Notes-Satellite Communication - 1

7/25/2019 Notes-Satellite Communication - 1

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Satellite CommunicationSatellite CommunicationIntroductory LectureIntroductory Lecture

http://web.uettaxila.edu.pk/CMhttp://web.uettaxila.edu.pk/CMS/teSCms/S/teSCms/
http://web.uettaxila.edu.pk/CMS/teSCms/http://web.uettaxila.edu.pk/CMS/teSCms/http://web.uettaxila.edu.pk/CMS/teSCms/http://web.uettaxila.edu.pk/CMS/teSCms/http://web.uettaxila.edu.pk/CMS/teSCms/http://web.uettaxila.edu.pk/CMS/teSCms/


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OverviewOverview

Satellite technology has progressed tremendouslyover the last ! years since "rthur C. Clarke #irstproposed its idea in $%& in his article in 'ireless'orld.

(oday) satellite systems can provide a variety o#services including broadband communications)audio/video distribution networks) maritimenavigation) worldwide customer service andsupport as well as military command and control.

Satellite systems are also expected to play animportant role in the emerging &* globalin#rastructure providing the wide area coveragenecessary #or the reali+ation o# the ,-ptimallyConnected "nywhere) "nytime vision that drivesthe growth o# modern telecom industry.


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Course ObjectivesCourse Objectives

(his course aims to: rovide a broad overview o# the status o# digital

satellite communications. 0iscuss main physical) architectural and

networking issues o# satellite systems. rovide in1depth understanding o# modern

modulation) coding and multiple access schemes. 2eview the state o# the art in open research areas

such as speech and video coding) satellitenetworking) internet over satellite and satellitepersonal communications.

3ighlight trends and #uture directions o# satellitecommunication


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Course Pre-requisitesCourse Pre-requisites

rinciples o# digital communications

(elecom systems design


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Section 1: The SATCOM Industr !

Sstem "esi#n Issues

"n -verview o# Satellite Communications4 5xamples o# current military and commercial systems.4 Satellite orbits and transponder characteristics 6L5-) M5-)

*5-7

4 (ra##ic Connectivity: Mesh) 3ub1Spoke) oint1to1oint)8roadcast 8asic satellite transmission theory

4 Impairments o# the Satellite Channel: 'eather and 0opplere##ects) Channel models.

4 Communications Link Calculations: 0e#inition o# 5I2) 9oise

temperature and */( ratio) 5b/9o. (ransponder gain and S0.Link 8udget Calculations. 0own1link re;uirements. 0esign o#satellite links to achieve a speci#ied per#ormance.

4 5arth Station "ntenna types: ointing/(racking. Smallantennas at


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Section $: %lements o& Trans'onder

"esi#n ! The (aseband

hysical Layer o# the (ransponder > (he 8asebandSystem

Introduction to the theory o# 0igitalCommunications: Modulation) 5;uali+ation and 5C

4 0igital Modulation (echni;ues: 8S


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Section ): Multi'le Access Issues

Spread Spectrum (echni;ues: Military andcommercial use o# spread1spectrum. 0irect1Se;uence 9) re;uency13op and C0M"systems.

rinciples o# Multiple "ccess Communications4 Multiplexing B Multiple "ccess 00/(00) 0M") (0M"

4 Concepts o# 2andom "ccess: "L-3") CSM"

Multiple "ccess (echni;ues: 0M") (0M") C0M".

0"M" and 8andwidth1on10emand 68o07. (0M" 9etworks: (ime Slots) reambles)Suitability #or 0"M" and 8o0.


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Section *: SATCOM +etwor,s and

Services Satellite Communication Systems B

9etworks4 Characteristics o# I and (C/=0 over

satellite: =nicast and Multicast. 9eed #or

er#ormance 5nhancing roxy 657 techni;ues.

4 AS"( 9etworks and their systemcharacteristics.

4 0A8 standards and M1(0M" (he uture o# S"(C-M4 S"(C-Ms role in the emerging &* In#ormation

and Communications 6IC(7 in#rastructure.


