A simplified structure of second-order volterra filters for nonlinear acoustic echo cancellation

The cascade connection of a 2^nd order Volterra filter (VF) with a linear transversal filter is often used in nonlinear acoustic echo cancellation (AEC) to model a nonlinear echo path comprising a nonlinear loudspeaker and a linear room impulse response. This cascade-form AEC, however, often suffers from divergence, since its nonlinear and linear constituents are updated separately and a global convergence toward the minimum residual echo error is hardly guaranteed. In this paper, we propose a simplified 2^nd order VF that is equivalent to the cascade structure for nonlinear AEC. The new structure has much fewer coefficients than the conventional direct-form 2^nd order VF does, while enjoys a better convergence performance compared to both the cascade canceller and the conventional 2^nd order VF. Computer simulation based experiments have confirmed the advantage of the proposed structure.