JP2002133481A - On-vehicle communication device between road and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle communication device between a road and a vehicle, detecting an electric field level of a reception signal, setting a threshold value of the electric field level, deciding that the vehicle is within a communication region when the electric field level exceeds the threshold value, and communicating only within the communication region to reduce a communication error. SOLUTION: In this communication device, an RF amplifier 2 amplifies an electric wave received by a receiving antenna 1, a mixer 3 converts its frequency into an intermediate frequency, an IF amplifier 4 amplifies the intermediate frequency, a level detection circuit 8 detects a received electric field level of the intermediate frequency, and a signal switching control circuit 9 compares the detected electric field level with the preset threshold value and controls the signal switching control circuit 7 when the electric field is not more than the threshold value, not to output a received detected signal to a signal processing part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ETC (Electronic
The present invention relates to an on-vehicle road-to-vehicle communication device mounted on a vehicle in a road-to-vehicle communication system such as a toll collection (automatic toll collection) system.

[0002]

2. Description of the Related Art Conventionally, ETC (Electronic Toll Collec)
In a vehicle-mounted device of a road-to-vehicle communication system such as a communication system, a wireless unit has both a transmitting unit and a receiving unit, and the receiving unit includes a receiving antenna 1 and an RF as shown in FIG. (Radio Frequency)
Amplifier 2, Mixer 3, IF (Intermediate Frequenc
(y, intermediate frequency) An amplifier 4, an IF detector 5, and a signal processing unit 6 are provided, and a reception antenna 1 receives, for example, a radio wave of a center frequency 5.8 GHz band transmitted from a roadside device,
The received radio wave is amplified by the RF amplifier 2, the frequency is converted by the mixer 3 to create an intermediate frequency, the IF is amplified by the IF amplifier 4, the signal is extracted by the IF detector 5, and the signal is processed by the signal processing unit 6. Data is output from the signal.

[0003]

However, in such a conventional ETC system, communication is performed at a roadside gate such that a specified electric field level exists within a communication area defined as a standard. In places other than the fixed communication area, especially in front of the roadside gate, radio waves leak directly from this communication area, reflect to surrounding objects, reflect to other cars, and near this gate An electric field may appear. If data is received by this electric field, it shifts to communication work for transmission and reception even though it is out of the communication area.Because it is out of the communication area, stable communication cannot be secured as a result. However, there is a problem in that the entire communication may cause an error and communication stability cannot be ensured.

The present invention has been made to solve such a problem, and detects the above-described electric field level, sets a threshold value of the electric field level, and performs communication when the electric field level exceeds the threshold value. It is intended to provide an on-vehicle road-vehicle communication device which determines that the vehicle is within the communication area and performs communication only within the communication area to reduce communication errors.

[0005]

According to the present invention, there is provided an on-vehicle road-to-vehicle communication device, comprising: an RF amplifier for amplifying a radio wave received from a roadside device; a mixer for converting the frequency of the amplified radio wave to generate an intermediate frequency; In-vehicle road-vehicle communication including an IF amplifier for amplifying an intermediate frequency, an IF detector for detecting the amplified intermediate frequency into a baseband reception signal, and a signal processing unit for outputting data from the baseband reception signal The apparatus has a configuration in which a level detection circuit for detecting the electric field level of the intermediate frequency is provided, and the reception processing is not performed when the detected electric field level is equal to or less than a preset threshold value. With this configuration, communication is not performed in an area where the electric field level is equal to or less than the threshold.

Here, it is preferable that the signal processing section has a threshold changing means for collecting error information of the received signal and changing the threshold based on the error information. With this configuration, the threshold is changed to a threshold suitable for the reception state.

Preferably, the error information is a bit error rate, and the threshold value changing means changes the threshold value by the number of times equal to or higher than a predetermined bit error rate by the end of communication. With this configuration, the threshold is changed according to the bit error rate.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of an on-vehicle road-vehicle communication device according to the present invention.

As shown in FIG. 1, a receiving section of a vehicle-mounted road-vehicle communication apparatus according to a first embodiment of the present invention includes a receiving antenna 1 for receiving a radio wave and an RF (Radio) for amplifying the received radio wave.
Frequency (radio frequency) amplifier 2, a mixer 3 for converting the frequency of the amplified signal to generate an intermediate frequency, and an IF (Intermediate Frequency,
(Intermediate frequency) amplifier 4, IF detector 5 for detecting the amplified intermediate frequency into a baseband received signal, signal processing unit 6 for outputting data from the received signal, and a signal of the received signal from IF detector 5 ON / OF input to processing unit 6
A signal switching circuit 7 for performing F / F and a level detection circuit 8 for detecting an electric field level of an intermediate frequency output from the IF amplifier 4
And a signal switching control circuit 9 for controlling the signal switching circuit 7 based on the electric field level detected by the level detection circuit 8.

