Jabil Circuit, Inc.

Jwalant Dholakia

Israel J Morejon

Yueping Zeng

An improved per-tone FEQ method with a noise reduction technique using periodic training pilot tones increases the throughput for long-reached modems. This method can reduce the noise effects in estimating FEQ equalizer coefficients. Each per-tone FEQ can be estimated by using the periodic training signals and an averaging technique to remove noise from each sub-channel (EQN. VI). After solving the system equations (EQN. IV), per-tone equalization coefficients of the FEQ equalizer for each group can be combined to obtain the optimized results in the form of the Toeplitz matrix (EQN. V). Each element within the Toeplitz matrix can be derived from the averaging technique used to remove noise from each sub-channel (EQN. VI). To demodulate a signal with the Toeplitz matrix, an inverse of every element in a row of the Toeplitz matrix is taken and multiplied by the sending signal which creates an N Log N matrix.

Method for initialization of per tone frequency domain equalizer (FEQ) through noise reduction for multi-tone based modems

The method and apparatus in accordance with the present invention provides signal-to-noise ratio improvement through noise reduction by means of spectral averaging and subcarrier based averaging techniques.

Method and apparatus for noise reduction by spectral and subcarrier averaging

A quadrature amplitude modulation implementation incorporating a symmetric spherical quadrature amplitude modulation constellation. The symmetric spherical quadrature amplitude constellation, as displayed in a multi-dimensional complex plane, is bounded by a surface comprising all symbol points at a predetermined distance from a center point and coincident with the intersection of at least two axes, and exhibiting correspondence in relative position of the symbol points on opposite sides of the at least two axes.

Symmetric spherical QAM constellation

The present invention discloses an improved initialization method for modem communication wherein the timing offset required for synchronization is estimated utilizing an entire received DMT frame and the channel impulse response is estimated utilizing the pilot tones received within the same DMT frames utilized for synchronization.

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St. Petersburg, FL, United States of America

Jwalant Dholakia