Reduction of Peak-To-Average-Power Ratio in a Telecommunications System

• US 20080075191A1
• Filed: 03/12/2007
• Published: 03/27/2008
• Est. Priority Date: 09/27/2006
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Haartsen, Jacobus Cornelis
• Granted Patent: US 7,848,446 B2
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2615 Reduction thereof using coding

Abstract

A single-carrier signal is generated from a number, N, of symbols in a way that results in a low PAPR. This includes generating an initial set of N complex frequency components from the N symbols. N_s different sets of N complex frequency components are generated by, for each of N_s times, permuting the initial set of N complex frequency components by one of N_s possible permutations. N_s different sets of M complex frequency components are generated by mapping each of the N_s different sets of N complex frequency components onto a set of M carrier frequencies. After shaping, an IDFT generates a candidate set of N time-domain symbols from each of the N_s different sets of M complex frequency components. That one of the N_s different candidate sets of N time-domain symbols that is associated with the smallest PAPR is selected for further processing.

Claims

1. A method of generating a single-carrier signal from a number, N, of symbols, the method comprising:

using a Discrete Fourier Transform (DFT) to generate an initial set of N complex frequency components from the N symbols;

generating N_s different sets of permuted complex frequency components by, for each of N_s times, permuting a derived set of complex frequency components by one of N_s possible permutations, where 2≦

N_s≦

N!, wherein the derived set of complex frequency components is derived from the initial set of N complex frequency components;

generating N_s candidate sets of at least N time-domain symbols by, for each of the N_s sets of derived permuted frequency components, using an Inverse Discrete Fourier Transform (IDFT) to generate a candidate set of at least N time-domain symbols from a respective one of the N_s sets of derived permuted complex frequency components, wherein each of the sets of derived permuted complex frequency components is derived from the set of permuted complex frequency components;

ascertaining which one of the N_s different candidate sets of at least N time-domain symbols is associated with a smallest Peak-to-Average-Power Ratio (PAPR); and

selecting, for further processing, that one of the N_s different candidate sets of at least N time-domain symbols that is associated with the smallest PAPR.

2. The method of claim 1, wherein permuting a derived set of complex frequency components by one of N_s possible permutations comprises:

cyclically shifting the derived set of complex frequency components by one of N_s possible shift amounts, S_i, wherein 0≦

S_i≦

(N−

1) and S_i≠

S_j for i≠

j, 0≦

i≦

(N_s−

1), 0≦

j≦

(N_s−

1).

3. The method of claim 2, wherein the different possible shift amounts, S_i, have values that are evenly distributed between 0 and N−

1.

4. The method of claim 3, wherein N_s=2, S₀=0 and S₁=(N/2).

5. The method of claim 3, wherein N_s=4, S₀=0, S₁=(N/4), S₂=(N/2), and S₃=(3N/4).

6. The method of claim 1, wherein permuting a derived set of complex frequency components by one of N_s possible permutations comprises:

using one of N_s possible binary permutations to reorder complex frequency components of the derived set of complex frequency components.

7. The method of claim 6, wherein using one of N_s possible binary permutations to reorder complex frequency components of the derived set of complex frequency components comprises:

using one of N_s possible butterfly permutations to reorder complex frequency components of the derived set of complex frequency components.

8. The method of claim 1, wherein the derived set of complex frequency components are identical to the initial set of complex frequency components.

9. The method of claim 1, comprising deriving the derived set of complex frequency components from the set of initial complex frequency components by performing a process that includes:

repeatedly mapping the N complex frequency components of the initial set of N complex frequency components onto different groups of N carrier frequencies selected from among M carrier frequencies until each of the M carrier frequencies is associated with one of the N complex frequency components.

10. The method of claim 9, comprising deriving each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components by performing a process that includes using a shaping filter to reduce PAPR.

11. The method of claim 1, comprising deriving each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components by performing a process that includes:

generating N_s different sets of M complex frequency components, where N≦

M, by, for each of the N_s different sets of N permuted complex frequency components, repeatedly mapping the N permuted complex frequency components onto different groups of N carrier frequencies selected from among M carrier frequencies until each of the M carrier frequencies is associated with one of the N complex frequency components.

12. The method of claim 11, wherein the process for deriving each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components includes using a shaping filter to reduce PAPR.

13. The method of claim 1, comprising deriving each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components by performing a process that includes:

generating N_s different sets of M complex frequency components, where N≦

M, by, for each of the N_s different sets of N permuted complex frequency components, mapping the N permuted complex frequency components onto every Kth carrier selected from among M carrier frequencies, wherein K=M/N.

