JP3777996B2 - Handover data control method in road-vehicle communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a handover data control method in a road-to-vehicle communication system in which a mobile station on a road communicates with a plurality of radio base stations arranged continuously along the road. Specifically, a road radio system in which microcells having a service coverage of several meters to 100 m are continuously arranged on a highway, an intersection, or a general road by a plurality of radio base stations, and are executed at the time of handover. The present invention relates to a data control method.
[0002]
[Prior art]
In conventional mobile / car telephone systems, PHS, and the like, in order to provide continuous and stable communication services to users, cell design has been performed so that there is no interruption in cell coverage. On the other hand, the cell size assumed in the road-to-vehicle communication system is as small as 30 m, and in order to provide a continuous communication service that is uninterrupted in radio waves, it is necessary to arrange a huge number of base stations. Furthermore, since only about 2 to 3 repetition frequencies can be secured, there is a high possibility that the line quality will deteriorate due to the influence of co-channel interference when the installation distance between base stations is short. Therefore, as shown in FIG. 1, when the handover function is implemented in the road-vehicle communication system, it is expected that microcells having a cell diameter of about 30 m are arranged at regular intervals. In this case, each time the vehicle enters a new cell, the vehicle repeatedly performs link connection and link disconnection with the base station, and exchanges information for handover between the base stations in order to realize continuous communication. There is a need.
[0003]
On the other hand, in a conventional road-to-vehicle communication system such as the “Toll Road Automatic Toll Collection System (ARIB STD-T55)” which is a standard of the Radio Industry Association (ARIB), a radio of about 10 to 30 m arranged in a spot manner. A two-way communication between a vehicle existing in a zone and a single radio base station is assumed, and a handover function required in a road-vehicle communication system which is a continuous or discrete spot communication system is not considered. In addition, for general-purpose DSRC currently being considered by the Dentsu Technical Trial etc., although continuous information communication service provision between a plurality of radio base stations and vehicles arranged continuously or discretely is assumed, Studies on modulation / demodulation methods and applications have been conducted in advance, and a handover method for realizing continuous information communication is not specifically defined.
[0004]
Also, in the existing PHS and cellular systems, handover is realized by switching the communication path between the base station and the control station by a line control station (switching station) that controls a plurality of base stations. In a vehicle-to-vehicle communication system, a conventional line switching handover cannot be applied because a vehicle moves between microcells at high speed, and handover control is directly performed between a plurality of radio base stations without using a line control station. There is no track record of practical use as a concrete system.
[0005]
[Problems to be solved by the invention]
In a road-to-vehicle communication system in which microcells having a cell diameter of about 30 m are continuously arranged on a road, in order for a plurality of vehicles traveling at high speed to perform continuous communication across a plurality of radio base stations, mobile vehicles are located in the area. When leaving the communication area of the wireless base station, the communication between the moving vehicle and the wireless base station is temporarily interrupted, and the moving vehicle enters the communication area of the next wireless base station and establishes a communication link. After re-establishment, a procedure is required to resume communication quickly and accurately. In particular, in the driving support system that aims to improve safety and efficiency of road traffic, improve the road traffic environment, and improve the convenience and comfort of drivers, driving support for obstacles, crossing vehicles, etc. It is necessary to provide the driver with accurate and real-time information on the vehicle.
[0006]
FIG. 9 is a configuration diagram of continuous wireless zones in the driving support system. According to FIG. 9, it is possible to provide information on a faulty vehicle stopped on the traveling lane and warning information for avoiding danger to the traveling vehicle over a plurality of continuous radio zone sections. is there. When the vehicle moves between the wireless zones arranged continuously in this way, the handover process between the vehicle and the wireless base station is performed quickly and reliably in consideration of the communication delay time required in the driving support system. Need to be done.
[0007]
Therefore, the present invention is necessary for efficiently realizing continuous communication for a plurality of vehicles traveling at high speed in a road-vehicle communication system in which microcells having a cell diameter of about 30 m are continuously arranged on a road. An object of the present invention is to provide a data control method during handover.
