High-speed Ethernet made easy to retrofit

In public transport in the Ruhr area, an operator is replacing the on-board computers of its active trams and light rail vehicles. As part of this, LÜTZE TRANSPORTATION is contributing a customized solution that enables data transmission over existing lines across couplings in a straightforward way.

Running on rails in the central Ruhr region is the Bochum-Gelsenkirchener Straßenbahnen Aktiengesellschaft (BOGESTRA). BOGESTRA vehicles operate in Bochum, Gelsenkirchen, Hattingen, Herne and Witten. On the CampusLinie U35, BOGESTRA’s light rail line, 37 vehicles of the B80 and Tango types run on standard gauge. For the tram lines, you hop onto one of the 95 Stadler-built Variobahns running on meter gauge. These even earned a Design Award when the manufacturer was commissioned by BOGESTRA.

Good design is timeless – sadly, IT is not. The originally installed on-board computers are reaching their performance limits, which is why all vehicles are gradually being upgraded with new ones. These new computers, now standardized for both trains and buses, allow the analogue IBIS vehicle bus to be replaced with IBIS IP for almost all components. The previous 50 Mb limit for courier data storage can now be easily expanded with a micro SD card. And a SIM card in the new on-board computer renders externally operated Wi-Fi structures obsolete when it comes to processing and forwarding data – the mobile network now powers the on-board systems. That’s just the start of what’s planned with the new computer.

To transmit data over existing lines via couplings, the Train Line Modem 10 (TLM-10) from LÜTZE TRANSPORTATION is used. With a transfer rate of up to 950 Mbit/sec, this solution is practically unrivalled. All passenger information data is to be transmitted – including text for internal and external displays, announcements, and driver announcements.In the first phase, BOGESTRA and engineers from LÜTZE measured how smoothly data was exchanged between on-board computers using installed samples on site.

For the standard gauge Tango vehicles with just one head-to-head transition, there was barely any loss. And in the multi-section meter gauge Variobahns, data still flowed sufficiently well despite seven connectors.According to Sebastian Röska, the responsible BOGESTRA employee, “The TLM-10 definitely transmits the data without any issues: with our standard gauge vehicles at nearly 1 Gbit, to be precise 900 Mbit/s.” In the meter gauge vehicles, the transmission of text data is somewhat lower, but still more than sufficient – even over longer distances. “A simple solution for using existing lines without touching the coupling,” he confirms. The retrofit project is now progressing as planned.

Secure gigabit Ethernet data across an entire train via the coupling – that’s what LÜTZE TRANSPORTATION makes possible with the Train Line Modem TLM-10. It’s suitable for new builds and for retrofitting older rail vehicles with outdated cabling. Connecting to the existing vehicle wiring is enough. The TLM-10 automatically searches for the matching partner and establishes a 128-bit encrypted connection between them. This works even if the existing wiring is already being used for low-frequency applications. To ensure optimal data throughput even in the presence of external interference, the TLM-10 monitors everything using a digital signal processor (DSP). Similar to the powerline principle used in private households, it operates based on the G.HN carrier frequency method.

The TLM-10 is used at BOGESTRA for passenger information. In other applications, the modem also proves its worth for Wi-Fi, video surveillance, GPS and mobile network applications, and the seat reservation system. Even multiple retrofitted analogue voice connections, such as driver announcements via the coupling, are possible. Here, the analogue voice data is processed before transmission and then reconverted accordingly.

With a wide voltage input from DC 24 V to 110 V, the TLM-10 can be used worldwide in all rail networks. It is 100% rail-compliant and meets all standards for vibration and shock loads, EMC safety, and fire behavior. Continuous operation is possible from -40 °C to +70 °C. Installation is also straightforward: either with a flange or in a 19-inch rack.

The TLM-X offers a robust transmission method that is ideal for retrofit projects with older, unshielded cabling. It provides a stable high-speed Ethernet connection of up to 860 Mbps between train sections, particularly in EMC-prone environments. In contrast, the TLM-10 uses a transmission method that shows its strengths in higher quality infrastructure.

Author: Leszek Szewczyk, sales engineer Lütze Transportation GmbH