In high-speed wireless systems, bandwidth, transmit power, the complexity of hardware, quality of services, and throughput are the major issues. The 'Multi-Input-Multi-Output (MIMO)' system specifically works to increase the capacity of the wireless channel and to improve the 'Bit-Error-Rates (BER)' performance. The 'Orthogonal-Frequency-Division-Multiplexing (OFDM)' system is used for diminishing interferences within the available bandwidth. The spatial diversity of MIMO and the spectral efficiency of OFDM schemes can be combined to improve the channel capacity and error performance remarkably within the available bandwidth. Also, this combination provides robustness against various channel impairments. This article illustrates antenna diversity by employing different antenna configurations for the improvement in ergodic channel capacity. The 'Maximal-Ratio-Combing (MRC)' scheme provides receiver antenna diversity which enhances the channel capacity and improves the error rates performance of the MIMO-OFDM-based wireless communication system. Simulation results show that the proposed schemes achieve better results for channel capacity and error-rate performance.