In todayâ€™s wireless communication system demand for higher data rates, higher transmission capacity and better quality of service is increasing. These challenges can be overcome by one of the key technology Orthogonal Frequency Division Multiplexing (OFDM). Generally, OFDM system is implemented using Fast Fourier Transform (FFT) but it has some drawbacks which can be reduces using one of emerging technology Discrete Wavelet Transform (DWT). In this paper, comparative performance analysis of OFDM system using FFT and DWT is done with STBC-MIMO system. Modulation technique used is 16-QAM under AWGN and Rayleigh channel. DWT-OFDM is simulated using Haar wavelet. BER vs SNR performance analysis is done using Matlab Simulink.