Railway Global System for Mobile Communications GSM-R
The railway Global System for Mobile Communications is also known as GSM-R & ‘GSM-Railway’.
GSM-R Global System for Mobile Communications) is an international standard, covering railway communications.
It is a sub-system of the European Rail Traffic Management System, or ERTMS .
ERTMS is used for communication between trains and the railway control centres.
The ERTMS system is based on the EIRENE – MORANE standards specifications.
The EIRENE – MORANE specfications guarantee that the system will operate, at train speeds of up to 310 mph / 500 kph, with zero communication loss.
GSM-R offers secure voice and data communication amongst railway staff.
Users include train drivers, engineers, station controllers etc.
Communication security is important, both for commercial and security reasons.
Components of a typical GSM-R include the base station, mobile units installed in trains, and handheld units.
Antenna masts, connected to the base station are installed close to the railway track.
Tunnels present a communication challenge, due to blocking and attenuation of the RF signals.
The solution used, is to either use a directional ‘yagi’ antenna, directed through the tunnel entrance, or to use a ‘leaky feeder’ type antenna.
A Yagi antenna when used as a transmit antenna, directs most of the Rf power in one direction, rather than in all directions.
The Yagi antenna works similarly, when operating as a receive antenna, in that it receives most of the signal from the direction it is pointing in. A tv aerial on a house roof is a common example of a receive Yagi.
The other solution for tunnels, is the ‘leaky feeder’ antenna.
The leaky feeder is like a long piece of coaxial cable, which is designed to emit & receive RF (Radio Frequency) signals along its length.
This allows communications to take place in tunnels and underground stations.
The Leaky Feeder antenna is used in underground stations, where radio communications are required.
The advantage compared with the Yagi antenna, in such locations is that leaky feeders can be positioned round tunnel bends.
As Yagi antennas operate on frequencies that provide ‘line of sight’ signal transmission, bends will affect the signal path, attenuating them at best, blocking them at worst.
The spacing distance on the surface between the base stations, is 4.3 – 9.3 miles (7-15 km).
The system is built with high levels of reliability and redundancy built in, and if communication is lost, the train will stop.
The GSM-R specification standard forms part of the European Rail Traffic Management System, or ERTMS.
The ERTMS is comprosed of the following parts:
European Train Control System (ETCS)
Global System for Mobile Communications – Railway (GSM-R)
European Traffic Management Layer (ETML)
European Operating Rules (EOR)
Operating frequency band
GSM-R uses similar frequencies to the public mobile phone (cell phone) servcice, in most regions, namely around 900Mhz (E-GSM) & also at 1800 Mhz (DCS 1800).
The exact frequency used by Railway operators, is dictated by national and regional regulation bodies, but the 900 Mhz & 1800 Mhz bands are used worldwide.