JPH07294617A - Communication system between road and vehicle - Google Patents

Abstract

PURPOSE:To communicate with a road beacon disposed for the different purpose by providing a data beacon including a modulating means and a transmitting means, and a vehicle-mounted device including an inquiry beacon, a receiving means, a demodulating means, a modulating means, etc. CONSTITUTION:A data beacon 3 is set on a road, and is provided with a modulating means 1 for a first beacon for modulating a predetermined carrier wave according to a digital angle modulation method with the use of transmitting data including road traffic data, thereby generating a first modulation signal, and a transmitting means 2 for the first beacon for transmitting the first modulation signal generated by the means 1. An inquiry beacon 6 is provided with a modulating means 4 for a second beacon, and a transmitting means 5 for the second beacon. The modulating means 4 modulates the carrier wave by one of a plurality of transmitting data including the same inquiry data, and modulates the modulated carrier wave by means of the other transmitting data of the plurality of transmitting data according to the other digital angle modulation method. A vehicle-mounted device 11 has an on-board receiving means 7 for receiving the modulation signal, an on-board signal-demodulating means 8, an on-board modulating means 9 and an on-board transmitting means 10.

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 capable of receiving each service provided by two roadside beacons installed on the road for different purposes by a single vehicle-mounted device having a simple structure. Regarding

[0002]

2. Description of the Related Art Conventionally, a communication device (hereinafter referred to as a "roadside beacon") is installed on a road, and the position of the intersection from the roadside beacon, the name of the intersection, the shape of the intersection, road regulation information,
By transmitting a signal containing road traffic information, location information, etc. useful for the driver such as traffic jam / accident information to a relatively narrow range, and receiving this transmitted signal by the in-vehicle device mounted on the vehicle A traffic information providing system has been devised that sets and displays the current position of a vehicle on a driver and provides the road traffic information (see, for example, Japanese Patent Application Laid-Open No. 2-183182).

In this traffic information providing system, it is desirable that a large number of roadside beacons (hereinafter referred to as "information beacons" in the traffic information providing system) be installed on highways and general roads all over the country. In order to realize this, the price of the information beacon itself should be reduced,
Moreover, it is necessary to prevent the signal transmission areas of the information beacons from interfering with each other. Therefore, the transmission output of the information beacon is set to be relatively small. Specifically, in the information beacon, a signal is transmitted with a small output of 1 to 10 (mW) in a minimal zone of about 50 to 100 (m) in the longitudinal direction of the road centering on the installation point of the information beacon.

The signal transmitted from the information beacon includes GMSK (Gaussian fil) in the road traffic information contained therein.
It is a modulated wave signal that has been subjected to digital angle modulation such as tered minimum shift keying). Here, the reason why the modulation method is set to the digital angle modulation is that the digital angle modulation method is relatively strong against external noise, so that good communication quality can be secured in the vehicle-mounted device even with a small transmission output.

On the other hand, as another method of using the roadside beacon, there is a so-called automatic toll collection system devised to eliminate the complexity of toll payment on toll roads and toll parking lots. With this automatic fee collection system,
Charges are collected using a general-purpose credit card to which the driver subscribes. More specifically,
A signal including question information is transmitted from a roadside beacon (hereinafter referred to as "question beacon" in the automatic fee collection system). The question information includes, for example, a request for a card number of a general-purpose credit card, a request for a balance that can be used by this general-purpose credit card, and a request for a reply such as whether or not to use this automatic fee collection system. In the vehicle-mounted device, when the signal is received, necessary data such as the card number of the general-purpose credit card responding to the question information included in the signal is returned to the question beacon.
In the question beacon, the returned card number is given to the host computer, and the host computer deducts the charge corresponding to the frequency of use of the driver from the account corresponding to the card number on a predetermined settlement day. Collection of charges is achieved by this.

The signal transmitted from the interrogation beacon includes the interrogation information contained therein in digital amplitude modulation (ASK:
Amplitude-Shift Keying) modulated wave signal. Here, the reason why digital amplitude modulation is adopted as the modulation method is that the signal subjected to digital amplitude modulation has a very simple circuit configuration in an in-vehicle device and an envelope curve using a diode that can reduce cost. This is because it can be demodulated by detection.

On the other hand, transmission of a signal including data in response to the question information transmitted from the question beacon in the vehicle-mounted device is easy to handle because it does not require a license as a wireless station, and the cost can be reduced. For the reason that it can be achieved, the so-called TAG method is used. That is, the non-modulated wave signal is transmitted from the interrogation beacon to the road for a predetermined period after the emission of the above signal, and when the non-modulated wave signal is received by the vehicle-mounted device, the received non-modulated wave signal is The data in response to the inquiry information is subjected to digital angle modulation such as digital frequency modulation (FSK: Frequency-Shift Keying) or digital phase modulation (PSK: Phase-Shift Keying) and reflected back to the inquiry beacon.

As described above, in the TAG method, the carrier wave is not generated by the vehicle-mounted device but is digitally angle-modulated and reflected back to the unmodulated wave signal transmitted from the inquiry beacon. Therefore, in the inquiry beacon, the transmission output of each of the above signals is made relatively large in order to secure the signal-to-noise ratio. Specifically, it is set to about 300 (mW).

[0009]

By the way, when it is desired to use both of the above-mentioned systems, it is necessary to mount both of the two vehicle-mounted devices corresponding to the respective systems on the vehicle. As a result, the cost for the driver is high, and since two vehicle-mounted devices must be mounted, there is a problem that the living space inside the narrow vehicle is further narrowed.

Therefore, if an in-vehicle device that simply combines the demodulation function of the traffic information providing system and the demodulation function and reflection function of the automatic toll collection system is installed in the vehicle so as to be compatible with both systems, the above problem will occur. Seems to be resolved. However, an in-vehicle device that simply combines the functions of both systems has a drawback that the configuration is complicated and the cost is higher than one in-vehicle device corresponding to either system.

[0011] Therefore, an object of the present invention is to solve the above-mentioned technical problem, and one road-vehicle communication system capable of communicating with road-side beacons installed for different purposes by one vehicle-mounted device having a simple structure. Is to provide.

