 QAM. The information on the coding may include information that the WLAN system supports Binary Convolutional Codes (BCC) or LDPC.

In addition, the first PPDU may further include an NGV-STF field and an NGV-LTF field.

According to the embodiment proposed in the present specification, NGV PPDUs can be configured to allow 802.11p and NGV to interoperate, thereby eliminating interference with each other, improving throughput, and ensuring fast communication speed.

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 a 5.9 GHz DSRC.

16 shows a frame format of an 802.11p system.

17 shows an example of the NGV PPDU format.

18 shows an example of an NGV PPDU format in which an NGV SIG is added only after the first 11p PPDU.

FIG. 19 shows an example of an NGV PPDU format in which an NDP is added to the NGV PPDU of FIG. 18.

20 shows an example of an NGV SIG field including only an NP field.

21 shows an example of an NGV SIG field including an NP field and a DDP field.

FIG. 22 illustrates an example of performing A-2) in the NGV PPDU including the NGV SIG field of FIG. 21.

FIG. 23 shows an example of an NGV PPDU format in which an NGV SIG is added after some 11p PPDUs.

FIG. 24 shows an example of an NGV PPDU format in which an NDP is added to the NGV PPDU of FIG. 23.

25 shows an example of an NGV SIG field including an NDDL field and an EoP field.

FIG. 26 illustrates an example of performing a method B in an NGV PPDU including the NGV SIG field of FIG. 25.

27 shows an example of an NGV PPDU format in which NGV SIG is added after every 11p PPDU.

FIG. 28 shows an example of an NGV PPDU format in which an NDP is added to the NGV PPDU of FIG. 27.

29 shows an example of an NGV SIG field including an NDDP field and an EoP field.

FIG. 30 illustrates an example of performing a C method in an NGV PPDU including the NGV SIG field of FIG. 29.

31 shows an example of using additional tones in the L-SIG.

32 shows an example of an NGV PPDU format for inserting a sequence.

33 shows an example of an NGV PPDU format in which a sequence is inserted only after the first 11p PPDU.

34 shows an example of an NGV PPDU format in which a sequence is inserted after all 11p PPDUs.

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

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

37 is a diagram for explaining an apparatus for implementing the method as described above.

38 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 STAs 103-1 and 105-2 that can be coupled 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) to another network (eg, 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 are not allowed to access a distributed system, and thus are self-contained. network).

A STA is any functional medium that includes medium access control (MAC) and physical layer interface to a wireless medium that is compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. 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, 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 is 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 there may be 26 units corresponding to each of 13 tones 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, ie 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, that is, 26-RU, 52-RU, 106-RU, 242-RU, etc., have been proposed. Since the specific sizes of such 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. You can also use 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 repeated 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 for MCS ( field indicating whether the module is modulated by a dual subcarrier modulation scheme, 7) a field indicating the number of symbols used for the HE-SIG-B, and 8) a field indicating whether the HE-SIG-B is generated over the entire band. Field, 9) a field indicating the number of symbols in the HE-LTF, 10) a field indicating the length and the CP length of the HE-LTF, 11) a field indicating whether additional OFDM symbols exist for LDPC coding, 12) A field indicating control information regarding a packet extension (PE), and 13) a field indicating information on a CRC field of 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 (ie, the fourth frequency band) of the 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, the 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 the first field of the HE PPDU, and a subcarrier space of 78.125 kHz may be applied to the 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, the interface may be inconsistent. 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, when 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 represented by the term uplink PPDU, uplink frame, and uplink data.

In the WLAN system to which the present embodiment is applied, the entire bandwidth may be used for downlink transmission to one STA and uplink transmission of 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 can 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 for a plurality of STAs to 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. 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 allocated frequency resources. The transmission method through these 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. Therefore, the STA can transmit the frame only through the primary channel, thereby being restricted 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 this embodiment, to solve this problem, a wireless LAN system supporting the OFDMA technology is disclosed. 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 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 can 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 corresponding 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 configuration 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 a receiving STA of a 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 the corresponding trigger frame, and the common information field 950 is common 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 per user information fields 960 # 1 to 960 # N corresponding to the number of receiving STAs receiving the trigger frame of FIG. 9. 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 the HE single stream pilot HE-LTF mode or the HE masked HE-LTF sequence mode. It is directed to either.

If the trigger frame does not allocate an RU that occupies 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 a per 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 a 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 RU 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. 4-6, RUs of various sizes may be used. These RUs can be largely divided into two types of RUs. For example, all of the RUs shown in FIGS. 4 to 6 may be divided 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 to 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 (ie, 80 MHz band) of the transmission frequency 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, when a single RU corresponding to the entire band of the transmission frequency band is allocated through the control identifier (for example, 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. 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 fields of the HE-SIG-B. The location of the RU assignment 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, the signaling that enables 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 to indicate 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 indicates 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, communication is fundamentally different from wired channel environments because the communication occurs 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 sensed at the Rx stage is momentarily larger than the power transmitted at Tx. However, in a wireless channel environment, various factors (e.g., attenuation of the signal may be large or may experience deep fading momentarily depending on the distance) affect the channel. Tx cannot accurately sense carrier. Therefore, 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 several 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.

The following briefly describes the random backoff time and procedure. 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 to minimize collision select random backoff counts 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, a 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 the MAC protocol data unit (MPDU) or A-MPDU (Aggregate MPDU) from the MAC stage into a single PSDU (PHY service data unit) at the PHY stage, and preambles, tail bits, and padding bits (if necessary). Is transmitted by inserting the

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 the PSDU configuration is obtained from the PHY header (L / HT / VHT / HE-SIG) to read the 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 contents of this octet have 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 latency in 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 of 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 alert 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 road side unit (RSU). 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 refers to a state in which direct communication between nodes is possible without a procedure 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 this specification, interoperability of a system proposed for supporting throughput improvement and high speed for V2X in the 5.9 GHz band, for example, Next Generation Vehicular (NGV) and a DSRC system based on the existing IEEE 802.11p, is provided. We propose a method for providing.

