Internet surfing in a train often demands a great deal of patience. Depending on the network provider, even on high-speed trains the success rate when surfing and displaying web pages varies between just 41 and 65 percent. One reason for this is that the window panes that provide protection against heat and sunlight act as an obstacle to good radio reception. That’s because they not only reflect heat and solar radiation but all other electro-magnetic waves as well. As a result, the coach acts as a Faraday cage. In high-speed trains the shielding effect reaches 99.9 percent. Researchers at Siemens Corporate Technology in Vienna, Austria have now succeeded in solving the problem by means of a technique known as frequency-selective coating of window panes.
Better Surfing in Trains
An innovative frequency-selective window coating from Siemens is improving mobile radio reception in passenger trains. Passengers are enthusiastic about the resulting signal quality, which is up to 50 times stronger. Railway operators are profiting from lower acquisition- and maintenance costs.
Lukas Mayer from Siemens Corporate Technology, explains how the new solution works: “Window panes are provided with an electrically conductive, transparent layer consisting of metals or metal oxides. The metallic coating of the window is vaporized along lines in a special structure by a laser. This enables radio signals in certain frequency ranges to pass through unobstructed, while radio signals at a different frequency are attenuated. The receive level for mobile terminals in such trains is substantially improved, while the thermal and solar protection effect is only minimally reduced,” he says. Existing solutions had the disadvantage that they were effective only in a very narrow frequency range, while actually making things worse in other ranges.
“With our solution, in a coach equipped with high-frequency windows, we achieve reduced shielding corresponding to a signal power increase that is fifty times stronger in mobile radio bandwidths as compared with existing solutions – a clearly noticeable improvement for passengers. Measurements based on a modified Austrian Railways Railjet vehicle have shown that the length of time during which good 4G reception is available increases by 33 percent,” notes Mayer.
“We wanted to find a low-cost solution for our customers,” stresses product manager Mehrdad Madjdi of the Siemens Mobility Division, adding, “The windows will need no maintenance over decades of service. By comparison with conventional in-train repeaters they offer significant savings in the long term.”
This is due to the low transmission attenuation of the windows over a broad frequency range from 700 megahertz to 3.5 gigahertz, which offers the advantage that the windows are not only suitable for current frequency bands, but also for future mobility standards. This means that the latest cell phone services are available immediately for passengers without any further investment. Installation in the train is also inexpensive since it requires no additional technical components or specially-trained personnel. The windows can be retrofitted in existing coaches at any time.
Entering Service Soon
Test subjects gave the innovation a high “coolness factor” rating and did not notice any impairment in visibility as a result of the windows either by day or at night. Thanks to the windows’ coating it is even possible to achieve improved energy efficiency in some cases, which makes for a more pleasant environment for passengers. The unanimous conclusion: More convenience and better travel quality. The innovative train windows will be used for the first time in the trains of the Rhine-Ruhr-Express (RRX) system, which will begin operating in the Rhein-Ruhr region at the end of 2018. The prototype of the trains was presented on July 12.