Field Experiments on Antenna Element Grouping for Smart Vertical MIMO in LTE-Advanced Downlink

This paper presents field experimental results on a vertical antenna element grouping for Smart Vertical (SV)-Multiple-Input Multiple-Output (MIMO) in the Long Term Evolution-Advanced downlink. Experimental results clarify that SV-MIMO achieves a higher fading correlation compared to a horizontally-arranged antenna configuration when the same antenna spacing is used. Then, when the combination of SV-MIMO and multi-user (MU)-MIMO is employed, we confirm that a gain is obtained by adaptively selecting the spacing among antenna element groups (group spacing) based on the different periods of the antenna grating lobes for each transmission mode. Finally, in measurement courses in urban and suburban areas, field experimental results show that the total throughput of greater than 1 Gbps is achieved for Rank 4 MU-MIMO by utilizing SV-MIMO with the group spacing of 3.1λ to 9.4λ.