chapt 4 data com

8/19/2019 Chapt 4 Data Com

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Transmission Media

CHAPTER 4


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CONTENT1) Guided Transmission

Twisted pair

Coaxial Cable

Optical Fiber

2) Wireless transmission

Antenna

Terrestrial/Satellite Microwae

!roadcast radio

"n#rared$) Wireless propa%ation

Ground Wae

S&' wae

(ine o# Si%t *ropa%ation

+) (ine o# Si%t Transmission Free Space (oss

Atmosperic Absorption

Multipat

,e#raction


3/53

(earnin% Outcomes

1) -iscuss te p'sical caracteristics o# twisted pair. coaxial cable and optical #iber

2) xplain ow #re0uenc' is determined #rom waelen%t #or optical

#iber transmission

$) nderstand te principle operation o# a parabolic antenna

+) xplain te di##erence between optical and radio lineo#si%t

3) (ist and explain te #actors tat a##ect lineo#si%t transmission


4/53

“Communication channels in the animal world include

touch, sound, sight, and scent. Electric eels even useelectric pulses. Ravens also are very expressive. By a

combination voice, patterns of feather erection and

body posture ravens communicate so clearly that an

experienced observer can identify anger,affection, hunger, curiosity, playfulness,

fright, boldness, and depression.”

Mind of the Raven,

Bernd Heinrich


5/53

Design Factors Determining Data

Rate and Distance

• Higher bandwidth gives higher data rate

Bandwidth

• m!airments" s#ch as atten#ation" $imit the distance

Transmission im!airments

• Over$a!!ing %reenc' bands can distort or wi!e o#t a signa$

nter%erence

• More receivers introd#ces more atten#ation

N#mber o% receivers


6/53

102Frequency

(Hertz) 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015

Power and telepone!otat"n# #enerator$%u$"cal "n$tru&ent$'o"ce &"cropone$

%"crowae!adar%"crowae antenna$%a#netron$

n*rared+a$er$,u"ded &"$$"le$!an#e-nder$

!ad"o!ad"o$ and tele"$"on$.lectron"c tu/e$nte#rated c"rcu"t$

ellular elepony

.+F 'F

(F 4 xtremel' low #re0uenc'

5F 4 5oice #re0uenc'

5(F 4 5er' low #re0uenc'

(F 4 (ow #re0uenc'

MF 4 Medium #re0uenc'

6F 4 6i% #re0uenc'

56F 4 5er' i% #re0uenc'

6F 4 ltrai% #re0uenc'

S6F 4 Superi% #re0uenc'

6F 4 xtremel' i% #re0uenc'

'+F +F %F HF 'HF HF HF .HF

w"$ted Pa"r

oa"al a/le

'"$"/lel"#t

pt"calF"/er

F% !ad"o

and '

% !ad"o erre$tr"al

and atell"teran$&"$$"on

aelen#t"n $pace(&eter$)

106 105 104 103 102 101 100 101 102 103 104 105 106

F"#ure 4:1 .lectro&a#net"c pectru& *or eleco&&un"cat"on$


7/53

Tab$e 4()

Point*to*Point Transmission

Characteristics o% +#ided Media

Frequency!an#e

1yp"cal6ttenuat"on

1yp"cal ;elay !epeaterpac"n#

Twisted pair

7wit loadin%)

8 to $93 &6: 892 d!/&m ; 1

&6:

38


8/53

(a) w"$ted pa"r

(/) oa"al ca/le

u?ercoat"n#

ladd"n#

tw"$tlen#t


9/53

Twisted Pair

Twisted !air is the $east e,!ensive and most wide$' #sed

g#ided transmission medi#m

Consists o% two ins#$ated co!!er wires arranged in a reg#$ars!ira$ !attern

A wire !air acts as a sing$e comm#nication $in- Pairs are b#nd$ed together into a cab$e Most common$' #sed in the te$e!hone networ- and %or

comm#nications within b#i$dings


10/53

18=18@18318+18$182

Fre0uenc' 76:)

A t t e n u a t i o n 7 d ! / & m )

(a) w"$ted pa"r (/a$ed on A!..'95B)

8

18$

1 &6: 1 M6: 1 G6: 1 T6:18@ 18> 1812 1813

8

3

18

13

28

23

$8

26, (0:4 &&)24, (0:5 &&)22, (0:6 &&)

19, (0:9 &&)

0:5 &&tw"$ted pa"r

183 18@ 18= 18?

