On-board terminal, base station, wireless communication system, control circuit, storage medium, and relay station selection method

Abstract

The in-vehicle terminal (11) includes a V2X communication control unit (41) that controls communication with surrounding vehicles capable of vehicle-to-vehicle communication, a surrounding vehicle information management unit (42) that manages surrounding vehicle information including position information of the surrounding vehicles and information on the communication state of the vehicle-to-vehicle communication acquired through the vehicle-to-vehicle communication, a V2N communication control unit (44) that performs control to provide information of a second base station that could not be connected through direct communication to a first base station that connects through direct communication, and to request the first base station to provide connection terminal information that is information on surrounding vehicles connected to the second base station, a relay management unit (46) that selects a relay station that is a surrounding vehicle that relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information, and a redundant system management unit (45) that manages the connection between the first base station and the second base station, and instructs the relay management unit to communicate indirectly with the second base station when a connection with the second base station cannot be made through direct communication.

Description

[Technical field]

[0001] The present disclosure relates to an in-vehicle terminal mounted in a vehicle, a base station, a wireless communication system, a control circuit, a storage medium, and a relay station selection method. [Background technology]

[0002] In recent years, communication using cellular networks has been used for various purposes. For example, 3GPP (registered trademark) (3rd Generation Partnership Project), an international standardization organization, is considering multiple path transmission to improve the reliability of communication in cellular networks. The purpose of multiple path transmission is to improve the reliability of communication by transmitting the same information through multiple paths. For multiple paths, a direct session between a base station and a terminal is the basis, but when direct sessions cannot be secured simultaneously, a method of securing multiple sessions using one direct session and one indirect session using side link communication is being considered.

[0003] When improving the reliability of communication by using multiple paths in a vehicle that is the subject of remote operation, remote monitoring, etc., the method of selecting a relay station for an indirect session is important. Much research has been conducted on relaying communication from a moving terminal in vehicle-to-vehicle communication, etc., and much research has also been conducted on methods of selecting a relay station. For example, Patent Document 1 discloses a technology for selecting a relay in vehicle-to-vehicle communication, in which the traveling direction and traveling speed of a vehicle are obtained from position information of surrounding vehicles obtained in vehicle-to-vehicle communication and the acquisition time of the position information, and a relay is selected using this information. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-212753 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the above conventional technology, the source vehicle-mounted communication device mounted on the vehicle selects as a repeater an in-vehicle communication device that is likely to be able to relay communication to the destination vehicle-mounted communication device, based on the position information of surrounding vehicles, etc. Therefore, there is a problem that the in-vehicle communication device selected by the source vehicle-mounted communication device may not actually be able to communicate with the destination vehicle-mounted communication device, and may not be able to relay communication between the source vehicle-mounted communication device and the destination vehicle-mounted communication device.

[0006] The present disclosure has been made in consideration of the above, and has an object to provide an in-vehicle terminal capable of improving the accuracy of selecting another in-vehicle terminal capable of relaying communication with a base station. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the present disclosure provides an on-board terminal mounted on a vehicle and performing wireless communication with multiple base stations via multiple paths. The on-board terminal is characterized by including: an inter-vehicle communication control unit that controls communication with surrounding vehicles that are present around the vehicle and capable of inter-vehicle communication; a surrounding vehicle information management unit that manages surrounding vehicle information including position information of the surrounding vehicles and communication state information of the inter-vehicle communication acquired through the inter-vehicle communication; a base station communication control unit that performs control to provide information of a second base station that is a base station that could not be connected through direct communication to a first base station that is a base station that connects through direct communication, and to request the provision of connection terminal information that is information of surrounding vehicles connected to the second base station; a relay management unit that holds the connection terminal information acquired from the first base station, and selects a relay station that is a surrounding vehicle that relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; and a redundant system management unit that manages the connection between the first base station and the second base station, and instructs the relay management unit to perform indirect communication with the second base station when it cannot connect to the second base station through direct communication. Effect of the Invention

[0008] The vehicle-mounted terminal according to the present disclosure has an effect of improving the accuracy of selecting another vehicle-mounted terminal capable of relaying communication with a base station. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration example of a wireless communication system according to a first embodiment; [Diagram 2] FIG. 1 is a block diagram showing a configuration example of an in-vehicle terminal according to a first embodiment; [Diagram 3] FIG. 1 is a diagram showing an example of nearby vehicle information managed by a nearby vehicle information management unit of an in-vehicle terminal according to the first embodiment; [Figure 4] FIG. 1 is a sequence diagram showing an operation of a vehicle equipped with an on-board terminal according to the first embodiment to obtain connection terminal information of a base station 31 via a base station 30. [Diagram 5] FIG. 1 is a block diagram showing a configuration example of a base station according to a first embodiment; [Figure 6] FIG. 1 is a diagram showing a configuration example of a processing circuit that realizes an in-vehicle terminal according to a first embodiment when the processing circuit is realized by a processor and a memory; [Figure 7] FIG. 1 is a diagram showing an example of a processing circuit for implementing an in-vehicle terminal according to a first embodiment, the processing circuit being configured with dedicated hardware; [Figure 8] FIG. 11 is a block diagram showing a configuration example of an in-vehicle terminal according to a second embodiment. [Figure 9] FIG. 11 is a block diagram showing a configuration example of a base station according to a second embodiment. [Figure 10] FIG. 13 is a diagram showing an example of an operation of an on-board terminal mounted on a vehicle in selecting a relay station in the wireless communication system according to the second embodiment; [Figure 11] FIG. 11 is a block diagram showing a configuration example of a base station according to a third embodiment. [Figure 12] A sequence diagram showing an operation of a vehicle equipped with an on-board terminal according to the third embodiment to obtain connection terminal information and relay station candidate information of a base station 31b via a base station 30b. [Figure 13] FIG. 13 is a diagram showing an example of nearby vehicle information managed by a nearby vehicle information management unit of an in-vehicle terminal according to a fourth embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an in-vehicle terminal, a base station, a wireless communication system, a control circuit, a storage medium, and a relay station selection method according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0011] Embodiment 1 FIG. 1 is a diagram showing a configuration example of a wireless communication system 1 according to a first embodiment. The wireless communication system 1 includes a vehicle 10, surrounding vehicles 20-22 around the vehicle 10, base stations 30 and 31, and roadside devices 70-72. The wireless communication system 1 shown in FIG. 1 assumes a case in which the vehicle 10 performs wireless communication with the base stations 30 and 31 using multiple paths. When the vehicle 10 can perform wireless communication with the base stations 30 and 31 and multiple direct sessions are secured, the vehicle 10 does not need an indirect session, but when multiple direct sessions are not secured, the vehicle 10 uses an indirect session. As shown in FIG. 1, the vehicle 10 is in a situation in which a direct session is established with the base station 30, but a direct session is not established with the base station 31. Therefore, in order to establish an indirect session with the base station 31, the vehicle 10 selects a relay station from the surrounding vehicles 20-22 that relays communication between the vehicle 10 and the base station 31. As a result, the vehicle 10 can secure a redundant line and perform highly reliable communication by one direct session and one indirect session.

