JP5888189B2 - Inter-vehicle communication system, inter-vehicle communication method, and in-vehicle terminal - Google Patents

Description

  The present invention relates to a technique for a plurality of vehicles to form a group and perform communication.

  A technique is known in which vehicles form a group and communicate with each other using inter-vehicle communication. A plurality of vehicles form a group and perform communication within the group using a common identifier, so that more efficient communication can be performed compared to a case where information is simply broadcast without forming a group.

  When a group is to be formed by a plurality of vehicles, it is necessary to appropriately discriminate between vehicles belonging to the group and vehicles not belonging to the group. As a technique for this, for example, there is a method described in Patent Document 1. According to this method, a group can be formed with a plurality of vehicles in the same wireless communication area as members.

JP 2009-516957 A

  When trying to group a plurality of vehicles, there is a problem that unrelated vehicles are added to members depending on the situation. For example, when a group member is determined based on whether or not wireless communication is possible as in Patent Document 1, for example, a vehicle in an oncoming lane or a parked vehicle may be added to the group member. .

  If it is determined that irrelevant vehicles belong to the same group, an originally unnecessary message is processed as being addressed to the user, which raises a safety concern. For example, receiving a sudden brake notification from an irrelevant vehicle may cause unnecessary avoidance behavior, thereby inducing another danger.

  It seems that this problem can be solved by checking the movement vector of the vehicle, that is, the speed and the traveling direction, and preventing the vehicles having similar movement vectors from forming a group. However, in this case, it is necessary to always obtain a movement vector of the target vehicle and monitor whether each vehicle is suitable as a member constituting a group. For this reason, another problem arises in that the amount of communication and the amount of processing increase and the responsiveness deteriorates. In vehicle-to-vehicle communication used for traffic safety, deterioration of responsiveness can be a fatal problem.

  Moreover, even if it is a case where a group is determined using the speed and the advancing direction of a vehicle, a misjudgment cannot be eliminated completely. For example, if there is a vehicle traveling on a highway on an elevated road and a vehicle traveling on a general road below the elevated road, the same group is used even though they are traveling on different roads because their movement vectors are similar. May be judged.

  In order to avoid such an erroneous determination, a further determination element can be added, for example, using altitude data obtained by GPS. However, when such a determination element is added, the overhead of arithmetic processing increases and the responsiveness is further deteriorated.

The present invention has been made in consideration of the above-described problems, and it is possible to determine whether or not the other party's vehicle that transmitted the information belongs to the same group as the own vehicle with a small amount of processing. An object is to provide a communication system and a vehicle-to-vehicle communication method.

The inter-vehicle communication system according to the present invention is a system including a roadside device and a plurality of vehicles.
Specifically, the roadside device includes a key transmission unit that transmits a group key that is a key unique to the roadside device to a vehicle that passes through a predetermined point, and the vehicle transmits the group key from the roadside device to the group. Key storage means for receiving and storing the key and transmission information that is information to be transmitted to other vehicles are generated, and exclusive OR of the transmission information and the group key stored in the key storage means is obtained. Message generating means for generating a transmission message that is data; message transmitting means for transmitting the transmission message to another vehicle by wireless communication; message receiving means for receiving a transmission message transmitted from another vehicle; and the reception The transmission message is exclusive-ORed with the group key stored in the key storage means, and the transmission message is obtained based on the decrypted data which is the obtained data. Vehicle and the host vehicle that has transmitted the di has a group determining means for determining whether or not belonging to the same group.

  The roadside device in the present invention is arranged at a predetermined point on the road and transmits a group key to vehicles passing therethrough. The group key is unique to each roadside device and is information for identifying a group. That is, a plurality of vehicles that have received a group key from the same roadside device constitute the same group until a group key is received from the next roadside device.

