I. Introduction
Expected to meet the demands of ultra-high speed, ultra-low latency and high connection density, 5G network is envisioned to be a multi-service network architecture supporting a wide range of vertical use cases, such as massive Internet of things (IoT), remote machinery, autonomous driving and virtual reality (VR) [1]. However, the current one-size-fits-all evolved packet core (EPC) network gradually becomes inefficient to handle diverse service requirements and numerous device types [2]. This impels the progress on updating the network architecture with the capabilities of on-demand networking and flexible service deployment for various scenarios.