Simulation results for QAM codes for DS-1 rate in subscriber loop plant (ISDN)

The author presents some of the simulation results when the transmission rate is enhanced to the primary rate. A series of results indicating the degradation of the 16 and 64 point quadrature amplitude modulation (QAM) constellations as the echo cancellation is reduced from 60 dB to 40 dB is given. The improvements as the loop configuration is altered to conform to the shorter carrier serving area (CSA) loops in the US are summarized. The results presented are indicative of typical CSA loop performance in US and Canada, and those of Australia, where fewer loop discontinuities and bridged taps are encountered. In Europe, the loops are also short with fewer discontinuities and few, if any, bridged taps.<>