FRMCS
The Future Railway Mobile Communication System, short FRMCS, is an international wireless communications standard for railway communication and applications. It is the successor for GSM-R (Global System for Mobile Communications – Railway) being primarily used in the European Train Control System (ETCS).

Background 

The GSM technology reaches end-of-life status by 2030. The UMTS systems, which came later, have already begun to be decommissioned in the 2020ies, but GSM had a large base of embedded systems using it, so that vendors did continue production setting a date however when they want to stop. As such the International Union of Railways (IUC) has opted for a breaking change using 5G NR mobile networks instead of a gradual modernization with LTE-R that was once proposed. The FRMCS rollout is effectively skipping over two generations of mobile communication generations.

In 20. November 2020 the Electronic Communications Committee of CEPT assigned the paired frequency band 874.4–880-0 and 919.4–925.0 MHz as well as the unpaired frequency band 1900–1910 MHz for usage by Railway Mobile Radio (RMR).  RMR is hereby an overarching term for the concrete technologies of GSM-R and FRMCS. During the transition phase, the railway operators can shift more frequencies to FRMCS as far as they are installed in the train onboard computers. On 28. September 2021 the European Commission mandated that member states of the European Union shall open up the assigned spectrum for railway usage.

The standardization process had begun in 2015. The requirement specification was resolved in February 2020. The testing project "5G Rail" was founded in November 2020 to be finished in 2023. A first draft of the standard was published at end of 2022, to be resolved in the beginning of 2023. The final specification is expected for 2024, so that the rollout can start in 2025.

Meanwhile, railway operators have already started the migration, primarily checking the locations for the base stations to be fit for FRMCS which requires more of them, as 5G has chosen to transmit more data in the same frequency band which makes the transmission range shorter. Finland's railway operator has volunteered to become pilot user. They have shown a specific interest to dismantle their own base stations using the public networks for railway operations. Using multipath routing they can use all three of the public network operators along their 6000 km of track. The creation of a test lab on a stretch of 190 km tack was started in 2022 (using the unfinished FRCMS standard) looking for a completion of tests in 2024.

Latest tenders for trains in Europe have shown that they include a clause that all deliveries in 2024 and later must be FRMCS-ready. In May 2023 the French railway operator SNCF contracted Frequentis to supply FRMCS for its complete rail network. Its strategic development plan is to transform the network until 2030. The Deutsche Bahn in Germany intends to migrate between 2026 and 2035 starting a live test in 2027. Switzerland has defined the locations of 3500 base stations in 2022. They intend to switch off GSM-R in 2035. In May 2023 they started to check whether the base stations of 5G public network operators can be used instead, or a mixture with transmissions using the public mobile networks can be used.

References 

European Rail Traffic Management System
GSM standard
Rail transport mobile telecommunications standards