GSM-R to FRMCS Evolution: A New Era for Railway Communications

The Intelligent railway, characterized by the deep integration of new-generation information technology with railways, is a crucial direction for the high-quality development of the railway industry. The railway-dedicated mobile communication system, as a vital component of the Intelligent railway technology system, is currently undergoing an intergenerational evolution from GSM-R to FRMCS. With the approval of FRMCS test frequencies and the comprehensive rollout of FRMCS tests, China's railway-dedicated mobile communication is entering the 5G era.

FRMCS Ushers in Rapid Development for Railway Construction

China’s railway construction ranks among the world’s leading levels, with rapid growth in high-speed railway mileage. According to the latest statistics from China Railway Corporation, by the end of 2023, China’s total railway operating mileage had reached 159,000 kilometers, including 45,000 kilometers of high-speed railway.

In line with the “Outline of the Plan for Building a Powerful Transportation Country with Railways Taking the Lead in the New Era,” by 2035, the nationwide railway operating mileage is expected to reach 200,000 kilometers, including 70,000 kilometers of high-speed railway. With an average annual construction of 3,500 kilometers, this will create a transportation network that covers cities with populations exceeding 200,000 and ensures high-speed railway accessibility for cities with populations over 500,000, thus establishing China as a powerful transportation country.

Following the conventional practice of adopting new standards for newly constructed railways, the FRMCS dedicated communication network is set to develop rapidly alongside China's future railway construction. Since 2015, China has promoted FRMCS standard projects systematically. In 2020, the China Railway Corporation issued the "Implementation Opinions on Accelerating the Application and Development of 5G Technology in the Railway Industry" and the "Three-Year Action Plan for Scientific and Technological Research on the Application of 5G Technology in the Railway Industry." It also proposed to complete key technological research and develop major equipment for the railway 5G private network by 2023, conduct urgent business tests and trials in areas like safety and travel services, and establish major technical standards. This laid the foundation for the railway 5G private network’s construction and application. With the three-year period now concluded, FRMCS is poised for rapid development.

Advantages of FRMCS Development

As the nerve center of the railway transportation system, railway communication is crucial for ensuring safety and efficiency. Since the introduction of GSM-R technology in the 1990s, railway communication has entered the digital era, providing a solid foundation for railway transportation. However, the rapid development of high-speed railways and the widespread application of cutting-edge technologies such as the Internet of things, big data, and cloud computing have highlighted the limitations of the GSM-R system. Its shortcomings in data transmission rates, network coverage, and device compatibility have made it inadequate for meeting the demands of modern railway communication.

Against this backdrop, the FRMCS technology has emerged, leveraging the advantages of 5G, such as high-speed data transmission, low-latency communication, and the capability to connect massive devices. FRMCS not only provides more stable and efficient communication services but also supports diverse service applications like autonomous driving, remote control, and intelligent scheduling. This significantly enhances the performance of railway communication networks and provides robust technical support for intelligent and automated development of railway transportation.

From a technical maturity perspective, China has achieved remarkable milestones in 5G, with mature and reliable products. By the end of 2023, China had built the world’s largest 5G network, with 3.377 million 5G base stations, serving 805 million 5G users and shipping over 810 million 5G terminals. Module prices have dropped to the hundred-yuan level. In the industrial applications, 5G has penetrated 71 major economic sectors, with over 29,000 virtual private networks, more than 240 industrial Internet platforms, and over 89 million industrial devices connected to 5G networks. Leveraging its substantial progress in 5G development, China is well-positioned to advance the digital transformation of the railway industry. 5G will provide faster and more reliable wireless communication, enhance railway operations and management, and drive modernization and intelligent development in the railway sector.

