Analysis of Polarization Characteristics in Outdoor-to-Indoor Wireless Channels for High-Speed Trains

To effectively deploy 5G network base stations (BSs) in railway communication systems and ensure reliable communication between train terminals and BSs, it is essential to study the outdoor-to-indoor (O2I) wireless channel characteristics in high-speed trains (HSTs). This letter utilizes data from the 2.6 GHz HST measurement campaign to calibrate and validate the ray-tracing simulation model for the specified scenario by identifying key parameters, such as the relative permittivity (6.27) and conductivity (0.54) of the HST glass windows. Using this calibrated model, we analyze the channel fading characteristics under various polarization modes. The results indicate that, under the horizontal co-polarized (H-H) mode, the path loss (PL), root-mean-square delay spread (RMS-DS), and angular spread (AS) are all lower compared to other polarization modes. These findings are intended to provide a reference for the future deployment of 5G base stations in HST environments.