JP2001345829A - Narrow area communication system - Google Patents

Abstract

(57) [Problem] To provide high reliability in data transfer using DSRC as a road-vehicle communication system. SOLUTION: An RSU transmission control unit of RSUs 3A to 3N stores an IP packet from an AP server in a DSRC frame and extracts an IP packet stored in the DSRC frame from the onboard unit. The OBE transmission control unit of the OBE 5 converts the IP packet from the PC 6 into a D
The IP packet stored in the SRC frame and extracted from any of the RSUs 3A to 3N in the DSRC frame is extracted. Then, the AP server 1 and the PC 6
In the data transfer control unit of
When an IP packet exchanged by a C frame is lost, retransmission control of the IP packet is performed based on the TCP protocol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-range communication system, and more particularly to a short-range communication (DSRC: Dedicated Short Radar).
The present invention relates to a short-range communication system for exchanging various data between a server and an in-vehicle terminal by using nge communication.

[0002]

2. Description of the Related Art Non-stop automatic toll collection (ETC: Electronic Toll) for toll collection on toll roads
Collection), a short-range communication (DSRC: Dedicated Short Range Commun
ication)). This kind of narrow-area communication system has been studied for the purpose of exchanging data of relatively small size (spot communication) between roads and vehicles on the premise of a narrow wireless communication range, and its protocol layer is a physical layer. It comprises an application layer (Layer 7) in addition to a layer (Layer 1) and a data link layer (Layer 2).

[0003]

As such a short-range communication system, application to applications other than ETC, for example, applications such as parking lots, gas stations, convenience stores, and drive-throughs, as a road-to-vehicle communication system, is being studied. ing. However, in such a conventional narrow-area communication system, it is assumed that data of a relatively small size is transferred. Therefore, if a data transfer error occurs due to an instantaneous interruption of a wireless communication path, the data is lost. When data of a relatively large size, such as image data, cannot be compensated for and data is transferred, for example, there is a problem that the probability of error occurrence increases and desired reliability cannot be obtained.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a narrow-area communication system using DSRC as a road-to-vehicle communication system, which can achieve high reliability.

[0005]

In order to achieve the above object, a narrow-area communication system according to the present invention is arranged along a road and performs wireless communication with a vehicle running on the road using DSRC. A communication control device, a server connected to each of these communication control devices via a LAN line, converts arbitrary data into IP packets, and exchanges the data with a vehicle via any of the communication control devices, and a DSRC mounted on the vehicle. A vehicle-mounted device that performs wireless communication with any of the communication control devices,
The vehicle includes a vehicle-mounted terminal that is mounted on the vehicle and connected to the vehicle-mounted device of the vehicle via a LAN line, converts arbitrary data into IP packets, and exchanges data with a server via the vehicle-mounted device.

[0006] Then, the communication control device sends the I
A roadside transmission control unit for storing the P packet in the DSRC frame and extracting the IP packet stored in the DSRC frame from the in-vehicle device is provided, and the in-vehicle device stores the IP packet from the in-vehicle terminal in the DSRC frame and performs communication. An in-vehicle transmission control unit for extracting the IP packet stored in the DSRC frame from the control device is provided, and the data transfer control unit of the server and the in-vehicle terminal, when the IP packet exchanged by the DSRC frame in the wireless communication section is lost. Is designed to perform retransmission control of IP packets based on the TCP protocol.

When the destination of an IP packet is managed when switching between communication control devices due to movement of a vehicle occurs, a relay connection is made between a server and each communication control device via a LAN line. An intelligent bridge that searches for a communication control device that manages the in-vehicle terminal to which the IP packet is to be transmitted in response to receiving the transmitted IP packet, and transfers data to the searched communication control device; The device may manage the in-vehicle terminal corresponding to the in-vehicle device that can wirelessly communicate with the communication control device using the DSRC, and may respond to the search by the intelligent bridge only when the in-vehicle terminal is managed.