Transmission information is information transmitted and received between vehicles. The transmission information may be data for traffic control such as vehicle speed, position information, and traveling direction, or may be data provided to vehicle occupants such as traffic information and weather information.
When a vehicle transmits transmission information to another vehicle, the vehicle transmits data (transmission message in the present invention) obtained by performing an exclusive OR of the transmission information to be transmitted and the group key received from the roadside device. In addition, the vehicle that has received the transmission message takes an exclusive OR with the group key received from the roadside device for the received transmission message, and obtains decrypted data. If the vehicle that received the transmission message has the same group key as the vehicle that transmitted the transmission message, the decrypted data matches the transmission information. That is, by determining whether or not the decoded data matches the transmission information, it is possible to determine whether or not the transmission source vehicle belongs to the same group as the own vehicle. Whether the decoded data matches the transmission information can be determined using a known technique. For example, an error detection code such as a checksum, parity, or cyclic redundancy check may be used, or a fixed value may be included in transmission information, and determination may be made based on whether or not the fixed value is obtained. If the decrypted data does not match the transmission information, it can be seen that the transmission message is transmitted from a vehicle having a different group key.

  The vehicle according to the present invention is characterized in that the processing is lightweight because the group is determined using only exclusive OR. In addition, since it is not necessary to monitor that the vehicle has joined or left the group, both the communication amount and the calculation amount can be reduced, and the responsiveness of the terminal is improved as compared with the conventional group configuration technology.

  Further, the message generation means includes shared data, which is information shared by a plurality of vehicles, in the transmission information, and the group determination means, when the shared data is included in the decoded data, It may be determined that the vehicle that has transmitted the transmission message and the host vehicle belong to the same group.

Whether the decrypted data is correct may be determined using information shared by the vehicle that transmitted the information and the vehicle that received the information. For example, when a fixed character string is used as shared data, the character string is obtained from the decrypted data only when the group key of the transmitting vehicle and the group key of the host vehicle are the same, and the group key is If it is different, you cannot get it. The shared data may be any information as long as it is information shared between different vehicles.

  The shared data may be information representing a current time. Using the current time eliminates the need for vehicles to share information in advance.

  The predetermined point may be a point where the vehicle flows out from the intersection. An intersection is a point where traffic merges or branches. As described above, a plurality of vehicles may form the same group in a section where no merging or branching occurs.

  According to the present invention, it is possible to provide a vehicle-to-vehicle communication system and a vehicle-to-vehicle communication method capable of performing determination as to whether or not a partner vehicle that has transmitted information belongs to the same group as the host vehicle with a small processing amount. Can do.

It is a figure explaining the structure method of a group. It is a figure explaining the arrangement | positioning method of the roadside apparatus in 1st embodiment. It is a figure explaining the method of the production | generation of the transmission message in 1st embodiment, and a decoding. It is a system configuration figure of the in-vehicle terminal concerning a first embodiment. It is a system configuration figure of the roadside device concerning a first embodiment. It is a process flowchart figure at the time of group key reception in 1st embodiment. It is a process flowchart figure at the time of data transmission in 1st embodiment. It is a figure showing the flow of the data at the time of data transmission in 1st embodiment. It is a process flowchart figure at the time of data reception in 1st embodiment. It is a figure showing the flow of data at the time of data reception in 1st embodiment. It is a figure explaining the arrangement | positioning method of the roadside apparatus in the modification of 1st embodiment. It is a figure explaining the method of the production | generation of the transmission message in 2nd embodiment, and a decoding.

(First embodiment)
<Outline of grouping>
The grouping of in-vehicle terminals in the first embodiment will be described. FIG. 1 is a schematic diagram showing the arrangement of roads. When there is a road having a shape as shown in FIG. 1, traffic does not merge or branch in the range indicated by the dotted arrows, so vehicles traveling in the range are in the same group. It can be treated as belonging. As described above, in the first embodiment, target roads are divided into sections, and vehicles traveling in the sections are assigned to the groups. In the following description, each group is described with a number. For example, the group 4 is a group to which vehicles traveling in the section shown in (4) of FIG. 1 belong.

The vehicle can communicate using the assigned group. For example, when a vehicle belonging to group 11 receives a message from another vehicle, only the message transmitted by the vehicle belonging to group 11 is processed, and other groups such as groups 8, 9, 10 are processed.
Messages sent by vehicles belonging to are discarded. By doing in this way, vehicles can communicate now in a group.

<Intra-group communication method>
A specific method for assigning groups to vehicles and performing intra-group communication will be described.
The designation of a group for a vehicle is performed by a roadside device installed on the roadside or on the road distributing a group key to the vehicle. FIG. 2 is an enlarged view of the intersection indicated by reference numeral 100A. The roadside devices 101 to 104 are respectively arranged on roads flowing out from intersections, and distribute group keys to passing vehicles by wireless communication.
The group key is distributed only to vehicles traveling in the target lane. Group keys are not distributed to vehicles traveling in different lanes, such as on the opposite lane or on an overpass, even if the distance is short. This can be implemented by means such as adjusting the strength and directivity of the radio signal output by the roadside device and appropriately setting the communication distance with the vehicle that is the communication partner.

