JP6444179B2 - Communication device - Google Patents

Description

  The present invention relates to a communication device.

  2. Description of the Related Art Conventionally, driving support systems that provide driving conditions and road conditions of surrounding vehicles to a driver who drives a vehicle and prevent a collision at an intersection are known. Inter-vehicle communication in which vehicles communicate directly with each other has high real-time characteristics. However, in vehicle-to-vehicle communication, if information is transmitted from a plurality of terminals at the same time, congestion may occur and data may be lost, which is a problem when used for a highly urgent service. Patent Document 1 discloses a communication device that switches from vehicle-to-vehicle communication to road-to-vehicle communication when entering the communication range of road-to-vehicle communication.

JP 2009-232065

  In the invention described in Patent Document 1, the occurrence of congestion in inter-vehicle communication cannot be suppressed.

The communication apparatus according to the present invention is mounted on a vehicle. The communication device includes a wide-area communication unit connected to the data communication network, a vehicle-to-vehicle communication unit that directly communicates with a communication device mounted on another vehicle, and transmission of data using the vehicle-to-vehicle communication unit according to predetermined conditions. The vehicle-to-vehicle communication control unit to be permitted, the position calculation unit that calculates the position of the vehicle, the position information of the other vehicle using the wide-area communication unit, and the position of the vehicle calculated by the position calculation unit And an inter-vehicle distance acquisition unit that acquires a distance between the vehicle on which the communication device is mounted and the other vehicle using a position information of the other vehicle and a threshold value calculation unit that calculates a threshold value to be compared with the distance. The inter-vehicle communication control unit permits transmission of data when the distance acquired by the inter-vehicle distance acquisition unit is shorter than the threshold value, and the threshold value calculation unit transmits the position calculated by the position calculation unit using the wide area communication unit. Corresponding to the position received by the wide area communication unit. Based on the information representing the degree of risk, increase calculated higher risk threshold.

  According to the present invention, it is possible to suppress the occurrence of congestion in inter-vehicle communication.

The figure which shows the communication object of the vehicle which mounts a communication apparatus Block diagram showing the configuration of the communication device Figure showing an example of the area parameter table Diagram showing an example of the acceleration parameter table Figure showing an example of the local parameter table Flow chart showing the process of data transmission in inter-vehicle communication

(Embodiment)
Hereinafter, an embodiment of a communication apparatus according to the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a communication target of a vehicle equipped with a communication device. In FIG. 1, three vehicles, that is, a vehicle 1, a vehicle 1A, and a vehicle 1B are traveling on a certain roadway. All three vehicles are equipped with a communication device. The configuration of the communication apparatus will be described later with reference to FIG.
The vehicle 1 communicates with other vehicles 1A and 1B running in parallel, the base station 2, the wireless communication spot 5, and a GNSS (Global Navigation Satellite System) satellite 6.

The vehicle 1 performs direct communication using radio, that is, vehicle-to-vehicle communication, with the parallel running vehicle 1A and vehicle 1B. The communicable range of inter-vehicle communication is several hundred meters, which is not necessarily wide. However, since no relay equipment is interposed, real-time information can be exchanged between vehicles. However, congestion may occur if a large number of vehicles transmit data at the same time. In inter-vehicle communication, a plurality of vehicles transmit their vehicle positions to improve safety, for example, avoid encounter collision at an intersection.
When the vehicle 1 receives the approach of another vehicle by inter-vehicle communication, the vehicle 1 notifies the driver of the vehicle 1 to call attention.

  The base station 2 is the end of the data communication network 3 installed on a steel tower or the like. The base station 2 corresponds to, for example, the LTE (Long Term Evolution) system. The data communication network 3 is connected to a wide area information provision server 4 that provides traffic conditions on the roadway. The wide area information providing server 4 acquires position information from each vehicle traveling on the roadway, and transmits the position information of each vehicle in response to a request. The wide area information providing server 4 includes risk map data and an area parameter table 31. In the risk level map data, for example, the risk level for each position on the road based on past traffic accident occurrence data is recorded. The area parameter table 31 will be described later with reference to the drawings. The wide area information providing server 4 refers to the risk map data and the area parameter table 31, calculates an index indicating the risk using the received position information, and transmits the calculated index to the vehicle 1.

