Study transmits radio signals in tunnels

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by Staff Writers
Gaihersburg, Md. (UPI) May 20, 2008
The U.S. National Institute of Standards and Technology says it's identified "sweet spot" frequencies capable of transmitting radio signals in tunnels.

The NIST scientists, as part of a project to improve emergency wireless communications, confirmed underground tunnels can have a frequency "sweet spot" at which signals can travel several times farther than at other frequencies.

The scientists said their finding might lead to strategies for enhancing rescue communications in subways and mines.

The optimal frequency depends on the dimensions of the tunnel. For a typical subway-sized tunnel, the sweet spot is found in the frequency range 400 megahertz to 1 gigahertz, the study found.

Up to now, companies have designed radios based on proprietary tests. The new data will support development of open standards for design of optimal systems, especially for emergency responders, NIST said.

Another new NIST report describes mapping radio signals in 12 large building structures including an apartment complex, a hotel, office buildings, a sports stadium and a shopping mall.

The reports -- "Measurements to Support Modulated-Signal Radio Transmissions for the Public-Safety Sector" and "Attenuation of Radio Wave Signals Into Twelve Large Building Structures" are available at http://www.boulder.nist.gov/div818/81802/MetrologyForWirelessSys/.

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