Data ComLocal Area Netw
Data ComLocal Area Netw TCOM 501
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This 42 page Class Notes was uploaded by Dalton Gerhold on Monday September 28, 2015. The Class Notes belongs to TCOM 501 at George Mason University taught by Shyam Pandula in Fall. Since its upload, it has received 21 views. For similar materials see /class/215144/tcom-501-george-mason-university in Telecommunications at George Mason University.
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Date Created: 09/28/15
i I Lecture 1 all Introduction Chapter 1 amp Network Model Chapter 2 amp Bandwidth Utilization Chapter 6 Instructor Shyam Pandula PhD Slides provided by Qiang Lin PhD Dept Of ECE GMU 1 TCOM 501 2009 l lFigure 11 Five components of data communication Rue391 Rule 1 Rule 2 Rule 2 Protocol Protocol Sender E Medium Recelveri In analog signal the transmission power varies over a continuous range with respect to sound light and radio waves On the other hand a digital signal may assume only discrete set of values within a given range Dept of ECE GMU TCOM 501 2009 In I Five components of data communication cont A sender source creates the message to be transmitted A medium carries the message A receiver sink receives the message Data a collection of facts in raw forms that become information after process1ng Signals electric or electromagnetic encoding of data Signaling propagation of signals across a communication medium Transmission communication of data achieved by the processing of Signals A message a usually short communication transmitted by words signals or other means from one person station or group to another A protocol a procedure of data transformation in the form of software Dept Of ECE GMU 3 TCOM 501 2009 i I Figure 12 Data ow simplex halfduplex and fullduplex Direction of data Q Mainframe Monitor aSimpIeX Direction ofdata at time 1 Station 3 Station i Direction ofdata at time 2 b Half duplex Direction of data all the time Station E Station i c Full duplex Dept Of ECE GMU 4 TCOM 501 2009 d lFigure 13 Types of connections pointtopoint and mullipoint Link Station i Station i a Point to point Link Mainframe Station Station i b Multipoint Dept of ECE GMU TCOM 501 2009 lFigure 14 Categories of topology Topology Topology in the context of communication network refers to the way computers or workstations in the network are linked together Dept of ECE GMU 6 TCOM 501 2009 m lFigure 15 Fully connected mesh topology for ve devices Station 5 Devices are connected with many redundant interconnections between network nodes such as routers and switches In a mesh topology if any cable or node fails there are many other ways for two nodes to communicate While ease of troubleshooting and increased reliability are de nite pluses mesh networks are expensive to install because they use a lot of cabling Dept of ECE GMU 7 TCOM 501 2009 lFigure 16 A star topology connecting four stations Hub Station i Station m Station U Station U A number of workstations or nodes are directly linked to a central node Any communication between stations on a star LAN must pass through the central node There is iii directional communication between various nodes The central node controls all the activities of the nodes Dept of ECE GMU 8 TCOM 501 2009 In lFigure 17 A bus topology connecting three stations Station i Drop line Cable end n Station i Drop line Station i Drop line Iil Cable end I I U Ta p Ta p Ta p D All workstations are connected to a single communication line called bus In this type of network topology there is no central node as in star topology Transmission from any station travels the length of the bus in both directions and can be received by all workstations Dept of ECE GMU TCOM 501 2009 lFigure 18 A ring topology connecting six stations Repeater Repeater Repeater Re peater quot iv Each station is attached nearby stations on a point to point basis so that the entire system is in the form of a ring In this topology data is transmitted in one direction only Thus the data packets circulate along the ring in either clockwise or anticlockwise direction Dept of ECE GMU TCOM 501 2009 Ii Categories of networks Network Local