英文原文
RESEARCH OF CELLULAR WIRELESS
COMMUNATION SYSTEM
Abstract
Cellular communication systems allow a large number ofmobile usersto seamlessly and simultaneously communicate to wireless modemsat fixed basestations usingalimited amount of radio frequency (RF) spectrum.TheRFtransmissions received at the base stations from each mobile are translatedtobaseband, or to a wideband microwave link, and relayed to mobile switchingcenters(MSC), which connect the mobile transmissions with the Public SwitchedTelephoneNetwork (PSTN). Similarly, communications from the PSTN are sentto the basestation, where they are transmitted to the mobile. Cellular systemsemploy eitherfrequency division multiple access (FDMA), time division multipleaccess (TDMA),code division multiple access (CDMA), or spatial division multipleaccess (SDMA).
1 Introduction
A wide variety of wireless communication systems have been developed toprovideaccess to the communications infrastructure for mobile or fixed users in a myriadof operating environments. Most of today’s wireless systems are based on thecellularradio concept. Cellular communication systems allow a large number ofmobile usersto seamlessly and simultaneously communicate to wireless modemsat fixed basestations usingalimited amount of radio frequency (RF) spectrum.TheRFtransmissions received at the base stations from each mobile are translatedtobaseband, or to a wideband microwave link, and relayed to mobile switchingcenters(MSC), which connect the mobile transmissions with the Public SwitchedTelephoneNetwork (PSTN). Similarly, communications from the PSTN are sentto the basestation, where they are transmitted to the mobile. Cellular systemsemploy eitherfrequency division multiple access (FDMA), time division multipleaccess (TDMA),code division multiple access (CDMA), or spatial division multipleaccess (SDMA) .
Wireless communication links experience hostile physical channel
characteristics,such as time-varying multipath and shadowing due to large objects in thepropagationpath. In addition, the performance of wireless cellular systems tendsto be limited by interference from other users, and for that reason, it is importantto have accuratetechniques for modeling interference. These complex channel conditionsare difficult to describe with a simple analytical model, although severalmodels do provideanalytical tractability with reasonable agreement to measuredchannel data . However, even when the channel is modeled in an analyticallyelegant manner, in thevast majority of situations it is still difficult or impossibleto construct analytical solutions for link performance when error control coding,equalization, diversity, and network models are factored into the link model. Simulationapproaches, therefore, are usually required when analyzing the performanceof cellular communication links.
Like wireless links, the system performance of a cellular radio system is mosteffectivelymodeled using simulation, due to the difficulty in modeling a large numberof random events over time and space. These random events, such as the locationofusers, the number of simultaneous users in the system, the propagation conditions,interference and power level settings of each user, and the traffic demandsof each user,combine together to impact the overall performance seen by a typicaluser in thecellular system. The aforementioned variables are just a small samplingof the many key physical mechanisms that dictate the instantaneous performanceof a particular user at any time within the system. The term cellular radio system,therefore, refers to the entire population of mobile users and base stationsthroughout the geographicservice area, as opposed to a single link that connects asingle mobile user to a single base station. To design for a particular system-levelperformance, such as thelikelihood of a particular user having acceptable servicethroughout the system, it is necessary to consider the complexity of multiple usersthat are simultaneously usingthe system throughout the coverage area. Thus, simulationis needed to consider the multi-user effects upon any of the individual linksbetween the mobile and the basestation.
The link performance is asmall-scale phenomenon, which deals with theinstantaneouschanges in the channel over a small local area, or small time duration,
overwhich the average received power is assumed constant .Such assumptions aresensible in the design of error control codes, equalizers, and other components thatserve to mitigate the transient effects created by the channel. However, in order todetermine the overall system performance of a large number of users spread over awide geographic area, it is necessary to incorporate large-scale effects such as thestatistical behavior of interference and signal levels experienced by individual usersover large distances, while ignoring the transient channel characteristics. One maythink of link-level simulation as being a vernier adjustment on the performance ofacommunication system, and the system-level simulation as being a coarse, yetimportant, approximation of the overall level of quality that any user could expectat any time.
