Method and apparatus for operating an adaptive decision feedback equalizer
US6215818A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 29, 1998 |
| Grant date | Apr 10, 2001 |
| Priority date | — |
| Expiry date | Apr 29, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2025/037
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A method of estimating signal-to-noise ratio at an output of an adaptive decision feedback equalizer receiving an input signal. The method of SNR estimation includes (a) calculating an average output error of the equalizer; and (b) estimating the signal-to-noise ratio (SNRest=k.sub.n -20 log.sub.10 (Eavg)) where k.sub.n is a constant based on a QAM index n and Eavg is the average output error of the equalizer. The estimated SNR can be used to detect proper equalizer convergence by comparing the estimated SNR to an SNR threshold (e.g. lowest SNR for a 4QAM signal), wherein the equalizer is not properly converged when the estimated SNR is lower than the SNR threshold. The estimated SNR can also be used to adjust the operating QAM index of the equalizer by comparing the estimated SNR to an ideal SNR based on an objective bit error rate for a prescribed QAM index, and reconverging the equalizer at a QAM index lower than the prescribed QAM index when the estimated SNR is lower than the ideal SNR.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.