Abstract: A transmission design of multiuser MIMO system is considered. One cellular base station configured with a transmit antennas array and a receive antennas array operates in in-band full-duplex transmission mode. To mitigate the effect of the self-interference (SI) on the uplink in such systems, the signal processing including the downlink precoding and the subsequent uplink transmit covariance matrix calculating is considered. To enhance the uplink sum rate, we propose a tentative downlink user selection. The basic idea is turning off data streams of one downlink user whose channel matrix norm is relatively smaller. Computer simulation results show that under the constraint of downlink total transmission power at the base station, the simple user selection scheme increases the downlink rate in low and moderate downlink SNR region. In addition, the downlink user selection can remarkably increase the uplink sum rate in high uplink SNR region.