Echo cancellation techniques for ADSL transceivers

Multicarrier transmission methods have long known to optimize the performance of data transceivers on bandlimited communication channels. One form of multicarrier transmission, known as discrete multitone modulation (DMT), is particularly attractive for its ability to be implemented using efficient digital signal processing techniques. The ANSI Tl committee has standardized discrete multitone modulation (DMT) as the line code to be used in the ADSL transmission system, due to its unique ability to overcome the severe distortion of the copper line at this frequency band. Given a basic DMT system, it is possible to increase the aggregate data rate with full duplex transmission using echo cancellation. This paper presents high speed echo cancellation techniques for full duplex data transmission using G. Lite ADSL standards. Time domain echo cancellation and mixed time and frequency domain echo cancellation techniques have been implemented for G. Lite ADSL applications. It has been observed that Time and frequency domain echo canceller (TAFDEC) achieve lower complexity for G. Lite ADSL systems that required by time domain echo canceller (TDEC) using traditional single carrier technique, such as least mean square (LMS) Hi algorithm. (author)