Some new research trends in wirelessly powered communications

The vision of seamlessly integrating information transfer (IT) and microwave-based power transfer (PT) in the same system has led to the emergence of a new research area, called wirelessly powered communications (WPC). Extensive research has been conducted on developing WPC theory and techniques, building on the extremely rich wireless communications literature covering diversified topics such as transmission, resource allocation, medium access control, and network protocols and architectures. Despite these research efforts, transforming WPC from theory to practice still faces many unsolved problems concerning issues such as mobile complexity, power transfer efficiency, and safety. Furthermore, the fundamental limits of WPC remain largely unknown. Recent attempts to address these open issues have resulted in the emergence of numerous new research trends in the WPC area. A few promising trends are introduced in this article. From the practical perspective, the use of backscatter antennas can support WPC for low-complexity passive devices, the design of spiky waveforms can improve the PT efficiency, and analog spatial decoupling is proposed for solving the PT-IT near-far problem in WPC. From the theoretic perspective, the fundamental limit of WPC can be quantified by leveraging recent results on super-directivity, and the limit can be improved by the deployment of large-scale distributed antenna arrays. Specific research problems along these trends are discussed, the solutions of which can lead to significant advancements in WPC.