An Investigation of SLM and PTS based Schemes for PAPR Reduction in WPM System

Wavelet Packet Modulation (WPM) is a novel Multi-Carrier Modulation (MCM) technique and a promising alternative to well established Orthogonal Frequency Division Multiplexing (OFDM) for futuristic Cognitive Radio technology. High peak-to-average power ratio (PAPR) is a major drawback for multicarrier modulations such as WPM. In this paper we first demonstrate the PAPR performance of two multicarrier schemes OFDM and WPM and their performance in terms of Bit Error Rate (BER) plot. Then we investigate two methods Selected Mapping (SLM) and Partial Transmit Sequence (PTS) to reduce PAPR in the developmental WPM system. These methods work on the principle that PAPR of a MCM system can be adjusted by varying the phase shifts of the subcarriers. Different PAPR values for the same information can be obtained by randomly altering the phases of the sub-carriers used to modulate the data. The WPM frame with the least PAPR can be then identified and transmitted. In all instances the proposed techniques reduces the PAPR between 3.8 and 4.8 dB. For a complementary cumulative distribution function (CCDF) value of 10−2, the PAPR of the original frame is around 13.2 dB; whereas SLM and PTS based phase-shifted frames produces PAPR values of around 9.4dB and 8.4dB respectively.