标题： 在无蜂窝大规模MIMO系统中 Pilot 复用：一种多样聚类方法 显示英文标题

标题： Pilot Reuse in Cell-Free Massive MIMO Systems: A Diverse Clustering Approach

摘要： 分布式或无单元（CF）大规模多输入多输出（mMIMO），最近被提出作为解决当前以网络为中心的系统在提供高速普遍传输方面局限性的方法。提供均匀服务等级的能力使CF mMIMO成为6G网络的潜在技术。获取准确的信道状态信息（CSI）对于不同的CF mMIMO操作至关重要。因此，使用上行导频训练阶段来高效估计传输信道。可用正交导频信号的数量有限，重复使用这些导频会增加同导频干扰。这会导致一种称为导频污染的不良效应，可能降低系统性能。因此，需要一个适当的导频复用策略来缓解导频污染的影响。在本文中，我们将CF mMIMO中的导频分配形式化为一个多样化聚类问题，并提出一种迭代最大值搜索方案来解决它。在这种方法中，我们首先形成用户设备（UEs）的聚类，使得簇内多样性最大化，然后为同一簇中的所有UE分配相同的导频。数值结果表明，所提出的技术在实现的上行和下行平均以及用户数据速率方面优于其他方法。 显示英文摘要

摘要： Distributed or Cell-free (CF) massive Multiple-Input, Multiple-Output (mMIMO), has been recently proposed as an answer to the limitations of the current network-centric systems in providing high-rate ubiquitous transmission. The capability of providing uniform service level makes CF mMIMO a potential technology for beyond-5G and 6G networks. The acquisition of accurate Channel State Information (CSI) is critical for different CF mMIMO operations. Hence, an uplink pilot training phase is used to efficiently estimate transmission channels. The number of available orthogonal pilot signals is limited, and reusing these pilots will increase co-pilot interference. This causes an undesirable effect known as pilot contamination that could reduce the system performance. Hence, a proper pilot reuse strategy is needed to mitigate the effects of pilot contamination. In this paper, we formulate pilot assignment in CF mMIMO as a diverse clustering problem and propose an iterative maxima search scheme to solve it. In this approach, we first form the clusters of User Equipments (UEs) so that the intra-cluster diversity maximizes and then assign the same pilots for all UEs in the same cluster. The numerical results show the proposed techniques' superiority over other methods concerning the achieved uplink and downlink average and per-user data rate.