Communication device, communication system, control method, and program

Abstract

To provide a communication device and the like that can extend a communication possible range by relaying Side-link communication.SOLUTION: A communication device (200) with a Side-link communication function includes determination means (201) for determining whether communication between another communication device (20C) and a relay device with a Side-link Relay function is possible, and communication means (204) for forwarding messages sent and received between another communication device (20C) and the relay device (10) when the determination means (201) determines that the communication between another communication device (20C) and the relay device (10) is not possible.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a communication device, a communication system, a control method, and a program. [Background technology]

[0002] In recent years, the 3GPP (registered trademark) (3rd Generation Partnership Project) has been formulating specifications for LTE (Long Term Evolution) and 5G (NR; New Radio). Among these, a standard specification called Sidelink communication (hereinafter referred to as Sidelink) has been formulated. This specification realizes direct wireless communication between devices (UE; User Equipment) using an interface called PC5, without going through a mobile communication network (core network, base station, etc.). In NR Sidelink communication, Layer-2 ID (L2ID; Sidelink communication identifier) ​​is used as an identifier for identifying the source device and destination device.

[0003] Meanwhile, systems are beginning to be provided that use Sidelink communication to directly communicate wirelessly between vehicles to obtain information about surrounding vehicles (position, speed, vehicle control information, etc.) and provide safe driving assistance to the driver as needed.

[0004] In the technology proposed in Patent Document 1, a server acquires location information and speed information of a moving vehicle, and stores map information that associates the current location of the vehicle with a Layer-2 ID assigned to the vehicle. Then, vehicles communicate with each other using the Layer-2 ID based on this map information, and exchange information between the vehicles.

[0005] Furthermore, 3GPP (registered trademark) is currently formulating specifications for expanding the communication range of sidelink communication by using a relay device (sidelink relay).

[0006] Furthermore, Patent Document 2 proposes a technique for connecting a terminal (UE) outside the coverage of a base station to a relay device (sidelink relay) installed within the coverage of the base station via sidelink communication, thereby enabling communication with the base station. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-188405 A [Patent Document 2] Patent Publication No. 2021-078140 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the conventional technology does not disclose a method for extending the communication range by relaying sidelink communication.

[0009] An object of the present disclosure is to provide a communication device etc. that can expand a communication range by relaying Sidelink communication. [Means for solving the problem]

[0010] A communication device according to an embodiment of the present disclosure includes the following configuration: A communication device having a Sidelink communication function, A determination means for determining whether communication between another communication device and a relay device having a sidelink relay function is possible; a communication means for transferring a message transmitted between the other communication device and the relay device when the determination means determines that communication between the other communication device and the relay device is not possible; A communication device comprising: Effect of the Invention

[0011] According to the present disclosure, the communication range can be expanded by relaying Sidelink communication. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a communication system according to the present disclosure. [Diagram 2] FIG. 2 is a block diagram showing an example of a functional configuration of a roadside device. [Diagram 3] 2 is a block diagram showing an example of a functional configuration of a communication device configured in a vehicle; [Figure 4] FIG. 2 is a block diagram showing an example of a hardware configuration of a roadside device. [Diagram 5] 10 is a diagram showing an example of the data structure of a message in Sidelink communication exchanged via a roadside device; [Figure 6] 10 is a flowchart illustrating a process in a roadside device. [Figure 7] 4 is a flowchart illustrating a process in a communication device configured in a vehicle. [Figure 8] 13 is a flowchart showing a Sidelink reception process (step S300). [Figure 9] 13 is a flowchart showing a connection request acceptance transfer process (step S500). [Figure 9A] 13 is a flowchart showing a message transfer process (step S600). [Figure 10] FIG. 2 is a diagram illustrating a sequence of communication between a roadside device and an in-vehicle terminal. [Figure 10A] FIG. 13 is a diagram showing an example of a sequence of communication between a roadside device and a vehicle, which does not include relay processing by other vehicles. [Figure 11] FIG. 1 is a diagram illustrating a Broadcast communication method. [Figure 12] FIG. 1 is a diagram illustrating a Multicast (Groupcast) communication method. [Figure 13] FIG. 1 is a diagram illustrating a Unicast communication method. [Figure 14]FIG. 11 is a diagram illustrating an example of the data structure of a discovery message when sidelink communication is performed directly by a terminal (UE). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numerals are used to denote the same or similar configurations, and duplicated descriptions are omitted.

[0014] Conventionally, when exchanging information between terminals by Sidelink communication without going through a relay device, the terminal as UE cannot exchange information until it is in a state where it can directly connect with the other terminal as UE. For example, at places where radio waves are blocked by the presence of buildings and many vehicles, such as intersections (especially intersections with poor visibility), the reach distance may be short or there may be many blind spots, resulting in a narrow communication range. For this reason, it is desirable to install roadside equipment as Sidelink Relays and relay Sidelink communication addressed to a specific Layer-2 ID to expand the communication range between terminals (UE).

[0015] However, since a terminal cannot normally determine whether or not a roadside unit is present at an intersection, it cannot request relaying to a specific roadside unit. Also, if a roadside unit does not know the specific Layer-2 ID to be relayed, it cannot determine whether or not to relay a received Sidelink message. The following embodiment solves such problems.

[0016] In the following embodiment, a roadside device that is set near an intersection for the purpose of exchanging information related to traffic near the intersection is exemplified as a relay device, but the relay device is not limited to this. The relay device can be set at any installation location, and the purpose of communication via the relay device is also arbitrary. Relaying may be performed while the relay device is moving. The relay device can be installed in a location where it cannot be connected to a mobile communication network, for example, in an environment without base station coverage, but may be installed in a location where it can be connected to a mobile communication network. The relay device may provide a relay function while connected to a mobile communication network. In addition, a plurality of Layer-2 IDs for relaying corresponding to each of a plurality of purposes may be set for one relay device.

[0017] <Embodiment>

[0018] [System configuration] 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment of the present disclosure. This communication system includes a roadside device 10 (an example of a relay device) installed near an intersection K and vehicles (vehicles 20A to 20E) traveling near the intersection K.

[0019] In Fig. 1, the roadside device 10 has a sidelink relay function (function as a sidelink relay) and is a device that relays sidelink communication using the sidelink relay function. In the example of Fig. 1, for example, the roadside device 10 is installed on the side of the road near an intersection K, and communicates with vehicles, pedestrians, etc. It is particularly suitable to install the roadside device 10 near the intersection K where visibility is poor.

[0020] In FIG. 1, vehicles 20A-20E indicate vehicles traveling on a road near intersection K. The vehicles 20A-20E are equipped with a function of a Sidelink communication device (UE; User Equipment) and are capable of performing Sidelink communication with an external communication device. The vehicles 20A-20E can acquire and display information from outside the vehicle via Sidelink communication, and can also control the vehicle based on the information. Furthermore, the vehicles 20A-20E can acquire information about their own vehicles and notify external devices via Sidelink communication.

[0021] The roadside device 10 is configured to, upon receiving a message with a relay request from a sidelink communication device (UE) including the vehicles 20A to 20E, retransmit a message with the same content or a modified message according to the content of the message. In Fig. 1, an area 10A indicates the communication range of the roadside device 10.

