Eigenvalue variation in MIMO OFDM systems

In this paper we consider the variation of eigenvalues and eigenvalue sums across the frequency bins of a MIMO OFDM system. In particular, we consider the changes in the ordered eigenvalues and the eigenvalue sum or link gain between two distinct frequency bins. The size of such changes has an important effect both on system performance and design. In addition these results have applications in other areas, including temporal variation, feedback delay and channel estimation. Novel results presented include distributions and moments for changes in link gain and the maximum eigenvalue and autocorrelation functions for the link gain and maximum eigenvalue. Furthermore, some very simple approximate results for the ordered eigenvalue differences are presented and the accuracy of the analysis is verified by Monte Carlo simulations.