Indoor Experiments on 4-by-2 Multi-User MIMO and Carrier Aggregation Achieving Real-Time 1-Gbps Data Transmission in LTE-Advanced Downlink

This paper presents indoor experimental results on 4-by-2 multi-user (MU)-MIMO transmission with carrier aggregation (90-MHz bandwidth) achieving real-time 1-Gbps data transmission using adaptive modulation and coding (AMC) in the LTE-Advanced downlink employing OFDMA radio access. In the experiments, eigenvalue decomposition (EVD)-based channel state information (CSI) feedback based on subband unit for MU-MIMO operation and inter-user interference whitening filter applied before maximum likelihood detection (MLD) are employed to achieve such a high data rate with realistic numbers of transmitter and receiver antennas. The indoor experiments are conducted in a conference room under line-of-sight conditions with multiple reflected waves where one mobile station (MS) travels at walking speed and the other MS is static. The experimental results show that the total throughput for the 2 MSs is greater than 1 Gbps at the average received signal-to-interference plus noise power ratio (SINR) of approximately 25 and 17 dB for the first and second streams of each MS, respectively, when the moving speed is up to approximately 1 km/h. The results also show that a centralized transmitter antenna arrangement is more effective in order to achieve a high data rate such as 1 Gbps compared to a distributed antenna arrangement for the measurement environment.