  Specifically, a group key corresponding to group 3 is distributed to vehicles passing through the roadside apparatus 101, and a group key corresponding to group 1 is distributed to vehicles passing through the roadside apparatus 102. Similarly, a group key corresponding to group 4 is distributed to vehicles passing through the roadside apparatus 103, and a group key corresponding to group 6 is distributed to vehicles passing through the roadside apparatus 104. The distributed group key is temporarily stored by the vehicle.

Although only the intersection 100A has been described here, roadside devices are similarly arranged at the intersection 100B and other intersections, and group keys are distributed to the vehicles. For example, a group key corresponding to the group 4 is distributed to vehicles heading from the intersection 100B to the intersection 100A.
Further, the group key stored in the vehicle is overwritten every time the vehicle passes the roadside device. For example, a group key corresponding to group 4 is distributed to vehicles passing through the roadside apparatus 103. However, when the vehicle travels straight through the intersection 100B, a group key corresponding to group 5 is distributed and corresponds to group 4. The group key to be overwritten is overwritten. Thus, the vehicle stores only the last distributed group key.

A method of identifying a group using a group key will be specifically described. FIG. 3 is a diagram for explaining a calculation method performed on a transmitted / received message.
As described above, the group key is a key transmitted from the roadside device and stored in the vehicle. Transmission data is information transmitted to other vehicles belonging to the same group. The content of the transmission data is not particularly limited and may be anything.
The current time information is the current time obtained from a clock mounted on the vehicle, and is information representing the hour and minute in this embodiment.

FIG. 3A shows processing performed by a vehicle that transmits information. A vehicle that transmits information first adds current time information to transmission data that is transmitted to another vehicle. The current time information is data of 11 bits in total composed of hours (0 to 23 represented by 5 bits) and minutes (0 to 59 represented by 6 bits). In this embodiment, the length of the transmission data is 117 bits, and the current time information is added to the upper bits to generate a total of 128 bits of data. The data is transmission information in the present invention.
Next, the exclusive OR of the transmission data and the data obtained by concatenating the current time information and the stored group key is calculated, and the obtained data is transmitted as a transmission message, that is, data actually transmitted by inter-vehicle communication. And In the present embodiment, the length of the group key is 128 bits.

  FIG. 3B shows processing performed by a vehicle that receives information. The vehicle that receives the information calculates the exclusive OR of the received transmission message and the stored group key, and acquires the calculation result (decrypted data in the present invention). As a result, if the upper 11 bits of the obtained decrypted data match the current time, the group key used when transmitting the transmission message and the group key stored in the host vehicle are the same, that is, the transmission message is It can be seen that the transmission is from a vehicle belonging to the same group as the own vehicle. On the other hand, if they do not match, it means that the group key used when sending the transmission message is different from the group key stored in the own vehicle, so the transmission message is sent from a vehicle belonging to a group different from the own vehicle. It can be seen that

<System configuration>
Details of the embodiment for realizing the operation described above will be described.
The in-vehicle terminal 10 is a terminal on which software (hereinafter referred to as application service) that provides information to an occupant or an in-vehicle computer operates. Further, the in-vehicle terminal 10 can receive a request from the application service and exchange information with other in-vehicle terminals by wireless communication. FIG. 4 is a system configuration diagram of the in-vehicle terminal 10.
The roadside device 20 is a wireless device for distributing a group key to the in-vehicle terminal 10. FIG. 5 is a system configuration diagram of the roadside apparatus 20.

First, the in-vehicle terminal 10 will be described.
The clock unit 11 is a means for acquiring the current time. Specifically, it is a means for obtaining the current time (data representing hours and minutes) from a built-in clock device. The timepiece device may be a general quartz timepiece, but preferably has a means for receiving a signal from a device serving as a parent timepiece, such as a standard radio wave or a GPS signal, and automatically correcting the time.
The group key storage unit 12 is a means for storing a group key received from the roadside device 20, which is configured by a nonvolatile memory or the like.

