Measurement of Time-Varying MIMO Channel for Performance Analysis of Closed-Loop Transmission

Abstract — A real-time multiple-input multiple-output (MIMO) channel measurement system was implemented by using a 4×4 MIMO software defined radio (SDR) testbed. A target application of this system is to evaluate realistic performance of closed-loop MIMO transmission in time-varying channels at 5GHz band. The results of indoor measurements showed that feedback delay of the closed-loop transmission causes severe degradation of channel capacity, and an interference canceller in eigenbeamspace is indispensable in achieving the benefits of channel state information (CSI) feedback. I