JP2009059120A - In-vehicle device for inter-vehicle communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that when a plurality of inter-vehicle communication modules for performing communication by CSMA control are installed in one in-vehicle device, one inter-vehicle communication module starts transmission without detecting that another vehicle is transmitting radio waves, and interferes with reception by the other inter-vehicle communication modules in the same vehicle. <P>SOLUTION: An in-vehicle device for inter-vehicle communication has a plurality of inter-vehicle communication modules comprising a transmission part for transmitting information on a user's vehicle by radio waves, a reception part for acquiring information on other vehicles by radio waves, and a CSMA control part for detecting the strength of the radio waves received, confirming that the other vehicles are not transmitting radio waves, and then starting the transmission of radio waves by the user's vehicle. The status of detecting the strength of the radio waves received in each of the inter-vehicle communication modules is provided to the other inter-vehicle communication modules. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle-mounted device having a plurality of communication devices, and more particularly to a vehicle-to-vehicle communication vehicle-mounted device used in a system that supports driving support by wirelessly exchanging information on a vehicle between vehicles.

  Currently, development of a driving support system that supports vehicle driving by exchanging vehicle information using inter-vehicle communication technology is underway. In this driving support system, each vehicle continues to transmit its own vehicle information such as its own vehicle position periodically while moving, and other vehicles receive the information to determine the risk and the like. In inter-vehicle communication, a plurality of vehicles transmit their own vehicle information using radio waves having a common frequency. For this reason, in the control of only the time period, there is a collision with the transmission of another vehicle, and therefore, a CSMA (Carrier Sense Multiple Access) control method for transmitting after confirming that the other vehicle is not transmitting is adopted. .

  When vehicle-to-vehicle communication is performed, the moving speed of the vehicle is high on an expressway or the like, so it is necessary to communicate with other distant vehicles to exchange information. If you increase the radio wave transmission power, you can communicate with other distant vehicles, but there is a limit to the radio wave transmission output, and you cannot increase the transmission output beyond this limit.

  Also, a method of installing a plurality of inter-vehicle communication devices in one vehicle is considered. As an example of a vehicle-to-vehicle communication device provided with a plurality of communication devices, as shown in Japanese Patent Application Laid-Open No. 2005-38202, the vehicle in front and the vehicle in the rear are separately communicated to obtain information on distant locations. An early technology is disclosed. Furthermore, Japanese Patent Laid-Open No. 2005-234921 discloses that a plurality of antennas having directivity in different directions are provided in one vehicle in order to efficiently transmit and receive information between oncoming vehicles and preceding and following vehicles. The providing technique is disclosed.

JP-A-2005-38202 JP-A-2005-234922

  When a plurality of communication modules that perform communication by CSMA control are installed in one in-vehicle device, depending on the reception status of radio waves, even though a certain communication module receives communication from another in-vehicle device, It is conceivable that another communication module cannot receive the communication and the other on-vehicle device determines that the communication is not performed and starts transmission, thereby disturbing the communication from the other on-vehicle device.

  Specifically, in order to extend the communication distance under a limited transmission output, the antenna of each communication device is given directional characteristics, and the direction of the directional characteristics of the communication device is directed in a different direction. By providing a front vehicle-to-vehicle communication device installed to transmit radio waves in the forward direction and a rear vehicle-to-vehicle communication device installed to transmit radio waves in the rear direction of the vehicle, And the distance that can be communicated toward the back will increase.

  However, at this time, the front inter-vehicle communication device can easily receive the front radio wave, but the rear radio wave is difficult to receive. Therefore, in the CSMA control in the front vehicle-to-vehicle communication device, it is impossible to detect that the other vehicle behind is transmitting radio waves, and transmission is started, which interferes with reception of the rear vehicle-to-vehicle communication device. Become. And it will also interfere with reception in other vehicles.