In the case where the relatively large file data is transferred continuously by the difference, the data transfer control of the transmission side for transmitting the file data among the data transfer control units provided in the server and the vehicle-mounted terminal. In the department,
When the transfer of the file data is started, the file name is notified to the data transfer control unit on the receiving side, and then the file name of the file data is notified according to the received file size notified from the data transfer control unit on the receiving side. Start data transfer for the unreceived portion of the, and of the respective data transfer control units provided in the server and the in-vehicle terminal,
The receiving-side data transfer control unit that receives the file data notifies the transmitting-side data transfer control unit of the size of the file data corresponding to the file name notified from the transmitting-side data transfer control unit as the received file size. At the same time, the received data may be sequentially added to the end of the file data and stored.

When detecting the disconnection of the TCP connection, control of the TCP protocol is performed so that the occurrence of an error can be detected in a shorter time by the respective data transfer control units provided in the server and the vehicle-mounted terminal as compared with the standard TCP protocol. The retransmission control of the IP packet may be performed by changing the value of the parameter. In this case, in the data transfer control unit, among the control parameters of the TCP protocol, the initial time for waiting for an ACK response at the time of transmission, the number of packet retransmissions, the value of a keep-alive timer, the initial time for waiting for an ACK response at the time of connection connection, and the number of connection retry times May be changed.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a short-range communication system according to one embodiment of the present invention. Hereinafter, a case where the present invention is applied to a parking lot management system that provides various services by exchanging various data with a vehicle that has entered a parking lot by using short-range communication (hereinafter, referred to as DSRC) will be described. However, the present invention is not limited to this, and can be applied to other systems that perform road-vehicle communication using DSRC.

An application server (hereinafter, referred to as an AP server) 1 is a server device for executing a parking lot management application, and exchanges necessary data with the vehicle 4. As this data, for example, file data of a relatively large size such as a map or guidance in a parking lot, data indicating an operation input by a user in the vehicle 4 and the like are exchanged. In the parking lot, besides entrance and exit,
A plurality of communication control devices (hereinafter referred to as RSUs: RSUs) 3A to 3N are arranged along a roadway or a parking space, and a LAN.
Each of the bridges is connected in parallel to an intelligent bridge (hereinafter, referred to as a bridge) 2 via a line 9B, and the bridge 2 is connected to the AP server 1 via a LAN line 9A.

The vehicle 4 includes an on-vehicle device (hereinafter, referred to as OBE) 5 for communicating with any one of the RSUs 3A to 3N using DSRC, and an OBE 5
And an in-vehicle terminal (hereinafter referred to as a PC) connected to the AP server 1 via the LAN line 9C to exchange various data with the AP server 1.
Personal Computer) 6. Also, L
In addition to the AP server 1, the AN line 9A is connected to an address management server 7 for managing the address of the PC 6 for each vehicle 4 entering the parking lot, and an Internet server 8 for connecting to the Internet. .

In the narrow area communication system shown in FIG. 1, TCP having a retransmission control (flow control) function for lost packets
By exchanging data between the AP server 1 and the PC 6 based on / IP, a data compensation function at the time of occurrence of a data transfer error which is not provided in the DSRC is complemented. Actually, in the wired communication section connected by the LAN lines 9A to 9C, the IP packetized data is converted to an L frame such as an Ethernet (registered trademark) frame.
Data communication is performed by encapsulation in an AN frame. In a wireless communication section between the RSUs 3A to 3N and the OBE 5, data encapsulated in IP packets is
Data communication is performed based on the C protocol.

Therefore, in the RSUs 3A to 3N, the AP
For the data from the server 1, the IP packet stored in the LAN frame is replaced with the DSRC frame and transmitted to the OBE 5, and for the data from the OBE 5, the IP packet stored in the DSRC frame is extracted and placed on the LAN frame. Instead, it transmits to the AP server 1. In the OBE 5, the data from the PC 6 is transferred to the RSUs 3A to 3N by replacing the IP packet stored in the LAN frame with the DSRC frame, and the data from the RSUs 3A to 3N is stored in the DSRC frame. The packet is changed to a LAN frame and transmitted to the PC 9. Thereby, when the DSRC frame storing the IP packet is lost, the AP server 1 determines that the IP packet is lost.
And the PC 6 and retransmission control of the IP packet is performed.

Next, the configuration of the AP server will be described with reference to FIG. FIG. 2 is a block diagram showing the AP server. The AP server 1 includes an application processing unit (hereinafter, referred to as an AP processing unit) 11, a storage unit 12, a data transfer control unit 13, and a LAN communication unit 14.

