A System Architecture for Battery-free IoT Networks

While much research effort has been invested in long-range and low-power uplink communication for battery-free IoT networks, current deployments lack a scalable bidirectional communication infrastructure for data collection and processing with battery-free devices. To fill this gap, we introduce Lo W-Fi, a system architecture specifically designed to meet the requirements of battery-free IoT applications. We show the suitability of LoW-Fi for deploying monitoring systems for precision agriculture indoors. This sector is revolutionizing with the installation of smart greenhouses that require the constant monitoring of ambient parameters to ensure optimal conditions for the crops growth. Our system is implemented using commercial off-the-shelf devices, and it works at the intersection of WiFi and LiFi for downlink and RF backscatter for uplink, retaining the advantages of each technology and solving their practical limitations. We evaluate LoW-Fi performance in a real greenhouse, and the experimental results show that it can achieve an uplink (downlink) range of 45m(70m) with 0% BER. The aggregated data rate is up to 4.5 Mb/s.

I. Introduction

It is expected that by the year 2025, 75 billion of Internet of Things (loT) devices will be deployed to enable new applications for our daily lives (i.e., smart homes and offices) and to solve critical global issues such as the food shortages due to population growth and climate change (i.e., precision agriculture in greenhouses and vertical farms). Many of these IoT devices will be sensors and actuators that will increasingly rely on battery-free IoT tags to reduce the carbon footprint of IoT deployments [1]. Multiple sectors requiring battery-free IoT devices are proliferating nowadays, such as precision agriculture, Industry 4.0 or smart homes, and current communication technologies cannot fulfill their real needs. As an example, sensors used in precision agriculture i) are pre-programmed and provided with uplink communication only, ii) involve a high-cost and inflexible infrastructure due to cabling and dedicated devices, which leads to low density deployments of sensors, and then a low measurement accuracy, and iii) involve a high-maintenance cost in case of wireless devices, due to the labor and battery replacement costs [2].