JP2007112326A - On-vehicle equipment for narrow band communication of sophisticated road traffic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide on-vehicle equipment for DSRC of low power consumption which is capable of prolonging the lifetime of a battery. <P>SOLUTION: The on-vehicle equipment comprises a radio unit 30 for performing the transmission/reception of the data to/from an on-road station, a vehicular operational state determination unit 40 which detects the intensity of the radiation radio wave radiated from the periphery and determines the operational state of a vehicle concerned based on the detected intensity of the radio wave, a battery 20 for supplying the power to the radio unit 30 and the vehicular operational state determination unit 40, and a control unit 10 which sets the vehicular operational state determination unit 40 to be in a periodically operational state by periodically supplying power to the vehicular operational state determination unit 40 from the battery 20, and changes the normal operational mode for supplying power from the battery 20 to the radio unit 30 and the vehicular operational state determination unit 40 and the power-saving mode for stopping the power supply from the battery to the radio unit 30 and the vehicular operational state determination unit 40 based on the result of the operational state determination result of the vehicle concerned determined by the vehicular operational state determination unit 40. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle-mounted device for narrow-range communication (Dedicated Short-Range Communication) used in an intelligent transport system, and more particularly to a vehicle-mounted device for narrow-range communication (DSRC) capable of reducing power consumption.

In general, a DSRC (Dedicated Short Rang Communications) system is an advanced road traffic communication system that uses a microwave band radio wave and performs communication only in a limited range on the road.
By performing wireless communication between the on-board device for narrow area communication (DSRC) installed on the road side and the vehicle station installed on the road, various data exchanges, etc., such as toll collection and road information provision It is a system that provides services and benefits drivers and managers such as roads and parking lots.
As a system using DSRC, there are various applications such as automatic toll collection system (Electronic Tool Collection System: abbreviated as ETC), gas station, toll collection at drive-through, provision of traffic information, etc. It is considered.

In such applications, as represented by environmental road pricing, in applications that plan discounts on tolls for vehicles that have passed a specific route, or other applications, “limited time discount” or “ There is also a usage method such as “customer discount”, and it is planned that DSRC settlement will be used not only for billing but also for discount services.
Environmental road pricing refers to charging for vehicles entering areas with significant traffic congestion and air pollution. Experiments have already begun in Tokyo and the Kinki region for commercialization.

For example, Patent Document 1 (Japanese Patent No. 2994362) discloses an “antenna, a data transmission / reception circuit that transmits / receives data to / from a road device via the antenna, and a first power supply circuit that supplies power to the data transmission / reception circuit; , Receiving electric field intensity detection means for measuring the intensity of the radio wave received from the road unit via the antenna, and communication in an area where the intensity of the radio wave from the road machine exceeds a predetermined value based on the output of the received electric field intensity detection means A communication area detecting means for recognizing as an area; a power supply starting means for starting the first power supply circuit based on an output of the communication area detecting means; a received electric field strength detecting means; a communication area detecting means; An onboard vehicle for narrow area communication of an intelligent road transportation system including a second power supply circuit to be supplied is disclosed.
In the conventional DSRC on-board unit as shown in Patent Document 1, power is supplied from the on-board battery to the radio unit and the data processing unit, and both the radio unit and the data processing unit circuit ( Alternatively, power is supplied to some circuits), and each circuit is continuously driven.

In general, the radio unit (that is, the data transmission / reception circuit) is realized by a low noise circuit configuration so as not to cause a bit error in received data, and energization to the control unit is also necessary. The DSRC in-vehicle device consumes a large amount of current (usually about 100 mA in a standby state).
Recently, there is an increasing need for battery-powered DSRC in-vehicle devices for the purpose of using DSRC in-vehicle devices for motorcycles (motorcycles) and improving mountability of in-vehicle devices.
However, the conventional DSRC vehicle-mounted device has a large current consumption (for example, about 100 mA) in the radio unit and the control unit as described above.
Therefore, even when a battery with a battery capacity (about 500 mAHh) used for a mobile phone is used, for example, when it is used with continuous energization, the continuous usable time is as short as about 5 hours, which is practical. No.
Further, even when the vehicle on which the DSRC on-board device is installed is parked and it is not necessary to use the DSRC on-vehicle device, the battery is consumed wastefully because the power is always supplied.
Japanese Patent No. 2994362 (FIG. 1, paragraph 0029)

