Simultaneous Wireless Information and Power Transfer for Internet of Things Sensor Networks

In this paper, we study simultaneous wireless information and power transfer (SWIPT) for Internet of Things (IoT) sensor networks. The transmitters (e.g., access point) employ hybrid beamforming and each IoT receiver adopts a power splitting (PS) method that divides the received signal into two parts for information recovery and energy harvesting. We propose a novel strategy for SWIPT in which the transmitters have the option to either send a private or a common message. The private message is recovered only by a designated IoT receiver while common messages are recovered by all the receivers. While requiring the receivers to recover a common message results in additional rate constraints, the overall system performance benefits by mitigating interference. We propose SWIPT schemes that minimize the total transmit power by properly selecting message configurations, designing hybrid beamforming vectors, and adjusting the PS ratio at the receivers to satisfy the individual rate and energy harvesting constraints. In particular, we develop tractable and efficient two-stage algorithms that, in the first stage determine the message configurations and in the second stage find the beamforming vectors (for both analog and digital components). Numerical simulations demonstrate that the proposed schemes significantly outperform conventional schemes that transmit private messages only using digital beamforming.