Fault-Tolerant Task Scheduling Algorithms For Real-Time Systems Based On ICM Model

Real-time systems are becoming more and more concerned, which are widely used in manufacturing, space or avionics, telecommunication, and industrial automation systems. The correctness of real-time systems depend not only on the result of computations, but also on the time instants at which these results become available, otherwise it will cause the whole system to fail, even lead to catastrophic consequences. Fault-tolerant algorithms become important research, which should guarantees the completion of a scheduled task before deadline in the presence of failures. Based on the classical real-time fault-tolerant scheduling algorithm, new heuristic fault-tolerant scheduling algorithms are proposed, which improve the fault-tolerant performance of the real-time system effectively. The main research in this paper include the following several respects: ICM model for task scheduling offers one flexible frame, and quantifies the trade-off between result quality and computation time. The imprecise computation technique can prevent timing faults and achieve graceful degradation by giving the user an approximate result of acceptable quality whenever the systems cannot produce the exact result in time. The mandatory subtask is required for an acceptable result and must be computed to completion before the task deadline. The optional subtask refines the result. Classical static scheduling algorithm (Rate Monotonic algorithm, RM) RM does not support dynamic systems very well, and (Earliest Deadline First algorithm, EDF) EDF and (Least Laxity First algorithm, LLF) LLF dynamic scheduling algorithms can't deal with transient overload in the systems. Maximum-critical-first (MCF) combines the advantage of the static algorithm and dynamic algorithms. The critical set and tasks priority is scheduled by the RM and EDF. LLF respectively. Simulations are described to evaluate the performance of this algorithm, and show that the processors can achieve high utilization.> Optimal-Point fault-tolerant scheduling algorithm is proposed based on the Imprecise Computation Model (ICM). Considering that the real-time task in the practical world has rigidly time restriction. Which can divide mandatory real-time tasks and optional real-time tasks. The algorithm guarantees real-time task to finish at the deadline, at the same time, meets the requirements of reward, response time and error.> With the increasing of computer applications and complexity, some components loseefficiency in the network. Network administrative system must locate the fault and get rid of it rapidly. The real-time video transmission problem is to transmit video with timing constraints. This paper discusses the network fault-tolerant software design, which is managed by Simple Network Management Protocol (SNMP). The system guarantees the high quality requirement of the video transmitting through the network, which trades the quality of the transmitted video with the amount of available time.