The communication unit 13 is a unit that communicates with other in-vehicle terminals or roadside devices wirelessly. The frequency used for communication is, for example, a frequency in an ITS (Intelligent Transport Systems) band assigned to the 700 MHz band for inter-vehicle communication. A frequency and a communication method are not particularly limited as long as other information can be transmitted and received by wireless communication.
The computing unit 14 is a means for mutually converting transmission data that is data that can be interpreted by the application service and transmission messages that are data actually transmitted and received between the in-vehicle terminals.

  The time comparison unit 15 is means for determining whether or not the current time acquired from the clock unit 11 is included in the decoded data. Since there is a possibility that the time information held by the different in-vehicle terminals is slightly shifted, the time comparison unit 15 performs determination in consideration of the time shift. For example, when the current time information is “hour” and “minute”, an error within one minute can be ignored. If the current time information includes “second”, an allowable error may be set in seconds. The allowable error can be an arbitrary value.

  The service providing unit 16 is means for executing an application service. The application service is, for example, a service that provides information for driving support to an in-vehicle computer or a service that provides collected traffic information to a passenger. The application service may be anything as long as it communicates with other vehicles and provides the exchanged information to the outside.

Next, the roadside device 20 will be described.
The group key storage unit 21 is a means for storing a group key that is a key unique to the roadside device. A different group key is assigned to each roadside device and does not overlap between different roadside devices. In this embodiment, a bit string having a length of 128 bits is used as a group key.
The communication unit 22 is means for performing wireless communication with other in-vehicle terminals. The wireless communication method performed by the communication unit 22 is the same as that of the communication unit 13.

<Group key distribution process>
Next, a process for distributing the group key from the roadside device to the in-vehicle terminal will be described. FIG. 6 is a flowchart of key reception processing performed by the roadside device and the in-vehicle terminal. The communication unit 22 included in the roadside device periodically transmits a radio signal toward a point on the road. When the communication unit 13 included in the in-vehicle terminal receives the wireless signal and the negotiation is established, the flowchart illustrated in FIG. 6 is started.

In step S <b> 11, the roadside device transmits the group key stored in the group key storage unit 21 to the in-vehicle terminal via the communication unit 22. In step S <b> 12, the in-vehicle terminal stores the group key received through the communication unit 13 in the group key storage unit 12. At this time, if the group key storage unit has already stored the group key, it is overwritten with the received group key.
Through the above processing, the in-vehicle terminal mounted on the vehicle can receive and store the group key of the roadside device every time it passes through the vicinity of the roadside device. For communication between the roadside device and the in-vehicle terminal, for example, a narrow communication system standard (STD-T75) standardized by the Radio Industries Association (ARIB) can be used.

<Transmission message transmission processing>
Next, processing in which the in-vehicle terminal 10 transmits a transmission message to other in-vehicle terminals will be described. FIG. 7 is a flowchart of transmission message transmission processing performed by the in-vehicle terminal 10. FIG. 8 is a diagram showing a data flow in transmission message transmission processing.
When the application service executed by the service providing unit 16 requests information transmission to another in-vehicle terminal, the flowchart of FIG. 7 is started.
First, the service providing unit 16 acquires transmission data that is information to be transmitted to another in-vehicle terminal from the application service (S21). The transmission data is 117-bit data as described above. The generated transmission data is transmitted to the calculation unit 14 (S22).

  Next, the calculation unit 14 acquires the current time from the clock unit 11 and generates current time information (S23). As described above, the current time information is 11-bit data representing hours (0 to 23) and minutes (0 to 59). Subsequently, the calculation unit 14 acquires a group key stored in the group key storage unit 12 (S24). If there is no stored group key, the processing may be terminated, or the group key storage unit 12 may generate a key representing “not belonging to a group” on the spot.

  Next, the calculation unit 14 combines the current time information acquired in step S23 and the transmission data acquired in step S22, and calculates an exclusive OR (XOR) with the group key acquired in step S24 (S25). ). Thereby, a 128-bit transmission message is obtained. The generated transmission message is transmitted to the communication unit 13 and broadcast by wireless communication (S26).

<Transmission message reception processing>
Next, processing in which the in-vehicle terminal 10 receives a transmission message from another in-vehicle terminal will be described. FIG. 9 is a flowchart of a transmission message reception process performed by the in-vehicle terminal 10.
FIG. 10 is a diagram illustrating a data flow in the transmission message reception process.