[0012] In the following description, when the surrounding vehicles 20-22 are not distinguished, they are simply referred to as surrounding vehicles, when the base stations 30 and 31 are not distinguished, they are simply referred to as base stations, and when the roadside devices 70-72 are not distinguished, they are simply referred to as roadside devices. In the following description, a direct session may be referred to as a direct connection, and an indirect session may be referred to as an indirect connection. In the example of FIG. 1, the wireless communication system 1 includes three surrounding vehicles, two base stations, and three roadside devices, but may include four or more surrounding vehicles, three or more base stations, and four or more roadside devices. In FIG. 1, only the surrounding vehicles 20-22 present in front of the vehicle 10 in the traveling direction are shown as an example of the wireless communication system 1, but the vehicle 10 can also select a surrounding vehicle (not shown) present behind the vehicle 10 in the traveling direction as a relay station in the indirect session with the base station 31. In addition, the vehicle 10 can also select a roadside device installed along the road on which the vehicle 10 travels as a relay station in the indirect session with the base station 31. The same applies to the following embodiments.

[0013] In the first embodiment, the vehicle 10 and the surrounding vehicles 20-22 are equipped with an on-board terminal 11. In the example of Fig. 1, the vehicle 10 and the surrounding vehicles 20-22 are equipped with the same type of on-board terminal 11, but as long as the operation described below is possible, the on-board terminals 11 mounted on the vehicle 10 and the surrounding vehicles 20-22 may have partially different configurations, functions, etc. depending on the manufacturers, models, etc. of the vehicle 10 and the surrounding vehicles 20-22. Hereinafter, a case will be described in which the vehicle 10 and the surrounding vehicles 20-22 are equipped with the same type of on-board terminal 11 as shown in Fig. 1.

[0014] The configuration and operation of the in-vehicle terminal 11 will be described. FIG. 2 is a block diagram showing a configuration example of the in-vehicle terminal 11 according to the first embodiment. The in-vehicle terminal 11 includes a V2X (Vehicle to Everything) communication unit 40, a V2X communication control unit 41, a surrounding vehicle information management unit 42, a V2N (Vehicle to Network) communication unit 43, a V2N communication control unit 44, a redundant system management unit 45, and a relay management unit 46. The relay management unit 46 includes a relay station candidate selection unit 47, a relay control unit 48, and a connection terminal information holding unit 49. Note that in the example of FIG. 2, the description of the configuration related to general communication of V2X communication such as communication of a Basic Safety Message (BSM) that is not directly related to the process for establishing an indirect session, and the configuration related to general communication of V2N communication are omitted. Hereinafter, the operation of the in-vehicle terminal 11 that is mounted on the vehicle 10 and performs wireless communication with multiple base stations through multiple paths will be described.

[0015] The on-board terminal 11 mounted on the vehicle 10 exchanges BSM and the like with the on-board terminals 11 mounted on the surrounding vehicles 20 to 22 through V2X communication, i.e., vehicle-to-vehicle communication, by the V2X communication unit 40 and the V2X communication control unit 41. In this way, in reality, the on-board terminal 11 mounted on the vehicle 10 performs V2X communication with the on-board terminals 11 mounted on the surrounding vehicles 20 to 22, but for the sake of simplicity, hereinafter, it may be described that the vehicle 10 performs V2X communication with the surrounding vehicles 20 to 22, that the on-board terminal 11 performs V2X communication with the surrounding vehicles 20 to 22, etc.

[0016] The V2X communication unit 40 is an inter-vehicle communication unit that performs V2X communication with surrounding vehicles 20 to 22 that are present around the vehicle 10 and are capable of V2X communication.

[0017] The V2X communication control unit 41 is an inter-vehicle communication control unit that controls communication with surrounding vehicles 20 to 22 that are present around the vehicle 10 and are capable of V2X communication.

[0018] The surrounding vehicle information management unit 42 manages surrounding vehicle information including position information of surrounding vehicles and information on the communication state of V2X communication acquired through V2X communication by the V2X communication unit 40 and the V2X communication control unit 41. That is, the surrounding vehicles managed as surrounding vehicle information in the surrounding vehicle information management unit 42 include the surrounding vehicles 20-22 as well as the roadside devices 70-72 as described above.

[0019] FIG. 3 is a diagram showing an example of surrounding vehicle information managed by the surrounding vehicle information management unit 42 of the in-vehicle terminal 11 according to the first embodiment. The surrounding vehicle information management unit 42 manages surrounding vehicle information in a table format as shown in FIG. 3. In FIG. 3, a vehicle ID (IDentifier) ​​is identification information for identifying a surrounding vehicle. The location information is information indicating a current location of the surrounding vehicle. The time is information indicating a time when the surrounding vehicle information is acquired from the corresponding surrounding vehicle. A received signal strength indicator (RSSI) is information of communication quality indicating a communication state of V2X communication with a surrounding vehicle of the corresponding vehicle ID, and here, a received signal strength is shown as an example. One cycle before is information of communication quality indicating a previous communication state in V2X communication with a surrounding vehicle of the corresponding vehicle ID. Two cycles before is information of communication quality indicating a communication state before the previous time in V2X communication with a surrounding vehicle of the corresponding vehicle ID. The information of communication quality is not limited to the received RSSI, and an error rate, a signal to noise ratio (SNR), etc. may be used.

[0020] The surrounding vehicle information shown in FIG. 3 is an example, and the surrounding vehicle information management unit 42 may manage information such as the vehicle type and driving speed of the surrounding vehicles as the surrounding vehicle information, as long as the information is obtained by V2X communication. The surrounding vehicle information management unit 42 may manage the surrounding vehicles in such a way that the surrounding vehicles having a better communication condition and a more stable communication quality of V2X communication in the most recent specified period are placed higher in the table. For example, the surrounding vehicle information management unit 42 manages the surrounding vehicles so that the surrounding vehicles having the highest and most stable reception RSSI in the past three times are placed higher. Here, being stable means, for example, that the fluctuation of the reception RSSI is the least and exceeds a specified threshold value. The surrounding vehicle information management unit 42 may obtain the surrounding vehicles predicted to be traveling on the same road as the vehicle 10, the surrounding vehicles having a similar relative speed to the vehicle 10, and the like, from the transition of the most recent position information, and manage the surrounding vehicle information by taking these factors into consideration.

[0021] In parallel with the V2X communication, the vehicle-mounted terminal 11 mounted on the vehicle 10 performs wireless communication with the base station by the V2N communication unit 43 and the V2N communication control unit 44. The wireless communication between the vehicle-mounted terminal 11 mounted on the vehicle 10 and the base station is used for communication of applications such as remote control and remote monitoring that require highly reliable communication by establishing multiple sessions. In addition, the wireless communication between the vehicle-mounted terminal 11 mounted on the vehicle 10 and the base station is used for communication of services using a cellular network, such as collection of location information and route information of the vehicle 10 by the base station, provision of congestion information, surrounding information, and the like. In this way, in reality, the vehicle-mounted terminal 11 mounted on the vehicle 10 performs wireless communication with the base station, but for the sake of simplicity, hereinafter, it may be described as the vehicle 10 performing wireless communication with the base station.

