MOD 4 SVIT NOTES VTU SYLABBUS 2018 SCHEME.pdf

SAT COMN MOD 4 NOTES 2018 SCHEME

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Satellitetelephonynetworksemploypoint-
to-pointduplexsatellitelinksenabling
simultaneouscommunicationinboththe
directions
SingleGEOsatellitesoraconstellationof
LEO,MEOandGEOsatellitesareusedfor
providingtelephonyservices.
Telephonesatellitelinksgenerallyemploy
circuit-switchedsystemsofferingaconstant
bitrateservices
Someofthemajorsatellitesystems
offeringvoiceservicesareIntelsat,
Eutelsat,Inmarsat,Globalstar,Iridium,
ICO,EllipsoandOdysseysystems.
Satellite Telephony

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1.Theuserliftsthereceiverwhenheorshewantstomakeacall.This
sendsarequesttothelocalEarthstation,whichinturnsendsaservice
requesttothemasterstation.
2.Ifthemasterstationisabletoprovidethesatellitecapacity,itsendsa
confirmationsignaltothelocalEarthstation,resultinginadialtonein
thetelephoneinstrument.
3.Theuserthendialsthedestinationnumber,whichistransferredtothe
controlstation,whichdeterminesthedestinationEarthstationand
signalsitthataconnectionneedstobeestablished.
4.ThedestinationEarthstationthensignalsthecalledpartyofthe
incomingcallbyringingthattelephoneinstrument.
Local ES
Master ES
DestES
Control
station
Satellite Telephony

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5.Thesatellitecapacityisallocatedtotheconnectionandthe
telephonelinkisestablishedoncethecalledpartyliftsthehandset.
6.Oncetheconversationisover,thecallingpartyhangsupthe
receiver,henceindicatingtothelocalEarthstationtoterminatethe
call.
Satellite Telephony

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Point-to-Point Trunk Telephone Networks
Trunk telephony services come under the domain of fixed satellite
services (FSS), mainly utilizing C and Ku bands.
Generally, GEO satellites are utilized for providing these services.
Intelast, Europestar, Eutelsat, PamAmSatare examples of some of
the satellites used for the purpose.

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Mobile Satellite Telephony
Oneoftheimportantservicesprovidedbymobilesatelliteservices(MSS)istheinteractivevoice
communicationtomobileusers.
MSSsatelliteslaunchedintheperiods1980–1990and1990–1998wereGEOsatellites,categorizedas
Generation-IandGeneration-IIsatellitesrespectively,
Third generation mobile satellites, comprising constellations of LEO, MEO, HEO and GEO satellites,
provide voice and multimedia services to mobile and hand-held terminals.
Thethirdgenerationmobilesatelliteserviceshaveenteredtherealmofpersonalcommunicationsand
are also referred to as global mobile personal communication services (GMPCS)
GMPCSisapersonalcommunicationsystemprovidingtransnational,regionalorglobaltwo-way
voice,fax,messaging,dataandbroadbandmultimediaservicesfromaconstellationofsatellites
accessiblewithsmallandeasilytransportableterminals

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There are several different types of GMPCS systems:
GEO systems
small LEO systems
big LEO systems
MEO systems
HEO systems and
broadband GMPCS systems.

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Satellite Television
SatellitescanprovideTVprogrammeseitherdirectlyto
theusers(direct-to-hometelevision)
or
indirectlywiththehelpofcablenetworksorterrestrial
broadcastingnetworks,wherethesatellitefeedsthe
signaltoacentraloperatorwhointurntransmitsthe
programmestotheuserseitherusingcablenetworksor
throughterrestrialbroadcasting
SatellitetelevisionemploysGEOsatellitesactingas
point-to-multipointrepeatersreceivingacertaintelecast
fromthetransmissionbroadcastingcenterand
retransmittingthesameafterfrequencytranslationtothe
cableTVoperators,homedishes,etc.,lyingwithinthe
footprintofthesatellite.

