ies to a satellite earth station to provide direct digital communication with the United States. In a campus environment (company or university), these radios provide quick and easy linking of wired LANs in different buildings. Metropolitan area networks (MANs) for electronic mail services are now being designed to allow home computer users access to Internet directly or to their own company computer networks. These require wireless packet net- work bridge/router functions distributed throughout. Another outdoor application for spread-spectrum radios is the intelligent vehicle highway system (IVHS) program, which uses radios with data-gath- ering devices, including digital video. These are now being tested with spread-spectrum radios transmitting data back to a central control hub. In the planning stage are automatic electronic toll booths that will use this tech- nology for radio communication between automobiles and toll booths. Other short-range and lower-cost spread-spectrum radios have been designed for utility meter devices and even for electronic parking meters. For isolated or rural areas where a wired system may be too costly, a wire- less telephone local loop using unlicensed spread-spectrum radios is afford- able, and in rural areas, the possibility of interference from other unlicensed radios is small. 3.2.3 Direct Sequence versus Frequency Hopping A comparison of direct-sequence and frequency hopping spread-spectrum radio techniques for commercial applications must take into account many issues, some addressed here. The FCC Part 15 Rules 3.2.3.1 Conversion of Narrowband Radios Conceptually, frequency hopping is easier to understand than direct- sequence spreading. In addition, most radio manufacturers can easily con- vert their narrowband radios to spread-spectrum radios in which the center frequency hops around according to a fixed pattern, or code. However, hop- ping around the transmitting radio carrier frequency is not enough: Now, the receiving radio must be synchronized to the hopping pattern o