[0012]

A vehicle-to-vehicle communication system according to claim 1 for achieving the above object is installed on a road as shown in FIG. 1 and includes a predetermined carrier wave and road traffic information. First beacon modulating means (1) for digitally angle-modulating transmission data to generate a first modulated wave signal
And a first beacon transmission means (2) for transmitting the first modulated wave signal generated by the first beacon modulation means (1)
An information beacon (3) including and, which is installed on the road, uses one transmission data of one of two transmission data that includes the same inquiry information as at least a part of a predetermined carrier wave to perform one of digital angle modulation or digital amplitude modulation. A second modulation is performed by modulating the modulated carrier wave with the other transmission data of the two transmission data and the other modulation method of the digital angle modulation or the digital amplitude modulation.
A second beacon modulating means (4) for generating a modulated wave signal,
The second generated by this second beacon modulating means (4)
An interrogation beacon (6) including a second beacon transmission means (5) for transmitting a modulated wave signal and transmitting a non-modulated wave signal after transmitting the second modulated wave signal; Vehicle-mounted receiving means capable of receiving the first modulated wave signal, the second modulated wave signal and the non-modulated wave signal transmitted from the first beacon transmitting means (2) or the second beacon transmitting means (5) (7) and this in-vehicle receiving means
An in-vehicle signal demodulating means (8) capable of demodulating the digital angle modulation component contained in the first modulated wave signal and the second modulated wave signal received by (7), and this in-vehicle signal demodulating means (8 ) To digitally angle-modulate the non-modulated wave signal received by the vehicle-mounted receiving means (7) with the data in response to the question information obtained as a result of demodulating the digital angle-modulated component contained in the second modulated wave signal. An in-vehicle modulating means (9) for generating a third modulated wave signal, and an in-vehicle transmitting means (10) for transmitting the third modulated wave signal generated by the in-vehicle modulating means (9) to the inquiry beacon (6). ) And an in-vehicle device (11), and the inquiry beacon (6) is a second beacon receiving means capable of receiving the third modulated wave signal transmitted by the in-vehicle transmitting means (10). (12) and received by this second beacon receiving means (12) The second beacon signal demodulation means (13) capable of demodulating the generated third modulated wave signal is further included.

In this configuration, the information beacon (3) generates and transmits the first modulated wave signal carrying the transmission data including the road traffic information. On the other hand, since the vehicle-mounted device (11) can demodulate the digital angle modulation component included in the transmitted first modulated wave signal, the road traffic information can be obtained. Also, Question Beacon (6)
In the second aspect, the second transmission data in which at least a part of the same question information is included as a digital angle modulation component and a digital amplitude modulation component, respectively.
The modulated wave signal is generated and transmitted, and
The non-modulation wave signal is transmitted after the transmission of the modulation wave signal. On the other hand, since the vehicle-mounted device (11) can demodulate the digital angle modulation component contained in the second modulated wave signal, the question information can be obtained.

In the vehicle-mounted device (11), the non-modulated wave signal is digitally angle-modulated by the data in response to the obtained inquiry information, and the third modulated wave signal obtained as a result is interrogated by the inquiry beacon (6). Sent to. On the other hand, when the inquiry beacon (6) receives the third modulated wave signal, the received third modulated wave signal is demodulated. As a result, data responding to the question information is acquired.

As described above, according to the above-mentioned configuration, it is possible to obtain road traffic information and obtain inquiry information and return and reply data in response to the in-vehicle device (11). Further, the vehicle-mounted device (11) having the above-mentioned configuration,
As long as it can demodulate the digital angle modulation component and also has a reflection / reply function to the inquiry beacon (6), both the digital angle modulation component and the digital amplitude modulation component can be demodulated and the reflection / reply to the inquiry beacon is returned. The configuration can be simplified as compared with a vehicle-mounted device having a function. Therefore, one vehicle-mounted device having a simple configuration can communicate with roadside beacons installed for different purposes.

Further, in the road-vehicle communication system according to the second aspect, the two transmission data to be transmitted from the inquiry beacon (6) are composed of the same inquiry information and have the same data transmission rate. It is characterized by being transmitted. According to this configuration, in the in-vehicle device (11), it is possible to simplify the data processing, and
The processing speed can be the same.

In the road-to-vehicle communication system according to the third aspect of the invention, the two transmission data to be transmitted from the inquiry beacon are composed of frames, and the change points of the bits in each frame change at the same time. It is characterized in that it is transmitted as follows. With this configuration, it is possible to reduce the influence of high-frequency noise that is likely to occur due to the digital amplitude modulation on the center of the bit.

Further, the road-vehicle communication system according to claim 4 is characterized in that the transmission data includes a code indicating a modulation method in the information beacon (3) or the inquiry beacon (6). With this configuration, the in-vehicle device (11) can perform appropriate processing according to the modulation method.

Further, in the road-vehicle communication system according to a fifth aspect of the present invention, the transmission data includes a code indicating whether the information beacon (3) or the inquiry beacon (6) is capable of bidirectional communication. Is characterized by. According to this configuration, the in-vehicle device
In (11), appropriate processing can be performed according to the communication mode.

In the road-vehicle communication system according to the sixth aspect, the data transmission rate of the transmission data to be transmitted from the inquiry beacon (6) is the data transmission rate of the transmission data to be transmitted from the information beacon (3). It is characterized by being an integral multiple of. According to this configuration, in the vehicle-mounted device (11),
The first modulated wave signal transmitted from the information beacon (3),
The second modulated wave signal transmitted from the interrogation beacon (6) can be synchronized with the same synchronization signal.

Further, in the road-vehicle communication system according to claim 7, the second beacon modulating means (4) further includes a low-pass filter (14) for passing only low-frequency components,
Only the low-frequency component is extracted by applying the other transmission data to the low-pass filter (14), and the extracted low-frequency component is modulated by one of the digital angle modulation or digital amplitude modulation methods. It is characterized in that the generated carrier wave is modulated by the other modulation method of digital angle modulation or digital amplitude modulation to generate a second modulated wave signal.

According to this structure, since the second modulated wave signal is generated by using the low frequency component of the transmission data, it is possible to prevent the high frequency noise from being mixed into the second modulated wave signal.
Further, in the road-vehicle communication system according to claim 8, the second beacon transmitting means (5) can secure the non-modulated wave signal in the second beacon receiving means (12). It is characterized by being transmitted with such an output.

According to this structure, the inquiry beacon (6) can accurately obtain the data in response to the inquiry information contained in the third modulated wave signal. Therefore, communication quality can be secured.

[0024]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a conceptual diagram showing an overall configuration of a road-vehicle communication system according to an embodiment of the present invention. This road-to-vehicle communication system is intended to use both the traffic information providing system and the automatic toll collection system, and is installed on the vehicle-mounted device 20 mounted on the vehicle and on the roadside of the toll road main line such as a highway. , Roadside beacons (hereinafter referred to as “information beacons”) 21a and 21b (hereinafter referred to as “information beacons 21” when collectively referred to as “information beacon 21”) that perform one-way communication with the vehicle-mounted device 20, and near the entrance gate of the toll road or the toll road Installed on the roadside of the main line,
A roadside beacon (hereinafter referred to as a "question beacon") 22a, which performs bidirectional communication with the so-called TAG system,
22b, 22c (hereinafter referred to as "question beacon 2"
2)) is included.

