5G for railway What are the advantages of 5G for the railway sector?
At a test site, DLR measured the safe data transmission over 5G between trains. Measurement results showed that communication up to 130 m is possible.
With 5G, C2Car communication can not only be established for cars: In rail traffic, this enables virtual coupling, i.e. the independent and contactless coupling of trains during the journey to longer, virtual units. Researchers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) carried out a measurement campaign at the test site of RWTH Aachen University to find out whether trains can communicate with each other at high data rates and with minimum delay times using a millimeter-wave radio system developed for this application. Initial results show that stable and secure communication is possible up to a distance of around 130 meters.
The automatic coupling of trains and the virtual connection of individual wagons or entire trains is an essential step towards greater flexibility and efficiency in rail transport. A radio wave transmission in the millimeter-wave band between 63 and 64 GHz is suitable for safe and fast communication between trains. Researchers at the DLR Institute of Communication and Navigation have developed a new millimeter-wave radio module for this frequency range, which is still little used in mobile communications. "For safe automation in train traffic, data transmission must function in real-time even under the most difficult conditions, such as high train speeds. That's why we took a close look at the transmission properties in our measurement campaign," says Stephan Sand, project manager and team leader for communications systems.
Measuring radio propagation in the millimeter-wave band
As part of their measurement campaign, the researchers investigated the transmission possibilities between train wagons at short and medium distances on a rail test site in Aachen. For the first time in Europe, the researchers were able to carry out dynamic measurements of radio propagation between trains in the millimeter-wave band. The Institute for Rail Vehicles and Transport Systems (IFS) at RWTH Aachen University provided two self-propelled test coaches, which made it possible to determine the measurements under railway-specific conditions. The millimeter-wave radio modules were mounted on the couplings of the train carriages. "In addition to the transmission properties, this test setup also enabled us to analyze the influence of train vibrations and the coupling process on the millimeter-wave systems," explains Sand.
To analyze the transmission characteristics, the millimeter-wave signals were recorded with the Channel Sounder, a measuring instrument developed by DLR to analyze the propagation of the radio signals. On this basis, safe and fast communication systems can then be developed.
Measuring millimeter waves up to 130 m
The results of the first study have shown that communication over millimeter waves is possible even over long distances of up to 130 m. This is a promising finding, as even physically coupled train cars will be able to transmit safety-critical data via millimeter-wave radio links in the future, enabling wireless train control and monitoring systems (TCMS). Wireless TCMS offers many advantages over currently wired TCMS. First, wireless TCMS offers an additional, extremely secure transmission path to the electrical coupling, which contains more than 100 sensitive electrical contacts.
Since the electrical couplings are subjected to high electromechanical loads during coupling and are also exposed to weather conditions, they often fail and must be repaired. This, in turn, leads to train cancellations and delays. Since wireless TCMS inherently transmits data contactless, no failure due to electro-mechanical stress can occur. 5G Ultra-Reliable Low Latency Communications (uRLLC) for wireless TCMS also provides precise and reliable distance estimation between trains during coupling. This allows the coupling process to be fully automated with wireless TCMS and 5G uRLLC.
This article was first published in German by Next Mobility.