FRMCS & 5G for rail
FRMCS (Future Railway Mobile Communication System) is the internationally standardised wireless communications system designed by the UIC to replace GSM-R as the radio bearer for ETCS and other safety-critical railway applications.
Technical specification
FRMCS is based on 5G New Radio (5G NR), standardised through 3GPP, bypassing an intermediate LTE-R step. It operates on two frequency allocations: the existing 900 MHz railway band (874.4–880.0 MHz / 919.4–925.0 MHz) and the new unpaired 1900–1910 MHz Time Division Duplex (TDD) band allocated by the CEPT Electronic Communications Committee in November 2020.
The European Commission mandated EU member states to make these frequencies available for railway applications in September 2021.
The 1900 MHz band provides substantially higher data throughput than 900 MHz but attenuates more rapidly with distance, requiring base station spacing approximately half that of GSM-R networks.
On-board antenna systems for FRMCS must accommodate both frequency bands simultaneously, typically using MIMO (Multiple Input Multiple Output) configurations on the rolling stock roof. The OBRAD (On-Board Radio Interface) specification, published as ETSI TR 104 006 V1.1.1 in January 2025, standardises the interface between onboard wireless devices and the gateway functions on the train.
Capabilities relative to GSM-R
GSM-R provides 9.6 kbps data throughput — sufficient for ETCS Level 2 movement authority packets but not for the data volumes required by ATO, onboard CCTV, continuous diagnostic telemetry, and position reporting at high train densities.
FRMCS offers multiple orders of magnitude more bandwidth, network slicing to partition safety-critical and non-safety traffic on shared physical infrastructure, and ultra-reliable low-latency communication properties required for future ETCS Level 3 and automated train operation. It is IP-based, which aligns its lifecycle with commercial 5G technology rather than the end-of-life 2G ecosystem underlying GSM-R.
Deployment timeline
FRMCS standardisation commenced in 2015; the requirements specification was finalised in February 2020. A preliminary standard draft was published in 2022. European train procurement contracts from 2024 specify FRMCS compatibility as a delivery requirement.
National deployment plans diverge in timing: SNCF awarded a network transformation contract in 2023, targeting completion by 2030. Deutsche Bahn plans live tests from 2027, with the complete transition from 2026 to 2035.
Switzerland identified locations for approximately 3,500 FRMCS base stations in 2022 and targets GSM-R deactivation by 2035. Austria’s ÖBB plans FRMCS production deployment from 2027.
Vendor support for GSM-R equipment is expected to become difficult by approximately 2030, establishing 2035 as the practical outer limit for the migration, although some countries with recent GSM-R deployments or extended supplier agreements may operate beyond that date.
Regulatory framework
FRMCS is incorporated into the Control-Command and Signalling Technical Specification for Interoperability (CCS TSI), which legally mandates its adoption across the European rail network as part of ERTMS.
The on-board interoperability interface specification ETSI TS 104 127 (formalisation underway as of April 2025) governs the OBRAD interface for vendor independence in onboard equipment procurement.