FRMCS FFFIS — Form Fit Functional Interface Specification (FFFIS-7950)

Scope

Defines the Form Fit Functional Interface Specification for the Future Railway Mobile Communication System (FRMCS), the 5G-based successor to GSM-R being standardised for the RMR (Radio Mobile Communication) part of the CCS TSI. It specifies the functional interface for FRMCS user equipment and the onboard/trackside radio applications feeding future ETCS/ATO radio bearers, and is developed by UIC and hosted by ERA among the informative CCS TSI specifications.

The FRMCS FFFIS (Form Fit Functional Interface Specification, reference FFFIS-7950) defines the functional interface for the Future Railway Mobile Communication System, the 5G-based successor to GSM-R being developed to serve as the long-term Radio Mobile Communication (RMR) bearer for ETCS, ATO and other railway applications. It specifies the functional interface between FRMCS user equipment and the onboard and trackside radio applications that will use the future FRMCS bearer, laying technical groundwork for the eventual migration of ETCS and ATO radio communication away from GSM-R, whose long-term equipment availability is a known industry concern. It is developed by UIC's FRMCS Programme and hosted by ERA among the informative specifications of the CCS TSI, reflecting that FRMCS is still an evolving specification rather than yet being a fully mandatory Annex A requirement in the way the core ETCS SUBSET specifications are. Railway undertakings, infrastructure managers and radio equipment suppliers planning for the GSM-R-to-FRMCS transition use it to understand the target functional interface FRMCS equipment will need to support. The current edition is version 2.1.0, published in 2025 and freely downloadable without registration.