Communication system

Abstract

The present invention relates to a communication system for suppressing excessive information received by a server in a communication system. A communication system (10) is provided with: a plurality of vehicles (20) including a first vehicle (20A) and a second vehicle (20B); and a server (40) capable of communicating with the plurality of vehicles. When a second vehicle (20B) travels in a following relationship with a first vehicle (20A), the first vehicle (20A) transmits absolute position information AI of the first vehicle (20A) and inter-vehicle distance information DI of the second vehicle (20B) to a server (40), the absolute position information AI including coordinate values of latitude and longitude at which the first vehicle (20A) is located. The second vehicle (20B) does not transmit the absolute position information (AI) of the second vehicle (20B) to the server (40). The server (40) calculates the absolute position of the second vehicle on the basis of the absolute position information AI of the first vehicle (20A) and the inter-vehicle distance information DI of the second vehicle.

Description

Technical Field

[0001] This invention relates to communication systems. Background Technology

[0002] Patent Document 1 describes a communication system comprising a first vehicle, a second vehicle, and a server. In this system, the first vehicle transmits its own location information and the location information of the second vehicle to the server. The location information includes latitude and longitude.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-212610

[0004] In the communication system described in Patent Document 1, the server receives the latitude and longitude information of the first vehicle and the second vehicle. Therefore, there is a concern that the server receives an excessive amount of information. Summary of the Invention

[0005] To address the aforementioned issues, the present invention provides a communication system comprising multiple vehicles, including a first vehicle and a second vehicle, and a server capable of communicating with the multiple vehicles. When the second vehicle and the first vehicle are traveling in a following relationship, the first vehicle acquires its absolute position information, including the latitude and longitude coordinates of the first vehicle, and acquires the vehicle's inter-vehicle distance information, representing the distance between the first vehicle and the second vehicle (i.e., the inter-vehicle distance). The first vehicle then sends its absolute position information and the vehicle's inter-vehicle distance information to the server. The second vehicle does not send its absolute position information, including its latitude and longitude coordinates, to the server. The server calculates the latitude and longitude coordinates of the second vehicle based on the first vehicle's absolute position information and the vehicle's inter-vehicle distance information.

[0006] The aforementioned communication system can prevent the server from receiving an excessive amount of information. Attached Figure Description

[0007] Figure 1 This is a simplified diagram of a communication system.

[0008] Figure 2 This is a flowchart illustrating the server's process of determining groups.

[0009] Figure 3 This is a flowchart illustrating how the server processes requests to each vehicle.

[0010] Figure 4 This is a flowchart representing the transmission control process performed on subsequent vehicles.

[0011] Figure 5 This is a flowchart representing the dispatch control process performed by the lead vehicle.

[0012] Figure 6 This is an illustration of the process of sending information from the lead vehicle to the server. Detailed Implementation

[0013] Hereinafter, one embodiment of the communication system will be described with reference to the accompanying drawings.

[0014] <Overview of Communication Systems>

[0015] like Figure 1 As shown, the communication system 10 includes multiple vehicles 20, a wireless communication network 30, and a server 40.

[0016] Vehicle 20 includes a vehicle communication device 21, a vehicle control device 22, and multiple information acquisition devices 23. The vehicle communication device 21 communicates wirelessly with the server 40 via a wireless communication network 30. Additionally, the vehicle communication device 21 communicates with other vehicles 20 via vehicle-to-vehicle communication. The vehicle control device 22 controls the communication of the vehicle communication device 21.

[0017] Multiple information acquisition devices 23 acquire various information about the vehicle 20. These devices include a GPS receiver 24, a vehicle speed sensor 25, and a vehicle distance sensor 26. The GPS receiver 24 receives absolute position information AI, representing the absolute position of the vehicle 20, from a GPS device. The absolute position is represented by latitude and longitude coordinates. Therefore, the absolute position information AI includes latitude and longitude information. The vehicle speed sensor 25 acquires the vehicle 20's speed as vehicle speed V. The vehicle distance sensor 26 detects the distance from the vehicle 20 to other vehicles 20 traveling ahead of it, i.e., the vehicle distance DV. An example of the vehicle distance sensor 26 is a LIDAR (Laser Imaging Detection and Ranging). Each information acquisition device 23 outputs the acquired information about the vehicle 20 to the vehicle control device 22.

