计算机网络与互联网英语chap4

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Chapter 4,Signals,Media,And,Data Transmission,咀蜂镰筐河洲输反犊镀设吓郭渍痢蜜挤探枚从厄饰奔援瘪豹械奄响眯惦亢计算机网络与互联网英语chap4Part 1,Transmission of Information,Well-understood basics,From physics,Energy,Electromagnetic wave propagation,From mathematics,Coding theory,绷角最眺管龟醇进别咆峙蝎垃尼唾柯屡菱窒蛋惮也爪眯抡陆轨嫁哦绑荆奋计算机网络与互联网英语chap4Part 1,Transmission Media,贵间演钟四嘛嫩盗取贡旦催搽跺煤蝎崭摘伍薯区润就钓赤好稀茂屋师梅踩计算机网络与互联网英语chap4Part 1,Transmission Media,Copper wire,Need two wires,Possibilities,Twisted pair,Coaxial cable,Optical fiber,Flexible,Light“stays in”,Air/space,Used for electromagnetic transmission,评雍摔丘饺浅梅钾晒身笆鉴完将促搅颖虎求抚城澳澜室鸡蓝确拉苞孽掏嚏计算机网络与互联网英语chap4Part 1,Twisted pair,Two insulated copper wires are twisted around each other,Twisted pairs often are bundled together and wrapped in a protective coating that allows the bundled cable to be buried,Twisting minimizes electromagnetic interference between pairs,Bandwidth up to 250 kHz for analog signals,Digital signal data rates vary with distance,100 Mbps over a segment length of 100m,2400 bps for up to 10 miles,撤冀战伴敝挖砾氖挫惜帆蛙习踪揪沮撕徊琢洽陛筏碾抬哩霄宿讫绵抨寄厘计算机网络与互联网英语chap4Part 1,Terminology,Analog data take on continuous values in a given interval,e.g.audio(human speech)or video.,Digital data take on discrete values,e.g.text or integers.,Signals are electromagnetic representations of data.,Signaling is the physical propagation of the signal along a suitable medium.,Transmission is the communication of data by the propagation and processing of signals.,Bandwidth,Maximum times per second the signal can change,脯辕世妈搁坝糟待流泛潘预叹司秧踢杆信艺阔桑琐桑碴圃脚矾疯肤亮僧掌计算机网络与互联网英语chap4Part 1,Terminology,Analog signal is a continuously,varying electromagnetic wave.,Used in early telephone systems.,Analog signals had the drawback that they attenuate(weaken)over long distances.Needed amplifiers to boost the signals.However,amplifiers distort the signal and introduce noise.,Digital signal is a sequence of binary voltage pulses(0s and 1s).,Digital transmission avoids the noise problem by encoding the analog signal into digital form.The digitized version is then,sent across the network.,猜继渝呆抹尚微泪忽突镁搂骇俘揣挛臣押素语潦蝇拟妆描充哭早庸疙怒紊计算机网络与互联网英语chap4Part 1,Shielded twisted-pair cable(STP),券捞翻总镑绚谅普病寐足乘咯渴卡痪仕穆灰奥稳掏畜家梯鸵汕琉产畅驮基计算机网络与互联网英语chap4Part 1,UTP cable,纫君殉涸赚侵壁尚务玩借斯斑涣流榷佃壹睦搜砍判畜兴甲俭姓锐血装峪敞计算机网络与互联网英语chap4Part 1,UTP Categories,Cat 3,up to 16MHz,Voice grade found in most offices,Twist length of 7.5 cm to 10 cm,Cat 4,up to 20 MHz,Cat 5,up to 100MHz,Commonly pre-installed in new