JP3823738B2 - Method for transferring mobile station information in road-to-vehicle communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile station information transfer method in a road-to-vehicle communication system having a plurality of radio base stations arranged continuously along a road in order to communicate with a mobile station on the road. Specifically, a road wireless system in which microcells having a service coverage of several m to 100 m are continuously arranged on a highway, an intersection or a general road by a plurality of radio base stations, and transfer of mobile station information thereof Regarding the 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. Further, since only about 2 to 3 repetition frequencies can be secured, there is a high possibility that the line quality is deteriorated due to the influence of co-channel interference when the installation distance between the base stations is short. Therefore, when a handover function is implemented in a 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 Industries 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 an inter-vehicle communication system, since a vehicle moves between microcells at a high speed, conventional line-switching handover cannot be applied, and control signals for handover control must be passed between base stations. 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. The information on the target moving vehicle and the continuation information of the data exchanged between the vehicle and the wireless base station are quickly transmitted from the wireless base station to the next wireless base station with which the moving vehicle communicates. It is necessary to hand it over. 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 information related to the driver to the driver in real time.
[0006]
FIG. 8 is a configuration diagram of continuous radio zones in the driving support system. According to FIG. 8, it is possible to provide information related to a faulty vehicle parked 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 data transfer between base stations during handover.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the present invention relates to mobile station information in a road-to-vehicle communication system having a plurality of radio base stations arranged continuously along a road in order to communicate with mobile stations on the road. In the transfer method,
When the mobile station leaves the communication area of the first radio base station, the first radio base station moves to the second radio base station that is the expected destination of the mobile station. Mobile station information transmission stage for transmitting the mobile station information of the station;
When the mobile station enters the communication area of the second radio base station, the second radio base station communicates with the mobile station based on the mobile station information transmitted from the first radio base station. A communication resumption stage for resuming continuous communication between
It is characterized by having.
[0009]
According to another embodiment of the present invention,
Even in a state where the communication line is disconnected between the mobile station and the first radio base station, the first radio base station holds the mobile station information of the mobile station,
In the mobile station information transmission stage, the first radio base station preferably discards the mobile station information when transmission of the mobile station information to the second radio base station is completed.
[0010]
According to the present invention,
In a method for transferring mobile station information in a road-to-vehicle communication system having a plurality of radio base stations arranged continuously along a road in order to communicate with a mobile station on the road,
When the mobile station leaves the communication area of the first radio base station, the first radio base station moves to the second radio base station that is the expected destination of the mobile station. Mobile station information transmission stage for transmitting the mobile station information of the station;
When the mobile station enters the communication area of the second radio base station, the second radio base station communicates with the mobile station based on the mobile station information transmitted from the first radio base station. A communication resumption stage for resuming continuous communication between
It is characterized by having.
[0011]
According to another embodiment of the present invention,
The second radio base station notifies the first radio base station of the communication resumption stage when the communication line is established between the mobile station and the second radio base station. When,
The first radio base station preferably includes a step of discarding the mobile station information when the notification is received.
[0012]
Furthermore, according to another embodiment of the present invention, the mobile station information includes control information related to the mobile station, and data information to be transmitted and received between the mobile station and the radio base station,
The data information preferably includes data information that has been transmitted / received between the mobile station and the radio base station, data information that has not been transmitted / received, or offset information that indicates a boundary between these two data information. .
[0014]
By applying the mobile station information transfer method according to the present invention to a road-to-vehicle communication system composed of spot beams with a cell diameter of about 30 m continuously arranged on the road, handover corresponding to high-speed movement of the vehicle is realized. It becomes possible to do. In addition, since the handover process can be quickly performed according to the present invention, the throughput characteristic of the road-to-vehicle communication system can be improved, the communication disconnection time caused by the handover can be suppressed as much as possible, and the continuous communication is provided to the user. be able to. 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 as in a cellular system, a costly dedicated line becomes unnecessary, Since control data is transmitted and received during handover between specific radio base stations, the amount of traffic flowing on a network connecting all the radio base stations can be minimized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
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. 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 with 7 moving vehicles traveling at high speed is performed in the up direction (10) and the down direction (11). Here, 9 indicates the traveling direction of 7 moving vehicles. Examples of the present invention will be described below.
[0017]
In FIG. 1, when 7 moving vehicles enter the wireless cell area 6-1, the 7 moving vehicles receive and detect 11 control signals periodically transmitted from the 4-1 wireless base station. Thus, the local station recognizes that it has entered the service area provided by the wireless base station 4-1. Next, the moving 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.