[0008]
[Means for Solving the Problems]
  to this end,According to the present invention, a handover is performed between two or more radio base stations continuously arranged along a road based on DSRC and a mobile station traveling on the road without providing a radio base station controller. A data control method for a road-to-vehicle communication system that realizes
For downlink data transmission, the server sends the same frame packet to two or more radio base stations,
The radio base station divides the frame packet received from the server into a plurality of radio packets defined by a fixed time length in a data link layer, adds order control information for each radio packet, Send wireless packets to mobile stations,
The mobile station composes the frame packet by combining the radio packets received from the radio base station in order using the sequence control information in the data link layer,
The first radio base station, when a handover to the mobile station occurs, the first step of holding the order control information of the radio packet that has been successfully transmitted until immediately before,
The first radio base station transmits the held order control information to the second radio base station when the mobile station establishes communication with the second radio base station. Steps,
A second step in which the second radio base station transmits a radio packet corresponding to the sequence control information next to the sequence control information received from the first radio base station to the mobile station;
It is characterized by having.
[0009]
  In addition, this departureClearlyAccording toRoad-to-vehicle communication that realizes handover between two or more radio base stations continuously arranged along the road based on DSRC and a mobile station traveling on the road without providing a radio base station control device A system data control method comprising:
For downlink data transmission, the server sends the same frame packet to two or more radio base stations,
The radio base station divides the frame packet received from the server into a plurality of radio packets defined by a fixed time length in a data link layer, adds order control information for each radio packet, Transmitting a wireless packet to the mobile station;
The mobile station composes the frame packet by combining the radio packets received from the radio base station in order using the sequence control information in the data link layer,
The mobile station, when a handover to the first radio base station occurs, a first step of holding the order control information of the radio packet that has been successfully received until immediately before,
The mobile station, when communication is established with the second radio base station, the second step of transmitting the retained order control information as a request signal to the second radio base station;
A second step of transmitting a radio packet corresponding to the sequence control information next to the sequence control information received from the mobile station to the mobile station;
It is characterized by having.
[0010]
  Furthermore, according to another embodiment of the present invention,The order control information preferably includes a code for identifying the order of the plurality of divided packet signals, a total number of the divided packet signals, and a code for identifying the presence / absence of a continuous divided packet signal.
[0015]
By applying the data control method at the time of handover according to the present invention to a road-to-vehicle communication system composed of spot beams having a cell diameter of about 30 m continuously arranged on a road, handover corresponding to high-speed movement of the vehicle can be accurately performed. And it becomes possible to implement | achieve efficiently. In addition, since the handover process can be performed quickly according to the present invention, it is possible to improve the throughput characteristics of the road-to-vehicle communication system and to suppress the disconnection time of the communication caused by the handover as much as possible, and to maintain a continuous and stable communication. Can be provided to the user. In addition, since a control signal is not basically transmitted and received between a radio control station that controls a plurality of radio base stations and a radio base station, unlike a cellular system, a costly dedicated line becomes unnecessary. In addition, since handover control is performed only between the mobile station and the limited radio base station, it is possible to suppress the traffic amount of the control signal flowing on the network connecting all the radio base stations to each other as much as possible. Furthermore, it is possible to implement a handover function for an ETC that has already been put into practical use without significantly modifying the device.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a system configuration diagram of a road-vehicle communication system according to the present invention. According to FIG. 1, a plurality of radio base stations 4-1 to 4-N (N is an arbitrary natural number) are continuously arranged on 8 roads and connected to 3 local area networks. It is configured to be able to communicate with all the wireless base stations connected to the external network via 2, 2 local servers, and 3 local area networks. In addition, the wireless base stations 4-1 to 4-N configure 6-1 to 6-N wireless cells on 8 roads using the wireless frequencies f1 to fN of 5-1 to 5-N, Communication is performed in the upward direction (10) and the downward direction (11) with seven moving vehicles traveling at high speed. Here, 9 indicates the traveling direction of 7 moving vehicles. Examples of the present invention will be described below.
[0018]
In FIG. 1, when 7 moving vehicles enter the wireless cell area 6-1, 7 moving vehicles receive and detect 11 frame control signals periodically transmitted from the 4-1 wireless base station. As a result, the local station recognizes that it has entered the service area provided by the wireless base station 4-1. Next, the mobile vehicle 7 sends a request signal for establishing a communication link to the radio base station 4-1, and the communication link is established by receiving the request signal at the radio base station 4-1. The At this time, as information exchanged for establishing a link, a mobile station identification code, a radio base station identification code, applicable application information, and the like are assumed. In the present embodiment, the description will be made assuming a downlink information download service as an application.
