First ČD Railjet With Mobile Signal Repeater

On 7 October 2022, a symbolic launch of the six-month trial operation of the 80-91 005 ČD non-powered multiple unit equipped with mobile signal repeater technology took place at the main railway station in Prague.

The repeater is capable of transmitting the signal of mobile operators to the train and possibly amplifying the output power of the signal. The amplification rate is dynamically adjusted according to the current coverage. The purpose is to eliminate interruptions in data services and passenger mobile calls caused by the design of the cars, which attenuates the signal propagation. One repeater can provide signal coverage for up to four adjacent cars, so in the case of a seven-car railjet, two repeaters are used, located in the second class cars, symmetrically in the third and fifth cars of the rake.

Michal Krapinec, ČD CEO, says: "I believe that the trial operation, which will serve primarily to verify the quality of the mobile signal when using the repeater technology and to obtain feedback from passengers, will be successful and we will soon be able to secure funding for the batch installation of repeaters in other long-distance units."

The work was carried out by ČD - Telematika at the premises of Praha Jih (south) depot on 5 - 6 October 2022. Specifically, it involved the installation, complete configuration and commissioning of the supplied technology, which came from the Swiss company COMLAB, Ittigen (north-east of Bern). The technical parameters of the repeaters must be optimised for each vehicle to avoid unwanted interference with the external environment, and the installation requires an individual technical solution for each vehicle type and separate approval by the DÚ, the Czech Railway Authority. 

The new technology supports a wide range of frequencies used by mobile operators in the Czech Republic and abroad, not only in the currently deployed 5G frequencies. The entire solution consists of:
- an external broadband antenna (700 - 5,000 MHz) supporting the transmission of GPS information, 
- the repeater itself, which will operate in the 800, 900, 1,800, 2,100 and 2,600 MHz frequency bands during the test period, 
- an attenuation filter to ensure the smooth operation of the GSM-R (and therefore also ETCS),
- the internal infrastructure on board the train to ensure signal distribution. 

In the case of the ČD pilot railjet, the so-called radiating cable technology is used. However, the solution in question also allows the use of internal antennas, which is particularly suitable for trains and trainsets whose internal equipment or materials do not allow signal distribution using a radiating cable. The railjet 80-91 005 NMU has been deployed by ČD on the Ex3 line Praha - Brno - Breclav - Wien - Graz. Passengers will recognise it by means of information posters inside the carriages.