# Towards the Internet of Smart Trains:
## 3 Overview on the Railway Applications Offered by GSM-R
### GSM-R: The Solution Preferred  
The _Union Internationale des Chemins de Fer_ (UIC) selected the GSM technology after comparing it with TETRA in terms of usability in railway scenarios. Moreover, GSM was supported by the GSM Association (GSMA) and it was standardized by ETSI as GSM Release 99. After a thorough analysis, GSM-R was eventually standardized by the European Railways and the UIC. In Europe, a relevant initiative for the evolution of the communications was the European Integrated Railway Radio Enhanced NEtwork (EIRENE) project. This cooperation was participated by the European Commission (EC), ETSI and several railway operators. EIRENE was aimed at specifying the requirements for railway mobile networks. To reach such a goal, a functional group and a project team were established within the project. The functional group was responsible for defining the Functional Requirements Specification (FRS), which guaranteed the interoperability across borders. Regarding the project team, it was focused on defining the System Requirements Specification (SRS). The SRS details the technical features related to operations, which involved the identification and specification of supplementary Advanced Speech Call Items (ASCI) features [41]. In 1995, a first draft of the EIRENE specifications was released. At the same time, the UIC became involved in the Mobile Radio for Railway Networks in Europe (MORANE) project, which also included the participation of the EC, the major railways of Italy, France and Germany, and a number of GSM suppliers. The objective of MORANE was to design and build prototypes of a new radio system that met the functional specifications and the system requirements proposed. Railways from all over Europe signed the Memorandum of Understanding (MoU) in 1998 and, in 2009, more companies were added, including railways outside Europe. In 2000, seventeen railway companies signed an Agreement on Implementation (AoI) to deploy national GSM-R networks no later than 2003. Thereafter, GSM-R became the reference communication technology in railways until today, when the evolution of the demand and the emergence of new technologies are fostering the research on alternative solutions. It is publicly recognized that GSM-R is not well-suited for services such as automatic pilot applications or for provisioning on-board Internet to the train staff and passengers [42]. GSM-R (based on GSM Phase 2 and Phase 2+ recommendations) was designed aiming to provide the maximum redundancy while achieving the maximum system availability. GSM-R provision two fundamental services: voice communications and the transmission of European Train Control System (ETCS) messages. The definition of European Rail Traffic Management System (ERTMS) was the result of the European efforts to promote interoperability. ERTMS includes three levels. Among them, ERTMS levels 2 and 3 employ GSM-R as the basis that supports communications. In Europe, a 4 MHz bandwidth is reserved for such communications. The main elements of ERTMS are: \begin{table}
\begin{tabular}{c} \hline
**Wireless Technology** \\ \hline IEEE 802.11 \\ IEEE 802.15.4 \\ Zigbee \\ Zigbee Pro \\ IEEE 802.15.1 \\ Bluetooth \\ WirelessHART \\ ISA 100.11a \\ WISA \\ \hline \end{tabular}
\end{table} 
Table 3: Comparison of the different WSN technologies. Color meaning: green (fully compliant with railway requirements), yellow (partial fulfillment) and red (non compliant). * ETCS: it allows for automating train control. It consists of a Radio Block Center (RBC) and a Lineside Electronic Unit (LEU). ETCS can be divided into three levels:
* ETCS level 1: the location of the train is determined by traditional means (i.e., no beacons are used for locating the train), whereas communications between fixed safety infrastructure and trains are performed by means of beacons (transponders placed between the rails of a railway track). GSM-R is only used for voice communications.