Simulation analysis of orthogonal frequency division multiplexing systems with diversity reception.

摘要

With the rapid increase in the utility of voice and data services, there is a demand for higher data rates and reliability in wireless communications. A wireless communication channel is prone to degrading effects such as multi-path fading, ISI etc. Orthogonal Frequency Division Multiplexing (OFDM), a candidate for the 4th generation wireless systems, mitigates these effects and supports higher data rates. The performance analysis of a complex system like OFDM, is a challenging task where analytical methods become cumbersome to be used. Simulation based approaches provide a fair estimate of the performance in such cases.;In this thesis, the performance of an OFDM system on AWGN, slow, fast, flat and frequency selective fading channels has been analyzed through Monte Carlo(MC) simulations. Some of the analytical techniques previously used to evaluate the performance of diversity combining schemes-Maximal Ratio Combining(MRC), Equal Gain Combining(EGC), on slow flat fading channels have been summarized. The effect of Inter-carrier Interference(ICI) and ISI on OFDM systems for different channel conditions has been studied and the performance of few techniques to mitigate the degradation due to ISI, ICI such as diversity-reception, equalization, coding and interleaving in OFDM have been investigated. System models for OFDM with post-FFT diversity-combining, equalization on dual antennas have been proposed and their performance is analyzed by MC simulation. Further, these results are compared with conventional detectors and it is found that OFDM systems with diversity are effective for lower signal to noise ratios in case of smaller Doppler spreads and for higher signal noise ratios in case of higher delay spreads.