FRMCS, and what we have tested

GSM-R has carried European rail operations for twenty years and it is being switched off. The Future Railway Mobile Communication System replaces it, and unlike its predecessor it is not a railway-specific radio technology but mission-critical services over 4G and 5G, built on the same 3GPP work as the rest of the mission-critical world.

For an infrastructure manager that is a long migration with no appetite for surprises. It is also the reason these test events exist.

The 5th ETSI FRMCS Plugtests, Paris, October 2025

27 to 31 October 2025, hosted by UIC and organised with ETSI. 96 testing sessions, more than 300 tests, run against 3GPP Release 18. ETSI reported 95.5 percent interoperability for the event. More than 180 delegates took part, over 100 of them on site from 20 countries.

Railway operators and national authorities attended as observers, among them BDBOS, SNCF Voyageurs, SBB, Bane NOR, Trafikverket, Erillisverkot and the French Ministry of the Interior.

As everywhere in this section: that percentage is the event’s aggregate result, published by ETSI. It is not a TASSTA score, and no product is certified at a plugtest.

What TASSTA tested there

MCPTT group calling, including creating an ad-hoc group and releasing it again;
Floor control, in the detail rail actually needs: priorities, timers, queueing, functional alias display, multiple simultaneous talkers and location sharing during a call;
5G QoS integration, with dedicated QoS flows over the Rx and N5 interfaces, which is what makes a call keep its priority when the network is carrying everything else as well.

What this means for a railway

Rail does not replace a communication system the way an enterprise replaces a telephone system. There is a network that works, staff trained on it, rolling stock fitted for it, and an authority that has to approve the change. The years in between are the problem to solve, not the end state.

Two things follow, and both are standards work rather than product promises:

The migration runs with the radios in service today. TASSTA implements Interworking Function connectivity per 3GPP TS 23.283, for IWF-1 (MCPTT) and IWF-2 (MCData and SDS), through T.Gravity, the gateway from T.XON to TETRA, DMR, analogue radio and SIP telephony;
Priority has to survive a loaded network, which is what the QoS work above is for.

Where we stand

We take part in these events because our customers’ customers sit in the observer list, and because a standard that is only implemented on paper is of no use to anyone.

What we test at the MCX Plugtests

TASSTA at the 5th ETSI FRMCS Plugtests in Paris

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