Vehicle data communication system, data transmitting device, and data receiving device

Abstract

To appropriately adjust throughput according to a situation in a configuration in which a data transmitting device and a data receiving device perform TCP communication.SOLUTION: In a data communication system 1, a data transmitting device 11 and a data receiving device 12 perform TCP communication. The data transmitting device transmits a desired delay Ack size for requesting an Ack transmission frequency to the data receiving device. The data receiving device receives the desired delay Ack size transmitted from the data transmitting device, determines the Ack transmission frequency based on the received desired delay Ack size, and transmits Ack to the data transmitting device.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a vehicle data communication system, a data transmission device, and a data reception device.

Background Art

[0002] In TCP (Transmission Control Protocol) communication, a technique for reducing the transmission frequency of Ack using delayed Ack is provided. For example, in Patent Document 1, in a data reception device that is a data reception side, a delayed Ack size serving as a reference for transmitting Ack is set, and when the free capacity of the reception buffer becomes less than a threshold value, the delayed Ack size is adjusted so that the transmission frequency of Ack increases. A technique is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technique disclosed in Patent Document 1 aims to avoid the received data staying in the reception buffer by adjusting the delayed Ack size and to stabilize the data communication, rather than from the viewpoint of improving throughput. Since transmitting Ack itself is a factor that hinders the improvement of throughput, a usage form that reduces the transmission frequency of Ack as much as possible when possible and increases it in other cases is desired.

[0005] However, in a configuration where the transmission frequency of Ack is adjusted based on the available capacity of the reception buffer, the transmission frequency of Ack can only be adjusted on the data reception side, i.e., the Ack transmission side. Also, for example, when updating the software of an in-vehicle electronic control unit (hereinafter referred to as ECU (Electronic Control Unit)) using OTA (Over the Air), a large amount of data downloaded from the OTA center needs to be transferred. However, if the throughput is low, there will be a problem that the time required to transfer the data becomes long.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle data communication system, a data transmission device, and a data reception device that can appropriately adjust the throughput according to the situation in a configuration where a data transmission device and a data reception device perform TCP communication.

Means for Solving the Problems

[0007] According to the invention described in claim 1, in a vehicle data communication system (1), a data transmission device (11) and a data reception device (12) perform TCP communication. The data transmission device specified of the transmission frequency to send Ack sends the desired delayed Ack size to the data reception device. The data reception device acquire the vehicle state, receives the desired delayed Ack size transmitted from the data transmission device, and determines the transmission frequency of Ack based on the received desired delayed Ack size and the acquired vehicle state and sends the Ack to the data transmission device.

[0008] In the data reception device, when receiving the desired delayed Ack size transmitted from the data transmission device, the received desired delayed Ack size and the vehicle stateAck is transmitted to the data transmission device at a transmission frequency based on [specific conditions]. Different from the conventional method where the transmission frequency of Ack can only be adjusted on the transmission side of Ack, by the data transmission device transmitting the desired delayed Ack size to the data receiving device, the transmission frequency of Ack can be adjusted on the receiving side of Ack. As a result, by the receiving side of Ack requesting the transmission frequency of Ack, the throughput can be appropriately adjusted according to the situation.

Brief Description of Drawings

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[0012] An embodiment will be described below with reference to the drawings. As shown in Fig. 1, an in-vehicle data communication system 1 mounted on a vehicle includes a communication device 2, an OTA master 3, and each domain ECU 4. The in-vehicle data communication system 1 is capable of data communication via OTA with an OTA center 5 located on the network side. When software in each domain ECU 4 needs to be reprogrammed, the OTA center 5 distributes update data including an update program to the in-vehicle data communication system 1.

[0013] When the communication device 2 downloads the update data from the OTA center 5, it transmits the downloaded update data to the OTA master 3. The OTA master 3 functions as a central ECU that controls reprogramming of various domain ECUs 4, and when it receives the update data transmitted from the communication device 2, it transmits the received update data to the domain ECU 4 to be reprogrammed.

[0014] The domain ECU 4 functions as a target ECU for reprogramming software. When it receives the update data transmitted from the OTA master 3, it reprograms the software based on the received update data. The domain ECU 4 includes, for example, an ADAS ECU 4a that performs ADAS (Advanced Driver-Assistance Systems) control, a meter ECU 4b that controls the meter device, a navigation ECU 4c that performs navigation control, a body ECU 4d that controls the body system, an engine ECU 4e that controls the engine system, and the like.

