Embodiments of a method in a base station for precoding a downlink transmission are disclosed. In some embodiments, the method comprises obtaining, for a time instant k, an estimate of a channel matrix for a wireless channel for a downlink from the base station to a wireless device and projecting the estimate of the channel matrix onto one or more sets of spatial orthonormal functions, thereby obtaining respective sets of coefficients. The method further comprises, for each set of spatial orthonormal functions, filtering the set of coefficients for the time instant k based on a filtering parameter that is specific to a downlink channel to be transmitted. The method further comprises generating beamforming weights using the filtered set of coefficients for at least one of the sets of spatial orthonormal functions, and precoding the downlink channel using the beamforming weights.