Peak to average power ratio reduction

• US 6,512,797 B1
• Filed: 05/19/1998
• Issued: 01/28/2003
• Est. Priority Date: 04/20/1998
• Status: Expired due to Term

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Cioffi, John M., Tellado, Jose
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US09/081,493
• Time in Patent Office: 1,715 Days
• Field of Search: 375/261, 375/275, 375/297, 375/298, 370/310, 370/319, 370/330, 370/333, 370/334, 370/430, 370/480, 455/102, 455/103, 455/115, 455/116, 455/126, 455/127
• US Class Current: 375/261
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

The present inventions provide methods and systems for reducing the peak to average power ratio of a multi-carrier signal. Reducing the peak to average power ratio of a signal ensures that amplifiers and transmitters are not saturated, causing loss of data. Further, reducing peak to average power ratios reduces the consumption of power during transmission. Peak to average power ratios are reduced by applying a peak reduction signal component to one or more of the plurality of information signals that make up the multi-carrier signal. In one embodiment the peak reduction signal is a basis function of the communication system. The information signal is mapped to duplicate constellation points, which may be easily decoded by a receiver by performing a modulo operation. Negation of the peaks may be performed iteratively to remove any peaks produced during prior peak reduction operations.

Claims

1. A transmitter configured to transmit a symbol in a communication system, wherein the transmitted symbol has a peak to average power ratio and is a function of a plurality of information signals each of which is based at least in part upon an associated information signal constellation that includes a plurality of information signal constellation points, the plurality of information signals including a modified signal, wherein the modified signal is based at least in part on one associated duplicate constellation, each duplicate constellation comprising at least one duplicate constellation point, wherein at least one of the plurality of information signal constellation points is mapped to at least one of the duplicate constellation points.

2. A transmitter as recited in claim 1 wherein the modified signal includes an information component and a peak reduction component, wherein the peak reduction component reduces the peak to average power ratio of the transmitted symbol.

3. A transmitter as recited in claim 1 wherein the mapping of at least one of the plurality of information signal constellation points to at least one of the duplicate constellation points is reversible by performing a modulo operation on the modified signal to obtain an unmodified signal.

4. A transmitter as recited in claim 1 wherein the mapping of at least one of the plurality of information signal constellation points to at least one of the duplicate constellation points minimizes any increase in the power used to transmit the symbol.

5. A transmitter as recited in claim 1 wherein the mapping of at least one of the plurality of information signal constellation points to at least one of the duplicate constellation points minimizes the bit error rate in the transmission of the symbol.

6. A transmitter that transmits a multi-carrier symbol in a multi-carrier communication system, wherein the transmitted multi-carrier symbol has a peak to average power ratio and is a function of a plurality of quadrature amplitude modulated information signals each of which is based at least in part upon an associated information signal constellation that includes a plurality of information signal constellation points, each of the plurality of information signals being centered at one of a plurality of frequencies, the plurality of information signals including a modified signal, the modified signal including an information component and a peak reduction component, wherein the peak reduction component of the modified signal is arranged to reduce the peak to average power ratio of the transmitted multi-carrier symbol;

wherein the modified signal has at least one associated duplicate constellation, each duplicate constellation including a plurality of duplicate constellation points, wherein the plurality of information signal constellation points of the information signal constellation associated with the modified signal are mapped to the plurality of duplicate constellations points in each duplicate constellation.

7. A transmitter as recited in claim 6, wherein the peak reduction component of the modified signal is a basis function of the multi-carrier communication system.

8. A transmitter as recited in claim 7, wherein the basis function is a sinusoid.

9. A transmitter as recited in claim 7, wherein the basis function is a wavelet.

10. A transmitter as recited in claim 7, wherein the basis function is a complex exponential.

11. A transmitter as recited in claim 6, wherein the peak reduction component of the modified signal is a basis function of the transmitter that is added to the information component such that the addition of the basis function to the information component maps the information component to a selected duplicate constellation point of the at least one duplicate constellation.

