SNR maximization through relay selection and power allocation for non-regenerative Cognitive Radio Networks

SNR maximization while adhering to interference constraint towards primary users is a key challenge in Cognitive Radio Networks (CRNs). Cooperative communication is a promising technique to achieve this goal by exploiting spatial diversity. We consider an Amplify-and-Forward based cognitive relay network comprising one source-destination pair and multiple relays in underlay spectrum sharing environment and solve the problem of relay selection and power allocation to the selected relays. In this scenario, we formulate an optimization problem aiming to maximize the signal-to-noise ratio (SNR) at the secondary destination under interference power constraint towards the PU as well as individual relay´s transmit power constraint. Our relay selection scheme allows more than one relay to cooperate in contrast to single relay selection methods which compromise on spatial diversity. We solve our optimization problem using Artificial Bee Colony (ABC). The proposed algorithm has low computational complexity and its effectiveness is proved through simulation results.