Reducing traffic impacts of PCS using hierarchical user location databases

To accommodate the large PCS user populations expected in the future, mobility management architectures in which location databases are organized in a tree have been proposed, e.g. for third-generation mobile systems such as the Universal Mobile Telecommunication System (UMTS). We propose the use of caching as an auxiliary strategy for reducing the network impacts of locating mobile users in a tree-structured architecture. We discuss several issues which arise for implementing caching strategies in such an architecture. We quantify the costs and benefits of caching for one particular variation of a caching strategy in order to illustrate the trade-offs involved, and present possible alternative strategies also. We show that under certain assumptions, with an eager caching strategy where the signaling architecture is a tree, for users whose regional call-to-mobility ratio (RCMR) exceeds 5, caching can result in up to 30% reductions in total network cost as well as call setup time.