KR20070082099A - Urban traffic information system - Google Patents

Abstract

An urban traffic information system is provided to define a communication frame as a communication protocol applicable to the urban traffic information system. An urban traffic information system requires a connection procedure for the transmission of data to an on-board device and a road side device or the data communication with the road side device. The connection is performed by the procedure of a CF(Connection Frame)-poll, a CF-request, and a CF-response. The CF-poll is used when the connection from the on board device to the road side equipment is requested and the transmission is performed from the road side device to the on board device. The CF-request is used when the transmission is performed from the on board device to the road side equipment and the on board equipment tries to be connected to the road side device. The CF-respond is used when the transmission is performed from the road side device to the on board device and a response is transmitted to the on board device. The on board device uses a CCA(Clear Channel Assesment) method when transmitting the data in order to determine whether a wireless state is busy or idle.

Description

Urban Traffic Information System

1 is a block diagram illustrating an overall data flow between a communication system and an application, including portions to which the present invention pertains;

2 is a schematic diagram showing a connection process between a roadside apparatus and a mounting apparatus;

3 is a schematic diagram of a backoff process;

4 is a schematic diagram of a connection process based on the backoff of FIG. 3;

5 is a schematic diagram of an individual data communication process;

6 is a schematic diagram of a broadcast data communication process;

The present invention relates to an Urban Traffic Information System (UTIS), and more specifically, to a near- and mid- and long-range communication system for intelligent transport system (ITS) and telematics, that is, to process a large amount of data. To this end, the present invention relates to a new communication protocol and a communication method using the same in a short-range communication system that extends communication distance, communication capacity, and communication speed by using CSMA / CA (carrier simultaneous use / collision avoidance) based polling method.

The existing ITS short-range communication method for transmitting and receiving connection, vehicle information and broadcast information between the base station installed near the intersection of the road and the vehicle moving on the road has a communication distance of 100m or less and a transmission speed in the 5.8GHz band. Is 1Mbps, and it is a service for transmitting and receiving small data of about 65 bytes at a time after connection.

The existing ITS short-range communication technique is based on dedicated short range communication (DSRC), which requires a connection procedure between a mobile device and a fixed device every time data is transmitted, and the data transmission amount is 65 bytes at a time. In case of transmission and reception of traffic information, real-time performance of 0-25.4 seconds should be secured, and transmission speed is as low as 1Mbps, and in case of broadcast data, there is no special consideration in Layer 2 and reception of broadcast data. In order to provide a simple information such as vehicle information, broadcasting, and fare calculation, the communication distance was less than 100m.

However, due to the expansion of service requirements such as the service proposed by UTIS, which is scheduled to be serviced by the Korea Road Traffic Safety Authority, the communication distance has increased to about 1km, the transmission speed is required to be up to 10Mbps or more, and large data transmission such as video is required. Using existing short-range communication techniques and protocols, it was difficult to meet the desired requirements for the following reasons.

Firstly, the range of fixed base station 20 has been expanded and installed in CCTV towers in addition to the places used for DSRC, so that the communication distance is increased by at least 1km and directional from unidirectional to multidirectional. Fixed equipment (RSE) has been installed in CCTV towers, highways, and motorways, and the number of mobile devices that need to be handled at the same time has increased dramatically.However, if there is still data to be sent or received even after accessing the roadside station fixed device, Since the cyclical access request with time is continuously attempted and a time slot is allocated from the road station station, there is a shortage of timeslots that can be received by several. The lack of timeslots, as well as the frequent collisions of timeslots, prevented normal connections.

Second, it is difficult to maintain the maximum speed unless the unnecessary headers and procedures on the protocol are omitted as the communication speed increases to 10Mbps or more.

Third, because it uses TDMA / TDD communication method and can transmit maximum 65 bytes at a time, it is impossible to transmit / receive large amount of data and data according to priority, and simultaneously transmit, access, broadcast and unicast data. In order to transmit data, connection and transmission are repeated until all data is transmitted by dividing 65 bytes each time, so there is a high possibility of overloading of a base station and collision of timeslots.

