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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

 

UNIT I: MODULATION SYSTEMS Time and frequenc d!main re"re#en$a$i!n !f 

#i%na&#' am"&i$ude m!du&a$i!n and dem!du&a$i!n' frequenc m!du&a$i!n and

dem!du&a$i!n' #u"er (e$er!dne radi! recei)er* +requenc di)i#i!n mu&$i"&e,in%* Pu&#e

-id$( m!du&a$i!n

Time and frequency domain representation of signals:

E&ec$rica& #i%na&# (a)e /!$( $ime and frequenc d!main re"re#en$a$i!n#* In $(e

$ime d!main' )!&$a%e !r curren$ i# e,"re##ed a# a func$i!n !f $ime a# i&&u#$ra$ed in +i%ure

8* M!#$ "e!"&e are re&a$i)e& c!mf!r$a/&e -i$( $ime d!main re"re#en$a$i!n# !f #i%na&#*

Si%na&# mea#ured !n an !#ci&&!#c!"e are di#"&aed in $(e $ime d!main and di%i$a&

inf!rma$i!n i# !f$en c!n)eed / a )!&$a%e a# a func$i!n !f $ime*

Si%na&# can a&#! /e re"re#en$ed / a ma%ni$ude and "(a#e a# a func$i!n !f 

frequenc* Si%na&# $(a$ re"ea$ "eri!dica&& in $ime are re"re#en$ed / a "!-er #"ec$rum a#

i&&u#$ra$ed in +i%ure ;* Si%na&# $(a$ are $ime &imi$ed i*e* are !n& n!n1Ber! f!r a fini$e

$ime are re"re#en$ed / an ener% #"ec$rum a# i&&u#$ra$ed in +i%ure*

C*T=IAGARA@AN1AP ECE DEPT* ;

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Ana&!% C!mmunica$i!n i# a da$a $ran#mi$$in% $ec(nique in a f!rma$ $(a$ u$i&iBe#

c!n$inu!u# #i%na&# $! $ran#mi$ da$a inc&udin% )!ice' ima%e' )ide!' e&ec$r!n# e$c* An

ana&!% #i%na& i# a )aria/&e #i%na& c!n$inu!u# in /!$( $ime and am"&i$ude -(ic( i#

%enera&& carried / u#e !f m!du&a$i!n* Ana&!% circui$# d! n!$ in)!&)e quan$iBa$i!n !f 

inf!rma$i!n un&i2e $(e di%i$a& circui$# and c!n#equen$& (a)e a "rimar di#ad)an$a%e !f 

rand!m )aria$i!n and #i%na& de%rada$i!n' "ar$icu&ar& re#u&$in% in addin% n!i#e $! $(e

audi! !r )ide! qua&i$ !)er a di#$ance*

Da$a i# re"re#en$ed / "(#ica& quan$i$ie# $(a$ are added !r rem!)ed $! a&$er da$a*

Ana&!% $ran#mi##i!n i# ine,"en#i)e and ena/&e# inf!rma$i!n $! /e $ran#mi$$ed fr!m "!in$1

$!1"!in$ !r fr!m !ne "!in$ $! man* Once $(e da$a (a# arri)ed a$ $(e recei)in% end' i$ i#

c!n)er$ed /ac2 in$! di%i$a& f!rm #! $(a$ i$ can /e "r!ce##ed / $(e recei)in% c!m"u$er*

Ana&!% c!mmunica$i!n ##$em# c!n)er$ m!du&a$e ana&!% #i%na&# in$! m!du&a$ed

ana&!% #i%na&#* C!mmunica$i!n ##$em# c!n)er$ inf!rma$i!n in$! a f!rma$ a""r!"ria$e

f!r $(e $ran#mi##i!n medium* T(e &!c2 dia%ram !f a c!mmunica$i!n ##$em i# %i)en

 /e&!-:

C*T=IAGARA@AN1AP ECE DEPT* ?

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

+i%*8 C!mmunica$i!n S#$em &!c2 Dia%ram

T(e S!urce enc!der c!n)er$# me##a%e in$! me##a%e #i%na& !r /i$#* T(e

Tran#mi$$er c!n)er$# me##a%e #i%na& !r /i$# in$! f!rma$ a""r!"ria$e f!r c(anne&$ran#mi##i!n ana&!%di%i$a& #i%na&* T(e C(anne& in$r!duce# di#$!r$i!n' n!i#e' and

in$erference* Recei)er dec!de# recei)ed #i%na& /ac2 $! me##a%e #i%na&* S!urce dec!der 

dec!de# me##a%e #i%na& /ac2 in$! !ri%ina& me##a%e*

Amplitude Modulation:

Am"&i$ude m!du&a$i!n AM i# a $ec(nique u#ed in e&ec$r!nic c!mmunica$i!n'

m!#$ c!mm!n& f!r $ran#mi$$in% inf!rma$i!n )ia a radi! carrier -a)e* AM -!r2# /

)arin% $(e #$ren%$( !f $(e $ran#mi$$ed #i%na& in re&a$i!n $! $(e inf!rma$i!n /ein% #en$* +!r 

e,am"&e' c(an%e# in $(e #i%na& #$ren%$( can /e u#ed $! #"ecif $(e #!und# $! /e

re"r!duced / a &!ud#"ea2er' !r $(e &i%($ in$en#i$ !f $e&e)i#i!n "i,e&#* C!n$ra#$ $(i# -i$(

frequenc m!du&a$i!n' a&#! c!mm!n& u#ed f!r #!und $ran#mi##i!n#' in -(ic( $(e

frequenc i# )aried0 and "(a#e m!du&a$i!n' !f$en u#ed in rem!$e c!n$r!&#' in -(ic( $(e

 "(a#e i# )aried*In !rder $(a$ a radi! #i%na& can carr audi! !r !$(er inf!rma$i!n f!r 

 /r!adca#$in% !r f!r $-! -a radi! c!mmunica$i!n' i$ mu#$ /e m!du&a$ed !r c(an%ed in

#!me -a* A&$(!u%( $(ere are a num/er !f -a# in -(ic( a radi! #i%na& ma /e

m!du&a$ed' !ne !f $(e ea#ie#$' and !ne !f $(e fir#$ me$(!d# $! /e u#ed -a# $! c(an%e i$#

am"&i$ude in &ine -i$( )aria$i!n# !f $(e #!und*

C*T=IAGARA@AN1AP ECE DEPT* >

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e /a#ic c!nce"$ #urr!undin% -(a$ i# am"&i$ude m!du&a$i!n' AM' i# qui$e

#$rai%($f!r-ard* T(e am"&i$ude !f $(e #i%na& i# c(an%ed in &ine -i$( $(e in#$an$ane!u#

in$en#i$ !f $(e #!und* In $(i# -a $(e radi! frequenc #i%na& (a# a re"re#en$a$i!n !f $(e

#!und -a)e #u"erim"!#ed in i$* In )ie- !f $(e -a $(e /a#ic #i%na& carrie# $(e #!und !r 

m!du&a$i!n' $(e radi! frequenc #i%na& i# !f$en $ermed $(e carrier*

  Fig.2 Amplitude Modulation, AM

4(en a carrier i# m!du&a$ed in an -a' fur$(er #i%na&# are crea$ed $(a$ carr $(e

ac$ua& m!du&a$i!n inf!rma$i!n* I$ i# f!und $(a$ -(en a carrier i# am"&i$ude m!du&a$ed'

fur$(er #i%na&# are %enera$ed a/!)e and /e&!- $(e main carrier* T! #ee (!- $(i# (a""en#'$a2e $(e e,am"&e !f a carrier !n a frequenc !f 8 M=B -(ic( i# m!du&a$ed / a #$ead

$!ne !f 8 2=B*T(e "r!ce## !f m!du&a$in% a carrier i# e,ac$& $(e #ame a# mi,in% $-!

#i%na&# $!%e$(er' and a# a re#u&$ /!$( #um and difference frequencie# are "r!duced*

T(eref!re -(en a $!ne !f 8 2=B i# mi,ed -i$( a carrier !f 8 M=B' a #um frequenc i#

 "r!duced a$ 8 M=B F 8 2=B' and a difference frequenc i# "r!duced a$ 8 M=B 1 8 2=B'

i*e* 8 2=B a/!)e and /e&!- $(e carrier*

If $(e #$ead #$a$e $!ne# are re"&aced -i$( audi! &i2e $(a$ enc!un$ered -i$( #"eec(

!f mu#ic' $(e#e c!m"ri#e man differen$ frequencie# and an audi! #"ec$rum -i$(

frequencie# !)er a /and !f frequencie# i# #een* 4(en m!du&a$ed !n$! $(e carrier' $(e#e

#"ec$ra are #een a/!)e and /e&!- $(e carrier*

C*T=IAGARA@AN1AP ECE DEPT* 5

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

I$ can /e #een $(a$ if $(e $!" frequenc $(a$ i# m!du&a$ed !n$! $(e carrier i# 6 2=B'

$(en $(e $!" #"ec$ra -i&& e,$end $! 6 2=B a/!)e and /e&!- $(e #i%na&* In !$(er -!rd# $(e

 /and-id$( !ccu"ied / $(e AM #i%na& i# $-ice $(e ma,imum frequenc !f $(e #i%na& $(a$

i# u#ed $! m!du&a$e $(e carrier' i*e* i$ i# $-ice $(e /and-id$( !f $(e audi! #i%na& $! /e

carried*

In Am"&i$ude M!du&a$i!n !r AM' $(e carrier #i%na& i# %i)en /

I$ (a# an am"&i$ude !f 9Am!du&a$ed  in "r!"!r$i!n $! $(e me##a%e /earin% &!-er frequenc #i%na&

$! %i)e

T(e ma%ni$ude !f m$ i# c(!#en $! /e &e## $(an !r equa& $! 8' fr!m rea#!n# (a)in%

$! d! -i$( dem!du&a$i!n' i*e* rec!)er !f $(e #i%na& fr!m $(e recei)ed #i%na&* T(e

m!du&a$i!n inde, i# $(en defined $! /e

T(e frequenc !f $(e m!du&a$in% #i%na& i# c(!#en $! /e muc( #ma&&er $(an $(a$ !f $(e

carrier #i%na&* Tr $! $(in2 !f -(a$ -!u&d (a""en if $(e m!du&a$in% inde, -ere /i%%er 

$(an 8*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Fig.3. AM modulation with modulation index .2

ote that the AM signal is of the form

This has frequency components at frequencies

.

Fig.!: AM modulation with modulation index .!

C*T=IAGARA@AN1AP ECE DEPT*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e )er#i!n !f AM $(a$ -e de#cri/ed i# ca&&ed D!u/&e Side and AM !r DSAM #ince

-e #end #i%na&# a$ /!$(

' and a$

I$ i# m!re efficien$ $! $ran#mi$ !n& !ne !f $(e #ide /and# #!1ca&&ed Sin%&e Side

and AM !r USAM' LSAM f!r u""er and &!-er #ide /and# re#"ec$i)e&' !r if $(e

fi&$erin% requiremen$# f!r $(i# are $!! ardu!u# $! #end a "ar$ !f !ne !f $(e #ide /and* T(i#

i# -(a$ i# d!ne in c!mmercia& ana&!% NTSC $e&e)i#i!n' -(ic( i# 2n!-n a# 3e#$i%ia& Sideand AM* T(e T3 )ide! #i%na& (a# a /and-id$( !f a/!u$ >*;5 M=B' /u$ !n& 8 M=B !f 

$(e &!-er #ide /and !f $(e #i%na& i# $ran#mi$$ed* T(e +CC a&&!ca$e# 6 M=B "er c(anne&

$(u# <*5 M=B i# &ef$ f!r $(e #!und #i%na&' -(ic( i# an +M #i%na& ne,$ #ec$i!n*Y!u

ma (a)e -!ndered (!- -e can &i#$en $! AM radi! c(anne&# !n /!$( #$ere! and m!n!

recei)er#* T(e $ric2 $(a$ i# u#ed $! %enera$e a m!du&a$in% #i%na& / addin% a DS )er#i!n

carrier a$ ?H (B #u""re##ed )er#i!n !f $(e !u$"u$ !f $(e difference /e$-een $(e Lef$

and Ri%($ c(anne&# added $! $(e #um !f $(e Lef$ and Ri%($ c(anne&# unm!du&a$ed* T(e

re#u&$in% m!du&a$in% #i%na& (a# a /and-id$( !f a/!u$ 6< =B* A m!n! recei)er %e$# $(e

#um #i%na& -(erea# a #$ere! recei)er #e"ara$e# !u$ $(e difference a# -e&& and rec!n#$i$u$e#

$(e Lef$ and Ri%($ c(anne& !u$"u$#*

Am"&i$ude m!du&a$i!n' AM' i# !ne !f $(e m!#$ #$rai%($f!r-ard -a# !f 

m!du&a$in% a radi! #i%na& !r carrier* T(e "r!ce## !f dem!du&a$i!n' -(ere $(e audi! #i%na&

i# rem!)ed fr!m $(e radi! carrier in $(e recei)er i# a&#! qui$e #im"&e a# -e&&* T(e ea#ie#$

me$(!d !f ac(ie)in% am"&i$ude dem!du&a$i!n i# $! u#e a #im"&e di!de de$ec$!r* T(i#

c!n#i#$# !f u#$ a (andfu& !f c!m"!nen$#:1 a di!de' re#i#$!r and a ca"aci$!r*

C*T=IAGARA@AN1AP ECE DEPT* H

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

 

Fig. " AM #iode #etector

In $(i# circui$' $(e di!de rec$ifie# $(e #i%na&' a&&!-in% !n& (a&f !f $(e a&$erna$in%

-a)ef!rm $(r!u%(* T(e ca"aci$!r i# u#ed $! #$!re $(e c(ar%e and "r!)ide a #m!!$(ed

!u$"u$ fr!m $(e de$ec$!r' and a&#! $! rem!)e an un-an$ed radi! frequenc c!m"!nen$#*

T(e re#i#$!r i# u#ed $! ena/&e $(e ca"aci$!r $! di#c(ar%e* If i$ -ere n!$ $(ere and n! !$(er 

&!ad -a# "re#en$' $(en $(e c(ar%e !n $(e ca"aci$!r -!u&d n!$ &ea2 a-a' and $(e circui$

-!u&d reac( a "ea2 and remain $(ere*

Ad)an$a%e# !f Am"&i$ude M!du&a$i!n' AM

T(ere are #e)era& ad)an$a%e# !f am"&i$ude m!du&a$i!n' and #!me !f $(e#e rea#!n# (a)e

mean$ $(a$ i$ i# #$i&& in -ide#"read u#e $!da:

• I$ i# #im"&e $! im"&emen$

• i$ can /e dem!du&a$ed u#in% a circui$ c!n#i#$in% !f )er fe- c!m"!nen$#

• AM recei)er# are )er c(ea" a# n! #"ecia&i#ed c!m"!nen$# are needed*

Di#ad)an$a%e# !f am"&i$ude m!du&a$i!n

C*T=IAGARA@AN1AP ECE DEPT* J

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Am"&i$ude m!du&a$i!n i# a )er /a#ic f!rm !f m!du&a$i!n' and a&$(!u%( i$#

#im"&ici$ i# !ne !f i$# ma!r ad)an$a%e#' !$(er m!re #!"(i#$ica$ed ##$em# "r!)ide a

num/er !f ad)an$a%e#* Acc!rdin%& i$ i# -!r$( &!!2in% a$ #!me !f $(e di#ad)an$a%e# !f 

am"&i$ude m!du&a$i!n*

• I$ i# n!$ efficien$ in $erm# !f i$# "!-er u#a%e

• I$ i# n!$ efficien$ in $erm# !f i$# u#e !f /and-id$(' requirin% a /and-id$( equa& $!

$-ice $(a$ !f $(e (i%(e#$ audi! frequenc

• I$ i# "r!ne $! (i%( &e)e&# !f n!i#e /ecau#e m!#$ n!i#e i# am"&i$ude /a#ed and

!/)i!u#& AM de$ec$!r# are #en#i$i)e $! i$*T(u#' AM (a# ad)an$a%e# !f #im"&ici$' /u$ i$ i# n!$ $(e m!#$ efficien$ m!de $! u#e'

 /!$( in $erm# !f $(e am!un$ !f #"ace !r #"ec$rum i$ $a2e# u"' and $(e -a in -(ic( i$ u#e#

$(e "!-er $(a$ i# $ran#mi$$ed* T(i# i# $(e rea#!n -( i$ i# n!$ -ide& u#ed $(e#e da# /!$(

f!r /r!adca#$in% and f!r $-! -a radi! c!mmunica$i!n* E)en $(e &!n%' medium and #(!r$

-a)e /r!adca#$# -i&& u&$ima$e& c(an%e /ecau#e !f $(e fac$ $(a$ am"&i$ude m!du&a$i!n'

AM' i# #u/ec$ $! muc( (i%(er &e)e&# !f n!i#e $(an are !$(er m!de#* +!r $(e m!men$' i$#

#im"&ici$' and i$# -ide u#a%e' mean# $(a$ i$ -i&& /e difficu&$ $! c(an%e quic2&' and i$ -i&&

 /e in u#e f!r man ear# $! c!me*

Frequency Modulation:

4(i&e c(an%in% $(e am"&i$ude !f a radi! #i%na& i# $(e m!#$ !/)i!u# me$(!d $!

m!du&a$e i$' i$ i# / n! mean# $(e !n& -a* I$ i# a&#! "!##i/&e $! c(an%e $(e frequenc !f 

a #i%na& $! %i)e frequenc m!du&a$i!n !r +M* +requenc m!du&a$i!n i# -ide& u#ed !n

frequencie# a/!)e ?< M=B' and i$ i# "ar$icu&ar& -e&& 2n!-n f!r i$# u#e f!r 3=+ +M

 /r!adca#$in%*

C*T=IAGARA@AN1AP ECE DEPT* 8<

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A&$(!u%( i$ ma n!$ /e qui$e a# #$rai%($f!r-ard a# am"&i$ude m!du&a$i!n'

ne)er$(e&e## frequenc m!du&a$i!n' +M' !ffer# #!me di#$inc$ ad)an$a%e#* I$ i# a/&e $!

 "r!)ide near in$erference free rece"$i!n' and i$ -a# f!r $(i# rea#!n $(a$ i$ -a# ad!"$ed f!r 

$(e 3=+ #!und /r!adca#$#* T(e#e $ran#mi##i!n# c!u&d !ffer (i%( fide&i$ audi!' and f!r 

$(i# rea#!n' frequenc m!du&a$i!n i# far m!re "!"u&ar $(an $(e !&der $ran#mi##i!n# !n $(e

&!n%' medium and #(!r$ -a)e /and#* In addi$i!n $! i$# -ide#"read u#e f!r (i%( qua&i$

audi! /r!adca#$#' +M i# a&#! #ued f!r a )arie$ !f $-! -a radi! c!mmunica$i!n ##$em#*

4(e$(er f!r fi,ed !r m!/i&e radi! c!mmunica$i!n ##$em#' !r f!r u#e in "!r$a/&e

a""&ica$i!n#' +M i# -ide& u#ed a$ 3=+ and a/!)e*

T! %enera$e a frequenc m!du&a$ed #i%na&' $(e frequenc !f $(e radi! carrier i#

c(an%ed in &ine -i$( $(e am"&i$ude !f $(e inc!min% audi! #i%na&*

Fig." Frequency Modulation, FM

4(en $(e audi! #i%na& i# m!du&a$ed !n$! $(e radi! frequenc carrier' $(e ne-

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

radi! frequenc #i%na& m!)e# u" and d!-n in frequenc* T(e am!un$ / -(ic( $(e #i%na&

m!)e# u" and d!-n i# im"!r$an$* I$ i# 2n!-n a# $(e de)ia$i!n and i# n!rma&& qu!$ed a#

$(e num/er !f 2i&!(er$B de)ia$i!n* A# an e,am"&e $(e #i%na& ma (a)e a de)ia$i!n !f K?

2=B* In $(i# ca#e $(e carrier i# made $! m!)e u" and d!-n / ? 2=B*

r!adca#$ #$a$i!n# in $(e 3=+ "!r$i!n !f $(e frequenc #"ec$rum /e$-een HH*5

and 8<H M=B u#e &ar%e )a&ue# !f de)ia$i!n' $"ica&& K5 2=B* T(i# i# 2n!-n a# -ide1

 /and +M 4+M* T(e#e #i%na&# are ca"a/&e !f #u""!r$in% (i%( qua&i$ $ran#mi##i!n#'

 /u$ !ccu" a &ar%e am!un$ !f /and-id$(* U#ua&& ;<< 2=B i# a&&!-ed f!r eac( -ide1/and

+M $ran#mi##i!n* +!r c!mmunica$i!n# "ur"!#e# &e## /and-id$( i# u#ed* Narr!- /and +M

N+M !f$en u#e# de)ia$i!n fi%ure# !f ar!und K? 2=B* I$ i# narr!- /and +M $(a$ i#

$"ica&& u#ed f!r $-!1-a radi! c!mmunica$i!n a""&ica$i!n#*

+i%* +requenc M!du&a$i!n

 Advantages of frequency modulation, FM 

+M i# u#ed f!r a num/er !f rea#!n# and $(ere are #e)era& ad)an$a%e# !f frequenc

m!du&a$i!n* In )ie- !f $(i# i$ i# -ide& u#ed in a num/er !f area# $! -(ic( i$ i# idea&&

#ui$ed* S!me !f $(e ad)an$a%e# !f frequenc m!du&a$i!n are n!$ed /e&!-:

 Resilience to noise: One "ar$icu&ar ad)an$a%e !f frequenc m!du&a$i!n i# i$#

C*T=IAGARA@AN1AP ECE DEPT* 8;

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

&e)e&' and $(eref!re ac$# a# a f!rm !f n!i#e reduc$i!n' and a #im"&e &imi$er can ma#2 

)aria$i!n# in $(e "&a/ac2 !u$"u$' and $(e +M ca"$ure effec$ rem!)e# "rin$1$(r!u%( and

 "re1ec(!* A c!n$inu!u# "i&!$1$!ne' if added $! $(e #i%na& a# -a# d!ne !n 3;<<< and

man =i1/and f!rma$# can 2ee" mec(anica& i$$er under c!n$r!& and a##i#$ $ime/a#e

c!rrec$i!n*

T(e#e +M ##$em# are unu#ua& in $(a$ $(e (a)e a ra$i! !f carrier $! ma,imum

m!du&a$i!n frequenc !f &e## $(an $-!0 c!n$ra#$ $(i# -i$( +M audi! /r!adca#$in% -(ere

$(e ra$i! i# ar!und 8<'<<<* C!n#ider f!r e,am"&e a 6 M=B carrier m!du&a$ed a$ a ?*5 M=B

ra$e0 / e##e& ana&#i# $(e fir#$ #ide/and# are !n J*5 and ;*5 M=B' -(i&e $(e #ec!nd

#ide/and# are !n 8? M=B and 8 M=B* T(e re#u&$ i# a #ide/and !f re)er#ed "(a#e !n F8

M=B0 !n dem!du&a$i!n' $(i# re#u&$# in an un-an$ed !u$"u$ a$ 68 5 M=B* T(e ##$emmu#$ /e de#i%ned #! $(a$ $(i# i# a$ an acce"$a/&e &e)e&*

$ound

+M i# a&#! u#ed a$ audi! frequencie# $! #n$(e#iBe #!und* T(i# $ec(nique' 2n!-n

a# +M #n$(e#i#' -a# "!"u&ariBed / ear& di%i$a& #n$(e#iBer# and /ecame a #$andard

fea$ure f!r #e)era& %enera$i!n# !f "er#!na& c!m"u$er #!und card#*

%adio

Ed-in =!-ard Arm#$r!n% 8HJ<.8J5> -a# an American e&ec$rica& en%ineer -(!

