Beamforming Matrix Transformation for Random Beamforming

The signal to interference plus noise ratio (SINR) feedback has been utilized in random beamforming (RBF) to select users for the provision of service in multiple-input multiple-output (MIMO) systems. A large number of users are required to obtain the gain of multi-user diversity for a downlink transmission. However, if the number is not large enough, it may be difficult to obtain multi-user diversity, leading to a rapid degradation in performance. To resolve this problem, it is necessary to find beamforming matrix close to the channels of the selected users. In this paper, a beamforming matrix transformation for RBF (BMT-RBF) is presented, demonstrating an efficient search of random beams correlated with user channels as opposed to conventional ones, over a small number of users.