Enhanced voice over LTE and its roaming aspects

This paper mainly explains an enhanced domain handover scheme for VoLTE (Voice over LTE) called eSRVCC. The scheme is essential in order to ensure the carrier-grade voice call quality; especially during the network migration phase from legacy circuit switched system to the All IP based EPS (Evolved Packet System). In addition, this paper explains the new mechanisms to support VoLTE in roaming scenarios.