Due to the significant growth of the wireless users number, and of the wireless multimedia applications (which require an increasingly larger bandwidth), the radio spectrum has become overloaded. The solution proposed by Joseph Mitola III, in order to provide spectrum resources according to the user needs, was the Cognitive Radio (CR), which allows dynamically using of the existing spectrum. In the recent years the CR technology imposed itself as a very good solution to the increasing spectrum utilization. This technology proposes the development of a new radio type – a cognitive radio – endowed with intelligence that senses, shares, and uses the spectrum opportunities (SOP) of the preexisting wireless networks, the channels that are not used by the licensed users.

Keywords: Cognitive Radio, Spectrum management, Spectrum sensing, Spectrum sharing, Wireless communications.