Communication device, communication system, control method, and program

Abstract

The communication device (200) having a sidelink communication function transmits a message that does not include any layer-2 ID for specifying a relay device having a function of relaying sidelink communication, and the destination of the message is a layer-2 ID different from the layer-2 ID of the relay device. The message includes information indicating a request to relay the message prior to the payload.

Description

Technical Field

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

[0002] In recent years, the development of the Long Term Evolution (LTE) and Fifth Generation (5G) (New Radio (NR)) specifications of the Third Generation Partnership Project (3GPP) (registered trademark) has been promoted. Among these specifications, a standard specification called side link communication (hereinafter referred to as "side link") has been formulated. This specification directly implements wireless communication between devices (user equipment (UE)) using an interface called PC5 without passing through a mobile communication network (core network or base station). In NR side link communication, a layer-2 (Layer-2) identifier (ID) (L2ID; identifier for side link communication) is used as an identifier indicating a sending source device or a sending destination device.

[0003] On the other hand, a system is increasingly being provided in which vehicles obtain information (position, speed, and vehicle control information) about vehicles near the vehicle by directly performing wireless communication with each other using side link communication, and assist a driver in safe driving when necessary.

[0004] In the technology discussed in Patent Document 1, a server acquires position information and speed information about a moving vehicle, and stores mapping information in which the current position of the vehicle and the layer-2 ID assigned to the vehicle are associated with each other. Then, the vehicles communicate with each other using the layer-2 ID based on the mapping information, and exchange information about the vehicles with each other.

[0005] In addition, in 3GPP (registered trademark), formulation of specifications for expanding a range in which a relay device (side link relay) can perform communication through side link communication is promoted.

[0006] Patent document 2 discusses a technology in which a terminal (UE) outside the coverage of a base station is connected to a relay device (side link relay) installed within the coverage of the base station through side link communication and can communicate with the base station.

[0007] Citation List

[0008] Patent Literature

[0009] PTL1: Japanese Patent Publication No. 2020-188405

[0010] PTL2: Japanese Patent Publication No. 2021-078140 Summary of the invention

[0011] Technical issues

[0012] However, the conventional technology does not discuss a method for relaying side link communication and thereby extending the range in which communication can be performed.

[0013] The present disclosure is directed to providing a communication device that relays side link communication and thereby can expand a range in which communication can be performed.

[0014] Solution to the problem

[0015] A communication device according to an embodiment of the present disclosure includes the following configuration: A communication device having a side link communication function includes a transmitting unit configured to transmit a message, the message not including a layer-2 identifier (ID) identifying a relay device having a function of relaying side link communication, the destination of the message being a layer-2 ID different from the layer-2 ID of the relay device, and the message including information indicating that the communication device expects relaying of the message before a payload.

[0016] Advantageous Effects of the Invention

[0017] According to the present disclosure, by relaying side link communication, the range in which communication can be performed can be expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] [ Figure 1 ] Figure 1 is a diagram illustrating an example of a configuration of a communication system according to the first exemplary embodiment of the present disclosure.

[0019] [ Figure 2 ] Figure 2 is a block diagram illustrating an example of a functional configuration of a roadside device according to the first exemplary embodiment.

[0020] [ Figure 3 ] Figure 3 is a block diagram illustrating an example of a functional configuration of a communication device composed of a vehicle according to the first exemplary embodiment.

[0021] [ Figure 4 ] Figure 4 is a block diagram illustrating an example of a hardware configuration of a roadside device according to the first exemplary embodiment.

[0022] [ Figure 5 ] Figure 5 is a diagram illustrating an example of a data structure of a discovery message including a relay request.

[0023] [ Fig. 6A ] Fig. 6A is a diagram illustrating an example of a data structure of a discovery response message indicating acceptance of a relay.

[0024] [ Figure 6B ] Figure 6Bis a diagram illustrating an example of a data structure of a discovery response message indicating acceptance of a relay.

[0025] [ Figure 7 ] Figure 7 is a diagram illustrating an example of a data structure of a communication message.

[0026] [ Figure 8 ] Figure 8 is a flowchart illustrating an example of processing of the roadside apparatus according to the first exemplary embodiment.

[0027] [ Fig. 9 ] Fig. 9 is a flowchart illustrating an example of processing of a communication device composed of a vehicle according to the first exemplary embodiment.

[0028] [ Fig.10 ] Fig.10 : is a diagram illustrating an example of a communication sequence between a roadside device and a vehicle-mounted terminal according to the first exemplary embodiment.

[0029] [ Fig.11 ] Fig.11 is a diagram illustrating a broadcast communication method.

[0030] [ Fig.12 ] Fig.12 It is a diagram illustrating a multicast (groupcast) communication method.

[0031] [ Fig.13 ] Fig.13 is a diagram illustrating a unicast communication method.

[0032] [ Fig.14 ] Fig.14 is a diagram illustrating an example of a data structure of a discovery message in a case where terminals (user equipments (UEs)) directly perform side link communication with each other.

[0033] [ Fig.15 ] Fig.15 is a flowchart illustrating an example of processing of a roadside apparatus according to the second exemplary embodiment.

[0034] [ Fig.16 ] Fig.16 is a flowchart illustrating an example of processing of a communication device composed of a vehicle according to the second exemplary embodiment. DETAILED DESCRIPTION

[0035] The exemplary embodiments will be described in detail below with reference to the accompanying drawings. The following exemplary embodiments do not limit the present invention according to the appended claims. Although multiple features are described in the exemplary embodiments, not all of the multiple features are necessary for the present invention, and multiple features can be optionally combined together. In addition, in the accompanying drawings, the same or similar components are designated by the same symbols and are not redundantly described.

[0036] <First Exemplary Embodiment>

[0037] Conventionally, in the case where terminals exchange information with each other through side link communication without via a relay device, terminals as user equipment (UE) cannot exchange information until each terminal as UE becomes directly connectable to a partner terminal as UE. For example, at a location where radio waves such as an intersection (particularly, a blind intersection) are blocked by the presence of buildings or many vehicles, the range in which communication can be performed may be narrowed because the arrival distance of the radio waves is short or there are many blind spots. Therefore, the range in which terminals (UE) can communicate with each other is expanded by installing a roadside device as a side link relay and having the roadside device relay side link communications with a destination being a specific layer-2 identifier (ID).

