JP2004322812A - Electronic license plate and in-vehicle communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend a function so as to commercially make use of an electronic license plate. <P>SOLUTION: A re-writable ROM for storing a commercial program is added to an ID tag of the electronic license plate. An in-vehicle communication device capable of performing the same communication process as a on-road communication device is installed to a vehicle near the electronic license plate and connected with the in-vehicle device. The commercial program is transmitted to the electronic license plate by the in-vehicle communication device or the on-road communication device and is stored in an ROM. One commercial application program is executed as the whole in cooperation of the electronic license plate, the in-vehicle communication device, the in-vehicle device, and the on-road communication device with one another. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology for extending the function of an electronic license plate for private use.
[0002]
[Prior art]
Attachment of an electronic license plate to a vehicle has been studied for the purpose of performing vehicle registration management, traffic volume management, and the like. This electronic license plate is an electronic license plate (for example, see Patent Documents 1 and 2) in which an ID tag is attached to a margin of a registration number display portion of a license plate such as a current metal material. Attached to the part. The ID tag 1 includes a CPU 2, a ROM 3, a RAM 4, a communication circuit 5, an antenna 6, and a power supply circuit 7, as shown in FIG.
[0003]
In the ROM 3, vehicle-specific information required by the external infrastructure, such as a vehicle owner, a vehicle number, a vehicle type, an external dimension, and a displacement, is written in a non-rewritable manner. As a method of supplying power, there are a built-in battery method, an external power supply method, a method of passively reflecting signal radio waves without receiving power supply, and the like.
[0004]
As shown in FIG. 4, a roadside communication device 8 installed on the roadside transmits a polling signal to a vehicle 11 having an electronic license plate 10 attached thereto via an attached antenna 9 by a predetermined wireless method. The ID tag 1 receives the information, reads the vehicle-specific information from the ROM 3, and returns it to the road communication device 8 as a response signal via the communication circuit 5 and the antenna 6.
[0005]
Once the ID tag 1 is removed after being attached to the license plate, the information written in the ROM 3 cannot be read out or is destroyed, thereby preventing the falsification and reuse of the vehicle information. are doing. Therefore, as long as the electronic license plate 10 has not been improperly replaced, the on-road communication device 8 receives the response signal from the electronic license plate 10 and transmits the vehicle-specific information of the vehicle 11 entering the communication area. Can be accurately grasped.
[0006]
Various uses of the electronic license plate in response to the development of ITS (Intelligent Transport System) technology are being studied by the government. However, if this electronic license plate is used only for official purposes such as registration management and traffic volume management of the vehicle, it cannot be said that there are many advantages of attaching the electronic license plate to the vehicle. For this reason, the memory of the electronic license plate is divided into the public use department and the private use department so that the public use department cannot be rewritten, but the private use department uses an electrically rewritable memory. The use of electronic license plates by the private sector is being considered.
[0007]
[Patent Document 1]
Published Japanese Utility Model Application No. 1-72441
[0008]
[Patent Document 2]
JP-A-5-85307
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an improved electronic license plate for paving the way for private use of electronic license plates, peripheral devices for private use, and related technologies. It is in.
[0010]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an electronic license plate configured by mounting an ID tag having a CPU, a memory, a communication circuit, and an antenna on a license plate of a vehicle. A public use ROM for storing public data and a public program, a private use ROM for private use, and a RAM shared for public use and private use are provided. The ID tag is configured to execute a public program, receive a private program and data transmitted from a road communication device or other communication devices, store the program and data in the private use ROM, and execute the program. The electronic license plate features.
[0011]
By having such a configuration and functions, this electronic license plate, in addition to executing a public program, receives a private program for private use of the electronic license plate and stores it in a private ROM, Can be performed. This paves the way for the private use of electronic license plates.
[0012]
According to a second aspect of the present invention, there is provided an on-vehicle communication device mounted on a vehicle near the electronic license plate, the same communication as a road communication device having a communication function related to public use of the electronic license plate. A function of transmitting a private program and data to the electronic license plate according to claim 1, in addition to the function, and wirelessly exchanging information with the electronic license plate when executing the private program received by the electronic license plate. An on-vehicle communication device characterized by additionally having a function of performing on-board communication.
[0013]
By installing the on-vehicle communication device having such a configuration and functions, a private program can be transmitted and stored in the electronic license plate, and it becomes easy to effectively execute the private program on the electronic license plate. .