The wireless communication spot 5 is a wireless communication device installed on the side of the roadway, that is, on the road. The wireless communication spot 5 is connected to the regional server 7. The regional server 7 collects information related to a very narrow area where the connected wireless communication spot 5 is installed, that is, local traffic. The regional server 7 includes a local parameter table 33 which will be described later, and refers to the local parameter table 33 to provide an index indicating a local risk level to a traveling vehicle.
The GNSS satellite 6 is an artificial satellite that constitutes a satellite navigation system, and transmits radio waves necessary for position calculation. The vehicle 1 receives radio waves from the GNSS satellite 6 and calculates its own vehicle position.

The vehicle 1 can perform wireless communication with the base station 2, that is, wide area communication. The vehicle 1 accesses the wide area information providing server 4 by wide area communication, transmits the position of the own vehicle, and acquires an index indicating the position of another vehicle and the risk level of the area.
The vehicle 1 performs wireless communication with the wireless communication spot 5 installed on the road, that is, road-to-vehicle communication. In road-to-vehicle communication, an index indicating a local risk level around the wireless communication spot 5 is acquired.

  FIG. 2 is a block diagram illustrating a configuration of the communication device 10 included in the vehicle 1. The communication device 10 is, for example, a vehicle-mounted communication device. The communication device 10 includes an arithmetic processing unit 11, an inter-vehicle communication unit 12, a wide area communication unit 13, a road-to-vehicle communication unit 14, a speedometer 15 that measures the speed of the vehicle 1, a position calculation unit 16, and an arithmetic operation. And a notification unit 17 that notifies the driver of the vehicle 1 based on the calculation result of the processing unit 11. The arithmetic processing unit 11 is connected to the inter-vehicle communication unit 12, the wide-area communication unit 13, the road-to-vehicle communication unit 14, the speedometer 15, the position calculation unit 16, and the notification unit 17 through a communication bus. However, they may be connected by a plurality of different types of buses. That is, the arithmetic processing unit 11, the inter-vehicle communication unit 12, the wide-area communication unit 13, the road-to-vehicle communication unit 14, and the position calculation unit 16 are connected by Ethernet (registered trademark), and the arithmetic processing unit 11, The total 15 and the notification unit 17 may be connected by CAN.

The arithmetic processing unit 11 includes a CPU, a ROM, and a RAM. The ROM of the arithmetic processing unit 11 stores a program whose operation is shown by a flowchart described later and an acceleration parameter table 32 described later. The CPU of the arithmetic processing unit 11 develops and executes a program stored in the ROM on the RAM. The arithmetic processing unit 11 gives an operation instruction to the inter-vehicle communication unit 12, the wide-area communication unit 13, the road-to-vehicle communication unit 14, the speedometer 15, the position calculation unit 16, and the notification unit 17 in accordance with the program procedure. Output. The arithmetic processing unit 11 has a timer function and calculates the acceleration of the vehicle 1 using the speed measured by the speedometer 15 with a predetermined time interval.
When the inter-vehicle communication unit 12 receives the position, speed, and acceleration of another vehicle, the arithmetic processing unit 11 outputs the received information to the notification unit 17 and alerts the driver.

The inter-vehicle communication unit 12 is a communication unit corresponding to, for example, an IEEE 802.11p communication method. The inter-vehicle communication unit 12 communicates wirelessly with vehicles that the vehicle 1 is traveling in the vicinity, such as the vehicles 1A and 1B. In the present embodiment, there is no restriction on reception using the inter-vehicle communication unit 12, but transmission using the inter-vehicle communication unit 12 is performed only when a predetermined condition is satisfied as described later.
The wide area communication unit 13 is a communication unit corresponding to LTE, for example. The wide area communication unit 13 is used when the vehicle 1 communicates with the base station 2. Transmission / reception of information using the wide area communication unit 13 is not particularly limited.
The road-vehicle communication unit 14 receives information from the wireless communication spot 5 and outputs the information to the arithmetic processing unit 11.

When the speedometer 15 receives a command from the arithmetic processing unit 11, it measures the speed of the vehicle 1 and outputs it to the arithmetic processing unit 11. The arithmetic processing unit 11 includes a timer, and calculates the acceleration by acquiring the speed a plurality of times.
The position calculation unit 16 includes a receiver that receives radio waves from the GNSS satellite 6 and an arithmetic circuit. When receiving a command from the arithmetic processing unit 11, the position calculating unit 16 receives radio waves output from the GNSS satellite 6, calculates the position of the position calculating unit 16, that is, the position of the vehicle 1, and outputs the calculated position to the arithmetic processing unit 11. .
The notification unit 17 includes a speaker and a display. The notification unit 17 alerts the driver of the vehicle 1 that another vehicle is approaching by outputting sound from the speaker and displaying on the display, based on a command from the arithmetic processing unit 11.