Conventional DSRC in-vehicle devices normally consume large amounts of current in the radio unit and control unit, and batteries are wasted even under conditions that do not require the use of applications such as ETC. There was a problem that there was no sex.
The present invention has been made to solve the above-described problems, and when it is not necessary, the power consumption of the DSRC in-vehicle device can be suppressed, and the low power consumption DSRC (narrow region communication) in-vehicle device that can extend the battery life. The purpose is to obtain.

  An in-vehicle device for narrow area communication of an intelligent road traffic system according to the present invention is mounted on a vehicle moving on a road and transmits / receives data by narrow area communication with a roadside station installed on the road. , Which detects the intensity of the radio wave radiated from the periphery of the on-board unit for narrow area communication and the radio unit that transmits and receives data to and from the roadside station. A vehicle operation state determination unit that determines an operation state of the own vehicle (that is, an operation state of the engine of the own vehicle or other in-vehicle device mounted on the own vehicle) based on the received radio wave intensity, the radio unit, and the vehicle A battery for supplying power to the operation state determination unit, and periodically supplying power from the battery to the vehicle operation state determination unit to bring the vehicle operation state determination unit into an operation state. Determined self A normal operation mode in which power is supplied from the battery to the wireless unit and the vehicle operating state determination unit based on a vehicle operating state determination result, and power supply from the battery to the wireless unit and the vehicle operating state determination unit is stopped. And a control unit that switches between power modes.

  According to this invention, the control unit determines whether or not the operation state of the own vehicle (that is, whether or not the engine of the own vehicle is operating, or whether other in-vehicle devices mounted on the own vehicle are operating). ) Is switched between the normal operation mode and the power saving mode on the basis of the determination result of (), when the operation of the vehicle-mounted device for narrow area communication (DSRC) is not necessary (that is, the engine of the own vehicle or other installed in the own vehicle) When the in-vehicle device is operating), the power saving mode can be automatically set, and a DSRC in-vehicle device with low power consumption can be realized.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In addition, the same code | symbol represents the same thing or an equivalent thing between each figure.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of an onboard device for narrow area communication (DSRC) in an intelligent road traffic system according to Embodiment 1 of the present invention. For example, an intelligent road traffic system mounted on a motorcycle (motorcycle). 1 shows a configuration of a vehicle-mounted device for narrow-area communication (DSRC) (hereinafter also abbreviated as “DSRC-mounted device”).
As shown in the figure, the DSRC OBE according to the present embodiment includes a control unit 10 that controls the entire DSRC OBE, a battery 20 that supplies power to the control unit 10 and the like, a roadside wireless device that is a roadside station (not shown) ) Detects noise radiated from the ignition coil of the vehicle (for example, a motorcycle) engine as a mobile station that communicates with the mobile station, and determines whether the engine of the vehicle is operating. The vehicle operation state determination unit 40 is configured.

The control unit 10 has a power saving mode and a normal operation mode. In the power saving mode, the control unit 10 is periodically activated in the normal operation mode to supply electric power supplied from the battery 20 to the vehicle operation state determination unit 40, and the vehicle operation state The determination unit 40 is periodically put into an operating state.
In addition, the control unit 10 supplies power supplied from the battery 20 to the radio unit 30 and the vehicle operation state determination unit 40 in the normal operation mode.
The vehicle operation state determination unit 40 detects the presence or absence of noise radiation radiated from the ignition coil of the engine of the own vehicle according to the radio wave condition around the DSRC on-vehicle device, and determines whether the engine is on / off. That is, the vehicle operation state determination unit 40 determines that the engine is on when noise radiation radiated from the ignition coil is detected, and determines that the engine is off when noise radiation is not detected.
When the vehicle operation state determination unit 40 determines that the engine of the host vehicle is off, the control unit 10 stops the power supply to the vehicle operation state determination unit 40 and switches from the normal operation mode to the power saving mode. Return to.
On the other hand, when the vehicle operation state determination unit 40 determines that the engine of the host vehicle is on, the normal operation mode is continued and power supply to the wireless unit 30 is started.

