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

Abstract

An in-vehicle terminal (11) is provided with: a V2X communication control unit (41) that controls communication with peripheral vehicles capable of vehicle-to-vehicle communication; a peripheral vehicle information management unit (42) that manages peripheral vehicle information including location information of peripheral vehicles and information of a communication state of the vehicle-to-vehicle communication acquired in the vehicle-to-vehicle communication; a V2N communication control unit (44) that provides information of a second base station that cannot be connected by direct communication to a first base station that is connected by direct communication, and performs control that delegates the provision of connection terminal information, which is information of a peripheral vehicle that is connected to the second base station; a relay management unit (46) that selects, on the basis of the peripheral vehicle information and the connection terminal information, a relay station that is a peripheral vehicle that relays indirect communication with the second base station; and a redundancy management unit (45) that manages connection to the first base station and the second base station, and instructs the relay management unit to indirectly communicate with the second base station when connection to the second base station by direct communication is not possible.

Description

Technical Field

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

[0002] In recent years, communications using cellular networks have been used for a variety of purposes. For example, 3GPP (registered trademark) (3rd Generation Partnership Project), an international standardization organization, is researching multipath transmission to improve the reliability of communications in cellular networks. The purpose of multipath transmission is to improve communication reliability by transmitting the same information over multiple paths. Multiple paths are essentially direct conversations between a base station and a terminal, but research is underway to ensure multiple conversations by combining one direct conversation with one indirect conversation using sidelink communication when direct conversations cannot be simultaneously ensured.

[0003] To improve communication reliability through multipath in vehicles subject to remote operation, remote monitoring, and other procedures, the selection of relay stations for indirect conversations is crucial. Numerous studies have been conducted on relaying communications from mobile terminals in inter-vehicle communication and other applications, and on methods for selecting relay stations. For example, Patent Document 1 discloses a method for selecting relays in inter-vehicle communication. The method uses the position information of surrounding vehicles obtained through inter-vehicle communication and the time at which the position information was acquired to determine the vehicle's direction of travel, speed, and other information, and then uses this information to select a relay.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-212753 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, according to the above-mentioned conventional technology, a vehicle-mounted communication device mounted as a communication source selects as a repeater a vehicle-mounted communication device that is highly likely to be able to relay communications to a vehicle-mounted communication device at a communication destination, based on information such as the location of surrounding vehicles. Consequently, there is a problem in that the vehicle-mounted communication device selected by the vehicle-mounted communication device at the communication source may not actually be able to communicate with the vehicle-mounted communication device at the communication destination, and thus communication between the vehicle-mounted communication device at the communication source and the vehicle-mounted communication device at the communication destination may not be relayed.

[0009] The present disclosure has been made in view of the above-mentioned circumstances, and an object thereof is to provide an in-vehicle terminal capable of improving the accuracy of selecting another in-vehicle terminal that can relay communications with a base station.

[0010] Means used to solve problems

[0011] To solve the aforementioned problems and achieve the objectives, the present invention provides an on-vehicle terminal mounted on a vehicle and capable of wireless communication with multiple base stations via multipath. The on-vehicle terminal is characterized by comprising: an inter-vehicle communication control unit for controlling communication with surrounding vehicles located around the vehicle and capable of inter-vehicle communication; a surrounding vehicle information management unit for managing surrounding vehicle information acquired during inter-vehicle communication, including positional information of surrounding vehicles and information on the communication status of the inter-vehicle communication; a base station communication control unit for providing information about a second base station, which is a base station connected via direct communication, with information about a base station that cannot be connected via direct communication, and requesting the provision of connection terminal information about surrounding vehicles connected to the second base station; a relay management unit for storing the connection terminal information acquired from the first base station and selecting a relay station, which is a surrounding vehicle, to relay indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; and a redundant system management unit for managing connections with the first and second base stations and, if direct communication with the second base station is unavailable, instructing the relay management unit to initiate indirect communication with the second base station.

[0012] Effects of the Invention

[0013] The vehicle-mounted terminal of the present disclosure has the effect of improving the accuracy of selecting other vehicle-mounted terminals that can relay communications with a base station. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram showing a configuration example of a wireless communication system according to Embodiment 1.

[0015] Figure 2 This is a block diagram showing a configuration example of the vehicle-mounted terminal according to the first embodiment.

[0016] Figure 3 This is a diagram showing an example of surrounding vehicle information managed by the surrounding vehicle information management unit of the in-vehicle terminal according to the first embodiment.

[0017] Figure 4 This is a sequence diagram showing an operation in which a vehicle equipped with the in-vehicle terminal according to the first embodiment acquires the connection terminal information of the base station 31 via the base station 30 .

[0018] Figure 5 This is a block diagram showing a configuration example of a base station according to Embodiment 1.

[0019] Figure 6This is a diagram showing a configuration example of a processing circuit in a case where the processing circuit of the in-vehicle terminal according to the first embodiment is realized by a processor and a memory.

[0020] Figure 7 This is a diagram showing an example of a processing circuit in the case where the processing circuit of the in-vehicle terminal according to the first embodiment is realized by a dedicated hardware configuration.

[0021] Figure 8 This is a block diagram showing a configuration example of an in-vehicle terminal according to the second embodiment.

[0022] Figure 9 This is a block diagram showing a configuration example of a base station according to the second embodiment.

[0023] Figure 10 This is a diagram showing an example of the operation of selecting a relay station by a vehicle-mounted terminal in the wireless communication system according to the second embodiment.

[0024] Figure 11 This is a block diagram showing a configuration example of a base station according to Embodiment 3.

[0025] Figure 12 This is a sequence diagram showing an operation in which a vehicle equipped with the in-vehicle terminal according to the third embodiment acquires the connected terminal information and relay station candidate information of the base station 31 b via the base station 30 b .

[0026] Figure 13 This is a diagram showing an example of surrounding vehicle information managed by a surrounding vehicle information management unit of the in-vehicle terminal according to the fourth embodiment. DETAILED DESCRIPTION

[0027] 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.

[0028] Implementation method 1.