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Tet (oo,Tet (oo,

Title:Title:(he Satellite Communication "pplications(he Satellite Communication "pplications

3andbook3andbook

Author:Author:8ruce 2. 5lbert8ruce 2. 5lbert

ISBN:ISBN:$@!D&%!E$@!D&%!E EAN:EAN:%F@$@!D&%!$%F@$@!D&%!$

Publisher:Publisher:

"rtech 3ouse ublishers"rtech 3ouse ublishers


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.e&erence (oo,s.e&erence (oo,s

Title:Title:Satellite CommunicationsSatellite Communications

Author:Author:0ennis 2oddy0ennis 2oddy

ISBN:ISBN:!!F$DF$FG$!!F$DF$FG$

EAN:EAN:%F@!!F$DF$FGG%F@!!F$DF$FGG Publisher:Publisher:

Mc*raw13ill ro#essionalMc*raw13ill ro#essional


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.e&erence (oo,s.e&erence (oo,s

Title:Title:Satellite Communication 5ngineeringSatellite Communication 5ngineering

Author:Author:Michael -.


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Pioneers in SatellitePioneers in Satellite

CommunicationCommunication Konstantin Tsiolkovsky (1857 1!"5#Konstantin Tsiolkovsky (1857 1!"5#

2ussian visionary o# space #light irst described the multi12ussian visionary o# space #light irst described the multi1stage rocket as means o# achieving orbit.stage rocket as means o# achieving orbit.4 Link:Link: (he li#e o#


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Satellite /istor CalendarSatellite /istor Calendar $%F$%F

4 -ctober &) $%F: 1 irst satellite 1 the 2ussian Sputnik !$-ctober &) $%F: 1 irst satellite 1 the 2ussian Sputnik !$4 irst living creature in space: Sputnik !Eirst living creature in space: Sputnik !E $%@$%@

4 irst "merican satellite: 5xplorer !$irst "merican satellite: 5xplorer !$4 irst telecommunication satellite: (his satellite broadcast a taped message: Scoreirst telecommunication satellite: (his satellite broadcast a taped message: Score

$%%$%%4 irst meteorology satellite: 5xplorer !First meteorology satellite: 5xplorer !F

$%G!$%G!4 irst success#ul passive satellite: 5cho $irst success#ul passive satellite: 5cho $4 irst success#ul active satellite: Courier $8irst success#ul active satellite: Courier $8

4 irst 9"S" satellite: 5xplorer !@irst 9"S" satellite: 5xplorer !@ "pril $E) $%G$: 1 irst man in space"pril $E) $%G$: 1 irst man in space $%GE$%GE

4 irst telephone communication B (A broadcast via satellite: 5cho $irst telephone communication B (A broadcast via satellite: 5cho $4 irst telecommunication satellite) #irst real1time active) "(B(: (elstar $irst telecommunication satellite) #irst real1time active) "(B(: (elstar $4 irst Canadian satellite: "louette $irst Canadian satellite: "louette $4 -n F-n FththJune $%GE at F:Dp the two1stage rocketK 2ehbar1I was success#ully launched #rom Sonmiani 2ocketJune $%GE at F:Dp the two1stage rocketK 2ehbar1I was success#ully launched #rom Sonmiani 2ocket

2ange. It carried a payload o# @! pounds o# sodium and soared to about $D! km into the atmosphere. 'ith the2ange. It carried a payload o# @! pounds o# sodium and soared to about $D! km into the atmosphere. 'ith thelaunching o# 2ehbar1I) akistan had the honour o# becoming the third country in "sia and the tenth in the worldlaunching o# 2ehbar1I) akistan had the honour o# becoming the third country in "sia and the tenth in the worldto conduct such a launching a#ter =S") =SS2) =


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Satellite /istor CalendarSatellite /istor Calendar $%G$%G

4 Intelsat $ becomes #irst commercial comsat: 5arly 8irdIntelsat $ becomes #irst commercial comsat: 5arly 8ird4 irst real1time active #or =SS2: Molniya $"irst real1time active #or =SS2: Molniya $"

$%GF$%GF4 irst geostationary meteorology payload: "(S Dirst geostationary meteorology payload: "(S D

$%G@$%G@4 irst 5uropean satellite: 5S2- E8irst 5uropean satellite: 5S2- E8

July E$) $%G%: 1 irst man on the moonJuly E$) $%G%: 1 irst man on the moon

$%F!$%F!

