JP2007318353A - In-vehicle communication apparatus and communication method for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the communication efficiency of an in-vehicle communication apparatus, thereby effectively utilizing communication resources. <P>SOLUTION: A server S1 creates traffic information, weather information, and district information as information data and a transmission base station A1 transmits the information data. Each vehicle receives the information data and transfers the information data to surrounding vehicles. When its own vehicle C0 can acquire the information data from the transmission base station A1 and the other vehicle C11, its own vehicle C0 selects an information transmission source depending on a type of the information transmission source (whether a fixed transmission source or a vehicle), a communication method, a communication rate, a positional relation with its own vehicle and a mobile state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an in-vehicle communication device that acquires information from the outside of a vehicle and a communication method for a vehicle, and more particularly to an in-vehicle communication device that relays information transmitted by a fixed communication facility between vehicles and the communication method thereof.

  In recent years, technology that gives vehicles a communication function has been put into practical use, and the development of technology for vehicle-to-vehicle communication that communicates between vehicles and road-to-vehicle communication that communicates between specific facilities and access points and vehicles has advanced. Yes. Accordingly, for example, as disclosed in Patent Documents 1 to 3, a cooperative system of road-to-vehicle communication and vehicle-to-vehicle communication has been devised.

JP 2004-080383 A JP 2004-077281 A Japanese Patent No. 3094106

  By coordinating road-to-vehicle communication and vehicle-to-vehicle communication, it is possible to relay information transmitted by a fixed communication facility between vehicles and increase the area where information can be acquired. Here, since there are a plurality of information providing sources capable of acquiring the same information, it is necessary to determine which information providing source should acquire the necessary information. Further, since the information providing source includes a vehicle, it is necessary to consider the movement of the vehicle in selecting the information providing source.

  However, since the conventional technology does not consider such information provider selection, it is difficult to select an appropriate information provider, resulting in a decrease in communication efficiency and a large amount of communication. There was a problem of causing pressure on communication resources.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide an in-vehicle communication device and a communication method thereof that improve communication efficiency and effectively use communication resources.

  In order to solve the above-described problems and achieve the object, the in-vehicle communication device and the vehicle communication method according to the present invention provide a type of information transmission source when receiving information from a plurality of information transmission sources including other vehicles. Depending on the communication method (communication source or vehicle), the communication method, the communication speed, the positional relationship with the host vehicle and the movement state, the information transmission source is selected from which information is to be received.

  The vehicle-mounted communication device and the vehicle communication method according to the present invention relay information when receiving information from a plurality of information transmission sources including other vehicles and transmitting the acquired information to the other vehicles. Transmission is permitted only when the number of via stages indicating the number of communication devices is less than the set maximum value.

  According to the present invention, in-vehicle communication device and vehicle communication method, when receiving information from a plurality of information transmission sources including other vehicles, the type of information transmission source (whether it is a fixed transmission source or a vehicle) Etc.), the communication method, the communication speed, the positional relationship with the host vehicle and the movement state, it is selected from which information is received from a plurality of information transmission sources, so communication is performed by receiving information from an appropriate information transmission source. There is an effect that an in-vehicle communication device and a communication method that improve efficiency and effectively use communication resources can be obtained.

  The vehicle-mounted communication device and the vehicle communication method according to the present invention relay information when receiving information from a plurality of information transmission sources including other vehicles and transmitting the acquired information to the other vehicles. Since the transmission is permitted only when the number of via stages indicating the number of communication devices is less than the set maximum value, an in-vehicle communication device and a communication method for suppressing the occurrence of unnecessary communication and effectively using communication resources are provided. There is an effect that it can be obtained.

  Exemplary embodiments of an in-vehicle communication device and a vehicle communication method according to the present invention will be described below in detail with reference to the accompanying drawings.

  First, the concept of the present invention will be described with reference to FIG. In the figure, the server S1 creates traffic information, weather information, regional information, and the like as information data, and the transmission base station A1 transmits the information data by radio waves. Each vehicle receives information data and transmits it to surrounding vehicles.

  For example, the other vehicle C11 transmits information data to the own vehicle C0, which is a rear vehicle, and the own vehicle C0 further transmits information data to another vehicle C12, which is a rear vehicle. By coordinating road-to-vehicle communication and vehicle-to-vehicle communication in this way, other vehicle C12 that cannot directly communicate with transmission base station A1 can also acquire information data.

