Power Allocation and Relay Selection for Cognitive Relay Networks with Primary QoS Constraint

In this letter, an optimal power allocation scheme between the secondary transmitter (ST) and secondary relay (SR) with best relay selection is proposed for a two-hop decode and forward cognitive relay network. Based on the joint consideration of the interference from ST and SR to the primary user (PU), the closed-form solution for optimal power allocation and relay selection (PARS) is presented under the quality of service (QoS) constraint of the PU transmission. Furthermore, a low complexity sub-optimal scheme is proposed. Simulation results verify the performance improvement of the proposed schemes.