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Harnessing Low-Dimensional Structures in Machine Learning and Signal Processing

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Signal and Data Analysis".

Deadline for manuscript submissions: 21 December 2026 | Viewed by 1186

Special Issue Editors

Department of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
Interests: machine learning; signal processing; numerical optimization; network science; high-dimensional statistics

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Guest Editor
Department of Electrical & Computer Engineering, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada
Interests: information and coding theory; machine learning; wireless communications; signal and image processing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Background:

The exponential growth in data generation has revealed the following fundamental insight: While modern datasets may exist in extremely high-dimensional spaces, they often possess underlying low-dimensional structures that can be identified and leveraged for improved analysis. From sparse representations in signal processing to low-rank adaptations in large language models, from neural network compression to latent diffusion models, the recognition and exploitation of these intrinsic structures have become central to advancing both theoretical understanding and practical performance. This paradigm shift has driven remarkable progress, enabling breakthrough results in compressed sensing, matrix completion, image reconstruction, and scalable AI systems through the principled integration of structural assumptions with sophisticated optimization techniques.

Aims:

This special issue showcases cutting-edge research advancing the understanding and application of low-dimensional structures across machine learning and signal processing. We seek theoretical advances, novel algorithms, and compelling applications. Topics include, but are not limited to, theoretical foundations such as sample complexity analysis, information-theoretic bounds, and nonconvex optimization theory; algorithmic advances in sparse, low-rank, and tensor-based methods; and applications spanning computational imaging, recommender systems, wireless communications, compressed deep learning models, and other data-intensive domains where low-dimensional structures enable efficient solutions.

Dr. Jiaxi Ying
Prof. Dr. Jun Chen
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Entropy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • low-dimensional structures
  • sparse representations
  • low-rank models
  • tensor decomposition
  • compressed sensing
  • nonconvex optimization
  • information-theoretic bounds
  • neural network compression
  • efficient AI systems

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Published Papers (2 papers)

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Research

23 pages, 9298 KB  
Article
High-Quality Representation Learning Approach to Spatio-Temporal Traffic Speed Data with Lp,ϵ-Norm
by Lei Yang, Ziwen Ma and Yikai Hou
Entropy 2026, 28(4), 435; https://doi.org/10.3390/e28040435 - 13 Apr 2026
Viewed by 251
Abstract
In the realm of intelligent transportation systems (ITS), achieving optimal system performance relies heavily on the acquisition of comprehensive and high-quality spatio-temporal traffic data. In practical data-gathering processes, factors such as sensor malfunctions or communication interruptions often lead to incomplete or missing data [...] Read more.
In the realm of intelligent transportation systems (ITS), achieving optimal system performance relies heavily on the acquisition of comprehensive and high-quality spatio-temporal traffic data. In practical data-gathering processes, factors such as sensor malfunctions or communication interruptions often lead to incomplete or missing data records, which in turn substantially hinder the advancement of ITS applications. To address missing spatio-temporal data, a widely adopted paradigm involves the Latent Factorization of Tensors (LFT) model. Traditional LFT frameworks often employ the standard L2 metric in their learning objective, making them easily affected by abnormal data points. Moreover, impulse noise frequently arises in sensors and communication scenarios. To address these limitations, this paper develops an Adaptive Lp,ϵ-norm-incorporated Latent Factorization of Tensors (Lp,ϵLFT) model founded on two-fold concepts: (a) constructing a generalized objective function grounded in the Lp,ϵ-norm distance to enhance robustness against outliers; (b) realizing the self-adaptation of model hyper-parameters through a fuzzy controller to enhance model practicality. Experimental evaluations on six traffic speed datasets derived from multiple metropolitan traffic networks demonstrate that the proposed Lp,ϵLFT model yields significantly higher imputation accuracy and superior computational efficiency compared with seven state-of-the-art approaches. Full article
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16 pages, 1206 KB  
Article
HASwinNet: A Swin Transformer-Based Denoising Framework with Hybrid Attention for mmWave MIMO Systems
by Xi Han, Houya Tu, Jiaxi Ying, Junqiao Chen and Zhiqiang Xing
Entropy 2026, 28(1), 124; https://doi.org/10.3390/e28010124 - 20 Jan 2026
Viewed by 529
Abstract
Millimeter-wave (mmWave) massive multiple-input, multiple-output (MIMO) systems are a cornerstone technology for integrated sensing and communication (ISAC) in sixth-generation (6G) mobile networks. These systems provide high-capacity backhaul while simultaneously enabling high-resolution environmental sensing. However, accurate channel estimation remains highly challenging due to intrinsic [...] Read more.
Millimeter-wave (mmWave) massive multiple-input, multiple-output (MIMO) systems are a cornerstone technology for integrated sensing and communication (ISAC) in sixth-generation (6G) mobile networks. These systems provide high-capacity backhaul while simultaneously enabling high-resolution environmental sensing. However, accurate channel estimation remains highly challenging due to intrinsic noise sensitivity and clustered sparse multipath structures. These challenges are particularly severe under limited pilot resources and low signal-to-noise ratio (SNR) conditions. To address these difficulties, this paper proposes HASwinNet, a deep learning (DL) framework designed for mmWave channel denoising. The framework integrates a hierarchical Swin Transformer encoder for structured representation learning. It further incorporates two complementary branches. The first branch performs sparse token extraction guided by angular-domain significance. The second branch focuses on angular-domain refinement by applying discrete Fourier transform (DFT), squeeze-and-excitation (SE), and inverse DFT (IDFT) operations. This generates a mask that highlights angularly coherent features. A decoder combines the outputs of both branches with a residual projection from the input to yield refined channel estimates. Additionally, we introduce an angular-domain perceptual loss during training. This enforces spectral consistency and preserves clustered multipath structures. Simulation results based on the Saleh–Valenzuela (S–V) channel model demonstrate that HASwinNet achieves significant improvements in normalized mean squared error (NMSE) and bit error rate (BER). It consistently outperforms convolutional neural network (CNN), long short-term memory (LSTM), and U-Net baselines. Furthermore, experiments with reduced pilot symbols confirm that HASwinNet effectively exploits angular sparsity. The model retains a consistent advantage over baselines even under pilot-limited conditions. These findings validate the scalability of HASwinNet for practical 6G mmWave backhaul applications. They also highlight its potential in ISAC scenarios where accurate channel recovery supports both communication and sensing. Full article
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