HANDOVER OF EMERGENCY CALL ANCHORED IN IMS TO A CIRCUIT SWITCHED ACCESS NETWORK

摘要

A method performs a Single Radio Voice Call Continuity (SRVCC) Packet Switched (PS) to Circuit Switched (CS) handover of an emergency call that is routed over an IP Multimedia Subsystem (IMS) network. The call is transferred from a first region served by a first Mobility Management Entity (MME) to a second region served by a second MME. The method includes sending a first handover request from the first MME to the second MME to transfer the call. The first handover request includes an Emergency Session Transfer Number for SRVCC (E-STN-SR) identifying an Emergency Access Transfer Function (EATF) in the first region. A second handover request for handover to a CS access is sent to a target Mobile Switching Centre, MSC, and includes the E-STN-SR. The call is handed over to the CS access using the E-STN-SR to route the call via the EATF in the first region.