METHODS AND SYSTEMS FOR REDUCING PAPR OF AN OFDM SIGNAL

• US 20100008432A1
• Filed: 07/08/2008
• Published: 01/14/2010
• Est. Priority Date: 07/08/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Naguib, Ayman Fawzy, Park, Jong Hyeon, Kim, Je Woo, Chang, Tae Ryun
• Granted Patent: US 8,509,324 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

Certain embodiments of the present disclosure provide a method and an apparatus for peak-to-average power ratio (PAPR) reduction of a transmission signal in a single carrier frequency division multiple access (SC-FDMA) system. The method may utilize a permutation of a time domain signal, and/or a permutation of a frequency domain signal or a permutation of a signal transformed by a unitary matrix. The apparatus may include an M-point DFT or some other M×M unitary matrix, N-point IDFT, interpolation and frequency conversion units, and a pair of possibly different permutation matrices of size M×M, where M can be less or equal than N.

Claims

1. A method for transmitting data in a wireless communication system using orthogonal frequency division multiplexing (OFDM), comprising:

performing a serial to parallel conversion of modulated symbols for the data to obtain a first sequence of samples;

performing a time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples, wherein the time-to-frequency transformation comprises;

performing a first permutation of the first sequence of samples to obtain a permuted sequence of samples;

performing a transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples; and

performing a second permutation of the transformed sequence of samples to obtain the second sequence of samples; and

generating an OFDM symbol for transmission from the second sequence of samples.

2. The method of claim 1, wherein the unitary matrix comprises a Vandermonde unitary matrix.

3. The method of claim 1, wherein performing the time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples comprises performing the first permutation in the time domain.

4. The method of claim 3, wherein indices of applied cyclic permutation matrices, i and j, are determined by simulations and a particular set of matrices are used for a particular modulation type.

5. The method of claim 1, wherein the first permutation comprises a cyclic permutation.

6. The method of claim 5, wherein indices of applied cyclic permutation matrices, i and j, are determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type.

7. The method of claim 1, wherein generating the OFDM symbol for transmission from the second sequence of samples comprises:

mapping the second sequence of samples into a set of subcarriers to obtain a third sequence of samples;

performing an inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples; and

performing a parallel to serial conversion of the fourth sequence of samples to obtain a fifth sequence of samples for transmission as an OFDM symbol.

8. The method of claim 7, further comprising performing an interpolation using the fourth sequence of samples after performing the IFDT.

9. The method of claim 7, wherein:

performing the transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples comprises performing a digital Fourier transform (DFT); and

performing the inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples comprises performing an inverse digital Fourier transform (IDFT).

10. The method of claim 9, wherein a size of the IDFT is equal to the size of DFT.

11. A transmitter for wireless communications using orthogonal frequency division multiplexing (OFDM), comprising:

logic for performing a serial to parallel conversion of modulated symbols for the data to obtain a first sequence of samples;

logic for performing a time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples, wherein the logic for performing the time-to-frequency transformation comprises;

logic for performing a first permutation of the first sequence of samples to obtain a permuted sequence of samples;

logic for performing a transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples; and

logic for performing a second permutation of the transformed sequence of samples to obtain the second sequence of samples; and

logic for generating an OFDM symbol for transmission from the second sequence of samples.

12. The transmitter of claim 11, wherein the unitary matrix comprises a Vandermonde unitary matrix.

13. The transmitter of claim 11, wherein the logic for performing the time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples is configured to perform the first permutation in the time domain.

14. The transmitter of claim 13, wherein indices of applied cyclic permutation matrices, i and j, are determined by simulations and a particular set of matrices are used for a particular modulation type.

15. The transmitter of claim 11, wherein the first permutation comprises a cyclic permutation.

16. The transmitter of claim 15, wherein indices of applied cyclic permutation matrices, i and j, are determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type.

17. The transmitter of claim 11, wherein the logic for generating the OFDM symbol for transmission from the second sequence of samples is configured to:

map the second sequence of samples into a set of subcarriers to obtain a third sequence of samples;

perform an inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples; and

perform a parallel to serial conversion of the fourth sequence of samples to obtain a fifth sequence of samples for transmission as an OFDM symbol.

18. The transmitter of claim 17, further comprising logic for performing an interpolation using the fourth sequence of samples after performing the IFDT.

19. The transmitter of claim 17, wherein:

the logic for performing the transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples is configured to perform a digital Fourier transform (DFT); and

the logic for performing the inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples is configured to perform an inverse digital Fourier transform (IDFT).

