Joint Power and Discrete Amplitude Allocation for STAR-RIS-Aided NOMA System

This paper studies a simultaneously transmitting and reflecting reconfigurable intelligent surface aided non-orthogonal multiple access system with two paired users. To ensure the quality of service requirement of the reflected user, we propose a joint power and discrete amplitude allocation scheme, which can reduce channel estimation workload and hardware complexity. To characterize the performance of our proposed scheme, a novel channel statistic over Nagakami-$m$ fading is derived by adopting Beaulieu series. Subsequently, closed-from expressions for outage probability and diversity order of the reflected user are obtained, respectively. Moreover, owing to the complex channel statistic of the transmitted user, we analyze a lower bound of outage probability for the transmitted user. Finally, numerical results confirm that our proposed scheme greatly improves the performance of the reflected user and yields a larger throughput in comparison with the existing work.