In cellular communication systems, it is conventional to assume the absence of a line of sight (LoS) path between the users and their associated access points (APs). This assumption however becomes questionable in the context of recent developments in the direction of cell free (CF) massive MIMO systems. In the CF massive MIMO, the AP density is assumed to be comparable with the user density, which increases probability of existence of an LoS path between the users and their associated APs. In this paper, we analyze the performance of an uplink CF massive MIMO system, with a probabilistic LoS channel model. Here, we first derive the effective statistics of this channel model, and argue that their behaviour is fundamentally different from that of the conventional rich scattering channels. Utilizing these statistics, we next compare the rates achievable by CF massive MIMO systems, under both stream-wise and joint decoding at the central processing unit. Following this, we also discuss the centralized MMSE based data detection to obtain a complexity/ performance trade-off. Finally, using detailed Monte-Carlo simulations, we validate our analytical results, and evaluate the performance of the three data detection schemes.
翻译:在蜂窝通信系统中,通常假设用户及其相关接入点之间缺乏视线路径。然而,这一假设在无细胞(CF)大型MIMO系统方向的最近发展过程中是值得怀疑的。在大型MIMO中,AP密度假定与用户密度相比,这增加了用户与其相关AP之间存在LOS路径的可能性。在本文件中,我们分析了一个CF大型MIMO系统上行连接的性能,并采用了一种概率性能LOS信道模型。在这里,我们首先得出了该频道模型的有效统计数据,并论证其行为与传统的富集分散渠道有根本不同。利用这些统计数据,我们接下来比较CFMIMO大型系统在中央处理单位的流向和联合解码下可达到的速率。随后,我们还讨论了基于MMSE的中央数据检测,以获得复杂/性交换。最后,我们通过详细的蒙特-卡罗模拟,验证了我们的分析结果,并评估了三个数据检测计划的执行情况。