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Marcel Kicken, head of planning and design at Ericsson Switzerland, identifies a strategy for a cost-efficient transition from 2G GSM-R to the Future Railway Mobile Communication System (FRMCS).
The railway sector is navigating a pivotal transformation as it transitions from GSM-R to the Future Railway Mobile Communication System (FRMCS). This shift represents far more than a generational technology upgrade. It is a strategic overhaul of how mission-critical railway communications networks are conceived, dimensioned, and deployed to meet the demands of fully digital, high-performance rail operations.
GSM-R, rooted in 2G cellular technology, has reliably supported voice and limited data services for decades. In contrast, FRMCS builds upon a 5G architecture engineered to deliver broadband, low-latency, and ultra-reliable connectivity for next-generation rail operations. This evolution underpins capabilities that range from real-time predictive maintenance and high-definition video surveillance to automatic train operation (ATO), all of which impose significant demands on network performance, reliability and availability.
Dimensioning for FRMCS extends beyond just coverage and capacity calculations - it is a multi-factor, service-centric process that ensures the network consistently meets stringent targets for coverage, throughput, availability, and reliability. Unlike GSM-R’s relatively straightforward design model, the FRMCS network calls for an integrated radio planning approach that accounts for spectrum efficiency, using technology enhancements such as beamforming and MIMO gains, train speed impacts on (handover) performance, and resilience for safety-critical applications.
The cost implications are substantial. FRMCS deployment requires significant capital investment, and precise radio network dimensioning is essential to optimise asset usage, prevent bottlenecks or over-dimensioning, and guarantee seamless coexistence with GSM-R during the migration window. This includes sophisticated spectrum planning to balance new FRMCS bands with legacy allocation and potential shared use strategies involving Mobile Network Operators (MNOs).
In other words, for railway infrastructure managers, accurate FRMCS planning not only safeguards operational safety and service continuity, but also serves as the blueprint for cost-efficient deployment and migration strategies for a future-proof transition. Railway-specific competences and AI-driven tools are enablers for best reuse of GSM-R assets and the best potential benefits from shared infrastructure with Public Mobile Network Operators (PMNOs).
Where GSM-R planning revolved around coverage and interference management, FRMCS planning is about ensuring end-to-end service quality under diverse operational conditions; from dense multi-track corridors and stations to high-speed lines where trains operate at more than 300km/h.
GSM-R technology has been a reliable backbone for European railways. It is designed primarily for voice services with limited packet data transmission, with the following main characteristics:
operation in the 900MHz band
planning driven by coverage and interference(parameters called Received Signal Level (RxLev) and Carrier-to-Interference (C/I) ratio, and
capacity scaling by adding more frequencies (carrier).
To ensure optimal coverage and to manage interference, GSM-R network planning focuses on carefully managing frequency optimisation.
In contrast, FRMCS is 5G-based and designed for multiple packet data services (broadband voice, video, and mission-critical data) and introduces a host of advanced features and characteristics:
operation in the 900MHz band and also 1900MHz band
advanced features for coverage and reliability (such as beamforming, MIMO), and
planning driven by throughput requirements with strong emphasis on interference mitigation (via site placement, antenna tilts, azimuths, and consideration of train speed dynamics).
Dimensioning is the process of ensuring that the network can meet performance targets for capacity, availability and reliability while considering the constraints of limited spectrum. FRMCS dimensioning requires a careful balance of multiple interdependent factors:
trackside radio network design such as spectrum use, features use (e.g. beamforming), pylon characteristics (heights etc.), intercell distances
throughput requirements such as for critical signalling data transmission (ETCS), predictive maintenance traffic, real time video transmission
mobility such as train speeds ranging from low-speed shunting yards to 350km/h high-speed lines, and
reliability and redundancy, as critical parameters for safety-related applications.
Accurate expertise is needed to apply FRMCS-specific system simulations that model service level requirements, antenna parameters, power levels, impact (cell-edge) throughput and intercell distances. These simulations also integrate train speed performance curves and specific configurations (MIMO/beamforming) for both radio base stations and cab radios. Advanced railway radio dimensioning tools calculate link budgets and capacity under realistic scenarios, enabling planners to avoid both over-dimensioning, which can lead to unnecessary costs, and under-dimensioning, which can pose risks to safety and service.
Planning a 5G FRMCS railway network requires a far more holistic approach than GSM-R:
capacity increases are achieved through network densification, not just channel additions
interference mitigation becomes multi-dimensional: site placement, antenna type, antenna tilts, azimuths, and train speed effects
railway-specific track planning is essential: scalable setups, cloud-based IT platforms for automation, and simulation environments tailored for both FRMCS and MNO cooperation
a full digital chain in the planning process ensures accuracy and efficiency, integrating high-resolution railway-specific geodata, calibrated propagation models, and AI-driven optimisation, and
continuous updates of planning guidelines based on evolving industry developments and standardisation ensure that FRMCS deployments remain future proof.
One of the most strategic benefits of thorough FRMCS planning is its role in shaping the most accurate migration path from GSM-R and analogue systems.
In fact, dimensioning enables key strategic approaches such as:
which GSM-R, MNO or analogue infrastructure could be reused, including sites, towers, backhaul links, and power supplies
where new densification is required, particularly around stations, yards, and high-traffic corridors
spectrum usage strategies, bBalancing own FRMCS spectrum with potential PMNO slices, if applicable
service-level requirements for different track categories, from single rural lines to multi-track high-speed corridors, and
redundancy and reliability models, enabling safe coexistence during the transition phase.
This knowledge translates into a solid FRMCS deployment and migration strategy that avoids unnecessary costs, reduces risk, and ensures operational continuity.
The migration from GSM-R to FRMCS is much more than a one-to-one radio layer upgrade – it is a shift in planning philosophy. GSM-R’s coverage-and frequency-based planning served well for voice and limited data needs, but FRMCS demands a multi-dimensional, throughput-driven, and service-quality-focused approach.
By starting with robust dimensioning, using railway-specific simulation tools, and embracing digital planning environments, infrastructure managers can avoid both over- and under-dimensioning, ensure compliance with stringent reliability demands, and position themselves to fully benefit from the potential of FRMCS.
Proper dimensioning and planning are essential to ensure FRMCS delivers on its promise, to offer safe, reliable, and future-proof communications for railways. Just as importantly, these activities provide the foundation for migration strategies that leverage existing GSM-R and analogue infrastructure, while also optimising investments by securing the right amount of trackside radio sites.
In this sense, it represents both the cornerstone for efficient Total Cost of Ownership in FRMCS deployment strategy, as well as the enabler of a smooth transition to digital rail operations and Gigabit trains.
Ericsson believes that digitalisation will empower the rail transport sector to enhance user experience, increase efficiency in day-to-day operations, and maintain network security. Learn more about Ericsson’s innovative 5G network solutions for faster, safer and greener rail travel here
