A low-complexity SLM approach based on time-domain sub-block conversion matrices for OFDM PAPR reduction

In orthogonal frequency division multiplexing (OFDM) systems, high peak-to-average power ratio (PAPR) is one of the major technical challenges, which brings serious impact on the hardware implementation. In literature, many schemes have been proposed for PAPR reduction, wherein the selective mapping (SLM) scheme is the most popular and widely discussed approach. However, SLM suffers from very high computational complexity because of the requirement of a large number of inverse fast Fourier transformation (IFFT) operations. In this work, we propose a modified SLM approach based on time-domain sub-block conversion matrices to reduce the computational complexity due to multiple IFFTs. This scheme is modified from the conversion matrix scheme. By dividing the frequency-domain signals into multiple sub-blocks, the number of the valid conversion matrices can be increased, and thus more candidate signals are available for PAPR reduction. By applying our scheme, the number of candidate signals can be increased from 12 in the original conversion matrix scheme to 28 and 128 for the two-subblock and four-subblock cases, respectively. According to the simulations, the PAPR reduction performance can be improved by 0.2 dB - 0.9 dB.