Power Minimization Through Relay Subset Selection Inunderlay Cognitive Radio Networks

Submitted: May 9, 2013; Accepted: Jun 16, 2013; Published: Jun 30, 2013 Abstract: In this paper, we consider a dual-hop Cognitive Radio Networkthat consists of a secondary sourcedestination pair assisted by cognitive relays in their communication. The whole network is operating in an underlay mode near a primary user. Underlay networks allow simultaneous primary and secondary transmissions but at the cost of strict interference constraints towards the secondary users, whichenforces them to limit their transmit power and hence their coverage area.Cognitive Relay networks offer a potential solution to such problems in the form of relay selection. In this work,we select an optimal subset of relays from a potential relay set aiming to ensure minimum QoS requirements at primary and secondary networks. Our proposed scheme considers Amplify-and-Forward relaying and declares that subset as the optimal choice after exhaustive search which minimizes the total transmit power at the relay network while satisfying interference and SNR (Signal-to-Noise Ratio) thresholds of the primary and secondary networks. The simulation results prove the effectiveness of relay selection for underlay cognitive radio networks.