A fast decoupled approach for optimum TDM assignment in constrained hierarchical switching systems

A three-tiered digital switching hierarchy is considered in which traffic from remote users is grouped, concentrated into time-multiplexed lines, and then transmitted to a central location for interconnection by a central space division switch. While the configuration provides efficient sharing of both transmission and switching resources, the TDM (time-division multiplexing) assignment problem for a conventional time-space-time (T-S-T) switch can become quite formidable due to the various hierarchical constraints. A time-slot assignment strategy is proposed that circumvents this problem by temporarily storing the incoming traffic at the central switch. Unlike the traditional T-S-T approach, the in-bound and out-bound assignments are entirely decoupled, which greatly simplifies the assignment process and produces a fast circuit switching capability. Necessary and sufficient conditions governing the assignability of traffic to the three-tiered switching system are stated and proved, and a block diagram of the proposed switching architecture is presented