Vehicle Communication System Cycle-Based Retransmission
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Solution Overview
Problem
Existing communication systems in vehicles face challenges with data transmission and reception accuracy when using TCP/IP protocol, as they rely on timeout periods for retransmissions, leading to delayed and outdated data transmission, which compromises control accuracy during automated driving and IoT applications.
Innovation Solution
A communication system with a first and second communication device configured to transmit and retransmit data using a predetermined control cycle, with retransmissions occurring based on a predetermined period of no ACK signal receipt, and switching to new data transmission in the next cycle, along with a transmission prohibition mechanism when disconnection is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TCP/IP protocol is used for communication, then large volume of data can be transmitted at high speed, but control accuracy deteriorates due to timeout-based retransmission delays
Solution Approach 1:
The system transmits data at predetermined timing intervals regardless of ACK receipt status, proactively ensuring data freshness. This preliminary action prevents the control accuracy deterioration that would otherwise occur due to timeout-based retransmission delays inherent in TCP/IP protocol
Solution Approach 2:
The communication device transmits data periodically at predetermined timing intervals rather than waiting for retransmission triggers. This periodic transmission ensures that control data remains fresh and accurate, resolving the contradiction between high-speed TCP/IP transmission and control accuracy requirements
2Reliability
If timeout period is set long for reliable retransmission, then data transmission reliability improves, but control accuracy deteriorates due to delayed data transmission
Solution Approach 1:
Data is transmitted at predetermined timing before any timeout or retransmission is needed. This preliminary action ensures that control data is always fresh and accurate, eliminating the need to balance timeout period length for reliability versus control accuracy
3Reliability
If retransmission is performed continuously until timeout, then data delivery reliability improves, but unnecessary retransmissions occur during disconnections increasing system complexity
Solution Approach 1:
The system uses ACK signals as feedback to detect communication disconnections. When disconnection is detected through absence of ACK signals, the system switches to disconnection handling mode, preventing unnecessary retransmissions and simplifying communication control while maintaining reliability
Solution Approach 2:
The communication control dynamically switches between normal transmission mode and disconnection handling mode based on ACK signal reception status. This dynamic adaptation optimizes system behavior according to actual communication conditions, reducing complexity while maintaining reliability
Data Source
AI summary
A communication circuit unit of an FI-ECU receives a signal from an AT-ECU. An arithmetic processing unit determines transmitted data at a control cycle ΔTn, transmits a communication data signal including the transmitted data to the AT-ECU at a time point t2 after the start point of the current control cycle ΔTn, and retransmits it at a time point t3 where a state, in which an ACK signal from the AT-ECU has not been received, has continued for a predetermined period of time. When the current control cycle ΔTn is ended in a state in which the ACK signal has not been received, at a time point t5 after the start point of the next control cycle ΔTn, the arithmetic processing unit transmits the communication data signal including a newest value of the transmitted data determined at the start point of the next control cycle ΔTn to the AT-ECU.