In view of such a problem in the related art, the present applicant filed a patent application 40458 entitled "Intelligent Traffic Information System and Communication System and Method for Telematics" on May 16, 2005. The present invention develops a new protocol for short-range and long-range communication to improve and compensate for the shortcomings of the prior art. As described above, the TDMA / TDD communication method is used to increase the number of connection processing of the payload device and to transmit a large amount of data. And a new communication method using the CSMA / TDD method, but the specific communication frame for such communication has not been developed yet.

Accordingly, an object of the present invention is to develop a specific communication frame applicable to the invention of the applicant's prior patent application, and to provide a communication method unique to such communication frame.

In order to achieve the above object of the present invention, a roadside device connected to a remote server and under the control of the server and installed at a roadside to form a fixed base station, and installed in a vehicle traveling on the road, and transmits data by wireless communication with the roadside device. In a wireless communication system between exchange devices, a roadside device allocates a communication medium to a vehicle's onboard vehicle passing through its own communication area, and uses the structure of a communication frame to enable smooth communication between the roadside device and the onboard device. In:

A Medium Access Control (MAC) header having a size of 32 bytes and providing general information about communication;

A payload having a size of 0 to 1514 bytes and carrying appropriate main data according to a frame type defined in a MAC header; And

There is provided a structure of a communication frame consisting of a frame check sequence (FCS) having a size of 4 bytes.

In a communication frame according to the present invention, the MAC header has a length of 4 bytes, and includes a frame control field for providing characteristics of a physical layer and communication information of a frame; Poll length (2 bytes), commonly used in roadside and payload equipment, used to identify service access points (SAPs) at MAC sublayer, LLC sublayer, and higher layers, and only valid until the end of the transaction. ID) field; A frame type field having a length of 2 bytes and indicating a type of a frame to be transmitted, and comprising a combination of a packet type field of 1 byte length and a data type field of 1 byte length; It has a length of 8 bytes and has a unique value as a receiving device identifier used for communication between the roadside device and the payload device.There is no destination of a specific receiving device when transmitting a frame, or a connection request from the broadcast data or the roadside device to the payload device is required. A Destination Equipment ID field, which defines an identifier of a destination device when present; A source equipment ID field having a length of 8 bytes and having a unique value as a transmitter equipment identifier used for communication between the roadside apparatus and the payload apparatus; It has a length of 4 bytes and indicates an application service such as a commercial image provided by the corresponding roadside device, and selects a function available to a loading device such as a moving picture according to the performance or function of the loading device according to the value of the frame control field. Service field for; It has a length of 1 byte and is used exclusively for unicast data communication to avoid duplicate reception of the same message, and it is incremented by 1 when there is individual communication data in the payload and has a value between 0 and 255. Sequence) field; And when the value of the received serial number does not match the value of the serial number, it is determined that the received message is not properly received, and the received serial number (ACK; acknowledgement) having a value of 0 to 255. Contains a field.

In addition, the frame control field of the communication frame of the present invention is a 2-bit protocol version subfield indicating the version of the protocol operating in the roadside device, a 6-bit length subfield indicating the frequency bath serviced by the roadside device, 4-bit length field indicating the physical wireless transmission speed serviced by the roadside device, 4-bit length device type subfield indicating whether the type of equipment transmitting data is a roadside device or a loading device A 4-bit long Connection Range subfield indicating the range in which the roadside device can be connected to the roadside device, a 2-bit long encryption identification subfield indicating whether communication between the roadside device and the onboard device is encrypted, It is preferable to include a 2-bit long individual data subfield used when making a connection request to a roadside device.

Further, in the present invention, when the protocol version subfield indicates that the roadside apparatus serves a higher version protocol than the protocol being operated on the loading apparatus, the loading apparatus preferably discards the communication frame.

In the communication frame according to the present invention, the value of the encryption identification subfield is preferably set to "1" when using encryption and "0" when not using encryption.

In addition, in the communication frame according to the present invention, if the value of the individual data subfield is "1", the payload apparatus may request bandwidth allocation from the roadside apparatus, and the roadside apparatus may allocate the payload apparatus requesting the allocation of individual data bandwidth. If resources are available, it is advisable to allow the use of individual data.

In the communication frame according to the present invention, the packet type field in the frame type field is used to distinguish bidirectional individual data, unidirectional broadcast data, and connection data, and the data type field includes these individual data, broadcast data, and connection data. It is used to distinguish the type of data such as null data with only MAC header or main data without main data.

