Frequency offset tracking for the Nyquist voiceband data echo canceller

The degradation in echo canceler performance caused by frequency offset (phase roll) in the far-end echo is investigated. It is determined that even a very small nonzero frequency offset, in extreme situations of -0.01 Hz, can lead to an acceptable degradation in the performance of the echo canceler. A method for compensating the frequency offset is also devised and recommended. The method directly estimates the offset frequency while maintaining the use of the Nyquist T/3 echo canceler. This latter feature contrasts with previous methods, which usually revert to the more computationally intensive cross-coupled echo canceler for the implementation. As acquisition of frequency offset in the presence of a strong double talker is very slow; a fast acquisition method is presumed.<>