  In the present invention, a transmitting unit that transmits information on the own vehicle by radio waves, a receiving unit that obtains information on other vehicles by radio waves, and the strength of the radio waves are detected, and the other vehicles are not transmitting radio waves. In a vehicle-to-vehicle communication vehicle-mounted device in which a plurality of communication modules having a CSMA control unit that starts transmission of radio waves of the vehicle after confirming this is installed in one vehicle, the strength of the received radio waves in each communication module The detection status is notified to other communication modules, and each CSMA control unit detects the strength of the radio wave received at the receiving unit of the own communication module and the strength of the received radio wave notified from the other communication module. It is characterized by confirming that the other vehicle is not transmitting the radio wave based on the situation.

  Further, the plurality of communication modules include at least a communication module connected to an antenna having directivity in front of the vehicle and a communication module connected to an antenna having directivity in the rear of the vehicle.

  Further, in the present invention, the detection status of the strength of the radio wave represents the strength of the received radio wave as a digital value, and depends on the reception capability of other communication modules mounted on the host vehicle. The digital numerical value of the detection status of the intensity of the radio wave is corrected and notified.

  According to the present invention, when communication is performed using a plurality of communication modules that perform communication by CSMA control, CSMA control can be performed without interfering with reception of radio waves from other devices.

  It is also possible to communicate with a farther vehicle under a limited transmission power.

  Hereinafter, embodiments of an on-vehicle device for inter-vehicle communication using the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an embodiment of an on-vehicle device for inter-vehicle communication using the present invention. FIG. 2 is a diagram for explaining inter-vehicle communication in an on-vehicle device for inter-vehicle communication using the present invention.

  First, the own vehicle 7 and the other vehicle 8 in FIG. 2 are each equipped with a vehicle-to-vehicle communication vehicle-mounted device. Among these, it is assumed that the vehicle-to-vehicle communication vehicle-mounted device 1 using the present invention is mounted on the own vehicle 7. In order to extend the communication distance under a limited transmission output, the own vehicle 7 has a forward directional antenna 4 in which transmission and reception characteristics of radio waves are concentrated in the front direction of the vehicle, and transmission of radio waves in the rear direction of the vehicle. A backward directional antenna 5 with a biased reception characteristic is provided. A directional communication area 18 and a directional communication area 19 indicate the directional communication areas of the front directional antenna 4 and the rear directional antenna 5, respectively.

  As shown in FIG. 1A, the vehicle-to-vehicle communication vehicle-mounted device 1 includes a front vehicle-to-vehicle communication module 2 connected to the front directional antenna 4 and a rear vehicle connected to the rear directional antenna 5. A plurality of independent wireless communication devices of the inter-vehicle communication module 3 are provided. Moreover, the data processing part 6 which processes the data which the front inter-vehicle communication module 2 and the rear inter-vehicle communication module 3 received, edited the data to transmit, etc. is provided. The front vehicle-to-vehicle communication module 2 and the rear vehicle-to-vehicle communication module 3 operate as independent wireless communication devices, and each performs CSMA control individually. In this CSMA control, a channel is observed before sending a packet, and once reception is attempted, it is confirmed whether there is another packet currently being communicated. Then, if no communication packet is received by another communication module, the own packet transmission is started, and if it is in use, the packet transmission is refrained.

  In FIG. 2, the other vehicle 8 is located behind the host vehicle 7 and transmits vehicle information of the other vehicle 8. At this time, the vehicle-to-vehicle communication module 3 for the rear of the host vehicle 7 can receive the vehicle information transmitted by the other vehicle 8, and when the other vehicle 8 is transmitting the vehicle information, It is possible to delay the transmission of the vehicle information of the own vehicle 7 by the communication module 3 by CSMA control. However, in the inter-vehicle communication module 2 for the front, the front directional antenna 4 has directivity in the front of the vehicle, so that the transmission of the other vehicle 8 is performed when the distance from the antenna of the other vehicle 8 is long. Cannot receive the vehicle information. For this reason, the front vehicle-to-vehicle communication module 2 determines that there is no other vehicle-mounted device that performs communication, and starts transmitting vehicle information of the vehicle. Since the front directional antenna 4 and the rear directional antenna 5 are installed in the same vehicle, the distance between them is short, and the radio wave transmitted from the front directional antenna 4 is the rear directional antenna 5. However, in the rear vehicle-to-vehicle communication module 3, the radio wave transmitted by the front vehicle-to-vehicle communication module 2 interferes with the radio wave transmitted by the other vehicle 8 and cannot be received correctly. End up.

