Since the origins of the railway in the XIX century most of the innovation and deployment efforts have been focused on aspects related to traffic management, driving support and monitoring of the train state (Shafiullah et al., 2007). The aim has been to ensure the safety of people and trains and to meet schedules, in other words, to ensure the railway service under secure conditions. To achieve this it has been necessary to establish a communication channel between the mobile elements (trains, infrastructure repair machinery, towing or emergency vehicle, and so on) and the earth fixed elements (command posts and stations, signals, tracks, etc.) (Berrios, 2007). Nowadays, safety is a priority too, but new requirements have arisen, mainly concerning the quality improvement of the transport service provided to the passengers (Aguado et al., 2005). Moreover, the current European railway regulation by establishing that railway services be managed by railway operators independent of railway infrastructure managers makes it necessary for infrastructure fixed elements to share information with mobile elements or trains (handled by railway operators). This new policy results in additional requirements on the exchange of information between different companies. How to fulfil these requirements is a new technological challenge in terms of railway communications (Shafiullah et al., 2007) that is explored in this chapter. The use of wireless technologies and Internet is growing in the railway industry which allows the deployment of new services that need to exchange information between the trains and terrestrial control centres (Shafiullah et al., 2007). In this sense, there are suitable solutions for other environments which allow to manage the bandwidth in terms of data rates. Therefore, these solutions are not designed for railway needs, and do not cover all the requirements that the railway industry has (California Software Labs, 2008; Marrero et al., 2008). This chapter describes a specific wireless communications architecture developed taking into account railway communications needs and the restrictions that have to be considered in terms of broadband network features. It is based on standard communication technologies and protocols to establish a bidirectional communication channel between trains and railway control centres.
