Abstract: Ubiquitous broadband Internet access is an important requirement to satisfy user demands and support a new set of real time services and applications. Worldwide Interoperability for Microwave Access (WiMAX) system has emerged as a strong candidate for providing mobile broadband wireless service to users. In this study we conduct simulation studies for different fading communication channel models to verify its effectiveness and the correctness of the channel performance analysis. We also compare adaptive digital modulation techniques (QPSK, 16-QAM and 64-QAM) performance. And the Wimax system incorporates Reed-Solomon (RS) encoder with Convolutional encoder with ½ rated codes in FEC channel coding. The simulation results of estimated Bit Error Rate (BER) displays that the implementation of interleaved RS code (255,239,8) with ½ rated Convolutional code under BPSK modulation technique is highly effective to combat in the Wimax communication system.