On-line identification of echo-path impulse responses by Haar-wavelet-based adaptive filter

Long-distance telephone communications of good quality require absence of echoes. The physical characteristics of an echo path are time varying and the impulse responses measured at different times can differ from each other. This means that an echo canceller must track the changes. Using a small number of coefficients in Haar-wavelet-based models we can efficiently identify echo paths which have certain typical impulse response shapes. The modeling error energy obtained is low (less than 2%). A simple wavelet-based LMS adaptive filter can be used for on-line estimation of the coefficients. A low number of time-consuming computations is obtained per input sample due to the usage of Haar wavelets. This number is less than the ones obtained by the FIR of DFT domain based modeling.