Collaborative spectrum sensing in OFDM-based Cognitive Radio

The rapid increase in the number of wireless devices highlights the importance of intensive dynamic use of the available spectrum. One technology to implement dynamic spectrum access is Cognitive Radio (CR). One of the main challenges of CR is gaining spectrum awareness, thus being able to undertake reliable and sufficiently sensitive spectrum sensing. In this paper, an OFDM-based CR system exploiting the inherent cyclic prefix (CP) and idle period of the transmission signals is proposed, assuming a realistic fading channel. Furthermore, collaborative spectrum sensing has been studied based on the proposed methodology, in the presence of Rayleigh fading and log-normal distributed shadowing. The simulation results indicate that the probability of detection can be significantly improved while maintaining the level of interference protection to the primary users by including the CP and idle period in the sensing time in both slow and fast fading channels. Moreover, collaboration of multiple secondary users improves the sensitivity of the sensing algorithm in terms of minimum detectable SNR. The analyses provided in this paper show that collaboration among 10 users facilitates detection at lower SNR levels up to -10 dB with 0.9 probability of correct detection and 0.1 probability of false alarm.