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An Efficient Subswath-Subband Chirp Z Transform Algorithm for Multiple-Receiver SAS Considering the Differential Range Curvature

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2025年 63卷

作者： Ning, Mingqiang Tang, Jinsong Wu, Haoran Zhong, Heping Ma, Mengbo Naval Univ Engn Wuhan 430033 Peoples R China Acad Mil Sci Beijing 100080 Peoples R China

The interpolation-free chirp z-transform (CZT) algorithm is efficient but requires approximating the accurate 2-D spectrum's phase. However, this approximation is invalid for data from multiple-receiver synthetic aperture sonar (MRSAS) systems with wide beamwidths, large fractional bandwidths, and wide subswaths. To address the issue above, this article derives a new range history and 2-D spectrum, and proposes a new method to limit the approximation error of the 2-D spectrum's phase. This article first represents the range history as a combination of basic functions and derives a new 2-D spectrum without any approximation. After the receiver dependence of the 2-D spectrum's phase is partially reduced, the echo data are divided into multiple subapertures in the receiver domain to ensure that the 2-D spectrum's phase difference of different receivers within each subaperture can be ignored. A frequency-domain filter is designed based on the 2-D spectrum of the reference receiver to compensate for all receivers' data in the subaperture. Therefore, only one imaging process is needed in a subaperture, rather than receiver-by-receiver imaging. The 2-D spectrum's phase is expanded up to the third range frequency and its error is limited by the subswath-subband processing rather than considering the higher order terms in Taylor expansion. The quadratic and cubic terms in each subband are linearized through subband-wise linear approximation (SLA) to facilitate the CZT algorithm. Finally, the high-resolution image of the whole swath is obtained through the subimage fusion. The superiority of the proposed range history and subswath-subband processing has been verified under wide beamwidths, large fractional bandwidths, and wide subswaths through simulation and measured data.

关键词： Receivers History Imaging Synthetic aperture sonar Accuracy Transmitters signal processing algorithms Approximation algorithms Chirp Azimuth 2-D spectrum Chirp z-transform (CZT) algorithm multiple-receiver synthetic aperture sonar (MRSAS) subband-wise linear approximation (SLA) subswath-subband processing

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Combining SEFDM Technique With IBFD Communication System in an ROF Link for Achieving Ultra-High Spectral Efficiency

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2025年第3期43卷 1089-1097页

作者： Chen, Yu Chen, Yang East China Normal Univ Sch Commun & Elect Engn Shanghai Key Lab Multidimens Informat Proc Shanghai 200241 Peoples R China

Oriented to the requirements of future high-frequency wireless communication systems, this paper proposes a method of combining spectrally efficient frequency-division multiplexing (SEFDM) technique with the in-band full-duplex (IBFD) communication system and applying it to microwave photonic transmission links to achieve ultra-high spectral efficiency. The microwave photonic link not only realizes the transmission of SEFDM signals received by the IBFD system but also realizes the analog self-interference cancellation (SIC) function. The digital SIC and SEFDM demodulation functions are seamlessly integrated following the analog SIC. Utilizing a cross-iterative algorithm, the adverse effects of the signal of interest (SOI) on the digital SIC of the received signal are mitigated, leading to a substantial improvement in both the SIC depth and demodulation performance of the SEFDM signal compared to the conventional least squares (LS) algorithm. An experiment has been conducted. The SOI and self-interference (SI) have symbol rates of 300 Msym/s and 600 Msym/s, respectively, and share a center frequency of 2 GHz and a bandwidth compression factor of 0.8. When the SI to SOI power ratio is 10.3 dB, the analog SIC depth is around 18.3 dB. The conventional LS algorithm achieves a digital SIC depth of 12.6 dB but the error vector magnitude (EVM) is 13.2%. In contrast, our proposed iterative method improves the SIC depth to 15.1 dB and reduces the EVM to 4.1%. The feasibility of the system is also verified by incorporating a 25.2-km fiber.

关键词： Interference cancellation Demodulation Microwave photonics Optical fibers Microwave theory and techniques Microwave communication Optical fiber dispersion Optical fiber communication Communication systems signal processing algorithms Digital signal processing in-band full-duplex microwave photonics self-interference cancellation (SIC) spectrally efficient frequency-division multiplexing (SEFDM)

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Cramer-Rao Lower Bounds for Unconstrained and Constrained Quaternion Parameters

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IEEE TRANSACTIONS ON signal processing 2025年 73卷 508-518页

作者： Sun, Shuning Xu, Dongpo Diao, Qiankun Mandic, Danilo P. Northeast Normal Univ Sch Math & Stat Key Lab Appl Stat MOE Changchun 130024 Peoples R China Imperial Coll London Dept Elect & Elect Engn London SW7 2AZ England

