Wireless Information and Power Transfer

5Multi‐antenna Energy Beamforming for SWIPT

Jie Xu¹* and Rui Zhang²

¹School of Information Engineering, Guangdong University of Technology, China

²Department of Electrical and Computer Engineering, National University of Singapore, Singapore

5.1 Introduction

Energy‐constrained wireless networks, such as sensor networks, are typically powered by batteries that have limited operation time. Although replacing or recharging the batteries can prolong the lifetime of networks to a certain extent, it usually incurs high costs and is inconvenient, hazardous (say, in toxic environments), or even impossible (e.g., for sensors embedded in building structures or inside human bodies). A more convenient, safer, as well as “greener” alternative is thus to harvest energy from the environment, which virtually provides perpetual energy supplies to wireless devices. In addition to other commonly used energy sources such as solar and wind, ambient radio‐frequency (RF) signals can be a viable new source for energy scavenging. It is worth noting that RF‐based energy harvesting is typically suitable for low‐power applications (e.g., sensor networks), but also can be applied for scenarios with more substantial power consumptions if dedicated wireless power transmission is implemented.

On the other hand, since RF signals carrying energy can at the same time be used as a vehicle for transporting information, simultaneous wireless information and power transfer (SWIPT) becomes an interesting new area ...