[0018] Vehicle control unit 22 controls the following movement of vehicle 20. Vehicle control unit 22 controls the following movement of other vehicles 20 that are traveling ahead of vehicle 20 based on user input. When vehicle 20 is following a vehicle, the vehicle 20 and the vehicle ahead are in a following relationship. While in following movement, vehicle control unit 22 generates following information FD indicating that following movement is in progress. Vehicle control unit 22 has a storage unit. The storage unit of vehicle control unit 22 includes a counter for counting the number NM of subsequent vehicles RV (described later). Additionally, the storage unit of vehicle control unit 22 can temporarily store information.

[0019] The vehicle control unit 22 acquires various information about the vehicle 20 obtained from multiple information acquisition devices 23, the time when the various information was acquired, and the vehicle 20's following information FD as moving body information VI. The moving body information VI is information about the vehicle 20 in the real world.

[0020] The vehicle control unit 22 outputs the movement information VI to the vehicle communication unit 21. Furthermore, the vehicle communication unit 21 sends the movement information VI to the server 40. Among these, in... Figure 1 In the diagram, details are shown for one of the multiple vehicles 20, while details for the other vehicles 20 are omitted. Each vehicle 20 sends its movement information VI to the server 40.

[0021] Server 40 is capable of communicating with multiple vehicles 20. Server 40 obtains multiple mobile body information VIs from the multiple vehicles 20. Server 40 is capable of sending various request DMs based on predicted mobile body information FI generated according to the mobile body information VIs (described later) to the vehicles 20. Server 40 includes a communication device 50, an information processing device 60, and a data center 70.

[0022] The communication device 50 communicates with multiple vehicles 20. The communication device 50 receives mobile body information VI transmitted from the vehicles 20. The communication device 50 outputs the received mobile body information VI to the information processing device 60. Additionally, the communication device 50 transmits information obtained from the information processing device 60 to the vehicles 20.

[0023] The information processing device 60 includes a CPU 61 as an execution device, peripheral circuitry 62, a data storage unit 63, a program storage unit 64, and a bus 65. The bus 65 connects the CPU 61, peripheral circuitry 62, data storage unit 63, and program storage unit 64 so that they can communicate with each other. The peripheral circuitry 62 includes circuitry for generating clock signals that define internal operations, a power supply circuit, and a reset circuit. The data storage unit 63 stores data generated in conjunction with the operations of the CPU 61. The program storage unit 64 stores a program P1 for generating prediction movement information FI, a program P2 for determining group GR, a program P3 for requesting the transmission of location information, and a program P4 for processing inter-vehicle distance information DI. The CPU 61 performs information processing by executing the various programs stored in the program storage unit 64.

[0024] Data center 70 stores predicted mobility information FI. Predicted mobility information FI is generated based on mobility information VI of multiple vehicles 20, including information on multiple mobility information VI after the time when the mobility information VI in a defined area is obtained. The defined area can be, for example, the scope of a country, a portion of a country, or the entire world. That is, predicted mobility information FI is a so-called digital twin. In addition, data center 70 stores time-series data of predicted mobility information FI generated by information processing device 60. Data center 70 obtains predicted mobility information FI generated by information processing device 60 multiple times over time. Therefore, data center 70 stores time-series data of predicted mobility information FI.

[0025] <Generation of Predicted Moving Body Information>

[0026] CPU61 repeatedly generates the predicted mobility information FI by repeatedly executing the predicted mobility information FI generation program P1 at a predetermined period. This predetermined period is, for example, determined to be 1 minute.