[0015] The communication device 2 and the OTA master 3 are connected by Ethernet. The communication device 2 transmits the update data to the OTA master 3 by performing TCP communication with the OTA master  3. In the data communication between the communication device 2 and the OTA master 3, the communication device 2 corresponds to the data transmission device, and the OTA master 3 corresponds to the data reception device. The OTA master 3 and each domain ECU 4 are connected by Ethernet. The OTA master 3 transmits the update data to each domain ECU 4 by performing TCP communication with each domain ECU 4. In the data communication between the OTA master 3 and each domain ECU 4, the OTA master 3 corresponds to the data transmission device, and each domain ECU 4 corresponds to the data reception device. Hereinafter, the data transmission device and the data reception device will be described.

[0016] As shown in FIG. 2, in the normal method of reducing the Ack transmission frequency using delayed Ack, the data reception device 12, which is the data receiving side, sets a delayed Ack size that serves as a reference for transmitting Ack, and updates the total received data size, which is the total capacity of the received data, every time it receives data transmitted from the data transmission device 11. If the total received data size does not exceed the delayed Ack size, the data reception device 12 does not transmit Ack to the data transmission device 11, and when the total received data size exceeds the delayed Ack size, it transmits Ack to the data transmission device 11. In the normal method, there is a problem that the Ack transmission frequency can only be adjusted on the Ack transmission side.

[0017] In contrast, as shown in FIG. 3 , the method of this embodiment is characterized in that the data receiving device 12 receives the desired delayed Ack size transmitted from the data transmitting device 11 and reflects it in the delayed Ack size, and acquires the vehicle state and reflects it in the delayed Ack size. The vehicle state indicates the on / off state of the drive mechanism, and indicates the on / off state of the ignition in a gasoline-powered vehicle with an internal combustion engine, and indicates the on / off state of the motor in an electric vehicle without an internal combustion engine. When the ignition is on or the motor is on, the drive mechanism is operating, and the environment is relatively likely to generate noise. Therefore, it is desirable to transmit Acks relatively frequently to ensure stable data communication. On the other hand, when the ignition is off or the motor is off, the drive mechanism is stopped, and the environment is relatively unlikely to generate noise. Therefore, the frequency of Ack transmission does not need to be relatively high. In this embodiment, the data receiving device 12 periodically acquires ignition information indicating the on / off state of the ignition as the vehicle state.

[0018] In the data transmitting device 11 and the data receiving device 12, the side that attempts to establish a session is the connection attempting side, and the side that accepts the establishment of the session is the connection accepting side. As shown in Figure 4, when the data transmitting device 11 and the data receiving device 12 are the connection attempting side, they each hold connection attempting side information, and when they are the connection accepting side, they hold connection accepting side information. In addition, the data transmitting device 11 and the data receiving device 12 hold ignition on / off information for monitoring the vehicle state as common information that should be commonly recognized. The connection attempting side information and the connection accepting side information each include the following information. Base table for delayed Ack Delayed Ack Factor Delay Ack Size Delayed Ack Size Array Vehicle stop flag ·Request flag Destination Delay Ack Size Connection request flag

[0019] As shown in Figure 5, the base table for delayed Ack is a table in which destination IP addresses, destination port numbers, delayed Ack sizes, and delayed Ack coefficients are registered. When a destination IP address and a destination port number are input, a delayed Ack size and a delayed Ack coefficient are output. In other words, the delayed Ack size and the delayed Ack coefficient are uniquely determined by the destination IP address and the destination port number. The delayed Ack size array indicates an array of delayed Ack sizes composed of a combination of a vehicle stop flag and a request / non-request flag. The vehicle stop flag is invalid when the ignition is on and the engine is not stopped, and is valid when the ignition is off and the engine is stopped. The request / non-request flag is invalid when the desired delayed Ack size has not been transmitted from the transmitting side and there is no request for a delayed Ack size, and is valid when the desired delayed Ack size has been transmitted from the transmitting side and there is a request for a delayed Ack size.

[0020] Next, the operation of the above-described configuration will be described with reference to Figures 6 to 18. Here, the processing during data communication and the processing during session establishment will be described in order. (1) Data communication processing (see Figures 6 to 14) As processing during data communication, the data transmission preparation processing in the data transmitting device 11, the Ack transmission determination processing in the data receiving device 12, and the delayed Ack size update determination processing in the data transmitting device 11 will be described in order.

