Communication device, control method for communication device, and program

Abstract

The communication device obtains absolute time; generating a message including first information indicating the absolute time and second information regarding a time source providing the absolute time; and transmitting the message to one or more other communication devices via a PC5 interface complying with a 3rd Generation Partnership Project (3GPP) standard.

Description

Technical Field

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

[0002] In the 3rd Generation Partnership Project (3GPP) (registered trademark), standard specifications regarding a wireless link between communication devices (which is called sidelink communication) are developed. Sidelink communication is a communication method for directly implementing wireless communication between communication devices using a wireless interface called PC5 without passing through a mobile communication network (core network).

[0003] A communication system that uses sidelink communication to directly perform wireless communication between vehicles (between communication devices of each vehicle) is disclosed in PTL 1. Using the technology disclosed in this document, sharing of information about surrounding vehicles (position, speed, vehicle control information, etc.) enables support of driver confirmation, determination, and operation.

[0004] Citation List

[0005] Patent Literature

[0006] PTL 1: Japanese Patent Laid-Open No. 2020-188405 Summary of the invention

[0007] Technical issues

[0008] There are various known methods for a communication device to acquire absolute time. For example, a method of receiving a global navigation satellite system (GNSS) signal, a method of receiving system information (system information block (SIB)) reported by a base station, a method of accessing a network time protocol (NTP) server on a network, etc. Absolute time means actual time, such as the coordinated universal time (UTC) on which the world standard time is based, or a system time set for a device.

[0009] In contrast, currently no mechanism has been developed to obtain absolute time in sidelink communication. For example, when a communication device is configured to enable sidelink communication but does not support a communication function for obtaining absolute time using the above method, it is not possible to obtain absolute time. Alternatively, when a communication device supports a communication function for obtaining absolute time but is temporarily outside a communication area, it is also not possible to obtain absolute time.

[0010] In order to solve the above problems, an object of the present invention is to provide a mechanism for obtaining absolute time in sidelink communication.

[0011] Solution to the problem

[0012] As a means for achieving the above purpose, the communication device of the present invention has the following configuration. Specifically, the communication device includes an acquisition component for acquiring absolute time; a generation component for generating a message including first information and second information, wherein the first information indicates the absolute time and the second information is information about a time source providing the absolute time; and a sending component for sending the message to one or more other communication devices via a PC5 interface conforming to the 3rd Generation Partnership Project (3GPP) standard.

[0013] Advantageous Effects of the Invention

[0014] According to the present invention, a mechanism for obtaining absolute time in sidelink communications is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a diagram illustrating an example of a configuration of a communication system.

[0016] Figure 2A An example of the hardware configuration of the communication device is illustrated.

[0017] Figure 2B An example of a functional configuration of a communication device is illustrated.

[0018] Figure 3 A sequence diagram illustrating a process for forming a sync group.

[0019] Figure 4A An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0020] Figure 4B An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0021] Figure 4C An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0022] Figure 4D An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0023] Figure 4E An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0024] Figure 4F An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0025] Figure 4GAn example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0026] Figure 4H An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0027] Fig. 4I An example of a window displayed in a display unit in a communication device in a process for forming a synchronization group is illustrated.

[0028] Figure 5A An example of the format of a message used in side link communication according to an embodiment is illustrated.

[0029] Figure 5B An example of the format of a message used in side link communication according to an embodiment is illustrated.

[0030] Fig. 6A A flow chart of a process of sending a time synchronization message according to an embodiment is illustrated.

[0031] Figure 6B A flow chart of a process of sending messages other than a time synchronization message according to an embodiment is illustrated.

[0032] Figure 7 A flow chart of a message receiving process according to an embodiment is illustrated. DETAILED DESCRIPTION

[0033] Embodiments will be described in detail herein with reference to the accompanying drawings. The embodiments described below are not intended to limit the invention according to the appended claims. Although multiple features are described in the embodiments, all features are not essential to the invention, and multiple features can be combined arbitrarily. The same reference numerals are added to the same or similar components in the drawings, and repeated descriptions of such components are omitted herein.

[0034] [Configuration of communication system]

[0035] Figure 11 is a diagram illustrating an example of the configuration of the communication system 10 according to the present embodiment. The communication system 10 is composed of communication devices 100, 200 and 201, a base station 202, and a global navigation satellite system (GNSS) satellite 203. In the present embodiment, the communication device 100, the communication device 200 and the communication device 201 are configured to be able to perform side link communication with each other. The side link communication is a communication via a PC5 interface that complies with the 3rd Generation Partnership Project (3GPP) standard. The communication device 100 is configured to be able to receive signals from the base station 202 and the GNSS satellite 203 as an external time source. Although it is assumed in the present embodiment that the communication devices 100, 200 and 201 have a shooting function, the communication devices 100, 200 and 201 are not limited to this.

