Abstract
OFDM system is very suitable in frequency selective channel because of its longer symbol time. Besides, it can transmit higher data rate if the bandwidth is limited. In this thesis, we will introduce some methods which can improve OFDM system performance.Some factors which make OFDM system performance degrade are MAI ( Multiple Access Interference ), ISI ( Inter-Symbol Interference ) and noise. When many users transmit signals synchronously, there must have interference from other users. Besides, ISI and noise also exist in communication system. In this thesis, MMSE ( Minimum Mean Square Error ) beamforming and turbo code will be used to make the performance improve. Finally, the symbol error rate performance in different channel model will be shown by computer simulation.