Double talk cancellation in echo cancelled DMT-systems

The existing ADSL standard allows for two possible transmission systems: frequency division duplexing (FDD) and echo cancelling (EC). Echo cancelling is particularly attractive for its ability to achieve higher data rates compared with FDD schemes. A disadvantage of EC is that adaptive schemes exhibit slow tracking properties in the presence of a far end signal or double talker. This paper presents an efficient method for updating echo canceller taps in ADSL transceivers in the presence of a far end signal, by effectively cancelling most of the received far end energy. The presented scheme extends existing multicarrier echo cancelling schemes with a feedback of decisions on the far end signal. As a result the convergence is much faster and hence fast tracking properties are possible at a low computational complexity.