12. A transmitter configured to transmit a symbol in a communication system, the symbol having a peak to average power ratio and being a function of a plurality of information signals, the transmitter comprising:

a kernel applicator, wherein the kernel applicator reduces the peak to average power ratio of the symbol by modifying a selected information signal of the plurality of information signals, wherein each of the information signals is based at least in part upon an associated information signal constellation that includes a plurality of information signal constellation points;

wherein the modified information signal is based at least in part on at least one duplicate constellation, each duplicate constellation comprising at least one duplicate constellation point, wherein at least one information signal constellation point is mapped to at least one duplicate constellation point.

13. A transmitter for use in a multi-carrier communication system, the transmitter transmitting a multi-carrier symbol, the multi-carrier symbol having a peak to average power ratio and being a function of a plurality of information signals, the transmitter comprising:

a kernel applicator, wherein the kernel applicator reduces the peak to average power ratio of the multi-carrier symbol by modifying a selected information signal of the plurality of information signals, wherein the modified signal includes an information component and a peak reduction component,

wherein each one of the plurality of information signals is a quadrature amplitude modulated signal that is based at least in part upon an associated information signal constellation that includes a plurality of information signal constellation points,

wherein the modified signal includes one or more duplicate constellations, each of the one or more duplicate constellations including a plurality of duplicate constellation points, wherein the plurality of information signal constellation points of the associated information signal constellation are mapped to the plurality of duplicate constellation points of the one or more duplicate constellations.

14. A transmitter as recited in claim 13, the transmitter further comprising

an encoder, wherein the encoder encodes a first set of data into a plurality of sets of data; and

a modulator, coupled to the encoder, that receives the plurality of sets of data and modulates each set of data of the plurality of sets of data to produce the plurality of information signals, which are combined, the modulator also coupled to the kernel applicator, the modulator providing the plurality of information signals to the kernel applicator.

15. A transmitter as recited in claim 14, wherein the kernel applicator includes:

a transformer, coupled to the modulator, the transformer performing a transform on the plurality of information signals producing a transformed signal; and

a kernel engine, coupled to the transformer, wherein the kernel engine analyzes the transformed signal and, when the kernel engine detects a peak in the transformed signal, the kernel engine applies a kernel to the detected peak of the transformed signal, further wherein the kernel is a basis function of the transmitter, the basis function being applied to the information component of the modified signal, whereby the basis function is the peak reduction component of the modified signal.

16. A transmitter as recited in claim 15, wherein the transform is an inverse Fourier transform.

17. A transmitter as recited in claim 15, wherein the transform is a discrete wavelet transform.

18. A transmitter as recited in claim 15, wherein the basis function is a sinusoid.

19. A transmitter as recited in claim 15, wherein the basis function is a wavelet.

20. A transmitter as recited in claim 15, wherein the basis function is a complex exponential.

21. A transmitter as recited in claim 14, wherein the kernel applicator includes:

a transformer, coupled to the modulator, the transformer performing a transform on the plurality of information signals producing a transformed signal; and

a kernel engine, coupled to the transformer, wherein the kernel engine analyzes the transformed signal and, when the kernel engine detects two or more peaks in the transformed signal, the kernel engine applies a kernel to the two or more detected peaks of the transformed signal, wherein the kernel is a basis function of the transmitter, the basis function being applied to the information component of the modified signal, whereby the basis function is the peak reduction component of the modified signal.

22. A transmitter as recited in claim 13, wherein the peak reduction component of the modified signal is a basis function of the transmitter that is added to the information component such that the addition of the basis function to the information component maps the information component to a selected duplicate constellation point of the one or more duplicate constellations.

23. A transmitter as recited in claim 22, wherein the modified signal of the transmitted multi-carrier symbol is mapped by a receiver from the selected duplicate constellation point of the modified signal to the associated information signal constellation.