Fre0uenc' 76:)

A

t t e n u a t i o n 7 d ! / & m )

(/) oa"al ca/le (/a$ed on A>.++90B)

8

3

18

13

28

23

$8

3C8@ ca/le(9:5 &&)

?88 >88 1888 1188 1288 1$88 1+88 1388 1@88 1=88

Waelen%t in acuum 7nm)

A t t e n u a t i o n 7 d ! / & m )

(c) pt"cal -/er (/a$ed on AF!..02B)

8

893

198

193

298

293

$98

Fre0uenc' 76:)

A

t t e n u a t i o n 7 d ! / & m )

(d) o&po$"te #rap

F"#ure 4:3 ttenuat"on o* yp"cal ,u"ded %ed"a

8

3

18

13

28

23

$8

typ"cal opt"cal-/er

9:5 &&coa

M a i n d

i % % e r e n

c e .


11/53

/nshie$ded and 0hie$ded Twisted Pair

/nshie$ded Twisted Pair 1/TP2

• Consists o% one or more twisted*!air cab$es" t'!ica$$'enc$osed within an overa$$ thermo!$astic 3ac-et which!rovides no e$ectromagnetic shie$ding

• Ordinar' te$e!hone wire

• 0#b3ect to e,terna$ e$ectromagnetic inter%erence

• The tighter the twisting" the higher the s#!!ortedtransmission rate and the greater the cost !er meter

0hie$ded Twisted Pair 10TP2

• Has meta$ braid or sheathing that red#ces inter%erence

• Provides better !er%ormance at higher data rates

• More e,!ensive


12/53

Tab$e 4(Twisted Pair Categories and C$asses

T* 4 nsielded twisted pair

FT* 4 Foil twisted pair

S/FT* 4 Sielded/#oil twisted pair

enuation

ross talk

o


13/53

Near*End Crossta$-

1NE5T2

Coupling of signal from one pair of conductors to

another Conductors may be the metal pins in a connector or

wire pairs in a cable

Near end refers to coupling that takes place

when the transmit signal entering the link

couples back to the receive conductor pair atthat same end of the link

Greater NEXT loss magnitudes are associated

with less crosstalk noise


14/53

!

y$te& y$te& >

!

ran$&"tted$"#nal

(powerPt )

ran$&"tted$"#nal

(powerPt )

!ece"ed

$"#nal(powerPr )

D.E(powerP

c)

F"#ure 4:4 "#nal Power !elat"on$"p$ (*ro& y$te& "ewpo"nt)


15/53

0 100

0

20

40

60

65200

d e c " / e l $

Frequency (%Hz)

F"#ure 4:5 ate#ory 6 annel !equ"re&ent$

!

D.E

D.E nearend cro$$talG ! attenuat"ontocro$$talG rat"o

ttenuat"on

300 400 500


16/53

Coa,ia$ Cab$e

Coa,ia$ cab$e can be #sed over $onger distances and s#!!ort

more stations on a shared $ine than twisted !air

Consists o% a ho$$ow o#ter c'$indrica$ cond#ctor that s#rro#nds a

sing$e inner wire cond#ctor s a versati$e transmission medi#m #sed in a wide variet' o%

a!!$ications

/sed %or T6 distrib#tion" $ong distance te$e!hone transmissionand 7ANs


17/53

Coa,ia$ Cab$e * Transmission

CharacteristicsFrequencycharacteristicssuperior to

twisted pair

erformance

limited byattenuationand noise

!nalog signals

• !mplifiers are

needed everyfew kilometers "closer if higherfrequency

• #sablespectrume$tends up to

%&&'()

*igital signals

• +epeater every

,km " closer forhigher datarates


18/53

18=18@18318+18$182

Fre0uenc' 76:)

A t t e

n u a t i o n 7 d ! / & m )

(a) w"$ted pa"r (/a$ed on A!..'95B)

8

18$

1 &6: 1 M6: 1 G6: 1 T6:18@ 18> 1812 1813

8

3

18

13

28

23

$8

26, (0:4 &&)24, (0:5 &&)22, (0:6 &&)

19, (0:9 &&)

0:5 &&tw"$ted pa"r

183 18@ 18= 18?

