JP2008191012A - Communication system, on-vehicle device, vehicle and transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system capable of precisely specifying a travel position of the own vehicle and precisely obtaining a distance from a prescribed position ahead of the own vehicle in the travel direction, to provide an on-vehicle device and a transmitter making up the communication system and to provide a vehicle equipped with the in-vehicle device. <P>SOLUTION: When the on-vehicle device 20 determines that the own vehicle exists in an area A where a communication with an optical beacon 10 can be carried out, the position of the own vehicle in the area A is precisely specified, and the distance from a stop line P is precisely computed, based on positional information of the area A stored in the in-vehicle device 20, positional information of transmitters 30, 40, a distance between the upstream end of the area A and the stop line P, and an arrival time difference between respective signals transmitted by the transmitters 30, 40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication system that can specify the position of a vehicle traveling on a road with high accuracy, an in-vehicle device and a transmitter that constitute the communication system, and a vehicle including the in-vehicle device.

Conventionally, in order to prevent traffic accidents between vehicles in and around the intersection or between a vehicle and a pedestrian, the display information of the light color of the traffic light installed at the intersection is used for vehicles traveling toward the intersection. Whether the vehicle can be safely stopped before the intersection based on the received display information, or the vehicle can safely pass through the intersection. There is a system that determines whether or not the vehicle can be operated and alerts the driver with voice according to the determination result. In addition, a traffic light-linked vehicle speed control device that determines whether or not it is possible to safely pass an intersection based on the display information of the traffic signal received by the in-vehicle device and performs vehicle brake control according to the determination result is provided. It has been proposed (see Patent Document 1).
Japanese Patent No. 2806801

  When the vehicle is safely stopped before the intersection, it is necessary to stop the vehicle surely before the stop line provided near the intersection, and it is necessary to accurately grasp the distance from the vehicle to the stop line. However, in the apparatus of Patent Document 1, since the distance from the vehicle to the stop line cannot be accurately determined even when the vehicle is decelerated automatically, the vehicle is surely stopped before the stop line. This is difficult and may cause problems such as overrun. For this reason, in the conventional technology, there has been an inadequate aspect for preventing the traffic accident at the intersection by surely stopping the vehicle before the stop line.

  On the other hand, a vehicle navigation system function using GPS (Global Positioning System) detects the traveling position of the host vehicle and identifies the position of the intersection based on the map data, so that the vehicle is ahead of the host vehicle from the current traveling position. The distance to the position of the stop line before the intersection can be calculated. However, in position detection by GPS or the like, a sufficient number of radio waves such as GPS cannot often be received due to the influence of buildings or vehicles in urban areas, and errors become large, so accurate driving support can be performed. It was difficult.

  The present invention has been made in view of such circumstances, and can accurately identify the traveling position of the host vehicle and accurately determine the distance to a predetermined position ahead of the traveling direction of the host vehicle. It is an object of the present invention to provide a system, an in-vehicle device and a transmitter constituting the communication system, and a vehicle including the in-vehicle device.

  A communication system according to a first aspect of the present invention is a communication system comprising a plurality of transmitters that transmit signals synchronized with each other in the same cycle, and an in-vehicle device that receives signals transmitted by the transmitter. A unit that stores a predetermined area on the road and position information of the plurality of transmitters, a determination unit that determines whether or not the vehicle exists in the area, and the plurality of transmitters transmit The time difference acquisition means for acquiring the arrival time difference of each signal, and the vehicle position based on the arrival time difference acquired by the time difference acquisition means and the position information when the determination means determines that the vehicle is in the area And a specifying means for specifying.

  A communication system according to a second aspect of the present invention includes, in the first aspect of the present invention, an optical beacon that transmits predetermined information to the vehicle-mounted device, and when the determination unit receives the predetermined information from the optical beacon, It is configured to determine that it exists in the area.

  The communication system according to a third aspect of the present invention is the communication system according to the first or second aspect, wherein the specifying means is configured to specify a position with respect to a predetermined first point in the area, Road shape information acquisition means for acquiring road shape information relating to a road shape between a predetermined second point on the downstream side of the traveling direction of the vehicle from the region, road shape information acquired by the road shape information acquisition means, and And calculating means for calculating a distance to the second point based on the position specified by the specifying means.

  In a communication system according to a fourth aspect based on the third aspect, the road shape information includes a distance, a gradient, and a gradient for each section obtained by dividing the road between the first point and the second point into one or a plurality of sections. It includes at least one of curvatures.

  A communication system according to a fifth invention is characterized in that, in the third or fourth invention, at least one of the plurality of transmitters and optical beacons comprises a transmission means for transmitting the road shape information to the vehicle-mounted device. And

  A communication system according to a sixth invention is the communication system according to any one of the first to fifth inventions, wherein the in-vehicle device includes a storage unit that stores height information of a mounting position, and the specifying unit includes the height information. Based on this, the vehicle position is specified.

  A communication system according to a seventh aspect of the present invention is the communication system according to any one of the first to sixth aspects of the present invention, wherein the plurality of transmitters are provided with modulation means for modulating a signal and transmit the signal modulated by the modulation means. The vehicle-mounted device includes a demodulating unit that demodulates the received signal, and the time difference obtaining unit is configured to obtain the arrival time difference of each signal based on the signal demodulated by the demodulating unit. It is characterized by being.

  A communication system according to an eighth aspect of the present invention is the communication system according to any one of the first to sixth aspects, wherein the plurality of transmitters include allocation means for allocating signals to orthogonal frequency multiplexing carrier waves, and the allocation means allocates signals. The vehicle-mounted device includes a receiving unit that receives the carrier wave, and the time difference acquisition unit acquires the arrival time difference of each signal based on the received carrier wave. It is comprised by these.

  A communication system according to a ninth invention is the communication system according to the seventh or eighth invention, wherein the plurality of transmitters are configured to transmit signals having rising edges at predetermined intervals, and the time difference obtaining means Based on the rising time of each signal, the arrival time difference between the signals is obtained.

  A communication system according to a tenth aspect of the present invention is the communication system according to any one of the first to sixth aspects, wherein the plurality of transmitters are configured to transmit a signal having an alternating waveform, and the time difference acquisition unit receives A feature is that the arrival time difference of each signal is acquired based on the phase difference of each signal.

