Communication device, method for controlling communication device, and control program

Abstract

To achieve low delay information exchange to communication devices at a plurality of changeable addresses.SOLUTION: A communication device comprises: establishing means that establishes a communication link on a layer 2 in wireless communication; and transmission means that transmits messages to a plurality of addresses via the communication link in a format including layer-2 IDs of the plurality of addresses.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] In recent years, the 3GPP (3rd Generation Partnership Project) has been formulating specifications for LTE (Long Term Evolution) and next-generation (NR). Among these, a standard called Sidelink communication has been formulated. Sidelink communication achieves direct wireless communication between devices using an interface called PC5, without going through a mobile communication network (core network).

[0003] Patent Document 1 proposes a technology that uses Sidelink communication to enable direct wireless communication between vehicles. The technology proposed in Patent Document 1 supports the driver's recognition, judgment, and operation by having vehicles share information such as their position, speed, and control information with surrounding vehicles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-188405 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology of Patent Document 1 uses an identifier for each management area, making it difficult to change the recipient of information depending on the content of the information. On the other hand, if the recipient changes for each message sent in the groupcast communication method of conventional Sidelink communication, changing the identifier becomes cumbersome and there is a risk of a lack of immediacy. The problem to be solved by the present invention is to realize low-delay information exchange with communication devices having multiple changeable destinations. [Means for solving the problem]

[0006] In order to solve the above problem, a communication device according to one embodiment of the present invention comprises an establishment means for establishing a communication link at Layer 2 in wireless communication, and a transmission means for transmitting a message to multiple destinations via the communication link in a format including the Layer-2 IDs of the multiple destinations. In addition, a communication device according to another aspect of the present invention includes an establishment means for establishing a communication link at Layer 2 in wireless communication, and a receiving means for receiving, via the communication link, a message transmitted in a format including multiple Layer-2 IDs, one of which indicates the device itself. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a platooning communication system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing an example of the functional configuration of a communication device according to the present embodiment. [Figure 3] FIG. 2 is a block diagram showing an example of the hardware configuration of a communication device. [Figure 4] FIG. 1 is a sequence diagram showing communication sequences in the "Broadcast communication method" and the "Groupcast communication method." [Figure 5] FIG. 10 is a sequence diagram showing a communication sequence in the "Unicast communication method." [Figure 6] FIG. 10 is a diagram showing a frame format when sending and receiving messages using a multiple ID communication method. [Figure 7] FIG. 10 is a sequence diagram showing the operation for establishing a connection and broadcasting using an L2 ID for Sidelink communication. [Figure 8] 5 is a flowchart showing a process for forming a vehicle group in the communication device of the present embodiment. [Figure 9] 10 is a flowchart showing a broadcast message transmission process in a communication device. [Figure 10] 10 is a flowchart showing a process of receiving a broadcast message in a communication device. [Figure 11] 10 is a flowchart showing a destination selection process based on the confidentiality of a message. [Figure 12] 10 is a flowchart showing a destination selection process based on the immediacy of a message. [Figure 13] 10 is a flowchart showing a destination selection process based on the number of destinations. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention, and not all combinations of features described in the embodiments are necessarily essential to the solution of the present invention. The configurations of the embodiments may be modified or changed as appropriate depending on the specifications and various conditions (usage conditions, use environment, etc.) of the system and device to which the present invention is applied. The technical scope of the present invention is defined by the claims, not by the individual embodiments described below.

[0009] <System configuration> FIG. 1 is a diagram showing an example of the configuration of a platooning communication system according to an embodiment of the present invention. The platooning communication system 10 is incorporated into an automatic control system (not shown) for platooning and is responsible for exchanging information necessary for platooning. Fig. 1 shows an example in which four vehicles 101 to 104 travel in a platoon under automatic driving control. The platooning communication system 10 includes a plurality of (four in the example of FIG. 1) communication devices 105-108 mounted on a plurality of (four in the example of FIG. 1) vehicles 101-104, respectively. In the following description, when the four vehicles 101-104 are to be distinguished from one another, the first vehicle 101 will be referred to as "vehicle A," the second vehicle 102 will be referred to as "vehicle B," the third vehicle 103 will be referred to as "vehicle C," and the fourth vehicle 104 will be referred to as "vehicle D."

