PERFORMANCE OF CODED OFDM IN WIRELESS ENVIRONMENTS

Abstract

The use of digital wireless communication and the need for high-speed mobile data transmission have increased. Here, the wireless channel is modeled as a frequency-selective fading channel. As it is known, Orthogonal Frequency Division Multiplexing (OFDM) systems are attractive to mitigate frequency-selective multi-path fading. In this thesis, we investigate the performance of a coded OFDM system in a wireless environment. We derive union bounds for single-antenna and multi-antenna convolutionally coded OFDM systems over correlated block fading (CBF) channel with perfect channel state information (CSI). Moreover, the union bounds for coded OFDM over CBF channel with imperfect CSI are derived. Only pilot estimation (OPE) and corrected data estimation (CDE) are used as models to estimate the CSI at the receiver. The differences between these receivers are compared and we observe that CDE receivers perform better than OPE receivers whereas the perfect CSI is the best case. In this thesis, simulation results show that the performance of coded OFDM system is improved by increasing the number of sub-carriers because the diversity order increases. Moreover, the coded OFDM systems over the longer delay-spread profile channel perform better because of frequency selectivity. In addition, multi-antenna systems perform better than single-antenna systems because of the space diversity. In general, the proposed bounds are too close to the simulation results and these bounds can be applied for coded OFDM systems employing different coding schemes over different channel models.