Downlink channel covariance matrix (DCCM) estimation for FDD SDMA
The downlink channel covariance matrix (DCCM) is of vital importance in determining downlink beamforming weights for base station (BS) antenna array systems. For frequency-division-duplex (FDD) mode, DCCM is difficult to obtain due to lack of direct measurement of downlink channel responses. A novel technique is proposed for estimating DCCM using uplink channel responses only, which does not need DOA estimation and its association. The new technique is much simpler than the DOA-based approach and the GF algorithm.