Novel Tight Jensen’s Inequality-Based Performance Analysis of RIS-Aided Ambient Backscatter Communication Systems

This paper presents a performance analysis of the reconfigurable intelligent surface (RIS)-aided ambient backscatter communication (AmBC) network. The system consists of a base station (BS), a backscatter device (BD), an RIS, and a destination (D). No direct link exists between the BS and RIS and between the BD and D. We propose a novel tight Jensen’s inequality. A new tighter upper bound is derived for the ergodic capacity, and we demonstrate that the proposed upper bound is much tighter than the existing bound. Monte Carlo simulations are performed to validate the analytical results. The tightened upper bound is found to be almost identical to that in the Monte Carlo simulation results, and the ergodic capacity significantly increases with the number of reflecting elements. In addition, the ergodic capacity improves when the RIS is placed close to the BD or D, and when the distance between the BS and BD is small, the ergodic capacity is severely affected.