In addition, the present invention is connected to a remote server, under the control of the server is installed on the road side of the roadside device to form a fixed base station, and installed on the vehicle running on the road and the roadside device and the on-board device for transmitting and receiving data by wireless communication In a wireless communication system, a communication device uses a communication frame as described above, which allocates a communication medium to a vehicle's onboard device passing through its own communication area and enables smooth communication between the roadside device and the onboard device. In:

When requesting connection from the onboard device to the roadside device, the onboard device receives CF-poll (Connection Frame poll) sent from the roadside device and operates after SIFS (Short Interframe Space) based on the backoff process. It also provides CF-req (Connection Frame request) requesting connection when idle state and stops backoff time reduction and returns to standby state when wireless state is busy state.

In the method according to the present invention, when two or more CF-reqs are received from a plurality of mounting apparatuses having the same ID for the CP-poll sent by the roadside apparatus, the connection response signal is the first to the mounting apparatus to which the CF-req is first sent. It is preferable to send a CF-rsp (Connection Frame Response), and the other payload devices sequentially send CF-rsp through a backoff process.

In the method according to the present invention, when communicating individual data capable of bidirectional communication, the roadside device sends the poll and the data to the payload device, the payload device receiving the poll is transmitted when returning the poll using Poll Ack If there is data, send an Ack with the data. If the roadside device does not receive an Ack, it is better to perform retransmission. In addition, when communicating broadcast data in one direction, it is preferable that the roadside apparatus waits for SIFS after transmitting one frame to the onboard apparatus and transmits the next frame.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating the overall data flow between a communication system and an application, including portions to which the present invention pertains. In FIG. 1, the application and application layers are at layer 3 and above, the data link layer is layer 2, and the physical layer is layer 1. FIG. The present invention described below is located in the data link layer of Layer 2. The data link layer is composed of a medium access control (MAC) sublayer and a logical link control (LLC) sublayer.

As described above, the wireless communication to which the present invention is applied is made between the roadside apparatus and the onboard apparatus. A roadside device is a device installed on a roadside, especially a roadside near an intersection, and serves as a base station. The roadside device is connected to a remote server and is controlled by a server. The onboard device is a device that is installed in a vehicle traveling on the road and exchanges data with the roadside device through wireless communication.

The structure of the communication frame, which is a constant unit of information transmitted between the roadside device and the payload device, is as follows.

MAC header Payload FCS 32 bytes 0 to 1514 bytes 4 bytes

The MAC header is 32 bytes long and consists of several fields as shown below.

The definition of each field is as follows.

(One) Frame control field ( Frame Control field )

The frame control field has a length of 32 bits and provides characteristics of the physical layer and communication information of the frame. The subfields of this field are as follows.

The definition of each subfield of the frame control field is as follows.

Protocol Version field

The Protocol Version field indicates the version of the protocol being operated on the roadside device. If the roadside device serves a higher version of the protocol than the protocol in operation on the onboard device, the onboard device discards the frame without delivering it to the LLC sublayer.

Frequency field

The frequency field represents the frequency being serviced by the roadside device. The ISM frequency band in Korea is currently in the 5.8 GHz band, so from this band, 5.735 GHz to 5.815 GHz

An example of a frequency field will be described using a band as an example. However, this is merely an example, and the frequency field may be used in the same principle even when the frequency band is different.

division Bit number b5 b4 b3 b2 b1 b0 meaning 5.8 GHz 0 0 0 0 0 0 5.735 GHz 0 0 0 0 0 1 5.745 GHz 0 0 0 0 1 0 5.755 GHz 0 0 0 0 1 1 5.765 GHz 0 0 0 1 0 0 5.775 GHz 0 0 0 1 0 1 5.785 GHz 0 0 0 1 1 0 5.795 GHz 0 0 0 1 1 1 5.805 GHz 0 0 1 0 0 0 5.815 GHz

Transmit Rate field

The transmission rate field indicates the physical RF transmission rate serviced by the roadside apparatus, and has a range of 3 to 27 Mbps in the 5.8 GHz band.