in)en$ed -ide/and frequenc m!du&a$i!n +M radi!* =e "a$en$ed $(e re%enera$i)e

circui$ in 8J8>' $(e #u"er(e$er!dne recei)er in 8J8H and $(e #u"er1re%enera$i)e circui$ in

8J;;* =e "re#en$ed (i# "a"er: A Me$(!d !f Reducin% Di#$ur/ance# in Radi! Si%na&in%

 / a S#$em !f +requenc M!du&a$i!n' -(ic( fir#$ de#cri/ed +M radi!' /ef!re $(e Ne-

Y!r2 #ec$i!n !f $(e In#$i$u$e !f Radi! En%ineer# !n N!)em/er 6' 8J?5* T(e "a"er -a#

 "u/&i#(ed in 8J?6*

C*T=IAGARA@AN1AP ECE DEPT* 8>

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A# $(e name im"&ie#' -ide/and +M 4+M require# a -ider #i%na& /and-id$(

$(an am"&i$ude m!du&a$i!n / an equi)a&en$ m!du&a$in% #i%na&' /u$ $(i# a&#! ma2e# $(e

#i%na& m!re r!/u#$ a%ain#$ n!i#e and in$erference* +requenc m!du&a$i!n i# a&#! m!re

r!/u#$ a%ain#$ #im"&e #i%na& am"&i$ude fadin% "(en!mena* A# a re#u&$' +M -a# c(!#en a#

$(e m!du&a$i!n #$andard f!r (i%( frequenc' (i%( fide&i$ radi! $ran#mi##i!n: (ence $(e

$erm +M radi! a&$(!u%( f!r man ear# $(e C ca&&ed i$ 3=+ radi!' /ecau#e

c!mmercia& +M /r!adca#$in% u#e# a -e&&12n!-n "ar$ !f $(e 3=+ /and$(e +M

 /r!adca#$ /and*

+M recei)er# em"&! a #"ecia& de$ec$!r f!r +M #i%na&# and e,(i/i$ a "(en!men!n

ca&&ed ca"$ure effec$' -(ere $(e $uner i# a/&e $! c&ear& recei)e $(e #$r!n%er !f $-! #$a$i!n#

 /ein% /r!adca#$ !n $(e #ame frequenc* Pr!/&ema$ica&& (!-e)er' frequenc drif$ !r &ac2 !f #e&ec$i)i$ ma cau#e !ne #$a$i!n !r #i%na& $! /e #udden& !)er$a2en / an!$(er !n an

adacen$ c(anne&* +requenc drif$ $"ica&& c!n#$i$u$ed a "r!/&em !n )er !&d !r 

ine,"en#i)e recei)er#' -(i&e inadequa$e #e&ec$i)i$ ma "&a%ue an $uner*

An +M #i%na& can a&#! /e u#ed $! carr a #$ere! #i%na&: #ee +M #$ere!* =!-e)er'

$(i# i# d!ne / u#in% mu&$i"&e,in% and demu&$i"&e,in% /ef!re and af$er $(e +M "r!ce##*

T(e re#$ !f $(i# ar$ic&e i%n!re# $(e #$ere! mu&$i"&e,in% and demu&$i"&e,in% "r!ce## u#ed in

#$ere! +M' and c!ncen$ra$e# !n $(e +M m!du&a$i!n and dem!du&a$i!n "r!ce##' -(ic( i#

iden$ica& in #$ere! and m!n! "r!ce##e#*

$uper heterodyne radio recei&er:

In #u"er(e$er!dne radi! recei)er#' $(e inc!min% radi! #i%na&# arc in$erce"$ed /

$(e an$enna arid c!n)er$ed in$! $(e c!rre#"!ndin% curren$# and )!&$a%e#* In $(e recei)er'

$(e inc!min% #i%na& frequenc i# mi,ed -i$( a &!ca&& %enera$ed frequenc* T(e !u$"u$ !f 

$(e mi,er c!n#i#$# !f $(e #um and difference !f $(e $-! frequencie#* T(e mi,in% !f $(e

$-! frequencie# i# $ermed(e$er!dnin%* Ou$ !f $(e $-! re#u&$an$ c!m"!nen$# !f $(e

mi,er' $(e #um c!m"!nen$ i# reec$ed and $(e difference c!m"!nen$ i# #e&ec$ed* T(e )a&ue

!f $(e difference frequenc c!m"!nen$ )arie# -i$( $(e inc!min% frequencie#' if $(e

frequenc !f $(e &!ca& !#ci&&a$!r i# 2e"$ c!n#$an$* I$ i# "!##i/&e $! 2ee" $(e frequenc !f 

C*T=IAGARA@AN1AP ECE DEPT* 85

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

$(e difference c!m"!nen$# c!n#$an$ / )arin% $(e frequenc !f $(e &!ca& !#ci&&a$!r 

acc!rdin% $! $(e inc!min% #i%na& frequenc* In $(i# ca#e' $(e "r!ce## i# ca&&ed

Su"er(e$er!dne and $(e recei)er i# 2n!-n a# a #u"er(e$er!dne radi! recei)er*

In +i%ure $(e recei)in% an$enna in$erce"$# $(e radi! #i%na&# and feed# $(e R+

am"&ifier' T(e R+ am"&ifier #e&ec$# $(e de#ired #i%na& frequenc and am"&ifie# i$# )!&$a%e'

T(e R+ am"&ifier i# a #ma&&1#i%na& )!&$a%e am"&ifier $(a$ !"era$e# in $(e R+ ran%e* T(i#

am"&ifier i# $uned $! $(e de#ired #i%na& frequenc / u#in% ca"aci$i)e $unin%*

Frequency di&ision multiplexing:

+requenc Di)i#i!n Mu&$i"&e,in% +DM a&&!-# en%ineer# $! u$i&iBe $(e e,$ra #"ace in

eac( -ire $! carr m!re $(an !ne #i%na&* frequenc1#(if$in% #!me #i%na&# / a cer$ain

am!un$' en%ineer# can #(if$ $(e #"ec$rum !f $(a$ #i%na& u" in$! $(e unu#ed /and !n $(a$

-ire* In $(i# -a' mu&$i"&e #i%na&# can /e carried !n $(e #ame -ire' -i$(!u$ (a)in% $!

di) u" $ime1#&ice# a# in Time1Di)i#i!n Mu&$i"&e,in% #c(eme#*In ana&!% $ran#mi##i!n'

#i%na&# are c!mm!n& mu&$i"&e,ed u#in% frequenc1di)i#i!n mu&$i"&e,in% +DM' in

-(ic( $(e carrier /and-id$( i# di)ided in$! #u/c(anne&# !f differen$ frequenc -id$(#'

eac( carrin% a #i%na& a$ $(e #ame $ime in "ara&&e& Tradi$i!na& $erre#$ria& micr!-a)e and

#a$e&&i$e &in2# em"&! +DM* A&$(!u%( +DM in $e&ec!mmunica$i!n# i# /ein% reduced'#e)era& ##$em# -i&& c!n$inue $! u#e $(i# $ec(nique' name&: /r!adca#$ ca/&e T3' and

c!mmercia& ce&&u&ar radi!*

C*T=IAGARA@AN1AP ECE DEPT* 86

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e #$andard $e&e"(!n )!ice /and Q?<< . ?><< =B i# (e$er!dned and #$ac2ed

!n (i%( frequenc carrier# / #in%&e #ide/and am"&i$ude m!du&a$i!n* T(i# i# $(e m!#$

 /and-id$( efficien$ #c(eme "!##i/&e* Mu&$ic(anne& /r!adca#$ and #(i"#(!re $ermina$i!n#

u#e fdm* 4i$( $(i# ##$em' eac( c(anne& !f $(e c!m"!#i$e $!ne "ac2a%e !f $(e /r!adca#$

i# a##i%ned an audi! frequenc* mu&$i"&e,in% $$ circui$#' u" $! 86 circui$# ma /e

carried in an !ne !f $(e ?'<<< (er$B mu&$i"&e,ed c(anne&# de#cri/ed a/!)e* D!n$

c!nfu#e $(e $-! $"e# !f mu&$i"&e,in%* In $(e fir#$ ca#e' ?'<<< (er$B audi! c(anne&# (a)e

 /een c!m/ined* In $(e #ec!nd ca#e' a num/er !f dc $$ circui$# are c!n)er$ed $! $!ne

2ein% and c!m/ined in a #in%&e ?'<<<1(er$B audi! c(anne&* +i%ure ?1?8 i&&u#$ra$e# a 861

c(anne&' mu&$i"&e,in% ##$em*

UNIT II: TRANSMISSION MEDIUM Tran#mi##i!n &ine# . T"e#' equi)a&en$ circui$'

&!##e#' #$andin% -a)e#' im"edance ma$c(in%' /and-id$(0 radi! "r!"a%a$i!n . Gr!und

C*T=IAGARA@AN1AP ECE DEPT* 8

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

-a)e and #"ace -a)e "r!"a%a$i!n' cri$ica& frequenc' ma,imum u#a/&e frequenc' "a$(

&!##' -(i$e Gau##ian n!i#e*

Transmission medium:

A $ran#mi##i!n &ine i# a ma$eria& medium !r #$ruc$ure $(a$ f!rm# a "a$( f!r 

direc$in% $(e $ran#mi##i!n !f ener% fr!m !ne "&ace $! an!$(er' #uc( a# e&ec$r!ma%ne$ic

-a)e# !r ac!u#$ic -a)e#' a# -e&& a# e&ec$ric "!-er $ran#mi##i!n*

=!-e)er in  c!mmunica$i!n#  and  e&ec$r!nic en%ineerin%'   $(e $erm (a# a m!re

#"ecific meanin%* In $(e#e fie&d#' $ran#mi##i!n &ine# are #"ecia&iBed ca/&e# and !$(er 

media de#i%ned $! carr a&$erna$in% curren$ and e&ec$r!ma%ne$ic -a)e# !f (i%( frequenc

radi! frequenc !r (i%(er' (i%( en!u%( $(a$ i$# -a)e na$ure mu#$ /e $a2en in$! acc!un$*

Tran#mi##i!n &ine# are u#ed f!r "ur"!#e# #uc( a# c!nnec$in% radi! $ran#mi$$er#  and

recei)er# -i$( $(eir an$enna#' di#$ri/u$in% ca/&e $e&e)i#i!n #i%na&#' and c!m"u$er ne$-!r2 

c!nnec$i!n#*

Ordinar e&ec$rica& ca/&e# #uffice $! carr &!- frequenc AC' #uc( a# main#

 "!-er ' -(ic( re)er#e# direc$i!n 5< $! 6< $ime# "er #ec!nd* =!-e)er' $(e cann!$ /e u#ed

$! carr curren$# in $(e radi! frequenc ran%e !r (i%(er' -(ic( re)er#e direc$i!n mi&&i!n#

$! /i&&i!n# !f $ime# "er #ec!nd' /ecau#e $(e ener% $end# $! radia$e !ff $(e ca/&e a# radi!

-a)e#' cau#in% "!-er &!##e#* Radi! frequenc curren$# a&#! $end $! ref&ec$ fr!m

di#c!n$inui$ie# in $(e ca/&e #uc( a# c!nnec$!r#' and $ra)e& /ac2 d!-n $(e ca/&e $!-ard $(e

#!urce* T(e#e ref&ec$i!n# ac$ a# /!$$&enec2#' "re)en$in% $(e "!-er fr!m reac(in% $(e

de#$ina$i!n* Tran#mi##i!n &ine# u#e #"ecia&iBed c!n#$ruc$i!n #uc( a# "reci#e c!nduc$!r 

dimen#i!n# and #"acin%' and im"edance ma$c(in%' $! carr e&ec$r!ma%ne$ic #i%na&# -i$(

minima& ref&ec$i!n# and "!-er &!##e#*

C*T=IAGARA@AN1AP ECE DEPT* 8H

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

 T"e# !f $ran#mi##i!n &ine inc&ude &adder &ine'  c!a,ia& ca/&e' die&ec$ric #&a/#'

#$ri"&ine'  !"$ica& fi/er ' and -a)e%uide#* T(e (i%(er $(e frequenc' $(e #(!r$er are $(e

-a)e# in a $ran#mi##i!n medium* Tran#mi##i!n &ine# mu#$ /e u#ed -(en $(e frequenc i#

(i%( en!u%( $(a$ $(e -a)e&en%$( !f $(e -a)e# /e%in# $! a""r!ac( $(e &en%$( !f $(e ca/&e

u#ed* T! c!nduc$ ener% a$ frequencie# a/!)e $(e radi! ran%e' #uc( a# mi&&ime$er -a)e#'

infrared' and &i%($' $(e -a)e# /ec!me muc( #ma&&er $(an $(e dimen#i!n# !f $(e #$ruc$ure#

u#ed $! %uide $(em' #! $ran#mi##i!n &ine $ec(nique# /ec!me inadequa$e and $(e me$(!d#

!f !"$ic# are u#ed*

$tanding wa&es:

In "(#ic#' a #$andin% -a)e a&#! 2n!-n a# a #$a$i!nar -a)e i# a -a)e $(a$ remain# in a

c!n#$an$ "!#i$i!n*

T-! !""!#in% -a)e# c!m/ine $! f!rm a #$andin% -a)e* T(i# "(en!men!n can

!ccur /ecau#e $(e medium i# m!)in% in $(e !""!#i$e direc$i!n $! $(e -a)e' !r i$ can ari#e

in a #$a$i!nar medium a# a re#u&$ !f in$erference  /e$-een $-! -a)e# $ra)e&in% in

!""!#i$e direc$i!n#* In $(e #ec!nd ca#e' f!r -a)e# !f equa& am"&i$ude  $ra)e&in% in

!""!#in% direc$i!n#' $(ere i# !n a)era%e n! ne$ "r!"a%a$i!n !f ener%*

C*T=IAGARA@AN1AP ECE DEPT* 8J

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A# an e,am"&e !f $(e #ec!nd $"e' a #$andin% -a)e in a $ran#mi##i!n &ine  i# a

-a)e in -(ic( $(e di#$ri/u$i!n !f curren$'  )!&$a%e' !r fie&d #$ren%$(  i# f!rmed / $(e

#u"er"!#i$i!n !f $-! -a)e# !f $(e #ame  frequenc "r!"a%a$in% in !""!#i$e direc$i!n#*

T(e effec$ i# a #erie# !f   n!de#  Ber! di#"&acemen$ and an$i1n!de#  ma,imum

di#"&acemen$ a$ fi,ed "!in$# a&!n% $(e $ran#mi##i!n &ine* Suc( a #$andin% -a)e ma /e

f!rmed -(en a -a)e i# $ran#mi$$ed in$! !ne end !f a $ran#mi##i!n &ine and i# ref&ec$ed

fr!m $(e !$(er end / an im"edance mi#ma$c(' i*e*' di#c!n$inui$' #uc( a# an !"en circui$

!r a #(!r$* T(e fai&ure !f $(e &ine $! $ran#fer "!-er a$ $(e #$andin% -a)e frequenc -i&&

u#ua&& re#u&$ in a$$enua$i!n di#$!r$i!n*

In "rac$ice' &!##e# in $(e $ran#mi##i!n &ine and !$(er c!m"!nen$# mean $(a$ a

 "erfec$ ref&ec$i!n and a "ure #$andin% -a)e are ne)er ac(ie)ed* T(e re#u&$ i# a "ar$ia&

#$andin% -a)e' -(ic( i# a #u"er"!#i$i!n !f a #$andin% -a)e and a $ra)e&in% -a)e* T(e

de%ree $! -(ic( $(e -a)e re#em/&e# ei$(er a "ure #$andin% -a)e !r a "ure $ra)e&in% -a)e

i# mea#ured / $(e #$andin% -a)e ra$i! S4R

An!$(er e,am"&e i# #$andin% -a)e# in $(e !"en !cean f!rmed / -a)e# -i$( $(e

#ame -a)e "eri!d m!)in% in !""!#i$e direc$i!n#* T(e#e ma f!rm near #$!rm cen$re#' !r 

fr!m ref&ec$i!n !f a #-e&& a$ $(e #(!re' and are $(e #!urce !f micr!/ar!m#  and

micr!#ei#m#*

'mpedance matching:

In e&ec$r!nic#' im"edance ma$c(in% i# $(e "rac$ice !f de#i%nin% $(e in"u$

im"edance  !f an e&ec$rica& &!ad  !r $(e !u$"u$ im"edance  !f i$# c!rre#"!ndin% #i%na&

#!urce $! ma,imiBe $(e "!-er $ran#fer  !r minimiBe #i%na& ref&ec$i!n fr!m $(e &!ad*

In $(e ca#e !f a c!m"&e, #!urce im"edance S and &!ad im"edance L' ma,imum "!-er 

$ran#fer i# !/$ained -(en

C*T=IAGARA@AN1AP ECE DEPT* ;<

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

-(ere $(e a#$eri#2 indica$e# $(e c!m"&e, c!nu%a$e !f $(e )aria/&e* Minimum ref&ec$i!n i#

!/$ained -(en

T(e c!nce"$ !f im"edance ma$c(in% f!und fir#$ a""&ica$i!n# in e&ec$rica&

en%ineerin%' /u$ i# re&e)an$ in !$(er a""&ica$i!n# in -(ic( a f!rm !f ener%' n!$

nece##ari& e&ec$rica&' i# $ran#ferred /e$-een a #!urce and a &!ad*

(andwidth:

and-id$( i# $(e difference /e$-een $(e u""er and &!-er frequencie# in a

c!n$inu!u# #e$ !f frequencie#* I$ i# $"ica&& mea#ured in (er$B' and ma #!me$ime# refer 

$! "a##/and /and-id$(' #!me$ime# $! /a#e/and /and-id$(' de"endin% !n c!n$e,$*

Pa##/and /and-id$( i# $(e difference /e$-een $(e u""er and &!-er cu$!ff frequencie# !f'

f!r e,am"&e' a /and"a## fi&$er ' a c!mmunica$i!n c(anne&' !r a #i%na& #"ec$rum* In ca#e !f 

a &!-1"a## fi&$er  !r /a#e/and #i%na&' $(e /and-id$( i# equa& $! i$# u""er cu$!ff frequenc*

and-id$( in (er$B i# a cen$ra& c!nce"$ in man fie&d#' inc&udin% e&ec$r!nic#'

inf!rma$i!n $(e!r' di%i$a& c!mmunica$i!n#'  radi! c!mmunica$i!n#'  #i%na& "r!ce##in%'

and #"ec$r!#c!"*

A 2e c(arac$eri#$ic !f /and-id$( i# $(a$ an /and !f a %i)en -id$( can carr $(e#ame am!un$ !f inf!rma$i!n' re%ard&e## !f -(ere $(a$ /and i# &!ca$ed in $(e frequenc

#"ec$rum*Qn!$e 8 +!r e,am"&e' a ? 2=B /and can carr a $e&e"(!ne c!n)er#a$i!n -(e$(er 

$(a$ /and i# a$ /a#e/and a# in a POTS  $e&e"(!ne &ine !r m!du&a$ed $! #!me (i%(er 

frequenc*

C*T=IAGARA@AN1AP ECE DEPT* ;8

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Factors in&ol&ed in the propagation of radio wa&es:

8* Gr!und -a)e !r #urface -a)e

;* S"ace -a)e !r $r!"!#"(eric -a)e

?* S2 -a)e !r i!n!#"(eric -a)e*

Gr!und -a)e -(ic( i# a&#! ca&&ed #urface -a)e e,i#$# -(en $(e $ran#mi$$in% and

recei)in% an$enna# are c&!#e $! $(e ear$( and are )er$ica&& "!&ari#ed* T(i# $"e !f -a)e

 "r!"a%a$i!n i# u#efu& a$ /r!adca#$ and &!- frequencie#* T(e /r!adca#$ #i%na&# recei)ed

durin% da1$ime are due $! %r!und -a)e#* I$ i# u#efu& f!r c!mmunica$i!n a$ 3L+' L+ and

M+*

S"ace -a)e i# a&#! ca&&ed $r!"!#"(eric -a)e* =ere' $(e -a)e "r!"a%a$e# direc$& fr!m

$(e $ran#mi$$er $! $(e recei)er in $(e $r!"!#"(eric re%i!n* T(e "!r$i!n !f $(e a$m!#"(ere

a/!)e $(e ear$( and -i$(in 86 2m i# ca&&ed $r!"!#"(ere* T(i# i# u#efu& a/!)e $(e

frequenc !f ?< M=B* +M rece"$i!n i# n!rma&& / #"ace -a)e "r!"a%a$i!n*

S2-a)e i# $(e "r!"a%a$i!n !f radi! -a)e# /en$ refrac$ed /ac2 $! $(e Ear$(# #urface

 / $(e i!n!#"(ere* A# a re#u&$ !f #2-a)e "r!"a%a$i!n' a ni%($1$ime /r!adca#$ #i%na& fr!m

a di#$an$ AM /r!adca#$in% !r #(!r$-a)e radi! #$a$i!n !r rare&' a T3 #$a$i!n can

#!me$ime# /e (eard a# c&ear& a# &!ca& #$a$i!n#* M!#$ &!n%1di#$ance =+ radi!

c!mmunica$i!n /e$-een ? and ?< M=B i# a re#u&$ !f #2-a)e "r!"a%a$i!n*

)round wa&e, reflection of radio wa&es *y the surface of the earth:

Gr!und 4a)e "r!"a%a$i!n i# a me$(!d !f radi! frequenc "r!"a%a$i!n $(a$ u#e#

$(e area /e$-een $(e #urface !f $(e ear$( and $(e $(e i!n!#"(ere  f!r $ran#mi##i!n* T(e

%r!und -a)e can "r!"a%a$e a c!n#idera/&e di#$ance !)er $(e ear$(# #urface "ar$icu&ar& in

$(e &!- frequenc and medium frequenc "!r$i!n !f $(e radi! #"ec$rum* Gr!und -a)e

radi! "r!"a%a$i!n i# u#ed $! "r!)ide re&a$i)e& &!ca& radi! c!mmunica$i!n# c!)era%e*

C*T=IAGARA@AN1AP ECE DEPT* ;;

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Gr!und -a)e radi! #i%na& "r!"a%a$i!n i# idea& f!r re&a$i)e& #(!r$ di#$ance

 "r!"a%a$i!n !n $(e#e frequencie# durin% $(e da$ime* S21-a)e i!n!#"(eric "r!"a%a$i!n

i# n!$ "!##i/&e durin% $(e da /ecau#e !f $(e a$$enua$i!n !f $(e #i%na&# !n $(e#e

frequencie# cau#ed / $(e D re%i!n in $(e i!n!#"(ere* In )ie- !f $(i#' &!-er frequenc

radi! c!mmunica$i!n# #$a$i!n# need $! re& !n $(e %r!und1-a)e "r!"a%a$i!n $! ac(ie)e

$(eir c!)era%e*

T"ica&&' -(a$ i# referred $! a# a  ground wave  radi! #i%na& i# made u" !f a

num/er !f c!n#$i$uen$ -a)e#* If $(e an$enna# are in $(e &ine !f #i%($ $(en $(ere -i&& /e a

direc$ -a)e a# -e&& a# a ref&ec$ed #i%na&* A# $(e name# #u%%e#$ $(e direc$ #i%na& i# !ne $(a$

$ra)e&# direc$& /e$-een $(e $-! an$enna# and i# n!$ affec$ed / $(e &!ca&i$* T(ere -i&&

a&#! /e a ref&ec$ed #i%na& a# $(e $ran#mi##i!n -i&& /e ref&ec$ed / a num/er !f !/ec$#

inc&udin% $(e ear$(# #urface and an (i&&#' !r &ar%e /ui&din%# $(a$ ma /e "re#en$* In

addi$i!n $! $(i# $(ere i# a #urface -a)e* T(i# $end# $! f!&&!- $(e cur)a$ure !f $(e Ear$(

and ena/&e# c!)era%e /e!nd $(e (!riB!n* I$ i# $(e #um !f a&& $(e#e c!m"!nen$# $(a$ i#

2n!-n a# $(e %r!und -a)e* e!nd $(e (!riB!n $(e direc$ and ref&ec$ed -a)e# are

 /&!c2ed / $(e cur)a$ure !f $(e Ear$(' and $(e #i%na& i# "ure& made u" !f $(e diffrac$ed

#urface -a)e* I$ i# f!r $(i# rea#!n $(a$ #urface -a)e i# c!mm!n& ca&&ed %r!und -a)e

 "r!"a%a$i!n*

C*T=IAGARA@AN1AP ECE DEPT* ;?

