Abstract: Cognitive radio (CR) technology is invented to solve the problems in wireless networks resulting due to the scarcity of spectrum and due to the inefficiency in the spectrum usage by making use of existing wireless spectrum opportunistically. The cooperative spectrum sensing schemes exploit spatial diversity of the Secondary Users (SUs), to detect an unoccupied licensed spectrum. A Soft energy combining scheme provide optimal detection performance by aggregating the actual sensed information from SUs. Alternately, a hard energy combining scheme offers lower cooperation overhead in which only local decisions taken by SU are reported to the fusion centre (FC). A Log-Likelihood Ratio (LLR) based cooperative spectrum sensing scheme in which each SU performs a local LLR based sensing test employing two threshold levels. Indeterministic region with two threshold level along with LLR is used to reduce the computational overhead. The detection performance of the proposed scheme is close to the soft combining techniques. In this work energy efficient LLR based cooperative spectrum sensing method for CRAHNs with clustering is proposed. Clustering organizes nodes into clusters in order to provide network-wide performance enhancement. Generally there are three main advantages of clustering to CR networks, scalability, stability, and supporting cooperative tasks, such as channel sensing and channel access, which are essential to CR operations, and these advantages have led us to use the clustering in CR networks. Effectiveness of proposed strategy will be verified through simulation study on the basis of signal to noise ratio (SNR), probability of detection and energy consumption.

Keywords: Cognitive Radio, Cooperative spectrum sensing, LLR, Clustering