In this paper, we investigate the downlink precoder design for two-user power-domain multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA). We propose a novel user-assisted (UA) simultaneous diagonalization (SD) based MIMO-NOMA scheme that achieves SD of the MIMO channels of both users through a combination of precoder design and low-complexity self-interference cancellation at the users, thereby considerably lowering the overall decoding complexity compared to joint decoding. The achievable ergodic user rates of the proposed scheme are analyzed for Rayleigh fading channels based on a finite-size random matrix theory framework, which is further exploited to develop a statistical power allocation algorithm. Simulation and numerical results show that the proposed UA-SD MIMO-NOMA scheme significantly outperforms orthogonal multiple access and a benchmark precoder design performing SD via generalized singular value decomposition in terms of the achievable ergodic rate region for most user rates. The ergodic rate region is further enhanced by a hybrid scheme which performs time sharing between the proposed UA-SD MIMO-NOMA scheme and single-user MIMO.

中文翻译：

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通过用户辅助的同时对角化为 MIMO-NOMA 进行预编码器设计和统计功率分配

在本文中，我们研究了双用户功率域多输入多输出 (MIMO) 非正交多址 (NOMA) 的下行链路预编码器设计。我们提出了一种新颖的基于用户辅助 (UA) 同时对角化 (SD) 的 MIMO-NOMA 方案，该方案通过结合预编码器设计和用户低复杂度自干扰消除来实现两个用户的 MIMO 信道的 SD，从而显着与联合解码相比，降低了整体解码复杂度。基于有限大小随机矩阵理论框架，针对瑞利衰落信道分析了所提出方案的可实现遍历用户速率，进一步利用该框架开发统计功率分配算法。仿真和数值结果表明，就大多数用户速率的可实现遍历速率区域而言，所提出的 UA-SD MIMO-NOMA 方案明显优于正交多址接入和通过广义奇异值分解执行 SD 的基准预编码器设计。遍历速率区域通过混合方案进一步增强，该方案在所提出的 UA-SD MIMO-NOMA 方案和单用户 MIMO 之间执行时间共享。