Types of Transmission MediaOpen-wire linesK carrier systemPaired cable(twisted pairs)gauges and lengthhigh speeds 144 kbps FDX -ADSLMbps rates experimentallyCoaxial cableL carrier system-basebandCTV cable- broadbandadapting for two-way trafficMicrowave radioT carrier systemsSatellitestransoceanicdirect broadcastOptical fiberhigh BW, low error rateElectronic bottleneckLANs, MANs, WANsCellular Radio

100

10

1

0.1

Loss (dB/km)

1kHz 1 MHz 1 GHz 1 THz 1000 THz

22 Gaugetwisted pair

TransmissionCharacteristics

7/8 coax

2 waveguide

Optical fiber

Wavelength(microns).8 1.0 1.2 1.4 1.6Attenuation(dB/km)Optical BandWindows .85 m 1.3 m 1.55 m

Example Window around 1.3 m = 0.13 mS/N=50 dB

C=BW log2(1+S/N)=500,000 Gbps

P=(5 X 1014 X 100 Ph/bit)/(7.5 X 1015 ph/mw)=6.66 mw

125 m

Core8-12 m

Cladding

Jacket

125 m

Core50 m(human hair)

Cladding

Jacket

Single-mode fiber Multimode fiber

Optical Fiber Transmission Modes

Mode propagation

Core

Optical Power Sources Item Light emitting diode(LED)Semiconductor laserData rateLow(noncoherent tranS)High(coherent trans)Mode MultmodeSingle modeDistance Short(LANs)Long (WANs)Lifetime Long lifeShort lifeTemp sensitivityLowHighCost LowHigh

Optical NetworksStar CouplerAll OpticalNetworksMANsWavelength Division Multiplexing(WDM)See Fig 2.2Point to PointOptical LinesRingStarElectronic bottlenck

Advantages of FiberHigh BandwidthLow Signal-to-Noise RatioLightweightElectrically inertHard to wiretap

100 102 104 106 108 1010 1012 1014 1016 1018 1020 1022 1024 Radio m wave IR UV X-ray Gamma ray Visible Light 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016Twisted Pair Coax Satellite Fiber optics AM Radio FM &TV MicrowaveFrequency in HzLF MF HF VHF UHF SHF EHF THFL S C X Ku K KaFrequency BandsRadio bands

Satellite TransmissionRemote sites-e.g. far northMobilityDirect Access-Last mile problemDelay problem-0.25 roundtrip for Geo

Keplers Third Law

GEO

LEO

MEO

Period(Hours)

Distance (km)

40000

30000

10000

5 10 15 20 25

Altitude vs Period of a Terrestrial satellite

Distance from earthDistance to Earth StationfabSDfElevationRSatellite Systems

104

2x104

3x104

Distance(km)

Coverage Angle(degrees)

LEO MEO GEO

Keplers First and Second LawsObits are elliptical with earths center as a focusOrbits sweep out areas at a constant rate

Apogee-39,400 km

Perigee-1000 km

Molniya Orbit

12-20 Transponders per satelliteeach with 36-50 MHz Bandwidth

50 MHz50 Mbps Data streamor800 voice channels(64 kbps)Spot beams and VSAT (see pp164-166)

Band

Frequencies

Downlink(Ghz)

Uplink(Ghz)

Problems

C

4/6

3.7-4.2

5.925-6.425

Terrestrial Interference

Ku

11/14

11.7-12.2

14.0-14.5

Rain

Ka

20/30

17.7-21.7

27.5-30.5

Rain

Personal Communication Satellite Systems

System

Iridium

Globalstar

ICO

Ellipso

ECCO

No. of active satellites

66

48

10

14

46

Orbit planes

6 circular polar-

8 circular inclined

2 circular inclined-

2 elliptical inclined-

1 elliptical equatorial

7 circular inclined-

1 circular equatorial

Orbit altitude -km

780-LEO

1414-LEO

10355-MEO

502-7846-MEO

4223-7847-MEO

2000-LEO

Satellites per orbit lane

11

6

5

4 elliptical

6 equatorial

5 inclined

11 equatorial

Beams per satellite

48

16

163

61

32 inclined

24 equatorial

Cost $billion

3.4

2.6

4.6

0.91

2.8

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The Telephone System

LocalNetwork

SWITCHING

Long Haul Network

Two-WayConnection

Customer Premises Equipment(CPE)