[0014]
According to a third aspect of the present invention, in the vehicle according to the second aspect, a function of exchanging information with an in-vehicle device for a car navigation system, a telematics system, or the like is added to the on-vehicle communication device. Upper communication device.
[0015]
If the onboard communication device has such a function, the electronic license plate, the onboard communication device, and the on-vehicle device can cooperate to execute one private application program.
[0016]
The invention according to claim 4 is characterized in that the on-vehicle communication device has a function of detecting whether or not the electronic license plate is communicating with the on-road communication device. 3. The on-vehicle communication device according to 3.
[0017]
If the onboard communication device is provided with such a function, the onboard communication device can detect a communication abnormality or the like between the electronic license plate and the roadside communication device.
[0018]
According to a fifth aspect of the present invention, in the on-vehicle communication device, the communication time between the electronic license plate and the on-road communication device is measured, and when the cumulative communication time reaches a predetermined value, the effect is indicated. The on-vehicle communication device according to any one of claims 2 to 4, wherein the on-vehicle communication device has a function of transmitting the information to an on-vehicle device.
[0019]
If the accumulated communication time becomes long, it means that the internal battery of the electronic license plate has been exhausted.If this is transmitted to the vehicle-mounted device, the vehicle-mounted device informs the driver of the fact by displaying it. You can let them know and take measures.
[0020]
Further, the invention according to claim 6 is characterized in that the on-vehicle communication device monitors communication between the electronic license plate and the on-road communication device, and detects an abnormal state such that a link is not established. 6. The apparatus according to claim 2, wherein the information and the time of occurrence of the abnormality are stored immediately or once and transmitted to the in-vehicle device when an inquiry is made from the in-vehicle device. It is an onboard communication device.
[0021]
According to such an on-vehicle communication device, the in-vehicle device that has received the notification of the occurrence of the abnormal state can notify the driver of the fact by display or the like and take measures.
[0022]
In the invention described in claim 7, the electronic license plate can transmit the free space in response to an inquiry about the free space of the private use ROM from the on-vehicle communication device or the on-road communication device. The electronic license plate according to claim 1, wherein the electronic license plate is configured as described above.
[0023]
If the electronic license plate is provided with such a function, the on-vehicle communication device and the on-street transmitting device can determine whether the private program that is to be transmitted to the electronic license plate and executed is normally stored in the electronic license plate. Can be determined in advance.
[0024]
The invention according to claim 8 is characterized in that the electronic license plate performs a predetermined security process at the start of communication with another communication device, and the security process is different for each communication device. 8. The electronic license plate according to 7.
[0025]
Since the electronic license plate wirelessly exchanges information with a plurality of communication devices, it is possible to prevent information leakage by performing security processing in this manner.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an outline of the arrangement and mounting of devices related to private use of the electronic license plate according to the present embodiment, and FIG. 2 is a block diagram showing the configuration and connection relationship of those devices. In the drawings, the same or corresponding parts as those in FIGS. 3 and 4 of the related art are denoted by the same reference numerals.
[0027]
Opening the Way to Private Use of Electronic License Plates The information exchange system shown in FIGS. 1 and 2 includes an electronic license plate 10 mounted on a vehicle 11, an on-board communication device 12, an on-vehicle device 13, and a plurality of road-side installed devices. And the on-road communication device 8.
[0028]
The in-vehicle device 13 is an on-board terminal device used for a traffic / communication / information processing system such as a car navigation system or a telematics system. Usually, it is configured to include a microcomputer, has a wireless communication device, and is configured to be capable of wirelessly exchanging information with a cellular phone network, a telematics center, or the like.
[0029]
The electronic license plate 10 is an electronic license plate in which an ID tag is attached to a blank portion of a registration number display portion of a license plate such as a current metal material, and is attached to the front and rear portions of the vehicle. The ID tag 1 of the present embodiment includes a CPU 2, a ROM 3, a RAM 4, a communication circuit 5, an antenna 6, and a power supply circuit 7, as shown in FIG.
