Very high-speed digital transport capability of passband ADSL

The loop length coverage of an asymmetrical digital subscriber line (ADSL) passband system operating at very high bit rates is determined. The ADSL is implemented using the quadrature amplitude modulation (QAM) scheme, and transmits information on the high-rate channel from the networking end to the customer end. Simulation results are presented for ADSL impairments arising from various combinations of self-far-end crosstalk (FEXT), background receiver and cable noise (excluding impulse noise), and near-end crosstalk (NEXT) from basic rate DSL and high-bit-rate DSL (HDSL). It is shown that the 16-QAM constellation generally achieves the best performance. Depending on the types of ADSL impairment, coverage of the extreme carrier serving area (CSA) is possible at bit rates that are well above 1.6 Mb/s