A Tracking Approach for Precoded MIMO-OFDM Systems with Low Data Rate CSI Feedback

To obtain the closed-loop capacity of a multiple-input and multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system, channel state information (CSI) is required at the transmitter. Sometimes, CSI can be only obtained through frequent feedback from the receiver and it occupies a large bandwidth in the reverse link to completely feedback CSI. To reduce the data rate of CSI feedback, precoding matrix has been proposed for MIMO systems in flat fading channels and it is also extended to MIMO-OFDM systems in frequency-selective fading channels by interpolation. In this paper, we develop a novel precoding matrix tracking approach for MIMO-OFDM systems. The proposed approach is based on subspace tracking in the Grassman manifold and requires a limited data rate feedback. It not only is flexible to multiple data transmission but also has better performance than the existing approaches