[0038] However, generally, a terminal cannot know the presence or absence of a roadside device at an intersection, and therefore cannot request relaying by specifying a roadside device. In addition, if the roadside device does not know the specific layer-2 ID for which the sidelink communication is to be relayed, the roadside device cannot determine whether a received sidelink message is to be relayed. The following exemplary embodiments solve such a problem.

[0039] Although the following exemplary embodiments illustrate a roadside device set near an intersection for the purpose of exchanging information related to traffic near the intersection, 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 any purpose. The relay device can perform relaying while the relay device is moved. The relay device can be installed at a location where the relay device cannot be connected to a mobile communication network, such as in an environment not covered by a base station. However, the relay device can be installed at a location where the relay device can be connected to a mobile communication network. The relay device can provide a relay function in a state where the relay device is connected to a mobile communication network. Multiple relay layer-2IDs corresponding to multiple purposes can be set for a single relay device.

[0040] [System Configuration]

[0041] Figure 11 is a diagram illustrating an example of a configuration of a communication system according to an exemplary embodiment of the present disclosure. The communication system includes a roadside device 10 installed near an intersection K and vehicles traveling near the intersection K (vehicles 20A, 20B, and 20C).

[0042] exist Figure 1 In the example of the roadside device 10 (an example of a communication device, a relay device, or a second communication device) is a device having a side link relay function (a function as a side link relay) and relaying side link communication through the side link relay function. Figure 1 In the example of , for example, the roadside device 10 is installed on the road side near the intersection K, and communicates with vehicles or pedestrians. It is particularly desirable that the roadside device 10 is installed near the blind intersection K.

[0043] exist Figure 1 , vehicles 20A, 20B, and 20C indicate vehicles traveling on a road near intersection K. Each of vehicles 20A, 20B, and 20C has a function of a sidelink communication device (user equipment (UE)) and can perform sidelink communication with an external communication device. Each of vehicles 20A, 20B, and 20C can obtain information from outside the vehicle through sidelink communication, display the information, and control the car based on the information. In addition, each of vehicles 20A, 20B, and 20C can obtain information about the vehicle itself through sidelink communication and notify the external device of the information.

[0044] The roadside device 10 is configured to resend a message having the same content as that of the relay request message or a message obtained by changing the relay request message according to the content of the message if the roadside device 10 receives a relay request message from any one of the side link communication devices (UE) including the vehicles 20A, 20B, and 20C. Figure 1 In FIG. 1 , area 10A indicates a range in which the roadside device 10 can communicate.

[0045] The roadside device 10 is assigned layer-2ID "RRR" as an identifier for side link communication. Vehicles 10A, 10B and 10C are respectively assigned layer-2ID "AAA", layer-2ID "BBB" and layer-2ID "CCC" as identifiers for side link communication. In this exemplary embodiment, in order to exchange information through side link communication at the intersection, intersection K is also assigned layer-2ID "KKK" as an identifier for side link communication. The layer-2ID assigned to intersection K is any layer-2ID. For example, intersection K can be assigned layer-2ID "RRR". Although in this exemplary embodiment, the vehicle is assumed to be a UE compatible with side link communication, the UE compatible with side link communication is not limited to this. For example, a UE compatible with side link communication can be a UE owned by a user such as a tablet terminal or a smart watch, or a terminal worn by a user such as a head-mounted display or a wearable terminal. The UE compatible with side link communication can also be a car navigation device installed in the vehicle.

[0046] [Functional configuration of the device]

[0047] Next, the functional configuration of the device according to the present exemplary embodiment is described. The configuration of the functional blocks described below is only an example. Some (in some cases all) of the described functional blocks can be replaced with other functional blocks with similar functions, or some of the functional blocks can be omitted, or additional functional blocks can be added. The single functional block shown in the following description can be divided into multiple functional blocks, or the multiple functional blocks shown in the following description can be integrated into a single functional block.

[0048] Figure 2 1 is a block diagram illustrating an example of a functional configuration of a roadside device according to the present exemplary embodiment. Figure 2 As shown in , the roadside device 10 includes a control unit 101 (an example of a setting unit), a storage unit 102, a communication processing unit 103, a relay processing unit 104, a wireless communication unit 105 (an example of a communication unit or a second communication unit) and a wired communication unit 106.

[0049] The control unit 101 controls the operation of the roadside device 10 according to the program stored in the storage unit 102. For example, the control unit 101 includes one or more processors such as a central processing unit (CPU) and a microprocessor unit (MPU) and controls the device by executing a computer program loaded into a random access memory (RAM) as the storage unit 102. The control performed by the device described with reference to the flowcharts and sequence diagrams described below is realized by the cooperation of the processors such as the CPU and the MPU of the control unit 101 and the hardware of the communication unit 105.

[0050] The storage unit 102 is a RAM and a nonvolatile storage area that stores information used for control by the control unit 101, programs related to wireless or wired communication, and other information. The control program stored in the nonvolatile storage area is loaded into the RAM and executed by a processor included in the control unit 101. As described above, the control unit 101 and the storage unit 102 function as a so-called computer.

[0051] The communication processing unit 103 analyzes the message about the side link communication. For example, the communication processing unit 103 analyzes the received message about the side link communication, thereby determining the content of the message. Then, the communication processing unit 103 generates the destination or sender information using the layer-2 ID, or generates the content of the message about the side link communication to be transmitted.

[0052] The relay processing unit 104 performs processing on the relay of the side link communication sent from another communication device. For example, the relay processing unit 104 analyzes the layer-2 ID about the destination, the sender and the relay, the content of the setting information about the relay, and the payload of the message, thereby determining the operation about the relay. Functions equivalent to the communication processing unit 103 and the relay processing unit 104 can be implemented as software modules implemented by the control unit 101.

[0053] The wireless communication unit 105 transmits information to and receives information from an external wireless device through side link 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 from the external device 31. For example, the roadside device 10 can acquire information from the external device 31 via the wired communication unit 106, cause the communication processing unit 103 to generate a side link message in response to the acquired information, and transmit the side link message via the wireless communication unit 105.

[0054] Figure 3 20A is a block diagram illustrating an example of a functional configuration of a communication device composed of each of vehicles (vehicles 20A, 20B, and 20C) according to the present exemplary embodiment.