FIG. 3 is a block diagram showing the electrical configuration of the information beacon 21. This information beacon 21
It is used in the traffic information providing system that provides the in-vehicle device 20 with road traffic information and location information useful for the driver such as intersection position, intersection name, intersection shape, road regulation information, traffic jam / accident information, etc. The road traffic information and the position information given from the host computer are given to the data modulator 30 as a transmission data frame.

FIG. 4 is a diagram showing the structure of the transmission data frame. This transmission data frame will be described according to its transmission order. The synchronization code 40, the header section 41,
It is composed of a real data part 42 and a cyclic redundancy code (CRC) 43. The numbers in parentheses represent an example of the number of bytes of each data. The road traffic information is stored in the actual data section 42.

The header section 41 includes a beacon number 41a unique to the information beacon 21, a secondary mesh code 41b indicating the position coordinates where the information beacon 21 is installed, a normalized coordinate 41c, an information service indicating the characteristics of the information beacon 21, and the like. List 41d, major division ID 41e indicating the data type of each transmission data frame, major division internal frame number 41f indicating the number of all transmission data frames to be transmitted, major division internal frame number 4 indicating the order of this transmission data frame
1g and an effective data length 41h indicating the data length of the actual data portion 42.

FIG. 5 shows an example of the first byte of the information service list 41d. The information service list 41d includes a modulation system designation code 44 indicating whether the transmission data frame is FSK-modulated or FSK-modulated and ASK-modulated. In particular,
The modulation method designation code 44 is set to "0" when only FSK modulation is performed, and is set to "1" when multiple modulation of FSK modulation and ASK modulation is performed. Therefore, in the transmission data frame to be transmitted from the information beacon 21, the modulation system designation code 44 is "0".

The information service list 41d includes
Communication mode designation code 4 indicating whether or not the roadside beacon transmitting this transmission data frame is capable of bidirectional communication
5 is included. Specifically, the communication form designation code 45 is "0" when the communication is one-way communication and "1" when the communication is bidirectional. Therefore, in the transmission data frame to be transmitted from the information beacon 21, the communication form designation code 45 is “0”.

Returning to FIG. 3, in the data modulator 30, the carrier C ₁ generated from the carrier generator 31 is FSK-modulated in the transmission data frame to generate the first modulated wave signal. Therefore, in this embodiment, the data modulator 30 and the carrier generator 31 correspond to the first beacon modulator. The generated first modulated wave signal is divided into two and AM
(Amplitude Modulation) It is given to the modulators 32a and 32b, respectively.

The modulation method in the data modulating section 30 is not limited to FSK modulation, and other digital modulation methods such as GMSK modulation and PSK modulation may be used. The transmission data frame is also given to the clock generator 33. The clock generator 33 receives the transmission data frame and generates the modulated signal C ₂ in response to the transmission data frame. The frequency f ₂ of the generated modulated signal C ₂ is lower than the frequency f _{1 of the} carrier C ₁ ( ₁ kHz).
z). The modulation signal C ₂ generated by the clock generation unit 33 is divided into _two , one is directly applied to the AM modulation unit 32a, and the other is once applied to the 180 ° phase shift circuit 34 to be 180 ° phase shifted, and then the AM modulation. Given to part 32b.

In the AM modulators 32a and 32b, the first
The modulated wave signal is the given modulated signal C _{2 of} opposite phase.
Are AM modulated respectively. This AM-modulated first modulated wave signal is transmitted from the beacon antenna 35 that functions as a first beacon transmission unit. At this time, the first modulated wave signal of the same phase is transmitted in the right direction, and the first modulated wave signal of the opposite phase is transmitted in the left direction.
A modulated wave signal is transmitted.

The transmission output of the first modulated wave signal transmitted from the information beacon 21 is about to reduce the price of the information beacon 21 itself and prevent the signal transmission areas of the information beacons 21 from interfering with each other. The output is as small as about 10 (mW). The data transmission rate of the AM-modulated first modulated wave signal transmitted from the information beacon 21 is, for example, 64 (kbps).

FIG. 6 is a block diagram showing an electrical configuration of the inquiry beacon 22. This question beacon 22
It is used for an automatic toll collection system that automatically collects tolls when a vehicle uses a toll road, and is connected to a host computer 50 that controls the control of all question beacons 22 via modems 51a and 51b. Has been done. The question beacon 22 has a CPU (not shown).
A data processing unit 52 that functions as a second beacon signal demodulating unit including a central processing unit, a ROM (read only memory), and a RAM (random access memory) is provided. Question information, which will be described later, is given from the host computer 50 and stored in the RAM.

The data processing unit 52 selectively reads the question information stored in the RAM according to the program stored in the ROM, and the read question information is used as a transmission data frame in the communication control unit 53a or the communication. It is given to the control unit 53b. Communication control unit 53a and communication control unit 5
The question information included in the transmission data frame given to 3b and the question information included in the transmission data frame are different from each other, and the selection criteria thereof are set on the program. Each transmission data frame is subjected to processing necessary for communication such as parallel / serial conversion by the communication control units 53a and 53b, and then the FSK modulation unit 54a,
54b.

The FSK modulators 54a and 54b
May be changed to, for example, a PSK modulator that performs PSK modulation or another digital angle modulator that performs digital angle modulation. The structure of the transmission data frame is almost the same as that described with reference to FIGS. 4 and 5, but the modulation scheme designation code 44 is used in the inquiry beacon 22 for both FSK modulation and ASK modulation as described later. Therefore, the point becomes "1" and the communication form designation code 45 is
In the question beacon 22, two-way communication is performed with the vehicle-mounted device 20 by the TAG method, so that the question beacon 22 is "1", and the content of the data to be stored in the actual data portion 43 is different.

In the FSK modulators 54a and 54b, the carrier C ₃ whose frequency is, for example, 2.5 (GHz) given from the oscillators 55a and 55b is subjected to FSK modulation in each of the given transmission data frames. . The carrier waves C ₃ which have been subjected to the FSK modulation are respectively supplied to the ASK modulator 56.
a, 56b. ASK modulators 56a and 56b
Is a transmission data frame which has the same contents and data transmission rate as the transmission data frames given to the FSK modulators 54a and 54b and whose heads are simultaneously transmitted. LP
F: Low Pass Filter) 57a, 57b. Therefore, only the low frequency component of each transmission data frame is given to the ASK modulators 56a and 56b. ASK modulating unit 56a, in 56b, the carrier C ₃ to the FSK modulation is performed are respectively ASK modulated by low-frequency component of the transmission data frame is given the second modulated wave signal is generated. Since each of the generated second modulated wave signals is ASK-modulated by the low frequency component of the transmission data frame, the high frequency noise that is likely to occur at the change point of the amplitude is hardly included.