[0021] (1-1) Pre-data transmission preparation process in the data transmitting device 11 (see FIGS. 6 to 8) The data transmitting device 11 waits for the conditions for starting the data transmission preparation process to be met. When the data receiving device 12 determines that the conditions for starting the data transmission preparation process have been met, it starts the data transmission preparation process.

[0022] When the data transmission device 11 starts the data transmission preparation process, it prepares a TCP segment (A1) and determines whether to change or reset the delay Ack size of the destination (A2, A3). If the data transmission device 11 determines not to change or reset the delay Ack size of the destination (A2: NO, A3: NO), it ends the data transmission preparation process and waits for the start condition of the next data transmission preparation process to be satisfied.

[0023] When a change request for the delay Ack size of the destination occurs and the data transmission device 11 determines to change the delay Ack size of the destination (A2: YES), it determines whether the request presence flag of the destination is invalid (A4). If the data transmission device 11 determines that the request presence flag of the destination is not invalid (A4: NO), it ends the data transmission preparation process and waits for the start condition of the next data transmission preparation process to be satisfied. If the data transmission device 11 determines that the request presence flag of the destination is invalid (A4: YES), it sets the request presence flag of the destination to valid (A5), stores the desired delay Ack size in the TCP option (A6), ends the data transmission preparation process, and waits for the start condition of the next data transmission preparation process to be satisfied. In this case, the data transmission device 11 stores a value exceeding "0" in the TCP option as the desired delay Ack size.

[0024] When the data transmission device 11 determines to reset the delay Ack size of the destination (A3: YES), it determines whether the request presence flag of the destination is valid (A7). If the data transmission device 11 determines that the request presence flag of the destination is not valid (A7: NO), it ends the data transmission preparation process and waits for the start condition of the next data transmission preparation process to be satisfied. If the data transmission device 11 determines that the request presence flag of the destination is valid (A7: YES), it sets the request presence flag of the destination to invalid (A8), stores the reset flag in the TCP option (A9), ends the data transmission preparation process, and waits for the start condition of the next data transmission preparation process to be satisfied.

[0025] As shown in FIGS. 7 to 8, the data transmission device 11 manages the association between the type of transmission data and the desired delayed Ack size. For example, when transmitting transmission data "BBB" and changing the delayed Ack size of the destination to "1400", the desired delayed Ack size "1400" is stored in the first segment, and the reset flag is stored in the last segment. When transmitting transmission data "CCC" and changing the delayed Ack size of the destination to "2800", the data transmission device 11 stores the desired delayed Ack size "2800" in the first segment and the reset flag in the last segment. Note that the data transmission device 11 determines the desired delayed Ack size based on at least one of the type of transmission data and the data size.

[0026] (1-2) Flowchart showing the Ack transmission determination process in the data reception device 12 (see FIGS. 9 to 13) The data reception device 12 monitors the reception of data transmitted from the data transmission device 11 and waits for the start condition of the Ack transmission determination process to be satisfied. When the data reception device 12 determines that it has received data transmitted from the data transmission device 11 and that the start condition of the Ack transmission determination process is satisfied, it starts the Ack transmission determination process.

[0027] When starting the Ack transmission determination process, the data reception device 12 determines whether the total received data size, which is the total data size of the received data, is "0" (B1). If the data reception device 12 determines that the total received data size is not "0" (B1: NO), it adds the data size of the current received data to the total received data size, updates the total received data size (B2), and proceeds to the desired delayed Ack size update determination process (B3).

[0028] When the data receiving device 12 starts the desired delayed Ack size update determination process, it determines whether the desired delayed Ack size is stored in the TCP option of the received data (B11). If the data receiving device 12 determines that the desired delayed Ack size is not stored (B11: NO), it ends the desired delayed Ack size update determination process and returns to the Ack transmission determination process.

[0029] When the data receiving device 12 determines that the desired delayed Ack size is stored (B11: YES), it checks the desired delayed Ack size, the reset flag, and the request presence / absence flag (B12, B13). When the data receiving device 12 determines that the desired delayed Ack size is greater than "0" and the request presence / absence flag is set to invalid (B12: YES), it changes the delayed Ack size array based on the desired delayed Ack size (B14) and sets the request presence / absence flag to valid (B15).

