Frequency domain technique for narrowband noise cancellation in DMT receivers

• US 6,763,061 B1
• Filed: 07/31/2000
• Issued: 07/13/2004
• Est. Priority Date: 07/31/2000
• Status: Expired due to Fees

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Sy, Eugene T., Strait, Jeffrey C.
• Primary Examiner(s): Emmanuel, Bayard
• Assistant Examiner(s): Nguyen, Dung X
• Application Number:
  US09/628,842
• Time in Patent Office: 1,443 Days
• Field of Search: 375/219, 375/148, 375/229, 375/232, 375/295, 375/316, 375/227, 375/224, 375/285, 375/346, 375/348, 375/350, 375/140, 375/144, 375/147, 375/341, 708/300, 708/322
• US Class Current: 375/219
• CPC Class Codes: H04L 27/2649 Demodulators

Abstract

The system and method of the preferred embodiments may be directed to improving the signal-to-noise ratio in frequency spectrum regions where narrowband interference may be present. The system and method of the preferred embodiments includes reducing the narrowband interference by determining a noise estimate. In accordance with the noise estimate and output of a frequency domain equalizer, a noise-cancelled output may be obtained.

Claims

1. A method of increasing a signal-to-noise ratio for at least one carrier in a multicarrier transceiver comprising steps of:

receiving and storing at least one decoder error for the at least one carrier;

determining at least one adaptive filter tap for each of the at least one carrier in accordance with the at least one decoder error, wherein at least one adaptive filter tap comprises the minimization of the means squared error;

determining a noise estimate relating to the at least one decoder error and the at least one adaptive filter tap;

receiving an equalizer output;

determining a signal having increased signal-to-noise ratio in response to the noise estimate and the equalizer output; and

wherein the minimization of the mean squared error is performed in accordance with the relation;

ξ

=E{(x(i)−

f(n)y(i)+h_k*ê

(i))²} where x(i) is a known transmitted symbol such as during receiver training and/or the decision for the current constellation, where f(n) is the equalizer coefficient corresponding to the nth bin, where y(i) is a FFT output of the corresponding nth bin, and where h_k*ê

(i) is the filtering of an uncanceled decoder error ê

(i) with the filter taps h_k.

2. The method of claim 1, wherein the at least one decoder error is an uncanceled decoder error.

3. The method of claim 1, wherein the minimization of the mean squared error is performed in accordance with the relation:

h<sub>k−

1</sub>=h_k−

α

(x(i)−

f(n)y(i)+h_k*ê

(i))conj(ê

(i)) where h_k is the current filter tap, where α

is a corrective coefficient, where h_k*ê

(i) is the filtering of an uncanceled decoder error ê

(i) with filter coefficients h_k, where ê

(i) is the uncanceled decoder error for the symbol i of a total J symbols, and where conj(ê

(i)) is the complex conjugate of the uncanceled decoder error for a symbol i of a total J symbols.

4. The method of claim 1, wherein the step of determining an adaptive filter tap is performed in accordance with the relationship:

$h_{k+1}=\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>h_k+\left(1-\mathrm{\alpha <br><br>}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{\hat{e}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(i\right)}{\hat{e}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(i-1\right)},$

where α

is the corrective coefficient, where h_k is the adaptive filter tap for symbol i, and where ê

(i) is an uncanceled decoder error for the symbol i.

5. A computer readable medium having stored therein instructions for causing a central processing unit to execute the method of claim 1.