Enabling 3D MIMO in LTE-Advanced — From the CSI acquisition perspective

Traditional multiple-input multiple-output (MIMO) systems mostly consider only the azimuth dimension of the three-dimensional (3D) multipath propagation. Recently, there has been interests in extending MIMO techniques to exploit the elevation dimension in addition to the azimuth dimension. In this paper we developed a rank-restricted representation of MIMO channels. Based on the cascading structure of the representation, we propose a two-stage precoding framework for 3D MIMO processing. Several design options under this framework are discussed. System-level performance evaluation is conducted for various antenna configurations. Simulation results show that significant cell-edge and median user throughput gain can be achieved compared to the legacy MIMO system.