Efficient transient error recovery in FlexRay using the dynamic segment

In safety-critical systems a global high-reliability is sought, including in the communication network when a distributed control system is used. The FlexRay protocol was developed within the automotive industry with the necessary characteristics to respond to the demands of safety-critical applications, e.g. X-by-wire. Nevertheless, the FlexRay protocol does not define a mechanism to guarantee message delivery, nor defines global error signaling, leaving the resolution of these problems to the application. This paper presents a preliminary proposal for a mechanism that uses temporal redundancy to recover transient errors in time-triggered messages. An extra node is used to trigger message retransmissions whenever errors or omissions do effectively occur. This mechanism uses the FlexRay dynamic segment to implement message retransmissions, leading to a minimum recovery time, typically one cycle, together with a very small bandwidth usage.