ws7 transmission media in communication system

8/9/2019 ws7 transmission media in communication system

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Classes of Transmission

MediaConducted or guided media use a conductor such as a ire or a

!"er optic ca"le to mo#e the signalfrom sender to recei#er

$ireless or unguided media

use radio a#es of di%erentfre&uencies and do not need a ire orca"le conductor to transmit signals


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Design 'actors

for Transmission MediaBandidth: (ll other factors remaining constant,the greater the "and-idth of a signal, the higherthe data rate that can "e achie#ed)

Transmission impairments) Limit the distance asignal can tra#el)

*nterference: Competing signals in o#erlappingfre&uency "ands can distort or ipe out a signal)

+um"er of recei#ers: ach attachmentintroduces some attenuation and distortion,limiting distance andor data rate)


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lectromagnetic .pectrum

for Transmission Media


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/uided Transmission

Media Transmission capacity depends onthe distance and on hether the

medium is point-to-point ormultipoint

0amples

tisted pair ires coa0ial ca"les

optical !"er


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Tisted Pair $ires

Consists of to insulated copperires arranged in a regular spiral

pattern to minimi1e theelectromagnetic interference"eteen ad2acent pairs

3ften used at customer facilities and

also o#er distances to carry #oice asell as data communications

Lo fre&uency transmission medium


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Types of Tisted Pair

.TP shielded tisted pair5 the pair is rapped ith metallic foil

or "raid to insulate the pair fromelectromagnetic interference

6TP unshielded tisted pair5

each ire is insulated ith plasticrap, "ut the pair is encased in anouter co#ering


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Tisted Pair (d#antages

*ne0pensi#e and readily a#aila"le

'le0i"le and light eight

asy to or= ith and install


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Tisted Pair

Disad#antages.uscepti"ility to interference andnoise

(ttenuation pro"lem 'or analog, repeaters needed e#ery ;-

=m

'or digital, repeaters needed e#ery >-8=m

elati#ely lo "andidth 8


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Coa0ial Ca"le or Coa05

6sed for ca"le tele#ision, L(+s,telephony

?as an inner conductor surrounded"y a "raided mesh

Both conductors share a common

center a0ial, hence the term @co-a0ialA


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Coa0 Layers

copper or aluminum conductor

insulating material

shield

(braided wire)

outer jacket

(polyethylene)


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Coa0 (d#antages

?igher "andidth 4


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Coa0 Disad#antages

?igh attenuation rate ma=es ite0pensi#e o#er long distance

Bul=y


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'i"er 3ptic Ca"le

elati#ely ne transmission mediumused "y telephone companies in placeof long-distance trun= lines

(lso used "y pri#ate companies inimplementing local datacommunications netor=s

e&uire a light source ith in2ectionlaser diode *LD5 or light-emitting diodesLD5


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plastic jacket glass or plastic

claddingfiber core

'i"er 3ptic Layers

consists of three concentricsections


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'i"er 3ptic Types

multimode step-inde0 !"er the reecti#e alls of the !"er mo#e the

light pulses to the recei#er

multimode graded-inde0 !"er acts to refract the light toard the center of

the !"er "y #ariations in the density

single mode !"er the light is guided don the center of an

e0tremely narro core


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fiber optic multimode

step-index

fiber optic multimode

graded-index

fiber optic single mode

'i"er 3ptic .ignals


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'i"er 3ptic (d#antages

greater capacity "andidth of upto > /"ps5

smaller si1e and lighter eightloer attenuation

immunity to en#ironmental

interferencehighly secure due to tap dicultyand lac= of signal radiation


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'i"er 3ptic Disad#antages

e0pensi#e o#er short distance

re&uires highly s=illed installers

adding additional nodes is dicult


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$ireless 6nguided Media5

Transmissiontransmission and reception are achie#ed"y means of an antenna

directional transmitting antenna puts out focused "eam

transmitter and recei#er must "e aligned

omnidirectional signal spreads out in all directions

can "e recei#ed "y many antennas


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$ireless 0amples

terrestrial microa#e

satellite microa#e

"roadcast radio

infrared


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Terrestrial Microa#e

used for long-distance telephone ser#ice

uses radio fre&uency spectrum, from > to 4</h1

para"olic dish transmitter, mounted high

used "y common carriers as ell as pri#atenetor=s

re&uires uno"structed line of sight "eteen

source and recei#ercur#ature of the earth re&uires stationsrepeaters5 E8< miles apart


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.atellite Microa#e

(pplications

Tele#ision distri"ution

Long-distance telephonetransmission

Pri#ate "usiness netor=s


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Microa#e Transmission

Disad#antagesline of sight re&uirement

e0pensi#e toers and repeaters

su"2ect to interference such aspassing airplanes and rain


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.atellite

Microa#e Transmissiona microa#e relay station in space

can relay signals o#er long distances

geostationary satellites remain a"o#e the e&uator at a height of

>>,8


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.atellite Transmission

Lin=searth stations communicate "ysending signals to the satellite on anuplin=

the satellite then repeats thosesignals on a donlin=

the "roadcast nature of the donlin=

ma=es it attracti#e for ser#ices suchas the distri"ution of tele#isionprogramming


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dishdish

uplink station downlink station

satellite

transponder

22,300 miles


Process


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(pplicationstele#ision distri"ution a netor= pro#ides programming from

a central location direct "roadcast satellite DB.5

long-distance telephone

transmission high-usage international trun=s

pri#ate "usiness netor=s


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Principal .atellite

Transmission BandsC "and: 4donlin=5 - uplin=5 /?1 the !rst to "e designated

Fu "and: 9>donlin=5 -94uplin=5 /?1 rain interference is the ma2or pro"lem

Fa "and: 9Gdonlin=5 - >Guplin=5 /?1 e&uipment needed to use the "and is still

#ery e0pensi#e


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adio

radio is omnidirectional andmicroa#e is directional

adio is a general term often usedto encompass fre&uencies in therange 8 =?1 to 8


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*nfrared

6ses transmittersrecei#erstranscei#ers5 that modulate

noncoherent infrared light) Transcei#ers must "e ithin line ofsight of each other directly or #iareection 5)

6nli=e microa#es, infrared doesnot penetrate alls)

ws7 transmission media in communication system

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