Fre0uenc' 76:)

A

t t e n u a t i o n 7 d ! / & m )

(/) oa"al ca/le (/a$ed on A>.++90B)

8

3

18

13

28

23

$8

3C8@ ca/le(9:5 &&)

?88 >88 1888 1188 1288 1$88 1+88 1388 1@88 1=88

Waelen%t in acuum 7nm)

A t t e

n u a t i o n 7 d ! / & m )

(c) pt"cal -/er (/a$ed on AF!..02B)

8

893

198

193

298

293

$98

Fre0uenc' 76:)

A

t t e n u a t i o n 7 d ! / & m )

(d) o&po$"te #rap

F"#ure 4:3 ttenuat"on o* yp"cal ,u"ded %ed"a

8

3

18

13

28

23

$8

typ"cal opt"cal-/er

9:5 &&coa


19/53

O!tica$ Fiber

O!tica$ %iber is a thin %$e,ib$e medi#m ca!ab$e o% g#iding an

o!tica$ ra'

6ario#s g$asses and !$astics can be #sed to ma-e o!tica$ %ibers Has a c'$indrica$ sha!e with three sections 8 core" c$adding"

3ac-et 9ide$' #sed in $ong distance te$ecomm#nications Per%ormance" !rice and advantages have made it !o!#$ar to #se


20/53

O!tica$ Fiber * Bene%its

Greater capacity *ata rates of hundreds of Gbps over tens of kilometers have been

demonstrated

-maller si)e and lighter weight Considerably thinner than coa$ial or twisted pair cable +educes structural support requirements

.ower attenuation

Electromagnetic isolation Not vulnerable to interference/ impulse noise/ or crosstalk (igh degree of security from eavesdropping

Greater repeater spacing

.ower cost and fewer sources of error


21/53

Categories o% A!!$ication

Five basic categories of application have

become important for optical fiber0 .ong"haul trunks 'etropolitan trunks +ural e$change trunks -ubscriber loops .ocal area networks


22/53

F"#ure 4:6 pt"cal o&&un"cat"on

.C oner$"on

pt"cal -/er

.lectr"cald"#"tal$"#nal

.lectr"cald"#"tal$"#nal

.lectron"c"nter*ace

.lectron"c"nter*ace

+.; orla$er

l"#t $ource+"#twae

pul$e$

;etector(l"#t

$en$or)

C. oner$"on

Transmitter ,eceierer


23/53

"nput pulse Output pulse

7a) Stepindex multimode


7c) Sin%le mode

F"#ure 4:7 pt"cal F"/er ran$&"$$"on %ode$


7b) Gradedindex multimode


24/53

Tab$e 4(:

Freenc' /ti$i;ation %or

Fiber A!!$ications

WDM = wavelength division multiplexing

Wavelength (invacuum) range

(nm)

FrequencyRange (THz)

BandLabel

Fiber Type Application

820 to 900 366 to 333 Multimode LAN

1280 to 1350 234 to 222 S Single mode Various

1528 to 1561 196 to 192 C Single mode WDM

1561 to 1620 192 to 185 L Single mode WDM


25/53


26/53

Atten#ation in +#ided Media


27/53

9ire$ess Transmission

Freencies

)+H; to4


28/53

Antennas

Electrical conductor or system of conductors used

to radiate or collect electromagnetic energy

+adio frequency electrical energy from thetransmitter is converted into electromagnetic