[0022] The roadside device 10 is assigned a Layer-2 ID "RRR" as an identifier for Sidelink communication. The vehicles 20A to 20E are assigned Layer-2 ID "AAA", Layer-2 ID "BBB", Layer-2 ID "CCC", etc. as identifiers for Sidelink communication. In this embodiment, the intersection K is also assigned a Layer-2 ID "KKK" as an identifier for Sidelink communication for information exchange at the intersection by Sidelink communication. In this embodiment, a vehicle or the like is assumed as a UE compatible with Sidelink communication, but this is not limited thereto. For example, the UE may be a tablet terminal, a smart watch, or the like, which is carried by a user, or a wearable terminal such as a head-mounted display, which is worn by a user. The UE may also be a car navigation device installed in a vehicle.

[0023] [Functional configuration of the device] Next, the functional configuration of each device according to this embodiment will be described. Note that the configuration of the functional blocks described below is merely an example. Some (or in some cases all) of the functional blocks described may be replaced with other functional blocks that perform similar functions, some functional blocks may be omitted, or further functional blocks may be added. Also, one functional block shown in the following description may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block.

[0024] 2 is a block diagram showing an example of a functional configuration of the roadside device in this embodiment. As shown in FIG. 2, the roadside device 10 includes a control unit 101, a storage unit 102, a communication processing unit 103, a relay processing unit 104, a wireless communication unit 105, and a wired communication unit 106.

[0025] The control unit 101 controls the operation of the roadside device 10 in accordance with a program stored in the storage unit 102 .

[0026] The storage unit 102 stores information used by the control unit 101 for control, programs related to wireless and wired communication, other information, and the like.

[0027] The communication processing unit 103 performs analysis of Sidelink communication messages, etc. For example, the communication processing unit 103 analyzes a received Sidelink communication message to determine the contents, generates destination and sending information using a Layer-2 ID, and generates the contents of a Sidelink communication message to be sent.

[0028] The relay processing unit 104 performs processing related to relaying Sidelink communication transmitted from another communication device. For example, the relay processing unit 104 analyzes the destination, sender and Layer-2 ID related to relay, setting information related to relay, contents of the payload of the message, etc., and determines the operation related to relay.

[0029] The wireless communication unit 105 transmits and receives signals corresponding to messages and the like with an external wireless device by sidelink communication via the antenna 105a. The wired communication unit 106 connects the roadside device 10 to an external device 31 such as an external server via a wired network including the Internet 30, and transmits and receives information to and from the external device 31. For example, the roadside device 10 acquires information from the external device 31 via the wired communication unit 106, and generates a sidelink message corresponding to the acquired information in the communication processing unit 103. Then, the roadside device 10 can transmit a signal corresponding to the message via the wireless communication unit 105.

[0030] FIG. 3 is a block diagram showing an example of a functional configuration of a communication device configured by a vehicle (such as vehicles 20A to 20E) in this embodiment.

[0031] 3, communication device 200 (an example of a communication device, a first communication device, or a second communication device) includes a control unit 201 (an example of a determination means), a storage unit 202, a communication unit 203, and a wireless communication unit 204 (an example of a communication means). Communication device 200 also includes a vehicle information acquisition unit 205, an operation unit 206, and a display unit 207.

[0032] The control unit 201 controls the operation of the communication device 200 according to a program or the like stored in the storage unit 202. The control unit 201 may be configured as a part of a control device related to operations of the vehicle other than the operation of the communication device 200, and may be configured to execute various processes in cooperation with the control device.

[0033] The storage unit 202 stores information used by the control unit 201 for control and information related to wireless and wired communication.

[0034] The communication processing unit 203 performs analysis of messages of Sidelink communication, etc. For example, the communication processing unit 203 analyzes the contents of a message of Sidelink communication received by the wireless communication unit 204, and if the communication is directed to the own device, performs processing according to the contents of the message and sends a reply as necessary.

[0035] The wireless communication unit 204 transmits and receives signals in which information is encoded by Sidelink communication with an external wireless device via the antenna 204a. The wireless communication unit 204 may be capable of supporting communication methods other than Sidelink communication.

[0036] The vehicle information acquisition unit 205 acquires vehicle information about the vehicle itself. The vehicle information includes the position information of the vehicle itself, information to be notified to other vehicles, and other information.

[0037] The operation unit 206 accepts operations related to the communication device 200 of the vehicle.

[0038] The display unit 207 displays information acquired by the vehicle from the outside via wireless communication, information related to operations on the operation unit 206, vehicle information acquired via the vehicle information acquisition unit 205, etc. The display unit 207 may be configured as a part of a display device that displays information related to the vehicle other than information related to the communication device 200.

[0039] [Hardware configuration] FIG. 4 is a block diagram illustrating an example of a hardware configuration of the roadside device.

[0040] 4, the roadside device 10 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, and an auxiliary storage device 14. The roadside device 10 also includes a communication I / F (Interface) 15 and a device I / F (Interface) 16.

[0041] The CPU 11 realizes each function of the roadside device 10 shown in Fig. 2 by controlling the entire roadside device 10 using computer programs and data stored in the ROM 12 or the RAM 13. Note that the roadside device 10 may be provided with one or more pieces of dedicated hardware different from the CPU 11, and at least a part of the processing by the CPU 11 may be executed by the dedicated hardware. Examples of the dedicated hardware include an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), and a DSP (digital signal processor).

[0042] ROM 12 stores programs that do not require modification. RAM 13 temporarily stores programs and data supplied from auxiliary storage device 14, as well as data supplied from the outside via communication I / F 15. Auxiliary storage device 14 is composed of, for example, a hard disk drive, and stores various data. In this way, CPU 11, ROM 12, RAM 13, and auxiliary storage device 14 function as a so-called computer.

[0043] The communication I / F 15 is used for communication with an external device. For example, the wireless communication unit 105 (FIG. 2) performs wireless communication with an external device using the communication I / F 15. In this case, for example, the roadside device 10 can judge the situation based on information from an external device 31 connected to the Internet 30, and can notify vehicles and pedestrians of necessary information based on the judgment by sidelink communication.

[0044] Various devices can be connected to the device I / F 16. For example, a display device or input device for a server administrator to check information managed by the roadside device 10, a sensor or a camera mounted on the housing of the roadside device 10, etc. are connected to the device I / F 16. In this case, for example, the roadside device 10 can determine the status of vehicles and pedestrians passing on the road based on information from the camera or sensor, and can notify the vehicles and pedestrians of necessary information based on the determination by Sidelink communication.

[0045] The communication device 200 configured by the vehicles 20A to 20E can also be realized by a similar hardware configuration. For example, when the communication device 200 configured by the vehicles 20A to 20E has a hardware configuration as shown in FIG. 4, an imaging unit having a mechanism for performing imaging and a sensor of the vehicle can be connected to the device I / F 16. In this case, for example, the vehicles 20A to 20E can determine the situation of other vehicles and pedestrians passing on the road based on information from the imaging unit and the sensor, and can notify other vehicles and pedestrians of necessary information based on the determination by Sidelink communication. In this embodiment, the necessary information can be transmitted to the roadside device 10, and can be notified to other vehicles and pedestrians by Sidelink communication via relay in the roadside device 10.

