Relay device, communication method, and computer program product

Abstract

The invention provides a relay device, a communication method and a computer program product. A relay device (5) is used in a communication system (100) mounted on a vehicle and configured so that a first communication device (1-3) and a second communication device (4) can communicate with each other, and is characterized by being provided with: a reception unit (54) configured so as to receive a frame transmitted from the first communication device; a determination unit (55) configured to determine whether or not a transmission timing, which is a timing at which the first communication device has transmitted the frame, is given to the frame; an assignment unit (56) configured so as to assign, as a transmission time, a pseudo transmission time, which is a time obtained on the basis of a reception time, which is a time at which the reception unit receives the frame, to the frame received by the reception unit when the determination unit determines that the transmission time is not assigned to the frame; and a transmission unit (57) configured so as to transmit, to the second communication device, the frame to which the pseudo transmission time has been assigned by the assignment unit.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a relay device, a communication method, and a computer program product. BACKGROUND

[0002] In Patent Literature 1 described below, a technique for estimating a time at which data is generated by a device is proposed. Specifically, a time-assignment device estimates a delay time in advance based on a time required from transmission of an echo request packet of an ICMP (Internet Control Message Protocol) to a device to reception of a response message. The time-assignment device calculates a time at which data is generated by the device, upon reception of the data from the device, taking into account the delay time estimated in advance. The time-assignment device forwards the data including the calculated time.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2019-213033 SUMMARY

[0006] However, as a result of detailed studies by the inventors, it has been found that a device that receives data can more simply assign a time at which data is generated, i.e., a time at which a frame is transmitted, to other components of the frame.

[0007] One aspect of the present disclosure provides a technique capable of simply assigning a transmission time to a frame received by a relay device.

[0008] One aspect of the present disclosure is a relay device used in a communication system mounted on a vehicle and configured so that a first communication device and a second communication device can communicate. The relay device includes a reception unit, a determination unit, an assignment unit, and a transmission unit. The reception unit is configured to receive a frame transmitted from the first communication device. The determination unit is configured to determine whether a time at which the first communication device transmits the frame, i.e., a transmission time, is assigned to the frame. The assignment unit is configured to, in a case where it is determined by the determination unit that the transmission time is not assigned to the frame, assign, as the transmission time, a time obtained based on a time at which the frame is received by the reception unit, i.e., a reception time, to the frame received by the reception unit, i.e., a pseudo transmission time. The transmission unit is configured to transmit the frame to which the pseudo transmission time is assigned by the assignment unit to the second communication device.

[0009] According to such a configuration, the relay device can simply assign a transmission time to a frame transmitted by the first communication device that does not have a function of assigning a transmission time to a frame. That is, a transmission time can be simply assigned to a frame received by the relay device.

[0010] A second aspect of the present disclosure is a communication method used in a communication system mounted on a vehicle and configured so that a first communication device and a second communication device can communicate, the method including: receiving, by a relay device, a frame transmitted from the first communication device; determining, in the relay device, whether a time at which the first communication device transmitted the frame, i.e., a transmission time, is given to the frame; in a case where it is determined in the relay device that the frame is not given the transmission time, giving, to the received frame, a time based on a time at which the frame is received, i.e., a reception time, i.e., a pseudo transmission time, as the transmission time; and transmitting, to the second communication device, the frame to which the pseudo transmission time is given by the relay device.

[0011] A third aspect of the present disclosure is a computer program product including a computer program that, when executed by a processor, implements the procedure of the method of the aforementioned second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a diagram showing an example of the outline configuration of a communication system.

[0013] Figure 2 is a block diagram showing the configuration of a communication system.

[0014] Figure 3 is a flowchart showing the first half of the transmission time giving process.

[0015] Figure 4 is a flowchart showing the second half of the transmission time giving process. DETAILED DESCRIPTION

[0016] Hereinafter, an exemplary embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0017] [1. Embodiment]

[0018] [1-1. Configuration]

[0019] Figure 1 and Figure 2The communication system 100 shown in the embodiment constitutes, for example, an Ethernet (registered trademark) network system installed in a vehicle such as a passenger car. Furthermore, it is not limited to Ethernet; any network utilizing any communication protocol may also be used. Any communication protocol may include LIN, CAN (registered trademark), FlexRay (registered trademark), MOST (registered trademark), and CXPI (registered trademark). LIN is an abbreviation for "Local Interconnect Network." CAN is an abbreviation for "Controller Area Network." MOST is an abbreviation for "Media Oriented Systems Transport." CXPI is an abbreviation for "Clock Extension Peripheral Interface."

