Performance analysis and optimization of dual-hop MIMO relay system with MIMO-MRC scheme in the presence of co-channel interference

In this paper, the performance of dual-hop multiple-input multiple-output (MIMO) relay system with transmit beamforming and maximum-ratio combining scheme (MIMO-MRC) for each hop is investigated. Both the relay and destination are subjected to multiple co-channel interferences (CCIs). An exact closed-form outage probability expression is derived for the Rayleigh fading channels. Then, to render more insights into the combined effects of multiple antennas and CCIs, the asymptotic behavior of the outage probability is also presented and discussed. Based on the asymptotic expressions, we explicitly characterize the system diversity order. The results show that the diversity order is essentially directly proportional to the number of antennas at the relay. Furthermore, employing both exact optimal power allocation (OPA) and asymptotic OPA methods, we determine the optimal power allocation (OPA) such that the outage probability is minimized. We show that OPA offers superior performance over uniform power allocation, and highlight a pivotal design choice for maximizing system performance without investing additional resources.