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Performance of Cell-Free Massive MIMO Under Imperfect Channel State Information and Reciprocity Calibration

IEEE SYSTEMS JOURNAL 2023年第3期17卷 4383-4394页

作者： Cao, Yang Liang, Xianghu Wang, Xiaoni Li, Yuan Fu, Qiang Wang, Dongming You, Xiaohu Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Peoples R China Pervas Commun Ctr Purple Mt Labs Nanjing 211100 Peoples R China ZTE Corp State Key Lab Mobile Network & Mobile Multimedia T Shenzhen 518055 Peoples R China

This article studies the downlink performance of a cell-free massive multiple-input-multiple-output (MIMO) system with imperfect channel estimation and reciprocity calibration. We present the statistical characteristics of the calibration error with the Argos algorithm and a relay-based calibration algorithm to obtain the calibration parameters of the whole network. Then, we derive approximate expressions of the downlink spectral efficiency for a cell-free massive MIMO system with imperfect channel state information and calibration error. The numerical results show the advantage of the proposed calibration algorithm and validate the accuracy of the theoretical expressions.

关键词： Calibration Downlink Radio frequency Precoding Uplink signal processing algorithms Transceivers Cell-free massive multiple-input-multiple-output (MIMO) reciprocity calibration spectral efficiency (SE)

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On the Primal Feasibility in Dual Decomposition Methods Under Additive and Bounded Errors

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IEEE TRANSACTIONS ON signal processing 2023年 71卷 655-669页

作者： Abeynanda, Hansi Weeraddana, Chathuranga Lanel, G. H. J. Fischione, Carlo KTH Royal Inst Technol Sch Elect Engn & Comp Sci S-11428 Stockholm Sweden Univ Oulu Ctr Wireless Commun Oulu 90014 Finland Univ Sri Jayewardenepura Dept Math Nugegoda 10250 Sri Lanka KTH Royal Inst Technol Sch Elect Engn & Comp Sci & Digital Futures S-11428 Stockholm Sweden

With the unprecedented growth of signal processing and machine learning application domains, there has been a tremendous expansion of interest in distributed optimization methods to cope with the underlying large-scale problems. Nonetheless, inevitable system-specific challenges such as limited computational power, limited communication, latency requirements, measurement errors, and noises in wireless channels impose restrictions on the exactness of the underlying algorithms. Such restrictions have appealed to the exploration of algorithms' convergence behaviors under inexact settings. Despite the extensive research conducted in the area, it seems that the analysis of convergences of dual decomposition methods concerning primal optimality violations, together with dual optimality violations is less investigated. Here, we provide a systematic exposition of the convergence of feasible points in dual decomposition methods under inexact settings, for an important class of global consensus optimization problems. Convergences and the rate of convergences of the algorithms are mathematically substantiated, not only from a dual-domain standpoint but also from a primal-domain standpoint. Analytical results show that the algorithms converge to a neighborhood of optimality, the size of which depends on the level of underlying distortions.

关键词： Convergence signal processing algorithms Distortion Optimization Linear programming Wireless communication Quantization (signal) Distributed optimization inexact coordination federated learning

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Communication-Efficient Federated Linear and Deep Generalized Canonical Correlation Analysis

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IEEE TRANSACTIONS ON signal processing 2023年 71卷 1379-1394页

作者： Shrestha, Sagar Fu, Xiao Oregon State Univ Sch Elect Engn & Comp Sci Corvallis OR 97331 USA

Classic and deep learning-based generalized canonical correlation analysis (GCCA) algorithms seek low-dimensional common representations of data entities from multiple "views" (e.g., audio and image) using linear transformations and neural networks, respectively. When the views are acquired and stored at different computing agents (e.g., organizations and edge devices) and data sharing is undesired due to privacy or communication cost considerations, federated learning-based GCCA is well-motivated. In federated learning, the views are kept locally at the agents and only derived, limited information exchange with a central server is allowed. However, applying existing GCCA algorithms onto such setting may incur prohibitively high communication overhead. This work puts forth a communication-efficient federated learning framework for both linear and deep GCCA under the maximum variance (MAX-VAR) formulation. The overhead issue is addressed by aggressively compressing (via quantization) the exchanging information between the computing agents and a central controller. Our synthetic and real-data experiments shows that the proposed algorithm enjoys a substantial reduction of communication overheads with virtually no loss in accuracy and convergence speed compared to the unquantized version. Rigorous convergence analyses are also presented, which is a nontrivial effort since generic federated optimization results do not cover the special problem structure of GCCA. Our result shows that the proposed algorithms for both linear and deep GCCA converge to critical points at a sublinear rate, even under heavy quantization and stochastic approximations. In addition, in the linear MAX-VAR case, the quantized algorithm approaches a global optimum in a geometric rate under reasonable conditions.