[0029] Figure 1 1 is a diagram showing a configuration example of a wireless communication system 1 according to Embodiment 1. The wireless communication system 1 includes a vehicle 10 , surrounding vehicles 20 to 22 existing around the vehicle 10 , base stations 30 and 31 , and roadside devices 70 to 72 . Figure 1 The wireless communication system 1 shown assumes that the vehicle 10 performs wireless communication based on multipath between base stations 30 and 31. If the vehicle 10 can perform wireless communication with the base stations 30 and 31 and can secure multiple direct sessions, an indirect session is not required. However, if multiple direct sessions cannot be secured, an indirect session is used. Figure 1As shown, vehicle 10 is in a situation where it can establish a direct session with base station 30 but cannot establish a direct session with base station 31. Therefore, to establish an indirect session with base station 31, vehicle 10 selects a relay station from surrounding vehicles 20-22 to relay communications between vehicle 10 and base station 31. This allows vehicle 10 to secure redundant links for highly reliable communications using one direct session and one indirect session.

[0030] In the following description, when the surrounding vehicles 20 to 22 are not distinguished, they are sometimes referred to as simply surrounding vehicles; when the base stations 30 and 31 are not distinguished, they are sometimes referred to as simply base stations; and when the roadside devices 70 to 72 are not distinguished, they are sometimes referred to as simply roadside devices. In addition, in the following description, direct conversations are sometimes referred to as direct connections, and indirect conversations are sometimes referred to as indirect connections. The wireless communication system 1 is Figure 1 In the example of , there are 3 surrounding vehicles, 2 base stations, and 3 roadside devices, but there may be 4 or more surrounding vehicles, 3 or more base stations, and 4 or more roadside devices. Figure 1 In the example of wireless communication system 1, only the surrounding vehicles 20 to 22 located ahead of vehicle 10 in its travel direction are shown. However, vehicle 10 can also select surrounding vehicles (not shown) located behind vehicle 10 in its travel direction as relay stations for indirect communication with base station 31. Furthermore, vehicle 10 can also select roadside devices installed along the road on which vehicle 10 is traveling as relay stations for indirect communication with base station 31. This applies to the following embodiments.

[0031] In the first embodiment, the vehicle 10 and the surrounding vehicles 20 to 22 are equipped with the vehicle-mounted terminal 11. Figure 1 In the example, the vehicle 10 and the surrounding vehicles 20 to 22 are equipped with the same type of vehicle-mounted terminal 11. However, as long as the operations described below can be performed, the structures and functions of the vehicle-mounted terminals 11 installed in the vehicle 10 and the surrounding vehicles 20 to 22 may be partially different depending on the manufacturing company, model, etc. of the vehicle 10 and the surrounding vehicles 20 to 22. Figure 1 As shown, the description will be made of a case where the vehicle 10 and the surrounding vehicles 20 to 22 include the same type of in-vehicle terminal 11 .

[0032] The configuration and operation of the vehicle-mounted terminal 11 will be described. Figure 2This is a block diagram showing a configuration example of the vehicle-mounted terminal 11 of embodiment 1. The vehicle-mounted 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 storage unit 49. In addition, Figure 2 In this example, the following description omits the general V2X communication structures, such as Basic Safety Message (BSM) communications, and V2N communication structures not directly related to the process of establishing an indirect session. The following describes the operation of the vehicle-mounted terminal 11, which is mounted on the vehicle 10 and wirelessly communicates with multiple base stations via multipath.

[0033] The onboard terminal 11 mounted on vehicle 10 exchanges BSMs and other messages with the onboard terminals 11 mounted on surrounding vehicles 20-22 via a V2X communication unit 40 and a V2X communication control unit 41. In practice, V2X communication is performed between the onboard terminal 11 mounted on vehicle 10 and the onboard terminals 11 mounted on surrounding vehicles 20-22. However, for simplicity, this will sometimes be described as V2X communication between the vehicle 10 and surrounding vehicles 20-22, or V2X communication between the onboard terminal 11 and surrounding vehicles 20-22.

[0034] 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 capable of performing V2X communication.

[0035] 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 capable of V2X communication.

[0036] The surrounding vehicle information management unit 42 manages surrounding vehicle information, including positional information of surrounding vehicles and the like and information on the communication status of V2X communication, acquired by the V2X communication unit 40 and the V2X communication control unit 41 during V2X communication. Specifically, the surrounding vehicles managed as surrounding vehicle information by the surrounding vehicle information management unit 42 include, in addition to the surrounding vehicles 20-22, the roadside devices 70-72, etc., as described above.

[0037] Figure 31 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 first embodiment. Figure 3 The table shown below manages the surrounding vehicle information. Figure 3 In the data, the vehicle ID (Identifier) ​​is identification information for identifying surrounding vehicles. The position information is information indicating the current position of the surrounding vehicles. The time is information indicating the time when the surrounding vehicle information is obtained from the corresponding surrounding vehicles. The received RSSI (Received Signal Strength Indicator) is information indicating the communication quality of the communication status of the V2X communication between the surrounding vehicles with the corresponding vehicle ID. Here, the received signal strength is shown as an example. 1 cycle ago is information indicating the communication quality of the previous communication status in the V2X communication between the surrounding vehicles with the corresponding vehicle ID. 2 cycles ago is information indicating the communication quality of the previous communication status in the V2X communication between the surrounding vehicles with the corresponding vehicle ID. Information about the communication quality is not limited to the received RSSI. Error rate, SNR (Signal to Noise Ratio), etc. can also be used.

[0038] in addition, Figure 3 The surrounding vehicle information shown is an example. As long as the information is obtained through V2X communication, the surrounding vehicle information management unit 42 may also manage information such as the vehicle model and driving speed of the surrounding vehicles as surrounding vehicle information. Furthermore, the surrounding vehicle information management unit 42 may manage such that surrounding vehicles with better communication conditions and more stable V2X communication quality over a recent specified period are ranked higher in the table. For example, the surrounding vehicle information management unit 42 may manage such vehicles so that the surrounding vehicles with the highest and most stable reception RSSI over the past three times are ranked higher. Stable here means, for example, that the fluctuation in reception RSSI is minimal and exceeds a specified threshold. Furthermore, the surrounding vehicle information management unit 42 may determine, based on recent changes in positional information, surrounding vehicles predicted to be traveling on the same road as vehicle 10, surrounding vehicles with a similar relative speed to vehicle 10, and other factors, and manage surrounding vehicle information taking these factors into consideration.

[0039] The vehicle-mounted terminal 11 on the vehicle 10 conducts wireless communications with the base station via the V2N communication unit 43 and the V2N communication control unit 44, in parallel with V2X communications. Wireless communications between the vehicle-mounted terminal 11 on the vehicle 10 and the base station establish multiple sessions and are used for applications requiring highly reliable communication, such as remote control and remote monitoring. Furthermore, wireless communications between the vehicle-mounted terminal 11 on the vehicle 10 and the base station are used for services utilizing cellular networks, such as the collection of location information and route information from the base station by the vehicle 10, and the provision of congestion information and surrounding information. While the vehicle-mounted terminal 11 on the vehicle 10 actually conducts wireless communications with the base station, for simplicity, this will sometimes be referred to as the vehicle 10 conducting wireless communications with the base station.

