A performance analysis of a discrete-time queueing system with server interruption for modeling wireless ATM multiplexer

Abstract

In this paper, we study the effect of channel errors on wireless ATM. The salient characteristic of the wireless channel is that it is time varying. This variability is modeled by a Markov chain with two states corresponding to high and low error states, respectively. The channel is modeled as being synchronous with the basic time unit being the slot. The transitions from high to low error states, and vice versa occur at the slot boundaries. It is assumed that no transmission over the channel is possible during the high-error state. The information source feeding into the channel is modeled as the superposition of independent sources. Each source is controlled by a two-state Markov chain which operates in synchronism with, but statistically independent of the channel. In the source Off state, no data is emitted while, in the On state, the source generates a random number of packets in a slot each of which fits into a channel slot. It is assumed that the traffic generated by all the sources will form a single global queue which will be served by the two-state Markov channel. A discrete-time queuing analysis derives the probability generating function (PGF) of the queue length under the assumption of an infinite buffer. From the PGF, we determine mean queue length and mean delay. Finally, numerical results are presented to demonstrate the effect of wireless channel error characteristics on performance.