Beamformer design for wireless energy transfer with fairness

Wireless energy harvesting is one of the promising alternative techniques to power wireless networks. To improve the energy harvesting capability, energy beamforming has recently drawn significant attention. In this paper, we consider energy harvesting in a multi-user multi-input single-output (MU-MISO) network, and investigate two energy beamforming schemes which ensure fairness among the energy levels harvested by all users in the network. In particular, we investigate how to maximize the minimum harvested energy in the network by using i) a single beamforming vector; and ii) multiple beamforming vectors. We solve these problems by using semidefinite programming. The performance of different beamforming techniques is discussed with the aid of numerical simulations.