ADMISSION CONTROL OF MIXED VBR SOURCES IN BROADBAND NETWORKS

摘要

In controlling the admission of variable bit rate (VBR) traffic, source classes are typically mixed in the sense that some can benefit from statistical multiplexing while others cannot. Moreover, such a mix of statistically multiplexable (S-VBR) and nonstatistically multiplexable (NS-VBR) sources is known to cause nonlinear interactions. Accordingly, if the boundary of the set of admissible connections is conservatively estimated by a linear approximation, the number of falsely rejected connections can become excessive. On the other hand, such an approximation permits admissibility to be easily decided in terms of the effective bandwidths of the traffic classes. Motivated by this background, the modified Chernov bound (MCB) is used to estimate the probability Psat of channel saturation and, with respect to a specified QOS bound on Psat, the set of admissible connections is formulated for worst-case regulated, periodic, on-off traffic. The S-VBR/NS-VBR dichotomy is characterized relative to this MCB-based admissible set and effective bandwidth computations are derived for S-VBR traffic. These results are then incorporated in an innovative, time-efficient admission control algorithm that applies to mixed S-VBR/NS-VBR traffic without compromising the accuracy of admission decisions. The algorithm relies on an ordering of classes according to their relative multiplexabilities along with a table of precomputed effective bandwidths for incremental values of residual capacity. The description of the invention concludes with an assessment of the algorithm's accuracy and computational efficiency as compared with alternative methods.