Hybrid CSI-RS transmission mechanism-based 3D beamforming scheme for FDD massive MIMO system

• Published in: China communications 2016, Vol.13 (Supplement2), p.109-119
• Main Authors: Zhang, Fangchao, Sun, Shaohui, Gao, Qiubin, Li, Hui
• Format: Article
• Language: English
• Subjects: 3D beamforming; Antenna arrays; Antenna radiation patterns; Array signal processing; codebook; CSI-RS; feedback; massive MIMO; MIMO; PMI; Precoding; Three-dimensional displays; Transmitting antennas
• ISSN: 1673-5447
• DOI: 10.1109/CC.2016.7833465

Massive multiple-input multiple-output (MIMO) refers to the idea that equipping base station (BS) with a large number of antenna elements, and features the ability of three dimensional (3D) beamforming technique to enable improvement in system performance. The prior works on massive MIMO generally rely on a common assumption of the whole channel characteristics are perfectly known at both user equipment (UE) and BS, however, this is quite difficult to realize in practical frequency division duplexing (FDD) system since the channel state information reference signal (CSI-RS) overhead and CSI feedback overhead are proportional to the number of antenna elements. In this paper, two hybrid CSI-RS transmission mechanism-based 3D beamforming schemes are proposed in FDD massive MIMO system, in which non-beamformed CSI-RS configuration is utilized in conjunction with beamformed CSI-RS configuration. In the proposed schemes, an angle quantization-based vertical codebook and a DFT-based horizontal codebook are designed, respectively, and an eigenvalue decomposition-based precoding matrix indicator (PMI) selection algorithm is also proposed for CSI acquisition. Simulation results show that the proposed 3D beamforming schemes achieve significant improvement in system capacity without incurring excessive CSI-RS overhead.