  A communication system according to an eleventh aspect of the present invention is the communication system according to the tenth aspect, wherein the plurality of transmitters include modulation means for modulating a signal, and are configured to transmit a signal modulated by the modulation means. Comprises demodulation means for demodulating the received signal, and the time difference acquisition means is configured to acquire the arrival time difference of each signal based on the phase difference of each signal demodulated by the demodulation means. Features.

  In a communication system according to a twelfth aspect of the present invention, in any one of the first to sixth aspects, the one transmitter transmits the synchronization signal to another transmitter at a time earlier than the signal transmission time by a predetermined time. The other transmitter is configured to specify a time point when the synchronization signal is transmitted based on a time point when the synchronization signal is received and a distance to the one transmitter, and It is characterized by comprising determining means for determining a signal transmission time based on the time specified by the specifying means and the predetermined time.

  A communication system according to a thirteenth aspect of the present invention is the communication system according to any one of the first to sixth aspects, further comprising a synchronization transmitter that transmits a predetermined synchronization signal, wherein the plurality of transmitters are transmitted by the synchronization transmitter. Receiving means for receiving a synchronizing signal, and determining means for determining a time point for transmitting a signal based on the received synchronizing signal and the distance to the synchronizing transmitter.

  A communication system according to a fourteenth aspect of the present invention is the communication system according to any one of the first to sixth aspects, wherein the transmitter generates a reference period signal having a predetermined period, and a reference period signal generated by the generation means. And determining means for determining the period of the signal.

  A communication system according to a fifteenth aspect of the present invention is the communication system according to the fourteenth aspect, wherein one transmitter is configured to transmit a signal to another transmitter wirelessly or by wire, and the other transmitter receives the received signal. And adjusting means for adjusting the period of the reference periodic signal generated by the generating means, and the determining means determines the period of the signal based on the reference periodic signal whose period is adjusted by the adjusting means. It is configured as described above.

  A communication system according to a sixteenth aspect of the present invention is the communication system according to the fourteenth aspect, further comprising a period adjustment transmitter that transmits a period adjustment signal having a predetermined period, wherein the transmitter receives the period adjustment signal transmitted by the period adjustment transmitter. Receiving means, and adjusting means for adjusting the period of the reference periodic signal generated by the generating means based on the received period adjusting signal, and the determining means is a reference periodic signal whose period is adjusted by the adjusting means Based on the above, the period of the signal is determined.

  The communication system according to a seventeenth aspect of the present invention is the communication system according to any one of the first to sixth aspects, wherein the transmitter is configured to receive a signal transmitted from the GNSS satellite and to set a signal cycle based on the received signal. Determining means for determining.

  An in-vehicle device according to an eighteenth aspect of the present invention is an in-vehicle device that receives signals synchronized with each other in the same cycle, and means for storing a predetermined area on a road and position information of a plurality of transmitters, Determining means for determining whether or not the vehicle is in the area, time difference acquiring means for acquiring the arrival time difference between the signals transmitted by the plurality of transmitters, and the vehicle being present in the area by the determining means. When it is determined, the vehicle includes a specifying unit that specifies the vehicle position based on the arrival time difference acquired by the time difference acquisition unit and the position information.

  A vehicle according to a nineteenth aspect includes the on-vehicle device according to the above-described invention.

  A transmitter according to a twentieth aspect of the invention is a transmitter for transmitting signals synchronized with each other, and receiving means for receiving a synchronization signal transmitted from another transmitter at a time earlier than a signal transmission time by a predetermined time. And specifying means for specifying the time when the synchronization signal is transmitted based on the time when the receiving means receives the synchronization signal and the distance to the other transmitter, the time specified by the specifying means, and the And determining means for determining a time point at which the signal is transmitted based on a predetermined time.

  In the first invention, the eighteenth invention, and the nineteenth invention, it is determined whether or not the own vehicle exists in a predetermined area on the road by an in-vehicle device mounted on the vehicle traveling on the road. The predetermined area on the road can be, for example, a communication area on the road between a roadside device such as an optical beacon, a radio beacon, and a DSRC (Dedicated Short Range Communication) and a vehicle. When it is determined that the vehicle is in a predetermined area, the in-vehicle device receives signals transmitted by a plurality of (for example, two) transmitters that transmit signals synchronized with each other in the same cycle, and each received Get the arrival time difference of signals. The in-vehicle device obtains a distance difference between the distance between the own vehicle and one transmitter and the distance between the own vehicle and the other transmitter based on the acquired arrival time difference. In this case, the own vehicle exists on a hyperbola where the position of the two transmitters is the focal point and the distance difference is constant. The in-vehicle device identifies the position of the hyperbolic focus based on the pre-stored transmitter position information, and further uses the position on the hyperbola in the predetermined region as the vehicle position based on the position information of the predetermined region. Identify. Thereby, the traveling position of the own vehicle can be specified with high accuracy. The position information may be acquired and stored from, for example, a map database, or may be received from a roadside device and stored.

  In the second invention, the in-vehicle device determines that the own vehicle exists in the predetermined area when the predetermined information is received from the optical beacon. For example, when the in-vehicle device receives downlink information transmitted from the projector / receiver of the optical beacon, the in-vehicle device transmits uplink information including the vehicle ID of the own vehicle to the projector / receiver. When the optical beacon receives uplink information from the in-vehicle device, the optical beacon transmits predetermined downlink information including the lane notification information storing the vehicle ID included in the received uplink information to the in-vehicle device. When the predetermined downlink information is received, it can be determined that the vehicle is present in a predetermined area (in the communication area of the optical beacon). In addition, since the lane notification information included in the predetermined downlink information is configured in a format in which the lane number is associated with the vehicle ID of the own vehicle, the in-vehicle device automatically identifies the associated lane number. It can be recognized as a driving lane of a car. That is, by using an optical beacon, a predetermined area can be limited to a narrow range of almost one lane on the road, and the position of the own vehicle can be specified with higher accuracy.

  In the third invention, the position information of the predetermined first point in the predetermined region is stored, and the in-vehicle device sets the position of the own vehicle to the position relative to the first point (for example, the distance from the first point). L2). As a 1st point, it can be set as the point (upstream end) of the upstream of the vehicle advancing direction of a predetermined | prescribed area | region, for example. The in-vehicle device is road shape information (for example, distance L1) regarding the road shape between the first point and a predetermined second point (for example, a stop line before the intersection) that is downstream of the region in the traveling direction of the vehicle. To get. The vehicle-mounted device calculates a distance L1-L2 to the second point based on the acquired road shape information (for example, distance L1) and the specified position (distance L2 from the first point). Thereby, the distance to the predetermined position ahead of the traveling direction of the own vehicle can be obtained with high accuracy.

