The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 10, 2001
Filed:
Apr. 29, 1998
Edgar Velez, Kanata, CA;
Ian Dublin, Ottawa, CA;
Richard Buz, Rohnent Park, CA (US);
Sisay Yirga, Nepean, CA;
Nortel Networks Limited, Montreal, CA;
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,−20 log,(Eavg)) where k,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.