The 5G mobile network is touted as the panacea for all types of backhaul problems, particularly if they're wireless. However, anyone who's been in the industry for a while is familiar with this story, which is often and best represented by the Gartner hype cycle.
I recently attended the biannual global rail trade show and conference, InnoTrans, which included a 5G workshop. In the opening session, many of the trade associations supporting the rail industry presented short summaries. Germany’s ZVEI, which represents its electro (including process control) and digital industries, reported it sees three trends driving industry: demography, decarbonization and digitalization.
The presenter suggested a fourth, diversification (of supply chain) as a driver for why we need the constant connectivity represented by the promise of 5G.
These opening keynote comments were appropriate because the “5G in Mobility” workshop was about how trains will require more bandwidth than is possible with the existing 1990s GSM-R-based standard for telecommunication services, particularly as autonomous trains become more common in the future. A key building block within the European Rail Traffic Management System (ERTMS), GSM-R has limited bandwidth.
With the increased need for more throughput, high-capacity and flexible deployment options, the International Union of Railways (UIC) and the European Union Agency for Railway (ERA) initiated working groups and specification activities to define the successor of the GSM-R radio communication system deployed on rails, called Future Railway Mobile Communication System (FMRCS). ERA worked with the UIC to charge 5GRail to develop and pilot the systems.
The FRMCS vision is to cover mission-critical railway communications by enabling an on-board mobile communication system for railway operators, including critical rail communications for ETCS and autonomous train operation (ATO). It's also intended to secure an emergency voice communications between driver and signaler or other groups, the “transport stratum” as well as the “service stratum.” In addition, it's intended to provide higher bandwidth performance communications to support on-train telemetry, maintenance of non-critical infrastructure, non-critical real-time video and similar applications, as well as business communications to enable applications such as information to the public and passenger communication connections.
The transport stratum is realized via 5G and forms the transmission layer for the service stratum, which is based on the current 3GPP Release 16 mobile communications standard and implemented via the 3GPP Mission Critical Services (MCx) framework. It's the MCx framework that provides additional functions such as authentication, group calls and video transmission, which are needed by existing and future railway applications such as automated driving or artificial intelligence (AI) based traffic management.
The service stratum uses hybrid network architectures in which a public mobile network serves as a fallback layer or as a capacity complement to the railway’s own mobile network.
Germany has allocated 100 MHz at the 1.9 GHz portion of the 5G spectrum for the critical components of FRMCS. The balance and emergency/overload will be seamlessly passed over to mobile carriers 5G network. Germany also has legislation for carriers to provide a minimum of 250 MB/s bandwidth along all rail right of ways from which the remaining requirements can pull at a priority over passenger network access.
The ERA mandated updating of the technical specifications for Interoperability of Control Command and Signaling (CCS TSI) (FRMCS V1) by the end of 2022 with a full description of FRMCS with respect to interoperability functions. 5GRail recently tested a 5G-based (FRMCS) communication network, after a mission-critical, push-to-talk (MCPTT) call was successfully made over a newly built 5G standalone cellular network using the allocated 1.9 GHz radio spectra.
