JP2003289582A - Road-vehicle communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road-vehicle communication system, which can secure a high quality of road-vehicle communication, can prevent undesirable road- vehicle communication caused by excessive emission of electromagnetic waves, and can reduce an error caused by a difference in the performances of mobile station communication devices when the positions of the mobile stations are identified on the basis of a DSRC inter-vehicle communication system. <P>SOLUTION: In a narrow-band wireless communication system, when bi- directional communication is carried out between a base station and a mobile station, the base station 10 monitors the intensity of the received electromagnetic wave transmitted from a mobile station 100, judges the intensity of the electromagnetic wave by comparing the received wave intensity with a preset judgement reference value, and adjusts establishment of the bi-directional communication between the base station and the mobile station. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road-to-vehicle communication system as a mobile communication system, and particularly to a short range wireless communication system (DSRC, Dedicated Short Rade) installed along a road.
nge Communications) based road-vehicle communication system between the base station and the mobile station moving at high speed on the road (hereinafter referred to as DSRC road-vehicle communication system).

[0002]

2. Description of the Related Art Conventional communication devices using a short-range wireless communication system tend to realize the upper limit of performance conditions such as the reception sensitivity specification stipulated in the wireless standard (ARIB STD-T55) in order to emphasize performance improvement. As a result, too many radio waves are seen to reach places where communication should not be performed. Further, in the example of the mobile phone, the reliability of communication is improved by controlling the transmission output of the mobile terminal.

However, in the communication control method adopted in the above-mentioned conventional system, the information communication area is set by the DSRC road-to-vehicle communication method in a form in which small regions are arranged along the road or in a form in which they are connected in a strip shape. When applied to a high-speed mobile communication system that provides highly regionalized information that differs for each information communication area, there are the following problems.

The first problem is that, as shown in FIG. 5, when the base station 10 is set to reliably communicate with the mobile station 100 traveling on the road 8 in the communication area A1. Also, even outside of that, for example, the radio wave weakens in the range of the communication area N3 but leaks out, and the performance of the communication device of the mobile station 101 even though the mobile station 101 moving on the adjacent road 81 should not communicate. Depending on the situation, the radio wave from the base station 10 is received and the communication is established. Base station 10 to prevent false communication
If the transmitted radio wave is weakened, the reception level of the mobile station 100 in the communication area A1 decreases, and the communication quality of the mobile station 100 cannot be secured.

The second problem is that when the position of a mobile station is specified by wireless communication by taking advantage of the characteristics of the DSRC road-to-vehicle communication system, as shown in FIG. Error is caused by. The electric field strength of the radio wave transmitted from the base station 10 when propagating on the road 8 is generally 300 in FIG. If the communication capability of the mobile station 100 is higher than that of 320 in FIG. 6, communication is possible when the mobile station 100 is between the points 321 and 322 of FIG. The mobile station acquires, as the position information, the 321 points at which the communication becomes possible first.

On the other hand, the performance of the communication device of the mobile station 100 is 3 in FIG.
If communication is possible at a level higher than 10 levels, the mobile station
When 100 is between points 311 and 312 in FIG. 6,
When the mobile station can communicate between the points 313 and 313 to the point 314, the mobile station first acquires the point 311 at which the communication becomes possible as the position information. Thus, there is an error between the position information acquired by the performance of the communication device of the mobile station and the communication point.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned conventional problems, ensures high-quality road-to-vehicle communication, and causes undesired road-to-vehicle communication caused by too many radio waves. It is possible to provide a road-to-vehicle communication method that can prevent communication and reduce an error caused by a difference in performance of a mobile station communication device when a mobile station is located by the DSRC road-to-vehicle communication method. To aim.

[0008]

In order to achieve the above object, the invention according to claim 1 is a narrow-range wireless communication system, in which the communication between a base station and a mobile station is bidirectional communication. , The base station monitors the reception intensity of the radio wave transmitted by the mobile station, and determines the reception intensity of the radio wave by comparing it with a preset reference value, so that the base station establishes bidirectional communication with the mobile station. It is characterized by adjusting. According to the invention of claim 2, in the short-range wireless communication system, when the communication between the base station and the mobile station is bidirectional communication and unidirectional communication from the base station to the mobile station, the mobile station is The determination condition for validating the reception of the one-way communication is a period in which the satisfaction condition of claim 1 is maintained in the mobile station.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 show
FIG. 1 is a diagram showing a highly reliable DSRC road-to-vehicle communication system capable of varying a communication area by setting a reception level of a base station as an embodiment.

1 and 2, it is assumed that the mobile station 100 traveling on the road 8 advances in the traveling direction 9. The base station 10 installed on the roadside has a switching function for transmitting / receiving between the antenna 11 and the base station antenna or a demultiplexing function 12 and a bidirectional communication function.
The mobile station 100 comprises a mobile station antenna 111 and a mobile station antenna transmission / reception switching function or a demultiplexing function 112, a bidirectional communication function 121, and a reception determination function ( 1) Consists of 131-1. Radio waves emitted by the base station 10 via the antenna 11 are on the road 8
Communication is performed between the mobile station 100 and the mobile station 100 that is directed upward, and the communication areas are defined as communication areas A, B, ...

