The transmission frequencies are determined by a spreading, or hopping, code. The receiver must be set to the same hopping code and must listen to the incoming signal at the right time and correct frequency in order to properly receive the signal. Current FCC regulations require manufacturers to use 75 or more frequencies per transmission channel with a maximum dwell time (the time spent at a particular frequency during any single hop) of 400 ms.

FCC Opens Spectrum
The Federal Communications Commission made a major policy shift in the federal rules that govern U.S. wireless communications.

Selecting a wireless LAN technology
Proxim white paper explaining two spread spectrum technologies: Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).

Spread Spectrum
Frequency hopping vs. direct sequence

Wireless LAN Alliance home page
Contains an organizational overview and links to an introduction to wireless LANs, user stories, resources, and contact information.