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A# a #urface -a)e "a##e# !)er $(e %r!und' $(e -a)e induce# a )!&$a%e in $(e

Ear$(* T(e induced )!&$a%e $a2e# ener% a-a fr!m $(e #urface -a)e' $(ere/

-ea2enin%' !r a$$enua$in%' $(e -a)e a# i$ m!)e# a-a fr!m $(e $ran#mi$$in% an$enna* T!

reduce $(e a$$enua$i!n' $(e am!un$ !f induced )!&$a%e mu#$ /e reduced* T(i# i# d!ne /

u#in% )er$ica&& "!&ariBed -a)e# $(a$ minimiBe $(e e,$en$ $! -(ic( $(e e&ec$ric fie&d !f 

$(e -a)e i# in c!n$ac$ -i$( $(e Ear$(* 4(en a #urface -a)e i# (!riB!n$a&& "!&ariBed' $(e

e&ec$ric fie&d !f $(e -a)e i# "ara&&e& -i$( $(e #urface !f $(e Ear$( and' $(eref!re' i#

c!n#$an$& in c!n$ac$ -i$( i$* T(e -a)e i# $(en c!m"&e$e& a$$enua$ed -i$(in a #(!r$

di#$ance fr!m $(e $ran#mi$$in% #i$e* On $(e !$(er (and' -(en $(e #urface -a)e i#

)er$ica&& "!&ariBed' $(e e&ec$ric fie&d i# )er$ica& $! $(e Ear$( and mere& di"# in$! and !u$

!f $(e Ear$(# #urface* +!r $(i# rea#!n' )er$ica& "!&ariBa$i!n i# )a#$& #u"eri!r $!

(!riB!n$a& "!&ariBa$i!n f!r #urface -a)e "r!"a%a$i!n* T(e a$$enua$i!n $(a$ a #urface -a)e

under%!e# /ecau#e !f induced )!&$a%e a&#! de"end# !n $(e e&ec$rica& "r!"er$ie# !f $(e

$errain !)er -(ic( $(e -a)e $ra)e&#* T(e /e#$ $"e !f #urface i# !ne $(a$ (a# %!!d

e&ec$rica& c!nduc$i)i$* T(e /e$$er $(e c!nduc$i)i$' $(e &e## $(e a$$enua$i!n* Ta/&e ;1;

%i)e# $(e re&a$i)e c!nduc$i)i$ !f )ari!u# #urface# !f $(e Ear$(*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

An!$(er ma!r fac$!r in $(e a$$enua$i!n !f #urface -a)e# i# frequenc* Reca&& fr!m

ear&ier di#cu##i!n# !n -a)e&en%$( $(a$ $(e (i%(er $(e frequenc !f a radi! -a)e' $(e

#(!r$er i$# -a)e&en%$( -i&& /e* T(e#e (i%( frequencie#' -i$( $(eir #(!r$er -a)e&en%$(#'

are n!$ n!rma&& diffrac$ed /u$ are a/#!r/ed / $(e Ear$( a$ "!in$# re&a$i)e& c&!#e $! $(e

$ran#mi$$in% #i$e* Y!u can a##ume' $(eref!re' $(a$ a# $(e frequenc !f a #urface -a)e i#

increa#ed' $(e m!re ra"id& $(e #urface -a)e -i&& /e a/#!r/ed' !r a$$enua$ed' / $(e

Ear$(* ecau#e !f $(i# &!## / a$$enua$i!n' $(e #urface -a)e i# im"rac$ica& f!r &!n%1

di#$ance $ran#mi##i!n# a$ frequencie# a/!)e ; me%a(er$B* On $(e !$(er (and' -(en $(e

frequenc !f a #urface -a)e i# &!- en!u%( $! (a)e a )er &!n% -a)e&en%$(' $(e Ear$(

a""ear# $! /e )er #ma&&' and diffrac$i!n i# #ufficien$ f!r "r!"a%a$i!n -e&& /e!nd $(e

(!riB!n* In fac$' / &!-erin% $(e $ran#mi$$in% frequenc in$! $(e )er &!- frequenc )&f

ran%e and u#in% )er (i%(1"!-ered $ran#mi$$er#' $(e #urface -a)e can /e "r!"a%a$ed%rea$ di#$ance#*

T(e Na)# e,$reme& (i%(1"!-ered )&f $ran#mi$$er# are ac$ua&& ca"a/&e !f 

$ran#mi$$in% #urface -a)e #i%na&# ar!und $(e Ear$( and can "r!)ide c!)era%e $! na)a&

uni$# !"era$in% an-(ere a$ #ea*

$pace wa&e propagation, considerations in space wa&e propagation:

T(e #"ace -a)e f!&&!-# $-! di#$inc$ "a$(# fr!m $(e $ran#mi$$in% an$enna $! $(erecei)in% an$enna!ne $(r!u%( $(e air direc$& $! $(e recei)in% an$enna' $(e !$(er 

ref&ec$ed fr!m $(e %r!und $! $(e recei)in% an$enna* T(i# i# i&&u#$ra$ed in fi%ure ;18?* T(e

 "rimar "a$( !f $(e #"ace -a)e i# direc$& fr!m $(e $ran#mi$$in% an$enna $! $(e recei)in%

an$enna*

S!' $(e recei)in% an$enna mu#$ /e &!ca$ed -i$(in $(e radi! (!riB!n !f $(e

$ran#mi$$in% an$enna* ecau#e #"ace -a)e# are refrac$ed #&i%($&' e)en -(en "r!"a%a$ed

$(r!u%( $(e $r!"!#"(ere' $(e radi! (!riB!n i# ac$ua&& a/!u$ !ne1$(ird far$(er $(an $(e

&ine1!f1#i%($ !r na$ura& (!riB!n*

C*T=IAGARA@AN1AP ECE DEPT* ;5

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A&$(!u%( #"ace -a)e# #uffer &i$$&e %r!und a$$enua$i!n' $(e ne)er$(e&e## are

#u#ce"$i/&e $! fadin%* T(i# i# /ecau#e #"ace -a)e# ac$ua&& f!&&!- $-! "a$(# !f differen$

&en%$(# direc$ "a$( and %r!und ref&ec$ed "a$( $! $(e recei)in% #i$e and' $(eref!re' ma

arri)e in !r !u$ !f "(a#e* If $(e#e $-! c!m"!nen$ -a)e# are recei)ed in "(a#e' $(e re#u&$

i# a reinf!rced !r #$r!n%er #i%na&* Li2e-i#e' if $(e are recei)ed !u$ !f "(a#e' $(e $end $!

cance& !ne an!$(er' -(ic( re#u&$# in a -ea2 !r fadin% #i%na&*

Atmospheric effect in space wa&e propagation:

4(en "r!"a%a$i!n i# acc!m"&i#(ed )ia mu&$i(!" refrac$i!n' rf ener% i# &!#$ eac( $ime $(e

radi! -a)e i# ref&ec$ed fr!m $(e Ear$(# #urface* T(e am!un$ !f ener% &!#$ de"end# !n

$(e frequenc !f $(e -a)e' $(e an%&e !f incidence' %r!und irre%u&ari$ie#' and $(e e&ec$rica&

c!nduc$i)i$ !f $(e "!in$ !f ref&ec$i!n* +ree #"ace L!## N!rma&&' $(e ma!r &!## !f 

ener% i# /ecau#e !f $(e #"readin% !u$ !f $(e -a)efr!n$ a# i$ $ra)e&# a-a fr!m $(e

$ran#mi$$er* A# $(e di#$ance increa#e#' $(e area !f $(e -a)efr!n$ #"read# !u$' muc( &i2e $(e

 /eam !f a f&a#(&i%($* T(i# mean# $(e am!un$ !f ener% c!n$ained -i$(in an uni$ !f area

!n $(e -a)efr!n$ -i&& decrea#e a# di#$ance increa#e#* $(e $ime $(e ener% arri)e# a$ $(e

recei)in% an$enna' $(e -a)efr!n$ i# #! #"read !u$ $(a$ $(e recei)in% an$enna e,$end# in$!

!n& a )er #ma&& frac$i!n !f $(e -a)efr!n$* T(i# i# i&&u#$ra$ed in fi%ure ;1;;*

C*T=IAGARA@AN1AP ECE DEPT* ;6

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

ELECTROMAGNETIC INTER+ERENCE EMI

T(e $ran#mi##i!n &!##e# u#$ di#cu##ed are n!$ $(e !n& fac$!r# $(a$ in$erfere -i$(

c!mmunica$i!n#* An addi$i!na& fac$!r $(a$ can in$erfere -i$( radi! c!mmunica$i!n# i# $(e

 "re#ence !f ELECTROMAGNETIC INTER+ERENCE EMI* T(i# in$erference can

re#u&$ in ann!in% !r im"!##i/&e !"era$in% c!ndi$i!n#* S!urce# !f emi are /!$( man1

made and na$ura&* Man1Made In$erference Man1made in$erference ma c!me fr!m

#e)era& #!urce#* S!me !f $(e#e #!urce#' #uc( a# !#ci&&a$!r#' c!mmunica$i!n# $ran#mi$$er#'

and radi! $ran#mi$$er#' ma /e #"ecifica&& de#i%ned $! %enera$e radi! frequenc ener%*

S!me e&ec$rica& de)ice# a&#! %enera$e radi! frequenc ener%' a&$(!u%( $(e are n!$

#"ecifica&& de#i%ned f!r $(i# "ur"!#e* E,am"&e# are i%ni$i!n ##$em#' %enera$!r#' m!$!r#'

#-i$c(e#' re&a#' and )!&$a%e re%u&a$!r#* T(e in$en#i$ !f man1made in$erference ma

)ar $(r!u%(!u$ $(e da and dr!" !ff $! a &!- &e)e& a$ ni%($ -(en man !f $(e#e #!urce#

are n!$ /ein% u#ed* Man1made in$erference ma /e a cri$ica& &imi$in% fac$!r a$ radi!

recei)in% #i$e# &!ca$ed near indu#$ria& area#* Na$ura& In$erference Na$ura& in$erference

refer# $! $(e #$a$ic $(a$ !u !f$en (ear -(en &i#$enin% $! a radi!* T(i# in$erference i#

C*T=IAGARA@AN1AP ECE DEPT* ;

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Man fac$!r# affec$ a radi! -a)e in i$# "a$( /e$-een $(e $ran#mi$$in% and

recei)in% #i$e#* T(e fac$!r $(a$ (a# $(e %rea$e#$ ad)er#e effec$ !n radi! -a)e# i#

ASORPTION* A/#!r"$i!n re#u&$# in $(e &!## !f ener% !f a radi! -a)e and (a# a

 "r!n!unced effec$ !n /!$( $(e #$ren%$( !f recei)ed #i%na&# and $(e a/i&i$ $! c!mmunica$e

!)er &!n% di#$ance#*Y!u &earned ear&ier in $(e #ec$i!n !n %r!und -a)e# $(a$ #urface -a)e#

#uffer m!#$ !f $(eir a/#!r"$i!n &!##e# /ecau#e !f %r!und1induced )!&$a%e* S2 -a)e#' !n

$(e !$(er (and' #uffer m!#$ !f $(eir a/#!r"$i!n &!##e# /ecau#e !f c!ndi$i!n# in $(e

i!n!#"(ere* N!$e $(a$ #!me a/#!r"$i!n !f #2 -a)e# ma a&#! !ccur &!-er a$m!#"(eric

&e)e&# /ecau#e !f $(e "re#ence !f -a$er and -a$er )a"!r* =!-e)er' $(i# /ec!me#

im"!r$an$ !n& a$ frequencie# a/!)e 8<'<<< me%a(er$B*

M!#$ i!n!#"(eric a/#!r"$i!n !ccur# in $(e &!-er re%i!n# !f $(e i!n!#"(ere -(ere

i!niBa$i!n den#i$i# %rea$e#$* A# a radi! -a)e "a##e# in$! $(e i!n!#"(ere' i$ &!#e# #!me !f 

i$# ener% $! $(e free e&ec$r!n# and i!n#* If $(e#e (i%(1ener% free e&ec$r!n# and i!n# d!

n!$ c!&&ide -i$( %a# m!&ecu&e# !f &!- ener%' m!#$ !f $(e ener% &!#$ / $(e radi! -a)e i#

rec!n)er$ed in$! e&ec$r!ma%ne$ic ener%' and $(e -a)e c!n$inue# $! /e "r!"a%a$ed -i$(

&i$$&e c(an%e in in$en#i$* =!-e)er' if $(e (i%(1ener% free e&ec$r!n# and i!n# d! c!&&ide

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

-i$( !$(er "ar$ic&e#' muc( !f $(i# ener% i# &!#$' re#u&$in% in a/#!r"$i!n !f $(e ener% fr!m

$(e -a)e* Since a/#!r"$i!n !f ener% de"end# !n c!&&i#i!n !f $(e "ar$ic&e#' $(e %rea$er $(e

den#i$ !f $(e i!niBed &aer' $(e %rea$er $(e "r!/a/i&i$ !f c!&&i#i!n#0 $(eref!re' $(e %rea$er 

$(e a/#!r"$i!n* T(e (i%(& den#e D and E &aer# "r!)ide $(e %rea$e#$ a/#!r"$i!n !f radi!

-a)e#*ecau#e $(e am!un$ !f a/#!r"$i!n !f $(e #2 -a)e de"end# !n $(e den#i$ !f $(e

i!n!#"(ere' -(ic( )arie# -i$( #ea#!na& and dai& c!ndi$i!n#' i$ i# im"!##i/&e $! e,"re## a

fi,ed re&a$i!n#(i" /e$-een di#$ance and #i%na& #$ren%$( f!r i!n!#"(eric "r!"a%a$i!n*

Under cer$ain c!ndi$i!n#' $(e a/#!r"$i!n !f ener% i# #! %rea$ $(a$ c!mmunica$in% !)er 

an di#$ance /e!nd $(e &ine !f #i%($ i# difficu&$.

Types of fading:

T(e m!#$ $r!u/&e#!me and fru#$ra$in% "r!/&em in recei)in% radi! #i%na&# i#)aria$i!n# in #i%na& #$ren%$(' m!#$ c!mm!n& 2n!-n a# +ADING* T(ere are #e)era&

c!ndi$i!n# $(a$ can "r!duce fadin%* 4(en a radi! -a)e i# refrac$ed / $(e i!n!#"(ere !r 

ref&ec$ed fr!m $(e Ear$(# #urface' rand!m c(an%e# in $(e "!&ariBa$i!n !f $(e -a)e ma

!ccur* 3er$ica&& and (!riB!n$a&& m!un$ed recei)in% an$enna# are de#i%ned $! recei)e

)er$ica&& and (!riB!n$a&& "!&ariBed -a)e#' re#"ec$i)e&* T(eref!re' c(an%e# in

 "!&ariBa$i!n cau#e c(an%e# in $(e recei)ed #i%na& &e)e& /ecau#e !f $(e ina/i&i$ !f $(e

an$enna $! recei)e "!&ariBa$i!n c(an%e#* +adin% a&#! re#u&$# fr!m a/#!r"$i!n !f $(e rf 

ener% in $(e i!n!#"(ere* A/#!r"$i!n fadin% !ccur# f!r a &!n%er "eri!d $(an !$(er $"e# !f 

fadin%' #ince a/#!r"$i!n $a2e# "&ace #&!-&* U#ua&&' (!-e)er' fadin% !n i!n!#"(eric

circui$# i# main& a re#u&$ !f mu&$i"a$( "r!"a%a$i!n* Mu&$i"a$( +adin% MULTIPAT= i#

#im"& a $erm u#ed $! de#cri/e $(e mu&$i"&e "a$(# a radi! -a)e ma f!&&!- /e$-een

$ran#mi$$er and recei)er* Suc( "r!"a%a$i!n "a$(# inc&ude $(e %r!und -a)e' i!n!#"(eric

refrac$i!n' reradia$i!n / $(e i!n!#"(eric &aer#' ref&ec$i!n fr!m $(e Ear$(# #urface !r 

fr!m m!re $(an !ne i!n!#"(eric &aer' e$c* +i%ure ;1;8 #(!-# a fe- !f $(e "a$(# $(a$ a

#i%na& can $ra)e& /e$-een $-! #i$e# in a $"ica& circui$* One "a$(' 7Y' i# $(e /a#ic

%r!und -a)e* An!$(er "a$(' 7EA' refrac$# $(e -a)e a$ $(e E &aer and "a##e# i$ !n $! $(e

recei)er a$ A* S$i&& an!$(er "a$(' 7++A' re#u&$# fr!m a %rea$er an%&e !f incidence and

$-! refrac$i!n# fr!m $(e + &aer* A$ "!in$ ' $(e recei)ed #i%na& i# a c!m/ina$i!n !f $(e

%r!und -a)e and $(e #2 -a)e* T(e#e $-! #i%na&# (a)in% $ra)e&ed differen$ "a$(# arri)e

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

a$ "!in$ a$ differen$ $ime#* T(u#' $(e arri)in% -a)e# ma !r ma n!$ /e in "(a#e -i$(

eac( !$(er* Radi! -a)e# $(a$ are recei)ed in "(a#e reinf!rce eac( !$(er and "r!duce a

#$r!n%er #i%na& a$ $(e recei)in% #i$e* C!n)er#e&' $(!#e $(a$ are recei)ed !u$ !f "(a#e

 "r!duce a -ea2 !r fadin% #i%na&* Sma&& a&$erna$i!n# in $(e $ran#mi##i!n "a$( ma c(an%e

$(e "(a#e re&a$i!n#(i" !f $(e $-! #i%na&#' cau#in% "eri!dic fadin%* T(i# c!ndi$i!n !ccur#

a$ "!in$ A* A$ $(i# "!in$' $(e d!u/&e1(!" + &aer #i%na& ma /e in !r !u$ !f "(a#e -i$( $(e

#i%na& arri)in% fr!m $(e E &aer*

Mu&$i"a$( fadin% ma /e minimiBed / "rac$ice# ca&&ed SPACE DI3ERSITY and

+REUENCY DI3ERSITY* In #"ace di)er#i$' $-! !r m!re recei)in% an$enna# are

#"aced #!me di#$ance a"ar$* +adin% d!e# n!$ !ccur #imu&$ane!u#& a$ /!$( an$enna#0

$(eref!re' en!u%( !u$"u$ i# a&m!#$ a&-a# a)ai&a/&e fr!m !ne !f $(e an$enna# $! "r!)ide

a u#efu& #i%na&* In frequenc di)er#i$' $-! $ran#mi$$er# and $-! recei)er# are u#ed' eac(

 "air $uned $! a differen$ frequenc' -i$( $(e #ame inf!rma$i!n /ein% $ran#mi$$ed

#imu&$ane!u#& !)er /!$( frequencie#* One !f $(e $-! recei)er# -i&& a&m!#$ a&-a#

 "r!)ide a u#efu& #i%na&*

$electi&e Fading:

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

+adin% re#u&$in% fr!m mu&$i"a$( "r!"a%a$i!n i# )aria/&e -i$( frequenc #ince eac(

frequenc arri)e# a$ $(e recei)in% "!in$ )ia a differen$ radi! "a$(* 4(en a -ide /and !f 

frequencie# i# $ran#mi$$ed #imu&$ane!u#&' eac( frequenc -i&& )ar in $(e am!un$ !f 

fadin%* T(i# )aria$i!n i# ca&&ed SELECTI3E +ADING* 4(en #e&ec$i)e fadin% !ccur#' a&&

frequencie# !f $(e $ran#mi$$ed #i%na& d! n!$ re$ain $(eir !ri%ina& "(a#e# and re&a$i)e

am"&i$ude#* T(i# fadin% cau#e# #e)ere di#$!r$i!n !f $(e #i%na& and &imi$# $(e $!$a& #i%na&

$ran#mi$$ed*

Maximum +sa*le Frequency:

A# -e di#cu##ed ear&ier' $(e (i%(er $(e frequenc !f a radi! -a)e' $(e &!-er $(e

ra$e !f refrac$i!n / an i!niBed &aer* T(eref!re' f!r a %i)en an%&e !f incidence and $ime

!f da' $(ere i# a ma,imum frequenc $(a$ can /e u#ed f!r c!mmunica$i!n# /e$-een $-!%i)en &!ca$i!n#* T(i# frequenc i# 2n!-n a# $(e MA7IMUM USALE +REUENCY

muf* 4a)e# a$ frequencie# a/!)e $(e muf are n!rma&& refrac$ed #! #&!-& $(a$ $(e

re$urn $! Ear$( /e!nd $(e de#ired &!ca$i!n' !r "a## !n $(r!u%( $(e i!n!#"(ere and are

&!#$* Y!u #(!u&d under#$and' (!-e)er' $(a$ u#e !f an e#$a/&i#(ed muf cer$ain& d!e# n!$

%uaran$ee #ucce##fu& c!mmunica$i!n# /e$-een a $ran#mi$$in% #i$e and a recei)in% #i$e*

3aria$i!n# in $(e i!n!#"(ere ma !ccur a$ an $ime and c!n#equen$& rai#e !r &!-er $(e

 "rede$ermined muf* T(i# i# "ar$icu&ar& $rue f!r radi! -a)e# /ein% refrac$ed / $(e (i%(&

)aria/&e +; &aer* T(e muf i# (i%(e#$ ar!und n!!n -(en u&$ra)i!&e$ &i%($ -a)e# fr!m $(e

#un are $(e m!#$ in$en#e* I$ $(en dr!"# ra$(er #(ar"& a# rec!m/ina$i!n /e%in# $! $a2e

 "&ace*

$ip #istance:

In fi%ure ;18J' n!$e $(e re&a$i!n#(i" /e$-een $(e #2 -a)e #2i" di#$ance' $(e #2i" B!ne'

and $(e%r!und -a)e c!)era%e* T(e SIP DISTANCE i# $(e di#$ance fr!m $(e $ran#mi$$er 

$! $(e "!in$ -(ere $(e #2 -a)e i# fir#$ re$urned $! Ear$(* T(e #iBe !f $(e #2i" di#$ance

de"end# !n $(e frequenc !f $(e -a)e' $(e an%&e !f incidence' and $(e de%ree !f 

i!niBa$i!n "re#en$*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

-ropagation paths:

T(e "a$( $(a$ a refrac$ed -a)e f!&&!-# $! $(e recei)er de"end# !n $(e an%&e a$ -(ic( $(e

-a)e #$ri2e# $(e i!n!#"(ere* Y!u #(!u&d remem/er' (!-e)er' $(a$ $(e rf ener% radia$ed

