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1、Lesson 15 Communication Networks,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升 电子工业出版社 ,15-Jan-19,2,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Lesson 15 Communication Networks,Backgrounds Text tour Language in use Vocabulary Structure Reading/writing techniques,15-Jan-19,3,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Backgrounds,Terminology Switch multip
2、lex (statistical multiplexing, time-division multiplexing, frequency-division multiplexing ) Internet Protocol multiple access modem,15-Jan-19,4,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Backgrounds,Terminology Header, trailer cyclic redundancy check (CRC) Ethernet LAN /WAN Cell route,15-Jan-19,5,通信与电子信息专业英语教程 陈杰美、
3、刘洪盛、饶渐升,switch,n. 开关, 电闸, 转换 vt. 转换, 转变 circuit switching 电路交换 packet switching 包交换，分组交换 store-and-forward packet-switching 存储转发分组交换,15-Jan-19,6,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,multiplex,多元的，复用的 statistical multiplexing 统计复用 time-division multiplexing 时分复用 frequency-division multiplexing 频分复用 demultiplex
4、解复用的,15-Jan-19,7,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Internet Protocol,Internet协议,15-Jan-19,8,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,multiple access,多路存取（访问） 通信(多个地面站用一个卫星进行通信) 多元联结, 多址方式, 多重存取,15-Jan-19,9,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,modem,调制解调器，该词是由mo(dulator)和dem(odulator)合成,15-Jan-19,10,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,header,
5、trailer,Header 信头 Trailer 包尾,15-Jan-19,11,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,cyclic redundancy check (CRC),循环冗余校验,15-Jan-19,12,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Ethernet,以太网,15-Jan-19,13,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,LAN /WAN,局域网/ 广域网 LAN=Local Area Network WAN=Wide Area Network,15-Jan-19,14,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Ce
6、ll,信元,15-Jan-19,15,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,route,路由,15-Jan-19,16,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Lesson 15 Communication Networks,Backgrounds Text tour Language in use Vocabulary Structure Reading/writing techniques,15-Jan-19,17,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Text tour,Outline Telephone networks Computer Net
7、works Cable Television Networks Wireless Networks,15-Jan-19,18,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Telephone networks,This is accomplished by circuit switching, where “circuit” refers to the capability of transmitting one telephone conversation along one link. 这是由电路交换来完成的，这里“电路”指的是在一个连接中只能传输一组会话。,15-Jan-19,19
8、,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Telephone networks,The additional bits are used to accommodate DS-0 channels with rates that deviate from the nominal 64 kbps because the signals are generated using clocks that are not perfectly synchronized. 由于在信号生成的时候时钟并非完全同步的，所以DS-0信道中的信号要添加附加位来与该信道64Kbps的速率保持一致。,15-Ja
9、n-19,20,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Telephone networks,ISDN makes available to subscribers the digital transmission facilities that were previously used between the switches of the network, thus extending the digital transmission all the way to the users. ISDN使得用户可以方便地进行数字传输，而以前数字传输只在网络中的交换机之间进行，因此，IS
10、DN将数字通信一直延伸到了普通用户。,15-Jan-19,21,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Telephone networks,Although the telephone voice channel is limited to a manner similar to a bandwidth of 3 kHz, the twisted pair cable itself which connects to the central office has a bandwidth of more than 1 MHz, limited by signal attenuati
11、on and noise. 尽管电话的话音信道只有3KHz的带宽，但实际上连接到中央交换机的双绞线可以提供超过1MHz的带宽，尽管存在信号衰减和噪声干扰。,15-Jan-19,22,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Computer Networks,A modem, or modulator-demodulator, transmits data by converting bits into tones that can be transported by the telephone network as if they were voice signals. The r
12、eceiving modem then converts these tones back into bits, thus enabling two computers with compatible modems to communicate over the telephone network as if they were directly connected by a serial link. 调制解调器将数据的比特流转换成声音在电话网络上传输，就如同话音信号一样。而接收端的调制解调器则将声音转换回比特流，这样，两台计算机通过相匹配的调制解调器就可以在电话网络中进行通信，就好像它们是直
13、接通过串口连接起来的一样。,15-Jan-19,23,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Computer Networks,But what if many computers are to be interconnected? 但是假如有许多计算机需要互连的时候该如何处理呢？,15-Jan-19,24,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Computer Networks,When B gets the packet from A, it reads the destination address and determines that it must fo
14、rward the packet to D. When D gets the packet, it reads the destination address and forwards the packet to E. In this scheme, when a node receives a packet, it must first store it, and then forward it to another mode (if necessary). 当B接收到该包后，它首先读信头中的目的地址，然后将包转发给D。D获得包之后，也是首先读信头中的目的地址，然后转发给E。在这个方案中，一
15、旦节点收到一个包，它首先需要将包存储下来，然后再转发给其它节点（如果必要的话）。,15-Jan-19,25,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Computer Networks,Statistical multiplexing contrasts with time-division multiplexing-based circuit switching which reserves for the duration of the conversation even through the parties connected by the circuit may not transmit continuously. 统计复用和基于时分复用的电路交换不同，电路交换在整个对话过程中，即便通信双方没有传输信息，该连接仍然被占有。,15-Jan-19,26,通信与电子信息专业英语教程 陈杰美、刘洪盛、饶渐升,Cable Television Networks,The span of a CATV network is limited by the noise power, which increases as more amplifiers are added to compensate for the signal power
