Capacity and performance of MIMO systems under the impact of feedback delay

Multiple input multiple output (MIMO) systems promise better performance and significant increases in channel capacity by utilizing the rich scattering environment to obtain diversity gain and spatial multiplexing. Maximum system capacity and performance can be achieved if the instantaneous channel state information (CSI) is known at both sides of the transmission link. In order to have such improvements, the CSI at both link ends must be updated timely. However, the updating process is always subject to non-ideality. We investigate the effect of delay in updating CSI on the MIMO spectral efficiency and performance with system capacity and BER as benchmarks.