As a means for changing the communication area, the radio wave transmitted by the mobile station 100 via the antenna 111 by the reception level monitoring function 31 and the reception level determination function 32 of the base station is transmitted to the base station 10.
Is received via the antenna 11, the base station 10 monitors the reception level in the reception level monitoring function 31, and the base station 10 moves if the reception level determination function 32 determines that the reception level is equal to or higher than the reference value. By making a response to the station 100, a communication area in which the mobile station 100 can communicate is set. The present invention makes it possible to change the size of the communication area with the mobile station 100 by changing the reference value in the reception level determination function 32.

FIG. 3 shows the base station 10 and the mobile station 100 of FIG.
FIG. 3 is a diagram showing a configuration in which a unidirectional communication function from the base station 10 to the mobile station 100 is added based on the above configuration. base station
In the mobile station 100, the unidirectional transmission function 22 is added, and in the mobile station 100, the unidirectional reception function 122 and the reception level monitoring storage function 132 are added.
The reception judgment function (1) is added to the reception judgment function (2) 131-
The configuration is changed to 2. In one-way communication, the establishment of two-way communication is applied as a condition for making the received information of the mobile station valid. The reception level when bidirectional communication is established is stored in the reception level monitoring storage function 132 as a determination condition for enabling the reception of unidirectional communication in the mobile station, and the reception level of unidirectional communication is equal to or higher than the stored reception level. The reception determination function (2) 131-2 determines that the reception of the unidirectional communication is valid, thereby ensuring the communication quality of the unidirectional communication.

Next, the operation of the embodiment of the highly reliable DSRC road-vehicle communication system will be described. The reason why the reception level of the mobile station can be adjusted to the level expected by the base station by adjusting the reception level of the base station is that the output level of the transmitter of the base station is Pb and the input of the receiver of the base station is Rb level
(It is higher than the receiving sensitivity of the receiver of the base station), the output level of the transmitter of the mobile station is Pm, and the input level of the receiver of the mobile station is Rm (from the receiving sensitivity of the receiver of the mobile station. High level), Pb +
If the relationship of Rb = Pm + Rm is established, Pb takes a certain constant value, and Pm takes a certain constant value within a certain range although there is a difference for each mobile station, Rm can be adjusted by adjusting the value of Rb.
It is based on the fact that the value of is adjusted to a value in a certain range according to Rb.

First, the operation of an embodiment of a highly reliable DSRC road-vehicle communication system for bidirectional communication between a base station and a mobile station will be described.

1 and 2, it is assumed that the mobile station 100 travels on the road 8 in the traveling direction 9. It is assumed that the base station 10 is installed on the road side of the road 8 and emits radio waves toward the road 8 for communication with the mobile station 100. Mobile station 10
0 receives radio waves from the base station 10 while traveling on the road 8. The position where the mobile station 100 can receive at this time depends on the strength of the radio wave emitted by the base station 10 and the reception performance of the receiver of the mobile station 100, and varies depending on the manufacturer and model of the mobile station. For example, it is assumed that the receiver of the mobile station 100 can receive when the mobile station 100 enters the communication area N3. The mobile station 100 emits a radio wave toward the base station 10 to start bidirectional communication with the base station 10. The base station 10 receives the radio wave radiated by the mobile station 10, and measures the intensity of the radio wave radiated by the mobile station by the reception level monitoring function 31.

It is assumed that the reception level determination function 32 of the base station 10 has preset values corresponding to the communication area A1, communication area B2, ... Communication area N3. For example, the communication area A1
If the value corresponding to is set, the received power from the mobile station 100 at this position does not satisfy the value, so the reception level determination function 32 of the base station 10 uses the two-way communication function 21 to move the mobile station. A negative response is given to 100 communication start requests. Or ignore it and do not return the answer. The mobile station 100 repeatedly requests the base station 10 to start communication,
When 100 goes on the road and enters the communication area A1, the output of the reception level monitoring function 31 of the base station 10 is the communication area A1.
And the reception level determination function 32 permits the start of communication. The reception determination function (1) 131-1 of the mobile station receives the permission from the base station 10 and determines the establishment of bidirectional communication.

Next, the operation of the embodiment of the highly reliable DSRC road-vehicle communication system for one-way communication from the base station to the mobile station will be described.

FIG. 3 shows a configuration in which the unidirectional transmission function 22 is added to the configuration of FIG. 2 in the base station 10. In the mobile station 100, a unidirectional reception function 122 is added to the configuration of the mobile station shown in FIG. 2, and reception determination function (2) 131-2 replaces the reception determination of the mobile station. Reception judgment function (2) 131-2
When the communication between the base station 10 and the mobile station 100 is bidirectional communication and unidirectional communication from the base station to the mobile station, the mobile station 100 has a function of determining the effectiveness of the unidirectional communication. Have. The mobile station 100 monitors the reception level when two-way communication is established in the mobile station 100 for the purpose of confirming that the conditions shown in FIG. 2 are maintained.
The reception determination function (2) 131-2 stores it in 132 and determines that the reception level of the one-way communication is equal to or higher than the reception level stored in the reception level monitoring storage function 132 and validates it.