4 irst Japanese satellite: -hsumiirst Japanese satellite: -hsumi4 irst Chinese satellite: 0ong ang 3ong !$irst Chinese satellite: 0ong ang 3ong !$

$%F$$%F$4 irst =< launched satellite: rosperoirst =< launched satellite: rospero4 I(=1'"2C #or Space (elecommunicationsI(=1'"2C #or Space (elecommunications4 I9(5LS"( IA LaunchedI9(5LS"( IA Launched4 I9(52S=(9I< 1 Soviet =nion e;uivalent o# I9(5LS"( #ormedI9(52S=(9I< 1 Soviet =nion e;uivalent o# I9(5LS"( #ormed

$%F&$%F&4 irst direct broadcasting satellite: "(S Girst direct broadcasting satellite: "(S G

$%FG$%FG4 M"2IS"( 1 irst civil maritime communications satellite service startedM"2IS"( 1 irst civil maritime communications satellite service started

$%FF$%FF4 5=(5LS"( 1 5uropean regional satellite5=(5LS"( 1 5uropean regional satellite4 I(=1'"2C #or Space (elecommunications in the Satellite ServiceI(=1'"2C #or Space (elecommunications in the Satellite Service

$%F%$%F%4 Creation o# InmarsatCreation o# Inmarsat


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Satellite /istor CalendarSatellite /istor Calendar $%@!$%@!

4 I9(5LS"( A launched 1 D axis stabili+ed satellite built by ord "erospaceI9(5LS"( A launched 1 D axis stabili+ed satellite built by ord "erospace $%@D$%@D

4 5CS 65=(5LS"( $7 launched 1 built by 5uropean consortium supervised by 5S"5CS 65=(5LS"( $7 launched 1 built by 5uropean consortium supervised by 5S" $%@&$%@&

4 =


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Satellite /istor CalendarSatellite /istor Calendar $%%G$%%G

4 I9M"2S"( III launched 1 #irst o# the multibeam mobile satellites 6built by *5/Marconi7I9M"2S"( III launched 1 #irst o# the multibeam mobile satellites 6built by *5/Marconi74 5chostar begins 0iresct 8roadcast Service5chostar begins 0iresct 8roadcast Service

$%%F$%%F4 I2I0I=M launches #irst test satellitesI2I0I=M launches #irst test satellites4 I(=1'2C%FI(=1'2C%F

$%%%$%%%4 "ceS launch #irst o# the L1band MSS Super1*S-s 1 built by Lockheed Martin"ceS launch #irst o# the L1band MSS Super1*S-s 1 built by Lockheed Martin4 Iridium 8ankruptcy 1 the #irst maor #ailureOIridium 8ankruptcy 1 the #irst maor #ailureO

E!!!E!!!4 *lobalstar begins service*lobalstar begins service4 (huraya launch L1band MSS Super1*S-(huraya launch L1band MSS Super1*S-

E!!$E!!$4 HM Satellite 2adio begins serviceHM Satellite 2adio begins service4 akistans Eakistans EndndSatellite) 8"0218 was launched on $! 0ec E!!$ at %:$a #rom 8aikonourSatellite) 8"0218 was launched on $! 0ec E!!$ at %:$a #rom 8aikonour

Cosmodrome)


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IntelsatIntelsat

I9(5LS"( is the original Inter1governmental SatelliteI9(5LS"( is the original Inter1governmental Satelliteorgani+ation. It once owned and operated most o# theorgani+ation. It once owned and operated most o# the'orlds satellites used #or international communications)'orlds satellites used #or international communications)and still maintains a substantial #leet o# satellites.and still maintains a substantial #leet o# satellites.

I9(5LS"( is moving towards privati+ation) with increasingI9(5LS"( is moving towards privati+ation) with increasingcompetition #rom commercial operators 6e.g. anamsat)competition #rom commercial operators 6e.g. anamsat)Loral Skynet) etc.7.Loral Skynet) etc.7.

I9(5LS"( (imeline:I9(5LS"( (imeline: Interim organi+ation #ormed in $%G& by $$ countriesInterim organi+ation #ormed in $%G& by $$ countries

ermanent structure #ormed in $%FDermanent structure #ormed in $%FD

Commercial spin1o##) 9ew Skies Satellites in $%%@Commercial spin1o##) 9ew Skies Satellites in $%%@

ull privati+ation by "pril E!!$ull privati+ation by "pril E!!$ I9(5LS"( has $&D members and signatories listedI9(5LS"( has $&D members and signatories listed herehere..
http://www.satcom.co.uk/Tables/im.asphttp://www.satcom.co.uk/Tables/im.asphttp://www.satcom.co.uk/Tables/im.asp


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Intelsat StructureIntelsat Structure


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%utelsat%utelsat

ermanent *eneral Secretariat opened September $%F@ermanent *eneral Secretariat opened September $%F@ Intergovernmental Con#erence adopted de#initive statutes with EGIntergovernmental Con#erence adopted de#initive statutes with EG

members on $& May $%@Emembers on $& May $%@E 0e#initive organi+ation entered into #orce on $ September $%@0e#initive organi+ation entered into #orce on $ September $%@

