The RF measurement of leaky feeder cables and the signal attenuation of subway cars in a metro tunnel

  • Funded by: T-Mobile CZ
  • Duration: 08-10/2014
  • Prime Contractor: CTU in Prague, Faculty of Electrical Engineering, Department of Electromagnetic Field

Team

    Project description

    „From 22nd of December in 2021, thanks to the cooperation of DPP, a consortium of operators (O2 Czech Republic, T-Mobile Czech Republic, Vodafone Czech Republic) and CETIN, passengers can call, send SMS messages or date in LTE quality in the entire Prague metro network.“ (https://www.dpp.cz/cestovani/mobilni-signal-v-metru)

    However, the story of the coverage of the Prague metro began to be written much earlier, and the staff of the Department of Electromagnetic Fields, CTU FEE also took part in it.

    After the final decision was made to cover not only the stations but also the metro tunnels with a mobile signal, it was necessary to resolve the manner and conditions under which this could be done. For this purpose, the team of the Department of Electromagnetic Fields from T-mobile Czech Republic was asked by T-mobile Czech Republic to perform a study evaluating the parameters of selected leaky feeders in the Prague metro, the influence of cast-iron tube on signal propagation and the influence of the subway car itself on the received high frequency signal quality. The actual implementation of the study took place in the “Muzeum A” metro station and in the part of the tunnel towards the Náměstí Míru station. The biggest challenge of the whole study was to obtain experimental data directly from the site, because due to safety regulations, access to the metro premises is limited and at the same time it was not possible to measure during normal subway operation. Therefore, it was necessary to measure only between about 1 and 3 o’clock in the morning, when the operation of the subway does not work. A wide representation of the department’s staff took part in the implementation of the study, as it was necessary to cover both the professional specialization and human resources due to complicated conditions. The results of the study then included, among other things, the parameters of selected leaky feeders with measurements in all used subway cars, measured levels of received signal in the subway tube and in the station, the effect of signal level in the subway car when filled with people, platform coverage and more. All these aspects were evaluated for different frequencies – namely 800, 900, 1800, 2100 and 2600 MHz to cover all considered frequency bands of mobile networks at that time. An example of the measurement can be seen in the following pictures.