A Nonstationary Geometry-Based Model for Channel Characterisation in Vactrains Scenarios Using Leaky Coaxial Cables

Abstract

The vacuum tube ultra-high-speed flying train (vactrain) is regarded as a promising candidate for future railway transportation, while the distinctive operating environment and ultra-high-speed conditions exact rigorous demands on the performance of the train-to-ground wireless communication system. For the optimal design of the communication system, a comprehensive understanding of channel characterisation is crucial, and an accurate channel model requires investigation. Therefore, in this paper, we propose a three-dimensional (3-D) multi-source geometric-based stochastic model (GBSM) for the vacuum tube scenario using leaky coaxial cables (LCX). The electric field distribution of LCX is deduced by equating the periodic slots to multiple magnetic dipole antennas. Based on this, the theoretical models for line-of-sight (LoS) and nonline-of-sight (NLoS) components of channel impulse response (CIR) are derived, respectively. Furthermore, the closed-form expressions of the multi-link spatial-temporal correlation functions, encompassing the spatial cross-correlation function (CCF) and temporal autocorrelation function (ACF), are further derived and examined at 900 and 1800 MHz. The simulation results indicate that in the vactrain scenario, the wireless channel exhibits nonstationary characteristics. Furthermore, at 1800 MHz, the channel correlation decreases more rapidly than at 900 MHz, and the stationary interval of the channel is shorter.