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 cont rol strategy can be tailored to a particular mix of traffic by making use of high-level information from the scheduler. This principle is pr esented in the context of asynchronous time-sharing (ATS), in which ex plicit guarantees of cell-level and call-level quality of service (QOS ) are given to several traffic classes. The separation principle allow s the formulation of an optimal admission control policy, which will m aximize the expected system utility while maintaining all QOS guarante es. Several heuristic admission control policies are considered, and a re 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. Numerica l calculations for a single MAGNET II switching node carrying two clas ses of real-time traffic are used to illustrate the effects of differe nt scheduling and admission control policies on both the expected util ity and the admissible load region.