The demand of different multimedia services and different internet supported applications on mobile devices requires a high speed data rate and good service of quality. This can be obtained by implementing multiple Antenna technology on both stations i.e. User terminal and base station with an appropriate coding technique, and on the other hand MIMO can fulfill 3G & 4G demand and standard with a combination of other techniques. The MIMO diversity and MIMO multiplexing are the key factors to discuss and matter of concern is to achieve and support high speed data rate. MIMO multiplexing is a way to gain robustness and achievement in speed of data information. This thesis work describes a brief overview of WiMAX technology and MIMO-OFDM system and it also discusses the simplest Space time block code (STBC) known as Alamouti Space Time Code. The research approach is a literary survey to have theoretical understanding of the MIMO-OFDM system and WiMAX. The system‘s error performance is analyzed through simulation which showed the simulated results of Multi-Rate Resource Control (MRRC) scheme and Alamouti scheme are identical. And also the Bit Error Rate (BER) were checked for different MIMO systems, the simulation results shows that the BER improved to agreeable value also gains maximum diversity when the number of antennas increased on the receiver side. By improving the BER, we will get the better QoS. Matlab simulation has been performed, and presented the results, which shows the considerable error free transmission (FEC) for MIMO systems in WiMAX technology.