[0030]
This electronic license plate 10 differs from the electronic license plate ID tag 1 shown in FIG. 3 in the section of the prior art in that the ROM 3 is divided into a public use ROM 3a and a private use ROM 3b. . The public use ROM 3a is a ROM corresponding to the ROM 3 in FIG. 3, and includes official data such as a vehicle owner, a vehicle number, a vehicle type, an external dimension, a vehicle verification entry, and the like (the Ministry of Land, Infrastructure, Transport and Tourism, The public data determined by the National Police Agency, etc., and a program (hereinafter, referred to as a public program) that handles the public data in a predetermined manner are irrevocably stored. When the ID tag 1 is once attached to the license plate and then removed, the information ROM 3a is made unreadable or destroyed, so that the publicly used ROM 3a is falsified. And prevent reuse.
[0031]
The private use ROM 3b is a ROM newly added in the present embodiment, and is a part for storing an application program (hereinafter, referred to as a private program) for private use of the electronic license plate 10 and data for the application program. The ROM 3b is constituted by a flash memory capable of electrically rewriting information.
[0032]
The private use ROM 3 b to be added may be mounted on the ID tag 1. Further, a bus line for adding a memory may be provided on the ID tag 1 and a mechanism for adding a memory may be provided at an end portion, and the memory may be attached to the outside of the ID tag 1 via a flexible cable. Further, a memory slot may be provided at the end of the ID tag 1 and a memory module may be inserted. After attaching the memory module to the electronic license plate 10, a cover may be provided and sealed with a water-resistant material such as silicon.
[0033]
The RAM 4 may be shared by the public program and the private program, or may be provided separately. When the RAM area becomes large, a RAM may be additionally provided outside the ID tag 1 similarly to the case of the private use ROM 3b described above.
[0034]
The communication circuit 5 transmits and receives information between the on-road communication device 8 and the on-vehicle communication device 12 via the antenna 6 by means of bidirectional DSRC (Dedicated Short Range Communication) communication.
[0035]
The power supply circuit 7 is a circuit that supplies power to each circuit of the ID tag 1. The power consumption of the ID tag 1 described in the section of the related art is small because the execution program is only a public program. Therefore, as described above, the circuit can be operated by using a built-in battery or passively reflecting a signal radio wave without receiving power supply. However, in the case of the present embodiment, power consumption is expected to increase because a private program as well as a public program is executed. If the life of the built-in battery is expected to be shortened due to power consumption, the built-in battery is used as a standby power supply, and a method of supplying main power from the outside is adopted.
[0036]
When power is supplied from the outside, the ID tag 1 is provided with an external power supply terminal, and power is supplied from a vehicle-mounted power supply such as a battery. Switching between an external power supply and a built-in battery as a standby power supply is performed by a power supply control circuit (not shown) in the power supply circuit 7. When the power consumption is small and an external power supply is not used, it is desirable to attach a waterproof film to the contact of the external power supply terminal in consideration of waterproofness.
[0037]
As another means for supplying power to the ID tag 1 from the outside, a method of supplying power in a non-contact manner using electromagnetic induction may be adopted. An advantage of this method is that a coil for receiving an electromagnetic wave as a power supply can be embedded in the resin of the module of the ID tag 1. When the coil is embedded in the resin, the water resistance can be significantly improved as compared with the case where the external power supply terminal is provided as described above. In this case, an external coil that generates an electromagnetic wave serving as a power supply is installed near the coil embedded in the resin of the ID tag 1.
[0038]
Next, the road communication device 8 will be described. The roadside communication device 8 of the present embodiment is based on a communication device having the same configuration and the same functions as a conventional roadside communication device used for performing public processing with a conventional electronic license plate. In this figure, some configuration and functions are added.
[0039]
As shown in FIG. 1, the on-road communication device 8 includes a CPU 14, a ROM 15, a RAM 16, a communication circuit 17, an antenna 18, and a communication port 19. The communication circuit 17 exchanges information with the electronic license plate 10 via the antenna 18 using the same communication method as that of the related art. The communication port 19 is a communication port for connecting the main road communication device 8 to a centralized control device that controls a large number of road communication devices or a network that comprehensively connects them.
[0040]
The functions newly added to the on-road communication device 8 are as follows.
(1) The above-mentioned private program and necessary data are wirelessly transmitted and stored in the electronic license plate 10 of the present embodiment.
(2) Inquire whether or not a free area of the memory sufficient for storing the private program and data is left in the private use ROM 3b and the RAM 4, and in response to the answer, whether or not the private program may be transmitted. to decide.