[0018]
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 second local server is temporarily stored in the 4-1 radio base station, and 13 data transfers are sequentially performed based on the communication protocol between the radio base station and the mobile station. Here, in general wireless access, in order to deal with deterioration factors such as multipath, fading, and shadowing that occur on the wireless line, the information data is divided into packets with a small amount of data, and transmitted and received in packet units. Information data is transferred while repeating confirmation notifications. Therefore, a processing function for packetizing information data is required on the transmission side, and a processing function for returning the fragmented and transmitted data on the reception side.
[0019]
Next, if 7 moving vehicles continue to move in the 9 direction, they will leave the service area provided by the wireless base station 4-1, that is, the wireless cell 6-1. Communication performed between the radio base station and the seven moving vehicles needs to be temporarily terminated. At this time, in order to continue the application (downlink data transfer in this embodiment), it is necessary to perform a handover process between the radio base station and the mobile station. 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 automatically by timer setting. A method of disconnecting the communication link is assumed.
[0020]
Hereinafter, a method for transferring data between base stations during handover according to the present invention will be described.
[0021]
FIG. 3 is a first explanatory diagram of a data transfer procedure in the road-vehicle communication system according to the present invention. According to FIG. 3, when 7 moving vehicles enter the service area provided by the 4-2 radio base station, that is, the 6-2 radio cell, the 7 moving vehicles receive 15 control signals, Based on the information, a request signal 14 for establishing a communication link is sent to the radio base station 4-2, and the communication signal is established by receiving the request signal at the radio base station 4-2. At this time, in order to establish a link, information concerning the identification marks No.及 beauty continues to be an application of the mobile station are transmitted and received. The 4-2 radio base station transfers information on the seven mobile vehicles to the 4-1 radio base station and information on the data transmitted and received between the 4-1 radio base station and the seven mobile vehicles. , 16 to request. The wireless base station 4-1 transfers information on 7 moving vehicles to the wireless base station 4-2 by 17 based on a request from the wireless base station 4-2. When the information transfer of 17 is completed, the wireless base station 4-1 can quickly respond to the newly entering vehicle by discarding the information on the 7 moving vehicles. However, if each radio base station has sufficient buffer capacity to store data passed between radio base stations at the time of handover, a method of periodically discarding old data by setting a timer or the like is also adopted. it can.
[0022]
FIG. 4 is an explanatory diagram for continuously providing a downlink data download service after the handover according to FIG. 3 is completed. The radio base station 4-2 is based on the information on the mobile vehicle transferred from the radio base station 4-1 and the data transmitted and received between the radio base station 4-1 and the mobile vehicle 7. The information data download continuation request is transmitted to, and a continuous data transfer service can be provided to seven moving vehicles by 18 and 19. As shown in FIG. 4, information to be downloaded between the 4-1 wireless base station and the two local servers other than the method in which the 4-2 wireless base station accesses the two local servers to continue the application. A method is also conceivable in which data is transferred in a lump and the information data itself is carried around between radio base stations. In this case, it is not necessary to access the local server 2 again from the wireless base station 4-2, and the service can be provided from the local server 2 without being aware of the cell where the mobile vehicle 7 is located. It becomes.
[0023]
FIG. 5 is a second explanatory diagram of the data transfer procedure in the road-vehicle communication system according to the present invention. According to FIG. 5, as soon as 7 mobile vehicles leave the service area provided by the 4-1 radio base station, that is, 6-1 radio cell, 7 mobile vehicles are expected to enter next. This is a method for transferring information relating to 7 mobile vehicles and information relating to data transmitted and received between the wireless base station 4-1 and 7 mobile vehicles to the wireless base station 4-2. . As a result, transmission and reception of information necessary for handover is completed before the seven moving vehicles enter the 6-2 wireless cell configured by the 4-2 wireless base station. Data communication can be resumed immediately after the communication link with the wireless base station 4-2 is established. That is, since the amount of data transmitted and received between the 4-2 radio base station and the seven mobile vehicles can be increased, it is possible to improve the effective throughput characteristics as a road-vehicle communication system.
