SPECTRAL SHAPING TO REDUCE PEAK-TO-AVERAGE RATIO IN WIRELESS COMMUNICATION

• US 20070183520A1
• Filed: 02/08/2007
• Published: 08/09/2007
• Est. Priority Date: 02/08/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Malladi, Durga Prasad, Kim, Byoung-Hoon
• Granted Patent: US 8,891,637 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 25/03828 Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties partial response systems H04L25/497
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Techniques for performing spectral shaping to achieve a desired peak-to-average ratio (PAR) are described. Spectral shaping may be selectively performed for a single-carrier frequency division multiplexing (SC-FDM) signal based on one or more criteria, e.g., in transmit power limited conditions and/or if a modulation scheme with lower PAR is unavailable. At least one parameter of a window function or spectral shaping filter may also be adjusted based on at least one characteristic of the SC-FDM signal. For example, the roll-off of the spectral shaping filter may be adjusted based on the modulation scheme and/or the number of subcarriers used for the SC-FDM signal. A transmitter may perform spectral shaping on modulation symbols, if enabled, to obtain spectrally shaped symbols. Spectral shaping may be performed in the frequency domain either within an allocated bandwidth or with bandwidth expansion. The SC-FDM signal may be generated based on the spectrally shaped symbols.

Claims

1. An apparatus comprising:

at least one processor configured to perform spectral shaping on modulation symbols to obtain spectrally shaped symbols, and to generate a single-carrier frequency division multiplexing (SC-FDM) signal based on the spectrally shaped symbols; and

a memory coupled to the at least one processor.

2. The apparatus of claim 1, wherein the at least one processor is configured to perform spectral shaping in frequency domain within an allocated bandwidth.

3. The apparatus of claim 1, wherein the at least one processor is configured to perform spectral shaping in frequency domain with bandwidth expansion.

4. The apparatus of claim 1, wherein the at least one processor is configured to transform the modulation symbols to frequency domain to obtain frequency-domain symbols, and to perform spectral shaping on the frequency-domain symbols to obtain the spectrally shaped symbols.

5. The apparatus of claim 4, wherein the at least one processor is configured to perform spectral shaping by multiplying the frequency-domain symbols with a window function to obtain the spectrally shaped symbols.

6. The apparatus of claim 1, wherein the at least one processor is configured to receive a command to perform spectral shaping and to perform spectral shaping as indicated by the received command.

7. The apparatus of claim 1, wherein the at least one processor is configured to determine whether or not to perform spectral shaping based on at least one criterion.

8. The apparatus of claim 1, wherein the at least one processor is configured to perform spectral shaping in transmit power limited conditions.

9. The apparatus of claim 1, wherein the at least one processor is configured to perform spectral shaping in transmit power limited conditions and if a modulation scheme with lower peak-to-average ratio (PAR) is unavailable.

10. The apparatus of claim 1, wherein the at least one processor is configured to determine whether or not to perform spectral shaping based on at least one characteristic of the SC-FDM signal.

11. The apparatus of claim 1, wherein the at least one processor is configured to determine whether or not to perform spectral shaping based on at least one of a modulation scheme used to generate the modulation symbols and number of subcarriers used for the SC-FDM signal.

12. The apparatus of claim 1, wherein the at least one processor is configured to adjust at least one parameter of a spectral shaping filter based on at least one characteristic of the SC-FDM signal, and to perform spectral shaping on the modulation symbols based on the spectral shaping filter.

13. The apparatus of claim 12, wherein the at least one processor is configured to adjust roll-off of the spectral shaping filter based on the at least one characteristic of the SC-FDM signal.

15. The apparatus of claim 1, wherein the at least one processor is configured to map the spectrally shaped symbols to a set of contiguous subcarriers and to generate the SC-FDM signal based on the mapped spectrally shaped symbols.

16. The apparatus of claim 1, wherein the at least one processor is configured to map the spectrally shaped symbols to a set of subcarrier distributed across system bandwidth and to generate the SC-FDM signal based on the mapped spectrally shaped symbols.

14. The apparatus of claim 14, wherein the at least one processor is configured to adjust the at least one parameter of the spectral shaping filter based on at least one of a modulation scheme used to generate the modulation symbols and number of subcarriers used for the SC-FDM signal.