As another embodiment of the invention in which the establishment of bidirectional communication is applied as a condition for validating the reception information of a mobile station in unidirectional communication, a cycle between the base station and the mobile station is set via the bidirectional communication function. An example of repeatedly repeating a communication request response will be shown. Referring to FIG. 4, in the base station 10, FIG.
In this configuration, the periodic communication request response function 33 is added. The mobile station 100 does not require the reception level monitoring and storing function of the mobile station configuration shown in FIG. 3, and the reception determination function (2) 131-2 is replaced with the reception determination function (3) 131-3. Figure 4
Shows an example in which the periodic communication request response function 33 is provided in the base station 10. The periodic communication request response function 33 may be provided in the mobile station instead of the base station, or may be provided in both the base station and the mobile station.

The reception determination function (3) 131-3 of the mobile station 100-3 is used when the communication between the base station and the mobile station is bidirectional communication and unidirectional communication from the base station to the mobile station.
Has a function of determining the effectiveness of one-way communication. base station
The periodic communication request response function 33 of 10 communicates with the bidirectional communication function 121 of the mobile station 100 via the bidirectional communication function 21. Two-way communication is repeated while this communication meets the conditions of the reception level monitoring function 31 and the reception level determination function 32 of the base station 10. In the mobile station 100, the reception determination function (3) 131-3 works so as to validate the reception of the unidirectional communication while the bidirectional communication continues. This allows the mobile station 1 of FIG.
The reception level monitoring and storing function 132 of 00 becomes unnecessary.

[0021]

As described above, according to the invention described in claim 1, it is possible to adjust the communication area of the mobile station on the side of the base station, which causes a difference in performance of the communication device of the mobile station. Since the difference in the size of the communication area can be suppressed,
It is possible to maintain the communication quality by maintaining the communication area at or above a predetermined radio wave intensity, and it is possible to solve the problem that the communication is established at a place which should not be received in an adjacent place due to too many radio waves. In addition, the communication quality between the base station and the mobile station can be maintained good. Also, compared to the case where the radio wave propagation distance is adjusted by lowering the transmission level of the base station due to excessive radio wave jumping, the transmission level of the base station does not change, so the reception level of the mobile station does not change and the communication quality deteriorates. There is no.

According to the second aspect of the present invention, since it is possible to finely adjust the communication area on the side of the base station, there is no dependence on the sensitivity of the receiver of the mobile station. By enabling the adjustment of various communication areas, it is possible to reduce the error caused by the difference in the performance of the communication device of the mobile station when the position of the mobile station is specified by the short range wireless communication.

With the above effects, it is possible to solve the problem that communication is established in a place which should not be received in an adjacent place due to too many radio waves. In addition, the communication quality between the base station and the mobile station can be maintained good. It is possible to reduce the error in specifying the position of the mobile station using the DSRC road-vehicle communication system.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example in which a highly reliable DSRC road-vehicle communication system according to an embodiment of the present invention is applied on a road.

FIG. 2 is a schematic diagram showing a configuration example when a high reliability DSRC road-vehicle communication system is applied to a base station and a mobile station having a bidirectional communication function.

FIG. 3 is a configuration example including a reception level storage function when the high-reliability DSRC road-vehicle communication system is applied to a base station and a mobile station having a bidirectional communication function and a unidirectional communication function from a base station to a mobile station. It is a schematic diagram showing.

FIG. 4 is a configuration including a periodic communication request response function when the high-reliability DSRC road-vehicle communication system is applied to a base station and a mobile station having a bidirectional communication function and a unidirectional communication function from a base station to a mobile station. It is the schematic which shows an example.

FIG. 5 is a schematic diagram showing an example in which communication is erroneously generated with a mobile station traveling on a road that should not be communicated due to too many radio waves.

FIG. 6 is a schematic diagram illustrating a difference in communication start position due to a difference in performance of mobile stations.

[Explanation of symbols]

1 Communication area A 2 Communication area B 3 Communication area N 8 roads 9 Mobile station traveling direction 10 base stations 11 Base station antenna 81 Adjacent road to road 8 100 mobile stations 101 Mobile stations running on roads that should not communicate 111 Mobile Station Aerial

Claims (2)

[Claims] 1. In a short range wireless communication system, when communication between a base station and a mobile station is performed by two-way communication,
The base station monitors the reception intensity of the radio wave transmitted by the mobile station and judges the reception intensity of the radio wave by comparing it with a preset reference value to determine whether the base station establishes bidirectional communication with the mobile station. Road-to-vehicle communication method characterized by adjustment. 2. In the short-range wireless communication system, when the communication between the base station and the mobile station is bidirectional communication and unidirectional communication from the base station to the mobile station, the mobile station is unidirectional. A road-to-vehicle communication system, wherein the determination condition for validating the reception is a period in which the satisfaction condition of claim 1 is maintained in the mobile station.