Apparatus and method for reducing peak-to-average power ratio in a broadband wireless communication system

• US 20060247898A1
• Filed: 04/20/2006
• Published: 11/02/2006
• Est. Priority Date: 04/20/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Cha, Sung-Keun
• Granted Patent: US 7,349,817 B2
• Time in Patent Office: Days
• US Class Current: 702/188
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2623 Reduction thereof by clipping

Abstract

An apparatus and method for PAPR reduction in a wireless communication system are provided. In the PAPR reducing apparatus, a first calculator calculates an ISF for each sample of baseband sample data. A successive peak detector adjusts the ISF of the each sample according to the spacing between successive peak samples. A second calculator subtracts the ISF of each sample received from the successive peak detector from a predetermined value. A window convolution calculator calculates a convolution of the difference received from the second calculator and a predetermined window function, and outputs a window operation value of each sample.

Claims

1. A wireless communication system for reducing the peak-to-average power ratio (PAPR) of a transmission signal, comprising:

a first calculator for calculating an intermediate scaling factor (ISF) for each sample of baseband sample data;

a successive peak detector for adjusting the ISF of the each sample according to the spacing between successive peak samples;

a second calculator for subtracting the ISF of each sample received from the successive peak detector from a predetermined value to output a difference; and

a window convolution calculator for calculating a convolution of the difference received from the second calculator and a predetermined window function, and outputting a window operation value of the each sample.

2. The wireless communication system of claim 1, wherein the first calculator detects samples having magnitudes exceeding a threshold, sets ISFs to ‘

1’

for the detected samples, and calculates ISFs for undetected samples.

3. The wireless communication system of claim 1, wherein the successive peak detector determines whether each sample is a peak by checking the ISF of each sample, compares the spacing between a previous peak and each sample with a predetermined window size, if each sample is a peak, multiplies the ISF of the each sample by a weighting value, if the spacing is less than or equal to the window size, and outputs the ISF of each sample if each sample is not a peak or the spacing is greater than the window size.

4. The wireless communication system of claim 1, further comprising:

a feedback portion for multiplying outputs of a number of shift registers from among a plurality of shift registers in the window convolution calculator by predetermined values, and summing the products; and

a third calculator for subtracting the sum received from the feedback portion from the output of the second calculator and outputting the difference to the window convolution calculator.

5. The wireless communication system of claim 1, further comprising a blocking negative value (BNV) portion for comparing a value input to the window convolution calculator with ‘

0’ and

providing the greater of the input value and ‘

0’

to the window convolution calculator.

6. The wireless communication system of claim 1, wherein the first calculator calculates the ISF by

$c$

( n ) = { 1 , 

x ⁡

( n ) 

≤

A A 

x n 

, 

x ⁡

( n ) 

>

A

where n is a sample index, A is a threshold, and |x(n)| is the magnitude of an n^th sample.

7. The wireless communication system of claim 1, wherein if the n^th sample is an (i+1)^th peak, the successive peak detector adjusts the ISF by

$b$

( n ) = { c ⁡

( n ) , P i + 1 - P i >

W α

·

c ⁡

( n ) , P i + 1 - P i ≤

W

where c (n) is the ISF, P_i is the sample index of an i^th peak, W is the window size represented as the number of samples, and a (>

1) is a weighting value.

8. The wireless communication system of claim 1, further comprising:

a fourth calculator for generating a final scaling factor for each sample by subtracting the window operation value of each sample from a predetermined value; and

a multiplier for scaling a peak by multiplying the final scaling factor by the magnitude of each sample.

9. The wireless communication system of claim 1, wherein the window function is one of Hamming, Hanning and Kaiser window functions.

10. A transmitter in a wireless communication system, comprising:

a multi-carrier modulator for generating sample data by modulating transmission data to multiple carriers;

a scaling factor calculator for calculating an intermediate scaling factor (ISF) for each sample in the sample data, adjusting the ISF of each sample according to the spacing between successive peak samples, and generating a scaling factor for each sample by performing a window convolution based on the adjusted ISF;

a separator for separating a phase and an amplitude from each sample of the sample data;

a multiplier for scaling a peak by multiplying the amplitude of each sample by the scaling factor; and

a combiner for generating a complex signal by combining the amplitude received from the multiplier with the phase received from the separator.

11. The transmitter of claim 10, further comprising:

a radio frequency (RF) processor for modulating the complex signal to an RF signal; and

a power amplifier for amplifying the power of the RF signal and transmitting the amplified RF signal.

12. The transmitter of claim 10, wherein the scaling factor calculator comprises:

a first calculator for detecting peak samples having magnitudes exceeding a threshold, sets ISFs to ‘

1’

for the detected peak samples, and calculates ISFs for undetected samples;

a successive peak detector for comparing the spacing between the peak samples with a predetermined window size, and adjusting the ISFs of the peak samples if the spacing is less than the window size;

a second calculator for subtracting the ISF of each sample from ‘

1’

;

a window convolution calculator for calculating a convolution of the difference received from the second calculator and a predetermined window function; and

a third calculator for generating the scaling factor of each sample by subtracting the output of the window convolution calculator from ‘

1’

.

13. The transmitter of claim 12, wherein the first calculator calculates the ISF by

$c$

( n ) = { 1 , 

x ⁡

( n ) 

≤

A A 

x n 

, 

x ⁡

( n ) 

>

A

where n is a sample index, A is a threshold, and |x(n)| is the magnitude of an n^th sample.

