In-vehicle communication system and communication method

Abstract

This onboard communication system comprises: an optical coupler; a first onboard device group constituted of a plurality of onboard devices connected to a first end of the optical coupler; and a second onboard device group constituted of a plurality of onboard devices connected to a second end of the optical coupler. Each onboard device of the first onboard device group can communicate with each onboard device of the second onboard device group via a shared transmission path in the optical coupler, and each onboard device of the second onboard device group can communicate with each onboard device of the first onboard device group via the shared transmission path in the optical coupler.

Description

Technical Field

[0001] The present disclosure relates to an in-vehicle communication system and a communication method. This application claims priority based on Japanese Patent Application No. 2020-179439 filed on October 27, 2020, and incorporates all of the disclosures thereof herein.

Background Art

[0002] Patent Document 1 (International Publication No. 2019 / 111447) discloses the following in-vehicle communication system. That is, the in-vehicle communication system is an in-vehicle communication system mounted on a vehicle, and includes a master function unit and a plurality of slave function units. The plurality of slave function units can transmit an upstream communication signal to the master function unit via at least a common optical fiber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The in-vehicle communication system of the present disclosure includes an optical coupler, a first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, and a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler. Each in-vehicle device in the first in-vehicle device group can communicate with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler, and each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via the common transmission path in the optical coupler.

[0005] The communication method of the present disclosure is an in-vehicle communication system comprising an optical coupler, a first group of in-vehicle devices connected to a first end of the optical coupler, and a second group of in-vehicle devices connected to a second end of the optical coupler. Each in-vehicle device in the first group of in-vehicle devices can communicate with each in-vehicle device in the second group of in-vehicle devices via a common transmission path in the optical coupler, and each in-vehicle device in the second group of in-vehicle devices can communicate with each in-vehicle device in the first group of in-vehicle devices via the common transmission path in the optical coupler. The communication method includes steps in which the in-vehicle devices in the first group of in-vehicle devices transmit optical signals to each in-vehicle device in the second group of in-vehicle devices via the optical coupler, and the in-vehicle devices in the second group of in-vehicle devices transmit optical signals to each in-vehicle device in the first group of in-vehicle devices via the optical coupler.

[0006] One aspect of the present disclosure can be implemented not only as an in-vehicle communication system, but also as a semiconductor integrated circuit that implements part or all of the in-vehicle communication system, or as a program for causing a computer to execute processing steps in the in-vehicle communication system.

Brief Description of the Drawings

[0007]

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[0008] Conventionally, in order to cope with an increase in data communication volume in a vehicle, a technique using an optical fiber for a vehicle-mounted communication system has been proposed.

[0009] [Problems to be Solved by the Present Disclosure] The technique described in Patent Document 1 enables a plurality of slave functional units to transmit communication signals to one master functional unit. Beyond the technique described in Patent Document 1, a technique that enables various communications using optical signals between a plurality of in-vehicle devices is desired.

[0010] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide an in-vehicle communication system and a communication method capable of performing various communications using an optical signal among a plurality of in-vehicle devices.

[0011] [Effects of the Present Disclosure] According to the present disclosure, various communications using an optical signal can be performed among a plurality of in-vehicle devices.

[0012] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0013] (1) The in-vehicle communication system according to an embodiment of the present disclosure includes an optical coupler, a first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, and a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler. Each in-vehicle device in the first in-vehicle device group can communicate with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler, and each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via the common transmission path in the optical coupler.

[0014] In this way, with a configuration in which each in-vehicle device in the first in-vehicle device group can communicate with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler, and each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via the common transmission path in the optical coupler, compared with one-to-one communication between in-vehicle devices and one-to-many communication between in-vehicle devices, communication can be performed among more in-vehicle devices with a simpler configuration. Therefore, various communications using an optical signal can be performed among a plurality of in-vehicle devices.

[0015] (2) Among the plurality of in-vehicle devices in the first in-vehicle device group, a master device, which is any one of the in-vehicle devices, transmits timing information, which is information used by the in-vehicle devices in the in-vehicle communication system for time synchronization processing, to the second in-vehicle device group via the optical coupler. Any one of the plurality of in-vehicle devices in the second in-vehicle device group may transmit the timing information received from the master device to the first in-vehicle device group via the optical coupler.

[0016] With such a configuration, in addition to time synchronization of each in-vehicle device in the second in-vehicle device group, time synchronization of each in-vehicle device other than the master device in the first in-vehicle device group can be performed. Therefore, in an in-vehicle communication system in which, for example, time-division multiplex communication is performed, each in-vehicle device can transmit an optical signal at a more accurate timing.

[0017] (3) The master device transmits slot information indicating time slots assigned to the respective in-vehicle devices in the in-vehicle communication system to the second in-vehicle device group via the optical coupler. Any one of the plurality of in-vehicle devices in the second in-vehicle device group may transmit the slot information received from the master device to the first in-vehicle device group via the optical coupler.

[0018] With such a configuration, the master device can notify the other in-vehicle devices in the first in-vehicle device group and the in-vehicle devices in the second in-vehicle device group of the time slots. Therefore, for example, the assigned content of the time slots can be dynamically changed.

[0019] (4) Among the plurality of in-vehicle devices in the first in-vehicle device group, the in-vehicle devices other than the master device may perform the time synchronization processing based on the timing information received from the second in-vehicle device group, the propagation delay of the optical signal transmitted from the master device to the second in-vehicle device group, and the propagation delay of the optical signal transmitted from the second in-vehicle device group to the first in-vehicle device group.

[0020] With such a configuration, considering the propagation delay of the optical signal, time synchronization can be performed more accurately.

[0021] (5) At least one of the in-vehicle devices in the in-vehicle communication system includes a clock synchronization circuit that performs clock synchronization processing with other in-vehicle devices, and the in-vehicle device including the clock synchronization circuit may turn off the clock synchronization circuit in the time slot assigned to the in-vehicle devices of its own group among the first in-vehicle device group and the second in-vehicle device group.

[0022] With such a configuration, the clock synchronization circuit can operate more stably, so that clock synchronization can be established more reliably and the time required to establish clock synchronization can be shortened, thus enabling effective utilization of the communication bandwidth. Also, compared with a configuration in which the clock synchronization circuit is always in an on state, power consumption can be reduced.

[0023] (6) The optical coupler includes a first transmission path that is the transmission path for transmitting an optical signal from the in-vehicle device of the first in-vehicle device group to the in-vehicle device of the second in-vehicle device group, and a second transmission path that is the transmission path for transmitting an optical signal from the in-vehicle device of the second in-vehicle device group to the in-vehicle device of the first in-vehicle device group, and a common time slot may be assigned to at least one of the in-vehicle devices among the plurality of in-vehicle devices of the first in-vehicle device group and at least one of the in-vehicle devices among the plurality of in-vehicle devices of the second in-vehicle device group.

[0024] With such a configuration, the amount of data that can be transmitted and received in one communication frame can be increased.

[0025] (7) The communication method according to an embodiment of the present disclosure includes an optical coupler, a first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, and a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler. Each in-vehicle device in the first in-vehicle device group can communicate with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler, and each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via the common transmission path in the optical coupler. The communication method in the in-vehicle communication system includes: a step in which the in-vehicle device in the first in-vehicle device group transmits an optical signal to each in-vehicle device in the second in-vehicle device group via the optical coupler; and a step in which the in-vehicle device in the second in-vehicle device group transmits an optical signal to each in-vehicle device in the first in-vehicle device group via the optical coupler.

[0026] In this way, in a configuration where each in-vehicle device in the first in-vehicle device group can communicate with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler, and each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via the common transmission path in the optical coupler, by a method in which the in-vehicle device in the first in-vehicle device group transmits an optical signal to each in-vehicle device in the second in-vehicle device group via the optical coupler, and the in-vehicle device in the second in-vehicle device group transmits an optical signal to each in-vehicle device in the first in-vehicle device group via the optical coupler, communication can be performed between more in-vehicle devices with a simpler configuration compared to communication between one-to-one in-vehicle devices and communication between one-to-many in-vehicle devices. Therefore, various communications using optical signals can be performed between a plurality of in-vehicle devices.

