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1、Unit 9Cellular Mobile Telephone System1Contentsn Revision n Pre-reading Activities n While-reading Activities uNew words and phrases uText organization uText and translation uPost-reading Activities n Further Development of the Theme-related Specialized Knowledge n AssignmentsRevisionn 上节课主要学习了第8单元关
2、于paging system 的知识。 n Please tell me the important new words related to paging system and whats the main idea of the text.返 回 Pre-reading Activitiesn 传统的移动电话系统有那些缺点？ n 理想的移动电话系统有什么特点？ n 本次课将给大家讲cellular mobile telephone system有关方面的知识。返 回 While-reading Activities / New words and phrasesn Deploy v. us
3、e something effectively n e.g. deploy ones arguments, resources etc. n mobile adj. that can move or be moved easily and quickly from place to place; mobility n. n conventional adj. following what is traditional or customary下 一 页While-reading Activities / New words and phrasesn allocation n. 配给， 分配，
4、拔出 n allocate v. allocate something to somebody or something: assign something to somebody or something for a special purpose n e.g. He allocated tasks to each of us.下 一 页While-reading Activities / New words and phrasesn Approach v. come near or nearer to somebody or something in space or time 在时间或空
5、间上靠近 n e.g. The time is approaching when we must think about buying a new house. n n. 接近； 方法 n vicinity n. in the vicinity of something : in the surrounding district; in the neighborhood n e.g. There isnt a good school in the vicinity. n Radius n 半径 diameter n. 直径上 一 页返 回 While-reading Activities /
6、Text organizationn Step 1:Ask students to preview the text for several minutes. n Step 2:Let students discuss the communication approaches in the past and nowadays. n Step 3:Analyze the language points in the text.返 回 Text and translationn Cellular Mobile Telephone System(1)翻 译下 一 页返 回 Text and tran
7、slationn One of many reasons for developing a cellular mobile telephone system and deploying it in many cities is the operational limitations of conventional mobile telephone systems: limited service capability, poor service performance, and inefficient frequency spectrum utilization.翻 译下 一 页上 一 页返
8、回 Text and translationn A major problem facing the radio communication industry is the limitation of the available radio frequency spectrum（2）. In setting allocation policy, the Federal Communications Commission (FCC) seeks systems which need minimal bandwidth but provide high usage and consumer sat
9、isfaction(3).翻 译下 一 页上 一 页返 回 Text and translationn The ideal mobile telephone system would operate within 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:翻 译下 一 页上 一 页返 回 Text and translationn
10、1. Single-sideband (SSB), which divides the allocated frequency band into maximum numbers of channels; n 2. Cellular, which reuses the allocated frequency band in different geographic locations; n 3. Spread spectrum, frequency-hopped, which generates many codes over a wide frequency band(4).翻 译下 一 页
11、上 一 页返 回 Text and translationn In 1971, the computer industry entered a new era. Microprocessors and minicomputers are now used for controlling many complicated features and functions with less power and size than was previously possible. 翻 译下 一 页上 一 页返 回 Text and translationn Large-scale integrated
12、 (LSI) circuit technology reduced the size of mobile transceivers so that they easily fit the standard automobile(5). These achievements were a few of the requirements for developing advanced mobile phone systems and encouraging engineers to pursue this direction(6).翻 译下 一 页上 一 页返 回 Text and transla
13、tionn Another factor was the price reduction of the mobile telephone unit. LSI technology and mass production contribute to reduced cost so that in the near future an average- income family should be able to afford a mobile telephone unit.翻 译下 一 页上 一 页返 回 Text and translationn On Jan. 4, 1979, the F
14、CC authorized Illinois Bell Telephone Co. to conduct a developmental cellular system in the Chicago area and make a limited commercial offering of its cellular service to the public. In addition(7), American Radio Telephone Service Inc. was authorized to operate a cellular system in the Washington,
15、D. C. (8)-Baltimore, Md., area. These first systems showed the technological feasibility of cellular service.翻 译下 一 页上 一 页返 回 Text and translationn Why 800 MHz(9)? The FCCs decision to choose 800 MHz was made because of severe spectrum limitations at lower frequency bands. FM broadcasting services o
16、perate in the vicinity of 100 MHz. The television broadcasting service starts at 41 MHz and extends up to 960 MHz.翻 译下 一 页上 一 页返 回 Text and translationn Air-to-ground systems use 118 to 136 MHz; military aircraft use 225 to 400 MHz. The maritime mobile service is located in the vicinity of 160 MHz(10). Also fixedstation services are allocated portions of the 30 to 100 MHz band.
