Codebook Design for LTE-A Downlink System

Multiple-input multiple-output (MIMO) has been adopted by long term evolution (LTE) and its updated version LTE-Advanced (LTE-A) to increase the spectrum efficiency. However, the benefits of multi-user (MU) MIMO highly rely on the accurate channel knowledge at the transmitter. So proper codebook design is a key problem for LTE-A FDD downlink system. In this paper, a codebook design with phase adjustment in the precoder targeting wideband channel properties is proposed. The average cell spectrum efficiency and cell-edge user spectrum efficiency of the proposed scheme are evaluated through system level simulation and compared to the discrete Fourier transform (DFT) based feedback scheme. The results show that the proposed codebooks significantly improve feedback efficiency and system performance for co-polarized linear antenna array.