As described above, in this embodiment, the FSK modulators 54a and 54b, the oscillators 55a and 55b, the ASK modulators 56a and 56b, and the low pass filters 57a and 57b.
Functions as the second beacon modulating means. After that, each of the second modulated wave signals is amplified to a level required for wireless communication by the transmission amplification units 58a and 58b, and the notice antenna 59 or the tollgate antenna 60 that functions as the second beacon transmitting unit and the second beacon receiving unit. Emitted from each.

The notice antenna 59 and the tollgate antenna 60 are installed so that their signal emission areas do not overlap each other, and the vehicle enters the signal transmission area in the order of the notice antenna 59 and the tollgate antenna 60. ing.
The notification antenna 59 is used, for example, to determine whether or not a vehicle entering the signal transmission area can use the automatic fee collection system, and to calculate a fee to be paid by the vehicle. On the other hand, the tollgate antenna 60 is used to identify the vehicle. The details will be described later.

The data transmission rate of the second modulated wave signal transmitted from the interrogation beacon 22 is an integer multiple of the data transmission rate (64 (kbps)) of the information beacon 21, for example, tripled to 192 (kbps). Is set. In this way, by setting the data transmission rate of the second modulated wave signal to be an integral multiple of the data transmission rate of the first modulated wave signal, the in-vehicle device 20 can receive and demodulate with the same synchronization signal. . Therefore, since the vehicle-mounted device 20 can be synchronized by the single synchronization circuit, the configuration of the vehicle-mounted device 20 can be simplified.

After the second modulated wave signal is transmitted, the non-modulated wave signal is transmitted for a predetermined period in order to be reflected and returned by the vehicle-mounted device 20. The non-modulated wave signal is generated in the data processing section 52 as follows.
That is, in the data processing unit 52, when the transmission of each transmission data frame to be included in the second modulated wave signal ends,
High-level continuous data is supplied to the ASK modulators 56a and 56b for a predetermined period, respectively, and F
A control signal indicating inhibition of modulation is sent to the SK modulators 54a and 54b, respectively. As a result, the oscillators 55a and 55b
Each carrier wave C ₃ oscillated from the ASK modulator 5
The signals 6a and 56b are subjected to ASK modulation. At this time, since the modulation data is high-level continuous data, each carrier C ₃ is eventually output as it is, and the transmission amplification unit 58
It is transmitted from the notice antenna 59 and the tollgate antenna 60 via a and 58b, respectively.

The transmission output of this unmodulated wave signal is such that the signal-to-noise ratio can be secured in the interrogation beacon 22.
It has a large output of about 300 (mW). If the unmodulated wave signal is transmitted with such a large output, the signal to be reflected back from the vehicle-mounted device 20 can be accurately demodulated in the inquiry beacon 22. The signal reflected back from the vehicle-mounted device 20 is received by the notice antenna 59 or the tollgate antenna 60. The signals received by the notice antenna 59 or the tollgate antenna 60 are amplified to the required levels by the reception amplification units 61a and 61b, respectively, and then the data demodulation units 62a and 62b.
Given to. In the data demodulators 62a and 62b, synchronous detection is performed based on the carrier waves C ₃ given from the oscillators 55a and 55b, and the data included in the received signal is restored. The restored data are provided to the data processing unit 52 via the communication control units 53a and 53b.

FIG. 7 is a block diagram showing the electrical configuration of the vehicle-mounted device 20. The vehicle-mounted device 20 is capable of receiving the first modulated wave signal transmitted from the information beacon 21 and the second modulated wave signal and the non-modulated wave signal transmitted from the inquiry beacon 22. The receiving antenna 70 is provided. The signals received by the receiving antenna 70 are first given to the frequency converter 71 for frequency conversion, and then given to the 1 kHz demodulator 72 and the data demodulator 73.

More specifically, the frequency converter 7
1 is a band pass filter (BPF)
71a is provided. In the signals received by the receiving antenna 70, components other than the band component are suppressed by the band pass filter 71a, and then the RF (Radio Frequency) signal is received.
ncy) is given to the amplification unit 71b and amplified to a required level. After that, in the mixer section 71c, the frequency is converted into an intermediate frequency signal of about 100 (MHz) based on the reference frequency signal given from the phase locked loop (PLL) 71d, and then the band pass filter (BPF) 71e and It is given to the 1 kHz demodulation unit 72 and the data demodulation unit 73 via the amplification unit 71 f.

The 1 kHz demodulation section 72 is provided with an automatic gain control (AGC) section 72a. The intermediate frequency signal is transmitted to the AGC section 72a.
After the gain is controlled to a required level by the detector 72,
It is detected at b. As a result, the modulated signal C _{2 of} 1 kHz
Is restored. That is, the 1 kHz demodulation unit 72
This is for restoring the AM modulation component of the first modulated wave signal radiated from the information beacon 21. The restored AM modulation component is amplified to a required level by the amplification unit 72c, then pulsed by the comparator 72d and given to the data processing unit 74.

On the other hand, the data demodulation section 73 includes a mixer section 7
3a is provided. The intermediate frequency signal is 10.7 (MHz) based on the reference frequency signal given from the phase locked loop (PLL) 73b in the mixer section 73a.
Is converted into a signal of degree. The converted signal is amplified by the amplification unit 73d after the components other than the band component are suppressed by the band pass filter (BPF) 73c, and the FSK detection unit 7
Given to 3e.

In the FSK detection section 73e, the above 10.7 (M
The frequency shift of the (Hz) signal is detected and the transmission data frame is restored. That is, in this FSK detection section 73e, the FSK modulation component contained in each of the above signals is detected, and the transmission data frame is restored. Then, the restored transmission data frame has the clock recovery unit 73f.
After the clock is given to the data processing unit 7
Given to 4. The clock reproduction unit 73f reproduces the clock in order to accurately determine the bit change point of the given transmission data frame in the data processing unit 74.

In the data processing unit 74, position detection is performed based on the 1 kHz pulse given from the 1 kHz demodulation unit 72. That is, a 1 kHz pulse is AM
The reception level of the AM modulation component, which is a modulation component, sharply drops immediately below the information beacon 21, as shown in FIG. In the data processing unit 74, when the pulse of 1 kHz is given, the reception level of the AM modulation component is monitored, and when the reception level sharply decreases, the vehicle receives the information beacon 21.
It is determined that it has reached the position immediately below, and a control signal indicating this is created.