[0020] The communication system 100 includes multiple ECUs 1, ECU 2, ECU 3, and ECU 4 (hereinafter referred to as ECUs 1 to 4) as electronic control devices and a relay device 5. ECUs 1 to 4 are connected to the relay device 5 via communication lines. ECU is an abbreviation for "Electronic Control Unit".

[0021] ECUs 1 to 4 are connected to sensors, actuators, etc. (not shown). ECUs 1 to 4, for example, transmit data (e.g., frames) obtained from sensors to other ECUs 1 to 4 via relay device 5. Additionally, ECUs 1 to 4, for example, operate actuators based on data received from other ECUs 1 to 4 via relay device 5. Furthermore, ECUs 1 to 4 have the function of sending and receiving data with the connected relay device 5.

[0022] That is, in the communication system 100, ECUs 1 to 4 are communicatively connected via relay device 5. In other words, ECUs 1 to 4 are configured to send and receive data to each other via relay device 5. Hereinafter, this embodiment will be described as an example where ECUs 1 to 3 function as data transmitting devices and ECU 4 functions as data receiving devices. For example, as... Figure 1 As shown, ECU1 sends data A, ECU2 sends data B, and ECU3 sends data C. Sometimes ECUs 1-3 are referred to as transmitting devices, and ECU 4 as receiving devices. Additionally, sometimes ECUs 1-4 and relay device 5 are referred to as nodes.

[0023] [1-1-1. Transmitting device]

[0024] like Figure 2As shown, the ECU 1 is provided with a CPU 11 and a memory 12. In the memory 12, a program for the CPU 11 to execute a predetermined function is stored.

[0025] The ECU 1 realizes the functions of the following sections by executing the program in the memory 12 by the CPU 11. That is, the ECU 1 is provided with the functions of a time synchronization section 13, a transmission time assignment section 14, and a transceiver section 15.

[0026] The time synchronization section 13 is configured to synchronize the time with other nodes provided with the time synchronization section. In the time synchronization, for example, IEEE 802.1AS is used. Specifically, the local time used in another node is synchronized with the global time used in one node. IEEE is an abbreviation for "Electrical and Electronics Engineers".

[0027] The transmission time assignment section 14 is configured to assign the transmission time ST of a frame to the header of the frame. To be exact, the transmission time ST of a frame can also be said to be the time immediately before the transceiver section 15 transmits the frame, or the time when the frame is generated. The header of the frame can use the format specified by IEEE 1722.

[0028] The transceiver section 15 is configured to transmit and receive frames. In the present embodiment, the transceiver section 15 transmits frames to the ECU 4 via the relay device 5.

[0029] The ECU 2 is provided with a CPU 21 and a memory 22. In the memory 22, a program for the CPU 21 to execute a predetermined function is stored.

[0030] The ECU 2 realizes the functions of the following sections by executing the program in the memory 22 by the CPU 21. That is, the ECU 2 is provided with the functions of a time synchronization section 23 and a transceiver section 24. In addition, the ECU 2 differs from the ECU 1 in that the ECU 2 is not provided with a transmission time assignment section.

[0031] The time synchronization section 23 is configured to synchronize the time with other nodes provided with the time synchronization section.

[0032] The transceiver section 24 is configured to transmit and receive frames. In the present embodiment, the transceiver section 24 transmits frames to the ECU 4 via the relay device 5. However, since the ECU 2 is not provided with a transmission time assignment section, the transmission time ST of a frame is not assigned to the header of the frame transmitted from the ECU 2.

[0033] The ECU 3 includes a CPU 31 and a memory 32. In the memory 32, a program for the CPU 31 to execute a predetermined function is stored.

[0034] The ECU 3 realizes the functions of the following sections by executing the program stored in the memory 32 by the CPU 31. That is, the ECU 3 has the function as the transceiving section 33. In addition, the ECU 3 is different from the ECU 1 in that the ECU 3 does not have the time synchronization section and the transmission time assignment section.

