WiMAX is called worldwide interoperability for microwave access. This is one of the methods of wireless communication standard named under IEEE 802.16 standard. In this technique, simulation of the WiMAX system is performed under different channel conditions. The same system is simulated in two different scenarios. In the first scenario, the system is made work under LDPC encoding and LDPC decoding method of channel coding. In the second scenario, the system is made to work under OSTBC encoder and OSTBC combiner (encoder) of MIMO. The performance of the system is s studied and compared under LDPC and MIMO encoder and decoder techniques. -WiMAX is called worldwide interoperability for microwave access. This is one of the methods of wireless communication standard named under IEEE 802.16 standard. In this technique, simulation of the WiMAX system is performed under different channel conditions. The same system is simulated in two different scenarios.　In the first scenario, the system is made work under LDPC encoding and LDPC decoding method of channel coding. In the second scenario, the system is made to work under OSTBC encoder and OSTBC combiner (encoder) of MIMO. The performance of the system is s studied and compared under LDPC and MIMO encoder and decoder techniques.