(3) When the electronic license plate 10 executes the private program stored in the above (1), the main communication device 8 (including the host computer of the main communication device 8) also executes the corresponding private program. As a whole, one private application program is executed while performing necessary information exchange in cooperation with each other.
These functions are common to the functions of the onboard communication device 12 described later.
[0041]
The addition of the configuration of the on-road communication device 8 means that the capacity of the ROM 15 and the RAM 16 is changed to execute a private program for private use of the electronic license plate 10 in addition to the public program. This is an extension of the conventional on-road communication device that executes only a public program.
[0042]
Next, the configuration and functions of the onboard communication device 12 newly provided in the present embodiment will be described with reference to FIG. As shown in FIG. 1, the on-vehicle communication device 12 is an intelligent communication device that relays information exchange between an on-vehicle device 13 for a car navigation system or a telematics system and the electronic license plate 10, and has an electronic number. Information is exchanged with the plate 10 wirelessly and with the vehicle-mounted device 13 by wire.
[0043]
Structurally, the onboard communication device 12 includes a CPU 20, a ROM 21, a RAM 22, a communication circuit 23, an antenna 24, a communication port 25, and a power supply circuit (not shown). The communication port 25 is a communication port for exchanging information with the in-vehicle device 13 by wire, and is connected to the in-vehicle device 13 by wiring.
[0044]
The communication circuit 23 is for performing wireless communication with the electronic license plate 10 via the antenna 24, and its communication method and communication protocol are the same as those of the roadside communication device 8. That is, with respect to the communication function, the on-vehicle communication device 12 has the same configuration and function as the on-road communication device 8, and looks like one of the on-road communication devices when viewed from the electronic license plate 10. However, since the on-vehicle communication device 12 is installed near the electronic license plate 10 and has a short communication distance, the on-vehicle communication device 12 can communicate with the electronic license plate 10 with a smaller transmission output than the on-road communication device 8. Therefore, the transmission output of the on-vehicle communication device 12 is extremely small in order to reduce power consumption and to prevent transmission information from being received by the electronic license plate of another vehicle.
[0045]
Similarly, when the electronic license plate 10 communicates with the on-board communication device 12, the transmission output is small and sufficient. Of consumption.
[0046]
Next, the functions of the onboard communication device 12 will be listed.
(1) The above-mentioned private program and necessary data are wirelessly transmitted and stored in the electronic license plate 10 of the present embodiment. This private program is stored in the in-vehicle device 13 in advance, and the on-vehicle communication device 12 receives it according to an instruction from the in-vehicle device 13 and transmits it to the electronic license plate 10.
[0047]
(2) Inquire whether or not a memory free area sufficient for storing the private program and data is left in the private use ROM 3b and the RAM 4, receive the answer, and transmit it to the vehicle-mounted device 13. This inquiry is also made in response to an instruction from the vehicle-mounted device 13. The in-vehicle device 13 determines whether or not the size of the received free memory area is enough to store the private program to be transmitted to the electronic license plate 10 and determines whether or not to transmit the private program in (1) above. Will be determined.
[0048]
(3) When the electronic license plate 10 executes the private program stored in (1) above, the on-vehicle communication device 12 and the on-vehicle device 13 also execute the corresponding private program, and cooperate with each other to obtain necessary information. By performing the exchange, a whole private application program is executed. This will be described later with an application example.
[0049]
(4) The communication time between the electronic license plate 10 and the roadside communication device 12 is measured, and when the cumulative communication time reaches a predetermined value, the fact is notified to the vehicle-mounted device 13. Since the communication system of the on-vehicle communication device 12 is exactly the same as the communication system of the on-road communication device 8, the on-vehicle communication device 12 monitors the communication status between the electronic license plate 10 and the on-road communication device 8. Is possible. More communication time means more power consumption. When the electronic license plate 10 operates only with the built-in battery, it is necessary to supply power from an external power supply. Accordingly, the fact that the total communication time has reached the predetermined value is transmitted to the vehicle-mounted device 13. If the in-vehicle device 13 that has received the notification displays the fact on its own display unit, the driver can switch the power supply of the electronic license plate 10 to an external power supply or supply the power by the electromagnetic induction method described above. And take other measures.
