An adaptive echo canceller utilizing the conjugate gradient method in a time-variant telecommunication channel

An efficient procedure using the conjugate gradient method (CGM) is presented for adaptively computing the optimal set of coefficients for an echo canceler such that the solution can be obtained in a time-variant environment as well as in an ordinary time-invariant situation. By setting a functional which monotonically decreases at each iteration, the convergence is guaranteed for any signal matrix. The fast convergence of the CGM enables the proposed method to be applied in a nonstationary signal environment in which the optimal solution must be computed independently at each sampling period. Computer simulations indicate that the technique can be used for canceling echo signals much more efficiently than conventional methods in terms of the convergence speed and conformation of the convergence itself.