Optimal Beamforming and Power Splitting Design for SWIPT under Non-Linear Energy Harvesting Model

This paper investigates the joint optimal beamforming and power-splitting receiver architecture design for simultaneous information and power transfer (SWIPT) under non-linear energy harvesting (EH) circuit environment, where hybrid access point (H-AP) equipped with multiple antennas simultaneously transmits information and power to multiple single-antenna users. For such a system, in order to achieve green communication design, we formulate an optimization problem to minimize the total transmit power of H-AP subjecting to the required signal-to-interference-plus- noise ratio (SINR) and the harvested power constrains at each user under non-linear EH model. Since the problem is non-convex, the relaxed semidefinite program (SDP) is used to solve it, and it is proved that the semidefinite relaxation (SDR) process is tight and our optimal solution achieves the global optimum. Numerical results show that a considerable gain could be achieved if the SWIPT beamforming vector and the power splitting ratios are jointly designed under the non-linear EH model compared with traditional linear EH model, since the non-linear EH model captures and matches the real EH circuits' non-linear features. Moreover, the feasible region of traditional linear EH model in the non-linear EH circuit environment is also characterized.