energy by the antenna and radiated into the

surrounding environment

+eception occurs when the electromagnetic signalintersects the antenna

2n two way communication/ the same antenna can

be used for both transmission and reception


29/53

Radiation Pattern

ower radiated in all directions *oes not perform equally well in all directions

+adiation pattern ! graphical representation of the radiation properties

of an antenna as a function of space coordinates

2sotropic antenna

! point in space that radiates powerin all directions equally

!ctual radiation pattern is a sphere

with the antenna at the center


30/53

y

a

ab

bc

f f

c

x d " r e c t r " 4

*ocu$

(a) Para/ola

$ource o* electro&a#net"cener#y

tran$&"tt"n#wae$

F"#ure 4:8 Para/ol"c !e=ect"e 6ntenna

(/) ro$$$ect"on o* para/ol"c antenna$ow"n# re=ect"e property


31/53

Antenna +ain

! measure of the

directionality of anantenna

*efined as thepower output in aparticular direction

versus thatproduced by an

isotropic antenna

'easured indecibels 3d45

The increasedpower radiated in agiven direction is at

the e$pense ofother directions

Effective area of anantenna is related

to the physical si)eof the antenna and

to its shape


32/53


33/53

Terrestria$ Microwave

'ost common type is theparabolic 6dish7

Typical si)e is about 1 m indiameter

!ntenna is fi$ed rigidly andfocuses a narrow beam to

achieve line"of"sighttransmission to the

receiving antenna

#sually located atsubstantial heights above

ground level

! series of microwave relaytowers is used to achieve

long"distance transmission


34/53

Terrestria$ Microwave

A!!$ications #sed for long haul telecommunications

service as an alternative to coa$ial cable or

optical fiber #sed for both voice and T8 transmission Fewer repeaters but requires line"of"sight

transmission

,"9&G() frequencies/ with higher frequencieshaving higher data rates

'ain source of loss is attenuation causedmostly by distance/ rainfall and interference


35/53

Tab$e 4(4T'!ica$ Digita$ Microwave

Per%ormance>and (,Hz) >andw"dt (%Hz) ;ata !ate (%/p$)

2 = 12

@ $8 >8

11 +8 1$3

1? 228 2=+

(oss due to attenuation is ( 4 18lo%d!

were d is te distance and te waelen%t in te same unit9

Brecall 4 c x #


36/53

0ate$$ite Microwave

! communication satellite is in effect amicrowave relay station

#sed to link two or more ground stations +eceives transmissions on one frequency band/

amplifies or repeats the signal/ and transmits iton another frequency Frequency bands are called transponder channels


37/53

atell"teantenna

.art$tat"on

ran$&"tter

%ult"plerece"er$

%ult"plerece"er$

(a) Po"nttopo"nt l"nG

atell"teantenna

(/) >roadca$t l"nG

F"#ure 4:9 atell"te o&&un"cat"on on-#urat"on$


38/53

0ate$$ite Microwave A!!$ications

'ost important applications for satellites are0

• rograms are transmitted to the satellite thenbroadcast down to a number of stations which thendistribute the programs to individual viewers

• *irect 4roadcast -atellite 3*4-5 transmits videosignals directly to the home user

• Navstar Globalositioning -ystem 3G-5

• -atellite providers candivide capacity intochannels and lease thesechannels to individualbusiness users

• 2s the optimum medium forhigh"usage internationaltrunks

.ong"distancetelephone

transmission

rivatebusinessnetworks

Televisiondistribution

Globalpositioning


39/53

u/and$atell"te

Hu/

erer

P$

Po"nto*$ale

er&"nal$

!e&ote$"te

!e&ote$"te

!e&ote$"te

F"#ure 4:10 yp"cal ' on-#urat"on


40/53

Transmission Characteristics

The optimum frequency range for satellite

transmission is , to ,& G()• 4elow , G() there is significant noise from natural sources

• !bove ,& G() the signal is severely attenuated by atmospheric

absorption and precipitation

-atellites use a frequency bandwidth range of

%:;