[0055] like Figure 3 As shown in the figure, the communication device 200 (communication device or first communication device) includes a control unit 201, a storage unit 202, a communication processing unit 203, a wireless communication unit 204 (an example of a sending unit or a first communication unit), a vehicle information acquisition unit 205, an operation unit 206 and a display unit 207.

[0056] The control unit 201 controls the operation of the communication device 200 according to the program stored in the storage unit 202. The control unit 201 may be configured as a part of the control device regarding the operation of the vehicle other than the operation of the communication device 200, and may be configured to cooperate with the control device to perform various types of processing.

[0057] The storage unit 202 stores information used by the control unit 201 for control and information related to wireless or wired communication.

[0058] The communication processing unit 203 analyzes the message regarding the side link communication. For example, the communication processing unit 203 analyzes the content of the message regarding the side link communication received by the wireless communication unit 204. If the content of the message indicates communication for the device, the communication processing unit 203 performs processing according to the content of the message and sends a reply when necessary.

[0059] The wireless communication unit 204 transmits and receives information to and from an external wireless device through side link communication via the antenna 204a. The wireless communication unit 204 may also be compatible with communication methods other than the side link communication.

[0060] The vehicle information acquisition unit 205 acquires vehicle information about the vehicle. The vehicle information includes position information about the vehicle, information to be notified to another vehicle, and other information.

[0061] The operation unit 206 receives an operation related to the communication device 200 of the vehicle.

[0062] The display unit 207 displays information acquired from the outside by the vehicle through wireless communication, information about operations on the operation unit 206, and vehicle information acquired via the vehicle information acquisition unit 205. The display unit 207 may be configured as a part of a display device that displays information about the vehicle in addition to information related to the communication device 200.

[0063] [Hardware Configuration]

[0064] Figure 4 is a block diagram illustrating an example of a hardware configuration of a roadside device.

[0065] like Figure 4 As shown in FIG. 1 , the roadside device 10 includes a central processing unit (CPU) 11, a read only memory (ROM) 12, a random access memory (RAM) 13, and an auxiliary storage device 14. The roadside device 10 also includes a communication interface (I / F) 15 and a device interface (I / F) 16.

[0066] The CPU 11 controls the entire roadside device 10 using the computer program and data stored in the ROM 12 or the RAM 13, thereby realizing Figure 2 1 and 10. In the roadside device 10, one or more dedicated hardware different from the CPU 11 may be provided, and the dedicated hardware may perform at least a part of the processing of the CPU 11. Examples of the dedicated hardware include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and a digital signal processor (DSP).

[0067] The ROM 12 stores programs that do not need to be changed. The RAM 13 temporarily stores programs and data supplied from the auxiliary storage device 14 and data supplied from the outside via the communication I / F 15. For example, the auxiliary storage device 14 includes a hard disk drive and stores various data.

[0068] The communication I / F 15 is used for communication with an external device. For example, the wireless communication unit 105 ( Figure 2 ) performs wireless communication with an external device using the communication I / F 15. In this case, for example, the roadside device 10 can also determine the situation based on information from an external device 31 connected to the Internet 30, and notify the vehicle or pedestrian of the required information through the side link communication based on the determination.

[0069] Various devices may be connected to the device I / F 16. For example, a display device and an input device for a server administrator to confirm information managed by the roadside device 10, and a sensor and a camera mounted on a housing of the roadside device 10 are connected to the device I / F 16. In this case, for example, the roadside device 10 may also determine the situation of a vehicle or pedestrian passing through the road based on information from the camera or the sensor, and notify the vehicle or pedestrian of necessary information through the side link communication based on the determination.

[0070] The communication device 200 composed of each of the vehicles 20A, 20B, and 20C can also be implemented by a similar hardware configuration. For example, in the case where the communication device composed of each of the vehicles 20A, 20B, and 20C has a Figure 4 In the case of the hardware configuration shown in , an imaging unit including 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, each of the vehicles 20A, 20B, and 20C can also determine the situation of another vehicle or pedestrian passing through the road based on the information from the imaging unit or the sensor, and based on the determination, notify the other vehicle or pedestrian of the required information through the side link communication. In the present exemplary embodiment, each of the vehicles 20A, 20B, and 20C sends the required information to the roadside device 10, so that the required information can be notified to the other vehicle or pedestrian through the side link communication via the relay of the roadside device 10.

[0071] More specifically, for example, the content of the communication between the roadside device 10 and the communication device 200 and another device through the side link communication is the surrounding traffic conditions detected based on the information about the sensor or camera, the reminder information based on the future prediction, the sensor data and the camera video. Through the sending and receiving of such information, each vehicle can not only grasp the presence or absence of oncoming vehicles at the junction such as the intersection K, but also grasp the information about the oncoming vehicle based on the position information and speed information about the oncoming vehicle. Therefore, the vehicle can assist the driver in driving. Since information can be exchanged with low latency, the vehicle can also handle the control of the merged order and the control of the brakes in an emergency. In addition, the vehicle receives road traffic information (such as accidents, traffic jams, emergency vehicles, construction vehicles or abnormal driving vehicles) detected by the roadside device 10 or another vehicle through the side link communication, and knows this information in advance, so that it can travel more safely.

[0072] A pedestrian or bicycle having a terminal (UE) including similar functions can know in advance the dangerous movement of vehicles near the pedestrian or bicycle, and thus can effectively reduce the possibility of the pedestrian or bicycle being involved in an accident.

[0073] [Processing example]

[0074] In the present exemplary embodiment, each of the vehicles (vehicles 20A, 20B, and 20C) transmits a discovery message including a relay request (relay request message) 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. The vehicle receives the discovery response message, thereby recognizing that the vehicle is a relay target of the roadside device 10. The vehicles as relay targets can perform communication with each other in which the roadside device 10 is a relay device.

[0075] Even a vehicle that is not a relay target can perform direct side link communication with another vehicle, that is, side link communication not via the roadside device 10. According to the present exemplary embodiment, the vehicle becomes a relay target, and thus can perform side link communication via the roadside device 10 with a vehicle or pedestrian that cannot perform direct side link communication due to reasons such as blocking of radio waves.

[0076] Figure 5 5G ProSe Direct Discovery may be used to send a discovery message including a relay request. A Soliciation message for 5G ProSe UE to Network Relay Discovery may be used to send. ProSe is an abbreviation for Proximity-Based Service.

