Impact of multi user selection on the performance of transmit precoding in MU-MIMO cellular systems

In this paper, we propose three different user selection methods for an OFDM based downlink closed loop multi-user MIMO cellular system. The first method is based on the maximization of orthogonality, the second on the maximization of alignment gain and the third on the maximization of post receiver SINR (estimated by the transmitter). To analyze the influence of these methods on downlink transmission, we consider three different classes of MU-MIMO transmit precoding schemes. We show that the choice of user selection method does not depend only upon the feedback and computational complexity but it also depends upon the type of precoding scheme adopted by the transmitter. We compare our selection methods with a standard selection method which is based on orthogonal selection. The results show that the orthogonal- selection is not always the best method in a multi-user cellular system.