[0019]
FIG. 2 is an explanatory diagram of a data transfer procedure that occurs in the road-vehicle communication system. The wireless base station 4-1 accesses 2 local servers based on requests from 7 moving vehicles and requests 12 data transfers. Next, the information data transferred from the local server 2 is temporarily stored in the wireless base station 4-1, and 13 data transfers are sequentially performed based on the communication protocol between the wireless base station and the mobile station. Here, in order to cope with deterioration factors such as multipath, fading, and shadowing that occur on a wireless line, the data control method according to the present invention divides information data into packets with a small amount of data and transmits them in units of packets. In addition, information data is transferred while repeating reception confirmation notification from the receiving side. Therefore, a data division processing stage for packetizing information data on the transmission side and a data combination processing stage for returning the data that have been subdivided and transmitted to the reception side are required on the reception side. When subdividing information data, control information for controlling the order of transmission / reception packets is added to the head of each packet. Specifically, the data type, the identification code of the in-vehicle terminal mounted on the wireless base station of 4-1 and the mobile vehicle of 7, the packet number for performing the order control of the subdivided packets, the total number of packets, the continuation It consists of codes that identify the presence or absence of a packet to be processed.
[0020]
Next, in FIG. 2, if 7 moving vehicles continue to move in the 9 direction, they will leave the service area provided by the 4-1 wireless base station, that is, the 6-1 wireless cell. Communication performed between the 4-1 radio base station and the 7 moving vehicles needs to be temporarily terminated. At this time, in order to continue the application (downward data transfer in this embodiment), data control for performing a handover process between the radio base station and the moving vehicle is required. That is, when the mobile station of 7 or the radio base station of 4-1 detects the timing when the mobile station of 7 exits the radio cell of 6-1, the mobile station of 7 has the radio base station of 4-1 Check the data type (application type) of the packet signal transmitted from the local station and the packet sequence control information, save the received information data in the memory in the order of the packet number, and indicate the packet completion point , And the number of incomplete packets are detected and recorded.
[0021]
On the other hand, in the wireless base station 6-1, by confirming the response packet indicating the reception success / failure returned from the 7 moving vehicles in packet units, the packet number of the information data that has been transmitted, and the remaining The number of packet transmissions, etc. is always known. Here, based on the separately detected handover activation timing, the data type (application type) of the packet signal transmitted to the mobile station 7 and the sequence control information of the final transmission packet are also transmitted to the mobile station 7-1. Confirmed and transferred together with the packet number indicating the transmission completion point, the number of incomplete packets, incomplete information data, the identification code of the mobile station, etc., to the radio base station 6-2 as 14 handover control information. As a method for determining the timing when the mobile station leaves the radio cell, the packet reception error rate, the reception signal level, etc. are observed, and the time when the threshold falls below a preset threshold level, or the timer is set automatically. A method of disconnecting the communication link is assumed.
[0022]
FIG. 3 is an explanatory diagram of a handover control procedure in the road-vehicle communication system according to the present invention. According to FIG. 3, when 7 mobile vehicles enter the service area provided by the radio base station 4-2, that is, the radio cell of 6-2, the 7 mobile vehicles receive 15 frame control signals, Based on this information, a request signal 16 for establishing a communication link is sent to the 4-2 radio base station, and the communication link is established by receiving the request signal at the 4-2 radio base station. At this time, in order to establish a link, an identification code of the mobile station, an identification code of the radio base station with which communication was last performed, information on an application to be continued, and the like are transmitted / received. Further, the handover control information stored in the local station is transferred from the moving vehicle 7 as part of the information data series of the first packet signal on the uplink. Based on the control information, the radio base station 4-2 reads out information on the 7 moving vehicles separately transferred from the radio base station 4-1 from its own memory and the like, and sets the data type (application type) of the packet signal. ), The sequence control information of the final transmission packet, that is, the offset information indicating the transmission completion point or the transmission incomplete point, the number of incomplete packets, and the incomplete information data are confirmed. Then, the radio base station 6-2 generates a packet signal including information data to be transmitted next and a header for handover control, and restarts downloading of the information data to the seven moving vehicles, thereby allowing a plurality of radio base stations to be transmitted. Continuous communication across base stations can be realized.
