Network beamforming in cognitive relay networks with QoS constraints

In this paper, we propose a distributed relay beam-forming design in an underlay based cognitive relay network. In the proposed approach, beamforming coefficients of the secondary relays are obtained through minimization of the peak interference power inflicted on the primary receiver subject to the signal to noise-interference ratio (SINR) constraint at the secondary destination. We prove that the proposed scheme lead to a closed-form solution. Simulation results show that our relay beamforming improve system performance considerably.