Description
The Future Railway Mobile Communication System (FRMCS) is a comprehensive set of 3GPP specifications defining the next-generation communication system for railway operators. It is designed as a direct evolution and replacement for the aging GSM-R (Global System for Mobile Communications – Railway) standard. Architecturally, FRMCS is not a standalone network but a service profile and application framework that utilizes 3GPP's 4G LTE and, primarily, 5G System (5GS) as its underlying bearer network. The core system components include the FRMCS Equipment, which is a 3GPP User Equipment (UE) – such as a modem or onboard unit – with a dedicated FRMCS Application client, and the corresponding FRMCS Application Server in the network.
The FRMCS Application provides the specific railway operational services, such as Mission-Critical Push-To-Talk (MCPTT), Mission-Critical Data (MCData), and Mission-Critical Video (MCVideo), as standardized by 3GPP for public safety, now tailored for railway operational needs. These applications run over 3GPP's IP Multimedia Subsystem (IMS) for voice and multimedia services and leverage the 5G core network's capabilities like Network Slicing, Ultra-Reliable Low-Latency Communication (URLLC), and enhanced Mobile Broadband (eMBB). A key architectural aspect is the support for dual connectivity or interworking with legacy GSM-R networks during the transition phase, allowing trains equipped with combined FRMCS/GSM-R devices to maintain continuous service.
How it works involves the FRMCS UE attaching to the 5G network, potentially using a dedicated network slice configured for railway operational services with guaranteed Quality of Service (QoS). For voice calls, the UE registers with the IMS core. When a driver initiates a group call (e.g., to a dispatcher), the FRMCS Application uses the MCPTT protocols over IMS to establish a low-latency, high-priority session. For critical data, such as European Train Control System (ETCS) signaling, the network provides a dedicated QoS flow with URLLC characteristics, ensuring packet delay and reliability targets are met even at high speeds. The system also defines specific railway-centric functionalities, such as functional numbering, location-dependent addressing (calls to a specific track section), and shunting mode operations.
Purpose & Motivation
FRMCS was created to address the technological obsolescence and limitations of GSM-R, which is based on 2G GSM technology. GSM-R, while highly reliable for voice and basic data, lacks the bandwidth, latency performance, and flexibility needed for modern digital railway applications. The limitations of GSM-R include insufficient capacity for video surveillance, inability to support high-speed data exchange for predictive maintenance and passenger information systems, and an end-of-life roadmap for its underlying 2G technology by many network operators and equipment vendors.
The primary motivation for FRMCS is to future-proof railway communications by leveraging the global scale, continuous innovation, and economic benefits of the 3GPP ecosystem, particularly 5G. 5G provides the necessary technical foundations: network slicing to create logically isolated, dedicated networks for railway operations on a shared physical infrastructure; URLLC for safety-critical control signaling; and massive IoT support for widespread sensor deployment. This transition enables new operational models, such as moving block signaling (which requires continuous, high-integrity train-to-ground communication), automated train operation (ATO), and real-time video feeds from trains and trackside for security and situational awareness.
Furthermore, FRMCS aims to ensure interoperability across national borders within Europe and globally, reducing costs and complexity for railway operators and rolling stock manufacturers. By standardizing within 3GPP, it avoids vendor lock-in and fosters a competitive market for equipment. Its creation was driven by the International Union of Railways (UIC) in close collaboration with 3GPP, ensuring the standards meet the specific, stringent safety and operational requirements of the railway industry, which are as critical as those for public safety networks.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (29 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-15, normative work from Rel-16.
In Release 16, 3GPP introduced the foundational system definitions and requirements for FRMCS to serve as the future successor to GSM-R. This included specifying the FRMCS system architecture, defining key entities like FRMCS Users, Equipment, and Functional Identities, and outlining core communication services such as mission-critical voice and data for railway operations. The release established the framework for on-network and off-network communications to support railway-specific applications like train control and shunting.
- CR to TS 38.104: Addition of BS performance requirements for URLLC PUSCH repetition Type A TS 38.104CR0249
In Release 17, the normative work for the Future Railway Mobile Communication System (FRMCS) focused on completing the analysis and specification of On-Network communication requirements. This built upon the foundational architecture defined in earlier releases, formally detailing the system components like the FRMCS User, FRMCS Equipment, and the FRMCS Network to support railway-specific services. The release thereby advanced the standardization of the system intended to succeed GSM-R, aligning requirements with existing 3GPP mission-critical communication frameworks.
