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Coverage evaluation of 4 by 4 MIMO base station antenna

Multiple-input and multiple-output (MIMO) techniques have been key to increasing the data rate and capacity in recent mobile systems. Focusing on antenna installation, one of the most serious problems is the limitation on installation space for additional antennas at base station (BS) sites. This manuscript evaluates the effectiveness of a 4 by 4 MIMO BS antenna configuration using vertically stacked dual polarized half size antennas for cellular BS antennas when there is limited installation space for additional antennas. The coverage area, the spatial correlation, and inter-cell interference are evaluated based on a statistical analysis model. The antenna configuration is advantageous in increasing the capacity around the BS because the number of MIMO branches is increased and the number of null points in the area is decreased. The optimum tilt angle is different according to policy of the cell design. For the case of focusing on the area size in cell design, the configuration yields degraded quality in the cell edge area compared to that for conventional full size antennas. On the other hand, for the case of focusing on the system capacity in cell design, the degradation in geometry for the target 4 by 4 antenna can be suppressed using an additional tilt of +4 degrees compared to the tilt angle of the 3G antenna in the scenario. The 4 by 4 antenna configuration is effective to increase the channel capacity in exchange for the area size.