Notice of Retraction: A Fuzzy EDF scheduling algorithm being suitable for embedded soft real-time systems in the uncertain environments

Abstract

EDF is a classic dynamic real-time task scheduling algorithm. In an embedded soft real-time system, the deadline missing ratio is an important metric to evaluate system performance. When an embedded soft real-time system is overloaded, EDF algorithm is not effective. In addition, considering the unsteadiness and unpredictability of a practical task running environment due to the unsteadiness of network communication and the time estimation deviation, it is necessary to introduce fuzzy concept and theory to the scheduling field of embedded soft real-time application systems. In this paper, we proposed a fuzzy EDF scheduling model which is more suitable for embedded soft real-time systems in the uncertain environment. In our model, all tasks are periodic and a task's criticality and deadline distance are described with fuzzy set. In scheduling algorithm, tasks with shorter fuzzy deadline distance are scheduled first; to those with same fuzzy deadline distance level, their criticalities are considered first. The simulation test shows that our fuzzy EDF model have less deadline missing ratios than those of traditional EDF algorithm and the important tasks have less deadline missing ratios than that of others tasks in an overloaded uncertain embedded soft real-time system.