[0027] If CPU 61 begins executing the program P1 for generating predicted mobile information FI, it first acquires the mobile information VI of each vehicle 20 in the communication system 10. Next, CPU 61 generates predicted mobile information FI based on the acquired mobile information VI. First, for the acquired mobile information VI, CPU 61 refers to information representing the time of acquisition. Next, CPU 61 uses the time of the latest acquired mobile information VI as a reference time, and predicts the mobile information VI at the reference time by correcting the difference between the time and other mobile information VI. For example, CPU 61 makes the prediction by correcting based on past mobile information VI such as vehicle speed V. Furthermore, CPU 61 generates various information about the predicted mobile information VI as predicted mobile information FI. Thus, CPU 61 acquires the mobile information VI of multiple vehicles 20 synchronized with the reference time as predicted mobile information FI. Then, CPU 61 stores the acquired predicted mobile information FI in the data center 70. In this way, information processing device 60 generates predicted mobile information FI.

[0028] <Determination of whether a group exists>

[0029] CPU 61 repeatedly executes the judgment procedure P2 for vehicles in a following relationship group GR at a predetermined period. This predetermined period is, for example, determined to be 1 minute. Thus, CPU 61 judges the vehicles 20 that constitute the group GR (i.e., vehicles 20 that are traveling in a following relationship) and the vehicles 20 that do not constitute the group GR (i.e., vehicles 20 that are not traveling in a following relationship) among the multiple vehicles 20 in the specified area.

[0030] like Figure 2 As shown, if CPU 61 starts executing the group GR determination procedure P2, it first begins the processing in step S11. In step S11, CPU 61 obtains a past specified period of time-series data of the predicted mobile information FI from data center 70. The past specified period is, for example, 3 minutes. Then, CPU 61 causes the processing to proceed to step S12.

[0031] In step S12, CPU 61 extracts multiple vehicles 20 that have continuously existed within a specified range during the past specified period based on the time-series data of the predicted mobility information FI obtained in step S11. The specified range is, for example, a range where the distance between the multiple vehicles 20 is within 100 meters. Then, CPU 61 proceeds to step S13. Furthermore, if CPU 61 cannot extract multiple vehicles 20 in step S12, CPU 61 appends non-constituent information (representing that they do not constitute a group GR) to the predicted mobility information FI for all vehicles 20, ending the current series of processes.

[0032] In step S13, the CPU 61 determines whether a predetermined proportion or more of the multiple vehicles 20 extracted in step S12 are in a following state. The predetermined proportion is, for example, determined to be 50%. Specifically, the CPU 61 determines whether the moving body information VI of the multiple vehicles 20 extracted in step S12 contains following information FD. Furthermore, the CPU 61 compares the number of moving body information VIs containing following information FD with the number extracted in step S12.

[0033] When there are more than a certain number of following information FDs (S13: Yes), CPU 61 causes the processing to proceed to step S14. In step S14, CPU 61 determines the multiple vehicles 20 extracted in step S12 as a group GR traveling in one group. Then, CPU 61 causes the processing to proceed to step S15.

[0034] In step S15, CPU 61 appends the constituent information of the group GR and the group identification information for identifying the group GR to the predicted moving body information FI for the multiple vehicles 20 that were determined to be a group GR in step S14. Then, CPU 61 ends the series of processes.

[0035] On the other hand, if the number of following information FDs does not exceed a certain proportion (S13: No), CPU 61 causes the processing to proceed to step S21. In step S21, CPU 61 does not determine the multiple vehicles 20 extracted in step S12 as a group GR. Then, CPU 61 causes the processing to proceed to step S22.

[0036] In step S22, CPU 61 appends non-constituting information indicating that multiple vehicles 20 that were not determined to form a group GR in step S21 to the predicted mobility information FI. Then, CPU 61 ends the series of processes. By executing the group GR determination procedure P2 in this way, the predicted mobility information FI becomes a state that includes information indicating whether or not a group GR is formed.

[0037] <Request from server to vehicle>

[0038] Next, the request DM made by the information processing device 60 to the vehicles 20 constituting the group GR will be described. The CPU 61 repeatedly executes the request procedure P3 for transmitting location information at a predetermined cycle. The CPU 61 repeatedly executes this process for each group GR consisting of multiple vehicles 20. Therefore, after the CPU 61 determines the object to which the request procedure P3 is to be executed by referring to the predicted moving body information FI, the execution of the request procedure P3 begins for each group GR.

