Outage and Diversity Analysis of Cognitive Relay Networks with Direct Link under Interference Constraints over Nakagami-M Fading

Cognitive relaying network is a promising technology to improve spectrum utilization and to enhance the performance in practice. In this paper, with maximal transmit power and peak interference power constraints taken into account, the outage and diversity performance of cognitive relay networks under spectrum sharing environments with direct link is investigated over Nakagami-m fading channels. Employing a selection combining receiver, the signals received from the decode-and-forward relay and from the source are combined. Exact and asymptotic expressions for the outage probability are derived. To gain further insights, we also analyze the diversity and coding gain of the considered system. Finally, simulation results are presented to validate our analytical expressions.