Tunnels


Tunnel vision C


onfi ned spaces come in a variety of shapes and sizes, each one presenting its own unique challenge. Road and


rail tunnels, service tunnels, underground sta- tions and even ships need careful planning and consideration when implementing a reliable radio communications system. Here, we look at the challenges that arise when working in tunnel networks, and the preparation needed to overcome them.


About the author


Andy Gamble is regional sales manager at Simoco Group


Plan to succeed Is it a tunnel or is it an underpass? T e UK De- partment of Transport Design Manual for Roads and Bridges Vol 2 section 9 BD78/99 defi nes a road tunnel as a subsurface highway structure of 150m or more in length but a similar defi ni- tion could apply for any tunnel be it rail, pe- destrian, cable or even a long passageway on a ship. A tunnel’s shape and length has a major infl uence on the design and performance of a radio network – a simple antenna in the mid- dle of a 150m road tunnel may suffi ce but for 1.5km it just won’t work. In the fi rst stages of designing an RF com- munication system, there are a number of con- siderations, such as how to ensure continuous coverage of the entire length of the tunnel. So what is meant by ‘coverage’? Coverage


is something that just works, or a system that provides predictable and measurable signal lev- els reliably throughout with little interference


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Confi ned spaces present a unique challenge for RF engineers. Andy Gamble, of Simoco Group, considers what needs to be done to ensure reliable communication


Image above: A tunnel can present some unique problems, as often a single radiating infrastructure has to provide coverage for a large number of different services, which may include PMR channels across several bands, cellular telephone services and services intended for domestic use such as AM/FM broadcast and DAB


and with a tunnel full of a train or buses for example. Reliable system operation means that wherever a user goes then the radio will work, so it’s important to ensure there is a safety mar- gin built in to the design. However this is really the same as designing any system. A tunnel can present some unique problems,


as often a single radiating infrastructure has to provide coverage for a large number of diff er- ent services, which may include PMR channels across several bands, cellular telephone services and services intended for domestic use such as


LAND mobile January 2013


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