Equalizers for layered modulated and other signals

• US 20040184521A1
• Filed: 10/22/2003
• Published: 09/23/2004
• Est. Priority Date: 04/27/2001
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Chen, Ernest C., Lin, Tung-Sheng, Lindsey, William C., Wang, Weizheng
• Granted Patent: US 7,184,473 B2
• Time in Patent Office: Days
• US Class Current: 375/231
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04L 2025/03477 not time-recursive
• CPC Class Codes: H04L 25/0305 using blind adaptation

Abstract

A method and apparatus for equalizing digital data signals is disclosed. The method comprises the steps of demodulating and decoding an input signal having input data to produce a data output, remodulating the data output to produce a training sequence including an idealized input signal, wherein the training sequence is comprised of adjacent symbols in the input data, and generating equalizer parameters from the training sequence. The apparatus comprises a demodulator (for demodulating an input signal to produce a data output), a modulator communicatively coupled to the demodulator (for remodulating the data output to produce a training sequence including an idealized input signal wherein the training sequence is comprised of adjacent symbols in the input data), and a parameter generation module communicatively coupled to the modulator (for generating equalizer parameters from the training sequence).

Claims

1. A method of equalizing digital data signals, comprising:

demodulating an input signal having input data to produce a data output;

remodulating the data output to produce a training sequence, wherein the training sequence is comprised of adjacent symbols in the input data; and

generating equalizer parameters from the training sequence

2. The method of claim 1, further comprising decoding the input signal after the demodulation.

3. The method of claim 2, further comprising re-encoding the input signal prior to the remodulation.

4. The method of claim 1, wherein the step of generating equalizer parameters comprises comparing the training sequence with the input signal to determine channel distortion.

5. The method of claim 4, wherein the step of generating equalizer parameters comprises subtracting the adjacent symbols from the input signal to reproduce channel impairments, wherein the channel impairments are subtracted from the input signal for equalization.

6. The method of claim 5, wherein the channel impairments comprise inter-symbol interference.

7. The method of claim 1, wherein the step of generating equalizer parameters from the remodulated data output comprises:

buffering the input signal; and

comparing the buffered input signal to the training sequence to produce the equalizer parameters.

8. An apparatus for equalizing digital data signals, comprising:

means for demodulating an input signal having input data to produce a data output;

means for remodulating the data output to produce a training sequence, wherein the training sequence is comprised of adjacent symbols in the input data; and

means for generating equalizer parameters from the training sequence

9. The apparatus of claim 8, further comprising means for decoding the input signal after the demodulation.

10. The apparatus of claim 9, further comprising means for re-encoding the input signal prior to the remodulation.

11. The apparatus of claim 8, wherein the means for generating equalizer parameters comprises means for comparing the training sequence with the input signal to determine channel distortion.

12. The apparatus of claim 11, wherein the means for generating equalizer parameters comprises means for subtracting the adjacent symbols from the input signal to reproduce channel impairments, wherein the channel impairments are subtracted from the input signal for equalization.

13. The apparatus of claim 12, wherein the channel impairments comprise inter-symbol interference.

14. The apparatus of claim 8, wherein the means for generating equalizer parameters from the remodulated data output comprises:

means for buffering the input signal; and

means for comparing the buffered input signal to the training sequence to produce the equalizer parameters.

15. An apparatus for equalizing digital data signals comprising:

a demodulator for demodulating an input signal to produce a data output;

a modulator, communicatively coupled to the demodulator, for remodulating the data output to produce a training sequence, wherein the training sequence is comprised of adjacent symbols in the input data; and

a parameter generation module, communicatively coupled to the modulator, for generating equalizer parameters from the training sequence.

16. The apparatus of claim 15, further comprising a decoder for decoding the input signal after the demodulation.

17. The apparatus of claim 16, further comprising a re-encoder for re-encoding the input signal prior to the remodulation.

18. The apparatus of claim 15, wherein the parameter generation module compares the training sequence with the input signal to determine channel distortion.

19. The apparatus of claim 18, wherein the parameter generation module subtracts the adjacent symbols from the input signal to reproduce channel impairments, wherein the channel impairments are subtracted from the input signal for equalization.

20. The apparatus of claim 19, wherein the channel impairments comprise inter-symbol interference.

21. The apparatus of claim 15, wherein the parameter generation module comprises:

means for buffering the input signal; and

means for comparing the buffered input signal to the training sequence to produce the equalizer parameters.

22. A blanket equalizer for equalizing digital data signals, comprising:

a transversal filter for receiving a reconstructed symbol sequence from another equalizer and for filtering the reconstructed symbol sequence; and

an adder for summing an input signal and the filtered reconstructed symbol sequence output from the transversal filter to create an estimated symbol sequence.

23. The blanket equalizer of claim 22, wherein the input signal is filtered by a matched filter and the matched filter'"'"'s output is input to the adder.