University of Oulu

N. T. Nguyen, K. Lee and H. Dai, "Hybrid Beamforming and Adaptive RF Chain Activation for Uplink Cell-Free Millimeter-Wave Massive MIMO Systems," in IEEE Transactions on Vehicular Technology, vol. 71, no. 8, pp. 8739-8755, Aug. 2022, doi: 10.1109/TVT.2022.3176389

Hybrid beamforming and adaptive RF chain activation for uplink cell-free millimeter-wave massive MIMO systems

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Author: Nguyen, Nhan Thanh1,2; Lee, Kyungchun3; Dai, Huaiyu4
Organizations: 1Seoul National University of Science and Technology, Seoul, Republic of Korea
2Centre for Wireless Communications, University of Oulu, 90014 Oulu, Finland
3Department of Electrical and Information Engineering and the Research Center for Electrical and Information Technology, Seoul National University of Science and Technology, Nowon-gu, Seoul 01811, Republic of Korea
4Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695 USA
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1 MB)
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Language: English
Published: Institute of Electrical and Electronics Engineers, 2022
Publish Date: 2023-03-23


In this work, we investigate hybrid analog–digital beamforming (HBF) architectures for uplink cell-free (CF) millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems. We first propose two HBF schemes, namely, decentralized HBF (D-HBF) and semi-centralized HBF (SC-HBF). In the former, both the digital and analog beamformers are generated independently at each AP based on the local channel state information (CSI). In contrast, in the latter, only the digital beamformer is obtained locally at the access point (AP), whereas the analog beamforming matrix is generated at the central processing unit (CPU) based on the global CSI received from all APs. We show that the analog beamformers generated in these two HBF schemes provide approximately the same achievable rates despite the lower complexity of D-HBF and its lack of CSI requirement. Furthermore, to reduce the power consumption, we propose a novel adaptive radio frequency (RF) chain-activation (ARFA) scheme, which dynamically activates/deactivates RF chains and their connected analog-to-digital converters (ADCs) and phase shifters (PSs) at the APs based on the CSI. For the activation of RF chains, low-complexity algorithms are proposed, which can achieve significant improvement in energy efficiency (EE) with only a marginal loss in the total achievable rate.

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Series: IEEE transactions on vehicular technology
ISSN: 0018-9545
ISSN-E: 1939-9359
ISSN-L: 0018-9545
Volume: 71
Issue: 8
Pages: 8739 - 8755
DOI: 10.1109/tvt.2022.3176389
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: This work was supported in part by the National Research Foundation of Korea (NRF) through Basic Science Research Program funded by the Ministry of Education under Grants NRF- 2019R1A6A1A03032119 and NRF-2016R1D1A1B03933122, in part by the Academy of Finland through 6G Flagship Program under Grant 346208, in part by EERA project under Grant 332362, and in part by Infotech Program funded by the University of Oulu Graduate School.
Academy of Finland Grant Number: 346208
Detailed Information: 346208 (Academy of Finland Funding decision)
332362 (Academy of Finland Funding decision)
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