1. A method for estimating the impulse response of a channel comprising: a-periodically cross-correlating a known training signal with a received training signal to produce a cross-correlation vector, the cross-correlation vector being characterized by a noise component resulting from the finiteness of the correlation; estimating a correction vector based on the known training signal, the correction vector being related to the noise component; and, iteratively subtracting truncated representations of the correction vector from the cross-correlation vector to produce a succession of cross-correlation outputs of increased accuracy.