Simultaneous Wireless Content and Power Transfer in F-RAN: Caching, eRRH Classification and Beamforming

Abstract

Radio frequency (RF) signal based wireless power transfer (WPT) is incorporated into fog radio access network (F-RAN) in order to simultaneously satisfy the content downloading demand of the content users (CUs) and the charging requirement of the energy users (EUs). Numerous enhanced remote-radio-heads (eRRHs) of F-RAN are distributed in a wide area, which are connected to the central base-band-unit (BBU) pool by fronthaul links. In order to reduce the adverse effect of the limited fronthaul capacity on the wireless content transfer (WCT), eRRHs are equipped with the content caching capability. A greedy algorithm based near-optimal caching design is then proposed for reducing the content responsive latency by considering the geographic distribution of CUs. Furthermore, given this caching design, a joint optimisation problem of eRRH classification (some for WCT and some for dedicated WPT) and distributed transmit beamforming is solved by a low-complexity heuristic algorithm. This algorithm aims for maximising the total energy harvested by the EUs, while satisfying the CUs’ minimum WCT rate and the limited fronthaul capacity. Intensive simulation results in the scenarios of both uniform and non-uniform users’ distribution validate our caching, eRRH classification and distributed transmit beamforming design in an F-RAN.