Today is a world of Technologies. In terms of communication, the demands of high speed applications are growing and starting from 2G to 3G, now we are moving towards 4G to meet these requirements. Most of applications are now uses 4G technology. COFDM based WiMax is outcome in this direction which promises to cater these high quality and high speed applications. WiMax is an IEEE 802.16 standard-based broadband wireless access (BWA) technology which employs Coded orthogonal frequency division multiplexing access (COFDM). This paper includes the theory and concepts behind OFDM, WiMAX IEEE 802.16, IEEE 802.16a, IEEE 802.16d, IEEE 802.16e standard and other blocks algorithms, its architectures used for designing as well as a presentation of how they are implemented and evaluates the performance of coded OFDM at different fading with 256 QAM Modulation. Further, Rayleigh, Rican, MIMO fading channels are investigated in detail. It has been observed that MIMO fading 256 QAM channel has better performance rather than other channels
