Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
2007-08-07
2007-08-07
Bayard, Emmanuel (Department: 2611)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
Reexamination Certificate
active
09585027
ABSTRACT:
Systems for generating a discrete multitone signal are provided in which N carriers, corresponding to respective subchannels, are modulated in each sample period (T) of the signal by performing an inverse discrete Fourier transform of N modulation symbols (Xk,{tilde over (X)}k), each of which symbols (Xk,{tilde over (X)}k) represents a signal point in a QAM constellation for a respective subchannel, the QAM constellation comprising a basic constellation of M≧2msignal points where m is the number of data bits to be communicated over the subchannel in a sample period. For each of Nc≦N of the subchannels, an expanded QAM constellation is defined which comprises pM signal points including said basic constellation of points, where p is an integer greater than 1. In each expanded constellation, p−1 equivalent signal points are defined for each signal point of the basic constellation, where each of the p−1 equivalent points is selected from redundant points in the opposite quadrant of the constellation to the corresponding point of the basic constellation. The discrete multitone signal is generated in a sample period (T) by selecting, for each of the Ncsubchannels, the modulation symbol (Xk,{tilde over (X)}k) representing either a basic constellation point or a corresponding equivalent point such that the peak value of the signal does not exceed a predetermined threshold.
REFERENCES:
patent: 5822323 (1998-10-01), Kaneko et al.
patent: 6459678 (2002-10-01), Herzberg
patent: 6483869 (2002-11-01), DesJardins
patent: 6512797 (2003-01-01), Tellado et al.
patent: 2002/0150152 (2002-10-01), Greszczuk et al.
Bayard Emmanuel
Cameron Douglas W
International Business Machines - Corporation
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