Equalization for DMT based broadband modems

Faced with fierce competition from cable operators, telephone companies are now aggressively investing in digital subscriber line technology with the objective of providing an economic broadband access alternative. However, high-bit-rate transmissions over the metallic access network is far from trivial. The subscriber loop predominantly consists of interconnection of twisted pair copper sections. This causes severe attenuation of the high-frequency components of the transmitted signal. Equalization refers to the signal processing in the transceiver to combat the effects of the dispersive channel on the transmitted signal. This article overviews equalization methods for discrete multitone modulation (DMT). The interference structure created by a non-ideally equalized channel is analyzed. Time modulation as well as frequency domain equalization methods are addressed.