Dual mode LMS nonlinear data echo canceller

An echo canceller for generating an estimated echo signal e(k) to cancel an echo signal e(k) generated by a transmission channel from a data signal X(k), where k is a time index, said echo canceller comprising

• memory means for storing a vector f(X.sub.k).sub.k where f(.) is a nonlinear function representative of a nonlinear component of an echo transmission path of said echo signal and X.sub.k is a vector formed from the values of the signal X(k) for the last n values of the time index k where n is an integer,
• means for obtaining a vector H.sub.k corresponding to an estimated finite impulse response of a linear component of said echo transmission path, and
• means for obtaining the product of (X.sub.k +f(X.sub.k).sub.k) and H.sub.k to form said estimated echo signal e(k).

A method for cancelling an echo in a telecommunications channel used to transmit a digital data signal, said method comprising the steps of

• during a training period, using a least mean square algorithm to estimate the finite impulse response of a linear component of an echo path, and
• during a subsequent dual mode phase, using a least mean square algorithm to both estimate a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path,
• wherein during said dual mode phase, alternately, said nonlinear function is estimated and said finite impulse response is held constant and said finite impulse response is estimated and said nonlinear function is held constant.

A method for cancelling an echo in a telecommunications channel used to transmit a digital data signal, said method comprising the steps of

• during a training period, using a least mean square algorithm to estimate the finite impulse response of a linear component of an echo path, and
• during a subsequent dual mode phase, using a least mean square algorithm to both estimate a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path,
• wherein said method further comprises the step of storing values of said nonlinear function in a random access memory.

The method of claim 10 wherein said nonlinear function representative of said nonlinear component of said echo path includes no delay.

A method for generating an estimated echo signal e(k) for use in an echo canceller to cancel an echo signal e(k) where k is a time index comprising the steps of storing a nonlinear data vector Y.sub.k =.psi.(X.sub.k), where X.sub.k is a data vector formed from the values of said signal X(k) being transmitted for the last n values of the index k where n is an integer and where .psi. is a nonlinear function representing the effect of a nonlinear component of a transmission path of said echo signal e(k), and forming the product of Y.sub.k H.sub.k where H.sub.k is an estimate of a finite impulse response of a linear component of said echo path to obtain said estimated echo signal e(k).

An echo canceller comprising

• means for storing values of a nonlinear function representative of a nonlinear component of an echo path,
• means for storing values representative of a finite impulse response of a linear component of said echo path, and
• means for executing a least mean square algorithm for alternately estimating said values of said nonlinear function and said values representative of said finite impulse response.

A method for cancelling an echo in a communications channel comprising

• storing values of a nonlinear function representative of a nonlinear component of an echo path,
• storing values representative of a finite impulse response of a linear component of an echo path, and
• executing a least mean square algorithm for alternately estimating said values of said nonlinear function and said values representative of said finite impulse response.