Methods and systems for reducing PAPR of an OFDM signal

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 cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by simulations where a particular set of matrices are used for a particular modulation type; 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 first cyclic permutation comprises performing the first cyclic permutation in a time domain.

4. 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 the OFDM symbol.

5. The method of claim 4 , further comprising performing an interpolation using the fourth sequence of samples after performing the inverse frequency-to-time transform.

6. The method of claim 4 , wherein:

performing the transformation involving the unitary matrix on the permuted sequence of samples to obtain the 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 the fourth sequence of samples comprises performing an inverse digital Fourier transform (IDFT).

7. The method of claim 6 , wherein a size of the IDFT is equal to a size of the DFT.

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

at least one processor configured to:

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

perform a time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples at least in part by:

performing a first cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by simulations where a particular set of matrices are used for a particular modulation type; and

generate an OFDM symbol for transmission from the second sequence of samples; and

a memory coupled to the at least one processor.

9. The apparatus of claim 8 , wherein the unitary matrix comprises a Vandermonde unitary matrix.

10. The apparatus of claim 8 , wherein the at least one processor performs the first cyclic permutation in a time domain.

11. The apparatus of claim 8 , wherein the at least one processor generates the OFDM symbol for transmission from the second sequence of samples at least in part by:

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 the OFDM symbol.

12. The apparatus of claim 11 , wherein the at least one processor is further configured to perform an interpolation using the fourth sequence of samples after performing the inverse frequency-to-time transform.

13. The apparatus of claim 11 , wherein:

the at least one processor performs the transformation at least in part by performing a digital Fourier transform (DFT); and

the at least one processor performs the inverse frequency-to-time transform on the third sequence of samples at least in part by performing an inverse digital Fourier transform (IDFT).

14. The apparatus of claim 13 , wherein a size of the IDFT is equal to a size of the DFT.

15. 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 cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by simulations where a particular set of matrices are used for a particular modulation type; and

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

16. The apparatus of claim 15 , wherein the unitary matrix comprises a Vandermonde unitary matrix.

17. The apparatus of claim 15 , wherein the means for performing the first cyclic permutation is configured to perform the first cyclic permutation in a time domain.

18. The apparatus of claim 15 , 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 the OFDM symbol.

19. The apparatus of claim 18 , further comprising means for performing an interpolation using the fourth sequence of samples after performing the inverse frequency-to-time transform.

20. The apparatus of claim 18 , wherein:

the means for performing the transformation involving the unitary matrix on the permuted sequence of samples to obtain the 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 the fourth sequence of samples is configured to perform an inverse digital Fourier transform (IDFT).

21. The apparatus of claim 20 , wherein a size of the IDFT is equal to a size of the DFT.

22. A computer-program product for processing data for transmission in a wireless communication system using orthogonal frequency division multiplexing (OFDM) comprising a non-transitory 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 cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by simulations where a particular set of matrices are used for a particular modulation type; and

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

23. The computer-program product medium of claim 22 , wherein the unitary matrix comprises a Vandermonde unitary matrix.

24. The computer-program product medium of claim 22 , wherein the instructions for performing a first cyclic permutation comprise instructions for performing the first cyclic permutation in a time domain.

25. The computer-program product of claim 22 , wherein the instructions for generating the OFDM symbol for transmission from the second sequence of samples comprise:

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 the OFDM symbol.

26. The computer-program product of claim 25 , wherein the set of instructions further comprise instructions for performing an interpolation using the fourth sequence of samples after performing the inverse frequency-to-time transform.

27. The computer-program product of claim 25 , wherein:

the instructions for performing the transformation involving the unitary matrix on the permuted sequence of samples to obtain the 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 the fourth sequence of samples comprise instructions for performing an inverse digital Fourier transform (IDFT).

28. The computer-program product of claim 27 , wherein a size of the IDFT is equal to a size of the DFT.

29. 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 cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type; and

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

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

at least one processor configured to:

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

perform a time-to-frequency transformation of the first sequence of samples to obtain a second sequence of samples at least in part by:

performing a first cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type; and

generate an OFDM symbol for transmission from the second sequence of samples; and

a memory coupled to the at least one processor.

31. 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 cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type; and

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

32. A computer-program product for processing data for transmission in a wireless communication system using orthogonal frequency division multiplexing (OFDM) comprising a non-transitory 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 cyclic permutation of the first sequence of samples utilizing a first cyclic permutation matrix 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 cyclic permutation of the transformed sequence of samples utilizing a second cyclic permutation matrix to obtain the second sequence of samples, wherein the first cyclic permutation matrix is characterized by a first index i, and the second cyclic permutation matrix is characterized by a second index j, and wherein the first index i and the second index j are each determined by selecting values that result in minimum peak-to-average power ratio (PAPR) values for a particular modulation type; and

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