Measurements of phase fluctuations for reliable MIMO space communications

The capacity of a multiple-input multiple-output (MIMO) satellite communication system heavily depends on the phase relations inside the channel transfer matrix. Beneficial phase conditions to achieve the maximum MIMO gain can be realized by sophisticated geometrical setups of the transmit and receive antennas. It has been shown that the maximum MIMO gain is maintained, if the antennas are moved within a certain limit around the optimum position. Contrarily, variations of the path length induced by the troposphere are in some cases quite harmful for the channel capacity of a satellited-based MIMO system. To measure the intensity of these distortions we present an interferometer located near Munich, Germany. Here shown observations are transferred to a model of MIMO systems with two satellites. The results indicate no remarkable capacity losses for small inter-antenna spacings on Earth.