Decision directed channel estimation for improving performance in LTE-A

The use of decision directed (DD) channel estimation in a MIMO-OFDM downlink receiver with a LTE pilot structure is studied in this paper. The space-alternating generalized expectation-maximization (SAGE) algorithm is used to improve the receiver performance from the one obtained by using the pilot symbol based least-squares (LS) channel estimator. The DD channel estimation improves the performance with high user velocities, where the pilot symbol density is not sufficient. The DD channel estimation can also be used to reduce the pilot overhead without any performance degradation by transmitting data instead of pilot symbols. The complexity of the SAGE channel estimator is discussed as well.