In this paper, we propose a novel spectrum-efficiency (SE) optimization scheme for amplify-and-forward (AF) cooperative relaying systems based on non-orthogonal multiple-access (NOMA). In this network, a weighted-sum-minimum mean-squared-error (WSMMSE) method is utilized to transform the original non-convex optimization problem into a tractable optimization problem. Then, the relay beamforming-matrix (BM) and the power-allocation (PA) coefficients are alternately optimized by use of the iterative beamforming method and the Lagrange-multiplier (LM) method subject to the quality-of-service requirements. Monte Carlo simulation results verify that our proposed new scheme can attain better performance than the optimal PA-NOMA technique and the conventional orthogonal multiple-access (OMA) technique.

在本文中，我们为基于非正交多址 (NOMA) 的放大转发 (AF) 协作中继系统提出了一种新颖的频谱效率 (SE) 优化方案。在该网络中，利用加权和最小均方误差 (WSMMSE) 方法将原始非凸优化问题转化为易于处理的优化问题。然后，根据服务质量要求，通过使用迭代波束成形方法和拉格朗日乘法器（LM）方法交替优化中继波束成形矩阵（BM）和功率分配（PA）系数。Monte Carlo 仿真结果验证了我们提出的新方案可以比最佳 PA-NOMA 技术和传统的正交多址 (OMA) 技术获得更好的性能。