Analysis Of The Queue Service Probability For The Edf Scheduling Algorithm

This paper is concerned with the Earliest-Deadline First (EDF) policy for scheduling a constrained multi-queue system with a single server in the overloaded environment. This study originates from the research of the controller area network (CAN). In the CAN system, variability and constraints, e.g. heavy (or overloaded) traffic, timing constraints, limited bandwidth, etc., have crucial impacts on its scheduling performance. Violating these constrictions may lead to a lack of the ability of maintaining the integrity of the system communication. In this sense, this paper discusses the applicability of Earliest Deadline First (EDF) technique to the scheduling of CAN messages. The EDF scheduling algorithm permits more general applications to the real time system under various situations and timing constraints. It assumes implicitly that a message's urgency increases with the imminence of its deadline. In this regard, the EDF policy minimizes the maximum lateness and the maximum tardiness. Therefore, a software-based EDF policy uses the message time-to-deadline as a measure of its priority is applied to schedule the message exchanges in the CAN. In this work, the closed form of queue service probability is also derived from solving a set of nonlinear equations. From the simulation analysis the concerned model, our theoretical results are well matched with the experimental results. Importantly, the theoretical results are not necessarily limited to the applications of CAN system. Instead, we hope to provide a general viewpoint of scheduling issues in the overloaded condition.