Future mobile communication systems will adopt the multiple antennas at both transmitter and receiver to improve system capacity and spectral efficiency. In such MIMO (Multiple Input Multiple Output) system, a channel separation method is indispensable because the parallel transmission is performed. When the ZF algorithm is used for the channel separation, serious signal quality degradation sometimes happens depending on the relation between the multiple channels. In such a case, the signal quality can be maintained with limiting the transmit channels. The research paper from Tokyo University of Science, propose the transmission channel control scheme for the MIMO - OFDM systems.