Spread-spectrum

This is a technique in which a Signalling (telecommunication)signal is transmitted on a bandwidth considerably larger than the frequency content of the original information.


Spread-spectrum telecommunications is a signal structuring technique that employs direct sequence, frequency hopping or a hybrid of these, which can be used for multiple access and/or multiple functions


This is done for a variety of reasons, including increasing resistance to natural interference or jamming and to prevent hostile detection.


http://en.wikipedia.org/wiki/Spread_spectrum