When the communication unit 13 receives a transmission message broadcast by another in-vehicle terminal, the flowchart of FIG. 9 is started. The received transmission message is transmitted to the calculation unit 14.
In step S <b> 31, the calculation unit 14 acquires a group key stored in the group key storage unit 12. If there is no stored group key, the same processing as step S24 is performed. For example, the process may be terminated, or a key indicating that the user does not belong to a group may be generated. If a key indicating that the vehicle does not belong to a group is used, vehicles that do not belong to the group can communicate with each other.

Next, the computing unit 14 computes an exclusive OR of the received transmission message and the group key acquired in step S31 (S32). The result of the calculation performed in step S32 is the decoded data in the present invention.
Subsequently, the time comparison unit 15 extracts a bit corresponding to the current time information from the received decoded data (S33), and compares it with the current time acquired from the clock unit 11 (S34). In this embodiment, the upper 11 bits of the decoded data are extracted, and it is confirmed whether or not the current time is the same as that converted into a bit string. At this time, as described above, the determination may be performed in consideration of a clock error. If the times match (S34-Yes), the process proceeds to step S35.

In step S <b> 35, the calculation unit 14 extracts bits corresponding to the transmission data and transmits them to the service providing unit 16. In the present embodiment, the lower 117 bits of the decoded data are to be extracted. Then, the transmission data transmitted to the service providing unit 16 is processed by the application service.
If the times do not match in step S34 (S34-No), the calculation unit 14 discards the received data and ends the process.

  In the first embodiment, whether the vehicle that transmitted the transmission message and the host vehicle belong to the same group is determined by the processing described above. Judgment processing is performed using only exclusive OR with a small amount of calculation, so intra-group communication is realized with a small amount of processing compared to the method of judging group members using vehicle movement vectors and position information. can do. Moreover, since the road is divided into sections and grouping is performed, there is an advantage that there is no overhead for monitoring whether the vehicle has joined or left the group.

  In this embodiment, the same group key is distributed on the same road regardless of the traveling direction of the vehicle, but even on the same road, the group is divided according to the traveling direction, and different group keys are distributed. Also good. For example, the group 4 shown in FIG. 1 may be divided into a group 4L that is a group that proceeds in the left direction and a group 4R that is a group that proceeds in the right direction. In this case, a group key corresponding to the group 4R is distributed to vehicles traveling from the intersection 100A to 100B, and a group key corresponding to the group 4L is distributed to vehicles traveling from the intersection 100B to 100A.

  Further, the group key storage unit 12 may delete a group key for which a predetermined time has elapsed since reception. When entering a section where no roadside equipment is installed, if a group key used in the past is stored, there is a possibility that an incorrect group may be formed at a place where the group should not be formed. This can be prevented by setting a valid time to delete the expired key. In addition, the group key may be deleted when the vehicle engine is stopped, or the group key may be deleted when the vehicle travels a predetermined distance.

  In the first embodiment, “hour” and “minute” are used as the current time information. However, any information may be used as long as the current time information is based on the current time. . For example, the current time encoded by an arbitrary function such as a hash function may be used. By encoding the current time and compressing the bit length, the data length of the transmission data can be increased.

  In the first embodiment, the current time information is used to confirm that the decoded data is correct. However, any data may be used as long as the data is shared by a plurality of vehicles. For example, a fixed character string may be used, and when the position information can be acquired, the latitude or longitude of the host vehicle may be used. Further, a traveling direction (azimuth angle), speed information, or the like may be used.

(Modification of the first embodiment)
In the first embodiment, the roadside device is arranged so as to distribute the group key to the vehicles that flow out from the intersection. Also good. In this modification, the target is a high-standard road, and roadside devices are arranged on the main line and on ramps flowing into and out of the main road. The configurations and functions of the in-vehicle terminal 10 and the roadside device 20 according to this modification are the same as those in the first embodiment.

  FIG. 11 is a layout diagram of the roadside apparatus according to the present modification. As an example, consider the case where the vehicle travels from left to right. When the vehicle passes the roadside device 201 installed on the main line, the group key corresponding to the group A is transmitted to the in-vehicle terminal of the vehicle. When passing through the roadside device 203, a group key corresponding to the group B is transmitted. Thus, in this modification, grouping is performed by dividing the road into predetermined sections. Also, different group keys are stored in the roadside devices installed in the opposite lane. By doing in this way, the vehicles which are advancing in the same direction can form the same group.