[0036] [Hardware configuration of communication device]

[0037] Figure 2A An example of a hardware configuration of the communication device 100 is illustrated. The communication device 100 includes a control unit 101, a nonvolatile memory 102, a working memory 103, an operation unit 104, a display unit 105, an imaging unit 106, a clock unit 107, and a communication unit 108 as an example of its hardware configuration. The communication device 100 may include a sensor unit (not illustrated) for detecting temperature, acceleration, etc.

[0038] The control unit 101 controls the components in the communication device 100 according to the input signal and the program that implements one or more functions of the embodiment. Instead of the control unit 101 controlling the entire device, multiple pieces of hardware may share processing to control the entire device. The non-volatile memory 102 is an electrically erasable and recordable non-volatile memory. The program executed by the control unit 101 and the like are stored in the non-volatile memory 102. The working memory 103 is used as a working area of ​​the control unit 101 and the like. The working memory 103 is also used for temporary storage of data and the like supplied from an external device via the communication unit 108.

[0039] The operation unit 104 is used to accept instructions from the user to the communication device 100. The operation unit 104 includes operation members such as a power button used by the user to instruct turning on and off the power of the communication device 100 and a dedicated connection button for starting communication with an external device via the communication unit 108. The operation unit 104 may include a touch panel formed in the display unit 105. The display unit 105 displays a user interface (UI), text, and the like for interactive operations.

[0040] The imaging unit 106 is a unit for capturing an image in a real space, and includes, for example, an optical system such as a lens, a complementary metal oxide semiconductor (CMOS), an imaging device such as a charge coupled device (CCD), an analog-to-digital (A / D) converter, a development processor, etc. The clock unit 107 generates time information (clock) based on, for example, a specific reference clock pulse to be used as a setting time of the communication device 100. The time information corresponds to the absolute time of the communication device 100. The time information can be supplied to each component in the communication device 100 shown in FIG.

[0041] The communication unit 108 is an interface for connecting to an external device. For example, the communication unit 108 is composed of one or more antennas for wireless communication, a modulation and demodulation circuit for processing radio signals, and a communication controller. The communication unit 108 in the communication device 100 is configured to perform side link communication (communication between terminals) with the communication devices 200 and 201, public network communication with the base station 202, and GNSS communication with the GNSS satellite 203. The public network is, for example, a long-term evolution (LTE) or a fifth generation (5G) cellular network that complies with the 3rd Generation Partnership Project (3GPP) standard. The communication unit 108 can obtain absolute time from the base station 202 through public network communication. In addition, the communication unit 108 can also obtain absolute time from the GNSS satellite 203 through GNSS communication.

[0042] Despite Figure 1 The communication unit 108 is illustrated as one block, but the communication unit 108 may be configured to include individual communication units 108 and one or more antennas in order to perform side link communication, public network communication, and GNSS communication.

[0043] The communication unit 108 may be configured to perform communication using a wireless local area network (LAN) conforming to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 series, or may be configured to perform communication using Ethernet (registered trademark).

[0044] The hardware configuration of the communication device 200 and the communication device 201 may be the same as the hardware configuration shown in Figure 2. Alternatively, the communication unit 108 in the communication device 200 and the communication device 201 may be configured not to have the functions for public network communication with the base station 202 and GNSS communication with the GNSS satellite 203.

[0045] [Functional configuration of communication device]

[0046] Figure 2BThe diagram shows an example of a functional configuration of the communication device 100. The communication device 100 includes a transmitter 111, a receiver 112, a display controller 113, an identifier (ID) acquirer 114, a group determiner 115, a message generator 116, a message analyzer 117, and a time controller 118 as an example of its functional configuration. The communication device 100 may further include an imaging controller (not shown) for controlling the imaging unit 106.

[0047] The transmitter 111 and the receiver 112 are respectively connected via the communication unit 108 ( Figure 2A ) performs sending processing and receiving processing. The display controller 113 performs sending processing and receiving processing on the display unit 105 ( Figure 2A ) performs display control. The ID acquirer 114 acquires a Layer-2 ID (hereinafter referred to as L2ID). L2ID is information for identifying each communication device and a group of communication devices in the side link communication. For example, the ID acquirer 114 may generate an L2ID to acquire the generated L2ID or may acquire the L2ID from the outside according to the 3GPP definition. The group determiner 115 determines whether the communication device 100 forms a group for communication. The message generator 116 generates a message to be sent by the transmitter 111. The message analyzer 117 analyzes the message received by the receiver 112. The time controller 118 manages and controls the clock unit 107 ( Figure 2A ). For example, the time controller 118 acquires the time information indicated by the clock unit 107 (the absolute time of the communication device 100), and updates the time information in the clock unit 107 (the set time of the communication device 100). Since the time controller 118 can update the time information according to the content analyzed by the message analyzer 117, the time controller 118 can be configured to have the function of the message analyzer 117.

