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Safety Critical Navigation on the Rails

To those engineers more familiar with automotive or marine navigation systems, the concept of using GNSS receivers for navigation on railways might seem a case of “overkill”. After all, there are only so many places a train can go, and these are firmly bounded by two steel rails. However, the exact knowledge of the position of any train on any rail system allows the rail operator to both improve service and increase traffic density by reducing the headways associated with fixed line-side signaling without compromising safety, making it key to maximising the efficiency of the network.

Unfortunately, railway networks are pretty hostile environments for GNSS receivers. Trains spend significant periods of time in deep cuttings and tunnels, obscuring signals or creating complex multipath effects, and the electrically noisy nature of the power systems involved adds further complications. So while GNSS tracking is desirable for rail operators, it is by no means easy to deploy reliably. And as safety is paramount in any public transportation system, the integrity and reliability of the systems is essential.

Although live-sky testing of GNSS systems on railway networks would appear to be obvious way of testing the effectiveness of the system, it is both unreliable and expensive. While any live-sky test scenario may be “real”, it will not be repeatable and will not be able to test the system under specific conditions that might affect its performance. What's more, the costs of obtaining a train path on a section of a busy rail network to test a GNSS system, and the cost of operating the train would be unacceptable.

GNSS simulation offers the solution, with the ability to test the system under all possible conditions. Spirent's SimGEN™ simulation software can be used to create test scenarios that recreate railway-specific conditions, giving rail operators complete confidence in the integrity and reliability of their GNSS systems. Further details can be found here.

 
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