13Spectral and Energy‐Efficient Wireless‐Powered IoT Networks

Qingqing Wu1*, Wen Chen2, and Guangchi Zhang3

1Department of Electrical and Computer Engineering, National University of Singapore, Singapore

2Department of Electronic Engineering, Shanghai Jiao Tong University, China

3School of Information Engineering, Guangdong University of Technology, China

13.1 Introduction

The number of connected devices globally will skyrocket to 30 billion by 2025, giving rise to the well‐known Internet of Things (IoT) [1]. With such a huge number of IoT devices, the lifetime of networks becomes a critical issue and conventional battery‐based solutions may no longer be sustainable due to the high cost of battery replacement as well as environmental concerns. As a result, wireless power transfer, which enables energy harvesting from ambient radio frequency (RF) signals, is envisioned as a promising solution for powering massive IoT devices [2–5]. However, due to the significant signal attenuation in wireless communication channels, the harvested RF energy at the devices is generally limited [6, 7]. Therefore, how to efficiently utilize the scarce harvested energy becomes particularly crucial for realizing sustainable and scalable IoT networks. To this end, a “harvest and then transmit” protocol is proposed in [8, 9] for wireless‐powered communication networks (WPCNs), where devices first harvest energy in the downlink (DL) for wireless energy transfer (WET) and then transmit information signals ...

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