An intrain repeater ( German "im-train amplifier") has the task of improving the communication on the train between cell phone and cell phone station in order to guarantee an interference-free radio connection. The aim of the repeater is to compensate for the high attenuation of the train caused by the car shell and the metal- coated windows . From a physical point of view, the train acts like a Faraday cage . With the ICE , the attenuation is around 30 dB ; the shielding is therefore 99.9%.
Without the intrain repeater, an interference-free connection without interruptions would only be possible in areas where the field strengths are sufficiently high to overcome the shielding of modern passenger trains. This is usually the case in metropolitan areas and in train stations. In rural areas in particular, the mobile phone networks are not so well developed, so that mobile phone coverage of the vehicles without an intrain repeater is not always guaranteed.
The repeater amplifies the cellular signal in both directions. In the downlink , the signal is picked up by the base station via an external antenna, which is located on the train roof, and passed on inside the train to the intrain repeater, which amplifies the signal. The amplified signal is emitted either via a slotted cable installed in the roof of the car (e.g. in the ICE car of Deutsche Bahn ) or via conventional antennas , e.g. in the case of the SBB in Switzerland. The same thing happens in the opposite direction (= uplink ). The transmission signal from the cell phone is picked up via the slotted cable or the antenna inside the car, sent to the intrain repeater, amplified and transmitted to the cell phone station via the roof antenna of the train.
GPS receivers are integrated in the train antennas, which switch off mobile communications technology abroad and in parking facilities.
Older intrain repeaters do not support MIMO for modern mobile communications. These older intrain repeaters only support SISO . Some newer intrain repeaters support MIMO. MIMO-capable intrain repeaters allow faster data transmission rates than SISO-capable intrain repeaters. For MIMO, both the cellular antenna and the mobile phone must support MIMO. A mobile phone of LTE device category 2 or higher supports MIMO. In the railway tunnel a MIMO-enabled must tunnel radio system installed.
Situation in Germany
In Germany, around 1495 ICE train wagons were equipped with repeaters at Deutsche Bahn by 2011, which support the GSM networks of all four mobile network operators as well as the internal rail network (GSM-R). This means that around 70 percent of the ICE cars have cell phone amplifiers.
The Intrain repeaters support the GSM-900 band, the complete DCS-1800 band, as well as the E-GSM band and GSM-R .
New intrain repeaters could in principle also support the UMTS radio standard, provided that the appropriate additional modules are installed. In order for UMTS to be available during the entire train journey, both the repeaters and the UMTS network infrastructure on the track must be in place. According to the Deutsche Bahn, UMTS and HSDPA are not supported because there are no UMTS radio cells along the lines. An alternative to mobile data reception via UMTS or GPRS or EDGE is in parts Railnet , wireless internet access in individual ICE trains via WLAN.
According to a study by a management consultancy, the supply for regional trains for voice telephony was around 90 percent in 2015. By 2020, local rail transport authorities also want to equip around 950 trains with cellular repeaters and / or WLAN in several pilot projects; this corresponds to around 8 percent of the entire fleet. According to information from Deutsche Bahn, equipping a local transport vehicle with repeaters costs around 30,000 euros.
The use of cell phone repeaters was tested in the two ICE idea trains . From 1995 the two ICE-1 trains ran between Hamburg and Basel and Stuttgart as scheduled . The former mobile communications providers DeTeMobil , Mannesmann Mobilfunk and E-Plus intended to expand network coverage along the railways with investments in the double-digit million range. The plans were to cover all important routes in Germany by 1997. In return, Deutsche Bahn intended to equip cars with intrain repeaters. The mobile communications provider VIAG-Interkom was not involved in the setup, as the VIAG network had not yet started at the time.
At the end of 1998, Deutsche Bahn announced that it would equip all ICE trains with facilities for improved cell phone reception by mid-1999. Up until the beginning of 1999, two cars in each of the ICE trains (at that time 103 multiple units) were equipped with cell phone amplifiers. The possibility of specifically reserving spaces in the quiet or mobile phone zone has also been introduced.
Repeaters from Hitachi and later also Mikom (now Andrew Wireless Systems) were used to start operations. On average, around 40 percent of all wagons in the ICE fleet were retrofitted with intrain repeaters. Cell phone pictograms in the car indicate improved cell phone reception. The cars can be specifically specified when making the reservation. Usually, intrain repeaters are installed in three cars per ICE (half) train; one of them in 1st class, two of them in 2nd class (as of April 2008).
