PAPR reduction techniques for RIS-NOMA and STAR-RIS-NOMA systems

Reconfigurable Intelligent Surfaces (RIS) and Simultaneous Transmitting and Reflecting Reconfigurable Intelligent Surfaces (STAR-RIS) are promising technologies for enhancing signal propagation in Non-Orthogonal Multiple Access (NOMA) systems. However, these systems can have high Peak-to-Average Power Ratio (PAPR), leading to inefficiencies in power amplifiers and increased signal distortion. To address this, we explore PAPR reduction techniques, focusing on their application at the base station, where power amplifiers are crucial and at the RIS or STAR-RIS surfaces, where signal distortion due to high PAPR can occur. Our approach considers the impact of channel conditions on PAPR as signals travel from the base station to RIS or STAR-RIS surfaces. PAPR reduction methods that are used in this paper are Partial Transmit Sequence (PTS), Selective Mapping (SLM), Tone Reservation (TR) and a new hybrid technique which is the combination of PTS and TR. From the results, we conclude that the hybrid technique outperforms all other methods employed.