area network Metropolitan area network Wide area network LAN MAN WAN Dept of ECE GMU 11 TCOM 501 2009 In lFigure 110 An isolated LAN connecting 12 computers to a hub in a closet Networks used to interconnect computers in a single room rooms within a building or buildings on one site are called Local Area Network LAN Dept Of ECE GMU 12 TCOM 501 2009 A relatively new class of network it serves a role similar to an ISP but for corporate users with large LANs Network size falls intermediate between LAN and WAN Many MANs cover an area the size of a city Not generally owned by a single organization Dept of ECE GMU 13 TCOM 501 2009 lFigure 111 WANs I switched WAN and a pointtopoint WAN End system End system Point to point 1 WAN Computer b Poi nt to poi nt WA N A computer network spanning a regional national or global area Dept of ECE GMU l4 TCOM 501 2009 lFigure 113 Hierarchical organization of the Internet Jl Who owns it a Structure ofa national ISP b Interconnection of national ISPs A network of networks Hundreds of millions of computers all over the world are connected through the Internet Dept Of ECE GMU 15 TCOM 501 2009 lFigure 21 Tasks involved in sending a letter Sender Receiver A Higher layers The letter is carried The letter is carried from the mailbox Middle layers from the post of ce to a post of ce to the mailbox Lower layers The parcel is carried from the source to the destination Dept Of ECE GMU 16 TCOM 501 2009 In lFigure 22 Seven layers of the OSI model 7 Application I Established in 1947 the International Standards I Organization ISO is a multinational body dedicated to worldwide 5 Session I agreement on international standards An ISO standard that covers all aspects of network 3 Network I communications is the Open Systems Interconnection OSI model It was first introduced in the late 1970s 6 Presentation Dept Of ECE GMU 17 TCOM 501 2009 l lFigure 23 The interaction between layers in the 0539 model Device Device A Intermediate Intermediate node node Peer to peer protocol 7th layer 7 A lication 7 Prese ntation Sessio n Tm nixWM Tramquot 39ili Hiquot v M w b39 4 3 interface Network il m n MM 7 i Physical communication Dept Of ECE GMU 18 TCOM 501 2009 IFigure 24 An exchange using the OSI model Dept Of ECE GMU 19 TCOM 501 2009 m IFigure 215 Summary of layers To allow access to network Application resources To translate encrypt and I Presentation I compress data I To establish manage and SeSSIOn terminate se55ions To prowde reliable process to process message delivery and error rECOVer To move packets from source to destination to provide internetworking To organize bits into frames to provide hop to hop delivery To transmit bits over a medium to provide mechanical and electrical speci cations Dept Of ECE GMU 20 TCOM 501 2009 lFigure 216 T CPIP and 0S1 model I The layers in the T CPIP protocol suite do not exactly match those in the OS SMTP FTP DNLS SNiMIP TELNET 39 39 39 model The original T CPIP protocol suite was de ned as having four layers host tonetwork internet transport and application However when T CPIP is compared to OS we can say that the T CPIP protocol suite is made of ve layers physical data link network transport and application Applications Protocols de ned by the underlying networks host to network Dept Of ECE GMU 21 TCOM 501 2009 d lFigure 217 Addresses in TCPIP Dept of ECE GMU 22 TCOM 501 2009 lFigure 218 Relationship of layers and addresses in T CPIP Application layer Transport layer Network layer Data link layer Physical layer Dept of ECE GMU Processes 23 TCOM 501 2009 lFigure 61 Dividing a link into channels Ll MUX Multiplexer DEMUX Demultiplexer n Output lines 1 link nchannels Whenever the bandwidth of a medium linking two devices is greater than the bandwidth needs of the devices the link can be shared Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link As data and telecommunications use increases so does traffic Dept Of ECE GMU 24 TCOM 501 2009 lFigure 62 Categories of multiplexing Multiplexing i l i iii an m M ii i l 39m v d i i i m39i wwl wivligvim iw39iiii li ipl iw Analog Analog Digital FrequencyDivision Multiplexing WavelengthDivision Multiplexing Synchronous TimeDivision Multiplexing