Pertemuan 3Transmission Media

TerminologiGuided - wireUnguided - wirelessCharacteristics and quality determined by medium and signalFor guided, the medium is more importantFor unguided, the bandwidth produced by the antenna is more importantKey concerns are data rate and distance

Design FactorsBandwidthHigher bandwidth gives higher data rateTransmission impairmentsAttenuationInterferenceNumber of receiversIn guided mediaMore receivers (multi-point) introduce more attenuation

Electromagnetic Spectrum

Media Transmisi TerbimbingTwisted PairCoaxial cableOptical fiber

Twisted Pair

Twisted Pair - ApplicationsMost common mediumTelephone networkBetween house and local exchange (subscriber loop)Within buildingsTo private branch exchange (PBX)For local area networks (LAN)10Mbps or 100Mbps

Twisted Pair - Pros and ConsCheapEasy to work withLow data rateShort range

Twisted Pair - Transmission CharacteristicsAnalog Amplifiers every 5km to 6kmDigitalUse either analog or digital signalsrepeater every 2km or 3kmLimited distanceLimited bandwidth (1MHz)Limited data rate (100MHz)Susceptible to interference and noise

Unshielded and Shielded TPUnshielded Twisted Pair (UTP)Ordinary telephone wireCheapestEasiest to installSuffers from external EM interferenceShielded Twisted Pair (STP)Metal braid or sheathing that reduces interferenceMore expensiveHarder to handle (thick, heavy)

UTP CategoriesCat 3up to 16MHzVoice grade found in most officesTwist length of 7.5 cm to 10 cmCat 4up to 20 MHzCat 5up to 100MHzCommonly pre-installed in new office buildingsTwist length 0.6 cm to 0.85 cm

Near End CrosstalkCoupling of signal from one pair to anotherCoupling takes place when transmit signal entering the link couples back to receiving pairi.e. near transmitted signal is picked up by near receiving pair

Coaxial Cable

Coaxial Cable ApplicationsMost versatile mediumTelevision distributionAriel to TVCable TVLong distance telephone transmissionCan carry 10,000 voice calls simultaneouslyBeing replaced by fiber opticShort distance computer systems linksLocal area networks

Coaxial Cable - Transmission CharacteristicsAnalogAmplifiers every few kmCloser if higher frequencyUp to 500MHzDigitalRepeater every 1kmCloser for higher data rates

Optical Fiber

Optical Fiber - BenefitsGreater capacityData rates of hundreds of GbpsSmaller size & weightLower attenuationElectromagnetic isolationGreater repeater spacing10s of km at least

Optical Fiber - ApplicationsLong-haul trunksMetropolitan trunksRural exchange trunksSubscriber loopsLANs

Optical Fiber - Transmission CharacteristicsAct as wave guide for 1014 to 1015 Hz Portions of infrared and visible spectrumLight Emitting Diode (LED)CheaperWider operating temp rangeLast longerInjection Laser Diode (ILD)More efficientGreater data rateWavelength Division Multiplexing

Optical Fiber Transmission Modes

Wireless TransmissionUnguided mediaTransmission and reception via antennaDirectionalFocused beamCareful alignment required OmnidirectionalSignal spreads in all directionsCan be received by many antennae

Frequencies2GHz to 40GHzMicrowaveHighly directionalPoint to pointSatellite30MHz to 1GHzOmnidirectionalBroadcast radio3 x 1011 to 2 x 1014InfraredLocal

Terrestrial MicrowaveParabolic dishFocused beamLine of sightLong haul telecommunicationsHigher frequencies give higher data rates

Satellite MicrowaveSatellite is relay stationSatellite receives on one frequency, amplifies or repeats signal and transmits on another frequencyRequires geo-stationary orbitHeight of 35,784kmTelevisionLong distance telephonePrivate business networks

Broadcast RadioOmnidirectionalFM radioUHF and VHF televisionLine of sightSuffers from multipath interferenceReflections

InfraredModulate noncoherent infrared lightLine of sight (or reflection)Blocked by wallse.g. TV remote control, IRD port

Required ReadingISM (Industrial, Scientis, Medical) dan aplikasinya .tugas..2,4 GHz