Design and Optimization of Switched FlexRay Networks

FlexRay is a promising communication protocol for in-vehicle systems. With the growth of functionalities delivered by in-vehicle systems, FlexRay is accommodating more and more signals (or messages) which have exceeded the capacity of a single FlexRay bus. Switched FlexRay networks have been studied to solve the problem. However, previous research mostly focused on reducing the number of overall consumed time slots, and hardly paid attention to load balance of each branch (i.e., switch-isolated FlexRay subnetwork). This paper proposes SSFN (Scalable Switched FlexRay Network). SSFN is based on a message-buffered Crossbar structure, and thus allows the inter-branch messages transmitting at different slots of sender and receiver branches. A MILP formulation is proposed to look for the optimal solution in terms of load balance on each FlexRay branch, number of consumed slots and size of switch buffer. We conduct experiments on two case studies to evaluate the proposed formulation and the result shows that a solution with far improved load balance and approximate time slot consumption (compared to existing research) can be found in a few seconds.