Optimal time allocation for multi-antenna wireless powered heterogeneous sensor network communications under imperfect CSI

Energy harvesting is a promising technology to overcome the energy bottleneck in batterypowered heterogeneous sensor networks (HSNs). In an energy harvesting HSN, heterogeneous sensor nodes harvest energy to power themselves, and use the harvested energy for data transmission. This paper investigates a multiple-input single-output wireless powered HSN with imperfect channel state information (CSI). The receiver harvests energy from the power transmitter via radio-frequency wireless power transfer (WPT) in the downlink to support wireless information transfer (WIT) in the uplink. To improve WPT efficiency, the power transmitter employs energy beamforming by using instantaneous CSI. Under imperfect CSI, the receiver performs channel estimation and feeds the CSI back to the transmitter. We focus on balancing the time duration for channel estimation, WPT, and WIT, so as to maximize the throughput while satisfying the time duration constraint. By solving this optimizing problem, we derive the optimal time resource allocation scheme. Numerical simulation results demonstrate the effectiveness of the proposed scheme. & 2015 Elsevier B.V. All rights reserved.