The Cramer-Rao lower bound (CRLB) is a fundamental result in statistical signal processing, however, the CRLB for quaternion parameters is not yet established. To this end, we develop the theory of quaternion Cramer-Rao lower bound (QCRLB), based on the generalized Hamilton-real (GHR) calculus. For generality, this is achieved in a way that conforms with the real and complex CRLB. We first provide the properties of the quaternion covariance matrix and the quaternion Fisher information matrix (FIM), paving the way for the derivation of the QCRLB. This serves as a basis for the formulation of the QCRLB without constraints and a criterion for determining whether the QCRLB is attained. We also establish the QCRLB for constrained quaternion parameters, including both nonsingular and singular cases of the quaternion FIM. These broaden the theoretical framework and enhance its applicability to diverse practical scenarios. The practical efficacy of the QCRLB is demonstrated through two illustrative examples. Numerical validations confirm that the maximum-likelihood estimator (MLE) attains the QCRLB for the linear model, and the quaternion gradient ascent (QGA) algorithm achieves the QCRLB at each iteration with theoretical guarantees. We also propose the quaternion constrained scoring (QCS) algorithm, which converges in one step in the linear constrained MLE case, for the linear model. These results significantly contribute to both the theory and practical application of quaternion signal processing, bringing valuable insights into the quaternion parameter estimation.

关键词： Quaternions Vectors signal processing Lower bound Calculus signal processing algorithms Covariance matrices Maximum likelihood estimation Three-dimensional displays Image color analysis Quaternion Cramer-Rao lower bound quaternion constrained Cramer-Rao lower bound quaternion Fisher information matrix quaternion parameter estimation GHR calculus

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Revisiting Frequency-Invariant Beamformer Design Using Weighted Spatial Response Variation

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IEEE signal processing LETTERS 2025年 32卷 991-995页

作者： Wang, Lingxin Feng, Congwei Chen, Huawei Nanjing Univ Aeronaut & Astronaut Coll Elect & Informat Engn Nanjing 210016 Peoples R China

The spatial response variation (SRV) is widely employed in frequency-invariant (FI) beamformer design, thanks to the fact that it provides more design degrees of freedom to achieve better FI performance. Recently, the weighted-SRV, a generalized form of SRV, was proposed for the FI beamformer design. It is shown that the weighted-SRV-based design outperforms the SRV-based design with mainlobe ripple and sidelobe level being able to be precisely controlled. However, the approximation error of reference beampattern in the weighted-SRV design may lead to slow convergence or even failure to converge. To address the problem, this paper reformulates the constrained weighted-SRV cost function into an unconstrained form. Under the reformulated cost function, the closed-form solutions of the weighted-SRV's weighting function are theoretically derived, and then an FI-beamformer design approach is proposed. Simulation results demonstrate the superior performance of the proposed approach.

关键词： Vectors Cost function Wideband Training Simulation signal processing algorithms Data mining Convergence Computational complexity Closed-form solutions Frequency-invariant beamformer wideband beamformer spatial response variation

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Hypothesis Perturbation for Active Learning

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IEEE JOURNAL OF SELECTED TOPICS IN signal processing 2025年第1期19卷 115-128页

作者： Cho, Seong Jin Kim, Gwangsu Yoo, Chang D. Korea Adv Inst Sci & Technol Sch Elect Engn Daejeon 34141 South Korea Korea Inst Oriental Med KM Sci Res Div Daejeon 34054 South Korea Jeonbuk Natl Univ Res Inst Mat & Energy Sci Dept Stat Jeonju 54896 South Korea

This paper introduces a computationally efficient Query-by-Committee (QBC) algorithm specifically designed for deep active learning. The algorithm leverages the concept of hypothesis perturbation (HP) to construct the committee. The conventional QBC algorithms often incur high computational costs due to the independent training required for each committee member. In contrast, the HP constructs the committee by strategically sampling hypotheses around a given hypothesis, and efficiently identifies data points located near the decision boundary of the current hypothesis. To quantify uncertainty, the algorithm leverages a novel metric termed disagreement in hypothesis perturbation (DHP). DHP quantifies the disagreement in predictions between the given hypothesis and its perturbed hypotheses. This metric effectively identifies data points with high uncertainty, making them ideal candidates for active learning. The effectiveness of the proposed DHP-based active learning algorithm is empirically validated through extensive experimentation. The results demonstrate that the algorithm consistently achieves superior performance compared to other established algorithms across various datasets and deep network architectures considered in the study.

