JP4334775B2 - Channel search device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a channel search device mounted on a vehicle such as an automobile in a DSRC (Dedicated Short Range Communication) system.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a DSRC system that transmits various types of information between a roadside device (communication device disposed on a road or other stationary part) installed on a road or the like and an in-vehicle device (in-vehicle communication device) is known. The DSRC system is expected to be used in a wide range of applications. Toll road automatic toll collection (ETC) system, front obstacle collision prevention support system, parking fee management system, payment system such as gas station, fast food store Drive-through systems and various information download systems are said to be widely used in the future.
[0003]
This DSRC system includes an application system (hereinafter referred to as a semi-stationary application) that assumes a case where the vehicle is stationary / semi-stationary (for example, 20 km / h or less), such as a download system for various information, and a ETC system, for example. It can be roughly divided into two types of application systems (hereinafter referred to as high-speed driving applications) assuming the case where the vehicle is in a high-speed driving state.
[0004]
[Problems to be solved by the invention]
By the way, in a DSRC system that performs wireless communication between a roadside device and a vehicle-mounted device for each application, the vehicle-mounted device needs to search for a frequency channel on the roadside device side for each application in a time division manner and start communication. There is. However, if each channel is monitored sequentially in time division as the number of frequency channels increases, it takes time to monitor all the channels, and the search time for one round becomes longer. There is a problem that it becomes impossible to search the frequency channel on the roadside unit side of the high-speed driving application because it passes.
[0005]
The present invention has been made in view of the above-described problems of the conventional example, and an object of the present invention is to provide a channel search device that can reliably search a frequency channel on the roadside unit side of a high-speed driving application even if the number of channels of the DSRC system is large. .
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a vehicle-mounted channel search device that searches the frequency channel of each roadside device of a semi-stationary application and a high-speed driving application of a DSRC system.
Vehicle speed detecting means for detecting the vehicle speed of the vehicle on which the in-vehicle communication device is mounted;
When the vehicle speed detected by the vehicle speed detecting means is less than a predetermined speed, the frequency channels of both the semi-stationary application and the high-speed driving application are searched, and when the vehicle speed is higher than the predetermined speed, only the high-speed driving application is searched. Means for searching for frequency channels;
The configuration was provided.
With the above configuration, since the frequency channel of the roadside unit for high-speed driving applications is searched only when the speed is higher than the predetermined speed, the frequency channel on the roadside unit side of the high-speed driving application must be searched reliably even if the number of channels of the DSRC system is large. Can do.
[0007]
The vehicle speed detecting means is configured to detect the vehicle speed based on a vehicle speed pulse.
With the above configuration, since the frequency channel of the roadside unit only for the high-speed driving application is searched when the speed exceeds the predetermined speed based on the vehicle speed pulse, the frequency channel on the roadside unit side of the high-speed driving application is selected even if the number of channels of the DSRC system is large. You can search reliably.
[0008]
The vehicle speed detecting means is configured to detect the vehicle speed based on a change in the vehicle position.
With the above configuration, the frequency channel of the roadside unit only for the high-speed driving application is searched when the speed is equal to or higher than the predetermined speed based on the change in the vehicle position, so the frequency on the roadside unit side of the high-speed driving application is high even if the number of channels of the DSRC system is large. The channel can be searched reliably.
[0009]
The vehicle speed detecting means is configured to detect the vehicle speed based on a difference between the transmission frequency and the reception frequency.
With the above configuration, since the frequency channel of the roadside unit only for the high-speed driving application is searched based on the difference between the transmission frequency and the reception frequency above the predetermined speed, the roadside of the high-speed driving application even if the number of channels of the DSRC system is large. The frequency channel on the machine side can be searched reliably.
[0010]
In order to achieve the above object, the present invention provides a plurality of electric field strength detecting means for detecting the electric field strength of the frequency channel of each roadside device of the semi-stationary application and the high-speed driving application of the DSRC system,
Means for simultaneously monitoring the electric field strength of each channel detected by the electric field strength detecting means and controlling to receive a frequency channel having the strongest electric field strength;
The configuration was provided.