[0046] More specifically, the contents of communication between the roadside device 10 and the communication device 200 and other devices through Sidelink communication include, for example, surrounding traffic conditions detected based on information from sensors and cameras, warning information based on future predictions, as well as sensor data and camera images. By sending and receiving such information, each vehicle can grasp not only the presence or absence of an oncoming vehicle at a merging point such as intersection K, but also information on the oncoming vehicle from its position information, speed information, etc., enabling driving support for the driver. In addition, since low-delay information exchange is possible, it is also possible to respond to merging order control, emergency brake control, and the like. Furthermore, safer driving is possible by receiving road traffic information such as accidents, congestion, emergency vehicles, construction vehicles, and abnormally running vehicles detected by the roadside device 10 and other vehicles, and information on the movements of pedestrians and bicycles, and knowing this information in advance through Sidelink communication.

[0047] In addition, pedestrians and cyclists who have terminals (UE) with similar functions will be able to know in advance about dangerous vehicle movements around them, effectively reducing the possibility of being involved in an accident.

[0048] [Processing example] In this embodiment, a discovery message including a relay request is transmitted from a vehicle (vehicles 20A to 20E) to the roadside device 10. In response to the received discovery message including the relay request, the roadside device 10 returns a discovery response message indicating acceptance of the relay. By receiving the discovery response message, the vehicle recognizes that it has become a target of relay by the roadside device 10. Vehicles that have become a target of relay can communicate with each other using the roadside device 10 as a relay device.

[0049] Even if a vehicle is not a relay target, it is possible to perform direct sidelink communication with other vehicles, i.e., sidelink communication without going through the roadside device 10. According to this embodiment, by making the vehicle a relay target, sidelink communication via the roadside device 10 is possible with vehicles or pedestrians with which direct sidelink communication is not possible due to reasons such as radio wave blocking. 5 is a diagram showing an example of the data structure of a message of Sidelink communication exchanged via a roadside device. 5G ProSe direct discovery can be used to transmit a discovery message including a relay request. Also, a Soliciation Message for 5G ProSe UE-to-Network Relay Discovery can be used for the transmission. ProSe is an abbreviation for (Proximity based Services). In FIG. 5, "Source Layer-2 ID" stores a Layer-2 ID indicating the source of information. For example, if the source is the vehicle 20A, the Layer-2 ID "AAA" is stored; if the source is the vehicle 20B, the Layer-2 ID "BBB" is stored; and if the source is the vehicle 20C, the Layer-2 ID "CCC" is stored. "Destination Layer-2 ID" stores a Layer-2 ID indicating the destination of information. "Relay Layer-2 ID" stores a Layer-2 ID indicating a device that relays a message (a device having a Sidelink Relay function). For example, when the device that relays a message is the roadside device 10, the Layer-2 ID "KKK" or "RRR" may be stored. "Relay Direction" stores information indicating whether the message is directed to a terminal (UE) or a Sidelink Relay. "Proxy mode" stores information indicating whether the message may be transferred by proxy. "Hop num" stores information regarding the number of times the message has been transferred (the number of hops). "Proxy Layer-2 ID" stores information that indicates the device that transferred the message. "Frame type" stores information that indicates the type of this message. "Frame Payload" stores the main body of the information exchanged between devices using this message.

[0050] Next, the processes in the roadside device 10 and the vehicles (vehicles 20A to 20E) will be described.

[0051] FIG. 6 is a flowchart illustrating a process in the roadside device.

[0052] In step S102 in Fig. 6, the control unit 101 (Fig. 2) of the roadside device 10 executes a process for setting parameters of the Sidelink Relay function in the roadside device 10 when the roadside device 10 is installed. For example, this process causes the Layer-2 ID "KKK" assigned to intersection K to be stored in the storage unit 102, thereby enabling the roadside device 10 to relay communication addressed to the Layer-2 ID "KKK". In this embodiment, the Layer-2 ID "KKK" corresponds to the Layer-2 ID for relaying.

[0053] In step S104, the control unit 101 determines whether or not a Sidelink communication message has been received via the wireless communication unit 105, and when the determination is affirmative, the control unit 101 advances the process to step S106.

[0054] In step S106, the control unit 101 determines whether the message whose reception was confirmed in step S104 is a discovery message (message requesting relay) (FIG. 5) including a relay request by the Sidelink Relay function via the communication processing unit 103. If the determination is affirmative, the control unit 101 advances the process to step S108, and if the determination is negative, the control unit 101 advances the process to step S112.

[0055] In step S108, the control unit 101 sets the intermediate Sidelink Relay function. Here, the control unit 101 sets the Layer-2 ID, which is the source of the discovery message including the relay request confirmed in step S106, as a relay target for Sidelink communication via the relay processing unit 104. Furthermore, based on the exchange of detailed information, parameters related to the Sidelink Relay function are also set in the communication device 200 of the vehicle (vehicles 20A to 20E). This makes it possible for the roadside device 10 to relay communication from the source of the discovery message including the relay request. Furthermore, the control unit 101 saves the validity period information specified in the discovery message. The setting contents and validity period information of the Sidelink Relay function are stored in the storage unit 102.

[0056] In step S110, the control unit 101 returns a discovery response message (FIGS. 6 and 6A) indicating acceptance of relaying to the source of the discovery message via the wireless communication unit 105, and proceeds to step S104. The return destination of the discovery response message is the source indicated in the discovery message (FIG. 5). Note that by including the Layer-2 ID "RRR" of the roadside device 10 in the discovery response message, the source of the discovery message can know this. If relaying cannot be accepted for some reason, the process of step S108 may be omitted and a message indicating that relaying cannot be accepted may be returned to the source of the discovery message.

[0057] As described above, a connection between the source of the discovery message including the relay request and the roadside device 10 is established by communication using the unicast communication method. The unicast communication method will be described in more detail later.

[0058] On the other hand, in step S112, the control unit 101 determines whether the validity period of relay in the message whose reception was confirmed in step S104 has expired via the communication processing unit 103. For this determination, the validity period information stored in the storage unit 102 in step S108 is used. If the determination is affirmative, the control unit 101 advances the process to step S116, and if the determination is negative, the control unit 101 advances the process to step S114.

[0059] In step S116, the control unit 101 stops the relay process for the sender of the message whose reception was confirmed in step S104. The parameter setting (step S108) related to the Sidelink Relay function is released.

[0060] In step S118, the control unit 101 transmits a relay end completion message indicating that the relay process of the message has been stopped to the vehicle (vehicles 20A to 20E) that requested the relay, and the process proceeds to step S104. The destination of the relay end completion message is the sender included in the message whose reception was confirmed in step S104.

[0061] On the other hand, in step S114, the control unit 101 determines whether the message whose reception was confirmed in step S104 is a message requesting the end of relay (relay end request message) via the communication processing unit 103. If the determination is positive, the control unit 101 advances the process to step S116, and if the determination is negative, the control unit 101 advances the process to step S120. Note that the relay end request message can include information on the period until the end of the relay operation. In this case, the process of step S116 is executed at the timing specified by the relay end request message.

[0062] In step S120, the control unit 101 determines whether or not the sender indicated by the message whose reception was confirmed in step S104 is a target for setting the Sidelink Relay function in step S108. If the determination is positive, the control unit 101 proceeds to step S122, and if the determination is negative, the control unit 101 proceeds to step S104.

[0063] In step S122, control section 101 rewrites necessary information, such as the Direction of the message whose reception was confirmed in step S104, via relay processing section 104, to create a message to be transmitted (relayed).

