Quantized linear MIMO precoding for multiuser downlink systems

We treat the problem of sum-rate maximization via scheduling and linear precoding in multi-user (MU-) MIMO systems with quantized feedback. We formulate the optimal quantized linear precoder design problem and provide the numerical procedure for finding the solution. We also provide a simple scheduling scheme that exploits the multi-user diversity gain. It is demonstrated that, with or without scheduling, the proposed optimal linear precoding scheme achieves a significant gain over the conventional linear precoder designs with similar feedback overhead such as the zero-forcing precoder. Moreover, although the proposed quantization codebook design improves the performance of other existing MU-MIMO precoding schemes, the performance gain offered by it is typically much higher when it is coupled with the proposed linear precoding design.