[0040] The V2N communication unit 43 is a base station communication unit that performs wireless communication with a base station. Figure 1 In the example, it is the base station 30 that has established a direct session.

[0041] The V2N communication control unit 44 is a base station communication control unit that controls wireless communication with a base station. Figure 1 In the example, the base station 30 with which a direct session has been established is referenced. Furthermore, the V2N communication control unit 44, under the control of the redundant system management unit 45, controls the base station 30 connected via a direct session to provide information about the base station 31 that cannot be connected via the direct session, and requests the base station 30 to provide information about surrounding vehicles connected to the base station 31, i.e., connected terminal information. In the following description, the base station 30 may be referred to as the first base station, and the base station 31 may be referred to as the second base station.

[0042] The redundant system management unit 45 manages multiple sessions with the base station. The redundant system management unit 45 manages the situation where multiple sessions can always be established. If a direct session cannot be established, the redundant system management unit 45 controls the situation such as switching to an indirect session and retrying to establish a direct session. For example, Figure 1As shown, 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. In this case, 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, i.e., that the connection with the base station 31 has failed, and requests information about surrounding vehicles connected to the base station 31, i.e., connection terminal information. Furthermore, if the base station 30 requests connection terminal information from the vehicle 10 after receiving notification of the connection failure with the base station 31, the redundant system management unit 45 may simply notify the base station 30 of the connection failure. The connection terminal information, i.e., information about surrounding vehicles connected to the base station 31, is identification information of surrounding vehicles, roadside devices, etc. connected to the base station 31, and may also include location information of surrounding vehicles, roadside devices, etc. connected to the base station 31. While the identification information is, for example, a vehicle ID, other information may also be used as long as it can identify surrounding vehicles, roadside devices, etc. In this way, the redundant system management unit 45 manages the connections with the base station 30 and the base station 31 , and when it is impossible to connect to the base station 31 through a direct session, it instructs the relay management unit 46 to establish an indirect session with the base station 31 .

[0043] When the redundant system management unit 45 instructs the relay management unit 46 to switch to an indirect session, the connection terminal information storage unit 49 obtains and stores information on surrounding vehicles connected to the base station 31 , namely, connection terminal information, from the base station 30 via the V2N communication unit 43 and the V2N communication control unit 44 .

[0044] The relay station candidate selection unit 47 obtains the surrounding vehicle information from the surrounding vehicle information management unit 42 and the connection terminal information from the connection terminal information storage unit 49, and selects a candidate relay station to be used in the indirect session with the base station 31 based on the surrounding vehicle information and the connection terminal information. When selecting a candidate relay station, the relay station candidate selection unit 47 selects, for example, Figure 3 The relay station candidate selection unit 47 selects a higher-ranking surrounding vehicle from the surrounding vehicle information displayed. If the selected surrounding vehicle is also included in the connection terminal information obtained from the connection terminal information storage unit 49, the selected surrounding vehicle is set as a candidate for the relay station. The relay station candidate selection unit 47 indicates the selected candidate for the relay station to the relay control unit 48.

[0045] The relay control unit 48 instructs the V2X communication control unit 41 to start relay-requested communication with respect to the surrounding vehicles selected as candidates for the relay station by the relay station candidate selection unit 47 .

[0046] The V2X communication control unit 41, via the V2X communication unit 40, delegates relaying to a neighboring vehicle that is a candidate relay station, as instructed by the relay control unit 48. If the relay delegation is successful, the V2X communication control unit 41 establishes an indirect session with the base station 31, using the neighboring vehicle that delegated the relay as a relay station, and begins wireless communication with the base station 31. If the relay delegation is unsuccessful, the V2X communication control unit 41 notifies the relay control unit 48 of the failure. The relay control unit 48 notifies the candidate relay station selection unit 47 of the failure. The candidate relay station selection unit 47 selects the next candidate relay station to be used in the indirect session with the base station 31 based on the neighboring vehicle information and the connected terminal information. The vehicle-mounted terminal 11 repeats the above operations until the indirect session with the base station 31 is established. In this way, in the vehicle-mounted terminal 11, the relay management unit 46 maintains the information of the surrounding vehicles connected to the base station 31 obtained from the base station 30, that is, the connection terminal information, and selects the surrounding vehicles, that is, the relay station, that relay the indirect session with the base station 31 based on the surrounding vehicle information and the connection terminal information.

[0047] Figure 4 This is a sequence diagram illustrating the operation of a vehicle 10 equipped with the in-vehicle terminal 11 according to Embodiment 1, obtaining connection terminal information from 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 (step S101). As described above, it is assumed that upon receiving notification of the connection failure from the vehicle 10, the base station 30 requests connection terminal information from the base station 31, and the vehicle 10 only notifies the base station 30 of the connection failure. Upon receiving notification of the connection failure from the vehicle 10, the base station 30 requests connection terminal information from the base station 31, which is information about surrounding vehicles connected to the base station 31 (step S102). The base station 31 provides the base station 30 with connection terminal information about the surrounding vehicles connected to the base station 31 (step S103). Upon receiving the connection terminal information about the surrounding vehicles connected to the base station 31 from the base station 31, the base station 30 provides the vehicle 10 with connection terminal information about the surrounding vehicles connected to the base station 31 (step S104). When vehicle 10 obtains information about surrounding vehicles connected to base station 31, i.e., connection terminal information, from base station 30, it selects a candidate relay station to be used in an indirect session with base station 31 based on the surrounding vehicle information and the connection terminal information (step S105), and entrusts the selected relay station to relay the indirect session with base station 31 (step S106).

[0048] Next, the structure and operation of base stations 30 and 31 will be described. Base stations 30 and 31 are base stations in wireless communication system 1, where a vehicle 10 equipped with an onboard terminal 11 wirelessly communicates with multiple base stations 30 and 31 via multipath. Assuming that base stations 30 and 31 have the same structure, base station 31 will be used as an example for the following description. Figure 5 This is a block diagram showing a configuration example of the base station 31 according to Embodiment 1. The base station 31 includes a communication unit 60 , a communication control unit 61 , and a connected terminal information acquisition unit 62 .

