Breaking the Interference and Fading Gridlock in Backscatter Communications: State-of-the-Art, Design Challenges, and Future Directions

As the Internet of Things (IoT) advances by leaps and bounds, a multitude of devices are becoming interconnected, marking the onset of an era where everything is connected. While this growth opens up opportunities for novel products and applications, it also leads to increased energy reliance on IoT devices, creating a significant bottleneck that hinders sustainable progress. Backscatter communication (BackCom), as a low-power and passive communication technology, emerges as one of the promising solutions to this energy impasse by reducing the manufacturing cost and energy consumption for IoT devices. However, BackCom systems also face some challenges, such as complex interference environments, including the direct-link interference (DLI) and the mutual interference (MI) between tags, which severely disrupt the efficiency of BackCom networks. Moreover, the double-path fading is another major issue that leads to a degraded system performance. To fully unleash the potential of BackComs, the purpose of this paper is to furnish a comprehensive review of existing solutions with a focus on addressing these challenges, offering an insightful analysis and comparison of various strategies. Specifically, we begin by introducing the preliminaries for BackCom, including its history, operating mechanisms, main architectures, etc., providing a foundational understanding of this field. Then, we delve into fundamental issues related to BackCom systems, such as solutions for the DLI, the MI, and the double-path fading. This paper thoroughly provides state-of-the-art advances for each case, particularly highlighting how the latest innovations in theoretical approaches and system design can strategically address these challenges. Finally, we explore emerging trends and challenges in BackComs by forecasting potential technological advancements and providing insights and guidelines for navigating the intricate landscape of future communication needs in a rapidly evolving IoT ecosystem.