(Three parameters)
The indices indicating the three risk levels, that is, the area parameter α, the acceleration parameter β, and the local parameter γ will be described with reference to FIGS.
The area parameter α is an index indicating the degree of risk calculated by the wide area information providing server 4 based on the current location of the vehicle 1. The wide area information providing server 4 includes risk map data in which a risk level is set, and an area parameter table 31. When the wide area information providing server 4 receives the current position from the communication device 10, the wide area information providing server 4 refers to the risk map data and determines the risk level to which the current position of the vehicle 1 belongs. The wide area information providing server 4 refers to the area parameter table 31 to determine the area parameter α corresponding to the determined risk level and outputs it to the vehicle 1.

  FIG. 3 is a diagram illustrating an example of the area parameter table 31. The risk map data included in the wide area information providing server 4 classifies a straight road with a good view into a risk level 1, a road with a good view into a risk level 2, and a road with a bad view, such as an intersection, into a risk level 3. The wide area information providing server 4 outputs the area parameter α as “−50” when the risk level of the current location of the vehicle 1 is 1, and sets the area parameter α as “−50” when the risk level of the current location of the vehicle 1 is 2. When the risk level of the current location of the vehicle 1 is 3, the area parameter α is output as “+50”. When the vehicle 1 is in a place with poor visibility, it is difficult to recognize the vehicle 1 from other nearby vehicles. Therefore, the area parameter α is changed to transmit the position of the host vehicle to the surrounding vehicles in order to avoid a collision at the time of encounter.

  The acceleration parameter β is an index indicating the degree of risk calculated by the arithmetic processing unit 11 based on the acceleration output from the speedometer 15. The arithmetic processing unit 11 calculates the acceleration of the vehicle 1 using the speed measured by the speedometer 15 with a predetermined time interval. The arithmetic processing unit 11 refers to the acceleration parameter table 32 stored in the ROM of the arithmetic processing unit 11 and determines the risk level and the acceleration parameter β according to the calculated magnitude of acceleration.

FIG. 4 is a diagram illustrating an example of the acceleration parameter table 32. When the absolute value of the acceleration is 0.15 G or less, the arithmetic processing unit 11 determines that the motion is substantially constant and the risk is small, and outputs the risk level 1 and the acceleration parameter β as “−50”. Here, “G” means “9.8 m / s ² ” which is a gravitational acceleration. When the absolute value of the acceleration is 0.3 G or less, the arithmetic processing unit 11 determines that the risk is moderate, and outputs the risk level 2 and the acceleration parameter β as “0”. If the absolute value of the acceleration is greater than 0.3 G, the arithmetic processing unit 11 determines that there is a dangerous state due to sudden braking / acceleration, and outputs the danger level 3 and the acceleration parameter β as “+50”.

  The local parameter γ is an index indicating the degree of danger in a very narrow area where the wireless communication spot 5 is installed. The regional server 7 collects information on events that are currently held within a few hours in the vicinity where the wireless communication spot 5 is installed. The regional server 7 refers to the local parameter table 33 stored in the regional server 7 and calculates the local parameter γ based on the degree of traffic jam estimated from the collected event information. The regional server 7 outputs the calculated local parameter γ from the wireless communication spot 5. That is, the local parameter γ output from the regional server 7 is calculated based on the prediction of the traffic jam at the place where the wireless communication spot 5 is installed.

  FIG. 5 is a diagram illustrating an example of the local parameter table 33. If there is no event in the vicinity of the wireless communication spot 5, the regional server 7 determines that there is no traffic volume increase, that is, no traffic jam occurs, and outputs the risk level 1 and the local parameter γ as “−50”. To do. If there is a small event, the regional server 7 determines that a small traffic increase, that is, a slight traffic jam occurs, and outputs the risk level 2 and the local parameter γ as “0”. If there is a large-scale event, the regional server 7 determines that a large-scale traffic volume increase, that is, heavy traffic congestion, and outputs the risk level 3 and the local parameter γ as “+50”.

(Communication device operation)
The operation of the communication device 10 will be described with reference to FIG. When the ignition switch of the vehicle 1 is turned on by the driver, the communication device 10 is activated in conjunction with this. When the communication device 10 is activated, the CPU of the arithmetic processing unit 11 expands and executes a program described below stored in the ROM on the RAM. The execution subject of each step described below is the CPU of the arithmetic processing unit 11.