[0049] The communication unit 60 performs wireless communications with the surrounding vehicles 20-22. Furthermore, the communication unit 60 performs communications with the base station 30, which is another base station. Communication between the base station 31 and the base station 30 can be either wired or wireless. While the communication unit 60 performs both wireless communications with the surrounding vehicles 20-22 and with the base station 30, the base station 31 may also include two communication units, one for wireless communications with the surrounding vehicles 20-22 and the other for communications with the base station 30.

[0050] The communication control unit 61 controls wireless communications with the surrounding vehicles 20 to 22 and with the base station 30 as another base station, and controls providing connection terminal information to the base station 30 as another base station when there is a request from the base station 30 as another base station.

[0051] The connection terminal information acquisition unit 62 acquires identification information of the surrounding vehicles 20 to 22 that are performing wireless communication and stores the information as connection terminal information.

[0052] Specifically, in the case of the base station 31, the connection terminal information acquisition unit 62 stores connection terminal information, which is information about the surrounding vehicles 20 to 22 connected to the base station 31, and the communication control unit 61 controls the provision of the connection terminal information to the base station 30 upon a request from the base station 30. Furthermore, in the case of the base station 30, the connection terminal information acquisition unit 62 stores connection terminal information, which is information about the vehicle 10 connected to the base station 30, and the communication control unit 61 controls the provision of the connection terminal information to the base station 31 upon a request from the base station 31.

[0053] For example, when the wireless communication system 1 is implemented according to the 3GPP standard, the surrounding vehicle information management unit 42 of the on-board terminal 11 collects parameters of surrounding 3GPP-compliant vehicles, i.e., the on-board terminals 11, as surrounding vehicle information, through inter-vehicle communication, road-to-vehicle communication, and other means via the PC 5. The connected terminal information acquisition unit 62 of the base station, located in an external application server (AF), manages the connected terminal information. The base station can also accept requests from the on-board terminal 11 to establish an indirect session with another base station via a direct session, triggering the indirect session process with the request from the on-board terminal 11. Thereafter, instead of monitoring the communication, the on-board terminal 11 uses the communication results obtained through the PC 5 interface to obtain, from the connected base station, the connected terminal information, a list of on-board terminals 11 connected to the desired base station. The connected terminal information represents each on-board terminal 11, for example, by a relay station number. The on-board terminal 11 selects a relay station using the surrounding vehicle information managed by the surrounding vehicle information management unit 42 and the connected terminal information acquired from the connected base station.

[0054] Next, the hardware structure of the vehicle-mounted terminal 11 will be described. In the vehicle-mounted terminal 11, the V2X communication unit 40 and the V2N communication unit 43 serve as 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 implemented by processing circuits. The processing circuits can be processors and memory that execute programs stored in memory, or they can be dedicated hardware. Processing circuits are also called control circuits.

[0055] Figure 6 This diagram shows a configuration example of a processing circuit 90 in which a processing circuit for realizing the in-vehicle terminal 11 according to the first embodiment is realized by a processor 91 and a memory 92 . Figure 6 The processing circuit 90 shown is a control circuit and includes a processor 91 and a memory 92. When the processing circuit 90 is composed of the processor 91 and the memory 92, the various functions of the processing circuit 90 are implemented by software, firmware, or a combination of software and firmware. The software or firmware is described in the form of a program and stored in the memory 92. In the processing circuit 90, the processor 91 reads and executes the program stored in the memory 92 to implement the various functions. In other words, the processing circuit 90 includes a memory 92 for storing a program for executing the processing of the vehicle-mounted terminal 11. This program can also be said to be a program for causing the vehicle-mounted terminal 11 to execute the various functions implemented by the processing circuit 90. This program can be provided by a storage medium storing the program, or by other means such as a communication medium.

[0056] The above program can also be said to be a program that causes the vehicle-mounted terminal 11 to execute the following steps: In the first step, the V2X communication control unit 41 controls the communication with the surrounding vehicles 20 to 22 that exist around the vehicle 10 and can communicate with each other; In the second step, the surrounding vehicle information management unit 42 manages the surrounding vehicle information obtained in the V2X communication, which includes the position information of the surrounding vehicles 20 to 22 and the communication status of the V2X communication; In the third step, the V2N communication control unit 44 controls the following: providing the base station 30 connected by direct communication, that is, the first base station, which cannot be connected by direct communication. The information of the base station 31 connected to the direct communication, i.e., the second base station, is entrusted to provide the information of the surrounding vehicles connected to the second base station, i.e., the connection terminal information; in the fourth step, the relay management unit 46 maintains the connection terminal information obtained from the first base station, and selects the surrounding vehicles, i.e., the relay station, that relays the indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; and in the fifth step, the redundant system management unit 45 manages the connection with the first base station and the second base station, and when it is impossible to connect to the second base station through direct communication, instructs the relay management unit 46 to perform indirect communication with the second base station.

[0057] 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). Furthermore, the memory 92 is, for example, a nonvolatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (registered trademark) (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a floppy disk, an optical disk, a high-density disk, a minidisc, or a DVD (Digital Versatile Disc).

[0058] Figure 7 This diagram shows an example of a processing circuit 93 in the case where the processing circuit of the in-vehicle terminal 11 according to the first embodiment is realized by a dedicated hardware configuration. Figure 7The processing circuit 93 shown may correspond to, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit may also be partially implemented by dedicated hardware and partially implemented by software or firmware. Thus, the processing circuit can implement the aforementioned functions using dedicated hardware, software, firmware, or a combination thereof.

[0059] While the hardware structure of the vehicle-mounted terminal 11 has been described, the hardware structure 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 connected terminal information acquisition unit 62 are implemented by processing circuitry. This processing circuitry can be a processor and memory that executes programs stored in memory, or it can be dedicated hardware.

[0060] As described above, according to this embodiment, when selecting a relay station for establishing an indirect session, the vehicle-mounted terminal 11 mounted on the vehicle 10 obtains information about surrounding vehicles connected to the desired base station, i.e., connected terminal information, via the base station with which the direct session has been established. This information is then used to select a relay station. This improves the accuracy of the vehicle-mounted terminal 11's selection of other vehicle-mounted terminals, i.e., surrounding vehicles, capable of relaying communications with the base station. Since the vehicle-mounted terminal 11 does not need to perform V2X communication to search for candidate relay stations, the time required to establish an indirect session can be shortened.