To optimize network coverage along railway lines and stations, framework agreements were concluded in 2003 between DB Telematik and the network operators Vodafone, T-Mobile and Eplus.
Intrain repeaters were occasionally installed in IC train wagons . The transmission loss of an IC car is only around 20 dB on average, which is less than that of the ICE. However, plans by Deutsche Bahn and the network operator from 2003 envisaged equipping an average of one 1st class car and one 2nd class car with a cell phone amplifier. These plans were only partially implemented, so that only some of the IC cars are equipped with repeaters. The 2nd class cars, which are equipped with intrain repeaters, are located directly next to the dining car. The train attendants and toddlers' compartments are also housed in these cars. In contrast to the ICE trains, the wagons of the EC / IC trains with intrain repeaters cannot be reserved explicitly.
During the renovation work from May 2008 to 2011, the ICE trains received new repeaters throughout, which support all four GSM cellular networks as well as the railroad's internal cellular network (GSM-R). At the same time, the number of cars supplied was increased from approx. 800 to 1,495. Since the completion of the measure, around 70 percent of the ICE wagons have been supplied with intrain repeaters, with some wagons - including partition walls - being designed partly as cell phones and partly as rest areas.
Before the retrofitting began in May 2008, Deutsche Bahn used intrain repeaters that reinforce the GSM -900 band and the part of the DCS-1800 band used by E-Plus . The UMTS band, the part of the DCS 1800 band used by O 2 and the E-GSM 900 band, which has been used by E-Plus and O 2 since the beginning of 2006 , were not transmitted by these broadband repeaters. Until 2011, only the mobile network operators T-Mobile, Vodafone and E-Plus were supported on trains equipped with these repeaters. Since the national roaming of O 2 in the T-Mobile network was completely switched off at the beginning of 2010, calls in the O 2 network via the intrain repeaters previously used were no longer possible.
From mid-2006, the network operator O 2 had been negotiating with Deutsche Bahn and the other network operators to replace or retrofit the repeaters. The new repeaters also support the E-GSM band and the complete DCS-1800 band, as well as GSM-R .
Repeater replacement began in May 2008. The repeaters were replaced during the maintenance intervals. At the same time, the rest areas were better marked. In mid-September 2009, half of the upgrade program was completed.
In addition, the mobile network operators closed gaps in the radio network along the ICE routes.
Before the conversion began in May 2008, around 800 cars in the ICE fleet had been equipped with repeaters. On average, around 40 percent of all wagons in the ICE fleet were equipped with intrain repeaters.
As of 2011, around 1495 ICE trains were equipped with repeaters that support the GSM networks of all four mobile network operators. This means that around 70 percent of the ICE cars have cell phone amplifiers.
|Deutsche Bahn wagons supplied with intrain repeaters
(before further expansion in 2008)
(after completion of the expansion in 2011)
|ICE 1||1, 3, 9, 11, 14||1, 3, 5, 6, 7, 9, 11, 14|
|ICE 2||21/31, 24/34, 26/36, 27/37||21/31, 23/33, 24/34, 26/36, 27/37|
|ICE 3||23/33, 26/36, 27/37||22/32, 23/33, 25/35, 27/37, 28/38, 29/39 *)|
|ICE T 7 pieces||23/33, 28/38||21/31 ( lounge is a quiet zone), 23/33, 24/34, 27/37, 28/38|
|ICE T 5 pieces||21/31, 23/33, 28/38||21/31, 23/33, 27/37, 28/38|
|ICE TD||27/37, 28/38||2x / 3x, 27/37, 28/38
x = 21/31 or 22/32 (car number not known)
|Metropolitan (BA116)||all cars except Silence||2, 3, 4, 5, 6
(used as ICE trains)
|DB night train (type Talgo )||Bistro car||Bistro car
mostly 1st class car
(cannot be reserved)
further expansion planned until the end of 2014
(currently not reservable)
Intrain repeaters were occasionally installed in IC train wagons. In contrast to the ICE trains, the wagons of the EC / IC trains with intrain repeaters cannot be reserved explicitly. A retrofitting of Intercity cars of the first class with Intrain repeaters is to take place by the end of 2014 [obsolete] .
