Firm real-time system scheduling based on a novel QoS constraint

Many real-time systems have firm real-time requirements which allow occasional deadline violations but discard tasks that are not finished by their deadlines. To measure the goodness of such a system, a quality of service (QoS) metric is needed. Examples of often used QoS metrics for firm real-time systems are average deadline miss rates and (m,k)-firm constraint. However, for certain applications, these metrics may not be adequate measures of system performance. This paper introduces a novel QoS constraint for networked feedback control systems. We show that this constraint can be directly related to the control system´s performance. We then present three different scheduling approaches with respect to this QoS constraint. Experimental results are provided to compare these approaches.