检索结果-内蒙古大学图书馆

PAPR Reduction in All-optical OFDM Systems Based on Phase Pre-emphasis

Journal of Physics: Conference Series 2011年第1期276卷

作者： Zhou He Wei Li Zhiyong Tao Ji ng Shao Xiaojun Liang Zhuanhua Deng Dexiu Huang Wuhan National Lab for Optoelectronics Department of Optoelectronics Engineering Huazhong University of Science and Technology Wuhan 430074 P.R.China State Key Laboratory of Optical Communication Technologies and Networks Wuhan Research Institute of Posts and Telecommunications Wuhan 430074 P.R.China School of Computer Science and Technology Hubei University of Economics Wuhan 430205 P.R.China

This paper investigates the peak-to-average power ratio (PAPR) theory in all-optical orthogonal frequency division multiplexing (OFDM) optical fibre communication systems. We find out that phase pre-emphasis could effectively reduce PAPR in all-optical OFDM communication systems which employ intensity modulation-direct detection (IM-DD) method. An equation is developed and proposed to calculate suitable phasing values for pre-emphasis. Furthermore, we find out that phase pre-emphasis cannot reduce PAPR effectively in all-optical OFDM systems that employ Phase Shift Keying (PSK) or Quadracture Amplitude Modulation (QAM) method.

关键词：

来源：评论

学校读者我要写书评

暂无评论

XPM statistics in 100% pre-compensated WDM transmission for different modulation formats and transmission fibres

XPM statistics in 100% pre-compensated WDM transmission for ...

引用

2009 14th OptoElectronics and communications Conference, OECC 2009

作者： Fan, Zhang State Key Lab. of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

XPM statistics in 100% pre-compensated WDM transmission depends on bit rates, transmission fibres and modulation formats. XPM in DPSK systems shows much less stochastic than that in OOK systems. © 2009 IEEE.

ISBN: (纸本)9781424441037

关键词： Stochastic systems

来源：评论

学校读者我要写书评

暂无评论

Loss temporal dependency characteristic inference in wireless sensor network

引用

Journal of Computational Information Systems 2008年第5期4卷 2303-2308页

作者： Li, Yongjun Ji, Wenli Dai, Yafei Computer Networks and Distributed Systems Laboratory Peking University Beijing 100871 China School of Computer Science Northwestern Polytechnical University Xi'an 710072 China School of Communication Engineering Xi'an University of Science and Technology Xi'an 710075 China State Key Lab. for Adv. Opt. Commun Syst and Networks Beijing 1000871 China

The internal link loss characteristic inference has become an increasingly important issue for operating and evaluating a wireless sensor network. Due to the inherent stringent bandwidth and energy constraints, it is usually impractical to directly collect link loss statistical data from each node in sensor network. Here we consider the problem of inferring the internal link loss characteristics from end-to-end measurement. We use the Gilbert error model to model the sensor link losses, formulate the problem of link loss characteristics estimation as a Bayesian inference problem, and propose a Markov Chain Monte Carlo (MCMC) algorithm to solve it. The simulation shows that the link loss performance parameters can be inferred accurately, and the proposed algorithm scales well according to the sensor network size. © 2008 Binary Information Press.

关键词： Inference engines

来源：评论

学校读者我要写书评

暂无评论

Generation and transmission of 86 Gbit/s hybrid polarization-division multiplexed OOK/DPSK signal

Generation and transmission of 86 Gbit/s hybrid polarization...

引用

Optical Transmission, Switching, and Subsystems VI

作者： Wu, Lin Li, Mingjin Luo, Yazhi Zhang, Fan Chen, Zhangyuan Xu, Anshi State Key Lab. of Advanced Optical Communication Systems and Networks School of Electronic Engineering and Computer Science Peking University Beijing 100871 China

86 Gbit/s hybrid polarization multiplexed OOK/DPSK signal is generated and transmitted at the same wavelength. Clear eye diagrams of demultiplexed OOK and DPSK signals are obtained after transmission over a 106.5 km S... 详细信息