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A typical satellite TV network, like any other satellite network,
can be divided into two sections:
the uplink section
the downlink section.
The uplink section comprises three main components:
the programming source,
the broadcasting center,
the main broadcasting satellite

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Theprogrammingsourcecomprises
TVchannelnetworks,
cableTVprogrammers,etc.,
thatprovidevariousTVprogrammingsignals,like
TVchannels,
sportscoverage,
newscoverage
orlocalrecordedTVprogrammes,
tothebroadcastingcentreeitherthroughterrestrialmeans,
likeusingtheline-of-sightmicrowavecommunication
and
thefiberopticcable,orusingsatellitesreferredtoasback-
haulsatellites.

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The satellite downlink comprises the main broadcasting satellite
and the TV receiving network.
Satellite–Cable Television
Direct-to-Home Satellite Television

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cableTVreferstotheuseofcoaxialandfiberopticcablesto
connecteachhousethroughapoint-to-multipointdistribution
networktotheheadenddistributionstation.CableTV,
originallyreferredtoasCATV(communityantennatelevision)
Satellite–Cable Television
Theheadendinthiscaseconsistsofvariousreceive-onlyEarth
stationswiththecapabilityofreceivingtelecastfromtwotosix
satellites.
TheseEarthstationseitherhavemultiplereceivingantennasor,
asingledishantennawithmultiplefeeds,witheachfeedso
alignedastoreceivetelecastfromadifferentsatellite.

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Satellite–Cable Television
Thetransmissionfromthesatelliteiseitherintheanalogueformat
(mainlyintheCband)orinthedigitalformat(mainlyintheKu
band).
Thisprocesseddigitaloranalogueinformationisthentransmitted
overatypicalcabledistributionnetworktoalargenumberof
housesknownassubscribers,whopayamonthlyfeefortheservice.
Thecableoperatorsscrambletheirprogrammestoprevent
unauthorizedviewing.
Thereceivingendthenconsistsofasettopboxtodescrambleand
retrievetheoriginalsignal.
ThecableTVoperatorsalsotransmitthevideotapedrecorded
programmesfromothersourcesinadditiontoshowing
programmesreceivedfromthesatellites.

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Satellite–Cable Television
Satellite–Local Broadcast TV Network
Herethesatellitedistributesprogrammingtolocal
terrestrialbroadcastingstationsinsteadofdistributingitto
thecableheadendstations
The broadcasting stations use powerful antennas to transmit
the received signals to various users within the line-of-sight
(50–150 km) using UHF and VHF microwave bands
TheusersreceivetheseTVsignalsusingdirectional
antennaslikeyagiantennas,reflectorantennasordipole
antennas

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Satellite–Cable Television
Direct-to-Home Satellite Television
Direct-to-home(DTH)satellitetelevisionreferstothedirect
receptionofsatelliteTVprogrammesbytheendusersfromthe
satellitethroughtheirownreceivingantennas
DTHservicescanbebroadlyclassifiedintotwotypes,namelythe
televisionreceive-only(TVRO)andthedirectbroadcasting
satellite(DBS)services,dependinguponthefrequencyband
utilizedandthesizeofthereceivingantennas.
TVROsystemsoperateintheCbandwhereastheDBSsystems
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Satellite–Cable Television
Television Receive-Only (TVRO) Services Direct Broadcasting Satellite (DBS) Services
TVROsystemsemploylargedishes(6to18feetacross)
placedintheuser’spremisesforthereceptionofanalogue
signalsfromthesatelliteoperatingintheCband
Generally,eachCbandtransponderprovidesoneanalogue
TVchannel,andhenceasatellitewith16such
transponderswillbeabletosupportonly16TVchannels.
Thesesystemsaremadeuserfriendlybyusing
microprocessorcontrol,allowingtheviewertoselectthe
desiredchannelwitharemotecontrolunit.
Theantennathenmovesautomaticallyusingelectronic
controlmethodstopointtothedesiredsatellite.
TVROsarebasedonopenstandardequipmentandprovide
thelargestvarietyofTVprograms,includingcableTV
programs,foreignstations,freeprogrammingchannelsand
liveuneditedfeedsbetweenbroadcastingstationslikenews,
sports,etc
TheDBSserviceuseshighpoweredKubandsatellitesthat
senddigitallycompressedtelevisionandaudiosignalsto
relativelysmall(45–60cmacross)fixedsatellitedishes
DBSsatellitestransmitsignalstoEarthintheBSSsegment
oftheKuband(between12.2and12.7GHz),makinguseof
MPEG-2(MovingPictureExpertsGroup)digital
compressiontechniques
Thechannelcapacitypertransponderisfivetotwelve
channelsdependinguponthedatarateandthecompression
parameters,andhencetheycanprovideabout200channels
fromonesatellite.