Even in the normal operation mode, the vehicle operation state determination unit 40 periodically performs on / off determination of the engine of the host vehicle, and if the engine is determined to be in the off state, the control unit 10 includes the radio unit 30. In addition, the power supply from the battery 20 to the vehicle operation state determination unit 40 is stopped, and the power saving mode is restored.
Note that the control unit 40 stops the power supply to the radio unit 30 during the period in which the vehicle operation determination unit performs on / off determination of the engine of the own vehicle in the normal operation mode.

Next, the operation of the vehicle operation state determination unit 40 will be described.
The vehicle operating state determination unit 40 detects the noise radio wave intensity around the vehicle-mounted device.
Fig. 2 shows the change in radio field intensity around the vehicle-mounted device when the engine of the vehicle is operated from off to on to off. The horizontal axis of the graph in Fig. 2 is the elapsed time, and the vertical axis is the radiation from the engine. Is the radio field intensity (noise intensity) of the noise to be generated.
In FIG. 2, T _ON indicates the time when the engine is turned on, and T _OFF indicates the time when the engine is turned off.
As shown in FIG. 2, the radio wave intensity (noise intensity) of noise radiated from the engine changes with the on / off state of the engine.
The vehicle operation state determination unit 40 determines that the engine of the host vehicle is on when the intensity of the radio wave radiated from the engine is higher than a predetermined determination level L _ON .
Further, when the intensity of the radio wave radiated from the engine is smaller than a preset determination level L _OFF , it is determined that the engine of the host vehicle is off.

  As described above, the on-board device for narrow area communication of the intelligent transportation system according to the present embodiment is mounted on a vehicle moving on a road, and data is transmitted by narrow area communication with a roadside station installed on the road. Intensity of radiated radio waves radiated from the periphery of the wireless unit 30 that transmits and receives data to and from roadside stations and the on-board unit for narrow-area communication Vehicle operation state determination unit 40 for determining the operation state of the vehicle based on the detected radio field intensity, battery 20 for supplying power to radio unit 30 and vehicle operation state determination unit 40, and vehicle operation The state determination unit 40 is periodically supplied with power from the battery 20 to set the vehicle operation state determination unit 40 to the operation state, and based on the operation state determination result of the own vehicle determined by the vehicle operation state determination unit 40. And car And a control unit 10 for switching between the power saving mode to the normal operation mode and the wireless unit 30 and the vehicle operating state determination unit 40 for supplying power from the battery 20 to the operation state determination unit 40 stops the power supply from the battery 20.

In addition, when the radiated radio wave radiated from the vicinity of the on-vehicle device for narrow area communication is a noise radio wave radiated from the ignition coil of the engine of the own vehicle, the vehicle operation state determination unit 40 determines the ignition of the engine of the own vehicle. Detects the intensity of noise radio waves radiated from the coil.
Then, based on the radio wave intensity detected by the vehicle operation state determination unit 40, the operation state of the own vehicle (that is, the on / off state of the engine) is determined.
The vehicle operation state determination unit 40 determines that the engine of the host vehicle is on when the detected radio wave intensity is greater than a predetermined determination level.

  Therefore, according to the on-vehicle device for narrow area communication of the intelligent transportation system according to the present embodiment, the control unit 40 switches between the normal operation mode and the power saving mode based on the determination result of the operation state of the own vehicle. When the operation of the on-board unit for regional communication is not necessary (for example, when the engine of the host vehicle is off), the power saving mode can be automatically set, and the power consumption of the battery 20 is reduced. A DSRC on-vehicle device for electric power can be realized.

