Intelligent Reflecting Surface Aided Wireless Energy and Information Transmission: An Overview

Intelligent reflecting surface (IRS) is a promising technology for achieving spectrum and energy efficient wireless networks cost-effectively. While most existing works focus on exploiting IRS to enhance the performance of wireless information transmission (WIT), the high beamforming gain achieved by passive IRS is also appealing for boosting the efficiency of radio-frequency (RF) based wireless power transfer (WPT) and improving its service coverage. Although IRS-aided WPT shares certain similar characteristics with IRS-aided WIT, they also differ significantly in terms of the design objectives, transmitter/receiver architectures and hardware/power constraints, and so on, which thus may lead to distinct solutions in practice. In this paper, we provide a tutorial overview on IRS-aided WPT and its more complicated integrations with WIT, namely IRS-aided simultaneous wireless information and power transfer (SWIPT) and IRS-aided wireless powered communication networks (WPCNs), from the communication and signal processing perspective. In particular, we identify their fundamental challenges in e.g. passive reflection optimization and channel estimation, propose potential solutions and draw useful insights for practical design. Furthermore, we point out important directions worthy of further investigation in future work.