JP2002261678A - Channel searching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure that a frequency channel of a road side apparatus of a fast speed run application is searched in a vehicle mounted communication apparatus for a DSRC system even if there exist many channels. SOLUTION: A control unit 4 controls a local oscillation signal issued by a local oscillator 3 to search a variety of frequency channels of a plurality of road side apparatuses and, in the case of a fast speed run, searches only a frequency channel of the road side apparatus of the fast speed run application based on a vehicle speed detected by a vehicle speed detector 5, and then starts communication.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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]

2. Description of the Related Art In recent years, a DSRC system for transmitting various information between a roadside device (communication device disposed on a road or other stationary part) installed on a road or the like and a vehicle-mounted device (vehicle communication device) has been developed. Are known. The DSRC system is expected to be used in a very wide range of applications. Examples of applications are toll road automatic toll collection (ETC) systems, front obstacle collision prevention support systems, parking fee management systems, payment systems such as gas stations, and fast food restaurants. It is said that drive-through systems and various information download systems will spread in the future.

[0003] The DSRC system is an application system (hereinafter, semi-stationary application) that assumes a case where the vehicle is stationary / semi-stationary (for example, 20 km / h or less), such as a system for downloading various information,
For example, it can be broadly divided into two types of application systems (hereinafter, high-speed running applications) that assume a case where the vehicle is in a high-speed running state, such as an ETC system.

[0004]

In a DSRC system for performing wireless communication between a roadside device and an on-vehicle device for each application, the onboard device divides a frequency channel of the roadside device for each application by time division. It is necessary to search by and start communication. However, when frequency channels increase, when monitoring each channel sequentially in a time-division manner, it takes time to monitor all the channels, and the search time for one cycle becomes longer. There is a problem that it becomes impossible to search for the frequency channel on the roadside machine side of the high-speed traveling application because the vehicle passes by.

The present invention has been made in view of the above-mentioned problems of the prior art, and
It is an object of the present invention to provide a channel search device capable of reliably searching for a frequency channel on a roadside device side of a high-speed traveling application even when the number of channels of an RC system is large.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a vehicle-mounted channel search apparatus for searching frequency channels of roadside units for a semi-stationary application and a high-speed traveling application of a DSRC system. Speed detecting means for detecting a vehicle speed of a vehicle on which the communication device is mounted, and a frequency channel of the roadside machine for both the semi-stationary application and the high-speed traveling application when the vehicle speed detected by the vehicle speed detecting means is lower than a predetermined speed. And a means for searching for a frequency channel of a roadside device only for a high-speed traveling application when the speed is equal to or higher than a predetermined speed. With the above configuration,
When the speed is equal to or higher than the predetermined speed, the frequency channel of the roadside device only for the high-speed traveling application is searched. Therefore, even if the number of channels of the DSRC system is large, the frequency channel of the roadside device for the high-speed traveling application can be reliably searched.

The vehicle speed detecting means is configured to detect a vehicle speed based on a vehicle speed pulse. With the above configuration, when the speed is equal to or higher than the predetermined speed based on the vehicle speed pulse, the frequency channel of the roadside device only for the high speed traveling application is searched. Search can be performed reliably.

Further, the vehicle speed detecting means is configured to detect the vehicle speed based on a change in the vehicle position. According to the above configuration, when the speed is equal to or higher than the predetermined speed based on the change in the vehicle position, the frequency channel of the roadside machine only for the high speed traveling application is searched. Channels can be searched reliably.

Further, the vehicle speed detecting means is configured to detect a vehicle speed based on a difference between a transmitting frequency and a receiving frequency. According to the above configuration, when the speed is equal to or higher than the predetermined speed based on the difference between the transmission frequency and the reception frequency, the frequency channel of the roadside device only for the high speed traveling application is searched. The frequency channel on the device side can be searched reliably.

In order to achieve the above object, the present invention provides a plurality of electric field intensity detecting means for detecting electric field intensity of a frequency channel of each roadside device for a semi-stationary application of a DSRC system and a high-speed running application; Means for simultaneously monitoring the electric field strength of each channel detected by the detecting means, and controlling to receive a frequency channel having the strongest electric field strength.
With the above configuration, since the electric field strength of each channel is monitored and the frequency channel having the strongest electric field strength is received, DS
Even if the number of channels of the RC system is large, it is possible to reliably search for a frequency channel on the roadside machine side for a high-speed traveling application.

Further, the electric field intensity detecting means is configured to exclusively detect the electric field intensity of the frequency channel of each roadside device for a high-speed traveling application. With the above configuration, it is possible to search for a frequency channel on the roadside device side of a high-speed traveling application during high-speed traveling with a low-cost configuration.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the channel search device according to the present invention, and FIG. 2 is an explanatory diagram showing the operation of the channel search device of FIG. This channel search device is assumed to be mounted on an automobile (not shown).

In FIG. 1, a radio (RF) signal transmitted from a roadside device for a semi-stationary application or a high-speed traveling application (not shown) is received via an antenna 1,
The signal received by the antenna 1 is mixed with the local oscillation signal from the local oscillator 3 in the mixer 2 and converted into an IF signal. This IF signal is input to the demodulation unit 6, subjected to predetermined demodulation, and applied to an amplification stage, a display device, a speaker, and the like (not shown). The control unit 4 controls the local oscillation signal generated by the local oscillator 3 to search various frequency channels of the plurality of roadside units, and based on the detection speed of the vehicle speed detection unit 5, at the time of high speed traveling, the roadside of the high speed traveling application. The communication is started by searching the frequency channel of only the device. Although FIG. 1 shows only the receiving unit, a transmitting unit can be provided as needed.