关键词： Amplitude shift keying

来源：评论

学校读者我要写书评

暂无评论

Loss cumulate generating function inference and application in wireless sensor network

引用

Journal of Computational Information Systems 2008年第4期4卷 1399-1407页

The internal link loss characteristic inference has become an increasingly important issue for operating and evaluating a wireless sensor network. Due to the inherent stringent bandwidth and energy constraints of sensors, it is usually impractical to directly monitor each node or link in wireless sensor network. We consider the problem of inferring the internal link loss characteristics from passive end-to-end measurement in this paper. Specifically, the link loss performance inference during the data aggregation is considered. Under the assumptions that the link losses are mutually independent, we elaborate a bias corrected link loss Cumulant Generating Function (CGF) algorithm. The simulation results show that the internal link loss CGF can be inferred accurately comparable to the sampled internal link loss CGF. At the end of this paper, we apply the result of internal link loss CGF inference to identify the lossy link in sensor network.

关键词： Sensor nodes

来源：评论

学校读者我要写书评

暂无评论

An all-normal-dispersion Yb-doped fiber laser without the spectral filtering

An all-normal-dispersion Yb-doped fiber laser without the sp...

引用

Advanced Solid-State Photonics, ASSP 2008

作者： Zhou, Chun Li, Peng Dai, Yongheng Zhang, Zhigang Institute of Quantum Electronics School of Electronics Engineering and Computer Science State Key Lab. of Advanced Optical Communication System and Networks University of Beijing 5 Yiheyuan Rd Beijing 100871 China

We demonstrated a simple all-normal-dispersion Yb-doped femtosecond fiber laser, which delivers a pulse with 8.9 nJ and 33 MHz. After the extracavity compression with a grating pair, the pulse was compressed to 210 fs... 详细信息

ISBN: (纸本)1557528500

关键词： Fiber lasers

来源：评论

学校读者我要写书评

暂无评论

Simultaneous transmission of high-speed point-to-point data and double broadcast services in a WDM-PON system with source-free ONUs

Simultaneous transmission of high-speed point-to-point data ...

引用

Optical Transmission, Switching, and Subsystems VI

作者： Chang, Qingjiang Huang, Mingfang Su, Yikai State Key Lab. of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University Shanghai 200240 China School of Electrical and Computer Engineering Georgia Institute of Technology GA 30332 United States

We propose that double broadcast services can be overlaid over high-speed point-to-point downlink data in a WDM-PON with source-free optical network units (ONUs). In the optical line terminal (OLT), a set of single-drive MachZehnder modulators (MZMs) are driven by downlink point-to-point data to generate a differential phase-shift keying (DPSK) format. The downlink DPSK signals from different wavelengths are multiplexed and then fed to a following dual-parallel MZM (DPMZM) as a double broadcast services transmitter. The broadcast service-l is an optical carrier suppression (OCS) format, while the broadcast service-2 is an inverse return-to-zero (IRZ) forma. After the transmission, at each ONU, the optical signals are separated by an optical filter. The filtered OCS signal is detected to retrieve the broadcast service-1. The DPSK/IRZ signals are split into three parts, one part is detected by an IRZ receiver to recover the broadcast service-2, the second part is detected by a DPSK receiver to retrieve the downlink data and the third part is re-modulated by the upstream amplitude shift keying (ASK). We also perform an experiment to verify the feasibility of the proposed scheme, where the power penalties of less than 1.5 dB are obtained after 25-km transmission with 1.25-Gb/s data rate. © 2008 SPIE.

关键词： Digital storage

来源：评论

学校读者我要写书评

暂无评论

Task scheduling and lightpath establishment in optical grids

Task scheduling and lightpath establishment in optical grids

引用

INFOCOM 2008: 27th IEEE communications Society Conference on computer communications

作者： Liu, Xin Wei, Wei Qiao, Chunming Wang, Ting Hu, Weisheng Guo, Wei Wu, Min-You Department of Computer Science and Engineering SUNY Buffalo NY 14260 United States NEC Laboratories America Princeton NJ 08540 United States State Key Lab. of Advanced Optical Communication Systems and Networks SJTU Shanghai 200030 China

