1

9

FALL 2000FALL 2000

Rob WolfeRob Wolfe

TelecommunicationsTelecommunicationsCh.11-A,B,CCh.11-A,B,C

DIT 2006 - Wolfe2

9 GoalGoal

Explain Shannon’s comm modelExplain Shannon’s comm model Define bandwidth and effectsDefine bandwidth and effects Difference between:Difference between:

simplex, half duplex, full duplex, echoplex

Odd/even parityOdd/even parity Synchronous/asynchronous commsSynchronous/asynchronous comms

DIT 2006 - Wolfe3

9 Goal (continued)Goal (continued)

Packet and circuit switchingPacket and circuit switching LAN standards/protocolsLAN standards/protocols Adv/Disadv of Internet over Adv/Disadv of Internet over

POTS, Cell, cable TV, satellite

DIT 2006 - Wolfe4

9 Data Communications (A)Data Communications (A)

DIT 2006 - Wolfe5

9 Model of Communication SystemsModel of Communication Systems

Simplex

Half Duplex

Full Duplex

DIT 2006 - Wolfe6

9 Communication SignalsCommunication Signals

Signal frequency is measured in Signal frequency is measured in Hertz (Hz) Megahertz (MHz) Gigahertz (GHz)

Hertz = one Hertz = one wavewave (oscillation) per (oscillation) per secondsecond

DIT 2006 - Wolfe7

9 Data Communications (cont)Data Communications (cont)

Communications ChannelCommunications Channel Communications MediumCommunications Medium

twisted pair, coax, fiber-optic

BandwidthBandwidth Digital(bps), Analog (Hz)

Transmission SpeedTransmission Speed Serial, Parallel transmission

Signal DirectionSignal Direction Simplex, Half-duplex, Duplex, Echoplex

Parity Protocol (even/odd parity)Parity Protocol (even/odd parity) Synchronous/Async ProtocolsSynchronous/Async Protocols

DIT 2006 - Wolfe8

9 Communications Links (B)Communications Links (B)

Twisted Pair CableTwisted Pair Cable Coaxial CableCoaxial Cable Fiber Optic CableFiber Optic Cable

DIT 2006 - Wolfe9

9 Twisted Pair CableTwisted Pair Cable

Terminates with RJ-45 connectorTerminates with RJ-45 connectorNote: Twisted pair cable used for

telephones use smaller RJ-11 connector

Shielded (STP) Shielded (STP) —— wires are coated wires are coated with a foil shield that reduces signal with a foil shield that reduces signal noise that might interfere with data noise that might interfere with data transmission.transmission.

Unshielded (UTP) Unshielded (UTP) —— contain no contain no shielding and are... shielding and are... less expensivemore susceptible to noise

DIT 2006 - Wolfe10

9

RJ-45 connector

RJ-45 wall

outlet

Each wire is coated with plastic so wires

don’t have direct contact.

To computer

Usually contains four pairs of copper wires

Plastic sheath

protects wires

Twisted Pair CableTwisted Pair Cable

DIT 2006 - Wolfe11

9 Twisted Pair CableTwisted Pair Cable

Category 1:Category 1:UTP are recommended for analog voice

communication but not dataReferred to as voice-grade cable

Category 2:Category 2:Higher grade of UTP suitable for voice

and data

Categories 3-5: (16, 20, 100Mbps)Categories 3-5: (16, 20, 100Mbps)Higher grade of UTP and STPSuitable for voice and dataReferred to as data grade cable

DIT 2006 - Wolfe12

9

Copper wire core

Metal BNC connector links cable to a T-shaped connector on back of a computer

Copper wire Copper wire conductorconductor

Non conducting Non conducting insulatorinsulator

Foil shieldFoil shield Woven metal outer Woven metal outer

shieldingshielding Plastic outer Plastic outer

coatingcoating

Coaxial cable — a high-capacity communications cable that consists of:

Coaxial CableCoaxial Cable

DIT 2006 - Wolfe13

9 Coaxial CableCoaxial Cable

Called Called Category 6Category 6 cable cable Has a bandwidth greater than Has a bandwidth greater than

twisted pair cable(100mbps+)twisted pair cable(100mbps+) Thin coax (3/16 inch)Thin coax (3/16 inch)

Found in local area networksUsed in home cable TV wiring

Thick coax (3/8 inch)Thick coax (3/8 inch)Found in older local area networksUsed in cable TV trunk lines

DIT 2006 - Wolfe14

9

Twisted Pair Coaxial

Coaxial Cable Coaxial Cable vs.vs. Twisted Pair Twisted Pair CableCable

Category 5 Category 5 Used more in Used more in

networks todaynetworks today More durableMore durable CheaperCheaper

Used to be widely Used to be widely used in LANused in LAN

Excellent Excellent bandwidthbandwidth

Less durableLess durable More expensiveMore expensive

DIT 2006 - Wolfe15

9

Fiber Optic Cable — a bundle of extremely thin tubes of glass called optical fibers.

Optical fibers are:

Fiber Optic CableFiber Optic Cable

Thinner than the diameter of a Thinner than the diameter of a human hairhuman hair

A relatively new development- since A relatively new development- since 1980s1980s

Purified glass without traces of water Purified glass without traces of water or metalsor metals

DIT 2006 - Wolfe16

9

Fiber is wrapped in cladding to reflect light that travels through the

fiber.

Category 7 Category 7 CableCable

Core of each fiber is a perfectly formed glass

tube.

