769 International Journal of Progressive Sciences and Technologies (IJPSAT) ISSN: 2509-0119. © 2020 International Journals of Sciences and High Technologies http://ijpsat.ijsht-journals.org Vol. 23 No. 1 October 2020, pp. 42-48 Corresponding Author: Bonaventure Ekengwu 42 Improving Peak to Average Power Ratio of OFDM Signal Using DCT Precoding with Combined Distortion Techniques Bonaventure Ekengwu 1 , Nnaemeka Asiegbu 1 , Chidiebere Muoghalu 2 and Ifeoma Ezeanya 3 1 Department of Electronic Engineering, University of Nigeria, Nsukka, Nigeria 2 Department of Electrical and Electronics Engineering Chukwuemeka Odumegwu Ojukwu University Uli, Nigeria 3 Department of Electrical and Electronics, Anambra State Polytechnic, Mgbakwu, Nigeria Abstract –This paper has presented Peak to Average Power Ratio (PAPR) reduction improvement in Orthorgonal Frequency Division Multiplexing (OFDM) system using discrete cosine transform (DCT) precoding with repeated clipping and filtering plus Mu-law companding techniques. Recent studies have shown the use of evolution algorithms and combination of two or more algorithms to reduce PAPR in OFDM system. The algorithms of DCT, RCF and Mu-law were studied and presented in form of mathematical equations. MATLAB codes were developed for PAPR analysis in OFDM system. The MATLAB codes for DCT, RCF and Mu-law companding were implemented and incorporated into the OFDM system to enhance the PAPR performance. Simulations were conducted considering uncoded (or conventional) OFDM, uncoded of OFDM with RCF, precoded of OFDM with RCF, and precoded OFDM with RCF plus Mu-law. Using the PAPR value of 10.43dB at CCDF of 10 - 3 for the uncoded OFDM signal as reference value, it was observed that the introduction of RCF into the uncoded OFDM provided a PAPR value of 6.834dB which is 34.48% improvement. Also, for the precoded OFDM with RCF, the PAPR was reduced to 6.799dB with 34.81% improvement. Finally, the proposed scheme using precoded OFDM with RCF and Mu-law provided an efficient reduction in PAPR with a value of 2.048dB and 80.36% improvement. Thus, the implemented scheme has shown to be effective based on MATLAB simulations conducted. Keyword –DCT, Mu-law, OFDM, PAPR, RCF I. INTRODUCTION Orthogonal Frequency Division Multiplexing (OFDM) has become one of the most famous techniques used in the transmission of data for a number of wireless communication systems. This can be attributed to the various benefits it offers such as high bandwidth efficiency, robustness to multipath fading, high data rate, mitigation of inter-symbol interference (ISI) and low implementation complexity [1,2]. Thus the use of OFDM as a multicarrier system has become attractive in application like Wireless Local Area Networks (WLAN) standards (e.g. HIPERLAN-2, IEEE 802.11a/g), Wireless Metropolitan Area Networks (WMAN), LTE standards, Worldwide Interoperability for Microwave Access (WiMAX), Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Asymmetric Digital Subscriber Line (ADSL) and power line communication [3-5]. Despite these advantages offered by OFDM technology, there are certain shortcomings that are still associated with its use and one of such disadvantages is the high Peak to Average Power Ratio (PAPR). High PAPR occurs due to the fact that the output of OFDM system is the superposition of multiple subcarriers such that some instantaneous power output might largely increase and become much higher than the average power of the system when these carriers are in the same phase. Hence, transmitting OFDM signals with high PAPR causes nonlinear distortion of power amplifier (PA) which is capable of degrading the performance efficiency of the system.