Toward Zero Blind-Zone Backscatter Communications: Real-Time System Design, Implementation, and Experimental Evaluation

Backscatter communication with amplitude modulation is promising for facilitating cost-effective and low-power transmission in Internet of things (IoT). Various backscatter communication systems with amplitude modulation have been investigated in the latest work. One critical issue is that only when the tag is placed in certain positions within the communication range can the system achieve good communication performance, where poor performance is seen in other blind zones. In this article, we address the blind zone problem in backscatter communications with amplitude modulation, and analyze the problem according to the Fresnel zone theory. We also design and implement real-time systems employing multi-antenna transmission and multi-receiver reception to deal with the blind zone problem. Experimental evaluation has verified that multi-receiver reception can improve the communication coverage with greatly decreased blind zone, and that the multi-antenna technique can facilitate full backscatter communications with no blind zone.

Introduction

With the development of wireless communication and network technology, the Internet-of-Things (IoT) technology has evolved rapidly and entered into the era of intelligent IoT [1]–[3]. IoT applications based on traditional battery-powered sensor nodes are with high production and maintenance costs and face great challenges to realize ubiquitous communications. Backscatter communication [4], [5] has the potential to meet the challenges by enabling low-cost and low-power transmissions based on battery-free senor tags and has been employed in practical applications in recent years [6]–[8]. Different from traditional communications, the backscatter tag transmits signals by backseattering the surrounding radio frequency (RF) signals rather than sending the signals by itself, thus reducing the energy consumption greatly. In addition, the tag can also collect the energy of RF signals or light from the surrounding environment for basic function operation [9], enabling battery-free communications. Therefore, backscatter communication technology has attracted much attention recently.