As a hybrid MIMO architecture, beamspace multiple input multiple output (MIMO) can significantly reduce the number of required radio frequency (RF) chains in millimeter wave (mmWave) massive MIMO systems without obvious performance loss, in which, however, the number of users supported cannot be larger than that of RF chains. To break this fundamental limit, we introduce the concept of code-domain non-orthogonal multiple access (NOMA) into beamspace MIMO. A beam selection scheme is proposed first to maximize the sum-rate by utilizing the quasi-orthogonality of the beamspace channel. Furthermore, a low-complexity detection algorithm is developed to realize the transceiver design in mmWave communications using lens antennas. Finally, numerical results of the decoding complexity at receiver side are analyzed. Simulation results show that the proposed beamspace MIMO-NOMA in code domain can achieve higher spectrum and energy efficiency compared with the existing beamspace MIMO.

中文翻译：

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使用透镜天线阵列进行毫米波通信的码域波束空间 MIMO-NOMA 混合收发器设计


作为一种混合 MIMO 架构，波束空间多输入多输出 (MIMO) 可以显着减少毫米波 (mmWave) 大规模 MIMO 系统中所需射频 (RF) 链的数量，而不会造成明显的性能损失，但其中的用户数量支持的不能大于射频链。为了打破这一基本限制，我们将码域非正交多址 (NOMA) 的概念引入波束空间 MIMO 中。首先提出了一种波束选择方案，以利用波束空间信道的准正交性来最大化总速率。此外，还开发了一种低复杂度检测算法，以实现使用透镜天线的毫米波通信中的收发器设计。最后，对接收端解码复杂度的数值结果进行了分析。仿真结果表明，与现有波束空间MIMO相比，所提出的码域波束空间MIMO-NOMA能够实现更高的频谱和能量效率。