XL-MIMO Based Hierarchical Receive Beamforming Subject to Hardware Impairments in the Uplink of Cell-Free Networks

Extremely large-scale multiple-input and multiple-output (XL-MIMO) exhibit substantial spatial multiplexing capabilities owing to their high degree of freedom. As the number of antenna elements increases, it becomes more practically suitable to utilize cost-effective antennas equipped with low-resol...

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Bibliographic Details
Published inIEEE transactions on vehicular technology pp. 1 - 11
Main Authors Li, Qingchao, El-Hajjar, Mohammed, Xu, Chao, Zhang, Chao, Hanzo, Lajos
Format Journal Article
LanguageEnglish
Published IEEE 2025
Subjects
Antenna arrays
Antennas
Array signal processing
cell-free network
Central Processing Unit
Computer architecture
Estimation
Extremely large-scale multiple-input and multiple-output (XL-MIMO)
Hardware
hardware impairment (HWI)
hierarchical detection
near-field
Signal processing algorithms
Signal to noise ratio
Vectors
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Summary:Extremely large-scale multiple-input and multiple-output (XL-MIMO) exhibit substantial spatial multiplexing capabilities owing to their high degree of freedom. As the number of antenna elements increases, it becomes more practically suitable to utilize cost-effective antennas equipped with low-resolution RF chains. However, hardware impairments (HWIs) associated with these cost-effective antennas lead to performance saturation in the high signal-to-noise ratio (SNR) region, which cannot be mitigated by merely increasing the transmit power. To address these challenges, we propose a hierarchical receive beamforming method for XL-MIMO based near-field cell-free networks with HWIs. Specifically, the antenna array of each access point (AP) is partitioned into multiple sub-arrays, with each sub-array independently harnessing the minimum mean-square error (MMSE) receive beamforming algorithm. The local data estimates at each AP are then optimized using the results from all sub-arrays, and the central processing unit (CPU) performs its final information recovery by integrating these local estimates. Our theoretical analysis shows that the proposed hierarchical receive beamforming method achieves a higher ergodic sum-rate than the state-of-the-art (SoA) scheme in XL-MIMO systems in the face of HWIs.
ISSN:0018-9545
1939-9359
DOI:10.1109/TVT.2025.3592149