Polarization diversity in a 2x2 MIMO communication system is investigated for Alamouti and spatial multiplexing transmission schemes. Parameters such as cross polar discrimination and correlation coefficients introducing the polarization diversity are included in the channel model. Receive antenna correlation coefficients are generated from a realistic random model. The relative performance of the single and dual polarizations depends significantly on the channel characteristics. Single and dual polarization BER performances are compared for constant and distance dependent random channel parameters. It is shown that polarization diversity results better BER performance for both Alamouti and spatial multiplexing schemes compared to single polarization for the distance dependent and fully characterized channel model.