The above configuration monitors the electric field strength of each channel and receives the frequency channel with the strongest electric field strength. Therefore, even if the number of channels of the DSRC system is large, the frequency channel on the roadside unit side of the high-speed driving application can be searched reliably. Can do.
[0011]
In addition, the electric field strength detecting means is configured to detect the electric field strength of the frequency channel of each roadside machine in a high-speed traveling application exclusively.
With the above-described configuration, it is possible to search for a frequency channel on the roadside machine side of a high-speed traveling application at a high-speed traveling with an inexpensive configuration.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a channel search apparatus according to the present invention, and FIG. 2 is an explanatory diagram showing the operation of the channel search apparatus of FIG. It is assumed that this channel search device is mounted on a vehicle (not shown).
[0013]
In FIG. 1, a radio (RF) signal transmitted from a roadside machine (not shown) of a semi-stationary application or a high-speed traveling application is received via an antenna 1, and the signal received by the antenna 1 is received by a local oscillator 3 in a mixer 2. The signal is mixed with the local oscillation signal from and converted into an IF signal. This IF signal is input to the demodulator 6, subjected to predetermined demodulation, and supplied to an amplification stage, a display device, a speaker, etc. (not shown). The control unit 4 controls the local oscillation signal generated by the local oscillator 3 to search various frequency channels of a plurality of roadside machines, and also, based on the detection speed of the vehicle speed detection unit 5, the roadside of the high-speed driving application during high-speed driving Search the frequency channel only for the machine and start communication. Although FIG. 1 shows only the receiving unit, a transmitting unit can be provided if necessary.
[0014]
FIG. 2 shows, as an example, a case where a roadside unit of a semi-stationary application transmits on the frequency channels of channels CH1, CH2, CH3, and CH4, and a roadside unit of a high-speed traveling application transmits on the frequency channels of channels CH5 and CH6. . In this case, the control unit 4 searches all the frequency channels CH1 to CH6 based on the detection speed of the vehicle speed detection unit 5 when the vehicle speed is lower than the predetermined speed, such as when the vehicle is stopped, and on the other hand, when the speed is lower than the predetermined speed. Searches only the frequency channels CH5 and CH6 of the high-speed driving application.
[0015]
The vehicle speed detector 5 includes a method for detecting the vehicle speed based on a vehicle speed pulse supplied from an in-vehicle engine, a method for detecting a change in the vehicle position obtained from GPS (Global Positioning System), and a difference between the transmission frequency and the reception frequency. The Doppler method can be used.
[0016]
<Second Embodiment>
Next, a channel search apparatus according to the second embodiment will be described with reference to FIG. In FIG. 3, a radio signal transmitted from a roadside machine (not shown) of a semi-stationary application or a high-speed traveling application is received via the antenna 1, and the signal received by the antenna 1 is converted into an IF signal by the mixer 2. This IF signal is distributed by the distributor 11 corresponding to the number n of various frequency channels CH1 to CHn of a plurality of roadside devices, and each of the distributed IF signals is bandpass filters (BPF) 12-1 to 12-12. -N to extract signals of frequency channels CH1 to CHn, respectively.
[0017]
The electric field strengths of the signals of the frequency channels CH1 to CHn are detected by RSSI detectors (Receiced Signal Strength Indicators) 13-1 to 13-n, respectively, and the control unit 14 determines the electric field strengths of the channels CH1 to CHn. The switch SW is controlled so as to select the channel with the highest electric field strength, and the oscillation frequency of the PLL 15 is controlled. The oscillation frequency output from the PLL 15 is applied to the quadrature demodulator 16, and the quadrature demodulator 16 demodulates the signal of the channel selected by the switch SW based on this oscillation frequency.
