Pilot contamination can spoil the accuracy of channel estimation and then has become one of the key problems influencing the performance of massive multiple input multiple out-put (MIMO) systems. This paper proposes a method based on cell classification and users grouping to mitigate the pilot contamination in multi-cell massive MIMO systems and improve the spectral efficiency. The pilots of the terminals are allocated one-bit orthogonal identifier to diminish the cell categories by the operation of exclusive OR (XOR). At the same time, the users are divided into edge user groups and central user groups according to the large-scale fading coefficients by the clustering algorithm, and different pilot sequences are assigned to different groups. The simulation results show that the proposed method can effectively improve the spectral efficiency of multi-cell massive MIMO systems.

中文翻译：

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多小区多用户大规模MIMO系统的导频分配方法

导频污染会破坏信道估计的准确性，因此已成为影响大规模多输入多输出（MIMO）系统性能的关键问题之一。本文提出了一种基于小区分类和用户分组的方法，以减轻多小区大规模MIMO系统中的导频污染并提高频谱效率。终端的导频被分配一位正交标识符，以通过异或（XOR）操作来减小小区类别。同时，利用聚类算法根据大规模衰落系数将用户划分为边缘用户组和中央用户组，并将不同的导频序列分配给不同的组。