*eneral Secretariat 1P 5xecutive -rgan*eneral Secretariat 1P 5xecutive -rgan

5xecutive Council 1P 5=(5LS"( 8oard o# Signatories5xecutive Council 1P 5=(5LS"( 8oard o# Signatories

Secretary *eneral 1P 0irector *eneralSecretary *eneral 1P 0irector *eneral

Current 0* is *iuliano 8errettaCurrent 0* is *iuliano 8erretta Currently almost ! membersCurrently almost ! members

Moving towards privati+ationMoving towards privati+ation Limited company owning and controlling o# all assets and activitiesLimited company owning and controlling o# all assets and activities

"lso a residual intergovernmental organi+ation which will ensure that"lso a residual intergovernmental organi+ation which will ensure thatbasic principles o# pan15uropean coverage) universal service) non1basic principles o# pan15uropean coverage) universal service) non1discrimination and #air competition are observed by the companydiscrimination and #air competition are observed by the company


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%utelsat Structure%utelsat Structure


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Communication SatelliteCommunication Satellite

" Communication Satellite can be" Communication Satellite can belooked upon as a large microwavelooked upon as a large microwaverepeaterrepeater

It contains several transpondersIt contains several transponderswhich listens to some portion o#which listens to some portion o#spectrum) ampli#ies the incomingspectrum) ampli#ies the incoming

signal and broadcasts it in anothersignal and broadcasts it in another#re;uency to avoid inter#erence with#re;uency to avoid inter#erence withincoming signals.incoming signals.


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Motivation to use SatellitesMotivation to use Satellites


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Source: =nion o# Concerned Scientists Qwww.ucsusa.orgRSource: =nion o# Concerned Scientists Qwww.ucsusa.orgR

Satellite MissionsSatellite Missions


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Satellite Microwave TransmissionSatellite Microwave Transmission

Satellites can relay signals over aSatellites can relay signals over a

long distancelong distance

*eostationary Satellites*eostationary Satellites

4 2emain above the e;uator at a height o#2emain above the e;uator at a height o#

about EED!! miles 6geosynchronousabout EED!! miles 6geosynchronous

orbits7orbits7

4 (ravel around the earth in exactly the(ravel around the earth in exactly thesame time) the earth takes to rotatesame time) the earth takes to rotate


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Satellite Sstem %lementsSatellite Sstem %lements


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S'ace Se#mentS'ace Se#ment

Satellite Launching hase (rans#er -rbit hase 0eployment -peration

4 ((BC 1 (racking (elemetry and CommandStation

4 SSC 1 Satellite Control Center) a.k.a.: -CC 1 -perations Control Center SC 1 Satellite Control acility

2etirement hase


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0round Se#ment0round Se#ment

Collection o# #acilities) =sers and "pplicationsCollection o# #acilities) =sers and "pplications

5arth Station Satellite Communication Station5arth Station Satellite Communication Station

6ixed or Mobile76ixed or Mobile7


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Satellite 'lin, and "ownlin,Satellite 'lin, and "ownlin,

0ownlink0ownlink4 (he link #rom a satellite down to one or more(he link #rom a satellite down to one or more

ground stations or receiversground stations or receivers

=plink=plink4 (he link #rom a ground station up to a satellite.(he link #rom a ground station up to a satellite. Some companies sell uplink and downlinkSome companies sell uplink and downlink

services toservices to

4 television stations) corporations) and to othertelevision stations) corporations) and to othertelecommunication carriers.telecommunication carriers.

4 " company can speciali+e in providing uplinks)" company can speciali+e in providing uplinks)downlinks) or both.downlinks) or both.


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Satellite 'lin, and "ownlin,Satellite 'lin, and "ownlin,


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Source: Cryptome QCryptome.orgRSource: Cryptome QCryptome.orgR

'hen using a satellite #or long'hen using a satellite #or long

distance communications) thedistance communications) the

satellite acts as a repeater.satellite acts as a repeater.

"n earth station transmits the"n earth station transmits thesignal up to the satellitesignal up to the satellite

6uplink7) which in turn6uplink7) which in turn

retransmits it to the receivingretransmits it to the receiving

earth station 6downlink7.earth station 6downlink7.

0i##erent #re;uencies are used0i##erent #re;uencies are used

#or uplink/downlink.#or uplink/downlink.

