Optimized Mitigation of Impulsive Noise in OFDM System using CSI

Abstract

Fourth generation (4G) technology aims to provide mobile users with high data rate wireless broadband services with full mobility. Many difficulties are encountered in wireless internet services while providing high speed communication services. These include multipath fading, inter-symbol-interference (ISI) and noise etc. Orthogonal-frequency-division-multiplexing (OFDM) is the technology that provides an effective solution for these problems encountered in high speed wireless transmissions and reception. OFDM has inherent spatial efficiency due to orthogonality between the consecutive subcarriers enabling them to overlap on each other. The use of cyclic prefix enables it to reduce the effects of ISI. Frequency-selective fading experienced in the channel reduces to flat fading in OFDM transmission. Deep fade conditions can hence be observed by limited number of symbols and not by the entire transmission. These advantages have led to replacement of the previously used technologies by OFDM, making it a strong contender for the next generation wireless communication systems. This thesis presents comparison between different impulsive noise mitigation techniques in orthogonal-frequency-division-multiplexing (OFDM) systems, which affect the performance of underlying communication system in terms of the bit-error-rate (BER). The main focus is on Zhidkov’s (ZKV) method (Zhidkov, 2003) and Jia’s method (Jia et al., 2014) for the impulsive noise mitigation using the imperfect channel-state-information (CSI). Though former scheme appears to be promising peak detection method based on the variance of estimated impulsive noise, but latter composite-comparison-value (CCV) method is found to be outperforming in alleviating the adverse effects of impulsive noise in the frequency-domain, at the receiving end. In ZKV and CCV methods, different parametric values are optimized to suppress the impulsive noise under the fading conditions in the presence of perfect CSI. Simulation results are presented for performance evaluation of these impulsive noise suppression schemes using imperfect CSI for the different modulation schemes, which illustrate the efficacy of CCV method in the field of communication engineering.