Efficient peak-to-average-power reduction for OFDM and MIMO-OFDM

1. A method for reducing a peak-to-average power ratio (PAPR) of a discrete-time orthogonal frequency division multiplexing (OFDM) signal by selecting a signal with low PAPR from a plurality of candidate discrete-time OFDM signals, the method comprising:

generating a partial update discrete-time OFDM signal by performing a sparse invertible transform operation on a base data symbol sequence; and

linearly combining a base discrete-time OFDM signal and the partial update discrete-time OFDM signal to produce an updated discrete-time OFDM signal, the updated discrete-time OFDM signal being designated as one of the plurality of candidate discrete-time OFDM signals;

wherein the base discrete-time OFDM signal is generated by performing a dense invertible transform operation on the base data symbol sequence or is selected from a previous updated discrete-time OFDM signal.

2. The method of claim 1 , wherein the sparse invertible transform operation comprises at least one of a sparse inverse fast Fourier transform (IFFT), a wavelet-based approximate IFFT, a sparse matrix-vector multiplication, a sparse-matrix sparse vector multiplication, or a matrix sparse-vector multiplication.

3. The method of claim 1 , further comprising generating at least one additional partial update discrete-time OFDM signal by at least one of linear combining a first partial update discrete-time OFDM signal with a second partial update discrete-time OFDM signal, or multiplying the partial update discrete-time OFDM signal with a complex-value scaling factor.

4. The method of claim 1 , wherein performing the sparse invertible transform operation includes at least one of:

performing a component-wise multiplication of the base data symbol sequence with a sparse weight matrix to generate a sparse update symbol sequence, and performing an invertible transform operation on the sparse update symbol sequence;

employing the sparse weight matrix to select at least one block of elements in a dense invertible transform operator to produce a sparse invertible transform operator, and using the sparse invertible transform operator to operate on the base data symbol sequence; or

selecting at least one block of elements in the dense invertible transform operator to produce the sparse invertible transform operator, selecting at least one element in the base data symbol sequence to produce the sparse update symbol sequence, and using the sparse invertible transform operator to operate on the sparse update symbol sequence.

5. The method of claim 1 , wherein performing the sparse invertible transform operation comprises optimizing the sparse invertible transform operation to run on a graphics processing unit.

6. The method of claim 1 , wherein the PAPR comprises a sum of PAPRs scaled with weights, each weight comprising a measure of PAPR sensitivity for a corresponding antenna or node.

7. The method of claim 1 , further comprising transmitting side information indicating a selected one of the plurality of candidate discrete-time OFDM signals to enable a receiver to decode the selected one of the plurality of candidate discrete-time OFDM signals.

8. An apparatus for reducing a peak-to-average power ratio (PAPR) of a discrete-time signal by selecting a signal with low PAPR from a set of candidate discrete-time signals, comprising:

a memory; and one or more processors operatively coupled to the memory, the one or more processors configured to:

generate a partial update discrete-time signal by performing a sparse transform operation on a base data symbol sequence; and

linearly combine a base discrete-time signal and the partial update discrete-time signal to produce an updated discrete-time signal, the updated discrete-time signal being included in the set of candidate discrete-time signals;

wherein the base discrete-time OFDM signal is generated by performing a dense invertible transform operation on the base data symbol sequence or is selected from a previous updated discrete-time OFDM signal.

9. The apparatus of claim 8 , wherein the sparse transform operation comprises at least one of a sparse inverse fast Fourier transform (IFFT), a wavelet-based approximate IFFT, a sparse matrix-vector multiplication, a sparse-matrix sparse vector multiplication, or a matrix sparse-vector multiplication.

10. The apparatus of claim 8 , wherein the one or more processors are configured for generating at least one additional partial update discrete-time signal by at least one of linear combining a first partial update discrete-time signal with a second partial update discrete-time signal, or multiplying the partial update discrete-time signal with a complex-value scaling factor.

