Robust Downlink Beamforming for Multiuser SWIPT Systems with Imperfect CSI

A multiuser multiple-input-single-output simultaneous wireless information and power transfer downlink system with imperfect channel is considered. This paper maximizes the worst-case harvested energy of all users and maintains the signal-to-interference and noise ratio requirement. The unknown channel estimate error is assumed within a certain range. Under the assumption, beamforming vector optimization is formulated as a semi-definite programming problem transformed by S-Procedure method. Using semidefinite relaxation technique, an optimal beamforming vector is obtained for the multi-antenna transmitter. The robustness and effectiveness of our proposed algorithm are provided by the simulation results compared with the non-robust design.