Effectiveness of beamfoming with user selection in non orthogonal multiple access for 5G systems

The Multiuser Multiple-Input Multiple-Output (MU-MIMO) has been much attracted much attention for improving the spectral efficiency within a limited frequency band. The MU-MIMO techniques have been introduced in the standardization of IEEE802.11ac and LTE-Advanced. However, it is not possible to communicate with the users that exceed the number of base station (BS) antennas in the MU-MIMO transmission. In this paper, we propose a new transmission method by using non orthogonal multiple access (NOMA) and Zero Forcing (ZF) at the BS and Minimum Mean Square Error (MMSE) at user terminals (UTs). Furthermore, we propose user selection algorithm for the proposed system by utilizing channel capacity equation of ZF algorithm. By the computer simulation, it is shown that the proposed method realizes the transmission with four users with only two antennas at the BS and the transmission rate by the proposed method is improved compared to that by conventional ZF algorithm.