关键词： Convergence signal processing algorithms Optimization Federated learning Correlation Quantization (signal) Manifolds Generalized canonical correlation analysis communication-efficient federated learning nonconvex optimization convergence analysis

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CGMM-Based Sound Zone Generation Using Robust Pressure Matching With ATF Perturbation Constraints

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IEEE-ACM TRANSACTIONS ON AUDIO SPEECH AND LANGUAGE processing 2023年 31卷 3331-3345页

作者： Zhang, Junqing Shi, Liming Christensen, Mads Graesboll Zhang, Wen Zhang, Lijun Chen, Jingdong Northwestern Polytech Univ Ctr Intelligent Acoust & Immers Commun Sch Marine Sci & Technol Xian 710072 Peoples R China Northwestern Polytech Univ Sch Marine Sci & Technol Shaanxi Prov Key Lab Artificial Intelligence Xian 710072 Peoples R China Minist Ind & Informat Technol Key Lab Ocean Acoust & Sensing Xian 710072 Peoples R China Chongqing Univ Posts & Telecommun Intelligent Speech & Audio Lab Commun & Informat Engn Chongqing 400065 Peoples R China Aalborg Univ Dept Elect Syst DK-9000 Aalborg Denmark

Personal sound zone (PSZ) refers to the technique that uses an array of loudspeakers and digital signal processing tools to achieve spatial soundfield control. To generate the target sound zones, this technique generally requires to know the acoustic transfer functions (ATFs) between the loudspeakers and the spots where soundfields are to be controlled. In practical applications, however, the true ATFs are never accessible and they have to be measured or estimated. Due to many sophisticated reasons, the measured ATFs generally deviate from the true ones, which may lead to significant degradation in performance of sound zone reproduction. In this work, a robust pressure matching (RPM) algorithm is presented for sound zone generation. It exploits a complex Gaussian mixture model (CGMM) to model the ATFs and their perturbations. The CGMM parameters are estimated using the expectation-maximization (EM) algorithm. To improve the robustness of the pressure matching method, an uncertainty constraint is applied to the ATF estimates and the pressure matching problem is then formulated as one of biconvex optimization. The coordinate descent algorithm is subsequently used to solve the optimization problem, thereby obtaining the optimal control filter. In comparison with the existing pressure matching methods without considering the effect of ATF perturbations, the presented algorithm is able to achieve lower normalized signal distortion energy and higher signal to interference ratio. Numerical simulations justify the effectiveness of the presented algorithm as well as its advantages over the traditional methods.

关键词： Loudspeakers Perturbation methods Optimization Speech processing Robustness signal processing algorithms Uncertainty Biconvex optimization complex Gaussian mixture model expectation maximization personal sound zone robustness semidefinite relaxation

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Generalized Unitary Approximate Message Passing for Double Linear Transformation Model

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IEEE TRANSACTIONS ON signal processing 2023年 71卷 1524-1538页

作者： Mo, Linlin Lu, Xinhua Yuan, Jide Zhang, Chuanzong Wang, Zhongyong Popovski, Petar Zhengzhou Univ Sch Elect & Informat Engn Zhengzhou 450001 Peoples R China Nanyang Inst Technol Coll Informat Engn Nanyang 473000 Peoples R China Soochow Univ Sch Elect & Informat Engn Suzhou 215006 Peoples R China Aalborg Univ Dept Elect Syst DK-9220 Aalborg Denmark

The double linear transformation model Y = AXB + W plays an important role in a variety of science and engineering applications, where X is estimated through known transformation matrices A and B from the noisy measurement Y. Decoupling X from Y is a formidable task due to the high complexity brought by the multiplication of the unknown matrix (vector) with the transformation matrix (M-UMTM). Unitary approximate message passing (UAMP) has been verified as a low complexity and strong robustness solution to the M-UMTM problems. However, it has only been used to tackle the problems with a single linear transformation matrix. In this work, we develop a generalized algorithm, namely, generalized double UAMP (GD-UAMP) for the target model, which not only inherits the low complexity of AMP, but also enhances robustness by employing double unitary transformation. As a generalized algorithm, GD-UAMP can be applied to address the generalized Bayesian inference problem, i.e., the arbitrary prior probability of X and likelihood function of Z, where Z = AXB is the noiseless measurement. We verify the feasibility of the proposed algorithm in the channel estimation problem for various wireless communication systems. Numerical results demonstrate that the proposed algorithm can perfectly fit different scenarios and showcase superior performance compared with benchmarks.