[0022] The V2N communication unit 43 is a base station communication unit that performs wireless communication with a base station, in the example of FIG. 1, the base station 30 with which a direct session is established.

[0023] The V2N communication control unit 44 is a base station communication control unit that controls wireless communication with a base station, in the example of FIG. 1, the base station 30 with which a direct session is established. In addition, under the control of the redundant system management unit 45, the V2N communication control unit 44 performs control to provide information on the base station 31 that could not be connected via the direct session to the base station 30 to be connected via the direct session, and to request the base station 31 to provide connected terminal information, which is information on surrounding vehicles connected to the base station 31. In the following description, the base station 30 may be referred to as a first base station, and the base station 31 may be referred to as a second base station.

[0024] The redundant system management unit 45 manages multiple sessions with the base station. The redundant system management unit 45 manages that multiple sessions are always established, and performs control such as switching to an indirect session and attempting to establish a direct session again when a direct session cannot be established. For example, as shown in FIG. 1, when a direct session cannot be established with the base station 31, the redundant system management unit 45 instructs the relay management unit 46 to switch to an indirect session. At this time, the redundant system management unit 45 notifies the base station 30 via the V2N communication control unit 44 and the V2N communication unit 43 that a direct session cannot be established with the base station 31, that is, a connection failure with the base station 31, and requests connection terminal information, which is information on surrounding vehicles connected to the base station 31. Note that, in the case where the base station 30 is configured to request connection terminal information from the base station 31 when notified of a connection failure with the base station 31 by the vehicle 10, the redundant system management unit 45 only needs to notify the base station 30 of the connection failure with the base station 31. The connection terminal information, which is information on the surrounding vehicles connected to the base station 31, is identification information of the surrounding vehicles, roadside devices, etc. connected to the base station 31, and may include position information of the surrounding vehicles, roadside devices, etc. connected to the base station 31. The identification information is, for example, a vehicle ID, but other information may be used as long as it is information that can identify the surrounding vehicles, roadside devices, etc. In this way, the redundant system management unit 45 manages the connection with the base station 30 and the base station 31, and instructs the relay management unit 46 to establish an indirect session with the base station 31 when a connection with the base station 31 cannot be established through a direct session.

[0025] When the redundant system management unit 45 instructs the relay management unit 46 to switch to an indirect session, the connected terminal information holding unit 49 acquires and holds connected terminal information, which is information about surrounding vehicles connected to the base station 31, from the base station 30 via the V2N communication unit 43 and the V2N communication control unit 44.

[0026] The relay station candidate selection unit 47 acquires surrounding vehicle information from the surrounding vehicle information management unit 42, acquires connection terminal information from the connection terminal information storage unit 49, and selects a relay station candidate to be used for an indirect session with the base station 31 based on the surrounding vehicle information and the connection terminal information. When selecting a relay station candidate, the relay station candidate selection unit 47 selects a higher-ranking surrounding vehicle from the surrounding vehicle information shown in FIG. 3, for example, and if the selected surrounding vehicle is also included in the connection terminal information acquired from the connection terminal information storage unit 49, the selected surrounding vehicle is set as a relay station candidate. The relay station candidate selection unit 47 instructs the relay control unit 48 of the selected relay station candidate.

[0027] The relay control unit 48 instructs the V2X communication control unit 41 to start communication of a relay request to the surrounding vehicles that are candidates for the relay station selected by the relay station candidate selection unit 47.

[0028] The V2X communication control unit 41 makes a relay request to a nearby vehicle of a relay station candidate instructed by the relay control unit 48 via the V2X communication unit 40, and if the relay request is established, an indirect session with the base station 31 is established with the nearby vehicle that made the relay request as a relay station, and wireless communication with the base station 31 is started. If the relay request is not established, the V2X communication control unit 41 notifies the relay control unit 48 that the relay request was not established. The relay control unit 48 notifies the relay station candidate selection unit 47 that the relay request was not established. The relay station candidate selection unit 47 selects a next relay station candidate to be used for the indirect session with the base station 31 based on the surrounding vehicle information and the connection terminal information. The in-vehicle terminal 11 repeats the above operation until an indirect session with the base station 31 is established. In this way, in the in-vehicle terminal 11, the relay management unit 46 holds the connection terminal information, which is information of the surrounding vehicles connected to the base station 31 acquired from the base station 30, and selects a relay station, which is a nearby vehicle that relays the indirect session with the base station 31, based on the surrounding vehicle information and the connection terminal information.

[0029] 4 is a sequence diagram showing an operation of the vehicle 10 equipped with the on-board terminal 11 according to the first embodiment acquiring the connection terminal information of the base station 31 via the base station 30. When the direct session with the base station 31 fails (step S100), the vehicle 10 notifies the base station 30 of the connection failure with the base station 31 (step S101). As described above, it is assumed that the base station 30 requests the connection terminal information from the base station 31 when the base station 30 is notified of the connection failure with the base station 31 from the vehicle 10, and the vehicle 10 notifies the base station 30 only of the connection failure with the base station 31. When the base station 30 is notified of the connection failure with the base station 31 from the vehicle 10, the base station 30 requests the connection terminal information, which is information of the surrounding vehicles connected to the base station 31, from the base station 31 (step S102). The base station 31 provides the connection terminal information, which is information of the surrounding vehicles connected to the base station 31, to the base station 30 (step S103). When the base station 30 is provided with the connection terminal information, which is information on the surrounding vehicles connected to the base station 31, from the base station 31, the base station 30 provides the connection terminal information, which is information on the surrounding vehicles connected to the base station 31, to the vehicle 10 (step S104). When the vehicle 10 acquires the connection terminal information, which is information on the surrounding vehicles connected to the base station 31, from the base station 30, the vehicle 10 selects a candidate relay station to be used for the indirect session with the base station 31 based on the surrounding vehicle information and the connection terminal information (step S105), and requests the selected relay station to relay in the indirect session to the base station 31 (step S106).

[0030] Next, the configuration and operation of the base stations 30, 31 will be described. The base stations 30, 31 are base stations in the wireless communication system 1 in which the vehicle 10 equipped with the on-board terminal 11 performs wireless communication with the multiple base stations 30, 31 via multiple paths. Assuming that the base stations 30, 31 have the same configuration, the base station 31 will be described here as an example. FIG. 5 is a block diagram showing an example of the configuration of the base station 31 according to the first embodiment. The base station 31 includes a communication unit 60, a communication control unit 61, and a connection terminal information acquisition unit 62.

