《通信与电子信息科技英语》课件unit 13.ppt

1、Mobile Wireless New words and phrases 1 corporation n.公司，企业2 subscriber n.用户，订户 3 infrastructure n.基础结构(设施)infrastructural adj.基础的4 cell n.(移动通信)蜂窝区，小区 cell phone(=cellular phone)蜂窝电话5 distinct adj.不同的6pattern n.模式，式样 downtown adv.在市区；adj.市区的8 house vt.收容，收藏9 applicable adj.可适用的，适当的，合适的10 cop n.警官，巡

2、警traffic cop n.交通警察11 handoff n.切换12 database n.数据库,资料库13 preassign v.预先指定，预先分配Mobile Wireless14 millennium n.一千年15 blocking n.阻塞(保护)16 simultaneous adj.同时的，同时发生的17 coexist vi.共存coexist with 与同时存在,与共存18 dual adj.双的,二重的,双重dualmode n.双重方式,双模19 roam v.漫游；n.漫游20 hybrid adj.混合的21 version n.版本,方案22 alphan

3、umeric adj.包括文字与数字的23 reciprocal adj.倒数的；n.倒数24 pager n.呼机,寻呼机25 idle adj.空闲的26 interstate adj.州际的 interstate highway 州际公路Mobile Wireless27 Nordic n.北欧人；adj.北欧人的28 administrator n.管理人,行政官29 charter n.合同，热照，许可证30 compress vt.压缩31 modem n.调制解调器32 pseudo adj.假的,伪的33 chip n.片，芯片34 modulo prep.以为模35 subt

4、raction n.减法36 composition n.成分37 impairment n.损害,损伤38 accommodate vt.容纳39 Seattle n.西雅图（美国港市）Mobile Wireless1 MTSO（mobile telephone switching office)移动电话交换局2 FDMA(frequencydivision multiple access)频分多址3 FCC(Federal Communications Commission)联邦通信委员会4 fullduplex 全双工5 overtheair 无线广播的6 TDMA(timedivisi

5、on multiple access)时分多址7 CDMA（codedivision multiple access)码分多址8 time slot 时隙9 move about 走来走去；到处活动Mobile Wireless10 be in operation 在运转中在实施中；在生效中11 DCC(digital control channel)数字控制信道12 SMS(short message service)短消息服务，短信息服务13 GSM(Global System for Mobile)全球通，全球移动通信系统14 PN(pseudo random)伪随机15 battery

6、 life 电池寿命16 in comparison to 和相比较Mobile WirelessMobile Communications Evolution During the 1970s,Bell Telephone Laboratories,which was then part of AT&T Corporation，developed the first wireless transmission system to provide service to mobile subscribers.That system consisted of three major compone

7、nts that continue to form the infrastructure for more modern mobile systems to this day.Those components include base stations,a Mobile Telephone Switching Office(MTSO),and cellular phones.Although significant technological developments have occurred in the field of mobile wireless communications si

8、nce the 1970s,the basic components of a cellular system retain the same infrastructural relationship.In addition,the basic concept behind cellular systems has remained the same.Basic Mobile Communications Infrastructure In a mobile communications environment,a geographic area is subdivided into cell

9、s that support operations on distinct frequencies.Mobile WirelessTo prevent interference between cells,the first type of mobile wireless communications system,which is referred to as the Analog Mobile Phone System(AMPS),employed a seven cell pattern,as illustrated in Fig.131.The cell pattern shown i

10、n Fig.131 ensures that no adjacent cells operate on the same frequency.In actuality,each cell consists of a base station and antenna that supports operations over a wide range of frequencies.However,only one call can occur at one of the frequencies supported in a cell at any given time;the cell patt

11、ern is used to ensure that two adjacent cells do not use the same frequency at the same time.Mobile WirelessCellular Component Relationship Each cell consists of a base station housing applicable electronics to support the wireless transmission method used and an antenna.As indicated in Fig.13.2,eac

12、h base station is connected to an MTSO.The MTSO,in turn,is connected to the public switched telephone network and provides the interconnection mechanism.As a mobile subscriber begins to leave the area of coverage of a particular cell,the baseMobile WirelessThe base station of one or more other cells

13、 notes an increase in the level of power as the subscriber moves toward a new cell.Both the serving cells base station and base stations adjacent to the serving base station communicate this information to the MTSO,which,in effect,functions as traffic cop,selecting the base station with the stronges

14、t increase in signal power to receive a handoff of the subscriber from the existing cells base station.In performing the handoff operation,the MTSO checks its database to determine what frequencies are available in the cell the subscriber is entering.The MTSO then communicates this information to th

15、e base station that the subscriber is entering,referred to as the“gaining”cell.The base station in the gaining cell then adjusts its transmit and receive frequencies,and sends a message to the subscriber on its old receive frequency that informs the cell phone to adjust itself to the new frequency p

16、air.Exercises.Please translate the following words and phrases into Chinese.1.transmission work operator4.PSTN5.MTSO 6.traffic cop7.analog cellular telephone system传输损伤传输损伤双重方式，双模双重方式，双模网络运营商，网络操作员网络运营商，网络操作员公共交换电话网（公共交换电话网（Public Switched Telephone Network)移动电话交换局（移动电话交换局（mobile telephone switching

17、 office)交通警察交通警察模拟蜂窝电话系统模拟蜂窝电话系统Exercises8.FDMA9.CDMA10.move about11.pager12.interstate highway13.PN14.overtheair15.FCC16.a base station频分多址频分多址(frequencydivision multiple access)码分多址码分多址(codedivision multiple access)走来走去走来走去;到处活动到处活动呼机呼机,寻呼机寻呼机州际公路州际公路伪随机伪随机(pseudo random)无线广播的无线广播的联邦通信委员会联邦通信委员会(F

