JP2003244061A - Vehicle roadside communication method, roadside wireless apparatus, on-vehicle wireless apparatus, and vehicle roadside communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roadside communication method, a roadside wireless apparatus, and an on-vehicle wireless apparatus and system wherein many roadside wireless apparatuses exist near a roadside wireless apparatus and a period of time required for switching wireless frequencies to maintain wireless communication is shortened in a vehicle roadside communication. <P>SOLUTION: In this vehicle roadside communication method wherein any of a plurality of the roadside wireless apparatuses makes wireless communication with the on-vehicle wireless apparatus, the on-vehicle wireless apparatus located in an area of the roadside wireless apparatus transmits a transmission signal including succeeding area frequency object information using one roadside wireless apparatus object able to make wireless communication next or over and searches and sets a succeeding wireless frequency on the basis of received succeeding area frequency object information. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a road-vehicle communication method,
The present invention relates to a roadside wireless device, a vehicle-mounted wireless device, and a road-vehicle communication system.

[0002]

2. Description of the Related Art In recent years, Intelligent Transport Systems (ITS: Intelligent Transport) aimed at improving traffic safety, etc.
System) is under development. As one form of communication of this ITS, a roadside wireless device fixedly installed on the roadside and a vehicle-mounted wireless device mounted on a vehicle transmit information (traffic information and weather information in front of the road) using a radio frequency. There is road-to-vehicle communication that gives and receives.

Conventionally, in a road-to-vehicle communication system, different radio frequencies are used in order to prevent radio wave interference between adjacent roadside radio devices, and a vehicle-mounted radio device mounted in a vehicle is By searching and receiving a transmission signal from the roadside wireless device, a radio frequency band to be used is set and road-to-vehicle communication is enabled. In addition, when the vehicle deviates from the permissible communication area (hereinafter referred to as “area”) of the roadside wireless device, when the vehicle enters the next new area, the frequency switching device included in the onboard wireless device causes the roadside of the next area to move. Road-to-vehicle communication is maintained by switching to the assigned radio frequency by the radio device.

[0004] For example, at the intersection of a two-lane road, a vehicle is installed on the road side of each lane, and a roadside wireless device is assigned different radio frequencies f1 to f8.
A conventional road-vehicle communication method for road-vehicle wireless communication is as follows.

In FIG. 2, an in-vehicle wireless device mounted on a vehicle traveling in area 1 determines a radio frequency f1 to which the roadside wireless device 1 is assigned based on a transmission signal transmitted from the roadside wireless device 1. It is set to enable roadside-vehicle communication between the roadside apparatus 1 and the vehicle. FIG. 3 is a signal format of a transmission signal transmitted by the roadside apparatus.

[0006] When the vehicle turns right from area 1 to area 6, the vehicle deviates from area 1, and the on-vehicle wireless device cannot maintain roadside-vehicle communication with the roadside wireless device 1. Therefore, when the vehicle enters the next traveling area 6, the on-vehicle wireless device searches for and receives a transmission signal from the roadside wireless device 6, and sets and switches to the radio frequency f6 to which the roadside wireless device 6 is assigned. This radio frequency switching is executed by a frequency switching device included in an in-vehicle wireless device mounted on the vehicle.

In this way, road-to-vehicle communication between the vehicle and the roadside apparatus is maintained.

FIG. 4 is a block diagram showing the overall structure of a receiving section of a conventional vehicle-mounted wireless device. In the conventional in-vehicle wireless device, the frequency switching device controls the first local oscillator 17 to operate at the radio frequency f2, the radio frequency f3, ..., On the basis of the transmission signal from the roadside wireless device 6, the control function of the on-vehicle wireless device causes the first local oscillator 17 to operate.
The radio frequency f8 is sequentially set and oscillated to switch the radio frequency.

Radio frequency f2 and radio frequency f oscillated
The determination as to whether or not the radio frequency f8 is the target radio frequency (the radio frequency f6 used by the roadside radio device 6) (hereinafter referred to as "area determination") is received by the in-vehicle radio device. The department is making the decision. In this area determination, for each radio frequency oscillated by the frequency switching device, it is sequentially determined whether it is the radio frequency of the target radio communication area, “appropriate” or “impossible” until the “appropriate” I can continue.

