الفهرس 
The Motivations for Cognitive RadioOnly 14 pages are availabe for public view
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Abstract
The rapid growth of services offered through wireless communication has as consequence an increase on the demand for electromagnetic radio frequency Spectrum, which is a scarce resource (according to the government agencies limitations), mainly assigned to license holders on a long-term basis for large geographical regions, causing a large portion of the spectrum to remain unused for a significant percentage of the time. A report by the FCC Spectrum Policy Task Force has stated that the spectrum scarcity problem is mostly due to the insufficient utilization of the RF spectrum rather than the lack of unoccupied frequency bands. In other words, many of the legacy-controlled frequency bands are being underutilized, while the access of potential spectrum users to these underutilized bands is limited due to legacy command-and-control regulation.
Cognitive Radio (CR) proposes a solution to spectrum scarcity problem by making the underutilized frequency bands available to use by secondary (non-legacy) users, hence improving the overall utilization of the RF spectrum. A new paradigm to overcome this apparent spectrum shortage that consists of radio devices with the ability to adapt their spectral environment and are , therefore , able to make use of the available spectrum in an opportunistic manner was put forward, (e.g. the Cognitive Radio paradigm). Cognitive radio has emerged as a solution to dynamic spectrum access, due to its capability and reconfigure ability and to overcome spectrum frequency allocation limitations. Cognitive radio is considered as a promising candidate to be employed in such systems as they are aware of their operating environments and can adjust their parameters. The aim of this study is to focus on spectrum sensing in cognitive radio, which is a hot research area recently introduced in order to improve spectrum utilization efficiency.