  In the fourth invention, the road shape information includes at least one of a distance, a gradient, and a curvature for each section obtained by dividing the road between the first point and the second point into one or a plurality of sections. . Thereby, regardless of the road shape between the first point and the second point, the distance between the first point and the second point can be acquired.

  In the fifth invention, at least one of the plurality of transmitters and optical beacons transmits the road shape information to the in-vehicle device. As a result, it is not necessary to store road shape information in advance in the vehicle-mounted device, and for example, road shape information necessary to calculate the distance from the vehicle to the front stop line every time it travels before the required intersection. Can be obtained.

  In the sixth invention, the in-vehicle device stores the height information of the mounting position when mounted on the vehicle, and specifies the own vehicle position based on the stored height information. Based on the arrival time difference (corresponding to the distance difference) of each signal received from the two transmitters, when the position of the own vehicle is specified on a hyperbola where the distance between the two transmitters is the focus and the distance difference is constant In addition, compared to the case where a constant value is used as the height from the road surface of the vehicle-mounted device, the height of the vehicle-mounted device that is different for each vehicle can be used, and the hyperbola can be identified more accurately. The position can be specified with higher accuracy.

  In the seventh invention, the plurality of transmitters transmit the modulated signal to the in-vehicle device, and the in-vehicle device demodulates the received signal and obtains the arrival time difference of each signal based on the demodulated signal. To do. For example, a signal having a frequency of about 10 kHz can be modulated with a carrier wave of about several hundred MHz. By using a carrier wave in a required frequency band, signals can be transmitted and received using the required frequency band of radio waves.

  In the eighth invention, the plurality of transmitters allocate the signals to orthogonal frequency multiplexing carrier waves and transmit the carrier waves to which the signals are assigned. For example, the signal to be transmitted is subjected to inverse Fourier transform and converted to at least one subcarrier (carrier wave) having a different frequency, and the converted signal is DA-converted and transmitted from the transmitter to the vehicle-mounted device. The vehicle-mounted device performs AD conversion on the transmitted carrier wave, and obtains the arrival time difference between the signals by pattern matching between the converted signals. By using the orthogonal frequency multiplexing method, it is possible to improve frequency band utilization efficiency while reducing interference with communication in other bands.

  In the ninth invention, the plurality of transmitters transmit signals having rising edges at a predetermined interval T1. The predetermined interval T1 is, for example, longer than the total value of the maximum time T2 required until the signal transmitted from the transmitter is received by the in-vehicle device and the time T3 when the delayed wave due to multipath affects the direct wave. To do. The in-vehicle device acquires the arrival time difference based on the time difference at the rising point of each signal transmitted by the plurality of transmitters. Thereby, the rising portion of the signal is not affected by the multipath, and the arrival time difference can be obtained with high accuracy.

  In the tenth invention, the plurality of transmitters transmit a signal having an alternating waveform (for example, a sine waveform), and the vehicle-mounted device acquires the arrival time difference of each signal based on the phase difference of the received signal. . For example, a sinusoidal signal can be transmitted from two transmitters, and the phase difference between the signals received by the vehicle-mounted device can be detected by the phase detector, and the arrival time difference can be obtained with a simple configuration.

  In the eleventh aspect, the plurality of transmitters modulate (eg, frequency modulate) a carrier wave (eg, frequency is several hundred MHz) with a sinusoidal signal (eg, frequency is 10 kHz), and the modulated signal Send. The in-vehicle device demodulates the received carrier wave, extracts the original signal, and acquires the arrival time difference based on the phase difference of each signal. The phase difference of each signal can be detected by the phase detector, and the arrival time difference can be acquired with a simple configuration.

  In the twelfth and twentieth inventions, one transmitter transmits a synchronization signal to another transmitter at a time t1 that is earlier than the signal transmission time by a predetermined time T4. The other transmitters specify the time t1 when the synchronization signal is transmitted based on the time t2 when the synchronization signal is received and the distance to the one transmitter. Here, the time difference from time t1 to time t2 is T5. The other transmitters determine the time when the time T6 (T6 = T4−T5) has elapsed from the time t2 when the synchronization signal is received as the time when the signal is transmitted. As a result, signals transmitted by a plurality of transmitters can be accurately synchronized.

  In the thirteenth aspect, the synchronization transmitter transmits a predetermined synchronization signal to a plurality of transmitters. Each of the plurality of transmitters receives the synchronization signal, identifies the time when the synchronization signal is transmitted based on the time when the synchronization signal is received and the distance to the synchronization transmitter, and the required time elapses from the identified time The time is determined as the signal transmission time. As a result, signals transmitted by a plurality of transmitters can be accurately synchronized.

  In the fourteenth aspect, each transmitter generates a reference period signal having a predetermined period (for example, a reference clock signal from a crystal oscillator), and determines the period of the signal based on the generated reference period signal. Since the signal transmitted by each transmitter is determined based on the reference periodic signal, the transmitters can transmit signals having the same period to each other.

  In the fifteenth invention, one transmitter transmits a signal to another transmitter wirelessly or by wire. The other transmitter adjusts the period (frequency) of the reference periodic signal based on the received signal, and determines the period of the signal based on the reference periodic signal whose period has been adjusted. Thereby, even if the period of the reference periodic signal changes from the initial value for some reason (for example, secular change), depending on the period of the signal transmitted by one transmitter, The period of the reference period signal is adjusted, and the other transmitter can transmit a signal having the same period as the period of one signal. Thereby, the period of the signal transmitted by each transmitter can be made the same.

  In the sixteenth aspect, the cycle adjustment transmitter transmits a cycle adjustment signal having a predetermined cycle (frequency) to each transmitter. Each transmitter receives the period adjustment signal, and adjusts the period (frequency) of the reference period signal based on the received period adjustment signal. Each transmitter determines the period of the signal based on the adjusted reference period signal. Thereby, the period of the signal transmitted by each transmitter can be made the same.

  In the seventeenth invention, each transmitter receives a signal (for example, a signal having a reference oscillation frequency of about 10 MHz) transmitted by a GNSS (Global Navigation Satellite System) satellite, and based on the received signal, Determine the period. Thereby, the period of the signal transmitted by each transmitter can be made the same.

