Patent ID: 9467907
Filing Date: 2016-10-11
CPC Classification: H04L,H04W

Claim Text:
1. A method of performing a Single Radio Voice Call Continuity (SRVCC) handover of a telecommunications call established by a User Equipment (UE) accessing a serving network using a Packet Switched (PS) access, the method comprising: receiving an indication from the serving network that the call established by the UE accessing the serving network using the PS access is a UE-undetected emergency call anchored in a serving Internet Protocol (IP) Multimedia Subsystem (IMS) network, wherein the serving network includes the IMS network and the call is established as the UE-undetected emergency call to a Public Safety Access Point (PSAP) and is anchored in the serving IMS network; receiving a SRVCC handover request to hand over the call from the PS access to a Circuit Switched (CS) access; and initiating a handover of the call that, in response to the indication that the established call is the UE-undetected emergency call, uses an Emergency Session Transfer Number-Single Radio (E-STN-SR) that causes the call to continue to be routed through the IMS network in which it is anchored.