Further, the control unit 10 may stop the power supply to the radio unit 30 during the period in which the vehicle operation state determination unit 40 determines the operation state of the host vehicle in the normal operation mode.
This suppresses noise radiated from the DSRC on-board device itself (that is, noise radiated from the radio unit 30), and the radiated radio wave detection means detects the radio wave radiated from the encidin by the noise radiated from the DSRC on-vehicle device itself. It can prevent that detection is inhibited.
Furthermore, the DSRC in-vehicle device is not hindered by noise radiated from the radio unit 30 by stopping the power supply to the radio unit 30 while the vehicle operation state determination unit 40 determines the operation state of the host vehicle. It is also possible to accurately detect radio waves radiated from other vehicle-mounted devices (for example, a navigation system described later) and accurately determine the operating state of the other vehicle-mounted devices.

Embodiment 2. FIG.
The vehicle-mounted device for narrow area communication of the intelligent road traffic system according to the present embodiment is the vehicle-mounted device for narrow-area communication of the intelligent road traffic system according to the first embodiment described above, and the vehicle operation state determination unit 40 emits radiation from the ignition coil. If the difference between the noise signal strength of the ignition coil detected this time and the noise signal strength of the ignition coil detected last time is greater than the predetermined judgment level The engine is determined to be on.
FIG. 3 shows the noise radio field intensity of the ignition coil detected by the vehicle operating state determination unit 40 of the vehicle-mounted device for narrow area communication of the intelligent road traffic system according to the present embodiment.
In FIG. 3, the symbol “L” indicates the level of noise radio wave intensity of the ignition coil when the engine is on.
Based on the difference between the level L of the noise radio wave intensity of the ignition coil detected last time and the level L of the noise radio wave intensity of the ignition coil detected this time, it is determined whether the engine of the host vehicle is on or off.

As described above, in the present embodiment, the vehicle operation state determination unit 40 detects and temporarily stores the radio wave intensity of noise radiated from the ignition coil a plurality of times when the engine of the host vehicle is on. If the difference (change amount) between the noise field intensity of the ignition coil detected and stored this time and the noise field intensity of the ignition coil previously detected and stored is greater than a predetermined judgment level, the engine of the host vehicle Is surely turned on.
Thus, in the present embodiment, since the engine on / off is determined based on the amount of change in the intensity of the noise radio wave radiated from the ignition coil when the engine is on, the engine ON / OFF can be determined.

Embodiment 3 FIG.
In the present embodiment, for example, an example in which a DSRC on-vehicle device according to the present invention is mounted on a vehicle mounted with a navigation system including an FM transmitter will be described.
FIG. 4 is a diagram showing a configuration of the vehicle-mounted device for narrow area communication (DSRC) of the intelligent road traffic system according to the present embodiment.
As shown in the figure, the vehicle-mounted device for narrow area communication (DSRC) according to this embodiment is a control unit 11 that controls the entire DSRC vehicle-mounted device, a battery 20 that supplies power to the control unit 11 and others, and a roadside station. The wireless unit 30 that communicates with a roadside wireless device (not shown), and other vehicle-mounted devices are operating by detecting radio waves from other vehicle-mounted devices (for example, navigation systems) mounted on the vehicle. Vehicle operation state determination unit 41 for determining whether or not, a switch (initial switch) 50 for a user to perform an initial setting operation of the DSRC OBE, a non-volatile memory (EEPROM) for recording an initial setting state of the DSRC OBE 60.

As in the case of the first embodiment described above, the control unit 11 has a power saving mode and a normal operation mode, and is periodically activated in the normal operation mode in the power saving mode, and the vehicle operation state determination unit 41 receives the battery 20. The electric power supplied from the vehicle is supplied, and the vehicle operation state determination unit 41 is periodically set to the operation state.
The vehicle operation state determination unit 41 detects a radio wave from another on-vehicle device (for example, a navigation system) mounted on the own vehicle, and determines whether another on-vehicle device is operating (that is, the other on-vehicle device is On or off).
In the following description, it is assumed that the other vehicle-mounted device is a navigation system.

