Remote Control of Transmit Beamforming for Multiuser TDD/MIMO Systems

Yoshitaka HARA  Kazuyoshi OSHIMA  

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.6    pp.1922-1931
Publication Date: 2008/06/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.6.1922
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
mobile communications,  MIMO,  beamforming,  remote control,  TDD,  

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This paper proposes a new control scheme in which the base station (BS) controls terminal's transmit beamforming in time-division duplex (TDD)/multi-input multi-output (MIMO) systems. In the proposed scheme, the BS transmits pilot signals using appropriate downlink beams to instruct a terminal on target transmit beamforming. Using responses of the downlink pilot signals, the terminal can perform transmit beamforming close to the target one. Our theoretical investigation reveals that the BS can control multiple terminals' transmit beamforming simultaneously. Furthermore, an efficient signal processing at the terminal is investigated to obtain precise weight of transmit beamforming in noise environments. Numerical results show that the terminal can perform precise transmit beamforming close to the target one in noise environments. It is also shown that the amount of downlink control signalling in the proposed scheme is much less than that in codebook-based approach.