In this way, the target radio frequency f6 is captured by determining the area of each radio frequency that is sequentially oscillated.

[0011]

However, in the conventional road-to-vehicle communication method, roadside wireless device, vehicle-mounted wireless device and system, for example, a roadside wireless device that is wirelessly communicating with the vehicle-mounted wireless device, such as the above-mentioned intersection, is used. Since many roadside wireless devices are located in the vicinity, the in-vehicle wireless device may have a problem that it takes a long time to switch the frequency to the radio frequency used by the roadside wireless device to be wirelessly communicated next. For example, the radio frequency band used is 5800M
In the general road-to-vehicle communication in which the comparison frequency of the circuit having the channel synthesizer is about 100 KHz in the Hz band, one frequency switching time (radio frequencies f1 to f2
It takes about 5 msec to switch to the radio frequency f1 to the radio frequency f6 five times, so at least 25 ms.
ec frequency switching time is required.

Therefore, in the radio frequency switching for continuing the road-to-vehicle communication, the road-to-vehicle communication method and the road-side radio that can reduce the time required to switch the radio frequency even if there are many road-side wireless devices that can next perform radio communication There is a demand for a device, an in-vehicle wireless device, and a road-vehicle communication system.

[0013]

In order to solve the above-mentioned problems, in the road-to-vehicle communication method of the present invention, any one of a plurality of roadside wireless devices and a vehicle-mounted wireless device is In roadside-to-vehicle communication in which wireless communication is performed using the radio frequency assigned to the roadside wireless device, each of the roadside wireless devices is connected to the vehicle-mounted wireless device that is located in the area of the roadside wireless device and then wirelessly communicates. The transmission signal including the next area frequency candidate information used by one or more roadside wireless device candidates to be obtained is given to the in-vehicle wireless device, and the in-vehicle wireless device is based on the given next area frequency candidate information,
It is characterized by searching and setting the next radio frequency.

Further, in order to execute the above-mentioned road-to-vehicle communication method, the roadside apparatus according to the present invention is a roadside apparatus for repeatedly wirelessly transmitting a transmission signal to a vehicle-mounted wireless apparatus. The on-vehicle wireless device further includes a next area frequency candidate information adding unit that includes next area frequency candidate information used by one or more roadside wireless device candidates that can wirelessly communicate next. Further, similarly, the vehicle-mounted wireless device according to the present invention searches for a radio frequency to which the roadside wireless device is assigned from the transmission signal transmitted from the roadside wireless device, and wirelessly communicates with the roadside wireless device. In the in-vehicle wireless device, the in-vehicle wireless device searches for and sets the next wireless frequency based on the transmission signal including the next area frequency candidate information used by the roadside wireless communication device candidate that can next perform wireless communication. It is characterized by having setting means.

Further, in the road-to-vehicle communication system according to the present invention, any one of the plurality of roadside wireless devices and the in-vehicle wireless device uses the radio frequency assigned to the roadside wireless device. In the road-vehicle communication system for wireless communication, the roadside wireless device includes the roadside wireless device, and the vehicle-mounted wireless device includes the vehicle-mounted wireless device.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION (A) First Embodiment Hereinafter, a signal format of a transmission signal given from a roadside wireless device in a roadside-vehicle communication, a roadside wireless device, a vehicle-mounted wireless device and a roadside-vehicle communication system according to the present invention. The application to the first embodiment having the features described above will be described with reference to the drawings.

The first embodiment will explain a road-to-vehicle communication method in the case where, for example, a vehicle located in area 1 makes a right turn and moves to area 6 at an intersection as shown in FIG.

(A-1) Configuration of the First Embodiment FIG. 4 is a block diagram showing the overall structure of a receiving section of an in-vehicle wireless device for obtaining a baseband signal by two-step down conversion.

