Patent ID: 7532568

Claim:
A method for transferring call control to a backup call server, comprising: transmitting call setup signals between a calling party mobile station and a Base Station Controller (BSC); transmitting call setup signals between the BSC and an originating Mobile Switching Center (MSC) and between the originating MSC and a gateway-MSC (G-MSC) by way of a first signaling gateway, and between the G-MSC and a Home Location Register (HLR), wherein the call setup signals are transmitted between the G-MSC and the HLR by way of a second signaling gateway, to determine a destination MSC; transmitting destination MSC information from the HLR to the G-MSC by way of the second signaling gateway; when the destination MSC fails, routing call setup signals received from the G-MSC to a backup MSC and establishing a call connection between the backup MSC and the originating MSC; when the G-MSC fails, routing the call setup signals received for the G-MSC to a backup G-MSC and establishing a call connection between the backup G-MSC and the originating MSC; and establishing a call connection between the calling party mobile station and a called party mobile station using at least one of the backup G-MSC and the backup MSC.