A SEPARATION PRINCIPLE BETWEEN SCHEDULING AND ADMISSION CONTROL FOR BROAD-BAND SWITCHING

A framework for joint scheduling arid admission control in broad-band switching systems is developed according to a principle of separation between these two levels of control. It is shown how an admission control strategy can be tailored to a particular mix of traffic by making use of high-level information from the scheduler. This principle is presented in the context of asynchronous time-sharing (ATS), in which explicit guarantees of cell-level and call-level quality of service (QOS) are given to several traffic classes. The separation principle allows the formulation of an optimal admission control policy, which will maximize the expected system utility while maintaining all QOS guarantees. Several heuristic admission control policies are considered, and are compared against the optimal policy as a benchmark. The admissible load region is introduced as a means of quantifying the capacity of a switch under the QOS constraints at the cell and call levels. Numerical calculations for a single MAGNET II switching node carrying two classes of real-time traffic are used to illustrate the effects of different scheduling and admission control policies on both the expected utility and the admissible load region.