When the vehicle operation state determination unit 41 determines that the navigation system is in the off state, the control unit 11 stops the power supply to the vehicle operation state determination unit 41 and returns to the power saving mode.
On the other hand, when the vehicle operation state determination unit 41 determines that the navigation system is in the on state, the normal operation mode is continued and power supply to the wireless unit 30 is started.
Even in the normal operation mode, the vehicle operation state determination unit 41 periodically performs on / off determination of the navigation system mounted on the host vehicle, and if it is determined that the navigation system is in the off state, the control unit 11 stops the power supply to the radio unit 30 and the vehicle operation state determination unit 41 and returns to the power saving mode.

Next, the operation of the vehicle operation state determination unit 41 in the present embodiment will be described.
As in the case of the first embodiment, the vehicle operation state determination unit 41 detects the radio field intensity around the DSRC in-vehicle device.
An example of the radio field intensity around the DSRC on-board unit is shown in FIG.
FIG. 5A shows the radio field intensity around the on-board DSRC device when the navigation system is powered off (non-operating), and FIG. 5B is the diagram when the navigation system is powered on (operating). It is a figure showing radio wave intensity, a horizontal axis of a graph is frequency and a vertical axis is radio wave intensity.
As shown in FIG. 5A, when the power of the navigation system is off, radio waves (for example, A, B, C, D in the figure) from the FM broadcast station are detected.
On the other hand, as shown in FIG. 5B, when the power of the navigation system is on, in addition to the radio wave from the FM broadcast station (for example, A, B, C, D in the figure) Radio waves (T in the figure) from the FM transmitter are detected.

The vehicle operation state determination unit 41 measures the radio field intensity for each frequency band used for each channel of the FM broadcast station and for some frequency bands used for the output frequency of the FM transmitter in the navigation system.
If the radio field strength T degree in the frequency band used for the output frequency of the FM transmitter is greater than a preset determination level (L _ON ), it is determined that the power of the navigation system is on.
Further, when the radio wave intensity T in the frequency band used for the output frequency of the FM transmitter is smaller than a predetermined determination level (L _OFF ), it is determined that the power of the navigation system is off.
In other cases, the previous judgment result is retained.

Next, initial processing (initial setting processing) of the DSRC on-vehicle device in the present embodiment will be described.
The initial process is generally performed only once when the vehicle-mounted device is attached.
In order to perform the initial process, the user turns off the main switch of the vehicle and waits until a predetermined time in which the DSRC in-vehicle device enters the power saving mode has elapsed.
Next, the user turns on the switch (initial switch) 50 connected to the control unit 11 of the DSRC OBE for a predetermined time in a state where the OBE is in the power saving mode.
The controller 11 of the on-board DSRC device is activated when the switch 50 is turned on, starts power supply to the vehicle operation state determination unit 41, and monitors the on / off state of the switch 50.
The vehicle operation state determination unit 41 measures the radio field intensity for all frequency bands of each channel of the FM broadcast station or for some frequency bands used for the output frequency of the FM transmitter in the navigation system.
In the control unit 11, when the switch is kept on for a predetermined time (about 5 seconds), the radio wave intensity measured by the vehicle operation determination unit 41 is temporarily recorded.

Next, the user turns on the main switch of the vehicle and then turns off the switch of the on-board DSRC device with the switch 50 of the on-board device of the DSRC turned on.
In the control unit 11, when the switch 50 is kept off for a predetermined time (about 5 seconds) from the time when the switch 50 of the on-board DSRC device is turned off, the vehicle operation determination unit for each frequency band in which measurement is performed. A value obtained by adding 3 dBm to an intermediate value between the radio field intensity measured at 41 and the temporarily recorded radio field intensity is recorded in the EEPROM as a system power-on determination level and a value obtained by subtracting 3 dBm as a power-off determination level.
If the difference between the measured radio wave intensity and the temporarily recorded radio wave intensity is smaller than 6 dBm, the frequency band is recorded as an invalid band in the EEPROM.
The vehicle operation determination unit 41 performs determination processing based on the determination level recorded in the EEPROM 60.
The invalid band and the recorded band are skipped without performing the determination process.