  Therefore, the data processing unit 6 obtains carrier sense status information that is a result of detection of the received electric field strength by the rear vehicle-to-vehicle communication module 3 and provides it to the front vehicle-to-vehicle communication module 2. In the front inter-vehicle communication module 2, the other vehicle 8 uses the received carrier sense status information of the rear inter-vehicle communication module 3 received from the data processing unit 6 and the carrier sense status information of the front inter-vehicle communication module 2. It can be detected that radio waves are being transmitted. Therefore, the vehicle-to-vehicle communication module 2 for the front uses the CSMA control to delay the start of transmission of vehicle information, so that the vehicle-to-vehicle communication module 3 for the rear can normally receive information on the other vehicle 8.

  Similarly, with respect to radio waves from a front vehicle (not shown), the vehicle-to-vehicle communication module 2 for the front obtains carrier sense status information as a result of detecting the received electric field strength, and uses the data processing unit 6 for the rear side. This is provided to the inter-vehicle communication module 3. The rear vehicle-to-vehicle communication module 3 uses the received carrier sense status information of the front vehicle-to-vehicle communication module 2 received from the data processing unit 6 and the carrier sense status information of the rear vehicle-to-vehicle communication module 3 to cause the vehicle in front to receive radio waves. And the vehicle-to-vehicle communication module 3 for the rear side delays the start of transmission of vehicle information by CSMA control, so that the vehicle-to-vehicle communication module 2 for the front side normally receives the information on the vehicle in front. Is possible. Thus, information can be displayed on the navigation system 9 when there is a danger. Here, the carrier sense status information indicates the result of carrier sense in each of the rear vehicle-to-vehicle communication module 3 and the front vehicle-to-vehicle communication module 2, and is not the received electric field intensity itself.

  FIG. 3 is a diagram for explaining the details of the vehicle-to-vehicle communication vehicle-mounted device shown in FIG. 1A, and FIGS. 5 and 6 are flowcharts explaining the flow of this process.

  The front vehicle-to-vehicle communication module 2 and the rear vehicle-to-vehicle communication module 3 each receive a radio wave transmitted by another vehicle via the front directional antenna 4 and the rear directional antenna 5, respectively. A transmission unit 12 that transmits the vehicle information to another vehicle as a radio wave, a CSMA control unit 13 that instructs the transmission unit 12 to start transmission based on the strength of the electric field received by the reception unit 11, and the received data The communication control unit 14 performs error correction, confirmation of validity, addition of error correction data to transmission data, transmission / reception and processing of control information of the inter-vehicle communication module, and the like.

  The data processing unit 6 includes a received data processing unit 15 that determines the importance of data received from the content of data received from the front vehicle-to-vehicle communication module 2 and the rear vehicle-to-vehicle communication module 3, and the vehicle information. The vehicle-to-vehicle communication module 2 for the front, the transmission data processing unit 16 that generates transmission data to be passed to the vehicle-to-vehicle communication module 3 for the rear, and the carrier sense status information from the vehicle-to-vehicle communication module 2 for the front 3 includes a CSMA auxiliary control unit 20 for notifying 3. The CSMA auxiliary control unit 20 also has a function of notifying the forward vehicle-to-vehicle communication module 2 of the carrier sense status information from the vehicle-to-vehicle communication module 3 for the rear.

  5 and 6 are flowcharts for explaining processing in the vehicle-to-vehicle communication vehicle-mounted device using the present invention. Here, a description will be given according to the configuration shown in FIG. Therefore, although the functions are clearly divided between the front and rear inter-vehicle communication modules, the front and rear inter-vehicle communication modules actually have the same functions.

