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Topic 7 - Guided Transmission Media.pdf

Apr 04, 2018

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    1Sumati J. Singh

    TRANSMISSION MEDIA

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    Classification2

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    Wired Media3

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    Twisted Pair

    2 conductors (copper) , own insulation , twisted

    1 used to carry signal

    Other used for ground reference

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    ece ver uses e erence e ween em Noise or crosstalk may affect both

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    Noise on Parallel Lines5

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    Noise on Twisted Lines6

    By adding the twist, reduction in the noise effect.1/23/2013Sumati J. Singh

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    Twisted Pair Generally color coded twisted pairs of insulated copper wires encased

    in plastic sheath

    Each wire has a diameter of 0.4 to 0.8 mm

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    ,

    Higher quality

    More expensive

    Number of twists per foot/meter is called twist ratio.

    More twists need more cable, may increase ATTENUATION.

    Balance is needed b/w minimizing crosstalk and reducing attenuation

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    Twisted Pair Various purposes

    Designs vary in twist ratio,grade of copper used, type of

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    .

    1 to 4200 pairs can bepacked.

    Modern networks use 4 pairspacked in together.

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    Characteristics

    Twisted pair is

    Relatively inexpensive

    Flexible

    Eas to install

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    Span significant distance before needing a repeater

    Easily accommodates different topologies

    Two categories : STP & UTP

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    Shielded Twisted Pair Consists of twisted wire pairs that are not only

    individually insulated, but also surrounded by a

    shielding made of a metallic substance such as foil.

    Sometimes braided copper shielding

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    Acts as barrier to external EM forces

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    Unshielded Twisted Pair Twisted wire pairs (insulated

    individually) covered in a plasticsheath

    No additional shieldin

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    Less expensive

    Less resistant to noise

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    Standards TIA/EIA finalized specifications in 1991 named

    TIA/EIA 568 TIA Telecommunications Industry Standards

    EIA Electronic Industries Standards

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    Divides twisted pair wiring in several categories

    Catfrom 1 to 7

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    TIA/EIA 568

    Category Bandwidth Data Rate Digital/Analog Use

    1 very low < 100 kbps Analog Telephone

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    < z ps na og g a - nes

    3 16 MHz 10 Mbps Digital LANs

    4 20 MHz 20 Mbps Digital LANs

    5 100 MHz 100 Mbps Digital LANs

    6 200 MHz 200 Mbps Digital LANs

    7 600 MHz 600 Mbps Digital LANs1/23/2013Sumati J. Singh

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    Cat 3 vs Cat 5Apart from the listed differences, some visual clues

    Higher twist ratio in Cat 5 , at-least 12 twists/ foot Cat 3 has 3 twists/foot

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    Cat 3 jacket is loose than Cat 5

    Cat 5 can support only a small amount of untwistingbefore termination.

    Cat 5 provides better throughput. 1/23/2013Sumati J. Singh

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    STP and UTP Cost STP is generally more expensive and also requires grounding

    and installation charges. UTP 6 is costly too.

    Throughput Ranges from 10 to 1000 Mbps depending on type ofwire.

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    Connector Both use RJ-45 and RJ-11 connectors

    Noise immunity STP is more resistant than UTP UTP may use filtering and balancing to offset the effects of noise

    Size & Scalability Max segment length is 100 m or 328 ft. OnEthernet support 1 Mbps to 10 Gbps with max 1024 nodes.

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    UTP Performance16

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    Terminating Twisted Pair18

    Cross over cable1/23/2013Sumati J. Singh

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    Coaxial Cable Also called coax

    Single core (copper wire) enclosed in insulating sheath,encased in outer conductor metal foil / braid /

    combination.

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    This outer wrap is used to shield and acts second conductorfor ground

    Outer conductor is insulated

    Covered in plastic sheath

    Insulator is PVC/Teflon 1/23/2013Sumati J. Singh

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    Coaxial Cable20

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    Characteristic High resistance to noise

    Carry signals to larger distances than twisted pair More expensive

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    STANDARDS Radio Guide Used to guide radio frequencies in broadband

    Different types provide different impedance,

    attenuation and throughput Size of core is in AWG ( American Wire Gauge ). High

    AWG smaller the diameter

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    RG - 6 Impedance of 75 ohms

    contains an 18 AWG conducting core.

    to deliver broadband cable Internet service and

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    over long distances

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    RG - 8 50-ohm impedance

    10 AWG core.

    the medium for the first Ethernet networks

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    o owe e ase- s an ar

    10 max throughput 10 Mbps

    baseband transmission

    maximum segment length of 500 meters. known as Thicknet

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    RG - 58 50-ohm impedance

    24 AWG core

    Popular Ethernet network medium in 80s

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    ma er ame er an - , more ex e, easy o

    install & handle

    10Base-2

    Thinner than RG-8, also called Thinnet

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    RG-59 75 ohm impedance

    20 or 22 AWG core

    Made of braided copper

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    ess expns ve, u grea er a enua on

    Used for short connections

    RG-6 and RG-59 are commonly used

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    Connector F-type

    Attach in a way so that the pin in the center of theconnector is the conducting core of the cable

    Compressed to attach to cable, connectors are

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    threaded and screw together like a nut and boltassembly

    Mostly used for RG-6

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    Connector BNC (Bayonet Neill-Concelman)

    Crimped, compressed and twisted on cable Connects to another BNC via turning & locking

    Do not use core of coax have their own conductin in

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    Used with RG 59 commonly

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    Applications Analog telephone networks

    Single cable carries 10000 voice signals

    Later used in digital data, carry upto 600 Mbps

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    Refraction29

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    Critical Angle30

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    Reflection31

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    Fiber Optic Cable Glass fibers at the core

    Covered by glass or plastic cladding Cladding should be of different density as of core

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    opaque, prevent light from escaping

    Strands of Kevlar (polymeric fiber) surrounds

    Plastic sheath

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    Fiber Modes33

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    SMF Narrow core ( less than 10 microns)

    Highly focused, expensive Limits beam to smaller range of angles, close to

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    Lower density material , critical angle close enough

    to 90 degree

    Propagation almost horizontal

    Delays are negligible

    Allows high bandwidth & longest distances (of all

    media) 1/23/2013Sumati

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