SLM-Based Radix FFT for PAPR Reduction in OFDM Systems

A radix FFT-based selective mapping (SLM) technique for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal is introduced. The intermediate signals within an N-point IFFT using a radix decimation in time (DIT) or decimation in frequency (DIF) IFFT algorithm are used for multiplying the phase sequences. Multiple IFFTs are then applied to the remaining stages. It is shown that DIF provides low multiplicative complexity in generating the SLM sequences compared to DIT, with the same PAPR reduction. In addition, a high radix FFT algorithm provides better PAPR reduction performance per stage with less multiplicative complexity compared to low radix algorithms.