As described above, the vehicle operation state determination unit 41 of the on-vehicle device for narrow area communication of the intelligent road traffic system according to the present embodiment determines the operation state of another on-vehicle device (navigation system) mounted on the own vehicle. When it has a function to detect the intensity of the radiated radio wave of a predetermined frequency band emitted by another on-vehicle device (navigation system), and the intensity of the radiated radio wave to be detected is larger than a preset judgment level Is determined that the power of the other vehicle-mounted device (navigation system) is off when the power of the other vehicle-mounted device (navigation system) is on and the detected radio wave intensity is lower than the preset judgment level. To do.
Therefore, it is possible to easily determine the operation state of another on-vehicle device (navigation system), and when the other on-vehicle device (navigation system) is operating, the DSRC on-vehicle device is automatically switched to the power saving mode, and the battery Can be saved.

Further, in the present embodiment, the vehicle operation state determination unit 41 detects the level of the radiated radio wave detected when the main power source of the vehicle is off and the level of the radiated radio wave detected when the main power source of the vehicle is on. It has a function of calculating and recording a determination level according to the detection level, and determining whether to turn on / off the power of another vehicle-mounted device (navigation system) based on the recorded determination level.
Therefore, since the determination level can be set according to the level of the radiated radio wave that varies depending on the in-vehicle device, the determination accuracy of the vehicle operation state determination unit 41 can be improved.

Embodiment 4 FIG.
The basic configuration and operation of the vehicle-mounted device for narrow area communication (DSRC) of the intelligent road traffic system according to the present embodiment are the same as those for the narrow area communication (DSRC) of the intelligent road traffic system according to the third embodiment shown in FIG. Since it is the same as the vehicle-mounted device, detailed operation description other than the operation of the vehicle operation state determination unit 41 is omitted.
The vehicle operation state determination unit 41 detects the radio wave intensity around the DSRC on-vehicle device.
FIG. 6 shows an example of the radio field intensity around the DSRC in-vehicle device in the present embodiment.
FIG. 6A shows the radio field intensity around the DSRC vehicle-mounted device when the power of the navigation system, which is another vehicle-mounted device, is off (non-operation), and FIG. 6B shows that the navigation system is powered on ( The horizontal axis of the graph represents frequency, and the vertical axis represents radio field intensity.
As shown in FIG. 6A, when the power of the other vehicle-mounted device (navigation system) is off, radio waves (for example, A, B, C, D in the figure) from the FM broadcast station are detected. The
On the other hand, as shown in FIG. 6B, when the navigation system is powered on, in addition to radio waves from FM broadcast stations (for example, A, B, C, and D in the figure), the FM transmitter (T in the figure) is detected.

The vehicle operation state determination unit 41 measures the radio field intensity and temporarily records the frequency bands of all the channels of the FM broadcast station and the frequency bands used for the output frequency of the FM transmitter of the navigation system.
As shown in FIG. 6 (b), the radio wave of each channel of the FM broadcast station (for example, A, B, C in the figure) and the radio wave from the FM transmitter (T in the figure) are respectively shown in FIG. The detection judgment level is set.
In FIG. 6B, the broken line indicates the determination level for the radio wave in each frequency band, the upper broken line corresponds to “L _ON ” in FIG. 5B, and the upper broken line indicates FIG. This corresponds to “L _OFF ” in (b).

If the radio field intensity of each frequency band measured is greater than the judgment level set for each band, radio waves are detected for that frequency band, and the radio field intensity of any frequency band of the measured channel is If it is smaller than the set judgment level, no radio wave is detected for that frequency band, and otherwise the previous detection result of radio wave intensity in each frequency band is held.
If the radio wave detection determination result is “detected” in all frequency bands, it is determined that the power of the navigation system is on.
On the other hand, if it is determined that radio waves are “not detected” in all frequency bands, it is determined that the power of the navigation system is off.
In other cases, the previous determination result is held.