The transition from GSM-R to FRMCS in railway communication networks represents both an upgrade of existing services and an introduction of new ones, such as multimedia and video communication. Technically, FRMCS outperforms GSM-R in bandwidth, uplink and downlink speeds, system latency, and security performance. Leveraging 5G technology, FRMCS offers up to 20 times the capacity and reliability of of GSM-R, enabling interconnectivity among intelligent devices like trains and signaling equipment. The FRMCS voice dispatching system, a broadband communication system based on IP switching technology, can drive upgrades in dispatching technology and enhance system reliability. Additionally, FRMCS supports network slicing and edge computing, ensuring quality of service for critical railway functions. The "5G" capabilities of FRMCS will also introduce new scenarios and applications, advancing railway informatization.

Future Technological Evolution

The three visions of 5G are enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Currently, 5G supports gigabit speeds and billions of connections. Looking ahead, it will evolve into 5G-Advanced, which aims to deliver terabit speeds and trillions of connections. This advancement will fulfill the three core 5G visions.

5G-Advanced will support key technologies for industrial digital upgrades across six areas: terabit experience, integrated sensing and communication (ISAC), trillion-level IoT, deterministic networking, built-in intelligence, and space-air-ground integration. These technologies will facilitate the 3D and cloud-based transformation of the internet industry, intelligent interconnection of everything, integration of communication and sensing, and flexible intelligent manufacturing. Applying these advancements to railway communication networks will drive the intelligent development of FRMCS (Fig. 1).

• Millimeter Wave

In hotspot areas such as high-speed railway hubs, where communication coverage and capacity are critical, traditional networks are limited. However, leveraging millimeter waves with their large bandwidth and low latency can significantly enhance user experience in these areas, offering the most robust air interface data channel with downlink speeds of 25 Gbps and uplink speeds of 16 Gbps.

Millimeter wave technology can excel in railway vehicle-to-ground data transfer and storage. The millimeter wave-based high-speed vehicle-to-ground data transfer and storage solution establishes an ultra-large bandwidth transmission channel between locomotives and ground data centers. This eliminates the need for manual data transfer after locomotives enter depots, supporting efficient locomotive data transmission and intelligent operation and maintenance. By deploying millimeter wave base stations at stations and depots, the solution enables ultra-high-speed uploading of onboard data to ground data centers. Through internal networks, video data analysts can remotely view, download, and analyze data online, significantly improving efficiency and reducing labor and time costs.

• RedCap Terminals

Reduced capability (RedCap) terminals are designed to simplify terminal devices by reducing complexity, cost, and power consumption while extending their lifespan. This is achieved by decreasing bandwidth, reducing the number of transceiver antennas, lowering transmission rates, adjusting modulation schemes, and introducing half-duplex modes, all while meeting application requirements and performance standards. This approach facilitates the large-scale commercial adoption of 5G networks.

Along railway lines, the communication needs of infrastructure are also significant. In the era of the Internet of everything, enhancing safety requires real-time monitoring of infrastructure, including electrical and engineering facilities. In recent years, natural disasters like floods and landslides have been more frequent along railway lines. To monitor these events, railway authorities have deployed numerous IoT monitoring nodes, which require extensive connections and high-speed video transmission. 5G RedCap is well-suited for this scenario, enabling rapid and cost-effective comprehensive monitoring.

• ISAC Base Station

To ensure the safe operation of high-speed rail, it is crucial to prevent unauthorized personnel and objects from entering the railway track area. Efficient monitoring and protective measures are necessary for high-speed rail security. An electronic fence created with a wireless base station that integrates sensing and communication capabilities can monitor train tracks in real time and prevent unauthorized access, including illegal entry by drones. Currently, the ISAC technology has been validated for low-altitude drone monitoring and vehicle-road coordination, with commercial deployment on the horizon.

As travel needs grow, the importance of railway transportation becomes increasingly prominent. The evolution from GSM-R to FRMCS is specifically designed to address the market’s demand for more efficient, safer, and more Intelligent railway communication systems. With ongoing technological advancements and socio-economic development, we can expect future railway communication systems to be even more advanced and intelligent, providing greater convenience and safety for railway operations.