Collaborative hierarchical caching in cloud radio access networks

To deal with the severe challenge from explosively increasing mobile users' multimedia service requests in mobile networks, introducing cloud-based computing platform and content caching into radio access networks (RANs) has become an effective emerging technique. In this paper, we propose a collaborative hierarchical caching framework in cloud RANs (C-RANs), which minimizes the access delay of content delivery under certain specific network constraints to improve users' Quality of Service (QoS) as well as offload network traffic. Specifically, based on the formed hierarchical caching topology consisting of two tiers of content caching at the base stations and the cloud central unit (CCU), we decompose the formulated large-scale optimization problem into a series of simpler subproblems, and then propose the corresponding low-complexity distributed heuristic solutions as well as a content request routing scheme. Trace-based evaluation results demonstrate the effectiveness of the proposed framework.