Higher demand in rapid data transmission makes the wireless technology become more popular in this new modern era. However due to the many users that want to have access in the same time, it can cause congested traffic and affect the data rate. OFDMA modulation scheme with combination of MIMO will support high data signal and become one of the best solutions that can fulfil everybody’s dream. These MIMO OFDMA system is based on the diversity coding and appropriate channel estimation in order to achieve maximum diversity order for each user and minimize the interference that have been generated during the transmission. Thus, in this paper in order to boost the overall system performances, Space Time Frequency Block Code (STFBC) and channel estimation technique involving Discrete Fourier Transform (DFT) and Discrete Cosine Transform (DCT) are going to be tested to compare their performance. The result states that when using STF block code, it will gain better performance in MIMO OFDMA system by producing lower bit error rate compare to existence DCT and DFT.