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Satellite–Cable Television
TherearenofreechannelsavailableonDBSsystems.DBS
systemsareeasytoinstallandarecheaperascomparedto
TVROsystems.
SomeoftheDBSserviceprovidersincludeDirecTV,
Echostar,PrimeStaroftheUSA,TataSkyandDishTVof
IndiaandStarChoiceofCanada.
TheFCChasallocatedeightorbitalslotsat61.5,101,110,
148,157,166and175westlongitudeGEOlocationsfor
DBSsystems
TVROsystemshavebetterpicturequalitythanDBSor
digitalcablesystems,whichtendtouselargeramountsof
digitalsignalcompression.

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Block schematic for the outdoor unit (ODU)
Direct-to-Home Satellite Television
Block schematic for the indoor unit (IDU)

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A satellite providing high fidelity audio broadcast services to the broadcast radio stations is referred to as a
satellite radio and is a major revolution in the field of radio systems.
Sound quality is excellent in this case due to a wide audio bandwidth of 5–15 kHz and low noise
provided over the satellite link.
Satellite radio like the satellite TV employ GEO satellites and the network arrangement for the satellite radio is
more or less identical to that used for TV broadcasting.
Using point-to-multipoint connectivity, the audio signals from various music channels, news and sports centres
are transmitted by the satellite to a conventional AM or FM radio station.
The signal is then de-multiplexed and the local commercials and other information is added here in the same way
as in a TV network and then sent to the users using terrestrial broadcasting topology.
The satellite can also transmit the signal directly to the user’s radio sets.
Some of the major providers of satellite radio services include Sirius and XM Radio of the USA.
Satellite Radio

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http://www.radio.garden

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VSATs (Very Small Aperture Terminals)
are used for providing one-way or two-way data broadcasting services, point-to-point voice services and
one-way video broadcasting services.
VSATnetworksareidealforcentralizednetworkswithacentralhostandanumberofgeographically
dispersedterminals
Typicalexamplesaresmallandmediumbusinesseswithacentraloffice,bankinginstitutionswith
branchesalloverthecountry,reservationandairlineticketingsystems,
VSATssufferfromamajorproblemofdelaybetweentransmissionandreceptionofdata(around250
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mostVSATsystemsoperateintheKuband
withtheantennadiameteroftheEarth
stationsbeingassmallas1to2m.
VSATnetworkscantransmitatarateof
64–1024kbps(64kbpsperremoteterminal)
intheoutbounddirectionand
64–256kbps(1.2to16kbpsperremote
terminal)intheinbounddirection.
VSATnetworksgenerallysupportdata,video
andvoiceservicesintheoutbounddirection
and
onlydataandvoiceservicesintheinbound
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VSAT Network Topologies
bidirectional star networks Unidirectional star networks
Mesh networks

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National Satellite Systems
National satellite systems, also referred to as domestic satellite systems, provide services to a
particular country
INSAT (Indian National Satellite)
Owned by the Indian Department of Space, named the Indian Space Research Organization (ISRO),
INSAT is one of the largest domestic communication satellite networks in the world, providing services
in the areas of
telecommunications,
television broadcasting,
mobile satellite services and
meteorology including disaster warning
INSAT is a joint venture of the
Department of Space (DOS),
Department of Telecommunications (DOT),
Indian Meteorological Department (IMD),
All India Radio (AIR) and
Doordarshan.

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