In the paper, we examine Doppler spectrum and bit-error rate (BER) performance of multiuser MIMO systems in an indoor time-varying environment based on our measured data conducted in a meeting room. Simulation results show that both Doppler spectrum and the BER performance are much dependent on the array orientation and the direction of the receiver motion. In the non-line-of-sight environment, the actual Doppler spectrum is quite different from the theoretical U-shaped spectrum in the Jakes' model. In addition, it has been shown that the BER performance is much degraded due to a channel change.