The process described below is a process of determining whether or not to transmit information on the own vehicle directly to another vehicle using the inter-vehicle communication unit 12. As described above, the arithmetic processing unit 11 outputs the data received by the inter-vehicle communication unit 12 to the notification unit 17 independently of the flowchart described below.
The thin two lines shown in the flowchart of FIG. 6 represent the synchronization process. That is, when step S401 is completed, steps S402, S403, and S404 are executed in parallel.

In step S <b> 401, the arithmetic processing unit 11 activates the inter-vehicle communication unit 12, the wide area communication unit 13, and the road-to-vehicle communication unit 14. Thereafter, the inter-vehicle communication unit 12, the wide-area communication unit 13, and the road-to-vehicle communication unit 14 can receive. Next, steps S402, S403, and S404 are executed in parallel.
In step S <b> 402, the arithmetic processing unit 11 connects to the base station 2 using the wide area communication unit 13 and acquires position information of other vehicles from the wide area information providing server 4. Next, the process proceeds to step S405.

In step S403, the arithmetic processing unit 11 calculates and acquires the position using the position calculation unit 16, and proceeds to step S405.
In step S <b> 404, the arithmetic processing unit 11 uses the speedometer 15 to calculate the speed of the vehicle 1 multiple times. The arithmetic processing part 11 calculates the acceleration of the vehicle 1 using a timer function together, and progresses to step S405.

In step S405, which is executed when all of steps S402 to S404 are completed, the arithmetic processing unit 11 temporarily stores the information acquired in steps S402 to S404 in the RAM. Specifically, the position of the other vehicle acquired in step S402, the position of the vehicle 1 acquired in step S403, and the acceleration calculated in step S404 are stored in the RAM. Next, steps S406, S408, S409, and S410 are executed in parallel.
In step S <b> 406, the arithmetic processing unit 11 connects to the base station 2 using the wide area communication unit 13 and transmits the position of the vehicle 1 to the wide area information providing server 4. Next, the process proceeds to step S407.

In step S407, the arithmetic processing unit 11 acquires the area parameter α corresponding to the position of the vehicle 1 from the wide area information providing server 4 using the wide area communication unit 13, and proceeds to step S411.
In step S <b> 408, the arithmetic processing unit 11 calculates an inter-vehicle distance. Specifically, the arithmetic processing unit 11 calculates the distance to the shortest other vehicle using the position of the other vehicle acquired in step S402 and the position of the host vehicle acquired in step S403. Next, the process proceeds to step S411.

In step S409, the arithmetic processing unit 11 acquires the local parameter γ from the wireless communication spot 5 using the road-to-vehicle communication unit 14, and proceeds to step S411.
In step S410, the arithmetic processing unit 11 calculates an acceleration parameter β using the acceleration calculated in step S404 and the acceleration parameter table 32 stored in the ROM.

In step S411, which is executed when all of steps S406 to S410 are completed, the arithmetic processing unit 11 calculates a threshold value used in later processing. Specifically, the sum of the initial value A stored in the ROM, the value of the area parameter α, the value of the acceleration parameter β, and the value of the local parameter γ is calculated. Next, the process proceeds to step S412.
In step S412, the arithmetic processing unit 11 determines whether the inter-vehicle distance calculated in step S408 is smaller than the threshold calculated in step S411. If it is determined that the inter-vehicle distance is smaller than the threshold, the process proceeds to step S413, and if it is determined that the inter-vehicle distance is greater than or equal to the threshold, the process returns to steps S402 to S404.

In step S413, the arithmetic processing unit 11 permits transmission of data using the inter-vehicle communication unit 12. Thereby, the data showing the position, speed, and acceleration of the vehicle 1 are transmitted to surrounding vehicles using the inter-vehicle communication unit 12. This data is received by the inter-vehicle communication unit 12 and output to the notification unit 17 in the communication device 10 mounted on another vehicle. Thereby, the approach of the vehicle 1 is alert | reported with respect to the driver | operator of another vehicle. Next, the process proceeds to step S414.
In step S414, the arithmetic processing unit 11 determines whether or not the ignition switch is turned off by the driver. When it is determined that the program has been turned off, the operation of the program whose operation is shown in FIG. 6 is terminated.

