Friday , 22 January 2021

Bringing a paradigm shift in Communication Systems for Railways

The railway sector is witnessing a tremendous change in the way it operates owing to recent advances in telecommunication technologies. Indian Railways carries more than 14 million passengers and 36% of the total freight traffic every day. Operating a railway network of such vast magnitude goes much beyond running trains. Behind the scenes is a whole machinery of multiple systems working in clockwork coordination to ensure that the services are operational twenty-four hours a day without any interruption. The telecommunication network forms the indispensable link between these systems located across the rail network. As shown in Figure 1, the telecommunication system forms a key part of the infrastructure that makes railway travel safer, more efficient and also more comfortable. Technological advances in optical transmission technologies have enabled converged communications with virtually limitless bandwidth. At the same time, rapid progress in wireless communications such as high-speed packet access has empowered people on the move through quad-play. Yet another promising area of advancement is M2M communications. These developments have enabled the railways to run many applications on a shared communication infrastructure, such as Automatic Ticket Vending Machine (ATVM), Access Control, CCTV, traction control, signalling, train safety systems, voice telephony, public address system, passenger information system, network time system and internet access to passengers at stations and on moving trains. Only by harnessing together the diverse technologies and systems in an effective manner is it possible to take full advantage of these multiple services.

Integrated Communications Approach

For running the large number of systems that are dependent on the communications network, it is necessary to take an integrated approach. This means that the communications backbone is shared among all these applications. An integrated approach is required not only for cost-efficiency, but also for assessing the size of the system during engineering design, and for interworking between the different systems. The sharp distinctions between telecommunications and information technology are no longer applicable as both domains extend into each other to create integrated applications and services. The following examples bring out the importance of taking an integrated approach in designing and operating mission-critical services over the telecom network in railway environments.

Suburban Train System in Mumbai

Mumbai has developed and grown extensively around the suburban railway system. Due to the high level of settlement and activity in the immediate vicinity of the railway corridors, apart from the heavy passenger loads, innumerable factors beyond control can easily lead to service slowdowns. The resulting delays have a cascading effect on schedules, and in order to rectify these unavoidable situations, an intelligent scheduling system has been put in place for comprehensive train management. The train management system provides information on the position of all the trains on a minute-to-minute basis so that decisions can be taken rapidly to pre-empt service disruption from emerging delay situations. The system controls the integrated management and monitoring of train movements, planning of routes, and diversions in case of blocked lines. Furthermore, the information generated by the system is used to make automated announcements and displays of train arrival status across all stations through the passenger information display system and public address system.

The train management system works on a command-and-control approach, and depends on a robust and integrated communication system. The communication system collects and transmits data from hundreds of low speed signals from instrumentation along the route to the operations control centre where it is processed to provide information for appropriate action to be taken in real-time in an automated manner. These low-speed lines are aggregated at each of the stations along the route, and then communicated back to the control centres of the respective railway over a high-speed optical fibre backbone. The communications infrastructure is made up of primary add-drop multiplexers for aggregating the low-speed signals into the high-bandwidth equipment along the optical fibre network. All communications equipment across the network are monitored from the central location using a network management system. The exchange of information occurs at the interfaces between the communications system and the train management system. To ensure uninterrupted connectivity, the fibre optic back-bone is protected with a microwave back-up link for the critical signalling and control data.

Furthermore, the connectivity provides for an integrated solution that also supports other applications such as ticketing, signalling and hand held radio trunking to enable voice communication.

Legacy Network Integration

The underlying communication technologies are as per established international telecommunication standards and protocols. However, the unique nature of the railway network makes the architecture of these networks often stand apart from a telecom operator’s network. An established and operational railway route with its existing and functional infrastructure faces its own set of challenges when providing for new applications and connectivity. For instance, situations are frequently encountered where instrumentation is located at significant distances from stations which have telecom cabinets in controlled environments. It is not practical to install an entire fibre node at such locations. In such scenarios, the network integrator needs to come up with innovative solutions such as the use of copper line-drivers from the field instrumentation up to the nearest access point to the fibre, by utilising existing copper infrastructure. Rapid advances in technology can also render the installed equipment obsolete, making it difficult to integrate them in future network expansions. Hence, it is important that any network deployed must be “future-proof” so that legacy equipment can continue to function seamlessly after network upgrades and technology migration.

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