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Signals And Systems

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CMPE 150 – Winter 2009 Lecture 3 January 13, 2009 P.E. Mantey CMPE 150 -- Introduction to Computer Networks       Instructor: Patrick Mantey [email protected] http://www.soe.ucsc.edu/~mantey/ Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia [email protected] Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/ Text: Tannenbaum: Computer Networks (4th edition – available in bookstore, etc. ) Syllabus Today’s Agenda     Standards Layered Network Architecture - review Networks and History Physical Layer    Signals and Systems Fourier Analysis Communication Theory Standards   Required to allow for interoperability between equipment Advantages    Ensures a large market for equipment and software Allows products from different vendors to communicate Disadvantages   Freeze technology May be multiple standards for the same thing Standards Organizations       IEEE ANSI Internet Society ISO ITU-T (formally CCITT) ATM forum Network Standardization    Who’s Who in the Telecommunications World Who’s Who in the International Standards World Who’s Who in the Internet Standards World ITU  Main sectors • • •  Radiocommunications Telecommunications Standardization Development Classes of Members • • • • National governments Sector members Associate members Regulatory agencies IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up. Metric Units The principal metric prefixes. Reference Models The TCP/IP reference model. Reference Models Protocols and networks in the TCP/IP model initially. Comparing OSI and TCP/IP Models Concepts central to the OSI model  Services  Interfaces  Protocols  A Critique of the OSI Model and Protocols Why OSI did not take over the world  Bad timing  Bad technology  Bad implementations  Bad politics  Bad Timing “The apocalypse of the two elephants.” A Critique of the TCP/IP Reference Model       Problems: Service, interface, and protocol not distinguished Not a general model Host-to-network “layer” not really a layer No mention of physical and data link layers Minor protocols deeply entrenched, hard to replace Hybrid Model The hybrid reference model used by Tannenbaum Internet Layering Level 4 -- Application Layer (rlogin, ftp, SMTP, POP3, IMAP, HTTP..) -- Transport Layer(a.k.a Host-to-Host) Level 3 Level 2 (TCP, UDP, ARP, ICMP, etc.) -- Network Layer (a.k.a. Internet) (IP) -- (Data) Link Layer / MAC sub-layer Level 1 (a.k.a. Network Interface or Network Access Layer) -- Physical Layer Level 5 Example Networks The Internet  Connection-Oriented Networks: X.25, Frame Relay, and ATM  Ethernet  Wireless LANs: 802:11  Architecture of the Internet TCP/IP Reference Model Protocols and networks in the TCP/IP model initially. Characteristics   Internet Layer  Connectionless  Internet Protocol (IP)  Task is to deliver packets to destination Transport Layer  Transmission Control Protocol (TCP)  Connection-oriented  Reliable  User Datagram Protocol (UDP)  Connectionless  Unreliable TELCO Networks  Connection-Oriented Networks X.25  Frame Relay  ATM   Fixed Route (set up at start of call) Quality of Service  Billing – for connection time  T’s and D’s http://www.netstreamsol.com.au/networking/notes/general/t1_e1_t3_e3_ds0_ds1_ds3.html T1 • Time-division multiplexed stream of 24 telephone channels • The basic technology upon which all T-carrier facilities are based • Uses a full-duplex digital signal over two wire pairs. • Bandwidth of 1.544 Mbps through telephoneswitching network • Uses AMI or B8ZS coding. O’s SONET • • • • • • Synchronous Optical NETwork Synchronous Digital Hierarchy (SDH) Europe Internet for CARRIERS Worldwide standard Multiplex multiple digital channels Management support for – Operations – Administration – Maintenance X.25 and Frame Relay • X.25 -- First Public Data Network – 1970s – Call and connect “Data Terminal Equipment” – Simple packet structure – Implemented “virtual