An OFDM signal consists of a number of independently modulated SCs, which can give a large peak-to-average power (PAP) ratio when added up coherently. The peak power is defined as the power of a sine wave with amplitude equal to the maximum envelope value. Hence, an unmodulated carrier has a PAP ratio of 0 dB. An alternative measure of the envelope variation of a signal is the Crest factor, which is defined as the maximum signal value divided by the RMS signal value. For an unmodulated carrier, the Crest factor is 3 dB. This 3-dB difference between the PAP ratio and Crest factor also holds for other signals, provided that the center frequency is large in comparison with the signal bandwidth.

1. Pauli, M. , and H. P. Kuchenbecker, "Minimization of the Intermodulation Distortion of a Nonlinearly Amplified OFDM Signal," Wireless Personal Communications, Vol. 4, No. 1, January 1997, pp. 93–101.
2. Rapp, C. , "Effects of HPA-Nonlinearity on a 4- PSK/OFDM Signal for a Digital Sound Broadcasting System," Proc. of 2nd European Conference on Satellite Communications, Liège, Belgium, October 22–24, 1991, pp. 179–184.
3. De Wild, A. , "The Peak-to-Average Power Ratio of OFDM," . Sc. thesis, Delft University of Technology, Delft, the Netherlands, September 1997.
4. May, T. , and H. Rohling, "Reducing the Peak-to-Average Power Ratio in OFDM Radio Transmission Systems," Proceedings of IEEE VTC'98, Ottawa, Canada, May 18–21, 1998, pp. 2774–2778.
5. Li, X. , and L. J. Cimini, "Effects of Clipping and Filtering on the Performance of OFDM," Proc. of IEEE VTC'97, 1997, pp. 1634–1638.
6. Wilkinson, T. A. , and A. E. Jones, "Minimization of the Peak-to-Mean Envelope Power Ratio of Multicarrier Transmission Schemes by Block Coding," Proc. of IEEE Vehicular Technology Conference, Chicago, IL, July 1995, pp. 825–829.
7. Golay, M. J. E. , "Complementary Series," IRE Transactions on Information Theory, Vol. IT-7, April 1961, pp. 82–87.
8. Sivaswamy, R. , "Multiphase Complementary Codes," IEEE Trans. on Information Theory, Vol. IT-24, No. 5, September 1978, pp. 546–552.
9. Frank, R. L. , "Polyphase Complementary Codes," IEEE Trans. on Information Theory, Vol. IT-26, No. 6, November 1980, pp. 641–647.
10. Popovic, B. M. , "Synthesis of Power Efficient Multitone Signals with Flat Amplitude Spectrum," IEEE Trans. on Communications, Vol. 39, No. 7, July 1991, pp. 1031–1033.
11. Van Nee, R. D. J. , "OFDM Codes for Peak-to-Average Power Reduction and Error Correction," IEEE Global Telecommunications Conference, London, England, November 18–22, 1996, pp. 740–744.
12. Van Nee, R. D. J. , "An OFDM Modem for Wireless ATM," IEEE Symposium on Communications and Vehicular Technology, Ghent, Belgium, October 7–8, 1996.

Subcarriers (scs) Peak-to-average Power (pap) Orthogonal Frequency Division Multiplexing (ofdm) Forward Error Correction (fec) Quadrature Phase Shift Keying (qpsk) Cumulative Distribution Function (cdf) Signal-to-noise Ratio (snr) Coded Ofdm (cofdm) Parallel-to-serial (p/s).