In recent years, wireless communications systems, such as 5th generation (5G) mobile systems, have been developed as a complex combination of various elementary technologies. Therefore, it is important to consider how to effectively and efficiently combine these technologies from the viewpoint of network operation and system configuration. In this context, theoretical analysis is essential as a means of bridging the gap between different technologies. Moreover, finding common objectives among different technologies is expected to reduce computational cost. In this paper, the combination of multiuser MIMO (MU-MIMO) and user scheduling, such as resource allocation or user selection, are taken up as examples based on an awareness of the above issues. As for network operation, MU-MIMO resource allocation based on theoretical channel capacity considering the effect of time selective fading is introduced. Moreover, the efficient combination of MU-MIMO employing Tomlinson Harashima precoding (THP) and user selection using space orthogonality as a common measure is presented.