Channel Characterization and Hybrid Modeling for Millimeter-Wave Communications in Metro Train

Metro is important public transportation in reducing traffic congestion, protecting the environment, and moving more people efficiently. Due to ever-increasing demands on high data rate, and seamless connections of the onboard passengers, millimeter-wave (mmWave) wideband communications are considered as potential options. Therefore, realistic mmWave channel characterization, and modeling are important for the system design, network planning, and performance prediction in metro. In this work, mmWave propagation channel is analyzed, and a hybrid channel model is proposed for inside metro environment. By conducting channel measurement at 26.5-40 GHz, and calibrating ray-tracing (RT) simulations, the propagation mechanisms are revealed, the influence of the objects is found, and principal specular reflected rays are traced. A hybrid ray, and graph channel model is proposed to effectively model the diffuse scattering components by adding scattered points around principle paths traced by RT. The proposed model is validated by measurements at different receiving positions. The analysis of the channel characteristics in power, delay, and angular domains indicates that the hybrid model is appropriate to model multipath propagation in the confined metro train environment, where many objects exist, and reverberation is important.