The data processing unit 74 can also detect the position by monitoring the change in the phase of the AM modulation component with respect to the transmission data frame. The above monitoring
The modulation method designation code 44 (see FIG. 3) obtained as a result of demodulating the transmission data frame by the data demodulation unit 73 is "0".
Only in case of. Therefore, the position detection is not performed when the second modulated wave signal and the non-modulated wave signal originally emitted from the interrogation beacon 22 that does not include the AM modulation component for position detection are received. That is, the data processing unit 7
In 4, it is possible to perform an appropriate process corresponding to the modulation method. Therefore, it is possible to prevent wasteful consumption of electric power.

The data processing unit 74 includes a CPU, ROM,
RAM (none shown) and writable EEP
A memory 74a including a ROM (electrically erasable programmable ROM) or the like is provided. The question beacon 22 from the vehicle-mounted device 20 described later is stored in the memory 74a.
The data to be reflected back to is stored. In the data processing unit 74, only when it is determined that the restored transmission data frame is included in the second modulated wave signal and the received signal is the non-modulated wave signal,
According to the program stored in the ROM, the data corresponding to the content of the question information included in the received second modulated wave signal is selectively read out from the data stored in the memory 74a. It

Whether or not the transmission data frame is included in the second modulated wave signal is determined by the communication form designation code 45 (see FIG. 2) included in the transmission data frame.
Is based on. That is, the communication form designation code 45
Is "1", it can be determined that the transmission data frame is included in the second modulated wave signal. That is, in the data processing unit 74, the communication form can be confirmed by the communication form designation code 45, and as a result, the processing according to the communication form can be performed.

Further, in the data processing section 74, it is judged whether or not the signal received by the receiving antenna 70 is a non-modulation wave signal, and whether the transmission data frame is obtained as a result of demodulation in the data demodulation section 73. It depends on whether or not. A navigation system 77 including a display control unit 75 and a display unit 76 is also connected to the data processing unit 74. The navigation system 77 is for detecting the current position of the vehicle by, for example, GPS (Global Positioning System) navigation or self-contained navigation, and displaying the detected current position of the vehicle on the display unit 76 together with a road map around the vehicle. is there.

The respective signals amplified by the RF amplifying section 71b are also given to the carrier wave reproducing section 78. The carrier wave reproducing unit 78 reproduces the carrier waves C ₁ and C _{3 of} each signal. The reproduced carriers C ₁ and C ₃ are given to the PSK modulator 79. The PSK modulator 79 is provided with data according to the content of the question information read by the data processor 74.

The PSK modulator 79 may be replaced with, for example, an FSK modulator for performing FSK modulation or another digital angle modulator for performing digital angle modulation.
In the PSK modulating section 79, when the data to be reflected and returned is given, the carrier wave given from the carrier wave reproducing section 78 at that time, that is, the unmodulated wave signal is subjected to PSK modulation with the data to be transmitted. Three modulated wave signals are generated. Therefore, in the present embodiment, the memory 74a, the carrier wave reproducing section 78 and the PSK modulating section 79 function as an in-vehicle modulating means. The generated third modulated wave signal is transmitted to the question beacon 22 from the transmission antenna 80 that functions as the vehicle-mounted transmission unit.

Next, the processing when the first modulated wave signal transmitted from the information beacon 21 in the in-vehicle device 20 is received will be specifically described. When the vehicle equipped with the in-vehicle device 20 reaches the signal transmitting area of the information beacon 21, the first modulated wave signal is received by the receiving antenna 70 provided in the in-vehicle device 20. The frequency of the received first modulated wave signal is converted by the frequency conversion unit 71, and then provided to the data demodulation unit 73. Data demodulation unit 73
Then, the transmission data frame including the road traffic information and the position information included in the first modulated wave signal is restored,
The restored road traffic information and position information are given to the data processing unit 74. The data processing unit 74 performs predetermined data processing on the given road traffic information and position information. The road traffic information and the position information subjected to this data processing are given to the navigation system 77 at a predetermined timing.

On the other hand, the first modulated wave signal that has been frequency-converted by the frequency converter 51 is also given to the 1 kHz demodulator 72, and a 1 kHz pulse is given to the data processor 74. In the data processing unit 74, this given 1k
Hz pulse and modulation system designation code 44 (see FIG. 2)
On the basis of the above, a control signal indicating that the vehicle has reached just under the information beacon 21 is created and sent to the navigation system 77.

In the navigation system 77, the given road traffic information is displayed on the display device 75. In addition, in the navigation system 77, when the control signal is given, it is determined that the vehicle has reached the installation point of the information beacon 21, and the position of the separately provided position information is displayed.
The detected current position of the vehicle is corrected. Next, the operation performed between the vehicle-mounted device 20 and the question beacon 22 when the vehicle-mounted device 20 enters the signal transmission area of the question beacon 22 will be specifically described.

In the interrogation beacon 22, the notice antenna 59 transmits the second modulated wave signal including the antenna type code indicating the notice antenna, and the tollgate antenna 60 indicates the tollgate antenna. The second modulated wave signal including the antenna type code is transmitted.
When the vehicle equipped with the on-vehicle device 20 reaches the signal transmission area of the notice antenna 59 of the inquiry beacon 22b (see FIG. 1) installed near the entrance gate of the tollgate, the second modulated wave signal is received. When the data processing unit 74 confirms that the antenna is a notice antenna based on the antenna type code included in the received second modulated wave signal, R
According to the program stored in the OM, the memory 74a
The general-purpose credit card number data and the balance data stored in are read, and a transmission data frame including the read number data and the balance data is created. The created transmission data frame is sent to the PSK modulation unit 79 after the data processing unit 74 confirms that the unmodulated wave signal is received. PSK modulator 7
In No. 9, the unmodulated wave signal is PS in the transmission data frame.
K modulation is performed to generate a third modulated wave signal, and the generated third modulated wave signal is transmitted from the transmitting antenna 80 to the interrogation beacon 22b.

In the question beacon 22b, the notice antenna 5
When this third modulated wave signal is received via 9, the transmission data frame is restored. Then, when it is confirmed that the restored balance data can use the automatic fee collection system, the transmission data frame including the restored number data and the data indicating that the automatic fee collection system can be used is subjected to the second modulation. It is transmitted from the notice antenna 59 as a wave signal.

Note that the number data is always transmitted and received between the question beacon 22 and the vehicle-mounted device 20, but this is merely for confirming the communication partner, and so on. In-vehicle device 2
At 0, when the transmitted transmission data frame is restored, data indicating that the automatic fee collection system is used is read from the memory 74a. Then, in the transmission data frame including the read data, after it is confirmed that the unmodulated wave signal is received, the PSK modulation unit 7
9 is provided to the interrogation beacon 22 as the third modulated wave signal.
b. This transmission is done to confirm availability.