 / a $ran#mi$$in% an$enna #"read# !u$ -i$( di#$ance* T(e ener% $(eref!re #$ri2e# $(e

i!n!#"(ere a$ man differen$ an%&e# ra$(er $(an a #in%&e an%&e* Af$er $(e rf ener% !f a

%i)en frequenc en$er# an i!n!#"(eric re%i!n' $(e "a$(# $(a$ $(i# ener% ma a&#!' reac(

$(e recei)in% an$enna !)er a "a$( in)!&)in% m!re $(an !ne &aer' / mu&$i"&e (!"#

 /e$-een $(e i!n!#"(ere and Ear$(' !r / an c!m/ina$i!n !f $(e#e "a$(#* +i%ure ;1;<

#(!-# (!- radi! -a)e# ma reac( a recei)er )ia #e)era& "a$(# $(r!u%( !ne &aer*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

4(en $(e an%&e i# re&a$i)e& &!- -i$( re#"ec$ $! $(e (!riB!n ra 8' $(ere i# !n& #&i%($

 "ene$ra$i!n !f $(e &aer and $(e "r!"a%a$i!n "a$( i# &!n%* 4(en $(e an%&e !f incidence i#

increa#ed ra# ; and ?' $(e ra# "ene$ra$e dee"er in$! $(e &aer /u$ $(e ran%e !f $(e#e

ra# decrea#e#* 4(en a cer$ain an%&e i# reac(ed ra ?' $(e "ene$ra$i!n !f $(e &aer and

ra$e !f refrac$i!n are #uc( $(a$ $(e ra i# fir#$ re$urned $! Ear$( a$ a minima& di#$ance

fr!m $(e $ran#mi$$er* N!$ice' (!-e)er' $(a$ ra ? #$i&& mana%e# $! reac( $(e recei)in% #i$e

!n i$# #ec!nd refrac$i!n ca&&ed a (!" fr!m $(e i!n!#"(eric &aer* A# $(e an%&e i#

increa#ed #$i&& m!re ra# > and 5' $(e rf ener% "ene$ra$e# $(e cen$ra& area !f ma,imum

i!niBa$i!n !f $(e &aer* T(e#e ra# are refrac$ed ra$(er #&!-& and are e)en$ua&& re$urned

$! Ear$( a$ %rea$ di#$ance#* A# $(e an%&e a""r!ac(e# )er$ica& incidence ra 6' $(e ra i#

n!$ re$urned a$ a&&' /u$ "a##e# !n $(r!u%( $(e &aer*

T(e %'T'A/ F%01+0  i# $(e ma,imum frequenc $(a$ a radi! -a)e can /e

$ran#mi$$ed )er$ica&& and #$i&& /e refrac$ed /ac2 $! Ear$(*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

#i&ersity reception:

  U#in% an$enna arra# f!r di&ersity rece"$i!n i# !ne !f $(e m!#$ #$rai%($f!r-ard

u#e# !f an$enna arra#* ecau#e $(e "!-er &e)e& !f a recei)ed #i%na& can )ar

#i%nifican$& -i$( #ma&& c(an%e# in di#$ance' a di)er#i$ arra #im"& u#e# a #e$ !f 

an$enna# and c!m/ine# $(e #i%na&# $! !/$ain $(e ma,imum #i%na&* C!n#ider $(e e,am"&e

!f +i%ure 8* S!me!ne i# $a&2in% !n $(eir ce&& "(!ne' and a ("!$(e$ica& $(!u%(

rea#!na/&e "!-er i# #(!-n in $(e area# ar!und $(e u#er*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

In $(e ca#e #(!-n in +i%ure ;' $(e #i%na& a$ an$enna num/er 8 (a# $(e &ar%e#$

#i%na&' and can $(eref!re /e u#ed* In $(i# manner' $(e effec$# !f fadin% are %rea$&

reduced' and $(e "r!/a/i&i$ !f (a)in% a #i%na& $!! #ma&& $! -!r2 -i$( decrea#e# a# $(e

num/er !f an$enna# increa#e#*+ina&&' di)er#i$ rece"$i!n can !ccur f!r $-! an$enna# n!$

#e"ara$ed' /u$ recei)in% !r$(!%!na&  "!&ariBa$i!n#* If !ne an$enna recei)e# )er$ica&&

 "!&ariBed -a)e#' a #ec!nd an$enna can /e "&aced near $(e fir#$ $(a$ recei)e# (!riB!n$a&&

 "!&ariBed -a)e# -(ic( in a fadin% en)ir!nmen$' are n!$ #$r!n%& c!rre&a$ed* In $(i#

manner' di)er#i$ can /e ac(ie)ed*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

+ina&&' di)er#i$ rece"$i!n can !ccur f!r $-! an$enna# n!$ #e"ara$ed' /u$ recei)in%

!r$(!%!na&  "!&ariBa$i!n#*  If !ne an$enna recei)e# )er$ica&& "!&ariBed -a)e#' a #ec!nd

an$enna can /e "&aced near $(e fir#$ $(a$ recei)e# (!riB!n$a&& "!&ariBed -a)e# -(ic( in a

fadin% en)ir!nmen$' are n!$ #$r!n%& c!rre&a$ed* In $(i# manner' di)er#i$ can /e

ac(ie)ed

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

UNIT III: DIGITAL COMMUNICATION Pu&#e c!de m!du&a$i!n' $ime di)i#i!n

mu&$i"&e,in%' di%i$a& T1carrier ##$em* Di%i$a& radi! ##$em* Di%i$a& m!du&a$i!n:

+requenc and "(a#e #(if$ 2ein% . M!du&a$!r and dem!du&a$!r' /i$ err!r ra$e

ca&cu&a$i!n*

#igital communication:

T(e $ran#mi##i!n !f di%i$a& da$a $(r!u%( a di%i$a& "&a$f!rm $(a$ (a# $(e a/i&i$ $!

c!m/ine $e,$' audi!' %ra"(ic#' )ide! and da$a* Di%i$a& c!mmunica$i!n ena/&e# da$a $! /e

$ran#mi$$ed in an efficien$ manner $(r!u%( $(e u#e !f di%i$a&& enc!ded inf!rma$i!n #en$

$(r!u%( da$a #i%na&#* T(e#e da$a #i%na&# are ea#i& c!m"re##ed and' a# #uc(' can /e

$ran#mi$$ed -i$( accurac and #"eed*

Un&i2e in an ana&!% c!mmunica$i!n# -(ere $(e c!n$inui$ !f a )arin% #i%na& can

n!$ /e /r!2en' in a di%i$a& c!mmunica$i!n a di%i$a& $ran#mi##i!n can /e /r!2en d!-n in$!

 "ac2e$# a# di#cre$e me##a%e#* Tran#mi$$in% da$a in di#cre$e me##a%e# n!$ !n& faci&i$a$e#

$(e err!r de$ec$i!n and c!rrec$i!n /u$ a&#! ena/&e# a %rea$er #i%na& "r!ce##in% ca"a/i&i$*

Di%i$a& c!mmunica$i!n (a#' in &ar%e "ar$' re"&aced ana&!% c!mmunica$i!n a# $(e idea&

f!rm !f $ran#mi$$in% inf!rma$i!n $(r!u%( c!m"u$er and m!/i&e $ec(n!&!%ie#*

-ulse code modulation:

Pu&#e1c!de m!du&a$i!n PCM i# a me$(!d u#ed $! di%i$a&&  re"re#en$ #am"&ed

ana&!% #i%na&#* I$ i# $(e #$andard f!rm !f di%i$a& audi!  in c!m"u$er#' C!m"ac$ Di#c#'

di%i$a& $e&e"(!n and !$(er di%i$a& audi! a""&ica$i!n#* In a PCM #$ream' $(e am"&i$ude !f 

$(e ana&!% #i%na& i# #am"&ed re%u&ar& a$ unif!rm in$er)a&#' and eac( #am"&e i# quan$iBed

$! $(e neare#$ )a&ue -i$(in a ran%e !f di%i$a& #$e"#*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Ad&antages of -ulse ode Modulation:

• Pu&#e c!de m!du&a$i!n -i&& (a)e &!- n!i#e addi$i!n and da$a &!## i# a&#! )er &!-*

• 4e can re"ea$ $(e e,ac$ $ran#mi$$ed #i%na& a$ $(e recei)er* T(i# i# ca&&ed

re"ea$a/i&i$* And -e can re$ran#mi$ $(e #i%na& -i$( an di#$!r$i!n &!## a&#!*

• Pu&#e c!de m!du&a$i!n i# u#ed in mu#ic "&a /ac2 CD# and a&#! u#ed in D3D f!r 

da$a #$!rin% -(!#e #am"&in% ra$e i# /i$ (i%(er*

• Pu&#e c!de m!du&a$i!n can /e u#ed in #$!rin% $(e da$a*

• PCM can enc!de $(e da$a a&#!*

• Mu&$i"&e,in% !f #i%na&# can a&#! /e d!ne u#in% "u&#e c!de m!du&a$i!n*

Mu&$i"&e,in% i# n!$(in% f!r addin% $(e differen$ #i%na&# and $ran#mi$$in% $(e #i%na&

a$ #ame $ime*

•

Pu&#e c!de m!du&a$i!n require# &ar%e /and-id$(

• Pu&#e c!de m!du&a$i!n "ermi$# $(e u#e !f "u&#e re%enera$i!n*

#isad&antages of -ulse ode Modulation:

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

• S"ecia&iBed circui$r i# required f!r $ran#mi$$in% and a&#! f!r quan$iBin% $(e

#am"&e# a$ #ame quan$iBed &e)e&#* 4e can d! enc!din% u#in% "u&#e c!de

m!du&a$i!n /u$ -e need $! (a)e c!m"&e, and #"ecia& circui$r*

• Pu&#e c!de m!du&a$i!n recei)er# are c!#$ effec$i)e -(en -e c!m"ared $! !$(er 

m!du&a$i!n recei)er#*

• De)e&!"in% "u&#e c!de m!du&a$i!n i# /i$ c!m"&ica$ed and c(ec2in% $(e

$ran#mi##i!n qua&i$ i# a&#! difficu&$ and $a2e# m!re $ime*

• Lar%e /and-id$( i# required f!r "u&#e c!de m!du&a$i!n -(en c!m"ared $!

 /and-id$( u#ed / $(e n!rma& ana&!% #i%na&# $! $ran#mi$ me##a%e*

•

C(anne& /and-id$( #(!u&d /e m!re f!r di%i$a& enc!din%*

• PCM ##$em# are c!m"&ica$ed -(en c!m"ared $! ana&!% m!du&a$i!n me$(!d# and

!$(er ##$em#*

• Dec!din% a&#! need# #"ecia& equi"men$# and $(e are a&#! $!! c!m"&e,*

Applications of -ulse ode Modulation -M4:

• Pu&#e c!de m!du&a$i!n i# u#ed in $e&ec!mmunica$i!n ##$em#' air $raffic c!n$r!&

##$em# e$c*

• Pu&#e c!de m!du&a$i!n i# u#ed in c!m"re##in% $(e da$a $(a$ i# -( i$ i# u#ed in

#$!rin% da$a in !"$ica& di#2# &i2e D3D' CD# e$c* PCM i# e)en u#ed in $(e da$a/a#e

mana%emen$ ##$em#*

• Pu&#e c!de m!du&a$i!n i# u#ed in m!/i&e "(!ne#' n!rma& $e&e"(!ne# e$c*

• Rem!$e c!n$r!&&ed car#' "&ane#' $rain# u#e "u&#e c!de m!du&a$i!n#.

Time di&ision multiplexing:

Time Di)i#i!n Mu&$i"&e,in% TDM i# a c!mmunica$i!n# "r!ce## $(a$ $ran#mi$#

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

$-! !r m!re #$reamin% di%i$a& #i%na&# !)er a c!mm!n c(anne&* In TDM' inc!min% #i%na&#

are di)ided in$! equa& fi,ed1&en%$( $ime #&!$#* Af$er mu&$i"&e,in%' $(e#e #i%na&# are

$ran#mi$$ed !)er a #(ared medium and rea##em/&ed in$! $(eir !ri%ina& f!rma$ af$er de1

mu&$i"&e,in%* Time #&!$ #e&ec$i!n i# direc$& "r!"!r$i!na& $! !)era&& ##$em efficienc*

Time1di)i#i!n mu&$i"&e,in% i# u#ed "rimari& f!r di%i$a&  #i%na&#' /u$ ma /e

a""&ied in ana&!% mu&$i"&e,in% in -(ic( $-! !r m!re #i%na&# !r /i$ #$ream# are $ran#ferred

a""earin% #imu&$ane!u#& a# #u/1c(anne&# in !ne c!mmunica$i!n c(anne&' /u$ are

 "(#ica&& $a2in% $urn# !n $(e c(anne&* T(e $ime d!main i# di)ided in$! #e)era& recurren$

$ime #&!$# !f fi,ed &en%$(' !ne f!r eac( #u/1c(anne&* A #am"&e /$e !r da$a /&!c2 !f #u/1

c(anne& 8 i# $ran#mi$$ed durin% $ime #&!$ 8' #u/1c(anne& ; durin% $ime #&!$ ;' e$c* One

TDM frame c!n#i#$# !f !ne $ime #&!$ "er #u/1c(anne& "&u# a #nc(r!niBa$i!n c(anne& and#!me$ime# err!r c!rrec$i!n c(anne& /ef!re $(e #nc(r!niBa$i!n* Af$er $(e &a#$ #u/1

c(anne&' err!r c!rrec$i!n' and #nc(r!niBa$i!n' $(e cc&e #$ar$# a&& !)er a%ain -i$( a ne-

frame' #$ar$in% -i$( $(e #ec!nd #am"&e' /$e !r da$a /&!c2 fr!m #u/1c(anne& 8*

Eac( )!ice $ime #&!$ in $(e TDM frame i# ca&&ed a c(anne&* In Eur!"ean ##$em#'

#$andard TDM frame# c!n$ain ?< di%i$a& )!ice c(anne&# E8' and in American ##$em#

T8' $(e c!n$ain ;> c(anne&#* !$( #$andard# a&#! c!n$ain e,$ra /i$# !r /i$ $ime #&!$#

f!r #i%na&&in% and #nc(r!niBa$i!n /i$#*

Mu&$i"&e,in% m!re $(an ;> !r ?< di%i$a& )!ice c(anne&# i# ca&&ed (i%(er !rder 

mu&$i"&e,in%* =i%(er !rder mu&$i"&e,in% i# acc!m"&i#(ed / mu&$i"&e,in% $(e #$andard

TDM frame#* +!r e,am"&e' a Eur!"ean 8;< c(anne& TDM frame i# f!rmed /

mu&$i"&e,in% f!ur #$andard ?< c(anne& TDM frame#* A$ eac( (i%(er !rder mu&$i"&e,' f!ur 

TDM frame# fr!m $(e immedia$e &!-er !rder are c!m/ined' crea$in% mu&$i"&e,e# -i$( a

 /and-id$( !f n6> 2/i$#' -(ere n 8;<' >H<' 8J;<

#igital T5carrier system:

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A dedica$ed "(!ne c!nnec$i!n #u""!r$in% da$a ra$e# !f 8*5>>M/i$# "er #ec!nd* A

T18 &ine ac$ua&& c!n#i#$# !f ;> indi)idua& c(anne&#' eac( !f -(ic( #u""!r$# 6>/i$# "er 

#ec!nd* Eac( 6>/i$#ec!nd c(anne& can /e c!nfi%ured $! carr )!ice !r da$a $raffic*

M!#$ $e&e"(!ne c!m"anie# a&&!- !u $! /u u#$ #!me !f $(e#e indi)idua& c(anne&#'

2n!-n a# frac$i!na& T18 acce##* T18 &ine# are a "!"u&ar &ea#ed &ine !"$i!n f!r /u#ine##e#

c!nnec$in% $! $(e In$erne$ and f!r  In$erne$ Ser)ice Pr!)ider# ISP# c!nnec$in% $! $(e

In$erne$ /ac2/!ne* T(e In$erne$ /ac2/!ne i$#e&f c!n#i#$# !f fa#$er T1?  c!nnec$i!n#* T18

&ine# are #!me$ime# referred $! a# DS8 &ine#*

T(e m!#$ c!mm!n &e%ac !f $(i# ##$em i# $(e &ine ra$e #"eed#* T8 n!- mean#

an da$a circui$ $(a$ run# a$ $(e !ri%ina& 8*5>> M/i$# &ine ra$e* Ori%ina&& $(e T8 f!rma$

carried ;> "u&#e1c!de m!du&a$ed' $ime1di)i#i!n mu&$i"&e,ed #"eec( #i%na&# eac( enc!ded

in 6> 2/i$# #$ream#' &ea)in% H 2/i$# !f framin% inf!rma$i!n -(ic( faci&i$a$e# $(e

#nc(r!niBa$i!n and demu&$i"&e,in% a$ $(e recei)er* T; and T? circui$ c(anne&# carr

mu&$i"&e T8 c(anne&# mu&$i"&e,ed' re#u&$in% in $ran#mi##i!n ra$e# !f 6*?8; and >>*?6

M/i$#' re#"ec$i)e&*

Su""!#ed&' $(e 8*5>> M/i$# ra$e -a# c(!#en /ecau#e $e#$# d!ne / ATT L!n%

Line#  in C(ica%!  -ere c!nduc$ed under%r!und* T! acc!mm!da$e &!adin% c!i&#' ca/&e

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

)au&$ man(!&e# -ere "(#ica&& ;<<< me$er 6'6<< f$ a"ar$' and #! $(e !"$imum /i$ ra$e

-a# c(!#en em"irica&&  $(e ca"aci$ -a# increa#ed un$i& $(e fai&ure ra$e -a#

unacce"$a/&e' $(en reduced $! &ea)e a mar%in* C!m"andin% a&&!-ed acce"$a/&e audi!

 "erf!rmance -i$( !n& #e)en /i$# "er PCM #am"&e in $(i# !ri%ina& T8D8 ##$em* T(e

&a$er D? and D> c(anne& /an2# (ad an e,$ended frame f!rma$' a&&!-in% ei%($ /i$# "er 

#am"&e' reduced $! #e)en e)er #i,$( #am"&e !r frame -(en !ne /i$ -a# r!//ed f!r 

#i%na&in% $(e #$a$e !f $(e c(anne&* T(e #$andard d!e# n!$ a&&!- an a&& Ber! #am"&e -(ic(

-!u&d "r!duce a &!n% #$rin% !f /inar  Ber!# and cau#e $(e re"ea$er# $! &!#e /i$ #nc*

=!-e)er' -(en carrin% da$a S-i$c(ed 56 $(ere c!u&d /e &!n% #$rin%# !f Ber!e#' #! !ne

 /i$ "er #am"&e i# #e$ $! 8 am /i$ &ea)in% /i$# , H'<<< frame# "er #ec!nd f!r da$a*

#igital radio system:

T(e "re#en$ in)en$i!n i# f!r a (i%( qua&i$ di%i$a& +M radi! ##$em $(a$ u$i&iBe# $(e

#u/carrier /and $! %enera$e di%i$a& audi! #i%na&#* T(e (/rid +M radi! ##$em u$i&iBe# $(e

#u/carrier /and $! $ran#mi$ $(e di%i$a& +M #i%na&# $(a$ are #nc(r!niBed $! $(e ana&!% +M

#i%na&#* T(e recei)er "r!ce##e# /!$( $(e ana&!% and di%i$a& #i%na&# and a (i%( qua&i$ +M

#i%na& re#u&$#* T(e recei)er ma #-i$c( /e$-een $(e $radi$i!na& ana&!% #i%na& and $(e

(i%(er qua&i$ di%i$a& #i%na& au$!ma$ica&& $! "re#en$ $(e /e#$ "!##i/&e audi! $! $(e u#er*

Di%i$a& radi! /r!adca#$in% #$andard# ma "r!)ide $erre#$ria&  !r #a$e&&i$e radi!  #er)ice*

Di%i$a& radi! /r!adca#$in% ##$em# are $"ica&& de#i%ned f!r (and(e&d m!/i&e de)ice#'

 u#$ &i2e m!/i&e1T3 ##$em#' /u$ a# !""!#ed $! !$(er di%i$a& T3 ##$em# -(ic( $"ica&&

require a fi,ed direc$i!na& an$enna* S!me di%i$a& radi! ##$em# "r!)ide in1/and !n1

c(anne& IOC #!&u$i!n# $(a$ ma c!e,i#$ -i$( !r #imu&ca#$ -i$( ana&!% AM !r +M

$ran#mi##i!n#' -(i&e !$(er# are de#i%ned f!r de#i%na$ed radi! frequenc /and#*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e &a$$er a&&!-# !ne -ide/and radi! #i%na& $! carr a mu&$i"&e, c!n#i#$in% !f 

#e)era& radi!1c(anne&# !f )aria/&e /i$ra$e a# -e&& a# da$a #er)ice# and !$(er f!rm# !f 

media* S!me di%i$a& /r!adca#$in% ##$em# a&&!- #in%&e1frequenc ne$-!r2 S+N' -(erea&& $erre#$ria& $ran#mi$$er# in a re%i!n #endin% $(e #ame mu&$i"&e, !f radi! "r!%ram# ma

u#e $(e #ame frequenc c(anne& -i$(!u$ #e&f1in$erference "r!/&em#' fur$(er im"r!)in% $(e

##$em #"ec$ra& efficienc*

4(i&e di%i$a& /r!adca#$in% !ffer# man "!$en$ia& /enefi$#' i$# in$r!duc$i!n (a#

 /een (indered / a &ac2 !f %&!/a& a%reemen$ !n #$andard# and man di#ad)an$a%e#* T(e

DA Eure2a 8> #$andard f!r di%i$a& radi! i# c!!rdina$ed / $(e 4!r&d DM +!rum*

T(i# #$andard !f di%i$a& radi! $ec(n!&!% -a# defined in $(e &a$e 8JH<#' and i# n!- /ein%

in$r!duced in #!me Eur!"ean c!un$rie#* C!mmercia& DA recei)er# /e%an $! /e #!&d in

8JJJ and' / ;<<6' 5<< mi&&i!n "e!"&e -ere in $(e c!)era%e area !f DA /r!adca#$#'

a&$(!u%( / $(i# $ime #a&e# (ad !n& $a2en !ff in $(e U  and Denmar2 * In ;<<6 $(ere are

a""r!,ima$e& 8'<<< DA #$a$i!n# in !"era$i!n* Q8 T(ere (a)e /een cri$ici#m# !f $(e

Eure2a 8> #$andard and #! a ne- DAF #$andard (a# /een in$r!duced*T(e DRM

#$andard (a# /een u#ed f!r #e)era& ear# $! /r!adca#$ di%i$a&& !n frequencie# /e&!-

?< M=B #(!r$-a)e' medium-a)e and &!n%-a)e* A&#! $(ere i# n!- $(e e,$ended

#$andard DRMF -(ic( ma2e i$ "!##i/&e $! /r!adca#$ !n frequencie# a/!)e ?< M=B*T(i#

-i&& ma2e i$ "!##i/&e $! di%i$a&iBe $ran#mi##i!n !n $(e +M1/and* Succe##fu& $e#$# !f 

DRMF (a# /een made in #e)era& c!un$rie# ;<8<1;<8; a# in raBi&' German' +rance'

India' Sri Lan2a' $(e U' S&!)a2ia and I$a& inc&* $(e 3a$ican* DRMF -i&& /e $e#$ed in

S-eden ;<8;*

C*T=IAGARA@AN1AP ECE DEPT* >>

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

DRMF i# re%arded a# a m!re $ran#"aren$ and &e## c!#$& #$andard $(an DAF and $(u# a