[0077] exist Figure 5 In "Source Layer-2ID", the layer-2ID indicating the transmission source of the information is stored. For example, if the transmission source is vehicle 20A, the layer-2ID "AAA" is stored. If the transmission source is vehicle 20B, the layer-2ID "BBB" is stored. If the transmission source is vehicle 20C, the layer-2ID "CCC" is stored.

[0078] In the “destination layer-2 ID”, the layer-2 ID indicating the destination of the information, that is, the layer-2 ID “KKK” assigned to the intersection K is stored.

[0079] Next, the "Relay Mode" and "Validity Period" which are data fields newly added to the Soliciation message to specify a relay request are described. In the "Relay Mode", information about a relay request for relay-side link communication is stored. For example, a code indicating a relay request for relay-side link communication is stored in the "Relay Mode", so that the roadside device 10 can recognize that the transmission source has made a relay request. For example, 1 means that the transmission source expects a relay request. 0 means that the transmission source does not expect a relay request.

[0080] In “Validity period”, information on the duration of the relay operation for relaying the side link communication, such as the validity period or the validity number of times, is stored.

[0081] In "Frame Type", information indicating the type of this message is stored.

[0082] In the "frame payload", the main body of information to be exchanged between devices using this message is stored.

[0083] Fig. 6A and Figure 6B is a diagram illustrating an example of a data structure of a discovery response message indicating acceptance of a relay.

[0084] exist Fig. 6A In the example of , in "Source Layer-2 ID", the layer-2 ID "KKK" of the intersection point K is stored. In "Frame Payload", information indicating whether relaying can be performed is stored.

[0085] Figure 6B The example of illustrates the data structure of the response message in the case where the roadside device 10 stores the layer-2 ID “KKK” of the intersection K in both the “source layer-2 ID” and the “relay layer-2 ID”.

[0086] Figure 7 20A, 20B, and 20C are diagrams illustrating an example of a data structure of a communication message when vehicles (vehicles 20A, 20B, and 20C) perform side link communication with each other via the roadside device 10 after the roadside device 10 starts a relay operation.

[0087] exist Figure 7 In the "source layer-2ID", the layer-2ID indicating the transmission source of the information is stored. In the "destination layer-2ID", the layer-2ID indicating the destination of the information is stored.

[0088] In "Relay Layer-2ID", a layer-2ID indicating a device having a side link relay function for relaying a message is stored. That is, in the case of performing communication via the roadside device 10, a message is transmitted by storing the layer-2ID "KKK" of the intersection K in "Relay Layer-2ID".

[0089] In “Relay direction”, information indicating which of the directions of the terminal (UE) and the sidelink relay (ie, the roadside device 10 ) the message is directed to is stored.

[0090] In “Relay direction”, information indicating which of the directions of the terminal (UE) and the roadside device 10 (sidelink relay) the message is directed to is stored.

[0091] In the “frame payload”, the main body of information to be exchanged between the terminals (UEs)—that is, the vehicles (the vehicle 20A, the vehicle 20B, and the vehicle 20C)—using this message is stored.

[0092] Next, the processing of each of the roadside device 10 and the vehicles (the vehicles 20A, 20B, and 20C) is described.

[0093] Figure 8 is a flowchart illustrating an example of processing of a roadside device.

[0094] exist Figure 8 In step S102, the control unit 101 ( Figure 2 ) is executed when the roadside device 10 is installed to set parameters regarding the side link relay function in the roadside device 10. For example, through this processing, the layer-2ID "KKK" assigned to the intersection K is stored in the storage unit 102. This enables the roadside device 10 to relay communications destined for the layer-2ID "KKK". In the present exemplary embodiment, the layer-2ID "KKK" corresponds to the relay layer-2ID.

[0095] In step S104, the control unit 101 determines whether a message regarding the side link communication is received via the wireless communication unit 105. The control unit 101 waits until the determination is affirmative. Then, the process proceeds to step S106.

[0096] In step S106, the control unit 101 determines via the communication processing unit 103 whether the message confirmed received in step S104 is a discovery message (relay request message) including a relay request for relay by the side link relay function ( Figure 5 ). If the determination of the control unit 101 is affirmative, the process proceeds to step S108. If the determination is negative, the process proceeds to step S112.

[0097] In step S108, the control unit 101 sets the side link relay function. In this step, the control unit 101 sets the layer-2 ID indicating the transmission source of the discovery message including the relay request confirmed in step S106 as the relay target of the side link communication via the relay processing unit 104. Based on the exchange of detailed information, the communication device 200 of the vehicle also sets parameters regarding the side link relay function. This enables the roadside device 10 to relay communications from the transmission source of the discovery message including the relay request. The control unit 101 also saves the validity period information specified by the discovery message. The setting content and validity period information of the side link relay function are stored in the storage unit 102.

[0098] In step S110, the control unit 101 returns a discovery response message ( ) indicating acceptance of the relay to the transmission source of the discovery message via the wireless communication unit 105. Fig. 6A or Figure 6B Then, the process proceeds to step S104. The return destination of the discovery response message is the transmission source indicated by the discovery message ( Figure 5 ). The discovery response message includes the layer-2 ID “RRR” of the roadside device 10, so that the transmission source of the discovery message can know the layer-2 ID “RRR”.

[0099] In the case where the relay cannot be accepted for some reason, the process of step S108 may be omitted, and a message indicating that the relay cannot be accepted may be returned to the transmission source of the discovery message.

[0100] As described above, the connection between the transmission 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 further described below.

[0101] On the other hand, in step S112, the control unit 101 determines via the communication processing unit 103 whether the validity period of the relay in the message confirmed to be received in step S104 has expired. In this determination, the validity period information stored in the storage unit 102 in step S108 is used. If the determination of the control unit 101 is affirmative, the process proceeds to step S116. If the determination is negative, the process proceeds to step S114.

[0102] In step S116, the control unit 101 stops the relay processing regarding the transmission source of the message whose reception is confirmed in step S104. The setting of the parameters regarding the side link relay function is canceled (step S108).

[0103] In step S118, the control unit 101 sends a relay end completion message indicating to stop the relay processing for the relay message to the vehicle (vehicle 20A, 20B or 20C) that has made the relay request. Then, the process proceeds to step S104. The transmission destination of the relay end completion message is the transmission source included in the message confirmed to be received in step S104.

