JP3635329B2 - Road-to-vehicle communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a road-to-vehicle communication system that enables mobile communication with an in-vehicle device by disposing a road antenna near a road and forming an area on the road.
[0002]
[Prior art]
FIGS. 7 and 8 show cases where base point information is provided in a road-to-vehicle communication system that provides road information providing services according to the prior art. In a service that provides road information, information on obstacles and sharp curves ahead captured by road sensors and cameras is provided to the vehicle using a road-vehicle communication system. In this case, it is necessary to indicate to the vehicle a reference position for indicating the position of the obstacle or the start position of the curve. This reference position and information on road antennas that provide service information for obstacles and curves are referred to as base point information (base point).
[0003]
In order to prevent radio wave interference between adjacent areas while transmitting radio waves in each area, it is necessary to change the carrier frequency of radio waves transmitted from base stations provided in each area. For example, in FIG. 7, a radio wave is transmitted along a road using a directional antenna. At this time, in order to make the carrier frequencies of adjacent radio waves different, f1 is used as a carrier frequency for transmitting base information, carrier frequency f2 is used for service information A, carrier frequency f3 is used for service information B, and service information C is used. Is assigned a carrier frequency f4. FIG. 8 shows the relationship between information provided in each area and carrier frequency allocation.
[0004]
Now, a case where a service is assigned to a carrier frequency in this way and a radio wave is received by a receiver mounted in a car will be described next. Prior art receivers can only receive one carrier frequency at a time. For example, when tuned to the carrier frequency f1, only the base point information can be received as shown in FIG. On the other hand, considering the case of passing the road from right to left in FIG. 7, the base point information is received at the carrier frequency f1, and immediately after passing through the base point information area, the service information A is received by switching to the carrier frequency f2. Similarly, it is necessary to switch to the carrier frequency f3 to receive the service information B and to switch to the carrier frequency f4 to receive the service information C.
[0005]
As described above, in the road-to-vehicle communication system according to the prior art, since the radio frequency is different when the radio area is switched, it is necessary to switch the radio frequency on the receiver side, and frequency search means and frequency switching procedures for that purpose are required. It was. In particular, when receiving a service at a complicated place such as an intersection, a receiver that moves at a high speed such as a car frequently switches the reception frequency. However, since it is difficult to switch the reception frequency instantaneously, there is a problem that the service cannot be received because the switching is not in time.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the conventional problems as described above and to provide a road-to-vehicle communication system that does not require switching of a received carrier frequency even when a radio area is switched.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is directed to an orthogonal frequency division multiplexing road-to-vehicle communication system that provides a service that provides road information. divided into a plurality of groups, and the use of some groups of which the communication base point information, the base point information is transmitted from the directivity of the road antenna, the moving reference position associated with the road information It is the information shown on the body .
[0008]
That is, the road-to-vehicle communication system of the present invention is based on a road base station apparatus for sending an OFDM (Orthogonal Frequency Division Multiplex) modulated signal, and a signal sent from the road base station apparatus. A road transmitting antenna for radiating radio waves of the same frequency into the area, a vehicle receiving antenna for receiving the radio waves radiated from the road transmitting antenna, and a vehicle receiving antenna for receiving and demodulating An in-vehicle device having a receiving means, and a base concentration station device that transmits information data for service to a plurality of road base station devices, the road base station device classifies subcarriers into a plurality of types, It has a transmission means for transmitting multiple types of data to each type of carrier wave, and is a roadside array located in an area that provides base information. Also sends the sub-carriers classified in the same manner in containers, and select the sub-carriers necessary from a plurality of sub-carriers, it is to receive a base point and service information.
[0009]
The invention according to claim 2, in an orthogonal frequency division multiplexing road-to-vehicle communication system that provides a service that provides road information, divides subcarriers used when communicating from the ground to a mobile unit into a plurality of groups, the communication base point information group of, for communication service information to another group, and be used in simultaneously allocated, the base point information is transmitted from the directivity of the road antenna, the reference and associated with the road information It is the information which showed the position which becomes to the said mobile body .
