Comparison of MIMO Antenna Configurations: Methods and Experimental Results

In this paper, the methods for comparing multipleinput-multiple-output (MIMO) antenna configurations using measured radio channels are considered. The expression of mutual information (MI) is factorized to give better understanding of the ability of MIMO antenna systems to transfer signal power, as well as to utilize parallel channels. An appropriate power normalization of channel matrices is shown to have a profound impact on the ranking of particularly directive MIMO antennas. It was found that the ability to transfer signal power from the transmitter to the receiver, instead of the rank properties, dominates in outage MI over a wide range of signal-to-noise ratios. The largest differences in outage MI between the antennas were found at low outage-probability levels, particularly in the line of sight. It was also verified that dual-polarized antenna systems are more robust for environmental variations but more sensitive for antenna orientation in comparison with single-polarized antenna systems both in eigenvalue dispersion and transferred signal power. At low outage-probability levels, the highest MI was achieved with vertically polarized dipole antennas.