SIGNALLING & TELECOMS
end, turnkey solution. All of these factors contributed to their decision to select us as their network partner.”
Once the contract was signed, Kapsch
CarrierCom architects created a network design that was closely mapped to Nexus’ technical requirements based on detailed information provided during the tender process. “We drew up a compliant design and created a detailed plan for commissioning, installing and testing the new infrastructure,” says Leindecker. “We will deliver all the key project milestones over the next 18 months.”
Delivering the TETRA network
Kapsch will deploy Nexus’ new TETRA infrastructure, including the core digital network, base stations and cab radios (the communications devices used in metro trains), as well as all the terminals required for the control centres. The new communications system will provide full coverage across Nexus’ area of operations, delivering significant performance improvements compared to the previous analogue infrastructure.
Migration risk will be minimised by Kapsch CarrierCom at every stage of the project.
“We will install the new system alongside the old system, with dispatcher terminals operating on both systems for a period of time,” Leindecker said. “The new TETRA system will be thoroughly tested to ensure that there are no issues before the switchover takes place and the old system is decommissioned.”
The solution in focus
The Kapsch CarrierCom solution for Nexus will include a TETRA core network built on geographically redundant equipment to ensure constant network uptime. In addition, 12 energy-efficient TETRA base stations will be installed, with 19 repeaters providing above-ground and in-tunnel coverage. Trains will connect to the TETRA infrastructure via 93 cab radios, with critical components and critical network communications monitored via state-of-the-art network management and dispatching systems.
To make sure Nexus’ communications systems are constantly available, resilience will be built into all layers of the network. “Our network design is based on four transmitters per site on a ‘2+2’ basis – meaning that there are two transmitters with two redundant spares at each site,” said Leindecker. “If a transmitter fails, the system will still operate as normal until staff arrive for their normal shifts, which reduces support costs dramatically. Technically, the system will remain operational even if three
The TETRA standard
TETRA (TErrestrial Trunked RAdio) is a digital trunked mobile radio standard developed to meet the needs of traditional professional mobile radio user organisations. It has a scaleable architecture allowing economic network deployments ranging from single site local area coverage to multiple site wide area national coverage.
Features include: • Wide area fast call set-up ‘all informed net’ group calls • Direct Mode Operation (DMO) allowing ‘back to back’ communications between radio terminals independent of the network • High level voice encryption to meet security needs • An emergency call facility that gets through even if the system is busy • Full duplex voice for PABX and PSTN telephony communications
Source: The European Telecommunications Standards Institute transmitters fail at any particular site.”
The new Kapsch CarrierCom cab radios will be built on a custom design that mirrors the layout of the previous devices. “The fact that the new cab radios will be set up in the same way as the old ones will make it much easier for train drivers to transition to the new system, minimising training requirements and costs,” Leindecker added.
The benefits for Nexus
Nexus is expecting to see vast improvements in the reliability and security of its radio communications compared to the previous analogue system, which dates back to the early 1990s.
Nexus’ rail infrastructure director Raymond Johnstone spoke to RTM earlier this year, saying: “The radio system we have is obsolete. In terms of quality, it still functions reliably, but you’ve always got to keep ahead of the game when it comes to essential kit like radios.”
He noted then that the next upgrade after the radio system will be the design and build phase of the upgrade of Metro’s train control system, PTI (Positive Train Identification), similar to ARS (Automatic Route Setting) as used by Network Rail.
Johnstone said: “Our system is obsolete and cumbersome in terms of being able to change the codes and to use it as flexibly as we’d like, so it’s definitely time for renewal for a whole host of reasons. It does more than ARS; it drives our passenger information systems and our performance management systems, so it’s got a lot of dependencies. We’ve done a feasibility study, and it will physically link into the radio system. We envisage going out to the market around January/February 2015.”
Leindecker explained more about the benefits of the new set-up. “The system will monitor itself for faults and send alerts to control
terminals automatically if there are any issues – helping to maximise service availability.
“In addition, TETRA signals are also more secure and harder to intercept, which will help Nexus prevent eavesdropping and make it harder for hackers to inject false signals into the network.”
The quality of voice communications will also improve dramatically with the digital TETRA network, he said. “TETRA signals are less susceptible to interference from mobile network signals and the audio quality is far superior to analogue systems.
“Both of these factors make voice
communications more secure and easier to understand in noisy environments, which will be a major benefit for Nexus train operators.”
The TETRA network also offers greater capacity than Nexus’ previous system, ensuring that voice communications are clear even on the busiest routes. “With analogue systems, there’s a risk that voice communications could be dropped due to lack of bandwidth,” said Leindecker. “Now, with the new TETRA solution, critical voice communications will always be available.”
As an additional benefit, the new network will be far more efficient, helping Nexus reduce its energy consumption and carbon footprint. “Modern applications and end user terminals consume less power,” said Leindecker.
“The efficiency of the network components will provide ongoing savings for Nexus, while helping to minimise the negative environmental impact of their operations.”
FOR MORE INFORMATION
W:
www.nexus.org.uk W:
www.kapsch.net/KCC
rail technology magazine Aug/Sep 14 | 89
Wolfgang Leindecker
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