**3.1 Towards a train-to-earth wireless communications architecture**

In this section the core components of the mentioned wireless communications architecture are described. This architecture allows a full-duplex transmission of information between applications and devices deployed in the trains, and applications that are in the railway control centres. The description of the architecture will be made at two levels: conceptual and physical level. The first level defines the basic concepts of the architecture, and the second one illustrates the technologies used to implement the architecture in two real scenarios.