[0031] The communication unit 60 performs wireless communication with the surrounding vehicles 20-22. The communication unit 60 also performs communication with another base station, that is, base station 30. The communication between the base station 31 and the base station 30 may be wired communication or wireless communication. Note that, here, the communication unit 60 performs wireless communication with the surrounding vehicles 20-22 and communication with the base station 30, but the base station 31 may have two communication units, one of which performs wireless communication with the surrounding vehicles 20-22 and the other communication unit which performs communication with the base station 30.

[0032] The communication control unit 61 controls wireless communication with surrounding vehicles 20-22 and communication with another base station, base station 30, and, upon request from the other base station, base station 30, controls the provision of connected terminal information to the other base station, base station 30.

[0033] The connection terminal information acquisition unit 62 acquires identification information of the surrounding vehicles 20 to 22 that are performing wireless communication, and holds the information as connection terminal information.

[0034] That is, in the case of the base station 31, the connection terminal information acquisition unit 62 holds connection terminal information which is information on the surrounding vehicles 20-22 connected to the base station 31, and the communication control unit 61 performs control to provide the connection terminal information to the base station 30 when requested by the base station 30. Also, in the case of the base station 30, the connection terminal information acquisition unit 62 holds connection terminal information which is information on the vehicles 10 connected to the base station 30, and the communication control unit 61 performs control to provide the connection terminal information to the base station 31 when requested by the base station 31.

[0035] For example, when the wireless communication system 1 is realized according to the 3GPP specifications, the surrounding vehicle information management unit 42 of the vehicle-mounted terminal 11 collects the parameters of the surrounding 3GPP-compliant vehicles, i.e., the vehicle-mounted terminal 11, as surrounding vehicle information by vehicle-to-vehicle communication, road-to-vehicle communication, etc. via the PC5. The connection terminal information acquisition unit 62 of the base station is installed in an external application server (AF: Application Function) and manages the connection terminal information. The base station can accept a request from the vehicle-mounted terminal 11 to establish an indirect session with another base station in a direct session, and can also start the indirect session process by using the request from the vehicle-mounted terminal 11 as a trigger. From this point, instead of monitoring, the vehicle-mounted terminal 11 uses the communication results in the PC5 interface so far to acquire connection terminal information, which is a list of the vehicle-mounted terminals 11 connected to the desired base station, from the connected base station. The connection terminal information represents each vehicle-mounted terminal 11 by, for example, a relay station number. The vehicle-mounted terminal 11 selects a relay station using the surrounding vehicle information managed by the surrounding vehicle information management unit 42 and the connection terminal information acquired from the connected base station.

[0036] Next, the hardware configuration of the in-vehicle terminal 11 will be described. In the in-vehicle terminal 11, the V2X communication unit 40 and the V2N communication unit 43 are communication devices. The V2X communication control unit 41, the surrounding vehicle information management unit 42, the V2N communication control unit 44, the redundant system management unit 45, and the relay management unit 46 are realized by processing circuits. The processing circuit may be a processor and memory that executes a program stored in a memory, or may be dedicated hardware. The processing circuit is also called a control circuit.

[0037] FIG. 6 is a diagram showing a configuration example of the processing circuit 90 in the case where the processing circuit for realizing the in-vehicle terminal 11 according to the first embodiment is realized by a processor 91 and a memory 92. The processing circuit 90 shown in FIG. 6 is a control circuit and includes a processor 91 and a memory 92. When the processing circuit 90 is configured with the processor 91 and the memory 92, each function of the processing circuit 90 is realized by software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the memory 92. In the processing circuit 90, each function is realized by the processor 91 reading and executing the program stored in the memory 92. That is, the processing circuit 90 includes a memory 92 for storing a program that results in the processing of the in-vehicle terminal 11 being executed. This program can also be said to be a program for causing the in-vehicle terminal 11 to execute each function realized by the processing circuit 90. This program may be provided by a storage medium in which the program is stored, or may be provided by other means such as a communication medium.

[0038] The above program includes a first step in which a V2X communication control unit 41 controls communication with surrounding vehicles 20 to 22 that are present around the vehicle 10 and are capable of vehicle-to-vehicle communication; a second step in which a surrounding vehicle information management unit 42 manages surrounding vehicle information including position information of the surrounding vehicles 20 to 22 and information on the communication state of the V2X communication acquired through the V2X communication; and a second step in which a V2N communication control unit 44 provides information on a second base station, which is a base station 31 that could not be connected through direct communication, to a first base station, which is a base station 30 that is connected through direct communication, and uses the information on the surrounding vehicles connected to the second base station. It can also be said that this is a program that causes the in-vehicle terminal 11 to execute the following steps: a third step of controlling to request the provision of certain connected terminal information; a fourth step of the relay management unit 46 retaining the connected terminal information obtained from the first base station and selecting a relay station which is a nearby vehicle that will relay indirect communication with the second base station based on the surrounding vehicle information and the connected terminal information; and a fifth step of the redundant system management unit 45 managing the connection with the first base station and the second base station and instructing the relay management unit 46 to communicate indirectly with the second base station when direct communication with the second base station cannot be established.

[0039] Here, the processor 91 is, for example, a CPU (Central Processing Unit), a processing device, an arithmetic device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor), etc. Also, the memory 92 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc), etc.

[0040] Fig. 7 is a diagram showing an example of a processing circuit 93 in the case where the processing circuit for implementing the in-vehicle terminal 11 according to the first embodiment is configured with dedicated hardware. The processing circuit 93 shown in Fig. 7 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination of these. The processing circuit may be partially implemented with dedicated hardware and partially implemented with software or firmware. In this way, the processing circuit can realize each of the above-mentioned functions by dedicated hardware, software, firmware, or a combination of these.

[0041] Although the hardware configuration of the in-vehicle terminal 11 has been described, the hardware configuration of the base station is similar. In the base station, the communication unit 60 is a communication device. The communication control unit 61 and the connection terminal information acquisition unit 62 are realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in a memory, or may be dedicated hardware.

[0042] As described above, according to the present embodiment, when the on-board terminal 11 mounted on the vehicle 10 selects a relay station to be used when establishing an indirect session, the on-board terminal 11 acquires connection terminal information, which is information on a surrounding vehicle connected to a base station to which the direct session is established, via the base station with which the direct session is established, and selects a relay station using the connection terminal information. This allows the on-board terminal 11 to improve the accuracy of selecting other on-board terminals capable of relaying communication with the base station, i.e., surrounding vehicles. Since the on-board terminal 11 does not need V2X communication to search for candidates for relay stations, it is possible to shorten the time required to establish an indirect session.

[0043] In the first embodiment, a case has been described in which vehicle 10 performing multi-path communication establishes an indirect session with base station 31, but surrounding vehicles 20 to 22 can also perform multi-path communication in a similar manner. For example, surrounding vehicle 21 shown in FIG. 1 has a direct session established with base station 31, and can perform multi-path communication by establishing an indirect session with base station 30 using vehicle 10 as a relay station. In this case, surrounding vehicle 21 performs an operation with base station 31 similar to the operation performed between vehicle 10 and base station 30 described above.