The receiving section of the in-vehicle wireless device can be roughly classified into a receiving device and a frequency switching device.

The receiving device comprises a receiving antenna 10, RF (Ra
dio frequency) amplifier section 11, first mixer section 12,
IF (Intermediate Frequency) amplifier unit 13, second
It has a mixer unit 14, a detection unit 15, and a data processing unit 16. The receiving device may be a conventional receiving device, as long as it has a control function of determining whether the radio frequency set by the frequency switching device is an appropriate radio frequency for wireless communication. Further, the control function of this area determination may be performed based on the baseband signal of the receiving device, or may be provided at the subsequent stage of the first mixer unit 12.

The receiving antenna 10 is an antenna that receives a transmission signal from a roadside apparatus.

The RF amplifier section 11 amplifies the received signal given from the receiving antenna and gives it to the first mixer section 12.

The first mixer section 12 includes an RF amplifier section 11
The received signal given by the above is down-converted by the output signal oscillated from the first local oscillator 17 to obtain an intermediate frequency signal, and given to the IF amplifier section 13.

The IF amplifier section 13 includes the first mixer section 12
The intermediate frequency signal given by the above is amplified and given to the second mixer section 14.

The second mixer section 14 is an IF amplifier section 13.
From the second local oscillator 18 to down-convert the intermediate frequency signal given by the above from the second local oscillator 18 to obtain a base band signal and give it to the detection section 15.

The detection section 15 detects the baseband signal supplied from the second mixer section 14 by, for example, filtering or the like, and supplies the detected baseband signal to the data processing section 16.

The data processing section 16 processes data from the detected baseband signal.

The frequency switching device comprises a first local oscillator 1
7, and has a second local oscillator 18.

The first local oscillator 17 is a conventional local oscillator that oscillates a frequency set to a predetermined cycle, and the oscillating radio frequency is set based on the signal received from the roadside radio device.

Next, FIG. 1 shows a signal format transmitted by the roadside apparatus according to the first embodiment.

The roadside radio devices 1 to 8 transmit the signal format of the transmission signal shown in FIG.

In FIG. 1, the signal formats are preamble (PR), unique word (UW), roadside radio device individual number, next area frequency candidate number, individual data,
It includes parity.

In the signal format shown in FIG. 3, the roadside wireless device 1 wirelessly communicating with the onboard wireless device mounted on the vehicle selects a roadside wireless device candidate with which the onboard wireless device can next wirelessly communicate. Then, the radio frequency information to which the selected roadside radio device candidate is allocated is given as a "next area frequency candidate number".

The point that this "next area frequency candidate number" is added is different from the conventional signal format.

For example, among the nine roadside wireless devices located near the roadside wireless device, the roadside wireless device wirelessly communicating with the onboard wireless device is the onboard wireless device, and then the onboard wireless device. Five roadside wireless devices capable of wireless communication are selected as roadside wireless device candidates. Conventionally, it was necessary to set the radio frequencies of the above-mentioned nine roadside radio devices,
By assigning this "next area frequency candidate number",
It is only necessary to switch to the radio frequency used by these five roadside wireless device candidates. The selection criterion is, for example, that in the road traffic situation, the statistics of the traveling routes of vehicles located in the same situation are taken, and the roadside wireless device corresponding to the next traveling route is selected based on the traveling route statistics. You may do so.

The "next area frequency candidate number" is provided between the "roadside wireless communication individual number" and the "individual data". This is an appropriate position for the in-vehicle wireless device to execute the radio frequency switching process.
The position to set is not limited, and may be set before the “roadside wireless communication individual number”, for example.

(A-2) Operation of First Embodiment At the intersection shown in FIG. 2, the operation of the road-to-vehicle communication method when the vehicle located in area 1 turns right and moves to area 6 will be described.

In FIG. 2, an in-vehicle wireless device mounted on a vehicle traveling in area 1 is performing wireless communication using a wireless frequency f1 based on a transmission signal from the roadside wireless device 1.

