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Time-Domain Traveling Wave Model of Single-Section Quantum Dot Mode-Locked Lasers with Optical Feedback

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Journal of Harbin Institute of Technology(New Series) 2021年第3期28卷 45-52页

作者： Xuefang Xiao Zewang Zhang Xiupu Zhang School of Opto-electronic and Communication Engineering Xiamen University of TechnologyXiamen 361024FujianChina Key Laboratory of Communication Network and Information Processing in Fujian Province Xiamen 361024FujianChina Photonics Labs. Department of Electrical and Computer EngineeringConcordia UniversityMontreal QC H3G 1M8Canada

The optical feedback modulations of a passively mode-locked semiconductor laser with quantum dot structure were investigated in this study. The delay-induced dynamics of QD MLL under the condition of optical feedback have been studied by exploiting a time domain traveling wave(TDTW) model. The conventional TDTW model was improved to make it suitable for studying optical feedback system, especially the system with long external cavity structure. Combing the TDTW model with optical feedback and carrier rate equations, the pulse variation of a single section QD MLL was studied. This new model shows good agreement with the published experimental data. The roundtrip time and local light intensity modulation to the pulse evolution of QD MLL were studied. The results show that when the time for a light to go to and return from external cavity is equal to the integral times of the period of laser pulse without external feedback, resonance will be formed, and the period of pulse sequence is the shortest. The results also show that the stronger the local light intensity modulation is, the shorter the pulse period is.

关键词： quantum dot structure passively mode-locked laser optical feedback

Integrating Sensing, Communication, and Computation in the Sky

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Integrating Sensing, Communication, and Computation in the S...

International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Yao Tang Guangxu Zhu Wei Xu Man Hon Cheung Tat-Ming Lok Shuguang Cui Department of Information Engineering The Chinese University of Hong Kong Hong Kong Shenzhen Research Institute of Big Data Shenzhen China Peng Cheng Laboratory Shenzhen China National Mobile Communications Research Lab Southeast University Nanjing China Department of Computer Science City University of Hong Kong Hong Kong School of Science and Engineering (SSE) Future Network of Intelligence Institute (FNii) The Chinese University of Hong Kong (Shenzhen) Shenzhen China

Unmanned Aerial Vehicle (UAV)-mounted edge devices are particularly advantageous for federated edge learning (FEEL) due to their flexibility and mobility in efficient data collection. In UAV-assisted FEEL, sensing, computation, and communication are coupled and compete for limited onboard resources, and UAV deployment also affects sensing and communication performance. Therefore, the joint design of UAV deployment and resource allocation is crucial to achieving the optimal training performance. In this paper, we address the problem of joint UAV deployment design and resource allocation for FEEL via a concrete case study of human motion recognition based on wireless sensing. Due to the nonideal sensing channels, we consider the probabilistic sensing model. Then, we derive the upper bound of the FEEL training loss as a function of the sensing probability. We formulate a training time minimization problem by jointly optimizing UAV deployment, integrated sensing, computation, and communication (ISCC) resources under a desirable optimality gap constraint. To solve this challenging mixed-integer non-convex problem, we propose our algorithm based on the alternating optimization technique. Simulation results demonstrate that our algorithm outperforms other baselines regarding convergence rate and testing accuracy.

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Performance Optimization for Intelligent Reflecting Surface Assisted Multicast MIMO networks

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Performance Optimization for Intelligent Reflecting Surface ...

GLOBECOM 2022 - 2022 IEEE Global Communications Conference

作者： Songling Zhang Zhaohui Yang Mingzhe Chen Danpu Liu Kai-Kit Wong H. Vincent Poor Beijing Laboratory of Advanced Information Network Beijing University of Posts and Telecommunications Beijing China Zhejiang University Hangzhou China Zhejiang Lab Hangzhou China Department of Electrical and Computer Engineering and Institute for Data Science and Computing University of Miami Coral Gables FL USA Department of Electronic and Electrical Engineering University College London London UK Department of Electrical and Computer Engineering Princeton University Princeton NJ USA

