I. Introduction
With the rapid development of big data, Internet of Things (IoT) [1], artificial intelligence (AI) [2], 5G and other intellectual technologies, massive amounts of data and service requests will be generated at the end devices [3]. According to the recent report from Gartner, more than half of the enterprise data will be generated in the edge of the network rather than the traditional data center (e.g., cloud platform) by 2022. Cloud computing (CC) as a centralized computing paradigm offers services for end users by migrating data, computation, and storage to the remote cloud data center. However, massive long-distance data transmission will inevitably cause delay and network congestion [4]. It indicates that CC cannot meet the increasing requirements for low latency and high quality of experience (QoE) application scenarios, especially in Internet of Vehicles (IoV) [5], intelligent networks [6], telemedicine [7], smart city [8], AR/VR [9], etc.