关键词： Perturbation methods Complexity theory Uncertainty Training signal processing algorithms Measurement uncertainty Prediction algorithms Machine learning active learning uncertainty hypothesis perturbation version space

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Low Complexity and Mobility-Aware Robust Radio, Storage, Computing, and Cost Management for Cellular Vehicular Networks

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2025年第2期74卷 3327-3344页

作者： Abedi, Mohammad Reza Mokari, Nader Javan, Mohammad Reza Saeedi, Hamid Jorswieck, Eduard A. Zorba, Nizar Tarbiat Modares Univ ECE Dept Tehran 14115111 Iran Shahrood Univ Technol Fac Elect Engn Shahrood *** Iran Univ Doha Sci & Technol Coll Engn & Technol Doha 24449 Qatar TU Braunschweig Inst Commun Technol D-38106 Braunschweig Germany Qatar Univ Coll Engn Doha 2713 Qatar

In this paper, a novel two-time scale task offloading/delivery framework is presented which dynamically manages radio, storage, computing, and cost aspects through multiple Mobile Edge Computing (MEC) servers distributed across Road Side Units (RSUs), Base Stations (BSs), vehicles, and pedestrians. To enhance flexibility, we introduce a smart dynamic task partitioning and cooperative offloading/delivery mechanism, enabling users to offload task partitions to various MEC servers. Uncertainties stemming from users' high mobility and traffic variations may lead to unpredictable task offloading demands and Imperfect Channel State Information (I-CSI), potentially causing unsuccessful task offloading/delivery. In response, we propose a robust and cooperative two-time-scale task offloading/delivery approach, adept at handling demand uncertainty and I-CSI. The problem formulation involves a two-time scale Markov decision process, aimed at minimizing task offloading/delivery costs while maximizing task completion rates. Large time-scale slots incorporate intelligent RSU activation/deactivation, while short time-scale slots focus on task offloading/delivery. To efficiently implement this framework, we propose Federated Reinforcement Learning (FRL) algorithm based on Deep Deterministic Policy Gradient (DDPG);namely Low overhead Multi-Agent DDPG (LoMADDPG) where at each slot, all agents tune their Actor and Critic neural network weights with the help of Global Software-defined Networking (SDN) Controller (GSC) which acts as a global weight tuner. Simulation results illustrate that our proposed task offloading/delivery scheme can result in significant improvement in task completion rate and cost reduction.

关键词： Uncertainty Servers Resource management Optimization Costs Delays signal processing algorithms Machine learning algorithms Vehicle-to-everything Vehicle dynamics Mobile edge computing two-time scale task offloading/delivery RSU activation/deactivation demand and channel uncertainties task partitioning task migration

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On the Convergence of Decentralized Stochastic Gradient Descent With Biased Gradients

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IEEE TRANSACTIONS ON signal processing 2025年 73卷 549-558页

作者： Jiang, Yiming Kang, Helei Liu, Jinlan Xu, Dongpo Northeast Normal Univ Sch Math & Stat Key Lab Appl Stat MOE Changchun 130024 Peoples R China Changchun Normal Univ Dept Math Changchun 130032 Peoples R China

Stochastic optimization algorithms are widely used to solve large-scale machine learning problems. However, their theoretical analysis necessitates access to unbiased estimates of the true gradients. To address this issue, we perform a comprehensive convergence rate analysis of stochastic gradient descent (SGD) with biased gradients for decentralized optimization. In non-convex settings, we show that for decentralized SGD utilizing biased gradients, the gradient in expectation is bounded asymptotically at a rate of O(1/root nT+ n/T), and the bound is linearly correlated to the biased gradient gap. In particular, we can recover the convergence results in the unbiased stochastic gradient setting when the biased gradient gap is zero. Lastly, we provide empirical support for our theoretical findings through extensive numerical experiments.

关键词： Optimization Convergence signal processing algorithms Stochastic processes Machine learning Estimation Vectors Machine learning algorithms Costs Convex functions Decentralized optimization non-convex optimization biased stochastic gradient descent convergence

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Hybrid signal processing Framework Based on Second-Order Differentiation and Harmonic Superposition for Non-Contact Heart Rhythm Monitoring

Hybrid Signal Processing Framework Based on Second-Order Dif...

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IEEE MTT-S International Microwave Bio Conference ((IMBIOC)

作者： Syed Doha Uddin Christopher Williams Changzhi Li Electrical and Computer Engineering Texas Tech University Lubbock TX USA

ISBN: (数字)9798331510473

ISBN: (纸本)9798331510480

In this article, a novel method was proposed to extract heartbeat information based on a 2 nd order differential technique complemented by leveraging the elevated strong harmonics of heartbeat in frequency domain signal by superimposing their magnitude to the fundamental frequency. A theoretical analysis of the working principle of the algorithm has been provided, along with a simulation, to demonstrate the algorithm's advantage in the existence of strong respiration harmonics. An experimental analysis was conducted, and the accuracy achieved using the proposed method was 1.47 Bpm for five subjects with a mean average error of over two minutes of collected data.

