Blind start-up of a dual mode CAP-QAM receiver

• US 6,252,903 B1
• Filed: 07/02/1998
• Issued: 06/26/2001
• Est. Priority Date: 07/02/1998
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Yang, Jian, Werner, Jean-Jacques
• Primary Examiner(s): Le, Amanda T.
• Application Number:
  US09/109,364
• Time in Patent Office: 1,090 Days
• Field of Search: 375/229, 375/232-235, 375/261, 375/324, 375/340, 375/350, 708/323
• US Class Current: 375/232
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 2025/03509 fractionally spaced H04L2025/03515 takes precedence
• CPC Class Codes: H04L 2025/03617 Time recursive algorithms H04L2025/03643 takes precedence
• CPC Class Codes: H04L 2025/0363 Feature restoration, e.g. constant modulus
• CPC Class Codes: H04L 2025/03732 according to the convergence state
• CPC Class Codes: H04L 25/03044 using fractionally spaced delay lines or combinations of fractionally integrally spaced taps
• CPC Class Codes: H04L 25/0305 using blind adaptation
• CPC Class Codes: H04L 25/4921 using quadrature encoding, e.g. carrierless amplitude-phase coding
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

A receiver has a dual mode of operation—a carrierless amplitude modulation/phase modulation (CAP) mode and a quadrature amplitude modulation (QAM) mode-yet only requires a single equalizer structure for both the CAP mode of operation and the QAM mode of operation during blind start-up. The receiver uses the same blind equalization updating algorithm independent of the type of received signal for converging the equalizer structure. The blind equalization updating algorithm incorporates a constant R, whose value is a function of the type of received signal, e.g., a QAM signal or a CAP signal. The type of received signal is determined as a function of the in-phase component of the mean-squared error, E[e²_n.

Claims

1. An improved apparatus for use in receiving a carrierless amplitude modulation/phase modulation (CAP) signal or a quadrature amplitude phase modulation (QAM) signal, the improvement comprising

a receiver that has a dual mode of operation, a CAP mode and a QAM mode, that utilizes only a single equalizer for both the CAP mode of operation and the QAM mode of operation

wherein the equalizer has an associated set of tap coefficients, wherein the same equalization updating algorithm is used in either the CAP mode of operation or the QAM mode of operation and wherein the equalization updating algorithm is a blind equalization algorithm having a constant whose value is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.

2. The improvement of claim 1 wherein the receiver further comprises a demodulator, operative during the QAM mode of operation, for demodulating an output signal of the equalizer.

3. The improvement of claim 1 wherein the blind equalization algorithm is a constant modulus type of algorithm.

4. The improvement of claim 1 wherein the blind equalization algorithm is a multimodulus type of algorithm.

5. The improvement of claim 1 wherein the blind equalization algorithm is a reduced constellation type of algorithm.

6. The improvement of claim 1 wherein the equalizer further comprises a two-filter structure.

7. The improvement of claim 1 wherein the equalization updating algorithm is a function of {tilde over (y)}_n²−

R², where the value of the constant R is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.

8. A receiver comprising:

a filter for filtering a signal to provide a filtered signal;

a demodulator operative in a first mode of operation for demodulating the filtered signal and operative in a second mode of operation for passing through the filtered signal; and

a slicer responsive to the output signal from the demodulator for providing a sliced output signal and wherein the mode of operation is selected as a function of an error value between the sliced output signal and the demodulator output signal

wherein the filter has an associated set of tap coefficients whose values are set by the same updating algorithm in either the first mode of operation or the second mode of operation.

9. The receiver of claim 8 wherein the error value is calculated as a function of a mean square error between the sliced output signal and the demodulator output signal.

10. The receiver of claim 9 wherein the demodulator output signal and the sliced output signal comprise in-phase and quadrature component signals and wherein the mean square error is calculated as a function of a difference between an in-phase value of the demodulator output signal and an in-phase value of the sliced output signal.

11. The receiver of claim 8 wherein the filter performs an equalizer function and further comprises a two-filter structure.

12. The receiver of claim of claim 8 wherein the updating algorithm is a blind equalization algorithm having a constant whose value is selected as a function of whether the receiver is in the first mode of operation or the second mode of operation.

