High resolution CSI feedback with beam space MIMO

In Frequency Division Duplexing (FDD) system with multiple antenna, user equipment (UE) usually reports channel state information (CSI) to assist base station (BS) to determine downlink data associated precoder. Conventional precoder for one data layer is represented by a DFT vector. However, with the increasing number of antenna ports, beam width becomes narrower. Beam formed by one DFT vector hardly captures energy of multi-paths spreading in a relative large angle range. In this paper, a new precoder is proposed, which is represented by linear combining a set of selected steering vectors. The numerical simulation shows the significant performance gain of the proposal over conventional precoder.