[0064] If the message whose reception is confirmed in step S104 corresponds to a message that has already been sent in step S124, the processes of steps S122 and S124 can be omitted. In other words, if the same message requested to be relayed is received multiple times, the processes of steps S122 and S124 can be omitted. This makes it possible to prevent the same message from being relayed multiple times.

[0065] In step S124, the control unit 101 transmits (transfers) the message generated in step S122 as a Sidelink communication message by the wireless communication unit 1055, and proceeds to step S104. The transmission destination (transfer destination) in step S124 may be limited to the terminal (UE) for which the Sidelink Relay function is set in step S108, or may not be limited to this. As a result, messages such as the information exchange message whose reception is confirmed in step S104 are relayed via the roadside device 10. The information exchange message is a message for exchanging information between vehicles, and includes vehicle information such as vehicle speed, vehicle acceleration, and accelerator opening.

[0066] If the determination in step S120 is negative, a message indicating that the message will not be relayed may be returned to the sender indicated by the message whose reception was confirmed in step S104.

[0067] Fig. 7 is a flowchart illustrating a process in a communication device configured by a vehicle (vehicles 20A to 20E). The example in Fig. 7 shows a case where the vehicle (vehicles 20A to 20E) passes through an intersection K (Fig. 1).

[0068] 7, the control unit 201 (FIG. 3) of the communication device 200 determines, based on the information acquired by the vehicle information acquisition unit 205, whether or not the host vehicle (vehicles 20A to 20E) has approached the intersection K. The control unit 201 waits for the determination to be affirmative, and then advances the process to step S204.

[0069] In step S202, for example, the control unit 201 compares position information obtained by a GPS (Global Positioning System) device or the like mounted on the vehicle with the intersection information stored in the storage unit 102. Then, based on the comparison result of these pieces of information, it can be recognized that the vehicle has approached intersection K. In this case, the intersection information stores the coordinates of each intersection including intersection K and the Layer-2 ID assigned to each intersection (for example, Layer-2 ID "KKK" assigned to intersection K) in association with each other. The control unit 201 can recognize that the vehicle has approached a specific intersection by comparing the position information (coordinates) acquired in real time by the vehicle information acquisition unit 205 with the coordinates of each intersection indicated in the intersection information.

[0070] In step S204, the control unit 201 performs a communication preparation process so as to enable sidelink communication with the Layer-2 ID "KKK" assigned to the intersection K. For example, in step S204, the Layer-2 ID "KKK" is registered in the storage unit 202 as a communication partner.

[0071] In step S206, the control unit 201 determines whether or not a request for relaying using the Layer-2 ID "KKK" assigned to the intersection K has been made to the roadside device 10 (step S208). If the determination is affirmative, the control unit 201 advances the process to step S210, and if the determination is negative, the control unit 201 advances the process to step S208.

[0072] In step S208, the control unit 201 transmits a discovery message (FIG. 5) of a relay request to the roadside unit 10 via the communication processing unit 203.

[0073] In step S210, the control unit 201 determines whether or not an event has occurred that should be relayed and notified via the roadside device 10, based on information acquired by the vehicle information acquisition unit 205, etc. If the determination is affirmative, the control unit 201 advances the process to step S212, and if the determination is negative, the control unit 201 advances the process to step S220.

[0074] In step S212, the control unit 201 determines whether or not a discovery response message (FIGS. 6 and 6A) indicating acceptance of relaying from the roadside device 10 has already been received and whether or not parameters related to the sidelink relay function have been set in the FIG. 6 communication device 200. This discovery response message indicating acceptance of relaying is the message transmitted from the roadside device 10 in step S110 (FIG. 6). In step S212, if the determination is affirmative, the control unit 201 advances the process to step S214, and if the determination is negative, the control unit 201 advances the process to step S220.

[0075] In step S214, the control unit 201 transmits a communication message (FIG. 7) related to the event that has occurred to the terminal that is the relay target via the roadside device 10 (Sidelink Relay). In the Frame Payload (FIG. 7) of this communication message, information that a specific event has occurred and other information related to the event that has occurred are described.

[0076] In step S220, the control unit 201 determines whether or not the host vehicle has left the intersection K based on the information acquired by the vehicle information acquisition unit 205. If the determination is affirmative, the control unit 201 proceeds to step S222, and if the determination is negative, the control unit 201 proceeds to step S224. In step S220, for example, the control unit 201 can recognize that the host vehicle has left the intersection K based on position information acquired by a GPS device or the like mounted on the host vehicle and the intersection information stored in the storage unit 102.

[0077] In step S222, the control unit 201 transmits a message requesting the end of relaying (relay end request message) to the roadside unit 10 via the communication processing unit 203. The relay end request message is a message whose reception is confirmed by the roadside unit 10 in step S114 (FIG. 6). The format of the relay end request message may be, for example, the same format (data structure) as that of the discovery message including the relay request (FIG. 5). In this case, the relay end request message can be indicated by setting the values ​​of Relay mode and Valid Period shown in FIG. 5 to predetermined values.

[0078] On the other hand, in step S224, the control unit 201 determines whether or not a sidelink communication message transmitted by another terminal (UE) has been received via the wireless communication unit 204. If the determination is affirmative, the control unit 201 advances the process to a sidelink reception process (step S300), and if the determination is negative, the control unit 201 advances the process to step S206.

[0079] FIG. 9A is a flowchart showing the sidelink reception process (step S300).

[0080] 9A, the control unit 201 determines whether the received Sidelink communication message is a message transmitted and received between another terminal device (UE) and the roadside device 10. If the determination is affirmative, the control unit 201 advances the process to step S304, and if the determination is negative, the control unit 201 advances the process to step S306.

[0081] In step S304, the control unit 201 determines whether the received Sidelink communication message is a message of a relay request to the roadside device 10 (Sidelink Relay) or a message of acceptance of the relay request. If the determination is affirmative, the control unit 201 proceeds to step S500 (connection request / acceptance transfer process), and if the determination is negative, the control unit 201 proceeds to step S600 (message transfer process). If the determination in step S304 is negative, the Sidelink communication message includes an information exchange message for exchanging information between vehicles. The information exchange message may include vehicle information such as vehicle speed, vehicle acceleration, and accelerator opening.

[0082] In this embodiment, if the determination in step S304 is negative, the process may return without executing step S600 (message forwarding process). In this case, the messages forwarded in the vehicle are limited to messages of relay requests and messages of acceptance thereof. Also, the determination in step S304 may be positive only when the received Sidelink communication message is a message of relay request to the roadside device 10 (Sidelink Relay), and may be negative in the case of other messages. In this case, the messages forwarded in the vehicle are limited to messages of relay requests.

[0083] In step S306, the control unit 201 determines whether the received Sidelink communication message is addressed to the own device, and if the determination is affirmative, the process proceeds to step S308, and if the determination is negative, the process returns. Here, the Sidelink communication message for which the determination is affirmative in step S306 is not limited to a message sent via the roadside device 10, but also includes a Sidelink communication message sent directly from another terminal (UE) to the own vehicle.