[0039] like Figure 3 As shown, if CPU 61 initiates a request for the execution of program P3, it first executes step S31. In step S31, CPU 61 determines whether the number of vehicles 20 constituting group GR is less than a predetermined quantity RN. The predetermined quantity RN is, for example, 10 vehicles. If the number of vehicles 20 constituting group GR is less than the predetermined quantity RN (S31: Yes), CPU 61 proceeds to step S32.

[0040] In step S32, CPU 61 determines the lead vehicle FV of group GR based on the predicted moving body information FI. For example, CPU 61 infers the column formed by multiple vehicles 20 by referring to the absolute position of the vehicles 20 in the predicted moving body information FI. Next, CPU 61 infers the direction of movement of the column by referring to the predicted moving body information FI. Moreover, CPU 61 infers the vehicle 20 at the front of the column in the inferred direction of movement as the lead vehicle FV. Then, CPU 61 causes the process to proceed to step S33.

[0041] In step S33, CPU 61 sends the lead vehicle FV with the inter-vehicle distance information DV of the vehicles 20 constituting the group GR (excluding the lead vehicle FV), i.e., the following vehicles RV, and a request DM to be sent to server 40. The inter-vehicle distance DV of the following vehicles RV is the distance between the following vehicle RV and the preceding vehicle that is ahead of it. Then, CPU 61 causes the process to proceed to step S34.

[0042] In step S34, CPU 61 sends a request DM to the subsequent vehicle RV to stop sending absolute position information AI to server 40. Then, CPU 61 causes the process to proceed to step S35.

[0043] In step S35, CPU61 sends a request DM to the following vehicle RV to send the inter-vehicle distance information DI to the leading vehicle FV. Thus, CPU61 terminates this series of processes.

[0044] On the other hand, when the number of vehicles 20 constituting the group GR is more than a predetermined amount RN (S31: No), CPU 61 causes the processing to proceed to step S36. In step S35, CPU 61 sends the stop-distance information DI to all vehicles 20 constituting the group GR and a request DM to send the absolute position information AI to the server 40. Thus, CPU 61 ends the current series of processes. Furthermore, when non-constituent information is added to the predicted moving body information FI, CPU 61 performs the same processing as in step S36.

[0045] <Subsequent vehicle information transmission>

[0046] Next, the process executed by the vehicle control device 22 of the following vehicle RV, which receives the request DM from the server 40 through steps S34 and S35, will be described. Hereinafter, the vehicle control device 22 of the following vehicle RV will be referred to as vehicle control device 22R. If vehicle control device 22R receives the request DM from the server 40, it controls the transmission of the inter-vehicle distance information DI to the leading vehicle FV.

[0047] like Figure 4 As shown, if the vehicle control device 22R initiates the transmission control, it first performs the processing in step S41. In step S41, the vehicle control device 22R obtains information representing the vehicle's distance DV detected by the vehicle's distance sensor 26 as the vehicle's distance information DI. The vehicle's distance DV is the distance between the vehicle and the preceding vehicle that is traveling ahead of it. Then, the vehicle control device 22R proceeds to step S42.

[0048] In step S42, the vehicle control device 22R sends the vehicle's inter-vehicle distance information DI to the preceding vehicle. Then, the vehicle control device 22R proceeds to step S43. In step S43, the vehicle control device 22R determines whether it has received the inter-vehicle distance information DI from the following vehicle RV that is acting as the preceding vehicle. Specifically, the vehicle control device 22R determines whether it has received the inter-vehicle distance information DI from the following vehicle RV before a predetermined period has elapsed since the start of step S43. If the vehicle control device 22R has not received the inter-vehicle distance information DI from the following vehicle RV (S43: No), the vehicle control device 22R terminates the current series of processes.