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. Also, at least a part of the embodiments described below may be arbitrarily combined.

[0028] [Configuration and Basic Operation] FIG. 1 is a diagram showing an example of the configuration of an in-vehicle communication system according to an embodiment of the present disclosure. Referring to FIG. 1, the in-vehicle communication system 401 includes an optical coupler 201, a first in-vehicle device group Gr1 composed of ECUs (Electronic Control Units) 101A, 101B, and 101C, and a second in-vehicle device group Gr2 composed of ECUs 101D, 101E, and 101F. Hereinafter, each of the ECUs 101A, 101B, 101C, 101D, 101E, and 101F is also referred to as an ECU 101. The ECU 101 is an example of an in-vehicle device.

[0029] The in-vehicle communication system 401 is mounted on a vehicle. For example, the in-vehicle communication system 401 is a PON (Passive Optical Network) system. Note that the in-vehicle communication system 401 may be an optical communication system other than the PON system.

[0030] The optical coupler 201 includes a film-shaped main body portion 220 and an optical waveguide 221 formed in the main body portion 220. For example, the optical coupler 201 is formed of resin. More specifically, the optical coupler 201 is generated by forming the optical waveguide 221 in the main body portion 220 formed of resin using a photolithography technique or the like.

[0031] The optical waveguide 221 is formed in the main body portion 220 so as to extend between connection portions 211A, 211B, and 211C provided at the first end of the optical coupler 201 and connection portions 211D, 211E, and 211F provided at the second end of the optical coupler 201. The optical waveguide 221 has a branching portion. For example, the optical waveguide 221 has a first end 221A connected to the connection portion 211A, a second end 221B connected to the connection portion 211B, a third end 221C connected to the connection portion 211C, a fourth end 221D connected to the connection portion 211D, a fifth end 221E connected to the connection portion 211E, and a sixth end 221F connected to the connection portion 211F. Hereinafter, each of the connection portions 211A, 211B, 211C, 211D, 211E, and 211F is also referred to as a connection portion 211.

[0032] The ECUs 101A, 101B, and 101C of the first in-vehicle device group Gr1 are connected to the first end of the optical coupler 201. More specifically, the ECUs 101A, 101B, and 101C are respectively connected to the connection parts 211A, 211B, and 211C via the optical fiber cable 212. Note that the first in-vehicle device group Gr1 may be composed of two or four or more ECUs 101.

[0033] The first end 221A of the optical waveguide 221 is optically connected to the corresponding optical fiber cable 212 at the connection part 211A. Also, the second end 221B of the optical waveguide 221 is optically connected to the corresponding optical fiber cable 212 at the connection part 211B. Also, the third end 221C of the optical waveguide 221 is optically connected to the corresponding optical fiber cable 212 at the connection part 211C.

[0034] The ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2 are connected to the second end of the optical coupler 201. More specifically, the ECUs 101D, 101E, and 101F are respectively connected to the connection parts 211D, 211E, and 211F via the optical fiber cable 212. Note that the second in-vehicle device group Gr2 may be composed of two or four or more ECUs 101.

[0035] The fourth end 221D of the optical waveguide 221 is optically connected to the corresponding optical fiber cable 212 at the connection part 211D. Also, the fifth end 221E of the optical waveguide 221 is optically connected to the corresponding optical fiber cable 212 at the connection part 211E. Also, the sixth end 221F of the optical waveguide 221 is optically connected to the corresponding optical fiber cable 212 at the connection part 211F.

[0036] The ECU 101 is, for example, an autonomous driving ECU, a navigation device, a TCU (Telematics Communication Unit), a gateway device, a camera ECU, a millimeter-wave sensor ECU, a LiDAR (Light Detection and Ranging) ECU, a storage ECU, or an antenna module.

[0037] As an example, ECUs 101D, 101E, and 101F are camera ECUs. Also, ECUs 101A and 101B are autonomous driving ECUs. Further, ECU 101C is a storage ECU. Since the in-vehicle communication system 401 can realize a redundant configuration of the autonomous driving ECUs by means of ECUs 101A and 101B, even if one of ECUs 101A and 101B fails, autonomous driving control can be continuously performed.

[0038] The ECUs 101A, 101B, and 101C of the first in-vehicle device group Gr1 can communicate with the ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2 via a common transmission path in the optical coupler 201. Also, the ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2 can communicate with the ECUs 101A, 101B, and 101C of the first in-vehicle device group Gr1 via a common transmission path in the optical coupler 201. For example, ECUs 101A, 101B, 101C and ECUs 101D, 101E, 101F can communicate with each other via the optical waveguide 221 in the optical coupler 201.

[0039] Here, the direction from the first in-vehicle device group Gr1 to the second in-vehicle device group Gr2 is referred to as the upstream direction, and the direction from the second in-vehicle device group Gr2 to the first in-vehicle device group Gr1 is referred to as the downstream direction. The in-vehicle communication system 401 is, for example, a TDM-PON system. Specifically, in the in-vehicle communication system 401, time-division multiplexing (TDM) communication is performed in both the upstream and downstream directions.

[0040] Each of ECU101D, 101E, and 101F can transmit an upstream optical signal including upstream communication data such as a frame via an optical fiber cable 212, a corresponding connection part 211, and an optical coupler 201 to ECU101A, 101B, and 101C. Also, each of ECU101A, 101B, and 101C can transmit a downstream optical signal including downstream communication data such as a frame via the optical fiber cable 212, the corresponding connection part 211, and the optical coupler 201 to ECU101D, 101E, and 101F. For example, each ECU101 transmits and receives an optical signal of the same wavelength. Each ECU101 is assigned a time slot TS which is a period during which it can transmit an optical signal, and transmits an optical signal in the assigned time slot TS.

[0041] Any one of the ECUs 101 in the first in-vehicle device group Gr1 is a master device. As an example, ECU101A is a master device. Also, any one of the ECUs 101 in the second in-vehicle device group Gr2 is a sub-master device. As an example, ECU101D is a sub-master device.

[0042] [ECU] FIG. 2 is a diagram showing an example of the configuration of an ECU in an in-vehicle communication system according to an embodiment of the present disclosure. FIG. 2 is a diagram showing the configuration of an ECU other than ECU101A.

[0043] Referring to FIG. 2, an ECU101 other than ECU101A includes an optical transceiver 10, a receiving unit 20, a transmitting unit 30, a processing unit 40, a counter 50, and a storage unit 70. The receiving unit 20 has a receiving CDR (Clock and Data Recovery) circuit 21. The transmitting unit 30 has a transmitting CDR circuit 31. The receiving CDR 21 is an example of a clock synchronization circuit.

[0044] The processing unit 40 is realized by a processor such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor), for example. The storage unit 70 is, for example, a non-volatile memory.

[0045] The processing unit 40 generates frames addressed to other ECUs 101 at regular or irregular intervals and outputs the generated frames to the transmission unit 30. More specifically, for example, the processing unit 40 in the ECU 101D which is a camera ECU receives image information indicating a captured image from a camera unit (not shown) that captures the front of the vehicle, and generates a data frame which is a frame storing a timestamp based on the received image information and the count value of the counter 50, and outputs the data frame to the transmission unit 30.

[0046] The transmission unit 30 outputs the frame received from the processing unit 40 to the optical transceiver 10.

