A More Realistic Modeling and Cost Analysis of Movement-Based Location Management in PCS Networks
(c) 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.
Location management (LM) is a mechanism used by personal communication service (PCS) networks to track the location of user equipments (UEs) in order to facilitate the delivery of incoming calls. Compared with static LM schemes, dynamic LM schemes can cater to the diverse mobility and traffic characteristics of individual UEs, and thus can achieve good tradeoff between location update (LU) cost and paging cost so as to minimize the overall cost. Among the dynamic schemes, the movement-based LM (MBLM) scheme is cost-effective and compatible with the existing PCS networks. Cost analysis plays an important role in optimizing the MBLM scheme. Existing studies on modeling and cost analysis of the MBLM scheme more or less have some flaws. Some overlooked the home location register (HLR)/visitor location register (VLR) architecture used by PCS networks for LM and/or focused only on one call handling model, which dictates whether an LU should be performed after the completion of a call. Some considered the HLR/VLR architecture but neglected the dependency between the cell andlocation area (LA) residence time. In this paper we develop a comprehensive embedded Markov chain model to analyze the signaling cost of the MBLM scheme. The Markov chain model takes into account the HLR/VLR architecture and two different call handling models, namely, call without LU (CWLU) and call plus LU (CPLU) model. We employ the fluid flow model to describe the dependency between the cell and LA residence time. We derive closed-form analytical results for the signaling costs of the CWLU and CPLU model. Besides these results, we also derive results that are necessary for designing optimal paging schemes. We find that the results of the existing studies are special cases of those derived in this paper, and that there are flaws with the results obtained in the existing studies considering the HLR/VLR architecture. Based on the analytical results, we conduct a numerical study to evaluate the influence of various parameters on the performance of the MBLM scheme. The numerical study reveals that one common conclusion drawn in the existing studies hardly holds in PCS networks with HLR/VLR architecture. The results derived in this paper are instrumental in implementing the MBLM scheme in practical PCS networks.