[0104] On the other hand, in step S114, the control unit 101 determines via the communication processing unit 103 whether the message confirmed received in step S104 is a message requesting to end the relay (relay end request message). If the determination of the control unit 101 is positive, the process proceeds to step S116. If the determination is negative, the process proceeds to step S120. The relay end request message may include information about the period until the end of the relay operation. In this case, the process of step S116 is performed at the timing specified by the relay end request message.

[0105] In step S120, the control unit 101 determines whether the transmission source indicated by the message confirmed received in step S104 is the setting target of the side link relay function in step S108. If the determination of the control unit 101 is affirmative, the process proceeds to step S122. If the determination is negative, the process proceeds to step S104.

[0106] In step S122 , the control unit 101 rewrites necessary information such as a direction in the message confirmed received in step S104 via the relay processing unit 104 , thereby creating a message as a target of transmission (relay).

[0107] If it is confirmed in step S104 that the received message corresponds to the message that has been sent in step S124, the processing of steps S122 and S124 can be omitted. That is, if the same message requested to be relayed is received multiple times, the processing of steps S122 and S124 can be omitted. This can prevent the same message from being relayed multiple times.

[0108] In step S124, the control unit 101 causes the wireless communication unit 104 to send (transmit) the message generated in step S122 as a side link communication message. Then, the processing proceeds to step S104. The sending destination (transmission destination) in step S124 may be limited to the terminal (UE) that is the setting target of the side link relay function in step S108, or may not be limited to this. Therefore, a message such as an information exchange message confirmed to be received in step S104 is relayed via the roadside device 10. The information exchange message is a message for exchanging information between vehicles, and includes vehicle information such as the speed of the vehicle, the acceleration of the vehicle, and the opening of the accelerator.

[0109] If the determination in step S120 is negative, a message indicating that the message is not relayed may be returned to the transmission source indicated by the message whose reception is confirmed in step S104.

[0110] Fig. 9 20A is a flowchart illustrating an example of processing of a communication device composed of each of the vehicles (the vehicles 20A, 20B, and 20C). Fig. 9 The example of FIG. 1 shows that the vehicle (vehicle 20A, 20B or 20C) passes through the intersection K ( Figure 1 ) situation.

[0111] exist Fig. 9 In step S202, based on the information acquired by the vehicle information acquisition unit 205, the control unit 201 ( Figure 3 ) determines whether the vehicle (vehicle 20A, 20B or 20C) is approaching the intersection K. The control unit 201 waits until the determination is affirmative. Then, the process proceeds to step S204.

[0112] In step S202, for example, the control unit 201 compares the position information obtained by the global positioning system (GPS) device installed on the vehicle with the intersection information stored in the storage unit 102. Based on the result of comparing these information, the control unit 201 can recognize that the vehicle is approaching the intersection K. In this case, in the intersection information, the coordinates of the intersection including the intersection K and the layer-2ID assigned to the intersection (for example, the layer-2ID "KKK" assigned to the intersection K) are stored in association with each other. The control unit 201 compares the position information (coordinates) acquired in real time by the vehicle information acquisition unit 205 with the coordinates of the intersection indicated by the intersection information, so that it can be recognized that the vehicle is approaching a specific intersection.

[0113] In step S204 , the control unit 201 performs communication preparation processing so that side link communication can be operated between the vehicle and layer-2 ID “KKK” assigned to intersection K. For example, in step S204 , layer-2 ID “KKK” is registered in the storage unit 202 as a communication partner.

[0114] In step S206, the control unit 201 determines whether the roadside device 10 has been requested to perform relay using the layer-2 ID "KKK" assigned to the intersection K (step S208). If the determination of the control unit 201 is affirmative, the process proceeds to step S210. If the determination is negative, the process proceeds to step S208.

[0115] In step S208, the control unit 201 transmits a discovery message as a relay request message ( Figure 5 ).

[0116] In step S210, based on the information acquired by the vehicle information acquisition unit 205, the control unit 201 determines whether an event to be notified via relaying by the roadside device 10 occurs. If the determination of the control unit 201 is affirmative, the process proceeds to step S212. If the determination is negative, the process proceeds to step S220.

[0117] In step S212, the control unit 201 determines whether a discovery response message ( Fig. 6A or Figure 6B ), and furthermore whether parameters regarding the side link relay function have been set in the communication device 200. The discovery response message indicating acceptance of the relay is in step S110 ( Figure 8 ) is a message sent from the roadside device 10. If the determination of the control unit 201 in step S212 is positive, the process proceeds to step S214. If the determination is negative, the process proceeds to step S220. In a predetermined case, the control unit 201 may repeat the transmission of the discovery message of the relay request until the discovery response message is received. For example, if even after the self-control unit 201 transmits the discovery message ( Figure 5 If the discovery response message is not received after a predetermined time has passed since (step S208), the control unit 201 may repeat sending the discovery message of the relay request.

[0118] In step S214, the control unit 201 transmits a communication message ( ) related to the event that has occurred to the terminal as the relay target via the roadside device 10 (side link relay). Figure 7 ). In the "frame payload" ( Figure 7) describes the occurrence of a specific event and information related to the event that has occurred.

[0119] In step S220, based on the information acquired by the vehicle information acquisition unit 205, the control unit 201 determines whether the vehicle leaves the intersection K. If the determination of the control unit 201 is affirmative, the process proceeds to step S222. If the determination is negative, the process proceeds to step S224. In step S220, for example, based on the position information obtained by the GPS device mounted on the vehicle and the intersection information stored in the storage unit 102, the control unit 201 can recognize that the vehicle leaves the intersection K.

[0120] In step S222, the control unit 201 sends a message (relay end request message) to the roadside device 10 via the communication processing unit 203 requesting the roadside device 10 to end the relay. The relay end request message is sent in step S114 ( Figure 8 ) is received by the roadside device 10. For example, a discovery message ( Figure 5 ) has the same format (data structure) as the format of the relay end request message. In this case, Figure 5 The values ​​of "relay mode" and "validity period" shown in are set to predetermined values ​​to indicate the relay end request message.

[0121] On the other hand, in step S224, the control unit 201 determines whether a side link communication message transmitted from another terminal (UE) is received via the wireless communication unit 204. If the determination of the control unit 201 is affirmative, the process proceeds to step S228. If the determination is negative, the process proceeds to step S206. The side link communication message that is the target of determination in step S224 is not limited to the message via the roadside device 10, and may be a side link communication message directly transmitted from another terminal (UE) to the vehicle.