For smooth V2X support in the 5.9GHz band, the technology for NGV considering DSRC's throughput improvement and high speed support is being developed. Therefore, there is a need for a method for interoperating and eliminating interference between the newly developed NGV and an existing system (ie, 802.11p). In this specification, a method for supporting interoperability between the newly proposed NGV and 11p, which is a legacy of the 5.9GHz band, is proposed.

16 shows a frame format of an 802.11p system.

As shown in FIG. 16, the 11p frame includes a SIG field including information on the STF for sync and AGC, the LTF for channel estimation, and the data field. In addition, in FIG. 16, the data field includes a service field, and the service field includes 16 bits.

The 11p frame has a symbol duration (one symbol duration is 8us) longer than 11a because it is configured by applying the same OFDM numerology as that of 11a for the 10MHz band. That is, the 11p frame has a length twice as long as the 11a frame.

PPDU for NGV is required to support Next Generation V2X Communication (NGV), and a PPDU format that 11p STA can decode is required to satisfy interoperability. In addition, in order for the 11p STA and the NGV STA to coexist, when the 11p STA receives the NGV PPDU, there is a need for a method capable of deferring transmission by decoding or PPDU length. Therefore, the present specification proposes a method capable of satisfying coexistence with the NGV PPDU format that can satisfy interoperability.

6.1. For Interoperability NGV PPDU  format (formerly 11p PPDU  Using NGV PPDU  produce)

17 shows an example of the NGV PPDU format.

In order to satisfy interoperability, both the 11p STA and the NGV STA should be able to decode the NGV PPDU. Most representatively, there is a method of using the existing 11p PPDU as it is, but the NGV PPDU format as shown in FIG. 17 may satisfy the interoperability and transmit the NGV PPDU.

In FIG. 17, an NGV PPDU is defined as a form in which 11p PPDUs are continuously connected. Although some overhead exists, the throughput can be improved by obtaining an aggregation effect of A-MPDUs that are widely used. Here, as well as the continuous connection form, there may be a constant interval between the 11p PPDUs as shown in the lower portion of FIG. 17 (shown as a gap in FIG. 17. There may be SIFS as an example of a gap). In addition, the corresponding PPDU format may be mainly used for broadcast transmission, and each data may be the same data or different data. In particular, when the same data exists, the data can be buffered to obtain a combining gain. In such a format, when the same data and different data are mixed between the PPDUs, it should be possible to indicate a location including the same data or different data from the perspective of the NGV STA, and the 11p STA or the NGV STA has a method of receiving the NGV PPDU need.

<11p STA receives>

The 11p STA recognizes each 11p PPDU as an independently transmitted PPDU, and the length of each PPDU can be known from the LENGTH field of the L-SIG. That is, after decoding the first received PPDU, the next PPDU is independently received and decoded.

<When NGV STA receives>

The NGV STA must know how the NGV PPDU constitutes the 11p PPDU. Therefore, there is a need for a method that can indicate this without affecting decoding by the 11p STA, as follows: 1) using the SIGNAL field (SIG), 2) adding an extra tone of the existing L-SIG. 3) there may be a method using a sequence.

1) How to add the SIGNAL field (SIG)

There are following ways to add SIG.

A. First 11p PPDU  Only after NGV  Signal field ( NGV SIG  add field

18 shows an example of an NGV PPDU format in which an NGV SIG is added only after the first 11p PPDU.

As shown in FIG. 18, the NGV SIG field is added immediately after the first 11p PPDU in connection or at a predetermined interval (eg, SIFS). In the case of the 11p STA, the NGV SIG field is regarded as a BUSY signal and passes, and decoding is performed when the 11p PPDU is found. Here, the data of each PPDU may be the same data or different data.

=> In this case NGV SIG cannot be decoded when PPDU # 1 fails to receive.

In contrast, in order to guarantee the reliability of the NGV SIG, a Null Data Packet (NDP) may be additionally transmitted before the NGV SIG.

FIG. 19 shows an example of an NGV PPDU format in which an NDP is added to the NGV PPDU of FIG. 18.

19 shows the possible NGV PPDU format when the NDP is added, and the NDP is composed of L-STF / L-LTF / L-SIG excluding data from 11p PPDU, where LENGS of L-SIG is up to NGV SIG. Indicate the length. The NDP + NGV SIG may be directly connected to the front and rear PPDUs and may maintain a constant interval (eg, SIFS). The 11p STA knows LENGTH from the L-SIG of the PPDU and the NDP and performs decoding, and the NGV STA can decode the NGV SIG through the NDP even if the PPDU # 1 fails. In detail, the NGV STA may decode the NGV SIG by estimating a channel through the L-STF and / or the L-LTF included in the NDP even if the decoding of the PPDU # 1 fails.

Contents that can configure the NGV SIG field based on the NGV PPDU format of the method A of 1) described above are as follows, but are not limited to the following contents or information. Where 2 ^ N _max is the maximum number of PPDUs that can be concatenated from the first PPDU to the last PPDU when transmitting NGV PPDUs.

Number of PPDUs (NP) : The number of consecutively connected PPDUs, expressed as N _max bits. For example, if the number of PPDUs is 1 plus this field value, up to 8 PPDUs can be connected when N _max = 3. Accordingly, if N _max = 3 and the field value is 110 (when the first bit is LSB (Least Significant Byte)), this means that there are four PPDUs currently connected.

Different data present ( DDP ) : A bitmap of whether each 11p PPDU constituting the NGV PPDU contains the same data or different data. 1) From the data of the first PPDU, it means that the data is different from the Nth data, and having 0 means the same data. The number of bits in the DDP field is not fixed because the number of PPDUs may vary depending on the value of the NP field. For example, if there is no need to inform information about the first PPDU, the number of DDP fields is one less than the number of PPDUs.

According to the field described above, the NGV SIG may be configured as follows.