Cellular systems achieve high capacity (e.g., serve a large number of users) byallowingthe mobile stations to share, or reuse a communication channel in differentregions of the geographic service area. Channel reuse leads to co-channel interferenceamong users sharing the same channel, which is recognized as one of themajorlimiting factors of performance and capacity of a cellular system. An appropriateunderstanding of the effects of co-channel interference on the capacity andperformance is therefore required when deploying cellular systems, or when analyzingand designing system methodologies that mitigate the undesired effects ofco-channelinterference. These effects are strongly dependent on system aspects ofthecommunication system, such as the number of users sharing the channel andtheirlocations. Other aspects, more related to the propagation channel, such aspath loss,shadow fading (or shadowing), and antenna radiation patterns are alsoimportant in thecontext of system performance, since these effects also vary withthe locations ofparticular users. In this chapter, we will discuss the application ofsystem-levelsimulation in the analysis of the performance of a cellular communicationsystem under the effects of co-channel interference. We will analyze a simplemultiple-usercellular system, including the antenna and propagation effects of atypical system.Despite the simplicity of the example system considered in thischapter, the analysispresented can easily be extended to include other features ofa
cellular system.
2 Cellular Radio System
System-Level Description：
Cellular systems provide wireless coverage over a geographic service area by dividingthe geographic area into segments called cells as shown in Figure 2-1. Theavailable frequency spectrum is also divided into a number of channels with a groupof channels assigned to each cell. Base stations located in each cell are equippedwith wireless modems that can communicate with mobile users. Radio frequencychannels used in the transmission direction from the base station to the mobile arereferred to as forward channels, while channels used in the direction from the mobileto the base station are referred to as reverse channels. The forward and reversechannels together identify a duplex cellular channel.When frequency divisionduplex(FDD) is used, the forward and reverse channels are split in frequency. Alternatively,when time division duplex (TDD) is used, the forward and reverse channelsare on the same frequency, but use different time slots for transmission.
Figure 2-1 Basic architecture of a cellular communications system
High-capacity cellular systems employ frequency reuse among cells. This requiresthat co-channel cells (cells sharing the same frequency) are sufficiently farapart from each other to mitigate co-channel interference. Channel reuse is implementedby covering the geographic service area with clusters of N cells, as shownin Figure 2-2, where N is known as the cluster size.
Figure 2-2 Cell clustering:Depiction of a three-cell reuse pattern The RF spectrum available for the geographic service area is assigned to eachcluster, such that cells within a cluster do not share any cha nnel . If Mchannelsmake up the entire spectrum available for the service area, and if the distribution ofusers is uniform over the service area, then each cell is assigned M/N channels. Asthe clusters are replicated over the service area, the reuse of channels leads to tiers ofco-channel cells, and co-channel interference will result from the propagation of RFenergy between co-channel base stations and mobile users. Co-channel interferencein a cellular system occurs when, for example, a mobile simultaneously receivessignals from the base station in its own cell, as well as from co-channel base stationsin nearby cells from adjacent tiers. In this instance, one co-channel forward link(base station tomobile transmission) is the desired signal, and the other co-channelsignals received by the mobile form the total co-channel interference at the receiver.The power level ofthe co-channel interference is closely related to the separationdistances among co-channel cells. If we model the cells with a hexagonal shape, asin Figure 2-2, the minimum distance between the center of two co-channel cells,called the reuse distance N
D, is
（2-1）
3
D N N
R
where R is the maximum radius of the cell (the hexagon is inscribed within theradius). Therefore, we can immediately see from Figure 2-2 that a small clustersize (smallreuse distance N
D), leads to high interference among co-channel cells.
The level of co-channel interference received within a given cell is also dependenton the number of active co-channel cells at any instant of time. As mentioned before,co-channel cells are grouped into tiers with respect to a particular cell of interest.Thenumber of co-channel cells in a given tier depends on the tier order and thegeometryadopted to represent the shape of a cell (e.g., the coverage area of anindividual base station). For the classic hexagonal shape, the closest co-channelcells are located in the first tier and there are six co-channel cells. The secondtier consists of 12 co-channelcells, the third, 18, and so on. The total co-channelinterference is, therefore, the sumof the co-channel interference signals transmittedfrom all co-channel cells of all tiers. However, co-channel cells belonging to the firsttier have a stronger influence on the total interference, since they are closer to thecell where the interference is measured.
Co-channel interference is recognized as one of the major factors that limitsthecapacity and link quality of a wireless communications system and plays animportant role in the tradeoff between system capacity (large-scale system issue)and link quality(small-scale issue). For example, one approach for achieving highcapacity (largenumber of users), without increasing the bandwidth of the RF spectrumallocated to the system, is to reduce the channel reuse distance by reducingthe cluster size N of a cellular system.However, reduction in the clustersizeincreasesco-channel interference, which degrades the link quality.
The level of interference within a cellular system at any time is random and mustbesimulated by modeling both the RF propagation environment between cells andtheposition location of the mobile users. In addition, the traffic statistics of eachuser andthe type of channel allocation scheme at the base stations determine theinstantaneous interference level and the capacity of the system.
