Cognitive Radio: State of the art
Bart Scheers, Vincent Le Nir · 2009
Cognitive Radio is a paradigm for wireless communication in which a wireless node (or a network) can change its transmission and reception parameters according to the user needs and the wireless environment. A cognitive radio transceiver is able to sense, learn, decide and react adaptively to avoid interference with licensed or unlicensed users and to achieve greater spectrum efficiency compared to existing systems. Cognitive radio opens a new era in digital communications involving numerous topics, such as spectrum sensing, spectrum management, spectrum mobility, etc. 1. Definition of cognitive radio Cognitive radio has been introduced by Mitola in 1999 [1]. Following the definition of Haykin [2]: “Cognitive radio is an intelligent wireless communication system that is aware of its surrounding environment (i.e., outside world), and uses the methodology of understanding-by-building to learn from the environment and adapt its internal states to statistical variations in the incoming RF stimuli by making corresponding changes in certain operating parameters (e.g., transmit-power, carrier-frequency, and modulation strategy)