Ambient Backscatter Communication Assisted by Fluid Reconfigurable Intelligent Surfaces

Abstract: This paper investigates the integration of a fluid reconfigurable intelligent surface (FRIS) into ambient backscatter communication (AmBC) systems. Unlike conventional reconfigurable intelligent surfaces (RISs) with fixed position elements, FRIS employs fluidic elements that can dynamically adjust their positions, offering enhanced spatial adaptability. We develop a system model where an AmBC tag communicates with a reader through an FRIS, which is particularly beneficial in scenarios where the direct tag-to-reader link is weak or blocked by obstacles. The achievable backscatter rate is analyzed, and the optimization of FRIS element positions is formulated as a non-convex problem. To address this, we employ particle swarm optimization (PSO) to obtain near-optimal configurations of the fluid elements. Simulation results demonstrate that FRIS-aided AmBC significantly outperforms conventional RIS-based AmBC systems in terms of achievable throughput.