[0122] In step S228 , according to the side link communication message whose reception is confirmed in step S224 , the control unit 201 sends the required side link communication message to the roadside device 10 .

[0123] Fig.10 is a diagram illustrating an example of a communication sequence between a roadside device and a vehicle-mounted terminal. Fig.10 The step numbers in Figure 8 and Fig. 9 The processing shown in corresponds to .

[0124] like Fig.10As shown in , if the roadside device 10 is installed at the intersection K, a side link relay function for relaying a side link message of layer-2 ID "KKK" sent to the intersection KK is set in the roadside device 10. After the side link relay function is set, the roadside device 10 starts (step S102).

[0125] If the vehicle 20A approaches an intersection, the communication device 200 of the vehicle 20A is set so that the communication device 200 of the vehicle 20A can send and receive a side link 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 of layer-2 ID “KKK” whose destination is the intersection K to the roadside device 10 (step S208 ).

[0127] The roadside device 10 having received the discovery message makes settings regarding the use of the side link relay function by exchanging information with the vehicle 20A. Then, the roadside device 10 transmits a message indicating acceptance of the relay as a reply to the discovery message (step S110).

[0128] Similarly, if the vehicle 20B approaches the intersection K, the vehicle 20B prepares for communication with the layer-2 ID of the intersection K (step S204), and transmits a discovery message including a relay request whose destination is the layer-2 ID of the intersection K (step SS208). If the roadside device 101 receives the discovery message, the roadside device 101 makes settings regarding the use of the side link relay function, and transmits a message indicating acceptance of the relay (steps S108 to S110).

[0129] Through the above operation, the vehicles 20A and 20B can perform communication with each other via the roadside device 10 with the layer-2 ID “KKK” assigned to the intersection K.

[0130] If an event (notification event) occurs in the vehicle 20B in this state, the vehicle 20B transmits information (step S214). As a result, the information is relayed to the vehicle 10A by the side link relay function of the roadside device 10 (step S124). In the case where the communication method applied is multicast, the information also reaches the vehicle 20B. However, based on the transmission source of the information, the vehicle 220B determines the information as information transmitted from the vehicle 20B itself, and discards or ignores the information. The communication method applied will be described below.

[0131] Furthermore, if the vehicle 20C approaches the intersection K, the processes of steps S204, S208 and S110 are performed by the roadside device 10 and the communication device 200 of the vehicle 20C. Thus, the vehicles 20A, 20B and 20C can perform communication with each other via the roadside device 10 with the layer-2 ID “KKK” assigned to the intersection K.

[0132] If an event (notification event) occurs in the vehicle 20C in this state, the vehicle 20C transmits information (step S214). As a result, the message is relayed to the vehicles 20A and 20B by the side link relay function of the roadside device 10 (step S124). In the case where the communication method applied is multicast, the information also reaches the vehicle 20B (step S124). However, the vehicle 20B determines the information as information transmitted from the vehicle 20B itself and discards or ignores the information.

[0133] Similarly, if an event (notification event) occurs in the vehicle 20A in this state, the information transmitted from the vehicle 20A is relayed to the vehicles 20B and 20C by the side link relay function of the roadside device 10 (step S124). In the case where the communication method applied is multicast, the information also reaches the vehicle 20A (step S124). However, the vehicle 20A determines the information as information transmitted from the vehicle 20A itself and discards or ignores the information.

[0134] In the case where relaying by the roadside device 10 becomes unnecessary, such as when the vehicle 20A leaves the intersection K, the vehicle 20A sends a relay end request message to the roadside device 10 (step S222). If the roadside device 10 that has received the relay end request message accepts the end of relaying, the roadside device 10 sends a relay end completion message to the vehicle 20A (step S118). Stopping and ending of the relay operation by the side link relay function of the roadside device 10 is performed by determining the situation by the roadside device 10.

[0135] In the present exemplary embodiment, the layer-2ID "RRR" as an identifier assigned to the roadside device 10 can also be appropriately used. By using the layer-2ID "RRR" as the destination, it can be recognized that the type and function of the communication message are different from those in the case of using an identifier for relay. For example, the terminal (EU) and the roadside device 10 that have received the communication message can recognize that the received communication message is not a communication message about the exchange of information at the intersection KKK, or a communication message that does not request the roadside device 10 to perform relaying.

[0136] Next, the side link communication method is described.

[0137] Fig.11 is a diagram illustrating a broadcast communication method. Fig.12It is a diagram illustrating a multicast (groupcast) communication method. Fig.13 is a diagram illustrating a unicast communication method.

[0138] exist Fig.11 In the case of the "broadcast communication method" shown in , the already shared layer-2 ID is set as the transmission destination and the reception destination in the devices on the transmission side and the reception side, respectively. Fig.12 and Fig.13 In the case of the "multicast (groupcast) communication method" and "unicast communication method" shown in , the device on the sending side sends a relay request to the already shared layer-2 ID ( Fig.12 and Fig.13 In response to this, the receiving device with the already shared layer-2 ID responds to the relay request ( Fig.12 and Fig.13 'Connection Request Response' in the ), so that devices can communicate data with each other.

[0139] Although the present exemplary embodiment is applicable to any of the communication methods, Figure 8 An example of using the “multicast communication method” in the processing of step S122 in FIG.

[0140] Incidentally, as described above, terminals (UE) such as vehicles 20A, 20B, and 20C can directly perform side link communications with each other without using a relay through the roadside device 10. That is, direct side link communications coexist with communications using a relay through the roadside device 10. Direct side link communications and communications using a relay through the roadside device 10 coexist. Therefore, the same terminal (UE) can receive messages with substantially the same content multiple times. However, processing in this case is left to the terminal (UE) that has already received the message. For example, messages with substantially the same content received from the second time onwards can be discarded or ignored.

[0141] Fig.14 is a diagram illustrating an example of a data structure of a discovery message in a case where terminals (UEs) directly perform side link communication with each other.

[0142] like Fig.14 As shown in , in the case where each of the terminals (UE) such as the vehicles 20A, 20B, and 220C searches for a terminal (UE) that does not have a relay function, the discovery message to be transmitted does not include information indicating a relay request.

[0143] <Second Exemplary Embodiment>

[0144] Next, refer to Fig.15 and Fig.16, illustrating an example in which the broadcast communication method is applied to the transmission of messages from the vehicle and the roadside device 10. The following describes portions different from the first exemplary embodiment.

