On the correlation analysis of antennas in adaptive MIMO systems with 3-D multipath scattering

The performance of multiple-input multiple-output (MIMO) systems improves substantially with the adaptation techniques like power allocation and antenna selection. These algorithms can he enhanced by considering characteristics of spatial correlation. In this study, the spatial correlation in MIMO systems is investigated to fully expose the parameters affecting it. The correlation analysis is performed by taking the effect of angle-of-arrival (AoA) statistics in three-dimensional (3-D) multipath scattering, mutual coupling, and near-field scatterers (NFS). The analysis shows that a valid model of the AoA statistics is the key parameter in the correlation analysis. Mutual coupling analysis for patch antennas reveals that coupling can reduce the correlation between antenna elements. On the other hand, the analysis on NFS suggest continuous correlation estimation. Fortunately, the rate of change of NFS is much slower than the MIMO channel variation. It is concluded that the performance of MIMO systems can be improved with accurate AoA models and tracking correlation changes.