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 ofdevices are becoming interconnected, marking the onset of an era where allthings are connected. While this growth opens up opportunities for novelproducts and applications, it also leads to increased energy demand and batteryreliance for IoT devices, creating a significant bottleneck that hinderssustainable progress. At this juncture, backscatter communication (BackCom), asa low-power and passive communication method, emerges as one of the promisingsolutions to this energy impasse by reducing the manufacturing costs and energyconsumption of IoT devices. However, BackCom systems face challenges such ascomplex interference environments, including direct link interference (DLI) andmutual interference (MI) between tags, which can severely disrupt theefficiency of BackCom networks. Moreover, double-path fading is another majorissue that leads to the degraded system performance. To fully unleash thepotential of BackComs, the purpose of this paper is to furnish a comprehensivereview of existing solutions with a focus on combatting these specificinterference challenges and overcoming dual-path fading, offering an insightfulanalysis and comparison of various strategies for effectively mitigating theseissues. Specifically, we begin by introducing the preliminaries for theBackCom, including its history, operating mechanisms, main architectures, etc,providing a foundational understanding of the field. Then, we delve intofundamental issues related to BackCom systems, such as solutions for the DLI,the MI, and the double-path fading. This paper thoroughly providesstate-of-the-art advances for each case, particularly highlighting how thelatest innovations in theoretical approaches and system design canstrategically address these challenges.