Channel equalization for very high-speed digital data communication

The performance analysis is presented of an adaptive receiver based on a decision feedback equalizer (DFE) that uses a fractionally spaced equalizer (FSE) for channel equalization at 400 kbaud signaling using a quaternary line code (800 kb/s data rate). The minimum mean-square error (MMSE) is used as the performance parameter, where the error is due to the sum of the residual near-end crosstalk (NEXT) and precursor intersymbol interference (ISI). The results of a comprehensive computer simulation study indicate that as a function of the sampling phase, the ratio of the average signal power to MMSE (SNR) is practically constant with a half baud-spaced FSE, whereas with a baud-spaced equalizer the SNR varies 1-3 dB on the lossy loops. A simulation study of an adaptive FSE/DFE receiver demonstrates that the 6 dB of NEXT noise margin is achievable with a 21-tap half baud-spaced FSE and a 60-tap DFE on a 9-kft 26-gauge loop