Spectrally constrained impulse shortening filter for a discrete multi-tone receiver
AssigneeTellabs Operations, Inc.
InventorsGopal Harikumar, Daniel Marchok
Life of this patent
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Abstract
A channel in a multiple carrier communication system is equalized by computing a target spectral response, shortening the impulse response of the channel so that a significant part of an energy of the impulse response is confined to a region that is shorter than a target length and filtering the signal based on the target spectral response.
Claims33
1-35. (canceled)
A spectrally constrained impulse shortening filter for a multiple carrier communication system, the system being configured to receive a signal and includes a channel that has an impulse response, the filter comprising:
- an input coupled to receive the signal;
- a digital filter structure configured to apply a frequency characteristic to the signal, the frequency characteristic being determined by filter coefficients;
- and
- taps coupled to the digital filter structure, wherein the filter coefficients are selected to shorten the impulse response of the channel so that a significant part of an energy of the impulse response is confined to a region that is shorter than a target length.
A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising:
- an analog-to-digital converter coupled to communication channel;
- and
- a spectrally constrained impulse shortening filter coupled to the analog-to-digital converter and configured to shorten the impulse response of the channel so that a significant part of an energy of the impulse response is confined to a region that is shorter than a target length.
A modem comprising:
- an encoder arranged to receive digital data and output a constellation of complex values;
- an inverse discrete Fourier transform arranged to receive the constellation;
- a digital-to-analog converter coupled to the inverse discrete Fourier transform and arranged to output a signal to a communication channel;
- an analog-to-digital converter arranged to receive the signal;
- and
- a spectrally constrained impulse shortening filter arranged to shorten an impulse response of the channel so that a significant part of an energy of the impulse response is confined to a region that is shorter than a target length.
A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising:
- an analog-to-digital converter coupled to receive the signal from the communication channel;
- and
- a spectrally constrained impulse shortening filter coupled to the analog-to-digital converter and configured to (1) measure received noise power spectral density, (2) compute a cost function using the noise power, the cost function being dependent on the impulse response, (3) reduce the dimensionality of a space over which the cost function is defined and (4) minimize the cost function.
A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising:
- an analog-to-digital converter coupled to the communication channel;
- and
- a spectrally constrained impulse shortening filter coupled to receive the signal from the analog-to-digital converter and configured to (1) measure received noise power spectral density, (2) compute a target spectral response having a magnitude constraint that is based on the measured noise power spectral density and (3) select a frequency response of the spectrally constrained impulse shortening filter based on the target spectral response.
A modem comprising:
- a digital-to-analog converter arranged to output a signal to a communication channel;
- an analog-to-digital converter arranged to receive the signal;
- and
- a spectrally constrained impulse shortening filter configured to (1) measure received noise power spectral density, (2) compute a cost function using the noise power, the cost function being dependent on the impulse response, (3) reduce the dimensionality of a space over which the cost function is defined and (4) minimize the cost function.
A modem comprising:
- an encoder arranged to receive digital data and output a constellation of complex values;
- an inverse discrete Fourier transform coupled to receive the constellation;
- a digital-to-analog converter coupled to the inverse discrete Fourier transform and arranged to output a signal to a communication channel;
- an analog-to-digital converter arranged to receive the signal;
- and
- a spectrally constrained impulse shortening filter configured to (1) measure received noise power spectral density, (2) compute a target spectral response having a magnitude constraint that is based on the measured noise power spectral density and (3) select a frequency response of the spectrally constrained impulse shortening filter based on the target spectral response.
Dependencies are inferred from the claim text.