[0048] [Processing Flow]

[0049] In this embodiment, Figure 1 In the communication system in FIG. 1 , the communication device 100 is able to obtain absolute time from an external time source such as a base station 202 and a GNSS satellite 203. In contrast, the communication device 200 and the communication device 201 do not communicate with an external time source and do not obtain absolute time from an external time source. In this embodiment, it is assumed that the communication device 200 obtains absolute time from a peripheral communication device (communication device 100 or communication device 201) through side link communication.

[0050] In this embodiment, a case where a process of acquiring absolute time in side link communication is performed by transmitting and receiving absolute time in a preformed synchronization group, and a case where a process of acquiring absolute time in side link communication is performed by transmitting and receiving absolute time without forming a synchronization group are described. A process for forming a synchronization group and a process when a synchronization group is not formed, which are preprocessing for transmission and reception of absolute time, will now be described.

[0051] <Preprocessing of sending and receiving absolute time (process for forming a synchronization group)>

[0052] In this embodiment, it is assumed that Figure 1 In the communication system 10 shown in FIG. 1 , the communication device 100 and the communication device 200 form a synchronization group. The communication device 100 is configured to be able to receive a signal about absolute time (hereinafter also referred to as absolute time) from the base station 202 and the GNSS satellite 203. Therefore, in this embodiment, an example is described in which the communication device 100 forms a synchronization group and serves as a transmission-side device of the absolute time and the communication device 200 serves as a reception-side device of the absolute time.

[0053] Figure 3 FIG. 1 is a sequence diagram showing a process in which the communication device 100 and the communication device 200 form a synchronization group. FIG. 4A to FIG. 4I describe Figure 3 The sequence diagram in . FIG. 4A to FIG. 4I An example of a window (UI) displayed in the display unit 105 of the communication device 100 or the communication device 200 in the process for forming a synchronization group is illustrated. Display on the window is performed by the display controller 113 and operation of the window is performed by the user using the operation unit 104. In the communication device 100 and the communication device 200, transmission and reception of signals are performed by the transmitter 111 and the receiver 112, respectively, and acquisition of the L2ID is performed by the ID acquirer 114. In the following description, "5G-BS" corresponds to the base station 202 and "GPS" corresponds to the GNSS satellite 203.

[0054] (1) Preparation for Synchronous Group Formation

[0055] The communication device 100 and the communication device 200 start respective preparation processes for forming a synchronization group ( F301 , F302 ).

[0056] The user of each of the communication apparatus 100 and the communication apparatus 200 receives the Figure 4A In the connection menu window shown in FIG. 1 , "Time synchronization between terminals" 401 indicating a connection for time synchronization between terminals is selected. The selection of "Time synchronization between terminals" 401 causes a transition to Figure 4B. In this example, the user selects "sender" 402 indicating the sending side in the communication device 100, and the user selects "receiver" 403 indicating the receiving side in the communication device 200. After selecting "sender" 412 or "receiver" 413, the window changes to Figure 4C 405. When performing transmission and reception of absolute time (synchronization process) in the formed synchronization group, the user of each of the communication device 100 and the communication device 200 selects "Group Synchronization" 405. After selecting "Group Synchronization" 405, the window changes to Figure 4D 406. In this example, it is assumed that the communication device 100 and the communication device 200 form a new group and the user of each of the communication device 100 and the communication device 200 selects "Formation of a new group" 406. After selecting "Formation of a new group" 406, the communication device 100 and the communication device 200 display Figure 4E A selection area (such as "Cancel" 407) for stopping or canceling an operation may be displayed on the waiting screen.

[0057] (2) Obtaining L2ID

[0058] After completing the preparation process for the formation of the synchronization group in F301 and F302, the communication device 100 and the communication device 200 acquire (prepare) Layer-2 ID (L2ID). L2ID is information for identifying each communication device in the side link communication and the synchronization group of the communication device. The L2ID prepared in the communication device 100 as the transmitting side is different from the L2ID prepared in the communication device 200 as the receiving side. Specifically, the communication device 100 prepares the L2ID of the communication device 100 itself and the L2ID for multicast used in the transmission (multicast communication) to the formed group. In contrast, the communication device 200 prepares the L2ID of the communication device 200 itself.

[0059] (3) Selection of Transmitter and Receiver

[0060] After completing the preparation of L2ID, in F305, the communication device 100 starts service announcement. The information to be announced includes information indicating the time synchronization service and information (identification information) capable of identifying the communication device 100. The information to be announced may include information about an external time source with which the communication device 100 can communicate. The announcement may be performed using ProSe Direct Discovery defined in 3GPP. Alternatively, when a network is formed in a wireless LAN, the announcement may be performed using Simple Service Discovery Protocol (SSDP) Discovery.