In the receiving unit having such a configuration, the radio wave received by the receiving antenna 1 is amplified by the RF amplifier 2, the frequency is converted by the mixer 3 to generate an intermediate frequency, and the intermediate frequency is amplified by the IF amplifier 4. Then, the signal is extracted by detecting the received signal in the baseband by the IF detector 5.

At the same time, the output of the IF amplifier 4 is also input to a level detection circuit 8, which detects the received electric field level of the intermediate frequency. The signal switching control circuit 9 outputs the detected electric field level. Is compared with a preset threshold value, and when the electric field level is equal to or less than the threshold value, the signal switching circuit 7 is controlled so that the signal detected and received is not output to the signal processing unit 6.

If the electric field level exceeds the threshold value, the signal switching control circuit 9 controls the signal switching circuit 7 to output the signal detected and received to the signal processing unit 6, and the signal processing unit 6 Output data.

As described above, the on-vehicle road-vehicle communication apparatus according to the present embodiment sets the threshold of the electric field level, and outputs the demodulated signal of the receiver only when the electric field level of the received signal is equal to or higher than this threshold. As a result, communication can be performed only in the specified communication area where stable communication can be performed.

FIG. 2 is a diagram showing a second embodiment of the road-to-vehicle communication device for mounting according to the present invention. In this embodiment,
Since the configuration is substantially the same as that of the above-described embodiment, the same components are denoted by the same reference numerals, and only the features will be described.

As shown in FIG. 2, in this embodiment, the CPU
(Threshold changing means) 10, and the communication quality (error information) is input from the signal processing unit 6 to the CPU 10,
Reference numeral 10 changes the threshold of the electric field level of the signal switching control circuit 9 based on the error information of the communication after the communication is completed.

Basically, the lower the electric field level, the lower the BER, but the installation conditions of the receiver (the mounting position of the antenna,
This relationship changes depending on peripheral reflectors and the like. Actually, the electric field level is sufficiently high in the communication area and the BER is stable and continuous, but outside the communication area, the electric field level is slightly higher in a spot manner, but the BER is not stable and continuous. Therefore, an attempt is made to set a threshold of the electric field level at which the area where the BER is low and stable until the end of communication can be set as the communication area, from the communication quality.

More specifically, the signal processing unit 6 performs data communication.
Bit error rate (BE)
R: Bit Error Rate) and the BER is, for example,
10 ^-FiveIf it becomes worse, the CPU 10 is notified. CPU
10 counts the number of times of this notification until the end of communication,
After the communication ends, this number exceeds the preset number.
Is determined (whether the electric field level is stable)
If the set number of times is exceeded (the electric field level is stable
The electric field of the signal switching control circuit 9
Increase the level threshold.

As described above, in the on-vehicle road-to-vehicle communication apparatus of the present embodiment, the CPU 10 changes the threshold of the electric field level of the signal switching control circuit 9 depending on the occurrence of an error during communication. Communication can be stabilized, and errors that occur can be reduced.

[0019]

As described above, the present invention detects the electric field level of a received signal and, if the detected electric field level is equal to or lower than a preset threshold, does not perform communication, thereby achieving a stable high level. It is an object of the present invention to provide a vehicle-mounted road-vehicle communication device having an excellent effect that quality communication can be performed between road and vehicle.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a first embodiment of an on-vehicle road-to-vehicle communication device according to the present invention.

FIG. 2 is a schematic block diagram showing a second embodiment of the on-vehicle road-to-vehicle communication device according to the present invention;

FIG. 3 is a schematic block diagram showing a conventional on-vehicle road-vehicle communication device;

[Explanation of symbols]

 Reference Signs List 1 receiving antenna 2 RF amplifier 3 mixer 4 IF amplifier 5 IF detector 6 signal processing unit 7 signal switching circuit 8 level detection circuit 9 signal switching control circuit 10 CPU (threshold changing means)

Claims (3)

[Claims] An R that amplifies radio waves received from a roadside device
An F amplifier, a mixer for converting the frequency of the amplified radio wave to generate an intermediate frequency, an IF amplifier for amplifying the intermediate frequency, an IF detector for detecting the amplified intermediate frequency to a baseband reception signal, and the base A vehicle-to-vehicle road-to-vehicle communication device comprising: a signal processing unit that outputs data from a band reception signal; and a level detection circuit that detects an electric field level of the intermediate frequency, wherein the detected electric field level is equal to or less than a preset threshold. A vehicle-to-vehicle road-to-vehicle communication device characterized in that no reception processing is performed. 2. The vehicle-to-vehicle road-vehicle communication system according to claim 1, wherein the signal processing unit has a threshold changing unit that collects error information of a received signal and changes the threshold based on the error information. Communication device. 3. The in-vehicle vehicle according to claim 2, wherein the error information is a bit error rate, and the threshold value changing means changes the threshold value by a number of times equal to or more than a predetermined bit error rate by the end of communication. Road-to-vehicle communication device.