Due to the superposition of data symbols on a large number of subcarriers, an OFDM waveform has a large peak-to-average power ratio (PAPR). Since nonlinear amplification causes inter modulation among subcarriers and undesired out-of-band radiation, the power amplifier at the transmitter must operate with a large backoff to limit nonlinear distortion. The severity of the PAPR issue in practical systems depends on the system operating conditions.
From the implementation point of view, more bits are needed for quantization to synthesize a signal with large PAPR, which adds to the transmitter complexity.
Next, we explore the PAPR issue of OFDM modulation, and then present three simple yet effective PAPR reduction methods.
Let denote one OFDM block in the passband, as in ...