In this thesis work, WiMAX (IEEE 802.16d) PHY layer with underlying OFDM technology and an optional feature called Adaptive Antenna System has been considered. The SUI-3 channel model (Rician fading) is used for creating fading phenomena. An Adaptive Antenna System has been deployed at the receiver module to reduce the fading effects caused by SUI-3 channel model. Adaptive Antenna Systems (AAS) uses different beamforming techniques to focus the wireless beam between the base station and the subscriber station. In this thesis, the transmitter (SS) and receiver (BS) are fixed and AAS installed at the receiver is used to direct the main beam towards the desired LOS signal and nulls to the multipath signals. Pre-FFT beamformer based on Least Mean Square (LMS) algorithm is used. Different aspects of the complete system model were investigated such as adaptive modulation, angle of arrival of the incoming signals and number of array elements. It has been demonstrated through MATLAB simulations that the performance of the system significantly improves by AAS, where beamforming is implemented in the direction of desired user. The performance of the system further increases by increasing the number of antennas at receiver.