Controlling window protocols for time-constrained communication in multiple access networks

The authors examine the use of a group random-access protocol based on time windows for supporting time-constrained communication applications in a multiple-access network. First they formulate a policy for controlling protocol operation to minimize the percentage of messages with waiting times greater than some given bound. A semi-Markov decision model is then developed for protocol operation, and three of the four optimal control elements of this policy are determined. Although the semiMarkov decision model can also be used to obtain performance results, the procedure is to computationally expensive to be of practical use. Thus, an alternate performance model based on a queuing system with impatient customers is developed. Protocol performance under the optimal elements of the control policy shows significant improvements over cases in which the protocol is not controlled in this manner. Simulation results are presented to corroborate the analytic results