  Here, the host vehicle C0 can acquire information data from both the transmission base station A1 and the other vehicle C11, so it is necessary to determine from which information data is acquired.

  Therefore, in the in-vehicle communication device and the communication method according to the present invention, information is obtained depending on the type of information transmission source (whether it is a fixed transmission source or a vehicle), the communication method, the communication speed, the positional relationship with the own vehicle, and the movement state. By selecting a transmission source, information is received with optimum communication efficiency, and by setting conditions for transferring information data in a vehicle, compression of communication resources is avoided.

  FIG. 2 shows a schematic configuration of the communication device mounted on the host vehicle C0. As shown in the figure, a communication device 1 mounted on a vehicle C0 is connected to a navigation device 2, a vehicle speed sensor 3, and another in-vehicle device 4.

  The navigation device 2 is an in-vehicle device that sets and guides a travel route using the position of the host vehicle specified by communicating with a GPS (Global Positioning System) artificial satellite and map data stored in advance. In addition, the navigation device 2 provides the communication device 1 with location information of the host vehicle, surrounding map information, a planned travel route, and the like.

  The vehicle speed sensor 3 detects the traveling speed of the vehicle C0 from the rotational speed of the tire and outputs it to the communication device 1. The in-vehicle device 4 is, for example, various devices of a vehicle travel control system that performs engine control and brake control based on data from the communication device 1.

  The communication device 1 includes a control unit 10, communication units 11 to 13, antennas 14 to 16, a data storage unit 17, and a gateway unit 18 therein.

  The communication units 11 to 13 are communication processing units corresponding to different communication methods, for example, the communication unit 11 is WiMAX (world interoperability for microwave access), the communication unit 12 is CDMA (Code Division Multiple Access), and the communication unit 13 is Communication processing by DSRC (Dedicated Short Range Communication) is performed, and data is decoded.

  Specifically, the communication unit 11 performs road-to-vehicle communication with the transmission base station via the antenna 14, the communication unit 12 performs road-to-vehicle communication with the store via the antenna 15, and the communication unit 13 includes the antenna 16. Inter-vehicle communication with other vehicles is performed via

  Note that the configuration of the communication unit shown here is merely an example. For example, a configuration having a communication unit corresponding to another communication method such as wLAN may be used, or a plurality of communication units corresponding to the same communication method may be provided. Also good. Moreover, the structure corresponding to a some communication system may be sufficient as a single communication part.

  Furthermore, the correspondence between the communication method and the communication partner can be changed as appropriate. For example, inter-vehicle communication with other vehicles may be realized by WiMAX or CDMA, and road-to-vehicle communication may be realized by DSRC with a transmission base station or a store.

  The data storage unit 17 is a storage unit that stores various types of data, and can store data related to nearby information transmission sources, in addition to information data acquired by the communication units 11 to 13 from outside the vehicle.

  The control unit 10 is realized by a microcomputer including a CPU, and is a control unit that performs network control for connecting, disconnecting, and monitoring each of the communication units 11 to 13, and includes a communication destination selection unit 10 a and a connection number setting unit. 10b and a lifetime control unit 10c. The communication destination selection unit 10a performs processing for selecting the information transmission source according to the type of information transmission source, the communication method, the communication speed, the positional relationship with the host vehicle, and the movement state. Moreover, the connection number setting part 10b sets the communication connection number which the own vehicle C0 establishes from the connection state of the communication parts 11-13 and the communication state in the periphery. Furthermore, the lifetime control unit 10c is a processing unit that controls whether or not information data can be transferred and stored based on the number of transit stages attached to the information data and the lifetime of the data.

  The gateway unit 18 is a device for transmitting data from the communication units 11 to 13 connected by the control unit 10 to the subsequent in-vehicle device 4 or the navigation device 2. For example, if the communication data is a map update, data is transmitted to the navigation device 2 via the gateway unit 18, and if the communication data is engine control maintenance data, it is transmitted to the in-vehicle device 4 via the gateway unit 18.

  Next, a communication destination selection method by the communication destination selection unit 10a will be described with a specific example. As shown in FIG. 3, when the same information can be acquired from a fixed facility such as a communication base station or a store and other vehicles, the communication destination selection unit 10a selects information reception from the fixed facility with priority. To do. This is because the communication state is more stable in road-to-vehicle communication with a fixed transmission source than in vehicle-to-vehicle communication with another vehicle that is a moving transmission source. This is because the communication performance is higher than that of the vehicle and the communication speed is likely to be high.

