PAPR Reduction in Wavelet Packet Modulation Using Tree Pruning

High peak-to-average power ratio (PAPR) of transmitted signals is a major drawback for multicarrier modulation systems such as orthogonal frequency division multiplexing (OFDM) and wavelet packet modulation (WPM). In this paper, wavelet packet tree pruning is proposed for the reduction of PAPR in WPM systems. In this technique, a full wavelet packet tree is dynamically pruned via joining and splitting of terminal nodes to achieve a minimized PAPR. Specifically, alternative mappings of data symbols onto different tree structures are generated, and the time domain sequence with the smallest PAPR is transmitted. The information about the pruned tree is sent as side information similar to techniques such as selective mapping (SLM) in OFDM systems. Using a small level of redundancy for side information, the proposed scheme achieves significant reduction in PAPR at the expense of acceptable computational complexity. The complementary cumulative distribution function (CCDF) of the PAPR optimized signal shows about a 3.5 dB improvement over the original WPM signal.