Novel 3D Non-Stationary mmWave Massive MIMO Channel Models for 5G High-Speed Train Wireless Communications

In fifth generation (5G) wireless communications, high-speed train (HST) communications is one of the most challenging scenarios. By adopting massive multiple-input multiple-output (MIMO) and millimeter wave (mmWave) technologies into HST communications, the underlying communication system design becomes more challenging and some new channel characteristics have to be studied, such as the non-stationarities in space, time, and frequency domains. This paper proposes a novel three-dimensional (3D) space-time-frequency non-stationary mmWave massive MIMO theoretical model, as well as a corresponding simulation model, for 5G HST wireless channels based on WINNER~II and Saleh-Valenzuela (SV) channel models. Cluster evolutions in space, time, and frequency domains are proposed and analyzed to ensure the models' non-stationarities in three domains. Moreover, based on the proposed channel models, important time-variant channel statistical properties are investigated, such as the time autocorrelation function (ACF), space cross-correlation function (CCF), delay power spectrum density (PSD), and angular PSD. Results indicate that the statistical properties of the simulation model, verified by simulation results, can match well with those of the theoretical model.