13. The receiver of claim 12 wherein the blind equalization algorithm is a constant modulus type of algorithm.

14. The receiver of claim 12 wherein the blind equalization algorithm is a multimodulus type of algorithm.

15. The receiver of claim 12 wherein the blind equalization algorithm is a reduced constellation type of algorithm.

16. The receiver of claim 12 wherein the first mode of operation corresponds to a carrierless amplitude modulation/phase modulation (CAP) mode of operation and the second mode of operation corresponds to a quadrature amplitude phase modulation (QAM) mode of operation.

17. The receiver of claim 16 wherein the updating algorithm is a function of {tilde over (y)}_n²−

R², where the value of the constant R is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.

18. A method for use in a receiver, the method comprising the steps of:

selecting one of a number of modes of operation for the receiver;

filtering a signal, with a filter, for providing a filtered signal; and

updating coefficients of the filter using an updating algorithm such that at least one constant value of the updating algorithm is selected as a function of the mode of operation of the receiver.

19. The method of claim 18 wherein the modes of operation include a carrierless amplitude modulation/phase modulation (CAP) mode of operation and a quadrature amplitude phase modulation (QAM) mode of operation.

20. The method of claim 19 wherein the updating algorithm is a function of {tilde over (y)}_n²−

R², where the value of the constant R is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.

21. The method of claim 18 wherein the selecting step includes the steps of:

determining an error value as a function of the filtered signal; and

selecting the mode of operation as a function of the determined error value.

22. The method of claim 21 wherein the determined error value is determined as a function of a mean square error function.

23. The method of claim 21 wherein the selecting the mode step compares the determined error value to a predetermined value such that if the determined error value is less than the predetermined value one mode of operation is selected otherwise a different mode of operation is selected.

24. The method of claim 18 further comprising the steps of:

processing the filtered signal for providing a processed signal such that in a first mode of operation the processing demodulates the filtered signal and in a second mode of operation the processing passes the filtered signal through; and

slicing the processed signal for providing a sliced signal.

25. The method of claim 24 wherein the selecting step includes the step of selecting the mode of operation as a function of a difference between the processed signal and the sliced signal.

26. The method of claim 25 wherein the selecting step includes the step of selecting the mode of operation as a function of a mean square error of a difference between the processed signal and the sliced signal.

27. The method of claim 26 wherein the processed signal and the sliced signal further comprise an in-phase component and a quadrature component.

28. The method of claim 27 wherein the difference is between the in-phase components of the respective signals.

29. The method of claim 18 wherein the updating algorithm is a blind equalization algorithm.

30. The method of claim 29 wherein the blind equalization algorithm is a constant modulus type of algorithm.

31. The method of claim 29 wherein the blind equalization algorithm is a multimodulus type of algorithm.

32. The method of claim 29 wherein the blind equalization algorithm is a reduced constellation type of algorithm.

33. A method for use in a receiver, the method comprising the steps of:

determining an error value as a function of a difference between a first version of a signal and a second version of a signal;

selecting a mode of operation as a function of the error value; and

setting a constant of a tap updating algorithm to a value as a function of the selected mode.

34. The method of claim 33 further comprising the step of updating tap coefficients of a filter using the tap updating algorithm.

35. The method of claim 33 wherein the determining the error value step includes the step of determining a mean square error of the difference between the first version of the signal and the second version of the signal.

36. The method of claim 35 wherein the difference is between respective in-phase components of the first version of the signal and the second version of the signal.

37. The method of claim 33 further comprising the steps of:

filtering a signal for providing a filtered signal;

processing the filtered signal to provide the first version of the signal such that in one mode of operation the first version of the signal represents a demodulated version of the filtered signal and in an other mode of operation the first version of the signal represents the filtered signal; and

slicing the first version of the signal for providing the second version of the signal.

38. The method of claim 33 wherein the updating algorithm is a blind equalization algorithm.

39. The method of claim 38 wherein the blind equalization algorithm is a constant modulus type of algorithm.

40. The method of claim 38 wherein the blind equalization algorithm is a multimodulus type of algorithm.

41. The method of claim 38 wherein the blind equalization algorithm is a reduced constellation type of algorithm.

42. The method of claim 33 wherein one mode of operation is a carrierless amplitude modulation/phase modulation (CAP) mode of operation and another mode of operation is a quadrature amplitude phase modulation (QAM) mode of operation.