Satellite CommunicationSatellite Communication


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Satellite Transmission 2in,sSatellite Transmission 2in,s

5arth stations Communicate by5arth stations Communicate by

sending signals to the satellite on ansending signals to the satellite on an

uplinkuplink

(he satellite then repeats those(he satellite then repeats those

signals on a downlinksignals on a downlink

(he broadcast nature o# downlink(he broadcast nature o# downlink

makes it attractive #or services suchmakes it attractive #or services such

as the distribution o# (A programsas the distribution o# (A programs


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"irect to ser Services"irect to ser Services

-ne way Service 68roadcasting7-ne way Service 68roadcasting7 (wo way Service 6Communication7(wo way Service 6Communication7


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Satellite Si#nalsSatellite Si#nals

=sed to transmit signals and data=sed to transmit signals and data

over long distancesover long distances

4 'eather #orecasting'eather #orecasting

4 (elevision broadcasting(elevision broadcasting

4 Internet communicationInternet communication

4 *lobal ositioning Systems*lobal ositioning Systems


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Satellite Transmission (andsSatellite Transmission (ands

Frequency Band Downlink Uplink

C 3,700-4,200 MHz 5,925-6,425 MHz

Ku 11.7-12.2 GHz 14.0-14.5 GHz

Ka 17.7-21.2 GHz 27.5-31.0 GHz

(he C band is the most #re;uently used. (he


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T'es o& Satellite OrbitsT'es o& Satellite Orbits

8ased on the inclination) i) over the e;uatorialplane:

4 5;uatorial -rbits above 5arths e;uator 6i!T75;uatorial -rbits above 5arths e;uator 6i!T7

4 olar -rbits pass over both poles 6i%!T7olar -rbits pass over both poles 6i%!T74 -ther orbits called inclined orbits 6!TUiU%!T7-ther orbits called inclined orbits 6!TUiU%!T7

8ased on 5ccentricity8ased on 5ccentricity

4 Circular with centre at the earths centreCircular with centre at the earths centre

4 5lliptical with one #oci at earths centre5lliptical with one #oci at earths centre


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T'es o& Satellite based +etwor,sT'es o& Satellite based +etwor,s

8ased on the Satellite "ltitude8ased on the Satellite "ltitude

4 *5- > *eostationary -rbits*5- > *eostationary -rbits DG!!! Medium 5arth -rbits 3igh bandwidth) 3igh power) 3igh latency3igh bandwidth) 3igh power) 3igh latency

4 L5- > Low 5arth -rbitsL5- > Low 5arth -rbits Low power) Low latency) More Satellites) SmallLow power) Low latency) More Satellites) Small

ootprintootprint

4 AS"(AS"( Aery Small "perture SatellitesAery Small "perture Satellites

4 rivate '"9srivate '"9s


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Source: ederation o# "merican Scientists Qwww.#as.orgRSource: ederation o# "merican Scientists Qwww.#as.orgR

Satellite OrbitsSatellite Orbits

*eosynchronous -rbit 6*5-7:*eosynchronous -rbit 6*5-7:

DG)!!! km above 5arth)DG)!!! km above 5arth)

includes commercial andincludes commercial and

military communicationsmilitary communications

satellites) satellites providingsatellites) satellites providing

early warning o# ballisticearly warning o# ballisticmissile launch.missile launch.

Medium 5arth -rbit 6M5-7:Medium 5arth -rbit 6M5-7:

#rom !!! to $!!! km) they#rom !!! to $!!! km) they

include navigation satellitesinclude navigation satellites

6*S) *alileo) *lonass7.6*S) *alileo) *lonass7.

Low 5arth -rbit 6L5-7: #romLow 5arth -rbit 6L5-7: #rom!! to $!!! km above 5arth)!! to $!!! km above 5arth)

includes military intelligenceincludes military intelligence

satellites) weather satellites.satellites) weather satellites.