[0061] In the first embodiment, the vehicle 10 performing multipath communication establishes an indirect session with the base station 31, but the surrounding vehicles 20 to 22 can also perform multipath communication. Figure 1 While a direct session is established between the neighboring vehicle 21 and the base station 31, multipath communication can be achieved by establishing an indirect session between the vehicle 10 and the base station 30 as a relay station. In this case, the operations between the neighboring vehicle 21 and the base station 31 are similar to those between the vehicle 10 and the base station 30 described above.

[0062] Implementation method 2.

[0063] In the first embodiment, the vehicle-mounted terminal 11 selects a relay station using surrounding vehicle information obtained as a result of V2X communication and connected terminal information (i.e., information about surrounding vehicles connected to a base station serving as an indirect session partner, obtained via a base station connected via a direct session). In the second embodiment, a method is described in which the vehicle-mounted terminal further uses positional information about surrounding vehicles connected to a base station serving as an indirect session partner, obtained via a base station connected via a direct session, to select a relay station, thereby further stabilizing communication.

[0064] Figure 8 This is a block diagram showing a configuration example of the vehicle-mounted terminal 11a according to the second embodiment. Figure 2 In the vehicle-mounted terminal 11 of the embodiment 1 shown in FIG. 1 , the relay management unit 46 is replaced with a relay management unit 46a. Figure 2 The relay management unit 46 of the first embodiment shown is supplemented with a communication area calculation unit 50. In the second embodiment, the connected terminal information obtained by the vehicle-mounted 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.

[0065] 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 a and includes position information of the surrounding vehicles, from the base station 30 a via the V2N communication unit 43 and the V2N communication control unit 44 .

[0066] 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 31 a based on the position information of the surrounding vehicles connected to the base station 31 a included in the connected terminal information.

[0067] The relay station candidate selection unit 47 obtains the surrounding vehicle information from the surrounding vehicle information management unit 42, obtains the connection terminal information and the communication area calculated by the communication area calculation unit 50 from the communication area calculation unit 50, and selects a candidate relay station used in the indirect session with the base station 31a based on the surrounding vehicle information, the connection terminal information and the communication area.

[0068] The operation of the relay control unit 48 is the same as that in Embodiment 1. Thus, in Embodiment 2, the relay management unit 46a calculates the communication area of ​​the base station 31a based on the connected terminal information and selects a relay station using the communication area of ​​the base station 31a.

[0069] Next, the configuration and operation of the base stations 30a and 31a will be described. It is assumed that the base stations 30a and 31a have the same configuration, and the description will be made using the base station 31a as an example. Figure 9This is a block diagram showing a configuration example of a base station 31a according to Embodiment 2. The base station 31a is Figure 5 The base station 31 of the illustrated first embodiment has a terminal position information acquisition unit 63 added thereto.

[0070] The terminal position information acquisition unit 63 acquires and stores position information of surrounding vehicles with which the base station 31 a is performing wireless communication.

[0071] When there is a request from the base station 30 a as another base station, the communication control unit 61 performs control to include the position information of surrounding vehicles in the connection terminal information and provide the connection terminal information to the base station 30 a as another base station.

[0072] Figure 10 1 is a diagram showing an example of the operation of selecting a relay station by the vehicle-mounted terminal 11a mounted on the vehicle 10 in the wireless communication system 1a according to the second embodiment. Figure 10 In the example, it is assumed that the vehicle 10 can communicate with the surrounding vehicles 20 to 26 via V2X and the surrounding vehicles 21 to 25 are connected to the base station 31a. The communication area calculation unit 50 of the vehicle-mounted terminal 11a mounted on the vehicle 10 calculates the approximate communication area 80 of the base station 31a based on the position information of the surrounding vehicles 21 to 25 connected to the base station 31a obtained via the base station 30a. The communication area 80 of the base station 31a calculated by the communication area calculation unit 50 is Figure 10 The range is shown inside the dotted line.

[0073] For example, when the relay station candidate selection unit 47 of the onboard terminal 11a mounted on vehicle 10 selects neighboring vehicle 25 as a relay station, neighboring vehicle 25 may soon exit communication area 80 and switch from base station 31a to another base station (not shown). When neighboring vehicle 25 switches from base station 31a to another base station, it becomes impossible to relay the indirect session between vehicle 10 and base station 31a. Therefore, the relay station candidate selection unit 47 selects a neighboring vehicle, such as neighboring vehicle 22, as a relay station, which is expected to be within base station 31a's communication area 80 until vehicle 10 enters communication area 80 and maintain good V2X communication conditions.

[0074] By selecting relay stations in this manner, the relay station candidate selection unit 47 can avoid a situation where a surrounding vehicle serving as a relay station leaves the communication area 80 of the base station 31 a in a short period of time and needs to search for a surrounding vehicle serving as a relay station again.

[0075] Furthermore, because the relay station candidate selection unit 47 has the position information of the surrounding vehicles 21-25 connected to the base station 31a, it can estimate the travel directions and speeds 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 based on the changes in the position information of the surrounding vehicles 21-25. Therefore, the relay station candidate selection unit 47 can also select a relay station based on the estimated travel directions, speeds, and 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 the relayable time, which is the time until the surrounding vehicles exit the communication area 80 of the base station 31a, and use this time to select a relay station.

[0076] Furthermore, the relay station candidate selection unit 47 is used not only to select a relay station within the communication area 80 of the base station 31a calculated by the communication area calculation unit 50, but also to determine whether the vehicle 10 has entered the communication area 80 of the base station 31a. Typically, the vehicle 10 measures its position using a GPS (Global Positioning System) or other device (not shown). Therefore, when the vehicle 10 enters the communication area 80 of the base station 31a, the redundant system management unit 45 of the on-board terminal 11a can control the V2N communication control unit 44 to attempt a direct communication with the base station 31a.

[0077] Next, the hardware structure of the onboard terminal 11a will be described. In the onboard terminal 11a, the relay management unit 46a is implemented by a processing circuit. This processing circuit can be a processor and memory that executes programs stored in memory, or it can be dedicated hardware. The hardware structure of the base station is similar. In the base station, the terminal location information acquisition unit 63 is implemented by a processing circuit. This processing circuit can be a processor and memory that executes programs stored in memory, or it can be dedicated hardware.

