PAPR Reduction in OFDM Using Wavelet Packet Pre-Processing

This paper introduces a novel peak-to-average power ratio (PAPR) reduction method in orthogonal frequency division multiplexing (OFDM) systems by deploying wavelet packet pre-processing of the quadrature amplitude modulation (QAM) symbols. Specifically, joint inverse discrete wavelet packet and Fourier transformations (IDWPT and IDFT) of QAM symbols are calculated at the transmitter with the purpose of minimizing the PAPR of the OFDM frame to be transmitted. The wavelet packet tree representing a reversible IDWPT chosen at the transmitter is communicated to the receiver as side information, where the output of the DFT block is passed through the DWPT to recover the QAM symbols. As the DWPT is a orthonormal transformation, the proposed method preserves the average transmitted energy while maintaining the integrity of the transmitted information. With a small level of redundancy for side information, the proposed scheme achieves 5.5 dB reduction in PAPR over the traditional OFDM system as measured using the complementary cumulative distribution function (CCDF) of the OFDM signals at the clipping probability of 10^-4.