Performance of spatial multiplexing in the presence of polarization diversity

In practice large antenna spacings are needed to achieve high capacity gains in multiple-input multiple-output (MIMO) wireless systems. The use of dual-polarized antennas is a promising cost effective alternative where two spatially separated antennas can be replaced by a single antenna element employing orthogonal polarizations. This paper investigates the performance of spatial multiplexing in MIMO wireless systems with dual-polarized antennas. We compute estimates of the symbol error rate as a function of cross-polarization discrimination (XPD) and spatial fading correlations. Using these estimates, we show that dual-polarized antennas can significantly improve the performance of spatial multiplexing systems. It is demonstrated that improvements in terms of symbol error rate of up to an order of magnitude are possible. We furthermore find that in general for a given SNR there is an optimum XPD for which the symbol error rate is minimum. Finally, we present simulation results and we show that our estimates closely match the numerical results