The use of massive multiple-input multiple-output (MIMO) systems is becoming progressively feasible, as well as progressively important, as the carrier frequency increases. Terahertz (THz) frequencies lead to smaller-sized RF components including antennas, so that even antenna arrays with a large number of antennas have a reasonable form factor while providing large beamforming gain and multi-user MIMO (MU-MIMO) capability. However, the THz propagation mechanisms differ in various ways from previously explored channels. In fact, reflections by a rough surface and diffuse scattering mechanisms are the most critical features contributing to spatial and temporal dispersion at THz frequencies. For this article, first, we develop a hybrid modeling approach of 3-D ray-tracing simulations in a realistic office room at 300 and 350 GHz to obtain estimates of the impact of surface roughness on the channel capacity which depends on generic channel characteristics. Then, the indoor multipath propagation and its impact on massive MIMO channels considering smooth and rough surfaces are investigated by employing the Beckmann-Kirchhoff (B-K) model. Finally, channel capacities of indoor THz massive MIMO channels with different surface roughnesses for both line-of-sight (LoS) and non-LoS (NLoS) scenarios are calculated. Though based on modeling results, the scattering properties of materials can favorably be exploited to maximize spatial multiplexing gains, especially in LoS scenarios.

中文翻译：

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太赫兹频率下大规模 MIMO 信道中的漫散射研究

随着载波频率的增加，大规模多输入多输出 (MIMO) 系统的使用变得越来越可行，也越来越重要。太赫兹 (THz) 频率导致包括天线在内的射频组件尺寸更小，因此即使是具有大量天线的天线阵列也具有合理的外形尺寸，同时提供大波束成形增益和多用户 MIMO (MU-MIMO) 功能。然而，太赫兹传播机制与之前探索的信道有多种不同。事实上，粗糙表面的反射和漫散射机制是造成太赫兹频率空间和时间色散的最关键特征。对于本文，首先，我们在 300 和 350 GHz 的真实办公室中开发了 3-D 光线追踪模拟的混合建模方法，以获得表面粗糙度对取决于通用信道特性的信道容量影响的估计。然后，采用贝克曼-基尔霍夫 (BK) 模型研究室内多径传播及其对考虑光滑和粗糙表面的大规模 MIMO 信道的影响。最后，计算了具有不同表面粗糙度的室内 THz 大规模 MIMO 信道在视距 (LoS) 和非视距 (NLoS) 场景下的信道容量。尽管基于建模结果，可以有利地利用材料的散射特性来最大化空间复用增益，尤其是在视距场景中。