Energy efficient content-centric beamforming in multicast fog radio access network

Fog Radio Access Network(F-RAN) is a promising technique for the fifth generation mobile communication system to provide high spectral and energy efficiency. In comparison with Cloud Radio Access Network, the Radio Units in F-RAN are equipped with local caches, which store popular content. In this paper, we investigate joint cooperative beamforming and radio units (RUs) operation in F-RAN system to balance the roles of transmit power, RUs activation and back-haul traffic rate to achieve energy efficiency. We aim at providing quality-of-service(QoS) guaranteed content-centric communication and minimizing the total network consumption of different multicast groups, which is formulated as a optimization problem with l
₀
-norm-based objective function and the nonconvex quadratic QoS constraints. To develop an upper bound algorithm, we first utilize the semidefinite relaxation (SDR) method and then transform the problem into a series of convex optimization problems by the successive convex approximation (SCA) method. Simulation results validate the advantage of wireless caching and highlight the impact of joint design.