As the successful development of IP technologies, the mobile communication system follows the trend of All-IP to deploy network architectures and services. In cellular system, the evolution of IP core network starts from circuit-switched domain of mo bile core network, and then the LTE network adopts flat All-IP network architecture. With the shift to flat All-IP architectures, more rich multimedia services can be provided, but supporting voice over LTE becomes a hot issue. This article briefly describes the early evolution of mobile core network based on IP technologies and then focuses on flat All-IP LTE network architecture and the solutions of voice over LTE.
3rd Generation Partnership Project 3GPP Circuit-Switched CS Long Term Evolution LTE Evolved Packet System EPS