language: en

On Scheduling Two Classes of Real Time Traffic With Identical Deadlines

Sridhar Pingali
Dept. of Electrical and Computer Engineering University of Masschusetts
Amherst, MA 01003
James F. Kurose
Dept. of Computer and Information Science Univeristy of Massachusetts
Amherst, MA 01003

Abstract The problem of scheduling two classes of real-time traffic with correlated time constraints is considered. Three scheduling disciplines are studied: a priority discipline which gives strict priority to one class of traffic, a threshold-based scheme in which priority is given to one class of traffic when the minimum laxity of its queued packets falls below some threshold, and a "balancing" scheme which assigns priority on the basis of the differences in minimum laxities in the two classes of traffic. Analytic results are obtained by using a discrete time model to obtain the state occupancy probabilities for the system. Here, the state is defined using the laxities of the queued real time packets. Parameters are defined to study the tradeoff in the performance of the two classes of traffic. Results are obtained to demonstrate how the balancing scheme permits us to achieve significant improvement in the performance of one class of traffic with only minimal effect on the performance of other class. A video application is suggested for this work.

1 Introduction