  As shown in FIG. 4, when the communication speeds of a plurality of information transmission sources are known, the communication destination selection unit 10a preferentially selects information reception from a transmission source with a higher communication speed. Also good. Furthermore, as shown in FIG. 5, it is also possible to preferentially select information reception from the closest information transmission source based on the positional relationship between the plurality of information transmission sources and the host vehicle.

  Further, the communication destination selection unit 10a can also preferentially select information reception from an information transmission source having a low relative speed with respect to the host vehicle when the same information can be received from a plurality of information transmission sources. .

  For example, in FIG. 6, the host vehicle is traveling at a speed of 40 km / h, and the other vehicle is traveling at the speed of 50 km / h in the same direction as the host vehicle. For this reason, the relative speed between the host vehicle and the other vehicle is 10 km / h, and the relative speed between the host vehicle and the fixed facility is 40 km / h. Therefore, reception of information from a vehicle having a small relative speed is selected. In this way, even if the information transmission source is a mobile body, if the relative speed with the host vehicle is small, the positional relationship is stable compared to the information transmission source with a fixed position, so communication with higher reliability can be performed. It becomes possible. This is because it is predicted that the higher the relative speed, the longer the distance between the vehicle and the information transmission source in the future and the lowering of the reception strength will lead to a decrease in data reception quality.

  Here, as shown in FIG. 7, when there are a plurality of information transmission sources (vehicles) having the same relative speed as the own vehicle, the communication destination selection unit 10a prioritizes information reception from the information transmission source ahead of the own vehicle. To select. This is because communication with the vehicle ahead is more reliable because the vehicle is traveling. For example, when the vehicle A in front of the host vehicle and the vehicle B in the rear of the host vehicle decelerate due to a right or left turn, the vehicle A in front of the host vehicle approaches the host vehicle, but the vehicle B in the rear of the host vehicle is separated from the host vehicle. Since the vehicle A moves away, the vehicle A can stably communicate for a long time.

  Furthermore, as shown in FIG. 8, when there are a plurality of information transmission sources having the same relative speed with the host vehicle in front of the host vehicle, the communication destination selection unit 10a compares the information source with the host vehicle. Thus, priority is given to information reception from an information transmission source having a low traveling speed. This is because the distance between the vehicle that is faster than the host vehicle and the host vehicle in front of the host vehicle is separated by the passage of time, but the distance between the vehicle that is slower than the host vehicle and the host vehicle is closer to the host vehicle over time, This is because a low-speed vehicle can stably communicate for a long time.

  Similarly, as shown in FIG. 9, when there are a plurality of information transmission sources having the same relative speed with the host vehicle behind the host vehicle, the communication destination selection unit 10a compares the information source with the host vehicle among the plurality of information transmission sources. Thus, priority is given to information reception from an information transmission source having a high traveling speed. This is because the distance between the vehicle behind the host vehicle and the vehicle slower than the host vehicle increases with the passage of time, but the distance between the vehicle behind the host vehicle and the host vehicle higher than the host vehicle approaches with the passage of time. This is because a high-speed vehicle can stably communicate for a long time.

  As described above, information can be received with optimum communication efficiency by selecting the information transmission source based on the type of information transmission source, the communication method, the communication speed, the positional relationship with the host vehicle, and the movement state. Here, information (type, communication method, communication speed, positional relationship with the own vehicle, and moving state) regarding the information transmission source that can be selected by the own vehicle is received in advance as a content notification from each information transmission source. Based on the information indicated in the content notification, it may be determined from which information transmission source the main body of the target information data is received.

  A specific example of the content notification received from the information transmission source is shown in FIG. In the figure, the information of the location information sender of the information transmission source, the communication method, the communication speed, the movement information, the possession information, the creation time, the number of steps, and the maximum number of steps are received by the content notification.

  `` 34 ° 41'25 '' N 135 ° 12'80 '' E '' or `` 34 ° 41'21 '' N 135 ° 12'87 '' E '' indicated in the location information is the latitude from which the information was sent It is information indicating a position by longitude. This information can be held in advance if it is a transmission source having a fixed position, such as a transmission base station or a store, and can be acquired by a GPS or the like if the transmission source is a vehicle or the like.

  The caller type is information indicating a type such as “vehicle”, “transmission base station”, “store”, the communication method is information indicating a communication method such as “DSRC” or “WiMAX”, and the communication speed is “100 kbps”. Or “9 Mbps” is information indicating a usable speed.

