Synthesis of Static Communication Schedules for Mixed-Criticality Systems

Throughout many application areas of embedded and cyber-physical systems there is a demand to integrate more and more applications such that they share common resources. These applications may have different levels of criticality with respect to temporal or fault-tolerance properties and we call the result of their integration a mixed-criticality system. The communication network is a resource of particular importance and nowadays the system architecture is highly determined by a network's capabilities. A network for mixed-criticality systems has to establish partitioning such that the influence of messages from different applications on each other is bounded and the impact of low-critical messages on high-critical ones is minimized or removed at all. A straight forward way to establish network-wide partitioning is the time-triggered communication paradigm in which the communication schedule on the network is defined at design time and executed with respect to a globally synchronized time base. In this paper we discuss static scheduling methods for time-triggered traffic such that it can co-exist with non-time-triggered traffic. We introduce the concept of "schedule porosity'' and show the impact of time-triggered traffic on unsynchronized traffic as a function of schedule porosity.