Evaluation of distributed and replicated HLR for location management in PCS network

Personal Communication Service (PCS) network is the integration of cellular Network and conventional wired network. To support user mobility, the locations of the mobile stations (MSs) should be constantly tracked using a database. The widespread deployment of PCS will lead to a tremendous increase in the number of updates and queries to the location database. The centralized, stand-alone Home Location Register (HLR) in GSM can be a potential bottleneck. In case of the location database failure, incoming calls may be lost. According to the analysis of the load in HLR, we suggest replicating the HLR in order to increase its capacity and reliability. In this paper we evaluate the effects of the number of replicas in terms of query response time, misrouting probability of incoming calls and average cost per query. Another issue incurred in the replicated databases is data consistency. A concurrency control protocol called preemptive Read-One-Write-All (PROWA) protocol is also proposed.