At the speeding edge: How railway digitalization is on the rise in India

The Vande Bharat Express is India’s first semi high-speed train operating between New Delhi and Varanasi, a city about 760km from the capital. Launched in February 2019, the journey of the Vande Bharat Express is not only the story of developing India's first world class, semi-high speed, intercity train – completely conceptualized, designed, and manufactured in India. It also marks the starting point of overhauling the legacy railway signaling system by moving towards the locally developed, digital Automatic Train Protection (ATP), and Train Collision Avoidance systems (TCAS). Long term, the vision also includes the implementation of fully digital railway operations and mobile broadband-based passenger services. 

Like many European countries, India is looking to embrace 3GPP Long Term Evolution (LTE) and New Radio as a future-proof base technology for railway applications. This will also allow Indian Railways to adopt many of the features planned for the Future Railway Mobile Communications System (FRMCS), the global standard for railway communications and a key enabler for global railway digitalization.

FRMCS is the future worldwide telecommunication system designed by the International Union of Railways, and in cooperation with the different stakeholders of the rail sector.

First, let’s look at how 3GPP technologies help to adopt FRMCS features.

Railway innovation: Automatic train protection and train collision avoidance

ATP and TCAS systems provide enhanced safety and allow trains to travel safely at very high speeds.

• ATP prevents accidents that stem from collision, signal passing at danger, and over-speeding. ATP continually checks that the speed of a train is compatible with the permitted speed indicated by train signaling, and activates emergency braking in case the train exceeds the speed limit.
•  TCAS processes positioning and sensory data to detect dangerous situations that may have been caused by human error or equipment failures. Without TCAS, trains cannot travel safely at speeds above 160kph as the driver is unable to react fast enough to lineside signals. With TCAS in place, the Vanda Bharat Express can travel faster and safer.

Just like the Vanda Bharat Express, ATP and TCAS are developed and manufactured locally, in this case by Indian research organizations and vendors, and are similar in their functionality to the European Train Control System (ETCS). But while they’re similar in functionality, the Indian design carries a lower cost to Indian Railway.

The Vande Bharat Express is the first step to overhauling the legacy railway signaling system in India.

TCAS relies on communication between trains and a regional, central control system, and is fully integrated in the railway signaling system. TCAS integrates standard trackside equipment, sensors, Internet of Things (IoT) devices and controlling equipment located within the locomotive. All lineside information, for example, ‘track work ahead’, ‘stopped train ahead’, is passed on to the locomotive wirelessly, so there’s no need for the driver to keep watch on these signals.

Long-term vision: Digital train operations and gigabit trains

The long-term vision of global digital train operations is to reduce railway congestion, improve punctuality, enhance safety and increase line capacity. An example of the latter is when trains are managed as moving blocks, trains can run closer together while maintaining required safety margins and can thereby increase the line's overall capacity. With digital train operations and wireless train-to-train communication, blocks are defined in real time by computers as safe zones around each train.

Other services include connectivity on the train for staff members, service assistance for personnel, onboard surveillance for passenger safety, and high quality mobile broadband and voice services.

In India, FRMCS architecture and services can be introduced later, while preserving ATP and TCAS as a railway application that connects through the FRMCS network.

The use of 3GPP technology as part of TCAS will improve line capacity and allow TCAS to evolve to manage the railway network from central locations covering large sections of track.

3GPP LTE and New Radio for railway signaling, ATP and TCAS

LTE offers ultra-reliable, low-latency communication in newer releases of the specification, suitable to support ATP and TCAS and provide passenger connectivity. 5G-NR comes with even better performance and flexibility in the network topology, which is required for more advanced use cases in the long term. As LTE and 5G-NR are commonly deployed in conjunction with public mobile networks, and the smartphone market evolves from LTE to 5G, mixed deployments and gradual migrations are already highly optimized.

FRMCS and 3GPP LTE and 5G-NR are a perfect match, since FRMCS keeps all railway-specific functionality in the application layer, while LTE and later 5G-NR can serve as the high bit rate, ultra-reliable and low latency transport bearer. This architecture is future-proof, since new applications can be easily introduced successively, while the physical layer can also be migrated and refined with the newest 3GPP release features.

This layered architecture also takes advantage of network slicing and can share parts of the rail signaling system with public mobile network service providers and/or public safety agencies. In addition, FRMCS over 5G-NR can be smoothly introduced in both lower and higher frequency bands, since NR is specified for frequency bands, including micro- and millimeter wave bands and is flexible in its design in terms of physical layer numerology, advanced antenna system support and deployment options.

The railway needs 5MHz of spectrum in the prime 700MHz band for ATP and TCAS. The Department of Telecommunications in India is in the final stages of allotting the required 5 MHz premium spectrum. When spectrum is secured, ATP and TCAS can become operational and provide safety functionality that is on par with the European counterpart, ETCS.

FRMCS over 5G for passenger convenience and mobile broadband services

Apart from rail signaling, FRMCS offers a number of attractive applications for train operators and passengers. Notably, employing 5G as the answer to onboard video surveillance for passenger safety, train health monitoring and cargo tracking for freight customers. These applications have vastly different requirements that are levied on the physical layer capabilities and end-to-end service quality in terms of bit rate, latency and reliability. Meeting these requirements is the strength of LTE and 5G-NR.

As mobile network operators will be deploying dense 5G networks along railway corridors to serve their customers as passengers, they can also leverage this connectivity towards the critical connectivity required by FRMCS. FRMCS features, for example video surveillance, require huge capacity, which cannot be provided by a dedicated railway FRMCS spectrum. Here, network slicing guarantees the isolation of passenger services from critical train operation services and allows the mobile network service provider to supplement capacity when the FRMCS feature requires it.

Migration and mixed deployments

LTE and 5G-NR are very similar with respect to how they are used for communication services, and how such services can interact with the network for configuration and provisioning purposes. Only minor adaptations are needed when migrating a service from LTE to 5G. The LTE and 5G core network are both typically deployed as virtualized network functions, on general purpose hardware, which is why the same hardware can be reused for both technologies, and flexible resource allocation is possible.

Furthermore, dual-core approaches exist, where all the network functions of the 4G and 5G core are integrated into a common core network deployment, enabling a smooth technology migration from 4G to 5G, as illustrated in Figure 1 and further elaborated in this article on 5G core.

Finally, the same radio hardware can be used for 5G-NR and LTE radio access network, and the radio access network can dynamically switch between both access types with millisecond granularity, based on user demand. This technology, called dynamic spectrum sharing, enables an extremely radio resource-efficient co-existence of 4G and 5G technology in the same spectrum, avoiding complicated spectrum re-farming strategies. Therefore, for rail and mobile network service providers, deploying 4G to enable FRMCS and Gbit train services is a viable option, since it allows a smooth migration path to 5G as the market for more advanced FRMCS services matures.

Figure 1: Tight interworking of 4G and 5G components, combined with dynamic spectrum sharing, enables a highly optimized co-existence of 4G and 5G-connected trains during a transition phase. The FRMCS application function handles interactions with the mobile network on behalf of ATP and TCAS, and therefore further facilitates the co-existence of clients connected via different networks.

If everything goes according to plan, 50 percent of Indian Rail Tracks will have an LTE based High Speed Communications Network capable of supporting TCAS, ATP voice and IoT based telemetry services by 2025. This will allow Indian trains to even exceed 200 kph with appropriate high-speed track alignments.

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