  In the present invention, the traveling position of the own vehicle can be specified with high accuracy, and the distance to a predetermined position ahead of the traveling direction of the own vehicle can be obtained with high accuracy.

Embodiment 1
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments. FIG. 1 is a schematic diagram showing an outline of a communication system according to the present invention. The communication system according to the present invention can be realized in particular as a road-to-vehicle communication system, and is installed at a predetermined position near an optical beacon 10, an in-vehicle device 20 mounted on a vehicle, and a road, and has the same period and each other. Transmitters 30 and 40 that transmit synchronized signals are provided.

  The optical beacon 10 is installed so as to be communicable with the in-vehicle device 20 in a predetermined area A on the road through the communication unit 11 having a projector / receiver. A stop line P is provided on the downstream side of the region A in the vehicle traveling direction.

  When the in-vehicle device 20 determines that the vehicle is in the area A in which communication with the optical beacon 10 is possible, the communication system according to the present invention is based on the arrival time difference between the signals transmitted from the transmitters 30 and 40. The positional relationship between the vehicle transmitters 30 and 40, that is, the position of the vehicle in the region A is specified with high accuracy, and the position (distance) to the stop line P is calculated with high accuracy. In FIG. 1, only one lane is shown on the road, but the number of lanes on the road is not limited to one lane. The present invention can also be applied to roads having lanes. This will be described in detail below.

  FIG. 2 is a block diagram showing the configuration of the communication system according to the present invention. The optical beacon 10 includes a light emitter / receiver, a communication unit 11 having a communication function with the vehicle-mounted device 20, a control unit 12 that controls the operation of the optical beacon 10, a terminal communication unit 13 having a communication function with the central device 50, A storage unit 14 that stores position information related to the region A on the road that can communicate with the in-vehicle device 20 and position information related to the transmitters 30 and 40 is provided. Various types of information stored in the storage unit 14 of the optical beacon 10 can be received from the central device 50. Various information stored in the storage unit 14 can also be stored in the storage unit 14 in advance when the optical beacon 10 is installed.

  The transmitter 30 includes a communication unit 31, a control unit 32, and the like. For example, the communication unit 31 transmits radio waves in the frequency band of the VHF / UHF band to the in-vehicle device 20. The communication unit 31 includes a carrier wave generation circuit, a modulation circuit, and the like (not shown). Under the control of the control unit 32, the communication unit 31 is based on a predetermined signal (for example, a rectangular wave signal having a frequency of about 10 kHz). Frequency is modulated about 100 MHz, about 200 MHz, or about 700 MHz), and the modulated carrier wave is transmitted through an antenna (not shown). The frequency band used by the transmitter 30 is an example, and is not limited to the VHF / UHF band, and may be another frequency band. For example, a 5.8 GHz band allocated exclusively for automobiles may be used, and a frequency band used for a mobile phone, a PHS, or the like may be used.

  The transmitter 40 includes a communication unit 41, a control unit 42, and the like, and is synchronized with a signal (for example, a rectangular wave signal having a frequency of about 10 kHz) transmitted by the transmitter 30 (the rising point of the rectangular wave signal is coincident). ) Is transmitted to the in-vehicle device 20. The configuration of the transmitter 40 is the same as the configuration of the transmitter 30. A method for synchronizing the signals transmitted by the transmitters 30 and 40 will be described later.

  The in-vehicle device 20 controls the operation of the first communication unit 21 having a communication function with the optical beacon 10, the second communication unit 22 having a communication function with the transmitters 30 and 40, and the in-vehicle device 20 using infrared rays. A control unit 23, a storage unit 24, a display unit 25, an operation unit 26, and the like are provided. The in-vehicle device 20 can also include a GPS (Global Positioning System) reception function, a map database (none of which is shown), and the like.

  The first communication unit 21 receives downlink information transmitted from the optical beacon 10 and transmits uplink information to the optical beacon 10.

  FIG. 3 is an explanatory diagram for explaining bidirectional communication between the optical beacon 10 and the in-vehicle device 20. A region A on the road indicates a region where the in-vehicle device 20 can communicate with the optical beacon 10. As shown in FIG. 3, the region A is divided into a region A1 on the upstream side in the traveling direction of the host vehicle C and a region A2 on the downstream side. The area A1 is an area in which downlink information can be transmitted from the optical beacon 10 to the in-vehicle device 20 and uplink information can be transmitted from the in-vehicle device 20 to the optical beacon 10. On the other hand, the area A2 is an area where downlink information can be transmitted from the optical beacon 10 to the in-vehicle device 20.

  For example, the optical beacon 10 repeatedly transmits downlink information including lane notification information to the area A on the road at a predetermined downlink period. When the own vehicle C equipped with the in-vehicle device 20 enters the area A, the first communication unit 21 receives the downlink information and outputs the received downlink information to the control unit 23.

  The control unit 23 can determine that the vehicle C exists in the area A by receiving the downlink information through the first communication unit 21. That is, the control unit 23 can determine that the vehicle C exists in the area A at the time point ta1 when the first communication unit 21 receives the downlink information.

  When receiving the downlink information, the in-vehicle device 20 repeatedly transmits uplink information including the vehicle ID to the optical beacon 10 through the first communication unit 21 at a predetermined uplink period.

  When the optical beacon 10 receives the uplink information, the optical beacon 10 performs downlink switching, lane notification information, position information regarding the area A (for example, position information of the most upstream point Q in the vehicle traveling direction of the area A, The positional relationship between the area A and the transmitters 30 and 40), the road shape information including the distance L1 from the point Q to the stop line P, and the downlink information after the downlink switching such as the positional information regarding the transmitters 30 and 40. It transmits with respect to the vehicle equipment 20. The position information may be an absolute position represented by latitude and longitude, or may be a relative position from a predetermined reference point.

  The first communication unit 21 receives the downlink information after downlink switching, and outputs the received downlink information to the control unit 23.

  The control unit 23 can also determine that the host vehicle C exists in the area A by receiving the downlink information after downlink switching through the first communication unit 21. That is, the control unit 23 can determine that the host vehicle C exists in the area A at the time ta <b> 2 when the first communication unit 21 receives downlink information after downlink switching. Further, since the lane notification information included in the downlink information after the downlink switching is configured in a format in which the lane number is associated with the vehicle ID of the own vehicle, the control unit 23 is configured to associate the lane with the associated lane. The number can be recognized as the traveling lane of the own vehicle. That is, by using an optical beacon, a predetermined area can be limited to a narrow range of almost one lane on the road, and the position of the own vehicle can be specified with higher accuracy. It should be noted that the time point when it is determined that the host vehicle C exists in the area A may be either the time point ta1 or the time point ta2.

