One way to simplify the design of flexible and efficient MIMO transmission schemes is to view a MIMO transmitter as a concatenated coding and modulation system, in which conventional coding is applied before space-time coding/modulation. This concatenated coding structure allows a salient choice from a large number of conventional codes for SISO systems and simplifies the design of the inner space-time modulation. The structure is also general as it subsumes many existing space-time coding schemes as special cases.  Based on the proposed general structure, a study on the effects of the inner space-time modulation on system performance is conducted. It is shown that well-known design criteria for space-time codes do not apply in a concatenated coding system. In fact, the design becomes much easier. Two MIMO transmission schemes are developed. The first is a simple delay-diversity scheme designed for optimized performance and the second scheme is a multi-layered MIMO transmission scheme aimed at applications that requires flexible tradeoff between performance and data rate. In addition, a joint iterative receiver is developed for the proposed concatenated transmission schemes. Simulation results are provided to show the merits of the proposed schemes.