Alan Bollard, managing director of Westermo UK, explains the role reliable data communications technology must play in the digitalisation of the rail network.
In today’s digital age, trackside and onboard data communications networks deliver real-time information about the position and speed of the train, which is critical in maintaining effective and secure traffic flow. They also support applications and systems, such as CCTV and passenger infotainment, that both enhance the passengers’ journey and increase their safety.
Now, however, the need to increase rail capacity is placing ever greater demands on these networks. Both onboard and trackside rail applications are challenging for data networking technology. These are harsh environments and products must be designed to withstand constant vibration, extreme temperatures and humidity.
They also need to meet the required standards for electromagnetic compatibility. Networking devices for trackside applications, such as routers and switches, must meet the EN 50121-4 standard, while the much more all-encompassing EN 50155 standard applies for onboard equipment.
Another important design consideration, especially for onboard applications, is device footprint, with compact design being vital in ensuring devices can be installed within the tight confines of rail carriages.
Power over Ethernet
Over recent years, Ethernet technology has become the standard for creating the data communication backbone used by train control management systems, passenger information systems, CCTV and infotainment systems. These networks are built and managed using robust Ethernet switches featuring a range of IP networking protocols. The IEC 61375-1 standard has been created to describe the general network architecture employed on trains.
With more types of equipment and systems being connected to these networks, this creates a need for more ports and increased capacity, as well as for more cables to be installed for power and data. Power over Ethernet (PoE) technology is an ideal solution to this challenge, as end devices can be powered through the network cable, enabling significant cost and space savings.
Traditional PoE solutions rely on additional external power supplies to provide the necessary voltage on the data cable. More advanced designs incorporate a DC/DC converter, allowing the train’s own power grid to be utilised directly. This methodology also makes it easier to provide electrical isolation between each Ethernet port, which is important in preventing over-voltages or short circuits propagating throughout the network.
Reconfiguration and recovery
Train networks face some specific challenges compared to traditional data networks. For example, they must deal with the demands of a dynamically changing topology, when rail cars are connected or disconnected to the train. Train inauguration is a process where the data network is automatically reconfigured as carriages are added or rearranged. The Train Topology Discovery Protocol (TTDP), as described in the IEC 61375-2-5 standard, is used by rail backbone routers to perform this reconfiguration, thus avoiding the need for staff operating the train to undergo data network training.
To ensure high uptime, train networks must be able to cope with potential failure scenarios. Failsafe backbone routers use a fast-ring network recovery protocol to create fault-tolerant Ethernet networks, while dual-bypass relay routers maintain aggregated links between carriages, even when one carriage suffers a power failure.
Of course, PoE requires the various devices to be connected by cables, down which the power passes. There are some rail applications where network cables cannot be used – for instance, getting information from the moving train to the ground, connecting carriages where a specialised train coupler is not available for network cables, or providing internet access for personnel and passengers.
Robust wireless local area network (WLAN) devices are now available for these applications, although other arrangements have to be made to power them. These ensure reliable, continuous, high-speed data communications to support applications such as monitoring train speeds and track conditions and providing onboard video surveillance and passenger hotspots.
The latest WLAN devices support communications from train to ground by offering high-output levels to achieve stable connection. Ensuring seamless communication as a train moves along the track, devices provide fast handover support, enabling switching from one trackside access point to the next.
Inter-Consist Link (ICL) mode provides stable and secure communication between consists, and without the cost of installing communication cabling over the couplers.
The latest WLAN devices are ideal for providing passengers with internet access. The high input sensitivity of these devices enables a good connection even to weak signals, while fast connection support speeds up the process of establishing connectivity for passengers.
Security is paramount
Network security to safeguard against cyberattacks and threats is critical, so it is important to correctly implement a device’s available security features. Here, network configuration tools simplify configuration of large and complex networks and make it easy to achieve good protection against cyberattacks.
As well as simplifying configuration, these tools can also perform a security analysis and suggest changes that enable system-wide security configuration to be quickly and efficiently applied.
Westermo manufactures an extensive range of network devices that can be used to create reliable solutions for many different applications, both on board trains and trackside. For more information, visit www.westermo.co.uk/industries/train-networks