A Comprehensive Survey on Ambient Backscatter Communications Toward Zero-Energy Devices and Networks

The future of wireless communications and the beyond fifth generation (B5G) and sixth generation (6G) standards are expected to constitute technologies that are self-sufficient in terms of energy requirements, without compromising on key performance factors such as high data rates and bandwidth, low latency, seamless connectivity and reliability. Recently, design and development of zero-energy networks (ZENs) or devices which consume net-zero energy, have enabled sustainable ultra-low power communication designs. One of the key technologies that is capable of realizing ZENs is the ambient backscatter communications (ABC). ABC is a low-power technique where backscatter devices communicate passively using an ambient source signal, useful in many applications such as internet-of-things. In this work, we present an elaborate discussion on the potential role, merits and applications of ABC in designing and implementation of ZENs. First, we introduce the design principles of ZENs and its potential enabling technologies. Next, we discuss the working principle, advantages and implementations of the fundamental ABC design. We then provide an elaborate discussion on the existing literature on ABCs with multiple antennas / tags, and the use-cases for ZENs having multiple network elements. Later, we discuss some of the machine learning (ML) / deep learning (DL) techniques that can be utilized for ABC systems enabling ZENs. Furthermore, we examine the integration of ABC with other ZEN-enabling technologies and discuss their performances. Finally, we provide insights into the potential applications of ABC-equipped ZENs and discuss the related future research challenges and avenues.