[0061] After receiving the service announcement, the communication device 200 displays Figure 4F The sender list window shown in . Identification information (different from L2ID) about the communication device that makes the service announcement and information about the time source (time source of the communication device) from which the communication device can obtain the absolute time are displayed on the sender list window. Figure 4F The example in FIG. 1 shows the fact that the time source of the communication device 100 is the 5G-BS (base station 202) and the GPS (GNSS satellite 203) and the fact that the time source of the camera (not shown) is the camera itself. In F306, the user of the communication device 200 Figure 4F In this example, the user of the communication device 200 selects "communication device 100" 408. In F307, the communication device 200 sends a time synchronization request to the selected device (i.e., the communication device 100). The identification information about the communication device 200 (different from the L2ID) is included in the time synchronization request. After sending the time synchronization request, the communication device 200 displays Figure 4E The waiting window shown in FIG. 1 and waits for a response to the time synchronization request from the selected device (ie, the communication device 100 ).

[0062] After receiving the time synchronization request from the communication device 200, the communication device 100 displays Figure 4G The receiver list window shown in . The receiver list window displays the communication devices that have sent the time synchronization request (devices that have requested the acquisition of the absolute time). Figure 4G The example in FIG. 4 shows that the communication devices that have sent the time synchronization request are the communication devices 200 and 201. The user of the communication device 100 determines whether to allow or reject time synchronization for each communication device displayed on the recipient list window. The user of the communication device 100 selects "Start synchronization" 418 at the moment when all the communication devices that are allowed to synchronize are displayed. Figure 4GIn the example in FIG. 1 , “communication device 200” is determined as a communication device that is allowed to synchronize time. After selecting “Start synchronization” 408 , the communication device 100 displays Figure 4E In F309 , the communication device 100 transmits a response indicating time synchronization permission to the communication device 200 that is permitted time synchronization.

[0063] (4) L2ID Sharing

[0064] After a response indicating that time synchronization is allowed is sent from the communication device 100 to the communication device 200 in F309, in F310, the communication device 100 and the communication device 200 transmit and receive the L2ID acquired in F303 and F304, respectively, to share the L2ID. The communication device 100 associates the L2ID of the communication device 200 received from the communication device 200 with the identification information about the communication device 200 to store the associated L2ID of the communication device 200 and the identification information about the communication device 200 in the working memory 103 as L2ID management information. The communication device 100 also stores the L2ID used for multicast in the working memory 103 as L2ID management information. The communication device 200 associates the L2ID of the communication device 100 received from the communication device 100 with the identification information about the communication device 100 to store the associated L2ID of the communication device 100 and the identification information about the communication device 100 in the working memory 103 as L2ID management information. The communication device 200 also stores the L2ID used for multicast in the working memory 103 as L2ID management information.

[0065] After the L2ID is shared, the communication device 100 displays Figure 4H The fact that the communication device 100 is in a state where the communication device 100 performs a transmission process of a message including an absolute time (hereinafter referred to as a time synchronization message) is indicated on the window (area 410). In F311, the communication device 100 starts the transmission of the time synchronization message. The transmission process will be described in detail below.

[0066] After the L2ID is shared, the communication device 200 displays Fig. 4I The fact that the communication device 200 is in a state where the communication device 200 performs a reception process of a time synchronization message is indicated on the window (area 411). In F312, the communication device 200 starts reception of a time synchronization message. The reception process will be described in detail below.

[0067] <Pre-processing of sending and receiving absolute time (process when no synchronization group is formed)>

[0068] Next, we will refer to FIG. 4A to FIG. 4IA process when a synchronization group for transmission and reception of absolute time is not formed is described. Here, the communication device 100 and the communication device 200 are exemplified for the description.

[0069] The user of each of the communication apparatus 100 and the communication apparatus 200 receives the Figure 4A In the connection menu window shown in FIG. 1 , "Time synchronization between terminals" 401 indicating a connection for time synchronization between terminals is selected. The selection of "Time synchronization between terminals" 401 causes a transition to Figure 4B . In this example, the user selects "sender" 402 indicating the sending side in the communication device 100, and the user selects "receiver" 403 indicating the receiving side in the communication device 200. After selecting "sender" 412 or "receiver" 413, the window changes to Figure 4C When transmission and reception of absolute time are performed without forming a group, the user of each of the communication device 100 and the communication device 200 selects “no group synchronization” 404 .

[0070] After selecting “No Group Sync” 404, the communication device 100 displays Figure 4H The menu window shown in FIG. 1 and the communication device 200 displays Fig. 4I The menu window shown in . Then, the communication device 100 starts sending the time synchronization message and the communication device 200 starts receiving the time synchronization message. Broadcast communication is enabled in the side link communication, and the sending of the time synchronization message is performed using the L2ID for broadcast (i.e., in a broadcast manner). The sending process and the receiving process will be described below.

