A state-of-the-art survey on IRS-NOMA for integrated sensing and communication

In recent years, the rapid advancements in wireless communication technologies have necessitated more efficient and integrated systems. An emerging paradigm addressing this need is the integration of Intelligent Reflecting Surfaces (IRS) with Non-Orthogonal Multiple Access (NOMA) for Integrated Sensing and Communication (ISAC). This paper offers a comprehensive survey of the state-of-the-art IRS-NOMA technologies, emphasizing their potential to enhance ISAC systems. We examine the fundamental principles of IRS and NOMA, investigating how their combined integration can markedly improve spectral and energy efficiencies, system capacity, and overall performance. The survey methodically categorizes and reviews recent research contributions, highlighting key innovations, design methodologies, advancements in the sophisticated algorithms, and performance metrics. Furthermore, we address the practical challenges and implementation issues associated with IRS-NOMA in ISAC, such as hardware limitations, signal processing complexities, and security concerns. Additionally, we outline open research directions and future prospects, aiming to stimulate further advancements in this promising field. Also, we highlight the interplay between the IRS assisted ISAC NOMA with the other emerging technologies towards the realization of 6G. Lastly, we present and summarize the lessons learned from this study. This survey serves as an invaluable resource for researchers and practitioners interested in understanding and advancing IRS-NOMA for next-generation integrated sensing and communication systems.