5G wireless communications will be a big part of the railway industry’s future. 5G systems will provide many new capabilities, higher reliability, lower latencies and ultra-broadband connectivity to support many new and important applications. But making 5G a reality and moving on from GSM-R or other legacy radio technologies is complex. The questions are, how soon, and what is the best route to get there? There are different aspects of the transition to consider.
The railway industry has long used wireless communications as part of its essential infrastructure. Originally specified in 2000, GSM-R has been the most prevalent system outside of North America, used on more than 13,000 route-miles on a daily basis, worldwide. But, as it is based on 2G+ mobile technology, GSM-R is getting a bit long in the tooth, especially as mobile network operators are now moving from 4G to 5G in most of the world.
In North America, there have been a variety of wireless technologies, with VHF and UHF still being used for voice communications. In the U.S., for example, Positive Train Control (PTC) uses the 220 MHz band, and Locotrol (for Distributed Power) uses 900 MHz.
With this in mind, the UIC, the railway standards-setting organization for just about everywhere globally except North America, is developing a standard that would replace many of these systems. It’s called the Future Railway Mobile Communications System (FRMCS). While the vision for FRMCS is to be functional without stipulating a particular technology, it is evident that 5G will be its foundational communications technology. Previous technologies such as GSM-R will be migrated to FRMCS. However, FRMCS is not merely a replacement for GSM-R, as it will introduce new capabilities such as support for smart maintenance, virtual coupling and monitoring of trackside components, among others.
5G Is Coming
The transition from GSM-R to FRMCS is expected to begin in 2025 and continue through 2035. The first national trials for the new system will only begin in 2024. In the meantime, where does this leave railways in terms of implementation?
The 5G communications standard, as set by 3GPP (3rd Generation Partnership Project, the mobile industry standards body), is a bit of a moving target, which can make things confusing for those outside the telecommunications industry. First, there are two versions of the standard, 5G Non-Standalone (NSA) and Standalone (SA). NSA operation is aided by existing 4G infrastructure.
This year, many mobile network operators are launching 5G services based on 5G NSA. This will provide new, higher-broadband services for consumers—think better video on smartphones—but it does not make the more complex changes needed in the network core that will be required for 5G SA.
The FRMCS railway standard will be based on 5G SA, which will not be fully defined until two future releases (R.16 and R.17) are agreed upon by the 3GPP. Thus, 5G SA is not expected much earlier than 2023. These two future releases will contain many of the features to support industrial applications, including European Train Control System (ETCS) data and automatic train operation (ATO).
How Best to Get There?
Do railways have to wait until 2025 to begin the move to 5G? Not necessarily.
There is a long way to go from GSM-R’s 2G+ technology to 5G, and a few things have changed over the intervening decades. Most notably, 4G/LTE, being a full IP (Internet Protocol) packet-based radio technology, provides a compelling phase for all mobile network operators to modernize their transmission networks and backhaul to IP networking.
This means that, for many railways, they can prepare for the move to 5G by upgrading their transmission network to IP/MPLS (Multi-Protocol Label Switching), and putting in more bandwidth in terms of optical, microwave and Ethernet. This will enable them to support new applications, such as multimedia broadband services, or CCTV security multicast services immediately, and with the same resilience and predictability of TDM (Time-Division Multiplexing) systems.
Those outside of Europe,who have less dependency on cross-border interoperability (which was one of the foundation principles to the adoption of ERTMS, European Rail Traffic Management System, for all European Union Member States), can also go directly to LTE/4.9G on the wireless side. By enabling the replacement of GSM-R or other legacy systems as they choose, this allows them to start implementing new use cases and testing new systems.
Advanced LTE, also known as 4.9G or pre-5G, can already support many of the mission-critical features needed by railways, including higher data rates and low-latency automation. Such a transmission network could support either LTE/4.9G now or 5G in the future.
For some railways, this may be the preferable route to 5G, because by breaking the transition into stages, it relaxes the adoption curve for operations. Breaking it into smaller chunks spread out over 10 or 15 years will be less costly and mitigate the overall risk.
Another step in this process would be to deploy a cloud-native core network. Cloud-native, virtual networks have many advantages, including the ability to scale quickly and assign resources to any application based on its explicit use case requirements. It makes the network extremely flexible and far easier to evolve, depending on future requirements.
However, virtual networks are software-driven and require different skill sets for the network operational team. In other words, they also have their own learning curve and transition period, which may be better to confront sooner rather than later.
Once the IP/optical transmission network and cloud-native core are in place, adopting full 5G SA would involve some small modifications to the core, and installation of new 5G radios. It’s important to understand that, except for the LTE radio network, all three of these pieces will be required to support 5G SA, even if railways do decide to do it all at once. And the LTE network might be usable for a decade or more, with 5G SA only being implemented where specific use cases demand and the LTE network continues to be used where it meets many of the basic requirements.
However railways choose to get there, 5G-based FRMCS offers a major opportunity to transform for the better. Combining high speed and extreme traffic handling capacity, together with ultra-low response times, high reliability and support for massive machine type communication (IoT), it will allow railways to improve safety, optimize costs and make their services more attractive. Its capabilities will make the telecommunications network the cornerstone of the railways’ ambitions for digital transformation.
Karsten Oberle received a Dipl.-Ing. (FH) degree in communications engineering from the University of Applied Sciences “Fachhochschule für Technik,” Mannheim, Germany, in 1998. In the same year, he joined the Alcatel Research Center in Stuttgart and worked for Bell Labs Research in various positions until 2015. Oberle acts globally as Head of Rail within Transportation Sales in the Nokia Enterprise TEPS (Transportation, Energy and Public Sector) Division. He is responsible for expanding Nokia’s business in the Railway Sector with current focus on the Future of Rail Communication (e.g. FRMCS, 5G), on cybersecurity for railways and IoT & Analytics (Internet of Things) for Railways. This includes building and managing new sales programs, steering of global business development activities and guiding regional sales and marketing teams on customer engagements.