3D massive MIMO channel model for high-speed railway wireless communication

In the fifth generation (5G) wireless communication, high-speed railway (HSR) communication is one of the most challenging scenarios. By adopting massive multi-input multi-output (mMIMO) technology in HSR communication, the design of the underlying communication system becomes more challenging. Some new channel characteristics must be studied, such as non-stationarity in space, time and frequency domains. In this paper, two models are established for the two states of HSR at rest or in motion. When the train is stationary, a three-dimensional (3D) stationary channel model based on the single-ring distribution of the scatterers is established for a uniform planar array in a stable propagation scene. When the train is moving, in order to describe the non-stationary characteristics of the channel, a geometric random non-stationary channel model based on a cylinder scattering model is established by introducing the birth and death process of the propagation path and time-varying characteristics of the channel parameters. Moreover, a time evolution algorithm for time-varying channel parameters is proposed, and a modularization study of key parameter update algorithms is conducted, including the geographical location parameters of the transceiver and the scatterer, the number of effective propagation paths, and the delay. Finally, the antenna array response and spatial correlation matrix are derived for the proposed 3D channel model. The influence of the number of antennas on beam directivity is mainly studied, also the influences 的参数，如散射体分布半径，天线高度，方位角，以及天线元件间隔上的相关矩阵的特征值 进行了分析。

在第五代（5G）无线通信领域，高速铁路（HSR）通信被视为最具挑战性的场景之一。通过在HSR通信中采用大规模多输入多输出（mMIMO）技术，其底层通信系统的设计变得更加复杂。必须研究一些新的信道特性，例如在空间、时间和频率域中的非平稳性。在本文中，针对HSR的静止或运动两种状态，建立了两个模型。当列车处于静止状态时，在稳定的传播场景中，针对均匀平面阵列，基于散射体的单环分布建立了一个三维（3D）静止信道模型。当列车运动时，为了描述信道的非平稳特性，通过引入传播路径的生成与消亡过程及信道参数的时间变化特性，建立了一个基于圆柱散射模型的几何随机非平稳信道模型。此外，提出了时间变化信道参数的时间演化算法，并对关键参数更新算法进行了模块化研究，包括发射机和散射体的地理定位参数、有效传播路径数量以及延迟。最终，推导了所提3D信道模型的阵列响应和空间相关矩阵。主要研究了天线数量对波束指向性的影响，并对相关矩阵的特征值进行了分析，包括散射体分布半径、天线高度、方位角以及天线元件间隔等参数的影响。