Mobile.

Commuuw cati on Cuestion Cank

Desenib e t h e Manges bi traws iesion in wialess eYnmnicaioy.

wineless coom cation transision eau be deseibed

)Tranimsion Range.
The distnce usitHhin w'ca a can be transniHed
from t e Senden to the tecei ve Suelh that t e wecive.
gets the sigaal witt an aceeptalbe les ese nate .
. wiHin t s Mauge, a deice eau uot oy eceive but also
eommhicate

Sender.
btectively giey act as ot eciven and
i)Dekeetiom Range
. The distance within whieh the siqual is
dekucked aud distiuguis hed tuom strong noug to be
baekgrnund' wolse"
"The e e hate is too igh Roe eliabe commuw att on-Thusy
commiieation cauuot be'utabtished deupite detection.
üi) Daterfenee Range
.The aa beyond te detction range
wot ushete slgual is
Ao be detected lout stiu aftecs
strag
trausmsous. bRer
Siquals in this wange add to backqund uoise, casing
iuukrnce
caut be
for other commicatian systam ewu
detected

Suudce
Dstauce
Tranamiss
Oetectiy
InteMCn
2 What do you meau by free spaee uss
ru Spoce Loss refeni to the heduwton n sisaal strength
that ocu sthu a wieles siqual tavels
Spare (a vacuum su upee atmosph)gum a sude to a
Teeive.
t is a watwal ohuomeun aud oCus eww uolheu there is
o obstaele boto2en the Seud aud t e Heceier.
Opuoi cal puopagatan and iwsse laus sauane form the bais of free spacl.
,skasing that the powe of the siqual decASeA Hapidly wite distante
 Key lhanastishe:
Propagatin
" Radio
ike iglt!
b9aes.
They trauel in a staiglt une ludepudewy fray
phoided thee is a lean ine-f -sigbt (Lo) batoen
tte snde aud ecever
u. Line of Sigut (Los):
1f thee is au wobstrueted pate loutween the sende a
the eeeivet, the si_ual folos a staight lue LOS pota
Eveu i peeyect LOS >, Psiu
deoeases ioi
distanee due spheadiul.

Sphwical tuopagation desoibs how the sigual spsendi

Tvose Squae Lauo aplalus hao wuch tus siqual stringt
Teduees.
3. Des Oibe the fundaneutal bahauiowcs of eadio wwes
depsudig
Radio waiey ean ea bit twee fwndamental propogaen
behavtous depeuding on thein fra uen :
I. Guound hdave Popagatton (< 2Mtz):
" behaiouy Thee wawes
aud can travel louy distaes ang
Applicatrns Used tn AM rodlo nd sulmane
communication

catlon
Key featwres- Suitable f loug- distanee eommi
without e nee for sateites or L0S.

Wave Propagatim (2-30 M2):

I: SuyBehaviout-Tçese usawes ae Kagueted by the ionashee
bach to eaxth, aling them to tuael awond
tthe world
lornging between the eaths
swfaee and tlie fousphene .
Apicatans Common in itenal boadcastiug aud.
hadlo. amateua
featwre- Cuables
qlolal covxag
even wittut taug apeeton,
direet vieibiUty
sende aud eceive. between
 i. Line o Sight (o-s) (730 MH):
waves travel fn atraight lies
and *ypicaly xeayine a dean ine -of-sight(Los)
betwee tue troaus mitte and eciven
Application - Used in mobile phnss , satellitu, condles foues
aud miare unws
Featwre - eee siquale do wt efect ot te iospes
aud ae'subjaet to sutractten by te atmesplwe,
wich beuds tae pat out does wt
iminate thi Los eaement
4. Define Grcund Wave and suy hiave.
done..
Alrenay
6. Explan Shadancing vadio siqnal. Comyae etfebs iftecin,
and biffroclion Pn wirelers cenminiatn:
Retroatiom ,Soatbung
Shadmaing
i: Defiuition - It occuwrs when a sadio siqual is bloched by
lange oljecs (bulaing, ile, wmowtaiw). hatis
vieh lingen than tie sigual's soavngt.
!t Caus-The Siqual cannt reae tthe SLwee
beeauce the doiect ats a "shado Zeue ,
dinecy
Sinilan to hao a nall lblochs visibte ialut.