[0035] The transceiving section 33 is configured to transmit and receive frames. In the present embodiment, the transceiving section 33 transmits frames to the ECU 4 via the relay device 5. However, since the ECU 3 does not have the time synchronization section, the time cannot be synchronized with other nodes having the time synchronization section. In addition, since the ECU 3 does not have the transmission time assignment section, the transmission time ST of the frame is not assigned in the header of the frame transmitted from the ECU 3.

[0036] [1-1-2. Relay device]

[0037] The ECU 4 includes a CPU 41 and a memory 42. In the memory 42, a program for the CPU 41 to execute predetermined functions is stored.

[0038] The ECU 4 realizes the functions of the following sections by executing the program stored in the memory 42 by the CPU 41. That is, the ECU 4 has the functions as the time synchronization section 43 and the transceiving section 44.

[0039] The time synchronization section 43 is configured to synchronize the time with other nodes having the time synchronization section.

[0040] The transceiving section 44 is configured to transmit and receive frames. In the present embodiment, the transceiving section 44 receives frames from the ECUs 1 to 3 via the relay device 5.

[0041] [1-1-3. Relay device]

[0042] The relay device 5 has a relay function of forwarding frames received from the ECUs connected to the relay device 5 to other ECUs connected to the relay device 5. That is, in the present embodiment, the relay device 5 relays the communication among the ECUs 1 to 4. In addition, the relay device 5 can have a function as a gateway device. By having the function as a gateway device, frames (data) among different communication protocols can be relayed.

[0043] The relay device 5 functions as a microcomputer having a CPU 51 and a memory 52. In the memory 52, a program for the CPU 51 to execute predetermined functions is stored. In addition, a forwarding table (not shown) is recorded in the memory 52. The forwarding table is a data table indicating a forwarding path. Specifically, the forwarding table is a data table in which the MAC address of the transmission source of the frame and the MAC address of the forwarding destination are associated with each other.

[0044] The relay device 5 realizes the functions of each of the following by the CPU 51 executing the program stored in the memory 52. That is, the relay device 5 has the functions of the time synchronization section 53, the reception section 54, the determination section 55, the assignment section 56, the transmission section 57, and the list management section 58.

[0045] The time synchronization section 53 is configured to synchronize the time with other nodes having the time synchronization section.

[0046] The reception section 54 is configured to receive the frame transmitted from the transmission device.

[0047] The determination section 55 is configured to determine whether the time at which the transmission device transmits the frame, that is, the transmission time ST, is assigned to the frame. Specifically, the determination section 55 determines whether the transmission time ST is assigned to the header of the frame received by the reception section 54.

[0048] The assignment section 56 is configured to, in a case where it is determined by the determination section 55 that the transmission time ST is not assigned to the frame, assign, to the frame, a time based on the time at which the frame is received by the reception section 54, that is, the reception time, as the transmission time ST. The transmission time assignment processing performed by the determination section 55 and the assignment section 56 will be described later in detail.

[0049] The transmission section 57 is configured to forward the frame based on the forwarding table. More specifically, the transmission section 57 is configured to directly transmit the frame received by the reception section 54 to the reception device as it is, or transmit the frame to which the pseudo transmission time is assigned by the assignment section 56 to the reception device.

[0050] Specifically, the transmission section 57 transmits the frames of the four patterns of the first frame, the second frame, the third frame, and the fourth frame to the reception device. The first frame is a frame to which the transmission time ST is originally assigned by the transmission device. The second frame is a frame to which the time considering the transmission delay described later is assigned as the pseudo transmission time, and the pseudo transmission time is assigned as the transmission time ST. The third frame is a frame to which the time at which the frame is received by the reception section 54, that is, the reception time, is assigned as the pseudo transmission time, and the pseudo transmission time is assigned as the transmission time ST. The fourth frame is a frame to which the transmission time ST is not assigned by the transmission device, and to which the pseudo transmission time is not assigned as the transmission time ST by the relay device 5. That is, the first frame and the fourth frame mean that the frame transmitted from the transmission device is directly forwarded as it is. On the other hand, the second frame and the third frame are frames to which the pseudo transmission time is assigned as the transmission time ST by the relay device 5.