14. The method of claim 13, comprising performing the further processing, wherein the further processing includes converting the selected at least N time-domain symbols into an analog signal, and shaping the analog signal to reduce the PAPR.

15. The method of claim 1, comprising deriving the set of derived complex frequency components from the set of initial complex frequency components by performing a process that includes:

generating a set of M complex frequency components, where N≦

M, by mapping the N complex frequency components of the initial set of complex frequency components onto every Kth carrier selected from among M carrier frequencies, wherein K=M/N.

16. The method of claim 15, comprising performing the further processing, wherein the further processing includes converting the selected at least N time-domain symbols into an analog signal, and shaping the analog signal to reduce the PAPR.

17. The method of claim 1, comprising communicating information to a receiver, wherein the information identifies which of the N_s possible permutations was used to generate the selected candidate set of at least N time-domain symbols.

18. The method of claim 1, comprising performing the further processing, wherein the further processing includes using the selected at least N time-domain symbols in a process that generates an analog signal;

and

transmitting the analog signal.

19. An apparatus for generating a single-carrier signal from a number, N, of symbols, the method comprising:

Discrete Fourier Transform (DFT) logic that generates an initial set of N complex frequency components from the N symbols;

logic that generates N_s different sets of permuted complex frequency components by, for each of N_s times, permuting a derived set of complex frequency components by one of N_s possible permutations, where 2≦

N_s≦

N!, wherein the derived set of complex frequency components is derived from the initial set of N complex frequency components;

logic that generates N_s candidate sets of at least N time-domain symbols by, for each of the N_s sets of derived permuted frequency components, using an Inverse Discrete Fourier Transform (IDFT) to generate a candidate set of at least N time-domain symbols from a respective one of the N_s sets of derived permuted complex frequency components, wherein each of the sets of derived permuted complex frequency components is derived from the set of permuted complex frequency components;

logic that ascertains which one of the N_s different candidate sets of at least N time-domain symbols is associated with a smallest Peak-to-Average-Power Ratio (PAPR); and

selecting logic that selects, for further processing, that one of the N_s different candidate sets of at least N time-domain symbols that is associated with the smallest PAPR.

20. The apparatus of claim 19, wherein the logic that generates N_s different sets of permuted complex frequency components comprises:

logic that cyclically shifts the derived set of complex frequency components by at least one of N_s possible shift amounts, S_i, wherein 0≦

S_i≦

(N−

1) and S_i≠

S_j for i≠

j, 0≦

i≦

(N_s−

1), 0≦

j≦

(N_s−

1).

21. The apparatus of claim 20, wherein the different possible shift amounts, S_i, have values that are evenly distributed between 0 and N−

1.

22. The apparatus of claim 21, wherein N_s=2, S₀=0 and S_i=(N/2).

23. The apparatus of claim 21, wherein N_s=4, S₀=0, S₁=(N/4), S₂=(N/2), and S₃=(3N/4).

24. The apparatus of claim 19, wherein the logic that generates N_s different sets of permuted complex frequency components comprises:

permutation logic that reorders complex frequency components of the derived set of complex frequency components by at least one of N_s possible binary permutations.

25. The apparatus of claim 24, wherein the permutation logic that reorders complex frequency components of the derived set of complex frequency components by at least one of the N_s possible binary permutations comprises butterfly permutation logic.

26. The apparatus of claim 19, wherein the derived set of complex frequency components are identical to the initial set of complex frequency components.

27. The apparatus of claim 19, comprising logic that derives the derived set of complex frequency components from the set of initial complex frequency components by performing a process that includes:

repeatedly mapping the N complex frequency components of the initial set of N complex frequency components onto different groups of N carrier frequencies selected from among M carrier frequencies until each of the M carrier frequencies is associated with one of the N complex frequency components.

28. The apparatus of claim 27, comprising logic that derives each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components by performing a process that includes using a shaping filter to reduce PAPR.

29. The apparatus of claim 19, comprising logic that derives each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components by performing a process that includes:

generating N_s different sets of M complex frequency components, where N≦

M, by, for each of the N_s different sets of N permuted complex frequency components, repeatedly mapping the N permuted complex frequency components onto different groups of N carrier frequencies selected from among M carrier frequencies until each of the M carrier frequencies is associated with one of the N complex frequency components.

30. The apparatus of claim 29, comprising a shaping filter used to reduce PAPR in the process for deriving each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components.

31. The apparatus of claim 19, comprising logic that derives each of the sets of derived permuted complex frequency components from the set of permuted complex frequency components by performing a process that includes:

generating N_s different sets of M complex frequency components, where N≦

M, by, for each of the N_s different sets of N permuted complex frequency components, mapping the N permuted complex frequency components onto every Kth carrier selected from among M carrier frequencies, wherein K=M/N.