  FIG. 5 will be described. First, the rear vehicle-to-vehicle communication module 3 performs carrier sense processing at regular intervals or prior to transmission of vehicle data. In this process, first, the reception field intensity is acquired as a digital value in the reception unit 11 (501). Then, the CSMA control unit 13 compares the set threshold value with the acquired received electric field strength (502). When the received electric field strength value is equal to or greater than the threshold value, it is determined that another vehicle is transmitting radio waves, and carrier sense is performed. The flag is set to 1 (503). When the received electric field strength value is smaller than the set threshold value, the carrier sense flag is cleared (504). Then, the communication control unit 14 stores the carrier sense flag in the carrier sense status 22 (505).

  On the other hand, the data processing unit 6 receives notification at regular intervals or every time the carrier sense status 22 is updated, and notifies the other vehicle-to-vehicle communication module of the carrier sense status in one vehicle-to-vehicle communication module. The carrier sense status notification process is performed. In this process, the CSMA auxiliary control unit 20 reads the value of the carrier sense flag from the carrier sense status 22 of one vehicle-to-vehicle communication module (510), and notifies the value of the read carrier sense flag to the other vehicle-to-vehicle communication module. (511). Thus, the carrier sense flag notified to the other inter-vehicle communication module is periodically overwritten, and always represents the latest situation.

  Next, the vehicle information transmission process will be described with reference to FIG. The forward inter-vehicle communication module 2 prepares transmission data (601), and starts CSMA control when the preparation is completed. At this time, the CSMA control unit 13 sets a random number in the counter (602). The receiving unit 11 acquires the received electric field strength as a digital value (603), and the CSMA control unit 13 acquires the latest carrier sense flag of the other vehicle from the data processing unit 6 (604). Then, when the received electric field strength is smaller than the set threshold value for a certain time and when the carrier sense flag of the other vehicle is not set to 1 (Yes in 605), the other vehicle transmits a radio wave. In addition, the receiving unit 11 acquires the received electric field strength as a digital value (606), the CSMA control unit 13 acquires the latest carrier sense flag of the other vehicle from the data processing unit 6 (607), When the received electric field strength is smaller than the set threshold value for a certain time and 1 is not set in the carrier sense flag of the other vehicle (Yes in 608), the value of the counter is subtracted (609), When the counter value reaches 0 (Yes in 610), transmission of vehicle information is started (611). If the value of the counter is not 0 (No in 610), the process returns to process 606 and the process is repeated. Also, in the determination processing of processing 605 and processing 608, when the received electric field strength is equal to or greater than the set threshold value for a certain period of time, or when the carrier sense flag of another vehicle is set to 1, Returning to 603, the process of examining whether another vehicle is transmitting radio waves is continued.

  Through the above processing, when the vehicle behind is transmitting radio waves and received by the rear vehicle-to-vehicle communication module 3, transmission from the front vehicle-to-vehicle communication module 2 is delayed, The inter-vehicle communication module 3 can normally receive information from the rear vehicle. The same applies when receiving information from the preceding vehicle in the inter-vehicle communication module 2 for the forward vehicle.

  FIG. 4 is a configuration diagram illustrating a modification of the data processing unit 6 in the vehicle-to-vehicle communication vehicle-mounted device using the present invention. In the configuration shown in FIG. 3, the value of the carrier sense flag, which is a result of comparing the value obtained by digitizing the received electric field strength received by the receiving unit 11 by AD conversion with a predetermined threshold, is used as the carrier sense status information. It was. In the embodiment shown in FIG. 4, a value obtained by digitizing the received electric field strength by AD conversion is used as carrier sense status information.