[0010] Of the four vehicles 101-104, vehicle A is the lead vehicle, and vehicles B-D travel in a line behind vehicle A. Each of vehicles 101-104 is an example of a moving body that moves and is equipped with on-board communication devices 105-108 capable of wireless communication. Each of the communication devices 105 to 108 captures images of the traffic conditions on the road 20 etc. via a camera mounted thereon, and analyzes the road conditions and the conditions of each vehicle traveling in the platoon from the captured images.

[0011] Each communication device 105-108 can wirelessly notify the other communication devices 105-108 of information such as analysis results, and the automatic control system for platooning uses the notified information to realize platooning. Each communication device 105-108 can also wirelessly notify each other of control information for platooning. In this embodiment, sidelink communication is used for wireless communication.

[0012] In this embodiment, a groupcast communication method and a communication method using a frame format including multiple Layer-2 IDs for identifying destinations are selectively used as the communication method for message transmission. In the following description, the frame format including the Layer-2 IDs of multiple destinations is referred to as the "multiple ID format," and the communication method using the multi-ID format is referred to as the "multiple ID communication method." Layer-2 ID may also be abbreviated as L2ID. The Layer-2 ID is a Layer-2 ID used in Sidelink communication, and is an identifier that indicates the destination of communication in Sidelink communication defined by 3GPP. Sidelink communication is Sidelink communication (PC5) defined by 3GPP.

[0013] <Functional configuration of communication device> Next, a description will be given of the functional configuration of the communication devices 105 to 108. In this embodiment, the communication devices 105 to 108 have the same functional configuration, so here, the functional configuration of the communication device 105 will be described as a representative. FIG. 2 is a block diagram showing an example of the functional configuration of the communication device 105 according to this embodiment. The communication device 105 includes an L2ID management unit 201 , a transmission method selection unit 202 , a message processing unit 203 , a storage unit 204 , a control unit 205 , a camera unit 206 , a communication unit 207 , and a video analysis unit 208 .

[0014] The L2ID management unit 201 generates an L2ID that identifies its own device (i.e., the communication device 105) and manages L2IDs that identify other devices (i.e., one or more of the communication devices 106 to 108). In this embodiment, the L2ID management unit 201 also determines the L2ID of a destination to be used for broadcasting a message from the L2IDs of other devices that it manages. When a message is to be broadcast via Sidelink communication, the transmission method selection unit 202 selects a communication method from a groupcast communication method and a multi-ID communication method. The criteria for selection by the transmission method selection unit 202 may include the confidentiality of the message, the immediacy of the message, and the number of destinations.

[0015] The message processor 203 generates messages for sharing road traffic information required for platooning and messages for controlling platooning. The message processor 203 converts the generated messages into transmission messages for Sidelink communication that include an L2ID in a predetermined frame format. The message processor 203 also includes a function for encrypting messages and a function for decrypting encrypted messages. The storage unit 204 stores the L2ID and other information required for sidelink communication. The control unit 205 controls the entire communication device 105, and controls, for example, each of the above-mentioned functional units.

[0016] The camera unit 206 has general camera functions such as photography, and photographs the traffic conditions on the road 20 and the like. The communication unit 207 performs wireless communication with other devices. For example, the communication unit 207 transmits a message generated by the message processing unit 203 to one of the communication devices 106 to 108. The communication unit 207 can transmit messages to all of the communication devices 106 to 108. The communication unit 207 can also transmit messages to a plurality of communication devices selected from the communication devices 106 to 108. The communication unit 207 also receives messages transmitted from other devices.

[0017] The communication unit 207 also transmits and receives L2IDs to and from other devices based on instructions from the L2ID management unit 201. That is, the L2ID management unit 201 notifies other devices of an L2ID that identifies its own device via the communication unit 207, and receives L2IDs notified from other devices via the communication unit 207. In other words, the L2ID management unit 201 shares L2IDs with other devices via the communication unit 207.

[0018] Communication unit 207 transmits and receives security information required for encrypting and decrypting messages to and from other devices. Communication unit 207 receives the security information from message processing unit 203 and passes the security information to message processing unit 203. In other words, message processing unit 203 shares security information with other devices via communication unit 207.

