Simulation Analysis Of Orthogonal Frequency Division Multiplexing Systems With Diversity Reception
Abstract
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 4^{th}
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(M.C) 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 M.C
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.