The Limited Feedback Precoding Based on the Triplex Codebooks

The precoding method based on the triplex codebooks with limited feedback has been put forward in the paper in order to solve the problem that the feedback accuracy of the CSI is not enough for the precoding based on the single codebook with limited feedback in the LTE-FDD mode. The triplex codebooks are composed of the original codebook, the enhanced codebook and the modified codebook. The enhanced codebook is used against the adverse circumstances that the condition number of channel matrix is too high, and the modified codebook could be used to reduce the quantization error. The simulation results of the proposed method show that the feedback overhead is only increased by 1bit, but the BER (bit error rate) performance can be enhanced about 2dB and the channel capacity can be improved about 1.2bps/Hz relative to the precoding method with the single codebook. Therefore, the precoding method proposed in the paper can significantly improve the precoding performance at the small cost of feedback overhead. In the practical application, the triplex codebooks can be designed by the off-line way, and the complexity of the proposed method will not be obviously increased.