A New Scheme for Locating User around Mobility-Database Failures

One of the main challenges in PCS is to locate mobile users to provide timely services. In addition to the two-level hierarchical method in IS-41 and GSM, several strategies have been proposed to improve the efficiency of location tracking. Pointer forwarding was used to reduce the costly HLR accesses. Previously, bypass forwarding was proposed to tolerate the failures of VLR on the traced pointer chain. However, this scheme may fail in bypassing the failed VLR when encounters the multipath situation. This paper proposed two strategies to resolve the potential problem: bypass forwarding with fast-response (FR) and bypass forwarding with shortest-path (SP). Based on the conducted simulations, bypass forwarding with SP outperforms the bypass forwarding with FR in terms of the length of chain; whereas, bypass forwarding with FR introduces less overhead during path discovery in comparison to that in SP.