In fifth-generation (5G) wireless communication systems, non-orthogonal multiple access (NOMA) has been considered as a promising multiple access technique. In this paper, a NOMA-based cooperative relay system (CRS) is proposed and analyzed. In contrast to the conventional cooperative relay NOMA system (system model in Kim and Lee (2015)), the proposed NOMA-based CRS allows a source and a relay to transmit a superimposed signal in the first and second time slots, respectively. The proposed scheme gives more reliable communication by fully leveraging the concepts of NOMA and cooperative relaying. The exact closed-form expressions for the outage probability are derived in a Rayleigh fading environment with imperfect successive interference cancellation (SIC) at the relay and destination. The outage performance of the proposed scheme is compared with the existing CRS-NOMA schemes. The paper also investigates the impact of various parameters on the outage performance of the proposed system. The accuracy of the analytical results is verified through simulations.

在第五代（5G）无线通信系统中，非正交多址（NOMA）被认为是一种有前途的多址技术。本文提出并分析了基于NOMA的协作中继系统（CRS）。与传统的协作式中继NOMA系统（Kim and Lee（2015）中的系统模型）相比，所提出的基于NOMA的CRS允许源和中继分别在第一时隙和第二时隙中传输叠加信号。通过充分利用NOMA和协作中继的概念，提出的方案可提供更可靠的通信。在中断和目的地处具有不完善的连续干扰消除（SIC）的瑞利衰落环境中，可以得出断电概率的精确封闭式表达式。将提议的方案的中断性能与现有的CRS-NOMA方案进行比较。本文还研究了各种参数对所提出系统的中断性能的影响。通过仿真验证了分析结果的准确性。