SIGNALING METHOD IN AN OFDM MULTIPLE ACCESS SYSTEM

• US 20110235747A1
• Filed: 06/10/2011
• Published: 09/29/2011
• Est. Priority Date: 09/13/2000
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Uppala, Sathyadev Venkata, Laroia, Rajiv, Li, Junyi
• Granted Patent: US 8,223,627 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/26025 Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking allocating sub-channels of the transmission path H04L5/003
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A method for reducing the peak-to-average ratio in an OFDM communication signal is provided. The method includes defining a constellation having a plurality of symbols, defining a symbol duration for the OFDM communication signal, and defining a plurality of time instants in the symbol duration. A plurality of tones are allocated to a particular communication device, and a discrete signal is constructed in the time domain by mapping symbols from the constellation to the time instants. A continuous signal is generated by applying an interpolation function to the discrete signal such that the continuous signal only includes sinusoids having frequencies which are equal to the allocated tones.

Claims

1. A processor-based apparatus for generating wireless communications, the processor-based apparatus comprising:

a first circuit configured to perform a Discrete Fourier Transform (DFT) on a discrete signal of complex data symbols to obtain a first frequency response vector of length M;

a second circuit configured to expand the first frequency response vector to obtain a second frequency response vector of length N;

a third circuit configured to perform an N-point Inverse DFT (IDFT) on the second frequency response vector of length N, by inserting zero-value symbols corresponding to tones other than tones allocated to a transmitter, to obtain a vector of digital signal samples; and

a fourth circuit configured to generate a low peak-to-average orthogonal frequency division multiplexing (OFDM) signal representing the vector of digital signal samples for transmission.

2. The processor-based apparatus of claim 1, wherein the second frequency response vector has entries corresponding to tones other than tones allocated to the processor-based apparatus.

3. The processor-based apparatus of claim 2, wherein the first circuit performs a DFT with a set of tones allocated to the processor-based apparatus for transmission.

4. The processor-based apparatus of claim 3, wherein the allocated tones are contiguous.

5. The processor-based apparatus of claim 3, wherein the allocated tones are equally spaced.

6. The processor-based apparatus of claim 1, wherein the first, second, and third circuits comprise a combination of hardware and software modules.

7. The processor-based apparatus of claim 1, wherein at least one of the first, second, and third circuits comprises a software module.

8. The processor-based apparatus of claim 1, wherein the fourth circuit comprises:

a circuit configured to convert the vector of digital signal samples to an analog signal.

9. The processor-based apparatus of claim 8, wherein the fourth circuit further comprises:

a circuit configured to modulate the analog signal to a carrier frequency for transmission.

10. The processor-based apparatus of claim 9, wherein the fourth circuit further comprises:

a pulse filter circuit configured to process the analog signal prior to modulation to the carrier frequency.

11. The processor-based apparatus of claim 9, further comprising:

at least one antenna; and

a power amplifier circuit configured to amplify the analog signal prior to transmission via the at least one antenna.

12. The processor-based apparatus of claim 1, further comprising:

a circuit configured to pre-pend a cyclic prefix to the vector of digital signal samples; and

wherein the fourth circuit is configured to generate a low peak-to-average orthogonal frequency division multiplexing (OFDM) signal representing the vector of digital signal samples with the cyclic prefix for transmission.

13. A method for wireless communications utilizing at least one processor, comprising:

performing a Discrete Fourier Transform (DFT) on a discrete signal of complex data symbols to obtain a first frequency response vector of length M;

expanding the first frequency response vector to obtain a second frequency response vector of length N;

performing an N-point Inverse DFT (IDFT) on the second frequency response vector of length N by inserting zero-value symbols corresponding to tones other than tones allocated to a transmitter; and

generating a low peak-to-average orthogonal frequency division multiplexing (OFDM) signal representing the vector of digital signal samples for transmission.

14. The method of claim 13, wherein the second frequency response vector has entries corresponding to tones other than tones allocated to an apparatus.

15. The method of claim 14, wherein the DFT is performed with a set of tones allocated to the apparatus for transmission.

16. The method of claim 15, wherein the allocated tones are contiguous.

17. The method of claim 15, wherein the allocated tones are equally spaced.

18. The method of claim 13, wherein the performing a DFT, expanding the first frequency response vector, and performing an N-point IDFT are performed by a combination of hardware and software modules.

19. The method of claim 13, wherein at least one of the performing a DFT, expanding the first frequency response vector, and performing an N-point IDFT is performed by a software module.

20. The method of claim 13, wherein generating low peak-to-average OFDM comprises:

converting the vector of digital signal samples to an analog signal.

21. The method of claim 20, wherein low peak-to-average OFDM further comprises:

modulating the analog signal to a carrier frequency for transmission.

22. The method of claim 21, wherein low peak-to-average OFDM further comprises:

performing pulse filtering of the analog signal prior to modulation to the carrier frequency.

23. The method of claim 21, further comprising:

amplifying the analog signal prior to transmission via at least one antenna.

24. The method of claim 13, further comprising:

pre-pending a cyclic prefix to the vector of digital signal samples; and

wherein the generating comprises generating a low peak-to-average OFDM signal representing the vector of digital signal samples with the cyclic prefix for transmission.

25. A processor-based apparatus for generating wireless communications, the processor-based apparatus comprising:

means for performing a Discrete Fourier Transform (DFT) on a discrete signal of complex data symbols to obtain a first frequency response vector of length M;

means for expanding the first frequency response vector to obtain a second frequency response vector of length N;

means for performing an N-point Inverse DFT (IDFT) on the second frequency response vector of length N by inserting zero-value symbols corresponding to tones other than tones allocated to a transmitter; and

means for generating a low peak-to-average orthogonal frequency division multiplexing (OFDM) signal representing the vector of digital signal samples for transmission.

26. The processor-based apparatus of claim 25, wherein the second frequency response vector has entries corresponding to tones other than tones allocated to the processor-based apparatus.

27. The processor-based apparatus of claim 25, wherein the means for performing a DFT performs a DFT with a set of tones allocated to the processor-based apparatus for transmission.

28. The processor-based apparatus of claim 27, wherein the allocated tones are contiguous.

29. The processor-based apparatus of claim 27, wherein the allocated tones are equally spaced.

30. The processor-based apparatus of claim 25, wherein the means for performing a DFT, means for expanding the first frequency response vector, and means for performing an N-point IDFT comprise a combination of hardware and software modules.

31. The processor-based apparatus of claim 25, wherein at least one of the means for performing a DFT, means for expanding the first frequency response vector, and means for performing an N-point IDFT comprises a software module.

32. The processor-based apparatus of claim 25, wherein the means for generating a low peak-to-average OFDM signal comprises:

means for converting the vector of digital signal samples to an analog signal.

33. The processor-based apparatus of claim 32, wherein the means for generating a low peak-to-average OFDM signal further comprises:

means for modulating the analog signal to a carrier frequency for transmission.

34. The processor-based apparatus of claim 33, wherein the means for generating a low peak-to-average OFDM signal further comprises:

means for performing pulse filtering of the analog signal prior to modulation to the carrier frequency.

35. The processor-based apparatus of claim 33, further comprising:

at least one antenna; and

means for amplifying the analog signal prior to transmission via the at least one antenna.

36. The processor-based apparatus of claim 25, further comprising:

means for pre-pending a cyclic prefix to the vector of digital signal samples; and

wherein the means for generating is configured to generate a low peak-to-average orthogonal frequency division multiplexing (OFDM) signal representing the vector of digital signal samples with the cyclic prefix for transmission.