Cognitive Radio Technology

Cognitive radio (CR) is a newly emerging technology [789, 790], which has been recently proposed
to implement some kind of intelligence to allow a radio terminal to automatically sense, recognize,
and make wise use of any available radio frequency spectrum at a given time. The use of the available
frequency spectrum is purely on an opportunity driven basis. In other words, it can utilize any idle
spectrum sector for the exchange of information and stop using it the instant the primary user of the
spectrum sector needs to use it. Thus, cognitive radio is also sometimes called smart radio, frequency
agile radio, police radio, or adaptive software radio,1 and so on. For the same reason, the cognitive
radio techniques can, in many cases, exempt licensed use of the spectrum that is otherwise not in use
or is lightly used; this is done without infringing upon the rights of licensed users or causing harmful
interference to licensed operations.