电子信息与通信工程专业英语

1、Chapter 5 Communication,5.1 A Short History of Communication 5.2 Wireless Communication Technology 5.3 Optical Fiber Communication 5.4 Basic Networking Concepts for Computer Network,TEXT 5.1 A Short History of Communication,1. Original technologies of communication 2. Communication at the speed of e

2、lectricity,convergence n. 集中, 收敛, 融合 courier n. 送快信的人, 旅行从仆 circuit switching 电路交换 cyber terrorism n. 网络 dot-coms n. 网络企业 ecommerce n. 电子商务 heliograph n. 日光仪,Interface Message Processors n. 接口信息处理机 message switching 报文交换 monopoly n. 垄断 semaphore n. 信号灯 shackle vt. 束缚 skeptics n. 怀疑学派 sabbatical n. 学

3、术假期 Telenet n. 远程通信网 Telecopier n. 远程复印机,No matter what career you enter, youll need to communicate with people. We believe that cultural, social, and personal experience improves through more effective understanding and practice of communication. Communication Studies seek to understand communicati

4、on and to improve its practice in a variety of relationships.,We focus on two person and family communication, communication in small groups and in large organizations, communication across communities, the nature of language and symbols, and the nature of argument and persuasion in political settin

5、gs and in social movements.,The history of communication can go back to thousands of years. However, the technologies that so many of us are addicted to today - mobile phones, the internet, satellite TV - are built on our achievements.,Each new development has transformed the world we live in. An un

6、derstanding of the journey we have taken to get where we are now shows that todays techniques are refinements of what came before. Really big revolutions may be still to come.,1. Original technologies of communication,Communication begins with the first conversations between people. Fire and the smo

7、ke it produces may also have been used for simple communication between separated groups.,The invention of the printing press in China some time after 300AD meant that the same message could be delivered to many people cheaply and more quickly than copying out the message many times by hand.,2. Comm

8、unication at the speed of electricity,With the discovery of electricity the speed and range of communication once again began to increase.,The invention of techniques such as Morse code allowed complex messages to be transferred at very high speeds over this new medium. These had huge repercussions

9、for many aspects of human life, for example, transport could be better coordinated, government could transmit decisions to distant offices almost instantaneously, and businesses could work with more businesses over larger distances.,The first amplitude modulation (AM) radio station began operating i

10、n Springfield, Mass., shortly after World War I, and the first frequency modulation (FM) station was authorized to operate by the Federal Communications Commission (FCC) in 1940.,The first television station was authorized by the FCC in 1941 and the first CATV station system began several years late

11、r.,See Table 5-1 Electrical communication history,At the same time as these developments in sound, people were working hard on capturing images. For hundreds of years artists and scientists had known that a small hole in the wall of a darkened room would project an image of the outside world on the

12、opposite wall.,In 1814 Joseph Nicphore Nipce used this principle to project an image of the world onto chemically treated paper in a box, so the first photograph had been taken. Images from one part of the world could be brought to another.,This allowed people in Tanzania to see what a London Street

13、 looked like, and people in London to marvel at Maasai warriors dressed in their finery. In 1877, Eadweard Muybridge developed a camera which could take a series of photographs in rapid succession.,He did this in order to win a bet on whether all a horses hooves left the ground when it ran. He lost

14、the bet, but invented the movie camera. By 1927 this had been combined with recorded sound, allowing people to share realistic experiences around the world.,The technologies that we have discussed have all helped us store and transmit communication. All these technologies are joining together in the

15、 form of computers and the internet.,5.2 Wireless Communication Technology,1 Introduction 2. Wireless communication technology,In 1895, Guglielmo-Marconi opened the way for modern wireless communications by transmitting the three-dot Morse code for the letter S over a distance of three kilometers by

16、 electromagnetic waves.,Introduction There are two fundamental aspects of wireless communication that make the problem challenging and interesting.,First is phenomenon of fading: the time variation of the channel strengths due to the small-scale effect of multipath fading and shadowing by obstacles.