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0%O - 0eostationar Orbit0%O - 0eostationar Orbit

In the e;uatorial planeIn the e;uatorial plane

-rbital eriod ED h G m &.!%$ s-rbital eriod ED h G m &.!%$ s

$ sidereal dayV $ sidereal dayV

Satellite appears to be stationary over any pointSatellite appears to be stationary over any pointon e;uator:on e;uator:4 5arth 2otates at same speed as Satellite5arth 2otates at same speed as Satellite4 2adius o# -rbit r -rbital 3eight W 2adius o# 5arth2adius o# -rbit r -rbital 3eight W 2adius o# 5arth

4 "vg. 2adius o# 5arth GDF@.$&


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+0SO - +on 0eostationar Orbits+0SO - +on 0eostationar Orbits

-rbit should avoidAan "llen radiationbelts:4 2egion o# charged

particles that cancause damage tosatellite

4 -ccur at XE!!!1&!!! km and X$D!!!1E!!! km


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2%O - 2ow %arth Orbits2%O - 2ow %arth Orbits

Circular or inclined orbit with U $&!! kmaltitude4 Satellite travels across sky #rom hori+on to

hori+on in 1 $ minutes P needs hando##

4 5arth stations must track satellite or have-mni directional antennas

4 Large constellation o# satellites is needed #orcontinuous communication 6GG satellites

needed to cover earth74 2e;uires complex architecture

4 2e;uires tracking at ground


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/%O - /i#hl %lli'tical Orbits/%O - /i#hl %lli'tical Orbits

35-s 6i GD.&T7 are suitable toprovide coverage at high latitudes6including 9orth ole in thenorthern hemisphere7

0epending on selected orbit 6e.g.Molniya) (undra) etc.7 two orthree satellites are su##icient #orcontinuous time coverage o# theservice area.

"ll tra##ic must be periodicallytrans#erred #rom the ,settingsatellite to the ,rising satellite6Satellite 3andover7


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Source: =nion o# Concerned Scientists Qwww.ucsusa.orgRSource: =nion o# Concerned Scientists Qwww.ucsusa.orgR



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3h Satellites remain in Orbits3h Satellites remain in Orbits


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Advanta#es o& SatelliteAdvanta#es o& Satellite

CommunicationCommunication Can reach over large geographical areaCan reach over large geographical area lexible 6i# transparent transponders7lexible 6i# transparent transponders7 5asy to install new circuits5asy to install new circuits Circuit costs independent o# distanceCircuit costs independent o# distance 8roadcast possibilities8roadcast possibilities (emporary applications 6restoration7(emporary applications 6restoration7 9iche applications9iche applications Mobile applications 6especially #ill1in7Mobile applications 6especially #ill1in7

(errestrial network by1pass(errestrial network by1pass rovision o# service to remote or underdevelopedrovision o# service to remote or underdeveloped

areasareas =ser has control over own network=ser has control over own network $1#or19 multipoint standby possibilities$1#or19 multipoint standby possibilities


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"isadvanta#es o& Satellite"isadvanta#es o& Satellite

CommunicationCommunication Large up #ront capital costs 6spaceLarge up #ront capital costs 6space

segment and launch7segment and launch7

(errestrial break even distance(errestrial break even distance

expanding 6now approx. si+e o#expanding 6now approx. si+e o#

5urope75urope7

Inter#erence and propagation delayInter#erence and propagation delay

Congestion o# #re;uencies and orbitsCongestion o# #re;uencies and orbits


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3hen to use Satellites3hen to use Satellites

'hen the uni;ue #eatures o# satellite communications'hen the uni;ue #eatures o# satellite communicationsmake it attractivemake it attractive

'hen the costs are lower than terrestrial routing'hen the costs are lower than terrestrial routing 'hen it is the only solution'hen it is the only solution 5xamples:5xamples:

4 Communications to ships and aircra#t 6especially sa#etyCommunications to ships and aircra#t 6especially sa#etycommunications7communications7

4 (A services 1 contribution links) direct to cable head) direct(A services 1 contribution links) direct to cable head) directto hometo home

4 0ata services 1 private networks0ata services 1 private networks4 -verload tra##ic-verload tra##ic

4 0elaying terrestrial investments0elaying terrestrial investments4 $ #or 9 diversity$ #or 9 diversity4 Special eventsSpecial events


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3hen to use Terrestrial3hen to use Terrestrial

S(9 1 satellite is becoming increasinglyS(9 1 satellite is becoming increasinglyuneconomic #or most trunk telephony routesuneconomic #or most trunk telephony routes

but) there are still good reasons to use satellitesbut) there are still good reasons to use satellites#or telephony such as: thin routes) diversity)#or telephony such as: thin routes) diversity)very long distance tra##ic and remote locations.very long distance tra##ic and remote locations.

