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Robust and Efficient Data Transmission over Noisy Communication Channels Using Stacked and Denoising Autoencoders

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China Communications 2019年第8期16卷 82-92页

作者： Faisal Nadeem Khan alan pak tao lau Department of Electrical Engineering The Hong Kong Polytechnic University

We study the effects of quantization and additive white Gaussian noise(AWGN) in transmitting latent representations of images over a noisy communication channel. The latent representations are obtained using autoencoders(AEs). We analyze image reconstruction and classification performance for different channel noise powers, latent vector sizes, and number of quantization bits used for the latent variables as well as AEs’ parameters. The results show that the digital transmission of latent representations using conventional AEs alone is extremely vulnerable to channel noise and quantization effects. We then propose a combination of basic AE and a denoising autoencoder(DAE) to denoise the corrupted latent vectors at the receiver. This approach demonstrates robustness against channel noise and quantization effects and enables a significant improvement in image reconstruction and classification performance particularly in adverse scenarios with high noise powers and significant quantization effects.

关键词： communication channels data compression deep learning autoencoders denoising autoencoders

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Theoretical analysis of PAM-N and M-QAM BER computation with single-sideband signal

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Science China(Information Sciences) 2021年第8期64卷 172-181页

作者： Dongxu LU Xian ZHOU Yuqiang YANG Jiahao HUO Jinhui YUAN Keping LONG Changyuan YU alan pak tao lau Chao LU Beijing Engineering and Technology Research Center for Convergence Networks and Ubiquitous Services University of Science and Technology Beijing Department of Electrical Engineering The Hong Kong Polytechnic University Department of Electronic and Information Engineering The Hong Kong Polytechnic University

In this paper, the theoretical bit error rate(BER) of N-level pulse amplitude modulation(PAMN)and M-ary quadrature amplitude modulation(M-QAM) have been studied and compared under different scenarios, including(i) PAM with intensity modulation with direct detection(IM/DD) and field modulation with detection(FMD)(including coherent detection and single-sideband modulation with direct detection(SSB-DD)), and(ii) QAM with coherent detection and SSB-DD. Considering the relationship between the symbol spacing and signal-to-noise ratio(SNR), we provide the mathematical BER equations, including the optical signal-to-noise ratio(OSNR) and carrier-to-signal power ratio(CSPR), especially for PAM *** verify the validity of our theoretical expressions for SSB systems, transmissions with 224-Gb/s SSBPAM4/16 QAM signals using the Kramers-Kronig(KK) receiver were implemented on a unified optical system platform. The simulation results agreed well with theoretical calculations both in back-to-back(BtB) and120-km transmission scenarios, which showed that the BER evaluation methods can serve as a theoretical guidance and system assessment criteria for SSB scenarios.

关键词： N-level pulse amplitude modulation(PAM-N) M-ary quadrature amplitude modulation(MQAM) BER computation single-sideband(SSB) Kramers-Kronig receiver

Decision-free radius-directed Kalman filter for universal polarization demultiplexing of square M-QAM and hybrid QAM signals

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Chinese Optics Letters 2016年第11期14卷 9-13页

作者：杨彦甫张群姚勇曹国亮 Kangping Zhong Xian Zhou alan pak tao lau Chao Lu Department of Electronic and Information Engineering Shenzhen Graduate SchoolHarbin Institute of Technology Photonics Research Center Department of Electrical EngineeringThe Hong Kong Polytechnic University Photonics Research Center Department of Electronic and Information EngineeringThe Hong Kong Polytechnic University

We propose and experimentally demonstrate a universal and blind polarization-state tracking scheme for M-quadrature amplitude modulation（QAM） signals based on a decision-free radius-directed linear Kalman filter（RD-LKF）.The polarization tracking performance is investigated through simulation and experiments for both quadrature phase-shift keying（QPSK） and 16-QAM *** influence of the filter parameters on the static polarization demultiplexing performance and dynamic tracking capability are discussed via *** optimization strategy of the filter parameters in modulation-format-independent scenarios is proposed and simulations are carried out to evaluate the polarization demultiplexing penalty for QPSK,16 QAM,and hybrid QPSK/16 QAM ***,the proposed decision-free RD-LKF is experimentally compared to the respective algorithms of constant modulus algorithm and multimodulus algorithm for QPSK and 16-QAM and the advantage of ultrafast polarization tracking ability is confirmed.

关键词： Coherent communications Metrological instrumentation

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Theoretical and numerical analyses for PDM-IM signals using Stokes vector receivers

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Science China(Information Sciences) 2020年第10期63卷 194-202页

作者： Jiahao HUO Xian ZHOU Chao SHANG Wei HUANGFU Jinhui YUAN Huansheng NING Keping LONG Changyuan YU alan pak tao lau Chao LU Beijing Engineering and Technology Research Center for Convergence Networks and Ubiquitous Services University of Science and Technology Beijing Department of Electronic and Information Engineering The Hong Kong Polytechnic University Key Laboratory of Luminescence and Optical Information Ministry of EducationInstitute of Optical InformationSchool of ScienceBeijing Jiaotong University Department of Electrical Engineering The Hong Kong Polytechnic University

Different from current coherent-detection-based long-haul transmission systems, inter-and intradatacenter transmissions require a simpler transmitter and receiver. A promising way to significantly meet the demands of datacenter transmission is polarization division multiplexing intensity modulation with direct detection(PDM-IM-DD) using a Stokes vector receiver(SVR). However, for different SVR architectures,the corresponding demultiplexing matrix is required to recover the Stokes vectors from the detected signals,which are combined with an arbitrary state of polarization(SOP), will change the effect of noise dynamically and significantly influence the system performance. In this study, PDM-IM signals using four SVRs,i.e., a 90? optical hybrid with 2 balanced photodetectors(BPDs) and 2 photodetectors(PDs), a 90? optical hybrid with 4 PDs, a Stokes analyzer and a 3×3 coupler with 4 PDs, are studied theoretically and numerically. Theoretical system models using the four SVRs are developed, and the noise power variations are analyzed quantitatively based on these models. Moreover, the performance of the systems is also investigated for 224 Gbit/s polarization division multiplexing pulse amplitude modulation 4 level with direct detection(PDM-PAM4-DD) transmission in a simulation. The simulation results show that the bit error rate(BER)performance of the systems is consistent with the theoretical noise power variation curves. The theoretical analysis scheme is helpful for the practical design of SVR-based systems.

