By Karsten Oberle, Railway Business Development Lead Europe at Nokia
Future Railway Mobile Communication System (FRMCS) is the next-generation global standard for railway communications, set to replace GSM-R and support operators’ transition to digital rail operations. Where GSM-R has reliably supported mission-critical voice and signalling, FRMCS brings higher bandwidth, lower latency and the flexibility to support smarter operations, richer passenger services and new digital applications.
The challenge lies in getting from one to the other. GSM-R is deeply embedded in daily operations and underpins safety-critical services, so communications cannot simply be switched off for an upgrade. For several years, GSM-R and FRMCS will need to operate in parallel, raising a practical question for operators: how to manage this dual-network phase while services remain safe and available. Technology alone will not solve that. Expert services, grounded in both rail and telecommunications expertise, are essential to simplify transformation, reduce operational burden and ensure new networks perform from day one.
From necessary modernisation to structured migration
GSM‑R was designed around 2G technology that is now reaching end of life. Component supply is tightening, the ecosystem is shrinking and maintaining bespoke infrastructure is becoming increasing complex. At the same time, railways are pursuing more automation, data‑driven operations and improved passenger experience – all of which depend on mission-critical, high-performance communications.
FRMCS improves on the technology by separating railway applications from the underlying transport layer, allowing future radio generations to be introduced with less disruption. Over time, this gives operators a flexible, future-ready platform. In the near term, the priority is more tactical: reproduce GSM-R services reliably on FRMCS, operate both systems in parallel and withdraw GSM-R line by line once the new environment is fully proven.
This creates significant operational complexity. Tenthousands of kilometres of track and large fleets of rolling stock will need to be upgraded under strict safety and regulatory constraints. Many operators will be designing, funding, deploying and operating two networks in parallel.
Early FRMCS pilots on dedicated bands such as 1900 MHz (n101) are already showing that 5G-based networks can support mission-critical requirements while coexisting with GSM-R on live test tracks. Migration can be staged without disruption, but only with careful planning, disciplined execution and the right operational support.
Phased migration and the role of expert services
Each operator will move at its own pace and adopt a tailored approach, shaped by regulation, funding, network maturity, spectrum availability and national priorities. This demands flexible migration strategies. What all operators share, however, is the need for specialist support across the full programme lifecycle: from planning and optimisation through to deployment, care and operations.
A typical FRMCS journey begins with defining the range of services the given operator would like to use at the start and in the future – the demand of these services will set the base requirements for the rail-specific Network Planning & Optimization (NPO). Planners must understand how the future network will look and how it will coexist with GSM-R. This includes accounting for ETCS and other mission-critical services, high-speed mobility along complex routes, strict availability and latency requirements, and opportunities to reuse existing sites and infrastructure. It must also align with international railway standards and regulatory frameworks from bodies such as the UIC and 3GPP, ensuring close coordination between network design, safety certification and long-term rail policy.
Specialist teams work with railway operators to model inter-site distances, coverage and capacity in the FRMCS bands, and to determine what can genuinely be reused without compromising safety or performance. These studies underpin investment cases and funding requests, and help shape realistic RFIs and RFQs.
After planning, attention turns to deployment, with the railway continuing to operate as the new network is rolled out. End-to-end deployment services support integration with legacy GSM-R and multi-vendor environments, preparation in labs and test tracks, and validation against regulatory and safety requirements.
As operators manage large numbers of sites and mixed new and existing infrastructure, automation and standardised tools for configuration, testing and acceptance help ensure consistent rollout and aligned software versions. This also provides full traceability for audit and certification.
Experience from 5G-based mission-critical network pilots, where new radio layers have been introduced with built-in failover and real-time monitoring, shows how disciplined validation and coexistence can de-risk deployment at scale.
Operating and sustaining an FRMCS environment
Care services for FRMCS build on decades of GSMR network experience while introducing new capabilities for software-driven architectures. Proactive monitoring of network health, combined with predictive analytics, can highlight potential faults before they affect service. Continuous software evolution, security patching and lifecycle management are aligned with rail’s low change tolerance, keeping the platform current without disrupting operations.
For many operators, the greater challenge is operational capacity. Designing, running and supporting dual networks for several years places a heavy load on internal staff. This is where managed services matter. By entrusting part of the operational workload to a specialist partner – whether for GSM-R, FRMCS or both – operators can access dedicated Network Operations Centre and Security Operations Centre capabilities. This enables consistent service and performance management across technologies, while freeing internal teams to concentrate on migration planning, safety cases and regulatory compliance.
Some will retain GSM‑R operations in‑house while outsourcing FRMCS; others may do the reverse. Regardless of the operating model, operators must still manage coexistence complexity and build the skills and processes required for an all‑FRMCS future.
Making FRMCS migration faster, safer and easier to manage
The transition from GSM‑R to FRMCS is one of the most significant changes railway communications has seen in decades. It is a necessary step to keep trains running safely as legacy technology reaches its limits, and a critical foundation for the next phase of digital railway services.
By combining robust technology with expert services across planning, deployment, care and operations, railways can turn a long and complex transition into a structured, manageable programme. A phased, services-led approach enables operators to move at the right pace, control risk and maintain safety-critical performance from day one, ensuring even the most demanding FRMCS deployments can be delivered with confidence.