division Bit number b3 b2 b1 b0 meaning 5.8 GHz 0 0 0 0 3 Mbps 0 0 0 1 4.5 Mbps 0 0 1 0 6 Mbps 0 0 1 1 9 Mbps 0 1 0 0 12 Mbps 0 1 0 1 18 Mbps 0 1 1 1 24 Mbps 1 0 0 0 27 Mbps

Equipment Type field

The equipment type indicates the type of equipment transmitting the data. At present, since there are only two roadside equipments and a payload equipment, the remaining number is reserved as a spare, and for example, a field may be defined as follows.

division Bit number b3 b2 b1 b0 meaning UTIS equipment 0 0 0 0 Spare 0 0 0 1 Roadside device 0 0 1 0 Mounting device 0 0 1 1 Spare

Connection Range field

The connection range field indicates the range to which the payload can connect to the roadside device. If the value of the poll identifier of the payload device is larger than the value of the connection range field of the packet received from the roadside device, the result value obtained by modulo operation of the value of the poll identifier of the payload device is used. Thus, connections can be limited or evenly distributed. The modulo operation is an arithmetic operation that results in the remainder when the first operation is divided by the second operation, such as 9mod5 = 4. The value of the connection range field is set only by the roadside device, and the onboard device is set to zero. The following example defines the value of the connection range field:

Bit number b3 b2 b1 b0 meaning 0 0 0 0 Stand-alone 0 0 0 1 One 0 0 1 0 4 0 0 1 1 8 0 1 0 0 16 0 1 0 1 32 0 1 1 0 64 0 1 1 1 128 1 0 0 0 256 1 0 0 1 512

Encryption Identifier (AES)

AES indicates whether the communication between the roadside device and the onboard device is encrypted. The encryption algorithm uses AES and sets the corresponding bit to 1 when using encryption and 0 when not using it. The AES used is defined as 128 bits.

Unicast Data field

Individual dates are bidirectional. Therefore, when the payload device is used to request access to the roadside device and the value of the field is '1', the roadside device may request allocation of individual data bandwidth. The roadside device permits the use of individual data if there is a resource to allocate for the onboard device that has requested individual data bandwidth allocation.

(2) identifier ( Poll Identifier )

Poll identifiers are commonly used in roadside and payload equipment and are used to identify service access points (SAPs) in the MAC sublayer, LLC sublayer and higher layers. A poll identifier is valid only until the transaction ends. The termination status of a transaction is determined by the higher layer. The poll identifier is used differently according to the case where the onboard device and the roadside device perform data communication and when they connect.

-In case of data communication

In this case, the value of the packet type field of the frame type field should be '01' or '10'. In case of data communication, poll identifier is used in two forms, individual address and broadcast address. The unicast address is used for point-to-point bidirectional communication between the roadside device and the payload device, and the broadcast address is used to transmit data in a broadcast form from the roadside device to the multiple payload devices. use.

-When connecting

In this case, the value of the packet type field of the frame type field should be '11', and is used as an identifier for connection between the roadside device and the on-board device.

(3) frame type field ( Frame Type field )

The frame type field indicates the type of a frame to be transmitted, and is a combination of a packet type field (1 byte) and a data type field (1 byte). The packet type field is used to distinguish individual, broadcast and access data, and the data type field is used to distinguish data, null data (only a MAC header exists), data with Ack, and the like.

An example of the value of a packet type field is as follows.

division Contents Bit number b7 b6 b5 b4 b3 b2 b1 b0 meaning Packet type field Individual data 0 0 0 0 0 0 0 1 Bidirectional individual data Broadcast data 0 0 0 0 0 0 1 0 One-way broadcast data Connection data 0 0 0 0 0 0 1 1 Connection data

An example of the value of the data type field is as follows.

division Contents Bit number b7 b6 b5 b4 b3 b2 b1 b0 meaning   Data type field  Individual data 0 0 0 0 0 0 0 1 Data 0 0 0 0 0 0 1 0 Null data 0 0 0 0 0 0 1 1 Ack + Data  Connection data 0 0 0 0 0 0 0 1 CF-poll data 0 0 0 0 0 0 1 0 CF-request data 0 0 0 0 0 0 1 1 CF-response data  Broadcast data 0 0 0 0 0 0 0 1 all 0 0 0 0 0 0 1 0 Specific group 0 0 0 0 0 0 1 1 Specific individuals

(4) receiving equipment ID  field( Destination ID field )

Destination ID is a receiver ID used for roadside and payload communication.

