Self-Reconfiguration for Fault-Tolerant FlexRay Networks

In this paper we present an approach for the self-reconfiguration of FlexRay networks to increase their fault tolerance. We propose a self-organized distributed coordinator concept which performs the self-reconfiguration in case of a node failure using redundant slots in the FlexRay schedule and combination of messages in existing frames and slots to avoid a complete bus restart. Therefore, the self-reconfiguration is realized by means of predetermined information about resulting changes in the communication dependencies and (re-)assignments from a introduced heuristic, which determines initial configurations and, based on that, calculates valid reconfigurations for the remaining nodes of the FlexRay network. The distributed coordinator concept, which is implemented by lightweight tasks not consuming any significant resources, uses these information and performs the reconfiguration of the FlexRay network at run time to increase the fault tolerance of the system. An evaluation by means of realistic safety-critical automotive real-time systems revealed that this reconfiguration approach determines valid reconfigurations for up to 80% of possible individual node failures and thereby offers applicable information for the self-reconfiguration approach. Furthermore, in an iterative design process these results can be improved to optimize the reconfigurations. The evaluation of our self-organized distributed coordinator concept and the comparison to a centrally organized solution with a dedicated coordinator proves its benefits regarding the additional hardware and communication overhead and the resulting reconfiguration time, which has an great impact on the fault tolerance of the FlexRay network.