User clusters based hierarchical cooperative spectrum sensing in cognitive radio networks

This paper investigates secondary user clusters based cooperative spectrum sensing. Secondary users in the cognitive radio network are grouped into multiple clusters and the cooperative spectrum sensing is performed on a hierarchical architecture of these user clusters, through two levels of user collaborations. The low level cooperation is carried out within each cluster while the high level one is accomplished inside the cluster of the clusterheads. We propose soft fusion and hard fusion according to the bandwidth constraints of the control channels and the spectrum sensing agility requirement. An optimal soft fusion scheme and a double-threshold strategy are proposed to improve the overall spectrum sensing performance in soft fusion and hard fusion, respectively. Analysis and simulations verify that the proposed hierarchical cooperative spectrum sensing schemes can significantly improve the spectrum sensing performance.