The AP processing unit 11 transfers various file data stored in the storage unit 12 to the PC 6,
Various services are provided using the data from 6. The data transfer control unit 13 manages connections used for data transfer based on TCP / IP,
It performs data transmission / reception processing including mutual conversion of packets, data retransmission control processing, and the like. In the LAN communication unit 14, the LAN
The LAN frame storing the IP packet is transmitted and received using the line 9A. The address management server 7 and the Internet server 8 have substantially the same configuration as the AP server 1, and a detailed description is omitted.

Next, the configuration of the bridge will be described with reference to FIG. FIG. 3 is a block diagram showing a bridge. The bridge 2 includes a LAN communication unit 21, a LAN communication unit 22, and a bridge processing unit 23.

The LAN communication unit 21 transmits and receives a LAN frame storing an IP packet using the LAN line 9A. The LAN communication unit 22 transmits and receives a LAN frame storing an IP packet using the LAN line 9B. In the bridge processing unit 23, the AP server 1 and the RSU3
ARP (Adderss Resolution Proto) on behalf of A-3N
col: address resolution protocol) In addition, LAN frames from one of the LAN lines 9A and 9B other than the ARP request are directly used for the other LAN line 9A.
B, 9A.

The bridge processing unit 23 transmits an APR request message to all the RSUs 3A to 3N in response to the ARP request message from the LAN communication unit 14 of the AP server 1. If there is an ARP response message from any of the RSUs, an ARP response message is returned to the AP server 1. At this time, the ARP response message notifies the MAC address of the bridge 2 on the LAN line 9A side. At the time of a data transmission request (at the time of data reception) from the AP server 1, an APR request message is transmitted to all the RSUs 3A to 3N, and if there is an ARP response message from any of the RSUs, the MAC notified by the ARP response message is sent. The address, that is, the data requested to be transmitted to any of the RSUs is transmitted as a LAN frame.

On the other hand, in response to an APR request message from RSUs 3A to 3N, an ARP request message is transmitted to each server connected to LAN line 9A.
If there is an RP response message, LAN line 9 of bridge 2
The MAC address of B side is notified by an ARP response message. At the time of a data transmission request (at the time of data reception) from RSUs 3A to 3N, an APR request message is transmitted to each server connected to LAN line 9A.
If there is an RP response message, the MAC address notified by the ARP response message, that is, the data requested to be transmitted to one of the servers is transmitted as a LAN frame.

Next, the configuration of the RSU will be described with reference to FIG. FIG. 4 is a block diagram showing the RSU.
The RSU 3 includes a LAN communication unit 31, a DSRC communication unit 3,
2. RSU transmission control unit (roadside transmission control unit) 33 and O
A BE management unit 34 is provided.

The LAN communication section 31 transmits and receives a LAN frame storing an IP packet using the LAN line 9A. The DSRC communication unit 32 uses the DSRC to
DS storing IP packet in wireless communication section with BE5
Send and receive RC frames. The RSU transmission control unit 33 performs an IP packet transfer process between the LAN frame and the DSRC frame. The OBE management unit 34 manages the PC 6 of the vehicle existing within the wireless communication range of the DSRC communication unit 32 by its IP address, and manages the PC 6 of the IP address specified by the ARP request message from the bridge 2. Notifies the MAC address of the LAN communication unit 31 with an ARP response message.

Next, the configuration of the OBE will be described with reference to FIG. FIG. 5 is a block diagram showing the OBE.
The OBE 5 includes a DSRC communication unit 51 and a LAN communication unit 5
2. An OBE transmission control unit (vehicle transmission control unit) 53 is provided.

The DSRC communication section 51 uses the DSRC to transmit an IP in a radio communication section with any of the RSUs 3A to 3N.
The transmission and reception of the DSRC frame storing the packet is performed.
The LAN communication unit 52 transmits and receives a LAN frame storing an IP packet using the LAN line 9C. OB
The E transmission control unit 53 performs a process of changing IP packets between the LAN frame and the DSRC frame.

Next, the configuration of the PC will be described with reference to FIG. FIG. 6 is a block diagram showing a PC. PC
4 includes an application processing unit (hereinafter, referred to as an AP processing unit) 61, a storage unit 62, a data transfer control unit 63, an LA
An N communication unit 64, an operation input unit 65, and a display unit 66 are provided.