  The data processing unit 6 in FIG. 4, like the data processing unit 6 in FIG. 3, determines the importance of the data received from the contents of the data received from the front inter-vehicle communication module 2 and the rear inter-vehicle communication module 3. A reception data processing unit 15 for determining, a transmission data processing unit 16 for generating transmission data for passing the vehicle information to the front vehicle-to-vehicle communication module 2 and the rear vehicle-to-vehicle communication module 3 are provided. Then, in place of the CSMA auxiliary control unit 20 of the data processing unit 6 in FIG. 3, the reception electric field strength information from the front vehicle-to-vehicle communication module 2 is corrected to a value that matches the reception capability of the rear vehicle-to-vehicle communication module 3. A sensitivity correction unit 17 is provided. The reception sensitivity correction unit 17 also corrects the received electric field strength information from the rear vehicle-to-vehicle communication module 3 to a numerical value that matches the reception capability of the front vehicle-to-vehicle communication module 2.

  In general, the receiving units 11 in the front vehicle-to-vehicle communication module 2 and the rear vehicle-to-vehicle communication module 3 have different reception capabilities due to variations in component characteristics. Therefore, the numerical value of the received electric field strength information of each inter-vehicle communication module does not match the received electric field strength. It is possible to adjust the reception capability when manufacturing the inter-vehicle communication module, but it takes a lot of adjustment steps. Therefore, the reception sensitivity correction unit 17 corrects the values to match the reception capabilities of the communication modules. This flow is explained in the flowchart of FIG. FIG. 8 is a flowchart illustrating a process of transmitting data by CSMA control using the value of the received electric field strength in the other inter-vehicle communication module corrected based on the reception capability. Here, the processing in each flowchart will be described with reference to the configuration example diagram of FIG. Therefore, although the functions are clearly divided between the front and rear inter-vehicle communication modules, the front and rear inter-vehicle communication modules actually have the same functions.

  First, FIG. 7 will be described. Similar to the processing shown in FIG. 5, the rear vehicle-to-vehicle communication module 3 performs carrier sense processing at regular intervals or prior to transmission of vehicle data. The received electric field strength of the radio wave received by the receiving unit 11 is acquired as a digital value by AD conversion (701), and the CSMA control unit 13 sets the acquired digital value of the received electric field strength as carrier sense information (702), and communication. The control unit 14 stores this carrier sense information in the carrier sense status 22 (703).

  Similarly to the processing shown in FIG. 5, the data processing unit also receives notification at regular intervals or every time the carrier sense status 22 is updated, and performs carrier sense status notification processing. Therefore, first, the reception sensitivity correction unit 17 reads a digital value of the received electric field strength set as carrier sense information from the carrier sense status 22 of one of the inter-vehicle communication modules (710), and reads the read digital value of the received electric field strength. Correction and level conversion are performed in accordance with the reception capability of the front vehicle-to-vehicle communication module (711). Thereby, the correction value of the received electric field strength notified to the other inter-vehicle communication module is periodically overwritten and always represents the latest value.

  Next, a data transmission process using the value of the received electric field strength in the other inter-vehicle communication module corrected based on the reception capability will be described with reference to FIG. The processing in FIG. 8 is the same as the processing in FIG. 6, and the same reference numerals are given to the same processing. In the vehicle-to-vehicle communication module 2 for the forward vehicle, the preparation of transmission data is completed (601), and CSMA control is started. At this time, a random number is set in the counter (602). The receiving unit 11 of the vehicle-to-vehicle communication module acquires the received electric field strength as a digital numerical value obtained by AD conversion (803), and acquires the latest correction value of the received electric field strength information of the other vehicle from the data processing unit 6. (804). If the digital value of the received electric field strength and the correction value of the received electric field strength of the other vehicle are smaller than the set threshold value for a certain time (Yes in 805), the other vehicle transmits radio waves. It is determined that it is not transmitted, and further, the digital value of the received electric field strength in the own receiving unit is obtained (806), and the correction value of the received electric field strength of the other vehicle is also obtained from the data processing unit 6 (807), Again, when the received electric field strengths of the own vehicle and the other vehicle are smaller than the set threshold value for a certain time (Yes in 808), the counter is subtracted (609), and the time when the counter value becomes 0 (in 610) Transmission of vehicle information is started at (Yes) (611). If the value of the counter is not 0 (No in 610), the process returns to process 806 and the process is repeated. If the received electric field strengths of the own vehicle and the other vehicle are smaller than the set threshold value for a certain period of time in the determination processes of step 805 and step 808, the process returns to step 803 and the other vehicle transmits a radio wave. Continue the process to check if it is.