[0145] Fig.15 is a flowchart illustrating an example of processing of a roadside device. Fig.15 In, with Figure 8 The corresponding processing in the Figure 8 The step number in the same step number is specified.

[0146] exist Fig.15 In step S102, the control unit 101 ( Figure 2 ) performs processing for setting parameters regarding the side link relay function in the roadside device 10 when the roadside device 10 is installed. For example, through this processing, the layer-2 ID "KKK" assigned to the intersection K is stored in the storage unit 102. This enables the roadside device 10 to relay communications destined for the layer-2 ID "KKK".

[0147] In step S104, the control unit 101 determines whether a message regarding a predetermined side link communication is received via the wireless communication unit 105. The control unit 101 waits until the determination is affirmative. Then, the process proceeds to step S1077.

[0148] In step S107, the control unit 101 determines, via the communication processing unit 103, the message ( Figure 7 ) is a relay request message for relay by the side link relay function. If the determination of the control unit 101 is affirmative, the process proceeds to step S112. If the determination is negative, the process proceeds to step S104. In step S107, the control unit 101 determines the destination ( Figure 7 That is, if the destination of the message is the layer-2 ID "KKK", the control unit 101 determines that the message is a relay request message.

[0149] On the other hand, in step S112, the control unit 101 determines via the communication processing unit 103 whether the validity period of the relay in the message confirmed to be received in step S104 has expired. In this determination, the validity period information stored in the storage unit 102 in step S108 is used. If the determination of the control unit 101 is affirmative, the process proceeds to step S116. If the determination is negative, the process proceeds to step S122.

[0150] In step S116 , the control unit 101 stops the relay processing regarding the transmission source of the message the reception of which is confirmed in step S104 .

[0151] In step S118, the control unit 101 transmits a relay end message instructing to stop the relay process for relaying the message to the vehicle (vehicle 20A, 20B or 20C) that has made the relay request.Then, the process proceeds to step S104.

[0152] In step S122, the control unit 101 rewrites necessary information such as a direction in the message whose reception is confirmed in step S104 via the relay processing unit 104, thereby creating a message as a transmission (relay) destination.

[0153] In step S124, the control unit 101 transmits (relays) the message generated in step S122 as a side link communication message to the transmission destination indicated by the message confirmed to be received in step S104 via the wireless communication unit 105. Then, the process proceeds to step S104. Therefore, the message confirmed to be received in step S104 is relayed to the transmission destination indicated by the message via the roadside device 10.

[0154] Fig.16 20A is a flowchart illustrating an example of processing of a communication device composed of each of the vehicles (the vehicles 20A, 20B, and 20C). Fig.16 The example of FIG. 1 shows that the vehicle (vehicle 20A, 20B or 20C) passes through the intersection K ( Figure 1 ) situation. Fig.16 In, with Figure 8 The corresponding processing in the Fig. 9 The step number in the same step number is specified.

[0155] exist Fig.16 In step S202, based on the information acquired by the vehicle information acquisition unit 205, the control unit 201 ( Figure 3 ) determines whether the vehicle (vehicle 20A, 20B or 20C) is approaching the intersection K. The control unit 201 waits until the determination is affirmative. Then, the process proceeds to step S204.

[0156] In step S204 , the control unit 201 performs communication preparation processing so that side link communication can be operated between the vehicle and layer-2 ID “KKK” assigned to intersection K. For example, in step S204 , layer-2 ID “KKK” is registered in the storage unit 202 as a communication partner.

[0157] In step S210, based on the information acquired by the vehicle information acquisition unit 205, the control unit 201 determines whether an event to be notified via relaying by the roadside device 10 has occurred. If the determination of the control unit 201 is affirmative, the process proceeds to step S214. If the determination is negative, the process proceeds to step S220.

[0158] In step S214, the control unit 201 transmits a communication message ( ) related to the event that has occurred to the terminal as the relay target via the roadside device 10 (side link relay). Figure 7 ). In the "frame payload" ( Figure 7 ) describes the occurrence of a specific event and information related to the event that has occurred.

[0159] In step S220 , based on the information acquired by the vehicle information acquisition unit 205 , the control unit 201 determines whether the vehicle has left the intersection K. If the determination of the control unit 201 is affirmative, the process proceeds to step S202 . If the determination is negative, the process proceeds to step S224 .

[0160] In step S224, the control unit 201 determines whether the side link communication message transmitted from another terminal (UE) is received via the wireless communication unit 204. If the determination of the control unit 201 is positive, the process proceeds to step S228. If the determination is negative, the process proceeds to step S210. The side link communication message as the determination target in step S224 is not limited to the message via the roadside device 10, and may be a side link communication message directly transmitted from another terminal (UE) to the vehicle.

[0161] In step S228, according to the side link communication message confirmed to be received in step S224, the control unit 201 sends the required side link communication message to the roadside device 10. The destination of the side link communication message ( Figure 7 The “destination layer-2 ID” in the destination layer-2 ID is layer-2 ID “KKK”. Therefore, if the roadside device 10 receives the side link communication message, the determination in step S107 is affirmative. That is, the roadside device 10 (control unit 101) determines that the side link communication message is a relay request message.

[0162] As described above, according to the above exemplary embodiment, each of the terminals (vehicles 20A, 20B and 20C; UE) uses a relay request message to request relay of a side link communication whose destination is a specific layer-2ID "KKK" assigned to intersection K. Then, the roadside device 10 can perform relaying based on the request for relaying. Therefore, even if the existence or non-existence of a roadside device 10 (side link relay) capable of performing relaying is unknown, the terminal (UE) can make a relay request. In addition, the terminal (UE) can know the layer-2ID of the relay device from the response to the relay request message. Based on the destination information included in the relay request message, the roadside device 10 can also know the specific layer-2ID to perform relaying. This enables the roadside device 10 to relay side link messages whose destination is layer-2ID "KKK".

[0163] Therefore, the roadside device 10 relays the side link communication, so that the range in which communication can be performed can be expanded.

[0164] Next, the relay of a message whose destination is a layer-2 ID in a unicast manner is also briefly described. In this case, a configuration can be adopted in which the roadside device 10 relays the exchange of the discovery of the relay request set. Then, using the execution of the relay as a trigger, the roadside device 10 stores information indicating that the exchange of various information exchanged between the devices from this point onwards is to be relayed. Finally, the roadside device 10 relays the exchange of various information exchanged between the devices. Through the above-mentioned processing, the range in which communication can be performed through unicast communication can also be expanded.

