Multi-tone transmission for asymmetric digital subscriber lines (ADSL)

Multi-tone transmission is a potentially viable technique for application on asymmetric digital subscriber lines (ADSLs). The results of a preliminary study on the performance of an ideal discrete multi-tone (DMT) signaling technique for a 1.6-Mb/s ASDL are presented. The performance margins using single-tone 16-point quadrature amplitude modulation (QAM) with ideal decision feedback equalization (DFE) are presented. The feedforward filter of the DFE is a quarter-baud spaced fractionally spaced equalizer (FSE). The interference is assumed to be the sum of far-end crosstalk (FEXT) and additive white Gaussian noise (AWGN). The subscriber loops are assumed to be in a plant environment where the maximum resistance does not exceed 1300 Ω. The projected performance of an ideal DMT with a sampling rate of 1.024 MHz and 256-subchannel segmentation offers potential margin enhancement up to 3 dB over a quarter baud-spaced FSE-based 16-QAM signaling