A Lazy Caching Location Strategy with Bypass Pointers in PCS

In this paper we propose an efficient tracking strategy, called the Precache strategy, for a hierarchical database architecture in Personal Communication Services (PCS). The main goal of our strategy is to reduce the overloads of a PCS system in the following two situations: (1) when a callee receives calls frequently, and (2) when a user crosses many registration area (RA) boundaries with the characteristic of locality. The Precache strategy keeps a callee’s bypass pointers when he/she moves around neighboring RAs. A threshold to predict and confine the roaming regions is used to estimate the trade-off of maintaining bypass pointers. The purpose of setting the value of a threshold is to avoid updating and reading location databases frequently when users move around in certain fixed regions (RAs). We also discuss how to set the threshold value to determine a user’s roaming regions and where to set the bypass pointers. Through mathematical cost analysis and experimental simulation, we demonstrate that the Precache strategy, without employing any users’ profile information, can reduce more traffic impacts than the traditional Basic and Caching strategies.