关键词： signal processing algorithms Approximation algorithms Message passing Complexity theory Inference algorithms Mathematical models Bayes methods Approximate message passing (AMP) channel estimation message passing Reconfigurable intelligent surface (RIS) unitary transformation

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Most Resource Efficient Matrix Vector Multiplication on FPGAs

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IEEE ACCESS 2023年 11卷 3881-3898页

作者： Lehnert, Alexander Holzinger, Philipp Pfenning, Simon Mueller, Ralf Reichenbach, Marc Brandenburg Univ Technol Cottbus Senftenberg Chair Comp Engn D-03046 Cottbus Germany Friedrich Alexander Univ Erlangen Nurnberg Chair Comp Architecture D-91058 Erlangen Germany Friedrich Alexander Univ Erlangen Nurnberg Inst Digital Commun D-91058 Erlangen Germany

Fast and resource-efficient inference in artificial neural networks (ANNs) is of utmost importance and drives many new developments in the area of new hardware architectures, e.g., by means of systolic arrays or algorithmic optimization such as pruning. In this paper, we present a novel method for lowering the computation effort for ANN inference utilizing ideas from information theory. Weight matrices are sliced into submatrices of logarithmic aspect ratios. These slices are then factorized. This reduces the number of required computations without compromising on fully parallel processing. We create a new hardware architecture for this dedicated purpose. We also provide a tool to map these sliced and factorized matrices efficiently to reconfigurable hardware. By comparing to the state of the art FPGA implementations, we can prove our claim by lowering hardware resources measured in look-up-tables (LUTs) by a factor of three to six. Our method does not rely on any particular property of the weight matrices of the ANN. It works for the general task of multiplying an input vector with a constant matrix and is also suitable for digital signal processing beyond ANNs.

关键词： Neural networks Computer architecture Matrix decomposition Field programmable gate arrays Sparse matrices signal processing algorithms Encoding Reconfigurable architectures Computational efficiency Constant matrix multiplication neural networks computer architecture reconfigurable architectures computational efficiency

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2-D Wavenumber Domain Autofocusing for High-Resolution Highly Squinted SAR Imaging Based on Equivalent Broadside Model

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2023年 61卷 1页

作者： Deng, Yuhui Sun, Guang-Cai Han, Liang Wang, Yuqi Zhang, Yu Xing, Mengdao Xidian Univ Natl Key Lab Radar Signal Proc Xian 710071 Peoples R China Xidian Univ Sch Optoelect Engn Xian 710071 Peoples R China Xian Univ Sci & Technol Sch Commun & Informat Engn Xian 710699 Peoples R China Xidian Univ Acad Adv Interdisciplinary Res Xian 710071 Peoples R China

The wavenumber domain algorithm is an ideal solution for high-resolution and highly squinted (HRHS) synthetic aperture radar (SAR) imaging in the case of an ideal straight trajectory. However, for airborne HRHS SAR imaging, the Stolt mapping leads to nonsystematic range cell migration (NsRCM) and secondary range compression (SRC) for the HRHS SAR, which causes the HRHS SAR image to defocus severely. To obtain a well-focused HRHS SAR image, a new autofocusing algorithm for HRHS SAR imagery based on an equivalent broadside model is proposed in this article. After coarse motion compensation, linear range walk correction and azimuth resampling are employed to transform the HRHS SAR data into the equivalent broadside SAR data, which has been proved to greatly reduce NsRCM and SRC. After that, the motion error prior structure in the 2-D wavenumber domain is revealed. According to the structure, a novel 2-D wavenumber domain autofocusing algorithm is proposed by the relationship between the 1-D azimuth phase error and the 2-D wavenumber domain phase error correction. Finally, the well-focused HRHS SAR imagery is obtained. Experiments based on simulated and acquired data are carried out to verify the necessity and effectiveness of the proposed algorithm for HRHS SAR imaging.

关键词： Radar polarimetry Azimuth Trajectory Radar imaging Radar Imaging signal processing algorithms 2-D wavenumber domain autofocusing azimuth resampling equivalent broadside model extended range migration algorithm (ERMA) high-resolution and highly squinted (HRHS) synthetic aperture radar (SAR)

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Spatial Distribution-Based Imbalanced Undersampling

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 2023年第6期35卷 6376-6391页

作者： Yan, Yuanting Zhu, Yuanwei Liu, Ruiqing Zhang, Yiwen Zhang, Yanping Zhang, Ling Anhui Univ Sch Comp Sci & Technol Key Lab Intelligent Comp & Signal Proc Minist Educ Hefei 230601 Anhui Peoples R China

