Joint Clustering Relay Selection and Beamforming in Cooperative Cognitive Radio Networks

This paper proposes a joint clustering relay selection and beamforming method for a more realistic cooperative cognitive radio network, in which a secondary network of multiple secondary links and a relay network coexist with a primary network of one primary link. We aim to improve performance of the system in terms of maximizing the received signal power of the secondary destinations, subject to the constraint of received interference plus noise power of the primary destination using the proposed method. Since different relays cooperate differently towards the signals at the secondary and primary destinations, the proposed method can improve the performance of the system and enables the relay network to simultaneously transmit signals of all secondary links toward the destinations by clustering the relays. Results of simulations confirm validity of the method and improve the system performance compared to the existing cooperative beamforming and Zero-Forcing beamforming, in which no relay selection strategy is used.