The Regulations

Spread spectrum technology (SST) is simply another radio frequency (RF) modulation technique. Just as AM radio signals have different bandwidth and range properties from FM and TV signals, SST also has different bandwidth and range properties. AM, and to a lesser degree, FM signals have historically been designed to concentrate energy close to their center frequency, resulting in range of tens to hundreds of kilometers. To manage the multiple stations in each geographic area, the FCC has subdivided the RF spectrum and licensed specific frequencies for the exclusive use of a station.

For SST, the FCC attempted to stimulate the production and use of wireless network products by modifying Part 15 of the radio spectrum regulation, which governs unlicensed devices. The 1985 modification to the regulation authorized wireless network products to operate in the Industrial, Scientific, and Medical (ISM) bands using spread spectrum modulation. The ISM frequencies are follows:

902-928 MHz
2.4-2.4835 GHz
5.725-5.850 GHz

Instead of subdividing the band, the FCC allows users to operate wireless products without obtaining FCC licenses if the products meet certain requirements (e.g. any device operating in these ranges may not exceed one-watt output power and be able to tolerate any interference generated in the band). Consequently, system design has emphasized reliable reception at low transmit power and relatively short range.

The deregulation of the frequency spectrum eliminated the need for user organizations to perform costly and time-consuming frequency planning to coordinate radio installations so that will avoid interference with existing radio systems. This is most advantageous for organizations that move their equipment frequently because they can now avoid the paperwork involved in licensing the product again at the new location.