The AP processing section 61 transfers data input from the operation input section 65 and various file data stored in the storage section 62 to the AP server 1, and displays data from the PC 6 on a display section 66. And provide various services using the data. In the data transfer control unit 63, T
It manages connections used for data transfer based on CP / IP, performs data transmission / reception processing including mutual conversion between file data and IP packets, and performs data retransmission control processing. L
The AN communication unit 64 transmits and receives a LAN frame storing an IP packet using the LAN line 9C.

Next, the operation of the present invention will be described with reference to the drawings. A TCP / TCP is transmitted between the equipment such as the AP server 1 disposed on the road side and the PC 6 of the vehicle 4 entering the parking lot.
When performing data transfer based on IP, the communication partner I
It is necessary to obtain a P address. Further, in order to specify a communication partner, it is necessary to use a unique IP address in the parking lot for each PC 6 of all vehicles that have entered the same parking lot.

As a method for managing such IP addresses, for example, an IP address previously assigned to the AP server 1 as a communication terminating device or the PC 6 of each vehicle 4 is notified to the other communication party. You may. In addition, a predetermined IP address may be allocated to the PC 6 of each vehicle 4 by performing a predetermined IP address allocation process between the address management server 7 and the PC 6 of each vehicle 4. In the present invention, as long as the above condition is satisfied, any method of managing the IP address may be used, and a detailed description thereof will be omitted.

Next, a case where data is transferred from the AP server 1 to the PC 6 will be described with reference to FIG. FIG.
FIG. 4 is a sequence diagram showing a data transfer operation. Usually T
In CP / IP, when performing data communication, it is necessary to set a connection in advance, but here, only the operation of transferring one data will be described. AP of AP server 1
The processing unit 11 starts transmission of the corresponding file data in response to an instruction to start the entrance processing from the address management server 7 or the like, a request operation by a passenger of the vehicle 4, and the like. First, the AP processing unit 11 makes a data transmission request to the data transfer control unit 13 by designating a file name and a destination IP address (step 110).

In response, the data transfer control unit 13 reads out the file data from the storage unit 12 and divides the file data into IP packets. Further, an ARP request is transmitted to the LAN line 9A via the LAN communication unit 14 in order to obtain a MAC address corresponding to the destination IP address (Step 111). Bridge processing unit 2 of bridge 2
3, the ARP request is received via the LAN communication unit 21 and transmitted to the LAN line 9 B via the LAN communication unit 22.
A P request is transmitted (step 112).

RSU for managing the IP address specified by the ARP request among RSUs 3A to 3N, for example, RSU3
A returns an ARP response (step 113). In response, the bridge 2 returns an ARP response to the AP server 1 (step 114). As a result, the bridge processing unit 23 obtains the MAC address corresponding to the destination IP address, and converts the MAC address and the IP packet to L.
Transfer to the AN communication unit 14.

The LAN communication unit 14 stores the IP packet in the LAN frame, sets a MAC address in the header of the LAN frame, and sets the MAC address in the LAN line 9A.
The data is transmitted to (step 115). The bridge processing unit 23 receives the LAN frame via the LAN communication unit 21 and acquires the RSU corresponding to the destination IP address, for example, the MAC address of the RSU 3A in steps 116 and 117 in the same manner as in steps 112 and 113 described above. Then, the LAN communication unit 22 transmits data to the LAN line 9B from the LAN frame in which the MAC address is set as a destination (step 118).

In the RSU transmission control unit 33 of the RSU 3A,
The IP packet stored in the LAN frame received by the LAN communication unit 31 is transferred to the DSRC frame, and the LID or OBE corresponding to the destination IP address is changed.
-Set the ID in the header, and transmit data from the DSRC communication unit 32 to the wireless communication path (step 119). OB
In the E5 OBE transmission control unit 53, the DSRC communication unit 51
The IP packet stored in the received DSRC frame is transferred to the LAN frame. Note that, since the information storage field length of the DSRC frame is shorter than the IP packet length, in this wireless communication section, 1
One IP packet is divided into a plurality of DSRC frames and transmitted, and the original IP packet is restored on the receiving side.

