Codebook Design for Cross-Polarized Linear Antenna Array in 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 system spectrum efficiency. However, the benefits of multi-user (MU) MIMO highly rely on an accurate channel knowledge at the transmitter. So proper codebook design is a key problem for LTE-A FDD downlink system. In this paper, the channel characteristic specific to cross-polarized linear antenna array is analyzed, then its codebook design based on amplitude and phase adjustment is proposed for LTE-A downlink system. The proposed codebooks are compared to the differential scheme [7] on the average cell spectral efficiency and cell-edge user spectral efficiency evaluated through system level simulations. Simulation results show that the proposed codebooks significantly improve channel feedback efficiency and system performance.