[0019] The video analysis unit 208 analyzes the video captured by the camera unit 206 and analyzes the conditions on the road while the vehicle A is traveling. Specifically, the video analysis unit 208 detects events that may affect the operation of the vehicle A, such as accidents, traffic jams, emergency vehicles, construction vehicles, or the presence or absence of vehicles operating abnormally. The road traffic information described above is generated by the video analysis unit 208 based on the detection results by the video analysis unit 208.

[0020] 2 is an example, and some (or in some cases all) of the functional blocks may be replaced with other functional blocks that perform similar functions, some functional blocks may be omitted, or additional functional blocks may be added. Furthermore, 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.

[0021] <Hardware configuration of communication device> Next, a description will be given of the hardware configuration of the communication devices 105 to 108. In this embodiment, the communication devices 105 to 108 have the same hardware configuration, so here, the hardware configuration of the communication device 105 will be described as a representative. FIG. 3 is a block diagram showing an example of the hardware configuration of the communication device 105. As shown in FIG. The communication device 105 has a CPU 301, a ROM 302, a RAM 303, an auxiliary storage device 304, a communication interface (I / F) 305, a device interface (I / F) 306, and a bus 307. The bus 307 interconnects the components. CPU stands for Central Processing Unit. ROM stands for Read Only Memory, and RAM stands for Random Access Memory.

[0022] The CPU 301 controls the entire communication device 105 using computer programs and data stored in the ROM 302 or RAM 303, thereby realizing each functional unit of the communication device 105 shown in FIG. The ROM 302 stores programs that do not require modification. The RAM 303 temporarily stores programs and data supplied from the auxiliary storage device 304, as well as data supplied from the outside via the communication I / F 305, and the like. The auxiliary storage device 304 is configured by, for example, a hard disk drive, and stores various data.

[0023] The communication I / F 305 is used for communication with an external device. For example, the communication unit 207 shown in FIG. 2 performs wireless communication with other in-vehicle communication devices 106 to 108, which are external devices, via the communication I / F 305. The device I / F 306 connects various devices to the communication device 105, either as components of the communication device 105 or as external elements. For example, the device I / F 306 can connect a display device for a user or the like to confirm information managed by the communication device 105 to the communication device 105. Further, the device I / F 306 can connect the camera unit 206 having a mechanism for executing imaging to the communication device 105.

[0024] FIG. 3 shows an example in which the components shown in FIG. 2 are realized by a program and the CPU 301, but the components shown in FIG. 2 may be implemented by one or more dedicated hardware. When the components shown in FIG. 2 are implemented by hardware, for example, a dedicated circuit may be automatically generated on the FPGA from a program for realizing each component by using a predetermined compiler. FPGA is an abbreviation for Field Programmable Gate Array. Also, a Gate Array circuit may be formed in the same manner as the FPGA and realized as hardware. Further, it may be realized by an ASIC (Application Specific Integrated Circuit).

[0025] <Sidelink Communication and Layer-2 ID> Here, the communication method in Sidelink communication will be described. The communication methods in Sidelink communication include a broadcast communication method, a groupcast communication method, and a unicast communication method. FIG. 4 is a sequence diagram showing communication sequences in the "Broadcast communication method" and the "Groupcast communication method". In the "Broadcast communication method" and "Groupcast communication method," an identifier called L2ID is shared between the sending and receiving devices (i.e., the sending device and the receiving device) during communication, or is already shared before communication begins. The common L2ID is then set as the sending destination and the receiving destination in the sending device and the receiving device, respectively.

[0026] The transmitting device assigns the L2ID set as the destination to the wireless frame and transmits it. The wireless frame is then received by a receiving device that has set the same L2ID as the L2ID assigned to the wireless frame as the destination. In other words, in the "Broadcast communication method" and "Groupcast communication method," data communication between devices is possible by setting the L2ID in the transmitting device and the receiving device. Therefore, if there are multiple receiving devices that have the same L2ID as the L2ID assigned to the wireless frame as their destination, the multiple receiving devices will receive the wireless frame simultaneously, making broadcast communication possible.

[0027] In this embodiment, messages used in the "Broadcast communication method" and the "Groupcast communication method" are not encrypted. In this embodiment, the L2 ID is an identifier stored in a 3-byte area in the frame format of Sidelink communication. In the Broadcast communication method, the L2ID has a fixed value for each byte that is stored in advance in all devices, for example, at the time of shipping the transmitting device and the receiving device. In contrast, in the Groupcast communication method, the L2 ID is determined within the group when the group is formed. That is, after the transmitting and receiving devices that form the group are identified, an L2 ID that can identify the group among the target devices is determined, and that L2 ID is shared among the communication devices.

