Performance evaluation of location information distribution strategies for mobility tracking

A user location information distribution strategy is proposed for mobile systems. Local anchors (LAs), replicated databases and forwarding pointers are applied in an integrated way that greatly reduces the location update rate and the call delivery cost incurred by location tracking. In particular, the visitor location registers (VLRs) associated with a user´s home and workplace are selected as the user´s LAs, which are connected by a forwarding pointer chain. When the user changes their registration area (RA) within a local signal transfer point (LSTP) region, the new location is reported to the home location register (HLR) and to the replicas. In the call delivery procedure, if a call orginates from one of the LAs or replicas, the HLR does not need to be queried. An analytic model is developed and numerical examples are given to compare the performance of the proposed scheme, the standard scheme, the replication scheme and the local anchoring scheme. The results show that the proposed strategy outperforms the other three strategies over a wide range of system parameters