11. The apparatus of claim 8 , wherein performing a sparse transform operation comprises at least one of:

performing a component-wise multiplication of the base symbol sequence with a sparse weight matrix to generate a sparse update symbol sequence, and performing an invertible transform operation on the sparse update symbol sequence;

employing the sparse weight matrix to select at least one block of elements in a dense invertible transform operator to produce a sparse transform operator, and using the sparse transform operator to operate on the base symbol sequence; or

selecting at least one block of elements in the dense invertible transform operator to produce the sparse transform operator, selecting at least one element in the base symbol sequence to produce the sparse update symbol sequence, and using the sparse transform operator to operate on the sparse update symbol sequence.

12. The apparatus of claim 8 , wherein the PAPR comprises a sum of PAPRs scaled with weights, each weight comprising a measure of PAPR sensitivity for at least one of a corresponding antenna or node.

13. The apparatus of claim 8 , wherein performing the sparse transform operation comprises optimizing the sparse transform operation to run on a graphics processing unit.

14. The apparatus of claim 8 , wherein the one or more processors are configured to provide for transmitting side information indicating a selected one of the candidate discrete-time signals to enable a receiver to decode the elected one of the candidate discrete-time signals.

15. A non-transitory computer-readable medium storing one or more instructions for reducing a peak-to-average power ratio (PAPR) of a transmitted discrete-time signal by selecting a signal with low PAPR from a set of candidate discrete-time signals, the one or more instructions, when executed by one or more processors, cause the one or more processors to:

generate a partial update discrete-time signal by performing a sparse transform operation on a base data symbol sequence; and

linearly combine a base discrete-time signal and the partial update discrete-time signal to produce an updated discrete-time signal, the updated discrete-time signal being included in the set of candidate discrete-time signals;

wherein the base discrete-time OFDM signal is generated by performing a dense invertible transform operation on the base data symbol sequence or is selected from a previous updated discrete-time OFDM signal.

16. The non-transitory computer-readable medium of claim 15 , wherein the sparse transform operation comprises at least one of a sparse inverse fast Fourier transform (IFFT), a wavelet-based approximate IFFT, a sparse matrix-vector multiplication, a sparse-matrix sparse vector multiplication, or a matrix sparse-vector multiplication.

17. The non-transitory computer-readable medium of claim 15 , wherein the one or more instructions, when executed by the one or more processors, cause the one or more processors to generate at least one additional partial update discrete-time signal by at least one of linear combining a first partial update discrete-time signal with a second partial update discrete-time signal, or multiplying the partial update discrete-time signal with a complex-value scaling factor.

18. The non-transitory computer-readable medium of claim 15 , wherein performing a sparse transform operation comprises at least one of:

performing a component-wise multiplication of the base symbol sequence with a sparse weight matrix to generate a sparse update symbol sequence, and performing an invertible transform operation on the sparse update symbol sequence;

employing the sparse weight matrix to select at least one block of elements in a dense invertible transform operator to produce a sparse transform operator, and using the sparse transform operator to operate on the base symbol sequence; or

selecting at least one block of elements in the dense invertible transform operator to produce the sparse transform operator, selecting at least one element in the base symbol sequence to produce the sparse update symbol sequence, and using the sparse transform operator to operate on the sparse update symbol sequence.

19. The non-transitory computer-readable medium of claim 15 , wherein the PAPR comprises a sum of PAPRs scaled with weights, each weight comprising a measure of PAPR sensitivity for at least one of a corresponding antenna or node.

20. The non-transitory computer-readable medium of claim 15 , wherein performing the sparse transform operation comprises optimizing the sparse transform operation to run on a graphics processing unit.

21. The non-transitory computer-readable medium of claim 15 , wherein the one or more instructions, when executed by the one or more processors, cause the one or more processors to provide for transmitting side information indicating a selected one of the candidate discrete-time signals to enable a receiver to decode the transmitted discrete-time signal.