[0051] The list management section 58 is a storage device for recording the first recording list and the second recording list described later.

[0052] Furthermore, the ECU 1 to 4 and the relay device 5 can each have one microcomputer or a plurality of microcomputers.

[0053] The method of realizing the functions of each part included in the ECU 1 to 4 and the relay device 5 is not limited to software, and a part or all of the functions thereof can be realized using one or a plurality of hardware. For example, in the case where the above functions are realized by an electronic circuit as hardware, the electronic circuit can be realized by a digital circuit or an analog circuit, or a combination thereof.

[0054] [1-2. Processing]

[0055] Using Figure 3 and Figure 4 The flowchart shown in FIG. 10 will be described as a transmission time assignment processing performed by the relay device 5. Further, the present transmission time assignment processing is repeatedly performed during the on period of the ignition switch.

[0056] First, in S101, the reception part 54 of the relay device 5 receives a frame from the transmission device.

[0057] Next, in S102, the determination part 55 of the relay device 5 determines whether or not the transmission time ST is assigned in the header of the frame. Specifically, the determination part 55 determines whether or not the time stamp is set in the header of the frame.

[0058] In S102, in the case where the determination part 55 determines that the transmission time ST is not assigned in the header of the frame, the processing proceeds to S103. On the other hand, in S102, in the case where the determination part 55 determines that the transmission time ST is assigned in the header of the frame, the processing proceeds to S111, and the transmission part 57 of the relay device 5 directly transmits the frame received from the transmission device in S101 to the reception device as it is. That is, the transmission part 57 transmits the first frame to the reception device.

[0059] In S103, the relay device 5 determines whether or not the reception device has a function of processing the information of the transmission time ST assigned to the frame. Specifically, the relay device 5 refers to the first record list recorded in the list management part 58, and determines whether or not the reception device can process the information of the transmission time ST. The first record list is a list in which it is recorded for the reception device of the forwarding destination whether or not the function of processing the information of the transmission time ST assigned to the frame is possessed. In the case where it is recorded in the first record list that the reception device can process the information of the transmission time ST, the relay device 5 determines that the reception device can process the information of the transmission time ST. As an example, the function of processing the information of the transmission time ST refers to the function of reading the time stamp of the transmission time ST.

[0060] The relay device 5 moves to S104 in a case where it is determined in S103 that the reception device is able to process the information of the transmission time ST. On the other hand, the relay device 5 moves to S110 in a case where it is determined in S103 that the reception device is not able to process the information of the transmission time ST. The relay device 5 does not assign a pseudo transmission time as the transmission time ST to the frame, and moves to S111, and the transmission section 57 directly transmits the frame received from the transmission device in S101 to the reception device as it is. That is, the transmission section 57 transmits the fourth frame to the reception device.

[0061] In S104, the relay device 5 determines whether the reception device needs the information of the transmission time ST. Specifically, the relay device 5 refers to the second record list recorded in the list management section 58, and determines whether the reception device needs the information of the transmission time ST. The second record list is a list in which it is recorded for the reception device that is the forwarding destination whether the reception device needs the information of the transmission time ST. The relay device 5 determines that the reception device needs the information of the transmission time ST in a case where it is recorded in the second record list that the reception device needs the information of the transmission time ST. As an example, the need for the information of the transmission time ST means the need to process the data in chronological order by reading the time stamp of the transmission time ST.

[0062] The relay device 5 moves to S105 in a case where it is determined in S104 that the reception device needs the information of the transmission time ST. On the other hand, the relay device 5 moves to S110 in a case where it is determined in S104 that the reception device does not need the information of the transmission time ST. The relay device 5 does not assign a pseudo transmission time as the transmission time ST to the frame, and moves to S111, and the transmission section 57 directly transmits the frame received from the transmission device in S101 to the reception device as it is. That is, the transmission section 57 transmits the fourth frame to the reception device.

