Resolving mobile database overflow with most idle replacement

In a personal communications service (PCS) network, mobility databases call ed visitor location registers (VLRs) are utilized to temporarily store the subscription data and the location information for the roaming users. Becau se of user mobility, it is possible that the VLR is full when a mobile user arrives. Under such a circumstance, the incoming user has no VLR record an d thus cannot receive PCS services. This issue is called VLR overflow. To r esolve the VLR overflow problem, a VLR record can be selected for replaceme nt when the VLR is full and then the reclaimed storage is used to hold the record of the requesting user. This paper considers the most idle replaceme nt policy to provide services to mobile users without VLR records. In this policy, the record with the longest idle time is selected for replacement. We propose an analytic model to investigate the performance of this replace ment policy. The analytic results are validated against simulation experime nts. The results indicate that our approach effectively resolves the VLR ov erflow problem.