0 4kHz

Components of Telephone Network

Local loopToll connecting trunksHigh BW intertoll trunksToll connecting trunksLocal loopCPE End office Toll office Switching officeEnd-to-end ConnectionBasic ComponentsLocal loops -twisted pairsFiber to home, fiber to curbTrunks - optical fiber,microwave, satellitesSwitching

RS-232 and RS-449Not part of telephone systemComputer or TerminalModem

GroundTransmitReceiveRequest to SendData set readyClear to sendCommon returnCarrier detectData Terminal ready

Trunks and MultiplexingFrequency Division Multiplexing(FDM)Essentially analogTime Division MultiplexingEssentially digital

Frequency Division Multiplexing

FrequencyMultiplexed Channel

l

l

l

1

2

N

Fig. 3 FDM

Guard Band

BW

Time

First Step in Analog Multiplexing Hierarchy1

2

...

12...60 108 kHz48 kHz

Analog Multiplexing Hierarchy

Voiceband 0-4 kHz

1 Voice Channel

Group 60-108 kHz

12 Voice Channels

Supergroup 312-552 kHz

60 Voice Channels Five Group bands

Mastergroup 60-2788 kHz

600 Voice Channels Ten Supergroup bands

Jumbogroup 3.1-20.1 MHz

3600 Voice Channels Six Mastergroups

Advantages of Digital SignalingRegeneration restores signalHigher data rateError correction and detectionCheaper implementationEasier to maintain Flexible multiplexingEasier encryptionCompression techniques-DPCM

Digitization of Voice ChannelVoiceSignal0 4 kHzQuantizer7 bits/sample +1 control bit/sample8000/secSampler64 kbpsPulse Code Modulation(PCM)DPCM

111110100101001011010000Analog InputDigital OutputQuantizationCompanding(Compression+Expansion)

l

TimeMultiplexed Channel

l

l

l

1

2

N

S1

S2

SN

Time

S1

S2

SN

Frame

Time Division Multiplexing

1 2 3 23 24 F 1 2 3 ...Channels Framing bitFrame =1/8000=125 m secEight bits/channel slotT1 Frame-Pulse Code Modulation(PCM)8000 x (24 x 8 +1) = 1.544 Mbps

Digital Multiplexing Hierarchy

DS0 - 64 kbps

1 voice channel

DS1 - 1.544 Mbps

24 voice channels - 24 DS0

DS1C - 3.152 Mbps

48 voice channels - 2 DS1

DS2 - 6.312 Mbps

96 voice channels - 4 DS1

DS3 - 44.736 Mbps

672 voice channels - 7 DS2

DS3C - 89.472 Mbps

1344 voice channels - 2 DS3

DS4 - 274.176 Mbps

4032 voice channels - 6 DS3

Synchronous Optical Network(SONET) Synchronous Digital Hierarchy(SDH)90 bytes9 rowsSection andline overheadPayload - 87 bytes125 m sec transmission timeBBBBasic transmission rate = 8000 x 90 x 9 x8 =51.84 Mbps Basic frame

Motivation for SONETInterconnection of Carriers (TELCOs)Unifying NA, European and Japanese systemsMultiplexing optical speedsOperations, administration and maintenancePointers

PathSectionSectionSectionSectionLineLineSONET PathSource Mux Repeater Mux Repeater Destination Mux

Synchronous Optical Network(SONET) Synchronous Digital Hierarchy(SDH)90 bytes9 rowsSection andline overheadPayload - 87 bytes125 m sec transmission timeBBBBasic transmission rate = 8000 x 90 x 9 x8 =51.84 Mbps Basic framePathOverhead

Optical Digital Tranmission HierarchyOC-1 51.84 Mbps Basic Optical ChannelOC-3 155.52 Mbps 3 OC-1OC-12 622.08 Mbps 12 OC-1 OC-24 1244.16 Mbps 24 OC-1OC-48 2.4888 Gbps 48 OC-1

Digital DataStreamsAnalogSignals

Fig. 1 Communication System

DigitalSink

Demod

DigitalSource

Modulator

...0110...

