CMPE 150 Winter 2009 Lecture 4 Januaryy 15 2009 P E Mantey CMPE 150 Introduction to Computer Networks Instructor Patrick Mantey mantey soe ucsc edu htt http www soe ucsc edu mantey d t Office Engr 2 Room 595J Office hours Tuesday 3 5 PM TA Anselm Kia akia soe ucsc edu Web site http www soe ucsc edu classes cmpe150 Winter09 Text Tannenbaum Computer p Networks 4th edition available in bookstore etc Syllabus Assignment 2 Available on the web site http www soe ucsc edu classes cmpe150 Winter09 Due Thursday January 22 2009 Today s Agenda Physical Layer Theoretical Basis for Data Communications Data Communications Where the data really get moved Nyquist Shannon Various Data Channels The Theoretical Basis for Data C Communication i ti Fourier Analysis Bandwidth Limited d dh d Signals l Maximum Data Rate of a Channel Bandwidth Limited Bandwidth Limited Signals A binary signal and its root mean square Fourier amplitudes b c Successive approximations to the original signal Bandwidth Limited Bandwidth Limited Signals 2 d e Successive approximations to the g signal g original Bandwidth Limited Signals 3 R l ti b Relation between t d data t rate t and dh harmonics i Maximum Data Rate Nyquist 1924 Noiseless capacity capacity C 2H log2V where H bandwidth of channel V number of discrete levels Maximum Data Rate Nyquist 1924 Noiseless capacity capacity C 2H log2V where H bandwidth of channel V number of discrete levels Shannon Sh 1948 error ffree capacity it capacity C H log2 1 S N where S N signal noise Guided Transmission Data Magnetic Media Twisted d Pair Coaxial Cable Fiber Optics Twisted Pair a Category 3 UTP b Category C t 5 UTP UTP http searchnetworking techtarget com sDefinition 0 sid7 gci211752 00 html Coaxial Cable A coaxial cable cable Fiber Optics a Three examples of a light ray from inside a silica fiber impinging on the air silica boundary at different angles b Light trapped by total internal reflection Transmission of Light through Fiber Attenuation of light through fiber in the infrared region Fiber Cables a Side view of a single fiber b E End d view i off a sheath h th with ith th three fibers Fiber Cables 2 A comparison of semiconductor diodes and LEDs as light sources sources Fiber Optic Networks A fiber optic ring with active repeaters Fiber Optic Networks 2 A passive star connection in a fiber optics network Wireless Transmission The Electromagnetic Th El t ti Spectrum S t Radio Transmission Microwave Transmission Infrared and Millimeter Waves Li ht Lightwave T Transmission i i The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication Radio Transmission a In the VLF VLF LF LF and MF bands bands radio waves follow the curvature of the earth b In the HF band band they the bounce bo nce off the ionosphere Politics of the Electromagnetic Spectrum The ISM bands in the United States Lightwave Transmission Convection currents can interfere with laser communication i ti systems t A bidirectional system with two lasers is pictured here Communication Satellites Geostationary Satellites Medium Earth Orbit Satellites Low Earth Orbit Satellites Satellites versus Fiber Communication Satellites Communication satellites and some of their properties including altitude above the earth earth round round trip trip delay time and number of satellites needed for global coverage Communication Satellites 2 The principal satellite bands bands Communication Satellites 3 VSATs using a hub Low Earth Orbit Satellites I idi Iridium a b a The Iridium satellites from six necklaces around the earth b 1628 moving cells cover the earth Globalstar a Relaying in space b Relaying on the ground Public Switched Telephone System St Structure t off the th Telephone T l h System S t The Politics of Telephones The Local Loop Modems ADSL and Wireless Trunks and Multiplexing Switching g Structure of the Telephone System a Fully interconnected network b C Centralized t li d switch it h c Two level hierarchy Structure of the Telephone System 2 A typical circuit route for a medium mediumdistance call Major Components of the Telephone System Local loops Analog twisted pairs going to houses and businesses Trunks Digital fiber optics connecting the switching it hi offices ffi Switching offices Where calls are moved from one trunk to another The Politics of Telephones The relationship of LATAs LECs and IXCs All the circles i l are LEC switching i hi offices ffi E Each hh hexagon belongs to the IXC whose number is on it The Local Loop Modems ADSL and Wireless ADSL The use of both analog and digital transmissions for a computer p to computer p call Conversion is done by the modems and codecs Modems a A binary signal b Amplitude modulation c Frequency modulation d Phase modulation Modems 2 a QPSK b QAM QAM 16 16 c QAM 64 Modems 3 a b a V 32 V 32 for 9600 bps bps b V32 bis for 14 400 bps Digital Subscriber Lines Bandwidth versus distanced over category 3 UTP for DSL Digital Subscriber Lines 2 Operation of ADSL using discrete multitone modulation modulation Digital Subscriber Lines 3 A typical ADSL equipment configuration Wireless Local Loops Architecture of an LMDS system y
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