The 35 different railway communication systems used in Europe did not do much to ensure cross-border interoperability
Did you know that GSM-R Is:
- an international standard with a minimum of modifications for railway applications
- proven in operation in public mobile networks
- integrating all railway services into one communication network
- cost effective, both in realization and operation
- using standardized transmission system components, so no railway specific implementation is necessary and investment can be minimized
- able ensure high reliability and availability, transmission quality for up to 500 km/h
- stable, but under active development
- future proof: GSM-R has the ability to smoothly integrate new services defined in future
GSM-R Technology At A Glance
At the end of the last century, more than 35 different systems for railway communications were used in Europe. That was of course not the best way to ensure interoperability for trains ever more rapidly moving from one European country to another.
The railway companies of Europe sat down together in order to create a cost-efficient, interoperable and digital standard for railway communications. The aim was to replace all analogue systems then in use. They laid down the requirements in the so-called EIRENE – MORAINE specifications, the basis on which the present day GSM-R standard is built.
These requirements included:
- Controller-driver operational communications
- Automatic train control
- Remote control
- Emergency area broadcast
- Train support communications
- Local communications at stations and depots
- Services for passengers
ERTMS And ETCS
Ten years after the initial start of the working groups, the ERTMS standard was devised. It consisted of two parts: ETCS and GSM-R. ETCS is used for railway safety and on-board train control. GSM-R is used for all sorts of communications in and around the train and railway track; this includes the communication necessary for ETCS to function. GSM-R thus plays a vital role in train safety.
ERTMS is currently adopted or in the process of being adopted by the railway companies in most European countries. GSM-R has been mandated as the standard for railway communications by the European Commission (EC) in 1997. But in the absence of other standards for digital railway communications, GSM-R is rapidly becoming not just a European standard, but a global one. That becomes clear if we look at the list of countries currently using or implementing GSM-R.
Current GSM-R coverage
In 2007, GSM-R was fully operational on several railways. Countries such as Norway and The Netherlands were well ahead, providing full GSM-R coverage on all lines. Italy provides almost 10.000 kilometers of GSM-R covered railways, while many of France’s high speed trains, such as the LGV Est Européenne and TGP Pos, also run on the GSM-R standard. The first high speed train to fully depend on GSM-R for communications was Germany’s ICE from Saarbrücken to Paris (France). New routes are covered with GSM-R every year: inside Europe, but increasingly also outside of the EU. In Northern Africa GSM-R is currently being implemented, while GSM-R feasibility studies are being finalized in Russia, Argentina, Brazil and the USA.
How is GSM-R Implemented?
GSM-R offers a secure transmission of voice, data and applications and is therefore used as the layer on which security and train tracking applications run.
The radio sub system of the GSM-R network is typically implemented using base transceiver stations and communication towers with antennas which are placed next to the railway with intervals of approximately eight to twenty kilometers. Through GSM-R, trains have a constant circuit switched digital modem connection to their respective train control center. If the modem connection is lost, the train will automatically stop. This modem operates with higher priority than normal users. The enhanced Multi-Level Precedence and Pre-emption service (eMLPP) provides different levels of precedence for call set-up and for continuity in case of handover, giving trains a higher priority than other users.
On top of that, GSM-R is also used for applications such as video surveillance, passenger information systems and cargo tracking.
GSM-R Frequency Spectrum
The frequency of GSM-R networks can differ slightly from country to country. GSM-R uses a lower extension of the 900MHz frequency: 876 MHz — 915 MHz for uplink and 921 MHz — 960 for downlink. In Europe, the 876 MHz to 880 MHz and the 921 MHz to 925 MHz bands are used for data transmission and data reception respectively. Channel spacing is 200 kHz. In China, GSM-R occupies a 4 MHz wide range of the E-GSM band (900 MHz-GSM).
The modulation used in GSM-R is GMSK. GSM-R is a TDMA system, which means that data transmission consists of periodical frames with periods of 4.615 ms for each physical channel. Each TDMA frame consists of 8 logical channels (time slots) carrying 148 bits of information.
Every GSM-R network requires constant, uninterrupted service and high availability - especially while moving at high speeds through diverse terrain. The GSM-R standard offers a flawless handover and guaranteed performance at speeds up to 500 km/h. As the GSM-R signaling information is carried directly to the train itself, GSM-R makes higher speeds and a greater traffic density possible while increasing the level of safety.
There are three main suppliers of GSM-R network equipment to railway operators: Huawei, Nokia Siemens Networks and Nortel. These companies often work together with telecommunication consultants for the planning, validation and optimization of GSM-R networks. One such a consultancy which specializes in GSM-R is Clear CinCom. Train borne equipment is manufactured by Alstom, Center Systems, Hoermann Funkwerk Kolleda, Huawei, NEC Portugal, Nortel, Sagem (the primary supplier of GSM-R handsets), Siemens Transportation Systems and Triorail.
Read an interview with GSM-R network Martijn Kuijpers of Clear CinCom, on why GSM-R radio network planning is different.
View a glossary of important GSM-R related terms and concepts