ON SELECTED AREAS IN COMMUNICATIONS 1 Fluid Analysis of Delay and PacketDiscard Performance for QoS Support inWireless

| Providing quality of service (QoS) guarantees over wireless links requires thorough understanding and quantiication of the interactions among the traac source, the wireless channel, and the underlying link-layer error control mechanisms. In this paper, we account for such interactions in an analytical model that we use to investigate the delay distribution and the packet discard rate over a wireless link. In contrast to previous studies, our analysis accommodates the inherent autocorrelations in both the traf-c source as well as the channel error characteristics. An on/oo uid process is used to model the arrival of packets at the transmitter. These packets are temporarily stored in a FIFO buuer before being transmitted over a channel with a time-varying and autocorrelated service rate. Using uid analysis, we rst derive the distribution for the queueing delay at the transmitter. As part of this analysis, we solve a fundamental uid problem, namely, the probability distribution for the workload generated by a 2-state uid source over a xed time interval. We then use the delay analysis to derive the packet discard rate at the receiver (a packet is discarded when the maximum number of retransmissions is reached). A closed-form expression for the eeective band-width subject to a delay constraint is provided as a function of the source, channel, and error scheme parameters. This expression enables fast assessment of the bandwidth requirement of real-time traac over QoS-based wireless networks. Numerical results and simulations are used to verify the adequacy of the analysis and to study the interactions among various system parameters.