The aim of this research work is to investigate error free transmission in wireless communications. In particular the thesis study MIMO multiplexing (spatial multiplexing) and diversity (space time coding) having OFDM modulation scheme. The report is based on the the fact that MIMO multiplexing increases a network capacity by splitting a high signal rate into multiple lower rate streams. It also fulfills the requirement by offering high data rate through spatial multiplexing gain and improved link reliability due to antenna diversity gain. Alamouti Space Time Block Code (STBC) scheme is used with orthogonal designs over multiple antennas which showed simulated results are identical to expected theoretical results. With this technique both Bit Error Rate (BER) and maximum diversity gain are achieved by increasing number of antennas on either side. This scheme is efficient in all the applications where system capacity is limited by multipath fading.