When the vehicle enters the intersection and leaves the area 1, the next areas in which the vehicle can travel are area 2 (turn left), area 4 (go straight), area 6 (turn right), and area 8.
(U-turn). That is, of the areas 2 to 8 other than the area 1 in which the in-vehicle wireless device mounted on the vehicle is located, the vehicle does not travel in the areas 3, 5, and 7 unless there is an abnormality. Impossible. From this, the transmission signal transmitted from the roadside wireless device 1 is the roadside wireless device 2, the roadside wireless device 4, the roadside wireless device 6, the roadside wireless device installed in the area 2, the area 4, the area 6, and the area 8. The radio frequency information of No. 8 is given as a “next area frequency candidate number” and transmitted to the in-vehicle wireless device.

The transmission signal transmitted to the in-vehicle wireless device is detected and received, and the frequency switching device reads the wireless frequency information of each roadside wireless device candidate included in the "next area frequency candidate number".

Based on the frequency setting information from the read "next area frequency candidate number", the first local oscillator 17 sequentially sets and oscillates the assigned wireless frequencies of the roadside wireless device candidates.

The "next area frequency candidate number" includes information for setting the radio frequencies to which the plurality of roadside wireless device candidates are assigned according to a predetermined order.

When the frequency setting information is set, for example, in the order of counterclockwise rotation from the roadside wireless device having a short distance from the roadside wireless device 1 at the intersection, the radio frequency f
2 (turn left), radio frequency f4 (straight ahead), radio frequency f6
The radio frequencies are sequentially set in the order of (right turn) and radio frequency f8 (U-turn).

Here, the order in which the radio frequencies are set is
The present invention is not limited to this, and for example, vehicle traveling statistics of a route along which a plurality of vehicles travel at the intersection are taken, and the vehicle is traveled in descending order of frequency, for example, radio frequency f4 (straight ahead), radio frequency. The frequency f2 (turn left), the radio frequency f6 (turn right), and the radio frequency f8 (U turn) may be set in this order.

In this way, the radio frequency f2 (turn left), the radio frequency f4 (go straight), the radio frequency f6 (turn right), and the radio frequency f8 (U turn) are set and oscillated in this order based on the frequency setting information. .

Here, FIG. 7 is a time chart of the operation of switching the frequency by the frequency switching device.

As shown in FIG. 7, while the in-vehicle wireless device is wirelessly communicating with the roadside wireless device 1, the first local oscillation unit 17 is provided.
Oscillates at a radio frequency f1. In-vehicle wireless device
At the timing of ending the wireless communication with the roadside wireless device 1 (when the vehicle leaves the area 1 and enters the next area 6), the radio frequency f2 used by the next roadside wireless device candidate f2 is based on the frequency setting information. Is set. The area determination is made that the set radio frequency f2 is not the radio frequency assigned to the roadside apparatus 6. At the timing when this area determination is determined to be “No”,
Based on the frequency setting information, the next roadside wireless device candidate f
The radio frequency f4 used by 4 is set.

In the in-vehicle wireless device, the radio frequency f6 to which the roadside wireless device 6 corresponding to the area 6 is allocated is set, and this processing is repeated until the area determination becomes "appropriate".

In this way, the target radio frequency f6 can be captured by the frequency switching times of three times.

That is, one frequency switching time is 5 m
If it is sec, the frequency switching time until the vehicle captures the target radio frequency f6 is 15 msec.

As described above, in the first embodiment, even when there are many roadside wireless devices with which communication is possible, the communicating roadside wireless device selectively transmits the next roadside wireless device information to the transmission signal. By including the "next area frequency candidate number", the time required for frequency switching can be shortened.

(A-3) Effects of First Embodiment As described above, according to the first embodiment, the road-to-vehicle communication method, the roadside radio device, the on-vehicle radio device, and the road-to-vehicle communication system according to the present invention are frequency-switched. Even if there are many roadside wireless devices that can be selected for, the currently communicating roadside wireless device selects a roadside wireless device candidate with which the vehicle can next communicate,
“Next area frequency candidate number” for the selected roadside wireless device candidate
As described above, by writing in the signal format of the transmission signal and notifying the in-vehicle wireless device, it is not necessary to set an impossible frequency as a switching frequency candidate, and the frequency switching time of the entire in-vehicle wireless device can be shortened.