(5) transmission equipment ID  field ( Source ID field )

Source ID is a unique identifier for the transmission equipment used for roadside and payload communications. The sending device identifier uses the identifier value of the device sending the data.

The identifiers of the transmitter and receiver follow the values defined below.

The identifier system of roadside devices is shown in the table below.

7 6 5 4 3 2 One 0 Installation area Serial Number

In addition, the payload device identifier system is shown in the table below.

7 6 5 4 3 2 One 0 Management code Model code Area code Manufacturer Code Serial Number

(6) Service field ( SVC ; Service field )

The service field indicates an application service provided by the corresponding roadside apparatus. The value of the service field is given by the parent application. If the value of the Unicast field in the Frame Control field is set to '1' during the connection process between the roadside device and the onboard device, the roadside device is assigned a poll identifier for data communication when it responds to the onboard device that has requested the connection. To indicate the value, set the poll identifier value in the service field. Set to 0 if no application service is specified.

(7) transmit serial number ( SEQ  : Sequence )

The transmission serial number is used to avoid duplicate reception of the same message. The transmission serial number used in data communication is incremented by 1 when there is individual communication data in payload, and the SEQ value is adjusted to 256. The SEQ value has a value between 0 and 255. The initial value is 0. When sending null data, the SEQ value is 0. In the access frame, the SEQ value is 0.

(8) incoming serial number ( ACK  : Acknowledgement )

Receive Serial Number (ACK) uses the value of the received transmit serial number (SEQ). If the value of the receiving serial number (ACK) does not match the value of the sending serial number (SEQ), it is determined that it will not be properly received and retransmit. The ACK value has a value between 0 and 255. The initial value is 0.

Next, the function of the MAC header will be described. MAC header has large connection function, data communication function and link adaptation function.

First, the connection function will be described with reference to FIG. 2 is a schematic diagram showing a connection process between a roadside apparatus and a mounting apparatus.

In order to transmit data to the onboard and roadside devices or to communicate data with the roadside device, a connection process is required. Connection is made through the process called CF-poll, CF-req, CF-rsp. CF-poll (Connection Frame poll) is sent from the roadside device to the payload device and is used to request the connection from the payload device to the roadside device. CF-req (Connection Frame request) is sent from the loading device to the roadside device and is used when the loading device receiving CF-poll attempts to connect to the roadside device. CF-rsp (Connection Frame response) is the loading device from the roadside device. Used to send a connection response to a CF-req loaded device. There is a short interframe space (SIFS) as a pause between each signal, which is necessary to process data stably.

The roadside apparatus may determine whether there is a connection by storing a time point of receiving the CF-req in the buffer.

The onboard device uses a Clear Channel Assement (CCA) method to determine whether the wireless state is busy / idle when transmitting data. If the radio is busy, it waits until the radio is idle. This waiting time is called a random backoff time. The maximum value of this time is 250usec.

In addition, a backoff process is used as an algorithm for minimizing data collision. 3 is a schematic diagram of a backoff process.

As shown in FIG. 3, the backoff process operates after the CF-poll-mounted device passes SIFS and reduces the backoff time when the wireless medium is idle. If the value of the backoff time is 0, CF-req is given to the roadside device. If the wireless medium becomes busy during the backoff process, it stops reducing the backoff time and returns to the standby state. Referring to FIG. 3, when the CF-poll comes from the roadside device, it can be seen that the back-off time is 0 and the CF-req is performed.

4 is a schematic diagram of a connection process based on such a backoff. The connection of the payload device operates based on the CCA method and the backoff.

The roadside unit transmits CF-poll to provide the onboard unit with access. The onboard device transmits CF-req to the roadside device after performing the backoff if the received poll value is the same as its poll value. The roadside unit transmits CF-rsp for the onboard unit on which the CF-req was received. The roadside device only accepts the preempted CF-req even if it receives more than two CF-reqs from multiple payloads for one CF-poll. If the roadside unit does not receive any CF-req from the onboard unit, it waits for CIFS and then transmits the next frame.

