Generation, detection and characterization of optical minimum shift keying data format

This paper presents the detailed principle on the generation and detection of optical minimum shift keying (MSK) format for high-speed and high spectral efficiency WDM systems. 10.7 Gb/s optical MSK data is successfully generated by experiment using the proposed scheme. The results show that optical MSK signal exhibits very compact optical spectrum, which is promising for high spectral efficiency WDM applications. Simulation results on dispersion and nonlinear tolerance comparison confirm that MSK signal has better dispersion tolerance and nonlinear tolerance compared with 50% duty cycle return-to-zero differential phase shift keying (RZ-DPSK) and 50% duty cycle RZ on-off-keying (RZ-OOK) formats.     

基于临近空间的目标探测及宽带通信

临近空间是未来军事装备体系发展的一个重要领域。在区域性应用中具有组网灵活、快速机动、定点不间断持续侦察和性价比高等优势。介绍了国内外对临近空间及临近空间飞行器的开发和研制情况,给出了基于临近空间的目标探测模式。通过论述平流层通讯体制,探讨了利用宽带数据链和多数据链融合技术构建临近空间传感器网络以支持协同探测的技术途径。     

Modeling of waveguide UV-induced Bragg gratings with arbitrary apodization function: Tools for designing high-performance related devices

We present a semi-analytical modeling suitable for the investigation of the spectral characteristics of UV-waveguide Bragg gratings (UV-WBGs) having arbitrary apodization function and extending both in the film layer and in the overlayer. The modeling is based on a proper combination of coupled mode theory and transfer matrix formalism and provides a powerful tool for designing and simulation of complex UV-grating based structures. The results of a detailed investigation of UV-WBGs in doped silica based channel optical waveguides are presented and critical issues for upgrading the performances of related device are discussed. Validation of the modeling is provided by means of an extensive comparison between theoretical and experimental results relevant to UV-WBGs realized in phosphorous (P)- and boron (B)-doped silica based waveguides.     

基于多载波的宽带无线接入策略的研究

呼叫接入控制是无线通信中保证用户服务质量的关键技术之一。本文提出了一种在多业务环境下,基于多载波通信的优先强占接入策略:当剩余无线资源不能接纳实时业务的呼叫时,实时业务呼叫强占部分非实时业务占用的子载波来保证实时业务的接入,与此同时增加了非实时业务的传输时延。本文通过二维Markov链模型对系统进行了建模和性能参数(呼叫阻塞概率及系统频带利用率)的求解。通过与保护信道策略和无优先策略的比较可以看到:优先强占策略将接入控制和服务质量保证有机地结合在一起,既保证了用户的QoS,又大大降低了系统中的实时业务用户的呼叫阻塞概率,提高了系统资源的利用率。     

Comparing the streaming of FGS encoded video at different aggregation levels: frame,GoP, and scene

Fine granularity scalability (FGS), a new coding technique that has recently been added to the MPEG‐4 video coding standard, allows for the flexible scaling of each individual video frame at very fine granularity. This flexibility makes FGS video very well suited for rate‐distortion optimized streaming mechanisms, which minimize the distortion (i.e. maximize the quality) of the streamed video by transmitting the optimal number of bits for each individual frame. The per‐frame optimization of the transmission schedule, however, puts a significant computational burden on video servers and intermediate streaming gateways. In this paper we investigate the rate‐distortion optimized streaming at different video frame aggregation levels. We find that compared to the optimization for each individual video frame, optimization at the level of video scenes reduces the computational effort dramatically, while reducing the video quality only very slightly. Copyright © 2005 John Wiley & Sons, Ltd.     

未来电磁频谱管理对信息通信技术的需求分析

无线电通信的高速发展,使频谱使用越来越广泛,频谱资源日益紧张,为使有限的频谱资源发挥更大的价值,一方面依赖于无线通信技术的进步,开发出频谱利用率更高的应用系统,另一方面要加强频谱的科学管理,将行政管理和科学技术紧密结合。信息通信技术在过去的50年中发展迅速,大量研究证实信息通信技术在管理创新和决策活动中的作用非常明显。文章针对电磁频谱管理技术手段的发展,对信息通信技术的需求做相关分析。     

全球移动卫星系统投资风险分析

在人们普遍给予全球移动通信系统高技术高效益评价的同时，其高投入高成本所带来的高负险也是不容忽视的。根据市场竞争的观点它同样面临着行为内和行业外多种力量的竞争。特别是近年来地面无线通信的迅速发展对该产业的怅惘敢巨大冲击。     

Single-mode fused coupler for undersea optical transmission systems

A single mode 3 dB fused coupler, to be used as a redundant laser combiner in the submerged repeater of an undersea optical fibre transmission system, is described. The fabrication and package design of the component for this high reliability application is discussed, and the results of a wide range of environmental tests are given.     

Diversity-and-multiplexing tradeoff and throughput of superposition coding relaying strategy

While the Network Coding cooperative relaying (NC-relaying) has the merit of high spectral ef-ficiency, Superposition Coding relaying (SC-relaying) has the merit of high throughput. In this paper, a novel concept, coded cooperative relaying, is presented, which is a unified scheme of the NC-relaying and SC-relaying. For the SC-relaying strategy which can be considered one-way coded relaying scheme with multi-access channel, the close-form solution of the outage probabilities of the basic signal and additional signal are obtained firstly. Secondly, the Diversity-and-Multiplexing Tradeoff (DMT) characteristics of ba-sic signal and additional signal are investigated entirely as well as the optimal close-form solutions. The compared numerical analysis shows the evaluation error of throughput based on the close-form solution is about 0.15 nats, which is within the acceptable error range. Due to the mutual effect between the both source signals, the available maximal values of the two multiplexing gains are less than 1.