《通信英语LESSON11章节》由会员分享，可在线阅读，更多相关《通信英语LESSON11章节（65页珍藏版）》请在金锄头文库上搜索。
1、Unit 11,Circuit Switching and Packet Switching,Contents,Revision Pre-reading Activities While-reading Activities New words and phrases Text organization Text and translation Post-reading Activities Further Development of the Theme-related Specialized Knowledge Assignments,Revision,Teacher uses the f
2、ollowing exercise to help the students to revise the important expressions or phrases or sentences which were learnt in the study of last unit. Teacher : When I say a phrase or an expression in Chinese, you respond by giving an English equivalent your learnt in the study of Unit 10 GMS.,Revision,Tea
3、cher ( Chinese ) Students ( English) 个人通信 personal communications 通信标准 communication standards 固定电话业务 fixed telephone service 网络容量 network capacity 移动交换中心 mobile switching center 国际漫游 international roaming 宽带业务 broadband services 接口转换 interface conversion 频谱分配 frequency allocation 模拟方式 analogue mode
4、 蜂窝通信原理 cellular communication principle 基站 base station 突发脉冲传输方式 burst transmission mode 接入方法 access method 收费功能 billing function 切换算法 handover algorithms 短消息服务 short message service 技术规范 technical specification,Pre-reading Activities,Ask the Ss the following two questions related to the theme of t
5、he text: Can you enumerate what you contacted in the study of the courses including Switching? Possible answers: Circuit Switching and Packet Switching . Can you enumerate the trait of Circuit Switching and Packet Switching? Possible answers: The circuit is set up by a special signaling message that
6、 finds its way through the network, seizing channels in the path as it proceeds. A variation of message switching is packet switching. Here the message is broken up into several pieces of a given maximum length, called packets. As with message switching, each packet contains a header and a checksum.
7、 Packets are transmitted independently in a store-and-forward manner,While-reading Activities / New words and phrases,分配，分派，配给 allocate 释放，放松，发布 release 行话，土语 jargon 处理，操纵 manipulate 抓住，占领，俘获 seize 进行，继续 proceed 通知，告诉 inform 干预，干涉，妨碍 intervention 子网，分网 subnet 一批，一组，一块 block 头，头部 header 检验和，检验项 check
8、sum,While-reading Activities / New words and phrases,与有关，涉及 regard 缚，系，捆 attach 完全地，彻底地 entirely 相应地 accordingly 行列，长队 queue 变动，变化，变更 variation 招致，惹起 incur 保证，担保 guarantee 平稳的，不变的 steady 缓冲，分摊 amortize 突发性，突发 bursty 随机，机遇 randomness 强迫，强制，制约 constraint 相对地，比较地 relatively,While-reading Activities / N
9、ew words and phrases,回答，响应 response 专用的 dedicated 分配，指派，委派 assign 利用 utilization 动态地，有生气地 dynamically 利益，好处，恩惠 benefit 同时地，同时发生 simultaneously 连续地，连贯地 consecutive 用管道输送 pipeline 过程，步骤 procedure 存在，实体 entity,While-reading Activities / Text organization,1. Ss read the text and point out the main idea
10、of the text. The main idea: The text mainly discusses the trait of Circuit Switching and Packet Switching 2. Ss make an analysis of the organization of the text . The text may be divided into three major sections. Section1 (Lines1-12): the principle of Circuit Switching; Section2 (Lines13-35): the p
11、rinciple of Packet Switching Section3(Lines36-76): the predominance of Packet Switching,Text and translation,Circuit switching and packet switching (1),Text and translation,There are two basic types of switching techniques: circuit switching and message switching. In circuit switching, a total path
12、of connected lines is set up from the origin to the destination at the time the call is made (2) , and the path remains allocated (2) to the source-destination pair (whether used or not) until it is released by the communicating parties.,Text and translation,The switches, called circuit switches (or
13、 office exchange in telephone jargon), have no capability of storing or manipulating (3) users data on their way to the destination. The circuit is set up by a special signaling message that finds its way through the network, seizing (4) channels in the path as it proceeds. Once the path is establis
14、hed, a return signal informs the source to begin transmission. Direct transmission of data from source to destination can then take place without any intervention on the part of the subnet.,Text and translation,In message switching, the transmission unit is a well-defined block of data called a mess
15、age. In addition to the text to be transmitted (5) ， a message comprises a header and a checksum. The header contains information regarding (6) the source and destination addresses as well as other control information; the checksum is used for error control purposes. The switching element is a computer referred to as (7) a message p
