5G & Rail: The Road to the National Championship

On October 17, 2023, China's Ministry of Industry and Information Technology (MIIT) kicked off the final of their annual 5G application competition in Shanghai. This year's 6th "Blooming Cup" Competition challenged participants to think about how "5G Drives Digital and Real Economy Development" and find new solutions that would deeply integrate 5G into industrial digital transformation.

Of the 45,728 projects submitted from across China this year, Wuhan Metro's 5G-powered Smart Urban Rail project stood out and took first prize. The project's application of public 5G networks in rail transit attracted significant praise from state agencies, China's carriers, and enterprises in related fields, as it presented a novel, and more importantly, feasible, business model for public 5G networks.

This 5G-powered Smart Urban Rail project, while a success, had not progressed without its own challenges and setbacks. And so, the summary presented at the Blooming Cup interested many as it answered two important questions: How did China Mobile persuade a customer from the rail transit industry to put its services on a 5G network? And, what implications did this project's success have for future 5GtoB services?

The road to a national championship

China Mobile initially kicked off this project to figure out how to market connectivity to the rail transit industry. As they dug deeper into how the industry's complex production systems worked, however, it became clear the project needed to refocus on broader industry digitalization, as true success could not be achieved by targeting an individual metro company – they needed to target the industry as a whole.

China Mobile had previous experience in 5GtoB services. They knew that industry customers often need patient persuasion before they decide to adopt 5G. They needed to take a chain-like approach to bridge gaps in the industry, going slowly and steadily in the early stages to pave the way for a boom in adoption at the later stages. They broke this strategy down into three parts:

First, they had to identify a correct overall direction at the beginning of the project. Once that direction was defined, all further efforts had to strictly stay the course. China Mobile chose the rail transit industry based on the logic presented in Figure 1. Many carriers are installing 5G networks in metros, but those network resources are often not being fully utilized due to the tidal effect in the number of passengers at different time periods. Traffic analysis showed that the physical resource block (PRB) usage of carrier 5G networks along most metro lines is only at about 20%.

At the same time, metro operators traditionally build their own private networks, which can cost over 1 million Chinese yuan per kilometer of track. Metro wireless network bandwidth is also typically not large enough to carry more data services, and the network can only run in a best-effort manner. Service data that cannot be transmitted needs to be manually copied, which increases OPEX. Idle carrier network resources can be leveraged to address this private-network bandwidth problem—one of the biggest headaches of metro operators. Fully transitioning to carrier networks, which could simultaneously serve multiple purposes, presented a win-win situation.

A smooth and workable business model required thorough analysis to determine the base logic. Once the general model was decided, China Mobile was able to call upon resources from across the industry to address the specific challenges that arose during implementation.

The second step was to establish a defined industry ecosystem to better aggregate industry resources. 5G application generally needs significant support from not only the carrier industry, but also the target industry. The more robust the industry ecosystem, the more collaborative resources they had to achieve shared success.

Industry adoption of a new technology is never just a technical matter. It has to be tackled from both the technological and the commercial ends. Technologically, carriers must ensure that industry customers are confident about 5G. 5G network slicing had already been piloted with Nanjing Metro, using dedicated resources to carry rail transit services. That pilot project set a benchmark that improved the industry's confidence. Carriers' existing expertise in 5G cybersecurity from other industries has also improved the rail transit industry's trust in the reliability of these services. Commercially though, many of China's carriers had years of experience in leasing, instead of building, networks that can best serve another industry. Under this model, customers pay carriers annually to use carrier 5G networks for around the same total cost as building their own traditional network.

By combining the technological and commercial elements, China Mobile was able to resolve 14 of the key problems facing the rail transit industry within just 3 years. This finally paid off in the Wuhan Metro project.

The third step was to develop scenario-based solutions to resolve key implementation issues. 5G networks are designed to essentially amplify connectivity for terminal devices, but data connections alone do not create real value. To effectively support metro operation services, technologies like AI, big data, and integrated communications were also needed to make the collected data a key part of production. Industry customers who actually use these solutions are most concerned about the practical value that they can create. The development of dedicated public 5G networks in Wuhan Metro therefore underwent three phases: reshaping connectivity, reshaping the platform, and building intelligence (Figure 2).

The 6th "Blooming Cup" Competition has helped promote 5G applications and explore new business models. Dedicated public 5G networks have been recognized across the rail transit industry as a feasible solution.

