浅谈第三代移动通信技术

移动通信技术自从兴起以来,因其满足了人们在任何时间、任何地点与任何个人进行通信的愿望，因此得到飞速的发展。与此同时，在信息支撑技术、市场竞争和需求的共同作用下,移动通信技术在短短的二三十年间，跨越式地发展。从传统的单基站大功率系统到蜂窝移动系统、卫星移动系统：从本地覆盖到全国覆盖，并实现了国内、国际漫游：从提供语音业务到提供包括数据的综合业务：从模拟移动通信系统到数字移动通信系统等，目前已经历了三代。     

GSM空中接口

GSM——泛欧数字蜂窝通信系统,是目前全球移动通信用户使用最多的系统。GSM数字蜂窝通信系统在整个系统中有多个接口,其中无线接口Um,即空中接口,是系统最重要的接口。     

一种实用的数字集群方案的研究

结合第二代移动通信系统GSM蜂窝网及陆地集群无线通信集群网提出了一种实用的数字集群移动通信方案．即采用TETRA系统的信源编解码和信道编解码技术，调制解调采用GsM蜂窝移动通信系统的GMSK技术，对国内成熟的模拟集群系统稍加改进，如将基带话音处理及载波调制数字化，就成为国内企业可批量生产的数字集群系统．并用硬件及软件对此方案进行了仿真，分析结果表明这是一种易于实现，性能良好的数字集群移动通信系统方案．     

CDMA数字蜂窝移动通信系统优化流程

研究了CDMA(Code division multiple access)数字蜂窝移动通信系统的优化、优化目标及优化过程。通过对系统的初始设计模拟、单一基站的初始优化、基站组有载条件下的网络优化数据采集、测试数据分析及优化方法的确定、系统参数的修改、检查优化效果并总结留档等问题的讨论，总结出一套基本的系统优化流程。该流程可作为CDMA数字蜂窝移动通信系统优化的一般流程或参考流程。     

移动通信技术的未来发展

１　概述移动通信始于蜂窝网（ｃｅｌｌｕｌａｒＮｅｔｗｏｒｋ），因而早年亦称蜂窝通信。蜂窝系统的观点由美国贝尔实验室于７０年代提出，它的提出是移动通信发展中的一次技术飞跃，它以小区的频率复用技术，克服了大区制频谱利用率低的缺点，真正解决了移动通信的广域覆盖和漫游问题。８０年代初，城市蜂窝网建成，蜂窝技术的发明标志着一个移动通信时代的到来，在短短十几年的时间内，移动通信无论在技术上，还是在业务量上都得到了巨大的发展。蜂窜网的发展过程，首先是模拟式过渡至数字式。早期应用的第一代蜂窝网是模拟电话式，以…     

浅议移动通信的起源及在我国我市的发展

1 移动通信的发展1．1移动通信的起源 移动通信的发展,可以追溯到本世纪20年代。这个时期主要完成通信实验和电波传输试验工作,在短波频段上实现了小容量专用移动通信系统,其话音质量差,自动化程度低,一般不能与公众网连接。1．2蜂窝理论的提出 蜂窝组网理论由美国贝尔实验室提出,是移动通信发展引发的构想,代表一种构造全新的网络系统。蜂窝组网的目的是解决常规移动通信系统频谱匮乏、容量小、服务质量差及频谱利用率低等问题,蜂窝组网理论等移动通信技术的发展为新一代多功能 设备的产生奠定了基础。蜂窝组网理论的要点如下： （…     

CDPD系统的切换机制研究

ＣＤＰＤ（ 蜂窝数字分组数据）系统的切换机制不同于模拟蜂窝通信系统和数字蜂窝通信系统。在研究了ＣＤＰＤ系统的无线资源管理规程（ＲＲＭＰ）、移动网络登记协议（ＭＮＲＰ） 和移动网络位置协议（ＭＮＬＰ）的基础上,对ＣＤＰＤ系统的切换机制和切换性能进行了深入的讨论,定量地分析了ＣＤＰＤ 系统的链路中断概率     

TDMA数字移动通信系统中MVA均衡器

ＴＤＭＡ数字移动通信系统中ＭＶＡ均衡器郭经红程时昕（东南大学移动通信国家重点实验室，南京２１００１８）ＧＳＭ数字蜂窝移动通信系统采用窄带时分多址（ＴＤＭＡ）传输方式．对于窄带ＴＤＭＡ系统来说，移动信道的多径效应会造成严重的符号间的干扰，必须采用均衡...     

数字移动通信中的关键技术

当前，随着大规模集成电路技术，计算机技术，片状元件及面安装工艺技术的发展，移动通信技术也得到了迅猛的发展，它是现代社会经济与技术高度发展的产物。体现当前移动通信技术最新水平的数字蜂窝移动通信技术得到迅速发展，使通信质量明显提高，业务种类增多，易于保密，也便于与ＩＳＤＮ，ＰＤＮ，ＰＳＴＮ等网络互联，对其主要技术在本文中作了一定的分析。     

当今的移动通信网络技术

十多年来,网络技术的发展经历了三代,即模拟时代(FDMA)、数字时代(TDMA)和CDMA时代。 第一代移动通信主要采用模拟技术,它的调制技术类似于调频广播,制式主要有AMPS、TACS,使用频分多址(FDMA)。模拟制式蜂窝移动电话系统出现于1979年,十多年间模拟移动通信技术获得了     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

正~~