The effect of nonlinearity on a QPSK-OFDM-QAM signal

Author

Liu, Chia-Liang

Author_Institution

Comput. & Commun. Res. Labs., Ind. Technol. Res. Inst., Hsinchu, Taiwan

Volume

43

Issue

3

fYear

1997

fDate

8/1/1997 12:00:00 AM

Firstpage

443

Lastpage

447

Abstract

The effect of nonlinearity on a QPSK-OFDM-QAM signal is analyzed. One of the characteristics of an OFDM-QAM signal is its wide range of envelope fluctuation: its crest factor, defined as the ratio of the peak instantaneous power to the average (rms) power in dB, is typically greater than 10. When an OFDM-QAM signal drives a nonlinear device, nonlinearity will result in signal compression and intermodulation among the sub-carriers at the output. An analytical method is used to predict the input back-off needed to keep the intermodulation below an acceptable level. For sufficient large number of sub-carriers, we show that to keep the intermodulation power 30 dB below the signal power, we need to back-off the input power by 6.5 dB. However, from the BER point of view, the degradation is less than 2 dB at BER=0.01% even for 1 dB input back-off

Keywords

coding errors; error statistics; frequency division multiplexing; intermodulation distortion; quadrature amplitude modulation; quadrature phase shift keying; signal processing; BER; QPSK-OFDM-QAM signal; RMS power; analytical method; average power; crest factor; envelope fluctuation; input back-off; input power; intermodulation power; nonlinear device; nonlinearity; peak instantaneous power; ratio; signal compression; signal power; subcarriers; Amplitude modulation; Bit error rate; Broadcasting; Degradation; Frequency modulation; Linearity; Quadrature amplitude modulation; Quadrature phase shift keying; Signal analysis; Signal to noise ratio;

fLanguage

English

Journal_Title

Consumer Electronics, IEEE Transactions on

Publisher

ieee

ISSN

0098-3063

Type

jour

DOI

10.1109/30.628655

Filename

628655