A-1) Only Number of PPDUs

20 shows an example of an NGV SIG field including only an NP field.

As shown in FIG. 20, only an NP field of N _max bits may exist to inform only the number of connected PPDUs.

It is not possible to know whether 11p PPDUs that are consecutively contain the same data can be used only when all connected PPDUs are the same data or different data.

A-2) Number of PPDUs and Different data present

21 shows an example of an NGV SIG field including an NP field and a DDP field.

As shown in FIG. 21, there is a NP field of N _max bits and a DDP field whose number of bits varies depending on the number of PPDUs. That is, the method A-2 of FIG. 21 informs the number of connected PPDUs and the location of the PPDU where data different from the data of the previous PPDU starts.

FIG. 22 illustrates an example of performing A-2) in the NGV PPDU including the NGV SIG field of FIG. 21.

22 shows an example according to a field value when N _max = 3 and the first bit is LSB. In this example, 11p PPDUs are concatenated, and the same result is obtained when a certain interval between PPDUs and NDP is added. When the NP field = 101, when the value is 5 plus 1 to indicate the number of PPDUs, the total number of PPDUs is 6, and when the information on the first PPDU is excluded, the DDP field has a size of 5 bits. The first bit in the DDP field is 0 because the second PPDU contains the same data (Data 1) as the first PPDU. On the other hand, since the third PPDU contains different data (Data 1-> Data 2) from the second PPDU, the second bit is 1. Similarly, the third, fourth, and fifth bits have 0, 1, and 0 values, respectively.

B. Some 11p PPDU  Since the NGV  Signal field ( NGV SIG  add field

FIG. 23 shows an example of an NGV PPDU format in which an NGV SIG is added after some 11p PPDUs.

As shown in FIG. 23, an NGV SIG field is added immediately after some 11p PPDUs or connected at regular intervals (eg, SIFS). Similarly, in the case of the 11p STA, the NGV SIG field is regarded as a BUSY signal and passes, and decoding is performed when the 11p PPDU is found. Here, the data of each PPDU may be the same data or different data. The PPDU with the NGV SIG field depends on the value indicated by the preceding SIG field.

In addition, in order to ensure the reliability of the NGV SIG, a Null Data Packet (NDP) may be additionally transmitted before the NGV SIG.

FIG. 24 shows an example of an NGV PPDU format in which an NDP is added to the NGV PPDU of FIG. 23.

Figure 24 shows the possible NGV PPDU format when NDP is added, where NDP consists of L-STF / L-LTF / L-SIG excluding data from 11p PPDU, where LENGS of L-SIG is up to NGV SIG. Indicate the length. The NDP + NGV SIG may be directly connected to the front and rear PPDUs and may maintain a constant interval (eg, SIFS). The 11p STA knows the LENGTH from the L-SIG of the PPDU and the NDP, and decodes it. The NGV STA can decode the NGV SIG through the NDP even if the previous PPDU reception fails. In detail, the NGV STA may decode the NGV SIG by estimating a channel through the L-STF and / or the L-LTF included in the NDP even if the decoding of the previous PPDU fails.

Contents that can configure the NGV SIG field based on the NGV PPDU format of the 1) -B method described above are as follows, but are not limited to the following information or information. Where 2 ^ N _max is the maximum number of PPDUs that can be concatenated from the first PPDU to the last PPDU when transmitting NGV PPDUs.

Next Different Data Location ( NDDL ) : Indicates the location of the next PPDU that contains data that is different from the data that the current SDU contains. It also indicates the location of the PPDU where the next NGV SIG field is present. This is expressed as N _max bit. For example, if the next PPDU location is 1 plus the NDDL field value, if the field value is 110 (when the first bit is the LSB), it means that other data is included from the fourth PPDU.

-End of PPDU ( EoP ) : 1bit means the end of NGV PPDU. That is, if this value is 1, the PPDU located in the value of the NDDL field means the last PPDU constituting the NGV PPDU.

=> In particular, the last NDDL field, that is, the field before the last PPDU, indicates 000 if the next is the same data, the position of the last PPDU if the other data, and the value of the EoP field described next. Must be 1

According to the contents described above, the NGV SIG can be configured as follows.

25 shows an example of an NGV SIG field including an NDDL field and an EoP field.

As shown in FIG. 25, in the method B of 1), an NDDL field and an EoP field exist.

FIG. 26 illustrates an example of performing a method B in an NGV PPDU including the NGV SIG field of FIG. 25.

FIG. 26 shows an example of a field value by the method B of 1) when the first bit is LSB when N _max = 3. In this example, 11p PPDUs are concatenated, and the same result is obtained when a certain interval between PPDUs and NDP is added. If the first NDDL field has a value of 010 and 1 added to the next PPDU location, the third PPDU is the position where data (data 1-> data 2) is different and EoP is 0 because it is not the end of the PPDU yet. Has a value. Since the second PPDU contains the same data (Data 1), the NGV SIG field is not attached. Since the next NDDL field has a value of 001, the fifth PPDU is a position where data (data 2-> data 3) is different, and still EoP has a value of zero. The last NGV SIG field must always be present, and the NDDL field will be 000 because EoP = 1 and the next PPDU is the same data (Data 3). If the sixth PPDU contained other data (eg, Data 4), it is indicated by 101 as the location of the last PPDU, that is, the sixth PPDU.

C. All 11p PPDU  Since the NGV  Signal field ( NGV SIG  field) (but last PPDU  except)

27 shows an example of an NGV PPDU format in which NGV SIG is added after every 11p PPDU. However, FIG. 27 does not add NGV SIG to the last 11p PPDU.

As shown in FIG. 27, the NGV SIG field is added immediately after all 11p PPDUs or connected at regular intervals (eg, SIFS). The last PPDU need not have an NGV SIG field. Similarly, in the case of the 11p STA, the NGV SIG field is regarded as a BUSY signal and passes, and decoding is performed when the 11p PPDU is found.