关键词： Heart beat Frequency-domain analysis signal processing algorithms Radar detection Radar Harmonic analysis Microwave theory and techniques Radar signal processing Monitoring Surface treatment

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Toward TMA-Based Transmissive RIS Transceiver Enabled Downlink Communication Networks: A Consensus-ADMM Approach

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IEEE TRANSACTIONS ON COMMUNICATIONS 2025年第4期73卷 2832-2846页

作者： Li, Zhendong Chen, Wen Qin, Haoran Wu, Qingqing Zhu, Xusheng Zhang, Ziheng Li, Jun Shanghai Jiao Tong Univ Dept Elect Engn Shanghai 200240 Peoples R China Xi An Jiao Tong Univ Sch Informat & Commun Engn Xian 710049 Peoples R China Southeast Univ Sch Informat Sci & Engn Nanjing 210096 Peoples R China

This paper presents a novel multi-stream downlink communication system that utilizes a transmissive reconfigurable intelligent surface (RIS) transceiver. Specifically, we elaborate the downlink communication scheme using time-modulated array (TMA) technology, which enables high order modulation and multi-stream beamforming. Then, an optimization problem is formulated to maximize the minimum signal-to-interference-plus-noise ratio (SINR) with user fairness, which takes into account the constraint of the maximum available power for each transmissive element. Due to the non-convex nature of the formulated problem, finding optimal solution is challenging. To mitigate the complexity, we propose a linear-complexity beamforming algorithm based on consensus alternating direction method of multipliers (ADMM). Specifically, by introducing a set of auxiliary variables, the problem can be decomposed into multiple sub-problems that are amenable to parallel computation, where the each sub-problem can yield closed-form expressions, bringing a significant reduction in the computational complexity. The overall problem achieves convergence by iteratively addressing these sub-problems in an alternating manner. Finally, the convergence of the proposed algorithm and the impact of various parameter configurations on the system performance are validated through numerical simulations.

关键词： Transceivers Downlink Array signal processing Convergence Costs Streams Antenna feeds 6G mobile communication Transmitting antennas signal processing algorithms Transmissive reconfigurable intelligent surface (RIS) transceiver time-modulated array (TMA) linear-complexity beamforming consensus alternating direction method of multipliers (ADMM)

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Faulty Feeder Detection for Successive Single Phase-to-Ground Faults Based on Line Model Recognition and Correlation Comparison

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IEEE TRANSACTIONS ON POWER DELIVERY 2025年第2期40卷 750-763页

作者： Yuan, Jiawei Feng, Chuan Ji, Yueming Liu, Xintong Dong, Xuan Liu, Jun Jiao, Zaibin Xi An Jiao Tong Univ Sch Elect Engn Xian 710049 Peoples R China State Grid Henan Elect Power Res Inst Zhengzhou 450000 Peoples R China

When a single phase-to-ground (SPG) fault occurs in distribution networks, the over-voltages in non-fault phases may cause insulation damage to entire networks, potentially leading to a secondary SPG fault in feeders. Existing detection methods fail to explore the underlying mechanisms of SPG faults, resulting in unsatisfactory detection performance in practical applications. Moreover, they cannot identify the second faulty feeder under successive SPG (SSPG) faults, thereby increasing the risks of bushfires and casualties. This paper proposes a faulty-feeder detection method for SSPG faults based on line model recognition and correlation comparison. Firstly, the fault characteristics under SPG and SSPG faults are analyzed, revealing that differences in the equivalent line models are essential for distinguishing between faulty and healthy feeders. Secondly, the derivative of zero-sequence voltage reflecting the capacitance characteristics is compared with the measured zero-sequence currents from the perspectives of similarity and distance. The first faulty feeder is detected using cosine similarity comparison, while the second faulty feeder is identified using Euclidean distance comparison. Thirdly, a comprehensive detection criterion is constructed based on the cooperation of the similarity comparison method and distance comparison method. The feasibility and applicability are verified using various simulation data, field tests, and practical data tests.

关键词： Circuit faults Capacitance Feature extraction Fault diagnosis signal processing algorithms Voltage measurement Grounding Coils Capacitance measurement Transient analysis Correlation comparison equivalent model faulty-feeder detection line model recognition successive single-phase-to-ground faults

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