  In this way, by correcting the digital value of the received electric field strength in the other inter-vehicle communication module according to the other receiving ability, the received electric field strength values acquired by the plurality of inter-vehicle communication modules are handled in a unified manner. Therefore, when CSMA control is performed by communication using a plurality of inter-vehicle communication modules, normal reception can be prevented even when antenna directivity is provided.

  FIG.1 (b) is a schematic block diagram which shows the deformation | transformation of one Example of the onboard equipment for vehicle-to-vehicle communication using this invention. The basic configuration is the same as that in FIG. 1A, but the vehicle-to-vehicle communication vehicle-mounted device shown in FIG. 1A includes a front vehicle-to-vehicle communication module 2, a rear vehicle-to-vehicle communication module 3, and data. Whereas the processing unit 6 is housed in the same casing, in the configuration shown in FIG. 1B, the front inter-vehicle communication module 2, the rear inter-vehicle communication module 3, and the data processing unit 6 are independent of each other. Each is connected by a wired or wireless in-vehicle network 10. By adopting such a configuration, it is also possible to directly exchange carrier sense status information between the front vehicle-to-vehicle communication module 2 and the rear vehicle-to-vehicle communication module 3 without using the data processing unit 6. Further, the front vehicle-to-vehicle communication module 2, the rear vehicle-to-vehicle communication module 3, and the data processing unit 6 in FIG. 1B are the same as those shown in FIGS.

  The processing flow in the configuration shown in FIG. 1B is the same as that in FIGS. The difference is that when the carrier sense status 22 is updated in the process 505 of FIG. 5, the notification is sent to the CSMA auxiliary control unit of the data processing unit 6 in the vehicle-to-vehicle communication device of FIG. On the other hand, in the case of the vehicle-to-vehicle communication vehicle-mounted device in FIG. 1B, the vehicle-to-vehicle communication module (in this case, the vehicle-to-vehicle communication module for the front) is passed. The carrier sense flag is periodically overwritten and always represents the latest situation. Also in processing 604 and processing 607 in FIG. 6, the carrier sense flag of the other vehicle is captured from the rear inter-vehicle communication module 3.

  FIG. 9 shows a rear vehicle in the configuration shown in FIG. 1B when the digital value of the received electric field strength is used as the carrier sense situation, as in the embodiments shown in FIGS. It is a flowchart explaining the carrier sense process in the inter-vehicle communication module 3. Here, the processing will be described in accordance with the communication state shown in FIG. Therefore, although the functions are clearly divided between the front and rear inter-vehicle communication modules, the front and rear inter-vehicle communication modules actually have the same functions.

  FIG. 9 will be described. The process shown in FIG. 9 is almost the same as the process shown in FIG. 7, and the same processes are denoted by the same reference numerals. The difference is that in the vehicle-to-vehicle communication vehicle-mounted device in FIG. 1A, the level conversion processing performed in the processing 711 in FIG. 7 in the data processing unit 6 is performed by the communication control unit 14 in the rear vehicle-to-vehicle communication module 3. It is the point where it comes to be done. This is for notifying the other vehicle-to-vehicle communication module directly of the digital numerical value of the received electric field intensity, which is the carrier sense status information, without going through the data processing unit 6.

  First, the received inter-vehicle communication module 3 acquires the received electric field strength as a digital value (701), sets the acquired digital value of the received electric field strength as carrier sense information (702), and uses this carrier sense information as the carrier sense status. 22 (703). The communication control unit 14 corrects the digital value of the received electric field strength according to the reception capability of the front vehicle-to-vehicle communication module 2 and notifies the front vehicle-to-vehicle communication module. The correction value is overwritten regularly and always represents the latest value. Further, the data transmission process in this case is the same as the process shown in FIG. 8, but the correction value of the received electric field strength of the other vehicle is directly taken from the rear inter-vehicle communication module 3 in the processes 804 and 807. Become.

