Energy Efficient Error Control Techniques for OFDM Systems with their Applicability to Power Line and Wireless Communication Channels

Abstract

The basic idea of multi carrier modulation is to divide the transmitted bit stream into many different sub streams and send them over many different sub channels which are orthogonal under ideal propagation conditions. Orthogonal frequency division multiplexing is a discrete multi tone system. An efficient implementation of OFDM system can be carried out using inverse fast Fourier transform for modulation and fast Fourier transform for demodulation. OFDM is a popular modulation technique in almost all the recent applications in the RF domain. OFDM has emerged as a successful modulation format in major communication standards, like digital subscriber loop, wireless LAN, DVB and DAB. Worldwide Interoperability for Microwave Access and Long-Term Evolution are the two popular 4G mobile network standards, which use OFDM modulation format. One of the major disadvantages of OFDM is its sensitivity to frequency and phase noise. One of the objectives in this research work is the development of a coded OFDM system that tackles the performance degradation due to carrier frequency offset in a much efficient manner as compared to the available methods. The second objective is to develop an additive white class-A noise model for coded OFDM system so that it can be used with better bit error rate performance in power line communication systems. Besides this, a performance evaluation and determination of the performance gain in soft iterative decoders as compared to hard iterative decoders is considered. This evaluation is done in support of the efficiency of Turbo and low density parity check codes. To check the suitability of the coded systems in free space optical communication, BER performance evaluation of coded communication system has been carried out. The overall objective of this research work is to develop coded OFDM systems that perform much efficiently in terms of the BER performance. It also aims to provide the possible SNR saving in the proposed methods as compared to the available methods.