(B) Second Embodiment Hereinafter, the road-to-vehicle communication method, roadside wireless device, vehicle-mounted wireless device, and road-to-vehicle communication system according to the present invention are appropriately provided by providing a plurality of local oscillators and using semiconductor switches. A second embodiment for selecting the local oscillator will be described with reference to FIG.

In the second embodiment as well, a case where the vehicle turns right from area 1 to area 6 at the intersection shown in FIG. 2 as in the first embodiment will be described.

(B-1) Configuration of the Second Embodiment FIG. 5 is a block diagram showing an overall configuration diagram of the receiving unit of the vehicle-mounted wireless device according to the second embodiment.

The receiving section of the in-vehicle wireless device can be roughly divided into a receiving device and a frequency switching device.

The receiving device includes an antenna unit 10, an RF (Radi
o Frequency) amplifier section 11, first mixer section 12, I
The F amplifier unit 13, the second mixer unit 14, the detection unit 15, and the data processing unit 16 are included.
It is a receiving device that down-converts a general mixer format in two stages. These receiving devices have the same functions as the receiving device according to the first embodiment, and are denoted by the same reference numerals. Here, the functional description of the receiving device is omitted.

The frequency switching device includes eight first local oscillators 22 (22-1 to 22-8) and a high-speed connection switching unit 2
0, and the connection switching control unit 21.

The first local oscillator 22 (22-1 to 22-
The radio frequency 8) always sets the radio frequency on the basis of the frequency setting information, the radio frequency used for the radio communication is selected by the high speed connection switching unit 20, and the radio frequency selected by the first mixer unit 12 is selected. Is to give. First
The local oscillator 22 may have a conventional radio frequency oscillation function. In the present embodiment, the first local oscillator 22 (2
2-1 to 22-8) is mounted in advance, but the number of the first local oscillators is not limited to eight, and the frequency of the number of roadside wireless devices predicted to be wirelessly communicated by the vehicle-mounted wireless device is not limited to eight. Just set the oscillator. For example, at the intersection of FIG. 2, it is considered that eight roadside wireless devices 1 to 8 wirelessly communicate with the in-vehicle wireless device. So here
Eight first local oscillators were provided.

The high speed connection switching unit 20 receives the instruction from the connection switching control unit 21 and then the first local oscillation unit 22 (22-
1 to 22-8). The high-speed connection switching unit 20 is, for example, a high-speed device using a gallium arsenide semiconductor or the like, and is an 8-input 1-output selection switch. For example, in a high-speed semiconductor switch element made of gallium arsenide semiconductor, the time required for frequency switching is generally 0.
It is 1 μsec or less, and the frequency can be switched within 1 μsec even when the processing time in the connection switching control unit 21 is taken into consideration. Here, the high speed connection switching unit 20 is not limited to the high speed semiconductor switch. That is,
It suffices that the connection can be switched at a substantially high speed.

The connection switching control unit 21 determines the radio frequency of the roadside apparatus with which it communicates from the received signal, and gives a frequency switching instruction signal to the high speed connection switching unit 20. That is, the connection switching control unit 21 instructs the high speed connection switching unit 20 to connect the first local oscillator.

As described above, by using the high-speed connection switching unit 20, the time required for frequency switching can be shortened, and the frequency switching time of 5 msec is required because the power supply of the in-vehicle wireless device is turned on. Only in time.

(B-2) The in-vehicle wireless device located in the operation area 1 of the second embodiment searches for and receives the transmission signal from the roadside wireless device 1 to use the radio frequency f1 to drive the roadside device. Wirelessly communicating with the wireless device 1.

When the in-vehicle wireless device leaves area 1,
It becomes impossible to maintain wireless communication with the roadside apparatus 1. When the vehicle turns right at the intersection and enters the area 6, a transmission signal is transmitted from the roadside wireless device 6 to the in-vehicle wireless device.

