Ergodic Capacity Analysis for Cooperative Ambient Communication System Under Sensitivity Constraint

Cooperative ambient backscatter communication (CABC) is a promising and energy-efficient wireless technique, particularly relevant for green Internet of Things applications. Previous studies on CABC have often assumed that the tag can always perform backscatter operations. However, this assumption is not accurate since the tag needs sufficient power to support its circuit consumption for successful backscatter. In light of this, this article focuses on studying a CABC system with sensitivity constraints at the tag. The main contributions of this work are as follows. First, we derive the ergodic sum capacity of both primary transmission from the RF source to the reader and backscatter transmission from the tag to the reader. The resulting expressions are solved using Gaussian-Chebyshev quadrature (GCQ) to ensure accuracy and efficiency. Second, we present compact asymptotic results for low and high signal-to-noise ratios, enabling simplified calculations and analysis. Finally, we provide simulations to validate our analytical results. By considering sensitivity constraints at the tag, our study enhances the potential of CABC implementations in real-world scenarios.