24. A transmitter as recited in claim 23, wherein the receiver maps the modified signal from the selected duplicate constellation point of the modified signal to the associated information signal constellation by performing a modulo operation on the modified signal to obtain the information component of the modified signal.

25. A transmitter as recited in claim 13, wherein the kernel applicator retains information about the reduction of the peak to average power ratio of the multi-carrier symbol such that the transmitter also transmits the information to a receiver to facilitate decoding of the transmitted multi-carrier symbol.

26. A transmitter as recited in claim 13, wherein the kernel applicator reduces the peak to average power ratio of the multi-carrier symbol as measured at the transmitter.

27. A transmitter as recited in claim 13, wherein the kernel applicator reduces the peak to average power ratio of the multi-carrier symbol as measured at a receiver that receives the transmitted multi-carrier symbol.

28. A transmitter as recited in claim 27, wherein the transmitter transmits the multi-carrier symbol to the receiver through a channel such that the kernel applicator takes into account a characteristic of the channel to reduce the peak to average power ratio of the multi-carrier symbol as measured at the receiver.

29. A transmitter as recited in claim 13, wherein each of the plurality of information signals are centered at each of a plurality of frequencies, wherein a selected frequency of the plurality of frequencies is selected to carry the modified signal.

30. A transmitter as recited in claim 29, wherein the selected frequency is selected from the plurality of frequencies to facilitate the reduction of the peak to average power ratio of the multi-carrier symbol.

31. A communication system for transmitting a symbol having a peak to average power ratio and being a function of a plurality of information signals, the communication system comprising;

a symbol transmitter comprising;

a kernel applicator, wherein the kernel applicator reduces the peak to average power ratio of the symbol by modifying a selected information signal of the plurality of information signals, wherein each of the information signals is based at least in part upon an associated information signal constellation that includes a plurality of information signal constellation points;

wherein the modified information signal is based at least in part on at least one duplicate constellation, each duplicate constellation comprising at least one duplicate constellation point, wherein at least one information signal constellation point is mapped to at least one duplicate constellation point.

32. A multi-carrier communication system for transmitting a multi-carrier symbol having a peak to average power ratio and being a function of a plurality of information signals, the multi-carrier communication system comprising;

a symbol transmitter comprising;

a kernel applicator, wherein the kernel applicator reduces the peak to average power ratio of the multi-carrier symbol by modifying a selected information signal of the plurality of information signals, wherein the modified information signal includes an information component and a peak reduction component;

wherein each one of the plurality of information signals is a quadrature amplitude modulated signal that is based at least in part upon an associated information signal constellation that includes a plurality of information signal constellation points;

wherein the modified information signal is based at least in part upon at least one duplicate constellation, each duplicate constellation including a plurality of duplicate constellation points, wherein the plurality of information signal constellation points of the associated information signal constellation are mapped to the plurality of duplicate constellation points of the one or more duplicate constellations.

33. A multi-carrier communication system as recited in claim 32, wherein the peak reduction component is a basis function of the multi-carrier communication system.

34. A multi-carrier communication system as recited in claim 32, wherein the transmitter further includes:

an encoder, wherein the encoder encodes a first set of data into a plurality of sets of data; and

a modulator, coupled to the encoder, that receives the plurality of sets of data and modulates each set of data of the plurality of sets of data to produce the plurality of information signals, which are combined, the modulator also coupled to the kernel applicator, the modulator providing the plurality of information signals to the kernel applicator.

35. A multi-carrier communication system as recited in claim 34, wherein the kernel applicator includes:

a transformer, coupled to the modulator, the transformer performing a transform on the plurality of information signals producing a transformed signal; and

a kernel engine, coupled to the transformer, wherein the kernel engine analyzes the transformed signal and, when the kernel engine detects a peak in the transformed signal, the kernel engine applies a kernel to the detected peak of the transformed signal, further wherein the kernel is a basis function of the transmitter, the basis function being applied to the information component of the modified signal, whereby the basis function is the peak reduction component of the modified signal.

