Multiple Antennas and Beamforming for SWIPT Systems

In conventional communication systems, the use of radio frequency (RF) signals is mainly constrained on information transfer. However, RF signals also contain energy and this fact leads to the emergence of various new research areas, like RF-enabled wireless power transfer (WPT) where wireless receivers could harvest energy from RF signals radiated by an energy transmitter. There is another technique that use the same RF signals for energy and information transfer jointly, this technique is regarded as simultaneous wireless information and power transfer (SWIPT). Although a lot of research efforts have made on these new areas in literature, from practical perspective, further development of WPT and SWIPT still faces some problems like low power transfer efficiency, safety concerns etc. These problems slow down the speed of transforming SWIPT and WPT from theory to practice. In this article, we first provide an overview of WPT and SWIPT which involves definition of these two paradigms, their possibilities and constrains as well as relevant technologies that are used to achieve efficient WPT and SWIPT. Then we focus on a SWIPT system and we aim to optimize the SWIPT system by maximizing its energy efficiency. A detailed discussion of this optimization problem is provided in this article.