A roadside device will also be installed on the ramp to enter and exit the road. For example, the same group key as the roadside device 203 is stored in the roadside device 203R. In this way, the same group key can be distributed to all the vehicles that flow into the corresponding section.
The roadside device 202 is a roadside device for deleting a group key stored in the in-vehicle terminal. The roadside device 202 does not transmit the group key, but notifies the in-vehicle terminal 10 that the stored group key should be deleted. The in-vehicle terminal that has received the notification deletes the group key stored in the group key storage unit 12. By doing in this way, the group key of the vehicle flowing out from the target section can be deleted.
The detailed description of the roadside devices installed in the opposite lane is omitted, but the operation is the same as that of the roadside devices (201, 202, 203, 203R) described above except that the stored group keys are different. .

  According to this modification, a group key is distributed to vehicles that flow into a closed road section, and when a vehicle flows out of the section, the group key is overwritten or deleted, The group key can be surely stored in the vehicle.

(Second embodiment)
In the first embodiment, it is determined whether the decoded data is correct using the current time information added to the transmission data. However, if there are two different group keys and the bits corresponding to the current time information (for example, the upper 11 bits) match each other, even if the group keys are different, the bits corresponding to the current time information Since it is normally decoded, it cannot be detected that the groups are different. In order to cope with this, the second embodiment is a form in which the validity of decoded data is verified using an error detection code.

Differences between the in-vehicle terminal 10 according to the second embodiment and the first embodiment will be described.
The in-vehicle terminal 10 according to the second embodiment is different from the first embodiment in that it does not have the clock unit 11 and the time comparison unit 15. The calculation unit 14 also generates and adds a CRC (Cyclic Redundancy Check) code to the transmission data, and a CR
C has a function of performing error detection of decoded data. Other configurations are the same as those of the first embodiment.

Next, the difference in the transmission / reception process from the first embodiment will be described with reference to FIG. 7 which is a flowchart of the transmission process performed by the in-vehicle terminal and FIG. 9 which is a flowchart of the reception process.
The calculation unit 14 generates the CRC code in step S23. CRC codes have various lengths depending on the number of bits that can be detected, but here, CRC-16 having a length of 16 bits is used. FIG. 12 is a diagram for explaining calculation in the second embodiment. Since the group key is 128 bits and the CRC code is 16 bits, the usable transmission data is 112 bits. Since CRC is a known error detection technique, description of the generation method is omitted.

  Further, the calculation unit 14 performs error detection of the decoded data in steps S33 and S34. In step S33, the calculation unit 14 extracts the lower 16 bits of the transmission message. In step S34, an upper 112-bit CRC code is calculated to check whether the lower 16 bits match. If they do not match, it can be estimated that the group keys are different, so the process is terminated (S34-No). If they match, the process proceeds to step S35.

As described above, in the second embodiment, the error detection code is used to check whether the transmission data is correct. Therefore, it is possible to accurately detect that the group key used at the time of transmission is different from the group key used at the time of reception. it can.
Note that, when an error detection code is used, a larger amount of calculation is required than when only an exclusive OR is used. Therefore, it is desirable to properly use the first embodiment and the second embodiment depending on whether priority is given to reducing the amount of calculation or reliability. Moreover, although CRC-16 was used in this embodiment, a lighter code | symbol may be used when a detection accuracy may be low. For example, a 1-bit CRC code, that is, a parity may be used, or a checksum may be used.

(Modification)
The above embodiment is merely an example, and the present invention can be implemented with appropriate modifications within a range not departing from the gist thereof. For example, grouping by exclusive OR as described in each embodiment may be used in combination with other grouping processing using a movement vector or the like.

For example, after filtering a received message by exclusive OR, grouping may be performed more finely according to a movement vector or a current position. By doing so, it is possible to exclude vehicles that are clearly irrelevant, such as vehicles on the opposite lane or on parallel roads, and to perform detailed grouping processing after narrowing down the processing target data become.
In the description of each embodiment, the effect that intra-group communication can be performed has been described. However, the present invention can also be used as a technique for filtering irrelevant information before performing other processing.