[0078] As described above, according to this embodiment, when selecting a relay station to use when establishing an indirect session, the vehicle-mounted terminal 11a mounted on the vehicle 10 obtains connection terminal information including the location information of surrounding vehicles connected to the desired base station via the base station with which the direct session is established. The vehicle-mounted terminal 11a uses this location information to select a relay station. In addition to achieving the effects described in Embodiment 1, this prevents the connected vehicle from immediately switching to a relay station, allowing the selection of a more efficient and appropriate relay station that enables stable communication and establishes a stable indirect session.

[0079] In addition, while Embodiment 2 describes, as an example, a case where the position information of surrounding vehicles obtained by terminal position information obtaining unit 63 is included in the connected terminal information obtained by connected terminal information obtaining unit 62, the present invention is not limited thereto. A base station may separately process the position information of surrounding vehicles obtained by terminal position information obtaining unit 63 and the connected terminal information obtained by connected terminal information obtaining unit 62, and provide them as separate information to other base stations.

[0080] Implementation method 3.

[0081] In Embodiments 1 and 2, the vehicle-mounted terminal performs relay station selection. In Embodiment 3, a case where a base station performs a portion of the relay station selection function will be described. While Embodiment 3 is applicable to both Embodiments 1 and 2, the following description will use the case of Embodiment 2 as an example.

[0082] In the third embodiment, the structure of the vehicle-mounted terminal 11a is the same as that of the vehicle-mounted terminal 11a. Figure 8 The structure of the vehicle-mounted terminal 11a in the second embodiment shown is the same. In the third embodiment, the base station that has established a direct session with the vehicle 10 is referred to as the base station 30b, and the base station that has not established a direct session with the vehicle 10 and with which the vehicle 10 attempts an indirect session is referred to as the base station 31b, which is omitted from the illustration.

[0083] The configuration and operation of base stations 30b and 31b will be described. It is assumed that base stations 30b and 31b have the same configuration, and the description will be made using base station 31b as an example. Figure 11 This is a block diagram showing a configuration example of a base station 31b according to Embodiment 3. The base station 31b is Figure 9 The base station 31 a according to the second embodiment shown in the figure has a relay station candidate selection unit 64 added.

[0084] Based on the connection terminal information including the position information of the surrounding vehicles 21-25, the relay station candidate selection unit 64 selects a vehicle that is a candidate relay station for use by vehicle 10, which is directly connected to base station 30b (another base station) via wireless communication, during indirect communication with base station 31b. 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. Based on the connection terminal information including the position information, the relay station candidate selection unit 64 can determine where the surrounding vehicles 21-25 are located within the communication area 80. Because surrounding vehicles located near the edge of the communication area 80 are likely to be switched immediately and have a long communication distance from base station 31b, good communication quality cannot be expected, the relay station candidate selection unit 64 selects surrounding vehicles near the center of the communication area 80 as relay station candidates.

[0085] The relay station candidate selection unit 64 may select multiple relay station candidates instead of a single one. In this case, the relay station candidate selection unit 64 prioritizes the multiple relay station candidates based on their locations, with higher-priority relay station candidates being ranked higher. Furthermore, since the relay station candidate selection unit 64 has the location information of the surrounding vehicles 21-25 connected to the base station 31b, it may estimate the travel direction, route, and speed of the surrounding vehicles 21-25 based on changes in their location information and select relay station candidates based on this estimated information. Furthermore, the relay station candidate selection unit 64 may use road information, such as information about accidents, congestion, or traffic restrictions, on the roads traveled by the surrounding vehicles 21-25, to select relay station candidates.

[0086] When there is a request from the base station 30b as another base station, the communication control unit 61 controls to provide the relay station candidate information, which is information on relay station candidates selected by the relay station candidate selection unit 64, to the base station 30b as another base station.

[0087] The base station 30 b requests the base station 31 b for the relay station candidate information, and provides the vehicle 10 with the relay station candidate information obtained from the base station 31 b.

[0088] In the on-board terminal 11a of the vehicle 10, the V2N communication unit 43 receives the relay station candidate information provided by the base station 30b. The connected terminal information storage unit 49 stores the relay station candidate information, similarly to the connected terminal information including position information, via the V2N communication control unit 44. The communication area calculation unit 50 obtains the relay station candidate information from the connected terminal information storage unit 49 and outputs it to the relay station candidate selection unit 47. The relay station candidate selection unit 47 uses the surrounding vehicle information, the connected terminal information including position information, the communication area 80, and the relay station candidate information to select a relay station from the relay station candidates indicated by the relay station candidate information. Thus, in the third embodiment, the relay management unit 46a stores the relay station candidate information, which is information on surrounding vehicles that are candidates for relay stations, obtained from the base station 30b, and uses the relay station candidate information to select a relay station. In addition, regarding the method of obtaining relay station candidate information, the redundant system management unit 45 of the on-board terminal 11a of the vehicle 10 can also request the base station 30b. Similar to the case of connection terminal information, when the base station 30b requests the relay station candidate information from the base station 31b upon being notified by the vehicle 10 of the failure of connection with the base station 31b, the redundant system management unit 45 of the on-board terminal 11a of the vehicle 10 only needs to notify the base station 30b of the failure of connection with the base station 31b.

[0089] Figure 12 This is a sequence diagram showing the operation of a vehicle 10 equipped with an on-board terminal 11a according to Embodiment 3, obtaining connection terminal information and candidate relay station information from 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). As described above, it is assumed that the base station 30b requests the connection terminal information and candidate relay station information from the base station 31b upon notification of the connection failure from the vehicle 10, and the vehicle 10 only notifies the base station 30b of the connection failure with the base station 31b. When the base station 30b receives notification of the connection failure from the vehicle 10, it requests the base station 31b for information on surrounding vehicles connected to the base station 31b, i.e., connection terminal information (step S202a), and also requests information on candidate relay stations selected by the base station 31b, i.e., candidate relay station information (step S202b). The base station 31b provides the base station 30b with information about connected surrounding vehicles, i.e., connection terminal information (step S203a), and information about candidate relay stations, i.e., candidate relay station information (step S203b). After receiving information about connected surrounding vehicles, i.e., connection terminal information, and candidate relay station information, i.e., information about candidate relay stations, from the base station 31b, the base station 30b provides the vehicle 10 with information about connected surrounding vehicles, i.e., connection terminal information (step S204a), and information about candidate relay stations, i.e., candidate relay station information (step S204b). After vehicle 10 obtains information about surrounding vehicles connected to base station 31b, i.e., connection terminal information, and information about candidate relay stations, i.e., relay station candidate information, from base station 30b, it selects a candidate relay station to be used in an indirect session with base station 31b based on the surrounding vehicle information, connection terminal information, and relay station candidate information (step S205), and entrusts the selected relay station to relay during the indirect session with base station 31b (step S206).

