MLD-Based MU-MIMO Detection Scheme for LTE Downlink

Currently Multi-User MIMO (MU-MIMO) attracts attention to improve frequency usage efficiency. When using Maximum Likelihood Detection (MLD) for MU-MIMO detection, we need to know the modulation type of the transmitted signals. However in 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, the user to whom MU-MIMO is applied cannot be informed about the modulation type of the signals for a multiplexed interference user. Therefore, linear filters such as Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) are typically applied. In this paper, we propose an MLD-based MU-MIMO detection method with modulation-type estimation. In this method, we perform MLD by assuming possible modulation types to calculate metrics, and by comparing them, we determine the modulation type of the signals for an interference user. From the computer simulation results, we find that the proposed method can obtain better performance than MMSE with a slight increase in complexity from SU-MIMO detection.