Digital summit: "Gigabit on the track" with big question marks

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Deutsche Bahn and the German network operators want to significantly improve mobile communications coverage along the rail network. At the start of the German government's digital summit in Frankfurt on Monday, they signed a declaration of intent for "Gigabit on the tracks". Deutsche Bahn, Deutsche Telekom, O2/Telefonica, Vodafone and 1&1 want to use the planned general refurbishment of the Berlin-Wittenberge-Hamburg line to expand better mobile network coverage with 5G.

From August 2025 until probably April 2026, Deutsche Bahn will be renovating the line between Berlin and Hamburg. During this time, no trains will run on this 278-kilometer route. As part of the refurbishment, Deutsche Bahn is renewing its own communication system and building the infrastructure for the 5G-based Future Rail Mobile Communication System (FRMCS), which is set to replace the current GSM-R rail radio across Europe by 2035.

A mast every two kilometers

Deutsche Bahn plans to erect a small mast every two kilometers or so along the route, which the network operators can also use. "Through the joint expansion of rail and mobile communications, we will realize considerable synergies and cost savings hand in hand," said Federal Digital Minister Volker Wissing (FDP). However, this is still only a declaration of intent – whether and when it will become a reality remains to be seen.

Deutsche Bahn wants to provide the network operators with the passive infrastructure – masts, power supply and connection. Antennas and mobile radio technology must be installed by the companies themselves. However, the space on the masts is very limited, meaning that each provider cannot install its own antennas, as is usually the case with larger antenna masts. It is therefore foreseeable that they will also have to share the active components. It remains to be seen how this will be done, but the network operators have signaled their willingness to cooperate.

The 5G project on the Hamburg-Berlin line is an investment in the future. FRMCS is also intended to digitally upgrade the railroads –, but the existing mobile communications infrastructure along the railroad lines would hardly be sufficient for their operation.

The project between Berlin and Hamburg is therefore also about the question of how the 5G-based FRMCS should be set up in practice in Germany. Railroads and network operators have already gained experience with the "Gigabit Innovation Track" pilot project. The infrastructure that will be available in ten years' time needs to be planned today, reports Karsten Kemeter, CTO Communications Technology at Deutsche Bahn.

Semi-autonomous trains thanks to 5G

The 5G network enables Deutsche Bahn to use new technologies. One goal is automation level 2, explains Kemeter – semi-automated train operation with a driver. In the long term, fully automated trains are also conceivable. However, this is also likely to take decades: The average service life of rolling stock on the railroads is 30 years.

At the same time, the network operators are trying to dampen expectations. They want to work with Deutsche Bahn to develop "a technically and economically viable mobile network and contract concept for equipping the line with active mobile radio technology", according to Monday's press release. "We are ready to contribute our know-how to the development of a test operation," said Klaus Werner, Head of Business Customers at Deutsche Telekom, emphasizing the experimental nature of the project.

The network operators initially want to test how the railroad's own infrastructure can be used to improve mobile communications coverage on trains. In principle, technologies such as the Multi Operator Core Network (MOCN) and the Multi-Operator Radio Access Network (MORAN) are being considered. At the same time, the aim is to test how mobile radio coverage and FRMCS can run in parallel without interference.

The possible interference with the current GSM-R rail radio by mobile radio is one of the reasons why cell phone reception on the railroads has so far been rather poor. Because the GSM-R frequencies are located directly next to the LTE frequencies in the 900 MHz band, the network operators are not allowed to expand LTE on this frequency in an eight-kilometer-wide corridor around the railroad line. Therefore, higher frequencies are used in this corridor, but these offer poorer range and penetration.

Impermeable windows

An additional hurdle for mobile communications is the metal coating on the windows, which is intended to protect passengers from the sun and the train from overheating: It also reflects radio waves. Deutsche Bahn is currently using a laser to treat the metal coating on the windows of its ICE trains to make them more permeable to mobile phone frequencies.

To mitigate the effect of the windows, Deutsche Bahn has installed repeaters in the trains that distribute the mobile phone signal from an external antenna in the compartment. However, not all carriages are equipped with repeaters. Also, the reception can only be as good as the network coverage on the track. The repeaters are also not capable of 5G, and Deutsche Bahn has no plans to upgrade them.

The grace period for the railroad's GSM-R devices, which are prone to interference, is now finally due to end in December 2024. The network operators will then also be allowed to use LTE on the 900 MHz area frequency on the lines and feed the Deutsche Bahn repeaters with it. This should be a noticeable step forward for rail customers – at least until the 5G experiment on the Berlin-Hamburg route is also recommended for use on other routes.

By the 2022 timetable change, Deutsche Bahn was supposed to have equipped its fleet with hardened GSM radios that are not susceptible to interference from the neighboring LTE. However, because too many trains were still running with old hardware at the end of 2022, the Federal Network Agency granted a postponement until the 2024 timetable change, which is due to take place on December 14.

However, this has not yet cleared all the hurdles for the expansion of the tracks. Many railroad lines run through nature conservation areas. Apart from the logistical challenges that arise when setting up a mobile communications system in nature conservation areas – Electricity and network supply often have to be implemented over long distances – German officials are particularly stubborn here – so that network operators have already given up even asking.

(vbr)