1940s - Wiener filter

1960s - Kalman filter

1960s - LMS (Least Mean Square)

1970s - NLMS (Normalized LMS)

1980s - Affine Projection

2000s - Adaptive Step Size Sub-band, Non-Linear Filter (AS3 NLF)

Chronicle
Echo cancellation has been through significant changes since the Wiener filter technology became available in 1940. The Kalman filter and LMS (Least Mean Square) algorithm replaced the Winier filter during 1960s, because the Wiener filter was not suitable for real time applications. Due to the increased computational requirements for the calculations in the embedded world, the cost of implementation of the embedded system is very high with the Kalmann algorithm. LMS algorithm has less stability while applied with real human voice communication applications. A modified and more stable algorithm, NLMS (Normalized LMS), became prevalent in eighties until the most recently introduced advanced technology from Fortémedia, the AS3NLF.

Fortemedia's AS3NLF technology is implemented in our state of art echo canceller, AMBIN FM1073. With cancellation in both time and frequency domain and innovative non-linear process, AS3NLF is able to handle extreme large echo.