Multi-user MIMO linear precoding schemes in OFDM systems

In this paper, several multi-user multiple-input multiple-output (MU-MIMO) linear precoding schemes with both perfect and imperfect channel state information (CSI) for downlink transmission are proposed. Compared to nonlinear precoding schemes which need perfect CSI to achieve the channel capacity, we focus on systems which are restricted to use only linear precoding schemes due to complexity constraints and limited feedback. The limited feedback and some improvement technologies have also been introduced. The proposed MU-MIMO schemes extend the point-to-point single-user precoding to point-to-multipoint multi-user precoding.