14. The transmitter of claim 12, wherein if the n^th sample is an (i+1)^th peak, the successive peak detector adjusts the ISF by

$b$

( n ) = { c ⁡

( n ) , P i + 1 - P i >

W α

·

c ⁡

( n ) , P i + 1 - P i ≤

W

where c(n) is the ISF, P_i is the sample index of an i^th peak, W is the window size represented as the number of samples, and a (>

1) is a weighting value.

15. The transmitter of claim 10, wherein the multi-carrier modulator is an inverse fast Fourier transform (IFFT) processor.

16. A method of reducing the peak-to-average power ratio (PAPR) of a transmission signal in a wireless communication system, comprising the steps of:

calculating an intermediate scaling factor (ISF) for each sample of baseband sample data;

adjusting the ISF of each sample according to the spacing between successive peak samples;

subtracting the adjusted ISF of each sample from a predetermined value and outputting the difference; and

performing a predetermined window convolution on the difference, and outputting a window operation value of each sample.

17. The method of claim 16, wherein the ISF adjusting step comprises:

determining whether the ISF of each sample is a peak by checking the ISF of each sample;

comparing the spacing between a previous peak and each sample with a predetermined window size, if each sample is a peak;

multiplying the ISF of each sample by a weighting value, if the spacing is less than or equal to the window size.

18. The method of claim 16, further comprising:

generating a feedback value by multiplying outputs of a number of shift registers used for the window convolution by predetermined values and summing the products; and

compensating an input for the window convolution by subtracting the sum from the difference.

19. The method of claim 16, further comprising determining whether the input for the window convolution is a negative value, and if the input is a negative value, setting the input for the window convolution to ‘

0’

.

20. The method of claim 16, where the ISF calculating step calculates the ISF, c(n) by

$c$

( n ) = { 1 , 

x ⁡

( n ) 

≤

A A 

x n 

, 

x ⁡

( n ) 

>

A

where n is a sample index, A is a threshold, and |x(n)| is the magnitude of an n^th sample.

21. The method of claim 16, wherein the ISF adjusting step comprises, if the n^th sample is an (i+1)^th peak, adjusting the ISF by

$b$

( n ) = { c ⁡

( n ) , P i + 1 - P i >

W α

·

c ⁡

( n ) , P i + 1 - P i ≤

W

where c(n) is the ISF, P_i is the sample index of an i^th peak, W is the window size represented as the number of samples, and a (>

1) is a weighting value.

22. The method of claim 16, further comprising:

generating a final scaling factor for each sample by subtracting the window operation value of each sample from a predetermined value; and

scaling a peak by multiplying the final scaling factor by the magnitude of each sample.

23. A transmission method in a wireless communication system, comprising the steps of:

generating sample data by modulating transmission data to multiple carriers;

calculating an intermediate scaling factor (ISF) for each sample in the sample data, adjusting the ISF of each sample according to the spacing between successive peak samples, and generating a scaling factor for each sample by performing a window convolution based on the adjusted ISF;

separating a phase and an amplitude from each sample of the sample data;

scaling the amplitude of each sample by multiplying the amplitude by the scaling factor; and

generating a complex signal by combining the scaled amplitude with the separated phase.

24. The transmission method of claim 23, further comprising:

modulating the complex signal to a radio frequency (RF) signal; and

amplifying the power of the RF signal and transmitting the amplified RF signal.

25. The transmission method of claim 23, wherein the scaling factor calculation step comprises:

detecting peak samples having magnitudes exceeding a threshold, setting ISFs to ‘

1’

for the detected peak samples, and calculating ISFs for undetected samples;

comparing the spacing between the peak samples with a predetermined window size, and adjusting the ISFs of the peak samples if the spacing is less than the window size;

subtracting the ISF of each sample from ‘

1’ and

outputting the difference;

calculating a window operation value for each sample by calculating a convolution of the difference and a predetermined window function; and

generating the scaling factor of each sample by subtracting the window operation value from ‘

1’

.

26. The transmission method of claim 25, wherein the ISF calculation step calculates the ISF by

$c$

( n ) = { 1 , 

x ⁡

( n ) 

≤

A A 

x n 

, 

x ⁡

( n ) 

>

A

where n is a sample index, A is a threshold, and |x(n)| is the magnitude of an n^th sample.

27. The transmission method of claim 25, wherein the ISF adjusting step comprises, if the n^th sample is an (i+1)^th peak, adjusting the ISF by

$b$

( n ) = { c ⁡

( n ) , P i + 1 - P i >

W α

·

c ⁡

( n ) , P i + 1 - P i ≤

W

where c(n) is the ISF, P_i is the sample index of an i^th peak, W is the window size represented as the number of samples, and a (>

1) is a weighting value.

28. A wireless communication system comprising:

a first calculator for calculating an scaling factor for each sample of baseband sample data;

a successive peak detector for adjusting the scaling factor of each sample according to the spacing between successive peak samples;

a second calculator for subtracting the adjusted scaling factor of each sample from a predetermined value to output a difference; and

a window convolution calculator for calculating a convolution of the difference from the second calculator and a predetermined window function, and outputting a window operation value of each sample.

29. A wireless communication system, comprising:

a modulator for generating sample data by modulating transmission data to multiple carriers;

a scaling factor calculator for generating a scaling factor for each sample by performing a window convolution;

a separator for separating a phase and an amplitude from each sample of the sample data;

a multiplier for multiplying the amplitude of each sample by the scaling factor; and

a combiner for combining the amplitude from the multiplier with the phase from the separator.