Fluid analysis of delay and packet discard performance for QoSsupport in wireless networks

摘要

Providing quality-of-service (QoS) guarantees over wireless linksnrequires thorough understanding and quantification of the interactionsnamong the traffic source, the wireless channel, and the underlyingnlink-layer error control mechanisms. We account for such interactions innan analytical model that we use to investigate the delay distributionnand the packet discard rate (PDR) over a wireless link. Our analysisnaccommodates the inherent autocorrelations in both the traffic source asnwell as the channel error characteristics. An on-off fluid process isnused to model the arrival of packets at the transmitter. These packetsnare temporarily stored in a first-in-first-out (FIFO) buffer beforenbeing transmitted over a channel with a time-varying and autocorrelatednservice rate. Using fluid analysis, we first derive the distribution fornthe queueing delay at the transmitter. As part of this analysis, wensolve a fundamental fluid problem, namely, the probability distributionnfor the workload generated by a two-state fluid source over a fixed timeninterval. We then use the delay analysis to derive the PDR at thenreceiver. A closed-form expression for the effective bandwidth subjectnto a delay constraint is provided as a function of the source, channel,nand error scheme parameters. This expression enables fast assessment ofnthe bandwidth requirement of real-time traffic over QoS-based wirelessnnetworks. Numerical results and simulations are used to verify thenadequacy of the analysis and to study the interactions among variousnsystem parameters