[0049] On the other hand, when the vehicle control device 22R receives the inter-vehicle distance information DI from the following vehicle RV (S43: Yes), the vehicle control device 22R proceeds to step S44. In step S44, the vehicle control device 22R sends the obtained inter-vehicle distance information DI of the following vehicle RV to the preceding vehicle. That is, the vehicle control device 22R forwards the inter-vehicle distance information DI from the following vehicle 20 to the vehicle 20 that is ahead of it. Then, the vehicle control device 22R proceeds to step S45.

[0050] In step S45, the vehicle control device 22R determines whether the distance information DI has been received from the following vehicle RV. Specifically, before a predetermined period has elapsed since the start of step S45, the vehicle control device 22R again determines whether the distance information DI has been received from the following vehicle RV. If the vehicle control device 22R has not received the distance information DI from the following vehicle RV, it determines that the distance information DI has been received from the following vehicle RV. On the other hand, if the vehicle control device 22R has received the distance information DI from the following vehicle RV, it determines that the distance information DI has not been received from the following vehicle RV. If the distance information DI has not been received from the following vehicle RV (S45: No), the vehicle control device 22R returns the process to step S44. Furthermore, the vehicle control device 22R retransmits the received distance information DI to the preceding vehicle. If the distance information DI has been received from the following vehicle RV (S45: Yes), the vehicle control device 22R ends the current series of processes.

[0051] <Information transmission for the lead vehicle>

[0052] Next, the process executed by the vehicle control device 22 of the lead vehicle FV, which receives the request DM from the server 40 through step S33, will be described. Hereinafter, the vehicle control device 22 of the lead vehicle FV will be referred to as vehicle control device 22F. If vehicle control device 22F receives the request DM from the server 40 for the lead vehicle FV, it controls the transmission of the inter-vehicle distance information DI of the subsequent vehicles RV to the server 40.

[0053] like Figure 5 As shown, if the vehicle control device 22F initiates the transmission control, it first performs the processing in step S51. In the processing of step S51, the vehicle control device 22F obtains the absolute position information AI from the GPS receiver 24. Then, the vehicle control device 22F causes the processing to proceed to step S52.

[0054] In step S52, the vehicle control unit 22F obtains information representing the vehicle speed V from the vehicle speed sensor 25. Then, the vehicle control unit 22F proceeds to step S53. In step S53, the vehicle control unit 22F obtains the inter-vehicle distance information DI of the following vehicle RV from the following vehicle RV. Then, the vehicle control unit 22F proceeds to step S54.

[0055] In step S54, the vehicle control device 22F increments the counter for the number of subsequent vehicles (RVs) NM. Then, the vehicle control device 22F proceeds to step S55. In step S55, the vehicle control device 22F stores the vehicle distance information DI. Then, the vehicle control device 22F proceeds to step S56.

[0056] In step S56, the vehicle control device 22F determines whether the receiving of the inter-vehicle distance information DI from the following vehicle RV has been completed. Specifically, the processing in step S56 is the same as that in step S45. If the receiving of the inter-vehicle distance information DI from the following vehicle RV has not been completed (S56: No), the vehicle control device 22F returns the processing to step S54. On the other hand, if the receiving of the inter-vehicle distance information DI from the following vehicle RV has been completed (S56: Yes), the vehicle control device 22F causes the processing to proceed to step S57.

[0057] In step S57, the vehicle control device 22F sends the absolute position information AI of the vehicle, the vehicle speed V, the stored inter-vehicle distance information DI of the subsequent vehicles RV, and the information NM of the number of subsequent vehicles RV to the server 40. After resetting the counter for the number of subsequent vehicles RV NM to zero, the vehicle control device 22F ends the current series of processes.

[0058] like Figure 1 As shown, upon receiving the vehicle distance information DI, CPU 61 begins execution of the vehicle distance information DI processing procedure P4. If CPU 61 begins execution of the vehicle distance information DI processing procedure P4, CPU 61 first confirms whether the required number of vehicle distance information DIs has been obtained. Specifically, CPU 61 compares the received number of subsequent vehicles RV NM with the number that is one less than the number of vehicles 20 constituting group GR. If the two numbers are inconsistent, CPU 61 performs the same processing as in step S36.