[0044] Embodiment 2 In the first embodiment, the in-vehicle terminal 11 selects a relay station by using the surrounding vehicle information that is the result of the V2X communication and the connected terminal information that is the information of the surrounding vehicles connected to the base station that is the target of the indirect session obtained via the base station that is connected via the direct session. In the second embodiment, a method will be described in which the in-vehicle terminal further selects a relay station to make the communication more stable by using the position information of the surrounding vehicles connected to the base station that is the target of the indirect session obtained via the base station that is connected via the direct session.

[0045] Fig. 8 is a block diagram showing a configuration example of the on-board terminal 11a according to the second embodiment. The on-board terminal 11a is obtained by replacing the relay management unit 46 with a relay management unit 46a in the on-board terminal 11 according to the first embodiment shown in Fig. 2. The relay management unit 46a is obtained by adding a communication area calculation unit 50 to the relay management unit 46 in the first embodiment shown in Fig. 2. In the second embodiment, the connection terminal information acquired by the on-board terminal 11a from the base station 30a described later includes, in addition to the information described in the first embodiment, position information of surrounding vehicles connected to the base station 31a described later.

[0046] The connection terminal information holding unit 49 acquires and holds connection terminal information, which is information about surrounding vehicles connected to the base station 31a and includes location information of the surrounding vehicles, from the base station 30a via the V2N communication unit 43 and the V2N communication control unit 44.

[0047] The communication area calculation unit 50 acquires the connected terminal information from the connected terminal information storage unit 49, and estimates the communication area of ​​the base station 31a from the position information of the surrounding vehicles connected to the base station 31a, which is included in the connected terminal information.

[0048] The relay station candidate selection unit 47 acquires surrounding vehicle information from the surrounding vehicle information management unit 42, acquires connected terminal information from the communication area calculation unit 50 and the communication area calculated by the communication area calculation unit 50, and selects relay station candidates to be used for an indirect session with the base station 31a based on the surrounding vehicle information, connected terminal information, and communication area.

[0049] The operation of the relay control unit 48 is the same as that in the embodiment 1. Thus, in the embodiment 2, the relay management unit 46a calculates the communication area of ​​the base station 31a based on the connected terminal information, and further selects a relay station using the communication area of ​​the base station 31a.

[0050] Next, the configuration and operation of the base stations 30a and 31a will be described. Assuming that the base stations 30a and 31a have the same configuration, the base station 31a will be described here as an example. Fig. 9 is a block diagram showing an example of the configuration of the base station 31a according to the second embodiment. The base station 31a is obtained by adding a terminal location information acquisition unit 63 to the base station 31 according to the first embodiment shown in Fig. 5.

[0051] The terminal position information acquisition unit 63 acquires and holds position information of surrounding vehicles with which the base station 31a is performing wireless communication.

[0052] When there is a request from the other base station, the base station 30a, the communication control unit 61 performs control to provide the other base station, the base station 30a, with the connected terminal information including the position information of the surrounding vehicles.

[0053] Fig. 10 is a diagram showing an example of an operation of the on-board terminal 11a mounted on the vehicle 10 in the wireless communication system 1a according to the second embodiment to select a relay station. In Fig. 10, it is assumed that the vehicle 10 can communicate with the surrounding vehicles 20-26 by V2X, and the surrounding vehicles 21-25 are connected to the base station 31a. The communication area calculation unit 50 of the on-board terminal 11a mounted on the vehicle 10 calculates an approximate communication area 80 of the base station 31a based on the position information of the surrounding vehicles 21-25 connected to the base station 31a acquired via the base station 30a. The communication area 80 of the base station 31a calculated by the communication area calculation unit 50 is set to the range inside the dotted line shown in Fig. 10.

[0054] When the relay station candidate selection unit 47 of the in-vehicle terminal 11a mounted on the vehicle 10 selects, for example, the nearby vehicle 25 as a relay station, the nearby vehicle 25 may immediately leave the communication area 80 and perform handover from the base station 31a to another base station (not shown). If the nearby vehicle 25 performs handover from the base station 31a to another base station, it will no longer be able to relay the indirect session between the vehicle 10 and the base station 31a. Therefore, the relay station candidate selection unit 47 selects, as a relay station, a nearby vehicle that is expected to be in the communication area 80 of the base station 31a until the vehicle 10 enters the communication area 80 and has a good V2X communication situation, for example, the nearby vehicle 22.

[0055] By selecting a relay station in this manner, the relay station candidate selection unit 47 can avoid a situation in which a nearby vehicle that can become a relay station leaves the communication area 80 of the base station 31a in a short period of time, and it becomes necessary to search again for a nearby vehicle that can become a relay station.

[0056] In addition, since the relay station candidate selection unit 47 grasps the position information of the surrounding vehicles 21-25 connected to the base station 31a, it can estimate the traveling direction of the surrounding vehicles 21-25, the traveling speed of the surrounding vehicles 21-25, whether the surrounding vehicles 21-25 are traveling on the same road as the vehicle 10, and the like from the transition of the position information of the surrounding vehicles 21-25. Therefore, the relay station candidate selection unit 47 may select a relay station by taking into consideration the estimated traveling direction of the surrounding vehicles 21-25, the traveling speed of the surrounding vehicles 21-25, and information on whether the surrounding vehicles 21-25 are traveling on the same road as the vehicle 10. For example, the relay station candidate selection unit 47 can estimate a relaying available time, which is the time until the surrounding vehicles go outside the communication area 80 of the base station 31a, and further select a relay station using the relaying available time.

[0057] The communication area 80 of the base station 31a calculated by the communication area calculation unit 50 can be used not only by the relay station candidate selection unit 47 to select a relay station, but also to determine whether the vehicle 10 has entered the communication area 80 of the base station 31a. In general, the vehicle 10 measures its own position using a GPS (Global Positioning System) (not shown) or the like. Therefore, when the vehicle 10 reaches the communication area 80 of the base station 31a, the redundant system management unit 45 of the in-vehicle terminal 11a can control the V2N communication control unit 44 to attempt a direct session with the base station 31a.

[0058] Next, the hardware configuration of the in-vehicle terminal 11a will be described. In the in-vehicle terminal 11a, the relay management unit 46a is realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in the memory, or may be dedicated hardware. The hardware configuration of the base station is similar. In the base station, the terminal location information acquisition unit 63 is realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in the memory, or may be dedicated hardware.

[0059] As described above, according to this embodiment, when the on-board terminal 11a mounted on the vehicle 10 selects a relay station to be used when establishing an indirect session, the on-board terminal 11a acquires connection terminal information including location information of a surrounding vehicle connected to a base station to which the direct session is established, via the base station to which the direct session is established, and selects a relay station using the connection terminal information including location information. As a result, in addition to the effects described in the first embodiment, the on-board terminal 11a can select a more efficient and appropriate relay station, such as by avoiding a situation in which a surrounding vehicle that is a connected relay station immediately performs handover and enabling stable communication, and can establish a stable indirect session.