[0090] Furthermore, when the vehicle 10's onboard terminal 11a notifies the base station 30b of a connection failure with the base station 31b in step S201, it may also notify the base station 31b of information such as the vehicle 10's location information, direction of travel, speed of travel, route information, and road information. In this case, the base station 30b also notifies the base station 31b of information such as the vehicle 10's location information, direction of travel, speed of travel, route information, and road information in step S202a or step S202b. This allows the base station 31b to select relay station candidates based on the vehicle 10's location information, direction of travel, speed of travel, route information, and road information. For example, the relay station candidate selection unit 64 of the base station 31b limits the number of nearby vehicles within a range that allows V2X communication with the vehicle 10 and, in descending order of priority, lists nearby vehicles with a low likelihood of immediate switching, nearby vehicles with a speed close to that of the vehicle 10, and nearby vehicles expected to travel on the same road for a certain period of time.

[0091] Next, the hardware configuration of the base station will be described. In the base station, the relay station candidate selection unit 64 is implemented 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.

[0092] As described above, according to this embodiment, when selecting a relay station to use when establishing an indirect session, the vehicle-mounted terminal 11a mounted on the vehicle 10 obtains connection terminal information including the location information of surrounding vehicles connected to the desired base station and relay station candidate information via the base station with which the direct session has been established. The vehicle-mounted terminal 11a selects a relay station using the connection terminal information including the location information and the relay station candidate information. This allows the vehicle-mounted terminal 11a to achieve the effects described in Embodiment 1 or 2 while also reducing the processing load associated with relay station selection.

[0093] Implementation method 4.

[0094] In Embodiments 1 to 3, the vehicle-mounted terminal 11 or 11a of the vehicle 10 obtains information about surrounding vehicles connected to a base station serving as an indirect session partner via a base station connected via a direct session. In Embodiment 4, a case will be described in which the vehicle-mounted terminal 11 or 11a of the vehicle 10 does not receive information from the base station but selects a relay station. While Embodiment 4 is applicable to both the vehicle-mounted terminal 11 and the vehicle-mounted terminal 11a, the following description will use the vehicle-mounted terminal 11 of Embodiment 1 as an example.

[0095] In vehicle 10, when the direct session with base station 31 fails, redundant system management unit 45 of vehicle-mounted terminal 11 notifies relay station candidate selection unit 47 of this failure. Relay station candidate selection unit 47 identifies surrounding vehicles 20-22 with which vehicle 10 is conducting V2X communications based on surrounding vehicle information managed by surrounding vehicle information management unit 42. Relay station candidate selection unit 47 requests information about the base stations connected to the surrounding vehicles 20-22 via V2X communications via relay control unit 48, V2X communication control unit 41, and V2X communication unit 40.

[0096] The surrounding vehicles 20-22 transmit information about the base stations to which the vehicle is connected via V2X communication. Furthermore, the information about the base stations to which the vehicle is connected may be transmitted by the surrounding vehicles 20-22 as separate information, such as a base station list, or may be transmitted together with the vehicle's position information, etc., during V2X communication when the surrounding vehicle information management unit 42 of the vehicle 10 manages the information about the surrounding vehicles 20-22 as surrounding vehicle information.

[0097] Figure 13 This 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. Figure 13 The surrounding vehicle information shown is an example in which the surrounding vehicle information management unit 42 of the vehicle-mounted terminal 11 of the vehicle 10 manages information on base stations connected to the surrounding vehicles 20 to 22 as the surrounding vehicle information. Figure 13 The surrounding vehicle information shown is relative to Figure 3 The surrounding vehicle information in the first embodiment shown here includes information on connected base stations. The number of base stations connected to each surrounding vehicle, i.e., connected base stations, is not limited to one; it may be two or more. Furthermore, the surrounding vehicle information management unit 42 may manage information on the base stations connected to the surrounding vehicles 20-22 in the form of a base station list transmitted from the surrounding vehicles 20-22.

[0098] The relay station candidate selection unit 47 is based on the information managed by the surrounding vehicle information management unit 42. Figure 13 The surrounding vehicle information or base station list shown selects surrounding vehicles connected to base stations other than the base station 30 to which the vehicle 10 is connected, for example, the base station 31 , as relay stations.

[0099] In addition, when the fourth embodiment is applied to the second embodiment or the third embodiment, the communication area calculation unit 50 in the vehicle-mounted terminal 11a mounted on the vehicle 10 can calculate the communication area based on the information managed by the surrounding vehicle information management unit 42. Figure 13 The surrounding vehicle information or base station list shown is calculated based on the location information of each surrounding vehicle. Figure 13In this case, the relay station candidate selection unit 47 further uses the communication area calculated by the communication area calculation unit 50 and selects a base station that is considered to be the most suitable relay station based on the position information of the vehicle 10, etc., so that the relay station can be selected.

[0100] As described above, in this embodiment, the surrounding vehicle information management unit 42 of the onboard terminal 11 or 11a manages surrounding vehicle information acquired during V2X communication, including location information of the surrounding vehicles 20-22, information on the communication status of the V2X communication, and information on the base stations to which the surrounding vehicles 20-22 are connected. Based on this surrounding vehicle information, the relay management unit 46 or 46a selects a relay station, a surrounding vehicle, to relay an indirect session with a base station that cannot be established through a direct session. This eliminates the need for the onboard terminal 11 or 11a to collect information via a base station. Therefore, even if a direct session with a base station cannot be established, information on candidate relay stations can be obtained when selecting a relay station.

[0101] For example, the vehicle-mounted terminal 11 may perform the operations of Embodiment 1 when at least one direct session can be established, and may perform the operations of Embodiment 4 when even one direct session cannot be established. Similarly, the vehicle-mounted terminal 11a may perform the operations of Embodiment 2 or 3 when at least one direct session can be established, and may perform the operations of Embodiment 4 when even one direct session cannot be established.

[0102] The configurations shown in the above embodiments are merely examples, and can be combined with other known technologies, and the embodiments can be combined with each other. Part of the configuration can also be omitted or modified without departing from the spirit of the invention.

[0103] Description of Reference Numerals

[0104] 1. 1a wireless communication system, 10 vehicle, 11. 11a vehicle-mounted terminal, 20-26 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 connection terminal information holding unit, 50 communication area calculation unit, 60 communication unit, 61 communication control unit, 62 connection terminal information acquisition unit, 63 terminal position information acquisition unit, 70-72 roadside devices, 80 communication area, 90. 93 processing circuit, 91 processor, 92 memory.