In addition, in order to ensure the reliability of the NGV SIG, the NDP may additionally be transmitted before the NGV SIG.

FIG. 28 shows an example of an NGV PPDU format in which an NDP is added to the NGV PPDU of FIG. 27.

FIG. 28 shows the possible NGV PPDU format when NDP is added, where NDP consists of L-STF / L-LTF / L-SIG excluding data from 11p PPDU, where LENGTH of L-SIG is up to NGV SIG. Indicate the length. The NDP + NGV SIG may be directly connected to the front and rear PPDUs and may maintain a constant interval (eg, SIFS). The 11p STA knows the LENGTH from the L-SIG of the PPDU and the NDP, and decodes it. The NGV STA can decode the NGV SIG through the NDP even if the previous PPDU reception fails.

Contents that can configure the NGV SIG field based on the NGV PPDU format of the 1) -C method described above are as follows, but are not limited to the following information or information. Where 2 ^ N _max is the maximum number of PPDUs that can be concatenated from the first PPDU to the last PPDU when transmitting NGV PPDUs.

Next Different Data Present ( NDDP ) : Indicates whether the data of the next PPDU is the same or different data than that of the current PPDU. It can be indicated by 1 bit. If this value is 1, it means that other data is included. If it is 0, it means that the same data is included.

-End of PPDU ( EoP ) : 1bit means the end of NGV PPDU. That is, if this value is 1, the PPDU located in the value of the NDDL field means the last PPDU constituting the NGV PPDU.

29 shows an example of an NGV SIG field including an NDDP field and an EoP field.

As shown in FIG. 29, the C method has an NDDP field and an EoP field.

FIG. 30 illustrates an example of performing a C method in an NGV PPDU including the NGV SIG field of FIG. 29.

30 shows an example according to a field value by the C method of 1) when N _max = 3. In this example, 11p PPDUs are concatenated, and the same result is obtained when a certain interval between PPDUs and NDP is added. Since the first NGV SIG field has a value of 00, it can be seen that the data of the next PPDU is the same data 1 and is not the end of the PPDU. Since the second NGV SIG field has a value of 10, it can be seen that data of the next PPDU is another data2 and not the end of the PPDU. Similarly, the remaining NGV SIG fields can be represented in the same way, and since the last NGV SIG field is a value of 01, the next data indicates the same data and the last PPDU of the NGV PPDU.

2) Original L- Of SIG  How to use extra tone

Conventional L-SIG uses a total of 24 bits (excluding pilot, encoding applied), but additional 2 tones (i.e. 2 bits) or 4 tones (i.e., 2 bits) in the L-SIG by channel estimation for extra tones in the L-LTF. That is, 4 bits) can be utilized.

31 shows an example of using additional tones in the L-SIG.

As shown in FIG. 31, in the case of 2 tones, the channel corresponding to index {-27,27} may be additionally estimated in the L-LTF to additionally use 2 bits in the L-SIG. -27,27,28} can additionally estimate the channel in the L-LTF and additionally use 4 bits in the L-SIG. This method can be applied to the L-SIG of the existing 11p PPDU or the L-SIG of the NDP mentioned in the method of 1).

A. 11p Of PPDU  L- SIG  If applicable

In the PPDU format of FIG. 17, since 2 bits or 4 bits may be additionally used in the L-SIG for every PPDU, the NGV STA may obtain information through this bit. Contents indicated by this bit may include contents (NDDL, EoP, etc.) mentioned in A, B, and C in 1), but are not limited to the above-mentioned contents or information. Since an extra tone is defined for every PPDU in the PPDU format of FIG. 17, the content mentioned in A, B, and C of 1) may also be indicated by 2 bits.

The PPDU format to which the extra tone is applied to the L-SIG is the one except for NGV SIG in the PPDU format mentioned in 1) -A, B, and C. The reason for excluding the NGV SIG is because the extra tone plays the role of the NGV SIG.

B. Of NDP  L- SIG  If applicable

The PPDU format to which NDP is applied is the PPDU format mentioned in 1) -A, B, and C except the NGV SIG. The reason for excluding the NGV SIG is because it uses an extra tone. Since the L-SIG of each NDP can additionally utilize 2 bits or 4 bits, the NGV STA can obtain information through this bit. Contents indicated by this bit may include contents (NDDL, EoP, etc.) mentioned in A, B, and C of 1), but are not limited to the above-mentioned contents or information.

In A of 2), it is assumed that an extra tone is applied to the L-SIG of all 11p PPDUs, and in B of 2), an NDP is defined after every 11p PPDU, so that an extra tone is applied to the L-SIG in the NDP. That is, since additional tones are defined and used in the L-SIG of every PPDU, only 2 bits (or 2 tones) may be sufficient to indicate the above-mentioned content or information.

3) In case of using Sequence

As in the method of 1), a sequence other than the encoded field may be inserted and indicated by auto or cross-correlation or sequence comparison. In the case of the 11p STA, since this sequence is different from the STF sequence, it is not regarded as an STF sequence. Therefore, decoding is performed only when the PPDU detects an STF. How to add a sequence and its meaning may be as follows. 32 to 34 describe the sequence as S. FIG.

A. NGV PPDU  Insert Sequence before

32 shows an example of an NGV PPDU format for inserting a sequence.

As shown in FIG. 32, the sequence is inserted before the NGV PPDU, and when the NGV STA finds the sequence, the sequence may recognize that the corresponding PPDU is the NGV PPDU. 11p PPDUs constituting the NGV PPDU may be directly connected or connected at regular intervals (eg, SIFS).

However, according to the NGV PPDU format of FIG. 32, the NGV STA should always be ready to discover the sequence. In addition, it is not possible to distinguish between the same data or different data between PPDUs.

B. First 11p PPDU  Insert sequence only after

33 shows an example of an NGV PPDU format in which a sequence is inserted only after the first 11p PPDU.