According to the embodiment described above, the following operational effects can be obtained.
(1) The communication device 10 is mounted on the vehicle 1. The communication device 10 uses a wide-area communication unit 13 connected to the data communication network 3, a vehicle-to-vehicle communication unit 12 that communicates with the communication device 10 mounted on another vehicle, and a vehicle-to-vehicle communication unit 12 according to predetermined conditions. A vehicle-to-vehicle communication control unit that permits transmission of the received data, that is, the arithmetic processing unit 11.
Since the communication device 10 is configured as described above, it is possible to suppress the occurrence of congestion in the vehicle-to-vehicle communication by restricting data transmission using the vehicle-to-vehicle communication unit 12.

(2) The communication device 10 includes an inter-vehicle distance acquisition unit (step S408 in FIG. 6) that acquires the distance between the vehicle 1 on which the communication device 10 is mounted and another vehicle, and a threshold value that calculates a threshold value to be compared with the distance. And a calculation unit (step S411 in FIG. 6). The arithmetic processing unit 11 transmits data when the distance acquired by the inter-vehicle distance acquisition unit is shorter than the threshold value.
Therefore, the shorter the inter-vehicle distance from other surrounding vehicles, that is, the closer the distance, the greater the risk of collision, the higher the possibility of performing inter-vehicle communication. In other words, when the risk of collision is small, transmission in vehicle-to-vehicle communication is not performed so as not to cause congestion, and when the risk of collision is large, transmission in vehicle-to-vehicle communication is performed. Therefore, it is possible to achieve both suppression of congestion and ensuring safety in inter-vehicle communication.

(3) The communication device 10 includes a host vehicle measurement unit (step S404 in FIG. 6) that measures the state of the vehicle 1. The threshold value calculation unit (step S411 in FIG. 6) calculates a threshold value based on the acceleration parameter β calculated using the acceleration.
Therefore, when the host vehicle is in a sudden acceleration state or a sudden braking state where the absolute value of acceleration is large, the risk of a collision with the surrounding vehicle is high, so even if the distance between the surrounding vehicles is long, The possibility of transmission in communication increases.

(4) The communication device 10 includes a position calculation unit 16 that calculates a position. The arithmetic processing unit 11 transmits the position calculated by the position calculating unit 16 using the wide area communication unit 13. The threshold value calculation unit (step S411 in FIG. 6) calculates a threshold value based on the area parameter α corresponding to the position calculated by the wide area information providing server 4 received by the wide area communication unit 13.
Therefore, an appropriate threshold value can be set according to the position of the host vehicle, and both congestion suppression and safety can be achieved. For example, when the user is in a place with a high risk of accidents, the position of the host vehicle is transmitted by inter-vehicle communication even if the inter-vehicle distance is long by setting the threshold value high. Thereby, since the driver of another vehicle recognizes the position of the own vehicle, a collision can be prevented beforehand.

(5) The communication device 10 includes a road-to-vehicle communication unit 14 that communicates with a communication device installed on the road, that is, the wireless communication spot 5. The threshold value calculation unit (step S411 in FIG. 6) calculates the threshold value based on the local parameter γ received by the road-vehicle communication unit 14.
Therefore, an appropriate threshold value can be set according to the road condition due to local factors such as an event held near the position of the host vehicle, and both congestion suppression and safety can be ensured.

The embodiment described above may be modified as follows.
(1) The communication device 10 may not be a vehicle-mounted communication device. For example, a terminal that can be carried outside the vehicle, such as a mobile phone, a notebook computer, or a PDA may be used.
(2) The configuration of the communication device 10 may not be configured as a whole. For example, the inter-vehicle communication unit 12, the speedometer 15, the notification unit 17, and the like may be provided as different modules, and the functions of the communication device 10 may be exhibited as a whole by connecting them.
(3) The vehicle-to-vehicle communication unit 12 and the road-to-vehicle communication unit 14 may be configured by the same hardware.

(4) The position calculation unit 16 may not include a GNSS receiver and may simply calculate the position using another communication unit. For example, the road-to-vehicle communication unit 14 may identify the wireless communication spot 5 that is communicating, and may determine that the vehicle 1 is within the communication range of the wireless communication spot 5.
(5) The vehicle 1 may include a sensor for measuring a distance to another vehicle, such as a camera or a laser range finder. Then, instead of inquiring the wide area information providing server 4 using the wide area communication unit 13, the inter-vehicle distance may be calculated using the output of the sensor.
(6) The arithmetic processing unit 11 may calculate the threshold using at least one of the area parameter α, the acceleration parameter β, and the local parameter γ, and may not calculate using all of them.

