Per band PMI selection in finite-rate closed-loop MIMO-OFDM systems

The performance of a MIMO system can be increased significantly, if the channel state information (CSI) is known at the transmitter. Sending the full CSI to the transmitter, however, requires a substantial feedback bandwidth. In a finite-rate closed-loop MIMO, the CSI is quantized into a codebook of a finite set of precoding matrices. In such a scheme, the receiver selects an optimal precoding matrix and sends only the precoding matrix index (PMI) to the transmitter reducing the feedback overhead. However, in MIMO-OFDM, if the precoding is performed per subcarrier the feedback overhead still remains large. To reduce the amount of overhead, one precoder per band of subcarriers can be used. In this paper, we propose per band PMI selection by extending the existing per subcarrier methods. Furthermore, we perform link-level simulations to verify the performance of the proposed methods on a system that operates on the IEEE 802.16e-2005 standard.