LAUSR

In this paper, a joint beamforming design for energy-throughput tradeoff is investigated in a sustainable cloud radio access network, where multiple remote radio heads powered by independent renewable energy sources collaboratively transmit wireless information and energy to the data receiver and the energy receiver simultaneously. To explore the optimal joint beamforming design for both time-invariant and time-varying channels, first, optimization problems are formulated to maximize the throughput of the data receiver while charging the energy receiver with sufficient radio-frequency energy over a finite time horizon. Then, the formulated non-convex optimization problems are relaxed into a convex form and shown to be upper bounded by the optimal value of the relaxed problem. This upper bound can be further proved to be tight as the optimal solution to the relaxed problem is rank one. Moreover, motivated by the derived optimal solution, an efficient online joint beamforming algorithm is proposed for practical implementation. Finally, extensive simulations are performed to verify the superiority of the proposed joint beamforming strategies to other beamforming designs.