Selective clipping and filtering: A low-EVM PAPR reduction scheme for OFDM standards

OFDM transmit signals typically have high PAPR (Peak to Average Power Ratio). This requires high back off operation of the power amplifier in the transmitter, resulting in higher hardware costs and/or low power efficiency for the overall transceiver system. Clipping and Filtering (CF) is a popular technique for reducing PAPR, because of its low complexity and its backward compatibility with existing standards. However, clipping and filtering distorts the OFDM signal, thus increasing the Error Vector Magnitude (EVM). When applying CF, some of the clipped peaks have very little contribution to PAPR, but the resulting distortion adds up in frequency domain causing a higher overall EVM value. To avoid this effect, we propose a modified form of clipping and filtering where fewer peaks are clipped, but where those peaks are clipped at a lower value. Our method, which we call Selective Clipping and Filtering (SCF), has been tested in simulations based on IEEE802.11a waveform. Results show that SCF achieves 0.9dB lower PAPR than CF for a similar EVM value. Alternatively, when considering Frame Error Rate (FER) at the receiver, we achieve 4.6 dB PAPR reduction with no increase in FER.