Research On Fault Tolerance For The Static Segment Of Flexray Protocol

With the development of the automotive electronic industry, automotive networktechnology has gradually become a hot topic for research and application. TheFlexRay network protocol is widely regarded as the next-generation standardautomotive network communication protocol because it has many excellent features.But the electromagnetic environment inside the car is very complex and the FlexRaylacks an application layer scheme to provide guarantees on reliability.This paper focuses on the reliability for the static segment of FlexRay. First, wemade an analysis for the existing researches and a brief introduction for automotivenetwork. Then we introduced the reliability of the static segment of FlexRay in theangle of reliability and media access control and build our system model and theproblem mathematic abstraction. Finally, two algorithms are present to increasingreliability by retransmitting messages and optimizing the bandwidth utilization rate.The main work is shown as follows.Firstly, we build the system model based on probability in the application layer.Some important equations are introduced and deduced. Then we explained the processof choosing the optimal objective by analysis other fields about the FlexRay andpresent the mathematic abstraction of the problem.Secondly, according to the system model and mathematical abstraction, wepresent a heuristics retransmission algorithm H-1based on the message scheduling. Itinnovatively put the ratio of contribution difference to bandwidth utilization rateincrease as the evaluation in selecting message to retransmit. So the resultretransmission scheme will be the most efficient in the usage of bandwidth whilesatisfying the reliable goal.Thirdly, according to the FlexRay design process, a detailed analysis shows theshortage of the H-1algorithm. Then another retransmission algorithm H-2is proposedbased on dynamic programming. We transform the original problem into the integerform which dynamic programming solution can be used to solve the problem and findany priority solutions. H-2is not only possible to increase reliability and keep optimalin bandwidth utilization, and is also able to calculate any priority messageretransmission scheme in the bandwidth utilization. Finally, we designed a simulation test based on the problem abstraction inMatLab to show the different performance of H-1, H-2and an existing algorithm inbandwidth utilization rate, reliability and running time. The result shows the H-1andH-2are better than the existing one.