[0084] In step S308, the control unit 201 performs necessary processing such as analysis of the received Sidelink communication message by the communication processing unit 203, and returns. In step S308, for example, the control unit 201 generates a necessary Sidelink communication message based on the analysis result in step S308, and transmits it by the wireless communication unit 204. The generated Sidelink communication message is transmitted to a communication device of another vehicle or pedestrian, or to the roadside unit 10 (with Layer-2 ID "KKK" as the destination).

[0085] FIG. 9 is a flowchart showing the connection request acceptance and transfer process (step S500).

[0086] 9, the control unit 201 judges whether the received Sidelink communication message is a message related to the roadside device 10 (Sidelink Relay) to which the own device is connected. If the judgment is positive, the control unit 201 advances the process to step S504, and if the judgment is negative, the control unit 201 returns. Note that whether the own device is connected to the roadside device 10 (Sidelink Relay) can be judged based on, for example, whether parameter setting (step S108) related to the Sidelink Relay function has been completed in the own vehicle.

[0087] In step S504, the control unit 201 determines whether the received sidelink communication message is a message requesting relay to the roadside device 10 (sidelink relay). If the determination is affirmative, the control unit 201 advances the process to step S506, and if the determination is negative, the control unit 201 advances the process to step S508.

[0088] In step S506, the control unit 201 judges whether the received relay request message is set to the forwarding permission mode, and if the judgment is affirmative, the process proceeds to step S510, and if the judgment is negative, the process returns. Whether the relay request message to be judged in step S506 can be forwarded, that is, whether the forwarding permission mode is set or not, can be determined by the source of the relay request message or the roadside device 10 (Sidelink Relay). Whether the forwarding permission mode is set or not may be included in the information of the message.

[0089] In step S510, the control unit 201 determines whether the hop count indicated in the received relay request message is equal to or less than a specified hop count, and if the determination is positive, the process proceeds to step S512, and if the determination is negative, the process returns.

[0090] In step S512, the control unit 201 waits for a predetermined time, and then advances the process to step S514.

[0091] In step S514, the control unit 201 determines whether a connection acceptance or connection denial message in response to the received relay request message has been transmitted from the roadside unit 10 (Sidelink Relay) (whether the message has been received by the control unit 201 itself). If the determination is positive, the control unit 201 returns, and if the determination is negative, the process proceeds to step S516. Note that in step S516, if the above-mentioned connection acceptance or connection denial message has been received by the wireless communication unit 204, the determination is positive.

[0092] In step S516, the control unit 201 transfers the relay request message sent from the other device (the relay request message recognized in step S504) to the roadside device 10 (Sidelink Relay) through the wireless communication unit 204.

[0093] On the other hand, in step S508, the control unit 201 determines whether the received Sidelink communication message is a connection acceptance message, and if the determination is affirmative, the process proceeds to step S520, and if the determination is negative, the process returns.

[0094] In step S520, the control unit 201 determines whether the received sidelink communication message is a response (reply) to the relay request message that the device itself transferred to the roadside device 10 (sidelink relay) in step S516. If the determination is affirmative, the control unit 201 advances the process to step S522, and if the determination is negative, the control unit 201 returns.

[0095] In step S522, the control unit 201 transfers a response (reply) message to the relay request message to the response destination (UE) indicated by the message via the wireless communication unit 204, and returns.

[0096] 9A is a flowchart showing the message transfer process (step S600). In the connection request / acceptance transfer process (step S600), relay processing is performed for communication messages between the roadside device 10 and the terminal UE (vehicles 20A to 20E) other than the above relay request message and its acceptance message.

[0097] In step S602 in Fig. 9A, the control unit 201 judges whether the received Sidelink communication message is a message related to the roadside device 10 (Sidelink Relay) to which the own device is connected. If the judgment is positive, the control unit 201 advances the process to step S604, and if the judgment is negative, the control unit 201 returns. Note that whether the own device is connected to the roadside device 10 (Sidelink Relay) can be judged based on, for example, whether parameter setting (step S108) related to the Sidelink Relay function has been completed in the own vehicle.

[0098] In step S604, the control unit 201 determines whether the communication is related to the device (UE) to which the control unit 201 has transferred the relay request message in step S516. If the determination is affirmative, the control unit 201 proceeds to step S606, and if the determination is negative, the control unit 201 returns.

[0099] In step S606, the control unit 201 determines whether the received sidelink communication message is set to the forwarding permission mode. If the determination is affirmative, the control unit 201 advances the process to step S608, and if the determination is negative, the control unit 201 returns. Whether the message to be forwarded in the determination in step S606 can be forwarded, that is, whether the forwarding permission mode is set or not, can be determined by the source of the message or the roadside device 10 (Sidelink Relay). Whether the forwarding permission mode is set or not may be included in the information of the message, the relay request message, or the message responding to the relay request message.

[0100] In step S608, the control unit 201 determines whether the hop count of the received Sidelink communication message is equal to or less than a specified hop count. If the determination is affirmative, the control unit 201 advances the process to step S610, and if the determination is negative, the control unit 201 returns.

[0101] In step S610, the control unit 201 determines whether the received sidelink communication message is a message transmitted from the roadside unit 10 (sidelink relay). If the determination is positive, the control unit 201 advances the process to step S612, and if the determination is negative, the control unit 201 advances the process to step S614. In step S610, if the sender of the received sidelink communication message is the roadside unit 10, the determination is positive. In addition, the determination is negative in step S610 if the sender of the received sidelink communication message is the device (UE) that forwarded the relay request message in step S516.

[0102] In step S612, the control unit 201 transfers the received sidelink communication message to the device (UE) that transferred the relay request message in step S516 via the wireless communication unit 204, and returns. Note that if the sender of the received sidelink communication message is the device (UE) that transferred the relay request message in step S516, the control unit 201 may return without executing step S612. In this case, it is possible to prevent the sidelink communication message that the control unit 201 itself transmitted from returning to the sender.

[0103] In step S614, the control unit 201 transfers the received Sidelink communication message to the roadside unit 10 (Sidelink Relay) by the wireless communication unit 204, and returns.

[0104] In this way, by executing both step S612 and step S614, message exchange is possible between the device (UE) that transferred the relay request message in step S516 and the roadside device 10 (Sidelink Relay). That is, messages (information exchange messages, other messages) transmitted and received between the two devices can be transferred in both directions. Note that either step S612 or step S614 may be skipped. In these cases, the transfer direction of the message transferred in the host vehicle is limited to one direction.

[0105] In the message forwarding process (step S600), it may be determined whether or not direct sidelink communication is possible between the device (UE) that forwarded the message of the relay request in step S516 and the roadside device 10 (Sidelink Relay). In this case, if it is determined that direct sidelink communication is possible between the two devices, forwarding may be terminated. Here, for example, it may be determined whether or not a response (reply) has been received in response to the transmission of a message from either the device (UE) that forwarded the message of the relay request in step S516 or the roadside device 10 (Sidelink Relay). If a response (reply) has been received (received by the vehicle), it can be determined that direct sidelink communication is possible. In addition, such a determination may be performed by either the device (UE) that forwarded the message of the relay request in step S516 or the roadside device 10 (Sidelink Relay). In this case, the result of the determination may be notified to the vehicle that is forwarding the message (the vehicle that is executing step S600) from either device.

[0106] In addition, in the message forwarding process (step S600), it may be detected that the vehicle is no longer able to communicate with the roadside device 10 (Sidelink Relay) or that the communication has been terminated. When this is detected, the end of forwarding may be notified to the device (UE) that forwarded the relay request message in step S516.