36. A transmitter as recited in claim 35, wherein the transform is an inverse Fourier transform.

37. A transmitter as recited in claim 36, wherein the transform is a discrete wavelet transform.

38. A multi-carrier communication system as recited in claim 35, wherein the basis function is a sinusoid.

39. A multi-carrier communication system as recited in claim 35, wherein the basis function is a wavelet.

40. A multi-carrier communication system as recited in claim 35, wherein the basis function is a complex exponential.

41. A multi-carrier communication system as recited in claim 34, wherein the kernel applicator includes:

a transformer, coupled to the modulator, the transformer performing a transform on the plurality of information signals producing a transformed signal; and

a kernel engine, coupled to the transformer, wherein the kernel engine analyzes the transformed signal and, when the kernel engine detects two or more peaks in the transformed signal, the kernel engine applies a kernel to the two or more detected peaks of the transformed signal, wherein the kernel is a basis function of the transmitter, the basis function being applied to the information component of the modified signal, whereby the basis function is the peak reduction component of the modified signal.

42. A multi-carrier communication system as recited in claim 32, wherein the peak reduction component of the modified signal is a basis function of the transmitter that is added to the information component such that the addition of the basis function to the information component maps the information component to a selected duplicate constellation point of the one or more duplicate constellations.

43. A multi-carrier communication system as recited in claim 42 further comprising:

a receiver that receives the multi-carrier symbol transmitted by the transmitter, wherein the modified signal of the transmitted multi-carrier symbol is mapped by the receiver from the selected duplicate constellation point of the modified signal to the associated information signal constellation.

44. A multi-carrier communication system as recited in claim 43, wherein the receiver maps the modified signal from the selected duplicate constellation point of the modified signal to the associated information signal constellation by performing a modulo operation on the modified signal.

45. A multi-carrier communication system as recited in claim 44, wherein the kernel applicator reduces the peak to average power ratio of the multi-carrier symbol as measured at the receiver.

46. A multi-carrier communication system as recited in claim 45, wherein the transmitter transmits the multi-carrier symbol to the receiver through a channel such that the kernel applicator takes into account a characteristic of the channel to reduce the peak to average power ratio of the multi-carrier symbol as measured at the receiver.

47. A multi-carrier communication system as recited in claim 32, wherein the kernel applicator retains information about the reduction of the peak to average power ratio of the multi-carrier symbol such that the transmitter also transmits the information to a receiver to facilitate decoding of the transmitted multi-carrier symbol.

48. A multi-carrier communication system as recited in claim 32, wherein the kernel applicator reduces the peak to average power ratio of the multi-carrier symbol as measured at the transmitter.

49. A multi-carrier communication system as recited in claim 32, wherein each of the plurality of information signals are centered at each of a plurality of frequencies, wherein a selected frequency of the plurality of frequencies is selected to carry the modified signal.

50. A multi-carrier communication system as recited in claim 49, wherein the selected frequency is selected from the plurality of frequencies to facilitate the reduction of the peak to average power ratio of the multi-carrier symbol.

51. A method of reducing a peak to average power ratio of a communication system symbol, wherein the symbol is a function of a plurality of signals, wherein each of the plurality of signals is based at least in part upon an associated signal constellation that includes a plurality of signal constellation points, the method comprising:

detecting a peak in the symbol;

determining a first signal that contributes to the peak, the first signal being one of the plurality of signals; and

mapping the first signal from the associated signal constellation to a selected duplicate constellation point of a selected duplicate constellation of one or more duplicate constellations to reduce the peak to average power ratio of the symbol.

52. A method as recited in claim 51 further comprising:

transmitting the symbol to a receiver; and

decoding the symbol when the receiver receives the transmitted symbol including decoding the modified first signal.

53. A method as recited in claim 51, the method further comprsing:

repeating the steps of detecting, determining and mapping until the peak to average power ratio is reduced to a predetermined level.