17、 Second, wireless users communicate over the air and there is significant interference between them.,The interference can be between transmitters communicating with a common receiver, between signals from a single transmitter to multiple receivers, or between different transmitter-receiver pairs.,Ho

18、w to deal with fading and interference is central to the design of wireless communication.,There are many wireless communications technologies that can be differentiated by frequency, bandwidth, range, and applications.,These categories range from wireless wide area networks (WWANs) which cover the

19、widest geographic area, to wireless personal area networks (WPANs) which cover less than 10 meters.,2. Wireless communication technology WPAN,A WPAN is a personal area network, a network for interconnecting devices centered around an individual persons workspace, in which the connections are wireles

20、s.,communication within about 10 meters used mainly as cable replacement technologies for data synchronization and connectivity for devices that are close to each other.,Bluetooth wireless technology is the prevalent WPAN technology today. It operates in the 2.4-GHz unlicensed frequency band. Ultra-

21、wideband (UWB) technology provides high bandwidth by transmitting at very low power across a broad frequency spectrum.,Wireless LANs,A Wire LAN (WLAN), which sometimes referred to as LAWN robust wireless network connectivity over a local area of approximately 100 meters operates in the 2.4-GHz frequ

22、ency band at 11 Mbps,802.11 standards use the Ethernet protocol and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) for path sharing and include an encryption method, the Wired Equivalent Privacy algorithm.,WiFi focus on user authentication and encryption Multiple-Input Multiple-Out

23、put (MIMO) radio frequency (RF),WMAN,A wireless MAN, or WMAN a wireless communications network that covers a large geographic area such as a city or suburb. back haul has the greatest short-term appeal,last mile could establish wireless as an alternative to residential broadband DSL/cable modem 2 to

24、11GHz frequency range,Two WWAN technologies, including Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA), dominate WWAN deployments worldwide.,These two technologies are expected to evolve on parallel paths for the foreseeable future. We also recognize the import

25、ance of industry standards to widespread adoption.,In the same way that early competing WLAN technologies gave way to the IEEE 801.11b standard, it is important that the industry drive toward worldwide standardization in other wireless technologies.,1.Optical fiber 2. Optical communication systems 3

26、. Advantages of optical fiber communication,TEXT 5.3 Optical Fiber Communication,Terminology,aperture n. 孔径 attenuation n. 衰减 dielectric waveguide 介质波导 carbon dioxide laser 二氧化碳激光器 cleave vt. 劈开 cylindrical adj. 圆柱状的 electric arc n. 电弧 geometric optics 几何光学 graded index fiber 梯度型光纤，渐变型光纤，梯度折射率光纤 het

27、erojunction n. 异质结 high numerical aperture 大数值孔径光纤,immune adj. 有免疫力的 indices n. index的复数 intersymbol interference 码间干扰 micron n. 微米 monochromaticity n. 单色性 meridional ray n. 子午射线 nanosecond n. 纳秒 neodymium laser 钕激光器 omnidirectional adj. 全方位的 pick up 获得 parabolic adj. 抛物线,silica n. 二氧化硅 splice vt. 拼

28、接 step index fiber 阶跃光纤，阶跃折射率光纤 sulphide n. 硫化物 transverse adj. 横向的 wavelength division multiplexing 分复用,The optical communication systems are different from microwave communication systems in many aspects: The carrier frequency is about 100 THz and the bit rate is about 1T bit/s.,Spreading of optic

29、al beams is always in the forward direction due to the short wavelengths. Suitable for free space communications above the earths atmosphere like intersatellite communications,1. Optical fiber,An optical fiber is a glass or plastic fiber that carries light along its length. Fiber optics is the overl

30、ap of applied science and engineering concerned with the design and application of optical fibers. Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF).,Fibers which can only support a single mode are called single-mode fibers (SMF). Advantages low atten

31、uation transmit signals over a wide bandwidth.,Construction An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis, by the process of total internal reflection. The fiber consists of a core surrounded by a cladding layer,Fig. 5-8 Optical fiber electromagnetic anal

32、ysis,2. Optical communication systems,A light source is made of semiconductor A transfer function is required to define the power loss associated with the coupling of the signal power from the light source to the fiber transmission line.,Fiber The loss involved in either joining the fiber by a perma