[0107] Fig. 10 is a diagram showing an example of a sequence of communication between a roadside device and a vehicle, involving relay processing by another vehicle. This sequence includes relay processing by vehicle 20B. The step numbers in Fig. 10 correspond to the step numbers in Figs. 6 to 9A.

[0108] 10, when the roadside device 10 is installed at an intersection K, a Sidelink Relay function is set in the roadside device 10 to relay a Sidelink message transmitted to the Layer-2 ID "KKK" of the intersection K. After that, the roadside device 10 starts up (step S102).

[0109] When the vehicle 20A approaches the intersection K, the communication device 200 of the vehicle 20A is set to be capable of transmitting and receiving a Sidelink message addressed to the Layer-2 ID "KKK" of the intersection K (step S204).

[0110] Next, the communication device 200 of the vehicle 20A transmits a discovery message including a relay request addressed to the Layer-2 ID "KKK" of the intersection K to the roadside device 10 (step S208).

[0111] The roadside device 10 that has received the discovery message exchanges detailed information with the vehicle 20A and performs operation settings for the Sidelink Relay function at the Layer-2 ID "KKK" of the intersection K. Thereafter, the roadside device 10 transmits a relay acceptance message as a response to the discovery message (steps 108 to 110).

[0112] Similarly, when the vehicle 20B approaches the intersection K, it prepares for communication using the Layer-2 ID of the intersection K (step S204). Then, it transmits a discovery message (connection request) including a relay request addressed to the Layer-2 ID "KKK" of the intersection K (step S208). The roadside device 10 that has received the discovery message performs operation settings for the Sidelink Relay function at the Layer-2 ID "KKK" of the intersection K. Then, the roadside device 10 transmits a relay acceptance message as a response to the discovery message (steps S108 to S110).

[0113] By the operations described above, the vehicle 20A and the vehicle 20B are able to communicate with each other via the roadside device 10 using the Layer-2 ID “KKK” assigned to the intersection K.

[0114] In this state, if an event (notification event) occurs in vehicle 20B, vehicle 20B transmits information (step S214). Then, the sidelink relay function of roadside device 10 relays the information to vehicle 20A (step S124). If the communication method applied is multicast, the information also reaches vehicle 20B, but vehicle 20B determines that the information was transmitted by itself based on the transmission source of the information, and discards or ignores it. The communication method applied will be described later.

[0115] Furthermore, when vehicle 20C approaches intersection K, it prepares for communication using the Layer-2 ID of intersection K (step S204), and transmits a discovery message including a relay request addressed to the Layer-2 ID of intersection K (step S208).

[0116] Here, the vehicle 20C is approaching the intersection K, but is unable to directly communicate with the roadside device 10 due to a slight distance or radio wave obstruction. Therefore, the discovery message including the relay request does not reach the roadside device 10, and the connection acceptance message from the roadside device 10 is not returned to the vehicle 20C. Meanwhile, the vehicle 20B is traveling between the roadside device 10 and the vehicle 20C, and is in a state (FIG. 1) where sidelink communication is possible with both the roadside device 10 and the vehicle 20C. In FIG. 1, the communication range SC of the vehicle 20C does not reach the roadside device 10, and the vehicle 20C is within the communication range SC.

[0117] When the vehicle 20B, which has already been connected to the Sidelink Relay function of the roadside device 10, receives a relay request message (a discovery message including a relay request) from the vehicle 20C to the roadside device 10, it makes a judgment regarding the connection acceptance (relay acceptance) message. Specifically, the vehicle 20B judges whether or not the connection acceptance (relay acceptance) message is returned within a certain time period after the relay request (step S514). If the relay request (relay acceptance) message is not returned, the vehicle 20B transfers the relay request message transmitted by the vehicle 20C to the roadside device 10 (step S516). In this case, when transferring the relay request message in step S516, the vehicle 20B executes an operation required for starting transfer in the roadside device 10, such as storing the Layer-2 address of the vehicle 20B in the message. The roadside device 10 that has received the forwarded relay request message returns a Sidelink Relay connection acceptance message for the Layer-2 ID "KKK" of the intersection to the vehicle 20B (step S110). The vehicle 20B forwards the received Sidelink Relay connection acceptance message to the vehicle 20C (step S522).

[0118] After that, the vehicle 20C and the roadside device 10 exchange detailed information via the vehicle 20B, and set parameters related to the Sidelink Relay function (steps S108, S308, S614, and S612).

[0119] By the operations described above, the vehicle 20C is able to communicate with not only the vehicle 20B but also the vehicle 20A via the roadside device 10 having the Sidelink Relay function using the Layer-2 ID "KKK" of the intersection.

[0120] After the roadside device 10 starts forwarding, an event (notifiable event) occurs in the vehicle 20C, and the roadside device 10 transmits information via the roadside device 10 (Sidelink Relay) (step S214), and the information is forwarded by the vehicle 20B to the roadside device 10 (step S614). The roadside device 10 also transmits the information to the vehicle 20A connected by the Sidelink Relay function (step S124). Note that, when information relating to the event (notifiable event) in the vehicle 20C is forwarded from the roadside device 10 and received by the vehicle 20B, in the example of FIG. 10, the information is not forwarded to the vehicle 20C.

[0121] Similarly, when an event (notification event) occurs in vehicle 20A in this state, the information transmitted from vehicle 20A is relayed to vehicles 20B and 20C by the sidelink relay function of roadside device 10 (steps S124 and S614). If the applied communication method is multicast, the information also reaches vehicle 20A, but vehicle 20A determines that this is information transmitted by itself and discards or ignores it.

[0122] For example, when relaying by the roadside device 10 is no longer necessary, such as when the vehicle 20A has left the intersection K, the vehicle 20A transmits a relay end request message to the roadside device 10 (step S222). When the roadside device 10 receives the relay end request message and accepts the end of relaying, it transmits a relay end completion message to the vehicle 20A (step S118). The roadside device 10 judges the situation and stops or ends the relay operation by the Sidelink Relay function of the roadside device 10.

[0123] Fig. 10A is a diagram showing an example of a sequence of communication between a roadside device and a vehicle, not including relay processing by other vehicles. The step numbers in Fig. 10A correspond to the step numbers in Figs. 6 to 9A.

[0124] As shown in FIG. 10A, when the roadside device 10 is installed at an intersection, a Sidelink Relay function that relays a Sidelink message sent to the Layer-2 ID “KKK” of the intersection is set and activated in the roadside device 10 (step S102).

[0125] When the vehicle 20A approaches the intersection, the communication device 200 of the vehicle 20A is set so as to be capable of transmitting and receiving a Sidelink message addressed to the Layer-2 ID "KKK" of the intersection (step S204).

[0126] Next, the communication device 200 of the vehicle 20A transmits a discovery message including a relay request addressed to the Layer-2 ID "KKK" of the intersection to the roadside device 10 (step S208).

[0127] The roadside device 10 that has received the discovery message exchanges detailed information with the vehicle 20A and sets up the operation of the Sidelink Relay function at the Layer-2 ID "KKK" of the intersection. After that, the roadside device 10 transmits a relay acceptance message as a reply to the discovery message (steps S108 to S110).