On the basis of the "roadside wireless device individual number" of the signal given to the in-vehicle wireless device, the connection switching control section 21 selects the wireless frequency f6 used in the area 6,
The high-speed connection switching unit 20 is instructed as a frequency switching instruction signal.

The frequency switching instruction signal connects the first local oscillator 22-6 to the high-speed connection switching unit 20,
The radio frequency f6 from the local oscillator 22-6 is provided to the first mixer 12.

In this way, even if there are many roadside wireless devices that can be selected, the radio frequencies of the plurality of roadside wireless devices are set in advance, and the radio frequency of the target area is selected from among these, so that The time required for switching the frequency can be shortened.

(B-3) Effects of the Second Embodiment As described above, in the second embodiment, a plurality of first local oscillators are set in advance, and a high-speed connection switching unit composed of a semiconductor switching device or the like that operates at high speed is provided. By providing the connection switching control unit, the radio frequencies are sequentially switched, and the corresponding radio frequency is selected without area determination, so that the frequency switching time can be shortened.

Further, by using a semiconductor switching device that operates at high speed as the connection switching unit, the selection processing speed of the first local oscillator can be increased.

(C) Third Embodiment Hereinafter, the road-to-vehicle communication method, roadside wireless device, vehicle-mounted wireless device, and road-to-vehicle communication system according to the present invention are used to transmit a road by a transmission signal including a "next area frequency candidate number". Inter-vehicle communication,
6 and 8 for a third embodiment applied to a road-to-vehicle communication method for selecting two preset first local oscillators by a high-speed semiconductor switch, a roadside wireless device, a vehicle-mounted wireless device, and a system. Explain.

(C-1) Configuration and Operation of Third Embodiment FIG. 6 is a block diagram showing an overall configuration diagram of a receiving section of an in-vehicle wireless device according to the third embodiment.

The receiving section of the in-vehicle wireless device can be roughly classified into a receiving device and a frequency switching device.

Regarding the receiving device, it is a receiving device that down-converts a general mixer format in two stages, has the same function as that of the first embodiment, and is given the same reference numeral. Here, the functional description of the receiving device is omitted.

The frequency switching device includes two first local oscillators 23 (23-1 to 23-2) and a high-speed connection switching unit 2
0, and the connection switching control unit 21. Since each component has the same function as in the second embodiment, the functional description of each component will be omitted.

Also in the third embodiment, the operation of the road-vehicle communication system when turning right from area 1 to area 6 at the intersection shown in FIG. 2 will be described.

In FIG. 2, the in-vehicle wireless device mounted on the vehicle traveling in the area 1 performs wireless communication using the wireless frequency f1 based on the transmission signal from the roadside wireless device 1. At this time, the high-speed connection switching unit 20 is connected to the first local oscillator 23-1, and the radio frequency f1 set and oscillated by the first local oscillator 23-1 is
It is provided to the first mixer unit 12 via the high-speed connection oscillator 20.

At this time, the first local oscillator 23-
2 sets the radio frequency f2 of the next roadside apparatus candidate 2 based on the frequency setting information of the "next area frequency candidate number" given to the transmission signal from the roadside apparatus 1. The "next area frequency supplement number" is, for example, the radio frequency f2, the radio frequency f4, the radio frequency f6, or the radio frequency f.
The instruction is to set the radio frequency in the order of 8.

When the on-vehicle wireless device leaves the area 1, the communication with the roadside wireless device 1 ends. At this end timing, the high speed connection switching unit 20 is connected to the first local oscillator 23-2 that sets the radio frequency f2.

In the in-vehicle wireless device, the first local oscillator 2
The radio frequency f2 set by 3-2 corresponds to the area 6
The area determination is made as to whether or not the radio frequency is.
Further, while the area determination is being performed, the first local oscillator 23-1 further sets the radio frequency f4 corresponding to the next roadside apparatus candidate 4 based on the frequency setting information.