  The present invention can be applied not only to a vehicle-to-vehicle communication module but also to a communication module in a wireless LAN system that requires directivity.

It is a figure which shows schematic structure of the onboard equipment for vehicle-to-vehicle communication using this invention. It is a figure explaining the example of the vehicle-to-vehicle communication by the onboard equipment for vehicle-to-vehicle communication using this invention. It is a block diagram of the onboard equipment for vehicle-to-vehicle communication using this invention. It is a figure explaining the deformation | transformation of the data processing part in the onboard equipment for vehicle-to-vehicle communication using this invention. It is a flowchart explaining the process of the carrier sense condition which concerns on this invention. It is a flowchart of the transmission process which concerns on this invention. It is a flowchart explaining the deformation | transformation of the process of the carrier sense condition which concerns on this invention. It is a flowchart explaining the deformation | transformation of the transmission process which concerns on this invention. It is a flowchart explaining the further deformation | transformation of the process of the carrier sense condition which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle-to-vehicle communication equipment 2 Front vehicle-to-vehicle communication module 3 Rear vehicle-to-vehicle communication module 4 Front directional antenna 5 Rear directional antenna 6 Data processing unit 7 Own vehicle 8 Other vehicle 9 Navigation system 10 In-car network 11 Reception unit 12 Transmission unit 13 CSMA control unit 14 Communication control unit 15 Reception data processing unit 16 Transmission data processing unit 17 Reception sensitivity correction unit 18 Directional communication area 19 for the forward directional antenna Directional communication area for the rear directional antenna 20 CSMA auxiliary controller

Claims (5)

A transmitter that transmits information about the vehicle using radio waves, a receiver that obtains information about other vehicles using radio waves, and the strength of the radio waves are detected to confirm that the other vehicle is not transmitting radio waves. A vehicle-to-vehicle communication on-vehicle device having a plurality of vehicle-to-vehicle communication modules that perform communication by CSMA control, having a CSMA control unit that starts transmission of radio waves of the vehicle after
The inter-vehicle communication module notifies the other inter-vehicle communication module of the detection status of the strength of the radio wave in the inter-vehicle communication module,
The CSMA control unit determines whether the other vehicle is based on the detection status of the strength of the radio wave received by the receiving unit of the vehicle-to-vehicle communication module and the strength of the received radio wave notified from the other vehicle-to-vehicle communication module. An on-vehicle device for vehicle-to-vehicle communication characterized by confirming that radio waves are not transmitted.   The on-vehicle communication device for vehicle-to-vehicle communication according to claim 1, wherein the detection status of the strength of the wireless radio wave represents the strength of the received radio wave as a digital numerical value. An on-vehicle device for vehicle-to-vehicle communication, wherein a digital value of a detection state of the strength of the radio wave is corrected according to a reception capability of another vehicle-to-vehicle communication module provided.   The vehicle-to-vehicle communication vehicle-mounted device according to claim 1, wherein the plurality of vehicle-to-vehicle communication modules are stored in a single housing.   The vehicle-to-vehicle communication vehicle-mounted device according to claim 1, wherein the plurality of vehicle-to-vehicle communication modules are separate casings, and the vehicle-to-vehicle communication modules are connected to each other by wire or wirelessly. Onboard equipment for communication.   2. The vehicle-to-vehicle communication vehicle-mounted device according to claim 1, wherein the plurality of vehicle-to-vehicle communication modules includes at least a vehicle-to-vehicle communication module connected to an antenna having directivity in front of the vehicle on which the vehicle-mounted device is mounted. A vehicle-to-vehicle communication vehicle-mounted device including a vehicle-to-vehicle communication module connected to an antenna having directivity behind the vehicle.

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