How can we get more use out of the radio spectrum? One way is by sharing radio bands between users who have never shared before. Consider radio frequencies near 3.5 GHz. Until recently, that part of the spectrum was used almost entirely by U.S. government radars, many of them on Navy aircraft carriers, enabling the same kind of air traffic control for the carriers as radars on land do at airports.
Now, we are preparing for new arrivals in the 3.5 GHz spectrum: communication systems such as cell phones. Operating on land, the new systems will be sharing frequencies with the Navy radars at sea.
More than decade ago, NTIA helped to blaze the trail for this kind of spectrum sharing when it did studies on exactly what it takes to share frequencies between regular radios and radars. Now NTIA has applied that knowledge to the new 3.5 GHz spectrum sharing. Industry and government, including NTIA, have developed a strategy to share 3.5 GHz without any interference from the new shore-based radios to the Navy’s aircraft carrier traffic control radars.
Here’s how it will work: When industry builds out a new 3.5 GHz network on shore, it will also build a network of shoreline radar detectors designed to see the Navy radar’s signal. When one of the Navy’s radars sails within about 120 miles of a detector, the station will see the radar’s signal, note its frequency, and alert the local on-shore communication network to immediately vacate that frequency.