In the recent testing, NIST examined whether a RF-enabled beacon issuing a firefighter-down signal could be transmitted to a base station located outside of a given building or subway station, whether the base station could send a response to the beacon, and how much distance and physical barriers reduced signal strength. Researchers found that signals were often not effectively transmitted from inside subway stations to the base station unless a repeater was placed inside the station; multiple repeaters might be needed in multilevel subways stations.
In addition, the tests inside the Empire State Building determined that only one of the four systems tested there were able to successfully carry out communications between beacons placed on the building's upper floors and a base station on the street nearby without the use of repeaters. NIST's next round of test methods will include tests for reliable voice radio and emergency beacon operations in higher path-loss environments.
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