Banverket, the Swedish rail operator, required a solution that would allow Internet Protocol (IP) traffic to be transmitted on long stretches of existing telecoms grade twisted pair cables running along the trackside. The Westermo Wolverine products were the perfect fit for this application and allowed a completely IP based system to be implemented without the need for the installation of costly fibre optic cables.
The requirement arose from the installation of a system conforming to the European Rail Traffic Management System (ERTMS). ERTMS is a major project developed by a number of major manufacturers in close cooperation with the European Union, railway stakeholders and the GSM-R industry.
ERTMS aims at replacing the different national train control and command systems across Europe. The deployment of ERTMS will enable the creation of a seamless European railway system and increase European railway’s competitiveness.
ERTMS is specified at different levels and the definition of the level depends on how the route is equipped and the way in which information is transmitted to the train. At Ådalsbanan in Sweden, Banverket together with Bombardier provided a section of railway with ERTMS level 2. This application is unique as it is the first level 2 installation ever to include equipment such as railway crossing barriers. In an ERTMS level 2 system the engine driver can receive basic track and rail information via the GSM –R radio network. This driver information is sent from Banverket’s control centre via an IP network, which is connected to control and monitoring devices along the railway.
Ideal balance of reliability and bandwidth
The equipment along the trackside has been linked to Banverket’s IP network using pre-existing twisted pair copper cables and the Westermo DDW-225. The DDW-225 uses SHDSL technology that allows data to be sent at a maximum speed of up to 5.7Mbit/s at shorter distances with ranges up to 15km possible at lower speeds. In this installation however, network resilience and reliability were prioritised rather than bandwidth. The best balance between range and signal to noise ratio was achieved at 2.3Mbit/s over distances from 2km to 7km.
The requirements for high reliability called for a redundant network solution, which is why the National Rail Administration created two individual networks connected to duplicated control equipment. The different networks are completely separate and connected to the backbone network by separate routers. Even if one network should fail, full access to the entire route can be achieved through the redundant network. In addition, the DDW-225 supports a number of features that allow configuration for optimal control. VLAN, QoS, SNMP, SSH, and extended diagnostics were part of the requirements from the Rail Administration.
The DDW-225 is a robust Ethernet extender with EN 50121-4-EMC approval for apparatus in trackside applications. The unit is designed for harsh environments and can operate in an extended temperature range (-40°C to +70°C). The DDW-225 has contributed to significant cost savings as new fibre installation could be avoided. The DDW-225 is also future-proofed as it can be upgraded to support future networking standards as and when they are required.