 /e$$er c(!ice f!r &!ca& radi!0 c!mmercia& !r c!mmuni$ /r!adca#$er#* I$ i# A&$(!u%(

DAF (a# /een in$r!duced in Au#$ra&ia $(e %!)ernmen$ (a# c!nc&uded ;<88 $(a$ a

 "reference f!r DRM and DRMF a/!)e =D Radi! c!u&d /e u#ed $! #u""&emen$ DAF

#er)ice# in #!me &!ca& and re%i!na& area#*A&& Di%i$a& Radi! r!adca#$ ##$em #(are

man di#ad)an$a%e# -(ic( d!n$ e,i#$ f!r Ana&!%ue $! Di%i$a& T3 c(an%e!)er: A/!u$ ,;<

m!re "!-er c!n#um"$i!n' Di%i$a& C&iff effec$ f!r M!/i&e u#e' )er #&!- c(anne& c(an%e'

e#"ecia&& f!r a differen$ DA mu&$i"&e, frequenc' (i%( $ran#mi##i!n c!#$ re#u&$in%

 "!!rer qua&i$ $(an +M and #!me$ime# AM due $! &!- /i$ra$e 6> m!n! ra$(er $(an

;56 #$ere!' (i%(er c!m"re##i!n i# m!re di#$!r$ed f!r (earin% aid u#er#' u#ua&& "!!r 

u#er in$erface# and Radi! audi! qua&i$' n!$ en!u%( fi&& in #$a$i!n# f!r "!r$a/&e m!/i&e

c!)era%e &i2e 8J5<# U +M*

T(e Mu&$i"&e, S+N c!nce"$# are ad)an$a%e!u# $! S$a$e r!adca#$er# and Lar%e

Pan Na$i!na& Mu&$i1c(anne& c!m"anie# and -!r#e f!r a&& L!ca&' C!mmuni$ and m!#$

Re%i!na& #$a$i!n#* In c!n$ra#$ a&m!#$ a&& $(e a#"ec$# !f Di%i$a& T3 )# Ana&!%ue T3 are

 "!#i$i)e -i$( a&m!#$ n! ne%a$i)e effec$#* T3# c!u&d /e u#ed -i$( a Se$1/!,* Di%i$a& Radi!

require# re"&acemen$ !f a&& radi!#' $(!u%( an a-2-ard DA recei)er -i$( +M !u$"u$ can

 /e u#ed -i$( e,i#$in% +M car Radi!#*

Frequency and phase shift eying:

+requenc1#(if$ 2ein% +S i# a frequenc m!du&a$i!n #c(eme in -(ic( di%i$a&

inf!rma$i!n i# $ran#mi$$ed $(r!u%( di#cre$e frequenc c(an%e# !f a carrier -a)e*Q8 T(e

#im"&e#$ +S i# /inar +S +S* +S u#e# a "air !f di#cre$e frequencie# $! $ran#mi$

 /inar <# and 8# inf!rma$i!n*Q; 4i$( $(i# #c(eme' $(e 8 i# ca&&ed $(e mar2 frequenc

and $(e < i# ca&&ed $(e #"ace frequenc*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Audi! frequenc1#(if$ 2ein% A+S i# a m!du&a$i!n $ec(nique / -(ic( di%i$a&

da$a  i# re"re#en$ed / c(an%e# in $(e frequenc   "i$c( !f an  audi! $!ne' ie&din% an

enc!ded #i%na& #ui$a/&e f!r $ran#mi##i!n )ia radi! !r $e&e"(!ne* N!rma&&' $(e $ran#mi$$ed

audi! a&$erna$e# /e$-een $-! $!ne#: !ne' $(e mar2' re"re#en$# a /inar !ne0 $(e !$(er'

$(e #"ace' re"re#en$# a /inar Ber!*

A+S differ# fr!m re%u&ar frequenc1#(if$ 2ein% in "erf!rmin% $(e m!du&a$i!n

a$  /a#e/and frequencie#* In radi! a""&ica$i!n#' $(e A+S1m!du&a$ed #i%na& n!rma&& i#

 /ein% u#ed $! m!du&a$e an R+  carrier u#in% a c!n)en$i!na& $ec(nique' #uc( a# AM  !r 

+M f!r $ran#mi##i!n*

A+S i# n!$ a&-a# u#ed f!r (i%(1#"eed da$a c!mmunica$i!n#' #ince i$ i# far &e##

efficien$ in /!$( "!-er and /and-id$( $(an m!#$ !$(er m!du&a$i!n m!de#* In addi$i!n $!

i$# #im"&ici$' (!-e)er' A+S (a# $(e ad)an$a%e $(a$ enc!ded #i%na&# -i&& "a## $(r!u%(

AC1c!u"&ed  &in2#' inc&udin% m!#$ equi"men$ !ri%ina&& de#i%ned $! carr mu#ic !r 

#"eec(*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

-hase5shift eying:

P(a#e1#(if$ 2ein% PS i# a di%i$a&  m!du&a$i!n #c(eme $(a$ c!n)e# da$a  /

c(an%in%' !r m!du&a$in%' $(e "(a#e !f a reference #i%na& $(e carrier -a)e*

An di%i$a& m!du&a$i!n #c(eme u#e# a  fini$e  num/er !f di#$inc$ #i%na&# $!

re"re#en$ di%i$a& da$a* PS u#e# a fini$e num/er !f "(a#e#' eac( a##i%ned a unique "a$$ern

!f /inar di%i$#* U#ua&&' eac( "(a#e enc!de# an equa& num/er !f /i$#* Eac( "a$$ern !f /i$#

f!rm# $(e #m/!& $(a$ i# re"re#en$ed / $(e "ar$icu&ar "(a#e* T(e dem!du&a$!r ' -(ic( i#

de#i%ned #"ecifica&& f!r $(e #m/!&1#e$ u#ed / $(e m!du&a$!r' de$ermine# $(e "(a#e !f 

$(e recei)ed #i%na& and ma"# i$ /ac2 $! $(e #m/!& i$ re"re#en$#' $(u# rec!)erin% $(e

!ri%ina& da$a* T(i# require# $(e recei)er $! /e a/&e $! c!m"are $(e "(a#e !f $(e recei)ed

#i%na& $! a reference #i%na& #uc( a ##$em i# $ermed c!(eren$ and referred $! a#CPS*

A&$erna$i)e&' in#$ead !f !"era$in% -i$( re#"ec$ $! a c!n#$an$ reference -a)e' $(e

 /r!adca#$ can !"era$e -i$( re#"ec$ $! i$#e&f* C(an%e# in "(a#e !f a #in%&e /r!adca#$

-a)ef!rm can /e c!n#idered $(e #i%nifican$ i$em#* In $(i# ##$em' $(e dem!du&a$!r 

de$ermine# $(e c(an%e# in $(e "(a#e !f $(e recei)ed #i%na& ra$(er $(an $(e "(a#e re&a$i)e

$! a reference -a)e i$#e&f* Since $(i# #c(eme de"end# !n $(e difference /e$-een

#ucce##i)e "(a#e#' i$ i# $ermed differen$ia& "(a#e1#(if$ 2ein% DPS* DPS can /e#i%nifican$& #im"&er $! im"&emen$ $(an !rdinar PS #ince $(ere i# n! need f!r $(e

dem!du&a$!r $! (a)e a c!" !f $(e reference #i%na& $! de$ermine $(e e,ac$ "(a#e !f $(e

recei)ed #i%na& i$ i# a n!n1c!(eren$ #c(eme* In e,c(an%e' i$ "r!duce# m!re err!ne!u#

dem!du&a$i!n*

T(e -ire&e## LAN  #$andard' IEEE H<;*88/18JJJ'Q8Q; u#e# a )arie$ !f differen$

PS# de"endin% !n $(e da$a1ra$e required* A$ $(e /a#ic1ra$e !f 8 M/i$#' i$ u#e# DPS 

differen$ia& PS* T! "r!)ide $(e e,$ended1ra$e !f ; M/i$#' DPS i# u#ed* In

reac(in% 5*5 M/i$# and $(e fu&&1ra$e !f 88 M/i$#' PS i# em"&!ed' /u$ (a# $! /e

c!u"&ed -i$( c!m"&emen$ar c!de 2ein%* T(e (i%(er1#"eed -ire&e## LAN #$andard'

IEEE H<;*88%1;<<?Q8Q? (a# ei%($ da$a ra$e#: 6' J' 8;' 8H' ;>' ?6' >H and 5> M/i$#* T(e 6

and J M/i$# m!de# u#e O+DM m!du&a$i!n -(ere eac( #u/1carrier i# PS m!du&a$ed*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e 8; and 8H M/i$# m!de# u#e O+DM -i$( PS* T(e fa#$e#$ f!ur m!de# u#e O+DM

-i$( f!rm# !f quadra$ure am"&i$ude m!du&a$i!n*

ecau#e !f i$# #im"&ici$ PS i# a""r!"ria$e f!r &!-1c!#$ "a##i)e $ran#mi$$er#'

and i# u#ed in R+ID  #$andard# #uc( a# ISOIEC 8>>>? -(ic( (a# /een ad!"$ed f!r 

 /i!me$ric "a##"!r$#' credi$ card# #uc( a# American E,"re### E,"re##Pa' and man !$(er 

a""&ica$i!n#*Q>

&ue$!!$( ; -i&& u#e 1DPS a$ i$# &!-er ra$e ; M/i$# and H1DPS a$ i$#

(i%(er ra$e ? M/i$# -(en $(e &in2 /e$-een $(e $-! de)ice# i# #ufficien$& r!/u#$*

&ue$!!$( 8 m!du&a$e# -i$( Gau##ian minimum1#(if$ 2ein%' a /inar #c(eme' #! ei$(er 

m!du&a$i!n c(!ice in )er#i!n ; -i&& ie&d a (i%(er da$a1ra$e* A #imi&ar $ec(n!&!%' IEEE

H<;*85*>  $(e -ire&e## #$andard u#ed / i%ee a&#! re&ie# !n PS* IEEE H<;*85*>

a&&!-# $(e u#e !f $-! frequenc /and#: H6H.J85 M=B u#in% PS and a$ ;*> G=B u#in%

OPS*

 N!$a/& a/#en$ fr!m $(e#e )ari!u# #c(eme# i# H1PS* T(i# i# /ecau#e i$# err!r1ra$e

 "erf!rmance i# c&!#e $! $(a$ !f  861AM  i$ i# !n& a/!u$ <*5 d /e$$er   /u$ i$# da$a ra$e

i# !n& $(ree1quar$er# $(a$ !f 861AM* T(u# H1PS i# !f$en !mi$$ed fr!m #$andard# and'

a# #een a/!)e' #c(eme# $end $! um" fr!m PS $! 861AM H1AM i# "!##i/&e /u$

difficu&$ $! im"&emen$*

(it error rate:

In di%i$a& $ran#mi##i!n' $(e num/er !f /i$ err!r# i# $(e num/er !f recei)ed /i$# !f a

da$a #$ream  !)er a c!mmunica$i!n c(anne&  $(a$ (a)e /een a&$ered due $! n!i#e'

in$erference'  di#$!r$i!n !r  /i$ #nc(r!niBa$i!n err!r#*T(e /i$ err!r ra$e !r /i$ err!r ra$i!

ER i# $(e num/er !f /i$ err!r# di)ided / $(e $!$a& num/er !f $ran#ferred /i$# durin% a

#$udied $ime in$er)a&* ER i# a uni$&e## "erf!rmance mea#ure' !f$en e,"re##ed a# a

 "ercen$a%e*

T(e /i$ err!r "r!/a/i&i$ pe i# $(e e,"ec$a$i!n )a&ue !f $(e ER* T(e ER can /e

c!n#idered a# an a""r!,ima$e e#$ima$e !f $(e /i$ err!r "r!/a/i&i$* T(i# e#$ima$e i#

accura$e f!r a &!n% $ime in$er)a& and a (i%( num/er !f /i$ err!r#*T(e ER ma /e

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

ana&Bed u#in% #$!c(a#$ic c!m"u$er #imu&a$i!n#* If a #im"&e $ran#mi##i!n c(anne& m!de&

and da$a #!urce m!de& i# a##umed' $(e ER ma a&#! /e ca&cu&a$ed ana&$ica&&* An

e,am"&e !f #uc( a da$a #!urce m!de& i# $(e ern!u&&i #!urce*

E,am"&e# !f #uc( #im"&e c(anne& m!de&# are:

• inar #mme$ric c(anne& u#ed in ana&#i# !f dec!din% err!r "r!/a/i&i$ in ca#e

!f n!n1/ur#$ /i$ err!r# !n $(e $ran#mi##i!n c(anne&

• Addi$i)e -(i$e %au##ian n!i#e A4GN c(anne& -i$(!u$ fadin%*

A -!r#$ ca#e #cenari! i# a c!m"&e$e& rand!m c(anne&' -(ere n!i#e $!$a&& d!mina$e#

!)er $(e u#efu& #i%na&* T(i# re#u&$# in a $ran#mi##i!n ER !f 5<V "r!)ided $(a$ a

ern!u&&i  /inar da$a #!urce and a /inar #mme$rica& c(anne& are a##umed' #ee /e&!-*ER c!m"ari#!n /e$-een PS and differen$ia&&1enc!ded PS   -i$( %ra1

c!din% !"era$in% in -(i$e n!i#e*

In a n!i# c(anne&' $(e ER i# !f$en e,"re##ed a# a func$i!n !f $(e n!rma&iBed

carrier1$!1n!i#e ra$i! mea#ure den!$ed  E/N<' ener% "er /i$ $! n!i#e "!-er #"ec$ra&

den#i$ ra$i!' !r E#N< ener% "er m!du&a$i!n #m/!& $! n!i#e #"ec$ra& den#i$*

+!r e,am"&e' in $(e ca#e !f  PS  m!du&a$i!n and A4GN c(anne&' $(e ER a# func$i!n

!f $(e

E/N< i# %i)en /:

Pe!"&e u#ua&& "&!$ $(e ER cur)e# $! de#cri/e $(e func$i!na&i$ !f a di%i$a&

c!mmunica$i!n ##$em* In !"$ica& c!mmunica$i!n' ERd )#* Recei)ed P!-erdm i#

u#ua&& u#ed0 -(i&e in -ire&e## c!mmunica$i!n' ERd )#* SNRd i# u#ed*Mea#urin%

$(e /i$ err!r ra$i! (e&"# "e!"&e c(!!#e $(e a""r!"ria$e f!r-ard err!r c!rrec$i!n  c!de#*Since m!#$ #uc( c!de# c!rrec$ !n& /i$1f&i"#' /u$ n!$ /i$1in#er$i!n# !r /i$1de&e$i!n#' $(e

=ammin% di#$ance me$ric i# $(e a""r!"ria$e -a $! mea#ure $(e num/er !f /i$ err!r#*

Man +EC c!der# a&#! c!n$inu!u#& mea#ure $(e curren$ ER*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

A m!re %enera& -a !f mea#urin% $(e num/er !f /i$ err!r# i# $(e Le)en#($ein

di#$ance* T(e Le)en#($ein di#$ance mea#uremen$ i# m!re a""r!"ria$e f!r mea#urin% ra-

c(anne& "erf!rmance /ef!re frame #nc(r!niBa$i!n' and -(en u#in% err!r c!rrec$i!n

c!de# de#i%ned $! c!rrec$ /i$1in#er$i!n# and /i$1de&e$i!n#' #uc( a# Mar2er C!de# and

4a$ermar2 C!de#

UNIT I3: DATA COMMUNICATION AND NET4OR PROTOCOL Da$a

C!mmunica$i!n c!de#' err!r c!n$r!&* Seria& and "ara&&e& in$erface' $e&e"(!ne ne$-!r2'

da$a m!dem' ISDN' LAN' ISO1OSI #e)en &aer arc(i$ec$ure f!r 4AN*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

#ata ommunication codes:

In inf!rma$i!n $(e!r and c!m"u$er #cience'   a c!de i# u#ua&& c!n#idered a#

an a&%!ri$(m -(ic( unique& re"re#en$# #m/!&# fr!m #!me #!urce a&"(a/e$'

 / enc!ded #$rin%#' -(ic( ma /e in #!me !$(er $ar%e$ a&"(a/e$* An e,$en#i!n !f $(e c!de

f!r re"re#en$in% #equence# !f #m/!&# !)er $(e #!urce a&"(a/e$ i# !/$ained /

c!nca$ena$in% $(e enc!ded #$rin%#*

ef!re %i)in% a ma$(ema$ica&& "reci#e defini$i!n' -e %i)e a /rief e,am"&e* T(e ma""in%

i# a c!de' -(!#e #!urce a&"(a/e$ i# $(e #e$ and -(!#e $ar%e$ a&"(a/e$ i# $(e

#e$ <88' and $(e#e in $urn can /e dec!ded $! $(e #equence !f #!urce #m/!&# <8 

< <88 * U#in% $(e e,$en#i!n !f $(e c!de' $(e enc!ded #$rin% <<88<<8<88 can /e %r!u"ed 

in$! c!de-!rd# a# < aca/c*

U#in% $erm# fr!m f!rma& &an%ua%e $(e!r'   $(e "reci#e ma$(ema$ica& defini$i!n !f $(i#

c!nce"$ i# a# f!&&!-#: Le$ S and T /e $-! fini$e #e$#' ca&&ed $(e #!urce and

$ar%e$ a&"(a/e$#' re#"ec$i)e&* A c!de i# a $!$a& func$i!n ma""in% eac(

#m/!& fr!m S $! a #equence !f #m/!&# !)er T' and $(e e,$en#i!n !f $!

a (!m!m!r"(i#m !f in$! ' -(ic( na$ura&& ma"# eac( #equence !f #!urce #m/!&#

$! a #equence !f $ar%e$ #m/!&#' i# referred $! a# i$# e,$en#i!n*

3aria/&e1&en%$( c!de#

Main ar$ic&e: 3aria/&e1&en%$( c!deIn $(i# #ec$i!n -e c!n#ider c!de#' -(ic( enc!de eac(

#!urce c&ear $e,$ c(arac$er / a c!de -!rd fr!m #!me dic$i!nar' and c!nca$ena$i!n !f 

#uc( c!de -!rd# %i)e u# an enc!ded #$rin%* 3aria/&e1&en%$( c!de# are e#"ecia&& u#efu&

-(en c&ear $e,$ c(arac$er# (a)e differen$ "r!/a/i&i$ie#0 #ee a&#! en$r!" enc!din%*

A "refi, c!de i# a c!de -i$( $(e "refi, "r!"er$: $(ere i# n! )a&id  c!de -!rd in $(e

##$em $(a$ i# a  "refi, #$ar$ !f an !$(er )a&id c!de -!rd in $(e #e$*  =uffman c!din% i#

$(e m!#$ 2n!-n a&%!ri$(m f!r deri)in% "refi, c!de#* Prefi, c!de# are -ide& referred $!

C*T=IAGARA@AN1AP ECE DEPT* 58

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

a# =uffman c!de#' e)en -(en $(e c!de -a# n!$ "r!duced / a =uffman a&%!ri$(m*

O$(er e,am"&e# !f "refi, c!de# are c!un$r ca&&in% c!de#' $(e c!un$r and "u/&i#(er "ar$#

!f ISN#' and $(e Sec!ndar Snc(r!niBa$i!n C!de# u#ed in $(e UMTS 41CDMA ?G

4ire&e## S$andard*raf$# inequa&i$ c(arac$eriBe# $(e #e$# !f c!de -!rd &en%$(# $(a$ are

 "!##i/&e in a "refi, c!de* 3ir$ua&& an unique& dec!da/&e !ne1$!1man c!de' n!$

nece##ar a "refi, !ne' mu#$ #a$i#f raf$# inequa&i$*

C!de# ma a&#! /e u#ed $! re"re#en$ da$a in a -a m!re re#i#$an$ $! err!r# in $ran#mi##i!n

!r #$!ra%e* Suc( a c!de i# ca&&ed an err!r1c!rrec$in% c!de' and -!r2# / inc&udin%

carefu&& craf$ed redundanc -i$( $(e #$!red !r $ran#mi$$ed da$a* E,am"&e#

inc&ude =ammin% c!de#' Reed.S!&!m!n' Reed.Mu&&er ' 4a&#(.=adamard' !#e. 

C(aud(uri.=!c(quen%(em' Tur/!' G!&a' G!""a' &!-1den#i$ "ari$1c(ec2 c!de#'

and #"ace.$ime c!de#* Err!r de$ec$in% c!de# can /e !"$imi#ed $! de$ec$ /ur#$ err!r#'

!r rand!m err!r#*

0rror control:

In inf!rma$i!n $(e!r and c!din% $(e!r -i$( a""&ica$i!n# in c!m"u$er 

#cience and $e&ec!mmunica$i!n' err!r de$ec$i!n and c!rrec$i!n !r err!r c!n$r!& are

$ec(nique# $(a$ ena/&e re&ia/&e de&i)er !f di%i$a& da$a !)er unre&ia/&e c!mmunica$i!n

c(anne&#* Man c!mmunica$i!n c(anne&# are #u/ec$ $! c(anne& n!i#e' and $(u# err!r#

ma /e in$r!duced durin% $ran#mi##i!n fr!m $(e #!urce $! a recei)er* Err!r de$ec$i!n

$ec(nique# a&&!- de$ec$in% #uc( err!r#' -(i&e err!r c!rrec$i!n ena/&e# rec!n#$ruc$i!n !f 

$(e !ri%ina& da$aErr!r de$ec$i!n i# m!#$ c!mm!n& rea&iBed u#in% a #ui$a/&e (a#(

func$i!n !r c(ec2#um a&%!ri$(m* A (a#( func$i!n add# a fi,ed1&en%$( $a% $! a me##a%e'

-(ic( ena/&e# recei)er# $! )erif $(e de&i)ered me##a%e / rec!m"u$in% $(e $a% and

c!m"arin% i$ -i$( $(e !ne "r!)ided*

T(ere e,i#$# a )a#$ )arie$ !f differen$ (a#( func$i!n de#i%n#* =!-e)er' #!me are

!f "ar$icu&ar& -ide#"read u#e /ecau#e !f ei$(er $(eir #im"&ici$ !r $(eir #ui$a/i&i$ f!r 

de$ec$in% cer$ain 2ind# !f err!r# e*%*' $(e cc&ic redundanc c(ec2 # "erf!rmance in

de$ec$in% /ur#$ err!r#*

C*T=IAGARA@AN1AP ECE DEPT* 5;

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Rand!m1err!r1c!rrec$in% c!de# /a#ed !n minimum di#$ance c!din% can "r!)ide a

#ui$a/&e a&$erna$i)e $! (a#( func$i!n# -(en a #$ric$ %uaran$ee !n $(e minimum num/er !f 

err!r# $! /e de$ec$ed i# de#ired* Re"e$i$i!n c!de#' de#cri/ed /e&!-' are #"ecia& ca#e# !f 

err!r1c!rrec$in% c!de#: a&$(!u%( ra$(er inefficien$' $(e find a""&ica$i!n# f!r /!$( err!r 

c!rrec$i!n and de$ec$i!n due $! $(eir #im"&ici$*

Re"e$i$i!n c!de#

Main ar$ic&e: Re"e$i$i!n c!de

A re"e$i$i!n c!de i# a c!din% #c(eme $(a$ re"ea$# $(e /i$# acr!## a c(anne& $!

ac(ie)e err!r1free c!mmunica$i!n* Gi)en a #$ream !f da$a $! /e $ran#mi$$ed' $(e da$a i#

di)ided in$! /&!c2# !f /i$#* Eac( /&!c2 i# $ran#mi$$ed #!me "rede$ermined num/er !f 

$ime#* +!r e,am"&e' $! #end $(e /i$ "a$$ern 8<88' $(e f!ur1/i$ /&!c2 can /e re"ea$ed$(ree $ime#' $(u# "r!ducin% 8<88 8<88 8<88* =!-e)er' if $(i# $-e&)e1/i$ "a$$ern -a#

recei)ed a# 8<8< 8<88 8<88 . -(ere $(e fir#$ /&!c2 i# un&i2e $(e !$(er $-! . i$ can /e

de$ermined $(a$ an err!r (a# !ccurred*

Re"e$i$i!n c!de# are )er inefficien$' and can /e #u#ce"$i/&e $! "r!/&em# if $(e err!r 

!ccur# in e,ac$& $(e #ame "&ace f!r eac( %r!u" e*%*' 8<8< 8<8< 8<8< in $(e "re)i!u#

e,am"&e -!u&d /e de$ec$ed a# c!rrec$* T(e ad)an$a%e !f re"e$i$i!n c!de# i# $(a$ $(e are

e,$reme& #im"&e' and are in fac$ u#ed in #!me $ran#mi##i!n# !f num/er# #$a$i!n#* 

Pari$ /i$#

Main ar$ic&e: Pari$ /i$

A "ari$ /i$ i# a /i$ $(a$ i# added $! a %r!u" !f #!urce /i$# $! en#ure $(a$ $(e

num/er !f #e$ /i$# i*e*' /i$# -i$( )a&ue 8 in $(e !u$c!me i# e)en !r !dd* I$ i# a )er

#im"&e #c(eme $(a$ can /e u#ed $! de$ec$ #in%&e !r an !$(er !dd num/er i*e*' $(ree' fi)e'

e$c* !f err!r# in $(e !u$"u$* An e)en num/er !f f&i""ed /i$# -i&& ma2e $(e "ari$ /i$

a""ear c!rrec$ e)en $(!u%( $(e da$a i# err!ne!u#*

E,$en#i!n# and )aria$i!n# !n $(e "ari$ /i$ mec(ani#m are (!riB!n$a& redundanc

c(ec2#' )er$ica& redundanc c(ec2#' and d!u/&e' dua&' !r dia%!na& "ari$ u#ed

in RAID1DP*

C*T=IAGARA@AN1AP ECE DEPT* 5?

