Joint Beamforming Design and Time Allocation for Wireless Powered Communication Networks

This paper investigates a multi-input single-output (MISO) wireless powered communication network (WPCN) under the protocol of harvest-then-transmit. The power station (PS) with reliable power supply first replenishes the passive user nodes by radio-frequency wireless power transfer (WPT) in the downlink, then each user node transmits independent information to the sink by a time division multiple access (TDMA) scheme in the uplink. We consider the joint time allocation and beamforming design to maximize the system sum-throughput. With perfect channel station information (CSI) at the PS, a semi-closed form solution is proposed by exploiting the strict concavity of the joint design problem. Then, in the case with Gaussian CSI errors, a robust algorithm is proposed to maximize the system throughput subject to the signal-to-noise ratio (SNR) outage probability constraints. Simulation results demonstrate the efficiency of the proposed fast algorithm and validate the robust algorithm.