[0060] In the second embodiment, as an example, the case where the position information of the surrounding vehicles obtained by the terminal position information acquisition unit 63 is included in the connection terminal information obtained by the connection terminal information acquisition unit 62 has been described, but the present invention is not limited to this. The base station may handle the position information of the surrounding vehicles obtained by the terminal position information acquisition unit 63 and the connection terminal information obtained by the connection terminal information acquisition unit 62 separately and provide them to other base stations as separate information.

[0061] Embodiment 3 In the first and second embodiments, the relay station is selected by the vehicle-mounted terminal. In the third embodiment, a case where a part of the relay station selection function is performed by the base station will be described. Although the third embodiment can be applied to the first and second embodiments, the following description will be given taking the case where the third embodiment is applied to the second embodiment as an example.

[0062] In the third embodiment, the configuration of the on-board terminal 11a is the same as the configuration of the on-board terminal 11a in the second embodiment shown in Fig. 8. Although not shown in the figure, in the third embodiment, the base station with which a direct session has been established with the vehicle 10 is the base station 30b, and the base station with which the vehicle 10 attempts to establish an indirect session with the vehicle 10 without establishing a direct session with the vehicle 10 is the base station 31b.

[0063] The configuration and operation of the base stations 30b and 31b will be described. Assuming that the base stations 30b and 31b have the same configuration, the description will be given here by taking the base station 31b as an example. Fig. 11 is a block diagram showing an example of the configuration of the base station 31b according to the third embodiment. The base station 31b is obtained by adding a relay station candidate selection unit 64 to the base station 31a according to the second embodiment shown in Fig. 9.

[0064] The relay station candidate selection unit 64 selects a vehicle that is a candidate for a relay station to be used by the vehicle 10 that is directly connected to the base station 30b, which is another base station, by wireless communication when indirectly communicating with the base station 31b, based on the connection terminal information including the position information of the surrounding vehicles 21 to 25. The relay station candidate selection unit 64 can obtain the connection terminal information including the position information by combining the information obtained from the connection terminal information acquisition unit 62 and the terminal position information acquisition unit 63. The relay station candidate selection unit 64 can grasp where the surrounding vehicles 21 to 25 are located in the communication area 80 from the connection terminal information including the position information. Since surrounding vehicles located near the edge of the communication area 80 may be handed over immediately and the communication distance from the base station 31b is long and good communication quality cannot be expected, the relay station candidate selection unit 64 selects surrounding vehicles that are close to the center position of the communication area 80 as candidates for a relay station, for example.

[0065] The relay station candidate selection unit 64 may select multiple relay station candidates instead of one relay station candidate. In this case, the relay station candidate selection unit 64 prioritizes the relay stations based on the positions of the multiple relay stations and holds the information of the relay station candidates in a list format in which the relay station candidates with higher priority are ranked higher. Since the relay station candidate selection unit 64 grasps the position information of the surrounding vehicles 21-25 connected to the base station 31b, the relay station candidate selection unit 64 may estimate the traveling direction, traveling route, traveling speed, etc. of the surrounding vehicles 21-25 from the transition of the position information of the surrounding vehicles 21-25, and may select the relay station candidates by taking into account the estimated information. In addition, the relay station candidate selection unit 64 may select the relay station candidates by using road information such as accidents, congestion, and road closures on the roads on which the surrounding vehicles 21-25 are traveling.

[0066] When a request is received from another base station, base station 30b, the communication control unit 61 performs control to provide relay station candidate information, which is information on the relay station candidates selected by the relay station candidate selection unit 64, to the other base station, base station 30b.

[0067] The base station 30b requests relay station candidate information from the base station 31b, and provides the relay station candidate information obtained from the base station 31b to the vehicle 10.

[0068] In the in-vehicle terminal 11a of the vehicle 10, the V2N communication unit 43 receives the relay station candidate information provided from the base station 30b, and the connection terminal information holding unit 49 holds the relay station candidate information as well as the connection terminal information including the position information via the V2N communication control unit 44. The communication area calculation unit 50 acquires the relay station candidate information from the connection terminal information holding unit 49 and outputs it to the relay station candidate selection unit 47. The relay station candidate selection unit 47 selects a relay station from the relay station candidates indicated in the relay station candidate information using the surrounding vehicle information, the connection terminal information including the position information, the communication area 80, and the relay station candidate information. Thus, in the third embodiment, the relay management unit 46a holds the relay station candidate information, which is information on the surrounding vehicles that are candidates for relay stations acquired from the base station 30b, and further selects a relay station using the relay station candidate information. Regarding the method of acquiring the relay station candidate information, the redundant system management unit 45 of the vehicle-mounted terminal 11a of the vehicle 10 may request the relay station candidate information from the base station 30b, or, as in the case of the connection terminal information, if the base station 30b is configured to request the relay station candidate information from the base station 31b when notified by the vehicle 10 of a failure to connect to the base station 31b, the redundant system management unit 45 of the vehicle-mounted terminal 11a of the vehicle 10 need only notify the base station 30b of the failure to connect to the base station 31b.

[0069] 12 is a sequence diagram showing an operation of the vehicle 10 equipped with the on-board terminal 11a according to the third embodiment to acquire the connection terminal information and relay station candidate information of the base station 31b via the base station 30b. When the direct session with the base station 31b fails (step S200), the vehicle 10 notifies the base station 30b of the connection failure with the base station 31b (step S201). Here, as described above, it is assumed that the base station 30b requests the connection terminal information and relay station candidate information from the base station 31b when the base station 30b is notified of the connection failure with the base station 31b from the vehicle 10, and the vehicle 10 notifies the base station 30b only of the connection failure with the base station 31b. When the base station 30b is notified of the connection failure with the base station 31b from the vehicle 10, the base station 30b requests the connection terminal information, which is information of the surrounding vehicles connected to the base station 31b, from the base station 31b (step S202a), and requests the relay station candidate information, which is information of the relay station candidates selected by the base station 31b (step S202b). The base station 31b provides the base station 30b with connection terminal information, which is information on the surrounding vehicles connected to the base station 31b (step S203a), and relay station candidate information, which is information on the relay station candidates (step S203b). When the base station 30b receives the connection terminal information, which is information on the surrounding vehicles connected to the base station 31b, and the relay station candidate information, which is information on the relay station candidates, from the base station 31b, the base station 30b provides the connection terminal information, which is information on the surrounding vehicles connected to the base station 31b, to the vehicle 10 (step S204a) and provides the relay station candidate information, which is information on the relay station candidates (step S204b). When the vehicle 10 acquires the connection terminal information, which is information on the surrounding vehicles connected to the base station 31b, and the relay station candidate information, which is information on the relay station candidates, from the base station 30b, the vehicle 10 selects a relay station candidate to be used for the indirect session with the base station 31b based on the surrounding vehicle information, the connection terminal information, and the relay station candidate information (step S205), and requests the selected relay station to relay in the indirect session to the base station 31b (step S206).

