The future mobile communication system will be distinguished by high integration of services, flexibility and higher throughput. Thus, the rapid growth in traffic volume and increase in new services has begun to change the configuration and structure of wireless networks. In the past, WiMAX has gained lot of interest for providing broadband communication. The present demand in the field of wireless communication is not only to provide data communication when the user is mobile, but also to provide high data rate by consuming less bandwidth. To meet these requirements, WiMAX provides specification for FEC (forward error correction), and optional schemes like advanced antenna systems (AAS), space time code (STC) and multiple input multiple output (MIMO) systems. Also it includes two MIMO profiles, which can be used for different purposes including diversity, spatial multiplexing and interference reduction. MIMO in conjunction with OFDMA promises to provide massive amelioration in system throughput. The objective of the paper is to propound a unified guideline for choosing optimal schemes for different scenario in WiMAX OFDMA systems. In this paper, a simple technique to switch between diversity and multiplexing has been proposed. It is discerned through simulations that the proposed scheme achieves significant performance improvement than that can be obtained with either multiplexing or diversity alone.