Fast recovery protocol for database and link failures in mobile networks

An important issue in the design of future personal communication services (PCS) networks is the efficient management of location information. The current IS-41 standard PCS architecture uses a centralized database, the home location register (HLR), to store service and location information of each mobile registered in the PCS network. If the HLR fails, all incoming calls to a mobile from hosts which are not in the same location area as the mobile are lost. Location updates from mobiles to the HLR are also lost. Once the HLR is functional it can not direct calls to mobiles immediately as mobiles could have changed their location during the HLR's failure. Fast recovery from a failure of the HLR is hence important. A link failure in the network could partition the network resulting in a loss of location updates from mobiles affected by the failed link. We present a new protocol for fast recovery of the HLR after a HLR failure or an intermediate link failure. The protocol does not require use of wireless bandwidth during the recovery process, has a bounded recovery period and is simple to implement making it an appealing choice in the design of future mobile networks. We analyze the protocol in order to find a medium between protocol cost and the recovery interval.