Adaptive transform scheme to reduce PAR of an OFDM signal

One major drawback in orthogonal frequency division multiplexing (OFDM) system is its high peak-to-average power ratio (PAR). Most of the PAR reduction techniques are based on changing the signal constellation symbols in a frame before evaluating the inverse discrete Fourier transformation (IDFT). A simple way to achieve this change is to use a linear transformation in the form of orthogonal matrix. Hadamard transform of data symbols has recently been proposed to reduced PAR. Motivated by this approach, we investigate the use of Fourier and cosine transforms to reduce the PAR. We also propose an adaptive transform scheme to further reduce the PAR with minimized complexity. This approach reduces the PAR by 4 dB for an OFDM signal with 128 subcarriers. We also compare the performance and the complexity of the proposed scheme with the selected mapping (SLM) technique.