Spectrally constrained impulse shortening filter for a discrete multi-tone receiver
First Claim
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1. 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:
- 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 being 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 length of a cyclic prefix of the signal.
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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.
175 Citations
24 Claims
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1. 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:
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 being 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 length of a cyclic prefix of the signal.- View Dependent Claims (2, 3)
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4. A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising:
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an analog-to-digital converter configured 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 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 length of a cyclic prefix of the received signal. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. A modem comprising:
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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 coupled to the analog-to-digital converter and 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 length of a cyclic prefix of the received signal. - View Dependent Claims (12, 13, 14)
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15. A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising:
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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.
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16. A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising:
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an analog-to-digital converter configured to receive the signal from 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. - View Dependent Claims (17, 18)
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19. A modem comprising:
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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 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. - View Dependent Claims (20, 21, 22)
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23. A modem comprising:
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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 couple to 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.
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24. A receiver for receiving a multiple carrier signal from a communication channel having an impulse response, the receiver comprising a spectrally constrained impulse shortening filter coupled to an 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 length of a cyclic prefix of the signal.
Specification