Use of Chaotic Oscillations for Precoding and Synchronization in OFDM

Abstract

This paper proposes a novel linear precoding method for Orthogonal Frequency Division Multiplex- ing (OFDM) based on the employment of the chaotic waveforms generated by the fourth-order chaotic os- cillator and orthonormalized by the Gram-Schmidt process. The proposed linear precoding method is aimed to increase resilience to the multipath propagation issues and reduce the Peak-to-Average Power Ratio (PAPR) of the transmitted signal. Moreover, the chaotic waveform enables novel timing synchronization methods to be implemented in the re- ceiver. The modeling of baseband Linear Precoded OFDM (LP-OFDM) data transmission system with Rayleigh channel has been performed in Simulink en- vironment to validate the proposed method and to com- pare the performance to the classic precoding meth- ods, such as Walsh-Hadamard Transform (WHT). Experiments have shown that in a high Signal-to-Noise Ratio (SNR) scenario, the employment of the novel precoding scheme allows reducing Bit Error Ratio (BER) by several dB compared to non-precoded OFDM. The proposed precoding method leads to the reduction of PAPR; however, it is not as efficient as classi- cal precoding schemes, such as WHT. Experimental evidence of synchronization of the chaotic oscillators within 50 samples long time interval is presented.