Then, similarly to the above steps 112 and 113, the MAC address of the PC 6 corresponding to the destination IP address is obtained in steps 120 and 121, and the MA
LA frame with C address set as destination
The data is transmitted from the N communication unit 22 to the LAN line 9B (step 122). In the data transfer control unit 63 of the PC 6,
The data is extracted from the IP packet stored in the LAN frame received by the LAN communication unit 64 and sequentially stored in the storage unit 62 as a file. This means that the data of the AP server 1 has been transferred to the PC 6 of the vehicle 4. Note that the data transfer operation when transferring various data from the PC 6 to the AP server 1 is performed in a procedure reverse to the above, and a detailed description thereof will be omitted.

In such a data transfer operation, when the vehicle 4 moves from the RSU 3A to the radio communication range of the RSU 3B, the RSU 3A cannot exchange the DSRC frame with the OBE 5 of the vehicle 4. In such a case, the RSU switching operation by the bridge 2 as shown in FIG. 8 is performed. FIG. 8 is a sequence diagram showing the RSU switching operation. If the DSRC connection between the RSU 3A and the OBE 5 is disconnected (step 150), the RS
The OBE management unit 34 of the U3A checks the
5 is set to the invalid state and the OBE management table with the set of OBE-ID, LID, and IP address (step 15).
1).

Thereafter, data transmission 1 from the AP server 1
If there is an ARP request from the bridge 2 according to 52 (step 153), the RSU 3A determines that the IP address specified in the ARP request is out of management and ignores it. Therefore, no ARP response is made from any of the RSUs 3A to 3N, and the ARP request is repeatedly made from the bridge 2 for a predetermined period. here,
The vehicle 4 moves into the radio communication range of the RSU 3B, and
When a DSRC connection is formed between the BE 5 and the RSU 3B (Step 154), Step 10 in FIG.
IP addresses are assigned in the same manner as in 1 to 107, and are set in the RBE3B OBE management table (step 155).

At this time, the address management server 7
The RSU 3B is notified of the IP address already assigned to the OBE-ID notified from the SU 3B. Therefore, the RSU 3B returns an ARP response in response to the ARP request from the bridge 2 (step 156) (step 157). Thereby, data transmission is performed from the bridge 2 to the RSU 3B (step 15).
8) The data is transmitted from the RSU 3B to the OBE 5 (step 159).

As described above, the vehicles 4 existing within the respective wireless communication ranges by the RSUs 3A to 3N are transmitted to the IPs of the PCs 6 thereof.
Since the RSU managing the destination IP address is sequentially searched for each data transmission request or ARP request from the AP server, the vehicle 4
, The communication path can be switched smoothly even when the RSU is switched.

Next, a file transfer operation for transferring one file as relatively large data from the AP server 1 to the PC 6 of the vehicle 4 will be described with reference to FIG. FIG. 9 is a sequence diagram showing a file transfer operation. In FIG. 9, an IP address has already been assigned to the PC 6 of the vehicle 4 when entering the parking lot, and the OBE of the vehicle 4
5 is connected to the RSU 3B. It is also assumed that a file transfer request is made from the PC 6 to the AP server 1.

The data transfer control units of the AP server 1 and the PC 6 are actually realized by the operation of a file transfer program. As the file transfer program, a server-side program used on the data transmission side and a client-side program used on the data reception side are prepared. The server-side program is used on the TCP connection receiving side, and the TCP connection is established on the request side. A client-side program is used. In the case of FIG. 9, the server side is used in the AP server 1, and the client side is used in the PC 6.

First, the function of the server-side program will be described. [Wait for connection connection] The server-side program waits for the connection connection request 200 from the client-side program in the parent process. At this time, even if connection connections are requested from a plurality of clients almost simultaneously, the connection connection requests are waited for in a plurality of queues so that the connection connection requests can be accepted in order. [Inherit connection to child process] When accepting a connection connection request from a client 201, a child process is generated, and the connection is taken over to the generated child process. This connection is called a control connection.

[Parent Process Processing] The parent process waits for a connection connection request from the next client. [Receive File Transfer Request] The child process receives the transfer file information (file name, transmission / reception type, first time / continuation type) 202 from the client as data using the control connection, and then performs the following processing. .