[0059] Once CPU 61 has obtained the required number of vehicle distance information DIs, it calculates the absolute position of the following vehicles (RVs) based on the absolute position information AI of the leading vehicle (FV) and the vehicle distance information DIs of the following vehicles (RVs). Specifically, CPU 61 uses the absolute position represented by the absolute position information AI of the leading vehicle (FV) as a reference to calculate the position of the vehicle distance DV represented by the vehicle distance information DIs to the rear as the absolute position of the following vehicle (RV), i.e., the latitude and longitude coordinates of the following vehicle (RV). If multiple vehicle distance information DIs of the following vehicles (RVs) have been obtained, CPU 61 calculates the absolute positions sequentially starting from the leading vehicle (FV). Specifically, CPU 61 uses the absolute position of the second following vehicle (RV) from the leading vehicle (FV) as a reference to calculate the position of the vehicle distance DV represented by the vehicle distance information DIs to the rear of the third following vehicle (RV). If the absolute positions of all vehicles 20 constituting the group GR have been calculated, CPU 61 terminates the execution of the vehicle distance information DI processing procedure P4.

[0060] When generating the predicted moving body information FI, CPU 61 uses the absolute position of the following vehicle RV calculated by the execution of the processing program P4 of the inter-vehicle distance information DI as the moving body information VI. CPU 61 generates the predicted moving body information FI by using the calculated absolute position of the following vehicle RV for which absolute position information AI has not been obtained.

[0061] <The Role of the Implementation Method>

[0062] like Figure 6 As shown, assume that five vehicles 20 form a group GR and are traveling. Starting from the lead vehicle 20, they are sequentially referred to as vehicle 1 20A, vehicle 20B, vehicle 3 20C, vehicle 4 20D, and vehicle 5 20E. In this case, vehicle 1 20A becomes the lead vehicle FV, and vehicles 20B through 20E become the following vehicles RV.

[0063] In this case, since the number of vehicles 20 constituting group GR is less than the specified quantity RN, server 40 performs steps S32 to S34. Thus, the first vehicle 20A begins... Figure 5 The series of processes shown are executed, and vehicles 20B through 50E begin. Figure 4 The execution of a series of processes is shown.

[0064] Therefore, vehicle 5 20E sends its distance information DI to vehicle 4 20D, which is the preceding vehicle. Vehicle 4 20D then sends its distance information DI and the distance information DI of vehicle 5 20E to vehicle 3 20C, which is the preceding vehicle. Vehicle 3 20C then sends its distance information DI, the distance information DI of vehicle 4 20D, and the distance information DI of vehicle 5 20E to vehicle 2 20B, which is the preceding vehicle, in sequence. Vehicle 2 20B then sends its distance information DI, the distance information DI of vehicle 3 20C, the distance information DI of vehicle 4 20D, and the distance information DI of vehicle 5 20E to vehicle 1 20A, which is the preceding vehicle, in sequence.

[0065] On the other hand, the second vehicle 20B to the fifth vehicle 20E, which are subsequent vehicles (RVs), do not send their absolute position information AI and information indicating their speed V to the server 40. Therefore, the second vehicle 20B does not send its absolute position information AI to the server 40.

[0066] Vehicle 20A 1 sends its absolute position information AI to server 40. Vehicle 20A 1 also sends its inter-vehicle distance information DI between vehicles 20B to 50E to server 40. Vehicle 20A 1 also sends its speed V to server 40. Finally, Vehicle 20A 1 sends the number of subsequent vehicles RV (RV) obtained through counting, NM, to server 40, which is 4.

[0067] Furthermore, server 40 receives the absolute position information AI of vehicle 1 20A, information indicating the speed V of vehicle 1 20A, the inter-vehicle distance information DI between vehicle 20B and vehicle 5 20E, and information indicating the number NM of subsequent vehicles RV. Then, server 40 calculates the absolute positions of vehicle 20B to vehicle 5 20E based on the absolute position information AI of vehicle 1 20A and the inter-vehicle distance information DI between vehicle 20B and vehicle 5 20E. Additionally, server 40 infers the speed V of vehicle 20B to vehicle 5 20E as the speed V of vehicle 1 20A.

