Polarization diversity performance of mobile terminals in multipath environment using MIMO channel characterization

Abstract

Polarization diversity, a technique where different polarizations are used to provide diversity, has proved to be an efficient way of reducing the size and numbers of the antennas needed for a mobile terminal working in modern wireless networks. This method does not require any extra bandwidth or more space for physical separations between the antennas. It uses only one dual-polarized antenna and it takes advantage of the multipath propagation characteristics to receive separate uncorrelated signals and reduce fading. The applicability of polarization diversity for mobile terminals in a multipath environment can be evaluated using as figures of merit the signal cross correlation and cross polarization discrimination (XPD), while the effectiveness of the diversity system can be measured by diversity gain. Since the XPD may be crucial to polarization diversity, the antenna radiation patterns should always include co- and cross-polar field components. In a multipath rich environment, regardless of the original polarization of radiated waves, multiple reflections depolarize radio waves and couple some energy into the orthogonal polarized wave. As a result, both orthogonal wave components are received by the antenna of the mobile terminal.