[0128] Similarly, when the vehicle 20B approaches an intersection, it prepares for communication using the Layer-2 ID of the intersection (step S204) and transmits a discovery message including a relay request addressed to the Layer-2 ID of the intersection (step S208). When the roadside device 10 receives the discovery message including the relay request, the roadside device 10 exchanges information with the other device to set up the use of the Sidelink Relay function and transmits an acceptance message (steps S108 to S110).

[0129] By the operations described above, the vehicle 20A and the vehicle 20B are able to communicate with each other via the roadside device 10 using the Layer-2 ID “KKK” assigned to the intersection K.

[0130] In this state, if an event (notification event) occurs in vehicle 20B, vehicle 20B transmits information (step S214). Then, the sidelink relay function of roadside device 10 relays the information to vehicle 20A (step S124). If the communication method applied is multicast, the information also reaches vehicle 20B, but vehicle 20B determines that the information was transmitted by itself based on the transmission source of the information, and discards or ignores it. The communication method applied will be described later.

[0131] Furthermore, when the vehicle 20C approaches the intersection, the roadside device 10 and the communication device 202 of the vehicle 20C execute the above-mentioned steps S204, S208, and S110. This enables the vehicles 20A, 20B, and 20C to communicate with each other via the roadside device 10 using the Layer-2 ID "KKK" assigned to the intersection K.

[0132] In this state, if an event (notification event) occurs in vehicle 20C, vehicle 20C transmits information (step S214). Then, the sidelink relay function of roadside device 10 relays the information to vehicles 20A and 20B (step S124). If the applied communication method is multicast, the information also reaches vehicle 20B, but vehicle 20B determines that this is information transmitted by itself and discards or ignores it.

[0133] Similarly, when an event (notification event) occurs in vehicle 20A in this state, the information transmitted from vehicle 20A is relayed to vehicles 20B and 20C by the sidelink relay function of roadside device 10 (step S124). If the communication method applied is multicast, the information also reaches vehicle 20C, but vehicle 20C determines that this is information transmitted by itself and discards or ignores it.

[0134] In this embodiment, the Layer-2 ID "RRR", which is an identifier assigned to the roadside device 10, can be used as appropriate. By using the Layer-2 ID "RRR" as the destination, it is possible to recognize that the type or function of the communication message is different from that in the case where a relay identifier is used. For example, the roadside device 10 and the terminal (EU) that received the communication message can recognize that the received communication message is not a communication message related to information exchange at the intersection KKK, or that the roadside device 10 has not been requested to relay the communication message.

[0135] Next, the Sidelink communication method will be described.

[0136] FIG. 11 is a diagram showing a Broadcast communication method, FIG. 12 is a diagram showing a Multicast (Groupcast) communication method, and FIG. 13 is a diagram showing a Unicast communication method.

[0137] In the case of the "Broadcast communication method" shown in FIG. 11, the shared Layer-2 ID is set as the transmission destination and reception destination in the transmitting and receiving devices, respectively.

[0138] On the other hand, in the case of the "Multicast (Groupcast) communication method" and "Unicast communication method" as shown in Figures 12 and 13, the transmitting device transmits a relay request to the shared Layer-2 ID ("Relay request" in Figures 12 and 13). When the receiving device having the shared Layer-2 ID responds to this, exchanges security information, and responds to the relay request ("Connection request response" in Figures 12 and 13), data communication becomes possible.

[0139] In this embodiment, either communication method is applicable, but the above process is described using the "Multicast communication method."

[0140] As described above, the terminals (UE) of the vehicles 20A, 20B, and 20C can directly communicate with each other through sidelink without using relaying by the roadside device 10. That is, direct sidelink communication coexists with communication using relaying by the roadside device 10. Note that direct sidelink communication and communication using relaying by the roadside device 10 coexist. For this reason, a message with substantially the same content may be received multiple times by the same terminal (UE), and in that case, the processing is left to the terminal (UE) that received the message. For example, a message with substantially the same content received the second or subsequent times may be discarded or ignored.

[0141] FIG. 14 is a diagram showing an example of the data structure of a discovery message when sidelink communication is performed directly by a terminal (UE).

[0142] As shown in FIG. 14, when a terminal (UE) such as vehicles 20A to 20E searches for a terminal (UE) without a relay function, information indicating a relay request is not included in the discovery message that is transmitted.

[0143] As described above, according to the above embodiment, the terminal (vehicles 20A to 20E; UE) requests relay of Sidelink communication addressed to a specific Layer-2 ID "KKK" assigned to the intersection K by a relay request message. Then, the relay request enables the roadside device 10 to execute relay. Therefore, the terminal (UE) can request relay even if it is not known whether or not there is a roadside device 10 (Sidelink Relay) that can relay. Furthermore, the terminal (UE) can know the Layer-2 ID of the relay device in response to the relay request message. Also, the roadside device 10 can know the specific Layer-2 ID to be relayed by the destination information included in the relay request message. This allows the roadside device 10 to execute relay of a Sidelink message addressed to the Layer-2 ID "KKK". Therefore, the relay of Sidelink communication by the roadside device 10 can expand the communication range.

[0144] Furthermore, according to the above embodiment, even if direct communication is not possible between the roadside device 10 (Sidelink Relay) and the terminal (vehicle 20C), the communication range can be expanded. That is, in such a case, messages can be transmitted and received between the roadside device 10 (Sidelink Relay) and the terminal (vehicle 20C) via message transfer by another terminal (vehicle 20B). This makes it possible to realize information exchange between all terminals (UE) related to an intersection, etc., in an environment where the reach of Sidelink communication is short or there are many blind spots due to the presence of buildings and many vehicles, such as an intersection.

[0145] <Modification> In the UE of the vehicles 20A to 20E, it is also possible to configure the UE to set whether or not to perform relay for extending the communication range by a user operation. In this case, when relaying is set, control for forwarding a message to other terminals described in the above embodiment is performed, and when relaying is not set, control for forwarding a message to other terminals is not performed. Also, it is possible to configure the UE to switch the setting of whether or not to perform relay for extending the communication range based on the remaining battery power.

[0146] <Other embodiments> The present disclosure can also be realized by a process in which a program for implementing one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions.

[0147] Also, for example, in the above-described embodiment, the wireless access method is NR (New Radio), which is a 5G wireless access method, but other access methods such as 6G and later and WiFi may be applied at least in part.

[0148] Furthermore, the Sidelink communication is not limited to a discovery message, and may be, for example, a message related to Direct Communication or a message related to V2X Communication.

[0149] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention.

[0150] The disclosure of this embodiment also includes the following configuration.

[0151] (Configuration 1) A communication device having a Sidelink communication function, A determination means for determining whether communication between another communication device and a relay device having a sidelink relay function is possible; a communication means for transferring a message transmitted between the other communication device and the relay device when the determination means determines that communication between the other communication device and the relay device is not possible; A communication device comprising:

[0152] (Configuration 2) The communication device described in configuration 1, wherein, after it is confirmed based on the signal received by the communication means that a relay request message has been sent from the other communication device to the relay device, if a response message from the relay device to the other communication device in response to the relay request message is not confirmed, the judgment means judges that communication is not possible between the other communication device and the relay device.

[0153] (Configuration 3) The communication device according to configuration 2, wherein the determination means determines that communication between the other communication device and the relay device is not possible when the response message is not confirmed even after a predetermined time has elapsed since it was confirmed that a relay request message was sent from the other communication device to the relay device.