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

C(ec2#um#

Main ar$ic&e: C(ec2#um

A c(ec2#um !f a me##a%e i# a m!du&ar ari$(me$ic #um !f me##a%e c!de -!rd# !f 

a fi,ed -!rd &en%$( e*%*' /$e )a&ue#* T(e #um ma /e ne%a$ed / mean# !f a !ne#1c!m"&emen$ !"era$i!n "ri!r $! $ran#mi##i!n $! de$ec$ err!r# re#u&$in% in a&&1Ber!

me##a%e#*

C(ec2#um #c(eme# inc&ude "ari$ /i$#' c(ec2 di%i$#' and &!n%i$udina& redundanc

c(ec2#* S!me c(ec2#um #c(eme#' #uc( a# $(e Damm a&%!ri$(m' $(e Lu(n a&%!ri$(m' and

$(e3er(!eff a&%!ri$(m' are #"ecifica&& de#i%ned $! de$ec$ err!r# c!mm!n& in$r!duced /

(uman# in -ri$in% d!-n !r remem/erin% iden$ifica$i!n num/er#*

Cc&ic redundanc c(ec2# CRC#Qedi$

Main ar$ic&e: Cc&ic redundanc c(ec2 

A cc&ic redundanc c(ec2 CRC i# a #in%&e1/ur#$1err!r1de$ec$in% cc&ic

c!de and n!n1#ecure (a#( func$i!n de#i%ned $! de$ec$ acciden$a& c(an%e# $! di%i$a& da$a in

c!m"u$er ne$-!r2#* I$ i# n!$ #ui$a/&e f!r de$ec$in% ma&ici!u#& in$r!duced err!r#* I$ i#

c(arac$eriBed / #"ecifica$i!n !f a #!1ca&&ed %enera$!r "!&n!mia&' -(ic( i# u#ed a#

$(e di)i#!r  in a "!&n!mia& &!n% di)i#i!n !)er a fini$e fie&d' $a2in% $(e in"u$ da$a a#

$(e di)idend' and -(ere $(e remainder  /ec!me# $(e re#u&$*

Cc&ic 8c!de# (a)e fa)!ra/&e "r!"er$ie# in $(a$ $(e are -e&& #ui$ed f!r 

de$ec$in% /ur#$ err!r#* CRC# are "ar$icu&ar& ea# $! im"&emen$ in (ard-are' and are

$(eref!re c!mm!n& u#ed in di%i$a& ne$-!r2# and #$!ra%e de)ice# #uc( a# (ard di#2 

dri)e#*

E)en "ari$ i# a #"ecia& ca#e !f a cc&ic redundanc c(ec2' -(ere $(e #in%&e1/i$ CRC i#

%enera$ed / $(e di)i#!r , F 8*

Cr"$!%ra"(ic (a#( func$i!n#

Main ar$ic&e: Cr"$!%ra"(ic (a#( func$i!n

C*T=IAGARA@AN1AP ECE DEPT* 5>

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e !u$"u$ !f a cr"$!%ra"(ic (a#( func$i!n' a&#! 2n!-n a# a me##a%e di%e#$' can

 "r!)ide #$r!n% a##urance# a/!u$ da$a in$e%ri$' -(e$(er c(an%e# !f $(e da$a are acciden$a&

e*%*' due $! $ran#mi##i!n err!r# !r ma&ici!u#& in$r!duced* An m!difica$i!n $! $(e da$a

-i&& &i2e& /e de$ec$ed $(r!u%( a mi#ma$c(in% (a#( )a&ue* +ur$(erm!re' %i)en #!me (a#(

)a&ue' i$ i# infea#i/&e $! find #!me in"u$ da$a !$(er $(an $(e !ne %i)en $(a$ -i&& ie&d $(e

#ame (a#( )a&ue* If an a$$ac2er can c(an%e n!$ !n& $(e me##a%e /u$ a&#! $(e (a#( )a&ue'

$(en a 2eed (a#( !r me##a%e au$(en$ica$i!n c!de MAC can /e u#ed f!r addi$i!na&

#ecuri$* 4i$(!u$ 2n!-in% $(e 2e' i$ i# infea#i/&e f!r $(e a$$ac2er $! ca&cu&a$e $(e c!rrec$

2eed (a#( )a&ue f!r a m!dified me##a%e*

Err!r1c!rrec$in% c!de#

Main ar$ic&e: +!r-ard err!r c!rrec$i!n

An err!r1c!rrec$in% c!de can /e u#ed f!r err!r de$ec$i!n* A c!de

-i$( minimum =ammin% di#$ance' d' can de$ec$ u" $! d 8 err!r# in a c!de -!rd* U#in%

minimum1di#$ance1/a#ed err!r1c!rrec$in% c!de# f!r err!r de$ec$i!n can /e #ui$a/&e if a

#$ric$ &imi$ !n $(e minimum num/er !f err!r# $! /e de$ec$ed i# de#ired*

C!de# -i$( minimum =ammin% di#$ance d ; are de%enera$e ca#e# !f err!r1

c!rrec$in% c!de#' and can /e u#ed $! de$ec$ #in%&e err!r#* T(e "ari$ /i$ i# an e,am"&e !f a

#in%&e1err!r1de$ec$in% c!de*

$erial and parallel interface:

In $e&ec!mmunica$i!n and c!m"u$er #cience' #eria& c!mmunica$i!n i# $(e "r!ce##

!f #endin% da$a !ne /i$ a$ a $ime' #equen$ia&&' !)er a c!mmunica$i!n c(anne& !r c!m"u$er 

 /u#* T(i# i# in c!n$ra#$ $! "ara&&e& c!mmunica$i!n' -(ere #e)era& /i$# are #en$ a# a -(!&e'

!n a &in2 -i$( #e)era& "ara&&e& c(anne&#*

Seria& c!mmunica$i!n i# u#ed f!r a&& &!n%1(au& c!mmunica$i!n and m!#$ c!m"u$er 

ne$-!r2#' -(ere $(e c!#$ !f ca/&e and #nc(r!niBa$i!n difficu&$ie# ma2e "ara&&e&

c!mmunica$i!n im"rac$ica&* Seria& c!m"u$er /u#e# are /ec!min% m!re c!mm!n e)en a$

#(!r$er di#$ance#' a# im"r!)ed #i%na& in$e%ri$ and $ran#mi##i!n #"eed# in ne-er #eria&

$ec(n!&!%ie# (a)e /e%un $! !u$-ei%( $(e "ara&&e& /u## ad)an$a%e !f #im"&ici$ n! need

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

f!r #eria&iBer and de#eria&iBer' !r  SerDe# and $! !u$#$ri" i$# di#ad)an$a%e# c&!c2 #2e-'

in$erc!nnec$ den#i$* T(e mi%ra$i!n fr!m PCI $! PCI E,"re## i# an e,am"&e*

T(e c!mmunica$i!n &in2# acr!## -(ic( c!m"u$er#!r "ar$# !f c!m"u$er#$a&2 $! !ne

an!$(er ma /e ei$(er #eria& !r "ara&&e&* A "ara&&e& &in2 $ran#mi$# #e)era& #$ream# !f da$a#imu&$ane!u#& a&!n% mu&$i"&e c(anne&# e*%*' -ire#' "rin$ed circui$ $rac2#' !r !"$ica&

fi/re#0 a #eria& &in2 $ran#mi$# a #in%&e #$ream !f da$a*

A&$(!u%( a #eria& &in2 ma #eem inferi!r $! a "ara&&e& !ne' #ince i$ can $ran#mi$ &e##

da$a "er c&!c2 cc&e' i$ i# !f$en $(e ca#e $(a$ #eria& &in2# can /e c&!c2ed c!n#idera/&

fa#$er $(an "ara&&e& &in2# in !rder $! ac(ie)e a (i%(er da$a ra$e* A num/er !f fac$!r# a&&!-

#eria& $! /e c&!c2ed a$ a (i%(er ra$e:

• C&!c2 #2e- /e$-een differen$ c(anne&# i# n!$ an i##ue f!r  

unc&!c2ed a#nc(r!n!u# #eria& c!mmunica$i!n &in2#*

• A #eria& c!nnec$i!n require# fe-er in$erc!nnec$in% ca/&e# e*%*' -ire#fi/re# and

(ence !ccu"ie# &e## #"ace* T(e e,$ra #"ace a&&!-# f!r /e$$er i#!&a$i!n !f $(e c(anne&

fr!m i$# #urr!undin%#*

• Cr!##$a&2  i# &e## !f an i##ue' /ecau#e $(ere are fe-er c!nduc$!r# in "r!,imi$*

In man ca#e#' #eria& i# a /e$$er !"$i!n /ecau#e i$ i# c(ea"er $! im"&emen$* Man IC# (a)e

#eria& in$erface#' a# !""!#ed $! "ara&&e& !ne#' #! $(a$ $(e (a)e fe-er "in# and are

$(eref!re &e## e,"en#i)e*

Telephone networ:

A $e&e"(!ne ne$-!r2 i# a $e&ec!mmunica$i!n# ne$-!r2  u#ed f!r $e&e"(!ne ca&&# /e$-een

$-! !r m!re "ar$ie#*

T(ere are a num/er !f differen$ $"e# !f $e&e"(!ne ne$-!r2:

• A fi,ed &ine ne$-!r2 -(ere $(e $e&e"(!ne# mu#$ /e direc$& -ired in$! a

#in%&e $e&e"(!ne e,c(an%e* T(i# i# 2n!-n a# $(e "u/&ic #-i$c(ed $e&e"(!ne

ne$-!r2  !r PSTN*

C*T=IAGARA@AN1AP ECE DEPT* 56

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

• A -ire&e## ne$-!r2 -(ere $(e $e&e"(!ne# are m!/i&e and can m!)e ar!und

an-(ere -i$(in $(e c!)era%e area*

• A "ri)a$e ne$-!r2 -(ere a c&!#ed %r!u" !f $e&e"(!ne# are c!nnec$ed "rimari& $!

eac( !$(er and u#e a %a$e-a $! reac( $(e !u$#ide -!r&d* T(i# i# u#ua&& u#ed

in#idec!m"anie# and ca&& cen$re# and i# ca&&ed a "ri)a$e /ranc( e,c(an%e P7*

Pu/&ic $e&e"(!ne !"era$!r# PTO# !-n and /ui&d ne$-!r2# !f $(e fir#$ $-! $"e# and

 "r!)ide #er)ice# $! $(e "u/&ic under &icen#e fr!m $(e na$i!na& %!)ernmen$* 3ir$ua&

 Ne$-!r2 O"era$!r# 3NO# &ea#e ca"aci$ -(!&e#a&e fr!m $(e PTO# and #e&&

!n $e&e"(!n #er)ice $! $(e "u/&ic direc$&*

#ata modem:

A m!dem m!du&a$!r1dem!du&a$!r i# a de)ice $(a$ m!du&a$e# an ana&!% carrier 

#i%na& $! enc!de di%i$a& inf!rma$i!n and dem!du&a$e# $(e #i%na& $! dec!de $(e $ran#mi$$ed

inf!rma$i!n* T(e %!a& i# $! "r!duce a #i%na& $(a$ can /e $ran#mi$$ed ea#i& and dec!ded $!

re"r!duce $(e !ri%ina& di%i$a& da$a* M!dem# can /e u#ed -i$( an mean# !f $ran#mi$$in%

ana&!% #i%na&#' fr!m &i%($ emi$$in% di!de# $! radi!*  T(e m!#$ fami&iar $"e i# a )!ice

 /and m!dem $(a$ $urn# $(e di%i$a& da$a !f a c!m"u$er  in$! m!du&a$ed e&ec$rica& #i%na&# in

$(e )!ice frequenc ran%e !f a $e&e"(!ne c(anne&* T(e#e #i%na&# can /e $ran#mi$$ed

!)er  $e&e"(!ne &ine# and dem!du&a$ed / an!$(er m!dem a$ $(e recei)er #ide $! rec!)er 

$(e di%i$a& da$a*

M!dem# are %enera&& c&a##ified / $(e am!un$ !f da$a $(e can #end in a

%i)en uni$ !f $ime' u#ua&& e,"re##ed in /i$# "er #ec!nd /i$# !r /"#' !r  /$e# "er 

#ec!nd #* M!dem# can a&#! /e c&a##ified / $(eir #m/!& ra$e' mea#ured in /aud* T(e

 /aud uni$ den!$e# #m/!&# "er #ec!nd' !r $(e num/er !f $ime# "er #ec!nd $(e m!dem

#end# a ne- #i%na&* +!r e,am"&e' $(e ITU 3*;8 #$andard u#ed  audi! frequenc #(if$

2ein% -i$( $-! "!##i/&e frequencie#' c!rre#"!ndin% $! $-! di#$inc$ #m/!&# !r !ne /i$

 "er #m/!&' $! carr ?<< /i$# "er #ec!nd u#in% ?<< /aud* c!n$ra#$' $(e !ri%ina& ITU

3*;; #$andard' -(ic( c!u&d $ran#mi$ and recei)e f!ur di#$inc$ #m/!&# $-! /i$# "er 

#m/!&' $ran#mi$$ed 8';<< /i$# / #endin% 6<< #m/!&# "er #ec!nd 6<< /aud

u#in% "(a#e #(if$ 2ein%

C*T=IAGARA@AN1AP ECE DEPT* 5

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

'$#:

In$e%ra$ed Ser)ice# f!r Di%i$a& Ne$-!r2 ISDN i# a #e$ !f c!mmunica$i!n

#$andard# f!r #imu&$ane!u# di%i$a& $ran#mi##i!n !f )!ice' )ide!' da$a' and !$(er ne$-!r2 

#er)ice# !)er $(e $radi$i!na& circui$# !f $(e "u/&ic #-i$c(ed $e&e"(!ne ne$-!r2 * I$ -a# fir#$defined in 8JHH in $(e CCITT red /!!2*Q8 Pri!r $! ISDN' $(e $e&e"(!ne ##$em -a#

)ie-ed a# a -a $! $ran#"!r$ )!ice' -i$( #!me #"ecia& #er)ice# a)ai&a/&e f!r da$a* T(e 2e

fea$ure !f ISDN i# $(a$ i$ in$e%ra$e# #"eec( and da$a !n $(e #ame &ine#' addin% fea$ure#

$(a$ -ere n!$ a)ai&a/&e in $(e c&a##ic $e&e"(!ne ##$em* T(ere are #e)era& 2ind# !f acce##

in$erface# $! ISDN defined a# a#ic Ra$e In$erface RI' Primar Ra$e

In$erface PRI' Narr!-/and ISDN N1ISDN' and r!ad/and ISDN 1ISDN*

ISDN i# a circui$1#-i$c(ed $e&e"(!ne ne$-!r2  ##$em' -(ic( a&#! "r!)ide# acce##

$! "ac2e$ #-i$c(ed ne$-!r2#' de#i%ned $! a&&!- di%i$a& $ran#mi##i!n !f )!ice

and da$a !)er !rdinar $e&e"(!ne c!""er -ire#' re#u&$in% in "!$en$ia&& /e$$er )!ice

qua&i$ $(an an ana&!% "(!ne can "r!)ide* I$ !ffer# circui$1#-i$c(ed c!nnec$i!n# f!r 

ei$(er )!ice !r da$a' and "ac2e$1#-i$c(ed c!nnec$i!n# f!r da$a' in incremen$# !f 

6> 2i&!/i$#* A ma!r mar2e$ a""&ica$i!n f!r ISDN in #!me c!un$rie# i#  In$erne$ acce##'

-(ere ISDN $"ica&& "r!)ide# a ma,imum !f 8;H 2/i$# in /!$( u"#$ream and

d!-n#$ream direc$i!n#* C(anne& /!ndin% can ac(ie)e a %rea$er da$a ra$e0 $"ica&& $(e

ISDN 1c(anne&# !f $(ree !r f!ur RI# #i, $! ei%($ 6> 2/i$# c(anne&# are /!nded*

ISDN #(!u&d n!$ /e mi#$a2en f!r i$# u#e -i$( a #"ecific "r!$!c!&' #uc( a# *J?8 -(erea#

ISDN i# em"&!ed a# $(e ne$-!r2' da$a1&in2 and "(#ica& &aer# in $(e c!n$e,$ !f $(e OSI

m!de&* In a /r!ad #en#e ISDN can /e c!n#idered a #ui$e !f di%i$a& #er)ice# e,i#$in% !n

&aer# 8' ;' and ? !f $(e OSI m!de&* ISDN i# de#i%ned $! "r!)ide acce## $! )!ice and da$a

#er)ice# #imu&$ane!u#&*

=!-e)er' c!mm!n u#e reduced ISDN $! /e &imi$ed $! *J?8 and re&a$ed

 "r!$!c!&#' -(ic( are a #e$ !f  "r!$!c!&# f!r e#$a/&i#(in% and /rea2in% circui$ #-i$c(ed

c!nnec$i!n#'  and f!r ad)anced ca&&in% fea$ure# f!r $(e u#er* T(e -ere in$r!duced in

8JH6*Q;In a )ide!c!nference' ISDN "r!)ide# #imu&$ane!u# )!ice' )ide!' and $e,$

$ran#mi##i!n /e$-een indi)idua& de#2$!" )ide!c!nferencin% ##$em# and %r!u" r!!m

C*T=IAGARA@AN1AP ECE DEPT* 5H

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

)ide!c!nferencin% ##$em#*T(e !$(er ISDN acce## a)ai&a/&e i# $(e Primar Ra$e In$erface

PRI' -(ic( i# carried !)er an E8 ;<>H 2/i$# in m!#$ "ar$# !f $(e -!r&d* An E8 i# ?<

c(anne&# !f 6> 2/i$#' !ne D c(anne& !f 6> 2/i$# and a $imin% and a&arm c(anne& !f 

6> 2/i$#*

In N!r$( America PRI #er)ice i# de&i)ered !n !ne !r m!re T8 carrier# !f$en

referred $! a# ;?FD !f 85>> 2/i$# ;> c(anne&#* A PRI (a# ;? c(anne&# and 8 D

c(anne& f!r #i%na&&in% @a"an u#e# a circui$ ca&&ed a @8' -(ic( i# #imi&ar $! a T8* In$er1

c(an%ea/& /u$ inc!rrec$&' a PRI i# referred $! a# T8 /ecau#e i$ u#e# $(e T8 carrier 

f!rma$* A $rue T8 c!mm!n& ca&&ed Ana&!% T8 $! a)!id c!nfu#i!n u#e# ;> c(anne&# !f 

6> 2/i$# !f in1/and #i%na&in%* Eac( c(anne& u#e# 56 2/ f!r da$a and )!ice and H 2/ f!r 

#i%na&in% and me##a%in%* PRI u#e# !u$ !f /and #i%na&in% -(ic( "r!)ide# $(e ;?

c(anne&# -i$( c&ear 6> 2/ f!r )!ice and da$a and !ne 6> 2/ D c(anne& f!r #i%na&in% and

me##a%in%* In N!r$( America' N!n1+aci&i$ A##!cia$ed Si%na&&in% a&&!-# $-! !r m!re

PRI# $! /e c!n$r!&&ed / a #in%&e D c(anne&' and i# #!me$ime# ca&&ed ;?FD F n;>*

D1c(anne& /ac2u" a&&!-# f!r a #ec!nd D c(anne& in ca#e $(e "rimar fai&#* N+AS i#

c!mm!n& u#ed !n a T?*

PRI1ISDN i# "!"u&ar $(r!u%(!u$ $(e -!r&d' e#"ecia&& f!r  

c!nnec$in% P7# $! PSTN*4(i&e $(e N!r$( American PSTN can u#e PRI !r Ana&!% T8

f!rma$ fr!m P7 $! P7' $(e POTS !r RI can /e de&i)ered $! a /u#ine## !r re#idence*

 N!r$( American PSTN can c!nnec$ fr!m P7 $! P7 )ia Ana&!% T8' T?' PRI' OC?'

e$c***E)en $(!u%( man ne$-!r2 "r!fe##i!na&# u#e $(e $erm ISDN $! refer $! $(e &!-er1

 /and-id$( RI circui$' in N!r$( America RI i# re&a$i)e& unc!mm!n -(i&#$ PRI circui$#

#er)in% P7# are c!mm!n"&ace*

'$656$' se&en layer architecture for 7A:

C*T=IAGARA@AN1AP ECE DEPT* 5J

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

 

T(e O"en S#$em# In$erc!nnec$i!n m!de& OSI i# a c!nce"$ua& m!de& $(a$

c(arac$eriBe# and #$andardiBe# $(e in$erna& func$i!n# !f a c!mmunica$i!n ##$em  /

 "ar$i$i!nin% i$ in$! a/#$rac$i!n &aer#* T(e m!de& i# a "r!duc$ !f $(e O"en S#$em#

In$erc!nnec$i!n  "r!ec$ a$ $(e In$erna$i!na& Or%aniBa$i!n f!r S$andardiBa$i!n  ISO'

main$ained / $(e iden$ifica$i!n ISOIEC >JH18*

T(e m!de& %r!u"# c!mmunica$i!n func$i!n# in$! #e)en &!%ica& &aer#* A &aer #er)e# $(e