Siguifiauty be
conplety Lst
a shadus
IV.. Enamle - # is sinilan to hpo ligkt ton
bahiud a sotid ooject
A mobile use behivd a lage building may not
eeive te slqual from a neby tvwe due 'to the
blocking of; the direet
Conupaison.
Efect Case Desciption Tmpaet
Shadoising Dustacle wuch langx Blocke dixeet siqual Cauies siqual oss
Hhan wavelengt. path, teatiug asigual wsak
shadouo ael.
xuptim
Refechiom Hits smocth Swface Signal brwces ct Creates multi pat
(arger than aeeyt odojcs ie oalli se sighali, can caee
buildings sigual' distorion.
 Cause Desouiption Iupact
Refroetion Paces trougl Sigual bendi as tt Ats pat
allos
media with
deusity (eq-aùj |Layers he the bayond LDS.
atnas phee
|Seatexing tits rougl Smal Syual is scattoned Signal stengt
reduoes, may eaeh
in'multiple diracHons aea.

wneapeoted
Enables reception inbut
|D{fractin Encounhus shap Slgual bendi anound shadooed weas,
edges. Comes or tbstaleu
with veduoed strenqt

G What is wuti pate paopagat ou ? Eaplain eteum delay Speead

in maltipat pruopagaton ding dagam
’Mutipat. p pagaton ocew. shn a traus mited Hadio siga
takes wltiple paths 'to ueach the Hecelve instead o.
the LOs patt T e addiHonal patts ae ceeated due to
Refletion ot buildings and uoala
D0ffrachon aond tostacles
Seatuing tro Small oojcts uhe trees, vhi oles , r
street itwe.
ead ikeles comnuni
Muli path pho pagatton is a
cation that caues delay spaea., to distrtion and
iutesymbot intenpnee (isr). Modeu eeivus use
eaubli~os aud traiing seauewe to nedee its
Delay Spead is tthe tine differenee betoeen the atval of
the easlest aud the latest sighal eompouts caued bt
multi pat puopagati on
Dntesnbol Intenjene(11): I{ the dyspuead fa too
lange gmbols nay ovolap at the Heceive
oiica eads o data e a i .

Signal Distorion : Diffeant ompornnts od the same sigual

may intuee wit ach otee,
 Reflecton DO
DIftracHon
(ShadodMA)
MS

. Define the tens - s het teum aud tong-tunadinA

în wineles commneat on, tadia refu Ho the vaiaion in
the straugt of a eceived siual oen ime ou distoance
suortt n fadng
xapia fuetuation siguad aiplitude
Caused boy wultipata pnopagatin
I+is allo kuaon as foaufading wnulti path fadiung
’ Causes:
" Occwes when wmultiple copies of the slgual,daovig
via diffMut paths (witth ditfunt delayi phases)>
Especialy uwhen the transmi ten b neceiven is moiug.
’ hanaet eistics :
Happe oveH shetn distauces (companable do the savelength
of the sigua
signal strug,Az
costrutHve ol destrete
eenee se deceease due to
fucease

Ezample: In veiedes ,uliledviug tnugh tes e

te heeeired
rapidly odue do

Lug tuum fodiug

’ Definition: Tt is the sLouo vaiatin in the areage prwe
ot a reeeived siqual OVeH tme.

shadaoing lsimo fading

fu the dstance btoen the tranmity and the

’ Chaactestes:
Laxge time and distance seoles
 Usuaty mgenate
So that the eeived
y adjuating e trausmislon pawe
remains within acceptable lims.
Eayle : Amobile phn moing b due tos .
apuienee a diop tn stgual stsugth

-Lomy texm

Sunt tuum
fadig
selective and eoteenee
banddth and coheece
Flat
Fading
’ Defitton: Tt occws when te mobile radio canel as a
conetaut gain aud unean phase spone bvea
a frau range tat is greateu tian tte
t e same lrel
"The utire sigual bauduoidte ezppriuees
aoss all
puequeueies.
Tt is alo called au
amplitude vaying chainel su oa
naoo band canne
Tue applied siual banduoidth wut be Smallw ttan t&e
channel's fat' fading baudwtdt.
-’ Gffeet:
he `pectral charateu stia af tte trausmi ted siqual axe
presewed.

