Degrees of Freedom From the Six-Polarized MIMO Antenna in 1-D, 2-D, and 3-D Scattering Channels

Six-polarized (SP) multiple-input–multiple-output (MIMO) channel modeling method in the two-mirror, waveguide and reverberation cavity scenarios are presented based on the theory of image source, through which accurate electromagnetic fields in both the near and far fields can be obtained conveniently. The validity of this channel modeling has been verified by full-wave numerical simulations. Over those channels, channel degrees of freedom (DoF) of the SP MIMO system are investigated with multipath scattering increased gradually from 1-D to 2-D and 3-D space. Results show that, in free space, DoF larger than 3 can only be obtained in the near field, and in the far field it is almost a constant value of 2.5, however, in scattering environment, DoF is greatly increased. Specifically, over a cross section with area of 16 m², separated from the transmitter antenna by 10 wavelengths, in 1-D scattering channel, the maximum DoF can reach 5.50, and its mean value is 4.25. In 2-D and 3-D scattering channels, the maximum DoF is 5.67 and 5.76, and the mean value is 4.70 and 4.93, respectively.