We investigate the achievable rate of a hybrid cell-free (CF) massive multiple-input multiple-output (MIMO) non-orthogonal multiple-access (NOMA) underlaid below a primary massive MIMO. We propose a low complexity sub-optimal user-clustering method and derive the closed-form sum rate expression for Rayleigh fading channels by considering the effects of intra-cluster pilot contamination, inter-cluster interference, imperfect successive interference cancellation (SIC) and statistical downlink channel state information (CSI) at secondary users (SUs). Our results reveal that NOMA based underlay CF massive MIMO-NOMA can exploit the scarce spectrum bands more efficiently than its counterpart orthogonal multiple-access (OMA).

中文翻译：

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无蜂窝大规模 MIMO-NOMA 的底层频谱共享

我们研究了位于主要大规模 MIMO 之下的混合无蜂窝 (CF) 大规模多输入多输出 (MIMO) 非正交多址 (NOMA) 的可实现速率。我们提出了一种低复杂度的次优用户聚类方法，并通过考虑簇内导频污染、簇间干扰、不完善的连续干扰消除 (SIC) 和统计的影响推导出瑞利衰落信道的封闭形式总和速率表达式次用户 (SU) 处的下行链路信道状态信息 (CSI)。我们的结果表明，基于 NOMA 的底层 CF 大规模 MIMO-NOMA 可以比其对应的正交多址 (OMA) 更有效地利用稀缺频段。