Abstract
<title>Abstract</title> <p>With the rapid increase in the number of Internet of Things (IoT) devices and the growing demand for wireless communication, improving energy efficiency and scaling up network capacity have become a major challenge for next generation wireless communication systems. Ambient backscatter communication (AmBC) and non-orthogonal multiple access (NOMA) are promising techniques for supporting energy-efficient and massive connectivity in future IoT networks, while unmanned aerial vehicles (UAVs) provide flexible coverage when terrestrial links are unavailable or severely blocked. This paper investigates the performance of a NOMA-assisted UAV-AmBC network, where the direct links between the base station and two ground users are blocked. A UAV equipped with a backscatter device acts as a decode-and-forward relay, while the backscatter link provides an additional signal copy to enhance transmission reliability. Considering both perfect and imperfect successive interference cancellation, analytical expressions for the outage probability and ergodic capacity are derived under selection combining (SC) and maximum ratio combining (MRC) schemes. Simulations are provided to validate the theoretical analysis and evaluate the effects of the reflection coefficient, path loss, residual interference, and signal-to-noise ratio. It is shown that imperfect SIC degrades the outage performance, whereas increasing the reflection coefficient improves link reliability. Moreover, MRC achieves lower outage probability than SC, and the proposed UAV-AmBC-assisted scheme significantly outperforms the benchmark system without AmBC.</p>