A Coherent PMI Estimation Scheme for Double Codebook

摘要

The double codebook structures are proposed and applied in LTE-advanced, which can track both long-term and short-term channel state information. In traditional incoherent estimation, precoding matrix indicators (PMI) estimation is performed on each individual subcar-rier and some form of averaging procedure then follows to combine the results from individual narrow-band processing. As a result, if there is a large deviation in any estimates of a subcarrier, it will lead to a larger deviation in the final result. Thus incoherent PMI estimation has a poor performance in low signal to noise ratio. This paper introduces a new PMI feedback scheme for wideband sources with coherent signal subspace method. This new technique estimates PMI based on an approximately coherent combination of each subcarrier by a focusing matrix. Simulation results show that the coherent estimation scheme has a better throughput performance than the traditional incoherent estimation.