circuit” connections – Flow control, hop-by-hop error control – Multiplexing – up to 4095 circuits at a time • Frame Relay – 1980s (up to 2Mbps) – Limited error control, flow control – VC based packet switching --“wide area LAN” Asynchronous Transfer Mode • • • • Vintage mid -1980s Goal to unify voice networks and data networks Packet Switching with virtual circuits (“channels”) Fixed-length packets (“cells”) - @ 53 bytes – 5 byte header, 48 byte “payload” – Virtual channel header (VCI) – No retransmission link-by-link Error correction codes only • Envisioned to reach the end user • Used widely today for backbones ATM Virtual Circuits A virtual circuit. ATM Virtual Circuits (2)  An ATM cell. The ATM Reference Model  The ATM reference model. The ATM Reference Model (2) The ATM layers and sublayers and their functions Ethernet Architecture of the original Ethernet. Wireless LANs   (a) Wireless networking with a base station. (b) Ad hoc networking. Wireless LANs (2)  The range of a single radio may not cover the entire system. Wireless LANs (3) A multicell 802.11 network. The ARPANET (a) Structure of the telephone system. (b) Baran’s proposed distributed switching system. The ARPANET (2) The original ARPANET design. IMP = Interface Message Processor (Honeywell DDP-316) The ARPANET (3) Growth of the ARPANET (a) December 1969. (b) July 1970.(c) March 1971. (d) April 1972. (e) September 1972. NSFNET The NSFNET backbone in 1988. http://www.internet2.edu/pubs/networkmap.pdf UC CENIC January 2009 http://doc.cenic.org/tools/topology_map.pl?network=uc SIGNALS and SYSTEMS SIGNALS and SYSTEMS What is a signal? SIGNALS and SYSTEMS What is a signal? What is a system? SIGNALS and SYSTEMS What is a signal? What is a system? SIGNALS and SYSTEMS What is a signal? What is a system? Signal: time varying function produced by physical device (voltage, current, etc.) SIGNALS and SYSTEMS What is a signal? What is a system? Signal: time varying function produced by physical device (voltage, current, etc.) System: device or process (algorithm) having signals as input and output Input x(t) output y(t) SIGNALS and SYSTEMS ax(t) ay(t) a1 x1(t) + a2 x2(t) a1 y1(t) + a2 y2(t) Superposition SIGNALS and SYSTEMS Periodic signals -- f(t+T) = f(t) Period = T (seconds) Frequency = 1/ Period (“cycles” / sec. = Hertz (Hz) f 0  1/ T0 SIGNALS and SYSTEMS Periodic signals -- f(t+T) = f(t) Period = T (seconds) Frequency = 1/ Period (“cycles” / sec. = Hertz (Hz) Radian frequency:   2 f (radians/sec.) SIGNALS and SYSTEMS Reference: Signals, Systems and Tranforms Leland B. Jackson Addison Wesley SIGNALS and SYSTEMS SIGNALS and SYSTEMS 100MHz square wave What bandwidth required for transmission? SIGNALS and SYSTEMS Periodic Signal --- Composed of sinusoids MATLAB Demo SIGNALS and SYSTEMS Periodic Signal --- Composed of sinusoids Fourier Series N 1 x(t )  a0   an cos(2 nf 0t )  bi sin(2 nf nt ) 2 n 1 an  bn  1  1  2  x(t ) cos(2 nf t )d ( t ) 0 0 0 2  x(t ) sin(2 nf t )d ( t ) 0 0 0 1 f0  T0 is the “fundamental frequency” 0t  2 f 0 t 1 2 d (0t )  2 f 0 dt  2 dt  dt T0 T0 Fourier Series N 1 x(t )  a0   an cos(2 nf 0t )  bi sin(2 nf nt ) 2 n 1 Integration limits: when 0t  2 2 2 1 t   0 2 / T0 T0 , then so we get: 2 an  T0 2 bn  T0 T0  x(t ) cos(2 nf t )dt 0 0 T0  x(t ) sin(2 nf t )dt 0 0 Fourier Series N 1 x(t )  a0   an cos(2 nf 0t )  bi sin(2 nf nt ) 2 n 1 x(t )   ce n  jn 2 f 0t n x(t )  Euler: e j 2 f i t   ce n  jn 2 f 0t i  cos(2 fi t )  j sin(2 fit ) Fourier Series x(t )   ce n  1 cn  T0 jn 2 f 0t n T0 2   x(t )e  jn0t dt T0 2 We can show cn  a  b 2 n 2 n ;   tan (bn / an ) 1 recall that b a cos( )  b sin( )  a  b cos(  tan ( )) a 2 2 1 Phasors: a b a b 2 Phasors 2 References      Stallings, W. Data and Computer Communications (7th edition), Prentice Hall 2004 chapter 1 Web site for Stallings book  http://williamstallings.com/DCC/DCC7e.html Web sites for IETF, IEEE, ITU-T, ISO Internet Requests for Comment (RFCs) Usenet News groups  comp.dcom.*  comp.protocols.tcp-ip