Brave New Spectrum World: Proposal Would Accommodate Many More Users in a Sensitive Band

The Federal Communications Commission has proposed a set of rules that look innocuous enough, and would apply only to a single, underused band. But they may herald a new way of managing spectrum – a suite of techniques having the potential to vastly increase the number of users that can share a given range of frequencies.

All of the radio spectrum is occupied – at least, all of the most useful parts, below about 60 gigahertz. But the demand for spectrum continues to increase. What the FCC needs most is a way to squeeze new users into spectrum that is already in use, without causing interference to either the incumbents or the newcomers. Current spectrum management relies on “allocating” each band of frequencies to (usually) several categories of users. Those categories, in turn, come in three different priorities. Those designated as “secondary” may not cause harmful interference to, and must accept all interference from, those called “primary.” Unlicensed users, permitted in most bands, must protect all other users (except each other) from interference, and must accept all interference that comes their way. A few bands, like that used for GPS reception, have only one active user category; a few have as many as seven or eight. Three to five is about typical. Yet even supposedly occupied spectrum is quiet in most places, for much of the time. Some services, like those using two-way radios, occupy their frequencies only sporadically; others, like some types of satellite earth stations, operate only at wide separated locations. All such users, however, vigorously resist letting others into their bands. A police officer at the scene of an accident, picking up his microphone to request an ambulance, hopes to find an empty channel to make the call. The satellite operator may want the option of installing earth stations at new locations, without interference from other kinds of transmitters nearby. As we explain below, the FCC thinks it can fully protect all such users while still letting new entrants share the same frequencies.