[0047] The optical transceiver 10 converts the electrical signal indicating the frame received from the transmission unit 30 into an optical signal and transmits the optical signal to other ECUs 101 via the optical fiber cable 212 and the optical coupler 201. More specifically, the optical transceiver 10 in the ECU 101 of the second in-vehicle device group Gr2 transmits an optical signal to the ECU 101 of the first in-vehicle device group Gr1 via the optical fiber cable 212 and the optical coupler 201. Also, the optical transceiver 10 in the ECU 101 of the first in-vehicle device group Gr1 transmits an optical signal to the ECU 101 of the second in-vehicle device group Gr2 via the optical fiber cable 212 and the optical coupler 201.

[0048] Also, the optical transceiver 10 receives an optical signal from other ECUs 101 via the optical fiber cable 212 and the optical coupler 201, converts the received optical signal into an electrical signal, and outputs the electrical signal to the reception unit 20. More specifically, the optical transceiver 10 in the ECU 101 of the first in-vehicle device group Gr1 receives an optical signal from the ECU 101 of the second in-vehicle device group Gr2 via the optical fiber cable 212 and the optical coupler 201, converts the received optical signal into an electrical signal, and outputs the electrical signal to the reception unit 20. Also, the optical transceiver 10 in the ECU 101 of the second in-vehicle device group Gr2 receives an optical signal from the ECU 101 of the first in-vehicle device group Gr1 via the optical fiber cable 212 and the optical coupler 201, converts the received optical signal into an electrical signal, and outputs the electrical signal to the reception unit 20.

[0049] The receiving unit 20 receives an electrical signal from the optical transceiver 10, reconstructs a frame from the electrical signal, and outputs the reconstructed frame to the processing unit 40.

[0050] The processing unit 40 receives a frame from the receiving unit 20 and performs various processes based on the received frame. More specifically, for example, the processing unit 40 in the ECU 101B which is an automatic driving ECU receives a data frame in which image information is stored, acquires the image information from the received data frame, and performs automatic driving control based on the acquired image information. Also, for example, the processing unit 40 in the ECU 101C which is a storage ECU receives a data frame in which image information is stored, acquires the image information from the received data frame, and accumulates the acquired image information in the storage unit 70.

[0051] FIG. 3 is a diagram showing an example of the configuration of an ECU in an in-vehicle communication system according to an embodiment of the present disclosure. FIG. 3 is a diagram showing the configuration of the ECU 101A which is a master device.

[0052] Referring to FIG. 3, the ECU 101A includes a receiving unit 20A and a transmitting unit 30A instead of the receiving unit 20 and the transmitting unit 30 as compared with the ECU 101 other than the ECU 101A, and further includes a clock generation unit 60.

[0053] The receiving unit 20A receives an electrical signal from the optical transceiver 10, reconstructs a frame from the electrical signal, and outputs the reconstructed frame to the processing unit 40 in the same manner as the receiving unit 20 in the ECU 101 other than the ECU 101A.

[0054] The processing unit 40 in the ECU 101A generates a frame addressed to another ECU 101 and outputs the generated frame to the transmitting unit 30A. For example, the processing unit 40 in the ECU 101A which is an automatic driving ECU receives a data frame in which image information is stored, acquires the image information from the received data frame, and performs automatic driving control based on the acquired image information in the same manner as the processing unit 40 in the ECU 101B.

[0055] The transmission unit 30A outputs the frame received from the processing unit 40 to the optical transceiver 10, similar to the transmission unit 30 in the ECU 101 other than the ECU 101A.

[0056] The clock generation unit 60 includes, for example, a VCO (Voltage Controlled Oscillator) and generates a clock pulse that is a reference clock. Each unit in the ECU 101A operates according to the timing of the reference clock generated by the clock generation unit 60.

[0057] The counter 50 counts the clock pulses received from the clock generation unit 60 and holds the count value, which is the counted value.

[0058] Note that in the in-vehicle communication system 401, the ECU 101A and the ECU 101 other than the ECU 101A may have the same hardware configuration. That is, in the in-vehicle communication system 401, the ECU 101A may include the receiving unit 20 and the transmission unit 30 instead of the receiving unit 20A and the transmission unit 30A, and the ECU 101 other than the ECU 101A may include the clock generation unit 60.

[0059] [Clock Synchronization Processing and Time Synchronization Processing] <Master Device> For example, the ECU 101A, which is the master device, transmits the timing information, which is the information used by other ECUs 101 in the in-vehicle communication system 401 for time synchronization processing, and the slot information indicating the time slot TS assigned to each ECU 101 in the in-vehicle communication system 401 to the second in-vehicle device group Gr2 via the optical coupler 201.

[0060] More specifically, the storage unit 70 in the ECU 101A stores slot information indicating the correspondence between the number of the time slot TS assigned to each ECU 101 and the ID (Identifier) of the ECU 101. Hereinafter, the IDs of the ECUs 101A, 101B, 101C, 101D, 101E, and 101F are respectively set as "ID-A", "ID-B", "ID-C", "ID-D", "ID-E", and "ID-F".

[0061] The processing unit 40 in the ECU 101A generates timing information based on the count value held by the counter 50, for example, at startup or at synchronous processing timing according to a predetermined period. More specifically, for example, the processing unit 40 generates timing information indicating the count value of the counter 50.

[0062] Note that the processing unit 40 may be configured to generate timing information indicating a count value in which the frequency deviation of the VCO in the clock generation unit 60 is taken into account. More specifically, for example, the storage unit 70 in the ECU 101A stores a correction amount preset based on the frequency deviation of the VCO. The processing unit 40 acquires the correction amount from the storage unit 70 and generates timing information indicating a value obtained by adding or subtracting the correction amount to / from the count value of the counter 50.

[0063] In this way, by correcting the count value based on the frequency deviation of the VCO, it is possible to notify other ECUs 101 of an accurate count value in which the frequency deviation unique to the VCO is taken into account. Note that the processing unit 40 may be configured to receive a frame storing a count value regularly transmitted from another ECU 101, calculate the frequency deviation of the VCO based on the comparison result between the count value in the received frame and the count value of its own counter 50, acquire a correction amount corresponding to the calculated frequency deviation from, for example, a correspondence table in the storage unit 70, and generate timing information using the acquired correction amount.

[0064] When the processing unit 40 generates timing information, it acquires slot information from the storage unit 70, generates a control frame that is a frame including the generated timing information and the acquired slot information, and outputs the generated control frame to the transmission unit 30A.

[0065] FIG. 4 is a diagram showing an example of the payload of a control frame generated by the processing unit in the ECU of the in-vehicle communication system according to the embodiment of the present disclosure. Referring to FIG. 4, in the payload of the control frame, as timing information, for example, "NNN", which is the count value of the counter 50 of the ECU 101A at the synchronization processing timing, is stored.

[0066] Further, in the payload of the control frame, the first time slot TS1 in one communication frame between the ECUs 101 is assigned to the ECU 101A, the second time slot TS2 is assigned to the ECU 101B, the third time slot TS3 is assigned to the ECU 101C, the fourth time slot TS4 is assigned to the ECU 101D, the fifth time slot TS5 is assigned to the ECU 101E, and the sixth time slot TS6 is assigned to the ECU 101F. Slot information indicating this is stored.

[0067] The transmission unit 30A in the ECU 101A outputs the control frame received from the processing unit 40 to the optical transceiver 10.

[0068] The optical transceiver 10 in the ECU 101A converts an electrical signal indicating the control frame received from the transmission unit 30A into an optical signal and transmits it to the ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2 via the optical fiber cable 212 and the optical coupler 201.

[0069] <Second In-Vehicle Device Group> Referring to FIG. 2 again, the receiving units 20 in the ECUs 101D, 101E, and 101F receive an electrical signal from the optical transceiver 10, reconstruct a control frame from the electrical signal, and output the reconstructed control frame to the processing unit 40.

[0070] (Clock synchronization processing) In the receiving units 20 of the ECUs 101D, 101E, and 101F, the receiving CDR circuit 21 performs a clock synchronization process to synchronize its own ECU 101 with the ECU 101A, which is the master device, based on the optical signal received from the ECU 101A. The receiving CDR circuit 21 generates a clock for its own ECU 101 to operate synchronously with the ECU 101A. Each unit in the ECU 101 operates according to the timing of the clock generated by the receiving CDR circuit 21.