1st class intercity cars were to be retrofitted with intrain repeaters as part of a modernization project that will run until the end of 2014. According to information from Deutsche Bahn, 2nd class equipment will be tested. In 1st class, the cars were equipped with LTE-capable repeaters as part of a modernization that was completed in early 2015.
At the end of October 2012, Deutsche Bahn put out a tender to equip approx. 86 Intercity cars (with an option of around 280 further cars) with repeaters. Around 370 IC cars are to be equipped with LTE- capable repeaters by the end of 2014 . Another 120 cars with older repeaters are also to be upgraded to LTE. From 2015 Vodafone is to install new repeaters for GSM, UMTS and LTE. The equipment is being carried out as a joint initiative of the four German network operators. At the end of 2014, the new repeaters were tested in two trains. "The latest generation of mobile radio repeaters" will be used in the ICE from August 2015; their introduction is planned for July 2016 in the Intercity.
Equipping the ICE trains with new repeaters that support UMTS, LTE and LTE Advanced is scheduled to begin in the second quarter of 2016.
The approval of repeaters by the Federal Railway Authority sometimes takes five years.
The double-decker Intercitys ("IC2") that have been in use since December 2015 are equipped with LTE cellular amplifiers.
In January 2020, Deutsche Bahn announced that it was currently trying out panes based on the Swiss model that are permeable to mobile communications and is considering using these instead of repeaters in the future.
ICE 1 telephone booths
The two telephone booths of the ICE-1 trains in service from 1991 onwards established a connection to Telekom's C network via 13 so-called base stations along the two new lines . For this purpose, amplifiers were installed in the 81 tunnels of the first two new lines at a distance of 1500 meters, which communicated with the moving trains via leakage cables . Directional antennas were used between the tunnels. The connection was established on the train side via antennas on the service vehicle. For telephone calls, 70 pfennigs were charged per unit of charge. The underlying tunnel radio system 91 became necessary because the B2 network of the Deutsche Bundespost, previously used in IC / EC trains, was not suitable due to the large number of tunnels and cuts in the new lines.
At the beginning of 1989, the contract to set up the tunnel radio system on a 450 MHz basis was awarded. A universal system based on 40 GHz, which was initially planned and which would also have served railway operations ( liner train control and railway operations radio), was discarded because it was not ready for use.
Situation in Switzerland
In Switzerland, all passenger cars on long-distance trains are equipped with an in-train repeater. The in-train repeaters on long-distance trains amplify the 2G / GSM , 3G / UMTS and 4G / LTE signals . All passenger cars on long-distance trains are equipped with a signal amplifier that improves both telephony and data reception on the train.
In Switzerland, only the newest are passenger cars of the regional transport with an in-train repeaters equipped. More and more older passenger cars for regional transport are being retrofitted with in-train repeaters.
Bandstop for GSM-R
All in-train repeaters used in Switzerland must have a band stop for the UIC frequency band . The UIC frequency band is used in Switzerland for GSM-R . The band blocker protects the Swiss GSM-R cellular network from broadband interference from the in-train repeater or cellular devices in the passenger compartment . The band-stop filter works both ways: both the GSM-R - uplink as well as the GSM-R downlink is blocked. Due to the band-stop, the cellular reception of GSM-P ( Swisscom -> "Swiss GSM") is better than with GSM-R ("GSM-R CH" ) with a GSM-R mobile radio device in passenger cars equipped with in-train repeaters. ).
Cellphone permeable car windows
The latest development are car windows that are permeable to mobile communications and have a laser-treated metal layer as thermal protection .
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- I-50079, Limits for In-Train Repeaters for Public Mobile Supply
- https://www.chip.de/news/Neue-Fenster-fuer-Zuege-ab-2018-50-Mal-durchlaessiger-fuer-Handy-Empfang_119111882.html Chip.de - New windows for trains from 2018: 50 Sometimes more permeable for cell phone reception
- https://www.toponline.ch/news/schweiz/detail/news/modernisierung-bei-der-sbb-mobilfunkdurchlaessige-fensterscheiben-und-neue-sitze-00104487/ Toponline.ch - IC2000-Modernisierung - Mobile radio-permeable window panes and new seats