Fault tolerance of PCS mobility databases

A personal communications services (PCS) network system constantly tracks the locations of the mobile stations (MS) so that incoming calls can be delivered to the target mobile stations. The overall architecture of the PCS mobility management in GSM is presented. In general, a two-level database is used to store the mobile station location information. The mobile station location update procedure and the call delivery procedure are described in detail. In case of location database failure, incoming calls may be lost. The database failure restoration procedure to reduce the number of lost calls in GSM are also described. Moreover, an efficient home location register (HLR) failure recovery procedure which utilizes the MS movement information to speedup the recovery procedure is also presented