[Open of Transfer File] When the file transfer is a transmission from the server, the transfer file 203A is opened from the beginning in the read mode. In addition, if the file transfer is the first processing with transmission from the client side,
The transfer file is opened in the write mode from the head, and if the file transfer is a transmission from the client side and the processing is continued, the transfer file is opened in the write mode from the end.

[Confirmation of File Transfer Start] When the file transfer is transmitted from the server, the server transmits the data using the transfer file size 204 as data using the control connection. Thereafter, the size of the transfer file received from the client side (0 at the time of the first transfer) 205
Is received as data using the control connection. Then, the read position of the file data to be transmitted is updated by the received size on the client side.

When the file transfer is a transmission from the client, the size of the transfer file received from the server (0 at the time of the first transfer) is transmitted as data using the control connection. Thereafter, the data is received using the control connection with the transfer file size from the client side as data. The write position of the received file data remains as it was when the transfer file was opened.

[Connection Connection Request] Next, a connection connection request 20 for transmitting and receiving file transfer data
6 is transmitted to the client, and acceptance 207 from the client side is confirmed. This connection is called a data connection. [File transfer by TCP / IP] When the file transfer is transmission from the server side, data (data after the received size) 208 read from the file is transmitted using the data connection, and A from the client side is transmitted.
CK (delivery notice) 209 is confirmed. When normal reception is confirmed by ACK, the next data is transmitted. When the file transfer ends normally, disconnection of data connection 210
I do. When the file transfer is a transmission from the client side, a process of receiving data of the file transfer (data after the received size) using a data connection and writing the data to a file is performed.

[Confirmation of File Transfer Completion] When the file transfer is a transmission from the server side, the file is received using the control connection, using the transfer file received size 211 on the client side as data. When the file transfer is transmission from the client side, the size of the transfer file received on the server side is transmitted as data using a control connection. [File transfer completed] When the file transfer is completed,
The transfer file is closed, the control connection is disconnected 212, and the child process ends.

[Start of continuous difference transfer] During file transfer,
When the disconnection of the data connection is detected due to the loss of the IP packet, the transfer file is closed, the control connection is disconnected, and the child process is terminated. Thereafter, since the parent process accepts the connection request for the control connection from the client side, continuous differential transfer of file transfer is started.

Next, the function of the client-side program will be described. [Connection Request] The client program issues a connection request 200 to the server program. When the connection of the connection fails, the connection connection request for the number of retries is repeated. [Operator confirmation when connection fails] If a connection fails even after repeating the connection connection request for the number of retries, a message is displayed to confirm to the operator whether to continue the operation or not. Wait for an instruction from the operator. When the instruction to continue is given, the connection connection request for the number of retries is repeated again. If you are instructed not to continue, end the program.

[Send File Transfer Request] When the connection is successfully accepted in the acceptance 201 of the connection request from the server, transfer file information (file name, send / receive type, first time /
After transmitting the continuation type) 202 to the server as data,
The following processing is performed. [Opening of Transfer File] When the file transfer is the first processing by transmission from the server side, the transfer file 203B is opened in the write mode from the beginning. When the file transfer is transmission from the server side and is a continuation process, the transfer file 203B is opened in a write mode from the end.
If the file transfer is transmission from the client side, the transfer file is opened in the read mode from the beginning.

[Confirmation of File Transfer Start] When the file transfer is a transmission from the server side, the file is received using the control connection with the transfer file size 204 from the server side as data. Thereafter, the size of the transfer file received on the client side (0 at the time of the first transfer) 20
5 is transmitted as data using the control connection. The write position of the received file data remains as it was when the transfer file was opened. When the file transfer is a transmission from the client, the size of the transferred file received on the server (0 at the time of the first transfer) is received as data using the control connection. Thereafter, the data is transmitted using the control connection with the transfer file size from the client side as data. Then, the read position of the file data to be transmitted is updated by the received size on the server side.

[Waiting for Connection] Next, a connection request from the server is awaited to connect a data connection for transmitting and receiving data for file transfer. [File transfer] When the file transfer is a transmission from the server side, a process of receiving the transmission data (data after the received size) 207 of the file transfer using the data connection and writing the received data to the file is performed. Also, ACK 209 is returned in response to reception of transmission data 207. Disconnection of data connection when file transfer is completed 21
Perform 0. When the file transfer is transmission from the client side, the file transfer data (data after the received size) read from the file is transmitted using the data connection.

