Impact of Multi User Selection on the Performance of Transmit Precoding in 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). Our methods differentiate in the performance due to different amount of feedback and the processing complexity. 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 information or complexity but it also depends upon the type of precoding scheme adopted by the transmitter. We compare our selection methods with a baseline selection method. The results show that the SINR based method outperforms all other selection methods. Moreover, the comparison of precodings with SINR based selection show that the interference-alignment based precoding outperforms other precodings that we have considered here.