Patent ID: 6721279
Filing Date: 2004-04-13
Classification: H04L,H04M

Abstract:
A method of creating a constellation for use by a first modem to compensate for digital impairments in a communication channel between said first modem and a second modem, said method comprising:training an equalizer having a feedforward portion and a feedback portion to yield feedforward and feedback tap values; receiving an analog representation of a digital impairment learning (DIL) by said first modem via said communication channel, said DIL including a plurality of segments, each of said plurality of segments being characterized by a PCM level, a PCM reference and a sign pattern; converting said analog representation of said DIL to generate a digital representation of said DIL; equalizing said digital representation of said DIL, using said equalizer, to generate equalized segments; arranging said equalized segments into a sequence of signal vectors; selecting level estimates to minimize a sum of squared errors, wherein said errors are based on differences between said signal vectors and a product of said feedforward and feedback tap values, values of said sign pattern and said level estimates; and defining a constellation based on said estimated sample magnitudes.