[0023]
Next, in order to clarify the procedures of FIGS. 2 and 3, FIG. 4 shows a communication sequence diagram of the handover control procedure according to the present invention. In FIG. 4, 7 mobile vehicles that have entered the radio cell 6-1 receive 21 frame control signals periodically transmitted from the radio base station 4-1, and 22 based on the designated timing. A request signal is transmitted to the radio base station 4-1. Next, the wireless base station 4-1 transmits 23 link establishment notifications to 7 moving vehicles when 22 request signals are normally received. The mobile vehicle 7 sends 24 application activation requests to the wireless base station 4-1, and the wireless base station 4-1, accepts the request, so that the divided information signal is transmitted via the downlink. It will be transferred sequentially. Here, for 25 information data signals # 1, 26 reception success notification signals are transmitted from 7 moving vehicles, and for 26 information data signals # 2, 28 reception success notification signals are transmitted from 7 moving vehicles. Accordingly, the wireless base station 4-1 can always grasp the identification number of the transmission completion packet. When 7 moving vehicles approach the end of the communication area of the wireless cell 6-1, 29 link disconnection procedures are started, and information regarding communication completion data or communication incomplete data is the identification number or application of the 7 moving vehicle. Along with information such as the type, the information is transferred to the radio base station 4-2 as 30 handover control information.
[0024]
Next, the mobile vehicle 7 that has moved into the radio cell 6-2 receives 31 frame control signals periodically transmitted from the radio base station 4-2, and 32 based on the designated timing. Is transmitted to the radio base station 4-2. After receiving the 33 link establishment notification transmitted from the radio base station 4-2, the mobile vehicle 7 transmits 34 handover control information as initial information for establishing the handover. The radio base station 4-2 executes the handover process based on the data control procedure described above based on the 34 handover control information. Then, by transmitting 35 information data signals # 3 to 7 moving vehicles, the information data transfer is resumed. FIG. 4 shows a procedure when reception of 35 information data signals # 3 is unsuccessful. When 36 reception failure notification signals are transferred from 7 moving vehicles to 4-2 radio base stations. , 37 information data signal # 3 is retransmitted and data communication is continuously performed.
[0025]
Hereinafter, a data division processing stage and a data combination processing stage, which are components of the data control method during handover according to the present invention, will be described.
[0026]
FIG. 5 shows an explanatory diagram of a packet division / combination processing method for information data according to the present invention. First, in 41 data division processing stages implemented on the transmission side, 48 information data portions of 46 information frames composed of 47 identification codes and 48 information data delivered from 43 higher layers The handover control headers 49-1 to 49-n and the identification code 47 are added to the divided information data 50-1 to 50-n, and these processes are performed 45. The packet signal group of −1 to 45-n is transferred as it is to the lower 40 layers that perform wireless transmission. At this time, the division of the information data is performed in consideration of the existing frame configuration, and the information data is prepared for transmission of the information data even when the control headers of the lower layers 51-1 to 51-n are added. Transmission data is divided so as not to exceed the data area. The handover control headers 49-1 to 49-n are composed of information such as an identification number for confirming the order, presence / absence of subsequent data, data length, total number of divided packets, and the like, and retransmission control by error detection code. Is implemented by 40 lower layer procedures.
[0027]
Next, in 42 data combining processing stages implemented on the receiving side, 49-1 to 49-n of packet signals 45-1 to 45-n passed through 40 lower layers are processed. The handover control header is sequentially decoded, and an identification number indicating the order of received packets is detected. At this time, in the data combination processing step 42, it is confirmed whether or not the identification number of the received packet is in the correct order. If it is the correct number, the received normal packet is recombined and the memory held by the own station Each time a process such as writing is performed. When all the divided packet signals are normally received by repeating the above procedure, the 48 information data recombined in the 42 data combining processing steps are passed to the application side via the upper layer. .
[0028]
Next, a processing procedure at the time of handover will be described. If the link is disconnected without completing the data transfer due to degradation of the wireless line quality, etc., the identification number of the last packet signal received continuously is confirmed in the data combination processing stage, and the application information The data is stored in a memory or the like together with the base station identification code. Here, at the time when the moving vehicle moves from the first radio control station to the communication area provided by the second radio control station and the communication link is reestablished, information of the packet signal transmitted first from the mobile vehicle An initial field for handover control shown in FIG. 6 is specially added to the data area. Here, 61 represents the entire field assigned to the information data, and is composed of 62 subfields 1, 63 subfields 2, and 64 subfields 3. Furthermore, 62 subfields 1 are composed of 66 data types 1, 67 data lengths, and 68 application numbers. In order, 62 subfields indicate the contents of the subfields, control information data lengths, control information ( Here, it means information about the application). The subfield 2 of 63 is composed of 69 data types 2, 70 data lengths, and 71 offset information. In particular, the 71 offset information has a data transmission incompletion point ( Alternatively, information on data transmission completion point) is included. The 64 subfields are composed of 72 data types 3, 73 data lengths, and 74 information data signals. The portion obtained by removing the 65 handover control initial fields from the 61 information data fields is the actual information. This field can be used for data transmission. By transferring this initial information for handover control from the moving vehicle to the second radio base station, the ongoing application information and the transmission completion point (transmission incomplete point), that is, the final identification number of the packet signal that has been received are obtained. The second radio base station is notified. The initial field for handover control is also added to the first packet signal of the downlink, so that information transfer in any direction of the uplink and downlink can be dealt with.