Finally, the initial process (initial setting process) of the DSRC vehicle-mounted device in the present embodiment will be described.
The initial process is generally performed only once when the vehicle-mounted device is attached.
In order to perform the initial process, the user turns off the main switch of the vehicle and waits until a predetermined time in which the DSRC in-vehicle device enters the power saving mode has elapsed.
Next, the user turns on the switch (initial switch) 50 connected to the control unit of the vehicle-mounted device for a predetermined time in a state where the vehicle-mounted device is in the power saving mode.
The controller 11 of the DSRC on-vehicle device is activated when the switch 50 is turned on, starts supplying power to the vehicle operation state determination unit 41, and monitors the on / off state of the switch.
The vehicle operation state determination unit 41 measures the radio field intensity for each channel of the FM broadcast station or for each of a part of bands used for the output frequency of the FM transmitter in the navigation system.

When the switch is kept on for a predetermined time (about 5 seconds), the control unit 11 temporarily records the radio wave intensity measured by the vehicle operation determination unit 41.
Next, the user turns on the main switch of the vehicle with the switch 50 of the on-board DSRC device turned on, and then turns off the switch of the on-board DSRC device.
In the control unit 11, when the switch 50 is continuously turned off for a predetermined time (about 5 seconds) from the time when the switch 50 of the DSRC on-vehicle device is turned off, the vehicle operation determination unit 41 performs measurement for each frequency band being measured. The difference between the recorded radio wave intensity and the temporarily recorded radio wave intensity is recorded in the EEPROM as a judgment level difference.
If the determination level difference is smaller than 6 dBm, the frequency band is recorded in the EEPROM 60 as an invalid band.
The vehicle operation determination unit 41 performs a determination process based on the determination level difference recorded in the EEPROM 60.
The invalid band and the recorded band are skipped without performing the determination process.

As described above, the vehicle operation state determination unit 41 of the on-vehicle device for narrow area communication of the intelligent road traffic system according to the present embodiment detects a radiated radio wave for each of a plurality of frequency bands, and has a determination level. It is set for each frequency band, and when it is determined that there is a detection of radiated radio waves in all frequency bands, it is determined that the power of other in-vehicle device (navigation system) is on, and in all frequency bands If it is determined that there is no detection of radiated radio waves, it is determined that the power of the other vehicle-mounted device (navigation system) is off, and otherwise, the previous determination result is retained.
Therefore, it is possible to prevent erroneous determination of power on / off of other vehicle-mounted devices (navigation system) due to radio waves temporarily coming from outside the vehicle, and reliably while other vehicle-mounted devices (navigation system) are in operation. The DSRC OBE can be automatically set to a power saving mode.

Further, in the present embodiment, the vehicle operation state determination unit 41 detects the level of the radiated radio wave detected when the main power of the vehicle is off and the level of the radiated radio wave detected when the main power of the vehicle is on. The determination level is calculated and recorded according to the detection level, and the on / off determination of the power of the other vehicle-mounted device is performed based on the recorded determination level difference.
Therefore, it is possible to set the determination level difference according to the level of the radiated radio wave that varies depending on the in-vehicle device, and the determination accuracy of the vehicle operation state determination unit 41 can be improved.

  The present invention is useful for realizing a low power consumption DSRC vehicle-mounted device that can suppress the current consumption when the power saving mode is not required.

It is a block diagram which shows the structure of the onboard equipment for narrow area communication of the intelligent transport system by Embodiment 1. FIG. It is a figure which shows the change of the radio field intensity around onboard equipment when the engine of the own vehicle is operated off-> on-> off. In Embodiment 2, it is a figure which shows the noise electromagnetic wave intensity | strength detected by the vehicle operation state determination part. It is a block diagram which shows the structure of the onboard equipment for narrow area communication of the intelligent transport system by Embodiment 3. It is a figure which shows the example of the radio wave intensity | strength around DSRC onboard equipment in Embodiment 3. FIG. It is a figure which shows the example of the electromagnetic wave intensity of the DSRC onboard equipment periphery in Embodiment 4. FIG.