20. The transmitter of claim 19, wherein a size of the IDFT is equal to the size of DFT.

21. An apparatus for wireless communications using orthogonal frequency division multiplexing (OFDM), comprising:

means for performing a serial to parallel conversion of modulated symbols for the data to obtain a first sequence of samples;

means for performing a time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples, wherein the means for performing the time-to-frequency transformation comprises

means for performing a first permutation of the first sequence of samples to obtain a permuted sequence of samples;

means for performing a transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples; and

means for performing a second permutation of the transformed sequence of samples to obtain the second sequence of samples; and

means for generating an OFDM symbol for transmission from the second sequence of samples.

22. The apparatus of claim 21, wherein the unitary matrix comprises a Vandermonde unitary matrix.

23. The apparatus of claim 21, wherein the means for performing the time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples is configured to perform the first permutation in the time domain.

24. The apparatus of claim 23, wherein indices of applied cyclic permutation matrices, i and j, are determined by simulations and a particular set of matrices are used for a particular modulation type.

25. The apparatus of claim 21, wherein the first permutation comprises a cyclic permutation.

26. The apparatus of claim 25, wherein indices of applied cyclic permutation matrices, i and j, are determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type.

27. The transmitter of claim 21, wherein the means for generating the OFDM symbol for transmission from the second sequence of samples is configured to:

map the second sequence of samples into a set of subcarriers to obtain a third sequence of samples;

perform an inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples; and

perform a parallel to serial conversion of the fourth sequence of samples to obtain a fifth sequence of samples for transmission as an OFDM symbol.

28. The transmitter of claim 27, further comprising means for performing an interpolation using the fourth sequence of samples after performing the IFDT.

29. The transmitter of claim 27, wherein:

the means for performing the transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples is configured to perform a digital Fourier transform (DFT); and

the means for performing the inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples is configured to perform an inverse digital Fourier transform (IDFT).

30. The transmitter of claim 29, wherein a size of the IDFT is equal to the size of DFT.

31. A computer-program product for processing data for transmission in a wireless communication system using orthogonal frequency division multiplexing (OFDM) comprising a computer readable medium having a set of instructions stored thereon, the set of instructions being executable by one or more processors and the set of instructions comprising:

instructions for performing a serial to parallel conversion of modulated symbols for the data to obtain a first sequence of samples;

instructions for performing a time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples, wherein the instructions for performing the time-to-frequency transformation comprise

instructions for performing a first permutation of the first sequence of samples to obtain a permuted sequence of samples;

instructions for performing a transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples; and

instructions for performing a second permutation of the transformed sequence of samples to obtain the second sequence of samples; and

instructions for generating an OFDM symbol for transmission from the second sequence of samples.

32. The computer-program product medium of claim 31, wherein the unitary matrix comprises a Vandermonde unitary matrix.

33. The computer-program product medium of claim 31, wherein the instructions for performing the time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples comprises instructions for performing the first permutation in the time domain.

34. The computer-program product of claim 33, wherein indices of applied cyclic permutation matrices, i and j, are determined by simulations and a particular set of matrices are used for a particular modulation type.

35. The computer-program product of claim 31, wherein the first permutation comprises a cyclic permutation.

36. The computer-program product of claim 35, wherein indices of applied cyclic permutation matrices, i and j, are determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type.

37. The computer-program product of claim 31, wherein the instructions for generating the OFDM symbol for transmission from the second sequence of samples comprises:

instructions for mapping the second sequence of samples into a set of subcarriers to obtain a third sequence of samples;

instructions for performing an inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples; and

instructions for performing a parallel to serial conversion of the fourth sequence of samples to obtain a fifth sequence of samples for transmission as an OFDM symbol.

38. The computer-program product of claim 37, wherein the set of instructions further comprise instructions for performing an interpolation using the fourth sequence of samples after performing the IFDT.

39. The computer-program product of claim 37, wherein:

the instructions for performing the transformation involving a unitary matrix on the permuted sequence of samples to obtain a transformed sequence of samples comprise instructions for performing a digital Fourier transform (DFT); and

the instructions for performing the inverse frequency-to-time transform on the third sequence of samples to obtain a fourth sequence of samples comprise instructions for performing an inverse digital Fourier transform (IDFT).

40. The computer-program product of claim 39, wherein a size of the IDFT is equal to the size of DFT.