[0071] More specifically, the receiving CDR circuit 21 includes a PLL (Phase Locked Loop) circuit, and uses the PLL circuit to extract a received clock from the signal received from the ECU 101A. Specifically, the receiving CDR circuit 21 generates a received clock based on the electrical signal received from the optical transceiver 10. The receiving CDR circuit 21 samples the received burst signal, which is the electrical signal received from the optical transceiver 10, using the received clock. Also, the receiving CDR circuit 21 outputs the received clock to the counter 50 and the transmitting CDR circuit 31.

[0072] The counter 50 counts the pulses of the received clock received from the receiving CDR circuit 21 and holds the count value, which is the counted value.

[0073] The transmitting CDR circuit 31 in the transmitting units 30 of the ECUs 101D, 101E, and 101F includes a PLL circuit, and uses the PLL circuit to generate a transmitting clock synchronized with the received clock extracted by the receiving CDR circuit 21. The transmitting CDR circuit 31 re-times the data to be transmitted to the ECU 101 of the first in-vehicle device group Gr1 with the generated transmitting clock. Specifically, the transmitting CDR circuit 31 outputs the frame received from the processing unit 40 and to be transmitted to the ECU 101 of the first in-vehicle device group Gr1 to the optical transceiver 10 according to the timing of the transmitting clock.

[0074] FIG. 5 is a diagram showing the configuration of a reception CDR circuit in a reception unit of an ECU according to an embodiment of the present invention. Referring to FIG. 5, the reception CDR circuit 21 includes a frequency division circuit 84, a sampling circuit 85, a multiplication circuit 86, a frequency comparator 87, and a PLL circuit 88. The PLL circuit 88 includes a phase comparator 81, a charge pump & loop filter 82, and a VCXO (Voltage Controlled Crystal Oscillator) 83.

[0075] The PLL circuit 88 controls the VCXO 83 based on the timing of the received burst signal received from the optical transceiver 10. More specifically, the PLL circuit 88 generates a control voltage VC based on the received burst signal received from the optical transceiver 10 and a reference clock generated in its own ECU 101, and supplies it to the VCXO 53. As a result, the PLL circuit 88 has a frequency component in which components having a frequency equal to or higher than a predetermined frequency among the frequency components of the received burst signal received from the optical transceiver 10 are attenuated, and generates a reception clock synchronized with the received burst signal.

[0076] Specifically, in the PLL circuit 88, the phase comparator 81 compares the phase of the received burst signal with the phase of the output signal of the VCXO 83, and outputs a phase difference signal indicating the comparison result to the charge pump & loop filter 82.

[0077] The followability of the PLL circuit 88 is set by the time constant of the charge pump & loop filter 82. Specifically, the time constant of the charge pump & loop filter 82 is set so that the PLL circuit 88 does not follow noise having a high frequency component such as a harmonic.

[0078] The VCXO 83 generates and outputs an oscillation signal. The VCXO 83 receives the phase difference signal that has passed through the charge pump & loop filter 82 as a control voltage VC, and changes the frequency of the oscillation signal according to the control voltage VC. The oscillation signal output from the VCXO 83 is output to the phase comparator 81 and the frequency division circuit 84.

[0079] The frequency division circuit 84 divides the oscillation signal received from the VCXO 83 and outputs it as a reception clock.

[0080] The sampling circuit 85 holds the received burst signal from the optical transceiver 10 in response to the reception clock received from the frequency division circuit 84 and outputs it as reception data. The receiving unit 20 reconstructs a frame from this reception data.

[0081] The multiplication circuit 86 outputs a clock obtained by multiplying a reference clock generated in its own ECU 101 by a predetermined number of times.

[0082] The frequency comparator 87 compares the clock received from the multiplication circuit 86 and the reception clock received from the frequency division circuit 84, and outputs a frequency difference signal indicating the frequency difference between these clocks to the charge pump & loop filter 82.

[0083] The control voltage VC is adjusted so that the frequency of the reception clock matches the frequency of the clock output from the multiplication circuit 86 according to the frequency difference signal output from the frequency comparator 87 to the charge pump & loop filter 82.

[0084] FIG. 6 is a diagram showing the configuration of a transmission CDR circuit in a transmission unit of an ECU according to an embodiment of the present invention. Referring to FIG. 6, the transmission CDR circuit 31 includes a frequency division circuit 94, a retiming circuit 95, a multiplication circuit 96, a frequency comparator 97, and a PLL circuit 98. The PLL circuit 98 includes a phase comparator 91, a charge pump & loop filter 92, and a VCXO 93.

[0085] The PLL circuit 98 controls the VCXO 93 based on the timing of the received clock received from the reception CDR circuit 21. More specifically, the PLL circuit 98 generates a control voltage VC based on the received clock received from the reception CDR circuit 21 and the reference clock generated in its own ECU 101, and supplies it to the VCXO 93. Thereby, the PLL circuit 98 has a frequency component in which components of a predetermined frequency or higher among the frequency components of the received clock received from the reception CDR circuit 21 are attenuated, and generates a transmission clock synchronized with the received clock.

[0086] Specifically, in the PLL circuit 98, the phase comparator 91 compares the phase of the received clock with the phase of the output signal of the VCXO 93, and outputs a phase difference signal indicating the comparison result to the charge pump & loop filter 92.

[0087] The followability of the PLL circuit 98 is set by the time constant of the charge pump & loop filter 92. Specifically, the time constant of the charge pump & loop filter 92 is set so that the PLL circuit 98 does not follow noise having a high frequency component such as a harmonic.

[0088] The VCXO 93 generates and outputs an oscillation signal. The VCXO 93 receives the phase difference signal that has passed through the charge pump & loop filter 92 as the control voltage VC, and changes the frequency of the oscillation signal according to the control voltage VC. The oscillation signal output from the VCXO 93 is output to the phase comparator 91 and the frequency division circuit 94.

[0089] The frequency division circuit 94 divides the oscillation signal received from the VCXO 93 and outputs it as a transmission clock.

[0090] The re-timing circuit 95 holds and outputs transmission data, which is a frame from the processing unit 40, in response to the transmission clock received from the frequency division circuit 94. The optical transceiver 10 converts the transmission data output from the re-timing circuit 95 into an optical signal and transmits it to another ECU 101.

[0091] The multiplier circuit 96 outputs a clock obtained by multiplying a reference clock generated in its own ECU 101 by a predetermined multiple.

[0092] The frequency comparator 97 compares the clock received from the multiplier circuit 96 and the transmission clock received from the frequency divider circuit 94, and outputs a frequency difference signal indicating the frequency difference between these clocks to the charge pump & loop filter 92.

[0093] The control voltage VC is adjusted so that the frequency of the transmission clock matches the frequency of the clock output from the multiplier circuit 96 according to the frequency difference signal output from the frequency comparator 97 to the charge pump & loop filter 92.

[0094] (Time synchronization process) The processing unit 40 in the ECUs 101D, 101E, and 101F receives a control frame from the receiving unit 20 and acquires timing information and slot information from the received control frame.

[0095] The processing unit 40 stores the acquired slot information in the storage unit 70. Further, the processing unit 40 performs a time synchronization process for synchronizing its own ECU 101 with the ECU 101A which is the master device based on the acquired timing information. More specifically, the processing unit 40 updates the count value of the counter 50 based on the acquired timing information.

[0096] For example, the ECU 101 of the second vehicle-mounted device group Gr2 performs a time synchronization process based on the timing information received from the ECU 101A and the propagation delay D1 of the optical signal transmitted from the ECU 101A to the second vehicle-mounted device group Gr2.

