Study and Analysis of ICI for OFDM System in the Doubly Selective Fading Channel

Abstract

In recent time, the demand for multimedia data services has grown up rapidly. One of the most promising multi-carrier system, Orthogonal Frequency Division Multiplexing (OFDM) forms basis for all 4G wireless communication systems due to its large capacity to allow the number of subcarriers, high data rate and ubiquitous coverage with high mobility. The propagation of radio waves for communication purpose through the wireless medium is affected by lot of impairments on their way like carrier frequency offset, phase noise. Due to such impairments, signal experience fading which has been an area of significant interest among the research fraternity in order to evaluate the performance of a digital communication system amplitude and phase distortions, which cause loss of orthogonality among the subcarriers, and hence, inter-carrier interference (ICI) is introduced in the transmitted signal. There are various methods to overcome from such impairments like frequency domain equalization, windowing, maximum likelihood estimation and ICI self cancellation scheme. This thesis mainly emphasis on ICI reduction using windowing technique which is a leading technique to deal with the severity of induced fading in signal transmitted over channel. Various window functions are applied like raised cosine window, better than raised cosine window, sinc pulse, improved sinc pulse. Adopting this windowing technique at transmitter side is effective and has improved performance of OFDM system. Goal of system designer is to reach at a unified set of mathematical models characterized by window functions. As a result there is much interest shown by the research fraternity in using this technique to improve SIR which also proving to be a very powerful tool for minimization of ICI and SIR improvement in communication networks.