[0028] FIG. 5 is a sequence diagram showing a communication sequence in the "Unicast communication method." In the "Unicast communication method," a transmitting device sends a connection request to a destination identified by a shared L2ID. On the receiving device side, if the receiving device has set an L2ID that is the same as the L2ID assigned to the connection request, it exchanges security information with the transmitting device. Once a secure communication link is established through the exchange of security information, wireless frames can be sent and received between the transmitting device and receiving device. Messages contained in wireless frames exchanged in the "Unicast communication method" are encrypted and decrypted using the exchanged security information.

[0029] Here, we consider a method of sharing position, speed, control information, etc. between vehicles by using Sidelink communication to perform direct wireless communication between vehicles. As mentioned above, wireless communication in Sidelink communication requires that L2IDs be shared between communication devices. In other words, in autonomous driving control via Sidelink communication, information exchange destinations are limited to communication devices identified by L2IDs.

[0030] In addition, when automatic driving control of platooning is implemented using Sidelink communication via communication devices installed in each vehicle, there is also a demand to send the same information to multiple information exchange destinations depending on the driving conditions between the lead vehicle and the following vehicles. The broadcast communication method uses a broadcast communication L2ID that is shared in advance among all communication devices, so the destination communication device is not limited, and all communication devices within the communication range that can receive the target wireless frame are the recipients. Therefore, it is not suitable for autonomous driving control of platooning, where information exchange must be limited to desired destinations.

[0031] With the groupcast communication method, it is necessary to define and share an L2ID for each target group every time the target group changes, which can make the sharing process cumbersome. For this reason, for communications that require immediacy, such as autonomous driving control, it is desirable to use a simpler method of broadcast communication. Furthermore, autonomous driving control communications may require secure communications, but the method for establishing secure communications in the groupcast communication method has not been specified. The unicast communication method is a communication method that establishes secure communication, but in order to exchange information during autonomous driving control of platooning, for example, the same information must be sent individually to each of multiple destination communication devices, resulting in poor communication efficiency.

[0032] In this embodiment, in addition to the "Broadcast communication method," "Groupcast communication method," and "Unicast communication method," communication is possible using a multi-ID communication method using a wireless frame containing multiple L2IDs that identify destinations. The multi-ID communication method is a communication method that uses the transmission and reception of wireless frames via Sidelink communication. As will be described later, the multi-ID communication method enables highly instantaneous communication that can be used for information exchange in autonomous driving control of platooning.

[0033] FIG. 6 is a diagram showing a frame format when a message is transmitted and received in a multi-ID communication system. The radio frame 701 is used to send and receive broadcast messages in Sidelink communication. A wireless frame 701 includes a destination identifier 702 at the beginning, a plurality of destination identifiers 703 and 704 (two in the example of FIG. 6) following the beginning, a source identifier 705, and a message payload 706.

[0034] The leading destination identifier 702 indicates that the wireless frame 701 is a wireless frame 701 in the multi-ID format, for example, by having the value "F0" in the most significant byte described as "2 bytes" in FIG. 6. The method of indicating that the wireless frame 701 is in the multi-ID format is not limited to the method described above. For example, the wireless frame 701 may be indicated as being in the multi-ID format by having the value "1" in the most significant bit of the most significant byte in the leading destination identifier 702. Alternatively, the wireless frame 701 may be indicated as being in the multi-ID format by using a predetermined byte sequence or bits at a predetermined position.

[0035] In this embodiment, the value of the middle byte, which is written as "1 byte", in the first destination identifier 702 indicates how many destination identifiers are included after the first destination identifier 702. In the example of Fig. 6, the value of the middle byte is "02", so two destination identifiers 703 and 704 are included after the first destination identifier 702. The number of destination identifiers included after may be indicated by the position of another byte or the number of bits in the first destination identifier 702. In this embodiment, the value of the least significant byte written as "0 byte" is fixed to "FF", but the least significant byte may be used for another purpose.