ISBN: (纸本)9781665435413

In this paper, the problem of maximizing the sum rate of all users in an intelligent reflecting surface (IRS)-assisted millimeter wave multicast multiple-input multiple-output communication system is studied. In the considered model, one IRS is deployed to assist the communication from a multi-antenna base station (BS) to the multi-antenna users that are clustered into several groups. Our goal is to maximize the sum rate of all users by jointly optimizing the transmit beamforming matrices of the BS, the receive beamforming matrices of the users, and the phase shifts of the IRS. To solve this non-convex problem, we first use a block diagonalization method to represent the beamforming matrices of the BS and the users by the phase shifts of the IRS. Then, substituting the expressions of the beamforming matrices of the BS and the users, the original sum-rate maximization problem can be transformed into a problem that only needs to optimize the phase shifts of the IRS. To solve the transformed problem, a manifold method is used. Simulation results show that the proposed scheme can achieve up to 13.3 % gain in terms of the sum rate of all users compared to the algorithm that optimizes the hybrid beamforming matrices of the BS and the users using our proposed scheme and randomly determines the phase shifts of the IRS.

关键词： Manifolds Multicast algorithms Array signal processing Surface waves Simulation Performance gain Matrices

A Microwave Photonic Multiple Frequency System with Tunable Frequency Multiplication Factor of 3-10 19

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A Microwave Photonic Multiple Frequency System with Tunable ...

19th International Conference on Optical Communications and networks, ICOCN 2021

作者： Chen, Zhijia Yin, Feifei Wan, Xin Dai, Yitang Xu, Kun State Key Laboratory of Information Photonics and Optical Communication Department of Electronic Engineering Beijing University of Posts and Telecommunications 100876 China National Computer Network Emergency Response Technical Team Coordination Center of China Beijing100029 China

ISBN: (纸本)9781665424462

A microwave photonic system with a tunable frequency multiplication factor of 3-10 is theoretically analyzed and simulated. The system mainly consists of three dual-parallel Mach-Zehnder modulators (DPMZM). With the use of programmable filter, a fixed-order optical sideband can be accurately obtained as a carrier for secondary modulation. By adjusting the parameters such as the direct current (DC) bias voltage and the radio frequency (RF) drive voltage of each DPMZM in the system, microwave signals with a frequency multiplication factor of 3-10 can be generated. The simulation results show that when the frequency of RF signal is 10GHz, microwave signals with frequencies of 30, 40, 50, 60, 70, 80, 90, 100GHz can be generated with an unwanted harmonic suppression ratio of 20dB. During the frequency multiplication process, the overlap of the signal in the frequency domain is well avoided because of combining an optical programmable filter. In addition, the process of multi-frequency signal generation is theoretically derived, and the effects of several non-ideal factors on the radio frequency spurious suppression ratio (RFSSR) are analyzed. © 2021 IEEE.

关键词： Microwave photonics

A Secure Beamforming Design: When Fluid Antenna Meets NOMA

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arXiv 2024年

作者： Mai, Lifeng Yao, Junteng Tang, Jie Wu, Tuo Wong, Kai-Kit Shin, Hyundong Adachi, Fumiyuki The Electric Power Research Institute China Southern Power Grid Guangzhou510663 China The Guangdong Provincial Key Laboratory of Power System Network Security Guangdong Guangzhou China The Faculty of Electrical Engineering and Computer Science Ningbo University Ningbo315211 China The School of Electronic and Information Engineering South China University of Technology Guangzhou510006 China The School of Electrical and Electronic Engineering Nanyang Technological University 639798 Singapore The Department of Electronic and Electrical Engineering University College London Torrington Place WC1E 7JE United Kingdom The Department of Electronic Engineering Kyung Hee University Gyeonggi-do Yongin-si17104 Korea Republic of Tohoku University Sendai Japan