Claims

1. A vehicle-mounted terminal, which is mounted on a vehicle and wirelessly communicates with multiple base stations via multipath, characterized in that: The vehicle-mounted terminal has: 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 acquired in the inter-vehicle communication, including position information of the surrounding vehicles and information on a communication state of the inter-vehicle communication; a base station communication control unit configured to control providing information of a second base station that is not connectable via direct communication to the first base station connected via direct communication, and requesting provision of connection terminal information of information of surrounding vehicles connected to the second base station; a relay management unit that stores the connection terminal information obtained from the first base station and selects the surrounding vehicle, i.e., the relay station, that relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; as well as The redundant system management unit manages connections with 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 direct communication with the second base station is impossible.

2. The vehicle-mounted terminal according to claim 1, wherein: The surrounding vehicles include roadside devices installed on the road side of the road on which the vehicle is traveling.

3. The vehicle-mounted terminal according to claim 1 or 2, characterized in that: The connection terminal information includes the position information of the surrounding vehicles connected to the second base station, The relay management unit calculates the 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.

4. The vehicle-mounted terminal according to claim 3, wherein: The relay management unit estimates a relayable time, which is a time until the surrounding vehicle comes out of the communication area of ​​the second base station, and selects the relay station using the relayable time.

5. The vehicle-mounted terminal according to claim 3 or 4, characterized in that: When the vehicle arrives at the communication area of ​​the second base station, the redundant system management unit controls the base station communication control unit to attempt direct communication with the second base station.

6. The vehicle-mounted terminal according to any one of claims 1 to 5, characterized in that: The relay management unit stores relay station candidate information, which is information on the surrounding vehicles that are candidates for the relay station, obtained from the first base station, and selects the relay station using the relay station candidate information.

7. The vehicle-mounted terminal according to any one of claims 1 to 6, characterized in that: The surrounding vehicle information management unit manages the surrounding vehicle information acquired in the inter-vehicle communication, including position information of the surrounding vehicles, information on the communication status of the inter-vehicle communication, and information on the second base station to which the surrounding vehicles are connected. The relay management unit selects the relay station that relays the indirect connection with the second base station that cannot be connected by direct connection, based on the surrounding vehicle information.

8. A base station, which is a base station in a wireless communication system in which a vehicle equipped with a vehicle-mounted terminal performs wireless communication with a plurality of base stations via multipaths, characterized in that: The base station comprises: a connection terminal information acquisition unit that acquires identification information of the vehicle performing the wireless communication and stores the information as connection terminal information; and The communication control unit controls wireless communication with the vehicle and communication with other base stations, and controls providing the connection terminal information to the other base stations when there is a request from the other base stations.

9. The base station according to claim 8, characterized in that The base station further includes a terminal position information acquisition unit that acquires and stores position information of the vehicle performing the wireless communication. The communication control unit performs control to include the position information of the vehicle in the connection terminal information and provide the connection terminal information to the other base station when there is a request from the other base station.

10. The base station according to claim 9, characterized in that The base station further includes a relay station candidate selection unit that selects the first vehicle as a candidate relay station used by a second vehicle for indirect communication with the base station based on the connection terminal information including position information of the first vehicle as the vehicle, wherein the second vehicle is directly connected to the other base station via wireless communication. The communication control unit performs control to provide the information of the candidate relay station to the other base station when there is a request from the other base station.

11. A wireless communication system, characterized in that: The wireless communication system comprises: The vehicle-mounted terminal according to claim 1 or 2; and The base station according to claim 8.

12. A control circuit for controlling an on-vehicle terminal, the on-vehicle terminal being mounted on a vehicle and wirelessly communicating with a plurality of base stations via multipaths, characterized in that: The control circuit causes the vehicle-mounted terminal to perform the following processing: controlling communication with surrounding vehicles that are present around the vehicle and capable of inter-vehicle communication; managing surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the inter-vehicle communication acquired in the inter-vehicle communication; The control is as follows: providing the base station connected by direct communication, namely the first base station, with information of the base station that cannot be connected by direct communication, namely the second base station, and requesting provision of connection terminal information, namely information of the surrounding vehicles connected to the second base station; retaining the connection terminal information acquired from the first base station, and selecting the surrounding vehicle, ie, a relay station, which relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; and The controller manages connections with the first base station and the second base station, and instructs indirect communication with the second base station when connection with the second base station cannot be established through direct communication.

13. A storage medium storing a program for controlling an on-vehicle terminal, the on-vehicle terminal being mounted on a vehicle and wirelessly communicating with a plurality of base stations via multipaths, characterized in that: The program causes the vehicle-mounted terminal to perform the following processing: controlling communication with surrounding vehicles that are present around the vehicle and capable of inter-vehicle communication; managing surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the inter-vehicle communication acquired in the inter-vehicle communication; The control is as follows: providing the base station connected by direct communication, namely the first base station, with information of the base station that cannot be connected by direct communication, namely the second base station, and requesting provision of connection terminal information, namely information of the surrounding vehicles connected to the second base station; retaining the connection terminal information acquired from the first base station, and selecting the surrounding vehicle, ie, a relay station, which relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; and The controller manages connections with the first base station and the second base station, and instructs indirect communication with the second base station when connection with the second base station cannot be established through direct communication.

14. A relay station selection method for a vehicle-mounted terminal that is mounted on a vehicle and wirelessly communicates with multiple base stations via multiple paths, characterized in that: The relay station selection method includes: In a first step, an inter-vehicle communication control unit controls communication with surrounding vehicles that are present around the vehicle and capable of inter-vehicle communication; In a second step, a surrounding vehicle information management unit manages surrounding vehicle information including position information of the surrounding vehicles and information on a communication state of the inter-vehicle communication acquired in the inter-vehicle communication; In a third step, the base station communication control unit controls the first base station connected by direct communication to provide information about the second base station that cannot be connected by direct communication, and requests the base station communication control unit to provide information about the surrounding vehicles connected to the second base station, that is, connection terminal information; In a fourth step, a relay management unit stores the connection terminal information obtained from the first base station and selects the surrounding vehicle, i.e., a relay station, which relays indirect communication with the second base station based on the surrounding vehicle information and the connection terminal information; and In step 5, the redundant system management unit manages the connection with 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 the redundant system management unit cannot connect with the second base station through direct communication.

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