The Digital Railway and FRMCS

There is a lot of news in the press concerning the ‘digital railway’ as if this is a recent development.  In fact the digital railway came into being with the first operational implementation of GSM-R in 1999.  The International Union of Railways (UIC) describe GSM-R as ‘the bearer for the first Digital Railway Radio Communications System’.  GSM-R is a second generation (2G) digital radio system based on the commercial GSM mobile telephony system, but adapted for use on the railways.  It have been hugely successful across Europe, being used in over 20 countries across 100, 000 Km of tracks and this number is expected to double in the next few years due to the ongoing installations across the world including locations such as Algeria, Saudi Arabia, India, China and Australia.

However, the technology is more than 20 years old and equipment vendors have indicated that they no longer wish to support their product range beyond 2030.  The commercial mobile operators have progressed from 2G through 3G, 4G and are now deploying 5G systems.  2G systems like GSM-R were designed for voice communications and low bit rate data services.  More recent technologies such as 5G are designed as flexible mobile broadband systems capable of supporting a range of applications from low bit rate data and voice through to applications demanding hundreds of megabits of data.

GSM-R was intended to be the bearer for the European Train Control System – an advanced train control system designed to replace all of the dissimilar signalling systems in use across European railways.  GSM-R and ETCS are two key parts of a major European project known as ERTMS – the European Rail Traffic Management System – this project will keep railway engineers busy until 2040 and beyond.  In view of the potential demise of GSM-R in 2030 a successor for GSM-R is required.

Another UIC project is underway and is known as FRMCS – Future Railway Mobile Communications System.  The project kicked off in 2012 with the publication of a UIC document called the User Requirement Specification (URS) which was designed to capture the user requirements for communications in the railway.  FRMCS is not simply a replacement for GSM-R it represents a huge opportunity to support many applications in the railway environment.

The latest version of URS is known as FU 7100-v5.0.0 and was published in May 2020.  This document will then be used to create ‘functional uses cases’.  Use cases are needed for two reasons; firstly they will be used to develop the Functional Requirement Specification (FRS) and in turn the System Requirement Specification (SRS).  The SRS is necessary to satisfy the European Directives with regard to interoperability across European railways.  Secondly, the use cases can be presented to ETSI and 3GPP for ‘gap analysis’.

The UIC state the FRMCS should be technology agnostic.  But it doesn’t make sense to develop a new technology when 3GPP have a suite of standards focused on Mission Critical Communications (MCX).  The gap analysis uses the use case documents to see which existing standards are applicable to FRMCS and what work needs to be done to address the communications needs of the railway community.

The FRMCS project is well underway with a FRMCS demonstrator planned for 2023 and the first national trials beginning in 2024.  The timescales are very short and there are a number of challenges that FRMCS faces but the benefits to the railway is extensive.