Hybrid Beamforming and Adaptive RF Chain Activation for Uplink Cell-Free Millimeter-Wave Massive MIMO Systems

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 f...

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Bibliographic Details
Published in:IEEE transactions on vehicular technology 2022-08, Vol.71 (8), p.8739-8755
Main Authors: Nguyen, Nhan Thanh, Lee, Kyungchun, Dai, Huaiyu
Format: Article
Language:English
Subjects:
Algorithms
Analog to digital converters
Antennas
Array signal processing
Beamforming
Cell-free massive MIMO
Central processing units
Chains
Channel estimation
Complexity
CPUs
hybrid beamforming
Massive MIMO
Millimeter waves
MIMO communication
mmWave communication
Phase shifters
Power consumption
Power demand
Radio frequency
RF chain activation
Uplink
Uplinking
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Summary: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.
ISSN:0018-9545
1939-9359
DOI:10.1109/TVT.2022.3176389