[0063] In S105, the relay device 5 determines whether the transmission device and the relay device 5 are time-synchronized. Specifically, the relay device 5 determines whether the transmission device is a transmission device that performs communication for time-synchronization with the relay device 5. The relay device 5 determines that the transmission device and the relay device 5 are time-synchronized in a case where the transmission device is a transmission device that performs communication for time-synchronization with the relay device 5. In addition, the relay device 5 can also hold in advance a list of transmission devices that directly or indirectly refer to a global time for time-synchronization, and determine whether the transmission device and the relay device 5 are time-synchronized by referring to the list.

[0064] The relay device 5 moves to S106 in a case where it is determined in S105 that the transmission device and the relay device 5 are time-synchronized. On the other hand, the relay device 5 moves to S108 in a case where it is determined in S105 that the transmission device and the relay device 5 are not time-synchronized.

[0065] In S106, the relay device 5 determines whether or not the frame contains control data. The control data is data corresponding to the operation of the vehicle with respect to the running system of the vehicle such as turning, running, stopping, and the like. For example, the control data is used in a powertrain ECU, an ECU that implements an automatic driving function and a driving assist function, and the like. The control data is sometimes used in the receiving device in combination with other control data. In other words, a plurality of control data is sometimes used by so-called sensor fusion. In this case, the plurality of control data is preferably sampled at a time as close as possible. That is, it is preferable that the control data be associated with a more accurate transmission time ST. On the other hand, data other than the control data contains data corresponding to a multimedia function such as audio, data corresponding to a comfort function such as air conditioning, and the like.

[0066] In a case where the relay device 5 determines in S106 that the frame contains control data, the process proceeds to S107. On the other hand, in a case where the relay device 5 determines in S106 that the frame does not contain control data, the process proceeds to S108.

[0067] Next, in S107, the relay device 5 sets a time that takes into account the transmission delay as the pseudo transmission time. Here, in a case where the transmission device and the relay device 5 are time-synchronized, the relay device 5 records the transmission delay in advance. As an example, the relay device 5 records, as the transmission delay, a difference between a time stamp indicating the transmission time ST of the frame transmitted from the transmission device and a time stamp indicating the reception time at which the relay device 5 receives the frame.

[0068] The relay device 5 sets, as the pseudo transmission time, a time obtained by subtracting a delay time, that is, a transmission delay, of a signal in a communication path from the transmission device to the relay device 5 from the reception time. In a case where it is preferable to associate a more accurate transmission time ST as with the control data, it is considered that a time that takes into account the transmission delay, which is closer to the actual transmission time ST than the reception time at which the reception section 54 of the relay device 5 receives the frame from the transmission device, is used as the pseudo transmission time.

[0069] On the other hand, in S108, the relay device 5 sets, as the pseudo transmission time, the reception time at which the reception section 54 of the relay device 5 actually receives the frame from the transmission device. In a case where the transmission device and the relay device 5 are not time-synchronized and the transmission delay cannot be measured, and in a case where the transmission time ST can be used as data even if the transmission delay time is not taken into account and the transmission time ST is calculated strictly, the reception time is used as the pseudo transmission time.

[0070] Next, in S109, the assignment section 56 of the relay device 5 assigns a pseudo transmission time to the header of the frame. Specifically, the assignment section 56 assigns the pseudo transmission time of S107 or the pseudo transmission time of S108 as the transmission time ST of the frame. That is, the assignment section 56 generates the second frame to which the pseudo transmission time of S107 is assigned or the third frame to which the pseudo transmission time of S108 is assigned.

[0071] Next, in S111, the transmission section 57 transmits the frame to the reception device. That is, the transmission section 57 transmits one of the first frame to the fourth frame to the reception device.

[0072] [1-3. Effects]

[0073] According to the above-described embodiments, the following effects can be obtained.

[0074] (1a) In the above-described embodiments, the relay device 5 assigns a pseudo transmission time as the transmission time ST to the frame in a case where it is determined that the frame is not assigned with the transmission time ST. According to such a configuration, the relay device 5 can simply assign the transmission time ST to the frame transmitted by the transmission device that does not have a function of assigning the transmission time ST to the header of the frame. Thereby, the reception device can process the frame taking into account the information of the transmission time ST, and thus it is easy to obtain matching with other frames received.

