Patent ID: 8660091

Claim:
A method of handling a call transfer from a circuit switched access network to a packet switched access network, the method comprising: at a Mobile Switching Centre, MSC, Server, receiving a notification that a call for a terminal requires handover from a circuit switched access network to a packet switched access network; at the MSC Server, determining based on a registration status for the terminal whether the terminal is currently registered in an IP Multimedia Subsystem, IMS, network and/or determining whether the MSC Server is registered such that it can perform handover from the circuit switched access network to the packet switched access network; when it is determined that the terminal is not currently registered in the IMS network and/or the MSC Server is not registered so as to be able to perform handover from the circuit switched access network to the packet switched access network, invoking an error handling procedure in the MSC Server; and when it is determined that the terminal is currently registered in the IMS network and the MSC Server is registered so as to be able to perform handover from the circuit switched access network to the packet switched access network, invoking return Single Radio Voice Call Continuity procedure to perform a handover of the call from the circuit switched access network to the packet switched access network, wherein the error handling procedure comprises invoking handover from the circuit switched network to a different circuit switched network using procedures other than those of a return Single Radio Voice Call Continuity procedure.