[0036] The following destination identifiers 703, 704 are L2IDs that indicate the destinations of the broadcast message. In the example shown in Figure 6, the first destination identifier 703 is an L2ID with a value of "BBBBBB" that indicates vehicle B, and the second destination identifier 704 is an L2ID with a value of "DDDDDD" that indicates vehicle D. 6, the source identifier 705 is an L2ID that indicates the source of the broadcast message, and has a value of "AAAAAA" that indicates vehicle A. A message payload 706 following the multiple destination identifiers 703 and 704 is an area where the above-mentioned road traffic information and control information are stored. As shown in Figure 6, the multi-ID format indicates the inclusion of multiple destination Layer-2 IDs and the number of such Layer-2 IDs in a byte area set at the beginning of the message for the destination Layer-2 IDs. The multi-ID format also includes multiple destination Layer-2 IDs as an extension area following the byte area.

[0037] <Sending and receiving process> The message transmission and reception process performed by the platooning communication system 10 of this embodiment will be described with reference to FIG. FIG. 7 is a sequence diagram showing the operation for establishing a connection and broadcasting using an L2 ID for sidelink communication. First, the formation of a vehicle group for platooning begins in each of the vehicles A to D (F601 to F604). Specifically, for example, a software application is started in the communication devices 105 to 108 mounted on each of the vehicles A to D.

[0038] Next, in each of the vehicles A to D, an L2ID for identifying the communication device 105 to 108 mounted on the vehicle is generated (F605 to F608). In this embodiment, the L2ID is automatically generated in the communication device 105 to 108 of each of the vehicles A to D. Note that a value that has been defined and stored in advance may be used as the L2ID in each of the vehicles A to D.

[0039] In this embodiment, the value of L2ID for vehicle A is, for example, "AAAAAA," and the value of L2ID for vehicle B is, for example, "BBBBBB." In addition, the value of L2ID for vehicle C is, for example, "CCCCCC," and the value of L2ID for vehicle D is, for example, "DDDDDD." Next, a search for devices to form a vehicle group is performed using broadcast communication of Sidelink communication. That is, a search message (F609) using a fixed L2ID defined as an L2ID for broadcast communication is transmitted and received between the communication devices 105 to 108. For example, this search message is a radio frame in which identification information, including whether or not a vehicle group is to be formed, is stored in the payload in a Sidelink communication format. In this embodiment, for example, the identification information is also defined in advance and stored in the communication devices 105 to 108 of the vehicles A to D that are to form a group.

[0040] When a target device for group formation (that is, the communication devices 105 to 108) is discovered by transmitting and receiving a search message, a message (F610) for exchanging L2ID is created and transmitted between the communication devices 105 to 108. The L2ID exchange message is a wireless frame in which the L2ID of the own device and the L2ID of the communication device that is the target of the vehicle group are included in the message payload and transmitted. The L2ID of each communication device that is the target of forming the vehicle group is shared among the vehicles by broadcasting the L2ID exchange message using the broadcast L2ID. The formation of the vehicle group is completed by sharing the L2ID. In this embodiment, when transmitting and receiving a message for L2ID exchange, the multi-ID format is also included in the message payload and transmitted and received. That is, the communication devices 105 to 108 notify other devices of a message including format information indicating the multi-ID format by broadcast communication.

[0041] In the example of FIG. 7, the search message (F609) and the message for L2ID exchange (F610) are described as separate messages, but these messages may be transmitted and received in one radio frame. After a vehicle group is formed, if road traffic information that should be broadcast occurs in vehicle A, for example, communication device 105 of vehicle A executes a transmission method selection process (F611). In the transmission method selection process, either the groupcast communication method or the multi-ID communication method is selected. That is, communication devices 105 to 108 transmit messages using a method selected from the multi-ID format transmission method and the groupcast communication method. Figure 7 shows the sequence when the multi-ID communication method is selected.

[0042] In this embodiment, the destinations of broadcast transmission are determined each time information is generated, depending on the content of the road traffic information to be broadcast. Fig. 7 shows a sequence in which, for example, communication device 106 of vehicle B and communication device 108 of vehicle D are determined as the destinations. In the example of Fig. 7, vehicle C is not a destination, but vehicle C could also be a destination in another broadcast transmission.

[0043] When a message is broadcast using the multiple ID communication method, a connection request including multiple L2IDs that identify the communication devices 106, 108 of the destination vehicles B and C is transmitted from the communication device 105 of vehicle A (F612). As a result of the connection request, a secure link is established between the communication device 105 of vehicle A and the communication device 106 of vehicle B (F613). After the link is established, the communication device 106 of vehicle B transmits a connection acceptance to the communication device 105 of vehicle A (F614).