[0097] More specifically, the storage unit 70 in the ECUs 101D, 101E, and 101F stores the propagation delay D1 measured or calculated in advance.

[0098] In the processing unit 40 in ECU101D, 101E, and 101F, in the time synchronization process, the count value of the counter 50 is updated to a value obtained by adding the count value indicated by the acquired timing information and the count value corresponding to the propagation delay D1 in the storage unit 70.

[0099] Also, for example, the processing unit 40 in ECU101D, 101E, and 101F acquires a correction amount preset based on the frequency deviation of the VCXO83 of the reception CDR circuit 21 from the storage unit 70, and updates the count value of the counter 50 to a value obtained by further adding or subtracting the correction amount. In this way, by updating the count value based on the frequency deviation of the VCXO83, it is possible to update to an accurate value considering the frequency deviation specific to the VCXO83. Note that the processing unit 40 may receive a frame storing a count value periodically transmitted from ECU101A, calculate the frequency deviation of the VCXO83 based on the comparison result between the count value in the received frame and the count value of its own counter 50, acquire a correction amount corresponding to the calculated frequency deviation from the storage unit 70, and update the count value of the counter 50 using the acquired correction amount.

[0100] Any one of the ECUs 101 in the second in-vehicle device group Gr2 transmits the timing information received from ECU101A and the slot information received from ECU101A to the first in-vehicle device group Gr1 via the optical coupler 201. For example, ECU101D, which is a sub-master device, transfers the control frame received from ECU101A to the first in-vehicle device group Gr1.

[0101] More specifically, the processing unit 40 in ECU101D outputs the control frame received from the reception unit 20 to the transmission unit 30.

[0102] The transmission unit 30 in ECU101D outputs the control frame received from the processing unit 40 to the optical transceiver 10.

[0103] The optical transceiver 10 in ECU101D converts the electrical signal indicating the control frame received from the transmission unit 30 into an optical signal and transmits it to the ECUs 101A, 101B, and 101C of the first in-vehicle device group Gr1 via the optical fiber cable 212 and the optical coupler 201.

[0104] <First in-vehicle device group> The receiving units 20 in ECUs 101B and 101C receive the electrical signal from the optical transceiver 10, reconstruct the control frame from the electrical signal, and output the reconstructed control frame to the processing unit 40.

[0105] (Clock synchronization process) The receiving CDR circuit 21 in the receiving unit 20 of ECUs 101B and 101C performs a clock synchronization process to synchronize its own ECU101 with the ECU101A, which is the master device, based on the optical signal received from ECU101D, similar to the receiving CDR circuits 21 in the receiving units 20 of ECUs 101D, 101E, and 101F. The receiving CDR circuit 21 generates a clock for its own ECU101 to operate synchronously with ECU101A. Each unit in ECU101 operates according to the timing of the clock generated by the receiving CDR circuit 21.

[0106] The counter 50 counts the pulses of the received clock received from the receiving CDR circuit 21 and holds the count value, which is the counted value.

[0107] The transmitting CDR circuit 31 in the transmitting unit 30 of ECUs 101B and 101C generates a transmitting clock synchronized with the received clock extracted by the receiving CDR circuit 21, similar to the transmitting CDR circuits 31 in the transmitting units 30 of ECUs 101D, 101E, and 101F, and retimes the data to be transmitted to the ECUs 101 of the second in-vehicle device group Gr2 with the generated transmitting clock.

[0108] (Time synchronization process) The processing unit 40 in ECUs 101B and 101C receives a control frame from the receiving unit 20 and acquires timing information and slot information from the received control frame.

[0109] The processing unit 40 stores the acquired slot information in the storage unit 70. Also, the processing unit 40 performs a time synchronization process to synchronize its own ECU 101 with ECU 101A, which is the master device, based on the acquired timing information. More specifically, the processing unit 40 updates the count value of the counter 50 based on the acquired timing information.

[0110] For example, ECUs 101B and 101C, which are ECUs other than ECU 101A among the ECUs 101 in the first vehicle-mounted device group Gr1, perform a time synchronization process based on the timing information received from the second vehicle-mounted device group Gr2, the propagation delay D1, and the propagation delay D2 of the optical signal transmitted from the second vehicle-mounted device group Gr2 to the first vehicle-mounted device group Gr1.

[0111] Also, for example, ECUs 101B and 101C perform a time synchronization process based further on the transfer delay time D3 required for the sub-master device ECU 101D to transfer the control frame from ECU 101A to the first vehicle-mounted device group Gr1.

[0112] More specifically, the storage unit 70 in ECUs 101B and 101C stores the propagation delays D1, D2, and the transfer delay time D3, which are measured or calculated in advance.

[0113] In the time synchronization process, the processing unit 40 in ECUs 101B and 101C updates the count value of the counter 50 to a value obtained by adding the count value indicated by the acquired timing information and the count values corresponding to the propagation delays D1, D2, and the transfer delay time D3 in the storage unit 70.

[0114] Also, for example, the processing unit 40 in the ECUs 101B and 101C acquires a correction amount set in advance based on the frequency deviation of the VCXO 83 of the reception CDR circuit 21 from the storage unit 70, and updates the count value of the counter 50 to a value obtained by further adding or subtracting the correction amount. Note that the processing unit 40 may be configured to receive a frame storing the count value periodically transmitted from the ECU 101A, calculate the frequency deviation of the VCXO 83 based on the comparison result between the count value in the received frame and the count value of its own counter 50, acquire a correction amount corresponding to the calculated frequency deviation from the storage unit 70, and update the count value of the counter 50 using the acquired correction amount.

[0115] [Example of Transmission Timing of Optical Signal] Each ECU 101 in the first in-vehicle device group Gr1 transmits an optical signal to the ECU 101 in the second in-vehicle device group Gr2 via the optical coupler 201 in the time slot TS assigned to itself. Also, each ECU 101 in the second in-vehicle device group Gr2 transmits an optical signal to the ECU 101 in the first in-vehicle device group Gr1 via the optical coupler 201 in the time slot TS assigned to itself.

[0116] FIG. 7 is a diagram showing an example of a timing chart indicating the timing at which an ECU in the in-vehicle communication system according to an embodiment of the present disclosure transmits an optical signal. Referring to FIG. 7, the ECU 101A transmits an optical signal to the ECU 101 in the second in-vehicle device group Gr2 via the optical coupler 201 in the time slot TS1 from time t0 to time t1. Also, the ECU 101B transmits an optical signal to the ECU 101 in the second in-vehicle device group Gr2 via the optical coupler 201 in the time slot TS2 from time t1 to time t2. Also, the ECU 101C transmits an optical signal to the ECU 101 in the second in-vehicle device group Gr2 via the optical coupler 201 in the time slot TS3 from time t2 to time t3.

[0117] Also, in time slot TS4 from time t3 to time t4, ECU101D transmits an optical signal to ECU101 of the first in-vehicle device group Gr1 via optical coupler 201. Also, in time slot TS5 from time t4 to time t5, ECU101E transmits an optical signal to ECU101 of the first in-vehicle device group Gr1 via optical coupler 201. Also, in time slot TS6 from time t5 to time t6, ECU101F transmits an optical signal to ECU101 of the first in-vehicle device group Gr1 via optical coupler 201.

[0118] More specifically, the processing unit 40 in each ECU101 outputs, based on the slot information in its own storage unit 70, the frame to be transmitted to another ECU101 in the time slot of its own ECU101 indicated by the slot information, to the optical fiber cable 212 via the transmission unit 30 and the optical transceiver 10.

[0119] For example, the processing unit 40 in ECUs 101B, 101C, 101D, 101E, 101F including the reception CDR circuit 21 turns off its own reception CDR circuit 21 in the time slot TS assigned to the ECU101 of its own group among the first in-vehicle device group Gr1 and the second in-vehicle device group Gr2. Also, for example, the processing unit 40 in ECUs 101B, 101C, 101D, 101E, 101F turns on its own reception CDR circuit 21 in the time slot TS assigned to the ECU101 of the group different from its own group among the first in-vehicle device group Gr1 and the second in-vehicle device group Gr2.