Channel

Encoder

Decoder

...0110...

11000...

11000...

A B C DA B C DA B C DTimeCallrequest signalCall acceptSlopeshowsPropagation123112233Circuit switching Message switching Packet switchingTrunksStoreand foward

Property

Circuit switched

Packet switched

Dedicated path

yes

Bandwidth committed

fixed

dynamic

Store and forward

no

yes

Fixed route

yes

Potential BW waste

yes

no

Overhead

Constant up front

per packet

Call setup

Required

Congestion occurrence

At call setup

Any time

Charging

Per minute

Per packet

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Ten regional officesfully connected withone anotherSwitching Hierarchy - AT&T67 regional offices230 primary offices1300 toll offices19,000 end officesDirect trunksas trafficwarrants

Switch Implementation001122...77...

ConnectionsCrossbar(Crosspoint) SwitchN(N-1)/2 cross pointsfor no self connectionand FDXSpace division switch

Multiple stages reduce cross point count nxknxknxkkxnkxnkxn(N/n)x(N/n)(N/n)x(N/n)N/n crossbarsk cross barsninputsN/n crossbarsN=1000, k=10 24,000 crosspointsN(N-1)/2=499,500 crosspointsBlocking-Clos networksninputsninputs

Time slotinterchanger0 1 2 3 4 5 6 7 4 7 6 3 0 5 2 1 n input linesn output linesNRAMFig 2-40 Time division switch

Virtual CircuitHostSwitchRouting TableTrunkBISDN-ATM

1 2 3 4 5 6 7 8 9 10 111213 1415 16 1718 19 202122 2324Synchonous transmissionAsynchonous transmissionT1 frame(each slot=1 byte)2One cell=53 bytes6143155.52 Mbps Primary rate

ATM Switches SwitchFabricI/OI/OTwo basic typesInput queueingOutput queueing155 Mbps = 360,000 cells/sec

Cycle time=2.77 m sec16 to 1024 input linesObjectives: 1) Low cell loss rate 2) Order preserved

Input QueuesInput Queueing0123 2 3 0 3Head-of-line blocking58% throughput

3 1 13

0123Output Queueing100% ThroughputN-fold increase in cycle timefor NxN switch

Switch FabricsKnockout Switch Crosspoint Output bufferingcalculated risk on lossBanyan switch-self routing i.e. addresses read directlyConflicts avoided by presorting in a Batcher network

0 1 70123

4567ConsentratorOutputBufferInputOutputKnockout SwitchCrossbarSize limitation

01234567101101000001010011100101110111000OutputportsBanyan switch(Self-routing )

0123456710110101000001010011100101110111000

Collision01234567111101000001010011100101110111

BatcherNetwork(presort-pairwise)BanyanNetworkBatcher-Banyan Switch

Wireless SystemsPagingmessaging capabilityone wayLimited bandwidth 930-950 MHzCordless Telephone(No standardization)Analog Cellular Telephone-Mobile radioAdvanced Mobile Phone System(AMPS)CellularFrequency reuse

BaseStationLand LineCell structureMobilesRest of Network

Colors represent different frequencies Frequency Reused=distance between cells using same frequencyr=cell radius d/r=4.6

Channels832 FDX Channels832 Transmit Simplex Channels 824 to 849 MHz30 kHz width 832 Receive Simplex Channels 869 to 894 MHz30 kHz width Four Categories of ChannelsControl(base to mobile) -system managementPaging (base to mobile)- Alert mobile of callAccess (bi-directional) - Call setup, channel assignmentData (bi-directional) -Voice, Fax, data

A Quick History Lesson1956 - Consent Decree-Bell Canada and Northern Electric split off

A Quick History Lesson

1984 Final JudgementAT&TManufacturingLong DistanceSeven Operating Companiese.g. NYNEX, Bell SouthBell LabsBell Communications Research(Bellcore)

Recent DevelopmentsAT & T splits into Lucent (Mfg) and AT&T(Carrier)Long Distance competition in Canada, e.g. SprintStentor under pressure from competition