Land mobile/personal communications 1 inLand mobile/personal communications 1 inurban areas o# developed countries newurban areas o# developed countries newterrestrial in#rastructure is likely to dominateterrestrial in#rastructure is likely to dominate6e.g. *SM) etc.76e.g. *SM) etc.7

but) satellite can provide #ill1in as terrestrialbut) satellite can provide #ill1in as terrestrialnetworks are implemented) also provide similarnetworks are implemented) also provide similarservices in rural areas and underdevelopedservices in rural areas and underdevelopedcountriescountries


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4requenc (ands Allocated to the4requenc (ands Allocated to the

4SS4SS re;uency bands are allocated to di##erent services at 'orldre;uency bands are allocated to di##erent services at 'orld

2adio1communication Con#erences 6'2Cs7.2adio1communication Con#erences 6'2Cs7. "llocations are set out in "rticle S o# the I(= 2adio"llocations are set out in "rticle S o# the I(= 2adio

2egulations.2egulations. It is important to note that 6with a #ew exceptions7 bandsIt is important to note that 6with a #ew exceptions7 bands

are generally allocated to more than one radio services.are generally allocated to more than one radio services. C-9S(2"I9(SC-9S(2"I9(S

4 8ands have traditionally been divided into ,commercial and8ands have traditionally been divided into ,commercial andgovernment/military bands) although this is not re#lected ingovernment/military bands) although this is not re#lected inthe 2adio 2egulations and is becoming less clear1cut asthe 2adio 2egulations and is becoming less clear1cut ascommercial operators move to utili+e government bands.commercial operators move to utili+e government bands.


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%arth5s atmos'here%arth5s atmos'here

Source: "ll about *S Qwww.kowoma.deRSource: "ll about *S Qwww.kowoma.deR


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Atmos'heric 2ossesAtmos'heric 2osses

0i##erent types o# atmospheric losses can0i##erent types o# atmospheric losses candisturb radio wave transmission in satellitedisturb radio wave transmission in satellite

systems:systems:

4 At%os/heri- absor/tionAt%os/heri- absor/tion

4 At%os/heri- attenuationAt%os/heri- attenuation

4 Travelin' ionos/heri- &isturban-esTravelin' ionos/heri- &isturban-es


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Atmos'heric Absor'tionAtmos'heric Absor'tion

5nergy absorption by atmospheric5nergy absorption by atmosphericgases) which varies with the #re;uencygases) which varies with the #re;uencyo# the radio waves.o# the radio waves.

(wo absorption peaks are observed 6#or(wo absorption peaks are observed 6#or%!Y elevation angle7:%!Y elevation angle7:

4 EE.D *3+ #rom resonance absorption inEE.D *3+ #rom resonance absorption inwater vapour 63water vapour 63EE-7-7

4 G! *3+ #rom resonance absorption inG! *3+ #rom resonance absorption inoxygen 6-oxygen 6-EE77

or other elevation angles:or other elevation angles:

4 Q""R Q""RQ""R Q""R%!%!coseccosec

Source:Satellite Communications, Dennis Roddy, McGraw-Hill


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Atmos'heric AttenuationAtmos'heric Attenuation

2ain is the main cause o# atmospheric attenuation2ain is the main cause o# atmospheric attenuation6hail) ice and snow have little e##ect on attenuation6hail) ice and snow have little e##ect on attenuation

because o# their low water content7.because o# their low water content7.

(otal attenuation #rom rain can be determined by:(otal attenuation #rom rain can be determined by:

4 " " L Qd8RL Qd8R4 wherewhere Qd8/kmR is called the speci#ic attenuation) andQd8/kmR is called the speci#ic attenuation) and

can be calculated #rom speci#ic attenuation coe##icients incan be calculated #rom speci#ic attenuation coe##icients in

tabular #orm that can be #ound in a number o#tabular #orm that can be #ound in a number o#

publicationspublications

4 where L QkmR is the e##ective path length o# the signalwhere L QkmR is the e##ective path length o# the signalthrough the rainK note that this di##ers #rom the geometricthrough the rainK note that this di##ers #rom the geometric

path length due to #luctuations in the rain density.path length due to #luctuations in the rain density.


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Travelin# Ionos'heric "isturbancesTravelin# Ionos'heric "isturbances

(raveling ionospheric disturbances are clouds(raveling ionospheric disturbances are cloudso# electrons in the ionosphere that provokeo# electrons in the ionosphere that provokeradio signal #luctuations which can only beradio signal #luctuations which can only bedetermined on a statistical basis.determined on a statistical basis.

