Title: On Optimizing Feedback Interval for Temporally Correlated MIMO Channels With Transmit Beamforming And Finite-Rate Feedback,
Abstract: A receiver with perfect channel state information (CSI) in a point-to-point
multiple-input multiple-output (MIMO) channel can compute the transmit
beamforming vector that maximizes the transmission rate. For frequency-division
duplex, a transmitter is not able to estimate CSI directly and has to obtain a
quantized transmit beamforming vector from the receiver via a rate-limited
feedback channel. We assume that time evolution of MIMO channels is modeled as
a Gauss-Markov process parameterized by a temporal-correlation coefficient.
Since feedback rate is usually low, we assume rank-one transmit beamforming or
transmission with single data stream. For given feedback rate, we analyze the
optimal feedback interval that maximizes the average received power of the
systems with two transmit or two receive antennas. For other system sizes, the
optimal feedback interval is approximated by maximizing the rate difference in
a large system limit. Numerical results show that the large system
approximation can predict the optimal interval for finite-size system quite
accurately. Numerical results also show that quantizing transmit beamforming
with the optimal feedback interval gives larger rate than the existing
Kalman-filter scheme does by as much as 10% and than feeding back for every
block does by 44% when the number of feedback bits is small.