A first adaptive filter having a first filter length estimates a channel weight
vector of an echo channel using an affine projection (AP) update. The echo channel
receives a send input sequence and a receive input sequence. The echo channel has
a plurality of sparse multi-path channels. A delay estimator determines a plurality
of delays in the echo channel using the estimated channel weight vector. A second
adaptive filter estimates a plurality of short weight vectors using the AP update
and the plurality of delays. The short weight vectors correspond to the sparse
multi-path channels. Each of the short weight vectors has a short filter length.