The effects of co-channel interference can be estimated by the signal-tointerferenceratio (SIR) of the communication link, defined as the ratio of
thepower of the desiredsignal S, to the power of the total interference signal, I. Sinceboth power levels S andI are random variables due to RF propagation effects, usermobility and traffic variation, the SIR is also a random variable. Co nsequently , theseverity of the effects of co-channel interference on system performance is frequentlyanalyzed in terms ofthe system outage probability , defined in this particular caseas the probability that SIR is below a given threshold 0SIR . This is
dx p ]SIR Pr[SIR P )x 0
SIR 0SIR 0outpage （?=<=（2-2）
Whereis the probability density function (pdf) of the SIR. Note the distinctionbetween the definition of a link outage probability, that classifies an outagebased on aparticular bit error rate (BER) or Eb/N0 threshold for acceptable voice performance, and the system outage probability that considers a particular SIR threshold for acceptable mobile performance of a typical user.
Analytical approaches for estimating the outage probability in a cellular system,
as discussed in before, require tractable models for the RF propagation effects, user mobility , and traffic variation, in order to obtain an expression for . Unfortunately, it is very difficult to use analytical models for these effects, due to their complex relationship to the received signal level. Therefore, the estimation of the outage probability in a cellular system usually relies on simulation, which offers flexibility in the analysis. In this chapter, we present a simple example of a simulation of a cellular communication system, with the emphasis on the system aspects of the communication system, including multi-user performance, traffic engineering, and channel reuse. In order to conduct a system-level simulation, a number of aspects of the individual communication links must be considered. These include the channel model, the antenna radiation pattern, and the relationship between Eb/N0 (e.g., the SIR) and the acceptable performance.
SIR(x)p SIR(x)p
英文论文审稿意见汇总 1、目标和结果不清晰。 It is no ted that your manu script n eeds careful edit ing by some one with expertise in technical English editing paying particular attention to English grammar, spelling, and sentence structure so that the goals and results of the study are clear to the reader. 2、未解释研究方法或解释不充分。 In general, there is a lack of explanation of replicates and statistical me thods used in the study. . Furthermore, an expla natio n of why the authors did these various experime nts should be provided. 3、对于研究设计的ratio nale: Also, there are few expla nati ons of the rati on ale for the study desig n. 4、夸张地陈述结论/夸大成果/不严谨： The con clusi ons are overstated. For example, the study did not show if the side effects from initial copper burst can be avoid with the polymer formulation.
Unconsciously, English songs and culture the door English elective course is approaching the end. Class see show students and the teacher introduce, played all kinds of English songs, let me develop the horizon and edify sentiment, at the same time, I have been thinking, so much is there any contact between songs, through access to information and personal perception of the songs, and draw some conclusion. The singers found that originated in the human inner original impulse, from the need of life rhythm. People have been using your own voice show their feelings, joy and sorrow. Overall, as a kind of human achievement, music is not only an individual creation consciousness performance art, also reflects some areas and even the whole social cultural ideological trend. To provide an overview of the development of western music, also confirm the western culture on context. Can say, a western music history, it is also a certain sense of western cultural history. From century religious music to a single to the liberation of the Renaissance, to modern music multiple that music development deeply branded with the background of The Times. Take for modern music, such as The s Bill Haley - Rock Around The Clock is in The twentieth century since The two world wars to The people of The world brought serious disaster, trample on The human spirit home. People no longer believe that traditional culture ideal type to save power, pop songs and jazz free rhythm, improvisation skills to reflect the birth of the. But in The s: Simon &garfunkel - The sound of silence is The opposition to The Vietnam war, against racial discrimination, President Kennedy was stabbed The troubled times of The United States was born in The rock. The 90 s Alan Jackson - where were you when the world stopped turning embodies the teenagers in war haze shrouded of anger, rebel emotion. So the western music is a cultural symbol, its carrying cultural connotation and social culture constitutes the echo relationship, to better understanding of western music, will have a better understanding of music background.
