Outage performance of MIMO multiple access interference channel with cognitive relay

In this paper, we consider a cognitive relay assisted multiple-input multiple-output (MIMO) communication scenario through Rayleigh fading channel where multiple primary and secondary users wish to communicate with two different receivers in the presence of a cognitive relay. We assume that secondary users transmit simultaneously with the primary users 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 the 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 secondary users are able to communicate with their 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.