A Non-Stationary 3-D Wideband GBSM for Narrow-Beam Channels in Smart High-Speed Railway Communication Systems

Beamforming based on massive multiple-input multiple-output (mMIMO) is one of the promising technologies in future smart high-speed railways (HSR) communication systems. This paper proposes a non-stationary three-dimensional (3-D) wideband geometry-based stochastic model (GBSM) for HSR narrow-beam channels. The proposed GBSM employs a sphere model and two ellipsoid models to describe common and uncommon clusters for different links. The Gaussian beam pattern is considered to model the antenna characteristics at base stations (BSs) and array-time-frequency cluster evolution is used to describe the dynamics of scattering clusters. Moreover, statistical properties of the narrow-beam channel model such as the single-link space-time-frequency correlation function (STFCF) and multi-link spatial cross-correlation function (CCF) are investigated. Numerical results and analysis show that the proposed model is capable of characterizing the narrow-beam channels in the smart HSR communication systems.