[0029]
In the data division processing stage of the second radio base station, the same application is continuously performed based on the application information stored in the initial field for handover control of the packet signal transmitted from the moving vehicle and the offset information. Processing is performed. That is, based on the offset information indicating the transmission completion point, the information data dividing process is resumed from the transmission incomplete point of the information data to be transmitted, and the packet transfer is continuously performed. Thereafter, the identification number of the packet signal is incremented by 1 from the final identification number, and the handover process is continued until the data transfer is completed by the same procedure. Here, FIG. 7 shows an explanatory diagram regarding offset information necessary for the handover process. In the figure, 81 is information data, 82 is the leading edge of the information data, and 83 is the trailing edge of the information data, and is divided into a plurality of small packets in the data division processing stage. Here, 87-1 to 87-k represent communication completion packet signals 84 that have already been transmitted, and 88-1 to 88-m represent communication incomplete packet signals 85 that have not been transmitted. , 86 communication completion points (communication incomplete points), which are intermediate points, represent offset information for handover.
[0030]
If the packet signal received first after the data transfer is resumed by the handover has already been received, it is determined that the packet is a duplicate packet, and is discarded at the data combination processing stage. On the other hand, if it is determined from the identification number of the first received packet signal that the packet has been dropped, the identification number of the missing packet is added from the moving vehicle side through a separately prepared control uplink. The control packet is transmitted to the radio base station, and based on the instruction, the packet signal designated by the radio base station is retransmitted, so that it is possible to cope with the loss of the packet signal.
[0031]
  Finally, FIG. 8 shows an embodiment of a data control method for handover targeting the OSI reference model which is an international standard. FIG. 8 shows 96 data link layers.IsPerform data partitioning and data merge processingLayerShows the configuration,Independent of the data link layer control header, prepare a control header for handover control in a part of the data area reserved for transmission of information dataRu. That is, by performing data frame control such as transmission data division, reception data recombination, and continuous communication control of incomplete transmission data in the newly defined 92 handover data control layers, Continuous communication across multiple radio base stations by handover without changing the frame format, access control procedure, medium access control sublayer variables, etc. of existing road-to-vehicle communication systems such as DSRC that communicate in the area Is feasible. Reference numeral 94 denotes a medium access control sublayer that is a part of the 96 data link layers, and 95 denotes a physical layer.Data division processing and data combination processing93 logical link control sublayers,Or94 media access control sublayerPrepare for.
[0032]
According to the various embodiments of the present invention described above, various changes, modifications, and omissions within the scope of the technical idea and the viewpoint of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.
[0033]
【The invention's effect】
As described above in detail, the present invention has the following effects.
(1) In a road-to-vehicle communication system composed of spot beams with a cell diameter of about 30 m continuously arranged on the road, it is possible to accurately and efficiently implement handover corresponding to high-speed movement of the vehicle. It becomes.
(2) Since the handover caused by the movement of the vehicle can be performed quickly, the throughput characteristics of the road-to-vehicle communication system can be improved.
(3) The disconnection time of communication caused by handover can be suppressed as much as possible, and continuous and stable communication can be provided to the user.
(4) Since a control signal is not basically exchanged between a radio base station and a radio base station that controls a plurality of radio base stations as in a cellular system, a dedicated high-cost line is not required.
(5) Since the handover control is performed only between the mobile station and the limited radio base station, the traffic amount of the control signal flowing on the network connecting all the radio base stations can be minimized.
(6) A handover function can be implemented on an ETC that has already been put into practical use without undergoing significant device modification.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a road-vehicle communication system according to the present invention.
FIG. 2 is an explanatory diagram of a data transfer procedure that occurs in a road-vehicle communication system.
FIG. 3 is an explanatory diagram of a handover control procedure in a road-vehicle communication system according to the present invention.
FIG. 4 is a communication sequence diagram showing a handover control procedure in the road-vehicle communication system according to the present invention.
FIG. 5 is an explanatory diagram of a handover data control method in a road-vehicle communication system according to the present invention;
FIG. 6 is an explanatory diagram of an initial field for handover control.
