Equalizers for layered modulated and other signals

• US 7,184,473 B2
• Filed: 10/22/2003
• Issued: 02/27/2007
• Est. Priority Date: 04/27/2001
• Status: Expired due to Term

• 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
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US10/691,133
• Publication Number:
  US 20040184521A1
• Time in Patent Office: 1,224 Days
• Field of Search: 375/229, 375/231, 375/232, 375/233, 375/234, 375/350, 375/295
• US Class Current: 375/229
• 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 an input signal comprising a lower layer signal non-coherendy layered with an upper layer signal, comprising:

delaying the input signal;

equalizing the delayed input signal according to equalizer parameters;

demodulating the input signal having input data to produce the upper layer signal;

remodulating the upper layer signal to produce a training sequence, wherein the training sequence is comprised of adjacent symbols in the input data;

subtracting the remodulated upper layer signal from the equalized and delayed input signal; and

generating the 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 equalizer parameters are generated by performing steps comprising comparing the training sequence with the input signal to determine channel distortion.

5. The method of claim 4, wherein the equalizer parameters are generated by performing steps comprising 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 delayed input signal is equalized by a blanket equalizer.

8. The method of claim 7, wherein the step of equalizing the delayed input signal according to equalizer parameters comprises the steps of:

receiving and filtering the training sequence with a transversal filter; and

summing the delayed input signal and the filtered training sequence to create an estimated symbol sequence.

9. The method of claim 1, wherein the delayed input signal is equalized by a first equalizer, and the method further comprises the steps of:

equalizing the input signal with a second equalizer before demodulation of the input signal;

equalizing the remodulated upper layer signal subtracted from the delayed input signal with a third equalizer.

10. The method of claim 9, wherein the second equalizer and the third equalizers are distributed feedback equalizers.

11. The method of claim 1, wherein the upper layer signal is a legacy signal and the lower layer signal is a non-legacy signal.

12. An apparatus for equalizing an input signal comprising a lower layer signal non-coherently layered with an upper layer signal, comprising:

means for delaying the input signal;

means for equalizing the delayed input signal according to equalizer parameters;

means for demodulating the input signal having input data to produce the upper layer signal;

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

means for subtracting the remodulated upper layer signal from the equalized and delayed input signal; and

means for generating the equalizer parameters from the training sequence.

13. The apparatus of claim 12, further comprising means for decoding the input signal after the demodulation.

14. The apparatus of claim 13, further comprising means for re-encoding the input signal prior to the remodulation.

15. The apparatus of claim 12, wherein the means for generating equalizer parameters comprises means for comparing the training sequence with the input signal to determine channel distortion.

16. The apparatus of claim 15, 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.

17. The apparatus of claim 16, wherein the channel impairments comprise inter-symbol interference.

18. The apparatus of claim 12, wherein the means for equalizing the delayed input signal comprises a blanket equalizer.

19. The apparatus of claim 18, wherein the means for equalizing the delayed input signal according to equalizer parameters comprises:

a transversal filter for receiving and filtering the training sequence; and

a summer for summing the delayed input signal and the filtered training sequence to create an estimated symbol sequence.

20. The apparatus of claim 12, wherein the delayed input signal is equalized by a first equalizer, and the apparatus further comprises:

a second equalizer for equalizing the input signal before demodulation of the input signal;

a third equalizer for equalizing the remodulated upper layer signal subtracted from the delayed input signal.

21. The apparatus of claim 20, wherein the second equalizer and the third equalizers are distributed feedback equalizers.

22. The apparatus of claim 12, wherein the upper layer signal is a legacy signal and the lower layer signal is a non-legacy signal.

23. An apparatus for equalizing an input signal comprising a lower layer signal non-coherently layered with an upper layer signal, the apparatus comprising:

a buffer, for delaying the input signal;

an equalizer, for equalizing the delayed input signal according to equalizer parameters;

a demodulator for demodulating the input signal to produce the upper layer signal;

a remodulator, communicatively coupled to the demodulator, for remodulating the demodulated input signal to produce a training sequence, wherein the training sequence is comprised of adjacent symbols in the input data;

a signal canceler, commumcatively coupled to the remodulator and the equalizer, for subtracting the remodulated demodulated input signal from the equalized delayed input signal;

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

24. The apparatus of claim 23, further comprising a decoder for decoding the input signal after the demodulation.

25. The apparatus of claim 24, further comprising a re-encoder for re-encoding the input signal prior to the remodulation.

26. The apparatus of claim 23, wherein the parameter generation module compares the training sequence with the input signal to determine channel distortion.

27. The apparatus of claim 26, 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.

28. The apparatus of claim 27, wherein the channel impairments comprise inter-symbol interference.

29. The apparatus of claim 23, wherein the equalizer comprises a blanket equalizer.

30. The apparatus of claim 29, wherein the equalizer comprises:

a transversal filter for receiving and filtering the training sequence; and

a summer for summing the delayed input signal and the filtered training sequence to create an estimated symbol sequence.

31. The apparatus of claim 23, further comprising:

a second equalizer for equalizing the input signal before demodulation of the input signal;

a third equalizer for equalizing the remodulated upper layer signal subtracted from the delayed input signal.

32. The apparatus of claim 31, wherein the second equalizer and the third equalizer comprise distributed feedback equalizers.

33. The apparatus of claim 23, wherein the upper layer signal is a legacy signal and the lower layer signal is a non-legacy signal.