As shown in FIG. 33, the sequence is inserted after the first PPDU, and similarly to the method A of 3), when the NGV STA finds this sequence, the NGV STA may recognize that the corresponding PPDU is an NGV PPDU. 11p PPDUs constituting the NGV PPDU may be directly connected or connected at regular intervals (eg, SIFS).

However, according to the NGV PPDU format of FIG. 33, the NGV STA cannot distinguish between the same data or different data between the PPDUs.

C. All PPDU  Insert Sequence next (last PPDU  except)

34 shows an example of an NGV PPDU format in which a sequence is inserted after all 11p PPDUs.

As shown in FIG. 34, the sequence is inserted after all the PPDUs except for the last, and when the NGV STA finds the sequence, the NGV STA may distinguish the data of the next PPDU from the same data or other data based on the correlation result or the sequence type. For example, after correlation, if it is determined that the data is different if the threshold value is greater than or equal to the threshold, and if the data is less than the same value, the correlation result with the first sequence of FIG. 34 is equal to or greater than the threshold value (that is, data 1-> data2), and the correlation with the second sequence is below the threshold (same data2). 11p PPDUs constituting the NGV PPDU may be directly connected or connected at regular intervals (eg, SIFS).

-> Since it is inserted into all PPDUs, the overhead is larger than that of B method of 3), but data can be distinguished between PPDUs.

Hereinafter, the above-described embodiment will be described with reference to FIGS. 17 to 34.

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

35 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 802.11bd.

An example of FIG. 35 is performed in a transmitter, and the transmitter may correspond to an AP. The receiving apparatus of FIG. 35 may correspond to an NGV STA supporting an NGV or 802.11bd system or an 11p STA supporting an 802.11p system.

This embodiment proposes a method for satisfying interoperability between a newly proposed NGV or 802.11bd WLAN system and a legacy 802.11p system. Specifically, the present embodiment proposes a method of configuring an NGV PPDU that can be decoded by both the NGV STA and the 11p STA.

In operation S3510, the transmitter generates a first PPDU.

In step S3520, the transmitting device transmits the first PPDU to the receiving device.

The first PPDU includes a plurality of second PPDUs. The plurality of second PPDUs may be connected continuously or at a predetermined interval. That is, the first PPDU may be defined as an A-MPDU format in which the plurality of second PPDUs are aggregated. The predetermined interval may be a short inter frame space (SIFS).

In addition, the first PPDU supports an NGV or 802.11bd system, and the plurality of second PPDUs supports an 802.11p system. That is, the first PPDU is defined in the NGV PPDU format, and the plurality of second PPDUs are defined in the 802.11p PPDU format.

NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added after the third PPDU transmitted first of the plurality of second PPDUs. An embodiment of adding an NDP and an NGV-SIG to the first PPDU (NGV PPDU format) in order to satisfy an interoperability between an NGV system and an 802.11p system is provided. When receiving the first PPDU, the receiver may regard the NGV-SIG as a BUSY signal and may decode again when it finds the STF of the second 11p PPDU that is transmitted after the NGV-SIG. .

The NDP may include a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), and a first Legacy-Signal (L-SIG). The L-STF and the L-LTF may be used to perform channel estimation of the channel through which the third PPDU is transmitted.

When the receiving device is an NGV STA, the receiving device may check information to be described later by decoding the NGV-SIG. The reason for adding the NDP to the first PPDU is as follows. If only the NGV-SIG is added to the first PPDU without the NDP, if the receiver fails to receive the third PPDU, the NGV-SIG may not be decoded. However, when the NDP is added to the first PPDU, the reception apparatus decodes the NGV-SIG based on the estimated channel by decoding the NDP and estimating a channel even if the reception of the third PPDU fails. can do.

The first L-SIG may include a first LEGNTH field. The first LENGTH field may include information on the length from a point at which transmission of the first PPDU starts to a point at which transmission of the NGV-SIG ends. That is, the receiving device can decode the first L-SIG of the NDP to know the length from the start of the first PPDU to the NGV-SIG.

The NDP may be connected to the third PPDU continuously or at predetermined intervals. That is, the NDP may be continuously aggregated to the 11p PPDU transmitted first of the plurality of second PPDUs or may be aggregated at a predetermined interval. The predetermined interval may be SIFS.

Information included in the NGV-SIG is as follows.

The NGV-SIG may include a Number of PPDUs (NP) field and a Different Data Present (DDP) field.

The NP field may include information on the number of the plurality of second PPDUs, and the DDP field may include a bitmap indicating whether data included in each of the plurality of second PPDUs is the same. The bitmap may be determined based on the number of the plurality of second PPDUs. For example, if the number of the plurality of second PPDUs is a total of six, whether the data included in each of the plurality of second PPDUs is equal to each other is determined as a 5-bit bitmap since information on the first 11p PPDU is unnecessary. Can be set. Specifically, when the NP field is set to 101, it can be seen that the total number of second PPDUs is six. If the DDP field is set to 01010, the second 11p PPDU has the same data as the first 11p PPDU (set to 0), and the third 11p PPDU has different data from the second 11p PPDU (set to 1). Can be indicated. Similarly, the fourth, fifth, and sixth PPDUs may be identified by the DDP field whether they have the same data as the previous 11p PPDU or other data.

The plurality of second PPDUs may each include a second legacy-signal (L-SIG) and data. The second L-SIG may include a second LENGTH field including information on the length of each of the plurality of PPDUs.

When the NGV-SIG is added and transmitted after some of the plurality of second PPDUs, the NGV-SIG may include a Next Different Data Location (NDDL) field and an End of PPDU (EoP) field. Data included in the some PPDUs may be different.

The NDDL field may include information on the location of the partial PPDU. The EoP field may include information on the existence of the last PPDU of the partial PPDUs.

When the NGV-SIG is added to the remaining PPDUs except for the last PPDU among the plurality of second PPDUs and transmitted, respectively, the NGV-SIG may include a Next Different Data Present (NDDP) field and an EoP field.