[0070] When the in-vehicle terminal 11a of the vehicle 10 notifies the base station 30b of the failure of connection with the base station 31b in step S201, the in-vehicle terminal 11a may notify the base station 30b of information such as the position information, traveling direction, traveling speed, route information, and road information of the vehicle 10. In this case, the base station 30b also notifies the base station 31b of information such as the position information, traveling direction, traveling speed, route information, and road information of the vehicle 10 in step S202a or step S202b. This allows the base station 31b to select a candidate relay station by taking into account the position information, traveling direction, traveling speed, route information, and road information of the vehicle 10. For example, the relay station candidate selection unit 64 of the base station 31b limits the number of vehicles to those within a distance range where V2X communication with the vehicle 10 is likely to be possible, and from among them, lists in high priority order the candidates for the relay station the vehicles that are unlikely to immediately hand over, the vehicles that have a relative speed close to that of the vehicle 10, and the vehicles that are expected to travel on the same road for a while.

[0071] Next, the hardware configuration of the base station will be described. In the base station, the relay station candidate selection unit 64 is realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in a memory, or may be dedicated hardware.

[0072] As described above, according to this embodiment, when the on-board terminal 11a mounted on the vehicle 10 selects a relay station to be used when establishing an indirect session, the on-board terminal 11a acquires, via the base station with which the direct session is established, connection terminal information including position information of a surrounding vehicle connected to a base station to which the vehicle wants to connect, and relay station candidate information, and selects a relay station using the connection terminal information including position information and the relay station candidate information. This allows the on-board terminal 11a to reduce the processing load when selecting a relay station, in addition to the effects described in the first or second embodiment.

[0073] Embodiment 4 In the first to third embodiments, the on-board terminal 11 or the on-board terminal 11a of the vehicle 10 acquires information on surrounding vehicles connected to the base station that is the target of the indirect session via the base station connected by the direct session. In the fourth embodiment, a case will be described in which the on-board terminal 11 or the on-board terminal 11a of the vehicle 10 selects a relay station without receiving information from a base station. Although the fourth embodiment is applicable to the on-board terminal 11 and the on-board terminal 11a, the following description will be given taking the on-board terminal 11 of the first embodiment as an example.

[0074] In the vehicle 10, when the direct session to the base station 31 fails, the redundancy system management unit 45 of the in-vehicle terminal 11 notifies the relay station candidate selection unit 47 of that fact. The relay station candidate selection unit 47 grasps the surrounding vehicles 20-22 that are communicating with the vehicle 10 in V2X communication, based on the surrounding vehicle information managed by the surrounding vehicle information management unit 42. The relay station candidate selection unit 47 requests information about the connected base station from the surrounding vehicles 20-22 that are connected by V2X communication, via the relay control unit 48, the V2X communication control unit 41, and the V2X communication unit 40.

[0075] The surrounding vehicles 20-22 transmit information on the base stations to which their own vehicles are connected by V2X communication. The surrounding vehicles 20-22 may transmit the information on the base stations to which their own vehicles are connected as standalone information such as a base station list, or may transmit the information together with the position information of their own vehicles during V2X communication when the surrounding vehicle information management unit 42 of the vehicle 10 manages the information on the surrounding vehicles 20-22 as surrounding vehicle information.

[0076] FIG. 13 is a diagram showing an example of surrounding vehicle information managed by the surrounding vehicle information management unit 42 of the vehicle-mounted terminal 11 according to the fourth embodiment. The surrounding vehicle information shown in FIG. 13 shows an example in which the surrounding vehicle information management unit 42 of the vehicle-mounted terminal 11 of the vehicle 10 manages information of base stations connected to the surrounding vehicles 20-22 as surrounding vehicle information. The surrounding vehicle information shown in FIG. 13 is obtained by adding information of connected base stations to the surrounding vehicle information of the first embodiment shown in FIG. 3. The number of connected base stations, which are base stations connected to each surrounding vehicle, is not limited to one, and may be two or more. The surrounding vehicle information management unit 42 may manage information of base stations connected to the surrounding vehicles 20-22 in the form of a base station list transmitted from the surrounding vehicles 20-22.

[0077] The relay station candidate selection unit 47 selects a base station other than the base station 30 to which the vehicle 10 is connected, for example, a surrounding vehicle connected to base station 31, as a relay station based on the surrounding vehicle information or base station list shown in Figure 13 managed by the surrounding vehicle information management unit 42.

[0078] In addition, when the fourth embodiment is applied to the second or third embodiment, the communication area calculation unit 50 in the vehicle-mounted terminal 11a mounted on the vehicle 10 can calculate the approximate communication area of ​​the base station listed in the surrounding vehicle information or base station list shown in Fig. 13 from the position information of each surrounding vehicle based on the surrounding vehicle information or base station list shown in Fig. 13 managed by the surrounding vehicle information management unit 42. In this case, the relay station candidate selection unit 47 can further use the communication area calculated by the communication area calculation unit 50 to select a base station that is considered to be optimal as a relay station based on the position information of the vehicle 10 and the like, and select a relay station.

[0079] As described above, in this embodiment, the surrounding vehicle information management unit 42 of the on-board terminal 11 or the on-board terminal 11a manages the surrounding vehicle information including the position information of the surrounding vehicles 20-22, the communication state information of the V2X communication, and the information of the base station to which the surrounding vehicles 20-22 are connected, which are acquired by the V2X communication, and the relay management unit 46 or the relay management unit 46a selects a relay station that is a surrounding vehicle that relays an indirect session with a base station that could not be connected by a direct session, based on the surrounding vehicle information. This makes it unnecessary for the on-board terminal 11 or the on-board terminal 11a to collect information via the base station, so that even if a direct session with the base station cannot be established, the on-board terminal 11 or the on-board terminal 11a can obtain information on the relay station that is a candidate when selecting a relay station.

[0080] For example, the in-vehicle terminal 11 may perform the operation of embodiment 1 when at least one direct session has been established, and may perform the operation of embodiment 4 when not even one direct session has been established. Similarly, the in-vehicle terminal 11a may perform the operation of embodiment 2 or 3 when at least one direct session has been established, and may perform the operation of embodiment 4 when not even one direct session has been established.

[0081] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0082] 1, 1a wireless communication system, 10 vehicle, 11, 11a in-vehicle terminal, 20 to 26 surrounding vehicles, 30, 31, 30a, 31a, 30b, 31b base station, 40 V2X communication unit, 41 V2X communication control unit, 42 surrounding vehicle information management unit, 43 V2N communication unit, 44 V2N communication control unit, 45 redundant system management unit, 46, 46a relay management unit, 47, 64 relay station candidate selection unit, 48 relay control unit, 49 connected terminal information storage unit, 50 communication area calculation unit, 60 communication unit, 61 communication control unit, 62 connected terminal information acquisition unit, 63 terminal position information acquisition unit, 70 to 72 roadside device, 80 communication area, 90, 93 processing circuit, 91 processor, 92 memory.