通信工程导论 论文题目 院系 专业 班级 学号 学生姓名 联系方式 年月 摘要 通信工程专业与信息的联系是密不可分的。信息是可以描述的客观现象，且具有一定物理含义的消息或知识，信息是可以用数值、文字、声音、图像等形式描述的状态，信息是用数据作为载体来描述和表达的客观现象，信息是对数据加工提炼的结果，是对人类有用的知识，信息是隐含在物理信号中具有一定含义的消息，信号处理的目的是为了从信号中获取有用的知识。信息技术的内涵包括传感，通信和计算机。主要分为两类：一类是管理信息系统；另一类是指面对自然科学领域的工程。 关键词：通信，技术，系统，光纤、数字微波、卫星、移动、3G、4G、CDMA 引言 在经过李老师的精彩讲解之后，我对通信工程专业有了更加清晰的认识，了解了通信专业的发展，我国目前通信产业的现状以及未来发展的方向。使我对自己未来大学四年的规划，目标更加明确。其中老师主要介绍了通信行业的发展趋势、通信系统的组成、通信工程专业的培养目标、通信工程专业的课程体系还有
与我们息息相关的生活方面的建议、简单说说毕业后的去向。在此表示衷心感谢！在科技发展如此迅速的今天，通信业在社会中占据着不可替代的地位，各种各样的信息每天都在变换着。何谓信息？不知道有多少人知道。从古老的结绳记事，烽火传烟，飞鸽传书，到当前的手机，网络，电话等等通信方式，人们的通信方式发生了翻天覆地的变化，变的更加方便，快捷，舒适，给人类的沟通带来了无与伦比的便捷，缩短了时空的距离，提高了沟通的效率，为经济发展全球化铺上了高速通道。可以说通信方式的发展促进了时代的进步，当然这离不开科技的发展，更重要的是离不开一门专业——通信工程的发展。合肥学院独具特色的第二课堂管理体系，使我校的办学能力不断的提升，下面将进行介绍。胡国华老师对我们通信工程专业的发展及就业方向、发展前景也进行了详细的介绍。下面我将给大家详细介绍。 目录 一、引子： (1) 二、通信工程的含义： (1) 三、通信工程专业的培养目标： (3) “平台+模块”形式的课程体系： (3) 四个平台+ 三个方向： (4) 四个平台 (4) （1）通识基础教育平台； (4) 三个方向 (4) 四、通信工程专业发展趋势和毕业生去向： (5) 光纤通信发展前景 (5) 无线通信发展前景 (5) 就业现状: (6) 就业前景: (6) 五、通信工程实验室建设背景： (7) 2、通信工程实训中心实验室建设内容 (7) 六、开设的实训项目 (7)
Acknowledgements I would like to express my gratitude to all those who helped me during the writing of this thesis. I gratefully acknowledge the help of my supervisor, Ms. Han Lin, who has offered me valuable suggestions in the academic studies and whose useful suggestions, incisive comments and constructive criticism have contributed greatly to the completion of this thesis. In the preparation of the thesis, her willingness to give me her time so generously has been much appreciated. Her tremendous assistance in developing the framework for analysis and in having gone through the draft versions of this thesis several times as well as her great care in life deserve more thanks than I can find words to express. Truly, without her painstaking efforts in revising and polishing my drafts, the completion of the present thesis would not have been possible. I do appreciate her patience, encouragement, and professional instructions during my thesis writing. She devotes a considerable portion of her time to reading my manuscripts and making suggestions for further revisions. I am also greatly indebted to all my teachers in Foreign Language School of Shaanxi University of Technology who have helped me directly and indirectly in my studies, from whose devoted teaching and enlightening lectures I have benefited a lot and academically prepared for the thesis. Any progress that I have made is the result of their profound concern and selfless devotion. Last but not the least, my gratitude also extends to my family who have been assisting, supporting and caring for me all of my life. Special thanks should go to my friends who have put considerable time and effort into their comments on the draft. I also owe my sincere gratitude to my fellow classmates who have given me the warm help and precious time to work out my problems during the tough course of the thesis.