&aer a/!)e i$ and i# #er)ed / $(e &aer /e&!- i$* +!r e,am"&e' a &aer $(a$ "r!)ide#

err!r1free c!mmunica$i!n# acr!## a ne$-!r2 "r!)ide# $(e "a$( needed / a""&ica$i!n#

a/!)e i$' -(i&e i$ ca&&# $(e ne,$ &!-er &aer $! #end and recei)e "ac2e$# $(a$ ma2e u" $(e

c!n$en$# !f $(a$ "a$(* T-! in#$ance# a$ !ne &aer are c!nnec$ed / a (!riB!n$a& c!nnec$i!n

!n $(a$ &aer*

Laer 8: "(#ica& &aer 

T(e "(#ica& &aer  (a# $(e f!&&!-in% ma!r func$i!n#:

C*T=IAGARA@AN1AP ECE DEPT* 6<

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

• i$ define# $(e e&ec$rica&  and "(#ica& #"ecifica$i!n# !f $(e da$a c!nnec$i!n* I$

define# $(e re&a$i!n#(i" /e$-een a de)ice and a "(#ica& $ran#mi##i!n medium

e*%*' a c!""er !r fi/er !"$ica& ca/&e* T(i# inc&ude# $(e &a!u$ !f "in#' )!&$a%e#'

&ine im"edance'  ca/&e  #"ecifica$i!n#' #i%na& $imin%' (u/#'  re"ea$er#'  ne$-!r2 

ada"$er#' (!#$ /u# ada"$er# =A u#ed in #$!ra%e area ne$-!r2# and m!re*

• i$ define# $(e "r!$!c!& $! e#$a/&i#( and $ermina$e a c!nnec$i!n  /e$-een $-!

direc$& c!nnec$ed n!de# !)er a c!mmunica$i!n# medium*

• i$ ma define $(e "r!$!c!& f!r f&!- c!n$r!&*

• i$ define# a "r!$!c!& f!r $(e "r!)i#i!n !f a n!$ nece##ari& re&ia/&e c!nnec$i!n

 /e$-een $-! direc$& c!nnec$ed n!de#' and $(e m!du&a$i!n !r c!n)er#i!n /e$-een

$(e re"re#en$a$i!n !f di%i$a& da$a in u#er equi"men$ and $(e c!rre#"!ndin% #i%na&#

$ran#mi$$ed !)er $(e "(#ica& c!mmunica$i!n# c(anne&* T(i# c(anne& can in)!&)e

 "(#ica& ca/&in% #uc( a# c!""er and !"$ica& fi/er  !r a -ire&e## radi! &in2 *

T(e "(#ica& &aer !f Para&&e& SCSI !"era$e# in $(i# &aer' a# d! $(e "(#ica& &aer# !f 

E$(erne$ and !$(er &!ca&1area ne$-!r2#' #uc( a# T!2en Rin%' +DDI' ITU1T G*(n' and

IEEE H<;*88' a# -e&& a# "er#!na& area ne$-!r2# #uc( a# &ue$!!$( and IEEE H<;*85*>*

Laer ;: da$a &in2 &aer 

T(e  da$a &in2 &aer   "r!)ide# a re&ia/&e &in2 /e$-een $-! direc$& c!nnec$ed n!de#' /

de$ec$in% and "!##i/& c!rrec$in% err!r# $(a$ ma !ccur in $(e "(#ica& &aer* T(e da$a

&in2 &aer i# di)ided in$! $-! #u/&aer#:

• Media Acce## C!n$r!& MAC &aer 1 re#"!n#i/&e f!r c!n$r!&&in% (!- c!m"u$er#

in $(e ne$-!r2 %ain acce## $! da$a and "ermi##i!n $! $ran#mi$ i$*

• L!%ica& Lin2 C!n$r!&  LLC &aer 1 c!n$r!& err!r c(ec2in% and "ac2e$

#nc(r!niBa$i!n*

T(e P!in$1$!1P!in$ Pr!$!c!&  PPP i# an e,am"&e !f a da$a &in2 &aer in $(e TCPIP

 "r!$!c!& #$ac2*

C*T=IAGARA@AN1AP ECE DEPT* 68

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e ITU1T G*(n #$andard' -(ic( "r!)ide# (i%(1#"eed &!ca& area ne$-!r2in% !)er e,i#$in%

-ire# "!-er &ine#' "(!ne &ine# and c!a,ia& ca/&e#' inc&ude# a c!m"&e$e da$a &in2 &aer 

-(ic( "r!)ide# /!$( err!r c!rrec$i!n and f&!- c!n$r!& / mean# !f a #e&ec$i)e1re"ea$

#&idin%1-ind!- "r!$!c!&*

Laer ?: ne$-!r2 &aer 

T(e ne$-!r2 &aer  "r!)ide# $(e func$i!na& and "r!cedura& mean# !f $ran#ferrin%

)aria/&e &en%$( da$a #equence# ca&&ed da$a%ram# fr!m !ne n!de $! an!$(er c!nnec$ed $!

$(e #ame ne$-!r2* A ne$-!r2 i# a medium $! -(ic( man n!de# can /e c!nnec$ed' !n

-(ic( e)er n!de (a# an addre## and -(ic( "ermi$# n!de# c!nnec$ed $! i$ $! $ran#fer 

me##a%e# $! !$(er n!de# c!nnec$ed $! i$ / mere& "r!)idin% $(e c!n$en$ !f a me##a%e

and $(e addre## !f $(e de#$ina$i!n n!de and &e$$in% $(e ne$-!r2 find $(e -a $! de&i)er r!u$e $(e me##a%e $! $(e de#$ina$i!n n!de* In addi$i!n $! me##a%e r!u$in%' $(e ne$-!r2 

ma !r ma n!$ im"&emen$ me##a%e de&i)er / #"&i$$in% $(e me##a%e in$! #e)era&

fra%men$#' de&i)erin% eac( fra%men$ / a #e"ara$e r!u$e and rea##em/&in% $(e fra%men$#'

re"!r$ de&i)er err!r#' e$c*

Da$a%ram de&i)er a$ $(e ne$-!r2 &aer i# n!$ %uaran$eed $! /e re&ia/&e*

A num/er !f &aer1mana%emen$ "r!$!c!&#' a func$i!n defined in $(e mana%emen$ anne,'

ISO >JH>' /e&!n% $! $(e ne$-!r2 &aer* T(e#e inc&ude r!u$in% "r!$!c!&#' mu&$ica#$

%r!u" mana%emen$' ne$-!r21&aer inf!rma$i!n and err!r' and ne$-!r21&aer addre##

a##i%nmen$* I$ i# $(e func$i!n !f $(e "a&!ad $(a$ ma2e# $(e#e /e&!n% $! $(e ne$-!r2 &aer'

n!$ $(e "r!$!c!& $(a$ carrie# $(em*

Laer >: $ran#"!r$ &aer 

C*T=IAGARA@AN1AP ECE DEPT* 6;

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e $ran#"!r$ &aer  "r!)ide# $(e func$i!na& and "r!cedura& mean# !f $ran#ferrin%

)aria/&e1&en%$( da$a #equence# fr!m a #!urce $! a de#$ina$i!n (!#$ )ia !ne !r m!re

ne$-!r2#' -(i&e main$ainin% $(e qua&i$ !f #er)ice func$i!n#*

An e,am"&e !f a $ran#"!r$1&aer "r!$!c!& in $(e #$andard In$erne$ "r!$!c!& #$ac2 i#

TCP' u#ua&& /ui&$ !n $!" !f $(e IP "r!$!c!&*

T(e $ran#"!r$ &aer c!n$r!&# $(e re&ia/i&i$ !f a %i)en &in2 $(r!u%( f&!- c!n$r!&'

#e%men$a$i!nde#e%men$a$i!n' and err!r c!n$r!&* S!me "r!$!c!&# are #$a$e1 and

c!nnec$i!n1!rien$ed* T(i# mean# $(a$ $(e $ran#"!r$ &aer can 2ee" $rac2 !f $(e #e%men$#

and re$ran#mi$ $(!#e $(a$ fai&* T(e $ran#"!r$ &aer a&#! "r!)ide# $(e ac2n!-&ed%emen$ !f 

$(e #ucce##fu& da$a $ran#mi##i!n and #end# $(e ne,$ da$a if n! err!r# !ccurred* T(e

$ran#"!r$ &aer crea$e# "ac2e$# !u$ !f $(e me##a%e recei)ed fr!m $(e a""&ica$i!n &aer*Pac2e$iBin% i# a "r!ce## !f di)idin% $(e &!n% me##a%e in$! #ma&&er me##a%e#*

OSI define# fi)e c&a##e# !f c!nnec$i!n1m!de $ran#"!r$ "r!$!c!&# ran%in% fr!m

c&a## < -(ic( i# a&#! 2n!-n a# TP< and "r!)ide# $(e fe-e#$ fea$ure# $! c&a## > TP>'

de#i%ned f!r &e## re&ia/&e ne$-!r2#' #imi&ar $! $(e In$erne$* C&a## < c!n$ain# n! err!r 

rec!)er' and -a# de#i%ned f!r u#e !n ne$-!r2 &aer# $(a$ "r!)ide err!r1free c!nnec$i!n#*

C&a## > i# c&!#e#$ $! TCP' a&$(!u%( TCP c!n$ain# func$i!n#' #uc( a# $(e %racefu& c&!#e'

-(ic( OSI a##i%n# $! $(e #e##i!n &aer* A&#!' a&& OSI TP c!nnec$i!n1m!de  "r!$!c!&c&a##e# "r!)ide e,"edi$ed da$a and "re#er)a$i!n !f rec!rd /!undarie#* De$ai&ed

c(arac$eri#$ic# !f TP<1> c&a##e# are #(!-n in $(e f!&&!-in% $a/&e:Q>

An ea# -a $! )i#ua&iBe $(e $ran#"!r$ &aer i# $! c!m"are i$ -i$( a "!#$ !ffice'

-(ic( dea&# -i$( $(e di#"a$c( and c&a##ifica$i!n !f mai& and "arce&# #en$* D! remem/er'

(!-e)er' $(a$ a "!#$ !ffice mana%e# $(e !u$er en)e&!"e !f mai&* =i%(er &aer# ma (a)e

$(e equi)a&en$ !f d!u/&e en)e&!"e#' #uc( a# cr"$!%ra"(ic "re#en$a$i!n #er)ice# $(a$ can

 /e read / $(e addre##ee !n&*

R!u%(& #"ea2in%' $unne&in% "r!$!c!&# !"era$e a$ $(e $ran#"!r$ &aer' #uc( a#

carrin% n!n1IP "r!$!c!&# #uc( a# IM# SNA  !r  N!)e&&# IP7 !)er an IP ne$-!r2' !r 

C*T=IAGARA@AN1AP ECE DEPT* 6?

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

end1$!1end encr"$i!n -i$(  IP#ec* 4(i&e  Generic R!u$in% Enca"#u&a$i!n  GRE mi%($

#eem $! /e a ne$-!r21&aer "r!$!c!&' if $(e enca"#u&a$i!n !f $(e "a&!ad $a2e# "&ace !n&

a$ end"!in$' GRE /ec!me# c&!#er $! a $ran#"!r$ "r!$!c!& $(a$ u#e# IP (eader# /u$ c!n$ain#

c!m"&e$e frame# !r "ac2e$# $! de&i)er $! an end"!in$* L;TP  carrie# PPP  frame# in#ide

$ran#"!r$ "ac2e$*

A&$(!u%( n!$ de)e&!"ed under $(e OSI Reference M!de& and n!$ #$ric$&

c!nf!rmin% $! $(e OSI defini$i!n !f $(e $ran#"!r$ &aer' $(e Tran#mi##i!n C!n$r!& Pr!$!c!&

TCP and $(e U#er Da$a%ram Pr!$!c!& UDP !f $(e In$erne$ Pr!$!c!& Sui$e are

c!mm!n& ca$e%!riBed a# &aer1> "r!$!c!&# -i$(in OSI*

/ayer ": session layer

T(e  #e##i!n &aer c!n$r!&# $(e dia&!%ue# c!nnec$i!n# /e$-een c!m"u$er#* I$

e#$a/&i#(e#' mana%e# and $ermina$e# $(e c!nnec$i!n# /e$-een $(e &!ca& and rem!$e

a""&ica$i!n* I$ "r!)ide# f!r fu&&1du"&e,' (a&f1du"&e,' !r  #im"&e, !"era$i!n' and e#$a/&i#(e#

c(ec2"!in$in%' ad!urnmen$' $ermina$i!n' and re#$ar$ "r!cedure#* T(e OSI m!de& made

$(i# &aer re#"!n#i/&e f!r %racefu& c&!#e !f #e##i!n#' -(ic( i# a "r!"er$ !f $(e

Tran#mi##i!n C!n$r!& Pr!$!c!&' and a&#! f!r #e##i!n c(ec2"!in$in% and rec!)er' -(ic( i#

n!$ u#ua&& u#ed in $(e In$erne$ Pr!$!c!& Sui$e* T(e #e##i!n &aer i# c!mm!n&

im"&emen$ed e,"&ici$& in a""&ica$i!n en)ir!nmen$# $(a$ u#e rem!$e "r!cedure ca&&#*

/ayer 8: presentation layer

T(e  "re#en$a$i!n &aer  e#$a/&i#(e# c!n$e,$ /e$-een a""&ica$i!n1&aer en$i$ie#' in

-(ic( $(e a""&ica$i!n1&aer en$i$ie# ma u#e differen$ #n$a, and #eman$ic# if $(e

 "re#en$a$i!n #er)ice "r!)ide# a ma""in% /e$-een $(em* If a ma""in% i# a)ai&a/&e'

 "re#en$a$i!n #er)ice da$a uni$# are enca"#u&a$ed in$! #e##i!n "r!$!c!& da$a uni$#' and

 "a##ed d!-n $(e TCPIP #$ac2*

T(i# &aer "r!)ide# inde"endence fr!m da$a re"re#en$a$i!n e*%*' encr"$i!n /

$ran#&a$in% /e$-een a""&ica$i!n and ne$-!r2 f!rma$#* T(e "re#en$a$i!n &aer $ran#f!rm#

da$a in$! $(e f!rm $(a$ $(e a""&ica$i!n acce"$#* T(i# &aer f!rma$# and encr"$# da$a $! /e

#en$ acr!## a ne$-!r2* I$ i# #!me$ime# ca&&ed $(e #n$a, &aer *Q5

C*T=IAGARA@AN1AP ECE DEPT* 6>

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e !ri%ina& "re#en$a$i!n #$ruc$ure u#ed $(e a#ic Enc!din% Ru&e#  !f A/#$rac$ Sn$a,

 N!$a$i!n One ASN*8' -i$( ca"a/i&i$ie# #uc( a# c!n)er$in% an ECDIC1c!ded $e,$ fi&e

$! an ASCII1c!ded fi&e' !r #eria&iBa$i!n !f !/ec$# and !$(er da$a #$ruc$ure# fr!m and $!

7ML*

/ayer 9: application layer

T(e a""&ica$i!n &aer  i# $(e OSI &aer c&!#e#$ $! $(e end u#er' -(ic( mean# /!$(

$(e OSI a""&ica$i!n &aer and $(e u#er in$erac$ direc$& -i$( $(e #!f$-are a""&ica$i!n* T(i#

&aer in$erac$# -i$( #!f$-are a""&ica$i!n# $(a$ im"&emen$ a c!mmunica$in% c!m"!nen$*

Suc( a""&ica$i!n "r!%ram# fa&& !u$#ide $(e #c!"e !f $(e OSI m!de&* A""&ica$i!n1&aer 

func$i!n# $"ica&& inc&ude iden$ifin% c!mmunica$i!n "ar$ner#' de$erminin% re#!urce

a)ai&a/i&i$' and #nc(r!niBin% c!mmunica$i!n* 4(en iden$ifin% c!mmunica$i!n "ar$ner#' $(e a""&ica$i!n &aer de$ermine# $(e iden$i$ and a)ai&a/i&i$ !f c!mmunica$i!n

 "ar$ner# f!r an a""&ica$i!n -i$( da$a $! $ran#mi$* 4(en de$erminin% re#!urce a)ai&a/i&i$'

$(e a""&ica$i!n &aer mu#$ decide -(e$(er #ufficien$ ne$-!r2 !r $(e reque#$ed

c!mmunica$i!n e,i#$#* In #nc(r!niBin% c!mmunica$i!n' a&& c!mmunica$i!n /e$-een

a""&ica$i!n# require# c!!"era$i!n $(a$ i# mana%ed / $(e a""&ica$i!n &aer*

C*T=IAGARA@AN1AP ECE DEPT* 65

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

UNIT 3: Or/i$a& #a$e&&i$e#' %e!#$a$i!nar #a$e&&i$e#' &!!2 an%&e#' #a$e&&i$e ##$em &in2 

m!de&#' #a$e&&i$e ##$em &in2 equa$i!n#0 ad)an$a%e# !f !"$ica& fi/er c!mmunica$i!n 1

Li%($ "r!"a%a$i!n $(r!u%( fi/er' fi/er &!##' &i%($ #!urce# and de$ec$!r#*

A #a$e&&i$e c!mmunica$i!n ##$em -i&& (a)e a num/er !f u#er# !"era$in% )ia a

c!mm!n #a$e&&i$e $ran#"!nder' and $(i# ca&&# f!r #(arin% !f $(e re#!urce# !f "!-er'

 /and-id$( and $ime* =ere -e de#cri/e $(e#e $ec(nique# and e,amine $(eir im"&ica$i!n#'

-i$( em"(a#i# !n "rinci"&e# ra$(er $(an de$ai&ed #$ruc$ure !r "arame$er# !f "ar$icu&ar 

ne$-!r2#' -(ic( $end $! /e )er ##$em #"ecific* T(e $erm u#ed f!r #uc( #(arin% and

mana%emen$ !f a num/er !f differen$ c(anne&# i# mu&$i"&e acce##*

6r*ital satellites:

In #!me a""&ica$i!n# (i%( Ear$( !r/i$# ma /e required* +!r $(e#e a""&ica$i!n# $(e

#a$e&&i$e -i&& $a2e &!n%er $(an ;> (!ur# $! !r/i$ $(e Ear$(' and "a$( &en%$(# ma /ec!me

)er &!n% re#u&$in% in addi$i!na& de&a# f!r $(e r!und $ri" fr!m $(e Ear$( $! $(e #a$e&&i$e

and /ac2 a# -e&& a# increa#in% $(e &e)e&# !f "a$( &!##*

T(e c(!ice !f $(e #a$e&&i$e !r/i$ -i&& de"end !n i$# a""&ica$i!n#* 4(i&e

%e!#$a$i!nar !r/i$# are "!"u&ar f!r a""&ica$i!n# #uc( a# direc$ /r!adca#$in% and f!r 

c!mmunica$i!n# #a$e&&i$e#' !$(er# #uc( a# GPS and e)en $(!#e #a$e&&i$e# u#ed f!r m!/i&e

 "(!ne# are muc( &!-er*

LEO /a#ic#

4i$( L!- Ear$( Or/i$ e,$endin% fr!m ;<< 2m $! 8;<< 2m i$ mean# $(a$ i$ i#

re&a$i)e& &!- in a&$i$ude' a&$(!u%( -e&& a/!)e an$(in% $(a$ a c!n)en$i!na& aircraf$ can

reac(*

=!-e)er LEO i# #$i&& )er c&!#e $! $(e Ear$(' e#"ecia&& -(en c!m"ared $! !$(er 

f!rm# !f #a$e&&i$e !r/i$ inc&udin% %e!#$a$i!nar !r/i$*

T(e &!- !r/i$ a&$i$ude !f &ead# $! a num/er !f c(arac$eri#$ic#:

C*T=IAGARA@AN1AP ECE DEPT* 66

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

• Or/i$ $ime# are muc( &e## $(an f!r man !$(er f!rm# !f !r/i$* T(e &!-er a&$i$ude

mean# (i%(er )e&!ci$ie# are required $! /a&ance $(e ear$(# %ra)i$a$i!na& fie&d*

T"ica& )e&!ci$ie# are )er a""r!,ima$e& ar!und H 2m#' -i$( !r/i$ $ime#

#!me$ime# !f $(e !rder !f J< minu$e#' a&$(!u%( $(e#e fi%ure# )ar c!n#idera/&

-i$( $(e e,ac$ de$ai&# !f $(e !r/i$*

• T(e &!-er !r/i$ mean# $(e #a$e&&i$e and u#er are c&!#er $!%e$(er and $(eref!re "a$(

&!##e# a &e## $(an f!r !$(er !r/i$# #uc( a# GEO

• T(e r!und $ri" $ime' RTT f!r $(e radi! #i%na&# i# c!n#idera/& &e## $(an $(a$

e,"erienced / %e!#$a$i!nar !r/i$ #a$e&&i$e#* T(e ac$ua& $ime -i&& de"end u"!n

fac$!r# #uc( a# $(e !r/i$ a&$i$ude and $(e "!#i$i!n !f $(e u#er re&a$i)e $! $(e

#a$e&&i$e*

• Radia$i!n &e)e&# are &!-er $(an e,"erienced a$ (i%(er a&$i$ude#*

• Le## ener% i# e,"ended "&acin% $(e #a$e&&i$e# in LEO $(an (i%(er !r/i$#*

• S!me #"eed reduc$i!n ma /e e,"erienced a# a re#u&$ !f fric$i!n fr!m $(e &!-' /u$

mea#ura/&e &e)e&# !f %a##e#' e#"ecia&& a$ &!-er a&$i$ude#* An a&$i$ude !f ?<< 2m i#

n!rma&& acce"$ed a# $(e minimum f!r an !r/i$ a# a re#u&$ !f $(e increa#in% dra%

fr!m $(e "re#ence !f %a##e# a$ &!- a&$i$ude#*

A""&ica$i!n# f!r LEO #a$e&&i$e#

A )arie$ !f differen$ $"e# !f #a$e&&i$e u#e $(e LEO !r/i$ &e)e&#* T(e#e inc&ude differen$

$"e# and a""&ica$i!n# inc&udin%:

• C!mmunica$i!n# #a$e&&i$e# 1 #!me c!mmunica$i!n# #a$e&&i$e# inc&udin% $(e Iridium

 "(!ne ##$em u#e LEO*

• Ear$( m!ni$!rin% #a$e&&i$e# u#e LEO a# $(e are a/&e $! #ee $(e #urface !f $(e Ear$(

m!re c&ear& a# $(e are n!$ #! far a-a* T(e are a&#! a/&e $! $ra)er#e $(e #urface

!f $(e Ear$(*

C*T=IAGARA@AN1AP ECE DEPT* 6

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

• T(e In$erna$i!na& S"ace S$a$i!n i# in an LEO $(a$ )arie# /e$-een ?;< 2m 8JJ

mi&e# and ><< 2m ;>J mi&e# a/!)e $(e Ear$(# #urface* I$ can !f$en /e #een

fr!m $(e Ear$(# #urface -i$( $(e na2ed ee*

S"ace de/ri# in LEO

A"ar$ fr!m $(e %enera& c!n%e#$i!n e,"erienced in L!- Ear$( Or/i$' $(e #i$ua$i!n

i# made muc( -!r#e / $(e %enera& &e)e& !f #"ace de/ri# $(a$ e,i#$#*

T(ere i# a rea& and %r!-in% ri#2 !f c!&&i#i!n and ma!r dama%e 1 an c!&&i#i!n#

$(em#e&)e# are &i2e& $! crea$e fur$(er #"ace de/ri#*

T(e US @!in$ S"ace O"era$i!n# Cen$er curren$& $rac2# !)er H 5<< !/ec$# $(a$(a)e dimen#i!n# &ar%er $(an 8< cen$ime$re#* =!-e)er de/ri# -i$( #ma&&er dimen#i!n# can

a&#! cau#e #i%nifican$ dama%e and c!u&d render a #a$e&&i$e un#er)icea/&e af$er a c!&&i#i!n*

)eostationary satellites:

A %e!#$a$i!nar !r/i$' %e!#$a$i!nar Ear$( !r/i$ !r %e!#nc(r!n!u# equa$!ria&

!r/i$ GEO' i# an !r/i$ -(!#e "!#i$i!n in #2 remain# $(e #ame f!r a #$a$i!nar !/#er)er 

!n ear$(* T(i# effec$ i# ac(ie)ed -i$( a circu&ar !r/i$ ?5'H6 2i&!me$re# ;;';?6 mi a/!)e

$(e Ear$(# equa$!r and f!&&!-in% $(e direc$i!n !f $(e Ear$(# r!$a$i!n* Q; An !/ec$ in #uc(

an !r/i$ (a# an !r/i$a& "eri!d equa& $! $(e Ear$(# r!$a$i!na& "eri!d !ne #iderea& da' and

$(u# a""ear# m!$i!n&e##' a$ a fi,ed "!#i$i!n in $(e #2' $! %r!und !/#er)er#*

C!mmunica$i!n# #a$e&&i$e# and -ea$(er #a$e&&i$e# are !f$en "&aced in %e!#$a$i!nar !r/i$#'

#! $(a$ $(e #a$e&&i$e an$enna# -(ic( c!mmunica$e -i$( $(em d! n!$ (a)e $! m!)e $! $rac2 

$(em' /u$ can /e "!in$ed "ermanen$& a$ $(e "!#i$i!n in $(e #2 -(ere $(e #$a* U#in%

$(i# c(arac$eri#$ic' !cean c!&!r #a$e&&i$e# -i$( )i#i/&e #en#!r# e*%* $(e Ge!#$a$i!nar

Ocean C!&!r Ima%er  GOCI can a&#! /e !"era$ed in %e!#$a$i!nar !r/i$ in !rder $!

m!ni$!r #en#i$i)e c(an%e# !f !cean en)ir!nmen$#*

A %e!#$a$i!nar !r/i$ i# a "ar$icu&ar $"e !f %e!#nc(r!n!u# !r/i$' $(e di#$inc$i!n

 /ein% $(a$ -(i&e an !/ec$ in %e!#nc(r!n!u# !r/i$ re$urn# $! $(e #ame "!in$ in $(e #2 a$

$(e #ame $ime eac( da' an !/ec$ in %e!#$a$i!nar !r/i$ ne)er &ea)e# $(a$ "!#i$i!n*

C*T=IAGARA@AN1AP ECE DEPT* 6H

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e n!$i!n !f a %e!#nc(r!n!u# #a$e&&i$e f!r c!mmunica$i!n "ur"!#e# -a# fir#$

 "u/&i#(ed in 8J;H /u$ n!$ -ide& #! / =erman P!$!Wni2 *Q? T(e fir#$ a""earance !f a

%e!#$a$i!nar !r/i$ in "!"u&ar &i$era$ure -a# in $(e fir#$ 3enu# Equi&a$era& #$!r / Ge!r%e

O* Smi$('Q>  /u$ Smi$( did n!$ %! in$! de$ai&#* ri$i#( #cience fic$i!n au$(!r Ar$(ur C*

C&ar2e di##emina$ed $(e idea -ide&' -i$( m!re de$ai&# !n (!- i$ -!u&d -!r2' in a 8J>5

 "a"er en$i$&ed E,$ra1Terre#$ria& Re&a# Can R!c2e$ S$a$i!n# Gi)e 4!r&d-ide Radi!