This letter proposes a secure beamforming design for downlink non-orthogonal multiple access (NOMA) systems utilizing fluid antenna systems (FAS). We consider a setup where a base station (BS) with M fluid antennas (FAs) communicates to a cell-center user (CU) and a cell-edge user (CEU), each with a FA. The CU is the intended recipient while the CEU is regarded as a potential eavesdropper. Our aim is to maximize the achievable secrecy rate by jointly optimizing the secure beamforming vectors and the positions of FAs. To tackle this, we adopt an alternating optimization (AO) algorithm that optimizes secure beamforming and the positions of the FAs iteratively while keeping the other variables fixed. Numerical results illustrate that when FAs meet NOMA, the proposed scheme greatly enhances the secrecy rate compared to conventional multiple-input single-output (MISO) fixed antenna NOMA systems and other benchmark schemes. © 2024, CC BY.

关键词： Beamforming

Implementation and evaluation of the school's COVID-19 prevention website

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Library Hi Tech 2022年第1期41卷 71-90页

作者： Jui-Hung Chang Chi-Jane Wang Hua-Xu Zhong Pei-Wen Chen Ai-Jou Pan Po-Sheng Chiu Department of Computer Science and Information Engineering National Cheng Kung University Tainan Taiwan Department of Computer and Network Center National Cheng Kung University Tainan Taiwan Department of Nursing National Cheng Kung University Tainan Taiwan National Cheng Kung University Tainan Taiwan Department of E-learning Design and Management National Chiayi University Chiayi Taiwan

Purpose The purpose of this study is to investigate the effects of the Perceptions of coronavirus 2019 (COVID-19) questionnaire and the Information System Success Questionnaire on students when using the school's COVID-19 epidemic prevention website. The study is aimed toward analyzing both questionnaires as well as evaluating an epidemic prevention website. Design/methodology/approach The school's COVID-19 prevention website and two questionnaires (Perceptions of COVID-19 and the Information System Success Questionnaire) are examined in order to investigate 73 students' COVID-19 perceptions. An open-ended question was used as the qualitative data to support quantitative data and evaluate a university's COVID-19 epidemic prevention website from a southern university in Taiwan. Findings The findings indicated that most students evaluated the school's COVID-19 website positively and were satisfied. In the open-ended questions, the majority of students rated the quality of the system positively and the need to fix some defects. Students have different COVID-19 perceptions and social distance compliance based on their current situations. Practical implications This study provides researchers and website developers a broader understanding of the construction of the school's COVID-19 prevention website and a better understanding of student's COVID-19 perceptions. Originality/value To the best of the authors' knowledge, this is the first study examining a school's epidemic prevention website, which is measured by the Information Success Questionnaire and the Perceptions of COVID-19 Questionnaire for college students.

关键词： COVID-19 Epidemic prevention website Evaluation Implementation Perception

To Make Yourself Invisible with Adversarial Semantic Contours

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arXiv 2023年

作者： Zhang, Yichi Zhu, Zijian Su, Hang Zhu, Jun Zheng, Shibao He, Yuan Xue, Hui Department of Computer Science and Technology Institute for Artificial Intelligence THBI Lab Tsinghua University Beijing100084 China Institute of Image Communication and Network Engineering Shanghai Jiao Tong University Shanghai200240 China Alibaba Group Hangzhou311121 China

Modern object detectors are vulnerable to adversarial examples, which may bring risks to real-world applications. The sparse attack is an important task which, compared with the popular adversarial perturbation on the whole image, needs to select the potential pixels that is generally regularized by an 0-norm constraint, and simultaneously optimize the corresponding texture. The non-differentiability of 0 norm brings challenges and many works on attacking object detection adopted manually-designed patterns to address them, which are meaningless and independent of objects, and therefore lead to relatively poor attack performance. In this paper, we propose Adversarial Semantic Contour (ASC), an MAP estimate of a Bayesian formulation of sparse attack with a deceived prior of object contour. The object contour prior effectively reduces the search space of pixel selection and improves the attack by introducing more semantic bias. Extensive experiments demonstrate that ASC can corrupt the prediction of 9 modern detectors with different architectures (e.g., one-stage, two-stage and Transformer) by modifying fewer than 5% of the pixels of the object area in COCO in white-box scenario and around 10% of those in black-box scenario. We further extend the attack to datasets for autonomous driving systems to verify the effectiveness. We conclude with cautions about contour being the common weakness of object detectors with various architecture and the care needed in applying them in safety-sensitive scenarios. © 2023, CC BY.