Now, the notice antenna 59 of the question beacon 22b where the vehicle is installed near the entrance gate of the toll gate
The operation ends when the signal has entered the signal transmission area.
Next, the operation when the vehicle is entering the signal transmission area of the tollgate antenna 60 of the inquiry beacon 22b installed near the entrance gate of the tollgate will be described.

When the vehicle reaches the signal transmission area of the tollgate antenna 60, the second modulated wave signal including the antenna type code indicating the tollgate antenna is received by the receiving antenna 70.
Will be received at. When the antenna type is confirmed, the data processing unit 74 reads the number data and the data indicating that the antenna is used from the memory 74a. The transmission data frame including the read data is confirmed by the PSK modulation section 7 after it is confirmed that the unmodulated wave signal is received.
9 is provided to the interrogation beacon 22 as the third modulated wave signal.
b.

In the inquiry beacon 22b, when the third modulated wave signal is received via the tollgate antenna 60, each of the above data is restored. As a result, in the data processing unit 52, when it is confirmed that the vehicle-mounted device 20 uses the automatic fee collecting system, the number data, the data indicating that the automatic fee collecting system is used, the ID unique to the tollgate, etc. A transmission data frame including entrance data and time data is transmitted from the tollgate antenna 60 to the vehicle-mounted device 20 as the second modulated wave signal.

In the vehicle-mounted device 20, when the second modulated wave signal is received via the receiving antenna 70, each of the above data is restored. The data indicating that the restored automatic fare collection system is used, the entrance data, and the time data are written in the memory 74a for use in calculating the usage fare at the exit of the toll road. In addition, for confirmation, it was confirmed that a non-modulated wave signal was received in a transmission data frame including the restored number data, data indicating that the automatic fee collection system is used, entrance data, and time data. After that, it is given to the PSK modulator 79,
The third modulated wave signal is transmitted from the transmission antenna 80 to the interrogation beacon 22b.

Now, the toll gate antenna 6 of the interrogation beacon 22b where the vehicle is installed near the entrance gate of the toll gate
When the signal transmission area of 0 is entered, the operation ends. Next, the operation when the vehicle is entering the signal transmission area of the notice antenna 59 of the inquiry beacon 22c installed near the exit gate of the tollgate will be specifically described.

When the vehicle reaches the signal transmitting area of the notice antenna 59, the second modulated wave signal including the antenna type code indicating the notice antenna is received via the receiving antenna 70. When the data processing unit 74 confirms that the antenna is a notice antenna, it uses the number data, the balance data, the entrance data, the route data indicating the road type and the waypoint ID for each road, and the automatic fee collection system from the memory 74a. And the vehicle type data indicating the plate number are read. Then, after it is confirmed that the non-modulated wave signal is transmitted, the transmission data frame including the above-mentioned data is given to the PSK modulator 79, and the third
Question beacon 2 from transmitting antenna 80 as a modulated wave signal
2c.

In the inquiry beacon 22c, when the third modulated wave signal is received via the notice antenna 59, the above respective data are restored. The data processing unit 52 calculates the usage fee based on the restored entrance data and route data. Then, a transmission data frame including the restored number data, data indicating that the automatic fee collecting system is used, and new balance data obtained by subtracting the calculated usage fee from the balance data is used as the second modulated wave signal. It is transmitted from the notification antenna 59 to the vehicle-mounted device 20.

In the vehicle unit 20, when the second modulated wave signal is received via the receiving antenna 70, the transmission data frame is restored. Then, the restored new balance data is written in the memory 74a, and for confirmation, a transmitted data frame including the restored number data, data indicating that the automatic fee collecting system is used, and the new balance data. However, after it is confirmed that the unmodulated wave signal is received, it is given to the PSK modulator 79 and transmitted from the transmission antenna 80 to the interrogation beacon 22c as the third modulated wave signal.

[0069] Now, the notice antenna 59 of the question beacon 22c where the vehicle is installed near the exit gate of the toll gate
The operation ends when the signal has entered the signal transmission area.
Next, the operation when the vehicle is entering the signal transmission area of the tollgate antenna 60 of the inquiry beacon 22c installed near the exit gate of the tollgate will be specifically described.

When the vehicle reaches the signal transmission area of the tollgate antenna 60, the second modulated wave signal including the antenna type code indicating the tollgate antenna is received antenna 70.
Will be received at. When it is confirmed that the antenna is the tollgate antenna, the data processing unit 74 stores the number data and the data indicating that the automatic toll collection system is used in the memory 74.
read from a. Then, after it is confirmed that the non-modulated wave signal is received, a transmission data frame including the above-mentioned data is given to the PSK modulation section 79 and transmitted from the transmission antenna 80 to the interrogation beacon 22c as a third modulated wave signal. To be done.

In the inquiry beacon 22c, when the third modulated wave signal is received via the tollgate antenna 60, the transmission data frame is restored. In the data processing unit 52, after it is confirmed that the in-vehicle device 20 is using the automatic fee collection system, the restored number data,
Exit data indicating the road type and the ID unique to the toll gate by road,
A transmission data frame including current time data is transmitted from the tollgate antenna 60 to the vehicle-mounted device 20 as a second modulated wave signal.

In the vehicle-mounted device 20, when the second modulated wave signal is received via the receiving antenna 70, the transmission data frame is restored. Then, the restored exit data and time data are written in the memory 74a, and the transmission data frame including the restored exit data and time data is interrogated from the transmission antenna 80 as a third modulated wave signal for confirmation. It is transmitted to the beacon 22c.

Now, the tollgate antenna 6 of the interrogation beacon 22c in which the vehicle is installed near the exit gate of the tollgate
When the signal transmission area of 0 is entered, the operation ends. In the inquiry beacon 22c installed near the exit gate of the toll gate, the number data and the calculated usage charge data are given to the host computer 50 via the modems 51a and 51b. Host computer 5
At 0, the usage fee data is added and stored for a predetermined period. Then, on the predetermined settlement date, the added usage fee is deducted from the account corresponding to the number data. This achieves the collection of charges.

FIG. 9 is a diagram showing the second modulated wave signal S _a and the non-modulated wave signal S _b transmitted from the inquiry beacon 22. With reference to this figure, first, a method of obtaining the modulation degree of the ASK modulation performed by the ASK modulators 56a and 56b of the present embodiment will be described. Amplitude of the non-modulated wave signal S _b sent from the interrogator beacon 22, that is, the second modulated wave signal S maximum amplitude of _a A, and the second modulated wave signal S _a minimum amplitude respectively a respective voltages of B of (V) , B (V), the modulation factor m is generally expressed by the following equation (1).