[0120] Specifically, the processing unit 40 in ECUs 101D, 101E, and 101F turns on its own reception CDR circuit 21 during time slots TS1, TS2, and TS3, while turning off its own reception CDR circuit 21 during time slots TS4, TS5, and TS6. Also, the processing unit 40 in ECUs 101B and 101C turns on its own reception CDR circuit 21 during time slots TS4, TS5, and TS6, while turning off its own reception CDR circuit 21 during time slots TS1, TS2, and TS3.

[0121] As an example, the processing unit 40 in ECUs 101D, 101E, and 101F turns on its own reception CDR circuit 21 at the start time t0 of time slot TS1 and turns off its own reception CDR circuit 21 at the start time t3 of time slot TS4. Also, the processing unit 40 in ECUs 101B and 101C turns off its own reception CDR circuit 21 at the start time t0 of time slot TS1 and turns on its own reception CDR circuit 21 at the start time t3 of time slot TS4.

[0122] Note that the processing unit 40 in ECUs 101D, 101E, and 101F may be configured to turn off its own reception CDR circuit 21 immediately before the start times t0, t1, and t2 of time slots TS1, TS2, and TS3, and then turn on its own reception CDR circuit 21 again immediately after the times t0, t1, and t2. Also, the processing unit 40 in ECUs 101B and 101C may be configured to turn off its own reception CDR circuit 21 immediately before the start times t3, t4, and t5 of time slots TS4, TS5, and TS6, and then turn on its own reception CDR circuit 21 again immediately after the times t3, t4, and t5.

[0123] [Modification Example] FIG. 8 is a diagram showing an example of the configuration of an in-vehicle communication system according to a modification example of the embodiment of the present disclosure. Referring to FIG. 8, the in-vehicle communication system 402 according to the modification example includes an optical coupler 202 instead of the optical coupler 201 compared to the in-vehicle communication system 401.

[0124] More specifically, the optical coupler 202 includes a main body 220 and optical waveguides 222 and 223 formed in the main body 220. The optical waveguide 222 is a first transmission path for transmitting an optical signal from the ECUs 101A, 101B, and 101C of the first in-vehicle device group Gr1 to the ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2. The optical waveguide 223 is a second transmission path for transmitting an optical signal from the ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2 to the ECUs 101A, 101B, and 101C of the first in-vehicle device group Gr1.

[0125] The optical waveguides 222 and 223 are formed in the main body 220 so as to extend between a connection part 211A, 211B, 211C provided at the first end of the optical coupler 202 and a connection part 211D, 211E, 211F provided at the second end of the optical coupler 202, respectively.

[0126] The optical waveguides 222 and 223 have a branching part. For example, the optical waveguide 222 has a first end 222A connected to the connection part 211A, a second end 222B connected to the connection part 212B, a third end 222C connected to the connection part 212C, a fourth end 222D connected to the connection part 212D, a fifth end 222E connected to the connection part 212E, and a sixth end 222F connected to the connection part 212F.

[0127] Also, for example, the optical waveguide 223 has a first end 223A connected to the connection part 211A, a second end 223B connected to the connection part 212B, a third end 223C connected to the connection part 212C, a fourth end 223D connected to the connection part 212D, a fifth end 223E connected to the connection part 212E, and a sixth end 223F connected to the connection part 212F.

[0128] ECUs 101A, 101B, and 101C are respectively connected to connection parts 211A, 211B, and 211C via optical fiber cables 213. The optical fiber cable 213 is a two-core cable. The first end 222A of the optical waveguide 222 and the first end 223A of the optical waveguide 223 are optically connected to the first core and the second core of the corresponding optical fiber cable 213 at the connection part 211A, respectively. The second end 222B of the optical waveguide 222 and the second end 223B of the optical waveguide 223 are optically connected to each of the first core and the second core of the corresponding optical fiber cable 213 at the connection part 211B, respectively. The third end 222C of the optical waveguide 222 and the third end 223C of the optical waveguide 223 are optically connected to each of the first core and the second core of the corresponding optical fiber cable 213 at the connection part 211C, respectively.

[0129] ECUs 101C, 101D, and 101E are respectively connected to connection parts 211C, 211D, and 211E via optical fiber cables 213. The fourth end 222D of the optical waveguide 222 and the fourth end 223D of the optical waveguide 223 are optically connected to the first core and the second core of the corresponding optical fiber cable 213 at the connection part 211D, respectively. The fifth end 222E of the optical waveguide 222 and the fifth end 223E of the optical waveguide 223 are optically connected to each of the first core and the second core of the corresponding optical fiber cable 213 at the connection part 211E, respectively. The sixth end 222F of the optical waveguide 222 and the sixth end 223F of the optical waveguide 223 are optically connected to each of the first core and the second core of the corresponding optical fiber cable 213 at the connection part 211F, respectively.

[0130] FIG. 9 is a diagram showing an example of a timing chart indicating the timing at which an ECU in a vehicle-mounted communication system according to a modified example of an embodiment of the present disclosure transmits an optical signal. Referring to FIG. 9, a common time slot TS is allocated to at least one of the ECUs 101 in the first vehicle-mounted device group Gr1 and at least one of the ECUs 101 in the second vehicle-mounted device group Gr2.

[0131] More specifically, time slots TS1 and TS4 are assigned to ECUs 101A and 101D. Specifically, ECU 101A transmits an optical signal to the ECU 101 of the second in-vehicle device group Gr2 via the optical waveguide 222 in the optical coupler 202 in time slots TS1 and TS4. Also, ECU 101D transmits an optical signal to the ECU 101 of the first in-vehicle device group Gr1 via the optical waveguide 223 in the optical coupler 202 in time slots TS1 and TS4.

[0132] Also, time slots TS2 and TS5 are assigned to ECUs 101B and 101E. Specifically, ECU 101B transmits an optical signal to the ECU 101 of the second in-vehicle device group Gr2 via the optical waveguide 222 in the optical coupler 202 in time slots TS2 and TS5. Also, ECU 101E transmits an optical signal to the ECU 101 of the first in-vehicle device group Gr1 via the optical waveguide 223 in the optical coupler 202 in time slots TS2 and TS5.

[0133] Also, time slots TS3 and TS6 are assigned to ECUs 101C and 101F. Specifically, ECU 101C transmits an optical signal to the ECU 101 of the second in-vehicle device group Gr2 via the optical waveguide 222 in the optical coupler 202 in time slots TS3 and TS6. Also, ECU 101F transmits an optical signal to the ECU 101 of the first in-vehicle device group Gr1 via the optical waveguide 223 in the optical coupler 202 in time slots TS3 and TS6.

[0134] [Operation flow] Each device in the in-vehicle communication system according to the embodiment of the present disclosure includes a computer including a memory, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including some or all of the steps of the following flowchart and sequence from the memory. The programs of these multiple devices can each be installed from the outside. The programs of these multiple devices are each distributed in a state stored in a recording medium.

[0135] Figure 10 is a flowchart defining an example of the operation procedure when the ECU in the in-vehicle communication system according to the embodiment of the present disclosure performs clock synchronization processing. Figure 10 shows the operation procedure when the ECU 101 other than the ECU 101A performs clock synchronization processing.

[0136] Referring to Figure 10, first, the ECU 101 waits for an optical signal from another ECU 101. More specifically, the ECUs 101D, 101E, 101F of the second in-vehicle device group Gr2 wait for an optical signal transmitted from the ECU 101A. Also, the ECUs 101B, 101C of the first in-vehicle device group Gr1 wait for an optical signal corresponding to the control frame from the ECU 101A transferred by the ECU 101D (NO in step S102). When the ECU 101 receives an optical signal (YES in step S102), it converts the received optical signal into an electrical signal (step S104).

