BW Online | December 15, 2003 | Beyond Wi-Fi: A New Wireless Age

This business week article does a very good job of explaining the state of wireless spectrum today.

On the clear morning of June 10, Mark McHenry climbed onto the rooftop of a seven-floor office building near Washington's busy Dupont Circle. Lugging an unwieldy 10-foot antenna and a gray metal box, he and another engineer set up an experiment to measure the actual usage of airwaves above the Nation's Capital during peak business hours. They were out to debunk a popular myth: With the explosion of wireless devices, the air is nearly saturated with zinging TV, radio, cell-phone, and BlackBerry signals, right? Not to mention satellite and air-traffic-control signals, police dispatches, and mushrooming Wi-Fi networks. And yet, the duo found that even in a heavily trafficked part of the airwaves above the District of Columbia, only 19% to 40% of the spectrum was occupied at any moment during an eight-hour period.