Base Station Cooperative Multiuser MIMO Using Block-Diagonalized Random Beamforming with Online Update

Nobuhide NONAKA  Anass BENJEBBOUR  Kenichi HIGUCHI  

IEICE TRANSACTIONS on Communications   Vol.E98-B    No.8    pp.1622-1629
Publication Date: 2015/08/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E98.B.1622
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
multiuser MIMO,  base station cooperation,  beamforming,  precoding,  random beamforming,  

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This paper proposes applying random (opportunistic) beamforming to base station (BS) cooperative multiuser multiple-input multiple-output (MIMO) transmission. This proposal comprises two parts. First, we propose a block-diagonalized random unitary beamforming matrix. The proposed beamforming matrix achieves better throughput distribution compared to the purely random unitary beamforming matrix when the average path loss determined by distance-dependent loss and shadowing loss is largely different among transmitter antennas, which is true in BS cooperative MIMO. Second, we propose an online update algorithm for a random beamforming matrix to improve the throughput compared to the purely random and channel-independent beamforming matrix generation, especially when the number of users is low. Different from conventional approaches, the proposed online update algorithm does not increase the overhead of the reference signal transmission and control delay. Simulation results show the effectiveness of the proposed method using a block-diagonalized random unitary beamforming matrix with online updates in a BS cooperative multiuser MIMO scenario.