(he disturbances o# maor concern are:(he disturbances o# maor concern are:

4 ScintillationKScintillationK4 olarisation rotation.olarisation rotation.

Scintillations are variations in the amplitude)Scintillations are variations in the amplitude)phase) polarisation) or angle o# arrival o# radiophase) polarisation) or angle o# arrival o# radiowaves) caused by irregularities in thewaves) caused by irregularities in theionosphere which change over time.ionosphere which change over time.

(he main e##ect o# scintillations is #ading o# the(he main e##ect o# scintillations is #ading o# thesignal.signal.


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3hat is Polarisation63hat is Polarisation6

olarisation is the property o# electromagneticolarisation is the property o# electromagneticwaves that describes the direction o# thewaves that describes the direction o# the

transverse electric #ield.transverse electric #ield.

Since electromagnetic waves consist o# anSince electromagnetic waves consist o# an

electric and a magnetic #ield vibrating at rightelectric and a magnetic #ield vibrating at rightangles to each other.angles to each other.

it is necessary to adopt a convention toit is necessary to adopt a convention to

determine the polarisation o# the signal.determine the polarisation o# the signal.

Conventionally) the magnetic #ield is ignored andConventionally) the magnetic #ield is ignored andthe plane o# the electric #ield is used.the plane o# the electric #ield is used.


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T'es o& PolarisationT'es o& Polarisation

Linear olarisationLinear olarisation6hori+ontal or vertical7:6hori+ontal or vertical7:

4 the two orthogonalthe two orthogonalcomponents o# thecomponents o# theelectric #ield are in phaseKelectric #ield are in phaseK

4 (he direction o# the line in(he direction o# the line in

the plane depends on thethe plane depends on therelative amplitudes o# therelative amplitudes o# thetwo components.two components.

Circular olarisation:Circular olarisation:

4 (he two components are(he two components areexactly %!Y out o# phaseexactly %!Y out o# phaseand have exactly theand have exactly thesame amplitude.same amplitude.

5lliptical olarisation:5lliptical olarisation:

4 "ll other cases."ll other cases.

Linear PolarisationCircular Polarisation Elliptical Polarisation


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Satellite CommunicationsSatellite Communications

"lternating vertical and"lternating vertical andhori+ontal polarisation ishori+ontal polarisation iswidely used on satellitewidely used on satellitecommunicationscommunications

(his reduces inter#erence(his reduces inter#erencebetween programs on thebetween programs on thesame #re;uency bandsame #re;uency bandtransmitted #rom adacenttransmitted #rom adacentsatellites 6-ne uses vertical)satellites 6-ne uses vertical)the next hori+ontal) and sothe next hori+ontal) and soon7on7

"llows #or reduced angular"llows #or reduced angularseparation between theseparation between thesatellites.satellites. Information Resources for Telecommunication Professionals

[www.mlesat.com]


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.elated In&ormation.elated In&ormation

http://web.uettaxila.edu.pk/uet/narchttp://web.uettaxila.edu.pk/uet/narc

/#lvplay.htm/#lvplay.htm
http://web.uettaxila.edu.pk/uet/narc/flvplay.htmhttp://web.uettaxila.edu.pk/uet/narc/flvplay.htmhttp://web.uettaxila.edu.pk/uet/narc/flvplay.htmhttp://web.uettaxila.edu.pk/uet/narc/flvplay.htmhttp://web.uettaxila.edu.pk/uet/narc/flvplay.htmhttp://web.uettaxila.edu.pk/uet/narc/flvplay.htm


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78A78A

OOOOOOOO


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Assi#nment 91Assi#nment 91

2ead the paper o# "rthur C. Clark and2ead the paper o# "rthur C. Clark and

summari+e his suggestions to supportsummari+e his suggestions to support

Satellite #or Communication purposesSatellite #or Communication purposes

AisitAisithttp://web.uettaxila.edu.pk/cms/teSCmshttp://web.uettaxila.edu.pk/cms/teSCms

and visit J(rack1D0 Link under Importantand visit J(rack1D0 Link under Important

Links section to complete the assignmentLinks section to complete the assignment

4 Nou need to #ind out the satellite name o#Nou need to #ind out the satellite name o#akSat1$ in J(rack1D0 and send a snapshot o#akSat1$ in J(rack1D0 and send a snapshot o#

J(rack1D0 with akSat1$ in itJ(rack1D0 with akSat1$ in it
http://web.uettaxila.edu.pk/cms/teSCmshttp://web.uettaxila.edu.pk/cms/teSCmshttp://web.uettaxila.edu.pk/cms/teSCms

Notes-Satellite Communication - 1

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