[0154] (Configuration 4) 4. The communication device according to configuration 2 or 3, wherein when the determination means determines that communication is not possible between the other communication device and the relay device, the communication means transfers the relay request message to the relay device.

[0155] (Configuration 5) A communication device described in any one of configurations 2 to 4, wherein when the judgment means judges that communication is not possible between the other communication device and the relay device, the communication means transfers the response message to the other communication device.

[0156] (Configuration 6) 6. The communication device according to any one of configurations 1 to 5, wherein the communication means transfers messages transmitted and received between the relay device to which the communication device itself is connected and the other communication device.

[0157] (Configuration 7) 7. The communication device according to any one of configurations 1 to 6, wherein the messages transferred by the communication means include an information exchange message.

[0158] (Configuration 8) The communication device according to configuration 7, wherein the communication means transfers the information exchange message in either one or both of a direction from the other communication device to the relay device and a direction from the relay device to the other communication device.

[0159] (Configuration 9) A communication device according to any one of configurations 1 to 8, wherein the communication means transfers only the message that has been permitted by the other communication device or the relay device and that includes information indicating that the transfer is permitted.

[0160] (Configuration 10) A communication device described in any one of configurations 1 to 9, wherein when it is determined based on a notification from the other communication device or the relay device that direct communication between the other communication device and the relay device has become possible, the communication means terminates the forwarding.

[0161] (Configuration 11) A communication device described in any one of configurations 1 to 10, wherein if communication between the communication means and the relay device becomes impossible, the communication means terminates the transfer and notifies the other device of the end of the transfer.

[0162] (Configuration 12) 12. The communication device according to any one of configurations 1 to 11, wherein the communication means does not forward the message if the hop count of the message received from the other communication device or the relay device exceeds a prescribed number.

[0163] (Configuration 13) A method for controlling a communication device having a Sidelink communication function, comprising: a determination step of determining whether communication is possible between another communication device and a relay device having a sidelink relay function; a forwarding step of forwarding a message transmitted between the other communication device and the relay device when it is determined in the determining step that communication between the other communication device and the relay device is not possible; A method for controlling a communication device comprising:

[0164] (Configuration 14) A computer of a communication device having a Sidelink communication function a determination step of determining whether communication is possible between another communication device and a relay device having a sidelink relay function; a forwarding step of forwarding a message transmitted between the other communication device and the relay device when it is determined in the determining step that communication between the other communication device and the relay device is not possible; A program for executing the above.

[0165] (Configuration 15) A first communication device having a Sidelink communication function; A second communication device having a Sidelink communication function; A relay device having a Sidelink Relay function; A communication system comprising: The first communication device is a determination means for determining whether communication between the second communication device and the relay device is possible; a communication unit that transfers messages transmitted and received between the second communication device and the relay device when the determination means determines that communication between the second communication device and the relay device is not possible; A communication system comprising:

[0166] (Configuration 16) 16. The communication system according to claim 15, wherein the relay device is disposed in correspondence with an intersection, and the first communication device and the second communication device move together with a moving object passing through the intersection. [Explanation of symbols]

[0167] 10 Roadside equipment 20A~20E Vehicles 101 Control section 102 Storage section 103 Communication processing unit 104 Relay Processing Unit 105 Wireless Communication Division 106 Wired Communications Department 200 Communication equipment 201 Control section 202 Storage section 203 Communication processing unit 204 Wireless Communication Department 205 Vehicle Information Acquisition Department 206 Operation section 207 Display section

Claims

1. A communication device having a Sidelink communication function, A determination means for determining whether direct communication between another communication device and a relay device having a Sidelink Relay function is possible; a communication means for transferring messages transmitted and received between the other communication device and the relay device when the determination means determines that direct communication between the other communication device and the relay device is not possible; A communication device comprising:

2. 2. The communication device according to claim 1, wherein, after it is confirmed based on the signal received by the communication means that a request message has been sent from the other communication device to the relay device, if a response message from the relay device to the other communication device in response to the request message is not confirmed, the determination means determines that direct communication between the other communication device and the relay device is not possible.

3. 3. The communication device according to claim 2, wherein the determination means determines that direct communication between the other communication device and the relay device is not possible if the response message is not confirmed even after a predetermined time has elapsed since it was confirmed that the request message was sent from the other communication device to the relay device.

4. 3. The communication device according to claim 2, wherein when the determining means determines that direct communication between the other communication device and the relay device is not possible, the communication means transfers the request message to the relay device.

5. 3. The communication device according to claim 2, wherein when the determining means determines that direct communication between the other communication device and the relay device is not possible, the communication means transfers the response message to the other communication device.

6. 2. The communication device according to claim 1, wherein said communication means transfers messages transmitted and received between said relay device connected to said communication device and said other communication device.

7. 2. The communication device according to claim 1, wherein the messages transferred by the communication means include information exchange messages.

8. 8. The communication device according to claim 7, wherein the communication means transfers the information exchange message in one or both of a direction from the other communication device to the relay device and a direction from the relay device to the other communication device.

9. The communication device according to claim 1 , wherein the communication means transfers only the message for which the transfer is permitted by the other communication device or the relay device and which includes information indicating that the transfer is permitted.

10. 2. The communication device according to claim 1, wherein when it is determined that direct communication between the other communication device and the relay device has become possible based on a notification from the other communication device or the relay device, the communication means terminates the transfer.

11. 2. The communication device according to claim 1, wherein, when communication between said communication means and said relay device becomes impossible, said communication means terminates said transfer and notifies said other device of the termination of said transfer.

12. 2. The communication device according to claim 1, wherein said communication means does not forward the message if the number of hops of the message received from said other communication device or said relay device exceeds a specified number.

13. A communication device having a Sidelink communication function, a relay means for relaying communication between another communication device and a relay device having a Sidelink Relay function; receiving means for receiving a discovery message from the other communication device; a determination means for determining whether or not to transfer the discovery message from the other communication device to the relay device; Equipped with The discovery message includes information regarding the number of hops.

14. A control method for a communication device having a Sidelink communication function, comprising: a determining step of determining whether direct communication between the other communication device and the relay device having the Sidelink Relay function is possible; a forwarding step of forwarding a message transmitted and received between the other communication device and the relay device when it is determined in the determining step that direct communication between the other communication device and the relay device is not possible; A control method for a communication device, comprising:

15. A computer of a communication device having a Sidelink communication function, a determining step of determining whether direct communication between the other communication device and the relay device having the Sidelink Relay function is possible; a forwarding step of forwarding a message transmitted and received between the other communication device and the relay device when it is determined in the determining step that direct communication between the other communication device and the relay device is not possible; A program to execute.

16. a first communication device having a Sidelink communication function; a second communication device having a Sidelink communication function; A relay device having a Sidelink Relay function; A communication system comprising: the first communication device, a determining means for determining whether direct communication between the second communication device and the relay device is possible; a communication unit that transfers messages transmitted and received between the second communication device and the relay device when the determination means determines that direct communication between the second communication device and the relay device is not possible; A communication system comprising:

17. The communication system according to claim 16, wherein the relay device is disposed in association with an intersection, and the first communication device and the second communication device move together with a moving object passing through the intersection.

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