[0050]
(5) The communication between the electronic license plate 10 and the on-road communication device 8 is monitored to detect an abnormality such as a link not being established or an abnormal response, and to notify the vehicle-mounted device 13 of the fact and the occurrence time of the abnormality. . The on-vehicle communication device 12 can monitor the communication between the electronic license plate 10 and the on-road communication device 8 as described above. Therefore, if such an abnormality is detected and transmitted to the in-vehicle device 13, and the in-vehicle device 13 displays the received information on the display unit to notify the driver, the driver can take an early action. Can be taken. When the vehicle is stopped in a parking lot or the like, the power of the vehicle-mounted device 13 may be turned off, and only the power of the on-vehicle communication device 12 may be turned on. In such a case, the on-vehicle communication device 12 stores the details of the abnormality and the time of occurrence, and after the power of the on-vehicle device 13 is turned on, itself or upon receiving an inquiry, stores the stored contents. introduce.
[0051]
Next, an application example in which the electronic license plate is used for private use under the overall configuration shown in FIGS. 1 and 2 will be described. For private use, it is necessary to first transmit a private program for private use to the electronic license plate 10 and write it in the ROM 3b therein. The transmission of the private program to the electronic license plate 10 is possible from either the on-board communication device 12 or the on-road communication device 8. Since the procedure is the same, the case of transmission from the in-vehicle device 13 via the on-vehicle communication device 12 will be described.
[0052]
First, the in-vehicle device 13 instructs the on-vehicle communication device 12 to check the free area of the private use ROM 3b of the electronic license plate 10. The onboard communication device 12 receives the instruction and issues a polling signal for establishing a link to the electronic license plate 10. When the electronic license plate 10 receives and responds to the signal, authentication for establishing a link between the electronic license plate 10 and the on-vehicle communication device 12 is performed. These authentication processes are performed by encrypting transmission information in order to prevent information leakage.
[0053]
When the authentication is completed and the link is established, the on-vehicle communication device 12 issues a request to return the size of the free area of the private use ROM 3b of the electronic license plate 10. When the electronic license plate 10 checks the size of the empty area and answers, the on-board communication device 12 receives the information and transmits it to the on-vehicle device 13. The in-vehicle device 13 compares the size of the received free area with the size of the private program to be transmitted from now on, and determines whether or not it can be stored in the electronic license plate 10. If the vacant area is insufficient, the in-vehicle device 13 displays the fact on the display unit to notify the driver.
[0054]
If the vacant area is sufficient, the in-vehicle device 13 transmits the private program to the on-vehicle communication device 12 and instructs transmission to the electronic license plate 10. The in-vehicle communication device 12 having received the instruction transmits the received private program to the electronic license plate 10. The electronic license plate 10 receives it and stores it in the private use ROM 3b.
[0055]
The stored private program may be programmed so as to immediately proceed to execution after storage, or to start execution upon receiving a new execution start instruction from the on-vehicle communication device 12 or the on-road communication device 8. You may keep it.
[0056]
An application example will be described in which this private use application is a process of acquiring the position coordinates from the roadside communication device 8, transmitting the coordinates to the in-vehicle device 13, and displaying the coordinates on the display unit. In accordance with the above-described procedure, a program (hereinafter, referred to as a position coordinate detection program) for communicating with the on-road communication device 8 to receive the position coordinates and transmit the received position coordinates to the on-vehicle communication device 12 is attached to the electronic license plate 10 in advance with the program ID. Store it. In addition, in response to an inquiry about the position coordinates from the electronic license plate 10, a program for notifying the own position coordinates is stored in the roadside communication device 8 via the communication port 19 in advance. In the on-vehicle communication device 12, a program for receiving the position coordinates from the electronic license plate 10 and transmitting it to the on-vehicle device 13 is also transmitted from the on-vehicle device 13 and stored in advance.
[0057]
From such a state, first, the in-vehicle device 13 gives an instruction to the on-vehicle communication device 12 by designating a program ID to activate the position coordinate detection program on the electronic license plate 10. Upon receiving the instruction, the on-vehicle communication device 12 establishes a link with the electronic license plate 10, and designates and instructs a program ID to activate the position coordinate detection program. The electronic license plate 10 recognizes from the received program ID that the designated program is the position coordinate detection program, and activates the position coordinate detection program.