  The movement information is information indicating a movement speed and a movement direction when the information transmission source is a moving body such as a vehicle. About this movement state, it is good also as notifying a plan route etc., for example.

  The possessed information is a type of information that can be transmitted by the information transmission source, and “weather # area132” indicates that weather information of a specific area (area132) can be transmitted. Further, the creation time indicates the time when the information is created, the number of stages indicates how many times the information is relayed, and the maximum number of stages indicates information indicating the maximum number of times that the information is allowed to be relayed.

  The information shown in the possession information and the creation time can be used as an information ID for specifying information held by the host vehicle. Based on these pieces of information, it is possible to determine whether the information held by the host vehicle is the same as the information held by another information transmission source, and the update state of the held information.

  A specific example of selection of a communication destination using this content notification will be described with reference to FIG. In the figure, at time t0, vehicles C21, C22, C23 and a transmission base station A1 exist around the host vehicle C0. For example, the communication unit 11 communicates with the transmission base station by “WiMAX”, and the communication unit 13 communicates with surrounding vehicles by “DSRC”.

  The own vehicle C0 receives the content notification from the transmission base station A1 between the time t0 and the time t1 by the communication unit 11, and receives the content notification from the vehicle C21 between the time t0 and the time t1 by the communication unit 13, A content notification is received from the vehicle C22 between time t1 and time t2, and a content notification is received from the vehicle C23 between time t2 and time t3.

  And a communication destination is selected based on each content notification. In the figure, the control unit establishes a communication connection with C22 that is currently most stable in communication based on the content notification received from each vehicle (to enable transmission and reception by DSRC), and at time t4, the vehicle Data reception is started from C22 via the communication unit 13. Note that the data referred to here is, for example, detailed local weather information.

  However, at time t5, the vehicle C22 moves (vehicle C22a), and communication is disconnected. As a result, the own vehicle C0 receives the content notification from the vehicles C21 and C23 and the transmission base station A1 again, and this time the transmission base station A1 is most stable in communication at this time, so the communication connection with the transmission base station A1 is established. And the data is received again from the transmission base station A1 via the communication unit 11.

  As described above, by appropriately acquiring the content notification and selecting the communication destination (establishing communication connection by the communication units 11 to 13), it is possible to select the optimum communication destination according to the situation.

  Next, setting of the number of connections by the connection number setting unit 10b will be described. The connection number setting unit 10b controls the number of communication connections established by the host vehicle in order to avoid wasting communication resources. Specifically, when the number of established communication connections reaches a predetermined upper limit, the connection number setting unit 10b does not establish any more communication connections. In addition, when there are a predetermined number or more of information transmission sources that provide the same information around the host vehicle, notification of contents and information provision from the host vehicle to other vehicles are not performed, and use of communication resources is avoided.

  Next, control of information data by the lifetime control unit 10c will be described. In order to avoid waste of communication resources, the lifetime control unit 10c permits transfer to another vehicle only when the number of via stages indicating the number of communication devices that relay information data is less than the set maximum value. Information data with the maximum number of vias is not transferred. Further, when a predetermined lifetime has elapsed from the creation time of the information data, the information data is deleted from the data storage unit 17.

  A specific example of transfer control based on the number of vias is shown in FIG. In the figure, information having the maximum number of vias, that is, the via upper limit “2” is transmitted from the transmission base station. At the stage of transmission from the transmitting base station, no relay is performed by another communication device, and the value of the number of vias is “0”, but when the first vehicle receives this information, The number of stages is rewritten to “1”.

  When the first vehicle transmits information, the received vehicle adds 1 to the number of vias and rewrites it to “2”. At this time, since the number of vias has reached the via upper limit, the second vehicle does not transmit information to other vehicles.

  Here, it is preferable to set the route upper limit based on the content of the information. For example, as shown in FIG. 13, information with high regionality, such as advertisement information from a store, is useful only for vehicles in the vicinity of the store, so it is preferable to set the upper limit of the number of vias to be small.

  Further, for information such as weather information that has a large time change, the content of the information may become inappropriate during repeated transfer. Therefore, it is preferable to set the upper limit of the number of vias to be small.

  On the other hand, for information that is highly important for vehicles such as accident information and traffic jam information, it is desirable to increase the upper limit of the number of vias and make it widely known to many vehicles.

  Thus, by setting the upper limit of the number of vias according to the content of information and controlling the transfer state, it becomes possible to use communication resources appropriately.

