Backhaul Traffic Balancing and Dynamic Content-Centric Clustering Based on Beamforming in the Downlink of Fog Radio Access Network

Recently an evolution of the Cloud Radio Access Network (C-RAN) has been proposed, named as Fog Radio Access Network (F-RAN) [1]. Compared to C-RAN, the Radio Units (RUs) in F-CAN are equipped with local caches, which can store some frequently requested files. In the downlink, users requesting the same file form a multicast group, and are cooperatively served by a cluster of RUs. The requested file is either available locally in the cache of this cluster or fetched from the CP via backhauls. Thus caching some frequently requested files can greatly reduce the burden on backhaul links. While whether a specific RU should be involved in a cluster to serve a multicast group depends on its backhaul capacity, requested files, cached files and the channel, thus has to be optimized for different objectives. In this paper we investigate the joint design of multicast beamforming, dynamic clustering and backhaul traffic balancing. The beamforming and clustering are jointly optimized in order to minimize the power consumed, while QoS of each user is met and the traffic on each backhaul link is balanced according to its capacity.