43. The method of claim 42 wherein the tap updating algorithm is a function of {tilde over (y)}_n²−

R², where the value of the constant R is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.

44. A method for use in a receiver, the method comprising the steps of:

equalizing a signal, with a filter, for providing an equalized signal; and

updating coefficients of the filter using a blind equalization type of tap updating algorithm such that at least one constant value of the updating algorithm is selected as a function of a mode of operation of the receiver, wherein the mode is determined by the type of received signal.

45. The method of claim 44 wherein one mode of operation is a carrierless amplitude modulation/phase modulation (CAP) mode of operation and another mode of operation is a quadrature amplitude phase modulation (QAM) mode of operation.

46. The method of claim 45 wherein the updating algorithm is a function of {tilde over (y)}_n²−

R², where the value of the constant R is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.

47. The method of claim 44 further comprising the step of selecting the mode of operation.

48. The method of claim 47 wherein the selecting step includes the steps of:

determining an error value as a function of the equalized signal; and

selecting the mode of operation as a function of the determined error value.

49. The method of claim 48 wherein the determined error value is determined as a function of a mean square error function.

50. The method of claim 48 wherein the selecting the mode step compares the determined error value to a predetermined value such that if the determined error value is less than the predetermined value one mode of operation is selected otherwise a different mode of operation is selected.

51. The method of claim 44 further comprising the steps of:

processing the equalized signal for providing a processed signal such that in a first mode of operation the processing demodulates the filtered signal and in a second mode of operation the processing passes the filtered signal through; and

slicing the processed signal for providing a sliced signal.

52. The method of claim 51 further comprising the step of selecting the mode of operation as a function of a difference between the processed signal and the sliced signal.

53. The method of claim 51 further comprising the step of selecting the mode of operation as a function of a mean square error of a difference between the processed signal and the sliced signal.

54. The method of claim 53 wherein the processed signal and the sliced signal further comprise an in-phase component and a quadrature component.

55. The method of claim 54 wherein the difference is between the in-phase components of the respective signals.

56. The method of claim 44 wherein the blind equalization algorithm is a constant modulus type of algorithm.

57. The method of claim 44 wherein the blind equalization algorithm is a multimodulus type of algorithm.

58. The method of claim 44 wherein the blind equalization algorithm is a reduced constellation type of algorithm.

59. A method for use in a receiver, the method comprising the steps of:

selecting a mode of operation;

setting a constant of a tap updating algorithm to a value as a function of the selected mode of operation;

determining an error value as a function of a difference between a first version of a signal and a second version of a signal; and

selecting a mode of operation as a function of the error value.

60. The method of claim 59 further comprising the step of updating tap coefficients of a filter using the tap updating algorithm.

61. The method of claim 59 wherein the determining the error value step includes the step of determining a mean square error of the difference between the first version of the signal and the second version of the signal.

62. The method of claim 61 wherein the difference is between respective in-phase components of the first version of the signal and the second version of the signal.

63. The method of claim 59 further comprising the steps of:

filtering a signal for providing a filtered signal;

processing the filtered signal to provide the first version of the signal such that in one mode of operation the first version of the signal represents a demodulated version of the filtered signal and in an other mode of operation the first version of the signal represents the filtered signal; and

slicing the first version of the signal for providing the second version of the signal.

64. The method of claim 59 wherein the updating algorithm is a blind equalization algorithm.

65. The method of claim 64 wherein the blind equalization algorithm is a constant modulus type of algorithm.

66. The method of claim 64 wherein the blind equalization algorithm is a multimodulus type of algorithm.

67. The method of claim 64 wherein the blind equalization algorithm is a reduced constellation type of algorithm.

68. The method of claim 59 wherein one mode of operation is a carrierless amplitude modulation/phase modulation (CAP) mode of operation and another mode of operation is a quadrature amplitude phase modulation (QAM) mode of operation.

69. The method of claim 68 wherein the tap updating algorithm is a function of {tilde over (y)}_n²−

R², where the value of the constant R is selected as a function of whether the receiver is in the CAP mode of operation or the QAM mode of operation.