What is GSM-R?
GSM-R stands for Global System for Mobile Communication for Railways and is based on the commercial system GSM. GSM is standardized by ETSI, the European Telecom Standards Institute and well supported by the GSM Association Group, the association of the GSM suppliers.
GSM-R is based on GSM. To integrate the specific requirements of railways in mobile communication some additional features had to be described, standardized and developed. These features are called ASCI features. ASCI stand for Advanced Speech Call Items. These features are:
All these features, which were developed together with ETSI, are incorporated into the GSM standards and are now also partly developed by GSM suppliers and available for public operators in some public networks.
For more information check out:
http://www.uic.org/IMG/pdf/gsm-r_guide.pdf
http://www.uic.org/spip.php?rubrique874
http://goo.gl/OBvEjM