M = (a−b) / (a + b) × 100 (%) (1) For example, the transmission output at the amplitude of A in the figure is 300 (mW).
Hereinafter, assuming that the transmission output with the amplitude of B in the figure needs to be 10 (mW) or more, b ≧ a × 1 / √30. Therefore, the modulation factor m when b = a × 1 / √30 is given by the following equation (2).

[0076]

[Equation 1]

Therefore, in this embodiment, the information beacon 2
Since the transmission output of 1 is 10 (mW) and the transmission output of the inquiry beacon 22 is 300 (mW), the modulation factor m is 69.
Must be less than or equal to%. Next, a line design example between the question beacon 22 and the vehicle-mounted device 20 in the present embodiment will be described.

The minimum power required for the interrogation beacon 22 to transmit the second modulated wave signal S _a , that is, the power P _A required to transmit a signal of amplitude B is the received power required by the vehicle-mounted device 20. Assuming −65 (dBm), P _A = −65 + (line loss) = − 65−G _t −G _r +20 log (4πR / λ) + L _t + L _r (3)

Further, the interrogation beacon 22 sends the unmodulated wave signal S
_The power P _B required to transmit _b must double the line loss in consideration of the reflection and return by the vehicle-mounted device 20. Therefore, the power P _B is obtained by P _B = −65 + (line loss) × 2 = −65 + (− G _t −G _r +20 log (4πR / λ) + L _t + L _r ) × 2 (4) .

Here, G _t is the gain of the notice antenna 59 or the tollgate antenna 60, G _r is the gain of the receiving antenna 70, and R is the vehicle when it reaches the signal transmission area of the notice antenna 59 or the tollgate antenna 60. The distance between the notification antenna 59 or the tollgate antenna 60 and the receiving antenna 70, λ is the wavelength of the second modulated wave signal S _a , L _t is the power feed line loss of the interrogation beacon 22, and L _r is the power feed line of the vehicle-mounted device 20. Represents a loss.

For example, the receiving antenna 70 has a height of 1 (m) above the ground, the notice antenna 59 or the tollgate antenna 60 has a height of 5 (m) above the ground, and the signal transmission area is 5 (m) at the maximum in the longitudinal direction of the road. If so, the above R becomes 6.4 (m), and if the frequency of the second modulated wave signal S _a is 2.5 (GHz), then the above λ becomes 0.12 (m). Further, when the type of the notice antenna 59 or the tollgate antenna 60 is a plane antenna, the above G _t is 15, and when the type of the receiving antenna 70 is a plane antenna, the above G _r is 3. Further, if the length of the power supply line of the question beacon 22 is 10 (m), the above L _t becomes 3, and the vehicle-mounted device 2
If the length of the feeder line of 0 is 2 (m), the above L _r is 4.

Assuming the above case, the power P
Substituting each of the above numerical values into the above equation (3), _A is obtained as in the following equation (5). P _A = −65−15−4 + 56.5 + 3 + 4 = −20.5 (dBm) ≈9 × 10 ⁻³ (mW) (5) Further, the transmission output required to transmit the non-modulated wave signal S _b P _B is obtained by substituting the above numerical values into the above equation (4) and
It is calculated like the formula.

P _B = −65 + (− 15−4 + 56.5 + 3 + 4) × 2 = 24 (dBm) ≈250 (mW) (6) As described above, according to the road-vehicle communication system of the present embodiment,
The vehicle-mounted device 20 that merely includes the FSK demodulation function and the reflection reply function can communicate with both the information beacon 21 and the inquiry beacon 22 having different purposes. Further, the vehicle-mounted device 20 that simply includes the FSK demodulation function and the reflection / return function has a simpler configuration than the vehicle-mounted device that includes the FSK demodulation function, the ASK demodulation function, and the reflection / return function. Therefore, it is possible to use both the traffic information providing system and the automatic fare collection system with one in-vehicle device 20 having a simple configuration.

In the question beacon 22, FSK
The transmission data frame to be modulated is the same as the transmission data frame to be ASK in terms of the same configuration contents, data transmission speed, and transmission timing at the beginning thereof.
The high frequency noise that is likely to occur at the amplitude change point due to modulation is F
This will affect the frequency change point due to SK modulation. Therefore, it is possible to prevent the high frequency noise from affecting the bit center of the FSK modulation component. Therefore, the in-vehicle device 20 can perform stable demodulation processing, and thus the transmission data frame can be accurately restored.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in the above embodiment, the case where the question beacon 22 is used in the automatic fee collecting system has been described.
For example, the question beacon 22 can also be used in an automatic vehicle identification system (AVI) devised for the purpose of automatically collecting license plates and the like of vehicles traveling on a road.

In the above embodiment, the question beacon 22
In the case where the transmission data frame given to the FSK modulators 54a and 54b and the transmission data frame given to the ASK modulators 56a and 56b have the same configuration contents, data transmission rate, and the transmission timing at the beginning, As described above, for example, the transmission data frames may be the same only in the configuration content and the data transmission rate. Further, at least a part of the configuration content of each transmission data frame may be the same. According to this configuration, road traffic information can be included in addition to the question information.

Further, in the above embodiment, the case where the data to be reflected and returned from the vehicle-mounted device 20 is stored in the memory 74a has been described. However, for example, the driver may input the data to be reflected and returned as needed. You may With this configuration, it is possible to prevent the automatic fee collection system from being used against the driver's will.

Furthermore, in the above-mentioned embodiment, in the inquiry beacon 22, the FSK-modulated transmission data frame is ASK-modulated, but, for example, the ASK-modulated transmission data frame may be FSK-modulated. Other various design changes can be made within the scope of the claims.

[0089]

As described above, according to the road-vehicle communication system of the present invention, the information beacon can be demodulated by the digital angle-modulated component, and the information beacon can be demodulated by the single vehicle-mounted device having the function of reflecting and replying to the inquiry beacon. And can communicate with both the beacon and the interrogation beacon. for that reason,
Both the traffic information system and the automatic toll collection system can be used inexpensively.

In particular, according to the road-to-vehicle communication system of the second aspect, since the two transmission data transmitted from the inquiry beacon have the same structure and the same data transmission speed, the processing in the vehicle-mounted device can be simplified. The processing speeds can be the same. Therefore, the configuration can be further simplified. According to the road-to-vehicle communication system of the third aspect, since the change point of each bit in each frame transmitted from the inquiry beacon is changed at the same time, digital amplitude modulation is performed. It is possible to reduce the influence of high-frequency noise that tends to occur on the center of the bit. Therefore, the noise removing circuit is not required, and the configuration can be further simplified.