原创性声明 （黑体、小2号、加粗、居中）（段前为0.5行、段后为0.5行） □□本人呈交的毕业论文，是在导师的指导下，独立进行研究工作所取得的成果，所有数据、图片资料真实可靠。尽我所知，除文中已经注明引用的内容外，本毕业论文的研究成果不包含他人享有著作权的内容。对本论文所涉及的研究工作做出贡献的其他个人和集体，均已在文中以明确的方式标明。本毕业论文的知识产权归属于培养单位。 （宋体小4号） 本人签名：（手签）日期：
摘□□要 （黑体小2 居中）（段前为0.5行、段后为0.5行） 《德伯家的苔丝》是19世纪英国批判现实主义小说家托马斯·哈代的代表作。哈代将其与其他几部作品一并归类于“性格与环境的小说”。以前对他的文学批评多以人物本身以及当时社会的人物构建为中心，采用马克思主义、消费主义和女性这一理论基础进行分析，本文将采用生态批评理论分析苔丝的悲剧成因。哈代认为社会转型期内的历史性的巨变不是进步，反而代表着失望和遗憾。工业革命和现代化的生活方式都导致女性逐步的脱离自然。在哈代的写作生涯中,他对人与自然、男性和女性的关系一直给予高度关注，他认为自然和人类是紧密相连的,自然是女性生存的沃土而女性则是自然的化身,女性和自然在经验与体验上都是相统一的,她们的命运也是相辅相成的,所以生态批评主义者倡导建构生态和谐的社会。不仅使大自然摆脱被剥削的命运,也激发人们对于日益严重的环境危机的生态保护意识。本文利用生态批评主义文学理论, 并通过文献综述法，从男性与女性关系和人类与自然关系两方面来揭示哈代《德伯家的苔丝》中苔丝的悲剧根源。通过揭示苔丝悲剧的根本所在不仅能够警示读者认识到人类文明进步是以对自然环境的破坏为代价的，而且使人类意识到保护自然环境，与自然和谐相处的重要性。 (宋体小4，1.5倍行距 ) 中间无标点符号 关键词：生态批评主义□苔丝悲剧根源□女性和自然□和谐 （黑体4）（宋体小4） （所有文本页边距：上边距为25mm，下边距为20mm，左边距为25mm，右边距为20mm） 顺序为:中英文摘要、中英文目录、这四页页码为罗马数字
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通信工程导论论文 细心的你是否留意到，十年前港台电影中黑帮大佬手里可以用来砸人的“大哥大”，早已变得如此纤细轻巧、色彩缤纷，并且飞入寻常百姓之手；从前只有数月飞鸽传书才能联系的国外亲友可以用简单方便快捷的伊妹儿（E-mail）互致问候、即时聊天，甚至装上摄像头开个网络会议！这一切都应该归功于通信工程（Communication Engineering）技术的迅猛发展。如果让科学家们选出近十年来发展速度最快的技术，恐怕也是非通信技术莫属。那么让我们来多了解一下这个年轻而又略显“神奇”的专业吧。 1.通信工程专业简介： 1988年，教育部本科专业调整正式命名了通信工程（Communication Engineering）专业，并定义了该专业学习和研究的内容，涉及通信技术、各种媒体处理、通信系统与通信网以及各种信息的传输、储存、变换、处理、检测与显示技术与系统等。 通信工程（Communication?Engineering）专业是信息科学技术发展迅速并极具活力的一个领域，尤其是数字移动通信、光纤通信、Internet网络通信使人们在传递信息和获得信息方面达到了前所未有的便捷程度。通信工程具有极广阔的发展前景，也是人才严重短缺的专业之一。本专业学习通信技术、通信系统和通信网等方面的知识，能在通信领域中从事研究、设计、制造、运营及在国民经济各部门和国防工业中从事开发、应用通信技术与设备。毕业后可从事无线通信、电视、大规模集成电路、智能仪器及应用电子技术领域的研究，设计和通信工程
附件一： 英语专业毕业论文格式要求 一、论文组成 本科毕业论文（设计）（以下简称为毕业论文）由封面、成绩评定表、内容摘要、关键词、目录、正文、参考文献、附录等八部分组成。毕业论文装订按以下顺序进行：封面、成绩评定表、中文内容摘要、英文内容摘要、目录、正文、注释、参考文献、附录。（每位学生定稿论文，按统一要求装订1份）。 二、排版与字体 毕业论文的文字图形一律从左至右横写横排。文字一律通栏编辑。字迹必须清楚，忌用异体字、复合字及一切不规范的简化字。除非必要，不要使用繁体字。 毕业论文文字、标点必须符合出版要求。正文标题为小二号粗黑体；正文内第一级标题用三号黑体，居中上下空一行；第二级标题用小三号黑体，靠左空两个字符，上下空一行；第三级标题用四号黑体，靠左空两个字符，不空行；正文用小四号宋体，行距为固定值20磅；图题及图中文字原则上用五号宋体。 中文“内容摘要”标题四字用三号粗黑体，其正文用四号宋体。英文内容摘要即“Abstract”标题词用三号Times New Roman字体加粗，其正文用Times New Roman四号。中英文摘要正文均以空两格格式开始行文。中文的“关键词”和英文的“Key words”分别用黑体四号和Times New Roman四号，并加粗左对齐。正文分别用四号宋体和四号Times New Roman。中文“内容摘要”正文要求300个汉字以内。英文内容摘要（“Abstract”）正文要求300个英文词左右。 注释和参考文献标题用粗三号，居中上下空一行。中文注释和参考文献正文用五号宋体。英文注释和参考文献正文用Times New Roman五号。 毕业论文中的英文均采用Times New Roman字体，其字体号与其相应的部分（注：正文、注释等）一致。注意文中代表变量的英文
扉页（英文） CulturalFactorsinChinese&EnglishProverbs Translation （TimesNewRoman二号加粗居中） by LiHairong WangZhiyun,Tutor （TimesNewRoman小二居中） RegisteredNo.09 FacultyofForeignLanguages Shanghai Business School December,2011 （TimesNewRoman小二） 论文摘要（英文）及关键词 Abstract （TimesNewRoman二号，加粗，居中） Proverbsreflectcolorfulnationalculturein（TimesNewRoman四号）…………………………………………………………………………………….…………………………………………………………………………………………………………………………………………………………........................... .....………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… （空一行） Keywords:proverbs;translation;culture;differences（TimesNewRoman四号） 说明： 1．关键词3-5个，词与词之间用分号隔开，除专有名词外，其他单词首字母不大写，最后一个词后面无标点符号。 2．“摘要”下空一行写摘要内容，摘要内容与关键词之间空一行。
The full-length novel Gone With The Wind, has been translated into more than thirty languages, and the bestseller for a long time in the world. Why could it’s charm last in such a long time? The reason mostly relied on it’s distinctive female characters---Scarlett, Melanie, Mammy and Belle Watling. 一．Scarlett O’Hara <一> Personality changes 1.Pre-war A. adolescent romantic B. simple capricious 2. Post-war A. strong persistent B. reality rational 3. Revelations to moderns A. in terms of workplace a. abreast of the times b. self-confidence B. in terms of interpersonal a. self-image b. unique personality <二> Views on marriage 1.Material view of marriage A. purpose B. just to be obtained not with pay 2.Revelations to moderns A. marriage is not a transaction B. balance in marriage <三> character full of contradictory and complexity 1.selfish---responsible 2.blind pursuit of love---casually take advantage of marriage 3.feminist consciousness---effect of Patriarchal society 一．Melanie Hamilton Wilkes <一> personality traits（the ordinary perfect） 1.ordinary---outside 2.perfect---intrinsic A. fraternity B. tolerant
