5G-A mmWave: A New Engine for Digital Transformation of Railways

In 2023, China State Railway Group Co., Ltd. (CHINA RAILWAY)  set clear goals in the "Digital Railway Plan": By 2027, railway digitalization will be significantly improved, with key areas achieving intelligence, a landscape covering business scenarios at all levels, and significant progress in digital railway construction. The top priority in building a digital railway is to enhance the capabilities of digital infrastructure.

The 5G for railways (5G-R) system promoted by CHINA RAILWAY mainly carries critical services such as high-speed train control and command dispatch communications, which are essential for ensuring railway operation safety. However, the capacity of the 5G-R system is limited, focusing on high-priority voice and data services along the railway. While the application scenarios outlined in the "Digital Railway Plan" are abundant and cover all operational aspects of railway business, 5G-R can't fully meet the dedicated network application needs across all railway scenarios. Big data services, such as massive data transfers between locomotives and the ground, as well as intelligent maintenance based on digital twins, require a foundational network with greater capacity and richer spectrum. With its unique technological advantages, millimeter wave (mmWave) is expected to become another significant technology for railway dedicated networks.

mmWave Enables Massive Train-to-Ground Data Dump

Monitoring equipment and data recording for locomotives play a crucial role in ensuring safe train operations and enhancing transportation efficiency. By deploying a series of advanced monitoring systems such as the remote monitoring and diagnostics system, train operation monitoring and management system, and derailment monitoring system, staff at the locomotive depot can collect and analyze real-time data from locomotive operations. This enables them to promptly identify and address potential safety risks, ensuring the safe and stable operation of trains.

Multiple systems on locomotives generate massive amounts of data during daily operations, and dumping this data is a key challenge in railway digital transformation. For example, the locomotive on-board safety protection system (6A system) generates approximately 1 GB of data per camera per hour, meaning that a single locomotive can accumulate about 24 GB of data per day. For locomotives operating continuously for several days, this can amount to hundreds of GBs. Wi-Fi has relatively low transmission rates and cannot support cross-station data transfer. Currently, data dumping mainly relies on manual copying by locomotive depot staff, which is time-consuming, labor-intensive, and prone to errors, increasing safety risks.

To meet these challenges, wireless equipment can be deployed along tracks, leveraging the ultra-wide bandwidth of mmWaves to build an efficient and stable wireless train-to-ground communication system. In particular, the valuable time windows when locomotives are stationary at major stations and locomotive depots can be fully utilized to enable the rapid wireless transfer of onboard equipment data.

ZTE has developed a comprehensive solution for railway bureaus, including a lightweight 5G dedicated core network, a series of wireless products, dedicated mmWave on-board terminals, and a network management system that integrates multiple products, meeting the unified end-to-end management of networks and services.

Data from multiple systems in the locomotive is aggregated and uniformly fed into the mmWave on-board terminal for transmission. Given that the transmission of the locomotive data spans multiple locations, such as stations and locomotive depots, the deployment of mmWave base stations need to be planned in advance to ensure that there are no significant obstructions between the on-board terminals and the base stations. For key locations where locomotives are stationed, 3D digital mapping of the site environment and channel model SLA simulation can be conducted to ensure optimal wireless network coverage and capacity.

In addition, since railway business data is primarily transmitted upwards, the system’s frame structure can be adjusted to 1D3U, allocating more resources to the uplink and increasing the system's uplink throughput several times. After the locomotive data is relayed back to the dedicated core network via mmWave base stations, it can be directly docked to the data analysis system for processing. This innovative solution provides an efficient approach for the rapid transfer and storage of massive amounts of data between the locomotive and the ground.

Compared to traditional Wi-Fi solutions, mmWave offers a significant advantage in transmission speed, capable of transferring large volumes of data much faster—such as completing the transmission of 50 GB data in just 5 minutes. In addition, mmWave uses a dedicated frequency, ensuring that all data remains within the railway company, and guaranteeing data security. The contactless transmission of multiple data streams efficiently aggregates data from multiple systems on the locomotive and transmits it back through an on-board terminal mounted on the top of the locomotive. This innovative technology, which supports segmented data transmission across multiple locations, greatly saves time and labor, bringing unprecedented convenience to locomotive data transmission.

mmWave Creates a Digital Space for Railways

In traditional locomotive maintenance workshops, there are a large number of locomotives with complex workflows, and operators need to perform a series of tedious tasks, such as monitoring locomotive components and debugging various performance parameters. These tasks rely heavily on manual observation and experience, leading to long maintenance cycles and low efficiency. Building a digital twin of the maintenance workshop enables real-time monitoring and in-depth data analysis of operations within the workshop, thereby improving the efficiency of maintenance work. This is undoubtedly a significant step towards digitalization in the railway industry.

To construct a digital maintenance depot, the digital twin system needs to synchronize all workshop data in real time, ensuring consistency between the virtual and real worlds. This requires a wireless network capable of supporting high-speed data transmission and instant feedback, allowing virtual operations to immediately impact physical entities. Due to the relatively small area within the locomotive depot maintenance workshop, ZTE provides a workshop-level 5G minimalist private network solution without the need for a dedicated core network. This solution is centered around the NodeEngine computing base station and the mmWave indoor product Micell, enabling real-time feedback between on-site services and the digital twin platform. The NodeEngine also serves as a lightweight cloud foundation, providing computing resources and a runtime environment for the digital twin platform at a low cost, accelerating the setup, deployment, and capability opening of on-site applications. The physical environment of the locomotive depot maintenance workshop is shown in Fig. 1.

When transmitting complex 3D model data and massive real-time operational data from devices, mmWave, with its superior low-latency characteristics, ensures that the digital twin platform operates smoothly without lag or delay during control and operation. This not only effectively prevents operational errors but also ensures seamless integration and consistency between the virtual and physical worlds.

Combining mmWave with digital twin technology enables real-time acquisition of dynamic data from the entire maintenance workshop, which is then fed back to the digital twin platform as a high-precision 3D model. This provides operators with unprecedented visual insights, enabling them to easily understand the internal structure of locomotives and the complex relationships between the components, allowing them to accurately identify potential failure points and predict maintenance needs, thereby enhancing the efficiency of preparation operations.

mmWave Brings More Possibilities

In November 2024, China’s Ministry of Industry and Information Technology and 11 other departments jointly launched an upgraded plan for the large-scale application of 5G. This second “set sail” action plan states that the construction of 5G dedicated networks will be promoted, and the innovative applications of 5G mmWave technology in key sectors such as manufacturing, railways, mining, and the defense industry will be explored. In this blueprint, mmWave is assigned a new mission to drive industry innovation and lead digital transformation. As mmWave technology and its industrial chain mature, its gigabit-level uplink transmission rate and millisecond-level network latency provide a solid technical foundation for the digital transformation and upgrade of railways.

In the railway industry, the application prospects of mmWave are extremely broad. It not only significantly improves the efficiency and security of locomotive data transmission, but also demonstrates enormous potential in key areas such as intelligent maintenance and automated inspections, driving the railway industry toward a smarter, more efficient, and safer future.