[0058]
The roadside communication device 8 constantly transmits a polling signal. When the vehicle 11 enters the communication area of the on-road communication device 8, the electronic license plate 10 recognizes the polling signal and returns a response signal to establish a link between the on-road communication device 8 and the electronic license plate 10. When the link is established, the position coordinate detection program running on the electronic license plate 10 issues a request to the roadside communication device 8 to transmit the position coordinates. The road communication device 8 receiving the request returns its own position coordinates to the electronic license plate 10 as a response signal. The electronic license plate 10 receives the transmitted position coordinates and temporarily stores it in the RAM 4. Subsequently, a link is established with the on-vehicle communication device 12, and the received position coordinates are transmitted to the on-vehicle communication device 12. The on-vehicle communication device 12 transmits the received position information to the on-vehicle device 13.
[0059]
In this way, each time the vehicle 11 enters the communication area of the roadside communication device 8, the position coordinates of the roadside communication device 8 are sent to the vehicle-mounted device 13. The in-vehicle device 13 displays the received position information together with, for example, the reception time on its own display unit to notify the driver. When the in-vehicle device 13 is a terminal of a car navigation system, the received position coordinates may be used for calibrating the position of the own vehicle detected by GPS.
[0060]
In the above application example, the on-road communication device 8 returns only its own position coordinates as a response signal. However, information on road conditions together with the position coordinates, for example, whether the road surface is frozen, the level crossing is near, or May be returned together with information indicating that there is a construction section, that there is heavy traffic, or that the exit of the expressway is near. If the in-vehicle device 13 that has received such information notifies the driver of the content by voice, the driver can accurately grasp the road conditions while staying at home.
[0061]
As described above, the information exchange system as shown in FIGS. 1 and 2 employing the electronic license plate and the on-vehicle communication device according to the present invention does not limit the electronic license plate to public use, but to private use. It is a function extension, and its application field is almost infinite. In the information exchange system, the electronic license plate and the on-vehicle communication device according to the present invention play a central role.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of an information exchange system employing an electronic license plate and an onboard communication device according to the present invention.
FIG. 2 is a diagram showing an arrangement state of each device according to the present invention.
FIG. 3 is a block diagram showing a configuration of a conventional electronic number plate ID tag.
FIG. 4 is a diagram corresponding to FIG. 2 according to the prior art.
[Explanation of symbols]
In the drawing, 1 is an ID tag, 2 is a CPU, 3 is a memory, 3a is a public use ROM, 3b is a private use ROM, 4 is a RAM, 5 is a communication circuit, 6 antennas, 8 is a road communication device, 10 is an electronic device. A license plate, 11 is a vehicle, 12 is an on-vehicle communication device, and 13 is a vehicle-mounted device.

Claims (8)

An electronic license plate comprising a license plate of a vehicle and an ID tag having a CPU, a memory, a communication circuit, and an antenna, wherein the memory includes a publicly-used ROM for storing public data and a public program, and a private-use ROM. The ID tag is composed of a private use ROM provided for use and a RAM shared for public use and private use. An electronic license plate configured to receive data, store the data in the ROM for private use, and execute the data. The on-vehicle communication device mounted on a vehicle near the electronic license plate, wherein the communication function is the same as that of a road communication device having a communication function related to public use of the electronic license plate. A vehicle having a function of transmitting a private program and data to the electronic license plate, and a function of wirelessly exchanging information with the electronic license plate when executing the private program received by the electronic license plate. Communication device. The on-vehicle communication device according to claim 2, wherein the on-vehicle communication device has a function of exchanging information with an on-vehicle device for a car navigation system, a telematics system, or the like. The on-vehicle communication device according to claim 2, wherein the on-vehicle communication device has a function of detecting whether the electronic license plate is communicating with the on-road communication device. The on-vehicle communication device measures a communication time between the electronic license plate and the road communication device, and when the cumulative communication time reaches a predetermined value, notifies the vehicle-mounted device of the fact. Item 5. The on-vehicle communication device according to any one of Items 2 to 4. The on-vehicle communication device monitors communication between the electronic license plate and the on-road communication device. The on-vehicle communication device according to any one of claims 2 to 5, wherein the information is stored and transmitted to the in-vehicle device when an inquiry from the in-vehicle device is made. The electronic license plate according to claim 1, wherein the electronic license plate transmits an available capacity in response to an inquiry about an available capacity of the private use ROM from the on-vehicle communication device or the on-road communication device. . The electronic license plate according to claim 1, wherein the electronic license plate performs a predetermined security process at the time of starting communication with another communication device, and the security process differs for each communication device.

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