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ZTE Communications ›› 2011, Vol. 9 ›› Issue (4): 25-31.

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Crest Factor Reduction for OFDM Using Selective Subcarrier Degradation

R. Neil Braithwaite   

  1. Powerwave Technologies, Santa Ana, CA 92705, USA
  • Online:2011-12-25 Published:2011-12-25
  • About author:R. Neil Braithwaite (nbraithwaite@pwav.com) received his B.Sc. degree in electrical engineering from the University of Calgary in 1985. He received his M.Sc. and Ph.D. degrees from the University of British Columbia in 1989 and 1992. From 1992 to 1995, he conducted postdoctoral research at the University of California, Riverside. From 1985 to 1987 and 1995 to 2002, he worked for Computing Devices Company (Canada), Nortel (Canada), and Agilent Laboratories (USA). Since 2002, he has been working for Powerwave Technologies (USA). He is the author of several papers and patents, as well as a recent book chapter on digital predistortion in RF power amplifiers [17].

Crest Factor Reduction for OFDM Using Selective Subcarrier Degradation

R. Neil Braithwaite   

  1. Powerwave Technologies, Santa Ana, CA 92705, USA
  • 作者简介:R. Neil Braithwaite (nbraithwaite@pwav.com) received his B.Sc. degree in electrical engineering from the University of Calgary in 1985. He received his M.Sc. and Ph.D. degrees from the University of British Columbia in 1989 and 1992. From 1992 to 1995, he conducted postdoctoral research at the University of California, Riverside. From 1985 to 1987 and 1995 to 2002, he worked for Computing Devices Company (Canada), Nortel (Canada), and Agilent Laboratories (USA). Since 2002, he has been working for Powerwave Technologies (USA). He is the author of several papers and patents, as well as a recent book chapter on digital predistortion in RF power amplifiers [17].

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Abstract: This paper describes a crest factor reduction (CFR) method that reduces peaks in the time domain by modifying selected data subcarriers within an OFDM signal. The data subcarriers selected for modification vary with each symbol interval and are limited to those subcarriers whose data elements are mapped onto the outer boundary of the constellation. In the proposed method, a set of peaks are identified within an OFDM symbol interval. Data subcarriers whose data element has a positive or negative correlation with the set peak are selected. For a subcarrier with an outer element and a significant positive correlation, a bit error (reversal) is intentionally introduced. This moves the data element to the opposite side of the constellation. Outer elements on negatively-correlated subcarriers are increased in magnitude along the real or imaginary axis. Experimental results show that selecting the correct subcarriers for bit reversals and outward enhancements reduces the peak-to-average power ratio (PAPR) of the OFDM signal to a target value and limits in-band degradation measured by bit error rate (BER) and error vector magnitude (EVM).

Key words: crest factor reduction, OFDM, PAPR, wireless communication system, digital transmitter

摘要： This paper describes a crest factor reduction (CFR) method that reduces peaks in the time domain by modifying selected data subcarriers within an OFDM signal. The data subcarriers selected for modification vary with each symbol interval and are limited to those subcarriers whose data elements are mapped onto the outer boundary of the constellation. In the proposed method, a set of peaks are identified within an OFDM symbol interval. Data subcarriers whose data element has a positive or negative correlation with the set peak are selected. For a subcarrier with an outer element and a significant positive correlation, a bit error (reversal) is intentionally introduced. This moves the data element to the opposite side of the constellation. Outer elements on negatively-correlated subcarriers are increased in magnitude along the real or imaginary axis. Experimental results show that selecting the correct subcarriers for bit reversals and outward enhancements reduces the peak-to-average power ratio (PAPR) of the OFDM signal to a target value and limits in-band degradation measured by bit error rate (BER) and error vector magnitude (EVM).

关键词: crest factor reduction, OFDM, PAPR, wireless communication system, digital transmitter