Planning is key

The bidding for the 5G 800 MHz trunking communications on Wuhan Metro's Line 19 was completed in early 2023. Since then, many other metro operators in China initiated similar projects. For example, Shanghai Metro plans to have all of its 23 lines covered by a dedicated public 5G network by the end of 2024. Guangzhou Metro also plans to expand the scope of its existing coverage from a single line to their entire metro system. Other cities have also produced blueprints for future rollout, including Nanning, Wuxi, Tianjin, and Suzhou. The clear industry demand presents large opportunities for dedicated public 5G network projects, but carriers still struggle with implementation speed and customer confidence.

Notably, this project has provided carriers with clear principles for future planning.

First, business models: The business model design must be based on actual service scenarios to keep the price of 5G reasonable for the target customer industry. In metro rail, a complete dedicated public 5G network project covers two parts: main lines and rail yards. For carriers, the cost of providing private network services mainly includes the following items:

1. C (Construction cost): The full cost of ensuring full coverage of new unmanned sections like train depots and turn-back tracks
2. B (Basic sharing): The cost of deploying public 5G networks that are under construction
3. X: The percentage of the public 5G network's uplink resource blocks used by metro operations within a security baseline
4. A (Annual fees): The fees charged for assurance services, such as slicing service, network optimization, and network maintenance over a 10- to 15-year period
5. T: Off-peak usage duration

The cost of using dedicated public 5G networks can then be calculated as:

C + B × X + A (by bandwidth)

or C + B × T ÷ 24 + A (by time)

Given this, the cost of using wireless 5G network resources on demand roughly equals that of building the metro operator's own wireless private network. Leaving resources unused outside metro service hours wastes 5G coverage along the line. Metro operators can also apply unmanned inspection robots to tunnel inspection, which use 5G networks for data backhaul, achieving unmanned and remote operations.

For metro ground services, 5G can provide the following alternative private network capabilities (Table 1).

The second principle relates to the network solution. To support train-ground backhaul services, 5G network transport must meet SLA requirements. For individual users, disconnections and dropped calls are not likely to cause serious loss. However, carrier 5G networks must ensure the services they carry are always available. Metro operators need these high-quality network capabilities to ensure continuous 5G access. They are also key for further application development. During the Wuhan Metro project's bidding, the key factor that drove the customer to choose China Mobile was not price, but network reliability, availability, system security, and data redundancy design.

China Mobile uses a customizable five-domain 5G network slicing solution that addresses the tidal effect in metro services. This solution consists of three steps: service analysis, existing network assessment and optimization, and slicing customization and provisioning.

During service analysis, plans are based on the actual needs of metro backhaul services. Depending on how services are used, services can be classified into three types: real-time services, quasi-real-time services, and off-peak services (Figure 3). Real-time services are identified and basic bandwidth is provided to guarantee these services.

During existing network assessment, they analyze the 5G networks already deployed in metro facilities. Due to the tidal effect in passenger traffic, network resource usage also sees peaks and troughs. By accounting for these traffic flows, they can use carrier networks for quasi-real-time metro services during off-peak hours. At night, when the trains are not in service and tunnel networks are completely idle, carrier networks can be utilized for the backhaul of off-peak services. This model maximizes the utilization of 5G network resources and reduces costs, and can be quickly replicated by the rest of the industry.

Finally, during slicing customization and provisioning, they determine time- and space-based 5GtoB service policies through network analysis (Figure 4). By setting parameters for each of the three domains – wireless network, transport network, and core network – they can guarantee SLAs for industry applications. The dedicated public 5G network slicing solution is customized for metro service scenarios to maximize resource utilization. This solution monitors the resource availability of each cell at different periods, and provides time- and space-domain service policies. It also sets up automatic parameter configuration for the core and wireless networks to implement a site-specific service design.

The third principle from this project relates to value-added innovation. An example of such innovation can be seen in the figures below, which show a 5G-based leaky cable positioning solution that aims to support positioning in rail transit (Figure 5). Customized leaky cable and wireless UTDOA features can help position people and vehicles in rail areas. People positioning is mainly used by maintenance personnel to accurately and quickly locate faults during track inspections. Vehicle positioning is used by the pantograph monitoring and O&M system to locate faults during train operations. Many metro systems currently use axle counters and UWB base stations for positioning, but this is costly, requiring about 2 million Chinese yuan in investment per line (for a standard 30-kilometer line). In contrast, utilizing the 5G networks already deployed in tunnels for positioning allows metro operators to save the cost of building their own UWB networks.

The success carriers are finding in rail transit is an important step in realizing the full value of 5G. The dedicated public 5G network model is rapidly becoming the new standard for the rail transit industry, and one that can potentially be applied to more scenarios, including civil airports, high-speed railway stations, and healthcare campuses.

More technological advancements and the promotion of other successful applications will help 5G continue creating value in more fields and help industries go digital and thrive.