When the area determination of the radio frequency f2 set by the first local oscillator 23-2 is "No", the high speed connection switching unit 20 disconnects from the first local oscillator 23-2 and further connects. Is switched. This process is repeated until the radio frequency f6 is reached.

FIG. 8 is a diagram showing the timing of frequency switching of the frequency switching device according to the third embodiment.

In FIG. 8, the first local oscillator 23-1
However, while oscillating the radio frequency f1 (while the on-vehicle radio device and the roadside radio device 1 are wirelessly communicating), the first local oscillator 23-2 is transmitted by the transmission signal from the roadside radio device 1.
Sets the radio frequency f2 of the next roadside wireless device candidate (roadside wireless device 2) with which communication is possible. Then, at the timing when the communication with the roadside apparatus 1 is completed, the high speed connection switching unit 20 switches from the first local oscillator 23-1 to the first local oscillator 23-2, and the first local oscillator 23-2.
At, the area determination of the already set radio frequency f2 is performed. Also, while the area determination of the radio frequency f2 is being performed, the first local oscillator 23-1
Sets the radio frequency f4 of the next roadside wireless device candidate (roadside wireless device 4).

That is, the two first local oscillators 23 are
The radio frequencies to be set can be set alternately, and while one of the first local oscillators 23-1 (or 23-2) is performing radio communication or area determination by the oscillated radio frequency (switching waiting time), the other First local oscillator 23-2 (or 2
3-1) can set the radio frequency to which the next roadside wireless device candidate to be communicated is assigned, thereby shortening the time required for the entire frequency switching device to switch the frequency. For example, 2 msec for area determination. Assuming that the time is required in the third embodiment, the time until the radio frequency is switched is 11 msec in total in the third embodiment, which can be further shortened as compared with the case of the first embodiment.

(C-2) Effects of the Third Embodiment As described above, according to the third embodiment, two systems of the first local oscillation circuit constituting the receiver of the on-vehicle wireless device are provided, and the first local oscillation circuit is provided for each of the first local oscillation circuits. The next area frequency candidates that have been notified in advance to the local oscillator circuit are sequentially set, and the output is appropriately selected by using the high-speed operation semiconductor switching element. Since the radio frequency for which the determination is required can be set, the frequency switching time of the entire frequency switching device can be shortened.

(D) Other Embodiments In the above-described first to third embodiments, the case where the receiving unit of the on-vehicle wireless device that down-converts in two steps is used has been described, but the mixer format of wireless communication is limited. However, the present invention can also be applied to the case where a receiving unit of an in-vehicle wireless device that outputs a baseband signal by one-step down conversion of a received signal is used. Also,
The in-vehicle wireless device that performs down conversion in three or more steps in order to oscillate a frequency with higher accuracy may be used.
When the frequency is oscillated by three or more stages of down-conversion, it is desirable to install the frequency switching device of the in-vehicle wireless device according to the present invention in the first stage from the viewpoint of improvement in accuracy and operation in the device. However, it is not limited to being set in the first stage, and may be installed in the second stage or later.

In the above-described first to third embodiments, the communication system of the transmission signal between the roadside radio device and the in-vehicle radio device is
For example, the present invention can be applied to a slot aloha system that adopts a time division communication system. Further, the transmission signal is not limited to the one adopting the time division communication system, and it is not limited as long as it is a signal which the base station and the mobile station regularly communicate with each other.

In the method of selecting the "next area frequency candidate number" by the roadside wireless communication device with which the in-vehicle wireless device is wirelessly communicating in the transmission signal of the first or third embodiment, for example, the vehicle travels. It is also possible to set a priority in advance for a traveling road that is expected to occur and select a roadside wireless device installed on a traveling road having a high priority. Of course, the priority may be used to determine the order of setting the radio frequencies.

The in-vehicle wireless devices shown in the above-described first to third embodiments are not limited to road-to-vehicle wireless communication, but wireless communication is performed in a permissible communication area such as a mobile phone or a wireless LAN using a specific radio frequency. It can be widely applied to mobile wireless communication.