[0071] <Messages sent and received in sidelink communication>

[0072] Now refer to FIG. 5A to FIG. 5B Messages used in side link communication according to the present embodiment are described. Figure 5AAn example of the format of a general message 500 used in sidelink communication according to the present embodiment is illustrated. A destination L2ID (Layer-2 ID) 501 indicates the destination of the message 500. As described above, L2ID is information for identifying each communication device in the sidelink communication. When unicast communication is performed, the communication device on the sending side sets the L2ID of the communication device on the receiving side in the destination L2ID 501. When multicast communication is performed, the communication device on the sending side sets the L2ID for multicast in the destination L2ID 501. In this case, as described above in F303 and F310, it is necessary to prepare the L2ID for multicast in advance and share the L2ID for multicast between the communication devices in the group before the multicast communication. When broadcast communication is performed, the device on the sending side sets the L2ID for broadcast in the destination L2ID 501. In this case, it is also necessary to prepare the L2ID for broadcast in advance and share the L2ID for broadcast between the communication devices before the broadcast communication. Setting a specific ID as the L2ID for broadcast enables avoiding the trouble of sharing the L2ID between communication devices. In the present embodiment, a specific (eg, fixed) ID is used as the L2ID for broadcast.

[0073] The L2ID of the communication device on the transmission side is set in the source L2ID 502. The ID indicating the type of the message is set in the frame type 503. The data corresponding to the frame type 503 is input in the frame payload 504.

[0074] Figure 5B An example of the format of a time synchronization message 510 used in side link communication according to the present embodiment is illustrated. Destination L2ID 501 and source L2ID 502 are the same as those in message 500. An ID indicating a time synchronization message is set in frame type 503. A time source type 511 and information 512 on absolute time are set as data for time synchronization in frame payload 504. Information on a time source from which a communication device on the transmission side acquires absolute time is set in time source type 511.

[0075] exist Figure 5B The lower part of indicates an example of information set in the time source type 511. For example, when the communication device on the transmission side reports the absolute time acquired from the GNSS satellite, information indicating the absolute time provided by the time source is set in the absolute time 512 when "001" is set in the time source type 511. In the case of the communication device 100, Figure 5B In the figure, “GNSS” corresponds to the GNSS satellite 203, “base station” corresponds to the base station 202, “communication device connected via PC5” corresponds to the communication devices 200 and 201 connected in the side link, and “internal clock” corresponds to the clock unit 107 in the communication device 100.

[0076] <Time synchronization message sending process>

[0077] Fig. 6A The flowchart of the sending process of the time synchronization message performed by the communication device 100 is illustrated. In S601, the receiver 112 determines whether the absolute time is acquired from the external time source (the base station 202 or the GNSS satellite 203 in this embodiment) via the communication unit 106. If the absolute time is acquired ("Yes" in S601), the process proceeds to S602. In the case that the receiver 112 does not acquire the absolute time from the external time source within a predetermined time in S601 (that is, the predetermined time has passed without acquiring the absolute time) ("Yes" in S601), the process also proceeds to S602.

[0078] In S602, the group determiner 115 determines whether to form a synchronization group with one or more other communication devices. This determination can be performed by the group determiner 115 by confirming the L2ID management information stored in the working memory 103. If the L2ID for multicast of the synchronization group is stored, the group determiner 115 determines to form a synchronization group ("Yes" in S602) and the process proceeds to S603.

[0079] In S603, the message generator 116 generates a time synchronization message for multicast. Figure 5B 504. The message generator 116 sets the L2ID for multicast acquired from the L2ID management information in the destination L2ID 501, and sets the L2ID of the communication device 100 itself in the source L2ID 502. The message generator 116 sets an ID meaning the time synchronization message in the frame type 503. The message generator 116 sets an ID corresponding to the time source acquired in S601 in the time source type 511 in the frame payload 504, and sets the acquired absolute time in the absolute time 512. If the time is not acquired from an external time source, the message generator 116 sets an ID indicating "internal clock" in the time source type 511, and sets the set time of the communication device 100 itself in the absolute time 512. After the generation of the message is completed, the process proceeds to S604. In S604, the transmitter 111 transmits the time synchronization message generated in S603 in a multicast manner. After sending the message, the process returns to S601, where the communication device 100 waits to receive the absolute time from the external time source again.

[0080] If it is determined in S602 that a synchronization group has not been formed (No in S602), the process proceeds to S605. In S605, the message generator 116 generates a time synchronization message for broadcast (to all communication devices). The time synchronization message is Figure 5B . The message generator 116 sets a specific ID as the L2ID for broadcast in the destination L2ID 501. The source L2ID 502, the frame type 503 and the frame payload 504 are set in the same manner as the time synchronization message for multicast generated in S603. After completing the generation of the message, the process proceeds to S606. In S606, the transmitter 111 transmits the time synchronization message generated in S605 in a broadcast manner. After sending the message, the process returns to S601, where the communication device 100 waits to receive the absolute time from the external time source again.

