UAV-RIS Enabled NOMA Network for Disaster Management with Hardware Impairments

In disaster-stricken areas, establishing reliable communication poses a significant challenge. Unmanned aerial vehicles (UAVs) offer a promising solution by serving as aerial relays, extending the network range, and providing communication services to affected areas. Cutting-edge technologies such as reconfigurable intelligent surfaces (RIS) and non-orthogonal multiple access (NOMA) are utilized to enhance UAV communication. This paper investigates the performance of a NOMA network equipped with a single UAV and an RIS. Specifically, we explore a NOMA-based transmission scenario involving a temporary base station (T-BS) and two ground users, integrating a UAV and a RIS mounted on it. Additionally, this work evaluates the end to-end outage probability and ergodic capacity, considering the Nakagami-m fading channel. Diversity combining techniques, including selection combining (SC) and maximum-ratio combining (MRC), is applied to the signals received via the UAV and RIS at the end users. The impact of diversity combining and imperfect successive interference cancellation (SIC) during the decoding process on outage and ergodic capacity is analyzed. Analytical expressions for outage probability and ergodic capacity based on SC and MRC are derived. Furthermore, the performance of both perfect and imperfect SIC-based NOMA schemes, considering the phase error of the RIS is analyzed. The effect of splitting the elements of the RIS for two ground users, indicating an optimal split factor is assessed.