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Electronics 2017, 6(4), 91; doi:10.3390/electronics6040091

Effectiveness of Implicit Beamforming with Large Number of Antennas Using Calibration Technique in Multi-User MIMO System

Faculty of Engineering, Niigata University, Ikarashi 2-nocho 8050, Nishi-ku Niigata 950-218, Japan
Faculty of Engineering, Nippon Institute of Technology, 4-1 Gakuendai, Miyashiro-machi, Minamisaitama-gun, Saitama 345-8501, Japan
Author to whom correspondence should be addressed.
Received: 12 September 2017 / Revised: 5 October 2017 / Accepted: 17 October 2017 / Published: 24 October 2017
(This article belongs to the Special Issue Smart Antennas and MIMO Communications)
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This paper examines the effectiveness of implicit beamforming (IBF), which enables transmission without channel state information (CSI) feedback in multi-user multiple-input multiple-output (MU-MIMO) systems with a large number of antennas. First, we explain why CSI feedback from terminal stations to the base station produces a very large overhead. A calibration technique is then introduced, which compensates for the difference between the complex amplitudes of the transmitters and receivers to facilitate CSI-feedback-free beamforming; this technique is called IBF. The efficacy of this calibration technique is demonstrated by measuring the amplitude and phase errors obtained using a 16-element array testbed and by performing a channel capacity evaluation. Finally, the throughput under IEEE802.11ac-based massive MIMO transmission, both with and without CSI feedback, is obtained in terms of the medium access control efficiency. View Full-Text
Keywords: multi-user MIMO; calibration; implicit beamforming; channel state information multi-user MIMO; calibration; implicit beamforming; channel state information

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Nishimori, K.; Hiraguri, T.; Mitsui, T.; Yamada, H. Effectiveness of Implicit Beamforming with Large Number of Antennas Using Calibration Technique in Multi-User MIMO System. Electronics 2017, 6, 91.

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