ISBN: (纸本)9781424420261

Data-intensive Grid applications require huge data transferring between multiple geographically separated computing nodes where computing tasks are executed. For a future WDM network to efficiently support this type of emerging applications, traditional approaches to establishing lightpaths between given source destination pairs are not sufficient because a computing task may be executed on any one of several computing nodes having the necessary resources. Therefore, lightpath establishment has to be considered jointly with task scheduling to achieve best performance. In this paper, we study the optimization problems of jointly scheduling both computing resources and network resources. We first present the formulation of two optimization problems with the objectives being the minimization of the completion time of a job and minimization of the resource usage/cost to satisfy a job with a deadline respectively. When the objective is to minimize the completion time, we devise an optimal algorithm for a special type of applications. Furthermore, we propose efficient heuristics to deal with general applications with either optimization objective and demonstrate their good performances via simulation. © 2008 IEEE.

关键词： Optimization

来源：评论

学校读者我要写书评

暂无评论

Audio-Visual Speech Processing Framework for Lip Reading

Audio-Visual Speech Processing Framework for Lip Reading

引用

International Conference on Information and communication Technologies: From Theory to Applications, ICTTA

作者： Abdulbaset M. Nasr Abd Rahman Ramli Mohammad Hamiruce Shamala K Subramaniam Robotics Lab Institute of advanced technology Universiti Putra Malaysia Serdang Selangor Darul Ehsan Malaysia Department of Computer and Communications Systems Faculty of Engineering Universiti Putra Malaysia Serdang Selangor Darul Ehsan Malaysia Department of Electrical and Electronics Engineering Faculty of Engineering Universiti Putra Malaysia Serdang Selangor Darul Ehsan Malaysia Department of Communication Technology & Networks Faculty of Computer Science and Information Technology Universiti Putra Malaysia Serdang Selangor Darul Ehsan Malaysia

It is well known that speech production and perception process is inherently bimodal consisting of audio and visual components. Recently there has been increased interest in using the visual modality in combination with the acoustic modality for improved speech processing. This field of study has gained the title of audio-visual speech processing. Lip movement recognition, also known as lip reading, is a communication skill which involves the interpretation of lip movements in order to estimate some important parameters of the lips that include, but not limited to, size, shape and orientation. In this paper, we represent a hybrid framework for lip reading which is based on both audio and visual speech parameters extracted from a video stream of isolated spoken words. The proposed algorithm is self-tuned in the sense that it starts with an estimations of speech parameters based on visual lip features and then the coefficients of the algorithm are fine-tuned based on the extracted audio parameters. In the audio speech processing part, extracted audio features are used to generate a vector containing information of the speech phonemes. These information are used later to enhance the recognition and matching process. For lip feature extraction, we use a modified version of the method used by F. Huang and T. Chen for tracking of multiple faces. This method is based on statistical color modeling and the deformable template. The experiments based on the proposed framework showed interesting results in recognition of isolated words.

关键词： Speech processing Image processing Parameter estimation Data mining Feature extraction Robots computer networks Systems engineering and theory communications technology computer science

来源：评论

学校读者我要写书评

暂无评论

Rotation sensing based on a slow-light resonating structure with high group dispersion

Rotation sensing based on a slow-light resonating structure ...

引用

作者： Chao, Peng Zhengbin, Li Anshi, Xu Natl. Lab. on Local Fiber-Optic Communication Networks and Advanced Optical Communication Systems School of Electronics Engineering and Computer Science Peking University Peking 100871 China

The concept of the Sagnac effect in a slow-light medium and resonator structure with a high group dispersion is investigated. It is found that a slow-light medium can be utilized for relative motion sensing, and a slow-light resonator structure is suitable to detect absolute rotation for navigation purposes. It is noted that the high group dispersion leads to a huge enhancement of the rotation sensor's sensitivity in a resonating structure, and an approach to evaluate and design resonator devices with slow-light property is proposed. Moreover, a folded loop-lattice-based structure is numerically simulated to verify the concept. © 2007 Optical Society of America.

关键词： Resonators

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：