Telecoms company Ericsson and Swiss national rail operator Schweizerische Bundesbahnen (SBB) have completed a live integration of the legacy GSM-R railway communications system with an IP Multimedia Subsystem (IMS) platform using Voice over LTE (VoLTE).
According to Ericsson, this marks Europe’s first such integration.
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The infrastructure upgrade is now supporting Switzerland’s 3,100km rail network and comes ahead of Swisscom’s planned 3G service decommissioning at the end of this year.
SBB has also upgraded onboard 4G services on around 1,000 trains.
Previously, Swiss railways depended on public 3G network roaming from Swisscom for voice communication in locations without GSM-R coverage.
With the upcoming withdrawal of 3G, SBB considered options for modernising its communications and selected Ericsson’s IMS and VoLTE-based solution to connect GSM-R functions with modern telephony systems.
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By GlobalDataEricsson delivered and integrated the new system, bringing together technology from multiple suppliers into a single IMS core.
The deployment process began with platform installation in June 2023.
Early 2024 saw the first end-to-end VoLTE-to-GSM-R calls. In January 2025, SBB conducted field tests with pilot trains, certified by Switzerland’s Federal Authority Office of Transport.
The nationwide system went live ahead of schedule in April 2025.
As of December 2025, about 450 trains and 1,000 operational devices are now using VoLTE.
The IMS/VoLTE platform retains safety-critical and rail-specific features such as EIRENE functional numbering, emergency stop calls, group calls, and onboard announcements.
The adoption of 4G technology prevents disruptions from the discontinuation of the older 3G service and prepares for future innovations such as the Future Railway Mobile Communication System (FRMCS) based on 5G.
SBB teams have received training to support the migration process.
Ericsson Europe, Middle East and Africa railways mission critical communications head Nicolas Segond said: “Our work with SBB demonstrates our capability to deliver complex digital transformations under tight timelines.
“We look forward to setting benchmarks in railway communication innovation and supporting the transition to FRMCS in the coming years.
“While the full migration of train fleet communications and smartphone operations continues toward its December 2025 completion, the collaboration has paved the way for future enhancements.
“Valuable insights gained during this project will guide improvements in strategies for similar railway transformations globally.”
