Underlay Cognitive Proactive DF Relay Networks with Multiple Primary Transmitters and Receivers

The performance of underlay cognitive relay networks with multiple primary users and multiple proactive decode-and-forward relays is investigated. Particularly, both interference power constraints at multiple primary receivers and multiple primary transmitters' interference at secondary transmission nodes are taken into account. Considering correlations among the received signal-to- interference-plus-noise ratios, exact closed-form expressions for the outage probabilities of secondary users are derived for the cases with or without a direct secondary link over Rayleigh fading channels. A novel method is proposed to analyze the outage probability for cognitive proactive decode- and-forward relay networks in the presence of a direct secondary link. Simulation results show that the diversity gain is zero in the presence of multiple primary transmitters' interference, but the outage floor in the high SNR can be significantly decreased by an increase of the number of relays or by exploiting a direct secondary link.