Modelling of Cooperative Spectrum Sensing over Rayleigh Fading Without CSI in Cognitive Radio Networks

It is proved that cooperation among secondary users (SUs) in a cognitive radio network (CRN) greatly improves the spectrum sensing performance. However, modelling and analysis of cooperative spectrum sensing in a CRN over fading channels is an important issue. This paper derives a new fusion rule based on likelihood ratio test which requires exact channel statistics instead of instantaneous channel state information. This scheme provides Neyman-Pearson criteria based optimal sensing while considering both sensing and reporting channels as independently Rayleigh faded. We derive closed form solutions for local probabilities of detection and false alarm by assuming that all SUs perform energy detection, which makes real-time computations simple. Further, closed form solutions for system-level performance are derived by considering that all SUs experience independent fading and statistically identical signal-to-noise ratios. Performance of the proposed cooperative sensing scheme has been evaluated both analytically and by simulations.