[0137] Next, the ECU 101 generates a reception clock based on the electrical signal (step S106).

[0138] Next, the ECU 101 starts an operation using the generated reception clock (step S108).

[0139] Next, the ECU 101 waits for a new optical signal from another ECU 101 (NO in step S102).

[0140] Figure 11 is a flowchart defining an example of the operation procedure when the ECU in the in-vehicle communication system according to the embodiment of the present disclosure performs time synchronization processing.

[0141] Referring to FIG. 11, first, the ECU 101 waits for a control frame from another ECU 101. More specifically, the ECUs 101D, 101E, 101F of the second in-vehicle device group Gr2 wait for a control frame transmitted from the ECU 101A. Also, the ECUs 101B, 101C of the first in-vehicle device group Gr1 wait for a control frame from the ECU 101A transferred by the ECU 101D (NO in step S202). When the ECU 101 receives a control frame (YES in step S202), it acquires timing information from the received control frame (step S204).

[0142] Next, the ECU 101 updates the count value of the counter 50 based on the acquired timing information. More specifically, the ECUs 101D, 101E, 101F update the count value of the counter 50 to a value obtained by adding the count value indicated by the timing information and the count value corresponding to the propagation delay D1. Also, the ECUs 101B, 101C update the count value of the counter 50 to a value obtained by adding the count value indicated by the timing information and the count values corresponding to the propagation delays D1, D2, and the transfer delay time D3 (step S206).

[0143] Next, the ECU 101 waits for a new control frame from another ECU 101 (NO in step S202).

[0144] FIG. 12 is a diagram showing an example of a communication sequence in an in-vehicle communication system according to an embodiment of the present disclosure.

[0145] Referring to FIG. 12, first, the ECU 101A of the first in-vehicle device group Gr1, which is the master device, converts an electrical signal indicating a control frame into an optical signal at the synchronization processing timing, and transmits the optical signal to the ECUs 101D, 101E, 101F of the second in-vehicle device group Gr2 via the optical coupler 201 in the time slot TS assigned to itself (step S302).

[0146] Next, the ECUs 101D, 101E, and 101F of the second in-vehicle device group Gr2 receive an optical signal from the ECU 101A, perform clock synchronization processing based on the optical signal, and perform time synchronization processing based on a control frame generated by reconstructing an electrical signal based on the optical signal (step S304).

[0147] Next, the ECU 101D, which is a sub-master device, transfers the control frame received from the ECU 101A to the first in-vehicle device group Gr1. More specifically, the ECU 101D converts an electrical signal indicating the control frame into an optical signal, and transmits the optical signal to the ECUs 101A, 101B, and 101C via the optical coupler 201 in its assigned time slot TS (step S306).

[0148] Next, the ECUs 101B and 101C receive an optical signal from the ECU 101D, perform clock synchronization processing based on the optical signal, and perform time synchronization processing based on a control frame generated by reconstructing an electrical signal based on the optical signal (step S308).

[0149] Next, the ECUs 101D, 101E, and 101F convert an electrical signal indicating a data frame in which image information is stored into an optical signal, and transmit the optical signal to the ECUs 101A, 101B, and 101C via the optical coupler 201 in their assigned time slot TS (step S310).

[0150] Next, the ECUs 101A, 101B, and 101C receive an optical signal from the ECU 101A, and acquire image information from a data frame generated by reconstructing an electrical signal based on the optical signal. The ECUs 101A and 101B perform automatic driving control based on the acquired image information. The ECU 101C stores the acquired image information in the storage unit 70 (step S312).

[0151] In the in-vehicle communication systems 401 and 402 according to the embodiments of the present disclosure, the ECU 101A, which is the master device, is configured to transmit timing information and slot information to the second in-vehicle device group Gr2. However, the present disclosure is not limited to this. The ECU 101A may be configured not to transmit at least one of the timing information and the slot information to the second in-vehicle device group Gr2.

[0152] Also, in the in-vehicle communication systems 401 and 402 according to the embodiments of the present disclosure, the ECU 101D, which is the sub-master device, is configured to transmit the timing information and the slot information received from the ECU 101A to the first in-vehicle device group Gr1. However, the present disclosure is not limited to this. The ECU 101D may be configured not to transmit at least one of the timing information and the slot information to the first in-vehicle device group Gr1. Further, instead of the ECU 101D, the ECU 101E or the ECU 101F may be configured to transmit the timing information and the slot information received from the ECU 101A to the first in-vehicle device group Gr1 based on an instruction from the ECU 101A, for example.

[0153] Also, in the in-vehicle communication systems 401 and 402 according to the embodiments of the present disclosure, the processing unit 40 in the ECUs 101B and 101C is configured to update the count value of the counter 50 to a value obtained by adding the count value indicated by the timing information, the count values corresponding to the propagation delays D1 and D2, and the transfer delay time D3 in the time synchronization process. However, the present disclosure is not limited to this. The processing unit 40 in the ECUs 101B and 101C may be configured to update the count value of the counter 50 to the count value indicated by the timing information.

[0154] Also, in the in-vehicle communication systems 401 and 402 according to the embodiments of the present disclosure, although the processing unit 40 in the ECUs 101B, 101C, 101D, 101E, and 101F is configured to turn off its own reception CDR circuit 21 in the time slot TS assigned to the ECU 101 of its own group, the present disclosure is not limited thereto. For example, the processing unit 40 in the ECUs 101B, 101C, 101D, 101E, and 101F may be configured to maintain the on state of its own reception CDR circuit 21 in the time slot TS assigned to the ECU 101 of its own group.

[0155] Also, although the in-vehicle communication systems 401 and 402 according to the embodiments of the present disclosure are configured to include a first in-vehicle device group Gr1 and a second in-vehicle device group Gr2, the present disclosure is not limited thereto. The in-vehicle communication systems 401 and 402 may further include an in-vehicle device group composed of one or more ECUs 101 in addition to the first in-vehicle device group Gr1 and the second in-vehicle device group Gr2.

[0156] The above embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims be included.

[0157] The above description includes the features appended below. [Appendix 1] An optical coupler, A first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, A second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler, and Each of the in-vehicle devices in the first in-vehicle device group is capable of communicating with each of the in-vehicle devices in the second in-vehicle device group via a common transmission path in the optical coupler. Each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via a common transmission path in the optical coupler. A master device, which is any one of the plurality of in-vehicle devices in the first in-vehicle device group, transmits timing information, which is information used by the in-vehicle devices in the in-vehicle communication system for time synchronization processing, to the second in-vehicle device group via the optical coupler. A slave master device, which is any one of the plurality of in-vehicle devices in the second in-vehicle device group, transmits the timing information received from the master device to the first in-vehicle device group via the optical coupler. An in-vehicle communication system in which in-vehicle devices other than the master device among the plurality of in-vehicle devices in the first in-vehicle device group perform the time synchronization processing based on the timing information received from the slave master device, the propagation delay of the optical signal transmitted from the master device to the second in-vehicle device group, and the propagation delay of the optical signal transmitted from the second in-vehicle device group to the first in-vehicle device group.

