A Prompt Retransmission Method for In-Vehicle Network FlexRay

FlexRay protocol has been developed as the de-facto industry standard for next generation in-vehicle communication with high bandwidth, time-triggered architecture and dual-channel redundancy. However, it does not define a mechanism to handle the transient errors, which is frequent on the common-used twisted wire cable. Thereby, FlexRay is hindered for the application in safety-critical communications. This paper presents a detailed Prompt ReTransmission Mechanism (PRTM) with acknowledgement and retransmission scheme to recovery the transient errors in the more safety-critical time-triggered messages. Considering the feasibility, failure probability reduction and bandwidth optimization, the amount of error messages permitted to be retransmitted in one cycle and the number of acknowledgement transmission is important for failure probability reduction; the schedule of the messages for acknowledgement and retransmission should be studied to optimize the bandwidth utilization. An example is used for demonstrating the effectiveness of PRTM, which can not only greatly reduce the messages failure probability but accomplish the retransmission within one cycle, together with an extra design cost and a small bandwidth waste. With PRTM, FlexRay would be notably promoted in safety-critical applications.