Orthogonal Frequency Division Multiplexing is an attractive technique for wireless high-rate data transmission. The basic principle of OFDM is to split a high-rate data stream into a number of lower rate streams that are transmitted simultaneously over a number of subcarriers. Because the symbol duration increases for lower rate parallel subcarriers, the relative amount of dispersion in time caused by multipath delay spread is decreased. Inter-symbol interference (ISI) is eliminated almost completely by introducing a guard time in every OFDM symbol . The major issue in OFDM system is high PAPR which causes peak overshoots. The paper deals with elaborate study of OFDM system and least crest method of reducing peaks. The crest factor or peak-to-average ratio (PAPR) is a measurement of a signal, calculated from the peak amplitude of the waveform divided by the RMS value of the waveform. The peak-to-average power ratio (PAPR) is a related measure that is defined as the peak amplitude squared (giving the peak power) divided by the RMS value squared (giving the average power).

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Slm(selective Level Mapping) Cf(crest Factor) Lcm(low Crest Method)