Polarization rotation evaluation for macrocell MIMO channel

In this paper, the impact of the polarization on the performance of the multiple-input multiple-output (MIMO) channel with cross-polarized antennas has been investigated based on the outdoor macrocell measurement at 2.53 GHz. A simple model which can capture the major characteristics of the cross polarized channel is proposed. The effective polarization rotation during the propagation is evaluated using the proposed model, and found to follow a bimodal Rayleigh distribution. The commonly accepted uniform distribution polarization rotation angle is a reasonable but coarse assumption compared with our estimated results. The vertical and horizontal polarization perform similarly in line-of-sight (LOS) scenario, but may be different in non-LOS (NLOS) scenario depending on the environment where the receiver is located. The polarization diversity outperforms the spatial diversity in LOS scenario, but shows relatively small gain in a rich scattering scenario. This is further proofed by the comparison of the capacity of a 4 times 4 MIMO channel with cross-polarized antennas.