A Study on Optimal Beam Patterns for Single User Massive MIMO Transmissions

Maki ARAI  Kei SAKAGUCHI  Kiyomichi ARAKI  

IEICE TRANSACTIONS on Communications   Vol.E102-B   No.2   pp.324-336
Publication Date: 2019/02/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2018EBP3030
Type of Manuscript: PAPER
Category: Antennas and Propagation
massive MIMO,  beamforming,  beam pattern,  directivity,  spherical mode expansion,  capacity maximization,  

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This paper proposes optimal beam patterns of analog beamforming for SU (Single User) massive MIMO (Multi-Input Multi-Output) transmission systems. For hybrid beamforming in SU massive MIMO systems, there are several design parameters such as beam patterns, the number of beams (streams), the shape of array antennas, and so on. In conventional hybrid beamforming, rectangular patch array antennas implemented on a planar surface with linear phase shift beam patterns have been used widely. However, it remains unclear whether existing configurations are optimal or not. Therefore, we propose a method using OBPB (Optimal Beam Projection Beamforming) for designing configuration parameters of the hybrid beamforming. By using the method, the optimal beam patterns are derived first, and are projected on the assumed surface to calculate the achievable number of streams and the resulting channel capacity. The results indicate OBPB with a spherical surface yields at least 3.5 times higher channel capacity than conventional configurations.