Statistical TimeDivision Multiplexing Dept of ECE GMU 25 TCOM 501 2009 lFigures 63 5 Frequencydivision multiplexing FDA T H D l HjT39t1 ri39 3 Input M W W 395 Output lines U U lines X HmEnlym X Q Modulator Demodulator Q Ca rrier fI Carrier f1 A M d 39at r MHHWH 0mm A H I 9 WW Carrieer Carrier f2 Modulator 39 I l Demodulator IA 4III J Baseband V 391 T l I Baseband analog SignaIS Carrier f3 I Carrlerf3 analog Signals Dept Of ECE GMU 26 TCOM 501 2009 m lFigure 66 Example 61 Shift and combine Assume that a voice channel occupies a bandwidth of 4 kHz We need to combine three voice channels into a link with a bandwidth of 12 kHz from 20 to 32 kHz Show the con guration using the frequency domain Assume there are no guard bands Filter and shift Dept Of ECE GMU 27 TCOM 501 2009 Dept of ECE GMU TCOM 501 2009 12 voice channels 5 groups pergroups Su pe rg roup Master group lFigure 69 Analoghierarchy lFigures 610 11 Wavelengthdivision multiplexing WDM k1 7L1 l2 A2 X3 X3 X1 k1 k2 k3 Fiber optic cable k2 7L3 k3 Multiplexer Demultiplexer Dept of ECE GMU 29 TCOM 501 2009 l lFigure 612 T imedivision multiplexing TDM Data ow gt TDM is a digital multiplexing technique for combining several lowrate channels into one highrate one Dept of ECE GMU 30 TCOM 501 2009 lFigures 61315 Synchronous timedivision multiplexing T T3 c3I33A3 C2BzA2 c1BIAI Frame 3 Frame 2 Frame 1 i Each frame is 3 time slots I I I Each time slot duration is T3 s Data are taken from each line every T s In synchronous TDM the data rate of the link is n times faster and the unit duration is n times shorter I I I l A3 A2 A1 A3 A2 A1 Frame3 Frame2 Framei 39 CSEB3EA3 czisziAzHCIiBIEAI 39 ll l I C3 C2 C1 C3 C2 C1 l Dept Of ECE GMU 31 TCOM 501 2009 IF igures 618 23 Empty slots ofSTDM and digital hierarchy III III II MUX DS O 24 Dept Of ECE GMU TCOM 501 2009 lFigure 626 T DM slot comparison LineA Line B lg LineC MUX Line D Line E Synchronous TDM m LineA LineB m aumma LineC MUX Line D m Line E b StatisticalTDM Dept Of ECE GMU 33 TCOM 501 2009 l lFigure 627 Spread spectrum B 355 llt gtl F d gt gt process Spreading code In spread spectrum SS we combine signals from different sources to t into a larger bandwidth but our goals are to prevent eavesdropping and jamming To achieve these goals spread spectrum techniques add redundancy Frequency Hopping Spread Spectrum FHSS Direct Sequence Spread Spectrum Synchronous DSSS Dept of ECE GMU 34 TCOM 501 2009 l lFigure 628 Frequency hopping spread spectrum FHSS Modulator Spread signal Original gt Signal Frequency synthesizer Pseudorandom code generator Frequency table Dept Of ECE GMU 35 TCOM 501 2009 lFigure 629 Frequency selection in FHSS First hop frequency k bit patterns 101 111001000 010110 011100 I I First selection Freuency table Dept of ECE GMU 36 TCOM 501 2009 lFigure 630 FHSS cycles Carrier frequencies kHz Cycle 1 Cycle 2 12345678910111213141516 Hop periods Dept Of ECE GMU 37 TCOM 501 2009 lFigure 631 Bandwidth sharing AU f Frequency Frequency Time Time a FDM b FHSS Dept of ECE GMU 38 TCOM 501 2009 lFi gure 632 Direct Sequence Spread Spectrum Synchronous DSSS Modulator Original Q Spread signal 7 signal Chips generator Dept of ECE GMU 39 TCOM 501 2009 Original signal Spreading code Spread signal Cl 1 11D1D1101UIJ11D1 11 r v g f HE 1D11uu1u1uun1uU11u1LI11 Chimpint and Skipping ESEiv any I l l DIE bit 1 3515 bit 1 3 V Cutput Sat Dept of ECE GMU 40 TCOM 501 2009 In I OFDM Orthogonal Frequency Division Multiplexing Excellent for multimedia applications because of more efficient and robust Sometimes referred to as multicarrier or discrete multitone modulation Utilize multiple subcarriers to transport information from one user to another An OFDMbased system divides a highspeed serial information signal into multiple lowerspeed subsignals so system transmits simultaneously at different frequencies in parallel Dept Of ECE GMU 41 TCOM 501 2009 I I OFDM in time domain 15 alu atartler E subcarrier w subtarriier FIGURE 3 Examp e Gill 3 subcan ier s transmitted in one OFDM syrmbGL In this example the subcamierand phase ntfsets are the same tor itllustrative simplicity Dept Of ECE GMU 42 TCOM 501 2009
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