Optimal Least Squares Estimator and Precoder for Energy Beamforming Over IQ-Impaired Channels

Usage of low-cost hardware in large antenna arrays and low-power wireless devices in Internet of Things (IoT) has led to the degradation of practical beamforming gains due to the underlying hardware impairments, such as in-phase and quadrature-phase imbalance (IQI). To address this timely concern, w...

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Bibliographic Details
Published in:IEEE signal processing letters Vol. 26; no. 8; pp. 1207 - 1211
Main Authors: Mishra, Deepak, Johansson, Hakan
Format: Journal Article
Language:English
Published: New York IEEE 01.08.2019
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Antenna array
Antenna arrays
Antennas
Array signal processing
Beamforming
Benchmark testing
Channel estimation
Channels
Design
Economic models
Gain
Hardware
Internet of Things
IQ imbalance
Least squares
MISO communication
Optimization
IQ imbalance
Antenna array
channel estimation
ISSN:1070-9908, 1558-2361, 1558-2361
Online Access:Get full text
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Summary:Usage of low-cost hardware in large antenna arrays and low-power wireless devices in Internet of Things (IoT) has led to the degradation of practical beamforming gains due to the underlying hardware impairments, such as in-phase and quadrature-phase imbalance (IQI). To address this timely concern, we present a new nontrivial closed-form expression for the globally optimal least squares estimator (LSE) for the IQI-influenced channel between a multiantenna transmitter and single-antenna IoT device. Thereafter, to maximize the realistic transmit beamforming gains, a novel precoder design is derived that accounts for the underlying IQI for maximizing received power in both single and multiuser settings. Finally, the simulation results, demonstrating a significant <inline-formula><tex-math notation="LaTeX">-{\text{8}}</tex-math></inline-formula> dB improvement in the mean squared error of the proposed LSE over existing benchmarks, show that the optimal precoder designing is more critical than accurately estimating IQI-impaired channels. Also, the proposed jointly optimal LSE and beamformer outperforms the existing designs by providing <inline-formula><tex-math notation="LaTeX">{\text{24}{\%}}</tex-math></inline-formula> enhancement in mean signal power received under IQI.
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ISSN:1070-9908
1558-2361
1558-2361
DOI:10.1109/LSP.2019.2925533