FIG. 2 shows, as an example, a case where the roadside device of the semi-stationary application transmits on the frequency channels of channels CH1, CH2, CH3 and CH4, and the roadside device of the high-speed running application transmits on the frequency channels of channels CH5 and CH6. Is shown. In this case, based on the detected speed of the vehicle speed detecting unit 5, the control unit 4 determines whether all of the frequency channels CH1 to CH
6 is searched, while if the speed is lower than the predetermined speed, only the frequency channels CH5 and CH6 of the high-speed running application are searched.

The vehicle speed detecting unit 5 detects a vehicle speed based on a vehicle speed pulse supplied from an onboard engine,
A method of detecting a change in vehicle position obtained from a GPS (Global Positioning System) and a Doppler method of detecting a difference between a transmission frequency and a reception frequency can be used.

<Second Embodiment> Next, a channel search apparatus according to a second embodiment will be described with reference to FIG.
In FIG. 3, a radio signal transmitted from a roadside device of a semi-stationary application or a high-speed traveling application (not shown) is received via an antenna 1, and a signal received by the antenna 1 is converted into an IF signal by a mixer 2. The IF signals are distributed by the distributor 11 in accordance with the number n of the various frequency channels CH1 to CHn of the plurality of roadside units, and the distributed IF signals are transmitted to bandpass filters (BPFs) 12-1 to 12-12. −n to extract signals of the frequency channels CH1 to CHn, respectively.

The frequency channels CH1 to CH
n of each signal of the RSSI detection unit (Receive
iced Signal Strength Indicator) 13-1 to 13-n
, And the control unit 14 controls each of the channels CH1 to CH1.
By monitoring the electric field strength of CHn, the switch SW is controlled so as to select the channel having the strongest 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,
The quadrature demodulator 16 demodulates the signal of the channel selected by the switch SW based on the oscillation frequency.

It should be noted that only high-priority channels such as the frequency of each roadside device for high-speed running applications may be monitored, and low-priority channels may not be monitored.

Although the above embodiment has been described with reference to an example in which the channel search device is mounted on an automobile, the present invention is not limited to vehicles running on roads such as automobiles, but is mounted on all vehicles such as ships and airplanes. Therefore, the meaning of “vehicle” means “vehicle = vehicle.
e "should be understood.

[0020]

As described above, according to the first aspect of the present invention, when the speed is equal to or higher than the predetermined speed, the frequency channel of the roadside device only for the high-speed traveling application is searched.
Even if the number of channels of the DSRC system is large, it is possible to reliably search for the frequency channel on the roadside machine side of the high-speed traveling application. According to the second aspect of the present invention, when the speed is equal to or higher than the predetermined speed based on the vehicle speed pulse, the frequency channel of the roadside device only for the high speed traveling application is searched. The frequency channel on the device side can be searched reliably. According to the third aspect of the invention, when the speed is equal to or higher than the predetermined speed based on the change in the vehicle position, the frequency channel of the roadside device only for the high-speed traveling application is searched. Can be reliably searched for the frequency channel on the roadside machine side. According to the fourth aspect of the present invention, when the speed is equal to or higher than the predetermined speed based on the difference between the transmission frequency and the reception frequency, the frequency channel of the roadside device only for the high-speed traveling application is searched.
Even if the number of channels of the DSRC system is large, it is possible to reliably search for the frequency channel on the roadside machine side of the high-speed traveling application. According to the fifth aspect of the present invention, since the electric field strength of each channel is monitored and the frequency channel having the strongest electric field strength is received, even if the number of channels of the DSRC system is large, the frequency channel on the roadside machine side of the high-speed running application is used. Can be surely searched. According to the invention described in claim 6, since the electric field strength of the channel with low priority is not detected, it is possible to search the frequency channel on the roadside device side of the high-speed traveling application at the time of 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 the operation of the channel search device of FIG.

FIG. 3 is a block diagram illustrating a channel search device according to a second embodiment;

[Explanation of symbols]

 3 Local oscillator 4 Control unit 5 Vehicle speed detecting unit 13-1 to 13-n RSSI detecting unit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akihiro Inui 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa F-term in Matsushita Communication Industrial Co., Ltd. (reference) 5H180 AA01 BB04 CC12 FF04 FF13 5K067 AA15 BB21 BB43 EE02 EE10 GG09 JJ12 JJ52

Claims (6)

[Claims] An on-vehicle channel search device for searching a frequency channel of each roadside device for a semi-stationary application and a high-speed traveling application of a DSRC system, wherein a vehicle speed detection for detecting a vehicle speed of a vehicle on which the on-vehicle communication device is mounted. Means, if the vehicle speed detected by the vehicle speed detection means is less than a predetermined speed, search the frequency channel of both the roadside machine of the semi-stationary application and the high-speed running application, if the speed is equal to or higher than the high-speed running application only Means for searching for a frequency channel of the roadside device. 2. The channel search device according to claim 1, wherein said vehicle speed detecting means detects a vehicle speed based on a vehicle speed pulse. 3. The channel search device according to claim 1, wherein said vehicle speed detecting means detects a vehicle speed based on a change in a vehicle position. 4. The channel search device according to claim 1, wherein said vehicle speed detecting means detects a vehicle speed based on a difference between a transmission frequency and a reception frequency thereof. 5. A plurality of electric field intensity detecting means for detecting electric field intensity of a frequency channel of each roadside machine for a DSRC system semi-stationary application and a high-speed traveling application, and electric field intensity of each channel detected by the electric field intensity detecting means. And a control means for simultaneously monitoring the frequency channel and receiving the frequency channel with the strongest electric field strength. 6. The channel search device according to claim 5, wherein said electric field intensity detecting means is configured to exclusively detect electric field intensity of a frequency channel of each roadside device for a high-speed traveling application.