- Big CR for TS 38.104 Demodulation requirements for Enhanced IIOT and URLLC support (Rel-17, CAT B) TS 38.104CR0426
- Complete analysis for Rel-17 On-Network FRMCS requirements TS 22.889CRSP-200882
- CR to TS 38.104: Correction of BS performance requirements for URLLC PUSCH repetition Type A TS 38.104CR0279
In Release 18, FRMCS introduced new capabilities for Railway Emergency Communication by adding MCX Service Ad hoc Group Communication as an alternative method. It also enhanced interworking with the legacy GSM-R system, specifically for procedures like inviting a FRMCS user to a voice communication and removing the requirement for presence service interworking. Furthermore, the release defined mechanisms for dynamically changing a user's communication privileges based on their identity or talker status and provided clarifications for NB-IoT operation in railway base stations.
- Adding MCX Service Ad hoc Group Communication as alternative capability to support Railway Emergency Communication TS 22.989CR0012
- Changes to Critical Support Applications “Inviting-a-FRMCS User to a voice communication” use case TS 22.989CR0002
- Merging of Railway Emergency Communications TS 22.989CR0003
- Changes to Critical Support Applications Inviting-a-FRMCS User to a voice communication use case to support Interworking with GSM-R TS 22.989CR0004
- Triggering a change of communication privileges for a particular FRMCS User based on identities and/or talker status TS 22.989CR0008
- Alignment between Changing conditions of Railway Emergency Alert and Merging Railway Emergency Alert TS 22.989CR0010
+ 3 more changes
In Release 19, the FRMCS function was enhanced with new use cases and definitions, including support for Virtual Coupling data communication and expanded emergency communication procedures for both public trains and railway staff. The release also introduced updates for multi-train voice communication, Quality of Service (QoS) parameters in a railway environment, and the FRMCS naming authority. Furthermore, it provided refined definitions for Smart railway concepts and conducted a gap analysis for emergency alert and communication arbitration use cases.
- Virtual Coupling data communication use case TS 22.989CR13
- Public Train Emergency Communication related use cases TS 22.989CR17
- Railway staff Emergency Communication related use cases TS 22.989CR18
- Enhancement and clean-up of Railway Emergency Communication related use cases TS 22.989CR16
- Enhancement of Multi-train voice communication for Drivers and Ground FRMCS User(s) related use cases TS 22.989CR0019
- Update of QoS in a railway environment Use Case TS 22.989CR0021
+ 5 more changes
In Release 20, FRMCS introduced new use cases and updated requirements for multi-train voice communications, specifically focusing on Ad hoc Group Communications. The release defined new procedures allowing a Train Controller or a Train Driver to merge two multi-train voice communications, and enabled a driver to take over an Ad hoc Group Call from another FRMCS device. Furthermore, it added a use case for indicating the availability status (presence) of a Mission Critical user, which in this context is a FRMCS User.
- New use cases: Merging of two multi-train voice communications by Train Controller (Ground FRMCS user) TS 22.989CR0033
- New use cases: Merging of two multi-train voice communications by the train driver TS 22.989CR0037
- New use case: Availability status of a MC User (Presence of a FRMCS User) TS 22.989CR0038
- New use case: Train driver takes-over an Ad hoc Group Call from another FRMCS device TS 22.989CR0036
- Update of requirements and gap analysis for multi-train voice communication for Drivers and Ground FRMCS User(s) using Ad hoc Group Communications TS 22.989CR0032
Explore further
Broader topics and technologies where FRMCS plays a role.
Defining Specifications
3GPP specifications that define or reference FRMCS, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 22.889 vh40 | FRMCS Study; Stage 1 | Rel-17 |
| TR 22.890 vj00 | Study on Railway Smart Station Services | Rel-19 |
| TR 22.989 vk30 | FRMCS Analysis and Requirements | Rel-20 |
| TS 23.790 vf00 | FRMCS Gap Analysis and Architecture Enhancements | Rel-15 |
| TR 37.829 vi00 | Technical Report | Rel-18 |
| TS 38.104 vj20 | NR Base Station RF Requirements | Rel-19 |
| TS 38.141 vj20 | NR Base Station RF Conformance Testing Part 1 | Rel-19 |