Referring to FIG. 4, when the roadside device makes a connection request to the payload device A, the payload device A makes a CF-req to the roadside device after the backoff, and the roadside device sends the CF-rsp to the payload device A. When the roadside device calls the payload with the poll ID value of 1, the load devices B and C back-off each CF-req to the roadside device, but the response is because the CF-req of the payload device B comes in first. Is sent to B. When the roadside device calls the onboard device with the poll ID value of 2, there is no onboard device with the poll ID value of 2.

Next, data communication will be described.

Data communication is based on polling. When the roadside device gives the polling device an assigned poll identifier, the onboarding device transmits the data to the roadside device with the poll-ack. Data communication can be divided into individual and broadcast data communication. Individual data communication is bidirectional and is subject to an ACK for data transmission. Broadcast data communication is available only from the roadside device to the onboard device and does not receive an ACK for data transmission.

5 is a schematic diagram of an individual data communication process.

Individual data basically performs polling data communication. The roadside device assigns polls to the onboard device when it is connected, and the onboard device that receives the poll must return the poll using Poll Ack in DIFS. If there is data to send when returning poll, the piggy-back ack will be sent with the data. In other words, data and ack are simultaneously transmitted. In private communications, the roadside device must receive an ack for all data, and if it does not receive an ack, it retransmits.

Send poll and data (D1) from roadside equipment to payload. The receiving payload device sends the data U1 with Poll Ack. The roadside unit sends the poll and ACK values and data (D2) to the next station. The receiving payload device sends data (U2) along with Poll ACK. The roadside unit sends the poll and data (D3) to the next station. However, because the payload does not respond, wait until DIFS and then call the next payload. After receiving, the payload returns the Poll Ack.

6 is a schematic diagram of a broadcast data communication process.

Broadcast data is basically a broadcast communication method. Unilaterally transmit data from roadside equipment to payload. When receiving broadcast data, ACK is not separately performed. The broadcast data is transmitted from the roadside device to the onboard device, and after the end of one frame, the UE waits for SIFS and transmits the next frame.

In addition, the link adaptation function may be different in the environment of the payload device in the communication between the payload device and the roadside device, so that the transmission speed may be flexibly adjusted to maintain the most appropriate communication state between the payload device and the roadside device. The function to optimize. Without this function, you will be forced to use a fixed communication speed regardless of the environment.

According to the present invention configured as described above, since the structure of the communication frame can be defined as a specific communication protocol that can be actually applied to the intelligent traffic information system, the frame can be applied to actual communication for practical use.

Claims (13)

