 Request/Handover Request message to the target 3G or 2G radio network system which acknowledges the prepared CS relocation/handover Target MSC then sends Prepare handover response message to the MSC server and the circuit connection gets established between the MGW associated with MSC server and target VoLTE Optimization As the Session Transfer procedure is executed, the remote end is updated with the SDP of the CS access leg, downlink flow of VoLTE packets is switched towards the CS access leg and source IMS access leg is released. The MSC server sends to MME a SRVCC PS to CS response PS Bearer Transfer Preparations in Core Network In parallel to the voice bearer transfer preparations, the MME initiates the relocation of the PS bearers by sending Forward Relocation Request message with information of all bearers except for the voice bearer to the target SGSN over either S4 or Gn/Gp as in any inter-system PS handover. Target SGSN sends Relocation Request/Handover Request message to the UTRAN or GERAN network in order to request for resources for the PS allocation. The target GERAN or UTRAN radio network system acknowledges the prepared PS relocation/handover by sending the Reloc Req Ack/Ho Req Ack message to the target SGSN which then sends a Forward Reloc Response message to the source MME. Handover from EUTRAN Once the above voice bearer and data bearers relocation/handover preparations are completed and the target 3G or 2G radio network system has received both the CS and PS reloca- tion/handover requests, the appropriate CS and PS resources can be allocated. The source MME synchronizes the relocations and sends Handover from EUTRAN Command message to the UE with information of all the bearers (e.g. QCI1, QCI5 and QCI9) that are transferred to GERAN or UTRAN and then releases the LTE radio bearers. Establishing Connection with Target Radio Network and CS Domain and Releasing VoLTE Resources from EUTRAN IRAT handover takes place once UE has received the Mobility from EUTRAN Command in which a NAS message Hando