  The second communication unit 22 receives signals transmitted from the transmitters 30 and 40. More specifically, the second communication unit 22 includes a demodulation circuit, receives the radio waves transmitted by the transmitters 30 and 40, demodulates the received radio waves, and extracts the original signal. The second communication unit 22 calculates the arrival time difference between the signals based on the extracted signals, and outputs the calculated arrival time difference to the control unit 23.

  FIG. 4 is an explanatory diagram illustrating an example of calculating the arrival time difference of signals. FIG. 4 shows signal waveforms transmitted by the transmitters 30 and 40 and signal waveforms received by the in-vehicle device 20 from the transmitters 30 and 40. As shown in FIG. 4, each of the transmitters 30 and 40 transmits signals having the same period and synchronized with each other.

  If the distance from the in-vehicle device 20 to the transmitter 30 is shorter than the distance from the in-vehicle device 20 to the transmitter 40, the signal from the transmitter 30 reaches the in-vehicle device 20 first, and the distance from the transmitter 40 The signal arrives with a delay of ΔT1. The second communication unit 22 calculates the arrival time difference ΔT1 based on each received signal, and outputs the calculated arrival time difference ΔT1 to the control unit 23. The in-vehicle device 20 can calculate the arrival time difference one by one by repeatedly transmitting the signals synchronized with each other by the transmitters 30 and 40. Moreover, after calculating the said arrival time difference in multiple times within predetermined time, the method of acquiring these average value or a median value etc. can also be used. According to such a method, the influence by noise etc. can be reduced and the stable arrival time difference can be obtained. The arrival time difference between the signals can be calculated not only at the rising portion of the signal waveform but also at the falling portion.

  When receiving the downlink information after downlink switching through the first communication unit 21, the control unit 23 includes information included in the received downlink information (for example, lane notification information, the most upstream in the vehicle traveling direction in the region A) The position information of the point Q, the distance L1 from the point Q to the stop line P, the position information regarding the transmitters 30 and 40, and the like) are stored in the storage unit 24.

  When it is determined that the host vehicle exists in the area A (for example, the above-described time point ta2), the control unit 23 specifies the position of the host vehicle based on the arrival time difference ΔT1 acquired through the second communication unit 22. Hereinafter, a method for specifying the position of the own vehicle will be described.

FIG. 5 is an explanatory diagram showing an example of specifying the vehicle position based on the arrival time difference of signals. As shown in FIG. 5, a straight line passing through the transmitters 30 and 40 is an x axis, and a straight line passing through the midpoint of the transmitters 30 and 40 and perpendicular to the x axis is a y axis. In the xy coordinate, the x coordinate of the transmitter 30 and the first power of 2 minutes (a ² + b ^2), by integrating the -1 to 1 square of half of the x-coordinate of the transmitter 40 (a ² + b ²⁾ Value. In this case, the position where the distance difference between the distance to the transmitter 30 and the distance to the transmitter 40 is constant can be expressed by Expression (1). This is a hyperbola that focuses on the position of the transmitters 30, 40.

  That is, as shown in FIG. 5, for example, when the arrival time difference is ΔT1, based on ΔT1, the distance from the vehicle position to the transmitter 30 and the distance from the vehicle position to the transmitter 40 are The distance difference can be calculated, and the position where the hyperbola indicated by ΔT1 in the figure overlaps the area A on the road can be specified as the position of the own vehicle. In addition, when specifying a hyperbola, the height from the road surface of the vehicle equipment 20 can be determined in advance, such as 50 cm and 1 m, for example. Or the installation height information of the vehicle equipment 20 is memorize | stored in the memory | storage part 24, and a hyperbola can be specified using the memorize | stored height.

  Further, when the installation positions of the transmitters 30 and 40 are different, when the arrival time difference calculated by the in-vehicle device 20 is ΔT2, a hyperbola (ΔT2) different from the hyperbola indicated by ΔT1 overlaps the region A on the road. Can be specified as the position of the vehicle. The installation positions of the transmitters 30 and 40 can be determined so that the position of the own vehicle can be specified in the area A on the road.

  Next, description will be made using specific numerical examples. Assume that the transmitters 30 and 40 are installed 20 m apart. If the signal from the transmitter 30 reaches 20 nanoseconds earlier than the signal from the transmitter 40 in the in-vehicle device 20, the arrival time difference is 20 nanoseconds. If the propagation speed of the signal is the speed of light, the distance from the in-vehicle device 20 to the transmitter 30 is 6 m shorter than the distance from the in-vehicle device 20 to the transmitter 40.

  When the position of the own vehicle is (x, y), the position of the own vehicle is on the curve represented by the equation (2). When Expression (2) is calculated, Expression (3) can be derived, and it can be seen that the own vehicle exists at a position where the hyperbola represented by Expression (3) overlaps the area A on the road.

  The display unit 25 is a liquid crystal display panel such as a head-up display, a car navigation system, or a monitoring monitor, and can display various traffic information to the driver. For example, a distance to the intersection or stop line, a warning when the vehicle cannot travel safely at the intersection, and the like are displayed.

  The operation unit 26 includes various operation panels and functions as a user interface between the driver and the in-vehicle device 20. For example, the operation unit 26 receives an operation for starting or stopping the operation of the in-vehicle device 20 by an operation of the driver.

  Next, the operation of the communication system according to the present invention will be described. FIG. 6 is an explanatory diagram showing the processing contents of the in-vehicle device 20 in the communication system according to the present invention. When the own vehicle C travels on the road toward the stop line and enters the area A in which communication with the optical beacon 10 is possible, the vehicle-mounted device 20 receives the position information of the transmitters 30 and 40, the upstream end of the area A, Downlink information including the positional information, the positional relationship between the area A and the transmitters 30 and 40, the distance L1 from the upstream end of the area A to the stop line, and the like is acquired from the optical beacon 10 and temporarily stored. The in-vehicle device 20 determines that the vehicle C exists in the area A at the time point ta2 when the downlink information is acquired.

