Outage Performance Analysis of SIMO Multiple Access Interference Channels with Cognitive Relay

In this paper, we analyze the outage performance of a cognitive relay assisted single-input multiple-output (SIMO) cognitive interference channel, where multiple secondary users each with single antenna wish to communicate with the secondary receiver equipped with multiple antennas through Rayleigh fading channels in the presence of a primary user. We assume that secondary users transmit simultaneously with the primary user over the same channel instead of waiting for an idle channel which is traditional for a cognitive radio. We consider both the cases when cognitive relay is present or not and derive the expressions for mutual information received at the primary and secondary receivers. We also present the closed form expressions for the outage probabilities and complementary cumulative distribution functions (CCDFs) of mutual information received at the primary and secondary receivers in the absence of cognitive relay. Our results show that with the help of a cognitive relay, not only both the primary and multiple secondary users are able to communicate with intended receivers compensating interferences created at their receivers, but also the outage performance of primary and secondary users are improved due to the additional diversity obtained via cognitive relaying.