[0075] (1b) In the above-described embodiments, the relay device 5 sets the reception time at which the reception section 54 of the relay device 5 receives the frame from the transmission device as the pseudo transmission time in a case where it is determined that the transmission device is not time-synchronized with the relay device 5, or in a case where it is determined that the frame does not contain control data. According to such a configuration, the relay device 5 can simply assign the transmission time ST.

[0076] In the in-vehicle network, the communication line connecting the transmission device and the relay device 5 is relatively short, and thus even if the reception time is set as the pseudo transmission time, the possibility of greatly deviating from the actual transmission time ST is low. Therefore, in a case where the transmission device and the relay device 5 are not time-synchronized and thus the transmission delay time cannot be measured, or in a case where the control data is not preferred to consider the transmission delay time and to strictly calculate the transmission time ST, setting the reception time as the pseudo transmission time can more simply assign the transmission time ST, and thus is preferred. As the transmission device, an ECU that does not have a time synchronization section or a transmission time assignment section like the ECU 3 is assumed. In particular, in a case where the transmission device and the relay device do not communicate via another relay device 5 but directly communicate with each other, even if the reception time is set as the pseudo transmission time, the deviation from the actual transmission time ST is less.

[0077] (1c) In the above embodiment, the relay device 5 sets, as the pseudo transmission time, a time obtained by subtracting the delay time from the reception time, in a case where it is determined that the transmission device and the relay device 5 are time-synchronized and the frame contains control data.

[0078] For example, consider a case where the transmission device has a function of time synchronization but does not have a function of assigning a transmission time ST to a frame. That is, consider an ECU that has the time synchronization section 23 but does not have the transmission time assignment section, like the ECU 2. As an example, consider a conventional ECU that does not have a function of assigning a transmission time ST to a frame, a cheap ECU that does not have a function of assigning a transmission time ST in order to suppress cost, and the like. According to the above configuration, the relay device 5 can simply assign a transmission time ST to a frame transmitted by such an ECU.

[0079] In addition, the control data is preferably associated with a more accurate transmission time ST, and the relay device 5 assigns, as the pseudo transmission time, a time that takes into account the transmission delay, so it can assign a transmission time ST simply and with higher accuracy. Therefore, the control data can be used for processing that requires real-time performance, processing that requires response speed.

[0080] (1d) In the above embodiment, the relay device 5 does not assign a pseudo transmission time to a frame, in a case where it is determined that the reception device does not need information of a transmission time ST. According to such a configuration, the relay device 5 can suppress transmission of unnecessary information to the reception device.

[0081] (1e) In the above embodiment, the relay device 5 does not assign a pseudo transmission time to a frame, in a case where it is determined that the reception device does not have a function of processing information of a transmission time ST assigned to a frame. According to such a configuration, the relay device 5 can suppress transmission of unnecessary information to the reception device.

[0082] [1-4. Correspondence]

[0083] In the above embodiment, the ECUs 1 to 3 correspond to the first communication device, and the ECU 4 corresponds to the second communication device.

[0084] [2. Other Embodiments]

[0085] The above describes embodiments of the present disclosure, but the present disclosure is not limited to the above embodiments, and various modes can of course be adopted.

[0086] (2a) In the above embodiment, the configuration in which the relay device 5 sets the reception time as the pseudo transmission time in S108 in the case where it is determined in S106 that the frame does not contain control data is exemplified. However, the relay device 5 can also proceed to S107 to set the time after the delay time is subtracted from the reception time as the pseudo transmission time in the case where it is determined in S106 that the frame does not contain control data.

[0087] (2b) In the above embodiment, the configuration in which the communication system 100 is provided with one relay device 5 is exemplified. However, the communication system 100 can also be provided with a plurality of relay devices. A relay device can also be provided between the transmission device and the relay device 5, and a relay device can also be provided between the relay device 5 and the reception device. If the forwarding table is recorded in any of the relay devices, and the time synchronization section is provided, the pseudo transmission time can be given to the frame transmitted from the transmission device by any of the relay devices.

[0088] (2c) In the above embodiment, the configuration in which the ECUs 1 to 3 are connected to the relay device 5 in parallel is exemplified. However, the manner in which the transmission device is connected to the relay device 5 is not limited thereto. For example, the transmission device can also be connected to the relay device 5 in a multipoint connection manner.

