Efficient and robust cancellation of echoes with long echo path delay

This letter presents an efficient and robust scheme to cancel echoes with long echo path delay. In the scheme, wavelet packet (WP) decomposition-based subband adaptation is applied to yield low computational complexity as well as high echo return loss. Meanwhile, a three-state switching architecture that switches among low-order normalized least mean square adaptation, delayless WP-based subband adaptation, and freezing state is proposed to further improve the performance. Theoretical analysis and comparative test results show that, while not introducing extra transmission delay, the proposed method achieves faster convergence rate at lower computational complexity, and additionally yields impressive performance, even during double talk or echo path change.