Diversity and correlation in Rayleigh fading MIMO channels

The performance of MIMO systems and the usefulness of dedicated signal processing and channel coding techniques is strongly affected by presence of fading correlation. For instance, space-time block coding is favored by low fading correlation, while beamforming techniques are advantageous at high amounts of correlation. In this paper we propose an easy to compute quantitative measure of fading correlation and a measure of diversity present in a MIMO channel. It turns out that channels with the same amount of diversity or correlation behave essentially the same with respect to channel capacity and throughput. On the other hand, channels which differ considerably in diversity and correlation measure, behave fairly differently with respect to channel capacity or throughput. In this way it becomes possible to perform a classification of MIMO channels.