Improved Relay Selection Strategy for 5G Non-Orthogonal Multiple Access Cooperative Communication Systems

Power-domain non-orthogonal multiple access (NOMA) is one of the key technologies in 5G communications, enabling efficient multi-user transmission over the same time-frequency resources through power multiplexing.In this study, an improved max-min relay selection strategy was proposed for NOMA cooperative communication systems to address the issue of insufficient channel fairness in conventional strategies.The proposed strategy optimizes the relay selection process with the objective of ensuring channel fairness.Theoretical derivations and simulation analyses were conducted to comprehensively evaluate the proposed strategy from the perspectives of user throughput and system outage probability.The results demonstrate that, compared to the conventional max-min strategy and other commonly used relay selection methods, the proposed strategy significantly reduces the system outage probability while enhancing user throughput, thereby verifying its superiority in improving system reliability and stability.