Channel Modelling and Wireless Propagation Challenges for mmWaves in Railways

Kurzfassung

This contribution discusses the channel modelling and wireless propagation challenges in the mmWave regime regarding mobility in railway environments. First, we will explain specific railway applications and their requirements on wireless communications such as virtual coupling and autonomous trains as well as high data rate links for external control or passengers. We will also present specifics with respect to the railway environment, e.g. the predictable movement of trains, large curve radius of railway tracks, obstacles such as catenaries, and scenarios like tunnels, bridges, viaducts, and cuttings. Next, we discuss the theory of stationarity and spatial coherence for channel modelling with implications on the mmWave regime and dynamic train measurements. Then, we consider the pros and cons of different channel modelling approaches such as stochastic, geometric-stochastic, and ray tracing-based channel models. Subsequently, we review issues related to the measurement equipment, e.g. train certified antennas and the synchronization of the transmitter and receiver. Then, we recapitulate three measurement campaigns, one for high-speed trains, one for metro and urban trains, and one for regional trains as well as lessons learned of these and first results for mmWave propagation. To conclude, we will discuss future work including but not limited to “how-to find the beam” for directional antennas, vibration issues, weather influence, and localization of the moving train.