DE3113394

A full-duplex, two-wire Nyquist sampled data communication system includes an adaptive echo canceller (24) at each terminal (e.g., 10'). The echo canceller generates a replica (zm) of the echo component of each sample (rM) of the incoming signal. The replica and the sample are subtractively combined to provide an echo compensated signal (SM). During intervals of simultaneous transmission and reception, i.e., double talk, the echo compensated signal may contain not only an uncancelled echo component but also a far-end data component. An adaptation error signal generator (80), operating in response to a stream of recovered data symbols (e.g., ân), estimates and removes the far-end data component from the echo compensated signal and, in response to the difference, generates an adaptation error signal ( gamma EM-D). This signal is applied as an error signal to the echo canceller. This allows the echo canceller to adapt its set of tap coefficients in response to the uncancelled echo component present in the echo compensated signal. Thus, stable and accurate echo cancellation results even during a double-talk interval.