Reducing Call-Setup Time for Location Tracking with Distributed HLR and Pointer Forwarding

Abstract

One of the main challenges in PCS is to locate many mobiles that may move frequently from place to place. This location tracking operation involves many network signals flow and database queries. In addition to the two-level hierarchical strategy in IS-41 and GSM, several strategies have been proposed to improve the efficiency of location tracking. Pointer forwarding was used to reduce the expensive HLR accesses. Previously, distributed HLRs scheme was proposed to prevent HLR becoming a bottleneck in the signaling network. However, the length of a forwarding pointer chain may be lengthened in a distributed HLR environment. In this paper, we propose a more efficient strategy to overcome this potential problem. This strategy attemps to migrate the locating chains in a distributed HLR system when a mobile issues a registration operation. As a consequence, the length of any forwarding pointer chain does not exceed one in our strategy. Simulation results indicate that our strategy significantly decreases the locating cost. In fact, this strategy provides an upper bound of location tracking time owing to the fact that its length of any locating path does not exceed one. Furthermore, obsolete entries in local databases (VLRs) can be reclaimed in this strategy.