[0018]
The channel to be monitored may be configured so that only a channel having a high priority such as a frequency of each roadside machine in a high-speed traveling application is monitored and a channel having a low priority is not monitored.
[0019]
In the above embodiment, the channel search device is described as being mounted on an automobile. However, the present invention is not limited to a vehicle traveling on a road such as an automobile, but a communication device mounted on any vehicle such as a ship or an airplane. Therefore, the meaning of “vehicle” should be understood as the meaning of “vehicle”.
[0020]
【The invention's effect】
As described above, according to the first aspect of the invention, since the frequency channel of the roadside unit for only the high-speed driving application is searched when the speed is equal to or higher than the predetermined speed, the roadside of the high-speed driving application even if the number of channels of the DSRC system is large. The frequency channel on the machine side can be searched reliably.
According to the second aspect of the present invention, since the frequency channel of the roadside machine only for the high-speed driving application is searched based on the vehicle speed pulse when the speed is equal to or higher than the predetermined speed, the roadside of the high-speed driving application even if the number of channels of the DSRC system is large. The frequency channel on the machine side can be searched reliably.
According to the invention described in claim 3, since the frequency channel of the roadside unit for only the high-speed driving application is searched when the vehicle speed is higher than the predetermined speed based on the change in the vehicle position, the high-speed driving application is available even if the number of channels of the DSRC system is large. The frequency channel on the roadside machine side can be searched reliably.
According to the invention described in claim 4, since the frequency channel of the roadside unit only for the high-speed driving application is searched based on the difference between the transmission frequency and the reception frequency when the speed is higher than the predetermined speed, the number of channels of the DSRC system is large. Also, it is possible to reliably search the frequency channel on the roadside side of the high-speed driving application.
According to the fifth aspect of the present invention, since the frequency channel with the strongest electric field strength is received by monitoring the electric field strength of each channel, the frequency channel on the roadside unit side of the high-speed driving application even if the number of channels of the DSRC system is large Can be searched reliably.
According to the sixth aspect of the present invention, since the electric field strength of the low priority channel is not detected, it is possible to search for the frequency channel on the roadside machine side of the high speed traveling application at high speed traveling with an inexpensive configuration.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a channel search device according to the present invention. FIG. 2 is an explanatory diagram showing an operation of the channel search device of FIG. 1. FIG. 3 is a channel search device of a second embodiment. Block diagram showing [Description of symbols]
3 Local oscillator 4 Control unit 5 Vehicle speed detection unit 13-1 to 13-n RSSI detection unit

Claims (6)

In the vehicle-mounted channel search device for searching the frequency channel of each roadside machine of the semi-stationary application and high-speed driving application of the DSRC system,
Vehicle speed detecting means for detecting the vehicle speed of the vehicle on which the in-vehicle communication device is mounted;
When the vehicle speed detected by the vehicle speed detecting means is less than a predetermined speed, the frequency channels of both the semi-stationary application and the high-speed driving application are searched, and when the vehicle speed is higher than the predetermined speed, only the high-speed driving application is searched. Means for searching for frequency channels;
A channel search device comprising: 2. The channel search device according to claim 1, wherein the vehicle speed detecting means detects a vehicle speed based on a vehicle speed pulse. 2. The channel search device according to claim 1, wherein the vehicle speed detecting means detects a vehicle speed based on a change in a vehicle position. 2. The channel search device according to claim 1, wherein the vehicle speed detecting means detects the vehicle speed based on a difference between a transmission frequency and a reception frequency thereof. A plurality of electric field strength detecting means for detecting the electric field strength of the frequency channel of each roadside device of the semi-stationary application and the high-speed driving application of the DSRC system;
Means for simultaneously monitoring the electric field strength of each channel detected by the electric field strength detecting means and controlling to receive a frequency channel having the strongest electric field strength;
Equipped with a channel search device. 6. The channel search device according to claim 5, wherein the electric field strength detecting means is configured to detect the electric field strength of the frequency channel of each roadside device in a high-speed driving application exclusively.

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