54. A method as recited in claim 51, wherein decoding the modified first signal includes performing a modulo operation on the modified first signal.

55. A method of reducing a peak to average power ratio of a multi-carrier symbol of a multi-carrier communication system, wherein the multi-carrier symbol is a function of a plurality of signals, wherein each of the plurality of signals is centered at each one of a plurality of frequencies, further wherein each of the plurality of signals is a quadrature amplitude modulated signal that is based at least in part upon an associated signal constellation that includes a plurality of signal constellation points, the method comprising:

detecting a peak in the multi-carrier symbol;

determining a first signal that contributes to the peak, the first signal being one of the plurality of signals; and

applying a peak reduction component to the first signal by mapping the first signal from the associated signal constellation to a selected duplicate constellation point of a selected duplicate constellation of one or more duplicate constellations to reduce the peak to average power ratio of the multi-carrier symbol;

transmitting the multi-carrier symbol to a receiver;

decoding the multi-carrier symbol when the receiver receives the transmitted multi-carrier symbol including decoding the modified first signal.

56. A method as recited in claim 55, wherein the peak reduction component is a basis function of the transmitter.

57. A method as recited in claim 55, the method further comprising:

repeating the steps of detecting, determining and applying until the peak to average power ratio is reduced to a predetermined level.

58. A method as recited in claim 55, wherein decoding the modified first signal includes performing a modulo operation on the modified first signal.

59. A method as recited in claim 55, the method further comprising:

transmitting information about the reduction of the peak to average power ratio of the multi-carrier symbol, wherein the information facilitates the decoding of the multi-carrier symbol.

60. A method as recited in claim 55, wherein the peak reduction component is a basis function of the transmitter that is applied to the first signal such that the addition of the basis function to the first signal maps the first signal to the selected duplicate constellation point of the one or more of duplicate constellations.

61. A method as recited in claim 60, wherein the decoding the first signal includes:

mapping the modified signal from the selected duplicate constellation point to the associated signal constellation to obtain the first signal.

62. A method as recited in claim 61, wherein mapping the modified signal from the selected duplicate constellation point of the first signal is accomplished by performing a modulo operation on the modified signal.

63. A communication system transmitter configured to transmit a signal having a peak to average power ratio and being a function of a plurality of information symbols, a selected information symbol of the plurality of information symbols being modified to reduce the peak to average power ratio of the signal;

wherein each one of the plurality of information symbols is based at least in part upon an associated signal constellation that includes at least one signal constellation point;

wherein the selected information symbol includes at least one duplicate constellation, each duplicate constellation including at least one duplicate constellation point, wherein at least one of the signal constellation points is mapped to at least one of the duplicate constellation points.

64. A transmitter for use in a communication system, the transmitter transmitting a signal wherein the transmitted signal has a peak to average power ratio and is a function of a plurality of information symbols, each symbol being transmitted at each one of a plurality of intervals of time, a selected information symbol of the plurality information symbols including an information component and a peak reduction component, wherein the peak reduction component modifies the information component and reduces the peak to average power ratio of the transmitted

wherein each one of the plurality of information symbols is a quadrature amplitude modulated symbols that is based in at least in part upon an associated information signal constellation that includes a plurality of information constellation points

wherein the selected information symbol includes a one or more duplicate constellations, each of the one or more duplicate constellations including a plurality of duplicate constellation points, wherein the plurality of information signal constellation points of the associated information signal constellation are mapped to the plurality of duplicate constellation points of the one or more duplicate constellations.

65. A transmitter as recited in claim 64, wherein the peak reduction component of the modified signal is a basis function of the transmitter.

66. A transmitter as recited in claim 65, wherein the communication system has an impulse response such that the basis function is the impulse response of the communication system.

67. A transmitter as recited in claim 64, wherein the peak reduction component of the selected information symbol is a basis function of the transmitter that is added to the information component such that the addition of the basis function to the information component maps the information component to a selected duplicate constellation point of the one or more duplicate constellations.