[0030] If the data receiving device 12 determines that the reset flag is stored and the request presence / absence flag is set to valid (B13: YES), it resets the delayed Ack size array (B16) and sets the request presence / absence flag to invalid (B17). The data receiving device 12 updates the delayed Ack size (B18), stores the updated delayed Ack size in the TCP option of the Ack (B19), terminates the desired delayed Ack size update determination process, and returns to the Ack transmission determination process.

[0031] On the other hand, if the data receiving device 12 determines that the total received data size is "0" (B1: YES), it starts counting the timer (B4) and proceeds to vehicle information update determination processing (B5). When the data receiving device 12 starts the vehicle information update determination processing, it compares the vehicle stop flag with the ignition information and determines whether the vehicle stop flag and the ignition information match (B21). If the data receiving device 12 determines that the vehicle stop flag and the ignition information match (B21: YES), it ends the vehicle information update determination processing and returns to the Ack transmission determination processing.

[0032] When the data receiving device 12 determines that the vehicle stop flag and the ignition information do not match (B21: NO), it updates the vehicle stop flag based on the ignition information (B22), updates the delayed Ack size (B23), stores the updated delayed Ack size in the TCP option of the Ack (B24), ends the vehicle information update determination process, and returns to the Ack transmission determination process.

[0033] The data receiving device 12 collates the total received data size and the delayed Ack size, and determines whether the total received data size exceeds the delayed Ack size (B6). When the data receiving device 12 determines that the total received data size exceeds the delayed Ack size (B6: YES), it transmits an Ack to the data transmitting device 11 (B7), initializes the total received data size (B8), initializes the measurement time of the timer (B9), ends the Ack transmission determination process, and waits for the start condition of the next Ack transmission determination process to be satisfied.

[0034] When the data receiving device 12 determines that the total received data size does not exceed the delayed Ack size (B6: NO), it collates the measurement time of the timer and a predetermined time, and determines whether the measurement time of the timer exceeds the predetermined time (B10). When the data receiving device 12 determines that the measurement time by the timer exceeds the predetermined time (B10: YES), in this case as well, it transmits an Ack to the data transmitting device 11 (B7), initializes the total received data size (B8), initializes the measurement time by the timer (B9), ends the Ack transmission determination process, and waits for the start condition of the next Ack transmission determination process to be satisfied. When the data receiving device 12 determines that the measurement time by the timer does not exceed the predetermined time (B10: NO), it ends the Ack transmission determination process without transmitting an Ack to the data transmitting device 11, and waits for the start condition of the next Ack transmission determination process to be satisfied.

[0035] When the data receiving device 12 determines that a desired delay Ack size with a value exceeding "0" is stored and the request presence / absence flag is set to invalid, as shown in FIG. 12, if the vehicle stop flag is invalid, the value of the desired delay Ack size is registered in the delay Ack size array, and if the vehicle stop flag is valid, the value obtained by multiplying the desired delay Ack size by the delay Ack coefficient is registered in the delay Ack size array, thereby changing the delay Ack size array.

[0036] When the data receiving device 12 determines that a reset flag is stored and the request presence / absence flag is set to valid, as shown in FIG. 13, the delay Ack size array is reset by copying the elements with an invalid request presence / absence flag to the elements with a valid flag and replacing them with the same value.

[0037] (1-3) Flowchart showing the delay Ack size update determination process in the data transmission device 11 (see FIG. 14) The data transmission device 11 monitors the reception of the Ack transmitted from the data receiving device 12 and waits for the start condition of the delay Ack size update determination process to be satisfied. When the data transmission device 11 determines that it has received the Ack transmitted from the data receiving device 12 and determines that the start condition of the delay Ack size update determination process is satisfied, it starts the delay Ack size update determination process.

[0038] When the data transmission device 11 starts the delay Ack size update determination process, it determines whether a delay Ack size is stored in the TCP option of the received Ack (A11). When the data transmission device 11 determines that no delay Ack size is stored in the TCP option of the received Ack (A11: NO), it ends the delay Ack size update determination process and waits for the start condition of the next delay Ack size update determination process to be satisfied. When the data transmission device 11 determines that a delay Ack size is stored in the TCP option of the received Ack (A11: YES), it updates the delay Ack size of the destination based on the stored delay Ack size (A12), ends the delay Ack size update determination process, and waits for the start condition of the next delay Ack size update determination process to be satisfied.