关键词： short-reach optical communications PAM4 polarization division multiplexing Stokes vector direct detection

Performance comparison among three different Stokes vector direct-detection receivers

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Chinese Optics Letters 2018年第10期16卷 18-23页

作者：申晓杰霍佳皓周娴钟康平苑金辉涂佳静隆克平余长源刘伯涛吕超 Institute of Artificial Intelligence University of Science and Technology Beijing (USTB) Department of Electronic and Information Engineering The Hong Kong Polytechnic University MACOM Technology Solutions Department of Electrical Engineering The Hong Kong Polytechnic University

Stokes vectors direct detection（SV-DD） is an effective solution for short-reach optical communications. In this Letter, we investigate two-dimensional-modulation direct-detection systems based on three Stokes vector receivers（SVRs）. The influences of three key factors including the states-of-polarization（SOP）, the splitting ratio of the coupler, and the excess loss（EL） are studied in detail. It is shown that the splitting ratio for achieving optimum performance will be changed with SOP and EL conditions. Among these SVRs, the3 × 3 coupler-based receiver with its optimal splitting ratio shows the best bit error rate performance and stability against the change of SOP.

关键词： SC dBm Performance comparison among three different Stokes vector direct-detection receivers SOP PDM

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An efficient protocol of cryo-correlative light and electron microscopy for the study of neuronal synapses

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Biophysics Reports 2019年第3期5卷 111-122页

作者： Rong Sun Yun-tao Liu Chang-Lu tao Lei Qi pak-Ming lau Z.Hong Zhou Guo-Qiang Bi Center for Integrative Imaging Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences University of Science and Technology of China Chinese Academy of Sciences Key Laboratory of Brain Function and Disease University of Science and Technology of China The California Nano Systems Institute and Department of Microbiology Immunology and Molecular GeneticsUniversity of California Chinese Academy of Sciences Center for Excellence in Brain Science and Intelligence Technology University of Science and Technology of China

Cryo-electron tomography is an emerging electron microscopy technique for determining three-dimensional structures of cellular architectures near their native state at nanometer resolution, with a shortcoming of lack of specific labels. Fluorescence light microscopy, on the other hand, specifically visualizes target cellular and molecular components with fluorescent labels, but is limited to a resolution of tens to hundreds nanometers. Combining the advantages of the two techniques, we have developed a cryocorrelative light and electron microscopy system. Our system consists a custom-designed cryo-chamber that allows for fluorescence imaging of frozen-hydrated samples, and an algorithm to achieve accurate correlation. With this system and our optimized protocol, high-quality tomograms of neuronal synapses labelled by specific fluorescent tags in cultured hippocampal neurons are obtained at high efficiency.

关键词： Cryo-correlative light and electron microscopy Cryo-electron tomography Neuronal synapse

Mesophasic organization of GABAA receptors in hippocampal inhibitory synapse

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Mesophasic organization of GABAA receptors in hippocampal in...

第六届全国冷冻电子显微学与结构生物学专题研讨会

作者： Yun-tao LIU Chang-lu tao Xiao-kang ZHANG Lei QI Rong SUN pak-ming lau Z.hong ZHOU Guo-qiang BI Center for Integrative Imaging Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences University of Science and Technology of China School of Medicine and Center of Cryo-Electron Microscopy Zhejiang University The California NanoSystems Institute University of California Department of Microbiology Immunology and Molecular GeneticsUniversity of California CAS Center for Excellence in Brain Science and Intelligence Technology University of Science and Technology of China

Neurotransmitter receptors play pivotal roles in synaptic functions. However, the structure and organization of individual receptor molecules has not been observed in situ. Here, we identified and determined the structure of GABAAR in the inhibitory synapses of cultured hippocampal neurons by cryo electron tomography. The GABAARs form super-complexes with a fixed 11nm inter-receptor distance but variable relative angles. These super-complexes then form

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突触可塑性与脑疾病的神经发育基础

生命科学 2014年第6期26卷 583-592页

作者：陈伟恒陶长路时美玉张继川徐程刘北明毕国强中国科学技术大学生命科学学院合肥微尺度物质科学国家实验室集成影像中心昆明理工大学生命科学与技术学院中科院脑功能与脑疾病重点实验室

大脑神经回路高度有序的神经元活动是高级脑功能的基础,神经元之间的突触联结是神经回路的关键功能节点。神经突触根据神经元活动调整其传递效能的能力,亦即突触可塑性,被认为是神经回路发育和学习与记忆功能的基础。其异常则可能导致... 详细信息

大脑神经回路高度有序的神经元活动是高级脑功能的基础,神经元之间的突触联结是神经回路的关键功能节点。神经突触根据神经元活动调整其传递效能的能力,亦即突触可塑性,被认为是神经回路发育和学习与记忆功能的基础。其异常则可能导致如抑郁症和阿尔茨海默病等精神、神经疾病。将介绍这两种疾病与突触可塑性的关系,聚焦于相关分子和细胞机制以及新的研究、治疗手段等进展。

关键词：神经突触可塑性抑郁症阿尔茨海默病