The Digital Railway supported by FRMCS

As discussed in our earlier post, the long-standing 2G cellular standard for rail communication, known as the Global System for Mobile Communications–Railway (GSM–R), remains in use across Europe, China, India, Africa, and Australia. However, software and hardware vendors predict that this early digital cellular technology will start to be phased out in 2025, as a new 5G-based system specifically for railway applications is expected to be introduced.

According to the European Union Agency for Railways (ERA), GSM–R supports communication between train drivers and traffic control centres with features such as group communication, location-dependent addressing, priority levels, railway emergency calls, and shunting communication. This system enables data transmission between trains and control centres at speeds exceeding 300 mph.

Yet, GSM–R is beginning to show its age. While it is adequate for basic voice communication, its 4 MHz bandwidth, which supports multiple 200 KHz channels, limits its functionality. Downlink communications use the 876–880 MHz range, while the uplink operates at 921–925 MHz.

The maximum data transmission rate for GSM–R is just 9.6 kbit/s, making it unsuitable for real-time data communication. Its capabilities are essentially limited to sending SMS text messages, with little capacity for anything more advanced.

The Future Railway Mobile Communication System (FRMCS), a 5G-based successor to GSM–R, will provide both voice and data services for railway communications. The FRMCS project is being led by the International Union of Railways (UIC) in collaboration with major rail infrastructure companies and telecom solution providers. It is set to be based on the 5G 3GPP standard, meaning it will not require a railway-specific cellular network technology.

FRMCS, which will use the standalone 5G NR specification, is expected to be finalised by the end of 2022. This new standard will operate on harmonised frequencies at 900 MHz and 1900 MHz to ensure interoperability for rail command and control systems as they transition from GSM–R to FRMCS.

This seems questionable from @SNCFVoyageurs

Asserts that train operational comms is mostly uplink & user connectivity downlink, so OK to share FDD public networks

Hmm. Growing use of uplink data from public usage, often with low latency needs pic.twitter.com/JNxHVJvaNL

— Dean Bubley (@disruptivedean) November 14, 2023

Mobile network operators will also be able to offer 5G connectivity for train passengers, collaborating with railway companies to provide the high-bandwidth digital services needed to streamline modern train operations.

Currently, many rail operators offer Wi-Fi onboard or install repeaters to enhance mobile network coverage within carriages. However, these solutions can be costly to maintain and upgrade, and repeated signals can cause interference when train doors open. An alternative solution is for public mobile operators to provide passenger connectivity through their existing 5G networks, with additional 5G towers placed along major rail lines.

To improve 5G signal penetration, train windows can be fitted with special “5G-friendly” glass, which allows signals to pass through more easily (standard window glass is often coated to reduce solar radiation inside the carriage). This approach reduces the need for expensive Wi-Fi and repeater systems, enabling mobile operators to deliver high-speed broadband services to passengers more efficiently.

In their webinar last year, Wray Castle stated that FRMCS is not simply a replacement for GSM-R nor is it a single specific technology. In fact, UIC have stated that FRMCS is technology agnostic. The webinar discussed:

• What is FRMCS and how does it differ from GSM-R?
• How soon will railways be replacing GSM-R?
• Is there a migration strategy?
• Do we have sufficient radio spectrum?
• What is the most probable technology that will be used?

The video of that is embedded below:

Wray Castle also conducts regular courses on this topic. Details here.

Related Posts:

• The 3G4G Blog: Future Railway Mobile Communication System (FRMCS)
• Connectivity Technology Blog: Future Spectrum Demand for Rail Communications
• Connectivity Technology Blog: 'Gigabit Innovation Track' (GINT) Gets Green Light in Germany