Quty tue amitude(strengt) of the xeLeived sigaal

vaie with ime.
Ti vaiation is due to wulti patt puopagation, wuic
euses
Prequency Selective Padig
’ Depiniion Tt ecewswhen te
Qud iuea
constant phase reeponee
Smalle
sighal.
Kiy Potut!
The neceived sigal azpsinees diffient fading
itaeut franeny ionmponeuks. usavefom
MuLti delayed veeitne of atte tranited
a e receinld.
Tues esults in TI, uslch can distort dota at te
recele

Cohereuee Baud widtt how mueh sange of oineles chanel

’ Definition: It is a statistical measwres
freanencies ovH oicl tte wireless channel semaing
ftat iey the ahannel erti bits constant gain and
Luaan phae aepováe
’ key Points :
" Tt refects the channel's abiity to transmit sigual ortsul
distorion aeruss a range of frtquuies
"It is invney psop stiral to the RMS
channel
Delay
spxohd
chawel cani
1f the coherece bandoidth is lage, the
transit uoideband siguals wtttsut frequency Selecte
I I+is Srnall, my nawbud Signade can be tranam-,
ited cleay
wchangcd)
Cohenence Time(ww leng a wirelegs,chael stays tte sanelbehantouy )
’ Detinition! t is a statstil measwe at the time dueatton
oves ouicle te ehanel's impulee relp onke
rmalwu invaaut

’ Key Points :
Suwy prepetonal to Doppler spLad..
Doyr ler
Spread
{ Tc is long lanel tays stable for a long time
-good for comiia
Tf Te is ghort,channel elange quickty -barder to malatoain
fliable t r a i s i b
 q. wuy the basebaud sigual before
heeds to be modulated
transinston u wirotess nutsork?
Rearsn:
Autena Size Sui talbi lity ": Gasebaud freaencies (eg 1MHz)
wlulch
autnnas (uendids if metes)
axe imgyaeeaoduaten
16Hz) l o s tue use
to wien Suitabe
for mobile dewices

Multipteaig FDM) : witout modutaton,

Divisiow. Sutts basehand siqnals to
not prssible. Modulatbu transnisslen in 'sahe mediwm
fOM is caeA freaeniles,enabing muHe
diffoet
bhaviour uke pati Los,
.'Mediun haxaetoistiu : SiauaipLuetraton depud on
regtecton, dffraction aud ttue
Modulatin welbs select e w i k o u and
t e
cauet fre,ueney Sulted to
derie typeleg shant usaves fo wmobile, long uas for.
Submanes)
D.
Enplain Ask, PSK and Fsa
Ampitude sift Kaying (aSK) techniane wshee biuany
|. Lt is a
simple digital modulation ttue
data (0 and 1) is trans i ted by vayng
o4 a cawie uoave.
Binany 4 is transmi
It. aud ted usig a higl aamplitude sigual
o is trasitted usiu lou or zwo
oin
amplitude.
M. ASK' requires low bandwidta but is aiglly cuseptilble to
woise,iukeutaneuee, andtrans
path miss'n
os, mamig
for mst wirles radlo
V. Howeven, it's wsed in wired System he optial fibeu t
wireless ingeard ,wwe stible sigual anplitudes can be
maintained' usina a dìrected bean
has to be an
caie siual

Phase Shift Kaying (PsK).

of the e a e wsare (e-g. (80 slift for 6Psk
betten woise than FsK aud ASK.
offo
complex tranmitteu and eceiven
setup he neceive must synclruze itt phase uoie a
tranitter ing a Puase ickud Loop (PL)
(v. More. reistaut to tutenfevence, maklug H wigay eliabe
for wieles communieatfon.
V. t is wsed ln wiei Wehoork atelll te commnicatt'on /
Bluetoo derices ete.

Freauenay Suipt (Esk)biuay 4 aud

Keuingusure Oae trausmitte
I. A dgtal modulatton
usiud tuoo diffoent fruaencies
thau ASK but ls more reslst
Keq,uwes a lageu baudusi d-th
ait to ww and intenfeence
Dmp teented by switcing between 2 osciuators or
coutiuus phae modution (cPM) to avotd
Sudden pluase
cdanges.
Commowy ed in wireles trausision.
 olloo|01|

Amputude suift keyiug (Asu)

digitol 4 1
stval

>t

M e d u a l e o

Erea ueney Shift Kayiug (Fs).

diqial

yt

Canuic
{nenuney

Cavvien

()

Moddaded
 20

Phase Suift Keytng (rs ) 360

4
digita! 1
Signal t
|
|
|

Caey
Sigual

hoduda!

i4nal