Title :
The effect of nonlinearity on a QPSK-OFDM-QAM signal
Author_Institution :
Comput. & Commun. Res. Labs., Ind. Technol. Res. Inst., Hsinchu, Taiwan
fDate :
8/1/1997 12:00:00 AM
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;
Journal_Title :
Consumer Electronics, IEEE Transactions on
