数字程控交换机与专网中的多媒体通信

本文以一个多媒体通信应用VISIT为实例,介绍了多媒体通信在数字程控交换机及专网中的应用情况。     

Approximate and Exact Small Signal Analysis for Single-Mode Fiber Near Zero Dispersion Wavelength with Higher Order Dispersion

This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies.     

通信用VRLA蓄电池可靠性指标及计算探讨

在说明通信局（站）电源系统对VRLA蓄电池组可靠性要求的基础上，阐述了为了达到电信设备的电压、电流需求，通过串联或串并联构成电池组的单体VRLA蓄电池应达到的可靠性指标。在确定单体VRLA蓄电池应达到的可靠性指标。在确定单体VRLA蓄电池可靠性参数时，可通过现场使用调查或加速寿命试验的办法来求得。在单体VRLA蓄电池可靠性指标过低的情况下，可通过多种冗余连接方式来提高电池组的可靠性。     

非常规突发事件下应急通信预案体系有效性评估研究

非常规突发事件下，应急通信是实施指挥调度和保障信息传递的关键，其重要的前提和基础是应急通信预案体系的合理、有效。基于此，本文在对国内外应急通信预案体系做大量理论和实践调研的基础上，科学界定“有效性”内涵，从预案体系“效率”和“效果”两个维度切入对其进行研究，为应急通信预案“有效性”的评估提供相应的参考，为政府相关部门制定应急管理政策提供决策依据。     

Time behavior of stressed nonhierarchical networks

In this paper it is shown, by means of simulation, that interesting time behavior is observed for damaged and overloaded networks, and that adaptive, decentralized intelligence can have a dramatic influence on the overall network performance. The time behavior of nonhierarchical networks is modeled by a system of nonlinear difference equations among global variables, and bistability is shown to exist. Using a simple adaptive control mechanism, it is shown that, depending upon the value of a certain network variable, either limit cycle or steady state behavior results. A few ideas are discussed for applications of nonhierarchical communications to cellular automata and to decision-making systems.     

电信管理网中的安全问题

在国际电联(ITU)提出的电信管理网(TMN)信息结构和功能体系结构基础上,探讨电信管理网所面临的安全问题。     

SMA同轴封装高速光电探测器

采用自制ＳＭＡ同轴管壳和普通ＴＯ－１８管壳对同型同批的ＩｎＧａＡｓＰＩＮ光电探测器芯片进行了封装，并用自建测试系统对其Ｃ－Ｖ特性和瞬态特性进行了测试比较，结果表明：与普通ＴＯ－１８管壳封装相比，ＳＭＡ同轴管壳封装器件电容减少了约０．４ｐＦ，上升时间ｔｒ由８５ｐｓ减至２５ｐｓ以下，半高全宽ＦＷＨＭ由２１０ｐｓ减至８５ｐｓ，等效－３ｄＢ带宽增至６ＧＨｚ以上，瞬态特性显著改善。     

对我国通信技术创新发展的思考

经过多年努力,我国通信业取得长足发展,在大多数领域已具备了生产世界先进产品的能力,部分企业拥有了较强的技术研发能力。但与世界先进水平相比,仍存在一定差距,技术创新势在必行。对各国通信技术发展与创新历程进行了总结,初步提出我国通信技术创新体系框架,以及技术创新过程中应把握的几个关键点。     

High Altitude Platform Station (HAPS): A Review of New Infrastructure Development for Future Wireless Communications

This paper looks into the relatively new field of high altitude platform stations. HAPS is seen as a ‘middle ground’ between the terrestrial and satellite cases, and aims to exploit of the advantages of both types of system. Since HAPS is such a new field, this paper focuses on the technology behind a HAPS communications system, how this has developed, and compares it to the terrestrial and satellite equivalents. One important area that is being investigated is the applications for which HAPS should be used. This is a critical issue if a significant business case is to be made for HAPS. Worldwide HAPS projects and research issues are also highlighted. Finally, the review concludes with the remarks on the future of HAPS for wireless communications systems.     

第三代移动通信经营权角逐的背后

目前，全球对第三代移动通信（３Ｇ）经营权的争夺已硝烟四起，各国已拍卖或即将拍卖的每张３Ｇ的经营执照都达到几十亿美元之多。各大通信公司出重金购买３Ｇ经营执照主要基于：３Ｇ的技术性能优势、自身的生存需要和巨额的赢利预期。３Ｇ经营权的争夺说明全球电信市场的开放实际上只是对少数实力雄厚的大公司的开发，各国的移动通信市场不可避免地被少数几家垄断寡头所控制，中国以此必须作出积极的反应。