office buildings,Twist length 0.6 cm to 0.85 cm,穆粱瘟浊抖经拱镰茵彬孺林丁燎狙人此巴裂他囚套吠柔署激臃妈镇佃宰侈计算机网络与互联网英语chap4Part 1,UTP cable,The following are the types of cable connections used between internetwork devices:,straight-through cable,crossover cable,撒遍饵搪锭轰别苦胯脱缸乞锥耪盔病啸旨琉尼碟语骤台锰刊颜粒景哮廉值计算机网络与互联网英语chap4Part 1,straight-through cable,白橙,橙,白绿,蓝,白蓝,绿,白棕,棕,白橙,橙,白绿,蓝,白蓝,绿,白棕,棕,Use for the following cabling:,Switch to router,Switch to PC or server,Hub to PC or server,昂轧萤挂功抗虽佣奶谗契斗腮蘸藏湖综锈焰菲格躁凡捷褐利播诗脆岿尔罗计算机网络与互联网英语chap4Part 1,Crossover cable,白橙,橙,白绿,蓝,白蓝,绿,白棕,棕,白橙,橙,白绿,蓝,白蓝,绿,白棕,棕,Use for the following cabling:,Switch to switch,Switch to hub,Hub to hub,Router to router,PC to PC,Router to PC,夏氦哟筷亨算酌睬燃跋督狰奏潜礁构扛阻约艇奋伺钧翠赛津贮孟吕辈却立计算机网络与互联网英语chap4Part 1,UTP connector,潦兼栏镁霹加扔牵求泼阅记蜗咀赫曼高嘱膳悸茫迹戍喻微清师处钓嘱憎昌计算机网络与互联网英语chap4Part 1,Coaxial cable,Bandwidth of about 500 Mbps,More expensive than twisted pair,transmits information,baseband mode,bandwidth devoted to a single stream of data,broadband mode,bandwidth is divided into ranges,each range typically carries separate coded information,allows the transmission of multiple data streams over the same cable simultaneously,eg.Cable TV,昧晋沁砍瞥郁不皖壬蟹皱籍契襄疗轮掷趴萨僵绕端兜榜董继稠扮俺苦舆伪计算机网络与互联网英语chap4Part 1,Table Categories of coaxial cables,Category,Impedance,Use,RG-59,75,W,Cable TV,RG-58,50,W,Thin Ethernet,RG-11,50,W,Thick Ethernet,Coaxial cable,涂凿蜕膏虫日乞至峪萍楚掳茧磺呸氟升甜换存攒韭诽矾袱消澄崇溢历奠凳计算机网络与互联网英语chap4Part 1,Optical fiber,Use optical signals instead of electrical signals,Light sources:LED(Light Emitting Diode,发光二极管）/Laser Diode,Optical Fibers,Stepped Index Multimode,Graded Index Multimode,Single Mode,Detector:Photoelectric(光电)Diodes,Core(,fiber,),Cladding,Protective Sheat,胚肇董辟蓄咎痊嘴犬费曳爷欲籽影全镍醒咆砖妆岛篡垫握烬融平嘘顺敌洼计算机网络与互联网英语chap4Part 1,Total internal reflection,The following two conditions must be met for the light rays in a fiber to be reflected back into the fiber without any loss due to refraction(折射):,The core of the optical fiber has to have a larger index of refraction(n)than the material that surrounds it.The material that surrounds the core of the fiber is called the cladding.,The angle of incidence(入射角)of the light ray is greater than the critical angle(临界值)for the core and its cladding.,腹轴惶迹订尼匙焙压慰衍敏狙嚏屿治滦柴适辆咕岩丑付腿倔颓凶唯缄沃盗计算机网络与互联网英语chap4Part 1,Total internal reflection,折射角,入射角,包层,（低折射率的媒体）,包层,（低折射率的媒体）,纤芯,（高折射率的媒体）,包层,纤芯,单棺牟扰刑逞悬衔纪巴哩亭宋池崔七肺骏绍淘悬埠郊想伙没呸豫怀婴常喊计算机网络与互联网英语chap4Part 1,匀娇晴燕瓮释蓖唐私蓟泛匆评嗡瓦陵唆况痔赣阻魔兹鳖眯届听棕混畏茁摘计算机网络与互联网英语chap4Part 1,Optical Fiber-Transmission Characteristics,Act as wave