Metal wire strengthens the

cable.

Plastic coating protects the bundle of glass

fibers.

Fiber Optic CableFiber Optic Cable

DIT 2006 - Wolfe17

9

How fiber optic cables work:

Miniature lasers Miniature lasers (LEDs)(LEDs) send pulses send pulses of light through the fibersof light through the fibers

Electronics at the receiving end Electronics at the receiving end convert light pulses into electrical convert light pulses into electrical signalssignals

Each fiber is a one-way Each fiber is a one-way communications channel communications channel

Fiber Optic CableFiber Optic Cable

DIT 2006 - Wolfe18

9 Low Earth Orbit Satellite Low Earth Orbit Satellite NetworksNetworks

A A low earth orbitlow earth orbit communications communications system requires system requires a web of a web of satellites to satellites to provide provide continual continual coverage over an coverage over an area such as area such as North America.North America.

DIT 2006 - Wolfe19

9 Communications Systems(C)Communications Systems(C)

POTSPOTS Integrated Services Digital Network Integrated Services Digital Network

(ISDN)(ISDN) T1, T3T1, T3 Cellular PhonesCellular Phones CATVCATV Internet/IntranetInternet/Intranet LANS (Ethernet, Token Ring)LANS (Ethernet, Token Ring)

DIT 2006 - Wolfe20

9 Communication via TelephoneCommunication via Telephone

Creates dial-up connection when you dialCreates dial-up connection when you dial Stops connection when you hang upStops connection when you hang up Uses analog audio signals Uses analog audio signals Must use a modem to send data signalsMust use a modem to send data signals ModulationModulation

Changing the characteristics of a digital pulse into an analog signal

DemodulationDemodulation Changing the signal back to its original state

Plain Old Telephone Service (POTS)

DIT 2006 - Wolfe21

9 Internet Access via Telephone Internet Access via Telephone SystemSystem

DIT 2006 - Wolfe22

9 Internet Access SpeedInternet Access Speed

Cable Modems Cable Modems (30 Mbps)(30 Mbps) DSL DSL (1.5-8 Mbps)(1.5-8 Mbps) T1/T3 (1.5/45 Mbps)T1/T3 (1.5/45 Mbps) ISDNISDN (.64-1.54 Mbps) (.64-1.54 Mbps) ModemsModems

56 Kbps 28.8 Kbps 14.4 Kbps

8-20 sec

10-52 sec

52 sec

10 min

24 min

46 min

90 min

DIT 2006 - Wolfe23

9 Local Area Networks (LANs)Local Area Networks (LANs)

TopologyTopology Three TypesThree Types

StarRingBus

Network StandardNetwork StandardEthernetToken Ring

Network Communications ProtocolNetwork Communications ProtocolTCP/IP, IPX, LAT, AFP

DIT 2006 - Wolfe24

9 What’s Happening in Telecom?What’s Happening in Telecom?

How long it took to reach 50 million How long it took to reach 50 million peoplepeopleRadio … 38 yearsTV … 13 yearsPC … 16 years Internet … 4 years

DIT 2006 - Wolfe25

9 What’s Happening in Telecom?What’s Happening in Telecom?

Cause of Cause of Information OverloadInformation Overload Average US office worker … Average US office worker …

Communicates with 24 different people per day

Six to 20 incoming messages per hour

Average UK office worker …Average UK office worker … Receives 48 phone calls, 23 e-mails, 11

voice mails, 20 letters, 15 memos, 11 faxes, 13 post-it-notes, 8 beeps

Snail mail growth … less than 2% a Snail mail growth … less than 2% a yearyear

The culprit is … The culprit is …

DIT 2006 - Wolfe26

9 What’s Happening in Telecom?What’s Happening in Telecom?

Cost Cost of Long-Distance Communicationof Long-Distance Communication1974 … NY to LA, 3 minutes, $1.45Today … same call, about a quarter

VolumeVolume of Long-Distance of Long-Distance CommunicationCommunication1984 … AT&T, 90% market share, 25

million calls per dayToday … AT&T, 50% market share, 250

million calls per day

DIT 2006 - Wolfe27

9 What’s Happening in Telecom?What’s Happening in Telecom?

How about How about FaxFaxes … es … In 1997, 3.2 billion pages were faxed.US Postal Service estimates that fax

drove USPS market share (for correspondence industry) from 77% in 1988 to less than 59% in 1998.

WirelessWireless Communications CommunicationsMore than 21 million sign-ups for

wireless account every month in the USWireless penetration in US is 21%. In

Finland, over 50%.

DIT 2006 - Wolfe28

9 What’s Happening in Telecom?What’s Happening in Telecom?

Digital ConvergenceDigital Convergence“Honey, would you please answer

the TV? I’m watching the phone.” JAVAC&C Convergence (Japanese)

??

DIT 2006 - Wolfe29

9 GoalGoal

Explain Shannon’s comm modelExplain Shannon’s comm model Define bandwidth and effectsDefine bandwidth and effects Difference between:Difference between:

simplex, half duplex, full duplex, echoplex

Odd/even parityOdd/even parity Synchronous/asynchronous commsSynchronous/asynchronous comms

DIT 2006 - Wolfe30

9 Goal (continued)Goal (continued)

Packet and circuit switchingPacket and circuit switching LAN standards/protocolsLAN standards/protocols Adv/Disadv of Internet over Adv/Disadv of Internet over

POTS, Cell, cable TV, satellite