SBB undertakes Europe’s first major railway with IMS, VoLTE comms

Looking to bridge and eventually transcend the world of traditional mobile networks with IP communications infrastructures ahead of the shutdown of 3G services in the country, leading Swiss national railway operator Schweizerische Bundesbahnen (SBB) has delivered what is claimed to be Europe’s first live integration of legacy railway communications system GSM-R with an advanced IP Multimedia Subsystem (IMS) platform with voice over LTE (VoLTE) service using Ericsson technology.

With the mission statement of connecting Switzerland, and with 35,500 employees, SBB transports over 1,410,000 people and 170,000 tonnes of freight to their destinations every day. It also operates the mobile network for all Swiss railways on the standard gauge network.

For years, voice roaming for Swiss rail communication relied on telco Swisscom’s public 3G network in areas where GSM-R coverage was not available. GSM-R is the current standard for secure, reliable railway communications, supporting essential voice and data for train control and operations.

With Swisscom’s decision to decommission its 3G services, Swiss railway operators faced an urgent need to modernise. Expanding the old GSM-R system was one option, but SBB engaged Ericsson to deliver a platform based on IMS and VoLTE, bridging GSM-R rail-specific functions with modern mobile and fixed telephony systems.

The infrastructure upgrade is intended to ensure uninterrupted, nationwide railway communication for Switzerland’s 3,100km rail network ahead of the planned decommissioning of Swisscom’s 3G services by the end of 2025. Furthermore, onboard 4G service upgrades have been implemented for about 1,000 trains, in a move that Ericsson says no less then redefines connectivity and reliability for SBB’s railway operations.

Said to offer resilience and innovation, the new system ensures continuous end-to-end rail communication, setting benchmarks for railway operators across Europe facing legacy telecom shutdowns.

In addition, the deployment strategy aimed to prioritise zero service interruptions and robust safety compliance. Key features of the IMS implementation included IMS-GSM-R interworking, GSM-R numbering adaptation and mandatory safety-critical functions such as emergency stop calls.

The IMS/VoLTE integration progressed through a number of key testing phases: platform deployment was initiated in June 2023; the first end-to-end VoLTE-to-GSM-R calls were successfully completed in early 2024; field tests across pilot trains, certified by Switzerland’s Federal Authority Office of Transport, took place in January 2025; and nationwide go-live of the system occurred in April 2025 ahead of schedule. The infrastructure is currently in operation with approximately 450 trains and 1,000 operational devices using VoLTE technology with zero downtime.

Ericsson says the live IMS/VoLTE platform guarantees high-performance rail communication with scalable, modernised dispatcher telephony, reducing risks and limitations of the legacy infrastructure. Key rail-specific functions – including EIRENE functional numbering (European Integrated Radio Enhanced Network), emergency stop calls, group calls  and onboard announcements – have been preserved.

By enabling 4G/5G, Switzerland’s railway network is attributed with avoiding service interruptions from the 3G shutdown while laying the groundwork for upcoming 5G-based Future Railway Mobile Communication System innovations. Migrations to date are said to have proceeded smoothly, supported by training provided to SBB’s operational teams.

While the full migration of train fleet communications and smartphone operations continues towards its December 2025 completion, the collaboration is said to have paved the way for future enhancements. Insights gained during this project will guide improvements in strategies for similar railway transformations globally.