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From GSM-R to FRMCS: a quiet revolution in railway radio
In the European rail system, radio is no longer just a communication tool: it is an essential link in traffic safety and operational performance.
It also provides ground-to-board communication during ETCS (European Train Control System) Level 2 operation, transmitting movement authorizations to trains.
These functions are currently provided by the European GSM-R standard, which is reaching the end of its life (it is based on 2G transmission, which is now obsolete). A new system is being prepared to take over: FRMCS.
A little history: solid foundations
Historically, communication between train drivers and ground operations was carried out using analog technologies specific to each network. In France, this was Radio Sol Train.
The first GSM-R specifications were developed in 1993 under the impetus of the UIC (International Union of Railways) as part of the EIRENE (European Integrated Railway Radio Enhanced Network) project. A unified communication system was needed to facilitate train interoperability between different countries.
The choice then fell on GSM technology, known as 2G, which is widely deployed and more affordable than other existing radio solutions.
These specifications are based on the European MORANE (Mobile Radio for Railways Networks in Europe) project, which lays the foundations for a common radio standard at European level.
In 2000, SNCF was a single company (EPIC). As a result, the project to deploy GSM-R ground infrastructure and on-board radios was pooled, which explains why the radios are now similar across all French-designed rolling stock.
More than twenty years later, in 2015, the UIC began considering its successor: the FRMCS (Future Railway Mobile Communication System).
The first part of the specifications was published in 2023. The complete version was announced in 2028 and is based on the European MORANE-2 experiment, the direct successor to the GSM-R experiment.
What is the purpose of onboard radio (GSM-R) today?
GSM-R is ubiquitous in modern railway operations. In particular, it enables the transmission of:
· Voice and SMS communications between train drivers and ground operations, particularly for safety alerts.
· other communications and sound systems (including passenger information systems for accompanying staff),
· data exchanges necessary for the operation of ETCS Level 2,
· and a wide range of other messages linked to the radio and vehicle design (for example, alerts issued in the event of driver inattention).
FRMCS: the railway radio of tomorrow
FRMCS is set to replace GSM-R by 2035.
The stakes are high: GSM-R is based on 2G technology, which is now considered obsolete. Although GSM-R is mainly based on a dedicated rail network, its deactivation on public networks signals the end of production of the components needed for its maintenance. By 2035, GSM-R maintenance will be hampered by the unavailability of spare parts.
The FRMCS is based on 5G technology, which, in addition to addressing this obsolescence, offers:
· Much higher speeds, particularly thanks to the addition of radio frequency bands.
· reduced latency,
· improved reliability,
· and the ability to transmit data between the edge and the ground, open to third-party applications.
Beyond a simple technological change, FRMCS will have to support many more flows, services, and use cases than GSM-R in order to meet the growing needs of railway digitization. Based on IP technology, its design will have to incorporate high cybersecurity requirements, recently reinforced by the Cyber Resilience Act. The FRMCS version 2 specifications have already been submitted to the ERA (European Union Agency for Railways). Version 3, intended for commercial operation, is currently in preparation (source: UIC FRMCS, October 2025 conference).
The challenges of transitioning to FRMCS
For travelers, this transition must be completely seamless. For rail operators, however, and in particular the SNCF Group, it represents a major technical, economic, and organizational challenge.
From a technical standpoint, the migration to FRMCS is an opportunity to design a scalable radio system, given the gap between the lifespan of digital technologies and that of rail vehicles. This scalability should enable equipment owners to integrate future features (faster deployment of patches, new cyber challenges, future migration to 6G and beyond) at a reasonable cost and without vendor lock-in (the challenge of open architecture).
Still on the technical side, the FRMCS specifications mainly define radio parameters (frequency bands, protocols, performance), but not messages or associated business functions. Work will therefore be required to define air-ground exchanges and ensure continuity of operation throughout the transition.
In organizational and financial terms, the migration must be completed by 2035, within the deadlines set by infrastructure managers: a train cannot be put into service without a functional radio system. This is an unprecedented project in terms of its scale, as it covers all rolling stock in Europe equipped with a driver's cab. To limit equipment downtime and the risks resulting from heavy pressure on contributing resources, it seems necessary to design an FRMCS architecture that can be deployed quickly and as close as possible to operations, and to plan the project in advance.
The transition from GSM-R to FRMCS marks a key milestone in the evolution of European railways. Much more than a simple change in radio technology, it represents a profound transformation of the communication systems that support the safety, performance, and capacity of the network.
While this transition remains invisible to passengers, it requires significant engineering efforts, adaptation of rolling stock, and coordination between stakeholders in the rail system. The success of this project will directly determine the continuity of operations and the integration of future digital services.
The FRMCS is paving the way for a more connected, more flexible railway system that is ready to meet the technological challenges of the coming decades.
Sources:
https://www.youtube.com/watch?v=UPiGLzszi8U
https://en.wikipedia.org/wiki/FRMCS
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