Channel assignment scheme in clustered multichannel cognitive radio networks with outdated CSI over Rayleigh fading channels

Summary This work investigates channel assignment for cooperative spectrum sensing in multichannel cognitive radio networks, where the heterogeneity of primary user (PU) activity and the effect of varying channel condition on the received signal‐to‐noise ratio during cluster formation are considered. With the objective to minimize interference to the PU while enhancing multiple spectrum utilization of the secondary user (SU), an overlapping cluster‐based assignment is formulated into a nonlinear integer optimization problem. To obtain an efficient solution, the nonlinear integer problem is transformed into a mixed integer linear problem, based on which, this paper proposes an exact solution and then two new heuristic algorithms for suboptimal solutions, respectively. Furthermore, a comparative study of four different cluster head selection schemes with respect to their performance in cooperative spectrum sensing, under cluster's heterogeneity in terms of SUs distribution relative to PU transmitter location is presented. Based on the study, a robust cluster head selection scheme is proposed. Simulation results show that good sensing performance and increased opportunistic spectrum utilization in multichannel cognitive radio networks are two sides of a coin that depend on the ratio of the SUs to the number of PU channels. How far away the PU is from the cluster center is also seen to be key in the optimal selection of cluster heads in cooperative spectrum sensing. Predicted channel state information provides a more reliable channel assignment in CRNs. It is also worth noting that for a target multiple spectrum utilization opportunity, a particular ratio of secondary users (SUs) to primary user (PU) channels exists for a desired sensing performance in cooperative spectrum sensing (CSS). Moreover, the distribution of SUs relative to the PU in a cluster is a key factor in selecting a cluster head for good sensing performance in CSS.