FRMCS (Future Railway Mobile Communication System) is the internationally standardised wireless system designed by the International Union of Railways (UIC) to replace GSM-R as the radio bearer for ETCS and other safety-critical railway applications.
FRMCS is based on 5G New Radio (5G NR), standardised through the 3rd Generation Partnership Project (3GPP), bypassing an intermediate LTE-Railway (LTE-R) step. Its future adoption is being written into European interoperability law, though the full technical specifications are not yet in force.
The system defines the future safety-critical radio bearer within railway connectivity and communications — the successor to a 2G-based platform whose commercial ecosystem is contracting.
Technical specification
FRMCS operates on two frequency allocations: the existing 900 MHz railway band (874.4–880.0 MHz / 919.4–925.0 MHz) and the unpaired 1900–1910 MHz Time Division Duplex (TDD) band allocated by the European Conference of Postal and Telecommunications Administrations (CEPT) 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 delivers substantially higher data throughput than 900 MHz but attenuates more rapidly with distance, requiring base station spacing approximately half that of GSM-R networks.
Onboard antenna systems must accommodate both bands simultaneously, typically in MIMO (Multiple Input Multiple Output) configurations on the rolling stock roof. The OBRAD (On-Board Radio Interface) concept, described in a European Telecommunications Standards Institute (ETSI) technical report (TR 104 006 V1.1.1, January 2025), defines the interface between onboard wireless devices and the train gateway; formal standardisation is proceeding separately through ETSI TS 104 127.
Capabilities relative to GSM-R
GSM-R provides 9.6 kbps of data throughput — sufficient for ETCS Level 2 movement authority packets, but not for Automatic Train Operation (ATO), onboard closed-circuit television (CCTV), continuous diagnostic telemetry, or position reporting at high train densities.
FRMCS raises throughput from GSM-R’s 9.6 kbps to megabit-level speeds, adds network slicing to partition safety-critical and non-safety traffic on shared infrastructure, and offers the ultra-reliable low-latency properties required for future ETCS Level 3 and automated train operation.
It is IP-based, aligning its lifecycle with commercial 5G technology rather than the end-of-life 2G ecosystem underlying GSM-R.
Deployment timeline
Standardisation commenced in 2015, and the requirements specification was finalised in February 2020. Some European train procurement contracts from 2024 specify FRMCS compatibility as a delivery requirement, though practice varies by operator.
National deployment plans diverge in timing. France’s FRMCS transition runs 2028–2035, with commercial rollout from 2032; SNCF’s 2023 contract with Frequentis covers fixed terminal and dispatcher systems, maintained through 2036.
Deutsche Bahn has run a live FRMCS 1900 MHz network on its Erzgebirge test line since 2025, with trials on operational lines from 2027, completing by 2035. Switzerland targets GSM-R deactivation by 2035; Austria’s ÖBB plans FRMCS piloting from 2027.
Vendor support for GSM-R equipment is expected to become harder to secure from around 2030, though some suppliers have signalled support toward 2040. Countries with recent deployments may operate the system well beyond 2035.
Regulatory framework
FRMCS is included in the Control-Command and Signalling Technical Specification for Interoperability (CCS TSI 2023/1695) as a Class A system at baseline 0, covering the interface rather than the full specification; complete FRMCS requirements are expected in the 2027 TSI revision, at which point EU-wide adoption becomes mandatory.
ETSI TS 104 127, under formalisation as of April 2025, is expected to govern the OBRAD interface and secure vendor independence in onboard equipment procurement.