[Confirmation of File Transfer Completion] When the file transfer is received from the server, the file is transmitted using the control connection as the data of the size 211 of the received file on the client. When the file transfer is transmission from the client side, the file is received using the control connection as the data of the size of the transfer file received on the server side. [File transfer completed] When the file transfer is completed,
Close the transfer file, disconnect the control connection, and exit the client.

[Start of continuous difference transfer] When disconnection of the data connection is detected during file transfer, the transfer file is closed and the control connection is disconnected.
2 and then resume from the connection request of the control connection to start the continuous differential transfer of the file transfer.

As described above, before the data transmission side starts transmission, information on the size of the received data is received from the data reception side, and the data is transmitted from the file data after that size. Even if the connection is disconnected during the transfer of data or the like, only the difference can be transferred continuously when the data transfer is resumed. Further, after the data transmitting side transmits the final data of the transfer file, the data receiving side notifies the transmitting side of the received size, so that the transmitting side can accurately determine the completion of the file transfer.

In order to efficiently repeat the above data transfer processing according to the switching of the RSU, it is necessary to quickly detect that the vehicle 4 has left the radio communication range of the RSU. In the present system, as shown in FIG.
By changing (tuning) the control parameters of the CP protocol, the disconnection of the vehicle 4 from the wireless communication range is quickly detected by disconnecting the TCP connection.

The detection of disconnection of the TCP connection differs between the data transmitting side and the data receiving side. First, on the data transmitting side, when a packet retransmission timeout of the TCP protocol occurs, the write function for the socket returns an error, thereby detecting the disconnection of the connection. The packet retransmission timeout of the TCP protocol can be quickly detected by making the “ACK response waiting initial time” and the “number of packet retransmissions” smaller than standard values.

On the other hand, on the data receiving side, when the keep-alive timeout of the TCP protocol occurs, the read function for the socket returns an error, so that the disconnection of the connection can be detected. The keep-alive timeout of the TCP protocol can be quickly detected by setting the “keep-alive timer value” smaller than a standard value. The failure detection of the TCP connection is detected only on the request side of the connection. On the connection connection accepting side, since only the window for accepting the connection request is opened, there is no need to detect the failure of the TCP connection connection. On the connection connection request side, when the connection connection request of the TCP protocol times out, the failure of the connection connection can be detected by the error return of the connect function for the socket.

The connection connection request timeout of the TCP protocol can be quickly detected by making the “ACK response waiting initial time”, “packet retransmission count”, and “connection connection retry count” smaller than standard values. As described above, by controlling the control parameters of the TCP protocol and performing retransmission control of the IP packet so that the occurrence of an error can be detected in a shorter time as compared with the standard TCP protocol, the wireless communication range of the next RSU is reached. In the meantime, the connection failure of the TCP connection can be quickly detected, and the connection of the TCP connection is retried at an appropriate interval to reach the next wireless communication range.
The subsequent file data transfer can be resumed quickly.

[0060]

As described above, according to the present invention, the communication control device stores the IP packet from the server in the DSRC frame and extracts the IP packet stored in the DSRC frame from the vehicle-mounted device. Section is provided. Further, the vehicle-mounted device is provided with a vehicle-mounted transmission control unit for storing the IP packet from the vehicle-mounted terminal in the DSRC frame and extracting the IP packet stored in the DSRC frame from the communication control device. Then, the data transfer control unit of the server and the in-vehicle terminal transmits D in the wireless communication section.
When an IP packet exchanged by the SRC frame is lost, retransmission control of the IP packet is performed based on the TCP protocol. As a result, even if a data transfer error occurs due to an instantaneous interruption of the wireless communication path,
The lost data can be compensated, and high reliability data transfer can be realized even when the error occurrence probability increases, for example, when transferring relatively large data such as image data.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a narrow area communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an AP server.

FIG. 3 is a block diagram showing a bridge.

FIG. 4 is a block diagram showing an RSU.

FIG. 5 is a block diagram showing an OBE.

FIG. 6 is a block diagram showing a PC.

FIG. 7 is a sequence diagram showing a data transfer operation.

FIG. 8 is a sequence diagram showing an RSU switching operation.