[0010]
That is, in the present invention, radio waves of the same frequency are radiated from the road transmitting antenna based on the OFDM modulated signal. In general, when radio waves arrive from a plurality of directions with respect to a vehicle, so-called multipath interference may occur. Specifically, a propagation delay time difference between radio waves radiated from the transmission antennas on each road occurs, resulting in intersymbol interference. However, in the present invention, the OFDM system is adopted, and a guard time is provided for each symbol so that interference codes do not overlap. Therefore, even if the same data is received from a plurality of directions, it is caused by delay due to multipath. Intersymbol interference can be avoided. By using the system of the present invention, base point information and service information can be simultaneously provided in one communication area by transmitting base point information and service information to subcarriers of the same carrier frequency.
[0011]
The invention described in claim 3 is the road-vehicle communication system of orthogonal frequency-division multiplexing to service that provides road information, divides the subcarriers to be used when communicating from the ground to the mobile into a plurality of groups, some The base point information is transmitted from the directional road antenna provided on the road heading to the intersection using the group, while one non-directional road antenna provided near the intersection using a group different from the above group. and transmits the service information from the base point information is characterized information der Rukoto showing the location as a reference associated with the road information to the mobile.
[0012]
If the method of the present invention is used, a plurality of small areas are not formed using directional antennas in adjacent areas at intersections, but large areas are used using omnidirectional antennas independently of transmission of base point information. It becomes possible to transmit service information collectively to the entire intersection.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment for providing a base point in a road-to-vehicle communication system according to the present invention will be described with reference to the accompanying drawings. The embodiment of the road-to-vehicle communication that provides base information shown in FIGS. In FIG. 1 , radio waves are transmitted using four directional antennas directed along the road. In the present invention, since the OFDM modulation method is used, there is no problem even if radio waves from a plurality of base stations are received in a mixed manner. Therefore, it is only necessary to transmit radio waves with the same carrier frequency F0 from each directional antenna.
[0014]
In the present embodiment, on the transmitter side, base point information and service information are assigned to subcarriers of different groups, and specifically, one group (hereinafter referred to as subcarrier group) is assigned to each. That is, each piece of information is transmitted in association with a carrier group. Also, different carrier groups are allocated to adjacent base stations, and different information (base information or service information) is transmitted. This is shown in FIG. For example, the base station 1 providing the base point information transmits the base point information transmitted from the base concentration station on one subcarrier group of the OFDM signal having the carrier frequency F0 (solid line). Similarly, the base station 2 that provides the service information A transmits the service information A sent from the base concentration station on one subcarrier group of the OFDM signal having the frequency F0 (solid line). Similarly, the base stations 3 and 4 allocate and transmit different subcarrier groups of the OFDM signal of the frequency F0 corresponding to the service information C and D (each solid line).
[0015]
In the present embodiment, on the receiver side, each area may be decoded using only one subcarrier group corresponding to the area. That is, it is possible to receive a service by collectively receiving OFDM signals having the frequency F0 and extracting only the subcarrier group carrying the necessary information. For example, considering the case of passing through the road from right to left in FIG. 1, a receiver mounted on a car always receives an OFDM signal having a carrier frequency F0, selects a subcarrier group, and decodes it. It ’s fine. Specifically, the subcarrier group corresponding to the base point information is first selected and decoded, and when entering the communication area of the base station 2, the subcarrier group corresponding to the service information A may be selected and decoded. Then, base point information and service information corresponding to each base station can be received.
[0016]
As described above, according to the present embodiment, since the carrier frequency of the OFDM signal received by the receiver is always F0, it is not necessary to switch the reception frequency as required in the prior art. Note that the subcarrier group to be decoded needs to be switched every time the reception area is moved. However, since the processing is performed after receiving the carrier wave, the processing time is not as long as the reception frequency switching process.
[0017]
In addition, it is more preferable that each base station transmits not only the service of its own communication area but also the service of the communication area adjacent or nearby. Specifically, the base station 1 places the base point information on one subcarrier group as indicated by the solid line in FIG. 2, and at the same time, the base stations 2, 3, 4 that are adjacent or close to each other as indicated by the broken line in FIG. Service information A, B, and C are transmitted on different subcarrier groups. In this way, the contents to be transmitted at each base station are all the same, so there is an advantage that preparation of transmission data is simplified.
