《电子与通信工程专业英语 教学课件 ppt 作者 徐存善 Unit 9》由会员分享，可在线阅读，更多相关《电子与通信工程专业英语 教学课件 ppt 作者 徐存善 Unit 9（64页珍藏版）》请在金锄头文库上搜索。
1、Unit 9,Mobile Communications,Mobile Communications,电子与通信工程专业英语,Unit 9 Mobile Communications,Mobile Communications,第 2 / 64页,电子与通信工程专业英语,Mobile Communications,Mobile Communications,Unit 9 Mobile Communications,第 3 / 64页,Mobile systems originally operated in analog mode in the 450MHz band，moving later
2、 to 900 MHz with digital GSM and then to1800MHz with personal communication systemsThe history of mobility can split into generationsThe first generation systems were the advanced mobile phone systems (AMPS) in the US，total access communication system (TACS) in most of Europe and Nordic mobile telep
3、hone system (NMT); which were all analogue systemsThe second generation(2G) is vary much dominated by the standard first set out in Europe by the group special mobile (GSM) committee，which was designed as a global mobile communication system,电子与通信工程专业英语,移动通信系统最初以模拟方式工作，由最初的频段在450MHz，后来逐渐发展到900MHz的数字
4、GSM系统，下一步是向工作在1800MHz的个人通信系统发展。移动通信的发展大致可分为三代。第一代系统如美国的高级移动电话系统(AMPS)、欧洲多数国家的全接入通信系统 (TACS)以及北欧的移动电话系统(NMT)，这些都是模拟系统。第二代移动通信系统(2G)在很大程度上是由欧洲特别移动小组(GSM)委员会所制定的标准决定的，这一系统被设计为一种全球移动通信系统。,Unit 9 Mobile Communications,Mobile Communications,第 4 / 64页,Four systems are in use now：D-AMPS，GSM，CDMA，and PDCThe
5、third generation mobile communication system(3G) currently being developed in Europe is intended to integrate all the different services of second generation systems and cover a much wider range of broadband services (voice，data，video and multimedia) consistent and compatible with technology develop
6、ments taking place within the fixed telecommunication networks,电子与通信工程专业英语,目前有四个使用的系统，分别是数字先进移动电话系统(DAMPS)，全球 移动通信系统(GSM)，码分多址(CDMA)和个人数字蜂窝电话(PDC)。目前第三代移动通信系统(3G), 在欧洲已经开发出，为了综合第二代系统的所有不同业务并覆盖更广泛的业务(话音、数据、视频、多媒体)范围，并且与固定电信网络的技术发展保持一致和兼容。,Mobile Communications,Unit 9 Mobile Communications,第 5 / 64页,T
7、he ideal mobile telephone system would operate with a limited assigned frequency band and would serve an almost unlimited number of users in unlimited areas. Three major approaches to achieve the ideal are： 1. Single-sideband(SSB)，which divides the allocated frequency band into maximum numbers of ch
8、annels； 2. Cellular，which reuses the allocated frequency band in different geographic locations； 3. Spread spectrum，frequency-hopped ,which generates many codes over a wide frequency band,电子与通信工程专业英语,理想的移动电话系统将在有限的给定频段上工作，但却可以向任意多的地区中几乎任意的用户提供服务。主要有三种方法来实现： 1单边带(SSB)，可将给定的频段分为最多的信道。 2蜂窝式，可在不同的地理位置上重
9、复使用使给定的频段。 3扩展频谱与跳频，可在宽频带上产生许多代码。,Mobile Communications,Unit 9 Mobile Communications,第 6 / 64页,Here we introduce some popular mobile telephone systems： 1Cellular Mobile Telephone System On Jan4，1979，the FCC authorized Illinois Bell Telephone Coto conduct a developmental cellular system in the Chicag
10、o area and make a limited commercial offering of its cellular service to the publicIn addition，American Radio Telephone Service Inc(ARTS) was authorized to operate a cellular system in the Washington，DC一Baltimore，Md，area. These first systems showed the technological feasibility of cellular service,电
11、子与通信工程专业英语,在这里我们介绍几种常用的移动电话系统： 1. 蜂窝式移动电话系统 1979年的1月4日，美国联邦通信委员会授权伊利诺斯贝尔电话公司在芝加哥地区开发蜂窝式系统，并向公众提供一定的商业服务。此外，美国无线电话服务公司(ARTS)被授权在华盛顿到马里兰州的巴尔的摩地区设立蜂窝式系统。这些早期的系统显示了蜂窝式移动通信的技术可行性。,Mobile Communications,Unit 9 Mobile Communications,第 7 / 64页,A basic cellular system consists of mobile stations，base station
12、s and a mobile switching center (MSC)The mobile station contains a transceiver, an antenna，and control circuitry，and may be mounted in a vehicle or used as a portable hand-held unitThe base stations consist of several transmitters and receivers which simultaneously handle full duplex communications
13、and generally have towers which support,电子与通信工程专业英语,一个基本的蜂窝系统包括移动站、基站和一个移动交换中心(MSC)。一个移动站包括无线电收发机、天线和控制电路，这种控制电路可以安装在传输系统或手机里。基站包括多台发射机和接收机，能同时进行全双工通信，通常还有用以支持收、发无线电的天线塔。基站就像一座桥梁建立在一个蜂窝小区,Unit 9 Mobile Communications,Mobile Communications,第 8 / 64页,several transmitting and receiving antennas. The ba
14、se station serves as a bridge between all mobile users in the cell and connects the simultaneous mobile calls via telephone lines or microwave links to the MSCThe MSC coordinates the activities of all of the base stations and connects the entire cellular system to the PSTNA typical MSC handles 100,0
15、00 cellular subscribers and 5,000 simultaneous conversations at a time，and accommodates all billing and system maintenance functions，as wellIn large,电子与通信工程专业英语,内所有用户和那些通过电话或微波链接到MSC的集群呼叫连接之间：MSC负责统一所有基站的操作并且把整个蜂窝系统连接到PSTN。一个典型的MSC一次可以处理100 000个蜂窝通信用户，同时进行5 000个通话，并且完成所有计费和系统维护功能。在大城市中，一个独立的载波可以服务于若
16、干个MSC。,cities，several MSCs are used by a single carrier,Mobile Communications,Unit 9 Mobile Communications,第 9 / 64页,2GSM-Global System for Mobile Communications The success of mobile systems across the world is a sign that communication is moving towards a more personalized, convenient system The GSM system is based on a cellular communications principle，but the use of digital radio transmission and the advanced handover algorithms between radio cells in GSM network
