Handover from E-UTRAN to UTRAN/GERAN CS

摘要

The present invention relates to a method for a handover of a UE (User Equipment) currently engaged in a voice call. More particularly, the invention relates to a handover from 1) a packet based radio where Voice Service is provided via VoIP over the radio and is controlled via Session Initiation Protocol (SIP) based signalling (e.g. LTE, E-UTRAN or WIMAX radio) to 2) a radio access network where Voice Service can be only provided via circuit switched (CS) domain (a visited mobile switching centre (VMSC) is needed) such as legacy 3GPP UMTS Terrestrial Radio Access Network (UTRAN)/GSM/Edge Radio Access Network (GERAN) coverage. A MSC-S entity acting as a Packet Core Control Node on a Packet Switched (PS) network and as an Anchor Visited Mobile Switching Centre (VMSC) for a handover to a Circuit Switched (CS) network on the CS domain side is proposed, the MSC-S preparing a new path with a remote UE-B and a CS domain handover towards a target legacy radio coverage before requesting a UE-A to execute the handover.