The NDDP field may include information on whether data included in adjacent PPDUs among the plurality of second PPDUs are the same. The EoP field may include information on the presence of the last PPDU among the plurality of second PPDUs.

The NGV-SIG field includes bandwidth, Modulation and Coding Scheme (MCS), Dual Carrier Modulation (DCM), Number of Space Time Streams (NSTS), midamble, doppler, and Space Time Block Coding (STBC). The information may further include information about coding, a low density parity check (LDPC) additional symbol, a cyclonic redundancy check (CRC), and a tail bit.

The bandwidth information may include information that the WLAN system supports a 10 MHz or 20 MHz band. The information on the MCS may include information supported by the WLAN system up to 256 QAM. The information on the coding may include information that the WLAN system supports Binary Convolutional Codes (BCC) or LDPC.

In addition, the first PPDU may further include an NGV-STF field and an NGV-LTF field.

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

36 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 802.11bd.

An example of FIG. 36 is performed in a receiving apparatus, and the receiving apparatus may correspond to an NGV STA supporting an NGV or 802.11bd WLAN system or an 11p STA supporting an 802.11p WLAN system. The transmitter of FIG. 36 may correspond to an AP.

This embodiment proposes a method for satisfying interoperability between a newly proposed NGV or 802.11bd WLAN system and a legacy 802.11p system. Specifically, the present embodiment proposes a method of configuring an NGV PPDU that can be decoded by both the NGV STA and the 11p STA.

In step S3610, the receiving device receives the first PPDU from the transmitting device.

In step S3620, the receiver decodes the first PPDU.

The first PPDU includes a plurality of second PPDUs. The plurality of second PPDUs may be connected continuously or at a predetermined interval. That is, the first PPDU may be defined as an A-MPDU format in which the plurality of second PPDUs are aggregated. The predetermined interval may be a short inter frame space (SIFS).

In addition, the first PPDU supports an NGV or 802.11bd system, and the plurality of second PPDUs supports an 802.11p system. That is, the first PPDU is defined in the NGV PPDU format, and the plurality of second PPDUs are defined in the 802.11p PPDU format.

NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added after the third PPDU transmitted first of the plurality of second PPDUs. An embodiment of adding an NDP and an NGV-SIG to the first PPDU (NGV PPDU format) in order to satisfy an interoperability between an NGV system and an 802.11p system is provided. When receiving the first PPDU, the receiver may regard the NGV-SIG as a BUSY signal and may decode again when it finds the STF of the second 11p PPDU that is transmitted after the NGV-SIG. .

The NDP may include a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), and a first Legacy-Signal (L-SIG). The L-STF and the L-LTF may be used to perform channel estimation of the channel through which the third PPDU is transmitted.

When the receiving device is an NGV STA, the receiving device may check information to be described later by decoding the NGV-SIG. The reason for adding the NDP to the first PPDU is as follows. If only the NGV-SIG is added to the first PPDU without the NDP, if the receiver fails to receive the third PPDU, the NGV-SIG may not be decoded. However, when the NDP is added to the first PPDU, the reception apparatus decodes the NGV-SIG based on the estimated channel by decoding the NDP and estimating a channel even if the reception of the third PPDU fails. can do.

The first L-SIG may include a first LEGNTH field. The first LENGTH field may include information on the length from a point at which transmission of the first PPDU starts to a point at which transmission of the NGV-SIG ends. That is, the receiving device can decode the first L-SIG of the NDP to know the length from the start of the first PPDU to the NGV-SIG.

The NDP may be connected to the third PPDU continuously or at predetermined intervals. That is, the NDP may be continuously aggregated to the 11p PPDU transmitted first of the plurality of second PPDUs or may be aggregated at a predetermined interval. The predetermined interval may be SIFS.

Information included in the NGV-SIG is as follows.

The NGV-SIG may include a Number of PPDUs (NP) field and a Different Data Present (DDP) field.

The NP field may include information on the number of the plurality of second PPDUs, and the DDP field may include a bitmap indicating whether data included in each of the plurality of second PPDUs is the same. The bitmap may be determined based on the number of the plurality of second PPDUs. For example, if the number of the plurality of second PPDUs is a total of six, whether the data included in each of the plurality of second PPDUs is equal to each other is determined as a 5-bit bitmap since information on the first 11p PPDU is unnecessary. Can be set. Specifically, when the NP field is set to 101, it can be seen that the total number of second PPDUs is six. If the DDP field is set to 01010, the second 11p PPDU has the same data as the first 11p PPDU (set to 0), and the third 11p PPDU has different data from the second 11p PPDU (set to 1). Can be indicated. Similarly, the fourth, fifth, and sixth PPDUs may be identified by the DDP field whether they have the same data as the previous 11p PPDU or other data.

The plurality of second PPDUs may each include a second legacy-signal (L-SIG) and data. The second L-SIG may include a second LENGTH field including information on the length of each of the plurality of PPDUs.

When the NGV-SIG is added and transmitted after some of the plurality of second PPDUs, the NGV-SIG may include a Next Different Data Location (NDDL) field and an End of PPDU (EoP) field. Data included in the some PPDUs may be different.

The NDDL field may include information on the location of the partial PPDU. The EoP field may include information on the existence of the last PPDU of the partial PPDUs.

When the NGV-SIG is added to the remaining PPDUs except for the last PPDU among the plurality of second PPDUs and transmitted, respectively, the NGV-SIG may include a Next Different Data Present (NDDP) field and an EoP field.

The NDDP field may include information on whether data included in adjacent PPDUs among the plurality of second PPDUs are the same. The EoP field may include information on the presence of the last PPDU among the plurality of second PPDUs.

The NGV-SIG field includes bandwidth, Modulation and Coding Scheme (MCS), Dual Carrier Modulation (DCM), Number of Space Time Streams (NSTS), midamble, doppler, and Space Time Block Coding (STBC). The information may further include information about coding, a low density parity check (LDPC) additional symbol, a cyclonic redundancy check (CRC), and a tail bit.

