Standardisation Roadmap for Next Train Radio Telecommunication Systems

3GPP LTE Third Generation Partnership Project --- Long Term Evolution cellular system first studies started in 2004. The system was designed initially for public voice and data services. Its scope has enlarged later on, to encompass public safety services and Machine-Type Communications MTC. It targets now vehicular domain V2X. In parallel, studies for the next generation system, a.k.a 5G, have started recently in 3GPP. This next generation aims at including from its very beginning, requirements for broadband public access services, Internet of Things IoT and vertical sectors, the latter ranging from vehicular services to factory automation needs. In Europe, several initiatives are on-going at International Railway Union UIC, European Railway Agency ERA and ETSI European Telecommunications Standards Institute to prepare the next train radio telecommunication system that would fit rail community requirements in replacement of GSM-R Global System for Mobile communications - Railways. Evolutions of 3GPP LTE are candidates, but 5G could jump in the list. This paper aims at providing an overview of current 3GPP status and roadmap toward 5G, and its level of compatibility with next train radio telecommunication system.