通信工程专业导论 结课论文 论文名称通信的发展史 所在学院信息工程学院 专业通信工程 班级 学号 姓名 授课教师 时间 2017/1/3
世界移动通信发展史 关键词通信的发展趋势5G将采用华为力挺的Polar 摘要现代移动通信技术的发展始于本世纪20年代，大致经历了五个发展阶段。 1 .概述与总体趋势 移动通信可以说从无线电通信发明之日就产生了。1897年，M·G·马可尼所完成的无线通信试验就是在固定站与一艘拖船之间进行的，距离为18海里。 现代移动通信技术的发展始于本世纪20年代，大致经历了五个发展阶段。 第一阶段从本世纪20年代至40年代，为早期发展阶段。在这期间，首先在短波几个频段上开发出专用移动通信系统，其代表是美国底特律市警察使用的车载无线电系统。该系统工作频率为2MHz，到40年代提高到30～40MHz,可以认为这个阶段是现代移动通信的起步阶段，特点是专用系统开发，工作频率较低。 第二阶段从40年代中期至60年代初期。在此期间内，公用移动通信业务开始问世。1946年，根据美国联邦通信委员会(FCC)的计划，贝尔系统在圣路易斯城建立了世界上第一个公用汽车电话网，称为“城市系统”。当时使用三个频道，间隔为120kHz，通信方式为单工，随后，西德(1950年)、法国(1956年)、英国(1959年)等国相继研制了公用移动电话系统。美国贝尔实验室完成了人工交换系统的接续问题。这一阶段的特点是从专用移动网向公用移动网过渡，接续方式为人工，网的容量较小。 第三阶段从60年代中期至70年代中期。在此期间，美国推出了改进型移动电话系统(IMTS)，使用150MHz和450MHz频段，采用大区制、中小容量，实现了无线频道自动选择并能够自动接续到公用电话网。德国也推出了具有相同技术水平的B网。可以说，这一阶段是移动通信系统改进与完善的阶段，其特点是采用大区制、中小容量，使用450MHz频段，实现了自动选频与自动接续。
英语论文选题 英语语言学 1. A Study of Adverbs in Legal English 2.Linguistic Features of Legal English 3.On Cultural Context in Legal English Articles 4.Sources of Chinese and English Legal Terms 5.Characteristics of Legal Terms 6.Functions of Languages in Legislation 7.Killing and its Hyponyms in Legal English 8.Punctuation in Legal English: for instance, comma, period, colon, etc. 9.Abbreviations in Legal English 10.Transitional Words in Legal English 11.The Application of the Fuzzy Words in Legal English法律语言模糊性词语的运用 12.The Differences of the Legal Discourse in Chinese and English英汉法律语篇的结构差异 13.On Abbreviations in Business English谈经贸英语中的缩略语现象 14.On the Multi-discipline of the Economic English V ocabulary论经济英语语汇的多学科性 15.On the Features of Business English Letters浅谈外经贸英语信函的写作特点 16.Adjusting the Tone in International Business English经贸英语缓和口吻表达方法探究 17.The Stylistic Features of the Contract English协议、合同英语的文体特点 18.On Modifiers of Nouns in English for Foreign Economy & Trade略谈外经贸英语中的名词 修饰语 19.The Negative and Active Function of Fuzzy Language in Business Writing论模糊语言在经 贸英语写作中的作用 20.The Application of PP (Polite Principle) in Business English Communication 21.CP（Cooperative Principle）and Business English Interpretation 22.Sexism as Reflected in the Chinese and English Languages 23.Lexical Items as Means of Cohesion in English Texts 24.Remarks on Modern American Slang 25.Stylistic Comparison Between Broadcast News and Newspaper News 26.News Headlines: Their Features and Style 27.A Comparative Study of English and Chinese Prepositions
成绩 Root and Affixation of Lexicology Abstract: It’s important and permanent to master the vocabulary in the English learning. Everyone who has ever set foot on English realizes that it’s somewhat incredible for us to reciting numerous and difficult words. Nevertheless, there are some skills we should acquire to make word-recitation easier and more effective. This paper mainly discusses the using of vocabulary root and affix. Only by having a good knowledge of the roots and affixes, can we prosper our English vocabulary and further our English study. Key words: root; affixation; detailed analysis; difficult words 1Introduction: Blindly reciting numerous and difficult words is a total waste