Crest factor reduction of carrier aggregated signals

• US 9,331,882 B2
• Filed: 06/30/2014
• Issued: 05/03/2016
• Est. Priority Date: 06/05/2013
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Fehri, Bilel, Boumaiza, Slim, Sich, Edward
• Primary Examiner(s): Jackson, Blane J
• Application Number:
  US14/319,599
• Publication Number:
  US 20140362951A1
• Time in Patent Office: 673 Days
• Field of Search: 455/115.1, 455/127.1
• US Class Current: 1/1
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04L 27/2623 Reduction thereof by clipping
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers

Abstract

The present disclosure advantageously provides methods and systems for crest factor reduction of multi-standard carrier aggregated signals. In one embodiment, a method of providing crest factor reduction for a carrier aggregated signal is provided. In one embodiment, the method comprises estimating a peak of a carrier aggregated signal based on a summation of instantaneous amplitudes of baseband representations of a number of component carriers of the carrier aggregated signal. The number of component carriers of the carrier aggregated signal is greater than or equal to 2. The method further comprises clipping the baseband representations of the component carriers if the estimated peak of the carrier aggregated signal is greater than a predefined clipping threshold.

Claims

1. A method of providing crest factor reduction for a carrier aggregated signal, comprising:

estimating a peak of a carrier aggregated signal comprising a plurality of component carriers based on a summation of instantaneous amplitudes of baseband representations of the plurality of component carriers, the number of component carriers in the plurality of component carriers of the carrier aggregated signal is greater than or equal to 2; and

clipping the baseband representations of the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than a predefined clipping threshold.

2. The method of claim 1 wherein estimating the peak of the carrier aggregated signal comprises:

determining the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal; and

summing the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal to provide the estimated peak of the carrier aggregated signal.

3. The method of claim 2 wherein clipping the baseband representations of the plurality of component carriers comprises applying equal peak reduction to each component carrier of the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

4. The method of claim 3 wherein the equal peak reduction is defined as (S−

C)/2 where S is the summation of the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal and C is the predefined clipping threshold.

5. The method of claim 2 wherein clipping the baseband representations of the plurality of component carriers comprises clipping the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for different Error Vector Magnitude, EVM, requirements for the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

6. The method of claim 5 wherein clipping the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for different EVM requirements for the plurality of component carriers comprises clipping the baseband representations of the plurality of component carriers according to:

7. The method of claim 1 wherein estimating the peak of the carrier aggregated signal comprises:

determining the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal;

weighting the instantaneous amplitudes according to average power levels of the plurality of component carriers of the carrier aggregated signal; and

summing the weighted instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal to provide the estimated peak of the carrier aggregated signal.

8. The method of claim 7 wherein weighting the instantaneous amplitudes comprises, for each component carrier of the plurality of component carriers, computing the weighted instantaneous amplitude for the component carrier as:

G_i·

|{tilde over (x)}_i(n)|,

where {tilde over (x)}_i(n) is the baseband representation of the component carrier and G_i is a weighting factor for the component carrier.

9. The method of claim 8 wherein the weighting factor for the component carrier is defined as:

10. The method of claim 8 wherein clipping the baseband representations of the plurality of component carriers comprises clipping the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for different average power levels for the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

11. The method of claim 10 wherein clipping the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for different average power levels for the plurality of component carriers comprises clipping the baseband representations of the plurality of component carriers according to:

12. The method of claim 10 wherein clipping the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for different average power levels for the plurality of component carriers comprises clipping the baseband representations of the plurality of component carriers according to:

13. The method of claim 8 wherein clipping the baseband representations of the plurality of component carriers comprises clipping the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for both different average power levels for the plurality of component carriers and different Error Vector Magnitude, EVM, requirements for the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

14. The method of claim 13 wherein clipping the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for both different average power levels for the plurality of component carriers and different EVM requirements comprises clipping the baseband representations of the plurality of component carriers according to:

15. A crest factor reduction system for a carrier aggregated signal, comprising:

a signal amplitude estimator configured to estimate a peak of a carrier aggregated signal comprising a plurality of component carriers, the signal amplitude estimator configured to estimate the peak of the carrier aggregated signal based on a summation of instantaneous amplitudes of baseband representations of the plurality of component carriers, the number of component carriers in the plurality of component carriers of the carrier aggregated signal is greater than or equal to 2; and

clipping circuitry configured to clip the baseband representations of the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than a predefined clipping threshold.

16. The system of claim 15 wherein signal amplitude estimator comprises:

a plurality of magnitude operators configured to provide the instantaneous amplitudes of the baseband representations of the plurality of component carriers, each magnitude operator of the plurality of magnitude operators configured to provide the instantaneous amplitude of the baseband representation of a different one of the plurality of component carriers;

determining the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal; and

an adder configured to sum the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal to provide the estimated peak of the carrier aggregated signal.

17. The system of claim 16 wherein the clipping circuitry configured to clip the baseband representations of the plurality of component carriers based on an equal peak reduction per component carrier scheme if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

18. The system of claim 17 wherein the equal peak reduction is defined as (S−

C)/2 where S the summation of the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal and C is the predefined clipping threshold.

19. The system of claim 16 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for different Error Vector Magnitude, EVM, requirements for the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

20. The system of claim 19 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for different EVM requirements for the plurality of component carriers by clipping the baseband representations of the plurality of component carriers according to:

21. The system of claim 15 wherein signal amplitude estimator comprises:

a plurality of magnitude operators configured to provide the instantaneous amplitudes of the baseband representations of the plurality of component carriers, each magnitude operator of the plurality of magnitude operators configured to provide the instantaneous amplitude of the baseband representation of a different one of the plurality of component carriers;

determining the instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal;

weighting circuitry configured to weight the instantaneous amplitudes according to average power levels of the plurality of component carriers of the carrier aggregated signal; and

an adder configured to sum the weighted instantaneous amplitudes of the baseband representations of the plurality of component carriers of the carrier aggregated signal to provide the estimated peak of the carrier aggregated signal.

22. The system of claim 21 wherein, in order to weight the instantaneous amplitudes, the weighting circuitry is configured to, for each component carrier of the plurality of component carriers, compute the weighted instantaneous amplitude for the component carrier as:

G_i·

|{tilde over (x)}_i(n)|,

where {tilde over (x)}_i(n) is the baseband representation of the component carrier and G_i is a weighting factor for the component carrier.

23. The system of claim 22 wherein the weighting factor for the component carrier is defined as:

24. The system of claim 22 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for different average power levels for the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

25. The system of claim 24 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for different average power levels for the plurality of component carriers by clipping the baseband representations of the plurality of component carriers according to:

26. The system of claim 24 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to the crest factor reduction scheme that accounts for different average power levels for the plurality of component carriers by clipping the baseband representations of the plurality of component carriers according to:

27. The system of claim 22 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for both different average power levels for the plurality of component carriers and different Error Vector Magnitude, EVM, requirements for the plurality of component carriers if the estimated peak of the carrier aggregated signal is greater than the predefined clipping threshold.

28. The system of claim 27 wherein the clipping circuitry is configured to clip the baseband representations of the plurality of component carriers according to a crest factor reduction scheme that accounts for both different average power levels for the plurality of component carriers and different EVM requirements by clipping the baseband representations of the plurality of component carriers according to: