Peak-to-Average Power Ratio Reduction Techniques for Wavelet Packet Modulation

Abstract

Wavelet Packet Modulation (WPM) is a novel multicarrier modulation technique and a promising alternative to the well established Orthogonal Frequency Division Multiplexing (OFDM). WPM has been shown to be an efficient technique with interesting features like adaptation and flexibility and improved characteristics in comparison to OFDM. A major drawback of multicarrier systems is their high peak-to-average power ratio (PAPR). The average signal power must be kept low in order to ensure that the transmitter amplifier operates in the linear region. This however will have a detrimental effect on the efficiency of power utilization particularly in mobile systems where battery lifetime is a premium resource. Minimizing the PAPR allows a higher average power to be transmitted for a fixed peak power, improving the overall signal to noise ratio at the receiver. In the literature several methods are reported to reduce the PAPR problem of OFDM. The PAPR for WPM is extremely novel. This thesis work presents several original contributions to the field of PAPR reduction for the multi-carrier WPM system. We focus on the selected mapping techniques since they are distortionless and their complexity is lower compared to other techniques. After studying the selected mapping with scrambling technique to reduce PAPR, we present a novel WPM architecture that employs our proposed secure PAPR reduction technique. Besides scrambling techniques, phase modification is another PAPR reduction technique and in this thesis we present how selected mapping with phase modification can be applied to reduce PAPR. In all instances the proposed technique reduces the PAPR between 1.5 and 2.5 dB. A smarter approach can be developed to optimize the selected mapping techniques. Consequently, we introduce an optimized WPM architecture that employs optimized selected mapping with phase modification technique. The designed optimization algorithm improves the PAPR reduction performance further than the selected mapping with phase modification. For a complementary cumulative distribution function (CCDF) value of , the PAPR of the original frame is around 10 dB; whereas, optimized phase-shifted frame produces a PAPR value around 8.2 dB. While, a PAPR value below 8.7 dB cannot be reached with the selected mapping techniques, which depends on randomization such as randomly phase-shifting or random scrambling.