Probability of error and capacity of multipolarization antenna systems for downlink mobile communications

A theoretical channel model is proposed to study the probability of error and channel capacity of multipolarization antenna systems for downlink mobile communications. The effect of scattering on polarization is first studied based on Fresnel reflection law. Expressions for correlation between antennas at both sides are derived for different polarizations. To simplify the analysis, it is assumed that there is only a single reflection and the path angular spread at the base station is approximately zero. Next, the probability of error and channel capacity are studied numerically for different antenna configurations. The impact of scattering environment on performance is also investigated. It is found that when a three-branch orthogonal structure is used for diversity at the mobile station, the error probability is invariant to receiver orientations, and the improvement is insignificant for more receive antennas. At the base station, both probability of error and channel capacity are substantially improved by using two transmit antennas that produce orthogonal polarizations in the direction of the mobile station, and the performance is invariant to rotations of the two transmit antennas. In addition, for almost all configurations, the performance becomes better in general for larger angular spread of reflectors.