Experimental MIMO Comparisons of a 4-Element Uniform Linear Array to an Array of Two Cross Polarized Antennas at 3.5 GHz

Motorola has developed a 20 MHz experimental wide-area mobile multi-antenna system at 3.5 GHz for characterizing the spatial channel. With this system, simultaneous channel measurements were taken using both a uniform linear array (ULA) and an array of two cross-polarized (XP) antennas for locations near the Motorola Schaumburg campus. The ULA consists of eight vertically-polarized elements with half wavelength spacing between elements and the XP array consists of two XP panels spaced at two wavelengths where each XP panel consists of two co-located antennas with one antenna having a +45° polarization while the other has a -45° polarization. The receive array consists of eight vertically-polarized antennas in a uniform circular array with a radius of 2.62 wavelengths. This paper compares the antenna correlation and the downlink performance of a ULA (with both half wavelength and one wavelength spacings) and the XP array in a power-fair scenario with four transmit elements for each array type in each sector. Eigen beamforming (EBF) for TDD, DOA-beamforming for FDD, and single-user MIMO (SUMIMO) algorithms are compared.