18、ederal Communications Commission)基站基站Exercises.Please translate the following words and phrases into English.1.频谱 2.全双工通信3.纠错 4.倒数5.时隙6.蜂窝电话frequency spectrum fullduplex communication error correctionreciprocaltime slotcellular phoneExercises7.个人通信系统8.短消息业务9.混合编码器10.电池寿命11.传输系统12.全球通13.漫游14.时分多址 Per

19、sonal Communication System(PCS)short message service(SMS)hybrid coderbattery life transmission system Global System for Mobile roam Time Division Multiple Access Exercises.Fill in the blanks with the missing word(s).1.Each cell consists of a base station housing applicable electronics to support the

20、 wireless transmission method used and an antenna.2.GSM is now known on a worldwide basis as Global System for Mobile Communications.3.If a signal on the control channel is not found,the phone performs another Rip Van Winkle operation and goes back to sleep.4.Each carrier was allocated 25 MHz,which

21、results in 832 cellular channelsavailable per call.5.As a result of the digital coding of speech,the first version of TDMA that operated at 800 MHz was also referred to as Digital Advanced Mobile Phone Services(D-AMPS).Exercises6.This also explains why its relatively easy to place a call using(used,

22、using,use,be used)a PCS cell phone in urban areas or along an interstate highway.7.The sequence of extended bits then is modulated over a 1.23 MHz channel.8.The key advantage associated with spreading a signal is that,from Shannons Law,channel capacity can be maintained at a lower power level.9.Time

23、division multiple access(TDMA)subdivides the frequency allocation of AMPS into time slots.10.TDMA can normally coexist with analog channels on the same network.Exercises.Answer the following questions according to the text.1.What are the three major components of the first wireless transmission syst

24、em?Those components include base stations,a mobile telephone switching office(MTSO),and cellular phones.2.How can a base station be connected to the public switched telephone network?Each base station is connected to an MTSO.The MTSO,in turn,is connected to the public switched telephone network and

25、provides the interconnection mechanism.3.What does MTSO do during the handoff operation?In performing the handoff operation,the MTSO checks its database to determine what frequencies are available in the cell the subscriber is entering.The MTSO then communicates this information to the base station

26、that the subscriber is entering,referred to as the“gaining”cell.Exercises4.Which multiple access methods does the AMPS system use?Please briefly describetheir principles.AMPS system uses FDMA and TDMA.The 50 MHz of frequency spectrum allocated by the Federal Communications Commission in the 800 MHz

27、band for AMPS operation was subdivided into distinct subchannels of 30 kHz bandwidth,with each subchannel capable of supporting a single conversation.When the FCC allocated frequency to AMPS,it permitted two companies to offer service,referred to as the A side and Bside carriers.Each carrier was all

28、ocated 25 MHz,which results in 832 cellular channels available per call.Time division multiple access(TDMA)subdivides the frequency allocation of AMPS into time slots.Each AMPS channel is divided into a repeating sequence of three time slots,with a subscriber allocated to a frequency and time slot.E

29、xercises5.What problems does the AMPS encounter as more user purchase the AMPScompatible cell phones?As more users purchased AMPS compatible cell phones,they began to experiencean inability to make calls,especially in urban areas.This situation,referred to as blocking,occurs when call 417 is attempt

30、ed with a cell whose maximum capacity is the support of 416 simultaneous calls.A second problem encountered by AMPS subscribers occurred when a cell lacked the capacity to assign a channel to a mobile user arriving in its area of coverage.This situation resulted in dropping a call in progress.Exerci

31、ses6.What is the difference between TDMA and AMPS?In North America,TDMAbased cellular systems operate at 800 MHz or 1900MHz.When operating at 800 MHz,TDMA can normally coexist with analog channels on the same network this enables subscribers with a dualmode phone to take advantage ofAMPS or digital

32、TDMA as they move about,a situation referred to as roaming.A second difference between TDMA and AMPS concerns the manner by which voice is transmitted.Under AMPS,which is an analog system,the 3020 000 Hz range of human voice is first filtered to remove very low and high frequencies that are not impo

33、rtant for understanding a conversation.Next,the remaining frequencies are frequency modulated using a carrier in the center of the channel.In comparison under TDMA voice is first encoded digitally at a low bit rate,typically using a hybrid coder that codes voice at a fraction of the 64 kbps PCM rate

34、.Exercises7.Why does the use of TDMA for DAMPS and GSM permit cell phones to obtain an extended battery life in comparison to AMPS phones?The key reason for the extended battery life is the fact that the use of TDMA normally results in only onethird of the transmission time used in comparison to tha

35、t of an AMPS phone.A second reason is based on the capability of a PCS phone in idle mode to periodically check the control channel to see if it has an incoming call.If a signal on the control channel is not found,the phone performs another Rip Van Winkle operation and goes back to sleep.8.What is t

36、he key advantage associated with spreading a signal?The key advantage associated with spreading a signal is that,from Shannons Law,channel capacity can be maintained at a lower power level.Thus,CDMA supports lowpower operations.Exercises9.What is a PN signal?The PN signal is referred to as a code of chips,with each chip representing a data bit in the PN code.10.Compare the system capacity among the TDMA,CDMA and AMPS systems.According to some studies,CDMA can support 10 times the capacity of a TDMA system,which,in turn,can support 3 times the capacity of an AMPS cell.