Undersampling is one of the most popular techniques for dealing with class-imbalance problems. Various undersampling methods have emerged over the past few decades. Each of them exhibits the superiority in some scenarios. However, selecting representative majority-class samples such that the structures of the selected groups are maintained according to the underlying imbalanced distribution remains a challenge. For this purpose, this paper proposes Spatial Distribution-based UnderSampling (SDUS) for imbalanced learning. SDUS uses a supervised constructive process to learn majority-class local patterns in terms of sphere neighborhoods (SPN). Two sample selection strategies, specifically, a top-down strategy and a bottom-up strategy, are proposed for maintaining the distribution pattern of original data in selecting majority-class sample subsets from different perspectives. SDUS introduces an ensemble technique that improves learning performance by utilizing the diversity caused by the randomness of the local-pattern learning process. Numerical experiments on 38 typical datasets from KEEL repository and 13 state-of-the-art comparison methods demonstrate the effectiveness of SDUS in maintaining the underlying distribution characteristics for imbalanced undersampling. The implementation of the proposed SDUS in programming language Python is available at https://***/ytyancp/SDUS.

关键词： Training Costs Biological neural networks Machine learning algorithms Clustering algorithms signal processing algorithms Proposals Undersampling imbalance local pattern sphere neighborhood ensemble learning

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A Provable Splitting Approach for Symmetric Nonnegative Matrix Factorization

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 2023年第3期35卷 2206-2219页

作者： Li, Xiao Zhu, Zhihui Li, Qiuwei Liu, Kai Chinese Univ Hong Kong Sch Data Sci Shenzhen 518172 Guangdong Peoples R China Shenzhen Inst Artificial Intelligence & Robot Soc Shenzhen Guangdong Peoples R China Univ Denver Dept Elect & Comp Engn Denver CO 80208 USA Alibaba Grp Damo Acad Decis Intelligence Lab Bellevue WA 98004 USA Clemson Univ Comp Sci Div Clemson SC 29634 USA

The symmetric Nonnegative Matrix Factorization (NMF), a special but important class of the general NMF, has found numerous applications in data analysis such as various clustering tasks. Unfortunately, designing fast algorithms for the symmetric NMF is not as easy as for its nonsymmetric counterpart, since the latter admits the splitting property that allows state-of-the-art alternating-type algorithms. To overcome this issue, we first split the decision variable and transform the symmetric NMF to a penalized nonsymmetric one, paving the way for designing efficient alternating-type algorithms. We then show that solving the penalized nonsymmetric reformulation returns a solution to the original symmetric NMF. Moreover, we design a family of alternating-type algorithms and show that they all admit strong convergence guarantee: the generated sequence of iterates is convergent and converges at least sublinearly to a critical point of the original symmetric NMF. Finally, we conduct experiments on both synthetic data and real image clustering to support our theoretical results and demonstrate the performance of the alternating-type algorithms.

关键词： Convergence Symmetric matrices signal processing algorithms Clustering algorithms Minimization Transforms Optimization Symmetric nonnegative matrix factorization convergence image clustering alternating minimization

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Regularized Optimal Transport Layers for Generalized Global Pooling Operations

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 2023年第12期45卷 15426-15444页

作者： Xu, Hongteng Cheng, Minjie Renmin Univ Beijing Key Lab Big Data Management & Analy Meth Gaoling Sch Artificial Intelligence Beijing 100872 Peoples R China Renmin Univ Gaoling Sch Artificial Intelligence Beijing 100872 Peoples R China

Global pooling is one of the most significant operations in many machine learning models and tasks, which works for information fusion and structured data (like sets and graphs) representation. However, without solid mathematical fundamentals, its practical implementations often depend on empirical mechanisms and thus lead to sub-optimal, even unsatisfactory performance. In this work, we develop a novel and generalized global pooling framework through the lens of optimal transport. The proposed framework is interpretable from the perspective of expectation-maximization. Essentially, it aims at learning an optimal transport across sample indices and feature dimensions, making the corresponding pooling operation maximize the conditional expectation of input data. We demonstrate that most existing pooling methods are equivalent to solving a regularized optimal transport (ROT) problem with different specializations, and more sophisticated pooling operations can be implemented by hierarchically solving multiple ROT problems. Making the parameters of the ROT problem learnable, we develop a family of regularized optimal transport pooling (ROTP) layers. We implement the ROTP layers as a new kind of deep implicit layer. Their model architectures correspond to different optimization algorithms. We test our ROTP layers in several representative set-level machine learning scenarios, including multi-instance learning (MIL), graph classification, graph set representation, and image classification. Experimental results show that applying our ROTP layers can reduce the difficulty of the design and selection of global pooling - our ROTP layers may either imitate some existing global pooling methods or lead to some new pooling layers fitting data better.

关键词： Task analysis Optimization Neural networks Machine learning Feature extraction Solids signal processing algorithms Global pooling regularized optimal transport Bregman ADMM Sinkhorn scaling set representation graph embedding

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