Simplified volterra filters for acoustic echo cancellation in GSM receivers

Acoustic echo cancellers commonly implement linear filters that have to identify as close as possible the impulse response of the acoustic echo path system. However such a system is highly nonlinear, and thus it is reasonable to suppose that a better system identification could be achieved by a nonlinear filter. Volterra filters are well suited for modelling that system but they need in general too many computational resources for a real time implementation. Here we present a novel nonlinear structure which exploits the echo path characteristics and thus is more efficient than conventional Volterra filters. For this structure we have considered two kinds of adaptive algorithms: standard LMS and Affine Projection (AP) algorithms that we adapted to this structure.