Message Scheduling for the FlexRay Protocol: The Static Segment
Klaus Werner Schmidt, Ece Güran Schmidt · IEEE Transactions on Vehicular Technology · 2008
In recent years,time-triggeredcommunication protocols have been developed to support time-critical applications for in-vehicle communication. In this respect, the FlexRay protocol is likely to become thedefactostandard. In this paper, we investigate the scheduling problem of periodic signals in thestaticsegmentof FlexRay. We identify and solve two subproblems and introduce associated performance metrics: (1) The signals have to be packed into equal-size messages to obey the restrictions of the FlexRay protocol, while using as little bandwidth as possible. To this end, we formulate a nonlinear integer programming (NIP) problem to maximize bandwidthutilization. Furthermore, we employ the restrictions of the FlexRay protocol to decompose the NIP and compute theoptimalmessagesetefficiently. (2) A message schedule has to be determined such that the periodic messages are transmitted with minimumjitter. For this purpose, we propose an appropriate software architecture and derive an integer linear programming (ILP) problem that both minimizes the jitter and thebandwidthallocation. A case study based on a benchmark signal set illustrates our results.