[0081] <Message sending process except time synchronization message>

[0082] The communication device 100 can simultaneously perform the transmission of another message in parallel with the transmission of the time synchronization message. The other message includes, for example, location information about the communication device 100 and sensor information about temperature, acceleration, etc. The location information can be derived based on radio waves received from the GNSS satellite 203. The sensor information can be acquired using a sensor unit (not shown) in the communication device 100. The format of the other message is similar to Figure 5A The format of the message 500 in FIG. 504 corresponds to that of the message 500. The ID corresponding to the information to be reported is set in the frame type 503, and the corresponding information is set in the frame payload 504.

[0083] Figure 6B A flowchart of a transmission process of a message other than a time synchronization message performed by the communication device 100 is illustrated. In S611, the control unit 101 in the communication device 100 confirms whether an event to be reported occurs. The event is, for example, reception of a radio wave from the GNSS satellite 203 in a report of position information and a change in the value of a thermometer as a sensor unit in the communication device 100 in a report of temperature information. If the occurrence of an event is detected ("Yes" in S611), the process proceeds to S612.

[0084] In S612, the group determiner 115 determines whether to form a group with at least one other communication device. This determination can be performed by the group determiner 115 by confirming the L2ID management information stored in the working memory 103. A group can be formed for each piece of information to be reported or the synchronization group described above can be used as a group. If a group is formed ("Yes" in S612), the process proceeds to S613.

[0085] In S613, the message generator 116 generates a message for multicast. Figure 5A 5. The message generator 116 sets an ID corresponding to the information to be reported in the frame type 503, and sets the corresponding information (or information about the corresponding information) in the frame payload 504. The destination L2ID 501 and the source L2ID 502 are set in the same manner as the time synchronization message for multicast generated in S603. After completing the generation of the message, the process proceeds to S614. In S614, the transmitter 111 sends the message generated in S613 in a multicast manner. After sending the message, the process returns to S611, where the communication device 100 waits for the occurrence of an event to be reported again.

[0086] If it is determined in S612 that no group has been formed ("No" in S612), the process proceeds to S615. In S615, the message generator 116 generates a message for broadcast (to all communication devices). The time synchronization message is Figure 5A 5. The message generator 116 sets a specific ID as the L2ID for broadcast in the destination L2ID 501. The source L2ID 502, the frame type 503 and the frame payload 504 are set in the same manner as the time synchronization message for multicast generated in S613. After completing the generation of the message, the process proceeds to S616. In S616, the transmitter 111 transmits the message generated in S615 in a broadcast manner. After sending the message, the process returns to S611, where the communication device 100 waits for the occurrence of an event to be reported again.

[0087] <Message Receiving Process>

[0088] Next, a reception process in the communication device 200 on the reception side of the message will be described. Figure 7 The flowchart of the message reception process performed by the communication device 200 is illustrated. In S701, the receiver 112 receives a message through the side link communication. At this time, the receiver 112 confirms whether the received message is a message to be acquired. In other words, the receiver 112 confirms the L2ID management information stored in the working memory by the communication device 200 to confirm whether the destination L2ID 501 of the received message is included in the L2ID management information and is a specific ID for broadcasting. When a synchronization group is formed, the receiver 112 determines whether the destination L2ID 501 of the received message is the L2ID for broadcasting shared with the communication device 100 in the formation of the group.

[0089] If it is determined that the received message is a message to be acquired ("Yes" in S701), the receiver 112 acquires the message. Then, the process proceeds to S702. If it is determined that the received message is not a message to be acquired ("No" in S701), the receiver 112 discards the received message and waits for receiving the next message (S701).

[0090] In S702, the message analyzer 117 determines whether the received message is a time synchronization message. This determination can be performed by confirming whether the frame type 503 of the received message is an ID indicating a time synchronization message. If the received message is a time synchronization message ("Yes" in S702), the process proceeds to S703.

[0091] In S703, the message analyzer 117 confirms whether the time source type 511 in the frame payload 504 of the received message indicates the GNSS satellite 203 or the base station 202. The GNSS satellite 203 or the base station 202 is a high-precision time source. If the time source type 511 indicates the GNSS satellite 203 or the base station 202 ("Yes" in S703), the process proceeds to S705, where the time controller 118 acquires the absolute time 512. If the time source type 511 does not indicate the GNSS satellite 203 or the base station 202 ("No" in S703), the process proceeds to S704.

