Study on Circuit Switched (CS) domain services over evolved Packet Switched (PS) access
The present document contains the results of the study of the architectural requirements of CS Domain Services over evolved PS access and concludes with a way forward. Considerations include overall requirements, architectural requirements, evaluation of potential architectural solutions and alternative architectures.
The objective is to describe an architecture that is capable of extending the 'traditional' MSC-Server based set of CS voice, supplementary and value-adding services and business principles (e.g. for roaming and interconnect) to the evolved PS access. The intention is also to give a CS handover-like user experience for voice calls when changing between evolved PS and legacy CS accesses. The architecture will however not be limited to the provision of speech services over evolved PS accesses; on the contrary, through the exploitation of the Combinational services, it will be possible to harness the capabilities of IMS to provide new, innovative services to the end user. Handover of the parallel PS session towards legacy 3GPP access will be considered as well, but may be limited by the capabilities of the legacy system and operator preferences.
Co-existence with IMS centric Single Radio VCC solutions shall be studied as well.