Effect of array orientation on performance of MIMO wireless channels

The orientations of the receive and transmit antennas are often omitted in research into the performance of wireless channels. The letter investigates the effect on performance of multiple-input-multiple-output (MIMO) wireless channels with an analytical method. Three results are obtained: 1) the effect cannot be neglected if either the transmit or the receive angular spread is small; 2) to attain higher capacity, each array should be rotated to make its normal point in the mean direction of arrival or departure (DOA or DOD); 3) the effect on the MIMO wireless channel capacity is dominated by the orientation of the array with the smaller angular spread.