[0089]

As described above, according to the present invention, the roadside wireless device selects a roadside wireless device candidate that can next wirelessly communicate with the on-vehicle wireless device, and obtains the radio frequency information to which the selected roadside wireless device candidate is assigned. By adding the transmission signal and transmitting it to the in-vehicle wireless device, the in-vehicle wireless device can shorten the search time required for the wireless frequency switching process necessary for maintaining the wireless communication.

[Brief description of drawings]

FIG. 1 is a diagram showing a signal format transmitted from a roadside apparatus according to a first embodiment.

FIG. 2 is a diagram showing a roadside wireless device, an allowable communication area, and a frequency arrangement set on the roadside of each lane at an intersection of a two-lane road.

FIG. 3 is a diagram showing a signal format transmitted from a conventional roadside apparatus.

FIG. 4 is a block diagram showing an overall structure of a receiving section of a conventional vehicle-mounted wireless device.

FIG. 5 is a block diagram showing an overall configuration of a receiving unit of the in-vehicle wireless device according to the second embodiment.

FIG. 6 is a block diagram showing an overall structure of a receiving unit of an in-vehicle wireless device according to a third embodiment.

FIG. 7 is a diagram showing the timing of frequency switching of the vehicle-mounted wireless device according to the first embodiment.

FIG. 8 is a diagram showing a timing of frequency switching of the vehicle-mounted wireless device according to the third embodiment.

[Explanation of symbols]

1 to 8 ... Roadside wireless device, 10 ... Receiving antenna, 11 ... R
F amplifier section, 12 ... First mixer section, 13 ... IF amplifier section, 14 ... Second mixer section, 15 ... Detection section, 16 ... Data processing section, 17, 23 (23-1 to 23-2) ... First Local oscillation unit, 18 ... Second local oscillation unit, 20 ... High-speed connection switching unit, 21 ... Connection switching unit

Claims (5)

[Claims] 1. One of a plurality of roadside wireless devices
In a road-to-vehicle communication method in which two roadside wireless devices and a vehicle-mounted wireless device wirelessly communicate using a radio frequency assigned to the roadside wireless device, each roadside wireless device is located in an area of the roadside wireless device. The on-vehicle wireless device that is currently performing wireless communication provides the on-vehicle wireless device with a transmission signal including next area frequency candidate information used by one or more roadside wireless device candidates, and the on-vehicle wireless device is provided with the transmission signal. A road-to-vehicle communication method characterized by searching and setting the next radio frequency based on the next area frequency candidate information. 2. A roadside wireless device for repeatedly wirelessly transmitting a transmission signal to an in-vehicle wireless device, wherein the transmission signal is used by one or more roadside wireless device candidates with which the in-vehicle wireless device can wirelessly communicate next. A roadside wireless device comprising: a next area frequency candidate information adding unit that includes next area frequency candidate information. 3. An in-vehicle wireless device wirelessly communicating with the roadside wireless device by searching for a radio frequency to which the roadside wireless device is assigned, from a transmission signal transmitted from the roadside wireless device. The device is equipped with a frequency search setting means for searching and setting a next wireless frequency based on the transmission signal including the next area frequency candidate information used by the roadside wireless communication device candidate that can next perform wireless communication. Wireless device. 4. A connection switching control means for searching a next radio frequency based on a transmission signal containing the next area frequency candidate information and selecting and instructing the searched radio frequency, and a search from the connection switching control means. 4. The connection switching means for selecting and switching the next radio frequency from among the radio frequencies set by at least two or more of the frequency search setting means in accordance with the radio frequency selection instruction. In-vehicle wireless device. 5. One of a plurality of roadside wireless devices
In a roadside-vehicle communication system in which one roadside wireless device and an in-vehicle wireless device wirelessly communicate using a radio frequency assigned to the roadside wireless device, the roadside wireless device according to claim 2 as the roadside wireless device. A vehicle-to-vehicle communication system comprising the vehicle-mounted wireless device according to claim 3 or 4 as the vehicle-mounted wireless device.