System-Level Throughput Evaluation of Multiuser MIMO Using Enhanced Codebook Considering User Mobility in LTE-Advanced Downlink

In LTE-Advanced downlink, multiuser (MU)-MIMO transmission with closed-loop precoding matrix indicator (PMI) selection and use of interference suppression ability of mobile station (MS) receiver are promising technologies to improve spectrum efficiency. In this paper, we investigate the throughput performance of a proposed MU-MIMO codebook that contains amplitude control information in addition to the phase control information. In system-level simulations, the impacts of the MS speed on the closed-loop control and the difference in the MIMO receiver capabilities for inter-user interference suppression are evaluated considering the overhead for different transmission modes (TMs). The simulation results show that the minimum mean square error (MMSE) receiver for inter-user interference suppression is necessary to obtain stable MU-MIMO performance gains irrespective of the MS mobility. The results also show that LTE TM 9, i.e., dynamic switching between single-user (SU)-MIMO and MU-MIMO, combined with the proposed codebook improves cell-average (cell-edge) throughput performance by approximately 10% (20%), compared to TM 4 with the Release 8 4-Tx codebook.