Home Tech Deutsche Bahn is testing new windows for better cell phone reception

Deutsche Bahn is testing new windows for better cell phone reception

by drbyos

Berlin “We can try it, but I’m on the train.” Those who travel by train often know the warning, which – in a way or something similar – is often preceded by phone calls made there. Finally, it is not unlikely that the conversation just started will be interrupted again after a few seconds. Mobile radio reception by rail is still too patchy.

“Even on main routes, radio coverage is not yet optimal,” says Karl-Peter Naumann, honorary chairman of the Pro Bahn passenger association. The reason for this is that Deutsche Bahn always refers to the infrastructure along the route: “Without a good and extensive network along the railway lines, good cell phone reception is not possible on the trains,” says the train. And for the expansion of the network, the three mobile operators are Telekom, Vodafone and Telefónica responsible.

By the end of last year, at least all ICE routes in Germany should be provided with fast mobile communications, i.e. LTE. So the Federal Network Agency had prescribed. However, the operators finally had to admit that they would not achieve this goal in time. At least Telekom had a network coverage of 96.4 percent, Vodafone 95 percent. Telefónica customers have good reception on only around 80 percent of the ICE routes.

If you ask the companies, however, they are not alone to blame for the fact that mobile surfing and phone calls often work so badly. “Disks in ICE massively degrade reception and thus ensure that, for example, of 30 MBit per second, which can be reached directly on the track outside the train, only 30 arrive on the ICE,” says a Vodafone spokesman. Telekom and Telefónica also agree: window panes can have a negative impact on reception.

It is no coincidence that many train windows actually do not allow reception to pass well: they are so insulated that the trains do not overheat. “These windows are provided with a thin metal layer that keeps solar radiation away,” explains the train – and admits: “Cellular waves are also difficult to get into the train through the metal layer.”

Radio masts are missing

To ensure that the signal arrives at the passenger, the train uses signal amplifiers – so-called repeaters. The radio waves on the outside of the train are picked up by antennas, transmitted to the inside and passed through the wagons via the repeaters.

“We have already equipped all ICE trains with cell phone repeaters,” said Sabina Jeschke, head of technology. “Now we are working on technically upgrading the IC fleet as well.” This is helpful for Pro-Bahn Honorary Chairman Naumann. “You can already tell the difference between sitting in a train with repeaters or in an old train that doesn’t have one,” he says.

Nevertheless, Deutsche Bahn is currently experimenting with an alternative: frequency-permeable windows. The heat-insulating metal layer of the windows is processed with a laser in such a way that it becomes transparent to all frequencies of radio waves.

This has several advantages: On the one hand, the panes are significantly less susceptible to maintenance. On the other hand, according to Bahn, they are compatible with all mobile radio standards and do not need to be converted or retrofitted – for example, when the new 5G standard will soon be expanded. The windows have nothing to do with the WLAN offer in long-distance rail transport; this signal still comes to customers via antennas and WLAN routers.

The tests with the windows would be carried out under real conditions and should be completed this year, the company says. “The first results show that there are no problems with the use in high-speed applications.” There is therefore no schedule for possible widespread use. But it is easy to imagine that the disks will replace the repeaters in the medium term.

Nevertheless, where there are no radio masts, even the best windows are of no use. “You also have to blame politics,” says Naumann. This failed to put enough pressure on the mobile operators. For example, the Federal Network Agency has so far been reluctant to pay fines due to missed deadlines.

Structural hurdles are often responsible for the fact that the construction of antennas on the rails is particularly problematic. For this purpose, one is now in discussion with the train, for example to better supply ICE tunnels, according to Telefónica and Vodafone.

According to the network agency, by the end of 2022 all “important rail routes”, i.e. ICE and IC routes with a large number of passengers, must be supplied with at least 100 Mbit / s. By the end of 2024, all other rails should be covered at least 50 Mbit / s. For some time, the tentative, often only very short, telephone calls should remain everyday on many German tracks.

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