  When it is determined that the host vehicle C exists in the area A, the on-vehicle device 20 determines the arrival time difference ΔT1 between the signals transmitted from the transmitters 30 and 40, the height from the road surface of the on-vehicle device 20, the transmitters 30 and 40 Based on the positional information, the positional relationship between the area A and the transmitters 30 and 40, etc., the hyperbola ΔT1 where the host vehicle C exists is specified, and the position where the hyperbola ΔT1 and the area A overlap is specified as the position of the host vehicle C To do. Note that the position of the hyperbola ΔT1 in the figure is an example, and the present invention is not limited to this.

  Even when the distance between the hyperbolic line segments that overlap with the area A is long, the position information of the area A (for example, the position information of each of the four corners of the area A, the road traveling direction and the straight line formed by the transmitters 30 and 40) Based on the angle etc.), for example, the midpoint of the line segment that overlaps the region A in the hyperbola can be set as the position of the vehicle C. If the transmitter 30 and 40 are arranged by adjusting the angle between the road traveling direction and the straight line formed by the transmitters 30 and 40, and the angle between the hyperbola and the road traveling direction is as orthogonal as possible, The position of the vehicle C can be specified with higher accuracy.

  The in-vehicle device 20 calculates the distance L2 from the upstream end of the region A to the own vehicle C based on the position of the own vehicle C and the position of the upstream end of the region A that are further specified. Moreover, the vehicle equipment 20 calculates the distance L1-L2 to the stop line of the own vehicle C based on the calculated distance L2 and the stored distance L1. Thereby, the traveling position of the own vehicle C can be specified with high accuracy, and the distance to a predetermined position (for example, a stop line) ahead of the traveling direction of the own vehicle C can be obtained with high accuracy.

  FIG. 7 is an explanatory diagram illustrating an example of a transmission interval of signals transmitted by the transmitters 30 and 40. As shown in FIG. 7, the transmitters 30 and 40 transmit a rectangular transmission waveform at a predetermined interval T1. The signals transmitted by the transmitters 30 and 40 are combined (superimposed) with the direct wave that directly reaches the vehicle-mounted device 20 and the delayed wave that arrives after being delayed by the direct wave after being reflected by a building or the like existing in the surroundings. It becomes a composite wave. Accordingly, the reception waveform of the signal received by the in-vehicle device 20 is a waveform in which a signal delayed by multipath is superimposed on the transmission waveform, and the time when the delayed wave due to multipath directly affects the wave is, for example, T3 Become. Further, the time when the vehicle-mounted device 20 receives a signal is delayed by, for example, the maximum time T2 from the time when the transmitters 30 and 40 transmit the signal according to the distance between the vehicle-mounted device 20 and the transmitters 30 and 40.

  In this case, by setting the transmission interval T1 of the signals transmitted by the transmitters 30 and 40 to T1> T2 + T3, the rising portion of each signal received by the in-vehicle device 20 is not affected by the multipath, and the accuracy is increased. The arrival time difference can be obtained well.

  FIG. 8 is an explanatory diagram illustrating an example of a synchronization method of signals transmitted by the transmitters 30 and 40. Assume that the transmitter 30 transmits a synchronization signal to the transmitter 40 at time t1, and transmits a positioning signal to the in-vehicle device 20 when time T4 has elapsed from the transmission time.

  In the transmitter 40, the synchronization signal is received at time t2 when time T5 has elapsed from time t1 according to the distance between the transmitter 30 and the transmitter 40. The transmitter 40 can calculate the time T5 that is the difference between the transmission time t1 and the reception time t2 of the synchronization signal by holding the distance information between the transmitter 30 and the transmitter 40.

  The transmitter 40 calculates a time T6 (T6 = T4-T5) based on the calculated time T5 and a previously held time T4, and the positioning signal is obtained when the time T6 has elapsed from the reception time t2 of the synchronization signal. Send. As a result, signals (positioning signals) transmitted by the transmitters 30 and 40 can be completely synchronized. Thereby, the signals transmitted by the transmitters 30 and 40 can be synchronized with high accuracy. The synchronization signal can be transmitted every time a signal (positioning signal) is transmitted, or after a signal (positioning signal) is repeatedly transmitted for a predetermined time, Signals can also be inserted. Further, the transmitter 40 may transmit a synchronization signal to the transmitter 30.

  In addition, the method of synchronizing the signal which the transmitters 30 and 40 transmit is not limited to the above-mentioned example, You may use another method. For example, a transmitter for synchronization is installed separately from the transmitters 30 and 40. The synchronization transmitter transmits a predetermined synchronization signal to the transmitters 30 and 40. The transmitters 30 and 40 receive the synchronization signal, identify the time when the synchronization signal is transmitted based on the time when the synchronization signal is received and the distance to the synchronization transmitter, and the required time elapses from the identified time. The time is determined as the signal transmission time. Thereby, the signals transmitted by the transmitters 30 and 40 can be synchronized with high accuracy.

  The signals transmitted by the transmitters 30 and 40 can be generated in synchronization with a reference clock signal, for example, so as to transmit signals having the same period. However, the oscillation frequency of the crystal oscillator that generates the reference clock signal may cause an error due to secular change or the like, and the period (frequency) of the signal transmitted by each transmitter 30 or 40 may be shifted. Hereinafter, a method of making the signal periods of the transmitters 30 and 40 the same will be described.

  FIG. 9 is an explanatory diagram showing an example of a method for making the periods of signals transmitted by the transmitters 30 and 40 the same. FIG. 9A shows a case where the signal period is deviated. The signal period transmitted by the transmitter 30 is T7, and the signal period transmitted by the transmitter 40 is T7 ′, which is different from T7. Yes. In this case, each transmitter 30 and 40 is provided with a phase-locked loop (PLL), and for example, the transmitter 30 transmits a signal to the transmitter 40 wirelessly or by wire. The transmitter 40 adjusts the cycle (frequency) of the reference clock signal based on the received signal, and determines the cycle of the signal based on the reference clock signal whose cycle has been adjusted. As a result, as shown in FIG. 9B, the cycle of the signal transmitted by the transmitter 40 can be corrected from T7 ′ to T7 so as to be the same as the cycle of the signal of the transmitter 30.

  In addition, the method of making the period of the signal which each transmitter transmits the same is not limited to the above-mentioned example, You may use another method. For example, a transmitter for period adjustment is installed separately from the transmitters 30 and 40. The cycle adjustment transmitter transmits a cycle adjustment signal having a predetermined cycle to the transmitters 30 and 40. The transmitters 30 and 40 receive the period adjustment signal, adjust the period (frequency) of the reference clock signal based on the period (frequency) of the period adjustment signal, and based on the reference clock signal whose period is adjusted, The period of the signal can be determined.

