Optimal Analog Precoder Design for Hybrid Beamforming is Possible

Hybrid beamforming is a cost-effective solution for millimeter wave massive multiple-input-multiple-output communications, which highly reduces the number of required radio frequency chains by jointly using a digital precoder and an analog precoder. The digital precoder can be optimized by using the...

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Bibliographic Details
Published in:IEEE transactions on vehicular technology Vol. 72; no. 7; pp. 9573 - 9578
Main Authors: Lv, Jiaen, Wang, Tianyu, Wang, Shaowei
Format: Journal Article
Language:English
Published: New York IEEE 01.07.2023
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Antennas
Array signal processing
Beamforming
Branch and bound
Branch and bound methods
hybrid beamforming
Integer programming
Least squares method
low-resolution phase shifters
Lower bounds
massive MIMO
Millimeter waves
Optimized production technology
Phase shifters
Radio frequency
Search problems
ISSN:0018-9545, 1939-9359
Online Access:Get full text
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Summary:Hybrid beamforming is a cost-effective solution for millimeter wave massive multiple-input-multiple-output communications, which highly reduces the number of required radio frequency chains by jointly using a digital precoder and an analog precoder. The digital precoder can be optimized by using the classical least squares method. However, due to the discrete resolution of analog phase shifters, the analog precoder design is a high-dimensional integer programming problem, for which the exsiting methods can only provide suboptimal solutions. In this article, we first show that optimal analog precoder design is possible in typical antenna settings. Specifically, we show that this high-dimensional problem can be divided into multiple low-dimensional subproblems in parallel and there exists an analytical lower bound for each subproblem that can be efficiently utilized to obtain the optimal solution by using the branch and bound method. Numerical results show that the proposed hybrid precoder with an optimal analog precoder can achieve 98<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula> performance of the fully digital solution in a typical antenna setting.
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ISSN:0018-9545
1939-9359
DOI:10.1109/TVT.2023.3245091