Scheduling in time-triggered networks

Modern avionics systems consist of distributed components that communicate over shared networks. Such networks offer - in contrast to point-to-point connections - more system flexibility and cost reduction due to reduced wiring. A key component for increasing the level of performance, and attaining a reliable and predictable communication in distributed avionics systems is an adequate scheduling strategy. When considering avionics architectures with distributed nodes communicating over a time-triggered shared medium, the problem is to generate a schedule that preserves hard-real time properties. For this, the general task scheduling policies have to be extended by also considering message scheduling to address the whole complexity of such systems. This paper presents a novel off-line scheduling approach for (hard) real-time systems based on a time-triggered communication network that integrates task scheduling at system level with message scheduling at communication level. The approach augments conventional scheduling rules with algorithms addressing the specific problems of time triggered system design, allowing therefore for the generation of a feasible communication schedule. This leads to an improvement in reliability and predictability of communication.