Description of Signs

[0158] 10 Optical transceiver, 20, 20A Receiver, 21 Receiver CDR circuit, 30, 30A Transmitter, 31 Transmitter CDR circuit, 40 Processing unit, 50 Counter, 60 Clock generation unit, 70 Memory unit, 81, 91 Phase comparator, 82, 92 Charge pump & Loop filter, 83, 93 VCXO, 84, 94 Frequency divider circuit, 85 Sampling circuit, 86, 96 Multiplier circuit, 87, 97 Frequency comparator, 88, 98 PLL circuit, 95 Retiming circuit, 101A, 101B, 101C, 101D, 101E, 101F ECU, 201, 202 Optical coupler, 211A, 211B, 211C, 211D, 211E, 211F Connection part, 212, 213 Optical fiber cable, 220 Main body part, 221 Optical waveguide, 221A, 222A, 223A First end, 221B, 222B, 223B Second end, 221C, 222C, 223C Third end, 221D, 222D, 223D Fourth end, 221E, 222E, 223E Fifth end, 221F, 222F, 223F Sixth end, 401, 402 In-vehicle communication system, Gr1 First in-vehicle device group, Gr2 Second in-vehicle device group

Claims

Claim 1. An in-vehicle communication system, comprising: an optical coupler; a first group of in-vehicle devices configured by a plurality of in-vehicle devices connected to a first end of the optical coupler; a second group of in-vehicle devices configured by a plurality of in-vehicle devices connected to a second end of the optical coupler, wherein each in-vehicle device in the first group of in-vehicle devices is capable of communicating with each in-vehicle device in the second group of in-vehicle devices via a common transmission path in the optical coupler; wherein each in-vehicle device in the second group of in-vehicle devices is capable of communicating with each in-vehicle device in the first group of in-vehicle devices via a common transmission path in the optical coupler; a master device, which is any one of the plurality of in-vehicle devices in the first group of in-vehicle devices, transmits timing information, which is information used by the in-vehicle devices in the in-vehicle communication system for time synchronization processing, to the second group of in-vehicle devices via the optical coupler; An in-vehicle communication system, wherein any one of the plurality of in-vehicle devices in the second group of in-vehicle devices transmits the timing information received from the master device to the first group of in-vehicle devices via the optical coupler. Claim 2. The master device transmits slot information indicating time slots assigned to each in-vehicle device in the in-vehicle communication system to the second group of in-vehicle devices via the optical coupler; The in-vehicle communication system according to claim 1, wherein any one of the plurality of in-vehicle devices in the second group of in-vehicle devices transmits the slot information received from the master device to the first group of in-vehicle devices via the optical coupler. Claim 3. Among the plurality of in-vehicle devices in the first group of in-vehicle devices, the in-vehicle devices other than the master device perform the time synchronization processing based on the timing information received from the second group of in-vehicle devices, the propagation delay of the optical signal transmitted from the master device to the second group of in-vehicle devices, and the propagation delay of the optical signal transmitted from the second group of in-vehicle devices to the first group of in-vehicle devices. The in-vehicle communication system according to claim 1 or claim 2. Claim 4. At least one of the in-vehicle devices in the in-vehicle communication system includes a clock synchronization circuit that performs clock synchronization processing with other in-vehicle devices. The in-vehicle device including the clock synchronization circuit turns off the clock synchronization circuit in a time slot assigned to the in-vehicle devices in its own group among the first in-vehicle device group and the second in-vehicle device group. The in-vehicle communication system according to any one of claims 1 to 3.

5. The optical coupler includes a first transmission path which is the transmission path for transmitting an optical signal from the in-vehicle device of the first in-vehicle device group to the in-vehicle device of the second in-vehicle device group, and a second transmission path which is the transmission path for transmitting an optical signal from the in-vehicle device of the second in-vehicle device group to the in-vehicle device of the first in-vehicle device group. A common time slot is assigned to at least any one of the in-vehicle devices among the plurality of in-vehicle devices of the first in-vehicle device group and at least any one of the in-vehicle devices among the plurality of in-vehicle devices of the second in-vehicle device group. The in-vehicle communication system according to any one of claims 1 to 4.

6. An in-vehicle communication system, an optical coupler, a first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler, each in-vehicle device of the first in-vehicle device group is capable of communicating with each in-vehicle device of the second in-vehicle device group via a common transmission path in the optical coupler, each in-vehicle device of the second in-vehicle device group is capable of communicating with each in-vehicle device of the first in-vehicle device group via a common transmission path in the optical coupler, at least any one of the in-vehicle devices in the in-vehicle communication system includes a clock synchronization circuit that performs clock synchronization processing with other in-vehicle devices, The in-vehicle device including the clock synchronization circuit turns off the clock synchronization circuit in a time slot assigned to the in-vehicle devices in its own group among the first in-vehicle device group and the second in-vehicle device group. An in-vehicle communication system.

7. An optical coupler, a first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler, Each in-vehicle device in the first in-vehicle device group can communicate with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler. Each in-vehicle device in the second in-vehicle device group can communicate with each in-vehicle device in the first in-vehicle device group via a common transmission path in the optical coupler. The optical coupler includes a first transmission path which is the transmission path for transmitting an optical signal from the in-vehicle device in the first in-vehicle device group to the in-vehicle device in the second in-vehicle device group, and a second transmission path which is the transmission path for transmitting an optical signal from the in-vehicle device in the second in-vehicle device group to the in-vehicle device in the first in-vehicle device group. An in-vehicle communication system in which a common time slot is allocated to at least any one in-vehicle device among a plurality of in-vehicle devices in the first in-vehicle device group and at least any one in-vehicle device among a plurality of in-vehicle devices in the second in-vehicle device group.

8. An optical coupler, A first in-vehicle device group composed of a plurality of in-vehicle devices connected to the first end of the optical coupler, A communication method in an in-vehicle communication system including a second in-vehicle device group composed of a plurality of in-vehicle devices connected to the second end of the optical coupler, A step in which the in-vehicle device in the first in-vehicle device group communicates with each in-vehicle device in the second in-vehicle device group via a common transmission path in the optical coupler; A step in which the in-vehicle device in the second in-vehicle device group communicates with each in-vehicle device in the first in-vehicle device group via a common transmission path in the optical coupler; A step in which a master device, which is any one of the plurality of in-vehicle devices in the first in-vehicle device group, transmits timing information, which is information used by the in-vehicle devices in the in-vehicle communication system for time synchronization processing, to the second in-vehicle device group via the optical coupler; A communication method including a step in which any one of the plurality of in-vehicle devices in the second in-vehicle device group transmits the timing information received from the master device to the first in-vehicle device group via the optical coupler.

9. An optical coupler, A first in-vehicle device group composed of a plurality of in-vehicle devices connected to the first end of the optical coupler, A communication method in an in-vehicle communication system including a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler, wherein: the in-vehicle devices in the first in-vehicle device group communicate with each of the in-vehicle devices in the second in-vehicle device group via a common transmission path in the optical coupler; the in-vehicle devices in the second in-vehicle device group communicate with each of the in-vehicle devices in the first in-vehicle device group via a common transmission path in the optical coupler; at least one of the in-vehicle devices in the in-vehicle communication system includes a clock synchronization circuit that performs clock synchronization processing with other in-vehicle devices; the communication method further includes: when the in-vehicle device including the clock synchronization circuit is in a time slot assigned to the in-vehicle devices in its own group among the first in-vehicle device group and the second in-vehicle device group, turning off the clock synchronization circuit. **Claim 10** An optical coupler, a first in-vehicle device group composed of a plurality of in-vehicle devices connected to a first end of the optical coupler, a communication method in an in-vehicle communication system including a second in-vehicle device group composed of a plurality of in-vehicle devices connected to a second end of the optical coupler, wherein: the in-vehicle devices in the first in-vehicle device group communicate with each of the in-vehicle devices in the second in-vehicle device group via a common transmission path in the optical coupler; the in-vehicle devices in the second in-vehicle device group communicate with each of the in-vehicle devices in the first in-vehicle device group via a common transmission path in the optical coupler; the optical coupler includes a first transmission path that is a transmission path for transmitting an optical signal from the in-vehicle devices in the first in-vehicle device group to the in-vehicle devices in the second in-vehicle device group, and a second transmission path that is a transmission path for transmitting an optical signal from the in-vehicle devices in the second in-vehicle device group to the in-vehicle devices in the first in-vehicle device group; a common time slot is assigned to at least one of the plurality of in-vehicle devices in the first in-vehicle device group and at least one of the plurality of in-vehicle devices in the second in-vehicle device group.

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