An efficient adaptive fusion scheme for cooperative spectrum sensing in cognitive radios over fading channels

Cognitive Radio is a novel technology that can potentially improve the utilization efficiency of the radio spectrum by opportunistically using the unused frequency bands. Spectrum sensing is the key function of cognitive radio technology. However, detection is compromised when a user experiences shadowing or fading effects. In such cases, user cannot distinguish between an unused band and a deep fade. Thus, cooperative spectrum sensing is proposed in the literature, to improve the sensing performance. In cooperative sensing, decision fusion technique greatly influences the overall sensing performance. We have studied the performance of cooperative spectrum sensing over Rayleigh fading channel with Adaptive Linear Combiner decision fusion algorithm. The weights which correspond to confidence levels of the secondary users are determined adaptively using the Normalized Least Mean Square(NLMS) algorithm to improve the sensing performance.