The bandwidth information may include information that the WLAN system supports a 10 MHz or 20 MHz band. The information on the MCS may include information supported by the WLAN system up to 256 QAM. The information on the coding may include information that the WLAN system supports Binary Convolutional Codes (BCC) or LDPC.

In addition, the first PPDU may further include an NGV-STF field and an NGV-LTF field.

6. Device Configuration

37 is a diagram for explaining an apparatus for implementing the method as described above.

The wireless device 100 of FIG. 37 is a transmission device capable of implementing the above-described embodiment and may operate as an AP STA. The wireless device 150 of FIG. 37 is a reception 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 transceivers 130 and 180 may transmit / receive radio signals and may be executed in a physical layer such as IEEE 802.11 / 3GPP. The processors 110 and 160 are executed at 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 an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and / or a data processor. 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 transmitting device is as follows. The processor 110 of the transmitting device generates a first PPDU and transmits the first PPDU to the receiving device.

In detail, operations of the processor 160 of the receiving apparatus are as follows. The processor 160 of the receiving device receives the first PPDU and decodes the first PPDU.

38 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 transmitting device, the processor 610 generates a first PPDU and transmits the first PPDU to a receiving device.

In the case of a receiving device, the processor 610 receives a first PPDU including the processor 160 of the receiving device and decodes the first PPDU.

The first PPDU includes a plurality of second PPDUs. The plurality of second PPDUs may be connected continuously or at a predetermined interval. That is, the first PPDU may be defined as an A-MPDU format in which the plurality of second PPDUs are aggregated. The predetermined interval may be a short inter frame space (SIFS).

In addition, the first PPDU supports an NGV or 802.11bd system, and the plurality of second PPDUs supports an 802.11p system. That is, the first PPDU is defined in the NGV PPDU format, and the plurality of second PPDUs are defined in the 802.11p PPDU format.

NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added after the third PPDU transmitted first of the plurality of second PPDUs. An embodiment of adding an NDP and an NGV-SIG to the first PPDU (NGV PPDU format) in order to satisfy an interoperability between an NGV system and an 802.11p system is provided. When receiving the first PPDU, the receiver may regard the NGV-SIG as a BUSY signal and may decode again when it finds the STF of the second 11p PPDU that is transmitted after the NGV-SIG. .

The NDP may include a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), and a first Legacy-Signal (L-SIG). The L-STF and the L-LTF may be used to perform channel estimation of the channel through which the third PPDU is transmitted.

When the receiving device is an NGV STA, the receiving device may check information to be described later by decoding the NGV-SIG. The reason for adding the NDP to the first PPDU is as follows. If only the NGV-SIG is added to the first PPDU without the NDP, if the receiver fails to receive the third PPDU, the NGV-SIG may not be decoded. However, when the NDP is added to the first PPDU, the reception apparatus decodes the NGV-SIG based on the estimated channel by decoding the NDP and estimating a channel even if the reception of the third PPDU fails. can do.

The first L-SIG may include a first LEGNTH field. The first LENGTH field may include information on the length from a point at which transmission of the first PPDU starts to a point at which transmission of the NGV-SIG ends. That is, the receiving device can decode the first L-SIG of the NDP to know the length from the start of the first PPDU to the NGV-SIG.

The NDP may be connected to the third PPDU continuously or at predetermined intervals. That is, the NDP may be continuously aggregated to the 11p PPDU transmitted first of the plurality of second PPDUs or may be aggregated at a predetermined interval. The predetermined interval may be SIFS.

Information included in the NGV-SIG is as follows.

The NGV-SIG may include a Number of PPDUs (NP) field and a Different Data Present (DDP) field.

The NP field may include information on the number of the plurality of second PPDUs, and the DDP field may include a bitmap indicating whether data included in each of the plurality of second PPDUs is the same. The bitmap may be determined based on the number of the plurality of second PPDUs. For example, if the number of the plurality of second PPDUs is a total of six, whether the data included in each of the plurality of second PPDUs is equal to each other is determined as a 5-bit bitmap since information on the first 11p PPDU is unnecessary. Can be set. Specifically, when the NP field is set to 101, it can be seen that the total number of second PPDUs is six. If the DDP field is set to 01010, the second 11p PPDU has the same data as the first 11p PPDU (set to 0), and the third 11p PPDU has different data from the second 11p PPDU (set to 1). Can be indicated. Similarly, the fourth, fifth, and sixth PPDUs may be identified by the DDP field whether they have the same data as the previous 11p PPDU or other data.

The plurality of second PPDUs may each include a second legacy-signal (L-SIG) and data. The second L-SIG may include a second LENGTH field including information on the length of each of the plurality of PPDUs.

When the NGV-SIG is added and transmitted after some of the plurality of second PPDUs, the NGV-SIG may include a Next Different Data Location (NDDL) field and an End of PPDU (EoP) field. Data included in the some PPDUs may be different.

The NDDL field may include information on the location of the partial PPDU. The EoP field may include information on the existence of the last PPDU of the partial PPDUs.

When the NGV-SIG is added to the remaining PPDUs except for the last PPDU among the plurality of second PPDUs and transmitted, respectively, the NGV-SIG may include a Next Different Data Present (NDDP) field and an EoP field.

The NDDP field may include information on whether data included in adjacent PPDUs among the plurality of second PPDUs are the same. The EoP field may include information on the presence of the last PPDU among the plurality of second PPDUs.

The NGV-SIG field includes bandwidth, Modulation and Coding Scheme (MCS), Dual Carrier Modulation (DCM), Number of Space Time Streams (NSTS), midamble, doppler, and Space Time Block Coding (STBC). The information may further include information about coding, a low density parity check (LDPC) additional symbol, a cyclonic redundancy check (CRC), and a tail bit.

