Flight-critical distributed systems - design considerations

With the proliferation of so-called "smart" components and the availability of small, low-cost, and high-speed data networks, avionics that have traditionally been centralized are becoming distributed. A distributed approach offers many potential benefits and can reduce the risk associated with design errors by splitting complex hardware and software into more manageable components. However, distributed systems also introduce new challenges in meeting real-time deadlines and providing fault tolerance. The automotive industry is addressing the challenges with the development of distributed, drive-by-wire systems, and the adaptation of these to avionic applications looks promising. In developing these new distributed systems, there are many fundamental system design considerations including: time or event-triggered data communication, distributed or centralized data network control, need and method for time-synchronization of distributed components, topology and amount of redundancy to provide fault tolerance. This paper examines these design considerations and identifies the strengths and weaknesses of each.