In a wireless communication system between a roadside device connected to a remote server, under the control of the server, and installed on a roadside to form a fixed base station, and a roadside device installed on a vehicle traveling on the road and exchanging data with the roadside device via wireless communication. In a structure of a communication frame in which a roadside device allocates a communication medium to a vehicle's onboard device passing through its own communication area, and enables the communication between the roadside device and the onboard device: A Medium Access Control (MAC) header having a size of 32 bytes and providing general information about communication; A payload having a size of 0 to 1514 bytes and carrying appropriate main data according to a frame type defined in a MAC header; And And a frame check sequence (FCS) having a size of 4 bytes. The method of claim 1, wherein the MAC header, A frame control field having a length of 4 bytes and providing characteristics of a physical layer and communication information of a frame; It has a length of 2 bytes and is commonly used in roadside and payload equipment. It is used to identify service access points (SAPs) at the MAC sublayer, LLC sublayer, and higher layers, and is valid only until the end of the transaction. Poll ID) field; A frame type field having a length of 2 bytes and indicating a type of a frame to be transmitted, and comprising a combination of a packet type field of 1 byte length and a data type field of 1 byte length; It has a length of 8 bytes and has a unique value as a receiving device identifier used for communication between the roadside device and the payload device.There is no destination of a specific receiving device when transmitting a frame, or a connection request from the broadcast data or the roadside device to the payload device is required. A Destination Equipment ID field, which defines an identifier of a destination device when present; A source equipment ID field having a length of 8 bytes and having a unique value as a transmitter equipment identifier used for communication between the roadside apparatus and the payload apparatus; It has a length of 4 bytes and indicates an application service such as a commercial image provided by the corresponding roadside device, and selects a function available to a loading device such as a moving picture according to the performance or function of the loading device according to the value of the frame control field. Service field for; It has a length of 1 byte and is used exclusively for unicast data communication to avoid duplicate reception of the same message, and it is incremented by 1 when there is individual communication data in the payload and has a value between 0 and 255. Sequence) field; And If the value of the received serial number does not match the value of the transmitted serial number, it is judged that it has not been properly received and the acknowledge serial number (ACK) field having a value of 0 to 255 is compared with the value of the received serial number. The structure of a communication frame comprising a. The apparatus of claim 2, wherein the frame control field is a 2-bit protocol version subfield indicating a version of a protocol being operated by the roadside apparatus, a 6-bit length frequency subfield indicating a frequency bath serviced by the roadside apparatus, and a roadside apparatus. 4 bit length field indicating the physical wireless transmission rate serviced by the service provider, 4 bit length device type subfield indicating whether the type of equipment transmitting data is a roadside or payload device, A 4-bit Connection Range subfield indicating the range of access to the device, a 2-bit encryption identification subfield indicating whether communication between the roadside device and the onboard device is encrypted, and the onboard device is a roadside device. Communication data, characterized in that it comprises a two-bit individual data subfield is used when the connection request Any structure. 4. The structure of claim 3, wherein the onboard device discards the corresponding communication frame when the protocol version subfield indicates that the roadside device serves a higher version of the protocol than the protocol in operation on the onboard device. 4. The structure of a communication frame according to claim 3, wherein the value of the encryption identification subfield is set to "1" when using encryption and "0" when not using encryption. 4. The method of claim 3, wherein if the value of the individual data subfield is "1", the payload device can request a bandwidth allocation from the roadside device, and if the roadside device has resources to allocate to the payload device requesting individual data bandwidth allocation, A structure of a communication frame, characterized by allowing the use of data. The packet type field of the frame type field is used to distinguish bidirectional individual data, unidirectional broadcast data, and access data, and the data type field includes only MAC headers without main data. A structure of a communication frame, characterized in that it is used to distinguish the type of data, such as null data or Ack data. In a wireless communication system between a roadside device connected to a remote server, under the control of the server, and installed on a roadside to form a fixed base station, and a roadside device installed on a vehicle traveling on the road and exchanging data with the roadside device through wireless communication The communication apparatus uses the communication frame according to any one of claims 1 to 7, wherein the roadside device allocates a communication medium to the onboard device of the vehicle passing through its communication area and enables smooth communication between the roadside device and the onboard device. In the way: When requesting connection from the onboard device to the roadside device, the onboard device receives CF-poll (Connection Frame poll) sent from the roadside device and operates after SIFS (Short Interframe Space) based on the backoff process. A CF-req (Connection Frame request) requesting a connection when the state is idle, and if the wireless state is busy, stops reducing the backoff time and returns to the standby state. The CF-req according to claim 8, wherein when two or more CF-reqs are received from a plurality of payloads having the same ID with respect to the CP-poll sent by the roadside device, the first connection response signal is only CF-req. Sending rsp (Connection Frame response), the remaining on-board communication method characterized in that to sequentially send CF-rsp through the back-off process. The method according to claim 8 or 9, wherein when communicating individual data capable of bidirectional communication, the roadside device sends the poll and data to the payload device, and the payload device receiving the poll transmits the poll when returning the poll using Poll Ack. If there is data, transmit the Ack together with the data, and if the roadside device does not receive the Ack, perform a retransmission. The communication method according to claim 8 or 9, wherein when the broadcast data communicated in one direction is communicated, the roadside apparatus waits for the SIFS after transmitting one frame to the payload apparatus and transmits the next frame. 10. The method according to claim 8 or 9, wherein when the roadside device and the payload device are connected, the connection limit is distributed or evenly distributed by using a result obtained by modularly calculating the pole identifier value of the payload device into the connection range field value. How to feature. 12. The method according to claim 11, wherein the presence or absence of a connection is determined by storing, in a buffer, a time point at which the CF-req is received when the roadside device and the payload device are connected.

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