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Efficiency and fairness of energy broadcasting systems with centralized massive MIMO

The batteries' life of wireless terminals has been considered as a significant metric in current communication networks, therefore, wireless energy transfer technology has gained lots of attentions. The objective of this paper is to investigate the efficiency and fairness of energy broadcasting system when the centralized massive multiple-input multiple-output (MIMO) is adopted at the energy station (ES) and a non-linear energy harvesting model at the energy users (EUs). In order to satisfy different requirements of efficiency and fairness for multiple EUs, two criterions are employed in this paper, which can maximize the efficiency and fairness, respectively. Under the total power constraint at the ES, the optimal precoders under two criterions are derived by considering the characteristics of massive MIMO. Simulation results compare the two proposed schemes with the existing equal power allocation scheme and show the advantages of the proposed precoding schemes.