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

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

1
Faculty of Engineering, Niigata University, Ikarashi 2-nocho 8050, Nishi-ku Niigata 950-218, Japan
2
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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Abstract

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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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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