US 2003/0076844 A1 · Method and system for filtering a signal and providing echo cancellation using an adaptive length filter

Abstract

The present invention provides for adaptive filters that have improved convergence, computational, and memory bandwidth proprieties. When applied to telecommunication applications, the present invention additionally provides for improved methods and systems of canceling echoes. In one embodiment of the adaptive filter of the present invention, a filter, preferably an adaptive finite impulse response (FIR) filter, of an appropriate length, N, is chosen. Once the filter is chosen, convergence is achieved using a convergence process. With convergence complete, the total energy of the filter coefficients is computed and two energy thresholds, a first energy threshold and a second energy threshold, are set relative to the computed total energy. Using the set energy thresholds, new filter coefficients are determined by relating the starting filter coefficient with the first energy threshold and the end filter coefficient with the second energy threshold. A first filter delay, in accordance with the determined start coefficient, is incorporated into the filter operation.

Claims46

Dependent claims

An adaptive filter, comprising:

a filter input for receiving a first signal;
a filter output for outputting a second signal based upon said first signal;
an error input for receiving an error signal;
a plurality of first coefficients, each having an associated energy, wherein said first coefficients are modified based upon the error signal;
and
a plurality of second coefficients having a start coefficient and an end coefficient, the second coefficients being a subset of the first coefficients, wherein the start coefficient and end coefficient are determined by applying at least one threshold value to an energy value, said energy value being a function of the energy of a plurality of first coefficients.

3 more elements

An echo cancellation system for canceling echo within a second signal generated by the transmittal of a first signal through a cross-coupling pathway, comprising:

a device for summing a third signal and the second signal to produce an error signal;
and
an adaptive filter comprising a filter input for receiving the first signal, a filter output for outputting the second signal based upon said first signal, an error input for receiving the error signal, a plurality of first coefficients, each having an associated energy, wherein said first coefficients are updated based upon the error signal, and a plurality of second coefficients having a start coefficient and an end coefficient, the second coefficients being a subset of the first coefficients, wherein the start coefficient and end coefficient are determined by applying at least one threshold value to an energy value, said energy value being a function of the energy of a plurality of first coefficients.

Dependencies are inferred from the claim text.

Method and system for filtering a signal and providing echo cancellation using an adaptive length filter

Life of this patent

Method and system for filtering a signal and providing echo cancellation using an adaptive length filter

Life of this patent

Abstract

Claims46