Hybrid Overlay/Underlay Transmission with Partial and Opportunistic Relay Selection in Cognitive Radio Networks

Objectives: In this paper, we consider a hybrid overlay/underlay strategy to maximize the throughput of primary users by use of idle secondary users as relays. Specifically, we focus on incorporating the advantageous features of underlay and overlay transmission methods into a hybrid cognitive radio technique. Analysis: By the use of the proposed technique both the primary and secondary users get benefited, as their communication link is uninterrupted. This scheme helps as an incentive for primary users to share their spectrum with the secondary users. Findings: The paper presents a resource allocation algorithm for the hybrid overlay/underlay transmission method. Also, the performance of the opportunistic and partial relay selection is investigated. This resource allocation algorithm is used to select the best channel from relay to destination, best relay and power allocated to best relay. Simulation results are presented to demonstrate the performance of the proposed hybrid technique over the traditional methods. The effectiveness of usage of the partial and opportunistic relay selection techniques is compared and the conclusions are drawn. Improvements: The proposed scheme will eliminate the need to switching between the overlay and underlay techniques. The resource allocation along with proposed hybrid transmission scheme will give significant improvement in SNR of primary user.