Caching in hierarchical user location databases for PCS

Mobility management architectures for future generations of PCS systems have been proposed where multiple location databases, organized in a tree, are used to cope with the large number of users. We have previously proposed the use of caching as an auxiliary strategy for reducing the network impacts of locating mobile users in a tree-structured architecture. In this paper we quantify the costs and benefits of caching for one particular variation of a caching strategy, called eager caching. Unlike our previous work where we only considered the user's calling and mobility behavior in terms of the aggregated regional call-to-mobility ratio (RCMR), in this paper the performance evaluation is done in terms of the local call-to-mobility ratio (LCMR) of the user. We show that under certain assumptions an eager caching strategy for users whose LCMR exceeds 5 can result in substantial reductions in total network cost as well as call setup time.