  Further, instead of the period adjusting transmitter, a signal transmitted by a GNSS (Global Navigation Satellite System) satellite including GPS is received, and a signal having a reference oscillation frequency (for example, about 10 MHz) is extracted from the received signal. The period (frequency) of the reference clock signal is adjusted based on the extracted signal of the reference oscillation frequency, and the period of the signal can be determined based on the reference clock signal whose period is adjusted.

  The waveform of the signal transmitted by the transmitters 30 and 40 is not limited to a rectangular waveform, and may be a sine waveform. FIG. 10 is an explanatory diagram showing an example of calculating the arrival time difference when a sinusoidal waveform signal is used. FIG. 10 shows signal waveforms transmitted by the transmitters 30 and 40 and signal waveforms received by the in-vehicle device 20 from the transmitters 30 and 40. As shown in FIG. 10, each of the transmitters 30 and 40 transmits signals having the same period and synchronized with each other.

  In this case, the second communication unit 22 includes a phase detector (not shown), receives signals transmitted from the transmitters 30 and 40, and outputs the received signals to the phase detector. The phase detector detects the phase difference of each signal, and thereby can calculate the arrival time difference ΔT of each signal with a simple configuration.

  In addition, when transmitting the signal of the above sine waveform, it is also possible to modulate and transmit the signal. For example, the transmitters 30 and 40 modulate (eg, frequency modulate) a carrier wave (eg, frequency is several hundred MHz) with a sinusoidal signal (eg, frequency is 10 kHz), and transmit the modulated signal. The in-vehicle device 20 can demodulate the received carrier wave, extract the original signal, and acquire the arrival time difference based on the phase difference of each signal.

  As described above, in the present invention, the traveling position of the host vehicle can be specified with high accuracy. Moreover, the distance to the predetermined position ahead of the traveling direction of the own vehicle can be obtained with high accuracy. Further, it is not necessary to store road shape information in advance by the in-vehicle device, and necessary road shape information can be acquired every time the vehicle travels before a required intersection. In addition, the height of the vehicle-mounted device that is different for each vehicle can be used, and the position of the own vehicle can be specified with higher accuracy. Further, by using a carrier wave in a required frequency band, signals can be transmitted and received using the required frequency band of radio waves. In addition, the rising portion of the signal is not affected by the multipath, and the arrival time difference can be obtained with high accuracy. In addition, signals transmitted by a plurality of transmitters can be accurately synchronized.

  In the above-described embodiment, the transmitters 30 and 40 modulate and transmit signals, and the in-vehicle device 20 demodulates and extracts the original signals, and calculates the arrival time difference between the signals. The transmitters 30 and 40 allocate signals to carriers having different frequencies in the orthogonal frequency multiplexing scheme, and transmit the carriers to which the signals are allocated. For example, the signal to be transmitted is subjected to inverse Fourier transform to be converted into at least one subcarrier (carrier wave) having a different frequency, and the converted signal is DA-converted and transmitted from the transmitters 30 and 40 to the in-vehicle device 20. The in-vehicle device 20 performs AD conversion on the transmitted carrier wave, and obtains the arrival time difference between the signals by pattern matching between the converted signals. Thereby, the utilization efficiency of a frequency band can be improved, reducing interference with communication in other bands.

  In the above-described embodiment, the position information or the like is transmitted from the optical beacon 10 to the in-vehicle device 20. However, the present invention is not limited to this, and any one of the transmitters 30 and 40 is located in the in-vehicle device 20. It can also be configured to transmit information or the like. Further, the in-vehicle device 20 may be provided with GPS, map data, and the like, and necessary position information may be stored in advance. In this case, it is not necessary to transmit position information or the like from the optical beacon 10 or the transmitters 30 and 40. In this case, the control unit 23 can determine that the host vehicle C exists in the area A at the time ta1 when the first communication unit 21 receives the downlink information.

  In the above-described embodiment, the configuration is such that two transmitters are used for positioning, but the number of transmitters is not limited to two, and may be a configuration in which three or more transmitters are used. By using three transmitters, road gradient (height information) can be obtained.

  As shown in the above-described embodiment, the road shape information may have the following format in addition to the method of setting the distance L1 from the point Q to the stop line P. For example, a plurality of nodes (road sections) are set between the point Q and the stop line P, the distance from the point Q to the node closest to the point Q, the distance between each node, and the node closest to the stop line P The distance from the stop line P to the stop line P can also be stored. The distance between the nodes may be set to be always constant (for example, 20 m), and the gradient or curvature between the nodes may be stored. That is, the road shape information may be in any format as long as the distance from the point Q to the stop line P can be acquired.

  According to the above-described invention, the position of the traveling vehicle can be specified with high accuracy. Therefore, by using the present invention, for example, display information of a traffic signal ahead is received by an in-vehicle device, and based on the received display information. Therefore, it is determined with high accuracy whether it is possible to stop safely before the intersection, or whether it is possible to safely pass the intersection, and the driver is alerted by voice according to the determination result. be able to. In addition, based on the display information of the traffic lights received by the in-vehicle device, it is possible to determine with high accuracy whether or not it is possible to pass through the intersection safely, and it is possible to perform vehicle brake control according to the determination result. Accidents can be prevented and traffic safety can be improved.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows the outline | summary of the communication system which concerns on this invention. It is a block diagram which shows the structure of the communication system which concerns on this invention. It is explanatory drawing explaining the bidirectional | two-way communication between an optical beacon and vehicle equipment. It is explanatory drawing which shows the example of calculation of the arrival time difference of a signal. It is explanatory drawing which shows the example which pinpoints the own vehicle position based on the arrival time difference of a signal. It is explanatory drawing which shows the processing content of a vehicle equipment in the communication system which concerns on this invention. It is explanatory drawing which shows the example of the transmission interval of the signal which a transmitter transmits. It is explanatory drawing which shows the example of the synchronizing method of the signal which a transmitter transmits. It is explanatory drawing which shows the example of the method of making the period of the signal which a transmitter transmits the same. It is explanatory drawing which shows the example of calculation of the arrival time difference at the time of using the signal of a sine waveform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical beacon 11 Communication part 12 Control part 13 Terminal communication part 14 Storage part 20 Vehicle equipment 21 1st communication part 22 2nd communication part 23 Control part 24 Storage part 25 Display part 26 Operation part 30, 40 Transmitter 31, 41 Communication Unit 32, 42 Control unit

