 - Cognitive radio (CR) is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference to other users.
In its most basic form, CR is a hybrid technology involving software defined radio (SDR) as applied to spread spectrum communications. Other functions of cognitive radio include the ability of a transceiver to determine its geographic location, identify and authorize its user, encrypt or decrypt signals, sense neighboring wireless devices in operation, and adjust output power and modulation characteristics. The idea for CR was developed by Joseph Mitola at the Defense Advanced Research Projects Agency (DARPA) in the United States.
The term SDR refers to wireless communication in which the transmitter modulation is generated or defined by a computer, and the receiver uses a computer to recover the signal intelligence. Spread spectrum is a form of wireless communication in which the frequency of the transmitted signal is deliberately varied according to a mathematical time-domain function. In order to intercept the signal, a receiver must be tuned to frequencies that vary precisely according to this function.
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18 Apr 2007
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