Modeling mobility database failure restoration using checkpoint schemes

This paper studies checkpointing and failure restoration of mobility database for Universal Mobile Telecommunications System (UMTS). By utilizing per-user checkpointing technique, individual Home Location Register (HLR) records are saved into non-volatile backup storage form time to time. When a failure occurs, the backup record is restored back to the mobility database. We consider three per-user checkpoint schemes for the HLR. An analytic model is developed to investigate these schemes in terms of the probability that a HLR backup record is obsolete and the expected checkpoint interval. This model is validated against simulation experiments. Our study provides guidelines for selecting an appropriate checkpoint scheme and parameters for various traffic conditions.