Beamforming for MIMO systems with limited feedback

Beamforming and power allocation at the transmitter are both effective means to improve the performance of multiple input multiple output (MIMO) system. They are both dependent on the channel state information (CSI). We propose a scheme including optimal beamforming and power allocation in which the CSI at the transmitter is obtained through limited feedback. Two codebooks of beamforming matrices and power allocation vectors are constructed offline and both known by the transmitter and the receiver. Using the MMSE criterion, we choose the optimal variables from the codebooks. The data to convey to the transmitter are the indexes of the variables. We validate the proposed scheme by computer simulations from which we see the scheme can achieve a fine performance with several bits of feedback.