Real-time Spectrum Sensing of Multiple OFDM Signals using Low Cost SDR based Prototype for Cognitive Radio

In Cognitive Radio networks, Secondary Users, or unlicensed users, are able to access the licensed spectrum in an opportunistic manner. For this reason, Spectrum Sensing can be considered one of the main challenging issues, as it is necessary to ensure an efficient sensing to avoid any possible interferences with the licensed users (Primary Users). In this paper, we provide an experimental study of two spectrum sensing techniques to detect the presence of OFDM (Orthogonal Frequency Division Multiplexing) Primary Users' signals by implementing and designing a low cost SDR based Prototype. The considered techniques are semi-blind; the SVD detector and Energy Detector. The prototype was built using two Universal Software Radio Peripheral programmed with LabVIEW software. The performance of the detectors were analyzed by measuring their detection probabilities in different real channel conditions and at different SNR (Signal to Noise Ratio) values. Various experimental measurements show that the SVD detector is robust than Energy Detector in fading environments as well as in low SNR values.