Explanation of symbols

10, 11 Control unit 20 Battery 30 Radio unit 40, 41 Vehicle operation state determination unit

Claims (10)

An in-vehicle device for narrow area communication of an intelligent road transportation system that is mounted on a vehicle moving on a road and transmits / receives data by narrow area communication with a roadside station installed on the road,
A radio unit that transmits and receives data to and from the roadside station;
A vehicle operation state determination unit that detects the intensity of a radiated radio wave radiated from the periphery of the on-board unit for narrow area communication, and determines the operation state of the own vehicle based on the detected radio field intensity;
A battery for supplying power to the radio unit and the vehicle operating state determination unit;
The vehicle operation state determination unit is periodically powered from the battery to place the vehicle operation state determination unit in an operation state, and based on the operation state determination result of the vehicle determined by the vehicle operation state determination unit The wireless unit and the vehicle operation state determination unit include a normal operation mode for supplying power from the battery, and the wireless unit and the vehicle operation state determination unit for switching between a power saving mode for stopping power supply from the battery. A vehicle-mounted device for narrow area communication of an intelligent road traffic system.   The vehicle operation state determination unit detects noise radio field intensity radiated from an ignition coil of an engine of the host vehicle, and determines an operation state of the host vehicle based on the detected radio field intensity. A vehicle-mounted device for narrow area communication of the described intelligent transportation system.   3. The intelligent road traffic system according to claim 2, wherein the vehicle operation state determination unit determines that the engine of the vehicle is on when the detected radio wave intensity is greater than a predetermined determination level. In-vehicle device for narrow area communication.   The said control part stops the electric power feeding to the said radio | wireless part during the period when the said vehicle operation state determination part determines the operation state of the own vehicle at the time of a normal operation mode. A vehicle-mounted device for narrow area communication of an intelligent transportation system according to any one of the above.   The vehicle operation state determination unit detects and temporarily stores the radio wave intensity of noise radiated from the ignition coil a plurality of times when the engine of the host vehicle is on, and detects and stores the ignition coil detected this time. The engine is determined to be on if the difference between the noise radio field intensity of the ignition coil and the noise radio field intensity of the ignition coil previously detected and stored is greater than a predetermined determination level. In-vehicle device for narrow area communication of intelligent transportation system.   The vehicle operation state determination unit determines an operation state of another on-vehicle device mounted on the own vehicle, and has a function of detecting the intensity of a radiated radio wave of a predetermined frequency band emitted from the other on-vehicle device. If the detected radio wave intensity is greater than the preset judgment level, the other on-board device is powered on and the detected radio wave intensity is less than the preset judgment level 2. The on-vehicle device for narrow area communication of an intelligent road traffic system according to claim 1, wherein it is determined that the power source of the other on-vehicle device is off.   The vehicle operation state determination unit calculates and records a determination level based on a detection level of the radiated radio wave detected when the main power source of the vehicle is off and a detection level of the radiated radio wave detected when the main power source of the vehicle is on. And a function for determining whether to turn on or off the power of the other vehicle-mounted device on the basis of the recorded determination level. Onboard equipment.   The vehicle operation state determination unit detects a radiated radio wave for each of a plurality of frequency bands, and the determination level is set for each of the plurality of frequency bands, and the radiated radio wave is detected in all the frequency bands. If it is determined that the power of the other vehicle-mounted device is on, it is determined that the radio wave is not detected in all frequency bands, and the power of the other vehicle-mounted device is determined to be off. In other cases, the previous determination result is retained, and the on-vehicle device for narrow area communication of the intelligent transportation system according to claim 6.   The vehicle operating state determination unit calculates and records the determination level based on the detection level of the radiated radio wave detected when the main power source of the vehicle is off and the detection level of the radiated radio wave detected when the main power source of the vehicle is on. The on-vehicle device for narrow area communication of an intelligent road traffic system according to claim 6, wherein on / off determination of the power source of the other on-vehicle device is performed based on the recorded determination level difference.   The on-vehicle device for narrow area communication of an intelligent road traffic system according to any one of claims 6 to 10, wherein the other on-vehicle device is a navigation system.

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