This paper investigates different functionalities that are needed in cognitive radio systems. Cognitive radio systems have the ability to observe their surrounding, become of aware of the particular needs in that surrounding and can adjust their operation to those needs. The paper presents a basic toolbox of functions that are needed to allow for basic cognition and a framework (extended toolbox) of more advanced functions that allow more advanced levels of awareness. The paper stresses the need for the development of a generic architecture that encompassed both centralized and decentralized elements. The centralized elements allow for coordination over larger areas, whereas the decentralized elements allow the exploitation of the radio spectrum in an opportunistic manner as a local resource.978-1-4244-4583-7/09/$25.00

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