FIG. 7 is offset information used for data control during handover.
FIG. 8 is a configuration diagram of an OSI model for handover.
FIG. 9 is a configuration diagram of continuous wireless zones in the driving support system.
[Explanation of symbols]
1 Gateway
2 Local server
3 Local network
4-1 to 4-N radio base station
5-1 to 5-N radio frequency
6-1 to 6-N wireless cell
7 Moving vehicles
8 road
9 Direction of movement
10 Request signal
11 Frame control signal
12 Data transfer from local server to radio base station
13 Data transfer from wireless base station to mobile vehicle
14 Handover control information
15 Frame control signal
16 Request signal
21 Frame control signal
22 Request signal
23 Link establishment notification
24 Application start request
25 Information data signal # 1
26 Reception success notification signal
27 Information data signal # 2
28 Reception success notification signal
29 Link disconnection
30 Handover control information
31 Frame control signal
32 Request signal
33 Link establishment notification
34 Handover control information
35 Information data signal # 3
36 Reception failure notification signal
37 Information data signal # 3
38 Reception success notification signal
39 Link disconnection
40 Lower layer
41 Data division processing stage
42 Data Join Processing Stage
43 Upper layer
44-1 to 44-n Packet signal group in lower layer
45-1 to 45-n Packet signal group delivered from the data division processing stage to the lower layer, or packet signal group delivered from the lower layer to the data combination processing stage
46 Information frame
47 Identification code
48 Information data
49-1 to 49-n Handover control header
50-1 to 50-n Divided information data
51-1 to 51-n Lower layer control header
61 Information frame
62 Subfield 1
63 Subfield 2
64 Subfield 3
65 Initial field for handover control
66 Data type 1
67 Data length
68 Application number
69 Data type 2
70 data length
71 Offset information
72 Data type 3
73 Data length
74 Information data signal
81 Information data
82 The tip of information data
83 End of information data
84 Communication completion packet signal group
85 Communication incomplete packet signal group
86 Communication completion point (communication incomplete point)
87-1 to 87-n Communication completion packet signal
88-1 to 88-n Communication incomplete packet signal
91 Application layer
92 Data control layer for handover
93 Logical link control sublayer
94 Medium Access Control Sublayer
95 Physical layer
96 Data link layer

Claims (3)

Implements handover between two or more radio base stations continuously arranged and connected along a road based on DSRC and a mobile station traveling on the road without providing a radio base station controller A data control method for a road-vehicle communication system,
  For downlink data transmission, the server sends the same frame packet to two or more radio base stations,
  The radio base station divides the frame packet received from the server into a plurality of radio packets defined by a fixed time length in a data link layer, adds order control information for each radio packet, Send wireless packets to mobile stations,
  The mobile station composes the frame packet by combining the radio packets received from the radio base station in order using the sequence control information in the data link layer,
  The first radio base station, when a handover to the mobile station occurs, the first step of holding the order control information of the radio packet that has been successfully transmitted until immediately before,
  The first radio base station transmits the held order control information to the second radio base station when the mobile station establishes communication with the second radio base station. Steps,
  A second step in which the second radio base station transmits a radio packet corresponding to the sequence control information next to the sequence control information received from the first radio base station to the mobile station;
A data control method for a road-to-vehicle communication system, comprising: Implements handover between two or more radio base stations continuously arranged and connected along a road based on DSRC and a mobile station traveling on the road without providing a radio base station controller A data control method for a road-vehicle communication system,
  For downlink data transmission, the server sends the same frame packet to two or more radio base stations,
  The radio base station divides the frame packet received from the server into a plurality of radio packets defined by a fixed time length in a data link layer, adds order control information for each radio packet, Transmitting a wireless packet to the mobile station;
  The mobile station composes the frame packet by combining the radio packets received from the radio base station in order using the sequence control information in the data link layer,
  The mobile station, when a handover to the first radio base station occurs, a first step of holding the order control information of the radio packet that has been successfully received until immediately before,
  The mobile station, when communication is established with the second radio base station, the second step of transmitting the retained order control information as a request signal to the second radio base station;
  A second step of transmitting a radio packet corresponding to the sequence control information next to the sequence control information received from the mobile station to the mobile station;
A data control method for a road-to-vehicle communication system, comprising: The sequence control information includes a code for identifying an order of the plurality of divided packet signals, a total number of the divided packet signals, and a code for identifying presence / absence of a continuous divided packet signal. The data control method according to claim 1 or 2.