Cache-Enabled Hierarchical Transmission Scheme for Fog Radio Access Networks

Fog radio access network (F-RAN) architecture is introduced, in which edge nodes are connected to a baseband unit via dedicated fronthaul links while also being endowed with caches, to reduce the burden on fronthaul links and the delivery latency. The full benefit of edge cache is leveraged on the design of content distribution and delivery strategies. In this paper, a novel cache-enable hierarchical transmission scheme is proposed. Specifically, the requested files cached at local cache are partially transmitted to the users. Then, the remain contents of requested files cached at local cache are transmitted to the users together with the uncached requested files. The goal is to maximize the delivery rate of F-RANs by jointly optimizing the beamformming vectors and the file partition factor under the constraints of the fronthaul capacity, the file size, and the transmit power per enhance remote radio head. We develop an effective method to solve the resulting difficult precoding optimization problem and provide numerical results to demonstrate the effectiveness of the proposed F-RAN design.