Twice cooperative spectrum sensing in CR system over fading channels

In cognitive radio network (CRN), traditional energy detection algorithm has a bad detection performance in fading and shadowing environment. So cooperative spectrum sensing among cognitive radio nodes is needed in order to overcome these drawbacks. However it will result in a large demand of communication bandwidth on the control channel when the number of nodes is great. To solve this problem, this paper proposes a twice cooperative spectrum sensing scheme over fading channels. In this scheme, all secondary users are grouped into multiple clusters. Double threshold cooperative sensing algorithm and hard fusion ruling are adopted respectively in each cluster and fusion centre. According to the diversity and complexity of wireless communication environment, the paper analyzes the performance of the scheme we proposed over Rayleigh channel and Rician channel respectively. By adopting this scheme, the numbers of bits transmitted to the fusion centre for decision result will be decreased. The simulation result shows that the proposed scheme can improve the detection performance.