of time and energy. Especially, situation becomes worse for the college students with little words storage and non-interest. However, most of the English words are comprised with roots and affixes, which are limited, stable and short. If we acquire them, it will be much simpler and rapider for us to recognize the unfamiliar and difficult words through the analysis on roots and affixes. If we can master and know how to use them properly, it will be a big step for the further study of this foreign language. A road of a thousand miles begins with each single step, so does the English words. Now we are going to learn the root and affixation respectively. Definition is the basic form of a word which cannot be further analyzed without total loss of identity and it carries the main component of meaning in a word. By learning the roots, we will find it not complicated for us to understand the long and difficult words which we often encounter in the tough reading test. However long and tough the word is, we can divide it into several parts, the fundamental part is the root and then we can understand what it means and fluently blurt it out without repeating it. Here are some detail analyses of the examples: Internationalist: nation is the root which means country or state, inter- is prefix meaning between or interactive, -al is the suffix and the –ist is the suffix meaning the person. So you will quite simply find its meaning. Invigorate: the root is vigor similar to power and energy, in- means making sth have the function of verb, here is make sth vigor, -ate is the verb suffix. So invigorate is to make sth vigorous. Antecedent: -ced- is the root referring to motion or going forward, ante- is before, and –ent means somebody. So antecedent is somebody who moves ahead of us, the same as forefather or ancestor. Protract: -tract is the root like pulling sth or extending sth make it wider or longer, pro- is the prefix meaning “ahead”. After analyzing this word, we know that “protract” is similar to prolong meaning make sth longer or longer to live. A lot of words contain this root, such as detract, extract, subtract, attract, tractable, intractable, etc. Arbitrariness: arbitrary is the root indicating to randomness or out of order, -ness is the noun suffix. The profound meaning of learning roots is that you will find it much easy to memorize words because there are so many word share the same root. No matter how long and hoe difficult the word is, the basic meaning of the word is stable and unchangeable. If we recite words according the
江西工业工程职业技术学院 通信概论论文 通信101 指导老师肖军 目录 摘要--------------------------------------1 第一章对通信概论的认识-----------------2 第二章对通信专业的了解------------------6 第三章对通信专业的规划-----------------11 摘要 随着计算机技术的广泛普及与计算机远程信息处理应用的发展，数据通信应运而生，它实现了计算机与计算机之间，计算机与终端之间的传递。由于不同业务需求的变化及通信技术的发展使得数据通信经过了不同的发展历程。 首先说明无线移动通信与有线固定通信一同快速发展的趋势；然后 着重讲述无线动通信蜂窝网从模拟至数字和即将进入第三代系统的快速发展历程和今后趋向；最后简单说明无线卫星通信微波通信也要加快步伐继续向前发展，以发挥重要作用。无线移动通信与有线固定通信一同发展 人们常把有线固定通信和无线移动通信作为信息基础结构（NII/GII）的两大组成部分。近年来它们都以明显的快速步伐向前推进，而且进入新世纪后将更加快速发展，为兴旺的信息时代作出贡献。传统的有线固定通信网是“公用交换电话网”PSTN（Public Switched Telephone Network），长期来一直保持平稳扩大建设，促使人们普遍装用固定终端的电话机。但是，自90年代中期起，国际互联网Internet兴起，使全世界的传统通信网受到前所未有的巨大冲击。广大的通信用户开始普遍装用计算机，数据通信的业务量每年急剧上涨，其增长率远远超过传统电话的每年增长率。按照这样的势头，进入新世纪后的五年左右，全世界的数据信息业务量总数将追上电话信息业务量总数，而且以后超过的越来越多。因此未来的通信传送网将是以数据信息为重点的分组交换网（Packet Switching），并且承担电话通信的传送，不再利用原有的电路交换（ Circuit Switching），但仍保证电话特有的业务质量（QoS）指标。随着计算机技术改进和功能加多，数据通信将延伸至包含音频、视频信息配合的多媒体通信。这样，未来的有线固定通信网，将能承担所有信息业务传送的统一通信网，必将是大容量通信网。 第一章对通信概论的认识 所谓通信，最简单的理解，也是最基本的理解，就是人与人沟通的方法。无论是现在的电话，还是网络，解决的最基本的问题，实际还是人与人的沟通。现代通信技术，就是随着科技的不断发展，如何采用最新的技术来不断优化通信的各种方式，让人与人的沟通变得更为便捷，
