Spread-Spectrum Radio; April 1998; Scientific American Magazine; by Hughes, Hendricks; 3 Page(s)
Conventional wisdom holds that radio airspace is a valuable--and limited--resource that has to be rationed, like water in a desert. That mind-set comes from traditional transmitters and receivers, whose operation must be restricted to narrow, dedicated slices of the electromagnetic spectrum to minimize interference. Thus, governments have parceled out and licensed radio channels like real estate. In the U.S., the Federal Communications Commission (FCC) has sometimes used a cash-bidding process to allocate precious frequency bands for a variety of purposes, including commercial television and radio broadcasts; military, marine and police transmissions; taxi dispatchers; CB communications; and ham radio operators and cell phone consumers.
Recent advances in digital communications, though, have opened the door to an entirely new model. Transmitters can now deploy so-called spread-spectrum techniques to share channels without running afoul of one another. Information can be diced into tiny electronic bundles of 1s and 0s and then transmitted over radio waves, with each packet sent over different channels, or frequencies, at low power. New studies have shown that, theoretically, millions of radio transmitters within the same metropolitan area can successfully operate in the same frequency band while transferring hundreds of megabits of data per second.