Sharing resources for enhanced dependability
Dependable systems are omnipresent and becoming more and more complex, such that subsystems may have different levels of critical performance. The ‘Complexity management for mixed-criticality systems’ (Commics) project was designed to enhance and extend the time-triggered architecture (TTA) developed at the Institut für Technische Informatik at the Vienna University of Technology to make it suitable for use in mixed-criticality dependable systems. TTA is a fault-tolerant protocol that enables continuous communication of all connected nodes at pre-defined periods of time enhancing safety and reliability. TTA has been successfully applied in the avionics industry where predictability of system operation is fundamental to safety. The Time-Triggered Protocol (TTP) used in the new Boeing 787 Dreamliner is based on TTA. In addition, TTEthernet technology, which enables real-time control over the Ethernet, has been selected for use in the NASA Orion Space Programme. However, as more and more dependable systems become mixed-criticality systems, a need has arisen for modification of the original TTA to enable sharing of resources between subsystems of different criticalities to overcome cost, size, weight and power restrictions of individual TTAs. The Commics project is addressing this need by developing novel scheduling approaches for time-triggered communication as well as boundaries on communication latencies related to TTEthernet. The researchers are also studying integrated time-triggered (do A at time t) and event-triggered (do A when B occurs) communications. Continuation of the project is expected to develop extensions for the TTEthernet and other protocols with specific functionalities, leading to enhancements in safety and reliability of the ever-growing class of complex mixed-criticality dependable systems.