C!)era%eX' "u/&i#(ed in 4ire&e## 4!r&d ma%aBine* C&ar2e ac2n!-&ed%ed $(e c!nnec$i!n

in (i# in$r!duc$i!n $! T(e C!m"&e$e 3enu# Equi&a$era&*Q5  T(e !r/i$' -(ic( C&ar2e fir#$

de#cri/ed a# u#efu& f!r /r!adca#$ and re&a c!mmunica$i!n# #a$e&&i$e#' Q6  i# #!me$ime#

ca&&ed $(e C&ar2e Or/i$*Q Simi&ar&' $(e C&ar2e e&$ i# $(e "ar$ !f #"ace a/!u$ ?5'H6 2m

;;';?6 mi a/!)e #ea &e)e&' in $(e "&ane !f $(e Equa$!r' -(ere near1%e!#$a$i!nar !r/i$#

ma /e im"&emen$ed* T(e C&ar2e Or/i$ i# a/!u$ ;65'<<< 2m 865'<<< mi &!n%*

/oo angles:

T(e ear$( #$a$i!n need# $! 2n!- -(ere $(e #a$e&&i$e i# in $(e !r/i$* T(en $(e ear$( #$a$i!n

en%ineer need# $! ca&cu&a$e #!me an%&e# $! $rac2 $(e #a$e&&i$e c!rrec$&* T(e#e an%&e# are

ca&&ed an$enna &!!2 an%&e* T(e &!!2 an%&e# f!r $(e %r!und #$a$i!n an$enna are $(e aBimu$(

and e&e)a$i!n an%&e# required a$ $(e an$enna #! $(a$ i$ "!in$# direc$& a$ $(e #a$e&&i$e* 4i$(

$(e %e!#$a$i!nar !r/i$ $(e #i$ua$i!n i# muc( #im"&er $(an an !$(er !r/i$* A# $(e an$enna

 /eam -id$( i# )er narr!- and $rac2in% mec(ani#m i# required $! c!m"en#a$e f!r $(e

m!)emen$ !f $(e #a$e&&i$e a/!u$ $(e n!mina& %e!#$a$i!nar "!#i$i!n* T(ree "iece# !f 

inf!rma$i!n $(a$ are needed $! de$ermine $(e &!!2 an%&e# f!r $(e %e!#$a$i!nar !r/i$ are

a* Ear$( #$a$i!n &a$i$ude

 /* Ear$( #$a$i!n &!n%i$ude

c* Sa$e&&i$e !r/i$a& "!#i$i!n

C*T=IAGARA@AN1AP ECE DEPT* 6J

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

U#in% $(e#e inf!rma$i!n an$enna &!!2 an%&e can /e ca&cu&a$ed u#in% Na"ier# ru&e

#!&)in% #"(erica& $rian%&e* ABimu$( an%&e den!$e# $(e (!riB!n$a& an%&e mea#ured a$ $(e

ear$( #$a$i!n an$enna end f!rm Green-ic( meridian $! #a$e&&i$e "!#i$i!n* E&e)a$i!n i# #uc(

an%&e den!$e# $(e )er$ica& an%&e mea#ured a$ $(e ear$( #$a$i!n an$enna end fr!m %r!und $!

#a$e&&i$e "!#i$i!n*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

$atellite system lin model:

  T(e "rimar c!m"!nen$ -i$(in $(e #ec$i!n !f a #a$e&&i$e ##$em i# $(e ear$( #$a$i!n

$ran#mi$$er*

A $"ica& ear$( #$a$i!n $ran#mi$$er c!n#i#$# !f an I+ m!du&a$!r' an I+ $! R+

micr!-a)e u"1c!n)er$er' a (i%( "!-er am"&ifier =PA*T(e I+ m!du&a$!r c!n)er$# $(e

in"u$ /a#e/and #i%na&# $! ei$(er an +M' a PS !r a AM m!du&a$ed in$ermedia$e

frequenc*T(e u"1c!n)er$er mi,er and P+ c!n)er$# $(e I+ $! an a""r!"ria$e R+ carrier 

frequenc*T(e =PA "r!)ide# adequa$e in"u$ #en#i$i)i$ and !u$"u$ "!-er $! "r!"a%a$e $(e

#i%na& $! $(e #a$e&&i$e $ran#"!nder* T(e =PA# c!mm!n& u#ed are 2&#$r!n# and TNT#*

2. The satellite transponder:

+i%* /e&!- #(!-# a #im"&ified /&!c2 dia%ram !f a #a$e&&i$e $ran#"!nder*

A $ran#"!nder i# a "ar$ !f a #a$e&&i$e' -(ic( i# a c!m/ina$i!n !f $ran#mi$$er and

recei)er* T(e main func$i!n !f $ran#"!nder i# frequenc $ran#&a$i!n and am"&ifica$i!n*

a#ed !n $(e frequenc $ran#&a$i!n "r!ce##' $(ere are $(ree /a#ic $ran#"!nder 

c!nfi%ura$i!n#* T(e#e are #in%&e c!n)er#i!n $ran#"!nder' d!u/&e c!n)er#i!n $ran#"!nder 

and re%enera$i)e $ran#"!nder*

C*T=IAGARA@AN1AP ECE DEPT* 8

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e u"&in2 #i%na& i# recei)ed / $(e recei)in% an$enna* T(e recei)ed #i%na& i# fir#$

 /and &imi$ed / and Pa## +i&$er P+' $(en i$ i# r!u$ed $! L!- N!i#e Am"&ifier LNA*

T(e am"&ified #i%na& i# $(en frequenc $ran#&a$ed / a mi,er and an !#ci&&a$!r*

=ere !n& $(e frequenc i# $ran#&a$ed fr!m (i%(1/and u"1&in2 frequenc $! $(e &!-1/and

d!-n &in2 frequenc* T(e mi,er !u$"u$ d!-n &in2 #i%na& i# $(en a""&ied $! P+ $(en i$

i# am"&ified / a =i%( P!-er Am"&ifier =P A* T(i# d!-n &in2 #i%na& i# $(en $ran#mi$$ed

$! recei)er ear$( #$a$i!n $(r!u%( a (i%( "!-er $ran#mi$$in% an$enna*

3. The downlin :

+i%* /e&!- #(!-# a /&!c2 dia%ram !f a $"ica& ear$( #$a$i!n recei)er*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

An ear$( #$a$i!n recei)er inc&ude# an in"u$ P+' an LNA and an R+ $! I+ d!-n c!n)er$er*

T(e P+ &imi$# $(e in"u$ n!i#e "!-er $! $(e LNA* T(e LNA i# a (i%(& #en#i$i)e'

&!- n!i#e de)ice* T(e R+1$!1I+ d!-n c!n)er$er i# a mi,er' P+ c!m/ina$i!n -(ic(

c!n)er$# $(e recei)ed R+ #i%na& $! an I+ frequenc*

T(e m!#$ c!mm!n frequencie# u#ed f!r #a$e&&i$e c!mmunica$i!n# are 6> and

8>8; G=B /and#* T(e fir#$ num/er indica$e# $(e u"&in2 ear$(#$a$i!n1$!1$ran#"!nder

frequenc and $(e #ec!nd num/er i# d!-n&in2 $ran#"!nder1$!1ear$(#$a$i!n frequenc*

Since C /and i# m!#$ -ide& u#ed' $(i# /and i# /ec!min% !)ercr!-ded*

6-T'A/ F'(0% 

An !"$ica& fi/er i# a f&e,i/&e' $ran#"aren$ fi/er made !f )er "ure %&a## #i&ica n!$

muc( /i%%er $(an a (uman (air $(a$ ac$# a# a -a)e%uide' !r &i%($ "i"e' $! $ran#mi$ &i%($

 /e$-een $(e $-! end# !f $(e fi/er* T(e fie&d !f a""&ied #cience and en%ineerin% c!ncerned

-i$( $(e de#i%n and a""&ica$i!n !f !"$ica& fi/er# i# 2n!-n a# fi*er optics* O"$ica& fi/er#

are -ide& u#ed in fi/er1!"$ic c!mmunica$i!n#' -(ic( "ermi$# $ran#mi##i!n !)er &!n%er 

di#$ance# and a$ (i%(er  /and-id$(#  da$a ra$e# $(an !$(er f!rm# !f c!mmunica$i!n*

+i/er# are u#ed in#$ead !f me$a& -ire# /ecau#e #i%na&# $ra)e& a&!n% $(em -i$( &e## &!##and are a&#! immune $! e&ec$r!ma%ne$ic in$erference* +i/er# are a&#! u#ed f!r 

i&&umina$i!n' and are -ra""ed in /und&e# #! $(e can /e u#ed $! carr ima%e#' $(u#

a&&!-in% )ie-in% in $i%($ #"ace#* S"ecia&& de#i%ned fi/er# are u#ed f!r a )arie$ !f !$(er 

a""&ica$i!n#' inc&udin% #en#!r# and fi/er &a#er#*

An !"$ica& fi/er unc$i!n /!, (a# $(e e&&!- ca/&e# are #in%&e m!de fi/er#0 $(e

!ran%e and /&ue ca/&e# are mu&$i1m!de fi/er#: 5<8;5 m OM; and 5<8;5 m OM?

fi/er# re#"ec$i)e&* O"$ica& fi/er $"ica&& c!n#i#$# !f a $ran#"aren$ c!re #urr!unded / a

$ran#"aren$ c&addin% ma$eria& -i$( a &!-er inde, !f refrac$i!n* Li%($ i# 2e"$ in $(e c!re /

$!$a& in$erna& ref&ec$i!n* T(i# cau#e# $(e fi/er $! ac$ a# a -a)e%uide* +i/er# $(a$ #u""!r$

man "r!"a%a$i!n "a$(# !r $ran#)er#e m!de# are ca&&ed mu&$i1m!de fi/er# MM+' -(i&e

$(!#e $(a$ !n& #u""!r$ a #in%&e m!de are ca&&ed #in%&e1m!de fi/er# SM+* Mu&$i1m!de

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

fi/er# %enera&& (a)e a &ar%er c!re diame$er' and are u#ed f!r #(!r$1di#$ance

c!mmunica$i!n &in2# and f!r a""&ica$i!n# -(ere (i%( "!-er mu#$ /e $ran#mi$$ed* Sin%&e1

m!de fi/er# are u#ed f!r m!#$ c!mmunica$i!n &in2# &!n%er $(an 8'<5< me$er# ?'>>< f$*

 

Ad&antages of optical fi*re communication:

+i/er1!"$ic c!mmunica$i!n ##$em# are /ec!min% increa#in%& c!mm!n in

m!dern #!cie$* 4(ere !nce $(e -ere re#$ric$ed $! %!)ernmen$ !r /u#ine## u#e' fi/er1

!"$ic ##$em# are n!- a)ai&a/&e $! indi)idua& (!u#e(!&d#* T(i# (a# /een dri)en / $(e

ri#in% demand f!r (i%( /and-id$( c!nnec$i!n# f!r a )arie$ !f indu#$ria& and re#iden$ia&

 "ur"!#e#*

+i/er1!"$ic ##$em# (a)e a &ar%e num/er !f ad)an$a%e# !)er c!""er -ire ca/&e#* Am!n%

$(e m!#$ im"!r$an$ are $(e f!&&!-in%:

• ecau#e fi/er1!"$ic ca/&e# are /!$( &i%($er and #ma&&er in diame$er $(an c!""er 

&ine#' $(e can /e m!re ea#i& "r!duced and in#$a&&ed*

• +i/er1!"$ic ##$em# u#e #i%nifican$& &e## ener% $(an c!""er &ine# and are $(u#

immune $! man dan%er# a##!cia$ed -i$( $(e e&ec$rica& curren$ u#ed in c!""er 

&ine#*

• +i/er1!"$ic c!mmunica$i!n ##$em# can /e u#ed $! $ran#mi$ m!re inf!rma$i!n

$(an c!""er ca/&e# and are -e&&1#ui$ed f!r u#e -i$( di%i$a& c!mmunica$i!n#*

• 4(en c!m"ared $! c!""er ca/&e#' fi/er1!"$ic ca/&e# are /!$( immune $!

e&ec$r!ma%ne$ic in$erference and "r!duce n! in$erference -(en !"era$in%*

• +ina&&' fi/er1!"$ic &ine# are &e## e,"en#i)e $(an c!""er ca/&e#' -(ic( can

dra#$ica&& reduce $(e c!#$ !f in#$a&&in% ne- &ine# !r main$ainin% !&der !ne#*

/ight propagation through fi*re:

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

Li%($ i# de#cri/ed / ra# $(a$ $ra)e& in #$rai%($ &ine# in an i#!$r!"ic and

(!m!%ene!u# medium* 4(en $(e ra #$ri2e# an in$erface /e$-een $(e $-! media' i$#

direc$i!n %e$# c(an%ed* A$ $(e in$erface /!$( $(e ref&ec$i!n and $(e refrac$i!n $a2e "&ace*

C(an%e !f direc$i!n in $(e #ame medium due $! #$ri2e a$ $(e in$erface i# 2n!-n a#

ref&ec$i!n' -(i&e $(e c(an%e !f direc$i!n in $(e #ec!nd medium i# 2n!-n a# refrac$i!n*

An i#!$r!"ic and (!m!%en!u# medium i# c(arac$eri#ed / $(e refrac$i)e inde,

-(ic( i# a mea#ure !f )e&!ci$ !f &i%($ in $(a$ medium* T(e medium (a# differen$

refrac$i)e indice# f!r &i%($ !f differen$ c!&!r#*

T(e ref&ec$i!n and refrac$i!n !f &i%($ a$ $(e in$erface are de#cri/ed / &a- !f 

ref&ec$i!n and &a- !f refrac$i!n* T(e#e &a-# are $(e f!unda$i!n !f %e!me$rica& !"$ic#* T(e

 "r!"a%a$i!n !f ra# and a&#! $(e ima%e f!rma$i!n / &en#e# and mirr!r# e$c* are %!)erned / $(e#e &a-#*

Under cer$ain c!ndi$i!n#' e,"&ained &a$er' $(e ra in#$ead !f refrac$in% %e$# $!$a&&

ref&ec$ed* T(i# "(en!men!n i# 2n!-n a# $!$a& in$erna& ref&ec$i!n and "&a# a )er

im"!r$an$ r!&e in &i%($ %uidance $(r!u%( fi/er#*

Refrac$i!n !f Li%($:

T(i# #ec$i!n "re#en$# $(e #$ud !f $(e "(en!men!n in$erac$i)e&* In"u$ "arame$er#'$(e refrac$i)e indice# !f $(e $-! media and $(e an%&e !f incidence can /e )aried and $(e

 "r!"a%a$i!n !f &i%($ can /e #$udied*

/ight sources and detectors:

6-T'A/ #0T0T6%$

T(e de$ec$i!n !f !"$ica& radia$i!n i# u#ua&& acc!m"&i#(ed / c!n)er$in% $(e

!"$ica& ener% in$! an e&ec$rica& #i%na&* O"$ica& de$ec$!r# inc&ude "(!$!n de$ec$!r#' in-(ic( !ne "(!$!n !f &i%($ ener% re&ea#e# !ne e&ec$r!n $(a$ i# de$ec$ed in $(e e&ec$r!nic

circui$r' and $(erma& de$ec$!r#' in -(ic( $(e !"$ica& ener% i# c!n)er$ed in$! (ea$' -(ic(

$(en %enera$e# an e&ec$rica& #i%na&* Of$en $(e de$ec$i!n !f !"$ica& ener% mu#$ /e

 "erf!rmed in $(e "re#ence !f n!i#e #!urce#' -(ic( in$erfere -i$( $(e de$ec$i!n "r!ce##*

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DEPT: EEE EE T56 COMMUNICATION

ENGINEERING

T(e de$ec$!r circui$r u#ua&& em"&!# a /ia# )!&$a%e and a &!ad re#i#$!r in #erie# -i$( $(e

de$ec$!r* T(e inciden$ &i%($ c(an%e# $(e c(arac$eri#$ic# !f $(e de$ec$!r and cau#e# $(e

curren$ f&!-in% in $(e circui$ $! c(an%e* T(e !u$"u$ #i%na& i# $(e c(an%e in )!&$a%e dr!"

acr!## $(e &!ad re#i#$!r* Man de$ec$!r circui$# are de#i%ned f!r #"ecific a""&ica$i!n#*

Avalanche photodetectors (APDs) are used in long-haul fber

optic systems, since they have superior sensitivity, as much as 10 dB

better than P! diodes" Basically, an APD is a P-! #unction photodiode

operated $ith high reverse bias" %he materials is typically nP&n'aAs"

ith the high applied potential, impact ioniation *rom the light$ave

generates electron-hole pairs that subse+uently cause an avalanche

across the potential barrier" %his current gain gives the APD its greater

sensitivity" APDs are commonly used up to " 'bps and sometimes to

10 'bps i* the e.tra cost can be #ustifed"

/ilicon photodiodes (APDs) are used in lo$er *re+uency systems

(up to 1" or ') $here they can meet lo$ cost and modest

*re+uency response re+uirements" /i devices are used in pairs in

$avelength sensors" %he ratio o* longer and shorter $avelength

sensors is proportional to the input $avelength" ope*ully, this short

tutorial provides a use*ul introduction to an important part o* optical

communication systems"

Li%($ Guidance:

T(i# #ec$i!n "re#en$# $(e in$erac$i)e #$ud !f $(e &i%($ "r!"a%a$i!n $(r!u%( $(e

fi/er#* )arin% $(e refrac$i)e indice# !f $(e medium in fr!n$ !f $(e fi/er' medium

in#ide $(e fi/er' medium !f $(e c&addin% !f $(e fi/er and $(e an%&e !f incidence' $(e

 "a##a%e !f &i%($ in $(e meridi!na& "&ane $(r!u%( $(e fi/er can /e $raced*

8* Princi"&e# !f La#er#

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ENGINEERING

T(e na$ure !f &i%($' /&ac2/!d radia$i!n' "(!$!n#' quan$iBed ener% &e)e&#'

emi##i!n and a/#!r"$i!n !f &i%($' !"$ica& am"&ifier#' !"$ica& re#!na$!r#' &a#er#' c!n$inuum

and "u&#ed &a#er#' #e&ec$ed %a#e!u# and #!&id1#$a$e ##$em#*

;* Semic!nduc$!r La#er# and Di!de#

In$rin#ic and e,$rin#ic #emic!nduc$!r#' &i%($1ma$$er in$erac$i!n' $ernar and

qua$ernar #emic!nduc$!r#' (e$er!#$ruc$ure#' quan$um -e&&#' -ire# and d!$#'

(!m!unc$i!n# and (e$er!unc$i!n#' &i%($ emi$$in% di!de#' inec$i!n &a#er#' di#$ri/u$ed

feed/ac2 &a#er# and )er$ica& ca)i$ #urface emi$$in% 3CSEL &a#er#*

?* O"$ica& De$ec$!r#

T(erma& de$ec$!r# and "(!$!n de$ec$!r#' quan$um efficienc !f #emic!nduc$!r de$ec$!r#' "(!$!c!nduc$!r#' "(!$!)!&$aic de$ec$!r#' PIN di!de#' a)a&ance "(!$!di!de#'

n!i#e and n!i#e equi)a&en$ "!-er*

>* M!du&a$!r# and Def&ec$!r#

S$a$e !f "!&ariBa$i!n' ac!u#$!!"$ic' e&ec$r!!"$ic and ma%ne$!!"$ic effec$#' +arada

r!$a$i!n and ma%ne$!!"$ic m!du&a$!r#' inde, e&&i"#!id' &inear e&ec$r!!"$ic effec$'

e&ec$r!!"$ic m!du&a$!r#' ac!u#$!!"$ic m!du&a$!r# and def&ec$!r#' Raman1Na$( and ra%%

diffrac$i!n*

5* P(!$!nic Cr#$a&# and Micr!re#!na$!r#

4a)e "r!"a%a$i!n in "eri!dic ##$em#' 8D;D?D cr#$a& e,am"&e#' "(!$!nic

 /and %a"' c!n$r!& !f emi##i!n' die&ec$ric micr!#"(ere# and $(eir !"$ica& "r!"er$ie#*

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ENGINEERING