The modern wireless systems are required to have high voice quality and data rate. Since our concern is most with cattering environment, antenna diversity is a practically effective and widely applied technique to reduce the effect of multipath fading. In this regard, Multiple Input Multiple Output (MIMO) techniques are an essential part of the IEEE 802.16e - 2005 specifications, which form the basis of mobile WiMAX systems. Mobile WiMAX systems define the physical (PHY) layer and Medium Access Control (MAC) layer for mobile and portable Broadband Wireless Access (BWA) systems. The IEEE 802.16e-2005 specifications actually define three different PHY layers: Single-carrier transmission, Orthogonal Frequency Division Multiplexing (OFDM), and Scalable Orthogonal Frequency Division Multiple Access (SOFDMA). Considering the importance of WiMAX systems based on IEEE 802.16e-2005 specifications, my focus is on the MIMO techniques in the domain of WiMAX technology. This thesis work describes the cellular networks in the context of different Generations of cellular communication and brief overview of the WiMAX technology. Moreover it describes the multiple antenna techniques in order to discuss the throughput and Bit Error Rate (BER) performance. In addition it describes the simplest Space Time Block Code (STBC) known as Alamouti STBC. Furthermore the capacity of MIMO systems has been analyzed. Matlab Simulation has been performed and results are presented, which shows the good contribution in the classical research of WiMAX Wireless Broadband Access (WBA) technology.