[0068] Then, server 40 uses the absolute value of the first vehicle 20A and its speed V, the calculated absolute positions of the second vehicle 20B to the fifth vehicle 20E and their speeds V to generate the predicted moving body information FI.

[0069] <Effects of the Implementation Method>

[0070] (1) According to the above embodiment, the first vehicle 20A sends its absolute position information AI and the inter-vehicle distance information DI of the second vehicle 20B to the server 40. The second vehicle 20B does not send its absolute position information AI to the server 40. Moreover, the server 40 calculates the absolute position of the second vehicle 20B based on the absolute position information AI of the first vehicle 20A and the inter-vehicle distance information DI of the second vehicle 20B. Therefore, the amount of information received by the server 40 can be less than in the case of receiving only the absolute position information AI of the second vehicle 20B. Thus, the communication system 10 can prevent the amount of information received by the server 40 from becoming excessively large.

[0071] (2) According to the above embodiment, the first vehicle 20A sends information representing its speed V to the server 40. The second vehicle 20B sends information representing its speed V to the server 40. Furthermore, the server 40 infers the speed V of the second vehicle 20B as the speed V represented by the information representing the speed V of the first vehicle 20A. Therefore, the server 40 does not need to receive information representing the speed V of subsequent vehicles RV.

[0072] (3) According to the above embodiment, the server 40 generates predicted mobility information FI based on the absolute positions of multiple vehicles 20. The server 40 determines whether the second vehicle 20B is traveling in a following relationship with the first vehicle 20A based on the predicted mobility information FI. Moreover, when the second vehicle 20B is traveling in a following relationship with the first vehicle 20A, the server 40 sends a request DM to the second vehicle 20B to stop sending the absolute position information AI of the second vehicle 20B. Therefore, the server 40 can generate the predicted mobility information FI and send the request DM based on the predicted mobility information FI while suppressing the amount of information received.

[0073] (4) According to the above embodiment, when the second vehicle 20B is not driving in a following relationship with the first vehicle 20A, the second vehicle 20B sends its absolute position information AI to the server 40. Therefore, the server 40 can suppress the situation where the absolute position of the second vehicle 20B cannot be obtained when the second vehicle 20B is not following the first vehicle 20A.

[0074] (5) If the first vehicle 20A sends the distance information DI of too many vehicles 20 to the server 40, excessive time will be spent from the time each vehicle 20 obtains the distance information DI to the time the server 40 receives the distance information DI. Regarding this, according to the above embodiment, when more than a predetermined number of vehicles 20 are following, subsequent vehicles RV do not send the distance information DI to the server 40, but each vehicle 20 sends its absolute position information AI to the server 40. Therefore, it is possible to prevent the absolute position of the vehicle 20 calculated by the server 40 from becoming outdated information.

[0075] <Other Implementation Methods>

[0076] This embodiment can be modified as follows. This embodiment and the following modifications can be combined with each other within the scope of technical inconsistency.

[0077] • When the number of following vehicles (RVs) (NM) is greater than or equal to a predetermined quantity (RN), server 40 may not send a request (DM) to the lead vehicle (FV) to not obtain the inter-vehicle distance information (DI) of the following vehicles (RVs). When the number of following vehicles (RVs) (NM) is greater than or equal to a predetermined quantity (RN), server 40 may not send a request (DM) to the following vehicles (RVs) to send absolute position information (AI).

[0078] Server 40 may not generate predicted mobility information FI. Server 40 may not use the absolute position of vehicle 20 in generating the predicted mobility information FI. Server 40 may not determine whether the second vehicle 20B is following the first vehicle 20A based on the predicted mobility information FI. For example, server 40 may determine the following relationship based on the following information FD instead of determining the composition of the group GR.