Claims (20)

A communication system comprising a plurality of transmitters that transmit signals synchronized with each other in the same cycle, and an in-vehicle device that receives signals transmitted by the transmitters,
The in-vehicle device is
Means for storing a predetermined area on the road and position information of the plurality of transmitters;
Determination means for determining whether or not the own vehicle exists in the area;
Time difference acquisition means for acquiring the arrival time difference of each signal transmitted by the plurality of transmitters;
And a specifying unit for specifying the vehicle position based on the arrival time difference acquired by the time difference acquisition unit and the position information when the determination unit determines that the vehicle is present in the area. system. With an optical beacon that transmits predetermined information to the in-vehicle device,
The determination means includes
The communication system according to claim 1, wherein when predetermined information is received from the optical beacon, the vehicle is determined to be present in the area. The specifying means is:
Configured to identify a position relative to a predetermined first point in the region;
Road shape information acquisition means for acquiring road shape information relating to a road shape between the first point and a predetermined second point located downstream of the region in the traveling direction of the vehicle;
The calculation means for calculating the distance to the second point based on the road shape information acquired by the road shape information acquisition means and the position specified by the specification means. 2. The communication system according to 2.   The road shape information includes at least one of a distance, a gradient, and a curvature for each section obtained by dividing the road between the first point and the second point into one or a plurality of sections. Item 4. The communication system according to Item 3.   5. The communication system according to claim 3, wherein at least one of the plurality of transmitters and the optical beacon includes a transmission unit that transmits the road shape information to an in-vehicle device. The in-vehicle device is
Comprising storage means for storing the height information of the mounting position;
The specifying means is:
The communication system according to any one of claims 1 to 5, wherein the vehicle position is specified based on the height information. The plurality of transmitters are:
Comprising modulation means for modulating the signal;
It is configured to transmit a signal modulated by the modulation means,
The in-vehicle device is
A demodulating means for demodulating the received signal;
The time difference acquisition means includes
The communication system according to any one of claims 1 to 6, wherein an arrival time difference between the signals is acquired based on the signal demodulated by the demodulation means. The plurality of transmitters are:
Allocating means for allocating signals to orthogonal frequency multiplexing carrier waves;
It is configured to transmit a carrier wave to which a signal is assigned by the assigning means,
The in-vehicle device is
Receiving means for receiving the carrier wave;
The time difference acquisition means includes
The communication system according to any one of claims 1 to 6, wherein an arrival time difference of each signal is acquired based on a received carrier wave. The plurality of transmitters are:
It is configured to transmit a signal having a rising edge at a predetermined interval,
The time difference acquisition means includes
The communication system according to claim 7 or 8, wherein a difference in arrival time of each signal is acquired based on a rising time of each received signal. The plurality of transmitters are:
It is configured to transmit an alternating waveform signal,
The time difference acquisition means includes
The communication system according to any one of claims 1 to 6, wherein an arrival time difference of each signal is acquired based on a phase difference of each received signal. The plurality of transmitters are:
Comprising modulation means for modulating the signal;
It is configured to transmit a signal modulated by the modulation means,
The in-vehicle device is
A demodulating means for demodulating the received signal;
The time difference acquisition means includes
The communication system according to claim 10, wherein an arrival time difference of each signal is acquired based on a phase difference of each signal demodulated by the demodulation means. One transmitter is
It is configured to send a synchronization signal to another transmitter at a time earlier than a signal transmission time by a predetermined time,
The other transmitter is
A specifying means for specifying a time point when the synchronization signal is transmitted based on a time point when the synchronization signal is received and a distance to the one transmitter;
The communication system according to any one of claims 1 to 6, further comprising a determination unit that determines a signal transmission time point based on the time point specified by the specifying unit and the predetermined time. A synchronization transmitter for transmitting a predetermined synchronization signal;
The plurality of transmitters are:
Receiving means for receiving a synchronization signal transmitted by the synchronization transmitter;
7. The communication according to claim 1, further comprising: a determination unit that determines a time point at which the signal is transmitted based on the received synchronization signal and a distance to the synchronization transmitter. system. The transmitter is
Generating means for generating a reference period signal of a predetermined period;
7. The communication system according to claim 1, further comprising: a determination unit that determines a cycle of the signal based on the reference periodic signal generated by the generation unit. One transmitter is
It is configured to transmit signals to other transmitters wirelessly or by wire,
The other transmitter is
An adjustment unit that adjusts the period of the reference periodic signal generated by the generation unit based on the received signal,
The determining means includes
15. The communication system according to claim 14, wherein a period of the signal is determined based on a reference period signal whose period is adjusted by the adjusting unit. A cycle adjustment transmitter for transmitting a cycle adjustment signal having a predetermined cycle is provided.
The transmitter is
Receiving means for receiving a period adjustment signal transmitted by the period adjustment transmitter;
Based on the received period adjustment signal, the adjustment means for adjusting the period of the reference period signal generated by the generation means,
The determining means includes
15. The communication system according to claim 14, wherein a period of the signal is determined based on a reference period signal whose period is adjusted by the adjusting unit. The transmitter is
Receiving means for receiving a signal transmitted by a GNSS satellite;
The communication system according to any one of claims 1 to 6, further comprising: a determination unit that determines a period of the signal based on the received signal. An in-vehicle device that receives signals in the same cycle and synchronized with each other,
Means for storing a predetermined area on the road and position information of a plurality of transmitters;
Determination means for determining whether or not the own vehicle exists in the area;
Time difference acquisition means for acquiring the arrival time difference of each signal transmitted by the plurality of transmitters;
When the determination means determines that the vehicle is present in the area, the vehicle includes: a specifying means for specifying the vehicle position based on the arrival time difference acquired by the time difference acquisition means and the position information. Machine.   A vehicle comprising the in-vehicle device according to claim 18. A transmitter that transmits signals synchronized with each other,
Receiving means for receiving a synchronization signal transmitted at a time earlier than a signal transmission time from another transmitter by a predetermined time;
A specifying means for specifying the time when the synchronization signal is transmitted based on the time when the synchronization signal is received by the receiving means and the distance to the other transmitter;
A transmitter comprising: a determination unit that determines a time point for transmitting a signal based on the time point specified by the specifying unit and the predetermined time.

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