现代通信技术基础（双语）小抄

一、1、信道channel 猫/调制解调器modems浏览器 browser有线电视Cable TV光纤 Fiber Optic路由器router兼容性compatibility失真distortion 铜缆coppercabling 搜索引擎search Engines 术语/行话terminology可靠性reliability窝蜂服务cellular services 2、DSPs: Digital signal Processors数字信号处理器 LANs: Local area Networks局域网 ATM：Asynchronous Transfer Mode异步传输模式HDTV：High-definition数字高清电视ISDN：Integrated Services Digital Network综合业务数字网 ISO ：International Standardization Organization国际标准化组织OSI ：Open System Interconnect Reference Model开放式互联系统BRI：Basic Rate Interface基本速率接口 3．ASCII：American standard code for information interchange美国信息交换标准码. IRA：International reference alphabet国际参比字母表。也称为国际版本的ASCII. EBCDIC：extended binary coded decimal inter-exchange code扩充的二进制编码的十进制交换码。 VoiceXML :Voice eXtensible Markup Language可扩展的标识语言 TCP/IP :Transmit Control Protocol/ Internet Protocol 传输控制/因特网协议MANs: Metropolitan Area Network城域网WANs: Wide Area Networks 广域网HTTP：Hypertext transfer protocol 超文本传输协议 HTML :Hypertext Markup Language超文本标识语言 DB :Database数据库 JEPG:Joint photographic Experts Group静态图像标准/专家组MEPG:Moving pictures Experts Group动态图像压缩标准/专家组 Lossless compression：无损压缩 Loss comprossion：有损压缩 sample theory：采样定理 pulses：脉冲 A/D转换【采样samoling量化numbering编码coding】 Network congestion：网络忙 capacity：能力容量 Binary bits：二进制 SONET：synchronoue Opic Net同步光纤网络 POTs：plain old telephone service普通老式电话设备 community antenna television:社区无线电视 Broadcast Local：当地广播 Optical multiple ring interface:光纤复用接口 Satellite TV:人造卫星电视 architectures:体系结构层 Broadcast TV services:广播电视服务 Infrared:红外线 two pairs of wire:双绞线 microwave:微波 Re-creation/repair:再生/修复 CWDM/DWDM:Dense/Coarse wavelength Division Multiplexing密集/粗波分复用技术 三、1. What are the analog signal and the digital signal? And please give corresponding examples of them, point out the sameness and difference during their transmission respectively.答：⑴ The analog signal is continuous in time domain. Such as the traditional audio signals, video signals and so on.⑵ The digital refers to the value discrete in time. For Example, Signals transmitted by the way of ones or zeros.⑶ Sameness: Impairments.The further the distance the more impairments.They all need amplifiers to boost the signal.⑷Difference:①The analog signal needs the analog amplifier while the digital one needs the digital one.②The analog amplifier can’t distintinguish the useful signal and noise,but the digital one can.③The analog signal will be interferenced by all kinds of the electricmagic interference while the digital one won’t. 2. Please give the definition of bit and byte. What does BPS refer to?答：①A bit means either one or zero.②A byte is a character that is made up of seven or eight bits. ③Bits per second are the actual number of bits sent in a second from point A to point B. 3. For analog services and digital services, what are their bandwidths respectively? 答：①The bandwidth of an analog service is the difference between the highest and lowest frequency within which the medium carries traffic. ②Speeds on digital services are expressed in bits per second (BPS). 4. Please point out the sameness and difference between compression and multiplexing. And what’s the standard of compression? And compression can be divided into _______and________, And multiplexing can be divided into _______, ________, ______and______. · Compression shrinks the data. Just as trash compactor makes trash smaller so that more refuse can be packed into a garbage barrel, compression makes data smaller so that more information can be packed into telephone lines. · Multiplexing combines traffic from multiple voice or data devices into one stream so that they can share a telecommunication path. · Like compression, multiplexing enables companies and carrier to send more information in media. · However, unlike compression, multiplexing does not alter the actual data sent. · Lossless compression and Loss compression · TDM，Time Division Multiplexing 时分复用 · FDM , Frequency-division multiplexing 频分复用 · CDMA , Code Division Multiple Access码分复用 · WDM , Wavelength division multiplexing波分复用 5. Give the definition of streaming media. and point out the difference between streaming media and downloading. 答:Streaming media techniques are the major reason the Internet is used to distribute music and multimedia content. It makes on-line music accessible to users without high-speed Internet connections. With streaming media. The user’s can’t wait too long to receive the text, music or video. But readers can’t listen to music after closing the web. And the only thing readers need to is to click a URL. While downloading actually stores the music files on a listener’s computer hard drive The entire file must be downloaded before it can be viewed. 6. Please tell how speech recognition works simply. 答：Speech recognition works by first detecting spoken words (utterances). Second: capturing spoken words (utterances). Third: removing background noises. Fourth: converting the captured utterances to a digital representing of the words. Capturing the speech and digitally representing it is done by digital signal processors (DSPs), which are high-speed specialized computer chips. Fifth: The speech recognition software then breaks up the sounds into small chunks, which are easier to define than larger pieces of sound. Sixth: The software compares various properties of the chunk of sound to large amount of previously captured data. Seventh: Based on these comparisons, the speech is assigned probabilities of matching particular phonemes. Eighth: The software compares phonemes, matching probabilities with possible user responses from a database. Finally, The software puts together possible responses made up of phonemes, vocabulary and grammar in the speech recognition software. 7.Please give each layer’s number and name. Layer one physical layer 第一层 物理层Layer two data link layer 第二层 数据链接层Layer three network layer 第三层 网络层Layer four transport 第四层 传输层Layer five session 第五层 会话层Layer six presentation 第六层 代表层Layer seven application 第七层 应用层 三、 For compression to work, both the sending and receiving ends must use the same compression method. The sending end looks at the data, voice or image. It then compresses it using a mathematical algorithm. The receiving end of the transmission decodes the transmission. When compression is used with text and facsimile, data to be transmitted is made smaller by removing white spaces and redundant images, and by abbreviating the most frequently appearing letters.为了使压缩器工作，发送端和接受端必须使用同一种压缩算法，发送端浏览数据，声音或图像信号，接着使用一种数学算法对其压缩。接受端对传输的信号进行减压。当压缩技术用于文本和传真时，我们可以通过除去空的空间和多余的图象以及压缩大部分常见的字符，就可将要传输的数据变小。