Spread-spectrum techniques are methods by which energy generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, and to prevent detection.
Reference:
http://en.wikipedia.org/wiki/Spread_spectrum
Reference:
http://en.wikipedia.org/wiki/Spread_spectrum
