Modeling and Cost Analysis of Movement-Based Location Management for PCS Networks With HLR/VLR Architecture, General Location Area and Cell Residence Time Distributions

Location management plays a central role in guaranteeing the effective operation of personal communication service (PCS) networks. In current PCS networks, a two-tier system of home location register (HLR) and visitor location register (VLR) databases is commonly used for location management. To improve the performance of PCS networks, several dynamic location management schemes have been proposed. Among the existing dynamic schemes, the movement-based location management may be the most practical due to its effectiveness and easy implementation under the framework of current PCS networks. To implement location management in PCS networks, cost analysis is a crucial aspect. However, most of the existing cost analyses for the movement-based scheme are too simple and not available for PCS networks with the HLR/VLR architecture. One reason for this is the complexity and the difficulty associated with the problem. Li et al. and Rodriguez-Dagnino et al. challenged this task by considering the HLR/VLR architecture. However, the cost analysis developed by Li et al. was carried out under the assumption that the cell and location area (LA) residence times are exponentially distributed. Rodriguez-Dagnino et al. furthered Li et al.'s work by assuming that the LA residence time follows a hyperexponential distribution and that the cell residence time is generally distributed. However, Li et al. and Rodriguez-Dagnino et al. failed to consider VLR location updates that are caused by terminal movements between LAs. In this paper, we relax the restrictions imposed on the distributions of the cell and LA residence times and propose an analytical model to study the movement-based scheme with HLR/VLR architecture. The issue of VLR location updates that are caused by movements between LAs is addressed carefully and successfully. Analytical formulas for the costs of HLR and VLR location updates are derived using a unified approach. Numerical study suggests that the total cost is a convex function of the movement threshold and is sensitive to the variances of the cell and LA residence times. The result presented in this paper can serve as a guideline for the system design and the implementation of the movement-based scheme for PCS networks.