[0039] (2) Processing when a session is established (see Figures 15 to 18) As shown in Figure 15, when a session is established, the connection attempting side sends a Syn with the Delayed Ack size and Delayed Ack coefficient stored in a TCP option to the connection accepting side. When the connection accepting side receives the Syn sent from the connection attempting side, it sends a Syn / Ack with the Delayed Ack size stored in a TCP option to the connection attempting side. When the connection attempting side receives the Syn / Ack sent from the connection accepting side, it sends an Ack to the connection accepting side. As the processes when a session is established, the Syn transmission decision process on the connection attempting side, the Syn / Ack transmission decision process on the connection accepting side, and the Ack transmission decision process on the connection attempting side will be explained in order.

[0040] (2-1) Syn transmission determination process on the connection attempting side (see Figure 16) The connection attempting side registers the destination IP address and destination port number of the connection destination in the configuration beforehand, and starts the SYN transmission determination process after referring to the base table and recognizing the delayed Ack size and delayed Ack coefficient. When the connection attempting side starts the SYN transmission determination process, it initializes the delayed Ack size array based on the delayed Ack size (C1), and initializes the vehicle stop flag and request presence / absence flag (C2). The connection attempting side creates a TCP segment (C3) and stores the delayed Ack size and delayed Ack coefficient in the TCP options (C4). The connection attempting side sends a SYN with the delayed Ack size and delayed Ack coefficient stored in the TCP options to the connection accepting side (C5), and ends the SYN transmission determination process.

[0041] (2-2) Syn / Ack transmission decision process on the connection accepting side (see Figure 17) The connection accepting side monitors the reception of Syn sent from the connection attempting side and waits for the conditions for starting the Syn / Ack transmission determination process to be met. When the connection accepting side determines that it has received Syn sent from the connection attempting side and that the conditions for starting the Syn reception determination process are met, it starts the Syn / Ack transmission determination process.

[0042] When the connection receiving side starts the Syn / Ack transmission determination process, it determines whether the delayed Ack size is stored in the TCP option of the received Syn (D1). If the connection receiving side determines that the delayed Ack size is stored in the TCP option of the received Syn (D1: YES), it updates the value of the destination information (D2).

[0043] The connection receiving side determines whether the information corresponding to the destination IP address and destination port number of the Syn is stored in the base table (D3). If the connection receiving side determines that the information corresponding to the destination IP address and destination port number of the Syn is not stored in the base table (D3: NO), it newly registers the destination IP address, destination port number, the delayed Ack size stored in the TCP option of the Syn, and the delayed Ack coefficient in the base table (D4).

[0044] The connection receiving side acquires the delayed Ack information from the base table (D5), initializes the delayed Ack size array (D6), and initializes the vehicle stop flag and the request presence flag (D7). The connection receiving side creates a TCP segment (D8), stores the delayed Ack size in the TCP option (D9). The connection receiving side transmits the Syn / Ack with the delayed Ack size stored in the TCP option to the connection attempt side (D10), and ends the Syn / Ack transmission determination process.

[0045] (2-3) Ack Transmission Determination Process on the Connection Attempt Side (see Figure 18) The connection attempt side monitors the reception of the Syn / Ack transmitted from the connection receiving side and waits for the start condition of the Ack transmission determination process to be satisfied. When the connection attempt side determines that it has received the Syn / Ack transmitted from the connection receiving side and determines that the start condition of the Ack transmission determination process is satisfied, it starts the Ack transmission determination process.

[0046] When the connection trial side starts the Ack transmission determination process, it determines whether a delayed Ack size is stored in the TCP option of the received Syn / Ack (C11). When the connection trial side determines that a delayed Ack size is stored in the TCP option of the received Syn / Ack (C11: YES), it updates the value of the destination connection information (C12), transmits an Ack to the connection acceptance side (C13), and ends the Ack transmission determination process.

[0047] As described above, according to this embodiment, the following operational effects can be obtained. In the data receiving device 12, when receiving the desired delayed Ack size transmitted from the data transmitting device 11, the Ack is transmitted to the data transmitting device 11 at a transmission frequency based on the received desired delayed Ack size. Different from the conventional case where the transmission frequency of the Ack can only be adjusted on the transmission side of the Ack, by the data transmitting device 11 transmitting the desired delayed Ack size to the data receiving device 12, the transmission frequency can be adjusted on the receiving side of the Ack. Thereby, by the data transmitting device 11 requesting the transmission frequency of the Ack, the throughput can be appropriately adjusted according to the situation.

