Channel Capacity Upper Bound on MIMO Systems in the Presence of Spatially Correlated Noise

In this paper, we derive an upper bound on the channel capacity of MIMO systems in the presence of correlated noise. We isolate the noise correlation factor in the channel capacity formula, enabling the identification of the noise correlation contribution on the MIMO channel capacity. We analyze the thermal noise correlation due to the mutual coupling effect. Then, we calculate the thermal noise correlation matrix in the multi-antenna system with closely-spaced antennae by applying the Nyquist’s thermal noise theorem. Simulation results shows that ergodic and outage MIMO channel capacity are underestimated if the noise correlation due to the mutual coupling effects is not accounted for. Additionally, it is demonstrated that the upper bound can be used for a first estimation of MIMO channel capacity in the presence of correlated noise, reducing the calculation complexity.