41/53

Broadcast Radio

4roadcast radio is omnidirectional andmicrowave is directional

Radio is the term used to encompass

frequencies in the range of 1k() to 1&&G()Broadcast radio 31&'() " ,G()5 covers0

? F' radio and #(F and 8(F television band

? *ata networking applications

.imited to $ine o% sight

-uffers from m#$ti!ath inter%erence +eflections from land/ water/ man"made obAects


42/53

n%rared

!chieved using transceivers that modulatenoncoherent infrared light

Transceivers must be within line of sight of

each other directly or via reflection*oes not penetrate wallsNo licensing is required

No frequency allocation issues


43/53

Tab$e 4(=

Freenc'

Bands

7Table can be

#ound on pa%e

1$@ in textboo&)


44/53

+ro#nd wave !ro!agation %o$$ows the conto#r o% the

earth and can !ro!agate distances we$$ over the vis#a$

hori;on This e%%ect is %o#nd in %reencies #! to abo#t MH; The best -nown e,am!$e o% gro#nd wave comm#nication

is AM radio

.art

(a) ,roundwae propa#at"on (/elow 2 %Hz)

tran$&"tantenna

rece"eantenna

$"#nalpropa#at"on

F"#ure 4:11 "rele$$ Propa#at"on %ode$


45/53

0-' wave !ro!agation is #sed %or amate#r radio and

internationa$ broadcasts s#ch asBBC

andVoice of America

A signa$ %rom an earth based antenna is re%$ected %rom the

ioni;ed $a'er o% the #!!er atmos!here bac- down to earth 0-' wave signa$s can trave$ thro#gh a n#mber o% ho!s"

bo#ncing bac- and %orth between the ionos!here and the

earth>s s#r%ace

.art

(/) Gywae propa#at"on (2 to 30 %Hz)

tran$&"tantenna

rece"eantenna



46/53

+ro#nd and s-' wave !ro!agation modes

do not o!erate above :< MH; * *

comm#nication m#st be b' $ine o% sight


.art

(c) +"neo*$"#t (+) propa#at"on (a/oe 30 %Hz)

tran$&"tantenna

rece"eantenna

$"#nalpropa#at"on


47/53

Re%raction

Bccurs because the velocity of an electromagnetic wave is afunction of the density of the medium through which it travels? 1 $ ,& m@s in a vacuum/ less in anything else

The speed changes with movement between a medium ofone density to a medium of another density

2nde$ of refraction 3refractive inde$5 The sine of the angle of incidence divided by the sine of the angle of

refraction 2s also equal to the ratio of the respective velocities in the two media 8aries with wavelength

Gradual bending *ensity of atmosphere decreases with height/ resulting in bending of

radio waves toward the earth


48/53

.art

pt"cal or"zon

!ad"o or"zon

ntenna

F"#ure 4:12 pt"cal and !ad"o Hor"zon$

(ine o# Si%t


49/53

(ine o# Si%t

Assume earth radius =

6oweer. te radio line o# si%t acieable distance is %ien d

4$93= 4 $9=3 9 - in &m and in m

An alternatie #ormula is d = were d is in miles. in #eet


50/53

7ine*o%*0ight Transmission

Free s!ace

$oss• 7oss o%

signa$withdistance

Atmos!heric

Absor!tion• From water

va!or ando,'genabsor!tion

M#$ti!ath

• M#$ti!$einter%eringsigna$s%romre%$ections

Re%raction• Bending

signa$awa' %romreceiver


51/53

601 5 10

;"$tance (G&)

F"#ure 4:13 Free pace +o$$

+ o $ $ ( d > )

50 100

70

80

90

100

110

120

130

140

150

160

170

180


52/53

(a) %"crowae l"ne o* $"#t

(/) %o/"le rad"o

F"#ure 4:14 .a&ple$ o* %ult"pat nter*erence


53/53

0#mmar'

Guided transmission

media Twisted pair

Coa$ial cable Bptical fiber

Direless transmission !ntennas Terrestrial microwave -atellite microwave 4roadcast radio 2nfrared

Direless propagation Ground wave

propagation -ky wave propagation .ine"of"sight

propagation

.ine"of"sight

transmission Free space loss !tmospheric absorption 'ultipath

chapt 4 data com

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