Multi-stage algorithm for energy efficiency and data rate trade-off in imperfect CSI downlink NOMA systems

Non-orthogonal multiple access (NOMA) is considered as a promising technique for improving energy efficiency (EE), spectral efficiency (SE), and data rate in 5 G and beyond wireless systems. Although power allocation plays a crucial role in maximizing EE in downlink NOMA systems, the challenge of obtaining full channel state information (CSI) at the base station in real-world systems affects overall performance. This study explores the trade-off between EE and data rate in imperfect CSI downlink NOMA systems. Specifically, a trade-off is proposed where the primary objective is to maximize EE while ensuring the highest possible data rate. A multi-stage algorithm, combining game theory and the false position numerical method, is proposed to achieve this goal. Game theory is employed to maximize the data rate, while the false position method is utilized to optimize energy efficiency. An expression for the outage probability is derived based on a lower bound of the formulated optimization problem's constraints, allowing for a thorough evaluation of system performance. The proposed method is rigorously analyzed and compared with conventional Orthogonal Multiple Access (OMA) and existing NOMA schemes in terms of energy efficiency, data rate, and outage probability. The results demonstrate that the proposed approach significantly outperforms these methods, highlighting its potential for enhancing system performance in practical NOMA deployments.