17. A method comprising:

performing spectral shaping on modulation symbols to obtain spectrally shaped symbols; and

generating a single-carrier frequency division multiplexing (SC-FDM) signal based on the spectrally shaped symbols.

18. The method of claim 17, further comprising:

determining whether or not to perform spectral shaping based on at least one criterion.

19. The method of claim 17, wherein the performing spectral shaping comprises performing spectral shaping in frequency domain within an allocated bandwidth.

20. The method of claim 17, wherein the performing spectral shaping comprises

adjusting at least one parameter of a spectral shaping filter based on at least one characteristic of the SC-FDM signal, and

performing spectral shaping on the modulation symbols based on the spectral shaping filter.

21. The method of claim 17, wherein the performing spectral shaping on the modulation symbols comprises

transforming the modulation symbols to frequency domain to obtain frequency-domain symbols, and

performing spectral shaping on the frequency-domain symbols to obtain the spectrally shaped symbols, and

wherein the generating the SC-FDM signal comprises

mapping the spectrally shaped symbols to a set of subcarriers, and

generating the SC-FDM signal based on the mapped spectrally shaped symbols.

22. An apparatus comprising:

means for performing spectral shaping on modulation symbols to obtain spectrally shaped symbols; and

means for generating a single-carrier frequency division multiplexing (SC-FDM) signal based on the spectrally shaped symbols.

23. The apparatus of claim 22, further comprising:

means for determining whether or not to perform spectral shaping based on at least one criterion.

24. The apparatus of claim 22, wherein the means for performing spectral shaping comprises

means for adjusting at least one parameter of a spectral shaping filter based on at least one characteristic of the SC-FDM signal, and

means for performing spectral shaping on the modulation symbols based on the spectral shaping filter.

25. A computer-readable medium including instruction stored thereon, comprising:

a first instruction set for performing spectral shaping on modulation symbols to obtain spectrally shaped symbols; and

a second instruction set for generating a single-carrier frequency division multiplexing (SC-FDM) symbols based on the spectrally shaped symbols.

26. The computer-readable medium of claim 25, further comprising:

a third instruction set for determining whether or not to perform spectral shaping based on at least one criterion.

27. An apparatus comprising:

at least one processor configured to receive a single-carrier frequency division multiplexing (SC-FDM) signal carrying spectrally shaped symbols, and to process the SC-FDM signal to obtain modulation symbol estimates for a set of subcarriers used for transmission; and

a memory coupled to the at least one processor.

28. The apparatus of claim 27, wherein the at least one processor is configured to transform received samples for the SC-FDM signal to frequency domain to obtain received symbols for a plurality of subcarriers, to scale received symbols for the set of subcarriers used to transmission to obtain scaled symbols, to perform data detection on the scaled symbols to obtain detected symbols, and to transform the detected symbols to time domain to obtain the modulation symbols estimates.

29. A method comprising:

receiving a single-carrier frequency division multiplexing (SC-FDM) signal carrying spectrally shaped symbols; and

processing the SC-FDM signal to obtain modulation symbol estimates for a set of subcarriers used for transmission.

30. The method of claim 29, wherein the processing the SC-FDM signal comprises

transforming received samples for the SC-FDM signal to frequency domain to obtain received symbols for a plurality of subcarriers,

performing data detection on received symbols for the et of subcarriers used for transmission to obtain detected symbols, and

transforming the detected symbols to time domain to obtain the modulation symbol estimates.

31. An apparatus comprising:

means for receiving a single-carrier frequency division multiplexing (SC-FDM) signal carrying spectrally shaped symbols; and

means for processing the SC-FDM signal to obtain modulation symbol estimates for a set of subcarriers used for transmission.

32. The apparatus of claim 31, wherein the means for processing the SC-FDM signal comprises

means for transforming received samples for the SC-FDM signal to frequency domain to obtain received symbols for a plurality of subcarriers,

means for performing data detection on received symbols for the set of subcarriers used for transmission to obtain detected symbols, and

means for transforming the detected symbols to time domain to obtain the modulation symbol estimates.