Signal processing techniques for spectrum sensing in cognitive radio systems: Challenges and perspectives

Cognitive radio (CR) is regarded as an emerging technology to utilize the scarce RF (radio frequency) spectrum in opportunistic manner to increase the spectrum efficiency. However, major challenge to successful operation and realization of CR system is the identification and detection of primary user signals in the wide band regime to identify spectrum opportunities reliably and optimally. Several signal detection techniques for spectrum sensing have been proposed in the literature in order to identify idle spectrum so that the CR user can use those idle spectrum bands opportunistically without causing harmful interference to the licensed/primary users. In this article, we provide a comprehensive study of signal detection techniques for spectrum sensing in CR system. We also outline current state of the research and future perspectives. With this article, readers can have a more thorough understanding of signal processing techniques for spectrum sensing in CR system and the research trends in this area.