Reduced complexity echo cancellation using orthonormal functions

Top reduce the echo canceler complexity associated with the cancellations of subscriber loop echo responses with long tails, a two-stage digital echo canceler, in which the second stage is an adaptively weighted combination of orthonormal IIR responses is proposed and investigated. Satisfactory performance (70-dB cancellation) was found for a variety of loops at 80 and 320 kB symbol rates with 15 such IIR responses, based on a Laguerre functions. The first echo canceler stage is a conventional transversal filter with 20-40 tap coefficients. Substantial complexity reduction was achieved by the new structure. Adaptation convergence was also analyzed and simulated.>