[0024]
FIG. 6 is an explanatory diagram of a data transfer procedure after the handover is completed. When 7 moving vehicles enter the 6-2 radio cell, the 7 moving vehicles receive 22 control signals and, based on the information, establish a communication link to the 4-2 radio base station. A communication link is established by transmitting the request signal 21 and receiving the request signal at the radio base station 4-2. At this point, the radio base station 4-2 notifies the radio base station 4-1 that the communication link with the mobile vehicle 7 has been established by 23, and the radio base station 4-1 Based on the notification information, the information related to the seven moving vehicles stored in the own station and the information related to the data transmitted and received between the wireless base station 4-1 and the seven moving vehicles are deleted. As a result, the wireless base station 4-1 can quickly respond to a newly entering mobile vehicle. The radio base station 4-2 transmits an application continuation request to the local server 2 at the time when the communication link with the mobile vehicle 7 is established. It is possible to provide a continuous data transfer service to 7 mobile vehicles.
[0025]
FIG. 7 is a data configuration diagram of mobile station information according to the present invention. According to FIG. 7, reference numeral 25 denotes information data transferred from a local server or the like to a mobile station via a radio base station, or from a mobile station to a local server or the like via a radio base station. 26 is the leading end of the information data, and 27 is the end of the information data. Reference numeral 28 denotes a data portion in which data transfer is completed between the radio base station and the mobile station in 25 information data, that is, communication completion data. 29 is an incomplete communication in which data transfer is not completed. Represents the data. Reference numeral 30 denotes offset information indicating a communication completion point (communication incomplete point). In the inter-base station data transfer method according to the present invention, as mobile station information transmitted / received between radio base stations, 28 communication completion data and 29 communication for information signals transmitted / received between the radio base station and the mobile station. Either incomplete data or 30 offset information can be applied.
[0026]
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.
[0027]
【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 having a cell diameter of about 30 m continuously arranged on a road, it is possible to realize handover corresponding to high-speed movement of a vehicle.
(2) Since the handover caused by the movement of the vehicle can be performed quickly, the throughput characteristics of the road-vehicle communication system can be improved.
(3) The communication disconnection time caused by the handover can be suppressed as much as possible, and continuous 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 costly dedicated line becomes unnecessary.
(5) Since control data is transferred between specific radio base stations at the time of handover, the amount of traffic flowing on the network connecting all the radio base stations can be minimized.
[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 a first explanatory diagram of a data transfer procedure in a road-vehicle communication system according to the present invention.
4 is an explanatory diagram for continuously providing a downlink data download service after completion of handover according to FIG. 3; FIG.
FIG. 5 is a second explanatory diagram of a data transfer procedure in the road-vehicle communication system according to the present invention.
FIG. 6 is an explanatory diagram of a data transfer procedure after handover is completed.
FIG. 7 is a data configuration diagram of mobile station information according to the present invention.
FIG. 8 is a configuration diagram of continuous wireless zones in the driving support system.
[Explanation of symbols]
DESCRIPTION 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 Radio cell 7 Moving vehicle 8 Road 9 Moving direction 10 Request signal 11 Control signal 12 Data transfer from local server to radio base station 13 Data transfer from radio base station to moving vehicle 14 Request signal 15 Control signal 16 Data transfer request for handover information 17 Handover information 18 Data transfer from local server to radio base station 19 Data transfer from radio base station to mobile vehicle 20 Handover information 21 Request signal 22 Control signal / Data transfer from radio base station to mobile vehicle 23 Handover information deletion instruction 24 Data transfer from local server to radio base station 25 Information data 26 Leading edge of information data 27 End of information data 28 Communication completed Data 29 Communication incomplete data 30 Communication complete point (communication incomplete point)

Claims (3)

In a method for transferring mobile station information in a road-to-vehicle communication system having a plurality of radio base stations arranged continuously along a road in order to communicate with a mobile station on the road,
When the mobile station leaves the communication area of the first radio base station, the first radio base station moves to the second radio base station that is the expected destination of the mobile station. Transmitting the mobile station information of the station, and transmitting the mobile station information;
When the mobile station enters the communication area of the second radio base station, the second radio base station moves the mobile station based on the mobile station information transmitted from the first radio base station. A method for transferring mobile station information in a road-to-vehicle communication system, comprising: a communication resuming step of resuming communication with a station. When the communication link is established between the mobile station and the second radio base station, the second radio base station notifies the first radio base station of the communication resumption stage. A communication establishment notification stage;
The first radio base station, when receiving the notification method according to claim 1, characterized in that it comprises a step discards the mobile station information. The mobile station information includes control information related to the mobile station, and data information transmitted and received between the mobile station and the radio base station,
The data information is either data information that has been transmitted / received between the mobile station and the radio base station, data information that has not been transmitted / received, or offset information that indicates a boundary between these two pieces of data information. The method according to claim 1 , wherein the method comprises.

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