英文版论文致谢六篇 英文版论文致谢篇一 First of all, I would like to extend my sincere gratitude to my supervisor, Zhang Hong, for her instructive advice and useful suggestions on my thesis. I am deeply grateful of her help in the completion of this thesis. High tribute shall be paid to Ms. Geng Li, whose profound knowledge of English triggers my love for this beautiful language and whose earnest attitude tells me how to learn English. I am also deeply indebted to all the other tutors and teachers in Translation Studies for their direct and indirect help to me. Special thanks should go to my friends who have put considerable time and effort into their comments on the draft. Finally, I am indebted to my parents for their continuous support and encouragement. 英文版论文致谢篇二 At the very first, I am honored to express my deepest gratitude to my dedicated supervisor, Miss Wang Chao, with whose able guidance I could have worked out this thesis. She has offered me valuable ideas,
Hello, everyone. Today, I will introduce one interesting paper: Human Behavior Prediction for Smart Homes Using Deep Learning. Before the presentation , let’s see who our group consists of. Then, it’s the outline of our presentation: motivation, purpose, basic idea, experiment, summary. Firstly, it ’s the motivation. As we can see from the picture, the fertility rate(生育率) all over the world tends to decrease by year and the average life continues to rise in future. As the result, the ratio of the number of persons aged over 65 to the number of persons aged between 15 to 64 will rise significantly. Because of this tendency, the need for smart homes which can help the old maintain independent lifestyles and increase the quality of life is emphasized. Therefore, an ability to provide a service to the users when it is needed without the user intervention is crucial for the success of smart homes. Next, it’s the purpose of the paper. Although humans can be able to understand other people ’s intention from their actions, it is difficult to extract relationship between actions and intentions in a structured way. The present paper attempts to extract the relationship between past actions and the future action using deep learning. Next, it’s the basic idea. The paper tries to improve learning method of an RBM model to solve the complex problems. Besides, they also want to explore new behavior prediction algorithms using the deep learning. Now, we briefly review deep belief network (DBN). DBN consists of multiple restricted Boltzmann machines (RBM), which are energy-based unsupervised learning models. The RBM model just looks like the right figure. Then I will make simple explanations to the RBM. One layer of an RBM consists of visible input units, which are connected to the other layer of hidden units. The distribution of state {v, h} of an RBM is specified by the following energy function: E v ,? θ =? w ij v i ?j F j =1D i =1? b i v i D i =1? a j ?j F j =1 Hinton, the man researched deep learning, proposed the contrastive divergence (CD) learning method. The method approximates the model distribution using Gibbs sampling with the probability distribution of input samples as follows: v i ?j data ? v i ?j model ≈ v i ?j data ? v i ?j G c v i ?j data =1n v i t n t =1P ?j (t )|v t ,θ v i ?j G c =1n v i t n t =1P ?j (t )|v t ,θ In fact, the conventional CD learning has some disadvantages such as an inaccurate approximation of the model distribution. Here, the paper proposes a new learning algorithm to improve the existing CD learning method. The overall