Indoor Experiments on 4-by-2 Multi-User MIMO Employing Various Transmitter Antenna Arrangements in LTE-Advanced Downlink

This paper presents indoor experimental results on the achievable throughput for 4-by-2 multi-user (MU)-MIMO using 2 mobile stations (MSs) and carrier aggregation with 5 component carriers (90-MHz bandwidth) considering various transmitter antenna arrangements in the LTE-Advanced downlink. Under two centralized and two distributed antenna arrangement (CAAs and DAAs) conditions, the throughput performance is evaluated using the implemented LTE-Advanced transceiver, where extended channel state information (CSI) feedback based on eigenvalue decomposition (EVD) is implemented for MU-MIMO operation. The experimental results show that the peak throughput of greater than 1 Gbps is achieved for the CAAs in an indoor environment. The results also showed that although the MS moving speed strongly influences the throughput for Rank-4 MU-MIMO, MU-MIMO is robust against the antenna separation, i.e., fading correlation. Furthermore, we confirm that, in the DAAs, although the peak throughput of 1 Gbps is not observed, the throughput of approximately 700 to 950 Mbps is achieved.