[0048] In the data transmitting device 11, the transmission frequency of the Ack is determined according to the type and size of the transmitted data. An appropriate throughput can be obtained according to the type and size of the transmitted data.

[0049] In the data receiving device 12, when ignition information is acquired as vehicle state, an Ack is transmitted to the data transmitting device 11 at a transmission frequency based on the acquired ignition information. The transmission frequency of the Ack can be adjusted on the transmitting side of the Ack according to the possibility of noise occurrence. If it is an ignition-on state where the possibility of noise occurrence is relatively high, the stability of data communication can be ensured by maintaining the transmission frequency of the Ack to some extent. If it is an ignition-off state where the possibility of noise occurrence is relatively low, the throughput can be increased by reducing the transmission frequency of the Ack. Thus, by considering the on / off state of ignition, the throughput can be appropriately adjusted according to the situation.

[0050] In the data receiving device 12, when the transmission frequency of the Ack is determined, the determined transmission frequency of the Ack is transmitted to the data transmitting device 11. The data transmitting device 11 can recognize the transmission frequency of the Ack.

[0051] In the data receiving device 12, the initial value of the transmission frequency of the Ack is determined based on the destination IP address and the destination port number registered in the base table held by itself. The data transmitting device 11 can register an appropriate delayed Ack size before transmitting data to the data receiving device 12.

[0052] Although the present disclosure has been described in accordance with the embodiments, it is understood that it is not limited to the embodiments and structures. The present disclosure also includes various modifications and modifications within the equivalent scope. In addition, various combinations and forms, and further other combinations and forms including only one element, more than one element, or less than one element thereof also fall within the scope and spirit of the present disclosure. Although the configuration applied to the data communication between the communication device 2 and the OTA master 3 and the data communication between the OTA master 3 and each domain ECU 4 has been exemplified, it may also be applied to the data communication between domain ECUs 4, the data communication between a domain ECU 4 and other devices such as sensors, and the data communication between other devices such as sensors.

[0053] The control unit and its method described in the present disclosure may be realized by a dedicated computer configured by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and its method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Or, the control unit and its method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

Explanation of Signs

[0054] In the drawings, 1 is a data communication system, 11 is a data transmission device, and 12 is a data reception device.

Claims

1. A vehicle data communication system (1) in which a data transmission device (11) and a data reception device (12) perform TCP communication, wherein the data transmission device transmits a desired delay Ack size for requesting to transmit an Ack at a predetermined transmission frequency to the data reception device, the data reception device acquires a vehicle state, receives the desired delay Ack size transmitted from the data transmission device, and determines a transmission frequency of an Ack based on the received desired delay Ack size and the acquired vehicle state, and transmits the Ack to the data transmission device. A vehicle data communication system.

2. The vehicle data communication system according to claim 1, wherein the data transmission device transmits a desired delay Ack size for requesting to transmit an Ack at a predetermined transmission frequency based on at least one of a type of transmission data and a data size to the data reception device.

3. The data reception device according to claim 1 or 2, wherein the data reception device acquires an on / off state of a drive mechanism as a vehicle state, and determines a transmission frequency of an Ack based on the acquired on / off state of the drive mechanism, and transmits the Ack to the data transmission device. A vehicle data communication system described above.

4. The vehicle data communication system according to any one of claims 1 to 3, wherein the data reception device transmits the determined transmission frequency of the Ack to the data transmission device.

5. The vehicle data communication system according to any one of claims 1 to 4, wherein the data reception device determines an initial value of a transmission frequency of an Ack based on a destination IP address and a destination port number registered in a base table held by itself.

6. A data transmission device (11) provided in a vehicle data communication system (1) that performs TCP communication with a data reception device (12) that determines a transmission frequency of an Ack based on a desired delay Ack size and a vehicle state received from the data transmission device and transmits the Ack to the data transmission device, wherein the data transmission device transmits a desired delay Ack size for requesting to transmit an Ack at a predetermined transmission frequency to the data reception device.

7. A data reception device (12) provided in a vehicle data communication system (1) that performs TCP communication with a data transmission device (11) that transmits a desired delay Ack size for requesting to transmit an Ack at a predetermined transmission frequency to the data reception device, A data receiving device that acquires a vehicle state, receives the desired delay Ack size transmitted from the data transmitting device, determines a transmission frequency of Ack based on the received desired delay Ack size and the acquired vehicle state, and transmits the Ack to the data transmitting device.

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