Further, according to the road-vehicle communication system of the fourth aspect, the modulation system of the received signal can be confirmed in the vehicle-mounted device, so that appropriate processing corresponding to the modulation system can be performed. Therefore, useless processing in the vehicle-mounted device can be minimized, and useless consumption of power can be prevented. Further, according to the road-vehicle communication system of the fifth aspect, it is possible to confirm whether or not the two-way communication is possible in the vehicle-mounted device, and therefore it is possible to perform an appropriate process according to the communication mode. Therefore, useless processing in the vehicle-mounted device can be minimized, and useless consumption of power can be prevented.

According to the road-vehicle communication system of the sixth aspect, since the data transmission rate of the inquiry beacon is an integral multiple of the data transmission rate of the information beacon, it is possible to synchronize with the same synchronization signal. Therefore, since synchronization can be achieved by the same synchronization circuit, the configuration of the vehicle-mounted device can be simplified. According to the road-to-vehicle communication system of claim 7, since the low frequency component of the transmission data is used to generate the second modulated wave signal in the inquiry beacon, the digital amplitude modulation to the second modulated wave signal is performed. It is possible to prevent the mixing of high-frequency noise that is likely to occur by being applied. Therefore, the data to be demodulated can be accurately demodulated in the vehicle-mounted device.

According to the road-vehicle communication system of the eighth aspect, the communication quality can be ensured.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a road-vehicle communication system for explaining the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of a road-vehicle communication system according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a transmission data frame to be transmitted from an information beacon forming a part of the road-vehicle communication system.

FIG. 4 is a diagram showing a configuration of a first byte of an information service list included in the transmission data frame.

FIG. 5 is a block diagram showing an electrical configuration of the information beacon.

FIG. 6 is a block diagram showing an electrical configuration of a question beacon forming a part of the road-vehicle communication system.

FIG. 7 is a block diagram showing an electrical configuration of a vehicle-mounted device that constitutes a part of the road-vehicle communication system.

FIG. 8 is a diagram for explaining a reception level in a vehicle-mounted device of a first modulated wave signal radiated from the information beacon.

FIG. 9 is a diagram showing a configuration example of a signal transmitted from an inquiry beacon.

[Explanation of symbols]

 11, 20 In-vehicle device 3, 21 Information beacon 6, 22 Question beacon 30 Data modulation unit 31 Carrier generation unit 35 Beacon antenna 44 Modulation method designation code 45 Communication mode designation code 52 Data processing unit 54a, 54b FSK modulation unit 56a, 56b ASK Modulation unit 59 Notice antenna 60 Tollgate antenna 70 Reception antenna 73 Data demodulation unit 74 Data processing unit 78 Carrier extraction unit 79 PSK modulation unit 80 Transmission antenna

Claims (8)

[Claims] 1. A first beacon modulating means (1) which is installed on a road and digitally angle-modulates a predetermined carrier wave with transmission data containing road traffic information to generate a first modulated wave signal, and the first beacon. Beacon (3) including a first beacon transmission means (2) for transmitting the first modulated wave signal generated by the modulation means (1) for use, and a predetermined carrier is at least partly installed on the road Of one of the two transmission data including the inquiry information of (1) is modulated by one of the digital angle modulation and the digital amplitude modulation, and the modulated carrier wave is the other transmission data of the two transmission data. And a second beacon modulating means (4) for generating a second modulated wave signal by modulating with the other modulation method of the digital angle modulation or the digital amplitude modulation, and the second beacon modulating means (4).
The second modulated wave signal generated by
An interrogation beacon (6) including a second beacon transmitting means (5) for transmitting an unmodulated wave signal after transmitting the second modulated wave signal.
A first beacon transmitted from the first beacon transmission means (2) or the second beacon transmission means (5) mounted on the vehicle.
A vehicle-mounted receiving means (7) capable of receiving a modulated wave signal, a second modulated wave signal and an unmodulated wave signal, and the first modulated wave signal and the second modulated wave signal received by the vehicle-mounted receiving means (7). An on-vehicle signal demodulation means (8) capable of demodulating the digital angle modulation component contained in the modulated wave signal, and a digital angle modulation component contained in the second modulated wave signal by this on-vehicle signal demodulation means (8) Thirdly, the non-modulated wave signal received by the vehicle-mounted receiving means (7) is digitally angle-modulated by the data obtained in response to the question information.
An in-vehicle modulating means (9) for generating a modulated wave signal, and an in-vehicle transmitting means (10) for transmitting the third modulated wave signal generated by the in-vehicle modulating means (9) to the inquiry beacon (6). The interrogation beacon (6) includes an in-vehicle device (11) including a second beacon receiving means (12) capable of receiving the third modulated wave signal transmitted by the in-vehicle transmission means (10). ) And second beacon signal demodulation means (13) capable of demodulating the third modulated wave signal received by the second beacon reception means (12). system. 2. The two pieces of transmission data to be transmitted from the inquiry beacon (6) are configured by the same inquiry information and are transmitted at the same data transmission rate. The road-vehicle communication system according to claim 1. 3. The two pieces of transmission data to be transmitted from the inquiry beacon (6) are composed of frames, and each bit in each frame is transmitted so that its change point changes simultaneously. Claim 2 characterized by the above.
The road-vehicle communication system described. 4. The road-vehicle communication system according to claim 1, wherein the transmission data includes a code indicating a modulation method in the information beacon (3) or the inquiry beacon (6). 5. The road-vehicle distance according to claim 1, wherein the transmission data includes a code indicating whether the information beacon (3) or the inquiry beacon (6) is capable of bidirectional communication. Communications system. 6. The data transmission rate of transmission data to be transmitted from the inquiry beacon (6) is an integer multiple of the data transmission rate of transmission data to be transmitted from the information beacon (3). Item 1. The road-vehicle communication system according to Item 1. 7. The second beacon modulating means (4) further includes a low-pass filter (14) for passing only a low-frequency component, and the other transmission data is transmitted to the low-pass filter (1).
4) to extract only the low-frequency component, and the extracted low-frequency component is used to convert the carrier wave modulated by one of the above digital angle modulation or digital amplitude modulation methods into digital angle modulation or digital amplitude modulation. The road-vehicle communication system according to claim 1, wherein the second modulated wave signal is generated by modulating with the other modulation method. 8. The second beacon transmission means (5) transmits the non-modulated wave signal with an output that can secure a signal-to-noise ratio in the second beacon reception means (12). The road-vehicle communication system according to claim 1, wherein the road-vehicle communication system is provided.