In the first embodiment, the transmission data is 117 bits. In the second embodiment, the transmission data is 112 bits. However, when the data transmitted / received by the application service is larger than this, the transmission / reception may be divided into a plurality of times. Good.
Further, the size of the transmission message may be variable while the length of the group key is fixed. For example, if the transmission message is longer than the group key, the missing bits of the group key may be filled by a predetermined procedure. As long as the predetermined procedure is the same on the transmission side and the reception side, communication can be performed normally.

DESCRIPTION OF SYMBOLS 10 In-vehicle terminal 11 Clock part 12,21 Group key memory | storage part 13,22 Communication part 14 Calculation part 15 Time comparison part 16 Service provision part 17 Message extraction part 20 Roadside apparatus

Claims (5)

A vehicle-to-vehicle communication system comprising a roadside device and a plurality of vehicles,
The roadside device is
It has a key transmission means for transmitting a group key, which is a key unique to the roadside device, to a vehicle passing through a predetermined point,
The vehicle is
Key storage means for receiving and storing the group key from the roadside device;
Message generating means for generating transmission information that is information to be transmitted to another vehicle, and generating a transmission message that is data obtained by exclusive ORing the transmission information and the group key stored in the key storage means; ,
Message transmitting means for transmitting the transmission message to another vehicle by wireless communication;
Message receiving means for receiving a transmission message transmitted from another vehicle;
An exclusive OR of the received transmission message and the group key stored in the key storage means is taken, and based on the decrypted data which is the obtained data, the vehicle and the own vehicle that transmitted the transmission message Group determination means for determining whether or not they belong to the same group;
I have a,
The message generation means includes shared data, which is information shared by a plurality of vehicles, in the transmission information,
The group determination means determines that the vehicle that transmitted the transmission message and the host vehicle belong to the same group when the shared data is included in the decoded data.
Vehicle-to-vehicle communication system. The shared data is information indicating the current time.
The inter-vehicle communication system according to claim 1 . The predetermined point is a point flowing out from the intersection,
The inter-vehicle communication system according to claim 1 or 2 . An in-vehicle terminal mounted on a vehicle and capable of communicating with a roadside device and other in-vehicle terminals,
A key acquisition means for receiving and storing a group key, which is a key unique to the roadside device, from the roadside device;
Message generating means for generating transmission information that is information to be transmitted to another in-vehicle terminal, and generating a transmission message that is data obtained by exclusive ORing the transmission information and the group key stored in the key storage means When,
Message transmission means for transmitting the transmission message to another in-vehicle terminal by wireless communication;
Message receiving means for receiving a transmission message transmitted from another in-vehicle terminal;
An exclusive OR of the received transmission message and the group key stored in the key storage means is taken, and based on the decrypted data that is the obtained data, the vehicle that transmitted the transmission message and the host vehicle are the same Group determination means for determining whether or not the group belongs to,
Have
The message generation means includes shared data, which is information shared by a plurality of vehicles, in the transmission information,
The group determination means determines that the vehicle that transmitted the transmission message and the host vehicle belong to the same group when the shared data is included in the decoded data.
In-vehicle terminal. A vehicle-to-vehicle communication method performed by a roadside device, a first vehicle, and a second vehicle,
A first transmission step in which the roadside device transmits a group key, which is a key unique to the roadside device, to a vehicle passing through a predetermined point;
A storage step in which the first and second vehicles receive and store the group key from the roadside device;
The first vehicle generates transmission information that is information to be transmitted to the second vehicle, and is data obtained by taking an exclusive OR of the transmission information and the group key stored in the key storage unit. A generation step for generating a transmission message;
A second transmission step in which the first vehicle transmits the transmission message to the second vehicle by wireless communication;
A receiving step in which the second vehicle receives a transmission message transmitted from the first vehicle;
The second vehicle takes an exclusive OR of the received transmission message and the group key stored in the key storage means, and based on the decrypted data, the obtained transmission message A determination step of determining whether or not the transmitted first vehicle and the host vehicle belong to the same group;
Including
In the generating step, the transmission information includes shared data that is information shared by the first and second vehicles,
In the determination step, when the shared data is included in the decoded data, it is determined that the vehicle that has transmitted the transmission message and the host vehicle belong to the same group.
Vehicle-to-vehicle communication method.

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