32. The apparatus of claim 31, comprising logic that converts the selected at least N time-domain symbols into an analog signal, and shapes the analog signal to reduce the PAPR.

33. The apparatus of claim 19, comprising logic that derives the set of derived complex frequency components from the set of initial complex frequency components by performing a process that includes:

generating a set of M complex frequency components, where N≦

M, by mapping the N complex frequency components of the initial set of complex frequency components onto every Kth carrier selected from among M carrier frequencies, wherein K=M/N.

34. The apparatus of claim 33, comprising logic that converts the selected at least N time-domain symbols into an analog signal, and shapes the analog signal to reduce the PAPR.

35. The apparatus of claim 19, comprising logic that communicates information to a receiver, wherein the information identifies which of the N_s possible permutations was used to generate the selected candidate set of at least N time-domain symbols.

36. The apparatus of claim 19, comprising:

logic that uses the selected at least N time-domain symbols in a process that generates an analog signal; and

logic that transmits the analog signal.

37. A method of receiving a single-carrier signal, comprising:

using a Discrete Fourier Transform (DFT) to generate an initial set of at least N complex frequency components from a number of received information samples;

receiving side information that identifies a selected one of N_s possible permutations, where 2≦

N_s≦

N!;

generating a set of permuted complex frequency components by permuting the initial set of at least N complex frequency components by the selected one of N_s possible permutations; and

generating a set of at least N time-domain symbols by applying an Inverse Discrete Fourier Transform (IDFT) to the set of permuted complex frequency components.

38. The method of claim 37, wherein the DFT is an N-point DFT that generates the initial set of at least N complex frequency components from N received information samples.

39. The method of claim 37, wherein the DFT is an M-point DFT that generates the initial set of at least N complex frequency components from M received information samples.

40. A method of receiving a single-carrier signal, comprising:

using a Discrete Fourier Transform (DFT) to generate an initial set of at least N complex frequency components from a number of received information samples;

generating N_s different sets of permuted complex frequency components by, for each of N_s times, permuting the initial set of at least N complex frequency components by one of N_s possible permutations, where 2≦

N_s≦

N!;

using a blind detection technique to determine which of the N_s different sets of permuted complex frequency components is a selected one of the N_s different sets of permuted complex frequency components; and

generating a set of at least N time-domain symbols by applying an Inverse Discrete Fourier Transform (IDFT) to the selected one of the N_s different sets of permuted complex frequency components.

41. The method of claim 40, wherein the DFT is an N-point DFT that generates the initial set of at least N complex frequency components from N received information samples.

42. The method of claim 40, wherein the DFT is an M-point DFT that generates the initial set of at least N complex frequency components from M received information samples.

43. A receiver for receiving a single-carrier signal, comprising:

Discrete Fourier Transform (DFT) logic that generates an initial set of at least N complex frequency components from a number of received information samples;

logic that receives side information that identifies a selected one of N_s possible permutations, where 2≦

N_s≦

N!;

logic that generates a set of permuted complex frequency components by permuting the initial set of at least N complex frequency components by the selected one of N_s possible permutations; and

logic that generates a set of at least N time-domain symbols by applying an Inverse Discrete Fourier Transform (IDFT) to the set of permuted complex frequency components.

44. The apparatus of claim 43, wherein the DFT is an N-point DFT that generates the initial set of at least N complex frequency components from N received information samples.

45. The apparatus of claim 43, wherein the DFT is an M-point DFT that generates the initial set of at least N complex frequency components from M received information samples.

46. A receiver for receiving a single-carrier signal, comprising:

logic that uses a Discrete Fourier Transform (DFT) to generate an initial set of at least N complex frequency components from a number of received information samples;

logic that generates N_s different sets of permuted complex frequency components by, for each of N_s times, permuting the initial set of at least N complex frequency components by one of N_s possible permutations, where 2≦

N_s≦

N!;

logic that uses a blind detection technique to determine which of the N_s different sets of permuted complex frequency components is a selected one of the N_s different sets of permuted complex frequency components; and

logic that generates a set of at least N time-domain symbols by applying an Inverse Discrete Fourier Transform (IDFT) to the selected one of the N_s different sets of permuted complex frequency components.

47. The apparatus of claim 46, wherein the DFT is an N-point DFT that generates the initial set of at least N complex frequency components from N received information samples.

48. The apparatus of claim 46, wherein the DFT is an M-point DFT that generates the initial set of at least N complex frequency components from M received information samples.