PAPR Reduction and Data Security Improvement for OFDM Technique Using Chaos System

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) is the most popular multicarrier technique because it produces several advantages such as higher spectral efficiency, high transmission rate, robustness to fading channel and etc.. In this technique, the data is carrying by multiple orthogonal subcarriers. If all subcarriers  are adding together with the same phase, it will result high Peak to Average Power Ratio (PAPR). Higher value of PAPR makes low power efficiency, several degradation of performance in the transmit power amplifier and increase the complexity of converters. It is important to decrease PAPR for avoid these problems. Another requirement of the modern communication system is the  security of transmission data. All these issues make strong motivation for building algorithm to improve performance and security of OFDM system. In this paper, a proposed algorithm is presented to both reduce PAPR and secure the OFDM signal by generating several Aperiodic PseudoRandom Binary Sequences (APRBSs) using chaos system. The proposed algorithm is scrambling the information by APRBSs, and one sequence is chosen for transmission which has smallest PAPR value. To inform receiver which sequence had been sent, a Side Information (SI) is enclosed with the transmitted sequence. Because SI very important at receiver, convolutional code with Viterbi-Soft Decision Decoding (V-SDD) is used to protect it against channel distortion. Simulation results state the proposed algorithm produces excellent PAPR reduction performance and approximately gives the same Bit Error Rate (BER) of the conventional OFDM system over AWGN and fading channels. In addition to get better performance, the proposed algorithm is providing a good data security due to chaos system. MATLAB program is used to build the proposed OFDM system and get the simulation results.