FIG. 9 is a sequence diagram showing a file transfer operation.

FIG. 10 is an explanatory diagram showing an example of changing a control parameter of the TCP protocol.

[Explanation of symbols]

1 ... AP server, 2 ... Bridge, 3A-3N ... RSU,
4 vehicle, 5 OBE, 6 PC, 7 address management server, 8 internet server, 9A to 9C LAN
Line, 11 AP processing unit, 12 storage unit, 13 data transfer control unit, 14 LAN communication unit, 21, 22 LAN
Communication unit 23 bridge processing unit 31 LAN communication unit
32 DSRC communication unit, 33 RSU transmission control unit, 34
... OBE management unit, 51 ... DSRC communication unit, 52 ... LAN
Communication unit 53 OBE transmission control unit 61 AP processing unit
62: storage unit, 63: data transfer control unit, 64: LAN
Communication unit 65: operation input unit 66: display unit

Continued on the front page (72) Inventor Masahiro Tsuda 1-6-1 Uchisaiwaicho, Chiyoda-ku, Tokyo NTT Communications F-term (reference) 5H180 BB04 EE10 5K033 BA08 CB04 CC01 DA01 DA03 DA19 EC03

Claims (5)

[Claims] 1. A plurality of communication control devices arranged along a road and performing wireless communication with a vehicle traveling on the road using DSRC, and an IP packet connected to each of the communication control devices via a LAN line and transmitting arbitrary data. A server that communicates with the vehicle through any of the communication control devices,
An in-vehicle device mounted on the vehicle and performing wireless communication with any one of the communication control devices using the DSRC; and an in-vehicle device mounted on the vehicle and connected to the in-vehicle device of the vehicle via a LAN line to convert arbitrary data into IP packets. An on-board terminal for exchanging with the server via the on-board unit, wherein the communication control device stores an IP packet from the server in a DSRC frame and stores the IP packet in the DSRC frame from the on-board unit. A roadside transmission control unit for extracting an IP packet, wherein the in-vehicle device converts the IP packet from the in-vehicle terminal into a DS.
An in-vehicle transmission control unit for extracting an IP packet stored in a DSRC frame from the communication control device while storing the RC packet in the RC frame;
A narrow-area communication system comprising: a data transfer control unit for performing retransmission control of an IP packet based on a TCP protocol when an IP packet exchanged by an SRC frame is lost. 2. The narrow-area communication system according to claim 1, wherein the LAN is connected via a LAN line between the server and each of the communication control devices, and in response to receiving an IP packet transmitted from the server. Further comprising an intelligent bridge that searches for a communication control device that manages the in-vehicle terminal that is the transmission destination of the IP packet, and transfers the data to the searched communication control device. A narrow-area communication system that manages an in-vehicle terminal corresponding to an in-vehicle device capable of wireless communication with a communication control device, and responds to a search by the intelligent bridge only when the in-vehicle terminal is managed. 3. The narrow-area communication system according to claim 1, wherein, of the respective data transfer control units provided in the server and the in-vehicle terminal, the data transfer control unit on the transmission side that transmits file data includes the file transfer unit. When the data transfer is started, the file name is notified to the data transfer control unit on the receiving side, and then the file data is notified according to the received file size notified from the data transfer control unit on the receiving side. The data transfer control unit on the receiving side, which receives file data among the data transfer control units provided in the server and the in-vehicle terminal, starts the data transfer control unit on the transmission side. The size of the file data corresponding to the file name notified from Notifies the transfer control unit, a narrowband communication system, characterized by storing the data received subsequently added sequentially to the end of the file data. 4. The narrow-area communication system according to claim 1, wherein each of the data transfer control units provided in the server and the in-vehicle terminal can detect an error occurrence in a shorter time as compared with a standard TCP protocol. A retransmission control of an IP packet by changing a value of a control parameter of a TCP protocol. 5. The narrow-area communication system according to claim 4, wherein the data transfer control unit is configured to include, among control parameters of a TCP protocol, an initial time for waiting for an ACK response at the time of transmission, a packet retransmission count, a keep-alive timer value, and a connection. A narrow-area communication system characterized by changing values of control parameters such as an initial time for waiting for an ACK response at the time of connection and the number of connection connection retries.