  In addition, when the same content as the information held by the own vehicle can be received from an information provider with a smaller number of vias, it is not necessary to receive the information itself. The number of via stages may be updated smaller.

  For example, in FIG. 12, the second vehicle has the information A with the number of vias “2”, but if it is in a state where it can communicate directly with the transmission base station after that, Since the number of steps is “0”, the number of vias of the information A in the host vehicle is rewritten to “1” obtained by adding 1 to this value. Therefore, information can be transmitted to other vehicles thereafter.

  The upper limit of the number of vias may be set by a server, a transmission base station, a store, or the like that first creates information data, or may be set on a relay side such as a vehicle. Here, when there is an upper limit set on the relay side and an upper limit preset on the server or the like, the upper limit set in advance may be given priority, or the setting on the relay side may be given priority. Further, a configuration may be adopted in which priority is given to the smaller upper limit value, or permission / non-permission of change of the upper limit setting on the transfer side is determined.

  Next, a processing operation by the control unit 10 will be described. FIG. 14 is a flowchart for explaining the processing operation when the control unit 10 receives data. The processing shown in the figure is started when the communication units 11 to 13 receive a content notification from the outside.

  First, the control unit 10 receives a content notification via the communication units 11 to 13 (step S101), and compares the information with information owned by the host vehicle with reference to the data storage unit 17 (step S102). As a result, if the information indicated in the content notification is the same as the information owned by the own vehicle, it is determined that data reception is unnecessary (step S103, No), and the process is terminated as it is.

  On the other hand, if the information shown in the content notification is information that the host vehicle does not own, or if the information is newer than the information owned by the host vehicle, it is determined that data reception is necessary ( In step S103, Yes), the communication destination selection unit 10a selects a reception destination (step S104), executes data reception (step S105), and ends the process.

  Next, the processing operation at the time of data transmission by the control unit 10 will be described with reference to FIG. The process shown in the figure is a process that is repeatedly started by the main routine of the communication apparatus 1 or the like.

  First, the control unit 10 refers to the data storage unit 17 and determines whether there is possession information (step S201). If the possession information exists (step S201, Yes), it is determined whether the number of transit stages of the information has reached the upper limit (step S202). If the upper limit has not been reached (step S202, Yes), further It is determined whether there is a margin in the number of connections (step S203). If there is a margin in the number of connections (step S203, Yes), a content notification indicating information held by the own vehicle is transmitted to the surrounding vehicles (step S204).

  If a data transmission request is received from another vehicle or the like that has received this content notification (step S205, Yes), the requested data is transmitted to the transmission request source (step S206), and the process is terminated.

  Moreover, when there is no ownership information (step S201, No), when the number of vias of the information has reached the upper limit (step S202, No), when there is not enough connection (step S203, No), and data If there is no transmission request (No in step S205), the process is terminated as it is.

  Here, the content notification from the own vehicle may be transmitted only to the rear of the own vehicle. Considering that the vehicle travels forward, there is a high possibility that the information is already owned even if it is transmitted forward, so transferring it only to the rear reduces wasteful communication and increases communication resource efficiency. Can be planned.

  As described above, the communication device 1 according to the present embodiment, in a system that shares information by coordinating road-to-vehicle communication and vehicle-to-vehicle communication, is the type of information transmission source (whether it is a fixed transmission source or a vehicle). Information is received with optimal communication efficiency by selecting the information transmission source according to the communication method, communication speed, positional relationship with the host vehicle and the movement state, and conditions for transferring information data in the vehicle. By setting, communication resource pressure can be avoided.

  In this embodiment, traffic information, weather information, and store information have been described as examples. However, the contents of the information can be changed as appropriate.

  Further, in this embodiment, the case where information data created by a fixed information transmission source such as a server is shared has been described as an example, but the present invention is similarly applied even when the information data creation source is a vehicle or the like. It goes without saying that it is possible.

  As described above, the in-vehicle communication device and the communication method according to the present invention are useful for communication control in a vehicle, and are particularly suitable for improving the efficiency of communication at the time of information sharing using transfer by a vehicle.

