Ranging with Ultra-Reliable and Low Latency mm-Wave Communication

Kurzfassung

In the face of growing demand, the way rail infrastructure is used must change. Although it is obvious that the infrastructure is underutilized, conventional safety systems and the lack of direct communication between trains are the main reasons for the limited use of railroad tracks. One of the applications that has the potential to enable a significantly more efficient use of railroad infrastructure is Automatic Train Coupling (ATC). ATC is a method for automatically coupling and decoupling train wagons. This can be done while one wagon is standing still or while both wagons are in motion. ATC has the potential to increase track utilization for passenger and cargo trains by allowing easy physical coupling of wagons when they occupy the same track block and decoupling when they otherwise do not. This thesis aims to address the theoretical and practical aspects of the realization of ATC. A wireless Train-to-Train (T2T) communication system capable of accurate ranging is required for the realization of ATC. To this end, standardized and non-standardized communication systems are analyzed and a communication system is recommended on the basis of the investigations. To evaluate the communication and ranging performance of the proposed communication system in realistic railroad environments, a measurement campaign was conducted with two train wagons. The measurement data was used to derive a channel model and thereby evaluate the performance of the communication system. The observation of the channel and the behavior of the received components from the measurement campaign data has shown that the ranging accuracy of the communication system can be improved. In this study, a novel ranging estimation method is proposed that benefits from the knowledge gained from the channel model. The novel ranging estimation method uses both Kalman filters and Space Alternating Generalized Expectation-Maximization (SAGE) to compensate for clock offsets by exploiting the knowledge of the mm-Wave channel. The interaction between the proposed wireless communication system and all other systems involved in the ATC maneuver is designed. Designing the complete maneuver and all possible scenarios allowed translating the performance of the mm-Wave communication system into ATC maneuver success rate figures. The figures used are Safety Integrity Levels (SIL) which shows at which conditions would the ATC maneuver remain below a certain SIL threshold. Results show that using the proposed mm-Wave communication system and the proposed ranging estimation method allow a guaranteed SIL level 4 throughout the ATC maneuver.