[0092] In S704, the message analyzer 117 determines whether the received message is a message for the group. This determination can be performed by confirming whether the destination L2ID 501 of the received message is an L2ID for multicast. If the received message is not a message for the group ("No" in S704), the time controller 118 does not obtain the absolute time 512, and the process returns to S701, where the communication device 200 waits to receive the message again. If the received message is a message for the group ("Yes" in S704), the time controller 118 obtains the absolute time 512 (S705). As described above, the communication device 200 is configured to obtain the absolute time reported to the synchronization group even if the communication device 200 determines that the time source is not a high-precision time source (i.e., not a GNSS satellite 203 or a base station 202).

[0093] After the time controller 118 acquires the absolute time 512 in S705, the time controller 118 updates the set time using the acquired absolute time in S706. After completing the update of the time, the process returns to S701, where the communication device 200 waits to receive a message again.

[0094] If it is determined in S702 that the received message is not a time synchronization message (No in S702), the process proceeds to S707, where the communication device 200 performs a process corresponding to the frame type 503. For example, when the frame type 503 indicates that the location information is included, the communication device 200 can acquire the location information from the frame payload 504 to use the acquired location information as the location information about the communication device 200 itself. Alternatively, when the frame type 503 indicates that the temperature information is included, the communication device 200 can associate the temperature information with the source communication device 100 to detect any abnormality of the communication device in the group using the temperature information. After completing the process corresponding to the frame type, the process returns to S701, where the communication device 200 waits for receiving a message again.

[0095] Due to the above reference Fig. 6A and Figure 6B The described transmission process of the communication device 100 is applicable to the transmission process of the communication device 201, so the description of the transmission process of the communication device 201 is omitted herein.

[0096] [Example of Operation in Communication System 10]

[0097] Now refer to Figure 1 The communication system shown in describes an example of the operation of each communication device.

[0098] First, the operation of transmitting and receiving absolute time in a preformed synchronization group will be described.

[0099] The communication device 100 and the communication device 200 form a group. The communication device 100 is set as the transmission side, and the communication device 200 is set as the reception side. Here, the communication device 201 is a device that does not belong to the group.

[0100] The communication device 100 acquires absolute time from the base station 202 or the GNSS satellite 203 as an external time source. The communication device 200 includes information indicating the absolute time and information about the time source in a time synchronization message and transmits the message in multicast using the L2ID for multicast of time synchronization.

[0101] Since the communication device 201 does not communicate with the base station 202 or the GNSS satellite 203, the communication device 201 acquires the absolute time of the communication device 201 itself. The communication device 201 includes information indicating the absolute time and information about the time source (communication device 201) in a time synchronization message, and transmits the message in a broadcast manner using the L2ID for broadcast.

[0102] The communication device 200 receives the time synchronization message from the communication device 100 , confirms that the time source is the base station 202 or the GNSS satellite 203 (ie, a high-precision time source), and acquires the absolute time from the message.

[0103] In contrast, the communication device 200 receives the time synchronization message from the communication device 201 , confirms that the time source is the communication device 201 (ie, a non-high-precision time source), and does not acquire the absolute time from the message.

[0104] Through the above operation, the communication device 100 and the communication device 200 forming the synchronization group can synchronize the time of the communication device 100 with each other.

[0105] As described above, the formation of a synchronization group makes it possible to limit the communication device to which the time is reported to exclude the influence of the time information reported by the third-party communication device. In addition, the communication device in the synchronization group can use the same absolute time in the group by obtaining the absolute time using the time synchronization message from another communication device in the group. In addition, by classifying each communication device into a sending side and a receiving side in the formation of the group and limiting the number of communication devices on the sending side to one, the communication device on the receiving side can receive the same time synchronization message.

[0106] Next, the operation of transmitting and receiving the absolute time without forming a synchronization group will be described.

[0107] The communication device 100 and the communication device 201 are set as the transmission side, and the communication device 200 is set as the reception side.

[0108] The communication device 100 acquires absolute time from the base station 202 or the GNSS satellite 203 as an external time source. The communication device 200 includes information indicating the absolute time and information about the time source in a time synchronization message, and transmits the message in a broadcast manner using the L2ID for broadcast.

[0109] Since the communication device 201 does not communicate with the base station 202 or the GNSS satellite 203, the communication device 201 acquires the absolute time of the communication device 201 itself. The communication device 201 includes information indicating the absolute time and information about the time source (communication device 201) in a time synchronization message, and transmits the message in a broadcast manner using the L2ID for broadcast.

[0110] The communication device 200 receives the time synchronization message from the communication device 100 , confirms that the time source is the base station 202 or the GNSS satellite 203 (ie, a high-precision time source), and acquires the absolute time from the message.

[0111] In contrast, the communication device 200 receives the time synchronization message from the communication device 201 , confirms that the time source is the communication device 201 (ie, a non-high-precision time source), and does not acquire the absolute time from the message.

