5G communications in high speed and metropolitan railways

Railway transportation is increasing very fast in all countries, and as a consequence new railways demand high quality communications for control and signaling of trains, as well as high capacity communications for passengers. However, current communications systems cannot provide these services, so 5G systems will be needed to replace old GSM-R and dedicated systems for railway signaling. Also, 5G terrestrial and satellite technologies will provide high data rate services to passengers. In this paper we describe the main characteristics and requirements for critical and non-critical communications in railways. Results are useful to choose the communications technologies that can fulfill these requirements in the near future.