[0018]
In the receiver, as in the above description, in each communication area, one subcarrier group corresponding to the information may be selected and decoded. In addition, FIG. 1 shows a case where the transmission antenna has directivity to transmit from the front of the car, but the directivity of the transmission antenna has directivity to transmit from both the front and rear of the car. It's okay. Then, in the vicinity of the middle where the adjacent communication areas overlap (for example, the vicinity of the middle between the base station 2 and the base station 3), the service information A and B from both the rear (base station 2) and the front (base station 3). A radio wave including a subcarrier group corresponding to For this reason, even if a large vehicle is traveling immediately before (or immediately after) the vehicle and the front side (or rear side) is behind the radio wave, it can receive radio waves from the opposite side. Can reduce the possibility of interruption. Since radio waves including both service information A and B arrive from both before and after, the subcarrier group to be decoded is changed from the subcarrier group corresponding to the service information A of the base station 2 to the service information of the base station 3. There is no problem even if the point of switching to the subcarrier group corresponding to B is shifted back and forth.
[0019]
In the above description, the receiver is described as selecting and decoding one subcarrier group. However, an embodiment in which one or a plurality of desired services are selected by decoding all the subcarrier groups is also possible. In addition, when it is necessary to provide the base information and service information at the same time on a road or the like where a plurality of services overlap such as service information B1 of service 1 and base information 2 of service 2 in FIG. The receiver can decode all the subcarrier groups and receive both desired base point information and service information at the same time. This is shown in FIG.
[0020]
As can be seen from the above description, radio waves having the same contents can be transmitted to roads in all directions at the intersection. In the conventional method, base point information and service information are provided by using directional antennas along four roads extending from an intersection as shown in FIG. According to the present invention, the same radio wave is transmitted to roads in four directions by one omnidirectional antenna of the base station 5 as shown in FIG. As can be seen from the comparison with FIG. 5, the configuration of the base station and the antenna is simplified compared to the case of using four directional antennas provided for each road.
[0021]
【The invention's effect】
As described above, the invention described in claim 1 does not require frequency switching, and therefore does not require a frequency search or a frequency switching protocol. Further, even if the car moves at high speed, it is possible to provide a service. Furthermore, since it is not necessary to prepare a dedicated frequency for the base information with a small amount of information, the frequency is effectively used.
[0022]
In the invention according to claim 2, the base point information and the service information can be provided simultaneously. In the invention according to claim 3, since the number of base stations can be reduced, the infrastructure maintenance becomes inexpensive.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment for providing a base point in a road-to-vehicle communication system according to the present invention.
FIG. 2 is a diagram showing an example of frequency allocation for providing a base point in a road-to-vehicle communication system according to the present invention.
FIG. 3 is a diagram illustrating an example of simultaneous provision of base point information and service information in the present invention.
FIG. 4 is a diagram showing an example of frequency allocation for simultaneous provision of base point information and service information in the present invention.
FIG. 5 is a diagram illustrating an example of a conventional intersection service.
6 is a diagram corresponding to FIG. 5 in which the number of base stations is reduced using omnidirectional antennas.
FIG. 7 is a diagram illustrating an example of providing a base point in a conventional road-vehicle communication system.
FIG. 8 is a diagram illustrating an example of frequency allocation for providing a base point in a conventional road-to-vehicle communication system.

Claims (3)

In an orthogonal frequency division multiplexing road-to-vehicle communication system that provides services that provide road information, subcarriers used for communication from the ground to a mobile unit are divided into a plurality of groups, and some of them are used as base information. and be used for communication, the base point information is transmitted from the directivity of the road antenna, the road-to-vehicle communication system, characterized in that the reference position associated with the road information is information showing the moving body . In an orthogonal frequency division multiplexing road-to-vehicle communication system that provides road information services, subcarriers used when communicating from the ground to a mobile unit are divided into a plurality of groups, and one of these groups is used for communication of base information. , the communication service information to another group, and be used in simultaneously allocated, the base point information is transmitted from the directivity of the road antenna, showed reference position associated with the road information to the mobile A road-to-vehicle communication system characterized by being information . In road-vehicle communication system of orthogonal frequency-division multiplexing to service that provides road information, divides the subcarriers to be used when communicating from the ground to the mobile into a plurality of groups, on the road towards the intersection with a group while transmitting the base point information from the directivity of the road antenna which is provided, with a different group and the group, and transmits the service information from one omnidirectional road antenna which is provided in the vicinity of the intersection, the base point information, road-vehicle communication system, wherein information der Rukoto showing the location as a reference associated with the road information to the mobile.

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