[0044] Similarly, the communication device 105 of vehicle A and the communication device 108 of vehicle D establish a secure link (F615). After the link is established, the communication device 108 of vehicle D transmits a connection acceptance to the communication device 105 of vehicle A (F616). When the communication device 105 of vehicle A receives connection acceptance from the communication device 106 of vehicle B and the communication device 108 of vehicle D, it broadcasts a message in a multi-ID format containing the road traffic information to be notified to vehicles B and D using the multi-ID communication method (F617).

[0045] That is, the communication device 105 of vehicle A establishes a communication link in wireless communication at Layer 2. Then, the communication device 105 of vehicle A transmits a message to multiple destinations via the communication link in a format including the L2IDs of the multiple destinations. Furthermore, the communication device 106 of vehicle B and the communication device 108 of vehicle D establish a communication link in wireless communication at Layer 2. Then, the communication device 106 of vehicle B and the communication device 108 of vehicle D receive, via the communication link, a message that is transmitted in a format including multiple L2IDs, and in which any one of the multiple L2IDs indicates the communication device itself.

[0046] Since the sharing of L2IDs required for the multi-ID communication method is completed when a vehicle group is formed, the time from when road traffic information to be notified is generated until communication is initiated is short, and real-time communication is possible with sidelink communication. Furthermore, with the multi-ID communication method, there is no need to share a new L2ID even if the destination changes. Furthermore, the multi-ID communication method can transmit a broadcast message to multiple destinations using a single wireless frame, which reduces the complexity of processing on the transmitting side. Therefore, the drivers of each vehicle 101-104 can exchange vehicle information and road traffic information with low latency.

[0047] Furthermore, in this embodiment, messages are encrypted and communicated even in a multi-ID communication system using a link that exchanges security information, making it possible to carry out broadcast communication with high confidentiality. The processing procedures of the communication devices 105 to 108 that realize the above-described sequence will be described with reference to a flowchart.

[0048] FIG. 8 is a flowchart showing the process of forming a vehicle group in the communication devices 105 to 108 of this embodiment. When group formation starts, the communication devices 105 to 108 generate their own L2IDs in the L2ID management units 201 (S801). Next, the communication devices 105 to 108 search for devices that are to form a vehicle group using the L2ID for broadcast communication (S802).

[0049] If a target device is found (Yes in S803), the communication devices 105 to 108 notify the target device of their own L2 ID using the L2 ID for broadcast communication (S804). When notifying the L2 ID, the communication devices 105 to 108 also include a multi-ID format in the radio frame for notification and share it with the target device. For example, even if some of the communication devices 105 to 108 do not store the multi-ID format, multi-ID communication within the vehicle group is possible due to sharing. If the target device is not found (No in S803), the process returns to S802, and the communication devices 105 to 108 continue searching for the target device.

[0050] After the L2 ID is notified in S804, the communication devices 105 to 108 wait to receive the L2 ID of the target device transmitted from the target device (S805). When the L2 ID of the target device is received (Yes in S805), the communication devices 105 to 108 store the received L2 ID of the target device in the storage unit 204 (S806) and manage it in the L2ID management unit 201.

[0051] FIG. 9 is a flowchart showing the process of transmitting a broadcast message in communication devices 105-108. When the message processing unit 203 generates a broadcast message including information to be transmitted to multiple destinations, the communication devices 105 to 108 execute a transmission method selection process (S807). The details of the transmission method selection process will be described later, but the transmission method selection process selects either the groupcast communication method or the multi-ID communication method as the transmission method for the broadcast message.

[0052] If the multi-ID communication method is selected as a result of the transmission method selection process in S807 (Yes in S808), the communication devices 105 to 108 establish security with the destination device (S810). After security is established, the communication devices 105 to 108 receive a connection acceptance from the destination device (S811), and then transmit a broadcast message using the multi-ID format (S812). That is, the communication devices 105 to 108 share security information required for message encryption with each of the multiple destinations indicated by the L2ID included in the message, and encrypt the message to be transmitted in the multiple ID format using the security information. If the groupcast communication method is selected as a result of the transmission method selection process in S807 (No in S808), the communication devices 105 to 108 transmit the broadcast message in the groupcast communication method (S809).