[0089] (2d) Each device (i.e., the ECUs 1 to 4 and the relay device 5) and the scheme of each device according to the present disclosure can also be implemented by a special-purpose computer that is provided by a processor and a memory that are programmed to execute one or more functions embodied by a computer program. Alternatively, each device and the scheme of each device according to the present disclosure can also be implemented by a special-purpose computer provided by a processor composed of one or more special-purpose hardware logic circuits. Alternatively, each device and the scheme of each device according to the present disclosure can also be implemented by one or more special-purpose computers composed of a combination of a processor programmed to execute one or more functions and a memory and a processor composed of one or more hardware logic circuits. In addition, the computer program can be stored as instructions executed by a computer in a non-transitory tangible recording medium readable by a computer. In the scheme in which the functions of each section included in each device are implemented, it is not necessarily required to include software, and all of the functions can be implemented using one or more hardware.

[0090] (2e) One of the constituent elements in the above-described embodiments can also realize a plurality of functions possessed by one of the constituent elements in the above-described embodiments, or one function possessed by one of the constituent elements in the above-described embodiments can be realized by a plurality of constituent elements. In addition, a plurality of functions possessed by a plurality of constituent elements can be realized by one constituent element, or one function realized by a plurality of constituent elements can be realized by one constituent element. In addition, a part of the configuration of the above-described embodiments can be omitted. In addition, at least a part of the configuration of the above-described embodiments can be added to or replaced with the configuration of another of the above-described embodiments.

[0091] (2f) In addition to the above-described communication system 100, the present disclosure can also be realized in various modes such as each device that becomes a constituent element of the communication system 100, a program for causing a computer to function as each device, a non-transitory tangible recording medium such as a semiconductor memory in which the program is recorded, a communication method, and the like.

Claims

1. A relay device for use in a communication system mounted on a vehicle and configured to enable communication between a first communication device and a second communication device, the relay device being characterized by comprising: The receiving unit is configured to receive frames transmitted from the first communication device; The determination unit is configured to determine whether the time when the first communication device sent the frame, i.e., the sending time, is assigned to the frame. The assignment unit is configured to, when the determination unit determines that the frame has not been assigned the transmission time, assign the false transmission time, obtained based on the time when the receiving unit receives the frame (i.e., the reception time), as the transmission time to the frame received by the receiving unit; and The transmitting unit is configured to transmit the frame, which has been assigned the pseudo-transmission time by the assigning unit, to the second communication device.

2. The relay device according to claim 1, characterized in that, The assignment unit is configured to set the receiving time as the pseudo-transmission time.

3. The relay device according to claim 1, characterized in that, The assignment unit is configured to set the pseudo transmission time as the time obtained by subtracting the signal delay time in the communication path from the first communication device to the relay device from the reception time.

4. The relay device according to claim 1 or 2, characterized in that, The assignment unit is configured to determine whether the second communication device needs the transmission time information by referring to a list of information pre-recorded indicating whether the second communication device needs the transmission time information. If it is determined that the second communication device does not need the transmission time information, the false transmission time is not assigned as the transmission time to the frame. The transmitting unit is configured to transmit the frame received by the receiving unit to the second communication device.

5. The relay device according to claim 1 or 2, characterized in that, The assignment unit is configured to determine whether the second communication device has the function of processing the transmission time information assigned to the frame by referring to a list pre-recorded with information on whether the second communication device has the function of processing the transmission time information assigned to the frame. If it is determined that the second communication device does not have the function of processing the transmission time information assigned to the frame, the false transmission time is not assigned to the frame as the transmission time. The transmitting unit is configured to transmit the frame received by the receiving unit to the second communication device.

6. A communication method used in a communication system mounted on a vehicle and configured to enable communication between a first communication device and a second communication device, the communication method being characterized by comprising: The relay device receives frames sent from the first communication device; In the relay device, it is determined whether the time when the first communication device sent the frame, i.e., the sending time, is assigned to the frame; If the relay device determines that the frame has not been assigned the transmission time, it assigns the false transmission time, which is the time obtained based on the time of receiving the frame, to the received frame as the transmission time. as well as The frame, which has been assigned the pseudo-transmission time by the relay device, is sent to the second communication device.

7. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the method described in claim 6.

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