On the impact of correlation on the capacity in MIMO systems without CSI at the transmitter

We study the impact of correlation on the ergodic capacity of a multiple-input multipleoutput (MIMO) system. Recently, results for the asymptotic case with in.nite many transmit and receive antennas were developed and it was shown that correlation decreases the ergodic capacity. In the high SNR range, the impact of correlation can easily be derived, too. In this work, we present analytical results for a .nite number of transmit and receive antennas and arbitrary SNR values. We extend the theory of, which was developed for systems with one receive antenna, to the case with two receive antennas. In addition to this, we show that the ergodic capacity is highest for uncorrelated transmit antennas, in general. Furthermore, the di.erence between the ergodic capacity with fully correlated and completely uncorrelated transmit antennas is analyzed. All theoretical results are illustrated by numerical simulations.