[0165] <Other embodiments>

[0166] The present disclosure may also be implemented by supplying a program for implementing one or more functions of the above exemplary embodiments to a system or device via a network or storage medium, and causing one or more processors of a computer of the system or device to read and execute the program. The present disclosure may also be implemented by a circuit (e.g., ASIC) for implementing one or more functions.

[0167] For example, in the above exemplary embodiments, the wireless access method is New Radio (NR), which is a fifth generation (5G) wireless access method, but is not limited thereto. That is, another access method such as Long Term Evolution (LTE), sixth generation (6G) or later, or WiFi may be at least partially applied to the wireless access method.

[0168] The sidelink communication is not limited to discovery messages. For example, the sidelink communication may be a message about direct communication or a message about vehicle-to-everything (V2X) communication.

[0169] The invention is not limited to the above-described exemplary embodiments, and may be changed and modified in various ways without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

[0170] The present invention is not limited to the above exemplary embodiments, and may be changed and modified in various ways without departing from the spirit and scope of the present invention. Therefore, the following claims are attached to disclose the scope of the present invention.

[0171] This application claims priority from Japanese Patent Application No. 2022-145755 filed on September 14, 2022, the entire contents of which are incorporated herein by reference.

[0172] Reference Character Description

[0173] 10 Roadside Devices (Side Link Relay)

[0174] 20A, 20B, 20C Vehicle (terminal, user equipment (UE))

[0175] 101 Control Unit

[0176] 102 Storage Unit

[0177] 103 Communication Processing Unit

[0178] 104 Relay processing unit

[0179] 105 Wireless Communication Unit

[0180] 106 Wired Communication Unit

[0181] 200 communication devices

[0182] 201 Control unit

[0183] 202 Storage Unit

[0184] 203 Communication Processing Unit

[0185] 204 Wireless Communication Unit

[0186] 205 Vehicle information acquisition unit

[0187] 206 Operation unit

[0188] 207 Display unit

Claims

1. A communication device, the communication device having a side link communication function, the communication device comprising: A sending unit, the sending unit being configured to send a message, the message not including a layer-2 identifier (ID) identifying a relay device having a function of relaying side link communications, the destination of the message being a layer-2 ID different from the layer-2 ID of the relay device, and the message including information before a payload indicating that the communication device expects relaying of the message. The communication device of claim 1 , wherein the message is a discovery message.

3. A communication device having a side link communication function, the communication device comprising: a sending unit, the sending unit being configured to send a relay request message with a destination of the relay layer-2 ID to a relay device having a function of relaying side link communication, thereby requesting the relay device to relay side link communication with a destination of the relay layer-2 ID and for other user equipment having a side link communication function, The relay layer-2 ID is shared by a plurality of communication devices, and the plurality of communication devices communicate with each other via relaying by the relay device. 4 . The communication device according to claim 3 , wherein the relay request message is a discovery message transmitted from the transmission unit and destined for the relay layer-2 ID.

5. The communication device according to claim 3, wherein the relay request message is a communication message different from the discovery message and destined for the relay layer-2 ID, and The transmitting unit transmits the communication message, thereby requesting the relay device to perform relaying. 6 . The communication device according to claim 3 , wherein the relay layer-2 ID is set according to an installation location of the relay device or use of communication via the relay device. 7 . The communication device according to claim 3 , wherein the relay request message further includes information specifying a validity period of a relay operation performed by the relay device.

8. The communication device according to any one of claims 3 to 7, wherein when relaying by the relay device that accepts the relay request with respect to the relay request message becomes unnecessary, the transmission unit transmits a message requesting the relay device to end relaying.

9. A communication device having a sidelink relay function for relaying sidelink communications, the communication device comprising: a communication unit, the communication unit being configured to receive a relay request message with a destination being a relay layer-2 ID; as well as A setting unit, wherein the setting unit is configured to set an operation to relay a message about side link communication from a sending source of the relay request message whose destination is the relay layer-2ID to other user equipment having a side link communication function when the communication unit receives the relay request message.

10. The communication device according to claim 9, wherein in response to the discovery message as the relay request message, the communication unit returns a response message to the transmission source of the relay request message, and The response message includes the relay layer-2 ID. 11 . The communication device according to claim 9 , wherein the relay request message is a discovery message regarding side link communication and is a message including information requesting relay before a payload. 12 . The communication device according to claim 9 , wherein in a case where the relay request message includes information indicating a validity period of a relay operation, the communication unit ends relaying based on the information indicating the validity period.

13. A communication device according to any one of claims 9 to 12, wherein when the communication unit receives a message requesting the end of relaying from the side link communication device requesting relaying, the communication unit stops the relay operation and sends a relay end completion message to the side link communication device requesting relaying.

14. The communication device according to any one of claims 9 to 13, wherein the message regarding the side link communication is another message different from the relay request message.

15. A communication system comprising a plurality of first communication devices having a side link communication function, and a second communication device having a side link relay function for relaying the side link communication, Each of the first communication devices comprises: a first communication unit configured to send a relay request message with a destination of the relay layer-2ID to a relay device having a function of relaying the side link communication, thereby requesting the relay device to relay the side link communication with a destination of the relay layer-2ID, The second communication device comprises: a second communication unit configured to receive the relay request message destined for the relay layer-2 ID; and a setting unit configured to set an operation to relay a message about the side link communication destined for the relay layer-2 ID to other user equipment having a side link communication function in a case where the second communication unit receives the relay request message, The relay layer-2 ID is shared by the plurality of first communication devices, and the plurality of first communication devices perform communication via relaying performed by the second communication device. 16 . The communication system according to claim 15 , wherein the relay device is placed in association with an intersection, and each of the first communication device and the second communication device moves with a moving body passing through the intersection.

17. A control method for controlling a communication device, the communication device having a side link communication function, the control method comprising: A message is sent, the message not including a layer-2 identifier (ID) identifying a relay device having a function of relaying side link communications, the destination of the message being a layer-2 ID different from the layer-2 ID of the relay device, and the message including information before the payload indicating that the communication device expects relaying of the message.

18. A program for causing a computer to execute the control method for controlling a communication device according to claim 17.

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