The bandwidth information may include information that the WLAN system supports a 10 MHz or 20 MHz band. The information on the MCS may include information supported by the WLAN system up to 256 QAM. The information on the coding may include information that the WLAN system supports Binary Convolutional Codes (BCC) or LDPC.

In addition, the first PPDU may further include an NGV-STF field and an NGV-LTF field.

Claims (17)

In the method for transmitting a first PHY protocol data unit (PPDU) in a WLAN system, Generating, by the transmitting device, the first PPDU; And Transmitting, by the transmitter, the first PPDU to a receiver; The first PPDU includes a plurality of second PPDUs, NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added and transmitted after the third PPDU transmitted first among the plurality of second PPDUs, The first PPDU supports an NGV or 802.11bd system. The plurality of second PPDUs support 802.11p systems Way. The method of claim 1, The NDP includes a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), and a first Legacy-Signal (L-SIG), The first L-SIG includes a first LEGNTH field, The first LENGTH field includes information on the length from the point at which transmission of the first PPDU starts to the point at which transmission of the NGV-SIG ends. The NDP is continuously connected to the third PPDU or connected at a predetermined interval, The preset interval is SIFS (Short Inter Frame Space) Way. The method of claim 2, The L-STF and the L-LTF are used to perform channel estimation of the channel through which the third PPDU is transmitted. Way. The method of claim 1, The NGV-SIG includes a Number of PPDUs (NP) field and a Different Data Present (DDP) field. The NP field includes information on the number of the plurality of second PPDUs. The DDP field includes a bitmap of whether data included in each of the plurality of second PPDUs is the same as each other, The bitmap is determined based on the number of the plurality of second PPDUs Way. The method of claim 4, wherein Each of the plurality of second PPDUs includes a second legacy-signal (L-SIG) and data. The second L-SIG includes a second LENGTH field that includes information about the length of each of the plurality of PPDUs. Way. The method of claim 1, The plurality of second PPDUs are continuously connected or connected at a predetermined interval, The preset interval is SIFS (Short Inter Frame Space) Way. The method of claim 1, When the NGV-SIG is added and transmitted after some of the plurality of second PPDUs, respectively, The NGV-SIG includes a Next Different Data Location (NDDL) field and an End of PPDU (EoP) field. The data contained in the some PPDUs are different from each other, The NDDL field includes information about the location of the partial PPDU. The EoP field includes information on the existence of the last PPDU of the partial PPDUs. Way. The method of claim 1, When the NGV-SIG is added to the remaining PPDUs except for the last PPDU of the plurality of second PPDUs and transmitted, The NGV-SIG includes a Next Different Data Present (NDDP) field and an EoP field. The NDDP field includes information on whether data included in adjacent PPDUs among the plurality of second PPDUs is identical to each other. The EoP field includes information on the existence of the last PPDU among the plurality of second PPDUs. Way. A transmitter for transmitting a first PDU protocol data unit (PPDU) in a WLAN system, the transmitter comprising: Memory; Transceiver; And A processor operatively coupled with the memory and the transceiver, the processor comprising: Generate the first PPDU; And Transmit the first PPDU to a receiving device; The first PPDU includes a plurality of second PPDUs, NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added and transmitted after the third PPDU transmitted first among the plurality of second PPDUs, The first PPDU supports an NGV or 802.11bd system. The plurality of second PPDUs support 802.11p systems Transmitter. The method of claim 9, The NDP includes a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), and a first Legacy-Signal (L-SIG), The first L-SIG includes a first LEGNTH field, The first LENGTH field includes information on the length from the point at which transmission of the first PPDU starts to the point at which transmission of the NGV-SIG ends. The NDP is continuously connected to the third PPDU or connected at a predetermined interval, The preset interval is SIFS (Short Inter Frame Space) Transmitter. The method of claim 10, The L-STF and the L-LTF are used to perform channel estimation of the channel through which the third PPDU is transmitted. Transmitter. The method of claim 9, The NGV-SIG includes a Number of PPDUs (NP) field and a Different Data Present (DDP) field. The NP field includes information on the number of the plurality of second PPDUs. The DDP field includes a bitmap of whether data included in each of the plurality of second PPDUs is the same as each other, The bitmap is determined based on the number of the plurality of second PPDUs Transmitter. The method of claim 12, Each of the plurality of second PPDUs includes a second legacy-signal (L-SIG) and data. The second L-SIG includes a second LENGTH field that includes information about the length of each of the plurality of PPDUs. Transmitter. The method of claim 9, The plurality of second PPDUs are continuously connected or connected at a predetermined interval, The preset interval is SIFS (Short Inter Frame Space) Transmitter. The method of claim 9, When the NGV-SIG is added and transmitted after some of the plurality of second PPDUs, respectively, The NGV-SIG includes a Next Different Data Location (NDDL) field and an End of PPDU (EoP) field. The data contained in the some PPDUs are different from each other, The NDDL field includes information about the location of the partial PPDU. The EoP field includes information on the existence of the last PPDU of the partial PPDUs. Transmitter. The method of claim 9, When the NGV-SIG is added to the remaining PPDUs except for the last PPDU of the plurality of second PPDUs and transmitted, The NGV-SIG includes a Next Different Data Present (NDDP) field and an EoP field. The NDDP field includes information on whether data included in adjacent PPDUs among the plurality of second PPDUs is identical to each other. The EoP field includes information on the existence of the last PPDU among the plurality of second PPDUs. Transmitter. In the method for receiving a first PHY protocol data unit (PPDU) in a WLAN system, Receiving, by a receiver, the first PPDU from a transmitter; And Decoding, by the receiving device, the first PPDU; The first PPDU includes a plurality of second PPDUs, NDP (Null Data Packet) and NGV-SIG ((New Generation V2X (Vehicle-to-Everything) -Signal) are added and transmitted after the third PPDU transmitted first among the plurality of second PPDUs, The first PPDU supports an NGV or 802.11bd system. The plurality of second PPDUs support 802.11p systems Way.

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