关键词： Semantics

SGDA: Towards 3D Universal Pulmonary Nodule Detection via Slice Grouped Domain Attention

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arXiv 2023年

作者： Xu, Rui Liu, Zhi Luo, Yong Hu, Han Shen, Li Du, Bo Kuang, Kaiming Yang, Jiancheng The School of Computer Science National Engineering Research Center for Multimedia Software Institute of Artificial Intelligence Hubei Key Laboratory of Multimedia and Network Communication Engineering Wuhan University Hubei Luojia Laboratory Wuhan China The Department of Computer and Network Engineering The University of Electro-Communications 1-5-1 Chofugaoka Chofushi Tokyo182-8585 Japan The School of Information and Electronics Beijing Insititute of Technology Beijing100081 China The JD Explore Academy Beijing China The Dianei Technology Shanghai200120 China The Shanghai Jiao Tong University Shanghai China Dianei Technology Shanghai China EPFL Lausanne Switzerland

Lung cancer is the leading cause of cancer death worldwide. The best solution for lung cancer is to diagnose the pulmonary nodules in the early stage, which is usually accomplished with the aid of thoracic computed tomography (CT). As deep learning thrives, convolutional neural networks (CNNs) have been introduced into pulmonary nodule detection to help doctors in this labor-intensive task and demonstrated to be very effective. However, the current pulmonary nodule detection methods are usually domain-specific, and cannot satisfy the requirement of working in diverse real-world scenarios. To address this issue, we propose a slice grouped domain attention (SGDA) module to enhance the generalization capability of the pulmonary nodule detection networks. This attention module works in the axial, coronal, and sagittal directions. In each direction, we divide the input feature into groups, and for each group, we utilize a universal adapter bank to capture the feature subspaces of the domains spanned by all pulmonary nodule datasets. Then the bank outputs are combined from the perspective of domain to modulate the input group. Extensive experiments demonstrate that SGDA enables substantially better multi-domain pulmonary nodule detection performance compared with the state-of-the-art multi-domain learning methods. © 2023, CC BY.

关键词： Convolutional neural networks

Energy Consumption Minimization in Secure Multi-antenna UAV-assisted MEC networks with Channel Uncertainty

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arXiv 2023年

作者： Mao, Weihao Xiong, Ke Lu, Yang Fan, Pingyi Ding, Zhiguo The Engineering Research Center of Network Management Technology for High Speed Railway Ministry of Education School of Computer and Information Technology Beijing Jiaotong University Beijing100044 China The Beijing National Research Center for Information Science and Technology The Department of Electronic Engineering Tsinghua University Beijing100084 China The School of Electrical and Electronic Engineering The University of Manchester ManchesterM13 9PL United Kingdom

This paper investigates the robust and secure task transmission and computation scheme in multi-antenna unmanned aerial vehicle (UAV)-assisted mobile edge computing (MEC) networks, where the UAV is dual-function, i.e., aerial MEC and aerial relay. The channel uncertainty is considered during information offloading and downloading. An energy consumption minimization problem is formulated under some constraints including users’ quality of service and information security requirements and the UAV’s trajectory’s causality, by jointly optimizing the CPU frequency, the offloading time, the beamforming vectors, the artificial noise and the trajectory of the UAV, as well as the CPU frequency, the offloading time and the transmission power of each user. To solve the non-convex problem, a reformulated problem is first derived by a series of convex reformation methods, i.e., semi-definite relaxation, S-Procedure and first-order approximation, and then, solved by a proposed successive convex approximation (SCA)-based algorithm. The convergence performance and computational complexity of the proposed algorithm are analyzed. Numerical results demonstrate that the proposed scheme outperform existing benchmark schemes. Besides, the proposed SCA-based algorithm is superior to traditional alternative optimization-based algorithm. © 2023, CC BY.

关键词： Energy utilization