(7) The arithmetic processing unit 11 directly compares the inter-vehicle distance calculated in step S408 of FIG. 6 with the threshold calculated in step S411, but compares the threshold with the value obtained by inputting the inter-vehicle distance into a predetermined function. May be. That is, a value based on the inter-vehicle distance may be compared with a threshold value.
For example, a function that outputs infinity may be used if the inter-vehicle distance is equal to or greater than a predetermined distance, or a function that outputs zero if the inter-vehicle distance is equal to or less than the predetermined distance.
(8) In the calculation of the threshold value, the arithmetic processing unit 11 may use an evaluation value based on the speed or the engine speed instead of the acceleration parameter β. This is because the engine speed represents the amount of kinetic energy generated by the vehicle 1, and thus the speed or the engine speed can be a simple substitute for acceleration.

(9) Communication between the wide area communication unit 13 and the base station 2 is not limited to the LTE system. Other communication systems that are wireless communication systems used in network services classified as WAN (Wide Area Network) such as WiMAX (registered trademark) system, WCDMA (registered trademark) system, GSM (registered trademark) system, etc. Good.
(10) The communication of the inter-vehicle communication unit 12 is not limited to IEEE 802.11p. Any communication method such as WiFi-Direct or Bluetooth (registered trademark) can be used as long as the communication devices 10 can communicate with each other without using a server.
(11) The communication device 10 may receive the area parameter α using the inter-vehicle communication unit 12. There is no problem even if the same area parameter α is applied to a vehicle at a distance where inter-vehicle communication is possible. The communication device 10 has an advantage that the area parameter α can be obtained without transmitting the position of the host vehicle.

(Modification 1)
In the first embodiment, the inter-vehicle communication unit 12 is always in a receivable state, but the inter-vehicle communication unit 12 may be in a state in which no reception is performed.
Communication between vehicles by the vehicle-to-vehicle communication unit 12 is intended to improve safety, for example, to prevent encounter collision at an intersection. Therefore, the inter-vehicle communication unit 12 does not have to perform transmission and reception when the inter-vehicle distance is longer than the predetermined second threshold or when there is no intersection over the predetermined distance in the traveling direction of the vehicle 1. That is, you may cut | disconnect the power supply of the vehicle-to-vehicle communication part 12 temporarily.
According to the first modification, unnecessary energy waste can be prevented.

The above-described embodiments and modifications may be combined.
Although the embodiment and the modification have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Vehicle 2 ... Base station 3 ... Data communication network 4 ... Wide area information provision server 5 ... Wireless communication spot 7 ... Regional server 10 ... Communication apparatus 11 ... Arithmetic processing part 12 ... Inter-vehicle communication part 13 ... Wide area communication part 14 ... Road Inter-vehicle communication unit 15 ... speedometer 16 ... position calculation unit 31 ... area parameter table 32 ... acceleration parameter table 33 ... local parameter table

Claims (4)

A communication device mounted on a vehicle,
A wide area communication unit connected to the data communication network;
An inter-vehicle communication unit that communicates with a communication device mounted on another vehicle;
A vehicle-to-vehicle communication control unit that permits transmission of data using the vehicle-to-vehicle communication unit according to a predetermined condition;
A position calculation unit for calculating the position of the vehicle;
Using the wide-area communication unit to acquire position information of the other vehicle, and using the position of the vehicle calculated by the position calculation unit and the position information of the other vehicle; An inter-vehicle distance acquisition unit that acquires a distance from another vehicle;
A threshold value calculation unit for calculating a threshold value to be compared with the distance,
The inter-vehicle communication control unit permits transmission of data when the distance acquired by the inter-vehicle distance acquisition unit is shorter than the threshold value,
The threshold value calculation unit transmits the position calculated by the position calculation unit using the wide area communication unit, and the risk level is high based on information indicating the risk level corresponding to the position received by the wide area communication unit. A communication device that calculates the threshold value as large as possible. The communication device according to claim 1 ,
A vehicle measurement unit that measures at least one of the speed, acceleration, and engine speed of the vehicle;
The said threshold value calculation part is a communication apparatus which calculates the said threshold value based on the output of the said own vehicle measurement part. The communication device according to claim 1 or 2 ,
A road-to-vehicle communication unit that communicates with a communication device installed on the road;
The said threshold value calculation part is a communication apparatus which calculates the said threshold value large, so that the said danger level is high based on the information showing the danger level corresponding to the place where the said communication apparatus received by the said road-vehicle communication part. The communication device according to claim 1 ,
The information indicating the degree of risk is a communication device that is output based on a prediction of traffic jam in a place where the communication device is installed.

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