  In this paper, we consider a general multiple input multiple output (MIMO)
system with channel state information (CSI) feedback over time-correlated
Rayleigh block-fading channels. Specifically, we first derive the closed-form
expression of the minimum differential feedback rate to achieve the maximum
erdodic capacity in the presence of channel estimation errors and quantization
distortion at the receiver. With the feedback-channel transmission rate
constraint, in the periodic feedback system, we further investigate the
relationship of the ergodic capacity and the differential feedback interval,
and we find by theoretical analysis that there exists an optimal differential
feedback interval to maximize ergodic capacity. Finally, analytical results are
verified through simulations in a practical periodic differential feedback
system using Lloyd's quantization algorithm.