33、nent splice or the use of a demountable connector is a transfer parameter to be included. Fiber-detector junction Photodetector Design algorithm,3. Advantages of optical fiber communication,Wider bandwidth Low transmission loss Dielectric waveguide Signal security Small size and weight,EXERCISES,1.P

34、lease translate the following words and phrases into Chinese. 2.Please translate the following words and phrases into English. 4. Answer the following questions according to the text.,TEXT 5.4 Basic Networking Concepts for Computer Network,1. Introduction 2. Network topology 3. Internet address 4. P

35、orts 5. Data transmission 6. Protocols,Terminology,ATM abbr. Asynchronous Transfer Mode异步传输模式 centralize vt. 把集中起来 client/server network 主从网，客服网 conversely adv. 相反地 criteria n. 标准 DNS abbr. Domain Name System域名系统 Encrypt vt. 加密,将.译成密码 entity n. 实体 FDDI abbr. Fiber Distributed Data Interface光纤分布式数据接口

36、 ISDN abbr. Integrated Services Digital Network综合 服务数字网 leased line 租用线，专用线,memonic adj.记忆的，记忆术的 peer-to-peer network 对等网 RFC abbr.Request For Comments请求讲解，Internet标准（草案） semantic adj.语义的 systematic adj.系统的，体系的 subnet n.子网络 syntax n. 语法，有秩序的排列 tiered application 分层应用 user authentication 用户认证,1. Intr

37、oduction,A network that connects computers located within a relatively limited area, such as an office, a building or a campus, is known as a Local Area Network (LAN). A network that spans a wide geographical area, usually across cities, countries or even continents, is known as Wide Area Network (W

38、AN).,Their major difference lies in how data and information is stored. See Table 5-7.,A LAN consists of networked computers, sometimes called workstations and other connecting devices. A WAN consists of two or more LANs connected via a communication channel that combines telephone lines, leased lin

39、es, microwave, or satellites. It can cover cities, countries, and continents.,Fig. 5-12 shows four common connecting devices,Hubs Repeaters Bridges Routers,Fig. 5-12 Hardware components of networking,2. Network topology,The common network topologies are Bus,Star Ring,Usually, more than one topology

40、is used in a network. For example, in a school network system, a bus-star topology is usually used with a high bandwidth bus as the backbone. That backbone connects a number of star networks. The star network is formed in a computer room. Each workstation is connected to the hub using UTP cable and

41、the backbone is often an optical fiber.,Examples of LAN technology,Ethernet Fibber Distributed Data Interconnect (FDDI) .,Ethernet LAN,An Ethernet LAN is based on a bus topology and broadcast communication Token ring. Ethernet is a family of frame-based computer networking technologies for LANs. a s

42、tandard for connecting computers into a LAN the name commonly used for IEEE 802.3 CSMA/CD,FDDI,FDDI specifies a 100-Mbps token-passing, dual-ring LAN using fiber-optic cable. Copper Distributed Data Interface (CDDI), has emerged to provide 100-Mbps service over copper.,3. Internet address,IP address

43、es are numeric quantities that are easy for computers to work with, but not for humans to remember. For example: 204.160.241.98. Domain Name System (DNS) servers are responsible for translating mnemonic textual Internet addresses into hard numeric Internet addresses.,Each organization that maintains

44、 a computer network will have at least one server handling DNS queries. That server, called a name server, will hold a list of all the IP addresses within its network, plus a cache of IP addresses for recently accessed computers outside the network. Each computer on each network needs to know the lo

45、cation of only one name server.,When your computer requests an IP address, one of three things happens, depending on whether or not the requested IP address is within your local network. If the requested IP address is registered locally, that is, its within your organizations network; youll receive

46、a response directly from one of the local name servers listed in your workstation configuration. In this case, there usually is little or no wait for a response.,4. Ports,An IP port will identify a specific application running on an Internet host machine. A port is identified by a number, the port number. The number of ports is not functionally limited, in contrast to serial communications where only 4 ports are allowed.,There are some port numbers which are dedicated for specific applications such as Table 5-8.,5.