[0053] FIG. 10 is a flowchart showing the process of receiving a broadcast message in the communication devices 105 to 108. When receiving a broadcast message, the communication devices 105 to 108 check whether there is a connection request for communication using a multi-ID communication method (S901). If there is no connection request for the multi-ID communication method (No in S901), the communication devices 105 to 108 execute reception processing using the groupcast communication method (S902). On the other hand, if there is a connection request for the multi-ID communication method (Yes in S901), the communication devices 105 to 108 establish security with the source device (S903).

[0054] After security is established, the communication devices 105 to 108 transmit a connection acceptance to the source device (S904), and then receive a broadcast message (message payload) from the source device using the multi-ID communication method (S905). That is, the communication devices 105 to 108 share security information required for decrypting a message with the sender of the message, and decrypt an encrypted message received in the multi-ID format using the security information. The destination selection process will now be described. The communication devices 105 to 108 select a transmission method for broadcast transmission in the transmission method selection unit 202. As described above, the criteria for selecting a transmission method may include the confidentiality of the message, the immediacy of the message, and the number of destinations.

[0055] FIG. 11 is a flowchart showing a destination selection process based on the confidentiality of a message. In the destination selection process shown in the flowchart of FIG. 11, it is determined whether or not the broadcast message requires secure communication (S1001). If the broadcast message is a low confidentiality broadcast message that does not require secure communication (No in S1001), it is determined that the broadcast message is to be transmitted by the groupcast communication method (S1002). If the broadcast message is a highly confidential broadcast message that requires secure communication (Yes in S1001), it is determined that the broadcast message is to be transmitted using the multi-ID communication method (S1003).

[0056] 11, if a message requires confidentiality, the multi-ID format is selected as the transmission method, and if the message does not require immediacy, the groupcast communication is selected as the transmission method. By using confidentiality as the criterion for judgment, broadcast transmission that complies with the confidentiality requirements of the broadcast message becomes possible.

[0057] FIG. 12 is a flowchart showing a destination selection process based on the immediacy of a message. In the destination selection process shown in the flowchart of FIG. 12, it is determined whether the broadcast message requires immediacy (S1101). If the broadcast message does not require immediacy (No in S1101), it is determined that the broadcast message is to be transmitted by the groupcast communication method (S1102).

[0058] If the broadcast message is one that requires immediacy (Yes in S1101), it is determined that the broadcast message is to be transmitted using the multi-ID communication method (S1103). 12, if a message requires immediacy, transmission in the multi-ID format is selected as the transmission method, and if the message does not require immediacy, transmission by groupcast communication is selected as the transmission method. By using immediacy as the criterion for judgment, it becomes possible to carry out broadcast transmission that is suited to the immediacy of the broadcast message.

[0059] FIG. 13 is a flowchart showing the destination selection process based on the number of destinations. In the destination selection process shown in the flowchart of FIG. 13, it is determined whether the number of destinations is less than a threshold value (S1201). If the number of destinations is equal to or greater than the threshold (No in S1201), it is determined that the broadcast message is to be transmitted by the groupcast communication method (S1202). If the number of destinations is less than the threshold value (Yes in S1201), it is determined that the broadcast message is to be transmitted using the multi-ID communication method (S1203).

[0060] 13, if the number of message destinations is less than the predetermined number, the multi-ID format is selected as the transmission method, and if the number of message destinations is more than the predetermined number, the groupcast communication is selected as the transmission method. By using the number of destinations as the criterion for judgment, it becomes possible to carry out broadcast transmission that is suited to the number of destinations.

[0061] <Other embodiments> The present invention can be embodied as, for example, a system, an apparatus, a method, a program, or a recording medium (storage medium), etc. Specifically, the present invention may be applied to a system consisting of multiple devices (for example, a host computer, an interface device, a web application, etc.), or may be applied to an apparatus consisting of a single device.

[0062] The present invention can also be realized by supplying a program (computer program) that realizes one or more functions of the above-described embodiments to a system or device via a network or a recording medium (storage medium). One or more processors in the computer of the system or device read and execute the program. In this case, the program (program code) itself read from the recording medium realizes the functions of the embodiments. Furthermore, the recording medium on which the program is recorded can constitute the present invention.