Claims

1. An in-vehicle terminal that is mounted on a vehicle and performs wireless communication with a plurality of base stations via a plurality of paths, a vehicle-to-vehicle communication control unit that controls communication with surrounding vehicles that are present around the vehicle and are capable of vehicle-to-vehicle communication; a surrounding vehicle information management unit that manages surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the vehicle-to-vehicle communication acquired through the vehicle-to-vehicle communication; a base station communication control unit that performs control to provide information on a second base station that is a base station that could not be connected via direct communication to a first base station that is a base station connected via direct communication, and to request the first base station to provide connection terminal information that is information on the surrounding vehicles connected to the second base station; a relay management unit that holds the connection terminal information acquired from the first base station and selects a relay station that is the surrounding vehicle that relays the indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; a redundancy management unit that manages a connection between the first base station and the second base station, and instructs the relay management unit to perform indirect communication with the second base station when a direct communication connection with the second base station cannot be established; An in-vehicle terminal comprising:

2. The surrounding vehicles include roadside devices installed on the roadside of the road on which the vehicle is traveling.

2. The vehicle-mounted terminal according to claim 1.

3. the connection terminal information includes position information of the surrounding vehicle connected to the second base station, the relay management unit calculates a communication area of ​​the second base station based on the connected terminal information, and further selects the relay station using the communication area of ​​the second base station.

2. The vehicle-mounted terminal according to claim 1.

4. The relay management unit estimates a relay available time, which is a time until the surrounding vehicle exits a communication area of ​​the second base station, and further selects the relay station using the relay available time.

4. The vehicle-mounted terminal according to claim 3.

5. when the vehicle reaches a communication area of ​​the second base station, the redundancy system management unit controls the base station communication control unit to attempt direct communication with the second base station.

4. The vehicle-mounted terminal according to claim 3.

6. The relay management unit holds relay station candidate information, which is information on the surrounding vehicles that are candidates for the relay station acquired from the first base station, and further selects the relay station using the relay station candidate information.

2. The vehicle-mounted terminal according to claim 1.

7. the surrounding vehicle information management unit manages the surrounding vehicle information including position information of the surrounding vehicle, information on a communication state of the vehicle-to-vehicle communication, and information on the second base station to which the surrounding vehicle is connected, the position information being acquired through the vehicle-to-vehicle communication; The relay management unit selects the relay station that relays an indirect connection with the second base station that could not be connected by a direct connection, based on the surrounding vehicle information.

7. The vehicle-mounted terminal according to claim 1, wherein the vehicle-mounted terminal is a vehicle-mounted terminal.

8. A base station in a wireless communication system in which a vehicle equipped with an on-board terminal performs wireless communication with a plurality of base stations by a plurality of paths, a connection terminal information acquisition unit that acquires identification information of the vehicle that is performing the wireless communication and stores the information as connection terminal information; a communication control unit that controls wireless communication with the vehicle and communication with other base stations, and controls to provide the connected terminal information to the other base stations when requested by the other base stations; a terminal location information acquisition unit that acquires and stores location information of the vehicle that is performing the wireless communication; a relay station candidate selection unit that selects the first vehicle, which is the vehicle, as a candidate for a relay station to be used by a second vehicle that is directly connected to the other base station through wireless communication when indirectly communicating with the base station, based on the connection terminal information including position information of the first vehicle, which is the vehicle; Equipped with The communication control unit, when requested by the other base station, performs control to include location information of the vehicle in the connection terminal information and provide the connection terminal information to the other base station, and performs control to provide information of the relay station candidates to the other base station. A base station comprising:

9. An in-vehicle terminal according to claim 1 or 2; a base station in a wireless communication system in which a vehicle equipped with the on-board terminal performs wireless communication with a plurality of base stations via a plurality of paths, the base station including: a connection terminal information acquisition unit that acquires identification information of the vehicle performing the wireless communication and stores it as connection terminal information; and a communication control unit that controls wireless communication with the vehicle and communication with other base stations and, when requested by the other base stations, controls the provision of the connection terminal information to the other base stations; A wireless communication system comprising:

10. A control circuit for controlling an in-vehicle terminal that is mounted on a vehicle and that performs wireless communication with a plurality of base stations via a plurality of paths, comprising: Controlling communication with surrounding vehicles that are present around the vehicle and capable of vehicle-to-vehicle communication; Managing surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the vehicle-to-vehicle communication acquired through the vehicle-to-vehicle communication; A control for providing information of a second base station which is the base station that could not be connected via direct communication to a first base station which is the base station connected via direct communication, and requesting the first base station to provide connection terminal information which is information of the surrounding vehicles connected to the second base station; retaining the connection terminal information acquired from the first base station, and selecting a relay station which is the surrounding vehicle and which relays the indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; managing a connection between the first base station and the second base station, and instructing indirect communication with the second base station when a connection with the second base station cannot be established through direct communication; The control circuit causes the in-vehicle terminal to execute the above.

11. A storage medium storing a program for controlling an in-vehicle terminal that is mounted on a vehicle and that performs wireless communication with a plurality of base stations via a plurality of paths, The program is Controlling communication with surrounding vehicles that are present around the vehicle and capable of vehicle-to-vehicle communication; Managing surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the vehicle-to-vehicle communication acquired through the vehicle-to-vehicle communication; A control for providing information of a second base station which is the base station that could not be connected via direct communication to a first base station which is the base station connected via direct communication, and requesting the first base station to provide connection terminal information which is information of the surrounding vehicles connected to the second base station; retaining the connection terminal information acquired from the first base station, and selecting a relay station which is the surrounding vehicle and which relays the indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; managing a connection between the first base station and the second base station, and instructing indirect communication with the second base station when a connection with the second base station cannot be established through direct communication; A storage medium for causing the vehicle-mounted terminal to execute the above.

12. A relay station selection method for an in-vehicle terminal that is mounted on a vehicle and that performs wireless communication with a plurality of base stations via a plurality of paths, comprising the steps of: A first step in which an inter-vehicle communication control unit controls communication with surrounding vehicles that are present around the vehicle and are capable of inter-vehicle communication; a second step of managing surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the vehicle-to-vehicle communication acquired by the vehicle-to-vehicle communication, by a surrounding vehicle information management unit; a third step in which the base station communication control unit performs control to provide information on the second base station, which is the base station that cannot be connected via direct communication, to the first base station, which is the base station that is connected via direct communication, and to request the first base station to provide connection terminal information, which is information on the surrounding vehicles connected to the second base station; A fourth step in which a relay management unit holds the connection terminal information acquired from the first base station, and selects a relay station that is the surrounding vehicle that relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; a fifth step in which a redundancy management unit manages a connection between the first base station and the second base station, and instructs the relay management unit to establish indirect communication with the second base station when a direct communication connection with the second base station cannot be established; A relay station selection method comprising:

Images