Bandwidth optimization for high speed data transmission over channels with severe intersymbol interference

Algorithms are presented for finding the optimal transmission bandwidth in terms of either maximizing the overall data throughput or maximizing the system performance margin, given a fixed target data rate, for high speed data transmission over channels with severe intersymbol interference. The system is constrained to have an equipartition of energy over the entire transmission band used at the input to the channel. This yields suboptimal performance relative to the system based on a water-pouring transmit energy distribution. Although the performance degradation is typically negligible, the proposed bandwidth optimization procedures offer a significant computational advantage. It is shown that the procedures apply equally well to multicarrier and single-carrier modulation/equalization techniques. The procedures are applied to the recently proposed asymmetric digital subscriber line (ADSL) service, and performance projections based on computer simulation are presented for two canonical test loops