Fault tolerant scheduling strategy in a NCS based on frequency transition

A hard real-time system is subject to timing and reliability constraints. In fault-tolerant real-time systems, tasks have deadlines to be met despite of the presence of fault. In this context primary-backup scheme has been one of the most important algorithm employed for fault-tolerant scheduling for real-time tasks. Each task has primary version and backup version and the versions must be scheduled on different processors. Commonly, this method has been used guaranteeing compliance with the primary tasks and backup without considering the optimal use of the communication media in networked control systems. In this paper a scheduling strategy is proposed based on frequency transition which uses primary-backup for tolerating faults considering the optimal use of network.