Guangyi Liu

Achieving 3D-MIMO With Massive Antennas From Theory to Practice With Evaluation and Field Trial Results

Exploiting multiple-input–multiple-output (MIMO) techniques by using massive antennas can significantly improve the capacity and reliability of wireless systems and has been considered as one key technique in future fifth-generation mobile communications system. Considering the limitation of antenna panel size, placing the massive antennas in 2-D grid is an effective way for its commercialization, which is termed as “3D-MIMO.” In this paper, we study the performance of 3D-MIMO with massive antennas by system-level simulation using practical assumption and 3-D channel model and test the 3D-MIMO in field trial with commercial terminal and networks. In addition, we compare the system-level simulation results and the field trial test measurements. Our system-level simulation results show that the 3D-MIMO with 64 antennas can significantly improve the performance with 56% and 147% gain on cell-average and cell-edge throughputs compared with 2D-MIMO. We perform field trial to test the 3D-MIMO, and the results verify its performance gain obtained by simulation. Furthermore, the measurement in typical high-rise scenario shows that the 3D-MIMO can significantly enhance the data rate of users located at higher floors due to the capability of flexible elevation beamforming.

A novel limited feedback mechanism based on mixed reciprocity and codebook in large scale 3D-MIMO systems

3D-MIMO, using two dimensional antenna array at base station, demonstrates promising throughput gain over conventional antenna system during recent academic and industry studies. To realize the performance gain, accurate channel state information (CSI) feedback is one essential aspect. However, traditional feedback method, either codebook based or reciprocity based, suffers from overhead and partial reciprocity issues, respectively. In this paper, a novel mixed feedback mechanism is proposed, in which reciprocity based feedback is complemented with minimal codebook based feedback, to enable full rank MIMO transmission but with minimal reference signal and CSI reporting overhead. The mechanism is optimized for the case with cross-polarized antenna at base station and two receive/one transmit antenna at UE, which is the most practical LTE cellular system configuration. Numerical evaluations verify that the mixed feedback mechanism can realize 3D-MIMO performance with minimal reference signal overhead, CSI reporting overhead and UE complexity.