An Energy Efficient Joint Energy Beamforming and Time Allocation with QoS Guarantee via Wireless Energy Transfer

Wireless energy transfer (WET) has been considered as a promising technology for providing mobile devices with untethered energy supply in wireless networks. In this paper, we assume one energy supplier (ES) and multiple WET powered terminals coexist. The ES wirelessly charge the terminals, and then terminals transfer their own information synchronously. The WET broadcast and wireless information transfer (WIT) take place in time duplexing manner. The WET powered terminals are assumed to have individual quality of service (QoS) requirements of information transfer. The joint design of down-link WET broadcast beamforming and time allocation between energy/information transfer is studied. An two step algorithm is proposed to jointly design both time duplexing factor and beamforming vector, in order to guarantee the terminals' QoS, meanwhile to minimize the WET power consumption by WET. To avoid iterative search, proposed algorithm first determine the time allocating factor by minimizing the lower bound of WET power. Then the optimal WET beamforming vector is obtained to guarantee terminals' QoS. Simulation results demonstrates proposed algorithm provides majority of the performance of global optimal solution while avoiding the computational burden of iterative optimization.