Efficiency and reliability of call admission control schemes using call-level behavior

While the efficiency of call admission control (CAC) schemes can be improved by taking advantage of call-level behavior, it is also important to make sure that the reliability of the CAC schemes is maintained. This paper studies the reliability aspect of CAC schemes for the reference model that consists of the M/M/c loss system at the call level, and the bufferless link with single-class exponential on-off fluid traffic at the burst level. As a measure of reliability, the probability that an admitted call violates a loss-ratio target is used, and its analytic expression is derived for the reference model by using performability analysis and the nearly completely decomposability approximation. It is shown that the CAC schemes previously proposed to take advantage of call-level behavior are not acceptably reliable. In addition, it is shown that, for most cases in practice, if the reliability of a CAC scheme taking advantage,of call-level behavior is to be maintained at a reasonable level, the improvement in efficiency relative to the static scheme will be small.