[0112] Through the above operation, the communication device 200 can acquire high-precision absolute time without forming a synchronization group.

[0113] The advantage of transmitting and receiving absolute time without forming a synchronization group is that time synchronization can be performed without a group formation process. In addition, when there is another communication device reporting absolute time around the communication device, the communication device can obtain the absolute time without performing control of the communication device on the transmission side.

[0114] As described above, according to the above embodiment, in a communication device capable of side link communication, a message including information about absolute time and time source is reported by a communication device on the transmitting side so that the communication device on the receiving side can obtain absolute time with desired accuracy. In addition, in the formation of a synchronization group, absolute time can be synchronized between communication devices performing side link communication.

[0115] Although the above embodiment describes an example of transmitting and receiving absolute time between a plurality of communication devices that perform side link communication via the PC5 interface, communication between a plurality of communication devices is not limited to side link communication. For example, the present embodiment can be applied to a case where communication using an interface other than the PC5 interface is performed and to a case where an arbitrary communication method capable of direct communication between communication devices is used.

[0116] Although in this embodiment, the base station (base station 202) and GNSS satellite (GNSS satellite 203) in the public network are used as external time sources (high-precision time sources), an NTP server on the network or any time providing system that can provide absolute time or reference time may be used.

[0117] [Other embodiments]

[0118] The present invention can be implemented by a process in which a program that implements one or more functions of the above embodiments is supplied to a system or device via a network or storage medium and one or more processors in a computer of the system or device read and execute the program. In addition, the present invention can be implemented by a circuit (e.g., an application specific integrated circuit (ASIC)) that implements one or more functions.

[0119] The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the claims are attached in order to disclose the scope of the present invention.

[0120] This application claims the benefit of Japanese Patent Application No. 2022-079250, filed May 13, 2022, which is hereby incorporated by reference herein in its entirety.

Claims

1. A communication device, comprising: An acquisition component for obtaining absolute time; A generating means for generating a message comprising first information indicating the absolute time and second information being information about a time source providing the absolute time; as well as Transmitting means for transmitting the message to one or more other communication devices via a PC5 interface compliant with the 3rd Generation Partnership Project (3GPP) standard.

2. The communication device according to claim 1, The sending component sends the message to the one or more other communication devices in a broadcasting manner.

3. The communication device according to claim 1 or 2, further comprising: forming means for forming a group including the communication device and at least one of the one or more other communication devices, The sending component sends the message to the group in a multicast manner.

4. The communication device according to any one of claims 1 to 3, in, If the acquisition component acquires the absolute time from the external time source within a predetermined time, the generation component includes information indicating the absolute time provided by the external time source and information about the external time source in the message as the first information and the second information, respectively.

5. The communication device according to claim 4, in, If the absolute time is not acquired from the external time source within the predetermined time, the acquisition component acquires the absolute time provided by the communication device, and The generating means includes in the message information indicating an absolute time provided by the communication device and information identifying the communication device as the first information and the second information, respectively.

6. The communication device according to claim 4 or 5, The external time source is a base station or a Global Navigation Satellite System (GNSS) satellite capable of communicating with the communication device.

7. A communication device, comprising: Receiving means for receiving a message comprising first information indicating an absolute time and second information about a time source providing the absolute time from another communication device via a PC5 interface compliant with the 3rd Generation Partnership Project (3GPP); as well as updating means for updating a setting time of the communication device based on the first information and the second information included in the message.

8. The communication device according to claim 7, wherein the updating component comprises a first determining component for determining whether the time source indicated by the second information included in the message is a specific device, and in, If the first determination section determines that the time source is the specific device, the updating section updates the set time of the communication device using the first information.

9. The communication device according to claim 8, wherein the updating means further comprises a second determining means for determining whether the message is a message for a group formed by another communication device and including the another communication device and the communication device, and in, If the first determination means determines that the time source is not the specific device and the second determination means determines that the message is a message for the group, the updating means updates the set time of the communication device.

10. The communication device according to claim 8 or 9, The specific device is a base station or a global navigation satellite system (GNSS) satellite capable of communicating with the communication device.

11. A control method for a communication device, the control method comprising: Steps to obtain the absolute time; a generating step of generating a message including first information indicating the absolute time and second information being information about a time source providing the absolute time; and The step of sending the message to one or more other communication devices via a PC5 interface conforming to the 3rd Generation Partnership Project (3GPP) standard.

12. A control method for a communication device, the control method comprising: A receiving step of receiving a message including first information indicating an absolute time and second information about a time source providing the absolute time from another communication device via a PC5 interface conforming to the 3rd Generation Partnership Project (3GPP); as well as An updating step of updating the setting time of the communication device based on the first information and the second information included in the message.

13. A program for causing a computer to function as the communication device according to any one of claims 1 to 9.

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