[0063] In addition, not only can the functions of the embodiments be realized by the computer executing the program it has read, but the operating system (OS) running on the computer may also perform some or all of the actual processing based on the instructions of the program, and the functions of the above-mentioned embodiments may be realized through that processing.

[0064] Furthermore, after the program read from the recording medium is written into the memory of a function expansion card inserted into the computer or a function expansion unit connected to the computer, a CPU or the like on the function expansion card or function expansion unit may perform some or all of the actual processing based on the instructions of the program, and the functions of the above-mentioned embodiments may be realized through this processing. When the present invention is applied to the above-mentioned recording medium, the recording medium stores a program corresponding to the flowchart described above. [Explanation of symbols]

[0065] 10... Platooning communication system, 101 to 104... Vehicles, 105 to 108... Communication devices, 201... L2ID management unit, 202... transmission method selection unit, 203... message processing unit, 204...storage unit, 205...control unit, 206...camera unit, 207...communication unit, 208...Video Analysis Department

Claims

1. A means for establishing a communication link at Layer 2 in Sidelink communication conforming to the 3GPP (3rd Generation Partnership Project) standard; a sending means for sending a message to the plurality of destinations via the communication link, the message including Layer-2 IDs of the plurality of destinations; A communication device comprising:

2. A means for establishing a communication link at Layer 2 in Sidelink communication conforming to the 3GPP standard; a receiving means for receiving a message including Layer-2 IDs of a plurality of communication devices, any one of the Layer-2 IDs of the plurality of communication devices indicating the communication device itself, via the communication link; A communication device comprising:

3. The Sidelink communication is Sidelink communication (PC5) conforming to the 3GPP standard.

3. The communication device according to claim 1, wherein the Layer-2 ID is an identifier indicating a communication destination in Sidelink communication conforming to 3GPP.

4. 2. The communication device according to claim 1, further comprising: a first field indicating that the Layer-2 IDs of the plurality of destinations are included or a first field indicating the number of the Layer-2 IDs, at the beginning of a message for the Layer-2 IDs of the destinations; and a second field indicating the Layer-2 IDs of the plurality of destinations following the first field.

5. encryption means for encrypting the message to be sent; a sharing means for sharing security information required for encrypting a message with each of the plurality of destinations indicated by a Layer-2 ID included in the message; The communication device of claim 1 , further comprising:

6. decryption means for decrypting the received encrypted message; A sharing means for sharing security information required for decrypting a message with a sender of the message; The communication device according to claim 2 , further comprising:

7. 7. The communication device according to claim 1, further comprising a notification unit that notifies other communication devices of the message by broadcast communication.

8. the transmitting means is means for transmitting the message in a manner selected from broadcast communication and group cast communication; 2. The communication device according to claim 1, further comprising a selection unit for selecting a method of transmission by said transmission unit.

9. The communication device according to claim 8, characterized in that the selection means selects broadcast communication as the method of transmission by the transmission means when the message is a message requiring immediacy, and selects group cast communication as the method of transmission by the transmission means when the message is a message not requiring immediacy.

10. The communication device according to claim 8, characterized in that the selection means selects broadcast communication as the method of transmission by the transmission means when the message is a message requiring confidentiality, and selects group cast communication as the method of transmission by the transmission means when the message is a message requiring no immediacy.

11. The communication device according to claim 8, characterized in that the selection means selects broadcast communication as the method of transmission by the transmission means when the number of destinations of the message is less than a predetermined number, and selects group cast communication as the method of transmission by the transmission means when the number of destinations of the message exceeds the predetermined number.

12. A communication system comprising the communication device according to claim 1 and the communication device according to claim 2.

13. An establishment step of establishing a communication link at Layer 2 in Sidelink communication compliant with the 3GPP standard; a sending step of sending a message to a plurality of destinations over the communication link, the message including Layer-2 IDs of the plurality of destinations; 13. A method for controlling a communication device, comprising:

14. An establishment step of establishing a communication link at Layer 2 in Sidelink communication conforming to the 3GPP standard; a receiving step of receiving, via the communication link, a message including a plurality of Layer-2 IDs, any one of the plurality of Layer-2 IDs indicating the own device; 13. A method for controlling a communication device, comprising:

15. A program for causing a computer to function as each of the means of the communication device according to any one of claims 1 to 13.

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