DMT-based ADSL: concept, architecture, and performance

We present various aspects of a high performance ADSL transceiver system using the powerful discrete multitone (DMT) modulation technology. DMT is the adopted ADSL line code for the emerging North American (ANSI), as well as the European (ETSI), ADSL standard. We first introduce the basic concept of DMT modulation, which effectively divides the transmission channel into a number of parallel subchannels and allows optimal usage of each subchannel to achieve "bandwidth-on-demand". We then address various implementational issues related to an ANSI standard compliant ADSL transceiver, including bit loading, channel coding, echo cancellation, and bit swapping. Finally, the performance, including both independent laboratory measurements of prototype ADSL systems and computer simulations, is presented.