Cell Scheduling and Bandwidth Allocation for a Class of VBR Video Connections

In this paper, we study the bandwidth allocation problem for an ATM multiplexer loaded with heterogeneous low-motion VBR video sources. We propose a cell scheduling scheme which balances cell loss among different sources so that they experience nearly the same cell loss rate. To estimate the bandwidth required by a VBR video source, we characterize its traffic by four parameters: peak rate, mean rate, coefficient of variation, and the coefficient of the autocorrelation function. Based on the effective bandwidth approach and the stationary Gaussian approximation, we derive simple formulas for estimating the required bandwidth using the four traffic parameters. From numerical results, we conclude that the stationary Gaussian approximation seems to be a very promising bandwidth allocation scheme for VBR video sources. The effective bandwidth approach performs not as well as when it is applied to on-off sources due to its incapability in making full use of statistical multiplexing gain. Extra care must be taken to ensure that the QoS requirement is satisfied when using Gaussian approximation in bandwidth allocation because it does not always overestimate the required bandwidth.