Survey on Intelligent Reflecting Surfaces (IRS)-Assisted UAV-NOMA Networks: Fundamentals, Integration, Use Case, and Future Directions

Abstract

The convergence of Non-Orthogonal Multiple Access (NOMA), Unmanned Aerial Vehicles (UAVs), and Intelligent Reflecting Surfaces (IRS) presents a transformative paradigm for future sixth-generation (6G) wireless networks. This survey paper provides a comprehensive survey of IRSassisted UAV-NOMA communication networks, focusing on the fundamental principles, integration strategies, and practical use cases of this synergistic architecture. NOMA enhances spectral efficiency and massive connectivity by enabling multiple users to share the same resource block through powerdomain multiplexing and successive interference cancellation (SIC). UAVs serve as agile aerial base stations (BSs), offering flexible deployment and improved line-of-sight (LoS) links, while IRSs provide another degree of freedom by passively controlling signal propagation to mitigate blockages and enhance coverage. This paper also examines the combined impact of these technologies through a detailed case study of a downlink IRS-assisted UAV-NOMA network serving two ground users. A system model is presented that incorporates quasi-static fading channels and an optimization framework for jointly maximizing the sum rate by adjusting UAV positioning, IRS phase shifts, and NOMA power allocation. The results underscore the potential of this integrated approach to overcome key challenges in wireless communication, including signal degradation, coverage gaps, and the need for energy-efficient operation, thereby establishing a foundational framework for next-generation aerial-assisted networks.