Scheduling of Dependent Real-Time Tasks Using Fuzzy Logic Technique
Medhat H A Awadalla, Afaq Ahmad, Samir Al‐Busaidi · American academic & scholarly research journal · 2014
Abstract. Many scheduling algorithms have been studied to guarantee the time constraints of real-time processes. Scheduling decision of these algorithms is usually based on parameters which are assumed to be crisp. However, in many circumstances the values of these parameters are vague. Moreover, reducing energy consumption is a critical issue in the design of battery-powered real time to prolong battery life. With dynamic voltage scaling (DVS) processors, energy consumption can be reduced efficiently by making appropriate decisions on the processor speed/voltage during the scheduling of real time tasks. Therefore, a fuzzy logic approach is proposed to reduce energy consumption by determining the appropriate supply-voltage/speed of the processor provided that timing constraints are guaranteed. Intensive simulated experiments and qualitative comparisons with the most related literature have been conducted in the context of dependent real-time tasks. Experimental results have shown that the proposed fuzzy scheduler saves more energy and creates feasible schedules for real time tasks. It also considers tasks priorities which cause higher system utilization and lower deadline miss time.Keywords: dynamic voltage scaling (DVS) processors, fuzzy logic approach, real-time tasks.(ProQuest: ... denotes formulae omitted.)1. INTRODUCTIONMany applications namely avionics, traffic control, automated factory, and military require real time communication and computation. In real-time systems, all tasks have specific parameters such as deadline, priority, etc. Many real-time are hard and missing deadline is catastrophic, Chen and Kuo (2007). A schedule which is executing all real-time tasks within their deadlines and all the other constraints are met, is called a feasible schedule. Tasks are classified as periodic and non-periodic (Behera et al., 2012). The execution requests of a periodic task repeatedly occur at regular intervals. On the contrary, execution requests of a non-periodic task are unpredictable. In all cases, time has an essential role and having the right answer too late is as bad as not having it at all. In the literature, these have been defined as: systems in which the correctness of the system depends not only on the logical results of computation, but also the time at which the results are produced. Such must react to the requests within a fixed amount of time which is called deadline. Scheduling algorithms of these may be considered one of the key components of a real-time system, which can either enable the system to thrive or bring it to its knees. Strict timing requirements must often be met within highly dynamic environments which do not lend themselves well to static scheduling algorithms. The level of uncertainty in dynamic, real-time environments is such as to require significant flexibility and adaptivity from real systems. Fuzzy logic contributes in this issue in the form of approximate reasoning, where it provides decision-support and expert with powerful reasoning capabilities bounded by a minimum number of rules. Theoretically, fuzzy logic is a method for representing analog processes, or natural phenomena that are difficult to model mathematically on a digital computer. Therefore, Fuzzy fit as scheduling algorithm building into the real-time system flexibility and adaptation to the uncertainty inherent in real-time environments and offers a means to improve several important characteristics of real-time (Venkatachalam and Franz (2005). Since most of real time (devices) are battery powered. As the applications on these devices are being complicated, the energy consumption is also effectively increasing. So, minimizing energy consumption is a critical issue in the design of these systems, and techniques that reduce energy consumption have been studied at different levels in details Liu (2007).One promising mechanism that provides the best of both low-power and high-performance processors in the same system is DVS. …