Tuesday 19 May 2009

The GSM-R Frequency Workshop

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GSM-R is the Train Radio technology and the ETCS bearer, at least in Europe. It is based on GSM 2+ technology, and it has specific functions, needed by the railways, and standardized.

It has a dedicated frequency bandwidth, allocated by European decision – ECC/DEC/ (02)05

The frequency bandwidth is: 876-880/921-925 MHz, 4 MHz paired, near the GSM bandwidth. The uplink part – Ground to Mobile communication part, through which, for instance, MA’s are sent - is in between the two Public GSM Frequency Bandwidths.

GSM-R was built to coexist with the GSM technology used by the Public Operators. Meantime, the mobile technology evolved to superior phases, and different technology, improving the communications and the data throughput. New technologies appeared like the UMTS (Universal Mobile Telecommunication System – 3rd Generation Mobile Telecommunications Technology), and lately the LTE (Long Term Evolution – 4th Generation Mobile Telecommunications Technology).

UMTS is a different technology, initially prepared for the 1800 MHz band, but now under deployment also in the 900 band, which will strongly affect GSM-R.
LTE is the next mobile communication generation: all different existing technologies will then converge.

ECC has produced an impact study, through the working group PT1, the so called Report 96, in which UIC managed to introduce some statements. The study does not rely on real measurements, but on the so called Monte Carlo method simulations. Also, it does not refer to moving scenarios, as it is a static model. The interference cases have been sent to the National Frequencies Authorities to be settled.

The GSM-R Cab Radio is considered as a normal mobile station, from standards points of view.
Nevertheless, it has a different working environment – bearer for ETCS and Train Radio, where dropped calls or interfered zones where no communications are possible are heavily impacting railway traffic and have therefore to be avoided. We have also to take into account that it is a very exposed “mobile station”, having its antenna on the locomotive’s roof, at 4 meters high.

Lately, in Sweden, a license for mobile operators who wished to use the new technology called LTE was granted. It was announced that parts of the new network will start to be operational in Q3 2009.

Due to the GSM-R networks deployment state (almost 60.000 km in operation, in Europe), and the increasing border traffic using GSM-R (10 countries interconnected), together with the UMTS Mobile Public Operators deployments in the GSM 900 bandwidth, the number of interference points is unfortunately constantly increasing.

UIC GSM-R Frequency Workshop

On 30 April 2009, UIC organized a GSM-R Frequency Workshop on this subject, which, as explained before, has become urgent now. The workshop gathered participants from Austria, Belgium, England, Finland, France, Germany, Sweden, the German Frequency Authority and UIC. Test campaign results from Finland, Sweden together with the situation in Germany – more than 130 interferences points, already officially reported were presented and discussed. The survey on the situation in each network showed similar problems, and the urgent need for supportive actions.

A rapid set of measures was decided:

1. All ERIG members will be requested to send the national technical reports, in order to be gathered in a single document, to be trigger for discussions at European authorities’ level – CEPT and ECC.

2. UIC will reinforce the railway representation at the European level, through the dedicated Working Group. It will also establish a liaison with GERAN on work arrangements for updating GSM-R technical characteristics (E-GSM-R frequencies, GSM-R Rx parameters & testing incl. ACS, blocking, spurious response rejection, IM3, additional cab radio filters), and will request to set up an ETSI STF (Special Task Force) to study and write a standardization proposal (application deadline for this STF: 15 of September)

3. A deep analysis will be made for the filtering solution – the technical and economical implications (the solution would be to introduce frequency filters between the antenna and the Cab Radio), as the GSM-R spectrum is in between the Public Operators frequency domains, and measures have to be taken in a very short term to survive in such an aggressive environment.

Next meeting for the frequency experts is scheduled for 8 September 2009.

For more information please contact Dan Mandoc, UIC Senior Advisor: mandoc@uic.org

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