It is a conceptual diagram explaining the concept of this invention. It is a schematic block diagram which shows the schematic structure of the communication apparatus concerning the Example of this invention. It is explanatory drawing explaining the priority of a fixed information transmission source. It is explanatory drawing explaining the selection of the communication destination based on a communication speed. It is explanatory drawing explaining the selection of the communication destination based on the distance from the own vehicle. It is explanatory drawing explaining selection of the communication destination based on a relative speed. It is explanatory drawing explaining selection of the communication destination between the vehicles which have the same relative speed. It is explanatory drawing explaining the case where two or more information transmission sources of the same relative speed exist ahead of the own vehicle. It is explanatory drawing explaining the case where two or more information transmission sources of the same relative speed exist in the back of the own vehicle. It is explanatory drawing explaining the specific example of a content notification. It is explanatory drawing explaining the specific example of selection of the communication destination based on a content notification. It is explanatory drawing explaining the transfer control based on the number of via | transit stages. It is explanatory drawing explaining the setting of a passage step number. It is a flowchart explaining the processing operation at the time of information reception. It is a flowchart explaining the processing operation at the time of information transmission.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Communication apparatus 2 Navigation apparatus 3 Vehicle speed sensor 4 In-vehicle apparatus 10 Control part 10a Communication destination selection part 10b Connection number setting part 10c Lifetime control part 11-13 Communication part 14-16 Antenna 17 Data storage part 18 Gateway part S1 Server A1 Transmission Base station C0 Own vehicle C11, C12, C21, C22, C23 Vehicle

Claims (14)

A plurality of communication means provided in the own vehicle, each communicating information from a plurality of information transmission sources including other vehicles;
Selecting means for selecting which of the plurality of information transmission sources communicates the information based on a relative relationship between the host vehicle and the plurality of information transmission sources;
An in-vehicle communication device that communicates information from an information transmission source selected by the selection unit via a corresponding communication unit.   The selection means preferentially selects reception of information from a fixed position transmission source when the information of the same content can be received from any other vehicle and the fixed position transmission source. The in-vehicle communication device according to Item 1.   The selection means preferentially selects information reception from an information transmission source closest to the host vehicle when information of the same content can be received from a plurality of information transmission sources. The in-vehicle communication device described in 1.   The selection means preferentially selects information reception from an information transmission source having a low relative speed with respect to the host vehicle when the same information can be received from a plurality of information transmission sources. The vehicle-mounted communication apparatus as described in any one of 1-3.   When there are a plurality of information transmission sources capable of receiving the same information and having the same relative speed with the host vehicle, the selection unit selects an information transmission source that is ahead of the host vehicle from the plurality of information transmission sources. 5. The in-vehicle communication device according to claim 4, wherein the information reception is preferentially selected.   The selection means is capable of receiving information of the same content, and when there are a plurality of information transmission sources having the same relative speed with the host vehicle in front of the host vehicle, the selection means is compared with the host vehicle among the plurality of information transmission sources. 6. The in-vehicle communication device according to claim 4, wherein information reception from an information transmission source having a low traveling speed is selected with priority.   The selection means can receive information of the same content, and when there are a plurality of information transmission sources having the same relative speed with the host vehicle behind the host vehicle, the selection means is compared with the host vehicle among the plurality of information transmission sources. The in-vehicle communication device according to claim 4, 5 or 6, wherein priority is given to information reception from an information transmission source having a high traveling speed. Receiving means for receiving information from a plurality of information transmission sources including other vehicles;
Transmitting means for transmitting information acquired by the receiving means to another vehicle;
A transmission control unit that permits transmission by the transmission unit only when the number of via stages indicating the number of communication devices that relayed the information is less than a set maximum value;
An in-vehicle communication device comprising:   9. The in-vehicle communication device according to claim 8, wherein the maximum value of the number of vias is set to be small when information content is highly region dependent.   The in-vehicle communication device according to claim 8 or 9, wherein the maximum value of the number of via steps is set to be small when the time dependency of information content is high.   The in-vehicle communication device according to claim 8, 9 or 10, wherein the maximum value of the number of via steps is set to be small when the importance of information content is high.   The in-vehicle communication device according to any one of claims 8 to 11, wherein the transmission control unit sets a maximum value of the number of via stages. A receiving step of receiving information from a plurality of information transmission sources including other vehicles;
A selection step of selecting from which of the plurality of information transmission sources the information is received;
The communication method for vehicles characterized by including. A receiving step of receiving information from a plurality of information transmission sources including other vehicles;
A transmission control step that permits transmission of information received by the reception step only when the number of via stages indicating the number of communication devices that relay the information is less than a set maximum value;
A transmission step of transmitting the information acquired by the reception step to another vehicle;
A vehicle communication method characterized by comprising:

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