Increasing in wireless communications systems is caused to increase in the need of the frequency spectrum. CR (Cognitive Radio) measure or sense frequency spectrum activities on spectrum bands whether they are idle or used by licensed users. According to sensing results, idle spectrum bands can be used opportunistically in order to mitigate scarce spectrum needs fairly and efficiently. CR technology is proposed as a candidate technology for mentioned issues and contains many opportunities inside. In this paper, the technology was introduced. The possible additive contributions to wireless communications were investigated and the researches and future trends on Cognitive Radio were summarized.  

Keywords - Cognitive Radio, Wireless communications, Dynamic Spectrum Acces

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