[0079] The second vehicle 20B can be a vehicle 20 that always follows the first vehicle 20A. In this case, since the second vehicle 20B will not fail to follow the first vehicle 20A, the second vehicle 20B does not need to send its absolute position information AI to the server 40. That is, multiple vehicles 20 may not be able to travel under a following relationship.

[0080] • Multiple vehicles 20 can stop sending absolute position information AI and vehicle distance information DI to forward vehicles without relying on requests DM from server 40.

[0081] The following vehicle (RV) can send information representing its speed (V) to server 40, or it can send it to the leading vehicle (FV). The following vehicle (RV) can send the distance between itself and the leading vehicle (FV) as the distance information (DI) instead of the distance (DV) between itself and the preceding vehicle.

[0082] In the above embodiment, an example of the lead vehicle FV sending the inter-vehicle distance information DI of the following vehicle RV to the server 40 was described. However, the vehicles 20 in the group GR that send the inter-vehicle distance information DI of other vehicles 20 to the server 40 are not limited to the lead vehicle FV. For example, the last vehicle 20 in the group GR could also send the inter-vehicle distance information DI of other vehicles 20 to the server 40. In this case, the other vehicles 20 only need to send the inter-vehicle distance DV of the vehicle 20 behind them as the inter-vehicle distance information DI of that vehicle to the last vehicle 20. That is, the following relationship can be either the second vehicle following the first vehicle or the first vehicle following the second vehicle. In addition, for example, a specific vehicle 20 in the group GR could also send the inter-vehicle distance information DI of other vehicles 20 to the server 40. In this case, other vehicles 20 only need to send the distance between themselves and the vehicle 20 closest to the specific vehicle 20 among the vehicles 20 traveling in front or behind them as the distance information DI of that vehicle 20 to the specific vehicle 20.

[0083] Explanation of reference numerals in the attached figures:

[0084] 10…Communication system; 20…Vehicle; 20A…First vehicle; 20B…Second vehicle; 30…Wireless communication network; 40…Server; 60…Information processing device; 61…CPU; 64…Program storage unit; AI…Absolute position information; DI…Device distance information; DM…Request; DV…Device distance; FI…Predicted moving body information; FV…Leading vehicle; GR…Group; RN…Specified quantity; RV…Following vehicle; V…Speed; VI…Moving body information.

Claims

1. A communication system comprising a plurality of vehicles, including a first vehicle and a second vehicle, and a server capable of communicating with the plurality of said vehicles, wherein, When the second vehicle and the first vehicle are traveling in a following relationship, the first vehicle obtains its absolute position information, including the latitude and longitude coordinates of the first vehicle, and obtains the vehicle's distance information, which represents the distance between the first vehicle and the second vehicle, i.e., the inter-vehicle distance. The first vehicle sends its absolute position information and the vehicle's distance information to the server. The second vehicle does not send its absolute position information, including the latitude and longitude coordinates of the second vehicle, to the server. The server calculates the latitude and longitude coordinates of the second vehicle based on the first vehicle's absolute position information and the vehicle's distance information.

2. The communication system according to claim 1, wherein, When the second vehicle and the first vehicle are traveling in the following relationship, the first vehicle sends information indicating its speed to the server, while the second vehicle does not send information indicating its speed to the server. The server infers the speed of the second vehicle as the speed indicated by the information indicating the speed of the first vehicle.

3. The communication system according to claim 1, wherein, The server generates predicted movement information based on the latitude and longitude coordinates of the first vehicle and the second vehicle, and determines whether the second vehicle and the first vehicle are traveling in the following relationship based on the predicted movement information. When the second vehicle and the first vehicle are traveling in the following relationship, the server sends a request to the second vehicle to stop sending the absolute position information of the second vehicle.

4. The communication system according to claim 1, wherein, When the second vehicle is not traveling in the following relationship with the first vehicle, the second vehicle sends its absolute position information to the server.

5. The communication system according to claim 1, wherein, When a certain number of vehicles, including the second vehicle, follow the first vehicle as the lead vehicle, the server sends a request to the following vehicles. This request sends the absolute position information of the following vehicles, including the latitude and longitude coordinates of the following vehicles.

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