Measurement-Based Doppler Analysis in Viaduct Scenarios for Railway

The channels of railway communication system are mostly characterized by nonstationary time-selective fading process caused by its high mobility. In this paper, the Doppler statistics of wireless channels, which shows the time-selective fading effect in railway viaduct scenarios, are characterized based on measurements conducted along the passenger dedicated line. Multi-tone channel sounding signal with the bandwidth of 20 MHz is employed as the excitation signal that is transmitted from the base station along the railway track. Furthermore, based on the field measured data, time-varying power delay profile and Doppler power spectral density (PSD) are estimated by the impulse responses from the measured channel. Time-varying Doppler shift and Doppler PSD are analyzed. Finally, the observed propagation mechanisms of the different regions of Doppler PSD are explained.